一类具有体液免疫反应,且染病细胞存在返回期的HIV模型的全局稳定性分析

研究了具有Beddington-DeAngelis发生率和体液免疫反应的HIV模型的全局性.模型包含了一个染病细胞返回期,在这个时期,染病细胞可能有一部分会返回到健康细胞当中.得到模型的基本再生数R0和免疫基本再生数R1.通过建立适当的Lyapunov函数,得出无病平衡点Q0,无免疫平衡点Q1和免疫平衡点Q2是全局渐近稳定的.     

Correlating temporal communication patterns of the Eclipse open source community with performance and creativity

This paper studies the temporal communication patterns of online communities of developers and users of the open source Eclipse Java development environment. It measures the productivity of each community and seeks to identify correlations that exist between group communication characteristics and productivity attributes. The study uses the TeCFlow (Temporal Communication Flow) visualizer to create movie maps of the knowledge flow by analyzing the publicly accessible Eclipse developer mailing lists as an approximation of the social networks of developers and users. Thirty-three different Eclipse communities discussing development and use of components of Eclipse such as the Java Development Tools, the different platform components, the C/C++ Development Tools and the AspectJ extension have been analyzed over a period of six months. The temporal evolution of social network variables such as betweenness centrality, density, contribution index, and degree have been computed and plotted. Productivity of each development group is measured in terms of two indices, namely performance and creativity. Performance of a group is defined as the ratio of new bugs submitted compared with bugs fixed within the same period of time. Creativity is calculated as a function of new features proposed and implemented. Preliminary results indicate that there is a correlation between attributes of social networks such as density and betweenness centrality and group productivity measures in an open source development community. We also find a positive correlation between changes over time in betweenness centrality and creativity, and a negative correlation between changes in betweenness centrality and performance.This paper was tied for Best Paper, NAACSOS (North American Association for Computational Social and Organizational Science) Annual Conference 2005, June 26–28, Notre Dame. Yared H. Kidane obtained a B.Sc. from Addis Ababa University, Ethiopia in Statistics and a M.Sc. in Information Technology specializing in engineering and management of information systems with honors from Royal Institute of Technology Stockholm, Sweden in June 2005. Yared completed his master’s thesis as an exchange student at MIT. He is currently working for Verizon Wireless as an analyst in the reporting and analysis section. Peter A. Gloor is a research fellow both at the MIT Center for Coordination Science and the Center for Digital Strategies at Tuck at Dartmouth and chief scientist at iQuest Analytics. Previously, he was a partner with Deloitte and PwC. He obtained a Ph.D. in Computer Science from the University of Zurich in 1989, and was a Post-Doc at the MIT Lab for Computer Science.     

Photoluminescence behavior of ZnO nanorods produced by eclipse PLD from a Zn metal target

In this work, arrays of one-dimensional ZnO nanostructures were deposited on c-axis sapphire by standard and eclipse pulsed laser deposition (EPLD) using a metallic Zn target. One reference sample was grown by standard PLD and nine were grown by EPLD using a 16 by 16 mm² square shadow mask. Three shadow mask positions were used, with three depositions at varying oxygen pressures for each mask position. The oxygen partial pressure was between 100 and 200 mTorr for all growth procedures with a substrate temperature of 600 C.SEM reveals that arrays of nanorods are formed when growing by standard PLD. When grown by EPLD the rods tend to clump together with ordering on the micron scale. Low temperature photoluminescence was carried out as a function of position over several of the samples with 1 or 2 mm spacing. In general, it was found that the luminescence intensity is maximum in the center of the samples and falls off toward the edges while the shape stays roughly the same. Free exciton emission was resolved in most samples along with several other emission peaks from donor-bound excitons. The integrated PL intensity for all the EPLD samples is an order of magnitude higher than for the standard PLD sample. Linewidths are significantly reduced as well. Hence, the EPLD grown samples have superior optical quality and this growth technique shows promise for growth of high quality ZnO nanostructures.     

“Eclipse”卷烟的热重/差热分析

为了对新型卷烟产品进行剖析,利用热重/差热分析研究了空气氛围下典型性碳加热卷烟"Eclipse"各组成成分的热行为,并计算了主要失重温度段的活化能。结合热失重数据和组成结构对其分解机理进行初步推断和验证。结果表明:1碳棒在356~560℃燃烧放热,失重65%,活化能为149.44 k J/mol,热重/差热分析显示含有碳酸钙成分,空气氛围下碳棒燃烧热解更完全;2200~380℃为卷烟纸主要的热解失重阶段,失重62%,主要是纤维素热解造成。其中碳酸钙含量为12%左右,金属箔为铝箔;3薄片1在191~364℃失重49%,可能是单糖、小分子物质以及纤维素热分解。薄片2在97~253℃失重51%,保润剂、水分和挥发性物质受热分解以及纤维素晶体单糖和其他一些小分子物质因热裂解。薄片1和薄片3结构和成分相似,都接近传统卷烟烟丝,薄片2含更多的单糖和水分。本研究为新型卷烟材料和热源的研发积累详实数据,为进一步研制烟叶原料加热非燃烧状态下化学成分释放和烟丝配比的实验装置和分析方法奠定基础。     

日食对Ne发射光谱强度的影响

为了观测日食时刻日－地空间发生的异常物理现象，本工作采用了观测Ne放电管光源的Ne光谱变化的方法，观测结果表明，日食对Ne光谱的强度产生影响，越接近食甚时刻，Ne光谱强度越弱。     

Eclipse环境下桥梁检测车三维模型的构建与控制

针对桥梁检测车操作人员无法直接观察桥检车机械臂的动作状态的问题,提出构建桥检车的三维模型,能够实时动态地跟踪显示出桥检车机械臂的动作状态.以Eclipse作为软件开发平台,基于OpenGL ES实现桥检车的三维模型构建和控制给出直接三维建模法与插件三维建模法.实验结果表明,2种方法均可实现桥检车三维模型的构建与控制,对于规则三维模型的构建与控制,直接三维建模法要优于插件三维建模法.