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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.
291

Železobetonová konstrukce bytového domu / Reinforced concrete construction of apartment building

Fusek, Aleš January 2020 (has links)
This diploma thesis deals with the analysis of reinforced concrete structure with masonry walls. Scia Engineer was used for finite element analysis. The spatial models include nonlinear behavior of masonry. Furthermore, the ceiling slab above the 1st floor, beams and columns were designed.
292

In-Plane Lateral Load Capacities of Vertically Oriented Interlocking Timber Panels

Decker, Brandon T 01 July 2014 (has links)
The Vertically Oriented Interlocking Timber (VOIT) panel is a new solid wood panel similar to Interlocking Cross Laminated Timber (ICLT) and the more commonly known Cross Laminated Timber (CLT). Like ICLT, VOIT panels use timber connections instead of the adhesives or metal fasteners common to CLT. The difference of VOIT is the orientation of the layers. Where CLT and ICLT panels alternate the orientation of each layer, VOIT panels orient all the layers in the same direction. The vertically oriented layers are then attached to one another by smaller horizontal dovetail members.Two types of VOIT panels were provided to be tested for in-plane lateral loading. Type I had three rows of horizontal dovetail members connecting the layers and Type II had four rows of dovetail members as well as two diagonal members to provide stiffness. Two panels of each type were provided, measuring 8 ft. wide, 8 ft. tall, and 13.75 in. thick. Each panel was disassembled after monotonic lateral in-plane loading to determine possible failure modes. Testing results suggest the VOIT panels to be comparable in shear strength to other wood shear walls, including light frame, CLT, and ICLT walls. A two-part analytical model was created to determine the deflection of the wall when loaded as well as the shear strength of the wall. The model predicted deflection and wall strength reasonably well. Due to the small sample size, additional testing is necessary to confirm the results of the Type I and Type II VOIT panels. Additional testing with more variations of the panel and member geometries is also needed to validate the scope of the model.
293

Optimalizace nástrojové řezné geometrie pro vysokorychlostní obrábění tenkostěnných součástí / Optimization of tool cutting geometry for high-speed machining of thin-walled parts

Barcuch, Jakub January 2013 (has links)
The theoretical part of the thesis deals with materials used in the aircraft industry with a focus on aluminium alloys. Then it describes high speed machining, its characteristics and its comparison with conventional machining. The following chapters describe strategies of machining thin-walled parts and a description of vibration that occurs during machining. The practical part deals with selection appropriate tool geometry, machining of thin-walled parts and evaluation of their deflection during machining.
294

Correction de trajectoires d'un robot manipulateur utilisé pour le soudage par friction malaxage / Path correction of an industrial robot used for friction stir welding

Kolegain, Komlan 10 October 2019 (has links)
Le procédé de soudage par friction malaxage ou Friction Stir Welding (FSW), est un procédé récent utilisé pour le soudage de pièces métalliques avec différentes applications dans les industries aéronautique, automobile, spatiale et ferroviaire. Les robots industriels sériels peuvent être utilisés comme moyen de soudage FSW mais, à cause de leur rigidité, ils se déforment sous l’effet des forces générées par le procédé. Ceci entraîne une déviation de trajectoire de l’outil de soudage en position et en orientation qui induit des défauts dans le cordon de soudure. Dans ce travail, deux méthodes de correction de déviations ont été développées. La première méthode est basée sur l’estimation des déviations en position et en orientation dans l’espace cartésien à partir des modèles du robot et de déformation élasto-statique des corps et transmissions. Les déviations estimées permettent de développer une approche de programmation de trajectoires adaptées au soudage FSW robotisé. Contrairement aux méthodes d’interpolation linéaire généralement envisagées, cette approche utilise des approximations de trajectoires par des courbes de Bézier ou B-splines. Les validations expérimentales pour des trajectoires complexes, avec un robot Kuka KR500-2MT, ont permis d’obtenir une déviation résiduelle moyenne de l’ordre de 0,3 mm et des cordons de soudure sans défauts. Cette précision de trajectoire atteinte pour le FSW permet de considérer une exploitation industrielle de la solution développée. La deuxième méthode de correction des déviations utilise un asservissement de position en temps réel avec un capteur de profil laser 2D dans la boucle de retour. Deux synthèses de lois de commande ont été explorées pour cet asservissement. Malgré les perturbations externes liées aux contraintes du procédé, les résultats expérimentaux sur des trajectoires de soudage rectilignes et curvilignes montrent une bonne stabilité de l’asservissement et conduisent à une déviation résiduelle moyenne de l’ordre de 0,1 mm. Les intérêts et les difficultés de la mise en œuvre de cette deuxième méthode ont également été mis en exergue. / Friction Stir Welding (FSW) is a recent process used for welding metallic parts in aerospace, automotive, and railway industries. Serial industrial robots may be used as FSW welding machines, but because of their lack of stiffness, they undergo elastic deformation under the effect of stresses produced by the process. This causes a welding tool path deviation both in position and orientation, which induces defects in the weld seam. In this work, two path correction methods were developed. The first method is based on the prediction of the position and orientation deviations in the cartesian space from robot models and stiffness model of the links and the joints. The knowledge of tool deviations enabled the synthesis of a path programming approach adapted for robotic FSW. Unlike linear interpolation methods often used, this approach is based on approximations of the adapted path by Bézier or B-splines curves. Experimental validations on a Kuka KR500-2MT robot welding complex paths showed an average residual deviation of 0.3 mm and weld seams without defects. The path accuracy achieved makes it possible to consider an industrial exploitation of the developed solution. The second proposed correction method uses position feedback with a 2D laser profile sensor in the feedback loop for real-time measurement of deviations. Two controllers were designed to correct the deviations. In spite of the external disturbances related to the constraints of the process, experimental results obtained on straight and curvilinear welding paths showed the stability of the feedback loop and a mean residual deviation of 0.1 mm was achieved. The interests and difficulties of deploying this second method were also highlighted.
295

Ultra precision metrology : the key for mask lithography and manufacturing of high definition displays

Ekberg, Peter January 2011 (has links)
Metrology is the science of measurement. It is also a prerequisite for maintaining a high quality in all manufacturing processes. In this thesis we will present the demands and solutions for ultra-precision metrology in the manufacturing of lithography masks for the TV-display industry. The extreme challenge that needs to be overcome is a measurement uncertainty of 10 nm on an absolute scale of more that 2 meters in X and Y. Materials such as metal, ceramic composites, quartz or glass are highly affected by the surrounding temperature when tolerances are specified at nanometer levels. Also the fact that the refractive index of air in the interferometers measuring absolute distances is affected by temperature, pressure, humidity and CO2 contents makes the reference measurements really challenging. This goes hand in hand with the ability of how to design a mask writer, a pattern generator with a performance good enough for writing masks for the display industry with sub-micron accuracy over areas of square meters.  As in many other areas in the industry high quality metrology is the key for success in developing high accuracy production tools. The aim of this thesis is therefore to discuss the metrology requirements of mask making for display screens. Defects that cause stripes in the image of a display, the so called “Mura” effect, are extremely difficult to measure as they are caused by spatially systematic errors in the mask writing process in the range of 10-20 nm. These errors may spatially extend in several hundreds of mm and are superposed by random noise with significantly higher amplitude compared to the 10-20 nm.  A novel method for measuring chromium patterns on glass substrates will also be presented in this thesis. This method will be compared to methods based on CCD and CMOS images. Different methods have been implementedin the Micronic MMS1500 large area measuring machine, which is the metrology tool used by the mask industry, for verifying the masks made by the Micronic mask writers. Using alternative methods in the same system has been very efficient for handling different measurement situations. Some of  the discussed methods are also used by the writers for calibration purposes. / QC 20110517
296

Long Term Performance of Corrugated HDPE Pipes Produced with Post-Consumer Recycled Materials Under Constant Deflection

Shaheen, Ehab T. January 2018 (has links)
No description available.
297

The "45 Degree Rule" and its Impact on Strength and Stiffness of a Shaft Subjected to a Torsional Load

Nation, Cory A. January 2014 (has links)
No description available.
298

A MAGNETICALLY-ACTUATED ROBOTIC CATHETER FOR ATRIAL FIBRILLATION ABLATION UNDER REAL-TIME MAGNETIC RESONANCE IMAGING GUIDANCE

Liu, Taoming 05 June 2017 (has links)
No description available.
299

Análisis del comportamiento de conductores en curvas de bajo ángulo de deflexión.

Ulpiano Cogollos, José Luis 17 January 2021 (has links)
[ES] Esta Tesis Doctoral se centra en el estudio de las curvas de bajo ángulo de deflexión, las cuales son esenciales para el diseño geométrico, pero cuyos criterios de diseño difieren del resto y pueden producir mermas en la seguridad vial. Fundamentalmente, se pueden distinguir tres tipos de afecciones: percepción errónea, trayectorias erráticas y velocidades excesivas. Una percepción errónea puede darse especialmente cuando el desarrollo de la curva es muy reducido. En este caso, la curva puede aparecer como un quiebro, que puede llevar a los conductores a realizar maniobras erráticas, según perciben su curvatura. Esto puede agravarse con la presencia de acuerdos en alzado. Las velocidades excesivas (que pueden darse en los casos de percepción errónea o no), son fruto de la elevada visibilidad en las mismas, combinada con radios intermedios y, en ocasiones, su sección transversal. En muchas ocasiones, los usuarios tienden a cortar ligeramente la trazada (invadiendo el arcén o el carril de sentido contrario), aumentando la posibilidad de choque frontal o salida de vía. La baja deflexión de estas curvas impide disponer curvas de transición (suele realizarse directamente la transición de recta a curva circular). Por ello, las diferentes normativas tienen expresiones particulares para determinar el radio o desarrollo mínimos de estas. El problema es que dichas expresiones no están basadas en estudios experimentales que corroboren su efectividad. En esta Tesis Doctoral se pretende profundizar en el conocimiento en ambos aspectos, con el fin de validar los criterios actuales, o bien proporcionar unos nuevos con fundamento científico. Mediante dos encuestas - una presencial y otra online - en las que se muestran vídeos de curvas de esta tipología, se consulta a voluntarios acerca de su percepción, velocidad y posición tentativas. Se han considerado más de 300 curvas en este estudio. La operación vehicular se analiza mediante un estudio naturalístico sobre cuatro curvas de bajo ángulo con diferente configuración transversal y nivel de tráfico. Se ha podido determinar que la sección transversal tiene una importante influencia sobre la velocidad desarrollada. Como resultado, se presenta un criterio de desarrollo mínimo, más simple que en la mayoría de actuales normativas, pues no es dependiente del ángulo de deflexión. Se ofrecen dos umbrales, uno recomendable a partir del cual la percepción es adecuada y no causa disminución en la velocidad, y otro obligatorio, por debajo del cual no se garantiza una percepción adecuada. / [CAT] Aquesta Tesi Doctoral es centra en l'estudi de les corbes de baix angle de deflexió, les quals són essencials per al disseny geomètric, però que tenen criteris de disseny diferents a la resta, amb possibles penalitzacions a la seguretat viària. Fonamentalment, es poden distingir tres tipus d'afeccions: percepció errònia, trajectòries erràtiques i velocitats excessives. Una percepció errònia pot donar-se especialment quan la llargària de la corba és molt reduïda. En aquest cas, la corba pot visualitzar-se com una finta, la qual pot fer que els conductors a fer maniobres erràtiques, segons perceben la curvatura. Això pot agreujar-se amb la coincidència d'acords verticals. Les velocitats excessives (que poden coincidir o no amb una percepció errònia), son resultat de la seua elevada visibilitat, combinada amb radis mitjans i, en ocasions, la seua secció transversal. Freqüentment, els usuaris poden retallar lleugerament la corba (envaït parcialment ell voral o el carril de sentit contrari), augmentant la possibilitat de xoc frontal o eixida de via. La baixa deflexió d'aquestes corbes impedeix disposar corbes de transició (sol realitzar-se directament la transició de recta a corba circular). És per això que les diferents normatives presenten expressions particulars per a determinar el radi o la llargària mínima d'aquestes. El problema es que aquestes expressions no estan basades en estudis experimentals que asseveren la seua efectivitat. En aquesta Tesi Doctoral es pretén profunditzar en el coneixement d'ambdós aspectes, amb l'objectiu de validar els criteris actuals, o bé proporcionar uns de nous amb fonament científic. Mitjançant dues enquestes - una presencial i altra online - en las que es mostren vídeos de corbes d'aquesta tipologia, es pregunta a voluntaris sobre la percepció, velocitat i posició temptatives. S'han considerat més de 300 corbes en aquest estudi. La operació vehicular s'ha analitzat mitjançant un estudi natural¿lístic sobre quatre corbes de baix angle amb diferent configuració transversal i nivell de trànsit. S'ha determinat que aquesta secció transversal té una influència important sobre la velocitat desenvolupada. Com a resultat, es presenta un criteri de llargària mínima, més simple que el d'altres normatives actuals, ja que no hi depèn de l'angle de deflexió. S'ofereixen dos umbrals, un recomanable a partir del qual la percepció és adequada i no redueix la velocitat, i un altre obligatori, sot a el qual la percepció estaria compromesa. / [EN] This Doctoral Thesis focuses on the analysis of low deflection curves. These curves are necessary for horizontal alignments, but the design criteria differ from other curves, sometimes causing lack of safety. There are three main safety concerns: erroneous perception, erratic trajectories, and speeding. Short low deflection curves are more prone to misperceptions. Such the case, these curves might appear as a kink, with drivers being more likely to perform erratic maneuvers. This would get even worse if combined with vertical curves. Speeding behaviors (which may happen at misperceived curves or not), are generally caused by the high sight distance, combined with medium-to-high radii and, occasionally, with a wide cross-section. Drivers tend to cut the curves, invading shoulder or the opposite direction. This increases the probability of run-of-road or head-on crashes. Due to the low angle, spirals are not required to perform tangent-to-curve transition (tangent is directly connected to the circular curve). Thus, different guidelines present particular expressions to determine their minimum radius or minimum length. Unfortunately, these expressions are not supported by experimental studies. This Doctoral Thesis aims at studying in depth these curves, in order to validate existing criteria or determine new criteria to apply. To questionnaires - in-person and online - showing videos covering these curves have been developed. Volunteers have been asked about preception, lateral position and speed. More than 300 curves have been considered in this study. Vehicle operation has been studied by means of a naturalistic study on four low-deflection curves, with different cross-section and traffic characteristics. As a result, cross-section has been found to contribute enormously to speeding. As a result, two-threshold criterion has been provided. This establishes minimum thresholds for the curve length. This criterion is simpler than most of the existing ones. A minimum recommended threshold is provided to ensure a good perception combined with no speed variation. A lower, critical threshold is provided to ensure a good perception. / Ulpiano Cogollos, JL. (2020). Análisis del comportamiento de conductores en curvas de bajo ángulo de deflexión [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/159263
300

Deformačně-napěťová analýza aneurysmatu břišní aorty / Stress-strain analysis of abdominal aortic aneurysm

Ryšavý, Pavel January 2011 (has links)
This thesis deals with problems of biomechanics of soft tissues, namely of stress-strain analysis of abdominal aortic aneurysm (AAA). The introduction describes briefly the possibility of aneurysm occurrence with a focus on an aneurysm in the abdominal aorta.

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