一类非线性脉冲时滞抛物型偏微分方程组解的振动性

讨论了一类含脉冲的时滞抛物型方程组非零解的振动性,利用了Green定理以及Jensen不等式,得出了该方程在Robin边界条件下非零解振动的若干准则。     

基于核函数的自适应聚类背景提取

随着目标的检测与跟踪的广泛应用,移动物体分割问题成为研究热点,而解决这类问题的关键需为对图像背景的更新和提取。通过对目前已有的背景提取方法的研究,提出了一种新的基于核函数的背景提取方法:进行预处理,制定删选法则来自适应获取所需处理的视频序列;定义核函数来衡量模式间相似性,对2类聚类中心进行初始化;利用最小距离准则来灰度归并,采取实时的自适应阈值选择;最后通过比较满足条件的像素总数,获取所需背景。实验证明,该方法有效。     

Blast resistance evaluation of urban utility tunnel reinforced with BFRP bars

To improve corrosion-resistance of shallow-buried concrete urban utility tunnels(UUTs),basalt fiber reinforced polymer(BFRP)bars are applied to reinforce UUTs.As the UUT must have excellent survival capability under accidental explosions,a shallow-buried BFRP bars reinforced UUT(BBRU)was designed and constructed.Repetitive blast experiments were carried out on this BBRU.Dynamic responses,damage evolutions and failure styles of the BBRU under repetitive explosions were revealed.The tunnel roof is the most vulnerable component and longitudinal cracks develop along the tunnel.When the scaled distance is larger than 1.10 m/kg1/3,no cracks are observed in the experiments.When the BBRU is severely damaged,there are five cracks forming and developing along the roof.The roof is simplified as a clamped-supported one-way slab,proved by the observation that the maximum strain of the transverse bar is much larger than that of the longitudinal bar.Dynamic responses of the roof slab are predicted by dynamic Euler beam theory,which can consistently predict the roof displacement under large-scaled-distance explosion.Compared with the UUT reinforced with steel bars,the BBRU has advantages in blast resistance with smaller deflections and more evenly-distributed cracks when the scaled distance is smaller than 1.260 m/kg1/3 and the steel bars enter plastic state.Longer elastic defamation of the BFRP bars endows the UUT more excellent blast resistance under small-scaled-distance explosions.     

基于双光频梳及受激布里渊散射的微波频率测量

提出了一种基于双光频梳和受激布里渊散射的高精度微波频率测量方法,利用两个双平行马赫-曾德尔调制器将待测微波信号和扫描信号调制在两路光频梳上,并分别作为信号光和泵浦光输入色散位移光纤中。利用双光频梳和不断频移的扫描信号,系统可同时实现波分复用和时分复用。同时,在双光频梳和受激布里渊散射的作用下,系统可发生一系列的受激布里渊散射,通过测量各信道输出的光功率实现待测微波频率的测量。为进一步提升测量精度,利用测量得到的光功率值构建幅度比较函数,从而实现频率测量误差修正。通过实验仿真验证了所提方法的有效性,测量误差为±2.5 MHz。     

India’s nuclear counter-revolution: nuclear learning and the future of deterrence

ABSTRACT

The India–Pakistan near war of February–March 2019 highlights India’s ongoing evolution in strategic thought and practice since its emergence in 1998 as an overt nuclear-weapon possessor. These changes, involving an increasing willingness to engage in the intentional escalation of conflict with a nuclear-armed rival willing to be the first to use nuclear weapons, challenge certain academic assumptions about the behavior of nuclear-weapon states. In particular, they undermine the expectations of the nuclear-revolution theory—which anticipates nuclear and conventional restraint among nuclear-armed rivals through fear of mutual assured destruction—and the model of nuclear learning which underpins this theory, in which new nuclear-weapon states gradually absorb this restraint through policy-maker learning. This article explores how India’s learning pathway since 1998 has deviated from these expectations. India is instead pursuing its own “revolution,” in the direction of creating capabilities for flexible response and escalation dominance. It concludes by illuminating the similarities between Indian strategic behavior and contemporary practices of other nuclear-armed states, and suggests that New Delhi’s emerging de facto nuclear doctrine and posture is part of a broader empirical challenge to our current conceptions of the nuclear revolution and of nuclear learning.     

程控交换机硬件系统建模研究

底层功能实现模块是程控交换机多媒体仿真训练系统通用设计平台的关键部分。硬件配置是交换机工作的基础 ,是底层功能实现模块的重要组成部分。该文介绍了交换机硬件系统的建模 ,利用两种典型机型硬件实际的工作情况 ,解释并验证了所建立的通用功能流程图 ,并介绍了参数接口的管理与应用