Thermal and electrohydrodynamic plumes: a compartive study

This paper deals with self similar thermal and electrohydrodynamic (EHD) plumes. The former arises from hot lines or points, whereas the latter arises when sharp metallic contours submerged in non conducting liquids support high electrostatic potential, resulting in charge injection. Although the motive force is buoyancy in one case and Coulomb force in the other, it is shown that the solution for EHD plumes is the same as for thermal plumes in the limit of large Prandtl numbers. We present the analysis of axisymmetric plumes for large values of Prandtl number, and this analysis is subsequently applied to EHD plumes. The validity of the approximations for EHD plumes is discussed in the light of experimental data.Ministerio de ciencia y tecnología PB93-118

Phase only transmit beamforming for spectrum sharing microwave systems

This paper deals with the problem of phase-only transmit beamforming in spectrum sharing microwave systems. In contrast to sub-6 GHz schemes, general microwave systems require a large number of antennas due to its huge path loss. As a consequence, digital beamforming needs a large number of computational resources compared to analog beamforming, which only needs a single radio-frequency chain, results the less computational demanding solution. Analog schemes are usually composed by a phase shifter network whose elements transmit at a certain fixed power so that the system designer shall compute the phase values for each element given a set of directions. This approach leads to non-convex quadratic problems where the traditional semidefinite relaxation fails to deliver satisfactory outcomes. In order to solve this, we propose a nonsmooth method that behaves well in several scenarios. Numerical evaluations in different spectrum sharing scenarios, which show the performance of our method, are provided.Peer ReviewedPostprint (author's final draft

Influence of serological factors and BMI on the blood pressure/hematocrit association in healthy young men and women.

The association between mean arterial blood pressure (MAP) and hematocrit (Hct) as a surrogate for blood viscosity was investigated in a young (average 20.0±2.3 years), healthy population of 174 men and 442 women. Health status was assessed by clinical examination and serological evaluation. Individuals with severe anemia or hemoconcentration, prior traumas or major surgical intervention, smokers, and pregnant or lactating women were excluded from the study. The MAP/Hct association was positive and significant (P=0.04) for women and negative, albeit not significantly so, for men. The MAP/Hct association was also evaluated in subgroups of the same population with a progressive step-by-step exclusion of: individuals with cholesterol >200 mg/dL; triglycerides >200 mg/dL; body mass index >25 kg/m(2); and glucose >100 mg/dL. This consecutively reduced the strength of the positive MAP/Hct association in women, which became negative - although not significantly so - when all anomalously high factors were excluded. The same trend was found in men. Our study indicates that previously reported positive trends in the relationship between the MAP and Hct in the population are not present in a young, healthy population of men or women that excludes individuals with the confounding factors of above normal serological values and BMI

A Study of a Road Landslide in Puerto Rico

Numerous landslides have plagued the construction of a 1.3 mile road sector in the mountainous region of central Puerto Rico. The area is underlain by a sequence of landslide deposits overlying a muddy limestone and hard overconsolidated clayey soils. Landslides have occurred in both cuts and fills that have delayed the road construction for a period of more than two years, bringing as a result, great economic losses for the Puerto Rico Highway Authority. The landslide trigger mechanism has been intimately related to high rainfall, commonly observed in this region. The geotechnical and geological studies performed previous to the construction of this road sector were few and meager. These studies did not recognize the presence of unstable deposits along the road sector alignment. As a result, several large slope failures developed during construction that halted the completion of the road. For investigating the slope failures, detailed geological and geotechnical studies were performed, including monitoring of groundwater levels, rainfall, and slope movements followed by laboratory and slope stability analyses. Remedial measures have been provided in the form of excavation, drainage, and stability berms. Renewal of the road construction with the remedial measures is prompt to start

Diffusion of the utopias. The academy and the media in times of pandemic

At the end of the 20th century, the disappearance of the great utopias occurs. Crises are favorable moments to imagine better worlds. Social scientists and humanists - because of their knowledge of reality and its possibilities for change - are privileged to visualize the Covid-19 crisis as an opportunity for change and transfer the orientation of change to all of society. This is a transcendental translation for the consolidation of utopia in the social imaginary. This work explores the rehabilitation of utopia in the exceptional circumstances of the pandemic's start by academics. Doing this identifies, classifies, and analyzes the specific proposals that these thinkers have published in the press to move towards a happy world. We note that the pandemic has not managed to rehabilitate the utopia and that the community's proposals for change are fragmented. We consider that this fragmentation is a symptom of micro-stories, which implies a shift towards micro-routes. However, medium-range utopias proliferate in which messages appear insistently and, in that sense, may be reflected in the social imaginar

VALORACIÓN AGROECOTURÍSTICA DE TEPEXILOTLA, CHOCAMÁN, VERACRUZ; DESDE LA PERSPECTIVA DEL VISITANTE

Agroecotourism seeks, in addition to the development of a rural society, to conserve its culture and biodiversity. Tepexilotla, in Chocamán, Veracruz, México, is characterized by being a high-marginalization community with broad landscape wealth based on its biodiversity. This community receives tourists annually during the Easter vacation period. The objective of this study was to evaluate the agroecotourism potential of Tepexilotla as a tourism destination, from the perspective of the visitor. The visitor’s profile and preferences were characterized through 63 interviews. The results indicated that the visitor is mainly from the region, and his motivation to visit Tepexilotla is to enjoy nature (65.1 %) and rest and tranquility (50.8 %). The main activities performed are swimming (61.9 %) and enjoying the landscape (50.8 %). The activities and services with potential were related to environment conservation, agricultural participation, sale of local products and hiking. According to the visitor’s perspective, the agroecotourism potential of Tepexilotla is high, although strategies that promote its development are required.Además de impulsar el desarrollo de una sociedad rural, el agro-ecoturismo busca conservar su cultura y biodiversidad. Tepexilotla, en Chocamán, Veracruz, México, se caracteriza por ser una comunidad de alta marginación y amplia riqueza paisajística, basada en su biodiversidad. Anualmente, esta comunidad recibe turistas en el periodo vacacional de Semana Santa. El objetivo del presente fue valorar el potencial agro-ecoturístico de Tepexilotla como destino turístico desde la perspectiva del visitante. Se caracterizó el perfil y las preferencias de los visitantes mediante 63 entrevistas. Los resultados indicaron que el visitante procede principalmente de la región; su motivación para visitar Tepexilotla es disfrutar de la naturaleza (65.1%), así como descansar y tener un momento de tranquilidad (50.8%). Las principales actividades realizadas son nadar (61.9%) y disfrutar del paisaje (50.8%). Las actividades y los servicios con potencial fueron relacionados con conservación del ambiente, participación agrícola, venta de productos locales y senderismo. De acuerdo con la perspectiva del visitante, el potencial agro-ecoturístico de Tepexilotla es alto, pero se requieren estrategias que impulsen su desarrollo

Mineralogía de la fracción arcilla de suelos y sedimentos de la Cuenca de Maceda

[Resumen] Se estudia la mineralogía de la fracción arcilla de los sedimentos terciarios y cuaternarios que rellenan la depresión de Maceda,así como de las rocas que constituyen el marco y sus productos de alteración. Las rocas que rodean la cuenca están sometidas actual mente a un proceso de alteración de tipo hidrólisis ácida (caolinita, gibbsita y oxihidróxidos de hierro son los productos de alteración más significativos) Los sedimentos terciarios presentan en su fracción arcilla un filosilicato 1:1 dioctaédrico(haloisítico o caolinítico) como mineral más ahlndante, micas, micas degradadas, goethita y, ocasionalmente, hematita,observándose la presencia de vermiculitas de baja carga en las capas mas profundas. Los depósitos más recientes contienen abundante filo silicato 1:1 dioctaédrico de bajo grado de orden y gibbsita, micas degradadas en cantidades variables y goethita.[Abstract] The igneous and metamorphic rocks that surround the Maceda depressian are subjected to a weathering of acidic hydrolysis type (kaol inite, gibbsite and Fe-oxihydroxides are the more repl'esenta"LJ.ve weathering products). The tertiary sediments have as principal component a 1:1 diocthaedral phyllosilicate (halloysite or kaolini te) associated wi th micas, degradated micas, goethita-:occasionally hematite and in the deepest layers, low charge vermiculites • - The newest deposits have disordered 1:1 diocthaedral phyllosilicate and gibbsite, changing proportions of degradated micas and goethit

Feed-forward Space Vector Modulation for Single-Phase Multilevel Cascade Converters with any DC voltage ratio

Modulation techniques for multilevel converters can create distorted output voltages and currents if the DC link voltages are unbalanced. This situation can be avoided if the instantaneous DC voltage error is not taken into account in the modulation process. This paper proposes a feed-forward space vector modulation method for a single-phase multilevel cascade converter. Using this modulation technique, the modulated output voltage of the power converter always generates the reference determined by the controller even in worst case voltage unbalance conditions. In addition the possibility of optimizing the DC voltage ratio between the H-bridges of the power converter is introduced. Experimental results from a 5kVA prototype are presented in order to validate the proposed modulation technique