无人机风梯度滑翔过程中能量变化

风梯度滑翔是一种能够使飞行器从飞行环境中获取能量的飞行方式。在已建立的飞行器动力学模型的基础上,分析了无人机在已知的梯度风场中一个滑翔周期内的能量变化过程。采取分段解析的方法,将一个风梯度滑翔周期分为4个阶段进行分析,即逆风爬升、高空转弯、顺风下滑和低空转弯,其中高空转弯为整个滑翔周期内的关键阶段。采用三维空间路径结合二维平面投影的计算方法,详细分析了无人机在高空转弯过程中的运动方程和能量转化方程,同时分析了影响飞行器从梯度风场中获取能量以及梯度风场中由于空气阻力导致飞行器能量损失的相关参数,为无人机最大程度地从梯度风场中获取能量,同时减少自身能源损耗提供了理论指导,并且根据理论建模进行了仿真分析,得出了逆风爬升和高空转弯的初期是获取能量主要阶段的结论,对指导无动力滑翔有很大的意义。     

动态滑翔动力学建模与风梯度能量获取*(专题约稿)

信天翁等鸟类能够不拍打翅膀而持续飞行很长的时间和距离,因为梯度风场的存在使得它们能从中获取能量,这项技术被称之为动态滑翔。临近空间也广泛存在梯度风场,如果临近空间长航时飞行器能够利用动态滑翔技术将是十分有前途的。本文首先对无动力飞机的动态滑翔问题做了假设来简化问题的描述,更便于数学操作。在这些假设下建立了无动力飞机动态滑翔的动力学模型,即三维速度空间中只有一个输入变量的常微分方程组。之后,从理论上得到了这个三维速度空间中机械能可以增加的最大范围,即能增纺锤体内部,并推导出最大的机械能增加率。最后,得出更大的风梯度、更小的阻力系数和更小的面质比更加有利于飞机获取能量的结论,该结论加深了对动态滑翔能量观点的认识,对实践有指导意义。     

动态滑翔动力学建模与风梯度能量获取

为简化问题描述和便于数学操作,对无动力飞机的动态滑翔问题做了假设,并在这些假设下建立了无动力飞机动态滑翔的动力学模型,即三维速度空间中只有一个输入变量的常微分方程组。之后,从理论上得到了这个三维速度空间中机械能可以增加的最大范围,即能增纺锤体内部,并推导出最大的机械能增加率。得出更大的风梯度、更小的阻力系数和更小的面质比更加有利于飞机获取能量的结论,该结论加深了对动态滑翔能量观点的认识,对实践有指导意义。     

飞行器动态滑翔的受力平衡状态

为了研究动态滑翔的物理本质,从受力平衡的角度出发,根据物理定律推导平衡方程,从数学上求解出方程解集构成的平衡曲线。以信天翁和某小型无人机在不同风梯度下滑翔为例对平衡曲线进行仿真。分析和仿真结果表明:平衡曲线是满足受力平衡的所有速度状态的集合,由上升和下降两个分支构成;上升分支只有当风梯度足够大时才存在,是动态滑翔的关键。     

基于态势预测的无人机防相撞控制方法

针对无人机自主飞行过程中,受空中非协作移动目标威胁较大,且空中移动威胁存在高机动性的特点,提出一种预测移动威胁情况下的无人机防撞控制方法,该方法采用交互多模(IMM)算法预测移动威胁的运动状态,同时利用滚动时域控制(RHC)思想建立无人机运动控制模型,构造有约束目标函数,运用微分进化算法(DE)求解目标函数,获取最优控制量,输入控制模型,完成防撞机动控制。仿真结果表明,该方法可以有效解决空中多架航空器同时入侵的防撞问题。     

高超声速伸缩翼变形飞行器轨迹多目标优化

针对高超声速条件下变形技术的应用模式，对具有伸缩翼的组合式飞行器滑翔弹道进行了多目标优化研究。介绍了伸缩翼的变形模式，给出了不同变形状态下的气动特性；建立了三自由度滑翔轨迹动力学模型和伸缩翼前缘热流计算模型；采用MOEA/D多目标优化算法，以变形条件和飞行攻角为设计变量、以最大射程和最小翼前缘总吸热量为目标函数，进行了多目标优化计算。优化结果表明，MOEA/D计算得到了相对均匀分布的Pareto最优解集，将伸缩翼外形与无变形外形相比，飞行器滑翔段射程得到了显著提高，同时伸缩翼前缘总吸热量有明显的降低。     

能量状态法的无人机节油轨迹优化

应用能量状态法研究了高空长航时无人机节油飞行的最优轨迹问题.构建了基于能量状态法的质点运动模型,简化了传统运动模型的维数,并利用变分法提出了基于能量控制的性能指标,推导出飞机纵向飞行过程(爬升、巡航和下降)的优化方程,得到整个飞行过程的全局最优解,给出了一种适用的算法,利用Matlab对该算法进行了计算仿真.仿真结果表明,优化的节油轨迹算法效率较高,可节省飞机燃油、缩短航行时间.     

滑翔增程弹飞行弹道

增程技术是弹箭技术重点发展方向之一,而滑翔增程是目前采用的较为有效的一种弹箭增程技术.阐述了滑翔增程弹的飞行过程,建立了滑翔弹的方案弹道模型和控制方程,对其飞行弹道特性进行了分析.仿真计算表明,滑翔弹道与常规弹道在升弧段上是一致的,而在降弧段上则出现了较大的差别;弹丸飞行速度沿全弹道的变化规律和最大射程角出现新变化;控制弹道很好地逼近了方案弹道,说明其控制方法是可行的,对滑翔增程弹的研制有一定的参考意义.     

基于混合算法的巡飞无人机轨迹优化策略

提出大型空中侦察无人机作为控制中继来控制陆基发射的巡飞无人机作战模式。以多脉冲固体火箭发动机为动力的巡飞无人机的航程末端速度大,可以有效提升无人机的战场生存能力;为使巡飞无人机末速最大,有效提高巡飞无人机飞行轨迹优化求解的鲁棒性和精度,提出了遗传算法与高斯伪谱法相嵌套的混合优化方法。同时与单脉冲推力模式的无人机进行了对比仿真,验证了该混合优化算法的实用性和有效性。     

基于模型预测控制的无人机避障路径规划方法

针对无人机飞行过程中避障问题,提出了一种基于模型预测控制的无人机避障路径规划方法。通过对无人机平台模型进行分析,构造了无人机状态空间预测模型。为保证路径规划过程输出的平稳性,采用一阶指数变化形式作为无人机飞行路径的参考轨迹。设计了预测模型调整策略,并给出了参数调整流程,以能力-时间组合最优为目标,建立了无人机避障路径优化模型,采用有限时域优化的滚动优化算法对无人机避障优化模型进行了求解。算例仿真结果表明,该算法可有效解决无人机飞行路径的避障问题。     

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.