1,208 research outputs found
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
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
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
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/
A two-stage sodium thermal electrochemical converter: Parametric optimization and performance enhancement
[EN]An asymmetric two-stage sodium thermal electrochemical converter and its optimum performance are studied by
means of an improved analytical model including the main losses in the overall system. Based on the study of a
single-stage sodium thermal electrochemical converter, the inner process is divided into two stages including one
at the 1300 K temperature (evaporator) and the other at the 800–1300 K intermediate temperature with the aim
of improving efficiency. The parametric optimum selection criteria of a few main parameters of the two-stage
device are provided and the coupling of the separate stages in an overall optimum system in terms of the
appropriate intermediate temperature is particularly stressed. The maximum efficiency of the proposed overall
system can attain 36.2%, which is 17.5% higher than that of the best performing single-stage device, and increase
up to 34.1% and 24.8% over the existing two-stage devices designed by two research groups, respectively. The
Pareto front obtained from numerical multiobjective and multiparametric methods endorses previous findings
and visually presents the space of the states and the energetic properties of the overall arrangement compared
with the corresponding data for the isolated first and second stages.China Scholarship Council under
the State Scholarship Fund (No. 201906310095
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