Topological hinge modes in Dirac semimetals

Dirac semimetals (DSMs) are an important class of topological states of matter. Here, focusing on DSMs of band inversion type, we investigate their boundary modes from the effective model perspective. We show that in order to properly capture the boundary modes, k-cubic terms must be included in the effective model, which would drive an evolution of surface degeneracy manifold from a nodal line to a nodal point. Sizable k-cubic terms are also needed for better exposing the topological hinge modes in the spectrum. Using first-principles calculations, we demonstrate that this feature and the topological hinge modes can be clearly exhibited in β-CuI. We extend the discussion to magnetic DSMs and show that the time-reversal symmetry breaking can gap out the surface bands and hence is beneficial for the experimental detection of hinge modes. Furthermore, we show that magnetic DSMs serve as a parent state for realizing multiple other higher-order topological phases, including higher-order Weyl-point/nodal-line semimetals and higher-order topological insulators.     

弹塑性岩土介质中渗透固结问题的参数二次规划法

岩土类介质在承受荷载时,不仅产生弹塑性变形,还伴随着渗流和固结,是一个关于时间的动态过程。本文建立起处理该问题的参变量变分原理以及相应的有限元方法,这样将原问题化为求解带约束条件(本构状态方程)的二次规划问题.文中讨论了单元的选取形式及具体的实施过程,还给出了一个实例.     

圆宝山隧道炭质板岩大变形段初期支护结构受力特性研究

为了准确掌握丽香铁路圆宝山隧道炭质板岩大变形段初期支护结构受力特性,结合深埋炭质板岩隧道大变形特点,通过调查分析发现炭质板岩具有显著的各向异性特征,在地下水、高地应力及施工扰动等复杂因素作用下表现出显著的蠕变特性,从而导致隧道发生大变形。同时,对圆宝山隧道展开围岩变形及初期支护受力监测,监测结果表明,薄层炭质板岩段围岩的变形速率、变形量整体上较中厚层炭质板岩段围岩大,且达到稳定所需的时间更长;围岩压力与钢拱架应力基本呈从拱顶到拱脚减小的趋势,且围岩压力最大值出现在拱肩,而钢拱架应力最大值分布位置不固定,常见分布位置为两侧拱墙上下,这与钢拱架因发生扭曲而设置横支撑基本吻合;变更支护参数后,围岩的时效特性有明显改善,尤以薄层炭质板岩段围岩最为明显,同时围岩压力分布更加均匀,钢拱架出现拉应力现象不再集中。基于上述研究成果,选择I18型工字钢焊制钢架、设置间距为0.6m、喷射厚为27cm的C25混凝土作为初期支护,同时采用"弱爆破、短进尺"的掘进方式,以达到控制深埋炭质板岩隧道围岩变形的目的。     

一种考虑剪切变形的平行四边形厚/薄板通用单元

根据Timoshenko二广义位移梁理论，构造了深梁位移场的插值函数。利用斜坐标系与直角坐标系的变换关系、有限条带思想和深梁位移插值函数，构造了一种考虑剪切变形的平行四边形厚／薄板弯曲通用单元的位移(曲率、剪应变、转角、横向位移)插值函数，导出了刚度矩阵和非结点荷载等效力。并对简支阍支方板、Razzaque斜板、四边简支斜交板弯曲进行了数值计算。算例表明此单元有较好的精度，对于薄板不出现剪切闭锁，可适应于目前桥梁建设中大量采用的斜交板桥结构分析。     

磁性敏感器用于冲击变形测量

一种新型的非接触式磁性位移敏感器,兼有高灵敏度(50-80mV/mm)、大线性范围(15-25mm)以及响应快(4kHz)等优点.用于测量20mm以内的冲击动态变形获得成功.     

ADAPTIVE MESHLESS METHOD BASED ON LOCAL FIT TECHNOLOGY

An h-adaptive meshless method is proposed in this paper. The error estimation is based on local fit technology, usually confined to Voronoi Cells. The error is achieved by comparison of the computational results with smoothed ones, which are projected with Taylor series. Voronoi Cells are introduced not only for integration of potential energy but also for guidance of refinement.New nodes are placed within those cells with high estimated error. At the end of the paper, two numerical examples with severe stress gradient are analyzed. Through adaptive analysis accurate results are obtained at critical subdomains, which validates the efficiency of the method.     

炮药断裂韧性初探

高膛压炮的问世,对炮药的力学性能提出了更高的要求。本文根据炮药的性质、加工和使用的特点,探讨炮药断裂韧性的测定。     

基于AutoCAD的有限元建模系统AutoFEM

介绍了基于ＡｕｔｏＣＡＤ平台开发应用程序的主要特点和在ＡｕｔｏＦＥＭ中采用的软件接口方案，数据模型及所见即所得等。     

Mathematical models arising from a survey of ferromagnetic materials under magnetisation

Ab This paper focuses on mathematical models describing the mechanical behavior of ferromagnetic materials under magnetization. Through combination of the electromagnetic field theory with the theory of elastic mechanics, several nonlinear systems of fourth-order partial differential equations were deduced. By making further assumption, the first-order approximation of the above equations was established, of which the solutions are good enough for engineering application.