A learning activity designed for a large group of students in a mechanical engineering subject using peer-assessment to encourage deeper learning

[EN] This paper presents a learning activity for the subject "Machines and Mechanisms" in a bachelor¿s degree in Electrical Engineering that allows to work on several specific and generic competences for a large group of students. This activity consists of seeking a real mechanism and following some steps to analyze it, so that the students can improve their knowledge and understanding of the subject area. This activity is planned in a way that forces the students to put different skills into play, further than just dealing with the technical issues of it. Peer-assessment is carried out alongside the activity to encourage deeper learning. A full description of the activity is presented, together with the assessment tools and the results for this course.The authors acknowledge the financial contribution by the Universitat Politècnica de València through the project PIME/2018/DPTO.IMM.Suñer Martinez, JL.; Carballeira, J. (2020). A learning activity designed for a large group of students in a mechanical engineering subject using peer-assessment to encourage deeper learning. IATED Academy. 4931-4935. https://doi.org/10.21125/edulearn.2020.1291S4931493

A Highly Available Cluster of Web Servers with Increased Storage Capacity

Ponencias de las Decimoséptimas Jornadas de Paralelismo de la Universidad de Castilla-La Mancha celebradas el 18,19 y 20 de septiembre de 2006 en AlbaceteWeb servers scalability has been traditionally solved by improving software elements or increasing hardware resources of the server machine. Another approach has been the usage of distributed architectures. In such architectures, usually, file al- location strategy has been either full replication or full distribution. In previous works we have showed that partial replication offers a good balance between storage capacity and reliability. It offers much higher storage capacity while reliability may be kept at an equivalent level of that from fully replicated solutions. In this paper we present the architectural details of Web cluster solutions adapted to partial replication. We also show that partial replication does not imply a penalty in performance over classical fully replicated architectures. For evaluation purposes we have used a simulation model under the OMNeT++ framework and we use mean service time as a performance comparison metric.Publicad

On the calculation of the Kalker's creep coefficients for non-elliptical contact areas

[EN] FastSim is the most widely used tangential contact method due to its accuracy and computational efficiency. However, its use is limited to elliptic contact areas, as it needs results from Kalker’s Linear Theory, a Hertzian contact theory, to obtain the so-called elastic parameters. This makes FastSim unable to face some of the current railway challenges, such as wear, corrugation, Rolling Contact Fatigue (RCF), wheel flats, etc. Taking this limitation into account, in the present work, an alternative methodology to Kalker’s Linear Theory is proposed, which will enable FastSim to deal with non-Hertzian conditions.The authors gratefully acknowledge the financial support of Agencia Estatal de Investigación and European Regional Development Fund (grant PRE2018-084067 and project TRA2017-84701-R).Gómez-Bosch, J.; Giner-Navarro, J.; Carballeira, J. (2022). On the calculation of the Kalker's creep coefficients for non-elliptical contact areas. En Proceedings of the YIC 2021 - VI ECCOMAS Young Investigators Conference. Editorial Universitat Politècnica de València. 288-294. https://doi.org/10.4995/YIC2021.2021.12313OCS28829

Working on Critical Thinking skills using the computer lab works of an Engineering subject

[EN] A practical intervention was devised in order to promote and to assess Critical Thinking in undergraduate students of Engineering. First, in collaboration with specialists in education, the concept of Critical Thinking, and its skills and dispositions on which to focus on, was determined. Second, a teaching strategy was designed in order to be as effective as possible, considering the limitations of the intervention. This strategy took advantage of the computer lab sessions where discussion and questioning encouraged the development of Critical Thinking. Then, the instruments to assess the acquired skills and attitudes of the students were developed. Finally, a quantitative analysis of the results was conducted in order to evaluate the validity and reliability of the strategy. This paper presents a full description of the intervention carried on for two years. Besides the desired effects on the students performance, some conclusions regarding the development of appropriate instruments to deal with a large group of students are drawn. This intervention has proven to be effective in order to help the students to develop their Critical Thinking skills, and it is particularly suitable for large groups.This research was funded by the Universitat Politècnica de València through the project PIME/2018/DPTO. IMM.Giner-Navarro, J.; Sonseca, Á.; Martínez-Casas, J.; Carballeira, J. (2022). Working on Critical Thinking skills using the computer lab works of an Engineering subject. Multidisciplinary Journal for Education, Social and Technological Sciences. 9(2):23-45. https://doi.org/10.4995/muse.2022.1790823459

Wepsim: an online interactive educational simulator integrating microdesign, microprogramming, and assembly language programming

Our educational project has three primary goals. First, we want to provide a robust vision of how hardware and software interplay, by integrating the design of an instruction set (through microprogramming) and using that instruction set for assembly programming. Second, we wish to offer a versatile and interactive tool where the previous integrated vision could be tested. The tool we have developed to achieve this is called WepSIM and it provides the view of an elemental processor together with a microprogrammed subset of the MIPS instruction set. In addition, WepSIM is flexible enough to be adapted to other instruction sets or hardware components (e.g., ARM or x86). Third, we want to extend the activities of our university courses, labs, and lectures (fixed hours in a fixed place), so that students may learn by using their mobile device at any location, and at any time during the day. This article presents how WepSIM has improved the teaching of Computer Structure courses by empowering students with a more dynamic and guided learning process. In this paper, we show the results obtained during the experience of using the simulator in the Computer Structure course of the Bachelor's Degree in Computer Science and Engineering at University Carlos III of Madrid

A vibroacoustic model of the stationary railway wheel for sound radiation prediction through an axisymmetric approach

[EN] In the literature, different dynamic models of the railway wheel have been developed to predict its sound radiation; however, there are still certain aspects that can be improved. Specifically, the high computational cost of these models, either because they solve the fluidstructure interaction or because they solve the dynamics and acoustics of the three-dimensional wheel, makes it difficult to carry out numerous simulations with the aim of achieving quieter designs. In the present work, a vibroacoustic model of the stationary wheel is developed through an axisymmetric approach, yielding an efficient and comprehensive acoustic prediction tool. The calculation methodology consists of, firstly, adopting an axisymmetric approach to solve the vibratory dynamics of the wheel from its cross-section, using finite element techniques; subsequently, the acoustic radiation of the three-dimensional wheel is calculated from the dynamics of the aforementioned section through an analytical formulation. Finally, the vibroacoustic model developed is validated via comparison with commercial software that solves the fluid-structure interaction, showing the aforementioned computational advantages that the former has over the latter.The authors gratefully acknowledge the financial support of Agencia Estatal de Investigación and European Regional Development Fund (grant FPU18/03999, project TRA2017-84701-R and project PID2020-112886RA-I00).Andrés Ruiz, V.; Martínez Casas, J.; Carballeira Morado, J.; Denia Guzmán, F. (2022). A vibroacoustic model of the stationary railway wheel for sound radiation prediction through an axisymmetric approach. En Proceedings of the YIC 2021 - VI ECCOMAS Young Investigators Conference. Editorial Universitat Politècnica de València. 320-325. https://doi.org/10.4995/YIC2021.2021.12584OCS32032

Rail corrugation growth accounting for the flexibility and rotation of the wheel set and the non-Hertzian and non-steady-state effects at contact patch

[EN] In this work, a simulation tool is developed to analyse the growth of rail corrugation consisting of several models connected in a feedback loop in order to account for both the short-term dynamic vehicle track interaction and the long-term damage. The time-domain vehicle track interaction model comprises a flexible rotating wheel set model, a cyclic track model based on a substructuring technique and a non-Hertzian and non-steady-state three-dimensional wheel rail contact model, based on the variational theory by Kalker. Wear calculation is performed with Archard s wear model by using the contact parameters obtained with the non-Hertzian and non-steady-state three-dimensional contact model. The aim of this paper is to analyse the influence of the excitation of two coinciding resonances of the flexible rotating wheel set on the rail corrugation growth in the frequency range from 20 to 1500 Hz, when contact conditions similar to those that can arise while a wheel set is negotiating a gentle curve are simulated. Numerical results show that rail corrugation grows only on the low rail for two cases in which two different modes of the rotating wheel set coincide in frequency. In the first case, identified by using the Campbell diagram, the excitation of both the backward wheel mode and the forward third bending mode of the wheel set model (B-F modes) promotes the growth of rail corrugation with a wavelength of 110mm for a vehicle velocity of 142 km/h. In the second case, the excitation of both the backward wheel mode and the backward third bending mode (B-B modes) gives rise to rail corrugation growth at a wavelength of 156 mm when the vehicle velocity is 198 km/h.The authors acknowledge the financial contribution by the Spanish Ministry of Economy and Competitiveness through the project TRA2010-15669.Vila Tortosa, MP.; Baeza González, LM.; Martínez Casas, J.; Carballeira, J. (2014). Rail corrugation growth accounting for the flexibility and rotation of the wheel set and the non-Hertzian and non-steady-state effects at contact patch. Vehicle System Dynamics. 52:92-108. https://doi.org/10.1080/00423114.2014.881513S9210852Grassie, S. L., & Kalousek, J. (1993). Rail Corrugation: Characteristics, Causes and Treatments. Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit, 207(1), 57-68. doi:10.1243/pime_proc_1993_207_227_02Hempelmann, K., Hiss, F., Knothe, K., & Ripke, B. (1991). The formation of wear patterns on rail tread. Wear, 144(1-2), 179-195. doi:10.1016/0043-1648(91)90014-lHempelmann, K., & Knothe, K. (1996). An extended linear model for the prediction of short pitch corrugation. Wear, 191(1-2), 161-169. doi:10.1016/0043-1648(95)06747-7GRASSIE, S. L., & ELKINS, J. A. (1998). RAIL CORRUGATION ON NORTH AMERICAN TRANSIT SYSTEMS. Vehicle System Dynamics, 29(sup1), 5-17. doi:10.1080/00423119808969548Egana, J. I., Vinolas, J., & Seco, M. (2006). Investigation of the influence of rail pad stiffness on rail corrugation on a transit system. Wear, 261(2), 216-224. doi:10.1016/j.wear.2005.10.004Igeland, A. (1996). Railhead Corrugation Growth Explained by Dynamic Interaction between Track and Bogie Wheelsets. Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit, 210(1), 11-20. doi:10.1243/pime_proc_1996_210_322_02Gómez, I., & Vadillo, E. G. (2003). A linear model to explain short pitch corrugation on rails. Wear, 255(7-12), 1127-1142. doi:10.1016/s0043-1648(03)00282-5Collette, C., Vanhonacker, P., Bastaits, R., & Levy, D. (2008). Comparison between time and frequency studies of a corrugated curve of RER Paris network. Wear, 265(9-10), 1249-1258. doi:10.1016/j.wear.2008.01.030Daniel, W. J. T., Horwood, R. J., Meehan, P. A., & Wheatley, N. (2008). Analysis of rail corrugation in cornering. Wear, 265(9-10), 1183-1192. doi:10.1016/j.wear.2008.02.030Fayos, J., Baeza, L., Denia, F. D., & Tarancón, J. E. (2007). An Eulerian coordinate-based method for analysing the structural vibrations of a solid of revolution rotating about its main axis. Journal of Sound and Vibration, 306(3-5), 618-635. doi:10.1016/j.jsv.2007.05.051Baeza, L., & Ouyang, H. (2011). A railway track dynamics model based on modal substructuring and a cyclic boundary condition. Journal of Sound and Vibration, 330(1), 75-86. doi:10.1016/j.jsv.2010.07.023Kalker, J. J. (1990). Three-Dimensional Elastic Bodies in Rolling Contact. Solid Mechanics and Its Applications. doi:10.1007/978-94-015-7889-9Xie, G., & Iwnicki, S. D. (2008). Simulation of wear on a rough rail using a time-domain wheel–track interaction model. Wear, 265(11-12), 1572-1583. doi:10.1016/j.wear.2008.03.016Igeland, A., & Ilias, H. (1997). Rail head corrugation growth predictions based on non-linear high frequency vehicle/track interaction. Wear, 213(1-2), 90-97. doi:10.1016/s0043-1648(97)00172-5Vila, P., Fayos, J., & Baeza, L. (2011). Simulation of the evolution of rail corrugation using a rotating flexible wheelset model. Vehicle System Dynamics, 49(11), 1749-1769. doi:10.1080/00423114.2011.552619Popp, K., Kruse, H., & Kaiser, I. (1999). Vehicle-Track Dynamics in the Mid-Frequency Range. Vehicle System Dynamics, 31(5-6), 423-464. doi:10.1076/vesd.31.5.423.8363Johnson, K. L. (1985). Contact Mechanics. doi:10.1017/cbo9781139171731Hiensch, M., Nielsen, J. C. O., & Verheijen, E. (2002). Rail corrugation in The Netherlands—measurements and simulations. Wear, 253(1-2), 140-149. doi:10.1016/s0043-1648(02)00093-5Jin, X., Xiao, X., Wen, Z., Guo, J., & Zhu, M. (2009). An investigation into the effect of train curving on wear and contact stresses of wheel and rail. Tribology International, 42(3), 475-490. doi:10.1016/j.triboint.2008.08.004Ilias, H., & Müller, S. (1994). A discrete-continuous track-model for wheelsets rolling over short wavelength sinusoidal rail irregularities. Vehicle System Dynamics, 23(sup1), 221-233. doi:10.1080/0042311930896951

Exposing data locality in HPC-based systems by using the HDFS backend

This work was partially supported by the project “CABAHLA-CM: Convergencia Big data-Hpc: de los sensores a las Aplicaciones” S2018/TCS4423 from Madrid Regional Government and the European Union’s Horizon 2020 research, New Data Intensive Computing Methods for High-End and Edge Computing Platforms (DECIDE). Ref. PID2019-107858GB-I00 and innovation program under grant agreement No 801091, project “ÀSPIDE: Exascale programming models for extreme data processing”

Group psychological abuse: Taxonomy and severity of its components

The purpose of this study was to delimit group psychological abuse through a psychosocial approach. An operational definition of the phenomenon and a taxonomy of group psychological abuse strategies were proposed based on a review of the scientific literature. A panel of 31 experts in the area evaluated the content of the taxonomy and judged the severity of the strategies through a Delphi study. Group psychological abuse was defined by the application of abusive strategies, their continued duration, and their ultimate aim, i.e., subjugation of the individual. The taxonomy showed adequate content validity. Expert's judgments allowed for hierarchically organizing the strategies based on their severity, being the most severe those directed to emotional area. Operationalizing, classifying and organizing the strategies hierarchically contributes to a better delimitation of the phenomenon, which is useful for both the academic and applied field

Improving performance using computational compression through memoization: A case study using a railway power consumption simulator

The objective of data compression is to avoid redundancy in order to reduce the size of the data to be stored or transmitted. In some scenarios, data compression may help to increase global performance by reducing the amount of data at a competitive cost in terms of global time and energy consumption. We have introduced computational compression as a technique for reducing redundant computation, in other words, to avoid carrying out the same computation with the same input to obtain the same output. In some scenarios, such as simulations, graphic processing, and so on, part of the computation is repeated using the same input in order to obtain the same output, and this computation could have an important cost in terms of global time and energy consumption. We propose applying computational compression by using memoization in order to store the results for future reuse and, in this way, minimize the use of the same costly computation. Although memoization was proposed for sequential applications in the 1980s, and there are some projects that have applied it in very specific domains, we propose a novel, domain-independent way of using it in high-performance applications, as a means of avoiding redundant computation.This work has been partially supported by the Spanish Ministry of Economy and Competitiveness under the project TIN2013-41350-P (Scalable Data Management Techniques for High-End Computing Systems)