• 한국전산유체공학회:학술대회논문집
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• 1998.11a
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• pp.62-69
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• 1998

Spiral tube heat exchangers can find numerous applications in many engineering field. Flow in spital tubes is interest to engineers due to occurrence of secondary flow which enhances the cross-sectional mixing and the heat transfer rate. In the present study, an incompressible viscous 3-D flow in spiral tubes with rectangular cross-section of various torsion rate and Reynolds number is studied by using a finite volume method. It is shown that the axial velocity profile is affected by the secondary flow motion. Because there is some difference from correlation proposed by Hur et al., a lot of analysis and arrangement of experimental results are needed. This study showed the results of variation of hydrodynamic entry length for torsion and Re numbers.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.917-922
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• 2008

In order to reduce energy consumption, secondary controlled system has been applied to many types of equipments. In lifting equipments or press machines using hydraulic cylinder, a hydraulic transformer is used as a control component instead of a valve for motion control and a component for recovering potential energy of load. The transformer is combination of a variable displacement pump/motor as a secondary controlled element and a fixed displacement pump/motor. Based on the nominal model derived from mathematical model, the feedback type two-degree-of-freedom controller is designed and implemented. From simulation results, the disturbances including nonlinear friction torque, leakage flow and load force can be compensated and good positioning accuracy is obtained. It show that the proposed controller is effective.

• Proceedings of the KOSOMBE Conference
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• v.1992 no.11
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• pp.43-46
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• 1992

$\underline{In\;vitro}$ velocity measurements were made using both the pulsed Doppler ultrasound (PDU) machine and laser Doppler anemometer (LDA) system in order to investigate the flow characteristics near the aortic bifurcation. Velocities measured from the PDU machine was in good agreement with those from the LDA. The flow in the daughter branches was three-dimensional with a secondary flow. The oscillating wall shear stress with this secondary fluid motion is well correlated with the localization of the atherosclerosis.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.2
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• pp.33-40
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• 2000

In order to investigate the exhaust structure and secondary oxidation of unburned hydrocarbon (HC) in the exhaust port, a numerical simulation was performed with 3-dimensional flow model and oxidation mechanism optimized for port oxidation. To predict the exhaust and oxidation process with consideration of flow, mixing, and temperature, 3-dimensional flow model and HC oxidation model were used with a commercial computational program, STAR-CD. The flow model were with moving grid for valve motion, which could predict the change of flow field with respect to valve lift. Optimization was performed to predict the HC oxidation with temperature range of 1200~1500K, low HC and oxygen concentration, existence of intermediate species, as typical in port oxidation. The constructed model could predict the port oxidation process with oxidation degree of 14~48% according to the engine operation conditions.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.7
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• pp.796-804
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• 2011

Railway vehicles are capable of indicating several types of instability. This phenomenon, which is called hunting motion, is a self excited lateral oscillation that is caused by the running velocity of the vehicle and wheel frail interactive forces. The interactive forces act to change effectively the damping characteristics of railway vehicle systems. This paper will show the impact of instability on the transfer function behavior using damping characteristics of secondary suspension. The vehicle dynamics are modeled using a 17 degree of freedom considering linear wheel/rail contact. The paper deals with certain condition of the damper characteristics that one is about various damping coefficient and another is equipped damper direction.

• Proceedings of the KWS Conference
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• 2006.10a
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• pp.26-28
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• 2006

When materials such as metal are into the secondary side of steam generator, they, so called foreign objects, may have influences on the integrity of the steam generator tubes. They cause the tube wear due to the relative motion between the tubes and foreign objects and the tube impact due to flow. The best way to avoid the effects is to remove all the foreign objects. However, it is not easy to remove the foreign materials thoroughly due to their condition such as the location. Considering the wear and impact by the foreign materials, KEPRI(Korea Electric Power Research Institute) developed the methodology to evaluate the foreign materials analytically. This methodology was described with a computer program in order to obtain the fast results. The program informs whether the tubes have the structural integrity when the foreign material strikes the tubes. Moreover, this gives us the remaining life of the steam generator tubes. In this paper, the program, which evaluates the effects of the foreign objects in the secondary side of steam generator, is introduced.

• Journal of the Korean Society of School Health
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• v.1 no.1
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• pp.114-132
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• 1988

Aiming to appraise student's health status and recommend improvement and strengthening of the school health services, statistical analysis of the results of health examination were done with summarized data which were collected nation-wide through the Ministry of Education. After analysis of data obtained, the results of the study summarized as follows; 1) Requested Adequate care Requested Adequate care showed from 5 % to 3% in 1962 and 1984 respectively. In sexes, Requested Adequate in girls (2.8%) more apparent than in boys (2.5%) 2) Eyes i) Weak vision, abnormal refraction of eyes (myopia, hypermetropia and astigmatism), eye diseases (trachoma, others) were found as shown in the Table 2, Figure 3. Weak vision and abnormal refraction of eyes showed from 2 % (Elementary), 5 % ( Secondary) to 4 % (Elementary), 14 % (Secondary) in 1962 and 1984 respectively. In both sexes, the older the age of students the more weak vision and abnormal refraction of eyes had rapidly increased especially in over 15-year old. ii) Eye diseases (trachoma, others) showed from 2% to age of students the more diseases had students. 3) Ear, nose and pharynx Hearing disturbance, ear diseases (otitis mediae, others), nose (empyema, hypertrophy) and pharynx diseases were found as following 1) Hearing disturbance was found from 0.3%(Elementary), 1 %(Secondary) to 0.05 % (Elementary), 0.4 % (Secondary) in 1962 and 1984 respectively, however, recently the older the age of students the more had students. ii) Ear diseases showed from 1.7 % (Elementary) 1.0 % (Secondary) to 0.3 %(Elementary), 0.5%(Secondary) in 1962 and 1984 respectively. iii) In diseases of the nose and pharynx, tonsilitis showed from 2.5% (Elementary), 3.5 % (Secondary) to 1.8 % ( Elementary). 2.5% (Secondary) in 1962 and 1984 respectively. 4) Skin Infectious skin diseases and other skin diseases were found from 1.5% to 0.6% in 1962 am 1984 respectively. 5) Teeth Dental caries (in milk and permanent teeth) and otner oral diseases are shown from 12 % (Elementary), 8%(Secondary) to 75%( Elementary), 25% (Secondary) in 1962 and 1984 respectively. 6) Other defects and diseases A relatively higher morbidity was shown in the tubercular diseases, in anemia, and in heart diseases among the tuberculous diseases, nodular diseases, Pleurisy, heart diseases, anemia, beriberi, hernia, neurasthenia, speech difficulty, mental disorders, bone dysformity, motion difficulty of extremities. In both sexes, tuberculous diseases were found almost equally in both sexes and anemia in girls was more apparent than in boys. Trying to provide more effective health services in schools : i) A better and more effective physical examination should be carried out in each school and prior to the physical examination, the qualified daily observation of children by teacher should be keenly practiced. ii) According to the results of the required annual physical examination the leading cause of morbidity were dental caries, myopia, angina and otitis mediae and fore these diseases follow up should be carried out. iii) For prevention and treatment of diseases and defects health education for students in the classroom as well as to parents is urgently requested.

• Journal of Ocean Engineering and Technology
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• v.24 no.6
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• pp.51-60
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• 2010

In this study, the performance evaluation of a conventional wave resonator at the entrance of a port or a pier against secondary undulation has been performed using 2D hydrodynamic modeling within port. A wave resonator has been designed for the attenuation of the secondary undulation induced by the long-periodic waves. The controlled performance of the wave resonator has been numerically investigated for CGWAVE MODULE of finite-element model of SMS (Surface water Modeling System) based on the elliptic mild-slope wave equation. SMS was verified though the comparisons with analytical solution performed by Ippen and Goda (1963). Also, It was confirmed that a wave resonator of a rectangular model harbor is effective enough to control the secondary undulation when it compares variation of water level with the case of no resonance system. From the above results, amplification phenomenon induced by long-period waves transferred from 1900 sec to 2100 sec when it applied a wave resonator in Busan Gamcheon Port which is a deep-sea. And it was confirmed that a wave resonator of Pohang New Port attenuates largely long-period waves which are within the range of 300 sec induced by long-period motion of the moored ship.

• Journal of Astronomy and Space Sciences
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• v.13 no.1
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• pp.63-71
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• 1996

A total of 546 UBV photoelectric observations of AG Per was carried out from January to December in 1993 at Chungbuk National University Observatory. With our observations, UBV light curves were constructed, three minimum times of JDHel. 2449284.213, JDHel. 2449360.060, and JDHel. 2449363.192 were determined. The phase displacement of secondary minimum time $\delta$=-0.046 were determined and orbital eccentricity e=0.071 was calculated. Forty-five times of minimum light (including ours) were collected from the literature and plotted on O-C diagram. We analyzed these data and apsidal motion period of U=76.17 (years) was obtained. Using e and U for AG Per, the internal structure constant, log k2, was found to be -2.13.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.1321-1326
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• 2011

THE RAILWAY VEHICLE IS CONSISTS OF CARBODY, BOGIE AND WHEELSETS, EACH OF COMPONENTS IS CONNECTED WITH RIGID MASS, SPRING AND DAMPER. EACH OF COMPONENTS HAS TRANSLATION MOTIONS OF LONGITUDINAL (X AXIS), LATERAL (Y AXIS) AND VERTICAL (Z AXIS) DIRECTIONS, ROTATION MOTIONS OF X, Y, Z AXIS WHICH ARE NAMED ROLLING, PITCHING AND YAWING. THE VIBRATION MODE OF RAILWAY VEHICLE IS DIFFICULT TO FIND THE CHARACTERISTICS OF MOTION DURING THE OPERATION ON THE TRACK BECAUSE THESE HAPPEN TO INDEPENDENCE OR DUPLICATION MOTION CAUSED BY VEHICLE, WHEEL/RAIL AND TRACK IRREGULARITY ETC. IT IS NAMED AN ABNORMAL VIBRATION THAT THE VIBRATION, WHICH WAS PASSED THE PRIMARY AND SECONDARY SUSPENSION, IS AFFECTED TO THE PASSENGER WITHOUT DAMPING. THIS PAPER DESCRIBES AN EXPERIENCE EVALUATION TO FIND THE CAUSE OF AN ABNORMAL VIBRATION WHICH WAS HAPPEN AT OPERATING SPEED 60KPH ZONE DURING THE MAINLINE TEST.