Performance analysis of switch-and-stay combining in two-way relay systems with analog network coding and time-division broadcast protocols

In this paper, weconsider switch-and-stay combining (SSC) in two-way relay systems with two amplify-and-forward relays, one of which is activated to assist the information exchange between the two sources. The system operates in either analog network coding (ANC) protocol where the communication is only achieved with the help of the active relay or timedivision broadcast (TDBC) protocol where the direct link between two sources can be utilized to exploit more diversity gain. In both cases, we study the outage probability and bit error rate (BER) for Rayleigh fading channels. In particular, we derive closed-form lower bounds for the outage probability and the average BER, which remain tight for different fading conditions. We also present asymptotic analysis for both the outage probability and the average BER at high signalto-noise ratio. It is shown that SSC can achieve the full diversity order in two-way relay systems for both ANC and TDBC protocols with proper switching thresholds. Copyright © 2014 John Wiley & Sons, Ltd.

Learning about probability from text and tables: Do color coding and labeling through an interactive-user interface help?

Learning from visual representations is enhanced when learners appropriately integrate corresponding visual and verbal information. This study examined the effects of two methods of promoting integration, color coding and labeling, on learning about probabilistic reasoning from a table and text. Undergraduate students (N = 98) were randomly assigned to learn about probabilistic reasoning from one of 4 computer-based lessons generated from a 2 (color coding/no color coding) by 2 (labeling/no labeling) between-subjects design. Learners added the labels or color coding at their own pace by clicking buttons in a computer-based lesson. Participants' eye movements were recorded while viewing the lesson. Labeling was beneficial for learning, but color coding was not. In addition, labeling, but not color coding, increased attention to important information in the table and time with the lesson. Both labeling and color coding increased looks between the text and corresponding information in the table. The findings provide support for the multimedia principle, and they suggest that providing labeling enhances learning about probabilistic reasoning from text and tables

Process virtualization theory (PVT) and institutional theory (INT) to explain SAAS adoption

Software as a service (SaaS) is a service model in which the applications are accessible from various client devices through internet. Several studies report possible factors driving the adoption of SaaS but none have considered the perception of the SaaS features and the pressures existing in the organization’s environment. We propose an integrated research model that combines the process virtualization theory (PVT) and the institutional theory (INT). PVT seeks to explain whether SaaS processes are suitable for migration into virtual environments via an information technology-based mechanism. INT seeks to explain the effects of the institutionalized environment on the structure and actions of the organization. The research makes three contributions. First, it addresses a gap in the SaaS adoption literature by studying the internal perception of the technical features of SaaS and external coercive, normative, and mimetic pressures faced by an organization. Second, it empirically tests many of the propositions of PVT and INT in the SaaS context, thereby helping to determine how the theory operates in practice. Third, the integration of PVT and INT contributes to the information system (IS) discipline, deepening the applicability and strengths of these theories.

An Information Theory framework for two-stage binary image operator design

The design of translation invariant and locally defined binary image operators over large windows is made difficult by decreased statistical precision and increased training time. We present a complete framework for the application of stacked design, a recently proposed technique to create two-stage operators that circumvents that difficulty. We propose a novel algorithm, based on Information Theory, to find groups of pixels that should be used together to predict the Output Value. We employ this algorithm to automate the process of creating a set of first-level operators that are later combined in a global operator. We also propose a principled way to guide this combination, by using feature selection and model comparison. Experimental results Show that the proposed framework leads to better results than single stage design. (C) 2009 Elsevier B.V. All rights reserved.

Information theory based detection against network behavior mimicking DDoS attacks

DDoS is a spy-on-spy game between attackers and detectors. Attackers are mimicking network traffic patterns to disable the detection algorithms which are based on these features. It is an open problem of discriminating the mimicking DDoS attacks from massive legitimate network accessing. We observed that the zombies use controlled function(s) to pump attack packages to the victim, therefore, the attack flows to the victim are always share some properties, e.g. packages distribution behaviors, which are not possessed by legitimate flows in a short time period. Based on this observation, once there appear suspicious flows to a server, we start to calculate the distance of the package distribution behavior among the suspicious flows. If the distance is less than a given threshold, then it is a DDoS attack, otherwise, it is a legitimate accessing. Our analysis and the preliminary experiments indicate that the proposed method- can discriminate mimicking flooding attacks from legitimate accessing efficiently and effectively.

Doctoral research and scholarly communication : candidates, supervisors and information literacy

This study investigates information literacy and scholarly communication within the processes of doctoral research and supervision at a distance. Both doctoral candidates and supervisors acknowledge information literacy deficiencies and it is suggested that disintermediation and the proliferation of information may contribute to those deficiencies. Further to this, the influence of pedagogic continuity—particularly in relation to the information seeking behaviour of candidates—is investigated, as is the concomitant aspect of how doctoral researchers practise scholarly communication. The well-documented and enduring problem for candidates of isolation from the research cultures of their universities is also scrutinised. The contentious issue of more formally involving librarians in the doctoral process is also considered, from the perspective of candidates and supervisors. Superimposed upon these topical and timely issues is the theoretical framework of adult learning theory, in particular the tenets of andragogy. The pedagogical-andragogical orientation of candidates and supervisors is established, demonstrating both the differences and similarities between candidates and supervisors, as are a number of independent variables, including a comparison of on-campus and off-campus candidates. Other independent variables include age, gender, DETYA (Department of Education, Training & Youth Affairs) category, enrolment type, stage of candidature, employment and status, type of doctorate, and English/non-English speaking background. The research methodology uses qualitative and quantitative techniques encompassing both data and methodological triangulation. The study uses two sets of questionnaires and a series of in-depth interviews with a sample of on-campus and off-campus doctoral candidates and supervisors from four Australian universities. Major findings include NESB candidates being more pedagogical than their ESB counterparts, and candidates and supervisors from the Sciences are more pedagogical than those from Arts, Humanities and Social Sciences, or Education. Candidates make a transition from a more dependent and pedagogically oriented approach to learning towards more of an independent and andragogical orientation over the duration of their candidature. However, over tune both on-campus and off-campus candidates become more isolated from the research cultures of their universities, and less happy with support received from their supervisors in relation to their literature reviews. Ill The study found large discrepancies in perception between the support supervisors believed they gave to candidates in relation to the literature review, and the support candidates believed they received. Information seeking becomes easier over time, but candidates face a dilemma with the proliferation of information, suggesting that disintermediation has exacerbated the challenges of evaluation and organisation of information. The concept of pedagogic continuity was recognised by supervisors and especially candidates, both negative and positive influences. The findings are critically analysed and synthesised using the metaphor of a scholarly 'Club' of which obtaining a doctorate is a rite of passage. Recommendations are made for changes in professional practice, and topics that may warrant further research are suggested.

Special issue : Computational intelligence models for image processing and information reasoning

Computational Intelligence (CI) models comprise robust computing methodologies with a high level of machine learning quotient. CI models, in general, are useful for designing computerized intelligent systems/machines that possess useful characteristics mimicking human behaviors and capabilities in solving complex tasks, e.g., learning, adaptation, and evolution. Examples of some popular CI models include fuzzy systems, artificial neural networks, evolutionary algorithms, multi-agent systems, decision trees, rough set theory, knowledge-based systems, and hybrid of these models. This special issue highlights how different computational intelligence models, coupled with other complementary techniques, can be used to handle problems encountered in image processing and information reasoning.

Essays on monetary and banking theory

Esta tese de Doutorado é dedicada ao estudo de instabilidade financeira e dinâmica em Teoria Monet ária. E demonstrado que corridas banc árias são eliminadas sem custos no modelo padrão de teoria banc ária quando a popula ção não é pequena. É proposta uma extensão em que incerteza agregada é mais severa e o custo da estabilidade financeira é relevante. Finalmente, estabelece-se otimalidade de transições na distribui ção de moeda em economias em que oportunidades de trocas são escassas e heterogêneas. Em particular, otimalidade da inflação depende dos incentivos dinâmicos proporcionados por tais transi ções. O capí tulo 1 estabelece o resultado de estabilidade sem custos para economias grandes ao estudar os efeitos do tamanho populacional na an álise de corridas banc árias de Peck & Shell. No capí tulo 2, otimalidade de dinâmica é estudada no modelo de monet ário de Kiyotaki & Wright quando a sociedade é capaz de implementar uma polí tica inflacion ária. Apesar de adotar a abordagem de desenho de mecanismos, este capí tulo faz um paralelo com a an álise de Sargent & Wallace (1981) ao destacar efeitos de incentivos dinâmicos sobre a interação entre as polí ticas monet ária e fiscal. O cap ítulo 3 retoma o tema de estabilidade fi nanceira ao quanti car os custos envolvidos no desenho ótimo de um setor bancário à prova de corridas e ao propor uma estrutura informacional alternativa que possibilita bancos insolventes. A primeira an álise mostra que o esquema de estabilidade ótima exibe altas taxas de juros de longo prazo e a segunda que monitoramento imperfeito pode levar a corridas bancárias com insolvência.

Quantum entanglement and information: The effect of entropy revisited

In non-extensive statistical mechanics [14], it is a nonsense statement to say that the entropy of a system is extensive (or not), without mentioning a law of composition of its elements. In this theory quantum correlations might be perceived through quantum information process. This article, that is an extension of recent work [4], is a comparative study between the entropies of Von Neumann and of Tsallis, with some implementations of the effect of entropy in quantum entanglement, important as a process for transmission of quantum information. We consider two factorized (Fock number) states, which interact through a beam splitter bilinear Hamiltonian with two entries. This comparison showed us that the entropies of Tsallis and Von Neumann behave differently depending on the reflectance of the beam splitter. © 2011 Academic Publications.

Coordination and Control of Autonomous Mobile Robots Swarms by using Particle Swarm Optimization Algorithm and Consensus Theory

This thesis presents some different techniques designed to drive a swarm of robots in an a-priori unknown environment in order to move the group from a starting area to a final one avoiding obstacles. The presented techniques are based on two different theories used alone or in combination: Swarm Intelligence (SI) and Graph Theory. Both theories are based on the study of interactions between different entities (also called agents or units) in Multi- Agent Systems (MAS). The first one belongs to the Artificial Intelligence context and the second one to the Distributed Systems context. These theories, each one from its own point of view, exploit the emergent behaviour that comes from the interactive work of the entities, in order to achieve a common goal. The features of flexibility and adaptability of the swarm have been exploited with the aim to overcome and to minimize difficulties and problems that can affect one or more units of the group, having minimal impact to the whole group and to the common main target. Another aim of this work is to show the importance of the information shared between the units of the group, such as the communication topology, because it helps to maintain the environmental information, detected by each single agent, updated among the swarm. Swarm Intelligence has been applied to the presented technique, through the Particle Swarm Optimization algorithm (PSO), taking advantage of its features as a navigation system. The Graph Theory has been applied by exploiting Consensus and the application of the agreement protocol with the aim to maintain the units in a desired and controlled formation. This approach has been followed in order to conserve the power of PSO and to control part of its random behaviour with a distributed control algorithm like Consensus.

Essays in Industrial Organization and Information Technology

Chapter 1 studies how consumers’ switching costs affect the pricing and profits of firms competing in two-sided markets such as Apple and Google in the smartphone market. When two-sided markets are dynamic – rather than merely static – I show that switching costs lower the first-period price if network externalities are strong, which is in contrast to what has been found in one-sided markets. By contrast, switching costs soften price competition in the initial period if network externalities are weak and consumers are more patient than the platforms. Moreover, an increase in switching costs on one side decreases the first-period price on the other side. Chapter 2 examines firms’ incentives to invest in local and flexible resources when demand is uncertain and correlated. I find that market power of the monopolist providing flexible resources distorts investment incentives, while competition mitigates them. The extent of improvement depends critically on demand correlation and the cost of capacity: under social optimum and monopoly, if the flexible resource is cheap, the relationship between investment and correlation is positive, and if it is costly, the relationship becomes negative; under duopoly, the relationship is positive. The analysis also sheds light on some policy discussions in markets such as cloud computing. Chapter 3 develops a theory of sequential investments in cybersecurity. The regulator can use safety standards and liability rules to increase security. I show that the joint use of an optimal standard and a full liability rule leads to underinvestment ex ante and overinvestment ex post. Instead, switching to a partial liability rule can correct the inefficiencies. This suggests that to improve security, the regulator should encourage not only firms, but also consumers to invest in security.