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ERA is a digital repository of original research produced at The University of Edinburgh. The archive contains documents written by, or affiliated with, academic authors, or units, based at Edinburgh that have sufficient quality to be collected and preserved by the Library, but which are not controlled by commercial publishers. Holdings include full-text digital doctoral theses, masters dissertations, project reports, briefing papers and out-of-print materials.

Information on current research activity including staff, projects and publications is available via the Edinburgh Research Explorer.

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Recent Submissions

Harnessing resonance with adjustable stiffness for persistent peak efficiency: design, fabrication, and characterization of a heart-inspired pulsatile pump
(The University of Edinburgh, 2026-06-01) Baisamy, Paul; Giorgio-Serchi, Francesco; Stokes, Adam; Engineering and Physical Sciences Research Council (EPSRC); UK Research and Innovation (UKRI)
Pulsatile flow is a fundamental mode of fluid transport in biological and environmental systems. This unsteady flow regime is exemplified in cardiovascular circulation, in the locomotion of cephalopods and jellyfish, in the roots of certain plants and many other natural phenomena. The temporal and spatial variations inherent in pulsatile flow not only regulates mass transport but can also support efficient energy usage, underscoring its importance in physiological functions. In the field of mechatronics, the capability to produce highly unsteady flow regimes constitutes a critical asset for the actuation of pressure-driven soft robotic systems, the regulation of fluidic circuitry, and the propulsion of autonomous aquatic platforms. Notably, in biomedical engineering, the generation of controlled pulsatile flow patterns is of particular significance for the development of cardiac assist devices that more faithfully emulate the physiological dynamics of the native heart. By enabling flow characteristics more closely aligned with natural cardiovascular function, this technological approach offers a promising pathway for improving therapeutic outcomes and addressing the increasing prevalence of cardiovascular diseases in an aging global population. Despite its significance, generating controlled and efficient pulsatile flow across a broad range of frequencies remains a challenge that current pumping technologies fail to meet. This thesis addresses this gap by investigating the physics underpinning optimal pulsatile pumping and by developing a novel pumping system capable of optimal operation over a wide frequency bandwidth. Inspiration is drawn from biological shape-changing mechanisms such as the beating heart or the mantle-driven propulsion of cephalopods as they present four highly sought-after features: pulsatility, compactness, efficiency and preservation of fluid integrity. Specifically, pulsatile self-propelling systems have been shown to successfully exploit resonance to enhance propulsive efficiency, similarly to what certain sea-dwelling organisms do, hinting at the opportunity to exploit the same benefit in pumping systems. Although resonance has been widely exploited in mechanical systems, its potential in fluid pumping mechanisms, and particularly in pulsatile flows, has never been systematically investigated. This work introduces, for the first time, a resonance-based approach to pulsatile fluid pumping, demonstrating its efficacy in improving flow performance and system efficiency. In order to leverage resonance across a broad range of pulsation frequencies, this work introduces variable stiffness as a means to actively tune the system’s natural frequency. Although stiffness modulation has been implemented in other engineering systems, its use for controlling transition to resonance is sparse and almost unheard of in the context of fluid displacement technology making this approach the first of its kind. This thesis presents the design, development, and experimental validation of a variable-stiffness, heart-inspired, pulsatile pump. We begin by designing a custom variable stiffness mechanism, specifically developed for seamless implementation within robotic artefacts that require adaptable mechanical properties. Building upon this, we engineer a pulsatile pump inspired by the heart’s dynamic pumping strategy, integrating the variable stiffness mechanism to actively modulate system compliance. The resulting device is experimentally tested, revealing how its flow patterns evolve as the pump approaches resonance. Characteristic features emerge in the pressure–flow rate relationship, including amplitude magnification and phase shifts, which collectively identify regions of maximum operational efficiency. Crucially, we demonstrate that the introduction of variable stiffness can enable the pump to transition smoothly across a range of pulsation frequencies while persistently maintaining peak performance. To our knowledge, this represents the first demonstration of a heart-inspired pumping system with the potential to sustain optimal efficiency across variable operating conditions through active stiffness modulation. In summary, this thesis proposes and validates a novel approach to harnessing mechanical resonance in pulsatile pumping through stiffness modulation. This new technology lays the groundwork for advanced soft robotics actuation systems and, crucially, for the development of next-generation cardiac implants. By enabling a mode of operation more closely aligned with the physiological dynamics of the human heart, while offering enhanced performance and persistent autonomy, this approach addresses some of the most critical challenges in the treatment of cardiac diseases. Moreover, by combining higher operational efficiency with a nature-inspired pulsatile pumping strategy, it promises to enhance biocompatibility and extend device longevity, overcoming longstanding limitations of both commercial and state-of-the-art cardiac assist systems and advancing the design of durable, adaptive, and physiologically harmonious cardiovascular therapies.
Implementation of angular diversity receiver for VLC-IoT sensor networks
(2026-06-01) Harada, Ryo; Popoola, Wasiu; Yang, Yunjie; Acquisition, Technology and Logistics Agency (ATLA), Ministry of Defence (MOD), Japan
The demand for wireless spectrum is increasing, leading to radio frequency (RF) congestion. As wireless technologies advance and applications such as smart cars, e-health, smart grids, and the Internet of Things (IoT) proliferate, the problem intensifies. Visible light communication (VLC) systems are suggested as a solution, offering a large unlicensed spectrum ideal for radiosensitive environments such as hospitals and aircrafts. However, a significant challenge for VLC implementation is achieving wide communication coverage due to a limited field of view (FOV). This thesis aims to explore and develop methods to enhance communication coverage in VLC-based IoT (VLC-IoT) systems. The thesis first analyses the performance of angular diversity receiver (ADR) configurations in indoor multi-cell VLC scenarios, focussing on square pyramid (SP), square frustum (SF), hexagonal pyramid (HP), and hexagonal frustum (HF) shapes. Through numerical and simulation analysis, performance is assessed using spatial multiplexing (SMP) and receive diversity techniques, including selection combining (SC), equal gain combining (EGC), and maximum ratio combining (MRC). The results from SMP applications indicate that the HF ADR provides the widest coverage for multi-stream transmission due to its largest number of photodiodes (PDs). However, for receive diversity, the HP and HF configurations with six sides PDs do not outperform the SP and SF types with four PDs, one on each side in terms of bit error rates (BERs) performance when using SC. Subsequently, this thesis analyses the performance of ADR systems in single-cell VLC scenario and proposes a novel ADR system in IoT sensor networks. The numerical analysis applying the combining techniques indicates that any combination of ADR types and diversity techniques can enhance performance. Therefore, a SF ADR is implemented with the EGC due to the low complexity. The proposed ADR system enhanced received signal-to-noise ratio (SNR), improved BERs, and provided more than double the coverage of the link. Furthermore, the effectiveness of the system is demonstrated with real-time sensor transmission and a duplex VLC communication link, showcasing its advantages in practical IoT applications. Following that, the integrated VLC and RF (VLC-RF) system using the ADR for secure industrial IoT applications is presented. The prototype with the custom-built ADR and analogue front end (AFE) is connected to the backbone network such as a wireless cloud server. As the fundamental VLC performance, SNR, secrecy capacity (SeCap) and BER coverage is measured. The result indicates that the prototype has better physical layer security (PLS) performance than the single PD receiver, and the coverage of the link is drastically expanded compared to the initial design. Furthermore, to evaluate the feasibility of the IoT application, real-time sensor network applications are demonstrated using the proposed integrated VLC-RF ADR system. These experiments, including real-time sensor transmission, image transmission, and integration of the robot arm system, indicate the benefits in a practical scenario by showing low latency. Finally, the wavelength division multiplexing (WDM) based VLC prototype using the colour PDs is implemented. This is an additional experimental study to show the method for ADR based multiplexing system. The BERs performance of three different wavelength channels (red, green, blue) is shown in comparison with the single PD receiver. The result shows that WDM can be possible using the colour PD and the ADR WDM system enhances SNR and communication range.
Evaluation of thermal ratings and loading limits of power system components and joint circuits
(2026-06-01) Duan, Chengyan; Djokic, Sasa; Harrison, Gareth; Judge, Paul
Met Office has reported that the top 10 warmest years in the UK from 1884 have occurred since 2002, clearly indicating an emerging pattern of higher temperatures due to climate change. These high temperatures (“heatwaves”) have drawn increased attention to the impact of climate change on the thermal ratings and loading limits of power system components and joint circuits in which these components operate. Thermal rating of a given component is based on the component’s maximum allowed design/operational temperature, typically representing its maximum loading capacity, which, however, changes with both ambient/weather conditions and operating conditions. Violating or exceeding component’s maximum temperature limit can, and usually will, result in a number of negative consequences, including, but not limited to: accelerated ageing, reduced safety clearances and degradation of electrical insulation, which in turn can cause equipment failures, fires and electric shocks, leading not only to the possible permanent damage of the component, but also to potentially wider power system blackouts. When two or more power system components operate in a joint circuit, as is usually the case, thermal ratings and loading limits of the joint circuit are generally determined by the component in the circuit which has the lowest maximum loading capacity for given ambient and operating conditions for the considered period of interest. As the ambient and operating conditions change, the specific component with the lowest maximum loading capacity in the joint circuit may also change, which further complicates accurate evaluation of circuit and system loading capacities. In order to more accurately evaluate thermal ratings and loading limits of power system components, this PhD research applies thermal modelling, based on the physical models and characteristics of the modelled components at 400kV to 132kV levels (Scotland high-voltage transmission level). Thermal ratings were calculated and assessed using the developed thermal models and considering different operating and ambient conditions, as well as time periods, for the three main power system components: oil-immersed power transformers, cables, and overhead lines. Cables are further divided into directly buried cables, cables in filled troughs, and cables exposed in the air. Thermal modelling processes and thermal-electrical models are formulated for unified ambient and operational conditions, allowing for the evaluation of: static thermal rating, based on and calculated from the assumed constant (seasonal or monthly) ambient conditions; dynamic thermal rating, calculated for actual ambient conditions; short-term and medium-term overloading rating, calculated for a set of given ambient conditions, pre-fault loading levels and specific durations; cyclic thermal rating, calculated for the given ambient condition, but considering daily cyclic variations of loading profile, with periods of high and low loading conditions, and, finally, exceedance level based ratings, calculated by acknowledging acceptable risk levels for component’s operational temperature exceeding its maximum temperature limit (the exceedance ratings directly apply only to overhead lines). A detailed review of existing standards and literature identified several limitations in current models. These include incomplete treatment of transformer losses that depend on winding temperature and tap position, simplified representation of cooling-mode transitions between oil-natural air-natural and oil-forced air-forced, and limited inclusion of weather effects such as wind speed and solar irradiance. To address these gaps, the transformer model was enhanced to include temperature- and voltage-dependent losses, cooling-mode transitions, exposure differences between tank and cooling plant, tertiary windings, and effective cooling areas. Cable models were extended to cover directly buried, filled-trough, and air-exposed configurations, with explicit consideration of solar irradiance and wind speed effects. In terms of the improvements of existing models and development of new models: The inconsistencies and gaps described previously are all being addressed accordingly. The previously developed cable thermal model for directly buried cables and cables in conduits is now extended to include cables in filled troughs. Thermal models for the cables exposed to air and solar irradiance are developed, also enabling the consideration of wind speed. Finally, there is currently no comprehensive approach in existing literature for modelling and evaluating the thermal ratings of joint circuits, while only some guidance is provided for selecting and coordinating ratings for joint circuits with multiple components. However, such guidance is very simple in order to meet the ease-of-use requirements. Building on the improved component-level models, a new methodology was developed to evaluate the thermal ratings of joint circuits that contain combinations of the mentioned multiple power network components. This method couples the steady-state and transient thermal behaviour of each component under common weather and loading conditions, identifying the limiting element at each time step. Using simulation-based analysis, the presented approach determines time-varying static thermal rating, dynamic thermal rating, cyclic thermal rating, short-term and medium-term overloading rating, and exceedance level-based ratings at the circuit level, and identifies when the circuit thermal loading limit shifts between components for different ambient operating conditions, including heatwave scenarios. This thesis develops and refines methodologies for accurately evaluating the thermal ratings and loading limits of transformers, cables, and overhead lines under changing climatic conditions. This thesis improves existing thermal models by including weather-dependent and operational factors, such as wind speed, solar irradiance, tap position, cooling-mode transitions, etc., and extending these methods to joint circuits. The work enables a consistent and realistic assessment of circuit/system capability across varying ambient scenarios. The results provide power system operators and planners with a reliable means to quantify the impact of climate change and heatwave events on the network performance, identify thermally constrained assets, and inform asset reinforcement.
Modeling and applications of discrete-time Hawkes processes: flexible and scalable methods
(The University of Edinburgh, 2026-06-01) Brisley, Trinnhallen; Ross, Gordon; Paulin, Daniel
Many count time series show short-term clustering: after one event, more tend to follow soon after. This thesis develops fast and flexible methods for modelling such self-exciting behaviour in data observed on a regular time grid using discrete-time Hawkes models. Our contributions are twofold: first, we derive linear-time algorithms for the log-likelihood and its gradient, which enable efficient estimation for long multivariate sequences. We also build a marked, multivariate model for operational risk in a forensic psychiatric hospital, with an alarm mark for rare severe incidents that prompt a hospital-wide response; in that setting the model improves prediction and yields management-relevant risk signals. Second, we propose the Gaussian Process Discrete Hawkes Process (GP-DHP), a Bayesian nonparametric model that places independent Gaussian process priors on the baseline intensity and the excitation kernel. A collapsed representation over the latent additive intensity supports scalable maximum a posteriori estimation with complexity proportional to the number of observations, and a post hoc decomposition recovers smooth, data-adaptive baseline and excitation functions that separate exogenous background from endogenous feedback. We evaluate the methods on synthetic data and on two applications: weekly Cryptosporidiosis counts and U.S. terrorism incidents. Across these studies GP-DHP outperforms parametric discrete Hawkes baselines in predictive accuracy while revealing a flexible excitation function and seasonal structure. The overall result is a practical toolkit for discrete-time self-excitation that is both scalable and interpretable.
Program lifting for acceleration
(The University of Edinburgh, 2026-06-01) De Souza Magalhães, José Wesley; O'Boyle, Michael; Polgreen, Elizabeth
The fast evolution of computer architectures brings the promise of increased performance. To leverage these advances and achieve high-performance, leg- acy code must be ported to new hardware. However, emerging hardware is increasingly complex and specialized, making the task of porting code highly challenging. Compilers must have a solid knowledge of the target architecture to generate efficient code, and developing such compilers for each new device is prohibitively costly in a scenario of rapid and constant change. New hardware is often programmed by specific interfaces or higher-level domain-specific languages (DSLs). DSLs embed knowledge about the applic- ation’s domain which is crucial for optimization. Hence, automatic translation or lifting of existing programs to hardware-oriented languages can bridge the gap between legacy implementations and unseen architectures and improve code portability. This thesis presents new solutions to automatically porting existing code to new architectures with Program Lifting: the translation of general-purpose code to higher-level application programming interfaces (APIs) or DSLs. It presents lifting techniques in the context of dense and sparse linear/tensor algebra, the fundamental blocks of many modern workloads, such as data science and ma- chine learning. This thesis shows that program lifting facilitates portability of code, enabling enormous performance gains on specialized hardware.