条（环）状干摩擦阻尼器的微滑移数值模型

提出一种求解弹性条(环)状阻尼器微滑移接触运动的数值方法。将阻尼器和外部激励历程在空间和时间上离散,将相同数量的干摩擦触点布置于离散阻尼器上;把接触运动判据应用到各离散接触点,确定其运动状态并修正刚度矩阵,求解整个阻尼器的平衡方程。该方法避免了有限元软件求解含摩擦接触问题的迭代过程,从而保证了求解的可执行性。同时,克服了微滑移模型理论解法对法向载荷分布规律及载荷时变性的限制,为求解具有局部性以及时变性的法向载荷的结构动态响应提供了更为精确的边界条件,从而可提高结构频响分析的准确性。应用多谐波平衡法分别计算宏滑移和微滑移阻尼器约束下的结构动态响应,发现在结构减振中,微滑移模型能够适应更宽范围的法向力。     

混合气体识别的响应等效性与瞬态信号正交分解模型

针对目前混合气体识别大多采用传感器稳态响应信号、基于线性混合假设或大量样本学习,而瞬态响应信号特征分析主要应用非正交分解的问题,提出一种基于响应等效性与瞬态信号正交分解的混合气体识别模型。分析金属氧化物半导体传感器对混合气体的响应特性,建立基于气体响应成分等效性假设的气体非线性混合模型,在此基础上,提出并应用一种新的正交基函数——扩展类Legendre正交基,对气体传感器瞬态响应信号进行分解;通过对正交分解系数与气体浓度的回归分析,验证二者之间的指数型关联关系,并以正交分解系数为特征参数,利用气体非线性等效混合模型对混合气体分解与辨识。实验结果表明,尽管这种混合气体识别模型仅用单一气体检测的先验知识,对混合气体的识别误差仍可达到15%以内。     

How and why Boko Haram blossomed: examining the fatal consequences of treating a purposive terrorist organisation as less so

Boko Haram (BH) is an insurgent group that operates mainly in northeastern Nigeria. Its stated aim is to establish an Islamic state, and it employs terrorism as its strategy. Earlier interests of security analysts centred on the drivers of BH uprising and the possibility of its internationalisation. Today's concerns relate more to why the rebellion has lasted this long. In toeing the same line, this article demonstrates that BH is a purposive terror group against which the government has evolved no viable strategy. It examines some gains of BH over the past six years and how it benefitted from the government's underestimation of its capacity and determination. It concludes that to effectively engage BH, the Nigerian government must revaluate its threat and sincerely pursue an expanded strategy beyond the current military-centric approach. To be effective, government's response must be packaged in such a way as to enhance human security in the region.     

基于频响函数的悬臂结构损伤识别

根据频响函数的Neumann级数展开式,提出了悬臂结构的损伤识别方法。首先根据频响函数的Neumann级数展开式,推导了损伤参数与频响函数的关系式,以此为基础建立损伤识别方程组;其次,考虑到噪声影响,求解时采用了多频率点的最小二乘法,以减小由噪声引起的误差;最后用一个悬臂结构模型对所提方法进行了验证。     

平流层飞艇合成孔径雷达成像优化策略

平流层飞艇具有驻空高度高且时间久、覆盖范围广、使用效费比高等特点,在侦察监视等领域应用前景广阔。结合平流层飞艇平台特性,分析平流层飞艇合成孔径雷达(Synthetic Aperture Radar,SAR)与机载SAR的异同;针对平流层飞艇SAR的脉冲重复频率冗余及大振幅低频率运动误差,提出优化方案,并开展仿真分析验证。仿真结果表明所提优化运动补偿方法能够有效消除平流层飞艇运动误差影响。     

锚杆支护岩质边坡地震动力响应分析

目前的锚杆支护边坡地震动力设计主要采用拟静力的方法，无法考虑锚杆和边坡在地震作用下的相互作用，汶川地震边坡破坏现象调研表明，锚杆具有良好的抗震效果，所以有必要对锚杆抗震效果进行研究。利用动力有限差分软件FLAC^3D，通过分析一个岩质边坡算例坡面上监测点动力响应加速度峰值放大系数在锚杆支护前后变化，研究了锚杆在各种不同地震波作用下的抗震效果。结果表明：在不同地震波作用下，锚杆都能显著降低坡面加速度峰值放大系数，提高边坡的动力稳定性，具有良好的抗震效果。最后结合强度折减动力分析法对锚杆在地震作用下的破坏机理进行了研究，为锚杆支护边坡的抗震设计奠定基础。     

元胞法模拟非线性弹性层合材料中的应力波

元胞法 (MethodofCell)是在有效刚度理论的基础上发展起来的新方法 ,可以用来构造具有周期性结构单元的材料的本构 ,也可以用来模拟应力波在材料中的传播问题 ,尤其是具有分层结构的材料。本文中给出两种常见的初值条件 ,并利用该方法模拟了非线性弹性材料的动态响应 ,研究了波在该层合材料中的振荡现象     

扭力矩对曲折槽保险机构动力学响应影响分析

在考虑扭力矩作用的基础上，建立曲折槽保险机构的动力学模型，以某机构为计算实例，与传统的动力学模型进行比较。数值计算结果表明：引信跌落到硬质地面时，扭力矩的影响作用不明显，而跌落到松软地面上时扭力矩使惯性简的位移响应明显增大，不能忽略。其结论为判断长储引信勤务处理意外跌落的安全状态提供了理论参考。     

Stochastic production capacity: A bane or a boon for quick response supply chains?

The quick response (QR) system that can cope with demand volatility by shortening lead time has been well studied in the literature. Much of the existing literature assumes implicitly or explicitly that the manufacturers under QR can always meet the demand because the production capacity is always sufficient. However, when the order comes with a short lead time under QR, availability of the manufacturer's production capacity is not guaranteed. This motivates us to explore QR in supply chains with stochastic production capacity. Specifically, we study QR in a two-echelon supply chain with Bayesian demand information updating. We consider the situation where the manufacturer's production capacity under QR is uncertain. We first explore how stochastic production capacity affects supply chain decisions and QR implementation. We then incorporate the manufacturer's ability to expand capacity into the model. We explore how the manufacturer determines the optimal capacity expansion decision, and the value of such an ability to the supply chain and its agents. Finally, we extend the model to the two-stage two-ordering case and derive the optimal ordering policy by dynamic programming. We compare the single-ordering and two-ordering cases to generate additional managerial insights about how ordering flexibility affects QR when production capacity is stochastic. We also explore the transparent supply chain and find that our main results still hold.     

基于VAR的物价对舰船维修工时费率影响的动态计量分析

在相关性、平稳性和协整性检验基础上,建立舰船维修工时费率与物价之间的VAR模型,并借助Granger因果关系检验、脉冲响应函数分析和方差分解对模型进行动态分析.研究发现:物价与舰船维修工时费率之间存在长期均衡关系,两者互为Granger原因;工时费率会对物价变化产生及时的正向响应,并具有长效性,短期内工时费率受自身惯性的影响较大,随后物价对其影响的贡献率迅速上升,达到与其自身惯性相近的均衡状态;物价对工时费率变化的响应有1 a的时滞,且响应程度相对较小.长期来看,两者相互影响的关系使得工时费率呈波动上升的趋势.