• Advanced Composite Materials
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• v.18 no.4
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• pp.351-364
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• 2009

The thermal stability and elevated temperature mechanical properties of $SiC_P$/Al-11.7Fe-1.3V-1.7Si (Al-11.7Fe-1.3V-1.7Si reinforced with SiC particulates) composites sheets prepared by spray deposition (SD) $\rightarrow$ hot pressing $\rightarrow$ rolling process were investigated. The experimental results showed that the composite possessed high ${\sigma}_b$ (elevated temperature tensile strength), for instance, ${\sigma}_b$ was 315.8 MPa, which was tested at $315^{\circ}C$, meanwhile the figure was 232.6 MPa tested at $400^{\circ}C$, and the elongations were 2.5% and 1.4%, respectively. Furthermore, the composite sheets exhibited excellent thermal stability: the hardness showed no significant decline after annealing at $550^{\circ}C$ for 200 h or at $600^{\circ}C$ for 10 h. The good elevated temperature mechanical properties and excellent thermal stability should mainly be attributed to the formation of spherical ${\alpha}-Al_{12}(Fe,\;V)_3Si$ dispersed phase particulates in the aluminum matrix. Furthermore, the addition of SiC particles into the alloy is another important factor, which the following properties are responsible for. The resultant Si of the reaction between Al matrix and SiC particles diffused into Al matrix can stabilize ${\alpha}-Al_{12}(Fe,\;V)_3Si$ dispersed phase; in addition, the interface (Si layer) improved the wettability of Al/$SiC_P$, hence, elevated the bonding between them. Furthermore, the fine $Al_4C_3$ phase also strengthened the matrix as a dispersion-strengthened phase. Meanwhile, load is transferred from Al matrix to SiC particles, which increased the cooling rate of the melt droplets and improved the solution strengthening and dispersion strengthening.

• Journal of Korea Foundry Society
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• v.26 no.1
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• pp.17-26
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• 2006

The substitution of cooling method from water quenching to air cooling after solution heat treatment was aimed for the development of a convenient and economical heat treatment process of duplex stainless steels without deterioration of mechanical and corrosion resistant properties for the industry. In order to achieve this goal, the mechanical properties and corrosion properties of a ASTM A890-4A duplex stainless steel were systematically investigated as functions of casting condition and cooling method after solution heat treatment. A 3-stepped sand mold and a permanent Y-block mold were used to check the effects of solidification structure and cooling rate after solution heat treatment. The microstructural characteristics such as the ferrite/austenite phase ratio and the precipitation behavior of ${\sigma}$ phase and carbides were investigated by combined analysis of OM and SEM-EDX with an aid of TTT diagram. Hardness and tension test were performed to evaluate the mechanical properties. Impact property at $-40^{\circ}C$ and corrosion resistance were also examined to check the possibility of the industrial application of this basic study. Throughout this investigation, air-cooling method was proved to effectively substitute for water-quenching process after the solution heat treatment, when the duplex stainless steel was sand mold cast with a thickness below 15 mm or permanent mold cast with a thickness below 20 mm.

• The Plant Pathology Journal
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• v.29 no.3
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• pp.323-329
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• 2013

The stationary-phase sigma factor, RpoS, influences the expression of factors important in survival of Pseudomonas chlororaphis O6 in the rhizosphere. A partial proteomic profile of a rpoS mutant in P. chlororaphis O6 was conducted to identify proteins under RpoS regulation. Five of 14 differentially regulated proteins had unknown roles. Changes in levels of proteins in P. chlororaphis O6 rpoS mutant were associated with iron metabolism, and protection against oxidative stress. The P. chlororaphis O6 rpoS mutant showed increased production of a pyoverdine-like siderophore, indole acetic acid, and altered isozyme patterns for peroxidase, catalase and superoxide dismutase. Consequently, sensitivity to hydrogen peroxide exposure increased in the P. chlororaphis O6 rpoS mutant, compared with the wild type. Taken together, RpoS exerted regulatory control over factors important for the habitat of P. chlororaphis O6 in soil and on root surfaces. The properties of several of the proteins in the RpoS regulon are currently unknown.

• The Korean Journal of Food And Nutrition
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• v.24 no.2
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• pp.258-267
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• 2011

14-3-3 is a highly conserved, ubiquitously expressed protein family. It associates with diverse cellular proteins through its specific phosphoserine/phosphothreonine-binding activity and thus contributes to the regulation of crucial cellular processes such as metabolism, signal transduction, cell-cycle control, apoptosis, protein trafficking, transcription and stress responses. This study aims to determine changes in levels of 14-3-3 isoforms and 14-3-3 - associated proteins in Helicobacter pylori(H. pylori)-infected gastric epithelial AGS cells. AGS cells were stimulated with H. pylori(NCTC 11637) at the ratio of 300:1(bacterium:cell). Western blot analysis revealed that 14-3-3 $\sigma$ was elevated at 3 hr after H. pylori treatment. Other isoforms were not significantly affected by H. pylori infection. Using immunoprecipitation to 14-3-3 $\sigma$, followed by proteomic analysis, we found that S phase kinase associated protein isoform 2 bound to 14-3-3 $\sigma$ has increased. In contrast, three proteins (DEAD-box polypeptide 3, heterogeneous nuclear ribonucleoprotein H2 and WD repeat-containing protein isoform 1) bound to 14-3-3 decreased by H. pylori infection. Our results suggest that 14-3-3 may play an important regulatory role in H. pylori-induced signal transduction in gastric epithelial cells.

• Journal of Korea Foundry Society
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• v.29 no.4
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• pp.181-186
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• 2009

The interrelationship between new parameter ${\sigma}$ and maximum diameter $D_{max}$ is elaborated and discussed in comparison with four other glass forming ability (GFA) parameters, i.e. (1) super-cooled liquid region ${\Delta}T_x (=T_x - T_g)$, (2) reduced glass transition temperature $T_{rg} (=T_g/T_l)$, (3) K parameter $K (=[T_x-T_g]/[T_l -T_x])$, and (4) gamma parameter ${\gamma}(=[T_x]/[T_l+T_g])$ in Ca-based bulk metallic glass (BMG) systems. The ${\sigma}$ parameter, defined as ${\Delta}T^*{\times}P^'$, has a far better correlation with $D_{max}$ than the GFA parameters suggested so far, clearly indicating that the liquid phase stability and atomic size mismatch dominantly affect the GFA of Ca-based BMGs. Thus, it can be understood that the GFA of BMGs can be properly described by considering structural aspects for glass formation as well as thermodynamic and kinetic aspects for glass formation.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.497-500
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• 2005

This paper presents a design of a hybrid sensor chip which integrates an A/D converter module and a phase measurement module for measuring power line phase. Recursive sliding DFT based phase measurement module is designed using time shared multiplier which can reduce the size of SoC implementation. A/D converter is based on the sigma delta modulation in order to minimize the implementation space of the analog part and designed to obtain 8-bit resolution. Computer simulations and FPGA implementation are performed to verify hybrid sensor chip design. The hybrid sensor chip for 4-channel power line phase measurement is fabricated by using 0.35 micrometer CMOS process.

• Nuclear Engineering and Technology
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• v.34 no.6
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• pp.574-585
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• 2002

The microstructural characteristics and its related mechanical properties of RPV cladding have been investigated using small punch (SP) tests. SA508 Cl.3 RPV steel plates were overlay cladded with the type ER309L welding consumables by submerged arc welding process. Although the RPV clad material had a small portion of 5 ferrite phase, it still showed the ductile to brittle transition behavior The transition temperature was determined by the SP test and it depended on the content of $\sigma$ phase, specimen size, and determination methods. The fracture appearance of SP specimen was changed from circumferential to radial cracking as test temperature became low, and below the transition temperature region, ER309L cladding usually fractured along the 6 ferrite by the low temperature failure of ferrite phase.

• Journal of Environmental Science International
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• v.19 no.4
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• pp.447-457
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• 2010

This study aims to monitor the variation of concentration of PCDD/DFs between the gaseous phase-particulate phases in the ambient air of urban area in Korea. This monitoring is evaluated by using the Junge-Pankow model and the Koa absorption model with the application of the Octanol-air partition coefficient. In this study, the ambient air samples were analyzed according to each congener group of the PCDD/DFs by HRGC/HRMS, which have been investigated for the past 5 years. In the results, the annual variation in the concentration level of $\Sigma$PCDD/DFs in TSP was increased from $1588\;fg/m^3$ in 1998 to $5123\;fg/m^3$ in 2002, and from 31 fg I-TEQ/$m^3$ to 94 fg I-TEQ/$m^3$ in the $\Sigma$I-TEQ. In the case of PUF of gaseous phase sample, their variation was increased from $1615\;fg/m^3$ in 1998 to $2237\;fg/m^3$ in 2002, and in the $\Sigma$I-TEQ from 12 fg I-TEQ/$m^3$ to 17 fg I-TEQ/$m^3$. The relative coefficient between the gas phase concentration of PCDD/DFs and the temperature was a value of 0.744; the contributive rate of the temperature to the gaseous phase concentration was 0.554. According to the results, the pattern of the coefficient of distribution based on log $p_L^0$ is similar to the ambient air of the urban areas.

• Journal of Environmental Health Sciences
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• v.29 no.4
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• pp.10-16
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• 2003

Atmospheric samples were conducted from September 2001 to July 2002 with GPS-l PUF sampler in rural site to concentration distributions of gas/particle PCBs and to calculate dry deposition flux of PCBs. $\Sigma$PCBs concentrations of gas/particle PCBs were 59.29$\pm$48.83, 6.56$\pm$6.59 pg/㎥, respectively. Gas contribution (%) of total PCBs (gas + particle) was 90% which existed gas phase in the atmosphere. The particle contribution (%) of PCB congeners increased relatively more of the less volatile congeners with the highest chlorine number. The correlation coefficients (r) between total PCBs and temperature ($^{\circ}C$) showed negative correlation in - 0.62 (p<0.0l) for particle phase, positive correlation in 0.63 (p<0.01) for gas phase. In other word, particle phase PCBs is enriched in colder weather which could be due to greater in corporation of condensed gas phase at low temperature. The calculated dry deposition of total PCBs (gas + particle) was 0.008, 0.008 $\mu\textrm{g}$ $m^{-2}$ da $y^{-l}$ which showed maximum dry deposition flux in December, minimum data in July Bs in the atmosphere. The calculated dry deposition fluxes of total PCBs were influenced by particle phase PCBs even though PCBs in the atmosphere were present primarily in the gas phase.e.

• Transactions of Materials Processing
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• v.4 no.2
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• pp.159-168
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• 1995

The torsion tests in the range of $550~800^{\circ}C$, $5.0{\times}10^{-3}~5.0{\times}10^0/sec$ were performed to study the effects of strain rate$(\.{\varepsilon})$ and temperature(T) on the hot strength of Cu-Zn alloy. High temperature flow stresses of this alloy increased with increasing $\.{\varepsilon}$ and/or decreasing T, and than the more grain refinement could be obtained. The flow curves exhibited a peak followed by a steady steady state regime as a result of dynamic recrystallization. The hot strength dependence of $\.{\varepsilon}$ and T was described by a hyperbolic sine law, $\.{\varepsilon}=A(sinh0.017{\sigma})^4.81$exp(-216KJ/mol). Hot strength could be reduced at the arbitary condition, $\.{\varepsilon}$ and T, by constitutive parameter Z(Zenner-Hollomon parameter), $Z=A(sinh{\alpha}{\sigma})^n=\.{\varepsilon}$exp(Q/RT).