Performance modelling and analysis of multiple coexisting IEEE 802.15.4 wireless sensor networks

With the features of low-power and flexible networking capabilities IEEE 802.15.4 has been widely regarded as one strong candidate of communication technologies for wireless sensor networks (WSNs). It is expected that with an increasing number of deployments of 802.15.4 based WSNs, multiple WSNs could coexist with full or partial overlap in residential or enterprise areas. As WSNs are usually deployed without coordination, the communication could meet significant degradation with the 802.15.4 channel access scheme, which has a large impact on system performance. In this thesis we are motivated to investigate the effectiveness of 802.15.4 networks supporting WSN applications with various environments, especially when hidden terminals are presented due to the uncoordinated coexistence problem. Both analytical models and system level simulators are developed to analyse the performance of the random access scheme specified by IEEE 802.15.4 medium access control (MAC) standard for several network scenarios. The first part of the thesis investigates the effectiveness of single 802.15.4 network supporting WSN applications. A Markov chain based analytic model is applied to model the MAC behaviour of IEEE 802.15.4 standard and a discrete event simulator is also developed to analyse the performance and verify the proposed analytical model. It is observed that 802.15.4 networks could sufficiently support most WSN applications with its various functionalities. After the investigation of single network, the uncoordinated coexistence problem of multiple 802.15.4 networks deployed with communication range fully or partially overlapped are investigated in the next part of the thesis. Both nonsleep and sleep modes are investigated with different channel conditions by analytic and simulation methods to obtain the comprehensive performance evaluation. It is found that the uncoordinated coexistence problem can significantly degrade the performance of 802.15.4 networks, which is unlikely to satisfy the QoS requirements for many WSN applications. The proposed analytic model is validated by simulations which could be used to obtain the optimal parameter setting before WSNs deployments to eliminate the interference risks.

The Wide-Field Plate Database: Development and Access via Internet

ACM Computing Classification System (1998): J.2.

Design and Implementation of a Cloud Infrastructure for Distributed Scientific Calculation

Cloud computing enables independent end users and applications to share data and pooled resources, possibly located in geographically distributed Data Centers, in a fully transparent way. This need is particularly felt by scientific applications to exploit distributed resources in efficient and scalable way for the processing of big amount of data. This paper proposes an open so- lution to deploy a Platform as a service (PaaS) over a set of multi- site data centers by applying open source virtualization tools to facilitate operation among virtual machines while optimizing the usage of distributed resources. An experimental testbed is set up in Openstack environment to obtain evaluations with different types of TCP sample connections to demonstrate the functionality of the proposed solution and to obtain throughput measurements in relation to relevant design parameters.

Desempenho internacional de empresas exportadoras: um modelo estrutural baseado em capacidades organizacionais e ambiente

The internationalization as an organizational phenomenon fundamentally strategic had as theoretical contributions some Schools that throughout the decades 60, 70, and 80 developed behavioral and economic approaches in order to explain the process. The behavioral approach deals with the perception of phenomenon as a gradual process from the perspective of the executives behavior (JOHANSON and VAHLNE, 1977; HALLÉN and WIEDERSHEIM - PAUL, 1979; CZINKOTA, 1985). This phenomenon in permanent theoretical and managerial evolution made an opportunity to build this investigation, whose goal is to analyse the impact comes from organizational capabilities and the external environment on the international performance of exporting firms. For both, were used as theoretical basis two types of analysis for the comprehension of international performance: Strategic Management - Industrial Organization and Resource-Based View and International Businesses - Current Economic and Behavioral. It was made a cross-sectional survey-based explanatory research, including 150 exporting companies with operations in the Northeast of Brazil. A conceptual model was made with eight constructs and eight research hypotheses, representative of the effects of external factors on international performance. The data were processed using the Exploratory Factor Analysis and Structural Equation Modeling. The structural equations model was reespecified and estimated through the use of the maximum-likelihood method up to achieve adequated values of indexes of adjustment. As the main theoretical contribution, were identified organizational and physical resources which shows the importance of the management skills development, of the learning capability and capability to establish strategic alliances abroad. That because the knowledge, as the operational point of view as in its strategic application, offers to organization conditions of market positioning which can create opportunities sustainable competitive advantages and which impact the performance of international companies

Desempenho internacional de empresas exportadoras: um modelo estrutural baseado em capacidades organizacionais e ambiente

The internationalization as an organizational phenomenon fundamentally strategic had as theoretical contributions some Schools that throughout the decades 60, 70, and 80 developed behavioral and economic approaches in order to explain the process. The behavioral approach deals with the perception of phenomenon as a gradual process from the perspective of the executives behavior (JOHANSON and VAHLNE, 1977; HALLÉN and WIEDERSHEIM - PAUL, 1979; CZINKOTA, 1985). This phenomenon in permanent theoretical and managerial evolution made an opportunity to build this investigation, whose goal is to analyse the impact comes from organizational capabilities and the external environment on the international performance of exporting firms. For both, were used as theoretical basis two types of analysis for the comprehension of international performance: Strategic Management - Industrial Organization and Resource-Based View and International Businesses - Current Economic and Behavioral. It was made a cross-sectional survey-based explanatory research, including 150 exporting companies with operations in the Northeast of Brazil. A conceptual model was made with eight constructs and eight research hypotheses, representative of the effects of external factors on international performance. The data were processed using the Exploratory Factor Analysis and Structural Equation Modeling. The structural equations model was reespecified and estimated through the use of the maximum-likelihood method up to achieve adequated values of indexes of adjustment. As the main theoretical contribution, were identified organizational and physical resources which shows the importance of the management skills development, of the learning capability and capability to establish strategic alliances abroad. That because the knowledge, as the operational point of view as in its strategic application, offers to organization conditions of market positioning which can create opportunities sustainable competitive advantages and which impact the performance of international companies

Internetalisation : the Internet's influence on international market growth in the firm's outward internationalisation process

It has been suggested that the Internet is the most significant driver of international trade in recent years to the extent that the term =internetalisation‘ has been coined (Bell, Deans, Ibbotson & Sinkovics, 2001; Buttriss & Wilkinson, 2003). This term is used to describe the Internet‘s affect on the internationalisation process of the firm. Consequently, researchers have argued that the internationalisation process of the firm has altered due to the Internet, hence is in need of further investigation. However, as there is limited research and understanding, ambiguity remains in how the Internet has influenced international market growth. Thus, the purpose of this study was to explore how the Internet influences firms‘ internationalisation process, specifically, international market growth. To this end, Internet marketing and international market growth theories are used to illuminate this ambiguity in the body of knowledge. Thus, the research problem =How and why does the Internet influence international market growth of the firm’ is justified for investigation. To explore the research question a two-stage approach is used. Firstly, twelve case studies were used to evaluate key concepts, generate hypotheses and to develop a model of Internetalisation for testing. The participants held key positions within their firm, so that rich data could be drawn from international market growth decision makers. Secondly, a quantitative confirmation process analysed the identified themes or constructs, using two hundred and twenty four valid responses. Constructs were evaluated through an exploratory factor analysis, confirmatory factor analysis and structural equation modelling process. Structural equation modelling was used to test the model of =internetalisation‘ to examine the interrelationships between the internationalisation process components: information availability, information usage, interaction communication, international mindset, business relationship usage, psychic distance, the Internet intensity of the firm and international market growth. This study found that the Internet intensity of the firm mediates information availability, information usage, international mindset, and business relationships when firms grow in international markets. Therefore, these results provide empirical evidence that the Internet has a positive influence on international information, knowledge, entrepreneurship and networks and these in turn influence international market growth. The theoretical contributions are three fold. Firstly, the study identifies a holistic model of the impact the Internet has had on the outward internationalisation of the firm. This contribution extends the body of knowledge pertaining to Internet international marketing by mapping and confirming interrelationships between the Internet, internationalisation and growth concepts. Secondly, the study highlights the broad scope and accelerated rate of international market growth of firms. Evidence that the Internet influences the traditional and virtual networks for the pursuit of international market growth extends the current understanding. Thirdly, this study confirms that international information, knowledge, entrepreneurship and network concepts are valid in a single model. Thus, these three contributions identify constructs, measure constructs in a multi-item capacity, map interrelationships and confirm single holistic model of ‗internetalisation‘. The main practical contribution is that the findings identified information, knowledge and entrepreneurial opportunities for firms wishing to maximise international market growth. To capitalise on these opportunities suggestions are offered to assist firms to develop greater Internet intensity and internationalisation capabilities. From a policy perspective, educational institutions and government bodies need to promote more applied programs for Internet international marketing. The study provides future researchers with a platform of identified constructs and interrelationships related to internetalisation, with which to investigate. However, a single study has limitations of generalisability; thus, future research should replicate this study. Such replication or cross validation will assist in the verification of scales used in this research and enhance the validity of causal predications. Furthermore, this study was undertaken in the Australian outward-bound context. Research in other nations, as well as research into inbound internationalisation would be fruitful.

On the (partially) inalienable rights of participants in virtual communities

As virtual communities become more central to the everyday activities of connected individuals, we face increasingly pressing questions about the proper allocation of power, rights and responsibilities. This paper argues that our current legal discourse is ill-equipped to provide answers that will safeguard the legitimate interests of participants and simultaneously refrain from limiting the future innovative development of these spaces. From social networking sites like Facebook to virtual worlds like World of Warcraft and Second Life, participants who are banned from these communities stand to lose their virtual property, their connections to their friends and family, and their personal expression. Because our legal system views the proprietor’s interests as absolute private property rights, however, participants who are arbitrarily, capriciously or maliciously ejected have little recourse under law. This paper argues that, rather than assuming that a private property and freedom of contract model will provide the most desirable outcomes, a more critical approach is warranted. By rejecting the false dichotomy between ‘public’ and ‘private’ spaces, and recognising some of the absolutist and necessitarian trends in the current property debate, we may be able to craft legal rules that respect the social bonds between participants while simultaneously protecting the interests of developers.

Virtual fences for controlling cows

We describe a moving virtual fence algorithm for herding cows. Each animal in the herd is given a smart collar consisting of a GPS, PDA, wireless networking and a sound amplifier. Using the GPS, the animal's location can be verified relative to the fence boundary. When approaching the perimeter, the animal is presented with a sound stimulus whose effect is to move away. We have developed the virtual fence control algorithm for moving a herd. We present simulation results and data from experiments with 8 cows equipped with smart collars.

Dynamic virtual fences for controlling cows

A virtual fence is created by applying an aversive stimulus to an animal when it approaches a predefined boundary. It is implemented by a small animal-borne computer system with a GPS receiver. This approach allows the implementation of virtual paddocks inside a normal physically-fenced paddock. Since the fence lines are virtual they can be moved by programming to meet the needs of animal or land management. This approach enables us to consider animals as agents with natural mobility that are controllable and to apply a vast body of theory in motion planning. In this paper we describe a herd-animal simulator and physical experiments conducted on a small herd of 10 animals using a Smart Collar. The Smart Collar consists of a GPS, PDA, wireless networking and a sound amplifier. We describe a motion planning algorithm that can move a virtual paddock subject to landscape constraints which is suitable for mustering cows. We present simulation results and data from experiments with 8 cows equipped with Smart Collars.

‘Please leave your mobile phone on’ : Social educational networking in a social society : Encouraging in-class engagement at QUT across physical and virtual learning environments

Though stadium style seating in large lecture theatres may suggest otherwise, effective teaching and learning is a not a spectator sport. A challenge in creating effective learning environments in both physical and virtual spaces is to provide optimal opportunity for student engagement in active learning. Queensland University of Technology (QUT) has developed the Open Web Lecture (OWL), a new web-based student response application, which seamlessly integrates a virtual learning environment within the physical learning space. The result is a blended learning experience; a fluid collaboration between academic and students connected to OWL via the University’s Wi-Fi using their own laptop or mobile web device. QUT is currently piloting the OWL application to encourage student engagement. OWL offers opportunities for participants to: • Post comments and questions • Reply to comments
 • "Like" comments
 • Poll students and review data • Review archived sessions. Many of these features instinctively appeal to student users of social networking media, yet avail the academic of control within the University network. Student privacy is respected through a system of preserving peer-peer anonymity, a functionality that seeks to address a traditional reluctance to speak up in large classes. The pilot is establishing OWL as an opportunity for engaging students in active learning opportunities by enabling • virtual learning in physical spaces for large group lectures, seminar groups, workshops and conferences • live collaborative technology connecting students and the academic via the wireless network using their own laptop or mobile device • an non- intimidating environment in which to ask questions • promotion of a sense of community • instant feedback • problem based learning. The student and academic response to OWL has been overwhelmingly positive, crediting OWL as an easy to use application, which creates effective learning opportunities though interactivity and immediate feedback. This poster and accompanying online presentation of the technology will demonstrate how OWL offers new possibilities for active learning in physical spaces by: • providing increased opportunity for student engagement • supporting a range of learners and learning activities • fostering blended learning experiences. The presentation will feature visual displays of the technology, its various interfaces and feedback including clips from interviews with students and academics participating in the early stages of the pilot.

An examination of the critical resources and internet capabilities for leveraging global performance in international entrepreneurial firms

This PhD research investigates the critical resources and Internet capabilities utilized by firms for leveraging global performance in entrepreneurial firms. Firm resources have been identified as important firm assets, which contribute to the firm's competitive global position. The Internet is a critical resource for a new generation of small and medium sized enterprise (SME) in pursuing international opportunities. By facilitating international business, the Internet has the ability to increase the quality and speed of communications, lower transaction costs, and facilitate the development of networks. Despite the increasing numbers of firms utilizing the Internet to pursue international opportunities, limited research remains. Adopting multiple case study methodology and structural equation modelling, the research identified the firm-level resources, which coincide with capabilities in a model predicting how international performance in firms is achieved.

Efficient multiple relay selection for cooperative communication using alamouti-coded virtual transmit antenna systems

An opportunistic relay selection scheme improving cooperative diversity is devised using the concept of a virtual SIMO-MISO antenna array. By incorporating multiple users as a virtual distributed antenna, not only helps combat fading but also provides significant advantage in terms of energy consumption. The proposed efficient multiple relay selection uses the concept of the distributed Alamouti scheme in a time varying environment to realize cooperative networking in wireless relay networks and provides the platform for outage, Diversiy-Multiplexing Tradeoff (DMT) and Bit-Error-Rate (BER) analysis to conclude that it is capable of achieving promising diversity gains by operating at much lower SNR when compared with conventional relay selection methods. It also has the added advantage of conserving energy for the relays that are reachable but not selected for the cooperative communication.

The impact of Internet marketing capabilities on international network capability, a cross country study comparison between Australia, Chile and Taiwan internationalised SMEs

The Internet has been shown to positively enhance internationalisation for SMEs, but scant empirical testing limits our understanding of the explicit impact of the Internet on firm internationalisation. This paper highlights key areas where the integration of the Internet can be leveraged through Internet-related capabilities within the internationalisation of the firm. Specifically, this study investigates how Internet marketing capabilities play a role in altering international information availability, international strategic orientation, and international business network relationships. This study provides evidence, indicating that these key relationships may vary between countries. To examine these key relationships this study utilises draws from data small and medium sized enterprises (SMEs) in three export intensive markets; Australia (215 international SMEs), Chile (204 international SMEs) and Taiwan (130 international SMEs); and tests a conceptual model through structural equation modelling. Results from the data show the impact of Internet marketing capabilities in positively impacting traditional internationalisation elements, which varies between countries. That is, our findings highlight the international business network relationships in Australia and Taiwan are directly impacted by Internet marketing capabilities, but not in Chile. We offer some insight into why we see variance across comparative exporting countries in how they leverage new technological capabilities for internationalisation and firm performance.

A CCG virtual system for big data application communication costs analysis

Network topology and routing are two important factors in determining the communication costs of big data applications at large scale. As for a given Cluster, Cloud, or Grid system, the network topology is fixed and static or dynamic routing protocols are preinstalled to direct the network traffic. Users cannot change them once the system is deployed. Hence, it is hard for application developers to identify the optimal network topology and routing algorithm for their applications with distinct communication patterns. In this study, we design a CCG virtual system (CCGVS), which first uses container-based virtualization to allow users to create a farm of lightweight virtual machines on a single host. Then, it uses software-defined networking (SDN) technique to control the network traffic among these virtual machines. Users can change the network topology and control the network traffic programmingly, thereby enabling application developers to evaluate their applications on the same system with different network topologies and routing algorithms. The preliminary experimental results through both synthetic big data programs and NPB benchmarks have shown that CCGVS can represent application performance variations caused by network topology and routing algorithm.

Susceptibility to social engineering in social networking sites: The case of Facebook

Past research has suggested that social engineering poses the most significant security risk. Recent studies have suggested that social networking sites (SNSs) are the most common source of social engineering attacks. The risk of social engineering attacks in SNSs is associated with the difficulty of making accurate judgments regarding source credibility in the virtual environment of SNSs. In this paper, we quantitatively investigate source credibility dimensions in terms of social engineering on Facebook, as well as the source characteristics that influence Facebook users to judge an attacker as credible, therefore making them susceptible to victimization. Moreover, in order to predict users’ susceptibility to social engineering victimization based on their demographics, we investigate the effectiveness of source characteristics on different demographic groups by measuring the consent intentions and behavior responses of users to social engineering requests using a role-play experiment.