Loading...
Search for:
magnetism
0.011 seconds
Total 1521 records
Electric field assisted amplification of magnetic fields in tilted Dirac cone systems
, Article Physical Review B ; Volume 100, Issue 4 , 2019 ; 24699950 (ISSN) ; Sharif University of Technology
American Physical Society
2019
Abstract
We show that the continuum limit of the tilted Dirac cone in materials such as 8-Pmmn borophene and layered organic conductor α-(BEDT-TTF)2I3 corresponds to deformation of the Minkowski space-time of Dirac materials. From its Killing vectors we construct an emergent tilted-Lorentz (t-Lorentz) symmetry group for such systems. As an example of the t-Lorentz transformations we obtain the exact solution of the Landau bands for a crossed configuration of electric and magnetic fields. For any given tilt parameter 0≤ζ<1, if the ratio χ=vFBz/Ey of the crossed magnetic and electric fields satisfies χ≥1+ζ, one can always find appropriate t-boosts in both valleys labeled by τ=±1 in such a way that the...
Biocompatibility and hyperthermia efficiency of sonochemically synthesized magnetic nanoparticles
, Article SPIN ; Volume 9, Issue 2 , 2019 ; 20103247 (ISSN) ; Malaie Balasi, Z ; Ahadian, M. M ; Hatamie, S ; Shahsavari Alavijeh, M. H ; Ghafuri, H ; Sharif University of Technology
World Scientific Publishing Co. Pte Ltd
2019
Abstract
Hereby, a sonochemical method for synthesis of pure magnetic Fe3O4Onanoparticles (Fe3O4-NPs) in large scale is being introduced. Synthesis proceeds via simple approach, at room temperature, under sonication, using cheap reagents, green antioxidant-reductant reagent and without using inert gas purge as protective atmosphere condition. During this procedure, hydrogen gas releases continuously as valuable byproduct at the anaerobic step of reaction. Characterizations' results indicate that the final product is pure spherical Fe3O4-NPs, with narrow size distribution and about less than 32nm in mean diameter while more than 99% of particles size were less than 40nm. According to Vibrational...
Intensification of heat transfer rate in a rectangular channel equipped with pins, using non-uniform magnetic field
, Article Journal of Nanofluids ; Volume 8, Issue 5 , 2019 , Pages 1041-1050 ; 2169432X (ISSN) ; Hariri, S ; Sharif University of Technology
American Scientific Publishers
2019
Abstract
In the present study, numerical simulation is used to evaluate the influence of the non-uniform magnetic field on the heat transfer of magnetic nanofluids inside a pinned channel. This article focused on the flow pattern and heat transfer of water-based nanofluids in the presence of a wire in a three-dimensional geometry. In this work, the fluid flow is laminar and constant heat flux is applied on the wall of the channel. A wire in various orientations, in comparison with the axis of the channel, generates the magnetic field. The base fluid is water and Nano-particles (Fe3O4 and Fe) add to base fluid with different volume concentrations (0, 0.5, 1%). The computational fluids dynamic is used...
Time dependence of magnetization in Fe1-xCox fine particles
, Article 4th International Conference on Magnetic and Superconducting Materials, MSM'05, Agadir, 5 September 2006 through 8 September 2006 ; Volume 3, Issue 9 , 2006 , Pages 3220-3224 ; 18626351 (ISSN) ; Seht, S. A ; Akhavan, M ; Sharif University of Technology
2006
Abstract
The change of the applied field in a medium containing anisotropic magnetic grains, makes the number of magnetic moments in the field direction, and in the opposite direction to vary. Near H = Hc, probability of transition between the two minimum energies (SW model) increases strongly and the magnetization of system varies rapidly. We measured the time dependence of magnetization for various Fe1-xCOx samples, in the presence of some step fields. These samples were grown via solving iron, and cobalt salts with borohydride and then, heat treatment was accomplished on them. The results of time measurement of magnetization in step fields reveals a linear proportionality between coercivity and...
Induced magnetic anisotropy in Fe0.7Co0.3 fine particles
, Article Journal of Physics D: Applied Physics ; Volume 39, Issue 23 , 2006 , Pages 4925-4929 ; 00223727 (ISSN) ; Zoriasatain, S ; Amirhoseini, M ; Akhavan, M ; Sharif University of Technology
2006
Abstract
In FeCo fine particles, induced anisotropy has a considerable contribution in increasing the coercivity. We have prepared Fe0.7Co0.3 fine particles by the borohydride method in the presence of various magnetic fields in the range 0 ≤ H0 ≤ 2 kOe. We have studied and analysed the factors affecting the induced anisotropy and magnetic structure of these particles by the use of SEM, XRD and vibrating sample magnetometer. It was found that heat treatment, and also the presence of a magnetic field of about 1 kOe during the grain growth, result in the maximum coercivity of Fe 0.7Co0.3 fine particles. The value of magnetic field intensity should be such that it causes formation of oriented atomic...
Control of shaft vibrations on magnetic bearings using neural network and sliding mode controller
, Article Proceedings of the 7th Biennial Conference on Engineering Systems Design and Analysis - 2004, Manchester, 19 July 2004 through 22 July 2004 ; Volume 1 , 2004 , Pages 787-793 ; 0791841731 (ISBN); 9780791841730 (ISBN) ; Salarieh, H ; Sharif University of Technology
American Society of Mechanical Engineers
2004
Abstract
This article discusses a method for complete control of the dynamics of a rotating shaft on magnetic bearings under the effects of mass imbalance. The electromagnetic bearings used in this research are 2 four-pole bearing at the two ends of the rotor, which are actuated by differential currents. Full dynamic behavior of 3- dimensional rigid rotor and its effects on dynamic model are included. The effects of rotating mass unbalance are also included in the equations. The geometric couplings between electromagnetic forces of the coils are included as uncertainty. By using sliding mode controller and a neural network to estimate the system nonlinear-coupled equations, in a way suitable for...
The influence of conductor sag on spatial distribution of transmission line magnetic field
, Article 5th IFAC Symposium on Power Plants and Power Systems Control 2003, 15 September 2003 through 19 September 2003 ; Volume 36, Issue 20 , 2003 , Pages 1145-1149 ; 14746670 (ISSN) ; Varahram, M. H ; Kumieh, S. P ; Sharif University of Technology
IFAC Secretariat
2003
Abstract
Common methods for the calculation of electric fields created by power transmission lines assume straight lines parallel to a flat ground and the influence of the sag due to the line weight is neglected. In this paper the magnetic fields of a catenary 3Phase line that has a change in direction was calculated and discussed. It is believed that this work has not been published before. © 2003 IFAC
Intensified photodegradation of nitrobenzene using ZnO-anchored spinel cobalt ferrite: Environmental application, mechanism, and degradation pathway
, Article Journal of Water Process Engineering ; Volume 49 , 2022 ; 22147144 (ISSN) ; Moslemzadeh, M ; Naderi, A ; Zehtab Salmasi, M ; Harati, M ; Rezaei Kalantary, R ; Kakavandi, B ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Aromatic and cyclic organic compounds such as nitrobenzene (NB) are widely used in various industries and are present in their wastewater. In addition, the photocatalytic process has received considerable attention due to its lower chemical consumption and more efficient degradation of refractory pollutants. In this study, a CoFe2O4-ZnO (CFZ) composite was prepared and evaluated its efficiency in the degradation of NB from aqueous solution under UV light. The optical, structural, and physicochemical properties of catalysts were characterized using PL, UV–vis DRS, XRD, TEM, FESEM-EDS, and VSM techniques and then discussed in detail. It was found that not only does the use of CF facilitate the...
Developing a neural network model for magnetic yoke structure
, Article 2008 IEEE International Conference on Computational Intelligence for Measurement Systems and Applications, IEEE CIMSA 2008, Istanbul, 14 July 2008 through 16 July 2008 ; 2008 , Pages 75-78 ; 9781424423064 (ISBN) ; Norouzi, E ; Sharif University of Technology
2008
Abstract
Magnetic flux leakage technique is used extensively to detect and characterize defects in natural gas and oil transmission pipelines. The amount of magnetic flux introduced into the test sample is an important factor in the resolution of flaw detection. It depends on the power of permanent magnets and the geometrical design of the magnetic yoke. Finite element method (FEM) is the most widely used method of analyzing magnetic yoke due to its power, accuracy and straightforwardness. On the other hand its calculations are so complicated and time consuming, and every single modification in the parameters of the problem requires a new run. In this paper, we present an innovative method to...
Modeling and Simulation of Magnetic Nanofluids Convective Heat Transfer around a Sphere in the Presence of External Magnetic Feild
, M.Sc. Thesis Sharif University of Technology ; Molaei Dehkordi, Asghar (Supervisor)
Abstract
The good performance in cooling, especially in systems with small dimensions, is one of the critical needs of many industries. Heat transfer around sphere in all systems that contain particles, is important. Many methods have been proposed to improve the heat transfer rate but using nanofluids is one of the ways that has attracted more attention than others. Ferrofluids have magnetic properties in addition to nanofluids properties and this has a significant impact in increasing the heat transfer rate. Controlling heat transfer by magnetic field is one of the unique characteristics of this fluid. The project aim is to investigate the effect of magnetic field on heat transfer around sphere in...
Sensorless control of non-salient PMSM using simultaneous injection of two HF signals
, Article Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC ; March , 2014 , p. 2463-2468 ; Yaghoubi, M ; Tahami, F ; Bakhshai, A ; Jain, P. K ; Sharif University of Technology
Abstract
In recent years sensorless techniques based on HF carrier injection have become very popular as they are capable to estimate rotor position in a wide speed range. They can provide precise control over interior PMSMs without the accompanying need for a position sensor. However, in surface-mounted PMSMs, the estimation of rotor position is only reliable at light loads due to the very small saliency arising from main flux saturation. The anisotropy caused by stator flux saturation is not necessarily in alignment with rotor position especially at heavy loads. In this paper a novel solution is proposed to make use of the sensorless scheme in a surface-mounted PMSM even at heavy loads
Poly(basic ionic liquid) coated magnetic nanoparticles: High-loaded supported basic ionic liquid catalyst
, Article Comptes Rendus Chimie ; Volume 16, Issue 10 , 2013 , Pages 906-911 ; 16310748 (ISSN) ; Hosseini, S. H ; AghayeeMeibody, S. A ; Hosseini, S. T ; Sharif University of Technology
2013
Abstract
A novel poly(ionic liquid) (PIL) coated magnetic nanoparticle was synthesized by distillation-precipitation-polymerization of 1-vinyl-3- ethyl imidazolium in the presence of surface modified magnetic nanoparticles. The resulting catalyst was used as magnetic heterogeneous base catalyst for the synthesis of 4H-benzo[b]pyrans in water. The separation of the catalyst from the reaction mixture was readily achieved by simple magnetic decantation and the catalyst could be easily recycled without appreciable loss of catalytic activity. Because of polymer layers coated the surface of the magnetic nanoparticles, the catalyst has a high loading level of ionic liquid
Approximating the distribution of flaws in magnetic materials using the generalized inverse
, Article 2011 IEEE International Conference on Imaging Systems and Techniques, IST 2011 - Proceedings, 17 May 2011 through 18 May 2011, Batu Ferringhi ; May , 2011 , Pages 137-141 ; 9781612848969 (ISBN) ; Abdollahi Jahdi, S ; Norouzi, E ; Sharif University of Technology
2011
Abstract
Non-destructive identification of voids in ferromagnetic materials is of great importance for industrial applications. Magnetic flux leakage technique is used here to examine the defected structure. To this end, an inverse problem should be solved in order to infer the location and depth of internal flaws from the measured leaked magnetic signals. Currently generalized inverse method and singular value decomposition are used for solving such inverse problem. Considering the cracks separation has significant effect on the absolute value of magnetic flux leakage signals, we study different distributions of cracks. In this paper, the magnetic dipole model is proposed to reconstruct the extent...
Cellulose acetate/magnetic graphene nanofiber in enhanced human mesenchymal stem cells osteogenic differentiation under alternative current magnetic field
, Article SPIN ; Volume 9, Issue 2 , 2019 ; 20103247 (ISSN) ; Mohamadyar Toupkanlou, F ; Mirzaei, S ; Ahadian, M. M ; Hosseinzadeh, S ; Soleimani, M ; Sheu, W. J ; Wei, Z. H ; Hsieh, T. F ; Chang, W. C ; Wang, C. L ; Sharif University of Technology
World Scientific Publishing Co. Pte Ltd
2019
Abstract
The three-dimensional (3D) nano scaffold of the cellulose acetate (CA) containing graphene/cobalt nanocomposite (0.1wt.%) was fabricated via electrospinning technique, and its impact on bone regeneration was investigated. Through this aim, bone marrow mesenchymal stem cells are cultured on the CA, and graphene/cobalt (rGO/Co)/CA nanocomposite scaffold surfaces and the samples are treated under low frequency alternative magnetic field (75Hz). The scaffolds are characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermal studies (TG/DSC). The proliferation behavior of stem cells on CA, and rGO/Co/CA nano scaffolds are studied by MTT assay, show their...
Performing assembly-based method engineering by architecture-centric method engineering approach
, Article EMS 2008, European Modelling Symposium, 2nd UKSim European Symposium on Computer Modelling and Simulation, Liverpool, 8 September 2008 through 10 September 2008 ; 2008 , Pages 181-186 ; 9780769533254 (ISBN) ; Rashidi, H ; Moaven, S ; Habibi, J ; Sharif University of Technology
2008
Abstract
Due to the necessity for methods that are able to handle complexities of systems, use of Method Engineering (ME) to construct more adaptable and flexible methods has become of importance. Assemblybased approach is the most well-known approach of ME that performs method construction by reusing and assembling different method fragments. This approach, like other approaches of ME, suffers from the lack of suitable guidelines. In this way, architecture-centric method engineering (ArCME) is a new approach which aims at performing ME processes in a more disciplined and cohesive way. In this paper, process of assemblybased ME is enhanced by ArCME. Furthermore, benefits of implementing the process...
Temperature and voltage dependence of magnetic barrier junctions with a nonmagnetic spacer
, Article European Physical Journal B ; Volume 42, Issue 2 , 2004 , Pages 187-191 ; 14346028 (ISSN) ; Saffarzadeh, A ; Sharif University of Technology
2004
Abstract
The temperature and voltage dependence of spin transport is theoretically investigated in a new type of magnetic tunnel junction, which consists of two ferromagnetic outer electrodes separated by a ferromagnetic barrier and a nonmagnetic (NM) metallic spacer. The effect of spin fluctuation in magnetic barrier, which plays an important role at finite temperature, is included by taking the mean-field approximation. It is found that, the tunnel magnetoresistance (TMR) and the electron-spin polarization depend strongly on the temperature and the applied voltage. The TMR and spin polarization at different temperatures show an oscillatory behavior as a function of the NM spacer thickness. Also,...
The role of milling atmosphere on microstructure and magnetic properties of a Nd12.8Fe79.8B7.4-type sintered magnet
, Article Journal of Magnetism and Magnetic Materials ; Volume 281, Issue 1 , 2004 , Pages 92-96 ; 03048853 (ISSN) ; Kianvash, A ; Sharif University of Technology
2004
Abstract
In this work, milled Nd12.8Fe79.8B7.4-type powders with three different oxygen contents were processed into sintered anisotropic magnets via a standard powder metallurgy technique. Minimizing the oxygen content within the powder material, resulted in an almost full densification in the sintered magnets even at the lower end of the sintering temperature limit. Under this condition, the amount of hard magnetic Φ phase (Nd2Fe14B) was maximized in the structure of sintered bodies, which resulted in the highest energy density [BHmax] values. In the sintered magnets made from the powder with a higher oxygen content, full densification could only be obtained at the upper end of the sintering...
Flux harmonic spectrum proccessing of direct torque controlled induction motor
, Article Proceedings of the 2003 IEEE International Symposium on Circuits and Systems, Bangkok, 25 May 2003 through 28 May 2003 ; Volume 3 , 2003 , Pages III383-III386 ; 02714310 (ISSN) ; Zolghadri, M. R ; Sharif University of Technology
2003
Abstract
Flux spectrum is greatly influenced by flux and torque controller hysteresis loops (dead bands) in direct torque control of AC motors. On the other hand iron loss in induction motor is closely related to flux harmonics. Hence flux spectrum must be observed in control process to minimize the motor losses. In this paper the relation between the magnetic-flux spectrum and electromagnetic-torque and magnetic-flux controller hysteresis loops (dead bands) as well as machine parameters is investigated. Simulation results are presented to justify the results
Switching field distribution of magnetic fine particles
, Article Journal of Magnetism and Magnetic Materials ; Volume 237, Issue 1 , 2001 , Pages 111-118 ; 03048853 (ISSN) ; Akhavan, M ; Sharif University of Technology
2001
Abstract
In the magnetic recording media the switching field distribution (SFD) is an important micromagnetic characteristic curve. However, in general case, methods of assessing SFD have not presented a reasonable relation between the macroscopic measurements and the microscopic properties of the system. The degree of alignment of particles easy axis in a texture and the angular dependence of switching field are two fundamental factors for the distribution function. A technique for determining the switching field distribution curve due to these factors is reported. This technique is performed for textured iron fine particles and samples of CrO2 and γFe2O3 commercial tapes. The distribution differs...
Cogging force mitigation techniques in a modular linear permanent magnet motor
, Article IET Electric Power Applications ; Volume 10, Issue 7 , 2016 , Pages 667-674 ; 17518660 (ISSN) ; Nasiri Gheidari, Z ; Sharif University of Technology
Institution of Engineering and Technology
Abstract
Modular linear doubly salient permanent magnet motors are well adapted to linear propulsion systems because of their distinct characteristics, such as high efficiency and power density, reduced maintenance and initial cost, low noise and permanent magnet (PM) leakage flux, and fault tolerance capability. However, such motors suffer from high cogging thrust. In this study, various techniques based on previously proposed methods for PM machines are applied on the studied motor and evaluated by using non-linear three-dimensional time-stepping finite element analysis; three novel, optimised techniques are then presented. The techniques presented are based on the minimisation of the variation in...