格栅对高速列车设备舱散热性能的影响

为研究在裙板不同位置增加格栅对高速列车设备舱散热的影响,建立3种不同设备舱的高速列车空气动力学模型,分别包括原始设备舱、裙板中间增加格栅的设备舱和裙板两端增加格栅的设备舱.基于三维不可压缩N-S方程和k-ε两方程湍流模型,利用FLUENT对250 km/h高速列车设备舱的温度场和流场进行模拟.对列车上行和下行时设备舱的流场与温度场进行分析,比较在不同位置增加格栅时设备舱内温度的变化.结果表明:在裙板不同位置增加格栅对设备舱内的温度场影响较大,在裙板中间增加格栅对头车和中间车设备舱的散热不利,建议在裙板两端增加格栅以更有利于设备舱散热.     

轿车乘员舱内气流对气动阻力影响的数值模拟

为揭示轿车侧窗开启程度和乘员舱内布置对气动阻力的影响规律,建立1∶1阶背式英国汽车研究协会(Motor Industry Research Association,MIRA)标准模型;基于FLUENT,在30 m/s风速下采用可实现k-ε湍流模型对不同侧窗开度的模型进行三维稳态数值模拟,得到气动阻力因数随侧窗开启程度的增大而增大的变化趋势.在侧窗全开时,改变舱内布置,得到气动阻力因数随假人个数的变化规律;对比不同情况下模型的流场分布发现,当考虑乘员舱内气流时,气动阻力的大小不仅与进气量有关,而且受舱内流场分布的影响.     

两种湍流模型在风洞拐角流场计算中的应用及比较

为降低风洞拐角压力损失,提高其气动性能,使用雷诺应力模型(Reynolds Stress Model,RSM)和k-ε湍流模型对其流场进行数值模拟,分析和比较两种模型在压力损失因数、壁面摩擦损失和二次流损失上的异同,得出:使用两种模型均能发现拐角压力损失因数并不随雷诺数变化而变化;使用RSM得到的压力损失因数与实验值更为接近;相同雷诺数下,使用RSM计算得到的壁面摩擦损失因数比k-ε湍流模型的大,但两种模型得到的壁面摩擦损失因数变化趋势一致;两种模型计算得到的二次流损失随雷诺数变化规律一致,但是在相同雷诺数下,使用k-ε湍流模型计算得到的二次流损失比RSM大.     

液-液旋流器内近壁湍流处理方法及数值模拟

无论k-ε模型及其修正模型,还是广泛应用于水力旋流器数值模拟的雷诺应力模型(RSM),都只是针对湍流核心区,对近壁区无效,如何确定液.液水力旋流器湍流场模拟的近壁处理方法亟待深入研究.在介绍湍流近壁区流动特点和处理方法的基础上,引入了2种湍流近肇处理函数--标准的和非平衡的壁面函数,在相同的网格系统和计算条件下计算了双锥双柱型水力旋流器内湍流场,结果与激光多普勒测速仪(LDV)测试结果基本吻合,但采用非平衡的壁面函数预报结果更为可信,为进一步精确研究旋流器内的流动过程打下良好的基础.     

湍流模型对电源车车舱内流场及散热的影响

针对某静音型电源车车舱结构及其通风散热特点,建立了车舱内部计算流体力学(Computational Fluid Dynamics,CFD)仿真模型,通过设置各类解析条件,分别利用Standardk-ε,Realizablek-ε,Standardk-ω和SSTk-ω四种湍流模型仿真模拟了车舱内流场和车载柴油发电机组的温度场,并分别测试了两条垂直线的风速对流场仿真结果进行了评价,测试了柴油发电机组和消声器不同测点的温度值,分析了散热的仿真精度.结果表明:k-ε模型的数值模拟结果比k-ω模型更加贴近实测结果,表明Realizablek-ε模型的仿真精度最高,适合静音型电源车车舱结构.     

履带式两栖运输设备多湍流模型的研究

关于履带式两栖运输设备精确建模问题,针对履带式两栖运输设备水上受湍流影响大,但湍流模型难于选择的问题,为达到使用恰当湍流模型提高仿真精度的目的,采用对比阻力系数和绕流场云图的方法进行湍流模型适用性的研究,明确各种湍流模型的特性。以某型履带式两栖运输设备水下绕流场为计算对象,基于RANS方程的求解,分别采用Spalart-All-maras、标准k-ε、RNG k-ε、Realizable k-ε、标准k-ω、SST k-ω湍流模型。对比多组仿真结果,表明Realizable k-ε、SSTk-ω模型计算得到的总阻力相对误差最小,RNG k-ε模型对复杂形体周围流场描绘最详细,Spalart-Allmaras模型也有较好的计算精度。     

刹车盘结构对车轮及整车流场的影响

为研究车轮刹车盘结构对旋转车轮和整车流场气动特性的影响,针对是否存在刹车盘两种情况分别建立等比例模型,采用可实现的k-ε两方程模型计算,对比分析气动升、阻力因数,表面压力因数及整体与局部流场,发现刹车盘结构在简化车体上对车轮局部和整车流场都具有突出影响,指出在整车气动特性模拟中刹车盘存在的必要性.进一步进行计算模型选择的研究,发现旋转壁面模型与多坐标参考系(Multiple Reference Frame,MRF)模型对旋转车轮的流场特性模拟结果有差异,在近车轮区域表现尤为明显.     

超音速扩压器喷雾冷却数值仿真研究

为了探讨研究喷雾冷却中冷却水流量、喷射速度及喷嘴轴向分布位置等因素对超音速扩压器壁面温度的影响,借助CFD计算软件FLUENT,采用标准k-ε湍流模型,对喷雾冷却下超音速扩压器内流场进行了数值仿真。通过计算,得到了扩压器内压强分布及壁面温度分布。分析了喷雾冷却中冷却水流量、喷射速度及喷嘴轴向位置对超音速扩压器壁面温度的影响。研究表明：随着冷却水流量的增大,扩压器壁面温度降低。同时,扩压器入口处静压升高,对应仿真高度降低;减小冷却水喷射速度,可以有效降低扩压器入口处壁面温度;喷嘴的轴向分布位置对扩压器壁面温度有较大影响,仿真结果证明,喷嘴沿轴向呈对数分布有利于降低扩压器壁面温度。     

湍流模型和网格分布对水下航行体回转水动力数值计算的影响

针对水下航行体安全操纵设计的关键环节水动力预报,用FLUENT求解不可压缩RANS方程,采用定常旋转运动坐标系,运用相对运动理论和运动叠加原理,计算RNG k-ε,可实现k-ε和SST k-ε等3种湍流模型以及不同网格分布对水下航行体做单平面回转运动所受垂向力和纵倾力矩,并与试验结果比较.结果表明在Re=11.7×106条件下,垂向力和纵倾力矩预报精度较高.该数值预报方法可行、有效,具有较好的工程实用价值.     

下反前掠地效翼三维数值模拟

为研究下反前掠地效翼的气动性能,利用FLUENT求解定常不可压N-S方程和可实现的k-ε湍流模型,建立在地面效应下地效翼流场的三维数值模型,对不同下反角和前掠角的地效翼进行数值模拟.计算结果揭示出下反角和前掠角对地效翼空气动力特性、流场特性和纵向稳定性的影响规律.对下反前掠地效翼的三维数值模拟可以为地效飞行器的设计和优化提供参考.     

Only connect: teaching, technology and telesis

Abstract This paper describes an approach to the design of interactive multimedia materials being developed in a European Community project. The developmental process is seen as a dialogue between technologists and teachers. This dialogue is often problematic because of the differences in training, experience and culture between them. Conditions needed for fruitful dialogue are described and the generic model for learning design used in the project is explained.     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Avoiding semantic and temporal gaps in developing software intensive systems

Development of software intensive systems (systems) in practice involves a series of self-contained phases for the lifecycle of a system. Semantic and temporal gaps, which occur among phases and among developer disciplines within and across phases, hinder the ongoing development of a system because of the interdependencies among phases and among disciplines. Such gaps are magnified among systems that are developed at different times by different development teams, which may limit reuse of artifacts of systems development and interoperability among the systems. This article discusses such gaps and a systems development process for avoiding them.     

Designing economic np control charts: A programmed simulation approach

This paper presents control charts models and the necessary simulation software for the location of economic values of the control parameters. The simulation program is written in FORTRAN, requires only 10K of main storage, and can run on most mini and micro computers. Two models are presented - one describes the process when it is operating at full capacity and the other when the process is operating under capacity. The models allow the product quality to deteriorate to a further level before an existing out-of-control state is detected, and they can also be used in situations where no prior knowledge exists of the out-of-control causes and the resulting proportion defectives.     

The development of robot art

Going through a few examples of robot artists who are recognized worldwide, we try to analyze the deepest meaning of what is called “robot art” and the related art field definition. We also try to highlight its well-marked borders, such as kinetic sculptures, kinetic art, cyber art, and cyberpunk. A brief excursion into the importance of the context, the message, and its semiotics is also provided, case by case, together with a few hints on the history of this discipline in the light of an artistic perspective. Therefore, the aim of this article is to try to summarize the main characteristics that might classify robot art as a unique and innovative discipline, and to track down some of the principles by which a robotic artifact can or cannot be considered an art piece in terms of social, cultural, and strictly artistic interest. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于QTE的蒙古文显示机制研究与实现

蒙古语言是中国蒙古族使用的通用语言,由于蒙古文区别于其他文字的书写方式和其自身变形机制等特点,在很多通用的文字处理引擎中都不被支持。在嵌入式产品开发与应用领域中Linux加QTE已经成为流行方式。该文给出了一种在QTE环境上实现基于标准Unicode的蒙古文点阵显示和变形算法, 并自定义了支持蒙古文的QTE组件,扩展了QTE功能,为在Linux加QTE方式的嵌入式体系结构中处理蒙古文提供了一种解决方法。     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。