• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2001년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2001
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• pp.364-372
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• 2001

An orifices fluid damper(OFD) having the capacity of about 2 tons was designed and fabricated and applied to a 6-story steel structure under random excitation and seismic excitation for the confirmation of its validity on structural vibration absorbtion. The experimental results demonstrated that the addition of an OFD to the test structure is very effective in reduction of vibration level of the higher modes as well as the fundamental mode. Maxwell model was adopted to described the frequency-dependent characteristics of the fabricated OFD and the numerical simulation was carried for the test structure. It was confirmed that the experimental and numerically simulated results agree well.

• 한국소음진동공학회논문집
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• 제12권6호
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• pp.469-477
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• 2002

An orificed fluid damper(OFD) having the capacity of about 2 tons was designed and fabricated, and series of tests were performed to grasp the fundamental performance characteristics of it. Several important findings were observed and introduced in this paper. It was applied to a 6-story steel structure under random excitation and seismic excitation for the confirmation of its validity on structural vibration absolution. The experimental results demonstrated that the addition of an OFD to the test structure is very effective in reduction of vibration level of the higher modes as well as the fundamental mode. Maxwell model was adopted to describe the frequency-dependent characteristics of the fabricated OFD and the numerical simulation was carried for the test structure. It was confirmed that the experimentally and numerically simulated results agree well.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2005년도 연구개발 발표회 논문집
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• pp.240-243
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• 2005

This study deals with the shape optimization of a wire spacer fuel assembly of Liquid Metal Reactors (LMRs). The Response Surface based optimization Method is used as an optimization technique with the Reynolds-averaged Navier-Stokes analysis of fluid flow and heat transfer using Shear Stress Transport (SST) turbulence model as a turbulence closure. Two design variables namely, pitch to fuel rod diameter ratio and lead length to fuel rod diameter ratio are selected. The objective function is defined as a combination of the heat transfer rate and the inverse of friction loss with a weighting factor. Three level full-factorial method is used to determine the training points. In total, nine experiments have been performed numerically and the resulting datas have been analysed for optimization study. Also, a comparison has been made between the optimized surface and the reference one in this study.

• 한국정밀공학회지
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• 제26권4호
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• pp.55-63
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• 2009

This paper reports on the theoretical and experimental study of the pressure ripples in a pressure unbalanced type vane pump which have widespread use in industry. Because they can infinitely vary the volume of the fluid pumped in the system by a control. Pressure ripples occur due to the flow ripples induced by geometry of side plate, leakage flow, reverse flow from the outlet volume produced by pressure difference between pumping chamber and outlet volume when the pumping chamber connected with the outlet volume. In this paper, we measured the pressure variation of a pumping chamber, reaction force on a cam ring, the mathematical model for analyzing the pressure ripples which included vane detachment and fluid inertia effects in notch area has been presented, and was applied to predict the level and the wave form of the pressure ripples according to operating conditions.

• Structural Engineering and Mechanics
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• 제16권4호
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• pp.423-440
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• 2003

Arbitrary Lagrangian Eulerian finite element methods gain interest for the capability to control mesh geometry independently from material geometry, the ALE methods are used to create a new undistorted mesh for the fluid domain. In this paper we use the ALE technique to solve fuel slosh problem. Fuel slosh is an important design consideration not only for the fuel tank, but also for the structure supporting the fuel tank. "Fuel slosh" can be generated by many ways: abrupt changes in acceleration (braking), as well as abrupt changes in direction (highway exit-ramp). Repetitive motion can also be involved if a "sloshing resonance" is generated. These sloshing events can in turn affect the overall performance of the parent structure. A finite element analysis method has been developed to analyze this complex event. A new ALE formulation for the fluid mesh has been developed to keep the fluid mesh integrity during the motion of the tank. This paper explains the analysis capabilities on a technical level. Following the explanation, the analysis capabilities are validated against theoretical using potential flow for calculating fuel slosh frequency.

• Nuclear Engineering and Technology
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• 제44권6호
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• pp.623-638
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• 2012

The volume of fluid (VOF) model of FLUENT and the lattice Boltzmann method (LBM) are used to simulate two-phase flows. Both methods are validated for static and dynamic bubble test cases and then compared to experimental results. The VOF method does not reduce the spurious currents of the static droplet test and does not satisfy the Laplace law for small droplets at the acceptable level, as compared with the LBM. For single bubble flows, simulations are executed for various Eotvos numbers, Morton numbers and Reynolds numbers, and the results of both methods agree well with the experiments in the case of low Eotvos numbers. For high Eotvos numbers, the VOF results deviated from the experiments. For multiple bubbles, the bubble flow characteristics are related by the wake of the leading bubble. The coaxial and oblique coalescence of the bubbles are simulated successfully and the subsequent results are presented. In conclusion, the LBM performs better than the VOF method.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.2005-2010
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• 2004

Ultrasonic cleaning is performed by cavitation which is caused by the change of the sound pressure due to the vibration in a cleaning tank. In this study, experiments on electric power and sound pressure with various temperatures, dissolved oxygen and the level of the fluid was done in order to find out how the changes in a cleaning tank affect cavitation. As a result of a series of experiments, we found that transducer impedance changes periodically in response to the variances of fluid and have a direct influence on cleaning efficiency.

• Journal of Chest Surgery
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• 제54권5호
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• pp.408-411
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• 2021

Tuberculosis (TB)-infected giant bullae are rare. A 55-year-old man was referred when an infected bulla did not respond to empirical treatment. Computed tomography showed a giant bulla in the right upper lobe with an air-fluid level and surrounding infiltrate. Sputum culture, acid-fast bacilli (AFB) stain, and polymerase chain reaction (PCR) for TB were negative. Percutaneous drainage of the bullous fluid was performed. AFB stain and PCR were positive in the drained fluid. The patient was given anti-TB drugs and later underwent obliteration of the pulmonary cavity using talc. To summarize, we report a patient with a TB-infected giant bulla that was treated successfully with anti-TB drugs and obliteration of the pulmonary cavity using talc.

• Nuclear Engineering and Technology
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• 제54권6호
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• pp.2120-2134
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• 2022

A hypothetical core destructive accident (HCDA) has received widespread attention as one of the most serious accidents in sodium-cooled fast reactors. This study combined recent advantages in numerical methods to realize realistic modeling of the complex fluid-structure interactions during HCDAs in a full-scale sodium-cooled fast reactor. The multi-material arbitrary Lagrangian-Eulerian method is used to describe the fluid-structure interactions inside the container. Both the structural deformations and plug rises occurring during HCDAs are evaluated. Two levels of expansion energy are considered with two different reactor models. The simulation results show that the container remains intact during an accident with small deformations. The plug on the top of the container rises to an acceptable level after the sealing between the it and its support is destroyed. The methodology established in this study provides a reliable approach for evaluating the safety feature of a container design.

• East Asian Economic Review
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• 제21권3호
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• pp.259-274
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• 2017

This study estimates the random utility function of fluid milk using 1,165 survey responses in Laos. It finds that both products' attributes and individual characteristics affect consumers' preference for the milk and the hypothetical brand of Laos-Korea has a potential compared to four real dairy products. Results also show that calories have a positive relationship with consumer's preference while the price and fat content have a negative one. The decision for choosing each brand is significantly affected by individual characteristics such as gender, age, whether or not respondents live with their children, the level of education, income, the frequency of purchasing milk per week, and the region where they live. The preference for five brands appears in the order of Foremost, Nabong, Thai-Danish, Meiji, and Lao-Korea, and probabilities of purchasing each brand at the mean level are 30.9%, 17.48%, 21.48%, 15.0% and 10.39%, respectively. Nabong that was Lao national milk brand still has a significant market power even though it was closed in 2008. The policies to promote milk industry by implementing its national milk brand again would be more effective if it focuses on the young generation, female consumers, families with children, quality of dairy products, and Vientiane capital areas.