In the last decade acoustic noise has become more and more regarded as a problem. In cars, boats, trains and aircraft, low-frequency noise reduces comfort. Lightweight materials and more powerful engines are used in high-speed vehicles, resulting in a general increase in interior noise levels. Low-frequency noise is annoying and during periods of long exposure it causes fatigue and discomfort. The masking effect which low-frequency noise has on speech reduces speech intelligibility. Low-frequency noise is sought to be attenuated in a wide range of applications in order to improve comfort and speech intelligibility. The use of conventional passive methods to attenuate low-frequency noise is often impractical since considerable bulk and weight are required; in transportation large weight is associated with high fuel consumption. In order to overcome the problems of ineffective passive suppression of low-frequency noise, the technique of active noise control has become of considerable interest. The fundamental principle of active noise control is based on secondary sources producing ``anti-noise.'' Destructive interference between the generated and the primary sound fields results in noise attenuation. Active noise control systems significantly increase the capacity for attenuating low-frequency noise without major increase in volume and weight. This doctoral dissertation deals with the topic of active noise control within the passenger cabin in aircraft, and within headsets. The work focuses on methods, controller structures and adaptive algorithms for attenuating tonal low-frequency noise produced by synchronized or moderately synchronized propellers generating beating sound fields. The control algorithm is a central part of an active noise control system. A multiple-reference feedforward controller based on the novel actuator-individual normalized Filtered-X Least-Mean-Squares algorithm is introduced, yielding significant attenuation of such period noise. This algorithm is of the LMS-type, and owing to the novel normalization it can also be regarded as a Newton-type algorithm. The new algorithm combines low computational complexity with high performance. For that reason the algorithm is suitable for use in systems with a large number of control sources and control sensors in order to reduce the computional power required by the control system. The computational power of the DSP hardware is limited, and therefore algorithms with high computational complexity allow fewer control sources and sensors to be used, often with reduced noise attenuation as a result. In applications, such as controlling aircraft cabin noise, where a large multiple-channel system is needed to control the relative complex interior sound field, it is of great importance to keep down the computational complexity of the algorithm so that a large number of loudspeakers and microphones can be used. The dissertation presents theoretical work, off-line computer experiments and practical real-time experiments using the actuator-individual normalized algorithm. The computer experiments are principally based on real-life cabin noise data recorded during flight in a twin-engine propeller aircraft and in a helicopter. The practical experiments were carried out in a full-scale fuselage section from a propeller aircraft. / Buller i vår dagliga miljö kan ha en negativ inverkan på vår hälsa. I många sammanhang, i tex bilar, båtar och flygplan, förekommer lågfrekvent buller. Lågfrekvent buller är oftast inte skadligt för hörseln, men kan vara tröttande och försvåra konversationen mellan personer som vistas i en utsatt miljö. En dämpning av bullernivån medför en förbättrad taluppfattbarhet samt en komfortökning. Att dämpa lågfrekvent buller med traditionella passiva metoder, tex absorbenter och reflektorer, är oftast ineffektivt. Det krävs stora, skrymmande absorbenter för att dämpa denna typ av buller samt tunga skiljeväggar för att förhindra att bullret transmitteras vidare från ett utrymme till ett annat. Metoder som är mera lämpade vid dämpning av lågfrekvent buller är de aktiva. De aktiva metoderna baseras på att en vågrörelse som ligger i motfas med en annan överlagras och de släcker ut varandra. Bullerdämpningen erhålls genom att ett ljudfält genereras som är lika starkt som bullret men i motfas med detta. De aktiva bullerdämpningsmetoderna medför en effektiv dämpning av lågfrekvent buller samtidigt som volymen, tex hos bilkupen eller båt/flygplanskabinen ej påverkas nämnvärt. Dessutom kan fordonets/farkostens vikt reduceras vilket är tacksamt för bränsleförbrukningen. I de flesta tillämpningar varierar bullrets karaktär, dvs styrka och frekvensinnehåll. För att följa dessa variationer krävs ett adaptivt (självinställande) reglersystem som styr genereringen av motljudet. I propellerflygplan är de dominerande frekvenserna i kabinbullret relaterat till propellrarnas varvtal, man känner alltså till frekvenserna som skall dämpas. Man utnyttjar en varvtalssignal för att generera signaler, så kallade referenssignaler, med de frekvenser som skall dämpas. Dessa bearbetas av ett reglersystem som generar signaler till högtalarna som i sin tur generar motljudet. För att ställa in högtalarsignalerna så att en effektiv dämpning erhålls, används mikrofoner utplacerade i kabinen som mäter bullret. För att åstadkomma en effektiv bullerdämpning i ett rum, tex i en flygplanskabin, behövs flera högtalare och mikrofoner, vilket kräver ett avancerat reglersystem. I doktorsavhandlingen ''Active Control of Propeller-Induced Noise in Aircraft'' behandlas olika metoder för att reducera kabinbuller härrörande från propellrarna. Här presenteras olika strukturer på reglersystem samt beräkningsalgoritmer för att ställa in systemet. För stora system där många högtalare och mikrofoner används, samt flera frekvenser skall dämpas, är det viktigt att systemet inte behöver för stor beräkningskapacitet för att generera motljudet. Metoderna som behandlas ger en effektiv dämpning till låg beräkningskostnad. Delar av materialet som presenteras i avhandlingen har ingått i ett EU-projekt med inriktning mot bullerundertryckning i propellerflygplan. I projektet har flera europeiska flygplanstillverkare deltagit. Avhandlingen behandlar även aktiv bullerdämpning i headset, som används av helikopterpiloter. I denna tillämpning har aktiv bullerdämpning används för att öka taluppfattbarheten.

Thesis (MA (Political Science))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: During the so-called third wave of democratisation, South Africa experienced a transition from authoritarian rule to democratic rule in 1994. This transition was coupled with a transformation process, which saw the establishment and introduction of democratic principles and norms, as well as democratic institutions. All these make South Africa a democracy in theory but do not necessarily mean that it is a democracy in practice. Moreover, democracy, unlike authoritarian rule, depends on the support of the populace. Lack of support for democratic rule renders the regime illegitimate, since it does not have enough support to continue as the authority of the country. Against the theoretical point of departure (i.e. support for democracy is closely tied to legitimacy of the authority), it is imperative to evaluate these types of support for democracy as well as their changing levels in the country. This will shed some light on whether the populace in the country embrace democracy as a form of governance – that is, whether the populace perceive democracy as a political regime that is entrenched not only in theory, but also in practice. This will be highlighted by their level of support, which determines whether the regime is perceived as legitimate or illegitimate. It will further shed some light on the degree or level of support for the political system governing the country. Support for democracy may be evaluated by using two models or types of support, i.e. diffuse and specific support. Diffuse support consists of three levels of support, namely, political community, regime principles and regime performance, whilst specific support consists of two levels of support, namely regime institutions and political actors. For this study, these models and levels of support are evaluated amongst the supporters of the ruling party, namely the ANC. For comparative purposes, however, support patterns for democracy, as measured in the World Values Surveys from 1995 to 2006, amongst the ANC supporters will be evaluated in relation to non-ANC supporters. These patterns are crucial, since they will highlight whether support for democracy is support for democratic rules and norms, i.e. democracy per se, or whether support for democracy is closely tied to party support and position. The study reveals that there are relatively high levels of support for political community, regime principles and regime performance amongst both the ANC supporters and non-ANC supporters, when compared to levels of support for regime institutions and political actors, meaning that there are high levels of diffuse support when compared to specific support. Moreover, the ANC supporters have higher levels of both diffuse and specific support for democracy when compared to non-ANC supporters. / AFRIKAANSE OPSOMMING: In die 1990‟s gedurende die derde golf van demokratisering in die wêreld, het Suid Afrika ook „n transformasie van „n outoritêre stelsel na „n demokrasie ondergaan. Hierdie transformasie het op die vestiging van demokratiese beginsels en norme sowel as demokratiese instellings uitgeloop. Hoewel dit Suid-Afrika ‟n demokrasie in teorie gemaak het, het dit die stelsel nie noodwendig ‟n demokrasie in die praktyk gemaak nie. Dit is belangrik om in ag te neem dat „n demokrasie, anders as „n outokrasie, die ondersteuning van die bevolking moet geniet. ‟n Gebrek aan genoegsame steun kan daartoe lei dat ‟n regering gesag op ‟n onlegitieme wyse uitoefen. Teen hierdie teoretiese agtergrond is dit dus belangrik om die tipes sowel as die veranderende vlakke van ondersteuning vir demokrasie te evalueer. Sodoende word ‟n insig verkry of die bevolking demokrasie as ‟n vorm van regering nie net in teorie aanvaar nie, maar ook in die praktyk. Die vlak van ondersteuning sal bepaal of die regime as legitiem of onlegitiem beskou word. Dit kan ook verder lig werp op die vlak van ondersteuning vir die politieke selsel wat in plek is. Ondersteuning vir demokrasie kan bepaal word deur gebruik te maak van twee modelle of tipes van ondersteuning, naamlik, verspreide (“diffuse”) en spesifieke (“specific”) ondersteuning. Verspreide ondersteuning bestaan uit drie vlakke van ondersteuning, naamlik, steun vir die politieke gemeenskap, regime beginsels en regime optrede. Spesifieke ondersteuning in teenstelling, bestaan uit twee vlakke van ondersteuning, naamlik steun vir regime instellings en vir die politieke akteurs. Vir hierdie studie is die modelle en vlakke van ondersteuning ge-evalueer met spesifieke verwysing na die ondersteuners van die ANC - die regerende party. Vir ‟n vergelykingsbasis is hierdie ondersteuningspatrone met die nie-ANC ondersteuners soos dit voorkom in die World Values opnames van 1995 tot 2006 gebruik. Hierdie patrone is van kardinale belang omdat dit vir ons ‟n aanduiding gee of ondersteuning vir demokrasie ook die ondersteuning vir demokratiese reëls en norme behels. Die bevindinge dui op relatiewe hoër vlakke van ondersteuning vir die politieke gemeenskap, regime beginsels en regime werkverrigting onder ANC ondersteuners sowel as nie-ondersteuners as dit vergelyk word met vlakke van ondersteuning vir regime instellings en politieke akteurs. Dit beteken dat daar hoër vlakke van verspreide ondersteuning bestaan in vergelyking met spesifieke ondersteuning. Verder is bevind dat ANC ondersteuners hoër vlakke van verspreide sowel as spesifiek ondersteuning vir demokrasie vertoon in vergelyking met nie-ondersteuners van die ANC.

Les réseaux véhiculaires font l'objet de recherches actives aussi bien dans le domaine des réseaux que dans celui des transports. Le potentiel des réseaux véhiculaires à fournir des services comme l'information sur le trafic en temps réel ou sur les accidents font de cette technologie un domaine de recherche très important. Ces réseaux peuvent comporter des communications véhicule-à-véhicule (V2V), véhicule-à-infrastructure (V2I), ou une combinaison des deux. La norme IEEE 1609.4 est la spécification multicanal pour l'IEEE802.11p/WAVE des réseaux véhiculaires (VANETs). Elle utilise sept canaux, l'un étant un canal de contrôle (CCH) qui est écouté par les équipements de façon périodique, et les six autres canaux sont utilisés comme canaux de service (SCH). Elle définit également une division du temps en alternance entre les intervalles CCH et les intervalles SCH. L'objet de cette thèse de doctorat est d'évaluer les performances des réseaux VANETs dans le cas des communications véhiculaires sans infrastructure, et au niveau des couches inférieures du standard 802.11p. Dans la première partie, nous proposons une approche MAC d'allocation multicanal opportuniste dans un contexte sans infrastructure. Cette approche est conforme à la norme IEEE1609.4 -2010 de l'architecture WAVE pour un fonctionnement multicanal, et elle est conçue pour des applications de services de données (non urgentes), tout en assurant la transmission des messages de sécurité routière et des paquets de contrôle. Pour maintenir la qualité de service des deux types de messages (urgents et non-urgents) en exploitant la capacité du canal, deux solutions sont proposées. Dans la deuxième partie, lorsque le véhicule sélectionne son canal et contrôle son alternance temporelle entre CCH et SCH, il commence à transmettre ses paquets, en particulier sur le canal CCH, lesquels ont une durée de péremption. Nous présentons une approche visant à minimiser les collisions des émetteurs tout en évitant la contention de début d'intervalle, en particulier dans un contexte de densité élevée de véhicules. Même si les mécanismes proposés ci-dessus diminuent le taux de collision, il n'est pas possible de les supprimer complètement. Dans la troisième partie, nous traitons le problème des collisions entre les paquets diffusés sur le CCH, en particulier quand la charge des messages transmis dépasse la capacité du canal. Pour cela, nous proposons un nouveau mécanisme de codage réseau analogique adapté à la modulation QPSK pour les messages diffusés sur le CCH. Dans cette approche des symboles connus sont envoyés avant d'envoyer les paquets pour estimer les paramètres du canal et une solution explicite est utilisée pour inverser le système de la superposition de deux paquets

Une nouvelle méthode de test pour les convertisseurs ADC et DAC embarqués dans un système complexe a été développée en prenant en compte les nouvelles contraintes affectant le test. Ces contraintes, dues aux tendances de design de systèmes, sont un nombre réduit de point d'accès aux entrées/sorties des blocs analogiques du système et une augmentation galopante du nombre et des performances des convertisseurs intégrés. La méthode proposée consiste à connecter les convertisseurs DAC et ADC dans le domaine analogique pour n'avoir besoin que d'instruments de test numériques pour générer et capturer les signaux de test. Un algorithme de traitement du signal a été développé pour discriminer les erreurs des DACs et ADCs. Cet algorithme a été validé par simulation et par expérimentation sur des produits commercialisés par NXP. La dernière partie de la thèse a consisté à développer de nouvelles applications pour l'algorithme.

The purpose of this study was to identify and describe factors that affect the utilisation of antenatal services by pregnant adolescents in Muheza district, Tanzania. Quantitative, descriptive study was used. The Andersen and Newman Framework of Health Services Utilisation were used as a conceptual framework. The study population consisted of 235 adolescents who delivered in the Muheza district while attending postnatal clinics and health centres providing reproductive health services between January 2012 and March 2012. The findings revealed a high percentage of under- utilisation of ANC due to low level of education, low individual and household income, inadequate knowledge about sexuality and poor attitudes towards reproductive health services as exemplified by low prevalence of contraceptive use. The distance from clinic, the use of family planning methods, source of antenatal care and having more than four children under 16 years were associated with adequate utilisation of antenatal services. Recommendations were made to promote antenatal services usage by pregnant adolescents in Tanzania. / Health Studies / M.A. (Public Health)

The study attempted to identify factors influencing women’s preference for home births in the Mutare District, Zimbabwe. A quantitative, descriptive, exploratory, cross sectional survey, gathering data by conducting structured interviews with 150 women, was used. All 150 women attended antenatal clinics but did not deliver their babies at health care facilities. The research results indicated that home deliveries might decline if: • the hospital/clinic fees were reduced or removed • transport would be available for women in labour to reach hospitals/clinics • shelters were built for pregnant women at hospitals/clinics • clinics were well equipped and had sufficient numbers of midwives • women had received more effective health education on the advantages of institutional deliveries and on the danger signs of pregnancy/labour complications • nurses/midwives would treat patients respectfully. Unless these factors are addressed, the number of home deliveries might not decline, and the high maternal/infant mortality and morbidity rates in this district will persist. / Health Studies / M. Public Health

Made available in DSpace on 2016-06-02T19:14:25Z (GMT). No. of bitstreams: 1 4656.pdf: 2653974 bytes, checksum: 054d6992f21b316926e3b5c82f65f5d5 (MD5) Previous issue date: 2012-05-29 / Universidade Federal de Minas Gerais / The objective of this thesis is to analyze the political performance of the Superior Labor Court (TST) and the Legislative Power in the context of changes to the Labor Law between 1987 and 2004. To reach this objective, we analyze the internal procedure of TST, classify the institutional changes factors responsible for altering the political performance of the TST in the course of the constituent process in the Constituent Assembly (ANC) during the 1987/1988 period, as well as in the constituent reform process in the Judiciary Power Reform (which gave rise to the Constitutional Amendment 24/1999 and Constitutional Amendment 45/2004). Likewise, these aspects of institutional change generated changes in the direction of jurisprudence and the policy of judiciary organization of the TST. In the ANC of 1987/1988, the political performance of the TST, which did not represent the Labor Court, returned to the constitutional articles of its structure and expertise, and attained little public visibility. In the Judiciary Power Reform, the TST started to participate in public hearings, increasing its public visibility and legitimizing itself as an outlet to represent the Labor Court when facing other powers, as well as about human rights issues related to employment. Therefore, this research reflects the support of the legislative model of labor relations in Brazil in the institutional consolidation process of the TST. / O principal objetivo da tese foi analisar a atuação política do Tribunal Superior do Trabalho (TST), junto ao Poder Legislativo, na alteração do Direito do Trabalho, entre 1987 a 2004. Para tanto, analisamos o funcionamento interno do TST, classificando os fatores de mudanças institucionais, responsáveis pela alteração de atuação política do TST, durante o processo constituinte da Assembléia Nacional Constituinte (ANC) de 1987/88 e no processo de reforma constitucional da Reforma do Poder Judiciário (que originou a Emenda Constitucional 24/1999 e Emenda Constitucional de 45/2004). Igualmente, esses fatores de mudanças institucionais provocaram alterações no direcionamento da jurisprudência e da política de organização judiciária do TST. Na ANC de 1987/88 a atuação política do TST, que não representava a Justiça do Trabalho, voltou-se para os artigos constitucionais sobre sua estrutura e competência e ganhou pouca visibilidade pública. Na Reforma do Poder Judiciário, o TST passou a participar de audiências públicas, ganhou maior visibilidade pública e legitimou-se como um dos porta-vozes para falar em nome da Justiça do Trabalho perante outros poderes, bem como sobre temas de direitos humanos relacionados com o trabalho. Com isso, o estudo apresenta o processo de consolidação institucional do TST e como o mesmo reforça o modelo legislado de relação do trabalho no Brasil.

Wireless networks have potential applications in wireless Internet connectivity, battlefields, disaster relief, and cyber-physical systems. While the nodes in these networks communicate with each other over the air, the challenges faced by and the subsequent design criteria of these networks are diverse. In this thesis, we study and discuss a few design requirements of these networks, such as efficient utilization of the network bandwidth in IEEE 802.11 infrastructure networks, evaluating utility of sensor node deployments, and security from eavesdroppers. The presence of infrastructure IEEE 802.11 based Wireless Local Area Networks (WLANs) allows mobile users to seamlessly transfer huge volumes of data. While these networks accommodate mobility, and are a cost-effective alternative to cellular networks, they are well known to display several performance anomalies. We study a few such anomalies, and provide a performance management solution for IEEE 802.11 based WLANs. On the other hand, in sensor networks, the absence of infrastructure mandates the use of adhoc network architectures. In these architectures, nodes are required to route data to gateway nodes over a multi-hop network. These gateway nodes are larger in size, and costlier in comparison with the regular nodes. In this context, we propose a unified framework that can be used to compare different deployment scenarios, and provide a means to design efficient large-scale adhoc networks. In modern times, security has become an additional design criterion in wireless networks. Traditionally, secure transmissions were enabled using cryptographic schemes. However, in recent years, researchers have explored physical layer security as an alternative to these traditional cryptographic schemes. Physical layer security enables secure transmissions at non-zero data rate between two communicating nodes, by exploiting the degraded nature of the eavesdropper channel and the inherent randomness of the wireless medium. Also, in many practical scenarios, several nodes cooperate to improve their individual secrecy rates. Therefore, in this thesis, we also study scenarios, where cooperative schemes can improve secure end-to-end data transmission rates, while adhering to an overall power budget. In spite of the presence of voluminous reservoirs of information such as digital libraries and the Internet, asking around still remains a popular means of seeking information. In scenarios where the person is interested in communal, or location-specific information, such kind of retrieval may yield better results than a global search. Hence, wireless networks should be designed, analyzed and controlled by taking into account the evolution of the underlying social networks. This alliance between social network analysis and adhoc network architectures can greatly advance the design of network protocols, especially in environments with opportunistic communications. Therefore, in addition to the above mentioned problem, in this thesis, we have also presented and studied a model that captures the temporal evolution of information in social networks with memory.

No description available.

Les réseaux véhiculaires font l’objet de recherches actives aussi bien dans le domaine des réseaux que dans celui des transports. Le potentiel des réseaux véhiculaires à fournir des services comme l’information sur le trafic en temps réel ou sur les accidents font de cette technologie un domaine de recherche très important. Ces réseaux peuvent comporter des communications véhicule-à-véhicule (V2V), véhicule-à-infrastructure (V2I), ou une combinaison des deux. La norme IEEE 1609.4 est la spécification multicanal pour l’IEEE802.11p/WAVE des réseaux véhiculaires (VANETs). Elle utilise sept canaux, l'un étant un canal de contrôle (CCH) qui est écouté par les équipements de façon périodique, et les six autres canaux sont utilisés comme canaux de service (SCH). Elle définit également une division du temps en alternance entre les intervalles CCH et les intervalles SCH. L’objet de cette thèse de doctorat est d’évaluer les performances des réseaux VANETs dans le cas des communications véhiculaires sans infrastructure, et au niveau des couches inférieures du standard 802.11p. Dans la première partie, nous proposons une approche MAC d’allocation multicanal opportuniste dans un contexte sans infrastructure. Cette approche est conforme à la norme IEEE1609.4 -2010 de l'architecture WAVE pour un fonctionnement multicanal, et elle est conçue pour des applications de services de données (non urgentes), tout en assurant la transmission des messages de sécurité routière et des paquets de contrôle. Pour maintenir la qualité de service des deux types de messages (urgents et non-urgents) en exploitant la capacité du canal, deux solutions sont proposées. Dans la deuxième partie, lorsque le véhicule sélectionne son canal et contrôle son alternance temporelle entre CCH et SCH, il commence à transmettre ses paquets, en particulier sur le canal CCH, lesquels ont une durée de péremption. Nous présentons une approche visant à minimiser les collisions des émetteurs tout en évitant la contention de début d’intervalle, en particulier dans un contexte de densité élevée de véhicules. Même si les mécanismes proposés ci-dessus diminuent le taux de collision, il n’est pas possible de les supprimer complètement. Dans la troisième partie, nous traitons le problème des collisions entre les paquets diffusés sur le CCH, en particulier quand la charge des messages transmis dépasse la capacité du canal. Pour cela, nous proposons un nouveau mécanisme de codage réseau analogique adapté à la modulation QPSK pour les messages diffusés sur le CCH. Dans cette approche des symboles connus sont envoyés avant d'envoyer les paquets pour estimer les paramètres du canal et une solution explicite est utilisée pour inverser le système de la superposition de deux paquets / Vehicular networks are the subject of active research in the field of networks as well as transport. The potential for vehicular networks to provide services such as traffic information in real time or accident makes this technology a very important research domain. These networks may support vehicle-to-vehicle communications (V2V), vehicle-to-infrastructure (V2I), or a combination of both. The IEEE 1609.4 is the specification of multichannel operations for IEEE802 .11p/WAVE vehicular networks (VANETs). It uses seven channels; one being a control channel (CCH) which is listened periodically by the vehicles and the other six channels are used as service channels (SCH). It also defines a time division between alternating CCH and SCH intervals. The purpose of this thesis is to evaluate the performance of VANETs in the case of vehicular communications without infrastructure, and at the lower layers of IEEE 802.11p standard. In the first part, we propose an opportunistic multichannel MAC allocation in an environment without infrastructure. This approach is consistent with the standard IEEE1609.4 -2010/WAVE for a multi-channel operation, and it is designed for data services applications (non-urgent), while ensuring the transmission of road safety messages and control packets. To maintain the quality of service of the two types of messages (urgent and non-urgent) by exploiting the channel capacity, two solutions are proposed. In the second part, when the vehicle selects its channel and controls its temporal alternation between CCH and SCH, it starts transmitting its packets, particularly on the CCH, which have an expiration time. We present an approach to minimize collisions between transmitters while avoiding contention at the beginning of CCH interval, especially in a context of high vehicular density. Although the mechanisms proposed above reduce the collision rate, it is not possible to completely remove these collisions. In the third part, we address the problem of collisions between broadcast packets on the CCH, especially when the load of transmitted messages exceeds the channel capacity. For this purpose, we propose a new analog network coding mechanism adapted to QPSK modulation for broadcast messages on the CCH. In this approach, known symbols are sent before sending the packets to estimate the channel parameters and an explicit solution is used to reverse the system of the superposition of two packets