局部腐蚀下耐压船体结构振动特性及稳定性研究

为探究局部腐蚀下耐压圆柱壳的承载特性,在均匀深水压力作用下,针对具有局部腐蚀的环加筋圆柱壳的振动特性及稳定性进行了研究,分析了腐蚀参数对振动特性与临界失稳载荷的影响。通过改变腐蚀面积、腐蚀位置和腐蚀深度,利用有限元软件NASTRAN进行系列仿真分析,得到了含有局部腐蚀环加筋圆柱壳结构的振动特性及失稳破坏模式。结果表明:当腐蚀深度大于3mm时,结构开始出现局部振动模态且固有频率单调下降;静水压力作用下带有局部腐蚀的环加筋圆柱壳一阶固有频率的平方与静水压力呈三段线性关系;在临界载荷方面,当腐蚀深度小于2mm时其对结构的临界失稳载荷几乎没有影响,当腐蚀深度大于2mm时临界载荷随即减小。     

剪切来流条件下的涡生振荡机理

将指数极坐标系建立在运动的圆柱上,推导了运动坐标中剪切来流条件下,涡生振荡的涡量-流函数守恒方程、其初始和边界条件、圆柱表面的水动力表达式、圆柱振荡方程。对圆柱从静止开始振荡到发展为稳定振荡状态进行了计算和讨论,描述了脱体涡街的发展过程、升阻力相图的连续变形和漂移、圆柱振荡和平衡位置的变化过程。研究了涡生振荡终态随剪切度K的变化。结果表明:剪切来流给流场加入了背景涡,使圆柱的上涡增强、下涡减弱,流场的对称性被破坏。随着剪切度K的增大,涡街的倾斜程度增大,压力曲线的漂移量增大,由此导致升力的绝对值增大,圆柱的振幅增大且平衡位置向圆柱下侧的漂移也增大。     

剪切来流条件下的涡生振荡机理的数值研究

将指数极坐标系建立在运动的圆柱上,推导了运动坐标中剪切来流条件下,涡生振荡的涡量-流函数守恒方程及其初始和边界条件,圆柱表面的水动力表达式以及圆柱振荡方程。对圆柱从静止开始振荡,到发展为稳定振荡状态进行了计算和讨论,描述了脱体涡街的发展过程,升阻力相图的连续变形和漂移,圆柱振荡和平衡位置的变化过程。并研究了涡生振荡终态随剪切度K的变化。结果表明,剪切来流给流场加入了背景涡,使圆柱的上涡增强而下涡减弱,流场的对称性被破坏。随着剪切度K的增大,涡街的倾斜程度增大,压力曲线的漂移量增大,由此导致升力的绝对值增大,圆柱的振幅增大且平衡位置向圆柱下侧的漂移也越大。     

基于LES的三维桅杆绕流的数值实验研究

以舰船棱柱形的全封闭桅杆为研究对象,利用计算流体力学软件ANSYS ICEMCFD和ANSYSCFX对模型进行数值实验。在雷诺数为5.74×105和7.66×105,桅杆的攻角从0°变化到90°,以15°为间隔的条件下,研究了表面倾斜且前后不对称的四边形棱柱状结构在均匀流场中所受的流体载荷。通过对桅杆绕流进行数值模拟,得到了漩涡发放随时间的变化规律;发现模型由于表面倾斜的原因,除了受到阻力和升力外,还受到垂直方向上的垂向力,这在以往的柱状结构中是没有的;同时分析了模型所受的定常力和脉动力系数随雷诺数和攻角的变化规律。     

等、变深度舰船水压场的理论计算

在浅水、薄船、无限宽水域的条件下,舰船以亚临界速度(F_H<1)运动时,利用E.O.Tuck提出的渐近匹配展开法,可以得到定深度扰动速度势的摄动方程。对水深缓慢变化的海底,舰船的绕流不再是定常的,根据A.Plotkin所采用的多重尺度法,可以得到变深度浅水舰船扰动速度势的摄动方程。如果仅考虑扰动速度势的一阶摄动方程,则可得到考虑了线性兴波影响的舰船水压场的计算公式。     

带有损伤凹陷的环肋圆柱壳应力和稳定性分析

为探寻局部受损伤潜艇结构的承载能力,以出现较大损伤变形的环肋圆柱壳舱段结构为研究对象,"涡形凹陷"作为损伤变形的典型形状,运用MSC/NASTRAN软件计算了这种结构在静水外压作用下的应力分布和失稳临界压力。结果表明:带有损伤凹陷的环肋圆柱壳与完好状态环肋圆柱壳相比,最大应力值提高,失稳临界压力值下降,应力的改变对环肋圆柱壳承载能力的影响更大;相同凹陷幅度下,损伤凹陷中心在肋骨位置时,对圆柱壳应力状态和稳定性的影响最为恶劣。肋骨分别采用梁单元或壳单元两种建模方式时,得出的应力和失稳临界压力变化规律一致,采用梁单元建模得出的肋骨应力偏安全。     

加热对圆柱绕流影响的热线测量

首次给出了风洞中加热圆柱涡脱落受加热功率控制的热线测量结果。实验表明:当Re>Re_c时,加热使涡脱落频率f下降,甚至完全抑制涡脱落;加热使涡脱落处于临界状态时,其涡脱落频率f_c与来流风速U成正比;加热可影响圆柱绕流的涡脱落模式,使热线功率谱的单峰变为双峰。     

基于后向散射的光尾流探测系统

研制了基于后向散射的光尾流探测系统,使用该系统进行了实验室环境下的模拟尾流气泡探测实验和海洋环境下的舰船尾流探测试验.结果表明,该探测系统具有较好的舰船尾流探测能力,验证了基于后向蝌散射的光尾流探测方法的可行性.     

线导+尾流自导鱼雷射击阵位优化研究

在目标运动要素未知的条件下,方位导引法是线导鱼雷常用的导引方法,尾流自导鱼雷的制导技术要求鱼雷必须满足一定的角度进入目标尾流,才能发现尾流并跟踪击毁目标.线导如何导引鱼雷满足进入尾流角的要求,是急需研究的问题.通过分析和仿真得出鱼雷满足进入尾流角要求时本艇阵位与目标速度和舷角之间的关系,并从技术角度对其射击阵位进行了优化分析及仿真,对线导 尾流自导鱼雷的作战使用具有一定的指导意义.     

尾流自导鱼雷及其射击控制的关键技术

从分析尾流自导鱼雷制导机理和弹道特性入手,指出选择瞄点是尾流自导/线导+尾流自导鱼雷射击或导引控制的关键及困难所在.     

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.     

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).     

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.     

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.     

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.