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An investigation into mass and volume reductions on Hydrogen-Electric Aircraft Propulsion Systems using biased magnetics in an interleaved DC-DC Buck Converter topology
Get PDFHydrogen-electric aircraft offer the potential to support reductions in CO2, NOX and noise emissions, from the aviation sector. However, integrating fuel cells and batteries into aircraft propulsion systems introduces the requirement for additional onboard power electronic converters. Power electronic converters utilise semi-conductor switching devices, and energy storage components, such as capacitors and inductors. Currently, these passive components account for approximately 50% of the converter's packaged volume. Reducing their mass or increasing power density could lead to overall aircraft mass reduction and package size reduction; providing a compelling incentive to investigate techniques for improvement.
This research includes two primary objectives. The first objective was to develop a novel hydrogen-electric aircraft simulation tool, capable of optimising propulsion system parameters for a selected measure of merit. The tool, designed for preliminary or conceptual commuter aircraft specifications, enables hybridisation of power inputs for a mission analysis and trade studies. Specifically, it assesses the impact of different power converter technologies and drag polar models on overall aircraft mass. Results indicate that a simplified drag polar model led to an overestimation of aircraft mass by approximately 6.6%, when using baseline converter technologies. Additionally, increasing the converter technology level showed diminishing returns in mass reduction, but still achieved a 1.6% decrease in aircraft mass when baseline technologies were doubled. Furthermore, in-flight battery recharging resulted in a 0.89% increase in total aircraft mass.
The second objective focused on enhancing the performance of magnetic components within an interleaved buck converter topology. A novel approach was investigated, leveraging permanent magnets to provide simultaneous DC biasing for a pair of AMCC-100 inductor cores, and placing them into an interleaved converter. Experimental testing, using the University of Nottingham's Galvano Electrochemical Impedance Spectroscopy (GEIS) test equipment, demonstrated significant improvement in current handling capabilities, before saturation, ranging from 87% to 125%, depending on magnet quantity. The complete magnetic arrangement was subsequently validated through experimental implementation in an interleaved buck converter rig, confirming the positive impact of biased magnetics on converter performance.
Overall, this study contributes to the advancement of hydrogen-electric aircraft propulsion systems, by introducing a simulation framework for investigating aircraft mass and propulsion system configuration, and demonstrating novel technique to improve the power density of power electronic converters
The impact of lifestyle factors, dietary energy restriction and religious fasting on body composition, gastrointestinal hormones and markers of health
Get PDFBackground
Intermittent fasting and dietary interventions to bring about weight-loss have received considerable attention for their potential metabolic health benefits. However, gaps still exist in understanding their effects on appetite regulation, body composition changes across different age groups, and the methodological challenges in assessing these outcomes. This thesis aimed to: 1. undertake a systematic review to examine the effect of Ramadan intermittent fasting on appetite-regulating hormones in healthy individuals (CHAPTER 3); 2. investigate relationships between lean body mass, physical activity, age, and body composition in overweight individuals with pre-diabetes (CHAPTER 4); 3. explore the impact of lifestyle factors and eating behaviours on body composition changes following an 8-week low-energy diet intervention (CHAPTER 5), and 4. validate commonly used assessment tools for dietary protein intake, body composition, and physical activity against their respective reference standards (CHAPTER 6).
Methods
1. A systematic review and meta-analysis examined 16 studies (n=664 participants) to investigate the effects of Ramadan intermittent fasting on circulating leptin, ghrelin, insulin, gastrin, glucagon-like peptide-1, peptide YY, and cholecystokinin concentrations. 2. A secondary analysis of cross-sectional data from 220 overweight and obese individuals with pre-diabetes (aged 25-70 years) from the Prevention of diabetes through lifestyle Intervention and population studies in Europe and around the World (PREVIEW) diabetes risk study to explore relationships between body mass, regional body composition (measured by Dual Energy X-Ray Absorptiometry; DXA), age and physical activity (assessed using accelerometry). 3. A secondary analysis of anthropometric, metabolic, and behavioural outcomes (including eating behaviours measured through validated questionnaires) from 221 participants (91 males, 130 females) from the PREVIEW cohort, collected before and after an 8-week low-energy diet intervention (810 kcal/day). 4. Dietary protein intake, assessed via 24-hour urinary nitrogen excretion, was compared with self-reported dietary records (n=264); body composition via bioelectrical impedance was compared with data from DXA scans (n=37), and physical activity estimation via the Baecke questionnaire was compared with accelerometry-derived time spent in sedentary and moderate/vigorous activity (MVPA).
Results
1. Ramadan intermittent fasting increased blood ghrelin concentration (3 studies; standardised mean difference (SMD) = 0.31 pg/mL, 95% CI: 0.03 to 0.60), but had no effect on leptin (12 studies; SMD = −0.11 μg/mL, 95% CI: −0.36 to 0.14), insulin (6 studies; SMD = −0.24 μU/mL, 95% CI: −0.54 to 0.02), or gastrin concentrations (3 studies; SMD = 0.23 pg/mL, 95% CI: −0.71 to 0.99), with high heterogeneity observed across leptin studies, suggesting varied individual responses. 2. In individuals with pre-diabetes, lean body mass and leg lean mass decreased with increasing age category in females, with males having greater lean leg mass compared with females across all age groups. Leg lean mass was positively associated with body weight, with physical activity only modifying this relationship in females, though in all participants, no association between leg lean mass and physical activity was observed. 3. The low-energy diet brought about substantial weight loss (median -11.3 kg) in participants, with males experiencing greater reductions in weight, lean mass (-4.5 vs -2.5 kg), and fat mass (-8.8 vs -7.3 kg) compared with females. Higher baseline dietary restraint scores were associated with greater weight loss success (R=0.276, P<0.001), while higher disinhibition predicted poorer outcomes (R=-0.173, P<0.05), with these behavioural influences differing between sexes. Baseline physical activity levels did not influence lean mass preservation or fat mass loss during the period of weight-loss. 4. The 8-week LED intervention resulted in improvements in metabolic parameters, including reduced fasting glucose, insulin, triglycerides, and C-peptide concentrations. Sex-specific responses were observed, with males showing greater reductions in fasting insulin (-25.7 pmol/L difference, P<0.001), C-peptide (-211 pmol/L difference, P<0.001), and triglycerides (-0.210 mmol/L difference, P<0.001) compared with females. Males also demonstrated larger improvements in insulin sensitivity indices (HOMA-IR and QUICKI) than females. 5. Validation studies revealed systematic differences between assessment methods: self-reported dietary protein intake differed from biomarker-derived estimates, with proportional bias between measures emerging during a weight maintenance intervention phase (overall R=0.394, P<0.001). Body composition assessed by BIA and DXA showed strong agreement between measurements (percentage body fat R=0.853, fat mass R=0.896, and fat-free mass R=0.841) supporting BIA as a practical alternative to DXA. Physical activity assessments demonstrated modest correlations between subjective and objective measures (R=0.320 for MVPA) reflecting the different aspects of physical activity being assessed by each tool.
Conclusion
Increased circulating ghrelin, reported during Ramadan fasting, may drive a stimulation of appetite.
Cross-sectional analysis revealed age-related differences in lean mass, with lower lean mass observed among older participants, particularly females. This pattern underscores the importance of women maintaining physical activity as they age to preserve muscle mass. The low-energy diet intervention demonstrated efficacy in reducing body weight and improving metabolic health, with notable sex-specific responses in insulin sensitivity and lipid metabolism, alongside baseline eating behaviours serving as important predictors of weight loss success. The method validation studies provided methodological insights for future research in nutritional epidemiology and clinical practice
Houseflies (Musca domestica) as potential vectors for the spread of ESBL-producing E.coli in humans
Get PDFAntimicrobial resistance (AMR) has emerged as a critical global health challenge, with the spread of Extended-Spectrum Beta-Lactamase (ESBL)-producing Escherichia coli being a major concern, particularly in urinary tract infections (UTIs). This research investigates the role of the common housefly (Musca domestica L.) as a vector for transmitting ESBL- producing E. coli from bovine farms and open markets to human environments. The flies collected were not identified to species level, however the housefly (Musca domestica) is considered the most widespread fly species in Malta and is reported to be one of the most abundant and widely distributed in the Maltese Islands. All collected specimens shared similar morphological characteristics and were considered to belong to a single species. Therefore they are referred to in this study as Musca domestica. Through a multidisciplinary approach—integrating field sampling, phenotypic and genotypic analysis, and whole-genome sequencing (WGS), the study explores the prevalence, resistance patterns, and genetic similarity of E. coli strains isolated from flies and UTI patients.
A total of 177 fly traps and 90 fresh manure samples were collected across Malta and Gozo between 2018 and 2021. Simultaneously, 70 UTI-related ESBL-E. coli strains were obtained from clinical samples. Selective culture using TBX agar supplemented with cefotaxime, disc diffusion-based Antimicrobial Susceptibility Testing (AST). The results summarized in Table 4.1, show that a significant number of manure samples harboured CTX-M E. coli isolates. Similarly in Table 4.2, houseflies collected from farms and open markets were analysed for the presence of CTX-M type. PCR screening revealed that 42 % of fly samples carried ESBL-producing E. coli, with 47 % of these harbouring the blaCTX-M resistance gene. Among the UTI isolates, 79 % carried the same gene. WGS identified the blaCTX-M-15 variant as dominant in both environmental and clinical isolates, often carried on IncF-type plasmids and mobilized by the insertion sequence ISEcp1. Crucially, both fly and UTI strains shared virulence genes associated with ExPEC and UPEC lineages, suggesting a strong potential for zoonotic transmission.
The findings underscore the significance of M. domestica as a vector not just for general pathogens but specifically for antimicrobial-resistant, clinically relevant strains of E. coli. The overlap in AMR gene profiles and virulence factors between fly-derived and clinical strains strengthens the hypothesis that flies may serve as a critical link in the environmental-human transmission chain of ESBL-producing E. coli, although they cannot be considered the sole potential carriers. This highlights an urgent need for improved hygiene practices, integrated surveillance across agricultural and healthcare sectors, and further research into environmental pathways of AMR transmission
When a hundred flowers blossom: (re)assembling the Chinese orchestra in contemporary Malaysia as a cultural ecosystem
Get PDFThe Chinese orchestra in Malaysia is a significant cultural emblem that represents the Malaysian Chinese identity, yet it remains understudied and widely misunderstood, generally construed through antiquated historical and descriptive perspectives that decontextualizes its existing struggles and adaptiveness to contemporaneity. Cultural ecology concepts from Titon (2020) and ecological metaphors from Deleuze and Guattari (1987) are adopted to frame the Malaysian Chinese orchestra as a complex and interdependent cultural ecosystem that is resilient and adaptable to environmental changes. Mainly, this study refreshes the perspectives of current and new audiences of the Chinese orchestra in Malaysia through a reassembling of its dynamics, constructs, and operations in the 2020s. Research methodology consists of experimentation and expert interviews, supported by the author’s own autoethnographic observations as a cultural insider. The gaoyin ruan modification experiment aims to enhance its musical versatility, and Experiment Ensembles are conducted to study organization, performativity, space, resilience, and musical hybridity. Collected data are coded and visualized for a balanced quantitative and qualitative analysis. A theoretical network is used to map opportunities and challenges through rhizomatic writing, along topics of spaces, performativity, identity, multiculturalism, musical hybridity, digitalization, and cultural sustainability. Findings reveal the Chinese orchestra’s roles and values in the search for a Malaysian Chinese identity in a multicultural country, while examining its resilience and adaptive management plans towards disruptions and socio-cultural shifts. There are conscious and subconscious efforts towards sustainability for both the cultural ecosystem and the natural environment. Cross-cultural and cross-disciplinary collaborations are budding to advance the value of huayue in creative practices and musical hybridity, fostering interculturalism. Finally, the proposed Cultural Sustainability Web is a model to outline sustainable future trajectories for traditional cultures and provide strategies for social cohesion, that can generate a long-term impact on the Malaysian Chinese orchestra cultural ecosystem
Transcriptome, physiological and biochemical analyses of the systemic resistance of banana (Musa acuminata cv. Berangan) induced by plant-growth-promoting rhizobacterium against blood disease bacterium
No full textBananas and plantains are the global top produced fruit with a total 135 million tonnes of production in 2022. Banana blood disease (BBD) is a deadly bacterial wilt disease in banana and caused by Ralstonia syzygii subsp. celebesensis (Rsc), also known as blood disease bacterium (BDB). BDB results in wilting appearance, brownish-red discoloration of internal vascular tissues, and eventually entire crop loss including ready-harvested fruit bunch. Despite being the third highest valued fruit crop in Malaysia, prevalence of banana blood disease has been part of the factor in impacting banana’s production since 2007 and its relapse draws attention to the need of effective long-term management strategy. Using biological control agent (BCA) such as plant-growth-promoting rhizobacterium (PGPR) has emerged as the preferred approach due to its environment friendly and sustainable properties. Therefore, understanding the pathogenesis of BDB supports the study on the applicability of PGPR to induce systemic resistance (ISR) in banana against BBD. In this project, BDB was firstly isolated from Malaysia’s plantation followed by identification and characterisation through molecular and phenotypic method. The identity of BDB isolated strains was first confirmed as Blood Disease Bacterium via Sanger sequencing analysis of 16s ribosomal ribonucleic acid (rRNA) gene. Standard biochemical tests and growth curve study manifested the BDB isolates were non-motile rod-shaped, Gram-negative, catalase-positive, oxidase-positive bacterium, and had an optimum growth rate at 35 °C. The pathogenesis of the characterised virulent BDB isolate (P1) was then studied via Koch’s Postulates in four local banana cultivars using disease rating scale that was newly developed. The pathogenicity test result showed that these four local banana cultivars (cv.) including cv. Berangan, cv. Nipah, cv. Awak and cv. Nangka demonstrated disease severity index (DSI) higher than 95%, indicating their susceptibility towards BDB. To determine the applicability of PGPR (MyIPO application no. PI2020006647) obtained from Malaysia Agricultural and Research Development Institute (MARDI) as BCA in banana against BDB, cv. Berangan and cv. Nipah was selected as plant model. Upon demonstrating promising growth-promoting effect in both cv., PGPR-induced plantlets challenged by BDB showed significantly lower DSI as compared to the non PGPR-induced plantlets in both cv., indicating the feasibility of PGPR (MyIPO application no. PI2020006647) as disease management approach to manage BBD. Hence, the mechanism of PGPR in inducing systemic resistance in banana plantlets was studied in cv. Berangan from the physiological, biochemical and molecular perspectives. Significant improvements were shown in the growth of leaf number, leaf area, pseudostem height and girth diameter in PGPR-induced plantlets by 14.22%-18.42% meanwhile DSI of PGPR-induced plantlets was significantly reduced by 18.41%. In the aspect of biochemical analysis, increased activities of defence-related enzymes such as polyphenol oxidase (PPO), peroxidase (POD), β-1,3-glucanase, phenylalanine ammonia lyase (PAL) along with the increased total phenolic content (TPC) in PGPR-induced plantlets, highlights the role of PGPR in constructing disease resistance through the upregulation of biosynthesis of secondary metabolites against BDB infection. Furthermore, the ability of PGPR in inducing oxidative burst of reactive oxygen species (ROS) included hydrogen peroxide (H2O2) and superoxide anion (O2-) to combat BDB infection while malondialdehyde (MDA) content remained at low level. This further proposed the ability of PGPR in inducing appropriate amplitude of defence response to prevent activation of programmed cell death. Differentially expressed genes (DEGs) of PGPR-induced plantlets were determined through the leaf transcriptomic profiling of PGPR-induced cv. Berangan upon BDB infection on 0, 1 and 3 dpi via Next Generation Sequencing. Out of 5328 DEGs, 565 upregulated and 755 downregulated DEGs were uniquely identified in the PGPR-induced plantlets against BDB on 0, 1 and 3 dpi. Kyoto Encyclopaedia Genes and Genomes (KEGG) pathway enrichment analysis further revealed the significant involvement of these DEGs in regulating metabolic pathways, starch and sucrose metabolism, biosynthesis of secondary metabolites, protein processing in endoplasmic reticulum, MAPK signalling pathway, plant-pathogen interactions, plant hormone signal transduction and lipid metabolism. Quantitative PCR (qPCR) further validated the RNA-seq results for nine genes selected from different signalling pathways in view of their significant regulations by PGPR in PGPR-induced plantlets. This included GBSSI-2 from starch and sucrose metabolism, LRR gene like PLA-I, PR proteins such as acidic-endochitinase, E3 ubiquitin protein ligase ATL42-like and sHSP from the defence signalling pathway, transcription factors (TF) including MYB protein-like, WRKY22 and ethylene-responsive TF ERF119-like, and ABA receptor PYL4-like from the plant hormone signal transduction. Taken together, the outcome of this project confirmed the growth-promoting effect of PGPR and highlighted the biocontrol ability of PGPR in ISR through the regulation of metabolic, plant hormone signal transduction and plant defence signalling pathways. Nevertheless, the set of validated genes contributing to the disease resistance by PGPR against BBD could serve as potential genetic biomarkers for developing BBD-free banana cultivars, thereby constructing resilience in banana production in Malaysia
Mesoporous silica nanoparticles as anticancer drug carriers in pancreatic cancer treatment
Get PDFPancreatic cancer, often referred to as “the silent killer”, presents with minimal or no symptoms in its early stages, resulting in late detection. When surgical resection is no longer the optimal treatment option, chemotherapy becomes crucial at this stage. However, the low 5-year survival rate highlights the limited effectiveness of current treatments. In recent years, mesoporous silica nanoparticles (MSNP) have gained significant attention in both scholar and pharmaceutical fields due to their unique combination of properties including stable porous structure and high loading capacities. This research aims to investigate the potential of MSNP as a co-delivery carrier for chemotherapeutic drugs and siRNA. In this project, the chemotherapy drug focused on gemcitabine (GEM), a commonly used chemotherapeutic drug in pancreatic cancer treatment and KRAS-siRNA, a mutated oncogene targeted siRNA. MSNP was successfully synthesized in the laboratory using sol-gel synthesis using tetraethyl orthosilicate (TEOS) as silica source with cetyltrimethylammonium bromide (CTAB) as surfactant template, and comprehensive characterizations were performed through TEM, FESEM, EDX and element mapping, XRD, BET and BJH analysis. The results demonstrate that MSNP exhibits desirable properties for drug delivery, including a stable mesoporous structure with pore size of 4.94 nm, a high surface area of about 278.32 m²/g, particle diameter of approximately 85 nm. MSNP was found to have a crystallinity index of ~ 50.24 % through the usage of XRD, which indicates MSNP was semicrystalline or semi-amorphous material. Additionally, the successful loading of GEM onto MSNP validates the tremendous potential of MSNP as an effective anticancer drug carrier in pancreatic cancer treatment. The highest amount of GEM bounded by 1 mg of MSNP was 8.22 μg. Cytotoxicity test determined the optimum PEI variant was MSNP-PEI (1.2B) which showed the least cytotoxicity in the test. MSNP-GEM-PEI was reported to have minimal anti-proliferation as GEM was encapsulated and not released from PEI coating. Hence, MSNP-PEI-GEM was chosen. Cellular uptake did take place and the rate reduced over time. KRAS siRNA was conjugated to both MSNP-GEM and MSNP-PEI-GEM. By conducting cell viability test on both cell lines AsPC-1 and SW1990, MSNP-GEM demonstrated a promising synergistic and high anti-proliferation effect with a reduction of 73.94 % of cell viability. MSNP-PEI-GEM was reported to have a reduction of 62.67 % of cell viability which made it an alternative treatment plan or design for future. qPCR results supported the findings by showing the knockdown of KRAS gene when comparing only GEM loaded sample to co-delivery sample. These findings provide a valuable reference for future research and investigations in this promising field
Investigation of immunomodulatory effects of phytosterols isolated from Clinacanthus nutans
No full textClinacanthus nutans (Burm. F.) Lindau, a traditional medicinal plant from the Acanthaceae family used in Southeast Asia to treat fever, skin rashes, viral infections, and insect bites. The plant is known for its anti-cancer, antimicrobial, anti-herpes simplex virus, antioxidant, and anti-inflammatory properties. Recent studies have reported on the immunomodulatory properties of C. nutans. However, most research to date has focused on crude extracts rather than purified compounds. This study aims to investigate the immunosuppressive effects of beta-sitosterol, stigmasterol, and shaftoside, isolated from C. nutans, in female C57BL/6 mice. Preliminary in vitro studies in Jurkat cells revealed that beta-sitosterol and stigmasterol shaftoside showed lower IC50 values than shaftoside and exhibited dose-dependent cytotoxicity in 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyl tetrazolium bromide (MTT) assay. All three compounds did not affect the lymphocytes proliferation in bromodeoxyuridine (BrdU) assay in vitro. Enzyme-linked immunosorbent assay (ELISA) showed that shaftoside possibly reduced Th2 cytokine IL-4, promoted anti-inflammatory IL-10 cytokine. Conversely, beta-sitosterol may stimulated Th1 cytokine IFN-γ while inhibiting Th2 cytokine IL-4, suggesting a Th1 bias, while stigmasterol demonstrated decrease in both Th1 and Th2 cytokines. Subsequent in vivo experiments in C57BL/6 mice orally administered with C. nutans isolated compounds provided more information on the immunosuppressive activity. Shaftoside reduced B and T lymphocytes proliferation, with suppression of Th1 (IFN-γ, IL-2) and Th2 cytokines (IL-4), while maintaining IL-10 production, Shaftoside also exhibited an increase in total IgG and suppressed IgM antibody production. Fluorescence-activated cell sorting (FACS) analysis indicated that shaftoside reduced populations of CD19+ B cells, CD3+ T cells, CD4+ T helper cells and CD8+ T cytotoxic cells. Beta-sitosterol and stigmasterol also demonstrated similar suppression in B and T lymphocytes proliferation and stimulated Th1 cytokines (IFN-γ, IL-2) dose-dependently but showed no significant impact on Th2 (IL-4, IL-10) cytokines. Both phytosterol compounds notably reduced CD4+ T helper cells while also decreasing CD19+ B cells, CD3+ T cells and CD8+ T cytotoxic cells. C57BL/6 treated mice were also challenged with a Cryptosporidium parvum infection model. Beta-sitosterol was discovered to induce immunosuppression with less severe tissue damage in the terminal ileum and liver compared to stigmasterol, shaftoside, and the control drug dexamethasone, while exhibiting higher oocyst shedding intensity, second only to dexamethasone. The challenge study results suggest beta-sitosterol could serve as a more tolerable natural alternative to synthetic immunosuppressive agents like dexamethasone. In conclusion, this study demonstrated the immunosuppressive potential of beta-sitosterol, stigmasterol, and shaftoside especially in conditions characterised by Th2 dominance, such as asthma and allergic diseases. In future perspective, beta-sitosterol, stigmasterol, and shaftoside could be potentially developed as naturally derived immunotherapeutic agents with less adverse effects
Stalking: Perceptions of victim responsibility, attributions of blame and interventions
Get PDFThis thesis investigates how perceptions of responsibility and blame are formed, maintained, and challenged in the context of stalking. This thesis considers how cultural narratives, victimisation and cognitive bias inform these perspectives. To address this issue, the thesis adopts a multi-method approach, combining a literature review, empirical research, psychometric critique, and a clinical case study. This methodological approach allows for a comprehensive review of stalking perceptions across public, professional, and offender contexts. Despite increased recognition of stalking as a serious offence, victims’ experiences are often misunderstood or minimised due to persistent myths and attitudinal biases. These perceptions have significant implications for justice outcomes, victim support, and therapeutic intervention. The thesis examines how these beliefs influence judgments of blame and responsibility across different settings.
Chapter Two presents a systematic review of factors influencing perceptions of victim responsibility, including gender, prior experience, the victim–perpetrator relationship, and stalking myth endorsement. Drawing upon extant findings in perception research (Scott et al., 2010; Scott & Sheridan, 2011; Scott & Tse, 2011; Sheridan et al., 2003, Duff & Scott, 2013; Scott et al., 2015), Chapter Three outlines the results of an empirical study using a community sample to examine how these variables predict attributions of blame. The narrative synthesis presented in Chapter Two, and further substantiated in Chapter Three, highlights the role of stalking myths, their role in shaping societal norms, particularly pertaining to gender and cultural perceptions, thus shaping various aspects of the criminal justice system (Scott et al., 2010). Chapter Four critically evaluates the Stalking Myths Scale (SMS; Sinclair, 2012), assessing its psychometric properties and theoretical underpinnings. Chapter Five offers a clinical case study of a convicted offender, illustrating how victim-blaming beliefs and cognitive distortions align with broader societal myths and how they may be addressed through psychological interventions.
Together, the findings offer a comprehensive understanding of how stalking is perceived and how these perceptions shape real-world responses. The thesis contributes to both theory and practice by highlighting the role of attitudes in shaping victim support, legal decision-making, and offender treatment
Investigation of low-temperature thermochemical energy storage for water heating in residential application
No full textThis study aims to develop a low-temperature thermochemical energy storage (TCES) water heating system for domestic use, designed to integrate with low-temperature sustainable energy sources like solar energy. The goal is to improve the utilization of renewable energy in residential applications, reduce reliance on fossil fuels, and lower greenhouse gas emissions.
This thesis provides a comprehensive review of the latest advancements in the field of low-temperature TCES systems, and finds research gaps at the system, material and reactor levels. At the system level, open TCES systems demonstrate advantages in output performance and cost-effectiveness compared to closed systems. However, open TCES systems are difficult to integrate directly into most existing domestic central heating systems due to their reliance on different heat transfer mediums. To address this, the thesis proposes two open TCES water heating systems: one incorporating an internal bare microchannel flat-tube heat exchanger (IBHEX-TCES system) and the other incorporating a detached finned microchannel flat-tube heat exchanger (DFHEX-TCES system). The performance of these two TCES water heating systems was subsequently studied through numerical simulations. The performance comparison under identical conditions shows that the IBHEX-TCES system has a slight advantage in water temperature increase, with the difference generally being less than 1 °C. However, the DFHEX-TCES system consistently outperforms in overall thermal efficiency, leading by 10 to 15 percentage points.
Subsequently, a multifunctional TCES system was developed to experimentally test the two proposed open TCES water heating systems. The test results show that while both systems achieved similar peak water temperature lifts, the DFHEX-TCES exhibited superior performance in terms of duration and operational efficiency. Further tests on the multilayer DFHEX-TCES revealed a slightly lower peak temperature lift. However, the duration during which the water temperature was lifted above 5 °C was at least twice as long, underscoring the effectiveness of the multilayer configuration.
Additionally, this thesis explores various impregnation methods for synthesizing vermiculite-CaCl2 composites (VCMs), focusing on analysing the effect of these methods on the performance of VCMs. The optimized synthesis methods achieved salt contents exceeding those obtained with traditional single-step impregnation methods (reporting a maximum of 68 wt%). Among these methods, VCM-vac (synthesised by vacuum impregnation) exhibited the highest volume energy storage density, reaching 2.05 GJ·m-3, which is approximately 1.5 times higher than the VCM sample synthesised by single-step. VCM-vac also demonstrated excellent cycling stability.
Finally, the structure of packed bed reactor was optimized based on experimental and simulation studies. The proposed two-layer and four-layer reactors extended the discharging duration by factors of 1.7 and 3 as compared to the conventional single-layer setup. Concurrently, these configurations achieved a doubling and a quadrupling of peak output power. Such performance improvements are difficult to achieve by simply scaling up traditional packed bed reactors
Performing the piano works of Maria Szymanowska: considerations of authenticity, history, and gender
Get PDFOver the past three decades, Historically Informed Performance (HIP) has become increasingly mainstream. Once confined to eighteenth-century music, it now informs approaches to nineteenth-century music and beyond, presents challenges to performers. For modern pianists, such historical considerations mean that they need to be aware of issues relating to authenticity when playing nineteenth-century repertoire. Yet what kind of authenticity should one seek? In addition, scholarly attention has focussed on only a small number of male canonical figures. But the piano in the nineteenth century was mainly played by females. Does gender make a difference? How, for instance, should a modern pianist perform works by an early nineteenth-century female pianist? Should one scour manuscripts for clues left by the composer? Should one play on a period instrument? Does one need to apply earlier techniques? Or is one supposed to lead the performance with one’s own instincts and feelings? How should historical evidence inform performance? And how might a pianist demonstrate their own take on the issues through a recital?
In this performance research, I take Maria Szymanowska (1789-1831) as a case study, with the aim of helping modern pianists to make informed choices when performing her repertoire by exploring the challenges faced by the modern performer of nineteenth-century piano music. Maria Szymanowska was a Polish female pianist/composer who was well received in early nineteenth-century Europe. She was one of the few successful professional female musicians, although she is hardly known today.
The research is divided into several objectives to address the aim. The first is to provide a context for Szymanowska’s musical style through her biography and social environment, offering important insights for performances. Second, historical evidence will be uncovered about the performance traditions that she may have followed, as records of her performances are not as informative as those of her male peers. Then, accompanied by reflections on authenticity as a modern female piano performer, suggestions for the modern performance of Szymanowska’s piano works will be explored through the application of my embodied learning. The final objective involves the public demonstration of the findings through two live recitals and recorded examples.
The research draws on written sources such as biographies, concert reviews, commentaries, early treatises, published scores, manuscripts, and literature on performance practice. Based on these, as a practical guide to performance, embodied learning is used to examine the application of incomplete evidence (including the examination of selected instruments and self-reflection in modern performance settings), to establish a dialogue with Szymanowska’s music. Representative examples from the recital repertoire are examined in terms of posture and movement, tempo, dynamics, tempo rubato and pedalling, to obtain some valuable insights into Szymanowska’s performance, while critically considering some aspects of the possible challenges in recitals and exploring solutions based on practical experience. Considerations of gender run through the study. And the findings will be applied in two live recitals
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