• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.5 no.1
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• pp.20-24
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• 2009

There is extensive tubing pipe in the nuclear power plant under high temperature and pressure. Erosion and corrosion defects are expected on this tubing pipe due to environmental and mechanical factors. In this study, Guided Ultrasonic Wave technique was applied to detect defects. The technique explores the advantages of the Guided Ultrasonic Wave method that inspects along the wall of the pipe and can travel long distances, providing rapid collection of data. This paper presents a case study of the Guided Ultrasonic Wave testing of 3/8" tubing pipe. This study offers to understand detected signals through correlation between amplitude and depth of defects.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1998.06a
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• pp.77-79
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• 1998

Metallic chromium was diffused in the{0001},{1120} white sapphires which were grown by the Verneuil method to enhance the physical properties of the sapphires. Chromium metal vapour pressure and {{{{ { N}_{2 } }}}} pressure were kept by {{{{ { 1$\times$10}^{-4 } }}}} torr at 21 50 $^{\circ}C$ and 6 atm in the quartz-tube, respectively. The color do the Cr-doped sapphires was changed to light red. Chromium was diffused faster in the {1120} than 수 the {0001} plane. It was speculated that the planar density was one the factors determining diffusion coeffcient

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.917-921
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• 1991

Hydraulic fitting impulse tester is equipment which produce impulse pressure waveform that specified foreign standard of SAE, JIS etc. Test conditions of SAE J1453 about waveform standard indicates frequency of 35-70 cycle/min, pressure of 560 bar, oil temperature of 93 .+-.3.deg. C etc. and required cycle is a million over. In additions, Test condition operated continuously equipment. This development item adopted new pattern method such as intensifier and rotary distributor is different from already established fitting impulse tester applied servo valve and high pressure direct directional control valve. Therefore, this development item which compares already established item is good reliability, low cost of manufacture and save of electric energy. especially, Domestic small and medium enterprise uses this tester because of economical cause. We develope appropriateness tester which conforms to demand of user.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.9
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• pp.2431-2442
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• 1994

In this paper the efficient space marching Viscous Shock Layer and Parabolized Navier-Stokes method have been applied to study the complex 3-D hypersonic equilibrium chemically reacting flowfilelds over sphere-cone($10^{\circ}$) vehicle at low angles of attack($0^{\circ}~5^{\circ}), Mach 20, and an altitude of 35km. The current bluntbody/afterbody space marching numerical method predicts the complex flowfields accurately and efficiently even on a small computer. The shock thickness from equilibrium air model is thinner than that from the perfect gas model. The windside wall heat-transfer rate, pressure and skin friction force were increased significantly when compared with those of leeside. The CA, CN, CM were increased almost linearly with the angle of attack in this region. The wall pressure, heat transfer, skin friction and axial force coeffient from equilibrium model were much higher than those from perfect gas model. The center of pressure moved forward with the increase of angle of attack.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.491-496
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• 2000

The physics of the flow field surrounding an engine nacelle afterbody is very complex. A high pressure jet from the nozzle interacts with the external flow and causes upstream influence on the afterbody surface field. At certain conditions, the nozzle boundary layer can separate, either by shock wave interaction or by adverse pressure gradient effect, resulting in a severe drag penalty. Furthermore, a finite afterbody base implies a recirculating flow region. A flow modeling method has been developed to analyze the flow in the annular base(rear-facing surface) of a circular engine nacelle flying at subsonic speed but with a supersonic exhause jet. Real values of exhaust gas properties and temperature are included.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.5
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• pp.94-101
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• 2013

Injection molding process is one of the most important methods to produce plastic parts with high efficiency and low cost. The objective of this study is to implement the best plastic injection molding process for LED TV speaker frame. Moldflow analysis and simulation of plastic injection molding process were carried out in order to predict optimal modeling operation conditions and then injection molded part was produced various type of resin temperature, filling time and injection pressure variation. the result was that the best injection molding condition is set as 60bar pressure, 2sec filling time and $310^{\circ}C$ degree. The study result would be useful to variety of plastic injection molding process.

• Journal of KSNVE
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• v.6 no.4
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• pp.513-519
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• 1996

This paper is concerned with the bubble sound at the accumulator which is generated by the difference of the high pressure side and the low pressure side in the cycle of the refrigerator. The causes of the bubble sound generation are verified by the visualized test of the operating refrigerant flow at the accumulator and the measurements of the temperature and pressure. Two cases were tested, one with the accumulator has a orifice and the other with the accumulator hasn't a orifice. So that, it is presented the comparison of the bubble sound levels and spectrums in each cases. To predict the bubble sizes when they are generated, the linearized equation driven by Strasberg is used.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.700-705
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• 2003

The general cooling tower is a device for making a cooling water in refrigerant condensers or industrial process heat exchangers. The present cooling tower have defects with noises, complicated structure and environmental problems. In this paper, we constituted a new water cooling system by using a evaporating latent heat in an enclosed tank, and this system is consisted of an enclosed vacuum tank and water driving ejector system. Several experimental cases were carried out for improvement methods of high vacuum pressure and water cooling characteristics. The ejector performance was tested in case of water temperature variations that flows in the ejector. Based on the vacuum pressure by water driving ejector, the water cooling characteristics were investigated for the vaporized air condensing effects.

• Journal of Korean Society for Atmospheric Environment
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• v.11 no.2
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• pp.171-178
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• 1995

The hydrodesulfurization (HDS) of dibenzothiophene (DBT) were performed simultaneously over CoPtMo/LaY catalyst under high H$_{2}$ pressure. The structure and physical properties of this catalyst were characterized using XRD, IR and surface area analyzer. The origin of acid site was mainly Bronsted. The structures of impregnated molybdenum and platinum were deactivated by DBT to MoS$_{2}$ and PtS, respectively. The activities of the HDS and the hydrocracking increased with increasing temperature and pressure. They decreased with increasing the DBT mole ratio(DBT/n-heptane). They remained constant with increasing the H$_{2}$/H.C. mole ratio. With increasing pressure and DBT mole ratio, the products of secondary cracking increased. To perform simultaneous HDS and hydrocracking effectively, the optimum condition were 500.deg.C, 4MPa.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.12
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• pp.1281-1288
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• 2009

Variation of dynamic characteristics of a low pressure turbine blade with crack length is studied in this paper via both experiments and finite element model. Since most of the turbine blades used in domestic power plants are imported from abroad, it is necessary to understand their dynamic behavior in advance. When experimentally obtained natural frequencies and mode shapes are compared with those from FEM results, they are close to each other in their magnitude. Then, it is more feasible to use finite element model for analyzing the dynamic characteristics of a blade under various operation conditions (rotation speed, temperature, etc) as well as with a crack in the blade.