园区网上的网络应用

介绍了网络的应用方式,并综合运用各种应用方式实现《海军工程学院学报》的网络发布．这对于充分运用网络资源,提高应用系统开发的灵活性与实用性具有实际意义．     

气相苯加氢低Ni/改性Al2O3催化剂性能评价

通过对γ－Ａｌ２Ｏ３载体进行化学改性处理,把Ｎｉ的含量降低（在５％以内）制得气相苯加氢低Ｎｉ／改性Ａｌ２Ｏ３催化剂。考察反应条件对其催化活性影响,并对催化剂的活性稳定性、耐热性、抗毒物能力进行评价。结果表明：该催化剂的性能良好     

基于热力学第二定律的直喷式柴油机性能分析

这项研究的目的是发展用热力学第二定律分析柴油机在不同运行工况性能的能力.研究是针对一台12150L型柴油机进行的,以发动机气缸内部压缩、燃烧、膨胀、瞬时传热和换气过程的理论模拟模型为基础,应用热力学第二定律分析,度量各种能量品质的优劣和不可逆损失值,并且与热力学第一定律的能量平衡进行了比较.分别改变循环喷油量、燃烧开始角、燃烧持续期及燃烧品质指数.研究了参数变化对缸内可用能和热力学第一定律效率和第二定律效率的影响.     

液氢液氧火箭发动机稳态数值仿真与故障分析

根据发动机工作的物理过程建立了大型液氢液氧火箭发动机稳态故障的数学模型,数学模型包含了70个工作参数和45个干扰因素,采用了布罗伊登法求解。确立了各种故障的正确仿真机制,对计算结果进行了分析,并与试车结果相比较,吻合良好。     

CLIENT／SERVER环境下的通用数据库开发工具POWERBUILDER

从面向对象的程序设计的角度,剖析了ＣＬＩＥＮＴ／ＳＥＲＶＥＲ环境下的通用数据库开发工具ＰＯＷＥＲＢＵＩＬＤＥＲ（ＰＢ）的特点、基本结构及其开发数据库应用系统的方法。     

网际间进程通信与客户-服务器的实现

TCP/IP协议簇是一个实际上的网际协议标准,4BSD UNIX操作系统提供了网际间通信的socket机制,以解决应用程序与TCP/IP软件的接口,客户-服务器模型已成为网际环境下的程序设计的实际标准模式。较详细分析了客户-服务器模型的原理,socket编程机制的系统调用,并给出了基于socket系统调用的客户服务器模型实现的方法。     

基于CZT算法的水声扩频多普勒匹配方法

阐述了基于DS/SS(直接序列扩频)的高分辨率扩频自导声纳系统的一种多普勒匹配方法。通过理论分析和仿真计算,证明基于CZT多普勒频偏匹配算法可以在极低信噪比条件下有效估计多普勒频偏和目标速度。     

Kinetic responses to global terrorism: Lessons from Africa

This essay recalls the immediate and longer-term responses of the US and its allies to the events of 9/11. It contends that the die for contemporary developments in transnational terrorism was cast in the immediate aftermath of 9/11 – in particular the launching of sustained ‘anti-terrorist’ military combat operations in Afghanistan and Iraq, and more covert ‘kinetic’ operations elsewhere in the Middle East and Africa. The essay seeks specifically to expose the counter-productivity of using military operations as the primary antidote to transnational terrorism. Focusing on the African ‘laboratory’ and the spread of transnational terrorism and Islamic militancy, particularly in West and East Africa, the essay concludes that radical Islamists have mastered the ‘battle of the narrative’ and that the Western penchant for dispensing a kinetic brand of medication is feeding rather than fighting the virus of global terrorism.     

GNSS接收机离散化处理对解扩性能的影响

建立扩频信号防混叠滤波、采样、量化与解扩输出关系的数学解析模型,推导得到解扩输出信噪比的解析表达式。分析与仿真表明,当量化位数大于等于4 bit,解扩得到总的信噪比损失可以分解为由量化引起的损失和滤波加采样引起损失的乘积,且量化器最优限幅系数只与量化位数相关;当量化位数小于4 bit时,信噪比损失在一定条件下可近似为量化损失和滤波加采样损失的乘积。当量化位数大于4 bit、滤波器带宽大于5倍码率、采样频率大于4倍码率时,再增大上述参数引起的信噪比损失波动小于0.05 dB,对解扩性能提升不明显。该结论可为实用型全球导航卫星系统接收机前端离散化处理优化设计提供理论指导。     

Combined variance reduction techniques in fully sequential selection procedures

In the past several decades, many ranking‐and‐selection (R&S) procedures have been developed to select the best simulated system with the largest (or smallest) mean performance measure from a finite number of alternatives. A major issue to address in these R&S problems is to balance the trade‐off between the effectiveness (ie, making a correct selection with a high probability) and the efficiency (ie, using a small total number of observations). In this paper, we take a frequentist's point of view by setting a predetermined probability of correct selection while trying to reduce the total sample size, that is, to improve the efficiency but also maintain the effectiveness. In particular, in order to achieve this goal, we investigate combining various variance reduction techniques into the fully sequential framework, resulting in different R&S procedures with either finite‐time or asymptotic statistical validity. Extensive numerical experiments show great improvement in the efficiency of our proposed procedures as compared with several existing procedures.