基于邻域结构和驱动力准则的非刚性点集配准

非刚性点集配准的关键是找到点集之间的正确对应关系。传统点集配准方法通常将特征点的全局空间距离作为判别准则,而未考虑点集的邻域结构信息,容易产生误匹配,为此,文中提出了一种基于邻域结构和驱动力的非刚性点集配准算法。首先,在一致性点漂移(CPD)算法的基础上,提出了一种局部距离计算方法,并将其与空间距离相结合,有助于提高匹配精度;此外,对传统形状上下文方法进行了改进,构建了一种新的驱动力准则,以在初始配准过程中提高搜索速度,在后期减小配准误差;最后,采用期望最大化(EM)算法迭代求解各点对的对应关系。在常用国际点集数据集上的仿真实验结果表明,在非刚性变形、噪声、异常点和遮挡等情况下,文中算法比经典算法具有更高的鲁棒性,匹配准确率也更高,并且对真实图像可以获得比较理想的配准效果。

纵向受压构件的横向固有频率分析——稳定的动力准则

本文推证了压杆稳定的动力准则，并推广到板壳等结构，得出纵向受压构件横向振动一阶固有频率的平方与纵向力成线性关系的结论，在此基础上提出了一种新的确定临界力的试验方案。

结构动力屈曲的研究进展

系统地回顾了结构动力屈曲的研究进展,着重阐述了板及加筋板结构在周期载荷、冲击载荷以及随动力作用下的动力屈曲问题.对常用的动力屈曲准则作了介绍.针对目前对复合材料结构冲击屈曲研究较少的情况,提出应开展该领域的深入研究,并指出研究面内动力载荷下板结构的动力极限强度具有重大意义.

单层鞍型网壳在地震作用下的动力稳定分析

根据网壳结构的动力稳定判别准则，分析了单层鞍型网壳在Ｐａｓａｄｅｎａ波（取不同时间压缩比）作用下的稳定性能，并将其动力稳定临界荷载与静力临界荷载相对比，得出了一些重要结论。

基于显式有限元方法的两相介质弹塑性动力反应计算分析

针对增量形式的流体饱和两相多孔介质弹塑性波动方程组,运用基于显式逐步积分格式的时域显式有限元方法对该波动方程组进行求解,并应用基于SMP破坏准则的弹塑性动力本构模型描述两相介质的动力反应性质,对两相介质在输入地震波作用下的弹塑性动力反应进行计算和分析,将计算结果与相应的弹性动力反应的计算结果进行对比;对本文应用的弹塑性动力本构模型进行参数研究,揭示模型参数的取值对两相介质弹塑性动力反应计算结果的影响。计算结果表明:两相介质弹塑性位移反应与相应的弹性位移反应具有较为显著的差别,表现为二者的峰值与反应时程的波形均有比较明显的差异;本文应用的弹塑性本构模型中的塑性势参数的取值对于两相介质弹塑性位移反应的计算结果具有显著的影响,而初始加载和卸载与重新加载阶段的硬化参数的比值仅影响动力反应结束后的塑性变形的幅值。本文工作表明,时域显式有限元方法是进行流体饱和两相多孔介质弹塑性动力反应计算分析的一种有效的方法。

张弦梁结构动力稳定判断方法探讨

基于经典结构动力稳定性能判断准则,针对张弦梁结构特点,提出适用于该种结构类型的动力稳定判定的建议方法,并通过算例验证该种判断方法的可行性.

超大跨组合钢网壳结构动力稳定性分析

网壳结构多为缺陷敏感性结构,当地震发生时,由于强烈的地面运动而迫使网壳结构产生振动,网壳结构在地震作用下产生内力和位移,有可能造成网壳结构破坏或倒塌。在ANSYS中建立底部为协同弹性支承的超大跨钢桁架弦支穹顶组合网壳结构的有限元模型,分析钢网壳结构存在初始缺陷的动力稳定性,着重介绍了动力稳定分析方法、初始缺陷的施加、动力稳定判别准则的理论及应用。通过对钢网壳结构进行动力稳定性分析,总结钢网壳结构动力失稳破坏的形式,找出钢网壳结构真正的薄弱部位,并提出改善、提高钢网壳结构动力稳定性的措施。

网壳结构动力稳定性发展和应用研究

网壳结构多为缺陷敏感性结构,当地震发生时,由于强烈的地面运动而迫使网壳结构产生振动导致网壳结构产生内力和位移,就很有可能会引起网壳结构发生破坏或者倒塌。在有限元软件中,分析存在初始缺陷的网壳结构的动力稳定性时,须要注意时程分析法、初始缺陷、动力稳定判别准则的理论及应用。

煤柱冲击地压的解析分析

提出应用煤层塑性软化理论和材料失稳的动力判别准则 ,对煤柱冲击地压进行的解析分析方法。计算顶板变形和煤柱应力分布规律 ,探讨有关参数对煤柱产生冲击地压的影响、临界载荷随煤的强度σc、E/λ的变化规律 。

Flow equation and similarity criterion during centrifugal casting in micro-channel

Liquid metal filling flow process in the microscale during the centrifugal casting process was studied by means of similar physical simulation. The research was focused on derived similarity criterion. Based on the traditional flow equations, the flow equation and the Bernoulli＇s equation for liquid metal flows in micro-scale space were derived, which provides a mathematical model for numerical simulation of micro-scale flow. In the meanwhile, according to the micro-flow equation and the similarity theory, the similarity criterion for the physical simulation of the mold filling behaviors was presented under centrifugal force field, so as to achieve the visual observation and quantitative analysis of micro-flow process.

道德情感与心灵改善--兼论康德理性宗教的道德奠基

康德将他的理性批判事业推广到宗教领域,限制宗教于纯然理性界限之内。"道德上恶的人能否弃恶从善以及如何弃恶从善"成为批判的宗教哲学所要解决的主要问题。这个问题不是匍匐在信仰之下的理性依靠信念能够解决的问题,而是一个只能在纯然理性界限内联系道德信仰由实践理性来解决的问题。康德通过批判实践理性,证明了道德情感是一种尊重理性自律而产生的对道德法则敬重的情感,又以"动力—关切—准则"三个连贯的概念分析道德的纯粹性,并依据"责任"概念批判基督教伦理原则——"爱的诫命",最终基于人之有限性原则证成人只能在实践理性所限定的道德领域实现弃恶从善的心灵转变。康德所完成的批判考察,理性地解决了宗教与哲学、信仰与理性之间的对立统一关系,为纯然理性界限内的宗教奠定了必要的理性基础。

一种应用于飞行品质研究的缩比模型控制律设计

从缩比模型在飞行品质中应用的角度出发,结合动力相似准则分析了飞行品质关键参数的缩比因子;针对引入电传飞控系统带来的非线性因素,开展了对原型机控制律的简化和参数调整设计研究,使得电传缩比模型飞行品质关键参数与原型机呈现线性的缩比关系,最后对该设计的控制律进行了仿真验证。

Response and energy dissipation of rock under stochastic stress waves

The response and energy dissipation of rock under stochastic stress waves were analyzed based on dynamic fracture criterion of brittle materials integrating with Fourier transform methods of spectral analysis. When the stochastic stress waves transmit through rocks, the frequency and energy ratio of harmonic components were calculated by analytical and discrete analysis methods. The stress waves in shale, malmstone and liparite were taken as examples to illustrate the proposed analysis methods. The results show the harder the rock, the less absorption of energy, the more the useless elastic waves transmitting through rock, and the narrower the cutoff frequency to fracture rock. When the whole stress energy doubles either by doubling the duration time or by increasing the amplitude of stress wave, ratio of the energy of elastic waves transmitting through rock to the whole stress energy (i.e. energy dissipation ratio) is decreased to 10%-15%. When doubling the duration time, the cutoff frequency to fracture rock remains constant. However, with the increase of the amplitude of stress wave, the cutoff frequency increases accordingly.

大尺度空间薄膜地面振动试验网格膜等效理论分析与数值模拟

针对薄膜结构对空气阻力效应敏感、难以进行全尺寸地面动力学验证试验的问题,提出采用网格膜作为矩形膜面的等效结构进行地面动力学验证试验。建立了矩形膜面与网格膜的动力学等效准则,对网格膜的预应力场及结构参数进行了限定。算例数值模拟表明,在该等效准则的约束下,网格膜与矩形膜面具有基本一致的动力学特性。同时,声固耦合仿真验证了网格膜对空气阻力效应不敏感。

Analytical solutions of stress and displacement in strain softening rock mass around a newly formed cavity

The closed form solutions of the stress and displacement in strain softening rock mass around a newly formed cavity are derived with a three step-wise elasto-plastic model. Hoek-Brown criterion is adopted as the yielding criterion of rock mass. Damage factors are proposed to account for degradation of the material parameters to reflect the degree of strain softening. The surrounding rock mass around the cavity is divided into three regions: elastic region, strain softening region and residual state region. The analytical solutions of stress, strain, displacement and radius of each region are obtained. The effects of the strain softening and shear dilatancy behavior on the results are investigated with parametric studies. The results show that the radii of the residual state region and strain softening region in the surrounding rock mass with higher damage degree are larger. The radii of the residual state region and strain softening region are 1-2 times and 1.5-3 times of the cavity radius, respectively. The radial and tangential stresses decrease with the increase of the damage factor. The displacement of the cavity wall for the case with maximum plastic bulk strain is nearly twice than that with no dilation. Rock mass moves more toward the center for the case with larger damage factor and shear dilation. The area of the plastic region is larger when the damage factors are considered. The displacements in the surrounding rock mass increase with the increase of the damage factors and shear dilation factors. The solutions can be applied to the stability analysis and support design of the underground excavation.

On the Possibilities of Leisure Studies in Mozambique： Historical and Sociological Considerations

In this paper, the author examines the possibilities of leisure （studies） in Mozambique. First, the author suggests that leisure can he looked at as a social construct which resulted from the colonial regulation of native labour, particularly between 1890s and 1974. Secondly, the author proposes that people look at the conditions of possibility of leisure in a context dominated by the new moral code of conduct, a cathartic purification of the colonial mentality, introduced through the ideology of the ＂New Man＂ created by the ruling party, Frelimo. Thirdly, the author examines the possibility of leisure in the context of Mozambique＇s adherence to neo-liberalism and market-driven economy after the collapse of socialism. The author concludes by providing the ground to establish lines of inquiry for an eventual field of leisure studies.

Zonal disintegration mechanism of isotropic rock masses around a deep spherical tunnel

In order to investigate zonal disintegration mechanism of isotropic rock masses around a deep spherical tunnel, a new mechanical model subjected to dynamic unloading under hydrostatic pressure condition is proposed. The total elastic stress-field distributions is determined using the elastodynamic equation. The effects of unloading rate and dynamic mechanical parameters of isotropic deep rock masses on the zonal disintegration phenomenon of the surrounding rock masses around a deep spherical tunnel as well as the total elastic stress field distributions are considered. The number and size of fractured and non-fractured zones are determined by using the Hoek-Brown criterion. Numerical computation is carried out. It is found from numerical results that the number of fractured zones increases with increasing the disturbance coefficient, in-situ stress, unloading time and unloading rate, and it decreases with increasing parameter geological strength index, the strength parameter and the uniaxial compressive strength of intact rock.

基于塑性应变能密度的钢筋混凝土墩柱损伤准则

为建立一个能够用于评估动力荷载作用下钢筋混凝土墩柱横截面损伤情况且具有较好精度的损伤模型,本文首先基于能量平衡原理,推导了塑性应变能密度损伤准则;然后,按照裂缝扩展情况,建立了钢筋混凝土墩柱性能水平划分等级,并采用ABAQUS软件对33根钢筋混凝土墩柱拟静力试验模型进行动力损伤分析,确定了损伤指数与性能水平划分等级之间的对应关系,量化了动力荷载作用下钢筋混凝土墩柱横截面损伤评价模型;最后,引入支持向量机算法对塑性应变能密度损伤准则的归一化参数值进行预测,并通过算例验证了塑性应变能密度损伤准则和支持向量机算法用于钢筋混凝土墩柱横截面损伤分析的精度和可行性。

Oscillation criteria for second order neutral dynamic equations of Emden-Fowler type with positive and negative coefficients on time scales

We investigate oscillation of certain second order neutral dynamic equations of Emden-Fowler type with positive and negative coefficients. We use some different techniques and apply Riccati transformation to establish new oscillatory criteria which include two necessary and sufficient conditions. Moreover, we point out that how the power γ plays its role. Some interesting examples are given to illustrate the versatility of our results.

Incubation time approach in rock fracture dynamics

The paper is summarizing latest results connected with application of the incubation time approach to problems of dynamic fracture of rock materials. Incubation time based fracture criteria for intact media and media with cracks are discussed. Available experimental data on high rate fracture of different rock materials and incubation time based fracture criteria are used in order to evaluate critical parameters of causing fracture in these materials. Previously discovered possibility to optimize (minimize) energy input for fracture is discussed in connection to industrial rock fracture processes. It is shown that optimal value of momentum associated with critical load in order to initialize fracture in rock media does strongly depend on the incubation time and the impact duration. Existence of optimal load shapes minimizing momentum for a single fracturing impact or a sequence of periodic fracturing impacts is demonstrated.