• Journal of Advanced Marine Engineering and Technology
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• v.23 no.5
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• pp.702-710
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• 1999

U-shaped bellows are usually used to piping system pressure sensor and controller for refriger-ator. Bellows subjected to internal pressure are designed for the purpose of absorbing deformation. Internal pressure on the convolution sidewall and end collar will be applied to an axial load tend-ing to push the collar away from the convolutions. To find out deformation behavior of bellow sub-jected to internal pressure the axisymmetric shell theory using the finite element method is adopted in this paper. U-shaped bellows can be idealized by series of conical frustum-shaped ele-ments because it is axisymmetric shell structure. The displacements of nodal points due to small increment of force are calculated by the finite element method and the calculated nodal displace-ments are added to r-z cylindrical coordinates of nodal points. The new stiffness matrix of the sys-tem using the new coordinates of nodal points is adopted to calculate the another increments of nodal displacement that is the step by step method is used in this paper. The force required to deflect bellows axially is a function of the dimensions of the bellows and the materials from which they are made. Spring constant is analyzed according to the changing geometric factors of U-shaped bellows. The FEM results were agreed with experiment. Using developed FORTRAN PROGRAM the internal pressure vs. deflection characteristics of a particu-lar bellows can be predicted by input of a few factors.

• Journal of Powder Materials
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• v.11 no.2
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• pp.124-129
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• 2004

Nanosized WC and WC-Co powders were synthesised by chemical vapor condensation(CVC) process using the pyrolysis of tungsten hexacarbonyl(W(CO)$_6$) and cobalt octacarbonyl(Co$_2$(CO)$_8$). The microstructural changes and phase evolution of the CVC powders during post heat-treatment were studied using the XRD, FE-SEM, TEM, and ICP-MS. CVC powders were consisted of the loosely agglomerated sub-stoichimetric WC$_{1-x}$ and the long-chain Co nanopowders. The sub-stochiometric CVC WC and WC-Co powders were carburized using the mixture gas of CH$_4$-H$_2$ in the temperature range of 730-85$0^{\circ}C$. Carbon content of CVC powder controlled by the gas phase carburization at 85$0^{\circ}C$ was well matched with the theoretical carbon sioichiometry of WC, 6.13 wt％. During the gas phase carburization, the particle size of WC increased from 20 nm to 40 nm and the long chain structure of Co powders disappeared.

• Journal of Powder Materials
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• v.11 no.2
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• pp.143-148
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• 2004

In the present study, $TiO_2$ imbedded composite powders have been successfully prepared from the (Cu. Zn)/$TiO_2$ composite salt solution. The composite (Cu, Zn)/$TiO_2$ powders were formed by drying the solution at 200~$600^{\circ}C$ in the hydrogen atmosphere. Photocatalytic characteristics was evaluated by detecting the decomposition ratio of aniline blue with UV-visible spectrophotometer(Shimazu Co., UV-1601). Phase analysis of (Cu, Zn)/$TiO_2$ composite powders was carried out by XRD and DSC, and powder size was measured with TEM. The mean particle size of composite powders was about 100mm. As the reduction temperature increases, a few zinc sulfide and oxide phases was formed and copper oxide phase was reduced. The decomposition ratio of aniline blue was about 80％ under the UV irradiation by the TiO$_2$ phase in the composite (Cu, Zn)/$TiO_2$ powders and similar decomposition ratio of 80％ was obtained at the UV lightless condition by virtue of Cu and Zn compounds.

• Journal of Powder Materials
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• v.14 no.3 s.62
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• pp.165-172
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• 2007

The purpose of this study was to analyze the sintering characteristics of gold and silver nanoparticles. In this study, gold and silver nanoparticles were prepared by using Inert Gas Cndensation (IGC). The sintering temperatures for gold and silver nanoparticles were $100{\sim}1000^{\circ}C\;and\'100{\sim}500^{\circ}C$, respectively. The sintering characteristics of gold and silver nanoparticles prepared by IGC were evaluated by X-ray diffraction(XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Gold and silver nanoparticles with the size of $1{\sim}100\;nm\;and\;10{\sim}100\;nm$, respectively, were obtained. The size of sintered gold and silver nanoparticles increased with an increase in the sintering temperature. XRD data showed that silver nanoparticles were similar with polycrystal single-phase.

• Journal of Haehwa Medicine
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• v.4 no.2
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• pp.273-297
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• 1996

Hexane fraction of Oldenlandiae diffusae Herba(ODH) which was being used for the treatment of caner in oriental medicine showed the best cytotoxicity against L1210 and A549 in the solvent fractions. Antitumor substance isolated from hexane fraction of ODH was identified as ursolic acid(UA) by photometric analysis. IC50 of UA against cancer cells as SNU-1, HCT15, XF498, SK-MEL2 and A549 was $13{\mu}g/m{\ell}$, $15{\mu}g/m{\ell}$, $12{\mu}g/m{\ell}$, $9{\mu}g/m{\ell}$ and $11{\mu}g/m{\ell}$ respectively. It significantly inhibited the metastasis to lungs and kidneys from pulmonary colonization assay and study on histological changes of organs and showed the enhancing effect on B cell dosage-dependently by FACS analysis. T/C % of UA against S-180 cells was 171 % and its cytotoxicity against SNU-1 iant was confirmed from the morphological changes by elctronic microscopes such as SEM and TEM that it induced undulated membrane 4 hr after UA treatment, and the breakdown of cell membrane and nucleus 24 hr after UA treatment.

• Journal of Industrial Technology
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• v.25 no.A
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• pp.157-162
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• 2005

In this study, the fabrication of PZT films was performed from a multilayer structure comprising $TiO_2$, $ZrO_2$ and PbO thin films prepared by rapid themal chemical vapor deposition(RTMOCVD). $TiO_2$, $ZrO_2$ and PbO are the component layers of oxide multilayer system for a single phase PZT thin film. The composition control of PZT thin film was done by the thickness control of individual component layer. The composition ratio of Pb:Ti:Zr with thickness were 1:0.94:0.55. Occurrence of a single-phase of PZT was initiated at around $550^{\circ}C$ and almost completed at $750^{\circ}C$ under the fixed time of 1hr. As the concentration of Pb increased, the roughness and crystallization in the film increased. From the as result of using XPS and TEM, the single phase formation through annealing is evident. The electrical properites of the prepared PZT thin film(Zr/Ti=40/60, 300 nm) on a Pt-coated substrate were as follow: dielectric constant ${\varepsilon}_r=475$, coercive field Ec=320 kV/cm, and remanant polarization $P_r=11{\mu}C/cm^2$ at an applied voltage of 18 V.

• Journal of the Korean Ceramic Society
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• v.43 no.9 s.292
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• pp.564-568
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• 2006

AlO(OH) nano gel is used in precursor of ceramic material, coating material and catalyst. For use of these, not only physiochemical control for particle morphology, pore characteristic and peptization but also studies of synthetic method for preparation of advanced application products were required. In this study, AlO(OH) nano gel was prepared through the aging and drying process of aluminum hydroxides gel precipitated by the hydrolysis reaction of dilute NaOH solution and aluminum sulfate solution. In this process, optimum synthetic condition of AlO(OH) nano gel having excellent pore volume as studying the effect of water and aluminum sulfate mole ratio on gel precipitates has been studied. Water and aluminum sulfate mole ratio brought about numerous changes on crystal morphology, surface area, pore volume and pore size. Physiochemical properties were investigated as using XRD, TEM, TG/DTA, FT-IR, and $N_2$ BET method.

• Journal of the Korean Ceramic Society
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• v.36 no.1
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• pp.36-42
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• 1999

Stacking faults in SiC whiskers grown by three different growth mechanisms; vapor-solid(VS), two-stage growth(TS), and vapor-liquid-solid (VLS) mechanism in the carbothermal reduction system were investigated by X-ray diffraction(XRD) and transmission electron microscopy (TEM). The content of stacking faults in SiC whiskers increased with decreasing the diameter of whiskers, i.e., the small diameter whiskers (<1 $\mu\textrm{m}$) grown by the VS, TS, and VLS mechanisms have heavy stacking faults whereas the large diameter whiskers(>2$\mu\textrm{m}$) grown by the VLS mechanism have little stacking faults. Heavy stacking faults of small diameter whiskers was probably due to the high specific lateral surface area of small diameter whiskers.

• Journal of the Korean Ceramic Society
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• v.36 no.5
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• pp.513-520
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• 1999

Alumina-coated SiC whiskers wee prepared by the calcination (1150$^{\circ}C$, 1h, Ar) of the alumina hydrate layer which was precipitated homogeneously on whisker surface from a solution of Al2(SO4)3 and urea as a precipitant. In addition carbon coated SiC whiskers were prepared by the pyrolysis (1000$^{\circ}C$, 4h Ar) of phenolic resin coated whisker. The effects of coating conditions on the thickness and morphology of the coated layers were examined by SEM and TEM. It was found that Al2O3-coating layers become thinner and more uniform with decreasing the Al2(SO4)3 concentration. Thin (0.075-0.1$\mu\textrm{m}$) and uniformly alumina-coating layers were obtained at the Al2(SO4)3 concentration 0.010mol/l. On the other han carbon-coating layers were uniform but very thin (5-16 nm) in thickness. For thicker carbon-coating layers ethanol as a disperse medium was found to be more efficient compared tousing acetone.

• Journal of the Korean Ceramic Society
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• v.50 no.6
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• pp.466-469
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• 2013

Currently, piezoelectric ceramics are being applied in various fields, such as ultrasonic sensors, vibration devices, sound filters, and various energy conversion devices. Flexible piezoelectric ceramics are widely studied in an effort to mitigate the disadvantages of their brittle and inductile properties. Structural damage to piezoelectric fibers is much less than that to thin films when piezoelectric fibers are twisted or bent. Therefore, stretchable devices can be fabricated if piezoelectric fibers are obtained using an elongated substrate. In this study, sintering processes of PZT ($Pb(Zr_{0.53}Ti_{0.47})O_3$) fibers prepared by electrospinning were optimized through the TGA and XRD analyses. The crystal structure and microstructure of the piezoelectric fibers were investigated by XRD, FE-SEM and TEM.