反作用控制系统电磁阀PWM控制技术研究

针对反作用控制系统（Reaction Control System,RCS）快速响应电磁阀频繁工作的特性,从节能控制的角度出发,设计了一种基于脉宽调制（Pulse Width Modulation,PWM）技术的电磁阀控制驱动方案。建立电磁阀电路模型,通过仿真计算,确定了PWM频率及占空比对电磁阀线圈电流的影响,为电磁阀驱动电路参数的选取提供依据。搭建RCS电磁阀电流测试平台,设定PWM占空比为50%,试验结果表明：流经电磁阀的保持电流仅为开启电流的1/2,既能保证电磁阀正常开启,又避免了电磁阀处于高负载工作状态,有效地验证了该节能控制方案的正确性。     

IIIB 型前列腺炎患者抑郁程度与社会支持的相关分析

目的 探讨IIIB 型前列腺炎患者抑郁水平和社会支持的相关性。方法 采用抑郁自评量表（SDS）和社会支持评定量表（SSRS）对48 例IIIB 型前列腺炎患者进行测评,抑郁和社会支持的相关性采用Spearman 相关性分析。结果 IIIB 型前列腺炎患者的抑郁发生率和SDS 评分明显高于对照组,差异有统计学意义（P＜0.01）;Spearman 相关性分析表明,抑郁程度与社会支持总和、主观支持、客观支持和支持利用呈显著负相关（均P＜0.05）。结论 大部分IIIB型前列腺炎患者存在抑郁情绪,其发生可能与社会支持程度较低有关;减轻IIIB 型前列腺炎患者的抑郁情绪可通过重视社会支持和加强护理干预来进行。     

Protic pyridinium ionic liquids: Synthesis, acidity determination and their performances for acid catalysis

Three new protic ionic liquids based on 2-methylpyridinium were prepared and characterized. Their catalytic activities for the tert-butylation of phenol and the esterification of cyclic olefins with acetic acid were examined and satisfactory results were obtained over 2-methylpyridinium trifluoromethanesulfonate ([2-MPyH]OTf). Hammett method was used to determine the acidity order of these ionic liquids and the results are consistent with the catalytic activities observed in the acid-catalyzed probe reactions.     

Dimensions of cookie-cutter-like sets

The cookie-cutter-like sets are defined as the limit sets of a sequence of classical cookie-cutter mappings. By introducing Gibbs-like measures, we study the dimensions, Hausdorff and packing measures of the CC-like sets, and then discuss the continuous dependence of the dimensions.     

半平面上随机Dirichlet级数的增长性

在较弱的系数条件下证明了右半平面上Dirichlet级数增长性定理,并应用到随机Dirich- let级数上去,得到了在一定条件下,两类级数a.s.有相同的增长级,从而推广和改良一系列定理,使相关问题的研究变得方便简洁．     

A differentiated service scheme to optimize website revenues

We consider a website host server with web quality of service (QoS) capabilities to offer differentiated services. A quantitative modelling framework is set up to analyse the economic benefits of differentiated services and to build optimization models for managing the website host's connection bandwidth to the Internet (which is assumed to be the bottleneck factor determining the QoS). Three models are formulated corresponding to three operational scenarios to provide differentiated services. The first is for the marketing manager to classify visit requests as premium or basic when the information technology (IT) manager has already reserved bandwidths for the two classes, and the second is for the IT manager to allocate the total available bandwidth to each class when the marketing manager has already designated which visit requests are premium and which are basic. The third is for the joint optimization of request classification and bandwidth allocation when centralized coordination is possible. Analytic results are obtained for a special case that corresponds to very impatient customers requesting large amounts of data. Qualitative insights gained and numerical results obtained strongly support the implementation of differentiated services. More interestingly, the decentralized models that use simple and rough-cut rules yield solutions almost as good as the joint optimization model.     

Phase distortions due to temperature rise of optics irradiated by periodically repeated short pulses

Temperature variation and wave front distortions due to temperature rise and thermal stress, in rotationally symmetric and isotropic optical elements irradiated by periodically repeated short pulses, have been calculated. The analytical expressions of the periodically varying temperature distributions have been obtained by making full use of the periodicity of the pulsed laser system. For the case where the diameter of optical element is considerably larger than the thickness and the temperature variation along the thickness direction is negligibly small, the plain approximation has been used to estimate phase distortions. The results have shown that the polarization-independent phase distributions due to thermal deformations of the optical element may be of concern, especially if one considers the fact that the phase distortions of the light wave may be accumulated after passing through several optics.     

广义次微分及其应用

通过应用广义次微分来研究不可微规划的最优解，得到了适当函数类在强意义下的最优性条件，并给出了广义次微分在稳定性理论和极小化方法中的应用     

高效液相色谱法测定水体中的氯虫酰胺残留量

采用Kromasil C18不锈钢柱(250mm×4.6mm i.d..5μm),以甲醇-水混合溶剂(65:35,V/V)为流动相,流速1.0mL/min,光电二极管阵列检测器,检测波长236nm和柱温35C,建立了不同水体中氯虫酰胺残留的高效液相色谱分析方法.氯虫酰胺水样直接用二氯甲烷进行液-液分配萃取.在0.10-10mg/L的浓度范围内,氯虫酰胺峰面积(y)与质量浓度(x)呈现良好的相关性,其线性回归方程为y=2170.4x 2641.7,r2=0.9991.井水和池塘水中添加质量浓度为0.01-1.00mg/L时,其平均回收率分别为94.70%-100.37%和89.14%-100.22%,变异系数分别为0.81%-5.11%和1.81%-5.30%,水样中的氯虫酰胺最低检测质量浓度(LOQ)为7.5×10-3mg/L,方法快速、灵敏度高、重现性好,具有较好的准确度和精密度,可用于环境中水样和土壤样中氯虫酰胺的残留检测分析.