• Advances in Traditional Medicine
• /
• 제4권3호
• /
• pp.179-185
• /
• 2004

The ethanol extract of Indigofera cordifolia was studied for in vivo gastroprotective activity, cytotoxic activity against oral tumor and normal cells, multidrug resistance (MDR) reversal activity, anti-human immunodeficiency virus (HIV) activity and radical scavenging activity. The extract of I. cordifolia showed potent gastric mucosal protective activity against stomach injury induced by HCl/EtOH solution. However, the gastroprotective activity could not be related to the radical mechanism, because the extract weakly scavenged both OH radical and $O_2*^-$. The extract also showed promising levels of MDR-reversing activity. This study demonstrates the tumor-specific cytotoxic action of the plant extract. However, the extract had no anti-HIV activity. From above results, the study suggests the medicinal importance of I. cordiforia extract.

• Corrosion Science and Technology
• /
• 제17권3호
• /
• pp.116-122
• /
• 2018

The secondary coolant of a nuclear power plant has small amounts of various impurities (S, Pb, and Cl, etc.) introduced during the initial construction, maintenance, and normal operation. While the concentration of impurities in the feed water is very low, the flow of the cooling water is restricted, so impurities can accumulate on the Top of Tubesheet (TTS). This environment is chemically very complicated and has a very wide range of pH from acidic to alkaline. In this study, the characteristics of the oxide and the mechanism of stress corrosion cracking (SCC) are investigated for Alloy 690 TT in alkaline solution containing Pb, Cl, and S. Reverse U-bend (RUB) specimens were used to evaluate the SCC resistance. The test solution comprises 3m NaCl + 500ppm Pb + 0.31m $Na_2SO_4$ + 0.45m NaOH. Experimental results show that Alloy 690 TT of the crevice environment containing Pb, S, and Cl has significant cracks, indicating that Alloy 690 is vulnerable to stress corrosion cracking under this environment.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2001년도 춘계학술대회 논문집
• /
• pp.1117-1120
• /
• 2001

Chemical mechanical planarization(CMP) has emerged as the planarization technique of choice in both front-end and back-end integrated circuit manufacturing. Conventional CMP process utilize a polyurethane polishing pad and liquid chemical slurry containing abrasive particles. There have been serious problems in CMP in terms of repeatability and defects in patterned wafers. Since IBM's official announcement on Copper Dual Damascene(Cu2D) technology, the semiconductor world has been engaged in a Cu2D race. Today, even after~3years of extensive R&D work, the End-of-Line(EOL) yields are still too low to allow the transition of technology to manufacturing. One of the reasons behind this is the myriad of defects associated with Cu technology. Especially, dishing and erosion defects increase the resistance because they decrease the interconnection section area, and ultimately reduce the lifetime of the semiconductor. Methods to reduce dishing & erosion have recently been interface hardness of the pad, optimization of the pattern structure as dummy patterns. Dishing & erosion are initially generated an uneven pressure distribution in the materials. These defects are accelerated by free abrasive and chemical etching. Therefore, it is known that dishing & erosion can be reduced by minimizing the abrasive concentration. Minimizing the abrasive concentration by using Ce$O_2$ is the best solution for reducing dishing & erosion and for removal rate. This paper introduce dishing & erosion generating mechanism and a method for developing a semi-rigid abrasive pad to minimize dishing & erosion during CMP.

• 한국어병학회지
• /
• 제24권2호
• /
• pp.141-152
• /
• 2011

Growth, oxidative stress and antioxidant capacity of Fucus serratus exposed to high doses of Cd were examined. Two sites in Southwest England (Restronguet Point and Bantham Quay) were selected since they had different histories of metal contamination. 1~10 mg Cd $L^{-1}$ were treated to Aquil medium for up to 14 days. Similar levels of lipid peroxidation but different values of relative growth rates, cupric ion reducing antioxidant capacity (CUPRAC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging capacity indicated that F. serratus has population-dependent antioxidant strategies. F. serratus demonstrated cadmium resistance with no visual symptoms for 14 days and the population from the polluted area seemed to have more powerful antioxidant strategies. However Fucus from the conserved area also showed protective anti oxidative mechanism.

• Journal of Electrochemical Science and Technology
• /
• 제11권3호
• /
• pp.257-272
• /
• 2020

This study covers the stages of testing whether the azo dye with chemical name (E)-5-[(4-(benzyl(methyl)amino)phenyl)diazenyl]-1,4-dimethyl-1H-1,2,4-triazol-4-ium zinc (II) chloride (DMT), known as Maxilon Red GRL in the dye industry, can be used as an anticorrosive feasible inhibitory agent, especially in industrial areas other than carpet, yarn and fibre dyeing. These test stages consist of the electrochemical measurement techniques such as potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) for diverse concentrations and durations. The adsorption of the viewed DMT molecule on the mild steel surface obeyed the Langmuir isotherm. The zero charge potential (PZC) of mild steel was also found to assess the inhibition mechanism in containing DMT solution. The inhibition performance of DMT on the mild steel in a 1.0 M HCl solution was also investigated using methods such as metal microscope, atomic force microscope (AFM) and field emission scanning electron microscope (FE-SEM).

• 한국세라믹학회지
• /
• 제40권8호
• /
• pp.791-797
• /
• 2003

진동성형용 캐스터블을 제조하기 위하여 p-알루미나를 주결합제로 사용하였으며 결합강도를 증진시키기 위하여 나노크기의 점토를 첨가하는 등 특별한 결합기구를 도입하여 기존 캐스터블보다 고밀도, 저기공율 그리고 높은 강도를 얻을 수 있었다. 그리고 적은 수분첨가로 치밀한 캐스터블을 제조할 수 있었다. 캐스터블의 매트릭스 부분을 잘 조절함으로서 치수 안전성을 확보한 기계적 강도 및 침식저항 특성이 개선되었다. 150$0^{\circ}C$에서 열처리한 후의 꺽임강도와 압축강도는 각각 92.34 kgf/$ extrm{cm}^2$ 및 370 kgf/$\textrm{cm}^2$ 이고 뮬라이트 형성을 위한 활성화에너지는 11.47 kcal/mo1이다.

• 연구논문집
• /
• 통권29호
• /
• pp.141-149
• /
• 1999

Brazing of Fe-Cr-Al alloy was carried out at $1200^{\circ}C$ in vacuum furnace using nickel-based filler metals : BNi-5 powder(Ni-Cr-Si-Fe base alloy} and MBF-50 foil (Ni-Cr-Si-B). The effect of boron content on the stability of oxide scale on the brazed joint was investigated by means of cyclic oxidation test performed at $1050^{\circ}C$ and $1200^{\circ}C$. Apparently, the joints brazed with MBF-50 containing boron showed relatively stable oxidation rates compared to boron-free BNi-5 at both temperatures. However, it was considered that the slower weight loss of MBF-50 brazed specimen wasn’t resulted from the low oxidation rate but from the spallation of oxide layer. The oxide layer consisted of thick spinel oxide on the surface and $Al_2 O_3$ internal oxide layer along the interface between mother alloy and braze, the mother alloy was also eroded seriously by the formation of spinel oxides such as $FeCr_2 O_4$ and $NiCr_2 O_4$ on the surface, likely to be induced by the change of oxide forming mechanism due to diffusion of boron from the braze. On the contrary, the joint brazed with BNi-5 showed the good oxidation resistance during the cyclic oxidation test. It seems that the oxidation can be retarded by the formation of stable $Al_2 O_3$ layer at the surface.

• 정보처리학회논문지C
• /
• 제11C권6호
• /
• pp.765-772
• /
• 2004

멀티캐스트는 송신자가 많은 수신자들에게 동시에 데이터를 전송하므로 송신자의 자원을 절약하고 네트워크의 점유율을 낮춤으로 효율성을 제공하는 통신 기술이나 여러 수신자들이 같은 그룹 주소를 사용하므로 공격을 받을 위험이 크다. 따라서 멀티캐스트 스트림에 대한 인증 및 서명은 중요한 문제이다. 본 논문에서는 패킷을 전송한 송신자의 신원을 확인하고 데이터가 변조되지 않았음을 확인하는 소스 인증 방법으로 다중 체인 인증기범을 제안하였다. 제안한 기법은 부인 방지를 제공하고 여러 패킷에 대한 전자서명으로 인증함으로써 오버헤드론 줄이며 지연없이 이루어지므로 실시간 멀티미디어 서비스에 사용할 수 있다.

• BMB Reports
• /
• 제38권5호
• /
• pp.507-516
• /
• 2005

Antimicrobial peptides (AMPs) have been isolated and characterized from tissues and organisms representing virtually every kingdom and phylum. Their amino acid composition, amphipathicity, cationic charge, and size allow them to attach to and insert into membrane bilayers to form pores by 'barrel-stave', 'carpet' or 'toroidal-pore' mechanisms. Although these models are helpful for defining mechanisms of AMP activity, their relevance to resolving how peptides damage and kill microorganisms still needs to be clarified. Moreover, many AMPs employ sophisticated and dynamic mechanisms of action to carry out their likely roles in antimicrobial host defense. Recently, it has been speculated that transmembrane pore formation is not the only mechanism of microbial killing by AMPs. In fact, several observations suggest that translocated AMPs can alter cytoplasmic membrane septum formation, reduce cell-wall, nucleic acid, and protein synthesis, and inhibit enzymatic activity. In this review, we present the structures of several AMPs as well as models of how AMPs induce pore formation. AMPs have received special attention as a possible alternative way to combat antibiotic-resistant bacterial strains. It may be possible to design synthetic AMPs with enhanced activity for microbial cells, especially those with antibiotic resistance, as well as synergistic effects with conventional antibiotic agents that lack cytotoxic or hemolytic activity.

• Composites Research
• /
• 제28권3호
• /
• pp.94-98
• /
• 2015

탄소섬유 에폭시 복합재료에 다양한 두께의 니켈 박막을 첨가한 복합재료를 제작하여 층간 계면 특성을 평가하고자 한다. 상온에서 스퍼터를 이용하여 니켈 박막을 프리프레그 위에 증착하고 이를 중간층으로 하여 복합재료를 제작하였다. 니켈 박막이 첨가된 탄소섬유 에폭시 복합재료는 니켈 박막 미첨가 탄소섬유 에폭시 복합재료에 비해 층간 전단 특성이 향상되었음을 확인하였다. 층간 파괴거동 분석을 위해 주사전자현미경으로 파단면을 관찰하였으며 니켈 박막이 복합재료 내에 층간 결합력을 높여 계면 특성을 향상시키며 전단시험 시 전단에너지를 흡수하는 역할을 한다는 것을 확인하였다.