Fatigue crack propagation of multiple coplanar cracks with the coupled extended finite element/fast marching method

A numerical technique for modeling fatigue crack propagation of multiple coplanar cracks is presented. The proposed method couples the extended finite element method (X-FEM) [Int. J. Numer. Meth. Engng. 48 (11) (2000) 1549] to the fast marching method (FMM) [Level Set Methods & Fast Marching Methods: Evolving Interfaces in Computational Geometry, Fluid Mechanics, Computer Vision, and Materials Science, Cambridge University Press, Cambridge, UK, 1999]. The entire crack geometry, including one or more cracks, is represented by a single signed distance (level set) function. Merging of distinct cracks is handled naturally by the FMM with no collision detection or mesh reconstruction required. The FMM in conjunction with the Paris crack growth law is used to advance the crack front. In the X-FEM, a discontinuous function and the two-dimensional asymptotic crack-tip displacement fields are added to the finite element approximation to account for the crack using the notion of partition of unity [Comput. Meth. Appl. Mech. Engng. 139 (1996) 289]. This enables the domain to be modeled by a single fixed finite element mesh with no explicit meshing of the crack surfaces. In an earlier study [Engng. Fract. Mech. 70 (1) (2003) 29], the methodology, algorithm, and implementation for three-dimensional crack propagation of single cracks was introduced. In this paper, simulations for multiple planar cracks are presented, with crack merging and fatigue growth carried out without any user-intervention or remeshing.     

Mesh‐independent p‐orthotropic enrichment using the generalized finite element method

This paper is aimed at presenting a simple yet effective procedure to implement a mesh‐independent p‐orthotropic enrichment in the generalized finite element method. The procedure is based on the observation that shape functions used in the GFEM can be constructed from polynomials defined in any co‐ordinate system regardless of the underlying mesh or type of element used. Numerical examples where the solution possesses boundary or internal layers are solved on coarse tetrahedral meshes with isotropic and the proposed p‐orthotropic enrichment. Copyright © 2002 John Wiley & Sons, Ltd.     

Restricted overlapping balancing domain decomposition methods and restricted coarse problems for the Helmholtz problem

Overlapping balancing domain decomposition methods and their combination with restricted additive Schwarz methods are proposed for the Helmholtz equation. These new methods also extend previous work on non-overlapping balancing domain decomposition methods toward simplifying their coarse problems and local solvers. They also extend restricted Schwarz methods, originally designed to overlapping domain decomposition and Dirichlet local solvers, to the case of non-overlapping domain decomposition and/or Neumann and Sommerfeld local solvers. Finally, we introduce coarse spaces based on partitions of unity and planes waves, and show how oblique projection coarse problems can be designed from restricted additive Schwarz methods. Numerical tests are presented.     

知识经济与强化人类活动的主体性效应

知识经济的发展，使知识和创新，成为人类活动的强大动力，人类的实践活动迈入了崭新阶段。人类的潜在智慧和才能，正源源不断地释放出来，转化为对象性存在，充分展示了人类活动的主体性效应，与此同时我们也必须正视人类活动的反主体性的效应。正确处理主体自觉能动性和客体自然性之间矛盾，是强化人类活动的主体性效应，防止反主体性效应的前提条件。     

对梁,底组合步进式加热炉半热滑轨的改进实践

介绍了间断式半热滑轨的研制和应用过程，以及经过节能技术改造，用新型半热滑轨代替老式滑轨的使用。实践表明，不但解决了以往的水梁漏水的问题，而且使线Ｃ级品率提高了３．３９％，每年可增产３５００ｔ线材，吨钢热涌单耗降低０．１４ＧＪ，年创经济效益２３９万元。     

论地下水运动规律及其研究方法

在长期实践中,指导人们研究地下水运动规律的最基本理论依据是达尔西定律.达尔西定律认为,渗流量与水头梯度成正比.然而,实践证明,渗流量的大小并不是直接决定于水头梯度,而是决定于地下水所受的作用.因此,直接反映地下水运动规律的定量函数应该是渗流量与其所受的作用量之间的关系函数.为了揭示地下水运动与其控制作用之间的关系规律,引入作用现象理论和作用的对立统一规律,进而建立了更为科学的地下水动力学理论.研究结果表明：渗流量的大小直接受虚作用量的大小控制（受孔隙度控制）,水头高度直接受实作用量的大小控制（受密实度控制）.     

一种高压摆率低电压CMOS AB类放大器的设计

为了增加单位增益频率与压摆率,并能够工作在低电源电压下,同时降低偏置电流,提出了一种改进的基于0.18μm CMOS工艺的AB类放大器,其采用多级放大器结构,第一级为具有电流镜负载的NMOS差分对,第二反相级由共源放大器实现,第三极为AB类放大器,其能够在±500 m V电源下工作.电路仿真结果显示该放大器相位裕度为87°;总补偿电容为5 p F,与传统放大器相比减少了50%;单位增益频率为21.17 MHz,比传统放大器增大约10倍;压摆率为7.5和8.57 V/μs,与传统电路相比,分别增加了2.8倍和2.6倍.此外,与其他文献相比,该放大器具有较大的单位增益带宽和压摆率以及较小的功耗.     

“阴阳互转”与武术技法哲理思想的和谐统一

中国古典哲学认为:宇宙间一切事物都存在阴阳,一切事物变化无不是相互对应、阴与阳相互作用的结果。阴阳学说理论所体现的中华武术传统文化及思维方式更是典型,是武术理论必不可少的基本构架之一。通过分析、归纳武术技法哲理思想中所蕴涵的"阴阳互转"的哲学思想,希望最终达到与武术技法哲理思想的和谐统一,为进一步学习武术,修炼武术并以此提升习武者自身内涵起到积极作用。     

高职商务英语人才培养与师生企联合机制的创新实践——以苏州工业职业技术学院为例

作为一般商务用途英语,高职商务英语的人才培养模式是基于工作过程的＂三室三岗＂工学结合。基于该模式的师生企联合机制,特别是师生企联合招生与就业、联合开发课程与教材、联合实习与实践、联合开发项目等,是校企深度合作育人的关键所在和有效形式。师生企联合只有进行时而没有完成时,还需进一步创新师生企联合育人机制、激发紧密合作型企业在育人中的主体作用、全面系统培养每一位学生的＂软＂实力,以更好地服务于苏州外向型经济特别是外贸业的转型升级和创新驱动。     

An n‐material thresholding method for improving integerness of solutions in topology optimization

It is common in solving topology optimization problems to replace an integer‐valued characteristic function design field with the material volume fraction field, a real‐valued approximation of the design field that permits ‘fictitious’ mixtures of materials during intermediate iterations in the optimization process. This is reasonable so long as one can interpolate properties for such materials and so long as the final design is integer valued. For this purpose, we present a method for smoothly thresholding the volume fractions of an arbitrary number of material phases which specify the design. This method is trivial for two‐material design problems, for example, the canonical topology design problem of specifying the presence or absence of a single material within a domain, but it becomes more complex when three or more materials are used, as often occurs in material design problems. We take advantage of the similarity in properties between the volume fractions and the barycentric coordinates on a simplex to derive a thresholding, method which is applicable to an arbitrary number of materials. As we show in a sensitivity analysis, this method has smooth derivatives, allowing it to be used in gradient‐based optimization algorithms. We present results, which show synergistic effects when used with Solid Isotropic Material with Penalty and Rational Approximation of Material Properties material interpolation functions, popular methods of ensuring integerness of solutions. Copyright © 2016 John Wiley & Sons, Ltd.