Radiation-induced magnetoresistance oscillation in a two-dimensional electron gas in Faraday geometry

Microwave-radiation induced giant magnetoresistance oscillations recently discovered in high-mobility two-dimensional electron systems in a magnetic field, are analyzed theoretically. Multiphoton-assisted impurity scatterings are shown to be the primary origin of the oscillation. Based on a model which considers the interaction of electrons with the electromagnetic fields in Faraday geometry, we are able not only to reproduce the correct period, phase and the negative resistivity of the main oscillation, but also to obtain secondary peaks and additional maxima and minima in the resistivity curve, some of which were already observed in the experiments.Comment: 4 pages, 1 figure, revised version to be published in Phys. Rev. Let

LEXTALE_CH: A quick, character-based proficiency test for Mandarin Chinese

Research in second language acquisition suggests that objective performance-based assessments may provide more reliable and valid measures of second language proficiency than subjective self-ratings. To measure proficiency in English as a second language, a quick, vocabulary-based test called LexTALE (Lexical Test for Advanced Learners of English) was developed and shown to be able to differentiate between various levels of English proficiency. Following in the line of adaptations of this test for other languages, we created a character-based adaptation for Mandarin Chinese: LEXTALE_CH. In this paper, we discuss the development and validation of LEXTALE_CH in detail. In short, LEXTALE_CH can discriminate between high and low levels of Mandarin proficiency and is sensitive to the significant differences in vocabulary size between native speakers and second language learners of Mandarin; further, it takes only a few minutes to administer and is simple to score, making it a practical tool for low-stakes estimation of Mandarin proficiency.http://www.lingref.com/bucld/42/BUCLD42-09.pdfPublished versio

Direct-current control of radiation-induced differential magnetoresistance oscillations in two-dimensional electron systems

Magnetoresistance oscillations in two-dimensional electron systems driven simultaneously by a strong direct current and a microwave irradiation, are analyzed within a unified microscopic scheme treating both excitations on an equal footing. The microwave-induced resistance oscillations are described by a parameter $\epsilon_\omega$ proportional to the radiation frequency, while the dc-induced resistance oscillations are governed by a parameter $\epsilon_j$ proportional to the current density. In the presence of both a microwave radiation and a strong dc, the combined parameter $\epsilon_\omega+\epsilon_j$ is shown to control the main resistance oscillations, in agreement with the recent measurement [Zhang {\it et al.} Phys. Rev. Lett. {\bf 98}, 106804 (2007)]Comment: 4 pages, 2 figues, published versio

Is adaptation of e-advertising the way forward?

E-advertising is a multi-billion dollar industry that has shown exponential growth in the last few years. However, although the number of users accessing the Internet increases, users don’t respond positively to adverts. Adaptive e-advertising may be the key to ensuring effectiveness of the ads reaching their target. Moreover, social networks are good sources of user information and can be used to extract user behaviour and characteristics for presentation of personalized advertising. Here we present a two-sided study based on two questionnaires, one directed to Internet users and the other to businesses. Our study shows that businesses agree that personalized advertising is the best way for the future, to maximize effectiveness and profit. In addition, our results indicate that most Internet users would prefer adaptive advertisements. From this study, we can propose a new design for a system that meets both Internet users’ and businesses’ requirements

Investigating the impact of social interactions in adaptive E-Learning by learning behaviour analysis

Adaptive Educational Hypermedia Systems (AEHSs) allow for personalization of e-learning1 . Social media tools enable learners to create, publish and share their study, and facilitate interaction and collaboration2 . The integration of social media tools into AEHS offers novel opportunities for learner engagement and extended user modelling, and thereby fosters so-called Social Personalized Adaptive E-learning Environments (SPAEEs) 3. However, there has been a lack of empirical design and evaluation to elaborate methods for SPAEEs. The goal of research, therefore, is to investigate 1) the learning behaviour patterns within SPAEEs and the use of these patterns for learner engagement, 2) the evaluation methodologies for SPAEEs, and 3) the design principles for SPAEEs. Topolor4 is a SPAEE that has been under iterative development for achieving our research goals. The first prototype was used as an online learning system for MSc level students in the Department of Computer Science, at the University of Warwick, and usage data was anonymously collected for analysis5 . This poster focuses on system features and learning behaviour analysis. We firstly present the methodologies applied in the research, followed by the social and adaptive features that Topolor provides6 . Then we revisit the analysis of learning behaviours7 . Finally we propose the follow-up work based on the evaluation results

Coulomb Blockade and Hopping Conduction in Graphene Quantum Dots Array

We show that the low temperature electron transport properties of chemically functionalized graphene can be explained as sequential tunneling of charges through a two dimensional array of graphene quantum dots (GQD). Below 15 K, a total suppression of current due to Coulomb blockade through GQD array was observed. Temperature dependent current-gate voltage characteristics show Coulomb oscillations with energy scales of 6.2-10 meV corresponding to GQD sizes of 5-8 nm while resistance data exhibit an Efros-Shklovskii variable range hopping arising from structural and size induced disorder.Comment: The document will be appeared in Physics Review

Designing social personalized adaptive e-learning

Here we introduce Topolor, a social personalized adaptive elearning system aiming to improve social interaction in the learning process as well as applying classical adaptation based on user modeling. Here, we focus on the system architecture and preliminary evaluation that showed high system usability

An exploratory study to design an adaptive hypermedia system for online-advertisement

The revolutionary world of the World Wide Web has created an open space for a multitude of fields to develop and propagate. One of these major fields is advertisement. Online advertisement has become one of the main activities conducted on the web, heavily supported by the industry. Importantly, it is one of the main contributors to any businesses’ income. However, consumers usually ignore the great majority of adverts online. This research paper studies the field of online advertisement, by conducting an exploratory study to understand end users’ needs for targeted online advertisement using adaptive hypermedia techniques. Additionally, we explore social networks, one of the booming phenomena of the web, to enhance the appropriateness of the advertising to the users. The main current outcome of this research is that end users are interested in personalised advertisement that tackles their needs and that they believe that the use of social networks and social actions help in the contextualisation of advertisement

Exploring participatory design for SNS-based AEH systems

The rapidly emerging and growing social networking sites (SNS) offer an opportunity to improve adaptive e-learning experience by introducing a social dimension, connecting users within the system. Making connections and providing communication tools can engage students in creating effective learning environment and enriching learning experiences. Researchers have been working on introducing SNS features into adaptive educational hypermedia systems. The next stage research is centered on how to enhance SNS facilities of AEH systems, in order to engage students’ participation in collaborative learning and generating and enriching learning materials. Students are the core participants in the adaptive e-learning process, so it is essential for the system designers to consider students’ opinions. This paper aims at exploring how to apply participatory design methodology in the early stage of the SNS-based AEH system design process