基于SI4432的高性能无线收发应用平台设计

针对无线产品设计中的产品可靠性、功耗、有效距离和成本问题,设计了一款基于SI4432和STM32F103的高性能无线收发应用平台。设计中实现了ACK双向通信、精简CSMA/CA发送机制,增强了系统的可靠性,减少了由于数据冲突造成的数据丢失现象,可满足不同的应用需求。实验表明,该平台简化了无线产品的设计,可应用于安防、无线抄表、无线传感器网络等系统。     

基于铱星的浮标远程监测与数据传输系统

针对海洋定点垂直剖面监测系统,设计并实现了一种基于铱星的浮标远程监测与数据传输系统。它主要由带有WINCE5.0操作系统的AT91SAM9G20主控板和铱星通信终端组成。为了降低系统功耗以达到长期无人值守监测要求,采用基于STC12C5A60S2的浮标状态监测板代替主控板监测浮标、锚灯和电池的状态。三者通过串口通信实现数据的传输。     

应用RFID技术实现医用植入装置的通信

典型的医用植入装置由体外部分和植入体两部分组成,二者之间通过射频载波传输能量和信息,这与广泛应用的射频识别技术非常相似。本文分析研究了它们在技术和应用层面的特点,提出了一种基于商用RFID技术及其器件实现的医用植入装置双向通信的设计,对于具体实现过程中的关键技术、必要的技术裁剪和技术扩展进行了较为详细的介绍。     

电力线通信自动抄表系统中的电能表捕获算法

针对目前电力公司按照面向人工抄表的习惯组织划分用户资料,致使理清配电台区与用电户的关系需要耗费很大的精力,现场排查困难等问题,提出了集中器自动获取表号的线性时间算法。该算法基于报文冲突和快速二分搜索技术,为抄表系统实现即插即用奠定了基础。     

一种基于系统总误码率的协同伙伴选择算法

提出了一种基于系统总误码率的协同伙伴选择算法。当系统总发送功率一定时,通过系统误码率公式,采用带CRC校验的DF协同通信的协同增益,来降低系统总的误码率。仿真表明,此算法有效地降低了系统总误码率,并且系统SNR越大,协同通信对系统数据传输的帮助越明显。     

电力线通信中动态子载波组分配

针对电力线通信自适应OFDM系统的限制条件,探讨在每OFDM符号内各RT用户要求的约束下,研究系统总功率地窖注水分配后多子载波上的速率自适应子载波分配模型,提出一种新的动态子载波组分配算法。在典型电力线信道环境下对其仿真,并与另外两种分配算法进行比较,结果表明,本文动态子载波组分配算法的复杂度大大减小,能满足多用户资源分配的多目标要求。     

A quantitative multimodal discourse analysis of teaching and learning in a web-conferencing environment – The efficacy of student-centred learning designs

This paper presents a quantitative approach to multimodal discourse analysis for analyzing online collaborative learning. The coding framework draws together the fields of systemic functional linguistics and Activity Theory to analyze interactions between collaborative-, content- and technology-related discourse. The approach is used to examine how the task subject matter, the activity design, and the choice of interface affected interaction and collaboration for a computing course conducted in a web-conferencing environment. The analysis revealed the critical impact of activity design on the amount and type of discourse that transpired. Student-centred designs resulted in over six times more student discourse as compared to teacher-centred designs and created a learning environment where students took greater ownership over the tasks and contributed more to the content-based discussion. The paper also incorporates a rationale for the approach to coding and a reflection on its efficacy for discourse analysis in technology-based learning environments.     

Understanding the ways in which design features of educational websites impact upon student learning outcomes in blended learning environments

This study investigated the effectiveness, in terms of the attainment of relevant learning outcomes, of the types of learning promoted by educational features commonly incorporated in course management systems. Twenty-one courses with significant use of the Internet, but with face-to-face teaching as the predominant instructional mode, were investigated. Five hundred and ninety-five students taking these 21 courses completed a questionnaire which gave feedback on the extent of use of and quality of implementation of internet features, as well as their perception of the attainment of outcomes relating to approaches to learning, communication skills and understanding of content. A confirmatory factor analysis of scales pertinent to information presentation and constructive dialogue features showed a very poor fit to the data, indicating that the two types of function did not act in concert. Structural equation modelling was used to test instructional models in presage–process–product format for ‘information’ and ‘dialogue’ features. The information one showed a marginal fit to the data, but the dialogue one a very good fit. This shows that using the Internet for presenting information in a blended environment does not seem to effectively help students achieve learning outcomes. Using features which promote constructive dialogue and interactive learning activities encourages a deep approach to learning, the development of communication skills and enhanced understanding of content.     

Cognitive,social and teaching presence in a virtual world and a text chat

Using a framework of cognitive, social, and teaching presence, the nature of learning experiences in a three-dimensional virtual world environment (Second Life) and a text-chat learning environment without visuals (TeachNet) were investigated. A mixed method of code frequencies, coherence graphs, interviews, and a survey was used. The results revealed that the TeachNet debates included more cognitive presence codes that indicate higher levels of cognitive processing than in SL debates. The teams were significantly different from each other in the collaboration style for developing arguments and in the ways to use utterances associated with cognitive, social, and teaching presences, and the groups’ collaboration style became more established with more experience with the tasks. The three critical factors–tool, tasks and group cohesion–that affect cognitive, teaching, and social presence are discussed.     

An investigation of student practices in asynchronous computer conferencing courses

This study investigated the online practices of students enrolled in graduate-level distance education courses. Using interviews and a questionnaire as data sources, the study sought to: (a) identify common practices that students adopt in asynchronous discussions, and (b) gain an understanding of why students adopt them. An analysis of the data suggests that many of the practices are coping mechanisms developed to help students more easily meet course participation requirements. Some of these are time saving strategies designed to reduce information overload (e.g., skimming messages rather than reading them carefully). Other strategies are designed to help students project an image of themselves as knowledgeable and collaborative course participants. It is argued that although these practices provide students with a level of efficiency in terms of meeting course requirements, they may inadvertently undermine learning.