• Journal of Animal Science and Technology
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• 제61권4호
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• pp.234-238
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• 2019

This experiment was conducted to evaluate the effects of dietary protease on growth performance, blood constituents, and carcass characteristics of growing-finishing pigs. A total of 48 growing pigs (initial body weight, $34.8{\pm}0.62kg$) were randomly assigned to 2 dietary treatments (6 pigs/pen; 4 replicates/treatment). The treatments were a diet based on corn and soybean meal (CON) and CON supplemented with 0.01 % of protease (PRO). Pigs were fed respective dietary treatments with a 2-phase feeding program for 12 weeks. Pigs fed PRO had higher average daily gain (ADG; phase I, 866.38 vs. 821.75 g/d; overall, 910.96 vs. 866.30 g/d; p < 0.05) and gain to feed ratio (G:F; phase I, 0.345 vs. 0.363 g/g; p < 0.05) than those fed CON. However, there were no differences on blood constituents and carcass characteristics between CON and PRO of growing-finishing pigs. In conclusion, dietary protease supplementation in the typical diet for growing-finishing pigs improved growth rate.

• 한국결정성장학회지
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• 제30권4호
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• pp.150-155
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• 2020

구조용 세라믹재료로 주로 사용되는 알루미나(Al₂O₃)는 우수한 기계적 특성을 위해 치밀한 미세구조를 요구하며, 소결온도를 낮추기 위해 상업적으로 액상소결(liquid phase sintering)이 적용된다. 본 연구에서는 SiO₂, MgO, CaO를 액상소결 조제로 사용하는 92 % 상업용 알루미나의 액상소결 시, 착색제(coloring agent)로 주로 사용되는 산화코발트(Co₂O₃)의 첨가량과 다양한 소결온도가 알루미나의 미세구조 및 기계적 특성에 미치는 영향을 고찰하였다. 약 11 w t% 산화코발트 첨가에 따라 1200℃부터 고상입자 재배열에 의한 수축이 시작되었고 1300℃ 이상의 온도에서 용해 재석출 및 합체(coalescence)에 의한 알루미나의 결정립 성장이 관찰되었다. 1400℃ 이상의 열처리 온도 혹은 과량의 Co₂O₃ 첨가는 액상의 점도를 낮추어 소결밀도를 감소시켰고, 이와 함께 경도값도 감소하였다. 산화코발트를 11 w t% 첨가하여 1350℃에서 소결할 경우, 3.86 g/㎤의 밀도와 12.32 GPa의 경도를 갖는 치밀한 소결체 제조가 가능하였다.

• 한국전기전자재료학회논문지
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• 제31권6호
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• pp.357-361
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• 2018

We demonstrated a crack-free ${\alpha}-Ga_2O_3$ on sapphire substrate by horizontal halide vapor phase epitaxy (HVPE). Oxygen-and gallium chloride-synthesized Ga metal and HCl were used as the precursors, and $N_2$ was used as the carrier gas. The HCl flow and growth temperature were controlled in the ranges of 10~30 sccm and $450{\sim}490^{\circ}C$, respectively. The surface of ${\alpha}-Ga_2O_3$ template grown at $470^{\circ}C$ was flat and the root-mean-square (RMS) roughness was ~2 nm. The full width at half maximum (FWHM) values for the symmetric-plane diffractions, were as small as 50 arcsec and those for the asymmetric-plane diffractions were as high as 1,800 arcsec. The crystal quality of ${\alpha}-Ga_2O_3$ on sapphire can be controlled by varying the HCl flow rate and growth temperature.

• Nuclear Engineering and Technology
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• 제54권1호
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• pp.226-233
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• 2022

In the present work, a phase-field model was developed to investigate the influence of recrystallization on bubble evolution during irradiation. Considering the interaction between bubbles and grain boundary (GB), a set of modified Cahn-Hilliard and Allen-Cahn equations, with field variables and order parameters evolving in space and time, was used in this model. Both the kinetics of recrystallization characterized in experiments and point defects generated during cascade were incorporated in the model. The bubble evolution in recrystallized polycrystalline of U-Mo alloy was also investigated. The simulation results showed that GB with a large area fraction generated by recrystallization accelerates the formation and growth of bubbles. With the formation of new grains, gas atoms are swept and collected by GBs. The simulation results of bubble size and distribution are consistent with the experimental results.

• 산업기술연구
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• 제19권
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• pp.75-79
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• 1999

Rotary bending fatigue tests were performed to investigate the effects of 2-phase matrix structure on fatigue limit with prepared specimens in high strength ductile irons. Two types of the specimens with different microstructures have been used. Series A has sorbite and series B has bainite. Fatigue limits of both specimens are improved comparing with as cast specimen. The fatigue limit is higher in series B than in series A. The reason why the fatigue limit of series A shows inferiority to that of series B is due to the transition of micro fatigue cracks to mesocrack occurs very rapidly, so increased stress intensity factor drives the fatigue crack growth. The higher fatigue limit of series B which has bainite is caused by the ${\gamma}$ layer contained in microstructure impede the rapid growth of micro fatigue crack to mesocrack and ${\alpha}$ layer around graphite has the higher capacity for the absorption of plastic deformation energy than sorbite.

• 한국수소및신에너지학회논문집
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• 제10권4호
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• pp.197-210
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• 1999

The hydrogen storage performance and electrochemical properties of $Zr_{1-X}Ti_X(Mn_{0.2}V_{0.2}Ni_{0.6})_{1.8}$(X=0.0, 0.2, 0.4, 0.6) alloys are investigated. The relationship between discharge performance and alloy characteristics such as P-C-T characteristics and crystallographic parameters is also discussed. All of these alloys are found to have mainly a C14-type Laves phase structure by X-ray diffraction analysis. As the mole fraction of Ti in the alloy increases, the reversible hydrogen storage capacity decreases while the equilibrium hydrogen pressure of alloy increases. Furthermore, the discharge capacity shows a maxima behavior and the rate-capability is increased, but the cycling durability is rapidly degraded with increasing Ti content in the alloy. In order to analyze the above phenomena, the phase distribution, surface composition, and dissolution amount of alloy constituting elements are examined by S.E.M., A.E.S. and I.C.P. respectively. The decrease of secondary phase amount with increasing Ti content in the alloy explains that the micro-galvanic corrosion by multiphase formation is little related with the degradation of the alloys. The analysis of surface composition shows that the rapid degradation of Ti-substituted Zr base alloy electrode is due to the growth of oxygen penetration layer. After comparing the radii of atoms and ions in the electrolyte, it is clear that the electrode surface becomes more porous, and that is the source of growth of oxygen penetration layer while accelerating the dissolution of alloy constituting elements with increasing Ti content. Consequently, the rapid degradation (fast growth of the oxygen-penetrated layer) with increasing Ti substitution in Zr-based alloy is ascribed to the formation of porous surface oxide through which the oxygen atom and hydroxyl ion with relatively large radius can easily transport into the electrode surface.

• 경영과학
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• 제26권3호
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• pp.101-115
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• 2009

In this paper, we propose a technology mining framework for mobile communication industry. We develop a two phase approach of new technology identification and service enhancement. The new technology identification process consists of R&D issues analysis, technology theme design, and emerging technology sampling. On the other hand, existing service enhancement process has technology landscaping, keyword based search, and technological growth analysis. By implementing these two phase frameworks, we develop a technology portfolio for mobile communication industry.

• 한국결정성장학회지
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• 제7권2호
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• pp.292-300
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• 1997

150~$190^{\circ}C$에서 2시간 동안의 수열반응을 통해 입방체 모양을 갖는 0.5~5 $\mu\textrm{m}$의 ($Pb_{0.95}Sr_{0.05})(Zr_{0.52}Ti_{0.48})O_3$ 결정분말을 제조하였다. 실험결과 반응온도가 증가함에 따라 PSZT의 핵생성과 결정성장 속도가 빨라져서 평균입경이 커짐을 알 수 있었다. 광화제로 사용한 KOH의 농도를 증가시켜 평균입경이 작고 입도분포의 폭이 좁은 분말을 얻을 수 있었으며 결정화가 일어나는 반응온도를 낮출 수 있었다. Zr/Ti의 조성비가 0.40/0.60에서 0.60/0.40으로 증가함에 따라 PSZT의 주요 결정상은 정방정의 결정상에서 능면정의 결정상으로 전이되었다.

• 한국결정성장학회지
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• 제9권3호
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• pp.289-294
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• 1999

The charged clusters or particles, which contain hundreds to thousands of atoms or even more, are suggested to from in the gas phase in the thin film processes such as CVD, thermal evaporation, laser ablation, and flame deposition. All of these processes are also phase synthesis of the nanoparticels. Ion-induced or photo-induced nucleation is the main mechanism for the formation of these nanoclusters or nanoparticles in the gas phase. Charge clusters can make a dense film because of its self-organizing characteristics while neutral ones make a porous skeletal structure because of its Brownian coagulation. The charged cluster model can successfully explain the unusual phenomenon of simultaneous deposition and etching taking place in diamond and silicon CVD processes. It also provides a new interpretation on the selective deposition on a conducting material in the CVD process. The epitaxial sticking of the charged clusters on the growing surface is getting difficult as the cluster size increases, resulting in the nanostructure such as cauliflower or granular structures.

• 한국결정성장학회지
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• 제20권5호
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• pp.216-220
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• 2010

Si(100) wafer와 $SiO_2$/Si(100) 웨이퍼에 증착된 NiFe 합금 박막의 결정상과 자기적 특성을 비교하고자 동시 스퍼터링법을 이용하여 두 기판 위에 150 nm의 박막을 제조하여 그의 상변화와 자기적 특성을 XRD, FE-SEM, VSM으로 비교하였다. 두 기판 위에 증착된 NiFe 박막은 BCC상으로 증착되었으나 $400^{\circ}C$에서 2시간 열처리를 한 결과 BCC에서 FCC로의 상전이가 일어나는 것을 관찰 할 수 있었으며 Si(100) wafer위에 증착된 박막에서는 $500^{\circ}C$에서 열처리 후에도 BCC와 FCC가 혼재하여 나타나는 것을 알 수 있었다. $450^{\circ}C$에서 열처리 하였을 때 각형비가 가장 높았으며 포화자화는 0.0118 emu로 나타나고 있었다. $500^{\circ}C$ 이상의 온도에서는 상전이로 인해 포화자화가 급격히 감소하는 것을 볼 수 있었다.