• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.2
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• pp.120-124
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• 2003

This paper describes a MEMS-based micro-fluxgate magnetic sensing element using Ni$\_$0.8/Fe$\_$0.2/ film formed by electroplating. The micro-fluxgate magnetic sensor composed of a thin film magnetic core and micro-structure solenoids for the pick-up and the excitation coils, is developed by using MEMS technologies in order to take advantage of low-cost, small size and lower power consumption in the fabrication. A copper with 20${\mu}$m width and 3${\mu}$m thickness is electroplated on Cr (300${\AA}$) / Au (1500${\AA}$) films for the pick-up (42turn) and the excitation (24turn) coils. In order to improve the sensitivity of the sensing element, we designed the magnetic core into a rectangular-ring shape to reduce the magnetic flux leakage. An electroplated permalloy film with the thickness of 3${\mu}$m is obtained under 2000 gauss to induce magnetic anisotropy. The magnetic core has the high DC effective permeability of ~1,100 and coercive field of ~0.1 Oe. The fabricated sensing element using rectangular-ring shaped magnetic film has the sensitivity of about 150 V/T at the excitation frequency of 2 MHz and the excitation voltage of 4.4 V$\_$p p/. The power consumption is estimated to be 50mW.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.04a
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• pp.41-42
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• 2006

Carbon nanotubes (CNTs) effects on physical properties of the liquid crystal and twisted nematic (TN) liquid crystal (LC) cells have been investigated. The minute doping of CNTs reduces rotational viscosity of the LC, and thus switching time of the TN cells is improved, especially in grey scale response time. In addition, the dielectric anisotropy and birefringence are not affected by such a small amount of CNT-doping and thus voltage-dependent transmittance remains the same.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.05a
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• pp.181-184
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• 2005

In this paper, we have improved a novel fast response time liquid crystal operating mode using tilt angle in the unique condition by hot-plate equipment. The new control of tilt angle for nematic liquid crystal (NLC) with negative and positive dielectric anisotropy on the rubbed homeotropic polyimide (PI) using baking method by Hot-plate equipment was investigated. LC tilt angle decreased with increasing baking temperature and time. Especially, the low LC tilt angle of positive type NLC (${\Delta}n$>0) on the rubbed homeotropic PI surface by increasing temperature and time was measured. The EO characteristics of the high tilted OCB(HTOCB) mode using control of tilt angle on the homeotropic surface than that of conventional OCB cell can be improved. We suggest that the developed the HTOCB cell using control of tilt angle on the homeotropic surface is a promising technique for the achievement of a fast response time and a high contrast ratio.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.05a
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• pp.109-113
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• 2005

We have studied a field sequential liquid crystal display (FSLCD) with electrically controlled birefringence (ECB). The ECB mode exhibiting fast response time, high transmittance, low operating voltage and adequate viewing angle. The positive liquid crystal (LC) is better than negative LC on dielectric anisotropy, birefringence and rotational viscosity. Because $K_{11}$ value out of the elastic coefficient of LC is also larger than $K_{22}$ value, decay time of VA-ECB is advantage. However, the transmittance & response time reduced with decreasing the cell gap. This drawback can be overcome by using LC with high ${\Delta}n$ but VA-ECB is occured loss of light efficiency because the $\gamma$ value increased by high ${\Delta}n$ of LC. Consequently, the HA-ECB mode is one of strongest candidate for FSLCD application.

• Macromolecular Research
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• v.12 no.6
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• pp.564-572
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• 2004

Modem applications could benefit from multifunctional materials having anisotropic optical, electrical, thermal, or mechanical properties, especially when coupled with locally controlled distribution of the directional response. Such materials are difficult to engineer by conventional methods, but the electric field-aided technology presented herein is able to locally tailor electroactive composites. Applying an electric field to a polymer in its liquid state allows the orientation of chain- or fiber-like inclusions or phases from what was originally an isotropic material. Such composites can be formed from liquid solutions, melts, or mixtures of pre-polymers and cross-linking agents. Upon curing, a 'created composite' results; it consists of these 'pseudofibers' embedded in a matrix. One can also create oriented composites from embedded spheres, flakes, or fiber-like shapes in a liquid plastic. Orientation of the externally applied electric field defines the orientation of the field-aided self-assembled composites. The strength and duration of exposure of the electric field control the degree of anisotropy created. Results of electromechanical testing of these modified materials, which are relevant to sensing and actuation applications, are presented. The materials' micro/nanostructures were analyzed using microscopy and X-ray diffraction techniques.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.193-195
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• 1996

In amorphous transformer core, magnetic field annealing is required for inducing uniaxial magnetic anisotropy to circular direction of the core. Generally annealing temperature is about foot, so insulator using in solenoid bed must have a high temperature stability, mechanical strength and good machinability. In this study, we made the magnetic field annealing apparatus using insulators, conductors, connectors and power supply. And then tested the apparatus in annealing process of 50 kVA amorphous transformers.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.171-173
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• 1994

Magnetic wedge is proposed for improving the motor performance and to reduce the ripple of air gap flux. Carter's coefficient plays very important role when the ampere turns or exciting current is calculated. In this paper, we calculate the Carter's coe. by FEM taking into account the magnetic anisotropy of magnetic wedge in simple manner and analyze the effect of the wedge. And we analyze the slot leakage flux according to the wedge property.

• Proceedings of the KIEE Conference
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• 1999.11a
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• pp.4-6
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• 1999

We have performed spin-spray ferrite plating of $Fe_{3-x}Zn_xO_4$($X=0.47{\sim}0.97$) films in the temperature region T=85[$^{\circ}C$]. A reaction solution and an oxidizing solution were supplied to a reaction chamber by supply pumps. The Zn composition X in the $Fe_{3-x}Zn_xO_4$ Film increases as the content of $ZnCl_2$ increase, from X=0.47 at O.05[g/l] to X=0.97 at 0.15[g/l]. All the films are polycrystalline with no preferential orientation, and the magnetization exhibits no definite anisotropy. Grain size in the films increases as X increases, reaching 0.98[${\mu}m$] at X=0.97.

• Proceedings of the KIEE Conference
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• 1999.11c
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• pp.766-768
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• 1999

인간시각체계의 특성을 이용하여 시각적으로 좋은 화질을 얻으면서도 효율적인 저 전송률의 웨이블릿 영상부호화를 실현하였다. MTF 함수를 이용하여 공간주파수 영역에서의 주파수 변화에 따른 콘트라스트의 민감도의 변화를 보상하였고, 공간 방향성에 대응하는 변수들을 추정하기 위하여 공간이방특성을 갖는 필터를 설계하였다. 이에 의하여 인간시각체계와 유사한 구조인 웨이블릿 변환영역에 적용할 수 있는 가중치를 도출하는 알고리즘을 개발하여 웨이블릿 변환 부호화에 적응하였다.

• Proceedings of the KIEE Conference
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• 2001.11b
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• pp.101-105
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• 2001

Due to their elastic anisotropy, ultrasonic testing of austenitic welds, frequently used in nuclear power plants, is much more difficult than that of isotropic elements. For accurate testing of austenitic welds, ultrasonic wave phenomena therein must be full understood. This study uses an accurate and effective numerical model, the mass-spring lattice model, for such phenomena. By comparing the numerical results with the corresponding analytical results, it is shown that the model is capable of accurately predicting the generation, reflection, refraction, and scattering phenomena of ultrasonic waves in anisotropic austenite welds. Therefore, the mass-spring lattice model will provide a very useful tool for simulating ultrasonic testing of austenitic welds, and thus will contribute to the enhancement of reliability of such ultrasonic testing.