Accepted
, , Received Date: 2025-07-13
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Metal hydrides are promising moderator materials in advanced reactors, where their thermal neutron scattering cross sections significantly affect the accuracy of reactor design. This study uses special quasi random structure (SQS) and first-principles lattice dynamics methods to calculate parameters such as the phonon densities of states of sub-stoichiometric zirconium hydride (ZrHx) and yttrium hydride (YHx). Based on these parameters, thermal scattering law (TSL) data for sub-stoichiometric hydrides are generated using the nuclear data processing code NECP-Atlas. The influences of hydrogen content on the thermal scattering cross sections of hydrides and the effective multiplication factor (keff) values of critical assemblies are analyzed. The result shows that variations in hydrogen content within hydrides lead to differences in thermal scattering cross sections, consequently affecting the neutron transport calculations of nuclear reactor. For the ICT003 and ICT013 benchmarks loaded with ZrHx (with H/Zr ≈ 1.6), using the TSL data derived from ZrHx with other hydrogen content results in a maximum deviation of 104 pcm in keff. For the HCM003 benchmarks loaded with ZrH2, the use of TSL from ZrHx with other hydrogen content leads to a maximum deviation of 147 pcm in keff.
, , Received Date: 2025-08-30
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The high-order Hermite-Gaussian (HG) mode squeezed light, as one of the important quantum sources, has significant application in quantum precision measurement and quantum imaging. The enhancement of spatial measurement precision largely depends on the squeezing level of high-order HG-mode quantum states. However, the squeezing level of high-order HG modes is primarily limited by the external pump power in the optical parametric oscillator (OPO) cavity. It is well known that the OPO with double resonance for both squeezed light and pump light enables to lower external pump power. The generation of $ {\rm HG_{10}} $ mode squeezed light differs from that of $ {\rm HG_{00}} $ mode squeezed light, with an additional Gouy phase shift introduced between the $ {\rm HG_{20}} $ pump mode and $ {\rm HG_{10}} $ down-conversion mode within the OPO cavity. In this paper, we present a theoretical analysis and the experimental generation of $ {\rm HG_{10}} $ mode squeezed light at lower external pump power using a doubly-resonant OPO based on a wedged periodically poled $ \rm KTiOP{O_4} $ (PPKTP) crystal. By precisely controlling both the propagation length of the optical field and temperature in the wedged PPKTP crystal, we simultaneously compensate for the Gouy phase shift between the $ {\rm HG_{20}} $ and $ {\rm HG_{10}} $ modes as well as the astigmatism induced by the frequency-dependent refractive index. This configuration allows double resonance for both the $ {\rm HG_{20}} $ pump mode and the $ {\rm HG_{10}} $ squeezed mode while operating close to optimum phase matching conditions. Increasing the reflectivity of the input coupler of OPO cavity enhances the intra-cavity circulating power of the pump light, thereby reducing the required external pump power. Here, the bow-tie-shaped OPO cavity consists of two plane mirrors and two concave mirrors with a radius of curvature of 50 mm. The wedged PPKTP is placed in the smallest beam waist of the cavity. The mode converter is employed to generate high-purity $ {\rm HG_{20}} $ pump mode with a measured purity of 98.0$ {\text{%}} $. The mode-matching efficiency of 93.0$ {\text{%}} $ is achieved between the high-purity $ {\rm HG_{20}} $ pump mode and the OPO cavity. The homodyne visibility of the $ {\rm HG_{10}} $ mode is 98.1$ {\text{%}} $. We experimentally demonstrate the generation of 9.10 dB $ {\rm HG_{10}} $ mode squeezed light using a doubly-resonant OPO with only 51 mW of $ {\rm HG_{20}} $ pump mode, and simultaneously achieve 9.20 dB of squeezing in the $ {\rm HG_{00}} $ mode with 27 mW of $ {\rm HG_{00}} $ pump mode. The inferred squeezing level of both $ {\rm HG_{10}} $ and $ {\rm HG_{00}} $ mode squeezed light reaches up to 12.15 dB. The quantum technology has solved the pump power limitations in optical parametric oscillators, enabling the generation of high-order HG mode states with high squeezing level and providing an effective method to enhance spatial measurement precision.
, , Received Date: 2025-06-15
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, , Received Date: 2025-07-24
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,
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In recent years, topological valley physics with valley pseudospin degrees of freedom have attracted significant attention. The topological valley boundary states in phononic crystals have important application prospects in efficient guidance and sensing for acoustic and elastic wave due to their unique transmission characteristics with backscattering immunity. However, the coupling effect of the valley edge states in multi-layer topological heterostructure was still a challenge in the elastic system due to the complicated multi-mode polarization of elastic waves. This article constructed a valley topological phononic crystal plate with multi-layer heterostructure to explore the multi-mode interference characteristics of the valley edge states based on the analogy of elastic wave quantum valley Hall effect. The coupling behavior of valley edge states for the out-of-plane polarized elastic wave in multi-layer topological heterostructure was systematically studied. By adjusting the layer numbers of the topological heterostructure, the formation mechanism and regulation law of coupled valley edge states for elastic wave in finite size multi-layer heterogeneous structures were revealed. Furthermore, through topological transmission calculations, the multi-mode interference effect of coupled valley edge states for elastic wave was achieved and its transmission robustness was well verified. Finally, as an application example, an elastic topological wavelength demultiplexing device was designed based on the multi-mode interference effect of valley edge state. By utilizing the difference in coupling wavelengths of elastic valley edge states at different coupling frequencies, directional separation of incident elastic waves in defect resistant channels was achieved, which could be as a prototype model for the novel application of elastic wavelength demultiplex device. This study provides a new paradigm for the manipulation of elastic wave topological transport, which is also expected to promote the practical design of new multifunctional elastic wave coupling and sensing devices.
,
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Due to its unique physical and chemical properties, hydrogen plasma is the preferred gas for cleaning reaction chambers. For better understanding of the transport and diffusion mechanism in hydrogen plasma, this paper presents a two-dimensional fluid model by COMSOL simulation software, and systematically investigates the characteristics of radio-frequency inductively coupled remote hydrogen plasma sources under varying discharge and geometric parameters. The results show that input power primarily affects electron density rather than electron temperature. This phenomenon may be due to the balancing mechanism between the ionisation rate and the loss rate in steady state discharges. The pressure has the opposite effect on the plasma in the driven and spatial afterglow regions. As the pressure rises, the electron density in the driven region increases gradually, while the electron density in the spatial afterglow region decreases gradually. This may be due to the shift from non-local to local electron kinetics as the pressure rises. Increasing input power effectively enhances hydrogen radical density and diffusion flux, suggesting that high power facilitates the transport of hydrogen radicals into the spatial afterglow region. However, elevating operating pressure has a similar effect while reducing hydrogen radical density in the spatial afterglow region. Furthermore, under fixed discharge conditions, increasing geometric parameters appropriately promotes the generation of higher and more uniform hydrogen radical densities within the afterglow region.
,
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In recent years, two-dimensional (2D) ferroelectric materials have garnered significant interest, distinguished by their ultrathin geometry, high stability, and switchable polarization states. Ferroelectric tunnel junctions (FTJs) constructed from 2D ferroelectric materials exhibit exceptionally high tunnel electroresistance (TER) ratios, establishing them as leading candidates for next-generation non-volatile memory and logic devices. However, advancing FTJ technology hinges on overcoming the critical challenge of precisely controlling quantum tunneling resistance. Therefore, this study proposes a strategy of interfacial work function engineering, which actively modulates the band alignment of a heterostructure via ferroelectric polarization switching to induce a reversible metal-insulator transition in the barrier layer and modulate TER. Using a van der Waals heterostructure composed of Al2Te3/In2Se3 as a model system, we demonstrate through first-principles calculations that the strategic manipulation of interfacial work functions can induce a reversible metal-insulator transition in the barrier, thereby drastically altering the tunneling conductance. Further analysis indicates that a work function mismatch between the two ferroelectric materials induces varying degrees of interfacial charge transfer, thereby triggering a metal-insulator transition in the van der Waals ferroelectric heterostructure as the external electric field is reversed. Non-equilibrium transport simulations reveal an unprecedented TER ratio of 2.69 × 105%. Our findings not only highlight Al2Te3/In2Se3 as a promising platform for high-performance FTJs but also establish a universal design strategy for engineering ultrahigh TER effects in low-dimensional ferroelectric memory devices. This work opens new avenues for developing energy-efficient, non-volatile memory with enhanced scalability and switching characteristics.
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Due to their unique nonlinear characteristics and memory effects, memristor-based chaotic systems have become a significant focus of research. However, studies on unstable periodic orbits in memristive chaotic systems remain relatively scarce. In this paper, a novel four-dimensional memristive chaotic system is constructed by introducing a trigonometric-function-based memristor to enhance a three-dimensional chaotic system. The dynamical behaviors of the system are analyzed using Lyapunov exponents, Poincaré sections, phase portraits, and time-domain plots. The proposed memristive chaotic system exhibits rich dynamical characteristics, including transient behavior, intermittent chaos, and diverse attractor dynamics under parameter variations. To overcome the limitations of the variational method in finding reliable initial guesses for unstable periodic orbits, an innovative optimization strategy leveraging the physical characteristics of trigonometric functions is proposed. Integrated with symbolic dynamics, this strategy enables the rapid acquisition of robust initial guesses for unstable periodic orbits within specific intervals. Furthermore, it allows for the migration of these guesses to other regions of the attractor, ultimately achieving full coverage of the attractor's unstable periodic orbits. Following a systematic analysis of the unstable periodic orbits in the new system, the adaptive backstepping method is employed to control the stability of the known unstable periodic orbits, namely 320 and 013. The pseudorandom sequences generated by the novel memristive chaotic system successfully passed the NIST suite, with all test items yielding P-values greater than 0.01, which confirms their excellent pseudo-random characteristics. The application of this system in image encryption achieves a key space of 10120, significantly enhancing the key space and key sensitivity of the algorithm. The encryption process begins with cross-plane scrambling operations among the RGB color channels for initial pixel processing, followed by intra-plane scrambling to further disrupt the pixel arrangement. XOR operations are then employed for pixel value diffusion. The algorithm demonstrates outstanding resistance to differential attacks, with average NPCR and UACI values reaching 99.6041% and 33.4933%, respectively. Comprehensive security analyses, including histogram analysis, correlation analysis, resistance to cropping attacks, and runtime evaluation, verify that the proposed encryption scheme not only possesses strong security capabilities but also maintains high computational efficiency, making it highly suitable for practical image encryption applications. Finally, the realizability of the system is verified by utilizing a DSP circuit.
,
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The boundary region between the solar radiation zone and the convection zone (T ~ 180 eV, ne ~ 9×1022 cm-3) is a critical interface where energy transport in the solar interior transitions from radiationdominated to convection-dominated regimes. This region also serves as a natural laboratory for studying hot dense plasma. The physical properties of this zone are essential for the reliability of stellar evolution models and the stability of energy transport mechanisms. One of major unresolved issue is how electron collision ionization affects the density of free electrons and radiation properties in this plasma, while accurately describing the impact of hot-dense environments on electron impact ionization (EII) (such as electron screening, ion correlation). To fill this gap, we systematically calculate EII cross sections for C, N, and O ions under realistic solar boundary conditions, with a focus on hot-dense environment impacts. We develop a novel computational framework that merges hot-dense environment effects into atomic structure calculations: the Flexible Atomic Code (FAC) for atomic structure is combined with the Hypernetted-Chain (HNC) approximation to capture electron–electron, electron–ion and ion-ion correlations, enabling self-consistent treatment of electron screening and ion correlation. Atomic wave functions are derived by solving the Dirac equation within the ion-sphere model, using a modified central potential that incorporates both free-electron screening and ion–ion interactions. EII cross sections are then computed via the Distorted-Wave (DW) approximation in FAC. The results demonstrate that hot-dense environment effects significantly enhance the electron-impact ionization cross sections of C, N, and O compared to those calculated under the free-atom model. Additionally, a notable reduction in the ionization threshold energy is observed. These effects are attributed to the overlap of atomic potentials due to strong ion coupling and the shift in bound-state energy levels caused by free-electron screening. For instance, under solar boundary conditions, the ionization cross section of C+ increased by up to 50%, with the ionization threshold decreasing from about 24 eV (isolated) to 18 eV (with screening). Similar enhancements were observed for nitrogen and oxygen ions across various charge states. By providing updated ionization cross sections for C, N, and O ions under realistic solar interior conditions, this work offers essential parameters for improving radiation transport models, ionization balance calculations, and equation-of-state models in stellar interiors. The results underscore the necessity of including hot-dense environment effects in atomic process calculations for hot dense plasmas, with implications for astrophysics and inertial confinement fusion research.
, , Received Date: 2025-07-14
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By studying the breakdown performance of ethylene-tetrafluoroethylene copolymer (ETFE) under low pressure via molecular dynamics simulations, and verifying the simulation results through low-pressure breakdown experiments, the insulation failure mechanism of ETFE materials under low pressure can be revealed on an atomic scale. First, molecular dynamics simulations are performed on ETFE. As the flight altitude gradually increases from 0 km to 24 km, the simulated pressure decreases from 101.300 kPa to 2.951 kPa. Correspondingly, the intermolecular distance increases by 9.692%, the interchain interaction energy decreases by 8.383%, the free volume fraction of ETFE increases by 65.000%, and the density of ETFE decreases by 7.737%. Subsequently, based on the electromechanical breakdown theory, it is deduced that the breakdown field strength of ETFE decreases by 17.626%. Finally, the low-pressure breakdown experiment shows that the breakdown field strength decreases by 40.078%, and the density measurement test indicates that the density decreases by 1.574%. Both simulation and experimental results confirm that the breakdown field strength of ETFE decreases with the reduction of pressure. This is because under low-pressure conditions, the increase in free volume fraction and the decrease in air density provide a longer mean free path for free electrons; the decrease in Young’s modulus leads to greater deformation under the same voltage, resulting in a higher applied field strength; the decrease in charge trap level weakens the charge trapping capability, leading to a higher concentration of free electrons. All these factors contribute to the reduction of the breakdown field strength of ETFE. This study provides performance prediction and failure mechanism analysis for the application of ETFE in aerospace and high-altitude extreme environments, and has guiding significance for the optimal design of aerospace insulation ETFE materials.
Study on risk of triboelectric charging and discharging of lunar rovers in lunar surface environment
, , Received Date: 2025-08-02
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, , Received Date: 2025-07-08
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, , Received Date: 2025-06-03
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Vanadium carbides commonly serve as strengthening phases in metallic materials, where their elastic and ductile-brittle characteristics are critical for mechanical performance. This work systematically investigates the structural stability, electronic properties, mechanical behaviors, and thermal characteristics of multi-component V1–xFexC carbides by using first-principles calculations, aiming to elucidate the influence of Fe content on their physical properties and provide a theoretical basis for the design and application of carbides in high-performance steels. The calculations are performed using the Vienna ab initio simulation package (VASP) based on density functional theory (DFT). Special quasirandom structures (SQS) are employed to construct five carbide models with varying Fe/V ratios (from V0.125Fe0.875C to V0.875Fe0.125C). Key parameters including formation enthalpy, electronic density of states, elastic constants, Debye temperature, and thermal conductivity are computed. The results indicate that as the Fe content decreases, the formation enthalpy shifts from positive to negative, reflecting a significant improvement in thermodynamic stability. Electronic structure analyses reveal metallic behavior of all compositions, with stronger covalent bonding in V-C than that in Fe–C. The V0.875Fe0.125C carbide exhibits the highest elastic modulus (C11 = 615.80 GPa) and Vickers hardness (21.06 GPa), which is attributed to its strong covalent interactions, though it also shows increased brittleness. The Debye temperature rises with the decrease of Fe content, further confirming superior mechanical strength at elevated temperatures. Calculations of the thermal conductivity for V0.875Fe0.125C yield values of 9.427 W·m－1·K－1 at 300 K and 2.357 W·m－1·K－1 at 1300 K. Its minimum lattice thermal conductivity (2.001 W·m－1·K－1) is comparable to that of typical thermal barrier coating materials, demonstrating high potential for high-temperature thermal insulation. This study reveals the structure-property relationships in V1–xFexC carbides on an atomic scale, indicating that low-Fe compositions are advantageous for high-temperature and high-strength applications. These findings provide important theoretical support for the development of novel heat-resistant coatings and high-strength steels.
, , Received Date: 2025-07-05
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