• Journal of the Korean Institute of Telematics and Electronics B
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• v.30B no.12
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• pp.12-20
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• 1993

In a conventional adaptive echo canceller, an ADF(Adaptive Digital Filter) with TDL(Tapped-Delay Line) structure modelling the echo path uses the LMS(Least Mean Square) algorithm to compute the coefficients, and NET detector using energy comparison method prevents the ADF to update the coefficients during the periods of the NET signal presence. The convergence speed of the LMS algorithm depends on the eigenvalue spread ratio of the reference signal and NET detector using the energy comparison method yields poor detection performance if the magnitude of the NET signal is small. This paper presents a new adaptive echo canceller which uses the pre-whitening filter to improve the convergence speed of the LMS algorithm. The pre-whitening filter is realized by using a low-order lattice predictor. Also, a new NET signal detection algorithm is presented, where the start point of the NET signal is detected by computing the cross-correlation coefficient between the primary input and the ADF output while the end point is detected by using the energy comparison method. The simulation results show that the convergence speed of the proposed adaptive echo canceller is faster than that of the conventional echo canceller and the cross-correlation coefficient yields more accurate detection of the start point of the NET signal.

• Proceedings of the Acoustical Society of Korea Conference
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• 1992.06a
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• pp.23-28
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• 1992

The purpose of this paper is to develop a new adaptive echo canceller improving convergence speed and near-end-talker detection performance of the conventional echo canceller. In a conventional adaptive echo canceller, an adaptive digital filter with TDL(Tapped-Delay Line) structure modelling the echo path uses the LMS(Least Mean Square) algorithm to cote the coefficients, and NET detector using energy comparison method prevents the adaptive digital filter to update the coefficients during the periods of the NET signal presence. The convergence speed of the LMS algorithm depends on the eigenvalue spread ratio of the reference signal and NET detector using the energy comparison method yields poor detection performance if the magnitude of the NET signal is small. This paper presents a new adaptive echo canceller which uses the pre-whitening filter to improve the convergence speed of the LMS algorithm. The pre-whitening filter is realized by using a low-order lattice predictor. Also, a new NET signal detection algorithm is presented, where the start point of the NET signal is detected by computing the cross-correlation coefficient between the primary input and the ADF(Adaptive Digital Filter) output while the end point is detected by using the energy comparison method. The simulation results show that the convergence speed of the proposed adaptive echo canceller is faster than that of the conventional echo canceller and the cross-correlation coefficient yield more accurate detection of the start point of the NET signal.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.3
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• pp.435-441
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• 2001

In this paper, we proposed adaptive MMSE receiver, which use channel equalizer to eliminate the interference due to multi-path fading and adaptive filter to eliminate the multiple access interference. The unique features of proposed receiver schemes are as following. We use pilot channel to estimate the channel coefficients exactly and guard symbols which are inserted periodically to estimate channel coefficients exactly without interference from user signals. The length of channel equalizer also can be reduced with the help of guard symbols. Especially utilizing adaptive code-matched filter(AMMSE) when the user population is high and SNR is not low we accepts excellent performance improvement.

• Advances in aircraft and spacecraft science
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• v.8 no.1
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• pp.53-67
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• 2021

The increasing interest in the exploration of Mars stimulated the authors to study aerodynamic problems linked to space vehicles. The aim of this paper is to evaluate the aerodynamic effects of a flapped wing in collaborating with parachutes and retro-rockets to reduce velocity and with thrusters to control the spacecraft attitude. 3-D computations on a preliminary configuration of a blunt-cylinder, provided with flapped fins, quantified the beneficial influence of the fins. The present paper is focused on Aerodynamics of a wing section (NACA-0010) provided with a trailing edge flap. The influence of the flap deflection was evaluated by the increments of aerodynamic force and leading edge pitching moment coefficients with respect to the coefficients in clean configuration. The study was carried out by means of two Direct Simulation Monte Carlo (DSMC) codes (DS2V/3V solving 2-D/3-D flow fields, respectively). A DSMC code is indispensable to simulate complex flow fields on a wing generated by Shock Wave-Shock Wave Interaction (SWSWI) due to the flap deflection. The flap angle has to be a compromise between the aerodynamic effectiveness and the increases of aerodynamic load and heat flux on the wing section lower surface.

• 한국노년학
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• v.31 no.4
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• pp.871-884
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• 2011

Standard Long-term care(LTC) Utilization Plan is a kind of care plan, which aims to help beneficiaries and their family choose services to meet their care needs. The objective of this study is to determine the relationships among family caregivers' perceived quality, overall satisfaction and utilization in Standard LTC Utilization Plan. Data were gathered from family caregivers with beneficiaries who have used community service in long-term care insurance system. A national cross-sectional descriptive survey was conducted in December 2008, using proportionate quota sampling. Finally, 351 family caregivers completed questionnaires which included demographic characteristics, perceived quality(9 items), overall satisfaction(1 item) and utilization(2 items). Path analysis was conducted to find a causal relationship. This study shows firstly, the quality of Standard LTC Utilization Plan was categorized into three dimensions, that is, assessment of care needs, recommended care plan, and management of monthly benefits. Secondly, reliability and validity of quality items were satisfied. Finally, in the effect of perceived quality and satisfaction for utilization, assessment of care needs(indirect effect, path coefficients=0.077) and overall satisfaction(total effect, path coefficients=0.324) were statistically significant. The findings of this study would be helpful in developing the strategies, which is needed to improve the role of Standard LTC Utilization Plan.

• Journal of Korea Water Resources Association
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• v.49 no.12
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• pp.1015-1025
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• 2016

In general, manholes installed as urban drainage facilities are a variety forms such as straight path manholes, 90 degree bend manhole, three-way combining manhole, and four-way combining manhole. In particular, the surcharged flow at a four-way manholes installed in the downstream of urban sewer system is the main cause of the urban inundation caused by the energy loss. Therefore, it is necessary to analyze the flow characteristics and estimate the head loss coefficients at surcharged four-way combining manholes. The hydraulic experimental apparatus which can change the manhole shapes (square, circle) and flow ratios were installed to estimate the head loss coefficients. In the experiments, two inflows ($Q_m$, $Q_{lat}$) were varied from 0 to $4.8{\ell}/sec$ and 24 combinations were tested in total. The flow ratios $Q_{lat}/Q_{out}$ were varied from 0 to 1 for a total flow $Q_{out}$ ($Q_{out}=Q_m+2Q_{lat}$) of 2, 3, 4, and $4.8{\ell}/sec$, respectively. The variation of head losses were strongly influenced by the lateral inflow because the head loss coefficient increases as the flow ratios $Q_{lat}/Q_{out}$ increases. It was estimated head loss coefficients of the circular manhole is slightly lower than those of the square manhole. However, there was no significant difference of head loss as discharges change. The range of head loss coefficients at four-way combining manhole according to the change of the lateral inflow ratio was estimated to be 0.4 to 0.8. Also, the relation equations between the head loss coefficients (K) and the lateral inflow ratios ($Q_{lat}/Q_{out}$) were suggested in this paper.

• The Research Journal of the Costume Culture
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• v.22 no.6
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• pp.930-942
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• 2014

The purpose of this study is to apply the expectancy disconfirmation model to consumer post-purchase behavior toward fast fashion brands. This study incorporated repurchase intention as a result of consumer satisfaction. It was hypothesized that consumer satisfaction, which is influenced by expectation, perceived performance, and disconfirmation, influences repurchase intention. It was also hypothesized that expectation influences performance. This study examined the brands and prices of the most recent purchases of fast fashion and also examined whether the purchases were planned or unplanned. The hypothesized path was tested and the relative influences of instrumental and symbolic performance on satisfaction were identified. Data were collected from questionnaires answered by 344 university students who were selected by convenience sampling. The results were as follows: 1) Purchased brands were, in the order of frequency of purchase, Uniqlo, Zara, H&M, and Forever21, followed by domestic brands, 8seconds, Spao, and Mixxo. The frequency of unplanned purchase was more than twice higher than planned purchase. 2) Based on expectation and performance, dissatisfactory group was larger than satisfactory group, which were 35.8% and 24.7% respectively. 3) It was revealed from the expectancy disconfirmation model analysis that expectation and performance had positive influence, but cognitive dissonance had negative influence on satisfaction. Satisfaction had significant influence on repurchase intention. The path analysis showed that all hypothesized path coefficients were significant. The results suggest some effective marketing strategies for marketers in the fast fashion industry.

• The Journal of the Korea Contents Association
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• v.21 no.2
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• pp.594-603
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• 2021

This study explored the moderating effects of task difficulty for flow, learning motivation, and interesting in distant PBL classes of pre-service teachers. For this, the research model was constructed by analyzing previous studies. The research model verification was conducted by 105 students of taking courses in the curriculum. The distant PBL used a real-time video conference system. Cooperative activities were carried out in real time. After the end of the distant PBL activity, the level of learning motivation, interesting, flow, and task difficulty perception were measured. The collected data were analyzed using a test of the structural model invariance across the groups using a structural equation model. This analysis verifies the difference in path coefficients between measurement models. The control effect of task difficulty was verified through the difference in path coefficient. As a result, it was verified that interesting mediates the influence of learning motivation on flow. And the moderating effect of the perceived task difficulty appeared on the path from learning motivation to interesting.

• Journal of Navigation and Port Research
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• v.46 no.3
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• pp.259-268
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• 2022

Unlike the general buyer-supplier relationship, there are cases wherein the bargaining power of suppliers is greater than that of buyers. This relationship can be found especially in the shipbuilding industry. Thus, this paper focused on strategic items presented in Kraljic's study. The purpose of this study was to examine factors influencing buyers' purchase of strategic items in a market wherein the bargaining power of suppliers is superior. Results show that the path coefficient between environment factor and satisfaction factor was the highest. Additionally, the path coefficient between environment factor and reliability factor was the next highest. Also, as a result of analyzing if there is a difference in perception according to the superiority and inferiority of bargaining power perceived by buyers, significant results were found in some path coefficients.

• 한국노년학
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• v.40 no.3
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• pp.531-541
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• 2020

The purpose of this study is to explain about the path effect through the structural equation model between the service experience, depression level, lifestyle and quality of life of middle-aged people for policy suggestions to improve the quality of life of middle-aged people. Using the 13th Korea Welfare Panel Study, SPSS were used for demographic analysis and analysis was carried out using AMOS to establish a structural equation model. The analysis showed that service experience, depression level, and lifestyle all had a direct and significant impact on quality of life, and that path coefficients between each path were all significant. This indicates the need for lifestyle-oriented management services for physical and mental health regardless of income level to improve the quality of life for middle-aged people, and there are implications of this study in providing a policy framework and suggestions that programs should be developed through research.