国内外流媒体点播系统服务模式的性能分析

在IPTV系统中,流媒体点播系统始终是这个系统得以实现的关键,也是系统能否高效工作的重要因素。本文在查阅现有与IPTV系统以及流媒体点播系统相关的国内外文献资料的基础上,对其进行了归纳和整理,并对其现有经典解决方案的优缺点进行了比较。     

Video classification for video quality prediction

INTRODUCTION Video content will be the main contributor to the future traffic in multimedia applications. Camcorders, digital cameras and lately mobile phones with video capturing capabilities have resulted in a wide spreading of multimedia to the masses. Quality of the captured/rendered videos is likely to be the major determining factor in the success of the new multi- media applications as well as product differentiation. Video processing chain includes video capturing, video pre-proce…     

Video-Based Analyses of Motivation and Interaction in Science Classrooms

An analytical framework for examining students’ motivation was developed and used for analyses of video excerpts from science classrooms. The framework was developed in an iterative process involving theories on motivation and video excerpts from a ‘motivational event’ where students worked in groups. Subsequently, the framework was used for an analysis of students’ motivation in the whole class situation. A cross-case analysis was carried out illustrating characteristics of students’ motivation dependent on the context. This research showed that students’ motivation to learn science is stimulated by a range of different factors, with autonomy, relatedness and belonging apparently being the main sources of motivation. The teacher’s combined use of questions, uptake and high level evaluation was very important for students’ learning processes and motivation, especially students’ self-efficacy. By coding and analysing video excerpts from science classrooms, we were able to demonstrate that the analytical framework helped us gain new insights into the effect of teachers’ communication and other elements on students’ motivation.     

edTPA,videotape, and occupational identity: a study of pre-service teachers

In conducting this study, I sought to contribute to the scholarly discourse of understanding how North American elementary pre-service teachers experienced evaluation via teacher performance assessments. Through extensive interviews and thematic data analysis, this study generally supported the contention that the process of completing edTPA deepened student teachers’ understanding of their educational experience in a number of domains, which in turn suggested a broader awareness and appreciation of the complexities of learning to teach. Data from a larger study indicated that the identified ‘realms of understanding’ fell into four areas of insight related to education: Understanding Children, Understanding Instructional Strategies, Understanding via Collective Learning, and Understanding Self as Teacher. For the purposes of this paper, the identified area of insight ‘Understanding Self as Teacher’ is explored. These findings lead to several practical ways in which teacher education might be improved, particularly in the area of utilization of video in teacher education programs.     

视频技术在学校拉丁舞教学中的应用研究

运用文献资料法、访谈法、教学实验法,本研究以益阳市起点健身会所拉丁舞培训班的学生为实验对象,对视频技术在拉丁舞教学过程中进行了单因素试验研究。结果表明：视频技术可充分调动学生学习的积极性,提高记忆效果,从而提高课堂教学效率,增大课容量,实现资源的高度共享。     

电磁波在地层中的传播窗口与波形

本文提出不同电参数地层中电磁波传输频带宽度和有相应频谱的新的电磁脉冲波形。     

A channel distortion model for video over lossy packet networks

Error-resilient video communication over lossy packet networks is often designed and operated based on models for the effect of losses on the reconstructed video quality. This paper analyzes the channel distortion for video over lossy packet networks and proposes a new model that, compared to previous models, more accurately estimates the expected mean-squared error distortion for different packet loss patterns by accounting for inter-frame error propagation and the correlation between error frames. The accuracy of the proposed model is validated with JVT/H.264 encoded standard test sequences and previous frame concealment, where the proposed model provides an obvious accuracy gain over previous models.     

Electromyographic analysis of exercise resulting in symptoms of muscle damage

Surface electromyographic (EMG) signals were recorded from the hamstring muscles during six sets of submaximal isokinetic (2.6 rad s -1 ) eccentric (11 men, 9 women) or concentric (6 men, 4 women) contractions. The EMG per unit torque increased during eccentric (P < 0.01) but not during concentric exercise. Similarly, the median frequency increased during eccentric (P < 0.01) but not during concentric exercise. The EMG per unit torque was lower for submaximal eccentric than maximum isometric contractions (P < 0.001), and lower for submaximal concentric than maximum isometric contractions (P < 0.01). The EMG per unit torque was lower for eccentric than concentric contractions (P < 0.05). The median frequency was higher for submaximal eccentric than maximum isometric contractions (P < 0.001); it was similar, however, between submaximal concentric and maximum isometric contractions (P = 0.07). Eccentric exercise resulted in significant isometric strength loss (P < 0.01), pain (P < 0.01) and muscle tenderness (P < 0.05). The greatest strength loss was seen 1 day after eccentric exercise, while the most severe pain and muscle tenderness occurred 2 days after eccentric exercise. A lower EMG per unit torque is consistent with the selective recruitment of a small number of motor units during eccentric exercise. A higher median frequency during eccentric contractions may be explained by selective recruitment of fast-twitch motor units. The present results are consistent with the theory that muscle damage results from excessive stress on a small number of active fibres during eccentric contractions.     

基于FLEX和J2EE多媒体远程答疑系统设计与实现

远程答疑系统是现代远程教育系统中重要组成部分,构建了一种面向用户,以用户为中心,集同步答疑、异步答疑和即时消息提醒的新型远程答疑系统。基于FLEX和J2EE多层架构体系的系统实现,有效提高了系统的可扩展性、可维护性、可重用性和用户体验。并将知识管理思想融入系统设计中,有助于提高教学质量,具有较强的可操作性。     

Effects of different video- or text-based reflection stimuli on pre-service teachers’ emotions,immersion, cognitive load and knowledge-based reasoning

To reflect on ones own or other teachers teaching practices as well as on different reflection stimuli (e.g. videos or texts) can evoke different emotions and entail varying degrees of cognitive load and knowledge-based reasoning for pre-service teachers. Participants in this study were distributed to four groups (“memory”; "video+memory”; “video other”, and “text other”) and reflected online on classroom management facets. Pre-service teachers in the “video+memory” group reported significantly more immersion and enjoyment while reflecting than the other three groups. All groups showed a moderate level of germane load and there were no differences between the groups. Participants in the video+memory and memory group showed higher levels of knowledge-based reasoning than those who reflected on other teachers’ classroom practice. Enjoyment was a significant positive predictor of both immersion and germane load, whereas boredom was a negative predictor. Implications for future research and reflection processes during teacher education are discussed.