• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.169-172
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• 2000

본 논문에서는 차량 환경에서 핸즈프리 단말기를 위한 잔향반향제거 방법을 제안한다. 제안된 방법은 기존의 음향반향제거와 잡음제거의 결합구조에 근거하며, 음성신호의 스펙트럼 특성을 배경잡음화함으로써 잔여 반향제거 성능을 향상시킨다. 일반적으로 음향반향제거에서 실제 충격응답보다 적은 차수의 적응필터를 이용할 경우 잔여반향의 전력이 증가하며, 잡음제거기법을 적용하여 잔여반향성분을 줄일 수 있다. 음성신호가 입력되는 음향반향제거기의 잔여반향을 효과적으로 제거하기 위해 음성신호의 AR 스펙트럼에 따른 역필터링을 수행함으로써 잡음제거기에 의한 잔여반향제거 성능을 향상시킬 수 있다. 제안된 기법은 현재 상용화되고 있는 이동통신용 음성부호화기에 포함된 잡음제거기법과 결합하여 사용할 경우 매우 적은 부가 계산량만으로 구현할 수 있다.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1794-1795
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• 2011

본 연구에서는 가속도 센서의 값을 디지털 신호 처리 과정을 통하여 저역통과 필터(low pass filter), 벡터의 크기(vector magnitude), 롤(roll) 그리고 피치(pitch)를 계산하는 알고리즘을 적용하였다. 필터의 경우 IIR(Infinite Impulse Response)을 이용하였으며 차수는 9차로 하였다. 피험자의 연령은 $25{\pm}5$세의 10명을 기준으로 실험하였으며 앞, 뒤, 좌, 우 방향으로 직각 낙하하도록 하였고 센서 모듈은 오른쪽 허리의 정중앙에 착용하도록 하여 피험자간의 오차가 발생하지 않도록 하였다. 환자의 낙상을 검출하기 위해서 벡터의 크기를 사용하였고 롤과 피치를 이용하여 환자의 낙상 방향을 검출하였다. 결과적으로 피험자 10명의 경우 낙상의 검출률은 100% 였으며 낙상 방향에 따른 앞, 뒤, 좌, 우 판별 정확도는 95% 정도이다. 낙상 방향의 판별은 사고 후 환자를 다룰 때의 주의할 신체부위를 참고하며 재활 운동 시 하체의 어느 쪽이 낙상의 주요인인지 분석하는 보조 자료가 될 수 있다.

• Journal of IKEEE
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• v.18 no.4
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• pp.523-531
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• 2014

In this paper, a fast single image blind denoising algorithm is presented, where noise parameters are estimated by local statistics of an observed degraded image without a prior information about the additive noise. The estimated noise parameters are used to define the constraints on the noise detection which is coupled with the 1st-order Markov Random Field. In addition, an adaptive modified weighted Gaussian filter is introduced, where variable window sizes and weighting coefficients defined by the constraints are used to control the degree of the smoothness of the reconstructed image. The experimental results demonstrate the capability of the proposed algorithm. Please put the abstract of paper here.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.570-575
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• 2019

Active muffler is implemented by applying active noise control technique to reduce exhaust noise of automobile muffler. Conventional Filtered_x LMS algorithm has a problem that the degree of control filter becomes very large and convergence deteriorates when acoustic feedback is present. The recursive LMS algorithm can compensate for this problem because it can be easily diverted in the adaptive filter adaptation process. In this paper, the structure of the primary path and the secondary path transfer function is designed as the IIR filter to improve the convergence performance and the computational burden, and the stabilization filter algorithm is applied to secure stability which is a disadvantage of the IIR filter structure. The stabilization filter algorithm plays a role of pulling the pole into the unit circle to prevent the pole of the transfer function corresponding to the acoustic feedback from diverging during the adaptation process. In this way, the computational burden of the active muffler system and the convergence performance can be improved. In order to show the usefulness of the proposed system, we compared the performance of the proposed Filtered_x LMS algorithm with the performance of the proposed system for the exhaust sound of a diesel engine, which is a variable environment. Compared to conventional algorithm, proposed algorithm's computational burden is less than half, and convergence performances are more than 4 times.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.1
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• pp.94-101
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• 2000

In this paper, a multi-channel active noise control(ANC) system using subband hybrid control techniques is proposed. Subband techniques could reduce computational burden and improve the performance of ANC systems by dividing several frequency subband and adjusting adaptive filter coefficients. So it can effectively cancel noises at wanted frequency range and use lower order adaptive filter than the existing algorithms. The adjoint LMS algorithm, which prefilter the error signals instead of the divided reference signals in frequency band, is also used for adaptive filter algorithms to reduce the computational burden of the subband adaptive systems. To improve performance of the ANC system, a weighted hybrid control technique, which has weightily properties of feedforward control systems and feedback control systems, is applied. This algorithm shows higher stability and good noise attenuation property in broad band ANC systems. Computer simulations were performed to show the effectiveness of the proposed algorithm.

• Bulletin of the Society of Naval Architects of Korea
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• v.26 no.2
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• pp.32-40
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• 1989

Dynamic ship positioning(DP) system is used to keep the position and heading of a ship, or a floating platform, above a pre-selected site on the seabed by using thrusters. This paper presents a control system based on filtering technique and optimal control theory. The planar motions of a vessel are assumed to consist of low frequency(LF) component and high frequency(HF) one. The former is mainly due to thrusters, current, wind and second order wave forces, while the latter is mainly due to first order oscillatory component of the wave force. Furthermore position measurement signals include the noise. By means of self-tuning filter and Kalman filter techniques, LF motion estimates and HF ones are seperately achieved from the position measurements of the vessel. The estimated LF motions are used as input to the feedback loops. The total thruster power is minimized using the Linear Quadratic Gaussian control theory. The performance of the vessel with the DP system is investigated by computer simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.6A
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• pp.464-472
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• 2012

In this paper, we propose a new super-resolution algorithm that uses successive frames by applying the block matching motion estimation algorithm. Usually, single frame super-resolution algorithms are based on probability or discrete wavelet transform (DWT) approach to extract high-frequency components of the input image, but only limited information is available for these algorithms. To solve this problem, various multiple-frame based super-resolution algorithms are proposed. The accuracy of registration between frames is a very important factor for the good performance of an algorithm. We therefore propose an algorithm using 6-Tap FIR filter to increase the accuracy of the image registration with sub-pixel unit. Proposed algorithm shows better performance than other conventional interpolation based algorithms such as nearest neighborhood, bi-linear and bi-cubic methods and results in about the same image quality as DWT based super-resolution algorithm.

• The Korean Journal of Applied Statistics
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• v.28 no.5
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• pp.871-883
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• 2015

Vector autoregressive (VAR) models in high dimension suffer from noisy estimates, unstable predictions and hard interpretation. Consequently, the sparse vector autoregressive (sVAR) model, which forces many small coefficients in VAR to exactly zero, has been suggested and proven effective for the modeling of high dimensional time series data. This paper studies coupling measures to select non-zero coefficients in sVAR. The basic idea based on the simulation study reveals that removing the effect of other variables greatly improves the performance of coupling measures. sVAR model coefficients are asymmetric; therefore, asymmetric coupling measures such as Granger causality improve computational costs. We propose two asymmetric coupling measures, filtered-cross-correlation and filtered-Granger-causality, based on the filtered residuals series. Our proposed coupling measures are proven adequate for heavy-tailed and high order sVAR models in the simulation study.

• Journal of the Korean Geotechnical Society
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• v.25 no.12
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• pp.47-55
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• 2009

As a conventional line-fitting method, the Bouwer and Rice method has been popularly adopted to estimate the hydraulic conductivity of an aquifer through a slug test. Because a vertical cutoff wall is usually very compressible and features a small wall thickness, the Bouwer and Rice method should be carefully applied to analyzing slug test results to estimate the hydraulic conductivity of vertical cutoff walls. In addition, a relatively impermeable layer, called a filter cake, formed at the interface between the cutoff wall and the natural soil formation makes it difficult to use the Bouwer and Rice method directly. In order to overcome such limitations, the original Bouwer and Rice method has been modified by incorporating the concept of the flow net method. In this modification, the geometry condition of cutoff walls including the filter cake is effectively considered in evaluating the hydraulic conductivity of a vertical cutoff wall.

• Proceedings of the Acoustical Society of Korea Conference
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• 1993.06a
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• pp.75-79
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• 1993

본 논문에서는 변화가 심한 음원파형을 추정하는 새로운 순차처리 알고리듬을 제안한다. 먼저, 1) 기존의 순차처리 분석법중 대표적인 분석법인 RLS(recursive least square)의 문제점들을 검토하고, 2) 이를 개선하기 위해서 관측행렬(observation matrix)을 최적차수의 SVD(reduced-rank singular value decomposition)로 재구성하고, 3) 이에 견실개념(robustness concept)을 적용해서 최적의 성도변수(vocal tract parameter)를 찾아내고 역필터를 적용해서 음원(voice source)을 효과적으로 구분해낸다. 본 논문에서 제안된 방법으로 음원을 추정할 경우, 변화가 심한 음원파형을 잘 추정할 수 있으며, 음원의 특성을 구분해낸 성도 파라미터도 효과적으로 추정할 수 있다. 본 연구내용은 음성합성에서 자연성 개선 및 개인성 구현을 위해서 필수적이며, 다양한 형태의 음성을 표현하기 위해 사용되어질 수 있다. 또한, 음성코딩, 화자인식, 음성인식에서도 사용되어질 수 있다.