This thesis studies the application of a multi-objective niched Pareto genetic algorithm on the design optimization of an electric field mill sensor. The original sensor requires resonant operation. The objective of the algorithm presented is to optimize the geometry eliminating the need for resonant operation which can be difficult to maintain in the presence of an unpredictable changing environment. The algorithm evaluates each design using finite element simulations. A population of sensor designs is evolved towards an optimal Pareto frontier of solutions. Several candidate solutions are selected that offer superior displacement, frequency, and stress concentrations. These designs were modified for fabrication using the PolyMUMPs abrication process but failed to operate due to the process. In order to fabricate the sensors in-house with a silicon-on-glass process, an anodic bonding apparatus has been designed, built, and tested.

This thesis studies the application of a multi-objective niched Pareto genetic algorithm on the design optimization of an electric field mill sensor. The original sensor requires resonant operation. The objective of the algorithm presented is to optimize the geometry eliminating the need for resonant operation which can be difficult to maintain in the presence of an unpredictable changing environment. The algorithm evaluates each design using finite element simulations. A population of sensor designs is evolved towards an optimal Pareto frontier of solutions. Several candidate solutions are selected that offer superior displacement, frequency, and stress concentrations. These designs were modified for fabrication using the PolyMUMPs abrication process but failed to operate due to the process. In order to fabricate the sensors in-house with a silicon-on-glass process, an anodic bonding apparatus has been designed, built, and tested.

Il s'agit dans ce travail de développer une démarche multiéchelles, afin d'identifier puis de modéliser le comportement mécanique d'un matériau à gradient de propriétés (un cordon de soudure) en relation avec les hétérogénéités microstructurales responsables de la déformation et de l'endommagement par fluage des aciers P91, matériaux retenus pour des applications de tenue mécanique à chaud des centrales thermiques à flamme. Cette étude porte sur l'utilisation des techniques de mesure de champs cinématiques par corrélation d'images couplées aux simulations numériques par éléments finis. Les différentes zones d'intérêt sont : le métal de base, l'ICHAZ (intercritical heat affected zone), la FGHAZ (fine grain heat affected zone), la CGHAZ (coarse grain heat affected zone) et le métal fondu. L'identification a porté dans un premier temps sur le comportement en traction et traction–relaxation à l'ambiante et à 625°C. Cette phase a permis d'établir une loi de comportement pour chacune des zones du joint soudé et de prédire la zone de localisation de déformation pour une gamme assez large de vitesse de sollicitation.Une attention particulière a ensuite été portée aux essais de fluage, pour lequel le glissement intergranulaire joue un rôle essentiel dans le comportement du cordon de soudure et notamment dans l'ICHAZ. Afin de mettre en évidence le glissement intergranulaire, une technique de microlithographie a été adoptée. L'effet de ce mécanisme sur le comportement macroscopique et à l'échelle locale a été étudié au moyen de simulations numériques par éléments finis avec introduction de zones cohésives. Pour cela une loi cohésive a été élaborée et validée sur une configuration simplifiée à quatre grains. Ce modèle permet également de rendre compte de la transition fluage dislocation – fluage diffusion en retardant le déclenchement du glissement aux joints de grains quand la vitesse de sollicitation augmente.Cette étude est financée par la Chaire EDF-GDF-SUEZ-GRT gaz - ENSMP –ENPC sur la «durabilité des matériaux et des structures pour l'énergie ». / The goal of this study is to develop a micromechanical approach, to identify and model the elementary mechanisms in connection with the microstructural heterogeneities accountable for the deformation and for the creep damage of P91 steels, material used for applications at high temperature in thermal power plants. This study deals with the use of kinematic full-fields measurements by digital image correlation coupled with finite element numerical simulations for the identification of constitutive equation parameters of materials presenting a strongly heterogeneous microstructure, leading to gradients of mechanical properties. The welded joint in P91 presents various microstructures along the joint: base metal, ICHAZ (intercritical heat affected zone), FGHAZ (fine grain heat affected zone), CGHAZ (coarse grain heat affected zone) and weld metal, which will be characterized by uniaxial tensile tests and tensile-relaxation tests performed at room temperature and at 625°C. These experimental tests enable to establish a constitutive law for each part of the welded joint and for a wide range of strain rate.A particular attention has then been focused on the behaviour at high temperature (creep) for which the intergranular glide plays an essential role, in particular within the ICHAZ. To characterize the grain boundary gliding mechanisms, a technique of microlithography is used. This mechanism is modelled with cohesive zones. A cohesive constitutive equation has been proposed and validated with a simplified four grain configuration. This model is able to take into account the dislocation creep – diffusion creep transition by delaying the beginning of the grain boundaries sliding when the strain rate increases.This study is granted by the EDF-GDF-SUEZ-GRT gas – Mines ParisTech – Ecole des Ponts ParisTech chair on the "durability of materials and structures for the energy ".

Noise pollution threatens marine ecosystems, where animals rely heavily on sound for navigation and communication. The largest source of underwater noise from human activity is shipping, and propeller-induced cavitation is the dominant source of noise from ships. Mitigation strategies require accurate methods for predicting cavitation-induced noise, which remains challenging. The present thesis explores prediction and modelling strategies for cavitation-induced noise from marine propellers, and provides insight into models that can be used both during propeller design and to generate intelligent vessel control strategies. I examined three distinct approaches to predicting cavitation-induced noise, each of which is discussed in one of the three main chapters of this thesis: a high-fidelity computational fluid dynamics scheme, a parametric mapping procedure, and the use of field measurements. Each of these three chapters presents different insight into the acoustic behaviour of cavitating marine propellers, as well both real and potential strategies for mitigating this critical environmental emission. A combined experimental and numerical study of noise from a cavitating propeller, focused on both the fundamental importance of experimental findings and the effectiveness of the numerical modelling strategy used, is detailed in the first main chapter of this thesis. The experimental results highlighted that loud cavitation noise is not necessarily associated with high-power or high-speed propeller operation, affirming the need for intelligent vessel operation strategies to mitigate underwater noise pollution. Comparison of the experimental measurements and simulations revealed that the simulation strategy resulted in an over-prediction of sound levels from cavitation. Analysis of the numerical results and experiments strongly suggested that the cavitation model implemented in the simulations, a model commonly used for marine propeller simulations, was responsible for the over-prediction of sound levels. Ships are powered primarily by combustion engines, for which it is possible to generate "maps" relating the emission of pollutants to the engine’s speed and torque; the second main chapter of this thesis presents the methodology I developed for generating similar "maps" relating the level of cavitation-induced noise to the speed and torque of a ship's propeller. A proof-of-concept of the method that used the model propeller from the first main chapter is presented. To generate the maps, I used a low-order simulation technique to predict the cavitation induced by the propeller at a range of different speed and torque combinations. A pair of semi-empirical models found in the literature were combined to provide the framework for predicting noise based on cavitation patterns. The proof-of-concept map shows a clear optimal operating regime for the propeller. The final main chapter of this thesis presents an analysis of field noise measurements of coastal ferries in commercial operation, the data for which were provided by an industrial partner. The key finding was the identification of cavitation regime changes with variation in vessel speed by their acoustic signatures. The results provide a basis for remotely determining which vessels produce less noise pollution when subject to speed limits, which have been implement in critical marine habitats, and which vessels produce less noise at a specific optimum speed. / Graduate

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No / The development and validation of a sensor for extrusion melt temperature field measurement is described. A grid of opposing thermocouple wires was constructed and held in position by a supporting frame. Wires were joined together at crossing points to form thermocouple junctions, which were computer monitored. The mesh was used to monitor melt temperature fields during single screw extrusion at the die entrance. Design and construction of the mesh is described in addition to experimental optimization of wire diameter and junction forming. Calibration of the sensor and potential measurement errors including shear heating effects are discussed. Initial results from single screw extrusion are presented for a commercial grade of low density polyethylene using five- and seven-junction thermocouple meshes. The dependence of melt temperature profile on screw speed is illustrated. At low screw speeds melt temperature profiles were flat in shape and higher than set wall temperatures. At higher screw speeds the profiles became more pointed in shape. Use of higher resolution sensors exposed more complex temperature profiles with shoulder regions.

No / Polymer extrusion is fundamental to the processing of polymeric materials and melt flow temperature homogeneity is a major factor which influences product quality. Undesirable thermal conditions can cause problems such as melt degradation, dimensional instability, weaknesses in mechanical/optical/geometrical properties, and so forth. It has been revealed that melt temperature varies with time and with radial position across the die. However, the majority of polymer processes use only single-point techniques whose thermal measurements are limited to the single point at which they are fixed. Therefore, it is impossible for such techniques to determine thermal homogeneity across the melt flow. In this work, an extensive investigation was carried out into melt flow thermal behavior of the output of a single extruder with different polymers and screw geometries over a wide range of processing conditions. Melt temperature profiles of the process output were observed using a thermocouple mesh placed in the flow and results confirmed that the melt flow thermal behavior is different at different radial positions. The uniformity of temperature across the melt flow deteriorated considerably with increase in screw rotational speed while it was also shown to be dependent on process settings, screw geometry, and material properties. Moreover, it appears that the effects of the material, machine, and process settings on the quantity and quality of the process output are heavily coupled with each other and this may cause the process to be difficult to predict and variable in nature. (C) 2013 Society of Plastics Engineers

Geotechnical sediment properties such as moisture content, relative density, bearing capacity, and undrained shear strength have been discussed in the context of coastal sediment dynamics. However, these properties have rarely been assessed in their respective relevance or quantitatively related to sediment transport and erodibility. Also, to date there is no framework available for collecting direct measurements of these properties for estimating initiation of motion and erosion rates. Here, it is postulated that improving the ability to measure geotechnical sediment properties in energetic foreshore environments can improve our ability to predict coastal response to climate change. Through a series of field measurements, the research presented here (1) provides a framework for conducting geotechnical measurements of beaches, (2) advances portable free fall penetrometer (PFFP) data analysis in intertidal environments through the introduction of an impact velocity dependent strain-rate correction factor, (3) relates textural and sediment strength properties derived from PFFP measurements to an erosion rate parameter and hydrodynamically driven bed-level change, and (4) uses PFFP measurements to develop a sediment classification scheme in terms of soil behavior and erosion behavior for a mixed sediment type Arctic environment. Relationships between sediment properties other than grain size, most significantly void ratio, and erodibility parameters highlight the relevance of these measurements in geomorphodynamically active sandy beach environments. For the cohesive sediments in the Arctic, undrained shear strength was also related to an erosion rate parameter, allowing for a categorical framework for erodibility classification to be developed. The cohesive framework was combined with the relationships developed for sandy sediments and used to highlight areas of active sediment transport in the context of local morphodynamic and ice gouging processes. Finally, a simple case study showed how implementing in-situ erodibility parameters was important for long-term morphological modelling. The results represent a step forward in our ability to predict and mitigate climate change related issues from coastal erosion. / Doctor of Philosophy / Climate change driven impacts on coastal environments include increasing frequency and severity of storms, coastal erosion, and inundation of populated areas. Specifically for Arctic environments, warming has caused more sediment to be introduced into coastal waters as well as accelerated rates of permafrost melting and shoreline retreat and decreases in sea ice. One aspect of understanding how these changes will continue to affect coastal communities and our ability to predict climate change effects is understanding the role of sediment properties on sediment erosion and shoreline change. Physical and geomechanical (strength) properties of coastal sediments are important for a variety of coastal applications but have rarely been investigated in the context of quantifying, predicting, and assessing erosion, specifically in the context of field measurements. Towards this end, a series of field surveys were conducted along the coast of North Carolina at a sandy beach, and in Harrison Bay, Alaska, an Arctic coastal zone with both sandy and muddy sediments. Tools for taking physical samples of the beach and seabed, measuring the sediment strength, among other properties in place were used to characterize the local sediments. Once a framework was developed for characterizing the type of sediment, the measured properties were then related to measurements of erosion rate from a series of laboratory experiments performed on physical samples taken from the sites. Finally, one of the instruments for measuring sediment strength both on land and in the water was used to develop classification schemes for seabed sediments in terms of their erodibility. The results of this work highlight the importance of geotechnical properties for coastal sediment transport processes, reveal new relationships between sediment properties and properties quantifying erosion behavior, and offer a framework for future research to classify erodibility of coastal environments in the field with a single piece of equipment. Overall, the work presented here contributes to our ability to measure, quantify, and predict coastal response to climate change.

Neste trabalho é apresentado um novo método de medição de descargas parciais, através de transformadores de corrente de alta frequência, instalados no condutor de aterramento dos equipamentos do sistema elétrico de potência e acoplados a um osciloscópio. Esse novo método de medição tem como grande ganho o fato dos equipamentos não precisarem ser retirados de operação para realização de medição. Pelo fato das transmissoras serem remuneradas pela disponibilidade das funções transmissão, o diagnóstico dos equipamentos em serviço faz com que os custos sejam reduzidos. Foi realizado um levantamento teórico onde foi definida a curva característica esperada como resposta do transformador de corrente a um sinal impulsivo. Foram levantadas curvas características, em laboratório, através de oscilogramas no domínio do tempo, das assinaturas de descargas parciais em equipamentos com isolação a óleo e a gás SF6, de modo a validar o sinal esperado na fundamentação teórica. Essas assinaturas foram utilizadas em medições em campo, que comprovaram a viabilidade da fundamentação teórica e das assinaturas obtidas em laboratório. Adicionalmente foram levantados fatores que podem influenciar nas medições e mostrados sinais que possuam características diferentes daquelas das descargas parciais, de modo a diferencia-los. / This work presents a new method of measuring partial discharges, through high frequency current transformers, installed in the equipment grounding conductor of the electrical power system and coupled to an oscilloscope. This new measurement method has as great gain, the fact that the equipment doesnt need to be removed from service to perform measurement. Because of the transmission being remunerated by the availability of the transmission functions, diagnosis of equipment in service makes the costs been reduced. A theoretical survey where the characteristic curve expected response from the current transformer to an impulsive signal was set has been done. Characteristic curves were raised in the laboratory through oscillograms in the time domain, of signatures of partial discharges in equipment with SF6 gas and oil isolation, in order to validate expected signal discharges in the theoretical foundation. These signatures were used in field measurements, which proved the feasibility of the theoretical foundation and signatures obtained in the laboratory. Further factors were raised that may influence the measurements and shown signs that have different characteristics from those of partial discharges in order to differentiate them.

This thesis proposed a near-field electromagnetic interference measurement framework to obtain sensitivity and spatial resolution of the characteristic parameters of magnetic probe based on International Electrotechnical Commission proposed for integrated circuits electromagnetic radiation measurement standards IEC 61967-6 : magnetic probe method. Using cross-coupled planar microwave bandpass filter which is realized by glass fiber board (FR4) for near-field measurement and electromagnetic simulation in comparsion. Nowadays, integrated circuits has become an important source of energy of overall electromagnetic interference in electronic systems. Finally, do near-field scanning measurement for a 64-pin wire-bond quad flat nonlead (WB-QFN) package and the voltage-controlled oscillator chip in 0.18 £gm CMOS technology by using high scanning resolution of microprobe. Then observes the chip-level and package-level electromagnetic interference, and achieve chip-level of near-field electromagnetic interference measurement techniques.