• 해양환경안전학회지
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• 제21권5호
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• pp.571-576
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• 2015

본 논문은 X-band 레이더 기반 파고추정 방법의 비교연구에 대한 내용으로, 신호 대 잡음비 및 음영비를 이용하였다. 신호대 잡음비의 경우 기존 파고 추정을 위한 방법으로 널리 사용되고 있으며, 음영비의 경우 새로이 제시되는 방법이다. 본 연구에 사용된 레이더 영상의 경우 울산 주전해안에서 계측된 자료이며, 기상청 등표에서 계측된 해양기상정보와 비교하였다. 자료는 약 34일동안 계측된 자료를 비교하였으며, 동해안 태풍 진출 기간 자료를 확보하여 다양한 파고분포에 대한 결과를 검증하였다. 분석 결과 음영비를 이용한 파고추정의 경우, 부이와의 보정이 필요 없는 장점과 실시간 파고 계측의 가능성을 확인하였으며, 일부 풍속, 타 물체 탐지 등 레이더 영상의 외적 요소에 의한 오차 발생의 요인을 파악하였다.

• 환경영향평가
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• 제9권3호
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• pp.177-183
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• 2000

The Landsat Thematic Mapper (TM) has suggested that spatial and spectral characteristics would be suited to evaluate water quality of lake. But, TM has not been commonly used for the analysis of in-land water quality, such as surface water temperature, chlorophyll-a, suspended sediments, and Secchi depth in domestic research. This paper summarizes the analysis of Landsat 5 - TM image collected on 22 Feb 1996 for evaluation of chlorophyll-a and surface temperature in the Lake Soyang. And, field measurements collected in the Lake Soyang were used to obtain water optical algorithms for calibration of satellite data. It is concluded that we can assess chlorophyll-a with remote sensing reflectance and surface temperature with thermal band in lake Soyang. However, surface temperature calculated with thermal band of Landsat TM are underestimated. Relationship between remote sensing reflectance and chlorophyll-a using the ratio of TM band 1 and band 3 is as follows; Y = 17.206 - 6.4711 * (Rrs(band1) / Rrs(band3)) $R^2$=0.8762 and, using the ratio of TM band 1 and band 2 as follows; Y = 57.77 - 35.771 * (Rrs(band1) / Rrs(band2)) $R^2$=0.8317.

• 대한전기학회논문지:시스템및제어부문D
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• 제55권4호
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• pp.181-188
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• 2006

The purpose of this study is to predict the defibrillation success of a ventricular Fibrillation ECG signal using time-frequency analysis. During CPR, coronary perfusion pressure and electrocardiogram were measured. Parameters extracted from time-frequency domain were served as predictor of resuscitation success. Time frequency distribution(TFD) of ECG signals was estimated from the smoothed pseudo Wigner-Ville distribution(SPWVD). Median frequency, peak frequency, 1/f slope, frequency band ratios$(2{\sim}4Hz,\;4{\sim}6Hz,\;6{\sim}8Hz,\;8{\sim}10Hz,\;10{\sim}12Hz,\;12{\sim}15Hz)$ were extracted from each TFD as function of time. Paired t-test was used to determine the differences in ROSC and non-ROSC groups. In the statistical results, we selected four significant parameters - median frequency, 1/f slope, $2{\sim}4Hz$ band ratio, $8{\sim}10Hz$ band ratio. We made an attempt to predict defibrillation success by combining features extracted from time frequency distribution. Independent t-test was used to determine the differences ROSC and non-ROSC groups. Consequently, we selected four significant parameters-median frequency, 1/f slope, $2{\sim}4Hz$ band ratio, $8{\sim}10Hz$ band ratio. The relationship between coronary perfusion pressure and ECG parameters was analyzed with linear regression analysis. R-square value was 55%. 1/f slope and $8{\sim}10Hz$ band ratio had the significant relationship with coronary perfusion pressure.

• 한국멀티미디어학회논문지
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• 제17권9호
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• pp.1064-1069
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• 2014

In this paper, we propose a novel approach to improve the performance of a voice activity detection(VAD) which is based on the adaptive band-partitioning with the likelihood ratio(LR). The previous method based on the adaptive band-partitioning use the weights that are derived from the variance of the spectral. In our VAD algorithm, the weights are derived from LR, and then the weights are incorporated with the entropy. The proposed algorithm discriminates the voice activity by comparing the weighted entropy with the adaptive threshold. Experimental results show that the proposed algorithm yields better results compared to the conventional VAD algorithms. Especially, the proposed algorithm shows superior improvement in non-stationary noise environments.

• JSTS:Journal of Semiconductor Technology and Science
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• 제13권6호
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• pp.546-550
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• 2013

We propose a novel negative differential resistance (NDR) device with ultra-high peak-to-valley current ratio (PVCR) by combining pn junction diode with depletion mode nanowire (NW) transistor, which suppress the valley current with transistor off-leakage level. Band-to-band tunneling (BTBT) Esaki diode with degenerately doped pn junction can provide multiple switching behavior having multi-peak and valley currents. These multiple NDR characteristics can be controlled by doping concentration of tunnel diode and threshold voltage of NW transistor. By designing our NDR device, PVCR can be over $10^4$ at low operation voltage of 0.5 V in a single peak and valley current.

• 대한원격탐사학회지
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• 제39권5_1호
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• pp.669-681
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• 2023

과일 나무의 생육을 평가하는 중요한 지표인 엽록소 함량을 추정하는데 비교적 많은 노동력의 투입이 요구되고 오랜 시간이 소요되는 기존의 파괴 조사 대신 비파괴적 조사 방식인 원격탐사기술을 적용하기 위한 연구가 시도되고 있다. 이 연구에서는 2년(2021, 2022) 간 무인기 기반의 초분광 영상을 이용하여 배나무 잎의 엽록소 함량을 비파괴적으로 추정하는 연구를 수행하였다. 영상 처리로 추출된 배나무 캐노피(canopy)의 단일 band 반사율은 시간 변화에 따라 불안정한 복사 효과를 최소화하기 위해 밴드비화(band rationing) 되었다. 밴드비(band ratios)를 입력 변수로 머신러닝 알고리즘인 elastic-net, k-nearest neighbors (KNN)과 support vector machine을 사용하여 추정(calibration, validation) 모델들을 개발하였다. Full band ratios 기반 추정 모델들의 성능과 비교하여 계산 비용 절감과 재현성 향상에 유리한 key band ratios를 선정하였다. 결과적으로 모든 머신러닝 모델에서 full band ratios를 이용한 calibration에 coefficient of determination (R²)≥0.67, root mean squared error (RMSE)≤1.22 ㎍/cm², relative error (RE)≤17.9%)와 validation에 R²≥0.56, RMSE≤1.41 ㎍/cm², RE≤20.7% 성능을 비교하였을 때, key band ratios 네 개가 선정되었다. 머신러닝 모델들 사이에 validation 성능에는 비교적 큰 차이가 없어 calibration 성능이 가장 높았던 KNN 모델을 기준으로 삼았으며, 그 key band ratios는 710/714, 718/722, 754/758, 758/762 nm가 선정되었다. Calibration에서 R²=0.80, RMSE=0.94 ㎍/cm², RE=13.9%와 validation에서 R²=0.57, RMSE=1.40 ㎍/cm², RE=20.5%를 나타내었다. Validation의 기준으로 한 성능 결과는 배나무 잎 엽록소 함량을 추정하기에 충분하지 않았지만, 앞으로의 연구에 기준이 될 key band ratios를 선정했다는 것에 의미가 있다. 추후 연구에서는 추정 성능을 향상하기 위해 지속적으로 추가 데이터세트를 확보하여 선정된 key band ratios의 신뢰성 검증과 함께 실제 과원에 재현 가능한 추정 모델로 고도화할 필요가 있다.

• 대한의용생체공학회:의공학회지
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• 제22권2호
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• pp.197-204
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• 2001

• 한국정보통신학회논문지
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• 제16권10호
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• pp.2247-2252
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• 2012

본 논문은 동시진공증발법(co-evaporation method)으로 CIGS 박막(thin film)을 제작을 하였다. 제작과정 중 기판온도(substrate temperature)변화와 Ga/(In+Ga) 조성비(composition ratio) 변화에 따른 저항율(resistivity) 및 흡수스펙트럼(absorbance spectra)을 측정하였다. 기판온도가 상승하면 저항율이 감소하였으며, Ga/(In+Ga) 조성비가 0.30에서 0.72까지 증가됨에 따라 밴드갭(band gap)이 1.26eV, 1.30eV, 1.43eV,1.47eV로 증가됨을 알 수 가 있었다. 동일한 조건에서 조성비를 증가하므로써 두께가 증가되었으며 저항율은 감소하였다. 본 실험을 통하여 CIGS 박막을 제작하면 광흡수률(optical absorbance ratio) 및 광전류(optical current)가 증가 될 것으로 예측할 수가 있다.

• 전기학회논문지
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• 제58권12호
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• pp.2462-2467
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• 2009

This paper proposes a dual band branch line coupler (BLC) using a composite right/left handed (CRLH) transmission line. The existing dual band BLCs with open stubs require hundreds of line impedance for the open stub as the frequency bands approach to each other, so it has been almost impossible to realize them. However in the proposed BLC, a CRLH transmission line replaces the open stub with an extremely high line impedance so that the BLC circuit may be realized even two frequencies are close to each other. As an example, a dual band BLC operating at 1800MHz and 2300MHz (the frequency ratio is 1:1.28) is designed and measured. Open stubs with $560\Omega$ line impedance are replaced by CRLH transmission lines for realizing the dual band BLC. The measured performances prove that the dual band operation is well acceptable and the proposed design method is successful even the ratio between two frequencies is not around two nor more.

• Journal of Photoscience
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• 제7권4호
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• pp.139-142
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• 2000

To examine applicability of some optical indices from reflectance to estimate photosynthetic light use efficiency, photosynthesis, and narrow band spectral reflectance were simultaneously measured at various intensities of light with mongolian oak leaves. Narrow band of the broad-band NDVI was better than photochemical reflectance index and simple ratio to estimate photosynthetic light use efficiency in this study. Changes in spectral reflectance were detected at several wavelengths (540nm, 690nm, 740nm, and 800nm) associated with physiological status of plant leaves that could be components for new optical indices.