• Radiation Oncology Journal
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• v.2 no.2
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• pp.271-280
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• 1984

The peripheral dose, defined as the dose outside therapeutic photon fields, which is responsible for the functional damage of the critical organs, fetus, and radiation. induced carcinogenesis, has been investigated for $^{60}Co\;\gamma$ ray and 10 MV Xray. It was measured by silicon diode controlled by semiautomated water phantom without any shielding or with lead plate of HVL thickness put horizontally or vertically to shield stray radiations. Authors could obtain following results. 1. The peripheral dose was larger than $0.7\%$ of central axis maximum dose even at 20cm distance from field margin. That is clinically significant, so it should be reduced. 2. Even for square fields of 10 MV Xray, radial peripheral dose distribution did not coincide with transverse distribution, because of the position of collimator jaws. 3. Between surface and $d_m$, the peripheral dose distributions show a pattern of the dose distribution of electron beams and the maximum doss was approximately proportional to the length of a side of square field. 4. The peripheral doses depended on radiation quality, field size, distance from field margin and depth in water. Distance from field margin was the most important factor. 5. Except for near surface, the peripheral dose from phantom was approximately equal to that from therapy unit. 6. To reduce the surface dose outside fields, therapist should shield stray radiations from therapy unit by lead plate of at least one HVL for 10 MV X-ray and by bolus equivalent to tissue of 0.5cm thickness for $^{60}Co$. 7. To reduce the dose at depth deeper than $d_m$, it is desirable to shield stray radiations from therapy unit by lead.

• Journal of the Korean Vacuum Society
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• v.5 no.1
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• pp.14-24
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• 1996

We have investigated atomic and electronic structures of a clean Pd(111) surface using low energy electron diffraction (LEED) and angle-resolved photoemission spectroscopy (ARPES). A typical clean LEED pattern with a 3-fold symmetry has been observed, corresponding to that for an fcc (111) surface. ARPES measurements have been performed along the $\Gamma-M,\Gamma-K,\Gamma-M$TEX> symmetry lines, from which the experimental band structure of Pd(111) has been determined. The experimental band structure and work function of Pd(111) surface are found to agree well with the calculated band structure of bulk Pd and the calculated work function of Pd(111), respectively. However, the peak positions in the experimental band structure are located closer to the Fermi level than in the theoretical band structure by 0.1~0.8 eV, depending on the $\kappa$-points in the Brillouin zone. In additin, the experimental band widths are narrower than the theoretical band widths by about 0.5eV. The effects of the localized surface Pd 4d states and the Coulomb interaction between Pd 4d bulk electrons have been discussed as possible origins of such discrepancies between experiment and theory.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.1023-1026
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• 2013

The electronic equipment which was exposed to high level pulsed radiation is damaged as Upset, Latchup, and Burnout. Those damages has come from the instantaneous photocurrent from electron-hole pairs generated in itself. Such damages appeared as losses of power in military weapon system or of blackout in aerospace equipment and eventually caused in gross loss of national. In this paper, we have implemented a RDC(Radiation detection and control module) as part of the radiation protection technology of the electronic equipment or devices from the pulsed gamma radiation. The RDC which is composed of pulsed gamma-ray detection sensor, signal processors, and pulse generator is designed to protect the important electronic circuits from the pulse radiation. To verify the functionality of the RDC, LM118s which had damaged by the pulse radiation were tested. The test results showed that the test sample applied with a RDC was worked well in spite of the irradiation of the same pulse radiation. Through the experiments we could confirm that the radiation protection technology implemented with RDC had the functionality of radiation protection to the electronic devices.

• Journal of radiological science and technology
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• v.43 no.5
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• pp.375-382
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• 2020

PET/CT is a medical equipment that detects 0.511 MeV of gamma rays. The radiation workers are inevitably exposed to ionizing radiation in the process of handling the isotope. Accordingly, PET/CT workers use syringe shields made of lead and tungsten to protect their hands. However, lead and tungsten are known to generate very high scattering particles by interacting with gamma rays. Therefore, in this study, we tried to find out the effect on the scattering particles emitted from the syringe shield. In the experiment, first, the exposure dose to the hand (Rod phantom) was evaluated according to the metal material (lead, tungsten, iron, stainless steel) using Monte Carlo simulation. The exposure dose was compared according to whether or not plastic is attached. Second, the exposure dose of scattering particles was measured using a dosimeter and lead. As a result of the experiment, the shielding rate of plastics using the Monte Carlo simulation showed the largest difference in dose of about 40 % in lead, and the lowest in iron, about 15 %. As a result of the dosimeter test, when the plastic tape was wound on lead, it was found that the reduction rate was about 15 %, 28 %, and 39 % depending on the thickness. Based on the above results, it was found that 0.511 MeV of gamma ray interacts with the shielding tool to emit scattered rays and has a very large effect on radiation exposure. However, it was considered that the scattering particles could be sufficiently removed with plastics with a low atomic number. From now on, when using high-energy radiation, the shielding tool and the skin should not be in direct contact, and should be covered with a material with a low atomic number.

• Korean Membrane Journal
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• v.1 no.1
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• pp.25-37
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• 1999

positron annihilation Lifetime Spectroscopy has been extensively applied in recent years to investigate the free volume in polymers owing to the capability of the electron-positron bound system (positronium) to probe the typical size of sub-nanometric cavities among the macromolecular chains. In this paper we show recent results obtained through this technique in some amorphous polymeric mem-branes(olyurethanes. PUs and polytrimethilsylilpropine PTMSP) after a brief survey of the general features of the annihilation process as well as of the experimental apparatus. Lifetime of o-ps decay({{{{ tau _3}}}}) in PUs increases going from sub {{{{ TAU _g}}}} to over {{{{ TAU _g}}}} temperatures following a sigmoid curve. The coefficient of dilatation of the free volume fraction is shown to be the sum of two contributes due to the variation with T of the number of holes and of their mean volume. PAL spectrum of PTMSP freshly prepared shows four lifetime components: {{{{ tau _3}}}} and {{{{ tau _4}}}}: only are useful for free volume study. Two kinds of holes of different equivalent radius are reported ({{{{ gamma _s}}}} 4.60 nm and {{{{ gamma _1}}}} 0.754) The equivalent volume does not change in a range of 100 K. however the physical aging increases density and decreases oxygen permeability while {{{{ gamma _s}}}} goes down to 0.374 and r1 to 0.735 The number of holes obtained from the intensities{{{{ IOTA _3}}}} and {{{{ IOTA _4}}}} of PAL spectra decreases with aging 21.7% and 3.5% for large and small holes respectively.

• Journal of Microbiology and Biotechnology
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• v.23 no.7
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• pp.942-952
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• 2013

Monoliths are functional porous materials with a three-dimensional continuous interconnected pore structure in a single piece. A monolith with uniform shape based on poly(${\gamma}$-glutamic acid) (PGA) has been prepared via a thermally induced phase separation technique using a mixture of dimethyl sulfoxide, water, and ethanol as solvent. The morphology of the obtained monolith was observed by scanning electron microscopy and the surface area of the monolith was evaluated by the Brunauer Emmett Teller method. The effects of fabrication parameters such as the concentration and molecular mass of PGA and the solvent composition have been systematically investigated. The PGA monolith was cross-linked with hexamethylene diisocyanate to produce the water-insoluble monolith. The addition of sodium chloride to the phase separation solvent affected the properties of the cross-linked monolith. The swelling ratio of the cross-linked monolith toward aqueous solutions depended on the buffer pH as well as the monolith fabrication condition. Copper(II) ion was efficiently adsorbed on the cross-linked PGA monolith, and the obtained copper-immobilized monolith showed strong antibacterial activity for Escherichia coli. By combination of the characteristic properties of PGA (e.g., high biocompatibility and biodegradability) and the unique features of monoliths (e.g., through-pore structure, large surface area, and high porosity with small pore size), the PGA monolith possesses large potentials for various industrial applications in the biomedical, environmental, analytical, and separation fields.

• Journal of the Korean Chemical Society
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• v.40 no.4
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• pp.264-272
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• 1996

Cluster models of the Υ-Al2O3(111) and the Pt(111) surfaces have been used in an atom superposition and electron delocalization molecular orbital study of interfacial bond strengths between them. The reduced extents for Al3+ are due to the ratio of oxygen to aluminum atoms. The greater the reduced extent for Al3+ is, the stronger the binding energy is to Pt atoms in a cluster. The oxygen-covered surfaces of Υ-Al2O3(111) are shown to bind more weakly to Pt atoms, while the binding to the oxygen-covered surface formed under oxidizing conditions of Pt atoms is strong. The interfacial bond of platinum-alumina may be possible by a charge-transfer mechanism from the platinum surface to the partially empty O-2p band and Al3+ dangling surface orbital.

• Nuclear Engineering and Technology
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• v.52 no.10
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• pp.2320-2327
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• 2020

The extreme hydrophobicity of expanded polytetrafluoroethylene (ePTFE) hinders bone-tissue integration, thus limiting the use of ePTFE in medical implant applications. To improve the potential of ePTFE as a biomaterial, 2-hydroxyethyl methacrylate (HEMA) was grafted onto the ePTFE surface using the gamma irradiation technique. The characteristics of the grafted ePTFE were successfully evaluated using attenuated total reflectance Fourier transform infrared (ATR-FTIR), field-emission scanning electron microscopy (FESEM)/energy dispersive X-ray (EDX), and X-ray photoelectron spectroscopy (XPS). Under the tensile test, the modified ePTFE was found to be more brittle and rigid than the untreated sample. In addition, the grafted ePTFE was less hydrophobic with a higher percentage of water uptake compared to the untreated ePTFE. The protein adsorption test showed that grafted ePTFE could adsorb protein, which was denoted by the presence of N peaks in the XPS analysis. Moreover, the formation of the globular mineral on the grafted ePTFE surface was successfully visualized using the FESEM analysis, with a ratio of 1.94 for Ca:P minerals by the EDX. To summarize, the capability of the modified ePTFE to show protein adsorption and mineralization indicates the improvement of the polymer properties, and it can potentially be used as a biomaterial for implant application.

• Journal of Radiation Industry
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• v.6 no.2
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• pp.159-164
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• 2012

Bacterial cellulose (BC) is generated from citrus gel by Gluconacetobacter hansenii TL-2C. BC has good properties such as high-burst pressure, high-water contact and the ultrafine highly nanofibrous structure of mimic natural extracellular matrix (ECM) for tissue engineering. In this study, acrylic acid (AAc) was grafted onto BC surfaces under aqueous conditions using gamma-ray irradiation, and then immobilized gelatin onto AAc-g-BC. The characterization of scaffolds was performed by scanning electron microscopy (SEM), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), toluidine blue O (TBO) assay. Morphology of gelatin and AAc incorporation onto BC nanofibers did not changed. Our study suggests that gelatin-immobilized BC nanofibers scaffold has a potentiality to fabricate 3D nanofibrous scaffolds for tissue engineering.

• Journal of Radiation Industry
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• v.7 no.1
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• pp.45-49
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• 2013

In tissue engineering application, a fibrous structure of scaffolds has been issued as an alternative system to regulate cell survival and tissue regeneration, and electrospinning technique has been popularly used to generate fibrous meshes or sheets mimicking the structure of native extracellular matrix (ECM). However, recent strategy in the scaffold development is expanded to provide the structural property as well as a biological property of native ECM, a variety of surface modification techniques have been used to introduce biological property. In this study, we developed biomimetic poly(L-lactide-co-${\varepsilon}$-caprolactone) (PLCL) nano- and micro-fibrous scaffolds as a unique platform with structural and biological properties with native ECM using electrospinning method and gamma-ray irradiation. Surface morphology of the scaffolds was observed by scanning electron microscopy, and alteration of surface property was evaluated with toluidine blue O staining, water contact angle measurement and ATR-FTIR analysis.