Articoli di riviste: "Magnetic sheet"

1

Shen, C., Z. J. Rong, X. Li, M. Dunlop, Z. X. Liu, H. V. Malova, E. Lucek e C. Carr. "Magnetic configurations of the tilted current sheets in magnetotail". Annales Geophysicae 26, n. 11 (17 novembre 2008): 3525–43. http://dx.doi.org/10.5194/angeo-26-3525-2008.

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Abstract. In this research, the geometrical structures of tilted current sheet and tail flapping waves have been analysed based on multiple spacecraft measurements and some features of the tilted current sheets have been made clear for the first time. The geometrical features of the tilted current sheet revealed in this investigation are as follows: (1) The magnetic field lines (MFLs) in the tilted current sheet are generally plane curves and the osculating planes in which the MFLs lie are about vertical to the equatorial plane, while the normal of the tilted current sheet leans severely to the dawn or dusk side. (2) The tilted current sheet may become very thin, the half thickness of its neutral sheet is generally much less than the minimum radius of the curvature of the MFLs. (3) In the neutral sheet, the field-aligned current density becomes very large and has a maximum value at the center of the current sheet. (4) In some cases, the current density is a bifurcated one, and the two humps of the current density often superpose two peaks in the gradient of magnetic strength, indicating that the magnetic gradient drift current is possibly responsible for the formation of the two humps of the current density in some tilted current sheets. Tilted current sheets often appear along with tail current sheet flapping waves. It is found that, in the tail flapping current sheets, the minimum curvature radius of the MFLs in the current sheet is rather large with values around 1 RE, while the neutral sheet may be very thin, with its half thickness being several tenths of RE. During the flapping waves, the current sheet is tilted substantially, and the maximum tilt angle is generally larger than 45°. The phase velocities of these flapping waves are several tens km/s, while their periods and wavelengths are several tens of minutes, and several earth radii, respectively. These tail flapping events generally last several hours and occur during quiet periods or periods of weak magnetospheric activity.

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Kai, Yuichiro, Yuji Tsuchida, Takashi Todaka e Masato Enokizono. "Three-Dimensional Magnetic Field Analysis for Local Induction Heating of Steel Sheet by Using Magnetic Flux Concentration Plate". Materials Science Forum 792 (agosto 2014): 87–92. http://dx.doi.org/10.4028/www.scientific.net/msf.792.87.

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In general, the magnetic properties of electrical steel sheets are strongly influenced by mechanical stress. We have reported the measurement results of vector magnetic properties of a non-oriented electrical steel sheet under stress conditions. From these results, it is possible to control the vector magnetic property by applying local mechanical stress. Therefore, we next focus on an induction heating technique that applies mechanical stress in a non-oriented electrical steel sheet. It is very important to control the eddy current distribution inside the non-oriented electrical steel sheet. This paper presents a magnetic flux concentration plate structure to control the eddy current in steel sheets by using an induction heating technique. The magnetic flux concentration plate structure is investigated in a three-dimensional magnetic field analysis by the finite element method.

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Lui, A. T. Y. "Observations of the Earth's Cross-Tail Current Sheet and Their Implications". Symposium - International Astronomical Union 107 (1985): 303–7. http://dx.doi.org/10.1017/s0074180900075768.

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Observations of the neutral sheet in the Earth's magnetotail are presented to show different magnetic signatures of the neutral sheet which have been used to infer (1) wave profiles on the neutral sheet surface, (2) magnetic islands embedded in the neutral sheet, and (3) localized turbulent magnetic field regions. The occurrence of these features even at magnetospheric quiet conditions suggests that the above features are intrinsic to the current sheet and may possibly play a role in its stability. There are indications that these features are common to other current sheets in space.

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Frank, Anna. "Distinctive features of the structure of current sheets formed in plasma in three-dimensional magnetic configurations with an X line (a review)". ADVANCES IN APPLIED PHYSICS 9, n. 6 (23 dicembre 2021): 464–78. http://dx.doi.org/10.51368/2307-4469-2021-9-6-464-478.

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A review is presented on experimental results related to investigation of distinctive features of the structure and evolution of plasma current sheets formed in three dimensional (3D) magnetic configurations with an X line, in the presence of a longitudinal magnetic field component (guide field) directed along the X line. It is shown that formation of a plasma current sheet results in enhancement of the guide field within the sheet. The excessive guide field is maintained by plasma currents that flow in the transverse plane relative to the main current in the sheet. As a result, the structure of the currents becomes three-dimensional. Increasing the initial value of the guide field brings about a decrease of compression into the sheet of both the electric current and plasma. This effect is caused by changing the pres- sure balance in the sheet when an excessive guide field appears in it. Deformation of plasma current sheets in 3D magnetic configurations, namely, an appearance of asymmetric and tilted sheets, results from excitation of the Hall currents and their interaction with the guide field. It is shown that the formation of current sheets in 3D magnetic configurations with an X line is possible in a relatively wide, but limited range of initial conditions

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Zhang, Wenbo, Chuo Yang, Yongxin Feng e Deyu Zhang. "Research on the Three Dimensional Detection Technology for Magnetic Sheet in Industrial Production". Open Mechanical Engineering Journal 9, n. 1 (16 settembre 2015): 585–93. http://dx.doi.org/10.2174/1874155x01509010585.

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This study proposes a three-dimensional size detection system for inerratic magnetic sheets according to specific size parameter requirements, such as the volume of the industrial micro magnetic sheet. Based on the noise interference generated by the corresponding detection environment of the magnetic sheet, a hybrid filtering method for the inerratic magnetic sheet is also proposed here, which effectively implements denoising filtering. In the image edge detection module, the edge detection operator most suitable for detecting image edge extraction is selected, and in order to realize the inerratic shape detection in Hough transform, the measurement function of size parameters (including the top surface radius, tilt angle of the profile and top surface, profile thickness, and volume) for the micro cylinder magnetic sheet are designed and implemented. Measurement data, gathered through repeated experiments, builds a more effective detection system for magnetic sheet size than traditional methods at the millimeter level.

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Petrukovich, A. A., T. l. Zhang, W. Baumjohann, R. Nakamura, A. Runov, A. Balogh e C. Carr. "Oscillatory magnetic flux tube slippage in the plasma sheet". Annales Geophysicae 24, n. 6 (3 luglio 2006): 1695–704. http://dx.doi.org/10.5194/angeo-24-1695-2006.

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Abstract. Cluster observations in the magnetotail revealed an abundance of strongly inclined current sheets. We determine the magnetic configuration of a particular subset of such phenomena: a series of sheet crossings, having significantly differing inclinations and occurring during quiet conditions. These wave-like variations appear to propagate azimuthally and their magnetic amplitude and magnetic gradient (current density) inside the sheet are proportional to their steepness (degree of inlcination). In spite of significant normal direction changes between neighboring crossings up to 150°, the magnetic field direction inside the neutral sheet remains almost constant. The wavelengths and spatial amplitudes are of the order of 2–5 RE. These observations are interpreted as crossings of a quasi-periodic dynamical structure produced by almost vertical slippage motion of the neighboring magnetic flux tubes in the high-β plasma sheet, rather than large-scale flapping of a stationary structure.

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Shahril, Mohd Khairul, Rose Farahiyan Munawar, Muhd Hafez Mohamed, Afraha Baiti Arif, Noraiham Mohamad, Mohd Edeerozey Abd Manaf, Jeeferie Abd Razak e Hairul Effendy Ab Maulod. "Green Magnetic Composite Sheet from Durian Shell and Nano-Magnetite Particles". Applied Mechanics and Materials 761 (maggio 2015): 515–19. http://dx.doi.org/10.4028/www.scientific.net/amm.761.515.

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Biomass-derived materials such as kenaf pulp and wood chips are a perfect candidate to produce magnetic paper. Furthermore, by using biomass waste, such as paddy straw, sugarcane, bagasse and durian shell, the cost of producing magnetic paper can be further reduced while giving added value to the waste. This paper investigates the potential of producing magnetic sheet from durian shell. Initially, durian shells were dried before undergoing the pulping process. The resulted sheet was then combined with magnetic particles, the nanomagnetite using either lumen loading or in-situ co-precipitation to produce a magnetic composite sheet. After being loaded with magnetic particles, the composite sheets were tested in terms of the homogeneity of the magnetic particles in the samples, degree of loading of the magnetic particles and the magnetic properties of the samples. Results obtained show a great success in producing the magnetic sheet from durian shell waste and nanomagnetite particles. It was also found that the lumen loading method gives better magnetic properties compared to the in-situ co-precipitation method.

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Zhang, Xiangyong, Haipeng Liu, Yunli He, Tingrui Peng, Bin Su e Huiyuan Guan. "Analysis of the Influence of Ferromagnetic Material on the Output Characteristics of Halbach Array Energy-Harvesting Structure". Micromachines 12, n. 12 (11 dicembre 2021): 1541. http://dx.doi.org/10.3390/mi12121541.

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Due to the particular arrangement of permanent magnets, a Halbach array has an significant effect of magnetism and magnetic self-shielding. It can stretch the magnetic lines on one side of the magnetic field to obtain an ideal sinusoidal unilateral magnetic field. It has a wide application range in the field of energy harvesting. In practical applications, magnetic induction intensity of each point in magnetic field is not only related to the induced current and conductor but also related to the permeability of the medium (also known as a magnetic medium) in the magnetic field. Permeability is the physical quantity that represents the magnetism of the magnetic medium, which indicates the resistance of magnetic flux or the ability of magnetic lines to be connected in the magnetic field after coil flows through current in space or in the core space. When the permeability is much greater than one, it is a ferromagnetic material. Adding a ferromagnetic material in a magnetic field can increase the magnetic induction intensity B. Iron sheet is a good magnetic material, and it is easy to magnetize to generate an additional magnetic field to strengthen the original magnetic field, and it is easy to obtain at low cost. In this paper, in order to explore the influence of ferromagnetic material on the magnetic field and energy harvesting efficiency of the Halbach array energy harvesting structure, iron sheets are installed on the periphery of the Halbach array rotor. Iron sheet has excellent magnetic permeability. Through simulation, angle between iron sheet and Halbach array, radian size of iron sheet itself and distance between iron sheet and Halbach array can all have different effects on the magnetic field of the Halbach array. It shows that adding iron sheets as a magnetic medium could indeed change the magnetic field distribution of the Halbach array and increase energy harvesting efficiency. In this paper, a Halbach array can be used to provide electrical power for passive wireless low-power devices.

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Wang, Zhen, Kai Xu e Yufeng Du. "Temperature Rise Calculation of Magnetic Core Considering the Temperature Effect of Magnetic Properties in an Electrical Steel Sheet". Symmetry 14, n. 11 (4 novembre 2022): 2315. http://dx.doi.org/10.3390/sym14112315.

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The magnetic properties of electrical steel sheets are affected by magnetization patterns, working temperature, and external pressure. In order to study the temperature effect of electrical steel sheets on the temperature rise of a transformer core, in this paper, based on the magnetic property test system of an electrical steel sheet, the permeability and loss of a 50AW600 grain non-oriented electrical steel sheet and a 30ZH120 grain oriented electrical steel sheet under different temperatures and excited frequencies were measured, and the influence of temperature on the properties of the material was analyzed. A magneto-thermal iterative coupling method considering the temperature effects of magnetic properties in the electrical steel sheet was investigated. Based on the above measurement data and iterative coupling method, the temperature distribution of the core of a 500-kV power transformer was simulated and analyzed, and compared with the simulation results of the traditional coupling method without considering the temperature effect of the electrical steel sheet. Magneto-thermal coupling simulation under no-load operation is a symmetrical problem. It was found that the temperature of the hottest spot of the transformer core calculated by the magneto-thermal iteration method proposed in this paper was significantly reduced, the temperature of the hottest spot on the core column was about 45 °C, and the temperature of the hottest spot on the upper and lower yoke was about 39 °C, which provides an effective simulation method for accurately calculating the temperature rise distribution of electrical products such as transformers.

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Ishii, H., M. Kaneko e F. Motegi. "Development of magnetic shielding compound sheet "AMORIK-SHEET"." Bulletin of the Japan Institute of Metals 27, n. 5 (1988): 385–87. http://dx.doi.org/10.2320/materia1962.27.385.

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Miao, B., B. Peng e G. Li. "Current sheets from Ulysses observation". Annales Geophysicae 29, n. 2 (2 febbraio 2011): 237–49. http://dx.doi.org/10.5194/angeo-29-237-2011.

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Abstract. Current sheet is a significant source of solar wind MHD turbulence intermittency. It has long been recognized that these structures can arise from non-linear interactions of MHD turbulence. Alternatively, they may also be relic structures in the solar wind that have a solar origin, e.g., magnetic walls of flux tubes that separate solar wind plasma into distinct parcels. Identifying these structures in the solar wind is crucial to understanding the properties of the solar wind MHD turbulence. Using Ulysses observations we examine 3-year worth of solar wind magnetic field data when the Ulysses is at low latitude during solar minimum. Extending the previous work of Li (2007, 2008), we develop an automatic data analysis method of current sheet identification. Using this method, we identify more than 28000 current sheets. Various properties of the current sheet are obtained. These include the distributions of the deflection angle across the current sheet, the thickness of the current sheet and the waiting time statistics between current sheets.

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DONG, Q. L., D. W. YUAN, S. J. WANG, Y. T. LI, X. LIU, S. E. JIANG, Y. K. DING et al. "Energetic electron generation by magnetic reconnection in laboratory laser-plasma interactions". Journal of Plasma Physics 78, n. 4 (6 luglio 2012): 497–500. http://dx.doi.org/10.1017/s0022377812000621.

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AbstractThe magnetic reconnection (MR) configuration was constructed by using two approaching laser-produced plasma bubbles. The characteristics of the MR current sheet were investigated. The driving energy of the laser pulse affects the type of the current sheet. The experiments present “Y-type” and “X-type” current sheets for larger and smaller driving energy, respectively. The energetic electrons were found to be well-collimated. The formation and ejection of plasmoid from the “Y-type” current sheet was expected to enhance the number of accelerated electrons.

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Mazgaj, Witold, Zbigniew Szular e Adam Warzecha. "Influence of magnetic anisotropy on flux density changes in dynamo steel sheets". Archives of Electrical Engineering 64, n. 1 (1 marzo 2015): 81–88. http://dx.doi.org/10.1515/aee-2015-0008.

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Abstract Magnetic measurements, carried out by means of the Epstein frame, have shown that most typical dynamo steel sheets have certain anisotropic properties. In numerical analysis, anisotropic properties are taken into account with the use of the special function of the grain distribution in the given dynamo sheet. For engineering purposes, it is desirable to assess the influence of these properties on the changes of the magnetic flux density in typical dynamo steel sheets, especially during the rotational magnetization. For this purpose, measurements of the flux density changes and field strength changes in the circular-shaped samples of two selected typical dynamo sheets were performed. These measurements were carried out for several values of the current flowing in windings which generated the axial or rotational magnetic field in the test dynamo sheet. The influence of the magnetic anisotropy on the magnetization process was briefly discussed for both types of the magnetization processes.

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Zelenyi, L. M., H. V. Malova, V. Yu Popov, D. Delcourt e A. S. Sharma. "Nonlinear equilibrium structure of thin currents sheets: influence of electron pressure anisotropy". Nonlinear Processes in Geophysics 11, n. 5/6 (23 novembre 2004): 579–87. http://dx.doi.org/10.5194/npg-11-579-2004.

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Abstract. Thin current sheets represent important and puzzling sites of magnetic energy storage and subsequent fast release. Such structures are observed in planetary magnetospheres, solar atmosphere and are expected to be widespread in nature. The thin current sheet structure resembles a collapsing MHD solution with a plane singularity. Being potential sites of effective energy accumulation, these structures have received a good deal of attention during the last decade, especially after the launch of the multiprobe CLUSTER mission which is capable of resolving their 3D features. Many theoretical models of thin current sheet dynamics, including the well-known current sheet bifurcation, have been developed recently. A self-consistent 1D analytical model of thin current sheets in which the tension of the magnetic field lines is balanced by the ion inertia rather than by the plasma pressure gradients was developed earlier. The influence of the anisotropic electron population and of the corresponding electrostatic field that acts to restore quasi-neutrality of the plasma is taken into account. It is assumed that the electron motion is fluid-like in the direction perpendicular to the magnetic field and fast enough to support quasi-equilibrium Boltzmann distribution along the field lines. Electrostatic effects lead to an interesting feature of the current density profile inside the current sheet, i.e. a narrow sharp peak of electron current in the very center of the sheet due to fast curvature drift of the particles in this region. The corresponding magnetic field profile becomes much steeper near the neutral plane although the total cross-tail current is in all cases dominated by the ion contribution. The dependence of electrostatic effects on the ion to electron temperature ratio, the curvature of the magnetic field lines, and the average electron magnetic moment is also analyzed. The implications of these effects on the fine structure of thin current sheets and their potential impact on substorm dynamics are presented.

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Büchner, J., e J. P. Kuska. "Sausage mode instability of thin current sheets as a cause of magnetospheric substorms". Annales Geophysicae 17, n. 5 (31 maggio 1999): 604–12. http://dx.doi.org/10.1007/s00585-999-0604-5.

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Abstract. Observations have shown that, prior to substorm explosions, thin current sheets are formed in the plasma sheet of the Earth's magnetotail. This provokes the question, to what extent current-sheet thinning and substorm onsets are physically, maybe even causally, related. To answer this question, one has to understand the plasma stability of thin current sheets. Kinetic effects must be taken into account since particle scales are reached in the course of tail current-sheet thinning. We present the results of theoretical investigations of the stability of thin current sheets and about the most unstable mode of their decay. Our conclusions are based upon a non-local linear dispersion analysis of a cross-magnetic field instability of Harris-type current sheets. We found that a sausage-mode bulk current instability starts after a sheet has thinned down to the ion inertial length. We also present the results of three-dimensional electromagnetic PIC-code simulations carried out for mass ratios up to Mi / me=64. They verify the linearly predicted properties of the sausage mode decay of thin current sheets in the parameter range of interest.Key words. Magnetospheric physics (plasma waves and instabilities; storms and substorms) · Space plasma physics (magnetic reconnection)

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Khan, Zarak, Mushtaq Khan, Syed Husain Imran Jaffery, Muhammad Younas, Kamran S. Afaq e Muhammad Ali Khan. "Numerical and experimental investigation of the effect of process parameters on sheet deformation during the electromagnetic forming of AA6061-T6 alloy". Mechanical Sciences 11, n. 2 (7 ottobre 2020): 329–47. http://dx.doi.org/10.5194/ms-11-329-2020.

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Abstract. Electromagnetic forming is a high-speed sheet metal forming technique to form metallic sheets by applying magnetic forces. In comparison to the conventional sheet metal forming process, electromagnetic forming is a process with an extremely high velocity and strain rate, which can be effectively used for the forming of certain difficult-to-form metals. During electromagnetic forming, it is important to recognise the effects of process parameters on the deformation and sheet thickness variation of the sheet metal. This research focuses on the development of a numerical model for aluminium alloy (AA6061-T6) to analyse the effects of three process parameters, namely voltage, sheet thickness and number turns of the coils, on the deformation and thickness variation of the sheet. A two-dimensional fully coupled finite-element (FE) model consisting of an electrical circuit, magnetic field and solid mechanics was developed and used to determine the effect of changing magnetic flux and system inductance on sheet deformation. Experiment validation of the results was performed on a 28 KJ electromagnetic forming system. The Taguchi orthogonal array approach was used for the design of experiments using the three input parameters (voltage, sheet thickness and number of turns of the coil). The maximum error between numerical and experimental values for sheet thickness variation was observed to be 4.9 %. Analysis of variance (ANOVA) was performed on the experimental results. Applied voltage and sheet thickness were the significant parameters, while the number of turns of the coil had an insignificant effect on sheet deformation. The contribution ratio of voltage and sheet thickness was 46.21 % and 45.12 % respectively. The sheet deformation from simulations was found to be in good agreement with the experimental results.

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Runov, A., V. A. Sergeev, R. Nakamura, W. Baumjohann, S. Apatenkov, Y. Asano, T. Takada et al. "Local structure of the magnetotail current sheet: 2001 Cluster observations". Annales Geophysicae 24, n. 1 (7 marzo 2006): 247–62. http://dx.doi.org/10.5194/angeo-24-247-2006.

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Abstract. Thirty rapid crossings of the magnetotail current sheet by the Cluster spacecraft during July-October 2001 at a geocentric distance of 19 RE are examined in detail to address the structure of the current sheet. We use four-point magnetic field measurements to estimate electric current density; the current sheet spatial scale is estimated by integration of the translation velocity calculated from the magnetic field temporal and spatial derivatives. The local normal-related coordinate system for each case is defined by the combining Minimum Variance Analysis (MVA) and the curlometer technique. Numerical parameters characterizing the plasma sheet conditions for these crossings are provided to facilitate future comparisons with theoretical models. Three types of current sheet distributions are distinguished: center-peaked (type I), bifurcated (type II) and asymmetric (type III) sheets. Comparison to plasma parameter distributions show that practically all cases display non-Harris-type behavior, i.e. interior current peaks are embedded into a thicker plasma sheet. The asymmetric sheets with an off-equatorial current density peak most likely have a transient nature. The ion contribution to the electric current rarely agrees with the current computed using the curlometer technique, indicating that either the electron contribution to the current is strong and variable, or the current density is spatially or temporally structured.

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Ghaly, Ahmed Y., e Elsayed M. E. Elbarbary. "Radiation effect on MHD free-convection flow of a gas at a stretching surface with a uniform free stream". Journal of Applied Mathematics 2, n. 2 (2002): 93–103. http://dx.doi.org/10.1155/s1110757x02000086.

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We investigate the problem of free convection heat transfer near an isothermal stretching sheet. This has been done under the simultaneous action of buoyancy, radiation, and transverse magnetic field. The governing equations are solved by the shooting method. The velocity and temperature functions are represented graphically for various values of the flow parameters: radiation parameterF, free convection parameterGr, magnetic parameterM, Prandtl numberPr, and the parameter of relative difference between the temperature of the sheet, and the temperature far away from the sheetr. The effects of the radiation and magnetic field parameters on the shear stress and heat flux are discussed.

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Željko Hederić, Muharem Mehmedović e Krešimir Miklošević. "A MORE ACCURATE CALCULATION OF MAGNETIC LOSSES IN THE INDUCTION MOTOR". Journal of Energy - Energija 58, n. 3 (16 settembre 2022): 290–307. http://dx.doi.org/10.37798/2009583302.

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The work presents a comparison of results of the calculation of eddy current losses in the induction motor teeth by virtue of the analytical method and the finite element method. Under the assumption that sheet permeability and conductivity are constant, total eddy current losses can be calculated as the aggregate of pulsation and surface losses. Instructions are given regarding the manner of calculation of total losses in the teeth for all teeth forms, taking into consideration the suppression of flows in the sheets, flow attenuation in the teeth and the sheet and sheet package processing factors. Valuation of the analytical model of loss calculation was also made by virtue of comparison with the measurements.

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DAHLBURG, RUSSELL B. "Transition to turbulent electric current sheet reconnection". Journal of Plasma Physics 57, n. 1 (gennaio 1997): 35–45. http://dx.doi.org/10.1017/s0022377896005247.

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Electric current sheets develop in the solar corona when different flux systems come into contact. At these sheets magnetic energy is transformed into heat and kinetic energy by means of reconnection. We have previously demonstrated how to accelerate neutral sheet energy conversion by means of a transition to turbulent reconnection via ideal, three-dimensional secondary instabilities, as conjectured by Montgomery. In this paper we describe how our previous results are modified by the presence of a finite mean sheetwise magnetic field. We find a stabilization from this field, due to a decrease in energy transfer from the basic magnetic field to the three-dimensional perturbed fields. An increase in perturbed dissipative energy losses is also observed.

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Cheng, C. Z., e G. S. Choe. "Formation of Thin Current Sheets in the Solar Atmosphere". International Astronomical Union Colloquium 167 (1998): 115–18. http://dx.doi.org/10.1017/s0252921100047400.

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AbstractIn a two-dimensional quadrupolar magnetic field geometry, it is demonstrated that various magnetohydrostatic equilibrium field configurations containing current sheets can be formed either by changes in thermal properties or by footpoint displacement. The shape of current sheets depends on the mass distribution in flux tubes. If the mass per flux tube is maximum at the center of the low-lying bipolar arcades, a current sheet is formed between these two arcades along the separatrix line as the plasma temperature (or the shearing footpoint displacement) is increased above a critical value. If the mass per flux tube is higher in the outer tubes of the bipolar arcades than in the inner ones, a current sheet with a sharp downward-pointed tip hanging at a distance above the bottom boundary is formed when the temperature is decreased below a critical value. Resistive magnetic reconnection in the latter type current sheet results in a magnetic island wrapped in dipped field lines, which is regarded as a plausible prominence field configuration.

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Yagita, Ryo, e Yohei Abe. "Scattering Behavior of Slivers in Shearing of Magnetized Ultra-High-Strength Steel Sheets". Metals 13, n. 1 (4 gennaio 2023): 110. http://dx.doi.org/10.3390/met13010110.

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The changes in the magnetization properties of high-strength steel and ultra-high-strength steel sheets are investigated, and then the sheared edges and the scattering behavior of slivers in shearing of the ultra-high-strength steel sheets are observed. The maximum magnetic flux density of the magnetized sheet is increased with the increasing tensile strength of the sheet. The maximum magnetic flux density in the magnetized blanks decreases, whereas the density in the demagnetized blanks increases. In the sheared edges, the ratio of the fracture surface becomes larger with the increasing tensile strength of the steel sheet. In shearing, the shearing slivers are observed at the time of crack penetration and at the time of punch rise. The mass of the slivers generated from the blank in shearing increases with the increasing tensile strength of the steel sheet. Two-thirds of the generated shearing slivers stick to the blank in the magnetized blank, whereas two-thirds of the slivers in the blank without magnetization scatter to the outside of the die.

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Tenerani, A., e M. Velli. "Spectral signatures of recursive magnetic field reconnection". Monthly Notices of the Royal Astronomical Society 491, n. 3 (27 novembre 2019): 4267–76. http://dx.doi.org/10.1093/mnras/stz3310.

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ABSTRACT We use 2.5D magnetohydrodynamic simulations to investigate the spectral signatures of the non-linear disruption of a tearing unstable current sheet via the generation of multiple secondary current sheets and magnetic islands. During the non-linear phase of tearing mode evolution, there develops a regime in which the magnetic energy density shows a spectrum with a power law close to B(k)2 ∼ k−0.8. Such an energy spectrum is found in correspondence of the neutral line, within the diffusion region of the primary current sheet, where energy is conveyed towards smaller scales via a ‘recursive’ process of fast tearing-type instabilities. Far from the neutral line, we find that magnetic energy spectra evolve towards slopes compatible with the ‘standard’ Kolmogorov spectrum. Starting from a self-similar description of the non-linear stage at the neutral line, we provide a model that predicts a reconnecting magnetic field energy spectrum scaling as k−4/5, in good agreement with numerical results. An extension of the predicted power law to generic current sheet profiles is also given and possible implications for turbulence phenomenology are discussed. These results provide a step forward to understand the ‘recursive’ generation of magnetic islands (plasmoids), which has been proposed as a possible explanation for the energy release during flares, but which, more in general, can have an impact on the subsequent turbulent evolution of unstable sheets that naturally form in the high Lundquist number and collisionless plasmas found in most of the astrophysical environments.

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Ebrahimi, Farzad, e Mohammad Reza Barati. "Vibration analysis of graphene sheets resting on the orthotropic elastic medium subjected to hygro-thermal and in-plane magnetic fields based on the nonlocal strain gradient theory". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 232, n. 13 (20 luglio 2017): 2469–81. http://dx.doi.org/10.1177/0954406217720232.

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This paper develops a nonlocal strain gradient plate model for vibration analysis of the graphene sheets under in-plane magnetic field and hygro-thermal environments. For more accurate analysis of the graphene sheets, the proposed theory contains two-scale parameters related to the nonlocal and strain gradient effects. The graphene sheet is modeled via a two-variable shear deformation plate theory needless of shear correction factors. Governing equations of a nonlocal strain gradient graphene sheet on elastic substrate are derived via Hamilton’s principle. Galerkin’s method is implemented to solve the governing equations for different boundary conditions. Effects of different factors such as moisture concentration rise, temperature rise, nonlocal parameter, length scale parameter, elastic foundation, and magnetic field on vibration characteristics of the graphene sheets are examined.

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ANZAI, Masahiro, Hiroshi ENDO, Toru SUDO e Takeo NAKAGAWA. "Magnetic Finishing of Titanium Sheet". Tetsu-to-Hagane 78, n. 2 (1992): 335–37. http://dx.doi.org/10.2355/tetsutohagane1955.78.2_335.

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Gerber, H. L. "Magnetic damping of steel sheet". IEEE Transactions on Industry Applications 39, n. 5 (settembre 2003): 1448–53. http://dx.doi.org/10.1109/tia.2003.816539.

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27

Shotri, Rishabh, Koen Faes, Guillaume Racineux e Amitava De. "Improved Coil Design for Magnetic Pulse Welding of Metallic Sheets". Journal of Manufacturing and Materials Processing 6, n. 6 (16 novembre 2022): 144. http://dx.doi.org/10.3390/jmmp6060144.

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Magnetic pulse welding of overlapping dissimilar metallic sheets is an emerging technique and usually employs flat electromagnetic coils with rectangular-, H-, I-, and E-shaped cross-sections. The asymmetric cross-section of these coils results in a non-uniform electromagnetic field and in a non-uniform connection in the interface between the overlapping sheets. In this article, the use of a novel O-shaped flat coil is proposed to join an aluminium flyer sheet with a target steel sheet. A finite element-based numerical model is developed to calculate the electromagnetic field, flyer velocity, and its gradual impact onto the target, and the deformations of the sheet assembly. The calculated results with the O-shaped coil show a high-intensity electromagnetic field, the concentration of which decreases radially outwards in a uniform manner. The numerically computed and experimentally measured flyer velocity are found to be in fair agreement. The calculated results show a regularly decreasing impact behaviour between the flyer and target and their resulting deformation. The measured results show the formation of an annular ring-shaped joint profile that is generally found to be stronger compared to that obtained with flat coils with a rectangular cross-section.

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28

Wiechen, H. "New aspects of plasma sheet dynamics - MHD and kinetic theory". Annales Geophysicae 17, n. 5 (31 maggio 1999): 595–603. http://dx.doi.org/10.1007/s00585-999-0595-2.

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Abstract. Magnetic reconnection is a process of fundamental importance for the dynamics of the Earth's plasma sheet. In this context, the development of thin current sheets in the near-Earth plasma sheet is a topic of special interest because they could be a possible cause of microscopic fluctuations acting as collective non-idealness from a macroscopic point of view. Simulations of the near-Earth plasma sheet including boundary perturbations due to localized inflow through the northern (or southern) plasma sheet boundary show developing thin current sheets in the near-Earth plasma sheet about 810 RE tailwards of the Earth. This location is largely independent from the localization of the perturbation. The second part of the paper deals with the problem of the macroscopic non-ideal consequences of microscopic fluctuations. A new model is presented that allows the quantitative calculation of macroscopic non-idealness without considering details of microscopic instabilities or turbulence. This model is only based on the assumption of a strongly fluctuating, mixing dynamics on microscopic scales in phase space. The result of this approach is an expression for anomalous non-idealness formally similar to the Krook resistivity but now describing the macroscopic consequences of collective microscopic fluctuations, not of collisions.Key words. Magnetospheric physics (plasma sheet) · Space plasma physics (kinetic and MHD theory; magnetic reconnection)

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29

ISMAIL, ALI I., e A. A. MUBARAK. "AB INITIO STUDY OF THE ELECTRONIC AND MAGNETIC PROPERTIES OF GRAPHENE WITH AND WITHOUT ADSORPTION OF M ATOM (M = C, N, O, F, Cl)". Surface Review and Letters 25, n. 03 (8 marzo 2018): 1850069. http://dx.doi.org/10.1142/s0218625x18500695.

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We present here an ab initio study for the energetic, electronic, magnetic and optical structures of the graphene sheet with and without the adsorption of M atom (M [Formula: see text] C, N, O, F, Cl). The calculations are preformed using the full-potential linearized augmented plane wave (FP-LAPW) within the generalized gradient approximation (GGA) to describe the exchange-correlation potential. The calculations show that N prefers the bridge site, while C, O, F and Cl prefer the top site above the graphene sheet. The calculated M-graphene bond length is found to be inversely proportional to the adsorption energy. The hybridization between sp-states of the graphene sheet and M adatom is determined by the analysis of the partial and local density of states (PDOS and TDOS). In case of O and F as adsorbed atoms, graphene sheets show a wide energy band-gap and some significant magnetic moments. The optical properties of the studied sheets are performed in different radiation regions using the real and imaginary parts of the dielectric function. We think that the energetic, electronic, optical and magnetic properties of the M-graphene sheets are governed by two main factors; the number of unpaired valence electrons and the electronegativity of the M atom.

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30

Houguang, Chu, Li Longfei, Liu Lei, Zhang Fei, Zhu Sirui, Zhou Libing, Du Zhaoguang e Wen Jintao. "Study of Electromagnetic Characteristics of Silicon Steel Sheet and Transformer Vibration Under Different Tension/Compression Stress". Journal of Physics: Conference Series 2320, n. 1 (1 agosto 2022): 012012. http://dx.doi.org/10.1088/1742-6596/2320/1/012012.

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Abstract In order to study the electromagnetic and vibration performance of transformer under different tensile and compressive stresses. This paper firstly studies the magnetic properties of core silicon steel sheets for transformers under different tensile and compressive stresses, the B-H curves, B-P curves, and permeability curves of silicon steel sheets under different tensile and compressive stresses are given. Secondly, based on the test results of magnetic characteristics of the silicon steel sheet, the electromagnetic performance and vibration of a 3kVA transformer are simulated and analyzed. In the simulation process, the influence of different tensile and compressive stresses on the performance of the silicon steel sheet core of the transformer is considered. It provides a new idea for the electromagnetic-vibration analysis of transformers.

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31

Artemyev, A. V., A. I. Neishtadt e L. M. Zelenyi. "Ion motion in the current sheet with sheared magnetic field – Part 2: Non-adiabatic effects". Nonlinear Processes in Geophysics 20, n. 5 (31 ottobre 2013): 899–919. http://dx.doi.org/10.5194/npg-20-899-2013.

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Abstract. We investigate dynamics of charged particles in current sheets with the sheared magnetic field. In our previouspaper (Artemyev et al., 2013) we studied the particle motion in such magnetic field configurations on the basis of the quasi-adiabatic theory and conservation of the quasi-adiabatic invariant. In this paper we concentrate on violation of the adiabaticity due to jumps of this invariant and the corresponding effects of stochastization of a particle motion. We compare effects of geometrical and dynamical jumps, which occur due to the presence of the separatrix in the phase plane of charged particle motion. We show that due to the presence of the magnetic field shear, the average value of dynamical jumps is not equal to zero. This effect results in the decrease of the time interval necessary for stochastization of trapped particle motion. We investigate also the effect of the magnetic field shear on transient trajectories, which cross the current sheet boundaries. Presence of the magnetic field shear leads to the asymmetry of reflection and transition of particles in the current sheet. We discuss the possible influence of single-particle effects revealed in this paper on the current sheet structure and dynamics.

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32

Chen, Alexander Y., Dmitri Uzdensky e Jason Dexter. "Synchrotron Pair Production Equilibrium in Relativistic Magnetic Reconnection". Astrophysical Journal 944, n. 2 (1 febbraio 2023): 173. http://dx.doi.org/10.3847/1538-4357/acb68a.

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Abstract Magnetic reconnection is ubiquitous in astrophysical systems, and in many such systems the plasma suffers from significant cooling due to synchrotron radiation. We study relativistic magnetic reconnection in the presence of strong synchrotron cooling, where the ambient magnetization, σ, is high and the magnetic compactness, ℓ B , of the system is of order unity. In this regime, e± pair production from synchrotron photons is inevitable, and this process can regulate the magnetization σ surrounding the current sheet. We investigate this self-regulation analytically and find a self-consistent steady state for a given magnetic compactness of the system and initial magnetization. This result helps estimate the self-consistent upstream magnetization in systems where plasma density is poorly constrained, and can be useful for a variety of astrophysical systems. As illustrative examples, we apply it to study the properties of reconnecting current sheets near the supermassive black hole of M87, as well as the equatorial current sheet outside the light cylinder of the Crab pulsar.

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33

AIZAWA, Tomokatsu. "Magnetic Pulse Welding for Sheet Metals". JOURNAL OF THE JAPAN WELDING SOCIETY 77, n. 8 (2008): 718–21. http://dx.doi.org/10.2207/jjws.77.718.

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34

AIZAWA, Tomokatsu, e Keigo OKAGAWA. "Magnetic Pulse Welding for Sheet Metals". Journal of the Japan Society for Technology of Plasticity 52, n. 603 (2011): 424–28. http://dx.doi.org/10.9773/sosei.52.424.

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35

Ruehl, Karl, e Karlheigz Bildner. "Magnetic, hot‐melt adhering soundproofing sheet". Journal of the Acoustical Society of America 87, n. 1 (gennaio 1990): 466. http://dx.doi.org/10.1121/1.399206.

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36

Antiochos, Spiro K. "Magnetic Topology and Current Sheet Formation". International Astronomical Union Colloquium 104, n. 2 (1989): 277–80. http://dx.doi.org/10.1017/s0252921100154338.

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AbstractWe describe a mechanism for coronal heating. The basic idea is that since the photospheric flux is observed to consist of a complex pattern of positive and negative polarity regions, the topology of the coronal magnetic field (in particular the connectivity) must be discontinuous over a complex network of surfaces and magnetic null points in the corona. Consequently, photospheric motions of the field line footpoints, even if arbitrarily smooth, result in discontinuous stressing of the field. This produces coronal current sheets, reconnection at the null points, and rapid heating.

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37

Vainshtein, S. I., e E. N. Parker. "Magnetic nonequilibrium and current sheet formation". Astrophysical Journal 304 (maggio 1986): 821. http://dx.doi.org/10.1086/164218.

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38

Morich Michael, A., John Patrick e D. DeMeester Gordon. "5424643 Magnetic resonance gradient sheet coils". Magnetic Resonance Imaging 13, n. 7 (gennaio 1995): X. http://dx.doi.org/10.1016/0730-725x(95)99166-u.

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39

Zeng, Jianhui, Liejun Li, Jixiang Gao, Xiangdong Huo e Zhengwu Peng. "Investigation of the main factors affecting the magnetic properties of silicon steel sheets by comparing three kinds of silicon steel". Journal of Physics: Conference Series 2390, n. 1 (1 dicembre 2022): 012030. http://dx.doi.org/10.1088/1742-6596/2390/1/012030.

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Abstract As an important magnetic material, silicon steel is widespread used in various motors, generators, relays and transformers. It is of great significance to explore the factors affecting the magnetic properties of non-oriented silicon steel. This paper introduces the production process of 50W800, 50W600 and 35W550 non-oriented silicon steel, and compares their magnetic properties, observes the microstructure of silicon steel sheet under hot rolling, cold rolling and annealing three technological states, analyzes the influence of sheet thickness, composition, microstructure and impurity on the magnetic properties of non-oriented silicon steel. The results can be summarized as follows: (1) The magnetic properties of the silicon steel sheet can be improved to a certain extent by reducing the thickness of the silicon steel sheet.(2) Increasing silicon content in a certain range can reduce core loss of silicon steel. (3) After annealing, the grain size of cold rolled silicon steel sheet becomes larger, the defect of grain decreases, the loss of iron core decreases, and the finished silicon steel sheet with good magnetic properties is obtained.

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40

Takeo, Takashi, Masato Kawaguchi, Taichi Ishihara e Toru Matsuzaki. "Effectiveness of Magnetic Sheets in Suppressing Magnetic Leakage in Automobile Wireless Energy Transfer Systems". Advances in Science and Technology 90 (ottobre 2014): 51–56. http://dx.doi.org/10.4028/www.scientific.net/ast.90.51.

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Recently, wireless energy transfer techniques are being developed for hybrid (HEV) or electric (EV) vehicles. However, without taking any measures, magnetic field strength around energy transfer systems that employ solenoid type antennas is known to exceed regulated values in most countries. In this study, the application of magnetic sheets, which are widely used as EMC components, is proposed to suppress the magnetic field leakage from an automobile energy transfer system and the ability of magnetic leakage suppression with the magnetic sheet has been evaluated by means of electromagnetic simulation. Through these investigations, desirable system arrangements are discussed. As a result, if combined with a metal plate, non-conductive magnetic materials having large permeability has been found to be preferable.

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41

Ido, Yasushi, Keisuke Asakura e Hitoshi Nishida. "Behavior of both Nonmagnetic Particles and Magnetic Particles in Magnetic Compound Fluids in a Micro-Tube with Axial Flow under Rotating Magnetic Field". Materials Science Forum 856 (maggio 2016): 9–14. http://dx.doi.org/10.4028/www.scientific.net/msf.856.9.

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Behaviors of both micrometer-size nonmagnetic abrasive particles and micrometer-size magnetic particles in a magnetic fluid are investigated by using the discrete particle method which is based on the simplified Stokes dynamics. Sheet-like clusters of nonmagnetic particles and sheet-like clusters of magnetic particles alternately appear one after another in the axis direction when the flow velocity is small.

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42

Lee, Taegyu, Hyeonjin Jung, Yeonghwan Song, Seungchan Cho, Dong-Hyun Kim, Yangdo Kim, Yoon-Seok Lee, Yongho Park e Moonhee Choi. "Development of a Highly Densified Magnetic Sheet for Inductors and Advanced Processes through Silane Surface Treatment of Fe Nanopowder". Applied Sciences 10, n. 14 (10 luglio 2020): 4770. http://dx.doi.org/10.3390/app10144770.

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For developing subminiature and highly integrated multilayer inductors, soft magnetic powder was used; however, its ferrite magnetic component is characterized by high resistivity and reduced direct current saturation, leading to the deterioration of the inductor under high currents. Therefore, herein, to improve the electromagnetic properties of thin-film inductors, Fe nanopowder was used to increase the volume fraction of magnetic sheets. Surface treatment was performed by using silane coupling agents, which improved the bonding strength and dispersibility of the Fe nanopowder with a heterogeneous epoxy binder. For uniform surface treatment on the nanopowder, the silane-treated powder was aged for 24 h, at a temperature of 3 °C. The surface-treated Fe nanopowder was used with a mixing ratio of the soft magnetic powder (coarse:fine:nano) of 7:2.5:0.5 wt.%; this was successful in producing a flexible and highly densified magnetic sheet. As a result, the volume fraction of the magnetic sheet for thin-film inductors to which a low-temperature aging-treated nanopowder was applied was significantly improved.

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43

Galbova, O., V. G. Peschansky e D. I. Stepanenko. "Magnetotransport phenomena in layered conductors under magnetic breakdown". International Journal of Modern Physics B 31, n. 14 (23 marzo 2017): 1750114. http://dx.doi.org/10.1142/s0217979217501144.

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We study the transport phenomena in layered conductors with rather general electron energy spectrum placed in a high magnetic field [Formula: see text], under conditions when the distance between various sheets of the Fermi surface (FS) may become small under the external effects, such as hydrostatic pressure or impurity atom doping, and electrons can transfer from one sheet of the FS to another due to magnetic breakdown. We calculate the dependence of the in-plane electrical conductivity and magnetoresistance on magnetic field and probability of magnetic breakdown and show that the field-induced quadratic increase of the in-plane resistance in the absence of magnetic breakdown is changed by a linear dependence on [Formula: see text]. With a further reduction of the energy gap between FS sheets, the in-plane resistance is saturated.

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44

Daldorff, Lars K. S., James E. Leake e James A. Klimchuk. "Impact of 3D Structure on Magnetic Reconnection". Astrophysical Journal 927, n. 2 (1 marzo 2022): 196. http://dx.doi.org/10.3847/1538-4357/ac532d.

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Abstract Results from 2.5D and 3D studies of the onset and development of the tearing instability are presented, using high-fidelity resistive MHD simulations. A limited parameter study of the strength of the reconnecting field (or shear angle) was performed. An initially simple 1D equilibrium was used, consisting of a modified force-free current sheet, with periodic boundary conditions in all directions. In all cases, the linear and nonlinear evolution led to a primary current sheet between two large flux ropes. The global reconnection rate during this later stage was analyzed in all simulations. It was found that in 2.5D the primary current sheet fragmented owing to plasmoids, and as expected, the global reconnection rate, calculated using multiple methods, increases with the strength of the reconnecting field owing to a stronger Alfvén speed. In 3D, the presence of interacting oblique modes of the tearing instability complicates the simple 2.5D picture, entangling the magnetic field of the inflow and introducing a negative effect on the reconnection rate. The two competing effects of stronger Alfvén speed and entangling, which both increase with the strength of the reconnecting field, resulted in a decrease in the reconnection rate with increasing reconnecting field. For all simulations, the 3D rates were less than in 2.5D but suggest that as one goes to weak reconnecting field (or strong guide field) the system becomes more 2.5D-like and the 2.5D and 3D rates converge. These results have relevance to situations like nanoflare heating and flare current sheets in the corona.

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45

You, Yuan. "Electronic and magnetic control in fully-hydrogenated boron nitride". Journal of Theoretical and Computational Chemistry 16, n. 04 (28 aprile 2017): 1750033. http://dx.doi.org/10.1142/s021963361750033x.

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We investigate the effects of vacancies on the electronic and magnetic properties in fully-hydrogenated boron nitride sheet by performing first-principles calculation. Our results reveal that this sheet fosters magnetic materials with finite magnetic moment under certain vacancies. This phenomenon can be explained by the charge redistribution in which the unpaired electrons in bands determine the magnitude of magnetic moment and thus the ground state of the systems. The magnetic moment can be tuned from 0 to 2 by introducing different vacancies. This picture explicitly demonstrates that the type of vacancy plays an important role in determining nonmagnetic or magnetic materials of fully-hydrogenated boron nitride sheet, indicating their functionalities and possible applications in spintronics.

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46

Singh, Jitender, A. B. Vishalakshi, U. S. Mahabaleshwar e Gabriella Bognar. "MHD Casson fluid flow with Navier’s and second order slip due to a perforated stretching or shrinking sheet". PLOS ONE 17, n. 11 (4 novembre 2022): e0276870. http://dx.doi.org/10.1371/journal.pone.0276870.

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The present work discusses the laminar boundary layer flow of an electrically conducting Casson fluid due to a horizontal perforated sheet undergoing linear shrinking/stretching with mass transpiration. Navier’s slip and second-order slip conditions are also imposed on the flow. The system is subjected to a transverse magnetic field. The non-Newtonian flow under consideration obeys the rheological equation of state due to the Casson model. The PDEs governing the bounder layer flow is reduced to a nonlinear boundary value problem in ODEs by utilizing appropriate similarity transformations and are expressed analytically. The similarity solution is found to be a function of the Casson parameter, magnetic parameter, mass suction/injection parameter, and the first/second-order slip parameters. Such a solution is either unique, or dual solutions exist in a region defined by the mass transfer induced slip parameter. The results of the present work are found to be an increase of the magnetic effects resulting in expansion of the unique solution region and contraction of the dual solution region for the flow due to the induced Lorentz force. In the unique solution region, an increase in magnitudes of mass suction induced slip and the first/second-order slip parameters result in a reduction of the wall shear stress in the shrinking sheet, while the wall shear stress with mass suction increases with the Casson and the magnetic effects. Similar results exist for the stretching sheet case with mass suction. However, only unique similarity solutions exist only for the case of stretching sheets with mass injection. The current work is a generalization of the classical works of Crane (1970) and Pavlov (1974) for a stretching sheet. Mass suction/injection induced slip enhances and achieves a dominant flow driven by reversing the flow direction of the moving sheet, which allows an adjacent flow against the sheet. The findings have possible industrial applications in fluid-based systems including stretchable/shrinkable things, automated cooling systems, power generation, microelectronics, and present new results to the problem.

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47

Xia, Q., e V. Zharkova. "Particle acceleration in coalescent and squashed magnetic islands". Astronomy & Astrophysics 635 (marzo 2020): A116. http://dx.doi.org/10.1051/0004-6361/201936420.

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Aims. Particles are known to have efficient acceleration in reconnecting current sheets with multiple magnetic islands that are formed during a reconnection process. Using the test-particle approach, the recent investigation of particle dynamics in 3D magnetic islands, or current sheets with multiple X- and O-null points revealed that the particle energy gains are higher in squashed magnetic islands than in coalescent ones. However, this approach did not factor in the ambient plasma feedback to the presence of accelerated particles, which affects their distributions within the acceleration region. Methods. In the current paper, we use the particle-in-cell (PIC) approach to investigate further particle acceleration in 3D Harris-type reconnecting current sheets with coalescent (merging) and squashed (contracting) magnetic islands with different magnetic field topologies, ambient densities ranging between 108 − 1012 m−3, proton-to-electron mass ratios, and island aspect ratios. Results. In current sheets with single or multiple X-nullpoints, accelerated particles of opposite charges are separated and ejected into the opposite semiplanes from the current sheet midplane, generating a strong polarisation electric field across a current sheet. Particles of the same charge form two populations: transit and bounced particles, each with very different energy and asymmetric pitch-angle distributions, which can be distinguished from observations. In some cases, the difference in energy gains by transit and bounced particles leads to turbulence generated by Buneman instability. In magnetic island topology, the different reconnection electric fields in squashed and coalescent islands impose different particle drift motions. This makes particle acceleration more efficient in squashed magnetic islands than in coalescent ones. The spectral indices of electron energy spectra are ∼ − 4.2 for coalescent and ∼ − 4.0 for squashed islands, which are lower than reported from the test-particle approach. The particles accelerated in magnetic islands are found trapped in the midplane of squashed islands, and shifted as clouds towards the X-nullpoints in coalescent ones. Conclusions. In reconnecting current sheets with multiple X- and O-nullpoints, particles are found accelerated on a much shorter spatial scale and gaining higher energies than near a single X-nullpoint. The distinct density and pitch-angle distributions of particles with high and low energy detected with the PIC approach can help to distinguish the observational features of accelerated particles.

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48

Soward, A. M., e E. R. Priest. "Magnetic field-line reconnection with jets". Journal of Plasma Physics 35, n. 2 (aprile 1986): 333–50. http://dx.doi.org/10.1017/s0022377800011375.

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Some recent numerical simulations of driven magnetic field-line reconnection by Biskamp show no evidence of the Petschek mechanism when the reconnection rate or magnetic Reynolds number are large. Instead, an electric current sheet forms on the symmetry axis, across which a magnetic field is annihilated. The sheet terminates at a Y-point. Fluid driven into the current sheet escapes as jets along the separatrices emanating from the Y-point. This paper shows how many of the features such as the jets can be explained by a simple analytical model. Since the numerical simulations are necessarily on a bounded domain, the importance of the external boundary conditions in setting up a steady-state solution is stressed by illustrative examples.

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49

Sedighi, Mohammad, H. Karimi-Nemch e M. Khandaei. "Effect of Sheet Thickness on Magnitude and Distribution of Magnetic Force in Electromagnetic Sheet Metal Forming Process". Applied Mechanics and Materials 110-116 (ottobre 2011): 3506–11. http://dx.doi.org/10.4028/www.scientific.net/amm.110-116.3506.

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Electromagnetic forming is one of the sheet metal forming processes in which force is applied by an electromagnetic pulse. In this process, sheet metal is deformed rapidly at high strain rates. In this paper, FE simulation has been applied to study distribution of magnetic field formed by spiral coil and inducted eddy current in a circular sheet. At first, magnitude and components of magnetic field intensity have been calculated and compared with experimental results taken from literature. After verifying of simulation results, the effects of sheet thickness on magnetic force magnitude and distribution have been investigated.

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Riahi, Mohammad, Mohammad Sedighi e Hassan Rahmanian. "State of the art automated chasing and repoussé through utilization of magnetic hammering". Rapid Prototyping Journal 22, n. 4 (20 giugno 2016): 727–34. http://dx.doi.org/10.1108/rpj-01-2015-0010.

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Purpose The paper aims to design a process to mechanize traditional chasing and repoussé which is the art of creating an artistic pattern on a sheet metal by making high and low points through utilization of hammer and chisel. In scientific literature, it is a kind of incremental sheet metal forming. Design/methodology/approach In the designed process, a magnetic actuator is used as a hammer which converts electric energy into kinetic reciprocal impact energy, and hammering sequence is completely controlled via the designed software. The sheet is bound not to move easily. Then, a hammering mechanism is connected to the numerical control machine. As the magnetic hammer is moved gradually along the defined path, the sheet is chased gradually by controlling the consecutive impacts. Different methods of test sheet entanglement are also discussed to reduce noise and undesired deformations of sheet, and indents are also clarified. Findings The designed mechanism enables the user to form desired art patterns faster with more precision via the automated process. The hammering sequence is controlled via computer successfully. The designed magnetic actuator could be commercialized easily. Experiments show that the pitch under sheet is the best. Typical art patterns are chased successfully. Originality/value In incremental sheet metal punching, there was no control on hammering sequence before. In this process, the designed magnetic hammer is quite controllable. Also, it is easily attached to the computerized numerical control (CNC) and is suitable for commercial use. Furthermore, the stuff under sheet was not taken into consideration before.

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