• Journal of Korea Foundry Society
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• v.3 no.3
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• pp.167-173
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• 1983

The effect of sand grain size on the various properties of mold is not only basic but important interest which we have to deal with.And the relation among the various properties of mold (strength, permeability, flowability, compactability, hardness, deformation, toughness etc.) is very complicated and inaccurate, so we can delineate the behavior of mixture (sand+water+bentonite) with experience only. Within recent years a so-called rigid-water theory has been accepted as a means of advancing logical explanations for the research aimed at delineating sand-clay-water relationships. By changing grain size or mesh no. of grain, specimens have been subjected to green compressive strength, permeability, deformation, flowability, compactablity, toughness at room temperature. Under constant mulling energy and ratio of water/bentonite, the results obtained were as follows: 1. With decreasing grain size green compressive strength of the specimen increased. 2. With decreasing grain size permeability decreased. 3. With decreasing grain size flowability and bulk density decreased but compactability increased. 4. With decreasing grain size deformation decreased but toughness increased. 5. At 60 mesh no., the properties of specimen are conspicuously changed. The reason is that the total surface area of sand grain which affects the type of bonding between sand grains is more changed at 60 mesh number.

• Journal of Welding and Joining
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• v.35 no.2
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• pp.35-42
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• 2017

The GMA welding process involves large number of interdependent variables which may affect product quality, productivity and cost effectiveness. The relationships between process parameters for a vertical weldment and mechanical properties are complex because a number of process parameters are involved. To make the vertical-position welding, a method that predicts bead geometry and accomplishes the desired mechanical properties of the weldment should be developed. In addition, a reliable welding process and conditions must be implemented to reduce weld structure failure. In this study, the welding process analysis of investigates the interaction between the heat input and welding parameter(Welding current, Arc voltage, Welding speed) for predicting the weldment hardness.

• Korean Journal of Materials Research
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• v.30 no.10
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• pp.550-557
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• 2020

Used in the ceramic tile market as a representative building material, relief ceramic tile is showing increased demand recently. Since ceramic tiles are manufactured through a sintering process at over 1,000 ℃ after uniaxial compression molding by loading granule powders into a mold, it is very important to secure the flowability of granular powders in a mold having a relief pattern. In this study, kaolin, silica, and feldspar are used as starting materials to prepare granule powders by a spray dryer process; the surface of the granule powders is subject to hydrophobic treatment with various concentrations of stearic acid. The effect on the flowability of the granular powder according to the change of stearic acid concentration is confirmed by measuring the angle of repose, tap density, and compressibility, and the occurrence of cracks in the green body produced in the mold with the relief pattern is observed. Then, the green body is sintered by a fast firing process, and the water absorption, flexural strength, and durability are evaluated. The surface treatment of the granule powders with stearic acid improves the flowability of the granule powders, leading to a dense microstructure of the sintered body. Finally, the hydrophobic treatment of the granule powders makes it possible to manufacture relief ceramic tiles having a flexural strength of 292 N/cm, a water absorption of 0.91 %, and excellent mechanical durability.

• Korean journal of food and cookery science
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• v.33 no.1
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• pp.37-44
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• 2017

Purpose: The purpose of this study was to simplify the traditional manufacturing method of Jeungpyun by developing a new process for Jeungpyun preparation using meringue and to also investigate the quality characteristics of Jeungpyun made with green tea powder. Methods: The Jeungpyun was manufactured as 4 sample preparations (Jeungpyun: J; Jeungpyun+0.5% green tea: J+0.5% GT; Jeungpyun+1% green tea: J+1% GT; and Jeungpyun+1.5% green tea: J+1.5% GT) through mixing rice flour, meringue, green tea powder (0-1.5%), dry yeast, water, and milk, steaming for 4 min at $180^{\circ}C$ and 3 min at $220^{\circ}C$, and then standing for 1 hr at room temperature. The quality characteristics of Jeungpyun were evaluated based on physicochemical properties, total mold, texture analysis, and sensory evaluation. Results: The pH of Jeungpyun batter was significantly lower in J+1.0% GT and J+1.5% GT than J. The specific gravity, weight, volume, and specific volume of J+0.5% GT and J+1% GT was not significantly different, as compared to J. In color, L value decreased and a and b value increased based on the increase of green tea powder. The antifungal activity was the highest in J+1.5% GT, followed by J+1.0% GT, J+0.5% GT, and J, in order. Samples with added green tea powder showed decreased hardness, as compared with J; its effect was significant in J+1.0% GT and J+1.5% GT after storage for 1 day. In sensory evaluation, the color of Jeungpyun was darkened by the addition of green tea powder. The egg smell and hardness significantly decreased by addition of green tea powder. Based on quantitative description analyses, overall acceptability was the highest in J+1% GT. Conclusion: Therefore, 1% green tea powder was the optimal amount for preparing Jeungpyun with meringue. For simplification of the traditional manufacturing method, Jeungpyun could be produced with meringue and green tea powder, which has potent physiological activities.

• Journal of Korea Foundry Society
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• v.4 no.2
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• pp.89-95
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• 1984

A Study on the Mechanical Properties of Molding Sand with Various Water/Clay Ratio A standard sample of molding sand was prepared by adding a various amount of bentonite, which has water/clay ratio from 0.4 to 0.6, into artificial sand, Hanyoung #6. The results obtained by measuring the room temperature properties of green mold are as follows. 1. This compressive strength of green molds which have 4% and 10% of bentonite decreased with increasing water/clay ratio, but the maximum strengths of 4.3 (psi) and 7.2 (psi) were observed in the samples with 6%, 8% bentonite respectively when the water/clay is 0.45. 2. The optimum water/clay ratio for strength and permeability increased from 0.4 to 0.5 with increasing clay. 3. The green compressive strength was proportional to the hardness. 4. Deformation increased with increasing water/clay ratio. 5. Flowability decreased with increasing water/clay ratio and clay content in molding sand.

• Korean Journal of Materials Research
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• v.11 no.10
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• pp.869-878
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• 2001

Alumina $(Al_2O_3)$ green bodies were fabricated by gel-casting using three kinds of alumina with different particle size (mean particle size: 4.6 $\mu\textrm{m}$, 0.32 $\mu\textrm{m}$, 10nm). The effects of particle size on gel-casting process and green microstructure were investigated. The optimum dispersion conditions using ammonium salt (D-3019) as dispersant were 0.2 wt% (4.63 $\mu\textrm{m}$), 0.5 wt% (0.32 $\mu\textrm{m}$), and 5.0 wt% (10 nm), in high solid loading. The optimum solid loading of each starting material for gel-casting was obtained as 59 vol% (4.63 $\mu\textrm{m}$), 57 vol% (0.32 $\mu\textrm{m}$), 15 vol% (10 nm), depending on particle size, indicating that nano-size particle (10 nm) represent lower solid loading as high specific surface area than those of other two starting materials. The drying at ambient conditions (humidity; $\thickapprox$90%) was performed more than 48hrs to enable ejection of the part from the mold and then at $120^{\circ}C$ for 2hrs in an air oven, showing no crack and flaw in the dried green bodies. The pore size and distribution of the gelcast green bodies showed the significant decrease with decreasing particle size. Green microstructure was dependent on the pore size and distribution due to the particle size, and on the deairing step. The green density maximum obtained was 58.9% (4.63 $\mu\textrm{m}$), 60% (0.32 $\mu\textrm{m}$), 47% (10 nm) theoretical density (TD), and the deairing step applied before gel-casting did not affect green density.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.2
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• pp.248-255
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• 2013

The objective of this study is to optimize the Metal Injection Molding(MIM) process with design of experiments(DOE) and numerical analysis. To derive the optimal process condition, experiment or numerical analysis was performed under various process conditions. To analyze the interaction among influential factors contributing to the temperature at flow front and response surface in MIM, both central point and axial point were added to the full factorial design with 2 levels and 5 factors and then their impacts on response variable in 43 experimental conditions were analyzed and the significance was evaluated. As a result, sprue, runner, and gate were completely filled in about 0.247 seconds after injection, the front part of the green body was filled in about 0.3344 seconds, the green body except gate, etc changed to almost solid state in about 3.29 seconds, the Packinging pressure was completed in about 6.29 seconds, and the green body inside and outside and sprue, etc became solid in 13.2 seconds. The impact of individual or reciprocal action of factors on the temperature at flow front was analyzed through regular probability, test statistics, main effect, and interaction effect. As a result, of a total of 31 combinations of factors, 9 unit factors and reciprocal actions were significant, and the screening was also possible. A proper regression equation was drawn with regression analysis and response surface design on the response variable of temperature at flow front, and the applicability could be verified.

• Journal of Life Science
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• v.23 no.12
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• pp.1415-1419
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• 2013

Electron beam (EB) irradiation was tested to determine the dose required to eradicate plant pathogens, such as Botrytis cinerea and Agrobacterium rhizogenes, from the infected seeds without affecting the germination rate of the irradiated vegetable seeds, including crown daisy, cucumber, hot pepper, green onion, leaf lettuce, and radish seeds. EB irradiation of 1.5 kGy and 2 kGy was sufficient to kill 100% of hairy root disease bacteria and gray mold conidia, respectively. EB irradiation showed no effect or minimal effect on the germination rate of the crown daisy, cucumber, green onion, and radish seeds. However, the germination rate of the hot pepper and leaf lettuce seeds was significantly reduced by using 2 kGy of EB irradiation. Difference in susceptibility to EB irradiation appears not to be related to the weight of each seed, but to the intrinsic characteristic of each plant. Conclusively, EB irradiation might be a useful way to decontaminate crown daisy, cucumber, green onion, and radish seeds.

• Research in Plant Disease
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• v.6 no.1
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• pp.36-38
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• 2000

A disease of Kalopanax pictus was found in Taebaec of Kang-won province. Korea, 1998. Typical symptoms were dark green to brown lesions appeared on the leaf and the stem canker. Many spores appeared on the lesions under humid conditions. A Botrytis species was consistently isolated from the infected plants. Conidia were obvoid to ellipsoid, 1-celled, hyaline or pale brown. The conidia were about 6-12${\times}$4-8$\mu\textrm{m}$ under scanning electron microscope, many micro-projections appeared on the surface of conidia. the isolated fungus infected heathy Kalopanax pictus. symptoms in inoculated plants were similar to those of originally diseased plants. The causal agent was identified as Botrytis cinerea. Gray mold of Kalopanax pictus was proposed to name this disease.

• Research in Plant Disease
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• v.6 no.1
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• pp.33-35
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• 2000

A disease of Cyclamen persicum was found in Kangnung of Kang-won prefecture, Korea, 1999. Typical symptoms were dark green to brown lesions appeared on petals and leaves. Many spores appeared on the lesions under humid conditions. A Botrytis species was consistently isolated from the infected plant. Conidia were obvoid to ellipsoid, 1-celled, hyaline or pale brown. The conidia were about 0.9-16.0$\times$6.0-10.4㎛(mean, 1.27$\times$7.8㎛) under scanning electron microscope, many micro-projections appeared on the surface of conidia. The isolated fungus infected heathy Cyclamen persicu. The causal agent was identified as Botrytis cinerea. Gray mold of Cyclamen persicum was proposed to name this disease.