• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.23 no.1
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• pp.6-10
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• 1987

The authors carried out an experiment to measure the hydrodynamic resistance of the gear and the efficiency of otter board of the midwater trawl, which is the same used in the former experiment in this series of studies. The whole resistance of the gear was measured by a 10 ton scale recording tension meter, and they were analyzed into the shearing force and the drag with relevant factors determined in the former experiments. The results obtained can be summarized as follows: 1. The whole drag of gear T(kg) and the drag of net R sub(N) (kg) can be expressed as T=2.15 v super(1.12). R sub(N)=1.96 v super(1.01) (v: towing speed in m/sec) 2. The formula of estimating the drag of net deduced by Koyama's method can be expressed as R sub(N)=4.3$\times$d/l$\times$abv 3. The shearing force and the drag of otter board is about 19 to 22% and 5 to 7% of the drag of net, respectively. Whereas, the shearing coefficient and the drag coefficient calculated by the resistance and the opening of gear are 1.5 and 0.42, respectively.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.5
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• pp.37-46
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• 2013

The gas jet from a coaxial porous injector for two-phase flows is discharged radially from the porous surface, which encloses the center liquid jet. Several hot-firing test using ethanol/nitrous oxide propellants was conducted to analyze the effect of oxidizer/fuel ratio on the combustion performance, and the uncertainty analysis was performed for the results. The characteristic velocity was affected by oxidizer/fuel ratio similarly with the results of CEA calculation except that the maximum characteristic velocity was appeared in the stoichiometric ratio. The characteristic velocity efficiency was increased as the oxidizer/fuel ratio increases.

• Economic and Environmental Geology
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• v.32 no.2
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• pp.129-139
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• 1999

Hydrothermal gold deposits of the Trabong district in Vietnam occur as single-stage quartz $\pm$ calcite veins (0.3-1.2 m thick) which fill fault fractures in graphite-bearing gneiss and schist of the Chulai Complex and Kham Duc Formation of the Proterozoic age. Ore grades are 1.3 to 92.4 g/ton Au. Ore mineralogy is very simple, consisting mainly of pyrite with minor amounts of base-metal sulfides and electrum. Gold grains occur in two assemblages as follows: (1) early, Fe-rich (7.2-10.4 mole % FeS) sphalerite + electrum (50.4-64.3 atom % Au) assemblage occurring as inclusions in pyrite; (2) late, Fe-poor «4.7 mole % FeS) sphalerite + galena + electrum (47.6-81.7 atom % Au) assemblage occurring along fractures of pyrites. Based on fluid inclusion data and thermochemical considerations of ore mineral assemblages, ore minerals were formed at high temperatures (about $230^{\circ}C$ to $420^{\circ}C$) from $H_{2}O-CO_{2}(-CH_{4})$-NaCI fluids with the sulfur fugacity of about $10^{-6}$ to $10^{-10}$ atm. Fluid inclusion data also indicate that ore mineralization occurred mainly as a result of fluid unmixing accompanying $CO_2$ effervescence. Calculated oxygen and measured hydrogen isotope compositions of mineralizing waters (${\delta}^{18}O_{V-SMOW}$ values = 5.3 to 8.6$\textperthousand$, ${\delta}D_{V-SMOW}$ values = - 60 to - 52$\textperthousand$), along with the sulfur isotope compositions of vein sulfides (${\delta}^{34}S_{CDR}$ values = - 1.2 to 2.8$\textperthousand$) and carbon isotope compositions of inclusion $CO_2$ (${\delta}^{13}C_{PDB}$ values = - 4.7 to - 2.0$\textperthousand$) indicate that the high temperature (mesohypothermal) gold mineralization formed from a magmatic fluid.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.12
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• pp.2385-2394
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• 1992

Granular solid propellants having energy and fast burning rate produce great thrusts within extremely short time intervals. Thus numerical researchs prevailed rather than experimental. Using a 2-phase fluid dynamics model among 1-dimensional 2-phase models, a numerical program was set up to describe reacting flow fields, moving boundary with oscillating pressure waves and constitutive laws research. It deserves special emphasis that correlations of convective heat transfer coefficient and viscous drag force among constitutive laws are tested and discussed because slight variations of their constants make a large influence on their results. In this calculations, some of correlations make the large difference in results. Therefore constitutive laws for convective heat transfer coefficient and viscous drag force need more considerations with experiments.

• Journal of Soil and Groundwater Environment
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• v.9 no.3
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• pp.20-26
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• 2004

In-situ photolysis is one of the most promising ways to clean up a soil contaminated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). This study focuses on the mathematical description and model development of the convective upward transport of an organic solvent driven by evaporation and photodecomposition at the surface as the major transport mechanism in the clean up process. A finite-element-based numerical model was proposed to incorporate effects of multiphase flow on the distribution of each fluid, gravity as a driving force, and the use of van Genutchen equation for more accurate description of k-S-p relations. This paper presents results of extensive numerical calculations conducted to investigate the various parameters that play a role in the solvent migration through a laboratory-scale unsaturated soil column. The numerical results indicate that gravity affects significantly on the fluids distribution and evaporation for highly permeable soils. The soil texture has a profound influence on the fluid saturation profile during evaporation process. The amount of solvent convective motion increases with increasing evaporation rates and decreasing initial water saturation. Simulations conducted in this study have shown that the developed model is very useful in analyzing the effects of various parameters on the convective migration of an organic solvent in the soil environments.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.1
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• pp.9-16
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• 2014

This paper presents the theoretical analysis of a flow driven by surface tension and gravity in an inclined circular tube. A governing equation is developed for describing the displacement of a non-Newtonian fluid(Power-law model) that continuously flows into a circular tube owing to surface tension, which represents a second-order, nonlinear, non-homogeneous, and ordinary differential form. It was found that quantitatively, the theoretical predictions of the governing equation were in excellent agreement with the solutions of the equation for horizontal tubes and the past experimental data. In addition, the predictions compared very well with the results of the force balance equation for steady.

• KSBB Journal
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• v.16 no.4
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• pp.327-331
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• 2001

Catechin compounds from the Green tea cultivated in Bosung (Chollanamdo) were extracted using supercritical fluid and various additives, and analyzed by reversed-phase high performance liquid chromatography (RP-HPLC). The chromatographic column was packed with LiChrospher 100RP-18(15 $\mu$m), and water was used as the mobile phase with 0.05% phosphoric acid and acetonitrile. Gradient election was applied to separate EGCG by changing the mobile phase compositions. Comparing the extraction yield of three different types of supercritical fluids, pure CO$_2$, with additives of water and ethanol (5 wt,%), the extraction amount of EGCG was most abundant in the suprcritical CO$_2$with ethanol. However, more was extracted and pure higher purity was achieved by solvent extraction using ethanol.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.5
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• pp.384-392
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• 2006

Reported are the heat transfer characteristics of a two-phase loop thermosyphon (TLT) with nanofluids consisted of nano-size silver particles and distilled water as the working fluid. The nanofluids used in the present study are dispersed solutions with various amount of silver nanoparticle in distilled water. It is seen from the present study that the heat transfer performance of the test TLT with nanofluids increased as much as about 2 times higher than that of a TLT with pure water as the working fluid based on same heat flux. The study also showed that there was no deterioration of the TLT performance with time, up to a period of 8 days of continuous operation which implies that there was no coagulation of nanoparticles within the working nanofluid during the operation of the test TLT.

• Economic and Environmental Geology
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• v.21 no.2
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• pp.149-164
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• 1988

Electrum-sulfide mineralization of the Samgwang and Sobo mines of the Cheongyang Au-Ag area was deposited in two stages of quartz and calcite veins that fill fault zones in granite gneiss. Radiometric dating indicates that mineralization is Early Cretaceous age (127 Ma). Fluid inclusion and sulfur isotope data show that ore mineralization was deposited at temperatures between $340^{\circ}$ and $180^{\circ}C$ from fluids with salinities of 1 to 8 wt. % equiv. NaCl and a ${\delta}^{34}S_{{\sum}S}$ value of 2 to 5 per mil. Evidence of fluid boiling (and $CO_2$ effervescence) indicates a range of pressures from < 200 to $\approx$ 700 bars, corresponding to depths of ${\approx}1.5{\pm}0.3\;km$ in a hydrothermal system which alternated from lithostatic toward hydrostatic conditions. Au-Ag deposition was likely a result of boiling coupled with cooling. Meaured and calculated hydrogen and oxygen isotope values of ore-forming fluids indicate a significant meteoric water component, approaching unexchanged paleometeoric water values. Comparison of these values with those of other Korean Au-Ag deposits reveals a relationship among depth, Au/Ag ratio and degree of water-rock interaction. All investigated Korean Jurassic and Cretaceous gold-silver-bearing deposits have fluids which are dominantly evolved meteoric waters, but only deeper systems (${\geq}1.5\;km$) are exclusively gold-rich.

• 한국전산유체공학회:학술대회논문집
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• 2003.08a
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• pp.43-48
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• 2003

When the Eulerian-Lagrangian method is used to analyze the particle laden two-phase flow, a large number of particles should be used to obtain statistically meaningful solutions. Then it takes too much time to track the particles and to average the particle properties in the numerical analysis of two-phase flow. The purpose of this paper is to reduce the computation time by means of a set of particle gird separate to the flow grid. Particle motion equation here is the simplified B-B-O equation, which is integrated to get the particle trajectories. Particle turbulent dispersion, wall collision, and wall roughness effects are considered but the two-way coupling effects between gas and particles are neglected. Particle laden 2-D channel flow is solved and it is shown that the computational efficiency is indeed improved by using the current method