Sistema experimental para la medición del ángulo de equilibrio entre imanes y superconductores

La expulsión del campo magnético del interior de un superconductor debido al efecto Meissner genera un conjunto de fuerzas que son capaces de hacer levitar un imán. Las fuerzas generadas por este efecto han sido estudiadas indirectamente en este proyecto midiendo el ángulo girado por un imán sometido a efecto Meissner- Oschenfeld en su posición de equilibrio. Las interacciones de las distintas superficies de la pastilla superconductora con el imán para diferentes posiciones relativas entre este y la pastilla hacen el ángulo de equilibrio girado por el imán varíe compensándose así los momentos generados por las fuerzas de origen electromagnético del superconductor sobre el imán. Con ello se corrobora un modelo teórico planteado por los profesores José Luís Pérez Díaz y Juan Carlos García Prada de la Universidad Carlos III de Madrid. Además el lector podrá consultar las condiciones de seguridad y precauciones a tener en cuenta cuando se emplea nitrógeno líquido, imanes y superconductores en el laboratorio, pudiéndose extrapolar algún conocimiento de este proyecto para el desarrollo de futuros experimentos similares. A partir del texto a continuación se ha extraído un artículo que a fecha de defensa del presente proyecto ha sido aceptado para discusión en la 55ª edición de la Conferencia Anual de Magnetismo y Materiales Magnéticos y para su posterior publicación en el Journal Applied of Physics. ___________________________________________________________________________The expulsion of the magnetic flux due to Meissner effect in a superconductor creates forces that allows a permanent magnet to levitate over the superconductor. These forces have been studied in this project indirectly measuring the equilibrium angle by a permanent magnet under Meissner- Ochsenfeld effect. The interaction of the different superconductor surfaces with the permanent magnet for different relative positions between the magnet and the superconductor makes the equilibrium angle to change, reaching the new equilibrium position. The experimental results are in agreement to a theoretical model proposed by Doctors José Luís Pérez Díaz and Juan Carlos García Prada from Universidad Carlos III de Madrid. The reader also can find the necessary measures to avoid the hazards of using liquid nitrogen, permanent magnets and superconductors.Ingeniería Industria

Superconducting non-contact linear slider for precision positioning in cryogenic environments

In this thesis, a novel device for precision positioning in a long stroke suitable for cryogenics environments has been proposed, designed, built and tested. The device is based on superconducting magnetic levitation. A set of high temperature superconductors allows a long permanent magnet to levitate stably over them. Furthermore, due to the high translational symmetry of the magnetic field applied on the superconductors for any position of the slider in its path, the superconductors not only provide stable levitation to the slider, but al so guide it. Therefore, a sliding kinematic pair is established between the permanent magnet and the superconductors. Finally, using a pair of coils, the position of the slider can be controlled with an open-Ioop control strategy of the current in the coils with nanometre resolution and reduced power consumption. Besides, a set of design rules has been proposed and experimentally verified at 77 K. Parameters of the performance of the mechanism such as the stroke, sensitivity, stiffness, natural frequency, run outs or the power consumption can be modified and optimized by an appropriate designo After this, two prototypes of a long stroke nanopositioner based on these design rules have been built and tested in a relevant environment (T~15 K, in a high vacuum < 10⁻⁶ Pa). Nanometre resolution in the positioning of a mass of about 170 g has been demonstrated in a stroke up to 18 mm. ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------En esta tesis doctoral se propone, diseña, construye y demuestra un dispositivo de alta resolución para posicionado en una carrera larga para entornos criogénicos. Este dispositivo está basado en levitación magnética superconductora de manera que, un conjunto de superconductores de alta temperatura (superconductores de tipo II) permiten a un imán permanente levitar de manera estable sobre ellos y, al mismo tiempo, ser guiado. De hecho, se establece un par cinemático de deslizamiento entre el imán y los superconductores gracias a la alta simetría traslacional del campo magnético aplicado en estos últimos. Además, la posición de la deslizadera puede ser controlada mediante una estrategia de control en bucle abierto de la corriente circulante en un par de bobinas diseñadas específicamente para esta tarea, obteniéndose una excelente resolución y un consumo de energía muy reducido. Así mismo, se proponen una serie de reglas de diseño que fueron verificadas a una temperatura de operación de 77 K. Estas reglas demuestran que hay una serie de parámetros característicos del desempeño del mecanismo como la sensibilidad, la rigidez, la frecuencia natural, las desviaciones o el consumo energético que pueden ser modificados mediante un diseño apropiado. Tras obtener estas reglas de diseño, un par de prototipos de un nanoposicionador de larga carrera han sido diseñados en consecuenCIa, construidos y probados en un ambiente relevante (T ~ 15 K, alto vacío < 10⁻⁶ Pa). Una resolución nanométrica en el posicionamiento de una masa de 170 gramos ha sido demostrada en una carrera de hasta 18 mm

Design and analysis of a non-hysteretic passive magnetic linear bearing for cryogenic environments

In this study, the mechanical design and analysis of a magnetic levitating linear bearing suitable for working in the nonhysteretic range of forces is presented. The semi-cylindrical design of the superconductor provides stable equilibrium positioning and restoring forces in all degrees of freedom except for two with a cylindrical magnet floating along the axis of revolution/displacement. Using finite element analysis, it has been proven that the magnet can float stably and passively in a complete non-hysteretic Meissner state. This non-hysteretic passive linear bearing could be suitable for long-stroke precision positioning. The high translational symmetry of the magnetic field seen by the superconductor assures a usable long stroke of around 90mm with full performance and 150mm with reduced performance. This linear bearing in combination with an actuating system for only one degree of freedom could be used for accurate precision positioning systems for cryogenic environments with zero hysteresis in the movement.European Community's Seventh Framework Progra

Magnetic Gearboxes for Aerospace Applications

Magnetic gearboxes are contactless mechanisms for torque-speed conversion. They present no wear, no friction and no fatigue. They need no lubricant and can be customized for other mechanical properties as stiffness or damping. Additionally, they can protect structures and mechanisms against overloads, limitting the transmitted torque. In this work, spur, planetary and "magdrive" or "harmonic drive" configurations are compared considering their use in aerospace applications. The most recent test data are summarized to provide some useful help for the design engineer

Performance of Magnetic-Superconductor Non-Contact Harmonic Drive for Cryogenic Space Applications

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 temperature

High incidence of PTSD diagnosis and trauma-related symptoms in a trauma exposed bipolar I and II sample

Post-traumatic stress disorder (PTSD) is an established comorbidity in Bipolar Disorder (BD), but little is known about the characteristics of psychological trauma beyond a PTSD diagnosis and differences in trauma symptoms between BD-I and BD-II. (1) To present characteristics of a trauma-exposed BD sample; (2) to investigate prevalence and trauma symptom profile across BD-I and BD-II; (3) to assess the impact of a lifetime PTSD diagnosis vs. a history of trauma on BD course; and (4) to research the impacts of sexual and physical abuse. This multi-center study comprised 79 adult participants with BD with a history of psychological trauma and reports baseline data from a trial registered in Clinical Trials (; ref: NCT02634372). Clinical variables were gathered through clinical interview, validated scales and a review of case notes. The majority (80.8%) of our sample had experienced a relevant stressful life event prior to onset of BD, over half of our sample 51.9% had a lifetime diagnosis of PTSD according to the Clinician Administered PTSD scale. The mean Impact of Event Scale-Revised scores indicated high levels of trauma-related distress across the sample, including clinical symptoms in the PTSD group and subsyndromal symptoms in the non-PTSD group. Levels of dissociation were not higher than normative values for BD. A PTSD diagnosis (vs. a history of trauma) was associated with psychotic symptoms [2(1) = 5.404, p = 0.02] but not with other indicators of BD clinical severity. There was no significant difference between BD-I and BD-II in terms of lifetime PTSD diagnosis or trauma symptom profile. Sexual abuse significantly predicted rapid cycling [2(1) = 4.15, p = 0.042], while physical abuse was not significantly associated with any clinical indicator of severity. Trauma load in BD is marked with a lack of difference in trauma profile between BD-I and BD-II. Although PTSD and sexual abuse may have a negative impact on BD course, in many indicators of BD severity there is no significant difference between PTSD and subsyndromal trauma symptoms. Our results support further research to clarify the role of subsyndromic PTSD symptoms, and highlight the importance of screening for trauma in BD patients

High incidence of PTSD diagnosis and trauma-related symptoms in a trauma exposed bipolar I and II sample

Background: Post-traumatic stress disorder (PTSD) is an established comorbidity in Bipolar Disorder (BD), but little is known about the characteristics of psychological trauma beyond a PTSD diagnosis and differences in trauma symptoms between BD-I and BD-II. Objective: (1) To present characteristics of a trauma-exposed BD sample; (2) to investigate prevalence and trauma symptom profile across BD-I and BD-II; (3) to assess the impact of a lifetime PTSD diagnosis vs. a history of trauma on BD course; and (4) to research the impacts of sexual and physical abuse. Methods: This multi-center study comprised 79 adult participants with BD with a history of psychological trauma and reports baseline data from a trial registered in Clinical Trials (https://clinicaltrials.gov; ref: NCT02634372). Clinical variables were gathered through clinical interview, validated scales and a review of case notes. Results: The majority (80.8%) of our sample had experienced a relevant stressful life event prior to onset of BD, over half of our sample 51.9% had a lifetime diagnosis of PTSD according to the Clinician Administered PTSD scale. The mean Impact of Event Scale-Revised scores indicated high levels of trauma-related distress across the sample, including clinical symptoms in the PTSD group and subsyndromal symptoms in the non-PTSD group. Levels of dissociation were not higher than normative values for BD. A PTSD diagnosis (vs. a history of trauma) was associated with psychotic symptoms [2(1) = 5.404, p = 0.02] but not with other indicators of BD clinical severity. There was no significant difference between BD-I and BD-II in terms of lifetime PTSD diagnosis or trauma symptom profile. Sexual abuse significantly predicted rapid cycling [2(1) = 4.15, p = 0.042], while physical abuse was not significantly associated with any clinical indicator of severity. Conclusion: Trauma load in BD is marked with a lack of difference in trauma profile between BD-I and BD-II. Although PTSD and sexual abuse may have a negative impact on BD course, in many indicators of BD severity there is no significant difference between PTSD and subsyndromal trauma symptoms. Our results support further research to clarify the role of subsyndromic PTSD symptoms, and highlight the importance of screening for trauma in BD patients

Z-Damper: A New Paradigm for Attenuation of Vibrations

Magnetic linear gear provides a new and unique opportunity for coupling mechanical impedances and optimizing vibration damping. In the present paper a new magneto-mechanical vibration damper (the so-called Z-damper) is described. Its expected theoretical dynamic behavior shows a particularly high damping capability, a low frequency, as well as an optimal behavior for high frequencies

Mechanical Impedance Matching Using a Magnetic Linear Gear

As part of the Fp7 Clean Sky Project, a linear magnetic gear prototype, called Z-transmitter, for aerospace application was designed, built, and tested. It demonstrates a maximum force capacity of 4700 N at 25°C and 4500 N at 90°C. Force ratio between slow and fast stages remains constant and equal to the design value: 7.0. The behavior of the real Z-transmitter as a mechanical impedance matching device when any stiffness is attached to the fast stage including the limit cases of a blocked fast stage or a free to move fast stage is experimentally explored. Although the real Z-transmitter deviates from the ideal, frictionless and massless, device, it still provides an impedance matching effect large enough to potentially become an extremely useful technology for vibration control when combined with other elements such as dampers, springs, or active elements