Northwest Institute of Nuclear Technology

In order to calculate the coupling current on the vehicle antenna, a CAD-based method for building the comprehensive FDTD model of vehicle and antenna is proposed. According to the electromagnetic simulation model, the vehicle belongs to three-dimensional (3-D) structure and the antenna belongs to thin-wire structure. The CAD model is made up of objects composed of triangular surfaces. The corresponding FDTD model is generated from every object of CAD model by ray-tracing method. According to the geometric characteristics of contiguous grids of FDTD model, the 3-D structure and thin wire structure are distinguished. The 3-D structure is associated with the difference formula of the corresponding material, and the thin wire structure is associated with the contour-path thin-wire model. Then the multi-structure FDTD calculation model is constructed. Taking a vehicle antenna HEMP coupling as an example, the effectiveness of a vehicle antenna comprehensive FDTD model based on CAD model is verified by comparing with the results of CST software. The modeling method presented in this paper can provide reference for the construction of high-precision FDTD model with monopole antenna.

Low-energy electrons emitted from self-powered neutron detectors(SPNDs) typically induce the space charge effect, attributed to the intrinsically high resistivity of insulator materials. As a pivotal phenomenon in SPND theoretical simulations, this effect directly impacts both the prediction accuracy of the response current and the overall reliability of the detector design. In this work, a calculation model dedicated to the SPND space charge effect based on the charge conservation principle is proposed. The nonlinear correlation between the potential distribution and the charge deposition rate of the insulator is established by analyzing the electron deposition-discharge equilibrium process under the internal electric field. Furthermore, the coupling between conductivity and the electric field is achieved, and the equilibrium time of the space charge effect is theoretically analyzed. The numerical method is validated through a series of experiments. The influence of the space charge effect on detector response current under various radiation fields is quantitatively evaluated by simulating the charge deposition process. In the central vertical hole experiment with multiple measurement points, this model reduces the maximum relative deviation of theoretical calculations to 5.82%. Moreover, the effectiveness of the proposed method is verified under both research reactor experimental conditions and rapid power variation processes. Compared with the measured values from the JSI TRIGA Mark II reactor, the relative deviation of the response current amounts to 6.97%, while the deviation of the current components is limited to within 0.7%.

In this paper, a vertical x-ray detector was fabricated using high-resistivity Fe-doped beta-gallium oxide (β-Ga2O3) material, and the x-ray response current–voltage characteristics were measured over a temperature range from 300 to 450 K. The dark current of the detector exhibited different slopes with bias voltage on a double-logarithmic scale, consistent with the space-charge-limited current (SCLC) mechanism at 300 K. This phenomenon resulted from the accumulation of space charge, arising from the capture and regulation of injected carriers. Under x-ray illumination, the nonequilibrium carriers generated by the x-ray were captured and trapped, thereby generating space charge and leading to space-charge-limited photocurrent (SCLP) during the x-ray response process. In this case, the output net current of the Fe-doped β-Ga2O3 x-ray detector showed non-monotonic temperature dependence. Initially, as the temperature increased, the net output current decreased, likely due to increased carrier thermal generation and the influence of traps within the material. Notably, the output net current began to rise above a threshold temperature, indicating enhanced performance at higher temperatures. This enhancement was caused by the release of trapped carriers, which enabled more free carriers to participate in SCLP transport, leading to a stronger response. However, at 450 K, the dark current increased rapidly, and thermally activated carriers dominated, rendering the SCLC mechanism ineffective. This phenomenon highlights the complex interplay between the thermal activation of carriers and the space-charge-limited mechanism in the high-resistivity, compensated monocrystal β-Ga2O3-based x-ray detector under x-ray illumination at elevated temperatures.

In path planning for 3D off-road environments, efficiently generating paths that satisfy relative slope constraints has long been a persistent challenge. Traditional algorithms, restricted by the limited adjacent directions in Regular Grids (DEM) or Triangulated Irregular Networks (TIN), not only struggle to produce slope-compliant paths in steep terrain but also frequently result in low-quality paths due to data redundancy or unnecessary detours. To address this issue, this study proposes a cross-node connection method based on contour-constrained TIN: First, a Relax-Slope strategy is designed, leveraging the geometric properties of contour-constrained TIN to construct relaxation sequences across contour nodes, enabling rapid identification of cross-node paths that meet relative slope thresholds. Simultaneously, an enhanced TIN network structure is built to explicitly store contour association information, supporting efficient computations. On this basis, the RS-A* embedded improved algorithm is proposed to realize cross-node path planning on TIN. Experimental verification shows that the proposed algorithm significantly outperforms traditional algorithms in path length and planning efficiency under relative slope constraints, indicating that this research effectively breaks through direction limitations and efficiency bottlenecks, and can plan off-road paths more aligned with real maneuver characteristics, thus providing a reliable path planning solution for scenarios such as military operations and emergency responses in complex terrain.