抛光液温控装置结构设计及温度场分析

为精确控制超光滑表面抛光过程中抛光液的温度,根据温控基本原理设计温控装置结构.将用UG建立的温控装置模型导入GAMBIT中进行温度场分析.针对装置内部温度分布不均匀问题,对其结构进行优化：在装置内加入导热隔板将其分为工作区和调温区,制冷器被置于调温区内;将温控装置的外形结构加入过渡圆角.结果表明：优化后的温控装置形成内外环流,工作区温度波动范围为±0.01℃,温度分布均匀对称,满足高精度温控的恒温和匀温要求.     

高温用多孔等温钠热管的研制

研制了用1Cr18Ni9Ti 不锈钢和 GH181高温合金作结构材料的两种多孔等温钠热管。它们已分别用在850℃以下和1064℃以下使用的高温铂电阻温度计的精密分度与校验装置中,效果显著。该热管装置的优点是温控稳定性好、温度场均匀、热惯性小、且结构简单。热管的测温孔内径为(?)12～13mm,长290mm。测温孔之间温度均匀性达0.02℃,在90mm 长度内单个测温孔的垂直温差为0.02℃。GH181/Na 热管系国内首次研制的高温等温钠热管。其短时间使用温度可达1100℃。试样热管在600～1100℃温度范围内经受了713小时的快速寿命试验。本文叙述了热管的结构设计、性能以及寿命试验结果。     

甲酸钠/氧化铜复合相变材料的制备与热力学性能测试

配制了甲酸钠/氧化铜复合相变材料。通过恒温槽实验对比了甲酸钠,乙酸钠,丙酸钠以及氯化铵的性能,选择了性能最优的甲酸钠。通过配制不同浓度的甲酸钠溶液,对比其性能,发现29.4 wt%甲酸钠溶液的效果最好。为了优化溶液的导热性能,通过对比不同纯金属纳米材料和金属氧化物纳米材料的种类以及对比添加同种纳米材料不同的质量分数,发现添加0.5 wt%的氧化铜效果最优。通过Hot Disk和DSC实验对配方进行了导热值以及潜热值的测量,结果显示添加了纳米材料的配方其潜热为250.4 J/g,相变温度为-16℃,导热系数为1.078 W/（m·K）,比未添加的导热能力提高了9.66%。实验过程中未发生化学沉降等现象。     

相变材料(PCM)储能器在自动控温系统的应用

利用相变储能技术把白天的太阳能储存起来,以供给夜间或者需要的时间和地点使用,调节环境的温度,改善人们的居住和工作环境的舒适度,节约能源,是当今科学家们研究的热点之一。本文简要地介绍了相变材料的主要性能和种类以及相变储能器的控温和储能功能,分析了相变储能器的能量传递过程并根据传热的基本定律,建立了该系统的温度和能量控制方程。     

类弹性蛋白多肽的分子动力学研究

类弹性蛋白多肽因其具有特殊的相变性质,故而在重组蛋白纯化方面展现出良好的应用前景,对其发生相变的机理进行研究具有重要意义.本文利用同源建模的方法构建了类弹性蛋白多肽的三维结构并进行能量优化,之后采用分子动力学模拟手段,在300 K～400 K间5个不同温度下,对含有100个氨基酸残基的类弹性蛋白多肽[KV8F-20]各进行了6 ns的模拟.模拟过程中,类弹性蛋白多肽发生疏水缩聚,初始结构变得更加紧凑,且温度越高折叠程度越大.水分子在类弹性蛋白多肽的相变行为中起到关键作用.经分析,结果发现疏水作用与水的排出在类弹性蛋白多肽发生相变过程中起到关键作用,类弹性蛋白多肽随着温度的升高,在疏水作用驱动下,其构象折叠程度因疏水缩聚而变得更大.此外,比较不同温度下蛋白的缩聚程度,推断类弹性蛋白多肽在375 K左右发生相变,这与实验观测的结果基本吻合.据此,推测该类弹性蛋白多肽变温度范围约为95℃～102℃.这对后续调控类弹性蛋白多肽的相变具有指导作用.     

套管换热器换热性能仿真及实验研究

在换热器性能评估平台优化设计的研究中,为了描述套管换热器在热流体动态输入温度下的换热行为,研究其温度分布变化规律,在综合考虑了流体沿流动方向的导热扩散特性、中间墙体的金属蓄热以及流体沿径向导热对出口温度瞬态响应的影响的基础上,提出了以墙体侧蓄热量为突破点的动态相变仿真交叉迭代简化模型,得到了在热流体动态输入温度下的换热器温度响应曲线以及换热系数的分布曲线,最后设计了换热器动态仿真平台,对仿真结果进行对比分析,结果表明墙体侧温度模型预测值和实验值数据吻合较好.最大相对误差在9％范围内,其仿真模型符合换热器的换热特性,说明上述简化模型对套管换热器相变换热的研究有较好的参考作用.     

石蜡热膨胀性能试验装置的研究

在微机电系统中,为了兼顾作用力强和形变量大两者的统一,采用以石蜡作为热膨胀材料的热驱动方式.介绍了水浴加热石蜡热膨胀性能试验装置,试验结果表明:石蜡在其熔点温度附近,试验中所用石蜡当温度从37℃升高到51℃时,其体膨胀系数可以达到甚至超过10%,而且,作用力大;不同成分(C原子)比例的石蜡,其熔点温度变化范围为30～70℃,这使驱动器在不允许有较大温度变化的环境中(如人体内)使用成为可能.     

计及故障持续时间的电力系统暂态稳定分布式控制

针对电力系统故障持续时间会影响暂态稳定控制的问题, 本文提出了一种使系统在固定时间内恢复暂态稳定运行的策略. 该策略通过电力系统通信拓扑建模方法为每个发电机建立“邻居发电机”, 利用发电机本地信息和其邻居发电机的信息设计分布式控制器, 通过控制储能装置作用于受扰动后的系统, 使其在固定时间内恢复稳定运行. 其次, 此控制策略还解决了一些实际挑战, 如控制器的输入延时、外部的干扰、储能装置的容量限制等. 通过构建李雅普诺夫函数并利用图论知识对该策略展开了稳定性分析, 推导出了稳定系统的时间界限. 最后, 将控制器投入新英格兰39节点测试系统中, 并与其它控制器进行比较, 仿真结果验证了在低容量储能装置限制下和抗干扰性上控制器性能的优势.     

基于数据驱动的用户侧储能安装潜力分层评估方法

用户侧分布式储能是安装在配电侧和用户处的储能装置,可以发挥平滑负载、提高供电可靠性和经济性的作用。在分布式储能经济性分析的基础上,提出了基于数据驱动的用户侧储能安装潜力分层评估方法,从优先评估和精细评估两个层面评估用户安装储能装置的潜力,为电网公司筛选用户安装储能装置提供了有效方法。结合常州市11家典型大工业用户实际数据进行仿真分析,验证了此评估方法的准确性与可行性。     

微网超级电容器储能系统的滑模控制策略研究

为改善微网运行不稳定的问题,针对与微网连接的超级电容器组储能装置的控制策略进行研究.储能装置由超级电容器组通过双向DC/DC变换器连接DC/AC变换器,通过滤波、升压后连入电网.通过对双向DC/DC转换器滑模控制的研究,使得任意操作条件均能正常工作,同时对运行中的稳定性进行了分析.最后,在Matlab中Simulink搭建储能系统仿真模型,验证了本文控制策略的可行性.     

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。     

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.     

Editorial: Special issue on recent advances in hybrid control theory and applications

正The demands of a rapidly advancing technology for faster and more accurate controllers have always had a strong influence on the progress of automatic control theory.In recent years control problems have been arising with increasing frequency in widely different areas,which cannot be addressed using conventional control techniques.The principal reason for this is the fact that a highly competitive economy is forcing systems to operate in regimes where     

Information for Authors

正Aim The Journals of Zhejiang University-SCIENCE(A/B/C)areedited by the international board of distinguished Chinese andforeign scientists,and are aimed to present the latest devel-opments and achievements in scientific research in China andoverseas to the world’s scientific circles,especially to stimulateand promote academic exchange between Chinese and for-eign scientists everywhere.     

Enhancing a leaf radiative transfer model to estimate concentrations and in vivo specific absorption coefficients of total carotenoids and chlorophylls a and b from single-needle reflectance and transmittance

The relative concentrations of different pigments within a leaf have significant physiological and spectral consequences. Photosynthesis, light use efficiency, mass and energy exchange, and stress response are dependent on relationships among an ensemble of pigments. This ensemble also determines the visible characteristics of a leaf, which can be measured remotely and used to quantify leaf biochemistry and structure. But current remote sensing approaches are limited in their ability to resolve individual pigments. This paper focuses on the incorporation of three pigments—chlorophyll a, chlorophyll b, and total carotenoids—into the LIBERTY leaf radiative transfer model to better understand relationships between leaf biochemical, biophysical, and spectral properties.Pinus ponderosa and Pinus jeffreyi needles were collected from three sites in the California Sierra Nevada. Hemispheric single-leaf visible reflectance and transmittance and concentrations of chlorophylls a and b and total carotenoids of fresh needles were measured. These data were input to the enhanced LIBERTY model to estimate optical and biochemical properties of pine needles. The enhanced model successfully estimated reflectance (RMSE = 0.0255, BIAS = 0.00477, RMS%E = 16.7%), had variable success estimating transmittance (RMSE = 0.0442, BIAS = 0.0294, RMS%E = 181%), and generated very good estimates of carotenoid concentrations (RMSE = 2.48 µg/cm², BIAS = 0.143 µg/cm², RMS%E = 20.4%), good estimates of chlorophyll a concentrations (RMSE = 10.7 µg/cm², BIAS = − 0.992 µg/cm², RMS%E = 21.1%), and fair estimates of chlorophyll b concentrations (RMSE = 7.49 µg/cm², BIAS = − 2.12 µg/cm², RMS%E = 43.7%). Overall root mean squared errors of reflectance, transmittance, and pigment concentration estimates were lower for the three-pigment model than for the single-pigment model. The algorithm to estimate three in vivo specific absorption coefficients is robust, although estimated values are distorted by inconsistencies in model biophysics. The capacity to invert the model from single-leaf reflectance and transmittance was added to the model so it could be coupled with vegetation canopy models to estimate canopy biochemistry from remotely sensed data.     

Mr. Twinn’s bombes

This article discusses the history and design of the special versions of the bombe key-finding machines used by Britain’s Government Code & Cypher School (GC&CS) during World War II to attack the Enigma traffic of the Abwehr (the German military intelligence service). These special bombes were based on the design of their more numerous counterparts used against the traffic of the German armed services, but differed from them in important ways that highlight the adaptability of the British bombe design, and the power and flexibility of the diagonal board. Also discussed are the changes in the Abwehr indicating system that drove the development of these machines, the ingenious ways in which they were used, and some related developments involving the bombes used by the U.S. Navy’s cryptanalytic unit (OP-20-G).