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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.
91

Kontinentální zalednění severovýchodní části Frýdlantského výběžku / Continental glaciation of the northeastern part of the Frýdlant Spur

Lehejček, Jiří January 2012 (has links)
North-eastern part of Frýdlantský Spur is situated at the northern foothills of the Jizera Mountains. It represents an area, which was at least twice covered by North-European ice sheet during the Middle Pleistocene. At the same time, it is the region whose hills have the summits around the expected altitudinal limit of the maximum ice sheet extent. Therefore, it is a suitable area to study glacial trimline altitude. Schmidt hammer testing was applied to determine different state of rock surface weathering. Obtained R-values were taken as the most relevant data for glacial trimline determination. Nevertheless, other approaches (GIS analysis, outcrops, block fields and erratics mapping) were also incorporated. Interpretation of these approaches gave the altitudinal limit of ice sheets in the north-eastern part of the Frýdlantský Spur at 500 m a. s. l. ± 20 m.
92

Změny vnitřní stavby klastických sedimentárních hornin při zkoušce Schmidtovým kladivem / Modification of rock fabric of clastic sedimentary rocks due to the Schmidt hammer test

Snížek, Petr January 2013 (has links)
iv Summary Schmidt hammer is the instrument which is used for the assessment of rock mechanical properties and this instrument is classified as the indirect method. This method is based on the assessment of rebound value (R) of the Schmidt hammer, which is measurred by the amount of rebound of the impact plunger from the surface of tested rock. Schmidt hammer is called as the non-destructive method of rock assessment and it is called as in situ testing method as well. The main objective of this work is provement, that Schmidt hammer testing is destructive method and define degree of damage which is caused in the rock mass. Sedimentary rocks were used for the testing, mostly sandstones and arkose sandstones with different types of cement. This made it possible to test the fraction of the rock mass and the relation between fraction and type of cement. The clasts of the rocks had different properties than it was possible to find the relation between grain size and fraction of the rock. Already in procedure of the testing by Schmidt hammer it was obvious, that this metod is definitely destructive. Rock surface after hitting by plunger of Schmidt hammer gains macroscopically observeable destruction. On the surface is the circular track of the plunger and the surface is grinded. It is possible to wipe the small...
93

New Orleans Auction Galleries: An Internship Academic Report

Connors, Grace Elizabeth 01 December 2015 (has links)
This internship academic report is the result of a 480--‐hour internship at New Orleans Auction Galleries completed from February--‐September 2015. New Orleans Auction Galleries is a for--‐profit arts organization located in the Arts District of New Orleans, Louisiana. During my internship, I worked closely with the Art Department and Office Administration, as well as preview receptions andauctions. This experience provided me with a valuable education of the inner workings of New Orleans Auction Galleries from its day--‐to--‐day operations to its vision as an organization. His report begins with the history and goals of New Orleans Auction Galleries and moves forward with discussing the structure of the organization as it stands today, a SWOT analysis, best practices, recommendations, and concludes with my final thoughts.
94

Contribution à la vérification et à la validation d'un modèle diphasique bifluide instationnaire. / Contribution to the verification and the validation of an unsteady two-phase flow model

Liu, Yujie 11 September 2013 (has links)
Cette thèse contribue à la vérification et à la validation du modèle bifluide de Baer-Nunziato, pour modéliser les phénomènes de transitoires hydrauliques dans les réseaux de tuyauteries industrielles. Il s’agit d’abord de modéliser les écoulements de transitoires hydrauliques avec le modèle bifluide en représentation eulérienne, puis d’étendre ce modèle en formalisme ALE (Arbitrary Lagrangian Eulerian) pour prendre en compte l’interaction fluide-structure (IFS). Pour modéliser les écoulements, des lois de fermetures du modèle bifluide concernant les termes interfaciaux, les termes sources et les lois thermodynamiques (EOS) ont d’abord été étudiées. Ensuite, le système complet a été simulé avec une méthode à pas fractionnaires qui admet deux étapes, l’une pour la résolution de la partie convective, l’autre pour les termes sources. L’ensemble de schémas a été vérifié et étendu aux EOS ‘Stiffened Gas généralisées’ afin de représenter le changement de phase eau-vapeur. Après avoir retrouvé certains phénomènes typiques associés aux transitoires hydrauliques, le modèle bifluide a été validé avec l’expérience de Simpson, l’expérience Canon, et comparé avec deux modèles homogènes sur ces deux expériences. Enfin, une version ALE du modèle bifluide a été mise en œuvre et vérifiée sur un cas de propagation d’ondes de pression dans une conduite flexible. La variation de la célérité des ondes dans le fluide liée au couplage fluide/structure a été bien retrouvée. La validation a été effectuée sur un cas expérimental d'explosion dans une tuyauterie en eau. Les simulations sont en bon accord avec les données expérimentales. / This thesis contributes to the verification and the validation of the Baer-Nunziato (BN) model, to modelize water hammer phenomena in industrial piping systems. It consists of two parts, the first is to modelize water hammer flows with the BN model in Eulerian representation and the second is to extend this model to the ALE (Arbitrary Lagrangian Eulerian) formalism so as to take into account fluid-structure interaction (FSI). To modelize water hammer flows, closure laws of the BN model concerning the interfacial/source terms and the equations of state (EOS) were first studied. Then the whole system was simulated with a fractional step method including two steps, one for the resolution of the convective part, the other for the source terms. All schemes have been extended to ‘generalized Stiffened Gas’ EOS in order to represent phase-change. After regaining some typical phenomena associated with water hammer flows, the BN model was validated with the Simpson experiment, a classical water hammer test case, and the Canon experience, a rapid decompression of fluid in a high pressure duct. Moreover, the model was compared with two homogeneous models on both experiments. Finally, an ALE version of the BN model was implemented, and verified on a case of wave propagation in a ‘single’ phase flow and a two-phase flow in a flexible pipe. The variation of wave propagation speed due to the coupling between the fluid and the structure has been well retrieved. The validation was performed on an experiment which examines the response of a pipe filled with water, subjected to a violent pressure peak (140 bar). The simulations are in good agreement with the experimental data.
95

Estimation of Pile Capacity by Optimizing Dynamic Pile Driving Formulae

Rauf, Awais January 2012 (has links)
Piles have been used since prehistoric times in areas with weak subsurface conditions either to reinforce existing ground, create new ground for habitation or trade, and support bridges and buildings. Originally piles were composed of timber and driven with drop hammers using very heavy ram weights. As technology improved so did the materials that piles are composed of as well as the equipment itself. Currently, piling is a multibillion dollar a year industry, thus the need to develop more accurate prediction methods can potentially represent a significant savings in cost, material, and man power. Multiple predictive methods have been developed to estimate developed pile capacity. These range from static theoretical formulae based on geotechnical investigation prior to pile driving even occurring using specific pile and hammer types to semi empirically based dynamic formulae used during actual driving operations to more recently developed computer modeling and signal matching programs which are calibrated with site condition during initial geotechnical investigations or test piling to full scale static load tests where piles are loaded to some predetermined value or failure condition. In this thesis, dynamic formulae are used to predict pile capacity from those installed by drop and diesel hammers and are compared to the results from pile load tests, which are taken as the true measure of developed bearing capacity. The dynamic formulae examined are the Engineering News Record (ENR), Gates, Federal Highway Administration (FHWA) modified Gates, Hiley, and Ontario Ministry of Transportation (MTO) modified Hiley formulae. Methods of investigation include calculating pile capacities from the formulae as they are, omitting the factors of safety, revising the formulae with averaged coefficients and conducting multi regression analysis to solve for one or two coefficients simultaneously and revising the dynamic formula to determine if more accurate bearing capacity prediction are possible. To objectively determine which formulae provide the most accurate bearing capacities, the predicted capacities will be compared to results obtained from static pile load tests and simple statistics on the resulting data set will be calculated including regression analysis, standard deviations, coefficients of variation, coefficients of determination, and correlation values.
96

Estimation of Pile Capacity by Optimizing Dynamic Pile Driving Formulae

Rauf, Awais January 2012 (has links)
Piles have been used since prehistoric times in areas with weak subsurface conditions either to reinforce existing ground, create new ground for habitation or trade, and support bridges and buildings. Originally piles were composed of timber and driven with drop hammers using very heavy ram weights. As technology improved so did the materials that piles are composed of as well as the equipment itself. Currently, piling is a multibillion dollar a year industry, thus the need to develop more accurate prediction methods can potentially represent a significant savings in cost, material, and man power. Multiple predictive methods have been developed to estimate developed pile capacity. These range from static theoretical formulae based on geotechnical investigation prior to pile driving even occurring using specific pile and hammer types to semi empirically based dynamic formulae used during actual driving operations to more recently developed computer modeling and signal matching programs which are calibrated with site condition during initial geotechnical investigations or test piling to full scale static load tests where piles are loaded to some predetermined value or failure condition. In this thesis, dynamic formulae are used to predict pile capacity from those installed by drop and diesel hammers and are compared to the results from pile load tests, which are taken as the true measure of developed bearing capacity. The dynamic formulae examined are the Engineering News Record (ENR), Gates, Federal Highway Administration (FHWA) modified Gates, Hiley, and Ontario Ministry of Transportation (MTO) modified Hiley formulae. Methods of investigation include calculating pile capacities from the formulae as they are, omitting the factors of safety, revising the formulae with averaged coefficients and conducting multi regression analysis to solve for one or two coefficients simultaneously and revising the dynamic formula to determine if more accurate bearing capacity prediction are possible. To objectively determine which formulae provide the most accurate bearing capacities, the predicted capacities will be compared to results obtained from static pile load tests and simple statistics on the resulting data set will be calculated including regression analysis, standard deviations, coefficients of variation, coefficients of determination, and correlation values.
97

Preform Design For Forging Of Heavy Vehicle Steering Joint

Gulbahar, Sertan 01 January 2004 (has links) (PDF)
In automotive industry, forgings are widely used especially in safety related applications, typically suspension, brake and steering systems. In this study, forging process of a steering joint used in heavy vehicles has been examined. This particular part has a non-planar parting surface and requires a series of operations, which includes fullering, bending and piercing on a forging press. Forging companies generally use trial-and-error methods during the design stage. Also to ensure complete die filling at the final stage, extra material is added to the billet geometry. However, the forging industry is becoming more competitive finding a way to improve the quality of the product while reducing the production costs. For this purpose, a method is proposed for the design of the preform dies to reduce the material wastage, number of applied strokes and production costs. The designed operations were examined by using a commercially available finite volume analysis software. The necessary dies have been manufactured in METU-BILTIR CAD/CAM Center. The designed process has been verified by the experimental work in a forging company. As a result of this study, remarkable reduction in the flash, i.e. waste of material, has been achieved with a reasonable number of forging operations. In addition to forging of the steering joint, forging of a chain bracket, which has bent sections with planar parting surface, has also been observed and analyzed during the study. An intermediate bending stage has been proposed to replace the manual hammering stage and satisfactory results have been observed in simulations.
98

Ram pump hydraulic air test. Pressure conditions and flow measurements: Experimental research and case study

Arizcun Zúñiga, Paula María January 2018 (has links)
This study consists of the development of a ram pump, which will allow the pumping of water without the need of external energy sources. It is considered an analysis of interest since, once it is finished; it can be applied in reality improving and facilitating different activities related to agriculture and health. Previous studies have been made related to the ram pump; however, in this case, it is intended to understand the system that has been built in the laboratory in order to find the best combination of parameters that will lead to obtain the highest possible efficiency.  The study will be carried out by studying scientific literature and by experimenting in the laboratory. Encompassing the experimental and literary field, it is expected to understand perfectly the advantages and disadvantages of the ram pump in order to determine if it is worth it to install in certain places. After the study, the most favourable parameters for the operation of the Bruzaholms Bruk pump have been obtained. It has been found that the use of a longer drive pipe favours the operation of the system, as it is possible to obtain a higher efficiency, although it must be taken into account that the mentioned length needs to be controlled, as it could reduce the working rhythm of the pump. It has also been seen that the pump gives better results if the impulse valve is completely opened. Finally, it has been proven that, as long as the height difference between the two tanks is enough, increasing the height of the water source will favour the operation of the system.
99

L'Ibéromaurusien, culture du Paléolithique supérieur tardif : approche technologique des productions lithiques taillées de Tamar Hat, Rassel et Columnata (Algérie) / Iberomaurusian, late upper paleolithic culture : technological approach of knapped lithic assemblages of Tamar Hat, Rassel and Columnata (Algeria)

Sari, Latifa 24 January 2012 (has links)
Cette étude expose les résultats d’une analyse technologique menée pour la première fois sur trois séries lithiques (Tamar Hat, Rassel, Columnata) attribuées à l’Ibéromaurusien de l’Algérie couvrant une phase ancienne attestée à Tamar Hat (20 600 ± 500 BP) et une phase récente à Columnata (10 800 ± 425 BP). L’analyse technologique a mis en évidence une variabilité, qui semble davantage s’affirmer vers la phase récente, au niveau des comportements techniques adoptés par les populations de chacun des sites. La prise en compte des stratégies d’approvisionnement des matières premières, des méthodes et techniques appliquées dans le débitage, ainsi que la transformation des supports en outillage et leur abandon a permis de cerner la variabilité observée en terme de comportements techniques inhérents aux populations de chacun des gisements étudiés. Ainsi, la variabilité diachronique, déjà observée dans les études typologiques précédentes, est interprétée par des conceptions différentes dans la réalisation des schémas opératoires de production lithique et à des activités cynégétiques et domestiques divergentes liées à des contraintes imposées par des contextes topographiques et paléoenvironnementaux variant de la phase ancienne à la phase récente. / This study exposes the results of a technological analysis led for the first time on three lithic assemblages (Tamar Hat, Rassel, Columnata) attributed to Iberomaurusien of Algeria covering the old phase attested at Tamar Hat (20 600 ± 500 BP) and a recent phase at Columnata (10 800 ± 425 BP). The technological analysis brought to light a variability which more seems to assert itself towards the recent phase related to the technical behaviors adopted by the populations of each of the sites. The consideration of the raw material procurement strategies, methods and techniques applied in the debitage as well as the finishing of the tools and there discard allowed to define the observed variability in term of technical behaviors inherent to the populations of each of the studied sites. So, the diachronic variability, already observed in the previous typological studies, is interpreted by different conceptions in the realization of the “chaine opératoire” of lithic production and in divergent hunting and domestic activities linked to imperative topographic and paleoenvironnemental constraints varying from the old to the recent phase.
100

Sécurité des réseaux d’adduction d’eau potable en présence de défaut superficiel sous l’effet du phénomène de coup de bélier / Safety of drinking water systems in the presence of surface defects under the effect of water hammer phenomenon

Bouaziz, Mohamed Ali 02 June 2016 (has links)
La crise de l’eau dans le monde et la pénurie des ressources en eau exigent une bonne gestion de cette précieuse ressource. La bonne gestion passe en premier lieu par un réseau d’adduction d’eau potable fiable avec un faible taux de fuite. Les fuites causées par la rupture des canalisations, phénomène assez fréquent en milieu urbain, s’amorcent sur un défaut dû à la corrosion ou autres. L’amorçage et la propagation de la fissure se fait par fatigue sous l’effet de contraintes engendrées par le passage des véhicules, ou brutalement à cause du phénomène de coup de bélier. La gravité de ces phénomènes dépend de plusieurs paramètres y compris la nature du matériau des conduites. Les matériaux polymères, comme le PEHD, occupent une bonne partie du marché de transport d’eau, grâce à leurs multiples qualités (coût réduit, facilité de pose, flexibilité), notamment dans les réseaux de distribution (réseau secondaire). L’utilisation de ce matériau dans les réseaux d’adduction (aqueducs) est en pleine expansion mais beaucoup moins étudier dans les travaux de recherche. L’objectif de la thèse consiste à étudier le risque de rupture des conduites en polyéthylène haute densité destinée à l’adduction d’eau potable ainsi que leurs résistances au phénomène de coup de bélier. Pour répondre à cette problématique, en premier lieu nous avons caractérisé expérimentalement le comportement mécanique à la rupture des conduites en PEHD. Ensuite, nous avons développé un outil numérique de calcul par élément fini permettant de modéliser la rupture des conduites. À l'issue de cette étude nous avons proposé un modèle semi-empirique reliant la pression d’amorçage d’une fissure à la taille du défaut préexistant ainsi qu’aux dimensions de la conduite. Finalement, nous avons appliqué les outils développés sur un réseau d’adduction d’eau potable existant. Le comportement d’une conduite en PEHD soumise à un phénomène de coup de bélier a été analysé / The water crisis in the world and the shortage of water resources require good management of this precious resource. Good management requires, first and foremost, a reliable drinking water supply system with low leakage rate. Leakage caused by the rupture of pipes, fairly frequent phenomenon in urban areas, initiate from a pre-existing defect in the pipe wall. The initiation and propagation of the crack occur under environmental stress caused by passing vehicles, or it can happen brutally due to water hammer phenomenon. The severity of these phenomena depends on several parameters including the nature of the piping material. Polymeric materials such as HDPE, take a great part of the water transport market, thanks to their many qualities (reduced cost, ease of installation, flexibility), especially in secondary network distribution system. Currently, the use of this material in the supply networks (aqueducts) is booming but less studied in research works. The aim of the present work is to study the failure of high density polyethylene pipes for the supply of drinking water and their resistance to water hammer phenomenon. In order to address this issue, first we have characterized experimentally the mechanical fracture behavior of HDPE pipe. Then, we have developed a finite element calculation tool allowing the modeling of pipes subjected to internal pressure loads. As a result of this numerical study, we proposed a semi-empirical model linking the failure pressure to the size of pre-existing defects as well as the pipe dimensions. Finally, we applied the developed tools on an existing drinking water system. The behavior of HDPE pipe subjected to a water hammer phenomenon was analyzed

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