高动态GNSS信号多普勒模拟任意阶直接数字合成器设计

为高精度模拟高动态条件下GNSS信号的多普勒特性,提出一种任意阶直接数字合成信号合成器的设计方法。设计任意阶直接数字合成信号合成器的结构;通过理论分析,推导各级累加器相位初值的计算公式;给出字长选择方法。经仿真验证,该方法能精确模拟GNSS信号的多普勒特性。此外,提出的直接数字合成器设计方法不受阶数的限制,可普遍应用于各类信号模拟器的设计。     

基于并行模拟的多核集群系统性能预测和分析

针对多核集群系统所表现出的新的性能特征,提出了面向多核集群系统消息传递应用程序的并行模拟模型并设计、实现了一个并行模拟器MCPSim(Multi-core Cluster Parallel Simulator),MCPSim在功能模型和性能模型上体现了片内核间、结点内片间以及结点间等三个层次上消息通信的特点,同时支持对应用的消息数量、通信量等的百分比分布的profiling功能,采用PRIMEJ、acobi3D、NPB IS以及HPL等Benchmark程序对MCPSim进行了测试,结果表明MCPSim性能预测的精度优于BigSim,同时能够广泛应用于针对多核集群系统消息传递应用程序的性能分析中。     

高层公寓建筑防火设计探讨

高层公寓的火灾特点不同于普通的高层住宅，其火灾危险性高于普通住宅。分析了高层公寓的火灾特点，并从消防车作业面、安全疏散、防火分隔、防排烟、灭火设施、内装修等方面提出了高层公寓防火设计应注意的问题。     

大椭圆停泊轨道月球探测器发射窗口运动学约束特性分析及转移轨道快速设计方法

通过分析大椭圆停泊轨道月球探测器发射窗口的运动学约束特性,给出了转移轨道运动学约束对发射窗口的影响规律,进一步明确了在该种情况下月球探测器的发射机会和增加窗口的可能性.并结合发射窗口运动学约束特性,提出了一种基于大椭圆停泊轨道的地月转移轨道快速设计方法.仿真结果验证了大椭圆停泊轨道下探测器发射窗口运动学约束特性分析的正确性,以及转移轨道设计方法的有效性.     

二维超声速空气引射器启动特性试验研究

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。     

RTI测试研究

运行支撑系统(RTI)作为应用高层体系结构(HLA)进行分布仿真的支撑系统,是实现HLA的核心。RTI的功能和性能直接关系到HLA仿真系统开发与应用的成败。首先阐述了RTI测试的内容和指标,接着结合例子详细研究了RTI测试的方法,最后对RTI测试研究进行了总结,为提高基于HLA的分布交互仿真系统的质量及可信度提供了基础。     

Effect of wave shaper on reactive materials jet formation and its penetration performance

Wave shaper effect on formation behavior and penetration performance of reactive liner shaped charge (RLSC) are investigated by experiments and simulations. The reactive materials liner with a density of 2.3 g/cm³ is fabricated by cold pressing at a pressure of 300 MPa and sintering at a temperature of 380 °C. Experiments of the RLSC with and without wave shaper against steel plates are carried out at standoffs of 0.5, 1.0, and 1.5 CD (charge diameter), respectively. The experimental results show that the penetration depths and structural damage effects of steel plates decrease with increasing the standoff, while the penetration depths and the damage effects of RLSC without wave shaper are much greater than that with wave shaper at the same standoff. To understand the unusual experimental results, numerical simulations based on AUTODYN-2D code are conducted to discuss the wave shaper effect, including the propagation behavior of detonation wave, the velocity and temperature distribution of reactive jet, and penetration depth of reactive jet. The simulations indicate that, compared with RLSC without wave shaper, there is a higher temperature produced inside reactive jet with wave shaper. This unusual temperature rise effects are likely to be an important mechanism to cause the initiation delay time of reactive jet to decline, which results in significantly decreasing its penetration performance.     

顶置武器站性能评估方法

在评估指标体系和虚拟样机仿真测试评估数据的基础上,对顶置武器站性能评估进行研究。对评估方法进行研究,提出了适合顶置武器站性能评估特点的灰色模糊综合评估法,选用灰色关联度分析计算指标权重,建立开放性的隶属矩阵,最终建立顶置武器站性能评估模型。通过实例评估表明该评估模型准确可靠。     

Estimating failure time distribution and its parameters based on intermediate data from a Wiener degradation model

Instead of measuring a Wiener degradation or performance process at predetermined time points to track degradation or performance of a product for estimating its lifetime, we propose to obtain the first‐passage times of the process over certain nonfailure thresholds. Based on only these intermediate data, we obtain the uniformly minimum variance unbiased estimator and uniformly most accurate confidence interval for the mean lifetime. For estimating the lifetime distribution function, we propose a modified maximum likelihood estimator and a new estimator and prove that, by increasing the sample size of the intermediate data, these estimators and the above‐mentioned estimator of the mean lifetime can achieve the same levels of accuracy as the estimators assuming one has failure times. Thus, our method of using only intermediate data is useful for highly reliable products when their failure times are difficult to obtain. Furthermore, we show that the proposed new estimator of the lifetime distribution function is more accurate than the standard and modified maximum likelihood estimators. We also obtain approximate confidence intervals for the lifetime distribution function and its percentiles. Finally, we use light‐emitting diodes as an example to illustrate our method and demonstrate how to validate the Wiener assumption during the testing. © 2008 Wiley Periodicals, Inc. Naval Research Logistics, 2008     

硅整流无刷发电机供电系统动态性能的研究

分析了坦克的供电系统中采用硅整流无刷发电机时的工作特点,建立了这种系统的数学模型,举例说明了计算方法,并在文章的最后进行了评价.