• Restorative Dentistry and Endodontics
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• v.21 no.1
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• pp.136-149
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• 1996

The effects of various All-Etching Agents (10% phosphoric acid, 10% maleic acid and 10 % citric acid) and 32 % phosphoric acid and varied etching time were evaluated by observing the morphology of the etched enamel surfaces using Scanning electron microscopy and by measuring the shear bond strength of a composite resin to human enamel. A total of 156 extracted premolar and molar teeth free of irregularities were employed in this study. Specimens for the observation of enamel morphology were divided into 12 groups of 3 teeth each, based on the type of etchant used and application time. After exposure to the etching agent specimens were washed air-dried and then glued to aluminum stubs and coated with a layer of gold for examination in the scanning electron microscope. Specimens for the evaluation of bond strength were divided into 12 groups of 10 teeth each also based on the type of etchant used and application time. After exposure to the etching agent the specimens were washed, air-dried and a thin layer of bonding agent was applied using a brush. Z 100 composite resin was light cured to the surface and stored at $37^{\circ}C$, 100% humidity for 7 days. An Instron Universal Testing Machine was used to apply a shearing force at $90^{\circ}$ angle from the enamel surface. It is concluded from this study that commercial All-etching agents can be used with a 15-second etching without adversely affecting retention of dental resin materials. At the same time, the acid concentration is probably a suitable compromise regarding the acid's function as a dentin demineralizing all-etch conditioning agent. The following results were obtained. 1. Specimens etched with 10 % citric acid showed a random superficial etching pattern which could not be related to prism morphology. 2. Specimens etched with 10 % and 32 % phosphoric acid and 10 % maleic acid showed a type I pattern in which core material was preferentially removed leaving the prism peripheries relatively intact or a type II pattern in which prism peripheries were preferentially removed. This delineation became more distinguished as etching time was increased. 3. All-Etching Agents and 32 % phosphoric acid showed a statistically significant higher shear bond strength at 15 seconds etching time.(p<0.05) 4. 10 % maleic acid and 32 % phosphoric acid exhibited a statistically significant higher shear bond strength than 10 % phosphoric and citric acid at 15 seconds etching time.(p<0.05).

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.2
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• pp.310-314
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• 2015

To improve the optical performance of the backlight unit with light guide plate(LGP), we investigated the effects of LGP patterns on the brightness and viewing angles properties of the backlight unit. We designed several patterns of LGP and calculated their optical properties by the optical simulation. The results reveal that the highest brightness and wide viewing angle was achieved with the extended-closed-polygon diffusion pattern and upper triangle prism pattern of the LGP.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.11a
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• pp.185-188
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• 2005

We present the method to obtain four speckle patterns with relative phase shift of ${\pi}/2$ by passive devices such as wave plate and polarizer, and calculate the phase at each point of the speckle pattern in shearographic system using Wollaston prism. And, we analyzed the phase error caused using wave plates by Jones matrix.

• Journal of the Optical Society of Korea
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• v.9 no.4
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• pp.145-150
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• 2005

The method to obtain four speckle patterns with relative phase shift of $\pi$/2 by passive devices such as two waveplates and a linear polarizer, and to calculate the phase at each point of the speckle pattern in shearography with a Wollaston prism is described. In this paper, we analyze its potential error sources caused by wave plates.

• Korean Journal of Optics and Photonics
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• v.31 no.6
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• pp.321-327
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• 2020

We investigated the light reflection from thin films coated on substrates. Using a prism with a high refractive index as the incident medium, the phenomena of the total internal reflection (TIR) of the prism/film/substrate system and the light coupling into the optical waveguide formed by the air/film/substrate system were comprehensively studied and compared. If the refractive index of the thin film is greater than that of the substrate, within the TIR region of the substrate, sharp reflection minima occur at specific angles where the waveguide modes are excited, that can be used to accurately measure the refractive index and thickness of a thin film. On the other hand, if the refractive index of the thin film is smaller than that of the substrate, such waveguide modes do not exist. In this case, although not so distinct as a bulk medium, the TIR effect of the thin film is still observable, accompanied by an interference pattern. In this study we analyzed the overall reflection phenomena occurring from prism/film/substrate structures, to investigate the possibility of measuring the refractive index of a thin film in both cases.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.10
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• pp.903-910
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• 1998

Ti:LiNbO$_3$ optical waveguides have been fabricated by Ti-diffusion in wet oxygen atmosphere. The fabrication conditions of furnace temperature, diffusion time and bubbler temperature were 105$0^{\circ}C$, 8 hours and 9$0^{\circ}C$, respectively and Ti thickness was varied from 700$\AA$ to 1500$\AA$. In this paper, the nearfield patterns, mode sizes (hirizontal/vertical) and insertion loss of waveguides were discussed at wavelength 1550 nm ad function of Ti thickness. With the planar waveguide, the effective index change and diffusion depth were calculated at 632.8nm using the prism coupling method. From these results, the best Ti thickness in our conditions seems like to by 1200$\AA$~1300$\AA$.

• The korean journal of orthodontics
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• v.34 no.6 s.107
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• pp.537-543
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• 2004

Microsatellit markers are considered to be very promising genetic markers for genetic linkage analysis. The majority of the markers are as informative as in Caucasians but there are significant ethnic differences in the genetic variations. In order to investigate the genetic variations in the Korean and Japanese populations and their ethnic differences, 51 microsatellite marker loci spanning the whole human chromosome 1 were arranged from a commercially available set (ABI PRISM Linkage Mapping Set-HD5, Applied Biosystems, Foster City, CA, USA), and then determined the allelic frequencies and heterozygosities for these marker loci in the 90 unrelated Korean subjects and 90 unrelated Japanese subjects. Of all 51 markers tested, significant differences were observed when microsatellite allele frequency pattern of Korean was compared with those of Caucasian, while this pattern was highly similar between Korean and Japanese populations. Our data indicate that an extensive verification of public microsatellite markers in a particular population study should be undertaken prior to their linkage studies. Moreover, this information should facilitate genetic linkage studies of various hereditary diseases, especially in the Koreans and Japanese.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.6
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• pp.1-6
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• 2010

Patterned optical components are widely used for optical products such as LCD and lighting. Since CCFL was used as a light source in the products, prism films having linear continuous optical patterns were widely used. However, LED which is a dot light source is popular recently, therefore, the optical products need new optical components having non-continuous optical patterns. Indentation machining method is a powerful method for machining of non-continuous pattern. When a copper mold and a brass mold were machined by this method, severe plastic deformation called pile-up was observed around the patterns. Since pile-up has negative relationship to ductility, this deformation can be eliminated by annealing treatment which makes the materials ductile. No plastic deformation occurred when machined after annealing at $600{^{\circ}C}$ and $575{^{\circ}C}$ for copper and brass, respectively. Finally, non-continuous optical patterns with high quality were machined on a copper mold and a brass mold successively.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.5
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• pp.64-69
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• 2014

This article presents machining experiments to assess the relationship between the profile accuracy and the workpiece hardness using a natural diamond tool on an ultra-precision diamond turning machine. The study is intended to secure a corner cube prism pattern for reflective film capable of high-quality outcomes. The optical performance levels and edge images of corner cubes having various hardness levels of the copper-coated layer on a carbon steel plate are analyzed. The hardness of the workpiece has a considerable effect on the profile accuracy. The higher the hardness of the workpiece, the better the profile accuracy and the worse the edge wear of the diamond tool.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.79-82
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• 2005

Fresnel lens has number of applications in the optical systems because of its advantages. It is nearly flat lens that has small weight. It is conventionally used in lighthouse beacons, condensing unit of overhead projector and etc. Recently, demands of small size optical systems such as display units, information storage systems, optical detecting units had increased. Conventional manufacturing process of high quality Fresnel lens is direct machining. But it is not suitable for mass production because of high cost and long cycle time. Replication process is more suitable for mass production. But the Fresnel lens has number of sharp blade shape prism. In the replication process, this blade shape causes defects that can affect optical efficiency. In this study, replication process of blade shape pattern that has maximum height of $280{\mu}m$, aspect ratio 1.4 for Fresnel lens application.