• Transactions of Materials Processing
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• v.31 no.4
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• pp.186-193
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• 2022

The application of UHSS sheet is being expanded up to 50% to reduce the weight of automobiles and improve safety. However, due to the high strength and low elongation of the ultra-high tensile strength steel sheet, product defects such as spring back and mold defects such as cracks and chippings also occur. In this study, Pin/Ring on Disc and Spiral wear tests were conducted to evaluate the durability of Ti/Cr-coated molds for forming 1.2GPa grade UHSS sheets. Component analysis and thickness were measured for each coating layer, and hardness and adhesion were investigated to determine mechanical properties. Combining the results of various wear tests, it was found that the TiAlN coating had the best wear and sticking resistance.

• Korean Journal of Agricultural Science
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• v.50 no.3
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• pp.365-371
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• 2023

This experiment was carried out to breed a medium maturing variety of Italian ryegrass (Lolium multiflorum Lam.) in Grassland and Forage Crops Division, National Institute of Animal Science, Rural Development Administration (RDA), Cheonan from 2019 to 2020. An Italian ryegrass variety, IR 604 is a tetraploid variety with green in leaf color and has half-erect growth habit in late autumn and erect growth habit in early spring, IR 604 was on May 17 in heading date as a medium maturing variety. Also, IR 604 was longer by 11 cm in flag leaf length and longer by 1.3 cm in plant height than those of the control variety, Kowinner, respectively. IR 604 was also thicker by 1.0 mm in stem thickness and strong in winter hardness. Dry matter (DM) yield (11,036 kg/ha) of IR 604 was 16.6% higher than that of Kowinner. Total digestible nutrient (TDN), crude protein (CP) and relative feed value (RFV) of IR 604 were 60.4, 13.8% and 100.6 which are 1.4, 3.3%, 7.7 higher than those of Kowinner, respectively. Acid detergent fiber (ADF) and neutral detergent fiber (NDF) of IR 604 were 35.5 and 56.7% which are 1.3 and 3.6% lower than those of Kowinner, respectively.

• Korean Journal of Soil Science and Fertilizer
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• v.30 no.2
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• pp.140-145
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• 1997

The change of physico-chemical properties of paddy soil was monitored under different tillage. This study was conducted on Jeonbug silty cly loam, in Honam Agricultural Experiment Station, for four years starting from 1992. Different tillage involved (1)Continued no tillage, (2)Rotavation only with tractor every year, (3)Spring plowing with power tiller plus rotavation with tractor every year. The result of this study can be summarized as: Non tillage, when continued for some years, tended to increase 1)the hardness of soil, 2)the root density in the top soil, 3)the occurrence of annual and perennial weeds, and tended to lower the yield of rice compared to normal tillage(tilling with ow tiller in the spring plus rotavation by tractor before planting.

• Journal of Sericultural and Entomological Science
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• v.38 no.2
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• pp.93-99
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• 1996

By treatment(dropping) of 0.1~0.4% colchicine solution on the sprouts of winter buds of hard wood cutting slips for 4~5 days, two lines of artificial autotetraploids from Yongchonppong and one line from Yeongbyonppong were bred and the important cultivative characteristics of those new lines were as follows. The greentip sprouting stage of the new bred lines in spring season is later than the parental varieties by two days, but growth speed of the new lines after sprouting was faster than that of the parental varieties reaching the same level development with the parental varieties at the fifth leaf sprouting stage to be mid varieties same as the origins. The leaf shape of the new bred lines was wide round and the petioloes were long and thick. The thickness of leaf was thicker than the parental varieties by 17-33% and single leaf weight was heavy. The leaf area weight increased by 21-31% and the content of chlorophyll was also higher by 11-33%. With all the characteristics, the new breds produced good quality of leaves. The length and number of branches were shorter and less, respectively, than the parental varieties, but the internode length was either same or longer than the parents. Looking at the characteristics, the constitution of shoots was slightly inferior to the parental varieties. The cold hardness expressed by the death top rate of Sawonppong 23 and Sawonppong 24 was same level as that of Yongchonppong, but Sawonppong 25 was stronger than Yeongbyonppong in it with a high infection rate of dwarf disease. The productivity was lower than the parental varieties, but young shoot rate to shoot and branch and the ratio of leaf to young shoot were higher than the parental varieties. The fertility of Sawonppong 23 and Sawonppong 24 was comparatively high with 62% of cross success, but that of Sawonppong 25 was low with 23.9% of cross success.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.6
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• pp.108-115
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• 2008

The wear on engine valve and seat insert is one of the most important factors affecting engine performance. The engine valve and seat insert must be able to withstand the severe environment that is created by: high temperature exhaust gases generated while the engine is running, rapid movement of the valve spring, high pressure generated in the explosive process. In order to study such problems, a simulator has been developed to generate and control high temperatures and various speeds during motion. The wear simulator is considered to be a valid simulation of the engine valve and seat insert wear process with various speeds during engine activity. This work focused on the test of various degrees of wear on four different exhaust valve materials such as HRV40, HRV40-FNV (face nitrided valve), STL #32, STL #6,. Throughout all tests performed in this study, the outer surface temperature of the seat insert was controlled at $350^{\circ}C$, the cycle number was $4.0{\times}10^6$, the test load was 6860 N, the fuel was LPG the test speed was 20 Hz (2400 RPM) and the seat insert material was HVS1-2. The mean (standard deviation) maximum roughness of the exhaust valve and seat insert was $25.44\;(3.16)\;{\mu}m$ and $27.53\;(3.60)\;{\mu}m$ at the HRV40, $21.58\;(2.38)\;{\mu}m$ and $25.94\;(3.07)\;{\mu}m$ at the HRV40-FNV, $36.73\;(8.98)\;{\mu}m$ and $61.38\;(7.84)\;{\mu}m$ at the STL #32, $73.64\;(23.80)\;{\mu}m$ and $60.80\;(13.49)\;{\mu}m$ at the STL #6, respectively. It was discovered that the maximum roughness of exhaust valve was lower as the high temperature hardness of the valve material was higher under the same test conditions such as temperature, test speed, cycle number, test load and seat insert material. The set of the HRV40-FNV exhaust valve and the HVS1-2 seat insert showed the best wear resistance.

• Korean Journal of Applied Biomechanics
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• v.25 no.4
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• pp.465-474
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• 2015

Objective : A study and development of Korean Bobsleigh athletes's shoe which considers their physical condition has yet to be completed. So this study examines the effects of running shoes used by athletes based on plantar pressure and sprint time in order to provide raw data for the development of bobsleigh shoes suitable for Koreans. Method : The study selected seven bobsleigh athletes as subjects and selected three pairs of spiked running shoes from three companies, which will be referred to as Company N (Type A), Company A (Type B), and Company M (Type C). To analyze sprint time and plantar pressure for each shoe, the subject of the study were instructed to wear the selected shoes and to drag a sled at maximum sprint for 15 meters for 15 meters for in each condition that would be in real bobsleigh competitions. Results : The average sprint intervals for each athlete in each pair of shoes revealed Type C produce the fastest sprint in the order of Type C < Type A< Type B. Shoe Type C also had the largest contact area in order of Type C > Type B > Type A (p<.01). None of the three shoe types seem to yield a distinct advantage in terms of maximum average pressure or maximum pressure. Conclusion : In the future, functional analysis should be carried out by comparing the material properties, hardness, and toe spring of shoes based on the Type C shoe from Company M in order to develop bobsleigh shoes suitable for Koreans.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.64-64
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• 2009

Atomic force microscopy (AFM) fabrication of oxide patterns is an attractive technique for nanoscale patterns and related device structures, SiC exhibits good performance in high-power, high-frequency, and high-temperature conditions that is comparable to the performance of Si. The AFM fabrication of oxide patterns on SiC is important for electronic applications. However, there has not been much reported investigations on oxidation of SiC using AFM. We achieved the local oxidation of 4H-SiC using the high loading force of ~100 nN, although the oxidation of SiC is generally difficult mainly due to the physical hardness and chemical inactivity. All the experiments were performed using atomic force microscopy (S.I.S. GmbH, Germany) with a Pt/Ir-coated Si tip at ~40% humidity and room temperature. The spring constant and resonance frequency of the tip were around ~3 N/m and ~70 kHz. We fabricated oxide patterns on n-type 4H-SiC ($\sim10^{19}/cm^3$) and n-type Si ($\sim1.9\times10^{16}/cm^3$). In summary, we demonstrated that the oxide patterns can be obtained over the electric field of ${\sim}\times10^7 V/cm$ and the high loading force using the tip as a cathode. The electric field transports the oxyanions (OH-) to the positively biased surface.

• Journal of Preventive Medicine and Public Health
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• v.7 no.2
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• pp.327-332
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• 1974

Wells are perticularly able to be a source of water-borne infections disease in the army society. Owing to untreated drinking water, high indidence of water-borne diseases are encounted in Korea. This study was carried out to evaluate the physicochemical and bacteriological states of 298 wells in army camps around Daegu city during a year from January to November, 1974. Main findings are summerized as follows: 1. Turbidity, Colorness & odor was within normal range in all samples. 2. Reaction of pH, cnsumption of KMnO4, total hardness and chlorine ion as over almost within normal range. 3. Free Ammonia was detected to 33.2% positive, and nitrite, 45.5% positive. 4. In the bacteriological test 40.3% of all samples were over the standard limit on E. Coli. 5. In comparison of nitrate and E. Coli detection, 60.1% of nitrite was over the standard limit out of the positive cases detected E. Coli. and all of E. Coli were over the standard limit out of the positive cases of nitrite. 6. The contamination was very remarkable in the spring and summer, and very diminished in the autumn and winter.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.5 no.1
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• pp.8-18
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• 2002

This research was conducted to establish the conservation strategy of stream water quality by analyzing the factors influenced on stream water quality in the northeastern part of Mt. Bughansan National Park from July 1998 to October 2001. The number of visitors resulted in the significant increase of electrical conductivity, which affected on pollution of the stream water quality. According to the multiple regression analysis, the pH of the stream water was related to dissolved oxygen and temperature of water at the 1% significant level. The electrical conductivity of the stream water was related to number of visitors, amount of $K^+$ and ${NO_3}^-$, total amount of ions, percentages of $Cl^-$ and $Na^+$ caused by solifluction soil at the 1% significant level. The anions($Cl^-$, ${NO_3}^-$ and ${SO_4}^{2-}$) of the stream water were related to number of visitors, electrical conductivity, air temperature, hardness, amount of ${NO_3}^-$, ${SO_4}^{2-}$, total ions, percentage of $Cl^-$, ${NO_3}^-$, ${SO_4}^{2-}$, amount of $Ca^{2+}$ caused by solifluction soil at the 1% significant level. To prevent the pollution of stream water in the northeastern part of Mt. Bughansan National Park, it is recommended that the number of visitors in the park should be managed and rehabilitated rapidly by measure to eco-friendly during the spring season.

• Journal of the Korean Society of Food Science and Nutrition
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• v.32 no.1
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• pp.62-66
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• 2003

Mass consumption of the surplus onion in the period of harvesting season by processing to various value-added functional food products would be one of the counterplot for stable market. This study was to develop functional sponge cakes with addition of onion powder, using physiochemical properties and sensory evaluation. The specific gravity and viscosity tended to increase according to the addition of onion powder. The water content was highest mark on the 4% onion powder added-cake. The color of lightness, yellowness, and redness of cake crust tended to decrease with the addition of onion powder. The addition of onion powder showed decrease in lightness and yellowness and increase in redness of cake crumb. The specific loaf volume was superior with the addition of 4% onion powder. The resilience, fracturability and adhesiveness showed a difference from the control. Sensory evaluation of cake indicated that addition of onion powder especially at the level of 2, 4%, enhanced appearance flavor, mouth feeling, and overall acceptability.