• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.690-693
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• 2003

Soft x-ray microscopy provides a unique set of capabilities in-between those of visible light and electron microscopy. It has long been recognized that nature provides a 'water window' spectral region between the K shell x-ray absorption edges of carbon (~290eV) and oxygen (~540eV), where organic materials show strong absorption and phase contrast, while water is relatively non-absorbing. This enables imaging of hydrated biological specimens that are several microns thick with high intrinsic contrast using x-rays with a wavelength of 2.3~4.4nm. Soft X-ray microscopy is therefore well suited to the study of specimens like single biological cells. The most direct advantage of X-ray microscope is their high spatial resolution when compared with visible light microscopes, combined with an ability to image hydrated specimens that are several microns with a minimum of preparation. Our study describes the conceptual design of soft x-ray microscope system based on a laser-based source for biomedical application with high resolution ($\leq$50nm) and short exposure time ($\leq$30sec).

• Journal of Astronomy and Space Sciences
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• v.10 no.2
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• pp.113-122
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• 1993

Using a simple analytic model based on the MHD stability arguments we obtain the size of the magnetosphere for the magnetic compact stars. We assume the ordered, field-aligned flow in the magnetosphere and estimate the wellknown Alfven radius. The dependence of the X-ray absorption in the magnetic funnel on the size of this radius is further considered. We show that such a determination of the magnetic interaction radius can be applied to the reconstruction of X-ray light curves of the magnetic binary stars.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.39.1-39.1
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• 2011

Coronal mass ejection (CME) plasmas have been observed in EUV and X-ray passbands as well as in white light. Mass of CME has been determined using polarized brightness observed by the Large Angle and Spectrometric Coronagraph Experiment (LASCO) on board Solar and Heliospheric Observatory (SOHO). Therefore, this mass obtained from the LASCO observation indicates the total CME mass. However, the mass of CME plasma in different temperatures can be determined in EUV and X-ray passbands using observations by SOHO/EIT, STEREO/EUVI, and Hinode/XRT. Prominence/CME plasmas have been observed as absorption or emission features in EUV and X-ray passbands. The absorption features provide a lower limit to cold mass. In addition, the emission features provide an upper limit to the mass of plasmas in temperature ranges of EUV and X-ray. We determine the mass constraints using the emission measure obtained by assuming the prominence/CME structures. This work will address the mass constraints of hot and cold plasmas in CMEs, comparing to total CME mass.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.8 no.3
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• pp.201-205
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• 2010

Most of iodine was captured by the block when NaI solution flowed through a bentonite block sorbed silver to retard the migration of iodine released from high-level radioactive wastes. In order to understand in detail the mechanism for the retardation of the iodine by the silver ion, X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) spectra of the silver sorbed bentonite before and after the contact with iodide were compared with those of AgO, $Ag_2O$ and AgI as references. This examination suggests that the silver ion sorbed on the bentonite is desorbed, and then it retards the migration of iodine by forming the cluster of AgI precipitate.

• Publications of The Korean Astronomical Society
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• v.15 no.spc1
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• pp.73-83
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• 2000

X-ray astronomy deals with measurements of the electromagnetic radiation in the energy range of $E\~0.1-100 keV (\lambda\~0.12-120{\AA})$. The wavelength of X-ray is comparable to the size of atoms, so that the photons in the X-ray range are usually produced and absorbed by the atomic processes. Since the launch of the first X-ray astronomy satellite 'Uhuru' in 1970, technological advances in a launch capability and a detection capability make X-ray astronomy one of the most rapidly evolving fields of astronomical research. Particularly, a spectral resolving power $E/{\Delta}E$ has been increased by an order of 2 - 3 (in the energy range of 0.1 - 10 keV) during the past 30years. In this paper, I briefly review a developing process of the resolving power and spectroscopic techniques. Then I describe important emission/absorption lines in X-ray astronomy, as well as diagnostics of gas property with line parameters.

• Nuclear Engineering and Technology
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• v.33 no.5
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• pp.514-525
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• 2001

Optimum characteristics of digital X-ray sensor components were analyzed to develop intra- oral dental digital X-ray image sensor using indirect method. Parametric analysis was carried out to optimize the phosphor thickness and the fiber optic plate (FOP) coupling to charge coupled device (CCD). X-ray absorption and light diffusion in the phosphor layer were analyzed by the Monte Carlo method. Real time X-ray image was obtained with prototype X- ray image sensor using general CCD camera with 1∼10 Ip/mm resolution. It has been previously shown that large resolution degradation in X-ray images was caused by miss alignment of FOP to CCD and optical adhesive selection. In this study, we reported that X-ray image quality was greatly improved by using optimized characteristics of alignment device and phosphor thickness.

• Progress in Medical Physics
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• v.33 no.2
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• pp.11-24
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• 2022

X-ray detection has widely been applied in medical diagnostics, security screening, nondestructive testing in the industry, etc. Medical X-ray imaging procedures require digital flat detectors operating with low doses to reduce radiation health risks. Recently, metal halide perovskites (MHPs) have shown great potential in high-performance X-ray detection because of their attractive properties, such as strong X-ray absorption, high mobility-lifetime product, tunable bandgap, low-temperature fabrication, near-unity photoluminescence quantum yields, and fast photoresponse. In this paper, we review and introduce the development status of new perovskite X-ray detectors and imaging, which have emerged as a new promising high-sensitivity X-ray detection technology. We discuss the latest progress and future perspective of MHP-based X-ray detection in medical imaging. Finally, we compare the conventional detection methods with quantum-enhanced detection, pointing out the challenges and perspectives for future research directions toward perovskite-based X-ray applications.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.403-406
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• 2006

A new medical X-ray PIV technique was developed using a conventional medical X-ray tube. To acquire images of micro-scale particles, the X-ray PIV system consists of an x-ray CCD camera with high spatial resolution, and a X-ray tube with small a focal spot. A new X-ray exposure control device was developed using a rotating disc shutter to make double pulses which are essential for PIV application. Synchronization methodology was also developed to apply the PIV technique to a conventional medical X-ray tube. In order to check the performance and usefulness of the developed X-ray PIV technique, it was applied to a glycerin flow in an opaque silicon tube. Tungsten particles which have high X-ray absorption coefficient were used as tracer particles. Through this preliminary test, the spatial resolution was found to be higher than ultrafast MRI techniques, and the temporal resolution was higher than conventional X-ray PIV techniques. By improving its performance further and developing more suitable tracers, this medical X-ray PIV technique will have strong potential in the fields of medical imaging or nondestructive inspection as well as diagnosis of practical thermo-fluid flows.

• Bulletin of the Korean Chemical Society
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• v.21 no.6
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• pp.588-594
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• 2000

Structural changes of an iron phthalocyanine (FePC) monolayer induced by adsorption and externally applied potential on high area carbon surface have been investigated in situ by iron K-edge X-ray absorption fine structure (XAFS) in 0.5 M $H_2S0_4.$ Fine structures shown in the X-ray absorption near edge structure (XANES) for microcrystalline FePC decreased upon adsorption and further diminished under electrochemical conditions. Fe(II)PC(-2) showed a 1s ${\rightarrow}$ 4p transition as poorly resolved shoulder to the main absorption edge rather than a distinct peak and a weak 1s ${\rightarrow}$ 3d transition. The absorption edge position measured at half maximum was shifted from 7121.8 eV for Fe(lI)PC(-2) to 7124.8 eV for $[Fe(III)PC(-2)]^+$ as well as the 1s ${\rightarrow}$ 3d pre-edge peak being slightly enhanced. However, essentially no absorption edge shift was observed by the 1-electron reduction of Fe(Il)PC(-2), indicating that the species formed is $[Fe(II)PC(-3)]^-$. Structural parameters were obtained by analyzing extended X-ray absorption fine structure (EXAFS) oscillations with theoretical phases and amplitudes calculated from FEFF 6.01 using multiple-scattering theory. When applied to the powder FePC, the average iron-to-phthalocyanine nitrogen distance, d(Fe-$N_p$) and the coordination number were found to be 1.933 $\AA$ and 3.2, respectively, and these values are the same, within experimental error, as those reported ( $1.927\AA$ and 4). Virtually no structural changes were found upon adsorption except for the increased Debye-Wailer factor of $0.005\AA^2$ from $0.003\AA^2.$ Oxidation of Fe(II)PC(-2) to $[Fe(III)PC(-2)]^+$ yielded an increased d(Fe-Np) (1 $.98\AA)$ and Debye-Wailer factor $(0.005\AA^2).$ The formation of $[Fe(II)PC(-3)]^-$, however, produced a shorter d(Fe-$N_p$) of $1.91\AA$ the same as that of crystalline FePC within experimental error, and about the same DebyeWaller $factor(0.006\AA^2)$.

• Journal of the Korean Society of Visualization
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• v.5 no.1
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• pp.30-36
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• 2007

The global environment is deteriorating at an alarming rate, despite of enhanced international environmental regulation. Many studies have been performed to reduce toxic pollutants. Recently, plant-based phytoremediation technology for moving toxic contaminants from soil and water has been receiving large attention. Arsenic-contaminated soil is one of the major pollutant sources for drinking water. Pteris erotica has been known as a hyper-accumulator of arsenic from soils. In this study, we investigated the effect of arsenic absorption on sap flow inside xylem vessels of Pteris. The synchrotron X-ray micro-imaging technique was employed to monitor the refilling process of water containing arsenic inside the xylem vessels of Pteris's leaves and stems non-invasively. The captured phase-contrast X-ray images show both anatomy of internal structure and transport of water inside Pteris. The exposure of Pteris to arsenic solution was found to increase largely the water raise speed in xylem vessels. The present results would provide important information needed for understanding the mechanisms of accumulation and transportation of toxic materials in plants.