The crack growth responses of as-received and as-welded Alloy 600/182 and Alloy 690/152 welds to constant loading were measured by a direct current potential drop method using compact tension specimens in primary water at 325 °C simulating the normal operating conditions of a nuclear power plant. The as-received Alloy 600 showed crack growth rates (CGRs) between 9.6 × 10−9 mm/s and 3.8 × 10−8 mm/s, and the as-welded Alloy 182 had CGRs between 7.9 × 10−8 mm/s and 7.5 × 10−7 mm/s within the range of the applied loadings. These results indicate that Alloys 600 and 182 are susceptible to cracking. The average CGR of the as-welded Alloy 152 was found to be 2.8 × 10−9 mm/s. Therefore, Alloy 152 was proven to be highly resistant to cracking. The as-received Alloy 690 showed no crack growth even with an inhomogeneous banded microstructure. The cracking mode of Alloys 600 and 182 was an intergranular cracking; however, Alloy 152 was revealed to have a mixed (intergranular + transgranular) cracking mode. It appears that the Cr concentration and the microstructural features significantly affect the cracking resistance and the cracking behavior of Ni-base alloys in PWR primary water.
The encapsulation of individual nanoparticles has gained great attention as a method for both stabilizing nanoparticles and tailoring their surface properties. In particular, the encapsulation of nanoparticles with silica shells is advantageous for bioconjugation and applications to (nano)biotechnology. Herein we report a method for constructing gold nanoparticle (AuNP)/silica core/shell hybrid structures by biomimetic silicification of silicic acids. The procedure consists of surface-initiated, atom transfer radical polymerization of 2-(dimethylamino)ethyl methacrylate (DMAEMA) from AuNPs and biomimetic polycondensation of silicic acids by using poly(DMAEMA) as a synthetic counterpart for silaffins that are found in diatoms. The resulting AuNP/silica hybrids were characterized by Fourier transform infrared spectroscopy, energy dispersive x-ray spectroscopy, UV-vis spectroscopy and transmission electron microscopy. In addition, the immobilization of biological ligands onto the hybrids was investigated for potential applications to biotechnology. As a model ligand, biotin was attached onto the AuNP/silica hybrids through substitution reaction and Michael addition reaction, and the attachment was confirmed by fluorescence microscopy after complexation with fluorescein-conjugated streptavidin.
The decolorization of paintings, photographs, and artworks is a common phenomenon related to the oxidative degradation of color dyes reacting with oxygen or water molecules, which also causes a critical problem in organic light-emitting diodes (OLEDs). It is expected that the gas-impermeable property of graphene and h-BN can be utilized to protect the color dyes from degradation. However, the transfer method has been limited to a polymer with high glass transition temperature (Tg) or a glass substrate due to hot or wet transfer conditions. Here, we report the dry transfer coating of the graphene barrier films on flexible substrates at room temperature using a roll-to-roll process to prevent the bleaching of color dyes, which can be widely used to protect various colorization and light-emitting materials for sustainable printing and display technologies in the future.
결핵은 일차적으로 폐에 주로 발생하지만 혈행성 전파를 통하여 모든 기관에 나타날 수 있으며 면역 억제자의 경우 특 히 가능성이 높다. 저자들은 평소 건강했던 속립성 폐결핵 환자에서 간, 비장, 신장, 뇌막 및 뇌실질에 동시에 나타난 다발성 결핵을 보고한다. (Tuberc Respir Dis 2007; 63: 67-71)Key Words: Miliary tuberculosis, Multiorgan, Immunocompetent.Address for Correspondence: Dong Jib Na, M.D. Division of Pulmonary Medicine, Department of Internal Medicine, Eulji University School of Medicine, 1036 Dunsan 2-dong, Seo-gu, Daejeon, 302-799, Korea. Phone: 82-42-611-3154, Fax: 82-42-611-3853 E-mail: djna13@gmail.comReceived: Apr. 20. 2007Accepted: Jun. 14. 2007
Aluminum nitride was synthesized by self-propagating high-temperature synthesis (SHS) with flaky aluminum powder in various conditions such as particle size, nitrogen pressure (PN 2 ), dilution factor f( Dil</sub), packing density, and bulk sample size. AlN content in the SHS product increases with an increase of fDil, and it eventually reaches about 95 % at fDil=0.6. Generally, reaction front velocity is significantly affected by P N2 and packing density, but not by f Dil . The degree of AlN conversion reduces more or less with an increase of bulk sample size, but that could be improved by using the SHS pre-prepared product as a diluent.
Growth model of a circumferential outer diameter stress corrosion crack (ODSCC) in a retired steam generator tube of the Kori 1 nuclear power plant was proposed based on extensive destructive examinations of the pulled tubes of Alloy 600 from the Kori 1 plant. A small ODSCC grows in a lateral direction as well as a forward direction until it meets a neighboring ODSCC which also grows in a lateral direction as well as a forward direction. And then, the two ODSCCs which meet on the same circumferential plane are consolidated into a single ODSCC. By repeating such a consolidation process with time, it seems that the apparent growth rate of an ODSCC in the lateral direction is much faster than that in the forward direction. Growth model of a circumferential ODSCC from a retired steam generator tube of the Kori 1 plant reveals that many ODSCCs are initiated and grow in both directions independently until they meet and finally they are consolidated.
A reactor vessel consists of carbon/low alloy steel (SA508) as the structural material, and a cladding layer (SS309) as a protective layer. Cladding layer experiences damage by accidents such as thermal sleeve detachments. Carbon/low alloy steel is weak to corrosion when exposed to the primary water especially during refueling time, which is a potential threat against the integrity of a reactor vessel. Therefore, the damaged cladding part should be repaired. Repairing the inside of the reactor vessel is difficult because of high radiation levels, poor accessibility, and the underwater condition. One promising repair technology is the electrochemical deposition (ECD) of nickel. Nickel plating through ECD has a lot advantages such as excellent corrosion resistance, no heavy thermal effect (near room temperature process), and proper mechanical properties for long-term nuclear operation. Moreover, the plating layer can be easily removed and is applicable to underwater conditions. The ECD technology used to repair the inside of the steam generator tube has been approved in the ASME code case N-569, titled “Alternative Rules for Repair by Electrochemical Deposition of Class 1 and Class 2 Steam Generator Tubing.” It is expected that an ECD layer can protect the corrosion/erosion of the exposed surface of damaged cladding/ carbon steel. The ECD process consists of many processes, such as surface cleaning, strike layer formation for the adhesion between ECD layer and cladding/carbon steel, activation, and a main electrodeposition process. “Alternative Rules for Cladding Repair by Underwater Electrochemical Deposition in Class 1 and 2 Applications” is proposed based on the Code Case N-569. This proposed code case includes material requirements, qualification, essential variables, and examination requirements.
It is well known that the transient and prolonged misfolding nature of amyloid-β (Aβ) makes it difficult to perform proper in vitro studies and obtain consistent results. From monomers to fibrils, the aggregated forms of Aβ are significant hallmarks
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