• Proceedings of the Korean Nuclear Society Conference
• /
• 1996.05b
• /
• pp.233-240
• /
• 1996

Analyses of the viscous and end effects on electromagnetic (EM) pumps of annular linear induction type for the sodium coolant circulation in Liquid Metal Fast Breeder Reactors have been carried out based on the MHD laminar flow analysis and the electromagnetic field theory. A one-dimensional MHD analysis for the liquid metal flowing through an annular channel has been performed on the basis of a simplified model of equivalent current sheets instead of three-phase currents in the discrete primary windings. The calculations show that the developed pressure difference resulted from electromagnetic and viscous forces in the liquid metal is expressed in terms of the slip, and that the viscous loss effects are negligible compared with electromagnetic driving forces except in the low-slip region where the pumps operate with very high flow velocities comparable with the synchronous velocity of the electromagnetic fields, which is not applicable to the practical EM pumps. A two-dimensional electromagnetic field analysis based on an equivalent current sheet model has found the vector potentials in closed form by means of the Fourier transform method. The resultant magnetic fields and driving forces exerted on the liquid metal reveal that the end effects due to finiteness of the pump length are formidable. In addition, a two-dimensional numerical analysis for vector potentials has been performed by the SOR iterative method on a realistic EM pump model with discretely-distributed currents in the primary windings. The numerical computations for the distributions of magnetic fields and developed pressure differences along the pump axial length also show considerable end effects at both inlet and outlet ends, especially at high flow velocities. Calculations of each magnetic force contribution indicate that the end effects are originated from the magnetic force caused by the induced current ( u x B ) generated by the liquid metal movement across the magnetic field rather than the one (E) produced by externally applied magnetic fields by three-phase winding currents. It is concluded that since the influences of the end effects in addition to viscous losses are extensive particularly in high-velocity operations of the EM pumps, it is necessary to find ways to suppress them, such as proper selection of the pump parameters and compensation of the end effects.

• 한국초전도학회:학술대회논문집
• /
• v.9
• /
• pp.210-213
• /
• 1999

Magnetoresistance and magnetization of Sr$_{l-x}K_xBiO_3$ were both measured as functions of temperature and magnetic field. Resistivity goes to zero at T=10.1K and the overall superconducting transition behavior under applied magnetic fields is similar to that of other BiO based superconductors. Also, below T<5K we have observed the reappearance of finite resistivity with a power law temperature dependence( ${\rho}$ ${\sim}$T$^1$); the reentrant superconducting transition of resistivity. Contrary to the Josephson weak link effect in polycrystalline samples, which gives the depression of the superconducting state with increasing electrical current or magnetic field, the superconducting state for T<5K is resumed by applying a higher current or magnetic field. Magnetic susceptibility( ${\chi}$ ) of Sr$_{l-x}K_xBiO_3$ for T<5K also shows similar trends to that observed in transport measurements: increase of ${\chi}$ (paramagnetic-like behavior) at a low magnetic fields(B=50 Oe) and, the resumption of perfect diamagnetism at high fields.

• Journal of Powder Materials
• /
• v.10 no.2
• /
• pp.83-88
• /
• 2003

Nanocrystalline materials of Ni and Ni-Cu alloy have been synthesized by the pulsed wire evaporation (PWE) method and these abnormal magnetic properties in the magnetic ordered state have been characterized using both VSM and SQUID in the range of high and low magnetic fields. Ni and Ni-Cu particles with an average size of 20 to 80 nm were found to influence magnetic hysterisis behavior and the results of powder neutron diffraction patterns and saturation magnetization curves are shown to indicate the absence of the NiO phase. The shifted hysterisis loop and irreversibility of the magnetization curve in the high field region were observed in the magnetic-ordered state of both Ni and Ni-Cu. The virgin magnetization curve for Ni slightly spillover on the limited hysterisis loop ($\pm$20kOe). This irreversibility in the high field of 50 kOe can be explained by non-col-linear behavior and the existence of the metastable states of the magnetization at the surface layer (or core) of the particle in the applied magnetic field. Immiscible alloy of Cu-Ni was also found to show irreversibility having two different magnetic phases.

• Journal of Magnetics
• /
• v.22 no.2
• /
• pp.214-219
• /
• 2017

Magnetic separators that clean the fluid stream from impurities, protect the installations in numerous industries. This paper introduces a graphical user interface (GUI) which proposes an optimized coil separating magnetic particles with a radius from 1 up to 500 µm. High gradient magnetic fields are employed in an arbitrary user defined fluidic channel which is made of a nonmetallic material. The effects of coil parameters are studied and adjusted to design an optimum coil with a minimum Ohmic loss. In addition, to design the coil scheme based on the particle movements, a mathematical particle-tracing model within the fluid channels has been utilized. In comparison to conventional magnetic separators, this model is reconfigurable by the user, produces a weaker magnetic field, allows for continuous purifying and is easy to install, with high separation efficiency. The presented GUI is simple to use, where the coil's manufacturing limitations can be specified.

• Journal of Surface Science and Engineering
• /
• v.32 no.6
• /
• pp.658-664
• /
• 1999

Helicon sources are attractive for plasma processing because they provide high plasma density in low magnetic fields. Helicon waves were excited by a Nagoya type III antenna in a magnetized plasma column. Plasma parameters were measured with a double probe, and the structure and adsorption of the helicon wave fields were determined with the probes. Argon is fed through a MFC (mass flow controller) for operation pressure of 10~110 mtorr. A 13.56 MHz r.f. power of 50~450 W is induced through the antenna. The plasma density and electron temperature are measured as functions of external magnetic field, r.f. power and pressure. The plasma density as functions of r.f. power and magnetic field at a constant pressure increased linearly, and the electron temperature did not change largely with various operation parameters and the value was around 5~7 eV.

• Publications of The Korean Astronomical Society
• /
• v.30 no.2
• /
• pp.87-88
• /
• 2015

We present results of our R-band polarimetry of a bright-rimmed cloud, IC1396A (with BRC 36), associated with the H II region S131 and the cometary globule LDN 1616 to study their magnetic field geometry. The distances of these clouds have been reported to be ~ 750 pc and ~ 450 pc, respectively in the literature. The young open cluster Trumpler 37 in the vicinity of IC1396A and the high mass stars in the Orion belt near L1616 are found to be responsible for the structure of these clouds. We made polarimetry of foreground stars inferred from their distances measured by the Hipparcos satellite to subtract the foreground contribution to the observed polarization results. We discuss the optical polarimetric results and compare our findings with MHD simulations towards BRCs and CGs.

• Journal of Magnetics
• /
• v.9 no.3
• /
• pp.75-78
• /
• 2004

Magnetic transmission soft X-ray microscopy has been used to study element-specifically the magnetization reversal behavior of ${(Co_{84}Cr_{16})}_{87}Pt_{l3}$ alloy thin films with a lateral resolution of 35 nm. Our results indicate that the magnetization switching is carried out by a random nucleation process that can be attributed to the reversal of individual grains. We found evidence of a large distribution of the switching fields at the nanogranular length scale, which has to be considered seriously for applications of CoCrPt systems as magnetic high density storage materials.

• Journal of applied mathematics & informatics
• /
• v.40 no.3_4
• /
• pp.587-601
• /
• 2022

We find the characterizations of the curvatures of Legendre curves and magnetic curves in Kenmotsu manifolds with C-parallel and C-proper mean curvature vector fields in the tangent and normal bundles. Finally, an illustrative example is presented.

• Progress in Superconductivity and Cryogenics
• /
• v.20 no.4
• /
• pp.1-5
• /
• 2018

A high gradient magnetic (HGM) separator prototype with the $2^{nd}$ generation high temperature superconducting (2G HTS) magnetic system operated in sub-cooled nitrogen is presently under development at NRC "Kurchatov Institute" (Moscow, Russia). The main goal of the project is an attempt to shift away from the complicated liquid helium cryostats towards simple cryocooler-based nitrogen cryogenics as much more convenient for HGM separators industrial applications. Using of commercial HTS tapes allows to get a sufficient level of magnetic fields and extraction forces with low energy consumption. The expected operational parameters of the device are 1.2-1.5 T in the empty operational gap and up to 3 T on the ferromagnetic filters. In this paper we briefly describe the design of the HTS rotary separator prototype with the horizontally oriented rotor axis and propose different types of ferromagnetic filters intended for weakly magnetic ores enrichment.

• The Bulletin of The Korean Astronomical Society
• /
• v.36 no.1
• /
• pp.85.1-85.1
• /
• 2011

Recently, Faraday rotation measure (RM) at high Galactic latitude has been investigated, partly to explore the Galactic magnetic fields and partly to study the extragalactic magnetic fields. The Galactic contribution to RM comes from the global component as well as the turbulent component. So far the turbulent field was used to be analytically modeled with a Kolmogorov-type power spectrum. Here, we present the initial results of the work where the turbulent field is modeled using data of MHD turbulence simulations. Our work is intended to be applied to simulations of RM surveys with LOFAR, ASKAP, MeerKAT, and SKA.