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Structural Topology Optimisation for Fibre Reinforced Composites
No full textFibre-reinforced composites are widely used in aeronautics and astronautics due to their high specific strength and lightweight properties. Though advanced manufacturing techniques like automated fibre placement and additive manufacturing have dramatically reduced fabrication costs by placing fibre tows along curvilinear paths and creating laminates with tailored stiffness, their great potential still has not been fully explored because of limitations in fibre path design. Therefore, it is necessary to develop a specific optimisation method for the properties and manufacturing of fibre-reinforced composites to take full advantage of their capabilities.
The primary aim of this thesis is to introduce a systematic optimisation method using the well-known non-uniform rational B-splines (NURBS) to express fibres in the composites and design their paths to enhance structural stiffness. Besides mean compliance, the repulsive energy is integrated into the objective function to avoid fibre knots and intersections. Furthermore, the NURBS control point coordinates are creatively set as design variables. Considering all fibre intersection possibilities, hybrid elements are used in finite element analysis to further improve design efficiency. The method of moving asymptotes is subsequently applied to update the control points’ coordinates, guided by the sensitivity of the objective function. A significant advantage of this method is the direct derivation of the NURBS-expressed fibre path, eliminating the need for post-processing. Furthermore, compared with element densities or level set functions used in previous studies, the proposed method significantly reduces the number of design variables to improve optimisation efficiency.
The project is the first to report using NURBS curves to express fibres and optimise their paths to meet manufacturing constraints. The key finding was that the intersection of fibres can cause thickness variations in the composite panel and excessive curvature can cause stress concentrations and ultimately degrade product performance. Adjusting fibre paths through post-processing can avoid intersections, but the calculation is complex and causes the fibres to deviate from the optimal distribution. This work introduces a fictitious repulsion energy to make the fibres evenly distributed and ensure the continuity of the objective function. This research aims to improve the practicality of optimisation algorithms for fibre-reinforced composites, ensuring that elegant configurations can be produced directly without post-processing.
The brief of the three topics included in this thesis are listed as follows:
The first research topic introduces a nodal-based evolutionary design optimisation algorithm for frame structures, utilizing the Delaunay triangulation of distributed nodes within the design domain. This method expands the solution space and reduces design variables by allowing free movement of non-loading and non-boundary nodes. The algorithm updates nodal coordinates and member thickness using the Method of Moving Asymptotes (MMA), informed by the objective function's sensitivity, which combines compliance and volume.
The second research topic extended the previous method to fibre optimisation of composite materials. This research considers the intersection of fibres with rectangular elements in finite analysis to determine mechanical responses accurately. The optimisation framework involves shifting truss network nodes, with node coordinates as design variables updated using the MMA solver, guided by a sensitivity analysis smoothed by a radial basis function. Each iteration includes path adjustments for twist prevention and gap control through polynomial interpolation. Numerical examples show the method's efficiency in generating optimised fibre paths quickly, with significantly fewer design variables. This approach theoretically ensures a global minimum, achieving lower objective values than existing methods.
The third research topic directly uses NURBS curves to describe fibres and optimise their paths. Mean compliance to prevent fibre knots and intersections. The p-norm method is applied for curvature constraints to mitigate sharp fibre turns. NURBS control point coordinates are innovatively used as design variables, and the hybrid element in the second research is used in FEA, thereby boosting design efficiency. Control points' coordinates are updated using the MMA solver, directed by the objective function's sensitivity. Numerical examples demonstrate this approach's effectiveness in a 2D VSC design. This method's significant advantage lies in directly deriving NURBS-expressed fibre paths, thus negating the need for post-processing and reducing the number of design variables compared to previous methods, enhancing overall optimisation efficiency. Compared with the previous method of using polynomial curve fitting, this work can obtain fibre paths without post-processing, and the NURBS curve is also conducive to using other CAD software.
In summary, the research outcomes demonstrate that the proposed node-shifting optimisation methods can be combined with NURBS-expressed fibres to improve optimisation efficiency and effectiveness. The optimisation results meet the manufacturing constraints, can be directly exported to computer-aided design software, and then fabricated.</p
Study on the Migration and Control of Slip Agents on the Surface of High Density Polyethylene Beverage Closers
No full textThe migratory slip additives permeate from the polymer matrix and modify the surface characteristics. This enables customisation of slip performance of the polymer products. To date, the migration behaviour of slip additives has primarily been studied on polyolefins with low crystallinity. Several factors such as the physicochemical properties and bulk loading of slip additives, crystallinity of polymer matrix, and storage temperature and time are found to affect the migration of these additives. Once the slip additives migrate to the surface, the extent of lubrication they produce depends on their surface concentration, distribution and morphology. Therefore, a similar study on the migration of industrially important slip additives such as erucamide, behenamide, oleamide and Incroslip Q (slip Q) is required in a highly crystalline polymer product such as high-density polyethylene (HDPE) screw cap.This thesis evaluates the migration of slip additives through HDPE screw cap matrix to its surface to control their application and removal torque during bottling. The research investigates the dependence of migration on physicochemical nature and bulk concentration of slip additives. Similarly, the interaction of slip additives with the polymer has also been quantified and explained. The effect of the most pertinent process variables such as temperature, concentration, time, and their interactions on the surface concentration and performance of slip additives has been determined. Finally, the optimum values of bulk concentration, storage temperature and storage time of above mentioned slip additives required to produce the industrially desired amount of surface concentration and the required torque for HDPE screw cap are identified.HDPE specimens (plaques and screw caps) with different slip additives were prepared by injection moulding and studied at different times after storing at different temperatures. The migration of slip additives to the surface was examined using an array of surface profiling techniques. The functional groups at a detection depth of 800 nm and the elemental composition on the surface at the penetration depth of 10 nm were measured using attenuated total reflection Fourier transform infrared (ATR¿FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS), respectively. Static contact angle was measured on the HDPE specimens as a function of storage temperature and time to determine the change in their surface energy. Gas chromatography with flame ionisation detector (GC-FID) was used to measure the amount of surface slip additive migrated from the bulk. The morphology of slip additives on the surface of HDPE was also captured using optical microscopy, atomic force microscopy (AFM) and scanning electron microscopy (SEM).Erucamide, behenamide, oleamide and slip Q (a blend of erucamide and behenamide) produced different surface concentration on HDPE plaques and caps at the same storage condition. Of these four slip additives, slip Q produced the highest surface concentration which was followed by oleamide and erucamide while behenamide produced the least. The surface concentration of erucamide was found to be higher than that of behenamide at an identical bulk loading and storage condition. The non-invasive FTIR method was found to be effective in quantifying the surface concentraton of slip additives. Increased intensity of spectral peaks of C=O and N-H correlated well with increase in surface concentration of slip additives. The surface concentration of each slip additive could be attributed to its physicochemical properties, bulk concentration and the storage condition. Surface concentration of slip additives determined by their physicochemical properties:The migration was significantly affected by the physicochemical property such as molecular structure of slip additives. The extent and the pattern of migration of each slip additive were explained well by their diffusion coefficients which were 5.63 × 10-15 cm2/s for behenamide, 1.53 × 10-13 cm2/s for erucamide, 1.16 × 10-13 cm2/s for oleamide, and 8.05 × 10-13 cm2/s for slip Q, respectively. These slip addtives were found to follow a Fickian diffusion behaviour while migrating through HDPE specimen. The diffusion coefficient of oleamide (18-C chain amide) was higher than that of erucamide (22-C chain amide) because of its smaller molar volume.The diffusion coefficient of behenamide was much lower than erucamide; even though the molar volume of the former is smaller than than that of the latter. This discrepancy on diffusion coefficient is can be attributed to higher interaction of linear behenamide molecules amongst themselves and with HDPE chains. Both of these interactions were weaker in the case of erucamide and oleamide due to the bend created by a cis -C=C- bond present in their carbon chains. The diffusion coefficient of slip Q was found to be the highest which was explained by the presence of erucamide. The kink induced by the double bond of erucamide disrupted the interaction of highly compatible behenamide with itself and with HDPE resulting in higher migration of slip Q.The morphological features of slip additives on HDPE surface depended on their surface concentration, physicochemical properties and storage conditions. Behenamide formed numerous asperities in HDPE surface while erucamide and oleamide formed flat placoid structures. The blend of erucamide and behenamide produced both asperities and flat plate-like structures. Numerous asperities were formed by behenamide and slip Q irrespective of temperature used, and they increased in size when more slip additives migrated to the surface. At higher temperatures, erucamide and oleamide collapsed into flat plate-like structures being softer than behenamide. The soft and detachable sheets of erucamide were more effective to reduce the torque of caps than the asperities of behenamide.The contact angle of HDPE specimens containing slip additives, used in this study, increased with time indicating the decrease in the surface energy. The increase in contact angle was consistent with an increase in the surface concentration of slip additives. However, the contact angle of HDPE loaded with slow migrating slip additive (behenamide) decreased from its initial value up to 6 h and then gradually increased. This decrease was caused by the exposure of polar amide groups on the air-solid interface with their hydrophobic chains embedded in the polymer. With subsequent migration, double layered crystalline structures were formed with their hydrophobic carbon chain exposed to the air-solid interface, which increased the contact angle to 135°.The diffusion of the slip additives through a highly crystalline HDPE matrix was found to be a complex process. The migration of all the slip additives used in this study followed Fick¿s law of diffusion and Arrhenius equation for their dependence on temperature. This study shows that the migration of slip additives and their performance in HDPE products can be tailored by utilising their material properties (initial concentration and physicochemical properties) and storage conditions (temperature and time). The molecular structure of each slip additive greatly affected its surface characteristics and morphologies. These morphologies ranged from softer plate-like structures to a harder asperities which affected the efficiency of the lubrication. Antislip behaviour, i.e. increase in surface energy on HDPE surface, observed in the case of slow migrating slip additive at the initial stage of migration could reduce the lubrication. Although relatively large number (three) independent variables were included in this study, it was possible to predict their optimum level to achieve required level of lubrication (torque). The holistic approach documented in this thesis to study the migration behaviour of slip additives through HDPE can be adopted to study other migratory additives in different polymers. Further, the models developed to predict the optimum level of variables which were needed to determine the required lubrication in HDPE screw caps can be applied in other migratory slip additives as well.</p
Evaluating the Dietary Safety of Australian Native Foods
No full textAs the native foods industry in Australia continues to grow, Indigenous Peoples of Australia are looking to become industry leaders. This has seen an emergence of traditional food items being developed for commercial markets. Even though many of these foods have a long history of use within various Indigenous communities, the evidence to suggest the safe use of these foods has rarely been recorded in written form. There has also been little research into the dietary safety of these foods. As such, supporting evidence to suggest these foods are safe for consumption within the general public is limited.
Despite the extensive experience of Indigenous groups, the current regulatory framework used to assess the dietary safety of traditional foods does not have the capacity to recognise the unwritten (‘undocumented’) oral history held by the Indigenous population. This is presenting an unnecessary barrier that is prohibiting the recognition of the practical knowledge held by those groups who have been using native foods within Australia for at least 65,000 years. These knowledges extend not only to the practical skills around the harvest and preparation, but also the occurrence of adverse effects that may exist. These knowledge systems become particularly important to a risk assessment when you consider that many traditional plants also feature in traditional pharmacopoeias, and/or may be toxic at various growth stages or may require a detoxification step before consumption.
In response to these shortcomings in current regulatory processes and the lack of supporting dietary safety evidence, the project outlined in this thesis was established as a joint collaboration between RMIT University and Food Standards Australia New Zealand (FSANZ). The overarching aim of the project was to establish a new methodological approach to the safety assessment of traditionally used native foods that would satisfy both industry and food safety regulators. This culminated in the proposed redevelopment of the current safety assessment framework and the establishment of safety assessment processes that are both accessible to small businesses entering the native foods market and appropriate for food safety regulators tasked with maintaining consumer safety.
Chapter 1 of this thesis provides an extensive literature review of the current native foods industry within Australia, including the involvement of Indigenous Peoples within the industry and the current policy that dictates the regulation of native foods both within Australia and abroad. Risks and toxic effects that can be associated with the consumption of plant-derived foods are also highlighted, as are several methodological approaches used to assess the dietary safety of newly developed food items. This information provided adequate justification to pursue each of the research aims presented in the following chapters of this thesis.
Chapter 2 addresses the first research aim by providing potential solutions to the shortcomings in the current regulatory procedures, including new proposed processes that can be incorporated into the current food regulatory frameworks to better assess the dietary safety of traditional foods. Importantly, these proposed processes would allow the dietary risk assessment of traditional foods to be completed in a manner that better accommodates the knowledge systems and interests of Indigenous Peoples, while also meeting the safety data requirements set out by regulatory bodies both within Australia and around the world.
The second and third research aims are addressed in Chapter 3, where a dietary safety assessment is performed on a traditionally used native grain. This particular grain species was chosen because it is being developed by Aboriginal groups but lacked adequate supporting evidence to satisfy food safety regulations. The dietary safety of the grain has been systemically analysed and compared side-by-side with commonly consumed wheat in a range of in vitro bioassays and chemical analyses. In this study, native grain extracts were shown to be no more toxic than wheat in human monocyte and hepatocyte screening systems. Chemical analysis showed that contaminant levels were below tolerable limits, and no chemical classes of concern were identified. These findings indicate that this native grain species is no less safe than commonly consumed wheat. To further strengthen this assessment, and as proposed in Chapter 2, it is intended that the long history of use held by the Traditional Custodians who have used this grain for millennia is also considered in the overall dietary risk assessment.
Chapter 4 addresses the fourth research aim, to further build upon the evidence base of the selected native grain by understanding its nutritional and functional properties. Compared with wheat, the native grain species contained 2-fold greater protein and total fats, and higher levels of essential minerals and trace elements, including 8-fold iron levels and >2.5-fold calcium, magnesium, zinc, copper and manganese levels. Functionally, the native grain contained 2.4-fold greater polyphenol content and displayed greater antioxidant potential in vitro in exposed human monocyte cultures. Importantly, the native grain was also found to be gluten-free. Altogether, this shows that the native grain is nutritionally and functionally superior to commonly consumed wheat for the measured parameters and could potentially serve as a grain alternative or be used to fortify current wheat-based and gluten-free products. These findings provide reassurance that the selected native grain is a viable product for further commercial development.
It is hoped that the ideas presented in Chapter 2 of this thesis will provide some guidance on how FSANZ may be able to incorporate culturally appropriate processes into the regulation of traditional foods within Australia. The experimental results presented in Chapters 3 and 4 should facilitate safe market access for the native grain, whilst also providing a greater understanding of the nutritional and marketable attributes. Lastly, the methodology presented throughout should provide some guidance and clarity on how to successfully assess the dietary safety of traditionally used native foods, so that moving forward, a larger range of traditional foods can be safely developed for the market.</p
Stakeholder Expectations in University Business Incubators – An Investigation of Performance Management Systems
No full textEntrepreneurship is crucial in strengthening innovation and promoting economic wealth. Business Incubators (BIs) are set up to assist such development by providing business consulting and physical spaces to start-ups, as well as fostering inter-actions between government, industry and universities. BIs’ sources of funding may depend on the above-mentioned stakeholders which all display expectations and demands over BI reporting and outcomes. Performance management systems (PMSs) may reflect those expectations depending on BIs’ prevailing values and beliefs, which are referred to as Institutional Logics. However, clear inconsistencies among BIs’ PMSs have been observed. In investigating BIs’ logics, in this thesis I address how PMSs are shaped and challenged by a multiplicity of stakeholders.
A multi-method, comparative case-study between two life-science BIs, in Italy and Australia, including document analyses and semi-structured interviews, is applied. The results demonstrate that a bureaucratic logic inspires the integration of certain performance measures (KPIs) to legitimise actions in front of public funders in both cases. In BI-Australia, performance improvement is driven by a community logic with a focus on start-up support through informal mechanisms. In BI-Italy, a community IL leads attention to societal welfare, as expected by the regional government. The decoupling between start-up incubation activities and socio-economic impact causes the development of a business logic for BI-Italy, with the aim to financially grow itself through the collecting of international funding for in-house research.
This study demonstrates how the requests for short-term socio-economic impact and BIs’ decoupled operational activities challenge the BI business concept. This adds to the accounting, entrepreneurship and innovation literatures by creating a more in-depth understanding of BI performance in relation to institutional logics and stakeholders’ influence. From a practical perspective, it shows how BIs balance start-up support and stakeholder expectations through their PMSs.</p
Charge and Energy Transfer in Plasmonic Nanostructures
No full textThe development of new materials capable of transforming solar to chemical energy has been the center of attention in materials science over the last 50 years, as the need for producing clean energy and reduce the consumption of non-renewable fossil fuels is urgent to stop climate change and avoid energy shortage worldwide.
Since the observation of photocatalytic activity of a titania-based catalyst doped with transition metals for nitrogen fixation in the early 1980s, numerous large band gap semiconductors have demonstrated photocatalytic energy conversion for nitrogen fixation, hydrogen evolution and CO2 reduction. However, because these photocatalysts only utilize light in the
UV region (due to their large band gap), makes them inefficient for harvesting solar energy (which is composed of 40% of visible light and 50% of Near Infrared light). Additionally, because photocatalysts need to fulfill other requirements, including: the capacity to generate charge-separated states with lifetimes and electrochemical potentials compatible with the targeted chemical reaction (e.g. water splitting, ammonia fixation, etc.), several new combinations of carbon-based materials, plasmonic nanostructures and bio-inspired substrates have been created to reach these properties making these systems more complex and efficiency dependent on elemental composition, size, shape and configuration.
This thesis provides a comprehensive study of the effect of geometrical and compositional parameters on the efficiency of charge separation on metal and metal-semiconductor nanostructures at the single particle level as it reveals the potential of hot carries derived from the surface plasmon of metal nanostructures for photocatalytic reactions. Furthermore, it allows
to evaluate the main parameters that needs to be addressed in order to improve charge transfer efficiency such as surface quality, contact between metal-semiconductor structures, shape and size effect.
In Chapter 1 - We provide a brief introduction to plasmonics photocatalysts, excitation and relaxation of localized surface plasmon resonances (LSPRs). How plasmonic photocatalysts operate. The methodology used to characterize plasmonic reactions by single particle spectroscopy techniques and current state of LSPR studies using electron beam microscopy
technology and the more important parameters to acquire and process electron energy loss spectroscopy data in a transmission electron microscope. Finally, an overview of synthetic methods used to obtain plasmonic nanostructures and hybrid metal-semiconductors.
In Chapter 2 - we developed a synthetic protocol to break plasmonic symmetric of gold rods by overgrowing one of their caps resulting in a "matchstick like" new shaped nanostructure. We present how this new nano-structure changes the LSPR distribution. Finally, we demonstrate how asymmetric Au nanorods exhibit improved surface-enhanced Raman scattering response compared to the Au nanorod seeds, attributed to the breaking of longitudinal localized surface plasmon resonance symmetry and the presence of reactive plasmonic hot spots.
In Chapter 3 - of this thesis we demonstrate the effects of breaking the symmetry of plasmonic Au rods on charge separation and transfer by modifying the shape and composition to hybrid Au rod- CdSe overgrowth tip. Moreover, we developed a standard protocol to analyse, at single particle level, the broadening of the longitudinal localized plasmon of
the Au nanorod due to localized plasmon damping at the chemical interface (CID). We found one of the highest yields of plasmon quenching through CID reported to date (∼ 48%). Furthermore, we found the main variables that influence CID: the quality of the metal-semiconductor (CdSe) interface, the size of the Au rod and CdSe tip. Also, we evaluate in which part of the hybrid structures photoreduction reaction starts by using electron energy loss spectroscopy and electron diffraction spectroscopy at the single particle level.
In Chapter 4 - we explore the effect of increasing the plasmonic - semiconductor interface area and quality by the assembly of a new type of metal-semiconductor configuration using silver cuboids (that contain large flat planes) dropcasted onto two-dimensional (2D) indium oxide antimony doped and tin oxide semiconductors, promising new types of 2D materials.
Additionally, we test their photo-electrochemical performance for water splitting and found that the surface of the 2D semiconductors influence significantly the plasmonic-semiconductor interaction.
Finally, In Chapter 5 we summarize the most significant contributions made by the author and provide an outlook for future investigations.</p
Unpacking Intersecting Complexities in Water, Sanitation, and Hygiene Programs for Challenging Contexts
No full textProgress is needed within the global water, sanitation, and hygiene (WASH) sector to ensure access to WASH services for all. In fact, a quadrupling of current global rates of progress is needed to achieve the Sustainable Development Goal for WASH (SDG 6) by 2030, with an even greater increase in rates required for communities most overlooked in conventional WASH programs. These communities are referred to as ‘challenging contexts’ throughout this thesis, and they can include informal settlements, refugee camps, and environmentally-challenging areas (e.g., flood-affected communities), among others. Ensuring access to WASH for all, particularly in challenging contexts, requires that practitioners in WASH programs understand, account for, and embrace the multidimensional and interconnected complexity that defines all contexts. Over-simplification of complexity – and failure to understand how factors of complexity are interconnected, referred to as ‘intersecting complexities’ in this thesis – has resulted in WASH programs that are not appropriate for the communities they hope to serve. Grounded in systems thinking and guided by inclusive practice, this thesis explored the following research opportunity: to investigate the multidimensional and interconnected complexity of WASH and determine how this complexity can be used to strengthen programs and ensure access for communities in challenging contexts.
The methodology guiding this research incorporated several overlapping research approaches – specifically intersectionality, decolonising approaches, participatory approaches, and strengths-based approaches – which were all grounded in reflexive practice. The research opportunity was explored through a multimethod sequential research design that encompassed four work packages, each containing multiple methods. Methods were qualitatively driven and allowed for the development of novel concepts as well as continued testing of these concepts.
Evaluation of the research opportunity began with a review of existing literature on intersecting complexities in WASH programs for challenging contexts. This review helped to develop the novel lens of intersecting complexities through which to examine persistent lags in access to WASH services in challenging contexts. The review uncovered that intersecting complexities have not been adequately understood or accounted for in WASH programs to date, resulting in WASH solutions that have been inappropriate for communities in challenging contexts. Primary concerns were WASH solutions that were unaffordable, not inclusive, and/or unsustainable. Furthermore, the review highlighted multiple dimensions of intersecting complexities present across different types of challenging contexts. The lens of intersecting complexities was presented along with six dimensions of contextual complexity identified through the review: environmental, spatial, economic, political and/or institutional, social and/or cultural, and temporal. These dimensions are interconnected and subjective, and early consideration of complexities across these dimensions may positively impact WASH programs for challenging contexts.
The lens of intersecting complexities was further developed to create an approach for practitioners in WASH programs. Methods included interviews, workshops, and focus group discussions with global practitioners to ensure a variety of perspectives. Findings demonstrated that practitioners already perceive the multidimensionality and interconnectedness of complexity affecting WASH programs; however, these findings showed only that practitioners think about complexity unconsciously and retroactively (i.e., after a WASH project is complete). Practitioner perspectives also demonstrated the importance of a further dimension of contextual complexity (informational) as well as the additional complexity of interpersonal dynamics (relationships, power dynamics, and priorities across multiple stakeholder levels in a WASH program). Findings further showed that practitioners understand the implications that intersecting complexities have for various scales and stages of a WASH program. The Intersecting Complexities Approach was developed based on these findings; the approach aims to guide practitioners through conscious and proactive consideration of intersecting complexities, strengthening the design of WASH programs.
Following development of the Intersecting Complexities Approaches, it was validated through collaboration with Engineers Without Borders Australia (EWB) and a case study of their Sanitation in Challenging Environments (SCE) Program in Cambodia. The history of the SCE Program was explored, and lessons learnt demonstrated the importance of WASH programs for communities most overlooked in conventional WASH programming (e.g., challenging contexts) to achieve SDG 6 by 2030. This work further underscored the importance of localisation and/or decolonisation of international programs. The application of the Intersecting Complexities Approach was then investigated through workshops and reflexive practice with EWB’s team in Cambodia; these methods helped to validate previous findings and adapt the approach for the team. Findings of these validation and adaptation processes showed the importance of appropriate and flexible approaches for practitioners to ensure appropriate WASH services for communities in challenging contexts.
The research presented in this thesis demonstrates the importance of understanding and accounting for intersecting complexities in WASH programs, ensuring that solutions are appropriate for communities most overlooked in challenging contexts. However, ensuring appropriate solutions requires that practitioners have appropriate approaches to do so. The Intersecting Complexities Approach has been shown to assist practitioners unpack intersecting complexities and consider them in decision-making processes. Doing so can help ensure effective WASH programs for all. Additionally, changes are needed in the systems that govern WASH programs, including decolonisation of programs, promotion of inclusive mindsets, and reconsideration of conventional funding models.</p
Enhancing Occupational Safety through Vision-based Integrative Technologies in the Construction and Building Industry
No full textThis thesis investigates the pivotal role of vision-based integrative technologies such as Deep Learning (DL), Augmented Reality (AR)/Virtual Reality (VR), the Internet of Things (IoT), and Building Information Modelling (BIM) in enhancing occupational safety in construction sites and building emergency management within the Architecture, Engineering, and Construction (AEC) industry. Recognising that both construction activities and emergency responses in buildings present distinct, complex arrays of risks, it becomes evident that traditional safety methods are no longer sufficient. By integrating advanced technologies, this thesis argues for the potential to significantly improve safety measures, offering comprehensive, adaptable solutions that not only protect onsite workers but also enhance the capabilities of emergency responders. This research aims to bridge the gap between outdated safety practices and the pressing need for innovative, real-time safety monitoring and response mechanisms tailored specifically to the construction and building sectors.
The investigation begins by highlighting the critical role of advanced vision-based technologies in high-risk environments, stressing their significance in the AEC industry for enhancing occupational safety. It outlines the necessity of these technologies in addressing the intricate challenges faced on construction sites and during emergency situations in buildings. The importance of transitioning from conventional safety practices to more innovative and real-time solutions is underscored, advocating for a paradigm shift towards integrating cutting-edge technologies for safety management.
A substantial portion of the thesis presented in Chapter 2 is dedicated to a comprehensive review of the application and effectiveness of DL in AEC safety management from 2010 to 2020. This analysis delves into the methodologies, applications, and outcomes of DL in the AEC industry, pinpointing the research gaps and potential future directions. It emphasises the crucial need for more effective DL applications to tackle the prevailing challenges in AEC safety management. By offering an in-depth examination of DL technologies, the research aims to showcase their vast potential in revolutionising safety practices within the industry, addressing both current limitations and future possibilities.
The real-world application developments begin in Chapter 3. A lightweight DL model, namely YOLOv4-EfficientNet-B0 (YOLOv4-EFNB0) was proposed to reduce the high computational burden of DL implementation. To address the data scarcity problem, a context-guided data augmentation method was proposed, resulting in the creation of the augmented dataset MOCS-DA. The YOLOv4-EFNB0 model, when trained on MOCS-DA, displays significant improvements in detection capabilities. Notably, F1 scores for worker detection increased from 0.68 to 0.85, and the model saw a rise in Mean Average Precision from 0.41 to 0.52. In terms of computational efficiency, YOLOv4-EFNB0 stands out with its reduced weight size of 136 MB, parameters decreased to 3.76 × 107, and a computational load minimised to 1.21 × 1010. This model also excels in proximity detection, achieving an impressive accuracy rate of 96.76% and an average processing speed of about 25 frames per second, enabling near real-time performance. The integration of data augmentation and the use of the MOCS-DA dataset were pivotal in achieving these enhanced results, demonstrating the model’s effectiveness in occluded environments and its potential for practical applications in real-time construction site safety monitoring.
Chapter 4 of the thesis presents the Visual Construction Safety Query (VCSQ) system, a groundbreaking integration of immersive AR and generative DL technologies, developed with the aim of enhancing the safety knowledge of construction workers. The motivation for developing the VCSQ system arises from the need to provide real-time guidance for the complex and dynamic safety challenges in construction sites, where traditional safety measures often fall short. By leveraging AR and DL, the system offers a more interactive and engaging approach to safety query, enabling workers to better understand and navigate the potential hazards of their surrounding environment. The VCSQ system features three core functionalities: real-time Image Captioning (IC), safety-centric Visual Question Answering (VQA), and keyword-based Image-Text Retrieval (ITR). These are powered by a vision-language model architecture, fine-tuned for accuracy in response to queries and integrated with a head-mounted AR device, providing an immersive experience that enhances situational awareness and decision-making capabilities in real-time. Performance evaluations of the VCSQ system demonstrate its effectiveness: the ITR module achieved high recall rates of 0.801, 0.835, 0.863, and 0.885 for Recall@5, @10, @50, and @100 respectively, and the VQA module recorded an average accuracy of 89%. These results underscore the system’s capability in accurately interpreting and responding to safety-related queries in a construction setting. Finally, the practical application and effectiveness of the VCSQ system are showcased through the examination of three use scenarios and the incorporation of survey feedback.
Chapter 5 of the thesis presents a novel framework integrating BIM, IoT, and AR/VR to enhance fire safety and emergency response in modern buildings. The chapter outlines the development of a BIM-based fire alarming system, VR training modules, and an AR navigation system. A pilot study in a simulated fire scenario shows the framework effectiveness in decision-making and situational awareness. The study includes a controlled experiment comparing two groups: one with pathfinding assistance and another without. The quantitative data showcases significant improvements in training efficiency. Specifically, the experimental group, aided by pathfinding indications, completed their training in an average time of 436.1 seconds, significantly faster than the control group’s average of 828.5 seconds. This difference, statistically significant with a p-value of less than 0.05, highlights the effectiveness of the pathfinding technology in reducing the time required for planning rescue routes. Moreover, the standard deviation in the control group (166.1) was about twice that of the experimental group (90.7), indicating a more consistent performance among trainees using the pathfinding system. This suggests that the digital pathfinding indications not only expedited the training process but also provided more intuitive and effective guidance, particularly in navigating smoke-filled environments.
Chapter 6 concludes the thesis by summarising its overarching findings and suggesting future research directions in the field of occupational safety in the AEC industry. It discusses the contributions made by the thesis in utilising vision-based technologies for safety enhancement and outlines recommendations for future advancements in the field.</p
Developing Quantitative Structure Toxicity Relationship (QSTR) Models using Relevant Physico-chemical Descriptors for Predicting Chemical Toxicity
No full textPredictive toxicology is a multidisciplinary approach to chemical toxicity assessment that employs a variety of non-animal testing methods to predict a chemical's effects on biological systems. Computational chemistry investigates the properties of atoms, molecules and reactions at the atomistic or electronic level. One of the most effective methods of modern quantum chemistry is the density functional theory (DFT) based on the Hohenberg-Kohn theorem. The project aims to theoretically investigate structural properties and interactions between various chemicals with biomolecules using quantum mechanics (QM), DFT, chemoinformatics and QSTR-based approaches. The thesis presents a comprehensive investigation for a series of chloro- and fluoropyrroles using DFT-based descriptors to elucidate physicochemical properties and their relevance to reactivity, charge transfer, site selectivity, and toxicity. Aquatic-quantitative structure toxicity relationship (Aqua-QSTR) models for predicting chemical toxicity in aquatic organisms is developed using the ECT descriptor in the subsequent study. Aqua-QSTR studies were carried out for Fathead minnow and Tetrahymena pyriformis using linear regression (LR), machine learning-based random forest regression (RFR), and support vector regression (SVR) methods. The utilization of computational approaches to profile the nature of the diverse set of chemical compounds (applications in fuel, food additives, and flammable products) and their risk to human health and the environment was undertaken in the latter study. Expert and statistical-based methods were carried out to predict various toxicity endpoints and utilized charge transfer analysis for 119 chemical compounds to understand the toxicity. A Daphnia magna EC50 (effective concentration) and Fathead minnow LC50 (lethal concentration) QSTR models were used to assess the environmental and ecological fate of compounds. A systematic investigation was carried out in the next study on ZnO clusters and Au (111) surface with embedded tyrosine molecule heterostructures to extract the structural and electronic properties for developing quantitative structure-toxicity relationships using quantum chemical DFT reactivity descriptors. The nature of ZnO NPs clusters’ reactivity was recorded and explored by studying frontier molecular orbitals, Mulliken atomic charges and molecular electrostatic potential surface. We herein also investigate the nature of the interaction between tyrosine and the Au (111) surface together with the bonding mechanism and their electronic interactions by calculating important surface characteristics such as the charge density difference, density of states, Bader charge analysis, and adsorption energies. Further, we discuss an in silico and DFT-based study which examines the impact of Pesticides Active Substances (PAS) (used as insecticides, acaricides, herbicides, fungicides and plant growth regulators) on human health and their binding with Muscarinic and Nicotinic acetylcholine receptors (AChRs). The chemical library was further screened for in silico ADMET, TOPKAT-based predictions (Rat Oral-LD50, Skin sensitization, Ames mutagenicity), molecular docking and charge transfer analysis against their target AChRs. An effort has been made to develop relevant chemical reactivity descriptors and the applications of these descriptors towards the prediction of toxicity, mechanism, biological activities, other properties, and recognition/identification of potential reactive sites of chemical interfaces. DFT-based quantum chemical calculations have been utilized for obtaining global reactivity descriptors and demonstrate the usefulness of the quantitative structure-toxicity relationship (QSTR) models for predictive toxicology. Interfacing with predictive analytics, this research provides a quality computational model for the toxicity prediction of chemicals. The developed model shall provide insight into designing safer chemical alternatives and risk management.</p
Satellite Imagery and Its Influence on People’s Perceptions of Landscape
No full textThe perception of a landscape involves the process of categorisation and differentiation of sensory information and individual experiences. Landscapes are modified and altered by natural and human processes and, therefore, are not static in nature, but vary in space and through time. Previous research has provided insights into how people perceive landscapes, and how these perceptions change in dynamic landscapes. Increasingly, digital globes such as Google Earth or Earth Explorer and mapping platforms such as Apple and Google Maps provide individuals with a view of the landscape from an unfamiliar perspective. Through these platforms, individuals may access visual information about their surrounding environment through satellite images, both of their own and of other landscapes from around the world. This way of looking at the landscape has the potential to shape how it is perceived and how its components are valued. To date, there has been little research that has focused on how this near-ubiquitous view of the landscape influences individual perceptions by the general community. This research project represents one of the first attempts to understand how satellite imagery can influence people’s perception and opinions of landscapes, which in turn can be used to inform landscape management decisions.
The first research question examined the influence that viewing satellite imagery may have on the abundance of land use and land cover (LULC) classes, as determined by individuals, within familiar landscapes. To achieve this a survey of 52 participants from, Yungay, Chile, was used to explore the influence that interacting with satellite imagery had on people's perceptions of the abundance of land cover in the surrounding area. Participants, who were local to the area, were asked to quantify how much the landscape was covered by four land cover classes (agricultural, urban, plantation forestry, and native forest) and the distribution of cover. They were then provided with a tablet and instructed to explore satellite images of the Yungay area through Google Earth. The participants were then again asked to estimate the abundance of each class within the area. The results showed a significant difference in some participants' responses following the viewing of satellite imagery. In particular, participants significantly lowered their estimate of urban cover along with changes to how agriculture was distributed throughout the area after viewing satellite imagery. These results indicate that satellite imagery may influence how we perceive the makeup of a landscape.
Given the evidence that viewing satellite imagery can alter people's perceptions of their surroundings, the second research question investigated whether one cause of this change might be due to satellite images opening up a view of areas of the landscape that are not visible from key vantage points. The visible landscape is an important consideration in landscape management activities, shaping residents' perceptions of their overall environment and providing them with a sense of landscape connectedness, sustainability, and identity. Satellite imagery offers a different perspective, providing a complete 2D view of landscape composition. To make this comparison, Sentinel 2A imagery from a similar point in time to the survey data collection was classified into the primary land use classes in Yungay, Chile (with an overall accuracy of 83 \%). Viewshed analysis was then used to determine the proportion of the landscape visible from the road network under different scenarios (varied by distances from the road and road type). The abundance of each LULC class for that viewshed was then compared to the responses of survey participants without viewing satellite imagery. This process demonstrated that the visible Yungay landscape was composed of different abundances of LULC classes than the overall landscape. Furthermore, while there were some similarities between the visual landscape composition and participants' estimates of LULC cover, there were also important differences. In particular, participants failed to recognise that plantation forestry was the dominant cover in the area.
Whilst similarities were found between the current landscape and people's perceptions, the evolution of the landscape through their lived experience is likely to be a consideration in an individual's perception. The third research question developed a method for observing the visible landscape through time using open geospatial data. This method uses the Landsat satellite imagery archive (from 1986 to 2018) to represent changes that have occurred within the area. For four time points within the archive, a LULC map for Yungay was generated using machine learning (with overall accuracy). The method then used a static digital surface model and dynamic road networks to determine the visibility of the Yungay landscape at each time point. While the native forests on the slopes of the mountains within the study area provide a natural backdrop, the flat topography of most of the area means that the foreground dominates the overall landscape view at each time point. While the road network (from 229 km in 1986 to 339 km in 2018) provided greater visible access to the landscape (an increase of 68 km2), a transition in the overall landscape composition from one dominated by agriculture to one dominated by plantation forestry was the dominant trend also seen in the visible landscape. This study highlights the role that geospatial data can play in understanding landscape perception, by developing a methodology using open-source satellite imagery to describe the visibility of LULC change from public road networks.
To further understand the influence of satellite imagery of people's perceptions of the landscape, the fourth research question explored how people perceive the representation of landscape in satellite imagery, looking at both interpretation and appreciation of the image. In particular, the study aimed to investigate the relationship between an individual's ability to interpret the content of images from both the ground and satellite perspectives, their familiarity with the landscape, and their appreciation of land cover as seen from these two perspectives. This was achieved through a survey in which respondents were presented with images of land cover classes taken from eye-level and satellite imagery of the municipality of Yungay, Chile. Respondents were asked to interpret the primary LULC class from the images and to indicate their appreciation of the landscape as seen in the images. While similar overall accuracy was observed in the interpretation of satellite and ground-level imagery, differences in interpretation were observed between classes. For example, respondents showed a greater ability to distinguish between plantation and native forest from eye-level imagery, whereas the opposite was found for agriculture. It was also found that both familiarity and accuracy of interpretation affected the appreciation of the landscape being viewed. In particular, when respondents perceived the image to be dominated by a land cover that is more traditionally valued (i.e. native vegetation), they provided a higher rating, even when the image was of a different class (i.e. plantation forestry). These results suggest that while the ability to interpret satellite imagery is high, as it becomes more ubiquitous in our lives, its consideration in shaping perceptions and thus supporting land management activities is crucial.
Landscape perception is complex; it involves individuals processing information from a range of sources. The research presented in this thesis has demonstrated that satellite imagery is one of these sources and has the potential to shape our perception of the landscapes in which we live. It was also shown that our interaction with this imagery is complex and our ability to understand and interpret the information we see in the imagery plays a role in how it may shape our perception. Along with this it was shown that satellite imagery has a role to play in further our understanding of how perceptions are formed, through changes to the landscape and changes to how we access it. Satellite imagery therefore represents a new tool for use to in forming and understanding perceptions.</p
Employers’ conceptions of quality and value in higher education
No full textIn this qualitative study, we research what constitutes the relationships between conceptions of quality and value associated with higher education as experienced by prospective employers of business graduates. Quality and value in higher education are often linked though the relationship is unclear. Employers are an important and under-researched stakeholder group on the demand side of higher education. Data are generated by interviewing prospective employers of business graduates from a UK university. Interviews are analysed using a phenomenographic method to determine the qualitatively different ways in which actors make sense of the relationships between quality and value. Understanding prospective employers’ conceptions of the relationships is important given the competitive pressures on universities and businesses. The research reinforces the experiential and idiosyncratic relationships between quality and value in higher education. Three conceptions of what constitutes quality and value in higher education are discussed: (a) quality is an antecedent of value; (b) quality is simple while value is complex; and (c) quality is internal to HE while value is created in the customer domain. The research outcomes provide important insights for researchers and practitioners through clearer understanding of how quality and value are related for this important stakeholder group.</p