• The Korean Journal of Ceramics
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• 제4권2호
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• pp.122-127
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• 1998

Conductivities of polycrystalline ceria doped with several rare earth oxides were measured by AC admittance and DC four probe method. The conductions were separated into grain and grain boundary contributions using the complex admittance technique as well as grain size dependence of conductivity. The grain size dependence of polycrystalline conductivity, which can be adequately described by the so-called brick layer model, appears to give a more reliable measure of the grain conductivity compared to the complex admittance method. Polycrystalline resistivity(1/conductivity) increases linearly with the reciprocal of grain size. The intercept of resistivity vs. inverse grain size plot gives a measure of the grain resistivity and the slope gives a measure of the grain boundary resistivity. It was also noted that errors involved in the analysis of experimental data may be different between the complex admittance method and the impedance method. A greater resolution of the spectra was found in the complex admittance method, insofar as the present work is concerned, suggesting that the commonly used equivalent circuit may require re-evaluation.

• 한국세라믹학회지
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• 제36권8호
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• pp.782-790
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• 1999

The compressibility sinterability sintering behaviour and thermal stability of AlOOH added UO2 pellt and PVA-Al(III) complex added UO2 pellet were investigated respectively. Compared with characteristics of AlOOH added UO2 pellet the green density and the sintered density of PVA-Al(III) complex added UO2 pellet were lowered but the grain size and the pore size of that were more increased in accordance with higher compacting pressure. The AlOOH added UO2 pellet had the grain size of about 14${\mu}{\textrm}{m}$ with monomodal pore size distribution while the PVA-Al(III) complex added UO2 pellet had the grain size of about 42 ${\mu}{\textrm}{m}$ with bimodal pore size distribution. The PVA-A(III) complex added UO2 pellet had a similiar open porosity to the AlOOH added UO2 pellet and a lower resintered density change than the AlOOH added UO2 pellet.

• 한국세라믹학회지
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• 제35권8호
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• pp.783-790
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• 1998

The characterization of the complexation reaction of PVA and Al(III) ion at different pH and the sint-ering behaviour of UO2 containing the PVA-Al(III) complexes were investigated. Compared with pure PVA powder the complexed PVA-Al(III) powder had compacter shape and lower decomposition temperature The major phase of PVA-Al(III) complex decomposed at 90$0^{\circ}C$ was $\alpha$-Al2O3 The PVA-Al(III) complex formed at pH 9 had the lowest relative viscosity the highest Al content of 36% and the smallest particle size of 19${\mu}{\textrm}{m}$ While the pure UO2 pellet appeared with bimodal one. The grain size of the pure UO2 pellet was 7${\mu}{\textrm}{m}$ but that of the PVA-Al(III) complex added UO2 pellet was increased up to 36${\mu}{\textrm}{m}$ The largest grain size was ob-tained when the PVA-Al(III) complex formed at pH9 was added and the PVA-Al(III) complex formed at pH 11 had the greatest effect on increasing pore size.

• 한국재료학회지
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• 제32권4호
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• pp.181-185
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• 2022

In this study, phase-pure titanium dioxide TiO₂ ceramics are sintered using standard high-temperature solid-state reaction technique at different temperatures (1,000, 1,100, 1,200, 1,300, 1,400 ℃). The effect of sintering temperature on the densification and impedance properties of TiO₂ ceramics is investigated. The bulk density and average grain size increase with the increase of sintering temperature. Impedance spectroscopy analysis (complex impedance Z^* and complex modulus M^*), performed in a broad frequency range from 100 Hz to 10 MHz, indicates that the TiO₂ ceramics are dielectrically heterogeneous, consisting of grains and grain boundaries. The complex impedance Z^* -plane indicates the resistance of grains of the TiO₂ ceramics increases with increasing sintering temperature, while that of grain boundaries develops in the opposing direction. The complex modulus M^*-plane shows a grain capacitance that seems to be independent of the sintering temperature, while that of the grain boundaries decreases with increasing sintering temperature. These results suggest that different sintering temperatures have effects on the microstructure, leading to changes in the impedance properties of TiO₂ ceramics.

• Current Research on Agriculture and Life Sciences
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• 제14권
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• pp.37-47
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• 1996

The main objectives of this studies are to present the most desirable rice processing complex model system in a given our situations by comparision and analyzing the major factors and, also recommend the future prospect of the rice processing complex in Korea. There are 3 different rice processing complex models in Korea. Those are concrete bin, flat type steel bin and square bin. These systems have a lot of differences and have their own characteristics such as capital requirement, efficiency, storage capacity and quality controls. The major problems of the existing rice processing centers in Korea are high fixed cost and the unbalnced systems. Following is summary to solve this problems: 1. Development of the large scale harvester and high speed continuous dryer. 2. Quality inspective system of bulk grain and large scale temporary storage facilities. 3. Large size readjustment of arable land. 4. Select the convenient location of rice processing center and formulation of well equipment facilities.

• Journal of Biosystems Engineering
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• 제16권3호
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• pp.263-271
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• 1991

When grains is subjected to oscillating load, the dynamic viscoelastic behavior of the material will be describe the complex modulus of the material. The complex modulus and therefore the storage modulus, the loss modulus, and the phase angle for the sample should be obtainable with a given static viscoelastic property of the material under static load. The complex relaxation moduli of the rough rice kernel were computed from the Burger's model describing creep behavior of the material which were obtained in the previous study. Also, the effects of cyclic load and moisture content of grain on the dynamic viscoelastic behavior of the samples were analized. The storage modulus of the rough rice kernel slightly increased with the frequency applied but at above the frequency of 0.1 Hz it was nearly constant with the frequency, and the loss modulus of the sample very rapidly decreased with increase in the frequency on those frequency ranges. It was shown that the storage modulus and the loss modulus of the sample increased with decrease in grain moisture content. Effect of grain moisture content on the storage modulus of the sample was highly significant than effect of the frequency applied, but effect of the frequency on the loss modulus of the sample was more significant than effect of grain moisture content.

• 농촌계획
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• 제25권2호
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• pp.63-74
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• 2019

As the awareness of food security has increased, the Korean government has established national projects, such as Saemangeum proclaimed land, to secure sources of grain. Saemangeum is a large-scale agricultural area that was constructed to maintain preparedness for unstable food markets. This study aims to develop a $6^{th}$ Industrialization Model (SIM) for Saemangeum Grain Complex by applying feasible strategies to wheat and two-rowed barley which have low self-sufficiency rates. In addition, this study estimates the potential economic value of each development strategy associated with a sixth industrialization model to create higher added values from production, processing and tourism experiences. The strategic plan for primary, secondary, and tertiary industries is to combine cultivating and processing wheat and two-rowed barley for sales and linking them to tourism experience. This study shows value added from the combination of the primary, secondary and tertiary industry of wheat and two-rowed barley are 7.5 and 23.0 times more than those of the primary and tertiary industry combination, respectively. Through branding Saemangeum Grain Complex's products, such as Saemanguem bread and craft beer, would further enhance the economic benefits derived from the complex.

• 한국농공학회논문집
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• 제60권4호
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• pp.1-13
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• 2018

The grain complex of Saemangeum is created for promoting the foundation of agriculture combined the global competitiveness. However, the masterplan is being also revised with changing of local conditions and social needs. Thus, the dynamic masterplan is needed to consider the change of time for Saemangeum project. The present study was made to set up the dynamic masterplan of Saemangeum grain complex for handling the change such as project progress, local environment, and project conditions flexibly. In this study, the dynamic masterplan for the progressive development of water supply, farmland composition, and introduction facilities is presented to the 6-2 zone in three stages. We believed that the water supply would be possible through the pumping and desalination facilities with the development stages. The farmland composition proceeded for each complex with reclamation, soil preparation, and soft soil processing. And it is planned to carry out crop cultivation from the complex where the construction is completed first. The introduction facilities were analyzed focusing on the silos and forage loading facilities, and the optimal location of them was selected using road and accessibility. The concept of dynamic masterplan may provide the direction for the planning and progress of reclamation project.

• 한국세라믹학회지
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• 제39권1호
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• pp.21-25
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• 2002

Effect of abnormal grain growth and heat treatment time on the electrical properties of donor-doped semiconductive BaTiO$_3$ceramics was examined. La-doped BaTiO$_3$ceramics was sintered at 134$0^{\circ}C$ for different times from 10 to 600 min in order to change the volume fraction of the abnormal grains in samples. As a result, samples with different volume fraction of abnormal grain growth from 22 to 100% were prepared. The samples were annealed at 120$0^{\circ}C$ for various times. The resistivity of the sam-ples at room and above Curie temperature was examined. The complex impedance measurement as functions of the volume fraction of abnormal grains and annealing time was conducted. Separation of complex impedance semicircle was observed in a sample in which abnormal and fine grains coexist. The results are discussed from a viewpoint of microstructure-property relationship.

• 한국토양비료학회지
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• 제26권2호
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• pp.72-77
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• 1993

피복요소복합비료(被覆尿素複合肥料) 시용과 벼 생육(生育) 및 미질(米質)과의 관련성을 밝히기 위하여 벼 측조시비용인 피복요소복합비료(18-12-13)를 공시하여, 피복요소복합비료 전량처리구(CUC I)와 피복요소복합비료 50%와 속효성비료 50% 혼합처리구 (CUC II)로 식양토(埴壤土)(덕평통(德坪統))와 사양토(砂壤土)(강서통(江西統))에서 검토한 결과는 다음과 같다. 1. 벼 잎색도(色度)는 전층(全層)시비와 측조(側條)시비 모두 토성(土性)에 관계 없이 벼 생육후기(生育後期)에는 피복요소복합비료시용구에서 높았다. 2. 질소흡수량(窒素吸收量)은 관행에 비하여 피복요소복합비료 시용구에서 많았고, 피복요소복합비료 II시용구보다 피복요소복합비료 I시용구에서 많았다. 3. 수확지수(收穫指數)는 피복요소복합비료 시용구에서 낮았고, 속효성 비료 혼합시용에 의해 그 정도를 줄일 수 있었다. 4. 피복요소복합비료시용은 완전미율(完全米率)이 감소(減少)되었고, 불완전미중(不完全米中)의 동할미율(胴割米率)이 현저히 증가되었으며, 미립중(米粒中)의 Hon치(値)(Mg/K.N)는 감소된 반면, 단백질(蛋白質), amylose 함량은 증가 되었다. 5. 취반특성(炊飯特性)인 호응집성(糊凝集性)(gel consistency)과 알칼리 붕괴도(崩壞度)(asv)는 피복요소복합비료시용에 의해 각각 길어지고, 낮아졌다. 6. 이상의 결과에서 미질(米質)은 피복요소복합비료 시용에 의해 나빠지는 경향이었고, 속효성비료(速效性肥料) 혼합(混合)시용에 의해 어느 정도 방지(防止)할 수 있었다.