• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.1
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• pp.9-18
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• 2013

Two-phase vapor-liquid flows exist in many shell and tube heat exchangers such as condensers, evaporators, and nuclear steam generators. To understand the fluid dynamic forces acting on a structure subjected to a two-phase flow, it is essential to obtain detailed information about the characteristics of a two-phase flow. The characteristics of a two-phase flow and the flow parameters were introduced, and then, an experiment was performed to evaluate the pressure loss in the tube bundles and the fluid-dynamic force acting on the cylinder owing to the pressure distribution. A two-phase flow was pre-mixed at the entrance of the test section, and the experiments were undertaken using a normal triangular array of cylinders subjected to a two-phase cross-flow. The pressure loss along the flow direction in the tube bundles was measured to calculate the two-phase friction multiplier, and the multiplier was compared with the analytical value. Furthermore, the circular distributions of the pressure on the cylinders were measured. Based on the distribution and the fundamental theory of two-phase flow, the effects of the void fraction and mass flux per unit area on the pressure coefficient and the drag coefficient were evaluated. The drag coefficient was calculated by integrating the measured pressure on the tube by a numerical method. It was found that for low mass fluxes, the measured two-phase friction multipliers agree well with the analytical results, and good agreement for the effect of the void fraction on the drag coefficients, as calculated by the measured pressure distributions, is shown qualitatively, as compared to the existing experimental results.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.2
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• pp.39-45
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• 2016

In a coaxial porous injector, a gas propellant is injected through the porous cylinder surface to the liquid jet which is encircled by a porous cylinder. In this study, to observe the differences in disintegration mechanisms between a shear coaxial injector and a coaxial porous injector, cold-flow tests and 2-D axisymmetric numerical analysis have been carried out. The shadowgraph images and Sauter mean diameters were compared in similar experimental conditions, and the effects of velocity distributions at the inner injector region on the disintegration of liquid jet were investigated through the numerical calculations. As a result, in high air mass flow rate condition, the disintegration performance of coaxial porous injector is better than shear coaxial injector, in spite of a lower velocity at the inner injector region.

• Development and Reproduction
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• v.16 no.2
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• pp.113-120
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• 2012

We examined the distribution of uterine mast cells in cycling mice of different ages between 7 weeks and 38 weeks by toluidine blue staining. Mast cell density increased gradually depending on the age and culminated at 30 weeks after birth. Of the estrous stages, uteruses at metestrus showed markedly higher density of mast cells than those at the other stages in cycling mice of all ages analysed in this study and the majority of the mast cells were found in myometrium. We also discriminated types of the uterine mast cells in cycling mice at 10 weeks old by Alcian blue-safranin double staining. Mucosal type was most abundant among three types, including connective-tissue types and mixed types, through the entire estrous cycles. The portion of mixed types increased slightly after estrous. The abundance of uterine collagen protein determined by Masson trichrome staining was exactly consistent with the density distribution of the uterine mast cells during estrous cycles. Taken together, these results may imply that uterine mucosal mast cells, together with collagen proteins, are heavily involved in tissue remodeling of cycling mouse uterus.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.12 no.3
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• pp.130-138
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• 2000

The friction factor equation of open channel flow is developed by using Prandtl's mixing length theory and considering the flow characteristics of smooth or rough turbulent flow. BYO model considers vertical velocity profile for the (:omputation of bottom friction of surface waves and current flow. The model computes the mean bottom friction of combined wave-current flow by the vectorial summation of wave velocity and current velocity at Bijker point. The near bottom flow is discriminated by three flow regimes; smooth, transitional and rough turbulent flow. The model, BYO, has been further refined considering the combination of smooth turbulent flow and rough turbulent flow.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.8
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• pp.1138-1144
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• 2002

Recently GDI(Gasoline Direct Injection) engine is spot-lighted to achieve higher thermal efficiency under partial loads and better performance at full loads. To realize this system, it is essential to make both stratified combustion and homogeneous combustion. Spray pattern must be optimized according to injection timing because ambient pressure in combustion chamber is varied with crank angle. In this experimental study, two types of visualization system such as laser scattering method and schlieren method were developed to clarity the spray behavior during on intake stroke. As the ambient pressure increases, thepenetration length and spray angle show a tendancy to decrease due to rising resistance caused by the drag force of the ambient air. Distribution of injected fuel on intake stroke has a significant effect on homogeneous mixture in the cylinder. These results provide the information on macroscopic wall-wet growth in the cylinder and design factors for developing GDI injector.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.5
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• pp.96-104
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• 2001

The present study experimentally investigates the concentration distribution of liquid and vapor phase with different injection timings in the in-cylinder flow field of a optically accessible engine. The conventional MPI, DOHC engine was modified into DI gasoline engine. The images of liquid and vapor phases in the motoring engine were captured by using exciplex fluorescence method. Dopants used in this study were 2% fluorobenzene and 9% DEMA(diethyl-methyl-amino) in 89% solution of hexane by volume respectively. Two dimensional spray fluorescence images of liquid and vapor phases were acquired to analyze spray behaviors and fuel distribution in the in-cylinder flow field. Measurements were carried out fur four different injection timings, namely BTDC 270$^{\circ}$, 180$^{\circ}$, 90$^{\circ}$, and 50$^{\circ}$. Experimental results indicate that behaviors and distribution of vapor phase were largely affected by in-cylinder tumble flow, and mixture formation process was also greatly affected by in-cylinder flow at early injection mode and by ambient pressure at late injection mode.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.2
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• pp.121-126
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• 2006

A gasoline-fueled stratified charge compression ignition (SCCI) engine with both direct fuel injection and intake temperature and compression ratio was examined. The fuel was injected directly by using the high temperature resulting from heating intake port. With this injection strategy, the SCCI combustion region was expanded dramatically without any increase in NOx emissions which were seen in the case of compression stroke injection. Injection timing during the intake temperature was found to be an important parameter that affects the SCCI region width. The effect of mixture stratification and the effect of fuel reformation can be utilized to reduce the required intake temperature for suitable SCCI combustion under each set of engine speed and compression ratio conditions.

• Journal of Ginseng Research
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• v.24 no.4
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• pp.157-161
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• 2000

Cell growth and production of phenolic compounds by callus cultures of Panax ginseng C. A. Meyer were investigated under various phytohormones concentrations and inoculum size. The results indicated that the cell growt was improved by a MS medium supplemented with 2 mg/L of CPA. The maximum cell yield was obtained at inoculum size of 1 g/flasd. The production of phenolic compounds in the callus cultures was higher than those in the ginseng root. Especially, one cell line (20601) showed the highest content of phenolic compounds and antioxidant activity.

• Korean Journal of Ecology and Environment
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• v.46 no.4
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• pp.488-498
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• 2013

A three-dimensional hydrodynamic model was applied to the Lake Euiam. The lake has three inflows, of which Gongji Stream has the smallest flow rate and poorest water. The dam-storage volume, watershed area, lake shape and discharge type of the Chuncheon Dam and the Soyang Dam are different. Therefore, it is difficult to analyze the water plume and mixing pattern due to the difference of the two dams regarding the amount of outflow and water temperature. In this study, we analyzed the effects of different characteristics on temperature and conductivity using the model appropriate for the Lake Euiam. We selected an integrated system supporting 3-D time varying modeling (GEMSS) to represent large temporal and spatial variations in hydrodynamics and transport of the Lake Euiam. The model represents the water temperature and hydrodynamics in the lake reasonably well. We examined residence time and spreading patterns of the incoming flows in the lake based on the results of the validated model. The results of the water temperature and conductivity distribution indicated that characteristics of upstream dams greatly influence Lake Euiam. In this study, the three-dimensional time variable water quality model successfully simulated the temporal and spatial variations of the hydrodynamics in the Lake Euiam. The model may be used for efficient water quality management.

• Analytical Science and Technology
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• v.12 no.2
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• pp.159-165
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• 1999

The adsorption and separation behaviors of transition metal ions using a merrifield resin bound 1,12-diaza-3,4:9,10-dibenzo-5,8-dioxacyclopentadecane (NTOE) and 1,12,15-triaza-3,4:9,10-dibenzo-5,8-dioxacycloheptadecane(NDOE) were investigated in aqueous solution. The orders of adsorption degree(E) and distribution ratio(D) of transition metal ions were Cu(II)$t_R$) of metal ions were affected by adsorption degree(E) and distribution ratio(D). This results showed good separation efficiency of Ag(I) from mixed metal solution.