• Journal of Information Technology Applications and Management
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• v.9 no.4
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• pp.127-149
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• 2002

Online consumers were classified four groups by online buying frequency and shopping mall loyalty in this study; high frequency-high loyalty, high frequency-low loyalty, low frequency-high loyalty, and low frequency-low loyalty groups. Four groups were compared by Internet usage, flow experience, innovativeness, perceived risks of Internet shopping, Internet shopping behaviors, and demographics. Through an online survey of 396 Internet shoppers, there found significant differences of those variables among four groups. The implications for customer relationship management of Internet shopping mall are discussed and further researches are suggested.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.5
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• pp.1047-1049
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• 2009

This paper presents an intelligent electronic device(IED) platform which is based on a new frequency estimation algorithm. The IED platform features not only the accurate estimation of frequency but also the fast network-based transmisstion of fault data and waveforms. The simulation results show that the proposed frequency estimation algorithm improves convergence speed, and has lower frequency estimation error compared with those of conventional algorithms. The network-based IED is designed to ensure transmission latency being less than 1.0% of sampling interval.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.20 no.3
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• pp.16-21
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• 2012

Global navigation satellite systems (GNSS) use dual frequency signals to remove ionosphere delay effect. GNSS receivers have their own biases, called inter-frequency bias (IFB) between dual frequencies due to differential signal delays in receiving each frequency codes. The IFB degrades pseudo-range and ionosphere delay accuracies, and they must be accurately estimated. Simultaneous estimation of ionosphere map and IFB is applied in order to analyze the IFB estimation accuracy and variability. GPS network data in Korea is used to compute each receiver's IFB. Accuracy changes due to ionosphere model changes is analyzed and the effect of external GNSS satellite IFB on the receiver IFB is analyzed.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.10a
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• pp.72-82
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• 1999

The microearthquake and explosion events recorded in the seismic KNUE(Korea National University of Education) network were analyzed. The seismic data were recorded from Dec. 1997 to Dec. 1998. Total of 118 records consisted of 24 earthquake and 4 explosion events were instrumented at 6 stations. Spectral values increases as magnitude increases and the predominant frequency band expands to low frequency. zone as magnitude increases. Three-dimensional spectrograms(time frequency. amplitude) were also synthesized in order to discriminate microearthquakes and artificial underground explosions. The waves from microearthquakes show that frequency content of dominant amplitude appeared above 10 Hz and the discrimination can be performed in almost all the frequency domain of 3-d spectrogram.

• Journal of Biomedical Engineering Research
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• v.28 no.2
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• pp.258-264
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• 2007

Spatiotemporal changes of brain rhythmic activity at a certain frequency have been usually monitored in real time using scalp potential maps of multi-channel electroencephalography(EEG) or magnetic field maps of magnetoencephalography(MEG). In the present study, we investigate if it is possible to implement a real-time brain activity monitoring system which can monitor spatiotemporal changes of cortical rhythmic activity on a subject's cortical surface, neither on a sensor plane nor on a standard brain model, with a high temporal resolution. In the suggested system, a frequency domain inverse operator is preliminarily constructed, considering the individual subject's anatomical information, noise level, and sensor configurations. Spectral current power at each cortical vertex is then calculated for the Fourier transforms of successive sections of continuous data, when a single frequency or particular frequency band is given. An offline study which perfectly simulated the suggested system demonstrates that cortical rhythmic source changes can be monitored at the cortical level with a maximal delay time of about 200 ms, when 18 channel EEG data are analyzed under Pentium4 3.4GHz environment. Two sets of artifact-free, eye closed, resting EEG data acquired from a dementia patient and a normal male subject were used to show the feasibility of the suggested system. Factors influencing the computational delay are investigated and possible applications of the system are discussed as well.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.5
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• pp.2244-2250
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• 2013

The purpose of this study was to examine the frequency of daily toothbrushing among Korean adolescents. The Korea Youth Risk Behavior Web-based Survey data were analysed. subject included 75,238 in 2008, 75,066 in 2009 and 73,238 in 2010, which included a nationally representative sample of middle and high school students. The frequency of daily toothbrushing was analysed according to socioeconomic status (gender, age, residential areas, type of school, parents' education and occupation). All survey data collected was processed using SPSS ver 19.0 for data analyses such as frequency analysis, t-test and Chi-square. The mean frequency of daily toothbrushing for 2008 was 3.92, 2009 was 3.96 and 2010 was 3.99. The appearance of toothbrushing after having lunch at school was indicated to be 34.5% in 2008, 38.0% in 2009 and 40.8% in 2010. This study has shown that need to systematic oral health promotion programmes for adolescent in Korea.

• Structural Engineering and Mechanics
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• v.64 no.3
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• pp.347-352
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• 2017

The poor maintenance practice increases the possibility of system failure. Subsequently, the consequences of failure fall on the aspects of output, safety and healthy, environmental integrity, system quality, and customer satisfaction. Conditionbased maintenance is seen as a potential strategy to improve performance. Whereby, the key success factor of this maintenance strategy is identified as the system inspection. This study aims to investigate the association between system breakdown rate and frequency of inspection. A mixed method approach is implemented by distributing questionnaire and interviewing for data collection. Subsequently, descriptive analysis, correlation analysis and regression are adopted to analyse the collected data from 100 respondents and the results are validated with interview data of 10 interviewees. The research result establishes significant relationship between the system breakdown rate and the frequency of inspection. Additionally, the result of regression analysis confirms that the frequency of inspection is the significant predictor of system breakdown rate. Planning of accurate inspection frequency is crucial to secure the system performance. Hence, the research signifies the importance to carry out regular inspection towards the building systems and components. As a recommendation, the maintenance personnel should assess the risk criticality of the building systems. Then, continuously monitor the condition of critical building systems; regularly inspect the condition of non-critical building systems and randomly inspect all of them.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.12 no.2
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• pp.163-172
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• 1994

As for the baseline measurement using geodetic GPS receiver, this paper puts forth the effective measurement range of a low-priced GPS system receiving Ll frequency only. Compared with the data of baseline eliminated the ionospheric effects with L1/L2 frequencies, the results with Ll frequency approximate to those with dual frequency within the range of 15 km (the baseline discrepancy of the two methods is less than 2 cm). The results with Ll frequency are better within the range of 18 km. Based upon the analysis of data, we find that the convergence limit of integer ambiguity-applicable to double difference fixed solution- is about 18 km and the ionospheric effects have a great influence on the results when the baseline are longer than 20 km. This study also presents a standard which makes it possible to select the favorable data from the results of the GPS relative distance measurements.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.12 no.4
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• pp.203-209
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• 2000

Mokpo coastal zone suffers from increase of tidal amplitude by the reclamation projects of Youngsan River Scadike, Youngam and Keumho Seawalls, resulting inundation oflower lands. Tidal records at Mokpo harbor show jumps just after each construction not only in the mcan high water level but also in extreme one. Thus the design water levels must be newly estimated by a frequency analysis with the data of period after the last construction. But this period is at most 6 years yet, which restrains the normal frequency analysis. In this paper, new approach of converting the past data to the present one by a numerical model is proposed. Converted 32 years and observed 6 years data enables normal frequency analysis.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.55 no.4
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• pp.356-362
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• 2019

We collected AIS information on fishing vessels operating near Jeju Island, and analyzed appearance density of the Chinese fishing vessels and inferred the movements of the fishing grounds. AIS information was received from October 16, 2016 to October 16, 2017 and stored on a hard disk through a program called AisDecoder. Unauthorized fishing vessels within the Exclusive Fisheries Agreement Zone (EFAZ) operated near the EFAZ boundary, and the frequency of appearance of fishing vessels were high in the middle waters of Korea and Japan, 252 and 250 fishing zones. Chinese fishing vessels authorized to enter appeared scattered outside the Prohibiting Fishing Zone of the Large Trawlers (PFZLT), and the closer they were to the PFZLT boundary, the higher the appearance density. And the appearance of Chinese fishing vessels with a speed from 0 to 3 knots was mostly outside the EFAZ, showing high density in the waters close to the boundary between Korea and Japan. On the other hand, within the EFAZ, the frequency of appearance of Chinese fishing vessels was also low and scattered. The appearance of Chinese fishing vessels with a speed from 3 to 5 knots mostly shows some variability within the EFAZ, but the frequency of appearance was high and the density was high. The seasonal appearance of Chinese fishing vessels in the waters south of Jeju Island appeared in the southwest in the autumn and then moved south and southeast of Jeju Island in the winter, and in the spring and summer. They were considered going to other fishing grounds without fishing in the waters south of Jeju Island.