• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.3
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• pp.396-400
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• 1998

The physical properties of KLN single crystals very significantly according to the $Nb_2O_5$ content in grown crystal, therefore, it is very important to control the composition of KLN single crystals. In this study, KLN single crystals of high content $Nb_2O_5$ were grown by temperature fluctuation and TSSG (Top-seeded solution growth) methods with increasing the $Nb_2O_5$ content of starting solution. To investigate the existence of defect due to the increase of $Nb_2O_5$ content, dielectric and optical properties were measured. Due to the increase of defects in grown KLN single crystal, the shift of cutoff-frequency to lower energy and a broad Curie range, which shows the DPT (diffuse phase transition) characteristics, were observed.

• Journal of the Korean Society for Heat Treatment
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• v.28 no.1
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• pp.17-23
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• 2015

Hydroxyapatite coatings were fabricated by a room temperature spray method on zirconia substrates and the influence of heat-treatment on their microstructure was also investigated. Phase composition of coated hydroxyapatite films was similar to the starting powder, but the grain size of hydroxyapatite particles was reduced to the size of nano-scale about 100 nm. Grain size, particle compactness, and adhesiveness to zirconia of hydroxyapatite coatings were increased with heat-treatment temperature, but some of cracks by heat-treatment above $1100^{\circ}C$ were initiated between hydroxyapatite coatings and zirconia substrate. Heat-treated hydroxyapatite layers show the dissolution in SBF solution for 5 days. Hydroxyapatite-coated specimen heat-treated at $1100^{\circ}C$ for 1 h has a good biocompatibility, which specimen induced the nanocrystalline hydroxyapatite precipitates on the coating surface by the immersion in SBF solution for 5 days.

• Journal of Welding and Joining
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• v.21 no.4
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• pp.39-45
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• 2003

Nano-TiO$_2$ photocatalytic coatings were deposited on the stainless steel 304(50$\times$70$\times$3mm) by the APS(Atmospheric Plasma Spraying). Photocatlytic reaction was tested in MB(methylene blue) aqueous solution. For applying nano-TiO$_2$ powders by thermal spray, the starting nano-TiO$_2$ powder with 100% anatase crystalline was agglomerated by spray drying. Plasma second gas(H$_2$) flow rate and spraying distance were used as principal process parameters which are known to control heat enthalpy(heat input). The relationship between process parameters and the characteristics of microstructure such as the anatase phase fraction and grain size of the TiO$_2$ coatings were investigated. The photo-decomposition efficiency of TiO$_2$ coatings was evaluated by the kinetics of MB aqueous solution decomposition. It was found that the TiO$_2$ coating with a lower heat input condition had a higher anatase fraction, smaller anatase grain size and a better photo-decomposition efficiency.

• Journal of the Mineralogical Society of Korea
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• v.16 no.3
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• pp.245-254
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• 2003

Stishovite was synthesized from hydrous basaltic starting materials at 10∼15 ㎬ and $1000∼1400^{\circ}C$. Water content of synthetic stishovite has been determined, and solid solution mechanism of $H_2$ and Al in stishovite was investigated. The maximum water content obtained from stishovite single crystal was up to $844\pm$44 ppm $H_2$O. The concentration of hydrogen increased with increasing substitution of trivalent cation, mainly Al. The temperature effect on the hydrogen content in stishovite is more sensitive than that on any other impurities. Among the nominally anhydrous mantle-minerals, stishovite could be an important water-containing phase and contribute to the transportation of $H_2$O to lower mantle.

• Journal of the Korean Applied Science and Technology
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• v.22 no.3
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• pp.281-288
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• 2005

The silica nanoparticles were used as support of catalyst, filling material, electronic assembler, thin film material, and sensor material. And, the titania nanoparticles were used as pigment, dielectric substance, sensor and photocatalyst. In this paper, the spherical composite particles of $TiO_2/SiO_2$with narrow size distribution and phase pure were synthesized by ultrasonic spray pyrolysis method from $TiOSO_4$ and colloidal silica solution. Using ultrasonic apparatus, this starting solution was vaporized to droplets, and these droplets were induced into tube furnace by carrier gas. The resulting composite powder was characterized by scanning electron microscopy, X-ray diffraction analysis, TG-DTA, in vitro sun protection factor(SPF) and BET surface area analysis.

• Structural Engineering and Mechanics
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• v.44 no.5
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• pp.681-704
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• 2012

The dynamic response of Euler-Bernoulli beams to resonant harmonic moving loads is analysed. The non-dimensional form of the motion equation of a beam crossed by a moving harmonic load is solved through a perturbation technique based on a two-scale temporal expansion, which permits a straightforward interpretation of the analytical solution. The dynamic response is expressed through a harmonic function slowly modulated in time, and the maximum dynamic response is identified with the maximum of the slow-varying amplitude. In case of ideal Euler-Bernoulli beams with elastic rotational springs at the support points, starting from analytical expressions for eigenfunctions, closed form solutions for the time-history of the dynamic response and for its maximum value are provided. Two dynamic factors are discussed: the Dynamic Amplification Factor, function of the non-dimensional speed parameter and of the structural damping ratio, and the Transition Deamplification Factor, function of the sole ratio between the two non-dimensional parameters. The influence of the involved parameters on the dynamic amplification is discussed within a general framework. The proposed procedure appears effective also in assessing the maximum response of real bridges characterized by numerically-estimated mode shapes, without requiring burdensome step-by-step dynamic analyses.

• Journal of the Korean Society of Systems Engineering
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• v.7 no.1
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• pp.1-7
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• 2011

This work describes a study on the Analysis of Alternatives (AoA) based defense decision making. Future battle-space is transformed into a System of Systems (SoS) concept which is accomplished missions and their functions through network based battle management systems under forming their grids of various sensors and shooters in a single theater. The acquisition process is, therefore, changing over from single system requirements to capabilities based acquisition of SoS. AoA help to justify the need for starting, stopping, or continuing an acquisition program. AoA identify potentially viable solutions and provide comparative cost, effectiveness, and risk assessments of each solution to a baseline. The decision making must consider not only cost-effectiveness, risk, and military worth, but also domestic policy, foreign policy, technological maturity of the solution, the environment, the budget, treaties, and a host of additional factors. In this point of view, this paper analyzes AoA template which are critical elements of the defense decision making. From results of this analysis of AoA template for Korean acquisition environment are presented.

• Korean Journal of Materials Research
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• v.12 no.8
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• pp.650-655
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• 2002

$SiO_2$ gels containing dispersed fine Te metal particles have been prepared by the sol- gel method using a starting solution containing Tetraethoxy Silane (Si($OC_2$ $H_{5}$ )$_4$), $H_2$O, Ethylalchol ($C_2$$H_{5}$OH), Nitric Acid ($HNO_3$) and Tellurium Tetracholoride ($TeCl_4$) in a several molar ratio. Gelling time of sols was about 3 days and viscosity of solution was very low about 2~3 cP for 3 days. Heat-treatments of the gel have been performed at 500, 700, 900, 1100 and $1300^{\circ}C$ for 1 hour, respectively. We have investigated TG-DTA, X-ray diffraction patterns and SEM of heat-treatmented gels. The size of Te fine particles dispersed in $SiO_2$ gel was about 0.8~1 $\mu\textrm{m}$ and the shape was almost quadrangle.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.304-304
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• 2006

The possibility to develop optoelectronic devices with improved properties by controlling the degree of organization at the molecular level of organic materials has been driving the design of new ${\pi}-conjugated$ systems. In particular, the organization by self-assembling processes (${\tilde{\Box}}{\d{\Box}}}$ interactions, hydrogen bonding) of well-defined oligomeric systems such as disubstituted oligothiophene derivatives has been demonstrated as a promising approach to conjugated materials with a high degree of structural order of the constituent building blocks. The self-organization of conjugated building blocks in solution or on surfaces, leading to the construction of nanoscopic and mesoscopic architectures, represents a starting point for the construction of molecular electronics or even circuits, through surface patterning with nanometer-sized objects.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.10a
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• pp.136-140
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• 2000

It is desirable to predict springback quantitatively and accurately for the tool and process design in sheet stamping operations, however, it is blown very difficult. The result of springback analysis by the finite element method is sensitively influenced by numerical factors such as blank element size, number of integration point, punch velocity, contact algorithm etc. In the present work, a parametric study by Taguchi method is performed in order to evaluate the influence of numerical factors on springback Quantitatively and to obtain the combination of numerical factors which yields the best approximation to experimental data. Since springback is determined by the residual stress after forming process, it is important to evaluate stress distribution accurately. The oscillation in the time history curve of stress obtained by explicit FEM says that the stress solution at termination time is in very unstable state. Therefore, a variability study is also carried out in this study in order to assess the stability of implicit springback analysis starting from the stress solution by explicit forming simulation. The 2D draw bending process, one of the NUMISHEET '93 benchmark problems, is adopted as an application model.