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Research and implementation on optical wireless communication technologies
Get PDFContinuous global growth and increasing demand for wireless communication cause a shortage of radio frequency (RF) spectrum. Optical wireless communication (OWC) is expected to alleviate this looming spectrum crisis. Among OWC technologies, free space optic (FSO) and visible light communication (VLC) have rapidly become a research hot spot because of significant development and application prospects.
This study aims to investigate the characteristics of OWC technologies and offer theoretical support for enhancing the transmission performance. To achieve this goal, simulation models are set up, and better system parameters and modulation schemes are selected.
In the FSO model, an established modulation, absolute added correlative coding (AACC), is compared with four-level pulse amplitude modulation (4-PAM) in terms of transmission distance, eye diagram and bitrate. The results indicate that AACC transmits longer distance and at a higher bitrate than 4-PAM. Using the bit error rate (BER) with an estimation of 10-9, the transmission distance achieved by AACC is 1.12 km, compared to 1.09 km for 4-PAM. And the bitrate of AACC is 18.7 Gbit/s, while it of 4-PAM is 16.7 Gbit/s. From the above results, the AACC modulation gives an improvement of 3% in the distance and 12% in the bitrate compared to 4-PAM modulation. In indoor VLC model, simulation results like illumination distribution, received power, signal-to-noise ratio (SNR) and root-mean-square (RMS) delay are evaluated. The illumination distribution between one light emitting diode (LED) array and four LED arrays is compared. It shows that four LED displays provide more uniform illumination. And the received power in LOS channel and NLOS channel are analysed. It shows that the contribution of LOS channel is decisive for the received power, and the assistance of NLOS channel is concentrated near the walls. In addition to these simulation results, measure algorithms of indoor positioning system (IPS) based on the same model are also investigated. It provides an experimental foundation for the construction of a robust and high data rate light fidelity (Li-Fi) system as well as a more accurate IPS. With the continuous improvement of OWC technologies, a more efficient and secure wireless communication network will be widely used
Assessing the Impact of GCC trade agreements with ASEAN and AfCFTA: implications for trade flows among key OIC member countries
No full textThis study investigates the intricate relationship between macroeconomic factors, trade agreements, and trade competitiveness, with a particular focus on the trade dynamics among the Gulf Cooperation Council (GCC), the Association of Southeast Asian Nations (ASEAN), and the African Continental Free Trade Area (AfCFTA) under the Organization of Islamic Cooperation (OIC) framework. The primary purpose of this research is to analyse how these trade-related variables and agreements influence trade flows and competitiveness within these regions, with the GCC serving as the anchoring point in these trade agreements.
Utilising a panel data set of 19 OIC member countries from these regions spanning from 1995 to 2023, the research employs an augmented gravity model to assess the impact of various determinants, including economic size, income levels, geographical distance, real exchange rates and policy-related factors such as trade openness and digitalisation. The methodology included estimation techniques such as Ordinary Least Squares, Fixed Effects, and the Generalized Method of Moments, ensuring robustness in the findings. The study also employed various econometric tests to address issues such as heteroskedasticity and multicollinearity, confirming the reliability of the results.
The findings reveal that the economic size of GCC countries significantly influences bilateral trade flows, highlighting the GCC's role as a dominant player in shaping trade dynamics with ASEAN and AfCFTA countries. Population size emerges as a critical determinant, with larger populations in GCC and partner countries positively correlating with higher trade volumes. Additionally, the study highlights the growing importance of digitalisation and trade openness, particularly in partner countries, which enhances trade competitiveness and facilitates smoother trade interactions. However, the analysis of real exchange rates reveals a complex relationship, where a positive correlation challenges the conventional assumption that stronger currencies reduce export competitiveness. The study finds that favourable exchange rates enhance trade competitiveness, although the significance of this variable varies across models.
The study also highlights the evolving role of trade agreements. It reveals that the GCC-ASEAN trade agreement positively influences bilateral trade flows, indicating successful economic integration between these regions. In contrast, the GCC-AfCFTA agreement shows an unexpected negative impact on trade flows, suggesting that the benefits of this agreement may not have been fully realised due to its early stage of implementation or structural challenges within the agreement itself. The study emphasises the importance of open trade policies and the impact of economic growth in partner countries post-2010.
The study's conclusions emphasise the pivotal role of the GCC in these trade agreements, influencing trade flows and economic integration with ASEAN and AfCFTA countries. By providing tailored policy recommendations, this research aims to aid policymakers in developing stable and beneficial trade relationships, ultimately contributing to enhanced economic cooperation and integration among key OIC member countries with the three economic blocs
The role of sustainability in attracting talent to Small & Medium Enterprises (Singapore)
No full textThis dissertation examines the role of sustainability in attracting talent to Small and Medium Enterprises (SMEs) in Singapore. As sustainability gains importance for businesses globally, job seekers, especially from younger generations, are placing more emphasis on a company's environmental and social impact when choosing their careers. The research aims to explore how SMEs in Singapore can leverage sustainability efforts as a key differentiator in the highly competitive talent market, where they often face challenges in competing with bigger companies for top talent. A quantitative survey of adult workers in Singapore will be conducted and analysed to determine the importance of sustainability in shaping sentiments about an employer’s attractiveness. The findings aim to investigate the importance of sustainability toward talent attraction but also in employee engagement. Many prospective employees, particularly Millennials and Generation Z, have a higher propensity to join companies that align with their values, prioritizing purpose, ethical business practices, and environmental responsibility alongside traditional benefits. However, beyond sustainability as a key factor, the research will verify if there are other contributing factors influencing perception, sentiments, reputation and job appeal. This dissertation will conclude by providing recommendations for SMEs on integrating sustainability and other aspects into their business strategies and employer branding, so as to enhance their appeal to talents, and enhance their competitiveness and overall success in Singapore's dynamic economic landscape
Disentangling diphtheria: an investigation into its persistence worldwide
Get PDFIntroduction: Diphtheria is a contagious disease primarily caused by Corynebacterium diphtheriae, which typically affects the respiratory tract and less often the skin. Transmission occurs via exposure to secretions of an infected person. Generally, respiratory diphtheria has a case fatality rate of 5–10%, with higher rates seen among certain groups (e.g., untreated, unvaccinated individuals). After years of decline, diphtheria is experiencing a resurgence, with 24,778 cases reported in 2023 – the highest global case count in over 20 years. The disease has severely affected Haiti, a country that is also facing vulnerability to natural disasters, concurrent health crises, and civil unrest. Despite its impact, diphtheria is still relatively understudied, with questions remaining about the determinants of the observed epidemiological trends and patterns. This PhD thesis aimed to explore drivers of global diphtheria persistence to fill current knowledge gaps.
Methods: The thesis consisted of three studies. The first study was a systematic review and meta-analysis to identify risk factors for diphtheria. The second study was a spatial analysis of the epidemiology of the disease in Haiti between December 2014 and June 2021 to examine the spatiotemporal distribution of cases, detect diphtheria hotspots, and identify potential risk factors for the disease. The third study was a mixed-methods analysis of posts shared from January 2012 to December 2022 on X (formerly Twitter) to understand global perceptions and attitudes towards diphtheria.
Results: The review identified three potential risk factors for diphtheria: incomplete vaccination, contact with a person with skin lesions, and low diphtheria knowledge. Evidence for other risk factors was less conclusive. The spatial analysis revealed that the reported diphtheria case rate exhibited spatial variability in Haiti, with nine out of 140 communes being classified as hotspots. This rate was positively associated with the number of healthcare facilities per 100,000 inhabitants and the proportion of urban population, while it had a negative association with female literacy. The mixed-methods analysis showed that a diversity of voices participates in diphtheria-related conversations on X, leading to the identification of various themes – with vaccination being the predominant topic of interest. The analysis also highlighted posts spreading false information alongside differences in tone and content between high-burden and low-burden countries, mirroring variations in healthcare priorities and challenges.
Conclusion: This thesis illustrates the complex nature of diphtheria, as evidenced by the multitude of biological, immunological, environmental, socioeconomic, behavioural, and informational factors that potentially contribute to the persistence of the disease. The in-depth investigation of diphtheria in Haiti highlighted the compounded difficulties in controlling the disease during a humanitarian crisis. Findings from this case study, alongside the risk factors and themes identified through the systematic review and mixed-methods analysis, can inform future research and interventions not only in Haiti but also in other countries facing similar challenges. While remaining context-specific, these interventions should seek to raise vaccination coverage, scale up access to healthcare services, strengthen surveillance systems, increase health literacy, and improve sanitation and hygiene conditions. Innovative tools like spatial analysis and social media monitoring can enhance surveillance, by facilitating the detection of disease trends, at-risk populations, and emerging public concerns
Development of landslide tolerable and acceptable risk criteria for Malaysia
Get PDFLandslide tolerable and acceptable risk criteria are strongly governed by utilitarian concerns i.e. financial power and the need for development and should be developed locally with historical landslide inventory, public perception, and engineering aspects being considered. The risk criteria of Hong Kong and that of the Australian Geomechanics Society are widely employed in many countries. The present study aims to develop and improve the landslide tolerable and acceptable risk criteria for Malaysia by taking into considerations of qualitative and quantitative inputs from various stakeholders. Based on the compiled landslide inventories, the Frequency-Number of fatalities (F-N) curve of Malaysia established from the present study have a similar slope gradient with those of Italy, Colombia, and Hong Kong. The F-N curve is a graphical tool (typically expressed on a log-log scale) used to depict the level of societal risk associated with a particular activity or project, which, in the present study, is landslides. As for the findings from the questionnaire surveys and interviews with landslide experts, public (non-experts) generally expressed the lowest acceptance in landslide risk for all scenarios (from low to high risk), whereas the experts were willing to accept a higher landslide risk as they understand that an ideal low landslide risk environment is not feasible under the current Malaysian scenario. Gender, occupation and educational level were the significant demographic factors influencing landslide risk acceptability in Malaysia. Modifications were proposed to the existing landslide risk criteria with a lower acceptance towards death upon taking into consideration findings from the present study. To demonstrate the application of the newly developed criterion and runout model, quantitative risk analyses (QRA) were performed to quantify landslide risk for a real-life case study. An important part of QRA concerns the development of a simple yet reliable model for predicting the impact / consequence of a landslide. A new empirical model for landslide runout estimation in Malaysia was proposed based on historical landslide data. The reliability of the proposed model was verified through a reasonable agreement between the actual runout and predicted values. Gumbel analysis was utilized to obtain the extreme rainfall scenario with a 10-year return period. It should be noted that Gumbel analysis is typically conducted for the probability distribution of extreme value in hydrologic studies for prediction of maximum rainfall. Seepage and probabilistic slope stability analyses were carried out to determine the probability of landslide occurrence of the studied slope. Using the newly developed empirical model, the runout of the landslide was predicted. The outcomes included a quantification of risks posed to elements within the runout path, such as houses and residents. The findings offer a quantitative estimation of the annual probability of fatalities for people. A F-N curve was employed to articulate the societal risk associated with this specific slope in the case study, which was then compared against the newly established risk criterion. These results carry significant societal implications and will furnish decision-makers and regulators with valuable insights for devising risk mitigation strategies for both existing slopes and forthcoming developments
Adverse childhood experiences, self-harm, and aggression: an emotion-regulatory pathway
Get PDFThe association between childhood adversity and negative outcomes including harm to self and others has been well established. Less is known however about the mechanisms that underlie these relationships. Harm to self and others has significant costs at an individual and societal level. Elucidating the causal pathways between adverse childhood experiences (ACEs) and harm to self and others is vital to informing clinical practice and is the focus of this thesis. Initially, a systematic review synthesises research investigating psychological mechanisms that mediate the relationship between childhood adversity and self-harm in clinical and forensic adult populations. Findings provide preliminary support for an emotion-regulatory pathway connecting childhood adversity to self-harm. Several other psychological mechanisms were also identified, albeit methodological limitations restrict the ability to draw firm inferences regarding causality and mediation effects. Moreover, there was a distinct lack of studies conducted with forensic inpatients, limiting the generalisability of findings to this population. Thereafter, an empirical study investigates the associations between ACEs, and self-harm and aggression, and the mediating role of emotion dysregulation, in a sample of male and female forensic inpatients detained in low- and medium-secure conditions. ACEs were positively correlated with self-harm and aggression, and emotion dysregulation partially mediated these relationships; an effect that remained after controlling for age and gender. Following this, a single case study of a female detained in a medium-secure unit, characterised by ACEs, emotion dysregulation, self-harm, and aggression, is presented. An evaluation of the intervention delivered to target the patient’s difficulties indicated positive outcomes, evidenced by changes in pre- and post-intervention psychometric tests and observed behavioural changes. Lastly, a critical evaluation of the Difficulties in Emotion Regulation Scale (DERS) examines its psychometric properties and clinical utility. The DERS was found to be a sound measure of emotion dysregulation appropriate for use among a range of populations and cultures. However, further research is needed to evaluate its psychometric efficacy and clinical utility amongst more unique populations, such as forensic inpatients. This thesis emphasises the importance of considering developmental perspectives and an emotion-regulatory pathway in the aetiology and maintenance of harmful behaviours, as well as the need for therapeutic interventions targeting the psychological mechanisms underpinning the relationships between childhood adversity, and self-harm and aggression
Patient safety culture in homecare in England: an exploratory study
Get PDFBackground: In the health and social care sector, patient safety culture is a key priority. However, research on patient safety culture has extensively focused on hospitals, with very few studies examining safety culture in homecare. Homecare is a crucial part of the health and social care system in England, and there has also been an increase in demand for homecare services due to the aging population and the impact of the COVID-19 pandemic. Consequently, the UK government has made significant efforts and strategic commitments to reform adult social care and highlight the importance of research in homecare.
Aims: This PhD thesis aims to explore the patient safety culture in homecare in England. The research seeks to identify the foundational factors that constitute high-quality and safe homecare, examine the prevalent safety issues in the sector, and address the fundamental challenges in delivering such care services. Additionally, the study aims to understand approaches to safety and investigate the role of HRM practices in shaping and strengthening homecare safety culture.
Methodology: This study adopts an interpretivist epistemology to explore the rich meanings of safety culture in homecare. Using an inductive approach, this study collects qualitative data to develop theoretical concepts from detailed interpretations of social actors. The research strategy employs narrative inquiry and triangulation, incorporating semi-structured interviews and documents for data collection. Thematic analysis is used for interview data, while qualitative content analysis is applied to written documents.
Findings: The study reveals a number of significant findings. First, safe homecare consists of several foundational factors of high-quality care, person-centred care, and the engagement of family members and informal support networks (e.g., friends, neighbours). Second, safety incidents are categorised into four types: medication safety, physical and health safety, emotional and social safety, and functional safety. Third, fundamental challenges that serve as barriers to high-quality care and act as risk factors leading to safety issues relate to the institutional context, organisational management, work environment, teams, individual staff, tasks, service users, and informal support networks. Fourth, initiatives and practices that have been made to improve care quality and safety culture include collaborations and partnerships, inclusive and personalised care service, strong leadership and staff support, digital technology integration, and effective HRM practices.
Discussions: The insightful findings help answer the research questions, achieve the primary research aim, and develop theoretical frameworks. First, the interconnected fundamental challenges framework depicts how homecare challenges are interconnected and function as barriers to high-quality care and risk factors for safety incidents. This is useful for identifying safety issues, understanding their origins, and proposing measures to minimise errors and risks, which is in line with the Safety-1 approach. Second, the homecare safety framework, which incorporates both Safety-1 and Safety-2 approaches, illustrates the link between best practices, fundamental challenges, and safety incidents. These frameworks offer a detailed, sector-specific approach to high-quality and safe care and present tailored insights for developing a robust safety culture in homecare organisations.
Contributions: This research contributes to the literature by offering sector-specific insights into homecare safety culture. The study also contributes to the literature on the link between effective HRM practices and organisational positive outcomes, especially in the context of homecare providers in England and during the COVID-19 pandemic. Furthermore, the frameworks developed in this research make a theoretical contribution to the field of safety approach and management in healthcare.
Implications: This research provides practical implications for stakeholders in homecare, emphasising continuous staff development, genuine care, clear communication, patient-centred approaches, and family engagement. It highlights the need for collaboration, personalised care, strong leadership, digital integration, and effective HRM practices to enhance safety culture and care quality, with frameworks providing sector-specific guidelines for risk mitigation and continuous improvement
Advancement of the Quantitative Blood Oxygenation Level-Dependent (qBOLD) MRI technique to improve clinical feasibility.
Get PDFQuantitative Blood Oxygenation Level Dependent (qBOLD) MRI offers a non- invasive method for measuring brain oxygenation, with potential applications in various neurological conditions. However, its clinical implementation has been hindered by methodological inconsistencies and challenges in standardisation. This thesis aims to address these obstacles and advance the clinical applicability of qBOLD techniques through three studies.
First, a comprehensive scoping review of the qBOLD literature was conducted. The review revealed four main qBOLD acquisition methods: multiparametric (mp- qBOLD), asymmetric spin echo (ASE), gradient echo (GRE), and gradient echo sampling of spin echo (GESSE). Notably, mp-qBOLD emerged as the most used technique, likely due to its easier implementation in clinical settings. However, significant variability in the reversible transverse relaxation rate (R2') measurements across different acquisition techniques was observed, highlighting the need for standardisation.
To address this variability and enable quality assurance, the second study focused on developing and validating a new qBOLD phantom using glass microspheres. A linear relationship between R2' contrast and glass bubble volume fraction was established, and the phantom demonstrated good reproducibility in construction and MRI measurements. Crucially, R2' measurements were consistent across different qBOLD acquisitions and MRI vendors and the phantom accurately replicated known in vivo R2' values for human brain tissue. However, challenges arose in matching the irreversible transverse relaxation rate (R2) values to the human brain range.
The third study explored a combined hyperoxia-BOLD and mp-qBOLD (hmp- qBOLD) approach to improve oxygen extraction fraction (OEF) estimation in a clinically translatable manner. This combined method overestimated OEF compared to an established technique, with values exceeding normal physiological ranges.
In conclusion, this thesis has made important contributions towards addressing key challenges to the clinical implementation of qBOLD imaging, laying a solid foundation for future advancements in quantitative oxygenation imaging and its translation to clinical practice
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