A Review of Methods for Missing Data

This paper reviews methods for handling missing data in a research study. Many researchers use ad hoc methods such as complete case analysis, available case analysis (pairwise deletion), or single-value imputation. Though these methods are easily implemented, they require assumptions about the data that rarely hold in practice. Model-based methods such as maximum likelihood using the EM algorithm and multiple imputation hold more promise for dealing with difficulties caused by missing data. While model-based methods require specialized computer programs and assumptions about the nature of the missing data, these methods are appropriate for a wider range of situations than the more commonly used ad hoc methods. The paper provides an illustration of the methods using data from an intervention study designed to increase students’ ability to control their asthma symptoms.     

More than smile sheets: Rasch analysis of training reactions in a medical center

Reaction questionnaires administered at the conclusion of a training program are a common method of evaluation. Because such questionnaires are often constructed and analyzed in an ad hoc manner, their usefulness is often difficult to gauge. However, if properly constructed and analyzed, such instruments can help to make clear the strengths and weaknesses of programs. This article presents a framework for questionnaire development and analysis to ensure that such questionnaires are psychometrically sound and useful for decision making. The data used for this research were from over 5,000 questionnaires completed by individuals at the conclusion of educational programs. The Rasch model was used to evaluate the data. Results suggest that the posttraining questionnaire is a valid and reliable indicator of program quality. In addition, the Rasch analysis provided empirically based methods for diagnosing needed improvements to assessment instruments.     

Teachers’ Critical Evaluations of Dynamic Geometry Software Implementation in 1:1 Classrooms

Although the use of dynamic software in high school mathematics in the United States has emerged as a research topic, little research has been conducted on how teachers integrate new software in relation to at-home technology networks. Interviews with eight mathematics teachers from four North Carolina counties participating in 1:1 laptop initiatives are analyzed to trace similar decision-making themes, including Internet access, laptop availability, software use, and teacher training. This article outlines how current technologies in classrooms were critically examined by the teachers and how network connectivity impressions affected hardware and software use.     

大规模ad hoc网络下的高效的主动RSA方案

A previous proactive RSA scheme for large-scale ad hoc network has been shown to be faulty. In this paper, we present a new proactive RSA scheme for ad hoc networks, which includes four protocols： the initial key distribution protocol, the share refreshing protocol, the share distribution protocol, and the signature generation protocol. This scheme has two advantages： the building blocks are secure, and the system is efficient.     

基于Google Earth的车辆防碰撞虚拟仿真系统

车载自组织网络（VANET）是近年来智能交通领域的研究热点之一。在VANET网络中,智能车辆通过交互共享道路环境信息,可提高交通安全水平。在现实环境中进行大规模的车载自组织网络实验,在经济性和可行性上都具有较大困难。在SUMO交通仿真基础上开发出车辆防碰撞虚拟仿真系统,通过Google Street Map获取真实道路环境（如路网、楼宇、植被等）,并结合 GEMV2软件对智能车辆在真实道路环境下的无线通讯链路质量进行评估,实现了虚拟行车交通流与车辆间无线通讯质量评估两位一体的模拟仿真,增强了车辆对周围道路交通环境的综合感知能力。     

Bringing democratic governance into practice: policy enactments responding to neoliberal governance in Spanish public schools*

This article explores different ways in which public primary schools sustain democratic governance structures created beyond those mandated by law in Spain. These new institutional designs, while not opposed to policy text requirements of having a governing body with representatives of parents, teachers and public administration, are being carried out against the grain of the hegemonic neoliberal managerial approach. The objective was to observe the different ways that some schools apply other institutional paths to the current governing bodies by aiming at widening decision-making not only to legal representatives but to all agents. Data come from focus groups, in-depth interviews and observations carried out in four public schools during fieldwork lasting two academic years. The findings show that while some schools are broadening current legal governing bodies, others generate ad hoc bodies transforming legal ones into new institutional arrangements.     

Cost management based security framework in mobile ad hoc networks

INTRODUCTION Mobile ad hoc networks are under active research focused on issues such as routing, security (Venkatra- man and Agrawal, 2003) and data management (Fan and Zhang, 2004). People have proposes many kinds of security mechanisms such as SAR (Yi et al., 2002), SRP (Papadimitratos and Haas, 2002), ARAN (San- zgiri et al., 2002), ARIADNE (Hu et al., 2005) and SEAD (Hu et al., 2002) for networks. The resource consumptions of security mechanisms are always large in mobile …     

The effect of electronic performance support systems on self-regulated learning skills

Electronic performance support systems (EPSSs) are the software programs commonly used in commercial environments since the early 1990s. These software programs are generally called performance-based systems and focus on the complete job rather than providing individual development. For that reason, the usage of these systems in learning environments has not been sufficiently investigated. In this empirical study, availability of using EPSS software for learning processes was investigated in order to contribute to the literature. An EPSS software was developed for undergraduate students to use in programming language courses and the effects of the software on students' self-regulation based learning skills were investigated. During the treatment process, while the experimental group was supported with EPSS, traditional teaching continued in the control group. The results of the study showed that there was no statistically significant difference between the groups in terms of motivational beliefs; however, there were significant differences in terms of cognitive, metacognitive, and resource management strategies.     

Applications of Educational Measurement: I s Optimum Optimal?

What would you do if you were asked to design an “optimal” school testing program, but had doubts about the criteria to apply? What strategies might help us make more use of performance assessment and computer-adaptive testing in district-level testing programs? Can an NCME President be whimsical when delivering her presidential address?     

Taking educational games seriously: using the RETAIN model to design endogenous fantasy into standalone educational games

We are witnessing a mad rush to pour educational content into games in an ad hoc manner in hopes that player/learners are motivated simply because the content is housed inside a game. A failure to base educational game design on well-established learning and instructional theories increases the risk of the game failing to meet its intended educational goals, and yielding students who are entertained but who have not acquired any academic skills or knowledge. Our review of standalone educational games has shown that they are not always based on sound educational principles and theories. We contend that, if academic learning is to take place, a new design paradigm must be developed. This article discusses the RETAIN design and evaluation model for educational games that was developed to aide in the evaluation of how well academic content is endogenously immersed and embedded within the game’s fantasy and story context, promoters transfer of knowledge, and encourages repetitive usage to that content becomes available for use in an automatic way.     

The role of analogical thinking in designing tasks for mathematics teacher education: An example of a pedagogical ad hoc task

This article discusses the design of tasks for teacher education. It focuses on tasks that are used in a university course for pre-service secondary school mathematics teachers. Special attention is given to tasks that use analogical thinking in their construction or implementation. These tasks are categorized by type of teacher education goal and analyzed with respect to the use of analogical thinking. Short examples are presented for three of the goal categories, while an elaborated example is given for the fourth one. The detailed example describes the goals and design of a task sequence following an emergent pedagogical need. Using the ad hoc constructed task-sequence the teacher educator avoids “telling” while demonstrating an alternative instructional approach, and seizing the opportunity to bring up additional pedagogical issues.     

无线网络适应动态拓扑变化的备份路径算法

针对Ad Hoc网络路由问题,本文将备份路径加入到AODV（ad hoc on-demand distance-vector）路由协议中,使用原AODV中的RREP（Route Reply）控制信号和Data包来建立网状的备份路径,建立一种适应动态拓扑网络的路由协议,从而改善网络性能.采用面向对象的建模技术在OMNET＋＋软件平台上进行了仿真,结果证明该方法提高了网络的QoS,为Ad-hoc网络路由协议的发展提供了一个新思路.     

移动自组织网络中QoS路由协议研究

随着移动自组织网络(MANET)的应用领域日益扩大,要求它必须提供一定的服务质量(QoS)保证,而QoS路由协议是MANET支持QoS的一个关键理论和技术,也是目前的一个研究热点。本文对当前自组织网络的QoS主要路由协议进行了详细的分析与研究,并从路由机制、单向链路的支持、多播功能、QoS参数选择以及节能几个方面进行了比较和分析;最后指出了今后的研究方向。     

Market segmentation for improved distance education program planning

Distance education planners face two basic, yet difficult decisions: which students should be targeted and which programs should be offered? This paper reports the process and results of the planning committee of a consortium of engineering schools in the United States that was tasked with these very decisions. A market research study measured the program preferences of potential students. Three program characteristics (course type, delivery method, and time availability) were examined. The results show there is no ‘average’ student and no single program will satisfy all the needs of the student population. Rather, the committee must choose one or more segments based on the program preferences of the students and the resources required to provide the programs.     

基于LoRa的雷场探测系统动态自组网研究

为了满足战后扫雷的实际需求,针对现有雷场探测技术的不足,设计基于多源信息同步探测、具有雷场扫描探测和疑似目标探测两种工作模式的雷场探测系统。系统由一个设置在安全位置的探测控制主机和多个具有飞行、探测功能的探测分机组成。采用基于LoRa的无线通信技术,进行LoRa无线通信模块硬件电路设计与动态自组网方式设计,并以Mesh网络拓扑实现自组网。最后,在雷场探测模拟试验场环境下对系统进行测试,在不同通信距离条件下对系统传输功率及丢包率的测试结果表明,该系统能满足雷场探测过程中的多任务处理要求。     

Article Productivity Among the Faculty of Criminology and Criminal Justice Doctoral Programs, 2010–2014

One important dimension of the quality of a graduate program is the quality of its faculty. Previous assessments of the publication productivity of criminology and criminal justice (CCJ) faculties have been needlessly incomplete and narrow, reflecting publications only in a small number of CCJ journals. Assessments covering only CCJ journals fail to reflect the multi-disciplinary nature of CCJ and bias results against programs whose most productive scholars publish in non-CCJ journals. The present research covers the full array of major journals in which CCJ-related research appears, by searching for articles using the Web of Science and ProQuest databases. This article is an update of two previous evaluations, covering 2000–2004 and 2005–2009. Based on article counts, the most productive faculties are those of Sam Houston State University, Florida State University and the University of Cincinnati. The article also summarizes changes in rankings of CCJ programs from 2000 through 2014.     

Ad hoc网络中基于状态检测的入侵防护策略

在Ad hoc网络中入侵检测问题已经成为研究热点,本文首先对存在的安全隐患进行了分析描述,然后从会话过滤的角度出发,结合Ad hoc网络自身特点的基础上,提出了一种基于状态检测的入侵防护策略,用于提高整个网络的安全性.     

周恩来与中央特科

大革命失败后,中共中央秘密迁到上海,在白色恐怖中领导全党进行英勇斗争。在恶劣的环境里,为了保证党中央的安全及工作的顺利开展,成立了由周恩来直接领导的中央特科。在周恩来的领导下,特科工作取得了巨大成绩,周恩来也逐渐形成了他的关于秘密工作的一些原则和方法,这些原则和方法对以后我党秘密工作起了巨大的推动作用。