Petri网模型代码映射研究

为了简化仿真系统的实现过程,分析总结了Petri网到程序代码的映射准则,从Petri网的基本元素和关系入手,根据逻辑关系建立映射的三类原子语句,并通过两种合成方式形成分子语句。以原型Petri网为例,遍历可达标识图的各种分支路径,提出循环路径到循环结构语句的代码映射方法。最后给出了带抑制弧的扩展Petri网和受控Petri网的代码映射方案,为Petri网向程序代码的转换提供了理论依据。     

Effect of Ca on microstructure and high temperature creep properties of AM60-1Ce alloy

A series of AM60-1Ce-xCa(x=0, 0.5, 1.5, 2.5) magnesium alloys were prepared by gravity casting method and analyzed by means of XRD, DSC and SEM. The effects of Ca on normal temperature mechanical properties and high temperature creep behavior of alloys were characterized by tensile and constant creep test.Microstructure analysis indicated that Ca was preferentially combined with Al in the alloy to form the high melting point Al_2Ca phase at the grain boundary. The addition of Ca can refine the crystal grains and reduces the content of β-Mg_(17)Al_(12) phase. With the increase of Ca content in the alloy, Al_2Ca phases at the grain boundary gradually changed to the network of lamellar structure, and replaced the β-Mg_(17)Al_(12) phase as the main strengthening phase gradually. The creep resistance of the alloy continuously increases because the high-temperature stable phase Al_2Ca firmly nailed at grain boundaries impedes the sliding of grain boundaries. However, when the addition of Ca was more than 1.5%, mechanical properties of the alloy started to decrease, which was probably due to the large amount of irregularly shaped Al_2Ca phases at the grain boundary. Experimental results show that the optimal addition amount of Ca is 1.5 wt.%.     

水雷武器安全保险系统可靠性评估探讨

可靠性是水雷武器完成预定作战任务的有力保障,尤其对于水雷武器安全保险系统这种结构、运行模式复杂的子系统,保证其达到可靠性指标尤为重要。评估可靠性的方法是可靠性研究的关键,尝试对其可靠性的评估方法进行了探讨,并结合某型水雷实例作出具体分析。     

Multiphase Nb–TiCo alloys: The significant impact of surface corrosion on the structural stability and hydrogen permeation behaviour

Multiphase Nb_xTi_(100-x)/2Co_(100-x)/2 (x = 30–60) alloys are a promising material for hydrogen separating membranes. These alloy membranes exhibit a rapid decline in hydrogen permeation flux within ∼12 h when operated at 773 K. To address this issue, a dense oxide (e.g. Nb₂O₅, TiO₂ and CoO) layer was prepared between a Pd coating layer and an Nb–TiCo substrate by surface corrosion for improving their thermal stability, and the corrosion resistance of Nb–TiCo alloys was investigated. An increase in the Nb content (x) lowers the corrosion resistance of these alloys, but makes it easier to form the above oxide layer. Substantial enhancement of hydrogen permeability and thermal stability at 773 K was observed for the alloys (x = 30 and 40) after corrosion, which can be ascribed to an increase in hydrogen diffusivity. This improved permeability and stability are closely related to the formation of the above surface oxide layer that impeded interdiffusion between the Pd film and Nb–TiCo substrates. This study demonstrates that insertion of a diffusion barrier between the Pd and Nb-based substrates by surface corrosion is a viable approach to enhance the high-temperature stability of Pd-coated Nb–TiCo alloys, an aspect not widely explored in Nb-based hydrogen separation and purification membranes.     

Effect of Pd overlayer and mixed gases on hydrogen permeation of Pd/Nb30Hf35Co35/Pd composite membranes

Effect of Pd overlayer and mixed gases on hydrogen permeation of Pd/Nb₃₀Hf₃₅Co₃₅/Pd composite membranes was investigated. The diameter of Pd particle increases with increasing sputtering power. With this change, the membrane shows a signification reduction in hydrogen permeability/or flux, but its durability and stability increases significantly, which can be mainly attributed to a decrease in hydrogen solubility coefficient. In addition, H₂S impurity in mixed gases can greatly degrade membrane performance, especially the hydrogen permeability, whereas the Ar impurity content has less effect in the temperature range of 523–673 K. Lowering of permeability caused by the change of gas purity can be attributed to a decrease in hydrogen solubility, which is closely related to the stronger adsorption of H₂S molecules to the Pd overlayer of the membrane. Thus, it is concluded that aside from the optimum design for composition of Nb-based hydrogen permeable alloy to improve their permeability, the control of Pd overlayer film on membrane surface and gas purity in the feed gas is important.     

装备仿真软件开发平台的分析与设计

首先分析了当前装备仿真软件开发面临的主要问题,深入探讨了装备仿真软件的逻辑组成,以此对装备仿真软件开发平台进行功能定位,设计了开发平台的体系结构,阐述了各主要组成部分的功能和实现方法,总结了该平台的技术特点。     

一种新的MPSK信号特征提取方法

针对MPSK信号的识别问题,提出了一种依据基带信号相位空间聚类提取码元序列的方法。基带信号相位空间聚类是宏观特征,对参数估计精度要求不高,受噪声影响较小,与传统依据参数估计提取码元序列的方法相比,不需要进行码元速率估计和码元对准,是一种简单有效的码元序列提取方法。仿真实验证明了该方法的有效性。     

基于特征分析的军用电子装备仿真训练软件开发环境建模

针对军用电子装备仿真训练软件目前开发中存在的复用率不高、开发效率低等问题,采用领域特征分析的方法,对该类软件的开发领域进行了服务、功能、行为三个层次的活动分析,并建立了该领域仿真对象管理、仿真模型驱动、运行支撑管理等服务的特征模型。实践证明,以此特征模型作为输入建立的集成开发环境,能够较好地解决该领域内软件开发过程中存在的构件重用问题,同时能使软件系统的开发效率得到显著提高。     

平面变换技术脉冲分选自动实现方法

平面变换技术是一种非常有效的脉冲分选方法,其关键技术包括在显示平面上的特征曲线搜索和特征曲线识别。对于特征曲线搜索,传统依靠人工的做法不但费时费力还限制了脉冲分选的自动实现;而对于特征曲线识别,目前只有定性的描述而没有具体的方法。为了克服人工搜索特征曲线的缺点并实现特征曲线有效识别,本文分析了平面变换后脉冲点的特征,设计了特征曲线的自动搜索方法,给出了特征曲线的识别方法。特征曲线的自动搜索方法适用于直线和曲线的自动搜索,且不依赖于初始脉冲点的选择,特征曲线的识别方法实用有效,最终实现了脉冲分选自动进行。仿真实验说明了方法的有效性。