During the last decade, power quality has been recognised asa global problem. Among different types of power qualityproblems, voltage sags have been identified to be one of themost severe problems for different process industries. The mostcommon reason to voltage sags is lightning strikes in powerlines. Protection equipment, usually located at switchyards,disconnect faulted power lines as soon as possible, which isapproximately 100 ms. Thus, the duration of voltage sags areapproximately 100 ms. The sensitivity to voltage sags ofelectrical equipment in process industries can be observed asfor instance malfunction, automatic turnoff or damages. This thesis gives an overview of three metals processes withfocus on the sensitivity to voltage sags and interruptions. Theinherent energy in the process is used to find the sensitivity.This energy may also be used to obtain "ride-through" for theprocesses. The three metals processes are a blast furnaceprocess, a hot rolling mill process and a cold rolling millprocess. The main attention in this thesis is paid to the blastfurnace process, which is powered by a line-operatedsynchronous machine. The thesis shows that the protection equipment forelectrical machines can be adjusted to avoid unnecessaryshutdowns. It is also explained why there are high torque andcurrents during voltage sags as well as after voltage sags. Itis shown that the first peak torque and current during thevoltage sags is almost proportional to the voltage change, thatis the voltage magnitude before the voltage sag minus thevoltage magnitude during the voltage sag. The first peak torqueand current after the voltage sag depends sinusoidal-like onthe duration of the voltage sag and almost proportional to thevoltage change during the voltage sag. There is no fluxsaturation during voltage sags, however after voltage sagssaturation is very likely to occur. The thesis explains why andalso how the flux is changed during and after voltage sags. The duration of voltage sags is in many cases set by theprotection equipment located in switchyards. It is shown thatthe durations of voltage sags can be changed to durations thatwill cause less peak torque and current after voltage sags forline-operated AC-machines. It is also shown how this istheoretically achieved. <b>Keywords:</b>Rolling mill, Blast furnace, Power Quality,Synchronous machine, Asynchronous machine, Voltage sag, Voltageinterruption, Ride-through, Process disturbances, Simulation,Modelling

Les systèmes complexes actuels (cockpits, contrôle de trafic aérien, pilotage de drones,...) amènent les opérateurs à gérer un ensemble de tâches évoluant dynamiquement dans le temps, et imposent des changements fréquents de situation au cours d'une même mission. Ces transitions entre contextes (provoqués par l'ajout, le retrait, l'interruption ou la récupération d'une tâche) peuvent induire une rupture de la conscience de situation (Situation Awareness) de l'opérateur. Dans le cadre de cette thèse, nous introduisons la méthodologie SAMANTA (Situation Awareness Modeling and ANalysis for Transition Amelioration). Celle-ci, mise en oeuvre par les experts en charge de l'analyse et de la conception de futurs systèmes, contribue à l'étude et la résolution des difficultés engendrées par de telles transitions. Le processus d'analyse des transitions proposé s'appuie sur une approche duale de description des transitions à travers la modélisation des tâches, et des éléments de situation associés à chacune d'entre elles (les contextes). Les caractéristiques des transitions ainsi obtenues sont utilisées par l'analyste afin d'émettre des recommandations sur les interfaces du système considéré. Les utilisateurs (opérateurs de systèmes et experts du domaine) sont intégrés aux étapes clés du processus de conception. Un outil dédié a été développé dans le cadre de cette thèse dans le but de faciliter la mise en oeuvre de la méthodologie SAMANTA par les analystes. Une application concrète à la conception de futurs systèmes de drone est présentée, développant l'étude de deux transitions spécifiques.

Les systèmes complexes actuels (cockpits, contrôle de trafic aérien, pilotage de drones,...) amènent les opérateurs à gérer un ensemble de tâches évoluant dynamiquement dans le temps, et imposent des changements fréquents de situation au cours d'une même mission. Ces transitions entre contextes (provoqués par l'ajout, le retrait, l'interruption ou la récupération d'une tâche) peuvent induire une rupture de la conscience de situation (Situation Awareness) de l'opérateur. Dans le cadre de cette thèse, nous introduisons la méthodologie SAMANTA (Situation Awareness Modeling and ANalysis for Transition Amelioration). Celle-ci, mise en oeuvre par les experts en charge de l'analyse et de la conception de futurs systèmes, contribue à l'étude et la résolution des difficultés engendrées par de telles transitions. Le processus d'analyse des transitions proposé s'appuie sur une approche duale de description des transitions à travers la modélisation des tâches, et des éléments de situation associés à chacune d'entre elles (les contextes). Les caractéristiques des transitions ainsi obtenues sont utilisées par l'analyste afin d'émettre des recommandations sur les interfaces du système considéré. Les utilisateurs (opérateurs de systèmes et experts du domaine) sont intégrés aux étapes clés du processus de conception. Un outil dédié a été développé dans le cadre de cette thèse dans le but de faciliter la mise en oeuvre de la méthodologie SAMANTA par les analystes. Une application concrète à la conception de futurs systèmes de drone est présentée, développant l'étude de deux transitions spécifiques.

As the 2010 Swedish election was closing in, there was a discussion about how the media represented the different party leaders in a differential and unfair manner. This study aims to identify if there were any differences in how four of these party leaders, Lars Ohly, Maud Olofsson, Fredrik Reinfeldt and Mona Sahlin were treated in four individual questioning sessions on Swedish television. Utilizing conversation analysis the study focuses on identifying differences in the usage of interruptions between the four different sessions. The study also analyzes the aggressiveness of the journalists’ questioning and how they designed their questions in the four different sessions. Results show some significant differences in how the four different party leaders were treated in their individual questioning sessions.

Many dangerous or tragic events such as airplane crashes and medical errors are often the result of human errors, and these errors are often the result of a professional worker being interrupted during a critical task. Although their impact can be serious, the ways that interruptions are affected by the physical environment have rarely been examined in the study of architecture. Therefore, this thesis investigates how the physical environment helps manage the interruptions by observing the process of medication administration by nurses in hospital units. Nurse shadowing observation data showed that the level of visibility of work areas in and around nurse stations significantly contributed to the number of interruptions initiated by others. Therefore, this thesis concludes that the physical environment affects interruption events and discusses the design implications of observation-based findings and the potential impact of the physical environment on major clinical errors. As for future directions for investigation, this thesis suggests that interruptions become a more prominent subject for consideration in architecture, and the physical environment as a subject for analyzing interruption and performance in human factors and health care.

A vacuum interrupter is a switching device used in vacuum circuit breakers, which are widely employed in medium voltage circuits for interrupting the short-circuit fault currents. The vacuum interrupter is the chamber in which the arc extinction and hence the current interruption takes place. On the occurrence of a fault, the breaker mechanism separates the contacts of the vacuum interrupter. As the contacts separate, an arc is established between the contacts. The arc evolves in the contact space and extinguishes at or near the current zero, thus interrupting the current. The processes of arc ignition, evolution and extinction are very complex. These processes are fundamental to the design and the performance of the vacuum interrupter and hence the circuit breaker. The evolution of the arc predominantly depends on the short-circuit current, the design and metallurgy of the contacts. The evolution of the vacuum arc has been the focal point of considerable research activity. Significant effort has been concentrated to understand the various modes of the arc, the transition between the modes, the arc movement and the dependency on the contact design and finally the effect of the arc evolution on the current interruption performance of the vacuum interrupter. The voltage across the contacts during the arcing, termed as the arc voltage, has been a focal point of several research projects. Research has shown that the arc voltage depends strongly on the mode and the evolution process of the arc. The dependency is observed with respect to the magnitude and the nature of the arc voltage. This dependency has been established through the comparison of the arc voltage trace and the actual arc photographs. The arc voltage is thus an important parameter in understanding the arcing process in the interrupter. Arc voltage could also be utilised to compare the arcing behaviour in vacuum interrupters with different contact geometries and metallurgies. Having understood how the arc voltage depends on the arc modes and how it can be used to analyse the arcing performance of the interrupter, this work aims to establish experimentally the dependency of the arc voltage on fundamental parameters of the short-circuit current and the contact design. The variation of the arc voltage is studied with respect to the magnitude of the short-circuit current. It is seen that the magnitude of the arc voltage is higher, for a higher short-circuit current. This dependency is also reflected in the nature of the arc voltage waveform. The effect of cumulative short- circuit operations has been understood through the study of arc voltage variation with respect to the accumulated arcing time. It has been found that the arc voltage consistently decreases as the accumulated arcing time increases. The effect of the contact diameter on the arc evolution has been studied by comparing the arc voltage variations for contacts of different diameters for the same short-circuit current. It is observed that the variation of arc voltage with respect to the contact diameter depends on the type of contact. In the case of radial magnetic field contacts, it has been observed that the arc voltage is lower for a contact with lower diameter. Whereas in the case of axial magnetic field contacts there is an inverse relation between the contact diameter and the arc voltage. Finally, the effect of the type and distribution of the magnetic field on the arc voltage variation as well as the contact erosion has been studied. In general, the observations show that the arc voltage magnitude for the radial magnetic field geometry is higher than the axial magnetic field geometry. Also, there is a significant difference in the appearance of the arc voltage waveforms for the arcs under the two types of magnetic fields. Finite element simulations and short-circuit evaluations have shown that the axial magnetic field contact system with 90 deg coil orientations yield a more uniform distribution of the flux density and hence lower erosion of the contacts. These results show a clear dependence of the arc voltage on the various above mentioned parameters. Thus the arc voltage could be utilised as a diagnostic parameter during the evaluation of the vacuum interrupter. In the present scenario, significant research is being done to increase the breaking capacity of the interrupters. This calls for optimization of design of the existing contacts and the design of novel contact geometries. The arc voltage would be used as an important diagnostic tool in this process. Also, the utilization of vacuum interrupter in high voltage and extra high voltage circuits is being explored. This application requires increase in the contact gap or series connection of gaps. The arc behaviour in longer gaps and gaps connected in series would be an important research area. Again the arc voltage could be used to study the arc evolution in these specialised conditions. The experiments in this research work have been performed on commercial vacuum interrupters. For a dedicated research on vacuum arcs and vacuum interrupter contacts, development of a vacuum arc research facility has also been attempted as a part of this research work.

<p>During the last decade, power quality has been recognised asa global problem. Among different types of power qualityproblems, voltage sags have been identified to be one of themost severe problems for different process industries. The mostcommon reason to voltage sags is lightning strikes in powerlines. Protection equipment, usually located at switchyards,disconnect faulted power lines as soon as possible, which isapproximately 100 ms. Thus, the duration of voltage sags areapproximately 100 ms. The sensitivity to voltage sags ofelectrical equipment in process industries can be observed asfor instance malfunction, automatic turnoff or damages.</p><p>This thesis gives an overview of three metals processes withfocus on the sensitivity to voltage sags and interruptions. Theinherent energy in the process is used to find the sensitivity.This energy may also be used to obtain "ride-through" for theprocesses. The three metals processes are a blast furnaceprocess, a hot rolling mill process and a cold rolling millprocess. The main attention in this thesis is paid to the blastfurnace process, which is powered by a line-operatedsynchronous machine.</p><p>The thesis shows that the protection equipment forelectrical machines can be adjusted to avoid unnecessaryshutdowns. It is also explained why there are high torque andcurrents during voltage sags as well as after voltage sags. Itis shown that the first peak torque and current during thevoltage sags is almost proportional to the voltage change, thatis the voltage magnitude before the voltage sag minus thevoltage magnitude during the voltage sag. The first peak torqueand current after the voltage sag depends sinusoidal-like onthe duration of the voltage sag and almost proportional to thevoltage change during the voltage sag. There is no fluxsaturation during voltage sags, however after voltage sagssaturation is very likely to occur. The thesis explains why andalso how the flux is changed during and after voltage sags.</p><p>The duration of voltage sags is in many cases set by theprotection equipment located in switchyards. It is shown thatthe durations of voltage sags can be changed to durations thatwill cause less peak torque and current after voltage sags forline-operated AC-machines. It is also shown how this istheoretically achieved.</p><p><b>Keywords:</b>Rolling mill, Blast furnace, Power Quality,Synchronous machine, Asynchronous machine, Voltage sag, Voltageinterruption, Ride-through, Process disturbances, Simulation,Modelling</p>

Depuis plusieurs décennies, le VIH/sida est reconnu comme une pandémie mondiale. Elle touche, on le sait, particulièrement l'Afrique et la Guinée, terrain de cette étude. Le traitement le plus efficace, du point de vue médical, est le traitement antirétroviral (ARV). Ces traitements sont de plus en plus disponibles en Guinée et ils sont gratuits depuis novembre 2007. La prise en charge globale et adéquate des personnes vivant avec le VIH est l'un des objectifs principaux du Cadre stratégique national de lutte contre le sida. L'accès aux soins et, principalement, aux antirétroviraux constituent l'un des dispositifs essentiels de cette prise en charge en Guinée. Néanmoins, en 2008 un phénomène de plus en plus important est observé : l'abandon du traitement antirétroviral pendant des durées variables, de quelques mois à plusieurs. Selon certaines données recueillies, ce phénomène atteindrait des taux approchant les 87 % dans une des villes guinéennes. Qu'est ce qui mène des personnes vivant avec le VIH/sida, auxquelles on a prescrit un traitement antirétroviral, à abandonner le traitement largement connu comme étant le plus efficace? C'est la préoccupation qui est au fondement de notre travail de recherche. Elle vise à comprendre les motifs de cet abandon et à analyser les justifications données. À partir d'entretiens semi-directifs réalisés auprès de femmes guinéennes vivant avec le VIH, en situation d'abandon du traitement des ARV, habitant la ville de Conakry et la préfecture de Kissidougou en Guinée, nous avons interrogé ces pratiques comme formes d'agir reposant sur différentes logiques et non comme simple acte passif. L'approche adoptée dans cette recherche permet d'aller au-delà de la seule question de non-respect de prescriptions ou de recommandations médicales, pour prendre en compte la manière dont est effectué le suivi médical, ainsi que la conciliation entre les contraintes du traitement et les contextes particuliers de vie des personnes vivant avec le VIH. Le traitement antirétroviral nécessite une réflexion à partir des personnes elles-mêmes et sur les conditions objectives de leurs actions ainsi que celles liées au système de santé et autres acteurs impliqués dans la prise en charge des personnes vivant avec le VIH. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : VIH/sida, PVVIH, ARV (antirétroviraux), abandon, stigmatisation, discrimination, prise en charge, statut sérologique, agir, vulnérabilisation, Guinée

Society relies more and more on a continuous supply of electricity. However, while underinvestments in reliability lead to an unacceptable number of power interruptions, overinvestments result in too high costs for society. To give incentives for a socioeconomically optimal level of reliability, quality regulations have been adopted in many European countries. These quality regulations imply new financial risks for the distribution system operator (DSO) since poor reliability can reduce the allowed revenue for the DSO and compensation may have to be paid to affected customers.This thesis develops a method for evaluating the incentives for reliability investments implied by different quality regulation designs. The method can be used to investigate whether socioeconomically beneficial projects are also beneficial for a profit-maximizing DSO subject to a particular quality regulation design. To investigate which reinvestment projects are preferable for society and a DSO, risk-based methods are developed. With these methods, the probability of power interruptions and the consequences of these can be simulated. The consequences of interruptions for the DSO will to a large extent depend on the quality regulation. The consequences for the customers, and hence also society, will depend on factors such as the interruption duration and time of occurrence. The proposed risk-based methods consider extreme outage events in the risk assessments by incorporating the impact of severe weather, estimating the full probability distribution of the total reliability cost, and formulating a risk-averse strategy. Results from case studies performed show that quality regulation design has a significant impact on reinvestment project profitability for a DSO. In order to adequately capture the financial risk that the DSO is exposed to, detailed risk-based methods, such as the ones developed in this thesis, are needed. Furthermore, when making investment decisions, a risk-averse strategy may clarify the benefits or drawbacks of a project that are hard to discover by looking only at the expected net present value. / QC 20110530

This quantitative, descriptive study investigated factors that contributed to TB patients registered in four Tembisa clinics in 2001, defaulting treatment. An interview schedule with closed and open-ended questions was used for 30 patients who could be traced who had interrupted treatment. The reasons for treatment interruption were related to socio-economic, TB policy-related and health care worker-related factors. The findings illustrate that TB management requires a multi-sectoral approach and joint efforts to tackle the disease that continues to kill people even though it is curable. / Health Studies / M.A. (Health Studies)