Engineering

Publication Search Results

Now showing 1 - 10 of 18
  • (2005) Russell, Carol; Lee, Adrian
    Conference Paper
    In this paper we describe an institutionally funded Fellowship running 2001– 2004, which seeded and cultivated new communities of practice in innovative teaching using educational technology. The literature identifies some inherent challenges in such schemes. The Fellowship was able to surface and deal with these through a team-based action research approach. Key features were the buying out of staff time for a semester and the development of discipline-based projects in a supported cross-disciplinary group. The Fellowship has been central to shifting systemic institutional blocks to educational innovation.

  • (2007) Zhu, Liming; Ali Babar, Muhammad; Staples, Mark; Nonaka, Makoto
    Book Chapter
    The possible variability of project delay is useful information to understand and mitigate the project delay risk. However, it is not sufficiently considered in the literature concerning effort estimation and simulation in software product line development. In this paper, we propose a project delay simulation model by introducing a random variable to represent the variability of adaptive rework. The model has been validated through stochastic simulations by comparing generated adaptive rework to an actual change effort distribution, and by sensitivity analysis. The result shows that the proposed model is capable of producing reasonable variability of adaptive rework, and consequently, variability of project delay. Analysis of our model indicates that the strength of dependency has a larger impact than the number of residual defects, for the studied simulation settings. However, high levels of adaptive rework variability did not have great impact on overall project delay.

  • (2008) Frances, Maude; Cox, Shane; Sidhunata, Harry; Leslie, Greg
    Conference Paper
    The Membrane Research Environment (MemRE), is a research infrastructure project of the Advanced Membrane Technologies for Water Treatment Research Cluster, a research project funded by the CSIRO flagship Water for a Healthy Country. The research cluster, a nationally distributed and multidisciplinary group of researchers including computational and physical chemists, physicists, material scientists, and chemical and mechanical engineers, aims to develop novel membrane materials in order to reduce the energy associated with desalination by 40%.

  • (2007) Theo, J.; Mazaheri, M.; Tabatabaei Balaei, Asghar; Dempster, A.G
    Conference Paper

  • (2009) Cox, Shane; Frances, Maude; Croucher, Joanne; Sidhunata, Harry; Leslie, Greg
    Conference Paper
    The Membrane Research Environment (MemRE) is a component research infrastructure project of the Advanced Membrane Technologies for Water Treatment Research Cluster, a research project funded by the CSIRO flagship Water for a Healthy Country. The research cluster, a nationally distributed and multidisciplinary group of researchers including computational and physical chemists, physicists, material scientists, and chemical and mechanical engineers, aims to develop novel membrane materials in order to reduce the energy associated with desalination by 40%. Common hurdles in multidisciplinary research projects include: a lack of consolidation of existing information relevant to the research from all the participating fields; an absence of information infrastructure to promote comparison of results; and the need for a common language to better enable project participants to communicate. MemRE has been designed and implemented as a solution to these hurdles, to provide an integrated research development tool and learning environment.

  • (2010) Cole, Fletcher; Cox, Shane; Frances, Maude
    Conference Paper
    An opportunity to explore the topic of data usages is presented by the collaborative research being undertaken by a federation of applied science research units affiliated with a number of different Australian research organizations (the Cluster). The research aims to investigate how members of the collaboration understand and work with data in their day-to-day practice.

  • (2022) Shahriari, Siroos
    Thesis
    Time series models are used to model, simulate, and forecast the behaviour of a phenomenon over time based on data recorded over consistent intervals. The digital era has resulted in data being captured and archived in unprecedented amounts, such that vast amounts of information are available for analysis. Feature-rich time-series datasets are one of the data sets that have become available due to the expanding trend of data collection technologies worldwide. With the application of time series analysis to support financial and managerial decision-making, the development and advancement of time series models in the transportation domain are unavoidable. As a result, this thesis redefines time series models for transportation planning use with the following three aims: (1) To combine parametric and bootstrapping techniques within time series models; (2) to develop a time series model capable of modelling both temporal and spatial dependencies in time-series data; and (3) to leverage the hierarchical Bayesian modelling paradigm to accommodate flexible representations of heterogeneity in data. The first main chapter introduces an ensemble of ARIMA models. It compares its performance against conventional ARIMA (a parametric method) and LSTM models (a non-parametric method) for short-term traffic volume prediction. The second main chapter introduces a copula time series model that describes correlations between variables through time and space. Temporal correlations are modelled by an ARMA-GARCH model which enables a modeller to describe heteroscedastic data. The copula model has a flexible correlation structure and is used to model spatial correlations with the ability to model nonlinear, tailed and asymmetric correlations. The third main chapter provides a Bayesian modelling framework to raise awareness about using hierarchical Bayesian approaches for transport time series data. In addition, this chapter presents a Bayesian copula model. The combination of the two models provides a fully Bayesian approach to modelling both temporal and spatial correlations. Compared with frequentist models, the proposed modelling structures can incorporate prior knowledge. In the fourth main chapter, the fully Bayesian model is used to investigate mobility patterns before, during and after the COVID-19 pandemic using social media data. A more focused analysis is conducted on the mobility patterns of Twitter users from different zones and land use types.

  • (2022) Nguyen, Minh Triet
    Thesis
    Singlet fission is a photo-physical process that generates two triplet excitons from one singlet exciton and can potentially enhance efficiency in photovoltaic systems. The combination of photovoltaics and singlet fission is a novel field for solar energy conversion when there is much interest in renewable, non-destructive, and continuously available energy sources. Singlet fission can also overcome thermalization losses in photovoltaics, which happens in traditional cells when the incident photon energy is higher than the silicon bandgap energy, using a carrier multiplication mechanism. This thesis will design, construct, and characterize photovoltaic devices incorporating singlet fission materials to study singlet fission in practical application. The research focuses on materials characterization, spin dynamics, and electron transfers between acene and the semiconductor layer in Au/TiO2 ballistic cells, and the incorporation of singlet fission layers on silicon-based cell structures. In detail, a set of investigations was developed and summarized by implementing singlet fission materials into a state-of-the-art ballistic photovoltaic device and silicon-based solar cell. The studies demonstrate proof of concept and rationally explain the process. The first part of the thesis investigates thin films of pentacene, TIPS-pentacene, and tetracene via crystallinity, morphology, absorption, and thickness characterization. Additionally, Au and TiO2 layers in Schottky device structures were optimized to achieve the best performance for energy transfer from an applied dye layer (merbromin). The drop-casted dye layer influences the device performance by increasing short-circuit current and open-circuit voltage, demonstrating the ability of charge transfer between the device and the applied film. This device structure provides a test bed for studying charge and energy transfer from singlet fission films. The latter part of the thesis describes several investigations to understand singlet fission in a thin film using this architecture. Magneto-photoconductivity measurements were primarily used to observe the spin dynamics via photoconductivity under an external magnetic field. Control experiments with bare Au/TiO2 devices showed no observable magneto-photoconductivity signal. In contrast, devices with pentacene and tetracene singlet fission layers showed a strong magnetoconductivity effect caused by ballistic electron transfer from the singlet fission layer into the TiO2 n-type semiconductor through an ultra-thin gold layer inserted between the layers. A qualitatively different behavior is seen between the pentacene and tetracene, which reveals that the energy alignment plays a crucial part in the charge transfer between the singlet fission layer and the device. The last section investigates the application of pentacene and tetracene evaporated thin-films as sensitizer layers to a silicon-based solar cell. The optimized Si cell structure with the annealing treatment improved the cell's performance by increasing short-circuit current and open-circuit voltage. The deposition of pentacene and tetracene as sensitizer layers into the device showed some results but posed several challenges that need to be addressed. As the current-voltage and external quantum efficiency measurements were taken, it was observed that material interfaces need to be designed to fully achieve the singlet fission of the acene layer into the Si devices.

  • (2022) Saavedra Moreno, Yesenia
    Thesis
    Frothers are widely used in flotation to primarily generate air bubbles, aid gas dispersion, and form a stable froth that provides a selective separation of particles. The current frother classification approaches are based on only three characteristics of the frothers. A number of studies have reported the use of characteristics of frothers including critical coalescence concentration and the ability to create an effective foam under dynamic conditions, as well as foam stability to group frothers. Moreover, the majority of studies are based on a two-phase system, ignoring to some extent the effect of particles, which is relevant to flotation. This thesis explores the effect of frother type on foam stability under dynamic and static conditions and provides a framework to classify frothers based on their foam generation ability. Three foam stability variables, dynamic foam stability index, static foam stability index, and decay rate index are quantified for eighteen different frothers. Four more frothers characteristics reported in the literature, MW, HLB, CCC, DL were defined. The hierarchical cluster analysis was conducted to group frothers based on similarity and provide a category system. Based on the similarities, frothers were grouped into four categories as opposed to the binary frother classification reported in the literature. The selectivity of frothers increases from Group 1 to Group 4, whereas frothers decrease their powerfulness from Group 1 to Group 4. To complement the proposed frother classification and assess the relevance to flotation, the effect of particles on the foam generation under dynamic conditions was explored for four frothers from different families. In terms of froth stability, the three-phase system showed a similar frother ranking to the two-phase system, except that TPG behaved as a more powerful frother in the presence of hydrophobic particles than MIBC. It was also found that the proposed frother classification system in a two-phase system translates well to the three-phase system as frothers were clustered in the same groups. Further insight into the changes of foam stability was gained by simulating the coalescence of two air bubbles at various frother concentrations using the volume of fluid method (VOF). It was observed that an increase in frother concentration damped the oscillation of coalesced bubbles by the surface elasticity, suggesting that the bubble surface area moves at a lower velocity, which may reduce the motion of particles attached to the interface and consequently, their detachment during the merging of two bubbles.

  • (2022) Idris, Nur Fadhilah
    Thesis
    Odours from the drying process at rubber processing plants have been identified as a major malodour contributor. The increasing number of complaints from these operations has resulted in the suspension and/or shutdown due to environmental impacts by local communities. Previous studies have indicated that packed-bed wet scrubber typically adopted as an odour abatement technology is ineffective at treating odours from these plants. Literature review reveals there is various chemical groups of volatile organic compounds emitted from the raw rubber processing. To date, no comprehensive analytical study was conducted on the effectiveness of wet scrubber in removing the VOCs. This research aims to understand the composition of VOCs emitted at full-scale drying processes in Malaysian rubber processing plants in terms of their chemical composition and sensorial profile. This led to the identification of key odorants responsible for the malodour issue. The wet scrubber performance to remove the VOCs was investigated as well as the operation optimisation to improve its performance. The adsorption by activated carbon was explored as a potential secondary treatment to improve the overall VOCs removal for emissions from rubber drying processes. Lastly, the sustainability of all options to upgrade the wet scrubber system was studied. The VOCs emissions samplings were performed at two typical commercial rubber processing plants in Malaysia. VOCs samplings were collected at both inlet and outlet of the wet scrubbers using a nalpohan bag attached to a vacuum drum and subsequently transferred to sorbent tubes at dry and wet seasons as well as at different operational times. The VOCs quantification was performed using a gas chromatography-mass spectrometry/olfactometry (GC-MS/O). Additionally, the presence of hydrogen sulfide (H2S) was determined using a H2S analyzer (Jerome 631-X) in one of the sampling periods. For the optimisation, the design and operating conditions of one of the plants were used in simulation and experimental studies. Meanwhile, the adsorption behaviour of selected VOCs was investigated on two types of virgin activated carbon (AC) namely coconut-based AC (CSAC) and palm kernel-based AC (PKSAC) manufactured in Malaysia. The ACs were characterised accordingly to determine their surface characteristics. The environmental impact of the proposed improved odour abatement technologies was compared by Life cycle Assessment (LCA). A total of 80 VOCs from various chemical functional groups was frequently detected by GC-MS/O with 11 new compounds not previously reported. 50 % of the chemical concentration of the emissions was dominated by the volatile fatty acids (VFAs) and 16 critical VOCs were identified including key odorants. H2S was detected in the emissions and potentially contributes to the odour impact. The composition of the emissions was observed to be influenced by the seasonal variation in terms of the number of VOCs detected for each season. Odour wheels were developed for the first time based on the sensory analysis of full-scale rubber emission before and after treatment by the wet scrubber as a management tool for on-site plant operators and regulatory authorities to assess the malodour impact on surrounding communities. The performance analysis of the existing wet scrubber technology revealed that it was ineffective at removing VOCs, indicated by the high chemical concentration and odour activity value (OAV) detected at the outlet emissions of the wet scrubber except for single-chain VFAs. The comparable odour categories and the number of sensory-related VOCs in both inlet and outlet emissions further revealed the wet scrubber’s poor sensory removal. The wet season observed a higher wet scrubber performance because of the greater VFAs concentration detected in the emissions. However, the wet scrubber is not suitable to remove the H2S due to its poor and inconsistent removal. The study demonstrated that the combination of sensory and quantitative analysis improved the accuracy to identify the odorants from rubber emissions and investigated wet scrubber poor performance. The simulation study revealed that the performance of the wet scrubber can be optimised (> 80 % chemical concentration removal) by modification of some of the operating conditions, namely the application of a higher liquid/gas ratio and greater interfacial area of packing to remove water-soluble VOCs and subsequently, reduce the odour impact (> 90 % OAV reduction). Laboratory-scale optimisation experiments demonstrated that the VOCs solubility is highly correlated with their absorption efficiency. Furthermore, the absorption of the VOCs is best at higher gas temperature (> 45 C) and low liquid temperature (< 10 C). The experimental results show the condition in the gas phase has a greater influence on the removal efficiency compared to the liquid condition. Optimal removal of the key odorants and other critical VOCs at this stage is necessary to minimise the odour impact and organic loading before subsequent treatment. The adsorption by activated carbon has the potential to be incorporated as a secondary treatment to remove the remaining low water-soluble VOCs that are inefficient to be removed by the wet scrubber. The boiling point of the VOCs was found to be the primary factor that influences AC adsorption behaviour whereas polarity and molecular structure were secondary factors. The emissions consist of multi-component VOCs, an adsorption competition has been observed where higher boiling point VOCs have a stronger affinity with the AC and displace the weaker adsorbed lower boiling point VOCs. The presence of high relative humidity (RH >70 %) was found to shorten the breakthrough times greatly and adversely affect the AC adsorption performance. The breakthrough of VOCs categorised as odorant is more critical because of the greater odour impact contribution than its chemical concentration. CSAC demonstrated greater adsorption capacity (average 38 %) than PKSAC (average 11 %) due to the different surface characteristics. However, both ACs showed comparable adsorption behaviour. Therefore, AC adsorption could be employed as a polishing (or secondary) stage after full-scale wet scrubber abatement to improve the overall odour mitigation from rubber drying processes. Life cycle assessment (LCA) was performed on the existing wet scrubber (WS), optimised wet scrubber (OWS) and a hybrid of the optimised wet scrubber with activated carbon (OWS+AC) at full-scale operation. It was found that the impact of malodorous emissions was the greatest for the direct emissions (> 99 %) of WS due to its lower efficiency in removing the malodour. 3-methylbutanal and 3-methylbutanoic acid have the greatest contribution from the direct emission of WS whereas H2S has a greater contribution from additional components used in OWS and OWS+AC. Electricity was found to be a major contributor to global warming and either ozone formation or human health potential impact categories with the increasing trend in WS, OWS and hybrid OWS+AC, accordingly. Meanwhile, the upgrading of the wet scrubber has also impacted the operational cost. In general, the environmental impact contributed by WS primarily came from direct emissions whereas the whole supply chain of OWS and hybrid OWS+AC has a greater environmental impact than their direct emissions. Nevertheless, the application of renewable energy is a good option to reduce the environmental impact.