• Journal of the Korea institute for structural maintenance and inspection
• /
• v.11 no.1
• /
• pp.130-140
• /
• 2007

Fiber-sheet and steel-plate strengthening methods have been mainly used for strengthening the RC structures. However, recently the application of these two methods have dramatically decreased due to premature debonding failure between concrete surface and fiber-sheet and heavy self-weight of steel-plate. This article presents experimental results of shear behavior in RC beams strengthened with GSP(Glass fiber-Steel composite Plate). The thin steel plate in GSP makes usage of the anchoring system possible, which could delay or prevent the premature debonding failure. Three reference beams and 60 strengthened beams with GSP were tested. The experimental results showed that strengthened beams with GSP considerably increased in shear capacity compared with the reference beams.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.12 no.3
• /
• pp.93-100
• /
• 2008

The use of fiber reinforced polymer (FRP) composites is significantly growing in construction and infrastructure applications where durability under harsh environmental conditions is of great concern. In order to examine the applicability of FRP rebar as a reinforcement in flexural member, flexural tests were conducted. 12 beams with different FRP materials such as CFRP, GFRP and Hybrid FRP and reinforcement ratio were tested and analyzed in terms of failure mode, moment-deflection, flexural capacity, ductility index and sectional strain distribution. The test results were also compared with the theoretical model represented in ACI 440.1R06. Test results indicate that the flexural capacity of the beams reinforced by FRP bars can be accurately predicted using the ultimate design theory. They also show that the current ACI model for computing the deflection overestimates the actual deflection of GFRP series and underestimates the deflection of CFRP series.

• Economic and Environmental Geology
• /
• v.36 no.3
• /
• pp.225-232
• /
• 2003

Three piston cores. obtained from the northwestern Ulleung Basin of the East Sea, are analyzed to study the tephrostratigraphy of the late Quaternary core sediments and to reveal the comparative characteristics of the tephra layers. The cores consist mainly of the muddy sediments that are partly interbedded with lapilli tephra and ash layers. The muds are further divided into hemipelagic and turbiditic mud facies. The hemipelagic facies is dominated by bioturbated mud and crudely laminated mud, whereas the turbiditic facies includes mainly thinly laminated mud and homogeneous mud, and often alternates with non-turbiditic muds. According to microscopic observation and EDX analysis, three tephra layers of the Ulleung-Oki (U-Oki; ca. 9.3 ka), Aira-Tanzawa (AT: ca. 22~24.7 ka) and Ulleung-Yamato (U-Ym; ca. 25~33 ka) are identified in the study cores. Among these, the U-Oki and U-Ym layers, originating from the Ulleung Island, consist mainly of massive-type glass shards with alkali feldspar. Both of the tephra layers contain a lower content of SiO$_2$ (57~66.5 wt.%) and a higher content of Na$_2$O+K$_2$O (11~16 wt.%) than the AT layer (SiO$_2$=75~78.5 wt.%, Na$_2$O+K$_2$O=6.5~9 wt.%) that consists of typical plane-type and/or bubble-wall glass grains. Compared with that of the U-Ym layer, a sedimentary facies of the U-Oki layer is very thick and contains three stratigraphic units, probably due to relatively large and different supplies of pyroclastic sediments. Thus, the eruption of Ulleung Volcano (ca. 7,300 B.C.) is thought to have had a more powerful effect on depositional environment than the U-Ym eruption.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.45 no.6
• /
• pp.828-834
• /
• 2016

The aim of this study was to evaluate the physicochemical properties and antioxidant and anti-proliferative activities of different plant parts of Elaeagnus umbellata Thunb. extracted with ethanol (EtOH). EtOH extract of stems presenting the highest content of polyphenols showed the strongest 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity ($EC_{50}=54.04{\mu}g/mL$). The total content of free amino acids decreased in the order of leaves (6,179.12 mg/100 g)> stems (1,211.69 mg/100 g)> fruits EtOH extract (378.88 mg/100 g), and asparagine (1,907.57 mg/100 g), ${\gamma}-aminobutyric$ acid (300.17 mg/100 g), and proline (233.48 mg/100 g) were the major free amino acid in leaves, stems, and fruits, respectively. Five phenolic compounds in each extract were measured by using liquid chromatography- tandem mass spectrometry, and gallic acid (98.95 mg/100 g) and (+)-catechin (1,575.99 mg/100 g) were present as major components in leaves and stems, respectively. EtOH extract of leaves showed the highest anti-proliferative activity against HepG2 cells as measured by 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazoliumbromide and lactate dehydrogenase assay but had no effects on Chang liver cells.

• Journal of Life Science
• /
• v.15 no.2 s.69
• /
• pp.236-241
• /
• 2005

To investigate the bioactivities of Solidago virga-aurea var. gigantea Mig. Root (SVR), we studied the effect of a SVR methanol extract on the activity of bone metabolism. Spraque-Dawley three-week-old female rats were randomly assigned to groups as follows : non-supplemented rats and supplemented with SVR at 10, 50, 100 mg/kg bw/day. Every week determined weight gain and food intake, urine and blood examination of mineral content of calcium and phosphorus was performed each at experimental periods of 3 and 9 weeks respectively; bone mineral density and bone mineral content were also assayed. There were no significant differences in body weight or feed efficiency ratio levels. However, the biological value of calcium and phosphorus excretion in the group supplemented with SVR extract decreased significantly more than that in the group not supplemented with SVR extract. Also, spine BMD, femur BMC and pelvis BMC per weight were significantly greater on SVR extract supplemented groups than that of the control group. In conclusion, it might be expected that methanol extract of SVR does not impair the growth of rats and may improve bone metabolism in rats.

• Korean Journal of Food Science and Technology
• /
• v.44 no.2
• /
• pp.173-178
• /
• 2012

The water extract of the fermented $Rhus$ $verniciflua$ stem bark (FRVSB) was prepared by hot water extracting at $100^{\circ}C$ for 8 h. The urushiol content of the FRVSB water extract was determined by HPLC. The urushiol was not contained in FRVSB water extract, whereas $Rhus$ $verniciflua$ stem bark (RVSB) water extract contained 3.4 mg%. At the lab scale size, suitable water extraction condition for a total solid, polyphenol and flavonoid from FRVSB was at over $100^{\circ}C$ for 6-8 h. The total solid contents was reduced in pilot scale processing system, with 5.7% of the extraction yield. The proximate composition (%) of FRVSB water extract obtained from industrial installation was moisture 4.34, crude fat 1.69, crude protein 10.21, and crude ash 15.80. Gallic acid (1,090.5 mg%) was the most abundant compound in phenolic acids, while fisetin (135.7 mg%) was the predominant flavonoid. The free sugar content was mannitol of 3.48%, glycerol of 0.19%, and glucose of 0.19%. Alanine (244 ppm), serine (231 ppm), and leucine (218 ppm) were predominant amino acids.

• Korean Journal of Food Science and Technology
• /
• v.42 no.1
• /
• pp.39-44
• /
• 2010

The process of the preparation of branched-chain amino acid (BCAA)-enriched hydrolysates from corn gluten was optimized through the parameters of pre-treatment (heating and cellulosic hydrolysis), hydrolysis method (acid, protease, and microbe plus protease), concentration, and spray drying condition. The protein yield of corn gluten was increased by heating and cellulase treatments. Among three different hydrolysis methods, the combined use of microbes and protease was the most effective in terms of free amino acid (FAA) and BCAA content of the corn gluten hydrolysates. In addition, the FAA and BCAA content in the hydrolysates prepared by microbial and enzymatic combined treatment were improved by a concentration process. Spray drying conditions for the preparation of the powder from the hydrolyzed reactant were an inlet temperature of $185^{\circ}C$, outlet temperature of $80^{\circ}C$, and the use of maltodextrin as an anticaking agent. Thus, this study established an economical process for preparation of value-added hydrolysates of excellent productivity and quality, in terms of high BCAA content and product stability.

• 한국신재생에너지학회:학술대회논문집
• /
• 2010.06a
• /
• pp.249.2-249.2
• /
• 2010

최근의 고유가와 환경오염에 대한 대응 수단으로 수송용 바이오연료의 보급에 대한 관심이 세계적으로 높아지고 있다. 이 중 바이오디젤은 동식물성 기름으로부터 메탄올과의 전이에스테르화 반응에 의해 생산되는 경유대체 연료로서 환경 친화성과 지속가능성이 인정됨에 따라 그 생산량이 급격히 증가하고 있다. 바이오디젤의 생산량이 증가함에 따라 대두유, 유채유, 팜유 등의 원료유 가격 상승 및 수급 불안정 문제가 대두되고 있으며 식량자원과의 충돌 문제도 발생되고 있다. 이를 해결하기 위한 방안으로 유리지방산 함량이 높은 저가유지 자원(폐식용유, 폐돈지, 폐우지, soapstock, trapped grease)을 이용한 공정 개발 연구가 활발히 진행되고 있다. 본 연구에서는 비활용되고 있는 해외 열대작물 열매씨앗에서 착유한 식물성 오일의 바이오디젤 원료유로서의 사용 가능성을 검토하였다. 열대작물 오일의 물성 분석 결과 고형물, 수분, 인, 유리지방산 함량이 대두원유보다 매우 높게 나타났다. 오일 중의 인지질은 바이오디젤 제조 반응후 에스테르와 글리세린의 층분리를 방해하여 공정 효율을 감소시키고 유리지방산은 염기촉매와 결합하여 지방산염을 생성해 생산수율을 감소시키는 문제를 일으킨다. 고형물과 수분은 여과와 감압증발에 의해 쉽게 제거가 가능하였다. 15~20%의 유리지방산 함유 열대작물 오일의 전처리를 위해 균질계 산촉매와 비균질 고체 산촉매를 이용해 에스테르화 반응 효율을 조사한 결과 황산이 가장 높은 효율을 보였다. 반응표면분석법(Response Surface Method, RSM)을 적용해 메탄올과 촉매량의 2변수 에스테르화반응 최적화를 수행한 결과 메탄올 26%, 촉매 0.98%로 최적 조건이 도출되었으며 초기 산가 33mgKOH/g에서 0.98mgKOH/g으로 감소됨을 확인하였다. 전처리 정제한 오일의 물성분석 결과 고형물 0.1%, 수분 0.10%, 산가 1.0mgKOH/g, 인함량 20ppm 이하로 바람직한 원료유가 생산됨을 알 수 있었다. 제조된 원료유를 이용해 전이에스테르화 반응 최적화 실험을 RSM에 근거하여 진행한 결과 KOH 0.8%, 메탄올:오일 몰비 6.2:1, 반응온도 $60^{\circ}C$, 교반속도 200rpm, 반응시간 30분으로 나타났으며 증류 정제전 97.3%, 증류후 100.0%의 바이오디젤을 생산 할 수 있었다. 열대작물 오일의 전처리 공정은 메탄올을 과잉양으로 사용함으로 효과적인 알콜 회수 공정이 중요하다. 전처리 후 층분리를 통해 회수되는 메탄올 중의 수분함량은 2%~7%로서 이를 전처리 반응에 재사용하기 위해서는 0.3%이하의 수분함량으로 정제가 필요하다. 본 연구에서는 고가의 증류탑 형태가 아닌 단증류방식으로 2단계 내지 3단계로 0.3% 수분의 메탄올 회수 조건을 도출하였으며 파일롯 공정 설계를 진행하고 있다. 이로서 본 연구의 열대작물 오일은 저가로 충분한 물량의 확보가 가능하다면 바이오디젤 원료 자원으로서 큰 활용가치가 있는 것으로 판단된다.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.21 no.5
• /
• pp.163-169
• /
• 2017

Although the strength of polyethylene terephthalate (PET) fibers which are generally used to make plastic bottles is low, the deformability of PET fibers is substantially high. Due to these material characteristics, a PET fiber can be used as a reliable strengthening material to resist a large deformation caused by earthquake and research pertinent to application of PET fibers is actively conducted in Japan. Therefore, in this study, experiments have been carried out to investigate the lateral confinement effect of PET fibers and to assess the applicability of PET fibers to construction fields by comparing the strengthening effect of PET fibers to that of carbon and glass fiber sheets. For this purpose, concrete cylinder specimens with parameters of different concrete strength and strengthening layers of carbon fiber sheets, glass fiber sheets, and PET fibers were respectively tested using two sets of cylinders for each parameter. As a result, specimens strengthened with carbon fiber sheets and glass fiber sheets failed due to sudden decrease of strength as with existing studies. However, specimens with PET fibers reached their maximum strength and then failed after gradual decrease strength without failure of PET fibers. In addition, although the strength of specimens with PET fibers did not significantly increase in comparison with that of specimens with carbon fiber sheets and glass fiber sheets, specimens with PET fibers indicated considerable deformability. Thus, a PET fiber can be considered as an effective strengthening material.

• Applied Biological Chemistry
• /
• v.36 no.3
• /
• pp.154-157
• /
• 1993

Based upon the antioxidative effectiveness of ether extracts of defated Crataegus pinnatifida B., phenolic antioxidative components were separated by gel column chromatography and identified by MS and H-NMR. Two or three individual compounds were found in free, soluble and insoluble bound phenolic acids, respectively and they were identified as caffeic acid, protocatechuic acid, phloroglucinol and pyrogallol.