Mechanical analysis of Genoa 03 stirling engine

Due to the new technologies development based on renewable sources of energy, in recent years Stirling engines have become very important in the energetic sector. Many of them do not allow the use of fluid lubricants and, thus, the effect of friction losses is important. For this purpose, a mathematical model has been developed based on the force balance in the crankshaft using the pressure distribution in the cylinders. The aim of this work is to characterize the mechanical losses in a Genoa 03 Stirling engine using a numerical model and experimentally via the drag method. The results of this model have been compared with those obtained experimentally on Genoa 03 Stirling engine. In the experimental results, a proportional increase in friction torque due to the average pressure and the speed of the crankshaft is observed. The first of these is caused by an increase of dry friction forces and the second, by the viscous friction between the working fluid and the inner walls of the engine. Also in this paper, irreversible processes in a beta type Stirling engine have been investigated in order to highlight the impact of losses on mechanical power and its performance. This article develops the first study of the mechanical losses of Genoa 03 experimental Stirling engine, which has an output power of 3 kW. Although the model response follows the same trends as the experiments, those simplifications provide errors which become more significant as the engine speed increases.Ministerio de Economía y Competitividad ENE2013-43465-

A Technique for Distributed Systems Specification

In this paper we show how an object-oriented specification language is usefvl for the specification of distributed systems. The main constructors in this language are the objects. An object consists of a state, a behaviour and a set of transition rules between states. The specification is composed by three sections: definition of algebraic data types to represent the domain of object attributes, definition of classes that group objects with common features, and definition of relationships among classes. We show two possible styles for defining the behaviour of objects, in one hand we use a transition system (state oriented) and in the other hand we use an algebraic model of processes description (constraint oriented). We illustrate the paper with the specification of the dining philosophers problem, a typical example in distributed programming

16 Years (2006–2021) of Surface Ozone Measurements in Córdoba (Southern Spain): Trends and the Impact of the COVID-19 Lockdown

Surface ozone concentrations (O3) during the period 2006–2021 are analysed at Córdoba city (southern Iberian Peninsula) in suburban and urban sampling sites. The aims are to present the levels and temporal variations, to explore trends and to quantity the variation in O3 concentrations in the context of the COVID-19 lockdown. The O3 means are higher in the suburban station (62 µg m−3 and 51.3 µg m−3), being the information level threshold only exceeded twice during this period. The daily evolution shows a maximum at about 17:00 UTC, whereas the minimum is reached at about 9:00 UTC, with higher levels in the suburban station. The seasonal evolution of this daily cycle also presents monthly differences in shape and intensity between stations. The trends are analysed by means of daily averages and daily 5th and 95th percentiles, and they show a similar increase in all of these parameters, with special emphasis on the daily P95 concentrations, with 0.27 µg m−3 year−1 and 0.24 µg m−3 year−1. Finally, the impact of the COVID-19 lockdown shows a decline in O3 concentrations over 10%

A considerable improvement of the traditional FPGA-based digital design methodology by using an Arduino sensor board

[EN] The traditional way to learn and teach Digital Systems has been changing over the last decades by the use of Hardware Description Languages (HDL) and Field Programmable Gate Array (FPGA) evaluation boards. The use of an Arduino development kit with different sensors connected to the FPGA upsizes the students experience in the area of Digital Systems. A temperature and humidity ambience sensor combined with an ultrasound sensor to measure distance can effectively be used by students to implement its first serial data converter that takes the sensor data and shows the obtained values from the Arduino in the seven segment display of the FPGA kit. After three years of experience in the new grade courses at the UPV Telecommunication School the number of students enjoying this new way to learn the subject Fundamentals of Digital Electronics (FSD) has dramatically risen up with an increase of a 20% in the number of students that pass the subject and that select the electronic branch of telecommunication studies in the future semesters.Martínez Peiró, MA.; Larrea Torres, MÁ.; Lidon Roger, J.; Jiménez Jiménez, Y.; Torres Curado, R.; Tébar Ruiz, Á. (2020). A considerable improvement of the traditional FPGA-based digital design methodology by using an Arduino sensor board. Editorial Universitat Politècnica de València. 81-89. https://doi.org/10.4995/INN2019.2019.10091OCS818

Experimental investigation and modelling of biodiesel combustion in engines with late direct injection strategy

The combination of alternate fuels, such as biodiesel, and low-temperature combustion (LTC) constitutes a promising solution to reduce pollutant emission and to avoid dependence on fossil fuels. However, this concept requires additional research to optimise LTC of biodiesel over wider operating ranges, specifically including the implementation of numerical models to assist in the development of these engines. In this work, an experimental analysis was carried out assessing both thermal performance and emissions derived from the LTC of diesel/biodiesel blends with late direct injection. Furthermore, this analysis allowed implementing a predictive tool to characterise in-cylinder pressure trace under this operation strategy. This model was coupled with an empirical law to simulate heat release during the combustion process. Least squares method was applied to fit this empirical law to experimental data involving different conditions in terms of percentages of rapeseed biodiesel in the fuel blend, rotational speed, fuel/air equivalence ratio and percentages of external exhaust gas recirculation. To build the predictive model, a multiple regression methodology was used to correlate the law parameters with the operating conditions. Finally, a validation process based on the simulation of in-cylinder pressure trace was developed, revealing that the predictions agreed well with the experimental data. This suggests that the proposed model is able to satisfactorily predict the LTC of diesel/biodiesel blends within the test range.Junta de Andalucía - Consejería de Economía AT17-5934-USUniversidad de Cádiz PB2022-04

Health and Habitability in the Solar Decathlon University Competitions: Statistical Quantification and Real Influence on Comfort Conditions

Medicine and architecture are disciplines with the main objectives of satisfying the fundamental needs of human beings: health, comfort, well-being, safety, and ensuring an acceptable quality of life in a sustainable habitat. In both areas of knowledge, the advances and the most innovative proposals in the fields of research and teaching are focused on transversal knowledge and the use of learning methods through problem solving (learning by doing). The student competitions called “Solar Decathlon” are focused on the development of these concepts, in which prototypes of sustainable and, as far as possible, healthy social housing are tested. In these university competitions, the design of energy-efficient and comfortable living environments that contribute to the health of the occupants are encouraged; however, the methodology for evaluating the “comfort conditions” stipulated in the competition rules considers only parameters that can be monitored by sensors. For this article, the prototypes presented by the “Solar Decathlon Team of the University of Seville” to the editions of said competition held in Latin America and Europe (in 2015 and 2019, respectively) are being studied. The present research starts from the fact that the unique consideration of measurable indices (such as temperature, humidity, etc.), is clearly insufficient when it comes to evaluating the real conditions of habitability and comfort that a domestic architectural space presents. For this reason, a theoretical–practical analysis is carried out by means of surveys, with the final objective of determining a methodology for evaluating comfort—complementary to that of the competition—which assesses other relevant issues and which, in short, takes into account the repercussion on people’s health. From our analysis, we conclude that at least these two methodologies should be used to evaluate comfort because they are individually considered incomplete in terms of the data provided by each one of them. The survey-based methodology provides complementary information on comfort and health that could be taken into account in future editions of Solar Decathlon

Implementing Associations among Classes in an Environment of Active Databases

The association is a native concept from relational databases, one that has been adapted to object oriented (OO) modelling. It is an interesting operator used to describe links among objects of a system, commonly included in the most popular diagram-based OO methodologies. However, those methodologies sometimes present a lack of formality that may undermine its use. In this paper we formalize the semantics of associations. Firstly, we will describe an OO model based on different kinds of constraints. Some of them will be especially useful for describing the semantics of associations. Finally, we will present some remarks about implementation by means of triggers, a new feature incorporated in databases to specify an inner active behavior.Comisión Interministerial de Ciencia y Tecnología TIC97-0593-C05-0

Hidrógeno : vector energético en el siglo XXI

Conocer el entramado mundo de las tecnologías del hidrógeno y su estrecha y necesaria relación con las energías renovables, así como con equipos que aún hoy se nos antojan muy sofisticados y escaso

Mesoporous niobium oxide for dehydration of D-xylose into furfural

Se ha demostrado que el óxido de niobio mesoporoso es un catalizador eficaz para la deshidratación de D-xilosa a furfural, alcanzando una conversión del 92% y un rendimiento de furfural 49,3% a 170º C y 90 minutos. La lixiviación de Nb, determinada por ICP-MS, era inferior al 0,5% en peso de la concentración de Nb inicial, confirmando de este modo la estabilidad del catalizador ácido sólido.El furfural posee un gran potencial como molécula plataforma de origen renovable para la síntesis de una alta variedad de compuestos químicos. Se obtiene mediante la deshidratación de pentosas, principalmente a partir de D-xilosa, proceso catalizado por ácidos minerales en fase homogénea. Por tanto, dentro de la química verde y la búsqueda de sostenibilidad de los procesos catalíticos, es necesaria su sustitución por catalizadores sólidos ácidos que sean tolerantes al agua, ya que es el disolvente más utilizado para esta reacción. El óxido de niobio posee propiedades ácidas y es insoluble en agua, pero su superficie específica es muy baja. Por lo tanto, resulta muy interesante la síntesis de un óxido de niobio mesoporoso para emplearlo como catalizador en esta reacción. En este trabajo, se ha sintetizado un Nb2O5 mesoporoso y se ha evaluado su comportamiento catalítico en la obtención de furfural a partir de D-xilosa.Spanish Ministry of Science and Innovation (ENE2009-12743-C04-03 project)Junta de Andalucía (P09-FQM-5070).Ministry of Science and Innovation for the financial support under the Program Ramón y Cajal (RYC-2008-03387)