145 resultados para Chevron


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Richly elegant copy of the Dīvān of the masterful poet Ḥāfiẓ (Khvājah Shams al-Dīn Muḥammad Shīrāzī, d.1390?).

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This Ph.D. thesis addresses current issues with ichnotaxonomic practice, and characterizes an exceptionally well preserved ichnological assemblage from the Carboniferous Stainmore Formation, Northumberland, United Kingdom. Samples were collected from closely localized float representative of various units throughout the succession, which was deposited in a storm-dominated marine shoreface. Three dominant ichnotaxa were selected for three-dimensional morphological analysis due to their complicated morphology and/or unclear taxonomic status: 1) Dactyloidites jordii isp. nov.; 2) Beaconites capronus, and; 3) Neoeione moniliformis comb. nov. Using serial grinding and photography, these ichnotaxa were ground and modelled in true colour. High-resolution models of three taxa produced in this study are the basis of the first complete three-dimensional consideration of the traces, and forms the basis for refined palaeobiological and ethological analysis of these taxa. Dactyloidites jordii isp. nov. is a stellate to palmate burrow composed of numerous long, narrow rays that exhibit three orders of branching arranged into tiered galleries radiating from a central shaft. It is considered to be the feeding structure produced by a vermiform organism. Beaconites capronus is a winding trace with distinctly chevron-shaped, meniscate backfill demonstrated herein to backfill the vertical shafts associated with its burrows in a comparable fashion to the horizontal portion of the burrow. This lack of a surface connection would result in the trace making organism being exposed to low-oxygen porewater. Coping with this porewater dysoxia could be approached by burrowing organisms in a number of ways: 1) revisiting the sediment-water interface; 2) creating periodic shafts; or 3) employing anaerobic metabolism. Neoeione moniliformis was originally introduced as Eione moniliformis, however, the genus Eione Tate, 1859 is a junior homonym of Eione Rafinesque, 1814. This led to the transfer of Eione moniliformis to Parataenidium. Through careful examination and three-dimensional characterization of topotypes, the transfer to Parataenidium moniliformis is demonstrated herein to be problematic, as Parataenidium refers to primarily horizontal burrows with two distinct layers and Eione moniliformis is composed of one distinct level. As such, the new ichnogenus Neoeione is created to accommodate Neoeione moniliformis.

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We appreciate very helpful reviews by Dr. Martin Stokes and three anonymous reviewers and editor Dr. Richard Marston. We also appreciate the encouragement for writing this paper from Dr. Timothy Horscroft. We acknowledge support of the sponsors of the Fluvial Systems Research Group consortium, BP, BG, Chevron, ConocoPhillips and Total.

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We appreciate very helpful reviews by Dr. Martin Stokes and three anonymous reviewers and editor Dr. Richard Marston. We also appreciate the encouragement for writing this paper from Dr. Timothy Horscroft. We acknowledge support of the sponsors of the Fluvial Systems Research Group consortium, BP, BG, Chevron, ConocoPhillips and Total.

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Copyright © 2015 Elsevier B.V. All rights reserved. Acknowledgements M. M. Lawan for his helpful discussions about Se and advice on ICP-MS. C. C. Brombach for his introduction to CV-AFS and to D. Bellis for valuable comments and reviewing the English language in the manuscript. ZG would also like to thank the College of Physical Sciences at the University of Aberdeen and Chevron USA for the provided studentship. FLR and AB acknowledge Scottish Marine Animal Stranding Scheme and Marine Scotland for the funding.

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This work was supported by the Fluvial Systems Research Group sponsors BG Group, BP, Chevron, ConocoPhilips, and Total. We thank reviews from Martin Stokes, an anonymous reviewer and Editor Stuart Jones.

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Two-phase flow heat exchangers have been shown to have very high efficiencies, but the lack of a dependable model and data precludes them from use in many cases. Herein a new method for the measurement of local convective heat transfer coefficients from the outside of a heat transferring wall has been developed, which results in accurate local measurements of heat flux during two-phase flow. This novel technique uses a chevron-pattern corrugated plate heat exchanger consisting of a specially machined Calcium Fluoride plate and the refrigerant HFE7100, with heat flux values up to 1 W cm-2 and flow rates up to 300 kg m-2s-1. As Calcium Fluoride is largely transparent to infra-red radiation, the measurement of the surface temperature of PHE that is in direct contact with the liquid is accomplished through use of a mid-range (3.0-5.1 µm) infra-red camera. The objective of this study is to develop, validate, and use a unique infrared thermometry method to quantify the heat transfer characteristics of flow boiling within different Plate Heat Exchanger geometries. This new method allows high spatial and temporal resolution measurements. Furthermore quasi-local pressure measurements enable us to characterize the performance of each geometry. Validation of this technique will be demonstrated by comparison to accepted single and two-phase data. The results can be used to come up with new heat transfer correlations and optimization tools for heat exchanger designers. The scientific contribution of this thesis is, to give PHE developers further tools to allow them to identify the heat transfer and pressure drop performance of any corrugated plate pattern directly without the need to account for typical error sources due to inlet and outlet distribution systems. Furthermore, the designers will now gain information on the local heat transfer distribution within one plate heat exchanger cell which will help to choose the correct corrugation geometry for a given task.

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A recuperação da energia térmica do escape afigura-se como uma vertente com importância relevante para o aumento da eficiência energética dos motores de combustão interna, tendo benefícios em termos económicos e ambientais. O presente trabalho centra-se no estudo e dimensionamento do condensador a integrar num sistema de ciclo de Rankine, tendo-se optado pela seleção de um permutador de placas do tipo “chevron”. O permutador para efeitos de cálculo é dividido em três zonas distintas: i) pré-arrefecedor; ii) condensador e iii) sub-arrefecedor. O presente estudo apresenta uma revisão bibliográfica alargada para o coeficiente de transferência de calor por convecção e perda de carga associada ao escoamento. Para cada zona do permutador são utilizados três fluidos de trabalho distintos: água, etanol e R245fa. Para o fluido refrigerante considerou-se água. Tendo em conta a revisão bibliográfica efetuada, foram implementados modelos para a perda de carga e para a transferência de calor no permutador, atendendo à seleção do fluido de trabalho e ao fluido refrigerante. Os resultados obtidos permitiram verificar que a utilização do fluido de trabalho água, conduz a um condensador mais compacto. Por último é efetuada a otimização do sistema, mediante alteração da temperatura de funcionamento do permutador. Os resultados permitiram verificar a diminuição da temperatura de saída do fluido refrigerante possibilita: i) uma redução do volume do permutador; ii) uma diminuição da perda de carga associada.

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Este estudio de caso analiza las razones por las cuales México adelantó una reforma constitucional en materia energética en 2013, y el interés que tuvo Estados Unidos en esta, puesto que se destaca la intención del gobierno estadounidense de convertir a América del Norte en una región más sólida. Es así como se exponen las razones por las cuales México decide reformar su constitución y por esa vía tener un impacto directo en Petróleos Mexicanos (Pemex), la cual es la mayor compañía del país, encargada de adelantar los procesos de exploración y explotación de hidrocarburos. Asimismo, se explica el interés de Estados Unidos en el tema del intercambio de hidrocarburos, ya que es primordial para lograr la seguridad energética en Norteamérica, una región donde se está realizando extracción de gas y petróleo a través del fracking, un método no convencional, que ha propiciado un nuevo panorama en los recursos energéticos.

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El presente estudio de caso analiza el papel de la Cooperación Sur-Sur (CSS) proveída por Brasil y Ecuador en materia de Educación Técnica en Haití después del terremoto del 2010 hasta el año 2015. Bajo el entendido que la CSS busca intercambiar, por medio de proyectos, los conocimientos y técnicas en los cuales estos países tienen experiencia, una de las formas de cooperación que tienen Brasil y Ecuador frente a Haití está basada en brindar capacidades en materia de Educación Técnica, con el fin de incentivar el desarrollo del recurso humano en los diferentes sectores a los cuales ésta va dirigida. En ese sentido, se escogieron dichos países al ser dos de los que más aportaron de América del Sur mediante la Educación Técnica hacia Haití después del terremoto. De ésta forma queda demostrado que por medio del intercambio de conocimientos, se puede hacer una apuesta fundamental al desarrollo de un país, enseñando y capacitando a personal de áreas específicas, con el ánimo de aumentar las capacidades productivas.