• 조명전기설비학회논문지
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• 제29권12호
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• pp.22-27
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• 2015

Conoscopic holography, which consists of two linear polarizers and two wave plates, and an uniaxial crystal, is incoherent holographic technology for three-dimensional display. In the uniaxial crystal, the wave from object divides into extraordinary and ordinary waves and phase difference between two waves is caused by the different refractive index of two waves. Four intensity patterns, which are made by phase difference, are obtained using LCLV(liquid crystal light valve) and conoscopic holography system. By combining four intensity patterns, the complex hologram without bias and conjugate image. In this paper, we propose the optimized system, which consists of a wave plate and a linear polarizer, and uniaxial crystal. In the proposed system, it doesn't need LCLV. By adjusting the azimuth angle of a linear polarizer and a wave plate, we derive four intensity patterns in recording plane. We demonstrate theoretically that the complex hologram with bias and a conjugate image is obtained using the proposed system.

• 터널과지하공간
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• 제10권1호
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• pp.70-79
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• 2000

입자수, 압력, 온도일정의 앙상블(NPT-ensemble) 분자동력학(MD) 시뮬레이션을 이용하여 300$^{\circ}$K에서 $\alpha$-quartz의 결정축에 따른 일축압축강도를 계산하고, 자연산 $\alpha$-quartz 단결정 코아를 제작하여 일축압축강도시험을 실시하였다. $\alpha$-quartz 단결정 코아에 대한 일축압축시험에서 측정된 결과에 의하면 재하 방향이 c축에 평행한 경우가 수직인 경우보다 높은 강도를 나타내지만, MD 시뮬레이션에서 계산된 완전무결함 $\alpha$-quartz의 경우 이와 반대의 결과를 보이고 있다. 두 경우 모두 재하방향에 따른 강도 이방성을 보이고 있으나, 그 이유는 서로 다르다. MD 시뮬레이션에 의해 계산된 무결함 $\alpha$-quartz의 강도 이방성은 결정구조의 차이에 기인하는 것으로 사료된다. 이에 반해 일축압축시험을 통해 측정된 $\alpha$-quartz의 강도 이방성은 결정성장과정에서 생기는 주상 미세결함에 의해 영향을 받는다.

• 소성∙가공
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• 제23권4호
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• pp.231-237
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• 2014

In the current study, a rate-dependent crystal plasticity finite element method (CPFEM) was used to simulate flow stress behavior and texture evolution of a body-centered cubic (BCC) crystalline material during plastic deformation at room temperature. To account for crystallographic slip and rotation, a rate-dependent crystal constitutive law with a hardening model was incorporated into an in-house finite element program, CAMPform3D. Microstructural heterogeneity and anisotropy were handled by assigning a crystallographic orientation to each integration point of the element and determining the stiffness matrix of the individual crystal. Uniaxial tensile tests of single crystals with different crystallographic orientations were simulated to determine the material parameters in the hardening model. The texture evolution during four different deformation modes - uniaxial tension, uniaxial compression, channel die compression, and simple shear deformation - was investigated based on the comparison with experimental data available in the literature.

• 소성∙가공
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• 제21권4호
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• pp.252-257
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• 2012

Crystallographic texture evolution during forming processes has a significant effect on the anisotropic flow behavior of crystalline material. In this study, a crystal plasticity finite element method (CPFEM), which incorporates the crystal plasticity constitutive law into a three-dimensional finite element method, was used to investigate texture evolution of a face-centered-cubic material - an aluminum alloy. A rate-dependent polycrystalline theory was fully implemented within an in-house program, CAMPform3D. Each integration point in the element was considered to be a polycrystalline aggregate consisting of a large number of grains, and the deformation of each grain in the aggregate was assumed to be the same as the macroscopic deformation of the aggregate. The texture evolution during three different deformation modes - uniaxial tension, uniaxial compression, and plane strain compression - was investigated in terms of pole figures and compared to experimental data available in the literature.

• Journal of the Optical Society of Korea
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• 제20권6호
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• pp.686-693
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• 2016

The analytical expressions for a partially coherent flat-topped vortex hollow beam propagating in uniaxial crystals orthogonal to the optical axis are derived, and the intensity and coherent vortex properties of partially coherent flat-topped vortex hollow beam propagation in uniaxial crystals orthogonal to the optical axis are analyzed by numerical examples. The influence of beam order parameter N, topological charge M, the coherence length and the ratio of refractive indices $n_e/n_o$ of uniaxial crystals on the normalized intensity distribution and coherent vortex of a partially coherent flat-topped vortex hollow beam propagating in uniaxial crystals are discussed in detail.

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 1987년도 제2차학술발표초록집
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• pp.12-13
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• 1987

• Journal of the Optical Society of Korea
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• 제20권4호
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• pp.510-514
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• 2016

The conventional liquid crystal displays (LCDs) have been using optically uniaxial liquid crystal (LC) medium and this often causes a significant image change at oblique viewing angles. We simulated the viewing angle properties of the biaxial nematic (N_b) phase of a bent-core liquid crystal (BLC) and compared the results with the vertically aligned (VA)- and the in-plane switching (IPS)-LCDs. The N_b phase of the BLC showed a smaller transmittance at the dark state as well as a greater contrast ratio at wide viewing angle. The viewing angle property of the N_b-mode without any compensation film was slightly superior to the IPS-mode with the compensation films eliminating the decross of the polarizers at oblique viewing angle.

• 한국전기전자재료학회논문지
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• 제26권1호
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• pp.27-32
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• 2013

According to the composition of LTCC material, though it was thought that bulk defect which was made in forming process effects on the densification during the sintering, it was not reported systemically. In this study, we evaluated crystal structure, 3 point bending strength, hardness and microstructure of the samples by uniaxial pressing and tape casting using the commercial powders of the crystallizing glass and the glass/ceramic composite. In the case of glass/ceramic composite, Viox-001 powder with residual glass in the sintering, 3 point bending strength was similar regardless of forming process due to fill the bulk defect by residual glass. In the case of crystallizing glass, MLS-22, because glass phase was small in the sintering, glass did not fill the pore in the sample by uniaxial pressing process, therefore, the 3 point bending strength of it was 167 MPa. However, the 3 point bending strength of the sample by tape casting was 352 MPa and much higher. Meanwhile, crystal structure and hardness were similar regardless of forming process.

• 한국결정성장학회지
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• 제8권2호
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• pp.356-364
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• 1998

$ZTA:\;Al_2O_3/\;15\;vol{%}\;ZrO_2$ (Zirconia Toughened Alumina : ZTA)를 상압소결에 의해 제조시 분무건조한 granule의 특성에 따른 성형밀도 및 소결밀도의 변화를 고찰하여, 소결밀도의 재현성을 향상시킬 수 있는 성령 공정 조건을 제시하였다. 결합제의 첨가 유무에 따라 granule의 구형도, 평균크기, granule 내의 hollow의 생성정도, 수분함유량 등이 다름을 확인하였다. granule의 물성 차이가 성형거동에 미치는 영향을 성형압(80~120MPa)과 성형방법(일축성형과 정수압 성형)에 따른 성형밀도의 변화를 통하여 조사하였다. granule의 특성 변화에 의한 밀도의 낮은 재현성은 성형압과 성형방법의 최적화를 통하여 극복될 수 있음을 확인하였다. 즉 가능한 낮은 압력(80MPa)에서 일축성형한 후 고압(500MPa)에서 정수압 성형하였을 때 소결후 밀도변화는 1%이내에서 조절되었다.

• Nuclear Engineering and Technology
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• 제51권2호
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• pp.501-509
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• 2019

In this paper a body-centered cubic(BCC) crystal plasticity model based on microscopic dislocation mechanism is introduced and numerically implemented. The model is coupled with irradiation effect via tracking dislocation loop evolution on each slip system. On the basis of the model, uniaxial tensile tests of unirradiated and irradiated RPV steel(take Chinese A508-3 as an example) at different temperatures are simulated, and the simulation results agree well with the experimental results. Furthermore, crystal plasticity damage is introduced into the model. Then the damage behavior before and after irradiation is studied using the model. The results indicate that the model is an effective tool to study the effect of irradiation and temperature on the mechanical properties and damage behavior.