• 한국세라믹학회지
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• 제32권1호
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• pp.90-94
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• 1995

In Sr-ferrite system, it has been attempted to inhibit the abnormal grian growth using Sr-ferrite powders synthesized by molten salt method as the matrix and the seeds, respectively. At each sintering temperature, the addition of seed more than 15% suppressed the abnormal grain growth, and the uniform microstructure resulted. Particularly, at 12$25^{\circ}C$, it was observed that the maximum number of the abnormal grain growth nuclei was achieved since the abnormal grain growth was suppressed even by the addition of 10% seed.

• 한국결정성장학회지
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• 제29권6호
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• pp.251-256
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• 2019

ZnO를 통상적인 소결온도 이상의 온도 1385℃에서 소결하는 과정에서 mm 크기로 거대 성장된 입자를 갖는 세라믹스를 제조하였다. 1400℃에서 8시간 소결하는 경우 성장에 참여하지 않은 입자의 크기는 30~40 ㎛이고 거대 성장된 입자는 1,000 ㎛에 달하여 부피비 최소 10,000배 이상의 급속한 성장이 이루어졌다. 이러한 급속한 성장의 원인으로 일차 입자 크기분포, 성형압 불균일 또는 불순물의 합입등을 고려하였으며, 이들 중 일차입자 크기 분포일 것으로 추정되나 확실한 증거를 확보하지 못하였다. 미세구조 관찰을 통해 거대입자 성장은 주변의 입자를 통째로 합치는 과정을 통해 성장하는 것으로 추정된다.

• Journal of the Korean Wood Science and Technology
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• 제39권5호
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• pp.437-443
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• 2011

In Korea, there has been a traditional post and beam wood construction with large roof load. Because a large friction is generated in wooden joint or members, it is important to evaluate the friction between wood members according to wood direction. Because most of studies have been concerned with friction between wood and steel, excluding effect of real area of contact, there are a few studies on the friction between wood members. The object of this study was to evaluate friction or coefficient of friction according to normal force and real area of contact of wood. With Japanese larch (Larix kaempferi) test specimens, five steps of normal force and combinations of test were prepared. Results indicated that normal force had almost no affection on the friction, however there was difference about friction or coefficient of friction according to real contact conditions of wood grain and contact area.

• 한국작물학회지
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• 제41권1호
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• pp.34-44
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• 1996

보리 분얼성 isogenic line 4계통(Kindred, Morex)을 이용하여 파종양 및 결주율에 따른 주요 형질의 변화를 조사하였다. t. 다얼성 계통은 단간성 계통에 비하여 곡립의 수양은 46％, 엽면적지수 56％가 높았으나, 단간성 계통은 정립률이 69％ 천립중은 27％가 높았다. 2. 단단성 계통은 출수기가 4∼8일, 성숙기는 2∼3일 빨랐다. 3. 곡립수양은 수수에 따른 직선회귀에 잘 적용되어 수수의 기여도가 매우 컷다. 4. 결주율이 증가함에 따라서 1수입수 및 천립중이 다소 증가하나 수수의 감소로 곡립의 수양이 현저히 감소되었다. 5. 반면에 결주율이 증가될 때 정립률, 엽의 광합성능 및 분얼수가 증가하였다. 6. 분얼성 isogenic line이 재해에 의해서 결주가 발생시 수수가 곡립의 수양을 좌우하였다. 7. 단간성 인자의 도입, 육종 및 보급을 위해선 이들 동질유전자 계통을 포장에 다년간 반복 실험하여 보다 정밀한 평가가 이루어져야 한다.

• 한국재료학회지
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• 제25권3호
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• pp.149-154
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• 2015

We evaluated the developed microstructures and mechanical properties of a severely plastically deformed Ni-30Cr alloy. Normal rolling and differential speed rolling were used as deformation processes, and the thicknesses of the specimens were reduced to 68 % of the original thickness after holding at $700^{\circ}C$ for 10 min and annealing at $700^{\circ}C$ for 40 min to obtain a fully recrystallized microstructure. Electron backscattering diffraction was used to analyze the characteristic distribution of the grain boundaries on the deformed and annealed specimens. Differential speed rolling was more effective for refining grains in comparison with normal rolling. The grain size was refined from 33 mm in the initial material to 8.1 mm with normal rolling and 5.5 mm with differential speed rolling. The more refined grain in the differential-speed-rolled material directly resulted in increases in the yield and tensile strengths by 68 % and 9.0%, respectively, compared to normal rolling. We systematically explain the relationship between the grain refinement and mechanical properties through a plastically deformed Ni-30Cr alloy based on the development of a deformation texture. The results of our study show that the DSR process is very effective when used to enhance the mechanical properties of a material through grain refinement.

• 한국작물학회지
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• 제47권3호
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• pp.206-210
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• 2002

종실 등의 특성을 기준으로 분류한 7가지 벼 이형주군의 변이와 분리양상은 다음과 같다. 1. Esterase 동위효소 분석에서 장립적미군은 1과 3 esterase isozyme zymogram(EIZ), 장립메성군은 1, 3 및 7 EIZ로 분류할 수 있었다. 2. 극만생 불임군은 EIZ가 1, 2, 1+2, 5, 6, 5+6, 7, 8, 7+8 및 12로 다양하게 분리되었다. 3. EIZ가 1인 장립적미군이 3 EIZ인 장립적미군에 비해 간장이 길고 현미의 장폭비가 낮았다. 4. EIZ가 3인 장립메성군은 1이나 7 EIZ인 장립메성군에 비해 간장이 길고 수장이 짧고 분얼수가 많고 현미의 장폭비가 낮으며 수당 립수가 적었다.

• 한국세라믹학회지
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• 제32권1호
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• pp.51-56
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• 1995

Variation of sintered density of BaTiO3 powder calcined at 120$0^{\circ}C$ and 135$0^{\circ}C$ was investigated with respect to the grain growth behavior. It was found that BaTiO3 powder, which was calcined at 120$0^{\circ}C$, showed abnormal grain growth behavior during sintering process. At initial stage of sintering process, the densification rate of specimen was accelerated with rapid grain growth caused by the abnormal grain growth. But with the increase of sintering time, abnormally grown grain met each other and the density of specimen decreased drastically due to coalescence of pores located in triple junction. On the contrary, BaTiO3 powder calcined at 135$0^{\circ}C$ showed normal grain growth behavior and gradually densified with the increase of sintering time.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 추계학술대회 논문집
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• pp.98-101
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• 1997

The nonuniformity of electrical characteristics of grain boundaries in ZnO varistors wei\ulcorner systematically analyzed. The high nonuniformity exist in barrier voltages and nonlinearity coefficients among different grain boundaries. The barrier voltages have normal distributions, only a few grain boundaries were electrically active, and the grain boundaries can be simply classified into good, bad, and ohmic ones according to the electrical characteristics of grain boundaries. The average barrier voltage is equal to 3.3 V by direct method, but it is only 2.3 V by indirect method. There is a high difference between the barrier voltages by direct and indirect measurement methods. The A1$_2$O$_3$ dopants affect the electrical characteristics of grain boundaries by changing the electron status In grain boundary and intragrain.

• 한국세라믹학회지
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• 제38권10호
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• pp.914-920
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• 2001

새로운 소결법인 방전플라즈마소결법(SPS: Spark Plasma Sintering)으로 제조된 $ZrB_2$-ZrC 복합체의 결정립 방위분포 및 결정입계의 특성을 EBSP(Electron Back-Scattered Pattern)법으로 분석하여 상압소결법(PLS, Pressureless Sintering)에 의한 시편과 비교하였다. 방전플라즈마 소결법으로 제조된 시편의 $ZrB_2$ 결정립은 상압소결된 시편과는 다르게 (0001)면이 시편표면에 수직한 배향(normal direction)을 나타냈으며, ZrC 결정립은 두 경우 무질서한 배향을 나타냈다. 결정입계 특성 분석에서 low angle $(<15^{\circ})$의 분포는 상압소결법인 경우 전체 입계 중 약 10%, 방전플라즈마 소결법은 8%로 두 소결체에서 큰 차이를 보이지 않았으나, CSL(Coincident Site Lattice) 입계의 분포에서는 방전플라즈마 소결법으로 제조된 복합체에서 $\Sigma$ 3,5,7,9,11의 CSL 분포가 상압소결법에 비해 높은 분율을 나타냈다.

• 한국세라믹학회지
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• 제37권1호
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• pp.102-109
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• 2000

When PbZrO3 (PZ) and PbTiO3 (PT) particles were scattered on polished surfaces of sintered Pb(Zr0.52Ti0.48)O3 (PZT; Zr/Ti=1.08) and then annealed, the PZT grain boundaries migrated. Near the scattered particles, grain boundaries were corrugated and thus the grain shape changed from a normal one to irregular ones. Especially, near the scattered PZ particles, fast grain growth occurred. In the regions swept by moving grain boundaries, the Zr/Tiratio was measured to be about 1.35 for of PZ scattering and about 0.8 for PT scattering, respectively. This result indicates that the grain boundary migration was induced by alloying of Zr and Ti ions in PZT grains, as in usual diffusion induced grain boundary migration(DIGM). A calculation showed that higher coherency strain energy was induced for PT scattering because of higher alloying of Ti than of Zr.