• 대한기계학회논문집A
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• 제25권1호
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• pp.54-60
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• 2001

This study is to investigate the mechanical properties and the fatigue crack propagation of fire resistance steel for frame structure as the chemical composition was changed by addition of N, B and rolled end temperature was varied. We used two kinds of specimen, the one is parallel and the other is perpendicular to the rolling directions. As rolled end temperature increased, volume fraction of ferrite and pearlite decreased, but volume fraction of baintie and grain size increased. Micro-hardness decreased as rolled end temperature increased, but tensile and yield strength increased. Volume fraction of ferrite and pearlite decreased by addition of N. But volume fraction of bainite, tensile and yield strength increased. Microstructure was changed to martensite by addition of B, and tensile and yield strength increased. Fatigue life of TL direction specimen was shorter than that of LT direction specimen. There was no significant effect to fatigue crack propagation rate by addition of N and changing rolling condition, but fatigue life was increased by addition of B.

• 한국약용작물학회지
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• 제18권2호
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• pp.93-97
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• 2010

Cultural practices of Asparagus cochinchinensis in highland area were performed for a potential medicinal crop. These studies were examined to propagation methods, planting densities, nitrogen treatments, and cropping years. The results are summarized as follows. The adequate number of buds per tuberous root was 4 for vegetative propagation because the number of tuberous root harvested was 16.8 and the yield was also the highest, exhibiting 1,060 kg/10a. The suitable planting time for vegetative propagation was later than early April. If the earlier tuberous roots were planted, the less they emerged. The highest emergence rate was obtained from the planting density of $30{\times}20cm$ as 97.2% while the yield was highest in the $30{\times}15cm$ density, exhibiting 1,883 kg/10a with emergence rate at 94.9. It seemed that the higher planting density promoted plant height growth and yield in Asparagus cochinchinensis. The highest fresh weight was recorded at 6 kg/10a of nitrogen fertilizer into the sandy loam soil compared to the level of 0, 3, 9 kg/10a. The yield was increased with cropping years. However, the proper harvesting time was the second year of cultivation because the rate of weight increase was maximized in the 2-year-old tuberous root. The yield in the third year was decreased as compared to that of the second year.

• 한국약용작물학회지
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• 제11권3호
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• pp.224-231
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• 2003

1. 종자형성 계통군의 출현은 흑색 PE 피복, 녹색 PE 피복 및 투명 PE 피복이 무피복보다 각각 1일, 2일 및 3일 빨랐으며, 유식물체형성 계통군의 출현은 흑색 PE 피복, 녹색 PE피복 및 투명 PE피복이 무피복보다 각각 2일, 2일 및 3일 빨랐다. 2. 생근경중은 종자형성계통 군에서 투명 PE 피복이 무피복보다 16.7% 증수하였으며, 유식물체형성 계통 군에서는 녹색 PE 피복 및 투명 PE 피복이 무피복보다 각각29.4%, 26.5% 증수하였다. 3. 메탄올엑스함량은 종자형성 계통 군에서는 투명 PE피복이 42.60%로서 가장 많았으며, 흑색 PE 피복이37.50%로서 무피복보다 많았으나, 유식물체형성 계통군에서는 각처리 모두 무피복과 차이가 없었다. 4.조사포닌 함량은 종자형성 계통군에서는 투명 PE피복이 8.25%로서 무피복, 흑백 PE 피복 및 녹색 PE피복보다는 높았으나, 흑색 PE 피복과는 차이가 없었으며, 유식물체형성 계통군에서는 투명 PE피복이 7.75%로서 흑색 PE 피복이나, 녹색 PE 피복보다 높은 함량을 나타냈으나, 무피복 및 흑백 PE 피복과는 차이가 없었다.

• 한국약용작물학회지
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• 제9권1호
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• pp.55-61
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• 2001

1. 종자형성계통군의 생엽중은 5월30일, 6월30일 및 6월15일 화경제거가 화경무제거 보다 약 $29{\sim}12%$ 무거웠으며, 유식물체형성계통군의 생엽중은 6월15일, 5월30일 및 6월30일 화경제거 순으로 무제거보다 약$21{\sim}4%$ 무거웠다. 2. 종자형성계통군의 생근경중은 5월30일, 6월15일 및 6월30일 화경제거가 화경무제거 보다 약$41{\sim}33%$ 증수하였으며, 유식물체형성계통군의 생근경중은 5월30일 화경제거가 화경무제거 보다 약 3% 증수하였으나, 통계적 유의성은 없었다. 3. 종자형성계통군의 메탄올엑스함량은 5월30일 화경제거와 6월 15일 화경제거가 39.77% 및 39.17%로 6월 30일 화경제거보다 높았으며, 유식물체 형성계통군의 메탄올엑스함량은 처리별 통계적 유의성이 없었다. 4. 종자형성계통군의 조사포닌함량은 5월 30일 화경제거가 7.50%로 무제거 (5.67%)보다 높았으며, 유식물체형성계통군의 조사포닌함량은 처리별 통계적 유의성이 없었다.

• Journal of Welding and Joining
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• 제18권5호
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• pp.33-40
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• 2000

Fatigue crack propagation life of weld toe crack through residual stress field was estimated with Elber's crack concept. Propagation of weld toe crack is heavily influenced by residual stress caused by welding process, so it is essential to take into account the effect of residual stress on the propagation life of weld toe crack. Fatigue crack at transverse and longitudinal weld toe was studied respectively, which represent typical weld joint in ship structure. Numerical and experimental studies are performed for both cases. Residual stress near weldment was estimated through nonlinear thermo-elasto-plastic finite element method, and residual stress intensity factor with Glinka's weight function method. Effective stress intensity factor was calculated with Newman-Forman-de Koning-Henriksen equation which is based on Dugdale strip yield model in estimating crack closure level U at different stress ratio. Calculated crack propagation life coincided well with experimental results.

• 한국작물학회지
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• 제52권2호
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• pp.220-227
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• 2007

Sweetpotato fields in Korea are highly infected with virus and virus like diseases that greatly diminish both yield and quality as indicated by field observations and laboratory tests. In order to solve this problem, there is an urgent need to produce and mass propagate virus-free planting materials for distribution to the farmers. These experiments were conducted, firstly, to determine the most appropriate culture media, nutrient solution, and cutting intervals to maintain growth and vigor of tissue cultured plantleta as mother plants for propagation in insect-proof greenhouse. And as a labor saving method, the production efficiency of plug trays for rapid propagation of stem cuttings as a source of planting materials was likewise evaluated. Results showed that plants grown in medium B supplied with 0.5 and 1.0 strength of MS nutrients had high growth rate, and 20-day cutting interval was the best. 72-plug tray was better than 128-plug. Secondly, it was to develop a technique for the production of first-generation seed roots using hydroponics cultivation system. The yield of virus-free plants propagated in the non-insect proof and open-field cultivation was 2,402 kg/10a, 6% higher than those in the insect-proof cultivation, and the rate of virus re-infection was 18% higher compared to 3.3% with insect-proof cultivation. Lastly, it was to investigate the growth performance of virus free plants in farmers' field. Differences were existed in the yield depending on the variety used, but virus free plants showed an increase of $6{\sim}24%$ over virus infected plants.

• 한국약용작물학회지
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• 제7권3호
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• pp.200-204
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• 1999

토천궁의 줄기마디를 이용한 효율적인 삽목번식 기술을 개발하고자 수행한 시험결과를 요약하면 다음과 같다. 1. 삽목시는 8월30일 $1{\sim}2$마디삽목에서 발근율이 81%로 가장 높았고 발근상태도 양호하였다. 2. 삽수채취에 따른 수량감소는 주당경수의 50%채취에서 9%이하 였으나 100% 채취에서는 $10{\sim}23%$로 비교적 높았다 3. 삽목묘의 포장정식후 활착율은 9월25일 및 10월25일 정식에서 각각 85%, 87%로 높았으나 11월25일 정식에서는 28%로 낮았다. 4. 10a당 수량은 9월25일및, 10월25일 정식에서 각각 127kg, 120kg으로 높았다.

• 펄프종이기술
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• 제31권5호
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• pp.57-72
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• 1999

Traditional theories of the tensile failure of paper have assumed that uniform strain progresses throughout the sheet until an imperfection within the structure causes a catastrophic break. The resistance to tensile elongation is assumed to be elastic , at first, throughout the structure, followed by an overall plastic yield. However, linear image strain analysis (LISA) has demonstrated that the yield in tensile loading of paper is quite non-uniform throughout the structure, Traditional theories have failed to define the flaws that trigger catastrophic failure. It was assumed that a shive or perhaps a low basis weight area filled that role. Studies of the fracture mechanics of paper have typically utilized a well-defined flaw around which yield and failure could be examined . The flaw was a simple razor cut normal to the direction of tensile loading. Such testing is labeled mode I analysis. The included fla in the paper was always normal to the tensile loading direction, never at another orientation . However, shives or low basis weight zones are likely to be at random angular orientations in the sheet. The effects of angular flaws within the tensile test were examined. The strain energy density theory and experimental work demonstrate the change in crack propagation from mode I to mode IIas the initial flaw angle of crack propagation as a function of the initial flaw angle is predicted and experimentally demonstrated.

• Journal of Advanced Marine Engineering and Technology
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• 제32권6호
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• pp.834-840
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• 2008

We carried out fatigue testing with materials of aluminum alloyC7075-T6, 2024-T4) by rotary bending fatigue tester. We investigated fatigue limit, fatigue crack initiation, fatigue crack propagation behavior and possibility of fatigue life prediction to the different small circular hole defect. The summarized result are as follows; Fatigue limit of the smooth specimens were related tensile strength and yield strength. In case of more large applied stress and small circular hole crack defect, the fatigue crack was grown rapidly. The fatigue crack propagation behavior proceed at according to inclusion. Fatigue crack propagation ratio appeared instability and retardation phenomenon in the first half of fatigue life but appeared stability and replied in the latter half. On other hand, this experimental data of the materials are appeared fatigue life predictability.

• 대한기계학회논문집
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• 제10권6호
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• pp.898-905
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• 1986

본 논문에서는 강의 피로균열진전거동과 미시조직과의 관계를 밝히기 위한 연 구의 일환으로 제이상 마르텐사이트 중에 모상 페라이트가 존재하는 복합조직강을 준 비하여 이들 강의 제이상 경도변화에 따른 피로균열진전저항을 균열휨과 균열닫힘을 통하여 검토하였다.