• Journal of Environmental Science International
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• v.4 no.2
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• pp.117-120
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• 1995

The comparision of sunshine duration meter was carried out on the roof of Korea Meteorological Research Institude by comparing Pyrheliometer(Eppley NIP model) to sunshine duration meter(Reflection type) during from Nov. 8, 1989 to Feb. 19, 1990. In the observation Period, daily mean sunshine duration time difference of Jordan sunshine duration meter was recorded 0.47hour and Reflect sunshine duration meter was recorded 0.39hour. More than one hour time difference was observed 15 cases by Jordan sunshine duration meter and 11 cases by Reflect sunshine duration meter.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.7 no.4
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• pp.320-327
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• 1996

This paper presents that the lossy or amplification property of the Finite Difference-Time Domain(FD-TD) method based on the leap-frog scheme is theoretically verified by using a plane wave analysis. The basic algorithm of the FD-TD method is introduced in order to help understanding the analysis procedure. Since our analysis is formulated by the Von Neumann's approach, the stability inequality is also produced as an another outcome.

• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.181-182
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• 2003

A preconditioned numerical method for gas-liquid to-phase flow is applied to solve cavitating flow. The present method employs a density based finite-difference method of dual time-stepping integration procedure and Roe's flux difference splitting approximation with MUSCL-TVD scheme. A homogeneous equilibrium cavitation model is used. The method permits simple treatment of the whole gas-liquid two-phase flow field including wave propagation, large density changes and incompressible flow characteristics at low Mach number. By this method, two-dimensional internal flows through a venturi tuve and decelerating cascades are computed and discussed.

• Proceedings of the KSR Conference
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• 2001.10a
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• pp.119-124
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• 2001

As the brake control valve of freight car, there are sliding valve and diaphragm one. In this study, we measured and analyzed pneumatic characteristics of brake system of the freight car by using real train experiment. The difference of the release time appears in the freight car incorporated with sliding and diaphragm valve respectively. We adapted quick release valve to reduce the difference of the release time and also found that this valve is useful for the purpose.

• Journal of electromagnetic engineering and science
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• v.8 no.4
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• pp.139-143
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• 2008

In this paper, a new scheme to calculate the weighting factor of the 2-D isotropic-dispersion finite difference time domain(ID-FDTD) is proposed. The weighting factor in [1] was formulated in free space, so that it may not be optimal in dielectric media. Therefore, the weighting factor was reformulated by considering the material properties and using the least mean square method. As a result, a minimum numerical dispersion error for any dielectric media is guaranteed.

• Journal of Hydrospace Technology
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• v.2 no.2
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• pp.80-87
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• 1996

A creep-buckling analysis is studied for a simply-supported viscoelastic column. The fluid-type four-parameter model is employed because of its general applicability to creep materials. Using the imperfection-based incremental approach, a nonlinear load deflection equation is derived. Safe load and critical (or life) time which characterize the stability of the viscoelastic column are obtained mathematically and interpreted physically. A finite difference algorithm is applied to solve the second-order differential equation of the viscoelastic stress-strain relation. Numerical calculation has been made and discussed far a SUS316 stainless steel column.

• Journal of the Korean Society of Safety
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• v.11 no.1
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• pp.129-132
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• 1996

This paper presents an experiment which examines eye movement characteristics of novice and experienced workers in the press operation. Significant difference between the novice and the experienced workers was observed in fixation time, eye movement patterns, and spatial distribution of fixations when the top die hits the bottom die. There were no significant difference between the novice and the experienced workers in eye movement time. The results could be used to set up a guide to train the novice workers and to determine how long the novice should be trained.

• Journal of the Korean Society for Nondestructive Testing
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• v.10 no.1
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• pp.38-46
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• 1990

It is difficult to detect such flaws as stress - corrosion cracking or corrosion wastage(loss of bolt diameter) in the threads. In many cases the critical size of a flaw is very small(1-2 mm order). This paper describes how it is possible to discriminate small flaw indications in threads using the time difference or thread signals(TDTS) by a signal-conditioning technique.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.2
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• pp.46-52
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• 2014

This paper presents a multiple gain controlled digital phase and frequency detector with a fast lock-time. Lock-time of the digital PLL can be significantly reduced by applying proposed adaptive gain control technique. A loop gain of the proposed digital PLL is controlled by three conditions that are very large phase difference between reference and feedback signal, small phase difference and before lock-state, and after lock-state. The simulation result shows that lock-time of the proposed multiple gain controlled digital PLL is 100 times faster than that of the conventional structure with unit gain mode.

• Journal of Chest Surgery
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• v.33 no.9
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• pp.723-728
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• 2000

Background: Minimally invasive techniques for open heart surgery are widely accepted in these days. There are minimally invasive approaches by the right or left parasternal incision and another approaches by mini-sternotomy of upper or lower half or sternum. We report the safety and efficacy of minimally invasive technique with right parasternal incision compared with the routine full sternotomy. Material and Method: From April 1997 through February 1999, 20 patients(Group A) underwent minimally invasive cardiac operations. We chose 41 patients(Group B) whose preoperative diagnosis were the same and general conditions were similar and who underwent routine full sternotomy before April 1997. We compared A group and B group in many aspects. We performed routine full median sternotomy in B group but we did a minimally invasive technique through a small right parasternal incision in A group. Result: mean age was 36.1 years in both groups. In disease entities, there were 11 cases of ASD, 9 cases of mitral valve disease in group A, and 16 cases of ASD, 25 cases of mitral valve diseases in group B. In ASD, operation time, cardiopulmonary bypass time of aortic occulusion time were 263 min, 82 min, and 41 min in group A and 180 min, 53 min, and 32 min in group B. In mitral valve disease, operation time, cardiopulmonary bypass time and aortic occlusion time were 267min, 106 min, and 70min in A group and were 207 min, 82 min, and 69 min in group B. There were significant differences in operation time, CPB time, and ACC time between group A and group B. There was a significant difference in the amount of bleeding in postoperative day 1 between group A and group B of mitral diasease. However, there was no significant difference in the amount of bleeding in other comparisons. Mean length of incision was 8.7 cm in group A. There was no significant difference in postoperative complications between A group and B group. There was no mortality in either group. Conclusion: We conclude that this minimally invasive technique with right parasternal incision is cosmetically excellent but it is not effective in reducing operative time and there was no significant difference in recovery time and postoperative complications compared with routine full sternotomy.