D. Ing. / Power electronics refers to electronic processing of electrical power. In this process the electrical power is controlled by switching of power semiconductor devices as well as electromagnetically stored in electrical and magnetic fields while the energy flow is directed through selective conduction paths. The losses/power-efficiency of all these actions is of paramount importance in the processing. The lack for standardisation and the absence of a modular approach is a barrier to the development of more compact systems. Recently more research resources have been invested in development of integrated power electronic modules as an attempt to solve this problem. By integrating power electronic components, an increase in the power density is achieved, which unfortunately also leads to higher internal heat-generation and higher operating temperatures. This has an unfavourable effect on electronic behaviour and the reliability of the structures. In order to maintain the advances made in volume reduction of integrated power electronics, efficient and cost effective methods for removing heat is of essence. In this investigation the performance of rectangular cross-section embedded solid-state heatextraction inserts to increase thermal heat spreading and the reduction of steady-state peak temperatures was evaluated theoretically and experimentally. Theoretically, the cross sectional aspect ratio of such inserts was thermally optimised for a wide range of dimensional, thermal, and material property conditions. Possible materials investigated for use as heat extractors in power electronics include aluminium nitride, beryllium oxide, and synthetic diamond. The presence of interfacial thermal resistance was theoretically found to have a significant detrimental influence on the thermal performance of an integrated heat-extraction system and should be minimised as far as possible. For conditions commonly found in integrated power passives, continuous embedded heatextraction layers are proposed. Theoretically it is shown that such inserts can aid in the increase of power density by reducing the temperature increase per unit volume of heat-generation. Experimental test results corresponded closely with the theoretically expected allowed increase in heat-generation that could be accommodated due to the heat-extraction action of the inserts. As an experimental system, insertion of aluminium nitride into ferrite in an integrated electromagnetic power passive module was investigated. An increase of 187% in the effective power density could be achieved due to the presence of aluminium nitride heat-extraction layers embedded into ferrite. Preliminary magnetic flux density optimisation, in terms of the volume fraction occupied by a parallel-layered heat-extraction system, was performed for a wide range of heat-extraction materials, and interfacial resistance values.

Le travail développé se place dans le contexte de l'identification thermique et du contrôle non destructif des systèmes. L'objectif est de décrire le comportement de milieux stables ou lentement évolutifs par une approche d'identification des paramètres thermophysiques. Le démarche adoptée consiste d'abord à établir le modèle théorique du système expérimenté dans la base "explicative" qui est généralement le temps puis, à partir de résultats expérimentaux, à déterminer par optimisation les paramètres recherchés. Le système étudié est caractérisé par ses focntions de réponses (fonction de transfert, impédance,...).Dans ces fonctions, le milieu est caractérisé par des paramètres globaux ou apparents. Notre analyse se place dans le domaine fréquentiel dans lequel le produit de convolution, qui existe dans l'espace du temps, se transforme en produit simple. Le système est alors caractérisé par sa fonction de transfert. L'étude des relations flux-température dans un plan conduit à introduire la notion d'impédance thermique. Les développements et applications effectués dans ce travail sont relatifs à la caractérisation thermique du béton en laboratoire et in situ ainsi qu'à la détection de défauts suffisamment contrastés positionnés à différentes profondeurs. L'objectif final est d'être capable d'utiliser les sollicitations naturelles pour l'identification des systèmes. La difficulté réside dans l'exploitation de données naturelles donc aléatoires, dans un processus de traitement situé dans le domaine fréquentiel. Les mesures de flux et de température sont effectuées sur une seule face d'accès, celle qui est en contact avec l'environnement microclimatique extérieur. / The work developed is located in the context of thermal identification and non-destructive testing of systems. The objective is to describe the behavior of stable or slowly progressive approach by identifying thermophysical parameters. The approach is to first establish the theoretical model of the system tested in the basic "explanation" which is usually the time and, from experimental results to be determined by optimizing the parameters sought. The system studied is characterized by its response function (transfer function, impedance,...). In these functions, the medium is characterized by global parameters or apparent. Our analysis is placed in the frequency domain where the convolution product, which exists in the space of time, turns into a single product. The system is then characterized by its transfer function. The study of flow-temperature relationships in a plane leads to introduce the concept of thermal impedance. Developments and applications made in this work are related to the thermal characterization of concrete in the laboratory and in situ and the detection of defects adequately contrasted positioned at different depths. The ultimate goal is to be able to use the solicitation for the identification of natural systems. The difficulty lies in the exploitation of natural data so random in a process located in the frequency domain. Flux measurements and temperature are performed on one side of access, which is in contact with the outside microclimatic environment.

Cette étude a pour objectif la compréhension des phénomènes de transfert de chaleur couplés conduction-rayonnement, en régime transitoire, dans les isolants thermiques du bâtiment, en vue de leur optimisation. Nous avons étudié deux matériaux poreux très différents : des mousses de polystyrène extrudé (XPS) et un isolant en fibres de bois. Les propriétés radiatives ont été identifiées par méthode inverse. Nous avons ainsi mis en évidence la très faible contribution du transfert radiatif pour la laine de bois étudiée. Un modèle de prédiction des propriétés radiatives à partir des données morphologiques a été adopté pour les mousses XPS, puis validé grâce à différentes mesures. Nous avons montré que les propriétés radiatives sont très dépendantes des paramètres morphologiques ainsi que des indices optiques du polystyrène, et qu'un effort de caractérisation doit être fait pour des structures anisotropes. Enfin nous avons validé le code de résolution du transfert couplé conduction-rayonnement en régime transitoire grâce à des mesures fluxmétriques effectuées sur les isolants pris séparément puis mis en assemblages. Dans le cadre de l'isolation thermique du bâtiment, nous avons montré que les flux thermiques aux frontières des isolants en régime transitoire étaient identiques au cas où on considère la conductivité thermique totale qui prend en compte les contributions radiative et conductive. Nous avons montré l'importance des inerties thermiques grâce à des simulations annuelles du comportement de parois. / The objective of this study is to better understand the mechanisms of the coupling radiative-conductive heat transfer of thermal building insulators used in a transient regime. Two insulating materials were studied in this work: extruded polystyrene foam (XPS) and wood wool. The radiative properties were determined using the inverse method. We demonstrated that the contribution of the radiative heat transfer of the wood wool was quite small. For XPS, radiative properties are more significant and are a function of the foam morphological structure as well as the optical indices of the polymer matrix. A model was developed for isotropic XPS material, however additional developments are needed to better characterize the effects of the foam anisotropy. The coupling radiative-conductive heat transfer in a transient regime was analyzed and validated with the heat flux meter measurement. The experiments were performed with a single insulating element and with various combinations of them. For building thermal insulation in a transient regime, we demonstrated the heat fluxes at the borders of insulators, determined by the coupling solution, are identical when considering the total thermal conductivity which includes radiative and conductive heat transfer. The individual contribution of radiative and conductive heat transfer was not noticeable, however the thermal inertia of the material contributed to delay the heat peak.

Introduction: Carpal tunnel syndrome (CTS) is the most common peripheral nerve entrapment seen within the outpatient orthopaedic clinic; therefore assessment and management of this common condition is of significant importance. Traditionally diagnosis has been made through detailed questioning; clinical examination and nerve conduction studies (NCS). There is however no true consensus as to the gold standard assessment of CTS and the use of NCS can confer additional costs and delay treatment. Previous studies have explored methods of predicting the presence of CTS including the clinician-administered Carpal Tunnel Questionnaire (CTQ) (Kamath and Stothard, 2003). The aim of the present studies is therefore to explore the versatility of the CTQ to see how a novel Patient-completed Version of the CTQ compares to the original Clinican-completed version. Psychometric properties of the questionnaire will be explored together the economic impact of integrating both versions within an orthopaedic care pathway. A further aim is to answer whether the CTQ more effective and cost-effective than NCS for patients referred to an orthopaedic clinic with suspected CTS. Method: 100 patients referred for further investigation of suspected CTS were assessed using parallel patient and clinician-completed versions of the CTQ and results were subsequently compared with those obtained from NCS. Item analysis explored each of the nine constructs of the questionnaire and the original scoring algorithm was validated using binary logistic regression and compared with alternative algorithms. Sensitivity and specificity of the questionnaire when compared to results of NCS was explored using Receiver Operating Characteristic (ROC) analyses. Inter-rater reliability was explored through Pearson’s correlation coefficient. Economic analysis and modelling was carried out to explore potential cost savings of use of the questionnaire rather than NCS for those with suspected CTS. Results demonstrated sensitivity of 92% and specificity of 54.67% (positive predictive value 95.35%) for the patient-completed questionnaire and 96% sensitivity with 70.67% specificity (98.15 positive predictive value) for the clinician-completed questionnaire when used to predict the outcome of NCS. Binary logistic regression confirmed the original scoring algorithm and a revised algorithm did not significantly improve sensitivity. Adoption of the clinician-completed CTQ would have screen out 54% of referrals for NCS, which in the case of the study site would have conferred cost savings of £73,305 per annum (base upon a referral rate of 750 per annum). The patient-completed CTQ in the current sample resulted in 43% of referrals with suspected CTS not requiring NCS to assist in diagnosis with a potential saving of £58,372.5 per annum. There are further considerations of the reduction in waiting times, which are explored further within the analysis. Conclusion: Economic evaluation is complex due to the variety of pathways adopted by different orthopaedic departments. While the results of the Patient-complete version of the CTQ may not be as convincing as the clinician completed the study does provide validation for its use and expands the versatility of this useful adjunct to the assessment of CTS. Both versions could potentially confer significant cost savings and reduce demands on investigative services, reducing waiting times and improving the patient journey in suspected CTS.

Part I of this dissertation is concerned with the problem of the magnetic field dependence of the surface impedance of superconductors, with particular reference to tin. In chapter 1 the predictions of the simple theory for the behaviour of the surface impedance for different frequencies and fieid configurations are described and compared with the results of previous experiments. Chapter 2 deals with the experimental side of the present work, where a frequency of 170 Mc/s was used, and in chapter 3 the results obtained are discussed. In chapter 4 the attempts which have been made to account theoretically for the experimental observations are reviewed. Part II of the dissertation is concerned with another problem in superconductivity, namely the behaviour of superconducting systems partitioned by thin barriers of substances which in bulk are not superconducting. The theory of such systems is developed, the consequences investigated in some detail and the present experimental situation reviewed.

Five formula methods and three numerical general methods for determining thermal process lethality were compared with a reference method to demonstrate their applicability to conduction heating foods in cylindrical containers. Hypothetical centerpoint temperature history curves for cans with height to diameter (H/D) ratios of 0.1 to 3.0 were generated for a range of processing conditions using computer simulation. A finite-difference model based on Teixeira et al. (1969b) was used as the basis of the simulation program. The delivered lethality to an organism characterized by Z=10C° was evaluated using each of the methods and compared to the lethality calculated using the reference method. For each of the test methods, simulation data were provided for one minute intervals, but for the reference method, data were provided for intervals of 0.05 min. Each of the selected formula methods was adapted to allow calculations to be done by computer without operator intervention. The most significant part of this adaptation was the development of a system that enabled the computer to select the linear portion of the heat penetration curve to facilitate calculation of the parameters f and j which are required by all of the formula methods. A method for handling large tables was also developed for use with some of the formula methods. For the general methods, the deviations from the reference method were greatest when the heating rate index (fh) and H/D were small and the unaccomplished temperature difference (g) was large. Whereas the the value of fh was the most significant factor affecting the accuracy of calculations done using the general method, it did not greatly affect the performance of the formula methods. The factors that most significantly influenced deviations between the formula methods and the reference method were H/D and g. The largest deviations in all cases occurred when g was large and H/D was close to unity. These errors were mostly on the "safe" side, but the energy use implications could be significant, especially for high retort temperature processes. / Land and Food Systems, Faculty of / Graduate

In the thesis are analysed influences of three shield gases, based on literary pursuit. Compared was influence of the gas consisting of pure Ar, mixture Ar with 3vol.% CO2 and the mixture Ar with 18vol.% CO2 on mechanical properties of conduction laser welded blunt welds made from structural steel DC01 and S235JR with thickness 3mm and 2mm. Compared were strength properties of the welds in tension, weld hardness and hardness of the heat affected area under the low stress. Further was observed and compared stream of the gases during welding process and its influences on the appearance of the trial welds. On the metallographical cuts of the welds were evaluated mistakes and dimensions of the welds.

Automated smartphone-based threshold audiometry has the potential to provide affordable audiometric services in underserved contexts where adequate resources and infrastructure are lacking. This study investigated the validity of the threshold version (hearTest) of the hearScreen™ smartphone-based application using inexpensive smartphones (Android OS) and calibrated supra-aural headphones. A repeated-measures, within-subject, study design was employed, comparing automated smartphone audiometry air conduction thresholds (0.5 to 8 kHz) to conventional audiometry thresholds. A total of 95 participants, with varying degrees of hearing sensitivity, were included in the study. 30 participants were adults, with known bilateral hearing losses of varying degrees (mean age of 59 years, 21.8 SD; 56.7% female). 65 participants were adolescents (mean age of 16.5 years, 1.2 SD; 70.8% female), of which 61 had normal hearing and 4 had mild hearing losses. Within the adult sample, 70.6% of thresholds obtained through smartphone and conventional audiometry corresponded within 5 dB. There was no significant difference between smartphone (6.75 min average, 1.5 SD) and conventional audiometry test duration (6.65 min average, 2.5 SD). Within the adolescent sample, 84.7% of audiometry thresholds obtained at 0.5, 2 and 4 kHz corresponded within 5 dB. At 1 kHz 79.3% of the thresholds differed by 10 dB or less. There was a significant difference (p&#060.01) between smartphone (7.09 min, 1.2 SD) and conventional audiometry test duration (3.23 min, 0.6 SD). The hearTest application using calibrated supra-aural headphones provided valid air conduction hearing thresholds. Therefore, it is evident that using inexpensive smartphones with calibrated headphones provides a cost-effective way to provide access to threshold air conduction audiometry. / Dissertation (M Communication Pathology)--University of Pretoria, 2016. / Speech-Language Pathology and Audiology / M Communication Pathology / Unrestricted

La presente investigación tiene por objetivo realizar un diseño del sistema de alcantarillado para la zona de Rinconada Pamplona Alta, que se encuentra ubicada en el distrito San Juan de Miraflores, el cual no cuenta con cobertura de un sistema de desagüe en la zona que les permita tener una adecuada calidad de vida a los pobladores y disminuir la contaminación. Debido a esto se propone realizar un diseño del sistema de alcantarillado usando el programa SewerCAD, con el fin de realizar diferentes proyectos y obtener los parámetros hidráulico de las distintas redes de distribución. Se presentan propuestas con tres tipos de materiales PVC, HDPE y Concreto que cumplan con la normativa OS.070. Finalmente, se realizó la evaluación económica costo efectividad y se concluyó que la Propuesta 1 PVC es la mejor opción, ya que presenta el menor índice de efectividad , lo cual asegurar la viabilidad de la propuesta. / The objective of this research is to design the sewer system for the Rinconada Pamplona Alta area, which is located in the San Juan de Miraflores district, which does not have a drainage system in the area that allows them have an adequate quality of life for residents and reduce pollution. Due to this, it is proposed to make a design with the purpose of carrying out of the sewerage system using the SewerCAD program, carry out different projects and obtain the hydraulic parameters of the different distribution networks. The proposals are presented with three types of PVC, HDPE, and concrete materials that comply with OS.070 rule. Finally, the economic evaluation of cost – effectiveness was carried out. It was concluded that first type of proposel, PVC, is the best option , since it presents the lowest effectiveness rate, which guarantees the viability of the proposal. / Tesis

n-Hexane and its metabolites are neurotoxic to animals and man. Studies have revealed a progressive neuropathy which affects the distal regions of motor and sensory peripheral nerves. This paper describes efforts to determine whether 2-hexanone or 2,5-hexanedione is more neurotoxic to rats when given in drinking water. Our results show that 2,5-hexanedione is more neurotoxic than 2-hexanone and that it first affects the distal axon. Concentrations of 20 mM produced no effects after 3 weeks but 40 mM increased distal latency after 2 weeks.