Defense spending and the macroeconomy

Given Kinsella's (1990, 1991) appeal for analysis to be pursued using sub‐annual level of data, we pursue such an endeavor in this paper. We examime the effect of defence spending on real output, the unemployment rate, price level, and interest rate covering a quarterly time frame 1960:1 to 1988:1 using an unrestricted vector autoregression framework. Our results parallel the findings of Kinsella in that there appears no causal relationship in either direction between defence spending and economic performance.     

基于FFT的自适应频率估计算法

为了解决FFT算法中因能量泄露和栅栏效应而导致的算法估计性能下降的问题,提出了一种基于FFT的自适应频率估计算法.分析了Rife算法,指出当信号频率位于量化频率附近时,由于插值方向错误,会导致频率估计性能下降;对于分段FFT相位差频率估计算法,当2段信号最大谱线处对应的相位相差比较大时,容易产生相位模糊,从而增大估计误差.基于FFT的自适应频率估计算法将2种算法进行了综合,既保留了2种算法的优点,又对算法性能有所改进.仿真结果表明:该算法的估计精度、稳定性和抗噪能力都有显著提高.     

基于区间数理论的空战目标威胁评估

针对空战目标威胁评估问题,提出了一种新的基于区间数理论的评估方法。在分析了现有的目标威胁评估方法中距离威胁模型存在不足的基础上,提出了改进的距离威胁模型。给出了区间数特征向量法求解威胁指标权重的计算步骤,建立了基于区间数理论的空战目标威胁评估的数学模型。最后给出了仿真算例,仿真结果表明该方法是合理和有效的。     

空投设备气囊缓冲系统的缓冲特性分析与匹配方法

采用解析分析法,根据排气口流量方程和载荷运动方程建立了无量纲的空投设备气囊缓冲过程数学模型,并根据此模型构造了气囊的匹配设计图。讨论了排气口面积、气囊高度、着陆初速度、载荷质量、气囊底面积及排气口开启压力等参数对气囊缓冲性能的影响,提出了空投设备气囊缓冲系统的参数匹配设计方法,为空投设备气囊缓冲系统的匹配设计提供了技术支持。     

Many‐player rendezvous search: Stick together or split and meet?

Rendezvous search finds the strategies that players should use in order to find one another when they are separated in a region. Previous papers have concentrated on the case where there are two players searching for one another. This paper looks at the problem when there are more than two players and concentrates on what they should do if some but not all of them meet together. It looks at two strategies—the stick together one and the split up and meet again one. This paper shows that the former is optimal among the class of strategies which require no memory and are stationary, and it gives a method of calculating the expected rendezvous time under it. However, simulation results comparing both strategies suggest that in most situations the split up and meet again strategy which requires some memory leads to faster expected rendezvous times. © 2001 John Wiley & Sons, Inc. Naval Research Logistics 48:710–721, 2001     

钢丝绳联轴器的性能试验及数学模型

对钢丝绳联轴器进行了动刚度性能实验 ,在此基础上建立了数学模型 ,并进行了参数辨识 ,指出钢丝绳联轴器具有强非线性 ,对减小轴系扭转振动具有良好的效果     

Optimal scheduling of reader—systems

We consider a reader—writer system consisting of a single server and a fixed number of jobs (or customers) belonging to two classes. Class one jobs are called readers and any number of them can be processed simultaneously. Class two jobs are called writers and they have to be processed one at a time. When a writer is being processed no other writer or readers can be processed. A fixed number of readers and writers are ready for processing at time 0. Their processing times are independent random variables. Each reader and writer has a fixed waiting cost rate. We find optimal scheduling rules that minimize the expected total waiting cost (expected total weighted flowtime). We consider both nonpreemptive and preemptive scheduling. The optimal nonpreemptive schedule is derived by a variation of the usual interchange argument, while the optimal schedule in the preemptive case is given by a Gittins index policy. These index policies continue to be optimal for systems in which new writers enter the system in a Poisson fashion. © 1998 John Wiley & Sons, Inc. Naval Research Logistics 45: 483–495, 1998