The Production and Deposition of the Guisborough Helmet

In September 1878 the British Museum received a donation of a folded metal plate which had been embossed and gilded. Restoration of the object revealed that the folded plate was in fact the outer casing of a Roman copper alloy cavalry sports type helmet which dates to the late second or third century AD. The story of what became known as the Guisborough helmet began 14 years earlier in what was then the North Riding of Yorkshire when workers employed by the Cleveland Railway Company discovered a ‘very curious plate of metal’ during road construction. It appears that the helmet was deliberately prepared for deposition and buried at a depth of c30 cm close to a stream. Examination by the authors suggests that this was a high value item that had been repaired many times. Experimental evidence suggests that the decoration alone required approximately 16 h to fashion.     

混合动力装甲车辆能量管理策略实时仿真

为解决混合动力装甲车辆多动力源输出优化匹配难题,针对一种具有3个动力源的混合动力系统中各动力源的输出特性和驱动电机功率需求特点,制定了具有双层结构的能量管理策略:顶层的系统功率分配策略完成负载功率估计及其在各动力源间的分配;底层的部件级控制策略实现发动机-发电机组和动力电池的优化控制。通过构建一种分布式硬件在环仿真平台对能量管理策略进行仿真验证。结果表明:混合动力系统能够很好地满足负载功率需求,实现了对多个目标的优化控制。     

风载荷对某发射装置待发射状态的影响

应用冯.卡门功率谱和谐波合成法生成了考虑脉动效应的瞬时风速时程曲线;计算了发射筒各段的等效风压及等效力矩,给出了作用于发射筒迎风面的风压总值及等效力矩;最后将载荷作为输入条件,进行动力学分析,获得了风载荷作用下发射装置的动态响应。通过分析可知:由于发射装置具有刚度强、质量大的特点,风载荷作用下发射装置的速度、加速度响应均较低,因此,风载荷主要影响发射筒的倾斜程度。     

COSMIC 掩星反演的水汽廓线质量分析

利用2006—2012年北半球冬季低纬度地区(30°S~30°N)无线电探空站数据及全球大气成分和气候监测再分析数据对1000 h Pa~200 h Pa高度层的气象、电离层与气候星座观测系统全球定位系统掩星反演的比湿廓线进行了精度和可靠性验证。结果表明,水汽对气象、电离层与气候星座观测系统掩星反演影响较大,尤其在中、低对流层及热带地区等水汽含量比较大的地区,且气象、电离层与气候星座观测系统掩星数据在850 hpa以下可能并不太适用于评估其他数据。     

On matched active redundancy allocation for coherent systems with statistically dependent component lifetimes

This study addresses the allocation of matched active redundancy components to coherent systems with base components having statistically dependent lifetimes. We consider base component lifetimes and redundancy component lifetimes which are both stochastic arrangement monotone with respect to a pair of components given the lifetimes of the other components. In this context, allocating a more reliable redundancy component to the weaker base component is shown to incur a stochastically larger system lifetime. Numerical examples are presented as an illustration of the theoretical results.     

From Nationalism to Factionalism: Faultlines in the Naga Insurgency

Do ceasefires or peace talks create fragmentation in the insurgent groups? Rather than proposing claims that can offer predictions about armed groups behaviour under ceasefires or peace processes, the analysts tend to focus largely on the dynamics between state and non-state actor. The experts pay little attention to overtime changes in social and local political context which might contribute to propelling a rebel group towards fragmentation and factionalism. The present study intends to fill this gap by exploring the shifting role of public opinion and ethnic support for the peace talks to ascertain whether it can increase the likelihood of factionalism in rebel groups or not. This article applies this approach to the case of Naga National Movement (1947–2015) in India, and finds that the proposed variable appears to have increased the frequency of factionalism in the movement.     

评估飞控系统的风洞虚拟飞行试验系统与关键技术

为向开展具体的风洞虚拟飞行试验技术提供引导,针对应用于飞控系统评估的风洞虚拟飞行试验系统及关键技术进行了分析。基于传统意义上的飞控系统评估方法的不足,分析风洞虚拟飞行试验应用于飞控系统评估的优势;按飞控系统常用的姿态控制回路及制导控制回路的组成形式,介绍风洞虚拟飞行试验系统方案与工作原理,详细分析它与半实物仿真系统的差异;分析风洞虚拟飞行试验应用于飞控系统评估需解决的关键技术问题,包括风洞虚拟飞行试验评估方法、飞行器模型设计技术、飞控系统改进技术及模型支撑技术。     

伞翼无人机线性自抗扰高度控制

针对伞翼无人机参数不确定性和复杂环境干扰敏感的问题,提出一种伞翼无人机线性自抗扰(Linear Active Disturbance Rejection Control,LADRC)高度控制方法。建立伞翼无人机8自由度飞行动力学模型,并引入风场和降雨模型以更加准确地模拟真实飞行环境。基于LADRC确定总体控制架构,设计线性扩张状态观测器对所有扰动进行估计,并引入误差反馈率在控制中实时补偿。使用该控制方法在多种扰动工况下进行伞翼无人机高度控制仿真实验。仿真结果表明,基于LADRC的高度控制方法能够有效克服内扰和外扰的影响,实现高精度高度控制;与传统PID控制效果相比,LADRC控制器具有更好的抗扰能力和鲁棒性。     

分段履带式水陆两栖车减阻增速试验及数值仿真

为了研究分段履带式水陆两栖车的水动力性能,实现减阻增速,将尾翼板安装到水陆两栖车的方艉部,并开展了水池试验和仿真研究,两者的研究结果具有较好的一致性。通过仿真研究了车体的纵向重心位置、尾翼板的长度和角度对水陆两栖车阻力性能的影响,并分析了阻力成分的变化趋势。研究结果表明:车体纵向重心位置在540～560 mm 时,车体所受水阻力最小;在速度为3～5 m/s时,长度为156 mm,与水平面夹角为10°的尾翼板减阻效果最明显,相比于原裸车体的阻力,减阻率达到34.3%;加装尾翼板可以增加车体的尾部中空区长度,相当于增加了水线长,增大了长宽比。该研究表明:适当调节重心位置和优化尾翼板参数,可以有效实现水陆两栖车的减阻增速。     

太阳风作用下航天器表面充电效应分析

针对太阳风等离子体中航天器的充电过程,基于欧洲航天局开发的航天器表面充电仿真软件,建立了航天器的数值计算模型,模拟了太阳风等离子体与航天器的相互作用,实现了不同表面材料时航天器表面电位以及尾迹结构的计算分析,给出了近日环境下航天器周围的空间电位结构以及等离子体密度分布情况。研究结果表明:表面材料的选择将影响空间势垒深度以及尾迹结构,表面充电至更低电位的表面材料具有较小尾迹区域;航天器向阳面电位分布主要由光电子以及二次电子主导,而背阳面的电位分布则主要受到尾迹效应的影响。以上结果对太阳风环境航天器探测和评估等相关工作以及工程研究具有一定的理论参考价值。