Survivability assessment of spacecraft impacted by orbit debris

To help optimize the spacecraft design and reduce the risk of spacecraft mission failure, a new approach to assess the survivability of spacecraft in orbit is presented here, including the following three steps:1) Sensitivity Analysis of spacecraft. A new sensitivity analysis method, a ray method based on virtual outer wall, is presented here. Using rays to simulate the debris cloud can effectively address the component shadowing issues. 2) Component Vulnerability analysis of spacecraft. A function"Component functional reduction degree — Component physical damage degree"is provided here to clearly describe the component functional reduction. 3) System-level Survivability Assessment of spacecraft. A new method based on expert knowledge reasoning, instead of traditional artificial failure tree method, is presented here to greatly improve the efficiency and accuracy of calculation.     

An experiment evaluating how the tiny mass eccentricities in spin-stabilized projectiles affect the position of impact points

This study investigates and quantifies some possible sources affecting the position of impact points of small caliber spin-stabilized projectiles (such as 12.7 mm bullets). A comparative experiment utilizing the control variable method was designed to figure out the influence of tiny eccentric centroids on the projectiles. The study critically analyzes data obtained from characteristic parameter measurements and precision trials. It also combines Sobol's algorithm with an artificial intelligence algorithm—Adaptive Neuro-Fuzzy Inference Systems (ANFIS)—in order to conduct global sensitivity analysis and determine which parameters were most influential. The results indicate that the impact points of projectiles with an entry angle of 0° deflected to the left to that of projectiles with an entry angle of 90°. The difference of the mean coordinates of impact points was about 12.61 cm at a target range of 200 m. Variance analysis indicated that the entry angle — i.e. the initial position of mass eccentricity — had a notable influence. After global sensitivity analysis, the significance of the effect of mass eccentricity was confirmed again and the most influential factors were determined to be the axial moment and transverse moment of inertia (Izz Iyy), the mass of a projectile (m), the distance between nose and center of mass along the symmetry axis for a projectile (Lm), and the eccentric distance of the centroid (Lr). The results imply that the control scheme by means of modifying mass center (moving mass or mass eccentricity) is promising for designing small-caliber spin-stabilized projectiles.     

Cooperative interception with fast multiple model adaptive estimation

For the case that two pursuers intercept an evasive target, the cooperative strategies and state estimation methods taken by pursuers can seriously affect the guidance accuracy for the target, which performs a bang For the case that two pursuers intercept an evasive target, the cooperative strategies and state estimation methods taken by pursuers can seriously affect the guidance accuracy for the target, which performs a bang-bang evasive maneuver with a random switching time. Combined Fast multiple model adaptive estimation (Fast MMAE) algorithm, the cooperative guidance law takes detection configuration affecting the accuracy of interception into consideration. Introduced the detection error model related to the line-of-sight (LOS) separation angle of two interceptors, an optimal cooperative guidance law solving the optimization problem is designed to modulate the LOS separation angle to reduce the estimation error and improve the interception performance. Due to the uncertainty of the target bang-bang maneuver switching time and the effective fitting of its multi-modal motion, Fast MMAE is introduced to identify its maneuver switching time and estimate the acceleration of the target to track and intercept the target accurately. The designed cooperative optimal guidance law with Fast MMAE has better estimation ability and interception performance than the traditional guidance law and estimation method via Monte Carlo simulation.     

Insensitive energetic microspheres DAAF/RDX fabricated by facile molecular self-assembly

Insensitive energetic materials are promising in the defense weapons field. However, energetic materials still suffer from great challenges and the concern about their safety limits their utilization. In this work, insensitive energetic explosive 3,3′-diamino-4,4′-azoxyfurazan/hexahydro-1,3,5-trinitro-1,3,5-triazine (DAAF/RDX) microspheres were fabricated by self-assembly method. Rod-like DAAF/RDX was prepared by mechanical ball milling for comparison. DAAF/RDX composites with different mass ratios (90:10, 80:20, and 70:30) were obtained. The morphologies and structures of as-obtained DAAF/RDX composites were characterized by scanning electron microscopy (SEM), powder x-ray diffraction (PXRD) and fourier transform infrared spectroscopy (FT-IR). The results showed that DAAF/RDX microspheres exhibited regular shaped microspheres with sizes from 0.5 to 1.2 μm. There was no crystal transition during the modification process. The thermal properties of as-obtained materials were then evaluated by differential scanning calorimetry (DSC) and materials studio software. DAAF/RDX microspheres showed an advanced decomposition peak temperature compared with rod-like DAAF/RDX. The binding energy and peak temperature values at zero β_i (T_P0) of DAAF/RDX (90:10) increased by 36.77 kJ/mol, 1.6 °C, and 58.11 kJ/mol, 12.3 °C compared to DAAF/RDX (80:20) and DAAF/RDX (70:30), indicating the better thermal stability of DAAF/RDX (90:10). The characteristic drop height (H₅₀) of DAAF/RDX (higher than 100 cm) composites was higher than that of raw RDX (25 cm), suggesting significant improvements in mechanical safety. The preparation of DAAF/RDX microspheres is promising for the desensitization of RDX and useful for the formation of other materials and future wide applications.     

Mitigation effects on the reflected overpressure of blast shock with water surrounding an explosive in a confined space

The mitigation of blast shock with water has broad application prospects. Understanding the mitigation effects on the reflected overpressure of the explosion shock with water surrounding an explosive in a confined space is of great significance for military explosives safety applications. To estimate the effects of the parameters on the reflected overpressure of blasted shock wave, a series of experiments were carried out in confined containers with spherical explosives immersed in a certain thickness of water, and numerical simulations were conducted to explore the corresponding mechanisms. The results reveal that the reflected overpressure is abnormally aggravated at a small scaled distance. This aggravation is due to the high impulse of the bulk accelerated water shell converted from the explosion. With increasing scaled distance, the energy will be gradually dissipated. The mitigation effects will appear with the dispersed water phase front impacting at a larger scaled distance, except in the case of a dense water phase state. A critical scaled distance range of 0.7—0.8 m/kg1/3 for effective mitigation was found. It is suggested that the scaled distance of space walls should be larger than the critical value for a certain water-to-explosive weight ratio range (5—20).     

基于模糊综合评判的野战输油管线部队人员绩效评估

本文探讨了野战输油管线部队人员绩效评估的原则,构建了野战输油管线部队人员绩效评估的指标体系和模糊评判模型,并给出了对某野战输油管线大队人员进行绩效评估的实例。     

程序进化器

研究用模拟进化方法进行程序设计的途径。构造了以形式文法为遗传表示的程序进化器,提出了这个进化器使用的有关算法。本文用程序进化器解决了人工蚁问题。     

美军军法官制度简介

美军的政治性工作一般由两“师”完成,一个是牧师,另一个则是随军律师。而随军律师是处理法律问题的军官的泛称,主要指的就是军法官(JudgeAdvocate)和其领导下的法律助手、律师等。2003年的伊拉克战争中,美军约有103位军法官、62名法律专职助手深入战场。①他们在拘押战犯,发表对外声明,与英军建立联合军事司法系统和提供交战规则,促使官兵遵守国际战争法、军事行动法上起了相当大的作用。一、起源与概念在美军中没有法律战的明确词汇和概念,但是这并不意味着美军不运用法律武器以达到军事目的。相反,他们相当擅长和重视这一工作,而且已有…     

对房地产策划的理性思考

随着房地产业的迅速发展,房地产策划在观念、专业化、组织、创新、协作和信息等方面存在着一些与发展不和谐的因素,通过对房地产策划的危机进行理性思考,以寻找战胜危机的可靠途径。在全面分析房地产策划危机的基础上,从贯穿市场意识、主动创造效益、强化整合功能、塑造品牌、引进管理等方面寻找形成房地产策划核心竞争力的源泉,以战胜暂时的危机。其结果证明了房地产策划仍然具有强大的生命力,暂时的危机一定能被克服。     

CAN总线在柴油机并车监控系统中的应用研究

介绍了 CAN总线的技术特点 ,以基于 CAN总线的并车监控试验系统的研制为例 ,论述了新型 CAN总线网络式监控系统的软硬件配置方案、技术实现途径及其重要意义 ,展望了 CAN总线在自动化领域的广阔发展前景 .