Digital Commons Network^™

Thermionic Cooling Of Optoelectronic And Microelectronic Devices, S. P. Lee, B. C. Lough, R. A. Lewis, C. Zhang

Faculty of Engineering - Papers (Archive)

Solid-state thermionic cooling has gained attention recently because of its potential high cooling power. Thermionic devices based on semiconductor heterostructures utilize the band-edge offset at a heterojunction as the thermionic emission potential barrier and a thin layer to separate the cold and hot junction. In this paper, we present the behavior of thermionic coolers with periodic barriers using gallium arsenide/aluminium gallium arsenide (GaAs/Al/sub x/Ga/sub 1-x/As) semiconductor heterostructures. The exact numerical calculation to model the device performance has shown that the thermal efficiency in a multilayer structure is optimised when the effect of phonon scattering is introduced in the model. Besides, …

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

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

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.

Outlook University Of Wollongong Alumni Magazine December 2000, University Of Wollongong

Wollongong Outlook: The University Alumni Magazine

No abstract provided.

University Of Wollongong Graduation Booklet - December 2000, University Of Wollongong

University of Wollongong Graduation Booklets

No abstract provided.

University Of Wollongong Campus News [December] 2000, University Of Wollongong

University of Wollongong Campus News

No abstract provided.

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

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.

Misattribution Of Sensory Input Reflected In Dysfunctional Target: Non-Target Erps In Schizophrenia, K. Brown, E. Gordon, L. Williams, H. Bahramali, A. Harris, J. Gray, C. J. Gonsalvez, R. Meares

Faculty of Health and Behavioural Sciences - Papers (Archive)

Background. While numerous studies have found disturbances in the Event-Related Potentials (ERPs) of patients with schizophrenia linked to task relevant target stimuli (most notably a reduction in P300 amplitude), few have examined ERPs to task irrelevant non-targets. We hypothesize, from current models of dysfunction in information processing in schizophrenia, that there will be less difference between ERPs to targets and non-targets in patients with schizophrenia than in controls.

Methods. EEGs were recorded for 40 subjects with schizophrenia and 40 age and sex matched controls during an auditory oddball reaction time task. ERPs to the targets and non-targets immediately preceding the …

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.

Performance Measures, Benchmarking And Value, Felicity Mcgregor

Senior Deputy Vice-Chancellor and Deputy Vice-Chancellor (Education) - Papers

[Extract] The announcement of the establishment of a Quality Audit Agency to evaluate the performance of universities, signalled an inevitable expansion of the incipient culture of measurement and evaluation in Australian universities. Those who consider that quality, and its associated tenets of measurement and evaluation are of dubious value, will be constrained to demonstrate goal achievement through whichever mechanisms are deemed appropriate by the Agency. Otherwise, they may face an uncertain funding future. Although the details of the audit process are not yet clear, there will be a single national body which will be responsible for overseeing independent external quality …

Chandra Observation Of Abell 2142: Survival Of Dense Subcluster Cores In A Merger, M. Markevitch, T. J. Ponman, P. Nulsen, M. W. Bautz, D. J. Burke, L. P. David, D. Davis, R. H. Donnelly, W. R. Forman, C. Jones, J. Kaastra, E. Kellogg, D. W. Kim, J. Kolodziejczak, P. Mazzotta, A. Pagliaro, S. Patel, L. Van Speybroeck, A. Vikhlinen, J. Vrtilek, M. Wise, P. Zhao

Faculty of Engineering - Papers (Archive)

We use Chandra data to map the gas temperature in the central region of the merging cluster A2142. The cluster is markedly nonisothermal; it appears that the central cooling flow has been disturbed but not destroyed by a merger. The X-ray image exhibits two sharp, bow-shaped, shocklike surface brightness edges or gas density discontinuities. However, temperature and pressure profiles across these edges indicate that these are not shock fronts. The pressure is reasonably continuous across these edges, while the entropy jumps in the opposite sense to that in a shock (i.e., the denser side of the edge has lower temperature, …

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

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

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

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

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

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.

An Instructional Design Framework For Authentic Learning Environments, J. Herrington, R. Oliver

Faculty of Education - Papers (Archive)

The instructional technology community is in the midst of a philosophical shift from a behaviorist to a constructivist framework, a move that may begin to address the growing rift between formal school learning and real-life learning. One theory of learning that has the capacity to promote authentic learning is that of situated learning. The purpose of this three part study was firstly, to identify critical characteristics of a situated learning environment from the extensive literature base on the subject; secondly, to operationalise the critical characteristics of a situated learning environment by designing a multimedia program which incorporated the identified characteristics; …

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

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).

Accountability, Democracy And The World Economic Forum, Jane Andrew

Faculty of Commerce - Papers (Archive)

Concerns about the state of the global environment has provided the catalyst for significant participation in 'anti-globalisation' protests. These concerns have led many to protest the general lack of social and environmental accountability displayed by multinational companies and elected government officials. This paper considers these issues within the context of a growing protest movement.

Improving Teaching And Learning Through Formative Evaluation: Using A Customised Online Tool To Collect Student Feedback, Robert M. Corderoy, Ray Stace, Sandra Wills, A. Ip

Senior Deputy Vice-Chancellor and Deputy Vice-Chancellor (Education) - Papers

Good teachers spend time reflecting on their teaching practice. What is working, what isn't - and more importantly, why is or isn’t it? Such reflection is an essential component of maintaining and improving both teaching practice and the learning outcomes for students. Changes in current teaching practice towards more flexible teaching and learning environments and especially towards more student-centred online environments make this an even more important process. To answer this kind of question requires data which reflect the student's viewpoint on the teaching process and the time to collect and analyse it. As the subject itself is more and …

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

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

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

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

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

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 …