• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.392-403
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• 2010

In this study, a new methodology by using the X-ray CT scan is proposed for estimating void ratio of very fine clayey soil. Since the particle size of the clay is too fine to calculate the volume of void inside the clays, CT scanning tests with a number of clay specimens that were artificially set to have various designated void ratios have been carried out. From the tests, a relationship between the CT values and void ratios is given to be used for estimating the invisible void ratio of very fine clay from a representative CT value scanned. The linear relationship was able to be acquired finally. It is expected that micro X-ray CT scanning can be capable of capturing the void ratio of very fine soils without any errors inherent in the conventional specific gravity tests.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.69.1-69.1
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• 2017

According to structure formation simulations, weak shocks with typical Mach number, M<3, are expected to form in merging galaxy clusters. The presence of such shocks has been indicated by X-ray and radio observations of many merging clusters. In particular, diffuse radio sources known as radio relics could be explained by synchrotron-emitting electrons accelerated via diffusive shock acceleration (Fermi I) at quasi-perpendicular shocks. Here we also consider possible roles of stochastic acceleration (Fermi II) by compressive MHD turbulence downstream of the shock. Then we explore a puzzling discrepancy that for some radio relics, the shock Mach number inferred from the radio spectral index is substantially larger than that estimated from X-ray observations. This problem could be understood, if shock surfaces associated with radio relics consist of multiple shocks with different strengths. In that case, X-ray observations tend to pick up the part of shocks with lower Mach numbers and higher kinetic energy flux, while radio emissions come preferentially from the part of shocks with higher Mach numbers and higher cosmic ray (CR) production. We also show that the Fermi I reacceleration model with preexisting fossil electrons supplemented by Fermi II acceleration due to postshock turbulence could reproduce observed profiles of radio flux densities and integrated radio spectra of two giant radio relics. This study demonstrates the CR electrons can be accelerated at collisionless shocks in galaxy clusters just like supernova remnant shock in the interstellar medium and interplanetary shocks in the solar wind.

• Bulletin of the Korean Chemical Society
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• v.19 no.5
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• pp.549-553
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• 1998

The structure and layer distribution of cadmium arachidate Langmuir-Blodgett film were analyzed by the small angle X-ray reflectivity measurements using synchrotron radiation. Y-to X type transition was ocurred during the 39th passage of deposition of cadmium arachidate. Based on the measurement of the consumed area of the monolayer, it was determined that about 27.5 layer was deposited. Using the synchrotron X-ray, the reflectivity profile of cadmium arachidate LB film over the wide range of grazing angle was obtained. The X-ray reflectivity profile was analyzed using the recursion formula. By fitting the location and dispersion of the subsidiary maxima between the Bragg peaks of the measured reflectivity profile with that of the calculated reflectivity profile, the average thickness and the distribution of layer thickness were evaluated. The genetic algorithm was adopted to the fitting of reflectivity profile to evaluate the optimum value of the number distribution of layer. Based on the morphology measurement with an atomic force microscopy (AFM), the domain structure and mean roughness of LB films were obtained. The mean roughness value calculated based on the number of layer distribution obtained from the measurement by AFM is consistent with that obtained from X-ray reflectivity analysis.

• Nuclear Engineering and Technology
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• v.53 no.5
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• pp.1626-1633
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• 2021

In an industrial field, non-destructive testing (NDT) is commonly used to inspect industrial products. Among NDT methods using radiation sources, X-ray laminography has several advantages, such as high depth resolution and low computational costs. Moreover, an X-ray laminography system with stationary source array and compact detector is able to reduce mechanical motion artifacts and improve inspection efficiency. However, this system, called stationary inverse-geometry X-ray laminography (s-IGXL), causes truncation artifacts in reconstructed images due to limited fields-of-view (FOVs). In this study, we proposed a projection data correction (PDC) method to reduce the truncation artifacts arisen in s-IGXL images, and the performance of the proposed method was evaluated with the different number of focal spots in terms of quantitative accuracy. Comparing with conventional techniques, the PDC method showed superior performance in reducing truncation artifacts and improved the quantitative accuracy of s-IGXL images for all the number of focal spots. In conclusion, the PDC method can improve the accuracy of s-IGXL images and allow precise NDT measurements.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.6
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• pp.942-948
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• 2017

Ray-tracing based method for computing projection image calculates the exact amounts of the intersection between voxels and a ray. Among several different implementations of the ray tracing based methods, Siddon's method is the earliest one. Later faster implementation such as Jacobs's method, Zhao's method, were investigated. To our knowledge, Zhao's method is the fastest one among these. We improve the speed of the Zhao's method by predicting the number of the same intersection length between voxel and a ray. In our experiment, the proposed method showed significantly faster computation speed than Zhao's method.

• Journal of Radiation Industry
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• v.9 no.3
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• pp.153-159
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• 2015

Reliability of printed circuit board (PCB), which is based on high integrated circuit technology, is having been important because of development of electric and self-driving car. In order to answer these demand, automated X-ray inspection (AXI) is best solution for PCB non-destructive test. PCB is consist of plastic, copper, and, lead, which have low to high Z-number materials. By using dual energy X-ray imaging, these materials can be inspected accurately and efficiently. Dual energy X-ray imaging, that have the advantage of separating materials, however, need some solution such as energy separation method and enhancing efficiency because PCB has materials that has wide range of Z-number. In this work, we found out several things by analysis of X-ray energy spectrum. Separating between lead and combination of plastic and copper is only possible with energy range not dose. On the other hand, separating between plastic and copper is only with dose not energy range. Moreover the copper filter of high energy part of dual X-ray imaging and 50 kVp of low energy part of dual X-ray imaging is best for efficiency.

• Journal of the Korean Wood Science and Technology
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• v.37 no.6
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• pp.531-536
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• 2009

Radial variations of ray spacing and frequency of biseriate ray were examined in the woods of most commercially important Korean softwood species of Pinus koraiensis and Larix kaempferi. Ray spacing, or ray number per mm in cross section, averaged 4.6 and 9.0 in Pinus koraiensis and Larix kaempferi, respectively. Thus, rays of Larix kaempferi appeared to be more closely arranged than those of Pinus koraiensis. Ray spacing was the densest around pith, and then slowly decreased toward bark. In tangential section, biseriate ray frequency of Larix kaempferi was higher than that of Pinus koraiensis. Biseriate ray was designated, based on the number of cells of biseriate portion in vertical extent, as the type of B+1 (one cell high), B+2 (two cells high), and so on. The dominated type was B+1 in Pinus koraiensis but B+2 in Larix kaempferi. The biseriate ray types of B+3, B+4, and B+5 were occasionally found in earlywood. Interestingly, even B+6 and B+7 types were observed in Larix kaempferi. In conclusion, it was considered that ray spacing could be used for separating juvenile wood from adult wood. Also, characteristics of ray spacing and biseriate ray might be used for identifying these two species.

• Journal of the Korean Society of Radiology
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• v.6 no.6
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• pp.499-505
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• 2012

The purpose of this study was to find out the difference of radiation dose value through energy, exposure number, fluoroscopy time, the number of days of exposed scatter X-ray when TLD and OSLD is used in diagnostic radiology. The difference of value were measured by relative ratio and interval. Energy makes high relative ratio of TLD($1.81{\pm}0.41$) than OSLD($1.40{\pm}0.26$), exposure number makes high of OSLD($1.40{\pm}0.26$) than TLD($2.10{\pm}0.10$). There are no significant differences between relative ratio of TLD and OSLD in fluoroscopy time and the number of days of exposed scatter X-ray. But interval of relative ratio in the number of days of exposed scatter X-ray was narrowed in less 0.2. That means, the measurement of scatter X-ray could more confident in TLD and OSLD than the measurement of direct ray. In conclusion, we have to recognize the relative ratio of TLD and OSLD could be vary depending on exposed condition of radiation. And in some cases, double test of TLD and OSLD get more creditable results of dose value.

• Journal of the Korean Wood Science and Technology
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• v.37 no.1
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• pp.19-28
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• 2009

Some wood anatomical characteristics of seven chestnut cultivars (Tanzawa, Ibuki, Arima, Ginyose, Tsukuba, Riheiguri, and Mansung) grown in Korea were examined in this study. We investigated the radial variation of wood components such as diameter and number of earlywood vessel element and ray density in cross section and number and height of ray in tangential section. Discs were taken from the stem of seven chestnut cultivars at breath height and cut into the radial strip. Cross, radial, and tangential sections, 10 to $20{\mu}m$ thick, were sliced with a sliding microtome. These sections were stained, dehydrated, and mounted with Canada balsam according to common procedure. Measurement and observation were performed with a light microscopy. In all chestnut cultivars, radial and tangential diameter of vessel element increased but number of vessel element per $mm^2$ decreased with increasing tree age. Ray spacing (per mm) in cross section from pith to bark showed no significant variation, while number of ray per $mm^2$ increased but ray height decreased with the increase of tree age. Conclusively, the results obtained in present study were thought to be some valuable information for separating juvenile and adult wood as well as identifying chestnut cultivars.

• Journal of the Korean Wood Science and Technology
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• v.16 no.1
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• pp.9-20
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• 1988

Lespedeza species have been widely used not only as plant resources for bark, leaves and honey, but also as erosion control materials. This study was carried out to investigate the structural and wood tiber characteristics in order to obtain basic information for the utilization of the wood. The wood structure was investigated for 10 selected species and the wood fiber, for the 5 selected species among Lespedeza species distributed all over the country. The following results were obtained. In the cross section, campylotropis showed ray diffuse porous wood, L. bicolor, L. cyrtobotrya, L. thunbergii var. intermedia, diffuse porous wood, and L. tomentella, L. angustifolioides. L. maritima, L. robusta, L. patentibicolor, ring porous wood. The maximum diameter of a single vessel ranged 66-123 ${\mu}$ in all species. Campylotropis showed the most number of vessels, L. angustifolioides, the least. The number of ray per mm ranged 7-22, Campylotropis showed the most number of rays, L. angustifolioides, the least. In the radial section the average length of vessel ranged 121-250 ${\mu}$ in all species. L. thunbergii var. intermedia showed the longest vessel, L. tomentella, the shortest. In tangential section the average width of the uniseriate ray ranged 9.2-14.7${\mu}$, that of the multiseriate ray, 19.2-42.1 ${\mu}$. The average height of the uniseriate ray ranged 143.0-1162.0 ${\mu}$. The width of fiber ranged 10.12-13.61 ${\mu}$, L. maximowiezii showed the narrowest tiber, L. thunbergii var. intermedia. the widest, the thickness of fiber wall ranged 2.93-3.71 ${\mu}$ in the five species. L. maximowiezii showed the most thin fiber wall, L. thunbergii var. intermedia, the thickest, L. cyrtobotrya showed the difference in the size of fiber between the shade and the sunny sites but L. maximowiezii showed no difference. There was significant difference in fiber length, fiber width and wall thickness between L. eyrtobotrya and L. maximowiezii.