• Advances in concrete construction
• /
• 제6권4호
• /
• pp.345-362
• /
• 2018

In this paper, mechanical and short-term durability properties of fly ash and slag based geopolymer concretes (FAGPC-SGPC) were investigated. The alkaline solution was prepared with a mixture of sodium silicate solution ($Na_2SiO_3$) and sodium hydroxide solution (NaOH) for geopolymer concretes. Ordinary Portland Cement (OPC) concrete was also produced for comparison. Main objective of the study was to examine the usability of geopolymer concretes instead of the ordinary Portland cement concrete for structural use. In addition to this, this study was aimed to make a contribution to standardization process of the geopolymer concretes in the construction industry. For this purpose; SGPC, FAGPC and OPC specimens were exposed to sulfuric acid ($H_2SO_4$), magnesium sulfate ($MgSO_4$) and sea water (NaCl) solutions with concentrations of 5%, 5% and 3.5%, respectively. Visual inspection and weight change of the specimens were evaluated in terms of durability aspects. For the mechanical aspects; compression, splitting tensile and flexural strength tests were conducted before and after the chemical attacks to investigate the residual mechanical strengths of geopolymer concretes under chemical attacks. Results indicated that SGPC (100% slag) is stronger and durable than the FAGPC due to more stable and strong cross-linked alumina-silicate polymer structure. In addition, FAGPC specimens (100% fly ash) showed better durability resistance than the OPC specimens. However, FAGPC specimens (100% fly ash) demonstrated lower mechanical performance as compared to OPC specimens due to low reactivity of fly ash particles, low amount of calcium and more porous structure. Among the chemical environments, sulfuric acid ($H_2SO_4$) was most dangerous environment for all concrete types.

• 대한본초학회지
• /
• 제30권5호
• /
• pp.51-58
• /
• 2015

Objectives : This paper aimed to verify the applicability of mixed extract ofAngelica gigasNakai,Cnidium officinaleMakino,Paeoniala ctifloraPall,Rechmannia glutinosaLibosch,Scutellaria baicalensisGeorgi, which were prescribed for improving inflammation in Donguibogam, as the materials for beauty food and functional medicinal herb cosmetics by manufacturing such mixed extract and evaluating the biological activity of the extract.Methods : The mixed medicinal herb water extract(MMW) and ethanol extract(MME) were freeze-dried to be used as the specimen. We performed electron donating ability, lipid acidification inhibitory activity, anti-inflammatory activity against skin flora, MTT assay, NO inhibitory activity and the protein expression inhibitory activity of iNOS and COX-2.Results : For anti-oxidation experimentation, the electron donating abilities of MMW and MME were above 60.0% and 90.0% at 500 μg/ml, respectively. In the inhibition rate of lipid peroxidation, MMW and MME showed 43.1% and 52.1% at 1,000 μg/ml, respectively. As a result of antimicrobial activity, both the MMW and MME showed significant clear zones forPropionibacterium acnesat 4 mg/disc, but did not indicated the clearzones forStaphylococcus aureus, Escherichia coliandStaphylococcus epidermidis. Anti-inflammatory activity by NO assay showed LPS-induced NO was significantly inhibited in a concentration-dependent manner. Also, the expression of iNOS and COX-2 proteins were significantly inhibited following treatment with MMW and MME of 50 μg/ml.Conclusions : Accordingly, it can be concluded that mixed medicinal herb extract has the potential to beused as a functional food and cosmetic material.

• 한국약용작물학회지
• /
• 제17권5호
• /
• pp.335-340
• /
• 2009

To evaluate the availability of Cudrania tricuspidata Bureau as a natural source of antimicrobials, the antimicrobial activity of methanol extracts of harvested parts was investigated using the paper disc diffusion method. The extracts from leaves and root bark had broad antimicrobial activity against various bacteria, including Bacillus subtilis, Bacillus cereus, Staphylococcus aureus, Streptococcus mutans, Listeria monocytogenes, Enterobacter aerogenes, Enterococcus faecalis, Salmonella choleraesuis subsp. choleraesuis, Vibrio vulnificus, and Pseudomonas aeruginosa and inhibited Bacillus cereus, Staphylococcus aureus, and Listeria monocytogenes, agents of food poisoning especially well. The extract from ripe fruit had a very high antimicrobial activity against Staphylococcus aureus with a 20.2 mm of clear zone at 50 mg/mL sample concentration. These results indicated that Cudrania tricuspidata could be used as new source for developing natural antimicrobial agents.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2003년도 제5회 학술대회 논문집 일렉트렛트 및 응용기술연구회
• /
• pp.61-64
• /
• 2003

This paper presents Bi thin films have been fabricated by atomic layer-by-layer deposition and co-deposition at an IBS method. The growth rates of the films was set in the region from 0.17 to 0.27 nm/min. Mg(100) was used as a substrate. In order to appreciate stable existing region of Bi 2212 phase with temperature and ozone pressure, the substrate temperature was varied between 655 and $820^{\circ}C$ and the highly condensed ozone gas pressure$(PO_3)$ in vacuum chamber was varied between $2.0{\times}10^{-6}$ and $2.3{\times}10^{-5}$ Torr. Bi 2212 phase appeared in the temperature range of 750 and $795^{\circ}C$ and single phase of Bi 2201 existed in the lower region than $785^{\circ}C$. Whereas, $O_3$ dependance on structural formation was scarcely observed regardless of the pressure variation. And high quality of c-axis oriented Bi 2212 thin film with $T_c$(onset) of about 90 K and $T_c$(zero) of about 45 K is obtained. Only a small amount of CuO in some films was observed as impurity, and no impurity phase such as $CaCuO_2$ was observed in all of the obtained films.

• Journal of Advanced Marine Engineering and Technology
• /
• 제33권1호
• /
• pp.104-111
• /
• 2009

This paper shows the behaviors of macro- and micro-structures and mechanical properties for specimen's welding region welded by FSW. according to welding conditions with 5mm thickness aluminum 5083O alloy plate. It apparently results in defect-free weld zone in case traverse speed was changed to 32 mm/min under conditions of anti-clockwise direction and tool rotation speed such as 800 and 1250 rpm with tool's pin diameter of 5 ${\Phi}mm$ and shoulder diameter of 20 ${\Phi}mm$, pin length of 4.5 mm and tilting angle of $2^{\circ}$. The ultimate stress of ${\sigma}_T=331$ MPa and the yield point of 147 MPa are obtained at the condition of the travel speed of 32 mm/min with the tool rotation speed of 1250 rpm. There is neither voids nor cracks on bended surface of $180^{\circ}$ after bending test. The improvement of toughness after impact test was found. The lower rotating and traverse speed became, the higher were yield point, maximum stress and elongation(%) with the stresses and the elongation(%) versus the traverse speed diagram. Vickers hardness for cross section of welding zone were also presented. The typical macro-structures such as dynamically recrystallized zone, thermo-mechanically affected zone and heat affected zone and the micro-structures of the transverse cross-section were also showed. However, the author found out that the region of 6mm far away from shoulder circumference was affected by friction heat comprehensively, that is, hardness softened and that part of micro-structures were re-solid-solution or recrystallized, the author also knew that there is no mechanically deformation on heat affected zone but there are the flow of plastic deformation of $45^{\circ}$ direction on thermo-mechanically affected zone and the segregation of Al-Mg on nugget. The solid solution wt(%) of parent material as compared against of friction stir welded zone was comprehensively changed.

• 식물병연구
• /
• 제9권2호
• /
• pp.99-103
• /
• 2003

본 연구는 국내산 은행나무(Ginkgo biloba) 뿌리, 열매껍질, 가지 등 부위별 추출물의 진균류, 일반세균 및 해충에 대한 생물활성을 조사하였다. 연구 결과 푸른곰팡이 병균(T.harzianum) 및 대장균(E.coli) 등에 대해 200 ug/disc 농도에서 저해활성을 나타냈으며, 줄기부위가 더 높은 항미생물활성을 보였다. 특히 버섯 배양상 표면에 1mg/ml 수준으로 처리할 경우 푸른 곰팡이병의 발생을 상당히 억제시키는 효과를 나타냈다. 한편, 은행나무 부위별 추출물을 500 ug/ml으로 공시 해충을 처리하였을 경우 대부분의 추출물이 살충활성을 보이며 벼멸구, 배추좀나방, 두점박이응애에 대해 높은 살충활성을 나타냈으며, 특히, 벼멸구에 대해서 8ug/ml의 낮은 농도에서도 살충활성을 나타냈다. 본 연구결과 국내산 은행나무 추출물이 항미생물 및 살충활성이 확인되었는 바 식물유래 병해충 방제용 천연물 농약으로서의 잠재성을 보여주었다.

• 콘크리트학회논문집
• /
• 제23권2호
• /
• pp.195-201
• /
• 2011

이 연구에서는 나선 철근으로 횡 구속된 전기로 산화 슬래그 골재를 사용한 콘크리트의 구조적 성능을 평가한다. 전기로 산화 슬래그는 철강 산업의 부산물로서, 그동안 유리석회와 유리마그네슘의 팽창성질 때문에 저부가가치적인 용도로만 이용되어 왔지만 최근 제강 기술의 발달에 힘입어 안정화된 전기로 산화 슬래그 골재의 생산이 가능하여 졌다. 구조용 콘크리트에 대한 전기로 산화 슬래그 골재의 적용성을 검증하기 위하여, 직경이 150 mm이고 높이가 300 mm인 실린더형 실험체를 총 27개 제작하고 횡 구속 실험을 수행하였다. 실험 변수는 골재의 종류와 나선 철근의 항복 강도로 하였다. 실험 결과, 전기로 산화 슬래그 골재를 사용한 실험체의 구조적 성능이 천연골재를 사용한 횡 구속된 콘크리트와 비교하여 동등 이상인 것을 확인할 수 있었다.

• BMB Reports
• /
• 제29권3호
• /
• pp.253-260
• /
• 1996

An enzyme that hydrolyzes flavin-adenine dinucleotide (FAD) was found to be present in rat liver lysosomal membrane prepared from Triton WR-1339 filled lysosomes (tritosomes) purified by flotation on sucrose. This FAD phosphohydrolase (FADase) exhibited optimal activity at pH 8.5 and had an apparent Km of approximately 3.3 mM. The activity was decreased 50~70% by dialysis against EDTA and this was restored by $Zn^{2+}$, $Mg^{+2}$, $Hg^{+2}$, and $Ca^{+2}$ ions inhibited the enzyme, but $F^-$ and molybdate had no effect. The enzyme was also inhibited by p-chloromercuribenzoate (pCMB), reduced glutathione and other thiols, cyanide, and ascorbate. The presence of ATP, ADP, AMP. ${\alpha}-{\beta}-methylene$ ATP, AMP-p-nitrophenyl phosphate (PNP), GMP, and coenzyme A (CoA) decreased the activity on FAD, but pyrimidine nucleotides, adenosine, adenine, or $NAD^+$ were without effect. Phosphate stimulated the activity slightly. FAD phosphohydrolase activity was separated from ATPase and inorganic pyrophosphatase activities by solubilization with detergents and polyacrylamide gel electrophoresis and by linear sucrose density gradient centrifugation suggesting that the enzyme is different from ATPase, inorganic pyrophosphatase, and soluble lysosomal FAD pyrophosphatase. Paper chromatography showed that FAD was hydrolyzed to flavin mononucleotide (FMN) and AMP which were further hydrolyzed to riboflavin and AMP by phosphatases known to be present in lysosomal membranes. Incubation of the intact Iysosomes with pronase showed that the active site of FAD phosphohydrolase must be oriented to the cytosol. The FAD hydrolyzing activity was detected in Golgi, microsome, and plasma membrane, but not in mitochondria or soluble lysosomal preparations.

• Journal of Advanced Marine Engineering and Technology
• /
• 제30권1호
• /
• pp.157-168
• /
• 2006

Recently, interest in using Al alloys in ship construction instead of fiber-reinforced plastic (FRP) has increased because of the advantages of A) alloy ships over FRP ships, including high speed, increased load capacity. and ease of recycling. This paper investigated the mechanical and electrochemical properties of Al alloys in a slow strain rate test under various potential conditions. These results will provide reference data for ship design by determining the optimum protection potential regarding hydrogen embrittlement and stress corrosion cracking. In general, Al and Al alloys do not corrode on formation of a film that has resistance to corrosion in neutral solutions. In seawater, however, $Cl^-$ ions lead to the formation and destruction of a Passive film. In a potentiostatic experiment. the current density after 1200 sec in the Potential range of $-0.68\~-1.5\;V$ was low. This low current density indicates the protection potential range. Elongation at an applied potential of 0 V was high in this SSRT. However, corrosion protection under these conditions is impossible because the mechanical properties are worse owing to decreased strength resulting from the active dissolution reaction in parallel parts of the specimen. A film composed of $CaCO_3\;and\;Mg(OH)_2$ confers corrosion resistance. However, at potentials below -1.6 V forms non-uniform electrodeposition coating, since there is too little time to form a coating. Therefore, we concluded that the mechanical properties are poor because the effect of hydrogen gas generation exceeds that of electrodeposition. Comparison of the maximum tensile strength, elongation, and time to fracture indicated that the optimum protection potential range was from -1.45 to -0.9 V (SSCE).

• 한국정밀공학회지
• /
• 제17권4호
• /
• pp.7-21
• /
• 2000

This paper describes an overview of the thixoforming and thixomolding processes. Semi-solid metalworking (SSM), which is called the thixoforming process of aluminium materials, incorporates the elements of both casting and for the manufacture of near net shape parts. The SSM has some advantages such as net shape or near net shape manufacturing, the ability to form thin walls, excellent surface finish, tight tolerance, and excellent dimensional precision. The thixomolding process of Mg alloy (AZ9l) is a combination of two technologies both conventional die casting and plastic injection molding. The feed material used is a machined chip with a geometry of approximately 1 mm square and a length of 2~3 mm. The semi-solid forming (SSF) of high quality aluminium and magnesium parts will be established in the automotive and electronic industry, in the future. The hybrid method of casting/forging has been caused attention. This process uses a preformed material made by casting instead of the wrought material and finishes it by a single forging process. This process is expected to lower costs without sacrificing the mechanical and finishes it by a single forging process. The process is expected to lower costs without sacrificing the mechanical properties. The authors, intending that the casting/forging process contributes to a reduction in production cost of aluminum automotive parts in Korea, describes the feature of the casting/forging process, aluminum alloys suitable for the cast preform, microstructure and mechanical properties of the cast preform, application examples of cast/forging, and further study.