An investigation on the unwillingness of nodes to participate in mobile delay tolerant network routing     

Jingwei Miao  Omar Hasan  Sonia Ben Mokhtar  Lionel Brunie  Kangbin Yim 《International Journal of Information Management》2013

Message routing in mobile delay tolerant networks inherently relies on the cooperation between nodes. In most existing routing protocols, the participation of nodes in the routing process is taken as granted. However, in reality, nodes can be unwilling to participate. We first show in this paper the impact of the unwillingness of nodes to participate in existing routing protocols through a set of experiments. Results show that in the presence of even a small proportion of nodes that do not forward messages, performance is heavily degraded. We then analyze two major reasons of the unwillingness of nodes to participate, i.e., their rational behavior (also called selfishness) and their wariness of disclosing private mobility information.  相似文献   

Preference and resistance to change in concurrent variable-interval schedules     

Matthew C. Bell  Ben A. Williams 《Learning & behavior》2002,30(1):34-42

Pigeons were trained on a multiple schedule in which separate concurrent schedules were presented in the two components of the schedule. During one component, concurrent variable-interval 40-sec variableinterval 80-sec schedules operated. In the second component, concurrent variable-interval 40-sec variableinterval 20-sec schedules operated. After stable baseline performance was obtained in both components, extinction probe choice tests were presented to assess preference between the variable-interval 40-sec schedules from the two components. The variable-interval 40-sec schedule paired with the variableinterval 80-sec schedule was preferred over the variable-interval 40-sec schedule paired with the variableinterval 20-sec schedule. The subjects were also exposed to several resistance-to-change manipulations: (1) prefeeding prior to the experimental session, (2) a free-food schedule added to timeout periods separating components, and (3) extinction. The results indicated that preference and resistance to change do not necessarily covary.  相似文献   

Peer assessment of oral presentations: effects of student gender,university affiliation and participation in the development of assessment criteria     

A. Mark Langan  C. Philip Wheater  Emma M. Shaw  Ben J. Haines  W. Rod Cullen  Jennefer C. Boyle 《Assessment & Evaluation in Higher Education》2005,30(1):21-34

Peer assessment provides a useful mechanism to develop many positive qualities in students studying in higher education (HE). Potential influences on peer‐awarded marks include student qualities such as gender, HE background (e.g. university affiliation) and participation in the development of the assessment criteria. Many studies that have investigated peer assessment have placed great emphasis on marks from a single tutor, or very few tutors, from a single university. This study examined grades awarded by 11 tutors (affiliated with four universities) to oral presentations delivered on a residential field course by second‐year undergraduate students from two universities studying environmental or biological disciplines. Student assessors awarded marks of fairly high precision (correlating strongly with tutor grades) but averaged 5% higher than their tutors (i.e. of only moderate accuracy). Marginally higher marks (circa 1.6%) were awarded by student assessors to speakers studying at the same university. Gender influences were detected as males tended to grade other male speakers very slightly more highly than female speakers. Marks from females were unaffected by speaker gender. Students who participated in the development of the assessment criteria did not achieve higher grades for their presentations. However, when these ‘participants’ were assessing, they awarded lower marks than their peers (i.e. closer to, but not as low as, those awarded by tutors). Lower marks were also awarded during the middle of sessions, possibly resulting from factors associated with motivation and attention of speakers and markers. Overall, the potential biases in marking by naive assessors examined in this study may influence the validity of marks generated by peer assessment schemes, but the experience of this type of assessment had positive effects on those involved.  相似文献   

高职产学研合作教育模式的探索与实践   总被引：1，自引：0，他引：1  

李本初  孔新舟 《孝感职业技术学院学报》2005,8(4):5-9

文章介绍了湖北职业技术学院产学研合作教育的几种模式，着重剖析了“围绕专业办产业，办好产业促专业”的专业实体化产学研合作教育模式。  相似文献   

Affordances of teacher professional learning in secondary schools     

Wilfried Admiraal  Joke Kruiter  Ditte Lockhorst  Wouter Schenke  Henk Sligte  Ben Smit 《Studies in Continuing Education》2016,38(3):281-298

It is commonly understood that teachers in secondary school should develop throughout their career in order to stay as an essential factor in student learning. Schools can offer opportunities to link teachers’ professional learning to their school practice with a positive impact on teachers’ motivation to learn and the effectiveness of their learning. In this field study, teachers, school leaders, policy-makers, educational consultants and educational scholars were asked for their perceptions of conditions for teacher learning in school and of interventions in school to enhance teacher professional learning. These conditions and interventions were understood as affordances in schools that enable and support teacher professional learning. The main affordance in school these stakeholders mentioned was an open, but critical way in which teachers share their practices, collaborate and reflect upon their teaching practice. Collaborative practices seem to stimulate many interventions of teacher professional learning in school. Two implications of this finding are discussed. First, we suggest that the maximum teaching time should be reduced, team teaching should be more implemented or classes should be scheduled in such a way that teachers can meet. Second, distributed leadership approaches match with our findings about the role of school leaders in teacher professional learning.  相似文献   

Comparing Examination Standards: is a purely statistical approach adequate?     

Ben E. Jones 《Assessment in Education: Principles, Policy & Practice》1997,4(2):249-264

There has recently been a renewed interest in three types of comparability of standards in the United Kingdom [1] public examination system: between years, between subjects and between the six examination boards. Whilst comparisons of raw grade distributions are now generally acknowledged to be invalid indicators of relative standards, comparisons are regularly made for this purpose between adjusted grade distributions. Such adjustments are typically the result of statistically controlling for some of the relevant variables. The dangers of such an approach are that only easily quantifiable variables are used in the adjustment and that any residual differences between distributions will automatically be attributed to difference in standard. Using candidate‐level data from four 1994 Advanced level (A level) [2] mathematics examinations (designed for 18‐year‐old students), and paying particular attention to the Schools’ Mathematics Project (SMP) 16‐19 [3] syllabus, the paper reports on two such analyses. It then discusses some reasons why attributing differences in the adjusted grade distribution to differences in standard could be invalid. Whilst the study focuses on four A level mathematics syllabuses, the same principles apply irrespective of the context in which statistical comparisons of examination results are made. The methodologies, their shortcomings and the pleas for caution are not, therefore, specific to this study, this type of comparison or this examination system.  相似文献   

复配型特稠原油降粘剂研究   总被引：3，自引：0，他引：3  

吴本芳  张敏涛 《洛阳师范学院学报》2003,22(2):45-49

文中优化了稠油、特稠油复配型降粘剂的组成配方 .实验表明 ,优化的复配型降粘剂较其单组分的降粘性能明显增强而非优化的复配型降粘剂甚至不及其某些单组分的降粘性能 ,说明复配型降粘剂组分间存在着配伍性和协同效应 .  相似文献   

VIEWPOINTS     

Ben Williamson  Dr. Yousef H. Al‐Maini  Saima Rana 《Learning, Media and Technology》2008,33(1):71-79

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A mixed-methods analysis of achievement disparities in Guatemalan primary schools     

Ben Meade 《International Journal of Educational Development》2012

Although most Guatemalan rural students currently have access to primary school, there are large differences in the levels of learning that take place among different populations and in different contexts. This paper uses multiple data and methods to examine the interrelated factors underlying achievement disparities in Guatemalan primary schools. The research suggests that strong levels of disadvantage connected to attending schools in poor rural communities are connected to systematic differences in the way school quality is supported in different contexts. There are inadequate resources, capacity, and authority to monitor and enforce fundamental educational issues, especially in marginal communities.  相似文献   

Report on a Boston University Conference December 7–8, 2012 on How Can the History and Philosophy of Science Contribute to Contemporary US Science Teaching?     

Peter Garik  Yann Benétreau-Dupin 《Science & Education》2014,23(9):1853-1873

This is an editorial report on the outcomes of an international conference sponsored by a grant from the National Science Foundation (NSF) (REESE-1205273) to the School of Education at Boston University and the Center for Philosophy and History of Science at Boston University for a conference titled: How Can the History and Philosophy of Science Contribute to Contemporary US Science Teaching? The presentations of the conference speakers and the reports of the working groups are reviewed. Multiple themes emerged for K-16 education from the perspective of the history and philosophy of science. Key ones were that: students need to understand that central to science is argumentation, criticism, and analysis; students should be educated to appreciate science as part of our culture; students should be educated to be science literate; what is meant by the nature of science as discussed in much of the science education literature must be broadened to accommodate a science literacy that includes preparation for socioscientific issues; teaching for science literacy requires the development of new assessment tools; and, it is difficult to change what science teachers do in their classrooms. The principal conclusions drawn by the editors are that: to prepare students to be citizens in a participatory democracy, science education must be embedded in a liberal arts education; science teachers alone cannot be expected to prepare students to be scientifically literate; and, to educate students for scientific literacy will require a new curriculum that is coordinated across the humanities, history/social studies, and science classrooms.  相似文献