• Journal of Advanced Marine Engineering and Technology
• /
• 제18권2호
• /
• pp.54-63
• /
• 1994

Mg thin films were prepared on SPCC(cold-rolled steel) substrates by vasuum evapoaration and ion-plating. The influence of argon gas pressure and substrates bias voltage on the crystal orientation and morphology of the film was determined by using X-ray diffraction and scanning electron micrography (SEM), respectively. And the effect of crystal orientation and morphology of the Mg thin films on corrosion behavior was estimated by measuring the anodic polarization curves in deaerated 3% NaCl solution. The crystal orientation of the Mg films deposited at high argon gas pressure exhibited a (002) preferred orientation, regardless of the substrate bias voltage. Film morphology changed from a columnar to a granular structure with the increase of argon gas pressure. The morphology of the films depended not only on argon gas pressure but also bias voltage ; i.e., the effect of increasing bias voltage was similar to that of decreasing argon gas pressure. The influences of argon gas pressure and bias voltage were explained by applying the adsorption inhibitor theory and the sputter theory. And also, this showed that the corrosion resistance of the Mg thin films can be changed by controlling the crystal orientaton and morphology.

• 한국전자파학회논문지
• /
• 제21권9호
• /
• pp.979-986
• /
• 2010

본 논문에서는 합성 개구 레이더(SAR: Synthetic Aperture Radar) 영상에서 SAR 보정용으로 설치된 삼각 전파 반사기(TCR: Trihedral Corner Reflector)의 레이더 단면적(RCS: Radar Cross Section)을 정확하게 추출하는 방법을 연구하고, SAR 보정 정확도를 분석한다. TCR의 이론적 RCS를 geometrical optics(GO)와 physical optics(PO) 방법을 이용하여 이론적으로 계산하고, 측정값과 비교하여 정확성을 검증한다. 이때에 단일 반사는 PO로, 이중 반사는 GO-PO로, 삼중 반사는 GO-GO-PO로 계산하고, 모서리 영향은 PTD(Physical Theory of Diffraction) 방법을 이용하여 이론적 RCS를 정확하게 계산한다. 크기가 다른 5개의 TCR를 설치하고, TerraSAR-X로 그 지역에 대한 위성 영상을 취득하여 그 TCR들에 대한 RCS를 추출한다. 레이더 IRF(Impulse Response Function) 특성에 의해 분산된 전력(power spill)을 모두 구하기 위해 정사각형 모양의 면적(window)을 설정하여 정확하게 RCS를 추출하고, 이 RCS를 이론적 RCS와 비교한다. 면적의 크기와 배경의 레이더 후방 산란 계수 크기에 따른 TCR의 RCS 오차를 계산하며, 최소 적분 면적과 최대 배경 산란계수 크기를 제안한다.

• 한국인터넷방송통신학회논문지
• /
• 제15권1호
• /
• pp.261-267
• /
• 2015

다층 격자구조에서 전파하는 평면파들의 회절특성을 나타내는 고유치 문제는 모드 확장 원리에 의하여 정확하게 설명할 수 있다. 그런 모드 확장 원리들에 의존하는 모드 해들은 간단한 회로이며 일반적인 형태인 등가 전송선로 망에 의하여 분석할 수 있다. 이 해석법은 어떤 조건에서든 필드들의 격자 회절과정에 대한 상당한 물리적 직관성을 제공하는 해석적인 특성을 준다. 특히, 등가 전송선로 망은 다른 해석법들에서 해석적으로 구할 수 없는 회절 격자구조의 산란특성, 방출효과 그리고 다른 광학적 특성들을 체계적으로 평가하기 위한 컴퓨터 알고리즘의 템플릿으로서 사용될 수 있다. 본 논문에서 제안한 정확한 해석법의 타당성을 입증하기 위하여 앞서 연구한 논문들의 결과를 수치해석적으로 비교 분석하였다. 그 결과 본 논문에서 얻은 내용과 잘 일치함을 확인할 수 있었다.

• Wind and Structures
• /
• 제29권1호
• /
• pp.33-41
• /
• 2019

The interaction of head waves with an infinite row of identical, equally spaced, rectangular breakwaters is investigated in the presence of uneven bottom topography. Using linear water wave theory and matched eigenfunction expansion method, the boundary value problem is transformed into a system of linear algebraic equations which are numerically solved to know the velocity potentials completely. Utilizing this method, reflected and transmitted wave energy are computed for different physical parameters along with the wave field in the vicinity of breakwaters. It is observed that the wave field becomes more complicated when the incoming wavelength becomes smaller than the channel width. A critical ratio of the gap width to the channel width, corresponding to the inflection point of the transmitted energy variation, is identified for which 1/3 of the total energy is transmitted. Similarly, depending on the incident wavelength, there is a critical breakwater width for which a minimum energy is transmitted. Further, the accuracy of the computed results is verified by using the derived energy relation.

• 복식
• /
• 제58권5호
• /
• pp.211-231
• /
• 2008

To conserve historic textiles, analyses of textile materials, pollutants and deterioration are prerequisite steps. Based upon analytical results, guides for conservation of historic textiles are established. In analyses of textile materials, pollutants and deterioration, there are chemical methods(burning, solubility and staining), physical methods(microscopy and density) and instrumental analysis(Fourier Transform Infrared Spectroscopy (FT-IR), Fourier Transform Raman Spectroscopy(FT-Raman), Gas Chromatography(GC), Mass Spectroscopy(MS), X-Ray Fluorescence (EDXRF, WDXRF), Energy Dispersive Spectroscopy(EDS), and X-Ray Diffraction(XRD), Tensile Testing Machine etc.). Combination of qualitative and quantitative analyses makes accurate diagnosis of textile condition possible. As examples of analyses and conservation of historic textiles, Chuninsan(19 century) similar to sunshade with handing down historic textile and golden decorative skirt(17 century) with excavated costume are taken.

• 대한한의학방제학회지
• /
• 제12권1호
• /
• pp.177-193
• /
• 2004

Objectives: This study has been done to compare the Haematite's composition before and after using processing method and to clarify its quality and naming through the historical herbal books. Methods: I studied the Haematite and processed Haematite using physical and chemical methods which contain microscopic analysis, X-ray diffraction analysis, thermal analysis, XRF, ICP, etc, to compare the compositions and its characters. Results: Haematite is a metallic oxide(Hematite, $Fe_2O_3$). Haematite contains a main ingredients of crude Haematite Fe 40.336% - 62.174%, processed Haematite $50.499%{\sim}62.791%$(a theory value is 69.944% the korean pharmacopoeia wants >45%) and small ingredients, also. Conclusion: A radio-element contents of U, Th contain less than average contents of the lithosphere's U 1.8ppm, Th 7.2ppm.

• 한국전자파학회논문지
• /
• 제11권6호
• /
• pp.929-938
• /
• 2000

복합구조물의 레이다 단면적 예측을 위하여 포항공과대학교에서 개발중인 컴퓨터 코드에 관한 개발과정과 검증에 관한 내용을 기술하였다. 복합구조물은 평판과 모서리로 모델링 되었으며 예측을 위한 컴퓨터 코드는 물리광학, 물리광학적 회절이론과 SBR 기법을 이용한다. 축소 모형을 제작하여 포항공대 단축거리 측정장치로 RCS를 측정하였다. 예측/측정된 결과는 RCS 패턴 및 ISAR 영상을 통하여 비교 검토되었으며 그 결과는 상당히 일치하였고 복합구조물의 국부 산란현상을 잘 설명한다. 이러한 예측 방법은 스텔스 설계와 표현인식기법연수에 직접 적용될 수 있다.

• 한국세라믹학회지
• /
• 제44권3호
• /
• pp.175-181
• /
• 2007

Molecular dynamics simulation (MD) of $(62-x)CaO{\cdot}38Al_{2}O_{3}{\cdot}xBaO$ glasses has been carried out using empirical potentials with the covalent term. The simulations closely reproduce the total neutron correlation functions of glass with 5 mol% BaO and physical properties of these glasses such as elastic constants. For these glasses, aluminum is tetrahedrally coordinated by oxygen, but there is a part of five-fold and six-fold coordination of aluminum. There are no major changes to the mid-range structure of glass, as barium is substituted for calcium. To predict the barium coordination number, we have used the bond valence (BV) theory and also compared the results of simulation with Bond valence. The coordination number for oxygen around barium atoms is close to 8 and the average distance of barium and oxygen is nearly 2.80 A. The viscosity of these glasses increases with the content of barium oxide substituted for calcium oxide.

• 한국광학회지
• /
• 제8권4호
• /
• pp.260-266
• /
• 1997

DCG(dichromated gelatin : 7.mu.m 두께) 필름을 이용하여 홀로그래픽 편광분리(Holographic Polarization Separation : HPS)소자를 설계 제작하였다. 제작한 HPS소자의 편광특성을 노출시간, 입사각, 편광각 등의 몇가지 물리적 변수들을 이용하여 조사하였다. 실험결과가 Kogelnik의 결합 파동이론에 기초한 이론적 결과와 잘 일치함을 알 수 있었다. 제작한 HPS소자는 633 nm 파장에서 편광 회절 강도비가 500:1(S편광:P편광)이상이였다. 또한 HPS소자의 광 스위치 및 자유공간 광 연결소자로서의 응용 가능성을 제시하였다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2000년도 하계학술대회 논문집
• /
• pp.783-786
• /
• 2000

In this paper, physical properties and dielectric characteristics of LLDPE and EVA which are used as a blending material to improve PE's performance are studied. LLDPE of 0.92[g/cm3] and EVA with the EVA contents of 12.5[%1 were selected as specimens, and X-ray diffraction(XRD) are used to analysis physical properties. We measured dielectric constant with the frequency range from 20[Hz] to 1 [MHz], applied voltage 6[V] and the temperature from 25[$^{\circ}C$] to 110[$^{\circ}C$]. From XRD, LLDPE has a crystallinity of 53[%] and, 46[%] for EVA. LLDPE has as low tan$\delta$ as of 10$^{-3}$ ~10$^{-4}$ and inflection point near 500[Hz]. At frequency region lower than 500[Hz], tan$\delta$ decreases with frequency and increases with temperature and it is considered to be caused by conductive carriers within specimen. Over 500[Hz], it is the reverse and we thought that it was caused by decrease of relaxation time due to Debye theory, EVA has tan$\delta$with the values of 10$^{-2}$ ~10$^{-3}$ , which is higher than that of LLDPE, and it has inflection point at 60[Hz]. It is shown that Dielectric characteristics of EVA are similar to LLDPE's.