• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 추계학술대회 논문집(III)
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• pp.473-478
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• 2003

The hydraulic buffer stop placed on the end of the railway brakes the train could not reduce the velocity sufficiently because of the braking system troubles or driver's mistakes. The hydraulic buffer stop is composed of 2 operating parts; hydraulic buffers and rail clamps. Hydraulic buffers brake trains non-destructively in low speed, otherwise rail clamps begin to work in higher speed. In this paper, The braking process of the hydraulic buffer stop is investigated by numerical methods. The hydraulic buffer is numerically analyzed and designed to absorb the kinematic energy of the train below 3.2km/h speed. The hydraulic buffer stop crushed by the train with 5km/h speed is analyzed by FEM package-PAM CRASH in order to obtain the stress profile in rail clamps and buffer stop frame.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1995년도 추계학술발표회논문집(1)
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• pp.377-382
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• 1995

An evaluation method of spacer grid thermal mixing performance in rod bundles is suggested based on hydraulic tests in a single phase flow. Heat transfer correlation was derived by the analogy between momentum and heat transfer. Three of major factors, such as blockage ratio of spacer grid, convective flow swirling, and turbulent intensity, were found to be significantly influential to the spacer grid thermal mixing performance. Local heat transfer near spacer grid was predicted for the hydraulic test of 6 ${\times}$ 6 rod bundles with neighboring different spacer grids.

• International Journal of Safety
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• 제3권1호
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• pp.32-37
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• 2004

Recently KAERI has developed the severe accident management guidance to establish Korea standard severe accident management system. On the other hand the PC-based severe accident training simulator SATS has been developed, and the MELCOR code is used as the simulation engine. SATS graphically displays and simulates the severe accidents with interactive user commands. The control capability of SATS could make a severe accident training course more interesting and effective. In this paper the development and functions of the electrical hypertext guidance module HyperKAMG and the SATS-HyperKAMG linkage system for the severe accident management are described.

• International Journal of Fluid Machinery and Systems
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• 제9권3호
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• pp.237-244
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• 2016

An unsteady three-dimensional simulation based on Reynolds time-averaged governing equation and RNG $k-{\varepsilon}$ turbulence model, was presented for pump-as-turbine, the pressure fluctuation characteristic of hydraulic turbine with guide vane was obtained. The results show that the time domains of pressure fluctuation in volute change periodically and have identical cycles. In volute tongue and inlet pressure fluctuations are light, while in dynamic and static coupling interface pressure fluctuations are serious; In impeller blade region the pressure fluctuation of pressure surface are lighter than that of suction surface. The dominant frequencies of pressure fluctuation concentrate in low frequency region, and concentrate within 2 times of the blade passing frequency.

• Journal of Advanced Marine Engineering and Technology
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• 제33권7호
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• pp.1052-1059
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• 2009

The effects of varying the inlet flow angle on the output power of a Francis hydraulic turbine were studied numerically and the result was compared to the experimental results conducted at Korea Institute of Energy Research to determine the brake power of the turbine for each set of operating conditions. The loss of mechanical power of the model turbine was determined by comparing the numerical and experimental results, and thus the turbine efficiency or energy conversion efficiency of the model turbine could be estimated. From the result, it was found that the maximum brake efficiency of the turbine is approximately 46% at an induced angle of 35 degrees. The maximum indicated mechanical efficiency of the turbine is approximately 93% at an induced angle of 25~30 degrees.

• Tribology and Lubricants
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• 제29권3호
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• pp.186-191
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• 2013

Hydraulic systems are used to transform mechanical energy into fluid energy and vice versa. They are widely applied in various industries; e.g., they are used in automobiles, public works, rockets, machine tools, heavy construction equipment, and airplanes. Hydraulic pumps are used to transform the energy in these systems. In this study, with the basic operation principles as a starting point, I attempted to clarify how the shape of a slipper affects the lubrication characteristics under practical conditions. A swashplate with a tilt angle of zero and capable of rotating motion was used, along with other devices. A slipper was located at 45 mm eccentricity from the center of the swashplate. The results of this experiment indicated that the shape of the bottom surface of a slipper affects the load capacity, leakage flow, and lubrication characteristics and that the slipper is one of the most important parts for improving the pump efficiency.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2004년도 학술발표회
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• pp.54-61
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• 2004

This paper deals with flow characteristics on the air entrainment and the energy dissipation in nappe flow over the stepped drop structure. Nappe flow occurred at low flow rates and for relatively large step height Dominant flow features include an air pocket, a free-falling nappe impact and a subsequent hydraulic jump on the downstream step. Air entrainment occurred from the step edge, through a free-falling nappe impact and a hydraulic jump. Most energy was dissipated by nappe impact and in the downstream hydraulic jump. It was related with the step height and the overflow depth, but not related with step slope. The stepped drop structure was found to be effcient for water treatment and energy dissipation associated with substantial air entrainment.

• 유공압시스템학회논문집
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• 제6권1호
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• pp.17-24
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• 2009

The performance improvement of a small-size integrated-type fully hydraulic breaker is studied in this paper. Mathematical modeling of the breaker is established and verified by experiment. Through sensitivity analysis using AMESim, the key design parameters are selected and nearly optimized to maximize the impact energy as well as to improve the dynamic characteristics such as the piston upper chamber pressure, piston and valve displacements. As a result, the impact energy, blows per minute(bpm) and output power are increased by 52.9%, 1%, and 55.6%, respectively compared with the current design. The dynamic characteristics of the piston upper chamber pressure, piston and valve displacements are also improved by the design change.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.401-404
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• 2008

The vegetation in the surrounding area of river is a primary factor to increase water level during flood. The influence of vegetation on the river flow in a bank has been investigated by using a hydraulic experiment. For a hydraulic experiment square-shaped piers are used as a model of unsubmerged rigid vegetation in a open channel. For fully developed uniform flows, the water elevation of the experiment was measured as varying the interval of piers and the porosity which presents the fraction of water flowing area in the cross-sectional area. The Manning's roughness coefficient, which implicates energy losses due to the vegetation, was obtained by using the experimental data. As a result, the energy losses were varied when the distance of piers and the porosity of area were changed, and the Manning's coefficient increased nonlinearly when a water elevation increased.

• Nuclear Engineering and Technology
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• 제31권6호
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• pp.39-50
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• 1999

The physicochemical, mineralogical, hydraulic, swelling and mechanical properties of a domestic bentonite for use as the buffer material in a high-level waste repository have been measured. The bentonite is identified to be a Ca-bentonite, and the hydraulic conductivity of the compacted bentonite with the dry density higher than 1.4 Mg/㎥ is lower than 10$^{-11}$ m/s When the dry densities are 1.4 to 1.8 Mg/㎥, the swelling pressures are in the range of 6.6 to 143.5 kg/$\textrm{cm}^2$. The unconfined compressive strength is about 94 kg/$\textrm{cm}^2$, and the coefficient of volume change and the coefficient of consolidation are in the range of 0.O0249 to 0.02142 $m^2$/MN and 0.018 to 0.115$m^2$/year, respectively.