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Dissertations / Theses on the topic 'Surface elements'
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1
Münch, Wolfram Helmut Patrick. "Turbulent distortion of line and surface elements." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316760.
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Hsu, Jiunn-Yann 1959. "The polarized light scattering matrix elements for rough surface." Thesis, The University of Arizona, 1992. http://hdl.handle.net/10150/278177.
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The light scattered from a scatterer depends on the geometrical properties such as size, shape, and their distributions as well as electromagnetic properties such as the complex index of reflection. The four major Mueller scattering matrix elements have been experimentally measured for an aluminum rough surface scattering laser light at lambda = 441.6nm for various incident angles. Measurements were also made for non-conducting diffuse surface and an aluminum coated diffuse surface. The sixteen Mueller matrix elements of these diffuse surfaces were measured in order to study the relative role of reflectance and roughness for scattering from a rough surface. Some representative matrix elements for the rough surfaces as well as for conducting and non-conducting rough surfaces are shown. S11 and S34 are sensitive to illumination angles and surface variation. S33 are sensitive to illumination angles only. S34 are very sensitive to the change of refractive index from real to complex.
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Emerton, Neil. "Design and fabrication techniques for surface relief diffractive optical elements." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/38000.
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Zerwer, André. "Near-surface fracture detection in structural elements, investigation using Rayleigh waves." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0022/NQ51243.pdf.
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Knight, Lucy. "Finite elements simulation of surface wear in total knee joint replacement." Thesis, University of Southampton, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.500828.
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Zerwer, Andr?? "Near-surface fracture detection in structural elements, investigation using Rayleigh waves." Thesis, National Library of Canada = Biblioth??que nationale du Canada, 2000. http://hdl.handle.net/10012/533.
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Lahrashe, Moktar. "Atomic force microscopy of soft surface : Characterisation of holographic optical elements." Université Louis Pasteur (Strasbourg) (1971-2008), 2005. http://www.theses.fr/2005STR13046.
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Les méthodes pour la measurement des surfaces ont progressé d’une façon significative les dernières années. Elles ont été favorisées par les besoins de lithographie avancée. Le but de cette thèse est d’appliquer les techniques récemment développées au problème spécifique de l'étude de la structure de surface des réseaux holographiques. Au début de cette thèse, nous avons fait une recherche bibliographique dans le but de trouver le meilleur dispositif pour notre travail. Le dispositif choisi est un microscope à force atomique (AFM). Ce dernier est un outil permettant une mesure localisée d’une résolution sans précédent. L'AFM fournit une image des structures de surface dans une plage de quelques nanomètres à quelques centaines de micromètres. Cette flexibilité permet de réaliser une analyse quantitative de la microrugosité des surfaces avec de grande sensitivité et précision. Plusieurs exemples de réseaux holographiques enregistrés sur les plaques sont étudiés. Nous avons procédé pour chaque type de plaque à l’analyse du profil du réseau, de sa profondeur, de sa rugosité et la mesuré de le module élastique a été effectue. En outre, le sondage AFM des structures sub-surfaciques a été réalisé pour les échantillons holographiques avec la gélatine comme étant la couche supérieure. Une méthode optique complémentaire nous a servit pour obtenir des informations sur les caractéristiques global des réseaux holographiques : Indice de réfraction, modulation d'indice de réfraction, période du réseau, épaisseur de l'émulsion et absorption et pertes de dispersion ont été mesuréDriven largely by the needs for advanced lithographic processes surface measurement methods have significantly advanced in the last decade. The aim of this thesis is to apply recently developed measuring techniques to the specific problem of investigating the surface structure of holographic recording gratings. At the start of thesis, search for relevant literature was given high priority, with the purpose to find the best measuring device suitable for this investigation. The device chosen was an atomic force microscope (AFM) which is a tool that enables the spatially localised measurements with unprecedented resolution. AFM provides high-resolution imaging of surface structures from few nanometres to hundreds of micrometres. This capability is useful for quantitative analysis of surface micro-roughness of technological surfaces with high sensitivity and accuracy. Various holographic gratings are studied, along with the sequence by which raw images are analysed for grating profile, profile consistency, grating depth, profile roughness and elastic modulus. In addition, AFM probing of subsurface structures has been achieved for holographic samples with gelatine - like top layers. The AFM characterisation is completed with optical characterisation of holographic gratings: i. E. The refractive index, the refractive index modulation, the groove period, the emulsion thickness and the absorption and the scattering losses are determined by this method
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Cao, Weimin. "Adsorption of surface active elements on the iron (100) surface a study based on ab initio calculations /." Licentiate thesis, Stockholm : Skolan för industriell teknik och management, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11234.
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Svitana, Kevin D. "Using trace elements as an indicator of materials eroded from surface soils." Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1133194308.
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Thesis (Ph. D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xv, 219 p.; also includes graphics. Includes bibliographical references (p. 112-114). Available online via OhioLINK's ETD Center
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LUQUET, CHRISTEL. "Modelisation par elements finis de surface du rayonnement d'antennes imprimees multicouches-multielements." Nice, 1998. http://www.theses.fr/1998NICE5126.
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Dans cette these, nous nous sommes interesses a la simulation numerique d'antennes imprimees multicouches, multielements. Plus precisement, nous avons introduit le formalisme des fonctions de green des milieux stratifies, dans un logiciel base sur les equations integrales resolues par une methode d'elements finis de surface. Les fonctions de green sont calculees de maniere originale et rapide. Le nombre d'inconnues et le temps de calcul sont ainsi considerablement diminues, notamment pour l'etude d'antennes arbitraires multicouches-multielements de grande taille.
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Korkmaz, Deniz. "Preconcentration Of Volatile Elements On Quartz Surface Prior To Determination By Atomic Spectrometry." Phd thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12604921/index.pdf.
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Hydride generation technique is frequently used for the detection of elements as As, Se, Sb, Sn, Bi, Ge, Te and Pb that form volatile hydrides in solution using a reductant. In this study, a novel quartz trap for on-line preconcentration of volatile analyte species was designed. Pb, Sb and Cd were selected as analyte elements and chemical vapour generation technique was employed for generation of their volatile species in flow systems. The trapping medium was formed by external heating of either the inlet arm of the quartz tube atomizer or a separate cylindirical quartz tube. Generated analyte species were trapped on quartz surface heated to the collection temperature and the collected species were revolatilized when the trap was heated further to releasing temperature and hydrogen gas was introduced in the trapping medium. The conventional quartz T-tube and multiple microflame quartz tube were employed as atomizers. The influence of relevant experimental parameters on the generation, collection and revolatilization efficiencies was investigated. Optimum conditions, performance characteristics of the trap and analytical figures of merit are presented. Experimental design was used for optimizations in some cases. Standard reference materials were analyzed to assess the accuracy of the proposed method. For a collection period of 1.0 minute for Pb, 2.0 minutes for Sb and 3.0 minutes for Cd, 3σ
limit of detections, in pg ml-1, were 19, 3.9 and 1.8, respectively. In cases of Sb and Cd, the limits of detections obtained are the same as the best attained with in-situ trapping in graphite furnaces.
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Almazroui, Mansour. "The relationship between atmospheric circulation patterns and surface climatic elements in Saudi Arabia." Thesis, University of East Anglia, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435308.
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Phaal, Robert. "A two-surface computational model for the analysis of thin shell structures." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358682.
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Sonde, Abayomi Emmanuel. "Etude et modélisation de procédés innovants de mise en compression de surfaces : Traitements de surface par cavitation et par impulsions électromagnétiques." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEI015/document.
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Les procédés de traitement de surface tels que le grenaillage sont utilisés pour introduire des contraintes résiduelles de compression dans les matériaux métalliques. Cela permet de prévenir l'initiation et la propagation des fissures afin d'augmenter la durée de vie en fatigue des pièces mécaniques. Les limites et inconvénients des procédés actuels généralement utilisés pour cette fin sont connus et ont été mis en avant dans plusieurs études. Il s'agit d'une modification importante de l'état de surface (rugosité), une profondeur traitée limitée, des difficultés de mise en œuvre, etc. Aussi, de nouveaux procédés permettant d'obtenir des résultats équivalents voire meilleurs tout en évitant ces problèmes suscitent un intérêt grandissant. Le traitement de surface par cavitation (cavitation peening) et la mise en compression par impulsions électromagnétiques font partie de ces procédés innovants dont la modélisation a fait l'objet de cette thèse. Le traitement de surface par cavitation consiste à générer un jet d'eau submergé contenant des bulles de cavitation et dirigé vers la surface à traiter. La principale difficulté dans la modélisation du cavitation peening est la détermination du chargement mécanique sur la surface provenant de l'implosion des bulles de cavitation. L'effondrement des bulles peut se faire de manière sphérique ou non-sphérique suivant leur proximité de la paroi solide. Des modèles analytiques et numériques ont donc été élaborés pour étudier la dynamique des bulles et déterminer l'onde de pression due à une bulle sphérique d'une part, et la pression d'impact du micro-jet (bulle asphérique) d'autre part. Ces deux types de sollicitations ont été comparés et un modèle macroscopique pour le traitement par cavitation a été dérivé, en s'appuyant sur une simulation numérique du jet de cavitation. Une comparaison avec des résultats expérimentaux a été effectuée et a montré la pertinence du modèle proposé. En ce qui concerne le traitement par impulsions électromagnétiques, il consiste à générer un puissant champ magnétique transitoire par induction dans la pièce de matériau conducteur. Les contraintes résiduelles proviennent de la déformation plastique créée par les forces de Laplace à l'intérieur du matériau. Un modèle numérique couplant l'électromagnétisme et la mécanique des solides a été mis en place pour la simulation du procédé. Grâce à une étude d'optimisation, ce modèle a permis d'obtenir les paramètres électriques nécessaires pour arriver à mettre en compression des matériaux de type alliage de base nickel ou d'aluminium par cette méthode. Les profondeurs de la mise en compression calculées sont théoriquement par calcul plus élevées que celles obtenues avec les méthodes classiques de traitement de surface. Une étude de l'influence des différents paramètres a été faite et a montré que le procédé peut être contrôlé de manière relativement aisée en variant l'intensité et la pseudo-fréquence du courant traversant l'inducteurSurface treatments methods like shot peening are used to introduce compressive residual stresses in metallic materials. The compressive stresses prevent the initiation and growth of cracks and hence improve the fatigue life of mechanical parts. The drawbacks and limitations of the existing processes generally used for this purpose are known and have been highlighted in many studies. These are, among others, an important surface modification (roughness), a limited compressive depth, difficulties in execution, debris and contamination problems, etc. Therefore, the interest in new surface treatment methods, which permit to obtain equivalent or even better compressive results while avoiding the previous problems, are growing. Cavitation peening and electromagnetic pulse peening are part of these innovative processes which modeling is the aim of this PhD thesis. Cavitation peening is a process of surface treatment which acts by the generation of cavitation bubbles near the workpiece surface. The modeling of this process is challenging because of the complexity of cavitation phenomenon and the main problematic point is the determination of the mechanical loading on the material due the bubbles collapse. In this thesis, an approach of modeling for cavitation peening based on the study of the dynamics of cavitation bubbles is proposed. Spherical and aspherical collapse of bubbles near a solid surface are studied by some numerical and analytical models. These two sources of loading pressures have been compared and a macroscopic model for cavitation peening have been derived by associating the numerical simulation of the cavitation jet and the localization of the cavitation zone. The comparison between the final residual stress profile calculated with the proposed model and the experimental results were satisfactory. Electromagnetic pulse peening (EMP) is a contactless process of surface treatment which could be used to introduce compressive residual stresses in conductive materials, by the generation of a high transient electromagnetic field. Laplace forces induced in the material by magnetic induction are the source of the material plastic deformation and compressive residual stresses introduction. To predict the EMP results, a numerical model have been built for the process simulation. The model, based on finite element method, coupled successfully electromagnetic and mechanical phenomena by using a sequential-coupled approach. It was proven theoretically, by the study of a reference case, that compressive residual stresses could be induced in metallic materials like nickel-based (Inconel) or aluminum alloys by the means of the present process. It was also shown by the calculations that much higher compressive depths than those of conventional peening processes could be achieved. The parametric study exhibited the influence of the maximum current intensity and frequency which affect both the compressive depth and the maximum residual stress
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Kostopoulou, Efthymia. "The relationships between atmospheric circulation patterns and surface climatic elements in the Eastern Mediterranean." Thesis, University of East Anglia, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.405217.
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Montagné, Nicolaïdes Nathalie. "Prediction de champs thermiques instationnaires : methode des elements finis." Toulouse 3, 1986. http://www.theses.fr/1986TOU30121.
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Lors de la simulation numerique d'une operation de formage de piece, il est necessaire d'associer au logiciel de deformation plastique, un code elements finis permettant de determiner l'evolution du champ des temperatures. Le type de piece metallique considere est axisymetrique, a meridienne evolutive. Quatre phases differentes sont considerees, au cours desquelles la piece pourra etre, seule, en contact avec le tas inferieur de la matrice, en contact avec les tas inferieur et superieur, puis en cours de deformation. Les divers contacts de surfaces peuvent etre des raccordements thermiques de conduction, parfaits ou imparfaits. Pour les frontieres exterieures de l'ensemble, une condition de troisieme espece (surface libre) est retenue. Ces differents types de contact et le probleme de base (transfert de chaleur) amenent a considerer l'equation de fourier completee des conditions aux limites. Cette equation est traitee par la methode des elements finis via une voie implicite de resolution. Etant donne la configuration complexe de l'ensemble apres deformation, ce sont les quadrilateres courbes et isoparametriques qui sont employes. Le systeme lineaire final, obtenu apres diverses approximations, est resolu en adaptant la methode matricielle de gauss au "stockage ligne de ciel" de la matrice. Ainsi, il est possible de traiter le cas de maillages fins et plus precis, comportant un grand nombre de noeuds.
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Kumar, Sharath. "Investigation of a Phased Array of Circular Microstrip Patch Elements Conformal to a Paraboloidal Surface." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/35464.
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This thesis investigates the performance of a phased array of antenna elements conforming to a paraboloidal surface. We hypothesize that such a conformal phased array would have performance comparable to that of a correspondingly sized planar array. The performance of a paraboloidal array of antenna elements was simulated using an array program, and the resulting gains, side-lobe levels, and half-power beamwidths compared to those of a similarly sized planar array. Furthermore, we propose a beam-forming feed network for this paraboloidal phased array, and discuss the influence that coupling between the elements could have on the array performance. Lastly, we propose that such an array be used in conjunction with a parabolic reflector antenna to form a versatile hybrid antenna with several potential applications.Master of Science
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Rusche, Max Thomas. "Structure of Turbulent Boundary Layers and Surface Pressure Fluctuations on a Patch of Large Roughness Elements." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/34773.
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Measurements were made in a zero pressure gradient turbulent boundary layer over two
roughness patches containing hemispherical and cubical elements. The elements were 3
mm in height and spaced 16.5 mm apart in an array containing 7 streamwise rows and 6
spanwise columns for a total of 42 elements per patch. The boundary layer thickness was
approximately 60 mm, so the ratio of element height to that thickness was a large amount
at k= = 1=20. A three velocity component laser Doppler velocimeter measured instantaneous
velocities. Mean flow and turbulence statistics were calculated as well velocity
energy spectra. Surface pressure fluctuations were measured using a two-microphone
subtraction method.
The results show that hemispherical elements produce larger turbulence quantities in
their wakes compared to the cubes. This is due to the hemispheres having a frontal area
nearly 60% larger than that of the cubes. The turbulence levels behind the hemispheres
is a maximum behind the first streamwise row of elements, and decreases afterwards.
The cubical elements maintain a nearly constant amount of turbulence in their wake,
signifying little interaction between cubical elements. Surface pressure fluctuations vary
little in the streamwise direction of the patches. The hemispherical elements produce
a larger sound pressure level behind them than the cube elements do. Velocity spectra
results show large normal stress energy for regions at and below the element height. The
energy for locations high in the boundary layer increases as the flow moves downstream.
Coherency plots show that there is a large correlation between the turbulent structure and
production of shear stress at the roughness height. Any measurements taken at or below
the roughness height are highly correlated under 10 kHz, while locations higher in the
boundary layer are correlated under 2 kHz.Master of Science
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Cochran, Michael Patrick. "A feasibility study of incorporating Surface Tension Elements to improve the efficiency of residential clothes dryers." Thesis, Manhattan, Kan. : Kansas State University, 2007. http://hdl.handle.net/2097/372.
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Shumskykh, Mykyta. "Release of trace elements from contaminated sediments into surface waters during sediments dynamics : an experimental study." Thesis, Tours, 2019. http://www.theses.fr/2019TOUR4008.
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Dans les systèmes aquatiques, la plupart des éléments traces métalliques (ETM) sont piégés dans les sédiments puis peuvent être relargués en fonction des conditions chimiques et de l’activité microbienne à l’interface eau-sédiment. L’objectif de cette étude était d’évaluer l’impact de remise en suspension des sédiments (lors de crues et d’opérations de gestion de barrages) sur la mobilité de certains ETM. Plusieurs conditions expérimentales de lessivage ont été choisies pour simuler ces événements : conditions oxiques et anoxiques sur des sédiments bruts et d’autres irradiés par rayons gamma. L’utilisation d’eau désionisée a permis de maximiser le processus de relargage. Deux types de sédiments, issus de contextes différents, ont été sélectionnés : le barrage de Villerest (France) et la rivière Xiang (Chine). Des expériences à long terme (30 jours) ont permis d’identifier la dégradation de la matière organique, l’activité microbienne et l’altération (voire la dissolution) de phases porteuses d’ETM comme principaux facteurs de contrôle. L’importance de l’activité microbienne n’a pas pu être quantifiée puisque l’irradiation n’a pas stérilisé totalement les sédiments. Enfin, l’impact de tels évènements parait très limité puisque moins de 1% des ETM contenus dans les sédiments ont été libérésIn aquatic systems, most of trace metals (TM) are buried in sediments and then can be released according to chemical conditions and microbial activity occurring at the sediment-water interface. The aim of this study was to assess the impact of resuspension events (flood or maintenance operations for dam reservoir) on the mobility of some TM. Different batch experiment conditions were chosen to mimic those events: under oxic and anoxic conditions on raw sediments and on gamma-irradiated ones (“sterilized” one). The use of deionized water allowed maximizing the release process. Two sediment types issued from different contexts were selected: the Villerest dam reservoir (France) and the Xiang River (China). Long term experiments (30-day long) allowed identifying that organic matter degradation, microbial activity and alteration/dissolution of trace metal bearing phases were the main controlling factors. The gamma-irradiation did not sterilize sediments but only limited aerobic bacteria and enhanced anaerobic activity. The impact of such 24h resuspension event on reservoir waters and downstream biota is very limited as less than 1% of trace elements was released
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BHANDARI, RISHABH. "ROLE OF CONSTITUENT ELEMENTS IN PROPANE OXIDATION OVER MIXED METAL OXIDES." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1116259229.
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Bugnicourt, Romain. "Simulation of the contact between a rough surface and a viscoelastic material with friction." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI112/document.
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Les pneus sont un organe déterminant dans la tenue de route des véhicules. Cette thèse porte sur la modélisation du contact entre la bande de roulement d'un pneumatique et une route sèche, afin de comprendre les différents phénomènes physiques mis en jeu ainsi que leurs rôles relatifs dans le frottement. La rugosité multi échelle des sols routiers les rendent difficiles à modéliser avec une simulation par élements finis standard. En utilisant l'hypothèse que la gomme de la bande de roulement est très grande devant la taille des rugosités, elle peut être considérée comme un massif semi-infini. Il est alors possible de résoudre efficacement le problème de contact en ne discrétisant que la surface du massif de gomme. Cette résolution est faite à l'aide d'un algorithme de Gradient Conjugué, au cours duquel les calculs matriciels sont effectués par Transformée de Fourier Rapide (FFT). La viscoélasticité de la gomme est prise en compte en régime transitoire. Les interactions à l'interface entre la gomme et le sol sont modélisés par une loi de frottement ainsi que par une énergie d'adhésion. Les résultats montrent le rôle primordial de la viscoélasticité qui, couplée à la rugosité multi-échelle du sol, modifie la surface du contact au cours des différents étapes de mise en glissement d'un pneumatique, faisant ainsi varier le frottementTires are a key component for the handling and safety of personal vehicles. In this thesis a model of the contact between the tire tread and a dry road is described. It aims at understanding the different physical phenomena taking place in such a contact and their relative role in tire friction. Modeling the multiple scales of road roughness is difficult using a standard Finite Element Method. The hypothesis that the rubber of the tire tread is very large compared to the largest scale of surface roughness is made, so that it can be considered as a semi-infinite half-space. This way, the contact problem can be solved by discretizing the rubber surface only. The solver is a specific Conjugate Gradient iterative method, in which the matrix-vector products are performed with Fast Fourier Transforms. Transient viscoelasticity is accounted for with a step-by-step approach. The algorithm is able to model surface interactions such as Coulomb friction and adhesion. Results show the crucial role played by viscoelasticity. Coupled with the road roughness, it changes the contact surface during the different steps of tire sliding, which in turns impacts friction
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Wu, Tsunghsueh Shannon Curtis. "Surface plasmon assisted spectroscopies and their application in trace element analysis, the study of biomolecular interactions, and chemical sensing." Auburn, Ala., 2008. http://repo.lib.auburn.edu/EtdRoot/2008/SUMMER/Chemistry_and_Biochemistry/Dissertation/Wu_Tsung%20Hsueh_20.pdf.
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Dorosh, Anastasiia. "Design of Microstrip Microwave Devices with Lumped Elements by Means of Modern CADs." Thesis, Linnéuniversitetet, Institutionen för fysik och elektroteknik (IFE), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-30365.
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In this report the analysis of microstrip electrodynamic structures on basis of high-temperature superconductors is carried out and a mathematical model of microstrip devices with lumped and distributed nonlinear properties is created. For this purpose nonlinear integral equations method and method of moments are used. In the issue of the work a SHF filter based on the equivalent circuit of elements with lumped parameters is also studied. It is ascertained that the received mathematical model allows to achieve more proper results of modeling on compensation of variation of current-density distribution nearby the edges of conductor break.
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Pablo, Fleurdelis, of Western Sydney Nepean University, and Faculty of Science and Technology. "Adsorptive stripping voltammetry of trace elements on a glassy carbon mercury film electrode." THESIS_FST_XXX_Pablo_F.xml, 1994. http://handle.uws.edu.au:8081/1959.7/207.
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This thesis describes the development of new adsorptive cathodic stripping voltammetric methods for reliable determination of some trace metals in biological and environmental materials on a glassy carbon mercury film electrode. In particular, the development of these methods involved selection of a suitable complexing agent for the respective metal ion studied, characterization of the electrode processes, investigation of factors affecting the voltammetric response such as concentration and pH of supporting electrolyte, concentration of complexing agent, accumulation potential, accumulation time and electrode rotation rate. Also, organic and inorganic interferences, linear concentration range, and detection limits were carefully considered. Furthermore, the analytical application of the method was demonstrated for each metal in biological and/or environmental materials, after optimization of the sample decomposition procedure. Some conclusions : the results obtained by the AdCSV method for the determination of tin in juices agreed reasonably with those obtained by atomic absorption method; the use of the adsorptive voltammetric technique after dry-ashing and UV treatment of the samples was successfully demonstrated for the determination of vanadium in standard reference materials such as urban particulate matter, peach leaves, apple leaves and bovine liver; and, the use of the adsorptive stripping voltammetric technique, after decomposition of samples by dry-ashing and UV treatment, was successfully demonstrated for the determination of molybdenum in peach leaves, apple leaves and bovine liver samples.Doctor of Philosophy (PhD)
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Karagoz, Taner. "A Finite Elements Based Approach For Fracture Analysis Of Welded Joints In Construction Machinery." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/3/12608675/index.pdf.
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This study aims to develop a computer program to perform finite elements based fracture mechanics analyses of three dimensional surface cracks in T-welded joints of construction machinery. The geometrical complexity of the finite elements models and the requirement of large computer resources for the analyses necessitate the use of shell elements for general stress distribution optimization. A sub-modeling technique, together with a shell to solid conversion method, enables the user to model a local region and analyze it by defining the weld and crack parameters. It is assumed that the weld material is the same with the sheet metal material and the surface cracks are considered to occur on two weld toes and weld root. The surface cracks are assumed to have a semi elliptical crack front profile. In order to simulate the square-root strain singularity around the crack front, collapsed 20-node three dimensional brick elements are utilized. The rest of the local model is modeled by using 20-node three dimensional brick elements. The main objective of this work is to calculate the mixed mode energy release rates around the crack front for a sub-model of a global shell model by using J-integral method.
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Attia, Abdelgayed Abdelgawad Sharaky Ibrahim. "A study of the bond and flexural behaviour of reinforced concrete elements strengthened with near surface mounted (NSM) FRP reinforcement." Doctoral thesis, Universitat de Girona, 2013. http://hdl.handle.net/10803/128331.
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The main objective of the thesis is to study the bond behaviour of NSM FRP reinforcement in concrete elements. With this aim an extensive program of experimental tests complemented with numerical analysis has been performed to study the effect of the variables affecting this technique. In the first part of this thesis the modified pull-out test is carried out. A Finite Element Analysis (using the program FEMIX V.4) was used to perform several trials to fit as much as possible (inverse analysis) the force versus loaded end slip responses obtained experimentally in direct pullout tests. In the second part of this thesis an experimental program of flexural tests on RC beams strengthened with NSM FRP has been carried out to study the effect on the flexural behaviour of some of the previous variables studied in the first partL’objectiu principal d’aquesta tesi és l’estudi del comportament adherent entre el reforç NSM FRP i l’element de formigó. D’aquesta manera s’ha realitzat un extens programa d’assajos experimentals complementat amb anàlisis numèriques per tal d’estudiar les variables que incideixen en aquesta tècnica. En la primera part de la tesi es fa un estudi de l’adherència emprant l’assaig de pull-out modificat. S’ha realitzat una anàlisi amb el MEF (emprant el programa FEMIX V.4) per tal de fer diverses proves per ajustar amb la màxima precisió possible (anàlisi inversa) la resposta força-lliscament de l’extrem carregat de la barra obtinguda experimentalment en els assajos de pull-out. A la segona part de la tesi s’ha portat a terme un programa d’assajos a flexió d’elements de formigó armat reforçats amb NSM FRP per tal d’estudiar l’efecte d’algunes de les variables analitzades en la primera part
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BOUSQUET, THIERRY. "Modelisation rigoureuse de structures filaires par elements finis de surface : application a des antennes 3d inhomogenes alimentees par sonde coaxiale." Nice, 1995. http://www.theses.fr/1995NICE4884.
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Ce memoire est consacre a la modelisation rigoureuse du rayonnement d'antennes tridimensionnelles inhomogenes comportant des structures filaires et alimentees par sonde coaxiale. La modelisation s'appuie sur un formalisme base sur une representation integrale du champ electromagnetique. Par application du concept de reaction, on en deduit une forme variationnelle. Des elements finis de forme triangulaire sont utilises pour la resolution numerique. Ils permettent de decrire la surface de la structure etudiee qui peut etre de forme arbitraire et composee de plusieurs dielectriques. Les exemples d'application sont des antennes dont certains elements ont de faibles dimensions vis a vis de la longueur d'onde. Des antennes imprimees constituees d'une couche dielectrique mince et alimentees par sonde coaxiale sont modelisees. Une antenne filaire en forme d'helice chargee par un noyau dielectrique a aussi ete etudiee. Elle a notamment permis de valider le logiciel
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Hill, Roger Alan. "The design of a dual band frequency selective surface and the effect of perturbing the elements and the interelement spacing." The Ohio State University, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=osu1345127869.
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Stewart, William Elliott. "A Response Surface Exit Crown Model Built from the Finite Element Analysis of a Hot-Rolling Mill." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/45203.
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Nine independent and four dependent variables are used to build a response surface to calculate strip crown using the difference in the industry standard strip height measurements. The single element response surface in use provides the advantages of continuous derivatives and decouples rolling load from the determination of exit height. The data points to build the response surface are the product of a calibrated finite element model. The rolling dynamics in the finite element model creates a transient that requires nonlinear regression to find the system steady-state values.
Weighted-least squares is used to build a response surface using isoparametric interpolation with the non-rectangular domain of the mill stands represented as a single element. The regression statistics, the 1-D projections, comparisons against other response surface models and the comparisons against an existing strip crown model are part the validation of the response surface generated.
A four-high mill stand is modeled as a quarter-symmetry 3-D finite element model with an elastic-plastic material model. A comparison of the pressure distribution under the arc of contact with existing research supports the pressure distribution found with experiments conducted by Siebel and Lueg [16] and it also suggests the need for one improvement in the initial velocity for the strip in the finite element model.
The strip exit heights show more sensitivity to change than strip exit crown in seven out of the nine independent variables, so a response surface built with the strip exit height is statistically superior to using the derived dependent variable strip exit crown. Sensitivity of strip exit crown and the strip exit heights to changes in work-roll crown are about equal. Backup-roll diameter sensitivity is small enough that oversampling for the mean trend has to be considered or ignore backup-roll altogether. Strip entry velocity is a new independent variable, unless the response surface is built from the derived variable, strip exit crown.
A problem found is that the sensitivity of strip entry crown and work-roll crown requires a larger than typical incremental change to get a reliable measure of the change strip exit crown. A narrow choice of high and low strip entry crowns limits the usefulness of the final response surface. A recommendation is to consider the use of the strip cross-section as an exit crown predictor.Master of Science
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Lopes, Nuno Filipe Ferreira. "Development and implementation of strategies for the incorporation of reinforcing elements in aluminium alloys by solid state processing." Master's thesis, Faculdade de Ciências e Tecnologia, 2012. http://hdl.handle.net/10362/7809.
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Dissertação para obtenção do Grau de Mestre em
Engenharia MecânicaThis investigation aimed to study new surface processing strategies to produce reinforced surface metal matrix composites by Friction Stir Processing. The first consisted on pre-placing reinforcing particles over the surface, while the second used consumables drilled holes filled with reinforcing particles. Each strategy was investigated using an electric current in a process under patenting. Aluminium AA5083-H111 plates were used as base material. Silicon carbide and alumina particles with median sizes of 35 and 45 μm, respectively, were used. Pre deposition of reinforcing particles proved to be more effective than the use of consumable tools packed with particles. The last ones produced coatings with a non homogeneous distribution and poor bonding between the substrate and the reinforcing coating. The pre deposition of alumina produced a higher extension and depth of reinforced layer and an increase in hardness of 60%, while silicon carbide produced an increase in hardness of 300 %, though in a smaller extension and depth than alumina under the same processing conditions. Using the electric current a significant raise of 500% and 40% was observed in extension and depth respectively, but hardness decreased by 10 %.
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Cianciolo, Thomas Raymond. "Temporal and longitudinal extent of surface coal mining influences on water quality and benthic macroinvertebrate communities in central Appalachian headwater streams." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/90282.
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Increased loading of dissolved ions (salinization) and trace elements from surface coal mining is a common alteration to headwater streams in the central Appalachian region. However, temporal and spatial trends of water quality and associated influences on biota in these stream systems have not been well-studied. To address this research need, I analyzed temporal trends in specific conductance, ion matrix, and benthic macroinvertebrate communities in 24 headwater streams, including 19 influenced by surface mining, from 2011-2019. There was limited evidence of recovery of water chemistry or macroinvertebrate communities in these streams, indicating lasting impacts from surface coal mining. Among benthic macroinvertebrates, Ephemeroptera and the scraper functional feeding group were most-impacted by chronic salinization in study streams. In addition, I analyzed spatial patterns of water chemistry in a subset of these streams using synoptic sampling of multiple constituents under baseflow and highflow conditions. Study results indicate that water chemistry is spatially dynamic and can be influenced by both groundwater dilution and inputs from tributaries. Lastly, I investigated patterns in selenium bioaccumulation across and within streams, from particulate matter to top trophic levels (i.e. fish and salamanders). I found that benthic macroinvertebrates had the highest concentrations of selenium in these ecosystems, with lower concentrations in salamander and fish species. However, there was limited evidence of longitudinal trends in bioaccumulation dynamics downstream of mining impacts. Collectively, this work indicates long-term (ca. decades) coal-mining influences but also highlights future research needs to better understand downstream impacts to water quality and biotic communities.Master of Science
Surface coal mining affects water quality in central Appalachian headwater streams. However, long-term and downstream patterns of impacted water quality and potential effects on aquatic life have not been well-studied. To address this research need, I analyzed trends in water quality parameters and aquatic insect communities in 24 headwater streams from 2011-2019. There was limited evidence of recovery of water chemistry or aquatic life in these streams, indicating lasting impacts from surface coal mining. Certain aquatic insects including Ephemeroptera (mayflies) appear to be more impacted than others by long-term altered water quality. In addition to trends over time, I also analyzed downstream variation in water chemistry in a subset of these streams under baseflow conditions and after a rain event. Results indicate that water chemistry can vary greatly within a stream network and is influenced by tributary inputs and dilution from groundwater. Concentrations of the trace element selenium can also be elevated as a result of surface mining. This is of environmental concern because selenium can biomagnify, where concentrations increase in organisms higher in the food chain and can cause toxic effects. Here, I investigated selenium bioaccumulation patterns across organisms in the food chain and with distance downstream across six headwater streams. I found that aquatic insects had the highest concentrations of selenium, with lower concentrations in salamanders and fish. This work indicates that surface coal mining has longterm (ca. decades) effects on headwater streams, but also points to future research to better understand downstream impacts to water quality and aquatic life.
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Oqielat, Moa'ath Nasser. "Modelling water droplet movement on a leaf surface." Queensland University of Technology, 2009. http://eprints.qut.edu.au/30232/.
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The central aim for the research undertaken in this PhD thesis is the development of a model for simulating water droplet movement on a leaf surface and to compare the model behavior with experimental observations. A series of five papers has been presented to explain systematically the way in which this droplet modelling work has been realised. Knowing the path of the droplet on the leaf surface is important for understanding how a droplet of water, pesticide, or nutrient will be absorbed through the leaf surface. An important aspect of the research is the generation of a leaf surface representation that acts as the foundation of the droplet model. Initially a laser scanner is used to capture the surface characteristics for two types of leaves in the form of a large scattered data set. After the identification of the leaf surface boundary, a set of internal points is chosen over which a triangulation of the surface is constructed. We present a novel hybrid approach for leaf surface fitting on this triangulation that combines Clough-Tocher (CT) and radial basis function (RBF) methods to achieve a surface with a continuously turning normal. The accuracy of the hybrid technique is assessed using numerical experimentation. The hybrid CT-RBF method is shown to give good representations of Frangipani and Anthurium leaves. Such leaf models facilitate an understanding of plant development and permit the modelling of the interaction of plants with their environment. The motion of a droplet traversing this virtual leaf surface is affected by various forces including gravity, friction and resistance between the surface and the droplet. The innovation of our model is the use of thin-film theory in the context of droplet movement to determine the thickness of the droplet as it moves on the surface. Experimental verification shows that the droplet model captures reality quite well and produces realistic droplet motion on the leaf surface. Most importantly, we observed that the simulated droplet motion follows the contours of the surface and spreads as a thin film. In the future, the model may be applied to determine the path of a droplet of pesticide along a leaf surface before it falls from or comes to a standstill on the surface. It will also be used to study the paths of many droplets of water or pesticide moving and colliding on the surface.
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Irci, Erdinc. "Low-Profile Wideband Antennas Based on Tightly Coupled Dipole and Patch Elements." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1316456337.
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Nouvel, Laurent-Xavier. "Etude de la diversité génétique de Mycoplasma agalactiae : plasticité des génomes, mobilome et dynamique de surface." Thesis, Toulouse, INPT, 2009. http://www.theses.fr/2009INPT013A/document.
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Mycoplasma agalactiae est responsable de l'agalactie contagieuse, maladie des petits ruminants difficilement contrôlée et figurant sur la liste de l’OIE. Afin d’évaluer la diversité génétique de ce pathogène, 101 isolats ont été comparés par trois techniques (VNTR, RFLP, répertoire vpma). Les résultats révèlent une grande homogénéité génétique dont la souche type PG2 est représentative. Quelques isolats font exception telle la souche 5632 que nous avons séquencée et analysée ici. La comparaison des génomes et des protéomes entre 5632 et PG2 indiquent que la plasticité de ces génomes est liée à d’importants échanges d'ADN et à la présence de nombreux éléments génétiques mobiles (10% du génome). Ces analyses révèlent également une forte dynamique au sein de répertoires de gènes codant des protéines de surfaces. Pour les mycoplasmes, bactéries minimales dépourvues de paroi, ces évènements ont certainement joués un rôle dans leur survie et leur adaptation à des hôtes complexesMycoplasma agalactiae is responsible of contagious agalactia, a disease of small ruminants that is still difficult to control and is listed by the OIE. In order to evaluate the genetic diversity of this pathogen, 101 isolates were compared using three techniques (VNTR, RFLP, vpma repertoire). Results revealed a high genetic homogeneity with the PG2 type strain as representative. Some isolates however diverged such as the 5632 which was sequenced and analysed here. Whole comparative genomic and proteomic analyses of the 5632 and PG2 strains indicate that their genomic plasticity resides in important genes flux and in the presence of several mobile genetic elements (10% of the genome). These analyses also revealed that specific loci encoding repertoire of surface proteins are highly dynamic. For these minimal bacteria that lack a cell-wall, these events have most likely played a major role in their survival and adaptation to complex hosts
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Prakash, Babu Chakka. "The marine geochemistry of biogenic and redox sensitive elements in the oxygen minimum zone of western continental margin of India surface sediments." [S.l. : s.n.], 1999. http://deposit.ddb.de/cgi-bin/dokserv?idn=95884917X.
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Monir, Md M. "A COMPUTATIONAL INVESTIGATION OF SECTORAL ZONING OF RARE EARTH ELEMENTS (REE) IN FLUORITE." Miami University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=miami1438881165.
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Moore, Katie Louise. "High resolution secondary ion mass spectrometry analysis of trace elements in cereal grain and roots." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:ab4f4a19-baca-48a7-af54-b9c5d87f3b7a.
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This thesis presents information on the subcellular localisation of two important trace elements, selenium and arsenic, in wheat, rice and rice roots for what is believed to be the first time. The general aim of this work was to illustrate the potential of using physical science techniques to solve biological problems. High resolution secondary ion mass spectrometry was undertaken using the CAMECA NanoSIMS50 with a sensitivity down to ppm concentrations and a lateral resolution of less than 100 nm. Selenium in wheat grain was found to be distributed across both the bran layer and the endosperm region with Se-rich hotspots found in the aleurone cells and a higher intensity of Se in the subaleurone region. Arsenic in rice grain was found in two key regions. In grains with high As and high dimethylarsinic acid (DMA) content, As was predominantly localised to the subaleurone region yet in lower concentration, hydroponically grown As(III)-treated grains the As was only localised to the aleurone layer near the ovular vascular trace (OVT). A combined NanoSIMS and S-XRF experiment revealed As hotspots near the OVT. A combination of high pressure freezing, high resolution secondary ion mass spectrometry and TEM was used to localise As in the roots of rice plants revealing a contrasting subcellular distribution of As and Si in the roots even though arsenite and silicic acid are transported across the plasma membranes by the same transporters. Fe plaque forms only on the root epidermis and was shown to be a strong sink for As. Colocalisation of S with As in the vacuoles of the endodermis, pericycle and xylem parenchyma supports the notion that As is stored as arsenite-phytochelatin complexes in the roots while Si is localised in the endodermis cell walls and is not strongly affected by the Lsi2 mutation.
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AZZOUZ, FOUAD. "Contribution a la modelisation de toles ferromagnetiques par impedance de surface et elements finis application au calcul des puissances du chauffage par induction." Nantes, 2000. http://www.theses.fr/2000NANT2107.
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Le chauffage par induction de materiaux ferromagnetiques en couches minces (toles) necessite l'emploi de frequences elevees ; ce qui complique aussi bien la modelisation des systemes que les mesures electromagnetiques ou thermiques. Les modeles physiques et mathematiques bases sur les equations de maxwell restent toujours d'actualite et le recours aux methodes numeriques est indispensable. La methode des elements finis (mef) a ete choisie comme outil de base de resolution et son couplage a une impedance de surface en non-lineaire permet de prendre en compte l'effet de peau. Des outils elements finis ont ainsi ete developpes dans le cadre de cette these sous environnement matlab en 1d, 2d, axisymetrie et en 3d, utilisant les elements nodaux, d'aretes et les elements mixtes. La validation des outils en 2d a ete effectuee par comparaison avec des calculs obtenus au sein de notre laboratoire en utilisant le logiciel fluxexpert, et avec des donnees experimentales. La validation des outils en 3d a ete effectuee par comparaison avec des mesures et des solutions de problemes proposees par la communaute scientifique internationale (ieee team workshops, ieej workshop) en magnetostatique et en magnetodynamique. D'autre part, nous avons propose une definition d'impedance de surface non-lineaire. Cette definition est obtenue a partir de l'energie electromagnetique et d'une identification en 1d utilisant une formulation en champ magnetique h. L'application de ce modele en 2d, utilisant une formulation en potentiel vecteur magnetique a a un cas reel (dispositif d'edf de chauffage par induction a inducteur monospire) a donne des resultats tres satisfaisants avec un faible cout tant en place memoire qu'en temps de calcul sur micro-ordinateur. Le modele a ensuite ete applique avec succes a un cas 3d, utilisant la formulation av-a, v etant le potentiel scalaire electrique. En vue d'un couplage du probleme electromagnetique avec le probleme thermique, nous avons etendu la definition de l'impedance de surface a la prise en compte des effets de la temperature.
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Oleinikova, Olga. "Dégradation photochimique et biodégradation des colloïdes organiques dans les eaux de surface boréales." Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30014/document.
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La matière organique dissoute (MOD) est un composant important des eaux naturelles, déterminant la forme des éléments et les émissions de gaz à effet de serre (CO2, CH4), et influence la biodiversité des milieux des eaux. Les eaux boréales sont connues pour être généralement riches en fer, et cela est vrai en particulier pour les eaux de la région étudiée (Carélie du Nord, Russie). Le fer est associée aux MOD dans les complexes de bas poids moléculaire et les colloïdes organo-ferreux de haut poids moléculaire, qui agissent comme les principaux transporteurs d'éléments traces métalliques dans le continuum hydrologique typiques de cette région : sol - marais - rivière - lac. La transformation des colloïdes organo-ferreux se fait sous l'influence de deux facteurs principaux: la dégradation bactérienne et la dégradation photochimique. Cette étude est consacrée à l'analyse du comportement du carbone organique dissous (COD) et des éléments traces (ET) des eaux de surface en zone boréale sous l'influence de l'activité métabolique des bactéries hétérotrophes et de l'oxydation photolytique des MOD sous l'effet de la lumière du soleil. Dans les expériences, un lixiviat de tourbière, un échantillon d'eau de marais, un échantillons d'eau de ruisseaux, un échantillon de rivière, un échantillon d'eau de lac humique, un échantillon d'eau de lac oligotrophique et un pluvio-lessivat collecté sous un pin, échantillons dans lesquelles dominent les MOD de nature humique, ont été utilisés comme substrats. Des expériences en laboratoire utilisant des communautés monosouches de bactéries aérobies hétérotrophes Pseudomonas aureofaciens et Pseudomonas saponiphila (prélevées sur le territoire de Carélie) ont permis d'établir que la MOD allochtone des milieux aquatiques en zone boréale possède une forte résistance à l'activité des bactéries étudiées. Le taux de minéralisation bactérienne du COD était de 0 à 4.3 mgC.L-1.jour-1 selon le substrat, et la fraction de faible poids moléculaire (<1 kDa) de la MOD est plus susceptible de destruction que celle de poids moléculaire élevé (de 1 kDa à 0.22 µm). L'interaction des bactéries avec divers substrats aqueux a montré pour une large gamme d'éléments (Al, Fe, Mn, Ni, Co, Cu, Cd, REE, U) une prédominance significative d'une adsorption rapide sur la surface cellulaire observée lors de la première heure d'expérience (t < 1h) par rapport à une diminution lente observée lors de la suite de l'expérience (1h < t < 96h), diminution lente lié à l'assimilation intracellulaire des métaux et à la coprécipitation extracellulaire des éléments avec des hydroxydes de Fe et Al. L'analyse de divers substrats a montré une augmentation de l'adsorption des métaux avec le rapport DOC/Fe dans la solution initiale, ce qui peut être due à la compétition entre Fe et d'autres cations métalliques pour les sites d'adsorption anioniques des surfaces des cellules bactériennes. Le suivi des dynamiques d'élimination des métaux des solutions expérimentales pendant 96 heures n'a pas mis en évidence de lien entre l'élimination des métaux et le pH et les valeurs absolues de concentration de DOC et de Fe. Une relation a été établie entre la diminution lente (96 h) des éléments et le degré initial de sursaturation de la solution en oxydes et hydroxydes de fer et d'aluminium. Des expériences en conditions naturelles avec des échantillons d'eau de rivière et de marais a montré que la destruction photolytique de la MOD est beaucoup plus efficace pour l'eau de maraisDissolved organic matter (DOM) is an important component of natural waters, determining the form of elements and the emission of greenhouse gases (CO2, CH4), as well as affecting water biodiversity. A feature of boreal waters, and in particular the study area waters (North. Karelia, Russia), is high concentration of Fe (III), associated with DOM in low-molecular complexes and in high-molecular organo-ferric colloids, which act as the main carriers of metallic trace elements in the most typical hydrological continuum soil - bog - river - lake. The transformation of organo-ferric colloids occurs under the influence of two main factors: bacterial and photochemical degradation. The present study is devoted to the analysis of dissolved organic carbon (DOC) and trace elements (TE) behavior in surface waters of the boreal zone under the influence of the heterotrophic bacteria metabolic activity and photolytic oxidation of DOM under sunlight exposure. For the purpose of experiments there were used substrates with predominate allochthonous DOM of humic nature, including peat leachate, pine crown throughfall, fen, humic lake, stream, river and oligotrophic lake. An experiment carried out in laboratory conditions using monocultures of heterotrophic aerobic bacteria Pseudomonas aureofaciens and Pseudomonas saponiphila (isolated on the territory of Karelia) allowed to establish that allochthonous DOM of the boreal zone reservoirs possesses high resistance to the activity of the explored bacteria. The rate of bacterial mineralization of DOC was observed in range from 0 to 4.3 mgC L-1day-1, depending on the substrate, and the low molecular weight fraction (<1 kDa) of DOM was found to be more prone to destruction than high molecular weight (from 1 kDa to 0.22 µm). The interaction of bacteria with various aqueous substrates showed a significant predominance of short-term (< 1 h) adsorption on the cell surface for a wide range of elements (Al, Fe, Mn, Ni, Co, Cu, Cd, REE, U) over a long term (1 h - 96 h) intracellular uptake of metals and extracellular coprecipitation of elements with Fe and Al hydroxides. Among different substrates, there was an increase in the adsorption with the increase of DOC/Fe ratio in solution, which can be linked to a competition between Fe and metal cations for anionic adsorption sites on cell surface. The long-term removal of dissolved metals did not show any link to pH, DOC, and Fe concentration
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Hiliare, Sheldon. "Impact of Manure Land Management Practices on Manure Borne Antibiotic Resistant Elements (AREs) in Agroecosystems." Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/102218.
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Rising global antibiotic resistance has caused concerns over sources and pathways for the spread of contributing factors. Majority of the antimicrobials used in the U.S. are involved in veterinary medicine, primarily with livestock rearing. Animal manure land application integrates livestock farming and agroecosystems. This manure contains antibiotic resistant elements (AREs) (resistant bacteria, resistance genes, and veterinary antibiotics) that contribute towards antimicrobial resistance. Altering manure application techniques can reduce surface runoff of other contaminants such as excess N and P, pesticides, and hormones, that can impact water quality. Conventional tillage practices in the U.S. has reduced or stopped, making subsurface injection of manure a promising option when compared to surface application. Our research compared manure application methods, manure application seasons, cropping system, and manure-rainfall time gaps to gauge the impact on AREs in the environment. Two field-scale rainfall simulation studies were conducted along with one laboratory study. Using the injection method lowered concentrations of manure associated AREs entering surface runoff. When manure was surface applied and rainfall occurred 7 d after application, 9-30 times less resistant fecal coliform bacteria (FCB) entered surface runoff when compared to 1 d time gap for that broadcast method. Within a day of manure application, antibiotic resistance gene (ARG) profiles in soil began to differ from each other based on manure application and soil ARG richness in all manure-amended soil increased compared to the background. Runoff from injection plots contained 52 ARGs with higher abundance compared to runoff from surface applied plots. ARGs in the former were more correlated to soil and more correlated to manure in the latter. The highest antibiotic concentrations were in the injection slit soil of those plots. Antibiotic concentrations in samples corresponded positively to concentrations of resistant FCB and ARGs, and there was a positive correlation between resistant FCB and their associated ARGs (Spearman's ρ = 0.43-0.63). A CRIISPR-Cas12a assay for quantification of ARGs in environmental samples was just as precise as conventional methods. There is also potential for in-situ detection. These combined results can hopefully help farmers improve manure management practices that mitigate spread of AREs to surrounding water, crops, and soil.Doctor of Philosophy
Rising global antibiotic resistance cause concerns over sources and pathways for the spread of contributing factors. Most of the antimicrobials used in the U.S. are involved in veterinary medicine, especially with livestock rearing. Overuse of antibiotics that are medically important to human medicine compromises the effectiveness of our medicines. Animal manure contains antibiotic resistant elements (AREs) such as resistant bacteria, resistance genes, and antibiotics) that contribute towards resistance issues. Once these AREs enter the environment, they can be taken up by crops, runoff into surface water or leached into ground water, or even reside within the animal products we consume. Altering manure application techniques is beneficial for nutrient conservation but also potentially for reducing ARE spread. With our research, we compared manure application methods, manure application seasons, cropping systems, and manure-rainfall time gaps to find ways to balance the need for manure application and the spread of resistance. We used two field-scale rainfall simulation studies along with one laboratory study. Overall, using the injection method resulted in significantly lower concentrations of manure associated AREs entering surface runoff. When manure was surface applied and rainfall occurred 7 d after application, less resistant fecal coliform bacteria (FCB) entered surface runoff when compared to the 1 d time gap for broadcast methods. Within a day of manure application, antibiotic resistance gene (ARG) profiles in soil began to differ from each other and soil ARG totals in all manure applied soil increased compared to the background. Runoff from injection plots contained more soil ARGs and runoff from surface applied plots containing more manure associated ARGs. The subsurface injection method also caused highest antibiotic concentrations in the injection slit soil of those plots. High antibiotic concentrations in samples generally meant high concentrations of resistant FCB and ARGs, and resistant FCB were also found with their associated ARGs as well. A CRISPR-Cas12a assay for quantification of ARGs in environmental samples was just as precise as conventional methods. There is also potential for onsite detection. These combined results can hopefully help farmers improve manure management practices that mitigate spread of AREs to surrounding water, crops, and soil.
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Le, Dour Olivier. "Simulation, par la methode des elements finis, du champ electromagnetique produit dans le corps humain par les sondes de surface d'imagerie par resonance magnetique." Université Louis Pasteur (Strasbourg) (1971-2008), 1993. http://www.theses.fr/1993STR13188.
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Ce travail porte sur le couplage capacitif entre la sonde de surface d'imagerie par resonance magnetique nucleaire et le patient. Nous avons dans un premier temps, simule, par la methode des elements finis, l'action d'un modele elementaire de sonde de surface sur un corps parfaitement homogene presentant les caracteristiques du muscle, et compare les resultats obtenus avec des estimations assez simples. Une serie de mesures du champ produit par une sonde identique a la sonde modelisee et placee dans des conditions analogues, a servi de validation experimentale de notre methode. Nous avons ensuite procede a la simulation de diverses ameliorations envisageables de la sonde (division des condensateurs, adjonction d'un anneau de garde) fonctionnant a 63,6 mhz, destinees a reduire l'interaction capacitive, en nous rapprochant des conditions reelles d'experimentation par adjonction d'une peau, et observe l'effet de ces artifices sur les densites de puissance deposees dans le corps et l'uniformite du balayage rf
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Cagaš, Radek. "Konstrukce dokončovacího stroje pro valivé elementy ložisek." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-231787.
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The thesis deals with the design of the device that is used to improve the quality of the surface of spherical rollers. Spherical rollers are used for the measuring of the conditions in the EHD contact. The high roughness and waviness of the spherical rollers’ surface is a problem. Several machining methods are described in the theoretical part. The overview in theoretical part has been used for choice of the machining methods (lapping and abrasive polishing). The spherical rollers‘ machining system, its construction, electronics and control systems are described in the next section. The last part is focused on testing of assembled device, and on checking its functionality. The desired roughness of the spherical rollers' surface, suitable for successful interferometric measurement, was achieved by combining the selected machining methods. The roughness and waviness achieved was Ra0.01 micron Wa0.022 microns.
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Venter, Daniel Petrus Rocco. "Friction factors and nusselt numbers for laminar flow in ducts / Daniel Petrus Rocco Venter." Thesis, North-West University, 2009. http://hdl.handle.net/10394/3995.
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By using the finite element method to solve the appropriate momentum and energy equations the friction factors and Nusselt numbers for fully developed laminar flow were determined for one- and two-dimensional flow systems. The Nusselt numbers were determined for domain boundaries subjected to a constant heat flux (H1) or a constant surface temperature (T) around the computational boundaries and in the axial directions. C++ programs, that were rewritten and extended from previous programs, were used to solve the laminar flow and to determine the values. The required wall shear stresses and heat fluxes were directly obtained for a duct as part of the primary finite-element solution; these values were then used to determine the Nusselt number and friction factor for the specific duct. The computations were performed for circular-, annular-, trapezoidal-, rectangular- and triangular ducts. Special emphasis was placed on trapezoidal ducts since only a limited number of studies have been performed on trapezoidal duct shapes and none of these studies employed the finite element method. Excellent agreement was found when the determined values were compared with the values reported in the literature. In general, the agreement of the values improved as the number of elements was increased. It was, therefore, concluded that the methods used in this study yielded friction factors and Nusselt numbers that are very accurate and usable.Thesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2009.
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Viallix, Anne. "Simulation de la structure de parois dans un matériau magnétique." Grenoble INPG, 1990. http://www.theses.fr/1990INPG0029.
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L'energie resultant d'une configuration d'aimantation dans un materiau magnetique a quatre composantes: l'echange, l'anisotropie, l'energie demagnetisante et l'energie de zeeman. C'est une fonction quadratique du vecteur aimantation qui est de norme constante dans tout le materiau. Mathematiquement, il s'agit d'un probleme de minimisation sous contrainte non lineaire. C'est le probleme qu'on se propose de resoudre numeriquement dans une petite portion du materiau. On a rencontre trois difficultes qui sont la taille des calculs, la prise en compte de l'energie demagnetisante et la non-linearite de la contrainte. On les a resolues par une methode de descente couplee avec un algorithme de maillage adapte et en faisant une hypothese de periodicite. Les equations sont discretisees par elements finis de type q1. Le champ demagnetisant est pris en compte par des elements finis de surface
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Skehan, Brian M. "Functional Elements of EspFu, an Enterohemorrhagic E. coli Effector that Stimulates Actin Assembly: A Dissertation." eScholarship@UMMS, 2009. https://escholarship.umassmed.edu/gsbs_diss/443.
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Enterohemorrhagic Escherichia coli O157:H7 (EHEC) is an attaching and effacing pathogen that upon attachment to host cells, induce characteristic attaching and effacing lesions and formation of F-actin rich pedestals beneath sites of bacterial attachment. EHEC harbors a Type III secretion system through which it delivers dozens of effectors into the host cell. The two secreted effectors critical for EHEC-mediated actin pedestal formation are the translocated intimin receptor (Tir) and EspFU. EspFU consists of an N-terminal secretion signal and a C-terminus containing six tandem 47-residue proline-rich repeats, each of which can bind and activate the actin nucleation promoting factor N-WASP. Structural and functional analyses described here have identified the mechanism of N-WASP activation by EspFU and the minimal domains and specific residues required for this activity. While EspFU and Tir are the only bacterial effectors required for F-actin pedestal formation, recruitment of EspFU to Tir is mediated by an unidentified putative host factor. To identify the host factor responsible for linking these two effectors, a combination of in vitro and functional assays were used to identify the host factor, IRTKS and the residues required for these interactions were defined. Further, the presence of at least two 47-residue repeats in all characterized clinical isolates of canonical EHEC strains led us to address the minimal requirements for EspFU functional domains to promote recruitment to Tir and N-WASP activation. Here we show that two proline-rich elements of EspFU are required for recruitment of EspFU by IRTKS to sites of bacterial attachment. Furthermore, once artificially clustered at the membrane, a single N-WASP binding element of EspFU can induce actin pedestal formation.
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Fourez, Sabrina. "Caractérisation de couches minces par ondes de surface générées et détectées par sources lasers." Thesis, Valenciennes, 2013. http://www.theses.fr/2013VALE0014/document.
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Les dépôts effectués sur substrats de silicium sont très courants notamment dans le domaine de la microélectronique. Les propriétés physiques recherchées pour ce type de structures dépendent fortement de celles de la couche. Il apparaît donc essentiel de connaître les paramètres élastiques ainsi que l’épaisseur des films considérés. De plus, la détection de certains défauts concernant la couche est souvent recherchée. L’objectif de ce travail a été de contribuer à la caractérisation de structures du type couche sur substrat. Pour cela, les ultrasons-lasers présentent de nombreux avantages puisqu’ils autorisent entre autres leur contrôle non destructif sans contact. Les ondes acoustiques de surface dans une gamme de fréquence s’étendant jusqu’à 45 MHz ont été utilisées. Nous avons développé différents modèles analytiques et les résultats expérimentaux ont aussi été comparés à certaines simulations par éléments finis. Plus particulièrement, nous avons montré qu’il était possible d’obtenir l’ensemble des paramètres élastiques du substrat et de la couche ainsi que l’épaisseur de cette dernière. Par ailleurs, nous nous sommes aussi intéressés à la détection de certains défauts en régime impulsionnel mais aussi quasi-monochromatique. Des résultats originaux concernant l’effet d’une absence de couche de forme déterminée sur le premier mode de Rayleigh ou bien encore de problèmes d’adhésion ont été présentés. Sur ce dernier point, une méthode innovante permettant de distinguer un fort niveau d’adhésion d’un faible a aussi été introduiteThin films deposited on silicon substrates are very common especially in microelectronic applications. The physical properties expected for these types of structures depend on the properties of the layer. Therefore, it is essential to know elastic parameters and thickness of the films considered. Furthermore, some layer defects detection is often required. The aim of this work was to contribute to the characterization of structures composed of a single layer deposited on a substrate. For this, laser ultrasonics offers many advantages since it is nondestructive and non-contact method. Surface acoustic waves excited in a frequency range up to 45 MHz are used. Analytical models have been developed and experimental results have also been compared with some finite element simulations. More specifically, we have shown that it was possible to obtain the thickness of the layer and all elastic parameters of both substrate and layer. In addition, we have been interested in the detection of various defects with a broadband and quasi-monochromatic excitation. Original results concerning the effect of a lack of layer with a specific geometry on the first Rayleigh mode or even adhesion problems were presented. Concerning this last point, an innovative method to tell difference between high and low adhesion was introduced
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Catche, Soraya. "Analyse des défauts de paroi de trou et de leur criticité sur la tenue mécanique des structures composites percées." Thesis, Toulouse, INSA, 2013. http://www.theses.fr/2013ISAT0002/document.
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Les structures composites sont de plus en plus présentes dans le domaine aéronautique. Le perçage, procédé qui permet le montage de fixations pour assembler ces structures, peut induire des défauts tels que délaminages, écaillages, arrachements de fibres ou surchauffes au niveau de l’alésage.Dans la littérature les auteurs s’intéressent principalement aux défauts créés en entrée et en sortie de trou. Aussi, cette recherche s’est focalisée sur les défauts de paroi crées par l’opération de perçage. Une caractérisation qualitative et quantitative a été proposée et le lien entre ces défauts et la tenue mécanique a été évalué.L’état de surface des parois est quantifié via sa rugosité qui mesure globalement les défauts générés lors du perçage. Jusqu’à présent, la qualité de la surface est estimée par un critère de rugosité géométrique Ra issu de la culture métallique. Il présente un certain nombre d’incohérences pour les perçages des composites. Dans ce travail de thèse, les relations entre les paramètres de perçage, le matériau de l’outil, sa géométrie et la qualité des alésages mesurée par les critères normalisés d’état de surface ont été établies. Un critère de qualité des parois de trou pour les matériaux composites autre que les critères normalisés a été proposé.La nature intime de la surface de contact influence clairement la qualité du transfert de charge par contact localisé. Dans un premier temps, l’influence des défauts de paroi sur la tenue en matage quasi-statique a été établie, ensuite, la tenue en compression quasi-statique des stratifiés C/E liée à la présence de défauts de paroi a été étudiée. Une analyse de la tenue en fatigue des stratifiés percés liée à la présence des défauts d’état de surface a aussi été réalisée. Enfin, une analyse numérique originale par éléments finis incluant une représentation géométrique des défauts observés, a permis de mieux cerner la cinétique d’endommagement des stratifiés percés liés à la présence de défauts de paroiComposite materials are finding an increasing number of applications in the aerospace industry. The drilling is the process that allows the fasteners installation. The drilling operation can induce defects such as delamination, fibers and matrix pull-out and matrix burning.Previous studies focused mainly on the defects created at the hole entry and exit. Only few of these studies concern the hole wall drilling defects. In this study, we focused on the hole wall defects created by the drilling operation. A qualitative and quantitative characterization of defects was proposed and the relationship between these defects and the mechanical strength was evaluated.The hole surface finish is quantified by the roughness criterion Ra, that comes from metallic culture. Because of their heterogeneous nature, composite materials do not present the same defects patterns as metallic materials. The question that arises is whether the roughness may have an influence on the mechanical behavior of composite materials. In this study, the relation between the drilling parameters, the drill material, its geometry and the hole quality quantified with normalized parameters has been established. A criterion used to quantify the hole surface finish of composites have been proposed.The inner nature of the contact surface clearly influences the load transfer quality. As a first step, the influence of the hole wall defects on the quasi-static bearing behavior has been established, then the compressive behavior linked to the presence of hole wall defects have been studied. An analysis of the fatigue behavior of drilled laminates due to the presence of hole wall defects have been conducted.Finally, a numerical analysis by finite elements including an original geometric representation of the defects observed, has allowed to further clarify the damage kinetics of drilled laminates linked to the presence of drilling defects
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Dillon-Leitch, Henry C. H. (Henry Cameron Hartley) Carleton University Dissertation Geology. "The Distribution of platinum-group elements and platinum-group minerals from the Donaldson West and surface deposits, Cape Smith Belt, Quebec: the roles of thermal and dynamic metamorphism." Ottawa, 1988.
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Jolivet, Simon. "Caractérisation tribodynamique de la bruyance denture pour la gestion du confort acoustique des conditions d’engrènement en fabrication." Thesis, Paris, ENSAM, 2015. http://www.theses.fr/2015ENAM0041/document.
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Les standards d’économie de carburant à venir génèrent un développement rapide des véhicules électriques et hybrids. Ces contraintes régulatrices vont affecter le design des boîtes de vitesse qui conduit à des changements au niveau du type, de la taille et de la qualité des engrenages. Ainsi, les fabricants de roues dentées ont besoin de créer des flancs de dentures de haute qualité avec des modifications topologiques spéciales. Les objectifs principaux sont l’accroissement de la capacité de tenue en chargement et la réduction de la bruyance denture. En effet, la surface des flancs est au cœur des mécaniques de l’engrènement et un des éléments générateur d’excitations. Les mécanismes d’usure les plus communs sont les micro-piqûres, les piqûres et l’écaillage, qui apparaissent dans les premières étapes de défaillance. Bien que les effets des défauts macro-géométriques des surfaces des flancs de denture ont été largement étudiés, les échelles micro- et méso-métriques et leur influence n’est pas encore entièrement compris. De plus le choix et l’optimisation de procédé de finition denture (rectification, powerhoning…) pour améliorer le confort acoustique des conditions d’engrènement reste une issue majeure dans la fabrication des engrenages. Ces travaux proposent une approche multiéchelle de la fabrication, à la fois expérimentale et numérique, dans le but d’identifier l’effet d’échelle des défauts micro- et méso-métriques sur les vibrations de l’engrenage. Un banc d’essai vibratoire instrumenté de faible puissance a été développé et validé par la comparaison de mesures sur boîte de vitesse sur un moyen industriel Renault. Les études expérimentales des relations entre la finition des surfaces des flancs, caractérisée par l’utilisation d’une décomposition multiéchelle basée sur la transformée par ondelettes continues, et les modes vibratoires générés mettent en avant un impact non-négligeable de des échelles de rugosité et d’ondulation. Les mesures de bruit de frottement sur les flancs ont par ailleurs permis de comprendre le lien entre la cinématique du contact (vitesse), les échelles de surface (espacement entre aspérités) et les fréquences vibratoires. Une simulation 3D d’un contact rugueux a alors été développée. Les résultats couplés avec une analyse statistique des contributions des paramètres surfaciques et de contact ont montré un large effet des échelles micrométriques. Enfin, un modèle éléments finis d’un engrenage hélicoïdal intégrant des topographies réelles mesurées et calculant l’erreur de transmission a aussi été développé et validé expérimentalement. L’importance de la qualité des engrenages et de leurs caractéristiques topologiques sur la densité de puissance et les problématiques acoustiques a alors été calculée et discutéeUpcoming fuel economy standards result in the rapid development of electric and hybrid vehicles. Such regulatory demands will affect the transmission design, which drives changes in the type, size and quality levels of gears. Thus, gear manufacturers need to create high quality gear flanks with special topological modifications. The main objectives are to increase the load-carrying capacity of gears, and also to reduce the gear noise behavior. The teeth surface is indeed at the heart of the gear meshing mechanics and one of the elements generating excitations. The most common wear mechanisms in gear are micro-pitting, pitting and spalling, which occur on the teeth surface at the early stage of failure. While the effect of the macro-geometric defects of the gear teeth surface on the acoustics response of spur gear pair has been studied quite thoroughly, the micro and meso scales and their influence are not entirely understood. Moreover, the choice and optimization of the tooth flank finishing process (grinding, powerhoning…) to manage the acoustic comfort of the meshing conditions is still a major issue in gear manufacturing. This study addresses a multiscale manufacturing approach, both experimental and numerical, in order to identify the scale effect of micro/meso defects on gear vibrations. A low-powered instrumented vibratory test bench has been developed and validated by comparing the measurements with the ones done at the industrial scale on a gear box test rig from Renault. The experimental work investigated the relationship between the surface finish of tooth flanks, which was characterized using a multiscale decomposition based on continuous wavelet transform, and the modes of the generated vibrations as a function of roughness and waviness scales. The friction noise measurements on tooth flanks have besides permitted to understand the link between the contact kinematics (speed), the surface scales (space between the asperities) and the vibration frequencies. A 3D finite-element simulation model of a rough contact was hence developed. The results coupled with the statistical analysis of the contributions of the surface and contact parameters have shown the large effect of the micro-scales. A 3D finite-element gear simulation using real measured topographies and transmission error calculation has also been performed and experimentally validated. The prevalence of the gear quality and its topological features on power density and sound issues are hence computed and discussed