• 한국기계연구소 소보
• /
• s.18
• /
• pp.21-27
• /
• 1988

In this study, a series of experiments and analyses are performed to estimate the static characteristics of hydrostatic journal bearing such as load capacity, pressure change in each recess, eccentricity of spindle, etc. The experiments are carried out for a multi-recess type journal bearing with capillary restrictor. The Finite Element Method(FEM) is used for the analyses. The predicted load capacity under the condition of stationary or eccentric ratio of bellow 0.2 of the spindle shows excellent agreement with the measured. But, with an increase of the eccentric ratio when the spindle is rotating, the predicted load capacity is largely estimated than the measured. It seems that the difference is mainly caused among others from the fact that the effect of oil-viscosity variation due to the temperature change in the bearing is not introduced into the analyses. The analysis method proposed to estimate the static characteristics of hydrostatic journal bearing is considered to be very reliable since the predicted results are overall in good agreement with the measured.

• Proceedings of the Korea Water Resources Association Conference
• /
• 1991.07a
• /
• pp.221-230
• /
• 1991

Various Models of the moisture content-capillary pressure hysteresie based on the approach of domain concept in porous media are compared with each other, Model III-1(Mualem, 1984) is superio to others as expected. A new model based on Model III-1 is proposed of which asuumption is the linearization of P$$($\theta$) accounting for the pore blockage effect against air-entry. The feature of this model is that only one branch of boundary curve is needed to calibrate it, which is the advantage to Model III-1. The prediction of boundary drying curve from boundary wetting curve using this model is better than that using Model I-1, II-1 compared with the experimental data. This model is to simulate scanning curves, while Model I-1, II-1 is not.

• The Journal of Internal Korean Medicine
• /
• v.25 no.4
• /
• pp.52-64
• /
• 2004

Objectives : This study was done to investigate the effect of Gamigehyuldeung-tang on hypertension. Methods : After administering Gamigehyuldeung-tang extract to SHR(Spontaneous Hypertensive Rats) for 5 weeks, changes in blood pressure, pulse rate, aldosterone and catecholamine levels in plasma were examined, and immunohistochemical changes and scanning electron microscopic changes were observed. Results : The following results were obtained; blood presure decreased significantly as well as levels of aldosterone, dopamine and epinephrine in SHR. But levels of norepinephrine were unaffected. No capillary vessel dilation was observed. A decrease in cell damage was seen in microscope investigation. Conclusions : These results support a role for Gamigehyuldeung-tang might be usefully applied in treatment of hypertension.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.31 no.11
• /
• pp.949-956
• /
• 2007

Pool boiling critical heat flux (CHF) of nanofluids with oxide nanoparticles of $TiO_2$ or $Al_2O_3$ was experimentally investigated under atmospheric pressure. The results showed that a dispersion of oxide nanoparticles significantly enhances the CHF over that of pure water. Moreover it was found that nanoparticles were seriously deposited on the heater surface during pool boiling of nanofluids. CHF of pure water on a nanoparticle-deposited surface, which is produced during the boiling of nanofluids, was not less than that of nanofluids. The result reveals that the CHF enhancement of nanofluids is absolutely attributed to modification of the heater surface by the nanoparticle deposition. Then, the nanoparticle-deposited surface was characterized with parameters closely related to pool boiling CHF, such as surface roughness, contact angle, and capillary wicking. Finally, reason of the CHF enhancement of nanofluids is discussed based on the changes of the parameters.

• Journal of Physiology & Pathology in Korean Medicine
• /
• v.20 no.3
• /
• pp.663-669
• /
• 2006

This study was done to investigate the effect of Ganyangsanghang-bang(GYSHB) on hypertension. After administering GYSHB extract to SHR for 5 weeks, changes in blood pressure, pulse rate, aldosterone and catecholamine levels in plasma were examined, and immunohistochemical changes were observed, and liver function test was done. The following results were obtained; blood presure decreased significantly as well as levels of aldosterone and norepinephrine in SHR. But levels of dopamine were unaffected. No capillary vessel dilation in adrenal cortex was observed. Safety against hepatic toxicity was showed. These results support a role for GYSHB might be usefully applied in treatment of hypertension.

• New & Renewable Energy
• /
• v.3 no.2 s.10
• /
• pp.47-52
• /
• 2007

Hydrate phase equilibrium for the binary $CO_{2}$+water and $CH_{4}$+water mixtures in silica gel pore of nominal 6, 30, and 100 nm were measured and compared with the cacluated results based on van der Waals and Platteeuw model. At a specific temperature three-phase hydrate-water-vapor (HLV) equilibrium curves for pore hydrates were shifted to the higher-pressure condition depending on pore sizes when compared with those of bulk hydrates. Notably, hydrate phase equilibria for the case of 100 nominal nm pore size were nearly identical with those of bulk hydrates. The activities of water in porous silica gels were modified to account for capillary effect, and the calculation results were generally in good agreement with the experimental data.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.05a
• /
• pp.922-929
• /
• 2006

In this study, flow characteristics of the FPN (Fountain Pen Nano-Lithography) using active membrane pumping are investigated. This FPN has integrated chamber, micro channel, and high capacity reservoir for continuous ink feed. The most important aspect in this probe provided control of fluid injection using active membrane pumping in chamber. The flow rates in channel by capillary force are theoretically analyzed, including the control of mass flow rates by deflection of membrane. The above results are compared with numerical simulations that calculated by commercial code, FLUENT. The velocity of fluid in micro channel shows linear behaviors. And the mass flows are proportional to the second order function of pumping pressure that is imposed to membrane.

• Water for future
• /
• v.24 no.1
• /
• pp.109-117
• /
• 1991

The governing equation of flow in porous media is developed on the bases of the continuity equation of fluid for transient flow through a saturated-unsaturated zone, and substitution of Darcy's law. The numerical solutions are obtained by finite element method based on the Galerkin principles weighted residuals. The analysis are carried out by using the unsteady storm data observed and rainfall intensities which are obtained by using the rainfall excess model in considering of the initial losses. The functional relationships between the hydraulic conductivity, capillary pressure head and volumetric water content are applied to the flow of water through unsaturated soil varied with changes of water content.

• Korean Journal of Hydrosciences
• /
• v.2
• /
• pp.13-24
• /
• 1991

The governing partial differential equation of flow in porous media is developed on the bases of the continuity equation of fluid for transient flow through a saturated-unsaturated zone, and substitution of Dercy's law. The numerical solution is obtained by the Galerkin finite element method based on the principle of weighted residuals. The analysis is carried out by using the unsteady storm data observed and the functional relationships between the hydraulic conductivities, capillary pressure heads, and volumetric water contents under saturated-unsaturated conditions. As the results the hydraulic conductivities, rates of change of storage and initial moisture conditions are significantly influened on the responses of subsurface flow on a hillslope.

• Laser Solutions
• /
• v.4 no.2
• /
• pp.13-19
• /
• 2001

When a high-power laser beam is irradiated on the surface of material, it is well known that a cavity, called a keyhole induced by the pressure action of the vapor plume, is generated in the molten material. This paper describes the interaction between a pulsed CO$_2$ laser beam and water. The laser-beam is used to generate and maintain a conical depression in the water surface similar to the keyhole created during laser penetration welding. Experimental results show that the depth of laser-beam penetration is limited by hydrodynamic instability. The instability of the surface cavity can be understood by the capillary instability of a hollow jet. Theoretical computation of the steady keyhole shape has been performed. modifying the model suggested by Andrews et al. (1976). The model predicts the qualitative behavior of the keyhole but significantly underestimates the average diameter.