1,298 results for Conference paper

  • Fuzzy exposure model

    Rajkumar, T.; Guesgen, Hans 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. This paper presents a fuzzy exposure model which deals with the uncertainties involved in analysing prolonged (chronic) chemical exposure for humans in risk assessment. The imprecise input information for the exposure model is expressed as fuzzy sets using linguistic variables such as high, low and constant. The risk assessor can extend these fuzzy sets with respect to the data availability. The result obtained from the calculations is a fuzzy number that indicates the life average daily exposure (LADE) to human beings. A case study is illustrated to present the methodology

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  • Self synchronising T-codes to replace Huffman codes

    Higgie, Gavin R. (1993)

    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 describes recent work on the T-Codes, which are a new class of variable length codes with superlative selfsynchronizing properties. The T-Code construction algorithm is outlined, and it is shown that in situations where codeword synchronization is important the T-Codes can be used instead of Huffman codes, giving excellent self-synchronizing properties without sacrificing coding efficiency

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  • Detecting termination in static and dynamic systems

    Ye, Xinfeng; Keane, John A. (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. Distributed termination detection concerns detecting the termination of a distributed computation spread across a set of processors. Most solutions to the problem are not intended for dynamic systems where processes can be created and destroyed during the computation. In this paper, a termination detection algorithm which can be applied to both static and dynamic systems is proposed. The scheme can be applied to any kind of connection topology. The number of control messages is lower than some previous approaches

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  • IMECO: A reconfigurable FPGA-based image enhancement co-processor framework

    Salcic, Z.; Sivaswamy, J. (1997)

    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 way to improve the computational speed of image contrast enhancement using low-cost FPGA-based hardware primarily targeted to X-ray images. The enhancement method considered here consists of filtering via the high boost filter (HBF), followed by histogram modification using histogram equalisation (HE). An image enhancement co-processor (IMECO) concept is proposed that enables efficient hardware implementation of enhancement procedures and hardware/software co-design to achieve high-performance, low-cost solutions. The co-processor runs on an FPGA prototyping ISA-bus board. It consists of two hardware functional units that implement HBF and HE and can be downloaded onto the board sequentially or reside on the board at the same time. These units represent an embryo of virtual hardware units that form a library of image enhancement algorithms. In trials with chest X-ray images performance improvement over software-only implementations was more than two orders of magnitude, thus providing real-time or near real-time enhancement

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  • Qualitative spatial reasoning under uncertainty in geographical information systems

    Loerch, Ute; Guesgen, Hans W. (1997)

    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 capability of geographical information systems (GIS) to display images and analyse them is one of the most powerful features, because people have a very consistent ability to reason about visual features according to their own knowledge model. Usually the abilities of GIS are restricted in dealing with quantitative data only, so that they fail whenever exact matches cannot be found. A solution to this problem is not only to allow the quantitative information, but also qualitative one. Proximity factors such as `close to' and `far from' are included. The qualitative approach offers a more natural way for the user of the system to specify what he actually wants, by using the proximity operators. This paper is an attempt of integrating qualitative spatial reasoning into geographic information systems. The idea is to associate qualitative information with fuzzy sets and to use the values of these fuzzy sets for spatial reasoning. The authors are concerned with the problem of image interpretation, which stands for the geometric and semantic recognition of the objects contained in one image

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  • Processing temporal aggregates in parallel

    Ye, Xinfeng; Keane, John A. (1997)

    Conference paper
    The University of Auckland Library

    An open access copy of this article is available and complies with the copyright holder/publisher conditions. Temporal databases maintain past, present and future data. TSQL2 is a query language designed for temporal databases. In TSQL2, the GROUP BY clause has the temporal grouping property. In temporal grouping, the time line of each attribute value is partitioned into several sections, and aggregate functions are computed for each time partition. This paper describes two approaches to parallelising an algorithm for computing temporal aggregates. The two approaches have been implemented on an SGI PowerChallenge SMP parallel system. The experimental results show that the performance of the two approaches depends on data skew ratio and the number of processors used in the computation

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  • Petri net-based visual language for specifying GUIs

    Li, Xiaosong; Mugridge, Warwick B.; Hosking, John G. (1997)

    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 describe PUIST, a visual language for graphical interface specification and prototyping. PUIST uses a Petri net notation, with a declarative means of defining nets which have complex, yet regular interconnections. This significantly improves the understandability of large specifications, permitting PUIST to be used for complex interface component specification and prototyping

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  • Petri net-based environment for GUI design

    Li, Xiaosong; Mugridge, Warwick B.; Hosking, John G. (1997)

    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 describe PUIST, a visual environment for graphical user interface specification and prototyping. PUIST uses a Petri net notation, with a declarative means of defining nets which have complex, yet regular interconnections. This significantly improves the understandability of large specifications, permitting PUIST to be used for complex interface component specification, analysis and prototyping

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  • Vising object-oriented techniques for integrated network management modeling

    Gutierrez, J.A. (1997)

    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 explains the main concepts associated with the definition of an integrated network management environment (INME) using object-oriented network models, and it proposes an extension to the OSI (Open Systems Interconnection) Reference Model by using three different models that are specified in an integrated way. The extended model incorporates the “de facto” standards used for Internet network management. A basic knowledge of the Internet and OSI-based network management systems is assumed

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  • Analysis of chemical exposure through inhalation using hybrid neural network

    Rajkumar, T.; Guesgen, Hans W. (1997)

    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 analysis, human health risk through inhalation due to exposure to Benzene from vehicular emissions in New Zealand is assessed as an example of the application of a hybrid neural network. Exposure factors affecting the inhalation are inhaled contaminant, age, body weight, health status and activity patterns of humans. There are four major variables affecting the inhaled contaminant viz., gas emissions from motor vehicles on the road, wind speed, temperature and atmospheric stability. The topic of uncertainty applies equally to all variables involved in exposure analysis. Neural network and fuzzy theory is implemented to solve the uncertainty, which exists to a greater extent. The architecture of hybrid neural network that is used to estimate the exposure of carcinogens through inhalation is explained in detail in this paper

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  • Towards more practical reinforcement learning

    Qualtrough, Paul (1997)

    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 fields of machine learning, mobile robotics and machine vision have grown steadily closer in recent years, to the extent that learning has been suggested as the best means of producing sophisticated controllers for mobile robots. Such an approach may have merit, but only if the structures and mechanisms provided for learning are tuned to the special needs of robots. These needs are outlined, and reinforcement learning is promoted as the best starting point for fulfilling them. In order to make good on the promise of learning to the level required of mobile robots, significant enhancements are required to current formulations of reinforcement learning. The issues involved in making improvements are discussed, and a simple enhanced model of reinforcement learning is suggested as a first step in this direction

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  • Iterative blind deconvolution of extended objects

    Biggs, David S.C.; Andrews, Mark (1997)

    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 describes a technique for the blind deconvolution of extended objects such as the Hubble Space Telescope (HST), scanning electron and 3D fluorescence microscope images. The blind deconvolution mechanism is based on the Richardson-Lucy (1972, 1974) algorithm and alternates between deconvolution of the image and point spread function (PSF). This form of iterative blind deconvolution differs from that typically employed in that multiple PSF iterations are performed after each image iteration. The initial estimate for the PSF is the autocorrelation of the blurred image and the edges of the image are windowed to minimise wrap around artifacts. Acceleration techniques are employed to speed restoration and results from real HST, electron microscope and 3D fluorescence images are presented

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  • Mining association rules with composite items

    Ye, Xinfeng; Keane, John A. (1997)

    Conference paper
    The University of Auckland Library

    An open access copy of this article is available and complies with the copyright holder/publisher conditions. Association rules can be used to express relationships between items of data. The process of mining associations rules is to analysis the data in a database to discover “interesting” rules. Existing algorithms for mining association rules require that a record in the database contain all the data items in a rule. This requirement makes it difficult to discover certain useful rules in some applications. To solve the problem, this paper describes an algorithm for mining association rules with composite items. The algorithm has the potential to discover rules which cannot be discovered by existing algorithms

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  • Application of variable structure control techniques for improving power system dynamic stability

    Samarasinghe, V.G.D.C.; Pahalawaththa, N.C. (1993)

    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, a second order PQ-coupled difference equation load model (PQ-DELM) is derived, which takes the interrelation between active and reactive currents into account. Load modeling is revealed to be a closed loop identification problem, and for the parameter estimation of the PQ-DELM an instrumental variable (IV) algorithm is put forward. The field test of actual load and the test in the laboratory validate the PQ-DELM and the IV algorithm

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  • Robust stabilization of time delay nonlinear systems with a triangular structure

    Nguang, Sing Kiong (1997)

    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 examine the problem of robust stabilization of time-delay nonlinear systems which are in parametric strict feedback form. We propose an iterative procedure of stabilizing controller construction similar to backstepping procedure for this class of time-delay nonlinear systems

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  • Breaking abstractions and unstructuring data structures

    Collberg, Christian; Thomborson, Clark; Low, Douglas (1998)

    Conference paper
    The University of Auckland Library

    An open access copy of this article is available and complies with the copyright holder/publisher conditions. To ensure platform independence, mobile programs are distributed in forms that are isomorphic to the original source code. Such codes are easy to decompile, and hence they increase the risk of malicious reverse engineering attacks. Code obfuscation is one of several techniques which has been proposed to alleviate this situation. An obfuscator is a tool which-through the application of code transformations-converts a program into an equivalent one that is more difficult to reverse engineer. In a previous paper (Collberg et al., 1998) we have described the design of a control flow obfuscator for Java. In this paper we extend the design with transformations that obfuscate data structures and abstractions. In particular we show how to obfuscate classes, arrays, procedural abstractions and built-in data types like strings, integers and booleans

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  • Fuzzy spatial reasoning in psycholinguistic experiments on braille reading

    Rodrigo, Surangi; Guesgen, Hans W. (1998)

    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 introduces a system for data collection and analysis of Braille reading experiments undertaken by psycholinguists. The system is intended as a replacement for the conventional collection of data by analogue video and the analysis of it by watching the video tapes. It takes a Braille reading movie and converts it into an abstract representation by taking into consideration the position of the reading finger and user-defined regions of the text. The spatial analysis module used by the system applies a set of efficient algorithms for reasoning about space and time, which allow for fuzziness in the spatial information (but do not exploit fuzzy logic in the traditional sense)

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  • Influence of correlated shadowing and base station configuration on in-building system capacity

    Butterworth, K.S.; Sowerby, K.W.; Williamson, A.G.; Neve, M.J. (1998)

    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 illustrates the impact of base station deployment on the performance of an indoor DS-CDMA system. It is shown that system performance can be altered dramatically by changing the base station configuration. Correlated shadowing is a significant factor contributing to the wide range of performance results. Outage probability analyses indicate that substantial capacity improvements can be achieved at the expense of increased complexity in the base station deployment scheme

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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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  • Efficient frequency conversion in optical fibers with tailored birefringence

    Murdoch, S.G.; Rong, Z.; Leonhardt, R.; Harvey, J.D. (1998)

    Conference paper
    The University of Auckland Library

    An open access copy of this article is available and complies with the copyright holder/publisher conditions. Four wave mixing in optical fibers has long been recognised as important method of generating new optical frequencies. The process holds promise as a means of wavelength switching for optical communications, but the presence of a nonlinear term in the phase-matching condition normally prevents strong energy exchange between the waves. We present here a scheme for optimising the conversion efficiency. The four wave mixing process considered here is called polarisation modulation instability (PMI) where a strong pump wave on one axis of a birefringent fiber results in the growth of two equally detuned sidebands on the other axis. In the absence of any external seed the sidebands start to grow with a frequency shift f0 where the wavevector mismatch is zero. This mismatch is a function of the power of the pump and the fibre's birefringence, dispersion, and nonlinearity. Our analysis of the evolution of the power in the sidebands utilises three coupled mode equations which describe the interaction of a monochromatic pump, with a pair of sidebands polarised along the orthogonal fibre axis. In the absence of Raman gain, it is possible to solve these equations so that by varying the birefringence along the fibre, the sidebands with a frequency shift of f 0 are phase matched for the entire length of the fibre

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