关闭部分导航信号阻止区域授时对全球定位授时性能的影响分析

在导航战中,在区域范围内阻止对手使用授时服务可通过关闭战区目标点的所有可见卫星信号来实现.以关闭部分导航信号阻止区域授时服务为例,描述了阻止区域授时服务的导航信号关闭仿真流程,提出了定位授时性能评估方法,并就关f闭部分导航信号阻止区域授时服务对全球定位服务和授时服务产生的影响进行了分析讨论.仿真结果表明,关闭部分导航信...     

结合像素局部对比度的直线特征检测算法

鲁棒高效的直线提取算法在空间目标位姿估计、跟踪、骨架重建等领域有广泛的应用。提出基于像素局部对比度和全局虚警抑制的直线段检测算法。算法分为四步:第一步,计算像素点的梯度以及局部对比度;第二步,将方向大致相同的像素点分成直线支撑区域(像素方向为像素梯度方向的顺时针垂直方向),并对支撑区域进行矩形近似;第三步,在直线支撑区域内拟合直线段,计算直线参数;第四步,根据直线支撑区域信息验证直线段,抑制虚警。实验测试结果表明:该算法在复杂条件下,特别是光照影响条件下,具有更好的鲁棒性和效率。     

基于局域模板的STAP非均匀检测器

分析了STAP(Space Time Adaptive Processing)中强干扰目标影响传统非均匀检测器性能的机理,针对强干扰目标引起的非均匀检测器性能下降和传统自适应功率剩余(APR)方法运算量大的问题,提出了一种基于局域模板的非均匀检测器(Local Template NHD,LT-NHD)。该方法不需要进行协方差矩阵求逆的耗时运算,便能获得较高的运算效率;此外,其检测不易受训练样本中的强目标样本影响,能获得比传统方法更为鲁棒的检测性能。实测数据实验验证了本文方法的有效性。     

爆炸冲击作用下加筋板结构变形研究

为了预报加筋板结构在爆炸冲击载荷作用下的变形程度,将加筋板的变形分为整体变形和局部变形,借助数值计算拟合了两者能量分配关系,进而提出了爆炸冲击作用下加筋板结构变形的理论计算方法,并与实验结果进行比较,结果吻合较好。     

Why internal conflict deteriorates state capacity? Evidence from Colombian municipalities

Previous work has documented a negative correlation between internal conflict and state capacity. We attempt to shed light on mechanisms that underlie this relationship, using data for Colombian municipalities. We rely on identifying heterogeneous effects of different types of violent events on state capacity, taking advantage of variability across municipalities in the prevalence of specific manifestations of conflict and their intensity. Our findings suggest that events making civilians feel targeted affect the state’s capacity to collect taxes, while those reflecting a stronger military capacity of illegal armies, in particular their large-scale attacks, affect the state’s capacity to provide public goods.     

舰船复合材料局部结构细节设计方法

由于复合材料结构具有各向异性、组份复杂、可设计变量多等特性,有效的复合材料结构设计应同时考虑整体结构宏观设计和局部结构细节设计,两者虽密切关联,但在分析方法上存在一定差异。对此,将整体结构简化分析与局部结构细节设计联系起来,重点针对局部结构细节设计方法进行探讨,提出了一种细节设计方法。该方法基于子模型与试验工况模型的对比分析,通过局部结构试件试验对整体结构承载特性进行了综合评价。以某型船复合材料甲板室结构设计为例,通过整体简化模型优化分析确定板架构件尺度参量和铺层设计方案;提取典型局部结构承载形变特征要求,并基于子模型分析技术探讨局部结构细节设计;最后,以局部结构试验验证与考核完成整体结构的优化设计。计算结果表明:该方法能在有效控制设计成本的同时,合理开展复合材料结构设计工作,可供研究和设计者参考。     

一类具有时滞的病毒动力学模型分析

研究一类具有时滞的病毒动力学模型。研究了系统解的有界性;讨论了各个非负平衡点的局部稳定性,应用比较定理得到了各非负平衡点全局渐近稳定的充分条件。     

Is South Africa's 20 years of democracy in crisis? Examining the impact of unrest incidents in local protests in the post-apartheid South Africa

This article assesses South Africa's 20 years of democracy, which has frequently been bedevilled by local protests. This article is particularly interested in those unrest incidents that have been distinct for one reason or another. In South Africa, the surge in local unrest incidents is often linked to police behaviour, which has become increasingly militant and brutal when quelling protests. While the right to protest is constitutional, the damage caused during protest action can be immense owing to acts of violence. Protestors' resorting to violent protest action is often linked to increased frustrations as a result of the government's inability to live up to the expectations of marginalised and poor communities. While this article draws primarily on existing scholarly debates focusing on social protests, the primary objective is to examine the impact of unrest incidents on local protests in post-apartheid South Africa. The article further argues that ‘spaces’ for participation in local governance should be created so that citizens can become architects of development and their own future.     

Lorentz序列空间光滑性

给出了Lorentz序列空间光滑性的判据,论证了当P>1时d(w,p)是局部光滑的。     

特殊半鞅的强大数定律

利用特殊半鞅的收敛定理和一般形式的Kronecker引理,给出了特殊半鞅和非负特殊半鞅强大数定律的一般形式,推广和完善了已有的结果.