Applications of the discrete element method in mechanical engineering

Compared to other fields of engineering, in mechanical engineering, the Discrete Element Method (DEM) is not yet a well known method. Nevertheless, there is a variety of simulation problems where the method has obvious advantages due to its meshless nature. For problems where several free bodies can collide and break after having been largely deformed, the DEM is the method of choice. Neighborhood search and collision detection between bodies as well as the separation of large solids into smaller particles are naturally incorporated in the method. The main DEM algorithm consists of a relatively simple loop that basically contains the three substeps contact detection, force computation and integration. However, there exists a large variety of different algorithms to choose the substeps to compose the optimal method for a given problem. In this contribution, we describe the dynamics of particle systems together with appropriate numerical integration schemes and give an overview over different types of particle interactions that can be composed to adapt the method to fit to a given simulation problem. Surface triangulations are used to model complicated, non-convex bodies in contact with particle systems. The capabilities of the method are finally demonstrated by means of application examples. Commemorative Contribution.     

Local Exact Particle Tracing on Unstructured Grids

For analyzing and interpreting results of flow simulations, particle tracing is a well established visualization method. In addition, it is a preliminary step for more advanced techniques such as line integral convolution. For interactive exploration of large data sets, a very efficient and reliable particle tracing method is needed. For wind channel experiments or flight simulations, large unstructured computational grids have become common practice. Traditional approachs, based on numerical integration methods of ordinary differential equations however fail to deliver sufficiently accurate path calculation at the speed required for interactive use. In this paper we extend the local exact approach of Nielson and Jung in such a way that it can be used for interactive particle tracing in large data sets of steady flow simulation experiments. This will be achieved by sophisticated preprocessing using additional memory. For further visual enhancement of the streamline we construct an implicitly defined smooth Bézier curve that is used for ray tracing. This allows us to visualize additional scalar values of the simulation as attributes to the trajectory and enables the display of high‐quality smooth curves without creating any visualization geometry and providing a good impression of the spatial situation at the same time. ACM CSS: I.3.3 Computer Graphics—Line and curve generation; I .3.7 Computer Graphics—Raytracing; G.1.2 Numerical Analysis—Spline and piecewise polynomial approximation     

我国矿业城市实现可持续发展的途径分析

详细分析我国矿业城市可持续发展所面临的社会、经济、资源和生态环境等问题，提出了我国矿业城市应树立可持续发展目标及其内涵，系统分析矿业城市可持续发展的结构和模式，结合我国矿业城市发展存在的主要问题，以矿业城市可持续发展理念为指导，提出我国矿业城市实现可持续发展的途径及其建议。     

钻速模式动态辨识方法研究

目的：钻进过程是一个复杂的工艺过程，影响钻速的因素错综复杂。为钻井参数优化和实时控制，提出钻速动态模型。方法：对影响钻速的因素进行分析，用系统辨识方法建立钻速模式。结果：利用该方法建立了华北油田岔河集地区的钻速模型，取得满意结果。结论：此动态钻速模式能更准确、科学地描述钻进过程，并在钻井参数最优化、钻井过程的闭环控制等方面具有广阔的应用前景。     

CIMS环境中的数据模式转换

本文在分析CIMS环境中数据模式冲关类型的基础上，提出一种互连数据库系统模式结构，论述了在异构数据库集成中解决模式冲突的基本方法．在这种方法体系中，不需要建立整个企业的全局数据模式，各局部DBA以简单的方式定义应用所需的模式变换，系统根据这种定义自动完成各种转换，使用户看到的模式和数据结果与应用要求的一致．     

单麦克风和双麦克风语音增强系统的研究

本文对采用减谱法和箱关法的语音增强系统进行了研究，系统的噪声为白噪声和普通机房噪声。减谱法采用单麦克风输入，试验中发现语音的分帧方法对消噪影响很大，通过比较得到了一种具有明显消噪效果的分帧方法，在相关法中采用双麦克风输入，对两个输入信号之间的时延差进行了补偿，在求维纳滤波器系数时，对信号谱进行统计平均，从而使消噪后的语音信号具有较好的自然度。在研究以上两种方法的基础上，我们提出了一种混合消噪系统，     

银行计算机系统维护的探讨

从机房建设、通讯线路、日常维护、诊断维修等几个方面探讨了银行计算机系统维护中的重点和难点     

钢管内径光电检测装置

介绍了一种检测细长钢管内径的光电检测装置。该装置利用线阵ＣＣＤ作传感器，采用８０３１单片机作为主控制。     

中国民航信息系统现状及发展展望

介绍了中国民航信息系统的现状和与实际业务需求的差距,接着从系统设计理念、核心系统、新系统新功能和信息系统整合等多个方面详细阐述了民航信息系统的发展思路,最后强调了建立新一代民航信息系统的紧迫性,具备很强的指导意义。