• Journal of the Optical Society of Korea
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• v.20 no.6
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• pp.778-783
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• 2016

We synthesized $Er^{3+}-Yb^{3+}$, $Pr^{3+}-Yb^{3+}$, and $Er^{3+}-Pr^{3+}-Yb^{3+}$ -doped oxyfluoride glass ceramics containing $CaF_2$ nanocrystals by proper thermal treatments. Spectral characteristics of down- and up-converted emissions in three kinds of glass ceramics under 365-nm and 980-nm excitations were compared and explained by cross relaxations, excited-state absorptions, and energy-transfer processes between different ions. The huge reduction of up-conversion emission in the triply doped glass ceramics under 980-nm excitation compared to the $Er^{3+}-Yb^{3+}$ codoped one was explained by the split pump power and the direct energy transfer from $Er^{3+}$ to $Pr^{3+}$ ions. Increasing $Yb^{3+}$ concentration from 2% to 10% in the triply doped glass ceramics showed more than quadratic enhancement of the absorbed power, and we explained it by the enhanced energy-transfer efficiency from $Yb^{3+}$ to $Er^{3+}$ ions. We also observed enhanced up-converted emissions of $Er^{3+}$ and $Pr^{3+}$ ions in three kinds of glass ceramics under simultaneous excitation at 980 nm and 1550 nm, and suggested detailed up-conversion mechanisms.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.61-61
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• 2010

In the present work, we present the optimized the hybrid structures of carbon nanotubes (CNTs) and metal nanocomposites including Cu, Al, Co and Ni using the first principle calculations based on the density functional theory. Introduction of CNTs into a metal matrix has been considered to improve the mechanical properties of the metal matrix. However, the binding energy between metals and pristine CNTs wall is known to be so small that the interfacial slip between CNTs and the matrix occurs at a relatively low external stress. The application of defective or functionalized CNTs has thus attracted great attention to enhance the interfacial strength of CNT/metal nanocomposites. Herein, we design the various hybrid structures of the single wall CNT/metal complexes and characterize the interaction between single wall CNTs and various metals such as Cu, Al, Co or Ni. First, differences in the binding energies or electronic structures of the CNT/metal complexes with the topological defects, such as the Stone-Wales and vacancy, are compared. Second, the characteristics of functionalized CNTs with various surface functional groups, such as -O, -COOH, -OH interacting with metals are investigated.We found that the binding energy can be enhanced by the surface functional group including oxygen since the oxygen atom can mediate and reinforce the interaction between carbon and metal. The binding energy is also greatly increased when it is absorbed on the defects of CNTs. These results strongly support the recent experimental work which suggested the oxygen on the interface playing an important role in the excellent mechanical properties of the CNT-Cu composite[1].

• Journal of Radiation Protection and Research
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• v.48 no.1
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• pp.44-51
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• 2023

Background: Aptamers are currently being used in various fields including medical treatments due to their characteristics of selectively binding to specific molecules. Due to their special characteristics, the aptamers are expected to be used to remove radionuclides from a large amount of liquid radioactive waste generated during the decommissioning of nuclear power plants. The radiological effects on the aptamers should be evaluated to ensure their integrity for the application of a radionuclide removal technique. Materials and Methods: In this study, Monte Carlo N-Particle transport code version 6 (MCNP6) and Monte Carlo damage simulation (MCDS) codes were employed to evaluate the radiological effects on the aptamers. MCNP6 was used to evaluate the secondary electron spectrum and the absorbed dose in a medium. MCDS was used to calculate the DNA damage by using the secondary electron spectrum and the absorbed dose. Binding experiments were conducted to indirectly verify the results derived by MCNP6 and MCDS calculations. Results and Discussion: Damage yields of about 5.00×10^-4 were calculated for 100 bp aptamer due to the radiation dose of 1 Gy. In experiments with radioactive materials, the results that the removal rate of the radioactive ⁶⁰Co by the aptamer is the same with the non-radioactive ⁵⁹Co prove the accuracy of the previous DNA damage calculation. Conclusion: The evaluation results suggest that only very small fraction of significant number of the aptamers will be damaged by the radioactive materials in the liquid radioactive waste.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.10 s.241
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• pp.1329-1335
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• 2005

An aluminum or CFRP (Carbon Fiber ReinfDrced Plastics)is representative one of light-weight materials but its axial collapse mechanism is different from each other. The aluminum member absorbs energy by stable plastic deformation, while the CFRP member absorbs energy by unstable brittle failure with higher specific strength and stiffness than those in the aluminum member. In an attempt to achieve a synergy effect by combining the two members, aluminum CFRP compound square members were manufactured, which are composed of aluminum members wrapped with CFRP outside aluminum square members with different fiber orientation angle and thickness of CFRP, and axial collapse tests were performed fur the members. The axial collapse characteristics of the compound members were analyzed and compared with those of the respective aluminum members and CFRP members. Test results showed that the collapse of the aluminum CFRP compound member complemented unstable brittle failure of the CFRP member due to ductile characteristics of the inner aluminum member. The collapse modes were categorized into four modes under the iuluence of the fiber orientation angle and thickness of CFRP. The absorbed energy Per unit mass, which is in the light-weight aspect was higher in the aluminum CFRP compound member than that in the aluminum member and the CFRP member alone.

• Journal of Radiation Protection and Research
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• v.47 no.3
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• pp.134-142
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• 2022

Background: This study investigated the characteristics of optically stimulated luminescence dosimeters (OSLDs) with fully filled deep electron/hole traps in the kV energy ranges. Materials and Methods: The experimental group consisted of InLight nanoDots, whose deep electron/hole traps were fully filled with 5 kGy pre-irradiation (OSLD_exp), whereas the non-pre-irradiated OSLDs were arranged as a control group (OSLD_cont). Absorbed doses for 75, 80, 85, 90, 95, 100, and 105 kVp with 200 mA and 40 ms were measured and defined as the unit doses for each energy value. A bleaching device equipped with a 520-nm long-pass filter was used, and the strong beam mode was used to read out signal counts. The characteristics were investigated in terms of fading, dose sensitivities according to the accumulated doses, and dose linearity. Results and Discussion: In OSLD_exp, the average normalized counts (sensitivities) were 12.7%, 14.0%, 15.0%, 10.2%, 18.0%, 17.9%, and 17.3% higher compared with those in OSLD_cont for 75, 80, 90, 95, 100, and 105 kVp, respectively. The dose accumulation and bleaching time did not significantly alter the sensitivity, regardless of the filling of deep traps for all radiation qualities. Both OSLD_exp and OSLD_cont exhibited good linearity, by showing coefficients determination (R²) > 0.99. The OSL sensitivities can be increased by filling of deep electron/hole traps in the energy ranges between 75 and 105 kVp, and they exhibited no significant variations according to the bleaching time.

• Journal of Mechanical Science and Technology
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• v.17 no.1
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• pp.48-56
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• 2003

This paper investigates the collapse characteristics of CF/Epoxy composite tubes subjected to axial loads as changing interlaminar number and outer ply orientation angle. The tubes are aften used for automobiles, aerospace vehicles, trains, ships, and elevators. We have performed static and dynamic impact collapse tests by a way of building impact test machine with vertical air compression. It is fanad that CF/Epoxy tube of the 6 interlaminar number (C-type) with 90$^{\circ}$ outer orientation angle and trigger absorbed more energy than the other tubes (A. B and D-types). Also collapse mode depended upon outer orientation angle of CF/Epoxy tubes and loading type as well； typical collapse modes of CF/Epoxy tubes are wedged, splayed and fragmentcl.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1178-1180
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• 1995

In this paper, structual, optical and electrical properties of CdTe thin films prepared by electron beam evaporation method were studied. The crystal structure of CdTe films deposited at substrate temperature of $100{\sim}400^{\circ}C$ was zincblend type with preferential orientation of the (111)plane parallel to the substrate. The result of optical absoption and transmittance show that solar radiation with energy larger than band gap is almost completely absorbed within an about $2{\mu}m$ thickness of the evaporated CdTe layer and optical band gap of the CdTe film was larger with increasing substrate temperature. The resistivity of CdTe films deposited on the glass substrate was about $10^5{\sim}10^7{\Omega}cm$.

• Journal of Biosystems Engineering
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• v.13 no.4
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• pp.20-29
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• 1988

Properties of agricultural products are important for engineering design and analysis with respect to their mechanical harvesting, handling, transporting and processing. Researcher have presented the data of properties for various kinds of agricultural products. These data, however, are obtained from the materials produced in foreign countries, and a very few data could be found in Korea. In this paper, emphasis put on the importance of measuring the properties of agricultural products through an extensive review of literatures, and some experimental results on the viscoelastic and elastic properties of the materials are presented. Viscoelastic characteristics of some agricultural materials, specifically the force-deformation-time relationship of the whole orange and cylindrical samples of cheese under different types of loading were investigated. In elastic test, the response of apple during an impact and the relationships among various parameters such u degree of damage, drop height and absorbed energy were determined.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.4
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• pp.47-53
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• 2011

Firstly, FEM model for the body frame of a fuel cell vehicle was built up and design optimization results based on different schemes were exhibited. One scheme was to minimize weight while maintaining the normal mode frequencies and the other was to increase the frequencies without weight change. Next, for a rear frame model, shape parameter study on collapse characteristics such as peak resistance load and absorbed energy was carried out. Also, the stiffness of frame mounting brackets was predicted using inertance calculation and the durability of those mounting brackets for vehicle system loads was evaluated. Finally, for a representative mounting model, the influence on durability due to thickness change was analyzed.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.9
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• pp.37-44
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• 1997

In this paper the bending collapse characteristics of square and rectangular steel tubes were studied with the pure bending test machine which apply pure bending moment without imposing shear and tensile forces. Under pure bending moment, delayed buckling modes occur and depend on test length and shape of section. For delayed mode, the endrgy of bending moment is absorbed by strain hardening energy. The pre- dictions of maximum moment and moment-rotation angle curve from those concepts are in good agreement with experimental observations.