• Kyungpook Mathematical Journal
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• v.47 no.3
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• pp.425-438
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• 2007

In this paper, we establish some new oscillation criteria for a second-order delay dynamic equation $$u^{{\Delta}{\Delta}}(t)+p(t)u(\tau(t))=0$$ on a time scale $\mathbb{T}$. The results can be applied on differential equations when $\mathbb{T}=\mathbb{R}$, delay difference equations when $\mathbb{T}=\mathbb{N}$ and for delay $q$-difference equations when $\mathbb{T}=q^{\mathbb{N}}$ for q > 1.

• Journal of Families and Better Life
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• v.21 no.2
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• pp.213-220
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• 2003

In this study, I analyzed dual-career commuting couples time use. Concretely, this study compared the husband with the wife on the becoming a commuter family, the living apart on weekdays. And it examined time use on weekdays and weekends by the time amount of each activities and the ratio of actor on each hour. The survey participants included 131 married people who were dual-career commuting couple and who were maintained separate residence and work place. The major findings are as follows: First, weekday separation of the dual-career commuting couples is largely due to career. This kind separation is mostly due to sociostructural labor market factor and individual factor to increasing working women. Second, 94.6%(53) of male participants were resident living apart from their family on weekdays. Third, the most wives mentioned some kind of emotional liberation such as freedom on weekdays. Finally, there was gender difference in the time spent on each activities when dual-career commuting couples are living together and they are apart. Especially the most gender difference on weekdays is household work time and leisure time.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2006.03a
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• pp.25-32
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• 2006

We present a imaging method of seismic sources by time reversal propagation of seismic waves. Time-reversal wave propagation is actively used in medical imaging, non destructive testing and waveform tomography. Time-reversal wave propagation is based on the time-reversal invariance and the spatial reciprocity of the wave equation. A signal is recorded by an array of receivers, time-reversed and then back-propagated into the medium. The time-reversed signal propagates back into the same medium and the energy refocuses back at the source location. The increasing power of computers and numerical methods makes it possible to simulate more accurately the propagation of seismic waves in heterogenous media. In this work, a staggered-grid finite-difference solution of the elastic wave equation is employed for the wave propagation simulation. With numerical experiments, we show that the time-reversal imaging will enable us to explore the spatio-temporal history of complex earthquake.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.5
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• pp.893-898
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• 2017

A TDC(Time-to-Digital Converter) of counter-type is designed by $0.18{\mu}mCMOS$process and the supply voltage is 1.5 volts. The converted error of maximum $T_{CK}$ is occurred by the time difference between the start signal and the clock when the period of clock is $T_{CK}$ in the conventional TDC. And the converted error of -$T_{CK}$ is occurred by the time difference between the stop signal and the clock. However in order to compensate the disadvantage of the conventional TDC the clock is generated within the TDC circuit and the clock is synchronized with the start and stop signals. In the designed TDC circuit the conversion error is not occurred by the difference between the start signal and the click and the magnitude of conversion error is reduced (1/2)$T_{CK}$ by the time difference between the stop signal and the clock.

• Journal of Gifted/Talented Education
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• v.23 no.3
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• pp.315-333
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• 2013

The purpose of this study was to compare the time management behaviors and life satisfaction of gifted students and general students, and to investigate relationships between the time management and the life satisfaction. For this study, 104 gifted middle school students and 203 regular middle school students in Kyunggi Province were participated. The results of this study were as follows.; First, there was significant difference in the time management behaviors between gifted students and general students. Analyzing by independent samples t-test showed that gifted students' time management behaviors showed significantly higher than that of general students'. There was no gender difference in gifted students' time management behaviors. However, there was a significant gender difference in general students. The interaction effect between the group and the gender did not appear. Second, there was significant difference in the life satisfaction between gifted students and general students. Analyzing by independent samples t-test showed that gifted students' life satisfaction showed significantly higher than that of general students'. There was no gender difference in both groups. The interaction effect between the group and the gender did not appear. Third, investigating the relationship between time management behaviors and life satisfaction of gifted students and general students, the results showed significantly positive correlations in both groups. Regression analysis was performed to investigate the impact of time management behaviors on life satisfaction, and it showed that time management behavior affects significantly on life satisfaction.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.8 s.185
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• pp.64-71
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• 2006

In this paper, a uniform speed controller for an ultrasonic rotary motor is developed using the phase-difference method. The phase difference method uses traveling waves to drive the ultrasonic motor. The traveling waves are obtained by adding two standing waves that have a different phase to each other. A compact phase-difference driver system is designed and integrated by combining VCO(Voltage Controlled Oscillator) and phase shifter. Theoretically the relationship between the phase difference in time and the rotational speed of the ultrasonic motor is sine function, which is verified by experiments. Then a series of experiments under various loading conditions are conducted to characterize the motor's performance that is the relationship between the speed and torque. Proportional-integral control is adopted for the uniform speed control. The proportional control unit calculates the compensating phase-difference using the rotating speed which is measured by an encoder and fed back. Integral control is used to eliminate steady-state errors. Differential control for reducing overshoot is not used since the response of ultrasonic motor is prompt due to its low inertia and friction-driving characteristics. The developed controller demonstrates reasonable performance overcoming disturbing torque and the changes in material properties due to continuous usage.

• The Journal of Korea Assosiation for Disability and Oral Health
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• v.10 no.2
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• pp.78-83
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• 2014

The objective of this study was to confirm the validity of classification of dental disability by measuring the dental treatment time required for disabled patients and identify the disability type that requires more of chair time. As a result of measuring a total of 123 patients who were admitted to the Seoul dental hospital for the disabled on Oct. 2014, I was able to make the following conclusions: 1. For dental counseling and check-up, the chair time did not show significant differences between the different types of disability. 2. For periodontal treatment, restorative treatment, root canal treatment, and surgical treatment, the difference of the chair time for dentally disabled patients was significantly longer than that of non-dentally disabled patients. 3. The difference in the total chair time for prosthetic treatment was statistically insignificant. However, each of the prosthetic treatment steps did show statistically significant differences.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.11
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• pp.1124-1129
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• 2008

Recently, two-port time-domain passivity approach was modified for time-varying communication delay. The newly proposed approach could achieve stable teleoperation even under the serious time-varying delay and packet loss communication condition. However, after some operation hour, the accumulated energy difference between the input energy from one port and the output energy at the other port caused unstable behavior until the passivity controller is activated. Resetting scheme is introduced for solving this problem, and stable bilateral teleoperation can be guaranteed without worrying about the accumulated energy difference.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.5
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• pp.367-375
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• 2000

It is proposed that the rotor time constant and inductance are compensated at the same time in the indirect vector control method of an induction motor. The proposed scheme compensates the rotor time constant using the difference between the Q-axis real stator current and estimated current that is calculated from the terminal voltage and current, and compensates inductance by using the difference between the D-axis real stator flux and estimated stator flux in the synchronous rotating reference frame. Although the rotor time constant and inductance vary at once, the proposed method compensates the rotor time constant and inductance with accuracy. In addition to, two variables can be compensated not only at the steady state condition, but also at the transient state, where the torque varies in a rectangular pulse waveform. Therefore, the performance of vector control is greatly improved as verified by experiment.

• Journal of Korean Academy of Nursing
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• v.6 no.1
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• pp.29-40
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• 1976

This study attempted to measure personality changes in collegiate nursing students as a result of their psychiatric nursing practice. The study population consisted of 310 students in 8 colleges of nursing in Korea, 96 with psychiatric practice, 103 with other clinical practice and III without clinical practice experience. The objectives of the study were to identify: 1. The self-actualization scores of nursing students resulting from psychiatric nursing practice. 2. The self-actualization scores of nursing students resulting from other clinical nursing practice. 3. The difference between scores for students with clinical practice experience and those without experience. 4. The relevance between self-actualization and sibling order. 5. The relevance between self- actualization and religion. 6. The coefficiently scores for students before and after clinical practice. The instrument used was the Personal Orientation Inventory (POI), developed by Shostrom. It provides a measure of values and behavior which are thought to be of importance in the development of self- actualization. The main findings of the study were as follows: 1. There was a significant difference in the Time Competence, Self Regard, and Nature of Man scales resulting from psychiatric nursing practice. 2. There was a significant difference in the Inner Directed, Existentialist, Feeling Reactivity, Spontaneity, Nature of Man and Capacity for Intimate Contact scales resulting from other clinical nursing practice. 3. There was a significant difference in the Inner Directed, Feeling Reactivity, Spontaneity, Self- Regard and Capacity for Intimate Contact scales between students with clinical practice and those without practice. 4. There was a significant difference in the Self-Acceptance scale for both the eldest and the youngest siblings. 5. There was a significant difference in the Time Competence, Inner Directed, Existentialist, Self-Acceptance and Capacity for Intimate Contact scales for middle and youngest siblings, 6. There was a significant difference in the Existentialist scale between students with a religion and those without one. 7. There was a significant difference for students without a religion in the Time Competence, Inner Directed, Self-Regard, Nature of Man, and Capacity for Intimate Contact scales after clinical practice. 8. There was a significant difference for students, with a religion in the Inner Directed, Existentialist, Spontaneity, and Nature of Man scales after clinical practice. 9. There was a significant difference for students in the Self- Actualizing value, Spontaneity, Nature of Man and Synergy scales according to whether their parents had a religion or not. 10. Before and after practice, significantly different correlations were found between the Time Competence and Capacity for Intimate Contact scales : the Inner Directed and Existentialist scales ; the Self- Actualizing Value and the Feeling Reactivity, Spontaneity, Self-Regard and Nature of Man scales : the Feeling Reactivity and Acceptance of Aggression scales: the Spontaneity and the Self-Regard and Nature of Man scales; and between the Self-Regard and Nature of Man scales.