• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5A
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• pp.519-529
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• 2009

Fiber reinforced composite materials have various advantages in mechanical and chemical aspects. Not only high fatigue and chemical resistance, but also high specific strength and stiffness are attained, and therefore, damping characteristics are beneficial to marine piles. Since piles used for marine structures are subjected to compression and bending as well, detailed research is necessary. Current study examine the mechanical behavior under flexural and/or compressive loads using concrete filled fiber reinforced plastic composite piles, which include large size diameter. 25 pile specimens which have various size of diameters and lengths were fabricated using hand lay-up or filament winding method to see the effect of fabrication method. The inner diameters of test specimens ranged from 165 mm to 600 mm, and the lengths of test specimens ranged from 1,350 mm to 8,000 mm. The strengths of the fill-in concrete were 27 and 40 MPa. Fiber volumes used in circumferential and axial directions are varied in order to see the difference. For some tubes, spiral inner grooves were fabricated to reduce shear deformation between concrete and tube. It was observed that the piles made using filament winding method showed higher flexural stiffness than those made using hand lay-up. The flexural stiffness of piles decreases from the early loading stage, and this phenomenon does not disappear even when the inner spiral grooves were introduced. It means that the relative shear deformation between the concrete and tube wasn't able to be removed.

• Applied Chemistry for Engineering
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• v.10 no.8
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• pp.1119-1123
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• 1999

In this paper, electrorefining of uranium metal was studied to develop pyrometallurgical processing technology in molten salt system. The reaction between uranium metal and $CdCl_2$ was taken about 3 hours and the uranium metal deposits were obtained in the form of dendrite grown on the cathode surface in every electrotransport experiment. The shapes of dendrite were changed according to the applied voltages. Current efficiency was decreased with the increase of current density. Deposition rate was not changed after 6 hours and its maxium was obtained at $100{\sim}150mA/cm^2$ of current density and about 75 rpm of stirring speed, respectively. Also, the current efficiency was increased with decrease of the pitch of spiral groove curved on cathode.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.9
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• pp.145-150
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• 2000

Out-of-sphericity is degree of deformation of an air bearing sphere deviated from a perfect sphere. This paper investigates numerically the effect of out-of-sphericity error on the radial stiffness of an air bearing Three types of out-of-sphericity modes are considered. in this study the stiffness is calculated from pressure distribution at the bearing surface which is obtained by solving th Reynolds equation. in some cases large out-of-sphericity errors are found to improve the stiffnesses of air bearings. This implies that an air bearing of perfect hemispheres is not necessarily of the best performance. Thus much labor and cost in manufacturing air bearings can be saved, In addition the radial stiffness of an air bearing depends greatly on the application direction.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.6
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• pp.3692-3697
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• 2015

A screw is a type of fastener characterized by a helical ridge known as thread. The demands for screws with the miniaturization and weight reduction are increasing for the trend of small size of mobile devices. The successful designs of mold and process are very important to obtain screws with good mechanical properties and high precision. In this study, the design of cold forging process of micro screw was carried out by using finite element method. In particular, in order to investigate the effects of die geometries and friction, design of experiment method was adopted and it was revealed that the friction was the dominant factor of folding defects. From these results, the design of die was modified and experiments were carried out with the modified die. From the experimental results, it was found that the folding defects disappeared.

• Archives of design research
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• v.11 no.1
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• pp.131-142
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• 1998

Gustav KJimt (l862-1916)was a pioneer in the field of painting and decorative art. He was severly critized by the art critics of the time because of his rebellous art style. He firmly believed that there should exist a new kind of art that should portray the essence of the new liberalized era and that shoud reveal the idea of an artist in his work. Klimt was an aesthetic who sought beauty in life. He represented man as a micro universe within the macro universe. In order to portray man's inner being and to depict the process of life and death in nature, he symbolically employed female entity as a medium. Through uses of the circles, triangles, rectangles, and the spiral forms in his paintings, Klimt symbolized the meanings of man and nature. The circle symbolizes the universe and female entity; the triangle, human being; the rectangle, the earth and male entity; and the spiral, a universal force that attracts the opposite poles. The highly decorative characteristic nature of Klint's paintings and murals has often been modified in the pattern design field. It has been applied to home-furnishings and apparel textile designs, stained glasses, tiles, and posters. The techniques and layouts of these designs have been modified so that they may suit their manufacturing processes. In general, these pattern designs have two spectrums. One is the kind of design that has faithfully carried out Klimt' s original painting style. The other is the kind that has extracted the essence from the Klimt' s original art work.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.679-684
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• 2017

Friction Stir Welding is a metal welding technique, in which friction heat between a welding tool and a welding material is used to weld parts at temperatures below the melting point of a material. In this study, the temperature and velocity changes in a magnesium alloy (AZ31) during the welding process were analyzed by computational flow dynamics technique while welding the material using a friction stir welding technique. For the analysis, the modeling and analysis were carried out using Fluent as a fluid analysis tool. First, the welding material was assumed to be a temperature-dependent Newtonian fluid with high viscosity, and the rotation region and the stationary region were simulated separately to consider the rotational flow generated by the rotation of the welding tool having a helical groove. The interface between the welding tool and welding material was given the friction and slip boundary conditions and the heat transfer effect to the welding tool was considered. Overall, the velocity and temperature characteristics of the welded material according to time can be understood from the results of transient analysis through the above flow analysis modeling.

• Ecology and Resilient Infrastructure
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• v.6 no.4
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• pp.295-303
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• 2019

This study investigated the effects of various cultivation pots on Betula platyphylla var. japonica seedlings in order to select suitable pots for the production of healthy seedlings for the ecological revegetation. We used six types of the pots natural pot, natural pot with inside 5 mm width root turning bump, natural pot with inside 10 mm width root turning bump, negative-phototropism pot, negative-phototropism pot with inside 5 mm width root turning bump, and negative-phototropism pot with inside 10 mm width root turning bump. As greenhouse cultivation provided a high level of control of irrigation and temperature, the seedlings did not show any significant differences in plant height, number of branches, and diameter at root collar, but showed a significant difference in root growth among the different types of pots. The root growth was best in the negative-phototropism pot. In the negative-phototropism, the roots grew in a vertical shape, while they grew abnormally in a spiral shape in the natural pots. In outdoor cultivation, the growth of seedlings showed significant differences according to container types. The seedlings grown in specially manufactured negative-phototropism pots were most excellent in all of the height, number of branches, diameter at root collar and root growth. As for the seedlings grown in the negative-phototropism pots, their roots grew vertically and thus their rooting was well established after they were transplanted outdoor. A size of less than 5 mm ridge installed in the negative-phototropism was found to be appropriate for the seedling growth. These results showed that the negative-phototropism pot would be best suitable for the growth of Betula platyphylla var. japonica seedlings and for the production of seedling for ecological revegetation.

• Korean Journal of Optics and Photonics
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• v.32 no.3
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• pp.120-125
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• 2021

We have developed a linearly polarized high-power Yb-doped fiber laser in the master oscillator power amplifier (MOPA) scheme for efficient spectral beam combining. We modulated the phase of the seed laser by pseudo-random binary sequence (PRBS), with the bit length optimized to suppress stimulated Brillouin scattering (SBS), and subsequently amplified seed power in a 3-stage amplifier system. We have constructed by coiling the polarization-maintaining (PM) Yb-doped fiber, with core and cladding diameters of 20 ㎛ and 400 ㎛ respectively, to a diameter of 9-12 cm for suppression of the mode instability (MI). Finally, we obtained an output power of 1.004 kW with a slope efficiency of 83.7% in the main amplification stage. The beam quality factor M² and the polarization extinction ratio (PER) were measured to be 1.12 and 21.5 dB respectively. Furthermore, the peak-intensity difference between the Rayleigh signal and SBS signal was observed to be 2.36 dB in the backward spectra, indicating that SBS is successfully suppressed. In addition, it can be expected that the MI does not occur because not only there is no decrease in slope efficiency, but also the beam quality for each amplified output is maintained.