• 천문학회보
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• 제42권2호
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• pp.43.1-43.1
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• 2017

A three-dimensional (3D) $Ly{\alpha}$ radiative transfer code is developed to study the Wouthuysen-Field effect, which couples the 21 cm spin temperature of neutral hydrogen and the $Ly{\alpha}$ radiation field, and the escape fraction of $Ly{\alpha}$ from galaxies. The Monte Carlo code is capable of treating arbitrary 3D distributions of $Ly{\alpha}$ source, neutral hydrogen and dust densities, gas temperature, and velocity field. It is demonstrated that the resonance-line profile at the center approaches to the Boltzmann distribution with the gas temperature. A plane-parallel ISM model, which is appropriate for the neutral ISM of our Galaxy, is used to calculate the $Ly{\alpha}$ radiation field strength as a function of height above the galactic plane. We also use a two-phase, clumpy medium model which is composed of the cold and warm neutral media (WNM). It is found that the $Ly{\alpha}$ radiation field is strong enough to thermalize the 21 cm spin temperature in the WNM to the gas kinetic temperature. The escape fraction of $Ly{\alpha}$ is found to be a few percent, which is consistent with the $Ly{\alpha}$ observations of our Galaxy and external galaxies.

• 열처리공학회지
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• 제17권5호
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• pp.271-277
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• 2004

Zr-xNb alloys (x = 0.2, 0.8, 1.5 wt.%) were prepared to study the characteristics of the phase transformation in Zr-Nb system. The samples were heat treated at ${\beta}$-temperature ($1020^{\circ}C$) for 20 min and then cooled with different cooling rate. The microstructures of the specimens having the same compositions were changed with cooling rate and Nb content. The Widmanst$\ddot{a}$tten structure was observed on the furnace-cooled sample. The relationship between ${\alpha}$-Widmanst$\ddot{a}$tten and ${\beta}$-phase was the {0001}${\alpha}$//{110}${\beta}$, <11$\bar{2}$0>//<111>. The ${\beta}$-phase in Widmanst$\ddot{a}$tten structure of Zr-Nb alloys containing Nb more than solubility limit was identified as ${\beta}_{Zr}$ phase which was a stable phase at high temperature. In the water quenched samples, two kinds of martensite structures were observed depending on the Nb-concentration. The lath martensite was formed in Zr-0.2, 0.8 wt.% Nb alloys and the plate martensite having twins was formed in Zr-1.5 wt.% Nb alloy.

• 접착 및 계면
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• 제2권2호
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• pp.11-19
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• 2001

트리카프릴메틸 암모니움 클로라이드를 상이동촉매로 사용하여 $Na_2S_2O_8$의 수용액과 톨루엔의 이상계에서 질소분위기하에 $60^{\circ}C$에서 스티렌의 라디칼중합을 행하였다. 중합시의 초기 중합속도는 촉매와 $Na_2S_2O_8$의 초기공급 농도보다는 수용액 상에서의 4급 암모늄양이온과 퍼록시디슬페이트 음이온의 농도로 나타낼 수 있었다. 관찰된 초기중합속도를 사용하여 분균일 액-액계에서의 순환 상이동에 의한 개시과정을 포함한 중함메카니즘을 밝힐 수 있었다. 폴리스티렌의 점도평균분자량은 $Na_2S_2O_8$의 농도에 역비례하였는데, 라디칼 중합메카니즘에 의하여 $[Q^+]([S_2O{_8}^{2-}]{\alpha}_2)^{1/2}$로 나타내어졌다.

• 한국재료학회지
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• 제19권6호
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• pp.305-312
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• 2009

The effects of Quenching and Partitioning (Q&P) and Annealed Martensite (AM) heat treatment on the microstructure and tensile properties were investigated for 0.24C-0.5Si-1.5Mn-1Al steels. The Q&P steels were annealed at a single phase ($\gamma$) or a dual phase (${\gamma}+{\alpha}$), followed by quenching to a temperature between $M_s$ and $M_f$. Then, enriching carbon was conducted to stabilize the austenite through the partitioning, followed by water quenching. The AM steels were intercritically annealed at a dual phase (${\gamma}+{\alpha}$) temperature and austempered at $M_s$ and $M_s{\pm}50^{\circ}C$, followed by cooling in oil quenching. The dual phase Q&P steels showed lower tensile strength and yieldyield strength than those of the single phase Q&P steels, and tThe elongation for the dual phase Q&P steel was partitioning 100s higher than that of that for the single phase Q&P steels as the partitioning time was less than 100s up to partitioning 100s. For AM steels, the tensile/yield strength decreased and the total elongation increased as the austempering temperature increased. The stability of the retained austenite controlled the elongation for Q&P steels and the volume fraction of the retained austenite controlled the elongation for AM steels.

• 한국재료학회지
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• 제9권3호
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• pp.322-326
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• 1999

본 연구는 냉간가공과 열처리를 통해 Cu-26.65Zn-4.05Al-0.31Ti(wt%) 형상기억합금의 결정립을 미세화하기 위한 목적으로 수행하였다. 냉간가공을 위하여는 α-상이 가능한 많이 존재하는 (α+β)-조직을 가져야 하는데, 이는 550℃에서 열처리함으로써 얻었고, 최종두께 1mm로 냉간압연하였다. 총 압연율은 70%와 90%이었다. 냉간압연한 판재를 800℃에서 가열 후 급랭함으로써 형상기억특성을 갖는 상으로 변태시켰으며, 이 대 결정립크기를 측정한 결과, 열간압연한 경우보다 냉간압연과 열처리를 한 경우의 결정립이 월등히 작아졌음을 보여주었다. 냉간압연과 열처리를 한 경우에는 냉간압연 변형율이 큰 경우가 결정립이 더 작아지는 경향을 보였다. 또한 결정립크기가 작아짐에 따라 변태온도가 저하되었으며 오스테나이트상이 더 안정하게 되었음을 확인할 수 있었다. In this study, cold-rolling and appropriate annealing was adopted for the grain refining of Cu-26.65Zn-4. 05Al-0.31Ti(wt%) shape memory alloy. For the cold deformation of this alloy the ducti1e α-phase must be contained. After heat treatment at 550℃ the (α+β)-dual phase with 40vol.% α-phase was obtained which could be rolled at room temperature. This alloy was cold rolled into a final thickness of 1.0mm with total reduction degrees of 70% and 90%. The rolled sheets were betanized at 800℃ for various times, then quenched into ice water. The grain size of co]d rolled samples were 60∼80 ㎛ which is much smaller comparing with the hot-rolled samples. And the 90% rolled sample showed smaller grain size than the case of the 70% rolled one. The small grain size had influence on the phase transformation temperatures and stabilization of the austenitic phases.

• Clinical and Experimental Reproductive Medicine
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• 제29권4호
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• pp.337-343
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• 2002

Objectives: To investigate the distribution of $ER{\alpha}$, $ER{\beta}$, c-fos and c-jun in the uterine myoma and myometrium in oder to know how the tamoxifen cause the growth of myoma. Methods: Myoma and myometrial tissue were obtained from the postmenopausal women treated with tamoxifen in the patients with breast cancer and in the premenopausal patients, who were undergoing myoma of uterus from 1998 through 2000. The espression of each gene was quantitated with quantitative RT-PCR. Results: The expression of $ER{\alpha}$ was slightly increased in the myoma than the myometrium in the proliferative phase, and was slightly decreased in the myometrium than the myoma in the secretory phase. However it was not significant statistically. In the postmemopausal women treated with tamoxifen, $ER{\alpha}$ was expressed in all myoma and myome1rial tissues and the expression was not statistically significant. The expression ofER~ was slightly increased in the myome1rium than the leiomyoma in the proliferative and secretory phase, but it was not significant statistically. In the postmemopausal women treated with tamoxifen, the expression of ER~ was significantly incresed in the myome1rium than the leiomyoma. The expression of c-fos was significantly increased in the myome1rium than the leiomyoma in the proliferative and secretory phase. In the postmemopausal women treated with tamoxifen, the expression of c-fos was slightly increased in the leiomyoma than the myomelrium, however, it was not statistically significant. Conclusion: Tamoxifen may cause the growth of leiomyoma by $ER{\alpha}$ with AP-l pathway reducing the counteraction of 6$ER{\beta}$ to $ER{\alpha}$.

• 한국재료학회지
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• 제21권10호
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• pp.563-567
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• 2011

We report the structural characterization of $Bi_xZn_{1-x}O$ thin films grown on c-plane sapphire substrates by plasma-assisted molecular beam epitaxy. By increasing the Bi flux during the growth process, $Bi_xZn_{1-x}O$ thin films with various Bi contents (x = 0~13.17 atomic %) were prepared. X-ray diffraction (XRD) measurements revealed the formation of Bi-oxide phase in (Bi)ZnO after increasing the Bi content. However, it was impossible to determine whether the formed Bi-oxide phase was the monoclinic structure ${\alpha}-Bi_2O_3$ or the tetragonal structure ${\beta}-Bi_2O_3$ by means of XRD ${\theta}-2{\theta}$ measurements, as the observed diffraction peaks of the $2{\theta}$ value at ~28 were very close to reflection of the (012) plane for the monoclinic structure ${\alpha}-Bi_2O_3$ at 28.064 and the reflection of the (201) plane for the tetragonal structure ${\beta}-Bi_2O_3$ at 27.946. By means of transmission electron microscopy (TEM) using a diffraction pattern analysis and a high-resolution lattice image, it was finally determined as the monoclinic structure ${\alpha}-Bi_2O_3$ phase. To investigate the distribution of the Bi and Bi-oxide phases in BiZnO films, elemental mapping using energy dispersive spectroscopy equipped with TEM was performed. Considering both the XRD and the elemental mapping results, it was concluded that hexagonal-structure wurtzite $Bi_xZn_{1-x}O$ thin films were grown at a low Bi content (x = ~2.37 atomic %) without the formation of ${\alpha}-Bi_2O_3$. However, the increased Bi content (x = 4.63~13.17 atomic %) resulted in the formation of the ${\alpha}-Bi_2O_3$ phase in the wurtzite (Bi)ZnO matrix.

• 한국재료학회지
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• 제7권12호
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• pp.1063-1069
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• 1997

급속응고법으로 Fe-Nd-C 합금을 제조하여 합금의 조성 및 제조 조건의 변화에 따른 상변화와 자기특성의 변화를 조사하였다. 강자성 $Fe_{14}Nd_2C_x$가 초정으로 정출할 수 있는지를 알아보기 위하여 냉각속도의 변화에 따른 as-spun 합금에서의 상변화를 조사해 본 결과，10m/s로 제조한 Fe-Nd-C 리본합금은 ${\alphs}-Fe$가 일차상, $Fe_{17}Nd_2C_x$가 이차상으로 존재하는 결정질이었으며. 20m/s에서는 ${\alpha}-Fe$의 정출이 억제되거나 비정질화하여, $Fe_{14}Nd_2C_x$가 일차상, ${\alpha}-Fe$가 이차상으로서 비정질상과 함께 존재하였다. 냉각속도의 증가에 따라 비정질화가 증가하여 30m/s에서는 대부분 비정질화되었으며，40m/s에서 비정질화가 완료되었다. 따라서 $Fe_{14}Nd_2C$는 as-spun 상태에서는 얻어지지 않고 주조합금의 경우와 마찬가지로 열처리를 통한 고상변태에 의해서만 얻을 수 있었다. $Fe_{14}Nd_2C$를 얻을 수 있는 유효온도구역은 주조합금의 경우보다 넓은 $700{\sim}900^{\circ}C$였고，비정질화가 완벽한 합금보다 다소 덜 완벽하거나 $Fe_{17}Nd_2C_x$와 비정질상이 혼합된 합금에서 열처리에 의한 보자력의 향상이 더욱 현저하였다. Fe를 다량 함유한 Fe-Nd-C 조성 중에서 높은 보자력이 기대되는 조성 범위는 극히 제한되어, $750{\sim}800^{\circ}C$에서 몇 분간의 열처리로 10kOe 이상의 높은 보자력을 얻을 수 있는 조성은 77~78 Fe, 7~8 C (at.%) 정도였다.

• Food Science and Biotechnology
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• 제14권1호
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• pp.131-136
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• 2005

The selective extraction behavior of lactoferrin (Lf) from whey protein mixture was examined using reverse micelles formed by the cationic surfactant, cetyldimethylammonium bromide (CDAB). The major whey proteins, including ${\beta}$-lactoglobulin, ${\alpha}$-lactalbumin and bovine serum albumin, were solubilized from aqueous phase to organic phase while Lf was recovered in the aqueous phase. The solubilization behaviors of the proteins were manipulated by the process parameters such as the pH and salt concentration of the aqueous phase and the surfactant concentration in the organic phase. Efficient forward extraction was achieved with sodium borate buffer (50 mM, pH 9) containing 50 mM KCl and organic phase containing 100 mM CDAB. Based on SDS-PAGE and densitometry, about 96% of the initial Lf remained in the aqueous phase after forward extraction. The dialyzed Lf fully maintained its bacteriostatic activity against E. coli O157:H7.

• BMB Reports
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• 제40권4호
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• pp.494-500
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• 2007

The endophytic bruchid pest Callosobruchus maculatus causes severe damage to storage cowpea seeds, leading to economical losses. For this reason the use of $\alpha$-amylase inhibitors to interfere with the pest digestion process has been an interesting alternative to control bruchids. With this aim, $\alpha$-amylase inhibitors from baru seeds (Dipteryx alata) were isolated by affinity chromatographic procedures, causing enhanced inhibition of C. maculatus and Anthonomus grandis $\alpha$-amylases. To attempt further purification, this fraction was applied onto a reversed-phase HPLC column, generating four peaks with remarkable inhibition toward C. maculatus $\alpha$-amylases. SDS-PAGE and MALDI-ToF analysis identified major proteins of approximately 5.0, 11.0, 20.0 and 55 kDa that showed $\alpha$-amylase inhibition. Results of in vivo bioassays using artificial seeds containing 1.0% (w/w) of baru crude extract revealed 40% cowpea weevil larvae mortality. These results provide evidence that several $\alpha$-amylase inhibitors classes, with biotechnological potential, can be isolated from a single plant species.