• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.76-76
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• 2007

Several kinds of photo-chromic polymers containing push-pull structure were synthesized and investigated on optical patterning by photo-induced surface relief gratings (SRG) technique. The azobenzene segment was introduced as a functional group for a photo-triggered tran-cis isomerization. Consequently, we have fabricated micro-size regular pattern by one-step process without photo-mask.

• Macromolecular Research
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• v.16 no.6
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• pp.532-538
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• 2008

Epoxy-based azopolymers were synthesized by the reaction of the diglycidyl ether of bisphenol A (DGEBA) or N,N-diglycidyl aniline (DGA) with disperse orange 3 (DO3) to give poly(DGEBA-co-DO3) or poly(DGA-co-DO3), respectively. Aniline-based azopolymers prepared from poly(DGA-co-An) precursors, synthesized by the reaction of DGA with aniline, were produced by the post-azo coupling reaction with diazonium salts containing various substituents. Holographic gratings were carried out to measure the diffractive efficiencies (DE) for the interference patterns of the $Ar^+$ laser from 50 to $300\;mW/cm^2$ intensity. The shorter repeating unit with higher chromophore density induced deeper surface relief gratings (SRG). Large surface gratings were observed for the aniline-based azopolymers with -COOH substituents, as compared with those for epoxy-based azopolymers. The aniline-based azopolymers with dimerized chromophores and various substituents were also synthesized to observe the effect of chromophore substituents and dimerization on the holography. The dimerized chromophores were more sensitively photoisomerized by the $Ar^+$ laser beam, and demonstrated a larger grating than that with one azo bond.

• Korean Journal of Materials Research
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• v.30 no.10
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• pp.550-557
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• 2020

Used in the ceramic tile market as a representative building material, relief ceramic tile is showing increased demand recently. Since ceramic tiles are manufactured through a sintering process at over 1,000 ℃ after uniaxial compression molding by loading granule powders into a mold, it is very important to secure the flowability of granular powders in a mold having a relief pattern. In this study, kaolin, silica, and feldspar are used as starting materials to prepare granule powders by a spray dryer process; the surface of the granule powders is subject to hydrophobic treatment with various concentrations of stearic acid. The effect on the flowability of the granular powder according to the change of stearic acid concentration is confirmed by measuring the angle of repose, tap density, and compressibility, and the occurrence of cracks in the green body produced in the mold with the relief pattern is observed. Then, the green body is sintered by a fast firing process, and the water absorption, flexural strength, and durability are evaluated. The surface treatment of the granule powders with stearic acid improves the flowability of the granule powders, leading to a dense microstructure of the sintered body. Finally, the hydrophobic treatment of the granule powders makes it possible to manufacture relief ceramic tiles having a flexural strength of 292 N/cm, a water absorption of 0.91 %, and excellent mechanical durability.

• Korean Journal of Optics and Photonics
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• v.9 no.2
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• pp.51-58
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• 1998

We investigated surface-relief profiles of the TPHK(telecentric paraxial holographic kinofrm) used as a Fourier-transform lens employing exact geometrical raytracing. For the TPHK of F/8 and focal length of 15 mm, we consider the cases where the thickness of the substrate is 0 and 50 ${\mu}{\textrm}{m}$, dividing the surface-relif profiles into fifty steps from plano-convex to convexplano shapes and varying the angle of incidence($0^{\circ},{2.5}^{\circ},5^{\circ}$). In order to identify appropriate surface-relief profiles, we employ, as criteria of performance, rms spot size, rms deviation from $f{\sin}{\theta}$, peak position and FWHM(full width at half maximum), number of rays abandoned from raytracing etc., which are determined from the result of exact raytracing. It is found that the profile with 80% of its relief thickness facing the image plane gives the best performance regardless of the presence of substrate.

• Journal of The Geomorphological Association of Korea
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• v.28 no.1
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• pp.1-12
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• 2021

This study tried to reveal relative surface denudation resistance and ranking by geologic types in the Southern Korean Peninsula using an 1:250,000 digital geologic map and ASTER GDEM. Among rock types such as igneous, sedimentary and metamorphic rocks, metamorphic rock showed the greatest resistance to surface denudation. The most resistant rock to surface denudation by geologic periods (e.g., the Precambrian, Paleozoic, Mesozoic and Cenozoic) was found from the Precambrian. Among the major tectonic settings in the Southern Korean Peninsula such as the Gyeonggi massif, Okcheon belt, Yeongnam massif, Gyeongsang basin and Pohang basin, the Okcheon belt indicated the greatest resistance. The most and least resistant rocks from the representative nine rocks in the Southern Korean Peninsula were Paleozoic limestone, and Cretaceous sedimentary rock and Cenozoic sedimentary rock, respectively. This study suggests that Paleozoic limestone, Cretaceous volcanic rock, Paleozoic sedimentary rock and Precambrian gneiss can be regarded as hard rocks with high elevation, steep slope and complicated relief, while soft rocks with low elevation, gentle slope and simple relief are Jurassic granite, Cretaceous sedimentary rock and Cenozoic sedimentary rock.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.5
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• pp.489-500
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• 2004

Statement of problem: The use of zirconia prostheses fabricated with CAD/CAM system is on an increasing trend in dentistry. However, evaluation of the fit related to internal relief and marginal reproducibility of zirconia has not been reported. Purpose : This study was to evaluate the fit related to internal relief and marginal reproducibility of zirconia core fabricated with CAD/CAM system. Materials and methods: The evaluation was based on 30 zirconia cores and 5 IPS-Empress2 cores. Zirconia cores were fabricated in different conditions of internal relief(0, 10, 20, 30, 40 and $50{\mu}m$), and IPS-Empress2 cores were fabricated in accordance with the manufacturer's instructions. Before cementation, the marginal discrepancies or cores were measured on metal die. And then, each core was cemented to stone die, embedded in an acrylic resin and sectioned in two planes(mesiodistally and labiopalatally). The internal gaps were measured at the margin and axial surface. Measurements for the marginal discrepancies, the internal marginal gaps and the internal axial gaps were performed under a measuring microscope(Compact measuring microscope STM5; Olympus, Japan) at a magnification of ${\times}100$. In addition, the marginal conagurations of metal die, zirconia core and IPS-Empress2 core were examined with SEM(S-2700, Hitachi, Japan). Results : Within the limits of this study the results were as follows. 1. Compared with IPS-Empress2 cores, the marginal discrepancies of zirconia cores had no significant differences. the internal marginal gaps were statistically smaller and the internal axial gaps were statistically larger in each condition of internal relief. 2. The marginal discrepancies and the internal marginal gaps of zirconia cores had no significant differences related to the conditions of internal relief(P>0.05). 3. The internal axial gaps of zirconia cores with $0{\sim}20{\mu}$m for internal relief were significantly larger than that with $50{\mu}m$ (P<(0.0001). 4. SEM micrographs showed favorable marginal reproducibility of zirconia core and smooth texture on the milling surface. Conclusion: The marginal discrepancy and the internal gaps of zirconia core were clinically acceptable and the milling surface was showed smooth texture. For fabrication of the durable esthetic restoration, further investigations on complex design of core, milling accuracy, compatability of enamel porcelain and porcelain firing seems to be needed.

• Applied Microscopy
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• v.42 no.1
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• pp.35-42
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• 2012

The skin is the largest organ of the integument system whose surface is closely related to many physiological and pathological conditions. The skin surface is closely related to functional status of the epidermis and dermis. The outermost surface of the skin shows characteristic pattern defined by small furrows are called micro-relief. The micro-relief change is according to physiological and pathological conditions of the skin. But, there is no data on health Korean skin micro-relief yet. This study presents some aspect of health Korean skin micro-relief from the twenties. The silicon replicas obtained from forearm, dorsum hand and finger were analyzed by profiles were accessed by stereoscopy. We measured density of furrow, width of furrow, and depth of furrow in micro-relief with sectioned silicon replica sample using stereoscope. Stereoscopic analysis showed that male group has a larger density of furrow and depth furrow in finger significantly. The densities of furrow were shown different not only between forearm and finger but also between finger and hand in male with female group. In conclusion, there were differences results between sex different and regional difference in skin replica profile. These quantitative data can be used for basis of further skin research for Korean.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.17 no.3
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• pp.245-256
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• 1999

Watershed delineation is the process of tracing surface water flow across a landscape to identify hydrologic basins. Manual and automated techniques have been developed to trace surface waters and locate watersheds on a variety of landscape. Low topographic relief landscapes, however, are particulary problematic for automated watershed delineation techniques. Therefore, this study aims at focusing the watershed delineation algorithm of low topographic relief landscape. By using topogrid, which manages enforcement drainage algorithms and incorporates topographic data into stream data, this study delineates watershed boundary in low relief landscape. Based on this research, in a low topographic relief landscape, enforcement drainage algorithms using topogrid generate better source grid to delineate watershed boundary than using only TIN. Also, comparing automated watershed delineation which incorporates contours and elevations into stream data with manual watershed delineation, we can know that the incorporation of both elevation and stream data generate more effective results.

• Journal of the Optical Society of Korea
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• v.1 no.1
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• pp.26-35
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• 1997

Rigorous coupled-wave analysis (RCWA) with a simplified eigenvalue problem is used to investigate the an-tireflective property of one-dimensional surface-relief gratings such as binary gratings, triangular gratings and gratings with triangle-like surface profiles. The convergence of RCWA is investigated by varying the number of layers and the number of space-harmonics used in the computation. For unpolarized light normally incident on a medium of refractive index 1.64 from vaccum, a triangle-like grating shows the reflectivity of $1.6 {\times} 10^{-4}$ in contrast to a minimum reflectivity of $3.8 {\times} 10^{-3}$ for a binary grating. We also study the dependence of reflectivity on the wavelength, and on the angle of incidence for a groove shape and depth which result in minimum reflectivity.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.1
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• pp.132-142
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• 2000

The objective of this study is to experimentally investigate the noise propagating characteristics, the noise reduction mechanism and the performance of a slotted tube attached at the exit plane of a circular convergent nozzle. The experiment is performed through the systematic change of the jet pressure ratio and the slot length under the condition of two kinds of open area ratios, 25% and 51%. The open area ratio calculated by the tube length equivalent for the slot length is defined as the ratio of the total slot area to the surface area of a slotted tube. The experimental results for the near and far field sound, the visualization of jet structures and the static pressure distributions in the jet passing through a slotted tube are presented and explained in comparison with those for a simple tube. The propagating characteristics of supersonic jet noises from the slotted tube is closely connected with the slot length rather than the open area ratio, and its propagating pattern is similar to the simple tube. It is shown that the slotted tube has a good performance to suppress the shock-associated noise as well as the turbulent mixing noise in the range of a limited jet pressure and slot dimension. The considerable suppression of the shock‘associated noise is mainly due to the pressure relief caused by the high-speed jets passing through the slots on the tube. Both the strength of shock waves and the interval between them in a jet plume are decreased by the pressure relief. Moreover, the pressure relief is divided into the gradual and the sudden relief depending upon the open area ratio of the slotted tube. Consequently, the shock waves in a jet plume are also changed by the type of pressure relief. The gradual pressure relief caused by the slotted tube with the open area ratio 25% generates the weak oblique shock waves. On the contrary, the weak normal shock waves appear due to the sudden pressure relief caused by the slotted tube with the open area ratio 51%.