• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.10
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• pp.542-549
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• 2004

The conventional fault location algorithms based on the travelling waves have an inherent problem. In cases of the close-up faults occurring near the relaying point and of the faults having zero degree inception angle of voltage signals, the conventional algorithms can not estimate an accurate fault distance. It is because the shapes of travelling waves are near sinusoidal in those cases. A new method solving this problem is presented in this paper. An FIR(Finite Impulse response) filter which makes high frequency components prominent and makes the power frequency component and dc-offset attenuated is used. With this method, the cross-correlation peak is to be very clear when a close-up fault or a fault having near zero-degree inception angle occurs. The cross-correlation peaks can be clearly distinguished and accurate fault location is practically possible consequently. A series of simulation studies using EMTP(Electromagnetic Transients Program) show that the proposed algorithm can calculate an accurate fault distance having maximum 2% or less error.

• Korean Journal of Applied Biomechanics
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• v.25 no.2
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• pp.149-155
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• 2015

Purpose : Recently, many researchers and golf coachers demonstrated that X-factor and X-factor stretch had a co-relationship with driving distance. However, its relationship is still controversial and ambiguous. Thus, the aim of this study was to examine the relationship among X-factor, X-factor stretch and swing-related factors, including driving distance in elite golfers. Method : Seventeen male elite golfers (handicap: ${\leq}4$) with no history of musculo-skeletal injuries participated in the study. Thirty spherical retro-reflective markers were placed on including the middle point of PSIS, the right/left ASIS, the right/left lateral acromion of the scapula, driver head and shaft grip. All motion capture data was collected at 100Hz using 6 infrared cameras. Carry distance, club speed, ball speed, smash factor, launch angle, and spin rate were collected from radar-based device, TrackMan. Results : Pearson's correlation coefficient method was used to find the correlations among X-factor, X-factor stretch and swing-related factors. Positive correlations between driving distance and other swing-related factors which include club speed(r=.798, p<.001), and ball speed(r=.948, p<.001) were observed. In contrast to the swing-related factors, X-factor and X-factor stretch had no relationship to driving distance. Conclusion : These results indicate that X-factor and X-factor stretch are not key regulators in driving distance.

• The Korean Journal of Emergency Medical Services
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• v.14 no.3
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• pp.5-11
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• 2010

Purpose: This study was to clarify correlation between en route distance and role time on call received hours. Methods: Data on en route distance(dependent variable), role time(independent variable) from 387 prehospital care reports documented by EMS in Kyonggi Provincial Fire and Disaster Headquarters and Seoul Metropolitan Fire and Disaster Department between 21 and 10 June 2010 were randomly chosen for simple regression analysis using Windows SPSS 12. OK. This analysis was conducted nine times on unit hour divided to eight call received and overall. Results: Statistically significant regression equations( Y=2.414+1.206X for 09:00~11:59, Y=3.753+.662X for 12:00~14:59, Y=2.215+1.458X for 15:00~17:59, Y=2.600+.822X for 21:00~23:59, Y=5. 445+.263X for overall) were derieved from the data. Conclusion: These equations having linear relationship may be utilized as a method for system status management to effectively response to emergency call.

• The Journal of Korean Association of Computer Education
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• v.11 no.6
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• pp.85-94
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• 2008

This study is to find strategies to promote distance learning effectiveness in the online learning environment. The research showed that the level of learner's perception of the structure of transactional distance was not significantly different according to sex (p>.05). There was significant correlation between the level of learner's perception of the structure and academic satisfaction(p<.01). And, the level of learner's perception of the structure and learning durability appeared to have statistically significant correlation. However there was no significant difference(p>.05) between academic achievement. Among the three subordinate factors, the course interaction organization had the most influence on the learner's academic satisfaction and the learner's learning durability was influenced the most by the content organization.

• Journal of Digital Convergence
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• v.16 no.1
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• pp.187-195
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• 2018

The purpose of this study was to identify the moderated effects of multicultural contact experience on the relationship between social distance and multicultural acceptability among nursing students. The sample for this study consisted of 174 nursing students from four universities located in Korea. Data were analyzed by descriptive statistics, t-test, ANOVA, $Scheff{\acute{e}}$ test, Pearson correlation and hierarchical multiple regression with SPSS/WIN 23.0. It was found that: (a) multicultural acceptability had a negative correlation with social distance(r=-.61, p<.001), whereas a positive correlation was observed with experience of multicultural contact(r=.24, p=.002); (b) the interaction effect by multicultural contact experience and social distance had a significant influence on the multicultural acceptability(${\beta}=-.18$, p=.003); (c) experience of multicultural contact moderated the relationship between social distance and multicultural acceptability(${\Delta}R^2=0.30$, p=.003). Results of the study suggest that the greater the experience of multicultural contact, the greater the negative effect of social distance on multicultural acceptability. Therefore, to increase the multicultural acceptability of nursing students, it is important to encourage the positive experiences of multicultural contact and thus reduce social distance.

• Journal of Sensor Science and Technology
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• v.9 no.4
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• pp.256-267
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• 2000

In this paper, we studied the ultrasonic urine volume sensor of urinary alarm system for home use to detect the time of urination as a assistive methodology for the incontinence patients and the correlation between urine volume and bladder interwall distance by using developed sensor. The developed sensor was designed to minimize the measurement error by using ultrasound with 2.25 MHz center frequency which provides higher resolution as well as longer penetration depth. To verify usefulness of the developed sensor, we performed a preliminary experiment of estimating bladder volume from the measured distance between interior and posterior wall of bladder. In the preliminary experiment, bladder volume estimated from the result using a commercial ultrasonography system. The experimental results show there exists god correlation between the actual urine volume and the measured interwall distance of the bladder. In conclusion, the developed ultrasound bladder volume sensor can be applied to an urine alarm system which provides patient the exact time of urination, it will be contribute in health care and welfare society.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2013.06a
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• pp.293-298
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• 2013

This research develops an ultrasonic sensor to measure the distance in underwater. The ultrasonic transducer transmits an acoustic signal to an object and receives the echo signal reflected from the object. The ultrasonic driver calculates a distance by multiplying the acoustic speed to the time of flight(TOF) which is the time necessary for the acoustic signal to travel from the transducer to the object. We apply a thresholding and a cross correlation methods to detect the TOF and show their results. When an echo pulse is corrupted with noise and its shape is distorted, the cross correlation method is used to find the TOF based on the maximum similarity between the reference and the delayed echo signals. The echoes used for the reference signal are achieved at the different environments, which improves the performance of the sensor. This paper describes the driver of the acoustic sensor and analyzes the performance of sensors in different measurement environments.

• Earthquakes and Structures
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• v.2 no.4
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• pp.357-376
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• 2011

Ground motion models predict the mean and standard deviation of the logarithm of spectral acceleration, as a function of predictor variables such as earthquake magnitude, distance and site condition. Such models have been developed for a variety of seismic environments throughout the world. Some calculations, such as the Conditional Mean Spectrum calculation, use this information but additionally require knowledge of correlation coefficients between logarithmic spectral acceleration values at multiple periods. Such correlation predictions have, to date, been developed primarily from data recorded in the Western United States from active shallow crustal earthquakes. This paper describes results from a study of spectral acceleration correlations from Japanese earthquake ground motion data that includes both crustal and subduction zone earthquakes. Comparisons are made between estimated correlations for Japanese response spectral ordinates and correlation estimates developed from Western United States ground motion data. The effect of ground motion model, earthquake source mechanism, seismic zone, site conditions, and source to site distance on estimated correlations is evaluated and discussed. Confidence intervals on these correlation estimates are introduced, to aid in identifying statistically significant differences in correlations among the factors considered. Observed general trends in correlation are similar to previous studies, with the exception of correlation of spectral accelerations between orthogonal components, which is seen to be higher here than previously observed. Some differences in correlations between earthquake source zones and earthquake mechanisms are observed, and so tables of correlations coefficients for each specific case are provided.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.12
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• pp.1690-1698
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• 2018

Recent advances in ICT technology have transformed many of our daily lives and attracted a lot of attention to personal health. Heart beat measurement that reflects cardiac activities has been used in various fields such as exercise evaluation and psychological state evaluation for a long time, but its utilization method is limited due to its differentiation from clinical electrocardiogram. Therefore, in this study, we could observe the change of the measured signal according to the change of the distance and the position of the measuring electrodes which are non-standard electrode configuration. Based on the electric dipole model of the heart, correlation with clinical electrocardiogram could be confirmed by synthesizing multiple surface potentials measured with a shorter electrode distance than standard one. From the electromagnetic point of view, the distance between the measuring electrodes corresponds to the distance that the electric potential by the cardiac electric dipole moves, and the electric potential measured at the body surface is proportional to the moving distance of the electric potential. Therefore, it is preferable to make the distance between electrodes as long as possible, and to position the measuring electrode close to the ventricle rather than the atrium. In addition, it was found that standard electrocardiographic waveforms could be synthesized by using arithmetic sum of multiple measuring electrodes due to the relationship of electrical dipole vectors, which is obtained by dividing and positioning a plurality of measuring electrodes on a reference electrode line, such as Lead-I, Lead-II direction. Also, we obtained a significant Pearson correlation coefficient ($r=0.9113{\pm}0.0169$) as a result of synthetic experiments on four subjects.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.4
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• pp.359-364
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• 2013

In this paper, we propose a direct sequence ultra wideband (DS-UWB) radar system based on correlation accumulation in the fields of the ship traffic control and the safe ship operation including docking guidance systems. The proposed DS-UWB radar system averages out the noise by accumulating correlator outputs, and thus, provides a reliable distance estimation performance with a shorter estimation time compared with conventional DS-UWB radar systems. From numerical results, it is confirmed that the proposed DS-UWB radar system has not only a shorter average correlation processing time, but also a better distance estimation performance.