• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.193-196
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• 2000

An stereophonic acoustic echo canceller cannot exactly estimate the echo path in the receiving room, because of the cross-correlation between stereo signals. In this paper, the new preprocessing filter is proposed to reduce the cross-correlation between the signals without influence on stereophonic sound. Two channel signals are linearly decorrelated by using orthogonality principles and the attenuated absolute values of the decorrelated signals are added to each channel input signals. Assuming that the power of each channel signal is larger than that of the cross-correlation, computational burden is reduced.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.21 no.2
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• pp.137-145
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• 2003

Currently, the availability of 3-D topographical survey by combination of GPS and Echo Sounder has been increased in the various field like as the construction of structure, the dredging and the reclamation in the ocean and river, and observation of topographic change in seabed or riverbed. In this case, the error of depth sounding can divide in form that is happened by combination of GPS and Echo Sounder, and form that is happened in Echo Sounder itself, In this study, in the case happen by Echo Sounder itself, analyzed error by specially about geological features of the seabed and riverbed that is specular surface of sound wave and wished to present solution way. The sounding error about the echo sounder and characteristic of estuary riverbed was found by understanding the relation of average diameter and residual error and we defined correction formula, Y=-0.00474$^{*}$In(X) -0.0045 by the regression analysis. and then we verified applicability of correction formula. As the result, if measure Preliminary investigation or pre-survey the geological features for the survey area at topographical survey of estuary riverbed, we presented the error correction formula that estimate and can correct of error by Echo Sounderer.

• The Journal of the Acoustical Society of Korea
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• v.21 no.1
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• pp.42-46
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• 2002

In this paper, a new pre-processing algorithm is proposed to improve the performance of stereo acoustic echo canceller. The proposed algorithm has the improved performance by the estimation error reduction of filter coefficient using input signal which was reduced reverberation of room in the basis MINT (Mu1tip1e-input/output Inverse Theorem) filtering. For real stereo speech signal and real room impulse response the results of simulation, we showed that the proposed method could improved 3∼5 dB ERLE (Echo Return Loss Enhancement) regardless of NLMS (Normalized Least Mean Square) and Projection adaptive algorithm.

• Journal of the Korean Institute of Intelligent Systems
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• v.24 no.5
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• pp.536-541
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• 2014

Data through meteorological radar includes ground echo, sea-clutter echo, anomalous propagation echo, clear echo and so on. Each echo is a kind of non-precipitation echoes and the characteristic of individual echoes is analyzed in order to identify with non-precipitation. Meteorological radar data is analyzed through pre-processing procedure because the data is given as big data. In this study, echo pattern classifier is designed to distinguish non-precipitation echoes from precipitation echo in meteorological radar data using RBFNNs and echo judgement module. Output performance is compared and analyzed by using both HCM clustering-based RBFNNs and FCM clustering-based RBFNNs.

• Journal of the Korean Institute of Intelligent Systems
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• v.25 no.3
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• pp.242-247
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• 2015

In this study, we propose the design of Radial Basis Function Neural Network(RBFNN) classifier in order to classify between precipitation and non-precipitation echo. The characteristics of meteorological radar data is analyzed for classifying precipitation and non-precipitation echo. Input variables is selected as DZ, SDZ, VGZ, SPN, DZ_FR, VR by performing pre-processing of UF data based on the characteristics analysis and these are composed of training and test data. Finally, QC data being used in Korea Meteorological Administration is applied to compare with the performance results of proposed classifier.

• Journal of IKEEE
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• v.26 no.4
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• pp.524-530
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• 2022

When radar return contains strong jammers along with ground clutter echo, a STAP(space-time adaptive processing) algorithms tend to suppress jammer components more severely than it does the clutter. This hinders moving target detection in that the target echo is apt to be buried by clutter echo. This paper presents a two-step STAP algorithm in which the pre-suppression of jammer by the spatial filtering is applied, prior to applying the STAP algorithm. We propose how to find the coefficients of the spatial filter and show that the spatial filtering barely alter the spectra of the target and the clutter echo, having only to suppress the jammers. Finally, we simulate a STAP scenario with strong jammers and show the proposed algorithm can improve STAP performance.

• The Journal of the Acoustical Society of Korea
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• v.16 no.3
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• pp.57-63
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• 1997

This paper proposes a new stereophonic acoustic echo canceller to preven the performance degradation at the instant of far-end talker's movement or change in transmission room environment in stereophonic teleconferencing system. In stereophonic acoustic echo canceller, the filter coefficients of the adaptive filters for echo cancellation do not have unique solutions and not converge to their optimum values. Therefore, the change of the far-end transmission room environment leads to degradation of ERLE(Echo Return Loss Enhanceement). Moreover, their computational complexity increases as the number of the filter coefficient increases, and their adaptive filters converge very slowly. So the real-time implementation is very difficult. To overcome these problems we propose a pre-processor consisting of an adaptive filter for making pseudo stereophonic signal, and it results in improved performance at the instant of environment change at far-end side and reduction of the total complexity.

• Korean Journal of Digital Imaging in Medicine
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• v.14 no.2
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• pp.57-61
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• 2012

To compare the accuracy of breath-hold magnetic resonance imaging sequences to establish the most effective superparamagnetic iron oxide-enhanced sequence for detection of hepatic metastases. A total of 100 patients(50men and 50women, mean age: 60years) with liver disease(including malignant and benign liver lesions) were investigated at 3.0T machine (GE, General Electric Medical System, Excite HD) with 8Ch body coil. Pulse sequence for MR imaging decided to the FS-T2-FSE-RT(TR/TE/Thick./Freq./Phase=12857ms/100ms/7mm/512/384), MGRE(TR/TE/Thick./Freq./Phase=100ms/9.7ms/7mm/384/288), in-out of phase echo(TR/$TE_1$, $TE_2$/Thick./Freq./Phase=140ms/2.4, 5.8ms/7mm/352/300), Images obtained before the injection of SPIO. Six sequences were optimized for lesion detection: FS-T2-FSE-RT, multigradient recalled echo data image(MGRE), T2-weighted MGRE with an 9.7msec echo time. Images were reviewed independently by five blinded observers. The accuracy of each sequence was measured by using picture archiving communication system analysis. All results were correlated with findings at multidectator computed tomography examination. Differences between the mean results of the six observers were measured by using paired student t-test analysis. Postcontrast T2-weighted MGRE sequences were the most accurate and were significantly superior to postcontrast FS-T2-FSE-RT, T2-weighted MGRE, in-out of phase MR sequences(p < .05). For all lesions that were malignant or smaller than 1 cm, respectively, contrast to noise ratio of pre and postcontrast sequences were -1and -0.3 for T2-weighted FSE, 0.53 and 4.5 in-out of phase, 7, 7.08, 5.08, 3.32, 1.7, 1.16, 0.79, 0.68 for GRE with 2.9, 7.5, 12.1, 16.6, 21.2, 25.8, 30.4, 35.0 TE values. Breath-hold various TE precontrast sequences offer improvement in sensitivity compared with fixed multigradient recalled echo sequences alone.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.10
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• pp.1965-1972
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• 1994

A standard on talker echo for ISDN telophone, mainly consisting of those on sending and receiving loudness ratings and terminal coupling loss(TCL), is necessary. Accordingly, if sending and receiving loudness ratings are pre-determined, we need a standard on TCL providing echo-free telephone communications to telephone users, and the standard can be classified into that weighted TCL($TCL_w$) and that on stability loss. In this paper, in order to make a national standard on TCL, based on users' perceived quality on a talker echo, we conducted user opinion tests on talker echo. From the results of correlation between echo and user opinion on quality and measurement on TCL of telephones, we proposed the standard as follows; we must preserve TCL_w of at least 40dB and stability loss of at least 10dB when overall loudness rating for ISDN telephone, sum of sending and receiving loudness ratings, is normalized to 10dB.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.29 no.2
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• pp.209-217
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• 2011

This study incorporate hydroacoustic sampling for bathymetry and sediment survey in Won Cheon reservoir, Suwon city, Korea. Bathymetric and sedimentation surveys were conducted using a echo sounder system and subbottom profiler in the reservoirs. Data were collected using echo sounder systems and subbottom profiler linked to a GPS, to maximize data accuracy and vessel use, and geo-referenced using a DGPS enabling the acoustic data to be used in a GIS. Echo sounder and subbottom survey data were merged within geographic information system(GIS) software to provide detailed visualization and analyses of current depths, pre-impoundment topography, distribution, thickness, and volume estimates of lacustrine sediment, and water storage capacity. These data and analyses are, necessary for development of long term management plans for these reservoirs and their watersheds.