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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
421

Active Lateral Secondary Suspension in a High-Speed Train to Improve Ride Comfort

Orvnäs, Anneli January 2009 (has links)
<p>Active secondary suspension in trains has been studied for a number of years, showing promising improvements in ride comfort. However, due to relatively high implementation and maintenance costs, active technology is not being used in service operation to a large extent. The objective of this study is to develop an active lateral secondary suspension concept that offers good ride comfort improvements and enables centring of the carbody above the bogies when negotiating curves at unbalanced speed. Simultaneously, the active suspension concept should be a cost-effective solution for future series production. The thesis consists of an introductory part and three appended papers.</p><p>The introductory part describes the concept of active secondary suspension together with different actuator types and control methods. Further, the present simulation model and applied comfort evaluation methods are presented. The introductory part also comprises a summary of the appended papers, an evaluation of track forces and suggestions for further work.</p><p>Paper A presents the initial development of an active lateral secondary suspension concept based on sky-hook damping in order to improve vehicle dynamic performance, particularly on straight tracks. Furthermore, a Hold-Off-Device (HOD) function has been included in the suspension concept in order to centre the carbody above the bogies in curves and hence avoid bumpstop contact. Preparatory simulations as well as the subsequent on-track tests in the summer of 2007 showed that the active suspension provides improved passenger ride comfort and has significant potential to be a cost-effective solution for future implementation.</p><p>In Paper B, measurement results from on-track tests performed in 2008 are presented. The active secondary suspension concept was slightly modified compared to the one presented in the first paper. One modification was the implementation of a gyroscope in order to enable detection of transition curves and to switch off the dynamic damping in these sections. Ride comfort in the actively suspended carbody was significantly improved compared to that in the passively suspended car. The satisfactory results led to implementation of the active suspension system in long-term tests in service operation in the beginning of 2009.</p><p>In Paper C, a quarter-car model in MATLAB has been used to investigate a more advanced control algorithm: <em>H</em><sub>∞</sub> instead of sky-hook. <em>H</em><sub>∞</sub> control provides more flexibility in the design process due to the possibility to control several parameters. In particular, this is done by applying weight functions to selected signals in the system. When comparing the two control strategies through simulations, the results show that <em>H</em><sub>∞</sub> control generates similar carbody accelerations at the same control force as sky-hook; however, the relative displacement displacement is somewhat lower.</p>
422

An experimental study of fiber suspensions between counter-rotating discs

Ahlberg, Charlotte January 2009 (has links)
<p>The behavior of fibers suspended in a flow between two counter-rotating discs has been studied experimentally. This is inspired by the refining process in the papermaking process where cellulose fibers are ground between discs in order to change performance in the papermaking process and/or qualities of the final paper product.</p><p>To study the fiber behavior in a counter-rotating flow, an experimental set-up with two glass discs was built. A CCD-camera was used to capture images of the fibers in the flow. Image analysis based on the concept of steerable filters extracted the position and orientation of the fibers in the plane of the discs. Experiments were performed for gaps of 0.1-0.9 fiber lengths, and for equal absolute values of the angular velocities for the upper and lower disc. The aspect ratios of the fibers were 7, 14 and 28.</p><p>Depending on the angular velocity of the discs and the gap between them, the fibers were found to organize themselves in fiber trains. A fiber train is a set of fibers positioned one after another in the tangential direction with a close to constant fiber-to-fiber distance. In the fiber trains, each individual fiber is aligned in the radial direction (i.e. normal to the main direction of the train).</p><p>The experiments show that the number of fibers in a train increases as the gap between the discs decreases. Also, the distance between the fibers in a train decreases as the length of the train increases, and the results for short trains are in accordance with previous numerical results in two dimensions.Furthermore, the results of different aspect ratios imply that there are three-dimensional fiber end-effects that are important for the forming of fiber trains.</p>
423

Modélisation de la microstructuration dans les polymères chargés. Application à la mise en forme.

Pruliere, Etienne 14 November 2007 (has links) (PDF)
Cette thèse étudie la possibilité de simuler des écoulements complexes (polymères chargés, suspensions de fibres courtes, polymères) en prenant en compte la structure à l'échelle microscopique dans le cadre de la théorie cinétique. Il y a un couplage fort entre la structure microscopique et la cinématique à l'échelle macroscopique. Le caractère multidimensionnel de l'équation de Fokker-Planck décrivant la microstructure du fluide rend la simulation difficile avec des approches déterministes classiques. Pour palier ce problème, plusieurs méthodes visant à réduire les dimensions sont développées et testées. <br /><br />Ces méthodes sont appliquées en particulier dans le cas des écoulements recirculants. Le cas d'une recirculation ajoute une difficulté supplémentaire car nous ne connaissons ni les conditions initiales, ni les conditions aux limites. Or les recirculations se trouvent dans beaucoup d'écoulements industriels, lors de la mise en forme des matériaux. Pour cette raison nous avons développé des méthodes numériques spécifiques à ce type d'écoulement.<br /><br />Finalement, une partie de la thèse est dédiée à une étude expérimentale permettant de valider les résultats numériques obtenus et d'étudier les phénomènes physiques entrant en jeu dans la mise en forme des polymères chargés.
424

Daugtaškio vartosena grožiniuose tekstuose ir jo stilistinės išgalės / The use of suspension points in the imaginative texts and their stylistic recources

Kuncaitė, Živilė 29 June 2009 (has links)
Darbe pristatomas daugtaškio vartojimas grožiniuose tekstuose. Kadangi skyrybos intonacinis-pauzinis ir prasmės principai vis labiau akcentuojami, tiriama daugtaškio įtaka teksto emociniam ir ekspresiniam atspalviui, intonacijai, prasminiams akcentams, raiškos gyvumui. Tiriamąją medžiagą sudaro pavyzdžiai su 1876 daugtaškiais, pavartotais neoromantizmo atstovės Šatrijos Raganos apysakų rinkinyje „Sename dvare“ ir postmodernistų Renatos Šerelytės romane „Vardas tamsoje“ ir Mariaus Ivaškevičiaus romane „Žali“. Autoriai pasirinkti siekiant palyginti rašymo laikotarpiams (juos skiria šimtmetis), tekstų tipams, pasirinktos literatūros krypčiai būdingą autorinę skyrybą. Teorinės žinios apie daugtaškį lyginamos su realia ženklo vartosena, aiškinamasi, kokias funkcijas tiriamuose tekstuose jis atlieka, aptariami galimi daugtaškio sinonimai. Nemažai dėmesio skiriama vartojimo dažnumo tyrimui statistiniu metodu. / This Master’s thesis presents the use of suspension points in the imaginative texts. As the intonation pause and meaning principles of punctuation are more and more emphasized, the influence of suspension points has been analyzed from the point of the emotional and expressive shade, intonation, meaningful focus, vividness of expression. The research material consists of 1876 examples of suspension points used in the collection of stories “In an Old Manor” by Satrijos Ragana and in the novels of post-modern writers: “The Name in the Darkness” by Renata Serelyte and the novel “The Greens” by Marius Ivaskevicius. The authors have been chosen aiming to compare the authors’ punctuation characteristic to the writing periods (the difference between them is one hundred years), types of the texts, and the chosen trend in literature. The theoretical knowledge about the suspension points have been compared with the real use of the punctuation mark, it has been targeted to ascertain what are the functions of this punctuation mark in the analyzed texts, the possible synonyms of suspension points have been discussed in the thesis. Great attention has been paid to the analysis of the usage frequency applying statistical method.
425

Transient tyre modelling for the simulation of drivetrain dynamic response under low-to-zero speed traction manoeuvres

Bartram, Matthew January 2011 (has links)
The work presented in this thesis is dedicated to the study of transient tyre dynamics and how these influence the dynamic behaviour of the vehicle and its driveline, with the main focus being on low-to-zero speed manoeuvres such as pull-away events. The bulk of the work focuses on the amalgamation of the hitherto disparate fields of driveline modelling and detailed tyre modelling. Several tyre models are employed and their relative advantages and disadvantages analysed. The observed dynamic behaviour is correlated to the inherent structure of each tyre model in order for the most appropriate for driveline studies to be identified. The main simulation studies are split into two parts: the first comprises a study into isolated driveline dynamics; where the yaw, pitch and roll behaviours of the vehicle body are neglected. A relatively detailed driveline model with an open differential is used with tyre models of increasing complexity with the aim of determining when increased model detail fails to increase the accuracy of the results. The second part is concerned with the study of how the dynamics of the vehicle body and suspension affect tyre model performance and associated effects on the driveline behaviour. For this, the driveline and tyre models are incorporated into a full six degree-of-freedom vehicle model with full suspension effects. Frequency migration on low-μ surfaces is successfully explained via the decoupling of the vehicle and driveline inertias. Frequencies observed in FFT analyses of the simulation results correspond to those obtained through eigen-analysis of appropriately modified state-space models with varying degrees of coupling that reflect the vehicle travelling on uniform low- or split-μ surfaces. The main finding of the thesis is that this decoupling theory can also be applied to high-speed take-off manoeuvres, as it is the position along the tyre slip-force curve that dictates decoupling; i.e. if the curve has saturated. This leads to the effective traction stiffness being zero, which modifies the equations of motion and subsequently the system eigenvalues. A series of measurements are taken in order to verify the findings from the simulation work. Manoeuvres analogous to those simulated are carried out. It is found that only the simulation of split-μ conditions is necessary, as the results from the low-μ test show a similar pattern to those seen on the split-μ surface.
426

Behaviour of nanocolloidal particles on mica : investigations using atomic force microscopy

Walker, Richard John January 2010 (has links)
In this thesis we used atomic force microscopy (AFM) to investigate systematically the behaviour of both electrostatically stabilised silica and sterically stabilised polystyrene (PS) colloidal systems on freshly cleaved mica substrates. For the silica colloidal nanoparticles we explored the effect of colloidal suspension concentration, particle size, and different application techniques on both the adsorption behaviour and subsequent structuring of the particles. For the PS colloidal nanoparticles we explored concentration effects and experimented with both dip-coating and droplet application techniques. We showed that silica nanoparticles adsorbed onto mica via irreversible adsorption that possessed lateral mobility due to the weak attraction between the nanoparticles and the substrate, facilitating subsequent capillary structuring of the nanoparticles during drying. We associated the effects of volume fraction with Debye screening, and kinetics effects with particle size and volume fraction. We also successfully imaged a partially dried film and showed the role of convective/capillary forces in the structuring of the nanoparticles. Studies with variations in particle size generated a number of different topography structures; with dewetting phenomena observed for 10 nm nanoparticles and the formation of crystalline structures for 100 nm nanoparticles. Spin coating techniques were used to produce even larger crystalline structures of nanoparticles. Size dependent ordering occurred for low concentration samples due to the polydispersity of the colloidal suspension. We showed that acceleration can affect interparticle spacing. We also studied the role of rotational speed on the crystallinity of the particle configurations and showed how fine tuning of rotational speed can generate large scale monolayer crystalline formations of nanoparticles.
427

Potential Wave Impacts On Shorelines In Intertidal Waterways

Ries, Collin 01 January 2016 (has links)
Coastal erosion is caused by a deficit in the sediment balance along coastal shorelines. Within the intertidal waterway of Jacksonville, Florida, the primary processes acting on the shoreline are tidal currents and waves generated by winds and passing vessels. This study focuses on the analysis of vessel-generated waves and their possible effects on different shoreline types. The experiment conducted herein examines variations in turbidity related to passing boats at a specifically selected site location, at which different tidal stages expose three different shoreline types, a non-vegetated scarp, a vegetated scarp and a vegetated area with no scarp in the breaking zone. Statistical analyses were used to quantify relationships between turbidity and wave height within these three different shoreline types. It was determined that both wave heights and the type of shoreline can affect local turbidity levels. Shorelines that contained vegetation experienced significantly less turbidity, than shorelines with no vegetation. Based on the findings here, some preventative measures are suggested to reduce the erosion of intracoastal shorelines into the channel. This would most likely entail boating restrictions or some protective measures to shelter the intracoastal banks.
428

Physico-chimie des matières en suspension de la Moselle et de ses affluents / Physico-chemistry of suspended matter in the Moselle and its tributaries

Duriez, Caroline 04 November 2010 (has links)
Afin de caractériser la physico-chimie des matières en suspension de la Moselle et de ses affluents, ce travail s’est appuyé sur une approche géochimique et minéralogique. Notre étude s’est concentrée sur l’analyse des polluants dans les compartiments dissous et particulaire. Ces études ont notamment permis de déterminer (i) la composition des constituants inorganiques dans les particules et colloïdes du milieu aquatique de la Moselle et d’un de ses affluents : la Fensch, (ii) l’évolution des contributions inorganiques le long de la Moselle et de la Fensch ainsi que leur transfert à la confluence Fensch-Moselle, tout en déterminant les sources principales de contamination, (iii) les associations organo-minérales et l’organisation des agrégats présents et (iv) d’étudier la spéciation de certains éléments par des microanalyses. Ce travail a ainsi permis de mettre en évidence l’importance des matières en suspension, souvent négligées par rapport aux autres compartiments Eau et Sédiments / This work uses geochemical and mineralogical approaches to characterize physical and chemical properties of suspended solids in the Moselle and its tributaries. The study focused on analyzing the pollutants in dissolved and particulate compartments. This allowed (i) the identification of inorganic components composition in particles and colloids in the aquatic environment of the Moselle and one of its tributaries: the Fensch, (ii) the determination of the evolution of inorganic contributions along Moselle and the Fensch and their transfer to the confluence Fensch-Moselle in addition to the determination of main contamination sources, (iii) the identification of organo-mineral associations and the determination of the organization of aggregates, (iv) the analysis of the speciation of some elements by microanalysis. This work highlighted the importance of studying suspended solids that are often neglected compared to water and sediments compartments
429

A Study of the Origins and Early Development of the Major Seventh Chord

Hanslowe, Nannette Reese 08 1900 (has links)
The purpose of this study is to trace the development of the major seventh chord from the earliest recorded music through the German School of composition up to the time of Johann Sebastian Bach. The term "major seventh chord" is used to denote the four-tone chord comprised of a major triad plus a tone which is a major seventh above the root. In major keys this chord may be built on the tonic and subdominant degrees of the scale without alterations, and in the "natural" minor on the mediant and the submediant. The full, or structural, name "major-major seventh chord"--used in the present thesis only when it is necessary to distinguish it from other seventh chords with major sevenths-- arises from the fact that the triad (1, 3, 5) is major and the interval between the root and the seventh is major.
430

Cabiakman et la suspension pour fins d’enquête en rapports collectifs

Girard, Fanny 01 1900 (has links)
La suspension pour fins d’enquête est une mesure administrative qui permet à l’employeur de suspendre la prestation de travail d’un salarié le temps de faire enquête sur des actes qui lui sont reprochés et qui sont susceptibles d’entacher la réputation ou l’image de l’entreprise. Les principes applicables en la matière ont été précisés par la Cour suprême en 2004 dans l’arrêt Cabiakman c. Industrielle-Alliance, Compagnie d’assurance sur la vie, qui traite d’un contrat individuel de travail. Notre mémoire porte sur les circonstances justifiant une suspension pour fins d’enquête en rapports collectifs. Afin de vérifier le traitement de cette mesure administrative, nous avons effectué une analyse qualitative de la jurisprudence arbitrale québécoise en matière de suspension pour fins d’enquête avant et après Cabiakman. D’abord, nous avons vérifié la compatibilité des principes formulés dans Cabiakman et des principes issus de la jurisprudence arbitrale québécoise antérieure à cet arrêt. Ensuite, nous avons analysé l’influence de cet arrêt en rapports collectifs en examinant si la jurisprudence arbitrale québécoise qui lui est postérieure s'y réfère et en applique les principes. Finalement, nous avons tenté de corréler l’influence ou l’absence d’influence de Cabiakman sur la jurisprudence arbitrale à l’adhésion des arbitres à la thèse de la coexistence ou à la thèse de l’autonomie. Nos résultats ont démontré que Cabiakman n’est pas parfaitement compatible avec la jurisprudence arbitrale qui lui est antérieure puisque des principes différents de ceux énoncés par la Cour suprême s’y retrouvent. Aussi, nous avons remarqué que la jurisprudence arbitrale postérieure à cet arrêt s’y réfère souvent et en applique certains principes. Toutefois, nous ne considérons pas que l’influence de cet arrêt sur la jurisprudence arbitrale soit entièrement corrélée au rattachement des sentences arbitrales à l’une ou l’autre des deux thèses. En effet, d’autres hypothèses pourraient expliquer les résultats que nous avons obtenus. / A suspension for investigation purposes is an administrative measure which allows the employer to suspend an employee for alleged acts that may damage the reputation or the image of the company. The principles which apply to this administrative suspension were established by the Supreme Court of Canada in 2004 in Cabiakman v. Industrial Alliance Life Insurance Co., which deals with an individual contract of employment. Our research focuses on the circumstances justifying a suspension for investigation purposes in collective labour relations. In order to study the treatment of this administrative measure, we conducted a qualitative analysis of the decisions of arbitration tribunals from Quebec regarding the suspension for investigation purposes before and after Cabiakman. We initially verified the compatibility of the principles established in Cabiakman and the principles of the arbitration decisions from Quebec rendered prior to this judgment. Subsequently, we analyzed the influence of this judgment in collective labor relations by examining if the arbitration tribunals from Quebec referred to Cabiakman and implemented its principles. Finally, we attempted to correlate the influence or lack of influence of Cabiakman on the arbitration decisions to the adhesion of the arbitrators to the coexistence thesis or to the autonomy thesis. Our results indicated that Cabiakman is not entirely consistent with the previous arbitration decisions because their principles are different from those expressed by the Supreme Court. In addition, we noticed that the posterior arbitral decisions often referred to Cabiakman and implemented some of its principles. However, we do not consider that the influence of this judgment on the arbitration decisions is entirely correlated to the linking of the arbitral decisions to one of the theses. Indeed, other hypotheses could explain the results of our research.

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