Distributed Context Retrieval and Consistency Control in Pervasive Computing

The challenge of saturating all phases of pervasive service provision with context-aware functionality lies in coping with the complexity of maintaining, retrieving and distributing context information. To efficiently represent and query context information a sophisticated modelling scheme should exist. To distribute and synchronise context knowledge in various context repositories across a multitude of administrative domains, streamlined mechanisms are needed. This paper elaborates on an innovative context management framework that has been designed to cope with free-text and location based context retrieval and efficient context consistency control. The proposed framework has been incorporated in a multi-functional pervasive services platform, while most of the mechanisms it employs have been empirically evaluated.     

What are users’ intentions towards real money trading in massively multiplayer online games?

This study investigates user behaviour in massively multiplayer online games from the perspective of their intentions to engage in real money trading. Players who engage in real money trading purchase resources instead of spending time to acquire them in the game. This behaviour influences not just their own gaming experience, but those of other players as well as the operator??s revenues. We present an online survey which targets the players of World of Warcraft. Players?? relationships with real money trading are investigated using insights from behavioural economics. We propose a model which includes a set of behavioural determinants grounded in empirical research on online games. The study??s findings indicate that a player??s social status and the disinhibiting effects of online play are positive influences on players?? intentions to engage in real money trading, while perceived fairness, anticipated regret and uncertainty about the seller??s behaviour are negative influences. Interestingly, neither the perceived enjoyment nor the potential punishments influence intentions.     

Boys’ and girls’ ICT beliefs: Do teachers matter?

This exploratory study took place in the context of middle school information science in Greece, to examine possible relations between boys’ and girls’: value and efficacy beliefs about computers and information science; perceived parental support; perceived teacher expectations; and perceptions of the nature of information science instruction. The participants of the study were 301 (135 male and 166 female) students who responded to a self-report questionnaire. Regression analysis showed that perceived teacher expectations were positively associated with students’ ability beliefs, perceptions of learning activities as creative and personally meaningful was a significant predictor of students’ interest in computing, and perceived parental support was related to both value and efficacy beliefs. Unlike previous research, the findings of this study did not support the conclusion that boys have more positive ICT self-efficacy and value beliefs than girls. They indicated however, that boys’ and girls’ beliefs are differentially affected by parents, teachers, and school IS instruction.     

Dropout prediction in e-learning courses through the combination of machine learning techniques

In this paper, a dropout prediction method for e-learning courses, based on three popular machine learning techniques and detailed student data, is proposed. The machine learning techniques used are feed-forward neural networks, support vector machines and probabilistic ensemble simplified fuzzy ARTMAP. Since a single technique may fail to accurately classify some e-learning students, whereas another may succeed, three decision schemes, which combine in different ways the results of the three machine learning techniques, were also tested. The method was examined in terms of overall accuracy, sensitivity and precision and its results were found to be significantly better than those reported in relevant literature.     

Characteristics of a rectangular waveguide containing a magnetized cylindrical ferrite post

A rigorous formulation of the scattering by a magnetized ferrite in a rectangular waveguide is presented. The EM field depends on the dimension, the frequency and the internal static magnetic field of the ferrite post. For some special values of the above quantitites the reflection or the transmission coefficient becomes equal to zero. These values give a family of filters and the results which follow explain their characteristics.     

采用水基前驱溶液喷墨印刷制备光催化活性TiO2薄膜

摘译 近年来,作为一种高能量带隙半导体,二氧化钛(TiO2)由于在紫外光照射下具有良好的光催化活性,已引起科研人员的广泛关注.由于TiO2无色透明,具有广泛的应用前景,如薄的TiO2涂层可用于创建自清洁、防雾、超亲水表面.同时,也能用于太阳能电池等光电子行业. 化学溶液沉积法因具有相对简单的大面积生产工艺,且较低的制膜成本和高可用性,成为TiO2薄膜制备常用的方法之一.针对另一种TiO2制备方法,即溶胶凝胶法,大量研究文献主要关注乙醇的水解控制.然而,工业需求鼓励开发水基前驱设计.其难度在于钛醇盐与水的高反应性.在有机介质中,加入少量的水往往导致水解.因此,需要采用络合剂作为稳定剂,阻止纯水中的水解反应和避免由此产生的产物沉淀.     

Synthesis of ferronickel slag-based geopolymers

This paper deals with the synthesis of geopolymers utilizing ferronickel slag as raw material. The utilized slag is produced in the Greek plant LARCO during the pyrometallurgical treatment of laterites for the production of ferronickel, specifically at the step of the reductive smelting in electric arc furnaces. The performed work includes the optimization of the slag-based geopolymeric system through the study of the effect of the synthesis parameters on the mechanical properties of the produced materials. The structure of geopolymers was determined with X-ray diffractometry (XRD), Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The obtained results showed that the ferronickel slag is an excellent raw material for the production of inorganic polymers using the geopolymerization technology. The materials produced under the optimum synthesis conditions were compact and rigid and presented high compressive strength (118 MPa), as well as extremely low water absorption (0.7–0.8%).     

Consumer behaviour in the mobile telecommunications’ market: The individual’s adoption decision of innovative services

Research in the adoption of innovative services in mobile communications markets has not offered a comprehensive explanation of how the individual makes a choice. This article proposes a theoretical framework for the analysis of the adoption decision of innovative mobile services such as mobile TV. The decision to adopt the service can be viewed as a choice based on two cognitive processes of reasoning and referencing, as postulated in behavioural decision making. The framework has both theoretical and practical value. From a theoretical perspective, it illustrates the manner in which referencing and reasoning influence the individual’s decision to adopt innovative services in the mobile telecommunications market. From a practical perspective the framework offers a market analysis tool which can generate useful insights for the vendors.