• 한국안전학회지
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• 제9권3호
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• pp.22-27
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• 1994

For the $\beta$=1 specimen with constant thickness, Crack growth rate is smoothly increasing in the a-N curve. On the other hand for $\beta$=2 specimen with various thickness, the inflection point is observed in crack growth rate near the thickness interface. da/dN before the inflection point is increased, and da/dN after the point is decreased, compared to the $\beta$=1 specimen. da/dN near the thickness interface is approached zero. The descending point was observed earlier as $\beta$ increased. Considering the relation between da/dN and λ, the crack propagation rates for the case of $\beta$ =1 incrased almost linearly, however, the crack propagation rates for $\beta$=2,3 decreased more rapidly near the thickness interface. Additionally, the decreased point in da/dN for $\beta$=3 is farther from the thickness interface than the case for $\beta$ =2.

• 한국주조공학회지
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• 제17권2호
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• pp.188-194
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• 1997

The effects of solidification condition and vibration on structure refinement were investigated for unidirectionally solidified $Al-CuAl_2$ eutectic composites. Eutectic composites were unidirectionally solidified under vibration with different growth rates (R) and thermal gradient(G). The lamellar structure was varied according to growth condition (G/R ratio). For the structure refinement the effect of G/R was found out to be greater than that of vibration. The interlamellar spacing(${\lambda}$) in this materials was varied with the growth rates(R) with "${\lambda}^2R$=Constant" relationship.

• 대한가정학회지
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• 제20권2호
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• pp.103-111
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• 1982

This study was designed to observe the effects of nutritional supplementation of general Korean diet on calcium metabolism and bone growth in rats. The results were summarized as follows. 1. The bone weight and the concentration of ash and calcium in femurs tended to be increased by calcium supplementation. It seemed that supplemental calcium feeding promoted bone calcification through increasing the amount of calcium retained in the body. 2. There were no differences in calcium absorption rates, retention rates in the body, urinary excretion, and serum calcium concentration, between calcium supplemented groups and the other cereal-vegetable groups. 3. The casein, vitamin B2, or vitamin A supplementation of cereal-vegetable diets did not have any significant effects on calcium metabolism and bone growth.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1996년도 춘계학술대회 논문집
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• pp.165-169
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• 1996

In this study residual stress in weldment was considered about the effect on the fatigue propagation and about the effect of redistribution of residual stress. Then, fatigue tests were conducted by the center notched specimens machined with welded plate. The residual stress and its redistribution after the crack growth were measured by the magnetizing stress indicator and hole-drilling method. Fatigue crack propagation was estimated by the specimens having residual stress redistributed after the cracks growth and having the effects of crack closure. Crack growth rates were predicted and compared with experimental results. It had been found that the predicted crack propagation rates have a good agreement with experimental results when the redistribution of residual stress was considerd.

• Composites Research
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• 제12권3호
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• pp.1-7
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• 1999

Al2024-T3 판재에 카본/에폭시(carbon/epoxy) 라미네이트를 섬유배열 방향 $0^{\circ}$/$90^{\circ}$ 및 $\pm$$45^{\circ}$로 2 Plies 보강하여 CPAL(Carbon Patched ALuminum alloy)재를 제작하고, 응력비 R=0.2, 0.5에서 피로균열전파 실험을 실시하였다. X-Ray와 초음파 C-Scan 장비를 이용하여 A/2024-T3 판재의 균열과 CFRP 라미네이트 박리 거동을 조사하여 피로균열 지연 거동과 지연기구(mechanism)를 연구하였다. A/2024-T3 시험편에 비해서 CPAL 시험편은 피로균열전파속도가 현저하게 지연되었으며, 지연 정도는 $0^{\circ}$/$90^{\circ}$ CPAL이 $\pm$$45^{\circ}$ CPAL 시험편보다 크고, 응력비 R=0.2에서 응력비 R=0.5보다 크게 나타났다. CPAL 시험편의 피로균열 지연 효과는 균열후방의 박리 및 비박리 CFRP 라미네이트가 A/2024-T3 판재의 균열열림(COD)을 감소시키는 균열브리징미케니즘(crack bridging medhanism) 때문에 발생함을 확인하였다.

• 환경생물
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• 제21권1호
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• pp.66-71
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• 2003

곤쟁이, Neomysis awatschensis의 염분 내성을 파악하기 위하여 40일동안 다양한 염분에 노출시켜 생존, 성장 및 산소소비율에 미치는 염분의 영향을 조사하였다. 생존율은 6.7$\textperthousand$ 이하의 염분에서 40일 이후 현저하게 감소하였다. 곤쟁이의 체장과 일간 성장률도 40일 이후, 6.7$\textperthousand$이하의 염분에서 10.1% 이상의 염분 농도구와 비교해 현저히 감소하였다. 산소소비율은 40일 동안 10.1~33.6$\textperthousand$에 노출된 곤쟁이의 경우에는 염분처리 전과 비교해 큰 변화를 나타내지 않았지만, 6.7$\textperthousand$ 이하에 노출된 곤쟁이의 산소소비율은 현저하게 감소하였다. 이상의 결과는 6.7$\textperthousand$ 이하의 낮은 염분 농도에서는 곤쟁이의 생존, 성장 및 산소소비율이 감소한다는 것을 나타내고 있으며, 하구나 연안지역에서 염분이 6.7$\textperthousand$ 이하로 낮아질 경우에 서식하는 곤쟁이의 자연 사망률에 잠재적으로 영향을 미칠 수 있다는 것을 암시한다.

• 한국양식학회지
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• 제7권1호
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• pp.9-20
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• 1994

전복을 육상에서 사육하기 위한 시설형태 및 적절한 사육밀도의 구명을 위해 수조형태 및 수용밀도별 사육실험을 한 결과 1. 수조형태, 단별에 따른 성장과 생존율의 차리는 인정되지 않았고, 유수식과 순환식사육의 비교에서는 유수식의 성장도와 생존율이 좋았다. 2. 수조단수별 (3단)에 따른 성장과 생존율의 차이가 인정되지 않아 동일량의 사육수로 단위면적 당 3배의 생산이 가능하였다. 3. 밀도별실험에서 $1000-2000마리/m^2$로 수용한 각장 약 20mm치패는 수용밀도에 따른 성장 차가 없었지만, 각각 200-600, 100-300마리의 밀도로 수용한 각장 약 40mm와 50mm의 치패는 수용밀도가 낮을수록 성장이 빨랐다. 4. 일간섭식률과 사료전환효율은 밀도가 낮을수록 높았고, 치패 크기가 작을수록 높았다

• Fisheries and Aquatic Sciences
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• 제14권4호
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• pp.323-332
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• 2011

To find seasonally optimal microalgae for mass culture of the rotifer Brachionus plicatilis, the growth rates of 12 microalgal species (two marine Chlorella spp., five marine Nannochloris spp., two marine Nannochloropsis spp., one estuarine Nannochloropsis sp., and two estuarine Chlorella spp.) were compared at $25^{\circ}C$ at 15 psu and 30 psu. Among these, six species showing high growth rates were chosen and examined again at high ($30^{\circ}C$ and $32^{\circ}C$) and low ($10^{\circ}C$) temperatures. Their amino and fatty acids and the dietary value of the rotifers that fed on each microalgal species were examined. Nannochloris sp. (KMMCC-119) and Chlorella vulgaris (KMMCC-120) showed the highest growth rates at temperatures over $30^{\circ}C$ and at $10^{\circ}C$, respectively. The growth rate of Nannochloris was higher than those of Chlorella and Nannochloropsis at high temperatures, but lower than those of the latter at low temperatures. The growth rate of rotifers fed on Nannochloropsis was highest and that of those fed on Chlorella was lowest. Levels of eicosapentaenoic acid and docosahexaenoic acid were highest in Nannochloropsis and lowest in Nannochloris. However, total amino acid content was highest in Nannochloris and lowest in Chlorella. In conclusion, Nannochloropsis sp. (KMMCC-33) was the best microalgal species for the mass culture of the rotifer. However, during high- or low-temperature seasons in which Nannochloropsis does not grow well, Nannochloris spp. (KMMCC-119, 395) and C. vulgaris (KMMCC-120) would adequately replace Nannochloropsis sp. (KMMCC-33).

• 대한환경공학회지
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• 제34권9호
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• pp.630-636
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• 2012

본 연구는 해양미세조류 Dunaliella salina을 LED 광원을 이용하여 배양한 연구로 배양에 필요한 최적의 파장, 광도, 공기공급속도 및 배양온도를 찾기 위하여 수행되었다. 낮은 배양온도에서보다는 높은 온도에서 성장이 빨랐으나, 본 실험에서는 $22^{\circ}C$에서 가장 잘 성장하는 것으로 확인되었다. LED 파장에 따른 성장실험에서는 백색 LED가 배양에 가장 효과적이었으며, 광도에 따른 실험에서는 실험 시 고려한 3가지 광도 중(3,000, 6,300, 8,000 Lux) 3,000 Lux에서 최대 세포농도인 1.30 g/L를 나타내었다. 공기공급속도의 증가는 Dunaliella salina의 성장속도와 반비례의 관계를 나타내었는데, 공기를 공급하지 않은 경우의 비증식속도 $1.12day^{-1}$와 비교하면 공기공급은 본 미세조류의 성장에 저해요인으로 작용함을 알 수 있었다.

• ALGAE
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• 제35권1호
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• pp.61-78
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• 2020

Species belonging to the dinoflagellate genus Prorocentrum are known to cause red tides or harmful algal blooms. To understand the dynamics of a Prorocentrum sp., its growth and mortality due to predation need to be assessed. However, there are only a few Prorocentrum spp. for which heterotrophic protist predators have been reported. We explored feeding by the common heterotrophic dinoflagellates Gyrodinium dominans, Oxyrrhis marina, Pfiesteria piscicida, Oblea rotunda, and Polykrikos kofoidii and the naked ciliate Strombidinopsis sp. (approx. 90 ㎛ cell length) on the planktonic species Prorocentrum triestinum, P. cordatum, P. donghaiense, P. rhathymum, and P. micans as well as the benthic species P. lima and P. hoffmannianum. All heterotrophic protists tested were able to feed on the planktonic prey species. However, O. marina and O. rotunda did not feed on P. lima and P. hoffmannianum, while G. dominans, P. kofoidii, and Strombidinopsis sp. did. The growth and ingestion rates of G. dominans and P. kofoidii on one of the seven Prorocentrum spp. were significantly different from those on other prey species. G. dominans showed the top three highest growth rates when it fed on P. triestinum, P. cordatum, and P. donghaiense, however, P. kofoidii had negative growth rates when fed on these three prey species. In contrast, P. kofoidii had a positive growth rate only when fed on P. hoffmannianum. This differential feeding on Prorocentrum spp. between G. dominans and P. kofoidii may provide different ecological niches and reduce competition between these two common heterotrophic protist predators.