• 한국지구과학회지
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• 제38권7호
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• pp.535-545
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• 2017

한반도 주변 해상사고가 증가함에 따라 원격탐사 자료를 활용한 선박탐지 연구의 중요성이 점점 더 강조되고 있다. 이 연구는 고해상도 광학영상에 의존하는 기존 선박탐지 분야에 수백 개 채널의 분광정보를 포함하는 초분광영상을 활용하여 새로운 선박탐지 알고리즘 제시하였다. 두 차례의 현장관측을 통해 측정한 선박 선체의 반사 스펙트럼과 AVIRIS (Airborne Visible/Infrared Imaging Spectrometer) 초분광센서 영상의 선박 및 해수 반사 스펙트럼 간의 분광정합 기법을 적용하였다. 총 다섯 개의 탐지 알고리즘 spectral distance similarity (SDS), spectral correlation similarity(SCS), spectral similarity value (SSV), spectral angle mapper (SAM), spectral information divergence (SID)를 사용하였다. SDS는 선박 일부가 해수로 탐지되는 오차를 나타내었고, SAM은 선박과 해수 사이에 약 1.8배의 차이를 나타내어 명확한 분류 결과를 보여주었다. 이와 더불어 본 연구에서는 각 기법의 최적 임계값을 제시하여 초분광 영상에 포함되어 있는 선박을 분류하였으며 그 결과 SAM, SID가 다른 탐지 알고리즘에 비해 우수한 선박탐지 능력을 보여주었다.

• 대한공간정보학회지
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• 제21권2호
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• pp.93-98
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• 2013

다중 시기에 수집된 고해상도 위성영상은 효과적인 도심지 분석과 모니터링을 위한 필수적인 자료이다. 그러나 같은 지역에 대해 다른 센서에서 수집된 영상은 물론, 동일 센서 영상이라 하더라도 두 영상간의 기하학적 위치정보가 서로 일치하지 않는 문제가 존재한다. 따라서 다중 영상의 효과적인 활용을 위해서는 영상 정합을 위해 매칭 포인트를 추출하는 일이 필수적이다. 그러나 도심지의 경우 건물, 교량, 나무, 기타 인공 구조물 등의 영향으로 넓은 영역에 그림자가 분포하며 그림자의 방향과 강도는 영상 수집 시기에 따라 달라지기 때문에 정확한 매칭 포인트를 추출하는데 어려움이 있다. 본 연구에서는 대표적인 매칭점 추출 기법인 SIFT(Scale-Invariant Feature Transform) 기법과 자동 그림자 추출 기법을 적용하여 도심지역의 그림자가 영상 정합에 미치는 영향을 분석하였다. 영상 분할을 통해 생성된 세그먼트의 분광 및 공간인자를 이용하여 그림자 객체를 추출하였으며 이 때 건물 버퍼 영역을 그림자의 인접정보로서 활용하였다. SIFT 기법을 통해 추출된 매칭점이 그림자에 위치하는 경우 이를 제거하고 영상 정합을 수행하였다. 최종적으로 고해상도 위성영상의 정합에 대한 그림자의 영향을 분석하기 위해 추출된 매칭점과 정합 결과의 정확도를 정량적, 시각적으로 평가하였다.

• 대한음성학회:학술대회논문집
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• 대한음성학회 2003년도 10월 학술대회지
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• pp.101-104
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• 2003

In this paper, speech quality is improved by removing abrupt noise intervals and then substituting the gaps with estimates of the previous speech waveform. An abrupt noise detection signal has been proposed as a prediction error signal by utilizing LP coefficients of the previous frame. Abrupt noise intervals are estimated by using spectral energy. After removing estimated noise intervals, we applied several waveform substitution techniques such as zero substitution, previous frame repetition, pattern matching, and pitch waveform replication. To prove the validity of our algorithm, the LPC spectral distortion test and the recognition test are executed and, the results show that the speech quality is fairly well improved.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 1999년도 Proceedings of International Symposium on Remote Sensing
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• pp.429-432
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• 1999

Vegetation cover classification is examined based on a time series NOAA/AVHRR data. Time series data analysis methods including Fourier transform, Auto-Regressive (AR) model and temporal signature similarity matching are developed to extract phenological features of vegetation from a time series NDVI data from NOAA/AVHRR and to classify vegetation types. In the Fourier transform method, typical three spectral components expressing the phenological features of vegetation are selected for classification, and also in the AR model method AR coefficients are selected. In the temporal signature similarity matching method a new index evaluating the similarity of temporal pattern of the NDVI is introduced for classification.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.676-681
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• 2000

This study describes a hydraulic fluid property compensator under the various operating conditions. Because hydraulic fluid systems have much more excellent features than other control systems, they are used in many fields. However, the characteristics of hydraulic fluid are changed due to various operating conditions. This phenomenon is called uncertainty. Especially, bulk modulus is considered as the most dominant parameter in this study. Under the wide range of temperature and pressure, bulk modulus is changed. In order to overcome the uncertainty, $H_{\infty}$ technique will be used for this study. Spectral factorization, model-matching problem and controller parametrization are also applied to achieve the desired robust control action. Designed controller using the $H_{\infty}$ technique, is adopted for the hydraulic fluid valve-motor system.

• 한국광학회:학술대회논문집
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• 한국광학회 2003년도 제14회 정기총회 및 03년 동계학술발표회
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• pp.224-225
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• 2003

Since group velocity (GV) mismatch significantly limits the efficiency of nonlinear interactions such as second harmonic generation (SHG), several techniques have been developed to compensate GV mismatch. The simplest way to avoid the GV mismatch problem is to reduce the device length. However, it results in a poor trade-off between the SHG spectral bandwidth and the conversion efficiency. (omitted)

• ETRI Journal
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• 제27권3호
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• pp.312-318
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• 2005

Mid-span spectral inversion (MSSI) has to utilize high optical pump power, for its operation principle is based on a nonlinear optical wavelength conversion. In this paper, a low pump-power operation of MSSI-based chromatic dispersion compensation (CDC) has been achieved successfully, for the first time to our knowledge, by introducing a noise pre-reduction scheme in cascaded wavelength conversions with periodically poled $LiNbO_3$ waveguides at a relatively low operation temperature. As preliminary studies, phase-matching properties and operation-temperature dependence of the wavelength converter (WC) were characterized. The WC pumped at 1549 nm exhibited a wide conversion bandwidth of 59 nm covering the entire C-band and a conversion efficiency of -23.6 dB at 11 dBm pump power. CDC experiments were implemented with 2.5 and 10 Gb/s transmission systems over 100 km single-mode fiber. Although it is well-known that the signal distortion due to chromatic dispersion is not critical at a 2.5 Gb/s transmission, the clear recovery of eye patterns was identified. At 10 Gb/s transmission experiments, eye patterns were retrieved distinctly from seriously distorted ones, and notable improvements in bit-error rates were acquired at a low pump power of 14 dBm.

• 말소리와 음성과학
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• 제5권4호
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• pp.33-41
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• 2013

This study investigated the perceptual and cepstral/spectral characteristics of phonation and their relationships in dysarthria in connected speech. Twenty-two participants were divided into two groups; the eleven dysarthric speakers were paired with matching age and gender healthy control participants. A perceptual evaluation was performed by three speech pathologists using the GRBAS scale to measure the cepstrual/spectral characteristics of phonation between the two groups' connected speech. Correlations showed dysarthric speakers scored significantly worse (with a higher rating) with severities in G (overall dysphonia grade), B (breathiness), and S (strain), while the smoothed prominence of the cepstral peak (CPPs) was significantly lower. The CPPs were significantly correlated with the perceptual ratings, including G, B, and S. The utility of CPPs is supported by its high relationship with perceptually rated dysphonia severity in dysarthric speakers. The receiver operating characteristic (ROC) analysis showed that the threshold of 5.08 dB for the CPPs achieved a good classification for dysarthria, with 63.6% sensitivity and the perfect specificity (100%). Those results indicate the CPPs reliably distinguished between healthy controls and dysarthric speakers. However, the CPP frequency (CPP F0) and low-high spectral ratio (L/H ratio) were not significantly different between the two groups.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2008년도 춘계학술대회 논문집
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• pp.195-200
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• 2008

The accuracy of classifying pixels in HIRIS images is usually degraded by noisy bands since noisy bands may deform the typical shape of spectral reflectance. Proposed in this paper is a statistical method for noisy band removal which mainly makes use of the correlation coefficients between bands. Considering each band as a random variable, the correlation coefficient measures the strength and direction of a linear relationship between two random variables. While the correlation between two signal bands is high, existence of a noisy band will produce a low correlation due to ill-correlativeness and undirectedness. The application of the correlation coefficient as a measure for detecting noisy bands is under a two-pass screening scheme. This method is independent of the prior knowledge of the sensor or the cause resulted in the noise. The classification in this experiment uses the unsupervised k-nearest neighbor algorithm in accordance with the well-accepted Euclidean distance measure and the spectral angle mapper measure. This paper also proposes a hierarchical combination of these measures for spectral matching. Finally, a separability assessment based on the between-class and within-class scatter matrices is followed to evaluate the performance.

• 대한원격탐사학회지
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• 제27권3호
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• pp.359-367
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• 2011

A suitable pan-sharpening method has to be chosen with respect to the used spectral characteristic of the multispectral bands and the intended application. The research on pan-sharpening algorithm in improving the accuracy of image classification has been reported. For a classification, preserving the spectral information is important. Other applications such as road detection depend on a sharp and detailed display of the scene. Various criteria applied to scenes with different characteristics should be used to compare the pan-sharpening methods. The pan-sharpening methods in our research comprise rather common techniques like Brovey, IHS(Intensity Hue Saturation) transform, and PCA(Principal Component Analysis), and more complex approaches, including wavelet transformation. The extraction of matching pairs was performed through SIFT descriptor and Canny edge detector. The experiments showed that pan-sharpening techniques for spatial enhancement were effective for extracting point and linear features. As a result of the validation it clearly emphasized that a suitable pan-sharpening method has to be chosen with respect to the used spectral characteristic of the multispectral bands and the intended application. In future it is necessary to design hybrid pan-sharpening for the updating of features and land-use class of a map.