• 한국전자파학회논문지
• /
• 제15권6호
• /
• pp.590-598
• /
• 2004

저잡음 특성과 함께 부성 저항과 수동 캐패시턴스의 특성을 보이도록 설계된, 직렬 피드백 회로를 이용한 FET능동 캐패시턴스 회로를 심도 있게 분석하였고, 이를 저잡음 능동 대역통과 여파기에 적용하였다. 부성저항을 이용한 마이크로파 대역 능동 여파기의 설계방식은 비교적 여러 차례 소개되었으나, 원하는 주파수에서 적절한 부성저항 성분을 구현하는 데에는 아직 어려움이 있으며, 이로 인한 능동 회로의 안정성 저하와 대역내 평탄도 증가 등으로 인해 실제 상용화에는 다다르지 못하고 있다. 이들 문제를 해결하고 실제 상용화에 이르기 위해서는 부성저항 회로의 세밀한 분석이 필요하며, 이를 이용한 부성저항 성분의 제어를 가능하도록 해야 한다. 이에 본 논문에서는 능동 캐패시턴스 회로의 부성저항 성분을 분석하였고, 또한 BPF의 통과대역의 평탄도를 개선할 수 있는 방법을 제시하였다. 제작된 4단 대역통과 여파기는 중심주파수 1.99 ㎓에서 60 MHz의 대역폭을 가지며, 0.67 ㏈ 삽입손실, 0.3 ㏈ 이내의 대역내 평탄도와 3.0 ㏈의 잡음 지수 특성을 보였다.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2007년도 춘계학술대회 논문집
• /
• pp.282-284
• /
• 2007

The hardening and the constitutive equation based on the crystal plasticity are introduced for the numerical simulation of hemispherical sheet metal forming. For calculating the deformation and the stress of the crystal, Taylor's model of the crystalline aggregate is employed. The hardening is evaluated by using the Taylor factor, the critical resolved shear stress of the slip system, and the sum of the crystallographic shears. During the hemispherical forming process, the texture of the sheet metal is evolved by the plastic deformation of the crystal. By observing the texture evolution of the BCC sheet, the texture evolution of the sheet is traced during the forming process. Deformation texture of the BCC sheet is represented by using the pole figure. The comparison of the strain distribution and punch force in the hemispherical forming process between crystal plasticity and experiment shows the verification of the crystal-based formulation and the accuracy of the hardening and constitutive equation obtained from the crystal plasticity.

• 열처리공학회지
• /
• 제21권3호
• /
• pp.144-149
• /
• 2008

It has been reported that copper and copper alloys have a large anisotropy of functional properties such as electrical, thermal and mechanical properties, which means that the texture of polycrystalline alloy should be considered to achieve better properties. In this study, the determination of grain growth orientation and texture formation in the cold-rolled, heat-treated and Ni-plated hybrid copper sheets was investigated. Grain growth direction and texture formation were analyzed by the X-ray pole figure. The influence of texture on the mechanical properties could be quantitatively confirmed by the results from the orientation distribution function and the tensile test. The heat-treated texture in the cold-rolled hybrid copper sheet is also investigated and discussed.

• 한국재료학회지
• /
• 제27권11호
• /
• pp.636-642
• /
• 2017

In the present study the microstructure of low-carbon steels fabricated by controlled rolling and accelerated cooling processes was characterized and identified based on various microstructure analysis methods including optical and scanning electron microscopy, and electron backscatter diffraction(EBSD). Although low-carbon steels are usually composed of ${\alpha}-ferrite$ and cementite($Fe_3C$) phases, they can have complex microstructures consisting of ferrites with different size, morphology, and dislocation density, and secondary phases dependent on rolling and accelerated cooling conditions. The microstructure of low-carbon steels investigated in this study was basically classified into polygonal ferrite, acicular ferrite, granular bainite, and bainitic ferrite based on the inverse pole figure, image quality, grain boundary, kernel average misorientation(KAM), and grain orientation spread(GOS) maps, obtained from EBSD analysis. From these results, it can be said that the EBSD analysis provides a valuable tool to identify and quantify the complex microstructure of low-carbon steels fabricated by controlled rolling and accelerated cooling processes.

• 한국진공학회지
• /
• 제5권2호
• /
• pp.133-138
• /
• 1996

단일 선구물질인 1, 3 -디실라부탄을 사용하여 고진공 하의 온도 영역 900-$1000^{\circ}C$에서 탄화규소 환충층이 형성된 Si(001) 기질 위에 입방형 탄화규소 박막을 적층 성장시켰다. 얻어진 탄화규소 박막의 화학량론적 비, 양질의 결정성 및 표면형태의 특성을 반사 고에너지 전자 회절, Xtjs 광전자 분광법, X선 회절, Xtjs 극접도, 주사 전자 현미경 및 투과 전자 현미경으로 확인하였다. 이들 결과로부터 단일 선구물질인 1, 3-디실라부탄이 입방구조를 가지는 탄화규소 박막의 적층 성장에 적절한 물질임을 밝혔다.

• 한국정보통신설비학회:학술대회논문집
• /
• 한국정보통신설비학회 2003년도 하계학술대회
• /
• pp.143-148
• /
• 2003

In this paper, we focused on the performance of reverse link in 1.8GHz CDMA 1x system including the Tower-Mount LNA in an urban environment. In order to study the benefit of TMLNA, Hata model is used and the effects of multiple cells are considered. Cell coverage extension ratio is proportional to the increased gain of TMLNA in CDMA cell site. However the cell coverage is not extended even if the noise figure of TMLNA is reduced in an urban area. When typical RSSI is between -70dBm and -80dBm, the increased gain and the reduced NF of TMLNA are not impact to the pole capacity of cell site. Namely, the benefit of TMLNA in an urban area is not the problem of capacity but the proble of sensitivity. The results are also shown that reverse link $E_b/N_o$ is improved by minimum 5dB and BER is lower than $10^{-6}$.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.II
• /
• pp.1576-1579
• /
• 2005

With varying rapid thermal annealing (RTA) temperature, luminescence properties of $Zn_{0.75}Mg_{0.25}S:Mn$ thin film deposited by RF-magnetron sputtering technique were investigated. In this study, $Zn_{0.75}Mg_{0.25}S:Mn$ thin film phosphor showed more red emission than those of the previous studies when annealed around 600 or $650^{\circ}C$. Although all samples were deposited from identical source composition, a main peak wavelength of photoluminescence spectra of $Zn_{0.75}Mg_{0.25}S:Mn$ shifted toward shorter wavelengths depending upon increase of RTA temperature. The same dependence of wavelength on RTA temperature was also observed in cathodoluminescence as well as electroluminescence measurements. It was revealed that the change of the luminescence properties were originated from structural changes in $Zn_{0.75}Mg_{0.25}S:Mn$ thin film phosphor from cubic to hexagonal phases analyze using conventional X-ray pole figure mapping. The phase transition would be the origin of luminescence property changes with respect to RTA temperature.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2002년도 하계학술대회 논문집
• /
• pp.98-104
• /
• 2002

CeO$_2$ and NiO buffers for YBCO coated conductors were deposited on biaxially textured Ni substrate by metalorganic chemical vapor deposition(MOCVD) and the deposition behavior were investigated. The degree of texture of deposited CeO$_2$ and NiO films was strongly dependent on the deposition temperature(T$\sub$d/) and oxygen partial pressure(P$\sub$O$_2$/). ($\ell$00) textured films were well deposited at specific deposition temperatures and oxygen partial pressures. The in-plane and out of plane textures estimated form the full width half maximum of the pole figure peaks were less than 10$^{\circ}$. The surface morphology showed that the CeO$_2$ films consisted of columnar grains grown normal to the Ni substrates, while NiO films were slate and clean like a mirror. The surface roughness of both films estimated by atomic force microscopy(AFM) were as smooth as 3-10 m. The growth rate of the films is much faster than that of other physical deposition methods.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2004년도 제5회 압연심포지엄 신 시장 개척을 위한 압연기술
• /
• pp.72-82
• /
• 2004

The deformation mechanism of hexagonal close-packed materials is quite complicate including slips and twins. A deformation mechanism, which accounts for both slip and twinning, was investigated for polycrystalline hop materials. The model was developed in a finite element polycrystal model formulated with initial strain method where the stiffness matrix in FEM is based on the elastic modulus. We predicted numerically the texture of Mg alloy(AZ31B) sheet by using FEM based on crystal plasticity theory. Also, we introduced the recrystallized texture employed the maximum energy release theory after rolling. From the numerical study, it was clarified that the shrink twin could not be the main mechanism for shortening of c-axis, because the lattice rotation due to twin rejects fur c-axis to become parallel to ND(normal direction of plate). It was showed that the deformation texture with the pyramidal slip gives the ring type pole figure having hole in the center.

• 한국분말재료학회지
• /
• 제14권1호
• /
• pp.13-18
• /
• 2007

The mother Ni-W (1-5 wt.%) alloy billets for coated conductor substrate were fabricated by powder metallurgy process. The tensile test results for the sintered Ni-W rods showed the increase of mechanical strength and decrease of ductility with increasing W content due to the solid solution hardening. All the fracture surfaces of the tested specimens showed the typical ductile fracture mode of dimple rupture due to the local necking. The Ni-W alloy billets were made into tape by cold rolling. After the appropriate heat treatment for recrystallization, the brass texture formed by the cold rolling was converted to the complete cube texture. The in-plane and out of plane texture of the tapes estimated by x-ray pole figure were smaller than 9 degree and 7 degree, respectively. The effect of the W addition on the texture development seems not to be significant.