Dissertations / Theses: 'Contact partiel'

1

Podgorski, Thomas. "Ruissellement en conditions de mouillage partiel." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2000. http://tel.archives-ouvertes.fr/tel-00003231.

Full text

Abstract:

L' écoulement d'un fluide sur une surface inclinée en conditions de mouillage partiel existe dans de nombreuses situations de la vie courante et dans des applications industrielles variées. A faible débit, des zones sèches stationnaires peuvent exister au sein d'un film en ruissellement, qui compromettent le fonctionnement de certains échangeurs de chaleur. Nous avons entrepris une etude expérimentale systématique de l' écoulement d'un film d'huile silicone sur un plan incliné convenablement traité pour obtenir un angle de contact statique fini. Nous montrons que des zones sèches stationnaires de forme bien définie et reproductible existent dans une certaine gamme de débit, et qu'elles sont supprimées au dessus d'un débit critique. Nous proposons une modélisation de ces phénomènes basés sur de subtils équilibres entre les effets de la gravité, de la viscosité et de la capillarité rendant compte des observations dans une large gamme de paramètres. Au premier ordre l' équilibre du bourrelet liquide délimitant une zone sèche résulte d'une compensation de son poids par les effets capillaires, et pour les forts angles de contact et des inclinaisons faibles du plan de l'écoulement, des effets secondaires liés à la courbure de la ligne de contact et à la pression hydrostatique dans le film jouent un rôle non négligeable et déterminent la stabilité du système. Nous avons également abordé le ruissellement de gouttes sur un plan incliné, pour lequel nous mettons en évidence l'existence de régimes d'écoulement variés. Suivant leur vitesse, les gouttes peuvent être ovales, pointues ou perlantes. Une interpr etation de l'existence du régime de gouttes pointues basée sur un modèle d'angle de contact dynamique est proposée. Enfin, nous présentons quelques résultats qualitatifs sur l'écoulement d'eau dans un faisceau de tubes tel qu'on en rencontre dans certains échangeurs de chaleur.

APA, Harvard, Vancouver, ISO, and other styles

2

Meriaux, Jean. "Etude expérimentale et modélisation de l'endommagement du contact aube-disque de soufflante soumis à des chargements de fretting fatigue." Phd thesis, Ecole Centrale de Lyon, 2010. http://tel.archives-ouvertes.fr/tel-00730679.

Full text

Abstract:

L'optimisation du dimensionnement des structures passe par une meilleure connaissance de leur mode d'endommagement. Cette étude se focalise donc sur la caractérisation de l'endommagement du contact aube/disque des moteurs aéronautique. Cet assemblage mécanique est soumis a une combinaison d'un effort normal (force centrifuge) et tangentiel (dynamique de l'aube). La portée du disque en Ti-6Al-4V subi donc un chargement complexe de type fretting fatigue. Ce type de sollicitation entraine, entre autre dégradation, de la fissuration dont la modélisation expérimentale et numérique est rendue difficile par les limitations des moyens et des connaissances actuelles. Le premier objectif de ce travail de thèse est de développer un moyen d'essai et une instrumentation associée afin d'étudier de façon qualitative et quantitative la fissuration d'un contact Ti-6Al-4V/Ti-6Al-4V. Le second but est d'utiliser les données issues de ce moyen expérimental afin de proposer un modèle de prédiction des durées de vie de cet assemblage. Un montage inédit de fretting fatigue double vérin mono-contact a été mis en place avec une instrumentation nouvelle pour ce type d'essai : suivi de fissuration par suivi de potentiel et par émission acoustique. Une attention particulière a été apportée aux calibrations et aux méthodologies expérimentales. Ce banc d'essai permet notamment de simuler des efforts de fretting applique en phase ou alors de telle manière a simuler un vrai cycle de vol. Cet outil a permis de décrire quantitativement les premières courbes de Wohler en fretting à amorçage (Effort de fretting vs Nombre de cycles à amorçage) pour deux configurations de contact (cylindre/plan et plan/plan). Les impacts des différents paramètres de fretting sur l'amorcage ont pu être quantifies. Les paramètres influant sont : la configuration du contact, les niveaux des efforts appliques et leur mode de combinaison (cycles en phase ou cycles de type vol). De plus des courbes de cinétique de propagation des fissures ont pu être extraites des différents essais, montrant un fort impact du fretting sur les vitesses de propagation des fissures. Une analyse qualitative via l'émission acoustique a montré un mécanisme d'amorçage et de propagation en 3 étapes suivant la perte d'influence du contact. Un modèle de prédiction de l'amorçage et de simulation de la propagation des fissures a été mis en place. Bien que limite dans la prise en compte des effets gradients (approches non locales), ce modèle se montre très performant surtout dans sa capacité à utiliser les données expérimentales dans l'identification des lois d'amorçage ou de propagation. Ce travail a donc permis d'importantes avancées dans la compréhension des mécanismes de fissuration et dans leur modélisation ouvrant ainsi la porte vers une prédiction fiable de l'endommagement des contacts aube/disque.

APA, Harvard, Vancouver, ISO, and other styles

3

Strubel, Vincent. "Particle entrapment in EHD contacts - Aerospace applications." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI098/document.

Full text

Abstract:

Une lubrification suffisante est essentielle au bon fonctionnement des mécanismes et/ou composants comme par exemple les paliers à roulement. Par contre, les lubrifiants contiennent souvent des débris d’usure ou des polluants extérieurs. Ces particules micrométriques peuvent pénétrer des contacts d’épaisseur inférieure au micromètre induisant des empruntes ou indents pouvant conduire à des endommagements irréversibles pour les surfaces en contact. L’objet de ce travail est l’étude du piégeage de polluants solides à l’aide de particules sphériques d’acier, d’un point de vue théorique, numérique et expérimental. Dans un premier temps, une étude phénoménologique a été proposée à l’aide d’une nouvelle méthode expérimentale basée sur la technique PIV combinée à un tribomètre bille/disque. Les trajectoires des polluants à l’entrée du contact ont pu ainsi être identifiées. En parallèle, un modèle numérique d’écoulement du lubrifiant a été développé pour permettre l’évaluation des conditions menant au piégeage ou non de particules. Finalement, des expériences sur une machine bi-disques en conditions de lubrification polluée contrôlée ont permis de valider les tendances observées pour le piégeage. Une première série de résultats a montré que le piégeage de contaminants est fortement dépendant du profil de vitesse du lubrifiant. Un taux de piégeage très hétérogène a été observé sur des contacts avec une ellipticité transverse à l’écoulement variable. De manière surprenante, malgré une augmentation de la largeur de contact, une forte diminution du nombre de particules piégées a été observée dans des contacts elliptiques. Il a été démontré que cette diminution pouvait être imputée à la présence d’importants reflux de lubrifiant dans les contacts elliptiques larges. L’étude de contacts hybrides, nitrure de silicium–acier, a montré une bonne résistance à l’indentation du nitrure de silicium. Il est à noter que les contacts hybrides présentent des niveaux de piégeage similaire à un contact tout acier
Contact lubrication is essential in a wide range of mechanical systems like rolling element bearings (REBs). A minimum quantity of clean lubricant all along the bearing life is necessary but difficult to ensure. In fact, lubricants contain inevitably wear debris or external particles, like dust. Carried by the lubricant in the vicinity of elastohydrodynamic (EHD) contacts, particles can be entrapped with disastrous consequences for contacting surfaces. Entrapment of micrometric particles in submicrometric contacting gaps means irreversible damages for the surfaces. Damages weaken the surfaces and reduce significantly the REBs lifetime. The goal of this work is to analyze the critical particle entrainments in the contact inlet. Entrapment of steel spherical particles was investigated from the numerical and experimental point of view. Firstly, the phenomenology of entrapment was explored with a new experimental method based on Particle Image Velocimetry (PIV) technique installed on a tribometer. It enabled the evaluation of velocity profiles in the contact inlet and the tracking of particles within EHD contacts. Secondly, a numerical modelling of the inlet flow for EHD contacts, including the particle tracking, was developed. Finally, tests on a twin-disc machine with a controlled level of well-defined contamination were conducted to validate previous conclusions. A first set of results showed that particle entrapment is highly dependent on the lubricant velocity profile. Depending on contact geometry, from point to wide elliptical contacts, different entrapment probability were revealed. Surprisingly, increasing contact width with wide elliptical contacts leads to a drop of entrapped particles. It was demonstrated that this phenomenon is due to backflows occurring upstream from these contacts. Introducing a hybrid pair of contacting materials (silicon nitride–steel), dents on the surfaces due to entrapped particles were explored. It has been confirmed that silicon nitride surface offers a real ability to resist to indentation. It was also noticed that the entrapment probability for silicon nitride–steel contacts is equivalent to a steel–steel one

APA, Harvard, Vancouver, ISO, and other styles

4

Delacroix, Bastien. "Développement d'un modèle intégral avec transport d'une fonction couleur pour la simulation d'écoulements de films minces partiellement mouillants." Electronic Thesis or Diss., Toulouse, ISAE, 2024. http://www.theses.fr/2024ESAE0005.

Full text

Abstract:

Pourquoi une goutte d’eau a tendance à prendre la forme d’une sphère ? Pourquoi reste-t-elle accrochée sur sa feuille lors de la rosée du matin ? Pourquoi, au contraire, ruisselle-t-elle jusque sur le sol ? Toutes ces questions en apparence simplistes font appel à des phénomènes microscopiques très complexes dont la nature physique est encore aujourd’hui sujet à débat. Leur compréhension est cependant un enjeu majeur dans de nombreux cas d'application industrielle. C’est notamment le cas en aéronautique où après le passage d’un aéronef au travers d’un nuage ou après une opération de dégivrage, un film mince se forme sur l’aile. L’évolution de la surface mouillée par ce film, comme lors de sa transition en ruisselets sous l’effet du cisaillement de l’air, ainsi que son éventuel regel un peu plus loin en dehors des zones de protection, n’est pas prise en compte dans les outils de simulations des dégivreurs thermiques ; ou alors de manière rudimentaire via des corrélations empiriques. Cependant, cette accrétion de givre se doit d’être contrôlée pour des raisons de sécurité et de performances aérodynamiques. C’est pourquoi, il est nécessaire d’améliorer les outils existant en développant de nouveaux modèles capables de prendre en compte l'influence des forces capillaires à l’échelle macroscopique, notamment au niveau de la ligne triple, pour pouvoir prédire la dynamique d’un film cisaillé.L’objectif général de cette étude est donc le développement d’un modèle adapté à la simulation à grande échelle d’écoulement de film mince partiellement mouillant.Dans cette optique, une approche basée sur un système d'équations de type Saint-Venant a été adoptée. Cependant, ce système sous sa forme classique ne permet pas la simulation de films minces avec effet de mouillage partiel. Une solution pour prendre en compte ces effets est d'ajouter une force macroscopique concentrée à la ligne de contact. Cette force singulière permet ainsi de vérifier localement la loi macroscopique de Young-Dupré. La difficulté de cette approche est alors de localiser la force uniquement à la ligne triple. Contrairement aux modèles rencontrés dans la littérature qui se basent tous sur l’utilisation d’un paramètre ajustable, permettant de faire la distinction entre zone sèche et zone mouillée, nous proposons ici une approche avec transport d’une fonction couleur. Cette fonction, définie comme égale à un dans les zones mouillées et nulle dans les zones sèches, présente l'intérêt d'avoir un gradient identiquement nul, sauf à la ligne triple, permettant de localiser la force de ligne de contact.L'introduction de cette fonction couleur oblige à reformuler en partie le système d'équations de Saint-Venant afin de tenir compte de cette nouvelle fonction dans l'expression des différents termes de forces agissant sur le film. Pour justifier le choix de cette nouvelle formulation, une méthode basée sur une formulation eulérienne du principe de Hamilton a été utilisée. Cette méthode permet d’obtenir une équation de quantité de mouvement compatible avec la conservation de l'énergie du système étudié avec comme unique point de départ une expression de la densité d'énergie du système en fonction des variables utilisées.Ce nouveau système d’équations, en plus d’être complètement affranchi d’un paramètre de calibration, présente l’avantage d’être complètement hyperbolique dans le cas où les effets de courbure ne sont pas pris en compte. Cela a permis le développement d’un solveur de Riemann de type HLLC pour résoudre numériquement ce système d’équations. Afin de tester la robustesse des modèles physiques et numériques, un ensemble de cas de vérification et de validation a été mis en place.Enfin, les termes de courbure ont été pris en compte dans le schéma numérique final permettant d’étendre considérablement le champ d’application de ce nouveau modèle avec fonction couleur. Ainsi des problèmes où les effets capillaires sont prédominants ont pu être simulés
Why does a drop of water tend to form a sphere? Why does it cling to its leaf in the morning dew? On the contrary, why does it flow down towards the ground? All these seemingly simplistic questions involve highly complex microscopic phenomena whose physical nature is still the subject of debate. However, understanding them is a major challenge in many industrial applications. This is particularly true in aeronautics, where a thin film forms on the wings after the aircraft has passed through a cloud or after a defreezing operation. The evolution of the wetted surface by this film, like its transition into rivulets under the effect of air shear, as well as its eventual refreezing a little further outside the protection zones, is not taken into account in thermal defrost simulation tools; or only in a rudimentary way via empirical correlations. However, this ice accretion must be controlled for safety reasons and aerodynamic performance. This is why it is necessary to improve existing tools by developing new models capable of considering the influence of capillary forces on a macroscopic scale, specifically at the contact line level, in order to be able to predict the dynamics of a sheared film.The overall objective of this study is therefore to develop a suitable model for large-scale simulation of partially wetting thin film flow.To answer this objective, an approach based on a Shallow-water equations was adopted. However, this system in its classical form does not allow the simulation of thin films with partial wetting effects. One solution to consider these effects is to add a macroscopic force concentrated to the contact line. This singular force enables the macroscopic Young-Dupré law to be verified locally. The issue with this approach is to localize the force at the contact line only. Unlike other models in the literature, which are all based on the use of an adjustable parameter allowing the distinction between dry and wet zones, we offer here an approach involving the transport of a color function. This function, defined as equal to one in wet zones and zero in dry zones, has the advantage of having an identically zero gradient, except at the contact line, enabling the contact line force to be localized.The introduction of this color function needs a partial reformulation of the Shallow-water equations, in order to integrate this new function in the expression of the various force terms acting on the film. In order to justify the choice of this new formulation, a method based on an eulerian formulation of Hamilton's principle was used. This method helps to obtain a momentum equation compatible with the conservation of energy of the system under study, with the only starting point being an expression of the system's energy density as a function of the variables used.This new system of equations, in addition to being completely calibration parameter free, has the advantage of being entirely hyperbolic in the case where curvature effects are not taken into account. This has helped us to develop an HLLC-type Riemann solver to solve this equation system numerically. In order to test out the robustness of the physical and numerical models, a set of verification and validation cases was set up.Finally, curvature terms were considered in the final numerical scheme, considerably extending the scope of application of this new color function model. In this way, problems where capillary effects are predominant could be simulated

APA, Harvard, Vancouver, ISO, and other styles

5

Manuelli, Lucas Ph D. Massachusetts Institute of Technology. "Localizing external contact using proprioceptive sensors : the contact particle filter." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/115739.

Full text

Abstract:

Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 61-65).
In order for robots to interact safely and intelligently with their environment they must be able to reliably estimate and localize external contacts. This paper introduces the CPF, the Contact Particle Filter, which is a general algorithm for detecting and localizing external contacts on rigid body robots without the need for external sensing. The CPF finds external contact points that best explain the observed external joint torque, and returns sensible estimates even when the external torque measurement is corrupted with noise. We demonstrate the capability of the CPF in multiple scenarios. We show how it can track multiple external contacts on a simulated Atlas robot, and also perform extensive simulation and hardware experiments on a Kuka iiwa robot arm.
by Lucas Manuelli.
S.M.

APA, Harvard, Vancouver, ISO, and other styles

6

Haider, Christine Irmingard. "Particle contact mechanisms in pressure agglomeration." Thesis, University of Sheffield, 2014. http://etheses.whiterose.ac.uk/6995/.

Full text

APA, Harvard, Vancouver, ISO, and other styles

7

Lahnane, Nabila. "Le déblocage des sources d'anéantissement du contrat en droit commun." Thesis, Perpignan, 2018. http://www.theses.fr/2018PERP0045/document.

Full text

Abstract:

Débloquer le contrat, relevant du droit commun, de ses sources d’anéantissement revient à le faire échapper à la nullité ou à la résolution grâce à l’application de sanctions alternatives. Le but n’étant pas de proposer toutes les solutions salvatrices possibles mais uniquement celles dont la primauté sur les sanctions destructrices peut être justifiée par une argumentation juridique solide. Afin de défendre cette idée, notre étude ne se contente aucunement de décrire ce que l’ord. du 10 fév. 2016 permet déjà à ce sujet (art. 1170, 1171 et 1195 C.civ.). En premier lieu, un fondement général est proposé. Les solutions alternatives au lieu et place de la nullité peuvent se fonder sur l’art. 1184 C.civ., en vertu duquel l’irrégularité partielle ne peut pas mener à autre chose qu’une sanction partielle maintenant le contrat. S’agissant des solutions alternatives à la résolution, elles ont été fondées sur une relecture, plus moderne, du principe de la force obligatoire du contrat. En second lieu, sont proposées des sanctions salvatrices, parfois inédites, basées sur une interprétation originale des nouveaux textes du droit commun des contrats. Par ex., est envisagée une requalification de l’indemnité octroyée en contrepartie d’un engagement de non-concurrence afin qu’elle ne soit plus considérée comme une rémunération salariale mais plutôt comme la rémunération d’une prestation de service. Pourrait ainsi être appliqué l’art. 1165 C.civ. qui autorise la détermination du prix postérieurement à la formation du contrat alors que selon le droit prétorien en vigueur, l’absence de fixation du prix au sein de la clause de non-concurrence, entraîne son annulation. En outre, au sein du nouveau droit des contrats ont été découverts des fondements tout à fait appropriés pour justifier, entre autres, le recours à la nullité partielle pour tous les vices du consentement incidents, ainsi que la possibilité de sanctionner l’abus dans la fixation du prix par sa réduction, etc
The saving adaptation of the contract threatened by a nullity or a termination amounts to get it out of a dead end and thus unblock it. Unblocking applied to the contract is not a notion but a mechanism in which the means, allowing it to pursue its destiny in a sustainable way, are integrated. Since it is a matter of giving priority to alternative remedies to the annihilation of the contract and that these are of a great diversity, it cannot be a question of a single notion, and even less of a unified legal regime. The identified blockages are solved by very different solutions, each with its own regime. However, they all come together for their purpose, which is to maintain an effective contract. This inevitably happens by reshuffling the Court's powers toward the contract because its release requires it to be rewritten almost systematically. The ordonnance of February 10, 2016 reforming the law of contract modifies this role only in a fragmented way. Indeed, we can note that it is more increased in unfair terms (Art. 1170 and 1171 civ. C.) and change of circumstances (Art. 1195 civ. C.) but the virtues of the unblocking of the contract that we have identified invite to a greater generalization of this recent dynamic. The techniques of unblocking the contract proposed in this thesis constitute either original interpretations of the new texts of the law of contract, or novel solutions for which we have discovered the appropriate juridical basis

APA, Harvard, Vancouver, ISO, and other styles

8

Olsson, Erik. "Micromechanics of Powder Compaction and Particle Contact." Licentiate thesis, KTH, Hållfasthetslära (Avd.), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-117608.

Full text

APA, Harvard, Vancouver, ISO, and other styles

9

Lindberg, Joacim. "Plastic contacts in particle based simulations." Thesis, Umeå universitet, Institutionen för fysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-149058.

Full text

Abstract:

Granular materials, large collections of macroscopic particles, are something that is commonly found in both nature and industry. Examples of such can be sand, ore, grains, seeds or snow. Simulations of granular materials are important in many industrial cases. It gives an opportunity to study the behavior of the particles as they interact with machinery and gives an indication of how eﬃcient new designs perform. In some areas, such as vehicle-terrain interaction, plastic deformation of the particles can be an important factor. The Ume˚a based company Algoryx Simulation can simulate granular materials in their physics engine AGX Dynamics using a nonsmooth discrete element approach (NDEM), but currently lack support for plastic deformation. The purpose of this thesis is to implement a plastic contact model in the source code of AGX Dynamics, such that plastic deformation can be observed. The implementation was ﬁrst tested for single particle-particle compression where measured contact forces were compared to theoretical models. Uniaxial compression tests were performed for bulk testing, ﬁlling a cylinder with particles and compressing them while monitoring the axial stress and strain. The results from the single particle compression correspond well to theory, giving the correct plastic deformation for a given contact force and correctly illustrates the eﬀects of changing diﬀerent model parameters. Plastic deformation could also be observed in the results from bulk testing. Additionally, it was observed that the current version of the implementation is best suited for simulating either very cohesive materials, where particles stick to each other when colliding, or cohesionless materials, where colliding particles are separated after impact. Additional research is needed to study how the separation velocity for colliding particles should be updated in a way that is consistent with the plastic model parameters and experimental results.

APA, Harvard, Vancouver, ISO, and other styles

10

Lindle, Molly Eileen. "Contact electrification and charge separation in volcanic plumes." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/43726.

Full text

Abstract:

Volcanogenic lightning has a long documented history in the scientific field, though its origins are still poorly understood. The interactions leading to electrification of ash plumes is essentially a function of the microphysics controlling and affecting ash particle collisions. This thesis presents measurements made on charged particle interactions in a fluidized bed, with large-scale applications to the phenomenon of volcanogenic lightning and charged particle dynamics in volcanic plumes. Using a fluidized bed of ash samples taken from Ecuador's Volcán Tungurahua, particles are introduced to a collisional environment, where they acquire an associated polarity. A charged copper plate is used to collect particles of a given polarity, and particle size distributions are obtained for different weight fractions of the ash. It is observed that relatively smaller particles acquire a net negative charge, while larger particles in the sample charge positively. This is a well-documented occurrence with perfectly spherical, chemically identical samples, but this work represents one of the first applications of the principle to volcanic ash. Image analysis is preformed to determine the size distribution associated with specific polarities, and the associated minimum charge on each particle is calculated based on the plate collection height and particle size. We also present results that demonstrate the relationship between particle collisions and the amount of charge exchanged. Using techniques developed to examine the collision rate within a flow, combined with the charging rates determined from this experiment, we determine a maximum charge exchange rate of 1.28±0.23 electrons transferred per collision.

APA, Harvard, Vancouver, ISO, and other styles

11

Lahnane, Nabila. "Le déblocage des sources d'anéantissement du contrat en droit commun." Electronic Thesis or Diss., Perpignan, 2018. http://www.theses.fr/2018PERP0045.

Full text

Abstract:

Débloquer le contrat, relevant du droit commun, de ses sources d’anéantissement revient à le faire échapper à la nullité ou à la résolution grâce à l’application de sanctions alternatives. Le but n’étant pas de proposer toutes les solutions salvatrices possibles mais uniquement celles dont la primauté sur les sanctions destructrices peut être justifiée par une argumentation juridique solide. Afin de défendre cette idée, notre étude ne se contente aucunement de décrire ce que l’ord. du 10 fév. 2016 permet déjà à ce sujet (art. 1170, 1171 et 1195 C.civ.). En premier lieu, un fondement général est proposé. Les solutions alternatives au lieu et place de la nullité peuvent se fonder sur l’art. 1184 C.civ., en vertu duquel l’irrégularité partielle ne peut pas mener à autre chose qu’une sanction partielle maintenant le contrat. S’agissant des solutions alternatives à la résolution, elles ont été fondées sur une relecture, plus moderne, du principe de la force obligatoire du contrat. En second lieu, sont proposées des sanctions salvatrices, parfois inédites, basées sur une interprétation originale des nouveaux textes du droit commun des contrats. Par ex., est envisagée une requalification de l’indemnité octroyée en contrepartie d’un engagement de non-concurrence afin qu’elle ne soit plus considérée comme une rémunération salariale mais plutôt comme la rémunération d’une prestation de service. Pourrait ainsi être appliqué l’art. 1165 C.civ. qui autorise la détermination du prix postérieurement à la formation du contrat alors que selon le droit prétorien en vigueur, l’absence de fixation du prix au sein de la clause de non-concurrence, entraîne son annulation. En outre, au sein du nouveau droit des contrats ont été découverts des fondements tout à fait appropriés pour justifier, entre autres, le recours à la nullité partielle pour tous les vices du consentement incidents, ainsi que la possibilité de sanctionner l’abus dans la fixation du prix par sa réduction, etc
The saving adaptation of the contract threatened by a nullity or a termination amounts to get it out of a dead end and thus unblock it. Unblocking applied to the contract is not a notion but a mechanism in which the means, allowing it to pursue its destiny in a sustainable way, are integrated. Since it is a matter of giving priority to alternative remedies to the annihilation of the contract and that these are of a great diversity, it cannot be a question of a single notion, and even less of a unified legal regime. The identified blockages are solved by very different solutions, each with its own regime. However, they all come together for their purpose, which is to maintain an effective contract. This inevitably happens by reshuffling the Court's powers toward the contract because its release requires it to be rewritten almost systematically. The ordonnance of February 10, 2016 reforming the law of contract modifies this role only in a fragmented way. Indeed, we can note that it is more increased in unfair terms (Art. 1170 and 1171 civ. C.) and change of circumstances (Art. 1195 civ. C.) but the virtues of the unblocking of the contract that we have identified invite to a greater generalization of this recent dynamic. The techniques of unblocking the contract proposed in this thesis constitute either original interpretations of the new texts of the law of contract, or novel solutions for which we have discovered the appropriate juridical basis

APA, Harvard, Vancouver, ISO, and other styles

12

Thaitirarot, Anothai. "Studies in partial slip contacts applied to fretting fatigue." Thesis, University of Oxford, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597103.

Full text

Abstract:

Detailed analysis of aU the fretting fatigue test results available in the literature is carried out by employing refined asymptotic solutions. Several different criteria are used and it is shown that two give an improvement over stress-based criteria. These procedures provide a practical method for both designing against fretting fatigue failure and quantifying the nucleation time when fretting is unavoidable. The reduced stiffness method is developed together with the evolutionary algorithm which is the direct implementation of the Signorini and Coulomb friction contact inequalities. This method is capable of solving two dimensional frictional contact problems in significantly less time and is more accurately than a traditional FE approach. In addition, algorithms for determining shakedown limit of coupled contacts have also been developed. A problem of a plane receding contact was considered where a strip is pressed against an elastically similar half-plane by normal pressure extending along the strip surface but stopping short of the end. These phenomena are analysed, together with the behaviour of the system when the pressure is removed. Interfacial characteristics of a lap joint formed using friction grip bolts is also considered as these produce a receding contact. The joints consist of two elastically similar laps pressed in contact by a constant normal force and subject to oscillatory bulk load at the free end of the laps. Bulk load applied at the free ends causes a smooth change in the size of contact and the development of the slip zones. The trend of energy dissipation with the extent of contact and magnitude of remote tension, at various friction coefficients, has been found. Lastly, axisymmetric receding contact between a circular elastic disc pressed against a half-space has been studied. The disc is first subjected to normal pressure followed by torsion. Normal pressure alone causes a contact interface to separate, if the loaded area is sufficiently small. Torsion is subsequently appl ied which causes a change in the size of contact and has a significant effect on the direction of the resultant slip displacement and the stick/slip boundaries. I

APA, Harvard, Vancouver, ISO, and other styles

13

Komendarczyk, Rafal. "Nodal sets and contact structures." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-05192006-231553/.

Full text

Abstract:

Thesis (Ph. D.)--Mathematics, Georgia Institute of Technology, 2007.
Belegradek, Igor, Committee Member ; Ghrist, Robert, Committee Chair ; Harrell, Evans, Committee Member ; Etnyre, John, Committee Member ; Symington, Margaret, Committee Co-Chair.

APA, Harvard, Vancouver, ISO, and other styles

14

Hayoun, Pascaline. "Partial wetting of thin liquid films in polymer tubes." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066202/document.

Full text

Abstract:

Les tubes polymères, de PDMS ou de PVC, sont des matériaux hydrophobes polyvalents et peu couteux. Ils sont très largement utilisés dans l'industrie pour transférer des fluides plus ou moins complexes tels que de l'eau potable, des émulsions (e.g lait), des suspensions (e.g café), ou encore des solutions de molécules actives (e.g médicament). La plupart de ces applications mettent en jeux des écoulements intermittents répétés de liquide qui peuvent contaminer le matériau. Cette étude a pour but de mieux comprendre comment ces écoulements de fluides complexes entraînent la contamination des tubes. Nous étudions expérimentalement et théoriquement les régimes d'un segment de liquide de faible viscosité s'écoulant dans un tube en conditions de mouillage partiel. Deux processus sont en compétition : à cause de la vitesse élevée du segment de liquide, un film de liquide se forme à l'arrière du segment, alors qu'à cause de des conditions de mouillage partiel le film de liquide démouille. Nous montrons qu'au-delà de la limite en vitesse correspondant à la transition de mouillage dynamique qui est bien inférieure à la prédiction de Cox-Voinov, un régime précédemment inconnu avec un film épais, dont l'épaisseur dépend de la vitesse, est obtenu bien avant la formation classique d'un film de Landau-Levich-Derjaguin. Nos simulations numériques sont en partie en accord avec nos observations
Polymer tubes, made of PDMS or PVC, are versatile, low cost, hydrophobic materials. They are heavily used in industry for transferring more or less complex fluids such as drinkable water, emulsions (e.g milk), suspensions (e.g coffee), or solution of active molecules (e.g pharmaceutics). Most of these applications involve repeated, intermittent flow of liquids which can lead to unwanted contamination. This study aims at better understanding the mechanisms of contamination for intermittent flow. We experimentally and theoretically investigate the flow regimes of low viscosity liquid slugs flowing down a vertical tube under partial wetting condition. Two processes are in competition: because of the large slug velocity, a liquid film tends to be created at the back of the slug whereas because of the partial wetting condition, the liquid film dewets. We investigate how this competition controls film deposition in hydrophobic tubes. We show that above the threshold velocity for dynamic wetting which is much lower than predicted by Cox-Voinov, a previously unknown regime is found where we observe a velocity dependent thick film well before the classical Landau-Levich-Derjaguin regime

APA, Harvard, Vancouver, ISO, and other styles

15

Hayoun, Pascaline. "Partial wetting of thin liquid films in polymer tubes." Electronic Thesis or Diss., Paris 6, 2016. http://www.theses.fr/2016PA066202.

Full text

Abstract:

Les tubes polymères, de PDMS ou de PVC, sont des matériaux hydrophobes polyvalents et peu couteux. Ils sont très largement utilisés dans l'industrie pour transférer des fluides plus ou moins complexes tels que de l'eau potable, des émulsions (e.g lait), des suspensions (e.g café), ou encore des solutions de molécules actives (e.g médicament). La plupart de ces applications mettent en jeux des écoulements intermittents répétés de liquide qui peuvent contaminer le matériau. Cette étude a pour but de mieux comprendre comment ces écoulements de fluides complexes entraînent la contamination des tubes. Nous étudions expérimentalement et théoriquement les régimes d'un segment de liquide de faible viscosité s'écoulant dans un tube en conditions de mouillage partiel. Deux processus sont en compétition : à cause de la vitesse élevée du segment de liquide, un film de liquide se forme à l'arrière du segment, alors qu'à cause de des conditions de mouillage partiel le film de liquide démouille. Nous montrons qu'au-delà de la limite en vitesse correspondant à la transition de mouillage dynamique qui est bien inférieure à la prédiction de Cox-Voinov, un régime précédemment inconnu avec un film épais, dont l'épaisseur dépend de la vitesse, est obtenu bien avant la formation classique d'un film de Landau-Levich-Derjaguin. Nos simulations numériques sont en partie en accord avec nos observations
Polymer tubes, made of PDMS or PVC, are versatile, low cost, hydrophobic materials. They are heavily used in industry for transferring more or less complex fluids such as drinkable water, emulsions (e.g milk), suspensions (e.g coffee), or solution of active molecules (e.g pharmaceutics). Most of these applications involve repeated, intermittent flow of liquids which can lead to unwanted contamination. This study aims at better understanding the mechanisms of contamination for intermittent flow. We experimentally and theoretically investigate the flow regimes of low viscosity liquid slugs flowing down a vertical tube under partial wetting condition. Two processes are in competition: because of the large slug velocity, a liquid film tends to be created at the back of the slug whereas because of the partial wetting condition, the liquid film dewets. We investigate how this competition controls film deposition in hydrophobic tubes. We show that above the threshold velocity for dynamic wetting which is much lower than predicted by Cox-Voinov, a previously unknown regime is found where we observe a velocity dependent thick film well before the classical Landau-Levich-Derjaguin regime

APA, Harvard, Vancouver, ISO, and other styles

16

Wüstner, Cornell. "Selbstorganisierte Strukturen mit Saturn-Partikeln." Doctoral thesis, Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-157631.

Full text

Abstract:

Die vorliegende Arbeit beschreibt Herstellungsmöglichkeiten für sogenannte Saturn-Partikel. Es handelt sich dabei um Partikel, die auf ihrer Oberfläche drei Bereiche mit unterschiedlichen Eigenschaften aufweisen. Zwei Kappen mit gleichen Eigenschaften sind durch einen Gürtel getrennt, der sich stark von den Kappen unterscheidet. Im Speziellen geht es hier um die unterschiedliche Benetzbarkeit der Bereiche. Die Herstellung von Saturn-Partikeln mit einem hohen Benetzungskontrast wurde auf zwei verschiedenen Wegen realisiert. Als Ausgangspunkt dienten Mikroglaskugeln, die zunächst zur Hydrophobierung ihrer Oberfläche mit einem Silan behandelt wurden. Eine Art der Saturn-Partikel wurde durch das Ätzen eines Gürtels rund um die Partikel mit Flusssäure in einer im Rahmen dieser Arbeit entwickelten Spülzelle erzeugt. Auf diese Weise konnten Partikel mit zwei hydrophoben Kappen und einem hydrophilen Gürtel erhalten werden. Eine weitere Art dieser Partikel wurde durch das Abschleifen der Partikelkappen nach vorheriger Einbettung in Polymerfilme erhalten, wodurch die hydrophobe Beschichtung abgetragen und das ursprünglich hydrophile Glas freigelegt wurde. Die so erhaltenen Partikel wiesen zwei parallele, hydrophile Bereiche auf, die durch einen hydrophoben Gürtel voneinander getrennt waren. Es wird gezeigt, dass Saturn-Partikel in Systemen mit Wasser und Öl beim Mischen von unterschiedlichen Anteilen der drei Phasen durch Selbstorganisationsprozesse verschiedene Strukturen wie Ketten oder Schichten ausbilden können. Des Weiteren sind sie in der Lage in einem System mit Wasser und Luft besondere Schäume auszubilden, die eine sehr hohe Stabilität aufweisen. Die Partikel stabilisieren darin Flüssigkeitsfilme zwischen den Luftblasen, wobei der hydrophile Gürtel im Wasserfilm und die hydrophoben Kappen in der Luft liegen.

APA, Harvard, Vancouver, ISO, and other styles

17

Sharma, Shashi Kant. "Transition from elastohydrodynamic to partial elastohydrodynamic lubrication in a point contact with asperity /." The Ohio State University, 1997. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487948807585738.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

Ibrahim, Mustapha. "Investigation of contact time and impact force of particle-surface impacts." Thesis, Glasgow Caledonian University, 2017. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.726774.

Full text

APA, Harvard, Vancouver, ISO, and other styles

19

Malhotra, Karun. "Particle flow and contact heat transfer characeristics of stirred granular beds." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74233.

Full text

Abstract:

Particle flow features and wall-to-bed contact heat transfer characteristics of beds of granular solids stirred by flat blades (paddle-type) in horizontal cylindrical troughs are presented and discussed. Variables examined include: bed-to-blade height ratio (2-10), agitator speed (0-60 rev/min), wall-to-blade clearance (2.3-80 mm), vessel diameter (250 and 500 mm), solids flowability (0.07-0.25), air flow rate (0-0.5 m/s), particle moisture content (0-0.85 kg water/kg dry particles), particle surface stickiness (0-1.3 $ times$ 10$ sp{-3}$ kg glycerine/kg dry particles) and blade configuration (perforated and non-perforated). Glass beads, rice, millet and linseed were used as model particles.
Overall mixing maps showing regimes of good and poor solids mixing are presented. Granular solids flowability was found to influence particle flow characteristics substantially within the bulk as well as the wall-to-blade clearance region of the bed. Bulk solids flowability in stirred vessels was characterized by a novel procedure which incorporated the combined effects of particle shape, surface roughness, moisture/stickiness and deformability. The torque required to stir the particulate bed is influenced strongly by the solids flowability and blade configuration.
A physical model for the wall-to-bed contact heat transfer coefficient based on particle renewal rates at the heated surface is proposed. The particle renewal rates and particle-surface contact times are evaluated exclusively from the particle flow information in the clearance region with no empirical parameters. The effects of particle shape and bed porosity at the contacting surface on the surface-to-particle thermal contact resistance were evaluated. Experimental results showing the effects of agitator speed, wall-to-blade clearance, solids flowability and air flow rate on the wall-to-bed average heat transfer rate are presented and discussed. The contact heat transfer model was found to predict the experimentally measured results reasonably well.

APA, Harvard, Vancouver, ISO, and other styles

20

Karuppanan, Saravanan. "Analysis of incomplete and complete contacts in sliding and partial slip." Thesis, University of Oxford, 2008. http://ora.ox.ac.uk/objects/uuid:f56f9ed2-3f52-4bc0-8d49-43450b9353db.

Full text

Abstract:

Fretting fatigue is a type of contact fatigue which causes premature failure in a number of engineering assemblies subjected to vibration or other forms of cyclic loading. It is concerned with the nucleation of cracks due to oscillatory micro slip between contacting bodies. Therefore, a detailed knowledge of the interface conditions and the means of quantifying crack nucleation are very important, and will be the ultimate goal of this thesis. The analysis of an incomplete contact (Herzian contact) is considered first followed by various complete contacts. Fretting fatigue tests employing a Hertzian contact are analysed accurately by introducing several modifications needed to the classical formulation. With the total state of stress in a strip established, the crack tip stress intensity factor for a crack growing inward from the trailing edge of the contact is determined by the distributed dislocation technique. The results are then correlated with local solutions for the contact stress field which enable an estimate of the crack nucleation life, and hence a characteristic material property quantifying initiation, to be found. The interfacial contact pressure distribution beneath a complete sliding contact between elastically similar components, in the presence of friction, has been studied in detail, with particular reference to contacts whose edge angles are 60 degree, 90 degree and 120 degree. The possible types of behaviour at the edge of contacts, namely power order singularity, power order bounded and square root bounded, are discussed. A full understanding of the behaviour requires a detailed study of a characteristic equation, and this shows the kinds of pressure distribution to be anticipated, which can vary very markedly. The transition from power order behaviour to local separation and bounded behaviour is examined, and an appropriate asymptotic form developed. The problem of trapezium shaped punches pressed into a frictional, elastically similar half-plane, and subject to sequential normal and shear loading, under partial slip, is studied. Detailed considerations have again been given to the specific cases of 60 degree, 90 degree and 120 degree punches, and maps have been developed showing the initial mix of stick, slip and separation regions, together with the steady state response when the shearing force is cycled. Conditions for full stick are established.

APA, Harvard, Vancouver, ISO, and other styles

21

Van, Wyk Geritza. "Simulation of tribological interactions in bonded particle-solid contacts." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/71941.

Full text

Abstract:

Thesis (MScEng)--Stellenbosch University, 2012.
ENGLISH ABSTRACT: In this study, tool forces from rock cutting tests were numerically simulated through a discrete element method (DEM) in association with PFC3D™. Tribological interactions such as contact, shearing, fracturing, friction and wear were presented during these cutting simulations. Particle assemblies, representing Paarl granite and Sandstone-2, were created in PFC3D™ through a material-genesis procedure. The macro-properties of these particle assemblies, namely Young’s modulus, Poisson’s ratio, uniaxial and triaxial compressive strength and Brazilian tensile strength, were calibrated by modelling the uniaxial and triaxial compressive strength test and the Brazilian tensile strength test. The calibration was done through adjustment of the micro-properties of the assembly, namely the stiffness and strength parameters of the particles and bonds. The influence of particle size on the calibration was also investigated. These assemblies were used in the rock cutting tests. Results suggested that DEM can reproduce the damage formation during calibration tests successfully. From the results obtained from the calibration tests, it was also concluded that particle size is not a free parameter but influences the macro-properties greatly. Different rock cutting tools were simulated, namely point-attack (conical) picks, chisel-shaped tools and button-shaped tools. The numerical cutting tools were treated as rigid walls to simplify the simulation and the tool forces were not influenced by wear. In each simulation the cutting tools advanced at a constant velocity. The tool forces acting on the cutting tool, in three orthogonal directions, were recorded during the numerical simulations and the peak cutting forces were predicted by theoretical equations. The damage to the Paarl granite and Sandstone-2 assemblies was revealed as broken bonds, which merge into microscopic fractures. The mean peak cutting forces of sharp cutting tools obtained from numerical, theoretical and experimental models (from the literature) were compared. Finally the influence of factors, including wear on the tool and depth of cut, on the value of tool forces was also investigated. The results from the rock cutting tests revealed that the correlation between the numerical and the experimental models as well as the theoretical and experimental models was not strong when using sharp point-attack and chisel-shaped picks. It was concluded that the influence of wear plays a substantial part in the cutting process and it has to be included during the numerical simulation for the results to be accurate and verifiable. This study also found that there is a non-linear increase in tool forces with an increase in depth of cut, since the contact area increases. At larger cutting depths, chip formation also generally increased and therefore damage to the sample as well as wear on the cutting tool will be minimized at shallow cutting depths. Overall this study concludes that DEM are capable of simulating calibration methods and rock cutting processes with different cutting tools and producing results which are verifiable with experimental data. Therefore numerical prediction of tool forces will allow the design of efficient cutting systems and the operational parameters as well as the performance prediction of excavation machines.
AFRIKAANSE OPSOMMING: In hierdie studie is die kragte wat tydens rotssny-toetse op die sny gereedskap inwerk, numeries gesimuleer met behulp van ‘n diskrete element metode (DEM) in samewerking met PFC3D™. Tribologiese interaksies soos kontak, skeer, breking, wrywing en slytasie is gedurende hiersie snytoetse voorgestel. Partikel versamelings, wat Paarl graniet en Sandsteen-2 verteenwoordig, is in PFC3D™ geskep deur middel van ‘n materiaal-skeppings prosedure. Die makro-eienskappe van die partikel versamelings, naamlik Young se modulus, Poisson se verhouding, eenassige en drie-assige druksterkte en Brasiliaanse treksterkte, is gekalibreer deur modellering van die eenassige en drie-assige druksterkte toets en die Brasiliaanse treksterkte toets. Die kalibrasie is gedoen deur aanpassing van die mikro-eienskappe, naamlik die styfheid en die sterkte parameters van die partikels en bindings. Die invloed van partikelgrootte is ook ondersoek. Daarna is hierdie versamelings in die rotssny-toetse gebruik. Resultate het daarop gedui dat DEM die kraakvorming gedurende kalibrasie toetse suksesvol kan reproduseer. Vanuit die kalibrasie is ook gevind dat die partikelgrootte nie ‘n vrye parameter is nie, maar die makro-eienskappe grotendeels beïnvloed. Verskillende rotssny gereedskap is gesimuleer, naamlik koniese, beitel-vormige en knopie-vormige instrumente. Die numeriese sny gereedskap is gesimuleer as rigiede mure om simulasies te vereenvoudig en die gereedskap-kragte is dus nie deur slytasie beïnvloed nie. Tydens elke simulasie is die sny gereedskap vorentoe beweeg teen ‘n konstante snelheid. Die gereedskap-kragte, in drie ortogonale rigtings, is aangeteken gedurende die numeriese simulasies en die piek snykragte is ook voorspel deur teoretiese vergelykings. Die skade aan die Paarl graniet en Sandsteen-2 versamelings, is voorgestel as gebreekte bindings, wat saamsmelt tot mikroskopiese frakture. Die gemiddelde piek snykragte van skerp sny gereedskap van numeriese, teoretiese en eksperimentele modelle (uit die literatuur) is vergelyk. Ten slotte is die invloed wat faktore, onder andere die slytasie van gereedskap en die snydiepte, op die grootte van die kragte het ondersoek. Die resultate van die rotssny-toetse het aan die lig gebring dat die korrelasie tussen die numeriese en eksperimentale modelle sowel as die teoretiese en eksperimentele modelle nie sterk is tydens die gebruik van skerp koniese en beitel-vormige instrumente nie. Die gevolgtrekking is gemaak dat die invloed van slytasie van sny gereedskap ‘n wesenlike rol speel in die snyproses en dat dit in die numeriese simulasie ingesluit moet word sodat die resultate akkuraat en virifieerbaar is. Hierdie studie het ook gevind dat daar ‘n nie-lineêre toename in die gereedskap-kragte is met ‘n toename in snydiepte aangesien die kontak-area toeneem met ‘n toename in die snydiepte. By groter snydieptes, het die formasie van afsplinterings verhoog en dus sal skade aan die partikel versamelings en die slytasie van die gereedskap geminimeer word by vlakker snydieptes. Algeheel het die studie tot die gevolgtrekking gekom dat DEM in staat is om kalibrasie metodes en rotssny-toetse met verskillende sny gereedskap te simuleer asook om resultate te produseer wat verifieerbaar is met eksperimentele data. Numeriese voorspellings van die gereedskap-kragte sal dus toelaat om doeltreffende sny prosesse en operasionele parameters te ontwerp sowel as om die werkverrigting van uitgrawings masjiene te voorspel.

APA, Harvard, Vancouver, ISO, and other styles

22

Baric, Valentin [Verfasser]. "Modeling of Particle Contacts in Aggregated Nanoparticles / Valentin Baric." Düren : Shaker, 2020. http://d-nb.info/1208599348/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

23

Lambert, Baptiste. "Modelling and Simulations of Contacts in Particle-Laden Flows." Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0190/document.

Full text

Abstract:

Les écoulements chargés en particules sont présents dans de nombreuses applications industrielles telles que le transport de boues ou l’industrie chimique en général. Dans des mélanges constitués de particules solides immergées dans un fluide visqueux, les interactions entre particules jouent un rôle essentiel dans la viscosité globale du mélange.Le phénomène de suspension est causé par des interactions hydrodynamiques à courte distance, connues sous le nom de lubrification. Les forces de lubrification sont généralement sous-estimées en raison de leur nature et de la discrétisation spatiale du problème.Dans cette thèse, nous proposons un modèle de lubrification qui estime les forces et couples hydrodynamiques non résolues par un solveur couplant la résolution des équations de Navier-Stokes incompressible par une méthode de volumes pénalisés, à la résolution de la dynamique des particules par une méthode aux éléments discrets. Les corrections des contraintes hydrodynamiques sont faites localement sur la surface des particules en interaction sans aucune hypothèse sur la forme générale des particules. La version finale du modèle de lubrification proposée peut être utilisée pour des suspensions de particules convexes sans aucune tabulation. La méthode numérique a été validée avec des particules sphériques et des ellipsoïdes, en comparant des simulations à des données expérimentales.Dans le cas de particules sphériques, le modèle de lubrification est aussi précis que les modèles de lubrification existants qui sont limités à ce type de géométrie. La compatibilité du modèle avec des particules convexes a été validée en comparant des simulations,utilisant des ellipsoïdes, à des mesures expérimentales que nous avons réalisées
Particle-laden flows can be found in many industrial applications such as slurry transport or the chemical industry in general. In mixtures made of solid particles emerged in a viscous fluid, particle interactions play an essential role in the overall mixture viscosity. The suspension phenomenon is caused by short-range hydrodynamic interactions, known as lubrication. Lubrication forces are usually underestimated due to their singularities and the spatial discretization of the numerical schemes. In this thesis, we propose a lubrication model for a coupled volume penalization method and discrete element method solver that estimates the unresolved hydrodynamic forces and torques in incompressible Navier-Stokes flows. Corrections are made locally on the surfaces of the interacting particles without any assumption on the global particle shapes. The final version of the local lubrication model can be used for suspension of convex particles without any tabulations. The numerical method has been validated against experimental data with spherical and ellipsoidal particles. With spherical particles, the lubrication model performs as well as existing numerical models that are limited to this specific particle shape. The model compatibility with convex particles has been validated by comparing simulations using ellipsoids to experimental measurements we made

APA, Harvard, Vancouver, ISO, and other styles

24

Wei, Deheng. "Granular Mechanics Across Length Scales: Contact, Breakage, Fracture, and Permeability." Thesis, University of Sydney, 2021. https://hdl.handle.net/2123/24546.

Full text

Abstract:

Particle morphology is of pivotal importance in granular materials at different length scales. This thesis begins with quantification and reconstruction of real particle shapes, then studies various kinds of granular material behaviour influenced by morphology features. The project background and related previous work are introduced in Chapters 1 and 2, respectively. Chapter 3 is firstly concentrated on reconstructing particle shapes using Spherical Harmonics (SH). DEM clumps are also used to approximate realistic particle shapes to simulate sand column collapse. The efficiency of SH analysis between different coordinate systems in FEM mesh qualities and reconstruction are also compared. Chapter 4 is on contact behaviour of rough spheres with different morphology features. Via FEM simulation, benchmarked with Hertzian solution, a semi-analytical model is proposed. In Chapter 5, to highlight the influences of contact curvature on single particle crushing behaviour, a rotational point loading in FDEM, benchmarked with an in-situ XCT experiment, is proposed. In Chapter 6, experiments of failure modes of cemented sands under different loading paths and the quantification of fracture fabric are conducted. FDEM simulations, benchmarked with a combined in-situ experiment with XCT and diffraction, of meso-scale concrete are also conducted. Effects of realistic aggregate morphology on overall concrete are investigated. In Chapter 7, permeability of uniformly graded 3D printed grains, is experimentally studied. Modified Kozney-Carman equation is also proposed. Chapter 8 concludes this work by summarising the findings and implications and provides an outlook on future works. This dissertation presents a new comprehensive understanding of granular behaviour influenced by its morphology features. Via the proposed framework combining both experimental and numerical information, it is helpful to design and optimise of various granular materials with specific morphology features.

APA, Harvard, Vancouver, ISO, and other styles

25

Singh, Harmeet. "Discontinuities, Balance Laws, and Material Momentum." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/86664.

Full text

Abstract:

This dissertation presents an analytical study of a class of problems involving discontinuities, also referred to as shocks, propagating through one dimensional flexible objects such as strings and rods. The study entails interrogation of the classical balance laws of momentum, angular momentum, and energy across propagating discontinuities. A major part of this dissertation also concerns itself with a non-classical entity called the ``material momentum''. The balance of material momentum is studied in a variational context, where both the local and singular forms of it are derived from an action principle. A distinguishing aspect of discontinuities propagating in continua is that, unlike in the bulk, the balance of momentum and angular momentum are not sufficient to describe their mechanics, even when the discontinuities are energy conserving. In this work, it is shown that the additional information required to close the system of equations at propagating discontinuities can be obtained from the singular form of energy balance across them. This entails splitting of the energy balance by its invariance properties, and identifying the non-invariant and invariant part of the source term with the power input and energy dissipation respectively at the shock. This approach is in contrast with other treatments of such problems in the literature, where additional non-classical concepts such as ``material momentum'' and ``configurational force'' have been invoked. To further our understanding of the connections between the classical and non-classical approaches to problems involving discontinuities, a detailed exposition of the concept of material momentum is presented. The balance and conservation laws associated with material momentum are derived from an action principle. It is shown that the conservation of material momentum is associated with the material symmetry of the continuum, and that the conditions for the conservation of physical and material momentum are independent of each other. A new classification of the deformed configurations of the planar Euler elastica based on conserved quantities associated with the spatial and material symmetry of the rod is proposed. The manifestation of the balance of material momentum in seemingly unrelated fields of research, such as fracture mechanics, ideal fluids, and the mechanics of rods with discontinuities, is also discussed.
Ph. D.
One dimensional flexible bodies such as strings and rods can exhibit fascinating and counterintuitive behavior when they interact with rigid obstacles. For instance, a chain falling on a rigid surface falls faster than it would have if it were falling freely. When one end of a long chain piled up in a container placed at an elevation is pulled across the rim and let go, the chain flows out of the container like a water fountain. Discontinuities in the cross-sectional properties of an elastic rod contained in a curved frictionless channel can result in the generation of forces that propel the rod along the channel. Such counterintuitive phenomena are a consequence of the physics taking place at the point of partial contact where the flexible body comes in contact with a rigid surface. The purpose of this dissertation is to study the mechanics of such points of discontinuity. Several such phenomena where effectively one dimensional bodies interact with rigid surfaces are all around us. A familiar example is the peeling of an adhesive tape, where the peeling front qualifies as a point of discontinuity propagating through the tape as the peeling progresses. A good understanding of the mechanics of the peeling front is crucial in estimating the strength of the adhesive. Another such example of practical importance is a mooring line being placed on the seabed. In such situations, the existence of a reaction force acting at the touchdown point depends on whether or not the cable develops a kink at that point. Similar questions of importance can be asked in the context of deployment and unspooling of space tethers. In this dissertation, an analytical study of the general physics of the phenomena described above is presented. Standard theoretical tools of classical physics are employed to understand the mechanics of points of partial contact between flexible and rigid bodies. The conditions under which a flexible body could experience sharp changes in its geometry (e.g. a kink) at such points are investigated. In addition to that, we explore the implications of a nonclassical law of physics called the balance of “material momentum” in the context of such problems.

APA, Harvard, Vancouver, ISO, and other styles

26

Zimmerman, Jeremiah D. "High Resolution Measurements near a Moving Contact Line using µPIV." PDXScholar, 2011. https://pdxscholar.library.pdx.edu/open_access_etds/118.

Full text

Abstract:

A moving contact line is the idealized line of intersection between two immiscible fluids as one displaces the other along a solid boundary. The displacement process has been the subject of a large amount of theoretical and experimental research; however, the fundamental processes that govern contact line motion are still unknown. The challenge from an experimental perspective is to make measurements with high enough resolution to validate competing theories. An experimental method has been developed to simultaneously measure interface motion, dynamic contact angles, and local fluid velocity fields using micron-resolution Particle Image Velocimetry (µPIV). Capillary numbers range from 1.7 x 10^(⁻⁴) to 6.2 x 10^(⁻⁴). Interface velocities were measured between 1.7 µm/s and 33 µm/s. Dynamic contact angles were manually measured between 1.1 µm and 120 µm from the contact line, and calculated from µPIV data to within several hundred nanometers from the contact line. Fluid velocities were measured over two orders of magnitude closer to the contact line than published values with an increase in resolution of over 3400%. The appearance of a recirculation zone similar to controversial prediction below previously published limits demonstrates the power and significance of the method.

APA, Harvard, Vancouver, ISO, and other styles

27

Byrne-Sutton, Pascale. "Le contrat de travail à temps partiel /." Zürich : Schulthess Juristische Medien, 2001. http://www.gbv.de/dms/spk/sbb/recht/toc/338249656.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

28

Deme, Mamadou. "Qualité des parties et contrat d'Etat." Rouen, 1993. http://www.theses.fr/1993ROUEL167.

Full text

Abstract:

Relativement au statut juridique des investissements privés internationaux, on peut faire les observations suivantes : - les contrats d'Etat, et les contrats internationaux conclus entre un Etat et un ressortissant étranger (personne physique ou personne morale) soulèvent des difficultés particulières à propos du droit applicable. Plusieurs ordres juridiques ont vocation à régir le rapport contractuel : l'ordre juridique international, l'ordre "juridique" transnational et l'ordre juridique interne. Dans l'hypothèse où un ordre juridique étatique est reconnu compètent, il faudra dans ce cas également envisager les difficultés liées au fait que l'Etat peut conclure une variété de contrats soit de droit privé, soit de droit public. Donc certains rapports contractuels de la puissance publique peuvent être exclusivement régis par le droit public en particulier le droit administratif. La réalisation de cette hypothèse, semble à partir de différentes précisions se vérifier à propos du contrat d'Etat - et cela dans tout ordre juridique étatique
A State contract or an international investment can be governed by different legal orders. A State legal system is mainly indicated by the parties. In this case, the problem is to demonstrate how the municipal law could govern a contract between a foreign owner (company or individual) and the state. International law rules state that the case can be resolved without sacrificing the rights of the private owner and the State

APA, Harvard, Vancouver, ISO, and other styles

29

Schmidt, Sonja. "Root responses to soil physical conditions and the role of root-particle contact." Thesis, Abertay University, 2011. https://rke.abertay.ac.uk/en/studentTheses/ab0e3468-93c7-40ab-8809-48c41cf5caa2.

Full text

Abstract:

This thesis considers the elongation of root and shoots in relation to matric potential and soil strength in contrasting species. The role of root-particle contact for root and shoot elongation in relation to particle/aggregate size and bulk density at various matric potentials is discussed. Root and shoot elongation of maize and lupin in soil and vermiculite at matric potentials ranging from -0.03 MPa to -1.6 MPa were investigated. Both root and shoot elongation rate of maize and lupin were significantly slower in vermiculite than in soil (p < 0.001). As vermiculite has very different particle size distribution and hydraulic properties from soil, the degree of contact between root and vermiculite was thought to provide a possible explanation for the slower elongation rates. A new method was developed to quantify root-particle contact using X-ray microtomography and verified using ‘phantoms’ (model systems of known dimensions). Root-particle contact was approximately 25 % greater in soil than in vermiculite. The greater root-particle contact in soil was thought to provide better growth conditions than in vermiculite. Root and shoot elongation were examined when plants were place in humid air above an osmotic solution (KC1) to evaluate the degree to which root elongation could occur in the absence of solution contact. No significant shoot elongation occurred and root elongation was more reduced than in vermiculite. Hairless maize and barley mutants and their wildtypes were used to investigate further the effects of root-particle contact when water availability is limiting in both soil and vermiculite systems. Root elongation rates of the hairless mutants were slower than those of the wildtypes, when the growth medium was wetter than -1.6 MPa. However the reduction in root elongation of hairless maize may have been due to pleiotropic effects slowing the elongation (the elongation rate relative to the maximum elongation rate was not significantly different). The combined effects of mechanical impedance and decreasing matric potentials on root and shoot elongation were tested. Maize and lupin were grown in soil packed to five bulk densities (bulk densities 1.1, 1.2, 1.3, 1.4 and 1.5 g cm'3) and wetted to three matric potentials ranging from -0.01 MPa to -1.2 MPa (Chapter 6). Root elongation rate decreased with increasing penetrometer resistance and maize was considerably more sensitive than lupin towards increase in these soil physical stresses. The effects of soil mechanical impedance dominated any improvement in root-soil contact. The averaged length of the root elongation zone (estimated from the distance between root hair zone and root tip) was linearly related to elongation rates. This is a possible method for estimating root elongation rates in situ. To manipulate root-soil contact in loosely packed aggregates, seedlings were grown at various matric potentials in soils of different aggregate sizes (4—2 mm, 2-1 mm, 1- 0.5 mm and <0.5 mm). The finer the aggregates were the faster the roots elongated, they also had better root-soil contact (72-79 % at <0.5 mm and 23-25 % at 4 -2 mm). A method was developed to investigate the role of liquid and solid contact with roots. Roots were exposed in different portions to the mist produced in an aeroponic system. In another experiment roots were placed above a water surface and supplied at different parts with water through cotton wool. Different portions of the total surface of the root were in contact with liquid or solid phase. Root and shoot elongation were not significantly affected by the portion of root surface in contact with water or solid phase. A good root-particle contact can can improve plant growth when water availability is limiting growth but the effects of greater contact area are dependant on matric potential, plant species, and soil strength.

APA, Harvard, Vancouver, ISO, and other styles

30

Wales, Michael Dean. "Membrane contact reactors for three-phase catalytic reactions." Diss., Kansas State University, 2015. http://hdl.handle.net/2097/20589.

Full text

Abstract:

Doctor of Philosophy
Chemical Engineering
Mary E. Rezac
Membrane contact reactors (MCRs) have been evaluated for the selective hydro-treating of model reactions; the partial hydrogenation of soybean oil (PHSO), and the conversion of lactic acid into commodity chemicals. Membranes were rendered catalytically active by depositing metal catalyst onto the polymer "skin" of an asymmetric membrane. Hydrogen was supplied to the support side of the membrane and permeated from the support side to the skin side, where it adsorbed directly onto the metal surface. Liquid reactant was circulated over the membrane, allowing the liquid to come into direct contact with the metal coated surface of the membrane, where the reaction occurred. Our membrane contact reactor approach replaces traditional three-phase batch slurry reactors. These traditional reactors possess inherent mass transfer limitations due to low hydrogen solubility in liquid and slow diffusion to the catalyst surface. This causes hydrogen starvation at the catalyst surface, resulting in undesirable side reactions and/or extreme operating pressures of 100 atmospheres or more. By using membrane reactors, we were able to rapidly supply hydrogen to the catalyst surface. When the PHSO is performed in a traditional slurry reactor, the aforementioned hydrogen starvation leads to a high amounts of trans-fats. Using a MCR, we were able to reduce trans-fats by over 50% for equal levels of hydrogenation. It was further demonstrated that an increase in temperature had minimal effects on trans-fat formation, while significantly increasing hydrogenation rates; allowing the system to capture higher reaction rates without adversely affecting product quality. Additionally, high temperatures favors the hydrogenation of polyenes over monoenes, leading to low amounts of saturated fats. MCRs were shown to operator at high temperatures and: (1) capture high reaction rates, (2) minimize saturated fats, and (3) minimize trans-fats. We also demonstrated lactic acid conversion into commodity chemicals using MCRs. Our results show that all MCR experiments had faster reaction rate than all of our controls, indicating that MCRs have high levels of hydrogen coverage at the catalyst. It was also demonstrated that changing reaction conditions (pressure and temperature) changed the product selectivities; giving the potential for MCRs to manipulate product selectivity.

APA, Harvard, Vancouver, ISO, and other styles

31

Rigalle-Dumetz, Corinne. "La résolution partielle du contrat /." Paris : Dalloz, 2003. http://catalogue.bnf.fr/ark:/12148/cb38986858n.

Full text

APA, Harvard, Vancouver, ISO, and other styles

32

Bao, Yanyao. "Smoothed Particle Hydrodynamics Simulations for Dynamic Capillary Interactions." Thesis, The University of Sydney, 2018. http://hdl.handle.net/2123/19592.

Full text

Abstract:

Complex interactions in porous media play an important role on many industrial and geotechnical applications, such as groundwater treatment, porous catalysts, carbon geosequestration, and oil recovery. Rate-dependent wetting effects are of great significance in understanding the multiphase behaviours of porous media thus further throw light on engineering solutions to the above problems. In this thesis, a modified smoothed particle hydrodynamics (SPH) model is applied to simulate (1) the contact angle dynamics and (2) stretching of liquid bridge at meso-scale. This SPH model adopted an inter-particle force formulation with short-range repulsive force and long-range attractive force to take into account single-phase and multiphase interactions. Particularly, a newly-introduced viscous force is imposed at the liquid-solid interface to capture the rate-dependent behaviours of contact angle without prescribing additional arbitrary condition or force. After identification of model parameters, the rate-dependent contact angle behaviours are studied for both wetting and dewetting phenomena. By analysing the contact angle results of fluid at triple-line region with different moving speeds, the dynamic contact angles and corresponding capillary numbers can be correlated by power law functions. The derived correlation and constants are compared with different forms of empirical power law functions and the results are satisfactory. Moreover, we investigated the properties of stretching liquid bridges, including shape evolution, liquid transfer ratio and flow condition under dynamic loading. Different stretching rates are applied, and the shapes of liquid bridge at same breakup distance is presented. By differentiating the wettability of top and bottom substrates, the liquid transfer ratio regarding wettability difference and substrate moving speed is studied.

APA, Harvard, Vancouver, ISO, and other styles

33

Brennan, James R. "Contracting with reading costs and renegotiation costs." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3255549.

Full text

Abstract:

Thesis (Ph. D.)--University of California, San Diego, 2007.
Title from first page of PDF file (viewed May 10, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 114-118).

APA, Harvard, Vancouver, ISO, and other styles

34

Duchesne, Louise. "Fusion partielle et microstructures associées dans l'auréole de contact du complexe igné de Duluth, Minnesota /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2004. http://theses.uqac.ca.

Full text

APA, Harvard, Vancouver, ISO, and other styles

35

Stover, Joseph Patrick. "A Stochastic Spatial Model for Invasive Plants and A General Theory of Monotonicity for Interaction Map Particle Systems." Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/194861.

Full text

Abstract:

Awareness of biological invasions is becoming widespread and several mathematical tools have been used to study this problem. Interacting particle systems, specifically the contact process, have been used to study systems with invasion/infection type dynamics. The Propp-Wilson algorithm is a method for exact sampling from the stationary distribution of an ergodic monotone Markov chain using a method called coupling from the past. The contact process is monotone so we can sample exactly from the stationary distribution of a modified finite grid version using the Propp-Wilson algorithm. In order to study an invasion, we would like to include at least 2 species; however, monotonicity is not well defined for contact processes with more than 2 particle types. Here we develop a general theory of monotonicity for interaction map particle systems, which are interacting particle systems with contact process type dynamics. This allows us to create monotone models with any number of particles and to use the Propp-Wilson algorithm for not only sampling from the stationary distribution, but analyzing the path of invasion leading to equilibrium. Virtual particle invasion models that fall into this new theoretical framework, which we develop here, present a wide range of biological dynamics. Computer simulation of the stochastic system and mean field analysis are two powerful tools that we use for analyzing these types of models. Statistics gathered along the path to invasion help us understand the spatial dynamics of this ecological process and what the stationary behavior looks like. This allows us to understand when the invasion is successful or if coexistence occurs and how these depend on the transition rates and interactions within the process.

APA, Harvard, Vancouver, ISO, and other styles

36

Schimann, Hubert C. R. "Force and Energy Measurement of Bubble-Particle Detachment." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/9963.

Full text

Abstract:

Possibilities for increasing the upper limit of floatable particle sizs in the froth flotation process have been examined since the early beginnings of mineral flotation. The economic implications of such an incresae are far ranging; from decreased grinding costs and increased recoveries to simplified flow-sheet design and increased throughput, all leading to increased revenue. Bubble-particle detachment has been studied to better understand the factors influencing the strength of attachment and the energies involved. Direct measurements of bubble particle detachment were performed using a hanging balance apparatus (KSV Sigma 70 tensiometer) and using a submerged hydrophobic plate in water. Three experiments were used; direct force measurement of bubble-particle detachment, detachment force and energy of a bubble from a submerged hydrophobic plate, and detachment force and energy of a cetyltrimethylammonium bromide coated silica sphere from a flat bubble. Octadecyltrichlorosilane was used as a hydrophobic coating in the first two experimental methods. These experiments were recorded with a CCD camera to identify the detachment processes involved. Energies for both methods were calculated and divided into the two main steps of the detachment process: Three-Phase-Contact pinning and three phase contact line sliding. The first step represents the energy barrier which must be overcome before detachment can begin. It is directly related to contact angle hysteresis. Detachment occurs during the second step, where the solid-vapor interface is replaced by solid-liquid and liquid-vapor. This step corresponds to the work of adhesion. The effects of surface tension, contact angle and hysteresis were well demonstrated with the three experimental methods. Good correlation was found between theoretical work of adhesion and measured energies.
Master of Science

APA, Harvard, Vancouver, ISO, and other styles

37

Can, Van Hao. "Processus de contact sur des graphes aléatoires." Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4709/document.

Full text

Abstract:

Le processus de contact est l'un des systèmes de particules en interaction les plus étudiés. Il peut s'interpréter comme un modèlepour la propagation d'un virus dans une population ou sur un réseau. L'objectif de cette thèse est d'étudier la relation entre la structure locale du réseau et le comportement global du processus sur le réseau tout entier.Le cadre typique dans lequel on se place est celui d’une suite de graphes aléatoires $(G_n)$ convergeant localement vers un graphe limite $G$.On étudie alors le comportement asymptotique du temps d’extinction $tau_n$ du processussur $G_n$; lorsqu’initialement tous les individus sont infectés. Nous montrons sur plusieurs exemples qu’il existe unetransition de phase lorsque $lambda$ - le taux d'infection du processus - traverse une valeur critique $ lambda_c (G)$, qui ne dépend que de $G$.Plus précisément, pour certains modèles de graphes aléatoires comme le modèle de configuration, le graphe d'attachement préférentiel, le graphe géométrique aléatoire, le graphe inhomogène, nous montrons que $ tau_n $ est d'ordre soit logarithmique soit exponentiel; selon que $ lambda$ est soit inférieur ou supérieur à $lambda_c (G) $.De plus, dans certains cas, nous montrons des résultats de métastablité: en régime sur-critique, $ tau_n $ divisé par son espérance converge en loi vers une variable aléatoire exponentielle de moyenne $1$, et la densité des sites infectés reste stable (et non nulle) sur une période de temps d’ordre typiquement $tau_n$
The contact process is one of the most studied interacting particle systems and is also often interpreted as a model for the spread of a virus in a population or a network. The aim of this thesis is to study the relationship of the local structure of the network and the global behavior of the contact process (the virus) on the whole network. Let $(G_n)$ be a sequence of random graphs converging weakly to a graph $G$. Then we study $tau_n$, the extinction time of the contact process on $G_n$ starting from full occupancy. We prove in some examples that there is a phase transition of $tau_n$ when $lambda$ - the infection rate of the contact process crosses a critical value $lambda_c(G)$ depending only on $G$. More precisely, for some models of random graphs, such as the configuration model, preferential attachment graph, random geometric graph, inhomogeneous graph, we show that $tau_n$ is of logarithmic (resp. exponential) order when $lambda < lambda_c(G)$ (resp. $lambda < lambda_c(G)$). Moreover, in some cases we also prove metastable results: in the super-critical regime, $tau_n$ divided by its expectation converges in law to an exponential random variable with mean $1$, and the density of the infected sites is stable for a long time

APA, Harvard, Vancouver, ISO, and other styles

38

Alemani, Mattia. "Particle emissions from car brakes : The influence of contact conditions on the pad-to-rotor interface." Doctoral thesis, KTH, Tribologi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-208701.

Full text

Abstract:

Due to their adverse health effects emissions have been regulated for over three decades. Brake wear particulate matter is the most important non-exhaust source, however current knowledge is mainly limited to observational studies. This thesis aims to investigate relations between the brake system contact conditions and the related emissions on a model scale; validate the results on a component level; and understand to what extent they are significant on a full-scale. Paper A investigates the influence of nominal contact pressure on a model scale. Results show that higher pressure corresponds to higher emissions Paper B investigates the influence of the nominal contact pressure, for different friction materials, on a model scale. A temperature threshold, responsible for a relevant emission increase, is identified. Paper C investigates particle characteristics and wear mechanisms for different nominal contact pressures, on a model scale. Results show an enhanced tribo-layer at higher pressure levels. Paper D investigates the influence of brake system conditions on emissions, on a model scale. Results show that frictional power is the most important parameter. A transition temperature independent of the contact condition is identified. Paper E investigates similarities occurring on a component scale and a model scale in terms of emissions. Results show a promising correlation, and the possibility of using a pin-on-disc tribometer for R&D activities. Paper F investigates analogies occurring on a component scale and a model scale, in terms of friction performance, fictional surface and chemical composition. Results show similar phenomena occurring for the two test stands. Paper G analyses real brake system working conditions in a urban environment defining, by means of an inertia dyno bench, the related emissions. Results reveal emission factors compliant to EURO6 and EURO2 regulations, in terms of number and mass, respectively.
På grund av deras negativa hälsoeffekter har partikel emissioner reglerats i över tre årtionden. Bromsslitagepartiklar är den viktigaste icke-avgaskällan, men nuvarande kunskaper är huvudsakligen begränsade till observationsstudier. Avhandlingen syftar till att undersöka förhållandena mellan bromssystemets kontaktförhållanden och de relaterade utsläppen på modellskala. Validera resultaten på komponentnivå och förstå i vilken utsträckning de är betydande i full skala. Papper A undersöker påverkan av nominellt kontakttryck i en modellskala. Resultat visar att högre tryck motsvarar högre utsläpp. Papper B undersöker påverkan av det nominella kontakttrycket, för olika friktionsmaterial, i modellskala. En temperaturtröskel, för en emissionsökning identifieras. Papper C undersöker partikelegenskaper och slitagemekanismer för olika nominella kontakttryck, i en modellskala. Resultat visar ett förbättrat triboskikt vid högre trycknivåer. Papper D undersöker påverkan av bromssystemets förhållanden på utsläpp i en modellskala. Resultat visar att friktionskraften är den viktigaste parametern. En övergångstemperatur oberoende av kontaktförhållandet identifieras. Papper E undersöker likheter som uppträder på komponentskala och modellskala när det gäller emissioner. Resultatet visar en lovande korrelation, och möjligheten att använda en pinne-på-skiva-tribometer för FoU-aktiviteter. Papper F undersöker analogier som förekommer på en komponentskala och en modellskala, vad gäller friktionsprestanda, friktionsyta och kemisk sammansättning. Resultat visar liknande fenomen som förekommer för de två testskalorna. Papper G analyserar verkliga bromssystem arbetsförhållanden i en stadsmiljö som definierar, med hjälp av en tröghetsdyno bänk, de relaterade utsläppen. Resultatet visar utsläppsfaktorer som är förenliga med EURO6 och EURO2-reglerna, i fråga om antal respektive massa.

QC 20170808

REBRAKE Project

APA, Harvard, Vancouver, ISO, and other styles

39

Feldman, Jonathan. "Dynamic refinement and boundary contact forces in smoothed particle hydrodynamics with applications in fluid flow problems." Thesis, Swansea University, 2006. https://cronfa.swan.ac.uk/Record/cronfa42459.

Full text

Abstract:

Smoothed Particle Hydrodynamics (SPH) is a relatively new, simple and effective numerical method that can be used to solve a variety of difficult problems in computational mechanics. It is a fully Lagrangian meshless method ideal for solving large deformation problems such as complex free surface fluid flows. This research was carried out with the support of BAE Systems and falls into two distinct areas. Firstly to investigate new methods for treating fixed boundaries and secondly to investigate refinement algorithms which allow for both sparsely and densely populated regions of particles within the same computational domain. Much work has been done in the modelling of particle-boundary interactions in SPH since the governing equations do not naturally incorporate essential boundary conditions. In this research a new technique for calculating boundary contact forces is developed. The forces are obtained from a variational principle and as such conserve both the linear and angular momentum of the system. The boundaries are explicitly defined using this new approach and so the need for additional boundary particles is removed. In the past most SPH derivations have been based on a uniform distribution of particles of equal mass. This leads to large simulations with many particles and long run times. In other mesh based schemes it has become common place to use mesh adaptivity to improve numerical results and reduce computation times. With a corresponding refinement strategy SPH can gain these same advantages. In this research a refinement strategy based upon particle splitting is developed. Candidate particles are split into several 'daughter' particles according to a given refinement pattern centred about the original particle position. Through the solution of a non-linear minimisation problem the optimal mass distribution for the daughter particles is obtained so as to reduce the errors introduced into the underlying density field. This procedure necessarily conserves the mass of the system. The unique daughter particle velocity configuration that conserves the linear and angular momentum of the system is also identified. The conclusion of the research was the successful implementation of these improvements into the existing SPH framework. As a result the capability and flexibility of the code is greatly increased and the computational expense needed for running large simulations has been reduced.

APA, Harvard, Vancouver, ISO, and other styles

40

Büchi, Felix Niklaus. "Elektrochemische Untersuchungen an partiell blockierten Elektroden und Polypyrrolfilmen /." [S.l : s.n.], 1989. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

Baldez, Carlos Alessandro da Costa. "Problemas de contacto transversal, estacionário e dinâmico." Laboratório Nacional de Computação Científica, 2012. https://tede.lncc.br/handle/tede/234.

Full text

Abstract:

Submitted by Maria Cristina (library@lncc.br) on 2016-11-09T13:12:11Z No. of bitstreams: 1 TeseBaldez.pdf: 2205858 bytes, checksum: a23b2f1dea8d7cc85600e36fce5fb295 (MD5)
Approved for entry into archive by Maria Cristina (library@lncc.br) on 2016-11-09T13:12:29Z (GMT) No. of bitstreams: 1 TeseBaldez.pdf: 2205858 bytes, checksum: a23b2f1dea8d7cc85600e36fce5fb295 (MD5)
Made available in DSpace on 2016-11-09T13:12:40Z (GMT). No. of bitstreams: 1 TeseBaldez.pdf: 2205858 bytes, checksum: a23b2f1dea8d7cc85600e36fce5fb295 (MD5) Previous issue date: 2012-08-27
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Capes)
In this thesis we study the transverse contact problem to Timoshenko beam' to elastic and thermoelastic model, whose the vertical displacement is restricted, with Signorini's contact condition. We make the mathematical modelling and well-posed model. We consider the discrete model and we make the computational modelling to the problem. The main result this work is to model the transverse contact problem and to show the qualitative properties of solution, for example, the exponential decay for energy of the system. We obtain numeric convergence rates to numeric solutions, and that enabled us to obtain numerical and computationally properties.
Nesta tese estudamos o problema de contacto transversal de uma viga, de Timoshenko, com propriedades elástica e termoelástica, restrita ao seu movimento transversal, com condição de contacto do tipo Signorini. Fazemos a modelagem matemática do problema mostrando a boa colocação do modelo. Discretizamos o modelo e fazemos a modelagem computacional do problema. O ponto alto de nosso trabalho consiste em modelar o problema de contacto transversal e mostrar as propriedades qualitativas da solução como, por exemplo, o decaimento exponencial da energia. Obtemos taxa de convergência da solução numérica, com esse resultado, tornou-se possível obter as propriedades numéricas e computacionais.

APA, Harvard, Vancouver, ISO, and other styles

42

Freij, Martin, and Andreas Gartnell. "Political Parties in Social Media : A case study of political parties’ crisis management in social media." Thesis, Linnéuniversitetet, Institutionen för marknadsföring (MF), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-35242.

Full text

Abstract:

Title: Political Parties’ in Social Media - A case study of political parties’ crisis management in social media Introduction: The emergence of social media platforms has transformed how organizations communicate with stakeholders. The concept of social media is top of agenda for many business executives today. While some argue social media to provide unique opportunities for organizations, others argue the opposite. The rise of social media enables crises to escalate, implying that organizations need to have well-established crisis management strategies. In the Swedish election of 2014, social media is predicted to have enormous influence on the end result for the political parties. Prior to this thesis, no previous research has looked deeper into the context of crisis management in social media for political parties in Sweden. It is in the political context where this study contributes to the research area. Purpose: The aim of this paper is to investigate political parties’ crisis management in social media, using strategies developed for commercial organizations, and thereby contribute to the research of non-commercial organizations. Methodology: A triangulation method was used of semi structured interviews and archival analysis on four crises of political parties. Eight parties in the Swedish parliament where deliberately selected. However, only four of the parties, Socialdemokraterna (S), Sverigedemokraterna (SD), Vänsterpartiet (V) and Centerpartiet (C), had the possibility to participate in the study. Conclusion: (S), (V) and (C) all used both Facebook and Twitter as a crisis communication channel especially due to its speed and spread. However, (SD) did not use social media as crisis communication channel. The crisis management in social media of each party could improve immensely, however limited resources of employees and finance was found to be the main reasons holding the progress back. Conclusively, dialogue strategies and to some extent response strategies used by commercial organizations are indeed frequently used by political parties as well.

APA, Harvard, Vancouver, ISO, and other styles

43

Kozłowska, Izabela. "Behavior of chicken primordial germ cells injected into the bloodstream of recipient embryo." PhD diss., University of Science and Technology, 2015. http://dlibra.utp.edu.pl/Content/834.

Full text

Abstract:

Aim of study was to investigate behavior of donor and recipient PGCs by 1. isolation method of gonadal PGCs from 28-29 (H&H) stage donor embryos to obtain possible highest number of non-aggregating cells; 2. examination of migratory capabilities of PGCs derived from Ross 308 and green-legged partridgelike in the role of donor or recipient of cells; 3. elaboration a new method of partial sterilization of recipients using cytostatic- terosulfan (TERO)

APA, Harvard, Vancouver, ISO, and other styles

44

Jandard, Léonor. "La relation entre l’arbitre et les parties : critique du contrat d'arbitre." Thesis, Paris 10, 2018. http://www.theses.fr/2018PA100085.

Full text

Abstract:

Forgé pour traduire juridiquement la relation nouée tout au long de l’instance arbitrale entre l’arbitre d’un côté, et les parties à la convention d’arbitrage de l’autre, le contrat d’arbitre est depuis longtemps reconnu par la doctrine et la jurisprudence. Sans doute l’origine privée de la mission de l’arbitre alliée à son caractère le plus souvent onéreux, a-t-elle inévitablement contribué à reconnaître l’existence de ce contrat comme une évidence. Cependant, une recherche et une mise à l’épreuve, à la lumière du droit positif, des mérites de l’approche contractuelle de la relation entre l’arbitre et les parties s’avèrent nécessaires. L’étude révèle en effet que le contrat d’arbitre, imposé comme un remède aux problèmes rencontrés par le droit de l’arbitrage à un moment de son histoire, engendre actuellement davantage de difficultés qu’il n’en résout. Cela tient au fait que nombre des obligations de l’arbitre traditionnellement rattachées à ce contrat relèvent déjà de son statut établi par le décret du 13 janvier 2011 portant réforme de l’arbitrage. Il en résulte de nombreuses incertitudes et incohérences mises en lumière à travers l’analyse du contentieux opposant les arbitres aux parties devant les juridictions étatiques de droit commun. À travers une analyse critique du contrat d’arbitre, l’étude se propose d’établir les fondements d’une approche renouvelée de la relation entre l’arbitre et les parties
The arbitrator's contract is designed to materialize from a legal point of view the relationship built up between the arbitrator and the parties to the arbitration agreement during the arbitral proceedings. In this respect, it has been recognized for a long time by both the doctrine and the case law. It is very likely that the private source of the arbitrator's mission, along with its usually onerous nature, have participated in deeming the existence of such contract a self-evident fact.However, the contractual approach of the relationship forged between the arbitrator and the parties is worth putting to the test in the light of positive law. The study carried out in the present thesis unveiled that the arbitrator's contract, although it has been imposed as a remedy to several difficulties arbitration had once to face, actually leads to more difficulties that it solves. This is due to the fact that various obligations that the arbitrator is considered to have to comply with according to the arbitrator's contract actually preexist as a result of the arbitrator's legal status, in accordance with the Decree of January 13th 2011 on the reform of arbitration law. This results in various uncertainties and inconsistencies brought to light through an extensive analysis of disputes between the arbitrators and the parties that have been brought to State courts. Through critical analysis, this thesis offers to lay the foundation of a renewed approach of the relationship between the arbitrator and the parties

APA, Harvard, Vancouver, ISO, and other styles

45

Gligorijevic, Jelena. "Context-aware Learning from Partial Observations." Diss., Temple University Libraries, 2018. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/484799.

Full text

Abstract:

Computer and Information Science
Ph.D.
The Big Data revolution brought an increasing availability of data sets of unprecedented scales, enabling researchers in machine learning and data mining communities to escalate in learning from such data and providing data-driven insights, decisions, and predictions. However, on their journey, they are faced with numerous challenges, including dealing with missing observations while learning from such data or making predictions on previously unobserved or rare (“tail”) examples, which are present in a large span of domains including climate, medical, social networks, consumer, or computational advertising domains. In this thesis, we address this important problem and propose tools for handling partially observed or completely unobserved data by exploiting information from its context. Here, we assume that the context is available in the form of a network or sequence structure, or as additional information to point-informative data examples. First, we propose two structured regression methods for dealing with missing values in partially observed temporal attributed graphs, based on the Gaussian Conditional Random Fields (GCRF) model, which draw power from the network/graph structure (context) of the unobserved instances. Marginalized Gaussian Conditional Random Fields (m-GCRF) model is designed for dealing with missing response variable value (labels) in graph nodes, whereas Deep Feature Learning GCRF is able to deal with missing values in explanatory variables while learning feature representation jointly with learning complex interactions of nodes in a graph and together with the overall GCRF objective. Next, we consider unsupervised and supervised shallow and deep neural models for monetizing web search. We focus on two sponsored search tasks here: (i) query-to-ad matching, where we propose novel shallow neural embedding model worLd2vec with improved local query context (location) utilization and (ii) click-through-rate prediction for ads and queries, where Deeply Supervised Semantic Match model is introduced for dealing with unobserved and tail queries click-through-rate prediction problem, while jointly learning the semantic embeddings of a query and an ad, as well as their corresponding click-through-rate. Finally, we propose a deep learning approach for ranking investigators based on their expected enrollment performance on new clinical trials, that learns from both, investigator and trial-related heterogeneous (structured and free-text) data sources, and is applicable to matching investigators to new trials from partial observations, and for recruitment of experienced investigators, as well as new investigators with no previous experience in enrolling patients in clinical trials. Experimental evaluation of the proposed methods on a number of synthetic and diverse real-world data sets shows surpassing performance over their alternatives.
Temple University--Theses

APA, Harvard, Vancouver, ISO, and other styles

46

Bioules, Julien. "Le financement de l'arbitrage international par les tiers." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0399.

Full text

Abstract:

Le financement de l’arbitrage international par les tiers constitue aujourd’hui une solution d’accès à cette justice privée, largement plébiscitée et privilégiée par les opérateurs économiques. Ce mécanisme offre à des acteurs variés la possibilité de transférer les coûts et les risques induits par la procédure dont ils sont partis vers un tiers. En contrepartie, ce tiers perçoit un pourcentage des sommes allouées à son client par la sentence. Cette relation, guidée par une communauté d’intérêts tournée vers le succès de l’arbitrage, se concrétise par le contrat de financement. Ce dernier, d’apparence sui generis, se caractérise par un objet spécifique, le financement d’un arbitrage international et par ses effets singuliers. Il est relatif à un procès mais se trouve, de par son objet, dépourvu d’effet relatif. Ainsi, le contrat emporte des conséquences, à la fois, sur les acteurs du procès arbitral, pour lequel le financeur n’est pas partie, et sur la procédure elle-même, son déroulement et son issue. Cette étude permet d'entrevoir une frontière poreuse séparant traditionnellement les notions de partie et de tiers à un contrat et à un arbitrage, invitant alors à réfléchir sur l’opportunité d’une réglementation de la pratique
Today third-party funding in international arbitration is definitely the number one solution for economic operators to access this private justice. This process allows various players to transfer the costs and the risks incurred by the proceedings to a third party. In return, the latter is granted a percentage of the sums allocated to their client by the arbitral award. This relationship resting on a community of interests and geared towards a successful arbitration takes on a concrete form with the litigation finance agreement. This seemingly sui generis agreement is characterized by a specific object that is the financing of international arbitration, and by its specific effects. It is relative to a lawsuit and yet deprived of privity by its very object. Therefore, the contract carries consequences on both the players of the arbitration proceedings for which the financer is not a party, and on the whole of the procedure and its outcome. The present study examines how the border that traditionally separates the concepts of party and third party becomes porous thus questioning the relevance of a regulation of the practice

APA, Harvard, Vancouver, ISO, and other styles

47

Cooper, Shane. "Two-scale homogenisation of partially degenerating PDEs with applications to photonic crystals and elasticity." Thesis, University of Bath, 2012. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.558889.

Full text

Abstract:

In this thesis we study elliptic PDEs and PDE systems with e-pcriodic coeffi- cients, for small E, using the theory of two-scale homogenisation. We study a class of PDEs of partially degenerating type: PDEs with coefficients that are not uniformly elliptic with respect to E, and become degenerate in the limit E -t O. We review a recently developed theory of homogenisation for a general class of partially degenerating PDEs via the theory of two-scale convergence, and study two such problems from physics. The first problem arises from the study of a linear elastic composite with periodically dispersed inclusions that are isotropic and (soft' in shear: the shear modulus is of order E2. By passing to the two- scale limit as E -t 0 we find the homogenised limit equations to be a genuinely two-scale system in terms of both the macroscopic variable x and the micro- scopic variable y. We discover that the corresponding two-scale limit solutions must satisfy the incompressibility condition in y and therefore the composite only undergoes microscopic deformations when a (microscopically rotational' force is applied. We analyse the corresponding limit spectral problem and find that, due to the y-incompressibility, the spectral problem is an uncoupled two-scale prob- lem in terms of x and y. This gives a simple representation of the two-scale limit spectrum. We prove the spectral compactness result that states: the spectrum of the original operator converges to the spectrum of the limit operator in the sense of Hausdorff. The second problem we study is the propagation of electro- magnetic waves down a photonic fibre with a periodic cross section. We seek solutions to Maxwell's equations, propagating down the waveguide with wave number k E2-close to some (critical' value. In this setting, Maxwell's equations are reformulated as a partially degenerating PDE system with z-periodic coeffi- cients. Using the theory of homogenisation we pass to the limit as E -t 0 to find a non-standard two-scale homogenised limit and prove that the spectral compact- ness result holds. We finally prove that there exist gaps in the limit spectrum for two particular examples: a one-dimensionally periodic 'multilayer ' photonic crystal and a two-dimensionally periodic two-phase photonic crystal with the in- clusion phase consisting of arbitrarily small circles. Therefore, we prove that these photonic fibres have photonic band gaps for certain k.

APA, Harvard, Vancouver, ISO, and other styles

48

Munro, David. "Toward a rigorous derivation of a stable and consistent smoothed particle hydrodynamics method." Thesis, Cranfield University, 2015. http://dspace.lib.cranfield.ac.uk/handle/1826/11164.

Full text

Abstract:

The aim of this thesis is to provide an investigation toward a rigorous derivation of a stable and consistent numerical method based on the established Smoothed Particle Hydrodynamics method. The method should be suitable for modelling the large deformation transient response of fluids and solids, the interests of the Crashworthiness, Impact and Structural Mechanics group (CISM) at Cranfield University. A literature review of the current state of the art of the SPH method finds that the conventional SPH equations are not derived in a rigorous way, often the equations are manipulated into a mathematically equivalent form in order to preserve conservation of linear momentum, which often leads to different results; the reasons for this are unknown and it is not fully understood how each particular form of the discrete equations effects the solution in terms of stability, accuracy and convergence. This leads to specific objectives being defined which underpin the overall aim of the thesis. The first objective is to develop an understanding of the SPH method and the implementation used at Cranfield University, this is done through a capability study which demonstrates the coupled SPH-FE method and a number of relevant improvements to the MCM code including the addition of a turbulence model and the modification of the SPH contact algorithm to model lateral forces between materials. This is demonstrated through the implementation of a friction model, which suggests that the contact algorithm is suitable for resolving lateral forces based on the relative velocity between materials, with the potential for coupling with a structural FE model ... [cont.].

APA, Harvard, Vancouver, ISO, and other styles

49

Mas, Ivars Diego. "Bonded Particle Model for Jointed Rock Mass." Doctoral thesis, KTH, Teknisk geologi och geofysik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-12055.

Full text

Abstract:

Jointed rock masses are formed of intact rock and joints. There-fore, proper characterization of rock mass behavior has to consid-er the combined behavior of the intact rock blocks and that of the joints. This thesis presents the theoretical background of the Synthetic Rock Mass (SRM) modeling technique along with example applica-tions. The SRM technique is a new approach for simulating the mechanical behavior of jointed rock masses. The technique uses the Bonded Particle Model (BPM) for rock to represent intact ma-terial and the Smooth-Joint Contact Model (SJM) to represent the in situ joint network. In this manner, the macroscopic behaviour of an SRM sample depends on both the creation of new fractures through intact material, and slip/opening of pre-existing joints. SRM samples containing thousands of non-persistent joints can be submitted to standard laboratory tests (UCS, triaxial loading, and direct tension tests) or tested under a non-trivial stress path repre-sentative of the stresses induced during the engineering activity under study. Output from the SRM methodology includes pre-peak properties (modulus, damage threshold, peak strength) and post-peak proper-ties (brittleness, dilation angle, residual strength, fragmentation). Of particular interest is the ability to obtain predictions of rock mass scale effects, anisotropy and brittleness; properties that can-not be obtained using empirical methods of property estimation. Additionally, the nature of yielding and fracturing can be studied as the rock mass fails. This information can improve our understand-ing of rock mass failure mechanisms.
QC20100720

APA, Harvard, Vancouver, ISO, and other styles

50

Reimers, Teresa M. "Parties, Process and Nurani Hati: How the Indonesian Press Constructed the 2004 Elections." Ohio : Ohio University, 2006. http://www.ohiolink.edu/etd/view.cgi?ohiou1147947223.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'Contact partiel'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles