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Algal biomass to hydrogen: optimising carbon negative hydrogen production from the supercritical water gasification of microalgae
No full textSupercritical water gasification (SCWG) of microalgae is a potentially viable alternative for hydrogen production that can simultaneously remove carbon from the atmosphere, without the environmental challenges associated with other biomass processes. However, due to the high costs of algal production, achieving these environmental benefits requires limiting the feedstock requirement. The work herein addresses this by optimising the hydrogen yield, while ensuring that significant carbon capture is achieved from the SCWG of the microalga Chlorella vulgaris.
A continuous SCWG rig was designed, constructed, commissioned and utilised to investigate the influence of operating conditions, catalysts and oxidant to find the optimal values. An initiative of using the algal growth water as the reaction media was adopted, as industrial applications would utilise this as the reaction medium in practice. A significant difference was observed upon using growth water compared to distilled water. Most notable was the decrease in carbon monoxide and increase in hydrogen produced, which was attributed to the elevated pH. Consequently, the algal growth water was utilised as reaction medium in subsequent experiments in this work.
To maximise the hydrogen production, it is important to find the ideal and cost-effective catalyst. Some literature outlined FeCl3 as potentially the most effective catalyst for achieving high hydrogen yields, yet further literature investigating this was scarce. Hence, this work investigates FeCl3 as a potential catalyst for the SCWG of Chlorella vulgaris, for a range of temperatures (400 - 600°C) and biomass concentrations (1 – 3wt.%). A significant decrease in hydrogen yield, energy efficiency and the amount of the feedstock carbon that is converted to gas was observed. This was attributed to the reduced pH caused by the Lewis acid activity of FeCl3 which suppressed the water gas shift reaction and increased polymerisation reactions. Accordingly, FeCl3 was deemed an unsuitable catalyst. The more established catalysts of potassium hydroxide (KOH) and ruthenium (Ru/C) were
found to be effective and were therefore used for subsequent work in this thesis.
An in-depth study of the influence of temperature (400 - 600°C), biomass concentration (1 - 3wt.%), KOH concentration (0 – 1wt.%), Ru/C catalyst (present or not present) and oxidant (oxidant coefficient 0 - 0.5), including any interactions, was completed. High temperatures, low biomass concentrations, high KOH concentrations and Ru/C catalyst were all found to be favourable for high hydrogen yields. Oxidant enhanced hydrogen yields up to 20% of the stoichiometric concentration for complete oxidation, after which hydrogen was oxidised causing a reduction in hydrogen product yield. Additionally, several significant interactive effects were observed between the catalysts and operating conditions. Hence, in the reaction alone, the greatest hydrogen yield was predicted to be23 mg/g at 1wt.% biomass, 600°C, 1wt.% KOH, Ru/C and an oxidant coefficient of 0.2.
A whole system model was developed in ASPEN plus ®, which incorporated the experimental work performed as part of this research, to find the true optimum conditions when system losses are considered. The use of experimental data to program the reactor in this model revealed significant deviations from equilibrium reactor models used in literature, which emphasises the importance of incorporation of experimental data in SCWG system analysis. The model of the whole system showed that, as with the reaction alone, higher temperatures and the presence of Ru/C favoured hydrogen yield and efficiency. Oxidant coefficient also showed a similar trend however, greater concentration of oxidant was preferred in the model, due to a larger reaction enthalpy. Higher heating requirements and pumping power required at lower biomass concentrations and poor reaction performance at higher biomass concentrations meant that a moderate 2wt.% was the optimal concentration. Also, KOH was found to be most effective at minimum or maximum concentration ( 0
or 1wt.%), which differed from the reaction alone. As a result, the optimum hydrogen yield predicted was 12.7mg/g at 2wt% biomass, 600°C, 1wt.% KOH, Ru/C and an oxidant coefficient of 0.3. At these conditions, 68% of the feedstock carbon was captured as CO2 (38%) or biochar (30%), making the process significantly carbon negative at those conditions
Gravitational wave modelling and analysis for binary Neutron Star inspirals
No full textThe detection of gravitational waves has revolutionised our understanding of the universe by providing direct insights into some of its most extreme phenomena. In particular, observations of gravitational waves from binary neutron star inspirals provide a unique opportunity to probe ultra-dense matter by placing constraints on the still-unknown neutron star equation of state. This information is encoded
within the tidal interactions between the neutron stars, which influence the merger dynamics, and imprint tidal information on the phase of the emitted gravitational waves. With dramatic increases in detector sensitivity anticipated, measurement accuracy will increase and currently undetectable features of the late inspiral and merger will be unveiled. To prepare for this, it is essential to: (i) quantify the tidal
measurements that can be expected from future detectors (ii) develop accurate, efficient and flexible tidal waveform models and (iii) assess the impact of assumptions on the resulting measurements. These are the key aims of this thesis. Firstly, we investigate the prospects of measuring higher order resonant tides with third generation detectors. Secondly, we develop a tidal waveform model for binary neutron star systems which provides efficiency whilst making minimal assumptions on nuclear matter. Finally we assess the validity of approximate equation of state
independent relations within gravitational wave analysis in the context of exotic matter
First observation of the rare decay at the NA62 experiment
No full textThe first observation of the rare decay using data collected by the NA62 Experiment in 2017 and 2018 is presented in this thesis. The branching ratio is measured using the process as a normalisation channel. The number of observed data candidates is 1832, with a background contamination of 168 ± 9. The analysis yields , including a complete treatment of relevant systematic effects.
The complete software package for the ANTI-0 detector, added to the NA62 setup in 2021, was developed by the author within the NA62 software framework and is described in detail. The software tools allowing for short and long-term verification of ANTI-0 data quality are presented, with their output used to summarise the commissioning and performance of the detector in the 2021, 2022 and 2023 NA62 datataking campaigns
Innovative methods of documenting memory evidence from victim-survivors of gender-based violence – a case study in Kenya
Full text linkAbstract not available
Preparation, characterisation and application of single and multilayer mixed-matrix membranes
No full textSingle layer and multilayer Nafion membranes incorporated with graphene oxide (GO) were investigated for application in polymer electrolyte fuel cells operating at intermediate temperatures (IT-PEFCs). The intermediate temperature regime has been utilised as a method to improve the power density output of fuel cells used in transport applications and graphene oxide was identified as the filler of choice due to its oxygen containing functional groups.
An experimental approach was taken, with membranes prepared with a variety of parameters such as graphene oxide weight loading, number of membrane layers, and membrane thickness. A variety of characterisation techniques were utilised to confirm successful incorporation of graphene oxide within the membrane, and subsequent samples were tested in a fuel cell at elevated temperatures.
Introducing graphene oxide suppressed the hydrogen crossover current density experienced during fuel cell operation in comparison to the reference Nafion sample. The multilayer membranes had even more pronounced hydrogen crossover barrier properties because of their three individual layers. Additionally, decreasing the membrane thickness led to improved fuel cell performance. The use of a Nafion/cerium oxide composite layer was found to maintain hydrogen crossover levels under 10 mA cm-2 for over a week at 100°C during accelerated stress tests (AST).
However, some challenges in producing multilayer membranes pertained due to frequent interruption of the interfaces of the separate layers, which was further emphasised when fabricating thinner membranes. The development of thinner membranes, the improvement of interlayer contact, and the optimisation of cerium oxide fillers are topics that should be further explored in future work
Investigating cybercrime amongst female students in Saudi Arabia and identifying how social work can respond to the challenges
No full textExisting literature has suggested that there is a need for Saudi Arabia’s social work sector to address cybercrime against women as an emerging social issue. Cybercrime has been steadily rising in Saudi Arabia, and studies have shown that young women are more likely to be the victims. There are, however, this study is the first qualitative study that explore the issue of cybercrime in Saudi Arabia from the perspective of both social workers and the people that they support.
This study therefore offers a contribution to the existing literature by critically investigating the role social workers in the university context play, in supporting female students with cybercrime. The research used an interpretative qualitative approach, conducting 30 semi- structured interviews with 15 female social worker participants, and 15 female student participants. The results of the study found that cybercrime against young women was very common, yet few of the students had sought out the help of social workers. The research identified that one of the most significant barriers to young female students seeking out the help of social workers in cybercrime related issues, was a fear of shame or familial punishment. The study also explored how the nature of social work in Saudi Arabia is shaped by the culture and origins for the country This has implications for both young women encountering cybercrime and highlights limitations of ethical and effective social work practice as it is experienced in Saudi
Arabia at present. The study also sought to explore how these findings could be applied to wider Saudi Arabian society, particularly in relation to the topic of female agency and gender norms in Saudi Arabia. and how this information could be used to improve and solidify the social work profession in Saudi Arabia
In search of the imaginary beams: how pupils with complex communication differences and/or autism diagnoses can be enabled to reflect on their experiences of school using individualised transactional support methods.
Full text linkThis ethnographic study, underpinned by the theory of intersubjectivity, was conducted in Southwest England and explored how to elicit the views of four primary-aged pupils with complex communication differences and/or autism diagnoses on their experience of their mainstream school.
A flexible, multi-method approach was employed and included the use of observation, field notes, semi-structured interviews and informal chatting. Transactional support methods were developed for and with the pupil participants to enable them to share their views in their interviews and play sessions. The elicitation methods used were Lego play and role play set within the context of the participants’ special interests, as well as bespoke visual supports.
Data was analysed using Interpretative Phenomenological Analysis and this produced themes at an individual level, as well as across cases. Four superordinate themes emerged at group level based on participants’ experiences of their school which revealed a communication gap between the participants and their teachers; the need for clearer learning structures within the classroom; improved autism training for school staff; and a lack of engagement with peers by participants.
Findings also highlighted that more individualised transactional support methods were required across all participants. As there has been limited research in this area, this study’s findings call for more research on how to co-develop elicitation methods with individual autistic participants, as research projects unfold, to ensure their voices are at the centre of research. Implications for practice include the need for education professionals to better understand autism and dedicate time to creating spaces for autistic pupils to be able to express their lived experiences through creative methods that they choose and can develop with or without support
Doppler beam sharpening for sub-THz marine radar imagery and small target detection
Full text linkThis thesis studies the use of Doppler Beam Sharpening (DBS) as a method of obtaining high resolution sub-THz radar imagery in the maritime environment for the purposes of detecting small, extended targets. The application of DBS in the maritime environment from a small vessel with radars at Sub-THz frequencies is a novel concept. The aim is to develop a radar system that enables radar measurements in the DBS modality, where the complete dataset enables automatic DBS processing for high resolution image production. This thesis presents the DBS technique from basic radar principles and discusses the limitations of using it in the context of maritime radar data. A simulation strategy was devised using Ansys’ HFSS software, which was used to simulate the scattering off target models, including models of the ocean.
The simulated data was then processed to understand DBS on a deeper level, where the limitations and optimisations of processing are discussed. A 150 GHz FMCW radar was upgraded by installing a new Direct Digital Synthesiser (DDS) and local oscillator to make it
suitable for DBS measurements. The radar was then integrated into a novel sensing system which provides all the required time-synchronised data for DBS processing, including kinematics and optical ground truth. Alongside this work, a review of potential anomaly detection techniques is discussed in the context of sub-THz radar, which will form the next stage of the research on this topic
Robotic disassembly of a permanent magnet DC brushless motor
Full text linkGlobally, the transition to electric vehicles (EVs) is accelerating. As these EVs reach the end of their service life, large quantities of valuable components, including electric motors, need to be remanufactured to achieve a more sustainable circular economy. Disassembly, the first step in the remanufacturing process, typically requires human intervention due to difficulties in automating it. This thesis investigates the robotic disassembly of a permanent magnet DC brushless motor. Six typical tasks are defined in motor disassembly, and four of them are studied, including the ‘Press-in’ task, ‘Press-on’ task, Unplugging task and Coil disassembly task.
Related to methodology, an analytical model implementing the magnetomotive force method was developed to calculate disassembly forces when removing a rotor with permanent magnets from a stator. This model provides reasonable accuracy in a very short calculation time without requiring high-performance computers compared with the finite element method. The average error rates of the FE method and MMF method are 16.7% and 26.3 %, respectively. By determining the material magnetic hysteresis, the improved analytical model predicts the force optimal positions, adapting to different cases of magnetic fields on the rotor with permanent magnets. Additionally, potential robotic solutions for the press-fit component disassembly tasks and the Coil disassembly task were investigated and experimentally validated.
A robotic cell, including two collaborative robots, a set of tools and two devices for disassembling press-fit components, is designed to fully automate the disassembly process. The disassembly quality in the robotic process is superior to that in the manual process, preventing unnecessary damage to the components. The time of the robotic process is 886 s at full capacity, which is 56.93% faster than that of the manual process (1390 s).
Robotic disassembly offers significant potential for advancing the circular economy in EV remanufacturing. However, although robotic automation improves disassembly efficiency and sustainability, it faces economic barriers due to high equipment costs. Future research should focus on cost-reduction strategies, expanding task automation, and hybrid approaches that combine robots and humans
‘God, you can’t teach sex education in a Catholic school’: Exploring the lived experiences of statutory Relationships and Sex Education for young women in English Catholic schools from a feminist perspective.
Full text linkLike all English secondary schools, faith schools have been required to adhere to the statutory RSE guidance since 2021. However, the guidance includes the stipulation that faith schools are permitted to deliver mandatory content from a ‘distinctive faith perspective’ (Department for Education, 2019a). Historically, sex education in England has been shown to uphold potentially harmful discourses of gender and sexuality, which in turn, shape societal understandings and experiences of girlhood. The delivery of statutory RSE from distinct faith perspectives sees secular sex education narratives intersecting with theological sexual values, the impact of which on young women is yet to be explored. The Catholic Church has historically upheld stringent sexual ethics which prohibit same-sex relationships, contraception, and pre-marital sex, and has in recent years explicitly contested progressive sex education agendas (Congregation for Catholic Education, 2019). In turn, the ability of Catholic schools to deliver RSE that adequately meets and reflects the needs of young women in relation to sexuality and relationships emerges as a pertinent question.
This thesis employs a feminist, qualitative methodology to explore the lived experiences of young women (n=11) and their teachers (n=3) in relation to statutory RSE provision across two Catholic secondary schools in England. This research employed semi-structured focus groups and interviews, combined with Interpretative Phenomenological Analysis to yield rich insight into the implementation and impact of Catholic RSE. Findings demonstrated that the teachers’ experiences of intersecting Catholic values with statutory requirements were shaped by their broader lived experiences and identity in relation to faith, sexuality and relationships, and teaching. The young women reported facing complex socio-sexual landscapes, yet their needs and lived-experiences were seldom addressed adequately within RSE provision. Across both schools, the participants reported often feeling disengaged, alienated and frustrated with RSE content. Issues in RSE engagement were not solely tied to the Catholic lens adopted in both schools, however, the teaching of Catholic sexual ethics was seen to compound failings in content relevance and attainability
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