• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.20 no.5
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• pp.130-145
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• 2021

As part of the Smart Seoul policy, the importance of using big urban data is being highlighted. Furthermore interest in the impact of transportation-related urban environmental factors such as PM10 and noise on citizen's quality of life is steadily increasing. This study established the integrated DB by matching IoT big data with transportation data, including traffic volume and speed in the microscopic Spatio-temporal scope. This data analyzed the impact of a spatial unit in the road-effect zone on environmental risk level. In addition, spatial units with similar characteristics of road traffic and environmental factors were clustered. The results of this study can provide the basis for systematically establishing environmental risk management of urban spatial units such as PM10 or PM2.5 hot-spot and noise hot-spot.

• Geophysics and Geophysical Exploration
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• v.18 no.2
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• pp.85-90
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• 2015

Orientation corrections for Korean seismic stations were calculated by using ambient noise cross-correlation. This method uses Rayleigh waves extracted from ambient noise cross-correlation instead of teleseismic waveforms from earthquakes, which have been generally used for previous studies. The theoretical background of the method is that the phase of radial-vertical cross-correlation function should be the same as that of $90^{\circ}$ phase-shifted vertical-vertical cross-correlation function. The results calculated from stacked cross-correlograms from Jan. 2007 to Sep. 2008 are comparable to the previous results obtained from teleseismic waveforms. In addition, overall the standard deviations of orientation corrections are less than $5^{\circ}$. The temporal variation in orientation corrections calculated for every 30 days shows no significant change and also standard deviations of them are mostly less than $5^{\circ}$. This means that the orientations of stations used in this study have been kept constant during the period. The sensitivity test for stacking period of the ambient noise cross-correlation method shows that continuous ambient noise record of at least about 30 days is required for estimating reliable orientation corrections.

• The Journal of the Acoustical Society of Korea
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• v.43 no.1
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• pp.95-102
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• 2024

Due to technological advances, the cruising speed of high-speed trains is increasing, and aerodynamic noise generated from the flow outside the train has been an important consideration in the design stage. To accurately predict the flow-induced noise, high-resolution generation of sound sources in the near field and low-dissipation of sound propagation in the far field are required. This should be accompanied by a numerical grid and time resolution that can properly consider both temporal and spatial scales for each component of the real high-speed train. To overcome these challenges, this research simultaneously calculates the external flow and acoustic fields of five high-speed train cars of real-scale and at operational running speeds using a threedimensional unsteady Large Eddy Simulation technique. To verify the numerical analysis, the measurements of the wall pressure fluctuation and numerical results are compared. The Ffowcs Williams and Hawking equation is used to predict the acoustic power radiated from the high-speed train. This research is expected to contribute to noise reduction based on the analysis of the aerodynamic noise generation mechanism of high-speed trains.

• ETRI Journal
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• v.29 no.3
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• pp.300-304
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• 2007

This paper proposes a new data-driven method for high-pass approaches, which suppresses slow-varying noise components. Conventional high-pass approaches are based on the idea of decorrelating the feature vector sequence, and are trying for adaptability to various conditions. The proposed method is based on temporal local decorrelation using the information-maximization theory for each utterance. This is performed on an utterance-by-utterance basis, which provides an adaptive channel normalization filter for each condition. The performance of the proposed method is evaluated by isolated-word recognition experiments with channel distortion. Experimental results show that the proposed method yields outstanding improvement for channel-distorted speech recognition.

• Transactions on Control, Automation and Systems Engineering
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• v.2 no.1
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• pp.40-46
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• 2000

In this paper, a transient identification based on a Hidden Markov Model (HMM) has been suggested and evaluated experimentally for the classification of transients in the dynamic process. The transient can be identified by its unique time dependent patterns related to the principal variables. The HMM, a double stochastic process, can be applied to transient identification which is a spatial and temporal classification problem under a statistical pattern recognition framework. The HMM is created for each transient from a set of training data by the maximum-likelihood estimation method. The transient identification is determined by calculating which model has the highest probability for the given test data. Several experimental tests have been performed with normalization methods, clustering algorithms, and a number of states in HMM. Several experimental tests have been performed including superimposing random noise, adding systematic error, and untrained transients. The proposed real-time transient identification system has many advantages, however, there are still a lot of problems that should be solved to apply to a real dynamic process. Further efforts are being made to improve the system performance and robustness to demonstrate reliability and accuracy to the required level.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.557-560
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• 2001

본 논문에서는 시공간 3차원 잡음 제거기의 ASIC 설계 및 구현결과를 소개한다. 구현된 잡음 제거기는 휘도와 색차신호에 대한 잡음제거 필터들로 구성된다. 휘도에 적용한 필터는 A-MEAN 필터와 A-LMMSE 필터를 결합한 형태의 필터를 시공간적으로 연결한 필터로써, 특히 시간방향으로 IIR 필터 형태를 갖도록 설계하여 평탄한 영상영역에서 보다 강한 잡음 제거 효과를 갖도록 하였다. 한편, 색차신호에 대해서는 5탭 길이를 갖는 1차원 A-MEAN 필터를 적용하였다. C-언어를 이용한 시뮬레이션을 통해 설계된 잡음 제거기의 성능을 평가하였고, VHDL과 C-언어에 의한 시뮬레이션 결과를 비교하여 VHDL-코드의 검증을 수행했다. 구현과정은 시뮬레이션과 논리합성 등 전반부 설계를 Synopsys 툴을 이용하여 수행했고, 레이아웃 등 후반부 설계를 Cadence 툴과 Apollo 툴을 이용하여 수행했다.

• Journal of Biomedical Engineering Research
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• v.16 no.2
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• pp.183-190
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• 1995

The use of ultrasound pulsed Doppler systems has become increasingly popular due to the advantages of easy measurements of blood velocity, volume blood blow, and irregularities of the circulatory system. However, the 2-D Doppler systems have several problems, such as range ambiguity, low signal to noise ratio, and slow frame rate. The mean frequency aliasing problem originating from the pulse repetition frequency is one of major limitations in pulsed Doppler systems. A conventional approach to resolve this problem is tracking the mean frequency close to and beyond the Nyquist frequency along the temporal axis. In this paper, a new concept of tracking the mean frequency along the spatial axis is proposed. The proposed technique is fault tolerant by nature and more suitable for multi gate and 2-D Doppler system than conventional methods.

• Korean Journal of Remote Sensing
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• v.27 no.6
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• pp.693-701
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• 2011

Image registration is an essential process to analyze the time series of satellite images for the purpose of image fusion and change detection. The Mutual Information (MI) is commonly used as similarity measure for image registration because of its robustness to noise. Due to the radiometric differences, it is not easy to apply MI to multi-temporal satellite images using directly the pixel intensity. Image features for MI are more abundantly obtained by employing a Gabor filter which varies adaptively with the filter characteristics such as filter size, frequency and orientation for each pixel. In this paper we employed Bidirectional Gabor Filter Energy (BGFE) defined by Gabor filter features and applied the BGFE to similarity measure calculation as an image feature for MI. The experiment results show that the proposed method is more robust than the conventional MI method combined with intensity or gradient magnitude.

• Journal of the Korea Computer Industry Society
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• v.5 no.9
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• pp.987-992
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• 2004

There is the temporal correlation of the video sequence between the motion vector of current block and the motion vector of previous block. In this paper, we propose the improved diamond search pattern using an motion vector prediction candidate search point by the predicted motion information from the same block of the previous frame. Simulation results show that PSNR(Peak-to-Signal Noise Ratio) values are improves as high as high as 14~24% in terms of average number of search point per motion vector estimation and improved about 0.02~0.37dB on an average except the full search(FS) algorithm.

• Journal of Astronomy and Space Sciences
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• v.24 no.4
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• pp.261-268
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• 2007

We have studied the temporal variation in the North-South asymmetry of the sunspot area during the period from 1874 to 2007. Though the 9-year periodicity is commonly reported, shorter periodicities is still under study. We employ the cepstrum analysis method to analyze the noisy power spectrum of the North-South asymmetry. We demonstrate that the cleaned power spectrum shows reduction of the spurious back-ground noise level. Some of short period peaks in the power spectrum disappear after deconvolution. It should be, however, pointed out that power spectrum might look less noisy because of a filtering process during deconvolution. We conclude by pointing out that a more sophisticate filtering algorithm is required to produce a precise and reliable periodicity estimate.