A simulation study on the influence of ties on uniform scores test for circular data

Uniform scores test is a rank-based method that tests the homogeneity of k-populations in circular data problems. The influence of ties on the uniform scores test has been emphasized by several authors in several articles and books. Moreover, it is suggested that the uniform scores test should be used with caution if ties are present in the data. This paper investigates the influence of ties on the uniform scores test by computing the power of the test using average, randomization, permutation, minimum, and maximum methods to break ties. Monte Carlo simulation is performed to compute the power of the test under several scenarios such as having 5% or 10% of ties and tie group structures in the data. The simulation study shows no significant difference among the methods under the existence of ties but the test loses its power when there are many ties or complicated group structures. Thus, randomization or average methods are equally powerful to break ties when applying uniform scores test. Also, it can be concluded that k-sample uniform scores test can be used safely without sacrificing the power if there are only less than 5% of ties or at most two groups of a few ties.     

论转型期中国建构可持续消费文化的条件与机制

随着经济发展和社会的进步,人类发展与人口、资源、环境之间的矛盾越来越突出,可持续发展已经成为全世界的共识。可持续发展包括可持续生产和可持续消费两个部分。本文尝试从消费社会学视角探讨了转型期中国建构可持续消费文化的条件及其社会文化机制问题。     

非英语专业学生听力焦虑现状的调查研究

本研究从负面评价焦虑、听力考试焦虑和听力课堂焦虑三个纬度,调查分析了非英语专业学生的听力焦虑现状。结果显示,多数非英语专业学生处于低度焦虑状态;听力成绩与听力焦虑呈负相关,中高度焦虑抑制听力学习;听力焦虑与性格相关;听力课堂焦虑与性别呈弱相关,而负面评价焦虑及听力考试焦虑与性别无关。     

武器装备建设管理信息集成化问题研究

提高国防实力必须加强武器装备建设,武器装备建设管理信息集成化是实现武器装备现代化建设的有效途径。本文介绍了武器装备建设信息集成化的内涵及作用,分别阐述了CALS、SBA、VR、IMS等先进的装备建设信息集成化技术和方法,给出了建设武器装备信息集成化系统的建议。     

An Empirical Investigation of Web Site Use Using a Commitment‐Based Model

Companies throughout industry are interested in retaining existing customers, because customers' continuous consumption of products and services is critical to the long‐term value propositions of most organizations. Thus, decision‐making strategies that promote continuous use and customer retention are of research interest, both theoretically and practically. In the present research, we investigate one important area of continuous usage, that of Web site use. In particular, we use several theories of commitment to understand how an individual's decision to continue to use a Web site is influenced by his or her commitment toward that Web site and the vendor that supports it. Results derived from data collected from 335 users of a variety of Web sites indicated that affective commitment, calculative commitment, quality of alternatives, and trust were significantly associated with an individual's behavioral intention to continue to use a Web site. Implications for customer retention and decision‐making strategies are discussed.     

对我国近五年田径成绩分析及“九运会”田径水平预测

通过对１９９６年至２００１年度我国男、女子田径前三名最好成绩的分析,揭示了近五年我国田径运动水平的变化趋势及原因,结合实际,初步预测了“九运会”田径项目的水平。     

关于体育中考200米项目训练的思考

本文通过介绍学校教学管理、体育教师指导和家长与学校之间的沟通配合等环节,对中考体育200米训练产生的影响的现状进行分析,使我们更加直观地了解影响学生中考体育成绩的各项因素,进而科学合理地进行教学与训练,全面提高学生的中考体育成绩。     

Partial orders with respect to continuous covariates and tests for the proportional hazards model

Several omnibus tests of the proportional hazards assumption have been proposed in the literature. In the two-sample case, tests have also been developed against ordered alternatives like monotone hazard ratio and monotone ratio of cumulative hazards. Here we propose a natural extension of these partial orders to the case of continuous and potentially time varying covariates, and develop tests for the proportional hazards assumption against such ordered alternatives. The work is motivated by applications in biomedicine and economics where covariate effects often decay over lifetime. The proposed tests do not make restrictive assumptions on the underlying regression model, and are applicable in the presence of time varying covariates, multiple covariates and frailty. Small sample performance and an application to real data highlight the use of the framework and methodology to identify and model the nature of departures from proportionality.     

Polyphasic sleep strategies improve prolonged sustained performance: A field study on 99 sailors

In situations where continuous prolonged work demands exist, the habitual nocturnal monophasic (6-8h duration) sleep pattern can rarely be accomplished, and performance effectiveness may sometimes be severely compromised by accumulation of sleep debt. Several studies have shown that naps can be disproportionately effective in recovering functioning during continuous work (CW).

In this study, sleep-wake patterns and their relationship to performance were studied for 99 sailors involved in solo and double-handed ocean sailing races (a model of a highly demanding CW situation). Most sailors spontaneously adopted multiple nap sleep-wake schedules and adapted without major difficulties to such polyphasic patterns. 66.5% had mean sleep episode durations (SEDs) ranging from 20 min to 2h. Overall mean Total Sleep Time (TST) per 24h was reduced from a baseline of 7.5 to 6.3h. Race performance correlated negatively and significantly with mean SEDs and TSTs. Best performance results were obtained by those sleeping for periods of between 20 min and 1 h and for a total of 4.5 to 5.5h of sleep per day.

The results are discussed together with several chronobiological, phylogenetic and experimental studies and issues, all of which suggest that adult humans may have a damped polyphasic sleep-wake tendency. It is also proposed that polyphasic sleep schedules could become promising and feasible solutions for the management of sleep requirements under prolonged CW situations.     

Estimation of regression parameters in generalized linear models for cluster correlated data with measurement error

Liang and Zeger (1986) introduced a class of estimating equations that gives consistent estimates of regression parameters and of their asymptotic variances in the class of generalized linear models for cluster correlated data. When the independent variables or covariates in such models are subject to measurement errors, the parameter estimates obtained from these estimating equations are no longer consistent. To correct for the effect of measurement errors, an estimator with smaller asymptotic bias is constructed along the lines of Stefanski (1985), assuming that the measurement error variance is either known or estimable. The asymptotic distribution of the bias-corrected estimator and a consistent estimator of its asymptotic variance are also given. The special case of a binary logistic regression model is studied in detail. For this case, methods based on conditional scores and quasilikelihood are also extended to cluster correlated data. Results of a small simulation study on the performance of the proposed estimators and associated tests of hypotheses are reported.