• Advances in materials Research
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• 제3권3호
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• pp.163-174
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• 2014

In this study, fatigue properties and crack growth characteristics of a polycarbonate (PC) were examined during cyclic loading at various mean stress (${\sigma}_{amp}$) and stress amplitude (${\sigma}_{mean}$) conditions. Different S vs. N and da/dN vs. ${\Delta}K$ relations were obtained depending on the loading condition. The higher fatigue strength and the higher resistance of crack growth are seen for the PC samples cyclically loaded at the higher mean stress and lower stress amplitude due to the low crack driving force. Non-linear S - N relationship was detected in the examination of the fatigue properties with changing the mean stress. This is attributed to the different crack growth rate (longer fatigue life): the sample loaded at the high mean stress with lower stress amplitude. Even if the higher stress amplitude, the low fatigue properties are obtained for the sample loaded at the higher mean stress. This was due to the accumulated strain energy to the sample, where severe plastic deformation occurs instead of crack growth (plasticity-induced crack closure). Shear bands and discontinuous crack growth band (DGB) are observed clearly on the fracture surfaces of the sample cyclically loaded at the high stress amplitude, where the lower the ${\sigma}_{mean}$, the narrower the shear band and DGB. On the other hand, final fracture occurred instantly immediately after the short crack growth occurs in the PC sample loaded at the high mean with the low ${\sigma}_{amp}$, i.e., tear fracture, in which the shear bands and DGB are not seen clearly.

• Korean Journal of Mathematics
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• 제17권4호
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• pp.507-519
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• 2009

We give a theorem of the existence of the multiple solutions of the Hamiltonian system with the square growth nonlinearity. We show the existence of m solutions of the Hamiltonian system when the square growth nonlinearity satisfies some given conditions. We use critical point theory induced from the invariant function and invariant linear subspace.

• 한국세라믹학회지
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• 제21권3호
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• pp.271-277
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• 1984

To study interface between crystals grown and molten state in the crusible. Pulling and rotating rate of the shaft were varied in LiF crystal growth by Czochralski method. Lower speed of the pulling and rotating rate increased the degree of convexity in solid-liquid interface and higher speed of the pulling and rotating rate decreased it. Optimum condition of LiF crystal growth obtained as pulling rate was 6.5cm/h when it rotated as 46rpm.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1998년도 춘계학술대회 논문집
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• pp.178-183
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• 1998

This paper examines the crack growth behavior of 7075-T651 and 5052-H32 aluminum alloys for variable load within tensile load range condition. The cantilever beam type specimen with a chevron notch is used in this study. The crack growth and closure are investgated by compliance method. The applied initial stress ratio is R=0.3 and variable load are R=0.65, 0.46. Crack length, stress intensity factor range, ratio of effective stress intensity factor range and crack growth rate etc. are inspected with fracture mechanics estimate.

• 품질경영학회지
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• 제23권2호
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• pp.53-67
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• 1995

The problem considered here is to find the optimal discriminant analysis method in growth curve model. It has been studied how to find correct prior probability for the effective classification in discriminant analysis. We use the balanced condition to calculate prior probability. From the informative simulation study, new classification rule for the growth curve model is suggested. The suggested classification rule has better classification result than the other previously suggested method in terms of error rate criterion.

• 대한금속재료학회지
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• 제49권1호
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• pp.58-63
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• 2011

The grain size and growth direction of a directionally solidified turbine blade were evaluated by the initial nucleation condition at the start block of directional solidification. The initial nucleation condition was controlled by inserting a Ni foil on the directional solidification plate of the directional solidification furnace. Fine grains with good orientation were obtained in the faster cooling condition at the start block. The nucleus number was compared with the cooling rate of the start block by electron back scattered diffraction (EBSD). DSC (differential scanning calorimeter) analysis was performed to compare the melting point and undercooling for nucleation of the coarse nuclei and fine nuclei of the start block. The faster cooling condition at the start block showed more undercooling for nucleation and smaller size of nuclei which resulted in a fine grain with good orientation in the directional turbine blade.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2002년도 생물공학의 동향 (X)
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• pp.399-402
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• 2002

Industrial wastewater with high ammonium concentration was treated in batch biological systems which was a modified Ludzack- Ettinger process. Up to 78% conversion of $NH_4\;^+-N$ to $NO_x\;^--N$ was achieved in batch culture condition. Under anoxic condition with methanol as the carbon source, the denitrifiers decreased $NO_x\;^--N$ concentration from 608 mg/L to 5.6 mg/L in 22 d. As well as anoxic denitrification of $NO_x\;^-$ to $N_2$, dissimilatory nitrate reduction to ammonium also occurred under the condition as respiratory denitrification.

• 한국해안·해양공학회논문집
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• 제26권4호
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• pp.217-224
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• 2014

Cochlodinium polykrikoides 적조생물은 우리나라 연안에서 가장 빈번하게 적조를 유발하는 생물이다. 적조는 식물플랑크톤의 급격한 번식(algal bloom)으로 발생하기 때문에 적조를 유발하는 적조생물에 대한 최적의 성장조건 정보가 가용하다면 정확한 적조성장 모형 구성이 가능하며, 적조 발생예측에도 활용할 수 있다. 그러나 적조 성장에 영향을 미치는 인자가 빛, 수온, 염분, 영양염류 농도 등으로 다양하고, 적조성장을 제어하는 함수형태가 다양하기 때문에 실험조건의 최적 성장조건에 대한 연구 성과를 활용하여 적조 수치모형에서 활용할 수 있는 최적 성장모형을 구성한 연구는 매우 미흡한 수준이다. 본 연구에서는 우리나라의 대표적인 적조생물에 해당하는 Cochlodinium polykrikoides 적조생물의 최적 성장조건에 관한 연구 자료를 이용하여 다양한 함수형태에 따른 최적 매개변수 추정 및 오차비교 분석과정을 거쳐 적조 모형에서 바로 활용할 수 있는 최적 성장모형을 개발 제시하였다. 개발된 성장모형은 실험조건에서 추정된 최적 성장모형이기 때문에 현장자료를 이용한 모형의 보정 및 검정과정에서 본 연구결과로 제시된 최적 함수형태, 최적 매개변수 및 보정 매개변수의 범위 등을 기본 정보로 활용할 수 있으며, 실험조건과 현장조건의 차이 평가에도 활용할 수 있다.

• 한방안이비인후피부과학회지
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• 제27권3호
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• pp.56-71
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• 2014

Objectives : This study was carried out to examine the change of scalp and hair condition and to evaluate the efficacy of hair growth, subject's satisfaction and safety of the Narasoo healing shampoo and Hair tonic Methods : We offered 25 subjects Narasoo healing shampoo and Hair tonic and observed the changes among the starting point, 3rd week and 6th week. Study methods include the measurement of water and sebum content of the scalp, photo of scalp and hair, thermographic images and questionnaires. Results : It is estimated that Narasoo healing shampoo and Hair tonic have the positive effects on increase of water contents hair gloss, removal of excessive hair keratin, facilitation of hair growth, and decrease of sebum contents. Conclusions : Several meaningful effects of Narasoo healing shampoo and Hair tonic are observed in this study. Additional research is needed forward.

• 생물환경조절학회지
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• 제4권2호
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• pp.240-245
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• 1995

온도 및 광량이 고추냉이의 지상부 및 지하부 생장과 주요 병해발생에 미치는 영향을 조사하기 위하여 생장상의 온도를 10, 17 및 23$^{\circ}C$ 처리구로 하고 차광처리조건을 25, 50 및 75%로 조절하여 실험을 수행하였던 바 그 결과를 요약하면 다음과 같다. 유묘 정식 180일후 조사결과 초장은 생육온도에 따라 차이가 현저히 인정되었으나 17$^{\circ}C$구에서 가장 좋은 결과를 보였으며, 엽병의길이와 직경은 17$^{\circ}C$구를 정점으로 이보다 온도가 높거나 낮음에 따라 감소되는 경향을 보였다. 지하경에 있어서 직경은 1$0^{\circ}C$, 23$^{\circ}C$구간에서는 유의차가 인정되지 않았으며, 17$^{\circ}C$구에서 가장 양호하였다. 길이는 각 처리구별로 유의차가 인정되었으며 역시 17$^{\circ}C$구에서 가장 길었다. 차광처리 75%구가 50, 25%구에 비하여 지하경의 크기는 유의성이 인정되었으나 50%와 25%구의 처리간에는 유의성이 인정되지 않았다. 지하경의 직경과 무게에 있어서 75%구가 기타 처리구에 비하여 양호하였으며 전체 생체중은 75%, 50% 및 25%처리구간에서는 유의차가 인정되었다. 연부병과 묵입병의 발병률은 온도가 증가할수록 증가되었으나 차광량이 많을수록 연부병과 묵입병의 발병율은 감소하는 경향이었다.