Made available in DSpace on 2016-08-17T14:53:08Z (GMT). No. of bitstreams: 1 Bartolomeu ferreira.pdf: 2681101 bytes, checksum: 05d2fad3f69568c193c20ccd8addecd7 (MD5) Previous issue date: 2007-04-13 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The goal of loss allocation methodologies is to share the responsibility for transmission losses among generators and loads. Several loss allocation methods have been developed to solve this problem. However, there is not consensus regarding to the most appropriated approach methodology. There are some methods presenting suitable accuracy, however, still remains the equity question. It can say that there isn t an ideal method, although it is desirable that any method achieve efficient allocation criteria. In this work, it is proposed a methodology for active power transmission loss allocation, based on circuit laws, proportional sharing and superposition principles. The methodology uses a load flow solution to share the global loss of the system among market participants. The problem is divided into operation scenarios and taking into account transmission paths used by generators to supply the loads. Tests, analyses and comparison with some methods proposed in literature are performed, using a five bus test system, and IEEE 30 and IEEE 118 systems. / Os métodos de alocação de perdas têm como objetivo distribuir entre os geradores e cargas a responsabilidade por perdas no sistema de transmissão, de uma forma equilibrada. Embora existam vários métodos de alocação propostos na literatura para resolver este problema, ainda não existe um consenso sobre o melhor critério a ser seguido, sendo que atualmente cada país utiliza uma metodologia diferente com maior ou menor grau de aproximação. Há alguns métodos que poderiam ser considerados como exatos , entretanto a questão da equidade ainda continua em aberto. Pode-se afirmar que ainda não existe nenhum método ideal, embora seja desejável que qualquer metodologia objetive atingir a critérios eficientes de alocação. Neste trabalho é proposta uma metodologia para alocação de perdas ativas de transmissão, baseada nas leis de circuito, no princípio da divisão proporcional e no teorema da superposição. A metodologia utiliza os resultados de um fluxo de carga para alocar eficientemente a perda total do sistema entre os participantes do mercado, dividindo o problema em cenários de operação e considerando os caminhos de transmissão utilizados pelos geradores para suprir as demandas das cargas. São realizadas simulações e análises e comparações com alguns métodos já propostos na literatura, utilizando-se: um sistema teste de cinco barras, e os sistemas IEEE 30 e IEEE 118.

L'utilisation de plus en plus fréquente de matériau composite, qui combine une raideur importante pour une faible masse, afin d'alléger les structures aéronautiques entraîne la dégradation des performances d'isolation acoustique aux bruits extérieurs. La plupart du temps, ces nuisances sonores sont réduites par l'installation de matériaux isolants. Ces méthodes, dites passives, deviennent inefficaces aux basses fréquences et il est possible de mettre en place un contrôle actif au moyen de transducteurs électromécaniques. Dans le but de réduire la puissance acoustique transmise à travers la double paroi aéronautique dans la cabine, des unités de contrôle composées d'un actionneur et d'un capteur colocalisé dual sont réparties sur le panneau intérieur afin d'en modifier la vibration. Cette stratégie de contrôle actif vibroacoustique permet, pour des perturbations primaires harmoniques, d'imposer localement une impédance mécanique virtuelle à la structure, au moyen d'un contrôleur décentralisé. Cependant, sans communication entre les unités, le contrôle peut difficilement minimiser un critère global comme la puissance acoustique rayonnée. Afin de calculer les impédances mécaniques virtuelles qui garantissent la minimisation de la puissance acoustique rayonnée par la structure, une approche en deux étapes est considérée : (1) la matrice diagonale des impédances mécaniques virtuelles optimales est calculée à partir de mesures acoustiques ou vibratoires de la perturbation primaire et des transferts avec les actionneurs secondaires, (2) l'objectif exprimé en terme d'impédances mécaniques virtuelles est atteint grâce à un contrôle en temps réel. Une attention particulière est portée à la comparaison de cette approche avec une stratégie classique d'amortissement actif réalisée par un contrôle par rétroaction sur la vitesse de la structure, où l'impédance mécanique virtuelle alors imposée est un réel positif. Le calcul optimal réalisé à l'issue de la première étape se faisant pour une perturbation primaire donnée, la robustesse de la méthode aux variations de la perturbation primaire est un aspect également développé dans cette étude. Des résultats théoriques et expérimentaux sont comparés dans le cas académique d'une plaque mince d'aluminium simplement appuyée et soumise à une onde plane incidente. Enfin, la méthode est appliquée au panneau intérieur d'une double paroi aéronautique, à savoir une structure courbée, en matériau composite, et composée d'un hublot. Contrairement à la majorité des études qui considèrent l'implantation d'impédances virtuelles dissipatives, il apparaît que dans certains cas, le contrôle optimal requiert l'injection d'énergie des unités à la structure. / Composite materials are widely used in the aeronautic industry for their low mass/stiffness ratio. However, this property tends to reduce the acoustic transmission loss, particularly at low frequencies. At these frequencies, active control is an effective mean of controlling sound transmission. Among the various approaches, Active Structural Acoustic Control (ASAC) has received considerable attention because transducers can be integrated to the structure. In order to reduce the acoustic power radiated by a flexible panel, dual colocated actuator sensor pairs are used to modify its vibration. The control strategy implemented for harmonic disturbances leads to locally impose a virtual mechanical impedance to the structure, using a decentralized controller. This virtual mechanical impedance is computed in order to minimise the radiated acoustic power. The challenging problem is then to find the local control to impose on each independent devices that minimizes the global acoustic radiation of the structure. The proposed approach consists in two steps : (1) the matrix of optimal virtual mechanical impedance is calculated by measuring the primary disturbance and the transfer functions between actuators and structural / acoustic sensors, (2) the virtual mechanical impedance objective is achieved using a real-time integral controller. Special focus is put on the discussion about such control approach versus a classical active damping strategy were the virtual mechanical impedance is defined as real positive. Considering that optimal control is computed during the first step for a given primary disturbance, the robustness of the method to variations of the primary disturbance between step 1 and step 2 is discussed. Theoretical and experimental results are compared in the case of a simply supported thin aluminum plate and a primary disturbance under the form of an incident plane wave. Then, the method is implemented on a curved composite aircraft panel comprising a window. Unlike most of previous studies where dissipative virtual mechanical impedance are imposed, it clearly appears that optimal control can require energy injection from the control units into the structure.

The pursuit of reducing energy consumption and enhancing thermal efficiency across various sectors to foster sustainable practices has gained significant prominence in recent years, driven by the global environmental crisis. Sweco consultancy has undertaken a study focusing on underfloor heating systems for bathrooms in low-energy buildings located in Sweden. The objective is to analyse the energy usage and thermal loss to the ground based on the thickness of insulation employed. Literature findings indicate that the thermal loss to the ground should comprise approximately 15 % of the total energy, and there exists a logarithmic relationship between the thermal conductivity and density of the insulation material. In the present study, multiple simulation models were developed using IDA-ICE to assess the supplied energy and the percentage of heating loss through the ground for two typical bathrooms situated on adjacent floors of a residential building in Stockholm. The analysis encompasses scenarios where the construction is directly built on the soil or on a concrete slab, as well as the potential thermal loss from the upper level bathroom to the lower level. The results demonstrate that without an insulation layer the heating loss through the ground is remarkably high, approximately 60 %. When employing an insulation thickness of 200 mm or greater, the distinction between constructing on a concrete slab or on the soil becomes negligible. Furthermore, with a 300 mm insulation thickness, the heating loss percentage decreases to over 15 %. The simulations also reveal that the lower level bathroom can benefit from the energy loss occurring in the upper level bathroom. In instances where there is no insulation, the upper level experiences a 56 % energy loss, resulting in energy savings of over 70 % for the lower level bathroom. By incorporating a 45 mm insulation thickness on the upper level floor, this percentage is reduced to 13 %, leading to energy savings of over 25 % for the lower level bathroom.

La mise en oeuvre de matériaux acoustiques est une méthode efficace et très utilisée pour réduire le bruit le long de sa propagation. Les propriétés acoustiques de nouvelles structures sandwich multifonctionnelles et de matériaux absorbants poreux sont étudiées dans la thèse. Les principales contributions de la thèse sont les suivantes: Les panneaux sandwich ont généralement d'excellentes propriétés mécaniques et un bon indice de perte en transmission sonore (STL), mais aucune capacité d'absorption acoustique. De nouvelles structures sandwich multifonctionnelles sont développées en intégrant des microperforations et des matériaux absorbants poreux aux panneaux sandwich ondulés et en nid d’abeilles conventionnels, structurellement efficaces pour obtenir de bons STL et de bonnes absorptions en basses fréquences. Le coefficient d'absorption acoustique (SAC) et la perte en transmission (STL) des panneaux sandwich ondulés sont évalués numériquement et expérimentalement en basse fréquence pour différentes configurations de perforations. Les modèles éléments finis (EF) sont construits en tenant compte des interactions vibro-acoustiques sur les structures et des dissipations d'énergie, visqueuse et thermique, à l'intérieur des perforations. La validité des calculs FE est vérifiée par des mesures expérimentales avec les échantillons testés obtenus par fabrication additive. Par rapport aux panneaux sandwich ondulés classiques sans perforation, les panneaux sandwich perforés (PCSPs) avec des perforations dans leur plaque avant présentent non seulement un SAC plus élevé aux basses fréquences, mais aussi un meilleur STL, qui en est la conséquence directe. L'élargissement des courbes des indices d’absorption et de transmission doit être attribué à la résonance acoustique induite par les micro-perforations. Il est également constaté que les PCSPs avec des perforations dans les plaques avant et les parois internes onduleés ont les fréquences de résonance les plus basses de tous les PCSPs. En outre, les performances acoustiques des panneaux sandwich en nid d'abeilles avec une plaque avant microperforée sont également examinées. Un modèle analytique est présenté avec l'hypothèse que les déplacements des deux plaques sont identiques aux fréquences inférieures à la fréquence de résonance des plaques. Le modèle analytique est ensuite validé par des modèles d'éléments finis et des résultats expérimentaux existants. Contrairement aux panneaux sandwich en nid d'abeilles classiques qui sont de piètres absorbeurs de bruit, les sandwichs en nid d'abeilles perforés (PHSPs) conduisent à un SAC élevé aux basses fréquences, ce qui entraîne en conséquence un incrément dans le STL basse fréquence. Les influences de la configuration du noyau sont étudiées en comparant les PHSPs avec différentes configurations de noyaux en nids d'abeilles. […] / Implementation of acoustic materials is an effective and popular noise reduction method during propagation. Acoustic properties of novel multifunctional sandwich structures and porous absorbing materials are studied in the dissertation. The main contributions of the dissertation are given as, Sandwich panels generally have excellent mechanical properties and good sound transmission loss (STL), but no sound absorption ability. Novel multifunctional sandwich structures are developed by integrating micro perforations and porous absorbing materials to the conventional structurally-efficient corrugated and honeycomb sandwich panels to achieve good SAC and STL at low frequencies. Low frequency sound absorption and sound transmission loss (STL) of corrugated sandwich panels with different perforation configurations are evaluated both numerically and experimentally. Finite element (FE) models are constructed with considerations of acousticstructure interactions and viscous and thermal energy dissipations inside the perforations. The validity of FE calculations is checked against experimental measurements with the tested samples provided by additive manufacturing. Compared with the classical corrugated sandwich panels without perforation, the perforated corrugated sandwich panels (PCSPs) with perforations in its face plate not only exhibits a higher SAC at low frequencies but also a better STL as a consequence of the enlarged SAC. The enlargement of SAC and STL should be attributed to the acoustical resonance induced by the micro perforations. It is also found that the PCSPs with perforations in both the face plates and corrugated cores have the lowest resonance frequencies of all the PCSPs. Besides, the acoustic properties of honeycomb sandwich panels with microperforated faceplate are also explored. An analytical model is presented with the assumption that displacements of the two faceplates are identical at frequencies below the faceplate resonance frequency. The analytical model is subsequently verified by finite element models and existing experimental results. Unlike classical honeycomb sandwich panels which are poor sound absorbers, perforated honeycomb sandwiches (PHSPs) lead to high SAC at low frequencies, which in turn brings about increment in the low frequency STL. Influences of core configuration are investigated by comparing PHSPs with different honeycomb core configurations. In order to enlarge the SAC bandwidth of perforated sandwich panels, porous absorbing materials are added to the cores of novel perforated sandwich panels. FE models are set up to estimate the SAC and STL of perforated sandwich panels with porous materials. Results show that perforated sandwich panels with porous material can provide SAC with broader bandwidth and lower resonance frequency than that without porous materials. Whereas the peak values in the SAC and STL curves are reduced due to the weakened acoustical resonance by the porous materials. […]

Windows are a weakness in building facade sound transmission loss (STL). This coupled with the detrimental effects of excessive noise exposure on human health including: annoyance, sleep deprivation, hearing impairment and heart disease, is the motivation for this investigation of the STL improvements active noise control (ANC) of windows can provide. Window speaker development, ANC window experiments and analytical modelling of ANC windows were investigated. Five different window speaker constructions were characterised then compared with a previously developed window speaker. ANC window testing used three different ANC configurations and was performed in two different environments, one with a reverberant receiving room, and the other with an anechoic receiving room. Optimisation of ANC systems with particular control source locations was the aim of the modelling. This enabled comparison with the ANC window tests and would aid in further development of ANC windows. Window speaker constructions were characterised by sound pressure level (SPL) measurements performed in an anechoic room. These measurements were made in a way that enabled comparison with the previously developed window speaker. Total sound energy reduction calculations were used to determine the relative performance of the tested ANC windows. An STL model, based on a modal panel vibration model, was initially created and verified against published STL data before it was expanded to include ANC control sources. The model was used to simulate the performed anechoic environment tests and an ideal ANC case.

[pt] Os engenheiros e projetistas enfrentam diversos desafios na fase de implantação das redes móveis celulares, sobretudo no planejamento da área de cobertura e da penetração da onda eletromagnética em ambientes indoor, em particular na faixa de 2.5 GHz. Adicionalmente, não se dispõe de muitos resultados sobre as constantes de propagação através das edificações que permitam calcular com precisão a contribuição de campo que atravessa edifícios que são especialmente importantes na predição de cobertura em sistemas microcelulares. A primeira parte desse estudo trata da caracterização do canal em banda larga e banda estreita a partir de resultados experimentais que fornecem informações essenciais na implementação e desenvolvimento de projetos de redes móveis. Em banda larga os resultados de dispersão temporal do canal, tais como, o retardo médio e o espalhamento de retardo, são obtidos através de dois métodos distintos e comparados entre si em condições de LOS e NLOS em ambientes urbano e suburbano. Em banda estreita é realizada a análise estatística do desvanecimento em pequena e larga escala característicos de cada região urbana e suburbana. Na segunda parte desse estudo discute-se a importância para a cobertura em regiões urbanas do campo eletromagnético que atravessa as edificações num ambiente microcelular e formula-se um modelo de perda de potência do sinal transmitido através de edificações características de ambientes urbanos e suburbanos. / [en] The engineers and designers face many challenges in the implementation of cellular mobile networks, especially in planning the coverage and penetration of the signal into indoor environments, in particular in the range of 2.5 GHz. Additionally, they do not have many results on the propagation constants through the buildings that allow the accurate calculation of the contribution of field that crosses buildings and are especially important in the prediction of coverage. The first part of this study deals with the broadband and narrowband characterization of the channel from experimental results that provide essential information to the development and implementation of projects of mobile networks. Broadband results of temporal dispersion of the channel, such as the mean delay and delay spread, are obtained by two distinct methods and compared for LOS and NLOS conditions in urban and suburban environments. The narrowband characterization includes the statistical analysis of the small-scale fading characteristic of urban and suburban region. In the second part of this study the representativeness of the signal going through the buildings is discussed and a model of loss of signal strength by the propagation through buildings in urban and suburban environments is formulated.

Lined silencers of various configurations are used to attenuate the noise from building HVAC equipment, gas turbines, and other machinery. First-mode analytical solutions are presented for sound attenuation along rectangular lined ducts, parallel-baffle silencers, and circular lined ducts. The sound absorptive lining is treated using a bulk property model. The analytical solutions entail solving a nonlinear characteristic equation in the transverse direction after the rigid-wall boundary condition is applied. The solution is compared to the boundary element solution and a local impedance analytical solution for several test cases.

La modélisation du comportement vibroacoustique en flexion des structures sandwich est devenue aujourd’hui de plus en plus d’un grand intérêt dans les différents secteurs industriels. Cette tendance est principalement due aux propriétés mécaniques avantageuses des structures sandwich. L’un des principaux avantages de ce type de structures réside principalement dans le rapport rigidité-poids élevé. En revanche, acoustiquement la diminution de la masse du panneau avec une rigidité élevée conduit à un confort acoustique insatisfait. Pour cette raison, il y a une demande croissante pour des approches de modélisation du comportement vibroacoustique des structures sandwich avec une précision maximale. La présente thèse propose une approche méso-macro basée sur une méthode numérique pour la prédiction des caractéristiques dynamiques des structures sandwich. La méthode est principalement utilisée pour résoudre le problème de transparence acoustique considéré dans ce projet de thèse. Le travail présenté porte principalement sur la topologie du coeur du sandwich pour traiter le problème abordé. Le principal avantage du modèle proposé réside dans les effets du cœur prises en compte telle que l’effet du cisaillement et celle de l’orthotropie du panneau sandwich. L’approche de modélisation proposée est basée sur la méthode des éléments finis ondulatoire, qui combine la méthode des éléments finis classique et la théorie des structures périodiques. La structure sandwich a été modélisée comme un guide des ondes tridimensionnelles qui garde absolument les informations à l’échelle mésoscopique du panneau modélisé. La fréquence de transition définie la fréquence à laquelle le cisaillement du coeur devient important. Cette fréquence spéciale a été identifié via deux méthodes numériques. Une expression de transmission acoustique à travers un panneau sandwich a également été dérivée. Ensuite, une étude paramétrique a été menée dans le but de révéler l’effet des différents paramètres géométriques sur les indicateurs vibroacoustiques. / Prediction of the flexural vibroacoustic behavior of honeycomb sandwich structures in the low-mid frequency is nowadays becoming of high interest in different industrial sectors. This trend is mainly owing to the advantageous mechanical properties of the sandwich structures. One of the main advantages of this kind of structures lies principally in the high stiffness-to-weight ratio. Even though, acoustically the decrease of the panel mass with a high stiffness leads to an unsuitable acoustic comfort. For this reason, there is an increasing demand for approaches modeling the vibroacoustic behavior of the sandwich structures with a maximum accuracy. The present thesis deals with a meso-macro approach based on a numerical method for modeling the vibroacoustic behavior of sandwich structures. The modeling description is mainly used to address the acoustic insulation problem considered in the thesis. The presented work focuses on the topology of the sandwich core to treat the addressed problem. The main advantage of the proposed model is that it takes into account the core shear and panel orthotropic effects. The modeling approach suggested here is based on the wave finite element method (WFE method), which combines the standard finite element method and the periodic structure theory. The sandwich structure has been modeled as a tridimensional waveguide which holds absolutely the meso-scale information of the modeled panel. The transition frequency, which indicates the frequency at which the core shear becomes important, was identified via two different numerical methods. An expression of the acoustic transmission for an equivalent isotropic sandwich panel was also derived. A parametric study was then conducted with a goal of revealing the effect of the geometric parameters of the sandwich core on the vibroacoustic indicators.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / In urban areas, where noise is significant, the facades and roofs must submit a performance capable of ensuring insulation required for the acoustic comfort of the users. The roof, although important elements of the envelope of buildings, has been little studied in Acoustics. The validity of ISO 15575 Residential Buildings - Performance impacted mainly the construction industry suppliers, who needed to characterize their products and systems. Also in 2015 came the NBR 16373 - tiles and thermoacoustic panels - Performance requirements. This Thesis aimed to establish a methodology to analyse the acoustic performance for sandwich tiles considering regulatory standards and experimental trials. It started from the requirements of ISO 16373 for performing absorption tests and sound transmission loss of sandwich type of shingle tiles + EPS. The experimental procedure used to determine the sound absorption coefficient (α) was the method of the reverberation chamber in a diffuse field standardized by ASTM C423. The results showed behaviour with greater absorption (0.29) in a narrow band around 250 Hz and stabilized above 1600 Hz, with values similar to 0.06. These factors mean rank 1 according to the NBR 16373, in other words, the worst performance scale. Regarding the sound insulation test, performed according to ISO 10140 in reverberation room, it was quantified the Weighted Sound Reduction Index, Rw = 20 dB, above the expected performance because resulted close to the performance of other more valued tile commercially. The information given on NBR 16373: 2015 for the experimental analysis of sandwich tile are very incomplete, so difficult the tests. To facilitate implementation, minimizing errors due to erroneous interpretations of the techniques involved standards, we established a specific analysis methodology for trials in shingles or tiles. Therefore, it is proposed that the adequacy of samples of the tests, the individual analysis of each material that compose the shingle and evaluation of the two faces of the composite tiles, in order that they may have different types of finish (liner, liner-film, perforated panel, among others) and therefore the analysis of the lower tile becomes effective in assisting in the determination of the acoustic conditioning of the interior environments. Another suggestion is the evaluation of the rain impact noise on tiles. Finally, we reiterate the importance of the technical product information are clear and complete, allowing consumers to obtain adequate acoustic performance in their buildings. / Em áreas urbanas, onde o ruído é significativo, as fachadas e coberturas devem apresentar um desempenho capaz de garantir a isolação necessária para o conforto acústico dos usuários. As coberturas, embora sejam elementos importantes da envoltória das edificações, tem sido pouco estudadas na área de Acústica. A vigência da NBR 15575 Edificações habitacionais Desempenho impactou, principalmente, o setor de fornecedores da construção civil, que necessitaram caracterizar seus produtos e sistemas. Além disso, em 2015, surgiu a NBR 16373 Telhas e painéis termoacústico Requisitos de desempenho. A presente Dissertação teve como objetivo principal estabelecer uma metodologia de análise da performance acústica para telhas sanduíche, considerando padrões normativos e ensaios experimentais. Partiu-se das exigências da NBR 16373 para a execução dos ensaios de absorção e perda de transmissão sonora das telhas sanduíche do tipo telha + EPS. O procedimento experimental utilizado para a determinação do Coeficiente de Absorção Sonora (α) foi o método da câmara reverberante em campo difuso, normatizado pela ASTM C423. Os resultados mostraram um comportamento com maior absorção (0,29) numa faixa estreita em torno de 250 Hz e uma estabilização acima de 1600 Hz, com valores similares a 0,06. Tais coeficientes significam classificação 1, de acordo com a NBR 16373, ou seja, o pior desempenho da escala. No que tange ao ensaio de isolamento sonoro, executado de acordo com a ISO 10140, em câmara reverberante, foi quantificado o Índice de Redução Sonora Ponderado, Rw= 20 dB, desempenho acima do esperado, pois resultou próximo ao desempenho de outra telha mais valorizada comercialmente. As informações constantes na NBR 16373:2015 para a análise experimental da telha sanduíche são muito incompletas, por isso dificultam a realização dos ensaios. Para facilitar a execução, minimizando os erros decorrentes de interpretações equivocadas das normas técnicas envolvidas, estabeleceu-se uma metodologia de análise específica para ensaios realizados em telhas ou coberturas. Assim, propõe-se a adequação das amostras dos ensaios, a análise individual de cada material que compõe a telha e a avaliação das duas faces das telhas compostas, tendo em vista que elas podem possuir diferentes tipos de acabamento (forro, forro-filme, painel perfurado, entre outros) e, por isso, a análise da parte inferior da telha torna-se eficaz no auxílio da determinação do condicionamento acústico no interior de ambientes. Outra sugestão é a avaliação do ruído de impacto da chuva em telhas. Por fim, reitera-se a importância de que as informações técnicas sobre os produtos sejam claras e completas, permitindo que os consumidores finais possam obter um adequado desempenho acústico em suas edificações.

Thesis (PhD)--University of Pretoria, 2013. / Electrical, Electronic and Computer Engineering