• Journal of the Korean Society for Precision Engineering
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• v.33 no.11
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• pp.893-898
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• 2016

Plastic array lens are cheap to manufacture; however, plastic is not resistant to high temperatures and moisture. Optical glass represents a better solution but is a more-expensive alternative. Glass array lens can be produced using lithography or precision-molding techniques. The lithography process is commonly used, for instance, in the semiconductor industry; however, the manufacturing costs are high, the processing time is quite long, and spherical aberration is a problem. To obtain high-order aspherical shapes, mold-core manufacturing is conducted through ultra-precision grinding machining. In this paper, a $4{\times}1$ mold core was manufactured using an ultra-precision machine with a jig for the injection molding of an aspherical array lens. The machined mold core was measured using the Form TalySurf PGI 2+ contact-stylus profilometer. The measurement data of the mold core are suitable for the design criterion of below 0.5 um.

• Journal of the Korea Furniture Society
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• v.17 no.1
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• pp.33-46
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• 2006

This study was carried out to investigate a radio-frequency/vacuum (RF/V) drying ability and physical properties of the green boards and the pre-kiln dried boards with 40 mm thickness, and the 70 mm-thick green board of Iroko (Milicia excelsa). The major results were summarized as follows; The drying time from initial moisture content (MC) of 110% to approximate 6% MC for a 40mm-thick green board was 192 hours, and about 200 hours for the 70 mm-thick green board, respectively and so the RF/V drying times were dramatically shortened compared to conventional kiln drying time. The case hardenings at the RF/V drying completion stage test were very negligible, thus represented almost no existence of the residual stress. The checks were very slightly formed on all of the boards during the RF/V drying test, but crook appeared quite severely. During the accelerating test, the water-resistant treated specimens had not experienced any signs of checking occurred, whereas the control boards had encountered very frequent occurrences of end checking and slight surface checking. There were no observations of warping and discoloring regardless of the treatment.

• Korean Journal of Food Science and Technology
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• v.30 no.5
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• pp.1024-1028
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• 1998

Crystalline structure of the extrudate of high amylose corn starch was studied by X-ray diffractometer and $^{13}C\;NMR$. The X-ray diffraction crystal ratio of the extrudates (barrel temperature $100^{\circ}C$ )of high amylose corn starch slightly increased from 6.08% to 8.37% by increasing feed moisture content from 25% to 45%. But extrudates of high amylose corn starch showed similar crystal ratio on various extrusion conditions. Extrudates of high amylose corn starch (feed moisture content 20%, barrel temp $140^{\circ}C$) showed more enlarged crystal structure than that of non-extrudates. The perpendicular distance of crystal increased by extrusion. Crystal ratio was changed from $6.3{\sim}8.3%$ to $4.5{\sim}5.8%$ during storage at $4^{\circ}C$. Starch configuration was examined with $^{13}C\;NMR$. Double helical content was measured by $^{13}C\;NMR$ method. The highest double helical content (60%) was obtained from high amylose corn starch extrudate (barrel temp.: $100^{\circ}C$, feed moisture content 45%). Double helical contents and resistant starch (RS) yield (pancreatin) were positively correlated. However, double helical content of the extrudates was not changed by the storage at $4^{\circ}C$.

• Korean Journal of Agricultural and Forest Meteorology
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• v.15 no.3
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• pp.178-185
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• 2013

Forest fires are expected to increase in severity and frequency under global climate change and thus better understanding of fire dynamics is critical for mitigation and adaptation. Researchers with different background, such as ecologists, physicists, and mathematical biologists, have developed various simulation models to reproduce forest fire spread dynamics. However, these models have limitations in the fire spreading because of the complicated factors such as fuel types, wind, and moisture. In this study, we suggested a simple model considering the wind effect and two different fuel types. The two fuels correspond to susceptible tree and resistant tree with different probabilities of transferring fire. The trees were randomly distributed in simulation space with a density ranging from 0.0 (low) to 1.0 (high). The susceptible tree had higher value of the probability than the resistant tree. Based on the number of burnt trees, we then carried out the sensitivity analysis to quantify how the forest fire patterns are affected by wind and tree density. The statistical analysis showed that the total tree density had greatest effect on the forest fire spreading and wind had the next greatest effect. The density of the susceptible tree was relatively lower factor affecting the forest fire. We believe that our model can be a useful tool to explore forest fire spreading patterns.

• Korean Journal of Environmental Agriculture
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• v.13 no.2
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• pp.183-190
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• 1994

To assess the effects of plant stress by light, temperature, NaCl and soil moisture on photosynthetic activity, the fluorescence method was used for Chinese cabbage(Brassica perkinensis Rupr.), strawberry(Fragaria grandiflora Ehrh.) and citrus tree(Citrus unshiu Marc.). With decreasing the light intensity, Fv/Fm ratios of intact leaves of Chinese cabbage and strawberry increased significantly, indicating lower photochemical efficiency in PS II system, resulting in an inverse relationship with the photosynthetic activity. Chinese cabbage and strawberry that were grown at higher temperature had higher Fv/Fm ratios and photosynthetic activities, while those given high concentration of NaCl and having low soil moisture had lower values. Chinese cabbage more resistant to salt stress and requiring more water had a greater Fv/Fm ratio than strawberry. In citrus tree, Fv/Fm ratio was lower in the non-irrigated group than the irrigated one. From these results, the fluorescence method was found to be a useful tool which can be used to assess the degree of in vivo stress induced by various environmental factors.

• Journal of the Korean Society of Food Culture
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• v.22 no.6
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• pp.820-826
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• 2007

Different types of bap(cooked rice) was cooked using barley or/and SoRiTae with rice as the base. Total(TS), rapidly digestible(RDS), slowly digestible(SDS) and resistant(RS) starch fractions were determined. Other physicochemical properties such as moisture, protein, amylose contents, protein digestion in vitro and color values as well as sensory properties of different bap were also investigated. Cooked rice with SoRiTae(RiSo) showed the highest moisture content of 63.9%, whereas other bap showed simillar content ranging from 62.3-63.0%. Crude protein content of RiSo was the highest, while that of cooked rice(Ri) was the lowest(p<0.05). Amylose content of RiBa was the highest, while that of RiSo was the lowest(p<0.05). In in vitro protein digestibility(IVPD), cooked rice with barley and SoRiTae(RiBaSo) was the highest, while Ri was the lowest, showing no significant difference at p<0.05. In starch fractions, as barley or/and SoRiTae were added to rice, a decrease in RDS content and increases in SDS and RS contents were observed. In addition, starch digestion index(SDI), which derived as an indicator of their in vitro starch digestibility and rapidly available glucose(RAG) value, which determined as a predictor of potential glycemic response decreased. A decrease in L value from RiSo and RiBaSo, which comprised of SoRiTae and increases in a and b values in RiSo and RiBa were observed, respectively. All sensory parameters involving color, glossiness, sweet taste, wetness, roughness, hardness and stickiness were shown to be a significant difference except sweet taste among different bap(p<0.05). L value of instrumental characteristic was negatively correlated with color of sensory characteristic and a value was positively correlated. Significant negative correlation was found between RS content and glossiness, however, positive correlation with roughness and hardness, respectively. These results suggested that cooked rice mixed with barley and SoRiTae contain significant RS and SDS contents and may improve diabetes and hyperlipidemia, due to the lowering RDS and RAG, respectively.

• Journal of the Korean Society of Safety
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• v.33 no.3
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• pp.15-20
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• 2018

There have been a number of major fatal fire accidents in Korea recently. The number of fires in 2017 were 44,178, which is not only increasing number of fires but also increasing in casualties. Particularly, the fire at Jecheon Sports Center, which suffered many casualties, is expected to have a huge impact. The cause of the fire has not been determined yet, but heat waves on the ceiling have also been pointed out. As such, the copper heating waves, which are used as a preventive measure against damage of pipes due to freezing of pipes, etc., always have a fire hazard. To determine the possibility of a flame-resistant heated fire, a positive electric cable product was used to artificially ignite and analyze the results. In case of a short circuit, the external covering of the positive electric cable is damaged, but not short circuit unless the heating material surrounding the wire is damaged. Due to the characteristics of heating cable for preventing copper waves, the chances of insulation becoming more severe due to moisture and temperature changes are higher than normal wires. If the internal heating system is carbonized by insulating deterioration without damage to the outer coating, it is likely to cause trekking, to form a winding loop in the heating materials, and to cause short circuit in the heated materials. For the positive temperature line, if the middle is shorted, the current continues to flow to the short circuit unless the breaker disconnects. Consequently, a heated fire that does not cut off the power immediately may leave multiple marks or cuts.

• Research in Plant Disease
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• v.14 no.2
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• pp.85-89
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• 2008

Clubroot of Chinese cabbage, caused by Plasmodiophora brassicae, is one of the most serious plant diseases in the world. The objectives of this study were to investigate the effect of the irrigation times on the development of club root after planting and to evaluate the effect of clubroot disease on yield of chinese cabbage in pot and field. The clubroot disease gradually increased with increasing irrigation frequency after planting. The growth characters and yield of chinese cabbage by irrigation times varied according to soil moisture and clubroot disease severity. Based on marketable yield and control value, an ideal irrigation point was at the soil matric potential of 0.06 MPa. These results suggest that the suppression on clubroot disease development could be achieved by initially reduced irrigation times after planting. Future studies on irrigation times using fungicide treatment and resistant cultivar under natural field conditions are required to improve the control effect of clubroot.

• Fire Science and Engineering
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• v.25 no.3
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• pp.91-98
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• 2011

This study is about fire resistance performance of wood framed lightweight wall including a middle lintel as a traditional wall form in Korea. The target wall is non-loadbearing system which constructed with $38{\times}89$ mm ($2"{\times}4"$) wood frame and fireproof gypsum board covering, including a middle lintel made of $150{\times}150$ mm section glue-laminated timber. As a test results, all specimens have showed fire resistant performance over 90 minutes and tests were maintained until flame occuring on Specimen-l, 2, 3 at 91 min, 97 min and 98 min respectively. Fire resistance of the heat side gypsum board was 45 minutes and charring rate of middle lintel was equivalant with that of usual timber. The wood stud inside wall system showed relatively quick combution characteristic when exposed to high temperature with no temperature rising delaying time caused by moisture evaporation because of the dehydration preceded during the early period of fire side gypsum board resist to heat.

• Preventive Nutrition and Food Science
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• v.21 no.3
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• pp.271-280
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• 2016

The effects of $CO_2$ injection and barrel temperatures on the physiochemical and antioxidant properties of extruded cereals (sorghum, barley, oats, and millet) were studied. Extrusion was carried out using a twin-screw extruder at different barrel temperatures (80, 110, and $140^{\circ}C$), $CO_2$ injection (0 and 500 mL/min), screw speed of 200 rpm, and moisture content of 25%. Extrusion significantly increased the total flavonoid content (TFC) of extruded oats, and ${\beta}$-glucan and protein digestibility (PD) of extruded barley and oats. In contrast, there were significant reductions in 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, PD of extruded sorghum and millet, as well as resistant starch (RS) of extruded sorghum and barley, and total phenolic content (TPC) of all extrudates, except extruded millet. At a barrel temperature of $140^{\circ}C$, TPC in extruded barley was significantly increased, and there was also an increase in DPPH and PD in extruded millet with or without $CO_2$ injection. In contrast, at a barrel temperature of $140^{\circ}C$, the TPC of extruded sorghum decreased, TFC of extruded oats decreased, and at a barrel temperature of $110^{\circ}C$, PD of extruded sorghum without $CO_2$ decreased. Some physical properties [expansion ratio (ER), specific length, piece density, color, and water absorption index] of the extrudates were significantly affected by the increase in barrel temperature. The $CO_2$ injection significantly affected some physical properties (ER, specific length, piece density, water solubility index, and water absorption index), TPC, DPPH, ${\beta}$-glucan, and PD. In conclusion, extruded barley and millet had higher potential for making value added cereal-based foods than the other cereals.