PWM型串联开关稳压电源的隔离测控

本文研究运用MCS—51系列单片机对战术导弹性能综合测试系统的电源系统实施隔离测控的办法,阐述了其电路的工作原理,并对测试精度进行了分析。     

采用RLS算法的功率倒置阵列的性能

为解决功率倒置阵列采用LMS算法时收敛速度和稳态失调误差不能兼顾的缺点,提出了采用RLS算法实现功率倒置阵列的方法。仿真结果表明,功率倒置阵列采用RLS算法和LMS算法都能达到较好的抗干扰效果。和LMS算法相比,RLS算法同时具有收敛速度快和稳态失调误差小的优点,代价是计算量增大。     

超高斯随机振动环境的疲劳强化机理

针对可靠性强化试验的全轴随机振动环境的超高斯幅值分布特性开展其疲劳强化机理研究。首先通过理论分析表明RS机振动激励下试件应力仍保持超高斯分布,然后证明了同等量级下的超高斯分布比高斯分布随机应力具有更高的疲劳强化效能,从而揭示RS机全轴随机振动环境超高斯幅值分布特性的疲劳强化机理。     

近地卫星Ka频段数传链路抗雨衰自适应模式设计

针对近地卫星数传时的信道时变性和严重的Ka频段雨衰现象,采用自适应编码调制(Adaptive Coding and Modulation, ACM)技术能够充分利用链路资源,相对于传统的固定编码调制方式,进一步提高链路的数据吞吐量。提出近地卫星Ka频段数传链路ACM模式设计方法,在降雨环境下建立Ka频段数传链路模型,根据链路预算的信道状况确定ACM选用模式;采用基于导频符号的最大似然信噪比估计算法结合移动平均的平滑方法实现信道估计,有效地减小了估计值的波动。仿真结果表明,无论晴天还是雨天,采用提出的卫星数传链路ACM模式设计方法,能够在保证系统可靠性的同时获取较高的数据吞吐量。     

Insurgent courts in civil wars: the three pathways of (trans)formation in today’s Syria (2012–2017)

As part of research on the meso-foundations of conflict, the field of ‘rebel governance’ examines political institutions that regulate the affairs of civilians in wartime as well as their relations with armed actors. Judicial institutions play an important role in this and research has shown that they are widespread among both historical and current insurgencies. However, usually these bodies have been analysed in the context of one hegemonic faction like the Tamil Tigers in Sri Lanka and the Afghan Taliban. What is missing so far is an analysis of different pathways of (trans)formation of rebel courts. As exemplified by the three case studies of judicial institutions in Eastern Ghouta, Idlib and Aleppo, these are shaped by the distribution of power between ‘same-side’ groups, yielding unipolar, bipolar, or multipolar constellations. The analysis is located on the meso or movement level of insurgent social structures, complementing research on the micro and macro levels.     

Classical geopolitics,realism and the balance of power theory

Since the end of World War II, classical geopolitics as a particular form of realism has been disengaged from the development of mainstream realist theories. This disengagement has not only concealed the value of classical geopolitics as a framework of analysis for policy and strategy, but also created an increasing rift between theory and policy in contemporary realist theories. This paper seeks to reengage classical geopolitics with mainstream realist theories by clarifying its realist traits and analytical characteristics, (re)stating its core propositions and probing into its potential contribution to the development of mainstream realist theories. This paper contends that classical geopolitics, while having a distinctive pedigree, can arguably be considered an integral part of the family of realist theories in view of its basic theoretical assumptions concerning international anarchy, the unit of analysis and power politics. As a framework of analysis, classical geopolitics incorporates three interrelated strategic propositions. Those three propositions not only constitute the theoretical core of classical geopolitics, but also manifest a peculiar balance-of-power conception that is essentially distinct from those proposed by mainstream realist theories. This paper argues that those three propositions combined promise to fill in prominent lacuna in the balance-of-power research programme, and also have significant implications for contemporary world politics.     

基于故障树分析的航空装备体系结构贡献率评估方法

针对航空装备体系构成复杂的特点,将故障树分析引入航空装备体系结构贡献率评估问题,提出基于故障树分析的评估方法.从作战装备、信息支援装备和保障装备三个方面构建航空装备体系结构,建造航空装备体系结构故障树;采用底事件的关键重要度指标来计算航空装备的体系结构贡献率,建立基于关键重要度的航空装备体系结构贡献率评估模型;以某航空...     

Tripwires and free-riders: Do forward-deployed U.S. troops reduce the willingness of host-country citizens to fight for their country?

This article investigates the relationship between U.S. overseas troops and the willingness of the citizens of host states to fight for their country. The study joins the long-running debate about burden-sharing and free-riding among U.S. allies. Unlike most previous empirical studies, we focus on non-material or intangible measures of the underlying concepts. Our dependent variable estimates the proportion of citizens expressing a willingness to fight for their country. Scores at the aggregate-national as well as the individual level are shaped by the presence of U.S. military forces, which act as a “tripwire” signaling credible security commitments. This increases opportunities of (non-material) free-riding. We present both bivariate and multivariate analyses covering the period 1981–2014 to test this supposition. Findings indicate that once U.S. troop levels reach a certain threshold (between 100 and 500 troops), citizens’ willingness to fight drops significantly. This likely reflects non-material free-riding.     

酚醛-石英混杂纤维增强苯并噁嗪复合材料高温失效特征

通过模压工艺制备了酚醛-石英混织纤维增强苯并噁嗪复合材料(P-Q/BZ)试样,考察了其力学性能、烧蚀性能和耐冲刷性能,分析了该试样在高温环境中的主要失效特征,研究其在高温环境中的适用性。结果表明,未经热处理的P-Q/BZ试样平均弯曲强度、弯曲模量和层间剪切强度分别为283 MPa、10.8 GPa和22.6 MPa;经300℃,N_2处理15 min后,试样均匀膨胀,厚度增加22%,弯曲强度、弯曲模量和层间剪切强度分别下降58%、41%和58%;在氧乙炔焰的平均质量烧蚀率和线烧蚀率分别为0.048 4 g/s和-0.081 mm/s,烧蚀后试样宏观不分层,表面炭层微观分层严重,酚醛纤维热解炭、树脂基体热解炭、熔融石英纤维以及碳硅氧化产物相互分离;该试样耐冲刷能力差,在发动机尾焰烧蚀平台模拟的热-力耦合环境中的质量损失率高达59%。P-Q/BZ复合材料需要解决热解膨胀问题,进一步提高抗冲刷性能。     

通道失配对GNSS阵列抗干扰性能的影响分析

卫星导航接收机极易受到电磁干扰的影响,基于阵列接收机的空时(频)抗干扰技术被证明是目前最有效的抗干扰手段。在工程实现时,阵列通道存在通道失配,本文以统计性能的评估方法评估了通道失配对阵列抗干扰性能的影响。研究结果表明,通道间群时延偏差和幅度失配是导致阵列抗干扰性能下降的主要因素,前者可通过增加空时滤波器阶数来消除影响,而后者对空时滤波器阶数不敏感,需要进行必要的校正。