• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2004.05a
• /
• pp.395-399
• /
• 2004

Four microalloyed steels containing B were investigated in terms of hardenability, mechanical properties and microstructure depending upon the cooling rates in order to develop the steel grade for the cold forged fasners. The alloy with the largest DI value among 4 alloys, which contains $0.12\%\;C,\;1.54\%\;Mn,\;0.65\%\;Cr,\;0.11\%V,\;0.040\%Ti\;and\;0.0033\%B$, showed the larest shift to the right hand side in the TTT diagram, implying the wide allowable cooling rate range subsequent to hot rolling in long bar processing, Mechanical tests indicated that yield strength are dependent upon the DI value in water quenched specimens but other properties showed almost the same values. In the same grade of steel, the increase in cooling rates causes the decrease in elongation but the increase in strength, reduction of area and Charpy impact values. Microstructural examination in steel grade with the larest DI values revealed martensitic structure In the water quenched state, a mixture of martensite and bainite in the oil quenched, and ferrite + pearlite in the air cooled and the forced air cooled but the latter showed finer microstructure.

• Journal of Plant Biology
• /
• v.32 no.4
• /
• pp.265-274
• /
• 1989

The effect of Ca2+ on auxin-induced ehtylene production in etiolated mungbean (Vigna radiata W.) hypocotyls was studied. Auxin-induced ethylene production by mungbean seedlings which had been germinated in the presence of 5-10mM Ca2+ (High Ca2+ ; HC) is greater than that by seedlings which had been germinated in distilled water (Low Ca2+ ; LC). The effect of Ca2+ on auxin-induced ethylene production was greatly increased after 12hr of incubation period. The stimulation of auxin-induced ethylene production by Ca2+ was specific, since divalent cations, such as Mg2+ and Mn2+ did not enhance auxin-induced ethylene production. Calcium also promoted ethylene evoluation induced by methionine and 1-Aminocyclopropane-1-carboxylic acid(ACC). The effect of Ca2+ on auxin-induced ethylene production was not caused by increase in free IAA or ACC contents of hypocotyl tissue. Dimethyl sulfoxide and Triton X-100, that disrupts the emembranes, inhibited ethylene production to a greater extent in LC segments than in HC segments. Addition of Ca2+ to the incubation medium for LC segments resulted in enchancement of ethylene production probalby because the membrane integrity is supported under these conditions. Comparison of activity of Ethylene Forming Enzyme(EFE) in LC and HC hypocotyl segments indicated that the enzyme activity of HC was about 2 times higher than that of L.C. It is suggested that Ca2+ increases the activity of plasma membrane-bound EFE through its stabilizing effect onn the membrane, which in turn brings about promotion of ethylene production.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2000.10a
• /
• pp.29-32
• /
• 2000

The static and metadynamic recrystallization of non-heat treated medium carbon steel(Fe - 0.45wt.$\%C\;-\;0.6wt.\%Si\;-\;1.2wt.\%Mn\;-\;-0.12wt.\%Cr \;-\;0.1wt.\%V \;-\;0.017wt\%$.Ti) were studied by the torsion test in the strain rate range of 0.05 - 5 $sec^{-1}$, and in the temperature range of $900\;-\;1100\;^{\circ}C$. Interrupted deformation was performed with 2 pass deformation in the pass strain range of $0.25 {\varepsilon}_p(peak strain)\;and\;{\varepsilon}_p$, and in the interpass time range or 0.5 - 100 sec. The dependence or pass strain(${\varepsilon}_i$), strain rate( $\dot{\varepsilon}$ ), temperature(T), and interpass time($t_i$) on static recrystallization (SRX) and metadynamic recrystallization (MDRX) were predicted from the modified Avrami's equations respectively. Comparison of the softening kinetics between SRX and MDRX was indicated that the rate of MDRX was more rapid than that of SRX under the same deformation variables.

• Journal of the Korean Ceramic Society
• /
• v.44 no.12
• /
• pp.727-732
• /
• 2007

In order to fabricate a highly performing cathode for low-temperature type solid oxide fuel cells working at below $700^{\circ}C$, electrode microstructure control and electrode polarization measurement were performed with an electronic conductor, $La_{0.8}Sr_{0.2}MnO_3$ (LSM) and a mixed conductor, $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3$(LSCF). For both cathode materials, when $Sm_{0.2}Ce_{0.8}O_2$ (SDC) buffer layer was formed between the cathode and yttria-stabilized zirconia (YSZ) electrolyte, interfacial reaction products were effectively prevented at the high temperature of cathode sintering and the electrode polarization was also reduced. Moreover, cathode polarization was greatly reduced by applying the SDC sol-gel coating on the cathode pore surface, which can increase triple phase boundary from the electrolyte interface to the electrode surface. For the LSCF cathode with the SDC buffer layer and modified by the SDC sol-gel coating on the cathode pore surface, the cathode resistance was as low as 0.11 ${\Omega}{\cdot}cm^2$ measured at $700^{\circ}C$ in air atmosphere.

• Journal of the Korean Ceramic Society
• /
• v.44 no.12
• /
• pp.715-719
• /
• 2007

STS444 with or without $La_{0.9}Sr_{0.1}MnO_3$ (LSM)-coating was contacted to $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3$ (LSCF) cathode on various electrolyte materials and the polarization resistance $(R_p)$ was measured by impedance spectroscopy. By making a symmetric half-cell and contacting only one side of the cathode with the interconnect, the effect of chromium (Cr) poisoning was separated from the aging effects. When the LSCF cathode was contacted with LSM-coated STS (stainless steel), $R_p$ of LSCF was lower than that contacted with the uncoated STS. Impedance patterns measured for the working electrode (W.E.), the counter electrode (C.E.) at $600^{\circ}C$ in air were analyzed. Normalized data of net Cr effect showed that $Ce_{0.9}Gd_{0.1}O_2$ (GDC) electrolyte is more tolerant to the chromium poisoning than $La_{0.9}Sr_{0.1}Ga_{0.8}Mg_{0.2}$ (LSGM) or 8 mol% $Y_2O_3-doped$ $ZrO_2$ (YSZ) electrolytes.

• Proceedings of the KSMRM Conference
• /
• 2001.11a
• /
• pp.176-176
• /
• 2001

목적： 기존의 역수신코일(inside-out receiver coil)로 관벽의 MR 영상을 얻을 때 영상영역이 좁고 수신감도가 불균일한 단점을 보완하면서 신호대 잡음비(S/N ratio)도 높일 수 있는 회전자계역수 신코일(quadratic inside-out receiver coil)의 개발을 목적으로 한다. 대상 및 방법： 8극형코일, 선형자계수신코일, 회전자계수신코일에 대하여 컴퓨터 모의실험으로 영상영역 및 감도의 균일성을 비교하였다. 회전자계수신코일은 안장 모양을 한 두 개의 선형자계코일이 서로 간섭이 일어나지 않도록 수직 방향으로 배열된 구조를 갖도록 하였다. 지름 3 cm 크기로 각 코일을 제작하였으며 지름 20 cm의 원통 중앙에 내경 4 cm의 관이 있는 팬텀을 만들어 MnC1$_2$를 섞은 물을 채운 다음 1.5T 초전도 MRI 장치와 0.3T 영구자석 MRI 장치에서 팬텀의 관벽 영상을 얻었다. 본 실험을 시행한 1.5T 장치의 구조 때문에 회전자계코일의 두 안장코일을 결합하는 회로를 제작하여 사용하였고 0.3T에서는 장치에 내장된 결합회로를 사용하였다. 또한 포르말린 용액에 보관된 소의 대장 조직 단면 영상을 FOV 10-12 cm로 얻어 회전자 계안장코일의 성능을 평가하였다.

• Textile Coloration and Finishing
• /
• v.12 no.1
• /
• pp.25-31
• /
• 2000

In order to decolorize disperse dyes by using biological treatment process, a strain which has potential ability to degrade disperse dyes was isolated from natural system. To increase the removal efficiency of decolorization in the aqueous solutions, the optimal condition of decolorization by this strain was investigated, and continuous plant test was also developed. The optimal culture conditions of temperature and pH were found to be 4$0^{\circ}C$ and 8.5~9, respectively. When yeast extract was mixed with polypeptone at the mixing ratio of 1:1 as a nitrogen source, decolorization efficiency was highest(93%) among the nitrogen sources. The strain to be screened was excellent to adjust to pH, and it seems to be have ability to control pH needed to growth. The optimal culture conditions in concentration of $MgSO_4\cdot{7H}_2O$ and $KH_2PO_4$ were 0.1%(w/v) and 0.2%(w/v). The result of continuous plant process using wastewater was as following : $COD_{Mn}$ removal efficiency was over than 50%, and this strain was very excellent in decolorization-efficiency for the wastewater of Taegu dyeing complex.

• Korean Journal of Veterinary Research
• /
• v.31 no.4
• /
• pp.425-431
• /
• 1991

Effects of recombinant bovine somatotropin$({\gamma}BST)$ on mineral composition of milk were investigated in Twenty-five multiparous Holstein dairy cows. Recombinant BST was administered by two different routes; intramusculary(12.5mg and 25mg/day) and subcutaneously (500mg and 750mg) in sustained-release vehicle every 2 weeks beginning 4 week postpartum and continuing for 7 months. Milks were collected 0,1,2,3,5 and 7 months after beginning of treatments in control and ${\gamma}BST$-administered groups. Mineral composition, such as Ca, Pi, Na, K, Mg, Zn, Fe and Mn, in milk were not affected by the administration of ${\gamma}BST$ regardless of dose and dosage forms. It is concluded from the observations of these experiments that the dose and dosage forms of ${\gamma}BST$ employed in this work might not affect milk mineral composition in dairy cows under the normal sanitary condition and adequate nutrient balance.

• Journal of Korean Society on Water Environment
• /
• v.22 no.4
• /
• pp.666-671
• /
• 2006

Effects of a rainfall event (July 28, 2005) on the hydrochemical characteristics of the Jungrang river, the biggest tributary of the Han river, was investigated. Significant spatial variations in the hydrochemical characteristics were observed. At JR2 location, concentrations of T-N and T-P were relatively low indicating occurrence of active oxidation in the stepped drop structure. At JR3 location, concentrations of Na, K, Cl, $NH_4-N$ and EC were elevated suggesting increased discharge from the nearby waste-water treatment plant and tributaries. The rain event diluted major dissolved ion concentrations in the river by 12~52%. The $NO_3-N$ levels were preserved during the rain then increased about twofold after rainfall, suggesting increased discharge of nitrate-contaminated groundwater. Heavy metals including Cd, Co, Cr, Cu and Pb were not detected in all water samples and the leachates from surface sediment samples. Concentrations of Fe, Mn, Al and Zn were below the Korean Drinking Water Guideline. Results of this study suggested that establishment of water-quality monitoring protocols describing temporal and spatial variations in parameters sensitive to rainfall events, relatively steady factors, and contaminant sources is required.

• Journal of Oral Medicine and Pain
• /
• v.26 no.4
• /
• pp.369-376
• /
• 2001

Objectives : The purposes of the study was to evaluate cephalometric characteristics in snorers and patients with obstructive sleep apnea (OSA) and to see any relationships between the cephalometric measurements and respiratory disturbance indices (RDI). Materials and Methods : Twelve snoring patients, 11 patients with OSA, and 10 normal subjects were included for the study. After taking a screening sleep study for a night to obtain RDI, $SaO_2$, and snoring index, a detailed cephalometric analysis was conducted to obtain SNA, SNB, SN-MP, IAS, MAS, SPAS, SAAS, Mn-H, and PNS-P. All the data were compared between groups. For a group including 12 snoring patients and 11 OSA patients, correlation coefficients were calculated between respiratory disturbance index and each item of cephalometric measurements. Results : The mandible and the maxilla are retropositioned. The oropharyngeal and hypopharyngeal airway is reduced in area and is a factor that could produce or enhance OSA symptoms. The hyoid bone is displaced inferiorly. The soft palate is significantly elongated. Conclusions : These data suggest that cephalometric evaluation could be useful to evaluate snoring and OSA patients, and to assist with the planning treatment for improvement of upper airway patency.