3,786 research outputs found
A direct A.C. to A.C. regenerative frequency and voltage converter
No full textIncludes bibliographical references.The reliable variable speed operation of an a. c. machine over a wide speed range is a problem that has received attention for some time. In this thesis a system to permit such operation from a fixed frequency fixed voltage supply is proposed, under the name of the asynchronous modulation converter. This converter is of the cycloconverter family, but is force-commutated and is not synchronised with the supply frequency. The power switching element comprises a power transistor in a diode bridge, coupled to the control circuitry by opto-isolators. The output of the a-mod converter is produced by a "chopper" modulation process and this results in the harmonics present being at frequencies well removed from the fundamental. A feedback system to ensure smooth commutation of the output current from the power switches is described. This feedback system operates by sensing the rate of rise of the inductive voltage surge on the load when a switch is opened to operate a freewheel path switch
Religión y política. Manuel Sabino Crespo, un cura párroco del sur de México
No full textValiéndose de Manuel Sabino Crespo, cura que colaboró con el gobierno instalado por Morelos, en Oaxaca y luego abrazó la causa insurgente, el artículo busca conocer cómo era la vida de un cura párroco en el sur de México y cuáles eran los alcances de su formación intelectual. Gracias a la información proveniente de las bibliotecas locales y particulares de los eclesiásticos, y en especial al registro de la participación de Crespo en las actas del cabildo catedralicio, es posible apreciar las fuentes en las que abrevaron los insurgentes para defender sus posturas en materia eclesiástica y cuáles fueron sus argumentos
La crisis de la República en el siglo I a.C.
No full textEl presente trabajo trata de analizar las causas y consecuencias de la crisis de la República romana durante el siglo I a.C. Con este fin de expondrá de manera cronológica los acontecimientos acaecidos desde los hermanos Graco hasta el fin de la República romana, y los principios en los que se basaba, finalizando con la instauración de la dictadura por Octavio Augusto en el año 27 a.C. Asimismo, se estudiarán los cambios que fueron impuestos tanto jurídicos como políticos impuestos por personalidades tan conocidas como Mario, Sila o Julio César. Del mismo modo, será expuesta la inestabilidad política y las continuas guerras entre las facciones de optimates y populares que se produjeron cuyo fin era alcanzar el poder.Departamento de Derecho Penal e Historia y Teoría del DerechoGrado en Derech
Zane Grey with Orange A.C. baseball team
No full textThis photograph shows Ohio native Zane Grey with the Orange A.C. Baseball Team, ca. 1896-1904. Prior to becoming a well-known author of western novels, Zane Grey was also a dentist and a semi-professional baseball player, with teams including the Orange Athletic Club and the Newark (New Jersey) Colts
Sobre Eberhard Crailsheim, The Spanish Connection. French and Flemish Merchant Networks in Seville (1570-1650)
No full textPeer reviewe
Experimental research on spatial distribution of overtopping
No full textThe overtopping empirical formulas calculate the discharge only at the top of the crest of a coastal protection structure. On the other hand, the tolerable overtopping discharges are defined at certain points behind the crest where the total overtopping is reduced. The scope of this thesis is to find an empirical formula to describe the distribution of overtopping at the space behind the crest. This thesis comes as a further investigation on the work conducted by v.Kester [2009] for regular waves. In this research, a physical model was developed on which irregular waves are tested. Because of the duration of the tests and the amount of collected water (significant lose of water during the test), a completely new measuring system was designed. Five influencing parameters (variables) are considered on this research: wave height, wave period/steepness, slope angle, crest freeboard and crest permeability. The entire overtopping process is analysed separately for the total overtopping discharge, the overtopping discharge directly behind the crest and the distribution of overtopping behind the structure. In the analysis of the data collected from the measurements, the impact of the varying parameters is investigated leading to useful conclusions and better understanding of the entire process. Additionally, the experimental findings are analysed and compared to the relative existing methods. Based on the TAW [2002] method which is proposed by the EurOtop Manual [2007], a prediction formula is developed. This formula is a generic version of TAW [2002] formula in which a new reduction factor ?c is introduced in order to describe the decay of the overtopping and thus predict the discharge at any certain distance behind the crest. Other relevant methods are also analysed (Juul Jensen [1984], Steenaard [2002], Besley [1999] and v.Kester [2009]) and conclusions for their applicability are drawn leading to suggested improvements or corrections. Apart from the distribution of overtopping, on this thesis the determination of crest freeboard (which is an ambiguous issue) is also investigated. Finally, suggestions of further research on this topic are discussed. The entire work has been perfomed in close cooperation with van Oord.Hydraulic EngineeringCivil Engineering and Geoscience
Flow over partially liquid filled cavity
No full textExperiments have been carried out to investigate the effect of liquid cavity filling on the behavior of the gas flow over a flat plate cavity. PIV measurements in the gas phase reveal that cavity filling can affect vortex shedding in the cavity mouth. Shear layer vortices can break-up into smaller vortices, thereby losing their periodic interaction with the aft wall and, hence, their sound producing potential. Expected is that this is one of the mechanisms causing sound mitigation in corrugated pipes with liquid addition, observed in literature
On modular lattices generated by chains
No full textDe La Maza, A.C. (reprint author). Instituto de Matematica y Fisica, Universidad de Talca. Casilla 747, Talca, Chile.We describe the free modular lattice generated by two chains and a single point, under the assumption that there are few meets
Antiguo Oriente: Cuadernos del Centro de Estudios de Historia del Antiguo Oriente, 2003, n° 1 (número completo)
No full textPrólogo -- Sustrato y continuidad cultural en la Edad de Hierro: el caso del Negev y el sur de Jordania / Juan Manuel Tebes -- Consideraciones sobre la organización sociopolítica anterior al advenimiento del Estado en el valle del Nilo / Marcelo Campagno -- El pasado de Israel en el Antiguo Testamento / Emanuel O. Pfoh -- Relaciones interétnicas entre libios y egipcios (siglos XII-VII a.C.) / Celeste María Crespo -- Ritualidad en el Antiguo Egipto: el Festival de Sed / Roxana Flammini -- Dualidad enterratoria en el Reino Medio: Sesostris III y sus complejos funerarios en Dahshur y Abidos / Roxana Flammini -- Reseñas Bibliográficas -- Normas para publicacione
Integrated assessment of climate change impacts on staple food production in southern Africa
No full textSpeakers: Dr Charles Nhemachema, EPDat HSRC, Dr Yacob Beletse, Crop Science, ARC, Dr Olivier Crespo, Climate System Analysis Group, University of Cape Town, 15 Jul
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