• Fibers and Polymers
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• v.6 no.3
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• pp.186-199
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• 2005

A selection of commercially available poly(ethy1ene terephtha1ate) fibers with different degrees of molecular alignment and crystallinity have been investigated utilizing a wide range of techniques including optical microscopy, infrared spectroscopy together with thermal and wide-angle X-ray diffraction techniques. Annealing experiments showed increased molecular alignment and crystallinity as shown by the increased values of birefringence and melting enthalpies. Crystallinity values determined from thermal analysis, density, unpolarized infrared spectroscopy and X-ray diffraction are compared and discussed in terms of the inherent capabilities and limitations of each measurement technique. The birefringence and refractive index values obtained from optical microscopy are found to decrease with increasing wavelength of light used in the experiments. The wide-angle X-ray diffraction analysis shows that the samples with relatively low orientation possess oriented non-crystalline array of chains whereas those with high molecular orientation possess well defined and oriented crystalline array of chains along the fiber axis direction. X-ray analysis showed increasing crystallite size trend with increasing molecular orientation. SEM images showed micro-cracks on low oriented fiber surfaces becoming smooth on highly oriented fiber surfaces. Excellent bending characteristics were observed with knotted fibers implying relatively easy fabric formation.

• Transactions of Materials Processing
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• v.20 no.7
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• pp.518-523
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• 2011

The three dimensional geometries of an aluminum open cell foam before and after uniaxial compressive loading were investigated using the X-ray micro CT(computed tomography). Aluminum 6101-T6 open cell foams of 10, 20, 40 ppi (pore per inch) were considered in this work. After the serial sectioning CT images of aluminum foams were obtained from non-destructive X-ray images, the exact 3D structure were reproduced and visualized with commercial image processing program. The relative density ratio was around the 7.0 to 9.0 range, the unit cells showed anisotropic shapes having the different dimensional ratios of 1.1 to 1.3 between the rise and the transverse directions. The yield stress increased with the relative density ratio and the volumetric strain increased proportionally with compressive strain. The plateau stress in the compressive stress-strain curve was caused by the buckling of ligaments.

• Nuclear Engineering and Technology
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• v.56 no.4
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• pp.1544-1551
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• 2024

A unique brick series based on Vietnamese clay was manufactured at 114.22 MPa pressure rate for γ-ray attenuation purposes, consisting of (x) metallic waste & (90%-x) red clay mineral & 10% (hardener mixed with epoxy resin), where (x) is equal to the values 0%, 20%, 40%, 50%, and 70%. The impacts of industrial metal waste ratio in the structure and radiation protective characteristics were evaluated experimentally. The increase in metallic waste doping concentrations from 0% to 70% was associated with an increase in the manufactured brick's density (ρ) from 2.103 to 2.256 g/cm³ while the fabricated samples' porosity (Φ) decreased from 11.7 to 1.0%, respectively. Together with a rise in fabricated brick's density and a decrease in their porosities, the manufactured bricks' γ-ray attenuation capacities improved. The measured linear attenuation coefficient (μ, cm^-1) was improved by 30.8%, 22.1%, 21.6%, and 19.7%, at E_γ equal to the values respectively 0.662, 1.173, 1.252, and 1.332 MeV, when the metallic waste concentration increased from 0% to 70%, respectively. The study demonstrates that manufactured bricks exhibit superior radiation shielding properties, with radiation protection efficiencies of 88.4%, 90.0%, 91.7%, 92.1%, and 92.4% for bricks with industrial metal waste contents of 0%, 20%, 40%, 50%, and 70%, respectively, at γ-ray energy (E_γ) of 1.332 MeV.

• The Journal of Korean Physical Therapy
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• v.15 no.4
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• pp.466-478
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• 2003

This study was to evaluate the body composition and bone mineral density according to aging in adult and investigated the relationship between various parameters such as body mass index(BMI), bone mineral density(BMD), bone mineral content(BMC), lean body mass(LBM), fat mass(FM) and the value obtained from dual energy X-ray absorptiometry(DEXA). The subjects were composed of healthy adult male and female who were $20^{\sim}73$ years old and they were divided three group according to age (A group : 20-39 yrs., B group : 40-59 yrs., C group : more than 60 yrs.). The conclusion derived from statistical analysis was as follows : 1. Bone mineral content and density were significantly affected by lean body mass(relatively, R=0.85 - 0.63). 2. There was significant difference among age groups in total bone mineral density. 3. There was significant difference among age groups in bone mineral content of male and female. 4. Lean body mass is diminished according to age, but there was not significant difference among age groups. 5. Fat mass of A group in male had the highest mass and followed by C group and B group. In female groups, fat mass of A group had the highest mass and followed by B group and C group. Abdominal fat mass is increased according to age. This result suggest that aging was closely relation with loss of muscle mass, bone mineral density and bone mineral content.

• Journal of Biomedical Engineering Research
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• v.44 no.2
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• pp.139-146
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• 2023

Osteoporosis is a disease in which the risk of bone fractures increases due to a decrease in bone density caused by aging. Osteoporosis is diagnosed by measuring bone density in the total hip, femoral neck, and lumbar spine. To accurately measure bone density in the lumbar spine, the vertebral region must be segmented from the lumbar X-ray image. Deep learning-based automatic spinal segmentation methods can provide fast and precise information about the vertebral region. In this study, we used 695 lumbar spine images as training and test datasets for a deep learning segmentation model. We proposed a lumbar automatic segmentation model, CM-Net, which combines the center point of the spine and the modified U-Net network. As a result, the average Dice Similarity Coefficient(DSC) was 0.974, precision was 0.916, recall was 0.906, accuracy was 0.998, and Area under the Precision-Recall Curve (AUPRC) was 0.912. This study demonstrates a high-performance automatic segmentation model for lumbar X-ray images, which overcomes noise such as spinal fractures and implants. Furthermore, we can perform accurate measurement of bone density on lumbar X-ray images using an automatic segmentation methodology for the spine, which can prevent the risk of compression fractures at an early stage and improve the accuracy and efficiency of osteoporosis diagnosis.

• The Korean Journal of Nuclear Medicine Technology
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• v.14 no.1
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• pp.40-45
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• 2010

Purpose: Recently, the performance of the X-ray tube was very much improved by the power generation of the technology. However, the overload of equipment is occurred by the increment of the equipment operating time according to the increment of the examination number of cases. The X-ray dose can change by heat occurrence of the X-ray tube due to this. Moreover, the change of the bone mineral density value is possible to occur. Therefore, We tries to whether the change of the bone mineral density value of each equipment according to the difference of the examination number of cases and operating time occur or not. Materials and Methods: The BMD value was measured by the Aluminum Spine Phantom and the European Spine Phantom in each equipment, in order to find out about the difference of the time general classification bone mineral density value by using the Dual energy X-ray absorptiometry. And after scanning each phantom by using X-ray dose meter (Unfors Mult-O-Meter), a dose was measured by the same condition. As to, an average and standard deviation were found and the change of each equipment much BMD value was compared and it evaluated. Results: $Mean{\pm}SD$ of each equipment by using the Aluminum Spine Phantom, A equipment was $1.174{\pm}0.002$, $1.171{\pm}0.005$, $1.173{\pm}0.005$, B equipment was $1.186{\pm}0.003$, $1.187{\pm}0.003$, $1.185{\pm}0.003$, C equipment was $1.180{\pm}0.003$, $1.182{\pm}0.004$, $1.183{\pm}0.002$, D equipment was $1.188{\pm}0.004$, $1.185{\pm}0.003$, $1.185{\pm}0.004$. By using the European Spine Phantom, A equipment was $1.143{\pm}0.006$, $1.153{\pm}0.009$, $1.161{\pm}0.003$, B equipment was $1.134{\pm}0.004$, $1.13{\pm}0.008$, $1.127{\pm}0.015$, C equipment was $1.143{\pm}0.006$, $1.134{\pm}0.01$, $1.133{\pm}0.006$, D equipment was $1.14{\pm}0.001$, $1.122{\pm}0.002$, $1.131{\pm}0.008$, altogether included in the normal range. Conclusion: There was no significant change of the BMD value of using a phantom by time zones. Therefore, if the quality control is made to use the extent management method of the equipment for beginning in the present application, the reliability of the BMD equipment will be able to be enhanced.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.41.1-41.1
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• 2014

Clusters of galaxies provide unique laboratories to study astrophysical processes on large scales, and are also important probes for cosmology. X-ray observations are still the best way to find and characterise clusters. The extended ROSAT-ESO flux-limited X-ray (REFLEX II) galaxy clusters form currently the largest well-defined and tested X-ray galaxy cluster sample, providing a census of the large-scale structure of the Universe out to redshifts of z-0.4. I will describe the properties of the survey and the X-ray luminosity function, which led to our recent cosmological constraints on omegaM-sigma8. They tighten the previous constraints from other X-ray experiments, showing good agreements with those from the Planck clusters, but some tension exists with the Planck CMB constraints. The second part of my talk will concern the structure of the local Universe, and the study of the first X-ray superclusters. The density of the clusters reveals an under-dense region in the nearby Universe, which has an interesting implication for the cosmological parameters. Using the X-ray superclusters, that are constructed with a physically motivated procedure, I will show environmental aspects that X-ray superclusters provide, and compare to cosmological N-body simulations.

• 한국가시화정보학회:학술대회논문집
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• 2002.11a
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• pp.31-34
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• 2002

Imaging techniques using x-ray beam at high energies (>6KeV) such as contact radiography, projection microscopy, and tomography have been used to nondestructively discern internal structure of objects in material science, biology, and medicine. This paper introduces the x-ray micro-imaging method using 1B2 micro-probe line of PAL (Pohang Accelerator Laboratory). Cross-sectional information on low electron density materials can be obtained by probing a sample with coherent synchrotron x-ray beam in an in-line holography setup. Living organism such as plants, insects are practically transparent to high energy x-rays and create phase shift images of x-ray wave front. X-ray micro-images of micro-bubbles of $20\~120\;{\mu}m$ diameter in an opaque tube were recorded. Clear phase contrast images were obtained at Interfaces between bubbles and surrounding liquid due to different decrements of refractive index.

• International Journal of Safety
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• v.8 no.1
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• pp.14-17
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• 2009

The $Co^{60}$ $\gamma$-ray irradiation effects on the electrical and thermal characteristics of low density polyethylene crosslinked by Dicumyl peroxide (DCP) were investigated. We experimented on electrical properties as following; electrical tree inception and growing type for applying AC step voltage, AC breakdown strength, volume resistivity with increasing dosage. Also, chemical analyses were performed TGA, gel fraction. These electrical properties changed depending upon its crosslinking degree and byproducts from crosslinking reactions. Crosslinking reactions were considered causing by $\gamma$-ray irradiation and DCP had contained in low density polyethylene.

• Fibers and Polymers
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• v.5 no.3
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• pp.225-229
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• 2004

The effect of UV and $^60{Co}$ gamma radiations on the physical and mechanical properties of nylon 6 mono-filaments with different draw ratios has been studied. Specimens were exposed to either up to 25 Mrad of gamma or up to 168 hrs of intense UV irradiation. The results show that nylon mono-filaments exposed to gamma rays, with much higher quantum energy than UV, undergo a larger extent of molecular chain scission. Higher irradiation dose also results in the production of insoluble, macroscopic three-dimensional cross-linked network structure. The amorphous regions with a lower density of cohesive energy (lower molecular orientation) show a higher extent of cross linking reaction whereas amorphous regions with a higher density of cohesive energy (higher orientation) show higher extent of chain scission reaction, irrespective of UV ray or gamma ray irradiation.