• 한국음향학회지
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• 제30권7호
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• pp.396-401
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• 2011

본 논문에서는 잡음환경에서 효과적인 음성을 검출하기 위한 새로운 음성검출 (VAD, voice activity detection) 알고리즘을 제안한다. 제안된 방법은 개선된 음성/비음성 검출을 위해 기존의 파워 스펙트럼 편차를 적용하는 대신 Teager 에너지 기반의 파워 스펙트럼 편차 (power spectral deviation)를 이용한다. 또한 향상된 VAD 성능을 위하여 각각의 주파수 밴드에 대한 음성부재확률 (speech absence probability)을 제안된 파워 스펙트럼 편차를 도출하는데 스무딩 (smoothing) 파라미터로 적용한다. 제안된 알고리즘은 기존의 방법과 객관적인 실험을 통해 비교 평가한 결과 다양한 배경잡음 환경에서 향상된 성능을 보였다.

• 대한전자공학회논문지SP
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• 제47권5호
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• pp.222-228
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• 2010

본 논문에서는 비정상적인 배경 잡음 환경에서 음성향상을 위한 신호의 스펙트럼 변이 (Spectral Deviation)을 적용한 Soft Decision 기반의 잡음전력 수정 기법을 제안한다. 기존의 Soft Decision 기반의 잡음전력 추정에 있어서 잡음신호의 정상성(Stationarity)을 가정한 스무딩 파라미터를 사용하여 잡음전력을 추정하고 갱신하였지만, 잡음신호의 주파수적인 특성이 상대적으로 빠르게 변하는 비정상적인 환경에서는 강인하지 못한 단점을 가지게 된다. 본 논문에서는 신호의 스펙트럼 변이를 추정하여 정상적인 잡음 환경과 비정상적인 잡음 환경에 따라 적응적으로 잡음전력을 추정하고 갱신하여 잡음신호에 의해 오염된 음성신호를 향상시킨다. 제안된 알고리즘은 다양한 배경 잡음 환경에서 객관적인 음질측정 방법인 ITU-T P.862 perceptual evaluation of speech quality (PESQ)에 의해서 평가되었으며, 기존의 Soft Decision 기반의 음성 향상 기법과 비교하여 보다 향상된 성능을 보여주었다.

• 재활복지공학회논문지
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• 제8권1호
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• pp.41-46
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• 2014

본 논문에서는 잡음 상황에서 강인한 음성 특성을 나타내는 TE (teager energy) 기반의 특징벡터를 이용한 음성 검출 알고리즘을 제안하였다. 입력 신호에 TEO (teager energy operator)를 적용하고, 이를 이용하여 음성 검출 알고리즘에서 우수한 성능을 보여주는 파워 스펙트럼 편차를 구하였다. 또한, 제안된 음성 검출 알고리즘의 성능 향상을 위하여 통계적 모델 기반의 우도비를 TE 기반의 파워 스펙트럼 편차의 가중치 요소로 적용하였다. 제안된 알고리즘의 성능 검증을 위해서 전체 오차율, ROC (receiver operating characteristics), PESQ (perceptual evaluation of speech quality)와 같은 객관적 실험을 수행하였다. 실험결과 5dB SNR 이하의 낮은 SNR을 갖는 비 정상 잡음 환경에서 제안한 음성 검출 알고리즘이 약 2.6%의 전체 오차율 감소와 약 0.053의 PESQ 점수 향상을 나타내었다.

• The Korean Journal of Physiology and Pharmacology
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• 제3권5호
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• pp.491-499
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• 1999

This study was designed to evaluate the efficacy of dynamic parameters, such as correlation dimension $D_2,$ by comparing spectral electroencephalographic (EEG) parameters. These parameters are used to estimate the depth of halothane anesthesia as defined by the presence of body movement in response to a tail clamp. Six rats were used and each of them was exposed to halothane sequentially at the concentrations of 0%, 0.5%, 1.0% and 1.5% for 30 min. A tail clamp was applied every five min and the movements were recorded at each concentration level. The spectral parameters and the dynamic parameters were derived from 20-sec and 10-sec segments, respectively, from the last 5-mins of EEG recording at each concentration level. Correlation coefficients between the parameters and the movements were calculated. Standardized values of three parameters, betaL power, median power frequency (MPF), and $D_2$ were derived by calculation based on the number of animals showing the movement in response to a tail clamp. The betaL power had the largest correlation coefficient to spontaneous movement and to the response to a tail clamp than any other band parameter. MPF had a better correlation with the movement than 90% spectral edge frequency. Among the dynamic parameters, $D_2$ on the parietal cortex had a better correlation with the movement. The level of deviation and variation of standardized $D_2,$ MPF, and betaL were significant (p<0.01). The order of deviation and variation was; betaL power > MPF > $D_2.$ The correlation dimension serves as a better index for the depth of halothane anesthesia defined in forms of a response to external stimulation.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2021년도 추계학술대회
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• pp.262-265
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• 2021

본 연구 목표는 조류 둥지에 의한 전신주 내의 사고를 사전에 방지하기 위해 전신주 중 둥지 설치가 가능한 공간 내에 센싱을 통해 조류가 둥지를 짓어 알을 낳기 전에 제거하기 위한 센서 노드 개발에 있다. 조류 둥지를 인식하기 위해서는 최초 설치하였을 때의 거리 측정 값과 이 후 측정되는 거리 값의 변화에 따라 예측 가능한 솔루션에 있다. 본 논문에서는 콘크리트, 철판, 나무, 비닐봉지를 대상으로 적외선을 설계하고 시험하였다. 전신주 내에 놓일 수 있는 물체를 대상으로 실험하여, 각 각의 분광 반사율에 의해 감지되는 분광을 포토다이오드를 통한 값의 표준 편차 그래프를 통해 물체의 대상을 예측하며, 거리 측정이 가능하게 되었다. 본 실험 결과로서 적외선 센서를 통해 전신주 내의 위험물에 대한 대상 정보(콘크리트, 철판, 나무, 비닐봉지)를 습득하게 되고 전력망 모니터링을 통해 안전한 전력망 구축과 자연과 상생 가능한 환경에 이바지 할 것으로 예측된다.

• Nuclear Engineering and Technology
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• 제53권12호
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• pp.4179-4188
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• 2021

This study identifies efficient earthquake intensity measures (IMs) for seismic performances and fragility evaluations of the reactor containment building (RCB) in the advanced power reactor 1400 (APR1400) nuclear power plant (NPP). The computational model of RCB is constructed using the beam-truss model (BTM) for nonlinear analyses. A total of 90 ground motion records and 20 different IMs are employed for numerical analyses. A series of nonlinear time-history analyses are performed to monitor maximum floor displacements and accelerations of RCB. Then, probabilistic seismic demand models of RCB are developed for each IM. Statistical parameters including coefficient of determination (R²), dispersion (i.e. standard deviation), practicality, and proficiency are calculated to recognize strongly correlated IMs with the seismic performance of the NPP structure. The numerical results show that the optimal IMs are spectral acceleration, spectral velocity, spectral displacement at the fundamental period, acceleration spectrum intensity, effective peak acceleration, peak ground acceleration, A95, and sustained maximum acceleration. Moreover, weakly related IMs to the seismic performance of RCB are peak ground displacement, root-mean-square of displacement, specific energy density, root-mean-square of velocity, peak ground velocity, Housner intensity, velocity spectrum intensity, and sustained maximum velocity. Finally, a set of fragility curves of RCB are developed for optimal IMs.

• The Journal of the Acoustical Society of Korea
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• 제26권3E호
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• pp.87-96
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• 2007

In this paper we propose a new noise reduction algorithm for stationary and nonstationary noisy environments. Our algorithm classifies the speech and noise signal contributions in time-frequency bins, and is not based on a spectral algorithm or a minimum statistics approach. It relies on calculating the ratio of the standard deviation of the noisy power spectrum in time-frequency bins to its normalized time-frequency average. We show that good quality can be achieved for enhancement speech signal by choosing appropriate values for ${\delta}_t\;and\;{\delta}_f$. The proposed method greatly reduces the noise while providing enhanced speech with lower residual noise and somewhat higher mean opinion score (MOS), background intrusiveness (BAK) and signal distortion (SIG) scores than conventional methods.

• 한국안전학회지
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• 제14권3호
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• pp.101-109
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• 1999

This study attempts to analyse the solid mixing in the feeder and the packing effect for pressure fluctuations in the fluidized bed. To study the mixing characteristics of solid in vibrating feeder for the stable operations of fluidized combustion, the system consisted of two groups of particles such that fine particles were located on the top of the coarse particles before vibratory mixing had started. The effects of packing materials on the pressure fluctuations in a fluidized bed were analysed by using a statistical method to interpret the behavior of fluidized bed. The experiments were carried out in a fluidized bed of 6.7cm-ID, and the experimental variables were particle sizes, of 115 to 1,015$\mu\textrm{m}$ in diameter and the multi-sized particles haying Rosin-Rammler and Gaussian distributions. The settled bed heights of particles to diameter ratios (L/D) were ranged from 0.5 to 2.0. And fluidizing of particles was carried out by air. The packing materials used were screen packing, and the properties of the pressure fluctuations in the fluidized bed were measured by a differential pressure transducer. The properties of the pressure fluctuations calculated were the mean, the standard deviation, and the major frequency of the power spectral density functions. From the characteristics of fluidizing, it was found that the standard deviation of pressure fluctuations could be effectively used to explain the fluidized phenomena, and the packing materials affected severely the properties of the pressure fluctuations. As a result, from the interpretation by spectral analysis, the effects of measuring radius of pressure fluctuations on standard deviation were constant in the case of the fluidized bed with and without packing materials. However, the effects of measuring the height of pressure fluctuations on standard deviations were linear increasing for the fluidized bed with packing materials, but were constant for the fluidized bed without packing materials at 4.5cm above the gas distributor. The major frequency of pressure fluctuations was found to be nearly independent of fluidized system. Also, the major frequency of pressure fluctuations decreased with increasing packing size, and it had maximum value at 10% of the packing amount.

• 한국음향학회지
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• 제26권3호
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• pp.123-128
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• 2007

본 논문에서는 수중 천이 신호에 대한 식별 알고리즘을 제안한다. 일반적으로 해양의 배경잡음은 스펙트럼 특성 및 에너지 변화가 적은 정재성을 갖는 반면에 천이 신호는 스펙트럼 및 에너지 변화가 큰 비정재성을 가진다. 따라서 수중 천이 신호 식별을 위하여 선행되어져야 하는 수중 천이 신호 탐지에서는 프레임 단위로 스펙트럼 변이와 에너지 변화를 이용한다. 제안한 수중 천이 신호 식별 알고리즘에서는 특징 벡터를 추출하기 위하여 위그너-빌 분포 함수를 기반으로 고유치 분해를 이용한다. 추출된 특징 벡터를 기반으로 탐지된 수중 천이 신호의 특징 벡터와 식별하고자 하는 데이터베이스에 있는 기준 신호의 특징 벡터와의 상관 값을 프레임 단위로 계산하고, 각 클래스별로 프레임 사상도를 산출하여 최대 값을 갖는 기준 신호로 탐지된 수중 천이 신호를 식별한다.

• Wind and Structures
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• 제31권3호
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• pp.269-285
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• 2020

The statistical characteristics of typhoon wind speed records tend to have a considerable time-varying trend; thus, the stationary wind model may not be appropriate to estimate the wind characteristics of typhoon events. Several nonstationary wind speed models have been proposed by pioneers to characterize wind characteristics more accurately, but comparative studies on the applicability of the different wind models are still lacking. In this study, three landfall typhoons, Ampil, Jongdari, and Rumbia, recorded by ultrasonic anemometers atop the Shanghai World Financial Center (SWFC), are used for the comparative analysis of stationary and nonstationary wind characteristics. The time-varying mean is extracted with the discrete wavelet transform (DWT) method, and the time-varying standard deviation is calculated by the autoregressive moving average generalized autoregressive conditional heteroscedasticity (ARMA-GARCH) model. After extracting the time-varying trend, the longitudinal wind characteristics, e.g., the probability distribution, power spectral density (PSD), turbulence integral scale, turbulence intensity, gust factor, and peak factor, are comparatively analyzed based on the stationary wind speed model, time-varying mean wind speed model and time-varying standard deviation wind speed model. The comparative analysis of the different wind models emphasizes the significance of the nonstationary considerations in typhoon events. The time-varying standard deviation model can better identify the similarities among the different typhoons and appropriately describe the nonstationary wind characteristics of the typhoons.