• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.530-533
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• 2002

Blending effects for generating a pretilt angle in nematic liquid crystal (NLC) with negative dielectric anisotropy on the blended polyimide (PI) of homeotropic and homogeneous alignment surface were studied. Also, we investigated the EO performances for the advanced VA-$\pi$ cell using this homeotropic blended PI surface. A many decrease of tilt angle on the polymer surface to blend homeotropic PI and homogeneous PI with side chain type was measured, and the tilt angle decreased as blended ratio and rubbing strength increase. The blended effects for generating a pretilt angle were clearly observed, and the many decrease of tilt angle can be achieved by using the blended PI surface. The electro-optical (EO) characteristics using the advanced VA-$\pi$ cell using the homeotropic blended PI surface than that of conventional VA cell can be improved. We suggest that the developed advanced VA-$\pi$ cell on a homeotropic blended PI surface is a promising technique for the achievement of a fast response time, and a high contrast ratio.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1317-1319
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• 1997

This paper is to study and develope a measurement apparatus for ferroelectricity. The apparatus consists of wave generation part, high voltage amplifier part, measurement part, data acquisition part and the related controll circuits. Single or double excitation wave is digitalized and sent to the external RAM of wave generation part by personal computer. These datas saved in the RAM are converted to analog excitation wave through D/A converter. The frequency of excitation wave is depend on the read-out speed of the RAM by clock pulse. Such generated wave is applied to high voltage amplifier as a input voltage. The output of high voltage amplifier is applied to ferroelectrics and the response is obtained from the charge amplifier of measurement part. The response is sampled and converted to digital datas through AID converter. These digital datas are automatically saved in the external RAM of acquisition part. The computer takes the digital datas and calculates the electric displacement D, the electric field and the dielectric constant $\varepsilon$. We tested for PZT ceramic sample and could observed the D-E hysteresis lops and ${\varepsilon}_s$-E hysteresis loops with good forms.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.9
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• pp.826-832
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• 2003

Blending effects for generating a pretilt angle in nematic liquid crystal (NLC) with negative dielectric anisotropy on the blended polyimide (PI) of homeotropic and homogeneous alignment surface were studied. Also, we investigated the EO performances for the advanced VA- $\pi$ cell using this homeotropic blended PI surface. A many decrease of tilt angle on the polymer surface to blend homeotropic PI and homogeneous PI with side chain type was measured, and the tilt angle decreased as blended ratio and rubbing strength increase. However, a small decrease of tilt angle on the polymer surface to blend homeotropic PI and homogeneous PI with main chain type was measured. The blended effects for generating a pretilt angle were clearly observed, and the many decrease of tilt angle can be achieved by using the blended PI surface. The electro-optical (EO) characteristics using the advanced VA- $\pi$ cell using the homeotropic blended PI surface than that of conventional VA cell can be improved. We suggest that the developed advanced VA-$\pi$ cell on a homeotropic blended PI 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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• 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.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.6 no.1
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• pp.45-50
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• 1981

Infrasonic transducer made with dielectric materials, such as polytetrafluoroethyleme(PTFE)film. The experimental result obtained that the response is within $\pm$1.5dB from 0.1Hz to 7KHz, and that sensitivities of typical transducer are fixed -60dB. The time constant of the transducer at room temperature is over 60 years, and the activation energy of the value of 1.1eV at 343K acquired. This transducer can have application to high-quality communication system, seismological observation etc.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.1137-1141
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• 2004

In this paper, we have improved a novel ECB mode using bend structure with high 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. We suggest that the development of the novel ECB cell using control of tilt angle on the homeotropic surface is a promising technique for the achievement of fast response time and high contrast ratio.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.149-150
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• 2009

In this paper we study on the semiconductor characteristic by calculating the variation of reflection function in microstrip lines, which has open-ended termination containing an optically induced plasma region. The variation of impedances resulting from the presence of plasma has evaluated with time and frequency domain. The responses have been also evaluated theoretically for changing the phase of the variation in the reflection.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2005.11a
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• pp.421-424
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• 2005

X-ray is currently most effective method in detecting small malignant breast tumors but has the several problems due to suppressing breast, ionizing radiation and not detecting small cancer. In this paper, a new method is proposed by using dielectric characteristics of pathological tissues and time delay of backscattered response. We have developed a detection algorithm and verified it by numerical simulation and measurement for a prototype system. For a prototype system, we have fabricated experimental model(artificial breast with a cancer) and UWB(ultra-wideband) antenna. The results of the measurement simulation show an excellent detection capability of a cancer tissue. It is found that a good UWB antenna is a key element of such detection system. Further study is ongoing to develop a commercial system.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1521-1522
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• 2011

뇌임펄스에 의한 절연유체 내 절연파괴 현상은 스트리머 채널에서의 유체유동과 기체유동이 동시에 발생한다. 스트리머 개시와 동시에 발생하는 기포들은 절연파괴에 직접적인 영향을 미치며 이를 모의해석하기위해서 2상유동이 고려되어야한다. 2상유동이 고려된 뇌임펄스 응답 유한요소해석은 전계에 의한 푸아송 방정식과 전자, 양이온, 음이온에 대한 전하연속방정식으로 구성되며 전계 방출과 열전자 방출효과를 경계조건으로 부여하였다. 기체 전리현상은 타운젠트 이론을 도입하였으며, 유체 전리현상은 제너 이온화 모델을 도입하여 수학적 모델링을 통한 2상유동으로 결합하였다. IEC standard #60897의 표준규격에 따라 침-구형 전극을 설계하였고 2차원 축대칭 간략화모델에 적용하여 실험적 결과와 비교분석함으로써 신뢰할 수 있는 수치해석기법이 제시되었다.

• Transactions on Electrical and Electronic Materials
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• v.14 no.4
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• pp.182-186
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• 2013

We studied the possibility that an air capacitor can be used as a humidity sensor by measuring capacitance change. In order to investigate the possibility, the change of capacitance of an air capacitor due to moisture in air was first considered theoretically, and was then experimentally verified. The capacitance was measured by an LCR impedance meter with a 100-kHz and 1-V ac. The results revealed that the changes in the experimentally measured capacitances were greater than those in the theoretically calculated values. Based on this fact, we knew that an air capacitor could be used as part of a humidity sensing device. We expect the humidity sensor with an air capacitor has characteristics of fast response time, high reliability, and high durability compared with other conventional methods.