• Journal of the Korean Magnetics Society
• /
• v.1 no.1
• /
• pp.1-5
• /
• 1991

The magnetic properties of the polycrystalline ${(Fe_{2}O_{3})}_{1-x-y}{(In_{2}O_{3})}_{x}{(Eu_{2}O_{3})}_{y}$(x=0.01, y=0.02과 x=0.02, y=0.03) have been studied by the methods of X-ray diffraction, $M\"{o}ssbauer$ effect, and magnetic hysteresis measurement. The X-ray diffraction patterns show that the samples have a same crystal structure as $\alpha-Fe_{2}O_{3}$. From the analysis of the temperature dependence of the quadrupole splitting and average half-width, it is found that the Morin transition occurs in the sample of x=0.01 and y=0.02 and the spin angle defined as the angle between the [111] crystal axis and antiferromagnetic vector, changes from about $35^{\circ}$ to the (111) plane as increasing the temperature in the sample of x=0.02 and y=O.03. The temperature dependence of magnetic hyperfine field is analyzed by using the spin-wave theory. The isomer shift values at room temperature are found to be given by about 0.35mm/s for the samples which means that the Fe ions belong to $3^{+}ion$. The temperature dependence of isomer shift was analyzed by using the Debye model.

• The Bulletin of The Korean Astronomical Society
• /
• v.41 no.1
• /
• pp.46.1-46.1
• /
• 2016

The formation process of a current sheet is important for solar flare from a viewpoint of a space weather prediction. We therefore derive the temporal development of the spatial and statistical distribution of electric current density distributed in a flare-producing active region to describe the formation of a current sheet. We derive time sequence distribution of electric current density by applying a nonlinear force-free approximation reconstruction to Active Region 12158 that produces an X1.6-class flare. The time sequence maps of photospheric vector magnetic field used for reconstruction are captured by a Helioseismic and Magnetic Imager (HMI) onboard Solar Dynamic Observatory (SDO) on 10th September, 2014. The spatial distribution of electric current density in NLFFF model well reproduce observed sigmoidal structure at the preflare phase, although a layer of high current density shrinks at the postflare phase. A double power-law profile of electric current density is found in statistical analysis. This may be expected to use an indicator of the occurrence of a solar flare.

• The Bulletin of The Korean Astronomical Society
• /
• v.36 no.2
• /
• pp.111.1-111.1
• /
• 2011

We present near-IR imaging polarimetry of the observed $5{\times}9$ fields (${\sim}39'{\times}69'$) in the Large Magellanic Cloud (LMC), using the InfraRed Survey Facility (IRSF). We obtained polarimetry data in J, H, and Ks bands using the JHKs-simultaneous imaging polarimeter SIRPOL. We measured Stokes parameters of point-like sources to derive the degree of polarization and the polarization position angle. We show a polarization vector map in the reduced 45 fields and the statistical distribution of the polarization degrees and angles. This poster presents the preliminary results to show the physical properties of the magnetic field in the observed LMC regions.

• Communications for Statistical Applications and Methods
• /
• v.31 no.1
• /
• pp.87-104
• /
• 2024

Most functional magnetic resonance imaging (fMRI) studies in resting state have assumed that the functional connectivity (FC) between time series from distinct brain regions is constant. However, increased interest has recently been in quantifying possible dynamic changes in FC during fMRI experiments. FC study may provide insight into the fundamental workings of brain networks to brain activity. In this work, we focus on the specific problem of estimating the dynamic behavior of pairwise correlations between time courses extracted from two different brain regions. We compare the sliding-window techniques such as moving average (MA) and exponentially weighted moving average (EWMA), dynamic causality with vector autoregressive (VAR) model, dynamic conditional correlation (DCC) based on volatility, and the proposed alternative methods to use differencing and recursive residuals. We investigate the properties of those techniques in a series of simulation studies. We also provide an application with major depressive disorder (MDD) patient fMRI data to demonstrate studying dynamic correlations.

• Journal of Institute of Convergence Technology
• /
• v.3 no.2
• /
• pp.11-15
• /
• 2013

These days, the quality of goods is required to improve in the process of manufacturing the semiconductor through the short working hours and clean transportation. The non-contact transport device using magnetic levitation can be a solution in the manufacturing process. The non-contact transport device, using electromagnetic actuation, is the system that can actually transport them by only using attraction force from the electromagnetic source without authentic contact. Moreover, the system using electromagnetic force has a substantial number of benefits ranging from unrestricted design to unlimited expansion. Especially, the price is competitive. The non-contact transport device, using electromagnetic force, has another merits in controlling by giving the same amount of attraction force to ferromagnetic body. By controlling the currents given to coil, the operator is able to decide the direction of the transportation. In order to design the optimal system, we implemented five different things such as the presence of the links below the electromagnetic, the electromagnet changes due to coupling method, the change according to the thickness of the links below electromagnet, due to changes in between electromagnetic distance direction, and the size of the current. Through simulations and the optimum design, it seems to control easily and figure out the exact size of power. It might definitely be the non-contact transport that can sharply reduce tiny scratches and particles in the process of manufacturing the semiconductor.