大拉臂和直臂扣球两种挥臂动作的比较分析

通过文献资料法和比较分析法,比较了大拉臂和直臂扣球两种挥臂动作的动作特点、轨迹及其适用范围。     

美国网络安全战略分析

从克林顿时代起,美国政府高度重视网络安全战略,将其视为国家安全战略的重要组成部分。该战略经历了从重视网络防御、网络攻防结合,到全球网络威慑的演变。网络安全战略演变的实质,就是逐步确立美国的制网权战略。为保证网络安全战略的实施,美国形成了组织管理保障、技术保障、法律法规保障和执行保障等体系。美国网络安全战略引发了网络军备竞赛,给国际法造成了严重挑战。本文通过对美国网络安全战略的分析,剖析其特点和实质,希望对我国网络安全建设有所启示。     

旋涡星系中旋臂的维持

为了避开旧物质臂理论中旋臂的缠绕困难，本文提出了旋涡星系的循环假设，并提供了旋涡星系的双臂、气体层反卷、银河系中旋臂物质径向向内的速度分量和棒旋星系中棒物质沿着棒向内的流动等观测证据。进而还尝试利用此循环假设去解释旋臂物质的平自转曲线和棒旋星系的棒结构等的成因。     

孔子山水“比德”的生态审美思考

"比德"将客观自在之物的某些性质比附于人的某些品德,是儒家重要的美学观点。文章从"比德"于山水、寄情于山水、效行于山水三个方面阐释了孔子山水"比德"的生态审美。     

体感交互式拟人手臂机器人

针对目前人体动作同步机器人造价高,使用过程繁琐,需要穿戴多种传感器设备等缺点,设计并研制了一种不需 要穿戴传感器的人体手臂动作同步机器人。介绍了机器人的结构和系统组成,给出了Kinect读取和共享数据以及转换 为机械臂可用数据的方法,设计PID结合PWM脉宽调速的控制驱动模块,完成了机械臂控制系统的软件。结果表明该 人体动作同步机器人在未经培训的操作者指挥下,能够从不同初始位置完成人类肢体动作发出的指令,并且精度较高。 这一研究可为无传感器肢体交互智能机器人研制提供参考     

通过聚乙二醇键合巯基苯并噻唑的交联聚苯乙烯基螯合树脂的合成及其吸附性能

以氯甲基化聚苯乙烯为原料,合成了在聚苯乙烯基体和杂环功能基2-巯基苯并噻唑(MBZ)之间引入聚氧乙烯亲水性悬臂的新型螯合树脂,对所合成的树脂进行了元素分析、红外光谱和扫描电镜表征,对比研究了引入悬臂前后树脂对Hg2 等5种金属离子的静态吸附性能.实验结果表明:经过多步反应,引入亲水性悬臂之后,树脂的表面形貌没有变化,仍保留大孔结构,吸附选择性和功能基的利用率显著提高.     

Sample size calculation for recurrent events data in one‐arm studies

In some exceptional circumstances, as in very rare diseases, nonrandomized one‐arm trials are the sole source of evidence to demonstrate efficacy and safety of a new treatment. The design of such studies needs a sound methodological approach in order to provide reliable information, and the determination of the appropriate sample size still represents a critical step of this planning process. As, to our knowledge, no method exists for sample size calculation in one‐arm trials with a recurrent event endpoint, we propose here a closed sample size formula. It is derived assuming a mixed Poisson process, and it is based on the asymptotic distribution of the one‐sample robust nonparametric test recently developed for the analysis of recurrent events data. The validity of this formula in managing a situation with heterogeneity of event rates, both in time and between patients, and time‐varying treatment effect was demonstrated with exhaustive simulation studies. Moreover, although the method requires the specification of a process for events generation, it seems to be robust under erroneous definition of this process, provided that the number of events at the end of the study is similar to the one assumed in the planning phase. The motivating clinical context is represented by a nonrandomized one‐arm study on gene therapy in a very rare immunodeficiency in children (ADA‐SCID), where a major endpoint is the recurrence of severe infections. Copyright © 2012 John Wiley & Sons, Ltd.     

网球双手反拍抽击球技术中“主发力手”辨析

今天双手反拍抽球技术已成为最重要、最基本的技术之一。双手反拍抽击球与底线正拍击球一样,能打出高质量、高难度的进攻球。但是怎样运用,如何提高击球的效果？传统的观念认为,双手反拍技术右手是主打。在击球过程中要身体放松,身体协调,在此情况下,完全可以左右手很自然的协调配合起来,发挥最大的效用。     

START: single‐to‐double arm transition design for phase II clinical trials

Phase II clinical trials designed for evaluating a drug's treatment effect can be either single‐arm or double‐arm. A single‐arm design tests the null hypothesis that the response rate of a new drug is lower than a fixed threshold, whereas a double‐arm scheme takes a more objective comparison of the response rate between the new treatment and the standard of care through randomization. Although the randomized design is the gold standard for efficacy assessment, various situations may arise where a single‐arm pilot study prior to a randomized trial is necessary. To combine the single‐ and double‐arm phases and pool the information together for better decision making, we propose a Single‐To‐double ARm Transition design (START) with switching hypotheses tests, where the first stage compares the new drug's response rate with a minimum required level and imposes a continuation criterion, and the second stage utilizes randomization to determine the treatment's superiority. We develop a software package in R to calibrate the frequentist error rates and perform simulation studies to assess the trial characteristics. Finally, a metastatic pancreatic cancer trial is used for illustrating the decision rules under the proposed START design.     

Nested combination tests with a time‐to‐event endpoint using a short‐term endpoint for design adaptations

Adaptive trial methodology for multiarmed trials and enrichment designs has been extensively discussed in the past. A general principle to construct test procedures that control the family‐wise Type I error rate in the strong sense is based on combination tests within a closed test. Using survival data, a problem arises when using information of patients for adaptive decision making, which are under risk at interim. With the currently available testing procedures, either no testing of hypotheses in interim analyses is possible or there are restrictions on the interim data that can be used in the adaptation decisions as, essentially, only the interim test statistics of the primary endpoint may be used. We propose a general adaptive testing procedure, covering multiarmed and enrichment designs, which does not have these restrictions. An important application are clinical trials, where short‐term surrogate endpoints are used as basis for trial adaptations, and we illustrate how such trials can be designed. We propose statistical models to assess the impact of effect sizes, the correlation structure between the short‐term and the primary endpoint, the sample size, the timing of interim analyses, and the selection rule on the operating characteristics.