• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 Handout for 2000 Inter. Machine Tool Technical Seminar
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• pp.19-27
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• 2000

High speed machining (HSM), specifically end milling and ball end cutting, is attracting interest in the die/mold or aerospace industries for the machining of complex 3D surfaces. HSM of difficult-to-cut materials such as die/mold steels, titanium alloys or nickel based superalloys generates the concentrated thermal/frictional damage at the cutting edge of the tool and rapidly decreases the tool life. Following a brief introduction on HSM and reated aerospace or die/mold work, the paper reviews published data on the effect of cutter/workpiece orientation and cutting environments on tool performance. First, experimental work is detailed on the effect of cutter orientation on tool life, cutting forces, chip formation, specific force and workpiece surface roughness. Cutting was performed using 8 mm diameter PVD coated solid carbide cutters with the workpiece mounted at an angle of 45 degree from the cutter axis. A horizontal downwards cutting orientation proveded the best tool life with cut lengths ∼50% longer than for all other directions (horizontal upwards, vertical downwards, vertical upwards). Second, the cutting environments were investigated for dry, flood coolant, and compressed chilly air coolant cutting. The experiments were performed for various hardened materials and various coated tools. The results show that the cutting environment using compressed cilly air coolant provided better tool life than the flood coolant or the dry.

• 환경생물
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• 제28권1호
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• pp.8-13
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• 2010

본 연구는 BRECs에서 AGEs로 유도된 세포의 이동 및 침윤에 있어서 AuNP의 역할에 관한 연구이다. 소 망막으로부터 내피세포를 분리하고, 세포 생존율은 MTT assay로 확인하였다. Wound migration assay는 BRECs의 이동력을 확인하기 위해 수행하였다. Tube formation은 on-gel system을 통해 확인하였다. AuNP의 apoptosis 유도는 caspase-3 assay를 통해 확인하였다. AGE-BSA은 세포증식 및 이동에 있어서 증가함을 보여주었다. 또한 AuNP는 AGE-BSA 존재 유무에 상관없이 세포의 증식, 이동, 신생혈관 형성을 억제하였고, caspase-3을 통해 apoptosis를 유도하였다. 이러한 결과, AuNP는 AGE로 유도된 신생혈관 형성 및 세포의 이동성을 억제하는 약재제로서, 당뇨성 합병증에 있어서 잠재적으로 중요한 분자가 될 것이다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
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• pp.101-102
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• 2014

Rising oil price and environmental problems are causing automotive industry to increase fuel efficiency. Improved fuel efficiency in gasoline engine was made possible by development of DISI gasoline engine. Since fuel is injected inside cylinder directly, in-cylinder temperature can be reduced than multi-port injection engine and this leads to increased compression ratio. However, engine performance is largely dependent on mixture formation process due to in-cylinder fuel injection. Especially for spray guided and air guided DISI gasoline engine, injection direction is important factor to mixture preparation. It is because interaction between intake flow and spray affect fuel-air mixture. Hence, in this study, mixture formation characteristics were analyzed by varying injection direction using KIVA 3V release2 code. Residual gas was considered for assuming combustion. Therefore, initial condition for in-cylinder temperature was set equal to the end state of exhaust stroke of combustion cycle. Since angle between intake air flow direction and spray direction affects fluid flow and evaporation field, mixture distribution was affected by fuel injection direction dominantly.

• 한국지형학회지
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• 제24권2호
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• pp.15-25
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• 2017

Subi basin is located at the crestline of Taebaek mountains. This paper aims to elucidate the geomorphic development of Subi basin through the analysis of river terraces built in Wangpi-cheon and Banbyeon-cheon. Wangpi-cheon flows northeastward from Subi basin, and Banbyeon-cheon flows southward at the west of Subi basin. Absolute age of terrace is measured by means of OSL methodology, long profile of Wangpi-cheon is made up with 10m interval contour line, and the elevation above river bed of high terraces is measured at the end part of terrace. The results are as follow: Firstly, high river terraces of Subi basin, Wangpi-cheon and Banbyeon-cheon are formed about 40 kyr(MIS 3) being interstadial stage of last glacial period. Secondly, the elevation above river bed of high terraces of Wangpi-cheon and Banbyeon-cheon tends to increase toward upstream. It means that the uplift of Taebaek Mountains influences considerably the formation of their terraces. Thirdly, the elevation above river bed of high terraces at the reach from Seomchon to Suha-ri of Wangpi-cheon tends to decrease toward upstream. This section is captured from Banbyeon-cheon flowing in the opposite direction. River piracy has occurred from the time of formation of Suha-ri high terrace to the time of formation of Hantee wind gap. Finally, for fluvial system of Wangpi-cheon to establish dynamic equilibrium, topographic axis will move toward Banbyeon-cheon.

• 대한본초학회지
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• 제32권6호
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• pp.1-7
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• 2017

Objectives : The heartwood of Sappan Lignum has been used since ancient times as an ingredient in folk medicines against anti-bacterial and anti-anemia purposes. Many bioactive constituents have been derived from this biomass such as chalcones and homoisoflavonoids. In the current investigation, the antioxidant and anti-diabetic properties using DPPH and $ABTS^+$ radicals scavenging, ${\alpha}-glucosidase$, and advanced glycation end products (AGEs) inhibition assays were evaluated by different extraction methods of Sappan Lignum. Methods : In our continuing investigation for bioactive natural ingredients, the antioxidant and ${\alpha}-glucosidase$ inhibitory properties of Sappan Lignum extracts were prepared from different extraction methods and the biological efficacies were investigated in vitro. The antioxidant properties were evaluated employing radical scavenging assays using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) ($ABTS^+$) radicals. In addition, the anti-diabetic effects of Sappan Lignum extracts were tested via ${\alpha}-glucosidase$ and AGEs formation inhibitory assay. The total phenolic contents were determined using a spectrophotometric method. Results : All the tested samples showed dose-dependent radical scavenging and ${\alpha}-glucosidase$ inhibitory activities. Among the tested extracts, the 80% methanolic extract of Sappan Lignum was showed the most potent activity with an $IC_{50}$ value of $82.3{\pm}1.7{\mu}g/m{\ell}$ against DPPH radical scavenging assay. While, $ABTS^+$ radical scavenging activity of 80% methanolic extract was higher than those of other extracts. Also, ${\alpha}-glucosidase$ inhibitory and AGEs formation effects of each extacts and total phenolic contents were evaluated. Conclusions : These results suggested that Sappan Lignum can be considered as a new effective source of natural antioxidant and anti-diabetic materials.

• 한국미생물·생명공학회지
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• 제2권1호
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• pp.37-43
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• 1974

1. 약 70여종의 보존 및 토양분리균에서 cysteine 분해능이 큰 새로운 균주를 분리검색 하였던 바 cysteine 분해능이 가장 높았던 토양분리균주인 No. I-3-2를 공시균주로 선정하여 이균주에 대한 균학적 제성질을 검토한 결과 No, I-3-2 균주는 Aerobacter aerogenes로 동정되었다. 2. No I-3-2 균주는 L-cysteine을 cysteinedesulfhydrase 생산의 가장 효과적인 유도제로 필요로 하였으며 또한 본균의 효소생산을 위한 몇가지 배양조건을 검토한 결과 배양배지의 initial PH가 7.0~7.5일때, 탄소원으로 glycerol을 0.1%, 무기염으로 CaCl$_2$를 0.2% 농도로 기초배지에 첨가 하였을때 가장 양호한 효소생산효과를 나타내었고 배양시간은 배양 8시간전후에서 균체증식 및 효소생산의 최대치를 나타내었다.

• Natural Product Sciences
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• 제12권4호
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• pp.210-213
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• 2006

A 4,5-dioxoaporphine type alkaloid, cepharadione B (1), a phenolic acid, protocatechuic acid (2), and flavonols, quercetin (3), afzelin (4), and quercitrin (5), were isolated from the EtOAc-soluble extract of the whole plants of Houttuynia cordata. All the isolates (1-5) were subjected to in vitro bioassays to evaluate advanced glycation end products (AGEs) formation and rat lens aldose reductase (RLAR) inhibitory activity. The three flavonols 3-5 exhibited a significant inhibitory activity on AGEs formation with $IC_{50}$ values of 66.9, 58.9, and $32.3{\mu}M$, respectively. While the two flavonol rhamnosides 4 and 5 showed a remarkable inhibitory activity against RLAR with $IC_{50}$ values of 0.81 and $0.16{\mu}M$, respectively.

• Natural Product Sciences
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• 제13권2호
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• pp.160-163
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• 2007

Four glycosides, rosamultin (1), tetracentronside B (2), 4-O-methylellagic acid 3-O-${\alpha}$-$_L$-rhamnopyranoside (3), and vanillic acid 4-O-${\beta}$-$_L$-glucopyranoside (4), isolated from the roots extract of Potentilla discolor, were subjected to in vitro bioassays to evaluate the inhibitory activity on advanced glycation end products (AGEs) formation and rat lens aldose reductase (RLAR). Compound 3 exhibited a significant inhibitory activity against both AGEs formation and RLAR with IC$_{50}$ values of 79.5 and 8.03 ${\mu}$M, respectively. All the compounds (1-4) were isolated for the first time from this plant.

• 한국환경보건학회지
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• 제24권2호
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• pp.126-133
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• 1998

Effects of B(a)P on preimplantation mouse embryos in vitro were studied. Preimplantation mouse embryos were exposed to a concentration of 0.3, 1, 3 and 10 $\mu$M B(a)P for 72 hrs. The toxicological effects of B(a)P were evaluated by morphological observation of embryos up to the blastocyst stage, and by measuring DNA, RNA and protein synthesis by radioactive precursor incorporation. At 1 $\mu$M B(a)P did not affect preimplantation development but interfered with hatching and ICM formation. Suppressing effect of ICM formation was dose dependent. At the eight cell stage, the developmental rate was decreased at above 3 $\mu$M of B(a)P. At the blastocyst stage, attachment and trophoblast outgrowth were diminished at the 10 $\mu$M of B(a)P and ICM formation was decreased at 1 $\mu$M of B(a)P. Inner cell number of blastocyst was decreased dose dependently. So, number of ICM was one of the most sensitive and toxicological end point. The RNA incorporation rate of 0.1 $\mu ^3$H-uridine was dosedependent and the protein incroporation of 0.5 $\mu Ci ^{35}$S-methionine showed a significant decrease after 48 hrs. But the DNA incorporation rate of methyl-$^3$H thymidine was not affected. Our results suggested that B(a)P did not affect the DNA replication but transcription was inhibited by dose dependent manner. There delay of development during the blastocyst stage was mainly due to the inhibition of RNA synthesis followed by protein synthesis.

• Journal of Gastric Cancer
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• 제4권2호
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• pp.121-125
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• 2004

Purpose: Esophagojejunal anastomotic complications after a total gastrectomy include leakage, stenosis, bleeding, and abscess formation. Especially, the mortality rate for esophagojejunal anastomotic leakage is $80\%$. Although these complications hare been reduced by the usage of the EEA stapler, they are still serious and depend on various factors: the surgeon's experience, the stage of disease, the extent of surgical intervention, the method of operation, and the patient. Some local factors, such as vascularization of the graft, traction on the anastomosis suture line, and local infections, have been implicated as contributing to these complications. Materials and Methods: During the period $1995\∼2003$, of the 850 gastrectomies for gastric carcinomas, 171 were intra-abdominal total gastrectomies. All of these 171 operations were performed by one surgeon using a routine D2 lymph-node dissection and a 25-mm EEA stapler on an antecolic end-to-side esophagojejunostomy. In the 77 cases a seromuscular reinforced suture at the esophagojejunostomy site was performed, and in 94 cases, a whole layer reinforced suture with absorbible materials was used. We evaluated the incidence of complications according to age, sex, stage of patients, and combined resection. Also, we compared the incidences of complications for seromuscular and whole layer reinforced sutures. Results: The complications are major leaks ($2.9\%$), minor leaks ($3.5\%$), stenosis, bleeding ($1.8\%$), and abscess formation formation ($1.8\%$). In the five cases of major leaks, there were four mortalities with operative methods. The other patients with stenosis, bleeding, and abscess formation were treated conservatively with success. The incidences of complications were not related with age, sex, stages, and combined resection. The incidences of complications for the whole layer reinforced suture group ($2.9\%$) were less than those for the seromuscular reinforced group ($8.8\%$, P=0.04). Conclusion: The most serious complication of esophagojejunal anastomosis is major leakage with an $80\%$ mortality. The other complications are stenosis, bleeding, and abscess formation, for which no mortalities occurred during this study. Whole layer suture of the esophagojejunal anastomotic site is an important method for preventing leakage.