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Some Galvanomagnetic and Thermomagnetic Effects in a Single Crystal of AntimonyParker, Donald L. 08 1900 (has links)
The purpose of this investigation is to develop techniques of experimentation in the field of electron transport phenomena.
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Convective Heat Transfer in Quasi-one-dimensional Magnetic Fluid in Horizontal Field and Temperature GradientsHuang, Jun 01 January 2015 (has links)
In this work we studied the convective heat transfer in a magnetic fluid in both zero and applied magnetic fields. The natural convection is observed in a quasi-one dimensional magnetic fluid in a horizontal temperature gradient. The horizontal non-homogeneous magnetic fields were applied across the sample cell either parallel or anti-parallel to the temperature gradient. The temperature profile was measured by eight thermocouples and temperature sensitive paint. The flow velocity field and streamlines were obtained by optical flow method. Calculated Nusselt numbers, Rayleigh number, and Grashof number show that the convective flow is the main heat transfer mechanism in applied fields in our geometry. It was found that when the field gradient is parallel with temperature gradient, the fields enhance the convective heat transfer while the fields inhibit it in anti-parallel configuration by analyzing the temperature difference across the sample, flow patterns, and perturbation Q field in applied fields. Magnetic Rayleigh number and magnetic Grashof number show that the thermomagnetic convections dominate in high magnetic fields. It is shown that the physical nature of the field effect is corresponding to the magnetic body force which is perpendicular to the gravity in our experiments. When the direction of the magnetic body force is same with temperature gradient in parallel configuration, the body force increases the convective heat transfer; while it has opposite effect in anti-parallel configuration. Our study will not only shed light on the fundamental mechanisms for thermomagnetic convection but also help to develop the potential field-controlled heat transfer devices.
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Thermomagnetic Phenomena in Antimony at Liquid Helium TemperaturesHaywood, Charles Thomas 01 1900 (has links)
The purpose of this investigation was to study head-transport phenomena in a single crystal of antimony at liquid helium temperatures. In particular, the longitudinal and transverse components of the thermal resistivity tensor were measured as a function of magnetic field up to eighteen kilogauss.
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Métodos analíticos para o cálculo de desempenho de motores termomagnéticos do tipo tesla. / Analytical methods for the performance calculation of tesla type thermomagnetic motors.Bessa, Carlos Vinicius Xavier 08 June 2018 (has links)
Motores termomagnéticos são dispositivos capazes de converter calor em energia mecânica através do efeito termomagnético, e são uma alternativa para a conversão de energia de rejeitos térmicos de baixa e baixíssima qualidade. Neste trabalho é proposta uma classificação dos motores termomagnéticos como sendo de dois tipos, os motores tipo Edison e os motores tipo Tesla. Feita a classificação, diferenciou-se o comportamento de operação e os ciclos termodinâmicos desenvolvidos pelos dois tipos de motores, mostrando que motores do tipo Tesla desenvolvem um ciclo termodinâmico que pode ser aproximado por um ciclo Brayton magnético, já motores do tipo Edison descrevem um ciclo mais complexo, não podendo ser aproximado por um ciclo Brayton. Compararam-se os parâmetros de interesse para ambos os motores através de análises termodinâmicas, onde se concluiu que motores do tipo Tesla apresentam melhores respostas de trabalho e eficiência que motores do tipo Edison, quando são consideradas as mesmas condições de operação. Além disso, identificou-se que a equação de força de Kelvin é a equação que corretamente descreve o comportamento da força magnética em um motor termomagnético, essa contribuição é importante, pois vários trabalhos publicados na literatura utilizam equações que não descrevem corretamente o comportamento da força magnética. Mostrou-se que o trabalho produzido em um motor termomagnético é igual ao trabalho produzido pela força magnética resultante no dispositivo. Foi desenvolvida e validada uma metodologia para o cálculo do trabalho específico produzido em um motor do tipo Tesla. Utilizando as metodologias validadas, verificou-se como a temperatura, o campo magnético aplicado, o fator de desmagnetização e o tipo de transição influenciam o comportamento dos motores termomagnéticos tipo Tesla, o que abre caminho para o desenvolvimento de dispositivos mais interessantes do ponto de vista termodinâmico. / Thermomagnetic motors are devices capable of converting heat into mechanical energy through the thermomagnetic effect. These devices are able to operate using low or very low quality thermal waste, being an alternative to avail that range of thermal energy. This work classifies the thermomagnetic motors in two types: The Tesla type and the Edison type thermomagnetic motors, differentiating the operational behavior and the thermodynamic cycles developed in each type. By using thermodynamic approaches, it is shown that the Tesla type thermomagnetic motors have best response in terms of work and efficiency than the Edison type thermomagnetic motors, when the same operating conditions are considered. In addition, an experimental approach is presented, proving that the Kelvin force equation describes the behavior of the force in thermomagnetic motors, and the work produced in a motor is the same that the work produced by the resultant magnetic force in the system. It was developed and validated a method to estimate the work produced by cycle in a Tesla type thermomagnetic motor, and using thermodynamic approaches, the relevance of the temperature, applied magnetic field, demagnetizing factor and transition type in the Tesla type thermomagnetic motor were verified.
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Métodos analíticos para o cálculo de desempenho de motores termomagnéticos do tipo tesla. / Analytical methods for the performance calculation of tesla type thermomagnetic motors.Carlos Vinicius Xavier Bessa 08 June 2018 (has links)
Motores termomagnéticos são dispositivos capazes de converter calor em energia mecânica através do efeito termomagnético, e são uma alternativa para a conversão de energia de rejeitos térmicos de baixa e baixíssima qualidade. Neste trabalho é proposta uma classificação dos motores termomagnéticos como sendo de dois tipos, os motores tipo Edison e os motores tipo Tesla. Feita a classificação, diferenciou-se o comportamento de operação e os ciclos termodinâmicos desenvolvidos pelos dois tipos de motores, mostrando que motores do tipo Tesla desenvolvem um ciclo termodinâmico que pode ser aproximado por um ciclo Brayton magnético, já motores do tipo Edison descrevem um ciclo mais complexo, não podendo ser aproximado por um ciclo Brayton. Compararam-se os parâmetros de interesse para ambos os motores através de análises termodinâmicas, onde se concluiu que motores do tipo Tesla apresentam melhores respostas de trabalho e eficiência que motores do tipo Edison, quando são consideradas as mesmas condições de operação. Além disso, identificou-se que a equação de força de Kelvin é a equação que corretamente descreve o comportamento da força magnética em um motor termomagnético, essa contribuição é importante, pois vários trabalhos publicados na literatura utilizam equações que não descrevem corretamente o comportamento da força magnética. Mostrou-se que o trabalho produzido em um motor termomagnético é igual ao trabalho produzido pela força magnética resultante no dispositivo. Foi desenvolvida e validada uma metodologia para o cálculo do trabalho específico produzido em um motor do tipo Tesla. Utilizando as metodologias validadas, verificou-se como a temperatura, o campo magnético aplicado, o fator de desmagnetização e o tipo de transição influenciam o comportamento dos motores termomagnéticos tipo Tesla, o que abre caminho para o desenvolvimento de dispositivos mais interessantes do ponto de vista termodinâmico. / Thermomagnetic motors are devices capable of converting heat into mechanical energy through the thermomagnetic effect. These devices are able to operate using low or very low quality thermal waste, being an alternative to avail that range of thermal energy. This work classifies the thermomagnetic motors in two types: The Tesla type and the Edison type thermomagnetic motors, differentiating the operational behavior and the thermodynamic cycles developed in each type. By using thermodynamic approaches, it is shown that the Tesla type thermomagnetic motors have best response in terms of work and efficiency than the Edison type thermomagnetic motors, when the same operating conditions are considered. In addition, an experimental approach is presented, proving that the Kelvin force equation describes the behavior of the force in thermomagnetic motors, and the work produced in a motor is the same that the work produced by the resultant magnetic force in the system. It was developed and validated a method to estimate the work produced by cycle in a Tesla type thermomagnetic motor, and using thermodynamic approaches, the relevance of the temperature, applied magnetic field, demagnetizing factor and transition type in the Tesla type thermomagnetic motor were verified.
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Heat transfer through thermomagnetic convection in magnetic fluids induced by varying magnetic fieldsSzabo, Peter Sebastian Benedek January 2017 (has links)
Magnetic fluid flow by thermomagnetic convection with and without buoyancy was studied in experiments and computational simulations. A mineral oil based ferro magnetic fluid was subjected to varying magnetic fields to induce thermomagnetic convection. As such fluids are mainly developed to increase heat transfer for cooling the fundamental effects on magnetic fluid flow was investigated using various magnetic field distributions. Computational simulations of natural and thermomagnetic convection are based on a Finite-Element technique and considered a constant magnetic field gradient, a realistic magnetic field generated by a permanent magnet and alternating magnetic fields. The magnetic field within the fluid domain was calculated by the magneto-static Maxwell equations and considered in an additional magnetic body force known as the Kelvin body force by numerical simulations. The computational model coupled the solutions of the magnetic field equations with the heat and fluid flow equations. Experiments to investigate thermomagnetic convection in the presence of terrestrial gravity used infrared thermography to record temperature fields that are validated by a corresponding numerical analysis. All configurations were chosen to investigate the response of the magnetic fluid to the applied body forces and their competition by varying the magnetic field intensity and its spatial distribution. As both body forces are temperature dependent, situations were analysed numerically and experimentally to give an indication of the degree by which heat transfer may be enhanced or reduced. Results demonstrate that the Kelvin body force can be much stronger than buoyancy and can induce convection where buoyancy is not able to. This was evident in a transition area if parts of a fluid domain are not fully magnetically saturated. Results for the transition from natural convection to thermomagnetic convection suggest that the domain of influence of the Kelvin body force is aligned with the dominance of the respective body force. To characterise the transition a body force ratio of the Kelvin body force to buoyancy was developed that identified the respective driving forces of the convection cells. The effects on heat transfer was quantified by the Nusselt number and a suitable Rayleigh number. A modified Rayleigh number was used when both body forces were active to define an effective body force by taking the relative orientation of both forces into account. Results for the alternating magnetic field presented flow fields that altered with the frequency of the applied magnetic field but with varying amplitude. This affected the heat transfer that alternated with the frequency but failed to respond instantaneously and a phase lag was observed which was characterised by three different time scales.
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Micro-electro-thermo-magnetic Actuators for MEMS ApplicationsForouzanfar, Sepehr 22 November 2006 (has links)
This research focuses on developing new techniques and designs for highly con-
trollable microactuating systems with large force-stroke outputs. A fixed-fixed mi-
crobeam is the actuating element in the introduced techniques. Either buckling
of a microbridge by thermal stress, lateral deflection of a microbridge by electro-
magnetic force, or combined effects of both can be employed for microactuation.
The proposed method here is MicroElectroThermoMagnetic Actuation (METMA),
which uses the combined techniques of electrical or electro-thermal driving of a mi-
crobridge in the presence of a magnetic field. The electrically controllable magnetic
field actuates and controls the electrically or electrothermally driven microstruc-
tures. METMA provides control with two electrical inputs, the currents driving
the microbridge and the current driving the external magnetic field. This method
enables a more controllable actuating system. Different designs of microactuators
have been implemented by using MEMS Pro as the design software and MUMPs as
the standard MEMS fabrication technology. In these designs, a variety of out-of-
plane buckling or displacement of fixed-fixed microbeams have been developed and
employed as the actuating elements. This paper also introduces a novel actuating
technique for larger displacements that uses a two-layer buckling microbridge actu-
ated by METMA. Heat transfer principles are applied to investigate temperature
distribution in a microbeam, electrothermal heating, and the resulting thermoelas-
tic effects. Furthermore, a method for driving microactuators by applying powerful
electrical pulses is proposed. The integrated electromagnetic and electrothermal
microactuation technique is also studied. A clamped-clamped microbeam carry-
ing electrical current has been modeled and simulated in ANSYS. The simulations
include electrothermal, thermoelastic, electromagnetic, and electrothermomagnetic
effects. The contributions are highlighted, the results are discussed, the research
and design limitations are reported, and future works are proposed.
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Micro-electro-thermo-magnetic Actuators for MEMS ApplicationsForouzanfar, Sepehr 22 November 2006 (has links)
This research focuses on developing new techniques and designs for highly con-
trollable microactuating systems with large force-stroke outputs. A fixed-fixed mi-
crobeam is the actuating element in the introduced techniques. Either buckling
of a microbridge by thermal stress, lateral deflection of a microbridge by electro-
magnetic force, or combined effects of both can be employed for microactuation.
The proposed method here is MicroElectroThermoMagnetic Actuation (METMA),
which uses the combined techniques of electrical or electro-thermal driving of a mi-
crobridge in the presence of a magnetic field. The electrically controllable magnetic
field actuates and controls the electrically or electrothermally driven microstruc-
tures. METMA provides control with two electrical inputs, the currents driving
the microbridge and the current driving the external magnetic field. This method
enables a more controllable actuating system. Different designs of microactuators
have been implemented by using MEMS Pro as the design software and MUMPs as
the standard MEMS fabrication technology. In these designs, a variety of out-of-
plane buckling or displacement of fixed-fixed microbeams have been developed and
employed as the actuating elements. This paper also introduces a novel actuating
technique for larger displacements that uses a two-layer buckling microbridge actu-
ated by METMA. Heat transfer principles are applied to investigate temperature
distribution in a microbeam, electrothermal heating, and the resulting thermoelas-
tic effects. Furthermore, a method for driving microactuators by applying powerful
electrical pulses is proposed. The integrated electromagnetic and electrothermal
microactuation technique is also studied. A clamped-clamped microbeam carry-
ing electrical current has been modeled and simulated in ANSYS. The simulations
include electrothermal, thermoelastic, electromagnetic, and electrothermomagnetic
effects. The contributions are highlighted, the results are discussed, the research
and design limitations are reported, and future works are proposed.
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Emulsions structurées et nanoparticules magnétiques dans un hydrogel : réalisation, caractérisation et validation en tant que système de délivrance thermomagnétique / Structured emulsions and magnetic nanoparticles in a hydrogel : achievement, characterization and validation as a thermomagnetic delivery systemMilosevic-Markovic, Irena 20 November 2009 (has links)
Le développement des nanotechnologies a permis à la médecine de progresser là où lesméthodes traditionnelles de diagnostic et de thérapie connaissaient certaines limites. La manipulationet le contrôle de l’infiniment petit permet aujourd’hui de créer des systèmes adaptés à l’environnementcellulaire.Dans ce travail, nous nous sommes intéressés au potentiel des nanoparticules magnétiques d’oxydede fer en nanomédecine et notamment à l’utilisation de leurs propriétés magnétiques particulièrespour la mise au point de nouveaux matériaux pour la délivrance de principe actif par activationthermomagnétique. Notre système est constitué d’un hydrogel physique biocompatible, denanoparticules magnétiques et d’émulsions de mésophases lipidiques (Isasomes). Les Isasomes sontdes dispersions de systèmes auto assemblés qui selon la température peuvent changer de structure(phases hexagonales, cubiques,…). L’ajout d’un principe actif aux Isasomes peut aussi modifier leurstructure interne ; des mesures de SAXS ont permis de confirmer cet effet. Ces émulsionsnanostructurées ont servi de réservoir aux molécules modèles de principe actif (le radical TEMPO).Après activation magnétique, la diffusion contrôlée du principe actif hors de l’hydrogel a été suivie parRPE. Enfin, les nanoparticules ont été fonctionnalisées de façon à concevoir un hydrogel réticulé parles nanoparticules magnétiques. Les diverses étapes de la fonctionnalisation ont été validées pardifférentes techniques expérimentales (Diffraction de rayons X, MET, Raman, IRTF, Zétamétrie, ATG,XPS). / The development of nanotechnology led to significant progress in medicine especially wheretraditional methods of diagnosis and therapy showed limits. The manipulation and control of thephysics at the nanoscale offered new opportunities for creating systems tailored to the cellularenvironment. In this work, we were interested in the high potential of magnetic nanoparticles of ironoxide in medicine. In particular, we would like to use their peculiar magnetic properties for developingnew materials for the delivery of active compounds through thermomagnetic activation. Our systemconsists of a biocompatible hydrogel with confined magnetic nanoparticles and lipid-based emulsions,called Isasomes. Those are dispersions of lipid mesophases (hexagonal, cubic,…) that can be tunedby temperature or composition. The incorporation of an active compound into the Isasomes canequally modify their internal structure as confirmed by SAXS measurements. These nanostructuredemulsions are used here as reservoirs for model molecules (radical TEMPO), which are trapped intothe hydrogel. After magnetic activation, the controlled release of TEMPO outside the hydrogel hasbeen followed by Electron Paramagnetic Resonance (EPR). Finally, magnetic nanoparticles havebeen functionalized and connected to hyaluronic acid in order to design a crosslinked hydrogel. Thevarious steps of functionalization have been checked by various experimental techniques (Xrays,Raman spectroscopy, TEM, FTIR, zetametry, TGA, XPS).
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Thermal Energy Conversion Utilizing Magnetization Dynamics and Two-Carrier EffectsWatzman, Sarah June 26 July 2018 (has links)
No description available.
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