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Hydrothermal processing of primary, waste-activated, and digested sewage sludge: Products characterisation, fate of heavy metals and nutrients, and process integration
No full textSewage sludges, such as primary sludge (PS), thickened waste-activated sludge (TWAS), and digested sludge (DS), are generated at different stages during the wastewater treatment process. The intrinsic difference in the biochemical and physicochemical properties of these sludge materials may impact their transformation during hydrothermal treatment. This study comprehensively investigated the hydrothermal processing of PS, TWAS, and DS over a range of hydrothermal carbonisation to liquefaction temperatures (180–270 °C). Organic matter conversion increased with temperature but varied with sludge types. The physicochemical, thermal, and textural properties of the produced hydrochar varied substantially with temperature and sludge types. Hydrochar produced from PS at 270 °C had a higher fuel ratio (0.80), calorific value (20.8 MJ/kg), carbon content (48.2 %), and lower ash content (24.4 %) compared to hydrochar produced from other sludge feedstocks. Heavy metals in the feed materials were largely retained in the hydrochar with more than 95 % recovery at all temperatures. Bio-oil products were fractionated into heavy and light bio-oil, and their compositions differed greatly. The aqueous phase product from TWAS and DS had total N, P, K content reaching 5000 mg/L. The findings of this work demonstrate the potential of hydrothermal processing for the valorisation of wastewater sludges into value-added products.</p
The Sonic Gathering Place Installation, Melbourne: User Experience and Post-Hoc Assessment of Sound Levels
No full textThe Sonic Gathering Place is a seating arrangement with planter boxes and speakers that plays back
natural sounds. The sounds were recorded in national parks where the plants are native. User’s enjoyment of
the SGP has previously been reported together with some evidence regarding effectiveness of its biophilic
sound design objectives. This paper now explores the levels of sound that users experience, during playback of
the introduced sounds, that gave rise to these positive experiences. This was post-hoc, as measurement had
played no role in determination of the playback levels. These had been set through trial-and-error as part of the
designer’s biophilic design intentions. The introduced sound levels were found to have been set only marginally
louder than sound levels that existed pre-installation. This may provide useful guidance for future installations
that include sound in their design, and aid in the selection of sites where sound designs may prove attractive to
users.</p
Precise Modelling and Dynamic Control of Single-phase Dual Active Bridge DC-DC Converters
No full textDual active bridge (DAB) converters are an appealing DC-DC converter solution to meet the energy conversion needs of globally burgeoning technologies in renewable energy generation, energy storage, and the transportation sector due to their bi-directional energy transfer capabilities and galvanic isolation.
The benefits of using a resonant coupling network to link the two bridges of a DAB are well established – a resonant network appropriately tuned to the converter’s switching frequency can reduce the reactive currents circulating between the converter bridges, lowering conduction losses, and facilitating more compact converter designs. However resonant DAB topology variants are known to have limited zero-voltage-switching (ZVS) capability, particularly when operated at low power levels.
This work presents detailed modelling of resonant LCL and CLC topology coupling networks that provide for more accurate resonance matching and precise mapping of the ZVS operation boundary conditions of these resonant DAB converter variants that accounts for all the switched harmonic contributions and the practicalities of switching dead-time and device commutation in the analysis.
Thereafter, derived expressions for the active and reactive power flows between DAB converter bridges are combined with these detailed network models for a deeper understanding of these power flows in a resonant DAB and to investigate variance in their fundamental and harmonic components across converter operating conditions. A subsequent selective triple-phase-shift (TPS) modulation angle strategy is presented to extend the ZVS operating range of both the LCL and CLC resonant variants, to maximise their inherent reactive current reducing capability within the bounds of soft-switching operation.
DAB control with a fast dynamic power response is essential in applications where power demands fluctuate rapidly (e.g. electric vehicles and renewable energy systems). A novel approach for dynamic power control that uses precisely timed synchronous current and voltage sample points for fast, per-cycle power estimation is proposed, using a simple inductive coupling for reduced complexity. This approach provides rapid and accurate, software-based direct power control for the conventional DAB, implemented with a proportional integral (PI) feedback controller, and hastened further with a TPS feedforward term. A novel carrier-shift approach to TPS modulation forms the basis of the direct power control strategy, enabling control over the converter’s entire operating range. The practical implementation of this control strategy demonstrates how to account for phenomena related to controller actuation (i.e. gate drive and switching device propagation delay) and measurement feedback (i.e. current sensor propagation analogue signal conditioning).
All modelling and design analyses presented in this thesis have been extensively verified by precisely matched switched simulations and in experiment on a reconfigurable laboratory prototype DAB converter.</p
Patient_data
No full textThe inputs for the problem instances are provided.New Patients (type, priority, weeks, cycles, duration, time window, location)Location data from 3 location classes (Random Cluster(rc), Random(r), Cluster(c)).Existing Patients (type, priority, weeks, cycles, duration, time window, location, scheduled treatment days)There are three levels of utilisation of the system according to the number of patients in the system (low(l), mid(m), high(h)).Location data from 3 location classes (Random Cluster(rc), Random(r), Cluster(c)).The location data was sourced from Homberger and Gehring (2005) (doi:10.1016/j.ejor.2004.01.027).</p
Fault Tolerant Control of Autonomous Underwater Vehicles
No full textUnderwater vehicles are complex nonlinear systems that operate in the difficulties and uncertainties presented by the underwater environment. This includes limited communication and sensor capabilities, varying water conditions, external disturbances, and actuator faults. The growing interest in using autonomous underwater vehicles (AUVs) for longer, more remote, or more dangerous operations has raised the need for underwater vehicle controllers that are robust to system uncertainties. To account for uncertainties in the controlled system, model-based AUV control laws have been developed to compensate or approximate the forces and moments acting on the vehicle which are not accounted for in the control model. Examples of such control law techniques include sliding mode control, adaptive control, and more recently control using machine learning. These control law techniques have been applied to produce controllers for a variety of AUV systems, but the variety in actuator configurations and control objectives prevents the quantitative comparison between many of the proposed controllers in the literature. Recent works have also been exploring the control of AUVs with hybrid actuator configurations - a combination of multiple thrusters and control surfaces. These configurations enable the vehicle to operate in a larger range of velocities and provide increased actuator redundancy that can be utilised for actuator fault tolerance methods. To achieve this, new control laws and control allocation methods must be adapted from the literature for traditional AUV actuator configurations.
This research began with the development of a nonlinear control design method for axisymmetric AUVs with a hybrid actuator configuration. The method utilises the available actuators to perform six degree of freedom trajectory tracking. By smoothly transitioning the controller’s desired orientation from the reference orientation to a drag-optimal orientation, the position tracking objective is achieved for a larger velocity range while enabling independent orientation control in fully actuated conditions. A Lyapunov analysis and simulations of the controlled system demonstrate the controller’s tolerance to constant external disturbances and parameter discrepancies in the control model.
The hybrid AUV model is then used to determine the fault tolerance of a model-based PID control method, which is applied to the hybrid AUV and simulated under faulty conditions. A fault compensating control allocation method for the system is proposed, and the control law is augmented with proposed saturation compensation terms that complement the control reallocation. A Lyapunov analysis and simulations are again conducted to demonstrate the stability of the final controlled system. The heave and depth trajectory tracking performance of the initial and final controllers are compared to determine the effectiveness of proposed control law and control allocation methods.
To develop a comprehensive understanding of the control performance benefits of fault compensation and uncertainty tolerance techniques not yet seen in the literature, a quantitative comparison of the trajectory tracking and path following performance from a set of control design methods is conducted. A selected set of control laws based on sliding mode control, adaptive control, and using machine learning are implemented on the same hybrid AUV model. The control laws are implemented in combination with static and fault compensating control allocation methods. The performance of the resulting controller variations for six degree of freedom trajectory tracking are compared in terms of transient response and steady-state tracking errors.
The main contribution of this thesis is the investigation and development of actuator fault and uncertainty tolerant control design methods for AUVs with hybrid actuator configurations. Both the control law and control allocation methods are utilised to consider the control loss from faults, and the actuator saturation resulting from control reallocation. Variations of the control design method based on the recent AUV control literature are developed to utilise the uncertainty tolerance of sliding mode control, adaptive control, and control utilising machine learning. A final quantitative comparison of the control performance produced by each of the method variations demonstrates the versatility and limitations of the proposed fault and uncertainty tolerant control design methods for AUVs with hybrid actuator configurations.</p
Micronized Sugar Beet Pulp Particles As Pickering Emulsifiers: Mechanism and Applications
No full textThere is a need for the food industry to adopt principles of green and sustainable food processing. As the main by-product of the beet sugar industry, sugar beet pulp (SBP) is available on a large scale globally, but the industrial utilization of SBP is still limited to animal feed and organic fertilizer. The industrial chain is short and the added value is low. Therefore, the exploration of a new strategy to broaden the high-value utilization of SBP is of great research interest.
Based on the concept of fully utilising agricultural by-products, this project focuses on fiber-rich SBP as the research subject, using micronized sugar beet pulp (MSBP) particles directly to stabilise emulsions without any separation or chemical modification. The properties and mechanism of this type of ‘whole particles’ Pickering emulsifier, which is utilized to stabilize Pickering emulsion, were investigated. It was confirmed that heating pretreatment combined with ultrasound efficiently break downs sugar beet pulp, and the mechanism of efficient particle dissociation was clarified. The emulsification mechanism of complex particles was systematically described from the perspective of soluble/insoluble fractions. Pickering emulsion techniques were applied in mayonnaise-like emulsions and fruit preservation. This work provided a feasible way to develop a Pickering emulsifier with cost-efficiency and high utilization rate, understand the contribution of various components in complex particles to emulsification, create high dietary fiber food ingredients and health foods, and improve the added value of the beet sugar-related industries. The main findings are as follows:
(1) The ‘top-down’ particle micronization technique was established using heating and ultrasonication, resulting in MSBP with good suspension stability and elucidating the dissociation mechanism. High-temperature (120 °C) softened the compact particle structure of SBP, thus forming a porous inner particle structure with a larger specific surface, which facilitated the micronizing process. During ultrasonication, the SBP particles were broken into smaller sizes with a fibrous morphology (diameter of 50-300 nm and dozens of micrometers), which was accompanied by progressive dissolution. The soluble substance was verified to be pectic polysaccharides, and the porous particle structure adsorbed most of the ultrasonic energy to prevent the degradation of the soluble polysaccharides. Micronization greatly improved the emulsifying capacity of the SBP particles. Both the tangled network of fibers and the surface-active soluble substance contributed to emulsification.
(2) The emulsification characteristics of MSBP were studied and the contribution of soluble substances and insoluble fibrous particles (IFPs) to emulsification was preliminarily investigated. Compared with high-speed shearing homogenization with low energy input, ultrasonic homogenization and microfludization homogenization with high energy input help to adsorb MSBP at the oil-water interface, thus forming a smaller particle size and a more stable emulsion. The fabricated emulsion shows a flocculated state, which can be disturbed by sodium dodecyl sulfate (SDS). The flocculation index was up to 500% with the increase of MSBP concentration (0.05–1.00 wt%) and the decrease of oil weight fraction (0.05–0.40). After storage, the flocculated oil droplet clusters and tangled fiber networks improved the gel-like properties and physical stability of the emulsions. The proportion of soluble substances and IFPs in MSBP was ~40% and ~60%, respectively. Both showed interfacial activity and played a synergistic effect in emulsification. Due to the steric hindrance between micron-scale IFPs, some empty emulsion surfaces are covered by soluble substances, forming a compact hybrid interface layer. This provides the emulsion with robust steric repulsion force, preventing oil droplets from coalescing. The presence of soluble components contributed to the formation of a smaller particle size emulsion and strengthened its gel properties.
(3) The interaction mechanism between soluble substances and IFPs and their contribution to emulsification were studied, thereby establishing a complex emulsification mechanism model for MSBP. The soluble substances mainly consisted of sugar beet pectic polysaccharides (SBPS). The quartz crystal microbalance test showed that SBPS and IFPs can interact through multi-layer adsorption, and the adsorption between them is irreversible and driven by hydrophobic interaction forces. In addition to the interaction between the neutral sugar side chain of SBPS and the hydrophobic cellulose crystal surface of IFPs, the non-sugar components of SBPS and IFPs (ferulic acid, protein, and lignin) also contributed to the irreversible adsorption. During the emulsification process, SBPS was first adsorbed onto IFPs to form SBPS-coated IFPs (IFPs(SBPS)), and then SBPS and IFPs(SBPS) are adsorbed together on the oil-water interface to form a hybrid interface layer. Emulsion droplets stabilized by soluble-insoluble binary system were covered by a hybrid interfacial layer with SBPS-coated IFPs and SBPS, and the interfacial adsorption proportion was significantly larger than the corresponding solo emulsifier. The tangled fiber network wrapped the oil droplets, acts as a physical barrier to restrict the movement of the oil droplets, and maintained the stability of the emulsion together with the compact interfacial layer.
(4) The potential of MSBP to stabilize the gel-like Pickering high internal phase emulsions under different preparation parameters was explored, and it was used as a replacement for egg yolk in the preparation of mayonnaise-like emulsions (oil content 75 wt%). Using a one-pot homogenization strategy, stable gel-like emulsions with controllable properties were fabricated by increasing the oil-volume fraction (≥ 0.4) and MSBP concentration (≥ 0.9 wt%). These emulsions showed good tolerance under a wide pH range (2–10), high ionic strength (1000 mM Na+), storage, and thermal treatment. MSBP can partially or completely replace egg yolks to create mayonnaise-like emulsions with appearance and rheological properties similar to commercial mayonnaise (CM). The presence of MSBP can delay the oxidation of oil and inhibit the hydrolysis of oil in mayonnaise-like emulsions. It has similar tribological properties to CM, but its lubricity still needs improvement.
Overall, this study adopted a thermomechanical strategy to transform SBP into a Pickering emulsifier. Although the micronization process did not reduce the size of MSBP to the nanoscale, MSBP in micron-scale still depicted excellent emulsification performance. SBP was substantially dissociated into soluble substance and fibrous particles, which showed an adsorption interaction and thus made contribution to the emulsification. Based on the results, the emulsification mechanism was established and MSBP was also used as a mayonnaise stabilizer. It provided a novel strategy to used ‘whole particles’ with complex composition as Pickering stabilizers.</p
Augmenting the Dark: Exploring Assistive Micro-guidance in Sonified Mixed Reality
No full textThis thesis proposes a series of evaluations of sonification methods rendered as AR via three user experiments in simulated and real-life scenarios. We aim to promote the use of spatialized sonification in situated Augmented Reality (AR) to model next-generation micro-guidance aids for low-visibility and vision-impaired (VI) scenarios. The solutions being proposed are compared in interactive sonifications of two- and three-dimensional positions in a series of hand-navigation assessments with visually impaired and blindfolded sighted users, to validate different approaches in environments without any visual feedback.
In a user experiment (N=47) in 2D hand-navigation, results outlined that methods based on sound spatiality had the most promising performance in average time taken and distance from target. In a follow-up experiment (N=19), assessing vertical guidance in a 3D task, results indicated a significantly higher accuracy for our novel method of representing height through pitch - Target-based Dynamic (TbD) pitch. Regarding workload, users initially self-reported that methods that exclusively used a single pitch signal to indicate a 2D distance as the least demanding, followed by the spatiality-based methods. When targeting multiple ways to express vertical distance as a third axis, users self-reported the TbD method as the least demanding in workload.
For our final user experiment, we gathered sighted people’s self-reported and perceived empathy with the BVI (Blind and Visually Impaired) community via an online survey, from both sighted (N = 77) and BVI people (N = 20) respectively. This highlighted a significant disparity between the two. Later, blindfolded sighted participants went through a blindness embodiment experience in AR (N = 15), while relying on a proposed assistive technology. By re-testing sighted people’s empathy, we found that their empathetic and sympathetic responses towards said community significantly increased. Furthermore, survey results suggest that the BVI community believes the use of these empathy-evoking embodied experiences may lead to the development of new assistive technologies.
Ultimately, this thesis evaluates how sonified AR can help users to have better and safer performances in a micro-navigation context, particularly in day-to-day manual tasks, such as handling a hot stove and discarding trash in a garbage can.</p
Drawing the Dialectical Image of the City
No full textThis PhD by Project contributes speculative design projects that use specific methods and techniques to reveal a condition that is largely invisible but affects the development and morphology of metropolitan urban peripheries. This condition, while shaping suburban growth, is not concerned with improving housing or even producing any housing at all, except to generate greater financial capacity and gain. Covert by nature, it remains hidden from view, but this research seeks to uncover and make it visible.
This research is especially timely in light of Australia’s ongoing housing crisis, which drives development in low-cost peripheral areas. Previous studies on suburban expansion at the periphery often focus on the visible outcomes, yet they fail to address the underlying cause of this condition, mainly because it is elusive and difficult to visualise.
The primary aim of this research is twofold: first, to develop methods for visualising the morphological effects of this hidden condition on Melbourne’s suburban fringe, and second, to propose design strategies that challenge this condition, imagining a future where its influence can be resisted. Using a theoretical framework that emphasises the power of the image, both written and visual, this project offers practical techniques for both design practitioners and scholars. It also establishes a conceptual framework that can support future research. The images produced through this process serve not just as documentation of the studied context but as catalysts for imagining a world beyond the stagnation of contemporary development.
The images grounding each project consist of two parts: a detailed analysis and a visualisation of capital-optimised realism (COR), a concept that illustrates how financial interests shape these suburbs. These images were developed through a focused study of Cloverton, a suburb located in Melbourne’s Northern Growth Corridor. While some of these images adhere to conventional architectural representations, others explore new methods of image-making that subvert disciplinary conventions, providing new ways of seeing the suburban landscape.
Projects one to three offer a conventional analysis of Cloverton, paying attention to its architectural vernaculars and urban fragments. Projects four to seven extend this analysis, introducing new visualisations that deepen our understanding of Cloverton’s architectural morphology. These projects reveal the specific impact that COR has had on the development of peripheral suburbs and provide new insights into hose these areas relate to the broader metropolitan context.
The final project, project eight, offers a method for collaborative urban design, synthesising the findings from earlier projects. It presents a new approach that can be used by others to engage with the language and knowledge generated by this research.
By reflecting on the outcomes of this work, I identify three key areas of knowledge, which I call ‘constellations’. These constellations not only influence my own research but also contribute to broader architectural discussions. The images that described each constellation serve as both a citation of the studied context and as tools for imagining alternatives to the current suburban reality. The design research projects presented here are knowledge in themselves, and their reflection is a catalyst for new kinds of understanding.</p
Online and Offline Evaluation in Search Clarification
No full textThe effectiveness of clarification question models in engaging users within
search systems is currently constrained, casting doubt on their overall
usefulness. To improve the performance of these models, it is crucial to employ
assessment approaches that encompass both real-time feedback from users (online
evaluation) and the characteristics of clarification questions evaluated
through human assessment (offline evaluation). However, the relationship
between online and offline evaluations has been debated in information
retrieval. This study aims to investigate how this discordance holds in search
clarification. We use user engagement as ground truth and employ several
offline labels to investigate to what extent the offline ranked lists of
clarification resemble the ideal ranked lists based on online user engagement.</p
Cryptocurrency Portfolio Allocation under Credibilistic CVaR Criterion and Practical Constraints
No full textThe cryptocurrency market offers attractive but risky investment opportunities, characterized by rapid growth, extreme volatility, and uncertainty. Traditional risk management models, which rely on probabilistic assumptions and historical data, often fail to capture the market’s unique dynamics and unpredictability. In response to these challenges, this paper introduces a novel portfolio optimization model tailored for the cryptocurrency market, leveraging a credibilistic CVaR framework. CVaR was chosen as the primary risk measure because it is a downside risk measure that focuses on extreme losses, making it particularly effective in managing the heightened risk of significant downturns in volatile markets like cryptocurrencies. The model employs credibility theory and trapezoidal fuzzy variables to more accurately capture the high levels of uncertainty and volatility that characterize digital assets. Unlike traditional probabilistic approaches, this model provides a more adaptive and precise risk management strategy. The proposed approach also incorporates practical constraints, including cardinality and floor and ceiling constraints, ensuring that the portfolio remains diversified, balanced, and aligned with real-world considerations such as transaction costs and regulatory requirements. Empirical analysis demonstrates the model’s effectiveness in constructing well-diversified portfolios that balance risk and return, offering significant advantages for investors in the rapidly evolving cryptocurrency market. This research contributes to the field of investment management by advancing the application of sophisticated portfolio optimization techniques to digital assets, providing a robust framework for managing risk in an increasingly complex financial landscape.</p