• Electrical & Electronic Materials
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• v.9 no.3
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• pp.240-245
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• 1996

Non-ozone layer destructive Chlorofluorocarbon(CFC) altematives(CHCIF$_{2}$ and $C_{2}$H$_{2}$F$_{4}$) have been initially used for laser-induced thenrmochemical etching of GaAs. High etching rate up to 188.mu.m/sec and an aspect ratio of 2.7 have been achieved by a single scan of laser beam, respectively. The etching rate at constant ambient gas pressure was found to saturate for beam power. The chemical compositions of the reaction products deposited on the etched groove were measured by Auger electron microscopy(AES). Etched profile, depth and width were observed by scanning electron microscope(SEM).

• Korean Chemical Engineering Research
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• v.52 no.3
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• pp.294-301
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• 2014

This study focuses on analysis and comparison of entropy generation in various cross-sectional ducts along with fully developed laminar flow and constant uniform wall heat flux. The obtained results were compared in ducts with circular, semicircular, and rectangular with semicircular ends, equilateral triangular, and square and symmetrical hexagonal cross-sectional areas. These results were separately studied for aspect ratio of different rectangular shapes. Characteristics of fluid were considered at average temperature between outlet and inlet ducts. Results showed that factors such as Reynolds number, cross section, hydraulic diameter, heat flux and aspect ratio were effective on entropy generation, and these effects are more evident than heat flux and occur more in high heat fluxes. Considering the performed comparisons, it seems that semicircular and circular cross section generates less entropy than other cross sections.

• Journal of the Korean Ceramic Society
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• v.53 no.2
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• pp.222-226
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• 2016

The synthesis of pure calcium carbonate nanocrystals was achieved using a simultaneous injection method to produce nano particles of uniform size. These were characterized using scanning electron microscopy and powder X-ray diffraction. The nano particles were needle-shaped aragonite polymorphs, approximately 100-200 nm in length. The aragonite polymorph of calcium carbonate was prepared using aqueous solutions of $CaCl_2$ and $Na_2CO_3$, which were injected simultaneously into double distilled water at $50^{\circ}C$ and then allowed to react for 1.5 h. The resulting whisker-type nano aragonite with high aspect ratio (30) is biocompatible and potentially suitable for applications in light weight plastics, as well as in the medical, pharmaceutical, cosmetic and paint industries.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.1
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• pp.104-109
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• 2013

In order to apply nano imprint technology in large area process, roller pressing is promising because of its low cost and high productivity. When pressing mold by roller, liquid resin is locally squeezed between mold and substrate. In this study, the main focus is to understand which process parameter affects residual layer. To do this, a simple analytical model was introduced. Especially, we consider the aspect ratio of patterns as essential cause of variation of the thickness in the equation. As a result, when the aspect ratio of pattern in the mold increases, the thickness of residual layer also increases. In conclusion, we show that the uniformity of residual layer could be accomplished by the control of velocity and pressing force in roller pressing imprint process.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.546-546
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• 2012

Traditional screen printing is still a dominant method to print electrodes on c-Si solar cells. In order to achieve higher efficiency for c-Si solar cells, improvement of the electrode material is one of the key approaches. Shadowing loss can be reduced by using high aspect ratio finger electrode with width of finger electrode less than 80um. The rheological properties of Ag paste for applying c-Si solar cells are improved by using Ag nanowires. The printing properties including the aspect ratio of printed electrode can be improved with higher Thixotropic index (T.I.) values.

• Journal of the Korean Ceramic Society
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• v.42 no.11 s.282
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• pp.753-757
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• 2005

In this study, we attempted to recycle the fly ash as a mullite whisker with addition of $Al_{2}O_{3}$ to obtain the high yield of mullite whisker. During the reaction process, mullite whisker was formed with the reaction of amorphous $\alpha$-Cristobalite and Anorthite above $1350^{\circ}C$. With increasing the heat treatment temperature and time, the mean length and aspect ratio of mullite whiskers was gradually increased.

• Journal of the Korean Ceramic Society
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• v.43 no.5 s.288
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• pp.320-326
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• 2006

Mullite whiskers were synthesized by a vapor-solid reaction with $Al(OH)_3-SiO_2-AlF_3$. The heat treatment temperature did not affect the shape of mullite whisker but the composition change resulted in different sizes. The first one was $30-50{\mu}m$ in size with the aspect ratio of 60 and above, and the second one was $600{\mu}m$ and below in size with the aspect ratio of 15 and below. The $Al_2O_3$ content in formed mullite whisker was 73.57-80.29 wt%, which is high $Al_2O_3$ content composition. The Young's modulus and the hardness measured by nano-indentation method were 136.7 GPa and 19.81 GPa, respectively.

• Solar Energy
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• v.20 no.4
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• pp.61-67
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• 2000

The purpose of this study is to improve heat transfer by attaching rectangular fins to tube. Experiments were carried out under the following conditions - Aspect ratio$(W_f/R_f)$ is 0.7, 1.2 and 1.8. Temperature conversion between high and low positions of water in the thermal storage appeared because maximum density point of water is about $4^{\circ}C$ and inlet direction of working fluid influenced conductive heat transfer Compared with the unfinned tube(bare tube), the rectangular tube increased the ice thermal storage energy and the ice thermal storage energy was increased as aspect ratio was increased.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1163-1164
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• 2006

TZM alloy having elongated coarse-grain structure was developed by three-step internal nitriding treatment at 1423 to 1873 K in $N_2$ and subsequent recrystallization treatment at 2173 K in vacuum. Some specimens were subjected to re-nitriding treatment at 1873 K for 16 h. After the recrystallization treatment, aspect ratio (L/W) of grains for rolling direction was about 50 at the maximum. Yield stress obtained at 1773 K after re-nitriding treatment was about 6 times as large as that of recrystallized specimen. Re-nitriding was very effective in the improvement in strength of TZM alloy having elongated coarse-grain structure.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.9
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• pp.1517-1523
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• 2003

Deep X-ray lithography (DXRL), a fabrication method for the production of microstructures with a high aspect ratio, plays an important role in the subsequent electroplanting process. However, secondary radiation is generated during X-ray exposure and damages the resist adhesion to the metal layer. To solve adhesion problems, we modified the conventional DXRL process, changing the sequence of polymer adhesion in DXRL process. With optimized X-ray exposure and development conditions based on a calculated and modified X-ray power spectrum, we fabricated various polymer microstructures and achieved a maximum aspect ratio of 40.