共查询到20条相似文献，搜索用时 203 毫秒
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This paper proposes a modification to distributed coordination function (DCF) to improve the channel utilization in IEEE 802.11 wireless local area networks (WLANs). In the modified DCF, when a station has contended for the channel, it may transmit multiple data frames continuously to the same destination, which is called transmission burst(TB). When the maximum number of data packets transmitted continuously in a TB is set to be 2, the performance is expected to be the best. The theoretical analysis and simulation results show that compared with the standard DCF, the modified DCF can increase the throughput and decrease the delay of the WLAN, and the modification does not introduce any additional control overhead. 相似文献
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Andrew A. McConney Mark D. Schalock H. Del Schalock 《Journal of Personnel Evaluation in Education》1998,11(4):343-363
The authors suggest that the gap between common evaluation practice in teacher preparation and the consensus reform goal of high levels of student learning for all students is an impediment to reinventing teacher preparation, professional development, and the professionalization of teaching. In the context of Oregons six-year-old educational transition to a standards-based design for schools and schooling, prospective teachers in Oregon have, since 1989, been required to design, develop, and implement teacher work samples as credible evidence of their effectiveness in fostering student learning as a condition for recommendation for an initial teaching license. This article describes teacher work sample methodology and evidence for its reliability and validity in evaluating the performance of prospective teachers. In short, this article describes a methodology that responds to one critical part of the National Commission on Teaching and Americas Futures challenge to reinvent teacher education and improve student learning. 相似文献
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This study examined the effect of strategy instruction and incentives on performance, confidence, and calibration accuracy. Individuals (N = 107) in randomly assigned treatment groups received a multicomponent strategy instruction intervention, financial incentives for high performance, or both. The authors predicted that incentives would improve performance, while strategy instruction would improve performance, confidence, and calibration accuracy as a result of better monitoring and self-regulation of learning. The authors compared pre- and posttest items and 20 new posttest-only items. They found significant effects for strategy training on performance, confidence, and calibration accuracy, as well as the interaction between strategy training and time on calibration accuracy. Incentives improved performance and calibration accuracy, either directly, or through an interaction with strategy training. Implications for future research are discussed. 相似文献
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Inrecent years ,IEEE802.11 wirelesslocal area net-work (WLAN) has emerged as a prevailing technology forthe (indoor) broadband wireless access to internet for themobile/portable devices . In IEEE 802.11 standards ,802.11b has become the most widely used v… 相似文献
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Ways to Fall Asleep看过《神雕侠侣》的人都记得,小龙女睡法奇特,她练就了在绳上入睡的功夫。无独有偶,为了尽快进入自己的梦乡,历史上许多名人绞尽脑汁,寻找入睡的方法,有的人终于找到了自己独特的入眠方法,而有的人却还是好梦难圆。你想探个究竟吗?请看“睡眠趣闻”。 相似文献
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What Are You Doing on Weekends?周末又到了,难道你不高兴吗?紧张的课堂学习告一段落,终于可以放松一下自己了。那么,干些什么,你计划好了吗?也许你的活动安排得不够丰富多彩,那就让我们一起看一看地球村另一端的孩子们周末都做些什么? 相似文献
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1.The Story of Sandwich三明治是上班族的最爱。这不仅是因为它味道鲜美,营养丰富,而且还因为它食用方便,节省时间,人们可以一边干活,一边享用。那么当初发明人是怎样突发灵感,做出了这种风靡全球的美味呢?请看“趣谈三明治”。In English there are som e interesting words.These words have som e interesting stories behindthem.The word“sandwich”,for exam ple,is verycom m on in English,but it has a good story.If wewant to know the story behind it,w e m ust knowsom ething about an E nglish noblem an.H is nam e… 相似文献
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A new attack is proposed to show that a specified group of verifiers can cooperate to forge the signature for any message by secret key substitution due to the leaked secret key or by the group public key adjustment because of the renewed members. This paper presents the improvement scheme which overcomes the security weakness of Laih and Yen's scheme. 相似文献
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A Friendly Cat一位先生惜猫如子,一日三餐与猫形影不离,有了好吃的东西,总忘不了和爱猫共同分享。久而久之,顽皮的猫也深受感动,总想寻找机会报答主人的知遇之恩。一天吃饭时,这只亲爱的猫不见了。正当主人 相似文献
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Pepper5s Wonderful Use胡椒味道辛辣,宜脾胃,通七窍,是调味之佳品。令人称奇的是,胡椒粉除了能做调味品外,有时还有其他意想不到的妙用!邻居阿姨仅用 相似文献
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Kamil Özerk 《Scandinavian Journal of Educational Research》2013,57(4):353-367
This article is a result of a small-scale study with the purpose of investigating teacher-student verbal interactions and questioning and students' curriculum-related performance in small and large mainstream classes. In mainstream classes the bilingual students were taught together with their monolingual Norwegian peers. The study shows that there are inter-group and intra-group differences with respect to: (i) teacher-student verbal interaction; (ii) academic questioning; (iii) curriculum-related performance of students in small classes compared with large classes. The bilingual minority students in general, and bilingual minority girls in particular, benefit from civics lessons in small classes more than they do in large classes. It is suggested that by creating rich possibilities for teacher-student verbal interaction and curriculum-oriented academic questioning, small classes can provide conditions for better academic performance in content area subjects, i.e. civics, for bilingual students in general and bilingual girls in particular than do large classes. 相似文献
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Jennifer Bragger Eugene J. Kutcher Gaynell Schettino Bridget Muzyczyn Pamela Farago Emily Fritzky 《Performance Improvement Quarterly》2016,29(2):97-124
Structuring job interviews is a method of decreasing bias and increasing the predictive validity of job performance, but research suggests that applicants can react negatively to structure (Chapman & Zweig, 2005) and that negative attitudes about selection tools can predict performance (Hausknecht, Day, & Thomas, 2004). The current exploratory study investigates how structuring the job interview in conjunction with priming the ethnicity and sex of the applicant, and in some conditions providing an explanation of the structure, affected post‐interview cognitive ability performance. Three levels of structure were randomly assigned. Those who experienced a structured interview without an explanation of its purpose scored lower than those who experienced an unstructured interview, but those who experienced a structured interview with an explanation of its purpose did not score lower than those who experienced an unstructured interview. Scores differed for females and Hispanics depending on the structure condition, but not in the same manner. Implications for recruitment, selection, and performance management are discussed. 相似文献
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Lǖ JinJian 《茂名学院学报》1992,(1)
This paper discussed the reasons for 2.13H CCDOS with MS DOS uncompatible, cive resolved methods, solved well problems of some English softwares, which can't execut under 2.13H CCDOS. 相似文献
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RAHIMI N SADEGHI M. H. MAHJOOB M.J. 《浙江大学学报(A卷英文版)》2007,8(9):1443-1451
In this paper,a geometric approach to fault detection and isolation (FDI) is applied to a Multiple-Input Multi-ple-Output (MIMO) model of a frame and the FDI results are compared to the ones obtained in the Single-Input Single-Output (SISO),Multiple-Input Single-Output (MISO),and Single-Input Multiple-Output (SIMO) cases. A proper distance function based on parameters obtained from parametric system identification method is used in the geometric approach. ARX (Auto Regressive with eXogenous input) and VARX (Vector ARX) models with 12 parameters are used in all of the above-mentioned models. The obtained results reveal that by increasing the number of inputs,the classification errors reduce,even in the case of applying only one of the inputs in the computations. Furthermore,increasing the number of measured outputs in the FDI scheme results in decreasing classification errors. Also,it is shown that by using probabilistic space in the distance function,fault diagnosis scheme has better performance in comparison with the deterministic one. 相似文献
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李伟明 《重庆大学学报(英文版)》2005,4(1):47-49
1 Introduction With advances in networking technology, iSCSI allows for the deployment of storage networks over a commodity internet. However providing storage services across networks increases communication costs: requests and results must be transported between iSCSI Initiator and iSCSI target [1,2]. Intensive overhead caused by network I/O limits the capacity of servers. This makes the study of iSCSI performance an import research topic. Earlier researches closely measure the perfo… 相似文献
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Although genetic algorithm has become very famous with its global searching,parallel computing,better robustness,and not needing differential information during evolution.However,it also has some demerits,such as slow convergence speed.In this paper,based on several general theorems,an improved genetic algorithm using variant chromosome length and probability of crossover and mutation is proposed,and its main idea is as follows:at the beginning of evolution,our solution with shorter length chromosome and higher probability of crossover and mutation;and at the vicinity of global optimum,with longer length chromosome and lower probability of crossover and mutation.Finally,testing with some critical functions shows that our solution can improve the convergence speed of genetic algorithm significantly,its comprehensive performance is better than that of the genetic algorithm which only reserves best individual. 相似文献
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John Gray David Jesson Harvey Goldstein Keith Hedger Jon Rasbash 《School Effectiveness & School Improvement》2013,24(2):97-114
The improvement of schools takes place over extended periods of time. Consequently longitudinal studies which track successive cohorts of pupils through their schooling are required if estimates of the extent of improvement are to be established. To date, hardly any studies have collected the necessary data. Those studies which have had appropriate data have tended to emphasise the extent of stability of schools' effectiveness over time rather than the extent of any changes. A shift in conceptual framework is called for if improvements in schools' effectiveness are to be the central focus of concern. The study is based on three successive cohorts of pupils passing through some 30 English secondary schools. It uses examination results as the outcome measure and includes a prior attainment measure amongst the variables used to control for differences between schools' intakes. A multi‐level strategy for conceptualising and modelling data on schools' changes in performance over time is offered. In common with earlier studies the research shows that there is a good deal of stability in schools' effectiveness from year‐to‐year; only a small proportion of the schools in the study (between a fifth and a quarter) were improving or deteriorating in terms of their effectiveness. A particularly striking finding of the research was that whilst several schools improved in effectiveness only one initially ‘ineffective’ school did so consistently. The implications of the study for future research on school improvement are discussed. 相似文献