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Articles 1 - 30 of 63
Full-Text Articles in Physical Sciences and Mathematics
Sag Testing Of Dairy Farm Milking Equipment, V. J. Gosbell, V. Smith, D. A. Robinson, B. S. Perera
Sag Testing Of Dairy Farm Milking Equipment, V. J. Gosbell, V. Smith, D. A. Robinson, B. S. Perera
Faculty of Informatics - Papers (Archive)
Sags are widely reported as being one of the worst power quality problems and are particularly common in rural areas. Automated milking equipment on dairy farms are thus very susceptible to malfunction by sags. In assessing the relative cost/benefits of sag mitigation in the dairy or the supply network it is important to know the dairy equipment immunity level. It is shown how a harmonic generator can be used to determine this information. Testing revealed that the motor contactor was a critical component as it was unable to ride through a 40% sag longer than about 0.5 seconds. The milking …
On Amicable Sequences And Orthogonal Designs, S. Georgiou, C. Koukouvinos, Jennifer Seberry
On Amicable Sequences And Orthogonal Designs, S. Georgiou, C. Koukouvinos, Jennifer Seberry
Faculty of Informatics - Papers (Archive)
In this paper we give a general theorem which can be used to multiply the length of amicable sequences keeping the amicability property and the type of the sequences. As a consequence we have that if there exist two, four or eight amicable sequences of length m and type (al, a2), (al, a2, a3, a4) or (al, a2, ... , a8) then there exist amicable sequences of length ℓ ≡ 0 (mod m) and of the same type. We also present a theorem that produces a set of 2v amicable sequences from a set of v (not necessary amicable) sequences …
Codes Identifying Bad Signatures In Batches, J. Pastuszak, J. Pieprzyk, Jennifer Seberry
Codes Identifying Bad Signatures In Batches, J. Pastuszak, J. Pieprzyk, Jennifer Seberry
Faculty of Informatics - Papers (Archive)
The work is concerned with identification of bad signatures in a sequence which is validated using batching. Identification codes (id-codes) are defined and their general properties are investigated. A taxonomy of id-codes is given. The generic construction for a wide range of id-codes is given and its instantiation using mutually orthogonal Latin squares is described. Hierarchical identification is studied for two cases when the identification procedure uses a family of id-codes and when there is a single underlying id-code. Remarks about future research conclude the work.
Label Switching Using The Ipv6 Address Hierarchy, P. Boustead, Joe F. Chicharo
Label Switching Using The Ipv6 Address Hierarchy, P. Boustead, Joe F. Chicharo
Faculty of Informatics - Papers (Archive)
Current label switching protocols can use routing, address, and address hierarchy information to group flows for cut-throughs that bypass IP forwarding. This paper examines a label switching solution that uses the IP version 6 (IPv6) address structure to classify and cut-through flows based on address hierarchy. The performance of this approach is examined using actual backbone traffic traces with associated hierarchical address information obtained from Internet address registries, routing arbiter databases and route servers. This hierarchical address information is used to map a hierarchical address structure over the packet level trace. We investigate the relationship between aggregation bit-mask size versus …
Formal Tools For Managing Inconsistency And Change In Re, Aditya K. Ghose
Formal Tools For Managing Inconsistency And Change In Re, Aditya K. Ghose
Faculty of Informatics - Papers (Archive)
Dealing with inconsistencies and change in requirements engineering (RE) is known to be a difficult problem. We propose a formal, integrated approach to inconsistency handling and requirements evolution with a focus on providing automated support. We define a novel representation scheme that is expressive and able to maintain several key semantic distinctions. Based on this scheme, we define a toolkit of inconsistency handling technique. We define a principled process for evolving such specifications, with minimal computational cost and user intervention. Finally, we describe the REFORM system which implements some of these techniques.
Using Labview To Prototype An Industrial-Quality Real-Time Solution For The Titan Outdoor 4wd Mobile Robot Controller, D. Ratner, Phillip J. Mckerrow
Using Labview To Prototype An Industrial-Quality Real-Time Solution For The Titan Outdoor 4wd Mobile Robot Controller, D. Ratner, Phillip J. Mckerrow
Faculty of Informatics - Papers (Archive)
In the Titan project we applied a new approach to prototyping mobile robots by choosing tools which are commonly used by leading aerospace manufacturers and many other industries. We have gained substantial experience when using the LabVIEW real-time programming environment coupled with the industrial quality data acquisition cards, both are made by National Instruments. The methodology of virtual instruments software tools combined with the graphical programming environment was found to be very efficient for interactive cycles of design and testing, which are at the core of robotics prototyping.
Establishment Of Typical Harmonic Voltage Levels In Radial Distribution Systems, D. A. Robinson, V. J. Gosbell, B. S. Perera, D. J. Mannix
Establishment Of Typical Harmonic Voltage Levels In Radial Distribution Systems, D. A. Robinson, V. J. Gosbell, B. S. Perera, D. J. Mannix
Faculty of Informatics - Papers (Archive)
This paper reports on a simple method to identify problem areas with relation to harmonic distortion within radial distribution systems at the planning stage. The purpose of the work is to produce a simple method of establishing harmonic distortion levels throughout a study distribution system when only limited system data and load information is available. The preliminary work presented in this paper is aimed at establishing useful planning guidelines for utilities to help with the analysis of harmonics in medium voltage (MV) distribution systems during the design phase. Harmonic analysis during the design of a distribution system is seen as …
Improved Signal Analysis And Time-Synchronous Reconstruction In Waveform Interpolation Coding, N. R. Chong-White, I. Burnett
Improved Signal Analysis And Time-Synchronous Reconstruction In Waveform Interpolation Coding, N. R. Chong-White, I. Burnett
Faculty of Informatics - Papers (Archive)
This paper presents a waveform-matched waveform interpolation (WMWI) technique which enables improved speech analysis over existing WI coders. In WMWI, an accurate representation of speech evolution is produced by extracting critically-sampled pitch periods of a time-warped, constant pitch residual. The technique also offers waveform-matching capabilities by using an inverse warping process to near-perfectly reconstruct the residual. Here, a pitch track optimisation technique is described which ensures the speech residual can be effectively decomposed and quantised. Also, the pitch parameters required to efficiently quantise and recreate the pitch track, on a period-by-period basis, are identified. This allows time-synchrony between the original …
Exploiting Simultaneously Masked Linear Prediction In A Wi Speech Coder, Jason Lukasiak, I. Burnett
Exploiting Simultaneously Masked Linear Prediction In A Wi Speech Coder, Jason Lukasiak, I. Burnett
Faculty of Informatics - Papers (Archive)
This paper uses a method of incorporating simultaneous masking into the calculation of a linear predictive filter (SMLPC) as the front end to a 2 kbps waveform interpolation (WI) speech coder. A modification to the masking threshold calculation used in SMLPC is proposed. This modification improves the performance of SMLPC in noise like sections by placing greater emphasis on strongly voiced speech. MOS test results reveal that the modified SMLPC improved the perceptual quality of the WI coder. The improvement is significant for female speakers whilst the quality for male speech is virtually unchanged. This result conflicts with previous results …
Exploring The Characteristics Of Analytic Decomposition Of Speech Signals, J Lukasiak, I. Burnett
Exploring The Characteristics Of Analytic Decomposition Of Speech Signals, J Lukasiak, I. Burnett
Faculty of Informatics - Papers (Archive)
This paper investigates the properties of analytic transformation of speech into envelope and phase functions. The envelope is shown to evolve slowly with the pitch of the input speech, whilst the phase consists of two components; one evolving slowly with pitch and another that exhibits a more rapid evolution. We investigate decomposing the phase component further using two distinct methods: (a) filtering of the phase in the pitch evolutionary direction and (b) performing a second analytic decomposition of the phase into secondary envelope and phase components. To examine the characteristics of the pitch cycle evolution, the analytic transform is employed …
Very Low Rate Speech Coding Using Temporal Decomposition And Waveform Interpolation, C. H. Ritz, I. Burnett, J Lukasiak
Very Low Rate Speech Coding Using Temporal Decomposition And Waveform Interpolation, C. H. Ritz, I. Burnett, J Lukasiak
Faculty of Informatics - Papers (Archive)
In very low rate coding the aim is to accurately represent speech characteristics as efficiently as possible. High coding gains for the spectral features can be achieved through the use of temporal decomposition. Waveform interpolation coders accurately represent the excitation using characteristic waveforms (CWs) extracted at a constant rate. In this paper, the two approaches are combined into a very low rate coder operating at around 1 kbps. It is shown that the evolution of the excitation is related to the evolution of the speech spectrum. To minimise bit rates, the transmission of CWs is adapted to the spectral parameter …
Query Scrambling In Distributed Multidatabase Systems, J. R. Getta
Query Scrambling In Distributed Multidatabase Systems, J. R. Getta
Faculty of Informatics - Papers (Archive)
This work addresses the problem of efficient query processing in multidatabase systems distributed over wide-area networks. The solution unifies the query scrambling and reduction approaches to dynamic optimization of query processing plans at the data integration stage. The paper presents a new data integration algorithm based on query scrambling and the extended reduction technique. The algorithm both reschedules data integration operations and reductions of arguments and permits the concurrent computations of operations and reductions.
Construction Of Cubic Homogeneous Boolean Bent Functions, Jennifer Seberry, Tianbing Xia, J. Pieprzyk
Construction Of Cubic Homogeneous Boolean Bent Functions, Jennifer Seberry, Tianbing Xia, J. Pieprzyk
Faculty of Informatics - Papers (Archive)
We prove that cubic homogeneous bent functions f : V2n → GF(2) exist for all n ≥ 3 except for n = 4.
On The Spectrum Of An F-Square, L. Fitina, Jennifer Seberry
On The Spectrum Of An F-Square, L. Fitina, Jennifer Seberry
Faculty of Informatics - Papers (Archive)
Given an F-square of some type F(n; αo, αl, ..., αv-1) what critical set sizes can we obtain for this type? Such a question was considered by Donovan and Howse (1999), in the case of Latin squares. In this note we solve this question for the type F(n;1,n – 1), and also obtain partial results for type F(n; 2,n – 2).
Normal Numbers Without Measure Theory, R. Nillsen
Normal Numbers Without Measure Theory, R. Nillsen
Faculty of Informatics - Papers (Archive)
Any number can be expanded to the base 10, leading to a sequence of digits between 0 and 9 corresponding to the number. Also, any number can be expanded to the base 2, leading to a sequence of digits, each one being either 0 or 1, corresponding to the number. It is result due to Émile Borel in 1904 that “almost all” numbers have the property that, when expanded to the base 2, each of the digits 0 and 1 appears with an asymptotic frequency of 1/2. That is, if we regard the sequence of digits in the expansion to …
An Improved Channel Model For Adsl And Vdsl Systems, D. Franklin, Jiangtao Xi, Joe F. Chicharo
An Improved Channel Model For Adsl And Vdsl Systems, D. Franklin, Jiangtao Xi, Joe F. Chicharo
Faculty of Informatics - Papers (Archive)
This paper examines existing channel models used with xDSL systems and identifies a key shortcoming - namely, the implicit assumption that all impulse noise originates at the transmitter. Based on extensive data collected from the local loop, a new model is proposed which addresses this problem by combining a digital filter model of the transmission line with a distributed noise source. This better reflects the nature of a real telephone line, and thus provides a more solid basis for simulation and optimisation of xDSL systems.
Boundary Filters For Segmentation-Based Subband Coding, Alfred Mertins
Boundary Filters For Segmentation-Based Subband Coding, Alfred Mertins
Faculty of Informatics - Papers (Archive)
This paper presents design methods for boundary filters for the processing of finite-length signals. In particular, it is shown how vanishing moments can be imposed during the design. Applications are found in segmentation-based audio and shape-adaptive image compression.
Memory Truncation Receivers For Transmultiplexers, Alfred Mertins
Memory Truncation Receivers For Transmultiplexers, Alfred Mertins
Faculty of Informatics - Papers (Archive)
In this paper, the design of optimal receive filter banks for transmultiplexer-based data transmission over frequency selective channels is investigated. A new design strategy based on the principle of memory truncation, rather than equalization, is presented. Through the receive filters, each subchannel is truncated to a certain length, and the actual data detection is then carried out via low-complexity, independently operating Viterbi detectors. Design examples are presented for high-speed transmission over copper wires. The examples show that memory truncation allows significant performance improvements over MMSE equalization.
On The Infomax Algorithm For Blind Signal Separation, Jiangtao Xi, Joe F. Chicharo, Ah Chung Tsoi, W. C. Siu
On The Infomax Algorithm For Blind Signal Separation, Jiangtao Xi, Joe F. Chicharo, Ah Chung Tsoi, W. C. Siu
Faculty of Informatics - Papers (Archive)
This paper provides an analytical examination of the INFOMAX algorithm and establishes its effectiveness for blind signal separation using extensive simulation results. Results obtained show that the INFOMAX is not able to separate signal sources unless signal pre-processing is carried-out whereby the data to train the separating matrix is decorrelated. Further, results also show that if one uses the decorrelation pre-process alone it is able to effectively separate signal sources in many instances. Hence we conclude that the INFOMAX algorithm may not be a useful approach for signal separation.
An Examination Of Ip/Atm Cut-Through Forwarding In Dynamically Routed Networks, P. Boustead, Joe F. Chicharo
An Examination Of Ip/Atm Cut-Through Forwarding In Dynamically Routed Networks, P. Boustead, Joe F. Chicharo
Faculty of Informatics - Papers (Archive)
Multiprotocol over ATM (MPOA), IP switching and multiprotocol label switching (MPLS) have distinctly different mechanisms for cut-through packet forwarding. MPOA and IP switching use flow-based cut-through (FBC) forwarding while MPLS uses routing table linked cut-through forwarding (TLC). This paper examines the sensitivity of each these cut-through forwarding mechanisms to changes in underlying routing tables. We examine a scenario where a congestion-sensitive dynamic routing protocol, such as OSPF optimised multipath, leads to frequently changing routing tables. We show that FBC forwarding reacts significantly worse than flow length distributions predict, taking up to 1200 seconds to react to route changes and forward …
Shape-Vq-Based Lossless Hybrid Adpcm/Dct Coder, J. Wang, F. Naghdy
Shape-Vq-Based Lossless Hybrid Adpcm/Dct Coder, J. Wang, F. Naghdy
Faculty of Informatics - Papers (Archive)
The discrete cosine transform (DCT) has been shown as an optimum encoder for sharp edges in an image (Andrew and Ogunbona, 1997). A conventional lossless coder employing differential pulse code modulation (DPCM) suffers from significant deficiencies in regions of discontinuity, because the simple model cannot capture the edge information. This problem can be partially solved by partitioning the image into blocks that are supposedly statistically stationary. A hybrid lossless adaptive DPCM (ADPCM)/DCT coder is presented, in which the edge blocks are encoded with DCT, and ADPCM is used for the non-edge blocks. The proposed scheme divides each input image into …
Building Mlp Networks By Construction, Ah Chung Tsoi, M. Hagenbuchner, A. Micheli
Building Mlp Networks By Construction, Ah Chung Tsoi, M. Hagenbuchner, A. Micheli
Faculty of Informatics - Papers (Archive)
We introduce two new models which are obtained through the modification of the well known methods MLP and cascade correlation. These two methods differ fundamentally as they employ learning techniques and produce network architectures that are not directly comparable. We extended the MLP architecture, and reduced the constructive method to obtain very comparable network architectures. The greatest benefit of these new models is that we can obtain an MLP-structured network through a constructive method based on the cascade correlation algorithm, and that we can train a cascade correlation structured network using the standard MLP learning technique. Additionally, we show that …
Accurate, Critically Sampled Characteristic Waveform Surface Construction For Waveform Interpolation Decomposition, N. R. Chong-White, I. Burnett
Accurate, Critically Sampled Characteristic Waveform Surface Construction For Waveform Interpolation Decomposition, N. R. Chong-White, I. Burnett
Faculty of Informatics - Papers (Archive)
A waveform-matched waveform interpolation (WMWI) technique is presented which offers improved signal analysis over standard WI coders and, in the unquantised case, perfect reconstruction. In WMWI, an accurate representation of speech evolution is formed by extracting consecutive pitch periods of a time-warped, constant pitch residual. A pitch track optimisation technique is described which ensures that the critically sampled pitch periods can be effectively decomposed into a slowly evolving and rapidly evolving waveform, allowing efficient quantisation.
Performance Analysis Of Qos Mechanisms In Ip Networks, D. Jia, E. Dutkiewicz, Joe F. Chicharo
Performance Analysis Of Qos Mechanisms In Ip Networks, D. Jia, E. Dutkiewicz, Joe F. Chicharo
Faculty of Informatics - Papers (Archive)
Integrated services IP networks are expected to provide a variety of services with differentiated QoS. This requires the implementation of mechanisms that can discriminate service classes in terms of QoS. The IETF has recently proposed a differentiated services (Diffserv) framework for provision of QoS. In this paper we analyse the performance of two Diffserv mechanisms: threshold dropping and priority scheduling in terms of packet loss and mean packet delay. A comparison of the two mechanisms is carried out with the requirement that both mechanisms provide the same level of packet loss for the preferred flow. This comparison extends the results …
Multiparty Key Agreement Protocols, J. Pieprzyk, C. H. Li
Multiparty Key Agreement Protocols, J. Pieprzyk, C. H. Li
Faculty of Informatics - Papers (Archive)
A class of multiparty key agreement protocols based on secret sharing is presented. The trust infrastructure necessary to achieve the intended security goals is discussed.
Differentiated Service Performance Analysis, L. V. Nguyen, A. Eyers, Joe F. Chicharo
Differentiated Service Performance Analysis, L. V. Nguyen, A. Eyers, Joe F. Chicharo
Faculty of Informatics - Papers (Archive)
Differentiated service (DiffServ) has been proposed as an alternative for Integrated service. It aims to provide the same service to a group of flows that have similar quality of service requirements. Assured forwarding (AF) and expedited forwarding (EF) are two proposals for DiffServ provision. We present a performance analysis of an N drop-precedences threshold dropping (TD) queue, which is one of the proposed mechanisms for AF. In this analysis, traffic flows are assumed Poisson with exponentially distributed service time. We present simulation results that verify the analysis. This paper is an extension of the work attempted by Bolot et al. …
Connection Admission Control In Micro-Cellular Multi-Service Mobile Networks, R. S. Raad, E. Dutkiewicz, Joe F. Chicharo
Connection Admission Control In Micro-Cellular Multi-Service Mobile Networks, R. S. Raad, E. Dutkiewicz, Joe F. Chicharo
Faculty of Informatics - Papers (Archive)
This paper investigates the use of fixed bandwidth reservation for multi-service mobile networks. In particular it extends previous fixed multi-service network results to the mobile scenario and presents analytical and simulation results for new and handover call blocking probabilities. It also investigates the performance sensitivity to different traffic load ratios as well as the cell dwell time distribution.
666 Or 616 (Rev. 13,18), M. G. Michael
666 Or 616 (Rev. 13,18), M. G. Michael
Faculty of Informatics - Papers (Archive)
No abstract provided.
Parameter Tracking For Stochastic Time-Varying Systems, Zheng Li
Parameter Tracking For Stochastic Time-Varying Systems, Zheng Li
Faculty of Informatics - Papers (Archive)
Describes a method for tracking fast time-varying parameters of dynamic systems under stochastic disturbances. Auxiliary information is used in addition to the plant input and output for better tracking accuracy.
Ip Forwarding Alternatives In Cell Switched Optical Networks, P. Boustead, Joe F. Chicharo
Ip Forwarding Alternatives In Cell Switched Optical Networks, P. Boustead, Joe F. Chicharo
Faculty of Informatics - Papers (Archive)
Optical switching will enable core Internet packet switching to scale with future transmission rate increases. Currently proposed optical ATM switches do not allow packet reassembly, which is necessary for packet level forwarding. This results in the requirement to create end to end ATM virtual connections for flows even if they contain only one packet. In electronically switched networks MPOA and MPLS allow both cell and packet level forwarding to overcome this problem. This paper examines the feasibility of implementing such protocols over an optically switched network. Two different architectures are examined: use of an adjunct electrical router; and native optical …