• 한국수산과학회지
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• 제30권2호
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• pp.244-251
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• 1997

생리활성을 지닌 신경펩타이드의 구조와 활성간의 관계를 규명하기 위하여 고상법으로 합성한 세 종류의 neuropeptide $\gamma$(mammalian-, trout- 그리고 goldfish-neu-ropeptide $\gamma$)를 사용하여 연구하였다. Circular dichroism spectra에 의하면 mammalian-, trout-와 goldfish-neurope-ptide $\gamma$는 완충액 조건하에서 모두 random한 구조를 나타내었다. 중성 및 산성 지질 존재 하에서, mammalian과 trout-neuropeptide $\gamma$는 여전히 random한 구조를 취했다. 그러나, goldfish-neuropeptide $\gamma$는 중성 및 산성지질하에서 부분적으로 $\alpha-helix$ 구조를 나타내었다. 장관 수축활성 에 있어서는 carp 장관, guinea-pig 회장 그리고 rat 십이지장에 대하여 비교하였다. Carp에 대해서는 goldfish-neuropeptide $\gamma\;\simeq$ trout-neuropeptide $\gamma\;>$ mammalian- neuropeptide $\gamma$ 순으로 활성이 나타났다. 그러나, guinea-pig 회장과 rat 십이지장에 대해서 mammalian-neuropeptide $\gamma$는 어류 유래성 neuropeptide g들 보다 높은 수축활성을 나타내었다. 이러한 결과들은 neuropeptide $\gamma$들이 종-특이적인 활성을 나타낸다는 것을 제시한다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2006년도 춘계학술대회 논문집
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• pp.429-433
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• 2006

High Temperature deformation behavior of newly developed beta-gamma TiAl alloy was investigated in this study. The optimum processing condition was investigated with the aid of Dynamic Materials Model (DMM). Processing maps representing the efficiency of power dissipation for microstructural evolution and instability were constructed utilizing the results of hot compression test at temperatures ranging from $1000^{\circ}C$ to $1200^{\circ}C$ and strain rate ranging from $10^{-4}/s$ to $10^2/s$. The Artificial Neural Network (ANN) simulation was adopted to consider the deformation heating. With the help of processing map and microstructural analysis, the optimum processing condition was presented and the role of $\beta$ phase was also discussed in this study.

• 한국자기학회지
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• 제17권2호
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• pp.76-80
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• 2007

화학기상응축공정법으로 세 가지 분해온도에서 제조된 나노 Fe-N 시료들을 뫼스바우어 분광기, XRD와 BET를 이용하여 자기적 특성의 변화를 연구하였다. 분해온도가 낮을수록 ${\gamma}'-Fe_4N$의 형성이 용이하였으며, 중간온도에서의 ${\epsilon}-Fe_{2.12}N$을 거쳐 높은 분해온도에서는 ${\gamma}-Fe$가 주로 형성되었다. 높은 분해온도에서는 Fe와 N이 서로 잘 결합되지 못하였는데, 이는 Fe와 N을 결합시키기 위해서는 분해온도를 낮게 하는 것이 바람직하다는 것을 의미한다.

• 한국세라믹학회지
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• 제23권3호
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• pp.1-8
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• 1986

The preparation and electrical conductivity of $\beta$-$Al_2O_3$ are investigated as a function of $Na_2O$ content from the-oretical composition of $\beta$-$Al_2O_3$ to that of $\beta$"-$Al_2O_3$. $\beta$-$Al_2O_3$ $\beta$"$Al_2O_3$$\alpha$-Al2O3 and ${\gamma}$-NaAlO2 phases appear in the calcined powder at 125$0^{\circ}C$ for 2 hours. The majoity phase is $\beta$-$Al_2O_3$ in sintered specimens at 155$0^{\circ}C$ and 1$650^{\circ}C$ for 30 mins respectively and ${\gamma}$-4NaAlO_2$ phase also exists when Na2O content is over 10.39w/o ${\gamma}$-4NaAlO_2$ phase does not affect the grain growth of $\beta$-$Al_2O_3$ in sintering at 155$0^{\circ}C$ but acts as a reactive liquid for the abnormal grain growth of $\beta$-$Al_2O_3$in sintering at 1$650^{\circ}C$ The electrical conduction of $\beta$-$Al_2O_3$is predominated by 4Na^+$ ion. Contribution of ionic con-ductivity to total conductivity is gradually decreased with increasing temperature at given oxygen pressure and to -tal conductivity is increased by positive hole due to interstitial oxygen with increasing oxygen pressure.

• 한국추진공학회지
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• 제2권1호
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• pp.67-77
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• 1998

Ni/$Ni_3$Al-$Ni_3$Nb(${\gamma}$/${\gamma}$'-${\delta}$), Ni-$Ni_3$Nb(${\gamma}$-${\delta}$) 공정복합재료를 일방향 응고하였으며, 성장속도에 따른 경도변화, 고온에서 미세조직의 안정성을 층상간격의 영향에 대해 연구하였다. 초내열합금 공정복합재료의 층상간격은 ${\lambda}^2$R＝상수라는 관계식에 의하여 성장속도(R)와 함께 변화하였다. 초내열합금 공정복합 재료를 위한 항온열처리의 결과는 이 연구에 이용되었다. 공정복합재료는 고온에서 미세구조의 안정성이 층상간격의 증가 때문에, 경도는 성장속도의 증가 때문에 향상되었다.

• 천문학회보
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• 제41권2호
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• pp.60.2-60.2
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• 2016

We present recent results of very long baseline interferometry (VLBI) observations of gamma-ray bright active galactic nuclei (AGNs) using Korean VLBI Network (KVN) at 22, 43, 86, and 129~GHz bands, which are part of a KVN key science program; Interferometric Monitoring of Gamma-ray Bright AGNs (iMOGABA). We selected a total of 34 radio-loud AGNs of which 30 sources are gamma-ray bright AGNs, including 24 sources monitored by the Fermi Gamma-ray Space Telescope using the Large Area Telescope on board. The selected sources consist of 24 quasars, 7 BL Lacs, and 3 radio galaxies. In this talk, we summarize recent results of the iMOGABA, including results of single-epoch multi-frequency VLBI observations of the target sources, conducted during a 24-hr session on 2013 November 19 and 20. All observed sources were detected and imaged at all frequency bands with or without a frequency phase transfer technique which enabled to detect and image 12 faint sources at 129 GHz, except for 0218+357 which was detected for only one baseline at all frequency bands.

• 대한금속재료학회지
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• 제50권9호
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• pp.645-651
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• 2012

This study investigated changes in phase fraction caused by the addition of Mo, as well as the subsequent behaviour of N and its effect on the mechanical properties of welded 24Cr-N duplex stainless steel weld metals. Filler metal was produced by fixing the contents of Cr, Ni, N, and Mn while adjusting the Mo content to 1.4, 2.5, 3.5 wt%. The delta ferrite fraction increased as the Mo content increased. In contrast, the ${\gamma}$ fraction decreased and changed from a round to an acicular shape. Secondary austenite (${\gamma}^{\prime}$) was observed in all specimens in a refined form, but it decreased as the Mo content increased to the extent that it was nearly impossible to find any secondary austenite at 3.5 wt% Mo. Both tensile and yield strengths increased with the addition of Mo. In contrast, the highest value of ductility was observed at 1.41 wt% Mo. At all temperatures, impact energy absorption showed the lowest value at 3.5 wt% Mo, at which the amount of ${\delta}$-ferrite was greatest. There was no significant temperature dependence of the impact energy absorption values for any of the specimens. As the fraction of ${\gamma}$ phase decreased, the amount of N stacked in the ${\gamma}$ phase increased. Consequently, the stacking fault energy decreased, while the hardness of ${\gamma}$ increased.

• Nuclear Engineering and Technology
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• 제56권7호
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• pp.2767-2774
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• 2024

In this study, investment casting shell waste successfully utilized to produce cordierite/mullite/zircon composites. Green pellets, consisting of investment casting shell waste, alumina, and magnesia, were prepared and sintered at temperatures between 1250 and 1350 ℃. The influence of the sintering temperature on the crystalline phase composition, densification behavior, flexural strength, microstructure, and radiation shielding properties of the cordierite/mullite/zircon composites is investigated. Phase analysis showed that characteristic cordierite peaks appear at 1250 ℃, but the complete conversation of silica from investment casting shell waste into cordierite requires a sintering temperature of at least 1300 ℃. Notably, the cordierite/mullite/zircon composite sintered at 1350 ℃ exhibited a sixfold increase in flexural strength compared to the ceramic composite directly fabricated from investment casting shell waste at the same sintering temperature. Furthermore, the effect of Y₂O₃ addition on composites' radiation shielding properties is investigated. The results show that the Y₂O₃ addition improves densification behavior, enhancing the shielding capabilities of the composites against fast neutron and gamma radiation. Our findings suggest that the developed ceramic composites show significant potential for gamma-ray and neutron shielding applications.

• 약학회지
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• 제43권3호
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• pp.300-305
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• 1999

A sensitive and efficient assay method was applied to determine the level of glutamic acid (GA) and ${\gamma}-aminobutyric$ acid (GABA) in frontal cortex and hippocampus of rat administrated with ethanol and drugs. The compounds were derivatized with ο-phthalaldehyde (OPA) and 2-mercaptoethanof for precolunm analysis. The condition for the simultaneous determination of GA, GABA and $\beta-aminobutyric$ acid (BABA) by high performance liquid chromatography with electrochemical detection was reverse phase $C_{18}$ column as stationary phase, 0.1 M phosphate buffer containing 0.1 mM $Na_4EDTA$ : methanol = 55:45 (v+v) pH 3.8 as mobile phase and 0.7V electrode voltage. The stability of reaction product of GA, GABA and BABA with OPA could be increased by adding the same volume of polyethylene glycol 400 to reaction mixture. The GABA level in frotal cortex of rat was significantly decreased by the administration of picrotoxin and diazepam, but it was significantly increased by the administration of red ginseng total saponin, N-methyl-D-glucamine and (-)-deprenyl.

• Journal of Advanced Marine Engineering and Technology
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• 제27권6호
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• pp.704-713
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• 2003

The effect of partial substitution of tungsten for molybdenum on the microstructure and corrosion resistance in 22Cr-5Ni-3Mo duplex stainless steel(DSS) aging heat treated in a temperature range of 600~$1000^{\circ}C$ has been investigated. Electrochemical tests were carried out for the evaluation of corrosion resistance. Aging treatment had hardly influenced the general corrosion resistance. With the increase of aging time, the pitting corrosion resistance of the DSS had decreased, After aging for 2min at 700~$900^{\circ}C$, the pitting potential of the 3Mo steel decreased remarkably, while that of the W-substituted steel hardly changed. During aging. the intermetallic $\sigma$ and secondary austenite ($\gamma_2$) phases were precipitated. and the pitting corrosion and intergranular corrosion resistance were significantly decreased after aging at 700~$750^{\circ}C$ for 10 h, which could be caused by the $\gamma_2$ formation. The ${\gamma}$$_2$ phase could affect the depletion of molybdenum and chromium in the $\gamma_2/\alpha and \gamma_2/\sigma$ boundaries.