Estimation of system reliability for exponential distributions based on L ranked set sampling

Abstract

In the case where strength and stress both follow exponential distributions, this paper considers the maximum likelihood estimator (MLE) of the system reliability based on L ranked set sampling (LRSS). The proposed MLE is shown to have existence, uniqueness and asymptotic normality, and its asymptotic variance is obtained by the Fisher information matrix of LRSS. The values of asymptotic relative efficiencies show that the proposed MLE is always more efficient than the MLE using simple random sampling (SRS). However, the MLE using LRSS cannot be written in closed form. Therefore, the modified MLE is proposed using the technique replaced some terms in the maximum likelihood equations by their expectations. The newly modified MLE using LRSS is shown to be superior to the MLE using SRS. Finally, the proposed method is applied to a real data set on metastatic renal carcinoma study.     

Separating psychological momentum from strategic momentum: Evidence from men’s professional tennis

In dynamic contests, strategic momentum and psychological momentum potentially coexist, which makes it difficult to distinguish between the two. We employ the setting of professional tennis, which allows us to separate psychological from strategic momentum. In tennis, converting a break point potentially triggers both strategic momentum—due to a change in the relative position of the players—and psychological momentum—due to a change in the perception of the players. To distinguish between these two momentum types, we employ exogenously given interruptions. Interruptions are predicted to affect psychological momentum negatively, while leaving strategic momentum unaffected. Using 4930 game-by-game observations from 141 Grand Slam men’s single matches, we show that the breaking players’ probability of winning a game increases after converting a break point, which provides evidence for momentum. Moreover, we show that this momentum effect is negatively affected by an interruption. Thus, psychological momentum seems to be the main trigger leading to a performance increase after a converted break point.     

Dynamic capabilities and high-tech entrepreneurial ventures’ performance in the aftermath of an environmental jolt

This paper contributes to studies on dynamic capabilities (DCs) by showing that a neglected environmental contingency – i.e. the occurrence of a jolt – shapes the DCs–performance relationship. We focus on high-tech entrepreneurial ventures because these are the firms that jolts affect most; in so doing, we also advance the understanding of DCs in the entrepreneurship field. We argue that, in the aftermath of an environmental jolt, the high-tech entrepreneurial ventures that use internationalization and new product development capabilities to modify their resource configuration and regain environmental fit enjoy better performance. Econometric estimates on a sample of 340 Italian high-tech entrepreneurial ventures confronting the consequences of the global economic crisis that began in 2008 confirm that separately using these two DCs has a positive performance effect. This effect is stronger for relatively smaller ventures. Interestingly, despite synergies should arise from the combined use of the two DCs, we do not detect any superadditive effects.     

探析我国出口信用证结算地位弱化的成因及影响

鉴于信用证具有比较强的收汇保障的性能和贸易融资功能，因此也一直是我国出口企业贸易结算的首选，使用率高居90％。但是近年来，其结算的“霸主”地位不断弱化，并由此对我国外贸出口产生了较大的不利影响。本文探讨了其中具体的原因及影响，并辅以对策。     

夹注式单词释义对二语阅读中词汇附带习得的影响

用一语夹注、二语夹注及无注释三种方式对同一篇英语文章中的生词加以处理,探究夹注式单词释义对二语阅读中词汇附带习得的影响。研究对象为我国某外国语大学英语专业二年级的3个平行班。实验时,控制班使用的阅读材料不含生词注释,两个实验班使用的阅读材料分别含有一语夹注和二语夹注。统计结果显示,实验班和控制班在词形辨认和形义联系两项即时测试中均无显著性差异。研究表明,不同于旁注及尾注等注释形式,夹注对二语阅读过程中的词汇附带习得并无显著的帮助作用。     

住房抵押贷款对启动住房消费的作用

国际经验表明 ,当一国的人均 GDP达到 30 0 - 10 0 0美元时 ,正是启动住房市场的关键时期 ;而住房抵押贷款在扩大内需、实现住房有效需求的转化中起着重要的作用。本文通过分析当前住房抵押贷款业务中存在的主要问题 ,探究影响我国住房抵押贷款发挥作用的一些主要因素 ,并客观评价现阶段我国住房抵押贷款所能起的作用     

企业劳动雇佣量的决策分析——兼论两种不同性质的培训及其成本负担

本文论述了企业在单期静态和多期动态的需求下的劳动雇佣量的决定。认为企业为实现利润最大化目标 ,其最佳劳动雇佣量是增雇最后一名员工的现值产品收益应等于现值劳动成本。当企业在雇佣初期对员工存在培训成本时 ,则要求员工在完成培训之后能为企业产生净剩余 ,以弥补企业初期的净成本。文章从理论上阐述了两种不同性质的培训 ,得出通用培训成本原则上由受训者员工自己承担 ;而特殊培训成本可由企业或者劳资双方共同承担。     

保水剂对上海青生长状况的影响

在海南省五指山市区种植上海青并施用不同量的保水剂,测定结果表明：3～4kg/亩效果较好,施用量少（1kg/亩）效果不明显;在干旱的条件下,施用量多（5 kg/亩）会阻碍上海青的生长。     

浅论提单的合同性

在国际货物买卖中,提单是被广泛使用的单据,其便利和快捷使其能极大的促进国际贸易的迅速发展。由于其得以发挥作用的价值所在乃法律所赋予它的功能,而确定提单关系的法律性质则是使其功能得以发挥的前提。然对此,目前学界尚存争议。笔者认为,无论从形式意义上还是实质意义上提单都彰显了一种意思自治的契约关系,故其应为一种合同。     

西方二语习得理论研究的两种认识论取向——对我国外语研究的启示

二语习得研究主要是科学系统地研究人们在习得了母语后是如何学会第二语言的.在二语习得研究中专家学者建构了很多二语习得理论.虽然这些理论对二语习得的本质、习得的过程及其影响因素关系的阐释和研究视角不同,但是可以概括为心灵认知主义和社会认知主义两种主要认识论取向.比较心灵认知主义取向的二语习得理论, 基于社会认知主义的二语习得理论为我国外语学习者的学习过程、学习动机、学习策略、社会文化环境等因素研究建立了理论基石,也为建构我国本土外语教学理论和教学实践提供了有利的理论支持.