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-

Diseño de una metodología para la optimización experimental del consumo y emisiones de un motor Diésel

The present Master¿s thesis is focused on the development of a method that minimizes both consumption and NOx and soot particles emissions of a diesel engine through design of experiments. For this purpose, 2 characteristics working points of the single-cylinder engine Z19DTH will be studied and the influence on the mentioned variables of the injection parameters, i.e., rail pressure, main injection advance and injection strategy, will be analyzed. From experimental measures, statistical models have been developed that reproduce the behavior of engine variables as a function of injection parameters. Using these models, an optimization of these parameters that satisfy different desirability functions will be carried out. Finally, the influence of reducing the number of observations on the precision of the results will be studied and it will be checked whether by combining the experimental model with a predictive tool (Siciclo), whether substantial improvements are achieved. After analyzing the results, it can be concluded that the parameters that affect engine consumption and emissions the most are the rail pressure and the main injection advance. Also, the addition of a post-injection in low-load points is translated into a 50% reduction in soot particles emissions and a slight performance improvement, all this without increasing Nox formation. In mid-load points, the influence of additional injections is insignificant and, in order to reduce the complexity of this models in future studies, and provided the minimum required precision allows it, they can be neglected.El presente Trabajo Fin de Máster está enfocado al desarrollo de un método para minimizar el consumo y las emisiones de NOx y partículas de hollín de un motor diésel a partir de diseños de experimentos. Con este propósito se estudiarán 2 puntos de funcionamiento característicos del motor monocilíndrico Z19DTH y se analizará la influencia de los parámetros de inyección (presión de inyección, avance de la inyección principal, masa de las inyecciones y separación entre ellas) sobre las variables citadas anteriormente. A partir de medidas experimentales se han desarrollado modelos estadísticos que reproducen el comportamiento de variables del motor en función de los parámetros de inyección. Utilizando estos modelos, se llevará a cabo una optimización de estos parámetros que satisfagan diferentes funciones de deseabilidad. Finalmente se estudiará la influencia de reducir el número de observaciones en la precisión de los resultados y se comprobará si combinando el modelo experimental con una herramienta predictiva (Siciclo), que incorpora modelos físicos, se obtienen mejoras sustanciales. Tras analizar los resultados obtenidos se concluye que los parámetros que más afectan al consumo y emisiones del motor son la presión de inyección y el avance de la inyección principal. Además, la adición de una post-inyección en puntos de baja carga supone una reducción del 50 % en emisiones de partículas de hollín y un ligero aumento del rendimiento y, todo esto sin incrementar la formación de NOx. En puntos de media carga la influencia de las inyecciones adicionales es insignificante y en aras de reducir la complejidad de estos modelos en futuros estudios y siempre que el nivel de precisión requerido lo permita, podrán ser despreciadas.El present Treball Final de Màster està enfocat al desenvolupament d’un mètode per a minimizar el consum i les emissions de NOx i partícules de sutge d’un motor dièssel a partir de dissenys d’experiments. Amb aquest propòsit s’estudiaran 2 punts de funcionament característics del motor monocilíndric Z19DTH i s’analitzarà la influència dels paràmetres d’injecció (pressió d’injecció, avanç de la injecció principal, massa de les injeccions i separació entre elles) sobre les variables nomenades amb anterioritat. A partir de mesures experimentals s´han desenrotllat Models estadístics que reproduïxen el comportament de variables del motor en funció dels paràmetres d’injecció. Utilitzant estos models, es durà a terme una optimizació d’estos paràmetres que satisfacen diferents funcions de deseabilidad . Finalment s’estudiará la influència de reduir el nombre d’observacions en la precisió de resultats i es comprobarà si combinant el model experimental amb una ferramenta predictiva (Silici), que incorpora Models físics, s’obtenen millores substancials. Després d’haver analitzat els resultats assolits es conclou que els paràmetres que més afecten al consum i emissions del motor són la pressió d’injecció i l’avanç de la injecció principal. A més, l’addició d’una post-injecció en punts de baixa càrrega suposa una reducció del 50% en emissions de partícules de sutge i un lleuger augment del rendiment i, tot açò sense incrementar la formació de NOx. En punts de mitja càrrega la influència de les injeccions adicionals és insignificant i amb la intenció de reduir la complexitat d’aquestos models en futurs estudis i sempre que el nivell de precisió requerit ho permeta, podran ser rebutjades.Aguilera Roldán, FDA. (2017). Diseño de una metodología para la optimización experimental del consumo y emisiones de un motor Diésel. http://hdl.handle.net/10251/88183.TFG

Thermal Characterization of Conductive Filaments in Unipolar Resistive Memories

A methodology to estimate the device temperature in resistive random access memories (RRAMs) is presented. Unipolar devices, which are known to be highly influenced by thermal effects in their resistive switching operation, are employed to develop the technique. A 3D RRAM simulator is used to fit experimental data and obtain the maximum and average temperatures of the conductive filaments (CFs) that are responsible for the switching behavior. It is found that the experimental CFs temperature corresponds to the maximum simulated temperatures obtained at the narrowest sections of the CFs. These temperature values can be used to improve compact models for circuit simulation purposesConsejería de Conocimiento, Investigación y Universidad, Junta de Andalucía (Spain)FEDER B-TIC-624-UGR20. M.B.GRamón y Cajal RYC2020-030150-

Modeling the variability of Au/ Ti/h BN/Au memris t ive devices

The variability of memristive devices using multilayer hexagonal boron nitride (h-BN) coupled with Ti and Au electrodes (i.e., Au/Ti/h-BN/Au) is analyzed in depth using different numerical techniques. We extract the reset voltage using three different methods, quantified its cycle-to-cycle variability, calculated the charge and flux that allows to minimize the effects of electric noise and the inherent stochasticity of resistive switching, described the device variability using time series analyses to assess the “memory” effect, and employed a circuit breaker simulator to understand the formation and rupture of the percolation paths that produce the switching. We conclude that the cycle-to-cycle variability of the Au/Ti/h-BN/Au devices presented here is higher than that previously observed in Au/h-BN/Au devices, and hence they may be useful for data encryption.Ministry of Science and Technology of China (2019YFE0124200, 2018YFE0100800)National Natural Science Foundation of China (61874075)Consejería de Conocimiento, Investigación y Universidad, Junta de Andalucía (Spain) and European Regional Development Fund (ERDF) under projects A-TIC-117-UGR18, A-FQM-66-UGR20, A-FQM-345- UGR18, B-TIC-624-UGR20 and IE2017-5414Grant PGC2018-098860-B-I00 supported by MCIU/AEI/FEDERMaria de Maeztu” Excellence Unit IMAG, reference CEX2020-001105-M, funded by MCIN/AEI/10.13039/501100011033King Abdullah University of Science and Technolog

Variability and power enhancement of current controlled resistive switching devices

characterized using both current and voltage sweeps, with the device resistance and its cycle-to-cycle variability being analysed in each case. Experimental measurements indicate a clear improvement on resistance states stability when using current sweeps to induce both set and reset processes. Moreover, it has been found that using current to induce these transitions is more efficient than using voltage sweeps, as seen when analysing the device power consumption. The same results are obtained for devices with a Ni top electrode and a bilayer or pentalayer of HfO2/Al2O3 as dielectric. Finally, kinetic Monte Carlo and compact modelling simulation studies are performed to shed light on the experimental resultsConsejería de Conocimiento, Investigaci´on y Universidad, Junta de Andalucía (Spain)FEDER program for the project B-TIC-624-UGR20Spanish Consejo Superior de Investigaciones Científicas (CSIC) for the intramural project 20225AT012Ramón y Cajal grant No. RYC2020-030150-I

Phase-type distributions for studying variability in resistve memories

A new statistical approach has been developed to analyze Resistive Random Access Memory (RRAM) variability. The stochastic nature of the physical processes behind the operation of resistive memories makes variability one of the key issues to solve from the industrial viewpoint of these new devices. The statistical features of variability have been usually studied making use of Weibull distribution. However, this probability distribution does not work correctly for some resistive memories, in particular for those based on the Ni/HfO2/Si structure thar has been employed in this work. A completely new approach based on phase-type modelling is proposed in this paper to characterize the randomness of resistive memories operation. An in-depth comparision with experimental results shows that the fitted phase-type distribution works better than the Weibull distribution and also helps to understand the physics of the resistive memories.Spanish Ministry of Economy and Competitiveness (FEDER program) TEC2017-84321-C4-3-R MTM2017-88708-PIMB-CNM (CSIC) (Barcelona

An Unusual Case of Solar Urticaria Exacerbated by Clothing: Confirmation Through Phototesting

This work has been supported by the project no. PID2020-117224RB-100of Spanish Ministry of Science and Innovation. // Funding for open access charge: Universidad de Málaga/CBUA

Resistive Switching and Charge Transport in Laser-Fabricated Graphene Oxide Memristors: A Time Series and Quantum Point Contact Modeling Approach

This work investigates the sources of resistive switching (RS) in recently reported laser-fabricated graphene oxide memristors by means of two numerical analysis tools linked to the Time Series Statistical Analysis and the use of the Quantum Point Contact Conduction model. The application of both numerical procedures points to the existence of a filament connecting the electrodes that may be interrupted at a precise point within the conductive path, resulting in resistive switching phenomena. These results support the existing model attributing the memristance of laser-fabricated graphene oxide memristors to the modification of a conductive path stoichiometry inside the graphene oxide.The authors thank the support of the Spanish Ministry of Science, Innovation and Universities under projects TEC2017-89955-P, TEC2017-84321-C4-3-R, MTM2017-88708-P and project PGC2018-098860-B-I00 (MCIU/AEI/FEDER, UE), and the predoctoral grant FPU16/01451

Multivariate analysis and extraction of parameters in resistive RAMs using the Quantum Point Contact model

A multivariate analysis of the parameters that characterize the reset process in RRAMs has been performed. The different correlations obtained can help to shed light on the current components that contribute in the Low Resistance State (LRS) of the technology considered. In addition, a screening method for the Quantum Point Contact (QPC) current component is presented. For this purpose the second derivative of the current has been obtained using a novel numerical method which allows determining the QPC model parameters. Once the procedure is completed, a whole RS series of thousands of curves is studied by means of a genetic algorithm. The extracted QPC parameter distributions are characterized in depth to get information about the filamentary pathways associated with LRS in the low voltage conduction regime.Spanish Ministry of Economy and Competitiveness TEC2014-52152-C3-2-R , MTM2013-47929-P (also supported by the FEDER program)IMB-CNM Spanish Ministry of Economy and Competitiveness TEC2014-52152-C3-1-R and TEC2014-54906-JIN (supported by the FEDER program)ENIAC Joint Undertaking-PANACHE project.Spanish ICTS Network MICRONANOFAB

Variability and power enhancement of current controlled resistive switching devices

Producción CientíficaIn this work, the unipolar resistive switching behaviour of Ni/HfO2/Si(n+) devices is studied. The structures are characterized using both current and voltage sweeps, with the device resistance and its cycle-to-cycle variability being analysed in each case. Experimental measurements indicate a clear improvement on resistance states stability when using current sweeps to induce both set and reset processes. Moreover, it has been found that using current to induce these transitions is more efficient than using voltage sweeps, as seen when analysing the device power consumption. The same results are obtained for devices with a Ni top electrode and a bilayer or pentalayer of HfO2/Al2O3 as dielectric. Finally, kinetic Monte Carlo and compact modelling simulation studies are performed to shed light on the experimental results.Junta de Andalucía - FEDER (B-TIC-624-UGR20)Consejo Superior de Investigaciones Científicas (CSIC) (project 20225AT012)Ramón y Cajal (grant RYC2020-030150-I