• Bulletin of the Korean Chemical Society
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• v.31 no.6
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• pp.1657-1660
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• 2010

An efficient and novel one-pot synthesis of new 3,4-dihydro-3-substituted-2H-naphtho[2,1-e][1,3]oxazine derivatives from 1-naphthol, various anilines and formalin at room temperature grinding is presented. The six-membered N,O-heterocyclic skeleton was constructed via zirconyl(IV) chloride promoted Mannich type reaction. In vitro antimicrobial activities of synthesized compounds have been investigated against Gram-positive Bacillus subtilis, Gram negative Escherichia coli and two fungi Candida albicans and Aspergillus niger in comparison with standard drugs. The results of preliminary bioassay indicate that some of title compounds possess significant antibacterial and antifungal activity.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.12
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• pp.56-65
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• 1997

This paper presents the robot program for propeller grinding. A robot manipulator is constructed by combining a parallel and a serial mechanism to increase high sitffness as well as workspace. The robot program involves inverse/direct kinematics, velocity mapping, Jacobian, and etc. They are cerived in efficient formulations and implemented in a real time control. A velocity control is used to measure the hight of a propeller blade with a touch probe and a position control is performed to grind the surface of the blade.

• Journal of Astronomy and Space Sciences
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• v.21 no.2
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• pp.141-152
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• 2004

Optics fabrication process for precision space optical parts includes bound abrasive grinding, loose abrasive lapping and polishing. The traditional bound abrasive grinding with bronze bond cupped diamond wheel leaves the machine marks of about $20{mu}m$ rms in height and the subsurface damage of about 1 ${mu}m$ rms in height to be removed by subsequent loose abrasive lapping. We explored an efficient quantitative control of precision CNC grinding. The machining parameters such as grain size, work-piece rotation speed and feed rate were altered while grinding the work-piece surfaces of 20-100 mm in diameter. The input grinding variables and the resulting surface quality data were used to build grinding prediction models using empirical and multi-variable regression analysis. The effectiveness of such grinding prediction models was then examined by running a series of precision CNC grinding operation with a set of controlled input variables and predicted output surface quality indicators. The experiment achieved the predictability down to ${pm}20$ nm in height and the surface roughness down to 36 nm in height. This study contributed to improvement of the process efficiency reaching directly the polishing and figuring process without the need for the loose abrasive lapping stage.

• Food Engineering Progress
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• v.13 no.4
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• pp.269-274
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• 2009

The main objective of this study was to establish optimum condition of wet grinding process for manufacturing microparticulated seaweed calcium. Process parameters such as concentration of forming agent, rotor speed, bead size, feed rate, and grinding time were adapted during wet-grinding of seaweed calcium. The particle size range of the raw seaweed calcium was 10-20 $\mu$m. The calcium particles were reduced to under 1 $\mu$m as nano scale after grinding. Gum arabic was suitable for forming agent and 5%(w/v) concentration was the most effective in grinding efficiency. A wet-grinding process operated at 4,000 rpm rotor speed, 0,4 mm bead size, and 0.4 L/hr feeding rate, respectively, produced less than 600 mm(>>90%)-sized particles. In batch systems, 8 cycles of grinding showed higher efficiency, but 20 min of grinding time in continuous processing was more efficient to reduce particle size than the batch processing. Based on the result, the optimum conditions of the wet grinding process were established: operation time of 20 minutes, rotor speed of 4,000 rpm, bead size of 0.4 mm, feed rate of 40 mL/min and 30% mixing ration with water. The size of the resulting ultra fine calcium particles ranged between 40 and 660 mm.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.7
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• pp.56-62
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• 2003

The precision fabrication of glass is increasingly demanded for the latest industrial applications of spherical lenses, micro-optical components, and so on. In many cases, the surface roughness of glass is required to be minute for improving the optical characteristics. In this paper, machining characteristics of SF-5 glass and quarts glass are studied by using the ELID grinding process to get mirror surface and productivity compared with a general lapping process. A rotary type grinder with air spindle was used for the experiments. Mitutoyo surface tester and AFM were also used to measure the grinded surface of glass. As the results of experiments, they showed that the surface roughness (Ra) of SF-5 glass was under 7.8 nm and that of quartz glass was under 3.0 m using the # 8000 grinder. So, the possibility of highly efficient and accurate surface for optical components can be achieved by the ELID grinding process.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.94-97
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• 2003

A precise fabrication technology of glass is increasingly demanded fer the latest Industrial applications of spherical lenses. micro-optical components, laser applications and so on. Most of cases, the surface roughness of glass is required to be minute for improving the optical characteristics. Then. the machining characteristics of SF-5 glass and quarts glass were studied by using the ELID grinding process to get mirror surface and productivity compared with a general lapping process. A rotary type grinder with ELID generator was used to make the mirror surface of glass and a Mitutoyo surface tester and a nano-hardness tester were also used to measure the grinded surface or glass. As the results of experiments. they showed that the surface roughness(Ra) of SF-5 glass was under 7.8 nm and that of quartz glass was under 3.0 nm using the # 8000 grinder. So, the possibility of highly efficient and accurate surface for optical components can be achieved by the ELID grinding process.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.6
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• pp.1139-1148
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• 2000

To treat and recycle a large quantity of converter slag. the milling properties of -14/ +24 mesh-sized slag has been considered. The optimal conditions in milling process were investigated for producing powder-type slag and the required consumption was derived for the economical grinding. The characteristics of milling processes were studied in the variation of the rotational speed, milling time, filling ratio of ball, and size and amount of feed. The grinding efficiency was also examined. The optimal rotational speed in this experimental condition was observed to be the value of 79% of critical speed. The extent of grinding was increased with increasing the grinding time. but the efficiency of milling was decreased with the time. 50% ball filling was shown to have the optimal grinding effect, and less amount and small-sized feed made the milling efficiency high. As the result, using Bond's equation, power required for efficient milling was considered and the highest value was observed in the condition of high grinding time and optimal rotational speed.

• Journal of the Mineralogical Society of Korea
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• v.23 no.3
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• pp.219-225
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• 2010

Optimal grinding condition was examined by changing only the size of screen opening with fixing other factors to produce coal fines of particle sizes required for circulating fluidized bed gasifier. At least 85 wt% of the coal particles should fall into the size range of 0.045~1.0 mm for efficient gasification. In this study, hammer mill was used to grind Chinese low rank lignite coal following grinding condition designed by Taguchi method. The analysis of signal to noise ratio showed that optimum grinding condition for the gasifier was 3 mm in primary screen size and 1.3 mm in secondary screen size on the 95% level of significance.

• Proceedings of the Optical Society of Korea Conference
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• 2004.02a
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• pp.204-205
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• 2004

• Clean Technology
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• v.10 no.3
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• pp.139-148
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• 2004

The recovery of stainless steel fiber by removing cutting oil from grinding swarf, which is classified as specified wastes, was investigated. Swarf loaded with grinding oil was regenerated by supercritical carbon dioxide. And, the effects of temperature(313.15K-323.15K), pressure(10MPa-30MPa) on regeneration efficiency were studied. Regeneration effiency was increased as the pressure was increased. Also, at the same pressure, the experiments at higher temperature were more efficient for regeneration. The experiment results was predicted by applying a one-parameter mathematical model assuming linear desorption kinetics. The predicted value showed good agreement with experimental data.