• Applied Science and Convergence Technology
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• v.27 no.2
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• pp.38-41
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• 2018

We demonstrate the growth of a sheet-like ZnO membrane on ZnO nano rod layers. The growth process is composed of 3 steps of ZnO seed formation, ZnO nano rod growth and sheet-like ZnO membrane formation on those nano rods. To confirm the fundamental growth mechanism, the lattice structures of each step were analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM) measurement. Analysis of the relation between the texture coefficient and the surface shape of the ZnO membrane on the ZnO nano rods shows that the surface morphology of ZnO nano structures can be controlled using the temperature of the growing solution and the concentration of the chemical solution.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.6
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• pp.91-97
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• 2002

Applications of brazing in the studying fields such as high-speed machining are very increasing in various industry fields. Therefore, applying to the fracture mechanics by numerical analysis method is very important to analyse the crack problem dissimilar materials in brazed interface. In this study, stress intensity factor(SIF) is analysed to investigate crack behavior on the crack tip of dissimilar materials in brazed interface such as a hardmetal and a HSS by two dimensional(2-D) BEM. Kelvin's solution was used as a fundamental solution in BEM analysis and stress extrapolation method was used to determine SIF.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.621-624
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• 1999

Metalization technology of the fine patterns by electroless plating is required in place of electrodeposition as high-density printed boards(PCR) become indispensable with the miniaturization of electronic components. Electroless nickel plating is a suitable diffusion barrier between conductor meta1s, such as Al and Cu and solder is essetional in electronic packaging in order to sustain a long period of service. Moreover, Electroless nickel has particular characteristics including non-magnetic property, amorphous structure. wear resistance, corrosion protection and thermal stability In this study fundamental aspects of electroless nickel deposition were studied with effort of complexeing agents of different kinds. Then the property of electroless deposit are controlled by the composition of the deposition solution the deposition condition such as temperature and pH value and so on. the characteristics of the deposits has been carried out.

• Textile Coloration and Finishing
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• v.2 no.3
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• pp.26-35
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• 1990

This study was carried out with the view of fundamental investigating to improve the tactile and the hygroscopicity of Poly(ethylene Terephthalate) (PET)fibers. Mono-sodium ethylene glycolate in ethylene glycol (MSEG-EG) solution was prepared and PET films were treated with it. The following conclusions were obtained. When PET films were decomposed in MSEG-EG solution, decomposition rate constant showed an exponential relationship with treating temperature; activition energy was 23.30 Kcal/mol, activation enthalpy was 22.52~22.60 Kcal/mol and activation entropy was -29.20~ -29.41 e.u. On the basis of the results obtained above and structure identification of decomposition products, it was found that the decomposition reaction proceeded through ester interchange reaction.

• Kyungpook Mathematical Journal
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• v.62 no.3
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• pp.533-555
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• 2022

In this paper, we introduce a new algorithm for finding a solution of an equilibrium problem in a real Hilbert space. Our paper extends the single projection method to pseudomonotone variational inequalities, from a 2018 paper of Shehu et. al., to pseudomonotone equilibrium problems in a real Hilbert space. On the basis of the given algorithm for the equilibrium problem, we develop a new algorithm for finding a common solution of a equilibrium problem and fixed point problem. The strong convergence of the algorithm is established under mild assumptions. Several of fundamental experiments in finite (infinite) spaces are provided to illustrate the numerical behavior of the algorithm for the equilibrium problem and to compare it with other algorithms.

• Kyungpook Mathematical Journal
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• v.62 no.3
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• pp.583-593
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• 2022

Lienard's equations are important nonlinear differential equations with application in many areas of applied mathematics. In the present article, a new approach known as the modified fractional Taylor series method (MFTSM) is proposed to solve the nonlinear fractional Lienard equations with Caputo fractional derivatives, and the convergence of this method is established. Numerical examples are given to verify our theoretical results and to illustrate the accuracy and effectiveness of the method. The results obtained show the reliability and efficiency of the MFTSM, suggesting that it can be used to solve other types of nonlinear fractional differential equations that arise in modeling different physical problems.

• Journal of Astronomy and Space Sciences
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• v.40 no.1
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• pp.11-18
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• 2023

The ionosphere is one of the key components of the near-Earth's space environment and has a practical consequence to the human society as a nearest region of the space environment to the Earth. Therefore, it becomes essential to specify and forecast the state of the ionosphere using both the observations and numerical models. In particular, numerical modeling of the ionosphere is a prerequisite not only for better understanding of the physical processes occurring within the ionosphere but also for the specification and forecast of the space weather. There are several approaches for modeling the ionosphere, including data-based empirical modeling, physics-based theoretical modeling and data assimilation modeling. In this review, these three types of the ionospheric model are briefly introduced with recently available models. And among those approaches, fundamental aspects of the physics-based ionospheric model will be described using the basic equations governing the mid-latitude ionosphere. Then a numerical solution of the equations will be discussed with required boundary conditions.

• Journal of the Korean Society of Clothing and Textiles
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• v.35 no.10
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• pp.1242-1251
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• 2011

This study investigates the effect of mixed characteristics of oily soil such as mixed ratio, polarity of oily soil on contact angle of fabric, removal of oily and particulate soil from PET fabric in oily/particulate soil mixed system. The contact angle of fabric in the surfactant solution with suspended oily soil was examined as a fundamental environment of detergency of soil from fabrics. Detergency was investigated as function of mixed ratios of oily/ particulate soil, type of oily soil, surfactants concentration, surfactant type and temperature of detergency in surfactant solution. The contact angle of fabric in surfactant solution sharply increased with mixing nonpolar oily soil; in addition, the contact angle slightly increased with increasing contents of oily soil and decreased with increasing surfactant concentration. The removal of oily and particulate soil from fabric was higher in the solution mixed with polar versus nonpolar oily soil. The detergency increased with increasing surfactant concentration and the increased temperature of surfactants solution that were relatively improved in NPE compared to DBS solutions, The results indicated that the detergency of oily and particulate soil showed a similar trend in oily/ particulate mixed soil systems. The general contact angle of fabric was well related with the detergency of oily and particulate soil in oily/particulate mixed soil system, therefore, the primary factor determining the detergency of soil in oily/particulate mixed soil system may be the contact angle of fabric caused by wettability.

• Journal of the Society of Naval Architects of Korea
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• v.56 no.5
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• pp.418-426
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• 2019

To derive a simplified analytic solution which can be utilized as a fundamental solution for the wave maker design, a segment of the wave board has been idealized as a submerged line segment in a two dimensional domain of a wave flume. The lower end of the line segment could be located at arbitrary depth of the wave flume and the upper end of the board could be also submerged to any depth from the free surface. The freely oscillating motion of the wave board is assumed to be defined by determining the condition of horizontal oscillation on both ends differently. The submerged wave board oscillating in horizontal direction could be specified by selecting the amplitude, frequency and the phase lag differently on lower and upper ends of the board. The simplified two dimensional wave generated by the wave board segment has been obtained by the first order perturbation method. It is found that the general solution of the freely oscillating wave board in two dimensional domain could be decomposed into the solution of flap motion with lower end hinge and swing motion with upper end hinge. The case study of the analytic solutions has been carried out to evaluate the effect on the wave height due to the difference of oscillation frequency, phase difference and variation of stroke between for the motion of both ends. It is found that the solution of the freely oscillating wave board could be utilized for the development of high performance wavemaker especially for irregular waves.

• Journal of the Korea Concrete Institute
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• v.14 no.3
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• pp.409-419
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• 2002

Nowadays, antiwashout underwater concrete is widely used for constructing underwater concrete structures but they, especially placed in marine environment, can be easily attacked by chemical ions such as SO$\^$2-/$\_$4/ Cl$\^$-/ and Mg$\^$2＋/, so the quality and capability of concrete structures go down. In this paper, to solve and improve those matters, flyash and GGBFS(ground granulated blast furnace slag) were used as partial replacements for ordinary portland cement. As results of experiments for fundamental properties of antiwashout underwater concrete containing 10, 20, 30％ of flyash and 40, 50, 60 ％ of GGBFS respectively, setting time, air contents, suspended solids and pH value were satisfied with the "Standard Specification of Antiwashout Admixtures for Concrete" prescribed by KSCE, and also slump flow, efflux time and elevation of head were more improved than that of control concrete. From the compressive strength test, it was revealed that the antiwashout underwater concrete containing mineral admixtures(flyash and GGBFS) is more effective for long term compressive strength than control concrete. An attempt to know how durable when they are under chemical attack has also been done by immersing in chemical solutions that were x2 artificial seawater, 5 ％ sulphuric acid solution, 10％, sodium sulfate solution and 10％ calcium chloride solution. After immersion test for 91days, XRD analysis was carried out to investigate the reactants between cement hydrates and chemical ions and some crystalline such as gypsum ettringite and Fridel′s salt were confirmed.