• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.508-511
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• 2004

This study focused on the effect of autonomic microcapsules on the mechanical properties of structural material. Several types of microcapsules with healing agents were manufactured by varying agitation speed of high speed stirrer. The size distribution of microcapsules was measured by a particle size analzer. The epoxy specimens embedded with microcapsules were manufactured and the degree of cure of such epoxy specimen was measured by a differential scanning calorimetry. The tensile modulus and tensile strength in epoxy specimens embedded with microcapsules were evaluated in order to investigate the effects of microcapsules on mechanical properties of structural materials. The configuration of microcapsules and morphology of fracture surfaces for the epoxy specimen were examined by an optical microcope and a scanning electron microscope. According to the results, tensile strength of the epoxy specimen embedded with microcapsules was indicated a little reduction, but tensile modulus was not much affected on microcapsules.

• Journal of the Korean Vacuum Society
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• v.11 no.1
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• pp.59-67
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• 2002

The structures and properties of Cu nanowires have been investigated using molecular dynamics simulations. Cylindrical multi-shell Cu nanowires maintain their structures at room temperature and their structural properties are different from the structural properties of nanowires with face-centered-cubic structure. The results from nanopillar and tensile testing of cylindrical multi-shell Cu nanowire showed structures related to pentagonal needle-like crystal structures. Since the subunits of pentagonal nanowire with needle-like crystal are face-centered-cubic structure, pentagonal multi-shell nanowires are stable one-dimensional structures in nanostructured materials.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.627-632
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• 1997

Recently, the prestressed concrete box girder bridges are increasingly built at various locations in the world. The mechanical and structural behavior of prestressed concrete brides varies because of time-dependent material properties and sequential change of structural system due to stepwise construction. The time-dependent behavior of concrete is of importance in the design and construction of segmentally constructed and cast-in-place prestressed concrete box girder bridges. The structural response is affected b variations in creep, shrinkage properties of concrete. In this study, the example of time-dependent deformations is extended to establish how the variability in concrete properties affects the accuracy of the calculated deformations in such a bridge, and finally the results are discussed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.6
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• pp.550-553
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• 2005

[ $Pb(Zr_{0.2}Ti_{0.8})O_3$ ] powders, prepared by the sol-gel method, were mixed with an organic vehicle and the PZT thick films were fabricated by the screen-printing techniques on Pt/alumina substrates. The structural and dielectric properties were examined as a function of sintering temperature. The particle size distribution of the powder is bimodal with the mean particle size of about $1.2\;{\mu}m$. The average grain size of the PZT thick films sintered above $1000^{\circ}C$ was about $3.1\;{\mu}m$ and the thickness of the specimens was approximately $41\;{\mu}m$. The relative dielectric constant and dielectric loss of the thick films sintered at $1050^{\circ}C$ were 337 and $1.24\%$, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.101-102
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• 2005

Cadmium telluride (CdTe) films have been prepared on Coming 7059 glass, molybdemium (Mo), and polyimide (PI) substrates by r.f. magnetron sputtering technique. The influence of the sputter pressure on the structural and optical properties of these films was evaluated. In addition, a comparison of the properties of the films deposited on different substrates was performed.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.149-149
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• 2011

CdS films were deposited on glass substrates by R.F. magnetron sputtering method and the films were annealed at various substrate temperatures ranging from room temperature to $300^{\circ}C$. Structural properties of the films were studied by X-ray diffraction analysis. The structural parameters as crystallite size have been evaluated. The crystallite sizes were found to increase, and the X-ray diffraction patterns were seen to sharpen by increasing substrate temperatures. X-ray diffraction patterns of these films indicated that they contain both cubic (zincblende) and hexagonal (wurtzite) structures as a mixture. Optical properties of the films were measured at room temperature by using UV/VIS spectrometer in the wavelength range of 190 to 1100nm and optical absorption coefficients were calculated using these data. The energy gap of the films was found to decrease, and the band edge sharpness of the optical absorption was seen to oscillate by annealing. The results show that heat treatments under optimal annealing condition can provide significant improvements in the properties of CdS thin films.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.11a
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• pp.161-164
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• 2009

This research is to show the mechanical properties of structural steels by welding at high temperature. Welding parts are divided with weld metal and HAZ(Heat Affected Zone). HAZ is formed by interval from welding heat source and heating and cooling rates. Then, the change of both microstructure and mechanical properties occurs. Discontinuity of mechanical and chemical property at HAZ is the cause of safety decrease of structure. At this point, in this research, tensile tests at high temperature with test pieces of base metal and weld metal of SS400 and SM490 are accomplished. From the results, the mechanical properties of both SS400 and SM490 are standardized without welding or non-welding.

• Structural Engineering and Mechanics
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• v.57 no.2
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• pp.369-387
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• 2016

In this work, random homogenization analysis for the effective thermal properties of a three-dimensional composite material with unidirectional fibers is presented by combining the equivalent inclusion method with Random Factor Method (RFM). The randomness of the micro-structural morphology and constituent material properties as well as the correlation among these random parameters are completely accounted for, and stochastic effective thermal properties as thermal expansion coefficients as well as their correlation are then sought. Results from the RFM and the Monte-Carlo Method (MCM) are compared. The impact of randomness and correlation of the micro-structural parameters on the random homogenized results is revealed by two methods simultaneously, and some important conclusions are obtained.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.106-107
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• 2006

Cadmium telluride (CdTe) films have been prepared on Corning 7059 glass, molybdenum (Mo), and polyimide (PI) substrates by r.f. magnetron sputtering technique. The influence of the sputter pressure on the structural and optical properties of these films was evaluated. In addition, a comparison of the properties of the films deposited on fferent substrates was performed.

• Bulletin of the Korean Chemical Society
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• v.18 no.5
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• pp.501-509
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• 1997

In recent papers[Bull. Kor. Chem. Soc. 1996, 17, 735; ibid 1997, 18, 478] we reported results of molecular dynamics (MD) simulations for the thermodynamic, structural, and dynamic properties of liquid normal alkanes, from n-butane to n-heptadecane, using three different models. Two of the three classes of models are collapsed atomic models while the third class is an atomistically detailed model. In the present paper we present results of MD simulations for the corresponding properties of liquid branched-chain alkanes using the same models. The thermodynamic property reflects that the intermolecular interactions become weaker as the shape of the molecule tends to approach that of a sphere and the surface area decreases with branching. Not like observed in the straight-chain alkanes, the structural properties of model Ⅲ from the site-site radial distribution function, the distribution functions of the average end-to-end distance and the root-mean-squared radii of gyration are not much different from those of models Ⅰ and Ⅱ. The branching effect on the self diffusion of liquid alkanes is well predicted from our MD simulation results but not on the viscosity and thermal conductivity.