No / Coalescence enhancement of water droplets in oil emulsions is commonly contemplated for the separation of an aqueous phase dispersed in a dielectric oil phase with a considerably lower dielectric constant than that of the dispersed phase. The characteristics and geometry of the electrode system have a large impact on the performance of an electrostatic coalescer and are actually strictly linked to the type of the applied electric field and the emulsion used. Furthermore, addition of chemicals and heating has also been revealed to further enhance the electrocoalescence of water droplets. In this work, the coalescence of two water drops sinking in a dielectric oil phase at an applied high voltage, pulsed dc electric field, in particular with regards to the effects of pressure and temperature on coalescence performance is investigated. The developed model should help to recognise and prove approaches to electrocoalescence mechanisms, the dispersion flow direction with respect to the applied electric field, as well as the electric field configuration.

The British cattle population hosts a diverse community of endemic pathogens that impact the sustainability of beef and dairy production. As such, there has been a tremendous amount of ongoing research to develop more cost-effective strategies for controlling disease at the industry level. Cattle movements have come under particular scrutiny over the past decade both because of their role in spreading many economically important diseases and because the movements of individual cattle in Great Britain have been explicitly recorded in a centralized electronic database since 1998. Numerous studies have shown that these cattle movements organize into complex networks with key structural and temporal features that influence transmission dynamics. Building on previous work, this thesis used a variety of epidemiological and statistical models to highlight limitations in the current approaches to controlling disease as well as opportunities for reducing endemic disease prevalence through targeted interventions. Empirical disease data from the national bovine tuberculosis (bTB) control programme and from two seroprevalence studies of bovine viral diarrhoea virus (BVDV) in Scottish cattle herds were used in conjunction with movement data from the Cattle Tracing System (CTS) database. Endemic diseases are often challenging to control due to lack of affordable and accurate diagnostic tests as well as the presence of subclinically infected carriers that can easily escape detection. There was evidence that combined issues with the sensitivity and specificity of routine surveillance methods for bTB were contributing to a low level of disease transmission within and between Scottish cattle herds from 2002 to 2009. For BVDV, herds that purchased pregnant beef dams, beef dams with a calf at foot, and open dairy heifers were significantly more likely to be seropositive even though these movements were responsible for only a small number of network contacts. In both cases, targeting the subset of high risk movements with disease specific biosecurity measures may be a more cost-effective use of limited national disease control resources. Other researchers have suggested that control strategies should target multiple diseases simultaneously to reduce trade-offs in resource allocation. Using key indicators of herd reproductive performance derived from the CTS database, it was shown that improving the reproductive management of herds operating below industry standards could reduce endemic disease prevalence by reducing the movements of replacement breeding cattle. A series of network generation algorithms were also developed to study the effects of restricting contact formation based on key demographic and network characteristics of actively trading cattle farms. Strategies that increased network fragmentation either by forcing highly connected farms to form contacts with other highly connected farms or preventing the formation of movements with a high predicted betweenness centrality were found to be particularly effective in limiting disease transmission. For these models to be useful in guiding future policy decisions, it is important to incorporate financial and behavioural drivers of dynamic network change. Following the introduction of pre- and post-movement testing requirements for cattle imported into Scotland from endemic bTB regions, there was a significant decline in cross-border movements, which has likely contributed to the decreasing risk of bTB outbreaks as much as testing itself. Many endemic cattle diseases such as BVDV also spread through local transmission mechanisms, which may undermine the success of disease control programmes that exclusively target cattle movements. There was also evidence that in the absence of national animal legislation, few farmers were likely to adopt biosecurity measures against BVDV. This may be related to the perceived inefficacy of recommendations as well as general unawareness of farm disease status due to the non-specific clinical signs of BVDV outbreaks. Although the CTS database was originally intended for use in slaughter traceback investigations, results from this thesis show how the basic records of births, deaths, and movements can be used to generate valuable insights into the epidemiology of endemic cattle diseases. The findings also emphasize that the management decisions of individual herds can have a substantial impact on industry level transmission dynamics, which offers unique opportunities to develop novel and more cost-effective disease control programmes.

High-speed transmission over contemporary communication networks has drawn many research efforts. Traffic scheduling schemes which play a critical role in managing network transmission have been pervasively studied and widely implemented in various practical communication networks. In a sophisticated communication system, a variety of applications co-exist and require differentiated Quality-of-Service (QoS). Innovative scheduling schemes and hybrid scheduling disciplines which integrate multiple traditional scheduling mechanisms have emerged for QoS differentiation. This study aims to develop novel analytical models for commonly interested scheduling schemes in communication systems under more realistic network traffic and use the models to investigate the issues of design and development of traffic scheduling schemes. In the open literature, it is commonly recognized that network traffic exhibits self-similar nature, which has serious impact on the performance of communication networks and protocols. To have a deep study of self-similar traffic, the real-world traffic datasets are measured and evaluated in this study. The results reveal that selfsimilar traffic is a ubiquitous phenomenon in high-speed communication networks and highlight the importance of the developed analytical models under self-similar traffic. The original analytical models are then developed for the centralized scheduling schemes including the Deficit Round Robin, the hybrid PQGPS which integrates the traditional Priority Queueing (PQ) and Generalized Processor Sharing (GPS) schemes, and the Automatic Repeat reQuest (ARQ) forward error control discipline in the presence of self-similar traffic. Most recently, research on the innovative Cognitive Radio (CR) techniques in wireless networks is popular. However, most of the existing analytical models still employ the traditional Poisson traffic to examine the performance of CR involved systems. In addition, few studies have been reported for estimating the residual service left by primary users. Instead, extensive existing studies use an ON/OFF source to model the residual service regardless of the primary traffic. In this thesis, a PQ theory is adopted to investigate and model the possible service left by selfsimilar primary traffic and derive the queue length distribution of individual secondary users under the distributed spectrum random access protocol.

The structural performance of Rounded Dovetail Connections (RDC) has been studied experimentally and numerically to provide information needed for connection structural design. RDC are mainly used to transfer vertical shear forces, but test results show that they can carry considerable load in tension and bending. Geometric parameters, such as dovetail flange angle and dovetail height are shown to significantly effect affect the structural performance of RDC. Results show that it is impractical to determine a set of empirical equations to describe the structural performance of RDC based on basic wood material properties. RDC manufactured and tested with low and constant moisture content outperformed those evaluated under other climatic conditions, and test results demonstrate that RDC should be produced at low machine speed and with minimal a gap between the connecting members. RDC in laminated strand lumber have higher capacity and fail under larger deformations compared to RDC in western hemlock. A three-dimensional finite element method model is presented and validated with experimental tests. Good agreement is achieved between the load deformation response predicted by the model and the experimentally observed load deformation response. Therefore the model is deemed suitable for estimating the stresses needed to develop failure criteria. A failure criterion for the analysis of RDC is presented taking into account size effect in the strength of wood. Based on the experimental and numerical studies, a design equation for RDC is presented that provides the engineering community with a new design tool. Finally, self tapping screws as reinforcement have been studied and are shown to significantly improve the structural performance of RDC under vertical shear loading.

The structural performance of Rounded Dovetail Connections (RDC) has been studied experimentally and numerically to provide information needed for connection structural design. RDC are mainly used to transfer vertical shear forces, but test results show that they can carry considerable load in tension and bending. Geometric parameters, such as dovetail flange angle and dovetail height are shown to significantly effect affect the structural performance of RDC. Results show that it is impractical to determine a set of empirical equations to describe the structural performance of RDC based on basic wood material properties. RDC manufactured and tested with low and constant moisture content outperformed those evaluated under other climatic conditions, and test results demonstrate that RDC should be produced at low machine speed and with minimal a gap between the connecting members. RDC in laminated strand lumber have higher capacity and fail under larger deformations compared to RDC in western hemlock. A three-dimensional finite element method model is presented and validated with experimental tests. Good agreement is achieved between the load deformation response predicted by the model and the experimentally observed load deformation response. Therefore the model is deemed suitable for estimating the stresses needed to develop failure criteria. A failure criterion for the analysis of RDC is presented taking into account size effect in the strength of wood. Based on the experimental and numerical studies, a design equation for RDC is presented that provides the engineering community with a new design tool. Finally, self tapping screws as reinforcement have been studied and are shown to significantly improve the structural performance of RDC under vertical shear loading.

The structural performance of Rounded Dovetail Connections (RDC) has been studied experimentally and numerically to provide information needed for connection structural design. RDC are mainly used to transfer vertical shear forces, but test results show that they can carry considerable load in tension and bending. Geometric parameters, such as dovetail flange angle and dovetail height are shown to significantly effect affect the structural performance of RDC. Results show that it is impractical to determine a set of empirical equations to describe the structural performance of RDC based on basic wood material properties. RDC manufactured and tested with low and constant moisture content outperformed those evaluated under other climatic conditions, and test results demonstrate that RDC should be produced at low machine speed and with minimal a gap between the connecting members. RDC in laminated strand lumber have higher capacity and fail under larger deformations compared to RDC in western hemlock. A three-dimensional finite element method model is presented and validated with experimental tests. Good agreement is achieved between the load deformation response predicted by the model and the experimentally observed load deformation response. Therefore the model is deemed suitable for estimating the stresses needed to develop failure criteria. A failure criterion for the analysis of RDC is presented taking into account size effect in the strength of wood. Based on the experimental and numerical studies, a design equation for RDC is presented that provides the engineering community with a new design tool. Finally, self tapping screws as reinforcement have been studied and are shown to significantly improve the structural performance of RDC under vertical shear loading. / Forestry, Faculty of / Graduate

Yes / Cooling towers are a relatively inexpensive and consistent method of ejecting heat from several industries such as thermal power plants, refineries, and food processing. In this research, an earlier model from literature was to be validated across three different case studies. Unlike previous models, this model considers the height of the fill as the discretised domain, which produces results that give it in a distribution form along the height of the tower. As there are limitations with the software used (gPROMS) where differential equations with respect to independent variables in the numerator and denominator cannot be solved, a derivative of the saturation vapour pressure with respect to the temperature of the air was presented. Results shown were in agreement with the literature and a parametric sensitivity analysis of the cooling tower design and operating parameters were undertaken. In this work the height of fill, mass flowrates of water and air were studied with respect to sensitivity analysis. Results had shown large variations in the outlet temperatures of the water and air if the mass flows of water and air were significantly reduced. However, upon high values of either variable had shown only small gains in the rejection of heat from the water stream. With respect to the height of the fill, at larger heights of the fill, the outlet water temperature had reduced significantly. From a cost perspective, it was found that a change in the water flowrate had incurred the largest cost penalty with a 1% increase in flowrate had increased the average operating cost by 1.2%. In comparison, a change in air flowrate where a 1% increase in flowrate had yielded an average of 0.4% increase in operating cost.

Yes / Sustainable operations management (SOM) can be defined as the operations strategies, tactics and techniques, and operational policies to support both economic and environmental objectives and goals. The subject of sustainability has gained much attention from both researchers and practitioners in the past 6–8 years. Most of the articles deal with sustainability from environmental perspectives, but a limited number of them integrate both economic and environmental implications or focus on trading-off between profitability, competitiveness and environmental dimensions. Moreover, there is a limited focus on modelling and analysis (MA) of SOM integrating and balancing the interests of both economic and environmental interests. Therefore, an attempt has been made in this paper to review the extant literature on SOM. The objective is to understand the definition of SOM and present the current status of research in MA, as well as future research directions in the field. Considering the recent focus of the subject, we review the literature on MA of SOM beginning in 2000 in order to make our study current and more relevant for both researchers and practitioners. Finally, a summary of findings and conclusions is reported.

No / In visual search experiments, the subject looks for a target item in a display containing different distractor items. The reaction time (RT) to find the target is measured as a function of the number of distractors (set size). RT is either constant, or increases linearly, with set size. Here we suggest a two-stage model for search in which items are first selected and then recognized. The selection process is modeled by (a) grouping items into a hierarchical cluster tree, in which each cluster node contains a list of all the features of items in the cluster, called the object file, and (b) recursively searching the tree by comparing target features to the cluster object file to quickly determine whether the cluster could contain the target. This model is able to account for both constant and linear RT versus set size functions. In addition, it provides a simple and accurate account of conjunction searches (e.g., looking for a red N among red Os and green Ns), in particular the variation in search rate as the distractor ratio is varied.

The convergence of multiservice heterogeneous networks and ever increasing Internet applications, like peer to peer networking and the increased number of users and services, demand a more efficient bandwidth allocation in optical networks. In this context, new architectures and protocols are needed in conjuction with cost effective quantitative methodologies in order to provide an insight into the performance aspects of the next and future generation Internets. This thesis reports an investigation, based on efficient simulation methodologies, in order to assess existing high performance algorithms and to propose new ones. The analysis of the traffic characteristics of an OC-192 link (9953.28 Mbps) is initially conducted, a requirement due to the discovery of self-similar long-range dependent properties in network traffic, and the suitability of the GE distribution for modelling interarrival times of bursty traffic in short time scales is presented. Consequently, using a heuristic approach, the self-similar properties of the GE/G/∞ are being presented, providing a method to generate self-similar traffic that takes into consideration burstiness in small time scales. A description of the state of the art in optical networking providing a deeper insight into the current technologies, protocols and architectures in the field, which creates the motivation for more research into the promising switching technique of 'Optical Burst Switching' (OBS). An investigation into the performance impact of various burst assembly strategies on an OBS edge node's mean buffer length is conducted. Realistic traffic characteristics are considered based on the analysis of the OC-192 backbone traffic traces. In addition the effect of burstiness in the small time scales on mean assembly time and burst size distribution is investigated. A new Dynamic OBS Offset Allocation Protocol is devised and favourable comparisons are carried out between the proposed OBS protocol and the Just Enough Time (JET) protocol, in terms of mean queue length, blocking and throughput. Finally the research focuses on simulation methodologies employed throughout the thesis using the Graphics Processing Unit (GPU) on a commercial NVidia GeForce 8800 GTX, which was initially designed for gaming computers. Parallel generators of Optical Bursts are implemented and simulated in 'Compute Unified Device Architecture' (CUDA) and compared with simulations run on general-purpose CPU proving the GPU to be a cost-effective platform which can significantly speed-up calculations in order to make simulations of more complex and demanding networks easier to develop.