长管水击最大水击压强的解析

从管道水击微分方程的特征分析入手,提出了水击特征方程的黎曼不变量和网格分析解,建立了管道水击问题的近似解析解,给出了长管水击最大水击压强的计算表达式。通过实际算例对解析解和数值解结果进行了比较。对水击微分方程的重力项也进行了讨论。     

Analysis of the mass of behind-armor debris generated by RHA subjected to normal penetration of variable cross-section EFP

Analyzing the mass of behind-armor debris (BAD) generated by Rolled Homogeneous Armor (RHA) subjected to normal penetration of variable cross-section Explosively Formed Projectile (EFP) is the purpose of this paper. So theoretical analysis, numerical simulation and experimental data are combined to analyze the influence of variable cross-section characteristic on the time history of crater radius. Moreover the relationships between time history of crater radius (as well as mass of BAD) and the thickness of RHA (from 30 mm to 70 mm) and the impact velocity of EFP (1650 m/s to 1860 m/s) are also investigated. The results indicate that: 1) being compared to the variable cross-section characteristic is ignored, the theoretical time history of crater radius is in better agreement with the simulation results when the variable cross-section characteristic is considered; 2) being compared to the other three conditions of plug, the theoretical mass of BAD is in the best agreement with the simulation results when the shape of plug is frustum of a cone and the angle between generatrix and bottom is 45° and the axial length of mushroom is considered.     

Operating Costs of Aging Air Force Aircraft: Adjusting for Aggregate Budget Effects

The rate at which operating costs grow as aircraft age is important for setting operating budgets and for deciding when to replace aging systems. While studies using data from the 1990's typically found 1–3 percent real rates of growth in operating costs as aircraft age, studies using data from the 2000's found greater rates, for example in the 4–6 percent range. Growth in the total U.S. Air Force budget during the 2000s appears to explain much of the higher estimated annual growth rates in operating costs per flying hour beyond the growth rate intrinsic to the aging of the fleet.     

溅板式层板喷注单元燃烧特性数值分析

为了获得喷注单元结构参数对喷注器燃烧特性的影响规律,利用数值分析方法对单喷嘴溅板式层板喷注单元气-气燃烧特性进行研究,考察燃烧室特征长度及出口层喷嘴宽度对气氧/甲烷流动及燃烧特性的影响。在求解气-气燃烧流场方面,采用带化学反应的湍流N-S方程进行描述,其中化学动力学反应模型采用简化的单步9组分模型。研究结果表明:燃烧室特征长度的增大有利于特征速度效率的增加;该条件下采用溅板式层板喷注单元所对应的燃烧室特征长度约为600 mm。对比分析发现,出口层喷嘴宽度取0.15 mm时,水组分摩尔分数与热力计算值差别最大;当其值取1.05 mm时,燃烧室头部区域截面温度上升最快,取0.45 mm时上升最慢。总的来说,出口层喷嘴宽度取0.75 mm时,燃烧长度最短,燃烧效率最大。     

Principles of Minimum Force and the Parachute Regiment in Northern Ireland, 1969–1972

Developing literature on Operation Banner, the codename for the British military operation in Northern Ireland, has indicated that the conduct of soldiers deployed was not always in line with principles of minimum force. Adherence to these principles would seem to have been essential to the success of the operation given the initial deployment of the soldiers was in the role of military aid to the civil power. This article will examine the role of one of the British Army’s most aggressive units, the Parachute Regiment, and will show how the responses of the regiment to the demands of the operation in Northern Ireland were frequently in contravention of minimum force principles.     

Exploring the subsidiarity principle in policing and the operations of the Nigeria Police Force

The provisions of the 1999 Constitution, which recognises the existence of a single police force and forbids parallel police organisations, have oftentimes generated controversies among actors in the Nigerian federal polity. Rising insecurity precipitates lingering questions on the utility and adequacy of a single, highly centralised and centrally controlled police force given Nigeria’s geographic vastness and demographic diversity. Conversely, arguments have also dwelt on the dangers of fragmentation considering Nigeria’s psychosocial, economic and political nature. This article attempts to balance these arguments by analysing policing and the operations of the Nigeria Police Force (NPF) through the lens of the subsidiarity principle. Subsidiarity is a governance principle in federations, captured in the founding documents of the European Union (EU), which prescribes that governmental powers, authorities and duties should be held by the tier that can best perform them equitably, efficiently, effectively, suitably and based on interest and need. Drawing largely on interviews with purposively selected police scholars, political actors, civil society organisations and police personnel, the paper contends that this principle offers a pragmatic solution to the perennial problems of intergovernmental frictions on the use of the police within the context of governance in the Nigerian federation.     

South African defence policy: the rationale and impact of the SANDF’s primary role and conventional force design

The 2015 South African Defence Review set out to reverse the deterioration of South African National Defence Force (SANDF) capabilities. Within the South African Department of Defence (DOD) this deterioration is expressed mainly in terms of a decreasing defence budget, subsequent declining conventional capabilities and obsolete prime mission equipment. Contemporary research and defence expert debates on this theme, point out the disjuncture between policy ends and the available means, with scepticism for an increased defence budget given the DOD’s lack of internal reform and strategy adjustment. One question that remains largely unanswered in the literature regarding the decline of the SANDF, is why both the policy-makers and the SANDF have remained focused on the primary role of the military (defending territorial integrity) accompanied with an unaffordable conventional force design? This question relates to the aim of this paper and is explored by revisiting initial defence policy decisions and compromises that were made in the 1990s. It is argued that the primary role of the SANDF and its conventional force design suited the interests of both the politicians and the military, but that the drawbacks thereof have harshly caught up with the DOD.     

新编制体制下武警部队装备任务需求

为加快建设现代化武警部队,解决配属装备与日益增长的任务需求之间的矛盾,论文以武警部队指挥体系变更、警种部队调整的现实背景,围绕武警部队遂行任务情况,整理分析出新编各警种对装备的任务需求,为推动武警部队装备体系发展提供理论参考。     

“作战云”理论视阈下的装甲兵装备保障

"作战云"的作战理念将引发装甲装备保障领域的深刻变革。文章剖析了"作战云"理论视阈下装甲兵装备保障问题的基本内涵,从装备保障力量部署、指挥控制方式、协同方式、防护手段四个方面分析了"作战云"视阈下装甲兵装备保障的主要特点,提出"探测——决策——保障——评估"的装备保障行动流程。     

永磁无刷直流直线电机齿槽力补偿控制研究

永磁无刷直流直线电机的齿槽定位力对其低速性能影响很大,而单纯的设计方法不可能完全消除齿槽力的影响,为此,必须在控制系统中对齿槽力进行补偿。针对包含齿槽力模型的理想电机控制系统进行了理论分析,指出通过引入位置反馈环节可以消除齿槽力的不良影响。利用有限元分析方法计算了电机的推力和齿槽力波形,验证了低速条件下推力波动主要由齿槽力引起,并说明可以通过位置反馈来补偿推力波动。最后,提出将一个齿槽力周期分为多个区间,然后分段进行线性补偿的简易控制方法。该方法无需高精度的定位装置和复杂的控制算法即可实现对电机齿槽力的补偿,实验结果表明,所提方法能够有效抑制电机的推力波动。