Analyzing imbalance among homogeneous index servers in a web search system

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.     

临床医学期刊在健康科普中的作用

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。     

Getting sloshed in outer space

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.     

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

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.     

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

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.     

Agency and Structure: Principals’ Ability to Bring about Sustainable Improvement in Underperforming Schools in South Africa

This article reports on a study of which the purpose was to understand the role of principals in changing underperforming schools towards sustainable improvement in one circuit area of North-West, South Africa. School principals play a crucial role in guiding schools towards sustainable improvement by shaping a vision of academic success for all learners. Managing teaching is one of the core modules in South Africa’s new national qualification for school principals, and that being the case, principals should play a central role in effecting the educational transformation of all learners. The quality of principals’ leadership is the key factor driving the transformational turnaround and improvement required in schools. They perform a highly complex and dynamic role in enhancing and sustaining school improvement. It was the goal of this qualitative study to explore cultural, structural, and agential challenges faced by principals in their effort to provide for change and improvement in their schools. Six schools were purposefully selected to participate in the study and semi-structured interviews were used to gather data from the principals. The study established that paying attention to cultural, structural and agential factors in schools increases their ability to sustain learner improvement.     

Refining Students’ Explanations of an Unfamiliar Physical Phenomenon-Microscopic Friction

Research in Science Education - The first phase of this multiphase study involves modeling of college students’ thinking of friction at the microscopic level. Diagnostic interviews were...     

If we build it,will they come? The effect of new athletic facilities on recruiting rankings for power five football and men's basketball programs

College athletics is currently in the midst of a building boom in which universities are competing with each other to reach an always-increasing standard of lavish athletic facilities. While these facilities are costing in the tens or hundreds of millions of dollars, little research is examining the return on investment for athletic programs. The purpose of this study was to examine the effect of new athletic facilities on recruiting rankings for Power Five football and men's basketball programs. Data was collected on athletic facilities newly constructed or renovated from 2005 through 2015 at Power Five NCAA Division I programs. Using LSDV fixed effects regression models, results found a lack of significant improvement within football and basketball recruiting rankings following the completion of new athletic facilities, but some significance in the two years before the project was completed. Significant control variables also highlighted the effects that coaching changes can have on recruiting.     

Variable uses of alternative conceptions: A case study in current electricity

Recent research related to the design of science instruction is often based on conceptual change theory and requires assessments of what knowledge students bring to instruction. The premise of this study was that it is also important to understand when and how students apply their knowledge. Fourteen elementary and middle school teachers in an in-service physics course were asked to solve qualitatively a variety of series and parallel circuit problems and explicate their reasoning. These teachers were found to share a common core of strongly held propositions that formed a coherent, but incorrect and contradictory model of sequential current flow. Yet their predictions about the circuits were highly variable. The variability in predictions resulted from differences and contradictions in additional “protective belts” of propositions, and differences in the ways in which the teachers changed and selectively applied those propositions to different problems. Understanding the variations in not only what teachers knew, but also the differences in when and how they applied their knowledge complicated the task of designing instruction. However, it also made possible the design of more precise instruction in which the teachers were required to recognize, confront, and reconcile specific inconsistencies in their beliefs.