Urban rail construction depends on shield tunneling because it allows underground space to be developed beneath active streets, buildings, and infrastructure with comparatively limited surface disruption. However, the method inevitably disturbs the surrounding ground and as the shield advances, excavation, face support, segment erection, and tail void closure interact within a narrow construction window, and even small mismatches between volume loss and compensation can appear later as surface settlement. In densely built ground, that settlement is not just a geometric response of soil; it becomes a serviceability and safety concern for nearby structures, utilities, and transport corridors. Tail grouting sits at the center of this control problem. The annular gap between the excavated soil and the newly installed tunnel lining must be filled by a material that can be transported and injected as a fluid, occupy the tail void effectively, and then develop enough stiffness and strength to restrain subsequent deformation. The scientific difficulty is that the grout is not a material with one fixed performance state. During mixing, pumping, and injection, its liquid properties dominate: density, bleeding rate, fluidity, consistency, and stone rate determine whether it can be placed reliably. After injection, the same material enters a different physical regime, where pressure, soil permeability, water dissipation, consolidation, and cementitious hardening govern compressed deformation and strength development. This liquid-to-solid transition makes grout proportioning more difficult than ordinary empirical mix adjustment. This is important because field performance depends on a balance between pumpability, filling stability, deformation resistance, and strength development. The challenge, therefore, is multi-performance optimization under construction-relevant conditions, not simply maximizing one index. In a recent research paper published in Computer-Aided Civil and Infrastructure Engineering, Dr. Jiaxin Liang, Prof. Wei Liu, Dr. Jingyi Gong, and Prof. Xiaoqiang Dong from Taiyuan University of Technology and Soochow University, working with Dr. Cheng Chen of Suzhou City University and Dr. Chunqing Fu of Beijing Uni-Construction Group Co. Ltd., addressed this problem by developing an explainable intelligent system for shield tunnel tail grout optimization. The system combines experimental liquid and solid performance databases, physics-constrained GAN data augmentation, Bayesian-optimized machine learning, and SHAP interpretation. Its technical distinction is the use of different optimal algorithms for different grout responses rather than a single uniform model. The system links mix proportions and ground conditions to workability, deformation, strength, and settlement-control performance.

The researchers organized the database around the actual performance sequence of tail grout. Fresh grout behavior was represented through water–binder ratio, bentonite–solid ratio, bentonite–water ratio, and cement–fly ash ratio, with five measured outputs: density, bleeding rate, fluidity, consistency, and stone rate. After hardening, the authors incorporated compressed deformation, 3-day unconfined compressive strength, and 28-day unconfined compressive strength. This separation was technically important because it allowed the system to distinguish workability during injection from mechanical performance after consolidation and hardening.

The authors conducted solid-performance tests under three soil conditions and three pressures. They used sand, silt, and clay to represent different permeability environments, while the applied pressures ranged from 100 to 300 kPa. This design choice links the testing strategy directly to the scientific problem: after grout enters the tail void, soil permeability and ground pressure influence water migration, compressed deformation, and the development of stiffness. The authors therefore did not evaluate hardened grout as a detached laboratory material, but as a material responding to boundary conditions that resemble the underground environment. The researchers used a physics-constrained generative adversarial network to expand the available data and their liquid-performance dataset was enlarged to 526 sets and the solid-performance dataset to 582 sets.  The generated data were guided by physical rules and screened to remain consistent with the expected mechanical and chemical behavior of cementitious materials.  

The team examined four algorithms: artificial neural network, random forest, extreme gradient boosting, and support vector regression. Bayesian optimization and 5-fold cross-validation were used to tune and evaluate these models. The final system did not force one algorithm onto all performance indicators. For liquid-state properties, the artificial neural network gave the strongest and most stable prediction across density, bleeding rate, fluidity, consistency, and stone rate. For solid-state behavior, the best algorithm depended on the output: extreme gradient boosting was selected for compressed deformation, artificial neural network for 3-day strength, and support vector regression for 28-day strength. This property-specific structure is technically important because liquid workability, consolidation deformation, and strength development do not have identical data behavior. The interpretive layer was built through SHAP analysis. Water–binder ratio appeared as the dominant variable for liquid properties and also strongly affected deformation. Cement–fly ash ratio was the main factor for strength development, especially early strength. Bentonite-related variables influenced bleeding and fluidity through water retention and thickening behavior, while confining pressure and soil permeability mainly influenced solid-state deformation. The parameter analysis sharpened these relationships: increasing water–binder ratio improved fluidity but increased bleeding and deformation sensitivity, whereas increasing cement–fly ash ratio enhanced both 3-day and 28-day strength, with stronger sensitivity at lower cement–fly ash ratios. Validation gave the system both laboratory and field grounding. Independent laboratory comparisons showed strong agreement between measured and predicted values for density, bleeding rate, consistency, stone rate, compressed deformation, and 28-day strength. In the Harbin Metro Line 2 case, the optimized grout reduced compressed deformation and lowered the required grouting volume per ring from 4.24 to 3.46 m³. The maximum surface settlement was reduced from about 6 mm to about 3.5 mm, corresponding to a reported reduction of approximately 42%. The paper also contrasts the rapid prediction time of the intelligent system with the lengthy traditional testing workflow, which can require about two months for a typical orthogonal experiment.

The findings of Dr. Jiaxin Liang and Prof. Wei Liu and colleagues have direct engineering value for shield tunnel construction, especially in projects where tail grouting must control both constructability and ground deformation. The developed system can be used to optimize grout formulations before construction by balancing fluidity, bleeding rate, density, consistency, stone rate, compressed deformation, and early- and later-age strength. By linking mix proportions, soil permeability, and pressure conditions to multiple grout responses, the new system gives engineers a rational basis for selecting mixtures suited to different ground conditions rather than applying one empirical formulation across an entire tunnel alignment. This approach enables site-specific optimization and adapts to varying geological conditions encountered along the tunnel, significantly improving project efficiency and deformation control. The intelligent system eliminates trial-and-error testing, substantially reducing testing time, labor costs, and material waste while enabling efficient multiperformance optimization. Engineers can now rapidly evaluate numerous formulation scenarios before construction, ensuring optimal grout selection tailored to site-specific ground conditions and project requirements, ultimately enhancing both construction efficiency and deformation control in complex tunneling projects.

Nuclear magnetic resonance is powerful because nuclear spins can retain quantum information for relatively long times while remaining sensitive to their local magnetic and structural environment. That same weak coupling, however, also makes nuclear spins difficult to initialize and detect with high sensitivity, especially when one wishes to move from ensemble-averaged spectroscopy toward small, well-defined spin systems. Optical access changes this balance. If a nuclear spin state can be prepared, manipulated, and read through an optical transition, NMR gains a route toward low-field sensitivity, molecular-scale addressability, and direct connection to photonic quantum architectures. The central difficulty is that optical and nuclear degrees of freedom are not naturally linked in most molecular systems in a way that permits coherent control without introducing additional decoherence channels.

A common strategy is to address nuclear spins indirectly through electron spins, using optical transitions connected to magnetic electronic states. This route has been powerful in solid-state defect systems, but it brings a physical compromise: the same electron spin that enables optical access can also add magnetic noise, restrict useful spin density, and limit the nuclear coherence that makes the spin attractive in the first place. Trivalent non-Kramers rare-earth ions offer a different route. In Eu3+, the absence of a net electronic spin allows the nuclear spin to be accessed through ultranarrow optical transitions without relying on a coupled electron spin. That distinction is central to the present paper.

In a recently published research paper in Nature Materials Dr. Evgenij Vasilenko, Vishnu Unni Chorakkunnath, Dr. Jeremias Resch, Nicholas Jobbitt, Dr. Diana Serrano, Dr. Philippe Goldner, Dr. Senthil Kumar Kuppusamy, and led by Professor Mario Ruben & Professor David Hunger from the Karlsruhe Institute of Technology in Germany  developed an optically detected nuclear magnetic resonance approach for coherently controlled 151Eu3+ nuclear spins in a stoichiometric europium molecular crystal. They combined spectral-pit-based optical spin initialization, RF control of two nuclear quadrupole transitions, and optical read-out of spin population changes through ultranarrow 7F0 to 5D0 transitions. The technically distinct advance is the demonstration of Rabi oscillations, Hahn-echo coherence, and CPMG dynamical decoupling in a molecular rare-earth complex with direct optical nuclear spin access. They also established a measurable correlation between optical transition frequency and nuclear spin resonance properties, linking local molecular crystal-field variation to both optical and RF response.

The researchers began with millimetre-sized single crystals of the europium complex grown by slow solvent evaporation, then incorporated an individual crystal into a fibre-based ferrule arrangement operated in liquid helium at 4.2 K. This experimental choice mattered because the optical transition itself served as the entry point to the nuclear spin system. The crystal quality therefore had immediate consequences for how selectively the Eu3+ ions could be addressed. Optical characterization of the 7F0 to 5D0 transition gave an inhomogeneous linewidth of 1.94 GHz, substantially narrower than previously reported for a microcrystalline powder of the same molecular material. Spectral hole burning yielded a homogeneous linewidth of 310 kHz, corresponding to an optical dephasing time just above one microsecond, while optical free-induction decay and photon echo measurements provided a more direct view of instantaneous optical coherence and optical coherence time. They also established that high-quality molecular crystals could provide a sufficiently narrow optical interface for nuclear spin experiments. The optical line was then used to prepare a spin-polarized sub-ensemble by burning a spectral pit through optical pumping. Rather than performing full hyperfine class preparation, the team used a 10 MHz-wide chirped optical burn that depleted one hyperfine ground-state population for a selected class of ions. The consequence of this design choice was a practical one with direct spectroscopic value: the spin preparation was fast enough and produced enough contrast to support repeated optically detected NMR measurements.

The authors obtained nuclear spin lifetime by monitoring recovery of the spectral pit. The decay required two time constants, a shorter component of 4.4 s and a longer component of 120 s. The long persistence of the optically prepared population made it possible to interrogate the quadrupole transitions of 151Eu3+ with radio-frequency pulses and detect the resulting population redistribution optically. Two ground-state nuclear quadrupole resonances were resolved at 21.475 MHz and 33.944 MHz, assigned to the |±1/2〉 to |±3/2〉 and |±3/2〉 to |±5/2〉 transitions, respectively. Their linewidths were not equivalent. The 34 MHz transition showed an 88 kHz inhomogeneous linewidth, while the 21.5 MHz transition was broader but gave stronger signal contrast under the same pulse conditions. They probed the 21.5 MHz transition at different positions across the optical inhomogeneous line, the researchers found that the spin transition frequency shifts with optical probing frequency, with an approximate gradient of −4 kHz GHz−1. The spin linewidth also increased toward the wings of the optical distribution. This correlation tied the nuclear quadrupole environment to the optical transition energy and showed that strain or local ligand-field variation affects both degrees of freedom in a linked, material-specific manner. In a molecular system where the crystal field symmetry differs from common inorganic hosts, this observation is especially informative because it connects the optical read-out channel to the local quadrupolar parameters that set the nuclear resonance.

The team tested coherent manipulation on the 21.5 MHz transition. Radio-frequency driving produced nuclear Rabi oscillations with a Rabi frequency of 14 kHz at 92 W, and the expected square-root dependence of Rabi frequency on RF power was observed. The damping of the oscillations reflected the inhomogeneous distribution of transition frequencies, which is precisely the kind of dephasing that pulsed NMR methods are designed to refocus. A Hahn-echo sequence extended the measurement from driven population oscillations to coherent spin evolution, giving a nuclear spin coherence time of 0.61 ms. Carr–Purcell–Meiboom–Gill dynamical decoupling then increased the observed coherence to 2.0 ms with eight refocusing pulses. The authors afterwards measured exponent, 0.53, differed from the value expected for a simple correlated noise bath of a single spin species. The authors attributed the more complex decoherence environment to a combination of nearby proton spins, randomly distributed 13C spins, possible residual paramagnetic impurities from the europium salt precursor, and quasi-localized low-frequency vibrational modes. The result is a coherent molecular nuclear spin system whose dephasing is not dominated by a single idealized noise source, but by the chemically and structurally specific environment of the molecular crystal.

The importance of the research work of Karlsruhe Institute of Technology scientists is its direct experimental connection between optical spectroscopy and coherent nuclear spin control in a molecular rare-earth complex. Previous molecular europium systems had already shown properties needed for optical nuclear spin access, but the present work completes a more demanding sequence: optical initialization, optically detected nuclear magnetic resonance, coherent RF-driven spin manipulation, spin echo refocusing, and dynamical decoupling. That combination establishes molecular Eu3+ nuclear spins as experimentally controllable quantum objects rather than only long-lived spectroscopic states. The findings also sharpen how molecular design should be viewed in this area. The ligand field is not a passive host environment surrounding an otherwise standard rare-earth ion. It determines the quadrupolar structure, influences the correlation between optical and RF transition frequencies, and contributes to the strain-sensitive inhomogeneous broadening observed across the optical line. Because the molecular complex has a defined coordination environment, these correlations can be treated as part of the material’s controllable physics. The paper therefore supports a design logic in which optical linewidth, nuclear quadrupole structure, spin lifetime, and spin-bath composition are considered together.

The coherence times reported here are measured in an ensemble molecular crystal at liquid-helium temperature, and the authors keep their future expectations tied to specific physical routes: stronger dynamical decoupling, lower temperature operation, magnetic-field polarization of paramagnetic impurities, suppression of low-frequency vibrational modes, isotopic or chemical purification, and ligand deuteration. These are not abstract claims of improvement; they follow from the dephasing sources identified in the measurements. The work also suggests that optically detected NMR in such complexes may become a sensitive probe of material properties, since optical and spin inhomogeneities carry linked information about strain and local crystal-field variation. For molecular quantum technologies, the result is technically meaningful because it brings together atomically defined molecular architecture with direct optical access to coherent nuclear spins. The demonstrated millisecond-scale nuclear coherence, optical spin preparation, and RF control form a platform on which more elaborate molecular spin registers could be explored, especially if future experiments move toward single-molecule read-out or nanophotonic integration.

Fenestration design can influence commercial building energy performance because windows function as architectural features, environmental interfaces, as well as thermal pathways. They provide daylight, view, and façade articulation, but they also create pathways for solar heat gain, conductive heat transfer, and seasonal shifts in heating and cooling demand. The same amount of glazing may perform differently depending on orientation, shape, and position on the façade. A horizontal opening may expose a different solar profile than a vertical one; a south-facing window may be desirable in one climate but burdensome in another; and a larger glazing ratio may reduce one energy load while increasing another. This means a fenestration strategy that reduces energy use in Honolulu or Houston may require a different balance of glazing area, orientation, and shape in Helena or Minneapolis.

Previous studies have examined individual window parameters such as window-to-wall ratio, aspect ratio, orientation, and glazing area, and they have shown that these features can influence building energy performance. However, the practical design problem is more complex than optimizing one variable at a time. Window-to-wall ratio, aspect ratio, and fenestration location interact with one another, and their combined effect determines the balance between heat gain, heat loss, and mechanical conditioning demand. This creates a need for a multi-parameter approach that can search for energy-efficient combinations rather than relying on isolated design rules. In a new research paper published in Journal of Cleaner Production, Associate Professor Reza Foroughi from the Department of Sustainable Technology and the Built Environment at Appalachian State University  developed a genetic-algorithm optimization model coupled with EnergyPlus to identify energy-efficient window-to-wall ratio, aspect ratio, and fenestration location for small commercial buildings.  They applied the model to a two-story commercial building across representative United States climate zones. The output is a climate-specific set of fenestration design parameters intended to reduce total building energy use at the early design stage.

Briefly, the building was square in plan, with eight windows distributed across the four orientations and two floors. The baseline model used centrally placed windows with a relatively large glazing proportion, and provided a consistent reference point for optimization. The envelope, glazing, HVAC system, occupancy schedule, and internal assumptions were specified so that changes in energy performance could be attributed to the geometric fenestration variables rather than to shifting building specifications.

The optimization model coupled a genetic algorithm with EnergyPlus simulations. This choice mattered because the design problem involved many coordinate-based variables and a search space with possible local optima. Instead of limiting the analysis to predefined window configurations, the algorithm repeatedly adjusted window coordinates within practical limits and evaluated the resulting total energy use. The objective function combined heating, cooling, lighting, and equipment energy, although the central trade-off was between heating and cooling loads. A design choice with direct scientific consequence was the decision to allow window coordinates to vary within architectural constraints; this converted window-to-wall ratio, aspect ratio, and placement into linked variables, which make it possible to identify energy-relevant configurations that would not necessarily arise from one-factor comparisons. The team found that hot climates generally favored smaller window-to-wall ratios, keeping glazing more restrained to limit cooling demand. On the other hand, cold climates behaved differently. In colder locations such as Helena and Minneapolis, the optimized designs allowed more south-facing glazing while keeping the other orientations more limited. The optimized aspect ratios also varied strongly by orientation and location. The authors observed although the Memphis case showed that a vertical south-facing window could be favored under specific climate and orientation conditions. In Helena, by contrast, the optimization favored a strongly elongated horizontal opening on the east façade.

These results show that window shape functioned as an energy-relevant design variable; it influenced the balance between incident solar gain and thermal demand. They found the optimized cases reduced total energy consumption in every climate zone and the decrease ranged from 15% in Honolulu to 2% in Helena and Minneapolis. Cooling energy dropped substantially under optimized fenestration, while heating energy increased slightly in several cases. The total balance still improved, meaning the reduction in cooling demand outweighed the added heating burden within the modeled conditions. Primary energy comparisons reinforced the same pattern, with larger gains in hot climates and smaller but still measurable reductions in cold climates.

The economic assessment translated these savings into annual cost terms for the modeled building where Honolulu showed the largest annual saving, while Helena showed the smallest. The authors emphasize that when these decisions are made at the early design stage of new construction, selecting optimized window dimensions and locations does not necessarily add construction cost in the same way that a technology retrofit might. The finding emphasizes the value of informed early-stage design, where placement and proportion can improve energy performance before costly changes are required.

The findings of Professor Reza Foroughi et al. have direct engineering value for early-stage design of small commercial buildings, where fenestration decisions are still flexible and can be changed without major cost penalties. The study shows that window-to-wall ratio, aspect ratio, and window placement should not be selected as independent architectural preferences, but as linked design variables that affect heating and cooling demand together. For engineers, this supports a more climate-responsive approach to envelope design, especially when preparing schematic layouts, façade studies, or energy models for small offices, retail buildings, educational facilities, and similar commercial structures. One practical application is the development of climate-specific fenestration guidelines. In hot locations such as Honolulu, Houston, and Memphis, the optimized results support restrained glazing areas to limit cooling demand. In colder climates such as Helena and Minneapolis, the findings support more selective use of larger south-facing windows while keeping north, east, and west glazing smaller. This gives designers a clearer basis for balancing solar heat gain against envelope heat loss rather than relying on uniform glazing ratios across all façades.

The study is also useful for simulation-driven building design. By coupling a genetic algorithm with EnergyPlus, the authors demonstrate how engineers can use optimization workflows to test many window configurations before construction. This is valuable for projects pursuing reduced operational energy, near-zero energy design, or improved façade performance while complementing later decisions about mechanical systems or renewable energy integration. When existing small commercial buildings undergo envelope renovation, the same logic can help determine whether reducing, reshaping, or relocating glazing would meaningfully reduce cooling or heating loads. Overall, the findings give engineers a practical method for converting fenestration design from a rule-of-thumb decision into a climate-specific energy optimization task.

Under ambient conditions, equiatomic zinc pnictides do not naturally form a free-standing monolayer whose atomic network remains both low in energy and resistant to distortion. That difficulty has kept ZnAs, ZnSb, and ZnBi in an uncertain position within the search for useful two-dimensional semiconductors: the bulk compounds already display unusual bonding, with electron-poor valence counts and multicenter connectivity, yet dimensional reduction has not produced a convincingly stable pristine sheet. For ZnSb in particular, prior interest came partly from thermoelectric behavior tied to low lattice thermal conductivity and anisotropic transport, while ZnAs added a related but not identical electronic character through its larger gap and different transport response. ZnBi complicates the family further, because even the bulk phase carries weaker energetic preference at zero temperature and pressure. If the bonding motifs that stabilize the orthorhombic bulk can survive exfoliation in some altered geometric form, one might obtain a two-dimensional phase with electronic behavior very different from the parent crystals. If those motifs cannot survive, the structure falls into the familiar pattern of hypothetical sheets that look plausible until phonons or relaxation break the idea apart.

The motivation here goes beyond the general interest in atomically thin semiconductors. The orthorhombic ZnX (X = As, Sb, Bi) compounds contain quasi-layered rhomboid Zn₂X₂ units embedded in a non-van-der-Waals 3D bulk framework. A bulk crystal without classic layered cleavage does not exclude monolayer design; it simply removes the comfort of obvious exfoliation routes and forces the structural problem back onto bonding topology. In a recent research paper published in ACS Omega, Assistant Professor Dinesh Thapa from Thomas More University working together with Professor Seong-Gon Kim from the Mississippi State University, developed a lattice-engineering framework for deriving and comparing six candidate monolayer structures of ZnAs, ZnSb, and ZnBi extracting from different phases of 3D bulk structures of ZnX using density functional theory (DFT) under periodic boundary conditions. They identified a rectangular 2D-L1 sheet built from relaxed Zn₂X₂ rhomboid units as the lowest-energy and dynamically stable monolayer across the series at zero strain.

The research team examined six monolayer candidates for each compound: the atomic configurations of three sheets obtained from the orthorhombic bulk and labeled L1, L2, and L3, alongside tetragonal, hexagonal (planar honeycomb), and trigonal (puckered honeycomb) symmetries. The investigators relaxed both atomic positions and lattice vectors for every candidate, and this symmetry design is important because fixing the cell too rigid would have hidden the geometry that the material actually preferred. They found that the bulk-derived L1 sheet relaxed into a rectangular monolayer built around quasi-layered rhomboid Zn₂X₂ rings, while L2 and L3 also retained rectangular character but did not match L1 energetically. The authors compared the geometrical stability and integrity of those phases by total energy, phonon behavior, exfoliation energetics, mechanical response, and finite-temperature stability, which made the structural claim rest on more than one criterion.

Thapa and Kim also observed that L1 occupied the lowest-energy position across ZnAs, ZnSb, and ZnBi, with the ordering L1 below L3 below L2 and such ranking alone would not have been enough, because metastable sheets often appear competitive before vibrational analysis exposes the problem. They therefore examined phonon dispersions and found that L1 remained free of imaginary modes at zero strain in all three compounds, whereas L2 and the tetragonal phase carried unstable modes, and L3 stayed fully stable only in ZnAs while showing slight soft-mode behavior in ZnSb and ZnBi. Tetragonal geometry came energetically close in ZnSb and even looked favorable in ZnBi, however, that apparent advantage failed to survive the dynamical test. For synthesis, a low static energy is not sufficient if the lattice still prefers to distort. The authors then reinforced the L1 assignment with ab initio molecular dynamics at 300 K and with elastic analysis, arguing that thermal persistence and mechanical admissibility align with the phonon result instead of contradicting it.

  The authors examined bulk ZnAs and ZnSb as narrow-gap semiconductors and bulk ZnBi as a semimetal, with the orthorhombic network built from edge-sharing tetrahedra and rhomboid multicenter units.  The researchers reported a slightly indirect gap for 2D-L1 ZnAs, but direct gaps for 2D-L1 ZnSb and 2D-L1 ZnBi. L3 remained semiconducting too, though its gap stayed indirect across the series. The investigators also found a more abrupt shift in the tetragonal monolayer, where orbital overlap at the Fermi level produced metallic behavior, thus indicating electronic transition from wide band gap semiconductor to metallic behavior while going from energetically competing 2D-L1 phase to 2D-tetragonal phase. In ZnAs, the team further extracted a negative Poisson ratio for L1, a mechanical response that links the peculiar rhomboid-ring geometry to auxetic behavior. A different local network would not be expected to yield the same coupling between deformation and lateral strain.

Thapa and Kim identified a structural principle for zinc pnictide monolayers: the stable sheet adopts a rectangular lattice inherited from the rhomboid-ring physics of the orthorhombic parent. Many computational searches for new 2D materials begin with familiar structural archetypes, after which chemistry-specific bonding preferences are examined in greater detail but in Thapa and Kim work the bonding chemistry leads to a different structural route. The multicenter bonding character of ZnX pushes the stable monolayer toward a less familiar geometry, and that outcome has consequences well beyond these three compounds. It shows that non-van-der-Waals parents with quasi-layered subunits may still yield viable two-dimensional descendants, but only when the descendant preserves the bonding logic embedded in the bulk.

The authors performed analysis in their paper beyond relaxed structures and band plots to include relative energies, phonons, exfoliation considerations, mechanical checks, thermal trajectories, and hybrid-functional electronic analysis. In the ZnBi case: bulk formation energy remained slightly positive at zero temperature and pressure, but the monolayer question remains open under those conditions. From an applications standpoint, the direct-gap 2D-L1 sheets in ZnSb and ZnBi could become useful where atomically thin semiconductors with larger gaps are needed, especially in optoelectronic settings that do not benefit from metallic leakage. ZnAs is considered interesting for a different reason: a stable auxetic semiconductor is mechanically unusual, and if synthesis catches up, its deformation response could matter in device architectures where strain is not a limitation but part of the operating condition. The new study established a strong theoretical basis, while practical use will depend on experimental validation.  Geometry selected by bond topology can control whether a monolayer survives as well as whether it ends up indirect, direct, or metallic. In zinc pnictides, the sheet that the lattice can actually tolerate appears to be the same sheet that produces the most interesting electronic and mechanical outcomes.

Ultra-wide-bandgap semiconductors are important in power electronics because they offer a route to switching devices that can withstand large electric fields while sustaining efficient operation under demanding voltage conditions. Within this class of materials, β-Ga₂O₃ are attracting a lot of attention because of its wide bandgap and high theoretical breakdown field make it a strong candidate for high-voltage power devices, particularly in settings where the material’s field-handling capability can be translated into practical transistor structures. That possibility has motivated sustained work on β-Ga₂O₃ device design, with both lateral and vertical transistor geometries being explored as researchers try to determine how best to use the material in real high-power operation.  The architectural distinction between lateral and vertical devices is not just geometric. Vertical transistors are especially relevant when the objective is to support both high blocking voltage and substantial current transport, since the current path and drift-region design can be arranged in a way that is more naturally suited to that regime. For β-Ga₂O₃, this has made vertical device development an important scientific and technological goal. Yet the central challenge has been clear for some time: the exceptional material properties of β-Ga₂O₃ do not automatically produce exceptional vertical transistor performance. To realize high-voltage operation in a vertical structure, the device must incorporate a drift region that is both sufficiently thick and sufficiently lightly doped, while the surrounding structure must also suppress electric-field crowding near the device edge. If any of these conditions is not met, the attainable breakdown voltage falls well below what the material itself would appear to allow.

That difficulty has given the field a very specific unresolved problem. Earlier β-Ga₂O₃ vertical transistors had already demonstrated kilovolt-class operation, but pushing the breakdown voltage substantially higher required more than incremental processing refinement. It required progress in the epitaxial platform itself. The paper makes this point in direct materials terms. High-voltage vertical transistors need high-quality epitaxial films with donor concentration at or below about 5 × 10¹⁵ cm⁻³ and thickness on the order of at least several tens of micrometers, yet obtaining such films is not straightforward. During halide vapor phase epitaxy, chlorine can be incorporated into β-Ga₂O₃ and act as a shallow donor, making it difficult to achieve the very low donor concentrations needed for a high-voltage drift layer. At the same time, even with an appropriate drift region, the device still depends on edge-termination measures capable of controlling local electric-field concentration.

In a recent research paper published in Applied Physics Express, Daiki Wakimoto, Dr. Chia-Hung Lin, Dr. Kentaro Ema, Dr. Yuki Ueda, Hironobu Miyamoto, Dr. Kohei Sasaki and Akito Kuramata from Novel Crystal Technology, Inc in Japan, developed a normally-off multi-fin beta-gallium-oxide vertical transistor built on a thick, low-donor-concentration epitaxial layer grown by halide vapor phase epitaxy on a (011) substrate.  Its main technical advance is the demonstration of a beta-gallium-oxide vertical transistor that withstands breakdown voltages above ten kilovolts while still preserving normally-off transistor operation, strong current switching, and low specific on-resistance.

Briefly, the research team fabricated a multi-fin vertical transistor based on beta-gallium oxide using a thick, lightly doped epitaxial layer grown by halide vapor phase epitaxy on a beta-gallium-oxide substrate with the crystallographic orientation chosen to support low donor incorporation. The fabrication sequence established the channel-access and contact structure through silicon implantation, annealing, dielectric formation, dry etching of the fins, planarization, gate formation, and final source and drain metallization. What matters scientifically is not the fabrication sequence alone, but how the device structure was designed to produce the intended electrical behavior: a thick, lightly doped drift region for high-voltage blocking, combined with a fin-based vertical channel and a field-plate-assisted gate arrangement that supports normally-off operation. The authors designed the multi-fin layout with clear attention to geometric control and device uniformity. The active fins were placed within an outer fin arrangement so that the operating channels would behave as consistently as possible and so that variations introduced during dry etching would be reduced. That choice matters because more uniform fin geometry leads to cleaner and more reproducible transistor behavior rather than performance shaped by local structural irregularities. The source electrode was also deliberately pulled back from the fin edge to avoid unintended gate-source contact in regions where etching could distort the fin profile. Electrical measurements showed that the device operated in a normally-off mode. The threshold behavior, strong current modulation, and steep subthreshold response all point to effective control of the channel by the gate. These characteristics are important when considered together, because they show that the fin-channel design and gate-stack integration did not sacrifice switching behavior in the effort to reach high blocking capability. The reported hysteresis remained modest, and the gate current stayed below the measurement limit under the tested conditions, which supports the view that the gate operation was well controlled.

The output characteristics are important for the same reason and the device can block high voltage and also maintains useful conduction performance in the on-state. The authors evaluated the current flow using an effective conductive area that accounts for current spreading in the drift region rather than relying only on the lithographic top-surface geometry.  Within that interpretation, the transistor combined solid current conduction with very high off-state blocking capability.

To prevent premature breakdown through air, the measurements were carried out in an insulating liquid, and the device sustained a breakdown voltage above ten kilovolts. In fact, the measurement was limited by the voltage range of the test system rather than by a confirmed breakdown of the device below that level. The estimated electric field in the trench region was correspondingly very high. The authors state that this is the highest breakdown voltage ever reported for a beta-gallium-oxide vertical transistor, exceeding the previous best result for this device class by more than a factor of two. They also report a strong power figure of merit, reinforcing that this was not a single-metric gain but a meaningful advance in vertical beta-gallium-oxide transistor performance. The authors’ work demonstrated what kind of material-device integration is required for β-Ga₂O₃ vertical transistors to enter a much higher breakdown-voltage regime.   The logic is visible throughout the paper: low donor concentration in a thick epitaxial drift layer, achieved on a (011) substrate where Cl incorporation is suppressed, is paired with a multi-fin normally-off structure and field management at the device edge. The breakdown performance is therefore not an isolated metric but the outcome of a coherent design direction grounded in how the electric field is distributed in the device. There is also a meaningful balance here between voltage blocking and transistor operation. In Daiki Wakimoto and colleagues work, the device still shows threshold control, a large on/off ratio, low measured gate current, and a specific on-resistance that keeps the conduction side of the story in view.   Its contribution is more disciplined than that. It shows that a normally-off β-Ga₂O₃ vertical transistor can be pushed past 10 kV while retaining a credible switching profile and a measurable power figure of merit.  Earlier β-Ga₂O₃ vertical transistors had already shown that kilovolt-class blocking was possible and the new device reported by the authors moves the conversation into a distinctly higher-voltage category and narrows the gap between what the material suggests in principle and what a vertical transistor has actually demonstrated in practice. Just as important, the result reinforces the value of the (011) orientation for HVPE-grown low-doped epitaxial layers when the target is vertical high-voltage operation. The paper’s final implication remains measured: it points to the strong potential of Ga₂O₃ vertical power devices.

Dynamic axial strain in lightweight subgrade fills does not remain proportional to repeated loading once pore collapse, interparticle slip, and local damage begin to compete within the same stress cycle. That problem matters acutely in transportation earthworks, where a material may be chosen not only for low unit weight, but for how it stores stiffness and dissipates vibrational energy under thousands of load reversals. Foamed concrete can reduce embankment weight, limit settlement, and provide useful thermal and damping behavior, however, it has environmental burden, since conventional formulations still depend heavily on Portland cement, and the carbon cost of that binder remains substantial. The search for a lighter fill with lower embodied emissions has pushed researchers toward binders that do more than harden the matrix and they also must alter the chemistry of curing itself. This is where serpentine carbon-sequestration foamed concrete has become more interesting to scientists. The material draws on reactive MgO, serpentine powder, silty clay, water, and CO₂ foam, so the gas phase is not just a pore-forming aid but part of the hardening route itself. In that sense, the scientific question is not simply whether a low-density geomaterial can be made from alternative constituents. The harder issue is whether carbonation-based bonding creates a cyclic response that differs in kind from the behavior already documented for cement-based foamed concrete and EPS-modified lightweight soils. A binder system built around magnesium carbonation develops through hydration, mineral precipitation, pore filling, and residual unreacted phases. That history leaves behind a skeleton whose stiffness, damping, and strain accumulation under repeated loading cannot be assumed from older constitutive traditions.

There are practical limitations because dynamic design of subgrades depends heavily on quantities such as dynamic elastic modulus and damping ratio, but those parameters are sensitive to stress state, loading frequency, curing condition, and microstructure. Existing models were largely framed around cement-stabilized soils or polymer-modified lightweight fills. They are useful as a starting point, though they do not automatically carry over to a material whose bonding arises from carbonate formation in a porous, closed-cell matrix. Even the testing is not trivial and a single monotonic strength value says very little about whether cyclic loading first compacts the pore system, then damages it, or does both in alternating sequence across strain levels. In a recent research paper published in Construction and Building Materials, Dr. Mengyao Li, Dr.  Xiang Zhang, and Professor Songyu Liu from the School of Transportation at Southeast University working together with Dr. Zhengcheng Wang from Chongqing Three Gorges University, developed a cement-free serpentine carbon-sequestration foamed concrete formulated with reactive MgO, serpentine powder, silty clay, and CO₂ foam, then characterized its cyclic behavior under multistage triaxial loading. They also developed a modified Darendeli-based model for dynamic elastic modulus evolution, with E_dmax expressed as a function of curing age, confining pressure, and vibration frequency.  The team examined specimens cured for 7 to 28 days under multistage cyclic triaxial loading across a range of confining pressures and frequencies which allowed the investigators trace stiffness and dissipation across a widening strain range within the same specimen, which reduced specimen-to-specimen noise at the very point where nonlinear behavior begins to emerge. The authors also kept the tests in an unsaturated state, consistent with the intended service condition of the material as a protected subgrade fill; saturating such a pore system would have changed the internal structure enough to blur the mechanism they wanted to examine. The researchers observed a clear change in hysteresis morphology as loading intensified. At small dynamic strains, loops remained close to linear and comparatively tight. With rising stress amplitude, the loops became spindle-shaped and later developed concave crescent-like forms, while asymmetry also grew, with tensile-side strain exceeding compressive-side strain. It means the material does not simply cycle elastically around a stable centerline; it accumulates irreversible deformation as pore collapse, contact friction, and microcrack growth begin to separate loading from unloading. The new study examined backbone curves alongside those loops and found a hyperbolic trend that shifted toward smaller strains as curing age, confinement, or frequency increased.

The authors found using SEM that after 28 days, enclosed and broken pores, partially carbonated MgO and serpentine particles, and interlaced dypingite and hydromagnesite, features that help explain the cyclic response. Carbonation products fill voids, cement particles together, and stiffen the internal skeleton; once loading rises far enough, that same carbonate-bonded framework begins to lose local integrity, so the initial compaction benefit gives way to stiffness loss and higher dissipation.  The researchers observed an early increase in E_d with strain amplitude, then a nonlinear drop. The damping ratio moved in the opposite way at first, decreasing to a minimum and then rising before stabilizing. Curing age, confining pressure, and frequency each changed that pattern differently. Longer curing shifted the material toward higher E_d and lower damping after the transitional strain range of about 0.03 to 0.04%, which fits a denser carbonate network and fewer loose particles. Increased confinement produced higher stiffness but also a sharper decline in modulus once degradation began, a reminder that a stiffer skeleton under stronger lateral restraint may carry larger cyclic stresses before it starts to lose integrity. Frequency raised Ed and reduced damping at larger strains without changing loop shape very much, so the rate effect was real but structurally selective. The authors then fitted the data with a modified Darendeli-type framework and showed that confining pressure dominated E_dmax, curing age followed, and vibration frequency contributed the least. Even so, the model showed some deviation under long curing, high confinement, and extreme loading rates, where early hardening and coupled effects become more difficult to capture within a compact equation.

To summarize, Professor Songyu Liu and colleagues demonstrated direct linkage between carbonate mineral formation, hysteretic deformation, and strain-dependent stiffness loss in a lightweight geotechnical material intended for repeated loading service. They showed mineral carbonation changes how a lightweight fill should be read mechanically. SC-FC does not behave like a generic porous filler. Its dynamic response comes from a carbonate-bonded skeleton whose stiffness can rise briefly under early cyclic compaction, then deteriorate once pore collapse and crack growth reach the point where dissipation begins to dominate. The authors treat dynamic elastic modulus and damping ratio not as isolated descriptors but as coupled traces of internal change. When E_d climbs slightly before decaying, and D drops before turning upward, the two curves together reveal a material that first reorganizes and then degrades. That interpretation gives engineers a more discriminating basis for selecting fill materials in rail approaches, embankments, and similar systems exposed to repeated traffic or seismic disturbance. A lightweight material that gains apparent stiffness at low strain but loses it abruptly at higher confinement cannot be judged by a single index and the research work push toward strain-dependent qualification criteria tied to realistic stress paths.

We believe it is important findings that SC-FC replaces Portland cement with reactive MgO and serpentine-derived constituents while incorporating CO₂ during foaming and curing because the combination creates a plausible route toward lower-emission geotechnical fills, but only if mechanical reliability survives the transition from laboratory concept to cyclic service condition. The environmental argument becomes more persuasive once the dynamic behavior is quantified in terms that geotechnical practice already understands. The proposed predictive model offers also a practical description of the tested response within the studied curing ages, confining pressures, and frequencies, although some deviations remain under more demanding conditions. Materials created through carbonation do not always soften from the first increment of cyclic loading; some briefly tighten before damage takes command, and a model that misses that moment also misses part of the physics.

Preparation method and SEM images of serpentine carbon sequestration foamed concrete

Viscous dampers are widely used in building structures to reduce dynamic response under earthquake and wind excitation, and their effectiveness depends not only on the constitutive behavior of the damper itself but also on the reliability of the connections through which structural deformation is transmitted. In practical applications, these dampers are commonly connected to the main structural system by shaft-pin joints so that the device can work primarily in axial action. Although this arrangement is mechanically simple and widely accepted in engineering practice, it contains a detail that is usually treated as unavoidable during fabrication and installation: a small gap between the shaft pin and the corresponding hole in the connected plate. Previous studies had already shown, in different structural and mechanical settings, that gaps or clearances can alter stiffness, modify load transfer, and degrade cyclic or dynamic performance. Work on viscous damper systems had also pointed to the detrimental effect of imperfect engagement and the zero-force platform that may appear in hysteretic response when a connection gap is present. Still, those studies largely clarified the consequences of the problem rather than offering a direct mechanical remedy for the shaft-pin joint itself. That left an unresolved question in practical damper design: whether the unavoidable clearance in a pin connection could be removed in a workable way without sacrificing the simplicity and functionality that make such joints attractive in the first place. In their paper published in Engineering Structures, Dr. Yi-Qiong Cui, Professor Yang Xiang, Dr. Bo Yang, Dr. Shi-Li Guo, and Professor Guo-Qiang Li from Tongji University address this issue by proposing a pin-joint configuration that incorporates paired tapered sleeves and thrust flanges to eliminate clearance between the shaft pin and the ear-plate holes. On that basis, they examine the connection behavior of the proposed joint under cyclic loading and then assess, through simplified structural modeling, how the removal of joint gap influences the efficiency of viscous dampers in frame systems subjected to seismic and wind actions.

The authors began with a direct comparison between two joint types: a conventional shaft-pin joint and the proposed tightknit version with tapered sleeves. The conventional specimen had a 20 mm pin and a 23 mm hole, giving a 3 mm assembly clearance chosen deliberately to make the mechanical consequence of the gap visible in testing. The tightknit specimen kept the same basic connection logic but inserted fourteen pairs of tapered sleeves and thrust flanges, with lubrication and machined contact surfaces used to support controlled assembly and sliding during tightening. The internal ear plate also retained an annular partition, which helped divide the sleeves into symmetric groups and improved alignment during installation. That design choice matters because the sleeve system is only useful if the radial expansion that removes the gap can be introduced in a balanced and assembly-friendly way. Under cyclic force-controlled loading, the contrast between the two specimens was immediate. The conventional joint developed a horizontal plateau near load reversal, especially as force passed through the vicinity of zero. Mechanically, that plateau corresponds to relative movement without effective force transmission while the pin traverses the internal clearance. The tightknit joint did not show that feature. Its load-deformation response remained continuous, with a nearly linear slope through reversal, which is exactly the behavior one would expect if the internal gap had been removed and compressive and tensile load transfer could proceed without slack.

The conventional joint showed an initial stiffness of 250 kN/mm, whereas the tightknit joint reached 583.3 kN/mm. Also, in the conventional specimen, plastic deformation began at about 150 kN with a relative displacement of 0.6 mm between the upper and lower end plates. In the tightknit specimen, yielding began at about 175 kN and only 0.3 mm. At 300 kN, the conventional joint reached 3.1 mm in that same displacement measure, while the tightknit joint reached 1.6 mm and the authors attributed this to the tapered sleeve assembly improving contact conditions, restricting shaft deformation, and producing a more uniform stress state along the pin-ear interface. The second displacement measure, taken between the shaft pin and the lower end plate, gave larger values for both specimens, but the qualitative picture did not change. That larger reading captured bending-induced geometric distortion of the pin as the upper and lower portions of the joint moved relative to one another under tension. The post-test pin shape confirmed that combined shear and bending had deformed the shaft. Even there, the tightknit joint retained a mechanical advantage, and the authors also note that by limiting severe deformation of the shaft, the proposed configuration helps maintain the integrity of the connection after heavy loading

Afterward, the researchers used OpenSees, to represent the frame, damper, linkage, and joint within a reduced damper-linkage-joint assembly. For conventional joints, they used bidirectional gap elements built from paired ElasticPPGap materials to reproduce the clearance behavior in both loading directions. For the tightknit case, the gap was taken as negligible. When sinusoidal dynamic loading was applied, the zero-gap assembly produced an ideal elliptical hysteresis loop. Once clearance was introduced, the loops broke into semi-elliptical branches separated by a horizontal no-force segment. As the gap increased from 0.5 mm to 1.5 mm, peak displacement rose and output force fell. Over two seconds of loading at the lower excitation amplitude, cumulative energy dissipation dropped from 19107.4 J in the zero-gap case to 12771.8 J at 1.5 mm, a 26% reduction. Even when the loading amplitude increased and the relative importance of the gap weakened somewhat, the adverse effect remained visible.

The study is important in connection mechanics, and Professor Yang Xiang and colleagues carry the joint model into structural response analyses under both earthquake and wind loading, and that move clarifies why the gap problem matters. In the four-story seismic model, dampers improved performance relative to the uncontrolled structure in every case, but the benefit was consistently strongest when the connection was tightknit. Under the El Centro record, the zero-gap configuration reduced drift, velocity, acceleration, and base shear more than the 1.5 mm-gap case. Across a broader set of 46 ground motions, the same pattern persisted: compared with the idealized tightknit condition, a 1.5 mm joint gap increased average peak inter-story drift by 7.6%, peak velocity by 6.4%, peak acceleration by 4.8%, and base shear by 7.9%. The wind analysis is particularly informative and because wind-induced structural deformations are smaller, a gap that might seem modest from a fabrication perspective can occupy a large fraction of the motion available to activate the damper. That is exactly what the twenty-story model showed. When total wind response was considered, the mean component dominated overall drift, so the difference among models was less dramatic. But once the fluctuating component was isolated, the sensitivity to clearance became unmistakable. A 0.3 mm gap brought the controlled structure much closer to the uncontrolled one, indicating a substantial loss in effective damping contribution. Under 24 synthetic wind histories, the tightknit case gave much stronger reductions in response than the conventional gap cases, including reductions relative to the 0.3 mm-gap model of 23.6% in peak inter-story velocity and 33.8% in roof acceleration. That distinction matters because it shifts the design logic. The issue is not simply that connection clearance is undesirable in an abstract sense. It is that clearance can erase a meaningful portion of the working deformation range of a supplemental damping device, and it does so most severely when the demand itself is small. The paper therefore sharpens the engineering interpretation of damper efficiency: performance depends not only on the constitutive behavior of the damper body, but also on whether the connection transmits motion without loss. In that respect, the tapered-sleeve joint is not treated as a secondary hardware refinement but becomes part of the force-transfer mechanism that strongly influences how effectively the damping system can function.

Underwater optical imaging is difficult because light does not travel through water in a simple, direct way. As it passes through suspended particles, part of the light is weakened and part of it is redirected which creates backscattered illumination that can mask the signal from the object being imaged. When the image must reveal boundaries, surface markings, material differences, or quantitative radiometric information, this scattering changes the measured intensity and makes the true scene radiance harder to recover. Polarization is well suited to fix this limitation because underwater backscattering is partially linearly polarized and measurements taken through different analyzer orientations make it possible to extract Stokes parameters and use the degree and angle of linear polarization to help separate direct radiance from scattered light. Classical polarization-difference and Stokes-based descattering methods have already shown that this information can suppress haze more directly than intensity-only enhancement. The central difficulty is that the practical underwater scene rarely follows the clean assumptions that make a simple Stokes inversion stable. Orthogonal analyzer channels may not be balanced. Scattering may be anisotropic. Target surfaces may contribute their own polarization. Multiple scattering, illumination residuals, and sensor response can shift the measured polarization away from an idealized model.

In a recently published research paper in Optics and Lasers in Engineering Dr. Ziqian Chen, Dr. Junkai Wu, Dr. Haofeng Hu, and Professor Xiaobo Li from School of Marine Science and Technology at Tianjin University developed a polarization-guided Stokes descattering method for underwater images acquired from multiple analyzer orientations. The technically distinct element is the joint use of a scene-induced Stokes mixing weight, an effective polarized visibility factor, and an asymptotic airlight scaling parameter, all estimated automatically rather than manually selected. They also developed a DoLP-gated airlight estimation step to reduce foreground polarization leakage into the scattering estimate. The complete method combines physical radiance inversion with a two-stage genetic algorithm and sequential quadratic programming optimization driven by contrast and entropy.

The research team built the method around three analyzer measurements, acquired at 0, 45, and 90 degrees and instead of applying the conventional Stokes relations directly, they introduced a scene-induced mixing parameter to adjust the contribution of the 90-degree channel. This modification preserves the Stokes structure while allowing the measured polarization state to compensate for unequal energy partition caused by anisotropic scattering, target reflection, illumination residuals, alignment effects, or sensor sensitivity. This matters because orthogonal-channel imbalance can affect the polarization parameters and the airlight estimate.

Airlight estimation is handled through a background window selected by high mean degree of linear polarization, which favors regions dominated by coherent backscattering. From that region, the method estimates a representative angle of polarization and intensity scale. A polarized background scale is then obtained using a robust high-quantile statistic, reducing sensitivity to isolated strongly polarized pixels. The new approach also introduces an effective polarized visibility factor, which accounts for the fraction of polarized background actually observable in the measured channel. Since some objects may produce stronger or more heterogeneous polarization than the background scattering itself, the gate suppresses the tendency to assign target-induced polarization to the backscattering term and by reducing foreground leakage into the airlight estimate, the inversion can preserve material and boundary information. The asymptotic airlight scale is also treated adaptively, using a global scaling parameter tied to the representative background intensity.

Because the three central parameters cannot be measured directly, the study estimates them through unsupervised optimization. The objective combines edge contrast with image entropy, so that the restored radiance is encouraged to retain both structural sharpness and gray-level richness. A genetic algorithm first searches the physically admissible parameter space, and sequential quadratic programming then refines the solution. This two-stage strategy reflects the non-smooth, nonconvex nature of the pipeline, where quantiles, clamping, and positivity enforcement make a purely local search unreliable. Experiments in a controlled water tank used semi-skimmed milk to vary turbidity, polarized illumination, a monochrome camera, and objects with different polarization characteristics, including metallic, plastic, paper, and polarizer-film targets. Under moderate turbidity, the proposed method recovered clearer boundaries, stronger contrast, and more visible fine structure than the classical Stokes-based comparison. The distinction between crossed polarizer films was especially informative because it tested whether the restoration preserved polarization-dependent target differences, instead of simply increasing contrast.

Quantitative comparisons using enhancement measure estimation, entropy, and peak signal-to-noise ratio supported the visual observations. The authors found across selected regions and the full image, the proposed method generally produced higher contrast and fidelity measures than the raw images and the classical Stokes approach. Additional comparisons with intensity-only enhancement methods and other polarization-based or learning-based methods showed that the new method retained sharper edges and more uniform background recovery as turbidity increased. Deep learning methods degraded under stronger turbidity in the reported comparisons, which the paper relates to differences between training and testing conditions.

The team extended across milk concentrations from low to high turbidity and noticed as scattering increased, all methods became more challenged, but the proposed method maintained higher contrast and higher peak signal-to-noise values than the alternatives over much of the range. Tests on additional samples showed recovery of structural features in plastic and metallic coins and restoration of printed or surface details across paper, metal, wood, and plastic targets. The researchers also evaluated real seawater data acquired with polarization cameras under active lighting, where fish, coral, seaweed, and rock textures became clearer after restoration. A further comparison under polarized and non-polarized illumination indicated that the method can still operate when ordinary non-polarized lighting is used, although higher turbidity remains associated with reduced signal-to-noise ratio.

The findings of Professor Xiaobo Li  and colleagues have direct engineering relevance for underwater imaging systems that must operate in scattering environments where conventional intensity images lose contrast and structural detail. In ocean observation, inspection, and monitoring tasks, the main requirement is not simply to make an image look clearer, but to recover enough reliable target information for interpretation, identification, or downstream decision-making. The polarization-guided Stokes descattering method addresses this need by combining a physically based imaging model with automatic scene adaptation, allowing the restoration process to respond to changes in turbidity, illumination, and material-dependent polarization behavior. One important application is underwater robotic inspection. Remotely operated vehicles and autonomous underwater platforms often rely on cameras to examine submerged structures, seabed objects, marine organisms, and engineered equipment. In turbid water, backscattering can hide edges, surface markings, cracks, contours, or material boundaries. By improving texture visibility, target-background separation, and structural contrast, the proposed method could support more reliable visual inspection when the water column is not optically clear. The real seawater demonstrations are particularly relevant here because they show that the approach is not limited to a controlled tank environment. The new method is also useful for marine environmental monitoring and biological observation. Underwater scenes often contain low-polarization natural objects, such as fish, coral, rocks, and vegetation-like structures, whose details may be weakened by scattered light. The reported seawater results indicate that polarization-guided descattering can enhance contours and surface texture under practical imaging conditions. This can make visual records more informative for documenting habitats, tracking marine organisms, or supporting image-based ecological analysis. A further engineering implication concerns system design. The procedure can work with polarized measurements and was also tested under non-polarized illumination, suggesting that practical systems may not always require complex polarized lighting arrangements. The use of automatically optimized, physically interpretable parameters also reduces dependence on manual tuning when the imaging scene changes. For maritime security, underwater search, and target discrimination, the ability to preserve fine structures and distinguish objects with different polarization characteristics is valuable. The method’s treatment of scene-induced Stokes imbalance and DoLP-gated airlight estimation gives engineers a more adaptable restoration tool for visually degraded underwater environments.

Aerostatic bearings are widely used in precision motion systems because they support moving components on a thin externally pressurized air film rather than through direct mechanical contact.  In precision manufacturing equipment and high-accuracy measuring instruments, this mode of support is attractive because it can provide clean, smooth, and highly repeatable motion. Pressure must be generated and distributed in a controlled manner, the air film must sustain external load, and the flow introduced through the restrictors must not disturb the stability that the bearing is intended to provide. A conventional aerostatic flat bearing often uses pocketed orifice-type restrictors to feed high-pressure air into the clearance. This arrangement can improve static support, yet it also introduces a difficult fluid-dynamic problem near the inlet region. Air supplied through an orifice perpendicular to the guideway surface impinges on the working surface and then turns sharply as it enters the bearing film. This sudden change in direction is associated with local acceleration, pressure depression, vortex formation, and turbulence. They can contribute to self-excited micro-vibrations, reduce the effective high-pressure region, and influence both load-carrying capacity and stiffness.

It must meter the supplied air so that a supporting pressure field is formed, and it must do so without creating unstable local flow structures that disturb the air film. Previous efforts to improve aerostatic bearing stability have therefore examined the geometry of the orifice chamber, the size and arrangement of orifices, and the influence of recess configuration on vortex behavior and micro-vibration. These studies point to a common physical concern: the flow structure near the restrictor shapes both the local pressure distribution and the dynamic steadiness of the bearing. In a recently published research paper in International Journal of Precision Engineering and Manufacturing Mr. Dong Zhang, PhD candidate  Senyu Yang, Pengfei Cao PhD candidate, Lubin Wang & led by Professor Weishi Li from Hefei University of Technology developed a vortex-type restrictor for aerostatic flat bearings in which two guideway-parallel, tangential orifices drive rotational airflow inside a circular recess before the air enters the bearing clearance. They also developed paired clockwise and counterclockwise restrictor configurations to compensate the torque generated by the rotating recess flow.  They evaluated the new design through CFD modelling and validated experimentally against a pocketed orifice-type bearing with matched main structural parameters.

Briefly, the researchers evaluated how the vortex-type restrictor alters the internal flow field and the bearing response and compared a circular aerostatic bearing with four conventional pocketed orifice-type restrictors against two vortex-type bearing configurations. Both vortex configurations used paired clockwise and counterclockwise restrictors, because a single vortex-generating recess produces torque; arranging opposite vortex directions allows that torque to be compensated while maintaining a symmetric bearing layout.

The flow simulations used ANSYS-Fluent with a realizable k–ε turbulence model and non-equilibrium wall functions. Their choice of modelling aligned with the problem being studied: the restrictor creates rotating and separating flow inside a small recess, and the pressure and velocity gradients near the inlet region are central to the bearing’s dynamic behavior. The computational domain used bearing symmetry to reduce cost while retaining the relevant flow structure, and the researchers treated the air as an ideal gas under supply pressures from 0.4 to 0.6 MPa. They focused in their comparison on bearings with the same main structural parameters except for the restrictor, so that the consequences of changing inlet geometry could be isolated. The simulated pressure field separated the two designs clearly. In the pocketed orifice-type bearing, the authors found the maximum pressure concentrated near the orifice, followed by a pressure depression at the orifice outlet. On the other hand, in the vortex-type bearing, the recess showed a more uniformly distributed high-pressure region, without the sharp local peak and depression seen in the conventional design. The velocity comparison was equally important. In the conventional bearing, the airflow velocity increased abruptly from 26 m/s to 205 m/s near the orifice outlet, whereas the vortex-type bearing kept the recess velocity lower and reached a maximum of 43 m/s at the recess outlet. The design choice of using tangential orifices to generate a controlled recess vortex therefore had the scientific consequence of reducing sudden pressure and velocity changes before the flow entered the bearing film.

The team performed streamline analysis and noticed the pocketed orifice-type restrictor, the jet impinged on the working surface, changed direction abruptly, and produced multiple vortices that were carried away and dissipated by the main flow. In the vortex-type restrictor, the air rotated along the recess wall and then moved into the gap more smoothly. The simulations also showed that torque from a single vortex-type restrictor increased with supply pressure, from 1.24 Nm at 0.4 MPa to 1.90 Nm at 0.6 MPa, which explains why paired opposite vortex directions were built into the bearing configuration rather than treated as an afterthought.

The experimental program tested bearings with four pocketed orifice-type restrictors and four vortex-type restrictors. Tests were taken for load-carrying capacity, stiffness, flow behavior, and micro-vibration under different supply pressures, film thicknesses, recess diameters, recess depths, and orifice heights. The low film thickness region received particular attention because the study identifies it as the operating condition of practical concern in precision equipment. The static results confirmed the main numerical trend. Increasing the recess diameter of the vortex-type restrictor substantially improved load-carrying capacity, especially at low film thickness, and the bearing with a 2.0 mm recess diameter exceeded the pocketed orifice-type bearing. Stiffness also improved under the conditions where the film thickness was below 5 μm, with the maximum reported stiffness increase reaching 286.6% relative to the pocketed orifice-type bearing. Recess depth had a limited effect on load-carrying capacity but influenced stiffness, while orifice height produced almost overlapping curves, indicating little effect on the measured static behavior.

The team also conducted vibration measurements and found that with a 2.0 mm recess diameter, the vortex-type bearing reduced micro-vibration amplitude by more than 60% at film thicknesses of 5 to 6 μm compared with the pocketed orifice-type bearing. With a recess depth of 0.6 mm, the reduction exceeded 70% in the same low film thickness range. Orifice height again had little influence between 3 and 8 μm. No pneumatic hammer phenomenon was observed for either bearing type during testing. The experimental evidence therefore connects the altered recess flow, the reduction in pressure depression, and the improved low-clearance stability in a consistent way.

The findings of Professor Weishi Li and his research team have direct relevance for the design of aerostatic bearings used in high-precision manufacturing equipment and high-precision measuring instruments, where motion stability at very small film thicknesses is essential. The study shows that the restrictor geometry itself can be used as an engineering tool to improve these characteristics, rather than treating the restrictor only as a passive air-supply element. The vortex-type restrictor is especially applicable where self-excited micro-vibration limits the useful operating range of aerostatic flat bearings.  The proposed design changes the inlet condition so that air rotates inside the recess before entering the bearing clearance, producing a smoother transition into the film and reducing the flow instability associated with the conventional configuration. For precision equipment operating at low film thickness, the reported improvements are particularly important. The same design approach also improved static performance: increasing recess diameter enhanced load-carrying capacity, and stiffness increased substantially at film thicknesses below 5 μm. These results suggest that the restrictor can be tuned to support both stability and load performance in the narrow-clearance regime where precision machines often operate. The work also provides practical guidance for bearing design. Recess diameter appears to be the most influential geometric parameter for improving load capacity, stiffness, and vibration suppression, while orifice height has little effect over the tested range.  At the same time, the paper notes that the vortex-type bearing consumes more air because each restrictor contains two orifices. For engineering implementation, this means the design is most suitable where improved stability and stiffness justify the higher air consumption, particularly in precision motion platforms, measuring systems, and manufacturing devices requiring low-vibration noncontact support.

Shield tunnelling beneath existing railway subgrades is still a problem in geotechnical engineering, largely because rail infrastructure responds poorly to even small vertical movements. Track systems tolerate very little distortion before operational limits are reached, and relatively minor differential settlement can translate into service restrictions, intensive monitoring, or unplanned reinforcement during construction. With the increase in cities density and heavier use of underground space, tunnelling beneath active rail corridors is now common and this shift has exposed the limitations of prediction methods that focus only on the final settlement profile, without addressing how deformation accumulates as excavation advances.

Although settlement induced by tunnelling has been studied for decades, its temporal development is still not straightforward to predict. Empirical approaches remain widely used, in part because they are easy to implement and grounded in accumulated field experience. However, these methods depend on simplified descriptions of settlement troughs and offer little transparency regarding the underlying mechanics. Their reliability also deteriorates when ground conditions are modified through reinforcement, since key parameters lose their original physical meaning. Numerical simulations provide a more explicit representation of construction sequences and soil–structure interaction, but this comes at the cost of extensive calibration, long runtimes, and sensitivity to modelling choices that are often difficult to justify during preliminary design. Data-driven techniques have attracted attention more recently, yet their reliance on dense monitoring records and limited interpretability restricts their usefulness before construction begins.

Indeed, analytical methods continue to play an important supporting role because   they provide a level of transparency that is often absent from other approaches by expressing settlement directly in terms of mechanical actions and material response. Solutions derived from the Mindlin framework have been especially influential, as they allow forces associated with tunnelling to be treated as distributed loads acting within an elastic ground mass. Extensions of this idea have accounted for face pressure, shield friction, grouting effects, and layered stratigraphy, yielding predictions that compare favourably with observations under controlled conditions. Still, most existing formulations treat settlement as an instantaneous outcome of applied loads. The excavation process, however, unfolds progressively, and the ground responds continuously as stresses are redistributed over time which are not easy to resolve in analytical settlement prediction.

A further difficulty arises from how ground loss is treated. Conventional analytical and semi-empirical models require assumptions regarding soil convergence or volumetric loss ratios, parameters that become uncertain once reinforcement modifies stiffness and stress redistribution. These assumptions hinder accurate description of how settlement accumulates during excavation and consolidation phases. A recent research paper published in Tunnelling and Underground Space Technology and conducted by Professor Yao Shan, Dr. Guankai Wang, Mr. Weifan Lin, Professor. Shunhua Zhou from the Shanghai Key Laboratory of Rail Infrastructure Durability and System Safety, at Tongji University in collaboration with Professor Frank Rackwitz from the Technical University of Berlin, the researchers developed a time-dependent analytical method for predicting railway subgrade settlement during shield tunnelling that integrates construction actions. They introduced a stress-release representation of ground loss that replaces assumed convergence models with an equivalent load framework and the method combines multiple excavation-related effects within a single Mindlin-based formulation while remaining computationally efficient.

The research team formulated an analytical framework that represents shield tunnelling as a sequence of mechanically distinct actions applied to a reinforced, layered soil mass. The authors first translated complex reinforcement schemes into equivalent elastic parameters by drawing on composite material theory, which allowed reinforced strata to be represented without sacrificing directional stiffness effects relevant to vertical deformation. The investigators then simplified the stratigraphy into an equivalent single-layer system so that established elastic solutions remained applicable while preserving the influence of stiffness contrasts above and below the tunnel axis. The authors examined settlement contributions by explicitly associating each construction action with a corresponding stress representation. They also demonstrated how face thrust, shield–soil friction, and synchronous grouting pressure could be expressed as spatially distributed loads whose influence migrated with tunnel advance through coordinate transformation. By embedding tunnel velocity directly into these transformations, the team ensured that settlement at a fixed monitoring point evolved continuously as excavation progressed, rather than appearing as a static superposition.

An important contribution emerged from the treatment of ground loss because instead of prescribing volumetric loss or convergence geometry, the investigators modeled excavation-induced loosening as a gradual release of in situ stress around the tunnel periphery. The team examined how this released stress could be recast as an equivalent load acting on the surrounding soil once the shield tail passed a given section and by linking the stress release rate to tunnel position, the authors aligned settlement development with excavation progress in a manner consistent with observed behaviour. The researchers observed that this formulation naturally reproduced distinct settlement phases reported in monitoring data, including early uplift or minor deformation during cutterhead approach, rapid settlement during shield passage, moderated response during grouting, and continued deformation during post-excavation consolidation. When applied to both a published benchmark case and a coastal railway undercrossing project, the analytical predictions followed measured time histories closely, especially in capturing prolonged settlement after excavation ceased. The study demonstrated that settlement patterns near the tunnel axis were predicted conservatively, while lateral distributions matched observed trough shapes with increasing accuracy away from the centreline.

In conclusion, Professor Yao Shan and colleagues provided a pathway for analytical prediction that remains valid even when reinforcement alters stiffness and load transfer by treating excavation-induced loosening as progressive stress release.  This perspective strengthens the physical basis of settlement analysis and reduces reliance on empirical calibration tied to specific soil conditions. Beyond its immediate application to railway undercrossing, the framework clarifies how time-dependent settlement emerges from the interaction between excavation actions and soil response. The explicit inclusion of tunnel advance allows engineers to anticipate not only peak settlement but also its rate of development, information that is critical for operational decision-making such as speed restrictions or monitoring thresholds. The method’s efficiency makes it suitable for early-stage evaluation, where multiple alignment or reinforcement scenarios must be assessed rapidly. Moreover, the new approach of Professor Yao Shan and co-workers provides a template for extending analytical solutions to other tunnelling contexts where staged construction and stress redistribution dominate ground response. While the formulation remains grounded in elastic theory, it suggests a bridge between short-term excavation effects and longer-term ground behaviour. With the increase in demand transparent, interpretable prediction tools in infrastructure projects the study work reinforces the continuing relevance of analytically grounded models within modern geotechnical practice.

Waste management and carbon mitigation remain major environmental and societal challenges, and integrating them remains difficult. Solid waste produces a significant fraction of global greenhouse gas emissions, and their conventional treatment methods such as landfilling, incineration, or partial recycling displace rather than resolve underlying carbon flows. Landfills introduce long-term environmental liabilities through leachate and methane generation, whereas incineration recovers energy at the expense of releasing stored carbon back into the atmosphere. Even waste-to-energy systems do not eliminate the carbon burden but instead shift how it appears within the system. This structural limitation has motivated researchers to find new approaches that treat waste as a functional carbon resource.

Activated carbon is a porous material capable of selectively adsorbing CO₂ from gas streams, it is already embedded in industrial separation processes. Its synthesis from carbon-rich precursors such as biomass and municipal waste creates the possibility of a closed-loop pathway in which waste-derived carbon is reconfigured into a sorbent that actively removes CO₂ from flue gases. The appeal lies in coupling two otherwise separate systems: waste valorization and carbon capture. Still, that connection must be evaluated at the full process level. The production of activated carbon is itself energy-intensive, involving hydrothermal treatment, carbonization, and activation steps that generate both direct and indirect emissions. Electricity demand, chemical inputs such as potassium hydroxide, and thermal processing all contribute to the environmental footprint. Therefore, proper evaluation of the viability of waste-derived activated carbon requires the emissions incurred during production must be weighed against the CO₂ captured during use.

Previous studies have examined isolated components of this problem but what has been less clear is how these factors interact across different materials and processing strategies, especially when the end-use performance of the activated carbon is included. In a recent research paper published in Environmental Science & Technology, PhD student Beomhui Lee and Assistant Professor Jiajun He from the University of Illinois at Urbana−Champaign developed a new integrated method that combines experimental CO₂ adsorption data, thermodynamic process modeling, and life cycle and techno-economic analysis across multiple waste-derived feedstocks. They implemented this method within a VPSA carbon capture system to quantify both environmental and economic performance. The approach links material properties to system-level outcomes, providing a unified basis for comparing waste-derived activated carbons as CO₂ sorbents.

Beomhui Lee and Jiajun He evaluated six feedstocks—sawdust, jujun grass, Arundo donax, municipal solid waste, coconut shell, and palm kernel shell—each processed through routes tailored to their physical and chemical characteristics. They selected hydrothermal treatment for certain biomass-derived materials because it operates at lower temperatures and yields higher solid carbon fractions, while pyrolysis-based carbonization was applied to others such as municipal waste and shell-based feedstocks. Activation, whether chemical or physical, serves as the defining step in establishing the porous structure necessary for CO₂ adsorption.

The researchers used isotherm data to define working capacities within a vacuum pressure swing adsorption (VPSA) process and this linkage ensured that material performance translates into process behavior. A higher adsorption capacity does not remain an isolated material property—it reduces the required sorbent mass, alters equipment sizing, and affects both capital and operating costs.

Chemically activated carbons consistently have higher CO₂ uptake, but this advantage is offset by increased production costs. Potassium hydroxide emerges as a dominant contributor, because of its unit cost as well as the quantities required during activation. This relationship becomes especially evident in the minimum selling price (MSP), which ranges from approximately $3.63 to $7.97 per kilogram depending on feedstock and process, with chemically activated systems occupying the upper end of that spectrum.

The authors found that across all feedstocks, variable costs especially chemical inputs and electricity have the strongest influence on MSP,  and produced deviations of up to roughly ±33%, on the other hand, fixed capital costs have much less variability which suggests that improvements in economic performance are more likely to arise from material and process optimization than from capital cost reductions alone.

When Lee and He deployed the activated carbons in a VPSA system, they found the performance has capture costs ranging from approximately $42 to $91 per tonne of CO₂, depending on feedstock. These reported values align with reported ranges in the literature, but the variation within the dataset show an important coupling: adsorption capacity influences both system size and energy demand. Higher-performing sorbents reduce equipment requirements but may still incur energy penalties associated with regeneration, leading to a near-parallel scaling of capital and electricity costs across most cases.

Afterward, the authors performed environmental analysis  and observed production-phase emissions range from roughly 2.2 to 6.9 tonnes of CO₂-equivalent per tonne of activated carbon, with electricity consumption accounting for a substantial fraction of the total. Replacing grid electricity with renewable sources such as solar or wind reduces life cycle emissions by as much as 72%, indicating that the carbon intensity of the energy input can dominate the overall environmental profile.  Another important finding was when production and utilization were considered together. Once deployed in carbon capture, the activated carbons offset their production-related emissions within a matter of days—typically between one and four days depending on feedstock. This rapid offset reflects the relatively high daily capture rates achievable in the VPSA system, which, when sustained over longer periods, lead to substantial net CO₂ removal.

Chemical activation enhances adsorption capacity, although it is also associated with higher chemical demand and corresponding cost and emissions contributions. Physical activation, by contrast, lowers some of these inputs but is associated with lower capture efficiency in the systems examined. The choice between these routes cannot be resolved at the material level alone; it depends on how production, energy supply, and operating context interact. By integrating experimental adsorption data with thermodynamic modeling and life cycle accounting, Lee and He shift the evaluation from isolated material metrics to full-system performance. A material with superior adsorption properties may not yield the lowest cost or the smallest carbon footprint once production emissions are included. Conversely, a less efficient sorbent may still perform competitively if its production pathway is less resource-intensive.

Energy sourcing emerges as a critical lever. Because electricity consumption contributes substantially to production emissions, the transition from grid-based to renewable energy fundamentally alters the environmental balance. Under renewable scenarios, even chemically activated carbons—with their higher intrinsic costs—approach more favorable carbon profiles. This dependence suggests that the sustainability of waste-derived activated carbon is not fixed but contingent on broader energy system conditions.

The analysis also highlights the temporal dimension of carbon accounting. The rapid offset of production emissions during operation reframes the initial carbon cost of material synthesis. Rather than representing a long-term penalty, these emissions are effectively amortized over a short operational period. This dynamic becomes particularly relevant when considering large-scale deployment, where cumulative capture over extended lifetimes dominates the overall carbon balance.

At larger scales, the conversion of waste streams into activated carbon introduces a pathway that links material recovery with carbon mitigation. By redirecting carbon from waste into functional sorbents, the system simultaneously addresses waste accumulation and flue gas emissions. The magnitude of this effect, as indicated by scenario analysis across high-waste-generating regions, suggests that the approach is not simply incremental but structurally significant within the bounds examined.

In many modern engineered systems, the condition of one component affects the role, loading, or operating status of another component, so the system-level response to failure depends on structural relationships as much as on component reliability. Balanced systems represent a clear example of this type of dependency. Their defining requirement is that operating units must remain arranged in symmetric working positions. A failure in one unit therefore does not simply remove that unit from service; it also forces the corresponding unit in the symmetric position to stop operating so that the system remains balanced. This feature gives balanced systems a distinct reliability and maintenance structure. In a conventional multi-component system, corrective maintenance is usually framed around replacing or repairing the failed component. In a balanced system, maintenance planning must account for more than the failed component itself. A failed unit may create a standby unit on the opposite side, and these standby units may later be rearranged into symmetric positions to restore part of the system’s operating capacity. Replacement remains important, but it is no longer the only route to recovery.

The problem becomes broader when spare-parts availability is included. Balanced systems such as unmanned aerial vehicles may operate from distributed bases, while spare parts are supplied through a two-echelon network consisting of a central depot and multiple bases. If a base has insufficient inventory, replacement actions may be delayed or become more costly. Holding too many spare parts, however, increases inventory cost. The practical decision is therefore not only how to maintain the system after shocks occur, but also how to replenish spare parts so that maintenance actions remain feasible without excessive stock accumulation. Traditional maintenance and inventory models are really not designed for this coupled decision environment. Longitudinal transshipment from a depot to a base is commonly considered, but lateral transshipment among bases may also be valuable because nearby bases can provide faster support when local stock becomes low. At the same time, replacement time, rearrangement time, and order completion time may not follow memoryless distributions, which calls for a formulation beyond simpler Markovian assumptions. These features create a methodological gap: balanced-system maintenance, rearrangement, longitudinal replenishment, and lateral replenishment need to be optimized together under random shocks and general action times.

In a recently published research paper in Reliability Engineering & System Safety, Professor Jingjing Wang, Lingyun Luo, and Yuxue Jin from Qingdao University of Technology, working together with Professor Li Yang from Beihang University, addressed this problem through an integrated optimization framework for maintenance and spare-parts transshipment in balanced systems. The new model treats the base state as a joint description of working units, standby units, and spare-parts inventory, which allows maintenance and replenishment decisions to be optimized together. They also developed a semi-Markov decision process formulation and a modified value-iteration algorithm to handle general action times and compute optimal stationary policies. The technically distinct element is that balanced-system rearrangement and two-way spare-parts transshipment are optimized together, allowing maintenance recovery and spare-parts movement to be coordinated within a single long-run cost framework.

The researchers represented the setting through a base-level state model that links working units, standby units, and inventory level. This state definition is important because it ties the physical condition of the balanced systems directly to the spare-parts situation at the base. A maintenance decision can then depend not only on whether a component has failed, but also on whether standby units are available and whether sufficient inventory exists to support replacement. They represented environmental shocks as a homogeneous Poisson process. When a shock causes a unit failure, the corresponding symmetric unit stops working and becomes a cold standby unit. If two standby units become available, a rearrangement action can place them into symmetric positions and return them to operation. If a failed unit is detected at an inspection epoch and spare parts are available, a replacement action can restore the failed unit and its paired standby unit to service.  For inventory control, the authors combined a longitudinal order policy and a lateral order policy. The longitudinal policy follows an (_s1, S) structure, where a base orders from the depot when its inventory drops below the longitudinal order point and replenishes up to a maximum level. The lateral policy follows a (Q, _s2) structure, where a base receives a fixed quantity from other bases when its inventory falls below a lower lateral order point. The condition _s2 < _s1 reflects the operational logic that lateral transshipment is reserved for a more urgent inventory state, while depot replenishment covers the broader replenishment need.

Because the completion times of replacement, rearrangement, and ordering actions do not provide a simple Markov structure, the researchers used a semi-Markov decision process. They derived transition probabilities for cases in which no activity occurs, one action occurs, or a maintenance action and an order action occur together. Costs were also assigned at the state-action level, including inspection cost, holding cost, replacement cost, rearrangement cost, longitudinal order cost, lateral order cost, failure penalty, and revenue associated with dispatching spare parts from the tagged base to another base. The objective was to minimize the long-run average operation and maintenance cost rate while requiring the probability of normal operation to exceed a specified threshold.

To solve the model, the authors developed a modified value-iteration algorithm. The semi-Markov problem was transformed into an equivalent discrete-time decision problem through a data transformation based on expected sojourn times. They also accounted for reducible Markov chains by removing states not connected with the other states, allowing the algorithm to operate on an irreducible chain. This connects the mathematical formulation to a practical computable policy. The numerical example used a UAV setting with two UAVs at each base and six propellers per UAV. The depot supplied eleven bases, and the lateral dispatch probability for a tagged base was set from the number of other bases. Under the specified cost and time parameters, the modified value-iteration algorithm converged within a finite number of iterations.  The team compared between policies which gave them most direct operational finding and found with only longitudinal ordering, increasing the depot order point raised the average cost rate, although it improved normal operation probability. A low order point reduced cost but could fail to meet the operational probability requirement. When lateral transshipment was added, the model identified policies that lowered the average cost rate while maintaining or improving the probability of operation. Afterward, the authors conducted sensitivity which clarified how order costs and order times shift the optimal balance among replenishment frequency, inventory risk, and operating cost.

The findings of Professor Jingjing Wang et al. have direct engineering value for UAV fleets with symmetrically arranged propellers. In such systems, the failure of one unit can force its paired unit to stop operating, so maintenance planning cannot be limited to replacing the visibly failed component. The proposed framework helps engineers decide when failed units should be replaced, when standby units can be rearranged into useful symmetric positions, and when spare parts should be replenished through either depot supply or nearby bases. For UAV fleet operation, the model can support base-level spare-parts planning. A central depot may hold the main inventory, but individual bases still need enough propellers or equivalent components to respond quickly to environmental shocks. This allows a low-stock base to recover spare-part availability without relying only on the longer depot route. The new approach can also be applied to other balanced engineering systems, such as dual-tire assemblies, shock absorber arrangements, balance bikes, or mechanical platforms where paired components must remain operational in symmetric positions. In these cases, the framework offers a way to coordinate maintenance actions with inventory movement rather than treating them as separate management problems. From an operations perspective, the authors’ proposed method is useful for minimizing long-run maintenance and logistics cost while maintaining a required probability of normal operation. It provides engineers and fleet managers with a structured decision tool for selecting inventory thresholds, lateral transfer quantities, and maintenance actions under random shocks and uncertain action times.

Fracture in rock rarely develops as a purely geometric extension of a pre-existing notch or crack. Even when the external loading condition is well defined, the material surrounding the crack tip responds through a localized process of microcracking, damage accumulation, and fracture process zone development. This distinction becomes especially important in quasi-brittle materials, where the crack tip can be considered as a finite region in which local tensile and shear influences may coexist. For mixed-mode fracture, the difficulty is therefore to both predict the direction of crack growth as well as understand how the local condition near the fracture tip differs from the nominal boundary condition imposed on the specimen. Classical linear elastic fracture mechanics provides a useful starting point. Under mixed tensile and in-plane shear loading, the local crack-tip stress intensity factors after an infinitesimal kink do not simply reproduce the global mode I and mode II components. The criterion of local symmetry was developed from this observation: fracture tends to evolve in a direction that removes the local mode II contribution, so that a mode I condition is eventually reached. However, this reasoning is most straightforward under small scale yielding, where the crack tip can be treated as an idealized point. In rock under large scale yielding, the fracture process zone has a finite size, and the local shear influence may not be visible as a simple kink angle or as sliding displacement along the fracture path. In a recent research paper published in Engineering Fracture Mechanics, Professor Peng-Zhi Pan from the State Key Laboratory of Geomechanics and Geotechnical Engineering Safety, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences led his team to develop an acoustic-emission-based method for visualizing and quantifying fracture asymmetry caused by local shear influence in rock under large scale yielding. They introduced the parameter ξ as an area-ratio measure of the symmetry degree of acoustic emission clusters on the two sides of a fracture trajectory. They also separated acoustic emission events by energy level, showing that local shear influence is concentrated mainly in Level 2 and Level 3 events rather than in the high-energy Level 1 events that dominate fracture creation. This combination of spatial cluster analysis and energy-level classification is the technically distinct contribution of the study.

The authors’ experimental strategy focused on a carefully chosen comparison between mode I and mixed-mode fracture. They tested Berea sandstone specimens using single edge notched bend geometry for mode I loading and eccentric single edge notched bend geometry for mixed-mode loading. The use of relatively small specimens was important because it placed the fracture process under large scale yielding conditions, where the fracture process zone becomes central to the interpretation. Acoustic emission sensors were arranged around the notch region, and the recorded events were located and classified by relative energy. In the mode I specimens, the acoustic emission clusters remained approximately symmetric around the fracture trajectory. This behavior provided the reference state needed to interpret the mixed-mode results. In the eccentric specimens, by contrast, acoustic emission events were distributed asymmetrically on the two sides of the fracture trajectory. High-energy Level 1 events, which accounted for most of the total acoustic emission energy, remained essentially symmetric. Medium- and low-energy events, designated Level 2 and Level 3, showed clear asymmetry in the mixed-mode specimens. This energy-dependent pattern is central to the interpretation, because the local shear influence was not distributed uniformly across the fracture process, but appeared mainly in the lower-energy and more numerous acoustic emission populations. To quantify this observation, the authors introduced the parameter ξ, defined as the ratio between the larger and smaller areas covered by acoustic emission events on opposite sides of the fracture trajectory. Because ξ is an area ratio rather than a direct stress measurement, it is best understood as an indicator of local shear influence rather than as a calibrated measure of local shear stress. The researchers determined acoustic emission cluster boundaries through a combination of event filtering and an alpha-shape procedure, then calculated separate ξ values for different acoustic emission energy levels.  The mode I tests gave reference values of about 1.3 for ξ₂ and 1.8 for ξ₃, reflecting the practical fact that perfect symmetry is not expected in real sandstone specimens and acoustic emission location data. In mixed-mode fracture, the initial ξ values were much larger than these reference levels. For Level 2 events, initial ξ values generally fell in the range of about 2 to 4.5, while Level 3 values could be much higher in some specimens. These elevated initial values supported the interpretation that local shear influence was present when the fracture initiated.

The evolution of ξ during fracture growth was equally important. In most mixed-mode specimens, ξ₂ gradually decreased toward the mode I reference value as the fracture process developed. This trend indicates that the local shear influence associated with Level 2 acoustic emission events was progressively removed. Level 3 events behaved less uniformly: ξ₃ also tended to decrease, but in some specimens it remained above the reference value even after substantial fracture development. Because Level 3 events accounted for less than five percent of the total acoustic emission energy, the authors interpreted this residual asymmetry as limited in its contribution to the dominant fracture process. The main fracture, in energetic terms, moved toward a mode I condition.

The engineering applications of the findings of Professor Peng-Zhi Pan and colleagues are in the modelling of mixed-mode fracture in rock and other quasi-brittle materials. In underground excavations, rock slopes, foundations, boreholes, and hydraulic-fracturing-related problems, cracks often develop under combined tensile and shear conditions rather than under pure opening mode. The study shows that local shear influence may be expressed through asymmetric acoustic emission damage around the fracture trajectory, even when the dominant fracture process progressively approaches a mode I condition. This is important because the visible crack path alone may not capture the full local fracture state. By introducing the symmetry parameter ξ and separating acoustic emission events by energy level, the work provides a practical way to quantify damage asymmetry and to follow the gradual reduction of local shear influence during fracture growth.

The findings are also relevant to acoustic-emission-based structural health monitoring and constitutive modelling of geomaterials. AE monitoring is widely used to detect microcracking in rock-like materials, but this study shows that the spatial pattern of AE events carries additional mechanical information. In particular, the asymmetry of medium- and low-energy AE clusters can indicate the presence of local shear influence, while the symmetry of high-energy events suggests that the main fracture core remains governed largely by opening damage. This distinction provides a more refined picture of the fracture process zone which suggest that local shear does not affect the whole damage field uniformly but acts more strongly on selected damage populations.

Hybrid testing has become an important approach for evaluating the seismic performance of engineering structures because it integrates physical experimentation with numerical simulation in a manner that can improve both efficiency and realism. Its reliability, however, depends strongly on the accuracy of the numerical substructure, since errors in that part of the system can directly compromise the credibility of the overall response prediction. For this reason, model updating has increasingly been incorporated into hybrid testing frameworks so that unknown model parameters can be identified from experimental measurements and the numerical model can be adjusted to remain consistent with the observed structural behavior. In this context, parameter identification is not merely a supplementary computational task; rather, it is fundamental to ensuring that hybrid testing produces mechanically meaningful results throughout the loading process. The difficulty is that model updating in hybrid testing imposes unusually strict demands on the identification algorithm. The method must operate effectively within a nonlinear structural setting, must remain stable without manual intervention during testing, and must also be computationally efficient because each integration step allows only limited time for updating. These requirements have made model-based identification methods especially attractive. Compared with non-model-based approaches, they are more compatible with finite element formulations commonly used in engineering practice and retain clearer physical interpretability. Among them, the unscented Kalman filter (UKF) has become a widely adopted choice because it can handle nonlinear systems without the Jacobian-based linearization required by the extended Kalman filter, while still maintaining relatively favorable computational efficiency and implementation simplicity.

Even so, existing UKF-based approaches still exhibit a notable limitation. When the statistical characteristics of system noise are uncertain, identification accuracy may deteriorate, computational efficiency may decline, and the filter may even diverge. This issue is particularly serious in model updating hybrid testing, where reliable performance is required throughout the test and where uncertainties introduced through measurement and data transmission cannot simply be ignored. In a recent research paper published in Mechanical Systems and Signal Processing, PhD candidate Yutong Jiang, Professor Guoshan Xu, and PhD candidate Jiedun Hao from the Harbin Institute of Technology built their method around a dual adaptive unscented Kalman filter, or DAUKF. This method retains the unscented transform as the core of the state estimation process while introducing two adaptive mechanisms within the identification loop. The first is a Sage–Husa adaptive noise estimator, which updates the measurement noise covariance based on the innovation sequence, thereby assigning greater weight to recent measurement information. The second is an adaptive variance module that uses innovation behavior to detect potential divergence and accordingly adjust the predicted measurement covariance and cross-covariance. That design choice matters because it directly links the discrepancy between measured and predicted restoring force to the weighting of prediction information at the next update, allowing the estimation process to respond more carefully when disturbances begin to affect the system.

The proposed identification algorithm was embedded within a model updating hybrid testing framework. The overall structure was modeled numerically using layered shell elements, while the experimental substructure provided measured displacements and restoring forces. The constitutive parameters to be identified comprised seven PSUMAT parameters: compressive strength, tensile strength, crushing strength, peak compressive strain, crushing strain, ultimate tensile strain, and shear retention factor. Before the filtering stage began, the team used experimental data together with a Sheffield genetic algorithm to determine practical starting values for the constitutive parameter vector. This step was not introduced as part of the online model updating procedure itself, but as a way to make the subsequent identification problem well posed in a high-dimensional nonlinear setting. The first stage of evaluation assessed the feasibility of DAUKF as an identification algorithm. Using experimental hybrid-testing data, the researchers first asked the algorithm to identify one sensitive PSUMAT parameter, then two simultaneously. In both cases, the identified parameters exhibited significant fluctuations during the early stages before gradually stabilizing. Compared with the adaptive UKF utilized as a reference, DAUKF achieved closer convergence to the true parameter values and produced lower relative errors and root mean square errors (RMSEs) across the tested cases.

Subsequently, the proposed MUHTM-DAUKF framework was evaluated on a two-story precast shear wall subjected to seismic excitation. Numerical simulations initially employed the El Centro record at 70 Gal, then a broader set of ground motions and peak ground accelerations including TAFT, Kobe, Turkey, and El Centro records under multiple loading levels. Compared with MUHTM-AUKF and MUHTM-DAFA, the proposed method consistently yielded lower error indicators for the identified PSUMAT parameters and lower RMSEs for displacement responses. For the 70 Gal numerical case, the displacement RMSEs of MUHTM-DAUKF remained below 1.17%, whereas the comparison methods exceeded 10.94% and 8.97%, respectively. Parameter-identification errors followed the same pattern: the DAUKF-based method consistently yielded the smallest relative errors and RMSEs among the three methods. The new research also reports visibly dynamic adjustment of the measurement noise covariance and adaptive factor during identification, which is exactly what one would expect if the dual adaptive modules are actively responding rather than functioning as passive add-ons.

Experimental validation at the Harbin Institute of Technology extended the numerical findings into physical testing of the precast shear wall specimen. With HyTest Connector and TCP-based data transmission linking the test hardware and numerical model, the same comparison among AUKF, DAFA, and DAUKF was carried out. The displacement responses from all three approaches remained in substantial agreement with the reference response, but the DAUKF-based method again produced the lowest displacement RMSEs and the smallest parameter-identification errors. Even under experimental conditions where the initial parameter values differed substantially from the true values, MUHTM-DAUKF maintained lower relative errors and lower RMSEs than the competing approaches. Importantly, the DAUKF algorithm required the shortest average computation time per integration step, meaning that the accuracy gains were not purchased by sacrificing the efficiency required for hybrid testing.

The study of Professor Guoshan Xu and colleagues treats model updating in hybrid testing as a problem of sustained estimation under uncertainty, alongside the challenge of nonlinear parameter fitting. This shift matters because hybrid testing depends on a numerical model that is being trusted in real time while physical loading is underway. If the filter handling that updating cannot adapt when noise statistics drift or when prediction errors become abnormal, then the numerical part of the hybrid system becomes a fragile partner. By placing noise adaptation and divergence control inside the identification loop, the method makes the model updating procedure less dependent on fixed statistical assumptions and less vulnerable to poor robustness when disturbances enter through measurement and transmission. In the paper, this manifests in three ways that are hard to separate in practice: smaller parameter-identification errors, more stable tracking of constitutive parameters, and lower displacement-response errors at the structural level. In hybrid testing, slow identification increases test duration and can raise both cost and operational risk. A method that improves accuracy while also shortening the average computation time per integration step is addressing the actual operating conditions of the technique rather than an idealized offline version of it.

The study demonstrates that the layered shell finite element models with PSUMAT parameters can be effectively updated online using measured restoring-force data in a way that remains workable across multiple seismic records and loading levels. This gives the method a broader practical footing within the paper’s stated domain of seismic performance assessment for complex structures. The claim remains bounded: the evidence comes from numerical simulations and experimental validation on a two-story precast shear wall structure. Within that demonstrated range, though, the work supports a more reliable and integrated approach to combining experimental data, parameter identification, and structural response prediction within a unified hybrid testing framework.

Under in-plane compression, many cellular architectures dissipate energy in an uneven way once local wall rotation gives way to unstable collapse, and that loss of order becomes a serious design problem when protection must persist beyond a single plateau. Lightweight cellular solids are attractive because they can combine low mass with load-bearing capacity and controlled crushing, however, the mechanical response that matters most in protective service is seldom governed by one property alone. Stress level, deformation sequence, lateral strain response, and the duration of stable crushing all become entangled once the unit cell starts folding. For structures intended for crashworthiness, packaging, or impact mitigation, the difficulty is not simply to absorb energy, but to do so progressively, predictably, and in more than one loading direction. Much of the earlier effort concentrated on auxetic and re-entrant topologies and those geometries can generate unusual deformation paths and favorable compressive behavior, but still they are limited. Large negative Poisson’s ratio effects may promote desirable folding modes, although they also make deformation control more demanding. Reinforcing ribs or hybrid inserts may steady the collapse, though each added feature narrows geometric freedom and complicates fabrication. Other approaches rely on thickness variation, rotation-based mechanisms, or mixed topologies to create secondary plateaus. Indeed, many reported systems provide only two-stage compression, or they express staged behavior in one in-plane direction while remaining less convincing in the orthogonal one. For engineering components exposed to uncertain loading paths, that directional asymmetry limits confidence in directional tunability. In a recent research paper published in Materials & Design, Qipeng Zhang, a master’s student at Northeast Forestry University, together with Professor Jie Jia of Northeast Forestry University, Lin Dong, a lecturer at Harbin University, and Guoliang Zhi, a PhD student at Southeast University, developed a star-isosceles triangular honeycomb that replaces the ribs of a star-shaped unit with isosceles triangular honeycomb that replaces the ribs of a star-shaped unit with isosceles triangular components while preserving a controllable relative-density formulation They also built a deformation-based theoretical model that predicts stage-specific plateau stresses and critical strains through plastic-hinge dissipation and external work balance. Distinct from earlier star-based hybrids that mainly produced secondary plateaus or directional staging, this architecture delivers three plateau stages under Y-direction compression and two under X-direction compression. The study also establishes an angular tuning framework linking θ and α to stage stresses, Poisson’s ratio evolution, and specific energy absorption.

The researchers built the honeycomb by tying the triangular hypotenuse length to the original star-cell wall length. The team fabricated PLA specimens by fused deposition modeling, measured the constitutive response of the printed material in tensile loading, and then compressed the cellular samples quasi-statically along both in-plane directions. In parallel, the authors constructed ABAQUS shell models with contact and friction to reproduce the experiments and to extend the analysis into an aluminum-alloy ideal elastic-plastic setting, where ductile buckling could be examined without the fracture behavior peculiar to PLA. The investigators demonstrated that the architecture does not crush in the same manner along the two principal directions and for instance under Y-direction loading, the star-derived oblique members rotated first and generated a layerwise collapse pattern, after which the triangularly defined rhombic region entered deformation and introduced a second transition. The measured response carried three plateau stages separated by two sharp stress rises. Under X-direction loading, the triangular units rotated inward at the outset, one major transition emerged when an oblique triangular side reached the horizontal position, and the structure then entered a second plateau regime driven by more complicated bending and contact. Indeed, the cell is not just stronger in one orientation than another; but its topology stores two different collapse logics and activates them according to loading direction.

The research team found close agreement between experiment and finite element prediction. For Y-direction compression, the reported differences between average experimental and numerical plateau stresses remained small across the three stages. The X-direction comparison showed the same pattern. The deformation images and the simulations tracked each other closely enough that the later parametric study had a credible foundation. At the same time, the paper also captures the more irregular part of the crushing response. Once internal contact intensified, the curves developed noticeable fluctuations, especially in the later stages where bending, rotation, and edge contact occurred simultaneously.  The authors then developed a plastic-hinge and energy-conservation model for the staged deformation process and used it to predict plateau stresses and critical strains in both loading directions. They complemented that framework with angular parametric analyses. The calculations showed that the geometric angles had limited effect on average plateau stress and specific energy absorption in a global sense, though they altered the stress carried by individual stages much more strongly. The same parameter study revealed a directional difference in lateral strain response: under Y-direction compression, the structure moved from negative Poisson’s ratio behavior into positive values, while under X-direction compression it retained negative Poisson’s ratio behavior throughout. Smaller values of the angle θ generally increased specific energy absorption in both directions because they demanded larger rotations before compaction and generated more plastic hinges; increasing α generally reduced specific energy absorption, with one low-angle exception under X loading linked to a longer low-force first plateau.

To summarize, Professor Jie Jia, PhD Guoliang Zhi, and colleagues demonstrated that staged crushing can be programmed through morphological transitions that differ by loading axis but still remain intelligible enough to model. In many cellular systems, multi-plateau behavior appears after the fact as an observed curve shape. The paper showed, the plateaus are tied directly to identifiable geometric events: rotation of star-derived members, reorientation of triangular oblique sides, contact formation, and later hinge-dominated collapse. That shift from empirical description toward mechanism-led design has practical value. A designer who can associate each plateau with a structural transition gains a more disciplined route for tuning protection systems than one who slightly adjusts density and waits for the stress–strain curve to cooperate.

Hybridization in honeycomb design is often treated as a way to borrow strengths from two parent motifs, yet the paper makes clear that the real benefit may lie in how one motif restrains the failure tendencies of the other.  The isosceles triangular addition contributes kinematic discipline. That pairing does not erase complexity; the later crushing stages still fluctuate once internal contact grows. In that sense, the triangular component does more than reinforce the cell. It organizes when and how the topology is allowed to deform, and that temporal control of collapse is what produces usable stress plateaus.

The comparison with previously reported star-based hybrid honeycombs strengthens this reading. Under equivalent relative density and loading conditions, the SITH configuration exceeded the compared structures in plateau stress and specific energy absorption, while also preserving staged behavior in both in-plane directions.   The new study establishes that a star–triangle combination built around isosceles components can outperform several existing star-derived designs within the particular quasi-static framework examined here.   A further consequence concerns constitutive simplification and modeling strategy and the paper opens a path toward geometry-driven design maps in which collapse sequence becomes a design variable. The authors point toward size effects and high-strain-rate response as the next questions and if the same transition-governed logic persists when inertia and scale enter the problem, this architecture could become useful in settings where loading is uncertain and directional robustness matters as much as total absorbed energy.

Panoramic imaging of closed surfaces sits at the intersection between geometry and optics. Many objects of scientific or practical interest don’t present themselves as open, planar targets, but most optical systems still assume that they do. When the surface wraps back on itself, conventional imaging strategies tend to fragment the view. One records partial perspectives, then stitches them together afterward, hoping the reconstruction doesn’t introduce distortions that matter for measurement. That hope often isn’t well justified, especially when fine spatial correspondence or phase fidelity is required. Current approaches rely heavily on motion, camera arrays, or computational assembly. A camera rotates, or several cameras observe the surface from different angles, and software attempts to reconcile the resulting data. This workflow works tolerably for visualization, but it struggles when accuracy matters. Calibration errors accumulate. Matching subsets of images isn’t trivial. Neural-network-based reconstruction can fill gaps, but it doesn’t enforce physical correspondence in any strict sense. These limitations persist because the optical system itself never acquires a full-pe spective field. It only samples pieces, then asks computation to guess the rest. The underlying difficulty is optical rather than algorithmic. Light propagates according to local material response, and most imaging systems don’t redirect waves from hidden portions of a surface in any systematic way. Without a medium that can guide electromagnetic fields from different orientations onto a single plane while preserving spatial ordering, direct panoramic capture remains out of reach. That’s why improvements in software haven’t resolved the problem. They’re compensating for a missing physical operation. Null media offer an unusual possibility here. In such media, electromagnetic waves propagate along a prescribed axis without reflection or phase delay, effectively projecting fields from one surface to another. Prior demonstrations of this behavior have largely lived in the microwave domain, where material realization is comparatively forgiving. Extending the same concept into the optical band isn’t straightforward. Optical frequencies impose severe constraints on dispersion, loss, and fabrication scale, and simplified implementations that work at longer wavelengths don’t translate automatically.

The motivation behind this work grows from that gap. If a practical optical analogue of a null medium could be constructed, even in an approximate form and for a restricted polarization, it might allow panoramic imaging to be handled optically rather than computationally. That would change how closed-surface imaging is framed. Instead of reconstructing views after the fact, the system could project the entire surface field directly onto a plane, in real time, because the medium itself enforces the mapping.

A recent research paper published in Journal of the Optical Society of America A  and conducted by Mr. Chao Yang, Professor Fei Sun, Ms.  Ran Sun, and Professor Yichao Liu from the Key Lab of Advanced Transducers and Intelligent Control System, Ministry of Education and Shanxi Province, College of Physics and Optoelectronics at Taiyuan University of Technology, the researchers developed a direct panoramic optical imaging lens based on a subwavelength silver–glass layered structure acting as a simplified null medium. The system projects optical field distributions from closed surfaces directly onto a flat image plane without reconstruction. Its design relies on spatially varying principal axes to preserve one-to-one correspondence across the surface. The new approach can be considered distinct because the imaging function is enforced by material anisotropy instead of post-processing.

The researchers built an effective optical null medium using a subwavelength silver–glass layered structure and designed a simplified version tailored to TM-polarized waves. The team arranged alternating silver and glass layers with thicknesses well below the operating wavelength, which allowed effective medium theory to describe the composite response. The authors designed the layered structure so that its effective permittivity became highly anisotropic. Along the principal axis, the response remained large, while perpendicular components approached zero. That anisotropy mattered because it forced electromagnetic fields to propagate directionally, projecting surface distributions along predetermined paths. The investigators didn’t treat this structure as uniform. Instead, they divided the lens volume into distinct regions, each with a locally defined principal axis, chosen to map different portions of a closed surface onto a common image plane. Plus, the research team Used numerical simulations to examine how point-like and patterned sources placed on different parts of a closed object surface propagated through the lens. When they positioned TM-polarized sources on the top, sides, and front of the surface, the fields traveled through the layered regions and arrived at corresponding positions on the image plane. The researchers observed that the spatial ordering of peaks and troughs remained intact, even though the propagation paths differed. Loss couldn’t be ignored at optical frequencies, especially with silver. The authors explicitly included material loss and tracked its effect. They found that attenuation occurred, and some broadening appeared, but the directional mapping persisted. That outcome followed directly from the null-medium-like response: loss reduced amplitude, but it didn’t scramble spatial correspondence because the propagation direction was constrained by design.

The study also examined patterned field distributions rather than isolated points. When the investigators imposed oscillatory magnetic-field patterns along the closed surface, the projected patterns on the image plane retained identical spatial frequencies and phase positions. Amplitude variations appeared under lossy conditions, but the structural form of the pattern survived. That distinction matters. It shows that the lens doesn’t just image points; it transfers continuous field information. Bandwidth posed another constraint. The team incorporated dispersion through a Drude description of silver and examined performance away from the design wavelength. Across a broad visible range, the mapping behavior held, with consistent peak locations despite frequency-dependent attenuation. Finally, the researchers successfully extended the design from two dimensions into a finite-height three-dimensional structure and simulations showed that the same projection behavior carried over, which confirmed that their concept wasn’t limited to a planar abstraction.

To sum up, the novel approach of Professor Fei Sun bypasses many sources of error that arise when images are stitched computationally by embedding the mapping operation into the optical medium itself. That matters for applications where spatial correspondence isn’t negotiable, such as surface metrology or biomedical imaging, because post-processing can’t recover information that was never optically acquired. The reliance on effective medium behavior also clarifies where the limits lie. The lens works because the layered structure enforces directional propagation. If fabrication tolerances drift or polarization conditions aren’t maintained, the mapping will degrade. That’s not a weakness of the concept so much as a reminder that the physics is doing the work. The imaging fidelity depends directly on how closely the structure approximates the intended anisotropy. Besides, instead of designing lenses to form images through focusing and interference, this system treats imaging as a transport problem. Fields are moved, not refocused. That distinction opens different design routes, particularly for nonconformal or irregular surfaces where traditional optics struggles. Downstream implications remain bounded by practical considerations. Large-area fabrication of subwavelength metal–dielectric structures isn’t trivial, and maintaining TM polarization in uncontrolled environments isn’t guaranteed. Still, if those constraints can be managed, the approach could support real-time panoramic imaging without heavy computation. Extensions to other frequency ranges or to alternative near-zero-index structures seem plausible, though they’d demand careful material choices.

Photonic integrated circuits have become central to the effort to move optical functions from discrete laboratory assemblies into compact, manufacturable chip-scale systems. Much of the strongest progress has occurred in the telecom band, where low propagation loss has enabled high-Q resonators, coherent optical synthesis, microwave generation, lidar architectures, and photonic processing. The shorter-wavelength region, extending from the violet through the visible and into the short near-infrared, presents a more difficult materials problem. As wavelength decreases, surface roughness becomes optically larger and Rayleigh scattering rises; at the same time, absorption becomes more severe as photon energy approaches the Urbach tail of common dielectric materials. These two loss channels are not merely inconvenient. They raise power requirements, degrade resonator performance, and constrain the use of integrated photonics in spectral regions needed for optical clocks, quantum systems, bioimaging, underwater communication, compact lidar, and atomic physics experiments. A useful platform would need to do several things at once. It would have to suppress scattering without distorting waveguide geometry, preserve broad spectral transparency, allow controlled dispersion for nonlinear photonics, and remain suitable for future integration with active or temperature-sensitive components. It would also need to support the physical mechanisms that make resonators useful beyond passive routing: high-Q optical storage, acoustic confinement, low thermorefractive noise, and stable laser feedback.   In a recent research paper published in Nature Journal, Postdoctoral fellow Dr. Hao-Jing Chen, graduate student Kellan Colburn, Peng Liu, Hongrui Yan, Hanfei Hou, Jinhao Ge, Jin-Yu Liu, Phineas Lehan, Qing-Xin Ji, Zhiquan Yuan,  Christopher Holmes, Dr. Henry Blauvelt & Professor Kerry Vahala from California Institute of Technology working together with Professor James Gates from University of Southampton and Professor Dirk Bouwmeester from Leiden University, developed a CMOS-foundry-compatible germano-silicate photonic integrated circuit platform using GeO2-doped silica cores on silicon wafers. The technically distinct element is the combination of fibre-like low material absorption, DUV-defined planar waveguides, ruthenium-assisted deep etching, and surface-tension reflow smoothing to produce ultrahigh-Q resonators from violet to telecom wavelengths. They also showed that the same platform can support dispersion-engineered soliton generation, optical–acoustic confinement for Brillouin lasing, and large-mode-area resonators for low-noise self-injection-locked lasers.

 The researchers developed a germano-silicate photonic integrated circuit platform in which GeO2 doping raises the refractive index of the core relative to silica cladding, allowing optical confinement in a material family closely related to optical fibre. The fabrication route used plasma-enhanced chemical vapour deposition to form a 4-μm-thick germano-silica layer with 25 mol% GeO2 on thermal oxide, followed by ruthenium and silica hard masking, deep-ultraviolet stepper lithography, and inductively coupled plasma etching. The ruthenium mask was important because its selectivity enabled deep, high-fidelity etching of germano-silica. A standard furnace anneal then exploited the low-viscosity reflow behavior of Ge-silica, smoothing etched sidewalls through surface tension while leaving the thermal oxide substrate essentially unaffected. This material feature has a direct scientific consequence: by reducing roughness-induced scattering, the platform addresses one of the major loss mechanisms that becomes increasingly severe at visible wavelengths.

The authors evaluated performance through microring resonators across a wide spectral span. Air-cladded 3-mm-diameter rings were used to avoid substrate leakage and bending loss during measurement. Using tapered-fibre coupling and calibrated tunable lasers, the team measured intrinsic Q factors from 458 nm to 1,550 nm. The resonators exceeded Q values of 180 million across this full range, reaching 463 million at 1,064 nm, corresponding to a waveguide loss of 0.08 dB m−1. At 458 nm, the measured loss was 0.49 dB m−1, reported as a 13-dB improvement over previous integrated-platform records in that wavelength region. The annealed loss values remained below 1 dB m−1 from the violet to the telecom band, which is the central experimental evidence that the platform can carry fibre-like material advantages into a planar chip format. The fabrication results also included an important anneal-free case. Even without reflow smoothing, air-clad resonators reached nearly 200 million Q and a lowest loss of 0.15 dB m−1 at 1,550 nm. The study emphasizes this because many active materials and heterogeneous integration schemes cannot tolerate high-temperature post-processing. In that sense, the anneal-free result is not a side observation; it changes how the platform can be considered for integrated systems that combine passive ultralow-loss routing with III–V materials, organic photonics, thin-film lithium niobate, quartz substrates, or germanium-on-silicon photodetectors.

The device demonstrations then tested whether low loss could coexist with functional photonic behavior. For soliton microcomb generation, the researchers designed a single Ge-silica microring with anomalous dispersion and single-mode transmission. Characterization of the mode family between 1,520 nm and 1,630 nm showed no observable distortion from mode crossings, and soliton triggering produced a spectrum with a sech2 envelope. The repetition rate was near 21.2 GHz, with electrical spectrum analysis supporting pulse-stream stability. For stimulated Brillouin scattering, the platform used the lower longitudinal acoustic velocity of Ge-silica relative to silica to confine both optical and acoustic modes. A 25-mm waveguide with a 4 μm × 6 μm Ge-silica core and thick silica claddings showed a measured SBS gain spectrum that agreed with simulation, with a gain peak at 9.55 GHz and a mechanical quality factor of about 210. Integrated resonators then produced a Brillouin laser with a 9.68 GHz frequency shift and a coherent microwave beatnote. A third demonstration addressed thermorefractive noise in self-injection-locked lasers. The large mode area possible in Ge-silica reduced simulated thermorefractive noise compared with low- and high-confinement silicon nitride resonators of the same diameter. Experimentally, a C-band distributed-feedback laser coupled to a Ge-silica resonator with Q above 100 million showed a 46-dB frequency-noise reduction under self-injection locking and reached a Hz-level fundamental linewidth. The same stabilization concept was extended into the visible using Fabry–Pérot diode lasers locked to high-Q microrings, yielding fundamental linewidths of 15 Hz at 632 nm, 12 Hz at 512 nm, and 90 Hz at 444 nm.

The engineering applications of Professor Kerry Vahala and colleagues are strongest in visible and short-near-infrared integrated photonics, where low loss has been a persistent barrier to compact system design. By achieving ultrahigh-Q germano-silicate resonators from violet to telecom wavelengths, the platform can support chip-scale optical systems that need stable, low-noise, wavelength-specific light in spectral regions that are difficult for conventional integrated platforms. Optical clocks, quantum sensors, quantum computing and networks, atom and ion control, bioimaging, astronomical observation, underwater communication, data-centre links, compact lidar, and atomic physics instruments are all directly aligned with the wavelength range identified in the new work. The practical engineering value is not simply that light can be guided at these wavelengths, but that it can be guided with very low propagation loss, reducing optical power requirements and preserving resonator performance. This matters for miniaturizing systems that currently rely on larger fibre- or free-space optical assemblies. The authors’ schematic concept of combining III–V lasers, germano-silicate resonators, lithium niobate electro-optic modulators, and grating couplers points to integrated visible photonic modules in which light generation, stabilization, modulation, routing, and delivery could be assembled on or near the same chip. The anneal-free ultralow-loss result is also important for engineering, because it makes the platform more compatible with temperature-sensitive active materials, including III–V devices, organic photonics, thin-film lithium niobate, quartz-based substrates, and germanium-on-silicon photodetectors.

The device demonstrations point to more specialized applications in frequency synthesis, precision navigation, microwave photonics, sensing, and low-noise laser engineering. Dispersion-engineered single-ring soliton microcombs could be useful for compact optical frequency comb sources, coherent ranging, portable precision clocks, and photonic systems that require stable multi-wavelength output from a small footprint. The stimulated Brillouin lasing demonstration is especially relevant to chip-scale gyroscopes, integrated microwave photonics, and temperature or strain sensing, because the platform combines ultralow optical loss with optical and acoustic mode confinement. In practical terms, that means the waveguide is not only a passive low-loss channel; it can mediate coherent photon–phonon interactions useful for narrowband signal generation and sensing. The large-mode-area resonators are equally important for low-noise lasers: by reducing thermorefractive noise and enabling self-injection locking of diode lasers, the platform supports Hz-level linewidth operation in the telecom and visible bands. That capability is directly relevant to metrology, coherent optical communication, quantum control, and instrumentation where laser phase noise limits measurement precision. The study also notes possible future use in solid-state gyroscopes, advanced frequency comb systems for portable clocks, large-scale low-loss quantum circuits, high-power amplifiers, and mode-locked lasers if deposition and fabrication continue to improve toward the material-loss limit.