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Articles 1 - 30 of 59
Full-Text Articles in Physical Sciences and Mathematics
Why Software Engineering Is Riskier Than Ever, A. Fuller, P. Croll, O. Garcia
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 …
A New Cryptanalytic Method Using The Distribution Characteristics Of Substitution Distances, B. Song, H. Wang, Jennifer Seberry
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.
Plant Acoustic Density Profile Model Of Ctfm Ultrasonic Sensing, Phillip J. Mckerrow, N. Harper
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 …
Fuzzy Clustering Evaluation Of Time-Frequency Distribution (Tfd) Schemes For Audio Stream Segregation, M. A. Jackson, I. Burnett
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 …
Using Boosting To Simplify Classification Models, V. Wheway
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 …
Control Of Servo Systems In The Presence Of Motor-Load Inertia Mismatch, Jeffrey W. Moscrop, C. Cook, P. Moll
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 …
An Optimal Importance Sampling Method For A Transient Markov System, H. Qi, Y. C. Wei, L. Wei
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.
New Results On Frame-Proof Codes And Traceability Schemes, R. Safavi-Naini, Yejing Wang
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.
Function Spaces And Multiplier Operators, R. Nillsen, S. Okada
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 …
Assessing Hybrid Classes In A Flexible Learning Environment, M. Lawrence-Slater
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 …
Keeping A Global Technology Working: A Study Into The Social And Technical Dimensions Of Broadcast Engineering In The Pacific Islands, William Tibben
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 …
Towards Securing 3g Mobile Phones, R. Safavi-Naini, Willy Susilo, G. Taban
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 …
On Multiple Watermarking, Nicholas Paul Sheppard, Reihaneh Safavi-Naini, Philip Ogunbona
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.
Simulation Of Capture Behaviour In Ieee 802.11 Radio Modems, C. Ware, Joe F. Chicharo, Tadeusz A. Wysocki
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 …
Optimization Of Orthogonal Polyphase Spreading Sequences For Wireless Data Applications, Beata J. Wysocki, Tadeusz A. Wysocki
Optimization Of Orthogonal Polyphase Spreading Sequences For Wireless Data Applications, Beata J. Wysocki, Tadeusz A. Wysocki
Faculty of Informatics - Papers (Archive)
We propose a simple but efficient method for optimizing correlation properties of polyphase spreading sequences for asynchronous DS CDMA applications. The proposed method can be used to minimize the mean square value of aperiodic crosscorrelation or the mean square value of aperiodic autocorrelation, the maximum value of aperiodic crosscorrelation functions, merit factor or other properties of the sequence set. The important feature of the method is that when applied to orthogonal sequences, it modifies correlation properties of the sequence set, while it preserves their orthogonality for perfect synchronization.
Visualization As A Key Element In Learning, J. Fulcher
Visualization As A Key Element In Learning, J. Fulcher
Faculty of Informatics - Papers (Archive)
Experience with teaching undergraduate and postgraduate computer science (CS) subjects has shown that students benefit substantially from being able to visualize fundamental topics. Examples are presented from five different CS areas, namely: (i) communications, (ii) parallel computing, (iii) artificial neural networks, (iv) genetic algorithms and (v) data mining. The majority of these examples stemmed from student projects, rather than commercial software products. Accordingly, students benefit twofold from the visually-oriented subject presentations, firstly in facilitating the learning of basic concepts, and secondly in the development of educational software packages as part of their project work.
The Advantage Of Industrial R&D In The Training Of University Students, J. Fulcher
The Advantage Of Industrial R&D In The Training Of University Students, J. Fulcher
Faculty of Informatics - Papers (Archive)
Experience gained through industrial R&D projects supports the proposition that several benefits flow through to both students and faculty staff beyond that of simply providing associated student project titles. To be more specific, enhancing lecture material with not only specific research findings but also general experience gained from working on such projects are secondary benefits of such university-industry links. Moreover, the reputation and standing of both individual researchers and university research groups are further enhanced by such relationships. This in turn often leads to subsequent industrial R&D projects (and so the cycle continues...).
Scalable Audio Coding Employing Sorted Sinusoidal Parameters, M. Raad, I. Burnett, Alfred Mertins
Scalable Audio Coding Employing Sorted Sinusoidal Parameters, M. Raad, I. Burnett, Alfred Mertins
Faculty of Informatics - Papers (Archive)
This paper describes the use of sorted sinusoidal parameters to produce a fixed rate, scalable, wideband audio coder. The sorting technique relies on the perceptual significance of the sinusoidal parameters. Sinusoidal coding permits the representation of a given signal through the summation of sinusoids. The parameters of the sinusoids (the amplitudes, phases and frequencies) are transmitted to allow signal reconstruction. The sinusoidal parameters are sorted according to energy content and perceptual significance. The most significant parameters are transmitted first, allowing the use of only a small set of the parameters for signal reconstruction. The proposed scheme incurs a low delay …
Boundary Filter Optimization For Segmentation-Based Subband Coding, Alfred Mertins
Boundary Filter Optimization For Segmentation-Based Subband Coding, Alfred Mertins
Faculty of Informatics - Papers (Archive)
This paper presents boundary optimization techniques for the nonexpansive decomposition of arbitrary-length signals with multirate filterbanks. Both biorthogonal and paraunitary filterbanks are considered. The paper shows how matching moments and orthonormality can be imposed as additional conditions during the boundary filter optimization process. It provides direct solutions to the problem of finding good boundary filters for the following cases: (a) biorthogonal boundary filters with exactly matching moments and (b) orthonormal boundary filters with almost matching moments. With the proposed methods, numerical optimization is only needed if orthonormality and exactly matching moments are demanded. The proposed direct solutions are applicable to …
Using Webct To Support Team Teaching, A. Fuller, Gene Awyzio, Penelope Mcfarlane
Using Webct To Support Team Teaching, A. Fuller, Gene Awyzio, Penelope Mcfarlane
Faculty of Informatics - Papers (Archive)
Advanced learning technologies facilitate team teaching at the college/university level. Team teaching has been shown to benefit both students and faculty. This paper explores the benefits of using a course management package in an interdisciplinary team environment. Among those benefits are: better communication, student monitoring and support, flexibility in subject deliver, and fostering a collaborative environment. The success in the early developmental stage of integrating one such learning technology (Web Course Tools, or WebCT) into our course has seen the package move from a simple tool to an essential member of a teaching team.
Irrational Rotations Motivate Measurable Sets, R. Nillsen
Irrational Rotations Motivate Measurable Sets, R. Nillsen
Faculty of Informatics - Papers (Archive)
In 1914 Constantin Carathéodory gave his definition of a measurable set, a definition that is crucial in the general theory of integration. This is because a “primitive” notion of area or measure, on a smaller family of sets, can be extended to the larger family of measurable sets, and it is this larger family that has the necessary properties for a natural and complete theory of integration. This more general theory of integration is of enormous practical importance, for it leads to quite broad conditions under which basic operations on integrals are valid. However, Carathéodory’s definition itself remains mysterious, and …
Low Rate Wi Sew Representation Using A Rew-Implicit Pulse Model, J. Lukasiak, I. Burnett
Low Rate Wi Sew Representation Using A Rew-Implicit Pulse Model, J. Lukasiak, I. Burnett
Faculty of Informatics - Papers (Archive)
Reducing the bit rate of waveform interpolation speech coders while maintaining the perceptual quality has been the focus of a great deal of research. This letter proposes a new method of slowly evolving waveform (SEW) quantization specifically targeted at low rate coding. The proposed method uses a pulse model whose parameters are implicitly contained in the quantized rapidly evolving waveform (REW) parameters, thus requiring no bits for transmission. Results indicate no degradation in perceptual speech quality when compared to that of the existing SEW quantization method. This retention of perceptual quality is in spite of a 12% reduction in the …
On Circulant Best Matrices And Their Applications, S. Georgiou, C. Koukouvinos, Jennifer Seberry
On Circulant Best Matrices And Their Applications, S. Georgiou, C. Koukouvinos, Jennifer Seberry
Faculty of Informatics - Papers (Archive)
Call four type 1(1,-1) matrices, x1,x2,x3,x4; of the same group of order m (odd) with the properties (i) (Xi-I)T = -(Xi-I), i=1,2,3, (ii)XT4 = X4 and the diagonal elements are positive, (iii) XiXj = XjXi and (iv) X1XT1 + X2XT2+X3XT3 +X4XT4 = 4mIm, best matrices. We use a computer to give, for the first time, all inequivalent best matrices …
Hidden Terminal Jamming Problems In Ieee 802.11 Mobile Ad Hoc Networks, C. Ware, Tadeusz A. Wysocki, Joe F. Chicharo
Hidden Terminal Jamming Problems In Ieee 802.11 Mobile Ad Hoc Networks, C. Ware, Tadeusz A. Wysocki, Joe F. Chicharo
Faculty of Informatics - Papers (Archive)
This paper addresses experimental measurements from an IEEE 802.11 ad hoc network testbed, which indicate a strong signal strength dependence in the ability of a hidden terminal to gain access to the radio channel. We present analytical results investigating the `hidden terminal jamming' ability of the IEEE 802.11 DSSS physical layer. Results indicate that in a hidden terminal topology, the presence of an interfering transmission with a signal strength marginally greater than the transmission currently being received will result in an intolerable increase in BER, effectively jamming the ongoing transmission. These results confirm previous experimental measurements which show that after …
A Security Analysis For Label Switching Routers, M. Al-Ibrahim, M. Savsar, W. Adi
A Security Analysis For Label Switching Routers, M. Al-Ibrahim, M. Savsar, W. Adi
Faculty of Informatics - Papers (Archive)
Label Switching Routers (LSR), such as IP switching of Ipsilon, use separate Virtual Circuits (VC)from different sources even having the same destination. Merging switches, on the other hand, allow multiple VCs of upstream traffic to use a single output VC if having same destination criteria. In this paper, we study IP switching of Ipsilon and identify certain security threats. We found that oscillation between routing and switching as a result of a malicious frequent suspension and releasing of flows is a main security threat that decreases performance of such systems. To stabilize the performance in face of such an attack, …
Perfect Reconstruction Integer-Modulated Filter Banks, Alfred Mertins, T. Karp
Perfect Reconstruction Integer-Modulated Filter Banks, Alfred Mertins, T. Karp
Faculty of Informatics - Papers (Archive)
In this paper, we present design methods for perfect reconstruction (PR) integer-modulated filter banks, including biorthogonal (low-delay) filter banks. Both the prototype filter and the modulation sequences are composed of integers, thus allowing,efficient hardware implementations. To derive such filter banks, we first extend the PR conditions known for cosine modulation to other, more general, modulation schemes. We present solutions where the PR conditions on the prototype and the modulation are entirely decoupled and where some simple coupling is introduced. The conditions are derived for both even and odd numbers of channels. Design examples are presented for both cases.
Structure Of The Internet?, Ah Chung Tsoi
Structure Of The Internet?, Ah Chung Tsoi
Faculty of Informatics - Papers (Archive)
We consider a major component in the design of an Internet search engine, viz., how the relevance of a Web page can be determined. A number of methods are described. A number of design issues related to search engines are also discussed.
Sew Representation For Low Rate Wi Coding, J. Lukasiak, I. S. Burnett
Sew Representation For Low Rate Wi Coding, J. Lukasiak, I. S. Burnett
Faculty of Informatics - Papers (Archive)
This paper considers low-rate waveform interpolation (WI) coding. It compares the existing, common slowly evolving waveform (SEW) quantisation scheme with two new schemes for representing and quantising the SEW. The first scheme uses a minimum phase estimate to reconstruct the SEW whilst the second scheme uses a pulse model whose parameters are implicitly transmitted in the quantised rapidly evolving waveform (REW). These new schemes maintain or reduce the bit rate required for transmission of the SEW. Results indicate that, for low rate WI coding, necessarily coarse SEW magnitude spectrum quantisation limits the contribution of the SEW to perceptual quality. Perceptual …
Audio Coding Using Sorted Sinusoidal Parameters, Mohammed Raad, I. Burnett
Audio Coding Using Sorted Sinusoidal Parameters, Mohammed Raad, I. Burnett
Faculty of Informatics - Papers (Archive)
This paper describes a new audio coding scheme based on sinusoidal coding of signals. Sinusoidal coding permits the representation of a given signal through the summation of sinusoids. The parameters of the sinusoids (the amplitudes, phases and frequencies) are transmitted to allow the signal reconstruction. In the proposed scheme, the sinusoidal parameters are sorted according to energy content and perceptual significance. The most significant parameters are transmitted first allowing the use of only a small set of the parameters for signal reconstruction. The proposed scheme incurs a low delay and uses a 20 ms frame length. Results show that the …
Boundary Filters With Maximum Coding Gain And Ideal Dc Behavior For Size-Limited Paraunitary Filter Banks, Alfred Mertins
Boundary Filters With Maximum Coding Gain And Ideal Dc Behavior For Size-Limited Paraunitary Filter Banks, Alfred Mertins
Faculty of Informatics - Papers (Archive)
This paper presents boundary optimization techniques for the processing of arbitrary-length signals with paraunitary multirate filter banks. The boundary filters are designed to maximize the coding gain while providing an ideal DC behavior. Thus, all filters except the lowpass filter are designed to have zero mean. The proposed methods give direct solutions to the problem of finding optimal boundary filters and do not require numerical optimization.