• 대한전자공학회논문지SP
• /
• 제48권3호
• /
• pp.30-41
• /
• 2011

산란선을 흡수하여 보다 선명한 x선 영상을 얻기 위하여 산란방지 그리드를 사용하여 투사영상을 얻는데, 이때 그리드로 인한 왜곡이 발생한다. 본 논문에서는 회전된 그리드를 사용하여 그리드 왜곡의 제거가 용이하도록 x선 디지털 영상을 얻는 방법에 있어서 기존의 왜곡 성분의 중심주파수를 가장자리로 보내는 경우를 보다 심도 있게 분석하여 확장된 결과를 도출하였으며, min-max 개념에서 주어진 그리드 밀도에 대하여 최적화하는 방법을 제시하였다. 또한 실질적으로 사용가능한 그리드 밀도에 대하여 적절한 그리드 각도를 제시하고 그러한 그리드를 사용하여 획득한 x선 디지털 영상에서 그리드 왜곡이 용이한 알고리듬을 제안하고 그 성능을 비교해보았는데, 원영상의 해상도를 어느 정도 유지하면서 그리드 왜곡을 줄일 수 있었다.

• Bulletin of the Korean Chemical Society
• /
• 제32권2호
• /
• pp.673-680
• /
• 2011

The compound 3-(2-Mercaptopyridine)phthalonitrile has been synthesized and characterized by IR, UV-vis, and X-ray single-crystal determination. The molecular geometry from X-ray determination of the title compound in the ground state has been compared using the Hartree-Fock (HF) and density functional theory (DFT) with the 6-31G(d) basis set. The calculated results show that the DFT and HF can well reproduce the structure of the title compound. The energetic behavior of the title compound in solvent media was examined using the B3LYP method with the 6-31G(d) basis set by applying the Onsager and polarizable continuum model. Using the TD-DFT and TD-HF methods, electronic absorption spectra of the title compound have been predicted and good agreement with the TD-DFT method and the experimental determination was found. The predicted nonlinear optical properties of the title compound are much greater than those of urea. Besides, molecular electrostatic potential of the title compound were investigated by theoretical calculations. The thermodynamic properties of the compound at different temperatures have been calculated and corresponding relations between the properties and temperature have also been obtained.

• Nuclear Engineering and Technology
• /
• 제48권3호
• /
• pp.778-784
• /
• 2016

HyperGam-U was recently developed to determine uranium enrichment based on ${\gamma}$- and X-ray spectroscopy analysis. The $XK_{\alpha}$ region of the uranium spectrum contains 13 peaks for $^{235}U$ and $^{238}U$ and is used mainly for analysis. To describe the X-ray peaks, a Lorentzian broadened shape function was used, and methods were developed to reduce the number of fitting parameters for decomposing the strongly overlapping peaks using channel-energy, energy-width, and energy-efficiency calibration functions. For validation, eight certified reference material uranium samples covering uranium enrichments from 1% to 99% were measured using a high-resolution planar high-purity germanium detector and analyzed using the HyperGam-U code. When corrections for the attenuation and true coincidence summing were performed for the detection geometry in this experiment, the goodness of fit was improved by a few percent. The enrichment bias in this study did not exceed 2% compared with the certified values for all measured samples.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
• /
• pp.318.1-318.1
• /
• 2014

Metal nano-crystals have been received much attentions owing to their excellent catalytic property and surface plasmon effect. In the last decade, many studies on synthesizing well-dispersive nanoparticles and on understanding their distinct physical properties have been performed. There were tremendous reports revealing the electrochemical activities and enhancement of surface plasmonic effect were dependent mainly on the size, shape, and composition. So far, most fabrication methods have been based on vacuum based deposition techniques, such as chemical vapor deposition and electron-beam evaporation, and then annealed them to transform into the nanoparticles. Recently, there were several reports regarding to the photoinduced nano-crystal synthesis as an effective way to produce the metal nanoparticles. In this study, we report synchrotron x-ray mediated synthesis of Au nanoparticles on ZnO nanowires. ZnO nanowires were fabricated by hydrothermal method, and then they were dip into a solution having Au clusters. Detailed structural evolution of Au nanoparticles was investigated using scanning electron microscopy and photoluminescence measurements. The results on formation of well-dispersive Au nanoparticles on ZnO nanowires will be presented.

• Imaging Science in Dentistry
• /
• 제31권1호
• /
• pp.17-22
• /
• 2001

Purpose: To compare the film density of Insight dental X-ray film (Eastman Kodak Co., Rochester, NY, USA) with that of Ektaspeed Plus film (Eastman Kodak) under manual and automatic processing conditions. Materials and Methods : Insight and Ektaspeed Plus films were exposed at three different exposure conditions with an aluminum step wedge on the films under the three different exposure times. The exposed films were processed by both manual and automatic ways. The Base plus fog density and the optical density made by exposing step wedge were calculated using a digital densitometer (model 07-443, Victoreen Inc, Cleveland, Ohio, USA). The optical densities of the Insight and Ektaspeed film versus thickness of alumimun wedge at the same exposure time were plotted on the graphs. Statistical analyses were applied for comparing the optical densities of the two films. Results: The film density of both Insight films and Ektaspeed Plus films under automatic processing condition was significantly higher over the manual processing. The film density of Insight films was significantly higher than that of Ektaspeed Plus films on both automatic and manual processing conditions. Conclusion: The radiation exposure time can be reduced when using Insight over Ektaspeed Plus film. To take the full advantage of reducing exposure time, Insight film should be processed automatically.

• Imaging Science in Dentistry
• /
• 제33권1호
• /
• pp.21-26
• /
• 2003

Purpose: To investigate the characteristics of the newly marketed, Insight dental X-ray film. Materials and Methods: Kodak Ultraspeed (DF-58), E-speed, Agfa Dentus M2, and Kodak Insight (IP-21) films were radiographed using a Trophy intra-oral radiographic machine. 10 step exposure times were prepared and each step exposure was monitored using a FH 40G (ESM Eberline Instruments) dosimeter for each of the 4 types of intra-oral film. All films were manually processed and the radiographic densities at 6 sites of each processed film were measured, and the characteristic curves of each of the 4 types intra-oral films were created utilizing these dosimetric data and radiographic densities, based on ISO 5779. The film contrast, speed, and base plus fog density of Insight film were compared with those of the 3 other films examined in this experiment. Results : E-speed film showed greatest average gradients followed by Insight film. E-speed and Ultraspeed film showed great average gradients at low density levels. Insight film showed the fastest speed followed by E-speed, Dentus M2 and Ultraspeed film. Dentus M2 film showed greatest base plus fog density level followed by Insight film. Conclusion : Kodak Insight film showed fastest film speed with comparable film contrast on characteristic curve.

• Bulletin of the Korean Chemical Society
• /
• 제17권7호
• /
• pp.643-647
• /
• 1996

1,2-Disubstituted chiral calix[4]arene "25-(3,5-dinitrobenzoyloxy)-26-methoxy-27,28-dihydroxycalix[4]arene" was synthesized by the reaction of 25-(3,5-dinitrobenzoyloxy)-calix[4]arene with methyl iodide in the presence of K2CO3. Methylation was occurred at the 26-position of calix[4]arene. The partial cone conformation and 1,2-substitution were characterized based on the 1H NMR, 13C NMR and X-ray diffraction analysis. The crystal structure has been determined by X-ray diffraction method. The crystals are orthorhombic, Pbca, a=10.652(1), b=17.687(1), c=32.247(3) Å, Z=8, V=6075.4(9) Å3, Dc=1.38gcm-3. The intensity data were collected on an Enraf-Nonius CAD-4 Diffractometer with a graphite monochromated Cu-Kα radiation. The structure was solved by direct method and refined by full-matrix least-squares methods to a final R value of 0.050 for 2368 observed reflections. The molecule is in the partial cone conformation. It has two strong intramolecular hydrogen bonds of O(1D)-H…O(1C)-H…O(1B).

• Nuclear Engineering and Technology
• /
• 제55권8호
• /
• pp.2854-2863
• /
• 2023

Objective: To present a hybrid approach that incorporates a constrained beam-hardening estimator (CBHE) and deep learning (DL)-based post-refinement for metal artifact reduction in dental cone-beam computed tomography (CBCT). Methods: Constrained beam-hardening estimator (CBHE) is derived from a polychromatic X-ray attenuation model with respect to X-ray transmission length, which calculates associated parameters numerically. Deep-learning-based post-refinement with an artifact disentanglement network (ADN) is performed to mitigate the remaining dark shading regions around a metal. Artifact disentanglement network (ADN) supports an unsupervised learning approach, in which no paired CBCT images are required. The network consists of an encoder that separates artifacts and content and a decoder for the content. Additionally, ADN with data normalization replaces metal regions with values from bone or soft tissue regions. Finally, the metal regions obtained from the CBHE are blended into reconstructed images. The proposed approach is systematically assessed using a dental phantom with two types of metal objects for qualitative and quantitative comparisons. Results: The proposed hybrid scheme provides improved image quality in areas surrounding the metal while preserving native structures. Conclusion: This study may significantly improve the detection of areas of interest in many dentomaxillofacial applications.

• 천문학회보
• /
• 제44권2호
• /
• pp.36.4-36.4
• /
• 2019

Ricci et al. (2017, Nature, 549, 488) discovered a lack of high accretion rate, obscured Active Galactic Nuclei (AGN) in the hard X-ray selected Swift/BAT local AGN survey. This was interpreted as radiative pressure driven AGN feedback clearing its immediate vicinity composed of dusty gas (having an effectively low Eddington limit in the order of 0.01-0.1), and governing the level of nuclear obscuration. As we find Eddington-limited accretion and high extinction values among obscured, luminous AGN (quasars) however, it may be that the local X-ray AGN and the distant quasars undergo different feedback mechanisms in clearing their surroundings. In this study, we simply compare the obscuring column density and Eddington ratio values for quasars selected by various methods, including X-ray obscured, optically blue, infrared red/luminous, and submillimeter bright AGN. We find obscured quasars lying on the column density-Eddington ratio diagram previously unoccupied by Ricci et al., suggesting that radiative pressure is insufficient to clear its dusty structure at high luminosity, or that the dust in obscured quasars are more extended than the low luminosity counterparts to become fully transparent. We discuss alternative feedback scenarios that may be more relevant for obscured quasars.

• 대한방사선기술학회지:방사선기술과학
• /
• 제39권2호
• /
• pp.263-271
• /
• 2016

최근 인구 고령화에 따른 골다공증 환자의 증가 및 의료기기 시장의 성장으로 인해 엑스선골밀도측정기 시장이 커지고 있으며, 이에 따른 의료기기 허가 심사건수가 증가하고 있다. 의료기기 기술문서는 의료기기의 허가 심사 시 가장 기본이 되는 문서로 필수 제출 첨부자료 중 하나이다. 기술문서는 의료기기 관련 법령 및 고시에 그 근거를 두고 있으며, 의료기기 전반적인 항목을 기술해야하는 만큼 작성자의 전문성이 필요한 항목이다. 하지만 최근 부정확한 작성의 증가로 인한 심사자들의 업무부담이 증가되고 있어 민원 처리 효율이 저하되고 있다. 특히 엑스선골밀도측정기의 경우 식품의약품안전처 기준규격이 없어, 의료기기 제조/수입업체 등에서 시험항목을 설정하는 데 많은 어려움을 겪고 있다. 따라서 본 연구에서는 개선된 제도가 반영된, 엑스선골밀도측정기 기술문서 작성 가이드라인 개발을 위해 첫째, 개선된 제도 운영에 대한 조사, 품목별 의료기기의 제도 적용에 따른 문서 작성 방법 검토, 기 허가된 품목에 대한 허가 및 기술문서 검토를 완료하였다. 둘째, 품목별 시장현황 조사, 적용 가능한 국내 외 규격을 조사 분석하여 품목별 국제조화된 안전성 및 성능평가 시험기준 및 방법을 도출하였다. 마지막으로, 산 연 관 전문가협의체 논의를 거쳐 기술문서 작성 가이드라인(안)을 최종 도출하였다.