• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.2
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• pp.177-185
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• 2015

City-based Lifeline is expected to cause significant social and economic loss accompanied the secondary damage such as paralysis of urban functions and a large fire as well as the collapse caused by earthquake. Earthquake Disaster Response System of Korea is being operated with preparation, calculates the probability of failure of the facility through Seismic Fragility Model and evaluates the degree of earthquake disaster. In this paper, the time history analysis of buried gas pipeline in city-based lifeline was performed with consideration for ground characteristics and also seismic fragility model was developed by maximum likelihood estimation method. Analysis model was selected as the high-pressure pipe and the normal-pressure pipe buried in the city of Seoul, Korea's representative, modeling of soil was used for Winkler foundation model. Also, method to apply developed fragility model at GIS is presented.

• Journal of Advanced Marine Engineering and Technology
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• v.13 no.4
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• pp.63-74
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• 1989

It is well-known that the fuel injection system if a diesel engine has taken a more important place in understanding of diesel combustion process with combustion chamber. But a diesel fuel injection system has an assembly of many complex and intricate problems such as the desired rate of injection, secondary injection and injection pump etc., in addition to the atomization for ignition and combustion, the penetration and diestribution for proper utilization of air. The analysis is carried out by simplifing and modeling the injection phenomena and dividing into three parts comprising of fuel injection pump, high pressure pipe and fuel injection nozzle. The purpose of this paper is to describe an analytical simulation of the injection system and to speed up the work of developing injection systems for new engines. The effects of important injection parameters as predicted by the present model are found to be in good agreement with experiment. It can be seen that there is an optimal pipe diameter for maximum quantity injected.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.6
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• pp.462-469
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• 2014

After drilling operations at the offshore plant, crude oil is producted under high pressure. After that time, oil recovery is reduced, because the pressure of the pipe inside is low during the secondary produce. At that time injection sea water at the pipe inside through water injection pump that the device increase to recovery. A variety of mathematical analysis during the detailed design analysis was not made through the dynamics characteristic at the domestic company. 2D model has reliability of analysis results for the uncomplicated model. Also element and the node the number of significantly less than in the 3D model. So, the temporal part is very effective. In addition, depending on the quality of mesh 3D is a real model and FEM model occurs error. So, user needs a lot of skill. In this paper, a 2D finite element analysis was performed through the dynamics analysis and the study model was validated.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.4
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• pp.317-326
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• 2020

In this study, damages caused by flash fire, overpressure, and thermal radiation based on the sizes of leak holes were evaluated using the areal location of hazardous atmospheres when natural gas leaked owing to the damage of pipeline in a LNG fueled ship. In addition, environmental variables (wind speed, atmospheric temperature, and atmospheric stability) and process variables (pipe pressure and pipe length) were classified to analyze the damage impact ranges caused by various scenarios. From the results, the damage range caused by the environmental variables was the largest, followed by overpressure and thermal radiation. Additionally, for the process variables, regardless of the pressure, length, or size of the leak holes, the damage range attributed to flash fire was the most significant, and the damage range was high in the order of overpressure and thermal radiation, similar to the environmental variables. The larger the size of the leak holes, the higher the values of the environmental and process variables, and the higher the damage range caused by jet fire compared to the environmental variables.

• Fire Science and Engineering
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• v.24 no.5
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• pp.94-101
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• 2010

The pipes using in water-based fire protection systems are used steel pipes for ordinary piping, carbon steel pipes for pressure service, copper and copper alloy seamless pipes and tubes, etc. By last buildings of high-rising, complexity, in fire protection systems, the corrosion resistance, easy construction, lightweight and cost-effective use of the pipes is being considered. Among the pipes, the possibility of used for fire protection system being used in the existing copper pipe of material properties, strength, corrosion resistance, heat resistance through and compare the performance was evaluated. As a result of that assessment light gauge stainless steel pipes for ordinary piping (KS D 3595) at a water pressure of less than 1.2 MPa can be used in sufficient physical properties, strength, corrosion resistance, heat resistance and have been observed.

• Journal of the Korean Geosynthetics Society
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• v.2 no.2
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• pp.3-11
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• 2003

Researches on the induced trench method using compressible materials such as clay, mud, straw, or EPS block have been performed to reduce the load acting on buried conduits under a high fill. The induced trench method has the problems that the arching area due to the compressible arching material is one dimensional or localized in a narrow zone. The main purpose of this study is to solve the problems of the induced trench method mentioned above. The various types of laboratory model tests are conducted to find the effects of the variations of EPS block width, multilayer application, soil density, and diameter of the flexible steel pipe. A series of model tests was conducted to evaluate the reduction of earth pressure on conduits using EPS block. Based on modeling test it is found that the magnitude of vertical earth pressure on conduits was reduced about 60% compared with conventional flexible conduit systems.

• Nuclear Engineering and Technology
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• v.49 no.3
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• pp.476-483
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• 2017

The decay heat that is produced by nuclear reactor spent fuel must be cooled in a spent fuel storage pool. A wickless heat pipe or a vertical two-phase closed thermosyphon (TPCT) is used to remove this decay heat. The objective of this research is to investigate the thermal performance of a prototype model for a large-scale vertical TPCT as a passive cooling system for a nuclear research reactor spent fuel storage pool. An experimental investigation and numerical simulation using RELAP5/MOD 3.2 were used to investigate the TPCT thermal performance. The effects of the initial pressure, filling ratio, and heat load were analyzed. Demineralized water was used as the TPCT working fluid. The cooled water was circulated in the water jacket as a cooling system. The experimental results show that the best thermal performance was obtained at a thermal resistance of $0.22^{\circ}C/W$, the lowest initial pressure, a filling ratio of 60%, and a high evaporator heat load. The simulation model that was experimentally validated showed a pattern and trend line similar to those of the experiment and can be used to predict the heat transfer phenomena of TPCT with varying inputs.

• Tribology and Lubricants
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• v.37 no.6
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• pp.253-260
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• 2021

Metal pipes are used in a wide range of applications, from plumbing systems of large construction sites to small devices such as medical tools. When a liquid is enforced to flow through a metal pipe, a higher flow rate is beneficial for higher efficiency. Using high pressures can enhance the flow rate yet can be harmful for medical applications. Thus, we consider an optimal geometrical design to increase the flow rate in medical devices. In this study, we focus on cannulas, which are widely used small metal pipes for surgical procedures, such as liposuction. We characterize the internal flow rate driven by a negative pressure and explore its dependence on the key design parameters. We quantitatively analyze the suction characteristics for each design variable by conducting computational fluid dynamics simulations. In addition, we build a suction performance measurement system which enables the translational motion of cannulas with pre-programmed velocity for experimental validation. The inner diameter, section geometry, and hole configuration are the design factors to be evaluated. The effect of the inner diameter dominates over that of section geometry and hole configuration. In addition, the circular tube shape provides the maximum flow rate among the elliptical geometries. Once the flow rate exceeds a critical value, the rate becomes independent of the number and width of the suction holes. Finally, we introduce a slippery liquid-infused nanoporous surface (SLIPS) coating using nanoparticles and hydrophobic lubricants that effectively improves the flow rate and antifouling property of cannulas without altering the geometrical design parameter.

• The Journal of the Acoustical Society of Korea
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• v.43 no.1
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• pp.122-130
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• 2024

Vibration of compressor in the air-conditioner outdoor unit have known to be main noise source radiated from outdoor unit. However, as the operating speed of compressor increase, the relative contribution of flow induced vibration and noise is also increase. In this paper, the numerical method was established to predict fluid-borne noise from compressor discharging pipe of air-conditioner outdoor unit. In this step, numerical result was compared to experimental one to verify numerical method. Additionally, the effects of pressure pulsation of compressor and compressor vibration into radiated noise were investigated in frequency domain. It was confirmed that the compressor vibration contributed to the low frequency band, while the pressure pulsation dose to the high frequency band.

• Journal of Ocean Engineering and Technology
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• v.13 no.2 s.32
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• pp.90-98
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• 1999

Boiler high-temperature pipelines such as main steam pipe, header and steam drum in fossil power plants are degraded by creep damage due to severe operationg conditions like high temperature and high pressure for an extended period time. Such material degradation lead to various component faliures causing serious accidents at the plant. Conventional measurement techniques such as replica method, electric resistance method, and hardness test method have such disadvantages as complex preparation and measurement procedures, too many control parameters, and therefore, low practicality and they were applied only to component surfaces with good accessibility. In this study, both artificial creep degradation test using life prediction formula and frequency analysis by ultrasonic tests for their preparing creep degraded specimens have been carried out for the purpose of nondestructive evaluation for creep damage which can occur in high-temperature pipelline of fossil power plant. As a result of ultrasonic tests for crept specimens, we confirmed that the high frequency side spectra decrease and central frequency components shift to low frequency bans, and bandwiths decrease as increasing creep damage in backwall echoes.