• Geophysics and Geophysical Exploration
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• v.10 no.4
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• pp.241-251
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• 2007

The observed spectra from Odaesan earthquake were fitted to a point-source spectral model to evaluate the source spectrum and spatial features of the modelling error. The source spectrum was calculated by removing from the observed spectra the path and site dependent responses (Yun, 2007) that were previously revealed through an inversion process applied to a large accumulated spectral dataset. The stress drop parameter of one-corner Brune's ${\omega}^2$ source model fitted to the estimated source spectrum was well predicted by the scaling relation between magnitude and stress drop developed by Yun et al. (2006). In particular, the estimated spectrum was quite comparable to the two-corner source model that was empirically developed for recent moderate earthquakes occurring around the Korean Peninsula, which indicates that Odaesan earthquake is one of typical moderate earthquakes representative of Korean Peninsula. Other features of the observed spectra from Odaesan earthquake were also evaluated based on the commonly treated random error between the observed data and the estimated point-source spectral model. Radiation pattern of the error according to azimuth angle was found to be similar to the theoretical estimate. It was also observed that the spatial distribution of the errors was correlated with the geological map and the $Q_0$ map which are indicatives of seismic boundaries.

• The Journal of the Acoustical Society of Korea
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• v.40 no.1
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• pp.46-54
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• 2021

In this paper, active noise control was performed to reduce radiated noise in the low frequency band of dishwashers. First, through an analysis of the noise environment of the dishwasher, it was confirmed that the pump noise contributed the most to the radiated noise in the low frequency band, From the result of the noise environment analysis, the reference signal was selected to be the vibration signal of the pump body. The reference signal was obtained by using the accelerometer on the pump body, which can prevent acoustic feedback. The error signal sensor was selected as a microphone located at 1 m in front of the dishwasher and 0.5 m in height. And to design the controller, the error signal and the reference signal were measured at the operational rpms of the dishwasher at 2,500 rpm, 2,600 rpm and 2,800 rpm, and the secondary path transfer function was measured. The designed controller was mounted on Digital Signal Processor (DSP) equipment, and the control performance was verified experimentally. As a result of the measurement at the 3 operational rpms, the 7th multiple component of pump operating frequency decreased by 1.93 dB, 4.43 dB, 5.15 dB per rpm, and the 12th multiple component decreased by 6.67 dB, 2.34 dB, 4.28 dB per rpm. And overall Sound Pressure Level (SPL) decreased by 0.84 dB, 2.58 dB, 1.48 dB by rpm.

• Journal of the Korean Association of Geographic Information Studies
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• v.13 no.2
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• pp.29-40
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• 2010

Car simulation by TRANSIMS is able to rapidly analyze the broad area based on CA(Cellular Automata) theory, which is the great advantage compared to other existing programs. As the source code of TRANSIMS is open, it may be modified by incorporating the network and traffic characteristics. This study uses the traffic thematic map built in the Korean National Traffic DB(KTDB) center among input date used for building network data of TRANSIMS. However, because the traffic thematic map is not composed as the type required by TRANSIMS, it was corrected and complemented to build a network, and the traffic volume at arterial roads and the traffic volume at each direction of the intersection was calculated through simulation for the area of Suseong-Gu, Daegu Metro. This was compared to the actual traffic volume. As a result of the simulation, it shows error from 14% to 42% at intersection, and from 3% to 8% at arterial roads. This result is very satisfactory because the entire traffic volume of Daegu Metro was not considered, and the tendency of drivers avoiding path due to construction on certain section, the status of road surface and chronic congestion was not reflected.

• Journal of Korean Society of Transportation
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• v.33 no.3
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• pp.315-321
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• 2015

ATMS calculates section travel time using two-way communication system called DSRC(Dedicated Short Range Communications) which collects data of RSE (Road Side Equipment) and Hi-pass OBU (On-board Unit). Travel time estimation in urban area involves uncertainty due to the interrupted flow. This study not only analyzed real-time data but also considered pattern data. Baek-Je-Ro street in Jeon-Ju city was selected as a test site. Existing algorithm was utilized for data filtering and pattern data building. Analysis results repoted that travel time estimation with 20% of real-time data and 80% of pattern data mixture gave minimum average difference of 37.5 seconds compare to the real travel time at the 5% significant level. Results of this study recommend usage of intermixture between real time data and pattern data to minimize error for travel time estimation in urban area.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.734-739
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• 2016

The globe valve is a linear motion valve that is designed primarily to stop, start, and regulate flow. The disk of a globe valve can be removed totally from the flow path or it can completely close the flow path. In this study, numerical analysis using ANSYS-CFX was initially performed to predict the flow coefficient and build a prototype model of a globe valve. The flow coefficient is the volume of water at $15.6^{\circ}C$ that will flow per minute through a valve with a pressure drop of 1 psi across the valve. In other words, it is an important factor for determining the size of the valve. From the analysis results, the fluid flux of water and flow coefficient of the valve were extracted. From the numerical results, a prototype of ultra-fine precision control valve, which can regulate the fluid flow of range 0 ~ 0.1 gal per min, was developed. The experimental results were compared with the numerical results using the flow coefficient ($C_v$) graph. From the comparative results, the flow coefficient ($C_v$) error percentage between the numerical and experimental results was very low, which is acceptable, proving that the proposed prototype model is convincing. In addition, it is possible to predict the flow coefficient using only numerical analysis.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.1C
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• pp.26-35
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• 2006

In this paper, an automatic mobile robot system for a intelligent path planning using the detection scheme of the spatial coordinates based on stereo camera is proposed. In the proposed system, face area of a moving person is detected from a left image among the stereo image pairs by using the YCbCr color model and its center coordinates are computed by using the centroid method and then using these data, the stereo camera embedded on the mobile robot can be controlled for tracking the moving target in real-time. Moreover, using the disparity map obtained from the left and right images captured by the tracking-controlled stereo camera system and the perspective transformation between a 3-D scene and an image plane, depth information can be detected. Finally, based-on the analysis of these calculated coordinates, a mobile robot system is derived as a intelligent path planning and a estimation. From some experiments on robot driving with 240 frames of the stereo images, it is analyzed that error ratio between the calculated and measured values of the distance between the mobile robot and the objects, and relative distance between the other objects is found to be very low value of $2.19\%$ and $1.52\%$ on average, respectably.

• Journal of Korean Academy of Nursing Administration
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• v.4 no.1
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• pp.193-214
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• 1998

The purpose of the present study was to examine the causal model of nurses' organizational commitment. Based on literature review and Fishbein's behavioral intentions model ((Fishbein. 1967: Fishbein & Ajzen. 1975). the organizational commitment was conceptualized within a motivational framework that mediate between antecedents variables and outcome variables. Antecedent variables were pay, promotional chances. continuing education opportunity. rigidity of the administration. paticipative decision making, latitude, group support, role conflict, work load, need for achievement. experience and pride for professional nursing. Outcome variable was turnover intention. The subjects were 373 nurses who were working at 2 large general hospitals located in Seoul. It represents a response rate of 94%. Data for this study was collected from August 29 to September 22 in 1997 by Questionnaire. Path analysis with LISREL 7.16 prigram was used to test the fit of the proposed conceptual model to data and to examine the causal relationships among variables. The result showed that both the proposed model and the modified model fit the data excellently. It needs to be notified, however. that path analysis can not count measurment errors: measurement error can attenuate estimates of coefficient and explanatory power. Nontheless the model revealed considerable explanatory power for organizational commitment (58%), pride for professional nursing (50%) and turnover intention(40%). In predicting nurses' organizational commitment, the findings of this study clearly demonstrated 'the pride for professional nursing' might be the most important variables of all the antecedent variables. Group support, role conflict, need for achievement were also found to be important determinants for the organizational commitment and turnover intention, The result showed experience might be a predictor for 'pride for professional nursing' and 'turnover intention' but not 'organizational commitment', 'Rigidity of the administration' and latitude were also found to have important roles in predictingr the organizational commitment, while participative decision making might have an impact on turnover intention. On the other hand promotional chance had an influence on all the outcome variables, while pay only on turnover intention. In predicting turnover intention, the result clearly revealed 'the pride for professional nursing' and 'organizational commitment' might be the most powerful predictors among all the variables. Theses results were discussed, including directions for the future research and practical implications drawn from the research were suggested.

• Journal of Korean Academy of Nursing Administration
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• v.4 no.1
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• pp.183-214
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• 1998

The purpose of the present study was to examine the causal model of nurses' organizational commitment. Based on literature review and Fishbein's behavioral intentions model ((Fishbein, 1967;Fishbein & Ajzen. 1975), the organizational commitment was conceptualized within a motivational framework that mediate between antecedents variables and outcome variables. Antecedent variables were pay, promotional chances, continuing education opportunity, rigidity of the administration, paticipative decision making, latitude, group support, role conflict, work load, need for achievement, experience and pride for professional nursing. Outcome variable was turnover intention. The subjects were 373 nurses who were working at 2 large general hospitals located in Seoul. It represents a response rate of 94%. Data for this study was collected from August 29 to September 22 in 1997 by Questionnaire. Path analysis with LISREL 7.16 prigram was used to test the fit of the proposed conceptual model to data and to examine the causal relationships among variables. The result showed that both the proposed model and the modified model fit the data excellently. It needs to be notified, however, that path analysis can not count measurement errors; measurement error can attenuate estimates of coefficient and explanatory power. Nontheless the model revealed considerable explanatory power for organizational commitment (58%). pride for professional nursing (50%) and turnover intention(40%). In predicting nurses' organizational commitment. the findings of this study clearly demonstrated 'the pride for professional nursing' might be the most important variables of all the antecedent variables. Group support. role conflict, need for achievement were also found to be important determinants for the organizational commitment and turnover intention. The result showed experience might be a predictor for 'pride for professional nursing' and 'turnover intention' but not 'organizational commitment'. 'Rigidity of the administration' and latitude were also found to have important roles in predictor for the organizational commitment, while participative decision making might have an impact on turnover intention. On the other hand promotional chance had an influence on all the outcome variables, while pay only on turnover intention. In predicting turnover intention, the result clearly revealed 'the pride for professional nursing' and 'organizational commitment' might be the most powerful predictors among all the variables. Theses results were discussed, including directions for the future research and practical implications drawn from the research were suggested.

• The Journal of the Acoustical Society of Korea
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• v.32 no.2
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• pp.95-103
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• 2013

An underwater acoustic (UWA) communication in shallow water is strongly affected by the water surface and the seabed acoustical properties. Every reflected signal to receiver experiences a time-variant scattering in sea surface roughness and a grazing-angle-dependent reflection loss in bottom. Consequently, the performance of UWA communication systems is degraded, and high-speed digital communication is disrupted. If there is a dominant signal path such as a direct path, the received signal is modeled statistically as Rice fading but if not, it is modeled as Rayleigh fading. However, it has been known to be very difficult to reproduce the statistical estimation by real experimental evaluation in the sea. To give an insight for this scattering and grazing-angle-dependent bottom reflection loss effect in UWA communication, authors conduct experiments to quantify these effects. The image is transmitted using binary frequency shift keying (BFSK) modulation. The quality of the received image is shown to be affected by water surface scattering and grazing-angle-dependent bottom reflection loss. The analysis is based on the transmitter to receiver range and the receiver depth dependent image quality and bit error rate (BER). The results show that the received image quality is highly dependent on the transmitter-receiver range and receiver depth which characterizes the channel coherence bandwidth.

• Journal of the Korean Institute of Intelligent Systems
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• v.21 no.5
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• pp.667-672
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• 2011

This paper presents to study the sensor fusion of positioning sensors using UKF(unscented Kalman filter) for positioning accuracy improvement of AGV(automatic guided vehicle). The major guidance systems for AGV are wired guidance and magnetic guidance system. Because they have high accuracy and fast response time, they are used in most of the FMS(flexible manufacturing system). However, they had weaknesses that are high maintenance cost and difficult of existing path modification. they are being changed to the laser navigation in recent years because of those problems. The laser navigation is global positioning sensor using reflecters on the wall, and it have high accuracy and easy to modify the path. However, its response time is slow and it is influenced easily by disturbance. In this paper, we propose the sensor fusion method of the laser navigation and local sensors using UKF. The proposed method is improvement method of accuracy through error analysis of sensors. For experiments, we used the axle-driven forklift AGV and compared the positioning results of the proposed method with positioning results of the laser navigation. In experimental result, we verified that the proposed method can improve positioning accuracy about 16%.