• 소성∙가공
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• 제18권6호
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• pp.482-487
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• 2009

A finite element based microstructural modeling for the size dependent strengthening of particle reinforced aluminum composites is presented. The model accounts explicitly for the enhanced strength in a discretely defined "punched zone" around the particle in an aluminum matrix composite as a result of geometrically necessary dislocations developed through a CTE mismatch. The density of geometrically necessary dislocations is calculated considering volume fraction of the particle. Results show that predicted flow stresses with different particle size are in good agreement with experiments. It is also shown that 0.2% offset yield stresses increases with smaller particles and larger volume fractions and this length-scale effect on the enhanced strength can be observed by explicitly including GND region around the particle. The strengths predicted with the inclusion of volume fraction in the density equation are slightly lower than those without.

• Journal of Biosystems Engineering
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• 제6권1호
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• pp.73-82
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• 1981

The physical properties of grain are very important for the design of handling, sorting, processing, and storage system. On the physical properties of grain, volume, bulk density, true density, specific gravity, and porosity arc the major factors affecting the thermal properties of grain. This study was conducted to determine experimentally the above physical properties of rough rice (3 Japonica-type, 3 Indica-type) and barley (covered, naked) as a function of moisture content ranged from about 10% to 25% (w.b). The results of this study are summarized as follows; 1. The volume of grain kernel increased with moisture content for both rice and barley. The volume of those grain kernel was in the range of $2.2068{\times}10^{-8}{\sim}3.3960{\times}10^{-8}m^3$ at the moisture content of 14%. 2. The bulk density of rice increased linearly with moisture content for Japonica-type rough rice and quadratically for Indica-type rough rice, but the bulk density of barley decreased linearly with moisture content. The bulk density of the grain was in the range of 501.14~689.13kg/$m^3$ at the moisture content of 14%. 3. The true density of whole grain decreased linearly with moisture content, and was in the range of 1019.49~1139.75kg/$m^3$ at the moisture content of 14%. 4. The porosity of rice decreased linearly with moisture content for Japonica-type rough rice and quadratically for Indica-type rough rice, but the porosity of barley increased linearly with moisture content. The porosity of the grain was in the range of 39.51~50.83% at the moisture content of 14%. 5. The regression equations of the physical properties such as volume, bulk density, true density, and porosity of the grain were determined as a function of moisture content.

• Journal of Medicine and Life Science
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• 제20권1호
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• pp.21-31
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• 2023

We aimed (a) to investigate the associations between age, body mass index (BMI), and breast size with mammographic density based on the breast imaging reporting and data system (BI-RADS) and volumetric breast density measurement (VBDM) with Volpara, (b) to evaluate the associations of age, BMI, and breast size with fibroglandular tissue volume (FGV), and (c) to demonstrate the association of mammographic density grade with FGV. From April 2012 to May 2012, 1,203 women consecutively underwent mammography, and their breast density was calculated using the density grade and volume determined by Volpara. In total, 427 women were included in this study. The BMI and breast size of the 427 women were determined. The associations between mammographic density and age, BMI, and bra cup size were assessed. In addition, the associations between FGV and age, BMI, bra cup size, and mammographic density were assessed. The mean age of the women was 51 years (range, 27-83). Age was associated with mammographic density based on BI-RADS (P<0.0001), and both age and BMI were associated with mammographic density based on Volpara (P<0.0001). The mean FGV significantly decreased as age increased (P<0.0001) and increased as BMI and bra cup size increased (P<0.0001 and P=0.0007, respectively). Age was associated with mammographic density, according to both the BI-RADS and VBDM; however, BMI was only associated with mammographic density based on the VBDM. Larger FGV was associated with younger age, higher BMI, larger bra cup size, and higher mammographic density

• 대한기계학회논문집B
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• 제33권6호
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• pp.443-453
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• 2009

The Rayleigh-Taylor instability, the bubble rising in both partially and fully filled containers and the droplet splash are simulated by an in-house solution code(PowerCFD), which are typical benchmark problems among multiphase flows with material interface due to density difference. The present method(code) employs an unstructured cell-centered method based on a conservative pressure-based finite-volume method with interface capturing method(CICSAM) in a volume of fluid(VOF) scheme for phase interface capturing. The present results are compared with other numerical solutions found in the literature. It is found that the present method simulates efficiently and accurately complex free surface flows such as multiphase flows with material interface due to both density difference and instability.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.572-575
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• 2008

Two-dimensional multiphase flows due to density difference such as the Rayleigh-Taylor instability problem and the droplet splash are simulated by an in-house solution code(PowerCFD). This code employs an unstructured cell-centered method based on a conservative pressure-based finite-volume method with interface capturing method in a volume of fluid(VOF) scheme for phase interface capturing. The present results are compared with other numerical solutions found in the literature. It is found that the present code simulates complex free surface flows such as multiphase flows due to density difference efficiently and accurately.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제3권1호
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• pp.57-73
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• 1999

Baroclinic hydraulic model experiments on the time-varying states of the flow pattern and water exchange in Sagami Bay were carried out based on quasi-steady state experiments on the flow pattern. For the model experiments, density changes as well as time changes in the volume transport of the upper layer were executed to investigate the flow response of the bay in the case of a sudden inflow of low density water and variable volume transport into the Sagami Bay. The results of the model experiments showed that when the volume transport was increased frontal eddies or frontal wave streamers from the Kuroshio Through Flow were transferred to the inner part of the bay along with cyclonic circulation in the bay. In addition, density boundary currents appeared and flowed along the eastern boundary of the bay. As the upper layer density decreased, frontal eddies, frontal streamers and coastal boundary density currents occurred and proceeded along the eastern boundary of the bay at a high speed.

• 소성∙가공
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• 제29권1호
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• pp.37-43
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• 2020

Increasing the critical current density of superconducting wire is one of the difficult challenges in the field of superconductivity. It is well known that the higher volume fraction of uniformly dispersed α-Ti is able to enhance the critical current density of superconducting material NbTi because α-Ti serves as a flux pinning center. The volume fraction of α-Ti highly depends on the grain size of NbTi because α-Ti precipitates at the grain boundaries or triple points. For this purpose, we investigated the effect of initial microstructures of NbTi obtained from hot rolling in various temperature conditions on the critical current density. In addition, subsequent heat treatment was assigned to precipitate α-Ti and groove rolling/cold drawing was adopted to produce a wire with a diameter of about 1.0 mm. It was observed that the band structure was formed after hot rolling at 500~600℃. It was also found that the volume fraction of α-Ti after hot rolling at 500~600℃ was higher and it led to the highest critical current density.

• Journal of Ginseng Research
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• 제17권3호
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• pp.224-227
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• 1993

Weight (g/root) and bulk density (g/$cm^3$) of tap root in 15-root-grade of 4-year-old white ginseng were investigated by specific gravity and weight-volume method. Bulk density measured by specific gravity ranged from 0.8 to 1.2g/$cm^3$ with almost normal distribution in frequency (number 1 of roots). Bulk density measured by volume-weight method had significant correlation with root weight. The percentage of high bulk density root (above 1.0) showed significant positive correlation with mean root weight or mean bulk density of root weight, indicating that the growth conditions for large root provide the better compactnes of root tissue.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2019년도 춘계 학술논문 발표대회
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• pp.168-169
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• 2019

This study examined the effect of foam volume ratio and curing temperature the air dry density and compressive strength of lightweight concrete using bottom ash. Test results showed that the lightweight concrete possessed the compressive strength of 3.4~22.7 MPa at the air dry density of 1,041~1,583 kg/m3.

• 한국자기학회지
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• 제23권6호
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• pp.188-192
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• 2013

수직 자기기록 매체로 알려진 CoPt 자성막을 전기도금법으로 제작하여 자기상호작용이 활성화 부피와 면적에 미치는 영향을 조사하였다. 모든 시료의 상호작용 기구는 쌍극자 상호작용이었으며, 낮은 전류밀도에서 제작한 시료일수록 두께가 두꺼울수록 상호작용 세기가 증가하였다. 한편 활성화 부피는 낮은 전류밀도에서 제작한 시료가 더 컸으나 두께에 따른 증감현상은 뚜렷하지 않았다. 그러나 활성화 면적은 상호작용의 세기가 강할수록 전류밀도가 낮을수록 감소하는 경향을 보였다.