Inefficiencies in unbalanced three-phase power systems. Relationship between system asymmetry and instantaneous power waves

[EN] This work analyzes the energy phenomena occurring in linear power systems characterized by the presence of load unbalances, using the principles of the Unifying General Theory of Electric Power [1],[2]. The energy fluxes characterize each phenomenon in the power system, especially the energy associated with the asymmetry phenomenon; thus it is possible to quantify the asymmetry phenomenon from the instantaneous power shapes, manifested by three unbalanced sinusoidal fluxes, whose resultant is a sinusoidal wave. In addition, this work presents the relationship between the quantification of the phenomenon and the amplitudes of the power fluxesSabater I Serra, R.; Donderis Quiles, V. (2004). Inefficiencies in unbalanced three-phase power systems. Relationship between system asymmetry and instantaneous power waves. Renewable Energy and Power Quality Journal. 1(2):112-117. doi:10.24084/repqj02.223S1121171

Influence of Heat Treatment in the Microstructure of a Joint of Nodular Graphite Cast Iron when Using the TIG Welding Process withPerlitic Grey Cast Iron Rods as Filler Material

[EN] The present article analyses the influence of preheating and a postweld heat treatment in the microstructure, mechanical properties and wear behaviour of a joint of nodular graphite cast iron when using the tungsten inert gas (TIG) welding process with perlitic grey cast iron rods as filler material. Data obtained from the tests and the microstructural study of the samples show that the absence of a postweld heat treatment and of preheating leads to the apparition of hard structures and a notable reduction in elongation. Preheating or annealing the weld avoid the presence of these hard structures and increase the ductile behaviour of the joint although at the cost of a further loss of mechanical strength. Wear rate was found to be higher at the weld bead than at the base metal, even when the hardness of both areas is the same.Cárcel Carrasco, FJ.; Pascual Guillamón, M.; Salas Vicente, F.; Donderis Quiles, V. (2019). Influence of Heat Treatment in the Microstructure of a Joint of Nodular Graphite Cast Iron when Using the TIG Welding Process withPerlitic Grey Cast Iron Rods as Filler Material. Metals. 9(1):1-11. https://doi.org/10.3390/met9010048S1119

Infrared Thermography Smart Sensor for the Condition Monitoring of gearbox and Bearings Faults in Induction Motors

[EN] The monitoring of machine conditions is very important from the viewpoints of productivity, economic benefits, and maintenance. Several techniques have been proposed where the sensors are the key to provide relevant information to verify the system. Recently, the smart sensor con-cept is tendency where the sensors are integrated with a data processing unit executing dedicated algorithms for generating in situ meaningful information about the system. Also, the infrared thermography has gained relevance for monitoring processes, since the new infrared cameras have more resolution, smaller dimensions, reliability, functionality, and lower costs. These units were firstly used as secondary elements in the condition monitoring of machines, but thanks to modern techniques for data processing the infrared sensors can be used to give a first, or even a direct, diagnosis in a nonintrusive way for industrial applications. Therefore, in this manuscript the structure and development of an infrared thermography-based smart sensor for diagnosing faults in the elements associated to induction motors, like rolling bearings and the gearbox, is described. The smart sensor structure includes five main parts: infrared primary sensor, pre-processing module, image processing module, classification of faults, and user interface. The in-frared primary sensor considers a low-cost micro thermal camera for acquiring the thermal im-ages. The processing modules and the classification module implement the data processing algo-rithms into digital development boards enabling the characteristic of smart to the system. Final-ly, the interface module allows the final users require to the smart sensor to perform processing actions and data visualization, with the additional feature that the diagnosis report can be get-ting out from the system. The smart sensor is validated in a real experimental test bench demon-strating its capabilities in different case studies.This research was funded in part by the Spanish 'Ministerio de Ciencia Innovacion y Universidades' and FEDER program in the framework of the `Proyectos de Generacion de Conocimiento 20210 del Programa Estatal para Impulsar la Investigacion Cientifico-Tecnica y su Transferencia, Subprograma Estatal de Generacion de Conocimiento' (ref: PID2021-122343OB-I00). This project was partially supported by CONACyT scholarship 1184196Alvarado-Hernandez, AI.; Zamudio-Ramirez, I.; Jaen-Cuellar, AY.; Roque Alfredo Osornio-Rios; Donderis Quiles, V.; Antonino-Daviu, JA. (2022). Infrared Thermography Smart Sensor for the Condition Monitoring of gearbox and Bearings Faults in Induction Motors. Sensors. 22(16):1-20. https://doi.org/10.3390/s22166075120221

Electroactive calcium-alginate/polycaprolactone/reduced graphene oxide nanohybrid hydrogels for skeletal muscle tissue engineering

[EN] Graphene derivatives such as reduced graphene oxide (rGO) are used as components of novel biomaterials for their unique electrical properties. Electrical conductivity is a crucial factor for muscle cells, which are electrically active. This study reports the development of a new type of semi-interpenetrated polymer network based on two biodegradable FDA-approved biomaterials, sodium alginate (SA) and polycaprolactone (PCL), with Ca2+ ions as SA crosslinker. Several drawbacks such as the low cell adhesion of SA and weak structural stability can be improved with the incorporation of PCL. Furthermore, this study demonstrates how this semi-IPN can be engineered with rGO nanosheets (0.5% and 2% wt/wt rGO nanosheets) to produce electroactive nanohybrid composite biomaterials. The study focuses on the microstructure and the enhancement of physical and biological properties of these advanced materials, including water sorption, surface wettability, thermal behavior and thermal degradation, mechanical properties, electrical conductivity, cell adhesion and myogenic differentiation. The results suggest the formation of a complex nano-network with different interactions between the components: bonds between SA chains induced by Ca2+ ions (egg-box model), links between rGO nanosheets and SA chains as well as between rGO nanosheets themselves through Ca2+ ions, and strong hydrogen bonding between rGO nanosheets and SA chains. The incorporation of rGO significantly increases the electrical conductivity of the nanohybrid hydrogels, with values in the range of muscle tissue. In vitro cultures with C2C12 murine myoblasts revealed that the conductive nanohybrid hydrogels are not cytotoxic and can greatly enhance myoblast adhesion and myogenic differentiation. These results indicate that these novel electroactive nanohybrid hydrogels have great potential for biomedical applications related to the regeneration of electroactive tissues, particularly in skeletal muscle tissue engineering.Financial support from the Spanish Ministry of Science and Innovation (MCIN (Spain) , AEI/FEDER funds) through the projects RTI2018-097862-B-C21 and PID2020-119333RB-I00/AEI/10.13039/501100011033 are acknowledged. CIBER-BBN initiative is funded by the VI National R & D & I Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program. CIBER actions are financed by the Instituto de Salud Carlos III (Spain) with assistance from the European Regional Development Fund.Aparicio-Collado, JL.; Garcia-San-Martin, N.; Molina Mateo, J.; Torregrosa Cabanilles, C.; Donderis Quiles, V.; Serrano-Aroca, A.; Sabater I Serra, R. (2022). Electroactive calcium-alginate/polycaprolactone/reduced graphene oxide nanohybrid hydrogels for skeletal muscle tissue engineering. Colloids and Surfaces B Biointerfaces. 214:1-13. https://doi.org/10.1016/j.colsurfb.2022.11245511321

Case study on peer assessment performed by engineering first year students

[EN] This paper presents a qualitative study on the evaluation work performed by students of two courses, Physics and Electricity, included in the first year of Electronic and Automatic Engineering Degree (School of Design Engineering) at the Universitat Politècnica de València. The teaching methodologies used include continuous and formative assessment. The activity analyzed, based on peer assessment, consists of a problem to be solved by students. The solution is reflected in a document to be evaluated by other students and instructors. In order to guide students in the evaluation process, a rubric was provided, which includes aspects to consider related to the assessment to be performed. In addition, effective communication transversal competence was assessed. Both tasks, problem resolution and evaluation, were performed in teams. Each team was made up of six members. The teams were the same in the two courses since they are consecutive, taught in first and second semester (one academic year). Each team had to solve six problems and evaluate six resolutions (from other teams) throughout both courses, without repeating the evaluated team (144 evaluations were analysed). The study has been developed in three parts; in the first one, it is analysed how the evaluation work of the teams evolved throughout the academic year. In the second part, the evaluations carried out by two different teams on the same problem resolution were compared, and finally, in the last part, the assessment made by students was compared with the one made by experienced instructors, both using the same rubric for the assessment. The results of the study show that students carry out thoughtful and rigorous assessment work. It was also found that evaluations of the same work carried out by different teams resulted in very close ratings, which supported the credibility of the evaluations. Therefore, we can conclude that methodologies based on peer assessment encourage the active participation of students and enhance their learning.This work has been supported by the Universitat Politècnica de València through the Project of Innovation and Educational Improvement Program (Projects PIME/2018/B26 and PIME/2018/B25 Convocatoria de Proyectos de Innovación y Convergencia).Meseguer Dueñas, JM.; Bernal-Perez, S.; Sabater I Serra, R.; Martínez Sala, RM.; Gámiz-González, M.; Quiles Casado, SDLS.; García-Sánchez, TM.... (2019). Case study on peer assessment performed by engineering first year students. IATED. 6306-6314. https://doi.org/10.21125/iceri.2019.15226306631

Performance analysis by bema of electricity and magnetism courses in engineering degrees using flip teaching metodologies

[EN] In recent years, new teaching methodologies have entered in the high education scenario: blended learning, problem-based learning, learning-oriented assessment, flip teaching, teamwork and effective oral and written communication are new pedagogical tools used in new instruction strategies. A key issue to guide the application of these new methodologies is the assessment of students performance. One broadly used tool for measure the student¿s performance in introductory physics is the Brief Electricity and Magnetism Assessment (BEMA), designed specifically as a standardized instrument to evaluate students¿ qualitative understanding of electricity and magnetism (E&M) key concepts. The reliability and discriminatory capability of BEMA has been previously studied. In this paper, BEMA is used to analyse the performance of E&M students. The E&M course analyzed is included in two different Bachelor¿s Degrees: Industrial Electronics and Automation Engineering (DIEA) and Aerospace Engineering (DA) both in Universitat Politècnica de València (UPV), Spain. They are semester traditional curriculums in which the use of traditional textbooks and screencast have been combined, including flip teaching methodologies. BEMA pre- and post-instruction tests were carried out at the beginning and end of the course respectively. To deepen understanding of student learning in the E&M course, correlations of pre- and post-instruction scores have been investigated, identifying the main gain and variance. The relevant information obtained through the BEMA test will allow instructors to monitor the use of new methodologies and teaching tools.This work has been supported by the Universitat Politècnica de València through the Project of Innovation and Educational Improvement Program (Projects PIME/2018/B26 and PIME/2018/B25 Convocatoria de Proyectos de Innovación y Convergencia).Bernal-Perez, S.; Sabater I Serra, R.; Riera Guasp, J.; Gámiz-González, MA.; Gómez-Tejedor, J.; García-Sánchez, TM.; Meseguer Dueñas, JM.... (2019). Performance analysis by bema of electricity and magnetism courses in engineering degrees using flip teaching metodologies. IATED. 6456-6462. https://doi.org/10.21125/iceri.2019.1552S6456646