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(2008)Conference PaperThe Job-Shop Scheduling Problem (JSSP) is considered as one of the difficult combinatorial optimization problems and treated as a member of NP-complete problem class. In this paper, we consider JSSPs with an objective of minimizing makespan while satisfying a number of hard constraints. First, we develop a genetic algorithm (GA) based approach for solving JSSPs. We then introduce a number of priority rules such as partial reordering, gap reduction and restricted swapping to improve the performance of the GA. We run the GA incorporating these rules in a number of different ways. We solve 40 benchmark problems and compared their results with that of a number of well-known algorithms. We obtain optimal solutions for 27 problems, and the overall performance of our algorithms is quite encouraging.
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(2007)Conference PaperThe Job-Shop Scheduling Problem (JSSP) is one of the most critical combinatorial optimization problems. The objective of JSSP in this research is to minimize the makespan. In this paper, we propose two Genetic Algorithm (GA) based approaches for solving JSSP. Firstly, we design a simple heuristic to reduce the completion time of jobs on the bottleneck machines that we call the reducing bottleneck technique (RBT). This heuristic was implemented in conjunction with a GA. Secondly; we propose to fill any possible gaps left in the simple GA solutions by the tasks that are scheduled later. We call this process the gap-utilization technique (GUT). With GUT, we also apply a swapping technique that deals only with the bottleneck job. We study 35 test problems with known solutions, using the existing GA and our proposed two algorithms. We obtain optimal solutions for 23 problems, and the solutions are very close for the rest.
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(2008)Conference PaperThe primary objective of this research is to solve the job-shop scheduling problems by minimizing the makespan. In this paper, we first developed a genetic algorithm (GA) for solving JSSPs, and then improved the algorithm by integrating with three priority rules. The performance of the developed algorithm was tested by solving 40 benchmark problems and comparing their results with that of a number of well-known algorithms. For convenience of im-plementation, we developed a decision support system (DSS). In the DSS, we built a graphical user interface (GUI) for user friendly data inputs, model choices, and output generation. An overview of the DSS and the analysis of experimental results are provided.
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(2007)Conference PaperThe philosophy of the “Warman Design and Build Competition” and some of the challenges of running it are described in this perspective by its National Coordinator since 2003. In particular, the need is for the competition to work effectively across a wide range of student group ability. Not every group engaging with the competition will be competitive nationally, yet all should learn positively from the experience. Reported also in this paper is the collective feedback from the 2006 campus organizers in respect to their use of the competition as an educational experience in their classrooms. Each University participating uses the competition differently with respect to student assessment and the support students receive. However, all academic campus organizer responses to the survey suggest that the competition supports their own learning objectives very well. The competition which was first run in 1988 will have its 20th anniversary final in September this year. While the projects have varied widely over the years, the intent to challenge 2nd year university (predominantly mechanical) engineering students with an open-ended statement of requirements in a practical and experiential exercise has been a constant. Students are faced with understanding their opportunity and their client’s value system as expressed in a scoring algorithm; they are required to conceive, construct and demonstrate their device with limited prior knowledge and experience, and the learning outcomes clearly impact their appreciation for teamwork, leadership and product realization. The competition has been successful due in part to its underpinning by the National Committee on Engineering Design (Engineers Australia), the sponsorship of Weir Minerals and the commitment of many engineering design educators across Australia and New Zealand.
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(2007)Conference PaperThis work presents the derivation of a comprehensive mathematical model for an off-road vehicle such as an agricultural tractor that drags behind it a heavy implement. The models are being developed with the aim of designing robust controllers that will enable the high precision control of the implement’s trajectory. The developed model is subjected to real conditions, such as ground undulation and uncertainty, sloping terrain, tyre slippage, and constrained steering of the tractor. The implement is assumed to possess independently steered wheels for aiding in implement alignment. A complete model is presented and simulated under varying conditions. Primarily this work demonstrates and validates the trailed vehicle system behavior when the trailing implement is subjected to large drag forces due to ground engagement and the significantly large lateral disturbances that occur in real life broad acre farming conditions.
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(2007)ThesisThe use of high performance concrete in construction has been enhanced by the use of pozzolanic materials. However, the use of these materials has not been optimized. Such optimization may be achieved by a systematic increase in the amount and combination of pozzolanic material additions, with accompanying studies of their effects on the mechanical, durability and microstructural characteristics of blended concrete. This work evaluated various concrete durability issues by studying systematic increases of pozzolanic materials such as fly ash and blast furnace slag (BFS) in the range of 25, 50 and 70%, and silica fume at 10% of total cementitious materials, forming various binary and ternary concrete blends. The concrete specimens were cured for a period of seven days after demoulding in line with widely practiced commercial curing procedures. The research explored the role and effectiveness of various binary and ternary blends of pozzolanic materials on the mechanical, durability and microstructural characteristics of concrete. Durability was evaluated by two independent rapid chloride permeability tests measured as charge passed and chloride conductivity from the RCPT and UCT tests respectively. These two rapid tests were coupled with long-term ponding tests to evaluate chloride ingress and the extent of corrosion for a period of two years. Further durability tests such as carbonation, drying shrinkage and porosity of these blends were also undertaken. This study also utilized micro-analytical techniques such as X-ray diffraction and Scanning Electron Microscopy to follow the hydration mechanism in various binary and ternary blends. Statistical significance testing was used to analyse and confirm all experimental results and conclusions. It is well known that a level of caution is exercised in the construction industry in the use of ternary blends. This study aims to evaluate the durability aspects of ternary concrete blends, in addition to binary blends, for resistance to chloride, corrosion, carbonation attacks and provide recommendations relating to the limits of blending level, as well as exposure conditions for blended concretes, based on the results of this study. It is expected that this will fill a major knowledge gap observed in the concrete industry. A comparison of two rapid chloride permeability tests such as UCT and RCPT indicates that the UCT test is easy and practicable, and does not contradict results obtained in the standard RCPT. However, the statistical significance of results obtained for some blends was only able to be established by using the RCPT. This effect can be attributed to the larger size specimens compared to UCT. The recommended blend to acquire both early-age and long-term strength development in fly ash is the ternary blends comprising 10% silica fume and 25% fly ash cast using lower w/b ratio. In addition, the same blend exhibited lower carbonation depth, lower charge passed from RCPT, lower chloride ingress and higher corrosion resistance characteristics from long-term ponding test compared to other blends of fly ash. In BFS blends, an increase in compressive strength was observed only in the specimens of 25% BFS compared to other higher percentage blends, while the higher addition of 50 and 70% replacement showed no significant difference in compressive strength between them and their corresponding ternary blends with addition of silica fume. The results of this study indicate that control (OPC) specimens cast with increased w/b ratio of 0.48 showed higher chloride ingress compared to both binary blends of 70% fly ash and 70% BFS specimens. This indicates that (OPC) cast using higher w/b ratio is to be avoided in chloride environments. On the other hand, though, the ternary blends of 10% silica fume and up to 50% fly ash exhibited lower chloride ingress compared to their respective binary blends of fly ash. However, these ternary blends exhibited lower compressive strength, more negative corrosion potential and higher corrosion rate, compared to the respective binary blends of 25% fly ash and its ternary blends. Therefore, the recommended blend observed in the long-term ponding test is the ternary blend of 25% fly ash and 10% silica fume. The recommended level of corrosion resistance in slag specimens is achieved by the use of ternary blends comprising silica fume at 10% added to the blend that contains up to 70% slag. However, the recommended level of slag for a lower carbonation effect is the use of a ternary blend comprising 50% slag and 10% silica fume (3B5S1) which showed a carbonation depth of 10.8 mm and a compressive strength of 53.2 MPa after 365 days of exposure. The drying shrinkage of concrete increased with the increase in fly ash and the same trend was observed in BFS specimens. However, the results were not significantly different between their respective blends. The extent of carbonation in fly ash specimens was higher compared to BFS blends specimens. This can be attributed to the formation of dusty and weak surfaces on the outer surface in addition to the excessive leaching of sodium chloride solution from the long-term ponding test in the former specimens compared to later. The high volume pozzolanic materials, irrespective of fly ash or BFS and addition of silica fume (70% fly ash and 10% silica fume, and 70% BFS and 10% silica fume), showed higher cumulative pore volume indicating that these blends with seven days of curing were not beneficial. These high volume ternary blends required prolonged curing to release portlandite from the hydration of cement to continue the pozzolanic reaction. This study has shown that 7-days curing of the pozzolanic concrete is inadequate if pozzolanic activity is to be invoked. This is particularly the case when it is expected that the concrete is likely to be subjected to a harsher than usual environment characterised by a dry atmosphere.
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(2007)ThesisInsitu cementitious stabilisation is an economical, environmentally sustainable and socially advantageous means of rehabilitating pavements. With the recent availability of a wide range of binders and advanced construction equipment, the characterisation of cementitiously stabilised pavement materials has become the focus of further advancement of this technology. Australian practice has moved towards the use of Indirect Diametric Tensile (IDT) methods for the characterisation of these materials. A draft protocol for the IDT test has been prepared and specifies samples to be compacted by gyratory compactor. This procedure provides for both monotonic and repeated load testing, which aims to measure the material’s strength, modulus and fatigue life. A range of host materials, including a new crushed rock and a reclaimed existing pavement base course, were assessed when stabilised with a General Purpose cement binder as well as with a slag-lime blended binder. Materials were assess for their inherent material properties, Unconfined Compression Strength (UCS), Unconfined Compression modulus, IDT strength and modulus under both monotonic and repeated load. A number of amendments and refinements to the testing protocol were recommended. These included the use of minimum binder contents to ensure the binder was uniformly distributed and to promote heavy binding of the materials to ensure they behaved elastically. It was also recommended that samples be gyratory compacted to a pre-determined sample height to allow a constant density to be achieved. The variability of the test results was examined. UCS results were found to be comparatively as variable as other researchers had reported. IDT strength results contained a similar level of variability, which was considered to be acceptable. Modulus results, both monotonic and repeated load, were found to be five to ten times more variable than strength results, which is a generally accepted trend for modulus testing. Under repeated loading, some challenges with the test protocol were encountered. The primary challenge was obtaining reliable and repeatable diametrical displacement data for modulus calculation. This was partially overcome by the insertion of smooth spacers to prevent the Linear Voltage Displacement Transformer (LVDTs) becoming caught on the sample sides. The achievement of reliable and repeatable IDT modulus results through improved displacement measurements should be the focus of future research efforts in this area.
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(2008)ThesisThe household has always been a place of information consumption. While much is known about the modern household as a consumer of information and adopter of information-related technologies, virtually nothing is known about how the household -as a collectivity - processes and manages its information. This research represents the first systematic study of the household as a human information system and presents an understandingtype theory of household information practices. Using dimensional analysis (including theoretical sampling) as proposed by Schatzman (1991), the information practices of eleven households (28 householders) were explored. Each householder completed a questionnaire to identify the information and information-related devices and services used in the household. This was followed by an unstructured group interview that explored the information practices in the household. Analysis of the questionnaires and interviews revealed that within a household it is individual householders who process and manage information. They do so because information has a role in their life, that is, particular information is meaningful for them. Each householder thus devises their own individual information practices, representing the unique way in which a householder comes to live with information. Household information practices are the sum of these individual information practices. They are mediated by two enabling processes - taking charge and negotiating - and nine dimensions of action. Six of the dimensions affect the information practices of individual householders - which are themselves a dimension - while the final two represent, respectively, the consequences of living with and without information. All processes and dimensions operate against, and interact with, a changing structural context of information, technology and society. As a result, each household has a characteristic mode for dealing with information. The centrality of negotiation in developing household information practices indicates that the practices are socially constructed and represent an emergent phenomenon. This, in turn, suggests that the household as an information system is a negotiated order. Insights from the research can be applied to other types of organisations and other aspects of the Information Systems discipline. Areas of further work are identified to expand upon the exploratory nature of this research.
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(2008)ThesisThe thesis deals with the design and implementation of an Adaptive Flight Control technique for Unmanned Aerial Vehicles (UAVs). The application of UAVs has been increasing exponentially in the last decade both in Military and Civilian fronts. These UAVs fly at very low speeds and Reynolds numbers, have nonlinear coupling, and tend to exhibit time varying characteristics. In addition, due to the variety of missions, they fly in uncertain environments exposing themselves to unpredictable external disturbances. The successful completion of the UAV missions is largely dependent on the accuracy of the control provided by the flight controllers. Thus there is a necessity for accurate and robust flight controllers. These controllers should be able to adapt to the changes in the dynamics due to internal and external changes. From the available literature, it is known that, one of the better suited adaptive controllers is the model based controller. The design and implementation of model based adaptive controller is discussed in the thesis. A critical issue in the design and application of model based control is the online identification of the UAV dynamics from the available sensors using the onboard processing capability. For this, proper instrumentation in terms of sensors and avionics for two platforms developed at UNSW@ADFA is discussed. Using the flight data from the remotely flown platforms, state space identification and fuzzy identification are developed to mimic the UAV dynamics. Real time validations using Hardware in Loop (HIL) simulations show that both the methods are feasible for control. A finer comparison showed that the accuracy of identification using fuzzy systems is better than the state space technique. The flight tests with real time online identification confirmed the feasibility of fuzzy identification for intelligent control. Hence two adaptive controllers based on the fuzzy identification are developed. The first adaptive controller is a hybrid indirect adaptive controller that utilises the model sensitivity in addition to output error for adaptation. The feedback of the model sensitivity function to adapt the parameters of the controller is shown to have beneficial effects, both in terms of convergence and accuracy. HIL simulations applied to the control of roll stabilised pitch autopilot for a typical UAV demonstrate the improvements compared to the direct adaptive controller. Next a novel fuzzy model based inversion controller is presented. The analytical approximate inversion proposed in this thesis does not increase the computational effort. The comparisons of this controller with other controller for a benchmark problem are presented using numerical simulations. The results bring out the superiority of this technique over other techniques. The extension of the analytical inversion based controller for multiple input multiple output problem is presented for the design of roll stabilised pitch autopilot for a UAV. The results of the HIL simulations are discussed for a typical UAV. Finally, flight test results for angle of attack control of one of the UAV platforms at UNSW@ADFA are presented. The flight test results show that the adaptive controller is capable of controlling the UAV suitably in a real environment, demonstrating its robustness characteristics.