• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1910-1913
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• 2005

As the various manufacturing technology of optical glass is developed, the aspherical lenses are applied to many fields. However, It is still very difficult to manufacture glass lens because of the high cost and the short life of core. In recent years, the demands of the aspherical glass lenses increase since it is difficult to obtain the desirable performance in the plastic lens. In the glass mold lens, it has merits of high productivity and reproductivity since lens is manufactured by the only forming with high precision mold. The fabricating conditions for glass mold lens are glass surface that does not cause fusion, viscosity of 108-1013 poise for the $0.2{\mu}m$ accuracy, and viscoelasticity for the roughness less than 100 angstrom. In this paper, ultra-precision grinding characteristics of tungsten carbide for forming the aspherical glass lens core were studied and the result of it is applied to manufacture the tungsten carbide-base cores of the glass lens used to the laser scanning unit and the camera phone.

• Korean Journal of Food Science and Technology
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• v.41 no.6
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• pp.657-661
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• 2009

Liquid microparticulated seaweed calcium was manufactured via a wet grinding process. Thereafter, different forming agents such as cyclodextrin, gum arabic, and Na-caseinate were added to the liquid calcium, which was then spray-dried to investigate the quality of the powdered calcium treatments. The moisture contents of samples were approximately 2%. It was also determined that the different kinds of forming agents did not affect the spray drying efficiency. In addition, calcium solubility was the highest in a solution of pH 2. In buffer solution and vinegar, the powdered calcium made with gum arabic showed the highest solubility among the treatments. The calcium contents of all the powdered microparticulate seaweed calcium samples were about 28%, and calcium content was not affected by the forming agents. The spray-dried calcium powder made by spray drying with gum arabic had the highest water vapor uptake, whereas the seaweed calcium was stable in terms of water adsorption. The results of SEM observations indicated that a portion of the spray-dried calcium powders were in nano-scale after wet-grinding. Among the treatments, the use of saccharides as a forming agent resulted in the most uniform particle distribution after spray-drying.

• Journal of Biosystems Engineering
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• v.26 no.1
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• pp.47-56
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• 2001

In order to prevent the possibility of mixing of metal powder during food grinding processing with the metal roll mill this study was conducted to develope the materials of ceramics roll as a substitute of gray cast iron mill. Since the ceramics is brittle material and can be broken easily by a crack, it was needed to develope engineering ceramics roll materials with high elastic modulus and fracture toughness. Adding 0∼50 wt% Al$_2$O$_3$as densification additives to porcelain body material and forming the ceramics an different condition, mechanical properties were evaluated. The material structure’s densification process was analyzed by SEM and XRD. The evaluation of the mechanical properties of ceramics roll materials were compared and analyzed by non-destructive test using Young’s modulus and destructive test using 3-point bending strength and fracture toughness. The results showed several correlative results. Porcelain body material with 40 wt% Al$_2$O$_3$content heated at 1,200$\^{C}$ for 5h was high bulk density of 2.77, Young’s modulus of 118.4Gpa, 3-point bending strength of 137 MPa and fracture toughness of 2.88 MPa$.$m$\^$$\sfrac{1}{2}$/ . After analyzing the relationship between non-destructive test and destructive test, the coefficient of determination was more than 0.9. Therefore, the evaluation of non-destructive test by ultrasonic was turned out to be feasible in evaluating the mechanical properties of ceramics.

• Korean Journal of Agricultural Science
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• v.12 no.1
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• pp.101-107
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• 1985

Since most farmers breeding livestocks in Korea is depended on imported feeds, the rate of self-supplying feeds is very important for a stable development of farmers. Therefore, it is considered necessary to increase the rate of self-supplying feeds. In this study, performance tests were carried out with barley and forage to find the design's parameters of hammer for a small size hammer mill which can be driven by 3.7-7.5 kW power tiller being used by most farmers. The revolution speed of hammer mill was 3000 rpm, widths of hammer were 20mm, 30mm, 40mm, and the levels of thickness of hammer were 2mm, 4mm and 6mm. Experimental materials used were barley and forage and screen openings for barley was 4.76mm, and 3.18mm for forage. The study results can be summarized as follows; 1. Results of grinding tests showed that particle sizes were 478-774 microns for barley and 350-434 microns for forage. They were decreased according to the increasing thickness and width of hammer. 2. Fineness modulus of grinded materials were 3.07-3.62 for barley and 2.69-2.93 for forage. They were inversely proportional to thickness and width of hammer. 3. The required power for grinding was 3.8-5.0 kW for barley and 0.9-1.4 kW for forage. The thickness of hammer was more important for less power requirement than width of hammer. 4. Grinding performance of a small size hammer mill was 99-170kg/kWh for barley and 11-21 kg/kWh for forage. The thickness of hammer was an important factor for grinding performance, and inversely proportional to grinding performance. For about 3.2 of fineness modulus, 4 mm thickness was the best, and an optimum width of hammer was 30mm for a small size hammer mill.

• Journal of the Korean Society for Railway
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• v.9 no.4 s.35
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• pp.371-378
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• 2006

This study investigates the effects of the material properties and the fatigue behaviors in the SM490A material butt weld specimens due to the heat-treatment and the grinding. In the fatigue behavior, the heat-treatment affects the fatigue life. The S-N curves of both matrix specimen and butt weld specimen are reversed at some cycle by the existence or nonexistence of heat-treatment. The grinding on the bead makes the fatigue limit decrease in the all specimens. But the reinforcement removed, the fatigue limit increases at the high cycle. Also, this study investigates the fatigue life estimation by examining butt weld bead profiles. The butt weld beads, which are welded by semi-robot method, have non-uniform bead profiles described by $\theta,\;\rho$ and h. The stress concentration factors $K_t$, are changed by each different $\theta,\;\rho$ and h from 1.395 to 2.863. Hence, the sensitivity of $K_t$ is changed by each $\theta,\;\rho$ and h. As $\theta$ becomes lower and $\rho$ and h become higher, $K_t$ increases. The fatigue life can he estimated very closely for the AAY specimens without residual stress using only butt weld bead profiles. But, fur the AAN specimens with residual stress, the fatigue life must be estimated by considering both the weld bead profiles and the residual stress data.

• Bulletin of the Korean Chemical Society
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• v.26 no.10
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• pp.1565-1568
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• 2005

A surface renewable pH electrode was prepared by utilizing composite electrode technique. Iridium oxide micro-fine particles was prepared by hydrolysis of $(NH_4)_2IrCl_6$ at elevated temperature. The iridium oxide particles were mixed with well-dispersed carbon black and then filtered. The mixture was suspended in DMF containing PVC as a binder. The mixture was precipitated rapidly by adding large amount of water. The precipitate was ground and pressure-molded to iridium oxide composite electrode material. The electrode showed linear response between pH 1-13 with 50 to 60 mV/pH slope. The electrode maintained the pH response without appreciable slope drift for 170 days if stored in deionized water. The electrode surface can be renewed reproducibly by simple grinding process whenever contaminated or deactivated.

• Korean Journal of Materials Research
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• v.1 no.2
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• pp.71-76
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• 1991

The superconducting powders in $YBa_2Cu_3O_{7-x}$ and Bi-Pb-Sr-Ca-Cu-O system were easily prepared from water in oil type emulsion by loading each cation into the aqueous phase. In $YBa_2Cu_3O_{7-x}$ system, the superconducting orthorhombic phase was formed by calcining at $750^{\circ}C$ for 10h in $O_2$. The size of the superconducting phase powders was submicron. The density of the sintered specimen using this powders was about 95% of the theoretical density and the resistance sharply decreases at about 90K, In Bi-Pb-Sr-Ca-Cu-O system the low Tc phase($(Bi, Pb)_2Sr_2Ca_1Cu_2O_y$) was formed by calcining at $800^{\circ}C$ for 10h in a low oxygen partial pressure of 1/20 atm The shape of clacined powder is thin plate of which size is about $2\mu\textrm{m}$ and thickness is smaller than $\mu\textrm{m}$. It was observed that the high Tc phase ($(Bi, Pb)_2Sr_2Ca_2Cu_3O_y$) was formed by sintering at $850^{\circ}C$ for 30h in oxygen pressure of 1/20 atm without intermediary grinding. The above sintered sample exhibited superconductivity with a Tc(zero)=105K.

• Korean Journal of Materials Research
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• v.19 no.12
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• pp.661-666
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• 2009

Froth flotation has been carried out in order to produce roasting-molybdenite concentrate from molybdenite ore in the Shin-yeomi mine. In our study, roasting-molybdenite (Mo 0.43%) from Shin-yeomi mine was recovered by varying the conditions of regrinding time, dosage of collector and alkalinity. Liberation and flotation efficiency more were effective at regrinding time of six minutes than at single grinding. Mo recovery curves increased considerably as dosage of kerosene increased, whereas Mo grade curves decreased gradually. The separation efficiency of molybdenite was effective when the dosage of collector (kerosene) was adjusted to 300 g/t. The molybdenite concentrate was agglomerated in the range of pH 5-7 and its separation efficiency increased to pH 9-10. The concentrate of 49.5% Mo grade ($MoS_2$, 82.6%) with 81.5% recovery from Shin-yeomi molybdenite ores was obtained under conditions of 20% pulp concentration, 300 g/t kerosene 325 g/t frother (AF65), 2.5 kg/t depressant ($Na_2SiO_3$), pH 9-10 and four cleaning times. In the future, a trial run that can separate up to 50% Mo grade from Shin-yeomi molybdenite ores will be performed.

• Resources Recycling
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• v.10 no.4
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• pp.3-9
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• 2001

The Sericite Powder W3S Comminuted in 1 M $KNO_3$solution for 0.5, 1, 2, 5 and 10 h, compared with the addition of distilled water. It has been found that the mean diameter of the ground particles decreases until the comminuting for 1 h, however, increases after 1 h due to the agglomeration between fine particles. The sericite powder comminuted with 1 M $KNO_3$solution for 1 h shows the mean particle size of $1.9\mu$m, and it also shows the mean particle size of 2.4 $\mu$m in case of comminution in distilled water for 1 h.

• Journal of the Korean Society of Food Science and Nutrition
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• v.26 no.5
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• pp.794-799
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• 1997

The effective fermentation methods of Kimchi juice for utilization of outer layer of Chinese cabbage, an waste of Kimchi industry were studied. The Kimchi juice prepared with brining and grinding the waste of Chinese cabbage and addition of spices was fermented at $25^{\circ}C$. Addition of 5$^{\circ}C$15% fermented Kimchi juice of pH 5.4 at initial stage and pH 4.4 at middle state resulted in a significant increase in fermentation rate and solid content after 12 hours of fermentation. The combined method of enzymatic hydrolysis(0.1% viscozyme) of the brined and ground cabbage and addition of 2.0% NaCl, 1.0% sucrose and 10% fermented juice of pH 5.4 first and 4.4 during fermentation, respectively resulted in more rapid fermentation. The solid concentration was 5 times higher than control at maximum point and acidic and total flavor intensity were also significantly high.