• Journal of the Korean Society for Precision Engineering
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• v.15 no.2
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• pp.146-153
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• 1998

NC machines with 4 or 5 axes are capable of various tool approach motions, which makes interference-free and high machinablity machining possible. This paper deals with how to integrate these two advantages (interference-free and high machinability machining) in multi-axes NC machining with a ball-end mill. Feasible tool approach region at a point on a surface is first computed, then among which an approach direction is determined so as to minimize the cutting force required. Tool and spindle volumes are considered in computing the feasible tool approach region, and the computing time is improved by trans-forming surface patches into minimal enclosing spheres. A cutting force prediction model is used for estimating the cutting force. The algorithm is developed so as to be applied to 4- or 5-axes NC machining in common.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.69-72
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• 1999

A Well oriented Bi$_2$re$_2$CaCu$_2$O$\sub$8/(Bi2212) superconductor thick films were formed successfully on a copper substrate by liquid reaction between a Cu-free precursor and Cu tape using method in which Cu-free BSCO powder mixture was printed on copper plate and heat-treated. And we examined the mechanism for the rapid formation of Bi2212 superconducting films from observing the surface microstructure with heat-treatment time. At heat-treatment temperature, the printing layer partially melt by reacting with CuO of the oxidizing copper plate, and the nonsuperconducting phases present in the melt are typically Bi-free phases and Cu-free phases. Following the partial melting, the Bi$_2$Sr$_2$CaCu$_2$O$\sub$8/ superconducting phase is formed at Bi-free phase/liquid interface by nucleation and grows. It was confirmed that the phase colony from the phase diagram of Bi$_2$O$_3$-(SrO+CaO)/2-CuO system is similar to the observed result.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.10a
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• pp.101-105
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• 1993

When machining a die cavity, many machining conditions must be considered. Especially when using a NC machine, The tool interference is a improtant problem. In this paper, we consider the tool interference of free-formed surfaces and analytic compound surfaces which having free_formed base and many primitives and present a method checking the tool interference regions and avoiding them

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 1999.02a
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• pp.22-25
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• 1999

A well oriented Bi-2212 superconductor thick films were fabricated by screen printing with a Cu-free Bi-Sr-Ca-Cu-O powder on a copper plate and heat-treating at 820- $880^{\circ}C$for several minute in low oxygen pressure or are. At minute in low oxygen pressure of air. At , the printing layer partially melted by reaction between the Cu-free precursor by reaction between the Cu-free$870^{\circ}C$ precursor and CuO of the oxidizing copper plate. It is believed that the solid phase is Bi : Sr : Ca : Cu = 2 : 2 : 0 : 1. It is likely that the Bi-2212 superconducting phase is formed at Bi-2212 superconducting phase is formed at Bi-free phase/liquid interface by nucleation and grows.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.7 no.1
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• pp.89-97
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• 1995

Experimental study was performed for free convection and ice formation around two horizontal circular tubes which were placed vertically. Temperature and velocity distributions were visualized with real time holographic interferometry technique and tracer method. When water was cooled, super cooled region was formed around cooling pipe. It was found that flow induced by free convection always directed downwards when the coolant temperature was low, while it directed upwards when the coolant temperature was comparably high though it directed downwards initially. Flow phenomena with free convection were investigated in detail with varying cooling rate and length between cooling pipes. And growing process of dense ice was also investigated. Dendritic ice is suddenly formed within a supercooled region, and a dense ice layer begins to develop from the cooling wall.

• Proceedings of the Ginseng society Conference
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• 1998.06a
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• pp.57-62
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• 1998

We hypothesized the primary effect of ginseng was to protect cell membrane fatty acids from decomposition caused by free radicals. To confirm the antioxidant effect of ginseng, we measured the inhibitory effect on the formation of thiobarbituric acid-reactive substances, an indicator of lipid peroxidation, and evaluated the free radical scavenging effect of ginseng by electron spin resonance spectrometer, and gas chromatography. The results showed that thiobarbituric acid-reactive substances formed and the loss of arachidonic acid during lipid peroxidation, and that hydroxyl (-like) radical peak formed by the iron complex (ferric nitrilotriacetate, an known free radical generator in vitro) were completely inhibited by ginseng extract. This antioxidant effect of ginseng may be responsible for its wide pharmacological actions in clinical practice. As the free radical reactions in general are rapid and non-specific, ginseng seems to act as a normalizer, rather than a general tonic, at the stages of acute or chronic active phase of the various diseases.

• 한국전산유체공학회:학술대회논문집
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• 1995.10a
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• pp.132-137
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• 1995

Numerical analysis is conducted on the deformation of free surface of magnetic fluid. Steady magnetic fields are induced by a circular current loop. Governing equations of magnetic fields are solved by using the concept of vector potential. The free surface of magnetic fluid is formed by the balance of surface force, gravity, pressure difference, magnetic normal pressure and magnetic body force. The deformations of free surface of magnetic fluid are qualitatively clarified. And, the patterns of steady non-uniform magnetic fields induced by a circular current loop are quantitatively presented.

• Korean Journal of Plant Tissue Culture
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• v.26 no.1
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• pp.31-35
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• 1999

Morphological characteristic during formation of tobacco crown gall tumor and genetic tumor, and their differential response to growth regulator were investigated in in vitro culture. Crown gall tumor was induced from tumor tissue transformed by infecting Agrobacterium tumefaciens C58. Genetic tumor was induced from tumor tissue which was induced spontaneously from reciprocal interspecific hybrids between Nicotiana glauca (2n=24) and Nicotiana langsdorffii (2n=18). Morphological characteristic of crown gall tumor, genetic tumor, and teratoma shoot was very similar, and they were actively proliferated on hormone-free medium. Typical tumor callus and teratoma shoot formed from crown gall tumor on the hormone-free medium. On the contrary, tumor callus derived from genetic tumor formed as a crown gall tumor callus on the medium supplemented with 0.5 mg/L of 2,4-D, and lots of teratoma shoots without any root formed on the hormone-free medium. Root development from the teratoma shoots was hardly obtained on the medium with IAA, GA and active carbon. However, teratoma shoots with roots, as normal shoots, were initiated occasionally on the hormone-free medium. These shoots also formed new genetic tumor on the stem, which leaves formed lots of teratoma shoot on the hormone-free medium in in vitro culture.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.1087-1088
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• 2013

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2006.04a
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• pp.154-154
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• 2006