• Journal of the Korean Ceramic Society
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• v.26 no.1
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• pp.43-50
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• 1989

This experiment was conducted to investigate correlation between microstructure and electrical properties according to Zr/Ti mole ratio in Rhombohedral Phase PZT. Domain behavoir was investigated by the change of thermal expansion coefficient. Piezoelectric properties, the temperature dependence of dielectric constant and the change of dielectric constant before and after poling were measured. Crystal structure, the measurement of lattice parameter were carried by X-ray analysis. Domain pattern before and after poling was examined by SEM.

• ETRI Journal
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• v.42 no.3
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• pp.420-432
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• 2020

The reconstruction of archaeological fragments in 3D geometry is an important problem in pattern recognition and computer vision. Therefore, we implement an algorithm with the help of a 3D model to perform reconstruction from the real datasets using the slope features. This approach avoids the problem of gaps created through the loss of parts of the artifacts. Therefore, the aim of this study is to assemble the object without previous knowledge about the form of the original object. We utilize the edges of the fragments as an important feature in reconstructing the objects and apply multiple procedures to extract the 3D edge points. In order to assign the positions of the unknown parts that are supposed to match, the contour must be divided into four parts. Furthermore, to classify the fragments under reconstruction, we apply a backpropagation neural network. We test the algorithm on several models of ceramic fragments. It achieves highly accurate results in reconstructing the objects into their original forms, in spite of absent pieces.

• Journal of the Korean Ceramic Society
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• v.42 no.10 s.281
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• pp.685-690
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• 2005

Pb(Zr,Ti)$O_{3}$Pb($Mn_{1/3}$$Nb_{2/3}$)$O_{3}$ powder was successfully synthesised by high-energy milling method, and the behavior of low­temperature sintering and piezoelectrical properties of Pb(Zr,Ti)$O_{3}$-Pb($Mn_{1/3}$$Nb_{2/3}$)$O_{3}$ ceramics were investigated as a function of mechanical alloying time. In order to confirm whether the Perovskite phase in this composition was formed by mechanical activation technique or not, we performed X-Ray Diffraction pattern analysis (XRD). The microstructure for the sintered samples were characterized using a Scanning Electronic Microscope (SEM). And the piezoelectrical properties ($k_{p}$ and $Q_{m}$) of the sintered samples was measured using HP 4194A impedance analyzer.

• 한국신재생에너지학회:학술대회논문집
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• 2008.10a
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• pp.246-249
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• 2008

IGCC (석탄가스화 복합발전) 시스템 공정 중 가스화기에서 발생되는 합성가스 내에는 높은 농도의 분진들이 함유되어 있기 때문에 하부 공정들을 보호하기 위해서는 가스화기 후단에 집진장치가 필히 설치되어야 한다. 집진장치의 설계 제작 운전에 있어서 점착성 분진층 부착,분진 브리징, 필터 파손 현상 등과 같은 다양한 문제점들로 인하여 고온의 합성가스를 처리하는 데는 아직 기술적 한계들이 산재해 있는 상황이다. 이와 같은 문제점들은 필터에 부착된 분진층의 탈진성능을 향상시키거나, 필터의 열피로를 줄일 수 있도록 필터 재생을 위한 탈진의 횟수를 줄이는 방법을 통하여 해결될 수 있다. 본 연구에서는 파일롯 규모의 IGCC용 세라믹캔들필터 집진장치에서의 가스 유입 및 탈진 조건에 따른 집진장치의 차압 특성 변화를 수치해석과 실험을 통하여 분석함으로써 탈진성능을 향상시킬 수 있는 조건과 탈진 횟수를 최소화시킬 수 있는 방안을 도출하고자 하였다.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.5
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• pp.108-117
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• 2004

In this paper, a measuring NDT(nondestructive testing) system using RUS(Resonant Ultrasound Spectroscopy) was built for nondestructive evaluation of the flaw in a ceramic Ferrule. The principle of RUS is that the mechanical resonant frequency of the materials depends on density, and the coefficient of elasticity. The RUS system is the measuring which is to exite specimen and to inspect the difference of natural frequency pattern between acceptable specimen and specimen which has some defects. RUS system is configured of spectrum analyzer, power amplifier, PZT sensor and support frame. For defect evaluation by the RUS, we performed to measure natural frequency of Ferrule, both acceptable and cracked. In the case of Ferrule, the resonant frequency of cracked-Ferrule existed to higher frequency band than acceptable-Ferrule.

• Journal of the Korean Ceramic Society
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• v.31 no.1
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• pp.62-68
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• 1994

It is compared the structures of the S-block in the Ba-Co-Zn Y-type hexagonal ferrites (Ba2Co2-xZnxFe12O22, x=0~2) and the Co-Zn spinel ferrites (Co1-xZnxFe2O4, x=0~1) expressed by a hexagonal axis system (space group R3m). The structures have been refined with a Rietveld analysis of the powder X-ray diffraction pattern with high precision (Rwp<0.13, RI<0.03). The overal dimension of the S-block is slightly different from the 1/3 of a hexagonal spinel unit cell as follow: 1.6~2.0% longer c-axis, 1.3~1.6% shorter a-axis and about 1% smaller volume. Upto Zn:Co=1:1 in the Ba-Co-Zn Y-type hexagonal ferrites, the zinc substitute primarily the tetrahedral sites in the S-block. Beyond that the zinc seems to go into the T-block as well.

• Journal of the Korean Ceramic Society
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• v.28 no.3
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• pp.225-233
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• 1991

In this study, we tried to find out the appropriate synthetic condition and magnetic properties of Ni-Zn ferrite {(NixZn1-x)Fe2O4} powders (where X=0, 0.1, 0.2, 0.3, ……0.9, 1). Ferrite powders were prepared by wet-direct method at 86℃ for 6hrs from FeCl36H2O, NiCl26H2O, and ZnCl2. The powders of (NixZn1-x)Fe2O4 (where X=0.4, 0.5, 0.6) have a good crystallinity, but the other ferrite powders consist of crystal and precursor ferrite. The ferrite powder's lattice constant is increased when ratio of ZnO contant is increased in the ferrite composition. And initial permeability was measured after sintering, result indicated regular pattern except (Ni0.4Zn0.6)Fe2O4 when the frequency were changed 10KHz to 10MHz.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.5
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• pp.464-467
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• 2005

BiSrCaCuO superconducting ceramic thick films were fabricated by chemical process. The x ray diffraction pattern of the BiSrCaCuO thick films contained 110 K phase. The critical temperature of BiSrCaCuO thick films were Tc=95 K-97 K. The critical temperature and critical density of BiSrCaCuO thick film grown at $750 {\circ}C$ were Tc = 95 K and $Jc= 7{\times}10^{6} A/cm^{2}$ We obtained high-Jc as-grown BiSrCaCuO on an MgO substrate by low fressure CVD.

• Journal of the Korean Ceramic Society
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• v.35 no.10
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• pp.1113-1119
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• 1998

Crystal structure of needle-shaped maghemite(${\gamma}$-{{{{ { {Fe }_{2 }O }_{3 } }}) has been studied by the Rieveld analysis of powder X-ray diffraction patterns. The tetragonal space group P41,.3212 and cubic space group P41,.32 have been have been used for the refinement of X-ray diffraction patterns. The crystal system of maghemite is closed to tetragonal more than cubic. The tetragonal lattice parameters are a=8.3460$\AA$ and c=25.034$\AA$ The standard X-ray diffraction pattern of the tetragonal maghemite analyzed with space group P41,.3212 is proposed.

• Journal of the Korean Ceramic Society
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• v.26 no.3
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• pp.390-394
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• 1989

The stored elastic strain energy due to the thermal expansion mismatch between the thermally oxidized crystalline layer (cristobalite) and CVD Si3N4($\alpha$-Si3N4) on cooling form high oxidation temperature (1000-140$0^{\circ}C$) to room temperature, releases through the crazing of film and lifting at the SiO2/Si3N4 interface. The ratial equation (1/n) which corresponds to the ratio of the relaxation of the stored elastic stain energy due to crazing of film to the total energy, is derived under the assumption of the square crazed pattern, as follow. 1/n={8${\gamma}$(1-v)2}/(ΔL2dE) The ratial equation suggests the reason for the lifting at the SiO2/Si3N4 interface which was observed in this research.