• Tribology and Lubricants
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• v.19 no.2
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• pp.85-93
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• 2003

In this study, a multigrid multi-integration method has been used to solve the steady-state, elastohydrodynamic lubrication (EHL) point contact problem of a ball joint mechanism used in small reciprocating compressors. Pressure and film thickness profiles have been calculated at minimum and maximum Moes M parameter conditions during one revolution of crankshaft. The effects of various lubricant viscosities, loads, ball velocities, elastic modulli, and radii of curvature on the calculated pressure distribution and film thicknesses have been investigated. The results indicate that the viscosity of lubricant, the sliding velocity of ball, and the reduced radius of curvature have considerable effects on the minimum and central film thicknesses. Solutions obtained with the multigrid analysis are compared with results calculated according to the Hamrock ＆ Dowson relations for the minimum and central film thicknesses.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.05a
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• pp.54-58
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• 2001

In recent years, hydroforming technology has been one of the most important technology in automotive industry in the points of weight saving, cost reduction and qualify improvement. However, compared with traditional metal forming technology, hydroforming has much fewer information in experience and empirical knowledge. But we don't have my sufficient time and money to produce hydroforming products using real blank directly Therefore Simulation is essential in hydrofonrung technology development. In this paper, we simulate the side member as the tubular hydroforming technology. The manufacturing process of side member' consists of pre_bending, pre_forming, and hydroforming of a thin tube. Variables such as internal pressure, end feeding, and tool geometry are optimized to improve the forming safety. And we simulate side member according to several lubricant conditions. from those simulations, we find that strain distributions can be reduced well by internal pressure and end feeding control, and lubrication is the most important thing in hydroforming process.

• Wind and Structures
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• v.9 no.3
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• pp.245-254
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• 2006

The pressure and drag measurements were carried out in the wind tunnel to investigate the drag reduction of the disk by using an interference rod placed upstream. The results indicate that there is a pair of standing vortices in the front stagnation region of the disk induced by the rod. The standing vortices can decrease the pressure on the disk upwind side; hence it can reduce the drag of the disk. With an increasing rod diameter, the standing vortices are strengthened and more drag reduction can be achieved for the disk. With rod diameter d/D = 0.05 (d, D are the diameters of rod and disk, respectively), the total drag of the disk can be reduced by about 9% compared with that of the bare disk.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.1
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• pp.107-112
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• 2009

This study was conducted for verification and systematization of estimation method about the headloss using CFD(Computational Fluid Dynamics). Head loss which happens between the inlet and outlet of in-line mixer can be a major factor for the design and construction. Also, this Case studies about the sensitivity related to the velocity in the piping system. As result, program's default calculation function was used to get each side's total pressure and the differential of each total pressure could be defined as head loss from in-line mixer. In the case of adopting pipe surface friction factor and geometry loss, Calculation residual can be much more reduced. It was found that residual of value between CFD method and field test ranged about 3 through 18 precent.

• YAKHAK HOEJI
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• v.23 no.2
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• pp.69-80
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• 1979

Effects of Astragali Radix Water Extract (ARWE) on the blood pressure were investigated in the whole rabbit and the spinalized rabbit. ARWE, when administered into the ear-vein or lateral ventricle, produced a fall in the blood pressure in the whole rabbit, but intravenous ARWE in the spinalized rabbit did not elicite the hypotensive action. Pretreatments with chlorisondamine, guanethidine, phentolamine and cyproheptadine in the whole rabbit weakened the depressor action of ARWE. The hypotensive action of the whole rabbit to ARWE was not influenced by the pretreatment of the animals with diphennylhydramine, propranolol, and vagotomization, whereas inhibited by atropine. ARWE did not affect the pressor response by angiotensin. However, it enhanced the hypertensive action by norepineprine and reduced the elevation in the blood pressure by carotid occlusion in the whole rabbit. These experimental observations suggest that ARWE may cause the depressor response via mechanisms of the central sympathetic blocking action, cholinergic action by peripheral origin and serotonin-like action.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.5
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• pp.63-68
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• 1998

The absolute pressure sensor using SDB wafer has been fabricated. the structure of the sensor consists of two wheatstone bridges and a diaphragm. One of the two wheatstone bridges is located on the edge of diaphragm, and the other is located on the center of diaphragm. The diaphragm cavity is sealted in vacuum (~10$^{5}$ Torr) to reduce the effect of temperature due to the vapor in the cavity on the sensitivity of pressure sensor. This is the minor method of temperature compensation method. In this experiment the main compensation method is to use the difference of the two bridge offset voltages. The drift of offset voltage with temperature is reduced by using this method so that temperature charcteristics is improved. In this method the temperature effect in the range of 22~100.deg. C was compensated over 80%.

• Journal of ILASS-Korea
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• v.6 no.3
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• pp.17-22
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• 2001

Recently LPG engine is developed to fulfill such new requirements as improved fuel efficiency in additional to further reduced exhaust emission. This experimental study is conducted to analyze spray characteristics for pintle type injector used in a LPLi (Liquid Phase LPG injection) engine. Since spray parameters including penetration length and spray angle make a role to design injector and engine intake system, spray visualization experiment is performed under atmosphere ambient and charging condition using Mie scattering method. From the experimental result under various LPG formation, the increased propane component decreases penetration length because boiling point of propane is lower than butane. To simulate intake charging condition in MPI engine, spray visualization is performed under high pressure condition. As a result, as ambient pressure is increased from atmosphere to 3.0 bar, penetration length is decreased. However, as ambient pressure is increased from atmosphere to 3.0 bar, spray angle is increased.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.435-441
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• 2008

More time is required for consolidating soft clay when its hydraulic conductivity around the vertical drains is reduced by soil disturbance. One of the methods to be proposed to solve such problem is the electro-osmotic flow application. This study presents the experimental results of model tests using a modified oedometer and a large-scale cylinder with a sand drain. Results show that the development of negative excessive pore water pressure due to the DC electrical field in saturated clay can be transformed to additional loads causing more consolidation settlement.

• Speech Sciences
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• v.14 no.4
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• pp.261-271
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• 2007

The purpose of this study was to determine the effectiveness of CPAP (Continuous Positive Airway Pressure) therapy on the treatment of hypernasality in patients with cleft lips and palates. 7 preschool children with severe hypernasality participated in the study. Acoustic measurements of nasality were done by using the NasalView (version 1.31). Results showed that the nasalance values were reduced linearly in both vowels according to the treatment period. The sharp treatment effect was observed at the beginning stage. The nasality values of the vowel /i/ showed a sharp decrease at the Evaluation Phase 1 and 2 and a small increase at the Phase 4 followed by a drop in the end. Further studies would be desirable for various patients with different disorder types.

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1450-1452
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• 1998

The chief advantage of polymer arrester, from a handling viewpoint, design of pressure relief, anti-contamination, electrical failuer was reduced by polymer arrester. The life expectancy of polymer arrester depend on a number of design factor. This paper introduced and study : new material housing (silicone composite, EPDM, EPA...), cap type sealing structure, knuckle type electrode, stress relief housing, supporting insulator and sub parts, of polymer arrester.