• 한국전기전자재료학회논문지
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• 제13권12호
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• pp.1063-1068
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• 2000

Water treeing in underground distribution power cable is not easy to observe by nondestructive method and it has very complex patterns. This study describes the principles and practices of a continuous observation of initiation and growth of tree in polymeric insulation material using an image measurement technique. Using this technique we could observe water tree and the growing process of electrical tree due to the water tree and the growing process of electrical tree due to the water tree. All of these growing process is analyzed quantitatively by image measurement program composed of borland c++. We fabricated the thin film type specimen to observe water tree easier and also the needle electrode was prepared by etching method using electrolytes. Initiation and the growth of three was observed somewhat different depending on the applied voltage and the water electrode. AgNO$_3$solution electrode accelerates the initiation and the growth of water tree, compared to those of distilled water electrode. The water and the electrical tree occurred by water tree has discontinuous growth characteristic.

• 한국결정성장학회지
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• 제12권6호
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• pp.317-322
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• 2002

Round brilliant cut와 cushion barion cut, marquise cut에 대한 sawing 방법에 대해 연구하였다. 연마작업시 발생하는 소모율을 파악하고 그에 따른 문제점들을 해결할 수 있었다. Sawing technique에 대한 연구를 통하여 소모율을 round brilliant cut는 2.5 %, cushion barion cut는 2.5 %, marquise cut는 5.5 %로 감소시킬 수 있었다.

• 설비공학논문집
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• 제18권6호
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• pp.477-485
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• 2006

A study on frost prevention of fin-tube heat exchanger is experimently performed by spreading antifreezing solution on heat exchanger surface. It is desirable that the antifreezing solution spreads completely on the surface forming thin liquid film to prevent frost nucleation and crystal growth and to reduce the thermal resistance across the liquid film. A small amount of antifreezing solution falls in drops on heat exchanger surface using two types of supplying devices, and a porous layer coating technique is adopted to enhance the wettedness of antifreezing solution on the surface. It is observed that the antifreezing solution liquid film prevents fin-tube heat exchanger from frosting, and heat transfer performance does not degrade through the frosting tests. The concentration of supplied antifreezing solution can be determined by heat transfer analysis of the first row of heat exchanger to avoid antifreezing solution freezing due to dilution by moisture absorption.

• International Journal of Aerospace System Engineering
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• 제7권1호
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• pp.7-15
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• 2020

In this paper the crack growth, modeling, and simulation of the stiffened and un-stiffened cracked panels presented using commercially available finite element software packages. Computation of stresses and convergence of stress intensity factor for single edge notch (SEN) specimens carried out using the finite element method (FEM) and extended finite element method (XFEM) and compared with an analytical solution. XFEM techniques like cohesive segment method and LEFM using virtual crack closure technique (VCCT), used for crack growth analysis and presented results for un-stiffened and stiffened panels considering various crack domain. The non-linear analysis considering both geometric and material non-linearity on stiffened panels with various stringers like a blade, L, inverted T and Z sections the results were presented. Arrived at the optimum stringer section type for the considered panel under axial loading from the numerical analysis.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.558-561
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• 2001

In this study, the ZnS nanosized thin films were grown by the solution growth technique (SGT), and their structural and optical properties were examined. X-ray diffraction patterns showed that the ZnS thin film obtained in this study had the cubic structure ($\beta$-ZnS). With decreasing growth temperature and decreasing concentration of precursor solution, the surface morphology of film was found to be improved. In particular, this is the first time that the surface morphology dependence of ZnS film grown by SGT on the ammonia concentration is reported. The energy band gaps of samples were shown to vary from 3.69 eV to 3.91 eV, demonstrating that the quantum size effect of SGT grown ZnS is remarkable. Photoluminescence (PL) peaks were observed at the positions corresponding to the lower energy than that to energy band gap, illustrating that the surface states were induced by the ultra-fineness of grains in ZnS films.

• 한국초지조사료학회지
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• 제17권4호
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• pp.345-350
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• 1997

수정된 Lincoln용액을사용하여 여러가지 목초의 상대생장율, 뿌리/지상부(RlS)비율, 상대적 뿌리 용적 및 표면적 등을 동시에 비교하기 위하여 수경재배법을 개발하였다. 수정된 Lincoln 용액에서 19가지 초종이 모두 잘 자랐으며, 뿌리특성 연구에 긴요하게 이용될 수 있었다. 상대생장율은 조사기간 동안 이상적으로 일정 값을 유지하며 같은 식물체로 성공적으로 측정할 수 있었다. Group 간과 마찬가지로 group 내에서도 초종간 RlS율에 큰 차이가 있었다. 뿌리 조직밀도는 두과목초나 herb보다 화본과에서 낮았다. 뿌리 면적지수는 화본과 목초와 herb가 높았는데 이 면적지수는 각각 다른 초종의 상대척 根界 평가에 유용하게 이용될 수 있을 것으로 사료되었다.

• 생물환경조절학회지
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• 제16권3호
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• pp.222-227
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• 2007

본 연구에서는 양수분 흡수율과 양이온 비율에 근거하여 백합과(부추)에 적합한 전용배양액을 개발하였다. 원예연구소 배양액액(NSH)을 1/2배액, 1배액, 3/2배액의 농도로 42일간 담액 수경재배를 한 결과 1/2배액에서 세가지 작물의 생육이 가장 좋았다. 양수분 흡수율에 근거하여 개발된 백합과 전용배양액(NSL)의 조성은 N 12, P 2.5, K 7, Ca 4 and Mg 2 me/L이다. NSL로 처리한 부추 작물의 상대생장율(RGR)은 1.11배 증가하였으며 엽록소 함량(SPAD value)은 1.16배 증가하였다. 그리고 부추의 가장 중요한 영양성분중 하나인 항산화성분-Ascorbic acid의 함량이 1.16배 증가하였다.

• 한국전기전자재료학회논문지
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• 제32권6호
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• pp.516-521
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• 2019

The top seeded solution growth (TSSG) method is an alternative technique to grow high-quality SiC crystals that has been actively studied for the last two decades. However, the TSSG method has different issues that need to be resolved when compared to the commercial SiC crystal growing method, i.e., physical vapor transport (PVT). A particular issue of the TSSG method of results from the presence of liquid droplets on the grown crystal that can remain even after crystal growth; this induces residual stress on the crystal surface. Hence, the residual droplet causes several unwanted effects on the crystal such as the initiation of micro-cracks, micro-pipes, and polytype inclusions. Therefore, this study investigated the formation of the residual droplet through multiphysics simulations and lead to the development of a liquid droplet removal method. As a result, we found that although residual liquid droplets significantly apply residual stress on the grown crystal, these could be vaporized by adopting thermal annealing processes after the relevant crystal growing steps.

• 생물환경조절학회지
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• 제4권1호
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• pp.43-49
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• 1995

양액재배에서 제주송이가 다른 배지와 비교하여 방울토마토의 수량 및 품질에 미치는 영향과 양액성분 변화를 조사하여 제주송이를 양액재배용 고형배지로 실용화하기 위하여 시험한 결과는 다음과 같다. 1. 건엽비, 건과비, 당산비는 1익㉣ 1회 1시간 담액후에 완전 배액한 구에서 높았다. 2. 방울토마토 생과중은 상위 화방으로 갈수록 암면구와 담액수경구는 작아졌으나, 송이구와 일향토구, 펄라이트구 등 고형배지경에서 무거웠다. 3. 방울토마토의 생육이 왕성한 시기에 양액성분중 다량원소를 분석한 결과는 송이 재배구에서 인산과 칼륨 농도가 낮았다. 4. 방울토마토의 수량과 당도는 암면과 일향토구에서 높은 경향을 보였다. 5. 일반적으로 양액재배에서는 수분의 증발과 식물의 수분 흡수 증산작용으로 비료염의 농도가 높아가는데 송이구도 다른 고형배지경과 비슷한 결과를 보였다. 6. 제주 송이 양액재배용 고형배지로 손쉽게 이용할 수 있는 가벼운 자재로 가공개발 연구가 있어야 할 것으로 본다.

• Journal of applied mathematics & informatics
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• 제41권4호
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• pp.893-906
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• 2023

In this article, we are devoted to study the problem of the existence, uniqueness and positivity of the global solutions of the 3 × 3 reaction-diffusion systems with the total mass of the components with time. We also suppose that the nonlinear reaction term has a critical growth with respect to the gradient. The technique that we used to prove the global existence is the method of the compact semigroup.