To enhance the protective performance of spacecraft cabin walls against hypervelocity debris, three types of biomimetic water-filled aluminum eggshell array metastructures were designed based on the biomechanical and mechanical properties of eggs. The ordered aluminum eggshell arrays were designed with internal water filling. Three configurations differ in eggshell orientation: one with all eggshell small ends contacting the faceplate, one with blunt ends contacting the faceplate, and one with alternating eggshell orientations. These structures were fabricated via three-dimensional printing technology. The material point method was employed to analyze the dynamics behaviors of the water-filled aluminum eggshell array metastructure under hypervelocity impact. A series of simulation analyses were conducted for the three types of water-filled aluminum eggshell array metastructures, a single-layer aluminum plate, and a water-filled aluminum spherical array metastructure subjected to the impact of spherical projectiles with a velocity of 7.5 km s−1. The energy-absorption mechanism of the water-filled aluminum eggshell array metastructures was revealed through a comparative analysis of the perforation size of target plates, debris cloud morphology, residual velocity of the projectiles, kinetic energy, and strain energy. The results indicate that the three water-filled aluminum eggshell array metastructures can significantly improve protection performance against hypervelocity impacts from space debris. In the context of these target plates, the aluminum eggshell array metastructure that small ends of all the eggshells contact faceplate offers the highest level of impact resistance. The water-filled aluminum eggshell array metastructure achieved a 64.9% reduction in the projectile velocity, while a single-layer aluminum plate reduced the projectile velocity by 51%.
We study spin magnetic moments near half-metallic Co2FexMn1−xSi (CFMS)/metal interfaces using depth-resolved x-ray magnetic circular dichroism (XMCD) and analyze their robustness against thermal fluctuations. We prepare epitaxial magnetic multilayered films with CFMS/CoFe and CFMS/Ag interfaces and observe the x-ray absorption spectroscopy (XAS) and XMCD spectra for both the interfacial and inner CFMS regions. By analyzing the observed XAS and XMCD spectra, we approximately extract the Mn-related magnetic moments. The results show that the Mn spin magnetic moment at the CFMS/CoFe interface exhibits almost no reduction compared with that in the inner CFMS layer, in contrast to the significant reduction observed at the CFMS/Ag interface. This suggests that the CFMS/CoFe interface provides a larger interfacial exchange stiffness than the CFMS/Ag interface, consistent with theoretical interface exchange stiffness values obtained from first-principles calculations. Furthermore, the large exchange stiffness at the CFMS/CoFe interface leads to the high stability of local spin magnetic moments to thermal fluctuation, resulting in a weaker temperature dependence of the magnetoresistance (MR) ratio in current-perpendicular-to-plane giant MR devices with a CoFe/CFMS/Ag/CFMS/CoFe structure than in those with a CFMS/Ag/CFMS structure.
Reliable prediction of detonation behavior in condensed-phase explosives requires models that offer quantitative robustness while maintaining computational efficiency for practically sized (centimeter-scale) systems. Advanced Detonation Shock Dynamics (ADSD) builds on the classical Detonation Shock Dynamics (DSD) framework by incorporating shock acceleration. In this work, we introduce methodological advances to ADSD to improve its ability to describe shock-to-detonation transition (SDT), diameter effect, and detonation failure with reactive-burn level accuracy at a substantially reduced computational cost. We then perform a comprehensive uncertainty quantification (UQ) analysis of the ADSD model parameters for PBX 9502 using experimental data from three experimental benchmarks: SDT, the diameter effect, and the shape effect. Statistical characterization is performed using UQ, yielding posterior parameter distributions that capture uncertainty and correlations; notably, many parameters showed low standard deviations, suggesting high confidence in their inferred values. The UQ-informed parameter sets are subsequently used to simulate corner-turning experiments, yielding predicted dead zones that show strong agreement with experimental observations. This combined optimization and Bayesian UQ framework provides the first systematic quantification of uncertainty in ADSD, enhancing confidence in its predictive capability and laying the groundwork for broader application of reduced-order detonation models in safety-critical engineering contexts.
The influence of surface preparation on the metal–semiconductor interface of pseudo-vertical GaN-on-Si Schottky diodes fabricated by selective-area growth on 200 mm silicon wafers is investigated. Devices were subjected to four surface conditions prior to anode metallization: no treatment, O2 plasma, HCl etching, and O2 plasma followed by HCl treatment. Electrical measurements show that HCl treatment yields the most favorable Schottky behavior, with a higher turn-on voltage (1.0 V) and a lower ideality factor (n ≈ 1), while O2 plasma degrades device performance (VTH = 0.2 and n ≈ 1.9). The combined treatment results in the poorest Schottky characteristics despite a thinner oxide layer than with plasma alone (VTH = 0.1 and n ≈ 2.2). X-ray photoelectron spectroscopy performed before and after Ni deposition reveals that these trends correlate with changes in interfacial oxide chemistry, including effective removal of GaOx by HCl, enhanced oxidation following O2 plasma exposure, and increased disorder in the top layers due to the plasma energy. When applied prior to cathode deposition, the combined treatment of O2 plasma and HCl increases forward current density by a factor of 6 without affecting the forward-bias characteristics, underscoring the interface-specific role of surface preparation. These results highlight the need for tailored surface treatments to optimize the performance of both contacts in GaN Schottky diodes.
Heat propagation, governed by phonon interactions, is described by partial differential equations linking thermal transport to material properties. Conventional thermography relies on surface emissions, limiting subsurface resolution, while existing tomographic methods capture only single-layer frames. Physics-informed neural networks (PINNs) integrate data with physics but mainly fit external temperatures, lacking direct access to internal fields. Here, we propose a Helmholtz-informed neural network (HINN) to predict internal temperature distributions without interior measurements. By converting the time-domain diffusion equation into a pseudo-Helmholtz form, HINN incorporates both real and imaginary components of the thermal field, followed by inverse Fourier transform to reconstruct 3D thermal maps with defects. A truncated operation and conjugate symmetry repair further improve efficiency and accuracy. Results show that HINN surpasses PINNs and inverse solvers, enabling non-invasive thermography for materials, biomedicine, and nondestructive evaluation.
With the development of neuromorphic computing, threshold-switching devices have been widely explored for implementing artificial neurons, but the stability of such circuits remains a critical challenge. This work systematically investigates the Hodgkin–Huxley (HH) neuron based on NbOx threshold devices from the perspective of firing instability. Through detailed modeling and simulation, various unstable firing patterns are reproduced, all of which are induced by mismatches of external factors or internal factors. Stable tonic spiking only appears within a very narrow parameter window, highlighting the poor robustness of the circuit. Therefore, significant circuit improvements are required to enhance the stability of neurons, limiting its immediate applicability in large-scale neuromorphic systems. More importantly, this work establishes a general analytical framework for investigating neuronal instability from the perspective of parameter mismatch and dynamic timing. It not only reveals the intrinsic instability of HH neurons implemented with threshold devices but also challenges the conventional assumption of their inherent robustness. Therefore, this work provides new insights for the design and evaluation of neuromorphic neuron circuits.
This study investigates the influence of holmium oxide (Ho2O3), a heavy rare-earth oxide, on the superconducting properties of MgB2. Bulk MgB2 samples containing 0–5 wt. % of Ho2O3 were synthesized via in situ solid-state reaction using magnesium and nanosized boron powders under an Ar atmosphere at 775 °C for 3 h. Prior to sample preparation, commercial Ho2O3 powder was subjected to ball milling, resulting in a reduction of the particle size from approximately 1.2 μm to 253 nm. Microstructural characterization confirmed the effective refinement of Ho2O3 particles and revealed a phase transformation from a cubic to a monoclinic crystal structure with increasing milling duration. X-ray diffraction results identified MgB2 as a primary phase in all samples. Most of the added Ho2O3 remained unreacted, while a small fraction reacted with boron to form minor HoB4 secondary phases. Magnetization measurements showed that both pure and Ho2O3 added samples exhibited a superconducting transition temperature (Tc) of approximately 37.5 K, with a sharp transition width of less than 0.7 K, indicating that Ho2O3 addition had a negligible effect on Tc. The critical current density (Jc) measured at 20 K under self-field conditions increased from 491.68 kA cm−2 for the undoped sample to 536 kA cm−2 for the sample containing 0.10 wt. % Ho2O3. At self-field, 15 K, the Jc reaches 664.54 kA cm−2 for optimum-doped MgB2 sample. This enhancement is attributed to improved flux pinning arising from the presence of finely dispersed secondary phases. These results demonstrate that effective Ho2O3 particle refinement through ball milling, together with the optimization of Ho2O3 addition, plays a crucial role in enhancing the superconducting performance of bulk MgB2 while preserving its superconducting transition characteristics.
Physical reservoir computing (PRC) has attracted considerable attention as a low-training-cost framework for edge computing. In this study, we propose a PRC system that uses nonlinear heat conduction in an alumina ceramic plate. In the proposed system, the input information is applied as heat, and the transient temperature responses generated by heat conduction are used as reservoir states. The temperature dependences of the thermal conductivity and specific heat of alumina provide nonlinearity without relying on nonlinear sensor elements. The PRC performance was evaluated using temperature data obtained by finite-element analysis of an alumina disk. The results showed that the short-term memory task was improved by shortening the input step duration and increasing the input heat flux, whereas the parity-check task was enhanced by increasing the input heat flux. These results indicate that the input step duration primarily controls the memory, whereas the input heat flux controls the nonlinear transformation through temperature-dependent thermal diffusion. A demonstration experiment was performed using a fabricated alumina ceramic device with embedded resistors for heating and temperature sensing. The experimental results showed trends that were qualitatively consistent with the numerical simulations, demonstrating the feasibility of PRC using heat conduction in an actual solid-state thermal system. This study suggests that heat, which is generally treated as an unavoidable by-product of electronic devices, can be used as a computational resource for edge-computing applications.
High-level radioactive waste requires long-term isolation, motivating the development of durable materials beyond conventional glass matrices, which are thermodynamically metastable. Crystalline ceramics, particularly fluorite-derived oxides, are promising due to their stability, radiation tolerance, and capacity to incorporate radionuclides. In this study, we performed swift heavy ion irradiation into β-Sc2Hf7O17, one of the fluorite structural derivatives in the Sc2O3–HfO2 pseudo-binary system, and investigated its order-to-disordered phase transformation by transmission electron microscopy (TEM). The rhombohedral ordered β-phase transformed into a cubic disordered phase due to damage accumulation. Electron diffraction experiments and dark-field TEM observations revealed the formation of an intermediate phase with an ordered structure distinct from both the β-phase and the other equilibrium phases present in the phase diagram. Irradiation-induced evolution in these materials is complex, involving not only disorder and amorphization but also the formation of intermediate ordered phases and nanoscale heterogeneity. Model systems such as β-Sc2Hf7O17 provide insight into these processes, revealing that local ordering can persist or re-emerge under irradiation, potentially enhancing defect accommodation and delaying structural degradation. This highlights the importance of understanding defect dynamics, local structure, and interfacial effects in designing radiation-resistant waste forms capable of maintaining integrity over geological timescales.
Andreev reflection at a normal/superconductor interface is studied in a system in which the normal region consists of a few-layer black phosphorus (BP) under an electric field applied perpendicularly to the material’s plane. The application of a strong electric field induces a phase transition, closing the BP gap and forming Dirac cones that preserve the unbiased material’s inherent anisotropic dispersion. This platform allows us to explore the effect of electric-field-tunable anisotropy on the Andreev reflection of massless Dirac quasiparticles, using a wave-packet time-evolution method. Our results show that the anisotropy of a BP electronic structure plays a central role in Andreev reflection, which results in a voltage–transmission relation that, in contrast to the case of isotropic materials, strongly depends on the wave vector angle and weakly depends on the Fermi level away from the superconducting gap, (i.e., for retro-reflection processes).
This review systematically maps the progress of waveguide-based wavelength converters, focusing on the critical push toward the far-ultraviolet band. To overcome material limitations, we propose utilizing the strong optical nonlinearity in nitride semiconductors via precise polarization control. This approach enables the novel transverse quasi-phase-matching structure, superior for short wavelengths. We present the world-first 229 nm emission from a polarity-inverted AlN waveguide, as well as several ways of wavelength conversion free from polarity inversion. These breakthroughs pave the way for compact, high-efficiency light sources and photonic integrated circuit platforms.
Understanding phase stability in immiscible alloys is essential for designing materials for extreme environments, including high-temperature and irradiation conditions. Here, Cu–Nb is used as a model system with a positive enthalpy of mixing, in which enthalpic and entropic contributions compete across composition and temperature. Molecular dynamics and well-tempered metadynamics simulations were combined to investigate thermodynamic preferences and transformation kinetics over the full composition range from 300 to 1700 K. Helmholtz free-energy trends for FCC, BCC, and liquid/amorphous structures were estimated from lattice-static and vibrational contributions derived from velocity autocorrelation functions and vibrational densities of states (VDOS). Lattice-static energy governs structural preference near the terminal compositions, favoring FCC in Cu-rich alloys and BCC in Nb-rich alloys. At approximately 30–50 at. % Nb, competing structures have comparable static energies, and the vibrational contribution increasingly favors liquid/amorphous configurations at elevated temperatures. VDOS analysis reveals phonon softening in FCC alloys with increasing Nb content, whereas BCC Nb primarily exhibits thermal broadening and spectral-weight redistribution with modest peak shifts. Metadynamics simulations show that increasing Nb from 30 to 40 at. % at 300 K stabilizes the amorphous state relative to FCC, while Nb-rich alloys retain an overall preference for BCC order. Increasing temperature from 300 to 1000 K reduces transformation barriers between crystalline and amorphous states in both composition regimes. These findings clarify how composition and temperature govern competing ordered and disordered states and provide guidance for designing heterogeneous immiscible alloys and interfaces for extreme environments.
The analysis and characterization of field-emission (FE) devices have been performed during the last 50 years by a variety of methods like the more accurate analytical methods using curvilinear coordinates, the particle-in-cell method, and the shape factor method. The oldest and most simple to implement, which is still used today, is the tangent method based on the Murphy–Good equation, an equation applicable in principle to planar emitting surfaces and in practice to low curvature surfaces. However, many modern emitters have apex radii of curvature R of 10–20 nm, and yet, their analysis and characterization are still performed, in many circumstances, the same way. In this paper, we analyze such nanometric FE devices by extending the tangent method using as an emission law the generalized Fowler–Nordheim equation of Kyritsakis and Xanthakis, Proc. R. Soc. A 471, 20140811 (2014), which is valid down to R = 4 nm. Then, we obtain the new slope and intercept correction factors appropriate for nanometric R. Upon examination of six FE experiments with nanometric R, we show that, if the traditional Murphy–Good equation is still employed instead of Kyritsakis and Xanthakis, Proc. R. Soc. A 471, 20140811 (2014), the errors in the enhancement factor β are only 10%–20%, but the errors in the effective emission area may be up to 400% and even up to an order of magnitude. Furthermore, we estimate the limiting curvature of emitting surfaces at which the Murphy–Good law ceases to be valid. This limit is obtained by looking not only at the emitted current density but also at the effective area as deduced by the extended tangent method for nanometric emitters and is estimated to be around R = 30 nm.
A contact model for ballistic and quasi-ballistic transport in two-dimensional (2D) semiconductors is presented. Improving transport properties in 2D semiconductors is essential for reducing contact resistance, but it drives carrier transport in the contact region into the quasi-ballistic regime, where the commonly used diffusive contact model breaks down. The proposed model captures the quantum limit of contact resistance in the ballistic limit when the metal–semiconductor interfacial resistivity is negligible and provides a framework for understanding the combined effects of carrier scattering and finite interfacial resistivity, which lead to the larger resistance values observed experimentally. The interplay between interfacial contact resistivity and quasi-ballistic transport in 2D semiconductors plays an important role in determining contact resistance and contact transfer length. The effects of contact length scaling and band non-parabolicity on the contact resistance are also examined. Numerical results are presented for monolayer transition-metal dichalcogenide semiconductors, using monolayer MoS2 as a representative example.
Li-alloy anodes have emerged as promising alternatives to the Li metal for all-solid-state batteries (ASSBs) due to their ability to mitigate interfacial side reactions and suppress dendrite growth. However, Li-ion diffusion limitation at the alloy/electrolyte interface remains a challenge. Herein, we propose a work function-tunable Li–Ag alloy design to reduce the electrostatic barrier at the Li–Ag/β-Li3PS4 interface based on a first-principles-informed thermodynamic model. Our calculations show that among Li–Ag alloys, Li-rich phases Li3Ag and Li11Ag2 exhibit ultralow Li diffusion barriers (∼0.1 eV) and favorable Li vacancy formation energies, enabling rapid Li diffusion. Our analysis of work functions of Li–Ag alloys as functions of orientation and termination reveals that surface termination is the primary determinant, with orientation playing a secondary role. A Li-terminated surface substantially lowers the work function, thereby reducing the interfacial potential drop and promoting Li-ion transport. While the influence of orientation is comparatively minor, its optimization can further reduce the barrier. Notably, the Li3Ag phase with a Li-terminated (111) surface achieves an interfacial potential drop as low as 0.20 V, much lower than that of the Ag-terminated (111) surface. Our findings highlight surface termination as a critical design principle and suggest that synergistic optimization of alloy composition, termination, and orientation is essential to minimize interfacial barriers in ASSBs.
Sunscreens are fundamental public health tools for mitigating the harmful effects of ultraviolet (UV) radiation on the skin. UVA radiation reaches the Earth's surface in greater proportion, contributing to photoaging and skin carcinogenesis. In this context, the efficacy of sunscreens depends not only on their spectral absorption capacity but also on their thermal behavior and photochemical stability under irradiation. In this work, six commercial cosmetic formulations, including sunscreens and makeup products with and without sun protection factor, were characterized using photoacoustic spectroscopy and front configuration of photopyroelectric techniques. Absorption spectra were obtained to evaluate protection in the UVB, UVA, and visible regions, and thermal transport properties, such as thermal diffusivity and conductivity, were determined. The results show that the analyzed formulations exhibit significant absorption in the UVB and UVA regions. Formulations with pigments extend this absorption into the visible region, providing additional protection against high-energy visible light. Thermal analysis revealed higher diffusivity and thermal conductivity values in sunscreens compared to makeup bases, suggesting greater heat dissipation efficiency. Furthermore, photostability tests revealed significant differences between formulations, with some products showing a decrease in absorption consistent with significant photodegradation processes after irradiation. These results provide a basis for designing and evaluating photoprotective formulations with improved performance under real-world exposure conditions. These results demonstrate that combining optical and photothermal techniques allows for a comprehensive performance evaluation of photoprotective formulations, highlighting the relevance of thermal properties, photochemical stability, and spectral coverage to the actual efficacy of these products.
How Majorana zero modes (MZMs) influence the Josephson transport is of fundamental importance for the detection of Majorana physics. In this work, we study the supercurrent transport through a quantum dot–MZM hybrid Josephson junction within the framework of Keldysh non-equilibrium Green’s function. The density of states with and without MZMs is discussed. The effects of quantum dot level, Majorana overlap, spin-dependent coupling, and Majorana nonlocality on the supercurrent transport properties are analyzed. Without Majorana states, the supercurrent exhibits a conventional 2π-periodic pattern. Finite Majorana overlap and asymmetric coupling trigger a 0 − π transition as well as a 2π-to-4π periodicity transition. Moreover, the nonlocality quality factor can strongly reshape the supercurrent line shape. We elucidate the underlying physical mechanisms in detail. Our results reveal unambiguous transport signatures for identifying Majorana states and offer insights for manipulating MZMs in topological quantum devices.
Two-dimensional fullerene macromolecular networks are layered architectures formed by covalently linked fullerene clusters of varying sizes. These structures exhibit significant catalytic potential owing to their fully exposed active sites, unique electronic properties, and relatively simple and uniform configurations. In this study, two-dimensional networks composed of fullerene molecules (C20, C24, C36, C60, and C72) were constructed in two symmetric configurations: quasi-tetragonal and quasi-hexagonal phases. First-principles calculations were employed to systematically investigate the structural stability, electronic properties, strain-dependent mechanical behavior, and catalytic performance of these networks. Analyses of binding energy, dynamic stability, and thermal stability at room temperature reveal a consistent stability ranking for both phases, from strongest to weakest: C24, C36, C20, C72, and C60. Electronic structure characterization further shows that qHP C20 and qTP C20 are metallic, qHP C72 is a narrow-bandgap semiconductor, and qHP C36 exhibits a semi-metallic character. In contrast, qTP C72, qTP C60, qHP C60, qTP C36, qTP C24, and qHP C24 are wide-bandgap semiconductors. These diverse electronic properties provide a physical basis for potential applications. In addition, detailed analysis of catalytic properties indicates that both compressive and tensile strains can effectively modulate the hydrogen evolution reaction and oxygen evolution reaction activities of these networks. This tunability is of significant importance for addressing energy-related challenges.
Stress-tunable thermopower in positively magnetostrictive amorphous ribbons offers a route to low-power magnetoelastic sensing that draws no excitation current through the ribbon, but no compact analytical law links uniaxial tensile stress to the relative Seebeck change. We present the first such law, a closed-form four-parameter response equation. It converts stress into an effective anisotropy field through the Villari effect. The resulting magnetization is described by a two-component modified Langevin function, and the thermoelectric response is obtained from Mott's formula with spin-disorder and magnon channels. Validation against measurements on METGLAS 2605SA1, 2605CO, and the newly reported 2605S3A yields coefficients of determination R2 ≥ 0.992 (adjusted R2 ≥ 0.990) with RMSE≤0.029% for stresses up to ∼217 MPa. At the mean temperature of ∼350 K, spin-disorder scattering dominates the stress-dependent Seebeck coefficient for all three alloys, consistent with spin-caloritronic transport in structurally disordered ferromagnets, while the magnon contribution is statistically negligible. The model provides a quantitative basis for comparing compositions and calibrating thermoelectric stress-sensitive elements.
The understanding of the properties of advanced materials requires a deep knowledge of chemical bonding beyond the classical chemical bonding picture of covalent, ionic, and metallic bonds. For this purpose, we need to include multicenter bonds into the equation. Here, we approach multicenter bonds in discrete molecular systems by resorting to experimental structural data of finite non-branched chain-like molecules and ions formed by main-group non-metallic elements (X) with s- and p-type valence electrons, as obtained from the Cambridge Structural Database. Using very basic concepts and methods, we demonstrate that multicenter bonds in Xn molecules with n ≥ 3 can be understood with the help of current knowledge of two-center bonds. We evidence that some of the studied chains exhibit covalent bonds, while others exhibit two types of multicenter bonds: electron-rich multicenter bonds (ERMBs), best known as three-center four-electron (3c–4e) bonds or hyperbonds, and electron-deficient multicenter bonds (EDMBs), whose better known example is the three-center-two-electron (3c–2e) bond. Interestingly, linear Xn molecules for n > 3 do not exhibit ERMBs, but “hybrid” multicenter bonds, which consist of a concatenation of ERMBs and EDMBs, where the ratio of EDMBs to ERMBs increases with n; i.e., the electron deficiency in the chain increases with n. Consequently, infinite linear atomic chains feature exclusively EDMBs (even for electron-rich elements). The above observations suggest that there is an inherent limitation to the formation of linear atomic molecules for n > 3 with only ERMBs. All these observations fully agree with the recently proposed unified theory of multicenter bonding, which suggests that multicenter bonds are the missing link between weak secondary bonds and strong primary bonds and promotes a unitary vision of chemical bonds (both in molecules and solids).
