• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.2 no.4
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• pp.39-46
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• 1991

전자파 문제는 넓은 의미로 산란(scattering)문제와 역산란(inverse scattering)문제로 나눌 수 있다. 먼저 산란 문제는 에너지 또는 정보가 실린 전자파를 한 지점에서 다른 지점으로 보낼 때 통과하는 경로상의 매질 분포에 따라 왜곡 또는 변형되는 정도를 알아내는 것으로 반사(reflection), 굴절(refraction), 회절(diffraction)등 의 현상을 수반한다. 이 때 전자파를 왜곡시키는 물체를 산란체라고 부르며, 이러한 산란체로서는 전송선, 도파관, 광섬유 등과 같은 도파구조(guided wave structure)자체일 수 있으며 그들 내부에 고의로 부착된 첨가물일 수도 있다. 또한 공기나 지하와 같은 개방 구조 내의 물체나 비균일 매질 분포도 산란체가 될 수 있다. 이와는 반대로 역산란 문제는 알고 있는 전자파를 미지의 산란체에 가한 후, 여기서 산란된 전자파를 측정하여 얻은 자료로 부터 역으로 산란체의 위치, 크기, 모양, 매질 특성 등을 알아내는 것이다. 이러한 역산란 문제는지하 탐사(geophysical probing), 원격탐사(remote sensing), 레이다 영상(radar imaging), 의료진단(medical diagnosis), 비파괴 검사(nondestructive testing)등과 같은 많은 응용분야에 걸쳐 있다. 본 원고에서는 전자파 산란 및 역산란 문제에 대한 기존의 다양한 해석기법들을 체계적으로 분류하고, 이들의 적용범위와 한계에 대해 간략히 소개하기로 한다.

• Current Applied Physics
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• v.18 no.11
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• pp.1218-1224
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• 2018

Pressure-dependent structural and morphological changes of two amphibole minerals, tremolite and actinolite, were investigated up to 7.0 GPa using synchrotron X-ray powder diffraction underthree different pressure transmission media (PTM): water (W), $CO_2$ and silicone oil (SI). The elastic response of tremolite and actinolite are found to be dependent on the PTM used. When using water (W) as PTM, tremolite and actinolite show normal volume contractions with bulk moduli of 74(1) and 78(1) GPa, respectively. When using $CO_2$ as PTM, we observe the formation of calcite from tremolite above 3.8(1) GPa, whereas actinolite did not show any carbonation reaction. Under silicone oil PTM, we observe modulated volume contraction behaviors in both samples, compared to water and $CO_2$ PTM, with bulk moduli in the order of 90(1) and 94(4) GPa for tremolite and actinolite, respectively.

• Korean Journal of Materials Research
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• v.13 no.5
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• pp.285-291
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• 2003

The nanosized silver and gold particles are prepared by ERC method in which metal vapors with high temperature is rapidly quenched by coolants such as liquid nitrogen or liquid argon. In order to monitor the crystal structural changes on the internal and the surface of the nanosized noble metal particles, lattice parameter, internal strain and Debye-Waller factor are investigated, and the calculation of X-ray diffraction scattering intensity is performed. The lattice parameters of silver and gold particles agree with those of bulk materials, and crystal internal strain of the metal particles is not changed by rapid cooling. The Debye-Waller factor of gold particles is increased with decreasing particle size because of the surface softening phenomenon of nanosized particles, but the crystal structural change on the surface of the particles is not detected from the comparison the calculated X-ray diffraction profile with the experimental profile on gold particles with the particle size of 4 nm.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.6
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• pp.1259-1265
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• 2013

In wireless environment such as wireless LAN, proper location of wireless LAN AP allows us to take an effective coverage to provide good wireless communication service. To simulate wireless environment, FDTD formulation is introduced and Gaussian pulse injection in grid space is considered to be replaced wireless LAN AP. So structural effect corresponding to location of arbitrary obstacle must be considered, and its received gain is estimated. An obstacle in scattering field should be modeled to be conductor and concrete wall and its diffraction effect for some cross wall is evaluated between transmitter and receiver point.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.177-177
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• 1999

The surface structure of epitaxial $\alpha$-Fe2O3(0001) grown on $\alpha$-Al2O3(0001) has been investigated using intermediate-energy x-ray photoelectron diffraction. Comparison of experiment with quantum mechanical scattering theory reveals that the surface is Fe-terminated, and that the first four layer spacings are -41%, +18%, -8%, and +47% of the associated bulk values, respectively. these results agree reasonably well with the predictions of molecular mechanics and spin-density functional theory previously reported in the literature for the Fe-terminated surface. however, we find no evidence for and O-terminated surface predicted to be stable by spin-density functional theory.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.49-50
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• 2013

In wireless environment, to provide more efficient service area is need to maintain proper location of wireless LAN AP. Since structural effect corresponding to location of arbitrary scatterers must be considered. Using FDTD method, an obstacle in scattering field should be considered and its diffraction effect for some cross wall is estimated between transmitter and receiver point.

• Journal of Navigation and Port Research
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• v.36 no.7
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• pp.561-569
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• 2012

In this paper, the boundary element method is applied to solve the diffraction of waves by multiple vertical cylinders under the assumption of linear wave theory. A numerical analysis by boundary element method is based on Green's theorem and introduced to an integral equation for the fluid velocity potential around the cylinders. The numerical results obtained in this study are compared with the experimental data and the results of the theory using multiple scattering techniques. The comparisons show strong agreement. This numerical analysis method developed by using boundary element method could be used broadly for the design of various offshore structures to be constructed in coastal zones in the future.

• Bulletin of the Korean Space Science Society
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• 2007.10a
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• pp.49.1-49.1
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• 2007

• Current Optics and Photonics
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• v.2 no.2
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• pp.140-146
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• 2018

In this paper, mesoscale optical surface structures are found to possess both geometric and wave optics features. The study reveals that geometric optic analysis cannot correctly predict the experimental results of light transmission or reflection by mesoscale optical structures, and that, for reliable analyses, a hybrid approach incorporating both geometric and wave optic theories should be employed. By analyzing the transmission patterns generated by the mesoscale periodic pyramid prism plates, we show that the wave optic feature is mainly ascribed to the edge diffraction effect and we estimate the relative contributions of the wave optic diffraction effect and the geometric refraction effect to the total scattering field distribution with respect to the relative dimension of the structures.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1939-1943
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• 2003

The precise structural analysis of $SnO_{2}$ thin film, which was prepared by PECVD and thickness 2400 ${\AA}$, was tried to do the structural refinement using X -ray diffraction data. The observed diffraction patterns of $SnO_{2}$ thin film had the strongly preferred orientation effect. WIMV method was used to correct the preferred orientation effect. The final weighted R-factor, $R_{WD}$ was 7.92 %. The lattice parameters, a = b == 4.7366(1) ${\AA}$ and c = 3.1937(1) ${\AA}$, were almost in accordance with ones of $SnO_{2}$ powder.