• 천문학회보
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• 제43권1호
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• pp.36.3-37
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• 2018

We present a new catalog of hard X-ray sources detected in the first 105 months of observations with the Burst Alert Telescope (BAT) on board the Neil Gehrels Swift observatory. The 105 month Swift-BAT survey is a uniform hard X-ray all-sky survey performed in the 14-195 keV band. The Swift-BAT 105 month catalog provides 1632 (422 new detections) hard X-ray sources in the 14 - 195 keV band above the 4.8 sigma significance level. Adding to the previously known hard X-ray sources, 34% (144/422) of the new detections are identified as Seyfert AGN in nearby galaxies (z < 0.2). The majority of the remaining identified sources are X-ray binaries (7%, 31) and blazars/BL Lac objects (10%, 43). As part of this new edition of the Swift-BAT catalog, we release eight-channel spectra and monthly sampled light curves for each object in the online journal and at the Swift-BAT 105 month Web site.

• 한국의학물리학회지:의학물리
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• 제22권3호
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• pp.117-123
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• 2011

방사광 영상은 내부가 보이지 않는 생물학적 검체의 구조를 관찰하는데 사용될 수 있으며, 조직의 고정이나 염색없이 비침습적으로 조직의 미세 구조를 관찰하는데 유용하다. 본 연구에서는 포항방사광가속기의 1B2 빔라인에서 개발한 경엑스선(hard X-ray) 현미경을 이용하여 11.1 KeV의 에너지에서 인간 유방 조직의 현미경적 영상을 얻고자 하였으며, 고해상도의 영상을 얻기 위해 동심원 회전판(zone plate)과 위상차 영상기법을 사용하였다. 실험 결과 경 엑스선 현미경을 이용하여 유방 섬유낭성변화와 유방암 조직의 방사광 미세 영상을 얻었으며, 이들 영상의 공간 해상도는 60 nm로 각각의 유방 조직의 미세 구조를 관찰하기에 충분하였다. 또한 방사광 미세 영상과 기존의 유방촬영 영상을 비교하였을 때, 방사광 미세 영상에서 각 조직의 특징적인 형태학적 변화가 더 뚜렷하게 나타나는 것을 관찰할 수 있었다. 결론적으로, 경엑스선 위상차 현미경을 이용한 방사광 영상은 유방 질환의 진단에 많은 도움을 줄 수 있을 것으로 생각되며, 임상적으로나 여러 연구 목적으로 유용하게 사용될 수 있을 것으로 기대된다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2007년도 춘계학술대회 논문집
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• pp.187-188
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• 2007

• 천문학회보
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• 제36권2호
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• pp.149.2-149.2
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• 2011

We performed the cross-correlation analysis on energy-dependent light curves of the Z-type source GX 5-1. We observed X-ray delays of a few hundred seconds between hard (16-30 keV) and soft (2-5 keV) X-ray light curves. During these phenomena, the centroid frequency of horizontal branch oscillation (HBO) was found to shift to lower or higher frequency indicating towards the dynamical movement of a Compton cloud or an inner disk front. Both eastern and western approaches were used to unfold the X-ray continuum and systematic changes were observed in soft and hard X-ray spectral components. Simultaneous energy spectral and power density spectral study shows that the production of HBOs is closely related to the Comptonizing region rather than the accretion disk. We discuss the results in the context of re-condensation of coronal material in the inner accretion disk region.

• 천문학회지
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• 제29권spc1호
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• pp.219-221
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• 1996

The x-ray pulsar GX 1+4 was observed by us in four balloon- borne experiments carried out from Hyderabad, India during 1991-1995 period with a hard x-ray telescope. The x-ray telescope consists of two collimated large area xenon-filled proportional counters with an effective area of $2400 cm^2$, a field of view of $5^{\circ}{\times}5^{\circ}$ and sensitive in the energy band of 20 - 100 keV. The pulsar was detected in bright state in two of the four experiments and x-ray pulsations with 120 second period were detected clearly. Pulsation period, rate of change of period with time, pulse fraction, pulse profile and energy spectra of the source were determined from these studies. During March 1995 observation, the x-ray pulse of GX 1+4 was found to be double-peaked compared to a single-peak pulse profile detected in December 1993. Details of these results are presented and their interpretation discussed in terms of the current accretion models of x-ray binaries.

• 한국방사선학회논문지
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• 제4권3호
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• pp.27-31
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• 2010

엑스선 영상의 공간분해능은 영상획득 장치에 사용되는 광학소자의 성능에 의해 결정된다. 8.5keV에서 높은 공간분해능 달성이 가능한 존 플레이트를 설계하였다. 방사광을 이용하는 대신 엑스선 튜브를 사용하는 영상시스템에서는 80nm의 공간분해능을 달성할 수 있음을 광선추적 기법을 이용하여 예측하였다. 전자빔 석판인쇄술을 이용하여 최외곽 폭 40nm를 갖는 존 플레이트가 제작하였다.

• 천문학회보
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• 제38권1호
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• pp.65.1-65.1
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• 2013

The 2011 August 09 Flare is one of the largest X-ray flares of Sunspot Cycle 24 to attract a lot of attention for its various activities detected in coronal images. In this study we concern ourselves mostly on information of high energy electrons produced during this flare provided by hard X ray data from the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) and radio data from the Korean Solar Radio Burst Locator (KSRBL) and Ondrejov. EUV images obtained by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory are used to provide the context of magnetic reconnection. In our results, (1) HXR spectra have a rich spectral morphology. Initially it could be fit by one thermal component (T~30MK) and one single power law nonthermal spectrum, but later a better fit could be made by introducing an additional thermal component (T~55 MK). (2) Time delays between the KSRBL burst and the RHESSI hard X-ray emission were found which are more obvious at low frequencies and insignificant at high frequencies. (3) The HXR source lies in the core of the quadrupolar active region. In our interpretation based on AIA 94 A images, the outer part of the active region erupted to be blown out, leaving the intense hard X-ray emission concentrated in the core. We relate the appearance of the second thermal component to the evolution of the AIA 171 and 94 A images. The time delays of microwave peaks to HXR peaks are interpreted as indicating presence of trapped electrons in larger closed magnetic loops. With these result we conclude that the hard X ray and microwaves are due to impulsive acceleration in the low and high heights and a sigmoidal reconnection scenario.

• Journal of the Optical Society of Korea
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• 제11권2호
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• pp.76-81
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• 2007

The compound refractive X-ray lens (CRL) for focusing hard X-rays is investigated to determine the parameters such as the focal length, the focal spot size, and spatial distribution at the focal spot using a simple theoretical calculations and CRLs fabricated by the self-assembly method. The number of individual compound lenses are defined for the given focal length of 1 m. The X-ray energy of 1 to 40 keV is used in the calculations. The CRL for focusing hard X-rays which generated from the X-ray tube is fabricated by nanoparticle-polymer composite in the form of circular concaves. The self-assembly method is applied to form the nanoaluminum-poly (methly meth-acrylate) composite and carbon-polymer composite CRL lenses. Aluminum nanoparticles of 100 nm and carbon microparticles are diffused in the polymer solution then the high gravity up to 6000G is applied in it to form the concave lens shape. X-ray energy at 8 keV is used for characterization of the composite CRLs. The FWHM of intensity for the fabricated nanoaluminium composite CRL system, N=10 is measured as 1.8 mm, which would give about $70{\mu}m$ in FWHM at 1 m of the focal length.

• 한국광학회:학술대회논문집
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• 한국광학회 2007년도 동계학술발표회 논문집
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• pp.13-14
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• 2007

• Tribology and Lubricants
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• 제17권3호
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• pp.209-215
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• 2001

In view of the effects of the hardness of material on fatigue, rolling contact fatigue process in hard metals seems to differ from it in soft metals. This paper has been aimed to compare the rolling contact fatigue process according to the hardness of materials. Rolling contact fatigue tests using the ball bearings assembled with the inner race of four different hardness have been carried out. In addition, residual stress and half-value breadth on/below the inner raceway during individual rolling contact fatigue have been measured by X-ray diffraction. The results of this study showed that the change of residual stress and half-value breadth during the rolling contact fatigue on race way in hard metals is the same as in soft metals. However, plastic deformation by rolling contact in hard metals is in microscopic scale but only for soft metals in macroscopic scale.