A novel formulation of material nonlinear analysis in structural mechanics

This article demonstrates a novel approach for material nonlinear analysis. This analysis procedure eliminates tedious and lengthy step by step incremental and then iterative procedure adopted classically and gives direct results in the linear as well as in nonlinear range of the material behavior. Use of elastic moduli is eliminated. Instead, stress and strain functions are used as the material input in the analysis procedure. These stress and strain functions are directly derived from the stress-strain behavior of the material by the method of curve fitting. This way, the whole stress-strain diagram is utilized in the analysis which naturally exposes the response of structure when loading is in nonlinear range of the material behavior. It is found that it is an excellent computational procedure adopted so far for material nonlinear analysis which gives very accurate results, easy to adopt and simple in calculations. The method eliminates all types of linearity assumptions in basic derivations of equations and hence, eliminates all types of possibility of errors in the analysis procedure as well. As it is required to know stress distribution in the structural body by proper modelling and structural idealization, the proposed analysis approach can be regarded as stress-based analysis procedure. Basic problems such as uniaxial problem, beam bending, and torsion problems are solved. It is found that approach is very suitable for solving the problems of fracture mechanics. Energy release rate for plate with center crack and double cantilever beam specimen is also evaluated. The approach solves the fracture problem with relative ease in strength of material style calculations. For all problems, results are compared with the classical displacement-based liner theory.     

Study on energy release characteristics of reactive material casings under explosive loading

Reactive Materials (RMs), a new material with structural and energy release characteristics under shock-induced chemical reactions, are promising in extensive applications in national defense and military fields. They can increase the lethality of warheads due to their dual functionality. This paper focuses on the energy release characteristics of RM casings prepared by alloy melting and casting process under explosive loading. Explosion experiments of RM and conventional 2A12 aluminum alloy casings were conducted in free field to capture the explosive fireballs, temperature distribution, peak overpressure of the air shock wave and the fracture morphology of fragments of reactive material (RM) warhead casings by using high-speed camera, infrared thermal imager temperature and peak overpressure testing and scanning electron microscope. Results showed that an increase of both the fireball temperature and air shock wave were observed in all RM casings compared to conventional 2A12 aluminum ally casings. The RM casings can improve the peak overpressure of the air shock wave under explosion loading, though the results are different with different charge ratios. According to the energy release characteristics of the RM, increasing the thickness of RM casings will increase the peak overpressure of the near-field air shock wave, while reducing the thickness will increase the peak overpressure of the far-field air shock wave.     

电子产品在振动环境中的损伤效应研究

在分析电子装备结构特点及冲击振动环境影响因素基础上,阐述了电子产品在冲击振动环境中的损伤机理与模式。以某型雷达装备为试验对象,选取该装备某型组合体与电路板进行冲击振动与扫频振动试验,分析了电子产品在振动环境中的损伤规律。试验表明:电子产品在振动环境中的损伤不仅与振动类型及幅值有关,也与其自身结构有着密切的关系。     

Proportional use of force in asymmetric military operation

This paper studies a strategic conflict between a state and a non-state military organization. The non-state military organization decides whether to attack or not to attack the state, while the state decides on its counter-measure. If the state uses a high level of violence against the non-state organization, it may be accused by the international community of ‘non-proportional’ use of force, and both sides of the conflict take this possibility into account. The model predicts that it may be rational for the non-state organization to attack the state, even if as a reaction the state will militarily destroy this organization, due to a positive probability the state will be punished by the international community for non-proportional use of violence.     

Africa's toy soldiers,non-state armed groups,and ‘voluntary’ recruitment

Armed conflict on the African continent has witnessed increasing recruitment of child soldiers, often at the hands of non-state armed groups. Unfortunately this practice continues unabated in the face of legal obligations prohibiting the recruitment of child soldiers under international humanitarian law, and international and regional human rights law. While international condemnation of the practice has led to attempts to increase the minimum age for recruitment to 18, a disjuncture persists between the legal obligations states sign up to, and the actual enforcement of these prohibitions at a domestic level.

International criminal law jurisprudence emanating from the Special Court for Sierra Leone and the International Criminal Court is being monitored closely, as these courts seek to enforce the prohibition in all armed conflicts, and against both state actors and non-state armed groups. International humanitarian law only protects child soldiers who have been unlawfully recruited. In this piece, the authors take a closer look at what amounts to unlawful recruitment in light of customary international humanitarian law, since this body of law also binds non-state actors, even without further criminalising legislation at a domestic level. Moreover, the article briefly explores whether a child can ever void this protected status by volunteering to participate directly in hostilities.     

THE EXERCISE OF NATIONAL SOVEREIGNTY

Skeptics of the Bush administration have castigated its strong aversion to formal international agreements in responding to the threat of the proliferation of weapons of mass destruction (WMD), citing unilateral actions as the default alternative. Yet this critique misses the growing emergence of a conscious framework guiding the administration's actions: an emphasis on the exercise of national sovereignty and the corollary principle of sovereign responsibility. Rejecting the paradigm of arms control as the answer to WMD proliferation, the current administration instead advocates a toolkit of alternative mechanisms based on the full exercise by individual nation, states of their domestic authorities and rights under international law, acting in their capacities as responsible citizens of the global community. This paper will examine that philosophical approach and its concrete application through the following policies: (1) the Proliferation Security Initiative; (2) enforcement of national laws and regulations as exemplified by United Nations Security Council Resolution 1540 and the U.S. proposals for consideration by Biological Weapons Convention signatories; and (3) preemptive warfare to disarm the WMD programs of a threatening state.     

Reforming the notion of national sovereignty by external intervention

In principle, national sovereignty is the right of a nation to govern its internal affairs without foreign interference. In practice, it is defined by one's interpretation of international law, which may permit legal external intervention under some circumstances, ultimately removing a nation's sovereignty. This paper will examine the current system of international law outlined by the United Nations, analyse the ambiguities contained within its Charter and elaborate on how external intervention can be justified. The case-study of recent developments related to Libya will demonstrate that the manner in which international law is interpreted is changing the notion of principles of sovereignty.     

太阳能光电热系统换热器性能实验研究

设计了新型半圆管形式的不锈钢板式换热器,对其作为太阳能光电热综合利用一体化系统集热组件的性能进行实验研究。通过新型集热光电热组件及光电组件系统的对比实验,研究该光电热组件在重庆地区夏季应用情况,分析其光电和光热特性。结果表明:在以晴朗为主的天气,半圆管形式的不锈钢板式光电热组件电热系统的电热性能与光电组件系统的相比较,前者的太阳能电池输出功率提高约26.48%,热利用效率提高23.70%以上,新型半圆管形式的光电热组件整体光电热(光电+光热)综合效率可达到25.70%,有效提高了光电热系统的综合效率。新型半圆管形式不锈钢板式换热器的换热面积增大,提高了换热效率,为太阳能光电热综合利用一体化系统在重庆等太阳辐射强度较小地区的应用提供了参考。     

The practice and theory of British counterinsurgency: the histories of the atrocities at the Palestinian villages of al-Bassa and Halhul, 1938–1939

This article details two largely unreported atrocities by British forces operating against Arab rebels during the Arab revolt, 1936–9, at the Palestinian villages of al-Bassa and Halhul. It then examines the military-legal system that underpinned and authorised British military forces operating in aid of the civil power, suggesting that the law in place at the time allowed for a level of reprisals and punitive actions, such as happened at al-Bassa and Halhul. The article does not conclude that the law allowed for atrocities but it does argue that it gave a basic form and understanding to an operational method that was brutal and could lead to atrocities. It thus tests the idea in much of the literature on counterinsurgency that the British were restrained and used minimum force when compared to other colonial and neo-colonial powers fighting insurgents.     

高焓高压空气加热器壁面传热过程数值计算

以一种高焓高压空气加热器为研究对象,对其冷却通道的流动和传热进行了三维数值仿真,冷却剂采用液态水,燃烧室和喷管分别采用不同的壁面材料,考虑壁面材料物性随温度的变化,并通过加热器热试验证了数值仿真结果的正确性。在此基础上,对比分析了气体辐射、冷却通道结构以及冷却水的流动方式对壁面换热的影响。结果表明:气体辐射对加热器燃烧室段壁面换热影响较大,对喷管壁面换热无明显的影响。在传热计算中,忽略气体辐射会引起较大的误差;冷却通道数和宽度存在最优组合,使得壁面换热量最大。冷却水的流动方式对燃气侧壁面温度影响较小,但对冷却液侧壁面温度的影响较大。