• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.12 no.3
• /
• pp.213-220
• /
• 2002

Modifying effects of the rectangular forward step for suppressing the unsteady pressure fluctuation during interaction between the upstream vortical flow and the edge are studied numerically. The vertical flow is modeled by a point vortex, and the unsteady pressure coefficient is obtained from the velocity and the potential fields. To investigate the effects of the edge shape the rectangular forward step is chamfered wish various angles. Calculation shows that the pressure peaks become decreased by increasing the vortex height as well as the chamfering angle. The pressure amplitudes are very sensitive to the change of the initial vertex height and its strength. From this study we can find out that the chamfered edge has two effects; the one is that it suppresses the pressure amplitude generated from the edge, and the other is that it decreases the time variation of unsteady pressure fluctuation. These modifying concepts can be applied to attenuate the self-sustained oscillation mechanism at the open cavity flow.

• The Journal of Korean Medicine
• /
• v.16 no.1 s.29
• /
• pp.403-418
• /
• 1995

In order to study the effects of Chungsimgangwhawhan on blood pressure in normal rats and rabbits, and hyperlipidemia induced by 1% cholesterol diet, triton WR-1339, and 75% fructose in mice and rats, the amount of total cholesterol, triglyceride, phospholipid and blood pressure were measured. The results were as follows : 1. After per os medication of Chungsimgangwhawhan, blood pressure in rats were increased but were not significant. 2. Chungsimgangwha-Whan showed strong effects on decreasing blood pressure, depending on the concentration in blood vessels of rabbits. 3. In the model of hyperlipidemia induced by 1% cholesterol diet in mice, Chungsimgangwhawhan showed decreasing effects on total cholesterol level in serum significantly (p<0.05) depending on the concentration, and on triglyceride (p<0.01) and phospholipid level (p<0.001) in serum. 4. In the model of hyperlipidemia induced by triton WR-1339 in rats, Chungsimgangwhawhan showed mild decreasing effects on total cholesterol level in serum, but was not significant. 5. In the model of hyperlipidemia induced by 75% fructose in rats, Chungsimgangwhawhan showed decreasing effects on total cholesterol and triglyceride level in serum significantly(p<0.01) depending on the concentration. According to the above results, Chungsimgangwhawhan showed significant decreasing effects on blood pressure and hyperlipidemia, and it is considered that it is appropriate to apply for hypertension and hyperlipidemia.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2008.03a
• /
• pp.25-34
• /
• 2008

In this paper, three-dimensional multiblade row unsteady Navier-Stokes simulations at a hot streak temperature ratio of 2.0 have been performed to reveal the effects of rotor tip clearance on the inlet hot streak migration characteristics in low pressure stage of a Vaneless Counter-Rotating Turbine. The hot streak is circular in shape with a diameter equal to 25% of the high pressure turbine stator span. The hot streak center is located at 50% of the span and the leading edge of the high pressure turbine stator. The tip clearance size studied in this paper is 2.0mm(2.59% high pressure turbine rotor height, and 2.09% low pressure turbine rotor height). The numerical results show that the hot streak is not mixed out by the time it reaches the exit of high pressure turbine rotor. The separation of colder and hotter fluid is observed at the inlet of low pressure turbine rotor. Most of hotter fluid migrates towards the rotor pressure surface, and only little hotter fluid migrates to the rotor suction surface when it convects into the low pressure turbine rotor. And the hotter fluid migrated to the tip region of the high pressure turbine rotor impinges on the leading edge of the low pressure turbine rotor after it goes through the high pressure turbine rotor. The migration of the hotter fluid directly results in very high heat load at the leading edge of the low pressure turbine rotor. The migration characteristics of the hot streak in the low pressure turbine rotor are dominated by the combined effects of secondary flow and leakage flow at the tip clearance. The leakage flow trends to drive the hotter fluid towards the blade tip on the pressure surface and to the hub on the suction surface, even partial hotter fluid near the pressure surface is also driven to the rotor suction surface through the tip clearance. Compared with the case without rotor tip clearance, the heat load of the low pressure turbine rotor is intensified due to the effects of the leakage flow. And the numerical results also indicate that the leakage flow effect trends to increase the low pressure turbine rotor outlet temperature at the tip region.

• The Journal of the Acoustical Society of Korea
• /
• v.15 no.4E
• /
• pp.72-77
• /
• 1996

A relatively simple theoretical model for predicting the shock thickness is applied to the weak shock propagation through sea water, where the boric acid and the magnesium sulfate are the major relaxation processes. The relaxation effects increases the shock thickness by the factor of 103 compared with the thickness based on the classical absorption only. In seawater with the ambient pressure of 125 atm and 15℃ temperature, the effects of the boric acid are dominant when the peak pressure is less than 0.3 atm and 3 atm. For the shocks of peak pressure greater than 5 atm, the effects of the classical absorption theory is enough to describe the shock thickness. The effects of the ambient pressure and temperature on the shock thickness are also evaluated.

• Journal of Welding and Joining
• /
• v.17 no.6
• /
• pp.70-77
• /
• 1999

Surface depression in the arc welding is calculated numerically to analyze its influence on pool convection and oscillation. The magnitude of surface depression due to arc pressure on the stationary GTA pool surface is relatively small, and fluctuations of the surface and velocity are caused mainly by arc pressure. The inward flow on the surface due to the electromagnetic force and positive surface tension gradient acts to decrease surface depression. Surface depression appears to have minor effects on average flow velocity and thus pool geometry. Pool oscillation occurs due to surface vibration, and oscillation frequencies are affected mainly by the surface tension and pool width. The input parameters such as arc pressure and current have negligible effects on the oscillation frequency, and the surface tension gradient has limited effects. Since the oscillation frequency varies slightly according to penetration, pool oscillation for the partial penetration weld pool is applicable to monitor the pool width.

• 한국전산유체공학회:학술대회논문집
• /
• 1999.05a
• /
• pp.29-34
• /
• 1999

A two-dimensional Navier-Stokes code based on AUSMPW+ scheme has been developed to simulate the hypersonic flowfield of hypersonic shock-shock interaction. AUSMPW+ scheme is a new hybrid flux splitting scheme, which is improved by introducing pressure-based weight functions to eliminate the typical drawbacks of AUSM-type schemes, such as non-monotone pressure solutions. To study the real gas effects, three different gas models are taken into account in this paper: perfect gas, equilibrium flow and nonequilibrium flow. It has been investigated how each gas model influences on the peak surface loading, such as wall pressure and wall heat transfer, and unsteady flowfield structure in the region of shock-shock interaction. With the results, the value of peak pressure is not sensitive to the real gas effects nor to the wall catalyticity. However, the value of peak heat transfer rates is affected by the real gas effects and the wall catalyticity. The structure of the flowfield also changes drastically in the presence of real gas effects.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.07a
• /
• pp.1065-1068
• /
• 2001

Effects of compacting pressure on the electrical and sintering characteristics of Cu25Cr contact material have been investigated. Cu25Cr contact materials were prepared by solid and liquid-phase sintering methods varying compacting pressure. Influence of compacting pressure on electrical characteristics were investigated in the cylindrical stainless-steel vessel using L-C resonant circuit. The physical and electrical properties of solid-phase sintered Cu25Cr material were found to be improved by increased compacting pressure. On the other hand, it was found that compacting pressure had little influence in case of liquid-phase sintered Cu25Cr material. After conditioning, contact resistance of Cu25Cr material was decreased regardless of compacting pressure. With increased compacting pressure, interrupting ability was shown to be increased.

• The Journal of Korean Physical Therapy
• /
• v.28 no.3
• /
• pp.201-204
• /
• 2016

Purpose: The purpose of this study was to compare the immediate effects of alternative treatment methods in lowering the blood pressure and pulse of prehypertensive patients. Methods: A total of 48 prehypertensive patients were randomly divided into 4 groups of 12 patients and each group received a different intervention. The control group was made to rest, the heat pack (HP) group received heat pack treatment, the ultrasound (US) group received an ultrasound massage, and the myofascial release (MFR) group received myofascial release. The blood pressure and pulse rate were measured before and after intervention. Results: Following intervention, the patients of the MFR group showed a decrease in systolic pressure, diastolic pressure, and pulse rate. Although blood pressure was similar in all groups, a significant decrease in pulse rate was seen in the MFR group compared to others. Conclusion: The application of MFR was shown to be an effective method for lowering the blood pressure and pulse rate in prehypertensive patients.

• The Bulletin of The Korean Astronomical Society
• /
• v.40 no.1
• /
• pp.48.3-48.3
• /
• 2015

Using numerical simulations, we study the effects of ram pressure stripping on dwarf galaxies. It is commonly assumed that ram pressure only affects the gas component of a galaxy. We find that it actually can affect the dynamics of the stars too, and even the dark matter surrounding the disk - an effect dubbed 'ram pressure drag'. We study the effects of ram pressure drag on tidal dwarf galaxies, and find the response is very strong. Tidal dwarfs may be entirely destroyed by gas removal, and their stellar dynamics may appear heavily dark matter dominated where no dark matter exists. We discuss the consequences for tidal dwarf evolution, tidal streams, and disk galaxy evolution in general.

• International journal of advanced smart convergence
• /
• v.6 no.4
• /
• pp.1-8
• /
• 2017

In this work, the effects of fairly influential factors on performance of vacuum system, such as constant pressure and outgassing effect were simulated to propose the optimum design factors. Outgassing effects of selected vacuum materials on the vacuum characteristics were simulated by the $VacSim^{Multi}$ simulation tool. This investigation examined the feasibility of reliably simulating the outgassing characteristics of common vacuum chamber materials (aluminum, copper, stainless steel, nickel plated steel, Viton A). The optimum design factors for vacuum systems were suggested based on the simulation results. And, the effects of throttle valve applications on vacuum characteristics were also simulated to obtain the optimum design model of variable conductance on high vacuum system. Simulated vacuum characteristics of the proposed modelling were agreed with the observed experimental behaviour of real systems. Pressure limit valve and normally on-off control valve were schematized as the modelling of throttle valve for the constant process-pressure. Simulation results were plotted as pump-down curve of chamber and variable conductance of throttle valve. Simulated behaviors showed the applications of throttle valve sustained the process-pressure constantly, stably, and reliably.