Development of a novel synthesis method of a rigid-body four-bar linkage into a compliant mechanism

The four-bar linkage mechanism is widely used in various machinery applications. This study presents a synthesis method to transform a rigid-body four-bar mechanism into a compliant mechanism using four leaf-type hinges based on linear theory and Castigliano's Theorem. The objective is to determine the dimensions and configuration of a flexible four-bar mechanism that replicates the behavior of the initial rigid-body mechanism. The meeting point between the two mechanisms is the flexure hinge of the compliant mechanism, which is determined using the Pseudo-Rigid-Body model (PRBM). To validate the proposed method, a program based on non-linear theory is employed. The results confirm that the dimensional differences between the two are minimal, ranging from 0% to 0.13%. This study demonstrates the feasibility of synthesizing a Rigid-Body Four-Bar Mechanism into a compliant mechanism using the PRBM, as long as the deformations are within the linear domain

Bending collapse analysis for thin and medium-thin-walled square and rectangular hollow shapes

Thin-walled hollow shapes are of great interest in many industries with weight constraints due to their availability, low price, and strength to weight ratio. However, they are also prone to localized bending collapse, which can be used as an energy absorption mechanism during deformation. Up until now, industrial applications have relied on numerical simulations, non-standardized tests, and a handful of theories to address the bending collapse behavior. In this paper, a modification to the most widely used theory is presented and adapted for hollow shapes with greater thickness that cannot be considered. To verify the accuracy of the proposed modification, a comparison with a detailed FEM model, validated through various three-point bending collapse experimental tests, has been performed. The results seem to show that the proposed modifications can predict the maximum load and collapse stage behavior of hollow shapes with more accuracy than the original analytical model. Thus, the proposed modification may be used to predict the collapse behavior of commercially available square and rectangular hollow shapes in different fields of application.D. Lavayen would like to recognize the financial support providedby CONCYTEC (Peru) and The World Bank, through the Pontifical Catholic University of Peru and FONDECYT (Peru): Funding Contract;10-2018-FONDECYT/WB PhD programs in strategic and generalareas. Part of this work has also been supported by Comunidad de Madrid - multiannual agreement with UC3M (Excelencia para el Profesorado Universitario - EPUC3M21 ) - Fifth regional research plan2016-202

Filtering Methods for Efficient Dynamic Access Control in 5G Massive Machine-Type Communication Scenarios

[EN] One of the three main use cases of the fifth generation of mobile networks (5G) is massive machine-type communications (mMTC). The latter refers to the highly synchronized accesses to the cellular base stations from a great number of wireless devices, as a product of the automated exchange of small amounts of data. Clearly, an efficient mMTC is required to support the Internet-of-Things (IoT). Nevertheless, the method to change from idle to connected mode, known as the random access procedure (RAP), of 4G has been directly inherited by 5G, at least, until the first phase of standardization. Research has demonstrated the RAP is inefficient to support mMTC, hence, access control schemes are needed to obtain an adequate performance. In this paper, we compare the benefits of using different filtering methods to configure an access control scheme included in the 5G standards: the access class barring (ACB), according to the intensity of access requests. These filtering methods are a key component of our proposed ACB configuration scheme, which can lead to more than a three-fold increase in the probability of successfully completing the random access procedure under the most typical network configuration and mMTC scenario.This research has been supported in part by the Ministry of Economy and Competitiveness of Spain under Grant TIN2013-47272-C2-1-R and Grant TEC2015-71932-REDT. The research of I. Leyva-Mayorga was partially funded by grant 383936 CONACYT-GEM 2014.Leyva-Mayorga, I.; Rodríguez-Hernández, MA.; Pla, V.; Martínez Bauset, J. (2019). Filtering Methods for Efficient Dynamic Access Control in 5G Massive Machine-Type Communication Scenarios. Electronics. 8(1):1-18. https://doi.org/10.3390/electronics8010027S11881Laya, A., Alonso, L., & Alonso-Zarate, J. (2014). Is the Random Access Channel of LTE and LTE-A Suitable for M2M Communications? A Survey of Alternatives. IEEE Communications Surveys & Tutorials, 16(1), 4-16. doi:10.1109/surv.2013.111313.00244Biral, A., Centenaro, M., Zanella, A., Vangelista, L., & Zorzi, M. (2015). The challenges of M2M massive access in wireless cellular networks. Digital Communications and Networks, 1(1), 1-19. doi:10.1016/j.dcan.2015.02.001Tello-Oquendo, L., Leyva-Mayorga, I., Pla, V., Martinez-Bauset, J., Vidal, J.-R., Casares-Giner, V., & Guijarro, L. (2018). Performance Analysis and Optimal Access Class Barring Parameter Configuration in LTE-A Networks With Massive M2M Traffic. IEEE Transactions on Vehicular Technology, 67(4), 3505-3520. doi:10.1109/tvt.2017.2776868Tavana, M., Rahmati, A., & Shah-Mansouri, V. (2018). Congestion control with adaptive access class barring for LTE M2M overload using Kalman filters. Computer Networks, 141, 222-233. doi:10.1016/j.comnet.2018.01.044Lin, T.-M., Lee, C.-H., Cheng, J.-P., & Chen, W.-T. (2014). PRADA: Prioritized Random Access With Dynamic Access Barring for MTC in 3GPP LTE-A Networks. IEEE Transactions on Vehicular Technology, 63(5), 2467-2472. doi:10.1109/tvt.2013.2290128De Andrade, T. P. C., Astudillo, C. A., Sekijima, L. R., & Da Fonseca, N. L. S. (2017). The Random Access Procedure in Long Term Evolution Networks for the Internet of Things. IEEE Communications Magazine, 55(3), 124-131. doi:10.1109/mcom.2017.1600555cmWang, Z., & Wong, V. W. S. (2015). Optimal Access Class Barring for Stationary Machine Type Communication Devices With Timing Advance Information. IEEE Transactions on Wireless Communications, 14(10), 5374-5387. doi:10.1109/twc.2015.2437872Tello-Oquendo, L., Pacheco-Paramo, D., Pla, V., & Martinez-Bauset, J. (2018). Reinforcement Learning-Based ACB in LTE-A Networks for Handling Massive M2M and H2H Communications. 2018 IEEE International Conference on Communications (ICC). doi:10.1109/icc.2018.8422167Leyva-Mayorga, I., Rodriguez-Hernandez, M. A., Pla, V., Martinez-Bauset, J., & Tello-Oquendo, L. (2019). Adaptive access class barring for efficient mMTC. Computer Networks, 149, 252-264. doi:10.1016/j.comnet.2018.12.003Kalalas, C., & Alonso-Zarate, J. (2017). Reliability analysis of the random access channel of LTE with access class barring for smart grid monitoring traffic. 2017 IEEE International Conference on Communications Workshops (ICC Workshops). doi:10.1109/iccw.2017.7962744Leyva-Mayorga, I., Tello-Oquendo, L., Pla, V., Martinez-Bauset, J., & Casares-Giner, V. (2016). Performance analysis of access class barring for handling massive M2M traffic in LTE-A networks. 2016 IEEE International Conference on Communications (ICC). doi:10.1109/icc.2016.7510814Arouk, O., & Ksentini, A. (2016). General Model for RACH Procedure Performance Analysis. IEEE Communications Letters, 20(2), 372-375. doi:10.1109/lcomm.2015.2505280Zhang, Z., Chao, H., Wang, W., & Li, X. (2014). Performance Analysis and UE-Side Improvement of Extended Access Barring for Machine Type Communications in LTE. 2014 IEEE 79th Vehicular Technology Conference (VTC Spring). doi:10.1109/vtcspring.2014.7023042Cheng, R.-G., Chen, J., Chen, D.-W., & Wei, C.-H. (2015). Modeling and Analysis of an Extended Access Barring Algorithm for Machine-Type Communications in LTE-A Networks. IEEE Transactions on Wireless Communications, 14(6), 2956-2968. doi:10.1109/twc.2015.2398858Widrow, B., Glover, J. R., McCool, J. M., Kaunitz, J., Williams, C. S., Hearn, R. H., … Goodlin, R. C. (1975). Adaptive noise cancelling: Principles and applications. Proceedings of the IEEE, 63(12), 1692-1716. doi:10.1109/proc.1975.1003

Influence of conical projectile diameter on perpendicular impact oh thin steel plate

A numerical study of conical projectiles for perpendicular impact on a thin steel plate is reported. The target material considered, Weldox 460 E steel, is frequently used for this kind of application and several results of experiments are available in the international literature to verify numerical simulations. The Johnson-Cook constitutive relation coupled with the Johnson-Cook failure criterion have been applied to analyse penetration of the target and also the failure process. The analysis has been focussed on the influence of the projectile diameter on the perforation process, assuming the same projectile mass. The aim was to preserve the same initial kinetic energy and identical nose angle. The goal is to estimate the ballistic limit, the residual velocity, the plastic work, and the temperature levels produced during the penetration process. The analysis has shown a linear increase of the ballistic limit with the projectile diameter.Publicad

Adaptive access class barring for efficient mMTC

[EN] In massive machine-type communications (mMTC), an immense number of wireless devices communicate autonomously to provide users with ubiquitous access to information and services. The current 4G LTE-A cellular system and its Internet of Things (IoT) implementation, the narrowband IoT (NB-IoT), present appealing options for the interconnection of these wireless devices. However, severe congestion may arise whenever a massive number of highly-synchronized access requests occur. Consequently, access control schemes, such as the access class barring (ACB), have become a major research topic. In the latter, the precise selection of the barring parameters in a real-time fashion is needed to maximize performance, but is hindered by numerous characteristics and limitations of the current cellular systems. In this paper, we present a novel ACB configuration (ACBC) scheme that can be directly implemented at the cellular base stations. In our ACBC scheme, we calculate the ratio of idle to total available resources, which then serves as the input to an adaptive filtering algorithm. The main objective of the latter is to enhance the selection of the barring parameters by reducing the effect of the inherent randomness of the system. Results show that our ACBC scheme greatly enhances the performance of the system during periods of high congestion. In addition, the increase in the access delay during periods of light traffic load is minimal.This research has been supported in part by the Ministry of Economy and Competitiveness of Spain under Grant TIN2013-47272-C2-1-R and Grant TEC2015-71932-REDT. The research of I. Leyva-Mayorga was partially funded by grant 383936 CONACYT-GEM 2014.Leyva-Mayorga, I.; Rodríguez-Hernández, MA.; Pla, V.; Martínez Bauset, J.; Tello-Oquendo, L. (2019). Adaptive access class barring for efficient mMTC. Computer Networks. 149:252-264. https://doi.org/10.1016/j.comnet.2018.12.003S25226414

Negative pressures in CaWO4 nanocrystals

Tetragonal scheelite-type CaWO4 nanocrystals recently prepared by a hydrothermal method show an enhancement of its structural symmetry with the decrease in nanocrystal size. The analysis of the volume dependence of the structural parameters in CaWO4 nanocrystals with the help of ab initio total-energy calculations shows that the enhancement of the symmetry in the scheelite-type nanocrystals is a consequence of the negative pressure exerted on the nanocrystals; i.e., the nanocrystals are under tension. Besides, the behavior of the structural parameters in CaWO4 nanocrystals for sizes below 10 nm suggests an onset of a scheelite-to-zircon phase transformation in good agreement with the predictions from our ab initio calculations. CaWO4 nanocrystals exhibit a reconstructive-type mechanism for the scheelite-to-zircon phase transition that seems to follow the tetragonal path that links both structures. This result is in contrast with the mechanism recently proposed for this transition in bulk ZrSiO4 where the transition goes through an intermediate monoclinic [email protected]

Finishing lambs using an integral feed under a restricted-feeding program in an intensive production system in Northern Mexico

The objective of this study was to compare the productive performance of finishing lambs using an integral diet under a restricted-feeding program. Ten Dorper lambs were assigned to two homogenous groups according to live weight and age under a complete randomised block design. Group 1 was fed a traditional diet commonly used by the producer and group 2 was fed an integral feed restricted to 75% of dry matter requirement of lambs. The evaluated variables were: dry matter intake, initial and final live weight, daily weight gain, feed efficiency and body growth expressed in height, body length, thoracic diameter, cane length and cane width. A partial cost analysis was carried out to evaluate the economic viability. Lambs fed with the integral feed had better feed efficiency, higher dry matter intake, daily weight gain, height, body length and thoracic diameter when compared with the lambs fed the traditional diet. The use of an integral feed under a restricted-feeding program reduced the cost of finishing lambs by 2.46 dollars per head and finishing length by 120 days. Overall, providing an integral feed under a restricted-feeding program is a viable alternative for improving finishing lambs under intensive conditions in the Northern Mexico

A comparison of the peers method and traditional methodologies, and risk behaviors in studies of the prevalence of drug consumption in a population of female, chilean students

Este estudio investiga el consumo de drogas y los comportamientos de riesgo de alumnas entre los 8º y 12º cursos en dos comunidades de la ciudad de Santiago, Chile. Empleando dos métodos para investigar el consumo, y basándonos en los estudios de poblaciones universitarias, hipotetizamos que los autoinformes de las alumnas sobre su consumo de drogas legales tenderán a ser consistentes con el uso real de dichas drogas, mientras que su consumo de drogas ilícitas será susceptible y tenderán a infra-informar de ello cuando se evalúa a través de medidas tradicionales de autoinforme. Para comparar los dos métodos, se diseñó un estudio transversal que compararía el consumo informado, primero empleando el método de pares, y después por medio del autoinforme tradicional, en un grupo de 350 alumnas. Los resultados muestran que los informes de las chicas sobre su consumo de drogas legales convergen empleando los dos métodos, mientras que, como se ha sugerido, infra-informaban sobre su consumo de drogas ilegales cuando se empleaban metodologías tradicionales.The present study investigates drug consumption and risk behaviors among female students between 8th and 12th grade in two communities in the city of Santiago, Chile. Based on studies of university populations, we hypothesize that the students’ reports of their consumption of licit drugs will tend to be consistent with their actual use of said drugs using two methods to investigate consumption, while their consumption of illicit drugs will be susceptible, and will tend to be under reported when evaluated through traditional self-report measures. In order to compare the two methods, a cross-sectional study was designed that would compare reported drug consumption, first using the peers method, and then by means of traditional self-report in a group of 350 students. The results show that women’s reports of licit drug consumption converge using the two methods, while as earlier suggested, women’s illicit drug consumption was found to be under reported when traditional methodologies were used

Impact of COVID-19 lockdown in telecommunications engineering competency-based alumni ranking

[EN] Higher education, as other social and economic sectors in Spain, was disrupted on 15th March 2020 following health emergency Laws enacted related to COVID-19. Non-presential lecturing was stablished country-wide until the end of the academic year 2019-20, as society was set in lockdown. In this context, it is necessary to evaluate the impact of the mandatory changes implemented in the education paradigm in order to assess the degree of acquisition of general and specific competencies altogether the acquisition of transversal competencies, as an important factor for the alumni career. This paper reports a comprehensive study on the competencies degree of acquisition considering the lockdown scenario in Spain. The results from the last four academic years have been comparatively evaluated in the core subject `Teoría de la Comunicación¿, lectured in the fourth semester of the Telecommunications Engineering Integrated Program (Bachelor and Master) in the Universitat Politècnica de València, Spain, comprising data from 745 alumni. The results indicate that the degree of acquisition of technical competencies in this scenario has been adequate, being marginally better compared to previous academic year, probably due to new lecturing materials prepared. Nevertheless, the acquisition of the transversal competency `analysis and problem solving¿ exhibits degraded results, indicating inhomogeneous acquisition probably due to limitations in the group-based problem-solving practice. The results suggest that specific materials and remote lecturing strategies should be developed and implemented to guarantee adequate acquisition levels.The support by the 2020 Science Parks program from the Consellería de Innovación, Universidades, Ciencia y Sociedad Digital, Generalitat Valenciana, Spain, is acknowledged.Llorente, R.; Rodríguez-Hernández, MA.; Hernandez Franco, CA.; Sastre, J.; Carrión García, A.; Madrigal-Madrigal, J. (2020). Impact of COVID-19 lockdown in telecommunications engineering competency-based alumni ranking. IATED Academy. 9599-9607. https://doi.org/10.21125/iceri.2020.2139S9599960

Culturable aerobic and facultative bacteria from the gut of the polyphagic dung beetle Thorectes lusitanicus Jeckel

Unlike other dung beetles, the Iberian geotrupid Thorectes lusitanicus exhibits polyphagous behavior; for example, it is able to eat acorns, fungi, fruits, and carrion in addition to the dung of different mammals. This adaptation to digest a wider diet has physiological and developmental advantages and requires key changes in the composition and diversity of the beetle's gut microbiota. In this study, we isolated aerobic, facultative anaerobic, and aerotolerant microbiota amenable to grow in culture from the gut contents of T. lusitanicus and resolved isolate identity to the species level by sequencing 16S rRNA gene fragments. Using BLAST similarity searches and maximum likelihood phylogenetic analyses, we were able to reveal that the analyzed fraction (culturable, aerobic, facultative anaerobic, and aerotolerant) of beetle gut microbiota is dominated by the phyla Proteobacteria, Firmicutes and Actinobacteria. Among Proteobacteria, members of the order Enterobacteriales (Gammaproteobacteria) were the most abundant. The main functions associated with the bacteria found in the gut of T. lusitanicus would likely include nitrogen fixation, denitrification, detoxification, and diverse defensive roles against pathogens.This study was supported by the project 065/2002 of the Ministry of Environment, and the projects “Thorbellota” (CGL2008/03878/BOS) and “NiTerDist” (CGL2011-515 25544) of the Secretaría de Estado de Investigación, Desarrollo e Innovación