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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.
161

Oxides in the dehydration of Magnesium Chloride Hexahydrate

Kashani-Nejad, Sina January 2005 (has links)
A novel and accurate method of chemical analysis was developed to identify and assay the products of the hydrolysis that occurred when magnesium chloride hexahydrate was heated and held at temperature and reacted with its own liberated waters of hydration. The novel method took advantage of the solubility of magnesium chloride and magnesium chloride hydrates in methanol and the concomitant insolubility of magnesium oxide and magnesium hydroxychlorides in methanol. The method was found to have a precision of 5-7 % and represents a substantial improvement over previous analytical methods. The method is also readily applied to any methanol soluble salt containing insoluble impurities, meaning that it can also be used for the monitoring of the fused salt electrolyte present the magnesium electrolysis cells. [...] / Une nouvelle méthode d'analyse chimique a été développée pour identifier et tester les produits d'hydrolyse qui se forment quand le chlorure de magnésium hexahydrate est chauffé, maintenu à température constante et qu'il réagit avec les eaux d'hydratation qu'il libère. La nouvelle méthode tire avantage de la solubilité du chlorure de magnésium, hydraté ou non, et en parallèle de l'insolubilité de l'oxyde et des hydroxychlorures de magnésium dans le méthanol. Il s'avère que la méthode a montré une précision de 5-7 %, ce qui apporte une importante amélioration aux méthodes analytiques précédentes. La méthode est aussi facilement applicable a tout sel soluble, qui contiendrait des impuretés insolubles, dans le méthanol, ce qui signifie qu'elle peut aussi être utilisée pour le suivi de l'électrolyse de sel fondu présent dans les cellules d'électrolyse du magnésium. [...]
162

Thermal Contraction and Moisture Creep in Concrete.

Chow, David Y.F. January 1953 (has links)
The properties of concrete are being investigated for the last thirty years. Aside from the action of direct load, deformations are produced in concrete by changes in temperature and in moisture content. Concrete, like steel and other structural materials, expands when heated, and contracts when cooled. In general, the coefficient of thermal expansion for concrete is considered to be not much different from that of carbon steel which is 6.5 x 10 -6 per degree F. Therefore, these two materials are assumed to contract or expand together in reinforced concrete structures. [...]
163

Pressure Drop During Evaporation of Water in Tubes.

Yano, George E. January 1953 (has links)
Many flow systems in engineering operations involve the simultaneous transport in pipes of a gaseous (or vapor) phase and a liquid phase. Examples of such systems are numerous; among them are water-steam mixtures in boiler tubes, petroleum liquids and their vapors in tube-stills, liquid-vapor mixtures in refrigeration systems, oil-laden compressed air, condensate return lines, gasoline engine manifolds, partial condensers in fractionation equipment, etc.
164

The physical properties of a Gaspé skarn.

Shih, Tso-min. January 1965 (has links)
This thesis describes the various tests which were carried out on 492 specimens of a Gaspe skarn to determine a number of the physical properties for this particular rock type.[...]
165

A Generalized method for the calculation of supersonic and hypersonic flow behind curved shock waves.

Shih, Lung Yu. January 1964 (has links)
A method of calculating the performance of a hypersonic air intake has been developed. The method is based on the equilibrium flow of a calorically imperfect gas. It is applicable to both axisymmetric and two-dimensional surfaces, the shape of which can be specified by a sixth order polynomial. The method is applicable to both blunt and sharp leading edges. Boundary layer calculations are included. [...]
166

Factors influencing the nitration of polyvinyl alcohol.

Foxlee, Frank Harold. January 1946 (has links)
Note: / The object of tbe investigation was to discover why the nitration of polyvinyl alcohol gave nltrates of highly variable themal stabil1ty. Samples of the comaerolel alcohol were thoroughly purified from soluble, colored impurities and were recovered in e. dry, fibrous form, apparently for the first time. [...]
167

Physical and Mathematical Modelling of Inert Gas Shrouded Ladle Nozzles, and their Role ion Fluid Fl

Chattopadhyay, Kinnor January 2009 (has links)
In the present study inert gas shrouding practices were simulated using a full scale, four strand, water model of a 12 tonne delta shaped tundish. Compressed air was aspirated into the ladle shroud, so as to model volumetric flow rates ranging between 2% and 10% of steel entry flows. Bubble trajectories, slag layer movements, and flow fields, were visualized. Flow fields were visualised using Particle Image Velocimetry (PIV). A numerical model was also developed using Discrete Phase Modelling (DPM), along with the standard K-£ turbulence model with two way turbulence coupling. Predicted flow fields and bubble trajectories were in good agreement with the water model experiments. From both the physical and mathematical modelling results it was evident that reversed flows were generated within the tundish in the vicinity of the ladle shroudwhich swept away the protective layer of slag and thereby created an exposed 'eye' of steel. The area of this exposed 'eye' increased with increasing amount of shroud gas / Dans la présente étude, la technologie d'injection de gaz inerte fut simulée à l'aide d'un modèle pleine grandeur de panier répartiteur d'une capacité de 12 tonnes, en forme delta et possédant quatre drains de coulée. De l'air comprimé fut aspiré dans le jet de coulée du creuset de façon à modéliser des débits volumiques de gaz variant entre 2% et 6% du volume d'acier entrant. Les trajectoires des bulles, les mouvements du laitier, et les champs vectoriels des écoulements furent observés. Les champs d'écoulement furent rendu visibles à l'aide d'un « Particle Image Velocimeter (PlV). Un modèle numérique fut aussi développé en utilisant la modélisation biphasée (Discrète Phase Modelling, DPM) et le modèle standard K-E de turbulence avec couplage bidirectionnel (des bulles au fluide et du fluide aux bulles). Les champs d'écoulement et les trajectoires des bulles prévues concordent bien avec les expérimentations sur le modèle réelle utilisant l'eau. À partir des résultats obtenus des deux modèles, mathématique et physique, il est évident que des écoulements inverses sont formés dans le panier répartiteur autour du jet principal par le gaz injecté. Ces écoulements inverses dispersent la couche protectrice de laitier créant ainsi une zone en forme d'œil exposé à l'air. La surface de cet œil augmente avec le débit de gaz .
168

An Experimental Study of the Earth Pressure Distribution on Cylindrical Shafts

Tobar Valencia, Tatiana January 2009 (has links)
Cylindrical shafts are often used as earth retaining structures for different geotechnical engineering applications (e.g. underground tunnels, pumping stations and hydroelectric projects). Due to their simplicity, classical earth pressure theories are usually used for shaft design. These theories were developed for two-dimensional plane strain problems. Several theoretical methods have been proposed to estimate the axisymmetric active earth pressure on cylindrical shafts, however there is no general agreement on the radial earth pressure distribution along the shaft. In addition, the wall movement needed to reach the calculated pressures is not completely understood. In this thesis, an experimental investigation has been conducted to study the distribution of earth pressure on a cylindrical wall embedded in dry sand and subjected to radial displacements. The initial and progressive changes in earth pressure along the shaft were continuously measured for different wall displacements. The results indicated a rapid decrease in the lateral earth pressure when a small wall movement was introduced. The earth pressure distribution along the shaft reached a minimum uniform value and became independent of any additional wall displacement, when a movement of about 2.5% of the shaft radius, or 0.2% of the wall height, was applied. It was concluded that present design standards overestimate the active earth pressure around cylindrical walls, and the difference between design and actually pressure values increases with depth. The experimental results were also compared with some of the available theoretical solutions for axisymmetric conditions; it was found that at wall movements greater than or equal to about 1 % of the wall height, the measured pressures fell into the pressure range calculated using Cheng and Hu (2005) method. / Les puits cylindriques sont souvent utilisés comme structures de soutènement de sol dans différentes activités géotechniques (ex. tUlli1els souterrains, stations de pompage et projets hydroélectriques). La simplicité des théories classiques de pression du sol est la raison principale pour leurs utilisations dans la conception des puits. Ces théories ont été développées pour les problèmes de déformation plane. Plusieurs méthodes théoriques ont été proposées pour estimer la pression axisymétrique active du sol sur les puits cylindriques, mais il n'existe toujours pas un consensus général sur la distribution radiale des pressions du sol sur les revêtements de puits. En plus, le mouvement nécessaire des murs pour atteindre les pressions calculées n'est pas complètement compris. Dans cette thèse, une investigation expérimentale a été réalisée pour étudier le profil des pressions du sol sur un mur cylindrique enfoui dans du sable sec et contraint à des déplacements radiaux. Le changement initial et progressif des pressions du sol autour des puits a été mesuré constamment pour différents déplacements de murs. Les résultats obtenus ont indiqué une réduction rapide des pressions du sol suite à l'introduction d'un mouvement minime du mur. La distribution des pressions du sol autour des puits a atteint une valeur minimale et uniforme et est devenue indépendante de tout déplacement additionnel du mur quand ce dernier est égal à 2.5% du rayon du puits. En conclusion, les méthodes de conception actuelles surestiment la pression active du sol autour des murs cylindriques, et la différence entre les valeurs de conception et les valeurs actuelles augmentent avec la profondeur. Les résultats expérimentaux ont aussi été comparés avec quelques-unes des solutions théoriques disponibles pour les conditions axisymétriques; on a constaté que pour les mouvements du mur supérieurs ou égaux à environ 1 % de la hauteur du mur, le
169

Virtual display of tactile graphics and Braille by lateral skin deformation

Lévesque, Vincent January 2009 (has links)
Graphical content is increasingly pervasive in digital interfaces and documents yetit remains accessible to visually impaired persons almost exclusively on media withlimited flexibility such as embossed paper. Textual content is more accessible butnevertheless limited by the cost and functionality of refreshable Braille displays andvoice synthesis. This thesis explores the use of a novel tactile stimulation approachthat relies on lateral skin deformation for the computerized display of virtual Brailleand tactile graphics. [...] / Le graphisme gagne en présence dans les interfaces et documents numériques maisest accessible aux personnes non-voyantes quasi-exclusivement sur media à flexibilitélimitée tel que le papier embossé. Le texte est plus accessible mais néanmoins limitépar le coût et les fonctionnalités des afficheurs Braille et de la synthèse vocale.Cette thèse explore l'utilisation d'une nouvelle approche pour la stimulation tactileopérant par déformation latérale de la peau pour l'affichage informatisé de Braille etde graphiques tactiles virtuels. [...]
170

an Investigation into Some Physical Properties of Rocks and their Relationship to Pressure Problems in Mines.

Cameron, E. Lee. January 1954 (has links)
Canada is known throughout the world as one of the fortunate "Have" as contrasted with the less fortunate 'Have not' countries. This is accepted as meaning that, as a country, Canada has been richly endowed with a great variety of high grade mineral deposits. The statement 'Canada has unlimited mineral resources" is encountered time and again in periodicals and the daily press.

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