L’écoulement de jeu dans les compresseurs axiaux est étudié à l’aide de la Zonal Detached Eddy Simulation (ZDES). L’objectif consiste à évaluer la capacité de méthodes hybrides URANS/LES à simuler l’écoulement de jeu d’un compresseur axial réaliste afin de mieux comprendre la physique de cet écoulement, notamment son comportement au vannage ainsi que l’effet de sillages venant du stator amont sur le rotor aval. Après avoir choisi la méthode hybride ZDES, un banc d’essai numérique est défini afin de simuler le premier rotor du compresseur de recherche CREATE. Ce banc a la particularité de pouvoir prendre en compte les effets instationnaires venant de la roue directrice d’entrée (RDE), notamment son sillage ainsi que les tourbillons générés en pied et en tête. Basé sur des critères de maillage ZDES, il est utilisé pour évaluer cette méthode comparativement aux méthodes classiques RANS et URANS. La ZDES est validée par étape jusqu’à une analyse spectrale de l’écoulement de jeu se basant sur des données expérimentales. Elle s’est révélée capable de capturer plus précisément l’intensité et la position des phénomènes instationnaires rencontrés en tête du rotor, notamment le tourbillon de jeu. Les densités spectrales de puissance analysées montrent que cela est dû en partie à une meilleure prise en compte du transfert d’énergie des grandes vers les petites structures de l’écoulement avant leur dissipation. De plus, l’écart entre les approches s’accentue lorsque le tourbillon de jeu traverse le choc en tête. Proche pompage, les effets d’interaction entre le choc, le tourbillon de jeu, la couche limite carter et le tourbillon venant de la tête de la RDE sont amplifiés. Le décollement de la couche limite carter s’accentue et une inversion locale de l’écoulement est observée. De plus, le tourbillon de jeu s’élargit et est dévié vers la pale adjacente, ce qui intensifie le phénomène de double écoulement de jeu. L’interaction du tourbillon venant de la tête de la RDE avec le choc et le tourbillon de jeu du rotor est ensuite étudiée au point de dessin. Un battement du tourbillon de jeu est rencontré lors de l’interaction de ce tourbillon avec le tourbillon de tête de la RDE, ce qui diminue le double écoulement de jeu. / The tip-leakage flow in axial compressors is studied with the Zonal Detached Eddy Simulation (ZDES). This study aims at evaluating the capability of hybrid URANS/LES methods to simulate the tip-leakage flow within a realistic axial compressor in order to better understand the involved physics, especially the behaviour of the flow near surge and the effects of stator wakes on the downstream rotor. Once the ZDES method is chosen, a numerical test bench is defined to simulate the first rotor of the research compressor CREATE. This bench takes into account the unsteady effects of the Inlet Guide Vane (IGV), such as its wake as well as vortices generated at the IGV hub and tip. It is based upon ZDES meshing criteria and is used to evaluate this method compared to classic RANS and URANS approaches. A method validation is carried out up to a spectral analysis compared to experimental data. The ZDES is capable to capture more accurately the intensity and position of the unsteady phenomena encountered in the tip region, especially the tip-leakage vortex. The power spectral densities highlight that this partly originates from a better capture of the energy transfer from large to small structures until their dissipation. The discrepancy between the methods is accentuated as the tip-leakage vortex crosses the shock. Near the surge line, the interactions between the shock, the tip-leakage vortex, the boundary layer developing on the shroud and the vortex generated by the IGV tip are amplified. The boundary layer on the shroud separates earlier and a local flow inversion occurs. Besides, the tip-leakage vortex widens and is deflected toward the adjacent blade. This strengthens the double leakage. At the design operating point, the interaction of the IGV tip vortex with the shock and the rotor tip vortex is studied. A vortex flutter is observed as the IGV tip vortex arrives on the rotor blade and stretches the rotor tip vortex. This phenomenon decreases the double leakage.

<p dir="ltr">Gas turbines are widely used to provide propulsion, electrical-power, and mechanical power. Though tremendous advances have been made since Frank Whittle’s patent of a turbojet in 1930 and Hans von Ohain’s patent of the first operational turbojet in 1936, industry still has aggressive goals on improvements in efficiency and service life. One area where further advances are needed is better control of the flow across the gap between the blade tip and the shroud, referred to as tip-leakage flow (TLF). This is because TLF accounts for up to one-third of the aerodynamic losses in a turbine stage.</p><p dir="ltr">In this study, hybrid LES-RANS based on IDDES and steady RANS based on the SST turbulence model were used to study the compressible flow in a 1.5-stage turbine with geometry and operating conditions that are relevant to power-generation gas turbines. The focus is on the flow in the tip-gap region that account for the flow features created by the upstream stator vanes, stator-rotor interactions, and downstream stator vanes. Results obtained reveal the flow structures about the tip-gap region and the flow mechanisms that create them. Results obtained also show where steady RANS with mixing plane could predict correctly when compared with results from IDDES that resolve the unsteadiness of the turbulence and the motion of the rotor blades passing the stator vanes. Turbulent statistics from the IDDES were generated to guide the development of better RANS models. Results were also obtained by using RANS to examine the effects of blade loading, where mass flow rate through the 1.5 stage turbine was varied with the rotor’s rotational speed fixed at 3,600 RPM – the speed at which power-generation gas turbines operate in the U.S.</p><p dir="ltr">Key findings are as follows: In the first-stage stator, horseshoe, passage, and corner vortices were found to be confined within 10 to 15% span from the hub and shroud, and both steady RANS and IDDES generated similar results. Steady RANS and IDDES, however, differed considerably in how they predicted the wake downstream of the vane’s trailing edge. This coupled with the use of mixing plane, steady RANS was unable to account for effects of stator-rotor interactions and their effects on the tip-leakage flow. In the rotor, steady RANS predicted passage vortices that extended up to 50% span from the hub and 25% span from the shroud. The flow through the tip gap was found to induce a separation bubble on the blade tip and one large and two small vortical structures on the suction side of the blade and a vortical structure next to the shroud. These structures were found to grow along the axial chord of the blade. Steady RANS also predicted the large tip leakage vortex that contained the fluid from the tip-leakage flow to breakdown. IDDES did not predict the vortex breakdown because all of the coherent vortical structures identified including the separated region on the blade tip were unsteady and constantly shedding. As a result, IDDES predicted much smaller mean passage vortices – albeit the instantaneous structures were nearly as large as those predicted by steady RANS.</p>

Submitted in fulfilment of the requirements for the degree of Master of Engineering, Department of Civil Engineering and Surveying, Faculty of Engineering and the Built Environment, Durban University of Technology, Durban, South Africa, 2016. / Water is a critical resource in Southern Africa. The region thus needs to protect both the quality and the quantity of its water resources through robust water conservation and demand management (WC/DM) measures. Water demand management encompasses activities that aim to decrease water demand, improve the efficiency of water use and prevent the deterioration of water resources. Water conservation refers to policies, measures or consumer practices that promote the conservation of water resources. Water resources should be used wisely to secure a water supply that is of good quality and enough for South Africa’s people and its natural environment, which provides the ecosystem that supports all forms of life. When a water utility systems experience water losses, the amount of water available to consumers is reduced, making it difficult to satisfy demand. Water losses also occur as a result of inaccuracies in customer meters, data errors in the billing system and unauthorised consumption. Such losses result in non-revenue water (NRW), which is a serious threat to the water supply sector. NRW refers to the water that is produced and lost without generating revenue for the utility. This research study investigated strategies that could be used to address the challenge of water losses, by developing a more suitable business model that could be incorporated into Ugu District Municipality (DM)’s existing NRW reduction strategies. The study was carried out in Amandawe and Umzinto zones of the District Municipality and it covered the period 01 March 2014 to June 2015. The study objectives were made up of four components. The first was to identify and prioritise the implementation of NRW reduction strategies. This was achieved by identifying the pipes to be closed off, which were supplying a significant number of consumers. For those pipes that were not closed off, flow meters were installed to measure the flow into and out of a zone. The system was then tested for zero pressure by isolating all closed valves to ensure that there were no potential feed-backs into the zone. Pressure gauges were set up on standpipes for routine pressure monitoring. The test was run at night (between 01.00 and 05.00 hours) when the system was under pressure. When the pressure dropped consistently, this meant that there was no feedback into a zone. Leaks were detected by logging the system in order to obtain night flows, which were analysed to determine the system behaviour. The results for Amandawe Zone after implementation of the pressure management programme, indicated that the average zone’s night pressure (AZNP) decreased from 7.38 bars to 5.95 bars. For Umzinto Zone, the AZNP dropped from 5.5 bars to 3.3 bars. The minimum night flows (MNFs) dropped from 34.80 m3/hr to 15.20 m3/hr in Amandawe Zone and from 6.4 m3/hr to 1.70 m3/hr in Umzinto Zone. The daily cost of excess night flow due to bursts was reduced from R2276.17/day to R862.61/day in Amandawe Zone and from R361.24/day to R40.46/day in Umzinto Zone, which provided huge savings. The second objective was to identify the sources and causes of water losses in the study area by conducting field measurements and observations. This was achieved by physically inspecting the infrastructure using visual observation, mechanical listening sticks, correlators, ground microphones and system loggers. The following indicators were used to physically identify underground leaks: unusually wet surfaces in landscaped areas, pools of water on the ground surface, noticeably green, soft and mouldy areas surrounded by drier surfaces, a notable drop in water pressure or flow volume, unexplained sudden increase in water demand or water use at a fairly steady rate for several billing cycles, cracks in paved surfaces, potholes or sink holes and the sudden appearance of dirty water in the main distribution system. For this study, the water losses in the system were found to be as a result of various causes including leaks, aging infrastructure, high pressure in the system, damaged pipes and illegal connections, among others. The third objective was to construct a water balance in order to determine the key performance indicators for the NRW reduction strategies. This was achieved by determining the system input volume (SIV), billed authorized consumption (BAC), unbilled metered consumption (UMC), unbilled unmetered consumption (UUC), real losses (RL), apparent losses (AL) and IWA Key Performance Indicators. Bulk and domestic meter readings were used to calculate the components of the water balance. The results of the water balance indicated that there was a decrease in the SIV from 904 kL/day to 523 kL/day in Amandawe Zone and from 382 kL/day to 221 kL/day in Umzinto Zone. The physical water losses were reduced from 611 kL/day to 377 kL/day in Amandawe Zone and from 93.8 kL/day to 45.8 kL/day in Umzinto Zone. The NRW was reduced from 659 kL/day to 395 kL/day in Amandawe Zone and from 94.2 kL/day to 46.2 kL/day in Umzinto Zone. The fourth objective was to develop the most suitable business model for Ugu DM based on the results arising from the first three objectives. Ugu DM needs to ensure both operational and financial efficiency. Operational efficiency could be achieved by minimising real water losses through reviewing water services standards, developing district metering areas, pressure management, leak detection and repair, reservoir control to stop overflows and pipe replacement programs. Financial efficiency could be achieved by carrying out regular meter testing and calibration, securing database integrity, managing illegal connections, ensuring that all customer connections have meters and ensuring that the tariff structures were cost reflective in order for the municipality to cover costs and generate revenue. Findings of this study could assist other water utilities operating under similar conditions. The implementation of this study’s results could have positive economic, social and environmental effects on Ugu DM. It was concluded that rezoning, pressure management and leak detection were the most critical NRW reduction strategies as they had a positive impact on the system. The main causes of leaks in the system were identified as aging infrastructure, high pressures in the system, and illegal connections. All the critical KPIs of IWA water balance responded positively after the implementation of the strategies by reducing. The operational and financial efficiencies were identified as critical for a WSA to develop a business model that could sustain itself.

Thesis (PhD)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: The main aim of this research programme was to compare the relative performance of different insulator materials used in South Africa when subjected to a severe marine pollution environment. A test programme and procedure, test facility and instrumentation were established. Some novel instrumentation and monitoring equipment were developed and built specifically for this research programme, supported by data analysing software programs. In order to compare material performance only, all non-material design variables between the test insulators had to be removed (e.g. creepage distance, connecting length, inter-shed spacing, profile, etc.). To achieve this some of the test insulators had to be specially manufactured. Leakage current, electrical discharge activity, climatic and environmental data was collected successfully over a one-year test period, starting with new test insulators. The peak and energy values of the leakage current were identified as the two main parameters needed to describe the leakage current activity on the test insulators. A correlation was found between the climatic and environmental data and the leakage current data, and it was found that the leakage current can be determined successfully from some of the climatic and environmental parameters monitored by using multiple regression techniques. Surface conductivity and energy were found to be the best parameters to show the maximum and continuous interaction of the insulator material surface with the electrolytic pollution layer. A natural ageing and pollution test procedure was developed, which has become a South African standard and is gaining international acceptance. A model and hypothesis are proposed to describe the electrical discharge activity that takes place on the test insulators and explain the difference in leakage current performance of the various materials. Keywords: Insulator, Pollution, High Voltage, Leakage current, Material performance. / AFRIKAANSE OPSOMMING: Die hoofdoel van hierdie navorsingsprogram was om die relatiewe prestasie van verskillende isolatormateriale wat in Suid-Afrika gebruik word te vergelyk in 'n swaar besoedelde marine omgewing. 'n Toetsprogram en prosedure, toets fasiliteit en instrumentasie is gevestig. 'n Paar nuwe instrumente en moniteer toerusting is ontwikkel en gebou spesifiek vir hierdie navorsingsprogram, gesteun deur data analise sagteware programme. Ten einde slegs materiaalprestasie te vergelyk, moes alle nie-materiaal ontwerpsveranderlikes tussen die toetsisolators verwyder word (bv. kruipafstand, konnekteer lengte, tussen-skerm spasiëring, profiel, ens.). Om dit reg te kry moes sommige van die toetsisolators spesiaal vervaardig word. Lekstroom, elektriese ontladingsaktiwiteit, klimaat en omgewingsdata is suksesvol versameloor 'n een-jaar toetsperiode, beginnende met nuwe toets isolators. Die piek en energie waardes van die lekstroom is identifiseer as die twee hoof parameters wat nodig is om die lekstroomaktiwiteit op die toetsisolators te beskryf. 'n Korrelasie is gevind tussen die klimaat- en omgewingsdata en die lekstroom data, en dit is gevind dat die lekstroom data suksesvol bepaal kan word van sekere van die klimaat- en omgewingsparameters wat gemoniteer is deur veelvoudige regressie tegnieke te gebruik. Oppervlakskonduktiwiteit en energie is gevind die beste parameters te wees om die maksimum en kontinue interaksie van die isolatormateriaaloppervlak met die elektrolitiese besoedelingslaag aan te toon. 'n Natuurlike veroudering en besoedeling toetsprosedure is ontwikkel, wat 'n Suid-Afrikaanse standaard geword het en besig is om internastionale aanvaarding te wen. 'n Model en hipotese word voorgestelom die elektriese ontladingsaktiwiteit wat op die toetsisolators plaasvind te beskryf en om die verskil in lekstroomprestasie van die verskeie materiale te verduidelik. S/eufelwoorde: Isolator, Besoedeling, Hoog Spanning, Leek stroom, Materiaal prestasie.

L'émergence du Web sémantique a mené à une adoption rapide du format RDF (Resource Description Framework) pour décrire les données et les liens entre elles. Ce modèle de graphe est adapté à la représentation des liens sémantiques entre les objets du Web qui sont identifiés par des IRI. Les applications qui publient et échangent des données RDF potentiellement sensibles augmentent dans de nombreux domaines : bio-informatique, e-gouvernement, mouvements open-data. La problématique du contrôle des accès aux contenus RDF et de l'exposition sélective de l'information en fonction des privilèges des requérants devient de plus en plus importante. Notre principal objectif est d'encourager les entreprises et les organisations à publier leurs données RDF dans l'espace global des données liées. En effet, les données publiées peuvent être sensibles, et par conséquent, les fournisseurs de données peuvent être réticents à publier leurs informations, à moins qu'ils ne soient certains que les droits d'accès à leurs données par les différents requérants sont appliqués correctement. D'où l'importance de la sécurisation des contenus RDF est de l'exposition sélective de l'information pour différentes classes d'utilisateurs. Dans cette thèse, nous nous sommes intéressés à la conception d'un contrôle d'accès pertinents pour les données RDF. De nouvelles problématiques sont posées par l'introduction des mécanismes de déduction pour les données RDF (e.g., RDF/S, OWL), notamment le problème de fuite d'inférence. En effet, quand un propriétaire souhaite interdire l'accès à une information, il faut également qu'il soit sûr que les données diffusées ne pourront pas permettre de déduire des informations secrètes par l'intermédiaire des mécanismes d'inférence sur des données RDF. Dans cette thèse, nous proposons un modèle de contrôle d'accès à grains fins pour les données RDF. Nous illustrons l'expressivité du modèle de contrôle d'accès avec plusieurs stratégies de résolution de conflits, y compris la Most Specific Takes Precedence. Nous proposons un algorithme de vérification statique et nous montrons qu'il est possible de vérifier à l'avance si une politique présente un problème de fuite d'inférence. De plus, nous montrons comment utiliser la réponse de l'algorithme à des fins de diagnostics. Pour traiter les privilèges des sujets, nous définissons la syntaxe et la sémantique d'un langage inspiré de XACML, basé sur les attributs des sujets pour permettre la définition de politiques de contrôle d'accès beaucoup plus fines. Enfin, nous proposons une approche d'annotation de données pour appliquer notre modèle de contrôle d'accès, et nous montrons que notre implémentation entraîne un surcoût raisonnable durant l'exécution / The emergence of the Semantic Web has led to a rapid adoption of the RDF (Resource Description Framework) to describe the data and the links between them. The RDF graph model is tailored for the representation of semantic relations between Web objects that are identified by IRIs (Internationalized Resource Identifier). The applications that publish and exchange potentially sensitive RDF data are increasing in many areas: bioinformatics, e-government, open data movement. The problem of controlling access to RDF content and selective exposure to information based on privileges of the requester becomes increasingly important. Our main objective is to encourage businesses and organizations worldwide to publish their RDF data into the linked data global space. Indeed, the published data may be sensitive, and consequently, data providers may avoid to release their information, unless they are certain that the desired access rights of different accessing entities are enforced properly, to their data. Hence the issue of securing RDF content and ensuring the selective disclosure of information to different classes of users is becoming all the more important. In this thesis, we focused on the design of a relevant access control for RDF data. The problem of providing access controls to RDF data has attracted considerable attention of both the security and the database community in recent years. New issues are raised by the introduction of the deduction mechanisms for RDF data (e.g., RDF/S, OWL), including the inference leakage problem. Indeed, when an owner wishes to prohibit access to information, she/he must also ensure that the information supposed secret, can’t be inferred through inference mechanisms on RDF data. In this PhD thesis we propose a fine-grained access control model for RDF data. We illustrate the expressiveness of the access control model with several conict resolution strategies including most specific takes precedence. To tackle the inference leakage problem, we propose a static verification algorithm and show that it is possible to check in advance whether such a problem will arise. Moreover, we show how to use the answer of the algorithm for diagnosis purposes. To handle the subjects' privileges, we define the syntax and semantics of a XACML inspired language based on the subjects' attributes to allow much finer access control policies. Finally, we propose a data-annotation approach to enforce our access control model, and show that our solution incurs reasonable overhead with respect to the optimal solution which consists in materializing the user's accessible subgraph to enforce our access control model, and show that our solution incurs reasonable overhead with respect to the optimal solution which consists in materializing the user's accessible subgraph

O objetivo deste estudo foi avaliar, in vitro, a capacidade seladora de três materiais obturadores endodônticos, com a proposição de uma nova forma de quantificação da infiltração e um novo agente traçador, utilizando um sistema semelhante ao do modelo experimental da glicose. Trinta e seis dentes unirradiculares extraídos tiveram as coroas removidas, permanecendo 12 mm das raízes. Os canais radiculares foram instrumentados e obturados com o sistema Epiphany (GE) ou com a condensação lateral da guta-percha e cimentos AH Plus (GA) ou Sealapex (GS). Com o auxílio de um calcador aquecido removeu-se 7 mm de material obturador. Seis espécimes com os canais completamente obturados tiveram as raízes totalmente impermeabilizadas com duas camadas de esmalte de unhas, constituindo o grupo controle negativo. Os espécimes foram separados em dois grupos para a realização de dois experimentos que diferiram quanto ao modo de adaptação do espécime no sistema (cianoacrilato ou resina epóxi). Uma solução de cafeína (pH 6.0) foi forçada no sentido coronário com uma pressão hidrostática de 2.55 kPa em direção apical. A infiltração foi medida em ng/mL, pela concentração de cafeína na solução receptora do reservatório, em intervalos de 10, 30 e 60 dias. Para a quantificação foi utilizada a cromatografia líquida de alta eficiência acoplada à espectrometria de massas (CLAE-EM/EM). Esta técnica apresentou alta sensibilidade e especificidade na quantificação do agente traçador. Em função da limitação dos agentes de vedação (cianoacrilato e resina epóxi) empregados no modelo experimental, não foi emitida conclusões a respeito da capacidade seladora dos materiais obturadores testados. / The objective of this study was to propose a new way to measure infiltration with a new tracing agent by using a system similar to that of the glucose penetration model. Thirty-six single-root extracted teeth had their root canals filled using the Epiphany system or with a lateral condensation of gutta-percha and AH Plus or Sealapex cement. Two experiments were carried out that used a different mode of adapting the specimen within the system (cyanoacrylate or epoxy resin). A caffeine solution (pH 6.0) was forced in a coronary direction with a hydrostatic pressure of 2.55 kPa towards the tooth apex. The infiltration was measured in ng/mL, by the concentration of caffeine in the receptor solution of the apical reserve at intervals of 10, 30, and 60 days. To quantify the measurements, a high-performance liquid chromatography coupled with mass spectrometry (HPLC-MS/MS) was used. This technique showed a high sensitivity and specificity for quantifying the tracing agent. Due to the limitations of the sealing agents (cyanoacrylate and epoxy resin) used in our experimental model, analysis of the sealing ability of the filling materials tested was not performed. It is necessary to carefully validate the principal variables of the systems that assess infiltration in order to standardize studies and give greater credibility to their results.

Este estudo laboratorial comparou a microinfiltração marginal e formação de microfendas em restaurações de classe II extensas, feitas com resina composta com margens situadas em dentina/cemento, utilizando diferentes tipos de retenções adicionais na caixa proximal. Cavidades padronizadas MOD extensas foram confeccionadas em 40 terceiros molares humanos, os quais foram divididos em 4 grupos de acordo com a retenção adicional confeccionada na caixa proximal: (G1) sem retenção adicional - controle; (G2) canaletas verticais nas paredes vestibular e lingual; (G3) orifícios na parede gengival e (G4) canaleta horizontal na parede gengival. Todos os grupos foram restaurados pela técnica incremental, com sistema adesivo (Prime Bond NT - Dentsply) e resina composta híbrida (QuiXfil - Dentsply). Todos os dentes restaurados foram imersos em corante com aplicação simultânea de cargas contínuas (forças variando entre 1kg e 17kg). Moldagens da margem gengival restaurada foram realizadas antes e após a ciclagem mecânica e réplicas de resina epóxica foram obtidas e analisadas em microscópio eletrônica de varredura para avaliação das microfendas marginais. Após as moldagens, todos os dentes foram seccionados para análise da microinfiltração marginal. Todas as micrografias da margem gengival e imagens dos cortes seccionados foram analisados quantitativamente no programa Image Tools (UTHSCSA). Os valores para microinfiltração foram submetidos a análise de variância e teste de Tukey (p< ou = 0,05). As extensões das fendas antes e após a ciclagem mecânica foram comparadas pelo teste \'t\'\' de Student. Também foi realizada uma análise de correlação entre a extensão das microfendas e microinfiltração marginal (teste de correlação de Pearson). Todos os grupos com retenção adicional (G2=11,59, G3=7,11 e G4=1,57) apresentaram microfendas significantemente menos extensas que o grupo controle sem retenção (G1=42,43) (p< ou = 0.05). Resultados similares foram obtidos para a análise de microinfiltração (G1= 82,84; G2=64,73; G3=45,42; G4=3,09), com diferenças significantes entre todos os grupos (p< ou = 0,05). Todos os grupos apresentaram aumento na extensão das fendas após a aplicação de cargas contínuas, com exceção do grupo da canaleta horizontal (grupo 4). Este tipo de retenção adicional apresentou os melhores resultados em ambos os parâmetros. Os resultados mostraram uma tendência a correlação entre os dois parâmetros estudados. Segundo os resultados, as retenções adicionais podem melhorar a adaptação marginal e minimizar a microinfiltração em restaurações de classe II extensas, feitas com resina composta. / This in vitro study compared marginal leakage and gap formation in resin composite class II cavities with gingival margin in cementum, using 3 different additional retention in proximal box. Standardized large MOD cavities, with gingival margins in cementum, were prepared in forty extracted human molars and divided into 4 groups according to the retention in proximal box: (G1) no retention; (G2) vertical grooves in buccal and lingual walls; (G3) pins in gingival wall; and (G4) horizontal grooves in gingival wall. All groups were restored with the incremental technique, using hybrid resin composite (QuiXfil - Dentsply) and bonding agent (Prime Bond NT - Dentsply). All restored teeth were immersed in dye with simultaneous mechanical loading (alternated loading between 1kg and 17kg). Impressions of gingival margins were made before and after mechanical loading and epoxic resin replicas were evaluated in scanning electron microscope for gap formation. After the impressions, all teeth were seccioned for microleakage evaluation. All SEM photomicrographs and seccioned teeth images were analysed with Image Tools (UTHSCSA) software for a quantitative analysis of both parameters. Microleakage data were evaluated by ANOVA and Tukey\'s test. Gap extension before and after mechanical loading were evaluated by Student\'s t test. A correlation analysis was made between gap extension and microleakage (Pearson\'s correlation test). All groups with additional retention (G2=11,59, G3=7,11 e G4=1,57) showed fewer gap formation than control group (G1=42,43) (p< or = 0.05). Similar results were found for microleakage tests (G1= 82,84; G2=64,73; G3=45,42; G4=3,09), with significant differences between all groups (p< or = 0,05). All groups presented an increase in gap extension after loading, with exception to group with gingival retention grooves (G4). This group (G4) showed the best results in both parameters (p< or = 0.05).The results showed a tendency for correlation between the parameters. According the results, additional retention may improve marginal adaptation and minimize leakage in large class II resin composite restorations.

No Brasil, são comuns sistemas de distribuição de água para abastecimento com elevados índices de perdas, nos quais parcela significativa das denominadas perdas físicas é devida às perdas por vazamento. Dessa maneira, o controle efetivo das perdas por vazamento e do comportamento do sistema sob as mais diversas condições operacionais é de fundamental importância, não só do ponto de vista financeiro, no que diz respeito ao desperdício da água bombeada e quimicamente tratada, mas principalmente da preservação deste recurso natural. Com o objetivo de se ter um maior conhecimento do comportamento real de uma rede de distribuição de água, técnicas de calibração, incluindo modelos para avaliação de perdas por vazamentos, vêm sendo propostas. Tais modelos devem considerar a relação pressão x vazamento, bem como a dependência pressão x demanda, face aos diferentes níveis de pressão atuantes em um sistema de distribuição de água. O presente estudo visa o desenvolvimento de uma rotina computacional que considere as perdas por vazamento e a dependência das demandas com a pressão, acoplada ao simulador hidráulico EPANET (ROSSMAN, 2000), utilizando dados de rede hipotética com vistas à calibração em termos das rugosidades absolutas, demandas, diâmetros, cotas topográficas e parâmetros do modelo de vazamentos, bem como a localização de componentes hidráulicos na rede. Para tanto, utilizam-se modelos inversos resolvidos com o suporte da tecnologia dos Algoritmos Genéticos (AGs) e procedimento híbrido (AGs e Método Simplex – NELDER & MEAD, 1965) / Brazil’s water distribution systems usually present a high percentage of so-called physical losses, of which a significant portion is caused by leakage. Therefore, it is of fundamental importance, not only from the financial standpoint – in terms of the pumped and chemically treated water – but also particularly from that of the preservation of this natural resource, to effectively control leakage and the systems’ behavior under several operational conditions. In order to gain a better understanding of the real behavior of a water distribution network, several calibration techniques, including models to evaluate leakage, have been proposed. Those models normally consider the correlation between pressure and leakage, as well as the interdependence of pressure and demand in response to the varying levels of pressure in a water distribution system. The present study seeks to extend these models through the development of a computational routine based on leakage and on pressure-dependent demand, in conjunction with the hydraulic simulator EPANET (ROSSMAN, 2000), using the data from a hypothetical network to calibrate the absolute roughness and diameter of pipes, demands and elevations of nodes and the parameters of the leakage model, as well as the location of hydraulic components in the network. To this end, inverse models are used based on the technology of Genetic Algorithms (GA) and the hybrid procedure (GA and Simplex Method - NELDER & MEAD, 1965)

O uso do cloro como desinfetante em sistemas de água para abastecimento é prática comum nas estações de tratamento de água. Introduzido durante o processo de tratamento, o cloro participa de diversas reações com compostos de naturezas orgânicos e inorgânicos no interior das tubulações. Tais reações ocorrem na massa líquida e junto às paredes das tubulações e são responsáveis pelo decaimento do cloro ao longo das redes. Visualizando a modelagem como uma ferramenta eficiente para gerenciar o cloro residual em sistemas de distribuição de água, muitos estudos foram realizados e reportados pela literatura, assumindo que os efeitos de decaimento de cloro podem ser bem representados pelos coeficientes kb e kw. Entretanto, a determinação de valores para parâmetros em questão não é uma tarefa fácil, devido à complexidade dos sistemas enfocados em termos da diversidade de materiais das tubulações e mananciais (superficiais e subterrâneos). No Brasil, apesar de legislação recente estabelecer limites restritivos para o cloro na água potável (após desinfecção, a concentração de cloro deve observar a concentração mínima de 0,5 mg/L, sendo o mínimo nível aceito em sistemas de distribuição de 0,2 mg/L e o máximo de 2,0 mg/L), poucos estudos enfocam a avaliação dos parâmetros de decaimento. Esta pesquisa apresenta a aplicação de um modelo inverso elaborado para determinar a ordem para o modelo de decaimento do cloro e os valores globais e/ou locais para o kb e o kw. Sendo programado com o suporte do simulador de EPANET 2 (toolkit) e os algoritmos genéticos como ferramenta de otimização, implementado através da biblioteca de GAlib C++. Os estudos foram realizados em dois sistemas reais da distribuição da água em que foram considerados parâmetros globais e parâmetros específicos da qualidade. Para a investigação da determinação de parâmetros de decaimento de cloro em sistemas de distribuição com vazamento em função da pressão, foi adotada uma rede hipotética com três fontes de cloro. Esse sistema permitiu a calibração e a validação do modelo, assim como a avaliação da influência hidráulica na determinação dos resultados de qualidade de água. / The use of chlorine as disinfectant in water supply systems has been a common practice adopted by the water industry. Introduced during the treatment process, chlorine participates in several reactions with compounds of organic and inorganic nature inside the pipes. Such reactions that occur in the bulk and the wall of the pipes are responsible for chlorine decay along the networks. Visualizing the modeling as an efficient tool to manage the chlorine residual in water distribution systems, many studies have been conducted and reported by the literature, assuming that the chlorine decay effects can be well represented by the decay coefficients kb and kw. However, the determination of values for theses parameters is not an easy task, due to the complexity of the focused systems in terms of pipe materials and water supply sources diversity (surface water and groundwater). In Brazil, instead of recent legislation stating more strict limits for chlorine in drinking water (after disinfection, chlorine concentration has to observe the minimum concentration of 0.5 mg/L, being the minimum accepted level in the distribution system of 0.2 mg/L and the maximum of 2.0 mg/L), few studies focus on the evaluation of the decay parameters. This research reports the application of an inverse model built to determine the order for chlorine decay model and the global and/or local values for kb and kw. It is codified with the support of EPANET 2 (Toolkit) simulator and technology of genetic algorithms as optimization tool, which is implemented by using the GAlib C++ library. The studies were conducted on two real water distribution systems considering both global and specific quality parameters. A hypothetical network with three sources of chlorine was studied too, admitting leakage as pressure function. This system permitted both calibration and validation of the model as well as the evaluation of hydraulic calibration influence on the water quality results.

Neste trabalho, foram caracterizados eletricamente capacitores MOS com alumina (Al2O3) e aluminato de háfnio (AlxHf1-xOy) como dielétricos de porta, além disso, estes filmes dielétricos foram caracterizados fisicamente. A alumina foi obtida da oxidação anódica de filmes de alumínio evaporados sobre p-Si (100) através de imersão em ácido nítrico por 4 ou 6 min, para diferentes etapas de limpeza finais do substrato: solução diluída de ácido fluorídrico (DHF) ou solução de peróxido sulfúrico (SPM). Análises de retroespalhamento de Rutherford (RBS), espectroscopia por dispersão em energia (EDS) e espectroscopia por dispersão de comprimento de onda (WDS) indicam a formação da alumina estequiométrica, sendo que a difração de raios-X (XRD), mostrou o caráter amorfo do dielétrico. Por intermédio de curvas capacitância x tensão (CV) foram obtidas a espessura equivalente ao óxido de silício (EOT2,8nm), a densidade de estados de interface (Dit1,4x1011ev-1cm-2) e a permissividade elétrica da alumina (high-k10,6). A admitância associada à corrente de fuga em capacitores MOS foi modelada através de emissão por Frenkel-Poole, tunelamento por Fowler-Nordheim e/ou corrente de fuga constante. Os aluminatos de háfnio (AlxHf1-xOy) foram obtidos sobre p-Si (100), através de deposição atômica por camadas (ALD) para diferentes proporções molares de háfnio (25, 50 ou 75%) e para diferentes tratamentos posteriores (1000ºC, 60s em N2 ou N2+O2 ou laser). A espessura e a rugosidade foram obtidas com a ajuda da técnica de reflectometria de raios-X (XRR). A proporção molar de háfnio adotada no processo de obtenção dos filmes foi confirmada através de análises RBS e WDS. Por XRD, foi verificado o caráter amorfo e a separação de fases nos aluminatos e, por espalhamento de raios-X em ângulo-rasante e pequena abertura (GISAXS), foram analisadas as novas fases formadas. Por fim, da análise CV, foram obtidos EOT9,54nm, resistência série (Rs68,3) e a permissividade elétrica para o aluminato de háfnio (high-k15,2). Finalmente, uma modelagem da admitância associada à corrente de fuga em função da frequência foi proposta para as estruturas MOS. / In this work, MOS capacitors were electrically characterized using alumina (Al2O3) and hafnium aluminate (AlxHf1-xOy) as gate dielectrics; also, the same dielectrics films were physically characterized. Anodic alumina was obtained from oxidation of evaporated aluminum films immersed in nitric acid for 4 or 6 min for different last step cleanings of the p-Si (100) substrates: diluted hydrofluoric acid (DHF) or sulfur peroxide mixture (SPM). Rutherford Backscattering (RBS), Energy Dispersive Spectroscopy (EDS) and Wavelength Dispersive Spectroscopy (WDS) have shown the formation of stoichiometric alumina and the dielectric amorphous structure was revealed by X-Ray Diffraction (XRD). From Capacitance x Voltage curves (CV), it was obtained the equivalent oxide thickness (EOT2.8nm), interface trap density (Dit1.4x1011ev-1cm-2) and Al2O3 dielectric constant (high-k10.6). The admittance that represents the leakage process was modeled according to Frenkel-Poole emission, Fowler-Nordheim tunneling and/or constant leakage admittance. Hafnium aluminates (AlxHf1-xOy) were obtained on (100) silicon wafer surfaces by Atomic Layer Deposition (ALD) for different hafnium molar ratios (25, 50 or 75%) and for different treatments (1000ºC, 60s in N2 or N2+O2 or laser). Thickness and roughness were extracted from X-Ray Reflectometry (XRR) spectra. The hafnium molar ratios used in ALD process were confirmed by RBS and WDS. XRD analysis was used to establish the amorphous structure and phase separation in the aluminates after thermal treatments and Grazing-Incidence Small-Angle X-Ray Scattering (GISAXS) was used to analyze the new phases formed. From CV analysis, it was extracted EOT9.54nm, series resistance (Rs68.3) and dielectric constant from hafnium aluminate (high-k15.2). Finally, the admittance that represents the leakage was modeled in function of the frequency for the MOS structures.