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Faculty of Informatics - Papers (Archive)

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Articles 1591 - 1620 of 2013

Full-Text Articles in Physical Sciences and Mathematics

Digital Watermarks For Copyright Protection, Nicholas Paul Sheppard, Reihaneh Safavi-Naini, Philip Ogunbona Jan 2002

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.

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Evaluating The Optimal Probability Distribution For Steganography Under Zero-Error Conditions, Gareth Brisbane, Reihaneh Safavi-Naini, Philip Ogunbona Jan 2002

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 …

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A Hybrid Approach To The Core Curriculum, I. Piper, P. Castle, A. Fuller, G. Awyzio Jan 2002

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.

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An Architecture For Carrier Grade Programmable Networks, T. V. Nguyen, P. Boustead, Farzad Safaei Jan 2002

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 …

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Generalised Minimum Variance Control Of Linear Time-Varying Systems, Zheng Li, R. J. Evans Jan 2002

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.

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The Analysis Of Zheng-Seberry Scheme, D. Soldera, Jennifer Seberry, C. Qu Jan 2002

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.

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Short Amicable Sets, S. Georgiou, C. Koukouvinos, Jennifer Seberry Jan 2002

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 …

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The Invariance Principle For Linear Processes With Applications, Q. Wang, Y. X. Lin, C. M. Gulati Jan 2002

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, …

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The Effect Of Using Household As A Sampling Unit, Robert Graham Clark, David G. Steel Jan 2002

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.

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Keeping E-Business In Perspective, Tim Coltman, T. M. Devinney, A. S. Latukefu, D. F. Midgley Jan 2002

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 …

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Executive Information Systems Use In Organisational Contexts: Understanding The User Behaviour, George Ditsa Jan 2002

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' …

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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 Jan 2002

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 …

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Ripple Signal Amplification In Distribution Systems: A Case Study, B. S. Perera, K. Nguyen, V. J. Gosbell, N. Browne, S. Elphick, J. Stones Jan 2002

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 …

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Neuron-Adaptive Higher Order Neural-Network Models For Automated Financial Data Modeling, M. Zhang, S. Xu, J. Fulcher Jan 2002

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 …

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Hadamard Matrices, Orthogonal Designs And Construction Algorithms, S. Georgiou, C. Koukouvinos, Jennifer Seberry Jan 2002

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.

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An Infinite Family Of Hadamard Matrices With Fourth Last Pivot N/2, C. Koukouvinos, M. Mitrouli, Jennifer Seberry Jan 2002

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.

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Why Software Engineering Is Riskier Than Ever, A. Fuller, P. Croll, O. Garcia Dec 2001

Why Software Engineering Is Riskier Than Ever, A. Fuller, P. Croll, O. Garcia

Faculty of Informatics - Papers (Archive)

The ultimate aim of software engineering methods and tools is to reduce risks associated with the development of software products. Accepted risk management procedures recognize that software development is inherently risky, however fail to take into account the changing nature of both software products and the organizations undertaking their development. SE research has traditionally focused on the needs of very large corporations undertaking equally mammoth and complex development projects, thus most tools and methods are predicated on this model. Yet most software development is undertaken by small to medium enterprises. Consequently, these development efforts are either undertaken with little or …

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A New Cryptanalytic Method Using The Distribution Characteristics Of Substitution Distances, B. Song, H. Wang, Jennifer Seberry Dec 2001

A New Cryptanalytic Method Using The Distribution Characteristics Of Substitution Distances, B. Song, H. Wang, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

In this paper, we suggest a new method for cryptanalysis of the basic structures of the block ciphers having SP network structure. The concept of the substitution difference is introduced and the distribution characteristics of substitution distances in an S-box is developed. This gives clues for cryptanalysis of the cipher. We then examine if this method is applicable to cryptanalysis of Rijndael. We present the method for cryptanalysis of the first round of Rijndael including the initial Round-Key addition part in order to illustrate our new method.

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Plant Acoustic Density Profile Model Of Ctfm Ultrasonic Sensing, Phillip J. Mckerrow, N. Harper Dec 2001

Plant Acoustic Density Profile Model Of Ctfm Ultrasonic Sensing, Phillip J. Mckerrow, N. Harper

Faculty of Informatics - Papers (Archive)

Many applications require the sensing of plants. When an ultrasonic sensor insonifies a plant, the resultant echo is the superposition of the echoes from the leaves. As a result, the echo contains information about the geometric structure of the foliage. In this paper, we present a model of sensing that facilitates the extraction of geometric features from the echo for plant classification, recognition and discrimination. We model the echo from a CTFM ultrasonic sensor with the acoustic density profile model. Then, we identify a set of features that represent plant geometric characteristics and use these to perform an inverse transform …

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Fuzzy Clustering Evaluation Of Time-Frequency Distribution (Tfd) Schemes For Audio Stream Segregation, M. A. Jackson, I. Burnett Dec 2001

Fuzzy Clustering Evaluation Of Time-Frequency Distribution (Tfd) Schemes For Audio Stream Segregation, M. A. Jackson, I. Burnett

Faculty of Informatics - Papers (Archive)

Audio stream segregation is a task performed constantly by the human auditory system, yet is difficult to reproduce with a computer. The research detailed in this paper looks at performing just one method of stream segregation - the temporal coherence boundary - using a fuzzy clustering system. The main focus of the paper is on examining the effectiveness of several time-frequency distributions as the feature vectors for the system. Three time-frequency distributions are examined and their effectiveness evaluated in terms of correct separation and computational complexity. The main evaluation compares the popular gamma-tone filter bank with the MPEG-7 audio spectrum …

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Using Boosting To Simplify Classification Models, V. Wheway Nov 2001

Using Boosting To Simplify Classification Models, V. Wheway

Faculty of Informatics - Papers (Archive)

Ensemble classification techniques such as bagging, boosting and arcing algorithms have been shown to lead to reduced classification errors on unseen cases and seem immune to the problem of overfitting. Several explanations for the reduction in generalisation error have been presented, with recent authors defining and applying diagnostics such as "edge" and "margin". These measures provide insight into the behaviour of ensemble classifiers, but can they be exploited further? In this paper, a four-stage classification procedure in introduced, which is based on an extension of edge and margin analysis. This new procedure allows inverse sub-contexts and difficult border regions to …

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Control Of Servo Systems In The Presence Of Motor-Load Inertia Mismatch, Jeffrey W. Moscrop, C. Cook, P. Moll Nov 2001

Control Of Servo Systems In The Presence Of Motor-Load Inertia Mismatch, Jeffrey W. Moscrop, C. Cook, P. Moll

Faculty of Informatics - Papers (Archive)

There are a number of performance limiting factors that concern the designers of machine tool servo systems. One such factor is the mismatch that often exists between motor and load inertias. This paper briefly discusses the results of a previous study on the factors that interact to introduce stability problems in the presence of a high motor-load inertia mismatch. The effects of such an inertia mismatch, on servo system performance, are then discussed and analysed using closed loop frequency responses. Various methods of improving the system response using fast feedback control are presented, including traditional PI control and modern methods …

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An Optimal Importance Sampling Method For A Transient Markov System, H. Qi, Y. C. Wei, L. Wei Nov 2001

An Optimal Importance Sampling Method For A Transient Markov System, H. Qi, Y. C. Wei, L. Wei

Faculty of Informatics - Papers (Archive)

In this paper an optimal importance sampling (IS) method is derived for a transient markov system. Several propositions are presented. It is showned that the optimal IS method is unique, and it must converge to the standard Monte Carlo (MC) simulation method when the sample path length approaches infinity. Therefore, it is not the size of the state space of the Markov system, but the sample path length, that limits the efficiency of the IS method. Numerical results are presented to support the argument.

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New Results On Frame-Proof Codes And Traceability Schemes, R. Safavi-Naini, Yejing Wang Nov 2001

New Results On Frame-Proof Codes And Traceability Schemes, R. Safavi-Naini, Yejing Wang

Faculty of Informatics - Papers (Archive)

In this correspondence we derive lower bounds on the maximum number of codewords in a class of frame-proof codes and traceability schemes, and give constructions for both with more codewords than the best known.

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Function Spaces And Multiplier Operators, R. Nillsen, S. Okada Nov 2001

Function Spaces And Multiplier Operators, R. Nillsen, S. Okada

Faculty of Informatics - Papers (Archive)

Let G denote a locally compact Hausdorff abelian group. Then a bounded linear operator T from L^2(G) into L^2(G) is a bounded multiplier operator if, under the Fourier transform on L^2(G ), for each function f in L^2(G), T(f) changes into a bounded function U times the Fourier transform of f. Then U is called the multiplier of T. An unbounded multiplier operator has a similar definition, but its domain is a dense subspace of L^2(G) and the multiplier function need not be bounded. For example, differentiation on the first order Sobolev subspace of L^2(R) is an unbounded multiplier operator …

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Assessing Hybrid Classes In A Flexible Learning Environment, M. Lawrence-Slater Oct 2001

Assessing Hybrid Classes In A Flexible Learning Environment, M. Lawrence-Slater

Faculty of Informatics - Papers (Archive)

This paper describes the development of a regime comprising a teaching platform and associated assessment processes. The objective behind these is to enable the equitable assessment of student assignments in hybrid courses. In this paper, the term hybrid refers to courses where the student body comprises both campus-based and off-campus students. Additionally, in either of these groups students may elect to undertake their studies using online resources rather than attend in person. The paper commences with a background discussion on the problem and reasons for seeking alternative approaches to teaching and assessment in hybrid courses. This is followed by a …

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Keeping A Global Technology Working: A Study Into The Social And Technical Dimensions Of Broadcast Engineering In The Pacific Islands, William Tibben Oct 2001

Keeping A Global Technology Working: A Study Into The Social And Technical Dimensions Of Broadcast Engineering In The Pacific Islands, William Tibben

Faculty of Informatics - Papers (Archive)

This paper is primarily concerned with exploring the technical and social dimensions of problem solving undertaken by technical staff in a Pacific Island radio station. Essentially, the paper addresses the question "what influence do physical and social contexts have on engineering knowledge development?". The paper notes that the concept of context is not given significant attention when looking to dominant philosophies of engineering. This stands in contrast to the importance accorded to context in development literature, particularly in. relation to technological knowledge. Using Macdonald's research into the role of information in innovation, the paper identifies a number of factors besides …

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Towards Securing 3g Mobile Phones, R. Safavi-Naini, Willy Susilo, G. Taban Oct 2001

Towards Securing 3g Mobile Phones, R. Safavi-Naini, Willy Susilo, G. Taban

Faculty of Informatics - Papers (Archive)

Third-generation (3G) mobile phones are capable of high data rate Internet connection and promise seamless connectivity for a free roaming user. They can provide an "always on" Internet, and make a range of services, traditionally available on desktop computers, accessible to mobile users, irrespective of their location. Providing adequate security for these phones and the services that they offer is a central concern for their acceptability and uptake. We briefly review the security of second generation mobile phones and then discuss security architecture proposed for 3G phones. The new security issues that are of importance because of the combination of …

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On Multiple Watermarking, Nicholas Paul Sheppard, Reihaneh Safavi-Naini, Philip Ogunbona Oct 2001

On Multiple Watermarking, Nicholas Paul Sheppard, Reihaneh Safavi-Naini, Philip Ogunbona

Faculty of Informatics - Papers (Archive)

Mintzer and Braudaway once asked: If one watermark is good, are more better? In this paper, we discuss some techniques for embedding multiple watermarks into a single multimedia object and report some observations on implementations of these techniques.

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Simulation Of Capture Behaviour In Ieee 802.11 Radio Modems, C. Ware, Joe F. Chicharo, Tadeusz A. Wysocki Oct 2001

Simulation Of Capture Behaviour In Ieee 802.11 Radio Modems, C. Ware, Joe F. Chicharo, Tadeusz A. Wysocki

Faculty of Informatics - Papers (Archive)

In this paper we investigate the performance of common capture models in terms of the fairness properties they reflect across contenting hidden connections. We propose a new capture model, Message Retraining,as a means of providing an accurate description of experimental data. Using two fairness indices we undertake a quantitative study of the accuracy with which each capture model is able to reflect experimental data. Standard capture models are shown to be unable to accurately reflect the fairness properties of empirical data. The Message Retraining capture model is shown to provide a good estimate of actual system performance in varying signal …

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