内压圆筒大开孔结构补强设计与应力分析

根据整体补强和厚壁接管补强2种型式,为内压圆筒大开孔结构确定满足结构和工艺要求的圆筒壁厚和3种规格接管壁厚。采用压力面积法和ASME规范对该大开孔结构进行强度校核,并运用有限元分析法进行结构的应力分析和数字模拟,比较不同壁厚接管的补强效果,从而确定容器的结构尺寸。设备实际运行结果表明:该结构强度满足工作要求。     

改进的遗传算法在图像边缘提取中的应用

提出了一种改进的遗传算法,采取了确定性采样选择算子对选择算子进行了改进;明确了非等概率融合单阈值单点交叉算子,对交叉算子进行了改进;同时还提出了一种新的变异算子,它依据一种新的判断群体"集中"与否的准则,根据群体的进化程度自适应地调整变异概率pm的值。将改进的遗传算法用于图像的边缘提取问题中,试验结果表明,与穷尽法和普通遗传算法相比,提出的算法在保证有效地提取出边缘的基础上,节省了运算时间。     

“This program will not be a threat to them”: Ballistic Missile Defense and US relations with Russia and China

Although the Obama Administration has differed from its predecessor in a number of respects, on the specific issue of Ballistic Missile Defense (BMD), there is a striking continuity. The Obama Administration has remained committed to the BMD project, even as it has modified the schedule of deployments and prioritized different systems from the Bush Administration. Significantly, this has led to Chinese and Russian balancing in the nuclear sphere. As a result, there is evidence of a security dilemma-type dynamics in US relations with China and Russia. At present, there is no study that analyzes Russian and Chinese hard internal balancing against the USA in the sphere of missile defense during the Obama Administration. This article fills this gap.     

一种模拟退火伪并行遗传算法

借鉴模拟退火算法的局部搜索能力,结合并行计算的思想设计了一种采用模拟退火机制的实数编码自适应交叉、全概率变异伪并行遗传算法,最后用这种方法对典型的多峰值函数求极值,并和基本遗传算法进行比较,结果表明:该算法具有较强的全局搜索能力和局部搜索能力,能够更有效地克服早熟收敛问题。     

The crisis of American military assistance: strategic dithering and Fabergé Egg armies

ABSTRACT

The United States has provided substantial amounts of military assistance and aid since the end of World War Two. During the Cold War, it proved vital in protecting numerous regimes from communist takeovers. Successful outcomes occurred when American leaders made large initial aid commitments, and the states had the capacity and political willpower to use it effectively. However, Vietnam was an example of how U.S. support lagged, as leaders in Saigon preferred political survival instead of creating regime legitimacy. Following 9/11, American security aid focused on making weak countries develop stronger security forces. Unfortunately, this created Fabergé egg militaries: expensive and easily broken by insurgents. This article suggests long-term strategic commitments need to be made alongside more resources for the American State Department and similar organizations to focus on the politics of state-building. Finally, this article suggests strategies, such as “whole-of-government” approaches, to improve long-term security and political institution building.     

基于输入特性分析的光电跟踪内模控制设计

内模控制是一种基于对象教学模型进行控制器设计的新型控制策略,其设计思路是将对象模型与实际对象相并联,控制器逼近模型的动态逆.根据内模控制原理及光电跟踪系统参考输入及扰动输入特性,设计了一种新型位置控制器.并分析了IMC跟踪控制器的零稳念偏差及抗干扰性能.从仿真结果看,与常规PID控制相比,内模控制器参数调整简单、跟踪性能良好.特别是在针对目标突然机动的情况下.IMC控制器具有良好的稳态误差重构能力,即能迅速收敛到稳态误差.根据仿真结果数据统计,系统跟踪误差的均方根可减小到0.5 tarad,表明该控制器能够提高系统的跟踪精度,为高性能光电跟踪系统提供了一种新的控制策略.