IEEE 802.15.4a工业无线标准的研究与应用

对目前常用的几种工业无线标准进行了简单比较,并着重介绍了低速无线个人区域网络的新标准IEEE802．15．4a及其关键技术MDMA和CCS。新标准采用Chirp扩频物理层技术作为物理层标准,对工业环境中的干扰等具有很强的鲁棒性。以IEEE802．15．4a为基础,在现场总线测控系统中构建了无线子网段,实验表明系统处于稳定运行状态,且满足一般流程工业要求。该实例为工业无线网络接入到有线网络提供了一种解决方案,新标准在工业现场的短距离传输方面将会有广阔的应用前景。     

物联网与感知矿山专题讲座之三——感知矿山物联网的特征与关键技术

指出了感知矿山物联网是在煤矿综合自动化基础上的延伸和扩展应用,因而,感知矿山物联网在很大程度上有别于综合自动化系统;由于煤矿应用的特点,感知矿山物联网与目前地面物联网应用也有一些不同之处;介绍了感知矿山物联网的特征,它主要表现在多系统综合应用、感知层开放、应用平台开放和适合构建逻辑子系统等几个方面;分析了感知层、网络层、应用层的关键技术和跨层的公共技术;给出了感知矿山物联网的开放性要求和标准建设。该文对更好地理解感知矿山物联网的建设具有一定的参考价值。     

Online formative assessment in higher education: A review of the literature

As online and blended learning has become common place educational strategy in higher education, educators need to reconceptualise fundamental issues of teaching, learning and assessment in non traditional spaces. These issues include concepts such as validity and reliability of assessment in online environments in relation to serving the intended purposes, as well as understanding how formative assessment functions within online and blended learning. This article provides a systematic qualitative review of the research literature on online formative assessment in higher education. As an integrative narrative review, the method applied in this review entailed systematic searching, reviewing, and writing this review of the literature to bring together key themes and findings of research in this field. The authors applied qualitative thematic criteria in selecting and reviewing the available literature from which they focused on identifying and analyzing the core themes that are central to the concept of formative assessment with a key focus on application of formative assessment within blended and online contexts. Various techniques were identified for formative assessment by the individual, peers and the teacher, many of which were linked with online tools such as self-test quiz tools, discussion forums and e-portfolios. The benefits identified include improvement of learner engagement and centrality in the process as key actors, including the development of a learning community. The key findings are that effective online formative assessment can foster a learner and assessment centered focus through formative feedback and enhanced learner engagement with valuable learning experiences. Ongoing authentic assessment activities and interactive formative feedback were identified as important characteristics that can address threats to validity and reliability within the context of online formative assessment.     

MEMS AC voltage reference for miniaturized instrumentation and metrology

This work explores MEMS (Micro-Electro-Mechanical Systems) potentialities to fabricate AC voltage references through mechanical-electrical transduction that could be used for high precision electrical metrology and for applications in miniaturized instrumentation. AC voltage reference ranging from 5 V to 90 V have been designed and fabricated using the same Epitaxial Silicon On Insulator (SOI) surface micromachining process allowing an accurate control of both dimensions and material properties. The measured MEMS AC voltage reference values have been found in a good agreement with CoventorWare calculations. These tests structures have also been used to develop the read-out electronics to drive the MEMS.     

基于模糊层次分析法的计算机网络安全评价

根据计算机网络的特点及网络安全涉及的因素,建立计算机网络安全评价的层次结构模型,运用基于三角模糊数的模糊层次分析法实现对网络安全的综合量化评价。实例的计算结果表明模糊层次分析法适用于定性判断的量化综合,它为计算机网络安全评价提供了一种探索性方法。     

一种使用分量组合的彩色图像压缩方法

为了适应图像的存储和传输,需要对图像进行压缩以减少数据量。对于彩色图像而言,其色彩模式和数据组合直接影响了压缩效率,压缩时通常采用每个分量单独压缩后再统一编码,未考虑分量之间的组合关系。根据彩色图像的数据结构将图像的RGB分量排列组合成新的灰度图像,将其中一个分量作为基准实行粗细分层操作,汇同该分量与其他两个分量的差值图像分别按JPEG压缩标准进行压缩编码。实验表明,该算法得到的压缩图像在与JPEG同等质量的条件下,数据量要小于JPEG压缩的数据量,耗时短,同时可为快速的彩色图像搜索和预览提供技术参考。     

Measuring individual learning performance in group work from a knowledge integration perspective

Evaluation is an important part of the teaching-learning process, and it becomes more difficult when individuals are developing a joint project and individual marks have to be assigned to the group members. Different strategies can be used to perform this task. In this work, an approach that combines the global group results and the individual performance is presented. This approach makes use of a semantic framework to rank the individual participation of each group member and to compare their results with those they should have obtained to achieve the final mark. An experiment performed in real settings is also reported in this paper.     

EPA功能安全协议的研究与实现

现场总线在通信传输过程中,会受到各种通信故障的影响,而现场总线与功能安全的结合可降低这种影响。该文描述EPA功能安全通信模型,针对通信传输过程中可能出现的通信错误,采用时间戳、序列号、CRC校验等功能安全通信技术。给出EPA功能安全协议层的报文结构,阐述功能安全协议层的具体实现过程。     

基于OPNET的AdHoc网络建模与仿真

利用OPNET软件自带的支持IEEE802．11标准的节点模型构建AdHoc网络模型。合理配置输入输出接口的参数,使网络达到最佳性能,并对网络的性能进行比较分析。仿真结果表明,网络参数之间存在关联性,网络最优化参数具有唯一性,通过网络负载与标准负载的比较,可选择出网络性能最优化状态。     

一类标准矩形网络节点间最短路径的求解方法

针对常见的交通道路最短路径问题, 提出标准矩形网络的概念, 分析其节点间最短路径的性质, 并在此基础上给出一种新颖的最短路径求解算法. 该算法利用标准矩形网络的几何性质, 简化了搜索方向和步长的判断, 同时指出常见的交通道路网络一般均可以整体或部分化为标准矩形网络. 与常见的求取最短路径的Dijkstra、Floyd、ACO、A* 等算法进行仿真实验比较, 实验结果表明, 对于大规模标准矩形道路网络, 所提出算法具有更好的寻优精度、稳定性和寻优速度.