关于麦克斯韦速率分布律教学的几点思考

麦克斯韦速率分布律是气体分子运动论的中心内容,是大学物理气体动力学理论中讲授的一个难点,公式抽象、繁难不易理解.本文从分布函数的意义及速率分布曲线讨论了麦克斯韦速率分布律的基本特征和成立条件,并由此得到平衡态下气体分子的最概然速率、平均速率、方均根速率等三种统计速率及其物理意义.     

Intertidal distribution,symbiotic association and reproduction of Pinnotheres bidentatus (Brachyura: Pinnotheridae) from Taiwan

The intertidal distribution of the free-swimming stage of the pea crab Pinnotheres bidentatus Sakai, 1939 was examined on the Kaomei coastal flat of western central Taiwan. Most pea crabs were collected from tidal waters close to the shoreline regardless of the collecting treatments utilized. Results suggest that the pea crab population remains inshore during ebb tides. Many hard and post-hard stages of P. bidentatus were discovered, including ovigerous females. The host was found to be Laternula marilina (Valenciennes, 1860) (Mollusca: Bivalvia: Laternulidae). The infestation percentage of the bivalve was high (average 74.6%). However, this may be due to collections of the bivalve population in the present study being skewed towards large sizes. This biased size structure of the host population may be also responsible for lack of positive size correlation between number and size of male and female symbiotic crabs and the host. Multiple infestations of P. bidentatus appear to be uncommon for L. marilina. Single infestations might be a model for bivalves in tropical regions where the sea is relatively oligotrophic and food competition may be enhanced with multiple infestations. In comparison to other members of the genus Pinnotheres or related species (e.g. P. pisum (Linnaeus, 1767) and Zaops ostreum (Say, 1817)), the body size of sexually mature female P. bidentatus is relatively small, even though it produces similar size eggs (approximately 300 microns). The general rule for size correlation between fecundity and female size in brachyuran crabs holds for P. bidentatus.     

A modified likelihood ratio test for homogeneity in bivariate normal mixtures of two samples

This paper investigates the asymptotic properties of a modified likelihood ratio statistic for testing homogeneity in bivariate normal mixture models of two samples. The asymptotic null distribution of the modified likelihood ratio statistic is found to be χ₂², where χ₂² is a chi-squared distribution with 2 degrees of freedom. This research was supported by the National Natural Science Foundation of China under Grant No. 10661003, SRF for ROCS, SEM under Grant No. [2004]527, and the Natural Science Foundation of Guangxi under Grant No. 0728092.     

随机变量的特征函数在一些问题中的应用

利用随机变量的特征函数的定义、性质及相关定理来解决一些较典型的问题。     

脂肪醇聚氧乙烯醚合成反应的动力学研究——产物分布的统计矩

碱催化条件下，以离子反应机理进行的脂肪醇聚氧乙醇醚合成反应中，链转移反应是影响产物分布的重要因素。根据反应动力学方程的递推关系，本文采用Ｌａｐｌａｃｅ变换的方法，研究了产物分布的统计特征，得到了描述反应随时间推进分布均值及方差的变化规律表达式。结果表明，链转移反应是关联原料醇加入量及催化剂特征的重要环节。     

一类二阶非线性泛函微分方程的振动性

研究了一类二阶非线性泛函微分方程的振动性,建立了4个新的振动定理,并给出了其应用.推广了有关文献中的部分结果.     

完善项目管理 提高企业效益

项目管理是一种科学的管理组织形式,在一定程度上能够保证施工企业健康发展。一个工程要想取得良好的经济效益,就必须提高项目管理水平,只有将成本降到最低,才能实现企业的利益最大化。     

玻璃粉粒度分布对胶凝材料性能的影响

为了给玻璃粉水泥用玻璃粉的颗粒级配优化提供理论指导,研究了不同粒度分布的玻璃粉对胶凝材料的性能影响。首先将废玻璃破碎、球磨、干筛、湿筛和沉降,获得化学组分相同、粒度分布不同的超细废玻璃粉。分别测定不同粒度分布的废玻璃粉在复合胶凝材料中的强度,运用活性因子法分析玻璃粉对复合体系贡献度。试验结果表明:复合胶凝材料的强度随着废玻璃粉掺量的增加而减少;玻璃粉颗粒细化对复合体系的强度起着积极作用;玻璃粉水泥浆水化早期时,大多数情况下玻璃粉的活性因子为负,这表明玻璃粉对复合体系的早期强度不仅不能起到增强作用,反而对复合体系的早期强度起着负面影响。     

浅述农村低压配电网接地系统改造及漏电保护器设置

根据农村电网的现状，对农村电网的接地系统存在的问题进行探讨，提出对现在广泛应用于农网的TT系统改造成为TN-C系统，并对现有应用于农村电网的漏电保护器进行相应的调整配置。     

基于ARM2410平台步进电机的控制

本文主要介绍了步进电机的工作原理,以及在基于ARM平台下,利用ARM2410的四路I/O通道实现脉冲分配,来控制步进电机的转动。