Mechanical and Materials Engineering Theses

Through listening, this thesis explores an historic private archive which is housed at the Killruddery estate in Bray, County Wicklow, in order to develop new ways of telling the story of an Irish aristocratic dynasty, the Brabazons, who have lived and worked on the estate since 1618. Its purpose is to contribute to a sonified understanding of the Big House in Irish cultural and social history. From conversations with the family, investigation of the written archives, and recordings of the architecture and surrounding landscape, the research examines the idea that the archive is haunted by its own past and that by summoning the sonic spectres of archive through technological intervention, via so-called 'Stone Tape Theory', the mythologies of its role as a heritage space in contemporary Ireland can be brought to audition. The primary field of knowledge is located within the discipline of Sound Studies. The cognate fields are Sonic hauntology, Soundwalking, Binaural Phonography, Mobile Media Art and Sonic Agency. The research utilises the practice-based methodology of an Artist-in-Residence to produce a critical construct entitled haunting the archive, drawing on a notion of hauntology initially developed by Derrida (2006), both as a means to investigate the archive and expressed in the creation of a public artwork, The Ancestors, made in response. Specifically, the principal research methods are soundwalking, field recording, interviews, studio composition, and performance leading to the creation of interactive soundscapes, historical re-enactments and audio essays, geo-fenced within the grounds of the Killruddery estate. The thesis and the practice together constitute an original and substantial contribution to knowledge by extending Labelle’s notion of 'sonic agency' (2018) through connecting elements of Critical Theory with related studies by Eshun, Voegelin and Schulze which explore ideas and practices of 'sonic fiction', to show how the creation of a hauntological sound trail informed by a critically engaged sonic arts praxis, can challenge our understanding of official narratives at a significant Irish heritage site.

Total Hip Arthroplasty is a surgical procedure that reforms the hip joint, replacing the pathological joint with an artificial prosthesis. Due to post-operative joint instability, complications such as dislocation are still a significant problem. Understanding the mechanics of the hip joint is key in the development of preventative methods to treat post-operative hip dislocation. The principal aim of this thesis is to develop a numerical model of the hip joint capable of realistically capturing musculoskeletal loading and joint mechanics. A finite volume structural solver, implemented in open-source software OpenFOAM, has been developed, which is capable of accurately predicting large displacements, large rotations and small strains. A contact procedure, based on an iterative penalty method, has been established and verified against the available Hertzian analytical solution. In order to accurately represent the musculotendon loading, Hill-type muscle models have been developed, and a novel mapped muscle attachment approach capable of accurately capturing the muscle fibre force directions has been implemented. A procedure for extracting the hip joint geometry from computed tomography and magnetic resonance imaging scans has been developed. A technique has been established to accurately extract the muscle-bone attachment sites from the tomographic images. Volumetric meshes of the bones have been constructed using hexahedral, tetrahedral, polyhedral and voxel based meshes and a comprehensive 3-D mesh analysis study has been conducted. Gait analysis has been performed on the same subject from which the tomography images were obtained, and custom analysis utilities have been developed to allow processing and visualisation of the data. Furthermore, a method has been established to process the obtained electromyography signals into a form suitable for input into the developed Hill-type muscle models. The hip joint has been simulated for three separate phases of the gait cycle. The relative positioning of the femur and pelvis bones has been determined from gait analysis, and the applied total hip joint forces have been established from literature. Each of the investigated models has been simulated with and without muscular loading, and the effect of muscle attachment approach has been investigated. The predicted average contact pressures and contact areas ranged from 5.93 to 10.1 MPa and 3.83 × 10-4 to 4.62 × 10-4 m2 respectively. Maximum von Mises stresses in the cortical bone ranged from 30 to 50 MPa and occurred in the acetabular roof, the body of the ilium superior to the acetabulum, near the iliosacral joint, the neck of the femur and the body of the femur. It has been found that the inclusion of musculotendon forces significantly

Polymeric micro parts and micro/nano scale features, as typically found on miniature medical devices and microfluidic chips, are mainly produced by the micro injection moulding process, because of its mass production capability. Because of high surface to volume ratios, filling small cavities and tiny features requires high temperature and high speed in order to prevent short shots from premature solidification. The polymer melts are consequently subject to high shear rates and thermal gradients. This thesis has characterized the micro injection moulding process, polymer rheological behaviour at the micro scale, micro/nano feature replication, and morphology development and mechanical properties of micro parts and micro features.An in-line process monitoring system was developed to characterize filling, packing, and cooling of a typical micro component having a large sprue and runner. A shot size optimization method was proposed, which successfully eliminates the effect of machine switchover and holding pressure on the cavity filling process. Using a slit flow model, polymer melt viscosity at the micro scale was found to be dependent on cavity thickness and was lower than conventional viscosity, which is attributed to wall slip and non-isothermal flow. Replication of multi-scale features, ranging from hundreds of microns to as small as 100nm, has been successfully achieved by micro injection moulding using Bulk Metallic Glass tool inserts. Feature replication is characterized with respect to the moulding process and to the material, design, and feature configuration. Bulk Metallic Glass tools can successfully retain mould patterns for ~20,000 moulding cycles. Poly (ether block amide) micro parts exhibit some unique morphological features: spherulite-free core, larger spherulites between a skin layer and fine-grained layer/core layer. Shear stress was shown to be a successful threshold for the onset of an orientated structure by comparing the micro injection moulding process to a "short-term shear protocol". The morphology of the micro features was found to be similar to that of the core region, and the skin layer deformed into micro feature cavities depending on local pressure. Process-morphology-mechanical properties are correlated for micro parts.

It has been widely reported that the delamination toughness of adhesive joints and polymer matrix composites can vary considerably depending on the mode of loading. For this reason, extensive research has been aimed at devising fracture test methods based on beam-like geometries, which enable the testing of these joint systems under variable modes of loading. However, central to the analysis of these mixed mode test methods, is the definition of a consistent parameter for the characterisation of the mode mixity in the fracture process zone for a given geometry and loading arrangement.This requirement has led to the development of a number of contrasting analytical partitioning theories in the literature which aim to address this problem. The most notable of these are the initial global analysis by Williams and a subsequent local analysis by Hutchinson and Suo. However, significant differences exist between the local and global approaches in the case of fracture in asymmetric geometries, and experimental evidence has been put forward on various occasions supporting each. Other semi-analytical and analytical partitioning theories have also been put forward by Davidson et al. and, more recently, Wang \& Harvey. However, much confusion still surrounds the area of mixed mode partitioning in beam-like geometries, and considerable disagreement remains within the fracture mechanics community as to which partitioning theory, if any, should be used in practice.In this thesis, a new semi-analytical partitioning scheme is proposed based on the findings from a finite element analysis of fracture in beam-like geometries. The fracture process zone is modelled using a cohesive zone model and the energy going into both opening and shearing, and hence the mode mixity, is obtained using a mode decomposed J-integral approach. A parametric study is carried out to examine the effect of various substrate and cohesive properties on the mode mixity. In an initial study, it is found that if no damage is modelled (purely elastic case), the numerical partitioning closely follows the local partitioning of Hutchinson and Suo. Once damage is introduced using the cohesive zone model, it is found that the numerical partition deviates away from the local solution and in all cases tends towards the global solution of Williams.The parametric study reveals that the numerical mode partition moves towards the global solution when the substrate stiffness $(E)$ or cohesive toughness $(G)$ is increased, or the cohesive strength $(t)$ is decreased. Each of these parameters that affect the mode mixity are linked through the developed cohesive zone length $(l_{cz}=f(EG/t^{2}))$. For each individual test geometry, it is found that the mode partition is uniquely dependent on the numerical cohesive zone length. At this point, it is hypothesised that the size of the cohesive zone relative to the size of the $K$ dominant region is the controlling factor in the mode mixity, where the upper and lower bounds of the partitioning solution are given by the local and global analytical solutions respectively (region of $K$ dominance scales with smallest characteristic dimensions). To test this hypothesis, the normalised mode mixity is plotted against the normalised cohesive zone length for all cases over a range of geometries, loadings and cohesive properties. A unique dependency is observed, thus supporting the proposed hypothesis. This hypothesis is further tested using a different cohesive zone formulation and it is still found to hold true. A best fit exponential function is fitted to the observed unique dependency and this forms the basis for the proposed semi-analytical cohesive analysis (SACA).SACA works on the basis that if the cohesive zone length can be estimated from known cohesive properties, then the mode mixity can be estimated from the unique dependency curve. Analytical expressions exist, which were presented by Suo (mode I) and Cox \& Yang (mode II), that can accurately estimate cohesive zone lengths in beam like geometries under mode I and mode II loadings. It is shown in this work that these expressions can also be used to accurately estimate the cohesive zone length under mixed mode loadings by using the maximum of the mode I and mode II cohesive lengths, where the mode I and mode II cohesive zone lengths are obtained by using the energy dissipated in mode I and mode II respectively. As the mode partition is not known initially for each case, the final estimated length, and hence mode mixity, is obtained using an iterative procedure. The final solution is shown to be independent of the initial guess of mode mixity. This procedure is coded into an excel macro and is available for download on the UCD Centre of Adhesion and Adhesives \href{http://adhesion.ucd.ie/caa/CAA_MixedMode.html}{webpage}.Finally, the SACA approach is assessed using an experimental program. In this series of experiments, the true delamination failure locus of a carbon fibre-epoxy composite is obtained using a range of symmetric double cantilever beam specimens loaded with uneven bending moments. A number of asymmetric fracture tests are then carried out and partitioned using a range of analytical partitioning theories including the new SACA approach. It is found that the SACA partitioning of the asymmetric specimens produces the best fit to the symmetrically measured failure locus. This experimental result supports the numerical findings that the true partitioning in the general case is neither local nor global and can only be accurately estimated by accounting for the effect of damage at the crack tip, as in the SACA approach. The SACA partitioning is also applied to previously contrasting experimental data available in the literature, and good agreement is obtained in all cases, suggesting that the proposed semi-analytical cohesive analysis provides an efficient and accurate method for predicting mixed mode partitions.

This project develops the capabilities of micro-abrasive jet machining (MAJM) for tailoring of surface integrity aspects responsible for osseointegration, adhesion strength, and lubrication of artificial articular joints (AAJs). The thesis starts with a literature review outlining six aspects of MAJM process, which must be addressed to enable surface functionalization of AAJs. In the second chapter, the project develops an analytical-numerical model of particle velocity field generated by micro-nozzle. The investigation highlights the effect of process parameters on the magnitude of particle velocity and the nature of its change. In the third chapter, an analytical solution is developed to describe the temperature rise during the impact of a single particle. Further, several numerical models and measurements are addressed for elaborating the steady-state thermal field during MAJM. The fourth chapter delivers a modified Hill’s ratio predicting lateral crack nucleation druing impact-induced fracturing and erosion rate of brittle materials. The following four chapters are application-focused. Fifth chapter is on the development of the bone/implant interfacial area. Six shape parameters of eight abrasive fractions and nine roughness parameters of Co-Cr-Mo surface eroded under sixteen blasting conditions are analysed. The fifth chapter improves adhesion strength and scratch-resistance of antibacterial coatings. The investigation contributes an extensive characterization of Ti-6Al-4V surface topography, microstructure, chemistry and wettability generated by milling, polishing, acid-etching and MAJM. The sixth and seventh chapters address the issue of poor tribological performance of AAJs, developing MAJM direct writing and a novel Tribo-blast surface texturing technique. This project delivers tools for managing particle velocity, jet kinetic energy, machining temperature, single crater size, surface roughness and erosion rate in MAJM. The bone/implant interfacial area, the scratch resistance of antibacterial coatings, and bearing index of the articular surface, all can be increased by a factor of two. The femoral head of a hip joint can be covered by micro-channels within a few minutes using only one nozzle and one gram of abrasives without the patterning masks or precision CNC actuators. Overall, the productivity and cost-effectiveness, makes MAJM a strong candidate for industrial implementation in the manufacturing chain of life-long AAJs.

Innovation is one of the key drivers of technological, economic and social development around the world, with innovative solutions to some of the most common or complex problems resulting in world-changing technologies, businesses and concepts. While these innovations may seem to appear suddenly and then revolutionise the world in which we live at a rapid pace, in fact, the development of these innovations is complex and often invisible from a surface-level view. Often, at least in the past, innovations came from the commercial and professional technological sectors and then transferred into mainstream use. But today, and in the future, the contributions of non-expert innovators to a more inclusive innovation ecosystem will make an increasing impact, so contributions from the public are also required. In order to facilitate user input into the process, as well as to increase impact from those more familiar with the innovation space, the concept of an ‘innovation methodology’ has developed. This thesis contributes to the emergent field of Innovation Methodology. An innovation methodology is a structured process that guides a user through the process of innovation, providing support, guidance and tools for use during innovation activities. Whilst there are a growing number of innovation activities in the general public domain due to the increased availability of rapid prototyping tools such as 3d printers et al., still, it is apparent that the most popular and impactful methodologies have a number of core advantages and disadvantages to be considered by users for maximum impact. These characteristics must be carefully assessed, evaluated and refined to develop the core aspects of an impactful innovation methodology. This thesis outlines the process of engagement, analysis, application and impact. The thesis thus grounds its core contributions in the main field of Innovation Methodologies, and extends carefully into specific areas of the cognate fields of STEM, Business and Social Impact, with the goal of examining the development of the practices of innovation in a number of fields over time, allowing the framing of the concept and potential areas of application. The aim of the project is the investigation, analysis and evaluation of currently proposed innovation methods & processes, in order to identify the most successful practices, details and inputs into these processes. This research is supported by the utilised research tools of bibliometric keyword evaluation, heuristic assessment and expert user input gathered via a structured survey that collected qualitative insights from these expert users. The data gathered through this process was analysed and applied to a proposal of a new innovation methodology: the “Double Helix Innovation” methodology, aimed at directly applied innovation action by “non-expert” users. In order to enable and enhance the successful future application of this methodology, a model of praxis - involving a selection of internal and external tools was also developed. The original and substantial contributions to knowledge offered via this thesis are: a new topography of current innovation methods, a categorisation of the highly impactful aspects of these methods, and a new applied innovation methodology and supporting praxis, named the “Double Helix Innovation” method, which has been strongly influenced by the best practice models and aspects of current methods, and refined to provide an easier to use, more flexible methodology to allow more people to innovate and create solutions to today’s interdisciplinary problems. It is hoped that this thesis will make a substantial original contribution to knowledge in the field of Innovation Methodology, with impact and applications for all practitioners & all cognate fields, and for scholars, engineers, artists and other practitioners in the open innovation ecosystem.

Computation has become synonymous with digital computation in the 21st century. The exponential growth in computational demand has been identical in trend to the exponential growth of compute resources available on a chip. However, recently the latter has started showing signs of slowing down as the physical limits are approached of the semiconducting substrates that have continually allowed transistor miniaturization for decades. This has brought into scrutiny the foundational architecture of general purpose computers established at the advent of the digital computer - the von Neumann architecture. Separating data and instructions, the von-Neumann architecture has been a simple yet highly successful model of computation. However, many classes of problems such as 'cognitive tasks' in image recognition, anomaly detection, speech recognition, etc. require very high throughput of data and are sub-optimally served by this architecture. Another class of problems is combinatorial optimization where a the optimal solution to a function with a large discrete configuration space is to be found. The exponential growth in the number of configurations even for moderate real-world problems makes this class among the hardest for traditional computers to solve. This thesis explores the potential of using coupled analog oscillators to construct non-von-Neumann architectures for such tasks where a significant advantage may be gained over traditional models. To solve combinatorial optimization, the concept of 'Ising Machines' has been proposed where dynamics of coupled oscillators is adapted to find the solution of the problem as the lowest energy state of a physical system. The Ising machine paradigm is studied using a general coupled oscillator model including amplitude dynamics for the first time. A control scheme called 'Parametric cycling' is proposed that prevents local minima traps to a significant extent. The performance is demonstrated on Max-Cut problems of fully connected graphs and cubic graphs. Further, drawing on the neuroscientific abstraction of neurons in the brain as coupled oscillators, a neuromorphic architecture is constructed suitable for anomaly detection problems. Spiking Neural Networks are proposed to solve structural health monitoring problems by extracting cepstral coefficients as features. The implementation is tested on a novel hardware platform named Intel Loihi, offering the potential of highly energy efficient operation of neuromorphic algorithms. This thesis showcases the computational potential of oscillators beginning with a single resonator, a piezoelectric energy harvester, which may be used to estimate extreme values of responses and fragility of structures. It progresses to coupled (Stuart-Landau) oscillators and demonstrates combinatorial optimization capability. Finally, coupled integrate-and-fire oscillators or spiking neurons are used to detect damage induced anomalies in the vibration response of a structure. The research presented in this thesis thus establishes coupled oscillator networks as prime contenders for computing primitives of the future in classes of problems where digital computers based on the von-Neumann architecture are fundamentally constrained.

Energy-efficient retrofits have become crucial in the building sector as approximately 80% of the buildings in developed countries are over 10 years old and consume a major portion of total energy demand. The development and use of thermal models are an integral part of the design process in new and existing buildings due for refurbishment. Building energy performance simulation tools have become quite popular and are now being used to provide estimates of energy consumption at different scales. These tools implement various types of models which differ based on enclosed details. Not all these models are effective in terms of computation and cost. Recently, the total number of developed energy models has grown tremendously, which vary considerably in terms of characteristics and features. Hence, it is crucial to identify the type and characteristics of a model most suited to a certain purpose and situation. Alongside, the sophistication of simulation tools has significantly increased the number of user inputs, thereby, introducing uncertainty in simulation outputs. Grey-box modelling combines the advantages of data-driven and physical modelling approaches. Therefore, these models deliver an appropriate level of accuracy and are also computationally efficient. However, the design approach of grey-box models is often application-specific, for instance, the design approach for grey-box modelling of commercial buildings differs on a case by case basis. Furthermore, the scalability of these models is limited by the network order, which defines the level of complexity incorporated in the model. There is a need for a generalization framework to address the limitations associated with grey-box networks. As different applications require models of varying complexities, it is necessary to identify the model features, such as scalability, flexibility and interoperability, associated with different stakeholders of the building stock. Furthermore, previous uncertainty analysis studies have either failed to segregate the existing uncertainties or considered only one type of uncertainty in the analysis. The thesis introduces a novel generalizable methodology which formulates grey-box networks for different types of commercial buildings. Physical parameters and the nature of the operation of individual buildings constitute the key elements of the developed framework. The framework also relies on the past retrofit history and installed HVAC systems to deduce the order of the grey box network. The methodology further formulates an experimental design technique to associate and assess various model features pertinent to reduced-order grey-box models using pre-defined key performance indicators. Lastly, this research systematically identifies the various sources of uncertainty in grey-box models and develops a framework to include these sources in overall uncertainty quantification. This thesis uses a combination of real-time commercial buildings and reference building archetypes to test and validate the devised techniques. The devised approach reduces the complexities associated with the identification of the network order while maintaining the desired level of accuracy. The approach provides additional insights and information to designers considering novel alternative design approaches, where prior information may not be readily available. The feature assessment frameworks act as a decision support tool in the identification of appropriate model characteristics. The results of this study could support the current need for the assessment of consumption patterns of commercial building stock. The framework could further be implemented to study the post-retrofit heat consumption patterns at the individual building as well as the district scale. A probabilistic framework employing advanced techniques would allow stakeholders to identify influential inputs by considering the factors behind the risks in a given family of distributions.

Today's problems are 'wicked': defined as complex and comprised of multiple, and contradictory threads that make addressing the 'whole problem' impossible without considering the inter-relations of the parts. These problems are often so knotty that they are unable to be solved. Add exponential growth and change in the economy, population, and factors around sustainability, to further compound these issues. The tools we have been using to solve these wicked problems are not sufficient; we need better and different tools and methods to achieve more. This thesis proposes that 'tacit knowledge' can be a powerful generator of new thinking but acknowledges that tacit knowledge cannot be accessed by simply asking questions. Cognitive biases may prevent people from fully engaging with new concepts and ideas. When intellectual or creative cognitive capacity is limited, connections are not made, and new ways of thinking and understanding are blocked. This thesis puts forward the hypothesis that a human’s capacity for original thought and radical discovery can be increased through virtual, experiential tools. The research for the thesis and the practical project underpinning it have explored – in theory, and in practice - how engagement in virtual future experiential worlds can provide a useful tool to help people develop new creative ideas. The research project scoped, designed, developed, tested, and analysed the use of novel virtual experiential worlds for this purpose, offering several original contributions including a novel tool for future use by scholars and practitioners. The thesis poses and answers the following research questions: Can immersion in Virtual Reality (VR) scenarios activate new creative thinking? Can ba, a place for knowledge creation be developed as a destination? Can VR immersion change a user's existing point of view? The research provides theoretical and evidence-based answers to these questions and then demonstrates the potential for solving wicked problems. A new method of creative exploration is offered: Elastic Action. This process begins with an effort to remove bias and blockage from the thinker's mind. Accommodation is created in the brain through exposure to 'awe', as defined at length in the thesis. Through this process, existing cognitive connections are broken, so new information can be accepted, and new ways of thinking can be enabled. The embodied cognition which takes place while the participant is immersed in a virtual future scenario can be called 'Extensible Realisations': another new concept of the thesis. Participants are then receptive to data from both mind and body. The virtual experiences were designed to 'stretch' the mind and discover new knowledge. This research successfully creates ba, a place for tacit knowledge creation enabled by a new tool of exposure: VR Time Portals. Participants travelled to divergent possible futures where they explored and discovered new ideas, perspectives, and possibilities. After immersion, they were 'snapped back' to their lived reality, where they sorted and codified their new ideas. The research design: seven residents experienced two divergent possible futures of their town in the year 2050. A change in the participants' abilities to create new ideas was experienced by all. While immersed, participants reported that they were "confronted with awe and wonder" and that they "felt their minds had been stretched" and "determined that their points of view had been altered". The results of this research provide a set of original contributions to knowledge, including a novel experiential design process that others may use to tackle wicked problems, along with a research tool in the form of the VR Time Portals. This research is intended to contribute to knowledge in the fields of Creative Thinking and Theory, as well as to Futures Studies, and Inclusive and Sustainable Design.

Myopia is posing a big threat to the global eye health and putting the young generation in danger of blindness. To prevent the development of high myopia, optical lenses have been developed based on the findings that the peripheral optical properties of the eye can affect myopia progression. As the core for many applications in myopia control, a realistic eye model should be established that reproduces the optical and structural features of the human eye. Based on the ocular data obtained from the recent measurement technologies, this thesis investigates the peripheral optical features of the ocular components and develops new models to achieve a more realistic description of the human eye for the wide visual field. As the most complex component in the eye model, a new crystalline lens model is proposed in Chapter 2 to represent the structural and functional features of the lens of children. The model has the capability of involving most parameters measurable on the in vivo human lens, while maintaining realistic values of optical power and spherical aberration. Starting from the lens model proposed in Chapter 2, Chapter 3 develops a method for evaluating the peripheral refracting properties of the lens. The impacts of the lens structural parameters to the peripheral lens power are systematically evaluated. Specifically, the contribution of the gradient refractive index structure to the peripheral lens power has been revealed. In Chapter 4, a fast computation method based on generalized ray tracing is developed to analyze the peripheral optical power of the cornea defined in a similarly way as proposed in Chapter 3. The method is tested on the realistic corneal model constructed from measurement data. The contribution of the cornea to the ocular refractions over the entire visual field can be formulated based on the proposed procedure. Chapter 5 and 6 investigates the role of the retinal contour to the peripheral optical properties of the eye. Specifically, a highly efficient method is proposed that can reproduce the peripheral spherical equivalent refraction over the entire visual field by retinal contour modeling. Overall, this work contributes a theoretical framework and knowledge base on the peripheral optics of the human eye, which are instrumental for developing potential approaches aimed for higher efficacy in myopia control.

The domain of SHM has known many developments in recent years. Among those, the improvement of damage detection algorithms was significant. That was especially the case for eigen-perturbation algorithms, like first order eigen-perturbation (FOP) which uses recursive rules to update an eigendecomposition. From such a result, the eigendecomposition of a multidimensional structural system's accelerations can be updated with reduced cost. Their impact in detecting damage from acceleration signals was well established through simulations and experiments. It was nonetheless observed that FOP had limitations in terms of accuracy over time and limited performance with mild to moderate damping ratios. This motivated the research presented here where it was proposed to increase the accuracy of such an algorithm through the development of higher order eigen-perturbation algorithms. These algorithms are subsequently tested with various structural and dynamical systems where their error performance and computational efficiency were quantified to show positive and significant gains. Alternatively, numerical simulations are a core pillar of the tools used to parameterize, analyse and make decisions regarding the design and control of structural systems. For this purpose, stochastic differential equations (SDEs) have been used to simulate structural systems in an alternative to avoid the use of an inconsistent call to ordinary calculus. The theory of stochastic calculus has been leveraged in many a case of random excitation. This is not yet the case of Pendulum Tuned Mass Dampers (PTMDs). It was therefore proposed to explore the realm of capabilities provided by stochastic calculus to simulate a structure under random excitation equipped with a PTMD. This was performed in many forms, with a three dimensional PTMD, a two dimensional PTMD equipped with an Shape Memory Alloy (SMA) wire and a 2-degree of freedom (DOF) building system. It further allowed tuning and optimal control of these systems. Both of these works, damage detection and stochastic simulation were lastly linked through the implementation of a damage detection and retuning process for a 2-DOF and PTMD system experiencing instantaneous damage.

This practice-based PhD set out to design and apply novel multi-channel and nonintrusive electroencephalographic wave analysers, along with environmental sensors, to provide extensive compositional biofeedback in gallery and non-gallery settings as well as public spaces where Virtual Reality, Augmented Reality and/or Mixed Reality technologies may also possibly be in use. There is a current gap in knowledge about the nature and behaviours of auditory processes and interactions in both sound art performances and in-built environment situations (whether in the art gallery or any other type of space); some research has been conducted but this unique combination of concerns has not to date been investigated in either practice or theory in the manner undertaken in this thesis. The methodology of the research is practice-based experimentation to contrive and assess sound art, in situ, ranging from small venues to outdoor public spaces. The intention is to better characterise sensory feedback established from a practice-based research to a comprehensive explorative framework. The intended result - as achieved in this PhD - is to map a multitude of possible correlations and interactions to create responsive immersive conditions. The intended outcome - also achieved - is to develop a new method for compositional design and perceptual analysis of relevance and applicability to a variety of spaces. The compositional aspect of this novel research project has built upon Sound Art and Sensorial Practice, and has woven in and informed this practice with theory and critical frameworks to help future practitioners and scholars engage with the work and take it further in their own ways, for their own purposes. The thesis as a whole delivers a written dissertation that builds upon and shares new knowledge gained from the practice-based study, and offers a new and novel set of techniques that future audio-visual artists and designers alike may choose to apply, in order to induce a sensorial dimension in their own works, whereas future scholars may build upon the methodology and the examples provided as a starting point for future Sound Art Practice research. The Sound Art practice is itself submitted as an integral part of the thesis and should be listened to in conjunction with reading of the materials. Overall, the perceptual findings inform a research methodology and educational foundation underpinning a new basis for research and development in the fields of Sound Art, Acoustics and Architecture.

Bioimplants are man-made medical devices to replace the malfunctional natural joints. In the past six decades, total joint replacement is credited as one of the most successful surgical operations. Metal alloy matching with polymer is the most common material combination used in the bearing parts of artificial joints. However, most commercial products have a relatively short in-vivo lifespan due to the unsatisfactory tribological performance of bearing parts. This study aims at increasing the longevity of bioimplants by modifying the surface topographies of bearing parts, including surface roughness and surface texturing. This thesis starts with the motivation of carrying out this project, followed by a comprehensive literature review. In Chapter 3, the validity of molecular-mechanical frictional theory is tested for the bioimplant application using the pin-on-disk tribometer. By a long-term sliding test (10 km) and the dynamic analysis, the study firstly highlights the importance for the metallic bearing surface to keep its original surface finish after implantation other than only getting a superfinished surface before implantation. As a result, surface texturing approach is proposed to achieve this goal. In Chapter 4, the impact of four potential working mechanisms related to surface texturing in bioimplants are investigated. An important finding on the role of hydrodynamic pressure on the tribological performance of textured implants is presented: the extra lifting force provided by hydrodynamic pressure is negligible. This unique property distinguishes the bioimplants application from other conventional bearing systems. Further numerical simulation and experimental experiments attribute this novel finding to the working conditions of implanted joints: slow sliding speed and low viscosity lubricating solution. Alternatively, a new understanding, namely squeezing effect, is established to explain the increased thickness of lubricant film which helps to improve the tribological performance of textured bioimplants. Meanwhile, a novel failure mechanism, interlocking effect (stress concentration and two-body abrasive wear), is put forward to explain why some pattern designs, such as sharp-corner structure, are detrimental to the bioimplants. Afterwards, a technical solution, namely round-corner structure, is developed to resolve the interlocking effect. In Chapter 5, sliding orientation is found to play a minor role on the tribological performance of textured bioimplants and this phenomenon is explained by the proposed working mechanism of squeezing effect. Furthermore, the regularly arranged texturing patterns are proved to be more suitable for bioimplants than the irregularly arranged micro patterns. Finally, an orthogonal experiment is designed to reveal the influential level of five main pattern parameters: area density > size > shape > depth > distribution mode. The conclusion is that the optimal pattern design with specific parameters: triangle structure with 200 µm side length, 8-10 µm depth, 10% area density and square distribution mode, can provide the optimized tribological performance. In Chapter 6, a long-term wear experiment with 1 million cycles is carried out to compare the tribological performance between the only polished bioimplants and the ones with optimal structured bearing part. The study confirms that, by applying the optimal structured surface, the in-vivo longevity of polymer-based bioimplants can be effectively increased.

Laser Based Powder Bed Fusion (PBF-LB) is an additive manufacturing process, which can be used for the manufacture of geometrically complex metallic structures. The focus of this thesis is to evaluate the properties of PBF-LB fabricated Ti-6Al-4V and 316L stainless steel lattice structures, obtained using multiple laser scanning strategies. Amongst the investigations carried out was to determine the effect of both strut diameter and overhang angle, two key lattice design parameters, on the lattice morphology and internal porosity. Ti-6Al-4V structures were manufactured using a point-based approach, in which laser parameters were varied in order to control strut diameter, 316L stainless steel structures were manufactured with a hatch and contour approach, in which strut diameter is varied via. CAD. Evaluation of the structures showed limitations of the minimum achievable overhang angle for both structures of approximately 20°. Porosity formation within the titanium alloy structures was found to be largely associated with keyholing defects, while stainless steel porosity was attributed to lack of fusion defects, both of which were attributed to the selected laser process parameters. In-process monitoring used in the manufacture of the titanium alloy struts, demonstrated that reduced optical emission intensities were obtained from melt pools, from which higher levels of strut failures occurred. A further study evaluated the morphological and compressive mechanical properties of diamond lattice structures fabricated from the titanium and stainless steel alloys. The diamond lattice structure was selected for its noted ease of manufacture and its application within the biomedical sector. Samples fabricated in titanium alloy were found to be of higher quality, with lower amounts of external particle adhesion and more cylindrical struts in comparison to the stainless-steel samples. Both titanium and stainless steel were found to have similar relative compressive strengths, while stainless steel samples were found to have higher relative elastic modulus. Despite the same lattice structures differences in failure modes between the two alloys were obtained. Titanium samples were found to deform in a brittle manner, showing failure through sudden rupture of struts along parallel planes, while stainless steel samples underwent ductile failure where struts and nodes were found to deform consistently without rupture.

The 2017 Health Evidence Awareness Report from the Irish Health Repository identified that 1- 2% of the global population has Autism Spectrum Disorder (ASD). This percentage was confirmed in 2021 by the US Disease Control and Prevention (CDC). Attempting to ‘fit into’ societal infrastructures and norms can present complex challenges for individuals with ASD, in a world that has not catered for their needs or tailored opportunities for their development. For instance, over 35% of young adults with ASD in the USA have not held a job, nor received formal education after leaving high school. Global comparators also show disparity and deprivation for this age group of young adults with ASD. This thesis offers novel design insights achieved through the design and testing of a novel Augmented Reality (AR) Digital Helper, the aim of which is to bridge the needs of individuals with ASD with possible societal supports. Augmented Reality is applied in this thesis projects as a technology tool that offers a layer of information and interpretation for young people with ASD engaged in real-world activities. AR as an Assistive Technology was applied in the project through the process of co-designing an AR helper with the young people in need of its affordances. In this way, an Inclusive Co-Design methodology was applied, establishing participants with ASD as co-designers of their own AR Digital Helpers and testing their responses to the use of their own Helpers in real-world settings. The research also gathered insights from the participants’ care ecosystems of family members and care workers. This research makes an original contribution to scholarship by introducing this novel assistive technology in the context of specific domains of knowledge, reaching across disciplines and practices to provide new insights focused on the characteristics of, and activities with which, AR Digital Helpers can assist. The thesis details the establishment of a new participatory design method, and includes a literature review covering the areas of Critical Disability Studies, XR capabilities in well-being practices, and the area of social challenges for young adults with ASD, alongside the technical areas and applicable research in Virtual Reality (VR), AR and 3D non player character guides or helpers. The PhD thesis, including the body of data, data analysis, and details of the Digital Helper prototype, are all offered together as a practice-based PhD making an original and substantial contribution to the Field of Knowledge of XR in Health and Wellbeing for individuals with ASD, and to the cognate fields of Extended Reality for ASD, and Inclusive Design. It is hoped that future scholars, design practitioners, clinicians, and people with ASD, will be able to apply this research to their studies and their lives.

To increase the number of electronic components in a single integrated circuit chip, the functional feature size should be reduced to the atomic and close-to-atomic scale (ACS). For this, the application of molecules could be utilised as a channel for current conduction. This thesis focuses on the fundamental aspects of this theme to help us achieve atomic scale device fabrication in the future. A literature review on advances in moletronics and atomic and close-to-atomic scale manufacturing (ACSM) research with the application of atomic force microscopy (AFM) is given in chapter 1. ACS device manufacturing using molecules as the building block requires to overcome mainly three fundamental problems. Firstly the orientation of the molecule when placed between the electrodes plays a critical role in electronic transport. This is explained in chapter 2, which gives a detailed ab-initio simulation studies of current flow in inorganic molecule, such as polyoxometalates (POMs) and organic molecules such as phthalocyanines (Pc) and porphyrins (Pr), by incorporating them between gold electrodes. For the POM molecule, longitudinal orientation showed better conduction than lateral orientation, whereas for Pc and Pr molecules, the geometrically optimised orientation displayed better electronic transport properties than the tautomerized structure. Secondly, the bonding interaction between the electrode and the molecular terminal atoms helps us to determine the rate of electronic transport at the junction. Chapter 3 inspects this interaction through a periodic energy decomposition analysis on Pc and Pr derivatives. The attractive and repulsive energy terms of the bonding interactions proved that Pr molecules are better interactive over the gold substrate in comparison to Pc molecules. Electronic transport studies performed on their derivatives with and without thiol linkers further supported this result. Thus, a link between these two studies were established. This paves path for future work to select appropriate molecules and electrodes to demonstrate transistor actions for atomic scale device fabrication. Finally, the possibility of the fabrication of ACS electrodes with a single atomic protrusion for the attachment of molecules needs to be experimentally validated. As a first step towards this, fundamental studies using AFM to achieve atomic layer removal were carried out taking into account different machining parameters. This is given in chapter 4 and chapter 5. In chapter 4, mechanical AFM-based scratching techniques over gold and silicon using diamond tips were performed. In silicon substrate, material removal having a minimum depth of 3.2Å which is close to about 3 silicon atom thickness, has been achieved. On gold, a minimum depth of 9.7Å, close to 7 atom thickness has been achieved. In chapter 5, electrochemical AFM-based lithography over HOPG and silicon using platinum coated tips were carried out. Results showed that in bare silicon local anodic oxidation took place instead of material removal. Even in hydrofluoric (HF) treated silicon, oxidation occurred but in a controlled and well defined manner. From this, it can be deduced that HF treated silicon is better suited for structure fabrication than bare silicon. In the case of HOPG, different patterns such as nano-holes, nanolines and intrinsic patterns were machined and material removal close-to-a single atomic layer, ~3.35Å was achieved. Results from chapter 4 and 5 reveal that controlled AFM-based scratching techniques can ensure the fabrication of well-defined atomic structures for the application of molecular devices. Since ACSM represents the next phase of manufacturing, this thesis proposes some of the primary works required to realise ACSM using the currently available techniques and simulation methodologies to bring us one step closer in achieving considerable advancements in this field in the near future.

The world is facing severe challenges, including climate change, hunger, pandemics and inequality. Several of these challenges will directly or indirectly impact everyone, and there is an urgent need for global action. It is necessary to adapt to a more sustainable way of living, and research can help develop and refine tools to support this transformation. This dissertation aims to contribute to the understanding of how virtual reality (VR) can support attitudinal and behavioural change leading to prosocial behaviour. A mixed-methods design was used to outline a framework for designing prosocial VR interventions, develop a pro-environmental VR intervention, and test its effectiveness in a two-group quasi-experiment involving 104 participants. Finally, the most impactful factors for a change in pro-environmental attitudes and behaviours were explored. The dissertation confirms findings from prior research that indicate the effectiveness of using VR to support prosocial change. It also provides additional insight into the understudied area of using VR in pro-environmental interventions. The participants in the VR condition reported an increased capability, opportunity and motivation for prosocial change, a higher degree of pro-environmental behaviour one month after the intervention, and participated to a higher degree in voluntary activities to learn about measuring and reducing their carbon footprint. The research offers novel insights and original contributions to the academic field of prosocial VR but also provides examples of how scholarship might inform and inspire prosocial action in practice. The ambition is that this work can be of value to future scholars and practitioners and that it may be utilised in schools and learning environments where young people may be inspired to take ownership and action.

This study aims at utilizing a self-developed hybrid polishing system to establish polishing capabilities of electropolishing (EP), abrasive fluid polishing (AFP), multiple polishing in different sequences and innovative hybrid polishing for the internal structures prepared by laser-based powder bed fusion (L-PBF). By studying polishing effects on various inner surfaces, the relationships between polishing processes and material removal mechanisms of L-PBF surface features are established considering microstructural differences of surface features. The thesis starts with a comprehensive introduction of the project and then a literature review outlining L-PBF process, application of typical L-PBF internal structures, surface characteristics, advantages and limitations of current polishing methods for L-PBF inner surfaces. Breakthroughs in the surface finish of L-PBF internal structures are required in order to improve surface quality to meet the specific requirements of product performance. It is notified that EP and AFP exhibit complementary advantages in the polishing of internal structures among various polishing technologies. In the chapter 3, different types of inner surfaces for fundamental investigation and typical internal structures for application development are designed, and prepared by L-PBF using 316L stainless steel and Ti6Al4V powders. Then, un-sintered powders and sintered area are characterized as common surface features on L-PBF top, face up, side and face down surfaces considering the differences of morphology and microstructure. Meanwhile, an innovative hybrid polishing system which could carry out EP, AFP, their multiple polishing and hybrid polishing is established for the surface improvement of the L-PBF inner surfaces and internal structures. In the chapter 4, a polishing mode consisting of two-step EP is developed by using different potentials and polishing time for L-PBF 316L stainless steel and Ti6Al4V inner surfaces after parametric study in the developed polishing system. Based on material removal characteristics of surface features, the effectiveness and high efficiency of the two-step EP are demonstrated. Considering polishing characteristics of AFP, the inlet design of polishing chamber is improved and the material removal process of various L-PBF internal surfaces are discussed by analyzing the evolution of surface morphology, roughness and microstructure on cross sections in the chapter 5. In the chapter 6, multiple polishing in different sequences and hybrid polishing based on EP and AFP are investigated for L-PBF inner surfaces. It is found that L-PBF inner surfaces after single polishing can be further improved by multiple polishing in different sequences because of the complementary characteristics of EP and AFP in removing L-PBF surface features. In addition, hybrid polishing can perform EP and AFP simultaneously without interfering with each other, showing great potential in improving polishing efficiency of L-PBF inner surfaces. In the chapter 7, different polishing processes are applied to three typical L-PBF internal structures. The superiority of multiple polishing in different sequences and hybrid polishing for L-PBF inner structures is verified. Overall, it is confirmed that the self-developed innovative hybrid polishing system is capable of polishing various L-PBF internal structures with reliable results. Fundamental research on material removal characteristics of L-PBF surface features during polishing provides a theoretical basis for the applications of multiple and hybrid polishing based on EP and AFP. High efficiency and cost- effectiveness make the hybrid polishing system a strong candidate for industrial implementation in the surface finish of L-PBF internal structures.

The European Union’s ambitious 2030 target to reduce energy consumption by 30% underscores the need for effective energy policies in the residential building sector. Accurate energy consumption estimation at various spatial and temporal scales is complex and computationally intensive. Archetypes simplify this task but often overlook critical factors such as occupancy uncertainty and the relationship between energy use and Indoor Environmental Quality (IEQ). This can lead to significant performance gaps between estimated and measured energy consumption. Addressing these challenges is essential for developing reliable decision-support tools and aligning energy estimates with measured energy usage. This thesis explores the impact of occupancy and the energy-IEQ relationship on energy consumption across multiple spatial and temporal scales, using Irish residential building archetypes as a case study. To achieve this, the thesis develops methodologies for creating various occupancy models, which are then integrated into residential archetypes to estimate energy consumption at different spatial and temporal scales. Furthermore, the correlation between energy consumption and IEQ is analysed to establish a balance between energy efficiency and maintaining healthy indoor environments. By deepening the understanding of occupancy and the energy-IEQ relationship, this study focuses on enhancing the capabilities and robustness of residential building archetypes for estimating energy consumption at multiple spatial and temporal scales through three distinct contributions to knowledge. The first contribution (Chapter 2) of this thesis focuses on developing a deterministic occupancy model, as a representative of a large number of dwellings, using Time Use Survey (TUS) data to generate day-wise occupancy schedules. This model is based on a specific set of rules, including the number of occupants, dwelling type, month of the year, and day of the week. The model converts the recorded activity in the TUS data into presence/absence profiles, providing insights into energy use related to daily activities. When validated against measured gas consumption data, the deterministic model demonstrates significant improvements in predicting heating energy consumption, with annual variations of approximately 10% and daily variations of up to 50% compared to standard occupancy models. Monthly heating and electricity consumption show variations of approximately 25% and 32%, respectively, compared to the base case. On a more granular level, daily variations in heating and electricity consumption are reported as 50% and 12%, respectively, compared to the base case with standard and conventional schedules. The second contribution (Chapter 3) devises a methodology to develop a Probabilistic Occupancy Model (UPOM), representative of a large number of dwellings, that is suitable for residential energy analysis over multiple spatial scales. The occupancy model is developed using Bayesian Neural Networks (BNNs) based on Time Use Survey (TUS) data. The multi-class classification model predicts four occupancy states, providing probability distributions that capture the uncertainty inherent in each prediction. The UPOM achieved 90% accuracy in predicting nighttime occupancy states and an average accuracy of 64% during the day, reflecting variations in daytime activities. Comparative analyses are conducted between the UPOM, a deterministic model, and standard occupancy models in terms of estimating heating energy consumption at various spatial and temporal scales. Statistical analyses using Analysis Of Variance (ANOVA) and Tukey’s honestly significant difference (Tukey HSD) tests confirmed the statistical significance of the differences among models, establishing UPOM as the most reliable for estimating energy consumption followed by the deterministic model. To further extend the capabilities of occupancy-based archetypes, the third contribution (Chapter 4) proposes a low-computational methodology based on a metamodel approach tailored for rapid prediction and optimisation of heating energy consumption (kWh), thermal discomfort (hours), and elevated CO2 levels (hours) under the influence of occupancy. The framework evaluates the impact of occupancy on the Pareto optimal front, balancing these three objectives for energy-efficient, naturally ventilated residential buildings in a temperate oceanic climate. For this purpose, a synthetic dataset is generated via parametric simulation using a validated EnergyPlus model of a representative dwelling archetype. The parametric simulation includes a range of occupancy-related parameters such as metabolic rates, occupancy density, clothing value and window operations, along with other building input parameters. The metamodel-based optimisation significantly reduces computation time by 80% compared to physicsbased optimisation, maintaining a high correlation coefficient of 0.98 between the two approaches. By including occupancy-related variables in the study, this study ensures that the predicted results and optimised design and operational parameters are resilient, and within acceptable limits, as recommended by the WHO and CIBSE TM59, whilst minimising the heating consumption to align with appropriate standards for energy-efficient homes. By integrating realistic occupancy behaviour and the strong relationship between energy consumption and IEQ, the study provides robust archetypes that enhance the prediction accuracy of energy consumption at multiple spatial and temporal scales. Policymakers can leverage these findings to refine and update building performance standards, ensuring they reflect real-world conditions and promote better compliance and implementation across the residential building sector. The enhanced predictive accuracy and reduced optimisation time facilitated by this research encourage the adoption of more efficient building management systems and retrofitting practices. This supports the development of sustainable building policies that prioritise both energy efficiency and IEQ in residential dwellings.