NCO相位截断对频域抗干扰性能影响分析

频域抗干扰易于工程实现、窄带干扰抑制性能好,是目前全球卫星导航系统(Global Navigation Satellite System,GNSS)抗干扰接收机中广泛采用的抗干扰算法。频域抗干扰接收机普遍采用数控振荡器(numerically controlled oscillator, NCO)生成本振信号。由于硬件约束,通常需要对NCO进行相位截断。而NCO相位截断是否合理对抗干扰性能影响较大。针对该问题,从NCO相位截断导致的本振杂散着手,从理论上分析其对混频和频域抗干扰环节的影响。在此基础上,给出一种NCO查找表地址位宽的理论计算模型,使得接收机的载噪比损耗接近无NCO相位截断的频域抗干扰接收机。仿真表明,抑制带宽大于100kHz、干信比小于80dBc的窄带干扰时,计算的NCO查找表地址位宽不超过10bit。无NCO相位截断的频域抗干扰接收机相比,采用NCO混频的抗干扰接收机的载噪比损耗最多增加0.6dB。     

基于扩张状态观测器的稳定控制算法

在稳定控制系统中,以PID控制算法为典型代表的传统负反馈设计,依靠系统在低频段的增益来实现对载体扰动作用的抑制,具有一定的局限性。以某陀螺稳定平台为研究对象,在PID负反馈稳定控制系统的基础上,通过加入扩张状态观测器对扰动进行了观测及补偿。仿真比较了加入扩张状态观测器前后的算法控制效果,结果表明扩张状态观测器是提高控制系统稳定精度的一种有效方法。     

基于无偏GM(1,1)幂模型的意图威胁建模

在态势威胁的基础上,利用无偏GM(1,1)幂模型设计了一种敌机意图威胁的模型。首先,提出了素质因子和探测概率因子,在此基础上,建立了改进的态势威胁模型。然后,将角度作为特征量对敌机机动进行预测,并建立了意图威胁模型。最后,分别对态势威胁和意图威胁模型进行仿真。结果表明,意图威胁模型行之有效。     

供电电缆磁场辐射的预测模型及优化设计

基于磁场叠加原理,建立了单相、三相、并联单相、并联三相供电电缆常见布局方式下的磁场辐射计算模型,并给出了降低电缆磁场辐射的优化布局方法。仿真与实验结果表明:该计算模型有较高的准确性,有助于把握供电电缆磁场辐射的决定因素,可用于快速指导供电电缆的优化设计,以避免反复的仿真或实验试探,缩短设计时间,降低设计成本。     

Book review

La Conversion économique du secteur militaire, J. FONTANEL, Economica, Paris, 1994, pp. 112. Paperback. ISBN 2–7178–2650–5.     

Does Health Spending Crowd out Defense in the United States? Evidence from Wavelet Multiresolution Analysis

Abstract

This study investigates the association between defense and health spending using multi-resolution analysis incorporating the structural change model. Our empirical results suggested that a negative correlation between defense and health spending persists over the entire period of 1941–2013 in the very long-run (over 16 years cycle), but there is a change in correlation between defense and health spending in the short-run (2–4 years cycle), medium-run (4–8 years cycle), and long-run (8–16 years cycle) during the same period. In particular, there appears to have been a trade-off relationship between defense and health spending during the ex-Korean War period, but there was a complementary relationship between defense and health spending during the post-Korean War period. The crowding-out effect of health spending on defense spending during the period when the Affordable Care Act was put into effect relies on the strength of the positive correlation in the long-run (8–16 years cycle) and negative correlation in the short-run (2–4 years cycle) and very long-run (over 16 years cycle).     

Modelling international conflict under conditions of state level economic and political uncertainty

Formal models of international conflict have tended to concentrate on change across the security dimension, assuming that the state level economic and political dimensions are constant. However, the conclusion of the Cold War suggests that over the long run these dimensions are not constant; indeed, the development of economic power, state level limits on defence expenditures, structural impediments to economic change, and several other ‘constants’ clearly do have an endogenous role in international conflict. This paper suggests one strategy for their inclusion as a causal factor in conflict modelling.     

FOOD AID

Abstract

This paper seeks to critically appraise Africa's position within the United Nations Security Council from the inception of the UN in 1945 until the end of 2010, spanning the entire history of the world body. A few factors make such an appraisal a useful exercise. These include the ongoing debates about the reform of the Council in particular and the UN as a whole, and the growing interest that many African students and observers of and actors in international relations seem to have developed in recent years in the working of the world body. In this appraisal, emphasis will be placed on the origin and rationale behind the establishment of the Security Council as well as the use of the veto power by its permanent members, with a special reference to Africa.     

EXTRAORDINARY VISITS

North Korea has the bomb but not much of a nuclear arsenal. For fifty years, it pursued the plutonium path to the bomb in parallel with its pursuit of nuclear electricity. My visits to North Korea's Yongbyon nuclear complex provided a window to its plutonium capabilities. After having made six visits to North Korea, Pyongyang surprised me during my seventh visit last November by showing me a small, modern uranium enrichment plant, which I was told was needed for its new indigenous light water reactor program. However, the same capabilities can be used to produce highly enriched uranium bomb fuel. Following a pattern of having made poor risk-management decisions during much of the past twenty years of diplomacy dealing with the North Korean nuclear threat, Washington remains in a standoff with Pyongyang.     

变距离静电电位检测研究

针对现有非接触式静电检测装置存在检测距离近且距离固定等问题,提出了对电位测量进行距离补偿的变距离静电电位检测方案。首先,从电位测量的基本原理出发,分析了距离测量误差与电位测量误差的关系,验证了精确测距的重要性,即要满足电位测量相对误差σV≤±10%,所选测距方式的距离测量相对误差-4.65%≤σd0≤5.41%的技术指标。然后,通过实验研究了检测距离与感应电位的关系,验证了0.5 m内对静电电位变距离测量的可行性,得到了对电位测量进行距离补偿的公式雏形Vs(V a,d)=Va(a+bd)c。依据此公式雏形以及大量的重复实验,可以得到公式中的各项参数值,编入单片机可实现对静电电位的变距离检测。