北京SARS疫情走势的模型分析与预测

北京SARS疫情的公布数据表明，4月下旬以来，确诊病例的相对增加率随累计确诊病例数的增加而下降．假设这是一个线性关系，并且一直持续下去，我们发现疫情走势是一个反转的Fermi-Dirac分布，根据现有的公布数据可以预期北京平均每日新增病例数将在5月中旬下降到50人以下，在5月下旬下降到10人以下，在6月上旬下降到1人左右，疫情可望在6月中得到控制，最后的累计病例总数约为3千人左右。     

Breakpoint Analysis for the COVID-19 Pandemic and Its Effect on the Stock Markets

In this research, statistical models are formulated to study the effect of the health crisis arising from COVID-19 in global markets. Breakpoints in the price series of stock indexes are considered. Such indexes are used as an approximation of the stock markets in different countries, taking into account that they are indicative of these markets because of their composition. The main results obtained in this investigation highlight that countries with better institutional and economic conditions are less affected by the pandemic. In addition, the effect of the health index in the models is associated with their non-significant parameters. This is due to that the health index used in the modeling would not determine the different capacities of the countries analyzed to respond efficiently to the pandemic effect. Therefore, the contagion is the preponderant factor when analyzing the structural breakdown that occurred in the world economy.     

广义边界条件和概率流密度的连续性

以四参量族－广义边界条件代替有限深方势阱内粒子波函数的对数的一阶导数连续性条件，表明这种替换比用广义边界条件取代一盒子内自由粒子波函数在两壁处为零的边界条件显行更加合理些。我们发现，如对参量ρ和θ取任意值，则会导致概率流密度连续性被破坏。我们找到了约束ρ和θ取值的条件，并得到一组新的解析解。     

激光新阈值理论及其实验研究

本文对激光的阈值给出了新的理论解释，提出了激光新阈值理论，导出了激光新阈值条件的解析表达式，并对各类激光器分别进行了讨论，而且从实验上测量了激光器的阈值反转粒子数密度ｎｔｈ与允许激光器获得振荡放大的持续时间△ｔ之间的关系，其结果与激光新阈值理论结果相一致。     

Analysis of stable components in the extended-range forecast for the coming 10-30 days in winter 2010 and 2011

In this paper we try to extract stable components in the extended-range forecast for the coming 10–30 days by using empirical orthogonal function （EOF） analysis, similarity coefficient, and some other methods based on the National Center for Environmental Prediction （NCEP）/National Center for Atmospheric Research （NCAR） reanalysis daily data. The comparisons of the coefficient of variance of climatological background field and truth data in winter between 2010 and 2011 are made. The method of extracting stable components and climatological background field can be helpful to increase forecasting skill. The forecasting skill improvement of air temperature is better than geopotential height at 500 hPa. Moreover, this method improves the predictability better in the Pacific Ocean. In China, the forecast in winter in Northeast China is more uncertain than in the other parts.     

场板抑制GaN高电子迁移率晶体管电流崩塌的机理研究

通过实验和数值器件仿真研究了钝化GaN高电子迁移率晶体管(HEMTs)、栅场板GaN HEMTs和栅源双层场板GaN HEMTs电流崩塌现象的物理机理,建立了电流崩塌强度与帽层中载流子浓度、陷阱电离率和电场的内在联系.研究结果表明,场板可以有效调制帽层中横向和纵向电场的强度分布,并可有效调制纵向电场的方向,减弱栅极附近电场强度,增加场板下方电场强度,这会减弱栅极附近自由电子的横向运动,增强场板下方自由电子的纵向运动,进而可以有效调制帽层中自由电子浓度的分布,提高陷阱的电离率,减小器件的电流崩塌. 关键词： 电流崩塌 钝化器件 场板器件 陷阱电离率     

Effect of the surface-modifying macromolecules on the duration of the surface functionalization

Functionalization of polystyrene films by the preferential surface enrichment of surface-modifying macromolecules (SMM) to achieve a hydrophilic surface with long effective duration is described. The comb-like amphiphilic copolymers (PKG-g-PS) based on styrene-maleic anhydride copolynier (SMA) backbone was synthesized by esterification of SMA with poly(ethylene glycol) (PEG). When PEG-g-PS was melt blended with polystyrene, the preferential surface enrichment of PEG-g-PS was much evident resulting in the large increase of the surface polarity. The effective duration of the surface functionalizatoin was also hugely extended as SMMs were added into the blends. Furthermore, more polyether chain segments on PEG-g-PS could selectively migrate to the surface by the inducement of polar solvent. Compared with the PEG-g-PS/PS and PEG/PEG-g-PS/PS blends, the surface polarity and the effective duration of surface modification both increased greatly when PEG-g-PS was used as the compatibilizer of PEG/PS blends. It was an effective solution to balance the conflict between the duration and efficiency of the surface-modifying additives.     

中子裂变链统计涨落问题的数值计算方法

研究了弱中子源驱动下,裂变系统中子裂变链统计涨落问题的数值计算方法。进行了数值计算建模、数值方法分析、数值计算检验、一类问题概率分布函数的统计涨落特征量的数值计算示范。特例数值检验表明:只要数值解方程组阶数(截断) N足够大,数值解满足归一(守恒) 律、指数增长律,并与精确解析解一致。对于非定常裂变系统中子裂变链统计涨落问题提出了一维等效模型下数值模拟的方法。     

光抽运信号与线圈电流的关系

分别固定水平线圈和垂直线圈的电流后,在不同的光抽运信号下测定了铷样品吸收池的透射光强度与垂直线圈和水平线圈电流的关系曲线．得到了只有在正常光抽运信号下,透射光强度才与cos^2θ成正比的结论．指出了只有在正常光抽运信号下,地磁场的垂直分量被垂直线圈的磁场抵消时,吸收池的透射光强度才最强．     

连续变量纠缠交换对系统物理参量的依赖关系

以量子关联度和相干态量子离物传送的保真度为判据，在增益因子取1和取最佳值两种情况下，计算了纠缠交换的质量对探测效率，传输效率及初始关联参量的函数依赖关系。计算结果可给实验设计提供有用参考。