• Macromolecular Research
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• 제11권6호
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• pp.481-487
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• 2003

Polypyrrole (PPy) was coated sequentially by chemical and electrochemical methods on a woven fabric, giving rise to a fabric having high electrical conductivity. We investigated the effects of the preparation conditions on the various properties of the resulting fabric. The PPy-coated fabric with optimum properties was obtained when it was prepared sequentially by chemical polymerization at the elevated temperature of 100$^{\circ}C$ under a pressure of 0.9 kgf/$\textrm{cm}^2$ and then electrochemical polymerization with a 3.06 mA/$\textrm{cm}^2$ current density at 25 $^{\circ}C$ for 2 hrs with the separator plate. The surface resistivity of the resulting fabric was as low as 5 Ω/$\square$ .The PPy-coated fabric prepared under the optimum conditions showed practically applicable heat generating property. When electrical power was supplied to the fabric using a commercial battery for a mobile phone (3.6 V, LGLl-AHM), the temperature of the fabric increased very quickly from room temperature to ca. 55 $^{\circ}C$ within 2 min and was maintained for ca. 80 min at that temperature. The heat generating property of the fabric was extremely stable, exhibiting similar behavior over 10 repeated cycles. Therefore, we suggest that the PPy-coated fabric in this study may be practically useful for many applications, including flexible, portable surface-heating elements for medical or other applications.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1311_1312
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• 2009

In this article, current state of development of energy storage system using superconductor was summarized. As a result of continuous efforts, high critical current density exceeding $10^4\;A/cm^3$ at 77K and strong levitation capacity have been achieved in Y-Ba-Cu-O superconductor which is fabricated by melting technique. Various applications using the levitation properties of high-Tc superconductor is expected to come true in near future.

• 한국전기전자재료학회논문지
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• 제19권4호
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• pp.344-349
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• 2006

A sublimation epitaxial method, referred to as the Closed Space Technique (CST) was adopted to produce thick SiC epitaxial layers for power device applications. We aimed to systematically investigate the dependence of SiC epilayer quality and growth rate during the sublimation growth using the CST method on various process parameters such as the growth temperature and working pressure. The etched surface of a SiC epitaxial layer grown with low growth rate $(30{\mu}m/h)$ exhibited low etch pit density (EPD) of ${\sim}2000/cm^2$ and a low micropipe density (MPD) of $2/cm^2$. The etched surface of a SiC epitaxial layer grown with high growth rate (above $100{\mu}m/h$) contained a high EPD of ${\sim}3500/cm^2$ and a high MPD of ${\sim}500/cm^2$, which indicates that high growth rate aids the formation of dislocations and micropipes in the epitaxial layer. We also investigated the Schottky barrier diode (SBD) characteristics including a carrier density and depletion layer for Ni/SiC structure and finally proposed a MESFET device fabricated by using selective epilayer process.

• 한국통신학회논문지
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• 제33권6C호
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• pp.520-528
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• 2008

현재 웹 콘텐츠의 다양화로 인해 콘텐츠의 관리를 위한 CMS(Contents Management System)가 다양하게 운영되고 있다. 그러나 각 업체의 CMS는 서로 다양한 형태의 메타데이터로 관리되고 있어, 웹 콘텐츠의 중복이 심각한 실정이다. 또한 일부 CMS에서 부분 지원하는 콘텐츠 보호만으로 풍부한 웹 콘텐츠의 저작권 기술을 보호하기는 매우 어렵다. 따라서 본 논문에서는 메타데이터를 기반으로 상호 이질적인 CMS의 연동을 통한 웹 콘텐츠의 중복을 해결 하였다. 또한 각 CMS를 기반으로 공유된 콘텐츠는 콘텐츠의 보호를 위해 웹 콘텐츠 인증코드를 이용한 DRM(Digital Rights Management) 기술을 기반으로 콘텐츠 사용 제한 및 저작권 보호를 지원함으로 다량의 콘텐츠 사용에 매우 안전함으로 유용하게 사용될 수 있다.

• Nuclear Engineering and Technology
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• 제56권5호
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• pp.1932-1940
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• 2024

The current work deals with investigation of the gamma ray shielding properties for various natural stones from Vietnam to be applied in the radiation shielding applications. The physical and chemical properties affecting the γ-ray shielding performance were examined. The MH-300A density meter was utilized to measure the density (ρ, g/cm³) of stone samples, as well as the chemical composition of Vietnamese natural stones was measured using the X-ray fluorescence analyzer (Olympus X-5000). The study shows that the increase in Fe + Ca concentrations within the stone samples increases their density (from 2.48 to 2.86 g/cm³) accompanied with a reduction in the porosity (Φ, %) (from 8.23 to 0.15%) and water absorption (K, %) (from 3.42 to 0.05%) factors. Additionally, the increase in Fe + Ca concentrations increases the linear attenuation coefficient (μ, cm^-1) of the studied stones, where the Vietnamese marble stone (M 3.1) with the highest Fe + Ca concentration (65.97 wt%) has the highest linear attenuation coefficient which varied between 3.781 and 0.155 cm^-1 with raising the gamma ray energy between 0.040 and 1.332 MeV.

• 한국작물학회지
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• 제38권3호
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• pp.213-218
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• 1993

모시풀의 생장촉진을 위한 생장조절제의 적정 살포시기, 회수 및 농도를 알아보기 위한 시험결과를 요약하면 다음과 같다. 1. 모시풀의 생장점에 Gibberellin을 살포하면 줄기의 신장에 효과가 켰으며 경장 50cm 때의 1회 살포에 비하여 경장 50및 100cm때의 2회, 50, 100 및 150cm 때의 3회로 살포회수가 많을수록 그 신장도가 켰으며 생육초기보다 후기살포가 더욱 효과적이었다. 2. Gibberellin 농도는 50ppm 보다는 100～300ppm액 살포에서 줄기의 신장이 뚜렷하였으며, 이는 절간장의 신장에서 연유되었고, 절수의 증가는 거의 없었다. 3. 어느 농도에서나 1회 살포의 경우는 엽의 생장도 다소 좋아지는 경향이나, 2회, 3회로 살포회수가 많고 농도가 높을수록 오히려 엽의 생장에 저해를 받는듯 하였다. 4. 섬유수량은 Gibberellin 100ppm 3회 살포의 경우 가장 다수였으며 섬유비율에 있어서도 무처리구의 4.6%에 비하여 5.3%로서 가장 높았다. 5. Atonic은 모시풀의 줄기신장 효과가 Gibberellin에 미치지 못하였으며, 생장조절제 처리는 모시풀의 인피섬유의 발달에도 효과가 있는 것으로 생각되었다.

• 한국측량학회지
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• 제29권2호
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• pp.201-208
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• 2011

스마트폰 사용자의 증가와 함께 다양한 응용분야에서 정밀한 3차원 위치정보가 요구되고 있다. 단일 주파수 민간용 코드 자료를 이용한 위치결정 정확도는 10m 내외이지만, 향후 스마트폰 응용프로그램은 서브미터 수준의 위치정확도를 안정적으로 확보할 필요가 있다. 따라서 일반적인 절대측위 대신 가상기준점을 기반으로 하는 상대측위 방식을 적용하였으며, 면보정계수를 이용하여 이중차분 오차를 보정하였다. 가상기준점은 로버 가까운 지점에 설정하고, 주 기준점 관측자료를 바탕으로 기하학적인 거리를 반영하였다. 이중차분으로 제거되지 않은 오차는 일반적으로 기선거리와 비례하므로, 로버 외부의 상시관측소 네트워크를 평면에 접합하여 면보정계수를 추정하였다. 이중차분 오차를 보정한 가상기준점과 로버의 24시간 C/A 코드 자료를 이용한 로버의 위치측정 결과 위도, 경도방향의 평균제곱근(RMS) 오차가 각각 37cm, 28cm 였으며, 높이 방향의 오차는 76cm 수준이었다. 또한 평면좌표의 성분별 오차는 전체의 약 90%에서 ${\pm}0.5m$ 이내의 결과를 보였으며, 특히 네트워크 기반의 오차모델링을 통해 평면좌표의 바이어스가 2-3cm 수준으로 크게 향상되었다. 따라서 가상기준점과 이중차분 오차모델링을 통해 단일 주파수코드 자료로부터 안정적인 서브미터 정확도의 위치결정이 가능하다.

• Journal of the Optical Society of Korea
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• 제16권3호
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• pp.292-298
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• 2012

The epitaxial layer structures for blue InGaN light emitting diodes have been optimized for high brightness applications with the output power levels exceeding 1000 $W/cm^2$ by using a self-consistent finite element method. The light-current-voltage relationship has been directly estimated from the multiband Hamiltonian for wurtzite crystals. To analyze the efficiency droop at high injection levels, the major nonradiative recombination processes and carrier spillover have also been taken into account. The wall-plug efficiency at high injection levels up to several thousand $A/cm^2$ has been successfully evaluated for various epilayer structures facilitating optimization of the epitaxial structures for desired output power levels.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.86.3-86
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• 2001

Hall effect sensor using 7um, 1.7 ohm-cm or 10um, 3.5 ohm-cm Bipolar process was successfully developed. The Hall sensor consists of various patterns, such as regular shapes, rectangles, diamond, hexagon and cross shapes to optimize offset voltage and sensitivity for proper applications. In order to measure offset voltage in chip scale the Agilent company´s 4156C and Nano-Voltage Meter were used and the best structure in offset voltage was finally selected by using ceramic package. The patterns appear to be the quadri-rectangular patterns entirely and three-parallelogram patterns. The measured offset voltages were found to be about 173-365uV. Meanwhile, in ...

• Journal of electromagnetic engineering and science
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• 제16권4호
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• pp.214-218
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• 2016

In this paper, we present an ambient light backscatter communication design that enables Internet of Things (IoT) devices to communicate through the backscattering ambient light emitted from lighting infrastructure or sunlight. The device can selectively modulate ambient light by switching a liquid crystal display (LCD) shutter located on its surface, so that a nearby smart device, which includes a photodiode or a camera, can demodulate this backscattered light information. To verify the practicality of the proposed concept, we design an IoT device equipped with a commercial LCD shutter and a microcontroller. Our device produces ambient light backscattered data at a speed of 100 bps, and these data are successfully decoded by a commercial photodiode module 10 cm away from the IoT device. We believe that our ambient light backscatter communication design is appropriate for implementation in various IoT applications.