• Journal of Technologic Dentistry
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• v.41 no.4
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• pp.279-285
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• 2019

Purpose: The dental CAD / CAM system has been popular with the development of the digital dental industry. Zirconia is a typical material in dental CAD / CAM systems. Zirconia crowns are classified into single layer and double layer. This study is about the double layer crown of zirconia. The surface roughness, bond strength and fracture patterns of the zirconia surface were observed. Methods: Zirconia blocks were cut using a low speed cutter. Sintered to form a plate shape (6mm × 6mm × 3mm). The prepared specimens were surface treated in four ways. Surface roughness and bond strength were measured. And the fracture pattern was observed. Results: Result of surface treatment of zirconia. The surface roughness test results were as ET 2.87 ㎛, ST 2.67 ㎛, LT 2.44 ㎛, AT 2.41 ㎛, CN 2.08 ㎛ order. Bond Strength results were as LT 25.09 MPa, AT 23.27 MPa, ST 21.27 MPa, ET 21.09 MPa, CN 16.12 MPa order. Fracture patterns showed cohesive failure of 25-50% of the bond area. Conclusion: Surface roughness, bond strength and fracture pattern of the zirconia surface were observed. Etching the surface treatment of zirconia materials has been shown to affect the surface roughness. Zirconia special binder treatment has been shown to affect the bond strength improvement.

• Journal of the Society of Naval Architects of Korea
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• v.44 no.2 s.152
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• pp.174-179
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• 2007

The cutting automation of boat's wooden pattern is strongly required to improve the productivity and quality of boats in leisure boat industry. This paper is concerned with the development of wooden pattern machining technology by the machining center. The leisure boat is designed with a 3 dimensional design s/w. The NC cutting data are generated in a CAM s/w and are verified using verification s/w. The cutting forces are monitored to analyse the cutting process. The surface characteristics of machined surface are investigated at various cutting conditions such as spindle speed, feed speed, the cutting direction of wood, and wood material.

• 보존과학연구
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• s.26
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• pp.41-56
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• 2005

A set of horse bit from the Eonnam-ri site consists of three parts, pyo , ham , andinsu , and each part takes a shape of a piece of bar. According to current typological study, the pyo is S type, the insu is two-braided line type, and the outer rim of the ham is double rim type, respectively. According to X-ray test, inlaid design seems to have been decorated on the whole surface of the iron bit, originally. However, inlaid pattern partially remained. While the part of bit stopper is designed with flame pattern, the part of rein joint is designed with cloud pattern. According to XRF and XGT analysis of inlaid material, the content of silver is not more than 50%. The line inlay method making grooves on the surface of iron, then in laying a silver thread into them, and grinding the surface in a direction was adoptedin the manufacture of the iron bit.

• International Journal of Naval Architecture and Ocean Engineering
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• v.8 no.1
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• pp.22-37
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• 2016

This article investigates numerical modeling of surface piercing propeller (SPP) in unsteady open water condition using boundary element method. The home code based on BEM has been developed for the prediction of propeller performance, unsteady ventilation pattern and cross flow effect on partially submerged propellers. To achieve accurate results and correct behavior extraction of the ventilation zone, finely mesh has generated around the propeller and especially in the situation intersection of propeller with the free surface. Hydrodynamic coefficients and ventilation pattern on key blade of SPP are calculated in the different advance coefficients. The values obtained from this numerical simulation are plotted and the results are compared with experiments data and ventilation observations. The predicted ventilated open water performances of the SPP as well as ventilation pattern are in good agreement with experimental data. Finally, the results of the BEM code/experiment comparisons are discussed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.91-95
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• 1997

ESPI(Electronic Speckle Pattern Interferometry) is new optical measuring method to be able to measure the surface deformations of engineering components and materials in industrial areas. Conventional measuring method of surface deformation such as the strain gauge have many demerits because it is contact and point-to-point measuring one. But ESPI that is non-contact, whole field measuring method can overcome previous disadvantages. The speckle pattern to be formed with interference phenomena of scattering light from rough surfaces illuminated by laser light have phase information of surface In this study we used this interference phenomena and the phase shifting method to measure the in- plane deformation, together with the use of digital equipment to process the information contained in the speckle pattern and to display consequent inter ferograms. Finally we obtained good agreement between the experimenta results and those of FEM..

• Journal of ILASS-Korea
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• v.17 no.1
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• pp.20-26
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• 2012

Inkjet printing is one of the direct writing technologies and is able to form a pattern onto substrate by dispensing droplets in desired position. Also, by inkjet technology manufacturing time and production costs can be reduced, and procedures can be more efficient. To form a metal pattern, it must be harmonized with conductive nano ink, printing process, sintering, and surface treatment. In this study, micro patterning of conductive line has been investigated using the piezoelectric printhead driven by a bipolar voltage signal is used to dispense $20-40{\mu}m$ diameter droplets and silver nano ink which consists of 50 nm silver particles. In addition, hydrophobic treatment of surface, overlap printing techniques, and sintering conditions with changing temperature and times to achieve higher conductivity.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.12 no.1
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• pp.81-87
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• 1999

The surface morphology of liquid crystal alignment layer has been investigated by using Brewster angle microscope(BAM) for the first time. The samples used in this work for liquid crystal alignment layer were mechanically rubbed polyimide films. The rubbing pattern on this layer has been analyzed with the terms of microgroove and rubbing induced optical birefringence. For the mechanically rubbed surface, the geometrical factors of microgroove play the major role for the formation of rubbing pattern. We propose that the BAM can be used as a powerful tool not only for observing the rubbing pattern, but also for inspecting the surface defects.

• Restorative Dentistry and Endodontics
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• v.12 no.2
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• pp.91-98
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• 1987

This study was designed to investigate the changing depositional pattern of inorganic enamel substances during enamel formation and maturation. For this purpose, white rat incisors which continuously grow and develop during the life, were chosen as specimens. And after treated with 20% KOH solution, outer surface of forming inorganic enamel were observed with the scanning electron microscope, dividing into 6 types according to the forming pattern from apical to cuspal direction. The observations lead to the following conclusions: 1. During the initial enamel forming stage, inorganic enamel substances were deposited with very irregular pyramidal shape on the root dentin surface. 2. During the enamel forming stage, inorganic enamel substances were deposited with relatively regular hexagonal, honey-comb appearance. 3. During the later enamel forming stage, inorganic enamel substances were deposited with very irregular and roughly amorphous appearance. 4. During the later enamel maturating stage, very small and round inorganic enamel substances were deposited densely, and made a flat enamel surface.

• Journal of the Korean Society for Heat Treatment
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• v.34 no.3
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• pp.130-136
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• 2021

With the development of the industry, bearings that require higher durability and efficiency are required, and various methods to reduce friction and wear of bearings are being studied. In this study, a wear test was conducted for STB2, a bearing steel material, by machining a micro-line pattern on the race surface of the bearing by machining. The pattern pitch of the specimens was processed to 40㎛, 80㎛, and 150㎛, and the coefficient of friction characteristics were investigated for the unpatterned specimen and the specimen with a DLC thin film deposited on the surface. As a result of the wear test, the pattern pitch showed the smallest coefficient of friction at 40㎛, and it was confirmed that the smaller the pattern pitch, the better the tribology characteristics.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.12
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• pp.800-805
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• 2017

Randomly patterned and wet chemical etching processes were used to treat anti-glare of display cover glasses. The surface and optical properties of grain size and surface morphology controlled by randomly patterned etching and wet chemical solution etching were investigated. The surface morphology and roughness of the etched samples were examined using a spectrophotometer and a portable surface roughness (Ra) measuring instrument, respectively. The gloss caused by reflection from the glass surface was measured at $60^{\circ}$ using a gloss meter. The surface of the sample etched by the doctor-blade process was more uniform than that obtained from a screen pattern etching process at gel state etching process of the first step. The surface roughness obtained from the randomly patterned etching process depended greatly on the mesh size, which in turn affected the grain size and pattern formation. The surface morphology and gloss obtained by the etching process in the second step depended primarily on the mesh size of the gel state etching process of the first step. In our experimental range, the gloss increased on decreasing the grain size at a lower mesh size for the first step process and for longer reaction times for the second step process.