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대학교 재학생에서 Fatigue Severity Scale의 신뢰도 및 타당도 연구
이정현,정현석,임수미,조한별,마지영,고은,임주연,이선혜,배수진,이유진,류인균,정도언,Lee, Junghyun H.,Jeong, Hyeonseok S.,Lim, Soo Mee,Cho, Han Byul,Ma, Ji-Young,Ko, Eun,Im, Jooyeon J.,Lee, Sun Hea,Bae, Sujin,Lee, Yu-Jin,Lyoo, In Kyoon,Je 대한생물정신의학회 2013 생물정신의학 Vol.20 No.1
Objectives There are only a limited number of studies on instruments assessing fatigue in university students, although fatigue exerts negative influences on their health and academic performances and fatigue-related complaints are more frequently reported in young adults than middle-aged adults. The aim of this study was to validate the 9-item Fatigue Severity Scale (FSS) among university students including both undergraduate and graduate students in South Korea. Methods A total of 176 university students completed a battery of self-report questionnaires, including the FSS, the Brief Fatigue Inventory (BFI), the Beck Depression Inventory-II (BDI-II), the Beck Anxiety Inventory (BAI), the Medical Outcomes Study Short Form 36 version 2 (MOS-SF36v2), and the Inclusion of Community in the Self Scale (ICS). The data were collected from February of 2012 to June of 2012. The reliability, convergent validity, divergent validity, and exploratory factor analyses were conducted to assess psychometric properties of the FSS. Results The mean FSS score was 3.20 (standard deviation = 1.43). The FSS demonstrated an excellent internal consistency (Cronbach's ${\alpha}$ = 0.93) and item-total correlations ranged from 0.56 to 0.90. Correlations of the FSS with the BFI (r = 0.71, p < 0.01), BDI-II (r = 0.54, p < 0.01), BAI (r = 0.46, p < 0.01), MOS-SF36v2 physical component summary (r = -0.28, p < 0.01), MOS-SF36v2 mental component summary (r = -0.55, p < 0.01), and ICS (Spearman's rho = -0.07, p = 0.33) showed acceptable convergent and divergent validity. Exploratory factor analysis defined one underlying factor (eigenvalue = 5.67) that explained 93.50% of the total variance. Conclusions To the best of our knowledge, this is the first study to investigate reliability and validity of the FSS in university students. The FSS exhibits good psychometric properties for evaluation of fatigue among university students in South Korea. Since the FSS is easy to administer, score, and interpret, it could be a useful tool in research and practice for assessing fatigue among university students.
랜덤액세스 장치의 속도성능 향상을 위한 모델추종 제어기의 적용
이정현,박기환,김수현,곽윤근,Lee, J.H,Park, K.H,Kim, S.H,Kwak, Y.K 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.1
In the time optimal control problem, bang-bang control has been used becaese it is the theoretical time minimum solution. However, to improve tracking speed performance in the time optimal control, it is important to select a switching point accurately which makes the velocity zero near the target track. But it is not easy to select the swiching point accurately because of the damping coefficient variation and uncertainties of modeling an actual system. The Adaptive model following control(AMFC) is implemented to relieve the difficulty and inconvenience of this task. The AMFC and make the controlled plant follow as closely as possible to a desired reference model whose switching point can be calculated easily and accurately, assuring the error between the states of the reference model and those of the controlled plant appoaches zero. The hybrid control method composed of AMFC and PID is applied to a tracking actuator of the magneto optical disk drive(MODD) in random access devices to improve its slow tracking performance. According to the simulaion and experimental results, the average tracking time as small as 20ms is obtained for a 3.5 magneto-optical disk drive. The AMFC also can be applied for other random access devices to improve the average tracking performance.
CAVITATION ANALYSIS IN A CENTRIFUGAL PUMP USING VOF METHOD
W.J. Lee(이원주),J.H. Lee(이정현),N. Hur(허남건),I.S. Yoon(윤인식) 한국전산유체공학회 2015 한국전산유체공학회지 Vol.20 No.4
Centrifugal pumps consume considerable amount of energy in various industrial applications. Therefore, improvement of the efficiency of these machines has become a major challenge. Cavitation is a phenomenon which decreases the pump efficiency and even causes structural demage. Hence, the goal of this paper is to investigate the cavitation problem in the single-stage and double-stage centrifugal pumps. The Volume of Fraction (VOF) method has been used for the numerical simulations together with Rayliegh-Plesset model for the gas-liquid two-phase flow inside the pump. In order to capture the turbulent phenomena, the standard k-ε turbulence model has been adopted, and the simulations have been done as unsteady cases. In addition, the motion of the rotating parts has been simulated using Multi Reference Frame(MRF) method. The results are presented and compared in terms of hydraulic head and NPSH for both the single-stage and double-stage pumps. The H-Q curves show the effects of cavitation on decreasing the pumps performances.
조진호(J. H. Cho),김종훈(J. H. Kim),조유진(Y. J. Cho),안형준(H. J. Ahn),박영빈(Y. B. Park),박효순(H. S. Park),우승탁(S. T. Woo),신동호(D. H. Shin),김동욱(D. W. Kim),임형규(H. G. Lim),이정현(J. H. Lee),성기웅(K. W. Seong) 한국재활복지공학회 2015 한국재활복지공학회 학술대회논문집 Vol.2015 No.11
In this paper, we present the development procedure of fully implantable hearing device with round window driving method which is named ACROSS-RW. The system consists of an implantable microphone, a signal processing body, and a vibration transducer. Each component is developed with needs of hearing losses and novel idea for overcoming lacks of previous studies. The performance of the system is evaluated from public certification organization and mechanical engineering laboratory of Stanford University in USA, which is well-known for testing of active middle ear implants. ACROSS-RW can provide natural sound and good cosmetic to people who suffer from hearing loss.