4,146 research outputs found
Multiscale thermo-hydraulic modeling of cryogenic heat exchangers
No full textThe cryogenic industry has experienced a continuous growth in the last decades, partially sustained by the worldwide development of Liquefaction of Natural Gas (LNG) projects. LNG technology provides an economically feasible way of transporting natural gas over long distances, and currently accounts for nearly 30% of the international trade of this resource. The economic feasibility of these projects, in terms of both capital and operating costs, is to a large extent controlled by the performance of the main cryogenic two-phase flow heat exchanger. This industrial scenario provides then the motivation for a detailed study of the heat exchanger from a design perspective. On the one hand, it is widely accepted that a highly detailed analysis is required at a micro scale to properly take account of the two phase heat transfer process. On the other hand, a process-level description corresponds to larger time and space scales. In general, determining the proper methodology for considering these scales and their interaction remains a challenging problem. For this reason, current techniques focus in only one particular scale. The main objective of this project is then to develop a multiscale model applicable for two-phase flow heat exchangers. In this context, a three-scale framework is postulated. This thesis was divided into macro, meso (medium) and micro scale analysis. First, a macroscopic analysis provides a broad description in terms of overall heat transfer and pressure drop, using simple models without taking into account the details of physical phenomena at lower scales. Second, at mesoscale level, flow in parallel channels is considered following a homogenization approach, thus including the effects of flow maldistribution and partial mixing. Third, the microscopic description conceives a phenomenological representation of boiling flows, following multifluid formulations, for two specific flow patterns: annular-mist and post-dryout regimes. Finally, a multiscale design algorithm is proposed.PhD i energi- og prosessteknikkPhD in Energy and Process Engineerin
Latin America's experience with export subsidies
No full textTwenty years ago, it ws believed that export subsidies would produce more diversification and better export performance. This has not happened. In most cases, export subsidies were not supported by more open import policies - so subsidies reduced only marginally the anti-export bias of Latin American countries. Unstable real exchange rates have also hurt exports. Export subsidies appear to have improved exports in Brazil, which also liberalized imports, stabilized exchange rates, and promoted other policies conducive to export growth. Yet Mexico, after reducing import barriers, also enjoyed improved exports - with minimum export subsidies, and with apparently lower social costs than Brazil experienced. Export subsidies have failed in other Latin American countries - and particularly hurt development in Argentina, where fraud, corruption, and rent-seeking have been rampant. The author contends that the failure of export subsidies should remind us of the importance of distinguishing what is possible from what is likely. Finally, export subsidies compete with other government programs, and, considering their failure rate, the money might be better spent on infrastructure, health, and education projects.Tax Law,Economic Theory&Research,TF054105-DONOR FUNDED OPERATION ADMINISTRATION FEE INCOME AND EXPENSE ACCOUNT,Environmental Economics&Policies,Economic Stabilization
Liquid Metals as Efficient High-Temperature Heat-Transport Fluids
No full textLiquid metals appear to be attractive heat-transport fluids, in particular if looking at their high thermal conductivities and low viscosities. Despite some pioneering technical applications in the past, complex handling, special requirements, safety concerns, and structural degradation of the materials have prevented their widespread application. However, progress in research and development on liquid-metal science and technology has advanced considerably in the last decade, and this has opened the gate to their broader use in the short term. This requires a more differentiated view on liquid metals, particularly on the specific properties of individual fluids within the context of specific applications. By doing so, many commonly mentioned prejudices vanish or are of minor significance. At the Karlsruhe Institute of Technology, a comprehensive research program on liquid-metal technology has been pursued for more than 50years, and some of the advances in different applications will be outlined in this article
Política cultural: Julio Cesar Trujillo
No full textThe text, a lecture by Dr. Julio César Trujillo, analyzes the period of transition Ecuador is experiencing, marked by the emergence of new times starting in the 1970s, driven by industrialization, urbanization, and oil exploitation. Trujillo argues that the country is at the threshold of a new era , where old values and ways of life are losing relevance, while new ones are not yet fully defined, generating deep social insecurity and confusion. It details how this transformation affects spheres such as the economy (gigantic projects), culture (mass media), politics (loss of the religious-based left/right division), and daily life (multifamily housing, new needs, and greater demand for job specialization). The author stresses that modern science and technology are advancing rapidly, have become a costly commodity, and require a specialization that the country lacks, exacerbating external dependence. In this context, Trujillo insists on the urgent need to design a cultural policy for Ecuador to rescue its own values, build a more just and humane society (addressing social marginalization) , and overcome the national characteristic of being a culturally fragmented and disintegrated people.El texto, una conferencia de Dr. Julio César Trujillo, analiza el período de transición que vive Ecuador, marcado por la emergencia de nuevos tiempos a partir de la década de 1970, impulsados por la industrialización, la urbanización y la explotación petrolera. Trujillo argumenta que el país se encuentra en los umbrales de una nueva época , donde los antiguos juicios de valor y modos de vida están perdiendo vigencia, mientras que los nuevos aún no están plenamente definidos, generando una profunda zozobra, inseguridad y confusión social. Se detalla cómo esta transformación afecta esferas como la economía (obras gigantescas), la cultura (medios de comunicación), la política (pérdida de la división izquierda/derecha por motivos religiosos), y la vida diaria (vivienda multifamiliar, nuevas necesidades, y mayor exigencia de especialización laboral). El autor subraya que la ciencia y la tecnología modernas avanzan rápidamente, se han convertido en una mercancía costosa y requieren una especialización de la que el país carece, exacerbando la dependencia externa. En este contexto, Trujillo insiste en la urgente necesidad de diseñar una política cultural para Ecuador que permita rescatar los valores propios, construir una sociedad más justa y humana (abordando la marginación social) , y superar la característica nacional de ser un pueblo culturalmente escindido y desintegrado
Multiscale thermo-hydraulic modeling of cryogenic heat exchangers
No full textThe cryogenic industry has experienced a continuous growth in the last decades, partially sustained by the worldwide development of Liquefaction of Natural Gas (LNG) projects. LNG technology provides an economically feasible way of transporting natural gas over long distances, and currently accounts for nearly 30% of the international trade of this resource. The economic feasibility of these projects, in terms of both capital and operating costs, is to a large extent controlled by the performance of the main cryogenic two-phase flow heat exchanger. This industrial scenario provides then the motivation for a detailed study of the heat exchanger from a design perspective. On the one hand, it is widely accepted that a highly detailed analysis is required at a micro scale to properly take account of the two phase heat transfer process. On the other hand, a process-level description corresponds to larger time and space scales. In general, determining the proper methodology for considering these scales and their interaction remains a challenging problem. For this reason, current techniques focus in only one particular scale. The main objective of this project is then to develop a multiscale model applicable for two-phase flow heat exchangers. In this context, a three-scale framework is postulated. This thesis was divided into macro, meso (medium) and micro scale analysis. First, a macroscopic analysis provides a broad description in terms of overall heat transfer and pressure drop, using simple models without taking into account the details of physical phenomena at lower scales. Second, at mesoscale level, flow in parallel channels is considered following a homogenization approach, thus including the effects of flow maldistribution and partial mixing. Third, the microscopic description conceives a phenomenological representation of boiling flows, following multifluid formulations, for two specific flow patterns: annular-mist and post-dryout regimes. Finally, a multiscale design algorithm is proposed
Casa Tomada by Julio Cortazar
No full textThe student analyzes the short story, Casa Tomada, by Julio Cortazar, with regard to story elements, form, author, historical context, and effects
Política cultural: Julio Cesar Trujillo
No full textThe text, a lecture by Dr. Julio César Trujillo, analyzes the period of transition Ecuador is experiencing, marked by the emergence of new times starting in the 1970s, driven by industrialization, urbanization, and oil exploitation. Trujillo argues that the country is at the threshold of a new era , where old values and ways of life are losing relevance, while new ones are not yet fully defined, generating deep social insecurity and confusion. It details how this transformation affects spheres such as the economy (gigantic projects), culture (mass media), politics (loss of the religious-based left/right division), and daily life (multifamily housing, new needs, and greater demand for job specialization). The author stresses that modern science and technology are advancing rapidly, have become a costly commodity, and require a specialization that the country lacks, exacerbating external dependence. In this context, Trujillo insists on the urgent need to design a cultural policy for Ecuador to rescue its own values, build a more just and humane society (addressing social marginalization) , and overcome the national characteristic of being a culturally fragmented and disintegrated people.El texto, una conferencia de Dr. Julio César Trujillo, analiza el período de transición que vive Ecuador, marcado por la emergencia de nuevos tiempos a partir de la década de 1970, impulsados por la industrialización, la urbanización y la explotación petrolera. Trujillo argumenta que el país se encuentra en los umbrales de una nueva época , donde los antiguos juicios de valor y modos de vida están perdiendo vigencia, mientras que los nuevos aún no están plenamente definidos, generando una profunda zozobra, inseguridad y confusión social. Se detalla cómo esta transformación afecta esferas como la economía (obras gigantescas), la cultura (medios de comunicación), la política (pérdida de la división izquierda/derecha por motivos religiosos), y la vida diaria (vivienda multifamiliar, nuevas necesidades, y mayor exigencia de especialización laboral). El autor subraya que la ciencia y la tecnología modernas avanzan rápidamente, se han convertido en una mercancía costosa y requieren una especialización de la que el país carece, exacerbando la dependencia externa. En este contexto, Trujillo insiste en la urgente necesidad de diseñar una política cultural para Ecuador que permita rescatar los valores propios, construir una sociedad más justa y humana (abordando la marginación social) , y superar la característica nacional de ser un pueblo culturalmente escindido y desintegrado
Notas etnográficas sobre el racismo: una perspectiva reflexiva. 4 Segunda época Año 2 (2018) julio-diciembre. Rutas de Campo. Trabajo de Campo: Experiencias para entretejer la antropología
No full textBarquín, Alfonso (2015). Antropología y poder político. El ejercicio de poder en las políticas de educación inter-cultural. México: INAH.Bartolomé, Miguel Alberto (1997). Gente de costumbre y gente de razón. Las identidades étnicas en México. México: INI. / Siglo XXI.Cardoso, Roberto (2007). Etnicidad y estructura social. México: CIESAS/UIA/UAM.Fuente, Julio de la, y Aguirre Beltrán, Gonzalo (1989). Relaciones interétnicas. México: Conaculta.Navarrete, Federico (2004). Las relaciones interétnicas en México. México: UNAM.Oehmichen, Cristina (2005). Identidad, género y relaciones interétnicas. Mazahuas en la Ciudad de México. México: IIA-PUEG-UNAM.Stavenhagen, Rodolfo (1968). Clases, colonialismo y aculturación. Ensayo sobre un sistema de relaciones interétnicas en Mesoamérica. Guatemala: Ministerio de Educación.Velázquez, María Elisa, y Correa, Ethel (2005). Poblaciones y culturas de origen africano en México. México: INAH._____, e Iturralde, Gabriela (2012). Afrodescendientes en México. Una historia de silencio y discriminación. México: Conapred / INAH.Wolf, Eric (2001). Figurar el poder. Ideologías de dominación y crisis. México: CIESAS
- …
