17837 research outputs found
Sort by
ENHANCED RECOVERY OF METEORITE SAMPLES ON UK TERRAIN USING DRONES, MULTISPECTRAL SENSORS AND MACHINE LEARNING
Full text link
Statistical Models with Uncertain Error Parameters - "Errors On Errors" - and their Application to Particle Physics
Full text linkIn particle physics, data are collected and compared to theoretical predictions by constructing a statistical model that captures both the intrinsic stochastic nature of the measurement process and potential biases introduced by approximations in theoretical predictions and in the modeling of the experimental setup, referred to as systematic uncertainties. However, these uncertainties are often derived from limited data or estimated through ad-hoc procedures, introducing uncertainty in the uncertainty itself - informally referred to as ``error-on-error''. The Gamma Variance Model (GVM) is a statistical framework developed to address this issue by explicitly treating systematic uncertainties as imperfect estimates of unknown error parameters. This effectively incorporates errors-on-errors into the statistical model. A key practical consequence is that the GVM naturally reduces sensitivity to outliers and captures internal tensions within datasets by treating them as an additional source of uncertainty. In this thesis, the mathematical properties of the GVM are studied, and the model is extended to simplify its application in practical contexts, such as the combination of measurements and the fitting of physical parameters. These developments are applied to relevant physics examples, demonstrating the practical use of the model. Applications include a study of the 7-8 TeV ATLAS–CMS top-quark mass combination, an investigation of the W-boson mass discrepancy between the CDF result and the ATLAS and CMS measurements, and the fitting of parton distribution functions
Using Bottom-Quark Hadrons from Top-Quark Decays at the ATLAS Detector to Measure Charge Parity Violation and Explore Lepton Flavour Universality Violation
Full text linkCharge and CP-violation asymmetries are measured in lepton+jets events using \mbox{\SI{13}{\tera\electronvolt}} centre-of-mass energy proton-proton collisions from Run 2 of the ATLAS detector at the LHC, with an integrated luminosity of \SI{140}{\per\femto\barn}. These charge asymmetries are extracted using soft muons from the semileptonic decays of -hadrons and prompt leptons from top-quark decays. Using -hadron decay chain fractions, these charge asymmetries are linked to four CP-violation asymmetries, which are compared with results from other experiments and the Standard Model predictions. Alongside this measurement, a feasibility study is presented, investigating the possibility of using soft muons to make a measurement of Lepton Flavour Universality Violation
Barriers and Facilitators to HIV Self-Testing for Black African Heterosexuals in the UK
Full text linkThis thesis begins with a conceptual review of psychological theories relevant to HIV testing behaviours, followed by an empirical study focusing on HIV self-testing (HIVST). HIV testing is central to early diagnosis, treatment, and the prevention of onward transmission. Despite the importance of testing for initiating the HIV continuum of care, individuals delay or avoid HIV testing due to a combination of emotional, psychological and structural factors. The conceptual review evaluated key psychological theories and models applied to HIV testing behaviours, including cognitive models such as the Health Belief Model (HBM) and the Theory of Planned Behaviour (TPB) and the Common-Sense Model of Self-Regulation, which highlights the role of emotions, such as anxiety and fear, stigma models such as Goffman’s Theory of Stigma, Earnshaw and Chaudoir’s HIV Stigma Model and Hatzenbuehler’s Psychological Mediation Framework (PMF). The Ecological Model was also applied to understand the broader societal and institutional influences on HIV testing. The review concluded that multi-level approaches, including cognitive, emotional, and structural factors, are needed to understand HIV testing. Building on this, the empirical study used a constructivist grounded theory–informed methodology to explore experiences and perceptions of HIVST among eight Black African heterosexual adults in the UK (five women and three men, aged 20–51). Black Africans in the UK are disproportionately affected by HIV, with higher rates of both new diagnoses and late diagnoses compared to other groups. Despite increasing availability of HIVST and home-based testing methods, there is limited understanding of how Black African heterosexual adults in the UK perceive, engage and experience HIVST. The analysis generated eleven theoretical codes, grouped into four interconnected conceptual categories: (1) Structural and External Influences, (2) Cultural Morality and Stigma, (3) Relational and Social Influence, and (4) Emotional Readiness and Internal Conflict. The resulting theoretical model conceptualises HIVST as a social and emotional process which is shaped by multiple layers of direct and indirect interacting influences, including access, knowledge, moral and anticipated stigma and emotional readiness. The findings highlight the need to integrate emotional and social support into HIVST delivery, supported with clear information, culturally relevant resources, as well as accessible testing services, including clinic testing
Leveraging ethnocentric staffing as a strategic tool in Indian information technology multinational corporations
Full text linkThis thesis examines the staffing policies adopted by major Indian multinationals operating in the United Kingdom and the factors influencing their staffing decisions. It focuses on the information technology service sector and aims to identify the reasons for their persistent ethnocentric staffing policies. Many studies have already focused on the challenges that multinational corporations face when they enter a new market. However, these challenges are more acute in the case of emerging market multinational corporations, due to the liability of emergingness. The thesis uses empirical data from twenty-eight semi-structured individual interviews including parent-country nationals (Indian citizens), host-country nationals, and third-country nationals. The analysis is supplemented by company reports and other secondary sources. Previous research highlights that emerging market multinationals often encounter employee resourcing problems when operating in developed economies. This study argues that such challenges faced by emerging market multinational corporations are particularly acute when they originate from developing countries that were formally colonised by the very nations in which they now operate, as is the case with Indian emerging market multinational corporations in the United Kingdom. The study draws on the insights of the dominance effect theory (Smith and Meiksins, 1995) and the evolutionary theory of multinational corporations (Perlmutter and Heenan, 1974) on the study of Indian information technology multinational corporations in the United Kingdom. If all early-stage multinationals prefer parent-country nationals (Perlmutter and Heenan, 1974), why should Indian multinational corporations differ from this trend and switch to hiring local employees? According to this research, an Indian information technology sector corporation’s decision between using a parent-country national expatriate or a local employee depends on three broad factors, namely, the availability of technically skilled employees on the local labour market; the proximity of the subsidiary to its headquarters; and the cost of hiring locally. In this study, the main contribution is to demonstrate that, even a well-established Indian firm such as Tata Consultancy Services, an entity within the Tata group of companies, has difficulties sourcing employees from the local labour market in the United Kingdom. This research argues that Indian multinationalshave a competitive advantage in the information technology sector worldwide including in the United Kingdom and the cheap Indian workforce is a key factor that contributes to this competitive advantage of Indian information technology service companies in the information technology sector. This theory adds to the literature by (1) challenging the evolutionary theory of multinationals, which has always been considered linear; and (2) discussing how staffing practices of dominant technology companies like Tata Consultancy Services are the way they are not simply because of the cost but also due to their competitive advantage and culture and work practices related factors
A Novel Sonar Image Preprocessing Method for AUV Positioning Based on Underwater SLAM
Full text linkImaging sonar, as an efficient sensor for underwater observation and measurement, plays a very important role in the positioning and mapping of autonomous underwater vehicles (AUVs). Compared to visual simultaneous localization and mapping (SLAM) susceptible to the water quality and distance, sonar SLAM based on acoustic images has a better perception range and immunity to the surrounding fluid characteristics. However, due to the complexity of underwater environments, imaging sonar is often severely affected by noise, and sonar images usually exhibit low resolution, insufficient contrast, and blurred target edges, resulting in severe errors in positioning and mapping. To solve these problems, a sonar image preprocessing method is proposed to effectively eliminate noise, while feature edges preserved. First, the proposed image preprocessing method employs a threshold filter to eliminate potential noises; then, the contrast-limited adaptive histogram equalization algorithm is used to enhance the image features, and the guided filter (GF) is used to eliminate the residual noise. In addition, we introduce a factor graph-based sonar SLAM method, and the preprocessed sonar images are integrated into the SLAM process. Through numerical evaluation, the effectiveness of our proposed preprocessing method is validated, and the results show that it improves the processing speed, detection precision, and matching precision by about 73.9%, 30.8%, and 20.0%, respectively. Furthermore, simulation experiments and real experiment demonstrate that our proposed method improves both positioning accuracy and stability of the AUV
Goal Legibility and Recognition for Anonymous Multi-Agent Pathfinding Systems:A Graph Theoretical Approach
Full text linkGoal legibility, one of the dimensions of agent interpretability, has gained significant attention in human-machine interaction research. This thesis explores goal legibility in relation to goal recognition in a multi-agent setting with an observer-in-the-loop. Specifically, it considers an environment where identical agents move from an origin to designated destinations, and an observer monitors their movements, aiming to infer their destinations as quickly as possible. Our approach generates legible paths that minimize overlap while satisfying budget constraints. We also developed a goal recognition framework that maps observation sequences to specific destinations, enabling the observer to infer an agent's goal with minimal (legibility) delay. The legible path planning problem is reformulated as a classical network flow problem for fully observable scenarios, using combinatorial optimization tools to create scalable algorithms. The method adapts efficiently to partially observable settings as well. While effective, these techniques can become computationally demanding. To address this, we introduced initial goal legibility, where the observer begins monitoring agents from their entry point. This variant focuses on inferring destinations by observing initial trajectories. Through mathematical reformulations, our approach computes paths that minimize trajectory overlap, and agents then follow optimal routes. This method is applicable to both fully and partially observable environments. Empirical evaluations demonstrate the scalability and efficiency of our techniques, confirming their practical relevance
Data sources:
Access Repository Dashboard
Do you manage Royal Holloway - Pure? Access insider analytics, issue reports and manage access to outputs from your repository in the CORE Repository Dashboard!