二维衰减谐波估计的四阶混合累积量方法

针对二维衰减谐波估计方法在大样本容量条件下计算量过大的问题,提出了一种基于二维四阶混合累积量的ESPRIT方法。在不影响估计精度的前提下,通过保持特征矩阵结构不变,有效地减小了算法的计算量。利用四阶混合累积量对高斯噪声的自动抑制,降低了参数估计的信噪比门限并提高了估计精度。仿真实验表明,在高斯色噪声条件下该方法的计算效率和估计性能优于现有方法。     

基于调制FFT有限域搜索的MUSIC频率估计算法

为满足跳频频率测量中频率估计高精度及实时性的要求,提出了一种将调制FFT和MUSIC算法相结合的频率算法:首先利用调制FFT对谐波频率进行预估计,确定感兴趣的频域区间;然后利用MUSIC算法在锁定区间内估计伪谱谱峰的位置,实现频率的精确估计。该算法可得到较高的频率分辨率,并减少了MUSIC算法的谱峰搜索范围。仿真试验表明:该算法的频率分辨率高,且实时性能满足频率测量需求。     

基于四阶累积量的双基地MIMO雷达收发角度估计

提出了一种基于四阶累积量的双基地MIMO雷达收发角度估计算法。在接收端,通过分别构造单阵元和双阵元的四阶累积量矩阵,采用基于四阶累积量的MUSIC算法和ESPRIT算法分别估计出目标的离开方向(DOD)和波达方向(DOA),并且DOD和DOA自动配对。该算法将二维参数的估计问题转化为两个一维形式,不需要二维谱峰搜索,在保证二维方位角估计性能的基础上,降低了运算量。利用四阶累积量有效地扩展了阵列孔径,并且适用于任意加性高斯噪声环境。仿真结果验证了算法的有效性。     

交流电子负载的谐波间谐波机理分析研究

分析了馈能型交流电子负载谐波间谐波产生的机理,基于馈能型电子负载工作原理,对电子负载输出信号进行研究,得出输出信号含有谐波间谐波等多种成分.采用MUSIC算法估计电力谐波信号频率,针对电力信号实值的特点,对MUSIC算法进行相应改进,获得较高的检测精度,同时对比了FFT算法的频率估计结果,得出MUSIC对电力谐波信号尤其是间谐波等负载谐波具有更高的精度,对电力系统监测及电能质量评估有较大应用价值.     

基于四阶累积量的相干信号二维波达方向估计算法

提出了一种基于四阶累积量的相干信号二维波达方向(DOA)估计的算法--CSS算法.该算法利用双平行线阵的接收数据以及平滑技术构造了一个平滑的渡达方向矩阵,通过对其进行特征分解估计出空间相干信号的二维到达角.在色噪声环境下,该算法能够精确地估计空间相干信号的二维到达角,无需谱峰搜索,并且信号的二维参数能够自动配对.计算机仿真结果验证了算法的有效性.     

部分极化信号多维参数联合估计的算法

基于双平行极化敏感阵列,提出了一种部分极化信号频率,二维到达角和极化参数联合估计的算法.该算法能精确地估计出部分极化信号的多维参数,无需多维谱峰搜索,具有计算量小,参数自动配对的优点,而且也适用于含有完全极化信号的情况.另外,算法也能有效地解决信源参数兼并问题.计算机仿真结果验证了算法的有效性.     

卫星通信新技术专题讲座(二) 第3讲 基于分段累加的大频偏估计算法

文章提出了一种基于分段FFT累加的前向频率估计算法,该算法不需要位定时辅助,只要采样频率足够高,即能适合于各种频偏的信号。该算法仅需要较短长度的FFT运算,并通过采用多段累加的方式提高估计效果。仿真表明,该算法可以在极低信噪比以及大频偏条件下获得令人满意的估计精度。     

改进的迟延相位差多信号频率估计应用

给出了一种多信号欠采样频率估计算法。该算法通过迟延相位差的允许误差求出频率大致取值区间,利用欠采样频谱结果求出多个信号的高精度频率估计值,并重点解决了当不同信号因欠采样出现谱峰重叠时测频不准确的难题。仿真表明,该算法具有良好的抗噪性能,且估计精度高。     

二维隐马氏模型的一种简化算法及其参数估计

针对现有的二维隐马氏模型算法给出了一种简化算法及参数估计方法。该算法与现有的算法相比非常简单。基于此方法给出了相应的识别方法和参数估计,并且该估计与极大似然估计是等同的。     

频率估计的多段异频等长信号相位积累算法

为提高信号频率估计精度和扩展已有方法的适用范围,提出一种基于相位积累的多段异频等长信号的频率估计算法。首先生成异频分析参数矩阵,克服分段信号频率不等问题;其次设计相位差补偿因子,克服分段信号相位不连续问题;最后搜索相位累积频谱最大值,获得信号频率估计值。为验证算法的正确性,给出了相应的数学推导证明。仿真实验结果表明,该算法具有较好的频率估计精度,频率估计误差约为现有方法的1/2,较为接近克拉美罗下限。     

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.