• Polymer(Korea)
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• v.24 no.5
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• pp.690-700
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• 2000

In this study, an elastomer-assistered compression molding process was investigated by experiments as well as modeling for the long-fiber reinforced thermoset composites. The consolidation pressure generated by fixed-volume and variable-volume conditions was thermodynamically derived for both elastomer and curing prepregs, and was compared with the pressure measured during curing of epoxy matrix. Exhibiting non-linear viscoelastic characteristics in the compressive stress-strain tests, the measured stress was well compared with a modifed KWW (Kohlrausch-Williame-Watts) equation, which is based on the Maxwell viscoelastic model. Using the developed model equations, the consolidation pressure generated by the elastomer was successfully predicted for the compression molding process of thermoset composite materials in tile closed mold system.

• Journal of the Korean Ceramic Society
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• v.36 no.2
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• pp.178-185
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• 1999

For the process control of silicon nitride gelcasting, the composition effect of acryamide system on the viscosity of slip and mechanical property of gelcast green body were investigated. The slip was prepared by ball milling of silicon nitride suspension prepared with acrylamide monomer and polyelectrolyte dispersant after premixing them by attritor. The slip mixed with initiator was vacuum deaired and cast into molds, and then polymerized. The consolidated green body was obtained by drying the gelated slip. The viscosity measument and the diametral compression test was done to evaluate the rheological behaviro of slip and mechanical property of gelcast body, respectively. Experimental results showed that the high solid loading of silicon nitride slip was obtained up to 46 vol% with a low viscosity. The mechanical property of gelcast body mainly increased with increasing the concentration of monomer. The gelcast body was machinable above the ∼3 MPa of tensile strength. The relative density of pressured-sintered body was 98.5% at 1760$^{\circ}C$, 3 h.

• Korean Journal of Materials Research
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• v.11 no.2
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• pp.132-136
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• 2001

Iron- silicide has been produced by mechanical alloying process and consolidated by hot pressing. As-consolidated iron silicides were consisted of $\beta$-FeSi$_2$ phase, and untransformed mixture of $\alpha$-$Fe_2Si_5$ and $\varepsilon$-FeSi phases. Isothermal annealing has been carried out to induce the transformation to a thermoelectric semiconducting $\beta$-$FeSi_2$ phase. The condition for $\beta$-FeSi$_2$ transformation was investigated by utilizing DTA, SEM, TEM and XRD analysis. The phase transformation was shown to be taken place by a vacuum isothermal annealing at $830^{\circ}C$ for 24 hours. The mechanical and thermoelectric properties of $\beta$-FeSi$_2$ materials before and after isothermal annealing were characterized in this study.

• Journal of the Korean Society of Food Science and Nutrition
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• v.33 no.5
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• pp.899-904
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• 2004

The objectives of the experiment were to examine the effects of extrusion process variables on the yield of extruded ginseng extract and to determine the effect of ratio of extruded ginseng extract and microcrystalline cellulose on characteristics of spheronized granules by cold extrusion-spheronization process. Extrusion process variables observed were feed moisture (15, 22, 29%), die temperature (90 110 13$0^{\circ}C$) and screw speed (150 200, 250 rpm). The results showed that moisture content of dried ginseng significantly affected extraction yield (P<0.05). The less moisture content of the feed resulted in the higher yield of the extract. Moisture content of 15%, screw speed of 250 rpm and die temperature of 13$0^{\circ}C$ gave the highest yield of ginseng extract. Mean extraction yield of extruded ginseng using hot water extraction was greatly improved by extrusion process The extract yield of extruded ginseng was 43.5% which was higher than that of red ginseng (38.3%) and white ginseng (29.0%) produced by traditional process. It was possible to make from the mixture of microcrystalline cellulose (200 g) mixed with different concentration of 200 mL solution (0, 5, 20, 30 40 50 60% of ginseng extract with 59.2% dry solid) by using cold extrusion spheronization. When the concentration of ginseng extract Increased, the granulation yield was improved but friability and compression index were reduced. Ginseng extract such as saponin was completely released from spheronized granules in distilled water within 10 min. It can be concluded that spheroniged granule with ginseng extract could be packed in gelatin capsule since granules Possessed proper physical properties and quick release of saponin.

• Transactions of Materials Processing
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• v.4 no.3
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• pp.204-213
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• 1995

A finite element program is developed to analyze the flow phenomena in SMC compression molding as a viscoplastic model. The calculation of temperature distribution is also carried out by uncoupling the thermal analysis from the flow analysis. SMC molding processes with a flat plate substructure and the one with a T-shaped rib are considered in numerical simulation. The numerical results provide deformed shapes, temperature distribution in a SMC charge, and the forming load. The simulation of compression molding of a flat plate with a T-shaped rib requires a remeshing technique for the whole process.

• Transactions of Materials Processing
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• v.13 no.2
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• pp.180-187
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• 2004

A computer code was developed to simulate the filling stage of the injection/compression molding process by a finite element method. The constitutive equation used here was the compressible Leonov model. The PVT relationship was assumed to follow the Tait equation. The flow-induced birefringence was related to the calculated flow stresses through the linear stress-optical law. Simulations of a disk part under different process conditions including the variation of compression stroke and compression speed were carried out to understand their effects on birefringence variation. The simulated results were also compared with those by conventional injection molding.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.12
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• pp.2550-2555
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• 2002

Hybrid composites usually are defined as composites having different types of reinforcements such as fibers and particles. The major advantage of hybrid composites is able to control the material properties such as optical, electrical, and mechanical properties. For this reason, hybrid composites are widely used in automotive, marine, household, and electrical industries. The objective of this work was to investigate processing characteristics in the compression molding of hybrid thermoplastic composites. The mechanical properties of composites manufactured in various forming conditions were monitored. The composites contained randomly oriented long carbon fiber and carbon black in polypropylene(PP) matrix were used. The carbon fiber contents of composites were 5%, 10%, 15%, and 20%, and carbon black contents were 5%, 10%, 15%, 20%, and 25% by weight. Compression molding was conducted at various mold temperatures. Crstallinity was also measured by using X-RD. The tensile modulus of the composites increased with increasing the mold temperature. However, the impact strength of the composites decreased as the mold temperature increased.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.4
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• pp.637-643
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• 2002

The objective of this study is to provide a simple methodology to find optimum processing conditions to fabricate sub-micron structured DVD-RAM substrates with superb optical and geometrical properties. It was fecund that the birefringence, which is regarded as one of the most important optical properties for an optical disk, was very sensitive to the mold wall temperature history. Also, the integrity of the replication, represented by the land-groove structure and the radial tilt were influenced by the mold temperature and the compression pressure. A set of optimum conditions were obtained by applying Design of Experiment and the objective functions composed of three different objectives.

• Resources Recycling
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• v.28 no.2
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• pp.31-39
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• 2019

The pelletizing of printed circuit board (PCB) sludge was researched for copper recovery in pyrometallurgical process. This pelletizing was carried out by using self-manufactured compression-type apparatus after pre-treatments (drying, water scrubbing, size classification) were proceeded. The physical properties (compression strength and drop-breakage test) were tested with a change of sludge sizing and the number of compression. In the case of using the undersized sludge of #140, its properties were improved to 0.6 MPa and 9.3 times. Moreover, they increased to 0.82 MPa and 19.0 times by using the #140 ~ 325 sludge. These imply that the packing density increases due to the elimination of large-sized sludge (#140), and also the weight of required binder decreases by the removal of fine-sized sludge (#325).

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.200-203
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• 2001

Micromolding methods such as micro-injection molding and micro-compression molding are most suitable for mass production of plastic micro-optics with low cost. In this study, plastic micro-optical components, such as refractive microlenses and diffractive optical elements(DOEs) with various grating patterns, were fabricated using micro-compression molding process. The mold inserts were made by ultrapricision mechanical machining and silicon etching. A micro compression molding system was designed and developed. Polymer powders were used as molded materials. Various defects found during molding were analyzed and the process was optimized experimentally by controlling the governing process parameters such as histories of mold temperature and compression pressure. Mim lenses of hemispherical shape with $250{\mu}m$ diameter were fabricated. The blazed and 4 stepped DOEs with $24{\mu}m$ pitch and $5{\mu}m$ depth were also fabricated. Optical and geometrical properties of plastic molded parts were tested by interferometric technique.