粗糙神经网络的航空电子系统故障诊断方法

提出了一种基于粗糙神经网络的航空电子系统故障诊断方法.该方法运用粗糙集理论进行知识规则的提取,用提取的规则对航空电子系统输出数据进行分类,再用神经网络对每一类进行辨识,最后用粗糙集分类结果与各个神经网络输出进行综合得到系统一步预测结果,将该预测结果与航空电子系统实际输出进行阀值比较,进而进行故障诊断.实际应用表明该方法可行并能够有效地检测系统故障,故障诊断率高.     

固体火箭发动机二次喷射控制矢量喷管流场仿真

采用基于Favre平均的三维N-S方程和k-ε湍流模型对固体火箭发动机二次喷射推力矢量喷管复杂干扰内流场进行数值模拟。空间上采用三阶精度差分格式进行求解,时间上采用隐式Jacobi点迭代方法进行迭代推进,直至流场收敛。数值模拟得到矢量喷管二次射流的激波系结构,以及复杂的主/次流干扰流动图像。二次喷射流场包含复杂的涡系结构和波系结构,还存在着边界层与激波的相互干扰、自由剪切层、激波、膨胀波和大尺寸分离。数值模拟还表明,高温燃气射流导致喷射孔附近喷管壁面处的温度相当高,需采取相应的热防护措施。     

可变形定向破片战斗部模型试验和数值模拟研究

基于可变形定向破片战斗部的作用原理,设计了试验结构模型,并对其进行了静爆试验研究。根据试验结果,建立了有限元分析模型,利用LS-DYNA程序对可变形定向战斗部变形过程以及破片的飞散过程进行了数值模拟。结果表明,在目标方向破片密度和速度都有较大幅度增益,数值模拟与试验结果比较吻合。     

Application of Markov renewal theory and semi-Markov decision processes in maintenance modeling and optimization of multi-unit systems

In this paper, a condition-based maintenance model for a multi-unit production system is proposed and analyzed using Markov renewal theory. The units of the system are subject to gradual deterioration, and the gradual deterioration process of each unit is described by a three-state continuous time homogeneous Markov chain with two working states and a failure state. The production rate of the system is influenced by the deterioration process and the demand is constant. The states of the units are observable through regular inspections and the decision to perform maintenance depends on the number of units in each state. The objective is to obtain the steady-state characteristics and the formula for the long-run average cost for the controlled system. The optimal policy is obtained using a dynamic programming algorithm. The result is validated using a semi-Markov decision process formulation and the policy iteration algorithm. Moreover, an analytical expression is obtained for the calculation of the mean time to initiate maintenance using the first passage time theory.     

OFDM系统中深度神经网络指导的IQ不平衡补偿算法

正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)是现代移动通信中一项重要的物理层通信技术,并且OFDM系统要求子载波间严格正交。然而,在实际系统中,振荡器和滤波器等器件的非理想特性会导致同相正交(In-phase and Quadrature-phase,IQ)不平衡,从而破坏子载波的正交性,严重影响OFDM系统的性能。通过研究IQ不平衡对OFDM系统的影响,提出了一种并联深度神经网络架构下的IQ不平衡补偿算法。该算法利用了深度神经网络不依赖于模型的特点,直接从接收到的频域信号恢复原输入信号的二进制序列,并利用干扰信号来自镜像子载波的先验知识来初始化模型驱动的神经网络,加快其网络优化的收敛速度。仿真结果表明,该算法能有效地补偿IQ不平衡失真,并且在幅度和相位失真的补偿上,其性能都优于传统的基于导频的最小二乘补偿算法,证明了深度学习方法解决物理层问题的优越性。     

美军作战试验与鉴定发展研究

当前,军队装备试验鉴定正由性能试验向作战试验、在役考核全领域拓展。在装备试验鉴定体系全面重塑的历史背景下,为适应军队装备试验鉴定发展新变化,探索装备试验鉴定新理论,推进装备试验鉴定自主创新发展,亟需开展装备试验鉴定技术研究。美军相对较早开展了装备试验与鉴定工作,在作战试验与鉴定工作方面已形成了较完善的法规制度体系和规范的操作流程,有较成熟的理论与方法成果可供借鉴。与此同时,美军作战试验与鉴定工作也面临许多新问题。本文剖析了美军作战试验与鉴定的内涵和管理模式,研究了2018和2019年美军作战试验与鉴定的重点技术领域,并进行了对比分析,以期掌握近期美军作战试验与鉴定工作的发展变化。     

美国陆军网络装备作战评估及启示

作战试验能有效地推动装备体系的建设发展,本文通过分析美国陆军网络集成评估与联合作战评估的作战试验特点,提出军队开展装备作战试验的几个建议。首先,总结了美国陆军网络集成评估到联合作战评估的发展演变,主要包括网络集成评估的地位和作用、网络集成评估的实施流程以及13次网络集成评估和3次作战评估的有关情况;其次,分析了网络集成评估的一系列作战试验特点,诸如实际作战需求牵引、逼真场景构建、试训一体化模式、部队战斗力的直接生成以及作战能力的军民融合式发展等;最后,提出了网络集成评估带来的若干启示,从满足实战能力需求开展作战试验、突出装备体系的互操作能力评估、探索试训结合的作战试验模式、组建专门的作战试验部队及鼓励工业部门参与作战试验等方面推动军队作战试验的发展。     

Performance evaluation and optimization design of photoelectric pyrometer detection optical system

The measurement and control of high temperature play very important roles in national defense, military, scientific experiments, industrial and agricultural production. Photoelectric pyrometer is one of the important radiation thermometers for non-contact temperature measurement. It has an important application in the field of high temperature measurement, and its performance directly affects the accuracy of temperature measurement. By improving the design of the detection optical system of the photoelectric pyrometer, the imaging performance of the photoelectric pyrometer can be improved effectively, and the temperature measurement accuracy can be improved. In this paper, the temperature measurement principle of photoelectric pyrometer, the working principle of the detection optical system and the composition of the system are introduced. The optical components that affect the imaging of the optical system of the photoelectric pyrometer are analyzed. The optical pyrometer detection optical system is simulated by ZEMAX software, based on the analysis results, the Modulation Transfer Function (MTF) and the spot Diagram are used as the main evaluation criteria to optimize the design of the objective lens of the photoelectric pyrometer detection optical system. The imaging performance of the photoelectric pyrometer detection optical system and the accuracy of temperature measurement of the photoelectric pyrometer are improved by optimization design of the detection optical system.     

Interface defeat studies of long-rod projectile impacting on ceramic targets

The interface defeat phenomenon always occurs when a long-rod projectile impacting on the ceramic target with certain velocity, i.e., the projectile is forced to flow radially on the surface of ceramic plates for a period of time without significant penetration. Interface defeat has a direct effect upon the ballistic performance of the armor piercing projectile, which is studied numerically and theoretically at present. Firstly, by modeling the projectiles and ceramic targets with the SPH (Smoothed Particle Hydrodynamics) particles and Lagrange finite elements, the systematic numerical simulations on interface defeat are performed with the commercial finite element program AUTODYN. Three different responses, i.e., complete interface defeat, dwell and direct penetration, are reproduced in different types of ceramic targets (bare, buffered, radially confined and oblique). Furthermore, by adopting the validated numerical algorithms, constitutive models and the corresponding material parameters, the influences of projectile (material, diameter, nose shape), constitutive models of ceramic (JH-1 and JH-2 models), buffer and cover plate (thickness, constraints, material), as well as the prestress acted on the target (radial and hydrostatic) on the interface defeat (transition velocity and dwell time) are systematically investigated. Finally, based on the energy conservation approach and taking the strain rate effect of ceramic material into account, a modified model for predicting the upper limit of transition velocity is proposed and validated. The present work and derived conclusions can provide helpful reference for the design and optimization of both the long-rod projectile and ceramic armor.     

An investigation on anti-impact and penetration performance of basalt fiber composites with different weave and lay-up modes

The woven basalt fiber composites (WBFC) and the unidirectional [0°/90°/45°/-45°]_s basalt fiber composites (UBFC) were prepared by hot-pressing. Three-point bending test, low velocity impact test, and ballistic test were performed to the prepared composites. After the tests, the specimens were recovered and analyzed for micromorphology. Three-point bending tests show that both the bending strength and stiffness of the WBFC surpass those of the UBFC. Low velocity impact test results show that the low velocity impact resistance to hemispherical impactor of the UBFC is higher than that of the WBFC, but the low velocity impact resistance to sharp impactor of the UBFC is lower than that of the WBFC. For the ballistic test, it can be found that the ballistic property of the UBFC is higher than that of the WBFC. After the tests, microscopic analysis of the specimens was applied, and their failure mechanism was discussed. The main failure modes of the UBFC are delamination and fibers breakage under the above loading conditions while the main failure mode of the WBFC is fibers breakage. Although delamination damage can be found in the WBFC under the above loading conditions, the degree of delamination is far less than that of the UBFC.