1,281 results for Conference paper

  • Towards non-invasive electrical heart imaging

    Cheng, L.K.; Pullan, A.J. (1999)

    Conference paper
    The University of Auckland Library

    An open access copy of this article is available and complies with the copyright holder/publisher conditions. Before accurate, non-invasive, electrical images of the heart can be reconstructed several issues must be addressed. Geometric models must be created to match the subject, the appropriate resolution of the computational mesh must be determined and a continuous potential field must be generated from discretely sampled ECG signals. We investigate each of these issues with reference to a porcine model

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  • Non-invasive electrical imaging of the heart. (Conference Paper)

    Pullan, A.J.; Cheng, L.K.; Nash, M.P.; Paterson, D.J. (1999)

    Conference paper
    The University of Auckland Library

    An open access copy of this article is available and complies with the copyright holder/publisher conditions. The performance of an electrical imaging procedure for the heart ideally needs to be validated against invasive electrical recordings made directly on the heart. We report an experimental and modelling program that is working towards obtaining the necessary in-vivo data required for model validation. We also present results illustrating the performance of a recently published activation imaging algorithm using some of the data obtained to date

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  • Agent and web-based technologies in network management

    Wren, Matthew J.; Gutierrez, Jairo A. (1999)

    Conference paper
    The University of Auckland Library

    An open access copy of this article is available and complies with the copyright holder/publisher conditions. A close look at agent and Web-based technologies and their use in the management of networks is the main theme of this paper. An analysis of how this area has changed substantially, resulting in new difficulties and challenges for information systems professionals is provided. The components of network management, including people, information; the network infrastructure, systems and network management, and their interactions are looked at initially. The changes that have occurred in this area will be outlined by this analysis, and the resulting problems and complexities described. From this point the potential role for agent technology in providing some degree of solution is explored. This exploration also considers some of the negative implications, and introduces a model proposed as the basis of an integrated agent and Web-based network management environment

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  • High resolution image reconstruction using mean field annealing

    Numnonda, Thanachart; Andrews, Mark (1994)

    Conference paper
    The University of Auckland Library

    An open access copy of this article is available and complies with the copyright holder/publisher conditions. A high resolution image can be reconstructed from a sequence of lower resolution frames of the same scene where each frame taken by the camera is offset by a subpixel displacement. In this paper, it is shown that such a reconstruction task can be cast as an optimisation problem, and that a reconstruction can be found using the mean field annealing algorithm. The proposed technique has the added advantage over existing techniques of not requiring the registration of the displacement of each low resolution frame. In addition, the proposed technique greatly reduces the required computation as compared to a simulated annealing approach

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  • Agent-supported information retrieval for natural language

    Loerch, Ute; Guesgen, Hans W. (1999)

    Conference paper
    The University of Auckland Library

    An open access copy of this article is available and complies with the copyright holder/publisher conditions. This paper addresses issues in using modeling techniques for a multi-agent system, which adapts and extends existing object-orientated (OO) representation techniques for parsing natural language. After concentrating on the main problems of natural language information retrieval, we focus on the details of the applied agent-orientated modeling techniques and assume a passing familiarity with OO modeling and representation techniques. In addition to the above, we discuss the utility of having a matchmaking agent which can reason over agent capabilities to recommend agents for specific tasks, where the capabilities and requirements are defined using a common service ontology. This ensures that the semantics of matching agent capabilities remains the same across the multi-agent system

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  • Modelling myocardial excitation wavefront propagation in ventricles by finite element solution of an eikonal equation

    Tomlinson, K.A.; Pullan, A.J.; Hunter, P.J. (1999)

    Conference paper
    The University of Auckland Library

    An open access copy of this article is available and complies with the copyright holder/publisher conditions. The spreading of excitation in ventricular myocardium is modelled by treating the thin region of rapidly depolarizing tissue as a propagating wavefront. The model determines tissue excitation time using an eikonal equation that includes the effects of wavefront orientation in the myocardial structure and wavefront curvature. Use of a Petrov-Galerkin finite element method with a no-inflow boundary condition enables the eikonal equation to be solved on reasonably coarse meshes of cubic Hermite elements. The method is applied successfully on a model of the complete canine ventricular myocardium

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  • Carnival and Construction – Towards a Scaffolding for the Inclusion of ICT in the Construction Process

    McMeel, Dermott (2006)

    Conference paper
    The University of Auckland Library

    An open access copy of this article is available and complies with the copyright holder/publisher conditions. In this paper we explore the process of construction, we consider the construc- tion site as a mediated collaborative environment in which many specialist crafts and esoteric skills are present and negotiated. Concrete information when pass onto a construction site becomes part of a fluid morphing object, the validity and meaning of information can change—or be lost—depending on where and when it is. We look at current models of construction and actual construction process and we explore the notion of Carnival as a tool to reconcile the concrete and fluid aspects to communication dynamics of mediated group working in general and of construction site practice specifically.

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  • Non-linearity measure of a problem's crossover suitability

    Mason, Andrew (1995)

    Conference paper
    The University of Auckland Library

    An open access copy of this article is available and complies with the copyright holder/publisher conditions. For any problem with an unknown fitness function, justification of an evolutionary algorithm as a research method necessarily relies upon conjectures about that fitness function. This paper formulates apparent crossover partition coefficients (a generalisation of Walsh transforms) and uses these to develop a new model of crossover non-linearity ratios. Experimental runs demonstrate that this theory can offer insights into the apparent tractability of problems under crossover

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  • Effect of receiver capture and cochannel interference on PRMA

    Orange, M.D.; Sowerby, K.W. (1996)

    Conference paper
    The University of Auckland Library

    An open access copy of this article is available and complies with the copyright holder/publisher conditions. The performance of a speech-only cellular PRMA system is analysed in an interference limited Rayleigh faded environment. The inter-cell interference present in such a system can significantly increase the probability of packet loss as well as reduce the overall system utilisation. In this paper an ideal 2-branch signal/interference ratio selection diversity scheme has been shown to be effective in combating the level of inter-cell interference. A cellular PRMA system with a cluster size of 4 was found to be the most efficient, in terms of system utilisation and number of users per cell able to be supported

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  • Recovery effect in cellular radio systems

    Carter, L.J.; Maclean, T.S.M. (1990)

    Conference paper
    The University of Auckland Library

    An open access copy of this article is available and complies with the copyright holder/publisher conditions. A novel expression for the attenuation of a radio wave propagating over a mixed land-sea path successfully predicts the recovery of field strength over the sea path. An initial series of measurements has been made in the Auckland area to determine whether the recovery effect is a significant factor at cellular radio frequencies. The results presented are limited by the fact that they were taken in a real environment, rather than in controlled laboratory conditions. It is therefore difficult to eliminate unwanted variables, particularly the effects of clutter. Nevertheless, the results do show consistently that signal enhancement occurs over a sea-water path at cellular radio frequencies

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  • Flow-based resource allocation in a multiple-access wireless market-setting using an auction

    Roggendorf, Matthias; Beltran, Fernando (2006)

    Conference paper
    The University of Auckland Library

    An open access copy of this article is available and complies with the copyright holder/publisher conditions. This paper presents a flow-based, auction-driven approach to resource allocation. This approach allows mobile stations to simultaneously negotiate for resources from competing providers. We use an auction at each provider to decide on the resource allocation, based on the offers made by agents representing mobile nodes. All agents in the system try to maximise their utility gained from the total allocation of resources. The focus of this paper is on the bidding strategy of a mobile station when faced with the opportunity to obtain network resources from multiple sources. We support the proposed bidding strategy by simulation experiments, which show that the resulting allocation is efficient under the limited scope of the simulation setup.We also show that multiple-access can increase the allocation efficiency compared to the situation in which agents have access to only one network.

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  • A Paradigmatic and Methodological Examination of KM Research: 2000 to 2004

    Zining, Guo; Sheffield, Jim (2006)

    Conference paper
    The University of Auckland Library

    An open access copy of this article is available and complies with the copyright holder/publisher conditions. This study addresses a long-standing and well-recognized problem in KM research, namely the lack of a cumulative tradition. This problem is addressed by an intensive and critical review of the knowledge management literature that identifies gaps and recommends how these should be filled. KM articles are classified by research paradigm, research methodology, and research interest (technical, practical, and emancipatory). The survey methodology is intensive. Leading journals that publish significant knowledge management research are identified. All articles relevant to knowledge management, organizational learning, and organizational memory for the five-year period 2000-2004 are surveyed and classified by multiple reviewers. The key finding is that inquiry in KM is starkly unbalanced. Overuse of the positivist paradigm and its dominant research method (sample survey) prevents the exploitation of the highly relevant insights available via the use of the interpretivist and critical pluralist paradigms and the field study method.

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  • Design of heterogeneous embedded systems using DFCharts model of computation

    Radojevic, Ivan; Salcic, Zoran; Roop, Partha (2006)

    Conference paper
    The University of Auckland Library

    An open access copy of this article is available and complies with the copyright holder/publisher conditions. Dataflow process networks have been successfully used for modeling signal processing systems which are data-dominated. In this family of models, the most popular one is synchronous dataflow (SDF). On the other hand, hierarchical concurrent finite state machines (HCFSM) have been successfully employed for control-dominated systems. Most complex embedded systems are heterogeneous, consisting of both control-dominated and data-dominated parts. In this paper, we introduce a new model of computation, called DFCharts, which targets heterogeneous embedded systems. It combines the HCFSM (with Argos semantics) and SDF models. It has a formal, operational semantics based on Boolean automata with variables.

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  • Numerical Simulation of Electrolyte Two-Phase Flow Induced by Anode Bubbles in an Aluminum Reduction Cell

    Zhou, Naijun; Xue, Yuqing; Chen , John; Taylor, Mark (2007)

    Conference paper
    The University of Auckland Library

    An open access copy of this article is available and complies with the copyright holder/publisher conditions. In the production process of aluminium reduction cells, the anode bubble laden layer has several important influences on the performance of the aluminium reduction cells. Especially for a “drained cathode cell”, without the agitating of movement of the melted metal, the bath flow field could be more important. In this paper, the electrolyte two-phase flow fields were studied by using numerically simulation method based on a two-phase turbulence model combining the k - model and the Discrete Random Walk model. The results show that: the motion of the bubbles mostly exists within a thin layer under the anode, which results in inducing local electrolyte to flow around the anode in various circulation flows; the flow field in the anode-cathode space can be divided into three regions with different characters; the results also show the Driving action of bubbles is closely related to the current density, inclination of anode and the anode-cathode distance. In general, the increasing in the current density increases the electrolyte velocity and the turbulent kinetic energy. The decrease in ACD significantly enhances the uniformity of the electrolyte flow field in the anode-cathode space. The increase in anode inclination angle increases the velocity of the electrolyte in the anode-cathode space, which would be beneficial to improving the diffusion and dissolution of the alumina and reducing the resistance between the anode and cathode.

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  • The thermo-hydrodynamics of a concentric ohmic heater for processing dairy fluids.

    Tham, H.J.; Chen, X.D.; Young, B.; Zhang, L.; Duffy, G. (2007)

    Conference paper
    The University of Auckland Library

    An open access copy of this article is available and complies with the copyright holder/publisher conditions. The thermo-hydraulic performance of a 300W concentric annular ohmic heater was investigated. To minimize possible electrochemical reactions and corrosion, a higher frequency was applied and factors of field strength and frequency were studied. 2D computer simulation solving momentum, thermal and electrical energy was performed using the FlexPDE software. A good agreement between experimental and analytical analysis of static heating was obtained. There were significant differences between calculated and measured wall temperature near the entrance. The calculated outlet temperature was however in reasonable agreement with the experiment value.

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  • Talking Dirty

    McMeel, Dermott; Coyne, Richard; Lee, John (2005)

    Conference paper
    The University of Auckland Library

    We analyse the emergence and use of formal and informal communication tools in group working to aid in understanding the complexity of construction projects. Our test case is the design and build of an interactive digital installation in an exhibition space, involving students. After the project we conducted focus group studies to elicit insights into the effective use of the digital communications available for the project. We recount key insights from the study and examine how digital messaging devices are contributing to or hindering creative discussion. Whereas the construction process is concerned with the removal of dirt and re-ordering, in this paper we reflect on construction’s ritualistic, contractual and unauthorized aspects, and dirt’s role within them. We draw on Bakhtin’s theories of the carnival in exploring ritual, and the mixing of the un-sanctioned (rumour) with the official (contractual). How does dirt impinge on issues of communication, open discussion, and the move towards “partnering” in construction practice? We conjecture that while physical dirt might be unpleasant, the removal of other forms of metaphorical dirt hampers construction as an efficient and creative process.

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  • Habermasian Inquiring System: Toward a General Framework for Knowledge Management Research

    Zining, Guo; Sheffield, Jim (2006)

    Conference paper
    The University of Auckland Library

    This study addresses a long-standing and well-recognized problem in KM research, namely the lack of conceptual integration and a cumulative tradition. Knowledge management needs an overarching framework to unify and direct research. This paper reports on the development of such a framework. Elements of the proposed framework are created by synthesizing concepts from the systems thinking and critical thinking traditions. It is argued that the synthesis of aspects of Churchman's inquiring systems and Habermas' critical social theory provides a philosophically grounded, universally pragmatic framework useful in managing the complexity, and conceptualizing the richness, of knowledge phenomena. The key architectural element in this framework is Habermas' knowledge interests. Habermas' three knowledge interests (technical, practical and emancipatory) form a three-level integrating structure. Framework development consists of describing how four other design elements (Habermas' three rationalities, Churchman's roles, knowledge dynamics, and research paradigms) are positioned within this integrating structure.

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  • Architecture and implementation of an agent-based simulation tool for market-based pricing in Next-Generation Wireless Networks

    Roggendorf, Matthias; Beltran, Fernando; Gutierrez, Jairo (2006)

    Conference paper
    The University of Auckland Library

    An open access copy of this article is available and complies with the copyright holder/publisher conditions. We present a generic, agent-based simulation environment for dynamic pricing in next-generation wireless networks. While a lot of effort has been put into simulation platforms for recreating the behaviour of IP-based traffic in fixed and wireless networks, no standard platform for simulating different pricing schemes in such networks has yet emerged. Our work is driven by the vision of a ubiquitous wireless network environment, in which users can dynamically request network resources for various use from different, potentially competing network providers. For such a scenario, new pricing approaches are needed to charge the user according to dynamic factors such as current congestion levels or the the number of customers present at a specific location. The developed simulation environment serves as a generic tool for implementing and testing different pricing approaches.

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  • Modeling blood flow in the gastrointesinal system

    Mabotuwana, Thusitha; Pullan, A J; Smith, N P; Cheng, Leo K (2006)

    Conference paper
    The University of Auckland Library

    Compared to cardiac ischemia, relatively little is known about ischemia that develops within the gastrointestinal system. The work presented here is a first step towards developing a detailed anatomically and biophysically based model of the mesenteric arterial system of the human intestine to be used to simulate normal and compromised blood flows. Data from the Visible Human project were used to develop an initial model of the mesenteric arterial tree. Using this tree, equations that govern blood flow within extensible vessels were set up and solved for pressure, radius and velocity. Results were analyzed for the four distinct phases of cardiac contraction - diastole, isovolumic contraction, ejection and isovolumic relaxation and the profiles showing the temporally varying pressure and velocity within the network for a periodic input varying between 10.29 kPa (77 mmHg) and 14.63 kPa (110 mmHg) at the abdominal aorta are presented in this paper.

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  • The maternal, fetal and postnatal somatotrophic axes in intrauterine growth retardation.

    Oliver, MH; Bloomfield, FH; Harding, JE; Breier, BH; Bassett, NS; Gluckman, PD (1999)

    Conference paper
    The University of Auckland Library

    Both the maternal and fetal somatotrophic axes are closely linked to fetal substrate supply. Nutritional insults at critical stages of fetal development may lead to permanent reprogramming of the relationships between these factors. The consequences of reprogramming during fetal life may be harmful to metabolic, endocrine and cardiovascular homoeostatic mechanisms in postnatal life. The exact mechanisms that lead to reprogramming during fetal life need thorough investigation before effective strategies to deal with this problem can be devised.

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