• 한국수산과학회지
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• 제16권4호
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• pp.410-412
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• 1983

On maturation of abalone KIKUCHI'S concept of accumulative temperature expressed ${\Sigma}(t_i-{\theta})$ have been apply importantly for an anniversary spawning of the animals. In case of Haliotis discus hannai he was formulated ${\Sigma}(t_i-7.6)>1300$. This expression is able to modify by UKI'S the relationship between the daily feeding rate ($\%$) (Y) ana temperature ($^{\circ}C$) (t) expressed Y= 0.4291 t-0.1501. The modified expression is as the formula ${\Sigma}(Y-3.05)>570$. And the concept its meaning involves is replaced with accumulative ingestion instead of accumulative temperature. This modified concept is understood that on maturation of abalone temperature decide on satiation level, food ingestion decide on gonad maturity rate.

• 한국약용작물학회지
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• 제17권6호
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• pp.458-463
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• 2009

This study was conducted to find out some conditions for optimum cultivation of Angelica gigas Nakai by the investigation of root yield and decursin content from different seeding sizes and accumulative temperature. Accumulative temperature from April to October was $4,309^{\circ}C$ on altitude 100 m, $4,242^{\circ}C$ on 250 m, $3,662^{\circ}C$ on 530 m, $3,435^{\circ}C$ on 730 m, and altitude 530~730 m was less $650{\sim}870^{\circ}C$ than altitude 100 m cultivation areas of A. gigas. Seedling stand rate was increased from 86.4% to more than 90% as accumulative temperature decreases, and was increased in above 7 mm of seedling size, and 10% in non-mulching more than PE film mulching. Yield was increased as accumulative temperature decreases and in PE film mulching as 310.2 kg/10a. Also, Yield was increased in 7~9 mm than seedling diameter 5~7 mm as 313.0 kg/10a. Decursin content of primary roots was increased as altitude rises, ie, as 2.55% on altitude 100 m, 3.33% on 250 m, 5.51% on 530 m, and 6.24% on 730 m. Decursinol angelate content appeared little than decursin content as 1.08% on altitude 100 m, 1.37% on 250 m, 1.99% on 530 m, 2.38% on 730 m, and as altitude was heightened, content was increased.

• The Korean Journal of Ecology
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• 제26권4호
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• pp.203-208
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• 2003

Losses in the dry weight of leaf litter from six tree species were studied during 16 months on the forest floor in temperate deciduous forest of Mt. Cheonma in the vicinity of Seoul in Korea by using litter bag method. The decomposition rate of each leaf litter varies with each species. After 16 months elapsed, the leaf litter of Acer pseudo-sieboidianum showed the highest decomposition constant (0.82) as Olson´s decomposition constant, while that of Pinus densiflora showed the lowest decomposition constant (0.33). The decomposition constant of Quercus mongolica, Q. serrata, Betula ermani and Carpinus laxiflora showed 0.43, 0.37, 0.66 and 0.75, respectively. The decomposition constant of leaf litter was considered with temperature and precipitation which accumulated daily during each term of litter bag collection. The decomposition constant of leaf litter showed closely positive correlation with daily accumulative temperature and precipitation. The relationships between decomposition constant and the daily accumulative temperature and precipitation at each period of litter bag collection were analyzed through multi-regression analysis. The correlation coefficients as a result of multi-regression analysis in Q. mongolica, Q. serrata, P densiflora, B. ermani, C. laxiflorais and A. pseudo-sieboldianum were 0.83, 0.81, 0.69, 0.77, 0.77 and 0.62, respectively. The precipitation showed higher effect, about 10 times, on the leaf litter decomposition than the daily accumulative temperature.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 춘계학술대회논문집
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• pp.84-87
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• 2003

Microstructural evolution and dry sliding wear behavior of ultra-fine grained 5052 Al alloy obtained by an accumulative roll-bonding process have been investigated. After 7 ARB cycles, ultra-fine grains with large misorientations between neighboring grains were obtained. The grain size was about 0.2$\mu\textrm{m}$. The hardness, tensile and yield strengths of the ultra-fine grained alloy increased as the amount of accumulated strain increased with the ARB cycles. Sliding wear teats of the ultra-fine grained 5052 Al alloy were conducted at room temperature. Wear rate of the ultra-fine grained alloy increased in spite of the increase of hardness. Surfaces of the worn specimens were examined with SEM to investigate wear mechanism of the ultra-fine grained alloy.

• 소성∙가공
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• 제12권4호
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• pp.376-381
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• 2003

Microstructural evolution and dry sliding wear behavior of ultra-fine grained 5052 Al alloy obtained by an accumulative roll-bonding process have been investigated. After 7 ARB cycles, ultra-fine grains with a large misorientation between neighboring grains were obtained. The grain size was about 0.2 $\mu$m. The hardness, tensile and yield strengths of the ultra-fine grained alloy increased as the amount of accumulated strain increased with the ARB cycles. Sliding wear tests of the ultra-fine grained 5052 Al alloy were conducted at room temperature. Wear rate of the ultra-fine grained alloy increased in spite of the increase of hardness. Surface of the worn specimens were examined with SEM to investigate wear mechanism of the ultra-fine grained alloy.

• 한국분말재료학회지
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• 제12권1호
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• pp.30-35
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• 2005

An aluminum powder compact consolidated by a powder-in sheath rolling (PSR) method was severely deformed by accumulative roll-bonding (ARB) process. The ARB process was performed up to 8 cycles at ambient temperature without lubrication. Optical microscope and transmission electron microscope observations revealed that microstructure of the ARB-processed Al powder compact is inhomogeneous in the thickness direction. The ultra-fine subgrains often reported in the ARB-processed bulky materials were also developed near surface of the Al powder compacts in this study. Tensile strength of the ARB-processed Al powder compact increased at the 1st cycle, but from the 2nd cycle it rather decreased slightly.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2013년도 춘계 학술논문 발표대회
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• pp.75-77
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• 2013

In this study, the characteristics of temperature history was evaluated for three hot wires with different capacity installed in slab concrete which are relatively thin. Results can be summarized as follows. First, for the case of material using 5W hot wire, all decreased to below zero at or around 24 hours. Similarly, the material using 20W hot wire decreased to 2℃ below zero at or around 80 hours but satisfied the accumulative temperature of 45° D·D at 7 days of material age. On the other hand, the case of 30W hot wire, the biggest capacity, showed the high temperature history of 5℃ in average at all areas except the corners. Thus, the target accumulative temperature was secured at or around the 3 days of material age. Considering the above, the initial damage by freezing can be prevented only if 20W or higher hot wires are used for the slabs at -10℃ of extremely low temperature environment.

• 한국재료학회지
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• 제21권12호
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• pp.655-659
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• 2011

An ultrafine grained complex aluminum alloy was fabricated by an accumulative roll-bonding (ARB) process using dissimilar aluminum alloys of AA1050 and AA5052 and subsequently annealed. A two-layer stack ARB process was performed up to six cycles without lubricant at an ambient temperature. In the ARB process, the dissimilar aluminum alloys, AA1050 and AA5052, with the same dimensions were stacked on each other after surface treatment, rolled to the thickness reduction of 50%, and then cut in half length by a shearing machine. The same procedure was repeated up to six cycles. A sound complex aluminum alloy sheet was fabricated by the ARB process, and then subsequently annealed for 0.5h at various temperatures ranging from 100 to $350^{\circ}C$. The tensile strength decreased largely with an increasing annealing temperature, especially at temperatures of 150 to $250^{\circ}C$. However, above $250^{\circ}C$ it hardly decreased even when the annealing temperature was increased. On the other hand, the total elongation increased greatly above $250^{\circ}C$. The hardness exhibited inhomogeneous distribution in the thickness direction of the specimens annealed at relatively low temperatures, however it had a homogeneous distribution in specimens annealed at high temperatures.

• 한국재료학회지
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• 제15권4호
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• pp.240-245
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• 2005

An oxygen free copper was severely deformed by accumulative roll-bonding (ARB) process for improvement of its mechanical properties. Two copper sheets 1 m thick, 30 mm wide and 300 m long are first degreased and wire-brushed for sound bonding. The sheets are then stacked to each other, and roll-bonded by about $50\%$ reduction rolling without lubrication at ambient temperature. The bonded sheet is then cut to the two pieces of same dimensions and the same procedure was repeated to the sheets up to eight cycles $(\varepsilon-6.4)$. TEM observation revealed that ultrafine grains were developed after the third cycle, and their size was slightly increased at higher cycles. Tensile strength of the copper increased with the strain at low strain levels, but it hardly increased from 3 cycles $(\varepsilon>2.4)$ due to occurrence of dynamic recovery, even if the imposed strain increased.

• 한국재료학회지
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• 제16권9호
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• pp.592-597
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• 2006

A deoxidized low-phosphorous (DLP) copper was processed by accumulative roll-bonding (ARB) for ultra grain refinement and high strengthening. Two copper sheets 1 mm thick, 30 mm wide and 300 mm long are first degreased and wire-brushed for sound bonding. The sheets are then stacked to each other, and roll-bonded by about 50% reduction rolling without lubrication at ambient temperature. The bonded sheet is then cut to the two pieces of same dimensions and the same procedure was repeated to the sheets up to eight cycles (${\varepsilon}{\sim}6.3$). TEM observation revealed that ultrafine grains were developed after the 4th cycle, and their size decreased at higher cycles. Tensile strength of the copper increased with the equivalent strain, and it reached 547 MPa which was 3 times higher than that of the initial material. It is concluded that the ARB process is an effective method for high strengthening of the DLP copper.