手动爬楼梯轮椅的运动过程分析

对一种手动爬楼梯轮椅的运动过程进行了分析。在各部件不与楼梯台阶相干涉的条件下，计算出了车辆质心位置的座标值，并依此绘出质心的位移轨迹曲线。计算了轮椅在上爬楼梯时运动期的中间段质心的速度、加速度以及人的操纵力值。为进一步进行动力学分析和轮椅的改进设计提供了依据。     

Partially Accelerated Life Tests for the Weibull Distribution Under Multiply Censored Data

This article aims to estimate the parameters of the Weibull distribution in step-stress partially accelerated life tests under multiply censored data. The step partially acceleration life test is that all test units are first run simultaneously under normal conditions for a pre-specified time, and the surviving units are then run under accelerated conditions until a predetermined censoring time. The maximum likelihood estimates are used to obtaining the parameters of the Weibull distribution and the acceleration factor under multiply censored data. Additionally, the confidence intervals for the estimators are obtained. Simulation results show that the maximum likelihood estimates perform well in most cases in terms of the mean bias, errors in the root mean square and the coverage rate. An example is used to illustrate the performance of the proposed approach.     

SurveyMotion: what can we learn from sensor data about respondents’ completion and response behavior in mobile web surveys?

Participation in web surveys via smartphones increased continuously in recent years. The reasons for this increase are a growing proportion of smartphone owners and an increase in mobile Internet access. However, research has shown that smartphone respondents are frequently distracted and/or multitasking, which might affect completion and response behavior in a negative way. We propose ‘SurveyMotion (SMotion)’, a JavaScript-based tool for mobile devices that can gather information about respondents’ motions during web survey completion by using sensor data. Specifically, we collect data about the total acceleration (TA) of smartphones. We conducted a lab experiment and varied the form of survey completion (e.g. standing or walking). Furthermore, we employed questions with different response formats (e.g. radio buttons and sliders) and measured response times. The results reveal that SMotion detects higher TAs of smartphones for respondents with comparatively higher motion levels. In addition, respondents’ motion level affects response times and the quality of responses given. The SMotion tool promotes the exploration of how respondents complete mobile web surveys and could be employed to understand how future mobile web surveys are completed.     

Modelling Accelerated Degradation Data Using Wiener Diffusion With A Time Scale Transformation

Engineering degradation tests allow industry to assess the potential life span of long-life products that do not fail readily under accelerated conditions in life tests. A general statistical model is presented here for performance degradation of an item of equipment. The degradation process in the model is taken to be a Wiener diffusion process with a time scale transformation. The model incorporates Arrhenius extrapolation for high stress testing. The lifetime of an item is defined as the time until performance deteriorates to a specified failure threshold. The model can be used to predict the lifetime of an item or the extent of degradation of an item at a specified future time. Inference methods for the model parameters, based on accelerated degradation test data, are presented. The model and inference methods are illustrated with a case application involving self-regulating heating cables. The paper also discusses a number of practical issues encountered in applications. This revised version was published online in July 2006 with corrections to the Cover Date.     

Parabolic acceleration of the EM algorithm

A new acceleration scheme for optimization procedures is defined through geometric considerations and applied to the EM algorithm. In many cases it is able to circumvent the problem of stagnation. No modification of the original algorithm is required. It is simply used as a software component. Thus the new scheme can be easily implemented to accelerate a fixed point algorithm maximizing some objective function. Some practical examples and simulations are presented to show its ability to accelerate EM-type algorithms converging slowly.     

单摆模型中重力加速度的探讨

本文主要从能量守恒的角度,在稳定性要求的限制下,通过单摆的摆角分析,突破传统中小角度(θ<5°)的限制,把周期公式推广到大角度(θ<180°)的情况.我们的研究得出较为精确的阐述重力加速度的表达式,这将为单摆实验中测量重力加速度带来便利.     

Global speed: a time view on transnationality

One of the most challenging aspects of the current processes of globalization is the accelerating pace with which communication, technological information, people and goods are ‘spinning’ around the world. With the growth of our spatial scope to a global level, we have become used to acceleration in a highly competitive world, which results in a feeling of real‐time experience, or instantaneity. The ways in which we deal with acceleration are determined by a specific understanding of the relationship between time and organization: from a Western perspective, managerial practices are based on the ratio‐economic, and therefore limited, idea of clock time. From a transcultural perspective, however, other modes of time interfere with the rigidity and linearity of clock‐time‐based organization. Moreover, on a global level a more encompassing, holistic understanding of time can be important to analyse tensions and contradictions in current managerial practices. It therefore seems important to introduce a perspective of time plurality into debates on transnational organization. How does a view of time complexity affect the management of cohesion and loyalty in the current practices of managers who deal with transnational networks?     

建设社会主义新农村带根本性的战略选择

统筹城乡发展,改革城乡二元结构是建设社会主义新农村的根本任务;实现城乡二元结构转换是建设社会主义新农村的必要与必然;要抓住新农村建设和二元结构转换的机遇期与关键期,加快我国工业化城市化现代化的发展步伐;积极面对和探析制约新农村建设的现实深层次的矛盾与问题;以科学发展观为指导,大力推进实施城乡二元结构转换的制度创新,为农民提供基本而有保障的公共产品。