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Faculty of Informatics - Papers (Archive)

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Articles 1351 - 1380 of 2013

Full-Text Articles in Physical Sciences and Mathematics

Equivalences Between Pure Type Systems And Systems Of Illative Combinatory Logic, Martin Bunder, Willibrordus Dekkers Jan 2005

Equivalences Between Pure Type Systems And Systems Of Illative Combinatory Logic, Martin Bunder, Willibrordus Dekkers

Faculty of Informatics - Papers (Archive)

Pure Type Systems, PTSs, were introduced as a generalization of the type systems of Barendregt’s lambda cube and were designed to provide a foundation for actual proof assistants which will verify proofs. Systems of illative combinatory logic or lambda calculus, ICLs, were introduced by Curry and Church as a foundation for logic and mathematics. In an earlier paper we considered two changes to the rules of the PTSs which made these rules more like ICL rules. This led to four kinds of PTSs. Most importantly PTSs are about statements of the form M : A, where M is a term …

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A Simple Element Inverse Jacket Transform Coding, Moon Ho Lee, Kenneth Finlayson Jan 2005

A Simple Element Inverse Jacket Transform Coding, Moon Ho Lee, Kenneth Finlayson

Faculty of Informatics - Papers (Archive)

Jacket transforms are a class of transforms which are simple to calculate, easily inverted and are size-flexible. Previously reported jacket transforms were generalizations of the well-known Walsh-Hadamard transform (WHT) and the center-weighted Hadamard transform (CWHT). In this paper we present a new class of jacket transform not derived from either the WHT or the CWHT. This class of transform can be applied to any even length vector, and is applicable to finite fields and is useful for constructing error control codes.

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Optical Phase Shifting With Acousto-Optic Devices, Enbang Li, Jianquan Yao, Daoyin Yu, Jiangtao Xi, Joe F. Chicharo Jan 2005

Optical Phase Shifting With Acousto-Optic Devices, Enbang Li, Jianquan Yao, Daoyin Yu, Jiangtao Xi, Joe F. Chicharo

Faculty of Informatics - Papers (Archive)

A novel optical phase-shifting method based on a well-known acousto-optic interaction is proposed. By using a pair of acousto-optic modulators (AOMs) and properly aligning them, we construct an optical phase shifter that can directly control the phase of a collimated beam. The proposed phase shifter is insensitive to the polarization of the incident beam when polarization-insensitive AOMs are used, and no calibration is necessary. The proposed approach is confirmed with experimental results.

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Effects Of Fiber Cladding On Uv Beams And Fringe Patterns In Side-Exposure Fbg Writing, Enbang Li, Jiangtao Xi, Joe F. Chicharo, Yanguang Yu, Jianquan Yao Jan 2005

Effects Of Fiber Cladding On Uv Beams And Fringe Patterns In Side-Exposure Fbg Writing, Enbang Li, Jiangtao Xi, Joe F. Chicharo, Yanguang Yu, Jianquan Yao

Faculty of Informatics - Papers (Archive)

The so-called side-exposure method has been widely used in the fabrication of fiber Bragg gratings (FBGs). The effects of the fiber cladding on the wavefronts of the UV writing beams and the interference fringes formed inside the fiber have been addressed in this study. The wavefronts of the UV beams have been analyzed and it has been demonstrated that the existence of the fiber cladding significantly alters the wavefronts of the UV beams in one plane and makes them highly astigmatic. Based on the calculated wavefront radii of the UV beams, a model has been established for prediction of the …

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Multi-Channel Fbg Sensing System Using A Dense Wavelength Division Demultiplexing Module, Enbang Li, Jiangtao Xi, Yanguang Yu, Joe F. Chicharo, Jianquan Yao Jan 2005

Multi-Channel Fbg Sensing System Using A Dense Wavelength Division Demultiplexing Module, Enbang Li, Jiangtao Xi, Yanguang Yu, Joe F. Chicharo, Jianquan Yao

Faculty of Informatics - Papers (Archive)

Fiber Bragg grating (FBG) sensing is gaining attention in both scientific research areas and engineering applications thanks to its distinguishing advantages including wavelength multiplexing capability, miniature size, high sensitivity, immunity from electro-magnetic interference, etc. FBG sensing is based on the detection of the shifted Bragg wavelength of the light reflected by a fiber grating which is sensitive to various physical parameters such as strain and temperature. One of the challenging tasks in FBG sensing is to determine the Bragg wavelength shift, which can be done by using an optical spectrum analyzer (OSA). An OSA is suitable for laboratory tests, but …

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Performance Comparison Of Sequences Designed From The Hall Difference Set And Orthogonal Gold Sequences Of Length 32, Jennifer Seberry, Beata J. Wysocki, Tadeusz A. Wysocki Jan 2005

Performance Comparison Of Sequences Designed From The Hall Difference Set And Orthogonal Gold Sequences Of Length 32, Jennifer Seberry, Beata J. Wysocki, Tadeusz A. Wysocki

Faculty of Informatics - Papers (Archive)

In the paper we perform a performance comparison between two sets of orthogonal spreading sequences i.e. sequences based on the Hadamard matrix of order 32 constructed using the Hall difference set and orthogonal Gold sequences of length 32. Both considered sets of sequences are characterised by low peaks in the aperiodic cross-correlation functions and have also good aperiodic auto-correlation properties.

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Agent-Based Coalitions In Dynamic Supply Chains, Chattrakul Sombattheera, Aditya K. Ghose Jan 2005

Agent-Based Coalitions In Dynamic Supply Chains, Chattrakul Sombattheera, Aditya K. Ghose

Faculty of Informatics - Papers (Archive)

Coalition formation is an important issue in multi-agent systems. Recent work in the area has focused on reducing the complexity of forming coalitions, i.e., each agent deliberately searches for potential coalition members before negotiating with them. We propose a framework for coalition formation of agents in a dynamic supply chain environment. The framework is composed of a negotiation protocol and a decision mechanism. The negotiation protocol allows thorough communication among agents across sectors (buyers, sellers, logistic providers). With the decision mechanism, agents take two steps to form coalitions: i) agents in each sector form loosely-coupled coalitions in order to decrease …

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Secure Key Extraction In Computer Networks, Willy Susilo, Yi Mu, Xinyi Huang Jan 2005

Secure Key Extraction In Computer Networks, Willy Susilo, Yi Mu, Xinyi Huang

Faculty of Informatics - Papers (Archive)

Security of computer networks normally relies on a trusted authority who is responsible for setting up the system and distributing cryptographic keys. If the trusted authority is compromised due to an attack, then the security of the entire system will be compromised. In this paper, we will look into this issue in terms of identity-based (or ID-based) cryptography. Since the introduction of identity-based (or ID-based) cryptography in 1984 by Shamir, IDbased cryptography has attracted many research due to its simplicity. However, ID-based cryptography suffers from several drawbacks, namely the requirement of having a secure channel during the key extraction and …

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Decision Aided Compensation Of Residual Frequency Offset For Mimo-Ofdm Systems With Nonlinear Channel, Shouyi Yang, Jiangtao Xi, Fang Wang, Xiaomin Mu, Hideo Kobayashi Jan 2005

Decision Aided Compensation Of Residual Frequency Offset For Mimo-Ofdm Systems With Nonlinear Channel, Shouyi Yang, Jiangtao Xi, Fang Wang, Xiaomin Mu, Hideo Kobayashi

Faculty of Informatics - Papers (Archive)

In this paper, we propose a new approach to compensate the residual frequency offset (RFO) in multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) system with nonlinear channel working in the burst mode. The proposed approach consists of two stages. Firstly a decision aided method is proposed to eliminate the nonlinearity introduced by high power transmit amplifier (HPA). Then a new decision aided approach is employed to achieve the RFO compensation on the nonlinearity-free symbols. The effectiveness of the proposed approach has been verified by computer simulations.

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Estimating The Parameters Of Semiconductor Lasers Based On Weak Optical Feedback Interferometry, Jiangtao Xi, Yanguang Yu, Joe F. Chicharo, Thierry Bosch Jan 2005

Estimating The Parameters Of Semiconductor Lasers Based On Weak Optical Feedback Interferometry, Jiangtao Xi, Yanguang Yu, Joe F. Chicharo, Thierry Bosch

Faculty of Informatics - Papers (Archive)

The paper presents a new approach for measuring the linewidth enhancement factor (LEF) of semiconductor lasers (SL) and the optical feedback level factor C in SLs. The proposed approach is based on the analysis of self-mixing signals observed in self-mixing optical feedback interferometry. Unlike existing approaches, the approach tries to estimate the parameters LEF and C by a gradient-based optimization algorithm that achieves best data-to-theoretical model fitting. The effectiveness and accuracy of the method have been confirmed and tested by theoretical analysis and computer simulations.

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Face Recognition With Ctfm Sonar, Kok Kai Yoong, Phillip J. Mckerrow Jan 2005

Face Recognition With Ctfm Sonar, Kok Kai Yoong, Phillip J. Mckerrow

Faculty of Informatics - Papers (Archive)

The use of biometrics, such as iris, thumbprints, voice, face, etc, for authentication have become commonplace. In this research, we are attempting to classify human faces using CTFM (Continuously Transmitted Frequency Modulated) sonar in place of the normally used computer vision. However, for this preliminary paper, the main objectives are to find out the range relationships between human facial features and how they are represented in echoes, and to test the quality of echo features for three faces from a single orientation. The tested features are features that were effective in past research into classifying objects from ultrasonic echoes. We …

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A New Strategy To Improve Proactive Route Updates In Mobile Ad Hoc Networks, Mehran Abolhasan, Tadeusz A. Wysocki, Justin Lipman Jan 2005

A New Strategy To Improve Proactive Route Updates In Mobile Ad Hoc Networks, Mehran Abolhasan, Tadeusz A. Wysocki, Justin Lipman

Faculty of Informatics - Papers (Archive)

This paper presents two new route update strategies for performing proactive route discovery in mobile ad hoc networks (MANETs). The first strategy is referred to as minimum displacement update routing (MDUR). In this strategy, the rate at which route updates are sent into the network is controlled by how often a node changes its location by a required distance. The second strategy is called minimum topology change update (MTCU). In this strategy, the route updating rate is proportional to the level of topology change each node experiences. We implemented MDUR and MTCU on top of the fisheye state routing (FSR) …

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Identity-Based Partial Message Recovery Signatures (Or How To Shorten Id-Based Signatures), Fangguo Zhang, Willy Susilo, Yi Mu Jan 2005

Identity-Based Partial Message Recovery Signatures (Or How To Shorten Id-Based Signatures), Fangguo Zhang, Willy Susilo, Yi Mu

Faculty of Informatics - Papers (Archive)

We propose a new notion of short identity-based signature scheme. We argue that the identity-based environment is essential in some scenarios. The notion of short identity-based signature schemes can be viewed as identity-based (partial) message recovery signatures. Signature schemes with message recovery has been extensively studied in the literature. This problem is somewhat related to the problem of signing short messages using a scheme that minimizes the total length of the original message and the appended signature. In this paper, firstly, we revisit this notion and propose an identity-based message recovery signature scheme. Our scheme can be regarded as the …

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Revised Land Freight External Costs In Australia, Philip Laird Jan 2005

Revised Land Freight External Costs In Australia, Philip Laird

Faculty of Informatics - Papers (Archive)

Publications in Australia to 1999 that comment on transport externalities include the former Inter-State Commission (ISC - 1990), the National Transport Planning Taskforce (NTPT - 1994) Victorian Environment Protection Authority (1994), Simpson and London (1995), Manins (1997), Brindle et al (1999), and the Bureau of Transport Economics (BTE - 1999). As noted by the ISC (1990, p89), road external costs are "…costs imposed outside market transactions and they fall on a number of individuals or groups - road users other than those individuals who give rise to the costs, individuals other than road users (such as those who live in …

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Factors Associated With Trends In Bare Ground In High Country, Heather North, Kenneth G. Russell Jan 2005

Factors Associated With Trends In Bare Ground In High Country, Heather North, Kenneth G. Russell

Faculty of Informatics - Papers (Archive)

Soil erosion in the Canterbury high country has been a concern for many years, and Environment Canterbury wishes to encourage land management practices that will preserve soil quality and vegetative cover. Environment Canterbury brought to MISG2005 a data set spanning three decades of bare ground monitoring in the Canterbury high country, along with data on factors with potential to impact on the processes of revegetation. These include topographic and climate data, soil nutrient status and land management factors. The study group analysed these data with the aim of determining whether trends in bare ground can be predicted from the potential …

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Exploring End-User Perceptions Towards Mandated Deployment Of Pda-Based Health Information Systems Within Ambulatory Care, Jason P. Sargent, Lois Burgess, Joan Cooper, Carole Alcock, Damien Ryan Jan 2005

Exploring End-User Perceptions Towards Mandated Deployment Of Pda-Based Health Information Systems Within Ambulatory Care, Jason P. Sargent, Lois Burgess, Joan Cooper, Carole Alcock, Damien Ryan

Faculty of Informatics - Papers (Archive)

The impact of many well intentioned technology integration projects has not always been viewed favourably. In fact, many projects are destined to fail from the outset by not considering fundamental IT system inves tment risks (technical failure, data failure, user failure, organizational failure) [Lyytinen & Hirschiem, 1987]. With any new technology ‘an element of uncertainty exists in the minds of decision makers with respect to the successful adoption of them’ [Bagozzi et al, 1992]. Uncertainty towards adopting new technologies is not solely the domain of decision makers. Apart from chief technology and information officers, system administrators and help desk personnel, …

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The Character Of Free Topological Groups Ii, Peter Nickolas, Mikhail Tkachenko Jan 2005

The Character Of Free Topological Groups Ii, Peter Nickolas, Mikhail Tkachenko

Faculty of Informatics - Papers (Archive)

A systematic analysis is made of the character of the free and free abelian topological groups on metrizable spaces and compact spaces, and on certain other closely related spaces. In the first case, it is shown that the characters of the free and the free abelian topological groups on X are both equal to the “small cardinal” d if X is compact and metrizable, but also, more generally, if X is a non-discrete k!-space all of whose compact subsets are metrizable, or if X is a non-discrete Polish space. An example is given of a zero-dimensional separable metric space for …

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Extending Asterism Decoding To Qam And Its Complexity In Rician Fading Mimo Systems, P. Conder, Tadeusz A. Wysocki Dec 2004

Extending Asterism Decoding To Qam And Its Complexity In Rician Fading Mimo Systems, P. Conder, Tadeusz A. Wysocki

Faculty of Informatics - Papers (Archive)

The area of Multiple Input Multiple Output (MIMO) communications systems has received enormous attention recently as they can provide a roughly linear increase in data rate by using Multiple Transmit and Receive antennas. The optimal detection strategy for a MIMO receiver is to perform a Maximum-Likelihood (ML) search over all possible transmitted symbol combinations has an exponential complexity when the constellation size of number of transmit antennas increase. A number of sub-optimal decoders, such as VBLAST, provide linear decoding only where the number of receive antennas is at least equal to the number of transmit antennas . Asterism decoding proposed …

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Load-Balanced Route Discovery For Mobile Ad Hoc Networks, Mehran Abolhasan, Justin Lipman, Tadeusz A. Wysocki Dec 2004

Load-Balanced Route Discovery For Mobile Ad Hoc Networks, Mehran Abolhasan, Justin Lipman, Tadeusz A. Wysocki

Faculty of Informatics - Papers (Archive)

This paper presents Flow-Aware Routing Protocol (FARP), a new routing strategy designed to improve load balancing and scalability in mobile ad hoc networks. FARP is a hop-by-hop routing protocol, which introduces a flow-aware route discovery strategy to reduce the number of control overheads propagating through the network and distributes the flow of data through least congested nodes to balance the network traffic. FARP was implemented in Glomosim and compared with AODV. To investigate the load distribution capability of FARP new performance metrics were introduced to measure the data packet flow distribution capability of the each routing protocol. The simulation results …

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Observations On The Message Integrity Code In Ieee802.11wireless Lans, Jianyong Huang, Willy Susilo, Jennifer Seberry Dec 2004

Observations On The Message Integrity Code In Ieee802.11wireless Lans, Jianyong Huang, Willy Susilo, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

This paper surveys the security of the message integrity code used in the IEEE802.11 Wireless LANs. To address the security flaws of Wired Equivalent Privacy (WEP), the IEEE802.11i draft defines two data confidentiality and integrity protocols, Temporal Key Integrity Protocol (TKIP) and Counter-Mode-CBC-MAC Protocol (CCMP). TKIP is based on RC4, andCCMP is based on the AES cipher. TKIP includes a keyed hash functions, called Michael, as the messag integrity code. The aim of this paper is to summarise the recent research results of Michael and analyse the practicability of two attacks against Michael.

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A Study Of Umts Turbo Codes Across Space Time Spreading Channel With The Case Of M = 1 And M = 2, I. S. Raad, Peter James Vial, Tadeusz A. Wysocki Dec 2004

A Study Of Umts Turbo Codes Across Space Time Spreading Channel With The Case Of M = 1 And M = 2, I. S. Raad, Peter James Vial, Tadeusz A. Wysocki

Faculty of Informatics - Papers (Archive)

The study presented in this paper is that of Universal Mobile Telecommunications Systems (UMTS) Turbo Codes across Space Time Spreading channel with one transmitter antenna, one receiver (m = 1) and two transmitter antennas and one receiver (m = 2) to see to what extent the bit error rate (BER) can be improved. Using the Max-log decoding algorithm and 12 iterations it is shown in the simulation results that an extra 5 dB is achievable.

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Image Quality Assessment Using A Neural Network Approach, Abdesselam Bouzerdoum, A. Havstad, A. Beghdadi Dec 2004

Image Quality Assessment Using A Neural Network Approach, Abdesselam Bouzerdoum, A. Havstad, A. Beghdadi

Faculty of Informatics - Papers (Archive)

In this paper, we propose a neural network approach to image quality assessment. In particular, the neural network measures the quality of an image by predicting the mean opinion score (MOS) of human observers, using a set of key features extracted from the original and test images. Experimental results, using 352 JPEG/JPEG2000 compressed images, show that the neural network outputs correlate highly with the MOS scores, and therefore, the neural network can easily serve as a correlate to subjective image quality assessment. Using 10-fold cross-validation, the predicted MOS values have a linear correlation coefficient of 0.9744, a Spearman ranked correlation …

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Ontology Trend Analysis Of Dynamic Signals, David A. Stirling, P. Zulli Dec 2004

Ontology Trend Analysis Of Dynamic Signals, David A. Stirling, P. Zulli

Faculty of Informatics - Papers (Archive)

This paper describes a novel approach to analysing trends of a performance signal indicator from an industrial metallurgical reactor over a number of years of operation. Using a minimum message length algorithm, a detailed ontology of the signal behaviours or modalities was established. An abstraction of these yielded a number of related super states that in turn provided an insightful correspondence for the domain experts. Further detailed identification of the likely composition and causal influences contributing to each mode was subsequently induced with supervised learning.

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Distributed Range Assignment For Reliable Channel Access And Reuse In Ad-Hoc Networks, G. Srivastava, P. Boustead, Joe F. Chicharo Dec 2004

Distributed Range Assignment For Reliable Channel Access And Reuse In Ad-Hoc Networks, G. Srivastava, P. Boustead, Joe F. Chicharo

Faculty of Informatics - Papers (Archive)

The available bandwidth in an ad-hoc network can decrease rapidly due to the shared access to the communication channel. Power control can enhance the available bandwidth by allowing non-interfering nodes to communicate simultaneously. A number of power aware topology control algorithms have been proposed, where low power transmissions are used to forward duta. However, evaluating the power level for the data packets is not sufficient. Reliable transmission of the data packets in a shared channel network requires a number of signalling messages at the Medium Access Channel (MAC) layer. The trmsmission power of the signalling messages is crucial for both …

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Accuracy Limitations Introduced By Digital Projection Sources In Profilometric Optical Metrology Systems, Matthew J. Baker, Joe F. Chicharo, Jiangtao Xi, Enbang Li Dec 2004

Accuracy Limitations Introduced By Digital Projection Sources In Profilometric Optical Metrology Systems, Matthew J. Baker, Joe F. Chicharo, Jiangtao Xi, Enbang Li

Faculty of Informatics - Papers (Archive)

The accuracy of profilometric optical metrology systems utilising Digital Fringe Projection (DFP) is analysed. An analytical model to describe theoretical accuracy limitation is derived and given as a function of object distance from the projector, projector resolution, projection angle and also object gradient. Associated limitations of the model are also discussed and analysed. The validity of the new model is demonstrated through practical experimentation.

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Measuring Multiple Parameters In A Self-Mixing Optical Feedback System, Yanguang Yu, Jiangtao Xi, Enbang Li, Joe F. Chicharo, Thierry Bosch Dec 2004

Measuring Multiple Parameters In A Self-Mixing Optical Feedback System, Yanguang Yu, Jiangtao Xi, Enbang Li, Joe F. Chicharo, Thierry Bosch

Faculty of Informatics - Papers (Archive)

We propose a new approach that yields the values of multiple parameters at the same time for self-mixing optical feedback interferometric systems. These parameters are the linewidth enhancement factor of Semiconductor Lasers, the optical feedback level factor as well as vibration information of a target including the frequency and the amplitude. The method is based on optical feedback interferometry. Its effectiveness has been confirmed by computer simulations and experiments.

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A Calibration Approach For Decoupling Colour Cross-Talk Using Nonlinear Blind Signal Separation Network, Y. Hu, Jiangtao Xi, Enbang Li, Joe F. Chicharo, Zongkai Yang, Yuanguang Yu Dec 2004

A Calibration Approach For Decoupling Colour Cross-Talk Using Nonlinear Blind Signal Separation Network, Y. Hu, Jiangtao Xi, Enbang Li, Joe F. Chicharo, Zongkai Yang, Yuanguang Yu

Faculty of Informatics - Papers (Archive)

We present a calibration approach to invert the nonlinear mixing process of colour cross-talk in multi-channel profilometry systems. Parameters of the inverse network are determined by a nonlinear blind signal separation algorithm. Experimental and simulation results demonstrate that proposed approach can effectively reduce colour leakages and improve the measurement accuracy.

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Role Of Wavelet Transforms In Image Restoration, Prashan Premaratne, I. Burnett Nov 2004

Role Of Wavelet Transforms In Image Restoration, Prashan Premaratne, I. Burnett

Faculty of Informatics - Papers (Archive)

Image processing techniques including image restoration rely heavily on discrete Fourier transform (DFT) for frequency domain representation for analysis of its frequency content. Even though wavelet analysis has been around for more than a decade, much of its potential as a tool to analyze time-frequency localization of signal has not been properly tapped. In blind iterative deconvolution where a degraded image is restored with minimum a priori information about the original image or the point spread function (PSF), it is almost impossible to evaluate whether a restoration is achieved or not without human observation. We propose a new approach using …

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Topology Control In Heterogeneous Ad-Hoc Networks, G. Srivastava, P. Boustead, Joe F. Chicharo Nov 2004

Topology Control In Heterogeneous Ad-Hoc Networks, G. Srivastava, P. Boustead, Joe F. Chicharo

Faculty of Informatics - Papers (Archive)

Topology control in an ad-hoc network can provide better spatial reuse of the wireless channel and conserve power. Topology construction and maintenance is a challenging issue. A number of distributed topology control algorithms have been proposed to remove the need of a centralised controller. Distributed algorithms such as location information no topology (LINT), location information link state topology (LILT) and mobile-grid (MG), aim to achieve overall network connectivity and low transmission range by maintaining a minimum node degree value. In the case of a non-uniform node distribution, maintaining a minimum node degree can unnecessarily partition a network. In this paper, …

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The Price We Pay For Using Tcp, D. King, K. Walker, D. Platt Nov 2004

The Price We Pay For Using Tcp, D. King, K. Walker, D. Platt

Faculty of Informatics - Papers (Archive)

This paper examines a hop-by-hop flow control scheme and compares it with the operation of TCP end-to-end flow control. The individual link control scheme is described. Both schemes are simulated under bursty traffic in a network with 50 nodes and 96 links. It is found that the hop-by-hop scheme results in similar levels of utilization to TCP, but that the average queue size is 30 times smaller.

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