School of Engineering, Computer and Mathematical Sciences - Te Kura Mātai Pūhanga, Rorohiko, Pāngarau

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https://hdl.handle.net/10292/553

AUT is home to a number of renowned research institutes in engineering, and computer and mathematical sciences. The School of Engineering, Computer and Mathematical Sciences strong industry partnerships and the unique combination of engineering, computer and mathematical sciences within one school stimulates interdisciplinary research beyond traditional boundaries. Current research interests include:

Artificial Intelligence; Astronomy and Space Research;

Biomedical Technologies;

Computer Engineering; Computer Vision; Construction Management;

Data Science;

Health Informatics and eHealth;

Industrial Optimisation, Modelling & Control;

Information Security;

Mathematical Sciences Research; Materials & Manufacturing Technologies;

Networking, Instrumentation and Telecommunications;

Parallel and Distributed Systems; Power and Energy Engineering;

Software Engineering; Signal Processing; STEM Education;

Wireless Engineering;

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Now showing 1 - 20 of 1448

230 GHz VLBI Observations of M87: Event-horizon-scale Structure During an Enhanced Very-high-energy Y-ray State in 2012
(IOP Publishing, 2015-07-10)
We report on 230 GHz (1.3 mm) very long baseline interferometry (VLBI) observations of M87 with the Event Horizon Telescope using antennas on Mauna Kea in Hawaii, Mt. Graham in Arizona, and Cedar Flat in California. For the first time, we have acquired 230 GHz VLBI interferometric phase information on M87 through measurement of the closure phase on the triangle of long baselines. Most of the measured closure phases are consistent with 0° as expected by physically motivated models for 230 GHz structure such as jet models and accretion disk models. The brightness temperature of the event-horizon-scale structure is ∼1 × 10¹⁰ K derived from the compact flux density of ∼1 Jy and the angular size of ∼40 μas ∼ 5.5 Rs, which is broadly consistent with the peak brightness of the radio cores at 1-86 GHz located within ∼10² Rs. Our observations occurred in the middle of an enhancement in very-high-energy (VHE) γ-ray flux, presumably originating in the vicinity of the central black hole. Our measurements, combined with results of multi-wavelength observations, favor a scenario in which the VHE region has an extended size of ∼20-60 Rs.
2D & 3D introductory processes in virtual groups
(IEEE, 2003) Clear, Tony; Daniels, M.
This paper reports on a collaborative learning trial conducted in 2002 between students at Auckland University of Technology, New Zealand and Uppsala University, Sweden. The trial design included an initial phase in which virtual groups became acquainted using different modes of cyber-icebreaker and a subsequent phase with a common task involving group decision making - evaluating and ranking the different icebreaker experiences. The software used in the trial comprised 1) a custom-developed web-based groupware database and 2) a Java 3D application, implying configurable avatars, which could be manipulated in a virtual world. Each of these applications supported icebreaking activities intended to establish trust between virtual group members, the latter in 3D mode and the former in 2D mode. The trial process and the software are initially outlined. The evaluation strategy and approaches to data analysis are then discussed and the paper concludes with a report of preliminary findings from the trial.
A 3D Cuboid Image Encryption Algorithm Based on Controlled Alternate Quantum Walk of Message Coding
(MDPI AG, )
In order to solve various security risks faced by image privacy protection, we propose a 3D cuboid image encryption scheme based on message-encoded controlled alternate quantum walks. Firstly, we calculated the initial parameters of the quantum system and performed a one-dimensional quantum walk to generate a probability distribution sequence. Secondly, we encoded the sequence into a quaternary message using multiple sets of encoded messages to control the alternate quantum walk model, generating a 3D probability amplitude matrix and 3D probability distribution matrix to obtain the 3D quantum hash sequence through the 3D probability distribution matrix. Then, the image was divided into blocks and integrated into a cuboid. The image cuboid was scrambled between layers using the probability value sequence, and the 3D probability distribution matrix was used to complete the scrambling of the cross-section between layers. Finally, we converted each pixel value of the scrambled cuboid into a binary cube and controlled it to perform the rotation operation through the 3D probability magnitude matrix, then used the 3D quantum hash sequence to XOR the obtained cuboid image and tilted it to obtain the final encrypted image. The simulation results show that the image encryption scheme can resist various typical attacks and has good security performance.
4D Printing in Biomedical Engineering: Advancements, Challenges, and Future Directions
(MDPI AG, 2023-06-29) Ramezani, Maziar; Mohd Ripin, Zaidi
4D printing has emerged as a transformative technology in the field of biomedical engineering, offering the potential for dynamic, stimuli-responsive structures with applications in tissue engineering, drug delivery, medical devices, and diagnostics. This review paper provides a comprehensive analysis of the advancements, challenges, and future directions of 4D printing in biomedical engineering. We discuss the development of smart materials, including stimuli-responsive polymers, shape-memory materials, and bio-inks, as well as the various fabrication techniques employed, such as direct-write assembly, stereolithography, and multi-material jetting. Despite the promising advances, several challenges persist, including material limitations related to biocompatibility, mechanical properties, and degradation rates; fabrication complexities arising from the integration of multiple materials, resolution and accuracy, and scalability; and regulatory and ethical considerations surrounding safety and efficacy. As we explore the future directions for 4D printing, we emphasise the need for material innovations, fabrication advancements, and emerging applications such as personalised medicine, nanomedicine, and bioelectronic devices. Interdisciplinary research and collaboration between material science, biology, engineering, regulatory agencies, and industry are essential for overcoming challenges and realising the full potential of 4D printing in the biomedical engineering landscape.
A 254-276 GHz On-Chip THz Antenna Using Substrate Integrated Waveguide and Metamaterials for Short-Range Wireless Communications
(IEEE Region 10 (Asia Pacific), 2023-09-08) Paudel, Biswash; Li, Jack; Seet, Boon-Chong
This paper presents a novel, low-profile on-chip antenna (OCA) based on metamaterials (MTM) and substrate-integrated waveguides (SIW), operating in the frequency range of 254–276 GHz. It consists of five stacked layers: copper patch, polyimide, copper ground, polyimide, and a copper microstrip feedline. The top copper layer consists of a 2×2 array of square patches with sub-wavelength-sized cross-sectional slots, which modify the array into a metamaterial. The antenna is excited by aperture coupling through the slot present in the ground layer. Both the top and bottom substrate layers are encapsulated by a series of metallic vias on either side. The proposed OCA is 500×500 × 130 µm 3 in size. Simulation results using Ansys High Frequency Structure Simulator (HFSS) indicate that the proposed OCA is promising for the integrated wireless system for short-range communications.
A cellular automaton framework for within-field vineyard variance and grape production simulation
(Institute of Electrical and Electronics Engineers (IEEE), 2011-07-26) Shanmuganathan, S; Narayanan, A; Robison, N
Winegrowers for generations know it all too well that grapes harvested from different areas within a vineyard will produce wines of different flavours, mainly due to within-field variance in vine vigour caused by environmental variability from various factors, such as soil properties, microclimate conditions, and rootstock. Recent research attempts on the use of state-of-the-art technologies to model/ simulate within-field variance at a vineyard scale are outlined. Consequently, the paper illustrates a cellular automaton (CA) framework being developed for simulating the within-field variance in grapevine plant vigour, phenological events and vineyard production using random or real thematic mappings of likely key factors that contribute to the observed variance. The CA approach provides an alternative software tool to conventional crop estimation methods that are dependent upon expensive yield sampling methods.
A closed-form exact solution for pricing variance swaps with stochastic volatility
(Wiley-Blackwell, 2011-04-01) Lian, G
In this paper, we present a highly efficient approach to price variance swaps with discrete sampling times. We have found a closed-form exact solution for the partial differential equation (PDE) system based on the Heston’s two-factor stochastic volatility model embedded in the framework proposed by Little and Pant. In comparison with the previous approximation models based on the assumption of continuous sampling time, the current research of working out a closed-form exact solution for variance swaps with discrete sampling times at least serves for two major purposes: (i) to verify the degree of validity of using a continuous-sampling-time approximation for variance swaps of relatively short sampling period; (ii) to demonstrate that significant errors can result from still adopting such an assumption for a variance swap with small sampling frequencies or long tenor. Other key features of our new solution approach include the following: (1) with the newly found analytic solution, all the hedging ratios of a variance swap can also be analytically derived; (2) numerical values can be very efficiently computed from the newly found analytic formula.
A collaborative learning trial between New Zealand and Sweden - using Lotus Notes Domino in teaching the concepts of Human Computer Interaction
(ACM, 1999) Clear, Tony
This paper reports the results of a collaborative learning exercise between students at Auckland Institute of Technology and Uppsala University. The exercise was conducted using both a Lotus Notes Domino collaborative database and electronic mail to support students working in remote groups to perform a common task. Issues concerning the logistics of such an exercise, student participation and evaluations of the process, ethical considerations and the quality of the learning process are discussed. Some conclusions are drawn concerning the value of Group Ware technology to support this form of collaborative learning, and suggestions are made for future developments.
A combined optical, thermal and electrical performance model of a Building Integrated Photovoltaic/Thermal Concentrator (BIPVTC)
(Electronics New Zealand/Massey University, 2011) Anderson, TN; Kunnemeyer, R; Duke, M; Carson, JK
The electrical output of concentrating photovoltaic devices is significantly affected by the temperature of the photovoltaic cells. The ability to actively cool photovoltaic cells under concentrated radiation allows their electrical efficiency to be maintained particularly during periods of high solar radiation when concentration offers the maximum benefit. In this study, the design of a novel photovoltaic/thermal solar concentrator for building integration (BIPVTC) is discussed. The optical, thermal and electrical performance of the collector was theoretically modelled and validated with experimental data. The results show that BIPVTC offers improved electrical yields from both concentrating radiation onto the photovoltaic cells and also by actively cooling them.
A Comparative Analysis of Opinion Mining and Sentiment Classification in Non-english Languages
(IEEE, 2013-12-11) Medagoda, N; Shanmuganathan, S; Whalley, JL
In the past decade many opinion mining and sentiment classification studies have been carried out for opinions in English. However, the amount of work done for non-English text opinions is very limited.In this review, we investigate opinion mining and sentiment classification studies in three non-English languages to find the classification methods and the efficiency of each algorithm used in these methods. It is found that most of the research conducted for non-English has followed the methods used in the English language with onlylimited usage of language specific properties, such as morphological variations. The application domains seem to be restricted to particular fields and significantly less research has been conducted in cross domains. Keywords—Natural Language processing, Text mining, Machine Learning.
A comparison of computational techniques of the key properties of Markov Chains
(Australia and New Zealand Industrial and Applied Mathematics (ANZIAM), 2015-02-01) Hunter, JJ
The presenter has recently been exploring the accurate computation of the stationary distribution for finite Markov chains based upon the Grassman, Taksar and Heyman (GTH) algorithm ([1]) with further extensions of this procedure, based upon the ideas of Kohlas ([2]), for finding the mean first passage time matrix. The methods are numerically stable as they do not involve subtraction. In addition, a number of perturbation techniques, where the rows of the transition matrix are sequentially updated, are also considered for computing these quantities. These techniques, together with some standard techniques using matrix inverses and generalized inverses, are compared for accuracy, using some test problems from the literature. References: [1} Grassman W.K., Taksar M.I., and Heyman D.P., Regenerative analysis and steady state distributions for Markov chains, Oper. Res. 33, (1985), 1107-1116. [2] Kohlas J. Numerical computation of mean first passage times and absorption probabilities in Markov and semi-Markov models, Zeit fur Oper Res, 30, (1986), 197-207.
A comparison of nonlinear control performance assessment techniques for nonlinear processes
(Wiley-Blackwell, 2012) Yu, W; Wilson, DI; Young, BR
Assessing the quality of industrial control loops is an important auditing task for the control engineer. However, there are complications when considering the ubiquitous nonlinearities present in many industrial control loops. If one simply ignores these nonlinearities, there is the danger of over-estimating the performance of the control loop in rejecting disturbances and thereby possibly overlooking loops that need attention. To address this problem, several techniques have been recently developed to extend the control performance assessment (CPA) of single input/single output linear systems to nonlinear systems. This article surveys these nonlinear CPA techniques and compares their performances using three case studies. These results can be used to guide control engineers to select the most suitable CPA techniques for their particular applications.
A comparison of teacher and lecturer perspectives on the transition from secondary to tertiary mathematics education
(Taylor & Francis, 2009) Hong, Y; Kerr, S; Klymchuk, S; McHardy, J; Murphy, P; Spencer, S; Thomas, M; Watson, P
The transition from school to tertiary study of mathematics comes under increasing scrutiny in research. This article reports on some findings from a project analysing the transition from secondary to tertiary education in mathematics. One key variable in this transition is the teacher or lecturer. This article deals with a small part of the data from the project – analysing secondary teachers’ and lecturers’ responses to questions on the differences they perceive between school and university and the importance of calculus, a bridging content. The results provide evidence of similarities and differences in the thinking of teachers and lecturers about the transition process. They also show that each group lacks a clear understanding of the issues involved in the transition from the other’s perspective, and there is a great need for improved communication between the two sectors.
A Comprehensive Multi-functional Controller for Hybrid Energy Storage Systems in DC Microgrids
(Institute of Electrical and Electronics Engineers (IEEE), 2023-02-09) Lin, Xin; Zamora, Ramon; Baguley, Craig A
A Comprehensive Review of Hybrid State Estimation in Power Systems: Challenges, Opportunities, and Prospects
(MDPI AG, 2024-09-25) Kamyabi, Leila; Lie, Tek Tjing; Madanian, Samaneh; Marshall, Sarah
Due to the increasing demand for electricity, competitive electricity markets, and economic concerns, power systems are operating near their stability margins. As a result, power systems become more vulnerable following disturbances, particularly from a dynamic point of view. To maintain the stability of power systems, operators need to continuously monitor and analyze the grid’s state. Since modern power systems are large-scale, non-linear, complex, and interconnected, it is quite challenging and computationally demanding to monitor, control, and analyze them in real time. State Estimation (SE) is one of the most effective tools available to assist operators in monitoring power systems. To enhance measurement redundancy in power systems, employing multiple measurement sources is essential for optimal monitoring. In this regard, this paper, following a brief explanation of the SE concept and its different categories, highlights the significance of Hybrid State Estimation (HSE) techniques, which combine the most used data resources in power systems, traditional Supervisory Control and Data Acquisition (SCADA) system measurements and Phasor Measurement Units (PMUs) measurements. Additionally, recommendations for future research are provided.
A computational theory of human perceptual mapping
(Cognitive Science Society, 2011-07) Yeap, WK
This paper presents a new computational theory of how humans integrate successive views to form a perceptual map. Traditionally, this problem has been thought of as a straightforward integration problem whereby position of objects in one view is transformed to the next and combined. However, this step creates a paradoxical situation in human perceptual mapping. On the one hand, the method requires errors to be corrected and the map to be constantly updated, and yet, on the other hand, human perception and memory show a high tolerance for errors and little integration of successive views. A new theory is presented which argues that our perceptual map is computed by combining views only at their limiting points. To do so, one must be able to recognize and track familiar objects across views. The theory has been tested successfully on mobile robots and the lessons learned are discussed.
A conceptual framework to evaluate suppliers for building infrastructure in the Malaysian electricity supply industry
(Universiti Teknologi Malaysia (UTM), 2012) Thiruchelvam, S; Tookey, JE; Rotimi, J.O.B.; Samarasinghe, DAS; Mustapha, KN; Kadirgama, K
In the current competitive business environment the relationship between buyers and suppliers is no longer antagonistic. Emphasis has shifted to the forging of partnerships that benefits all parties in any business setting. The emergence of supply chain concepts have brought about the realization of long-term cooperation based on mutual trusts. Frequently high priority is given towards suppliers that are able to deliver, and are committed to buyer’s business objectives. However, proper supplier selection is pertinent to meeting these business objectives as it dictates operational and financial positions. The current study discusses a construct that could facilitate supplier selection in a typical government linked company. It presents the key items that could be considered in a supplier selection metric using a comprehensive approach. The study is an aspect of a doctoral research programme that aims to develop a supplier selection model for an electricity supply organization. The paper concludes that having a good set of supplier selection metric is of critical importance to business success in any supply chain.
A Contemporary Survey on Deepfake Detection: Datasets, Algorithms, and Challenges
(MDPI AG, 2024-01-31) Gong, LY; Li, XJ
Deepfakes are notorious for their unethical and malicious applications to achieve economic, political, and social reputation goals. Recent years have seen widespread facial forgery, which does not require technical skills. Since the development of generative adversarial networks (GANs) and diffusion models (DMs), deepfake generation has been moving toward better quality. Therefore, it is necessary to find an effective method to detect fake media. This contemporary survey provides a comprehensive overview of several typical facial forgery detection methods proposed from 2019 to 2023. We also analyze and group them into four categories in terms of their feature extraction methods and network architectures: traditional convolutional neural network (CNN)-based detection, CNN backbone with semi-supervised detection, transformer-based detection, and biological signal detection. Furthermore, it summarizes several representative deepfake detection datasets with their advantages and disadvantages. Finally, we evaluate the performance of these detection models with respect to different datasets by comparing their evaluating metrics. Across all experimental results on these state-of-the-art detection models, we find that the accuracy is largely degraded if we utilize cross-dataset evaluation. These results will provide a reference for further research to develop more reliable detection algorithms.
A control system for an unmanned micro aerial vehicle
(AUT University, 2011-12) Huang, L; Murton, C
This paper presents the development of a PCbased control system for an unmanned micro aerial vehicle (UAV) that has been converted from a helicopter model. The hand-controller of the helicopter model is modified to be a wireless link between a ground control computer (GCC) and the UAV, which carries sensors including an inertia measurement unit (IMU) and the actuators for the main rotor and pitch angle controls. A programming environment, written with the C# programming language, is set up for the implementation of control algorithms for the UAV. Manual and automatic modes of controlling the UAV are achieved. Implementation issues, such as the reliability of the IMU data for closed-loop control, are also discussed.
A controlled Natural Language Interface to Class Models
(SciTePress, 2011) Naeem, M; Bajwa, IS; Naeem, MA; Chaudhri, AA; Ali, S
The available approaches for automatically generating class models from natural language (NL) software requirements specifications (SRS) exhibit less accuracy due to informal nature of NL such as English. In the automated class model generation, a higher accuracy can be achieved by overcoming the inherent syntactic ambiguities and semantic inconsistencies in English. In this paper, we propose a SBVR based approach to generate an unambiguous representation of NL software requirements. The presented approach works as the user inputs the English specification of software requirements and the approach processes input English to extract SBVR vocabulary and generate a SBVR representation in the form of SBVR rules. Then, SBVR rules are semantically analyzed to extract OO information and finally OO information is mapped to a class model. The presented approach is also presented in a prototype tool NL2SBVRviaSBVR that is an Eclipse plugin and a proof of concept. A case study has also been solved to show that the use of SBVR in automated generation of class models from NL software requirements improves accuracy and consistency.

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