• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.375-380
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• 2008

This study have processed the developing of vane damper with accurate control by using gear which is a flow-control equipment of marine boiler's FD fan on this research. For the developing of vane damper, we have corrected some problem from welding & assembly process by changing the design, and for the case of an emergency case, we have applied the easy disassembly & assembly on that vane damper. Compared to Rink type vane damper in current, we have focused on high efficiency with low price of that new developing damper. For selection of actuator, we have tried to find the propriety with our developing focus. Also, we have developed a jig of assembly processing for high productivity with quality, it caused the best assembly performance with heat-treated & processed parts.

• Nuclear Engineering and Technology
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• v.40 no.3
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• pp.233-238
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• 2008

This study investigates the surface modification of a Hastelloy X plate and diffusion bonding in the assembly of surface modified plates. These types of plates are involved in the key processes in the fabrication of a process heat exchanger (PHE) for a $SO_3$ decomposer. Strong adhesion of a SiC film deposited onto Hastelloy X can be achieved by a thin SiC film deposition and a subsequent N ion beam bombardment followed by an additional deposition of a thicker film that prevents the Hastelloy X surface from becoming exposed to a corrosive environment through the pores. This process not only produces higher corrosion resistance as proved by electrolytic etching but also exhibits higher endurance against thermal stress above 9$900^{\circ}C$. A process for a good bonding between Hastelloy X sheets, which is essential for a good heat exchanger, was developed by diffusion bonding. The diffusion bonding was done by mechanically clamping the sheets under a heat treatment at $900^{\circ}C$. When the clamping jig consisted of materials with a thermal expansion coefficient that was equal to or less than that of the Hastelloy X, sound bonding was achieved.

• Journal of the Society of Naval Architects of Korea
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• v.52 no.2
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• pp.135-142
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• 2015

The Anti-Rolling Tank(ART) has an advantage over the other roll stabilizing devices, when ship is staying and working at one site of sea. An important design point of ART is the tank tuning, that is, matching the tank natural period to the ship's roll natural period. Since the load condition and consequently the roll natural period of ship is to be changed widely, the natural period of ART also has to be changed widely. In case of the existing U-tube type ART with a single layer duct, the tank natural period can be changed in a relatively narrow range. This paper suggests a new U-tube type ART system using a double layer duct to enable wide change of ART natural period. Through the roll experiments performed in regular beam waves for a box-type model ship, it is shown that the double layer duct ART has about two times wider period range and a better reducing effect of roll magnitude than the single layer duct ART.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.2
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• pp.157-164
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• 2006

Purpose: The purpose of this study was to compare the fracture strength of the zirconia monolithic all-ceramic crowns according to the thickness(0.5 mm, 0.8 mm, 1.1 mm) and IPS Empress II ceramic crown of 1.5 mm thickness. Material and method: Eight crowns for each of 3 zirconia crown groups were fabricated using CAD/CAM system(Kavo, Germany) and eight Empress II crowns were made from silicone mold and wax pattern. Each crown group was finished in accordance with the specific manufacturer s instruction. All crowns were luted to the metal dies using resin cement and mounted on the testing jig in a universal testing machine. The load was directed at the center of crown with perpendicular to the long axis of each specimen until catastrophic failure occurred. Analysis of variance and Tukey multiple comparison test(p<.05) were applied to the data. Results and Conclusion: 1. The fracture strength of the zirconia monolithic all-ceramic crown was higher thickness increased(p<.05). 2 The fracture strength of 1.1 mm thickness zirconia monolithic all-ceramic crown was higher than the fracture strength of 1.5 mm thickness IPS Empress II crown(p<.05). 3. The fracture strength of 0.5 mm thickness zirconia monolithic all-ceramic crown exceeded maximum occlusal forces.

• Journal of the Microelectronics and Packaging Society
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• v.16 no.3
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• pp.45-51
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• 2009

Vertical wet equipment was newly developed in stead of horizontal wet equipment which has been widely used for BGA develop process. We intended to eliminate the collision problem between equipment's transferring rollers and fine circuit patterns, which could be achieved by fixing the BGA panel vertically using jig unit. The process characteristics of vertical wet equipment were evaluated by conducting uniformity evaluation, pattern damage evaluation and defect analysis. The process uniformity of the vertical equipment was measured to be the same level as the uniformity of horizontal equipment. And it was measured that $3{\sim}4{\mu}m$ finer circuit pattern could be processed adopting vertical equipment rather than horizontal equipment.

• Journal of the Korean Society of Safety
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• v.31 no.3
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• pp.82-88
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• 2016

Ballasted gravel will be damaged or worn by the repetitive train load. And these damages of ballast gravel could be increased by increasing vehicle speed. Therefore, various techniques for reducing the ballast pressure have been proposed, such as the attached pad type of sleeper bottom for ballasted track. In this study, spring stiffness test method were proposed to evaluate the performance of under sleeper pad for ballasted track. Standard ballast plate(SBP) was developed to simulate the ballast gravel and compared with the foreign test results. Experimental results showed a trend similar to the previous studies according to various loading plate type. specimen type(Type A, Type B) differences in spring stiffness according to hardness were not significant. Also, the FSP (Flat steel plate) - shaped jig is about 80% of the spring stiffness was greater than SBP. Therefore, to evaluate the actual spring stiffness of under sleeper pad for ballasted track, it was important to adopted the appropriate spring stiffness test method using the SBP to simulate actual field conditions.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2214-2216
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• 2005

This paper is researched discharge and ozone generation characteristics of ozonizer using $Al_2O_3$ Ceramic dielectric. The discharge characteristics with variation of the discharge electrode area is studied. The characteristics of ozone concentration. ozone generation and ozone yield were measured to discharge power, discharge electrode area and supplied gas flux for oxygen and air. The solubility of ozone for water concentrations and ozone generations proportional to discharge power and discharge electrode area. Ozone yield has slowly increase with Increasing discharge power at high flow-rate. As the result, the maximum values of ozone characteristics ozone generation and ozone yield, can be obtained 5817[ppm] and 36[g/kWh]. We make enough the ozone concentration as the air in the home. An electric discharge electrode area is apt to shrink gradually into a miniaturization trend of the ozonizer but the enlargement of the occurrence flight of the electric discharge area gives the characteristic enhance the aid in the identity condition through the structure improvement.

• Journal of Korea Foundry Society
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• v.25 no.6
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• pp.254-258
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• 2005

Semisolid process is possible in any material system possessing a freezing range where the microstructure should consist of the nondendritic globular solid phase separated and enclosed by the liquid phase, referred to as semisolid slurry. There are two primary semisolid processing routes, thixocasting and rheocasting. Especially, rheocasting process has become a new focus in the field of semisolid process because of its many advantages such as no special billet required and possibility of in-house scrap recycling, compared with the thixocasting process. In-Ladle direct thermal control (DTC) rheocasting has been developed, based on the fact that there is slurry and mush transition in every molten metal and the transition, which normally occurs in the range of liquid traction of 0.1 to 0.6, could be controlled by controlling solid shape and relative solid-liquid interfacial energy. In this study, A356 Al alloy was investigated to verify In-Ladle DTC rheocasting for obtaining semisolid slurry. Modeling of heat transfer was carried out to investigate the effect of pouring temperature and ladle material, geometry and temperature and the simulation results were compared with the actual experiments.

• Journal of Korea Foundry Society
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• v.22 no.2
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• pp.75-81
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• 2002

The main objectives were to investigate the suitability of CaO crucible for melting TiAl alloys and to develop investment mold for investment casting of TiAl alloys. TiAl alloy specimen were prepared by plasma arc furnace under argon atmosphere. After melting of TiAl alloy using CaO crucible, the results showed that there is little contamination of oxygen in the TiAl bulk. Conventional vacuum induction furnaces can be readily adaptable to produce cast parts of TiAl without high skilled techniques. The determination of optical metallography and microhardness profiles in investment cast TiAl alloy rods has allowed the gradation of the relative thermal stability of the oxides examined. The molds used for the present study were $ZrO_2$, $Al_2O_3$, CaO stabilized $ZrO_2$ and $ZrSiO_4$. Even although high temperature of mold preheating, $Al_2O_3$ mold is a promising mold material for investment casting of TiAl alloys in terms of thermal stability, cost and handling strength. It is important to take thermal stability and preheating temperature of mold into consideration for investment casting of TiAl alloys.

• Journal of Korea Foundry Society
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• v.17 no.5
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• pp.472-479
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• 1997

The effect of size and mass fraction of SiC particulate on the fatigue and wear have been investigated for semi-liquid formed SiCp/AZ91HP Mg composites. In the study, different particulate sizes of 7, 20, $50 {\mu}m$ were prepared with various mass fraction for sample preparation. By tension-tension fatigue tests, whose procedures are standardized in ASTM standard 647E-93, the da/dN vs. ${\Delta}K$ curves were obtained. Also, the crack propagation paths were observed by optical microscope. As a result of wear test, specific wear loss is decreased with increasing mass fraction and particulate size. Specific wear loss of 30 mass% $50 {\mu}m$ SiC reinforced Mg composite is compared to SKD11.