基于Huber权函数的Allan方差非相关差分抗差估计方法

原子钟频率稳定度计算时由于钟差观测异常会导致Allan方差出现较大的估计偏差。本文首先建立了Allan方差的差分估计模型,根据钟差的差分序列统计特性分析了相关差分估计的噪声识别与白化等计算复杂度问题;针对上述难点提出了一种基于Huber权函数的非相关差分抗差估计方法,建立了一种非相关差分序列的构造方法,有效避免了复杂的噪声识别及白化计算,给出了Allan方差的非相关差分抗差估计的推导,并对抗差过程引入的误差累积给出了一种抵消方法;最后给出了完整的抗差估计方案,并利用实测数据进行了实验验证,结果表明本文方法对相位单点跳变、相位阶跃跳变具有显著的抗差能力,抗差估计可使异常引入的相对偏差由近200%降至5%以内。     

应用抗差无迹卡尔曼滤波的再入弹道处理技术

针对现有无迹卡尔曼滤波在再入弹道处理中可能出现的异常观测、观测随机误差模型不准确以及动力学模型不合理等问题,在无迹卡尔曼滤波中引入自适应与抗差估计理论,研究适用于再入弹道处理的自适应抗差滤波方法。该方法可以自适应地估计测量噪声等价协方差阵和状态噪声等价协方差阵,并可实现异常值的分离和维纳模型方差的自适应调整。数值仿真结果表明:该方法计算简单,并能有效减弱测量误差和动力学模型误差对弹道处理精度的影响。     

Gold序列跳变扩频在毫米波敌我识别系统中的应用

在毫米波敌我识别系统中,识别信息在低频部分经过数字信号处理后,进行扩频调制后由微波收发信机进行传输。介绍了毫米波敌我识别系统中采用扩频调制设计原则和跳变Gold码扩频序列的设计方法,分析了扩频抗截收/截获的能力,并给出了一种用STEL2000-A芯片产生Gold序列进行跳变扩频调制的具体实现实例。     

一种相位编码信号参数盲估计方法

针对电子侦察中相位编码信号参数盲估计问题,提出一种新的相位编码信号载频和码元宽度盲估计方法。该方法首先将信号划分为等长度区间,并计算每个区间内信号的频谱,然后根据包含相位跳变区间频谱与不含相位跳变区间频谱的特征差异,以各区间内信号频谱峰值序列的方差最小为准则,不断改变区间划分长度完成码元宽度和载频估计。仿真结果表明,本算法在没有任何先验知识的情况下,可以对相位编码信号参数进行精确估计。     

再入飞行器弹道系数的自适应估计

运用Kalman滤波方法对再入飞行器的跟踪问题进行了分析,在动力学噪声已知的情况下,给出了一种弹道系数的自适应估计方法;在动力学噪声未知时,给出了弹道系数和动力学噪声方差的自适应估计方法。仿真算例表明这种方法是合理有效的。     

空间非平稳高斯噪声背景下混合信号的DOA估计

针对空间非平稳高斯噪声背景下混合信号的DOA估计问题,提出了基于四阶累积量对混合波源的DOA估计算法。该算法首先构造四阶累积量矩阵,利用类似ESPR IT方法估计出所有非相关信源的DOA,然后对四阶累积量进行修正空间差分平滑去相干,消除非相关源和空间非平稳高斯噪声的影响,从而实现了对相干源的DOA估计。此方法通过分别估计非相关和相关或者相干信号的DOA,能够以较少的阵元实现对多个信号DOA估计,最后仿真实验也验证该算法的有效性。     

基于空间差分平滑的非相关与相干信源数估计

针对非相关信源与相干信源共存时信源数估计问题,提出了一种新的基于空间差分平滑的信源数估计算法。该算法首先利用SORTE法估计相互独立信源个数,结合非相关信源阵列导向矢量与噪声子空间正交关系特性,实现非相关信源数估计;其次基于空间差分法消除非相关信号并构造新矩阵,利用构造矩阵进行前向空间平滑,实现对相干信源解相干;最后利用SORTE法得到相干信源数估计。仿真实验结果验证了该算法的有效性。     

基于地形差分矩的 TERCOM 地图性能估计

提出了一种非平稳地形中TERCOM地图匹配性能的估计方法。首先利用地形差分过程研究相关匹配算法度量值的统计特性 ,获得度量值的均值和方差关于地形差分矩的解析表达。然后讨论度量值统计特性与局部匹配搜索截获概率的关系 ,建议用地形差分矩和局部搜索截获概率作为TERCOM地图匹配性能的估计。通过对实际地形的试验 ,说明基于地形差分矩的匹配性能估计方法是有效的。     

关于自适应滤波技术的一些思考

本文研究工程实践中应用Ｋａｌｍａｎ滤波时出现的滤波异常现象。文中从滤波异常的检测出发,由此构成动力学噪声方差阵的自适应估计。对于常用的衰减记忆滤波,提出了衰减因子的自适应确定方法,对于未知的动力学噪声和观测噪声的方差阵,运用Ｂａｙｅｓ－ＭＬ估计方法给出了递推估算方案。对于构造自适应滤波的技术途径,提出了一些看法。     

一种Turbo码中伪随机交织器的盲识别方法

目前Turbo码的构造中广泛应用的是伪随机交织器,要完成对Turbo码的识别,必不可少地需要得到伪随机交织器的参数。针对伪随机交织器的识别问题,通过引入扩频通信中PN序列盲估计的方法,利用功率谱二次处理法求出交织长度即m序列周期,再用特征分解方法对序列进行估计。仿真实验表明,该方法能够求出m序列的相关参数,完成对伪随机交织器的识别需求。     

Terrorism,insurgency, kidnapping,and security in Africa's energy sector

Energy continues to serve as the bedrock of modern economies and the main driver of modern society. For Africa, the production and supply of energy resources such as crude oil, natural gas, uranium, coal, biomass, biofuels and other renewables are an important source of employment, rents, taxes, royalties and profits. This sector brings in several tens of billions of dollars of revenue annually. The production and delivery of such resources, however, depend on critical infrastructures such as pipelines, refineries, processing plants, terminals, rigs, electrical energy pylons, substations, pump stations, vessels, and tankers. These infrastructures have been attacked by terrorists, insurgents, vandals and saboteurs, all of whom see them as targets against which to register their grievances and extract concessions from the state. This paper is a chronological account of some of the documented incidents of terrorism, insurgency, kidnapping, destruction, sabotage, and human casualties suffered in the oil and gas sectors in Africa between 1999 and 2012. It is based on data extracted from the databases of the RAND Database of World Terrorism Incidents and the University of Maryland's Global Terrorism Database (GTD).     

Helping hands: civil–military cooperation and Italy's military operation abroad

In the Post-Bipolar Era the growing complexity of the military operations requires a new approach for the resolution of international crises. Since the end of the Cold War, peace support operations (PSO) have become the mainstay and principal occupation of most Western armies. At the same time, Italy has been one of the most important actors in such an area. The article focuses on the cooperation between military and civil components (a process called CIMIC) as a key variable in the Italian PSOs. We will analyse in detail the main lessons learned from past military interventions as well as the general context in which new tendencies are taking place. The maintaining of a minimum security frame becomes essential to fulfil activities ‘collateral’ to the mission: reconstructing services and infrastructure, food distribution, water and medication, law and order, de-mining, training of local forces, and supporting local institutions. These are the main tasks to obtain thrust and support from the population.     

Tacit support for terrorism: The rapprochement between the USSR and Palestinian guerrilla organizations following the 1967 war

This article demonstrates the inconsistent and wavering Soviet attitude towards national liberation movements in general and the Palestinian organizations in particular. Until the late 1960s, the Soviets viewed these organizations with suspicion, hesitating to engage in political dialogue with them. However, in the 1970s, political and military events in the region, as well as modifications in the Kremlin's Cold War strategies, led to a general shift towards the Middle East in Soviet foreign policy. Soviet leaders showed increased willingness to provide certain Palestinian organizations with arms with which to conduct terrorist activities against Israeli, pro-Israeli, Jewish and Western targets. The article explores the complex relations between Palestinian organizations and the USSR in the field of international terror. The study also exposes and analyzes the nature and content of Soviet–Palestinian arms dialogues and transactions. It provides clear evidence that Soviet policymakers and other luminaries were fully informed of, and sometimes directly involved in, these transactions and dialogues at the highest levels.     

A1 Qaeda and the radical Islamic challenge to western strategy

The September 11 global crisis prompted by the attacks on the World Trade Center and the Pentagon raises major questions concerning the nature and trajectory of terrorism in the post-Cold War global order. Hitherto, terrorism has been largely debated by analysts at the level of nation states. Terrorist and insurgent movements have also been largely anchored in nationalist and ethnic power bases even when they have sought to mobilise a transnational ideological appeal on religious or class grounds. There have been a few exceptions to this pattern such as the alliance between the German Baader-Meinhof group and the Japanese Red Army Faction, but even such international alliances as this did not, until at least the 1980s, presage anything like a global terrorist network necessitating a global strategic response. This study examines terrorism and global strategic responses.     

Helping hands: external support for the KNU insurgency in Burma

This article analyses to what extent the Burmese KNU insurgency made use of external support from states, refugees, and diasporas. Based on extensive fieldwork it is concluded that support from neighbouring states and refugees has for years kept the Karen rebellion alive. Western countries perceived forms of resistance to the illegitimate Burmese regime as just and have therefore played a crucial role in the continuation of conflict in Karen State. It is important that policymakers and donors as well as executing organizations continue to reflect critically on the way they exercise their work.     

基于GTST-DMLD-ESD的装备RMS建模仿真

装备的RMS是装备的重要设计参数,是影响战备完好和保障能力的关键因素.引入GTST-DMLD作为主要建模工具,建立起装备系统的RMS描述模型,以ESD为补充和扩展,对维修过程进行建模.并以GTST-DMLD-ESD模型作为装备RMS仿真的核心,对装备RMS仿真模型的总体框架进行了研究,并对各模块进行了较为详细的探讨.     

Cyber sheiks and grassroots jihadis: the war in Syria and the devolution of the Bosnian Salafi communities

ABSTRACT

What was the scope of the Bosnian jihadi participation in the war in Syria? Did the Bosnian volunteers tend to join one particular faction? Why did the Bosnian youngsters decide to join the holy war in the Levant? Was this an organized and hierarchical process or was this a grassroots movement? Last, were all the Salafis in Bosnia supportive of this dynamic or did this process cause internal frictions? These are some of the questions that this research will try to answer.     

Country survey XVI the defence sector in the economy of a declining superpower: Soviet Union and Russia, 1965-2001

The Soviet Union was able to develop a large military-industrial complex and become the world's second superpower despite deficiencies in its centrally planned economy because defence was given high priority status and special planning, rationing and administrative mechanisms were used to attain national security objectives. However, in the period 1976-85 the effectiveness of priority protection diminished and defence institutions experienced more of the problems typical of the shortage economic system. The heavy defence burden also created growing difficulties for the civilian economy. The attempts by the Gorbachev government to reform the defence sector and improve defence-economic relationships during perestroika (1985-91) uniformly failed. For most of the transition period, the Russian military-industrial complex has been adversely affected by its low priority status, cuts in defence spending, instability of the hybrid politico-economic system, and negative growth of the economy. The armed forces and defence industry have been reduced in size and their outputs of military services and equipment have fallen to low levels. Nevertheless, the Russian armed forces still have over one million troops, significant stocks of sophisticated conventional weapons, and a large nuclear arsenal. The government of President Putin has raised the priority of the defence sector, increased real defence spending, and adopted ambitious plans to revive Russian military power. It is likely, though, that tight resource constraints will hamper efforts to reform the armed forces and to upgrade weapons. By 2010 Russia will be an important, but not dominant, military power in Eurasia.     

Traffickers,terrorists, and a ‘new security challenge’: Russian counternarcotics strategy and the Federal Service for the Control of the Drugs Trade

The collapse of the Soviet Union precipitated the massive expansion of drug use and trade in Russia. The country now has one of the largest populations of injecting drug users in the world and has become the largest single-country market for Afghan heroin. In 2003 the Federal Service for the Control of the Drugs Trade was created to coordinate a comprehensive counternarcotics strategy appropriate to the scale of this threat. The service continues to face a number of challenges in its early stages of development. However, it has made considerable advances in improving responses to large-scale organised crime and in building international cooperation.