Physical Sciences and Mathematics Commons^™

On The Step Response Of The Dct, Jim Andrew, Philip Ogunbona

Faculty of Informatics - Papers (Archive)

We show that the discrete cosine transform (DCT) is the best orthogonal transform, in terms of energy packing efficiency, for coding input steps of uniformly distributed random phase. Over sufficiently small block sizes, edges in an image can be modeled as such step inputs. This characteristic of the DCT, coupled with its high energy packing efficiency for highly correlated data, helps explain the impressive performance of the DCT for image compression.

Wavelet-Based Feature-Adaptive Adaptive Resonance Theory Neural Network For Texture Identification, Jiazhao Wang, Golshah Naghdy, Philip Ogunbona

Faculty of Informatics - Papers (Archive)

A new method of texture classification comprising two processing stages, namely a low-level evolutionary feature extraction based on Gabor wavelets and a high-level neural network based pattern recognition, is proposed. The design of these stages is motivated by the processes involved in the human visual system: low-level receptors responsible for early vision processing and the high-level cognition. Gabor wavelets are used as extractors of ‘‘lowlevel’’ features that feed the feature-adaptive adaptive resonance theory (ART) neural network acting as a high-level ‘‘cognitive system.’’ The novelty of the model developed in this paper lies in the use of a self-organizing input layer …

Content-Based Retrieval From Compressed-Image Databases, Philip Ogunbona, P Sangassapaviriya

Faculty of Informatics - Papers (Archive)

There is an enormous amount of multi-media data including images, video, speech, audio and text, distributed among the various computer nodes on the Internet. The extent to which a user wiU be able to derive useful information from these data depends largely on the ease with which required data can be retrieved from the databases. The share volume of the data also poses a storage constraint on the databases; hence these data will need to exist in the compressed form on the databases. In this paper we concentrate on image data and propose a new paradigm in which a compressed …

Edge Image Description Using Fractal Interpolation, P Motallebi, P O. Ogunbona

Faculty of Informatics - Papers (Archive)

Edge images derived from compressed image databases are described using fractal techniques. The proposed method is able to give affine transformation-invariant description suitable for use in a query-by-example database application. Comparison among the proposed method, polynomial interpolation and spline interpolation is given. It is concluded that fractal interpolation can give a compact description of image contours and is able to cope with random perturbation of the coordinates of the contour points by as much as 25 percent.

A Cause Of Chaos, R. Nillsen

Faculty of Informatics - Papers (Archive)

An abstract dynamical system consists of a collection S of points together with a transformation, or function, f which maps points of S into points of S. The points in S stand for all possible states of the system. The transformation is a “process of change” over one time unit, that changes each state x in S into another state f(x). Then we can interpret the equation f(x)=y as meaning that if the system is in state x, over the next time unit it will change into the state y. Alternatively, x is a “cause” of y, or x is …

An Audio Representation For Content Based Retrieval, Kathy Melih, Ruben Gonzalez, Philip Ogunbona

Faculty of Informatics - Papers (Archive)

Despite: the increasing interest in multimedia data retrieval audio data has received little attention. This is due, not to a lack of interest but rather to unique difficulties posed by the medium. In particular existing unstructured audio representations do not easily lend themselves to content based retrieval and especially browsing. This paper aims to address hs oversight by developing an audio representation that provides direct support for browsing and content based retrieval. This support is the result of a structured representation based on psychoacoustic ptincip1.e~in which salient attributes of audio are directly accessible. In addition, the representation is compact thus …

On The Computational Complexity Of The Lbg And Pnn Algorithms, Jamshid Shanbehzadeh, Philip Ogunbona

Faculty of Informatics - Papers (Archive)

This correspondence compares the computational complexity of the pair-wise nearest neighbor (PNN) and Linde–Buzo–Gray (LBG) algorithms by deriving analytical expressions for their computational times. It is shown that for a practical codebook size and training vector sequence, the LBG algorithm is indeed more computationally efficient than the PNN algorithm.

Similarity Measures For Compressed Image Databases, P Sangassapaviriya, Philip Ogunbona

Faculty of Informatics - Papers (Archive)

For image database applications it is desirable that functions such as searching, browsing and partial recall be done without the need to totally decompress the image. This has the advantage of alleviating possible burden and degradation that the network may suffer. Edge images derived from wavelet-compressed images are considered as index that can be queried by example. Zernike moment invariants are used as descriptors for the index edge image and the query sketch image. The descriptions are compared for the purpose of database searching. The query images were allowed to undergo translation, rotation, scaling and some deformation. Simulation results gave …

Index-Compressed Vector Quantisation Based On Index Mapping, Jamshid Shanbehzadeh, Philip Ogunbona

Faculty of Informatics - Papers (Archive)

The authors introduce a novel coding technique which significantly improves the performance of the traditional vector quantisation (VQ) schemes at low bit rates. High interblock correlation in natural images results in a high probability that neighbouring image blocks are mapped to small subsets of the VQ codebook, which contains highly correlated codevectors. If, instead of the whole VQ codebook, a small subset is considered for the purpose of encoding neighbouring blocks, it is possible to improve the performance of traditional VQ schemes significantly. The performance improvement obtained with the new method is about 3dB on average when compared with traditional …

Subcritical, Transcritical And Supercritical Flows Over A Step, Y. Zhang, Song-Ping Zhu

Faculty of Informatics - Papers (Archive)

Free-surface flow over a bottom topography with an asymptotic depth change (a `step') is considered for di erent ranges of Froude numbers varying from subcritical, transcritical, to supercritical. For the subcritical case, a linear model indicates that a train of transient waves propagates upstream and eventually alters the conditions there. This leading-order upstream influence is shown to have profound e ects on higher-order perturbation models as well as on the Froude number which has been conventionally de ned in terms of the steady-state upstream depth. For the transcritical case, a forced Korteweg{de Vries (fKdV) equation is derived, and the numerical …

Minimal Critical Set Of A Room Square Of Order 7, Ghulam R. Chaudhry, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

A Room square R of order r is an r x r array each of whose cells may either be empty or contain an unordered pair of objects 0,1,2,...,r, subject to the following conditions:

(i) each of the objects 0,1,2.....r occurs precisely once in each row of R and precisely once in each column of R, and

(ii) every possible unordered pair of objects occurs precisely once in the whole array.

"Albert Leon Whiteman (1915-1995)", S. Golomb, T. Harris, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

The Mathematical Family Tree of Hans Rademacher (with A. Whiteman branch)

Secure Access To Electronic Strongboxes In Electronic Commerce, Thomas Hardjono, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

Two protocols for access to electronic strongbox are described in the context of electronic commerce. The notion of electronic strongboxes is discussed, and the participants of the strongbox system are presented. The two protocols concern two participants of the strongbox systemn namely the Customer who wishes to access a strongbox maintained by a Strongbox Provider. The security aspects of the protocols are then analysed, focusing on possible methods of cheating by the two involved participants.

Factors From Trees, Jacqueline Ramagge, A G. Robertson

Faculty of Informatics - Papers (Archive)

We construct factors of type III,/n for n E N, n > 2, from group actions on homogeneous trees and their boundaries. Our result is a discrete analogue of a result of R.J Spatzier, where the hyperfinite factor of type III1 is constructed from a group action on the boundary of the universal cover of a manifold.

Discrete-Event Modelling, Simulation And Control Of A Distributed Manipulation Environment, Fazel Naghdy, N. Anjum

Faculty of Informatics - Papers (Archive)

Conventional robotics has proved to be inflexible and non-generic. The concept of Distributed Manipulation Environment (DME) is introduced to overcome some of these shortcomings. This concept proposes a distributed approach to robotics and flexible automation. The work is concerned with modelling, simulation and event based control of DME. The modelling, conducted both at the atomic and the coupled level, is quite generic and provides a framework for static and dynamic behaviour analysis of DME systems. The simulation models serve as a mean of performance evaluation of the system on a computer before the actual implementation in real time. The event-based …

On The Smith Normal Form Of Weighing Matrices, Christos Koukouvinos, C. Mitrouli, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

The Smith normal forms (SNF) of weighing matrices are studied. We show that for all orders n ≥ 35 the full spectrum of Smith normal forms (SNF) exists for weighing matrices W(n,9) ie there exists a W(n,9) with SNF 1^1/2(n-s)3^s9^1/2(n-s), for s in a set, which is described, of consecutive integers.

Security Issues In Mobile Information Networks, Thomas Hardjono, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

During the last decade the decrease in the size of computing machinery, coupled with the increase in their computing power has lend to the development of the concept of mobile computing. Effects of this new vision is currently evident in the flourishing numbers of mobile telephones and portable computing units. In this paper we briefly investigate some issues concerning the security of mobile computing systems, within the framework of the categories of mobility, disconnection, data access modes and scale of operation (Imielinski & Badrinath, 1993). In contrast to previous works which concentrate on security in wireless communications, we focus on …

Beacons For Authentication In Distributed Systems, Azad Jiwa, Thomas Hardjono, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

Reliable authentication of communicating entities is essential for achieving security in a distributed computing environment. The design of such systems as Kerberos, SPX and more recently KryptoKnight and Kuperee, have largely been successful in addressing the problem. The common element with these implementations is the need for a trusted third-party authentication service. This essentially requires a great deal of trust to be invested in the authentication server which adds a level of complexity and reduces system flexibility. The use of a Beacon to promote trust between communicating parties was first suggested by M. Rabin in "Transactions protected by beacons", Journal …

New Weighing Matrices, Christos Koukouvinos, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

New weighing matrices and skew weighing matrices are given for many orders 4t ≤ 100. These are constructed by finding new sequences with zero autocorrelation. These results enable us to determine for the first time that for 4t ≤ 84 a W{4t,k) exists for all k = 1, ... ,4t -1 and also that there exists a skew-weighing matrix (also written as an OD(4t;1,k)) for 4t ≤ 80, t odd, k = a² + b² + c²,a,b,c integers except k = 4t - 2 must be the sum of two squares.

On Sufficient Conditions For Some Orthogonal Designs And Sequences With Zero Autocorrelation Function, C. Koukouvinos, M. Mitrouli, Jennifer Seberry, P. Karabelas

Faculty of Informatics - Papers (Archive)

We give new sets of sequences with entries from {0, ±a, ±b, ±c, ±d} on the commuting variables a, b, c, d and zero autocorrelation function. Then we use these sequences to construct some new orthogonal designs. This means that for order 28 only the existence of the following five cases, none of which is ruled out by known theoretical results, remain in doubt: OD(28; 1, 4, 9, 9), OD(28; 1, 8, 8, 9), OD(28; 2, 8, 9, 9), OD(28; 3, 6, 8, 9), OD(28; 4, 4, 4, 9). We consider 4 - N PAF(S_l, S₂, …

Necessary And Sufficient Conditions For Some Two Variable Orthogonal Designs In Order 36, Christos Koukouvinos, Nikos Platis, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

We give new sets of sequences with entries from {0, ±a, ±b, ±c, ±d} on the commuting variables a, b, c, d with zero autocorrelation function. We show that the necessary conditions are sufficient for the existence two variable orthogonal designs constructed from circulant matrices in order 36. Further we show that the necessary conditions for the existence of an OD(36;S₁,S₂) are sufficient except possibly for the following five cases: (3,29) (11,20) (11,21) (13,19) (15,17).

On The Smith Normal Form Of D-Optimal Designs, Christos Koukouvinos, M. Mitrouli, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

The Smith normal forms (SNF) of V-optimal designs of size < 100 are determined by a computer search. A theorem is given for the SNF of V-optimal designs of order 4t + 2 when 4t + 1 is square free, and bounds for the minimum number of 2's which can appear in the SNF are derived.

Multiplication Of Ternary Complementary Pairs, Marc Gysin, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

We present a computer-search method for concatenating or "multiplying" binary or ternary complementary pairs. All multiplications by a particular number m are considered. The computer-search method is new and leads to a large set of new results. The results and equivalences are discussed and some applications and numerical consequences are shown.

Minimal And Maximal Critical Sets In Room Squares, Ghulam Rasool Chaudhry, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

In this paper we introduce critical sets in Room squares. We give the cardinality of the minimal critical sets (min. cs) and maximal critical sets (max. cs) for inequivalence classes of Room squares of side 7,9, and 11. We also describe algorithms to compute min. cs and max. cs and conjecture the lower and upper bounds for min. cs and max. cs.

Shared Cryptographic Bits Via Quantized Quandrature Phase Amplitudes Of Light, Yi Mu, Jennifer Seberry, Yuliang Zheng

Faculty of Informatics - Papers (Archive)

We propose a novel quantum cryptographic protocol without using polarized photons. The protocol consists of an optical coupler and four nonorthogonal coherent states which are analyzed by means of quadrature phase amplitudes of quantized light field.

Replicating The Kuperee Authentication Server For Increased Security And Reliability, Thomas Hardjono

Faculty of Informatics - Papers (Archive)

The current work proposes a new scheme for the replication of authentication services in Kuperee based on a public key cryptosystem, in response to the two main shortcomings of the traditional single server solutions, namely those of low availability and high security risks. The work represents further developments in the Kuperee authentication system. The Kuperee server is presented in its simplified design to aid the presentation of the replication scheme. The replication approach is based on the sharing of session public keys, together with a threshold or secret sharing scheme. However, unlike previous approaches, in the current work the object …

Secret Sharing Schemes Based On Room Squares, Ghulam Rasool Chaudhry, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

In this paper, we describe secret sharing schemes. We discuss Room squares and their critical sets. We propose a model of sharing based on critical sets of Room squares.

Design And Security Issues In Strongbox Systems For The Internet, Thomas Hardjono, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

This paper presents and discusses some design and security issues surrounding electronic strongboxes as an electronic counterpart of physical strongboxes typically found in large traditional financial institutions. The concept of electronic strongboxes is briefly discussed, comparing against physical strongboxes. A basic system for electronic strongboxes is then provided and the functional and security requirements of the system's components is presented.

Strong Boxes For Electronic Commerce, Thomas Hardjono, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

As electronic commerce becomes a reality, additional services related to electronic commerce will also emerge. The current paper proposes the provision of electronic strongboxes as an integrated part of the wider electronic commerce. The strongbox concept is introduced as an electronic counterpart of physical strongboxes typically found in large traditional financial institutions, such as banks, having secure vaults or other secure physical storage. The work identifies some requirements of electronic strongboxes both from the functionality perspective and from the security point of view. A simple framework for an electronic strongbox system is also presented.

Triangle Buildings And Actions Of Type Iii 1/Q2, Jacqueline Ramagge, Guyan Robertson

Faculty of Informatics - Papers (Archive)

We study certain group actions on triangle buildings and their boundaries and some von Neumann algebras which can be constructed from them. In particular, for buildings of order q ≥ 3 certain natural actions on the boundary are hyperfinite of type III_1/q².