Sistema de iluminación con lámparas LEDs alimentadas por inducción electromagnética aplicado en el laboratorio de electrónica básica de la Unan-Managua

El mundo atraviesa actualmente problemas de consumo energético, día a día se busca la manera de reducir el consumo energético. En este trabajo se presenta una solución a este problema el cual es:La tecnología LEDs se está poniendo hoy en día a flote, por lo que en la actualidad se pretende sustituir las lámparas tradicionales incandescentes o fluorescentes) por la razón de su mayor consumo de potencia, haciendo que los LEDs (diodo emisor de luz) pasen a un primer plano ya que su consumo de potencia es aproximado a un 50% menos que las lámparas tradicionales. La tecnología LEDs se está empleado en la gama de televisores haciéndoles más nítidas las imágenes y menos volumen en su diseño, en semáforos haciéndoles a estos que consuman menos potencia y sean más visibles y duraderos que los semáforos normales. La potencia de los LEDs, como fuente de luminación general (luz blanca), es actualmente una de sus principales promesas de cara al futuro.En este documento se presenta un sistema de iluminación utilizando tecnología LEDs basado en u

Thermodynamic performance of coupled enzymatic reactions: A chemical kinetics model for analyzing cotransporters, ion pumps, and ATP synthases

[EN]Previous research has suggested that molecular energy converters such as ATP synthases, ion pumps, and cotransporters operate via spatially separate pathways for free energy donor and acceptor reactions linked by a protein molecule. We present a chemical kinetics model based on these works, with the basic assumption that all molecular energy converters can be thought of as linked enzymatic reactions, one running downhill the chemical potential gradient and driving the other uphill. To develop the model we first look at how an enzyme process can be forced to go backwards using a basic kinetic model. We then use these findings to suggest a thermodynamically consistent method of linking two enzymatic reactions. Finally, in the context of the aforementioned energy converters, the thermodynamic performance of the resulting model is thoroughly investigated and the obtained results are contrasted with experimental data.Conacyt-M´exico, Grant No. CDF19-568462; University of Salamanca, Contract No. 0218 463AB0

Past, present and future of membrane technology in Spain

The following review aims at analyzing the contribution of Spanish researchers to membrane science and technology, with a historical compilation of the main milestones. We used a bibliometric analysis based on the Scopus database (1960?2020) dealing with 8707 documents covering the different disciplines and subject areas where membranes are involved. Furthermore, the information has been updated to the present moment of writing this manuscript in order to include the latest research lines and the different research groups currently active in Spain, which may lead the way to the development of the field in the coming years

The implant-supported milled bar overdenture : a literature review

Purpose: This bibliographical review aims to determine the present situation of the implant-supported milled bar overdenture as a therapeutic option in implantology, as well as to set and compare the techniques and materials currently used for making them. Materials and methods: By searching the main electronic bibliographical data in indexed Medline articles, we obtained a total number of 20 articles that fulfilled the requirements of this bibliographical review. Results: The implant-supported milled bar overdenture offers excellent long-term successful results, although complication rates are higher in emergency cases of patients initially planned for a fixed prosthesis. Krenmair and collaborators found cumulative survival rates of implants on milled bars after 5 years, of 99% in mandible cases, and of 97.8% in maxilla cases. No detailed protocols specifying the necessary number of implants or their characteristics have been found, though they are never made with less than 4 implants in mandible or 4-6 in the maxilla. Milled bars are screwed, generally cast in a precious metal alloy, with a metal or acrylic suprastructure and include attachments that regulate the tightness. The suprastructure adjusts precisely and rigidly to the milled bar, and presents similar biomechanical movements to those of fixed prostheses. The overdenture is removable and its prophylaxis is simple. Conclusions: The implant supported milled bar overdenture is a very interesting option in the treatment of patients with moderate to severe reabsorbed maxilla problems. It offers both the advantages of removable prostheses as well as the stability and retention of a fixed prosthesis

Local-stability analysis of a low-dissipation heat engine working at maximum power output

[EN]In this paper we address the stability of a low-dissipation (LD) heat engine (HE) under maximum power conditions. The LD system dynamics are analyzed in terms of the contact times between the engine and the external heat reservoirs, which determine the amount of heat exchanged by the system. We study two different scenarios that secure the existence of a single stable steady state. In these scenarios, contact times dynamics are governed by restitutive forces that are linear functions of either the heat amounts exchanged per cycle, or the corresponding heat fluxes. In the first case, according to our results, preferably locating the system irreversibility sources at the hot-reservoir coupling improves the system stability and increases its efficiency. On the other hand, reducing the thermal gradient increases the system efficiency but deteriorates its stability properties, because the restitutive forces are smaller. Additionally, it is possible to compare the relaxation times with the total cycle time and obtain some constraints upon the system dynamics. In the second case, where the restitutive forces are assumed to be linear functions of the heat fluxes, we find that although the partial contact time presents a locally stable stationary value, the total cycle time does not; instead, there exists an infinite collection of steady values located in the neighborhood of the fixed point, along a one-dimensional manifold. Finally, the role of dissipation asymmetries on the efficiency, the stability, and the ratio of the total cycle time to the relaxation time is emphasized. © 2017 American Physical Society.Consejo Nacional de Ciencia y Tecnología Instituto Politécnico Nacional Ministry of Economy, Industry and Competitivenes

Link between optimization and local stability of a low-dissipation heat engine: Dynamic and energetic behaviors

[EN]In the present paper we study the connection between local stability and energetic properties in low-dissipation heat engines operating in the maximum-power and maximum-compromise ( ) regimes. We consider two different feedback regulatory pathways: (1) one in which restitutive forces linearly depend on the deviations from the stationary values of the heat exchanges with the hot and cold reservoirs and (2) another where restitutive forces depend on the deviations from the stationary values of the power output and the heat outflux into the cold reservoir. The first dynamics leads to an isolated stable point while in the second one the system is metastable. Further analysis of random perturbations from the steady state gives valuable information about the dynamic behavior of thermodynamic properties like entropy, power, and efficiency in both operation regimes

Innovación docente en la asignatura Iniciación a la In-­‐ vestigación Educativa en la especialidad de Física y Química

Memoria ID12-0184. Ayudas de la Universidad de Salamanca para la innovación docente, curso 2012-2013

Incorporación de técnicas experimentales y bibliométricas en la asignatura Iniciación a la Investigación Educativa en Física y Química”

Memoria ID-006. Ayudas de la Universidad de Salamanca para la innovación docente, curso 2013-2014

Propuesta de mejora de la asignatura Iniciación a la investigación educativa en la especialidad de física y química (MUPES) en relación con la asignatura de ciencias para el mundo contemporáneo (Bachillerato)

Memoria ID-0319. Ayudas de la Universidad de Salamanca para la innovación docente, curso 2014-2015

An alkali metal thermoelectric converter hybridized with a Brayton heat engine: Parametric design strategies and energetic optimization

[EN]A model for a novel integrating system consisting of an alkali metal thermoelectric converter and a non-recuperative irreversible Brayton heat engine is presented. The efficiency and power output density of the overall system is analyzed at light of the main characteristic losses in each subsystem: the thickness of the electrolyte, the current density of the converter, and the internal losses of the Brayton cycle coming from the compressor and turbine. A detailed study on the behavior of the overall maximum power and maximum efficiency regimes is also presented. An analysis on compromise performance regimes from multi-objective and multi-parametric optimization techniques based on the Pareto front, for both the subsystems and the overall system, enhance the obtained results. The numerical results of the present model are compared with those of alkali metal thermoelectric converter working alone and with other different existing hybrid models. It is found that the exhaust heat discharged by the converter can be efficiently utilized by an irreversible Brayton heat engine. So, the maximum efficiency and maximum power output density of the present model attain 41.7% and W/m2 which increase about 44.8% and 158% compared to the values of the alkali metal thermoelectric converter working alone and 20.5% and 80.4% when compared with a hybridized configuration including a thermoelectric energy converter.National Natural Science Foundation of China (No. 11675132) People’s Republic of China and China Scholarship Council (CSC) under the State Scholarship Fund (No. 201806310020) Junta de Castilla y Leon under project SA017P17. J.G.A. acknowledges Universidad de Salamanca contract 2017/X005/