Efren Diez-Jimenez

Prof. Dr. Efren Diez-Jimenez

Mechanic engineering area, Universidad de Alcalá
orcid

Research Focus & Metrics

Academic Career Length

17Years (2010-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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1 January 2019 in Shock and Vibration
Verified
Journal Article
Open access
PDF file
EDEfren Diez-Jimenez
Efren Diez-Jimenez
RRRocco Rizzo
Rocco Rizzo
María Jesús Gómez GarcíaMaría Jesús Gómez García
María Jesús Gómez García
ECEduardo Corral
Eduardo Corral
Passive electromagnetic devices for vibration damping and isolation are becoming a real alternative to traditional mechanical vibration and isolation methods. These types of devices present good damping capacity, lower cost, null power consumption, and higher reliability. In this work, a state‐of‐the‐art review has been done highlighting advantages and drawbacks, application fields, and technology readiness level of most recent developments. In addition, a general introductory section relates presents key considerations that any engineer, electrical or mechanical, needs to know for a deep comprehension and correct design of these types of devices.

7 April 2021 in Computer Applications in Engineering Education
Verified
Journal Article
Open access
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ECEduardo Corral
Eduardo Corral
María Jesús Gómez GarcíaMaría Jesús Gómez García
María Jesús Gómez García
EDEfren Diez-Jimenez
Efren Diez-Jimenez
PMPedro Manuel Moreno-Marcos
Pedro Manuel Moreno-Marcos
CSCristina Castejón Sisamon
Cristina Castejón Sisamon
Over decades, Mechanical Engineering students often find some difficulties to grasp some contents and/or struggle with some parts of the course. With the increasing development of new technologies, promising innovations can be implemented enhancing learning and improving success rates. In this study, a new learning interactive method is proposed and evaluated using the experience of over 600 students of Mechanical Engineering. This study describes a 4‐year experiment based on new interactive applications for education. The experiment has been implemented using E‐learning techniques and new technologies (a combination of remote and virtual examples, videos, quizzes, and theory). Specifically, several applications have been programmed to be executed on different devices, such as mobile phones and PC/laptops (Android and Windows). The experiment is applied using small applications that help the students identify the most challenging contents and guide them throughout step‐by‐step. The main objective of this interactive method is to help students find their lack of knowledge and offer them contents to cover it. These didactic applications are portable and intuitive. Thanks to these interactive applications, it is possible to accomplish better practices of “E‐learning” and “Computer Simulation and Animation” together. Since they are portable applications, they allow the student to interact and check conceptual understandings at any place. Students really appreciate this aspect. The results of the course titled Mechanism and Machine Theory have been analyzed during these four last years in which these interactive applications have been offered to the students.

1 July 2015 in Machines
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Journal Article
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JPJose Luis Perez-Diaz
Jose Luis Perez-Diaz
EDEfren Diez-Jimenez
Efren Diez-Jimenez
IVIgnacio Valiente
Ignacio Valiente
CCCristian Cristache
Cristian Cristache
MAMarco-Antonio Alvarez-Valenzuela
Marco-Antonio Alvarez-Valenzuela
JRJuan Rojas-Martinez
Juan Rojas-Martinez
Harmonic drives are profusely used in aerospace mainly because of their compactness and large reduction ratio. However, their use in cryogenic environments is still a challenge. Lubrication and fatigue are non-trivial issues under these conditions. The objective of the Magnetic-Superconductor Cryogenic Non-contact Harmonic Drive (MAGDRIVE) project, funded by the EU Space FP7, is to design, build, and test a new concept of MAGDRIVE. Non-contact interactions among magnets, soft magnetic materials, and superconductors are efficiently used to provide a high reduction ratio gear that smoothly and naturally operates at cryogenic environments. The limiting elements of conventional harmonic drives (teeth, flexspline, and ball bearings) are substituted by contactless mechanical components (magnetic gear and superconducting magnetic bearings). The absence of contact between moving parts prevents wear, lubricants are no longer required, and the operational lifetime is greatly increased. This is the first mechanical reducer in mechanical engineering history without any contact between moving parts. In this paper, the test results of a −1:20 inverse reduction ratio MAGDRIVE prototype are reported. In these tests, successful operation at 40 K and 10−3 Pa was demonstrated for more than 1.5 million input cycles. A maximum torque of 3 N·m and an efficiency of 80% were demonstrated. The maximum tested input speed was 3000 rpm, six times the previous existing record for harmonic drives at cryogenic temperatures.

1 April 2014 in IEEE/ASME Transactions on Mechatronics
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Journal Article
Closed access
JPJose Luis Perez-Diaz
Jose Luis Perez-Diaz
IVIgnacio Valiente
Ignacio Valiente
EDEfren Diez-Jimenez
Efren Diez-Jimenez
JSJuan Sanchez-Garcia-Casarrubios
Juan Sanchez-Garcia-Casarrubios
In this paper, a noncontact linear positioner based on superconducting magnetic levitation for high-precision positioning has been tested under cryogenic conditions (~20 K and ~10 -6Pa). The prototype is able to achieve submicrometric positioning resolution of 230 ± 30 nm RMS along a stroke of ±9 mm length with a current resolution of 15 μA, and a peak current requirement lower than ±500 mA. In addition, it was demonstrated that an open-loop control strategy could be used for positioning the moving part with the accuracy of the order of 1 μm. On the other hand, deviations of the slider position were found to be ±650 μrad for the pitch, lower than 100 μrad for the yaw, ±2000 μrad for the roll, and ±4 μm for the lateral run, all of them related to a full stroke motion. These results reveal a good performance of the device and demonstrate the potential of a new tool for applications, where high-precision positioning is required within a long range in cryogenic environments like far-infrared interferometry.

22 August 2013 in Tribology Letters
Verified
Journal Article
Closed access
PDF file
IVIgnacio Valiente
Ignacio Valiente
EDEfren Diez-Jimenez
Efren Diez-Jimenez
CCCristian Cristache
Cristian Cristache
MAMarco A. Alvarez-Valenzuela
Marco A. Alvarez-Valenzuela
JPJose Luis Perez-Diaz
Jose Luis Perez-Diaz

15 March 2011 in Journal of Applied Physics
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Journal Article
Closed access
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EDEfren Diez-Jimenez
Efren Diez-Jimenez
JPJose Luis Perez-Diaz
Jose Luis Perez-Diaz
JGJuan Carlos Garcia-Prada
Juan Carlos Garcia-Prada
Several models exist for calculating superconducting repulsion forces in the Meissner state that are based on the method of images. The method of images, however, is limited to a small number of geometrical configurations that can be solved exactly, and the physical interpretation of the method is under discussion. A general local model based on the London equations and Maxwell’s equations has been developed to describe the mechanics of the superconductor-permanent magnet system. Due to its differential form, this expression can be easily implemented in a finite elements analysis and, consequently, is easily applicable to any shape of superconductor in the Meissner state. It can solve both forces and torques. This paper reports different experiments undertaken in order to test the model’s validity. The vertical forces and the angle of equilibrium between a magnet and a superconductor were measured, and a positive agreement between the experiments and theoretical calculations was found.