• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.4
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• pp.266-269
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• 2012

The most recently IGBT (insulated gate bipolar mode transistor) devices are in the most current conduction capable devices and designed to the big switching power device. Use this number of the devices are need to high voltage and low on-state voltage drop. And then in this paper design of field stop IGBT is insert N buffer layer structure in NPT planar IGBT and optimization design of field stop IGBT and trench field stop IGBT, both devices have a comparative analysis and reflection of the electrical characteristics. As a simulation result, trench field stop IGBT is electrical characteristics better than field stop IGBT.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.38 no.10
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• pp.840-847
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• 1989

It is an important problem that the plasma of high B value is to be confined safely in the research of plasma fusion. So, the Reversed Field Pinch (RFP) plasma has been studied. RFP is stable pinch having self-reversal phenomenon that forms reversed field of itself, but its process of formation is unstable. Therefore, in this paper, we configured the stable RFP by supplying the radio-frequency rotating field just before the RFP is configured by self-reversal phenomenon. Moreover, when conductivity wall is used, toroidal configured by self-reversal phenomenon. Moreover, when conductivity wall is used, toroidal flux is subject to heavy fluctuation in case of high bias field compared with low bias field.

• Journal of the Korean housing association
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• v.18 no.2
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• pp.59-63
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• 2007

In the suburbs near the capital area in Korea, many apartment house complexes are dotted that encircled by field. These apartment house complexes encircled by field, have not park and are abutting on the field, unlike large scale new town. This study is aimed to clear the characteristic of field around these apartment house complexes, consists in development the suburbs near the capital area. As a method of study we conducted greenery evaluation from view of Inhabitant by questionnaire survey. We concluded as follows: inhabitants attach importance to the nature around apartment house complex when move into that; inhabitants are satisfied and feel nature about the field; inhabitants tend to take field as a sight; inhabitants need low-rise development for harmony with field.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.7
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• pp.1084-1092
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• 1994

An induction machine can be operated in the constant power region over an extended high speed range by means of field weakening. A conventional field weakening method is to set the flux reference inversely proportional to the rotor speed. With this method, however, the machines can't yield the maximum torque over the entire high speed range. In this paper, a new field weakening method for the field oriented induction machine drive by the voltage control strategy is presented. The proposed scheme ensures not only producting the maximum torque over the entire field weakening region but also the robust control independent on machine parameters. Also the smooth transition into the field weakening operation and fast dynamic response during transient operation can be obtained. Simulation and experimental results from a 3hp laboratory induction motor drive system are done to confirm the proposed control algorithm.

• Journal of Magnetics
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• v.22 no.1
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• pp.85-92
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• 2017

This research is proposed with the efficient searching method of deperming protocol for magnetic silence. The deperming protocol has been changed depending on the initial magnetic field, the final magnetic field, and the shot number, so deciding parameter is highly important. Therefore, in this paper, the value of the initial magnetic field is supposed to be fixed to that of the saturation field, and excluding the initial magnetic field in the variable, the deperming protocol has been analyzed depending on the final magnetic field and the change of the shot number. In the result of this experiment, the final magnetic field gets high performance to the reverse of the direction of the initial magnetization, and it is resulted that the shot number inverse proportion to the size of the final magnetic field.

• Progress in Superconductivity and Cryogenics
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• v.24 no.3
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• pp.52-56
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• 2022

Single-grain (c-normal or c-parallel) and multi-grain YBCO superconductors were prepared by a melt growth process with/without seeding. The magnetic levitation force and trapped magnetic field at liquid N₂ temperature (77 K) of the YBCO superconductors were investigated. Samples for the levitation force measurement were zero-field cooled (ZFC) to 77 K, and samples for trapped field measurement were field-cooled (FC) using Nd magnets. As for the magnetic levitation force, the c-normal, single grain sample showed the largest value, whereas the multi-grain sample showed the lowest value. The trapped magnetic field of the c-normal and c-parallel single-grain samples was 4-5 times that of the multi-grain sample. In addition, as the external magnetic field (the number of magnets) increased, the both properties increased proportionally. These results were explained in terms of the orientation dependence of the levitation forces and the magnetic field trapping capability of the YBCO superconductor.

• Journal of Korean Elementary Science Education
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• v.22 no.2
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• pp.173-180
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• 2003

The purpose of this study was to investigate about current status of science field study in elementary schools. A total of 72 elementary teachers in Busan and Gyungnam districts were involved and the data from questionnaire was gathered. The questionnaire was comprised two parts: items on general level include the epistemological aspect and actual condition and items on concrete level according to chapters of elementary school science curriculum. The major findings are as follows: 1. Many teachers cognize the requirement of science field study in 7th Korean elementary school science curriculum is larger than 6th one. But they respond the actual number of science field study in 7th curriculum is nearly equal to 6th. 2. In analysis to grades, the actual number of field study decrease as grade is high. 3. In the science content aspects, the requirement of field study is the largest on biology domain and earth science domain. 4. Many teachers have pointed out “the difficulty of administration for field study” and “inappropriated surrounding of their school” as the problems of science field study in elementary school.

• Journal of Korean Institute of Industrial Engineers
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• v.27 no.2
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• pp.190-196
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• 2001

This study aims to develop three types of the visual fields: stationary field, eye field, and head field, which are classified depending upon the eye and head movements. A visual experiment taking target size, target color, and meridian into account was conducted, in which the L32 orthogonal array was employed. The results showed that target size and meridian were significant at ${\alpha}$=0.01 in all three visual fields. Contrary to expectation, target color was significant at ${\alpha}$=0.10 only in the head field. Furthermore, the differences in size of the head field depending upon four target colors were negligibly small. Three linear regression models were provided to generate visual fields which are appropriate for given visual task's characteristics. In addition, a simple method using adjusting factor was also proposed so that anyone without knowledge for human factors/ergonomics can easily generate and use them when designing or evaluating visual tasks. It is expected that the visual fields presented in this study can be easily used even by non-ergonomic experts in real situations due to their simplicity.

• Progress in Superconductivity and Cryogenics
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• v.19 no.1
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• pp.51-55
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• 2017

To obtain Nuclear Magnetic Resonance (NMR) measurement of membrane protein, an NMR magnet is required to generate high intensity, homogeneity, and stability of field. A High-Temperature Superconducting (HTS) magnet is a promising alternative to a conventional Low-Temperature Superconducting (LTS) NMR magnet for high field, current density, and stability margin. Conventionally, an HTS coil has been wound by several winding techniques such as Single-Pancake (SP), Double-Pancake (DP), and layer-wound. The DP winding technique has been frequently used for a large magnet because long HTS wire is generally difficult to manufacture, and maintenance of magnet is convenient. However, magnetic field generated by the slanted turns and the splice leads to field inhomogeneity in Diameter of Spherical Volume (DSV). The field inhomogeneity degrades performance of NMR spectrometer and thus effect of the slanted turns and the splice should be analyzed. In this paper, field gradient of HTS double-pancake coils considering the slanted turns and the splice was calculated using Biot-Savart law and numerical integration. The calculation results showed that magnetic field produced by the slanted turns and the splice caused significant inhomogeneity of field.

• Journal of the Korean Magnetics Society
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• v.4 no.2
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• pp.150-153
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• 1994

Magnetic field annealing method has been used to obtain proper hysteresis loop shapes which are useful to a device using amorphous ribbon. In this study, two pairs of Helmhotz coils were used to apply longitudinal and transverse magnetic field during annealing. For the measurement of coercive field strength noise which depends on magnetic field annealing, Co-based amorphous alloy ribbon $VITROVAC^{\circledR}$ 6030 was used. For the sample which was annealed under dc transverse and dc longitudinal magnetic field, coercive field strength noise was nearly independent of magnetizing frequency ranging from 1 to 100 kHz, but dc transverse and ac longitudinal magnetic fields annealed samples show that the coercive field strength noise decreased in power of magnetizing frequency. When magnetic domain nucleation occurred, the coercive field strength noise increased remarkably and decreased in power of magnetizing frequency.