Improvements in CO2 Booster Architectures with Different Economizer Arrangements.

CO2 transcritical booster architectures are widely analyzed to be applied in centralized commercial refrigeration plants in consonance with the irrevocable phase-out of HFCs. Most of these analyses show the limitations of CO2 cycles in terms of energy e ciency, especially in warm countries. From the literature, several improvements have been proposed to raise the booster e ciency in high ambient temperatures. The use of economizers is an interesting technique to reduce the temperature after the gas cooler and to improve the energy e ciency of transcritical CO2 cycles. The economizer cools down the high pressure’s line of CO2 by evaporating the same refrigerant extracted from another point of the facility. Depending on the extraction point, some configurations are possible. In this work, di erent booster architectures with economizers have been analyzed and compared. From the results, the combination of the economizer with the additional compressor allows obtaining energy savings of up to 8.5% in warm countries and up to 4% in cold countries with regard to the flash-by-pass arrangement and reduce the volumetric displacement required of the MT compressors by up to 37%

Experimental determination of the optimum working conditions of a transcritical CO2 refrigeration plant with integrated mechanical subcooling

Subcooling methods for transcritical CO2 plants are being studied in order to improve their behavior. Among them, the Integrated Mechanical Subcooling system is one of the most promising owing that performs with high efficiency and it is a total-CO2 system. This work presents the experimental determination of the optimum working conditions of a transcritical CO2 plant working with an integrated mechanical subcooling system. The plant was tested at different pressure and subcooling conditions in order to optimize the COP of the plant and determine the optimal conditions for three ambient temperatures 25.0 °C, 30.4 °C and 35.1 °C and evaporation levels between −15.6 °C and −4.1 °C. Optimum operating conditions were determined and two correlations are proposed to determine the optimal pressure and subcooling as function the gas-cooler outlet temperature and the evaporation level

Environmental impact assessment of vernacular thatch building tradition in Mexico: Case studies of three palm species and related technology along the Trans-Mexican Volcanic Belt

This project involves research into vernacular buildings, in particular traditional and contemporary coastal palm thatch buildings in the middle-west coast deciduous forest environments in Mexico. The fieldwork-based grounded theory research investigates the natural materials and techniques involved in constructing thatched vernacular buildings using three different palm species (Attalea guacuyule, Brahea dulcis and Sabal rosei) in different climatic contexts along the Trans Mexican Volcanic Belt (TMVB). The aim is to achieve a holistic approach to the environmental assessment of these building types through a life-cycle assessment. The present research emerges from the premise that vernacular buildings are generally taken for granted as sustainable, and yet they are under-investigated meaning this assumption may not be correct. In general the performance of vernacular buildings in terms of sustainability and in relation to their embodied energy is under reported, particularly in terms of vernacular case studies in Mexico. However the deterioration of the environments where such buildings are located through anthropogenic causes is of world-wide importance, therefore it is a priority for this research to study the relationship of the vernacular traditions with their immediate environment. The first section of the thesis analyses theoretical frameworks for sustainability and vernacular architecture. Both terms are widely used and carry many different meanings, so it is important to establish the definitions used in this research to better set the boundaries of the study as a basis for seeking the best methods for assessing the environmental impact of the selected vernacular thatch building technologies. The second section undertakes qualitative and quantitative fieldwork on traditional practices of palm thatch buildings in selected regions of Mexico and related case studies, six in total. The fieldwork was combined with investigation into ethnographical, ethnobotanical and historical records and data for the three palms used for thatching and their related materials and technologies in order to derive data concerning yield factors, lifespan of the building materials, carrying capacities, embodied energy of transport and embodied energy of materials. The third section applies the collected information for a life-cycle environmental assessment (LCA) of two typical buildings for each of the three different palm species and the diverse techniques involved. The assessment is carried out based on various assumptions that are commonly used in LCA to give a carbon account and an ecological footprint for each building component both after construction and for a 50 year building life. However, during the research particular variables in the analysis were revealed, such as operating energy, recycling of building elements, durability of materials and transport practices, which can vary widely from case to case, therefore the limits and scope of the assessment excluded such data for a better comparative scenario of the building process itself. This suggests that a different way of life-cycle accounting may be needed when assessing vernacular structures. The results show the environmental impact of these techniques in terms of carbon and ecological footprints, and reveal that the rural vernacular case studies had lower environmental impacts than the suburban and urban vernacular case studies as measured by their carbon content, energy expressed in Giga Joules (GJ) and their ecological footprints

Materias primas para la fabricación de clinker de cemento portland en el área de Madrid.

En Madrid y su area de influencia se ha incrementado la demanda de materiales de construcción, como consecuencia del espectacular desarrollo de las obras de infraestructura y de la edificación. Los problemas derivados del impacto ambiental y la futura expansión y/o renovación de las plantas de fabricación de cemento portland, aconsejan una investigación en el area, de las materias primas para la fabricación de clinker. Los materiales aflorantes en la cuenca Terciaria sobre la que se asienta Madrid, han sido divididos en tres unidades estratigráficas, con importantes diferencias litológicas. La Unidad Superior, presenta un volumen de mas de 1500 Mt de calizas de buena calidad para ser usadas como componente principal . La Unidad Inferior o Salina, esta formada localmente por sedimentos lutítico-arcillosos, que pueden ser usados en función de su naturaleza mineralógica y química, como un buen componente secundario. Estos materiales constituyen la materia prima para la fabricación de cerámica basta, por lo que en algunas zonas ambos tipos de uso deben de coexistir. Los yesos detríticos y primarios de la Unidad Intermedia, pueden ser usados como componente regulador de fraguado. Los modelos de dosificación elaborados muestran que no es necesaria la adición de un tercer componente al crudo del portland, para obtener una composición química adecuada

Ezagutza baseak itzultzaile neuronaletan

Proiektu honetan itzulpen automatikoko sistemetan kanpoko ezagutza sartzea aztertzen da gaur egungo arloaren egoeraren arkitekturan, Transformerran, itzulpenak hobetzeko asmoz. Testuetan maiz agertzen ez diren hitzak, domeinu jakin bateko hitz eta termino teknikoak izan ere, itzultzea zaila da itzultzaile automatikoentzat. Horregatik, kanpoko ezagutza sartzea onuragarria da emaitza hobeak lortzeko. RNNetan erabili diren hurbilpenak aztertzen dira eta Transformerrarentzako berri bat diseinatzen da, arkitektura honek erabiltzen duen teknologiaz aprobetxatuz, autoarreta. Emaitzak ebaluatzeko domeinu biomedikoko testuen itzulpenen kalitatea aztertzen da. SNOMED CT ontologia klinikokoak batzen dituen terminoak eta hemendik ikasitako termino hauen errepresentazioak, word embeddingak, erabiltzen dira kanpoko ezagutza bezala

Control remoto de un drone

En este proyecto se presenta una alternativa al control remoto convencional de un drone cuadricóptero. En este caso, se ha desarrollado un sistema que permite controlar un drone mediante el movimiento de una sola mano. La idea se basa en poder controlar el cuadricóptero con los movimientos naturales de la mano. Si se quiere elevar el drone, se debe elevar la mano. Así mismo, para rotar el drone, rotar la mano. Y por último, si se desea inclinar el drone, simplemen te se debe inclinar la mano. Para poder capturar estos movimientos se requiere de una unidad de medición inercial o IMU (la cual debe incorporar como mínimo un acelerómetro y magnetómetro de tres ejes) y un sensor de ultrasonidos. Añadir también, que para gestionar estos periféricos y otros adicionales se necesita un microcontrolador. Por último se diseña una placa de circuito impreso o PCB donde conectar el microcontrolador con los diferentes periféricos necesarios. También se ha diseñado y fabricado un chasis donde se aloja todo el sistema

La perspectiva académica en las políticas públicas educativas en México. El caso de la Universidad Veracruzana

1 archivo PDF (9 páginas). magyeoipRESUMEN: Las políticas públicas están enfocadas a orientar y regir la actuación de la autoridad en un sector determinado, encaminado a su ejecución, y aquí documentaremos cómo son observadas las políticas educativas en una institución de educación superior. Nuestro objetivo es conocer la percepción de los académicos de la Universidad Veracruzana, en la región Veracruz, específicamente del área académica económica-administrativa, respecto a las políticas educativas. En la primera parte se presenta la perspectiva organizacional del tema con autores como Simon y Lindblom, Cohen, March y Olsen; se da sustento teórico al concepto de políticas públicas con autores como Cabrero y Pardo. Posteriormente se comenta un ejemplo de América Latina —Chile específicamente— de cómo la participación ciudadana ha coadyuvado en la definición, normatividad y ejecución de las políticas educativas. En segundo lugar, se resumen los objetivos del programa sectorial de educación para el periodo 2007-2012, y, para el énfasis que se pone en la calidad educativa como uno de los ejes de las políticas educativas en nuestro país, se expone el sustento teórico de Crozier. En la tercera parte se presentan los resultados de una encuesta aplicada a los académicos de la Universidad Veracruzana para conocer su participación en las políticas públicas educativas. Abstract Here we are able to see troubles of public politics in the High Educational System of Mexico. Public politics are focused to direct and govern authorities in a given sector and their executions. We will see how educational politics are observed in a high education institution. The objective of this work is to know the Veracruzana University academics’ perception, Veracruz locality, specifically in the economic-management areas with respect of the educational politics. In the first part, you will see the organizational perspective from Simon and Lindblom, Cohen, March and Olsen; it gives theoretical support to the public politic concept from Caballero and Pardo. Later it comments about a Latin America example –Chile specifically– on which citizen participation has helped in definition, regulation and execution of the educational politics. In the second part, you will find an educational sector program objectives 2007-2012 summary and the emphasis on educational quality as a main line of the educational politics in Mexico, based on Crozier theoretical support. In the third part, youwill find results from academics’ interview from the Veracruzana University in order to know their participation in educational public politics. PALABRAS CLAVE: Veracruz, educación. KEYWORDS: Veracruz, educatio

Evaluation of Natural Rubber Specific Heat Capacity at High Pressures from DSC Experimental Data at Atmospheric Pressure

[EN] The natural rubber specific heat capacity dependence on pressure was estimated on thermodynamic grounds on the basis of the values empirically determined from differential scanning calorimetry data, (in the temperature range of 70 to 50 C), and by means of the Tait equation of state (in the pressure range of 0.1 240 MPa). It was found that the specific heat capacity decreases with pressure, being the dependency more pronounced at low pressures.This work was financially supported by the DGCYT through Grant MAT2008-06725-C03 and by Generalitat Valenciana through Grant No. ACOMP/2010/204.Ortiz Serna, MP.; Díaz Calleja, R.; Sanchis Sánchez, MJ. (2012). Evaluation of Natural Rubber Specific Heat Capacity at High Pressures from DSC Experimental Data at Atmospheric Pressure. Journal of Applied Polymer Science. 128(4):2269-2272. doi:10.1002/app.38118S22692272128

Relaxation behavior of semiflexible polymers at very low frequencies

[EN] The dielectric activity of poly(monocyclohexylmethylene itaconate) (PMCI) and poly(dicyclohexylmethylene itaconate) (PDCI) in the glassy region and in the glass-rubber transition is studied by thermostimulated discharge current (TSDC) techniques. The spectra obtained by global TSDC experiments show a prominent alpha-glass-rubber relaxation peak with maxima located at 97 and 55 degrees C for PMCI and PDCI, respectively, following in decreasing order of temperature for a well developed beta absorption and a comparatively low intensity relaxation. Better resolution of the relaxation behavior of these polymers in the glassy region is obtained by calculating the components of the complex dielectric permittivity epsilon* at extremely low frequencies from partial TSDC experiments. The ac spectra thus obtained suggest that the beta absorption is composed by two relaxations, each of them presumably associated with the motions of a side group. The differences observed in these spectra with those reported for the beta mechanical relaxation reported for these polymers in the literature are interpreted in terms of the restrictions that the side groups produce in the conformational space of phase of the backbone. These restrictions also explain the small changes in enthalpy in the glass-rubber transition which preclude the possibility of obtaining the glass-rubber transition temperature of these polymers by differential scanning calorimetric techniques. (C) 1997 American Institute of Physics.Díaz Calleja, R.; Sanchis Sánchez, MJ.; Alvarez, C.; Riande, E. (1997). Relaxation behavior of semiflexible polymers at very low frequencies. Journal of Applied Physics. 81(8):3685-3691. doi:10.1063/1.364743S3685369181