高Schmidt数下喷射器内湍流混合的多尺度模拟放大研究

本文从微观与宏观两个方面考察了喷射器的混合性能.利用CFD模拟软件Fluent 6.2求解了混合模型方程、流体流动方程及k-ε湍流模型方程,对不同结构、不同工况下的喷射器进行了考察,结果表明:1)在喷射器结构一定的情况下,喷嘴速度和引射流体速度比越大混合效果越好;2)在喷射器结构、喷嘴速度与引射流体速度比为定值的情况下,其绝对速度越小混合效果越好;3)在喷射器速度为定值的情况下,混合段直径与喷嘴直径比越小混合效果越好,二者之间存在着线性关系;4)在喷射器速度、混合段直径与喷嘴直径比为定值的情况下,其绝对直径越小混合效果越好,且二者之间存在着线性关系;5)在多数情况下,微观混合速度要慢于宏观混合,微观混合才是喷射器内混合过程的控制步骤.     

蒸汽喷射器混合段流场激波特性分析

蒸汽喷射器广泛应用于过程工业,但对其理论研究并不完善。本文建立了蒸汽喷射器的二维计算机流体力学模型,研究了主动流体和引射流体在混合段相互作用的流场特征,并对流场内激波的产生、发展和结束进行了分析。在此基础上,对不同混合段喉管直径和混合段长度的喷射器性能进行了模拟,并给出了设计工况的最优值。通过对最优性能下激波特征的分析显示,钻石激波在混合段出口附近结束是喷射器获得最佳性能的必要条件。本文结论可以为蒸汽喷射器的优化设计提供技术依据。     

喷射反应器内液-液湍流微观混合的研究

通过定义局部分离度,来定量表征喷射器内液-液湍流微观混合规律。其定义式为:(实验所得H~+浓度-模拟所得H~+浓度)/模拟所得H~+浓度。选用酸碱反应体系,利用PLIF技术得到沿喷射器轴线的H~+浓度;采用Fluent软件,利用Standard k-ε模型,模拟获得相同操作条件下的H~+浓度变化趋势。得到不同操作条件下,分离度沿喷射器轴线的变化,结果表明:(1)引流速度不变,喷嘴速度越大,两流体越容易达到微观尺度的均匀混合;(2)喷嘴速度不变,引流速度越大,两流体反而不容易达到微观尺度上的均匀混合;(3)速度比一定的情况下,喷嘴速度越大,越有利于流体的微观混合。     

液-液喷射器不同进料方式下混合过程的CFD模拟

利用计算流体力学(CFD)软件CFX5对液-液喷射器混合段物料的混合性能进行了模拟,确定了工作流体和引射流体都平行于混合管轴线进料时物料完全混合所需的混合管长度,并分析了三种不同进料方式:(1)工作流体和引射流体都与混合段轴线平行进料;(2)工作流体与混合段轴线平行进料,引射流体与轴线成30°进料;(3)引射流体与混合段轴线平行进料,工作流体与轴线成30°,对混合管内混合过程的影响,结果表明,工作流体和引射流体都与混合段轴线平行进料时混合效果最好。     

上喷式喷射器内气液两相流的流体力学特征

喷射器作为气液混合装置,比传统接触混合器具有更高的混合强度和传质系数.计算流体力学(computational fluid dy-namics,CFD)模拟作为研究气液混合流的方法,有助于理解喷射器的流体力学和混合特征.它能提供详细的信息来量化操作条件对喷射器性能的影响.本文利用CFD模拟了上喷式喷射器内的气液两相流的流体力学特征.结果表明在较高的混合段长径比下,混合段入口处的压力较低.但是存在一个最大的压力降,此时混合段长径比约为4.0.在相同的喷嘴速度下,混合段入口处压力降最低,气体卷吸量最大.模拟中混合管与喷嘴面积比范围为1～16.无论是保持喷嘴直径不变还是混合管直径不变,混合段入口处的压力都随着D2M/D2N的增加而增加.但是对应的最大气体卷吸率发生在面积比为4.0.当喷射器的结构参数不变,混合段入口处的压力降和气体卷吸率随着喷嘴速度的增加而增大.     

混合驱动精压机的动力学分析与仿真

以混合驱动精压机为研究对象，应用拉格朗日方程建立了混合驱动精压机的非线性动力学模型，根据直流电动机、永磁无刷直流伺服电动机的等效电路模型，分别建立了它们的动力学模型和负反馈控制模型；然后用数值方法对动力学方程进行求解和仿真，并对仿真结果进行了分析．     

气相色谱分离过程的模拟

建立了描述多组分气相色谱柱内运动过程的数学模型 ,模型包括物料平衡方程、吸附方程和传质方程 ,采用数值方法求解。对多种操作条件及色谱柱特征参数对色谱分离过程的影响进行模拟 ,为色谱过程的应用提供设计和优化的基本条件 ;模拟结果与实验结果一致 ,表明本文所建立的模型能够正确描述各种条件下的色谱过程。该模型还可以推广用于各种不同的色谱程序操作     

三维Navier-Stokes方程的差分-谱方法混合法在GPU上的实现与优化

差分-谱方法通常在槽道湍流的直接数值模拟中使用,本文主要研究差分-谱方法在单GPU卡上的实现。由于GPU的硬件发展十分迅速,不同的GPU硬件对双精度计算的支持有所不同,本文首先验证GPU上数值计算的精度,用差分-谱混合法求解标量扩散方程,并将GPU和CPU上获取的数值结果与解析解进行对比,以确定GPU上数值算法实现的精确度。标量扩散方程在Nvidia S2050单GPU卡上求解,获得接近20倍的加速比,三维不可压缩Navier-Stokes方程达到了25倍的加速比。     

缩合反应喷射混合器的数值模拟与验证

采用Fluent软件数值模拟缩合反应制多胺系统的喷射混合器,根据不同几何尺寸喷射器内的速度、压力、组分浓度分布情况,提出优化的喷射器设计并中试装置验证,表明物料的混合效果良好,喷射器压力变化的实验值与模拟值几乎相符,本文所建模型可为工业规模的喷射混合器设计、放大提供依据和参考.     

喷嘴结构对液-液喷射器性能影响的CFD模拟

利用CFD的模拟方法研究了液-液喷射器中喷嘴结构的影响行为和优化选择问题,选择四种喷嘴出口形状,圆形、标准椭圆形、三角形和方形的喷嘴为考察对象,建立液-液喷射器三维模型,考察喷射器内部流体流动特性。模拟结果表明,相同工况下,喷嘴出口形状为椭圆形的喷射器其混合性能优于其他三种喷嘴结构的喷射器,达到完全混合所需时间最短。模拟结果可为喷射器的设计和性能优化提供一定参考。     

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。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.