• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1684-1689
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• 2003

This paper concerns the analytical modeling and dynamic analysis of advanced cantilevered blade structure implemented by a dual approach based on structural tailoring and viscoelastic materials technology. Whereas structural tailoring uses the directionality properties of advanced composite materials, the passive materials technology exploits the damping capabilities of viscoelastic material(VEM) embedded into the host structure. The structure is modeled as a composite thin-walled beam incorporating a number of nonclassical features such as transverse shear, secondary warping, anisotropy of constituent materials, and rotary inertias. The case of VEM spreaded over the entire span of the structure is considered. The displayed numerical results provide a comprehensive picture of the synergisitic implications of the application of both techniques, namely, the tailoring and damping technology on vibration response of thin-walled beam structure exposed to external time-dependent excitations.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1994.11a
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• pp.97-100
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• 1994

The present paper is devoted to the physical and electrical characteristics of N-docosyl- quinolinium-TCNQ films compared with the films doped with I$_2$. Iodine affects the degree of charge transfer and the conductivity of the films. The UV-visible absorption spectra of the film doped with I$_2$ shows that the peak of I$_3$ which had electronic transition at 300∼350nm and (TCNQ-)$_2$ dimer absorption disappered. The in-plane electrical conductivity of the films doped with I$_2$ were 1.4${\times}$10$\sub$-6/S/cm, which is two orders of magnitude higher conductivity than undoped LB films. The film structural difference between Y and Z-type may cause the conductivity. Another possible reasons of the structural difference was the overlapping TCNQ anion radical in LB films.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.3
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• pp.234-240
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• 2001

Using RF magnetron sputtering, amorphous carbon(a-C) thin films as electron filed emitter were fabricated. these a-C thin films were deposited on Si(001) substrate at several temperatures. The field electron emission property of these a-C thin films was estimated by a diode technique. As the result, we observed that the field emission properties of the films were changed singnificantly with the substrate temperature and structural features of a-C film. The field emission properties were promoted by higher substrate temperatures. Furthermore N-doped a-C film exhibits more field emission property than that of undoped a-C film. These results are explained as change of surface morphology and structural properties of a-C film.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.250-251
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• 2005

Tin dioxide (SnO$_2$) thin films have been prepared on Si wafer (100) by Plasma Enhanced Chemical Vapor Deposition (PECVD). SnO$_2$ thin films were prepared from mixtures of dibutyltin diacetate as a precursor, oxygen as an oxidant at 275, 325, 375, 425$^{\circ}C$, respectively. The microstructure of deposited films was characterized by X-ray diffraction and field emission scanning electron microscopy. Structural characteristics of prepared SnO$_2$ thin films were investigated with different substrate temperature. The deposition rate was linearly increased with substrate temperature. Surface morphology and uniformity of prepared thin film was excellent at 375$^{\circ}C$ and grain size was averagely 25nm.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.05a
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• pp.1.1-5
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• 1996

Structural characteristics in Se thin film fabricated by EBE method had been studied. Se thin film was deposited with noncrystalline until substrate temperature of 100$^{\circ}C$. But Se film was grown with monoclinic at substrate temperature of over 150$^{\circ}C$. Lattice constants of it were as follow: a=12.76[${\AA}$], b=9.15[${\AA}$], c=10.4[${\AA}$]. Finally, after heat-treatment at 150$^{\circ}C$ for 15 min with substrate temperature of 100$^{\circ}C$, noncrystalline Se was proved to be hexagonal. Lattice constants of it were as follow: a=4.27[${\AA}$], c=4.83[${\AA}$].

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1994.11a
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• pp.24-27
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• 1994

Variations with structural and electrical properties of Yttrium added PZT thin films were observed and measured respectively. Area of rosette was increased by Yttrium added and shapes of hysteresis curves were changed to slim type. $Y^{3+}$ ion substituted $Pb^{2+}$ ion and played the role of doner. Because the creation of space charges was restricted by Yttrium, degradation of remanent polarizations by cumutation of polarization reversals of PZT was protected. But coercive field was increased because of vacancies generated Yttrium added.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.2
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• pp.115-124
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• 2003

A prestressed concrete slab bridge is analyzed by the specially orthotropic laminates theory. Both the geometry and the material of the cross section of the slab are considered symmetrical with respect to the mid-surface so that the bending extension coupling stiffness, $B_{ij}=0$, and $D_{16}=D_{26}=0$. Each longitudinal and transverse steel layer is regarded as a lamina, and material constants of each lamina is calculated by the use of rule of mixture. This bridge with simple support is under uniformly distributed vertical and axial loads. In this paper, the finite difference method and the beam theory are used for analysis. The result of beam analysis is modified to obtain the solution of the plate analysis.

• Proceeding of KASS Symposium
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• 2005.05a
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• pp.125-132
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• 2005

Membrane structures, a kind of lightweight soft structural system, are used for spatial structures. The material property of the membrane has strong axial stiffness, but little bending stiffness. The design procedure of membrane structures are needed to do shape finding, stress-deformation analysis and cutting pattern generation. In shape finding, membrane structures are unstable structures initially. These soft structures need to be introduced initial stresses because of its initial unstable state, and it happens large deformation phenomenon. And also there are highly varied in their size, curvature and material stiffness. So, the approximation inherent in cutting pattern generation methods is quite different. Therefore, in this study, to find the structural shape after large deformation caused by Initial stress, we need the shape analysis considering geometric nonlinear ten And the geodesic line on surface of initial equilibrium shape and the cutting pattern generation using the geodesic line is introduced.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.2
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• pp.202-206
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• 2011

Works on the strength and stiffness in the structural members are carried out widely with various material and cross-sections with ever increasing safety concerns, they are presently applied in various fields including railroad trains, air crafts and automobiles. In addition to this, problem of lighting structural members became important subject by control of exhaust gas emission, fuel economy and energy efficiency. So, Light weight of member structures is necessary for the high performance and various functions. In this study, the CFRP flat and circular member was manufactured by CFRP prepreg sheet in autoclave. Carbon FRP is an anisotropy material whose mechanical properties change with its fiber orientation angle, so this study apply to the effects of the fiber orientation angle on the bending characteristics of the member. Each CFRP flat and circle are compared by strength and stiffness.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.205-210
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• 2001

Fatigue crack growth tests were carried out using high manganese cast steel under constant amplitude loading. Average crystal grain sizes of the material are $200{\mu}m$ and $1000{\mu}m$. For this material, ${\Delta}K_{th}$ is about $8MPa{\sqrt{m}}$ which is quiet large as compared to the general structural steels and the crack growth rate is lower than the general structural steels especilly in the low ${\Delta}K$ regsion. The reason of this behavior is crack closure due to fracture surface roughness and fretting oxide. The relationship between da/dN and the ${\Delta}K_{eq}$ was represented by narrow band regardless of the stress ratio.