（中国微米纳米10035）基于叠层定向结构调控的高导热柔性聚偏氟乙烯/膨胀石墨复合材料

利用二次成型工艺制备了PVDF/EG叠层定向结构复合导热材料,并采用X衍射、扫描电镜对PVDF/EG复合材料及形貌进行表征,同时,研究了PVDF/EG叠层定向结构复合导热材料不同方向的热扩散特性、热导特性及材料的机械力学特性.叠层定向结构沿内部薄膜面内方向热扩散系数是其竖直方向的4.1倍,在EG质量分数为15wt％,20 wt％and 25％25wt％时,叠层定向结构PVDF/EG复合材料热导率分别为1.595 W/(m·K)、2.87 W/(m·K)和3.9843 W/(m·K),具有较低的"渗漏"阈值,表明利用二次成型工艺对PVDF/EG复合材料定向结构调控,能达到提高复合材料热导率的目的.而且,PVDF/EG叠层结构复合导热材料具有较好柔韧性,适合作为界面热导材料.     

球型Al2O3-AlN颗粒复配填充型硅橡胶的制备及导热性能研究

以Al2O3和AlN的球形粉体颗粒作为导热填料、以硅橡胶为基体,通过特定的工艺手段得到具有高导热特征的Al2O3-AlN/硅橡胶复合材料.结果表明:根据颗粒级配理论模型的计算可得最密堆积配方,该配方的复合材料在96 wt％填料填量下的热导率可高达9.6 W/(m·K),其热导率相比只填充Al2O3颗粒的样品提高了60％...     

超细AlN填充环氧树脂热性能研究

采用钛酸酯偶联剂对超细氮化铝(AIN)粉末改性,通过高速机械搅拌和超声波分散相结合的方法,在高真空条件下,制得NTC热敏电阻器用AIN改性环氧树脂(EP)灌封材料。通过对材料的性能测试表明:改性后的EP材料热膨胀系数明显下降,填料高质量分数时下降达到3.05×10-5/℃;导热系数明显提高,由EP的0.28W/(m.K)提高到1.07W/(m.K),提高了2.8倍;DMA分析发现:偶联剂质量分数为3%时,填料与基体的界面结合能比较好,其样品性能最好。     

高热导率的聚偏氟乙烯/ 石墨烯复合材料

芯片散热问题限制了芯片技术的进一步发展,寻求高热导率的热界面材料成为突破该瓶颈的 重要手段之一。有机-无机复合材料由于其柔软性以及热导率可调控,有望取代常规材料——硅脂,成 为新一代热界面材料。实验上,有机-无机复合材料的制备方法包括物理混合、分相析出和原位氧化。 该文采用物理混合方法制备聚偏氟乙烯/石墨烯复合材料,并使用非稳态测量方法得到其热导率高达 83 W/(m·K)(温度 T＝360 K、体积分数 f＝76 vol%)。此外,复合材料的热导率与填料的体积分数、颗 粒大小形状以及填料与基体之间的相互作用等因素密切相关,利用改进的有效介质理论 Bruggeman 模 型和 Agari 模型来解释复合材料热导率的物理机制时发现,改进的有效介质理论 Bruggeman 模型并不 能很好地解释该复合材料的高热导率。由 Agari 模型可知,当填料含量较高时,填料之间更容易形成 导热通道,从而提高了复合材料的热导率。     

超细AIN填充环氧树脂热性能研究

采用钛酸酯偶联剂对超细氮化铝(AIN)粉末改性,通过高速机械搅拌和超声波分散相结合的方法,在高真空条件下,制得NTC热敏电阻器用AIN改性环氧树脂(EP)灌封材料。通过对材料的性能测试表明:改性后的EP材料热膨胀系数明显下降,填料高质量分数时下降达到3.05×10-5/℃;导热系数明显提高,由EP的0.28W/(m.K)提高到1.07W/(m.K),提高了2.8倍;DMA分析发现:偶联剂质量分数为3%时,填料与基体的界面结合能比较好,其样品性能最好。     

氮化硼/ 二硫化钼- 环氧复合材料的导热性能研究

随着现代电子产品的快速发展,研发具有高效的热管理材料正成为全球性的挑战。研究表明 界面热阻是限制导热复合热管理材料高导热性能的最主要因素。该文设计并利用水热法合成了低界面 热阻的六方氮化硼(BN)/二硫化钼(MoS2)异质结构,并将高导热性的 BN/MoS2 异质结构填充到环氧树 脂中制备纳米复合材料。在水热反应过程中,MoS2 生长在 BN 纳米片上,确保了较好的界面接触。其 中,BN 充当结构骨架和传热通道,而 MoS2 纳米片具有较大的比表面积,故能有效地收集热量。借助 MoS2 的浸润性,可以降低填料和聚合物基质之间的界面热阻。实验结果表明,合成的 BN/MoS2-环氧 纳米复合材料导热率从 0.254 W/(m·K)提高到 0.526 W/(m·K),比纯环氧树脂的导热率提升了 107%。 该研究结果有助于开发新型高性能导热材料。     

液晶环氧树脂/ 氮化硼片/ 玻璃纤维三相复合材料的制备与性能研究

随着电子产品中电子元器件逐渐趋向于小型化和高度集成化,其内部产生的大量热量会使电 子器件的各项性能受到影响。为了及时散出热量,需要制备出一种高热导率的复合材料。该研究采用 性能优异的液晶环氧树脂作为基体,以六方片状氮化硼和玻璃纤维作为填料,制备出一种热导率高 且综合性能优异的液晶环氧树脂基复合材料。结果显示,所制备的液晶环氧树脂/氮化硼片/玻璃纤维 复合材料的热导率在厚度方向最高可达 1.6 W/(m·K)、在平面方向最高可达 5.85 W/(m·K)。同时, 该复合材料还具有较高的玻璃化转变温度(高于 180 ℃)和优异的热稳定性(热分解温度高于 365 ℃)。     

氢键连接的石墨烯纳米片之间界面传热的分子模拟研究

石墨烯的高热导率使其成为导热复合材料中重要的填料,然而填料间的界面热阻极大地阻碍 了填料间的热传输。对石墨烯边缘进行官能化可以在石墨烯边缘界面间引入共价键或氢键连接,以取 代范德瓦尔斯(Van Der Waals)相互作用连接,从而有望增强界面热传导。该文系统研究了边缘化学吸 附—COOH 的石墨烯片间界面传热性质,探讨了石墨烯片间距离以及官能化密度对于界面热阻的影 响。研究表明,随着两片石墨烯边缘间距减小,边缘化学吸附—COOH 的石墨烯片间界面热导逐渐收 敛于5×108 W/(m2·K)附近。这相比于 H 边缘官能化的石墨烯片间界面热导提高了一个数量级。界面 热导随着官能化密度的提高显示出非线性单调提升。进一步的研究显示,官能化密度与石墨烯边缘界 面间距存在协同效应,官能化密度的增加提高了界面间的相互作用,减小了石墨烯边缘界间距,从而 增强了界面热导。该研究结果可为氢键对于石墨烯填料界面传热调控提供重要参考。     

基于CMOS工艺钨微测辐射热计阵列集成芯片的设计与制作

采用0.5μm标准CMOS工艺和微机械加工工艺,设计并制作了低成本4×4钨微测辐射热计阵列集成芯片。阵列中每个钨微测辐射热计均由微悬桥结构和钨热敏电阻组成,CMOS读出电路集成在阵列下方。微悬桥结构由表面牺牲层技术实现,不需要任何的光刻工艺。钨微测辐射热计像元尺寸为100μm×100μm,填充因子为20%。测试结果表明,在真空环境下,钨微测辐射热计等效热导为1.31×10-4W/K,等效热容为1.74×10-7J/K,热时间常数为1.33 ms。当红外光源的斩波频率为10 Hz时,钨微测辐射热计的电压响应率为1.91×103V/W,探测率为1.88×107cm·Hz1/2/W。     

平衡态分子动力学 Green-Kubo 方法计算氮化硼 单层结构热导率的模型尺寸效应研究

分子动力学模拟可以直接表征体系原子的行为,因此成为研究氮化硼相关材料微观导热机理的重要工具,但目前尚没有关于氮化硼材料模型尺寸对其热传导相关性质影响规律的研究。该文采用平衡态分子动力学并结合 Green-Kubo 方法,研究了纯净氮化硼单层结构热导率、声子色散关系以及态密度随模拟尺寸的变化规律,并解释了其内部机理。实验发现,氮化硼单层材料热导率随着模拟尺寸的增大而减小,并在单层面积约 4.1 nm×4.1 nm 时收敛于(349±22)W/(m?K),此收敛值远小于平衡态分子动力学计算中石墨烯热导率的收敛尺寸(10 nm×10 nm),这说明氮化硼单层中声子之间的散射大于石墨烯。此外,不同于热导率,氮化硼单层结构的声子色散曲线、态密度几乎不受模拟尺寸的影响。该研究结果可为采用平衡态分子动力学研究氮化硼相关材料的微观导热机理提供重要参考。     

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.