• 디지털산업정보학회논문지
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• 제8권4호
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• pp.193-203
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• 2012

This study analyzed regular transportation costs between port warehouses and processing plants and between processing plants and central distribution centers and further transportation costs relations according to empty transfer rates in each circulation by examining the distribution routes of imported grain including wheat, barley, corn, and soybean, namely port warehouses, processing plants, and central distribution centers. Based on the results, the study compared and reviewed the logistics transportation costs. The analysis results of the alternative model show that logistics operational costs could be considerably cut down by introducing a flexible vehicle transportation operational method, which is to change the vehicle loading parts for proper substitute transportation after unloading and transport them to other locations such as central distribution centers instead of returning empty, as an alternative to high operational costs deriving from empty vehicle operation in each circulation after unloading items in case of transportation of imported grain and processed items. The results allow for a more realistic approach to general problems with large-scale distribution network operation and provide a theoretical foundation to serve as a guide to establish policies for corporate operation of imported grain logistics systems.

• 한국전기전자재료학회논문지
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• 제16권12호
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• pp.1131-1135
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• 2003

In the sintering of YIG, abnormal grain growth phenomena were observed. This abnormal grain growth is related to the sintering temperature in this experiment. In the sintering below 1450$^{\circ}C$, the sintered body showed narrow size distribution. However, in the sintering at 1450$^{\circ}C$, a few grains grew rapidly with respect to other grains, and bimodal size distribution was appeared. From the observation of the microstructure, liquid phase was not observed far from the abnormally grown large grains, but only near the large grains. This means that the abnormal grain growth was caused by the nonuniform distribution of liquid phase which promote the grains growth. Because the growth rate of grains near the liquid phase is much higher than that of the other grains, a few grains grow rapidly. This nonuniform distribution of liquid phase was thought to be due to the nonuniform mixing of the calcined powders. This abnormal grain growth was suppressed by enhancement of the compositional uniformity by multiple calcination.

• 한국농공학회논문집
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• 제48권6호
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• pp.59-67
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• 2006

Particles of soil are crushed when soil is compacted in the in-situ or lab. Among many factors that affect the crush of particles, compaction energy is a major factor. Because the crush of particles can change physical properties, the analysis of effect of compaction energy is very important. In this study, the fragmentation fractals were used for determining the change in grain size distribution and the effect due to change in grain size distribution was estimated. Compaction energy was increased by 50, 100, 200 and 300% based on the energy of standard A compaction test. As a result, grain size distribution curves were changed and fine particles increased as compaction energy were increased. Relative compaction were ranged between $93.38{\sim}107.67$. Fractal dimension of each site increased as compaction energy increased. Relative compaction is proportional to the fractal dimension but coefficients of permeability were in inverse proportional to the involution of fractal dimension.

• 한국해양학회지
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• 제28권2호
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• pp.114-120
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• 1993

입도분포의 특징분석에 종래의 조직특성치 대신 수치해석적인 분해법의 적용을 시 도하였다. 그 결과 이 방법이 제주해협의 대륙붕 표층퇴적물과 같은 복모드형 입 도분포의 분석에 매우 유용함이 입증 되었다. 복모드형 입도분포 퇴적물은 제주해협 대륙붕에서는 86%의 높은 비율을 점한다. 종래의 입도특성치(평균, 표준편차, 왜도, 첨도)는 복모드형 입도분포에 대해서는 왜곡된 값을 보인다. 따라서 입도분포의 모드 에 대체로 대응되는 정규성분으로 분해해서 각 정규성분의 특성치를 해석함으로써 입 도특성치에서와 같은 특징의 누락이나 왜곡을 피할 수 있다. 제주해협 대륙붕의 167개 퇴적물 입도분포곡선을 비선형 최소자승법을 사용하여 정규성분으로 분해해서 총 387 개의 정규성분을 얻었다. 정규성분의 평균은 1-3 phi 8-9 phi에 집중되는 것이 많다. 이중 조립질 정규성분의 평균치는 복잡하고 특징적인 지리적 분포를 보인다. 이러한 분포는 퇴적물 총층후 분포와 매우 유사하며 해저면의 지질과 지형을 면밀하게 반영하 고 있다. 해저면을 형성하는 퇴적층은 플라이스토세 후기의 해침성 모래층이며 해저지 형은 플라이스토세말 빙하기 저해수면시기의 침식에 의해 형성된 것으로 보인다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 봄 학술발표회 논문집
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• pp.663-668
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• 2000

In this study, the Atterberg limit and grain-size analysis were carried for the purpose of investigating the influence on drying and organic matter of Ulsan marine deposited clay. The results revealed that Atterberg limit was decreased and grain-size distribution was variable on drying. The presence of organic matter also influenced on the physical properties of the soils. The physical properties of marine deposited clay were variable on drying, so that we recommended grain-size analysis and Atterberg limit test were performed under the wet condition of the soils after sampling.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.96-99
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• 2007

The microstructure with fine and uniform AGS(austenite grain size) along thickness direction over no recrystallization temperature is strongly required for production of the high strength steels. The previous AGS prediction only based on the average strain improves to find the rolling conditions for accomplishment of the fine grain, but cannot find those for uniform grain. In this paper, an integrated mathematical model for prediction of the strain distribution along thickness direction is developed by carrying out finite element simulation for a series of rolling conditions. Also, the AGS distribution after rough rolling is predicted by applying the proposed model with AGS prediction model.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1995년도 제2회 단조심포지엄 단조기술의 진보
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• pp.100-123
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• 1995

The relationship between plastic deformation and crystal grain change in warm forging processes of SM100 carbon steel is studied. If the carbon steel is deformed in warm forging temperature (about recrystallization range), the crystal grain and cementite of the internal part are changed, so material properties are changed. Some experimental values, such as the elliptic degree of cementite, the grain size of cementitie and ferrite grain size, are investigated. When the plastic deformation proceeds, the elliptic degree of cementite becomes large, the grain size of cementite particle is small, and the size of ferrite grain appears fine by recrystallization. The elliptic degree of cementite has a considerable effect on formability. The distribution of effective strain in the forging is calculated by the rigid visco-plastic FEM analysis. The effective strain distribution obtained from the FEM simulation is compared with the experimental result. At effective strain 0.3 dynamic recovery and dynamic recrystallization begin, over 2.5 the organization of material has better quality that is suitable for the following cold forming.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.336-337
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• 2006

During sintering of cemented carbides abnormal grain growth is often observed but cannot be understood from the classical LSW-theory. A model based on 2-D nucleation of new crystalline layers and a grain-size distribution function is formulated and the equations are solved numerically. Experimental studies and computer simulations show that the initial grain size distribution has a strong effect on the grain growth behavior. For example, a fine-grained powder can grow past a coarser powder.

• Journal of Welding and Joining
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• 제27권6호
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• pp.62-67
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• 2009

Friction stir welding (FSW) was carried out for Al-Mg-Si series aluminum alloys which are being used for automotive body structure. Consequently, Post weld heat treatment (PWHT) was applied to the friction stir welds to evaluate the effect of the paint baking process which is one of the automotive fabrication process on friction stir welded zone (FSWZ) in 443K for 1.2Ks. Grain structure and its crystal orientation distribution was measured about both the as welded specimens and the post weld heat treated specimens. An optical microscope (OM) and an field emission scanning electron microscope (FE-SEM) was used for observing the grain structure and measuring its crystal orientation distribution, respectively. Changes on the grain structure and its crystal orientation distribution were not detected. From the present results, it was confirmed that the paint baking process after FSW do not affect on the grain structure and its crystal orientation distribution of FSWZ. The comprehensive investigations will be performed for various automotive aluminum alloys manufactured by different processes, in the future.

• 한국분말재료학회지
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• 제13권2호
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• pp.119-123
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• 2006

The grain growth behavior of $0.95Na_{1/2}Bi_{1/2}TiO_{3}-0.05BaTiO_{3}$ (NBT-5BT) has been investigated with respect to the grain shape. The powder compacts of NBT-5BT were sintered at 1200 for various times. The corresponding equilibrium shape was a round-edged cube with flat {100}-faces. Abnormal grains were not observed in the specimens sintered for 1 to 12 h but abnormal grains appeared when sintered for 24 h. Before the formation of abnormal grains, a valley was observed in the measured grain size distribution of NBT-5BT, showing that the grain size distribution was a combination of two unimodal distributions. The present result suggests that the grain growth in NBT-5BT was governed by the growth of facet planes which would occur via 2-dimansional nucleation and growth.