• Elastomers and Composites
• /
• v.52 no.4
• /
• pp.237-241
• /
• 2017

The tensile strength (TS) and elongation-at-break (EB) loss of a CR/CB rubber composite sample prepared for the automotive parts were measured after accelerated thermal ageing at temperatures of 100, 120, 140, and $150^{\circ}C$. The change in TS was observed to be linear from the master curve prepared using the time-temperature superposition-principle (TTSP). An Arrhenius type of shift factor, $a_T$ was used to predict the life time of the sample, and a plot of ln $a_T$ vs. 1/T was also shown to be linear. The activation energy ($E_a$) of the sample was calculated as 70.30 kJ/mole from the Arrhenius plot. The expected life time of the sample was predicted at the given operating conditions by applying Arrhenius analysis. Assuming the $E_a$ value was constant at lower operating condition, life time of the sample was calculated as 2.3 years when the life limit was set as time to reach the 20% decrease of the initial TS value at operating temperature of $40^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.06a
• /
• pp.141-141
• /
• 2009

Blue light-emitting diodes (LEDs), violet laser diodes 같은 광전소자들은 질화물 c-plane 기판위에 소자로 응용되어 이미 상품화 되어 왔다. 그러나 2족-질화물 재료들은 wurtzite 구조를 가지므로 c-plane에 평행한 자연적인 극성을 띌 뿐만 아니라 결정 내부 stress로 인한 압전현상 또한 나타나 큰 내부 전기장을 형성하게 된다. 이렇게 생성된 내부 전기장은 전자와 홀의 재결합 효율을 감소시키고 소자 응용 시 red-shift의 원인이 되곤 한다. 따라서 최근 들어 m-plane(1-100), a-plane (11-20)같은 무극성을 뛰는 기판 위에 소자를 만드는 방법이 각광을 받고 있는 추세다. 그러나 무극성 기판을 소자에 응용 시 Chemical Mechanical Planarization (CMP)에 의한 가공은 반도체 기판으로써 이용하기 위한 필수 불가결의 공정이다. c면(0001) SiC wafer에 대한 연구는 현재 많이 발표가 되어 있으나 무극성면 SiC wafer에 대한 CMP 공정에 대한 연구사례는 없는 실정이다. 본 연구에서는 C면 (0001)으로 성장된 잉곳을 a면(11-20)과 m(1-100)면으로 절단 후, slurry type (KOH-based colloidal silica slurry, NaOCl), 산화제, 연마제등을 변화하여 CMP 공정을 거침으로서 일어나는 기계 화학적 가공 양상에 대하여 알아보았다. 그 후 표면 형상 분석 하기위해 Atomic Force Microscope(AFM)을 사용하였고, 표면 스크레치를 SEM을 이용해서 알아보았다.

• Journal of Environmental Health Sciences
• /
• v.27 no.1
• /
• pp.36-43
• /
• 2001

Chitosans were prepared from red crab chitin under various alkali treatment conditions(different alkali concentrations, reaction times and temperatures) and theirphysicochemical properties were investigated. The nitrogen content and deacetylation degree of red crab chitin were 6.15% and 22.17A%, respectively. By the IR spectra, red crab and reference chitin showed the sharp bands at 1650 $cm^{-1}$ / and 1550 $cm^{-1}$ /, which are characteristic of chitin. The nitrogen contents of prepared chitosans ranged from 6.19~7.48%. Thedeacetylation degree was increased from 63~76% and 48~78% with increasing reaction time and temperature, whereas viscosity was decreased. The nitrogen content and yield of red crab chitosan perpared from chitin with 50% NaOH, 1:25(w/v) for 3.0 hr at 120$cm^{-1}$ / were 7.26% and 85.0%, respectively. and viscosity, deacetylation degree and molecular weight, 67.0 mPa.s, 75.0% and 6.5$\times$10$^{5}$ Dalton, respectively. From the IR spectra, the amide absorption bands of red crab and reference chitosan became very weak, similarly. And at solid state $^{13}$ C-NMR spectra, C=O(carbonyl carbon) signals absent, whereas $CH_3$(methyl carbon) was residues. Chemical shift of $^{13}$ C-NMR spectra of red crab and reference chitosans were in good agreement with slight experimental deviation.

• Journal of Radiopharmaceuticals and Molecular Probes
• /
• v.5 no.2
• /
• pp.145-151
• /
• 2019

Fluorine-18 is considered to be the radionuclide of choice for positron emission tomography (PET). Thus, the development of small molecule-based radiopharmaceuticals for use in diagnostic imaging relies heavily on efficient radiofluorination techniques. Until the early 2000s, diaryliodonium salts and aryliodonium ylides were widely employed as labeling precursors to yield aromatic PET radiotracers with cyclotron-produced [¹⁸F]fluoride ion. Rapid recent progress in the development of efficient borylation methods has led to a paradigm shift in ¹⁸F-labeling methods. In addition, deoxyfluorination has attracted a great deal of interest as an alternative approach to aryl ring activation with ¹⁸F^-. In this review, methods for radiolabel development are discussed with a specific focus on the progress made in the last 5 years. Other interesting ¹⁸F-based protocols are also briefly introduced. New methods for exploiting ¹⁸F^- are expected to increase the number of ¹⁸F-labeling methods, to allow applications in a range of chemical environments.

• Proceedings of the Microbiological Society of Korea Conference
• /
• 2005.05a
• /
• pp.105-109
• /
• 2005

Heat Shock Transcription Factor (HSF), and the promoter heat Shock Element (HSE), are among the most highly conserved transcriptional regulatory elements in nature. HSF mediates the transcriptional response of eukaryotic cells to heat, infection and inflammation, pharmacological agents, and other stresses. While HSF is essential for cell viability in yeast, oogenesis and early development in Drosophila, extended life-span in C. elegans, and extra-embryonic development and stress resistance in mammals, little is known about its full range of biological target genes. We used whole genome analyses to identify virtually all of the direct transcriptional targets of yeast HSF, representing nearly three percent of the genomic loci. The majority of the identified loci are heat-inducibly bound by yeast HSF, and the target genes encode proteins that have a broad range of biological functions including protein folding and degradation, energy generation, protein secretion, maintenance of cell integrity, small molecule transport, cell signaling, and transcription. Approximately 30% of the HSF direct target genes are also induced by the diauxic shift, in which glucose levels begin to be depleted. We demonstrate that phosphorylation of HSF by Snf1 kinase is responsible for expression of a subset of HSF targets upon glucose starvation.

• Biotechnology and Bioprocess Engineering:BBE
• /
• v.6 no.4
• /
• pp.274-278
• /
• 2001

Polymer membranes composed of N, N-dimethylaminoethyl methaccrylate(DMAEMA) and acrylamide(AAm)(or ethyl acrylamide(EAAm) were prepared to demonstrated the thermo-control of solute permeation. Poly DMEMA has a lower critical solution temperature(LCST) at around 50$\^{C}$ in water, With the copolymerization of DMAEMA with AAm (or EAAm) a shift in the LCST to a lowere temperature was observed, probably due to the formation of hydrogen bonds between the amide and N-N-dimethylamino groups. However, the temperature-induced phase transition of poly(DMAEMA-co-EAAm) did not show a similar trend to that of poly(DMAEMA- co-AAm) in the gel state. The hydrogen bonds in poly(DMAEMA-co-EAAm) were significantly disrupted with the formation a gel network, which led to a difference in the swilling behavior of polymer gels in response to temperature. To apply these polymers to temperature-sensitive sol-ute permeation, polymer membranes were prepared. The permeation pattern of hydrocortisone, used as the model solute, was explained based on the temperature-sensitive swelling behavior of the polymer membranes.

• Journal of Biomedical Engineering Research
• /
• v.31 no.6
• /
• pp.464-471
• /
• 2010

Compressed sensing can be used to reduce scan time or to enhance spatial resolution in MRI. It is now recognized that compressed sensing works well in reconstructing magnitude images if the sampling mask and the sparsifying transform are well chosen. Phase images also play important roles in MRI particularly in chemical shift imaging and magnetic resonance electrical impedance tomography (MREIT). We reconstruct MRI phase images using the compressed sensing technique. Through computer simulation and real MRI experiments, we reconstructed phase images using the compressed sensing technique and we compared them with the ones reconstructed by conventional Fourier reconstruction technique. As compared to conventional Fourier reconstruction with the same number of phase encoding steps, compressed sensing shows better performance in terms of mean squared phase error and edge preservation. We expect compressed sensing can be used to reduce the scan time or to enhance spatial resolution of MREIT.

• Journal of the Korean Magnetic Resonance Society
• /
• v.12 no.2
• /
• pp.65-73
• /
• 2008

HP1298 (Swiss-Prot ID ; P65108) is an 72-residue protein from Helicobacter pylori strain 26695. The function of HP1298 was identified as Translation initiation factor IF-l based on sequence homology, and HP1298 is included in IF-l family. Here, we report the sequence-specific backbone resonance assignments of HP1298. About 97% of all the $^{1}HN$, $^{15}N$, $^{13}C{\alpha}$, $^{13}C{\beta}$, and $^{13}CO$ resonances could be assigned unambiguously. We could predict the secondary structure of HP1298, by analyzing the deviation of the $^{13}C{\alpha}$ and $^{13}C{\beta}$ shemical shifts from their respective random coil values. Secondary structure prediction shows that HP1298 consists of six $\beta$-strands. This study is a prerequisite for determining the solution structure of HP1298 and investigating the structure-function relationship of HP1298. Assigned chemical shift can be used for the study on interaction between HP1298 and other Helicobacter pylori proteins.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2003.11a
• /
• pp.63-63
• /
• 2003

The nanotopography of silicon wafers has emerged as an important factor in the STI process since it affects the post-CMP thickness deviation (OTD) of dielectric films. Ceria slurry with surfactant is widely applied to STI-CMP as it offers high oxide-to-nitride removal selectivity. Aiming to control the nanotopography impact through ceria slurry characteristics, we examhed the effect of surfactant concentration and abrasive size on the nanotopography impact. The ceria slurries for this study were produced with cerium carbonate as the starting material. Four kinds of slurry with different size of abrasives were prepared through a mechanical treatment The averaged abrasive size for each slurry varied from 70 nm to 290 nm. An anionic organic surfactant was added with the concentration from 0 to 0.8 wt %. We prepared commercial 8 inch silicon wafers. Oxide Shu were deposited using the plasma-enhanced tetra-ethyl-ortho-silicate (PETEOS) method, The films on wafers were polished on a Strasbaugh 6EC. Film thickness before and after CMP was measured with a spectroscopic ellipsometer, ES4G (SOPRA). The nanotopogrphy height of the wafer was measured with an optical interferometer, NanoMapper (ADE Phase Shift)

• Korean Journal of Microbiology
• /
• v.28 no.2
• /
• pp.134-144
• /
• 1990

In order to examine that what kind of system correlated with cadmium detoxification mechanism in Klebsiella aerogenes ATCC 10031, we tried to investigate the effect of phosphate upon the detoxification and also elucidate whether the cadmium phosphate and/or polymeric Cd-Pi complex is formed actually in cell or not. As the results, it was shown that growing pattern had long lag adaptive phase of 12 hr to 24 hr, at the concentrations of 0.02 mM and 0.08 mM cadmium, respectively. Cadmium was accumulated more highly in the fraction of cell wall and membrane than in those of cytoplasm. In case of phosphate starving cells added cadmium, inorganic polyphosphate system was primarily correlated with Cd-detoxification during the lag phase for the accommodation to cadmium, on the other hand, Cd:Sulfide complex system secondarily correlated it during the stationary phase. These results implied that polyphosphate system and Cd:sulfide complex system, these two systems were operated compensatively each other. Considering the results obsdrved with EM and examined tha changes of sulfide and polyphosphate amount, it was reflected that Cd:S complex was located at the cell surface. In the results of $in-vivo^{31}$P NMR spectra in the cells with cadmium pressure, several phosphate signals arose newly from the polyphosphate region with moving chemical shift of it. This phinomenon strongly implied the actual existence of Dd:Pi comples and /or Cd:poly-P complex in the cell and also the cellular compartmentalization of cadmium detoxifying mechanism.