Simulation of top-down crack propagation in asphalt pavements

Top-down crack in asphalt pavements has been reported as a widespread mode of failure.A solid understanding of the mechanisms of crack growth is essential to predict pavement performance in the context of thickness design,as well as in the design and optimization of mixtures.Using the coupled element free Galerkin (EFG) and finite element (FE) method,top-down crack propagation in asphalt pavements is numerically simulated on the basis of fracture mechanics.A parametric study is conducted to isolate the effects of overlay thickness and stiffness,base thickness and stiffness on top-down crack propagation in asphalt pavements.The results show that longitudinal wheel loads are disadvantageous to top-down crack because it increases the compound stress intensity factor (SIF) at the tip of top-down crack and shortens the crack path,and thus the fatigue life descends.The SIF experiences a process "sharply ascending—slowly descending—slowly ascending—sharply ascending again" with the crack propagating.The thicker the overlay or the base,the lower the SIF; the greater the overlay stiffness,the higher the SIF.The crack path is hardly affected by stiffness of the overlay and base.     

以“唱红”和“打黑”为例试论“动词＋颜色形容词”结构

＂V＋颜色adj＂这种语言组合现象古已有之,近期活跃在各大媒体的＂唱红＂、＂打黑＂引起社会的广泛关注,本文作者拟从语言学的角度对＂唱红＂、＂打黑＂这种现象进行分析,并把它们与旧的＂V＋颜色ad j＂形式进行对此,试图发现此类词语出现的语言学理据。     

断裂力学的工程应用

脆性破坏是零件失效的主要形式之一,传统的防脆断方法要么很保守要么照样产生脆性破坏.从断裂力学的角度讨论带裂纹体在实际工程中的应用.     

Exact solution of an external circular crack in a piezoelectric solid subjected to shear loading

A three-dimensional, exact analysis is presented in this paper for the problem of an external circular crack in a transversely isotropic piezoelectric medium subjected to arbitrary antisymmetric shear loading. A recently proposed general solution of three-dimensional piezoelectricity is employed. It is shown that four quasi harmonic functions involved in the general solution can be respresented by just one complex potential. Previous results in potential theory are then used to obtain the exact solution of the problem. For point shear loading, Green’s functions for the elastoelectric field are derived in terms of elementary functions. Project supported by Scientific Research Foundation for Returned Overseas Chinese Scholars, State Education Ministry and partly by National Natural Science Foundation of China (NSFC) (10002016).     

一种智能性自动换肤技术研究

人脸表情识别和软件换肤分别作为人机交互中的智能化和人性化技术得到了深入的研究。本文结合以上两种技术提出了基于人脸表情识别的软件界面自动换肤思想,介绍了一种软件界面自动换肤系统的设计,并讨论了主成分分析检测定位模型。仿真结果证明了该方案的可行性。     

含横向裂纹的转动轴的振动基频分析

利用等效线弹簧模型近似计算了含裂纹转动轴的自由振动基频。裂纹轴的横向位移看成是由无裂纹轴的横向位移和由裂纹引起的附加位移的叠加。具体讨论了裂纹深度、裂纹所处的位置以及裂纹角对轴自由振动基频的影响,其结果与实际情况吻合。     

高层建筑大体积混凝土裂缝的预防

阐述如何控制大体积泵送混凝土水泥水化热引起的混凝土内外温差和混凝土收缩产生的裂缝,指出在水泥中加入纤维可以提高混凝土抗拉强度,控制基体中微裂缝的形成和发展,结合某工程混凝土抗裂安全度计算,提出采用掺入杜拉纤维方法来防止高层建筑大体积混凝土温度裂缝产生是可行有效的。     

我国大型飞机发展战略的思考

中国民用航空工业20年来不成功的根本原因在于没有坚持走自主开发的道路,其根源是体制。本文通过理论概括和分析中国发展大飞机的三个历史教训,指出中国民用航空工业要想在21世纪打翻身仗,就必须突破旧的体制并坚持自主创新的方针。     

分子力与分子间距离关系的模拟演示

本介绍了用表面张力与水膜高度来模拟演示分子力与分子间距离关系的方法，阐述了演示原理，描述了演示过程，并给出简单演示装置图．     

大体积混凝土温度裂缝的控制系统

依据最新信息技术,建立了大体积混凝土温度裂缝控制系统,详细介绍了温度场分析和CP温度应力解析的过程。该系统可以采用对话式操作,对大体积混凝土温度裂缝的控制具有广泛的指导意义。