• International Journal of Fluid Machinery and Systems
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• v.3 no.4
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• pp.369-378
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• 2010

The creation of the hydraulic turbine flow factor map will undoubtedly benefit its design by decreasing both the design cycle time and product cost. In this paper, the geometry and flow variables, which effectively affect the flow factor, are proposed, analyzed and determined. These flow variables are further used to create the operating condition maps by using different model approaches categorized into Response Surface Method (RSM) and Artificial Neural Network (ANN). The accuracies of models created by different approaches are compared and the performances of model approaches are analyzed. The influences of chosen variables and the combination of Principle Component Analysis (PCA) and model approaches are also studied. The comparison results between predicted and actual flow factors suggest that two-hidden-layer Feed-forward Neural Network (FFNN), and one.hidden-layer FFNN with PCA has the best performance on forming this mapping, and are accurate sufficiently for hydraulic turbine design.

• Bulletin of the Korean Mathematical Society
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• v.42 no.1
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• pp.75-85
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• 2005

In this paper, the visco-Da-Rios equation; (0.1) ($$\frac{{\partial}{\gamma}}{{\partial}t}=\frac{{\partial}{\gamma}}{{\partial}s}{\bigwedge}\frac{D}{ds}\frac{{\partial}{\gamma}}{{\partial}s}+{\nu}\frac{{\partial}{\gamma}}{{\partial}s}$$) is investigated on 3-dimensional complete orientable Riemannian manifolds. The global existence of solution is discussed by trans-forming (0.1) into a cubic nonlinear Schrodinger equation for complete orient able Riemannian 3-manifolds of constant curvature.

• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.239-248
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• 2002

Bentonite slurries in a slurry wall construction must fulfill a stabilizing function by forming impermeable membrane (surface cake and penetrated cake) on the excavated soil faces. Thus problems are occurring in practice for the construction of diaphram walls and cut-off walls with a low permeability for wastes disposal areas in some deep excavations or different grounds. In this paper, the fundamental mechanics of fluid loss and filter cake formation in various soil beds are investigated using large scale laboratory apparatus. The sealing efficiency of filter cake from the large scale tests and the significance of fluid loss in a slurry trench are utilized for practical situation as a recommended design procedure.

• Wind and Structures
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• v.34 no.5
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• pp.451-467
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• 2022

The flow around a high-speed train with three underbody structures in the bogie area is numerically investigated using the improved delayed detached eddy simulation method. The vortex structure, pressure distribution, flow field structure, and unsteady velocity of the wake are analyzed by vortex identification criteria Q, frequency spectral analysis, empirical mode decomposition (EMD), and Hilbert spectral analysis. The results show that the structures of the bogie and its installation cabin reduce the momentum of fluid near the tail car, thus it is easy to induce flow separation and make the fluid no longer adhere to the side surface of the train, then forming vortices. Under the action of the vortices on the side of the tail car, the wake vortices have a trend of spanwise motion. But the deflector structure can prevent the separation on the side of the tail car. Besides, the bogie fairings do not affect the formation process and mechanism of the wake vortices, but the fairings prevent the low-speed fluid in the bogie installation cabin from flowing to the side of the train and reduce the number of the vortices in the wake region.

• Journal of Mechanical Science and Technology
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• v.17 no.10
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• pp.1507-1519
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• 2003

The two-phase flow patterns for both non-loop and loop type oscillating capillary tube heat pipes (OCHPs) were presented in this study. The detailed flow patterns were recorded by a high-speed digital camera for each experimental condition to understand exactly the operation mechanism of the OCHP. The design and operation conditions of the OCHP such as turn number, working fluid, and heat flux were varied. The experimental results showed that the representative flow pattern in the evaporating section of the OCHP was the oscillation of liquid slugs and vapor plugs based on the generation and growth of bubbles by nucleate boiling. As the oscillation of liquid slugs and vapor plugs was very speedy, the flow pattern changed from the capillary slug flow to a pseudo slug flow near the annular flow. The flow of short vapor-liquid slug-train units was the flow pattern in the adiabatic section. In the condensing section, it was the oscillation of liquid slugs and vapor plugs and the circulation of working fluid. The oscillation flow in the loop type OCHP was more active than that in the non-loop type OCHP due to the circulation of working fluid in the OCHP. When the turn number of the OCHP was increased, the oscillation and circulation of working fluid was more active as well as forming the oscillation wave of long liquid slugs and vapor plugs in the OCHP. The oscillation flow of R-142b as the working fluid was more active than that of ethanol and the high efficiency of the heat transfer performance of R -142b was achieved.

• Economic and Environmental Geology
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• v.25 no.2
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• pp.115-131
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• 1992

Late Cretaceous (90.5 Ma), epithermal gold-silver vein mineralization of the Weolseong and Samchang mines in the Sulcheon area, 60 km southeast of Taejeon, can be separated into two distinct stages (I and II) during which fault-related fissures in Precambrian gneiss and Cretaceous (102 Ma) porphyritic granite were filled. Fluid inclusion and mineralogical data suggest that quartz-sulfide-electrum-argentite-forming stage I evolved from initial high temperatures $({\approx}340^{\circ}C})$ to later lower temperatures $({\approx}140^{\circ}C})$ at shallow depths of about 400 to 700 m. Ore fluid salinities were in the range between 0.2 and 6.6 wt. % eq. NaCl. A simple statistic model for fluid-fluid mixing indicates that the mixing ratio (the volumetric ratio between deep hydrothermal fluids and meteoric water) systematically decreased with time. Gold-silver deposition occurred at temperatures of $230{\pm}40^{\circ}C$ mainly as a result of progressive cooling of ore-forming fluids through mixing with less-evolved meteoric waters. Measured and calculated hydrogen and oxygen isotope values of hydrothermal fluids indicate meteoric water dominance, approaching unexchanged meteoric water values. The geologic, mineralogic, and geochemical data from the Weolseong and Samchang mines are similar to those from other Korean epithermal gold-silver vein deposits.

• Korean Journal of Materials Research
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• v.15 no.10
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• pp.671-677
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• 2005

Ti and Ti alloys are known to have excellent corrosion properties, which is an important aspect for biocompability of these implants in human body. In our study, four types of samples (Cp-Ti, Ti-6Al-4V, $0.5wt.\%$ Fe-Ti and ECAP Ti) were tested for their apatite forming ability and corrosion properties. The micropolished samples were treated with 5M NaOH solution at $60^{\circ}C$ for 24 hours. Each samples was gently washed with distilled water and heat-treated at 600"C for 1 hour. The heat-treated samples were soaked in Simulated Body Fluid (SBF) solution at $36.5^{\circ}C$ in an incubator for different period of time. The test revealed that $0.5 wt.\%$ Fe-Ti showing faster apatite growth on the surface (7th day) compared to other samples. Polarization curve test (PCT) was also carried out to determine the corrosion resistance of each samples in SBF solution. ECAP-Ti showed highest corrosion resistance compared to any other samples. $0.5wt.\%Fe-Ti$ showed higher corrosion potential and corrosion current compared to other samples.

• KSBB Journal
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• v.18 no.2
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• pp.117-121
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• 2003

The study was carried out to determine the effect of storage property and qualities on soybean sauce and paste by adding different amount of pyroligneous liquor obtained by sujpercritical fluid extraction(SFE). Purified pyroligneous liquor obtained by SFE at 4$0^{\circ}C$/110 bar contained p-cresol, o-cresol and m-cresol food sterilizers, but no toxic substances such as tar, scorched, furfuraland and monophenol. Thus pyroligneous liquor was considered to be suitable as natural food preservative. In case of soybean sauce, pyroligneous liquor was tested to determine the potential of natual food preservative to prevent flim formation on soybean ksauce 15days at 3$0^{\circ}C$. Increasing amounts of purified pyroligneous liquor added to soybean sauce prevented film forming yeasts. In case of paste, pyroligneous liquor was tested to determine the potential of natural food preservative to inhibit browning on paste 60 days at 3$0^{\circ}C$. Purified pyroligneous liquor added to paste inhibited brown pigment. As a result, purified pyroligneous liquor offered a promising way of improving the quality and storage property of soybean sauce and paste.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.11
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• pp.1622-1629
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• 2002

To enhance isothermal characteristics of glass-farming surface, a rectangular parallelepiped heat pipes was fabricated, tested, and analyzed. The working fluid was sodium and the wall material was stainless steel 304. The dimension of the heat pipe was 210 (L) $\times$ 140(W) $\times$ 92(H)mm. A lattice structure covered with screen mesh was inserted to promote return of working fluid. The bottom side of heat pipe was heated electrically and the top side was cooled by liquid circulation. The temperature distribution at the bottom surface was of major concern and was monitored to determine isothermal characteristics. A frozen start-up of rectangular parallelepiped liquid metal heat pipe was tested. The operating mode of the sodium heat pipe was affected by the temperature of cooling zone, input heat flux, and the operating temperature of heat pipe. The heat pipe operated in a normal fashion as long as the heat flux was over 5.78W/cm$^2$, and the inside wall temperature of condenser part was above 95$^{\circ}C$ The maximum temperature difference at the bottom surface was observed to be 32$^{\circ}C$ when the operating temperature of the heat pipe was operating normally around 50$0^{\circ}C$. The result showed that a sodium heat pipe was very effective in reducing significantly the temperature difference in the glass-forming surface.

• The Journal of the Petrological Society of Korea
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• v.15 no.2 s.44
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• pp.81-89
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• 2006

Pb isotopic compositions were determined from the ore deposits of Beonam, Dongjin, Jeoksang and Bukchang mines distributed within Jeolabuk-do. As a result, individual mine shows significantly different values of Pb isotopic compositions from each other. Pb isotopic values of the Beonam, Bukchang and Dongjin mines altogether from linear variation, but it is too steep to represent their formation age. Instead, such trend suggests that these ore leads were originated from binary mixing. Precambrian basement rocks and Mesozoic granitoids are suggested for such two end-members. The relative contribution of lead from each source seems to be quite different for each ore deposit, implying that the circulation of the ore-forming fluid was very localized when they were formed. In the case of Dongjin mine it seems significant portion of the ore leads were originated from the basement rocks, which suggests that related igneous rock seems to have acted as heat source to generate circulation of the fluid rather than the source of the ore-forming elements.