• 한국지형학회지
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• 제27권2호
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• pp.19-28
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• 2020

Grain size analysis is the most basic procedure for identifying the origin, transport and sedimentation processes of sediments, and is widely used in geomorphology and sedimentology. Traditionally, grain size was determined by a sieve-pippette method, but the use of automated analyzers is increasing in recent years. These analyzers have many advantages over traditional techniques, but the measurement results are not always the same. It is still difficult to solve the pretreatment problem such as incomplete diffusion and residual organic matter, and inappropriate results may be obtained. This study compared image-based grain size analysis and sieve analysis to verify its statistical reliability, and conducted experiments to enhance the measurement accuracy using shape parameters. The results showed that the image-based analysis overestimated the grain size of sand dunes by about 7% compared to the sieve analysis, but the two measurements were not statistically different. In addition, by using shape parameters, such as aspect ratio, sphericity, and convexity, improved statistics were obtained compared to the original data. Using the morphological properties of the individual grains is a complementary method to the incomplete pretreatment of the grain size analysis process, and at the same time, it will contribute to improving the accuracy and reliability of the results.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 춘계학술대회 논문집
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• pp.143-146
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• 2001

The evolution of dynamic recrystallization (DRX) was studied with torsion test for AISI 304 stainless steel in the temperature range of $900-1000^{\circ}C$ and strain rate range of 0.05-5/sec. The evolution of DRX was investigated with microstructural analysis and change of flow stress curve slope. The investigation of serrated grain boundaries using electron back scattered diffraction (EBSD) analysis indicated that the nucleated new DRX grain size was similar to the size of bulging part. Before the steady state, the dynamically recrystallizing grains do not remain a constant size and gradually grow to the size of fully DRX grain at steady state. The calculation of grain size was based on $X_{DRX}$ and the assumption, which the nucleated DRX grains are growing to the steady state, continuously. It was found that the calculated results agreed with the microstructure of the alloy.

• 대한금속재료학회지
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• 제48권9호
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• pp.847-855
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• 2010

The grain size of a cross-section of $8{\mu}m$-thick copper film was determined by electron backscatter diffraction analysis. Grain size distribution histogram showed the presence of a large fraction of small-sized grains, and the mean grain size was significantly affected by handling of them. A cut-off grain size, below which all grains are ignored as noise and eliminated for the calculation of the mean value, should be three or four times as large as the step size. Due to the presence of small grains, the linear intercept method derived larger mean grain size, which depends less sensitively on the cut-off grain size than the equivalent circle diameter method.

• 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.

• 소성∙가공
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• 제11권5호
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• pp.439-446
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• 2002

This study presents a new computational model to analyze the grain deformation in a polycrystalline aggregate in a discrete manner and based directly in the underlying physical micro-mechanisms. When scaling down a metal forming process, the dimensions of the workpiece decrease but the microstructure of the workpiece remains the similar. Since the dimensions of the workpiece are very small, the microstructure especially the grain size will play an important role in micro forming, which is called size effects. As a result, specific characteristics have to be considered for the numerical analysis. The grains and grain boundary elements are introduced to model individual grains and grain boundary facets, respectively, to consider the size effects in the micro forming. The constitutive description of the grain elements accounts for the rigid-plastic and the grain boundary elements for visco-elastic relationships. The capability of the proposed approach is demonstrated through application of grain element and grain boundary element in the micro forming.

• 대한지리학회지
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• 제48권6호
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• pp.819-836
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• 2013

본 연구는 백령도 사곶 사빈에서 채취한 사질 시료를 대상으로 레이저 회절 입도분석기를 이용한 입도분석에 있어서 전처리 및 굴절율과 흡수율의 영향을 비교하고, 사질 시료의 적절한 입도분석 절차 및 방법을 제시하고자 한다. 본 연구에 적용된 세 가지 전처리 방법에 따라 입도분석 결과는 서로 큰 차이를 보이지 않지만, 과산화수소 처리를 했을 경우, 그렇지 않았을 때와 차이를 보이고 있어, 과산화수소 처리를 통해 유기물은 제거되어야 한다. 시료의 입도분석 결과는 굴절율 1.3과 흡수율 0.01 이하에서 다른 지수가 적용되었을 때와 차이를 보이고 있다. 이러한 차이는 세립질 시료에 비하면 그리 크지 않으며 따라서 굴절율과 흡수율도 사질 시료의 입도분석 결과에 큰 영향을 미치지 않는다. 그러나 굴절율 1.3과 흡수율 0.01 이하 이외의 다른 지수를 적용할 필요가 있다.

• 한국해안·해양공학회논문집
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• 제35권6호
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• pp.164-172
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• 2023

백사장 모래의 입도분포는 해빈의 침식과 퇴적을 파악하는 데 중요한 정보를 제공한다. 모래의 입도분포 분석에 보편적으로 사용되는 체가름시험은 분석 시간이 길고 개별 입자의 형상과 색에 대한 정보를 얻을 수 없다는 한계점이 있다. 본 연구에서는 체가름시험법 보다 측정 과정이 간편하고 효율적인 스마트폰 디지털 이미지를 이용한 입도분포 분석 방법을 제안하였다. 이미지 분석 과정 중 이미지 기울기(Image Gradient) 계산을 통한 입자 경계 추출로 해상도가 상대적으로 낮은 스마트폰 디지털 이미지의 배경으로부터 입자를 효과적으로 검출하였다. 경상북도 4곳의 해수욕장에서 채취한 시료를 이용해 본 연구에서 제안한 경계 추출 이미지 분석법과 경계를 추출하지 않는 분석법을 각각 체가름시험 결과와 비교 검증하였을 때, 본 연구에서 제안한 방식은 D₅₀에서 평균 8.21%의 평균 오차율을 보여 경계를 추출하지 않는 분석법 보다 65% 낮은 오차를 보였다. 따라서 스마트폰 디지털 이미지를 이용한 입도분포 분석은 간편하고 효율적이며 체가름시험에 준하는 정확성을 가짐을 확인하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1337-1342
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• 2008

The whisker grows at the plating of a lead frame so that it causes the serious problem like the short. To prove this case, many people have studied the cause and influence of the tin whisker growth. This study explains the grain size affects the growth of the whisker in the lead frame. By these studies about the whisker, the whisker growth is discovered by stresses generated by the intermetallic compound and CTE mismatch in both plating and base metal. The stresses or lattice defect generated in the plating process changes grain structure of plating. Consequently, these various stresses are stabilized by forming unspecified whiskers through lots of grain boundaries. Because the grain boundary is the path of the whisker growth, the smaller grain size exists, the more whiskers grow.

• 열처리공학회지
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• 제36권2호
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• pp.77-85
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• 2023

In this study, the mechanical properties of the Al-Mg-X (X=Cr, Si) alloy, which clearly showed the influence of the specimen and grain size, were investigated by changing the specimen size extensively. In addition, the effect on the specimen size, grain size and aging condition on the mechanical properties of the grain refining alloy according to the addition of Cr was clarified, and the relationship between these factors was studied. As the specimen size decreased, the yield stress decreased and the fracture elongation increased. This change was evident in alloys with coarse grain sizes. Through FEM analysis, it was confirmed that the plastic deformation was localized in the parallel part of specimen S2. Therefore, when designing a tensile specimen of plate material, the W/L balance should be considered along with the radius of curvature of the shoulder. In the case of under-aged materials of alloys with coarse grain size, the fracture pattern changed from intergranular fracture to transgranular fracture as W/d decreased, and δ increased. This is due to the decrease in the binding force between grains due to the decrease in W. In the specimen with W/d > 40 or more, intergranular fracture occurred, and local elongation did not appear. Under-aged materials of alloys with fine grain size always had transgranular fracture over a wide range of W/d = 70~400. As W/d decreased, δ increased, but the change was not as large as that of alloys with coarse grain sizes. Compared to the under-aged material, the peak-aged material did not show significant dependence on the specimen size of σ_0.2 and δ.

• Environmental Engineering Research
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• 제18권3호
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• pp.129-137
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• 2013

The infiltration of rainwater into the surface soil is highly dependent on hydraulic variables, such as the infiltration rate, capillary fringe, moisture content, and unsaturated/saturated hydraulic conductivity. This study estimates the hydraulic conductivity (K) of fluvial deposits at three sites on the right and left banks of Nakdong River in Gyeongbuk Province, South Korea, including the Gumi, Waegwan, and Seongju bridge sites. The K values of 80 samples from 13 boreholes were estimated by using six grain-size methods (Hazen, Slichter, Kozeny, Beyer, Sauerbrei, and Pavchich formulae). The Beyer, Hazen, and Slichter methods showed a better relationship with K values along with an effective grain size than did the other three methods. The grain-size, pumping test, and slug test analyses resulted in different K values, but with similar K values in the grain-size analysis and pumping test. The lower K values of the slug test represent the uppermost fine sand layer.