• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.12
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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.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.6
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• pp.317-322
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• 2002

We have studied the sawing sach as the round brilliant cut, cushion barion cut and marquise cut. Through this study, we could examined the rate of waste from the grinding work, and find a solution for many problems which could be derived from the grinding work. We could reduce the rate of waste by this study about sawing technique; 2.5 % for round brilliant cut, 2.5 % for cushion barion cut and 5.5 % for marquise cut.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.6
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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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• v.7 no.1
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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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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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.

• Journal of The Korean Society of Grassland and Forage Science
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• v.17 no.4
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• pp.345-350
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• 1997

Using modified Lincoln solution, hydroponic system was developed to compare simultaneously a range of pasture species in terms of relative growth rate(RGR), rate of roots to shoots, and relative root volume and root area. Modified Lincoln solution achieved optimum growth of nineteen forage species tested, and was proved to be a good method for studying plant root characteristics. RGR was measured sucesshlly showing reasonably consistant values over time. There was a much differences in rootkhoot ratio between species within groups as between groups. Root tissue density was lower in grasses than legume or herb group. Root area index was very high for grasses and herbs, and this index should be useful for evaluating the comparative root system of different species.

• Journal of Bio-Environment Control
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• v.16 no.3
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• pp.222-227
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• 2007

In this study, nutrient solution for Liliaceae (Chinese chive) leafy vegetable was developed. The various strength (1/2, 1 and 3/2) of nutrient solution recommended by National Horticultural Research Institute (NSH) was applied to the crops in deep flow technique (DFT) system for 42 days. The growth of Chinese chive were highest in the treatment of 1/2 strength. The proper constitution of nutrient solution developed for liliaceae crops (NSL) was N 12, P 2.5, K 7, Ca 4 and Mg 2 met. The crops were grown two times in March and September to examine the appropriateness of the NSC. As a result, the relative growth rate and the amount of chlorophyll (SPAD value)of Chinese chive treated with NSL were increased 1.11 times. The most important nutrient factor of ascorbic acid were also increased 1.16 times.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.6
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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.

• Journal of Bio-Environment Control
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• v.4 no.1
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• pp.43-49
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• 1995

The main purpose of these studies were to clarify differences in Cheju - scoria and other solid media on quantity and quality of cherry tomatoes and on shift of component of the nutrient solution, and to use Practically Cheju-scoria as an excellent solid culture medium. The results obtained were summarized as follows ; 1. Among scoria plots, the rates of dry weights, fruits and their sugar-acid ratio were higher in the plot that was drained well with deep flow for one hour once a day. 2. Fresh fruit weights were lighter in rockwool and deep flow technique, but larger in scoria, Hyugashi (artificial gravel, $\Phi$10-12mm) and perlite in moving to higher flower cluster. 3. The results of analysis on microelement among solution components showed decrease of concentrations of P and K in the period of growth and development. 4. Yields and brix of cherry tomato showed a tendency to increase in rockwool and Hyugashi than anothers. 5. The concentration of fertilizer base was increased in general solution culture. Transpiration and absorption were similar in scoria plot and other media. 6. More studies of the Cheju-scoria development is required in order to use it as a solid medium for solution culture.

• Journal of applied mathematics & informatics
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• v.41 no.4
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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.