• Steel and Composite Structures
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• v.15 no.2
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• pp.151-162
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• 2013

In this study, an electrolyzing device for the production of metal powders was designed and fabricated. The production of copper powders was performed using a variety of current densities, anode-cathode distances and power removal times. The effect of these parameters on powder particle size and shape was determined. Particle size was measured using a laser diffraction unit while the powder shape was determined by SEM. Experimental results show that an increase in current density leads to a decrease in powder particle size. In addition particle shape changed from globular dendritic to acicular dendritic with increasing the current density. Distance between the cathode and anode also showed a similar influence on powder particle size and shape. An increase in time of powder removal led to an increase in powder particle size, as the shape changed from acicular dendritic to globular dendritic.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.136-145
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• 2009

Factors influencing shear behavior of granular material include particle size, shape, distribution, relative density, particle crushing, etc. In this study, these factors are characterized by viewpoint of shear behavior using numerical analysis based on DEM. Geometrical particle shape is represented by a combination of small circular particles and influence of particle shape on crushing is studied through relative comparisons between clump (uncrushable) and cluster (crushable) models which are modeled using DEM. Also, particle shape is quantified by the dimensionless parameters such as circularity and convexity. The results indicate that particle shape indexes have a negative association with internal friction angle. Also, internal friction angle becomes reduced and failure envelop curve becomes nonlinear due to the particle crushing. It is also found that numerical results are quite good agreement with the experimental test conducted in this study.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.1182-1189
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• 2010

The mechanical behavior of a granular material is governed by the applying effective stresses and its skeletal structure which is considered to be the packing of particles giving overall density and degree of anisotropic. Factors that affect soil packing are the particle size, size distribution and shape, and the arrangement of grain contact. Soil particle size and shape are the most important factor, but difficult to quantify. In this study, 2D Fourier analysis is applied to quantify the shape of granular particles. Jumunjin sand was used in the experiment and particle images are captured using an optical microscope. The results showed that three lower order Fourier descriptor are closely related with roundness, sphericity of the granular particle. Also statistical approach is used to determine roundness, form factor, elongation ratio, roughness of Jumunjin sand.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.702-703
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• 2006

The particle size distribution and shape are among the important parameters for characterisation of quality of metal powders. Specific material properties such as ability to flow, reactivity as well as compressibility and its hardening potentials hence the most important characteristics of sintered metals - are determined by the size distribution and shape. The correct particle size distribution and particle shape information are the key to best product quality in atomisation processes of aluminium, milling of pure metals and other processes. This paper presents state-of-the-art technology for characterization of particle size distribution and shape.

• Proceedings of the KWS Conference
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• 2005.06a
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• pp.158-160
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• 2005

Zener coefficient on cubic shaped particle was proposed. Most previous researches about Zener coefficient were developed on the assumption that the shape of particle is spherical. But, some particle has other shape, and modification of Zener coefficient needs with shape of particle. In this research, TiN particle that has a cubic shape was considered. A Zener coefficient of a cubic shape TiN was theoretically calculated with appropriate assumptions. And, using a semi-empirical method, Zener coefficient was also measured. Finally, the proposed Zener coefficient was proved by comparing with experimentally measured data.

• Atmosphere
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• v.22 no.2
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• pp.175-186
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• 2012

In this study, we investigate the effects of elliptical shape of Asian dust particles on the estimation of aerosol optical depth by implementing T-matrix method into WRF/Chem Dust Model. The phase function calculated by assuming elliptical particle shape near $110{\sim}160^{\circ}$ of scattering angle showed about 20 times larger than that calculated by assuming spherical particle shape. Significant difference of extinction efficiency was found with an increase of size parameter and aspect ratio. From the simulations of two Asian dust events occurred on 1 April 2007 and 16 March 2010, we found that the difference of extinction efficiency between elliptical and spherical particle shape was about 5~8%. The aerosol optical depth calculated by assuming elliptical particle shape with 1.6, 1.4 and 1.2 of aspect ratio was about $4.0{\pm}0.5%$, $2.0{\pm}0.2%$, and $1.0{\pm}0.1%$ larger than those estimated by assuming spherical particle shape.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2004.05a
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• pp.71-74
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• 2004

Recently, with the wide shortage of natural sand resources, it has been increasingly used the crushed sand. rushed sand is made by the process of crushing the rocks artificially, which has different particle properties compared with that of natural sand. Because such different panicle properties of crushed sand results in an undesirable effects of concrete. improvement technology for crushed sand particle properties like grain shape and fine particle needed during the manufacturing process. In this paper, improvement technology of grain shape and fine particle is reported. According to test results, adequate investment for manufacturing facilities like impact crusher and abrasion test machine is required to meet the advanced grain shape and grading of crushed sand. Based on the investigation of test result, mixing of natural land and crushed sand with given proportion can achieve the improvement of grain shape. For improving excessive fine panicle contents. current manufacturing system also can enhance the existing technology for fine particle without additional investment. It can be concluded that adequate investment and research can improve the quality of crushed sand.

• Journal of the Korean Geotechnical Society
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• v.25 no.10
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• pp.41-53
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• 2009

In order to analyze the influence of particle shape on evolution of particle crushing and characteristic of shear behavior of granular soil, direct shear test was simulated by using DEM (Discrete Element Method). Six particle shapes were generated by clump and cluster model built in PFC (Particle Flow Code). The results of direct shear test for six particle shapes were compared and analyzed with those for circular particle shape. The results of numerical tests showed a good agreement with those of experimental tests, thus the appropriateness of numerical modelling set in this study was proved. As for particle shape, more angular and rougher particle induced larger internal friction angle and more particle crushing than relatively round and smooth particle. When particles were crushed, crushing was concentrated on the shear band adjacent to the shear plane. Finally, it can be concluded that the numerical models suggested in this study can be used extensively for other studies concerning the shear behavior of granular soil including soil crushing.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.10a
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• pp.115-123
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• 1998

The morphological analysis of wear particle is a very effective means for machine condition monitoring and fault diagnosis. In order to describe morphology of various wear particle, the wear test was carried out under different experimental conditions. And fractal descriptors was applied to boundary and surface of wear particle with image processing system. These descriptors to analyze shape and surface wear particle are shape fractal dimension and surface fractal dimension. The shape fractal dimension can be derived from the boundary profile and surface fractal dimension can be determined by sum of intensity difference of surface pixel. The morphology of wear particles can be effectively obtained by two fractal dimensions.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.4
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• pp.53-59
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• 2009

The purpose of this research is particle shape evaluation of granular soil and aggregate using Digital Image Process(DIP). DIP is very useful to measure the roughness and particle shape of aggregates. Couple of aggregates, like standard sand, two different crushed stones, and two different marine aggregates, have been employed. Shape factor of two different marine aggregates is ranged 0.35 to 0.54. Crushed stone I is that of 0.74 which is highly flat, but standard sand is elongated shape. Especially, two marine aggregate showed a big difference of width and length which meaned a long shape. There is any significant difference of elongation ratio and flakiness for each aggregate with different measuring system, like direct measurement of vernier calipers and DIP method. Within the limited test results, DIP is one of useful to get the particle shape of aggregate with limitation of measuring errors and to apply the particle distribution curve.