Identification and control of induction machines using artificial neural networks

This paper proposes the use of artificial neural networks (ANNs) to identify and control an induction machine. Two systems are presented: a system to adaptively control the stator currents via identification of the electrical dynamics; and a system to adaptively control the rotor speed via identification of the mechanical and current-fed system dynamics. Various advantages of these control schemes over other conventional schemes are cited and the performance of the combined speed and current control scheme is compared with that of the standard vector control scheme

Assessment of the suitability of public mobile data networks for aircraft telemetry and control purposes

This paper provides a review of the state of the art relevant work on the use of public mobile data networks for aircraft telemetry and control proposes. Moreover, it describes the characterisation for airborne uses of the public mobile data communication systems known broadly as 3G. The motivation for this study was the explore how this mature public communication systems could be used for aviation purposes. An experimental system was fitted to a light aircraft to record communication latency, line speed, RF level, packet loss and cell tower identifier. Communications was established using internet protocols and connection was made to a local server. The aircraft was flown in both remote and populous areas at altitudes up to 8500 ft in a region located in South East Queensland, Australia. Results show that the average airborne RF levels are better than those on the ground by 21% and in the order of - 77dbm. Latencies were in the order of 500ms (1/2 the latency of Iridium), an average download speed of 0.48Mb/s, average uplink speed of 0.85Mb/s, a packet of information loss of 6.5%. The maximum communication range was also observed to be 70km from a single cell station. The paper also describes possible limitations and utility of using such communications architecture for both manned and unmanned aircraft systems.

Communication patterns within social networks : a case study of Australian women

Based on the perception that “individual bonds to one another is the essence of society” (Fischer, 1982a, p. 2), this paper examines contemporary networks of friends: friendworks, of adult women in an Australian sea change community. Communication patterns are examined drawing on findings from a case study of 26 women aged 35-76 years. Among the case study participants, many have undertaken a ‘sea change’ as adults, which in most cases has led to a significant reconstruction of their friendworks. Location and lifestyle are identified as impacting factors on communication patterns with friends; face-to-face interactions are by far the most frequent and preferred method of communication among the participants. The landline telephone and internet are the main communication methods used to maintain friendships with distant loved ones, while the mobile phone is reported as the communication method employed the least. The infrequency of mobile phone use can be attributed to cost issues, highlighting a discrepancy between these women’s social and communication needs and the current Australian mobile phone policy.

Peak power demand reduction under moving block signalling using an expert system

The concept of moving block signallings (MBS) has been adopted in a few mass transit railway systems. When a dense queue of trains begins to move from a complete stop, the trains can re-start in very close succession under MBS. The feeding substations nearby are likely to be overloaded and the service will inevitably be disturbed unless substations of higher power rating are used. By introducing starting time delays among the trains or limiting the trains’ acceleration rate to a certain extent, the peak energy demand can be contained. However, delay is introduced and quality of service is degraded. An expert system approach is presented to provide a supervisory tool for the operators. As the knowledge base is vital for the quality of decisions to be made, the study focuses on its formulation with a balance between delay and peak power demand.

Signalling layout for fixed-block railway lines with real-coded genetic algorithms.

Signalling layout design is one of the keys to railway operations with fixed-block signalling system and it also carries direct effect on overall train efficiency and safety. Based on an analysis to system objectives, this paper presents an optimization model with two objectives in order to devise an efficient signalling layout scheme. Taking into account the present railway line design practices in China, the paper describes steps of the computer-based signalling layout optimisation with real-coded genetic algorithms. A computer-aided system, based on train movement simulator, has also been employed to assist the optimisation process. A case study on a practical railway line has been conducted to make comparisons between the proposed GA-based approach and the current practices. The results illustrate the improved performance of the proposed approach in reducing signal block joints and shortening minimum train service headway.

Camera calibration in wireless multimedia sensor networks

Wireless Multi-media Sensor Networks (WMSNs) have become increasingly popular in recent years, driven in part by the increasing commoditization of small, low-cost CMOS sensors. As such, the challenge of automatically calibrating these types of cameras nodes has become an important research problem, especially for the case when a large quantity of these type of devices are deployed. This paper presents a method for automatically calibrating a wireless camera node with the ability to rotate around one axis. The method involves capturing images as the camera is rotated and computing the homographies between the images. The camera parameters, including focal length, principal point and the angle and axis of rotation can then recovered from two or more homographies. The homography computation algorithm is designed to deal with the limited resources of the wireless sensor and to minimize energy con- sumption. In this paper, a modified RANdom SAmple Consensus (RANSAC) algorithm is proposed to effectively increase the efficiency and reliability of the calibration procedure.

The old face of 'new' social networks : the republic of letters as a virtual community

This paper explores the idea of virtual participation through the historical example of the republic of letters in early modern Europe (circa 1500-1800). By reflecting on the construction of virtuality in a historical context, and more specifically in a pre-digital environment, this paper calls attention to accusations of technological determinism in ongoing research concerning the affordances of the Internet and related media of communication. It argues that ‘the virtual’ is not synonymous with ‘the digital’ and suggests that, in order to articulate what is novel about modern technologies, we must first understand the social interactions underpinning the relationships which are facilitated through those technologies. By analysing the construction of virtuality in a pre-digital environment, this paper thus offers a baseline from which scholars might consider what is different about the modes of interaction and communication being engaged in via modern media.

Performance analysis of IEEE 802.11 DCF based WNCS networks

Wireless network technologies, such as IEEE 802.11 based wireless local area networks (WLANs), have been adopted in wireless networked control systems (WNCS) for real-time applications. Distributed real-time control requires satisfaction of (soft) real-time performance from the underlying networks for delivery of real-time traffic. However, IEEE 802.11 networks are not designed for WNCS applications. They neither inherently provide quality-of-service (QoS) support, nor explicitly consider the characteristics of the real-time traffic on networked control systems (NCS), i.e., periodic round-trip traffic. Therefore, the adoption of 802.11 networks in real-time WNCSs causes challenging problems for network design and performance analysis. Theoretical methodologies are yet to be developed for computing the best achievable WNCS network performance under the constraints of real-time control requirements. Focusing on IEEE 802.11 distributed coordination function (DCF) based WNCSs, this paper analyses several important NCS network performance indices, such as throughput capacity, round trip time and packet loss ratio under the periodic round trip traffic pattern, a unique feature of typical NCSs. Considering periodic round trip traffic, an analytical model based on Markov chain theory is developed for deriving these performance indices under a critical real-time traffic condition, at which the real-time performance constraints are marginally satisfied. Case studies are also carried out to validate the theoretical development.

Network structure, knowledge governance, and firm performance : evidence from innovation networks and SMEs in the UK

It is increasingly understood that learning and thus innovation often occurs via highly interactive, iterative, network-based processes. Simultaneously, economic development policy is increasingly focused on small and medium-sized enterprises (SMEs) as a means of generating growth, creating a clear research issue in terms of the roles and interactions of government policy, universities, and other sources of knowledge, SMEs, and the creation and dissemination of innovation. This paper analyses the contribution of a range of actors in an SME innovation creation and dissemination framework, reviewing the role of various institutions therein, exploring the contribution of cross-locality networks, and identifying the mechanisms required to operationalise such a framework. Bivariate and multivariate (regression) techniques are employed to investigate both innovation and growth outcomes in relation to these structures; data are derived from the survey responses of over 450 SMEs in the UK. Results are complex and dependent upon the nature of institutions involved, the type of knowledge sought, and the spatial level of the linkages in place but overall highlight the value of cross-locality networks, network governance structures, and certain spillover effects from universities. In general, we find less support for the factors predicting SME growth outcomes than is the case for innovation. Finally, we outline an agenda for further research in the area.

An enhanced explicit rate algorithm for ABR traffic control in ATM networks

A high performance, low computational complexity rate-based flow control algorithm which can avoid congestion and achieve fairness is important to ATM available bit rate service. The explicit rate allocation algorithm proposed by Kalampoukas et al. is designed to achieve max–min fairness in ATM networks. It has several attractive features, such as a fixed computational complexity of O(1) and the guaranteed convergence to max–min fairness. In this paper, certain drawbacks of the algorithm, such as the severe overload of an outgoing link during transient period and the non-conforming use of the current cell rate field in a resource management cell, have been identified and analysed; a new algorithm which overcomes these drawbacks is proposed. The proposed algorithm simplifies the rate computation as well. Compared with Kalampoukas's algorithm, it has better performance in terms of congestion avoidance and smoothness of rate allocation.

Restarting trains under moving block signalling : an expert system approach

A high peak power demand at substations will result under Moving Block Signalling (MBS) when a dense queue of trains begins to start from a complete stop at the same time in an electrified railway system. This may cause the power supply interruption and in turn affect the train service substantially. In a recent study, measures of Starting Time Delay (STD) and Acceleration Rate Limit (ARL) are the possible approaches to reduce the peak power demand on the supply system under MBS. Nevertheless, there is no well-defined relationship between the two measures and peak power demand reduction (PDR). In order to attain a lower peak demand at substations on different traffic conditions and system requirements, an expert system is one of the possible approaches to procure the appropriate use of peak demand reduction measures. The main objective of this paper is to study the effect of the train re-starting strategies on the power demand at substations and the time delay suffered by the trains with the aid of computer simulation. An expert system is a useful tool to select various adoptions of STD and ARL under different operational conditions and system requirements.

A multi-train movement simulator with moving blocking signalling

Abstract Being as a relatively new approach of signalling, moving-block scheme significantly increases line capacity, especially on congested railways. This paper describes a simulation system for multi-train operation under moving-block signalling scheme. The simulator can be used to calculate minimum headways and safety characteristics under pre-set timetables or headways and different geographic and traction conditions. Advanced software techniques are adopted to support the flexibility within the simulator so that it is a general-purpose computer-aided design tool to evaluate the performance of moving block signalling.

Detecting attacks in encrypted networks using secret-sharing schemes

Secret-sharing schemes describe methods to securely share a secret among a group of participants. A properly constructed secret-sharing scheme guarantees that the share belonging to one participant does not reveal anything about the shares of others or even the secret itself. Besides being used to distribute a secret, secret-sharing schemes have also been used in secure multi-party computations and redundant residue number systems for error correction codes. In this paper, we propose that the secret-sharing scheme be used as a primitive in a Network-based Intrusion Detection System (NIDS) to detect attacks in encrypted Networks. Encrypted networks such as Virtual Private Networks (VPNs) fully encrypt network traffic which can include both malicious and non-malicious traffic. Traditional NIDS cannot monitor such encrypted traffic. We therefore describe how our work uses a combination of Shamir's secret-sharing scheme and randomised network proxies to enable a traditional NIDS to function normally in a VPN environment.

Governance networks and stakeholders : engaging through salience

Across Australia, construction and redevelopment of public infrastructure, continues to be a key factor in economic development. Within this context, road transport has been identified as key building block of Queensland‟s future prosperity. However, since the late twentieth century, there has been a shift away from delivery of large infrastructure, including road networks, exclusively by the state. Subsequently, a range of alternative models, have emerged in infrastructure project delivery. Among these, governance networks have become a widespread mechanism for planning and delivering infrastructure. However, despite substantial public investments in road infrastructure that are made through governance networks, little is known about how these networks engage with stakeholders who are potentially affected by road infrastructure projects. Although governance networks undertake management functions, it is unclear what drives stakeholder engagement within this networked environment and how stakeholder relationship management is operationalised. This paper proposes that network management functions undertaken by governance networks incorporate stakeholder engagement and that network managers play a key role in creating and sustaining connections between governance networks and their stakeholders Drawing on stakeholder theory and governance network theory, this paper contributes to the literature by showing that stakeholder engagement is embedded within network management and identifying the critical role of network managers in establishing and maintaining stakeholder engagement.

Stakeholder engagement by governance networks

As the problems involving infrastructure delivery have become more complex and contentious, there has been an acknowledgement that these problems cannot be resolved by any one body working alone. This understanding has driven multi-sectoral collaboration and has led to an expansion of the set of actors, including stakeholders, who are now involved in delivery of infrastructure projects and services. However, more needs to be understood about how to include stakeholders in these processes and ways of developing the requisite combination of stakeholders to achieve effective outcomes. This thesis draws on stakeholder theory and governance network theory to obtain insights into how three multi-level networks within the Roads Alliance in Queensland engage with stakeholders in the delivery of complex and sensitive infrastructure services and projects. New knowledge about stakeholders will be obtained by testing a model of Stakeholder Salience and Engagement which combines and extends the stakeholder identification and salience theory, ladder of stakeholder management and engagement and the model of stakeholder engagement and moral treatment of stakeholders. By applying this model, the broad research question: “Who or what decides how stakeholders are engaged by governance networks delivering public outcomes?” will be addressed. The case studies will test a theoretical model of stakeholder salience and engagement which links strategic decisions about stakeholder salience with the quality and quantity of engagement strategies for engaging different types of stakeholders. A multiple embedded case study design has been selected as the overall approach to explore, describe, explain and evaluate how stakeholder engagement occurs in three governance networks delivering road infrastructure in Queensland. The research design also incorporates a four stage approach to data collection: observations, stakeholder analysis, telephone survey questionnaire and semi-structured interviews. The outcomes of this research will contribute to and extend stakeholder theory by showing how stakeholder salience impacts on decisions about the types of engagement processes implemented. Governance network theory will be extended by showing how governance networks interact with stakeholders through the concepts of stakeholder salience and engagement. From a practical perspective this research will provide governance networks with an indication of how to optimise engagement with different types of stakeholders. 2