• 한국지구물리탐사학회:학술대회논문집
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• 2006.06a
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• pp.281-284
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• 2006

The resistive V dipole (RVD) is a V antenna with both arms loaded with the continuous Wu-King resistive profile. The RVD has many advantages for surface and subsurface probing, such as the ability to radiate a short pulse in a desired direction. The radiated pulse is simply related to the input pulse, e.g., derivative. In addition, it mostly eliminates the multiple reflections between the surface of the ground and the antenna because of its low radar cross section. The drawbacks of the RVD include the high input impedance and the difficulty in implementation. This paper presents ways to improve the accuracy and easiness of the implementation and to improve the low-frequency performance while maintaining the characteristics of the V antenna that are good for probing applications. The implemented antenna is used to form a bistatic radar to scan targets underground, and the result is imaged.

• The Journal of Engineering Geology
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• v.3 no.2
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• pp.167-176
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• 1993

The high resolution studies for shallow seismic reflection are carried out using 24-channel seismograph and the high sensitivity geophone(50-500Hz). In order to study the underground structures such as small faults, fractures, cracks and cavities, it is of great importance to enhance high resolution of the seisrnic records for the targets vertically and laterally. In analysis of high resolution seismic reflection, Nyquist frequency($F_N$) should be lager than the highest frequency in the records and the highest wave number should not be exceed the Nyquist wave number($1/2{\Delta}x$). The highest frequency above the Nyquist will be removed using low pass filter or antialias filter. The trace interval Ax should be taken into account so that the highest wave number(f/v) can be less than $1/2{\Delta}x$. The Fraunhofer diffraction of a hyperbola seismic section above the tunnel appeares on the common offset method, and little first arrivals of direct wave on the single-end shooting, delayed strong impulsive reflections are also shown above the tunnel. Ray Method(Cherveney and Psencik, 1983) also represents the same results that the reflected waves from the tunnel are delayed and single impulsive with little first arrivals, while transrnitted waves through the tunnel are delayed with low frequency.

• Geophysics and Geophysical Exploration
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• v.4 no.1
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• pp.8-18
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• 2001

To delineate the inhomogeneities including fractures and to estimate the freshness of rock borehole radar consisting of the reflection and tomography methods, and GPR surveys were conducted at a granite quarry mine. The borehole reflection survey using the direction finding antenna was also conducted to get the spatial orientations of reflectors. 20 MHz was adopted as the central frequency for the borehole radar reflection and tomography surveys and 100 MHz was for GPR. Through the interpretation of borehole reflection data using dipole and direction finding antenna as well as GPR images, which are good agreement with each other, we could determine the orientation of the major fractures in three dimensional way. Parts of travel time curves of tomography data showed the anisotropy, which is uncommon in granite quarry. By comparing the tomography data and TeleViewer images, the anisotropy effect in this area are closely related to fine fissures aligned in the same direction. The area confined by the two fractures, MF2 and MF5, might consist of the most fresh granite in the surveyed area, which was concluded from the borehole radar tomography, and GPR images as well as the distribution of anisotropy.

• Journal of the Korean earth science society
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• v.32 no.1
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• pp.33-45
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• 2011

The characteristics and vertical structure of the rainfall are examined in terms of rain types using TRMM (Tropical Rainfall Measuring Mission) PR (Precipitation Radar) data during the JJA period of 2002-2006 over three different regions; midlatitude region around the Korean Peninsula (EA1), subtropical East Asia (EA2), and tropical East Asia (EA3). The convective rain fraction in the EA1 region is 12.2%, which is smaller by 6% than those in the EA2 and EA3 regions. EA1 shows less frequent convective rain events, which are about 0.5 times as many as those in EA3. EA1 produces the mean convective rain rate of 10.4 mm/h that is about 40% larger than EA2 and EA3 while all regions have similar mean stratiform rain rate. The relationships between storm height and rain rate indicate that the rain rate is proportional to the storm height. Based on the vertical structure of radar reflectivity, EA1 produces deeper and stronger convective clouds with higher rain rate compared to the other regions. In EA3, radar reflectivity increases distinctly toward the land surface at altitude below 5 km, indicating more dominant coalescence-collision processes than the other regions. Furthermore, the bright band of stratiform rain clouds in EA3 is very distinct. In convective rain clouds, the first EOFs of radar reflectivity profiles are similar among the three regions, while the second EOFs are slightly different. The larger variability exists at upper layers for EA1 while it exits at lower levels for EA3.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.37 no.2
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• pp.121-127
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• 2011

Skin darkness is the source of trouble to many women. Skin darkness is the state that while skin redness and brightness are reduced, skin yellowness is increased. Skin translucency which is measured by skin color, especially brightness is an another expression of skin darkness. Skin brightness is usually expressed by L value of $L^{*} \;a^{*}\; b^{*}$ (CIELAB color space system). However, it is hard to find the relationship between L value and perceptive efficacy such as translucency because the L value is just a factor of evaluation of skin darkness. The skin with high translucency has high scattering reflective light value than low value. In this study, we measured the skin translucency of 20 ~ 30 ages men and women face by both our designed previous device which use polarized light to detect surface and scatter reflective light independently and $Lumiscan^{TM}$ which is improved designed to confirm our new device working ability by calculation of relationship between trnaslucency and scattering reflective light value. The result of this study indicate that there is a high correlation (R = 0.732, p < 0.01) between translucency and scattering reflective light value, and suggest that $Lumiscan^{TM}$ is portable and easy measuring device more that previous device.

• Korean Journal of Remote Sensing
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• v.33 no.3
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• pp.313-324
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• 2017

A lava tube is one of the hot issues of lunar science because it is regarded as a good candidate place for setting a lunar base. Recently much effort has been made to find lunar lava tubes. However, preceding works mainly made use of high-resolution lunar surface image data in conjunction with geomorphological consideration to present some lava tube candidates. Yet, those candidates stay no more than indirect indications. We propose a new data analysis technique of High Frequency (HF) radar observation data to find lunar lava tubes of which location depth is smaller than the range resolution of the radar pulse. Such shallow target echoes cannot be resolved from surface echoes, which presents the different location of the lunar surface compared to that of real lunar surface. The proposed technique instead finds the surface range (distance from LRS to the reflector of the most intense signal) anomaly which occurs as a result of the low range resolution of LRS pulse. We applied this technique to the surface range of Kaguya Lunar Radar Sounder (LRS) data. The surface range was deduced to make LRS surface elevation which was compared with the average surface elevation of Kaguya Digital Terrain Model (DTM). An anomalous discrepancy of the surface elevation was found in the Rima Galilaei area, which suggests the existence of a shallow lava tube.

• Korean Journal of Remote Sensing
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• v.35 no.2
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• pp.203-215
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• 2019

As hyperspectral sensors that can be mounted on drones are developed, it is possible to acquire hyperspectral imagery with high spatial and spectral resolution. Although the importance of atmospheric correction has been reduced since imagery of drones were acquired at a low altitude,studies on the conversion process from raw data to spectral reflectance should be done for studies such as estimating the concentration of surface materials using hyperspectral imagery. In this study, a vicarious radiometric calibration and an atmospheric correction algorithm based on atmospheric radiation transfer model were applied to hyperspectral data of drone and the results were compared and analyzed. The vicarious calibration method was applied to an empirical line calibration using the spectral reflectance of a tarp made of uniform material. The atmospheric correction algorithm used ATCOR-4 based Modran-5 that was widely used for the atmospheric correction of aerial hyperspectral imagery. As a result of analyzing the RMSE of the difference between the reference reflectance and the correction, the vicarious calibration using the tarp in a single period of hyperspectral image was the most accurate, but the atmospheric correction was possible according to the application purpose of using hyperspectral imagery. If the correction process of normalized spectral reflectance is carried out through the additional vicarious calibration for imagery from multiple periods in the future, accurate analysis using hyperspectral drone imagery will be possible.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.423.2-423.2
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• 2016

태양전지 모듈은 다층 구조를 형성하고 있으며, 신뢰성과 출력 향상을 위해 다양한 연구가 진행 중에 있다. 이를 위해서 모듈에 사용되는 전면 유리는 AR 코팅과 투과도가 좋은 저철분강화유리를 사용하고, 후면에는 반사도가 높은 Backsheet를 사용하게 된다. 또한 태양전지 모듈의 제작 조건 중 하나는 비슷한 출력을 갖는 태양전지를 사용하는 것이다. 만약 태양전지의 출력 불균일이 발생하게 되면 모듈 전체 출력이 낮아질 뿐만 아니라 출력이 낮은 태양전지가 주변 태양전지보다 높은 온도를 나타낸다. 태양전지 모듈에서 온도 편차가 발생한다는 것은 전지의 출력 불균일이 발생한다고 예상할 수 있는 지표이다. 따라서 태양전지 모듈의 후면에 온도 센서를 부착하여 모니터링하였으며, 태양전지 위치에 따라서 약 $3^{\circ}C$의 온도 차이가 발생하는 것을 확인 할 수 있었다.

• 한국공간정보시스템학회:학술대회논문집
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• 2005.05a
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• pp.427-433
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• 2005

인공적으로 조성한 저수지의 대부분은 유역면적이 넓고 집중강우로 인하여 매년 입자성 물질이 상당량 유입하는 편이며 이들의 장기간 축적으로 인하여 저수지 용량을 줄이고 수질관리에 어려움을 야기 시킨다. 따라서 이들에 대한 정화한 예측이 필요한 실정이지만 지표에서의 침식현상은 토양조건, 피복조건, 그리고 지형조건 등의 복합적 요소에 의하여 지배되기 때문에 정확한 유입량을 산정하기에 많은 어려움이 존재한다. 본 연구에서는 높은 정확도를 갖는 LiDAR(Light Detection and Ranging)기술을 이용하여 DEM, DSM을 제작하고 반사강도 데이터로부터 물질적 특성을 분류하여 연구지역내 범용토양유실공식(USLE; Universal Soil Loss Equation)에 의한 유입퇴적량을 산정하였다. 또한 이들 분포를 기준으로 퇴적물의 유입 가능성이 큰 위치를 파악하였으며 지형특성에 따른 퇴적물의 유입경로를 분석하였다.

• 한국공간정보시스템학회:학술대회논문집
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• 2005.11a
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• pp.35-39
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• 2005

선형혼합분광분석(LSU, Linear Spectral Unmixing) 모델은 위성 영상의 한 화소 값이 공간 내에 포함된 다양한 지표 대상물의 반사에너지가 혼합된 결과로 나타난다는 가정을 통해 화소이하(Sub-Pixel) 단위의 영상 분석을 수행하는 알고리즘의 한 형태이다. 분석의 결과는 한 화소에 존재하는 순수 대상물(Endmember)의 비율로 나타나며, 최소제곱법을 이용하여 결과를 도출하는 것이 일반적인 방법으로 알려져 있다. 하지만, 최소제곱법을 이용한 선형혼합분광분석모델은 기본적인 가정을 만족시키지 못하며, Endmember를 사용자가 임의로 지정해야 하기 때문에 영상 분석에 많은 어려움이 있다. 이런 단점을 극복하기 위해 무감독으로 추출된 Endmember를 이용한 제약선형분광혼합분석(Constrained Linear Spectral Unmixing) 모델을 본 연구를 통해 제안하고자 한다. 결과를 통해, 무감독 제약선형분광혼합분석 모델은 선형분광혼합분석 모델에 비해 각각의 Endmember에 대하여 제약조건을 만족하는 점유비율(Abundance) 정보를 제공하였으나, 비슷한 Endmember를 중복 추출할 수 있는 가능성도 지니고 있음을 확인할 수 있었다.