汽液两相流键合图建模与仿真

为了研究汽液两相流管道系统动态特性,从质量守恒、能量守恒和动量守恒方程出发,采用交错网格有限体积法,推导出汽液两相流通用微分方程的离散形式,结合键合图理论建立了分段集总参数键合图模型.为了求解工质热力性质,利用多领域统一建模语言Modelica建立了键合图模型的仿真程序,并以直流锅炉受热管为例,在Dymola平台上进行仿真.仿真结果反映了热负荷阶跃变化时管内压力、温度、含汽率动态变化与分布情况,为管道系统设计与分析提供了依据.     

质子交换膜燃料电池稳态模型及仿真

质子交换膜燃料电池(PEMFC)发电装置具有高能效,低噪音,常温启动和环境友好等特点.文中将对PEMFC进行稳态建模,使模型能正确反映电堆的实际输出性能.PEMFC实验模型主要是通过实验方法,建立描述电池输出特性(输出电压与电流密度关系)的经验公式.为了提高模型的精度,以便模型能更好地反映真实的PEMFC电对性能,则需要对模型的参数进行优化.通过不同的Matlab优化函数对所建模型进行参数辨识,比较得出其中结果较好的对模型进行仿真,以验证模型的正确性.     

PEM燃料电池加湿器温度系统的模型辨识与控制

本文分析了质子交换膜燃料电池的膜加湿器系统,介绍了采用本课题组开发的NetCon控制器对加湿器系统进行数据采集和温度控制的系统集成方案。在此基础上辨识了加湿系统的温度模型,并采用变速积分PID控制算法控制加湿器的温度。仿真和实验结果表明,辨识得到的加湿系统温度模型能够准确地描述被控对象,本文采用的控制策略可以得到满意的控制效果。     

计算反射技术综述

计算反射技术是提高软件系统灵活性、可扩展性的重要技术。它使得软件系统具有自适应能力,在运行时随环境变化而改变自身,实现程序的动态演进。该文介绍了计算反射的基本概念、发展历程、方法分类、实现环境,帮助读者学习和掌握计算反射。文章的最后阐述了计算反射今后发展应重点关注的若干问题。     

Two-Equation RNG Transport Modeling of High Reynolds Number Pipe Flow

New solutions of two-equation RNG turbulence transport model are used to calculate high Reynolds number pipe flows. The results are compared with experimental Superpipe data of Zagarola et al. (1996) up to Reynolds number of 3.5 × 10⁷.     

面向信息流的安全模型与评估综述

对系统进行攻击的本质之一是在信息流动过程中的非授权泄露与修改,进而破坏系统的安全性,这使得非常有必要对信息流的安全进行分析。从安全保障目标和安全保障方式上对安全信息流模型进行了分类,综述了不同类型的信息流模型研究现状,分析了现有面向信息流的量化评估方法,展望了面向信息流安全评估的发展趋势。     

燃料电池电能与热能建模研究

为分析燃料电池的动态特性,对其发电和发热过程进行了建模研究。燃料电池划分为阳极动态模型、阴极动态模型、电化学电压模型和温度动态模型,分别从流量平衡、能量平衡和经验公式角度进行了机理建模;并采用改变负载和冷却水流量的方式进行测试。仿真结果表明,该模型能模拟燃料电池的电热动态过程,可用于辅助控制设计。     

Computational Mechanisms of Pulse-Coupled Neural Networks: A Comprehensive Review

Pulse-coupled neural networks (PCNN) have an inherent ability to process the signals associated with the digital visual images because it is inspired from the neuronal activity in the primary visual area, V1, of the neocortex. This paper provides insight into the internal operations and behaviors of PCNN, and reveals the way how PCNN achieves good performance in digital image processing. The various properties of PCNN are categorized into a novel three-dimensional taxonomy for image processing mechanisms. The first dimension specifies the time matrix of PCNN, the second dimension captures the firing rate of PCNN, and the third dimension is the synchronization of PCNN. Many examples of processing mechanisms are provided to make it clear and concise.     

Multiphase Flow in Deforming Porous Media: A Review

In this work we present a general model for the analysis of multiphase flow in deforming porous media with particular regard to concrete and biological tissues. Such problems are typically multi-physics ones with overlapping domains where diffusion, advection, adsorption, phase change, deformation, chemical reactions and other phenomena take place in the porous medium. For the analysis of such a complex system, the model here proposed is obtained from microscopic scale by applying the thermodynamically constrained averaging theory which guarantees the satisfaction of the second law of thermodynamics for all constituents both at micro and macro-level. Furthermore, one can obtain some important thermodynamic restrictions for the evolution equations describing the material deterioration. Two specific forms of the general model adapted to the cases of cementitious and biological materials respectively are shown. Some numerical simulations aimed at proving the validity of the approach adopted, are also presented and discussed.     

Computational Fluid Dynamics in Turbomachinery: A Review of State of the Art

Computational fluid dynamics (CFD) plays an essential role to analyze fluid flows and heat transfer situations by using numerical methods. Turbomachines involve internal and external fluid flow problems in compressors and turbines. CFD at present is one of the most important tools to design and analyze all types of turbomachinery. The main purpose of this paper is to review the state of the art work carried out in the field of turbomachinery using CFD. Literature review of research work pertaining to CFD analysis in turbines, compressors and centrifugal pumps are described. Various issues of CFD codes used in turbomachinery and its parallelization strategy adopted are highlighted. Furthermore, the prevailing merits and demerits of CFD in turbomachinery are provided. Open areas pertinent to CFD investigation in turbomachinery and CFD code parallelization are also described.     

A Review of Digital Terrain Modeling

Terrains are a crucial component of three‐dimensional scenes and are present in many Computer Graphics applications. Terrain modeling methods focus on capturing landforms in all their intricate detail, including eroded valleys arising from the interplay of varied phenomena, dendritic mountain ranges, and complex river networks. Set against this visual complexity is the need for user control over terrain features, without which designers are unable to adequately express their artistic intent. This article provides an overview of current terrain modeling and authoring techniques, organized according to three categories: procedural modeling, physically‐based simulation of erosion and land formation processes, and example‐based methods driven by scanned terrain data. We compare and contrast these techniques according to several criteria, specifically: the variety of achievable landforms; realism from both a perceptual and geomorphological perspective; issues of scale in terms of terrain extent and sampling precision; the different interaction metaphors and attendant forms of user‐control, and computation and memory performance. We conclude with an in‐depth discussion of possible research directions and outstanding technical and scientific challenges.     

智能需求获取与建模研究综述

需求获取和建模是指从需求文本或记录中获取显式和隐式的需求,并通过表格化、图形化、形式化等方法构建相应模型的过程,是软件开发过程中极为关键的一步,为后续系统设计与实现铺平道路,提高软件开发效率和质量,提升软件系统稳定性和可行性.研究者们在需求获取与建模方面获得了一系列研究成果,根据其关注阶段不同,可以将它们分为需求知识提...     

Modeling the Growth of Transportation Networks: A Comprehensive Review

This paper reviews the progress that has been made over the last half-century in modeling and analyzing the growth of transportation networks. An overview of studies has been provided following five main streams: network growth in transport geography; traffic flow, transportation planning, and network growth; statistical analyses of network growth; economics of network growth; and network science. In recognition of the vast advances through decades in terms of exploring underlying growth mechanisms and developing effective network growth models, the authors also point out the challenges that are faced to model the complex process of transport development.     

行人运动建模及仿真研究综述

根据行人运动建模及仿真发展历史以及已经提出的一些模型和算法,从宏观和微观两个层面对行人运动建模策略进行系统分析,包括宏观建模策略:行人动力学模型、空间交互/熵最大化模型以及微观建模策略:元胞自动机模型、磁力场模型、社会力模型、智能体模型、空间句法模型、马尔可夫模型.在建模策略分析基础上,重点研究了Legion,PAXPORT,NOMAD,STEPS以及BuildingEXODUS五种主流行人仿真系统,总结了各系统的建模思想、核心模型及优缺点.指出了未来行人系统建模及仿真的研究趋势.     

Computational dynamics: Modeling and visualizing trajectory flows in phase space

This paper describes a computational technique for modeling and visualizing dynamical behaviors of complex systems in phase space. The technique employs a novel idea offlow pipes to model trajectory bundles that exhibit the same qualitative features. It parses a continuous phase space of a dynamical system, consisting of an infinite number of individual trajectories, into a manageable discrete collection of flow pipes that a computer can efficiently reason about. The technique provides a computational way for both machines and humans to visualize and manipulate dynamics of a physical system. The flow-pipe modeling technique is implemented in a program called MAPS. The technique has been applied to the automatic control synthesis in which programs automatically analyze and design high-performance, global controllers.     

情景感知的软件需求获取与建模技术综述

情境感知的移动应用能够适应用户当前状态,因此这类应用越来越受到青睐。但由于上下文情景的维度是无数的,这使得获取和建模情境感知系统的情景需求成为一大挑战。本文通过文献综述的方法,旨在:(1)发现有哪些情境感知的需求获取与建模方法;(2)评估这些方法的技术转移成熟度。通过对所选择的61篇相关文献,进行数据抽取和分析综合,本文总结并识别出11种需求获取的方法、10种需求建模的方法以及它们的技术转移现状。结果显示:(1)最受欢迎的情景感知需求获取方法是用例和场景,而最常用的情境感知需求建模方法则是面向目标的方法;(2)在大多数相关文献中的需求获取与建模技术的技术成熟度都不高,不利于其面向工业界进行技术转移。     

一种基于GPRS的燃料电池远程监控系统

燃料电池是一种新型的绿色能源,其高效率,零排放,受到人们普遍的关注。文章在分析了燃料电池的工作过程的基础上,根据其特点和控制要求,介绍如何采用ADUC812系列单片机为核心构建底层控制器和基于SI协但NSTC45芯片的GPRS网络节点模块的设计方法,以及一种基于GPRS的燃料电池程监控系统的软、硬件技术。在此基础上。实现了燃料电池发电过程的远程监控,经实际运行,取得了令人满意的结果。     

A Review of Trimming in Isogeometric Analysis: Challenges,Data Exchange and Simulation Aspects

We review the treatment of trimmed geometries in the context of design, data exchange, and computational simulation. Such models are omnipresent in current engineering modeling and play a key role for the integration of design and analysis. The problems induced by trimming are often underestimated due to the conceptional simplicity of the procedure. In this work, several challenges and pitfalls are described.