Analyzing imbalance among homogeneous index servers in a web search system     

C.S. Badue  R. Baeza-Yates  B. Ribeiro-Neto  A. Ziviani  N. Ziviani 《Information processing & management》2007

The performance of parallel query processing in a cluster of index servers is crucial for modern web search systems. In such a scenario, the response time basically depends on the execution time of the slowest server to generate a partial ranked answer. Previous approaches investigate performance issues in this context using simulation, analytical modeling, experimentation, or a combination of them. Nevertheless, these approaches simply assume balanced execution times among homogeneous servers (by uniformly distributing the document collection among them, for instance)—a scenario that we did not observe in our experimentation. On the contrary, we found that even with a balanced distribution of the document collection among index servers, correlations between the frequency of a term in the query log and the size of its corresponding inverted list lead to imbalances in query execution times at these same servers, because these correlations affect disk caching behavior. Further, the relative sizes of the main memory at each server (with regard to disk space usage) and the number of servers participating in the parallel query processing also affect imbalance of local query execution times. These are relevant findings that have not been reported before and that, we understand, are of interest to the research community.  相似文献   

临床医学期刊在健康科普中的作用     

李娜  刘洋  李玉乐  孙静 《编辑学报》2020,32(2):177-180

随着泛在网络时代的到来,新媒体已成为人们获取健康知识的首要途径;但当前网络健康知识来源芜杂,各种夸大甚至歪曲医学事实的报道层出不穷,健康科普的“含金量”亟须提高。临床医学期刊是权威医学成果发布和交流的重要平台,拥有由作者、审者和编者等众多优秀医学专业工作者组成的专家团队,具有天然的健康科普优势和媒体属性。《协和医学杂志》通过将医学论文科普化、捕捉新闻热点、培养科普人才、充分利用新媒体平台等途径,证明临床医学期刊有责任更有能力在健康科普中发挥重要作用。  相似文献   

变化世界中的科学素养:科技博物馆和科学中心能发挥什么作用？          下载免费PDF全文

埃里克·雅克敏  刘怡 《自然科学博物馆研究》2020,(4):62-68

当今世界正以前所未有的速度发生着各种各样的变化。一些大的趋向,即所谓的世界大趋势,在一定程度上影响每个人的生活。科学、技术和创新在这个不断变化的世界中发挥着重要作用。科学素养比以往任何时候都更加重要。科技博物馆和科学中心作为公众参与科学技术的重要角色,面临着一系列的机遇和挑战。在不断变化的世界里,它们在提高公众科学素养方面能发挥什么作用?如何使它们在提高科学素养方面更具相关性和影响力?本文通过分析当前世界在全球化、人口变化、技术变革、信息爆炸、可持续发展等方面的现实,论述科学素养的必要性以及科技博物馆和科学中心在变化的世界中应该如何发挥作用。  相似文献   

Emotional eavesdropping: infants selectively respond to indirect emotional signals   总被引：1，自引：1，他引：0  

Repacholi BM  Meltzoff AN 《Child development》2007,78(2):503-521

Two experiments examined whether 18-month-olds learn from emotions directed to a third party. Infants watched an adult perform actions on objects, and an Emoter expressed Anger or Neutral affect toward the adult in response to her actions. The Emoter then became neutral and infants were given access to the objects. Infants' actions were influenced by their memory of the Emoter's affect. Moreover, infants' actions varied as a function of whether they were currently in the Emoter's visual field. If the previously angry Emoter was absent (Experiment 1) or turned her back (Experiment 2), infants did not use the prior emotion to regulate their behavior. Infants learn from emotional eavesdropping, and their subsequent behavior depends on the Emoter's orientation toward them.  相似文献   

The role of gender constancy in early gender development     

Ruble DN  Taylor LJ  Cyphers L  Greulich FK  Lurye LE  Shrout PE 《Child development》2007,78(4):1121-1136

Kohlberg's (1966) hypothesis that the attainment of gender constancy motivates children to attend to gender norms was reevaluated by examining these links in relation to age. Ninety-four 3- to 7-year-old children were interviewed to assess whether and how constancy mediates age-related changes in gender-related beliefs. As expected, results indicated a general pattern of an increase in stereotype knowledge, the importance and positive evaluation of one's own gender category, and rigidity of beliefs between the ages of 3 and 5. Moreover, the stability phase, rather than full constancy, mediated some of these relations. After age 5, rigidity generally decreased with age, with relations primarily mediated by consistency.  相似文献   

Getting sloshed in outer space     

N.?AnanthkrishnanEmail author 《Resonance》2007,12(12):40-45

We document some basic facts about how liquids behave in the low gravity of outer space and how this poses challenges to space scientists and engineers who need to design and test systems that handle fluids in outer space while working in the 1-g environment on Earth. N Ananthkrishnan is Director, Coral Digital Technologies (P) Ltd, a Bangalore-based company working in the area of multidisciplinary simulation and system integration of aerospace, naval and surface vehicles, and in the design and development of autonomous unmanned/micro air vehicles.  相似文献   

An Autonomist Biopolitics of Education: Reproduction,Resistance, and the Specter of Constituent Bíos     

Gregory N. Bourassa 《Educational theory》2019,69(3):305-325

In considering the enigmatic relationships between philosophy, politics, and pedagogy, this essay attempts to map some of the currents in educational scholarship, particularly those running between reproduction theories and resistance theories. While these two theoretical frameworks have been at odds with one another, Gregory Bourassa suggests that both share orthodox commitments that prevent them from appreciating the constituent dimensions of revolutionary subjectivity. In seeking an alternative orientation, Bourassa proposes an autonomist biopolitics of education. This framework inverts the traditional circuits of resistance and suggests that schools follow behind and resist the constituent life forms (constituent bíos) of students. If resistance theory only attempts to identify the ways in which students resist school practices, it risks obscuring the potentiality of constituent bíos as a social ontology that is primary, always already present, and subject to the resistant practices of the school. Therefore, a key contribution of this essay is its development of an autonomist biopolitics of education. Within this framework, constituent bíos is recognized as the foundational and constitutive motor to which schools are constantly reacting. The adoption of this perspective, alongside more conventional understandings of resistance, offers a more nuanced conception of the relation between forms of life and schools.  相似文献   

Gender differences in mathematics and science competitions: A systematic review     

Anneke M. Steegh  Tim N. Höffler  Melanie M. Keller  Ilka Parchmann 《科学教学研究杂志》2019,56(10):1431-1460

Gendered patterns in mathematics and science interest emerge in early childhood, develop over time, and ultimately reflect advanced course selection in secondary education. During the crucial time adolescents become aware of their strengths and interests and specialize accordingly, they get the opportunity to participate in out-of-school learning programs such as mathematics and science competitions. This raises the question whether mathematics and science competitions contribute to gender equity by equally promoting female and male interests. In this article, we present a systematic review on gender differences and the mechanisms explaining success and failure in mathematics and science competitions. On an international level, we found large gender differences regarding participation in all Olympiads with the exception of the biology Olympiad. In fairs and national Olympiads, overall participation rates were not gendered as such, but females preferred biology topics whereas males preferred physics related topics. Male and female achievement in fairs was comparable, but males clearly outperformed female participants at the Olympiads, with the smallest differences in the biology Olympiad. Variables and theoretical frameworks explaining participation and achievement and the role of gender in mathematics and science competitions are discussed. We suggest that gender stereotypes, through their influence on self-concept and interest, play an important role in the mechanisms resulting in low female participation rates in and beyond mathematics and science competitions (especially in physics and chemistry). The mechanisms we found explaining female representation during a national selection competition might be considered as reflecting those in female mathematics or science careers and could thus serve as food for thought on countering the gender gap in mathematics and science.  相似文献   

Teachers’ role and attitudes concerning ADHD medication: A qualitative analysis     

Maruschka N. Sluiter  Albert W. Wienen  Ernst D. Thoutenhoofd  Jeannette M. Doornenbal  Laura Batstra 《Psychology in the schools》2019,56(8):1259-1270

The increased use of Attention Deficit/Hyperactivity Disorder (ADHD) medication by children has led to growing concerns. In a previous study, we found that many of the teachers that were interviewed about ADHD spontaneously associated ADHD with medication. The present study is a qualitative reanalysis of what precisely these 30 primary school teachers had spontaneously said about medication in our previous semi‐structured interviews on ADHD. Almost all respondents had experience with pupils taking ADHD medication. The majority of spontaneously mentions medication as the treatment of ADHD. Attitudes towards ADHD medication use by pupils are mainly ambivalent, but more positive than negative effects of medication are reported. However, what teachers say about ADHD medication is often not based on sound information; their attitudes tend to be formed by personal experiences rather than founded on professional and scientific sources. We conclude from our analysis that it will be in the interest of reducing the number of children on ADHD medication that teachers have good access to verified and up‐to‐date information on ADHD and medication so that they are better supported in making evidence‐based pedagogical judgments.  相似文献   

A tribe hidden in plain sight: the ambiguous role of the instructor in a Caribbean university     

Erik Blair  Georgette Briggs 《Journal of Higher Education Policy & Management》2019,41(3):292-305

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