多样化实时刚体破碎模拟

目的 现有刚体破碎仿真模拟中,基于物理受力分析的方法往往难以应用在对实时性要求较高的场景中;而基于非物理方法的破碎模拟,破碎效果大多缺乏多样性。为了使得破碎模拟同时满足实时性和破碎效果多样化,提出了一种多样化实时刚体破碎模拟方法。方法 进行破碎模拟时首先由选定的种子点生成类型得到种子点集,采用Sweep Plane算法生成Voronoi图后基于Voronoi图信息对模型进行空间剖分;然后选择破碎时行为模拟方式,对物体破碎时所受外力进行模拟;最后对破碎时碰撞检测及碰撞后碎片的运动过程进行模拟并渲染显示。结果 通过组合不同的种子点生成类型和破碎时行为模拟方式,得到了多样化的刚体破碎效果。对单个刚体进行破碎模拟时,碎片数目不超过200个时帧率可以达到75帧/s,满足实时性的需求;对多个可破碎目标同时存在的复杂场景,破碎仿真模拟的平均帧率可以达到50帧/s,同样满足实时性要求;与现有方法对比的结果也验证了本文方法在计算效率和破碎效果多样性两方面达到了较好的平衡。结论 本文方法在满足实时性要求的同时,丰富了刚体破碎的效果,不同种子点生成类型和破碎时行为模拟方式的组合可以实现破碎效果多样性。     

The use of computer simulation in the pulp and paper industry

Pulp and paper mill processes have certain typical features in common with other simulation objects. However, computer simulation can serve as a useful tool in the design and construction of process units and the entire mill, as well as comparison of various production and control strategies of the pulp and paper mill processes. Simulation problems in this area are related to the adjustment of simulation models to mill material balances with many recycles. When the internal behaviour of the processes are considered the lack of sufficiently complete or applicable models sets a limitation on simulation studies.     

基于近场动力学方法的水力压裂过程数值模拟

利用近场动力学方法便于处理多裂纹萌生、扩展和分叉的优点,将其应用于页岩水力压裂过程的数值模拟.结合页岩水力压裂机理提出在近场动力学中由破坏度跟踪裂纹扩展路径,并通过在新生成裂纹面法线方向施加水压载荷的裂纹追踪方法,成功模拟单射孔横剖面开裂水压实验以及单射孔和多射孔水平井纵剖面的水力压裂过程,得到压裂导致的裂纹缝网结构.数值结果还表明初始射孔裂纹会显著影响后续的水力压裂过程.     

The use of computer simulation in teaching clinical diagnosis

Previous studies have shown that feedback of the weighting used in making complex judgements can greatly improve learning when the correct weighting is known. This paper describes the application to teaching medical diagnosis of a microcomputer program which calculates and displays factor weighting based on answers to clinical case simulations. In one application, students learning to diagnose urinary tract infusion with computer feedback of weighting progressed much more rapidly than a control group who received outcome feedback alone. Other applications in the clinical setting suggest that this type of learning can improve diagnostic accuracy and predictive calibration through more accurate assimilation of the clinical information available.     

The use of simulation in discrete-event dynamic systems design

The use of simulation as a tool to design complex stochastic systems is often inhibited by cost. We present a procedure for estimating a value for the controllable input parameter which generates a desirable output. Since the output has to be matched by varying the input parameter, an iterative method of solution is applied. The proposed solution algorithm is based on Newton's method using a single-run simulation approach to estimate the needed derivative. The major contribution of this paper is to provide a framework for arriving at a target value for product, process and service attributes through Monte Carlo experiments. The effectiveness of the proposed procedure is demonstrated by determining a desirable service rate in a queueing system with known analytical solution.     

The use of splitting methods in the numerical simulation of reacting flows

The aim of this paper is to study discretizations of convection-diffusion-reaction equations using splitting methods. Estimates for the physical splitting errors and the numerical splitting errors are established. These estimates lead to the selection of optimal sequences and coupling of physical phenomena and adequate use of implicitness and explicitness. Numerical simulations of two chemical industry problems are included.     

Monte Carlo simulation of rock slope reliability

One of the most important problems encountered in probabilistic rock slope stability analysis is the correlation that exists among the random variables involved in the design equation. Some existing probabilistic models assume independence between the random variables by ignoring all possible correlations. Other models realize the importance of including the correlations in the mathematical formulation; however, the associated mathematical complications require inclusion of some simplifying assumptions, such as Gaussian distribution of all random variables involved in the design equation. Therefore, it is important to develop techniques to deal with the correlations while maintaining the desired accuracy.

This paper is concerned with reliability analysis of rock slopes against single plane sliding under the influence of water. A modified Monte Carlo Simulation is used to determine the reliability of rock slopes including possible correlations between the variables entering into the design equation. These variables do not have to be normally distributed and can have different probability density functions. Finally, a computer program has been developed to perform all the necessary calculations.     

基于LS-DYNA刨刀刨削煤岩的模拟研究

利用有限元分析软件LS-DYNA,建立刨煤机刨刀刨削煤层的三维模型,模拟刨刀刨削煤层的动态过程。研究中,获取了刨刀刨削阻力、应力分布等时间历程曲线,分析了刨刀不同刨削深度、刨刀间距和刨刀宽度对刨削能耗的影响。     

The use of a procedure-oriented language for process-oriented simulation

It is fairly easy to use a language like ALGOL W1 for event- or activity-oriented simulation. A method is described to use such a language for process-oriented simulation. The illusion of co-routines necessary in this type of simulation is maintained by low-level language procedures which alter the run-time stack. Two new scheduling procedures are also described.     

The use of a generic simulation model in evaluating manufacturing processes

In recent years the application of simulation models to analyze the production capabilities of manufacturing processes has been increasing at IBM's Poughkeepsie plant. To avoid major programming effort for each new application, a generic simulation model was developed. The model, written in SIMPL/1 (Simulation Language Based on PL/1), was designed in modules defined on a functional basis. This language was chosen because it allowed full use of the PL/1 programming language, reduced the excessive run times experienced with large, specialized GPSS models, simplified the procedure for making input changes and provided output that could be easily interpreted by the non-programmer. The input data bases are user-oriented so that changes can be made to the system being modeled without programming support. The output generated by the model can provide the user with information on resource utilization, major process bottlenecks, overtime requirements, process throughput and process cycle time. This data is evaluated by the user to determine how well the process functions under given operating conditions so that cost effective decisions can be made. An example is provided on the model's application to a logic and memory card assembly process.     

The simulation and use of a TABLE data type in algol W

This paper reviews the role of RECORD and REFERENCE variables in Algol W, points out some restrictions in their use, and describes a method for simulating a new TABLE data type within the existing syntax. It is shown how the use of a few simple procedures generated in a preprocessor phase enable this new type to be used freely within dynamic structures of data. A comparison is made with some alternative methods of implementation in Algol W.     

The Lowry model of land use simulation and its derivatives

The Lowry family of urban land use simulation models is one of the most widely used, both as an aid in scientific investigation, and as a tool for making predictions concerning growth and change in the distribution and intensity of land use activities. This paper outlines the theoretical work and modelling experience which led to the development of the Lowry family of land use simulation models and sketches the main features of its logical structure. The paper commences with a discussion of procedural relationships between modelling and planning, focusing upon difficulties which are frequently encountered when predictive models are to be designed for planning purposes. Next, the paper describes the conceptual foundations of the gravity and entropy-maximizing models of spatial interaction, followed by an explanation of how the gravity idea was applied in the Lowry model of urban land use and its successors. Finally, the last section of the paper is devoted to ITLUP, in which Lowry-type land use models embodying entropy-maximizing trip functions are linked with a transportation network simulation model.     

水中武器仿真系统中的HLA环境成员

为使训练具有真实、逼真的效果,对水雷作战环境的合成是一个至关重要的环节.根据水雷作战的特点和环境,通过环境数据采集和实时变化模型,构建了一个水雷作战环境.在作战环境仿真过程中,对象的状态、运动等,都会受到环境的影响.为反映出这些影响因素,并保持其一致性,在HLA(high level architecture)仿真中设计专用的环境成员,通过统一的接口,实现对所有环境数据的统一控制.通过在水中武器综合仿真系统中的实际应用,很好的完成了仿真任务.     

煤岩刨削中的刨刀受力有限元模拟研究

建立刨煤机刨刀刨削煤层的三维模型,利用有限元分析软件LS-DYNA,模拟刨刀刨削煤层的过程。通过研究,得到了刨削速度、刨刀刨削阻力等的时间历程曲线,分析了不同刨削深度、刨刀间距和刨刀宽度对刨削阻力的影响。     

Convergent results about the use of fuzzy simulation in fuzzy optimization problems

We discuss the convergence of fuzzy simulation as it is employed in fuzzy optimization problems. Several convergence concepts for sequences of fuzzy variables are defined such as convergence in optimistic value. A new approach to approximating essentially bounded fuzzy variables with continuous possibility distributions is introduced. Applying the proposed approximation method to our previous work, we prove three convergence theorems about the use of fuzzy simulation in computing the credibility of a fuzzy event, finding the optimistic value of a return function, and calculating the expected value of a fuzzy variable.     

土地利用最佳模拟尺度选择及空间格局模拟

土地利用变化是一个受到多重因素相互影响的动态过程。目前,已经成为全球环境变化和可持续发展的重要内容,而区域土地利用空间格局模拟已成为LUCC研究的关键内容。以2000年以及2010年的TM遥感影像解译数据以及数字高程模型、水系、铁路、公路、降雨量和气温等数据为基础,运用二元逻辑斯蒂回归模型对黄土台塬区的土地利用最佳模拟尺度进行了选择,并在此基础上对研究区的各种土地利用进行了空间格局模拟。研究结果显示：（1）在土地利用格局模拟的十个空间尺度上,土地利用变化空间格局与其驱动力因子之间存在着一定的尺度相关性特征;（2）黄土台塬区耕地、林地、草地的ROC值在十个空间尺度上均呈现出先增加后减少的趋势,转折点在400 m尺度附近,说明黄土台塬区的土地利用在尺度效应和尺度转换的效应下,400 m×400 m是此区域土地利用格局优化的最佳模拟尺度;（3）在400 m最佳模拟尺度上所模拟出的草地和林地的分布格局都与人均GDP和地形综合指数两个变量显著相关,而对耕地的分布影响最为明显的变量则是地形综合指数。     

Large-scale fluid–structure interaction simulation of viscoplastic and fracturing thin-shells subjected to shocks and detonations

The fluid–structure interaction simulation of shock- and detonation-loaded thin-walled structures requires numerical methods that can cope with large deformations as well as local topology changes. We present a robust level-set-based approach that integrates a Lagrangian thin-shell finite element solver with fracture and fragmentation capabilities and an Eulerian Cartesian fluid solver with optional dynamic mesh adaptation. As computational applications, we consider the plastic deformation of a copper plate impacted by a strong piston-induced pressure wave inside a water pipe; and the induction of large plastic deformations and rupture of thin aluminum tubes due to the passage of ethylene–oxygen detonations.