• Journal of the Korean Chemical Society
• /
• v.52 no.1
• /
• pp.7-15
• /
• 2008

Molecular motion influencing the absorption spectrum of a chromophore in liquid is theoretically described by a quantum mechanical time correlation function. In the present paper, we developed a theoretical method to calculate such a quantum mechanical time-correlation function from a classical time-correlation function using semi-classical approximations. The calculated time-correlation function was combined with the second order cumulant expansion method to calculate the absorption spectrum of nile blue in acetonitrile. Reasonably good agreement with experimental spectrum was obtained. From the comparison with experimental spectrum, we concluded that the time scale of solvation dynamics of the system should be longer then 1ps and the first shell of solvent is the major contribution to the solvation dynamics.

• Journal of Korean language education
• /
• v.28 no.3
• /
• pp.85-104
• /
• 2017

The purpose of this study is to explore the effects of listening comprehension ability, self-efficacy, comprehension anxiety, and exposure time on Korean language understanding. In order to achieve our goal, listening examinations and surveys were conducted among 95 students from a university in Thailand, studying Korean language. As a result, it was revealed that the most influential factor on one's listening ability was self-efficacy. In addition, when the correlation between listening self-efficacy and other factors was examined, it was shown that there existed a statistically significant relationship. Particularly, listening comprehension anxiety had the most significant correlation with listening self-efficacy. Similarly, cognitive strategy demonstrated a significant correlation with listening self-efficacy. On the other hand, the effects of self-efficacy and other factors on listening scores such as the degree and types of strategy that students used were also studied. The findings revealed that, in most cases, strategy-intensive group's test results were influenced more by exposure time, while the less intensive group's scores were influenced more by their self-efficacy. Finally, after analyzing the effects of time spent on conversing with friends and watching Korean television on listening self-efficacy, it was discovered that both factors had statistically significant relationships with listening self-efficacy. Through this study, such results can be integrated and applied to education in various ways. The most important part for listening comprehension ability is enhancing self-efficacy and in order to do so, the appropriate education methods should be used to reduce listening comprehension anxiety, stimulate strategy use, and increase listening exposure time.

• Journal of Sasang Constitutional Medicine
• /
• v.33 no.3
• /
• pp.127-137
• /
• 2021

Objectives The purpose of this study was to identify the effects of personality by each Sasang constitution on sleep using Positive Affect and Negative Affect Schedule(PANAS) and NEO-personality inventory(NEO-PI). Methods The subjects of this study were 2,078 people who had information on Sasang constitutional type and personality(PANAS, NEO-PI) among the data established at the Korean Medicine Data Center. Sleep time and sleep quality were investigated through self-written questionnaires. Sleep time was collected by hand-writing, and sleep quality was checked on a 4 point Likert scale. Pearson correlation analysis was conducted to see the correlation between personality and sleep in each constitutional type. Logistic regression was performed using personality as independent variables to find out how much personality affects sleep time. In order to find out how much personality affects sleep quality, regression analysis was performed using personality as independent variables. Results & Conclusions Sleep time was hardly affected by personality. As a result of Pearson correlation analysis, sleep time in all subjects did not show a significant correlation with personality. In logistic regression on sleep time as the dependent variable, no statistically significant results were obtained except for the Negative Affect(NA) in Taeeumin. Sleep quality showed a statistically significant correlation with the negative affect(NA), neuroticism(N), extraversion(E), Physical Component Summary(PCS) and Mental Component Summary(MCS). As a result of regression analysis on sleep quality as the dependent variable, neuroticism(N), negative affect(NA), positive affect(PA), and extraversion(E) were found in the factors affecting sleep quality. Besides, how much personality affected sleep quality might differ in each constitution. In all constitutions, sleep quality was affected by N, but the rank of N was different in each constitution. The sleep quality of Soyangin was not affected by E, and the sleep quality of Taeeumin was specifically affected by O.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.14 no.10
• /
• pp.1079-1088
• /
• 2003

In this paper, we propose a high-resolution time-frequency domain reflectometry technique as a methodology of detection and estimation of faults on a wire. This method adopts the time-frequency cross correlation characteristics of the observed signal in both time and frequency domains simultaneously. The accuracy of the proposed method is verified with experiments using a RG type coaxial cable and comparing it with traditional time domain as well as frequency domain reflectometry methods. It is clearly shown here that the proposed algorithm produces excellent results compared to the conventional methods for single as well as multiple fault cables.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2004.09a
• /
• pp.113-114
• /
• 2004

In order to classify the groundwater recharge characteristics in an urban area, a time series analysis of groundwater level data was performed. For this study, the daily groundwater level data from 35 monitoring wells were collected for 3 years (Fig. 1). The use of the cross-correlation function (CCF), one of the time series analysis, showed both the close relationship between rainfall and groundwater level change and the lag time (delay time) of groundwater level fluctuation after a rainfall event. Based on the result of CCF, monitored wells were classified into two major groups. Group I wells (n=10) showed a fast response of groundwater level change to rainfall event, with a delay time of maximum correlation between rainfall and groundwater level near 1 to 7 days. On the other hand, the delay time of 17-68 days was observed from Group II wells (n=25) (Fig. 1). The fast response in Group I wells is possibly caused by the change of hydraulic pressure of bedrock aquifer due to the rainfall recharge, rather than the direct response to rainfall recharge.

• Journal of the Regional Association of Architectural Institute of Korea
• /
• v.21 no.3
• /
• pp.11-21
• /
• 2019

The purpose of this study was to present an analysis model for finding the correlation between visibility and evacuation time as users move in the outpatient department of the general hospital. The spatial scope of the study was limited to the first floor and second floor which are used for the outpatient department. Traffic density in outpatient departments was surveyed on site. Based on the surveyed traffic density, the evacuation simulation model was established for calculating the escape route and evacuation time for an individual user. The traffic density of the outpatient department as per the evacuation time was also calculated. With using evacuation simulations, the flow of evacuees was calculated through the density of traffic over the time of evacuation. Visibility data were set in the simulation model for users' escape routes. A correlation analysis between the product of evacuation flow measure and visibility measure of the evacuation population and evacuation time was performed. The analysis result showed negative correlation within a specific distance range. This study presented an analysis model showing that the evacuation condition considering spatial visibility in the outpatient department of general hospital visibility was negatively related to the analyzed evacuation time at the design stage.

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.30 no.1
• /
• pp.1-11
• /
• 2022

The capacity of Jeju International Airport has reached its limit due to a surge in air traffic demand such as passengers and cargo and the continuous expansion of Low Cost Carriers (LCC). Despite COVID-19 that has began in November 2019, Jeju International Airport still has continuous demand in terms of passenger and cargo transportation. As a result, it is undeniable that the delay rate also unexpectedly increased as the air traffic volume at Jeju International Airport continued to increase. In this study, the correlation between Turnaround Time and delay rates of national airlines is analyzed based on past flight data at Jeju International Airport, and the cumulative delay time trend for sampled airlines is compared with Turnaround Time. Through this study, it is expected to contribute to securing aircraft operation efficiency and on-time by analyzing delays related to Turnaround Time at Jeju International Airport.

• The Journal of the Acoustical Society of Korea
• /
• v.32 no.2
• /
• pp.116-123
• /
• 2013

This paper represents generation of time-varying underwater acoustic channels by performing scattering simulation with time-varying ocean surface and Kirchhoff approximation. In order to estimate the time-varying ocean surface, 1D Pierson-Moskowitz ocean power spectrum and Gaussian correlation function were used. The computed scattering coefficients are applied to the amplitudes of each impulse of BELLHOP simulation result. The scattering coefficients are then compared with measured doppler spectral density of signal components which were scattered from ocean surface and the correlation time used in the Gaussian correlation function was estimated by the comparison. Finally, bit-error-rate and channel correlation simulations were performed with the generated time-varying channel based on passive time-reversal communication scenario.

• Communications for Statistical Applications and Methods
• /
• v.21 no.4
• /
• pp.335-347
• /
• 2014

This paper employs dynamic conditional correlation (DCC) model to examine time-varying comovement in the Korean stock market with a focus on the financial industry. Analyzing the daily returns of KOSPI 200 eight sector indices from January 2008 to December 2013, we find that stock market correlations significantly increased during the GFC period. The Financial Sector had the highest correlation between the Constructions-Machinery Sector; however, the Consumer Discretionary and Consumer Staples sectors indicated a relatively lower correlation between the Financial Sector. In terms of model fitting, the DCC with t distribution model concludes as the best among the four alternatives based on BIC, and the estimated shape parameter of t distribution is less than 10, implicating a strong tail dependence between the sectors. We report little asymmetric effect in correlation dynamics between sectors; however, we find strong asymmetric effect in volatility dynamics for each sector return.

• Proceedings of the KSRS Conference
• /
• 2004.10a
• /
• pp.208-211
• /
• 2004

Landmark matching is one of an important algorithm for navigation of satellite images. This paper proposes a fast landmark matching algorithm using a MGLI (Moving Guide-Line Image). For searching the matched point between the landmark chip and a part of image, correlation matrix is used generally, but the full-sized correlation matrix has a drawback requiring plenty of time for matching point calculation. MGLI includes thick lines for fast calculation of correlation matrix. In the MGLI, width of the thick lines should be determined by satellite position changes and navigation error range. For the fast landmark matching, the MGLI provides guided line for a landmark chip we want to match, so that the proposed method should reduce candidate areas for correlation matrix calculation. This paper will show how much time is reduced in the proposed fast landmark matching algorithm compared to general ones.