邻频干扰对跳频GMSK接收机的性能影响分析

在考虑跳频系统中系统用户数、可用频点数、信道参数和环境噪声因素的条件下,重点研究邻频干扰(ACI)对跳频系统典型GMSK接收机误码率(BER)性能的影响。研究了GMSK非相干平方律接收结构和包络检波接收结构,通过分析接收信号经过各接收单元的变化,得出判决信号的解析表达式;通过分析判决信号的概率密度函数和特征函数,推导得出跳频系统在ACI影响下的系统BER公式。仿真结果表明,该理论能够评估ACI对跳频系统典型GMSK接收机的BER性能影响。     

临空高超声速飞行器目标特性分析

临空高超声速飞行器经过几十年的发展,已经从概念原理探索阶段进入到成果应用阶段,其军事潜力和作战效能日益凸显。主要以美军高超声速无人飞行器、空天飞机和高超声速巡航导弹为研究对象,从临空高超声速飞行器的运动特性、电磁特性和红外特性3个方面展开论述,同时结合典型目标进行建模仿真分析;着重探讨了目标特性对未来作战性能的影响。临空高超声速飞行器目标特性的分析研究,为新型防空体系的构建提供了参考,为未来探测跟踪拦截此类目标奠定了基础。     

二维超声速空气引射器启动特性试验研究

xxxx超声速引射器是高空模拟试车台的重要组件,在发动机启动前利用引射器对试验舱预抽真空可避免发动机启动初始时刻燃气漏入试验舱造成燃气在发动机中分离,对获取发动机在高空环境下的完整推力特性具有重要意义。而该工况下超声速引射器的启动过程是引射器工作过程中最为恶劣的工况,设计不合理的引射器会导致启动压力过高甚至不能实现启动。建立了缩比超声速空气引射器试验台对超声速引射器的启动特性进行研究,采用压力测量方法结合纹影技术对超声速引射器处于极限启动压比时的流场进行了描述,研究结果表明混合室收缩比越小,引射器极限启动压比越低。同时给出了定位超声速引射器不启动原因的判据：当引射器不启动是由引射总压不足引起时,盲腔压力在引射总压提高时降低,并在临界启动状态下达到最小值;而由混合室收缩比过小导致的引射器不启动在引射总压提高时盲腔压力单调上升。     

Defence and firm performance in the UK

The UK Ministry of Defence is British industry's largest single customer and a number of firms and industries are highly dependent on defence sales. Various hypotheses have been proposed about the impact of defence procurement on firms and these are investigated using four performance indicators: financial structure, investment, productivity and profitability. With regard to the borrowing ratio, capital investment and the rate of return, there is no statistically significant difference between the mean financial ratios for low and high dependence firms. However, non‐dependents appear to have a higher level and rate of growth of labour productivity than dependents.     

位置随动系统动态性能自动检测研究

通过分析某型位置随动系统的组成和动态技术指标,提出了位置随动系统动态性能自动检测的设计方案和测试方法,利用信号仿真模块和基于DSP的高速数据采集与处理模块,建立了自动检测的硬件电路和软件结构,确定了测试位置随动系统的动态性能指标、测试方法和软件功能,实现了对某型位置随动系统动态性能的自动检测．     

月壤参数对月面着陆气囊缓冲性能的影响

为研究月壤参数对气囊缓冲性能的影响,根据“嫦娥三号”的着陆工况设计了月面着陆气囊,并基于可压溃泡沫模型建立了考虑月壤特性的气囊缓冲动力学模型。对不同月壤下气囊的缓冲过程进行分析,发现月壤越软有效载荷冲击加速度越小,但气囊会陷入月壤中,不利于对外排气,影响其缓冲效果。因此,采用气囊峰值压力、有效载荷最大加速度和最大下落高度3个指标对气囊缓冲性能进行综合评价,定量研究了月壤参数的影响规律。结果表明:月壤密度、剪切模量及屈服参数a₀和a₁对缓冲性能的影响较大,且对前两个指标为正影响,对后一个指标为负影响。进一步研究发现,这4个月壤参数与3个缓冲性能指标之间〖BHDWG8,WK10YQ,DK1*2,WK1*2D〗〖XCZX.TIF;%129%129〗听语音 聊科研与作者互动 均为指数函数关系。     

Thermal hazard assessment of TKX-50-based melt-cast explosive

In the present study, thermal hazards of TNT and DNAN used as the molten binder in TKX-50-based melt-cast explosives were comparatively studied through accelerating rate calorimeter (ARC) and Cook-off experiments. Two kinds of ARC operation modes were performed to investigate the thermal safety performance under adiabatic conditions (HWS mode) and constant heating (CHR mode). The obtained results demonstrated that at both heating modes, DNAN/TKX-50 outperformed TNT/TKX-50 from the thermal safety point of view. However, the sensitivity to heat of the samples was reverse because of the different heating modes. In addition, the results of thermal hazard assessment obtained from the cook-off experiment complied with ARC analysis which indicated the molten binder TNT replaced by DNAN would reduce the hazard of the TKX-50 melt cast explosive. Furthermore, the results of cook-off experiments also showed that DNAN/TKX-50 outperformed TNT/TKX-50 from the aspect of thermal stability, which was consistent with the result of CHR mode because of the similar heating process.     

节点实时性能自适应的集群资源分配算法

由于配置和所运行作业的不同,集群各节点的实时性能差异较大。为提高集群性能,提出节点实时性能自适应的集群资源分配算法 (node real-time performance adaptive cluster resource scheduling algorithm,NPARSA)。节点实时性能用其配置(CPU核数及速度、内存容量、磁盘容量)和实时状态参数(CPU、内存和磁盘的剩余数量及磁盘读写速度)表示。NPARSA根据作业类型自主选择节点性能评价指标的权值,实现节点实时性能对于作业类型的自适应。实时性能最优的节点分配给作业。虚拟机实验和物理集群实验表明,与Spark默认资源分配算法、没有考虑作业类型与节点匹配的算法、使用作业和节点匹配差异程度作为资源分配依据的算法相比,NPARSA能更有效地缩短作业执行时间、提高集群性能。     

Analysis on damage characteristics and detonation performance of solid rocket engine charge subjected to jet

To further explore the damage characteristics and impact response of the shaped charge to the solid rocket engine (SRE) in storage or transportation, protective armor was designed and the shelled charges model (SCM)/SRE with protective armor impacting by shaped charge tests were conducted. Air overpressures at 5 locations and axial acceleration caused by the explosion were measured, and the experimental results were compared with two air overpressure curves of propellant detonation obtained by related scholars. Afterwards, the finite element software AUTODYN was used to simulate the SCM impacted process and SRE detonation results. The penetration process and the formation cause of damage were analyzed. The detonation performance of TNT, reference propellant, and the propellant used in this experiment was compared. The axial acceleration caused by the explosion was also analyzed. By comprehensive comparison, the energy released by the detonation of this propellant is larger, and the HMX or Al particles contained in this propellant are more than the reference propellant, with a TNT equivalent of 1.168–1.196. Finally, advanced protection armor suggestions were proposed based on the theory of woven fabric rubber composite armor (WFRCA).     

定常态不可逆卡诺热机面积特性

对定常态不可逆卡诺热机进行了有限时间热力学分析.定义了功率、效率和面积比系数,并导出三者的关系式,由此对热机最佳功率、效率和面积特性进行了分析和讨论,给出了一些有益的结论.