内混式空气雾化喷嘴雾化性能的实验及模拟研究

费托合成装置气液分离器的分离性能研究中,雾滴粒径的准确测量和控制是关键。本文对内混式空气雾化喷嘴的喷雾性能进行了实验研究,考察了液滴索特尔直径D_(32)的轴向分布,以及气液比、液体流量与黏度对其的影响规律;同时结合CFD数值模拟,进一步研究了气液相对速度、雾化锥角及液体表面张力对液滴D_(32)的影响。结果表明:液滴D_(32)沿喷雾方向不断增大;液体雾化主要通过喷嘴内气流对液膜的剪切、冲击作用,因此增大气液比可增强雾化效果,但存在"饱和"现象;液量的增大不利于液膜破碎雾化;增大气液相对速度可显著提高雾化效果;同时,液体黏度和表面张力对雾化效果影响很大,黏度或表面张力越大,雾化显得更为困难。此外,液滴轴向速度沿喷雾方向先迅速下降随后缓慢降低。     

气泡雾化喷嘴雾化射流场性能仿真

研究气泡雾化喷嘴外部射流场的特性问题,由于喷嘴出口处液膜破碎过程的复杂性,有时会影响雾化质量.为了提高雾化性能,提出将雾化过程细分两个子过程,利用FORTRAN语言程序计算液膜破碎过程,得出液滴初始数据,再用计算流体仿真软件Fluent,建立描述气流-液滴两相流动的合理模型,用Realizable κ-ε湍流模型与DPM离散相组合,进行二次雾化过程,并考虑气液两相间的耦合作用以及液滴破碎和碰撞模型,对雾化射流中的液滴粒径SMD沿喷嘴轴向的分布进行仿真,计算结果与实验数据进行比较吻合较好,可为雾化性能的优化提供有效的数据支持.     

深海采矿矿浆泵固液两相流数值计算及分析

在深海采矿的矿浆泵结构优化设计问题的研究中,针对大洋多金属结核采矿系统中矿浆泵易磨损等问题,基于欧拉-欧拉理论模型,采用SMPLEC算法及RNG κ-ε湍流模型,对矿浆泵首级叶轮及空间导叶内固液两相流进行数值计算及分析,研究颗粒粒径及颗粒体积分数对矿浆泵内颗粒流动规律及磨损特性的影响.结果表明:颗粒粒径越大,颗粒逐渐向叶片压力面出口处聚集,与导叶吸力面发生冲击的位置逐渐移向导叶头部,颗粒与叶片压力面及导叶压力面发生冲击的速度及角度也越大,降低矿浆泵的抗冲蚀磨损能力;颗粒体积分数越高,颗粒有向叶片压力面进口处及导叶吸力面进口处聚集的趋势,空间导叶流道内颗粒流动愈加絮乱.上述研究为优化矿浆泵高层设计提供依据.     

考虑液滴尺寸分布气液两相爆轰流场数值仿真

研究脉冲爆轰发动机喷射装置模型问题,针对两相爆轰流场中燃料液滴半径实际上分布的不均匀性,为了建立更符合实际的模型,提出了多尺寸分布的两相爆轰方程.应用二维守恒元和求解元方法(CE/SE方法)对其进行数值仿真,得到了液滴初始半径分布对管内流场的影响.液滴初始半径分组时爆轰波速度介于不分组时最小液滴半径和最大液滴半径的计算值之间;分析了液滴初始半径不同分组时,液滴平均半径越小,爆轰波最大压力和爆轰波出口速度越大.仿真结果证明用CE/SE方法可有效捕获两相爆轰波间断能力.研究成果为脉冲爆轰发动机喷射雾化装置设计提供设计依据.     

颗粒粒径及速度对火箭发动机结构参数的影响

在Mg/CO2粉末火箭发动机的研究中,镁颗粒的燃速、颗粒粒径以及颗粒喷注速度是影响金属粉末燃烧特性的主要因素,金属粉末的燃烧特性决定了燃烧室的结构参数.采用RNG k-ε方程和层流有限速率化学反应模型对轴向喷注式圆柱型燃烧室燃烧性能进行了三维定常数值仿真,研究了颗粒粒径及喷注速度对燃烧室中反应特性的影响,旨在为发动机结构尺寸确定提供参考,所建立计算模型与实际参数吻合较好.仿真结果表明:小粒径镁粉燃烧比较充分,颗粒粒径过大导致燃烧效率低下;镁粉燃烧放热峰随喷注速度的增加而向燃烧室后端移动,喷注速度过大则导致燃烧不完全;金属颗粒径向扩散很少,导致燃烧室壁面附近化学反应量较少且温度较低,可以利用来增强热防护能力.     

涡流冷壁推力室传热模型分析计算

研究发动机燃烧室温度优化控制问题,由于燃烧室温度控制较难,为了预估新型涡流燃烧冷壁火箭发动机的壁面温度,根据发动机内部流动和传热分析,对组合化学平衡、辐射传热和热传导特性,提出了一维传热模型.采用模型对以氢氧为推进剂的涡流燃烧室进行了传热过程和影响因素的仿真分析,获得了稳定状态下的壁面温度,以及燃烧室压力、氧化剂喷注速度、燃烧室长度等参数对壁温的影响关系,仿真结果与实验一致.证明模型为涡流燃烧发动机设计提供了重要工具,对进一步的实验研究有指导意义.     

平孔喷嘴内柱塞流判定模拟分析

平孔喷嘴作为被广泛应用的雾化设备之一,其内部流型对雾化效果具有至关重要的影响。而目前对喷嘴内流型的判定方法还并不统一。本文建立了喷嘴内流型变化判定方法的数学模型,并利用模型喷嘴长度与直径比(L/d)、喷嘴入口倒角半径与直径比(r/d)和操作压力对流型的影响规律进行了模拟分析。结果表明:L/d对喷嘴内流型有一定的影响,L/d越大,越不易发生柱塞流;r/d对喷嘴内空穴区的强度影响显著,r/d越大,空化强度越低,越不易发生柱塞流,但喷嘴r/d大于0.05时,柱塞流依然可以发生;喷射压力对喷嘴内流型变化以及流量系数影响显著,流量系数与喷嘴内流型有一定的对应关系。应用本文的研究成果,可以通过合理地设计喷嘴结构和操作条件,使得喷嘴内流型始终处于空穴流区间,以达到强化雾化效果的目的。     

生物柴油溶LPG喷雾特性试验研究

在不改变喷油器结构参数、喷射压力和试验背压的前提下,采用马尔文激光粒度分析仪改变液化石油气（LPG）在生物柴油中的掺混比,研究不同的 LPG 掺混比对生物柴油雾化质量的影响。试验结果表明,LPG 的掺混比越大,生物柴油的雾化质量越好。     

干旱区地表L波段微波辐射特性分析穿透深度的影响

利用２０１２年黑河中游HiWATER实验区戈壁和大满超级站的土壤水分和温度廓线数据,基于LＧMEB微波辐射传输模型,分析了L波段微波穿透深度随土壤水分的变化.在此基础上,分析了不同深度土壤水分和温度作为LＧMEB模型输入,对L波段微波发射率和亮度温度的影响.研究结果表明:L波段微波穿透深度随土壤水分、温度的变化,呈现明显的差异,在本研究区L波段微波穿透深度在４~２２cm 之间;在土壤水分较高的超级站,计算的L波段亮度温度与０~４cm土壤层的亮度温度更为接近,而在土壤水分较低的戈壁站,计算的L波段亮度温度与０~４０cm土壤层的亮度温度更为接近.因此,在利用L波段微波数据反演土壤水分时,应考虑穿透深度的影响,以提高反演精度.     

基于元胞自动机的肿瘤生长形态动态模拟

为了模拟肿瘤生长和附近组织发生机械作用过程以及自身所发生形变,研究了肿瘤生长过程形态的连续性,穿透深度的计算以及肿瘤的真实感绘制。用元胞自动机模拟肿瘤动态生长过程,并在模型每次发生形变后对元胞状态进行更新,以增强肿瘤生长形态的连续性;模型顶点穿透深度的准确性直接影响力学模型计算形变结果的合理性、准确性,采用基于隐式曲面的方法计算穿透深度的大小和方向;为了增强肿瘤模型的真实感,采用隐式曲面的方法渲染每个生长时刻的肿瘤形态。实验结果表明：该方法能得到形态较连续的生长过程;改进后的穿透深度计算方法能得到一致性较好的深度矢量;基于模型表面点集隐式曲面绘制的肿瘤模型具有平滑表面,有较好的仿真效果。     

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.