• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2008년도 International Symposium on Remote Sensing
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• pp.151-154
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• 2008

Information on the area and spatial distribution of crop fields is needed for biomass production, arrangement of water resources, trace gas emission estimates, and food security. The present study aims to monitor crops status during the growing season by estimating its aboveground biomass and leaf area index (LAI) from field reflectance taken with a hand-held radiometer. Field reflectance values were collected over specific spectral bandwidths using a handheld radiometer(LI-1800). A methodology is described to use spectral reflectance as indicators of the vegetative status in crop cultures. Two vegetation indices were derived from these spectral measurements. In this paper, first we analyze each spectral reflectance characteristics of vegetation in the order of growth stage. Vegetation indices (NDVI, GNDVI) were calculated from crop reflectance. And assess the nature of relationships between LAI and VI, as measured by the in situ NDVI and GNDVI. Among the two VI, NDVI showed predictive ability across a wider range of LAI than did GNDVI. Specific objectives were to determine the relative accuracy of these two vegetation indices for predicting LAI. The results of this study indicated that the NDVI and GNDVI could potentially be applied to monitor crop agriculture on a timely and frequent basis.

• 대한원격탐사학회지
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• 제17권2호
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• pp.131-139
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• 2001

Extraction of waterline in tidal flat has been one of the main concerns in the remote sensing of coastal region. This study aimed to define the spectral characteristics of turbid water near the shoreline and to find the appropriate spectrum to delineate the waterline at the inter-tidal flat in the western coast of Korean Peninsula. Spectral reflectance curves were obtained by the field measurements under the diverse condition of water depth and turbidity at the study area in Kyong-gi Bay. Spectroscopy measurements showed that reflectances of the exposed mudflat, shallow turbid water, and normal coastal water were significantly different by wavelength. Shallow water near the waterline showed diverse conditions of turbidity. Spectral reflectance tends to increase as turbidity increases, particularly at the visible and near infrared spectrum. At the middle infrared wavelength, tidal water showed very little reflectance regardless of the turbidity and water depth and was easily disting from the exposed tidal flat. The exact waterline between exposed tidal flat and seawater should be extracted from the image data obtained at the middle infrared wavelength.

• Journal of Biosystems Engineering
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• 제23권6호
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• pp.591-598
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• 1998

Light intensity and spectral characteristics of different types of fluorescent lamps were tested to investigate their possibility as the artificial lighting sources for the close illumination applied in the transplant production factory. Photosynthetic photon flux densitiy(PPF), illuminance and irradiance for all lamps decreased logarithmically with an increase of the vertical distance from the lighting source. The fluorescent lamp specially designed plant growth (PG lamp) showed a maximum spectral irradiance at the wavelength of 660nm. However, it showed lower irradiance than that of a standard fluorescent lamp at the range of wavelength between 500 and 600nm. On the other hand, PG lamp showed higher PPF and lower illuminance than those of the standard fluorescent lamp. The maximum peak of spectral characteristics for both of the single and twin three-bind fluorescent lamps was shorn at the wavelength of 545m and the next peaks were shown at the wavelength of 610nm and 435nm, respectively. Since the red fluorescent lamp has a narrower peak at the wavelength of 660nm, it may be useful for the supplementary red lighting. For three of standard, single three-band and twin three-band fluorescent lamps, the values of conversion factor for converting illuminance to PPF fell within the narrow range from 76 to 791x/$\mu$molㆍm$^{-2}$ ㆍs$^{-l}$ . However, for PG lamp, it was 29.71x/$\mu$molㆍm$^{-2}$ ㆍs$^{-1}$. Also, the values of conversion factor for converting PPF to irradiance of fluorescent lamp used in this study ranged between 4.85 and 5.34$\mu$molㆍm$^{-2}$ ㆍs$^{-1}$/Wㆍm$^{-2}$ .

• 한국전자파학회논문지
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• 제23권4호
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• pp.515-523
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• 2012

본 논문에서는 구형 유전체 위에 있는 구형 패치의 전파 특성으로서 공진 특성과 방사 특성을 분석하였다. 공진 주파수와 Q를 계산하여 특정 모드의 공진 특성을 해석하였으며, 원거리에서의 전기장을 계산하여 방사 특성을 해석하였다. 구형 유전체의 해석을 위해 스펙트럴 영역 해석법(spectral domain analysis method)를 적용하였으며, Vector Legendre transform pair와 Galerkin's method를 이용하여 스펙트럴 영역으로 변환한 후 대수식으로 정리하여 효율적인 계산을 할 수 있었으며, 이를 통해 구형 패치의 반지름이나 곡률, 유전체의 특성이 구형 패치의 특성에 미치는 영향을 해석하였다.

• 한국감성과학회:학술대회논문집
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• 한국감성과학회 2002년도 춘계학술대회 논문집
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• pp.44-50
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• 2002

The fast Fourier transform (FFT) is a good method to estimate spectral density, but the frequency resolution is limited to the sampling window, and thus the precise characteristics of the spectral density for short signals are not clear. To solve the limitation, a multiple band-pass filter was introduced to estimate the precise time course of the spectral density for flash visual evoked potentials (VEPs). Signals were recorded during -200 and 600 ms using balanced noncephalic electrodes, and sampled at 1 K Hz in 12 bits. With 1 Hz and 10 ms resolutions, spectral density was estimated between 10 and 100 Hz. Background powers at the alpha-and beta-bands were high over the posterior scalp, and powers around 200ms were evoked at the same bands over the same region, corresponding to P110 and N165 of VEPs. normalized's spectral density showed evoked powers around 200 ms and suppressed powers following the evoked powers over the posterior scalp. The evoked powers above the 20Hz band were not statistically significant. However, the gamma band was significantly evoked intra-individually; details in the gamma bands were varied among the subjects. Details of spectral density were complicated even for a simple task such as watching flashes; both synchronization and desynchronization occurred with different distributions and different time courses.

• 한국지리정보학회지
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• 제12권4호
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• pp.125-135
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• 2009

FIHS(Fast Intensity Hue Saturation) 융합은 빠른 계산 능력 때문에 널리 이용되고 있으나 IHS(Intensity Hue Saturation) 융합과 마찬가지로 분광정보 왜곡 현상이 나타난다. 본 논문에서는 각 분광 대역의 비율을 이용하여 분광정보 왜곡을 줄일 수 있는 융합법(FIHS-BR)과 공간정보 및 분광 대역의 비율을 활용한 적응 FIHS 융합법(FIHS-SABR)을 제안하였다. 제안한 FIHS-BR 융합은 각 분광 대역의 비율을 이용하여 구한 분광 대역별로 서로 다른 공간 해상도 개선 값을 더하여 분광정보 왜곡을 줄일 수 있도록 하였으며, FIHS-SABR 융합은 국부 영상의 공간정보 특성에 따라 적응적으로 결정된 공간 해상도 개선 값을 각 분광 대역의 비율에 따라 분광 대역별로 재조정하여 분광 정보 왜곡을 더 많이 줄일 수 있도록 하였다. 제안한 FIHS-BR 융합과 FIHS-SABR 융합의 성능을 확인하기 위하여 IKONOS 위성 영상에 대하여 컴퓨터 시뮬레이션을 수행하였으며, 실험 결과 제안 방법들이 기존 융합 영상에서 색상 왜곡이 심하게 나타나는 삼림지역 등에서 색상 왜곡 현상이 적게 나타남을 확인할 수 있었으며, 융합 영상의 분광정보 특성 평가 결과도 가장 우수함을 확인할 수 있었다.

• Journal of Biosystems Engineering
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• 제26권1호
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• pp.11-20
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• 2001

Experiments under the stationary and harvesting condition, were performed in order to investigate the vibration characteristics of a head-feeding combine. 6 degrees of freedom components of acceleration at the location of the center of the gravity, and 3 degrees of freedom components of acceleration at the location of the operator seat were measured independently. The vibration characteristics of the combine were estimated with the power spectral density of the time series data of accelerations. From this research, the following results were obtained. 1. Vibration of a head-feeding combine under the stationary condition(engine, thresher and cutter are driven without harvesting) is mainly influenced by the engine. Further, 1/3, 1/2 (sub-harmonic) frequency components of the engine are observed besides engine driving frequency component(45Hz). 2. Vibration of a head-feeding combine under the harvesting condition is influenced by the engine, threshing unit and driving unit. Namely, some kinds of vibration frequency components in harvesting are observed compared with stationary condition. Further, sub-harmonic frequency components of the engine are observed besides engine driving frequency component as same as stationary condition. From these results, it may be concluded that vibration of a head-feeding combine is characteristics of semi-periodic and nonlinear vibration.

• The Journal of the Acoustical Society of Korea
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• 제23권4E호
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• pp.125-133
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• 2004

In this paper, we propose a critical banded wavelet packet-based spectral subtraction for speech enhancement. Critical banded wavelet packet, which reflects the human auditory system, may lead to minimization of intelligibility loss and quality improvement of the enhanced speech in the spectral domain, when combined with an appropriate spectral subtraction gain function. The proposed method shows better performance than the conventional one in comparative assessments. We also show that, for effective evaluation of enhanced speech, it is essential to consider the characteristics of speech quality measures.

• 한국항공우주학회지
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• 제33권10호
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• pp.1-9
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• 2005

단조성 유지 개념을 기반으로, 임의의 격자계에서 적용할 수 있는 새로운 제한자를 개발하였다. 본 논문에서 개발된 제한자는 임의의 계산 격자계에서 정확성과 단조성을 유지할 수 있는 특성을 가졌으며, 이러한 특성으로 인하여 spectral volume 기법으로의 적용이 가능하다. 또한 이 제한자는 smooth extremum에서 물성치의 변화를 허용하여 내삽된 물성치의 정확도를 향상시켜주는 역할을 한다. 일차원, 이차원 수치 해석의 결과를 통하여 본 논문에서 개발된 제한자의 특성을 검증하였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 Ⅳ
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• pp.2343-2346
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• 2003

The spatial resolution of multispectral images can be improved by merging them with higher resolution image data. A fundamental problem frequently occurred in existing fusion processes, is the distortion of spectral information. This paper presents a spatially adaptive image fusion algorithm which produces visually natural images and retains the quality of local spectral information as well. High frequency information of the high resolution image to be inserted to the resampled multispectral images is controlled by adaptive gains to incorporate the difference of local spectral characteristics between the high and the low resolution images into the fusion. Each gain is estimated to minimize the l$_2$-norm of the error between the original and the estimated pixel values defined in a spatially adaptive window of which the weight are proportional to the spectral correlation measurements of the corresponding regions. This method is applied to a set of co-registered Landsat7 ETM＋ panchromatic and multispectral image data.