• Bulletin of the Korean Space Science Society
• /
• 2003.10a
• /
• pp.34-34
• /
• 2003

To better understand how high-latitude electric fields influence thermospheric dynamics, we study winds in the high-latitude lower thermosphere using the Thermosphere-Ionosphere-Electrodynamics General Circulation Model of the National Center for Atmospheric Research (NCAR/TIEGCM). In order to compare with Wind Imaging Interferometer (WINDII) observations the model is run for the conditions of 1992-1993 southern summer. The association of the model results with the interplanetary magnetic field (IMF) is also examined to determine the influences of the IMF-dependent ionospheric convection on the winds. The wind patterns show good agreement with the WINDII observations, although the model wind speeds are generally weaker than the observations. It is confirmed that the influences of high-latitude ionospheric convection on summertime thermospheric winds are seen down to 105 km. For negative and positive IMF By the difference winds, with respect to the wind during null IMF conditions, show significantly strong anticyclonic and cyclonic vortices, respectively, down to 105 km. For positive IMF Bz the difference winds are largely confined to the polar cap, while for negative IMF Bz they extend to subauroral latitudes. The IMF Bz-dependent diurnal wind component is strongly correlated with the corresponding component of ionospheric convection velocity down to 108 km and is largely rotational. The influence of IMF By on the lower thermospheric summertime zonal-mean zonal wind is substantial at high latitudes, with maximum wind speeds being 60 m/s at 130 km around 77 magnetic latitude.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.24 no.3
• /
• pp.348-354
• /
• 2015

Using a magnetic gear, the speed and torque of the driving axis can be decreased and increased, respectively, similar to a mechanical speed reducer. In particular, because the driving side can be isolated mechanically from the load side, the magnetic gear was developed for application with environmental constraints. Of the existing topologies used for the magnet gear, the filtering method of a specified magnetic component is the most competitive. In this paper, a novel unified harmonic modulator is applied to filter the specified component. The torque conversion method using this modulator is described in detail, and the key factors of the modulator are derived from the influence on the resulting torque. The experimental setup was constructed and its torque transmission efficiency measured for varying loads. The transient characteristic from an excessive load is compared with the theoretical simulation.

• Journal of Magnetics
• /
• v.16 no.3
• /
• pp.318-321
• /
• 2011

A new Fe-based amorphous compound powder was prepared from Fe-Si-B amorphous powder by crushing amorphous ribbons as the first magnetic component and Fe-Cr-Mo metallic glassy powder by water atomization as the second magnetic component. Subsequently by adding organic and inorganic binders to the compound powder and cold pressing, the new Fe-based amorphous compound powder cores were fabricated. This new Fe-based amorphous compound powder cores combine the superior DC-Bias properties and the excellent core loss. The core loss of 500 kW/$m^3$ at $B_m$ = 0.1T and f = 100 kHz was obtained When the mass ratio of FeSiB/FeCrMo equals 3:2, and meanwhile the DC-bias properties of the new Fe-based amorphous compound powder cores just decreased by 10% compared with that of the FeSiB powder cores. In addition, with the increasing of the content of the FeCrMo metallic glassy powder, the core loss tends to decrease.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.13 no.5
• /
• pp.70-75
• /
• 2014

Permanent magnets have recently been considered as device that can be used to control the behavior of mechanical systems. Neodymium magnets, a type of permanent magnet, have been used in numerous mechanical devices. These are permanent magnets made from an alloy of neodymium, iron, and boron to form the Nd2Fe14B tetragonal crystalline structure. The magnetic selection, magnet core design and mechanical errors of the magnetic component can affect the performance of the magnetic force. In this study, the coercive force, residual induction, and the dimensions of the design parameters of the magnet core are optimized. The design parameters of magnet core are defined as the gap between the magnet and the core, the upper contact radius, and the lower thickness of the core. The force exercised on a permanent magnet in a non-uniform field is dependent on the magnetization orientation of the magnet. Non-uniformity of the polarization direction of the magnetic has been assumed to be caused by the angular error in the polarization direction. The variation in the magnetic performance is considered according to the center distance, the tilt of the magnetic components, and the polarization direction. The finite element method is used to analyze the magnetic force of an optimized cylindrical magnet.

• Journal of Mechanical Science and Technology
• /
• v.18 no.4
• /
• pp.640-648
• /
• 2004

This paper describes a new magnetization method for non-destructive testing with magneto-optical sensor (denoted as MO sensor) which have the following characteristic : high observation sensitivity, independence of the crack orientation, and precise imaging of a complex crack geometry such as multiple cracks. When a magnetic field is applied normally to the surface of a specimen which is significantly larger than its defects, approximately the same magnetic charge per unit area occurs on the surface of the specimen. If there is a crack in the specimen, magnetic charge per unit area has the same value at the bottom of the crack. The distribution of the vertical component of the magnetic flux density, B$\_$Z/, is almost uniform over the no-crack area (denoted as B$\_$Z,BASE/), while the magnetic flux density is smaller in the surroundings of the crack(denoted as B$\_$Z,CRACK/) If B$\_$Z, BASE/ is a bit larger than the saturated magnetic flux density of the MO sensor (B$\_$s/) , then small magnetic domains occur over the crack area and a large domain over the non-crack area because B$\_$Z,CRACK/ is smaller than B$\_$s/.

• Journal of the Korean Geophysical Society
• /
• v.7 no.1
• /
• pp.11-21
• /
• 2004

The variation of geomagnetic field and absolute magnetic field at the geomagnetic observatory of King Sejong Station has been measured with 3-component ring core fluxgate magnetometer, proton magnetometer and D-I magnetometer. With data obtained from King Sejong Station during 2003, thediurnal and annual variations of geomagnetic field were researched and compared with those at other observatories. The deviation of daily variation of magnetic field in antarctica decreased gradually during winter season due to sun effect. The rates of componental annual variation of magnetic field at King Sejong Station were calculated using the least-square method under the assumption that the annual variation of magnetic field is linear. The rates are -55.93 nT/year in horizontal intensity, -0.87 min./year in declination, 58.30 nT/year in vertical intensity, and -69.85 nT/year in total intensity of magnetic field. A remarkable variation was caused by the magnetic storms occurred on 29~30 October, which were so powerful that the variation was observed in mid latitudes as well as high latitudes. The values of variation are generally 1500 2000 nT in Antarctica including King Sejong Station, 350 500 nT in East Asia. The measurement of absolute magnetic field shows that ring core fluxgate magnetometer has relatively large error range under cold temperature.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.18 no.6
• /
• pp.775-780
• /
• 2008

In this paper, unmanned driving of robotic vehicle using magnetic marker is proposed. One of the most important component of autonomous vehicle is to detect the position of a magnetic marker on the road. In order to calculate the precise position of a magnet embedded on the road, the relation of magnetic field and a sensor is analyzed, and a new position sensing system using arrayed magnetic sensor is proposed. Also, the steering control system using a stepping motor is developed for driving by automatic mode as well as manual mode. For the verification of usability, the developed robotic vehicle is tested on magnetic road.

• Proceedings of the KSME Conference
• /
• 2007.05a
• /
• pp.1617-1620
• /
• 2007

This paper presents a magnetostrictive transpositioner and its fabrication process. To get a transposition movement without shifting or twisting, it is designed as an array type. To fabricate the suggested design, micromachining and selective DC magnetron sputtering processes are combined. TbDyFe film is sputter-deposited on the back side of the bulk micromachined transpositioner, with the condition as: Ar gas pressure below $1.2{\times}10^{-9}$ torr, DC input power of 180W and heating temperature of up to $250^{\circ}C$ for the wireless control of each array component. After the sputter process, magnetization and magnetostriction of each sample are measured. X-ray diffraction studies are also carried out to determine the film structure and thickness of the sputtered film. For the operation, each component of the actuator has same length and out-of-plane motion. Each component is actuated by externally applied magnetic fields up to 0.5T and motion of the device made upward movement. As a result, deflections of the device due to the movement for the external magnetic fields are observed.

• Journal of Microbiology and Biotechnology
• /
• v.17 no.10
• /
• pp.1682-1687
• /
• 2007

The differences in the nonvolatile metabolites of pine-mushrooms (Tricholoma matsutake Sing.) according to different parts and heating times were analyzed by applying principal component analysis (PCA) to $^1H$ nuclear magnetic resonance (NMR) spectroscopy data. The $^1H$ NMR spectra and PCA enabled the differences of nonvolatile metabolites among mushroom samples to be clearly observed. The two parts of mushrooms could be easily discriminated based on PC 1, and could be separated according to different heattreated times based on PC 3. The major peaks in the $^1H$ NMR spectra that contributed to differences among mushroom samples were assigned to trehalose, succinic acid, choline, leucine/isoleucine, and alanine. The content of trehalose was higher in the pileus than in the stipe of all mushroom samples, whereas succinic acid, choline, and leucine/isoleucine were the main components in the stipe. Heating resulted in significant losses of alanine and leucine/isoleucine, whereas succinic acid, choline, and trehalose were the most abundant components in mushrooms heat-treated for 3 min and 5 min, respectively.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.3 no.1
• /
• pp.53-60
• /
• 1998

In this paper, the principle of operation, the part characteristic, characteristic of component movement, analysis are carried out for camcoder iris assembly which is one of the important element component in Video camera large projection TV instrument. And some Know-how for development of element component is also included. The magnetic field circuit for the small and simple structure with low power consumption is introduced and new materials of yoke for small motor system is suggested. Especially, the relation with remained magnetic field and operation duration time is analyzed by experimental results. Some problems of nonlinear torque characteristics included in this system is considered to obtain the simple and low cost structure in domestic production. Furthermore, development procedure is suggested for iris assembly and some methods to reduce the burr with some check points for small precise accessories are explained.