Jianhong Hao

Neutral beams are considered a competitive technology for space junk disposal. To prepare neutral beams using solid targets, in this study, a particle-in-cell with Monte Carlo collisions (PIC-MCCs) calculation model is constructed to simulate the neutralization of negative hydrogen ions using gaseous carbon target with solid-equivalent density instead of solid carbon foils. The transmission of negative hydrogen ions through the gaseous carbon target is simulated, and three main collision reactions are considered: single-electron stripping of negative hydrogen ions to form hydrogen atoms, further stripping of hydrogen atoms to form protons, and double-electron stripping of negative hydrogen ions to directly form protons. In addition, changes in particle composition (negative hydrogen ions, hydrogen atoms, and protons) during beam transmission are analyzed as a function of target thickness. The PIC-MCC simulation results are consistent with theoretical calculations and experimental data, verifying the feasibility of using gaseous carbon instead of solid carbon foils to simulate anion neutralization. On this basis, the model was used to calculate the neutralization efficiency and electron-stripping efficiency of negative hydrogen ions at different energies. The results indicate that the electron-stripping efficiency increases progressively with increasing target thickness Meanwhile, the neutralization efficiency increases rapidly to a maximum value and then decreases gradually. The maximum neutralization efficiency for hydrogen ions is approximately 55% and remains unaffected by the negative hydrogen ion energy. Nevertheless, higher beam energy requires greater optimal target thickness. To achieve high neutralization efficiency, the required target thickness for an 800-MeV beam is approximately in the range of 30– $68~\mu $ g/cm².

During electron beam sounding experiments, the emission of electron beam pulses can result in a continuous increase in spacecraft potential, impeding the normal emission of subsequent pulses. Plasma contactors can mitigate the increase in spacecraft potential through “ion emission”, but whether they are effective in addressing the active charging effect of high-current electron beam pulses remains uncertain. This paper employs the PIC method to explore the ion sheath occurring on the contactor emitting surface after increasing the electron beam current, along with its influence on spacecraft potential. A key emphasis is placed on contrasting the intrinsic connection between the contactor characteristic parameters and spacecraft potential variation during continuous emission and pulse emission with different pulse widths. Ultimately, an analysis is conducted on the variation of optimal contactor characteristic parameters with changes in the beam current. The research findings of this paper indicate that suppressing the pulse active charging effect necessitates thorough consideration of the impact of the contactor electron quantity on the ion sheath. Reducing the electron beam pulse width while correspondingly adjusting the contactor pre-emission time and current can effectively prolong the stable emission duration of electron beam pulses.

This paper introduces an Enhanced-Dueling Deep Q-Network (EDDQN) specifically designed to bolster the physical security of electric power substations. We model the intricate substation security challenge as a Markov Decision Process (MDP), segmenting the facility into three zones, each with potential normal, suspicious, or attacked states. The EDDQN agent learns to strategically select security actions, aiming for optimal threat prevention while minimizing disruptive errors and false alarms. This methodology integrates Double DQN for stable learning, Prioritized Experience Replay (PER) to accelerate the learning process, and a sophisticated neural network architecture tailored to the complexities of multi-zone substation environments. Empirical evaluation using synthetic data derived from historical incident patterns demonstrates the significant advantages of EDDQN over other standard DQN variations, yielding an average reward of 7.5, a threat prevention success rate of 91.1%, and a notably low false alarm rate of 0.5%. The learned action policy exhibits a proactive security posture, establishing EDDQN as a promising and reliable intelligent solution for enhancing the physical resilience of power substations against evolving threats. This research directly addresses the critical need for adaptable and intelligent security mechanisms within the electric power infrastructure.

This study develops a high-performance polypropylene (PP) substrate platform by optimizing micro/macrostructures and introduces an efficient catalyst. Key findings include: (1) microstructural analysis identifies ash content impurities (>20 ppm) as triggers for partial discharge-induced insulation failure. PP molecular weights (10⁵–10⁶) with narrower distributions enhance mechanical strength, while functional groups (-CH₂/-CH₃) show no structural variations across samples. (2) Macroscopically, mixed α-β crystal interfaces increase insulation failure risks, necessitating single-crystalline structures. Higher temperatures reduce dielectric constants but increase losses, requiring environmental consideration. Crystallinity positively correlates with DC breakdown strength (443.31 kV/mm at 54.13% crystallinity). (3) Among three endo-donor catalysts, the internal electron donor 3-based catalyst achieved optimal die-test activity (47.7 kg PP/g cat·h). With 20 mL triethylamine, the catalyst reduced PP ash content by 42.1%, narrowed molecular weight distribution by 31.6%, and increased crystallinity by 8.74%. These results establish microstructure–property relationships for PP capacitors and provide technical guidelines for performance enhancement. The work addresses current limitations in PP evaluation methods and offers a practical strategy for manufacturing high-insulation PP materials through structural control and catalytic optimization.

In a complex space environment, high-energy ions can cause radiation damage effects on MOSFETs, leading to functional errors and even permanent damage. This study uses the finite element method to establish floating-body MOSFETs with bulk silicon, PDSOI, and FDSOI structures, comparing the single particle upset effects of different MOSFET structures. It examines the impact of heavy ion parameters and voltage bias on transient drain current using PDSOI MOSFETs as a research object, presenting the damage variation laws of MOSFETs in radiation environments. The results show that under heavy ion irradiation, spatial charge distributions in the three MOSFETs are similar, but there are significant differences in static potential and transient drain current. For PDSOI MOSFETs, vertically incident heavy ions cause the earliest and largest transient drain current peaks, resulting in the most severe damage. With increasing LET and penetration depth, the transient drain current pulse exhibits two peaks, and the amplitude of the second peak increases with LET and penetration depth. Increasing the drain bias voltage affects the charge collection process, resulting in a longer drain current tail.

Ensuring the physical security of electric power substations is crucial for maintaining a reliable supply of electricity. The increasing prevalence of physical threats, such as physical attacks, vandalism, sabotage, etc., on electric power substations worldwide has resulted in widespread power outages. To enhance physical security in light of these high-impact, low-probability events, this paper proposes a physical security threat assessment approach to evaluate and enhance substation security against physical attacks utilizing the Substation Criticality Index (SCI) and the Threat–Vulnerability–Consequences Index (TVCI) on risk-based security-constrained economic dispatch. The primary objective is to provide power utilities with actionable insights to proactively strengthen their defenses within budgetary constraints by considering the criticality level of each substation. By incorporating social, economic, and electrical factors, this study simulated a physical attack (specifically a bus-isolating attack), on an IEEE 39-bus test system, and evaluated the resultant consequences and load loss. Upon computation of the SCI, substations are ordered according to their criticality, and computing the TVCI gives the risk of each substation which is used to obtain an optimized physical security investment based on substation vulnerability and the consequences of attacks. Thus, based on these results, decisions for prioritizing substation physical security and investments for hardening physical security are made. Furthermore, the experimentation showed that with the physical security investment, the overall TVCI score has significantly decreased with certain budgetary constant.

Satellite-to-ground terahertz communication is limited by the power of signal source and antenna gain level, and has large path loss, which is difficult to implement. In this paper, a feasible scheme of satellite-to-ground terahertz communication using High Altitude Platforms (HAPs) as relay is presented, and the path loss on terahertz communication links is modeled and analyzed. Combined with the path loss model, the transmission loss along HAP-to-ground paths under different seasons and complex weather environment in Ali, Tibet, China is calculated. The results show that the transmission characteristics of terahertz waves in winter and summer are significantly different, mainly reflected in the number and bandwidth of usable atmospheric windows. Furthermore, the additional attenuation caused by the typical sand dust and ice cloud environment on terahertz band can reach 6.1 dB and 1.9 dB at the maximum respectively. With the aid of high gain antenna, the usable communication frequencies of the HAP-to-ground links in winter are significantly more than those in summer. When the transmitting and receiving antenna gain is 40 dBi respectively, the usable communication frequency can reach 1.35 THz in winter, while it is limited to less than 1 THz in summer, up to 0.493 THz.

In this paper, polypropylene (PP) film samples were obtained at different stretching ratios. The dielectric properties of PP samples were studied. The crystal morphology and orientation degree of the materials were characterized. The findings indicate that the PP film sample with the stretching ratio 5 × 5 has the lowest conductivity and the highest breakdown strength. Moreover, the effect mechanism of the stretching ratio on the dielectric properties of PP films was explored. A reasonable stretching ratio can make the molecular chains of PP aligned, form an orderly crystalline morphology, and improve the crystallinity. When the stretching ratio is too high, the orientation degree of PP will decrease and the spherulite structure will be destroyed, leading to a decrease in dielectric properties. The research results can serve as a reference for improving the dielectric properties of PP films.

Electric power substations, as critical components of modern power grids, are increasingly becoming targets for intentional physical attacks, including vandalism, theft, and sabotage. These threats, coupled with the potential for cyber-attacks and the weaponization of technologies, necessitate robust security measures and comprehensive auditing practices. Despite utilities providers’ focus on understanding grid vulnerability and implementing physical security upgrades, there is a recognized gap in evaluating the effectiveness and long-term usability of these measures. This paper addresses the need for regular security audits to identify vulnerabilities and ensure the overall resilience of substations against evolving threats. The rationale behind this study is to propose a conventional auditing method that includes an auditing framework, checklists, inspections, and post-inspection suggestions. Through the systematic identification and addressing of vulnerabilities via security auditing, the framework aims to significantly enhance the resilience of substations against physical threats. This paper provides a comprehensive guideline for the physical security auditing procedure, which is essential for the reliable operation of the power grid.

With the large-scale development of distributed energy on the demand side, the trend of “supply exceeding demand” has gradually become prominent, and regional peer-to-peer (P2P) energy trading has become an important measure to improve the local consumption of distributed energy. However, most existing studies usually assume that prosumers behave entirely rationally with the goal of maximum benefit, which has been proved to deviate from the observed actual behaviors. Aiming at the optimal energy of prosumers participating in the P2P market, a prospect theory-based two-stage stochastic optimization model considering the bounded rationality was proposed to accurately simulate the decision-making behavior. Then, a benefit maximization model for the energy trading service provider (ETSP) was constructed considering the power flow constraint to ensure the safe operation of the system. Finally, an improved R-ADMM algorithm considering timeout was proposed to solve the above model and improve the convergence speed. The effectiveness of the proposed model and algorithm was verified via simulation.