• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.8
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• pp.1023-1032
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• 2003

The effect of local forcing on the separated flow over a backward-facing step is investigated through hot-wire measurements and flow visualization with multi-smoke wires. The boundary layer upstream of the separation point is laminar and the Reynolds number based on the free stream velocity and the step height is 13800. The local forcing is given from a slit located at the step edge and the forcing signal is always defined when the wind tunnel is in operation. In case of single frequency forcing, the streamwise velocity and the reattachment length are measured under forcing with various forcing frequencies. For the range of 0.010〈S $t_{\theta}$〈0.013, the forcing frequency component of the streamwise velocity fluctuation grows exponentially and is saturated at x/h = 0.75 , while its subharmonic component grows following the fundamental and is saturated at x/h = 2.0. However, the saturated value of the subharmonic is much lower than that of the fundamental. It is observed that the vortex formation is inhibited by the forcing at S $t_{\theta}$ = 0.019 . For double frequency forcing, natural instability frequency is adopted as a fundamental frequency and its subharmonic is superposed on it. The fundamental frequency component of the streamwise velocity grows exponentially and is saturated at 0.5 < x/ｈ < 0.75, while its subharmonic component grows following the fundamental and is saturated at x/ｈ= 1.5 . Furthermore, the saturated value of the subharmonic component is much higher than that for the single frequency forcing and is nearly the same or higher than that of the fundamental. It is observed that the subharmonic component does not grow for the narrow range of the initial phase difference. This means that there is a range of the initial phase difference where the vortex parring cannot be enhanced or amplified by double frequency forcing. In addition, this effect of the initial phase difference on the development of the shear layer and the distribution of the reattachment length shows a similar trend. From these observations, it can be inferred that the development of the shear layer and the reattachment length are closely related to the vortex paring.

• 한국전산유체공학회:학술대회논문집
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• 1995.10a
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• pp.55-63
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• 1995

The flow field around a high-speed train including cross-wind effects has been simulated. This study solves 3-D unsteady incompressible Navier-Stokes equations in the inertial frame using the iterative time marching scheme. The governing equations are differenced with 1st-order accurate backward difference scheme for the time derivatives, 3th-order accurate QUICK scheme for the convective terms and 2nd-order accurate central difference scheme for the viscous terms. The Marker-and-Cell concept was applied to efficiently solve continuity equation, which is differenced with 2nd-order accurate central difference scheme. The 4th-order artificial damping is added to the continuity equation for numerical stability. A C-H type of elliptic grid system is generated around a high-speed train including ground. The Baldwin-Lomax turbulent model was implemented to simulate the turbulent flows. To validate the present procedure, the flow around a high speed train at constant yaw angle of $45^{\circ}\;and\;90^{\circ}$ has been simulated. The simulation shows 3-D vortex generation in the lee corner. The flow separation is also observed around the rear of the train. It has concluded that the results of present study properly agree with physical flow phenomena.

• The KSFM Journal of Fluid Machinery
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• v.10 no.6
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• pp.50-56
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• 2007

In this study, we have performed some experimental works on the effects of variation of low, middle and high turbidity for understanding of optical characteristics which is very important factor for the turbidity measurement. The various output frequencies were obtained by the experimental apparatus which consist of detectors, a light source, a frequency counter and so on. From the result of analysis of these frequencies, Firstly, The difference of signal value for each degrees of low turbidity was the smallest of three scopes around the Nephelometric position. Second, the characteristics of each degrees of middle turbidity was proved that signal values of all degrees were larger those of low turbidity but the difference of each signal value of the forward direction was smaller than that of the backward direction. Third, the characteristics of each degrees of high turbidity was proved that though similar to the characteristics of middle turbidity, each signal value of all degrees was larger and the difference of each signal value of all degrees was smaller than those of low and middle turbidity

• Journal of the Korea Fashion and Costume Design Association
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• v.5 no.1
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• pp.13-24
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• 2003

The purpose of this study is to design Jugori model compatible with the body types of the middle-aged women especially from 40 to 59 years old. The result is as follows: We decided five items as the necessary items for designing jugori model : the bust girth (the breast & shoulder width), the B.P length, the neck width, the armhole circumference, and Hwa-jang. The breast & shoulder width are the size that comes out if the bust is divided by the breast & shoulder width on the basis of the side line, and Hwa-jang is a length measured with arms stretched out to 0° direction. With each person's physical characteristics considered, the application of the size of each body types and body parts is as follows: 1. The breast & shoulder width (1/4 portion) : We decided B/4+2cm as a standard size and, we adjusted the extra room on the basis of the discrepancy between the breast width and the shoulder width to make it fit well to the each body type. For the breast width (1/2 portion), we bisected the difference between the breast width and the shoulder width of the bust, and moved Gut-sup to the center of the Sup and Sup-sun for An-sup. According to the body type, the movement of the Sup for the people with big breasts gets bigger because there should be a big difference between the breast width and the shoulder width for them, and for the people with small breasts the movement will be relatively smaller. For the shoulder width (1/2 portion), we curved the back center line after we shortened as much as the difference between the amount of the shoulder width/2+1cm and of B/4+2cm. The movement of back center line will be bigger for a person with leaned-backward body type. 2. The front & back length: We made the front length to B.P length+2.5cm to have Jugori cover the breast point fully around the bust line, which is a vogue nowadays. For an upright body type, we decided the back length as (AH/2.2)+5cm. And for a bent-forward and a leaned-backward body type, we adjusted the calculation formulae differently taking the physical characteristics into account. We decided the back length (A) as (A.H/2.2)+5cm, and the front length (B) as the back length+5cm. So, (A+B) is the sum of the front length and the back length. Going back to the original formula, the front length is B.P+2.5cm. So, we can decide the back length if we subtract B.P+2.5cm from the sum of the front length and the back length. To make well-fit Jugoris, the front & back length are areas that we should pay attention to if we take each person's physical characteristics into consideration. 3. Go-dae (1/2 portion) : We decided Go-dae as the neck width/2+0.5cm. For an upright body type, because the base line which went down vertically from the tragion was straight, we generally decided Go-dae Dalim line as 1.0cm. But we decided Go-dae Dalim line down to 1.5cm for bent-forward type and up to 0.2cm for leaned-backward type because the upper half of the body of them was bent forward or leaned backward from the base line. 4. The armhole : We decided the armhole circumference as A.H/2+2cm with the whole extra room of 4cm. 5. The side line length : We can calculate the side line length to (the back length-the armhole)/2, and, in terms of the trend, 2.5cm will be appropriate.

• Journal of Korean Academy of Nursing
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• v.21 no.2
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• pp.129-149
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• 1991

Circadian rhythm is entrained in the 24-hour time interval by periodic factors in the environment, known as zeitgeber. But most rotating work schedules are outside the range of the entrainment of the pacemaker timing the human circadian sleep - wake cycle. It has been postulated that physiological and emotional disturbances occur in most human functions when the circadian rhythm is disturbed. So application of circadian principles to the design of shift schedules can aid in maintaining the temporal integrity of the circadian system and thereby minimize for the shift worker any detrimental consequences of circadian disruption. This study was a quasi-experimental study to test the effect of shift intervals for the clinical nurse on the circadian rhythm. Twenty nurses newly employed in general units of two hospitals were selected as an experimental group and twelve college nursing students as a control group. Both groups were selected according to an established criteria using a purposive sampling technique. Ten subjects were assigned to a weekly shift group and another ten to a biweekly shift group engaged in a semi -continuous shift schedule(sunday off) with a backward direction, that is, morning -evening - night shift. The control group worked a morning shift for 42 days. Oral temperature rhythm, waking tim, sleep - wake cycle, fatigue, and mental performance were measured during the experimental period. The data collection period was from April 30, 1990 to June 10, 1990. MANOVA, paired t-test, ANOVA, and Student Newman Keuls method were used for statistical analysis. The results are summarized as follows. 1. Phase delay in the acrophase of temperature rhythm was shown according to the backward rotating shift. A complete adaptation to work on the night shift was achieved between the sixth and ninth day of the night shift. 2. There was no difference in either waking time or sleep- wake cycle according to the duration of the working day for every shift group. Significant difference was found in the waking time and the sleep -wake cycle for subjects on the morning, evening, and night shift in both of the shift groups(weekly shift group : λ＝0.121, p＜0.01, λ＝0.112, p＜0.01, biweekly shift group : λ＝0.116, p＜0.01, λ＝0.084, p＜0.01). 3. There was no difference in fatigue between the first working day and the last working day for the control group and for the biweekly shift group. In the weekly shift group, physical fatigue was significantly different for the first day and the sixth day of the night shift(t＝-2.28, p＜0.05). Physical fatigue and total fatigue on the first day of the night shift showed a significant difference among the control group, the weekly shift group, and the biweekly shift group(F＝5.79, p＜0.01, F＝4.56, p＜0.05). There was a significant difference between the shift groups and the control group(p＜0.05), Physical fatigue, neurosensory fatigue and total fatigue on the last day of the night shift showed a significant difference among the control group, the weekly shift group, and the biweekly shift group(F＝12.65, p＜0.01, F＝7.77, p＜0.01, F＝9.68, p＜0.01). There was a significant difference between the shift groups and the control group(p＜0.05). 4. No difference in mental performance was seen between the first day and the last day of work in each case. An arithmatic test on the first day of the night shift revealed a significant difference among the control group, the weekly shift group, and the biweekly shift group(F＝3.79, p＜0.05). There was a significant difference between the shift groups and the control group(p＜0.05) . The digital symbol substitution test and the arithmetic test on the last day of the night shift showed a significant difference among the control group, the weekly shift group, and the biweekly shift group(F＝3.68, p＜0.05, F＝5.55, p＜0.01), and both showed a significant difference between the shift groups and the control group(p＜0.05). Accordingly, this study showed that during night duty, the waking time, sleep- wake cycle, and fatigue increased and mental performance decreased compared with morning and evening duty. It was also found that the weekly shift group had a higher fatigue score on the sixth day of night duty as compared to the -first day, but the waking time, sleep- wake cycle, and mental performance revealed no difference for the duration of the night duty or between shift groups, and complete adaptation of temperature rhythm was achieved between the sixth and ninth day of night duty. It is possible to conclude from these results that for intermediate circadian type in a healthy young woman, a biweekly shift system is more compatible with the circadian timing system than weekly shift system.

• Korean Journal of Applied Biomechanics
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• v.17 no.4
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• pp.89-98
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• 2007

The purpose of this study was to evaluate the trunk motion and knee joint moment during deep stand to sit and sit to stand according to the trunk weight increase. These experimental subjects were 9 males, who had no skeletal muscular disease. They were performed a SATS(stand to sit), STS(sit to stand) according to the trunk weight increase. Trunk weight increase were classified into 4 bearing trunk weight of 0%, 8%, 16%, 24% of the subject' weight. 1-way(4) RM ANOVA is applied to get the difference of trunk displacement movements and knee joint moments according to he trunk weight increase. significant level of each experiment is set as $\alpha$=.05. 1. Significant difference was classified into 3 bearing trunk weight of 0%, 16%, 24% in maximum forward backward displacement of trunk COM(center of mass). Significant difference was classified into 4 bearing trunk weight of 0%, 8%, 16%, 24% in maximum upward downward displacement of trunk COM during the SATS, STS. 2. Significant difference was classified into 4 bearing trunk weight of 0%, 8%, 16%, 24% in maximum extension knee joint moment. Significant difference was classified into 2 bearing trunk weight of 0%, 16% in maximum internal rotation knee joint moment during the SATS, STS. Therefore we expect that biomechanical model of this study will used to study for mechanical characteristics of obese people.

• Korean Journal of Applied Biomechanics
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• v.22 no.3
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• pp.373-378
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• 2012

The purpose of this study was to develop an electric riding machine for cycle fitting to control riding posture easily, to measure frame size quantitatively, and to overcome disadvantages of the traditional systems. The electric riding machine consisted of actuator, load controller, and display & control unit. The actuator unit by BLDC(BrushLess Direct Current) motor drives the saddle height up and down, the crank forward and backward, the handlebar up and down, and the handlebar forward and backward. The load controller unit controls loads by Eddy current controller with electromagnet and aluminum circular plate. The display & control unit consisted of frame size controller and display panel which shows top tube length(485~663mm), head tube length(85~243mm), seat tube length(481~671mm), and seat tube angle($62.7{\sim}76.4^{\circ}$). The range of frame size control for developed electric riding machine did not have difference compared to traditional commercial systems, but quantitative and precise control with 0.1 mm length and $0.1^{\circ}$ angle was possible through digital measurement. Unlike traditional commercial systems, frame size control was possible during riding through motor driven method, thus fitting duration decreased. It is necessary for further improvement to have feedback from users. It is believed that developed electric riding machine can help to develop domestic fitting system.

• Atmosphere
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• v.17 no.4
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• pp.407-420
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• 2007

Optical characteristics of aerosols in Seoul are investigated from the measurements of sky radiance by Skyradiometer at Yonsei University from December 2005 to November 2006. Aerosol optical depth (AOD) shows a maximum in June due to weak ventilation and particle growth by aging process and hygroscopic effect. Single scattering albedo (SSA) and Angstrom Exponent (AE) show the lowest value in spring due to the Asian dust. It is clear that coarse mode is dominant in spring and fine mode is dominant in summer from the volume size distribution measured in this study. The explanations on the changes of aerosol loadings are provided through the correlation between AOD and AE, while the pattern of wavelength dependency related to particle size is shown through the correlation between SSA and AE. Backward trajectory analysis by HYSPLIT provides information about origin of aerosol, which allows us to classify the case according to the source region and the path distance. Although the direction of backward trajectory traces back mostly to west, coarse mode particle is dominant in the case of long pathway and fine mode particle is dominant in the case of short pathway. This discrepancy is caused by the regional difference of emitted particles.

• Korean Journal of Adult Nursing
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• v.16 no.2
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• pp.245-255
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• 2004

Purpose: this study was to evaluate Cognitive Function Test for the Korean population. Digit Forward (DF), Digit Backward (DB) and Trail Making Test-A(TMT-A) and the translated version of the Trail Making Test-B (TMT-B) were used. The study examined the performance of Korean normal adult population whose age ranged from 20 to over 80. It was predicted that performances of the Korean population would be different from that of the United States population due primarily to their differences in language, and education. Method: Normal Korean adults at the Daejeon Metropolitan City and Chungchung Province (N=298) participated in this study. Seven age scores were evaluated; 20~29, 30~39, 40~49, 50~59, 60~69, 70~79, & >80s. The effects of age, gender, and years of education was examined, which yielded significant age and education effects. The scores were further specified accordingly in terms of years of education (0, 1~6, 7~12, 13~16, & >17), and gender. Result: As the age increased cognitive function score decreased. As the years of education increased, cognitive function scores increased. There was no difference in cognitive function scores according to gender. Age and year of education had significant effects on cognitive function and explained 52-58% of variants of each test. Conclusion: The data of the cognitive function tests are expected to be utilized for research purposes such as basic and clinical studies, as well as practical purpose such as cognitive assessment for traumatic brain injury, stroke, and elderly and nursing education for assessment tools.

• Journal of the Korean Regional Science Association
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• v.32 no.4
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• pp.3-18
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• 2016

National research and development(R&D) project plays an important role in the economic growth of a country as well as a company. This article aim to examine the development of the performance evaluation framework for assessing the contribution of national research and development(R&D) program to productivity growth. The main idea of this paper begins with the employment of between-group analysis for evaluating the returns to R&D. The method of this study is based on the comparison of productivity growth between different groups with time series data, not cross-sectional approach with one period. In these regards, backward effect and forward effect are operationally defined as a measurement for contributions of R&D in this study. The results of analysis gives that the outcomes of between-group analysis shows the lower performance of R&D compared to the within-group analysis. while the difference was not especially evident with the case of operating profit variable, but sales variable.