• 자원리싸이클링
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• 제11권6호
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• pp.31-37
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• 2002

폐알루미늄 캔으로 제조된 2차지금과 신지금의 혼합비율에 따라 캔용 소재를 주조하고 미세조직을 조사하였다. 또한 주조후 열처리에 따른 상변화의 거동을 조사하였다. 2차지금의 혼합비율(20, 30, 40, 50, 60%)에 따라 캔용 소재를 전기로로 용해하고, ceramic filter를 사용하여 주조하였다. 주조후에는 주조조직 제어를 위해 균질화 열처리($615^{\circ}C$$\times$10hrs)를 하였다. 주조상태에서는 $\alpha$ 상($Al_{12}$ $(Fe,Mn)_3$Si), $\beta$상($Al_{6}$/(Fe,Mn)), 그리고 미세한 $Mg_2$Si상이 알루미늄 기지에 존재하며, 특히 가공성에 나쁜 영향을 미치는 것으로 알려진 $\beta$상이 많이 존재하였다. 그러나 균질화 열처리에 의해 이러한 $\beta$상은 유해성이 없는 $\alpha$상으로의 상변태가 일어났다. 기지내의 미세한 $Mg_2$Si상도 열처리에 의해 $\alpha$상으로 변화하였다. 주조시 여과된 조직을 분석한 결과 Fe, Cu, Si 등의 금속간화합물이 검출되었다.

• 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.

• 한국세라믹학회지
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• 제35권4호
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• pp.413-419
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• 1998

${\beta}$-silicon carbides with yttrium aluminum garnet of 2,5,10 mol% were prepared by a liquid--phase sint-ering and the microstructural evolution and phase transformation were investigated during sintering as functions of liquid-phase amount and sintering time. The rate of grain growth decreases with the addition of the amount of yttrium aluminum garnet (YAG) in the SiC starting powder however the apparent density and the aspect ratio of grains in sintered body increase. The phase transformation from ${\beta}$-SiC to ${\alpha}$-SiC were dependent on the liquid-phase amount and sintering time.

• Journal of Power Electronics
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• 제18권5호
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• pp.1424-1433
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• 2018

This paper presents a novel space vector pulse-width modulation (SVPWM) to synthesize an arbitrary non-sinusoidal phase voltage. The key of the proposed method is that the switching vectors used to comprise the reference vectors in the ${\alpha}_1-{\beta}_1$ frame and the ${\alpha}_3-{\beta}_3$ frame are decoupled. In the ${\alpha}_1-{\beta}_1$ frame, the reference vector is comprised by near two large vectors. The corresponding vector comprised by the two vectors in the ${\alpha}_3-{\beta}_3$ frame is considered as a disturbance, which is restrained by close-loop control. In the ${\alpha}_3-{\beta}_3$ frame, there are two methods to comprise the reference vector. Method I is a near two middle vectors method. Method II uses near four vectors (two middle and two little vectors). The proposed SVPWM using decoupled switching vectors can guarantee a maximum modulation index in the ${\alpha}_1-{\beta}_1$ frame. The effectiveness of the proposed method is verified by simulated and experimental results under various operation conditions.

• Journal of Pharmaceutical Investigation
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• 제22권1호
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• pp.33-40
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• 1992

This study was aimed to control the release characteristics of ketoprofen by microencapsulating $ketoprofen-{\beta}-cyclodextrin\;(KF-{\beta}-CyD)$ solid dispersion with Eudragit RS by the phase separation method using a nonaqueous vehicle. KF alone was also microencapsulated with Eudragit RS by the evaporation process in water phase. The results obtained showed that it was not possible to microencapsulate KF alone by phase separation in a chloroform-cyclohexane system while it was easy to microencapsulate $(KF-{\beta}-CyD)$ solid dispersion system. For the microcapsules, the release test was performed in the first fluid (pH 1.2) and the second fluid (pH 6.8) of K.P.V disintegration medium at $37^{\circ}C$. The release of KF from $(KF-{\beta}-CyD)$ solid dispersion microcapsules (1:1 core wall ratio) was more sustained than that from KF microcapsules, and followed zero-order kinetics. Especially, solid dispersion microcapsules showed pH-independent release patterns with higher wall to core ratio (1:1 w/w).

• 대한금속재료학회지
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• 제50권2호
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• pp.164-170
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• 2012

Nanotubular structure formation on the Ti-6Al-4V and Ti-Ta alloy surfaces by electrochemical methods has been studied using the anodizing method. A nanotube layer was formed on Ti alloys in 1.0 M $H_3PO_4$ electrolyte with small additions of $F^-$ ions. The nanotube nucleation and growth of the ${\alpha}$-phase and ${\beta}$-phase appeared differently, and showed different morphology for Cp-Ti, Ti-6Al-4V and Ti-Ta alloys. In the ${\alpha}$-phase of Cp-Ti and martensite ${\alpha}^{\prime}$ and in the ${\alpha}^{{\prime}{\prime}}$ and ${\beta}$-phase of the Ti-Ta alloy, the nanotube showed a clearly highly ordered $TiO_2$ layer. In the case of the Ti-Ta alloy, the pore size of the nanotube was smaller than that of the Cp-Ti due to the ${\beta}$-stabilizing Ta element. In the case of the Ti-6Al-4V alloy, the ${\alpha}$-phase showed a stable porous structure; the ${\beta}$-phase was dissolved entirely. The nanotube with two-size scale and high order showed itself on Ti-Ta alloys with increasing Ta content.

• 한국유기농업학회지
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• 제18권3호
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• pp.401-418
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• 2010

영지버섯에서 추출한 균사체 함량은 배지 L당 8.52g, 균체외 다당류는 4.49g으로 $\beta$-glucan 생산능력이 우수한 영지버섯을 선발하였으며, 대두분과 수용성전분 등을 이용한 최적의 산업용 버섯배양배지를 개발하였다. 원심분리와 냉동건조방법으로 제조한 $\beta$-glucan을 자돈사료에 첨가하여 이유자돈의 성장능력, 설사, 폐사율 및 경제성을 비교하여 항생제대체효과를 구명하기 위하여 실시하였다. 삼원교잡종(Landrace${\times}$Large White${\times}$Duroc) 이유자돈(8.6kg) 144두를 선발하여 28일간 사양시험을 실시하였다. 본 시험은 4처리 4반복의 난괴법 배치로 T1 처리구(-control)는 무항생제, T2 처리구(+control)는 항생제, T4 처리구는 무항생제에 $\beta$-glucan 0.2% 첨가, T3 처리구는 항생제와 $\beta$-glucan 0.2% 첨가하였다. 이유전기 (phase I, 0~14일)에서는 일당증체량과 사료섭취량은 처리간에 유의적인 차이가 없었으나 사료효율은 처리간에 차이가 있었다(p<0.05). 한편 이유후기(phase II, 15~28일)와 전 기간(0~28일)에서는 사료섭취량과 사료효율은 처리간에 유의적인 차이가 없었으나 일당증체량은 처리간에 유의적인 차이가 있었다(p<0.05). 전 기간의 일당증체량의 비교에서 설사지수와 분변의 수분함량은 T3와 T4 처리구가 다른 처리구보다 높았다(p<0.05). 이유자돈 분변의 수분함량은 T3와 T4 처리구가 다른 처리구보다 높았으나(p<0.05), 설사지수와 폐사율은 처리간에 유의적인 차이가 없었다. 이유자돈 시험의 경제성분석 결과 이유전기에서는 항생제와 $\beta$-glucan을 첨가함에 따라 사료비가 증가하였으나, 섭취량과 증체량을 고려한 사료비에서는 $\beta$-glucan을 첨가한 처리구(T3 및 T4)가 첨가하지 않은 처리구(T1 및 T2)보다 감소하여 $\beta$-glucan의 효과가 있었다. 그러나 이유후기의 $\beta$-glucan의 효과가 이유전기의 효과가 적 었다. 이상의 이유자돈시험을 결과를 종합해 보면 기능성 $\beta$-glucan은 이유자돈의 증체량, 영양소 소화율 및 경제성에 효과가 있었으며, 특히 항생제 대체제로서 일정 부분 개선 효과가 있는 것으로 사료된다.

• 대한수의학회지
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• 제27권2호
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• pp.347-359
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• 1987

To investigate the changes of pituitary gland associated with ovarian cyst in Korean native cattle, pituitaries and ovaries were collected from 54 Korean native cattle at abbatoir. Pituitaries were stained with HerIant pituitary stain method and all the tissues were examined under light microscope. The results obtained were summarized as follows; 1. The delta cells and beta cells in the pars distalis were dull blue and violet in colors respeetively. Basophil size in the follicular phase and pregnant groups was larger than those of luteal phase and ovarian dysfunction groups. 2. The numbers of delta cells in the pars distalis of follicular cyst group were larger than those of remaining groups (p<0.01). 3. The distribution of delta cells in the acidophil zone was greater than that in the basophil zone of the follicular cyst and follicular phase groups. 4. The granulations of delta cells were more intensive in follicular cyst, follicular phase and pregnancy groups than in luteal phase and ovarian dysfunction groups (p<0.01). 5. The numbers of beta cells in follicular phase and ovarian dysfunction groups were larger than those in luteal phase and follicular cyst groups respectively (p<0.01). 6. In all groups, the distribution of beta cells was greater in basophilic zone than in acidophilic zone (p<0.01).

• KSBB Journal
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• 제16권6호
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• pp.533-537
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• 2001

유청 단백질 중에서 $\alpha$-lactalbumin, $\beta$-lactoglobulin를 고성능 막 크로마코그래피를 이용하여 분리하는 것이다. 분리 메카니즘은 음이온 교환작용이며 고정상은 CIM DEAE, QA, So$_3$ disk (16$\times$3 mm)을 사용하였다. 이동상은 buffer A (20 mM Tris-HCI, pH 7.3)와 buffer B (buffer A + 1 M NaCl)를 사용하였으며 $\alpha$-lactalbumin, $\beta$-lactoglobulin를 분리하기 위해서 구배용매 조성법을 사용하였다. 각 이동상의 조성에 따른 최적의 이동상 조성(Buffer A/Buffer B=100/0 - 30/70 vol%, gradient time 1 min, 30/70 - 10/90 vol%, gradient time 2 min)을 실험적으로 얻었고 4 ml/min의 이동상 유속에서 3분내에 $\alpha$-lactalbumin, $\beta$-lactoglobulin를 분리 할 수 있었다. 유청 단백질 중에 $\alpha$-lactalbumin, $\beta$-lactoglobulin을 HPMC을 적용하여 분리하였고, 유청 단백질의 기능적 성질, 분리 방법에 대해 알아보았다.

• The Korean Journal of Ceramics
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• 제1권1호
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• pp.45-54
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• 1995

Four kinds of silicon nitride based ceramic materials have been hot pressed. Effect of the sintering additives on the phase transformation, microstructural development and mechanical properties was investigated. While sintering under the same condition a big difference among the microstructures of the specimens, they appeared alike if sintered to have a similiar $\alpha$-$\beta$ phase ratio. The specimen of the stoichiometric $\alpha$-$\beta$ sialon composition showed very limited amount of the intergranular glassy phase and a significant degree of the residual stress. It exhibited almost no strength degradation up to $1300^{\circ}C$, and the strength of the specimen degraded more as its composition deviated from the stoichiometry.