• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.143-148
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• 2002

Recently, to consider economical and constructive aspect, Usage of Admixture, like Blast-Furnace Slag and Fly-Ash, are increased. Blast-Furnace Slag, a by-product of steel industry, have many advantage, to reduce the heat of hydration, increase in ultimate strength and etc. But it also reduces early-age strength, it is prevented from using of Blast-Furnace Slag at cold-weather-concrete. In this study, for the purpose of increasing usage of Blast-Furnace Slag at cold-weather-concrete, it is investigated the strength properties of concrete subjected to time and period of frost damage for early age curing. According to this study, if early age curing is carried out before having frost damage, the strength of concrete, subjected to frost damage, is recovered. And that properties is not connected with the frost cause.

• Journal of the Korea Institute of Building Construction
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• v.17 no.1
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• pp.73-81
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• 2017

In this paper, the periods of cold weather concrete and early frost damage depending on each region in South Korea were studied using the climate data from Korea meteorological administration. The specifications of Korea Concrete Institute(KCI) and Architectural Institute of Japan(AIJ) were applied to provide the periods of cold weather concrete. The periods of early frost damage risk(EFD) were calculated by Hasegawa's suggestion depending on 91 cities in Korea. Climate data for 5 years (2008~2012) were used to obtain both of the periods. Existing data from 1971 to 2000 were also used to compare differences in the periods between past and present study. The periods of cold weather concrete by KCI were calculated about 98 days on average. As the latitude goes up and close to mountain areas, the periods tend to be increased. The periods by present study was shown to be reduced compared to that of previous study by 1~2days. The period of EFD was provided with the level of daily lowest temperature from $-5^{\circ}C$, $-2^{\circ}C$ and $0^{\circ}C$. The beginning day of the period of EFD was earlier than the period of cold weather concrete and the finishing day of the period of EFD was later than the period of cold weather concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.571-574
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• 2000

When fresh concrete is exposed to low temperature, the concrete may suffer from the frost damage at early ages and the strength development may be delayed. To solve such problems of cold weather concreting admixtures called agent for enduring cold climate are developed to prevent the fresh concrete from being frozen at early ages. In this study, the experiments are carried out on several kinds of agent for enduring cold climate to present their performance. According to experimental results, most kinds of agent for enduring cold climate show the strength development in the range $-5^{\circ}C$ of curing temperature, it tends to be delayed at long term maturity without agents for enduring cold climate. while it gains high strength maturity when agents for enduring cold climate is applied.

• Transactions of Materials Processing
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• v.31 no.6
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• pp.376-383
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• 2022

The potential damage region of a WC-Co cemented carbide die is investigated for cold forging process of a wheel-nut by numerical simulation with its chemical composition considered. Numerical simulation is utilized to calculate internal stress, especially for the WC-Co die, during the forging process. Finite element model is established, in which the elasto-plastic properties are applied to the work-piece of bulk steel, and elastic properties are considered for the lower die insert of the WC-Co alloy. This stress analysis enables to distinguish the potential damage regions of the WC-Co die. The regions from calculation are comparatively analyzed along with the crack area observed in the die after repetitive manufacturing. Effect of chemical composition of the WC-Co is also evaluated on characteristics of potential damage region of the die with variance of mechanical properties considered. Derived from Mohr-Coulomb fracture model, furthermore, a new stress index is presented and used for die stress analysis. This index inherently considers hydrostatic pressure and is then capable of deducing wide range of its distribution for representing stress state by modification of its parameter implying pressure sensitivity.

• Journal of Korean Medical classics
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• v.22 no.1
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• pp.103-109
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• 2009

It was described in "Somun Jogyeongron" that Eum(Yin)-Yang' deficiency, excess and exuberance. According to "Somun Jogyeongron", It was known that the syndrome of Yang deficiency and exuberance is belong to external contraction, Eum deficiency and exuberance is belong to internal damage. The syndrome of Yang deficiency is belong to Gyejitang[contraction of wind] which constitutional weakness as the main etiological factor of deficiency conditions. The syndrome of Yang exuberance is belong to Mahwangtang[cold damage] which constitutional strong as the main etiological factor of exuberance conditions. Eum deficiency is so dysfunction of the spleen and stomach that Eum fluid and essence is not engender, distributed. So the dysfunction of spleen and stomach makes dampness-heat obstruction and then makes Internal heat at last. The syndrome of Eum deficiency is applicable to bojungikgitang. As contrasted with Eum deficiency, Eum exuberance is occurred cold-dampness obstruction, which we call 'Eum exuberance'. The syndrome of Yang exuberance is applicable to Ijungtang. In the light of "Somun Jogyongron", We explain that the syndrome of Yin deficiency and Yin exuberance, which was caused by dampness-heat, cold-dampness obstruction and internal damage based on disorder of the spleen and stomach.

• Korean Journal of Environmental Agriculture
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• v.32 no.1
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• pp.55-60
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• 2013

BACKGROUND: The buds of persimmon trees are susceptible to cold damage, often with the late frost, at the time of budburst. This study was conducted to determine effect of the cold damage on shoot and fruit growth the current season. METHODS AND RESULTS: 'Fuyu' trees, grown in 50-L pots, were placed for 1 h at $-2.2{\pm}0.5$, $-2.6{\pm}0.5$, or $-3.0{\pm}0.5^{\circ}C$ within a cold storage, at their budburst on April 5. Some trees under ambient temperature at $10-17^{\circ}C$ served as the control. Cold damage of the buds containing flower buds was 54% at $-2.2^{\circ}C$, and significantly increased to 95% at $-3.0^{\circ}C$. The bud damage included the complete death of all, complete death of main buds only, or the late and deformed shoot growth in the spring. Number of flower buds in early May dramatically decreased as the damage ratio increased. Since the thinning of flower buds in mid-May and fruitlets in early July was done in no or slightly damaged trees, the final number of fruits and yield did not decrease compared with the control when the damage increased by 60% and 70%, respectively. Average fruit weight and skin coloration tended to be better with increasing bud damage. Shoot growth was more vigorous in those trees whose buds were severely damaged by low temperature. CONCLUSION(S): Shoot growth and the yield may depend on the number of flower buds and percent fruit set after the cold damage.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.801-806
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• 2001

In the latest, the construction period became the most important factor in the domestic building works because buildings is higher and larger gradually. Accordingly, cold-weathering concrete constructions are performed more and more. So, the demands of concrete quality management methods are increased in cold-weathering concrete constructions. In this study, the mock-up experiment was performed to correct input data in the kimpo H construction field. Using the results of this experiment, the method of temperature analysis was presented to prevent early aged freezing damage and to control thermal crack in this study.

• Journal of Environmental Science International
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• v.29 no.7
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• pp.773-784
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• 2020

In order to protect the lives and property of citizens, the central and local governments are responding by enacting municipal ordinances and regulations as the frequency of extreme weather conditions due to climate change increases and intensity increases gradually. Accordingly, the basic contents and strategies of domestic and foreign policies to cope with cold and heat waves were reviewed, referring to measures suitable for application to the Daegu metropolitan area. In addition, it is intended to provide a policy alternative to Daegu metropolitan area to minimize damage from extreme weather by identifying the current status, characteristics, and future prospects of extreme weather in Daegu metropolitan area. Since the damage caused by the cold wave in Daegu area is not as great as that of other regions, it is urgent to come up with cold wave measures for the health and transportation sectors, and to come up with measures against the heat wave as the damage caused by the heat wave is the most serious in the country. Also we will identify spatial characteristics so that the districts and counties with high vulnerability to extreme weather can be identified and implemented first, and present civic life-oriented facilities and civic action guidelines to overcome cold and heat waves.

• Transactions of Materials Processing
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• v.32 no.6
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• pp.335-343
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• 2023

Spur Gear parts for automobile actuators using existing former forging technology were produced in a total of three processes on a former forging machine. However, in order to improve cost increase due to frequent mold breakage, Spur Gear parts were designed and manufactured in the cold forging process after forming the preform through former forging. In other words, in the existing former forging mold, product seating defects occurred due to horizontal movement, resulting in many product defects and mold damage, so there was an urgent need to improve mold life and product defects. In order to improve this, we tried to improve the mold life by improving the existing 3 former forging processes to a former forging process and 2 cold forging processes. Therefore, We developed Spur Gear parts for automobile actuators were developed by applying precision cold forging technology through a former forging process and 2 cold forging processes to improve mold life.

• Korean Journal of Exercise Nutrition
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• v.23 no.1
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• pp.48-54
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• 2019

[Purpose] The combined effect of different types of post-exercise treatment has not been fully explored. We investigated the effect of combined cold water immersion (CWI) and compression garment (CG) use after maximal eccentric exercise on maximal muscle strength, indirect muscle damage markers in the blood, muscle thickness, and muscle soreness score 24 h after exercise. [Methods] Ten men performed two trials (CWI + CG and CON) in random order. In the CWI + CG trial, the subjects performed 15 min of CWI (15℃), followed by wearing of a lower-body CG for 24 h after exercise. In the CON trial, there was no post-exercise treatment. The exercise consisted of 6 × 10 maximal isokinetic (60°·s^-1) eccentric knee extensions using one lower limb. The maximal voluntary contraction (MVC) and maximal isokinetic (60°·s^-1) strength during knee extension, as well as the indirect muscle damage markers, were evaluated before exercise and 24 h after exercise. [Results] The maximal muscle strength decreased in both trials (p < 0.001), with no difference between them. The exercise-induced elevation in the myoglobin concentration tended to be lower in the CWI + CG trial than in the CON trial (p = 0.060). The difference in the MVC, maximal isokinetic strength, muscle thickness, and muscle soreness score between the trials was not significant. [Conclusion] CWI followed by wearing of a CG after maximal eccentric exercise tended to attenuate the exercise-induced elevation of indirect muscle damage markers in the blood.