• Journal of the Korean Society for Marine Environment & Energy
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• v.6 no.4
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• pp.45-51
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• 2003

The reflection and transmission of submerged breakwater with trapezoidal type are computed numerically using boundary element method. The analysis method is based on the wave pressure function with the contlnuit? in the analytical region including fluid and porous structures. Wane motion within the porous structures is simulated by introducing the linear dissipation coefficient and added mass coefficient. The results indicate that transmission and reflection coefficient are determined due to the change of slope of submerged breakwater with trapezoidal type.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.357-360
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• 2002

The effect of distance between ninety degree elbow close to upstream face of orifice plate and orifice plate on discharge coefficient was investigated. The distributions of discharge coefficient and differential pressure caused by elbow and short upstream straight length were examined and modified discharge coefficient was introduced. The results presented in this study could be useful when orifice plate is installed under the condition of simple flow disturbance element and short upstream straight length.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.4
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• pp.62-66
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• 2012

The objective of this study is to simulate flow coefficient and flow characteristics such as velocity and pressure distribution for butterfly valve. Butterfly valves used in this study are 65A, 80A and 100A, in size, and of which the opening angle is varied. The flow coefficient, Kv, increases as the disc opening and valve size are increase. When using flow coefficient meanwhile specific curve of flow rate is also determined. The flow velocity between disc and seat increase as the disc opening decrease. The re-circulating zone is also observed in downstream behind disc.

• Transactions of Materials Processing
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• v.22 no.4
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• pp.223-228
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• 2013

The friction coefficients of advanced high strength steel sheets were experimentally determined. In the friction test, the pulling and holding forces acting on the sheet for various friction conditions, such as lubricant viscosity, pulling speed, blank holding pressure, sheet surface roughness, and hardness of the sheet were measured and the friction coefficient was calculated based on Coulomb's friction law. While the friction coefficient, generally, decreases as the value of friction factor increases, the factor associated with the sheet surface roughness shows U shape behavior for the friction coefficient. Furthermore, the relationship between friction coefficient and the wear volume, which was computed for the roughness of both sheet surfaces and the friction area, is linearly proportional.

• Tribology and Lubricants
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• v.19 no.3
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• pp.159-166
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• 2003

This research for replacement of chlorine or sulfur based EP(extreme pressure) -additives which is restricted materials by environmental regulation. The subject of this study is as follows, 4-ball test and friction coefficient test were experimented in accordance with temperature and velocity, compounding with several organic or inorganic metallic elements. After 4-ball test, wear area of steel ball was analysed by SEM-EDX. As the analysis, organic and inorganic elements make a effect for extreme pressure lubricity. It is shown that the friction coefficient of lubricant which includes chlorine or sulfur additives, the scoring phenomenon is found accord-ing to temperature and the scuffing phenomenon at 200$^{\circ}C$. Applying to Na, P, S, Zn, Ca based on inorganic and organic elements, the result showed that friction coefficient is decreased more and more, as increasing temperature of lubricant. The additive based on S, Cl, P elements is effect far extreme pressure in the sample#1 and Na, P, S, Zn, Ca in sample #2. These elements are environmental contaminants and S, Cl based on EP additives which are very popular in domestic industry, when they are properly composed with non-chlorine based on additives and Na, P, S, Zn, Ca organic or inorganic elements. It is showed that lubricity and excellent anti-wear properties.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.6
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• pp.1026-1036
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• 2004

In this study, single-phase heat transfer experiments were conducted with Oblong Shell and Plate heat exchanger using water. An experimental water loop has been developed to measure the single-phase heat transfer coefficient and pressure drop in a vertical Oblong Shell and Plate heat exchanger. Downflow of hot water in one channel receives heat from the cold water upflow of water in the other channel. Similar to the case of a plate heat exchanger, even at a very low Reynolds number, the flow in the Oblong Shell and Plate heat exchanger remains turbulent. The present data show that the heat transfer coefficient and pressure drop increase with the Reynolds number. Based on the present data, empirical correlations of the heat transfer coefficient and pressure drop in terms of Nusselt number and friction factor were proposed. Also, performance prediction analyses for Oblong Shell and Plate heat exchanger were executed and compared with experiments. $\varepsilon$-NTU method was used in this prediction program. Independent variables are flow rates and inlet temperatures. Compared with experimental data, the accuracy of the program is within the error bounds of $\pm$5% in the heat transfer rate.

• Journal of Mechanical Science and Technology
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• v.17 no.10
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• pp.1563-1571
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• 2003

A fast response NO analyzer was applied to investigate the relation between cycle-by-cycle NO emissions and combustion chamber pressure. NO emissions were sampled at an isolated exhaust manifold of 4-stroke spark ignition engine to avoid the interference of exhaust gas from other cylinders. The linear correlation analysis was performed with collected data of NO emissions and combustion chamber pressure with respect to the various air-fuel mixture ratios and engine loads. The sampled data sets were obtained during 200 cycles at each operating condition. The results showed that there was a typical pattern in NO emissions from an exhaust port through a cycle. It was possible to set a block of crank angle in which the linear correlation coefficient between NO emissions and combustion chamber pressure was high. As the engine load increased, NO emissions were more dependent on combustion chamber pressure after TDC. It was also analyzed that the correlation between two parameters with respect to air-fuel mixture ratio tended to increase as mixture went leaner. Furthermore, this correlation coefficient for the mixture near the lean limit seemed to be kept high even though combustion was unstable.

• Geomechanics and Engineering
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• v.6 no.1
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• pp.17-31
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• 2014

This paper investigates the development of failure surfaces induced by an embankment on soft marine clay deposits and the characteristics of such surfaces through numerical simulations and its comparative study with monitoring results. It is well known that the factor of safety of embankment slopes is closely related to the vertical loading, including the height of the embankment. That is, an increase in the embankment height reduces the factor of safety. However, few studies have examined the relationship between the lateral movement of soft soil beneath the embankment and the factor of safety. In addition, no study has investigated the distribution of the pore pressure coefficient B value along the failure surface. This paper conducts a continuum analysis using finite difference methods to characterize the development of failure surfaces during embankment construction on soft marine clay deposits. The results of the continuum analysis for failure surfaces, stress, displacement, and the factor of safety can be used for the management of embankment construction. In failure mechanism, it has been validated that a large shear displacement causes change of stress and pore pressure along the failure surface. In addition, the pore pressure coefficient B value decreases along the failure surface as the embankment height increases. This means that the rate of change in stress is higher than that in pore pressure.

• Journal of Power System Engineering
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• v.12 no.4
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• pp.26-31
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• 2008

The evaporation heat transfer coefficient and pressure drop of R-22 and R-407C in a small diameter copper tube were investigated experimentally. The main components of the refrigerant loop are a receiver, a compressor, a mass flow mete, a condense and a double pipe type evaporate (test section). The test section consists of a smooth copper tube of 4.3 mm inner diameter. The refrigerant mass fluxes were varied from 100 to $300[kg/m^{2}s]$ and the saturation temperature of evaporator were $5[^{\circ}C]$. The evaporation heat transfer coefficients of R-22 and R-407C increase with the Increase in mass flux and vapor quality. The evaporation heat transfer coefficient of R-22 is about $7.3\sim47.1%$ higher than that of R-407C. The evaporation pressure drop of R-22 and R-407C increase with the increase of mass flux. The pressure drop of R-22 is about $8\sim20%$ higher than that of R-407C.

• Journal of Korean Association for Spatial Structures
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• v.17 no.4
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• pp.103-113
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• 2017

Spatial Structure has suffered from a lot of damage due to the use of lightweight roofs. Among them, the damage caused by strong winds was the greatest, and the failure of the calculation of the wind load was the most frequent cause. It provides that wind tunnel test is used to calculate the wind load. However, it is often the case that the wind load is calculated based on the standard of wind load in the development design stage. Therefore based on this, the structure type and structural system and member design are often determined. Spatial structure is usually open at a certain area. The retractable roof structure should be operated with the open roof in some cases, so the wind load for the open shape should be considered, but it is not clear on the basis of the wind load standard. In this paper, the design wind pressure of a closed and retractable roof structure is calculated by KBC2016, AIJ2004, ASCE7-10, EN2005, and the applicability of wind pressure coefficient is compared with wind tunnel test.