• Journal of the Korean Ceramic Society
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• v.35 no.12
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• pp.1308-1315
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• 1998

Effects of particle size of alumina on densification behavior during liquid-phase sintering of alumina-talc system were investigated with emphasis on particle rearrangement process. In the case of using coarse alu-mina powder densiication of specimens was rapidly accelerated after formation of liquid phase due to easy particle rearrangement process with addition of talc and increase of sintering temperature. On the contrary when fine alumina powder was used premature densification of alumina matrix region formed before for-mation of liquid phase rigid skeleton structure and then it seemed to inhibit rearrangement process during crease of sintering temperature. As results the densification of specimens using coarse alumina powder was higher than that of the case of using fine one.

• Journal of the Korean Ceramic Society
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• v.34 no.9
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• pp.979-985
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• 1997

The three-dimensional particle packing process is simulated using Lahey FORTRAN 90 as a programming language running on a personal computer. Particle clusters constructed with rearrangement which occurs during packing have higher average coordination number and packing density than particle clusters rearranged after packing. Rearranging particles can not completely block other particles from entering pore volume in 3-dimensional packing unlike in 2-dimensional packing. It is found that there is a region of instability where lower packing density results from the destruction of the ordered packing.

• Journal of the Korean Ceramic Society
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• v.29 no.12
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• pp.956-962
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• 1992

The predominant sintering mechanisms of low firing temperature ceramic substrate which consists of borosilicate glass containing alumina as a filler are the rearrangement of alumina particles and the viscous flow of glass powders. In this system, sintering condition depends on the volume ratio of alumina to glass and on the particle size. When the substrate contains about 35 vol% alumina filler and the average alumina particle size is 4 $\mu\textrm{m}$, the best firing condition is obtained at the temperature range of 900∼1000$^{\circ}C$. The extensive rearrangement behavior occurs at these conditions, and the optimum sintering condition is attained by smaller size of glass particles, too. The formation of cristobalite during sintering causes the difference of thermal expansion coefficient between the substrate and Si chip. This phenomenon degradates the capacity of Si chip. Therefore, the crystallization should be prevented. In the alumina filled borosilicate glass system, the crystallization does not occur. This effect may have some relation with aluminum ions in alumina. For aluminum ions diffuse into glass matrix during sintering, functiong as network former.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.68-69
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• 2006

When an alloy such as Ni-W is liquid phase sintered, heavy solid W particles sedimentate to the bottom of the container, provided that their volume fraction is less than a critical value. The sintering process evolves typically in two stages, diffusiondriven macrosegregation sedimentation followed by true sedimentation. During macrosegregation sedimentation, the overall solid volume fraction decreases concurrently with elimination of liquid concentration gradient. However, in the second stage of true sedimentation, the average solid volume fraction in the mushy zone increases with time. It is proposed that the true sedimentation results from particle rearrangement for higher packing efficiency.

• Journal of the Korean Ceramic Society
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• v.34 no.12
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• pp.1213-1220
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• 1997

Effect of particle size of alumina and amount of talc on tape casting and densification behaviors of alumina-talc system were investigated. The pseudoplastic behaviors of slurries increased with increase in amount of talc addition and decrease in alumina particle size. In case of using coarse alumina powder, densification of specimens were accelerated with increase of sintering temperature and amount of talc addition. On the contrary, fine alumina powder retarded of rearrangement of alumina particle during liquid phase sintering due to premature densification of alumina matrix region before formation of liquid phase and then densification of specimens were suppressed with increase of sintering temperature and amount of talc addition.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1554-1561
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• 2005

Geotextiles form one of the two largest groups of geosynthetics and it is consisted two major types of synthetic material (Woven, Non-woven). The functions of geotextiles are separation, reinforcement, filtration, drainage and as a moisture barrier. Within these functions, however, there are a large number of applications or use areas. Although the many research scholar and engineer developed and established the design criteria and construction methodology of geosynthetics filter layer, because the lack of suitable design terminology and uncertainty of long term durability, sustainable research still needed for optimum design methodology to the complicate field conditions. Especially, more intensive research needed about under the cyclic flow condition and fine silty sand base material. In this paper, the filter model test performed under cyclic flow with various boundary conditions (period and frequency of cyclic flow, types of geosynthetic filter material, surcharge etc.).

• The Korean Journal of Ceramics
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• v.6 no.1
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• pp.1-5
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• 2000

Particle packing properties are important to develop high technology products in the field of cement and concrete. Two types of particle packing models for aggregates with sand and cement were introduced: the loose and the dense aggregate packing. Aggregate packing models with randomly generated sand and cement particles in the interstices of aggregates fit the Furnas model very well. Different aggregate models show different packing properties with the experimental results. Main reason for the difference with the experimental results is due to sand rearrangement in the loose aggregate packing model and to aggregate relaxation in the dense aggregate packing model. In the experimental situation, aggregates seem to be more disordered and have a relaxed packing structure in the dense packing, and sands seem to have a more rearranged packing structure in the loose packing model.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.4
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• pp.96-106
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• 2017

In pressable polymer bonded explosives (PBXs), densification occurs due to rearrangement and deformation of explosive particles during pressing. If brittle explosives are compressed till particle fraction become higher than theoretical random close packing fraction (RCPF), bigger particles should be fractured to fill the void. In this study, multi-modal particle system was introduced for the decrease in possibility of particle fracture during compression expecting decrease in shock sensitivity of highly filled pressable PBX. The experimental results showed the trimodal particle system had low sensitivity with high density, compared to bimodal particle system.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.808-809
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• 2006

The decrease of the distance between particle centers due to the growth of the sinter necks can be explained by the well known two-particle model. Unfortunately this model fails to provide a comprehensive description of the processes for 3D specimens. Furthermore, there is a significant discrepancy between the calculated and the measured shrinkage because particle rearrangements are not considered. Only the recently developed analysis of the particle movements inside of 3D specimens using micro focus computed tomography $({\mu}CT)$, combined with photogrammetric image analysis, can deliver the necessary experimental data to improve existing sintering theories. In this work, ${\mu}CT$ analysis was applied to spherical copper powders. Based on photogrammetric image analysis, it is possible to determine the positions of all particle centers for tracking the particles over the entire sintering process and to follow the formation and breaking of the particle bonds. In this paper, we present an in-depth analysis of the obtained data. In the future, high resolution synchrotron radiation tomography will be utilized to obtain in-situ data and images of higher resolution.

• International Journal of Concrete Structures and Materials
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• v.9 no.4
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• pp.453-462
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• 2015

A critical review on existing creep theories in calcium-silicate-hydrate (C-S-H) is presented with an emphasis on several fundamental questions (e.g. the roles of water, relative humidity, temperature, atomic ordering of C-S-H). A consensus on the rearrangement of nanostructures of C-S-H as a main consequence of creep, has almost been achieved. However, main disagreement still exists on two basic aspects regarding creep mechanisms: (1) at which site the creep occurs, like at interlayer, intergranular, or regions where C-S-H has a relatively higher solubility; (2) how the structural rearrangement evolutes, like in a manner of interlayer sliding, intra-transfer of water at various scales, recrystallization of gelled-like particles, or dissolution-diffusion-reprecipitation at inter-particle boundary. The further understanding of creep behavior of C-S-H relies heavily on the appropriate characterization of its nanostructure.