• Carbon letters
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• v.13 no.1
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• pp.17-22
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• 2012

Currently, graphene is a topic of very active research in fields from science to potential applications. For various radio-frequency (RF) circuit applications including low-noise amplifiers, the unique ambipolar nature of graphene field-effect transistors can be utilized for high-performance frequency multipliers, mixers and high-speed radiometers. Potential integration of graphene on Silicon substrates with complementary metal-oxide-semiconductor compatibility would also benefit future RF systems. The future success of the RF circuit applications depends on vertical and lateral scaling of graphene metal-oxide-semiconductor field-effect transistors to minimize parasitics and improve gate modulation efficiency in the channel. In this paper, we highlight recent progress in graphene materials, devices, and circuits for RF applications. For passive RF applications, we show its transparent electromagnetic shielding in Ku-band and transparent antenna, where its success depends on quality of materials. We also attempt to discuss future applications and challenges of graphene.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.1564-1569
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• 2010

토양수분은 수문현상 즉, 물의 순환과정을 이해하고 기상변화를 고려하는데 중요한 인자 중 하나이며 이는 최근 이상기후로 인한 가뭄 및 홍수 등의 자연재해가 우리나라 전역에 빈번히 발생되고 있는 가운데 이러한 현상을 보다 정확히 해석하기 위해 토양수분의 중요성이 더욱 부각되고 있다. 현재 이를 관측 및 분석하고 있으나 대부분 관측기간이 짧고 장비가 노후화되어 많은 결측치를 나타내고 있으며 관측치가 있더라도 여러 가지 요인으로 인해 관측에 대한 분석의 신뢰도가 떨어진다. 이로 인하여 본 연구에서는 광역적 범위에서 정확한 토양수분량 측정을 하고 있는 Advanced Microwave Scanning Radiometer E (AMSR-E) 위성관측 데이터를 기존의 토양수분 자료와 비교/검증하여 이의 활용방안을 모색하고자 한다.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.7
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• pp.314-318
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• 2003

This paper describes the construction, measurement, and characterization of an instrument for the distribution of luminous flux. This is done by measuring the flux around a light source while a detector and a source is rotating, and integrating it over an entire imaginary surface surrounding the source. We make a gonio radiometer to realize the scales of total luminous flux and geometrically integrate to get total spectral flux from standards of irradiance and illuminance. The uncertainties of a total flux in the gonioradiometry are 1.3%, and 0.4% below the standard lamps of NIST and NIM for each other.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.367-372
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• 2002

Asian dust aerosol layer of 4-6 km altitude accompanied by low clouds was observed by LIDAR and sky-radiometer in Tokyo urban area on April 10, 2001. To synthesize the top of atmosphere (TOA) reflectance, radiative transfer simulation conducted assuming aerosol/cloud vertical structure and aerosol size distribution that were modeled after the ground observations. The refractive index of Asian dust is derived from a laboratory measurement of sampled Chinese soil particles. The synthesized TOA reflectance is compared to the SeaWiFS-derived one sampled at the low cloud pixels whose airmass is the same as the one passed at the observation site. While the two TOA reflectances compare generally well with few percent difference in reflectance, possible sources of the discrepancy are discussed.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.1230-1232
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• 2003

This study aims to extract maximum geological information using the ASTER (Advanced Spaceborne Thermal Emission and Reflection radiometer) images of a part of south India. The area chosen for this study is characterized by rock types such as Migmatite, Magnetite Quartzite, Charnockite, Granite, dykes, Granitoid gneiss and Ultramafic rocks, and minerals such as Bauxite, Magnesite, Iron ores, Calcite etc. Advantage was taken of the characteristic reflectance and absorption phenomenon in the VNIR, SWIR and TIR bands for these rocks and minerals, and they were mapped in detail. Image processing methods such as contrast stretching, PC analysis, band ratios and fusion were used in this study. The results of the processing matched with the field details and showed additional details, thus demonstrating the usefulness of ASTER (especially the SWIR bands) data for better geological mapping.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.1359-1361
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• 2003

A set of microwave remote sensing data collected with the newly developed UMass Imaging Wind and Rain Airborne Profiler (IWRAP) during the 2002 Atlantic Hurricane Season was analyzed to further our understanding of the effect of precipitation on scatterometer wind vector retrieval. Coincident surface wind speed and precipitation measurements were provided by the UMass Simultaneous Frequency Microwave Radiometer (SFMR). The differences between the wind estimations from IWRAP and SFMR under precipitation conditions of 0-100mm/hr and wind speed of 0-60m/s was calculated, from which the effect of precipitation on the wind vector retrieval using scatterometry is analyzed qualitatively.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.1445-1456
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• 2003

The ASTER TIR (thermal infrared radiometer) sensor has 5 spectral bands over 8 to 12 ${\mu}$m region. Rock type classification using the ASTER TIR nighttime data was performed in the Erta Ale range of the Ethiopian Rift Valley. Erta Ale range is the most important axial volcanic chain of the Afar region. The petrographic diversity of lava erupted in this area is very important, ranging from magnesian transitional basalt to rhyolites. We tried to classify the rock types based on the spectral behavior of each volcanic rock types in thermal infrared range and estimated SiO$_{2}$ content with emission data by the ASTER TIR.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.528-530
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• 2003

We present here, some of the studies carried for estimation of rainfall over land and oceanic regions in and around South Korea. We use active and passive microwave measurements from TRMM ? TMI and Precipitation Radar (PR) respectively during a typhoon even named ? RUSA that took place during 30 Aug. 2002. We have followed due approach by Yao at. all (2002) and examined the performance of their algorithm using two main predictor variable, named as Scattering Index (SI) and Polarization Corrected Brightness Temperature (PCT) while using TMI data. The rainfall fnus estimated using PST and SI shows some Underestimation as compared to the 2A25 rainfall products from the PR in common area of overlap. A larger database thus would be used in future. To establish a new rain rate algorithm over Korean region based on the present case study.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.535-536
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• 2005

Organic photovoltaic effects were studied in a device structure of ITO/CuPc/Al and ITO/CuPc/$C_{60}$/BCP/Al. A thickness of CuPc layer was varied from 10 nm to 50 nm, we have obtained that the optimum CuPc layer thickness is around 40 nm from the analysis of the current density-voltage characteristics in CuPc single layer photovoltaic cell. From the thickness-dependent photovoltaic effects in CuPc/$C_{60}$ heterojunction devices, higher power conversion efficiency was obtained in ITO/20nm CuPc/40nm $C_{60}$/Al, which has a thickness ratio (CuPc:$C_{60}$) of 1:2 rather than 1:1 or 1:3. Light intensity on the device was measured by calibrated Si-photodiode and radiometer/photometer of International Light Inc(IL14004).

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.63-66
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• 2012

최근 기후변화와 관련하여 수많은 자연재해 현상이 빈번하게 발생하고 있다. 특히 국지적인 폭설과 관련한 자연재해는 재산상의 피해뿐만 아니라 수많은 인명피해를 야기하고 있다. 또한 적설은 단순히 방재 차원을 넘어서 물의 순환과정을 해석하는 데에도 중요한 부분으로 인식되고 있다. 특히 수문학적 측면에서 적설은 인근 하천유량 및 토양수분에 영향을 미치는 주요한 인자로서 이에 관한 세밀한 연구가 진행되고 있다. 따라서 기존의 접근 방식을 넘어서 더욱 능동이고 즉각적인 형태의 적설 관측의 필요성이 대두 되고 있는 시점이다. 지점 관측의 한계성을 보완하기 위해 인공위성에 탑재된 마이크로파 센서를 활용한 적설 관측시스템이 제안되어 이에 대한 검증도 활발히 진행되고 있다. NASA의 Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E)는 마이크로파 센서로서 전 지구적인 물과 에너지 흐름에 관한 다양한 정보를 제공하고 있으며, 이중에는 적설 관측을 위하여 AMSR-E의 SNOW WATER EQUIVALENT PRODUCT (SWE)를 이용한 연구가 이루어지고 있다. 본 연구에서는 한반도내에서의 관측소 실측 자료를 바탕으로 AMSR-E SWE에 대한 검증작업을 실시하였으며, 현재 인공위성을 활용한 적설관측 체계의 오차를 유발하는 요인에 대해 분석했다.