• Korean Journal of Materials Research
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• 제14권10호
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• pp.713-718
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• 2004

To study the dynamic strain aging behavior of Zr-0.4Sn-1.5Nb-0.2Fe sample tube for nuclear fuel cladding in the range of pressurized water reactor (PWR) operation temperature, the tensile tests of the tube specimens, which had been finally heat-treated at $470^{\circ}C\;and\;510^{\circ}C$, had been carried out with the strain rate $1.67{\times}10^{-2}/s\;and\;8.33{\times}10^{-5}/s$ at the various temperatures from room temperature to $500^{\circ}C$. It was observed that the elongation of the specimens got shortened as the temperature increased from $200^{\circ}C\;to\;340^{\circ}C$. The specimens that were finally heat-treated at $470^{\circ}C$ showed a plateau more remarkably on the plot of yield strength-temperature than those heat-treated at $510^{\circ}C$. In the range of $310\sim400^{\circ}C$, the strain rate sensitivity of the specimens finally heat-treated at $510^{\circ}C$ was $30.4\%\sim33.7\%$ lower but the work hardening exponent index of the specimens was a little higher than that without dynamic strain aging effect.

• Korean Chemical Engineering Research
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• 제43권4호
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• pp.531-536
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• 2005

Inductively coupled plasma reactive ion etching of CoTb and CoZrNb magnetic materials with the photoresist mask was performed using $Cl_2/Ar$ and $C_2F_6/Ar$ gas mixtures and characterized in terms of etch rate and etch profile. As the concentrations of $Cl_2$ and $C_2F_6$ gases increased, the etch rates of magnetic films decreased and the etch slopes became slanted. The $Cl_2/Ar$ gas was more effective in obtaining fast etch rate and steep sidewall slope than the $C_2F_6/Ar$ gas. As the coil rf power and dc bias increased, fast etch rate and steep etch slope were obtained but the redeposition on the sidewall was observed. This is due to the increase of ion and radical densities in plasma with increasing the coil rf power and the increase of incident ion energy to the substrate with increasing the dc bias voltage. By applying high density reactive ion etching to magnetic tunnel junction stack containing various magnetic films and metal oxide, steep etch slope and clean etch profile without redeposition were obtained.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제5B권3호
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• pp.289-295
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• 2005

Instrumentation and Control (I&C) of the Neutral Beam Test Stand (NB- TS) Facility at the Korea Atomic Energy Research Institute (KAERI) for the Korea Superconducting Tokamak Advanced Research (KSTAR) project has been underway since the start of the project to answer the diverse requests arising from the various facets of the development and construction phases of the project. Optical signal transmission constitutes a significant portion of I&C works and has been performed for the entirety of the project. During the NB- TS construction and related experiments, significant achievements to a more accurate as well as more refined optical signal transmissions have been made. Examples of those I&C works that utilized the optical signal transmission are the Langmuir probe signal transmission, gradient grid current signal transmission, gas flow control and signal transmission, ion source temperature measurement, beam line component temperature monitoring, and coolant flow signal transmission, etc. These optical signal transition provisions are now performing part of the indispensable functions for the proper operation of the NB- TS facility. Attained experience and expertise are expected to be well applied to the upcoming main neutral beam injection (NBI) system construction for the KSTAR project.

• Journal of Power System Engineering
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• 제8권3호
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• pp.30-35
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• 2004

In the steel making industries, the continuous casting process has been applied to the number of company because of its economical benefit. Casting rolls are utilized for frictional drive and transport of solidifying slap. Dimensional tolerances, mechanical stability and surface condition of the cast roll can affect both the surface and internal quality of the product being cast. To overcome these problems, the industry is accelerating on the rate of technology improvements. Samples were overlaid on the S45C steel by submerged arc welding process. And the hardness, wear, electrochemical corrosion and oxidation tests were carried out. Test results were that all these materials were satisfying basic requirements of caster rolls. By these results, the addition of 0.1%Nb and 0.15%V increase mechanical properties and tempering resistance by its superior carbide forming characteristics in low carbon $12{\sim}13%Cr$ martensitic stainless steels.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 1995년도 추계학술대회 논문집
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• pp.14-17
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• 1995

In this study, fur the use of portable communication multilayer devices. 0.15wt% V$_2$O$\_$5/ added BiNbO$_4$which is low-fire microwave dielectric ceramic as able to co-fire with high conductors was made into specimens with the additions of Cr$_2$O$_3$0.04, 0.2, 0.4, 0.8, 1.2wt%. These specimens were sintered at 930, 960. 990, 1030$^{\circ}C$ respectively to make the microwave dielectric resonators. These resonators were investigated by measuring the structure and dielectric properties. The density of the specimens was increased by the amounts of the Cr$_2$O$_3$and increased by increasing the temperature. 0.8wt% Cr$_2$O$_3$added and sintered at 960$^{\circ}C$ specimen skewed 49 dielectric constant. Q$.$f values were increased by the amounts of Cr$_2$O$_3$. And Q value was deteriorated by the additions of Cr$_2$O$_3$at sufficiently sintered temperatures. Negative resonant temperature coefficients were moved to positive by the amounts of Cr$_2$O$_3$and returned negative again at 1.2wt%. Temperature characteristics were deteriorated at 1030$^{\circ}C$.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 한국결정성장학회 1999년도 PROCEEDINGS OF 99 INTERNATIONAL CONFERENCE OF THE KACG AND 6TH KOREA·JAPAN EMG SYMPOSIUM (ELECTRONIC MATERIALS GROWTH SYMPOSIUM), HANYANG UNIVERSITY, SEOUL, 06월 09일 JUNE 1999
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• pp.305-320
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• 1999

It was grown Er2O3 doped LiNbO3 single crystal thin films with high crystal quality by liquid phase epitaxial (LPE) method. Er2O3 was doped with a concentration of 1, 3, and 5 mol% respectively. After the growth of single crystal thin film, we examined the crystallinity and the lattice mismatch along the c-axis between the film and the substrate with the variation of Er2O3 dopant using X-ray double crystal technique. There were no lattice mismatches along the c-axis for the undoped and the films doped with 1 and 3 mol% of Er2O3. For 5 mol% of Er2O3 doped film, there was a lattice mismatch of 7.86x10-4nm along the c-axis.

• Journal of the Korean Institute of Telematics and Electronics D
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• 제35D권4호
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• pp.9-17
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• 1998

BiNbO$_{4}$ ceramics with 0.07wt% V$_{2}$O$_{5}$ and 0.03wt% CuO (BNC3V7) sintered at 900 .deg. C where it is possible for these to be co-fired with ag electronde. Dielectric constant of 44.3 TCF (Thermal Coefficient of resonance Frequency) of 2 ppm/.deg. C and Qxf value 22,000 GHz can be obtained from BNC3V7. the laminatedchip LC filter is indispensible to the minimaturization of PCS (Personal Communication System) terminals. Therefore, multilayer type BPF has been fabricated by screen-printing with silver electrode after tape casting. The simulated characteristics of the fabricated filters sintered at 900.deg. C werecomparedwith the designed ones. for Band Pass Filter widths was similar that ofdesigned ones. For Low Pass Filter (LPF), insertion loss value of band pass widths (2.4 dB) which is a few higher than that of designed (1dB), but characteristization of band pass widths was similar that of designed ones.s.of designed ones.s.

• Journal of the Korean Ceramic Society
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• 제45권3호
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• pp.139-141
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• 2008

The piezoelectric properties of tetragonal 0.88Pb$(Zn_{1/3}Nb_{2/3)O_3-0.12PbTiO_3$ single crystals are characterized along the <111> direction, which composed the engineering domain configuration in the tetragonal phase. The <111>-oriented crystal possessed smaller $d_{33}$ values compared to the crystal along the <001> spontaneous polarization direction. Based on phenomenological theory, it is shown that the engineering domain configuration does not enhance the piezoelectric constant in tetragonal 0.88Pb$(Zn_{1/3}Nb_{2/3)O_3-0.12PbTiO_3$ single crystals. In addition, the electrostrictive coefficients of $Q_{12}=-0.03706m^4/C^2,\;Q_{11}=0.10765m^4/C^2,\;and\;Q_{44}=0.02020m^4/C^2$ of tetragonal 0.88PZN-0.12PT single crystals were calculated.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• 제14권4호
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• pp.269-273
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• 2001

W fabricated thin film using Na$_{0.5}$K$_{0.5}$NbO$_3$ volatile material by pulsed laser deposition (PLD) and studied characterization from EM, XRD, P-E. The density and scale of droplet, which is the defect of PLD, was investigated by SEM but large droplet was not found. The degree of assemble oriented C-axis measured with X-ray diffraction suggests that this film oriented C-axis achieved by $\theta$-2$\theta$ scan and rocking curves shows good self-assemble phenomenon, finally $\phi$-scan does that all of the four directions of the lattice in film equals to those of substrate. P-E hysteresis loop shows residual remnant polarization or saturation polarization value, but it is applicable to memories.ies.

• Korean Journal of Crystallography
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• 제1권1호
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• pp.1-7
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• 1990

It is shown that the symmetry of the incommensurate phase in Ba2NaNb5O15(BSH) belongs to the four dimensional superspace group C from an analysis of the systematic extinction or the rxtra reflections due to the incommensllrate structure. The resulting superstructure is characterizetl by the space group Ima2(C3l) and the origin of the incommensurability in BSN is briefly discussed. Especially. HREM image have shown the prrscnce of discommensurations. In addition. a group-theoretical consideration of structural phase transitions in BSN is suggested.