军用嵌入式操作系统安全性增强措施

操作系统是紧靠硬件的基础软件,它既是应用软件安全的坚实基础,又是硬件不安全因素的屏蔽器.在操作系统安全隐患和嵌入式操作系统技术特点的基础上,提出信息保护、空间域保护和时间域保护等增强操作系统安全性的几种方法,以提高嵌入式系统抗击系统本身缺陷或敌方恶意攻击等安全威胁的能力.上述几种安全保护技术已在嵌入式Linux中进行验证,并取得满意的结果.     

Solution algorithms for the parallel replacement problem under economy of scale

We consider the parallel replacement problem in which machine investment costs exhibit economy of scale which is modeled through associating both fixed and variable costs with machine investment costs. Both finite- and infinite-horizon cases are investigated. Under the three assumptions made in the literature on the problem parameters, we show that the finite-horizon problem with time-varying parameters is equivalent to a shortest path problem and hence can be solved very efficiently, and give a very simple and fast algorithm for the infinite-horizon problem with time-invariant parameters. For the general finite-horizon problem without any assumption on the problem parameters, we formulate it as a zero-one integer program and propose an algorithm for solving it exactly based on Benders' decomposition. Computational results show that this solution algorithm is efficient, i.e., it is capable of solving large scale problems within a reasonable cpu time, and robust, i.e., the number of iterations needed to solve a problem does not increase quickly with the problem size. © 1998 John Wiley & Sons, Inc. Naval Research Logistics 45: 279–295, 1998     

Pairwise model discrimination with applications in lifetime distributions and degradation processes

Reliability data obtained from life tests and degradation tests have been extensively used for purposes such as estimating product reliability and predicting warranty costs. When there is more than one candidate model, an important task is to discriminate between the models. In the literature, the model discrimination was often treated as a hypothesis test and a pairwise model discrimination procedure was carried out. Because the null distribution of the test statistic is unavailable in most cases, the large sample approximation and the bootstrap were frequently used to find the acceptance region of the test. Although these two methods are asymptotically accurate, their performance in terms of size and power is not satisfactory in small sample size. To enhance the small‐sample performance, we propose a new method to approximate the null distribution, which builds on the idea of generalized pivots. Conventionally, the generalized pivots were often used for interval estimation of a certain parameter or function of parameters in presence of nuisance parameters. In this study, we further extend the idea of generalized pivots to find the acceptance region of the model discrimination test. Through extensive simulations, we show that the proposed method performs better than the existing methods in discriminating between two lifetime distributions or two degradation models over a wide range of sample sizes. Two real examples are used to illustrate the proposed methods.     

多输入多输出雷达恒模稳健波形联合优化算法

针对目标冲激响应及杂波冲激响应分布特性先验知识不准确导致的多输入多输出雷达检测性能下降的问题,提出恒模稳健波形与接收机滤波器联合优化算法。将目标冲激响应及杂波冲激响应分布特性先验知识不准确时的优化问题建模为一个极大极小化问题。运用迭代优化算法将联合优化问题分解为两个子优化步骤:将波形固定时的接收机滤波器权值优化问题建模为广义瑞利商模型,求解得到相应的接收机滤波器权值矢量;利用半正定松弛技术对权值固定时的波形优化问题进行求解,获得对应的波形矩阵,并根据得到的波形矩阵,通过高斯随机化的方法获得所需的恒模波形。对所提算法的收敛性进行了证明,仿真结果表明所提算法有效。     

俄罗斯应对导航战举措

卫星导航系统作为重要的战场传感器,已经成为现代战争不可或缺的重要组成部分,围绕卫星导航系统的攻防博弈由此兴起。针对美国首先提出的导航战概念,俄罗斯为进一步提升导航战作战实力,有针对性地采取了应对举措。文章介绍了导航战概念及相关作战案例,具体分析了俄罗斯应对导航战威胁的主要举措,并结合美俄围绕导航战开展的攻防博弈,得出掌握现代战争制导航权的改进方向。     

系统频率偏差对同时全极化测量的影响及其校准

目标极化散射矩阵的精确测量是全极化雷达极化信息处理的前提和基础。基于正负线性调频信号,针对采用数字解线性调频处理的同时全极化测量体制雷达,分别推导了雷达中频频率偏差和采样频率偏差对同时全极化测量影响的数学模型,提出一种雷达中频频偏和采样频偏的联合估计与校准方法。仿真和实测数据表明：雷达系统频率稳定度会引起不同通道极化测量结果峰值位置和相对相位的变化,采用所提方法能够有效校正峰值偏移,补偿相位误差,提高目标极化散射矩阵测量的精度。     

反电动势对无扰载荷航天器精确定向的影响

无扰载荷航天器中非接触式作动器反电动势会引起有效载荷模块与支持模块之间的耦合,影响有效载荷模块的精确定向性能。通过建立无扰载荷航天器的耦合动力学模型,分析非接触式作动器反电动势对有效载荷模块精确定向性能的影响。考虑六支杆立方构型无扰载荷接口,结合拉格朗日方程和牛顿欧拉方法建立有效载荷模块平台动力学模型。推导非接触式作动器的输出力模型,并引入有效载荷模块平台动力学模型,给出考虑非接触式作动器反电动势的耦合动力学模型。将支持模块上飞轮动静不平衡引起的谐振作为干扰力矩,建立了无扰载荷航天器在轨定向状态的Simulink仿真模型。仿真结果表明,反电动势系数越大,干扰力矩对有效载荷模块的影响越大,有效载荷模块精确定向精度越低。     

炸药装药在压剪加载下的起爆特点

进行了两类压剪加载实验：（１）利用石英的平面正碰撞产生压剪加载的实验,采用电磁质速法测试装药试件内部不同质点的运动情况,分析炸药装药中发生化学反应的可能性;（２）在压剪炮上采用平行倾斜碰撞产生压剪加载的实验,观测炸药装药爆炸的可能性。由实验可以看出：在亚爆轰状态的压缩加载应力条件下,剪切的联合作用对炸药的起爆起到敏化作用,适当比例的压剪加载造成更加敏感的炸药起爆响应。文中给出了起爆响应规律和响应机制的实验分析。     

The conditional p-center problem in the plane

An algorithm is given for the conditional p-center problem, namely, the optimal location of one or more additional facilities in a region with given demand points and one or more preexisting facilities. The solution dealt with here involves the minimax criterion and Euclidean distances in two-dimensional space. The method used is a generalization to the present conditional case of a relaxation method previously developed for the unconditional p-center problems. Interestingly, its worst-case complexity is identical to that of the unconditional version, and in practice, the conditional algorithm is more efficient. Some test problems with up to 200 demand points have been solved. © 1993 John Wiley & Sons, Inc.     

微机上运行的多功能仿真语言GASP/PC

文中介绍了IRM-PC机上多功能仿真软件GASP/PC的开发,叙述了GASP/PC仿真语言的形成以及对于连续、离散和复合仿真模型的GASP/PC语言的结构与仿真方法。