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- AMS Subject Classification Primary 62K05 (1)
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Articles 31 - 60 of 60
Full-Text Articles in Physical Sciences and Mathematics
A New Approach To Teaching Software Risk Management With Case Studies, A. Fuller, P. Croll, L. Dei
A New Approach To Teaching Software Risk Management With Case Studies, A. Fuller, P. Croll, L. Dei
Faculty of Informatics - Papers (Archive)
Software development is inherently risky, however the need to adapt processes intended for larger organisations introduces a new element of risk. In addition, the nature of many new software products can be described as "critical" and therefore should undergo a formal risk assessment procedure. Despite the majority of software projects involving these additional elements of risk, risk management planning is virtually non-existent, as managers have not been trained in risk management. Few current software engineering curricula provide comprehensive coverage of risk, nor any practical experience in risk assessment. In this paper we propose that risk be repositioned in the software …
Golay Sequences For Ds Cdma Applications, Jennifer Seberry, Beata J. Wysocki, Tadeusz A. Wysocki
Golay Sequences For Ds Cdma Applications, Jennifer Seberry, Beata J. Wysocki, Tadeusz A. Wysocki
Faculty of Informatics - Papers (Archive)
Golay complementary sequences, often referred to as Golay pairs, are characterised by the property that the sum of their aperiodic autocorrelation functions equals to zero, except for the zero shift. Because of this property, Golay complementary sequences can be utilised to construct Hadamard matrices defining sets of orthogonal spreading sequences for DS CDMA systems of the lengths not necessary being a power of 2. In the paper, we present an evaluation, from the viewpoint of DS CDMA applications of some sets of spreading sequences based on Golay complementary sequences. We then modify those sets of sequences to enhance their correlation …
Asymptotic Inference For Spatial Cdfs Over Time, Jun Zhu, S N. Lahiri, Noel A. Cressie
Asymptotic Inference For Spatial Cdfs Over Time, Jun Zhu, S N. Lahiri, Noel A. Cressie
Faculty of Informatics - Papers (Archive)
A spatial cumulative distribution function (SCDF) is a random function that provides a statistical summary of a random process over a spatial domain of interest. In this paper, we consider a spatio-temporal process and establish statistical methodology to analyze changes in the SCDF over time. We develop hypothesis testing to detect a difference in the spatial random processes at two time points, and we construct a prediction interval to quantify such discrepancy in the corresponding SCDFs. Using a spatial subsampling method, we show that our inferences are valid asymptotically. As an illustration, we apply these inference procedures to test and …
Spatial Mixture Models Based On Exponential Family Conditional Distributions, M Kaiser, Noel A. Cressie, J Lee
Spatial Mixture Models Based On Exponential Family Conditional Distributions, M Kaiser, Noel A. Cressie, J Lee
Faculty of Informatics - Papers (Archive)
Spatial statistical models are applied in many problems for which dependence in observed random variables is not easily explained by a direct scientific mechanism. In such situations there may be a latent spatial process that acts to produce the observed spatial pattern. Scientific interest often centers on the latent process and the degree of spatial dependence that characterizes it. Such latent processes may be thought of as spatial mixing distributions. We present methods for the specification of flexible joint distributions to model spatial processes through multi-parameter exponential family conditional distributions. One approach to the analysis of these models is Monte …
Fast, Resolution-Consistent Spatial Prediction Of Global Processes From Satellite Data, Hsin-Cheng Huang, Noel A. Cressie, John Gabrosek
Fast, Resolution-Consistent Spatial Prediction Of Global Processes From Satellite Data, Hsin-Cheng Huang, Noel A. Cressie, John Gabrosek
Faculty of Informatics - Papers (Archive)
Polar orbiting satellites remotely sense the earth and its atmosphere, producing datasets that give daily global coverage. For any given day, the data are many and measured at spatially irregular locations. Our goal in this article is to predict values that are spatially regular at different resolutions; such values are often used as input to general circulation models (GCMs) and the like. Not only do we wish to predict optimally, but because data acquisition is relentless, our algorithm must also process the data very rapidly. This article applies a multiresolution autoregressive tree-structured model, and presents a new statistical prediction methodology …
The Estimation Of Continuous Pq Disturbance Levels In Distribution Systems, Victor J. Gosbell, D A. Robinson
The Estimation Of Continuous Pq Disturbance Levels In Distribution Systems, Victor J. Gosbell, D A. Robinson
Faculty of Informatics - Papers (Archive)
A simple method is given for estimating the continuous PQ disturbance level at a site. It is based on determining a "Voltage Distortion Increment" (VDI) for each segment of the network and then adding the VDIs from a given site back to an upstream site where levels are taken to be zero. The VDI is conveniently expressible in the form of S(MVA) times length (km), where "length" correspond to the physical length in the case of MV overhead lines and an equivalent length for other components. The method is verified by a comparison with field survey data. The voltage distortion …
Sources Of Error In Unbalance Measurements, Victor J. Gosbell, H Herath, Sarath Perera, D A. Robinson
Sources Of Error In Unbalance Measurements, Victor J. Gosbell, H Herath, Sarath Perera, D A. Robinson
Faculty of Informatics - Papers (Archive)
The paper aims to assess sources of error in attempting to meet standards for the measurement and reporting of negative sequence voltage unbalance. This is of importance when making use of low performance instrumentation where three difficulties may arise: (i) rms voltages rather than the fundamental is used; (ii) the magnitude but not the phase of line-neutral voltages are available; and (iii) voltage values are averaged over a period longer than standards require. The presence of harmonics at normal levels is shown to give negligible error on unbalance calculations. When lineneutral voltages are used, and zero sequence is present, the …
Cohomology Of Buildings And Finiteness Properties Of An-Groups, Jacqueline Ramagge, Wayne W. Wheeler
Cohomology Of Buildings And Finiteness Properties Of An-Groups, Jacqueline Ramagge, Wayne W. Wheeler
Faculty of Informatics - Papers (Archive)
Borel and Serre calculated the cohomology of the building associated to a reductive group and used the result to deduce that torsion-free S-arithmetic groups are duality groups. By replacing their group-theoretic arguments with proofs relying only upon the geometry of buildings, we show that Borel and Serre's approach can be modied to calculate the cohomology of any locally nite ane building. As an application we show that any nitely presented e An-group is a virtual duality group. A number of other niteness conditions for e An-groups are also established.
Use Of Cryoelectronics To Reduce Power Losses, Christopher J. Hawley, Steve Gower, Dominic Cuiuri
Use Of Cryoelectronics To Reduce Power Losses, Christopher J. Hawley, Steve Gower, Dominic Cuiuri
Faculty of Informatics - Papers (Archive)
The operational characteristics of power electronics operating at ambient temperatures are well known. Less well known are the characteristics of these devices when operating at cryogenic temperatures. This emerging field is known as cryoelectronics. The primary driver for operation at reduced temperatures is the promise of a resultant reduction in device operation losses. The operating characteristics of Metal Oxide Silicon Field Effect Transistors (MOSFETs) and Insulated Gate Bipolar Transistors (IGBTs) at Liquid Nitrogen (LN) temperature have been experimentally analysed. The results have been used to evaluate the viability of using cryoelectronics in medium - high power applications, considering trade-offs between …
Modelling Of High Temperature Superconducting Wires And Coils, Christopher David Cook, T Hardono
Modelling Of High Temperature Superconducting Wires And Coils, Christopher David Cook, T Hardono
Faculty of Informatics - Papers (Archive)
This paper discusses modelling techniques for high temperature superconducting (HTSC) wires and coils. Models are developed based on the behaviour of Bi-2223/Ag wires and coils. For many power-engineering applications it is necessary to form HTSC wires into coils. PSpice models for HTSC coils will be presented in this paper. The aim is to develop models for HTSC wires and coils so that they can be treated as circuit elements in PSpice. The critical current of a coil will in general be different from the wire it is manufactured from and this change in current for a HTSC coil will be …
Sensorless Force Estimation For Robots With Friction, John L. Simpson, Christopher David Cook, Zheng Li
Sensorless Force Estimation For Robots With Friction, John L. Simpson, Christopher David Cook, Zheng Li
Faculty of Informatics - Papers (Archive)
No abstract provided.
Cmos Sensor Cross-Talk Compensation For Digital Cameras, Wanqing Li, Philip Ogunbona, Yu Shi, Igor Kharitonenko
Cmos Sensor Cross-Talk Compensation For Digital Cameras, Wanqing Li, Philip Ogunbona, Yu Shi, Igor Kharitonenko
Faculty of Informatics - Papers (Archive)
This paper presents two algorithms for removing the cross-talk effect in CMOS sensor based color-imaging systems. The algorithms work on the Bayer raw data and have low computational complexity. Experimental results on Macbeth color chart and real images demonstrated that both algorithms can effectively eliminate the cross-talk effect and produce better quality images with conventional color interpolation and correction algorithms designed for CCD image sensors. Complexity of the algorithms is also analyzed.
Modelling Of Color Cross-Talk In Cmos Image Sensors, Wanqing Li, Philip Ogunbona, Yan Shi, Igor Kharitonenko
Modelling Of Color Cross-Talk In Cmos Image Sensors, Wanqing Li, Philip Ogunbona, Yan Shi, Igor Kharitonenko
Faculty of Informatics - Papers (Archive)
This paper presents a way to model the cross-talk effect in CMOS image sensors. Two algorithms are derived from the model; both of them work on the Bayer raw data and have low computational complexity. Experiments on Macbeth color chart and real images have shown the effectiveness of the modeling to eliminate the cross-talk effect and produce better quality images with traditional color interpolation and correction algorithms designed for CCD image sensors.
Method Of Color Interpolation In A Single Sensor Color Camera Using Green Channel Separation, Chaminda Weerasinghe, Igor Kharitonenko, Philip Ogunbona
Method Of Color Interpolation In A Single Sensor Color Camera Using Green Channel Separation, Chaminda Weerasinghe, Igor Kharitonenko, Philip Ogunbona
Faculty of Informatics - Papers (Archive)
This paper presents a color interpolation algorithm for a single sensor color camera. The proposed algorithm is especially designed to solve the problem of pixel crosstalk among the pixels of different color channels. Interchannel cross-talk gives rise to blocking effects on the interpolated green plane, and also spreading of false colors into detailed structures. The proposed algorithm separates the green channel into two planes, one highly correlated with the red channel and the other with the blue channel. These separate planes are used for red and blue channel interpolation. Experiments conducted on McBeth color chart and natural images have shown …
Digital Watermarks For Copyright Protection, Nicholas Paul Sheppard, Reihaneh Safavi-Naini, Philip Ogunbona
Digital Watermarks For Copyright Protection, Nicholas Paul Sheppard, Reihaneh Safavi-Naini, Philip Ogunbona
Faculty of Informatics - Papers (Archive)
It is feared that the ease with which digital media can be copied will lead to a proliferation of copyright infringement. One proposed technical solution is digital watermarking, which embeds a hidden signal into host data that can be used in a variety of protocols that attempt to either prevent or deter copyright infringement. In this paper, we give a brief overview of digital watermarking and discuss some of the issues involved in providing effective digital watermarking systems for deterring copyright infringement.
Evaluating The Optimal Probability Distribution For Steganography Under Zero-Error Conditions, Gareth Brisbane, Reihaneh Safavi-Naini, Philip Ogunbona
Evaluating The Optimal Probability Distribution For Steganography Under Zero-Error Conditions, Gareth Brisbane, Reihaneh Safavi-Naini, Philip Ogunbona
Faculty of Informatics - Papers (Archive)
Information hiding can be performed under the guise of a digital image. We consider the following scenario: Alice and Bob share an image and would like to use it as a cover image to communicate a message m. We are interested in answering two questions: What is the maximum amount of information that can be sent for a given level of degradation to an image? and How can this level of efficiency be achieved in practice? We require the recovered message to be the same as the embedded one. Our model begins with Alice compressing a message to obtain a …
A Hybrid Approach To The Core Curriculum, I. Piper, P. Castle, A. Fuller, G. Awyzio
A Hybrid Approach To The Core Curriculum, I. Piper, P. Castle, A. Fuller, G. Awyzio
Faculty of Informatics - Papers (Archive)
In this paper we review the IEEE/ACM CC2001 model. We then describe our proposed core CS curriculum comprising four strands: programming languages, algorithms, discrete mathematics and systems. These sequences are to be taught over the first two years of the Bachelor of Computer Science Degree and need to be taken in parallel.
An Architecture For Carrier Grade Programmable Networks, T. V. Nguyen, P. Boustead, Farzad Safaei
An Architecture For Carrier Grade Programmable Networks, T. V. Nguyen, P. Boustead, Farzad Safaei
Faculty of Informatics - Papers (Archive)
Active and programmable networks allow innovative new services to be deployed rapidly. However, in a carrier grade network, it is imperative to maintain a scalable fast path mechanism so that the delay and throughput requirements are met. This is particularly important since, in many cases, network-level processing is only needed for a subset of packets and the remainder of traffic must be forwarded on the fast path. It is a challenge to design a cost effective node architecture that can satisfy this requirement. Current models are often 'revolutionary' and may not scale to the required performance levels of a carrier …
Generalised Minimum Variance Control Of Linear Time-Varying Systems, Zheng Li, R. J. Evans
Generalised Minimum Variance Control Of Linear Time-Varying Systems, Zheng Li, R. J. Evans
Faculty of Informatics - Papers (Archive)
The problem of generalised minimum variance control of linear time-varying discrete-time systems is studied. Standard time-varying controlled autoregressive moving average models are considered, and the sum of plant output tracking error variance plus a penalty term on plant input is chosen as the cost functional. The time-varying controller described is able to minimise the generalised tracking error variance and guarantees closed-loop exponential stability for a large class of linear time-varying systems, including plants which have long time delays and are not stably invertible.
The Analysis Of Zheng-Seberry Scheme, D. Soldera, Jennifer Seberry, C. Qu
The Analysis Of Zheng-Seberry Scheme, D. Soldera, Jennifer Seberry, C. Qu
Faculty of Informatics - Papers (Archive)
The Zheng-Seberry (ZS) encryption scheme was published in 1993 and was one of the first practical schemes that was considered secure against a chosen ciphertext adversary. This paper shows some problems that the semantic security of the one-way hash variant of the ZS scheme is insecure on some special circumstances. Attempts to modify the ZS scheme resulted on an El-Gamal variant that is provably secure in the random oracle model.
Short Amicable Sets, S. Georgiou, C. Koukouvinos, Jennifer Seberry
Short Amicable Sets, S. Georgiou, C. Koukouvinos, Jennifer Seberry
Faculty of Informatics - Papers (Archive)
Abstract: A pair of matrices X and Y are said to be amicable if XYT = YXT. In this paper, if X and Y are orthogonal designs, group generated or circulant on the group G, these will be denoted 2—SAS(n; ul, u2; G). Recently Kharaghani, in "Arrays for orthogonal designs", J. Combin. Designs, 8 (2000), 166-173, extended this concept to an amicable set, {Ai}2n, i=1, of 2n circulant matrices, which satisfy ∑(Aσ(2i-1)AT σ(2i-1) - Aσ(2i) AT (2i-1) = 0. In this paper we concentrate on constructing short amicable sets, which satisfy the same equation but contain four, called short, or …
The Invariance Principle For Linear Processes With Applications, Q. Wang, Y. X. Lin, C. M. Gulati
The Invariance Principle For Linear Processes With Applications, Q. Wang, Y. X. Lin, C. M. Gulati
Faculty of Informatics - Papers (Archive)
Let Xt be a linear process defined by [refer paper], where [refer paper] is greater than or equal to 0 is a sequence of real numbers and (ek, k = 0, plus or minus 1, plus or minus 2, ...) is a sequence of random variables. Two basic results, on the invariance principle of the partial sum process of the Xt converging to a standard Wiener process on [0,1], are presented in this paper. In the first result, we assume that the innovations ek are independent and identically distributed random variables but do not restrict [refer paper]. We note that, …
The Effect Of Using Household As A Sampling Unit, Robert Graham Clark, David G. Steel
The Effect Of Using Household As A Sampling Unit, Robert Graham Clark, David G. Steel
Faculty of Informatics - Papers (Archive)
The effect of sampling people through households is considered. Results on design effects for two stage surveys are reviewed and applied to give design effects of household samples. The main factors that determine the design effect are identified for the designs in which one person, or all people, are selected from each selected household.Within household correlation is one factor.We show that the relationships between household size and the mean and variance within households are also important factors. Census and survey data are used to empirically compare the design effects for a range of estimators, variables and designs.
Keeping E-Business In Perspective, Tim Coltman, T. M. Devinney, A. S. Latukefu, D. F. Midgley
Keeping E-Business In Perspective, Tim Coltman, T. M. Devinney, A. S. Latukefu, D. F. Midgley
Faculty of Informatics - Papers (Archive)
The article reveals that not all business fit the model of electronic business (e-business). Since the bubble burst in April 2000, many have become pessimistic about the future of e-business. Having been through process reengineering, enterprise resource planning, and now e-business with disappointing results, experienced managers are wary of large IT investments. Multiple failures in B2C, B2B, and other forms of e-business have raised questions regarding the pace at which the networked economy is emerging and ultimately the suitability of e-business for many firms. Claims that e-business is driving revolutionary business change are misleading and only partly correct. The most …
Executive Information Systems Use In Organisational Contexts: Understanding The User Behaviour, George Ditsa
Executive Information Systems Use In Organisational Contexts: Understanding The User Behaviour, George Ditsa
Faculty of Informatics - Papers (Archive)
Executive Information Systems (EIS) are designed to enhance the managerial roles of top-level managers in organizations. Despite reports of the growing popularity of EIS, there are reports of low usage of these systems that, in part, contributes to their failures in organizations. Majority ofprior EIS research has focused on documenting the features, benefits, development methodologies, and implementation of the systems. Regrettably, there are very few studies addressing the problem of low EIS usage. This paper reports on a research in progress on the use ofEIS in organizational settings. The primary focus ofthe research is to investigate factors that explain users' …
Electronic Commerce And Market Focus: Some Findings From A Study Of Swedish Small To Medium Enterprises, Lejla Vrazalic, Robert Macgregor, Deborah Bunker, Sten Carlsson, Monika Magnusson
Electronic Commerce And Market Focus: Some Findings From A Study Of Swedish Small To Medium Enterprises, Lejla Vrazalic, Robert Macgregor, Deborah Bunker, Sten Carlsson, Monika Magnusson
Faculty of Informatics - Papers (Archive)
In the past, organisations relied on traditional quantitative metrics, such as return on investment (ROI) to make decisions when investing in technology. With the advent of electronic commerce (EC), these decisions are becoming less reliant on ROI measures. Instead different driving forces are taking precedence in the decision making process. This paper presents the findings of a study of 118 Swedish small to medium enterprises (SMEs) that have adopted EC. The results of the study suggest that improvements to customer service, internal efficiency and organisational competitiveness have become equally important when making EC investment decisions. The study also examined whether …
Ripple Signal Amplification In Distribution Systems: A Case Study, B. S. Perera, K. Nguyen, V. J. Gosbell, N. Browne, S. Elphick, J. Stones
Ripple Signal Amplification In Distribution Systems: A Case Study, B. S. Perera, K. Nguyen, V. J. Gosbell, N. Browne, S. Elphick, J. Stones
Faculty of Informatics - Papers (Archive)
Use of high frequency ripple signals for the control of loads such as off-peak hot water systems and street lighting systems is common within distribution utilities. Although injected signal levels are small and within stipulated limits, in distribution systems dominated by underground cables the signal levels received at the load ends can be relatively large due to resonance. One significant problem associated with the excessive signal levels is racing digital clocks caused by the additional zero crossings of the mains waveform. This paper presents the results from a detailed modelling study undertaken on a 22 kV system. The dependency of …
Neuron-Adaptive Higher Order Neural-Network Models For Automated Financial Data Modeling, M. Zhang, S. Xu, J. Fulcher
Neuron-Adaptive Higher Order Neural-Network Models For Automated Financial Data Modeling, M. Zhang, S. Xu, J. Fulcher
Faculty of Informatics - Papers (Archive)
Real-world financial data is often nonlinear, comprises high-frequency multipolynomial components, and is discontinuous (piecewise continuous). Not surprisingly, it is hard to model such data. Classical neural networks are unable to automatically determine the optimum model and appropriate order for financial data approximation. We address this problem by developing neuron-adaptive higher order neural-network (NAHONN) models. After introducing one-dimensional (1-D), two-dimensional (2-D), and n-dimensional NAHONN models, we present an appropriate learning algorithm. Network convergence and the universal approximation capability of NAHONNs are also established. NAHONN Group models (NAHONGs) are also introduced. Both NAHONNs and NAHONGs are shown to be "open box" and …
Hadamard Matrices, Orthogonal Designs And Construction Algorithms, S. Georgiou, C. Koukouvinos, Jennifer Seberry
Hadamard Matrices, Orthogonal Designs And Construction Algorithms, S. Georgiou, C. Koukouvinos, Jennifer Seberry
Faculty of Informatics - Papers (Archive)
We discuss algorithms for the construction of Hadamard matrices. We include discussion of construction using Williamson matrices, Legendre pairs and the discret Fourier transform and the two circulants construction. Next we move to algorithms to determine the equivalence of Hadamard matrices using the profile and projections of Hadamard matrices. A summary is then given which considers inequivalence of Hadamard matrices of orders up to 44. The final two sections give algorithms for constructing orthogonal designs, short amicable and amicable sets for use in the Kharaghani array.
An Infinite Family Of Hadamard Matrices With Fourth Last Pivot N/2, C. Koukouvinos, M. Mitrouli, Jennifer Seberry
An Infinite Family Of Hadamard Matrices With Fourth Last Pivot N/2, C. Koukouvinos, M. Mitrouli, Jennifer Seberry
Faculty of Informatics - Papers (Archive)
We show that the equivalence class of Sylvester Hadamard matrices give an infinite family of Hadamard matrices in which the fourth last pivot is n/2 . Analytical examples of Hadamard matrices of order n having as fourth last pivot n/2 are given for n = 16 and 32. In each case this distinguished case with the fourth pivot n/2 arose in the equivalence class containing the Sylvester Hadamard matrix.