• 대한기계학회논문집B
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• 제24권6호
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• pp.792-801
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• 2000

The problem of phase change from liquid to solid in the inviscid plane-stagnation flow is theoretically investigated. The solution at the initial stage of freezing is obtained by expanding it in powers of time, and the final equilibrium state is determined from the steady-state governing equations. The transient solution is dependent on the three dimensionless parameters, but the equilibrium state is determined by one parameter of (temperature ratio/conductivity ratio). The effect of the fluid flow on the growth rate of the solid in the pure conduction problem can be clearly seen from the solution of the initial stage and the final equilibrium state. The characteristics of the transient heat transfer at the surface of the solid and the liquid side of the solid-liquid interface for all the dimensionless parameters are elucidated.

• 한국정밀공학회지
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• 제15권6호
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• pp.139-144
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• 1998

In Semi-Solid Forging, it is necessary to control the forming variables accurately in order to make near-net-shape products. Generally, the defects of products may occur due to liquid segregation which can be caused by the degree of deformation and strain rate, and condition of friction in Semi-Solid Forging, where the segregation is to be predicted by flow analysis. This paper presents the feasibility of theoretical analysis model using the new yield function for compressible P/M materials which is proposed by Doraivelu et at. to the flow analysis of the semi-solid dendritic Sn-15％Pb alloys instead of adopting the yield criterion of Shima and Oyane which is used by Charreyron and Flemings. The simple compression process is taken into consideration as the model to confirm the usefulness of the adopted yield function. The distribution of the liquid fraction at various strains and strain rates in radial direction, and the influence of friction are estimated by upper-bound method.

• 한국주조공학회지
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• 제18권3호
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• pp.234-239
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• 1998

Unidirectional solidification of $Al-CuAl_2$ eutectic composites was studied under the condition of forced convection by vibration. It has been shown that thermal gradient for solid is different from that for liquid during solidification under force convection by vibration. With increase of vibration, mobility of liquid increases, but decreases with decreasing vibration. The rate of solidification is very high initially, and decreases suddenly. For further solidification, the rate of solidification decrceases slowly, and shows a L-type behavior. The mechanical vibration during solidification effects efficiently on nucleation, and induces a forced convection in liquid. By the forced convection, great thermal gradient of liquid interface between solid and liquid can be obtained. The amount of solute near the interface also decreases as solute distribution is improved by the forced convection.

• 한국레이저가공학회지
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• 제12권4호
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• pp.17-25
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• 2009

The surface cleaning method based on the laser-induced breakdown (LIB) of gas and subsequent plasma and shock wave generation can remove small particles from solid surfaces. In the laser shock cleaning (LSC) process, a high-power laser pulse induces optical breakdown of the ambient gas above the solid surface covered with contaminant particles. The subsequently created shock wave followed by a high-speed flow stream detaches the particles. In this work, a novel surface cleaning process using laser-induced breakdown of liquid is introduced and demonstrated. LIB of a micro liquid jet increases the shock wave intensity and thus removes smaller particle than the conventional LSC method. Experiments demonstrate that the cleaning force and cleaning efficiency are also increased significantly by this method.

• 한국균학회지
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• 제49권4호
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• pp.525-530
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• 2021

The cultivation in sawdust media, mushroom productivity, and fruiting body characteristics of Lentinula edodes strains NIFoS 2778 and NIFoS 3363 were compared according to the inoculation conditions. The cultivation period was 5% shorter when liquid spawn was used. Fruiting bodies were induced after 113 days of incubation on media inoculated with liquid spawn, and the cultivation period was 119 days on media inoculated with solid spawn. Mushroom productivity of NIFoS 2778 was the highest (661.4 g) when 36 mL of liquid spawn was used. For NIFoS 3363, mushroom production was higher under liquid inoculation conditions when the same amount of liquid and solid spawns were used. The mushroom characteristics of the two strains were not significantly different, except for gill width and stipe diameter.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 고액공존금속의 성형기술 심포지엄
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• pp.5-15
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• 1997

It is the objective of this study that by conducting the serni-solid extrusion using A12024, the effect of various process variables on the quality of extruded product and extrusion force is understood. The results of experiment are compared with those of finite element simulation in order to verify the effectiveness of the developed FE-simulation code. In order to simulate densification in the deformation of serni-solid material, the semi-solid material is assumed to be composed of solid region as porous skeleton following compressible visco-plastic model and liquid region following Darcy's equation for the liquid flow saturated in the interstitial space. Then the flow and deformation of the semi-solid alloy are analyzed by coupling the deformation of the porous skeleton and the flow of the eutectic liquid. It is assumed that initial solid fraction is homogeneous. Yield and plastic potential function presented by Kuhn and constitutive model developed by Gunasekera are used for solid skeleton.

• 한국수소및신에너지학회논문집
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• 제32권6호
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• pp.565-572
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• 2021

Hydrogen is currently produced from natural gas reforming or industrial process of by-product over than 90%. Additionally, there are green hydrogens based on renewable energy generation, but the import of green hydrogen from other countries is being considered due to the output variability depending on the weather and climate. Due to low density of hydrogen, it is difficult to storage and import hydrogen of large capacity. For improving low density issue of hydrogen, the gaseous hydrogen is liquefied and stored in cryogenic tank. Density of hydrogen increase from 0.081 kg/m³ to 71 kg/m3 when gaseous hydrogen transfer to liquid hydrogen. Density of liquid hydrogen is higher about 800 times than gaseous. However, since density and boiling point of liquid hydrogen is too lower than liquefied natural gas approximately 1/6 and 90 K, to store liquid hydrogen for long-term is very difficult too. To overcome this weakness, this paper introduces storage method of hydrogen based on liquid/solid (slush) and facilities for producing slush hydrogen to improve low density issue of hydrogen. Slush hydrogen is higher density and heat capacity than liquid hydrogen, can be expected to improve these issues.

• 한국염색가공학회지
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• 제22권4호
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• pp.341-348
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• 2010

Sodium sulfate is commonly added in reactive dyebath in order to increase substantivity of the reactive dye to cellulose fiber by reducing repulsion between anionic dye and fiber. While sodium sulfate is mostly used in solid form, it is inconvenient to dissolve a large amount of powder sodium sulfate. Furthermore, if there is undissolved salt in dyebath it might cause unlevel dyeing. In this study, sodium sulfate in liquid or solid form was used in dyeing of cellulose fabric with reactive dyes of three primary color and the effect of type or amount of sodium sulfate on dyeing and fastness properties was investigated. When the amount of sodium sulfate rose to 30-50 g/l, K/S value of the dyed fabric markedly increased; further rise in sodium sulfate concentration resulted in slow increase in K/S value. For light color, optimum amount was about 30 g/l in solid form and 50-100 g/l in liquid form while, for medium to deep color, it was 50 g/l and 100-150 g/l in solid and liquid form, respectively. When using each optimum amount of salt in solid or liquid form for medium color, shape of dyeing curve as well as exhaustion was similar to each other. On the whole, similar color fastness results were obtained regardless of type or amount of sodium sulfate.

• Journal of Mechanical Science and Technology
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• 제19권8호
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• pp.1649-1661
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• 2005

We consider. a horizontal static liquid layer on a planar solid boundary. The layer is evaporating when the plate is heated. Vapor recoil and thermo-capillary are discussed along with the effect of mass loss and vapor convection due to evaporating liquid and non-equilibrium thermodynamic effects. These coupled systems of equations are reduced to a single evolution equation for the local thickness of the liquid layer by using a long-wave asymptotics. The partial differential equation is solved numerically.

• Journal of Biosystems Engineering
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• 제30권1호
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• pp.32-37
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• 2005

This study was conducted the slurry pig manure treatment by condensation drying of liquid from the slurry manure with a heat-pump and electric heater combined with air flow channel system. The system was designed as liquid and solid matters separation of slurry manure, and it can doing continuous input of slurry manure from a pig house, and it can operated year round use for pig farms. The separation of liquid and solid matters from slurry manure needed the prevention of solid accumulation in the system. The system was designed as closed space from outside air space for maximized evaporation of liquid and the condensation of liquid from slurry manure. The system can be operated the pig slurry manure treatment regardless of seasons in a yew. The separated evaporation water from the pig slurry manure by the heat-pump was satisfactorily pure water that can be used as washing water in livestock farms. The system can applicate to about 100 heads of pig, and the proper area of evaporation plate system was considered around $10\;m^2$. The input electrical energy of about 15 kWh which the cost equal to 250,000 won per month.