基于小波包分解和样本熵的电磁干扰分析方法

为了定量分析不同状态下电磁环境的变化,并有效提取电磁环境变化的干扰特征,提出了基于小波包分解和样本熵的电磁干扰分析方法.首先,时电磁环境的样本信号进行小波包分解,然后分别计算分解后备频带信号的能量谱系数和样本熵,通过能量谱系数和样本熵这两个指标的对比,综合判断电磁环境是否发生变化.仿真分析表明:样本熵可以弥补能量谱系数...     

采用包络检波去除SISAR直达波干扰的新方法

为了去除直达波干扰,从强的直达波干扰背景中有效提取SISAR侧影成像的目标全息信号,提出了对接收的含有目标全息信号和强直达波的混合信号直接进行包络检波,然后通过对检波后的输出进行时域的正交分解,恢复目标的全息信号的新方法.仿真结果验证了理论分析的正确性.     

子空间分解与淘汰优化方法

提出一种新的多学科设计优化方法,即子空间分解与淘汰优化方法.该方法通过子空间的分解和淘汰,提高剩余子空间的近似模型精度,基于子空间近似模型优化获取最优解.首先,基于设计空间近似模型获取最优解,如果近似模型达到满意精度,则终止优化;否则将设计空间分解为多个子空间.然后,各子空间基于近似模型优化,如果子空间没有可能获得优于...     

Recent advances in catalytic combustion of AP-based composite solid propellants

Composite solid propellants (CSPs) have widely been used as main energy source for propelling the rockets in both space and military applications. Internal ballistic parameters of rockets like characteristic exhaust velocity, specific impulse, thrust, burning rate etc., are measured to assess and control the performance of rocket motors. The burn rate of solid propellants has been considered as most vital parameter for design of solid rocket motors to meet specific mission requirements. The burning rate of solid propellants can be tailored by using different constituents, extent of oxidizer loading and its particle size and more commonly by incorporating suitable combustion catalysts. Various metal oxides (MOs), complexes, metal powders and metal alloys have shown positive catalytic behaviour during the com-bustion of CSPs. These are usually solid-state catalysts that play multiple roles in combustion of CSPs such as reduction in activation energy, enhancement of rate of reaction, modification of sequences in reaction-phase, influence on condensed-phase combustion and participation in combustion process in gas-phase reactions. The application of nanoscale catalysts in CSPs has increased considerably in recent past due to their superior catalytic properties as compared to their bulk-sized counterparts. A large surface-to-volume ratio and quantum size effect of nanocatalysts are considered to be plausible reasons for improving the combustion characteristics of propellants. Several efforts have been made to produce nanoscale combustion catalysts for advanced propellant formulations to improve their energetics. The work done so far is largely scattered. In this review, an effort has been made to introduce various combustion catalysts having at least a metallic entity. Recent developments of nanoscale combustion catalysts with their specific merits are discussed. The combustion chemistry of a typical CSP is briefly discussed for providing a better understanding on role of combustion catalysts in burning rate enhancement. Available information on different types of combustion nanocatalysts is also presented with critical comments.     

Adaptive subspace detection based on two-step dimension reduction in the underwater waveguide

In the underwater waveguide, the conventional adaptive subspace detector (ASD), derived by using the generalized likelihood ratio test (GLRT) theory, suffers from a significant degradation in detection per-formance when the samplings of training data are deficient. This paper proposes a dimension-reduced approach to alleviate this problem. The dimension reduction includes two steps: firstly, the full array is divided into several subarrays; secondly, the test data and the training data at each subarray are transformed into the modal domain from the hydrophone domain. Then the modal-domain test data and training data at each subarray are processed to formulate the subarray statistic by using the GLRT theory. The final test statistic of the dimension-reduced ASD (DR-ASD) is obtained by summing all the subarray statistics. After the dimension reduction, the unknown parameters can be estimated more accurately so the DR-ASD achieves a better detection performance than the ASD. In order to achieve the optimal detection performance, the processing gain of the DR-ASD is deduced to choose a proper number of subarrays. Simulation experiments verify the improved detection performance of the DR-ASD compared with the ASD.     

稳定正规环分解定理

提出了稳定正规环的概念；推广了正规环的分解定理；给出了正则局部环整性的一个简单证明；指出了研究正则环的一条新途径。     

非结构动网格分区并行计算方法

针对包含运动边界的非定常流动问题,基于弹簧近似法设计了一套非结构动网格分区并行计算流程,引入了METIS软件进行非结构网格二次剖分,研究了对接边界通信类型及其处理方法,基于消息传递并行编程模式实现了非结构动网格求解器的并行化。测试结果表明:该求解器具有较高的并行效率,网格变形模块对非结构动网格并行计算性能具有重要影响。     

基于协同相关度的作战任务分解优化

针对协同作战中任务分解的优化问题,构建了任务协同相关度的量化模型。对作战任务中几个基本概念进行定义,从时间、逻辑、功能3个维度对任务间的协同关系进行了形式化描述,在此基础上,建立了任务协同关系的综合度量模型。最后,通过设置任务协同度阈值的方法,对协同紧密的任务进行聚合,实现任务分解的优化。通过仿真实验验证了模型的可行性和有效性。     

Optimally scheduling interfering and non‐interfering cranes

This article treats the problem of scheduling multiple cranes processing jobs along a line, where cranes are divided into different groups and only cranes in the same group can interfere with each other. Such crane scheduling problems occur, for example, at indented berths or in container yards where double rail‐mounted gantry cranes stack containers such that cranes of the same size can interfere with each other but small cranes can pass underneath larger ones. We propose a novel algorithm based on Benders decomposition to solve this problem to optimality. In a computational study, it is shown that this algorithm solves small and medium‐sized instances and even many large instances within a few seconds or minutes. Moreover, it improves several best known solutions from the literature with regard to the simpler problem version with only one crane group. We also look into whether investment in more complicated crane configurations with multiple crane groups is actually worthwhile.