发电机转子在不对称运行下固有频率分裂规律的研究

发电机转子是一个水平刚度和垂直刚度基本相同的柔性体,转子的固有频率与转子本身有关,但当发电机的外接负载不对称时,转子的固有频率还与三相负载的不对称度有关,并且固有频率随激励电流变化而产生了奇特的分裂现象。     

现代远程教育模式探析

本文就现代教育新形式———远程教育进行了探析。从现代远程教育产生的历史背景、与传统教育相比所具备的独有特征、远程教育的开放教育模式、管理模式以及现代远程教育的可行性五方面阐述了作者的观点。对高等教育多元化发展有一定的参考价值。     

Reflections on gains and losses: A 2 × 2 × 7 experiment

What determines risk attraction or aversion? We experimentally examine three factors: the gain-loss dichotomy, the probabilities (0.2 vs. 0.8), and the money at risk (7 amounts). We find that the majority display risk attraction for small amounts of money, and risk aversion for larger amounts. Yet the frequency of risk attraction varies according to the gain-loss dichotomy and the probabilities. Kahneman and Tversky studied gain-loss reflections. We submit that a reflection can be decomposed into a translation and a probability switch. We find significant translation and switch effects, which are of comparable magnitude, a result that is equidistant from the diverging two popular views inspired by Prospect Theory: the gain-loss asymmetry, and the fourfold pattern.     

Extreme value index estimator using maximum likelihood and moment estimation

ABSTRACT

When a distribution function is in the max domain of attraction of an extreme value distribution, its tail can be well approximated by a generalized Pareto distribution. Based on this fact we use a moment estimation idea to propose an adapted maximum likelihood estimator for the extreme value index, which can be understood as a combination of the maximum likelihood estimation and moment estimation. Under certain regularity conditions, we derive the asymptotic normality of the new estimator and investigate its finite sample behavior by comparing with several classical or competitive estimators. A simulation study shows that the new estimator is competitive with other estimators in view of average bias, average MSE, and coefficient of variance of the new device for the optimal selection of the threshold.     

Asymptotic distributions of order statistics and record values arising from the class of beta-generated distributions

In this paper, we show that both the class of beta-generated distributions G_F and its base distribution F belong to the same domain of maximal (or minimal or upper record value or lower record value) attraction. Moreover, it is shown that the weak convergence of any non-extreme order statistic (central or intermediate order statistic), based on a base distribution F, to a non-degenerate limit type implies the weak convergence of G_F to a non-degenerate limit type. The relations between the two limit types are deduced.     

新型吡唑去甲斑蝥酰亚胺衍生物的核磁共振波谱分析

利用1,3-偶极环加成合成了新的去甲去氢斑蝥素衍生物,借助1HNMR、13CNMR及相关的2DNMR谱的分析,对斑蝥素衍生物的氢谱和碳谱进行了归属,并确证了该类化合物的构象.     

基于动态因果模型的运动执行和运动想象脑网络研究

利用动态因果模型,分析右手运动执行和想象过程中功能磁共振实验数据对侧初级运动皮层(M1)和双侧辅助运动区(SMA)的动态功能网络,发现了左侧SMA在右手运动执行和运动想象过程中的主导作用,以及运动想象过程中左侧SMA对左侧M1的抑制作用;进一步分析了运动执行和想象过程的动态功能网络的差异,发现了实验刺激模式在两种不同的动态网络中对激活脑区的激活和抑制作用的转化,揭示了运动执行和想象动态功能网络转换的神经机制。