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。     

氯酸钾对不锈钢在硫酸和盐酸混合溶液中的缓蚀行为

研究了缓蚀剂ＫＣｌＯ３在７０％Ｈ２ＳＯ４和０．２％ＨＣｌ溶液中对１８—８不锈钢的缓蚀行为。运用线性极化技术测定了缓蚀剂的缓蚀效率为９６％。动电位极化曲线、循环极化曲线及交流阻抗的测量表明,缓蚀剂ＫＣｌＯ３是一种阳极钝化型缓蚀剂,添加缓蚀剂ＫＣｌＯ３后,不锈钢表面氧化膜进一步加强,从而有效地抑制不锈钢的均匀腐蚀和孔蚀。     

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。     

光学表面的分形特点与模拟表征算法

根据光学表面在微观结构呈现出的自相似性,利用尺度无关的分形模型描述了其结构特征;采用结构函数法对抛光表面的分形维数进行计算,分析了粗糙度参数RMS值、误差波长、测量尺度、采样长度和采样点数对分形维数的影响规律。在此基础上,提出了采用一阶自回归分形模型对抛光表面进行模拟的新方法,分析了界定尺度、模型参数对分形特征和分形维数的影响规律。利用分形维数描述光学表面的微观结构具有评价方法简单、在一定范围内与测量尺度无关等优点。     

India nuclear weapons: No first use or no full disclosure?

This article argues India is laying the foundation to move away from “no-first-use” (NFU) as its nuclear weapons employment policy. Since the inception of its nuclear weapons program, India has claimed NFU as the centerpiece of its nuclear strategy. But India has a history of developing foundational changes to its nuclear weapons program before such changes actually occur. For example, the infrastructure of India’s nuclear weapons program was already being created in the 1950s under the guise of civilian nuclear power. Similarly, the weaponization of India’s program, which did not officially occur until after the 1998 tests, had its genesis in far earlier decisions. A close examination of trends in India’s nuclear weapons production complex, its delivery systems, and its command and control complex all lead to the conclusion that India is laying the groundwork for more flexible employment options, up to and including first use. This article does not argue such a decision has been taken. Rather, it argues the underpinning is in place to allow for a move to more flexible options, perhaps very quickly, at some point in the future. This could occur during crisis or it could occur incrementally over time.     

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.     

L(0,1)模态导波在小管径管道弯头处的散射特性

采用实验和有限元模拟的方法研究了L(0,1)模态导波在小管径管道弯头处的模态转换和反射、透射特性,分别使用不同频率的激励信号对含不同弯曲半径弯头的管道进行检测。研究结果表明:L(0,1)模态导波在管道弯头处发生模态转换,转换成F(1,1)模态,并且其偏振方向与弯头拱背—拱腹方向一致;随着检测频率和弯曲半径的增大,反射F(1,1)模态呈减小趋势,透射F(1,1)模态呈非单调变化趋势;反射L(0,1)模态导波呈减小趋势,透射L(0,1)模态导波呈增大趋势;当检测频率或弯曲半径增大到一定程度时,两参数的变化对反射F(1,1)模态、反射L(0,1)模态和透射L(0,1)模态的影响不大。实验结果与模拟结果吻合度高,验证了模拟结果的正确性。研究结论为检测小管径含弯头管道提供了理论指导。     

重力梯度对超大柔性空间结构在轨动力学特性的影响

空间太阳能电站是一种具有超大和高柔性特征的空间结构,这种空间结构在尺寸上远超以往的航天器,给轨道动力学特性的研究带来了新现象与新问题。以千米量级的哑铃模型为研究对象,考虑重力梯度影响,建立了Hamilton体系下的在轨动力学模型,利用辛龙格库塔法得到了不同参数取值下的动力学响应。通过对比仿真结果,得到了结构尺寸与重力梯度对轨道运动、姿态运动影响的定量关系。仿真结果表明,重力梯度引起了姿态-柔性振动耦合现象,姿态运动影响了结构振动曲线外部包络线样式,而柔性振动改变了姿态运动周期。     

多阶段任务系统可靠性分析的二元决策图模型

为了实现计算机自动生成多阶段任务系统的二元决策图可靠性模型,提出了二元决策图可靠性建模的通用方法。定义了嵌套的二元决策图数据结构BDD_Element,给出了二元决策图模型的描述和存储方法,提出了与门、或门和k/n表决门向二元决策图模型的自动转化算法。给出了建立多阶段任务系统二元决策图可靠性模型的2个步骤:基于逻辑门转化算法,将部件逻辑关系结构函数转化为阶段二元决策图模型;基于二元决策图布尔操作规则整合阶段二元决策图模型。卫星姿态调整任务的可靠性分析表明:该方法可以有效应用于多阶段任务系统的可靠性分析。