School of Information Technology and Electrical Engineering Publications - UQ eSpace
http://espace.library.uq.edu.au/
The University of QueenslandenFez http://blogs.law.harvard.edu/tech/rssAir target detection via bistatic radar based on LEOS communication signals
http://espace.library.uq.edu.au/view/UQ:61718
The paper discusses the bistatic radar parameters for the case when the transmitter is a satellite emitting communication signals. The model utilises signals from an Iridium-like low earth orbiting satellite system. The maximum detection range, when thermal noise-limited, is discussed at the theoretical level and these results are compared with experimentation. Satellite-radar signal levels and the power of ground reflections are evaluated.2007-08-14T17:24:21Z
Cherniakov, M.; Nezlin, D.; Kubik, K. Airway sizes and proportions in children quantified by a video-bronchoscopic technique
http://espace.library.uq.edu.au/view/UQ:8572
Background: A quantitative understanding of airway sizes and proportions and a reference point for comparisons are important to a bronchoscopist. The aims of this study were to measure large airway areas, and define proportions and predictors of airway size in children. Methods: A validated videobronchoscope technique was used to measure in-vivo airway cross-sectional areas (cricoid, right (RMS) and left (LMS) main stem and major lobar bronchi) of 125 children. Airway proportions were calculated as ratios of airways to cricoid areas and to endotracheal tube (ETT) areas. Mann Whitney U, T-tests, and one-way ANOVA were used for comparisons and standard univariate and backwards, stepwise multivariate regression analyses were used to define airway size predictors. Results: Airways size increased progressively with increasing age but proportions remained constant. The LMS was 21% smaller than the RMS. Gender differences in airways' size were not significant in any age group or airway site. Cricoid area related best to body length (BL): cricoid area (mm2) = 26.782 + 0.254*BL (cm) while the RMS and LMS area related best to weight: RMS area (mm2) = 23.938 + 0.394*Wt (kg) and LMS area (mm2) = 20.055 + 0.263*Wt (kg) respectively. Airways to cricoid ratios were larger than airway to ETT ratios (p=0.0001). Conclusions: The cricoid and large airways progressively increase in size but maintain constant proportional relationships to the cricoid across childhood. The cricoid area correlates with body length while the RMS and LMS are best predicted by weight. These data provide for quantitative comparisons of airway lesions.2006-03-06T00:00:00Z
Masters, Ian B.; Ware, Robert S.; Zimmerman, Paul V.; Lovell, Brian; Wootton, Richard; Francis, Paul V.; Chang, Anne B. A joint design of transmit antenna selection and multiuser scheduling for multiuser MIMO systems employing block diagonalization precoding scheme
http://espace.library.uq.edu.au/view/UQ:316922
2013-11-28T01:13:33Z
Wang, Feng; Bialkowski, Marek E. A joint vibration and arcing measurement system for online condition monitoring of on-load tap changer of power transformer
http://espace.library.uq.edu.au/view/UQ:380185
Vibration measurement has been adopted in some utilities in Australia, Canada and several European countries for online condition monitoring of power transformer’s On-Load Tap Changer (OLTC). By comparing measured vibration signals at different stages, it might be possible to assess changes of OLTC’s condition. However, there are still considerable difficulties in correlating vibration signals to events of OLTC operation, which may impair the capability of vibration measurement for OLTC condition monitoring. Therefore, arcing measurement is proposed in this paper to complement to vibration measurement. Arcing is provoked when OLTC switching contact closes at a fixed tap position and it can lead to electromagnetic signals flowing through transformer windings and finally reaches earth. The arcing measurement is achieved by using a High Frequency Current Transducer (HFCT) clamping on the transformer’s grounding cable. The joint vibration and arcing measurement can provide a better means for interpreting events involved in OLTC operation and facilitating an improved OLTC condition monitoring. Since HFCT measured arcing signals can be coupled with noise, a probabilistic wavelet transform is thus employed in this paper to extract arcing signals from noise. Field measurements on two different types of OLTCs are performed using the joint vibration and arcing measurement system to validate the proposed methodology.2016-02-22T12:07:00Z
Seo, Junhyuck; Ma, Hui; Saha, Tapan A kantorovich-monadic powerdomain for information hiding, with probability and nondeterminism
http://espace.library.uq.edu.au/view/UQ:317253
We propose a novel domain-theoretic model for nondeterminism, probability and hidden state, with relations on it that compare information flow. One relation is Smyth-like, based on a structural, refinement-like order between semantic elements; the other is a testing order that generalises several extant entropy-based techniques. Our principal theorem is that the two orders are equivalent. The model is based on the Giry/Kantorovich monads, and it abstracts Partially Observable Markov Decision Processes by discarding observables' actual values but retaining the effect they had on an observer's knowledge. We illustrate the model, and its orders, on some small examples, where we find that our formalism provides the apparatus for comparing systems in terms of the information they leak.2013-11-28T08:30:19Z
McIver, Annabelle; Meinicke, Larissa; Morgan, Carroll A Ku-band active transmit-array module with a horn or patch array as a signal launching/receiving device
http://espace.library.uq.edu.au/view/UQ:60075
This paper is concerned with the design of a Ku-band active transmit-array module of transistor amplifiers excited by either a pyramidal horn or a patch array Optimal distances between the active transmit array and the signal-launching:receiving device, which is either a passive corporate-fed array or a horn, are determined to maximise the power gain at a design frequency: Having established these conditions, the complete structure is investigated in terms of operational bandwidth and near-field and far-field distributions measured at the output side of the transmit array, The experimental results show that the use of a corporate-fed array as an illuminating/receiving device gives higher gain and significantly larger operational bandwidth, An explanation for this behavior is sought.2007-08-14T16:14:55Z
Bialkowski, Marek E.; Song, Hyok J. A Labelled Tableau Calculus for Nonmonotonic (Cumulative) Consequence Relations
http://espace.library.uq.edu.au/view/UQ:9621
In this paper we present a labelled proof method for computing nonmonotonic consequence relations in a conditional logic setting. The method is based on the usual possible world semantics for conditional logic. The label formalism KEM, introduced to account for the semantics of normal modal logics, is easily adapted to the semantics of conditional logic by simply indexing labels with formulas. The inference rules are provided by the propositional system KE+ - a tableau-like analytic proof system devised to be used both as a refutation and a direct method of proof - enlarged with suitable elimination rules for the conditional connective. The resulting algorithmic framework is able to compute cumulative consequence relations in so far as they can be expressed as conditional implications.2005-04-07T00:00:00Z
Artosi, Alberto; Governatori, Guido; Rotolo, Antonino ALARM: An adaptive load-aware routing metric for hybrid wireless mesh networks
http://espace.library.uq.edu.au/view/UQ:236747
Hybrid Wireless Mesh Networks (WMN) can be quickly deployed at disasters sites to provide high-capacity wireless communications. As with other WMN networks, a routing protocol is required to find a path between non-neighboring source and destination nodes. The routing metric used by the routing protocol can have a significant impact on the performance of the network. Most of the existing routing metrics for multiradio, multihop WMNs are calculated using external information (such as link quality statistics and channel information). In a network with highly mobile nodes, such as an Hybrid WMN, the required frequent exchange of this information can be very expensive, resulting in degraded performance. In this paper, we present the ALARM routing metric, which is computed using the number of packets queued per wireless interface. This computed value offers an accurate representation of the traffic load, link quality, interference and noise levels. As only this one value need be exchanged to compute ALARM, the overhead associated with the metric is less than existing approaches. With the help of extensive simulations, we show that ALARM outperforms well-know routing metrics like ETT and WCETT under varying mobility and traffic load conditions in HybridWMNs. Validation of these simulation results is obtained from a small-scale testbed deployment. †2011-03-16T11:49:27Z
Pirzada, Asad Amir; Wishart, Ryan; Portmann, Marius; Indulska, Jadwiga ALASA: When service overlay networks meet peer-to-peer networks
http://espace.library.uq.edu.au/view/UQ:103080
2007-08-23T21:20:59Z
Zhou, S.; Hogan, M.; Ardon, S.; Portmann, M.; Hu, T; Wongrujira, K; Seneviratne, A. A latent usage approach for clustering web transaction and building user profile
http://espace.library.uq.edu.au/view/UQ:103186
2007-08-23T21:24:54Z
Zhang, Y.; Xu, G; Zhou, X. A lattice-theoretic analysis of vector perturbation for multi-user MIMO systems
http://espace.library.uq.edu.au/view/UQ:175655
This paper considers the use of multiple transmit antennas to deliver independent data streams to multiple users. In particular, we examine a multi-user technique known as vector perturbation. We provide a new lattice-theoretic approach to analyze its performance in the presence of Rayleigh fading. Vector perturbation is based on performing a channel inversion, with the additional step of perturbing the data signal prior to linear preceding to significantly reduce the required transmit power. To analyze such systems it is necessary to calculate the resulting average energy of the sphere-encoded signal vector, as this determines the signal-to-noise ratio (SNR) at the output of the demodulator. Previous results presented in the literature were partially analytic, requiring further numerical evaluation. Here, we derive a concise approximation to the output SNR. We also provide tight upper and lower bounds on the bit error rate for the reception of QAM symbols using the required modulo demodulator, as a function of the average energy of the sphere- encoded signal vector.2009-04-14T16:38:23Z
Ryan, D. J.; Collings, I. B.; Clarkson, I. V. L.; Heath, R. W. A Layout-Aware Circuit Sizing Model Using Parametric Analysis
http://espace.library.uq.edu.au/view/UQ:9875
We propose a circuit sizing model that takes layout parasitics into account. The circuit and layout parameters are stored in a parameterized layout description format, GBLD. The layout parasitics are stored as closed form expressions. Layout optimization tools can modify the layout and recalculate parasitics on the fly. If the results of sensitivity analysis are passed to those tools, optimization for performance can be achieved with relatively few iterations involving time consuming circuit simulations.2005-02-21T00:00:00Z
Tseng, I-Lun; Postula, Adam A learning approach for performance evaluation of local network
http://espace.library.uq.edu.au/view/UQ:99238
In this paper, a novel approach is developed to evaluate the overall performance of a local area network as well as to monitor some possible intrusion detections. The data is obtained via system utility 'ping' and huge data is analyzed via statistical methods. Finally, an overall performance index is defined and simulation experiments in three months proved the effectiveness of the proposed performance index. A software package is developed based on these ideas.2007-08-24T02:27:42Z
Zhang, Y.; Liu, W.; Dong, Z. Y. ALE Defeasible Description Logic
http://espace.library.uq.edu.au/view/UQ:7708
One of Semantic Web strengths is the ability to address incomplete knowledge. However, at present, it cannot handle incomplete knowledge directly. Also, it cannot handle non-monotonic reasoning. In this paper, we extend ALE Defeasible Description Logic with existential quantifier, i.e., ALE Defeasible Description Logic. Also, we modify some parts of the logic, resulting in an increasing efficiency in its reasoning.2006-12-04T00:00:00Z
Pothipruk, P.; Governatori, G Algebraic Curve Fitting Support Vector Machines
http://espace.library.uq.edu.au/view/UQ:10633
An algebraic curve is defined as the zero set of a multivariate polynomial. We consider the problem of fitting an algebraic curve to a set of vectors given an additional set of vectors labelled as interior or exterior to the curve. The problem of fitting a linear curve in this way is shown to lend itself to a support vector representation, allowing non-linear curves and high dimensional surfaces to be estimated using kernel functions. The approach is attractive due to the stability of solutions obtained, the range of functional forms made ossible (including polynomials), and the potential for applying well understood regularisation operators from the theory of Support Vector Machines.2004-03-19T00:00:00Z
Walder, Christian; Lovell, Brian C.; Kootsookos, Peter J. Algebraic Reasoning for Probabilistic Action Systems and While-Loops
http://espace.library.uq.edu.au/view/UQ:7961
Back and von Wright have developed algebraic laws for reasoning about loops in the refinement calculus. We extend their work to reasoning about probabilistic loops in the probabilistic refinement calculus. We apply our algebraic reasoning to derive transformation rules for probabilistic action systems and probabilistic while-loops. In particular we focus on developing data refinement rules for these two constructs. Our extension is interesting since some well known transformation rules that are applicable to standard programs are not applicable to probabilistic ones: we identify some of these important differences and we develop alternative rules where possible. In particular, our probabilistic action system and while-loop data refinement rules are new: they differ from the non-probabilistic rules.2006-09-05T00:00:00Z
Meinicke, Larissa; Hayes, Ian J. Algebraic reasoning for probabilistic action systems and while-loops
http://espace.library.uq.edu.au/view/UQ:176450
Back and von Wright have developed algebraic laws for reasoning about loops in a total correctness framework using the refinement calculus. We extend their work to reasoning about probabilistic loops in the probabilistic refinement calculus. We apply our algebraic reasoning to derive transformation rules for probabilistic action systems and probabilistic while-loops. In particular we focus on developing data refinement rules for these two constructs. Our extension is interesting since some well known transformation rules that are applicable to standard programs are not applicable to probabilistic ones: we identify some of these important differences and we develop alternative rules where possible.2009-04-16T18:30:13Z
Meinicke, Larissa; Hayes, Ian J. Algorithm for the determination of loadability boundaries of distribution
http://espace.library.uq.edu.au/view/UQ:279377
Currently, the coordination of dispersed energy resources, like domestic micro-CHP systems, Photovoltaic systems or the charging of electric vehicles is widely discussed. A major issue that has to be addressed in this context is the possibility of an overload of the public power system. In order to guarantee overload prevention, a robust mechanism is needed for making the coordination system aware of the system's loadability limits and to provide them with information for corrective measures if necessary. In this paper the authors present a reference algorithm allowing for an on-line constraint violation detection and mitigation under hard real-time constraints by predetermining the overall set of allowable grid usage patterns a-priori.2012-08-28T13:51:04Z
Krause, Olav; Lehnhoff, Sebastian Algorithms and metrics for processing multiple heterogeneous continuous queries
http://espace.library.uq.edu.au/view/UQ:259072
The emergence of monitoring applications has precipitated the need for Data Stream Management Systems (DSMSs), which constantly monitor incoming data feeds (through registered continuous queries), in order to detect events of interest. In this article, we examine the problem of how to schedule multiple Continuous Queries (CQs) in a DSMS to optimize different Quality of Service (QoS) metrics. We show that, unlike traditional online systems, scheduling policies in DSMSs that optimize for average response time will be different from policies that optimize for average slowdown, which is a more appropriate metric to use in the presence of a heterogeneous workload. Towards this, we propose policies to optimize for the average-case performance for both metrics. Additionally, we propose a hybrid scheduling policy that strikes a fine balance between performance and fairness, by looking at both the average- and worst-case performance, for both metrics. We also show how our policies can be adaptive enough to handle the inherent dynamic nature of monitoring applications. Furthermore, we discuss how our policies can be efficiently implemented and extended to exploit sharing in optimized multi-query plans and multi-stream CQs. Finally, we experimentally show using real data that our policies consistently outperform currently used ones.2011-10-23T03:15:22Z
Sharaf, Mohamed A.; Chrysanthis, Panos K.; Labrinidis, Alexandros; Pruhs, Kirk Aliasing Artefact Suppression in Compressed Sensing MRI for Random Phase-Encode Undersampling
http://espace.library.uq.edu.au/view/UQ:368870
2015-09-08T00:47:18Z
Yang, Yang; Liu, Feng; Jin Z.; Crozier S. A light-weight client mobility approach for infrastructure mesh networks
http://espace.library.uq.edu.au/view/UQ:136359
Infrastructure mesh networks offer a high-capacity wireless backhaul network through which clients, such as PDAs, can connect to one another or with external networks. To use the mesh network, a client must route its outbound traffic via one of the mesh routers in the infrastructure mesh. As the clients are mobile, they may move out of range of the mesh router they were using and need to associate with another. Client handoff mechanisms enable this change in mesh routers to occur in a manner that limits disruption to any transport or application layer sessions the client may be running. In this paper we present an extremely light-weight handoff approach for clients that relies on gratuitous ARP messages broadcast at regular intervals from mesh routers within the infrastructure mesh. An evaluation of our approach using a 5 node testbed has shown that client handoffs can be conducted quickly, and with minimal loss of packets for both TCP and UDP traffic.2008-04-24T16:56:38Z
Wishart, R.; Pirzada, A. A.; Portmann, M. A lightweight encryption algorithm for mobile online multimedia devices
http://espace.library.uq.edu.au/view/UQ:100747
Online multimedia data needs to be encrypted for access control. To be capable of working on mobile devices such as pocket PC and mobile phones, lightweight video encryption algorithms should be proposed. The two major problems in these algorithms are that they are either not fast enough or unable to work on highly compressed data stream. In this paper, we proposed a new lightweight encryption algorithm based on Huffman error diffusion. It is a selective algorithm working on compressed data. By carefully choosing the most significant parts (MSP), high performance is achieved with proper security. Experimental results has proved the algorithm to be fast. secure: and compression-compatible.2007-08-23T19:42:50Z
Liu, Zeng; Li, Xue; Dong, Zhaoyang A light-weight internet gateway discovery scheme for infrastructure mesh networks
http://espace.library.uq.edu.au/view/UQ:176590
2009-04-17T10:03:51Z
Wishart, Ryan; Pirzada, Asad Amir; Portmann, Marius; Indulska, Jadwiga A linear algorithm for optimal probabilistic planning
http://espace.library.uq.edu.au/view/UQ:376485
The maximum probability path problem has been applied in many real fields. However, the problem of computing a path of maximum probability often is transformed into a shortest path problem so as to use suitably the existed shortest path algorithm such as Dijkstra's algorithm. We propose a new algorithm for maximum probability path problem, which is linear in size of a system and does not need to transform. The algorithm mainly exploits probability-first strategy, a probability ordered queue and some FIFO (First In First Out) queues. We prove our algorithm's soundness and completeness with respect to optimal probability problem, and take project application as an example to show our algorithm's application.2016-01-05T01:20:22Z
Wu, Lijun; Wang, Kai; Li, Jiajun A linearly polarized radial-line slot-array antenna with a broadened beam
http://espace.library.uq.edu.au/view/UQ:139714
The beam shaping of a linearly polarized radial-line slot-array (LP RLSA) antenna is demonstrated with the production of a prototype with a broadened main beam pointed in an arbitrary direction. The method of synthesis is presented, which utilizes a simple but accurate radiation model for the RLSA antenna to predict radiation characteristics. Experimental results for a Ku-band LP RLSA antenna manufactured using the described techniques show good agreement with the theoretically predicted performance. (C) 2000 John Wiley & Sons, Inc.2008-06-10T10:52:45Z
Bialkowski, M. E.; Davis, P. W. A linear-time nearest point algorithm for the lattice A(n)*
http://espace.library.uq.edu.au/view/UQ:194348
2010-01-31T00:07:38Z
McKilliam, R. G.; Clarkson, I. V. L.; Smith, W. D.; Quinn, B. G. All binary representations are equal: But some or more equal than others
http://espace.library.uq.edu.au/view/UQ:96950
2007-08-24T00:56:36Z
Willadsen, K.; Wiles, J. H. All-optical logic devices with cascaded nonlinear couplers
http://espace.library.uq.edu.au/view/UQ:139793
2008-06-10T10:57:25Z
Wang, Y.; Wang, Z.; Bialkowski, M. E. All simple groups with order from 1 million to 5 million are efficient
http://espace.library.uq.edu.au/view/UQ:313506
2013-11-05T18:44:46Z
Campbell, C. M.; Havas, G.; Ramsay, C.; Robertson, E. F. A local sensitivity analysis method for developing biological models with identifiable parameters: Application to cardiac ionic channel modelling
http://espace.library.uq.edu.au/view/UQ:312793
2013-10-22T15:36:49Z
Sher, Anna A.; Wang, Ken; Wathen, Andrew; Maybank, Philip John; Mirams, Gary R.; Abramson, David; Noble, Denis; Gavaghan, David J. A Logic Framework of Normative-based Contract Management
http://espace.library.uq.edu.au/view/UQ:23748
We explore of the feasibility of the computationally oriented institutional agency framework proposed by Governatori and Rotolo testing it against an industrial strength scenario. In particular we show how to encode in defeasible logic the dispute resolution policy described in Article 67 of FIDIC.2007-06-17T15:22:33Z
Wang, Miao; Governatori, Guido A loss sensitivity factor method for locating ES in a distribution system with PV units
http://espace.library.uq.edu.au/view/UQ:380771
This paper presented an approach to place single and multiple Energy Storage (ES) units in a distribution network with photovoltaic (PV) units considering energy losses. The approach is based on ALSFmax, which is defined as a difference between the minimum and maximum Loss Sensitivity Factor (LSF) values. The GridLAB-D simulation software is used to model test systems under the study and to validate the proposed method. Results show that the proposed ALSFmax approach can yield lower energy losses and better voltage profiles than other methods: average LSF, centralized ES (i.e. ES is located at the substation) and ES located near the PV units. Some interesting results are also presented in the paper.2016-02-27T22:16:07Z
Sardi, Junainah; Mithulananthan, N.; Hung, Duong Quoc A low-complexity algorithm for static background estimation from cluttered image sequences in surveillance contexts
http://espace.library.uq.edu.au/view/UQ:229635
2011-02-20T00:04:52Z
Reddy, Vikas; Sanderson, Conrad; Lovell, Brian C. A low-complexity lattice-based low-PAR transmission scheme for DSL channels
http://espace.library.uq.edu.au/view/UQ:70445
This paper presents a new low-complexity multicarrier modulation (MCM) technique based on lattices which achieves a peak-to-average power ratio (PAR) as low as three. The scheme can be viewed as a drop in replacement for the discrete multitone (DMT) modulation of an asymmetric digital subscriber line modem. We show that the lattice-MCM retains many of the attractive features of sinusoidal-MCM, and does so with lower implementation complexity, O(N), compared with DMT, which requires O(N log N) operations. We also present techniques for narrowband interference rejection and power profiling. Simulation studies confirm that performance of the lattice-MCM is superior, even compared with recent techniques for PAR reduction in DMT.2007-08-15T03:35:57Z
Collings, I. B.; Clarkson, I. V. L. A low-cost, easy-to-use, real-time power system simulator
http://espace.library.uq.edu.au/view/UQ:101682
We present the design rationale and basic workings of a low-cost, easy-to-use power system simulator developed to support investigations into human interface design for a hydropower plant. The power system simulator is based on three important components: models of power system components, a data repository, and human interface elements. Dynamic Data Exchange (DDE) allows simulator components to communicate with each other within the simulator. To construct the modules of the simulator we have combined the advantages of commercial software such as Matlab/Simulink, ActiveX Control, Visual Basic and Excel and integrated them in the simulator. An important advantage of our approach is that further components of the simulator now can be developed independently. An initial assessment of the simulator indicates it is fit for intended purpose.2007-08-23T20:20:10Z
Memisevic, R.; Sanderson, P. M.; Choudhury, S.; Wong, W. A low power neural recording amplifier with programmable gain and bandwidth
http://espace.library.uq.edu.au/view/UQ:295900
In this paper we present the design and implementation of a low power neural amplifier which has two programmable gains in two programmable bandwidths. The bandwidths are programmable between 0.7-300Hz, suitable for measuring local field potentials and 1.95-5.4kHz, suitable for measuring action potentials. The amplifier achieves a maximum gain of 79dB in the higher bandwidth. A chip has been designed and implemented using a 0.5μm technology with 8 neural amplifiers. On average the neural amplifier consumes less than 14μW at 3.3V.2013-04-04T16:24:24Z
Thanigaivelan, Balavelan; Wiles, Janet; Hamilton, Tara Julia A low-profile dual-band antenna for a wireless LAN access point
http://espace.library.uq.edu.au/view/UQ:71292
The design of dual-band 2.45/5.2 GHz antenna for an acces point of a Wireless Local Area Network (LAN) is presented. The proposed antenna is formed by a Radial Line Slot Array (RLSA) operating at 2.4 GHz and a Microstrip patch working at 5.2 GHz, both featuring circular polarization. The design of this antenna system is accomplished using commercially available Finite Element software. High Frequency Structure Simulator (HFSS) of Ansoft and an in-house developed iteration procedure. The performance of the designed antenna is assessed in terms of return loss (RL), radiation pattern and polarization purity in the two frequency bands.2007-08-15T03:52:17Z
Bialkowski, K.; Zagriatski, S.; Postula, A. J.; Bialkowski, M. E. Alternative analytical approaches for renewable DG allocation for energy loss minimization
http://espace.library.uq.edu.au/view/UQ:279391
The paper develops two new approaches based on alternative analytical expressions to determine the optimum sizes and power factors of distributed generation (DG) units at various locations for minimizing power losses and a methodology to identify the best location. These approaches can be easily adapted to accommodate different types of renewable DG units (i.e., biomass, wind and photovoltaic) for minimizing energy losses by considering the time-varying demand with all possible operating conditions of DG units. The results obtained on a 69-bus distribution system demonstrate that the proposed methods based on one load level can be adequate to determine the location, size and power factor of DG unit for minimizing energy losses.2012-08-29T09:03:41Z
Hung, Duong Quoc; Mithulananthan, Nadarajah Alternative expression of the electric field in the source region without the source dayadic term
http://espace.library.uq.edu.au/view/UQ:111937
An alternative expression is derived for the evaluation of the electric field in the source region. This expression caters for a finite size, instead of an infinitesimally small, principal volume and does not contain the source dyadic term. This expression provides a fast and accurate evaluation of the electric field inside an arbitrary shape finite size principal volume. Numerical calculations on using the new expression are provided.2007-09-19T18:43:04Z
Hui, HT A machine learning approach to intraday trading on foreign exchange markets
http://espace.library.uq.edu.au/view/UQ:102954
Foreign Exchange trading has emerged in recent times as a significant activity in many countries. As with most forms of trading, the activity is influenced by many random parameters so that the creation of a system that effectively emulates the trading process will be very helpful. In this paper we try to create such a system using Machine learning approach to emulate trader behaviour on the Foreign Exchange market and to find the most profitable trading strategy.2007-08-23T21:15:51Z
Hryshko, Andrei; Downs, Tom A macro-level model for investigating the effect of directional bias on network coverage
http://espace.library.uq.edu.au/view/UQ:352738
Random walks have been proposed as a simple method of efficiently searching, or disseminating information throughout, communication and sensor networks. In nature, animals (such as ants) tend to follow correlated random walks, i.e., random walks that are biased towards their current heading. In this paper, we investigate whether or not complementing random walks with directional bias can decrease the expected discovery and coverage times in networks. To do so, we develop a macro-level model of a directionally biased random walk based on Markov chains. By focussing on regular, connected networks, the model allows us to efficiently calculate expected coverage times for different network sizes and biases. Our analysis shows that directional bias can significantly reduce coverage time, but only when the bias is below a certain value which is dependent on the network size2015-03-02T10:07:42Z
Smith, Graeme; Sanders, J. W.; Li, Qin A magnetization mapping approach for passive shim design in MRI
http://espace.library.uq.edu.au/view/UQ:104292
A new passive shim design method is presented which is based on a magnetization mapping approach. Well defined regions with similar magnetization values define the optimal number of passive shims, their shape and position. The new design method is applied in a shimming process without prior-axial shim localization; this reduces the possibility of introducing new errors. The new shim design methodology reduces the number of iterations and the quantity of material required to shim a magnet. Only a few iterations (1-5) are required to shim a whole body horizontal bore magnet with a manufacturing error tolerance larger than 0.1 mm and smaller than 0.5 mm. One numerical example is presented2007-08-23T22:16:34Z
Sanchez Lopez, H; Liu, F; Trakic, A.; Crozier, S A market simulation model for long-term power system planning studies
http://espace.library.uq.edu.au/view/UQ:175135
2009-04-10T18:00:53Z
Fonseka, P.A.J.; Dong, Z. Y.; Saha, T. K. A Markov-chain model for sensor scheduling in electronic support
http://espace.library.uq.edu.au/view/UQ:100397
2007-08-23T19:27:37Z
El-Mahassni, E. D.; Howard, S.D.; Clarkson, I.V.L. A Massively Parallel Imaging System Based on the Self-Mixing Effect in a Vertical-Cavity Surface-Emitting Laser Array
http://espace.library.uq.edu.au/view/UQ:8066
In this work we propose a massively parallel self-mixing imaging system, based on an array of VCSELs, to measure surface profiles of displacement, distance, velocity and liquid flow rate. The feasibility of this concept is demonstrated by the successful operation of a small scale prototype consisting of eight individual commercial VCSELs with integrated photodetectors. The system is used to accurately measure the velocity at different radial points on a rotating disk. The results show no influence of crosstalk. A massive version of the system will be useful in many industrial and biomedical applications where real-time surface profiling, vibrometry and velocimetry will be very beneficial.2006-07-31T00:00:00Z
Tucker, John R.; Lim, Yah Leng; Zvyagin, Andrei V.; Rakic, Aleksandar D. A mathematical modelling technique for the analysis of the dynamics of a simple continuous EDA
http://espace.library.uq.edu.au/view/UQ:104699
This paper presents some initial attempts to mathematically model the dynamics of a continuous estimation of distribution algorithm (EDA) based on a Gaussian distribution and truncation selection. Case studies are conducted on both unimodal and multimodal problems to highlight the effectiveness of the proposed technique and explore some important properties of the EDA. With some general assumptions, we show that, for ID unimodal problems and with the (mu, lambda) scheme: (1). The behaviour of the EDA is dependent only on the general shape of the test function, rather than its specific form; (2). When initialized far from the global optimum, the EDA has a tendency to converge prematurely; (3). Given a certain selection pressure, there is a unique value for the proposed amplification parameter that could help the EDA achieve desirable performance; for ID multimodal problems: (1). The EDA could get stuck with the (mu, lambda) scheme; (2). The EDA will never get stuck with the (mu, lambda) scheme.2007-08-23T22:33:12Z
Gallagher, M. R.; Yuan, B. A maximum loading margin method for static voltage stability in power systems
http://espace.library.uq.edu.au/view/UQ:188036
In this paper, the maximum loading margin (MLM) approach is proposed in finding generation directions to maximize the static voltage stability margin, where the MLM is evaluated at various possible generation directions in the generation direction space. An approximate and simple model representing the relationship between the generation direction and the LM is used to obtain the MLM point. The proposed method is validated in the modified IEEE 14-bus test system and applied to the Thailand power system. LMs of the system with the generation directions are compared for different generator combinations using the proposed technique.2009-11-26T14:32:26Z
Sode-Yome, Arthit; Mithulananthan, Nadarajah; Lee, Kwang Y. Ambient interaction framework: Software infrastructure for the rapid development of pervasive computing environments
http://espace.library.uq.edu.au/view/UQ:97362
2007-08-24T01:12:24Z
Sutton, P. R.; Brereton, M. F.; Heyer, C. M.; MacColl, I. D. Ambiguous decision trees for mining concept-drifting data streams
http://espace.library.uq.edu.au/view/UQ:197249
In real world situations, explanations for the same observations may be different depending on perceptions or contexts. They may change with time especially when concept drift occurs. This phenomenon incurs ambiguities. It is useful if an algorithm can learn to reflect ambiguities and select the best decision according to context or situation. Based on this viewpoint, we study the problem of deriving ambiguous decision trees from data streams to cope with concept drift. CVFDT (Concept-adapting Very Fast Decision Tree) is one of the most well-known streaming data mining methods that can learn decision trees incrementally. In this paper, we establish a method called ambiguous CVFDT (aCVFDT), which integrates ambiguities into CVFDT by exploring multiple options at each node whenever a node is to be split. When aCVFDT is used to make class predictions, it is guaranteed that the best and newest knowledge is used. When old concepts recur, aCVFDT can immediately relearn them by using the corresponding options recorded at each node. Furthermore, CVFDT does not automatically detect occurrences of concept drift and only scans trees periodically, whereas an automatic concept drift detecting mechanism is used in aCVFDT. In our experiments, hyperplane problem and two benchmark problems from the UCI KDD Archive, namely Network Intrusion and Forest CoverType, are used to validate the performance of aCVFDT. The experimental results show that aCVFDT obtains significantly improved results over traditional CVFDT.2010-03-01T15:31:39Z
Liu, Jing; Li, Xue; Zhong, Weicai A measurement system for determining radiation efficiency of a small antenna
http://espace.library.uq.edu.au/view/UQ:103952
The paper describes a system for measuring radiation efficiency of a small antenna operating alone or in the presence of objects similar to those as in an actual service. The system applies the direct approach to determining the antenna efficiency by measuring the radiated field over the entire sphere surrounding the tested antenna. In order to overcome problems associated with the conventional measuring equipment, the antenna under test is equipped with a miniature built-in VCO signal generator and supported by a low reflectivity dielectric positioner. The positioner is of sufficient size and strength to hold a human head phantom to investigate changes in radiation characteristics when the antenna operates in the presence of a human operator.2007-08-23T21:56:40Z
Kabacik, P.; Byndas, A.; Hossa, R.; Bialkowski, M. E.