Caracterización de propiedades mecánicas de paneles sándwich de polietileno y espuma polietileno/poliuretano

[Resumen] Debido al gran aumento del uso del panel sándwich en la industria, es necesario conocer su comportamiento estructural., para lograr optimizar todo el potencial de este tipo de estructuras. Es necesario caracterizar las propiedades mecánicas de los materiales que constituyen el panel sándwich. En el presente trabajo se realiza un ensayo de flexión a 3 puntos para obtener el módulo elástico aparente y la resistencia a flexión según la norma UNE-ISO 1209-2:2007. También se ensaya una probeta de panel sándwich para recabar datos de su comportamiento y compararlos con los resultados obtenidos de la simulación por MEF. Al mismo tiempo se realiza un ensayo de fluencia en flexión para conseguir determinar si este tipo de estructuras presentan fluencia. Encargar este tipo de ensayos a laboratorios externos es muy caro debido la larga duración que conlleva. Por este motivo se realiza un ensayo de bajo coste para determinar aproximadamente si la fluencia es importante en este tipo de productos.[Resumo] Debido ao gran incremento no uso do panel sándwich na industria, é necesario coñecer o seu comportamento estrutural, para obter todo o potencial deste tipo de estruturas. É necesario caracterizar as propiedades mecánicas dos materiais que compoñen o panel sándwich. No presente traballo realízase unha proba de flexión de 3 puntos para obter o módulo elástico aparente e a resistencia á flexión de acordo coa norma UNE-ISO 1209-2: 2007. Tamén se proba unha probeta de panel sándwich para recoller datos sobre o seu comportamento e comparalos cos resultados obtidos da simulación por MEF. Ao mesmo tempo, realízase unha proba de fluencia de fluidez para determinar se este tipo de estruturas teñen fluidez. Confiar este tipo de probas a laboratorios externos é moi caro debido ao longo tempo que implica. Por este motivo, lévase a cabo unha proba de baixo custo para determinar se a fluencia é importante neste tipo de productos.[Abstract] Due to the great increase in the use of the sandwich panel in the industry, it is necessary to know its structural behavior, in order to optimize the full potential of this type of structure. It is necessary to characterize the mechanical properties of the materials that make up the sandwich panel. In the present work, a 3-point bending test is carried out to obtain the apparent elastic modulus and the flexural strength according to the UNE-ISO 1209-2: 2007 standard. A sandwich panel test piece is also tested to collect data on its behavior and compare them with the results obtained from the simulation by MEF. At the same time, a fluence fluency test is carried out to determine if this type of structures have fluency. Entrusting this type of tests to external laboratories is very expensive due to the long duration involved. For this reason, a low-cost test is carried out to determine approximately whether creep is important in this type of product.Traballo fin de grao (UDC.EPS). Enxeñaría mecánica. Curso 2017/201

PREVI Lima y la experiencia del tiempo

Compuesto por 26 proyectos, y a más de treinta años de su inicio, la experiencia del Proyecto Piloto 1 del PREVI1 en Lima, Perú, es materia de investigación por la valiosa complejidad de factores que intervienen: el collage de proyectos, la variedad tipológica, el carácter experimental de la propuesta y el tiempo que lleva sometida a diferentes intervenciones autogestionadas. EqA viajó a Lima a reconstruir el proceso de transformación de los proyectos realizados a partir de levantamientos de croquis sobre los planos originales, levantamientos fotográficos y entrevistas a las familias que los habitan. A partir del levantamiento de las viviendas actuales y el cruce con la historia familiar, se descubre el proceso que articula el proyecto profesional y el proyecto del habitante.Peer ReviewedAward-winnin

Hydrolytic Dehydrogenation of Ammonia Borane Attained by Ru-Based Catalysts: An Auspicious Option to Produce Hydrogen from a Solid Hydrogen Carrier Molecule

Chemical hydrogen storage stands as a promising option to conventional storage methods. There are numerous hydrogen carrier molecules that afford satisfactory hydrogen capacity. Among them, ammonia borane has attracted great interest due to its high hydrogen capacity. Great efforts have been devoted to design and develop suitable catalysts to boost the production of hydrogen from ammonia borane, which is preferably attained by Ru catalysts. The present review summarizes some of the recent Ru-based heterogeneous catalysts applied in the hydrolytic dehydrogenation of ammonia borane, paying particular attention to those supported on carbon materials and oxides.This work was financed by the MICINN, FEDER (RTI2018-095291-B-I00). MNG thanks the Plan GenT project (CDEIGENT/2018/027) for their financial support. DST thanks MICINN for the “Juan de la Cierva” contract (IJCI-2016-27636) and the Vicerrectorado de Investigación y Transferencia de Conocimiento de la Universidad de Alicante (GRE19-16)

Mexican Medical Students Protest During COVID-19 Pandemic

During February  2021, a protest was organized by Mexican medical students through social media. About 200 interns, social service physicians and physicians protested peacefully in front of the city hall of Monterrey, Nuevo Leon, the capital of Mexico's second largest metropolitan area. Due to the current contingency situation, it was requested to attend with face shield and masks. The reason for the protest was to raise their voice due to the precarious situation where social service physicians are sent to rural areas of the country in which they have all the obligations of workers but without belonging to the working class - lacking the the benefits of this same as a living wage or fair working hours. The protesters were in limbo between student and worker. The protest also demanded justice for the sensitive death of young doctors due to malpractice situations of the Mexican authorities. We believe that a total reform of the social service in medicine is necessary. It is the responsibility of the authorities to cover the rural areas with permanently trained doctors without depending on recently graduated doctors. It is always important to assert our fundamental rights, including the right to protest in a peaceful manner

Further Remarks on Irrational Systems and Their Applications †

Irrational Systems (ISs) are transfer functions that include terms with irrational exponents. Since such systems are ubiquitous and can be seen when solving partial differential equations, fractional-order differential equations, or non-linear differential equations; their nature seems to be strongly linked with a low-order description of distributed parameter systems. This makes ISs an appealing option for model-reduction applications and controls. In this work, we review some of the fundamental concepts behind a set of ISs that are of core importance in their stability analysis and control design. Specifically, we introduce the notion of multivalued functions, branch points, time response, and stability regions, as well as some practical applications where these systems can be encountered. The theory is accompanied by some numerical examples or simulations

Pensar la ciudad global desde sus representaciones escolares : un estudio de caso entre Valencia (España) y Bogotá (Colombia)

The conceptions of the urban space of Secondary Education students of several centres of Valencia and Bogotá approach us to the school representation of the global city. The relationship between social representations and the geography of perception and behaviour reveals that students build ideas about the immediate urban space within the social community to which they belong. Mobility, social relations and attachment to the immediate urban space are dissimilar aspects in both cities, but they lead us to affirm the need to strengthen teaching strategies that include the lived space and the local scale to face the learning of the global city.

Surgical management of tricuspid regurgitation: a new algorithm to minimise recurrent tricuspid regurgitation

Introduction Recurrent tricuspid regurgitation (TR) is frequently observed after cardiac surgery; however, the correct approach remains controversial. We developed an algorithm for action on the tricuspid valve (TV) and conducted a 1-year follow-up study. The aim was to assess the efficacy of the algorithm to minimise residual TR after TV surgery. The hypothesis was that the TR rate at 1 year would be reduced by selecting the surgical approach in accordance with a set of preoperative clinical and echocardiographic variables. Methods A prospective, observational, single-centre study was performed in 76 consecutive patients with TV involvement. A protocol was designed for their inclusion, and data on their clinical and echocardiographic characteristics were gathered at 3 months and 1-year postsurgery. The treatment of patients depended on the degree of TR. Surgery was performed in all patients with severe or moderate-to- severe TR and in those with mild or moderate TR alongside the presence of certain clinical or echocardiographic factors. They underwent annuloplasty or extended valve repair when the TV was distorted. If repair techniques were not feasible, a prosthesis was implanted. Residual TR rates were compared with published reports, and predictors of early/late mortality and residual TR were evaluated. Results TR was functional in 69.9% of patients. Rigid ring annuloplasty was performed in 35.7% of patients, De Vega annuloplasty in 27.1%, extended repair in 11.4% and prosthetic replacement in 25.7%. TR was moderate or worse in 8.19% of patients (severe in 3.27%) at 1 year postintervention. No clinical, surgical or epidemiological variables were significantly associated with residual TR persistence, although annulus diameter showed a close-to- significant association. Total mortality was 12.85% for all causes and 10% for cardiovascular causes. In multivariate analysis, left ventricular ejection fraction was related to both early and late mortality. Conclusions Severe residual TR was significantly less frequent than reported in other series, being observed in less than 4% of patients at 1-year postsurgery

QoE estimation in mobile networks using machine learning

Quality of experience (QoE) can be defined as the overall level of acceptability of an application or service, as perceived by the end-user. The perceived QoE of mobile user plays a key role in the business of the telecom carriers. This work has focused in design a model capable of predicting the QoE of the end-user using a number of Machine Learning approaches, based on quality of service (QoS) metrics from different sources like the mobile device, the mobile network and also subjective metrics given by the user (QoE and Mood surveys) in a real life setup. An android app, a metric collection platform, a system for data processing and semi-automatic analysis of metrics has been developed as a part of this work. The experimental results show that by assembling a combined model of the algorithms with best observed individual performance, improvements in the overall performance of the prediction can be achieved.CONACYT – Consejo Nacional de Ciencia y TecnologíaPROCIENCI