• 천문학회보
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• 제37권2호
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• pp.99.1-99.1
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• 2012

We report the results of our analysis of far ultraviolet (FUV) observations made for the broad region around the ${\alpha}$ Vir (Spica) including the interaction zone of the Loop I and the Local Bubble. We employed the datasets of the GALEX and the FIMS, which made observations at similar FUV wavelengths. First, we noted that the GALEX image was enhanced in the southern region where the interaction zone exists. We attribute this enhanced FUV emission to dust scattering of the stellar photons, mostly from the background field stars with small contributions from the central star Spica. While the region is optically thin in general, the FUV intensity did not correlate well with the dust extinction level, indicating that the local radiation field has significant fluctuations. On the other hand, the GALEX FUV intensity well with the $H{\alpha}$ intensity as well as the dust extinction level in the northern part. In fact, the neutral hydrogen column density correlated very well with the dust extinction level throughout the whole region in consideration. The relationship between the neutral hydrogen column density and the color excess was estimated to be ${\sim}7{\times}10^{21}atoms\;cm^{-2}$, which is a little higher than the previous observations made for a diffuse interstellar medium. The spectral analyses of the FIMS observations showed the enhanced C IV emission throughout the whole region, indicating that the C IV emission arises by the interaction of the hot gases with the shell boundaries. A simple model showed that a large portion of the C IV emission comes from the Loop I side of the interaction zone, compared to the Local Bubble side. The FIMS spectrum also showed indications of the molecular hydrogen fluorescence lines for the interaction zone.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2005년도 추계학술대회 논문집
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• pp.43-46
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• 2005

레이더 물표에 대한 반사성능은 RCS(Radar Cross Section)에 의하여 결정된다. 형상이 비교적 간단한 물체에 대해서는 고유함수 접근법에 의하여 RE를 정확하게 예측할 수 있으나, 해상물표와 같은 복잡한 물표에 대해서는 저주파 및 고주파 산란해석 기법 등을 이용하여 근사적인 해를 찾을 수 밖에 없고 계산적으로도 복잡하다. 본 연구에서는 수신신호의 파라미터를 정도 높게 추정할 수 있는 MUSIC 알고리즘을 이용하여 RCS 간을 근사적으로 구할 수 있는 알고리즘을 제안한다. 제안된 방법에 서는 레이더 물표는 산란체의 링으로서 가정되고 레이더 물표로부터 반사된 신호들의 진폭은 통계적 성질을 지니고 분포하게 된다. 결과적으로 제안된 레이더 신호모델에 MUSIC 알고리즘이 적용되고, 레이더 물표의 RCS는 간단한 대수적인 방법으로 계산된다.

• 한국의류학회지
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• 제42권3호
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• pp.503-515
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• 2018

In this research, the three-dimensional structural and colorimetrical modeling of yarn-dyed woven fabrics was conducted based on the Kubelka-Munk theory (K-M theory) for their accurate color predictions. In the K-M theory for textile color formulation, the absorption and scattering coefficients, denoted K and S, respectively, of a colored fabric are represented using those of the individual colorants or color components used. One-hundred forty woven fabric samples were produced in a wide range of structures and colors using red, yellow, green, and blue yarns. Through the optimization of previous two-dimensional color prediction models by considering the key three-dimensional structural parameters of woven fabrics, three three-dimensional K/S-based color prediction models, that is, linear K/S, linear log K/S, and exponential K/S models, were developed. To evaluate the performance of the three-dimensional color prediction models, the color differences, ${\Delta}L^*$, ${\Delta}C^*$, ${\Delta}h^{\circ}$, and ${\Delta}E_{CMC(2:1)}$, between the predicted and the measured colors of the samples were calculated as error values and then compared with those of previous two-dimensional models. As a result, three-dimensional models have proved to be of substantially higher predictive accuracy than two-dimensional models in all lightness, chroma, and hue predictions with much lower ${\Delta}L^*$, ${\Delta}C^*$, ${\Delta}h^{\circ}$, and the resultant ${\Delta}E_{CMC(2:1)}$ values.

• 한국조경학회지
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• 제26권3호
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• pp.297-311
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• 1998

Landscaping on artificial ground is currently served as a means to imposing a greenery benefit on high-density and high-rise apartment sites. It functions as a sub-hierarchy in apartment planning such as ornamental element from the past. Major parking space tends to be allocated on the basement area in response to the required parking regulation. Therefore, competitive relatioinship between the parking and greenery space I limited outdoor of apartments leads to the development planning strategy and technology of artificial ground. This study aims at evaluating landscape planning on artificial ground of apartment complex through several approaches such as site survey, plan drawing analysis, and interview with related field experts. 15 survey apartment sites including Bundang Model, Shindaebang-dong, Pyoungchon Hyundai Apartments have been selected for conducting the research. Main results of this study are summarized below : First, scattering allocation of artificial ground between apartment building units is a dominant plan layout type among the survey sites. Even though unifying allocation type has an advantage to maximize underground parking space, it has a difficulty in maintaining proper soil ground base for nurturing plants. Therefore, underground parking space should be planned by unifying allocation type placed separately from apartment units. This plan type can provide a balanced planting between soil and artificial ground on surface level. Second, It is strongly recommended to integrate the whole planting base which involves architectural structure, drainage, and water proofing above the planting design. When considering that process as a professional subject dealing with natural material such as trees and shrubs, those tasks should be directed by landscape architectural divison and landscape architect. And planting area for artificial ground has to be specified in initial phase of architectural design. This step provides an opportunity to make a proper decision on structural load, drainage, and water proof design as an integrated part of the management.

• 한국정보통신학회논문지
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• 제20권11호
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• pp.2085-2092
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• 2016

IC 기판의 가장 중요한 성질들의 하나는 넓은 영역에 걸쳐 균일해야만 한다는 것이다. 웨이퍼 결함 분석의 다양한 물리적 접근 방법 중에서 적외선 조사 기법에 특별한 관심이 모아지고 있다. 특히, 높은 공간적 분해력을 가지고 있는 근적외선 흡수 방법은 반-절연 GaAs 내의 결함들을 직접적으로 관찰하는데 이용되고 있다. 적외선 전송에 기초를 둔 이 기법은 신속하고 비파괴 적이다. 이 방법은, 직접적으로 GaAs 반도체의 적외선 영상은 결함의 광흡수 작용에 기인한 것임을 밝히고 있다. 반-절연 GaAs 내의 EL2에 관련된, 비 균일 적으로 분포된 결함들의 적외선 흡수 영상에서 콘트라스트가 반전되는 현상에 대해 새로운 모델을 제시하고 있다. 저온 포토퀀칭 실험은, 직접적인 방법으로, GaAs 웨이퍼의 콘트라스트 반전 영상은 밴드갭의 지엽적인 변동이나 전하 재분포에 의한 것이 아니라 흡수와 산란의 두 메커니즘에 의한 것임을 증명하고 있다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.4-5
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• 2010

The surface phonon is defined as a coherent vibrational excitation of surface atoms propagating along the surface. It is characterized by a phonon dispersion curves, which were extensively studied in 1990's using helium atom scattering and high-resolution electron-energy-loss spectroscopy (HREELS)[1].The understanding is mainly based on the theoretical framework of a classical bond model or cluster calculations. The recent sample preparation and first principles calculations open the naval way to deep insight for surface phonon problems. The surface phonon dispersion on the hydrogen-terminated Si(111)-($1{\times}1$) surface [H:Si(111)] is the typical system and already reported experimentally [2] and theoretically [3], although the understandingis incomplete. The sample contaminated by the oxygen atoms on the surface and the calculations were also classical. In this study, firstly, we have prepared an ultra-clean H:Si(111) surface [4] and measured the surface phonon dispersion curvesusing HREELS. Secondly, we have performed first-principles density functional calculations with the projector augmented wave functionals, as implemented in VASP, using generalized gradient approximations. We used aslab of six silicon layers and both top and bottom surfaces were terminated with hydrogen atoms. Finally, we have compared with the surface phonon dispersion of deuterium-terminatedSi(111)-($1{\times}1$) surface[5] and led to our conclusions. The Si-H stretching and the bending modes are observed at 258.5 and 78.2 meV, respectively. These energies are the same as the previously reported values [2], but the energy-loss peaks at the lower energy regions are dramatically shifted. Through this combination study, we have formulated the procedure of preparing ultra-clean H:Si(111)/D:Si(111), which was confirmed by HREELS vibrational analysis. The Si surface will be utilized for further nano-physics research as well as for the materials for nano-fubrication.

• Nuclear Engineering and Technology
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• 제47권7호
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• pp.791-803
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• 2015

The effective cross sections (XSs) in the direct whole core calculation code nTRACER are evaluated by the equivalence theory-based resonance-integral-table method using the WIMS-based library as an alternative to the subgroup method. The background XSs, as well as the Dancoff correction factors, were evaluated by the enhanced neutron-current method. A method, with pointwise microscopic XSs on a union-lethargy grid, was used for the generation of resonance-interference factors (RIFs) for mixed resonant absorbers. This method was modified by the intermediate-resonance approximation by replacing the potential XSs for the non-absorbing moderator nuclides with the background XSs and neglecting the resonance-elastic scattering. The resonance-escape probability was implemented to incorporate the energy self-shielding effect in the spectrum. The XSs were improved using the proposed method as compared to the narrow resonance infinite massbased method. The RIFs were improved by 1% in $^{235}U$, 7% in $^{239}Pu$, and >2% in $^{240}Pu$. To account for thermal feedback, a new feature was incorporated with the interpolation of pre-generated RIFs at the multigroup level and the results compared with the conventional resonance-interference model. This method provided adequate results in terms of XSs and k-eff. The results were verified first by the comparison of RIFs with the exact RIFs, and then comparing the XSs with the McCARD calculations for the homogeneous configurations, with burned fuel containing a mixture of resonant nuclides at different burnups and temperatures. The RIFs and XSs for the mixture showed good agreement, which verified the accuracy of the RIF evaluation using the proposed method. The method was then verified by comparing the XSs for the virtual environment for reactor applicationbenchmark pin-cell problem, as well as the heterogeneous pin cell containing burned fuel with McCARD. The method works well for homogeneous, as well as heterogeneous configurations.

• 대한원격탐사학회지
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• 제38권1호
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• pp.83-101
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• 2022

Accurate atmospheric correction is essential for the analysis of land surface and environmental monitoring. Aerosol optical depth (AOD) information is particularly important in atmospheric correction because the radiation attenuation by Mie scattering makes the differences between the radiation calculated at the satellite sensor and the radiation measured at the land surface. Thus, it is necessary to use high-quality AOD data for an appropriate atmospheric correction of high-resolution satellite images. In this study, we examined the Second Simulation of a Satellite Signal in the Solar Spectrum (6S)-based atmospheric correction results for the Sentinel-2 images in South Korea using raster AOD (MODIS) and single-point AOD (AERONET). The 6S result was overall agreed with the Sentinel-2 level 2 data. Moreover, using raster AOD showed better performance than using single-point AOD. The atmospheric correction using the single-point AOD yielded some inappropriate values for forest and water pixels, where as the atmospheric correction using raster AOD produced stable and natural patterns in accordance with the land cover map. Also, the Sentinel-2 normalized difference vegetation index (NDVI) after the 6S correction had similar patterns to the up scaled drone NDVI, although Sentinel-2 NDVI had relatively low values. Also, the spatial distribution of both images seemed very similar for growing and harvest seasons. Future work will be necessary to make efforts for the gap-filling of AOD data and an accurate bi-directional reflectance distribution function (BRDF) model for high-resolution atmospheric correction. These methods can help improve the land surface monitoring using the future Compact Advanced Satellite 500 in South Korea.

• 한국광학회지
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• 제33권3호
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• pp.113-121
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• 2022

본 연구에서는 우리나라의 위성-지상 하향 무선 광통신 시스템의 링크 가용성을 분석하였다. 주요 5개 도시(서울, 부산, 대구, 대전, 광주)의 최근 10년간의 기상 데이터를 활용했으며, 대기의 흡수 및 산란 손실과 신틸레이션 손실, 그리고 에어로졸 손실을 모두 고려하여 링크 가용성을 이론적으로 예측하였다. 정확하면서도 보수적인 링크 가용성 계산을 위하여 수적(cloud droplet)의 최대 개수 밀도를 사용하는 새로운 손실 모델을 제시하였다. 지상 기지국이 주요 5개 도시 중 한 곳에 위치하며, 대기 손실에 20 dB의 링크 버짓을 할당할 것을 전제한 경우 우리나라 위상-지상 하향 무선 광통신 링크의 가용성은 45-70%로 예측되었다. 그러나 3개 또는 5개 도시의 위치 다이버시티를 적용하면, 링크 가용성이 각각 90%와 97%로 크게 향상될 수 있을 것으로 예측되었다.

• 한국음향학회지
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• 제28권3호
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• pp.174-186
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• 2009

경계면이 존재하는 해양에서의 수중 음파 전달 모델링 시 일반적으로 평평한 경계면을 가정하고 Rayleigh가 제안했던 반사계수를 이용해 반사파를 계산할 수 있다. 하지만 해수면이나 해저면과 같은 실제 해양의 경계면은 불규칙적인 거칠기를 가진다. 이러한 경계면에서의 반사 손실은 실험식이나 산란 이론에 기반한 간섭 반사 계수를 계산하여 구할 수 있다. 본 논문에서는 섭동 이론, Kirchhoff 근사법, 작은 가지 근사법과 같은 산란 이론을 이용하여 유체-유체 경계면에 대한 간섭 반사 계수를 각각 유도한다. 이를 이용하여 임의의 거칠기를 가지는 해수면과 해저면에 대한 각 산란 이론의 간섭 반사계수를 계산하며, 이 결과를 Rayleigh 반사 계수와 비교하여 경계면의 거칠기에 따른 반사 손실을 분석한다. 또한, 섭동 이론과 Kirchhoff 근사법의 결과를 일반적으로 적용 범위가 넓은 작은 기울기 근사법의 결과와 비교하여 각 이론의 유효범위에 대해 고찰한다.