• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.10a
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• pp.292-296
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• 2002

In the present investigation, the improvement of processing efficiency in the high speed machining of GC250 is explored. This study is to evaluate the tool performance in difficult-to-material using the new developed tool. Tool performance evaluation are conducted by tool wear, surface roughness, chattering in machined surface. The tool wear of A type was smaller than B type. In type B tool the chatter mark was observed in machined surface. The good surface roughness was obtained in type A tool. Consequently, the tool performance of A type is better than B type.

• Analytical Science and Technology
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• v.10 no.1
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• pp.1-8
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• 1997

We identified nicotine, cotinine and toluene in high school volunteer's urine by using GC/NPD, GC/FID and GC/MS. To analyze of nicotine and cotinine, urine samples were extracted with diethylether and centrifuged on a benchtop centrifuge for 5 min. The upper organic layer was injected into a GC. The distributions of nicotine and cotinine were $4{\sim}630{\mu}g/L$ and $63{\sim}1,602{\mu}g/L$ in smoking-group, respectively. To analyze of toluene, head space vial was filled with 2mL sodium citrate solution and 1mL of urine. The vial was warmed in a water bath at $55^{\circ}C$ for 20min, and then $250{\mu}L$ of head space air was injected into a GC. The result show that toluene was not detected in all of the volunteers' samples. However, the range of toluene was 0.1~28.0mg/L in glue sniffer's urine samples(NISI data).

• Journal of the Korean Society for Heat Treatment
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• v.37 no.2
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• pp.49-57
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• 2024

We investigated the changes in microstructure and surface roughness of the compound layer of GC250D gray cast iron, commonly used in brake discs, during gas nitriding. The gas atmosphere of the nitriding process was controlled with a hydrogen partial pressure of 49.5%, and the process was conducted at a nitriding temperature of 520℃ with various process times. As the nitriding process time of the GC250D material increased, both the depth of hardening and the thickness of the compound layer increased, with a maximum surface hardness of approximately 1265 HV_0.1 was measured. Additionally, the surface roughness increased with the process time. Phase analysis of the compound layer revealed an increase in the proportion of the γ' phase as the nitriding process time increased. Changes in the formation of the compound layer were observed depending on the orientation of graphite within the material, leading to the formation of wedges. Therefore, the increase in surface roughness appears to be attributed to the uneven compounds, the expansion of the compound layer and wedges formed on the surface during the nitriding process.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.26 no.3
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• pp.337-343
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• 2017

The laser cladding process on structural steel (SCM440) and gray cast iron (GC250) substrates with Co-based powder (Stellite 12) was studied. A diode laser (2 kW) was used as a heat source, and the powder was supplied by a disc rotary powder feeder. The relationship between the laser cladding process and the cross-sectional analysis of coating was examined based on coating shape and microstructure. Additionally, the microhardness was measured to confirm the mechanical property improvements. As a result, proper laser cladding conditions were selected through this study and verified by cross-sectional analysis. In addition, the evaluation process for laser cladding feasibility was conducted on the selected materials.

• The Korea Journal of Herbology
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• v.24 no.2
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• pp.93-98
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• 2009

Objectives : Previously we reported that the roots of Panax ginseng C.A. Meyer (Araliaceae) increased sperm count and motility. also induced spermatogenesis via cAMP-responsive element modulator(CREM) activation in rat testes. In this study, for the first step of spermatogenesis in germ cell lines, the antioxidant activity of Panax ginseng were examined in mouse GC-1 spermatogonia cells. Methods : The extract was studied on diphenyl-picryl-hydrazyl (DPPH) radical scavenging activity, GC-1 cell viability by a modified MIT assay. H202-induced cytotoxicity by MIT assay and lipid peroxidation by malondialdehyde (MDA) formation. respectively. Results: The results showed that the extract scavenged DPPH radical with the IC50 being 0.631 mg/mi. The extract at concentrations of 5, and 10, 50, 100, 250 ${\mu}$g/mi increased GC-1 cell viability significantly(p < 0.05, and p < O.O1). Hydrogen peroxide-induced cytotoxicity (73.8%, p < O.O1) was blocked by the extract at concentrations of 50, and 100, 250, 500 ${\mu}$g/ml significantly (p < 0.05, and p < O.O1). The extract at concentrations of 10. and 50 ${\mu}$g/ml decreased the MDA formation on hydrogen peroxide-induced lipid peroxidation. Conclusions : In conclusion, the extract of Panax ginseng has potent antioxidant activity and increases the survival rate of GC-1 spg cells against $H_20_2$-induced cytotoxicity.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10a
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• pp.250-252
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• 2003

현재 무선단말기를 비롯한 많은 내장형 기기에서 자바 플랫폼을 채택하고 있다. 내장형 기기는 제공되는 메모리 용량의 제약으로 인하여 J2ME 플랫폼을 주로 사용하고 있다. J2ME 플랫폼은 CDC와 CLDC 컨피큐레이션으로 나뉘며. CDC는 JAVA 어플리케이션의 수행에 있어서 JVM보다 적은 동적 수행 메모리를 요구하는 CVM을 채택하고 있다. CDC는 CLDC에 비하여 메모리의 제약이 상대적으로 적은 셋탑박스 등과 같은 내장형 기기에서 주로 사용된다. 본 논문에서는 J2ME 플랫폼의 VM중에 하나인 CVM상에서 어플리케이션 수행에 따른 Generational GC의 특성에 대하여 알아본다. 특히 오브젝트의 life time, 가비지 컬렉션 주기 pause time 및 young generation의 크기에 따른 동작 특성을 중점적으로 고찰한다.

• Korean Journal of Environmental Agriculture
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• v.24 no.2
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• pp.164-168
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• 2005

An experimental design has been used to optimize the analysis of volatile component from fresh ginseng using solvent free solid injector (SFSI). The analysis were performed at three different sample preparing methods (fresh, oven drying and freezed drying), different injector port temperatures (100, 150, 200, 250 and $300^{\circ}C$) and different preheating time (3, 5, 7, 10 and 15 min) according to the above experimental design. The optimum conditions from analytical results were fresh sample (sample preparing methods), $250^{\circ}C$ (injector temperature) and 10 min (preheating time). Ginsengs grown for six years at Gumsan were prepared for fresh, white and red ginsengs. These fresh, white and red singsengs were analyzed for their volatile components by GC/MS equipped with SFSI according to the above the optimum conditions. A total of thirty-three volatile components were identified in fresh ginseng by SFSI, thirty-six in white ginseng and thirty-eight in red ginseng. These results suggested that the SFSI method could be used for isolating volatile component in ginsengs.

• Journal of Ginseng Research
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• v.13 no.2
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• pp.183-188
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• 1989

A gas chromatographic method was developed for determination of the concentration of three major polyacetylene compounds in ginseng roots---panaxynol, panaxydol and panaxytriol. The column and the detector used were an SPB-1 fused silica capillary (0.2mm i.d.$\times$30m, Supelco) and a flame ionization detector (FID). The column oven temperature was kept at $250^{\circ}C$ isothermally The retention times of panaxynol, panaxydol and panaxytriol peaks were 4.2,5.1 and 6.9 min before TMS-derivatitration and 4.5,5.4 and 7.4 min after TMS-derivatization, respectively. The minimum determinable concentrations of panaxynol, panaxydol and panaxytriol before TMS-derivatiEation were at the 20, 50 and 100 ppm levels, while the concentrations of panaxydol and panaxytriol as well as panaxynol after TMS- derivatisation could be towered to the 5 ppm level. The panaxynol, panaxydol and panaxytriol contents in red ginseng were determined by use of this method after TMS-derivatization : the amounts obtained were 724, 721 and 71$\mu\textrm{g}$/g, respectively.

• Journal of Physiology & Pathology in Korean Medicine
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• v.19 no.6
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• pp.1541-1545
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• 2005

The purpose of this study is to examine the antioxidant activity in the germ cells of the extract of Corm fructus. The extract was studied for diphenyl-picryl-hydrazyl (DPPH) radical scavenging activity, GC-1 cell viability by a modified MTT assay, the effects on $H_2O_2$-induced cytotoxicity by MTT assay and lipid perixidation by malondialdehyde (MDA) formation, respectively. The results showed that the extract scavenged DPPH radical with the IC50 being $200{\mu}g/mL$. The extract at concentrations of $10-500{\mu}g/ml$ showed dose-dependent in growth of GC-1 cell. $H_2O_2$-induced cytotoxicity (63.0%) was blocked by the extract (10, 50, 100, 250 and $500{\mu}g/ml$) concentration-dependently. Furthermore, the extract (50, 100 and $250{\mu}g/ml$) also displayed a dose-dependent reduction of MDA formation on $H_2O_2$-induced lipid peroxidation. In conclusion, the extract of Corm fructus has potent antioxidant activity.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2001.11a
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• pp.249-250
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• 2001

최근 대도시 지역에서의 오존농도가 환경기준을 초과하는 빈도가 날로 증가하고 있는 실정이며, 이에 국내의 경우 오존농도 증가에 대비하여 대기 중 오존농도가 일정기준(시간당 0.12 ppm)보다 높게 나타났을 때 신속하게 경보를 발령, 시민들의 건강과 생활환경상의 피해를 최소화하기 위해 오존경보제를 시행해오고 있다. 한편 전세계적으로 대도시 지역에서의 지표면 오존농도가 환경기준을 초과함에 따라 오존생성과 관련된 전구물질(precursor)에 대한 제어과정이 지표면 오존농도의 저감을 실현하기 위한 가장 시급한 과제로 대두되고 있으며, 특히 미국의 경우 1993년부터 광화학평가측정망(Photochemical Assessment Monitoring Stations;PAMS)을 설치하여 이들 물질에 대한 보다 집중적인 모니터링을 실시하고 있는 것으로 알려져 있다. (중략)