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  • Experimental investigations and finite element analyses of interface heat partition in a friction brake system. New modelling paradigm for describing friction brake systems to support studies of interface temperature, contact pressure, heat flux distribution and heat partition ratio by experiment and FE simulation

    Qi, Hong Sheng; Wood, Alastair S.; Qui, Le (University of BradfordFaculty of Engineering and Informatics, 2018)
    Operating temperature range is one of the primary design considerations for developing effective disc brake system performance. Very high braking temperatures can introduce effects detrimental to performance such as brake fade, premature wear, brake fluid vaporization, bearing failure, thermal cracks, and thermally-excited vibration [2]. This project is concerned with investigating deficiencies and proposing improvements in brake system Finite Element (FE) models in order to provide high quality descriptions of thermal behaviour during braking events. The work focuses on brake disc/pad models and the degree of rotational freedom allowed for the pad. Conventional models [10] allow no motion/or free motion of the pad. The present work investigates the effect on disc/pad interface temperature and pressure distributions of limited relaxations of this rotational restriction. Models are proposed, developed and validated that facilitate different rotational degrees of freedom (DoF) of the pad. An important influencing factor in friction brake performance is the development of an interface tribo-layer (ITL). It is reasonable to assume that allowing limited rotational motion of the pad will impact the development of the ITL (e.g. due to different friction force distributions) and hence influence temperature. Here the ITL is modelled in the numerical simulations as a function of its thickness distribution and thermal conductivity. Different levels of ITL thermal conductivity are defined in this work and results show that conductivity significantly a1qwffects interface temperature and heat partition ratio. The work is based around a set of test-rig experiments and FE model developments and simulations. For the experimental work, a small-scale test rig is used to investigate the friction induced bending moment effect on the pad/disc temperature. Significant non-uniform wear is observed across the friction surface of the pad, and reasons for the different wear rates are proposed and analyzed together with their effect on surface temperature. Following on from experiment a suite of models is developed in order to evidence the importance of limited pad motion and ITL behaviours. A 2D coupled temperature-displacement FE model is used to quantify the influence of different pad rotational degrees of freedom and so provide evidence for proposing realistic pad boundary settings for 3D models. Normal and high interface thermal conductance is used in 2D models and results show that the ITL thermal conductivity is an important factor influencing the maximum temperature of contact surfaces and therefore brake performance. The interface heat partition ratio is calculated by using the heat flux results and it is confirmed that this value is neither constant nor uniform across the interface surfaces. Key conclusions from the work are (i) that ITL thermal conductivity is an important factor influencing the interface temperature/heat flux distribution and their maximum values, (ii) that allowed motion of the pad significantly affects the interface pressure distribution and subsequently the temperature distribution, (iii) that the transient heat partition in friction braking is clearly quite different to the conventional friction-pair steady heat partition (the heat partition ratio is not uniformly distributed along the interface) and (iv) that the thickness of the ITL increases through braking events, reducing the heat transfer to the disc, and so providing a possible explanation for increasing pad temperature observed over the life time of a brake pad.
  • Prostanoid-mediated Inhibition of IL-6 Trans-Signalling in Pulmonary Arterial Hypertension: a Role for Suppressor of Cytokine Signalling 3?

    Palmer, Timothy M.; Williams, Jamie J.L.; Nasim, Md. Talat; Elies, Jacobo; Durham, Gillian A. (University of BradfordSchool of Pharmacy and Medical Sciences Faculty of Life Sciences, 2019)
    Pulmonary arterial hypertension (PAH) is a rare, devastating disease with no cure. Current treatment consists of a cocktail of vasodilators which relieve symptoms of PAH but do not treat the cause. Thus, there is a need for novel drugs that target the underlying pathological causes of PAH. PAH is a multi-factorial, but one key contributor is the pro-inflammatory cytokine IL-6 which stimulates pro-inflammatory and pro-angiogenic signalling mediated by the JAK/STAT pathway. One way in which IL-6 signalling via JAK/STAT is inhibited is via SOCS3 in a type of negative feedback loop whereby IL-6 induces transcription of SOCS3, which then attenuates further JAK/STAT signalling. SOCS3 can also be induced by cAMP. This is interesting as prostanoids, a type of drug used in the treatment of PAH due to its vasodilator effects and the only type to show any efficacy improving the life expectancy of PAH patients, acts by mobilising cAMP. Thus, prostanoid stimulation of cAMP could potentially limit IL-6 signalling via the induction of SOCS3. This is a novel mechanism of prostanoids which has not previously been considered. This study investigated the capability of prostanoids to limit the pro-inflammatory/pro-angiogenic effects of IL-6 that enable PAH to develop. Initial experiments confirmed that vascular endothelial cells responded to prostanoids which increased SOCS3 and limited IL-6 signalling activity. Further experiments utilising SOCS3 KO endothelial cell models demonstrated prostanoid inhibition of IL-6 signalling was due in part to SOCS3. In conclusion, this project has confirmed that prostanoids do limit the pro-inflammatory effects induced by IL-6 and that this is in part due to SOCS3. Although the exact mechanism is yet to be discovered, it will be beneficial in the treatment of PAH as it provides currently unexploited drug targets which can be considered for future PAH therapies.
  • Managing risk; how doctors, nurses and pharmacists optimise the use of medicines in acute hospitals in Northern Ireland: a grounded theory study.

    Lucas, Beverley J.; Blenkinsopp, Alison; Friel, Anne B.M. (University of BradfordSchool of Pharmacy and Medical Sciences, Faculty of Life Sciences, 2018)
    Medicines optimisation requires healthcare professionals to work collaboratively to meet the medication needs of patients. A grounded theory was produced which explains how doctors, nurses and pharmacists work to optimise the use of medicines in acute hospital settings in Northern Ireland. Seventeen semi-structured, one-to-one interviews were conducted with doctors, nurses and pharmacists. Concurrent data collection and analysis was carried out using coding, particular to grounded theory, adopting a constant comparative approach, writing memos and using theoretical sampling as described by Strauss and Corbin (1998). The core category was managing risk. Participants had an implicit understanding of the need to continually manage risk when working with the complex and the routine. They used personal and systemic checks and balances which could be viewed either as duplication of effort or indicative of a culture of safety. Multi-professional interdependencies and support for new, professional, non-medical roles were highlighted. Working together was a further strategy to ensuring each patient gets the right medicine. Establishing an agreed framework for working with medicines at ward level could support the safer use of medicines. It is anticipated that this theory will contribute to the design of systems involved in medicines use in acute hospitals in Northern Ireland.
  • Development of digital imaging technologies for the segmentation of solar features and the extraction of filling factors from SODISM images

    Qahwaji, Rami S.R.; Ipson, Stanley S.; Alasta, Amro F.A. (University of BradfordSchool of Electrical Engineering and computer. Science Faculty of Engineering and Informatics, 2018)
    Solar images are one of the most important sources of available information on the current state and behaviour of the sun, and the PICARD satellite is one of several ground and space-based observatories dedicated to the collection of that data. The PICARD satellite hosts the Solar Diameter Imager and Surface Mapper (SODISM), a telescope aimed at continuously monitoring the Sun. It has generated a huge cache of images and other data that can be analysed and interpreted to improve the monitoring of features, such as sunspots and the prediction and diagnosis of solar activity. In proportion to the available raw material, the little-published analysis of SODISM data has provided the impetus for this study, specifically a novel method of contributing to the development of a system to enhance, detect and segment sunspots using new hybrid methods. This research aims to yield an improved understanding of SODISM data by providing novel methods to tabulate a sunspot and filling factor (FF) catalogue, which will be useful for future forecasting activities. The developed technologies and the findings achieved in this research will work as a corner stone to enhance the accuracy of sunspot segmentation; create efficient filling factor catalogue systems, and enhance our understanding of SODISM image enhancement. The results achieved can be summarised as follows: i) Novel enhancement method for SODISM images. ii) New efficient methods to segment dark regions and detect sunspots. iii) Novel catalogue for filling factor including the number, size and sunspot location. v) Novel statistical method to summarise FFs catalogue. Image processing and partitioning techniques are used in this work; these methods have been applied to remove noise and detect sunspots and will provide more information such as sunspot numbers, size and filling factor. The performance of the model is compared to the fillers extracted from other satellites, such as SOHO. Also, the results were compared with the NOAA catalogue and achieved a precision of 98%. Performance measurement is also introduced and applied to verify results and evaluate proposal methods. Algorithms, implementation, results and future work have been explained in this thesis.
  • Design and Linearization of Energy Efficiency Power Amplifier in Nonlinear OFDM Transmitter for LTE-5G Applications. Simulation and measurements of energy efficiency power amplifier in the presence of nonlinear OFDM transmitter system and digital predistortion based on Hammerstein-Wiener method

    Abd-Alhameed, Raed A.; Mohammed, Buhari A. (University of BradfordFaculty of Engineering and Informatics, 2019)
    This research work has made an effort to understand a novel line of radio frequency power amplifiers (RFPAs) that address initiatives for efficiency enhancement and linearity compensation to harmonize the fifth generation (5G) campaign. The objective is to enhance the performance of an orthogonal frequency division multiplexing-long term evolution (OFDM-LTE) transmitter by reducing the nonlinear distortion of the RFPA. The first part of this work explores the design and implementation of 15.5 W class AB RF power amplifier, adopting a balanced technique to stimulate efficiency enhancement and redeeming exhibition of excessive power in the transmitter. Consequently, this work goes beyond improving efficiency over a linear RF power amplifier design; in which a comprehensive investigation on the fundamental and harmonic components of class F RF power amplifier using a load-pull approach to realise an optimum load impedance and the matching network is presented. The frequency bandwidth for both amplifiers was allocated to operate in the 2.620-2.690 GHz of mobile LTE applications. The second part explores the development of the behavioural model for the class AB power amplifier. A particular novel, Hammerstein-Wiener based model is proposed to describe the dynamic nonlinear behaviour of the power amplifier. The RF power amplifier nonlinear distortion is approximated using a new linear parameter approximation approach. The first and second-order Hammerstein-Wiener using the Normalised Least Mean Square Error (NLMSE) algorithm is used with the aim of easing the complexity of filtering process during linear memory cancellation. Moreover, an enhanced adaptive Wiener model is proposed to explore the nonlinear memory effect in the system. The proposed approach is able to balance between convergence speed and high-level accuracy when compared with behavioural modelling algorithms that are more complex in computation. Finally, the adaptive predistorter technique is implemented and verified in the OFDM transceiver test-bed. The results were compared against the computed one from MATLAB simulation for OFDM and 5G modulation transmitters. The results have confirmed the reliability of the model and the effectiveness of the proposed predistorter.
  • The Organic Material Culture of Western Ulster: An Ethno-historical and Heritage Science Approach

    Croucher, Karina T.; Wilson, Andrew S.; McElhinney, Peter J. (University of BradfordFaculty of Life Sciences, 2019)
    This research attempts to describe the material culture of the Gaelic labouring classes living in western Ulster in the Late Medieval period. The research combines ethnohistorical contextual and technical scientific analysis of ‘chance’ finds discovered in the region’s bogs. Technical analysis dates fifteen museum objects, characterises the materials from which they were made, and explores their cultural significance. Absolute dating indicates that one third of the 15 objects analysed relate to the Gaelic lordships of late medieval western Ulster, with the remainder reflecting aspects of Iron Age and Post-Medieval material culture and related cultural pracrices. Contextual analysis of the later medieval objects and their find locations provides new insights into Gaelic Irish culture and landscape interactions in this period and place. In addition, the research explores the trajectory of indigenous materiality in western Ulster beyond the Late Medieval period. To this end, the thesis examines the relationship between Late Medieval indigenous materiality, and the folk material culture that emerges in western Ulster in the Modern period.
  • Performance Analysis of Virtualisation in a Cloud Computing Platform. An application driven investigation into modelling and analysis of performance vs security trade-offs for virtualisation in OpenStack infrastructure as a service (IaaS) cloud computing platform architectures.

    Kouvatsos, Demetres D.; Kiran, Miriam; Kamala, Mumtaz A.; Maiyama, Kabiru M. (University of BradfordDepartment of Computer Science, Faculty of Engineering and Informatics, 2019)
    Virtualisation is one of the underlying technologies that led to the success of cloud computing platforms (CCPs). The technology, along with other features such as multitenancy allows delivering of computing resources in the form of service through efficient sharing of physical resources. As these resources are provided through virtualisation, a robust agreement is outlined for both the quantity and quality-of-service (QoS) in a service level agreement (SLA) documents. QoS is one of the essential components of SLA, where performance is one of its primary aspects. As the technology is progressively maturing and receiving massive acceptance, researchers from industry and academia continue to carry out novel theoretical and practical studies of various essential aspects of CCPs with significant levels of success. This thesis starts with the assessment of the current level of knowledge in the literature of cloud computing in general and CCPs in particular. In this context, a substantive literature review was carried out focusing on performance modelling, testing, analysis and evaluation of Infrastructure as a Service (IaaS), methodologies. To this end, a systematic mapping study (SMSs) of the literature was conducted. SMS guided the choice and direction of this research. The SMS was followed by the development of a novel open queueing network model (QNM) at equilibrium for the performance modelling and analysis of an OpenStack IaaS CCP. Moreover, it was assumed that an external arrival pattern is Poisson while the queueing stations provided exponentially distributed service times. Based on Jackson’s theorem, the model was exactly decomposed into individual M/M/c (c ≥ 1) stations. Each of these queueing stations was analysed in isolation, and closed-form expressions for key performance metrics, such as mean response time, throughput, server (resource) utilisation as well as bottleneck device were determined. Moreover, the research was extended with a proposed open QNM with a bursty external arrival pattern represented by a Compound Poisson Process (CPP) with geometrically distributed batches, or equivalently, variable Generalised Exponential (GE) interarrival and service times. Each queueing station had c (c ≥ 1) GE-type servers. Based on a generic maximum entropy (ME) product form approximation, the proposed open GE-type QNM was decomposed into individual GE/GE/c queueing stations with GE-type interarrival and service times. The evaluation of the performance metrics and bottleneck analysis of the QNM were determined, which provided vital insights for the capacity planning of existing CCP architectures as well as the design and development of new ones. The results also revealed, due to a significant impact on the burstiness of interarrival and service time processes, resulted in worst-case performance bounds scenarios, as appropriate. Finally, an investigation was carried out into modelling and analysis of performance and security trade-offs for a CCP architecture, based on a proposed generalised stochastic Petri net (GSPN) model with security-detection control model (SDCM). In this context, ‘optimal’ combined performance and security metrics were defined with both M-type or GE-type arrival and service times and the impact of security incidents on performance was assessed. Typical numerical experiments on the GSPN model were conducted and implemented using the Möbius package, and an ‘optimal’ trade-offs were determined between performance and security, which are crucial in the SLA of the cloud computing services.
  • Rethinking the design and implementation of financial services for poverty reduction: A case of Northern Ghana

    Arora, Rashmi; Anand, Prathivadi B.; Naab, Gilbert Z. (University of BradfordFaculty of Management, Law and Social Sciences, 2019)
    The thesis empirically examines how microfinance products are designed and implemented, and the implications for clients’ households and sources of livelihood. The study argues that the design of products and implementation that reflect the livelihood needs and poverty context of clients is one of the effective ways to reduce poverty. It investigates the microfinance operations of three financial institutions: Sinapi Aba Trust (SAT), St Joseph’s Cooperative Credit Union (CCU) and Sonzele Rural Bank (SRB) in Jirapa, a municipality in Northern Ghana. The study deployed a mixed-methods approach to collect data from six rural and urban communities. Data was sought from secondary sources, 20 interviews, 10 focus group discussions and 120 questionnaires. The research adopted the Sustainable Livelihoods and the Making Markets Work for the Poor approaches as a guide in the framework of analysis. The study, using qualitative and quantitative analytical tools found that product designs of SAT and SRB did not reflect the needs and poverty context of the majority of their clients. Clients of SAT and SRB were found to be less involved in the product design processes, suggesting a top-down institutional approach that seldom incorporated the needs of the poor. The method of group formation has a substantial implication on members’ poverty outcomes. Groups involving only females had a significant and positive relationship with members’ household and business outcomes, while members of male-only groups had a negative relationship with their household outcomes. The thesis concludes that accessible interest on loans and incentives to encourage savings would make microfinance markets work more sustainably for the rural poor. The findings challenge a reconsideration of the design of microfinance products to integrate financial technology as an efficient approach to deliver financial services, especially in rural areas.
  • Resilient and Sustainable Supply Chain Networks: A Case Study of the Perishable Food Industry in the US

    Mishra, Jyoti L.; Hussain, Zahid I.; Barber, Kevin D.; Drabble, Brian; Chiwenga, Kudzai D. (University of BradfordFaculty of Management, Law and Social Sciences, 2019)
    Contemporary supply chain management (SCM) issues are multiplex and continually evolving catalysed by complexities and dynamism. The perishable food industry exemplifies this phenomenon, driven by globalisation, technological advancements and a highly competitive business environment. Inescapably, food supply chains are increasingly operating as supply chain networks (SCN). SCNs are typified by a higher level of interdependence and connectivity amongst firms, consequently evolving from dyad and triad relationships, which have dominated SCM research. These changes generate divergent risks and vulnerabilities that perturb perishable food supply chains in unconventional ways. Thus, the purpose of this empirical study is to investigate how firms within a perishable food supply chain network can build resilience and sustainability. The research focuses on advancing the management of fast-moving consumer goods (FMCG). Methodologically, an empirical qualitative study is undertaken within a food manufacturer (focal firm) and 18 independent firms operating across all tiers of its SCN. Applying a pragmatic philosophical positioning, the study draws concepts from key supply chain theories to investigate the phenomena. The investigation uses Nicolini’s Zooming in and Zooming out as an analytical lens. The zooming in and out is established by shifting analytical lenses and re-positioning actors’ praxis, to ensure certain facets of their actions are fore-grounded while others are put in a background position and contrariwise moving the background to the foreground. The purpose of this technique is to draw meaning from everyday practices and trace the actions of actors across the entire SCN. The results uncover four distinct but intertwined main categories; whose subtle and often ignored interplay is crucial in attaining SCN resilience and sustainability. These main categories are Collaboration, Power Dynamics, SCN Culture and Information Systems. Current supply chain literature argues that collaboration is an essential enabler of resilience and sustainability. Building on this, the findings make a significant contribution by teasing out the intangible and predominately unacknowledged antecedents and salient sustaining factors of effective SCN collaboration. Furthermore, the study develops a resilience and sustainability (RS) matrix, which renders different impacts and outcomes of varying levels of SCN collaboration between firms operating in a perishable food SCN. Therefore, this thesis contributes knowledge towards constructing resilient and sustainable perishable food SCNs by proffering pragmatic propositions. These aim to address challenges facing industry stakeholders and ignite pertinent future research avenues for scholars.
  • Towards a multidimensional approach to measure quality and safety of care in maternity units in Oman

    Mohammed, Mohammed A.; Faisal, Muhammad; Al Nadabi, Waleed K.A. (University of BradfordFaculty of Health Studies, 2019)
    Improving the quality and safety of maternity services is an international top agenda item. This thesis describes the progress towards the development of a multidimensional approach to measure the quality and safety of care in ten maternity units in Oman based on three of the five dimensional Patient Safety Measurement and Monitoring Framework (PSMMF) which include measuring "past harm" and "anticipation and preparedness”. The three monitoring approaches used in this research are: (1) measuring the patient safety culture (2) measuring patient satisfaction (3) and monitoring caesarean section rates. The specific objectives of the research are to (1) measure patient safety culture level, (2) examine the association between nurse’s nationality and patient safety culture, (3) validate an Arabic language survey to measure maternal satisfaction about the childbearing experience, (4) measure patient satisfaction about the childbearing experience, and (5) to examine caesarean section rates across maternity units using statistical process control charts. This thesis started with four systematic reviews that focused on (1) the use of patient safety culture for monitoring maternity units (2) the available interventions to improve patient safety culture (3) Arabic surveys available for measuring maternal satisfaction and (4) the use of statistical process control charts for monitoring performance indicators. The overall conclusion from these reviews that these approaches are being increasingly used in maternity, found feasible and useful, and there are areas that need attention for future work. Five field studies were conducted to address the research aim and objectives. Patient safety culture was measured by a cross-sectional survey of all staff in the ten maternity units. It was found that safety culture in Oman is below the target level and that there is wide variation in the safety scores across hospitals and across different categories of staff. Non-Omani nurses have a more positive perception of patient safety culture than Omani nurses in all domains except in respect of stress recognition and this difference need further investigation and needs to be considered by designers of interventions to enhance patient safety culture. Using two existing validated English surveys, an Arabic survey was developed, validated, and used to measure maternal satisfaction with childbirth services. It was found that the new survey has good psychometric properties and that in all the ten hospitals, mothers were satisfied with the care provided during child delivery but satisfaction score varied across hospitals and groups of participants. Caesarean section rate in the last 17 years was examined using statistical process control charts to understand the variation across the ten hospitals. It was found that caesarean section rate is above the rate recommended by the World Health Organisation. Special cause variations were detected that warrant further investigation. In conclusion, the field studies demonstrated that it is feasible to use the three approaches to monitor quality and safety in maternity units. However, further work is required to use these data to enhance the quality and safety of care. Additionally, future work is needed to cover the other three dimensions of the PSMMF.
  • Development and Feasibility of a Measure of Self in Dementia

    Smith, Sarah J.; Oyebode, Jan R.; Surr, Claire A.; Bradley, Rosemary J.
    Methods A standardised measurement tool was developed by identifying aspects of self that can be measured, and research methods that are effective at investigating self in people without dementia. The measure consists of three sets of illustrated ‘I am…’ statements representing Activities, Traits and Physical Characteristics, and Relationships and Occupations. Participants were asked to (i) sort these according to whether each was ‘just like me’, ‘a bit like me’ or ‘not at all like me’ (ii) sort their ‘just like me’ choices to identify the statement most like them; (iii) describe memories associated with this statement. The measure was tested with 20 people with dementia to inform refinement. The refined measure was tested for reliability and validity by comparing results from five people with dementia and six age-matched people without dementia. Results Outcome measures were strength, complexity and quality of self and an ‘episodicity’ score reflecting the descriptive richness of memories. The initial administration to 20 people indicated that the measure was suitable for people with mild to moderate dementia, and the outcomes were meaningful and reliable. An ‘Observational Framework’ was developed to enable measurement of self via gestures and expressions of people with limited verbal abilities. The second study indicated that the new measure has good test-retest reliability, but convergent validity was not demonstrated. Participants with dementia demonstrated strength, complexity and quality of self scores comparable to participants without dementia. The results suggest that providing visual cues bypasses the cognitive processes required for effortful recall.
  • An Investigation of Group Key Management with Mobility Protocol for 5G Wireless Mobile Environment. A Case analysis of group key management security requirements with respect to wireless mobile environment of different proposed solutions

    Abd-Alhameed, Raed A.; Shepherd, Simon J.; Noras, James M.; Eya, Nnabuike N. (University of BradfordSchool of Engineering and Informatics, 2019)
    Group communication, security and 5G technology present a unique dimension of challenges and security remains crucial in the successful deployment of 5G technology across different industry. Group key management plays a vital role in secure group communication. This research work studies various group key management schemes for mobile wireless technology and then a new scheme is proposed and evaluated. The main architecture is analysed, while the components and their roles are established, trust and keying relationships are evaluated, as well as detailed functional requirements. A detailed description of the main protocols required within the scheme is also described. A numerical and simulation analysis is employed to assess the proposed scheme with regards to fulfilling the security requirement and performance requirements. The impact of group size variation, the impact of mobility rate variation are studied with regards to the average rekeying messages induced by each event and 1-affects-n phenomenon. The results obtained from the simulation experiments show that the proposed scheme outperformed other solutions with a minimal number of rekeying messages sent and less number of affected members on each event. The security requirements demonstrate that backward and forward secrecy is preserved and maintained during mobility between areas. Finally, the research work also proposes a 5G-enabled software-defined multicast network (5G-SDMNs), where software-defined networking (SDN) is exploited to dynamically manage multicast groups in 5G and mobile multicast environment. Also, mobile edge computing (MEC) is exploited to strengthen network control of 5G-SDMN.
  • Security and Performance Engineering of Scalable Cognitive Radio Networks. Sensing, Performance and Security Modelling and Analysis of ’Optimal’ Trade-offs for Detection of Attacks and Congestion Control in Scalable Cognitive Radio Networks

    Kouvatsos, Demetres D.; Chuku, Ejike E. (University of BradfordSchool of Engineering and Informatics, 2019)
    A Cognitive Radio Network (CRN) is a technology that allows unlicensed users to utilise licensed spectrum by detecting an idle band through sensing. How- ever, most research studies on CRNs have been carried out without considering the impact of sensing on the performance and security of CRNs. Sensing is essential for secondary users (SUs) to get hold of free band without interfering with the signal generated by primary users (PUs). However, excessive sensing time for the detection of free spectrum for SUs as well as extended periods of CRNs in an insecure state have adverse effects on network performance. Moreover, a CRN is very vulnerable to attacks as a result of its wireless nature and other unique characteristics such as spectrum sensing and sharing. These attacks may attempt to eavesdrop or modify the contents of packets being transmitted and they could also deny legitimate users the opportunity to use the band, leading to underutilization of the spectrum space. In this context, it is often challenging to differentiate between networks under Denial of Service (DoS) attacks from those networks experiencing congestion. This thesis employs a novel Stochastic Activity Network (SAN) model as an effective analytic tool to represent and study sensing vs performance vs security trade-offs in CRNs. Specifically, an investigation is carried out focusing on sensing vs security vs performance trade-offs, leading to the optimization of the spectrum band’s usage. Moreover, consideration is given either when a CRN experiencing congestion and or it is under attack. Consequently, the data delivery ratio (PDR) is employed to determine if the network is under DoS attack or experiencing congestion. In this context, packet loss probability, queue length and throughput of the transmitter are often used to measure the PDR with reference to interarrival times of PUs. Furthermore, this thesis takes into consideration the impact of scalability on the performance of the CRN. Due to the unpredictable nature of PUsactivities on the spectrum, it is imperative for SUs to swiftly utilize the band as soon as it becomes available. Unfortunately, the CRN models proposed in literature are static and unable to respond effectively to changes in service demands. To this end, a numerical simulation experiment is carried out to determine the impact of scalability towards the enhancement of nodal CRN sensing, security and performance. Atthe instant the band becomes idle and there are requests by SUs waiting for encryption and transmission, additional resources are dynamically released in order to largely utilize the spectrum space before the reappearance of PUs. These additional resources make the same service provision, such as encryption and intrusion detection, as the initial resources. To this end,SAN model is proposed in order to investigate the impact of scalability on the performance of CRN. Typical numerical simulation experiments are carried out, based on the application of the Mobius Petri Net Package to determine the performance of scalable CRNs (SCRNs) in comparison with unscalable CRNs (UCRNs) and associated interpretations are made.
  • Contributions to evaluation of machine learning models. Applicability domain of classification models

    Neagu, Daniel; Rado, Omesaad A.M. (University of BradfordFaculty of Engineering and Informatics, 2019)
    Artificial intelligence (AI) and machine learning (ML) present some application opportunities and challenges that can be framed as learning problems. The performance of machine learning models depends on algorithms and the data. Moreover, learning algorithms create a model of reality through learning and testing with data processes, and their performance shows an agreement degree of their assumed model with reality. ML algorithms have been successfully used in numerous classification problems. With the developing popularity of using ML models for many purposes in different domains, the validation of such predictive models is currently required more formally. Traditionally, there are many studies related to model evaluation, robustness, reliability, and the quality of the data and the data-driven models. However, those studies do not consider the concept of the applicability domain (AD) yet. The issue is that the AD is not often well defined, or it is not defined at all in many fields. This work investigates the robustness of ML classification models from the applicability domain perspective. A standard definition of applicability domain regards the spaces in which the model provides results with specific reliability. The main aim of this study is to investigate the connection between the applicability domain approach and the classification model performance. We are examining the usefulness of assessing the AD for the classification model, i.e. reliability, reuse, robustness of classifiers. The work is implemented using three approaches, and these approaches are conducted in three various attempts: firstly, assessing the applicability domain for the classification model; secondly, investigating the robustness of the classification model based on the applicability domain approach; thirdly, selecting an optimal model using Pareto optimality. The experiments in this work are illustrated by considering different machine learning algorithms for binary and multi-class classifications for healthcare datasets from public benchmark data repositories. In the first approach, the decision trees algorithm (DT) is used for the classification of data in the classification stage. The feature selection method is applied to choose features for classification. The obtained classifiers are used in the third approach for selection of models using Pareto optimality. The second approach is implemented using three steps; namely, building classification model; generating synthetic data; and evaluating the obtained results. The results obtained from the study provide an understanding of how the proposed approach can help to define the model’s robustness and the applicability domain, for providing reliable outputs. These approaches open opportunities for classification data and model management. The proposed algorithms are implemented through a set of experiments on classification accuracy of instances, which fall in the domain of the model. For the first approach, by considering all the features, the highest accuracy obtained is 0.98, with thresholds average of 0.34 for Breast cancer dataset. After applying recursive feature elimination (RFE) method, the accuracy is 0.96% with 0.27 thresholds average. For the robustness of the classification model based on the applicability domain approach, the minimum accuracy is 0.62% for Indian Liver Patient data at r=0.10, and the maximum accuracy is 0.99% for Thyroid dataset at r=0.10. For the selection of an optimal model using Pareto optimality, the optimally selected classifier gives the accuracy of 0.94% with 0.35 thresholds average. This research investigates critical aspects of the applicability domain as related to the robustness of classification ML algorithms. However, the performance of machine learning techniques depends on the degree of reliable predictions of the model. In the literature, the robustness of the ML model can be defined as the ability of the model to provide the testing error close to the training error. Moreover, the properties can describe the stability of the model performance when being tested on the new datasets. Concluding, this thesis introduced the concept of applicability domain for classifiers and tested the use of this concept with some case studies on health-related public benchmark datasets.
  • Multiuser Multi Input Single Output (MU-MISO) Beamforming for 5G Wireless and Mobile Networks. A Road Map for Fast and Low Complexity User Selection, Beamforming Scheme Through a MU-MISO for 5G Wireless and Mobile Networks

    Abd-Alhameed, Raed A.; Hameed, Khalid W.H. (University of BradfordFaculty of Engineering and Informatics, 2019)
    Multi-User Multi-Input Multi-Output (MU-MIMO) systems are considered to be the sustainable technologies of the current and future of the upcoming wireless and mobile networks generations. The perspectives of these technologies under several scenarios is the focus of the present thesis. The initial system model covers the MU-MIMO, especially in the massive form that is considered to be the promising ideas and pillars of the 5G network. It is observed that the optimal number of users should be served in the time-frequency resource even though the maximum limitation of the MU-MIMO is governed by the total receiving antennas (K) is less than or equal to the base station antennas (M). The system capacity of the massive MIMO (mMIMO) under perfect channel state information (CSI) of uncorrelated channel is investigated and studied. Two types of precoders were applied, one is directly based on channel inversion, and the other uses the Eigen decomposition that is derived subject to the signal to a leakage maximization problem. The two precoders show a degree of equivalency under certain assumptions for the number of antennas at the user end. The convex optimization of multi-antenna networks to achieve the design model of optimum beamformer (BF) based on the uniform linear array (ULA) is studied. The ULA is selected for its simplicity to analyse many scenarios and its importance to match the future network applied millimetre wave (mmWave) spectrum. The maximum beams generated by the ULA are explored in terms of several physical system parameters. The duality between the MU-MIMO and ULA and how they are related based on beamformer operation are detailed and discussed. Finally, two approaches for overloaded systems are presented when the availability of massive array that is not guaranteed due to physical restrictions since the existence of a large number of devices will result in breaking the dimension rule (i.e., K ≤ M). As a solution, a low complexity users selection algorithm is proposed. The channel considered is uncorrelated with full and perfect knowledge at the BS. In particular, these two channel conditions may not be available in all scenarios. The CSI may be imperfect, and even the instantaneous form does not exist. A hybrid precoder between the mixed CSI (includes imperfect and statistical) and rate splitting approach is proposed to deal with an overloaded system under a low number of BS antennas.
  • A qualitative exploration of autism and transition into further and higher education

    Rogers, Chrissie; Simmons, Amy L. (University of BradfordFaculty of Management, Law and Social Sciences, School of Social Sciences, 2019)
    In this thesis, I explore 42 autistic individuals’ transitions into further and higher education (FHE) in England, drawing on personal experience as well as interview data. I was diagnosed with Asperger’s Syndrome in 1998 at the age of 13. At the age of 15, my mother introduced the topic to me, and autism soon became the foundation of my socio-political identity. The discussion is divided into three themes; stigma and perception management strategies, formal and informal support networks and the interplay of autism with institutional factors. I draw upon Tringo’s (1970) work on the hierarchy of impairment and Goffman’s (1963) work on stigma. Tringo’s (1970) hierarchy of impairment led me to my intra-communal hierarchy of impairment (perpetuated by autistic individuals against autistic individuals) and Goffman’s (1963) work on stigma led me to my four degrees of openness; autistic individuals can be indiscriminately open, or indiscriminately reticent, but openness if relevant, and openness if necessary, are more common strategies. UPIAS’ (1976) work on the social model of disability laid the foundation for my socio-political identity and this thesis. I argue autism has been largely absent from the political arena. I outline how there are four ideals; the ideals of self-regulation, normalcy, ability and independence. Eager to conform to these ideals, eager to self-present as ‘independent’, ‘self-regulating’, ‘normal’ or ‘capable’, some autistic students are reluctant to request support and accommodations, complicating the transition to FHE.
  • A study of the relationships of power between humanitarian workers and local leaders in Haiti

    Kelly, Rhys H.S.; Quintiliani, Pierrette (University of BradfordFaculty of Social Sciences and Humanities, 2018)
    Like many former colonised countries, Haiti has been plagued by insecurity and conflicts caused by internal and external influences as well as natural disasters. In 1804, after a protracted conflict between slaves and French colonialists, Haiti became the first black country to gain its independence through a revolution. Today, Haiti is the poorest country in the Western hemisphere, ranking 153rd on the Human Development Index and a significant number of humanitarian organisations are present on the island aspiring at improving the standard of living of the population. The following study examines how the relationships of power emerging through the relationship between humanitarian and local leaders affect their perceptions of each other and identified the emotions emerging from these perceptions. The perceptions identified are the coloniality of power, corruption and distrust, the occurrence of conspiracy theories and the obstacles encountered in the implementation of a relief-development continuum model envisioned by general humanitarian policies. These perceptions create tensions between the humanitarian and local leaders, contributing to fuelling negative emotions such as regret, sadness, sense of failure, disappointment and anger. Negative emotions in this study affect the collaboration between humanitarians and local leaders, diminishing the positive influences and impact of humanitarian action on the well-being of the Haitian population. One of the components to increase these positive influences of humanitarian action is to lessen the asymmetricality of power between humanitarian and local leaders through the adoption of a Cultural Competence model by humanitarians.
  • Examining causal effects of Emotional Intelligence on human related challenges occurring in Agile managed Information Systems projects

    Sivarajah, Uthayasankar; Weerakkody, Vishanth J.P.; Luong, Tan T. (University of BradfordFaculty of Management and Law, 2020)
    Agile project management has become a widely implemented project management approach in Information Systems (IS). Yet, along with its growing popularity, the amount of concerns raised in regard to human related challenges is rapidly increasing. Nevertheless, the extant scholarly literature has neglected to identify the primary origins and reasons of these challenges. The purpose of this study is therefore to examine if these challenges are caused by a lack of Emotional Intelligence (EI) by means of a quantitative approach, which includes two main steps. Firstly, based on a sample of 447 IS-professionals, the psychometric properties of their EI in regard to their personal characteristics is examined. Secondly, based on the findings of the first analysis, the causal inference of EI on these challenges is computed using Propensity Score Matching based on a second sample of 194 agile practitioners. Different dimensions of EI were found to have a low to medium impact on human related challenges occurring in agile teams in regard to anxiety, motivation, mutual trust and communication competence. Hence, these findings offer important new knowledge for IS-scholars, project managers and human resource practitioners, about the vital role of EI for educating, staffing and training of IS-professionals working in agile teams.
  • Bond Performance between Corroded Steel and Recycled Aggregate Concrete Incorporating Nano Silica

    Ashour, Ashraf F.; Alhawat, Musab M. (University of BradfordFaculty of Engineering and Informatics, 2020)
    The current research project mainly aims to investigate the corrosion resistance and bond performance of steel reinforced recycled aggregate concrete incorporating nano-silica under both normal and corrosive environmental conditions. The experimental part includes testing of 180 pull-out specimens prepared from 12 different mixtures. The main parameters studied were the amount of recycled aggregate (RCA) (i.e. 0%, 25%, 50% and 100%), nano silica (1.5% and 3%), steel embedment length as well as steel bar diameter (12 and 20mm). Different levels of corrosion were electrochemically induced by applying impressed voltage technique for 2, 5, 10 and 15 days. The experimental observations mainly focused on the corrosion level in addition to the ultimate bond, failure modes and slips occurred. Experimental results showed that the bond performance between un-corroded steel and recycled aggregate concrete slightly reduced, while a significant degradation was observed after being exposed to corrosive conditions, in comparison to normal concrete. On the other hand, the use of nano silica (NS) showed a reasonable bond enhancement with both normal and RCA concretes under normal conditions. However, much better influence in terms of bond and corrosion resistance was observed under advancing levels of corrosion exposure, reflecting the improvement in corrosion resistance. Therefore, NS was superbly effective in recovering the poor performance in bond for RCA concretes. More efficiency was reported with RCA concretes compared to the conventional concrete. The bond resistance slightly with a small amount of corrosion (almost 2% weight loss), then a significant bond degradation occurs with further corrosion. The influence of specific surface area and amount of nano silica on the performance of concrete with different water/binder (w/b) ratios has been also studied, using 63 different mixtures produced with three different types of colloidal NS having various surface areas and particle sizes. The results showed that the performance of concrete is heavily influenced by changing the surface area of nano silica. Amongst the three used types of nano silica, NS with SSA of 250 m2 /g achieved the highest enhancement rate in terms of compressive strength, water absorption and microstructure analysis, followed by NS with SSA of 500 m2/g, whilst NS with SSA of 51.4 m2 /g was less advantageous for all mixtures. The optimum nano silica ratio in concrete is affected by its particle size as well as water to binder ratio. The feasibility of the impact-echo method for identifying the corrosion was evaluated and compared to the corrosion obtained by mass loss method. The results showed that the impact-echo testing can be effectively used to qualitatively detect the damage caused by corrosion in reinforced concrete structures. A significant difference in the dominant frequencies response was observed after exposure to the high and moderate levels of corrosion, whilst no clear trend was observed at the initial stage of corrosion. Artificial neural network models were also developed to predict bond strength for corroded/uncorroded steel bars in concrete using the main influencing parameters (i.e., concrete strength, concrete cover, bar diameter, embedment length and corrosion rate). The developed models were able to predict the bond strength with a high level of accuracy, which was confirmed by conducting a parametric study.
  • The Construction of Care in Computed Tomography. Exploring Care from the Perspective of Patients and Radiographers

    Not given; Forton, Rachael K. (University of BradfordFaculty of Health Studies, 2019)
    Purpose: Patient centred care and the ‘patient voice’ are core components of UK healthcare policy and practice guidance. This study explores how care is perceived and experienced within the high technology environment of CT. Methods and Materials: A two-phase approach of Critical Discourse Analysis (CDA) and adapted Grounded Theory (GT) methodology using semi structured interviews, was used to obtain primary data from CT radiographers and patients. Recruitment and data collection were performed at a 1200 bed teaching hospital over a 6-month period. Results: The radiographer patient relationship and the radiographer’s role in providing care within CT are complex and multifaceted. Both patients and radiographer’s perceive CT imaging to be an integral part of the overall patient care and treatment pathway. As such, the act of being imaged is perceived as a care process and while image acquisition is recognised as a task orientated and technical process, the human element of providing care is cognitive, dynamic and responsive to individual need. Importantly, patient confidence in the care received was influenced by the radiographer’s ability to build a trusting relationship and display technical competence and this in turn facilitated active compliance resulting in a technically accurate examination. Despite previous literature suggesting that the technical environment created a barrier to patient care, patients within this study confirmed that radiographers provide care commensurate to the nursing ideals represented by the 6C’s (Care; Compassion; Competence; Communication; Courage; Commitment). Conclusions: A co-constructed model of care encompassing both technical components and patient-centeredness has been identified. This model promotes a new vision of patient centred care based on care perceptions within the high technology environment of CT.

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