L’essor des nouvelles techniques de traitement en radiothérapie externe a rendu nécessaire la mise en place de nouveaux contrôles qualité (CQ). Il est en effet capital de s’assurer que la dose délivrée au patient est bien conforme à celle qui lui a été prescrite. Les détecteurs EPID, initialement utilisés pour contrôler l’exactitude du positionnement du patient, sont de plus en plus employés pour vérifier la conformité du traitement. L’image qu’ils enregistrent au cours d’une irradiation peut par exemple être comparée à une image de référence, qui correspond à ce qui aurait été mesuré si le traitement s’était déroulé dans les conditions de sa planification. Le succès de ce CQ repose (1) sur la précision avec laquelle on peut prédire l’image EPID (ou portale) de référence et (2) sur les performances de l’outil de comparaison d’image utilisé. Nous avons étudié au cours de cette thèse ces deux points clés. Nous nous sommes tout d’abord tournés vers une méthode de prédiction d’images EPID haute résolution basée sur le couplage de simulations Monte-Carlo (MC) et de la technique de débruitage DGPLM. Pour la mettre en œuvre, nous avons modélisé un accélérateur linéaire d’électrons à usage médical (linac) dans le code MC PENELOPE et optimisé les paramètres de sa source d’électrons primaires pour des calculs de dose dans l’eau. L’analyse d’un fichier d’espace des phases (PSF) de 71 Go stocké sous le cône égalisateur nous a ensuite permis de développer un modèle de sources virtuelles (MSV) représenté par des histogrammes corrélés (environ 200 Mo). Ce nouveau MSV, plus compact que le PSF, est tout aussi précis pour les calculs de dose dans l’eau si son maillage est déterminé selon une méthode adaptative. La modélisation du détecteur EPID dans PENELOPE suggère que les hypothèses faites sur les propriétés de la tâche focale du linac sont trop simplistes et doivent être reconsidérées. L’évaluation du MSV pour la prédiction d’images EPID haute résolution a quant à elle conduit à d’excellents résultats. Une fois la chaine de prédiction de l’image portale de référence validée, nous l’avons utilisée pour détecter des irrégularités dans les traitements de RCMI. Dans une étude préliminaire, nous avons volontairement introduit des erreurs de traitement dans le calcul d’images EPID (dérive du faisceau d’irradiation, modification de la morphologie ou de la position du patient). Le γ-index traditionnellement utilisé en routine s’est avéré moins performant que le χ-index pour les détecter. Une étude plus approfondie aura pour objet de déterminer des seuils de détection d’erreurs en fonction de leur nature et d’éprouver les performances d’autres tests. / Advanced techniques used in radiotherapy for cancer treatment, such as Intensity-Modulated Radiation Therapy (IMRT), require extensive verification procedures to ensure the correct dose delivery. Electronic Portal Imaging Devices (EPIDs) are widely used for quality assurance in radiotherapy, and also for dosimetric verifications. For this latter application, the images obtained during the treatment session can be compared to a pre-calculated reference image in order to highlight dose delivery errors. The quality control performance depends (1) on the accuracy of the pre-calculated reference image (2) on the ability of the tool used to compare images to detect errors. These two key points were studied during this PhD work. We chose to use a Monte Carlo (MC)-based method developed in the laboratory and based on the DPGLM (Dirichlet process generalized linear model) denoising technique to predict high-resolution reference images. A model of the studied linear accelerator (linac Synergy, Elekta, Crawley, UK) was first developed using the PENELOPE MC codes, and then commissioned using measurements acquired in the Hôpital Nord of Marseille. A 71 Go phase space file (PSF) stored under the flattening filter was then analyzed to build a new kind of virtual source model based on correlated histograms (200 Mo). This new and compact VSM is as much accurate as the PSF to calculate dose distributions in water if histogram sampling is based on adaptive method. The associated EPID modelling in PENELOPE suggests that hypothesis about linac primary source were too simple and should be reconsidered. The use of the VSM to predict high-resolution portal images however led to excellent results. The VSM associated to the linac and EPID MC models were used to detect errors in IMRT treatment plans. A preliminary study was conducted introducing on purpose treatment errors in portal image calculations (primary source parameters, phantom position and morphology changes). The γ-index commonly used in clinical routine appears to be less effective than the χ-index. A future in-depth study will be dedicated to determine error detection threshold according to their nature and to evaluate other comparison test robustness. The developed portal image prediction method associated to robust analysis tools will then constitute an adapted way to assure treatment quality control.

The primary objective of this study is to evaluate the seismic hazard in the Eastern Marmara Region using improved seismic source models and enhanced ground motion prediction models by probabilistic approach. Geometry of the fault zones (length, width, dip angle, segmentation points etc.) is determined by the help of available fault maps and traced source lines on the satellite images. State of the art rupture model proposed by USGS Working Group in 2002 is applied to the source system. Composite reoccurrence model is used for all seismic sources in the region to represent the characteristic behavior of North Anatolian Fault. New and improved global ground motion models (NGA models) are used to model the ground motion variability for this study. Previous studies, in general, used regional models or older ground motion prediction models which were updated by their developers during the NGA project. New NGA models were improved in terms of additional prediction parameters (such as depth of the source, basin effects, site dependent standard deviations, etc.), statistical approach, and very well constrained global database. The use of NGA models reduced the epistemic uncertainty in the total hazard incorporated by regional or older models using smaller datasets. The results of the study is presented in terms of hazard curves, deaggregation of the hazard and uniform hazard spectrum for six main locations in the region (Adapazari, Duzce, Golcuk, Izmit, Iznik, and Sapanca City Centers) to provide basis for seismic design of special structures in the area. Hazard maps of the region for rock site conditions at the accepted levels of risk by Turkish Earthquake Code (TEC-2007) are provided to allow the user perform site-specific hazard assessment for local site conditions and develop site-specific design spectrum. Comparison of TEC-2007 design spectrum with the uniform hazard spectrum developed for selected locations is also presented for future reference.

Dans le contexte actuel de réchauffement climatique et d'épuisement des ressources énergétiques fossiles conventionnelles, la production d'énergie à partir de combustibles renouvelables (biomasse et déchets) présente un intérêt croissant. Cependant les brûleurs industriels conventionnels sont mal ou pas adaptés pour la valorisation énergétique de combustibles pauvres qui sont pourtant peu couteux et largement disponibles. Les électro-brûleurs, basés sur une assistance à la combustion par plasma thermique, sont alors une solution pour ce type de combustible. Ce travail de thèse a pour objectif le développement d'une torche à plasma triphasée d'une puissance de 100 kW, fonctionnant à l'air et facilement intégrable dans un électro-brûleur industriel. Le premier challenge consiste à rendre possible le fonctionnement à l'air en réduisant autant que possible l'érosion à l'air des électrodes en graphite. Pour cela, des solutions de gainage des électrodes à l'azote ou au méthane, de contrôle aérodynamique de l'écoulement de l'air et d'injection de particules de carbone ont été étudiées. Le deuxième challenge est l'optimisation des transferts de masse et de chaleur, ce qui a été réalisé en améliorant l'écoulement du gaz plasmagène et en choisissant les matériaux adéquats pour l'isolation thermique. Une double approche théorique et expérimentale a été adoptée. Au niveau théorique, un modèle d'écoulement turbulent de plasma a été développé avec une modélisation de l'arc électrique par une source stationnaire de chaleur et de quantité de mouvement. Un modèle de rayonnement à bandes du plasma ainsi qu'un modèle de cinétique chimique ont été intégrés. Les résultats de la simulation montrent le rôle important du rayonnement, la limitation du gainage à l'azote et le potentiel intéressant du gainage au méthane. La simulation a permis aussi de valider le design de la nouvelle torche avant les essais. Au niveau expérimental, une nouvelle conception de torche a été proposée et testée. Les essais réalisés montrent que la protection des électrodes par injection de particules de carbone ne suffit pas pour créer une atmosphère neutre autour des électrodes mais que le contrôle aérodynamique de l'écoulement de l'air permet un meilleur contrôle de l'érosion des électrodes. Des essais préliminaires de combustion assistée par plasma de biomasse solides ont été ensuite réalisés et analysés. / Energy production from renewable combustibles like biomass and organic wastes presents an increasing interest with the urgent need to reduce greenhouse gas emissions and the depletion of conventional fossil energy resources. Meanwhile, standard industrial burners are not adequate for the energetic valorization of renewable poor LHV combustibles despite their low price and their abundance in nature. Electro-burners, with plasma assisted combustion technology, are a promising solution for this type of combustible. In this PhD dissertation is detailed the development of a 100 kW plasma torch working in air and embeddable in an industrial electro-burner. It consists firstly, in making possible an operation in oxidizing environment by reducing as much as possible the air erosion of the graphite electrodes. For this purpose, multiple solutions are tested such as sheathing with nitrogen and methane, aerodynamic control of air flow and injection of carbon black particles. The second challenge is the optimization of heat and mass transfers by improving the plasma flow and by choosing the appropriate materials for thermal insulation. Theoretically, a turbulent model of plasma flow is developed with the modeling of the electric arc column as a stationary source of heat and momentum. A multi-band radiation model and a reactional kinetic model are also integrated. The results show the important role of radiation, the limitation of the nitrogen sheathing and the potential of methane injection in reducing electrode erosion. They allowed also validating the design of the plasma torch before the tests. Experimentally, the new torch design is built and tested. It comes out that reducing the electrode erosion by carbon powder injection is not efficient to achieve a neutral environment around the electrodes whereas a control of the nearby air flow appears to be beneficial. Finally, tests of plasma assisted combustion of some biomasses are performed and analyzed.

<p>Signal processing within the neurophysiological field is challenging and requires short processing time and reliable results. In this thesis, three main problems are considered.</p><p>First, a modified line source model for simulation of muscle action potentials (APs) is presented. It is formulated in continuous-time as a convolution of a muscle-fiber dependent transmembrane current and an electrode dependent weighting (impedance) function. In the discretization of the model, the Nyquist criterion is addressed. By applying anti-aliasing filtering, it is possible to decrease the discretization frequency while retaining the accuracy. Finite length muscle fibers are incorporated in the model through a simple transformation of the weighting function. The presented model is suitable for modeling large motor units.</p><p>Second, the possibility of discerning the individual AP components of the concentric needle electromyogram (EMG) is explored. Simulated motor unit APs (MUAPs) are prefiltered using Wiener filtering. The mean fiber concentration (MFC) and jitter are estimated from the prefiltered MUAPs. The results indicate that the assessment of the MFC may well benefit from the presented approach and that the jitter may be estimated from the concentric needle EMG with an accuracy comparable with traditional single fiber EMG.</p><p>Third, automatic, rather than manual, detection and discrimination of recorded C-fiber APs is addressed. The algorithm, detects the Aps reliably using a matched filter. Then, the detected APs are discriminated using multiple hypothesis tracking combined with Kalman filtering which identifies the APs originating from the same C-fiber. To improve the performance, an amplitude estimate is incorporated into the tracking algorithm. Several years of use show that the performance of the algorithm is excellent with minimal need for audit.</p>

Signal processing within the neurophysiological field is challenging and requires short processing time and reliable results. In this thesis, three main problems are considered. First, a modified line source model for simulation of muscle action potentials (APs) is presented. It is formulated in continuous-time as a convolution of a muscle-fiber dependent transmembrane current and an electrode dependent weighting (impedance) function. In the discretization of the model, the Nyquist criterion is addressed. By applying anti-aliasing filtering, it is possible to decrease the discretization frequency while retaining the accuracy. Finite length muscle fibers are incorporated in the model through a simple transformation of the weighting function. The presented model is suitable for modeling large motor units. Second, the possibility of discerning the individual AP components of the concentric needle electromyogram (EMG) is explored. Simulated motor unit APs (MUAPs) are prefiltered using Wiener filtering. The mean fiber concentration (MFC) and jitter are estimated from the prefiltered MUAPs. The results indicate that the assessment of the MFC may well benefit from the presented approach and that the jitter may be estimated from the concentric needle EMG with an accuracy comparable with traditional single fiber EMG. Third, automatic, rather than manual, detection and discrimination of recorded C-fiber APs is addressed. The algorithm, detects the Aps reliably using a matched filter. Then, the detected APs are discriminated using multiple hypothesis tracking combined with Kalman filtering which identifies the APs originating from the same C-fiber. To improve the performance, an amplitude estimate is incorporated into the tracking algorithm. Several years of use show that the performance of the algorithm is excellent with minimal need for audit.

A number of experimental and theoretical studies, performed in the field of technical flow duct acoustics are presented in this thesis. The acoustical methods treated are implemented on turbocharged IC-engines and engine gas exchange system components. A new method based on the well-known two-load technique has been developed. The method was applied to characterise the source data of various piston-engines with non-linear behaviour including a 6 cylinder turbo-charged truck diesel engine. The source characterisation results were compared to the results obtained using the linear two-load technique. It was demonstrated that the new non-linear multi-load technique gives improved results when the source is slightly non-linear. The use of active one-port models has been tested to characterize an air terminal device (ATD) as a source of flow generated noise. In order to predict the noise generation at different operating points of the device a scaling law was derived and verified. In the experimentally derived scaling law a flow speed dependence of 3 was found for the narrow band spectra, corresponding to a dipole-like behavior of the source in the plane wave range. The proposed technique was validated successfully and the results indicated a good prediction of in-duct sound generation by the air terminal device. Sound reflection from hot flow duct openings has been investigated experimentally. The reflection coefficient was measured for flow temperatures up to 500 ºC and jet velocities up to 108m/s. The results have been compared with famous Munt’s theory. It was concluded that at low Mach number and Helmholz number cases the results agree well with the Munt’s model. This was the first experimental validation of the theory for hot flow conditions. Experimental procedures to determine the sound transmission through automotive turbo-charger compressors were developed and described in detail. An overview of a unique turbocharger testing facility established at KTH CICERO in Stockholm is given. The facility can be used to measure acoustic two-port data for turbo-compressors. Results from measurements on a passenger car turbo-compressor are presented and the influence of operating conditions on the sound transmission is discussed. Current wave action models developed in CMT for computation of the gas exchange processes in I.C. engines have been implemented to determine the acoustic wave transmission through the turbo- compressor. The models are validated with the experimental data and the results are presented for different operating conditions of a Volvo passenger car turbo-compressor. / QC 20100809

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In diesem Beitrag wird über die erzielten Ergebnisse der durchgeführten simulativ-experimentellen Untersuchungen für additive Fertigung von komplexen Bauteilgeometrieflächen mittels 3D – Plasma-Auftragschweißen berichtet. Hierbei wurde mittels des 3D – Plasma-Pulver-Auftragschweißenes von komplexen Konturflächen für ein Werkzeugmodell und ähnliche Bauteilgeometrien aus reinem Schweißgut in Mehrlagentechnik beanspruchungsgerecht hergestellt. Infolge der Besonderheiten des 3D – Plasma-Auftragschweißenes mit großer Schweißgutvolumina wie stark abweichende Eigenschaften zwischen Grund-/ Auftragswerkstoff und asymmetrischer Wärmeeintrag sind die entstehenden Schrumpfungen, Verformungen/ Eigenspannungen besonders kritisch. Diese führen demzufolge zu Maß- und Formabweichungen sowie Bildung von Bauteilrissen, welche die Qualität der additiv plasma-auftraggeschweißten Bauteilstrukturen negativ beeinflussen können. Mittels des aufgebauten thermo-elastisch-plastischen Simulationsmodells wurden die auftretenden Temperaturfeldverteilung, Verformungen und Eigenspannungen während des additiven 3D – Plasma-Auftragschweißenes von Werkzeugkonturflächen vorausbestimmt und analysiert. Anhand des aufgebauten Ellipsoid-Wärmequellenmodells für Plasma-Pendelschweißprozess wurden die Temperaturfeldverteilung und deren Gradienten ermittelt. Darauf aufbauend wurden eine gekoppelte thermisch-elastisch-plastische struktur-mechanische Analyse durchgeführt. Mittels der Durchführung von werkstofflich-fertigungstechnischen Maßnahmen wie Verwendung von zähen Werkstofflegierungen, Grundköpervorwärmen und -festeinspannen wurden die damit entstehenden Bauteilverformung und -eigenspannungen simulativ kompensiert bzw. minimiert. Demzufolge wurden die damit erreichten Ergebnisse für die Herstellung endkonturnaher Werkzeugkonturflächen mit vordefinierten Schichteigenschaften praxisnah genutzt. Die dabei erreichten Simulationsergebnisse der Temperaturfeldverteilung und des Verformungs- und Eigenspannungszustandes präsentierten eine gute Übereinstimmung mit den Experimentresultaten.

Pass-by noise testing is an important step in vehicle design and regulation compliance. Finite element analysis simulations have been used to cut costs on prototyping and testing, but the high computational cost of simulating surface vibrations from complex geometries and the resulting airborne noise propagation is making the switch to digital twin methods not viable. This paper aims at investigating the use of equivalent source methods as an alternative to the before mentioned simulations. Through the use of a simple 2D model, the difficulties such as ill-conditioning of the transfer matrix and the required regularisation techniques such as TSVD and the Tikhonov L-curve method are tested and then applied to a mesh of a 3D engine model. Source and pressure field errors are measured and their origins are explained. A heavy emphasis is put on the model geometry as a source of error. Finally, rules of thumb based on the regularisation balance and the wavelength dependent pressure sampling positions are formulated in order to achieve usable results. / Bullerprovning vid passage är ett viktigt steg i fordonsdesign och regelefterlevnad. Simuleringar med finita elementanalyser har använts för att minska kostnaderna för prototypframtagning och provning, men de höga beräkningskostnaderna för att simulera ytvibrationer från komplexa geometrier och den resulterande luftburna bullerspridningen gör att övergången till digitala tvillingmetoder inte är genomförbar. Denna uppsats syftar till att undersöka användningen av ekvivalenta källmetoder som ett alternativ till de tidigare nämnda simuleringarna. Genom att använda en enkel 2D-modell testas svårigheterna som dålig konditionering av överföringsmatrisen och de nödvändiga regulariseringsteknikerna som TSVD och Tikhonov L-kurvmetoden och tillämpas sedan på ett nät av en 3D-motormodell. Käll- och tryckfältsfel mäts och deras ursprung förklaras. Stor vikt läggs vid modellgeometrin som en felkälla. Slutligen formuleras tumregler baserade på regulariseringsbalansen och de våglängdsberoende tryckprovtagningspositionerna för att uppnå användbara resultat.

The Swedish law requires a set of noise limit for residential buildings for health and safety. Conventionally, the Nordic Prediction Method (NMT) is used to predict the noise. However Nord2000 and CNOSSOS is going to be introduced to replace NMT. An investigation was made to determine which is more accurate in predicting railway noises, particularly reflected railway noises due to the uncharacteristic result in preliminary test. Compromises were made to recreate the measured scenarios in SoundPLAN 8.1. CNOSSOS features an alternative source model requiring new data on the trains and tracks and therefore unable to be compared. The conversion between NMT and Nord2000 was not successful due to the poor documentation of the method. An equivalent value in octave band was used instead. The result were not conclusive as no correlation was found. This might be partly due to the lacking of source model data in the form of track roughness. Result in reflected sound was not conclusive as well since 2 of 3 cases favour Nord2000 and the remaining one favours NMT. The uncertainty introduced in using of the standards and measurements were also rather large, which is also one of the factor in non correlating results. / Svensk lag kräver en viss uppsättning bullergränser gällande boende i bostadshus för deras hälsa och säkerhet. Konventionellt används den nordiska beräkningsmodellen för tågbuller (NMT) för att förutsäga bullret. Nord2000 och CNOSSOS kommer dock att införas för att ersätta NMT. En undersökning gjordes för att avgöra vilken eller vilka modeller som är mest exakta för att kunna förutsäga järnvägsljud, i synnerhet reflekterade järnvägsljud på grund av tidigare osäkerhet i resultatet i det preliminära testet. Kompromisser gjordes för att återskapa de uppmätta scenarierna i SoundPLAN 8.1. CNOSSOS erbjuder en alternativ modellering men kräver ny data från både tåg och räls och omöjliggjorde därför att kunna jämföras. Konverteringen mellan NMT och Nord2000 lyckades inte på grund av den bristfälliga dokumentationen av metoden. Ett ekvivalent värde i oktavband användes istället. Resultatet var inte definitivt eftersom ingen korrelation upptäcktes. Detta kan delvis bero på bristande källmodelldata i form av spårgrovhet. Resultatet av reflekterat ljud var inte heller definitivt eftersom 2 av 3 fall förespråkar Nord2000 och det återstående förespråkar NMT. Osäkerheten som implementeras vid användning av standarder och mätningar är också av betydande storlek, vilket också är en av faktorerna som härleder korrelerande resultat.