• Radiation Oncology Journal
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• v.19 no.1
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• pp.74-80
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• 2001

Purpose : Irradiation cones by using backscatter electrons are made for the treatment of superficial small lesions of skin, oral cavity, and rectum where a significant dose gradient and maximum surface dose is desired. Methods and Materials : Backscatter electrons are produced from the primary electron beams from the linear accelerators. The design consists of a cylindrical cone that has a thick circular plate of high atomic number medium (Pb or Cu) attached to the distal end, and the plate can be adjusted the reflected angle. Primary electrons strike the metal plate perpendicularly and produce backscatter electrons that reflect through the lateral hole for treatment. Using film and a parallel plate ion chamber, backscatter electron dose characteristics are measured. Results : The depth dose characteristic of the backscatter electron is very similar to that of the hard x-ray beam that is commonly used for the intracavitary and superficial lesions. The basckscatter electron energy is nearly constant and effectively about 1.5 MeV from the clinical megavoltage beams. The backscatter electron dose rate of $35\~85\;cGy/min$ could be achieved from modern accelerators without any modification. and the depth in water of $50\%$ depth dose from backscatter electron located at 6mm for $45^{\circ}$ angled lead scatter. The beam flatness is dependent on the slit size and the depth of treatment, but is satisfactory to treat small lesions. Conclusions : The measured data for backscatter electron energy, depth dose flatness dose rate and absolute dose indicates that the backscatter electrons are suitable for clinical use.

• Journal of Periodontal and Implant Science
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• v.27 no.4
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• pp.829-844
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• 1997

Dentin hypersensitivity must be one of the most frequent postoperative complaints in periodontal patients. Obliterating the open dentinal tubules or decreasing the diameter of their orifices would, therefore, be an objective of treatment for hypersensitive teeth. The purpose of this study was to evaluate the effect of a pulsed Nd:YAG laser irradiation on obliteration of dentinal tubules and to determine any difference according to irradiation methods. The 45 posterior teeth that had been extracted due to periodontal disease were initially treated with tetracycline HCI(100 mg/ml, 4 min.) to remove the smear layer after root planing. The root surfaces were then irradiated by a pulsed Nd:YAG laser(EL.EN.EN060, Italy) by different laser beam spot size and different exposure condition: ${\cdot}$ group 1: irradiated group by small spot(beam diameter=1mm, lW, 2 sec) ${\cdot}$ group 2: irradiated group by large spot(beam diameter=10mm, 1W, 200 sec) ${\cdot}$ group 3: irradiated group by gradual increase of watt (from 0.3W to 1.0W), beam diameter=4mm ${\cdot}$ group 4: irradiated group by fixed watt(1.0 W), beam diameter=4mm ${\cdot}$ control group: no irradiation but root planing and tetracycline HCI conditioning only. Additionally, the specimens were retreated with tetracycline HCI(100mg/ml, 4min.) to evaluate the stability of obliteration effect by Nd:YAG laser. Specimens were examined under the scanning electron microscope(JEOL, JSM-840A, Japan). Photomicrographs were taken at ${\times}4,000$ magnification and were analyzed statistically. The results were as follows: l. Scanning electron micrographs of root surface treated by tetracycline HCI alone(control group) showed widened, funnel-shaped dentinal tubules, while those of the root surface irradiated by various methods showed partially or completely obliterated dentinal tubules and various surface alterations, eg, flat, multiple pitted, melted and resolidified surface at the same energy density. 2. There was no significant difference in the obliteration effect of dentinal tubules between group 1 and group 2, and between group 3 and group 4(p>0.05). 3. The obliteration effect of dentinal tubules by a Nd:YAG laser irradiation was relatively stable to tetracycline HCI. The results demonstrate that a pulsed Nd:YAG laser irradiation within 1.0W, regardless of irradiation methods, can obliterate dentinal tubules effectively.

• Journal of the Korean Vacuum Society
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• v.11 no.3
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• pp.171-175
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• 2002

The change in work function was studied on Indium-Tin-Oxide(ITO) surface after O-plasma treatment using $\gamma$-Focused ion Beam($\gamma$-FIB). As the surface of ITO experienced more O-plasma treatment, both the surface resistivity and the work function got higher. Auger Electron Spectroscopy identified the increase of oxygen as well as the decrease of Sn. The rise of work function and surface resistivity is considered to be due to the change in oxygen and Sn on the surface of ITO.

• Transactions of Materials Processing
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• v.12 no.5
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• pp.487-492
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• 2003

Tension variations with heat treatment in shadow mask for flat braun tubes are investigated in this study. In CRT, landing shift of the electron beam due to thermal deformation of the tension mask made the color purity of screen worse. In order to get the final results of thermal deformation, the tensile force within the mask and the welding processes between the rail and the extended mask have to be analysed sequentially. In this study, the effect of heat treatment is studied in terms of tension variations of shadow mask during its manufacturing process.

• Radiation Oncology Journal
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• v.5 no.2
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• pp.157-163
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• 1987

It is known that fixed source to skin distance (SSD) cannot be used when the treatment field is sloped or larger than the size of second collimator in electron beam irradiation and inverse square law using effective ssd should be adopted. Effective SSDs were measured in different field sizes in each 6, 9, 12, 15 and 18MeV electron energy by suing NELAC 1018D linear accelerator of Kosin Medical Center. We found important parmeters of effective SSD. 1. Minimum effective SSD was 58.8cm in small field size of $6\pm6cm$ and maximum effective SSD was 94.9cm in large field size of $25\pm25cm$, with 6MeV energy. It's difference was 36.1cm. The dose rate at measuring point was quite different even with a small difference of SSD in small field $(6\times6cm)$ and low energy (6 MeV). 2. Effective SSD increased with field size in same electron energy. 3. Effective SSDs gradually increased with the electron energies and reached maximum at 12 or 15 MeV electron energy and decreased again at 18MeV electron energy in each identical field size. And so the effective SSD should be measured in each energy and field size for practical radiotherapy.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.7
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• pp.605-610
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• 2006

We have investigated $Al_{0.25}Ga_{0.75}As/In_{0.2}Ga_{0.8}As$ structures for pseudomorphic high electron mobility transistor(pHEMT), which were grown by molecular beam epitaxy(MBE) and consequently annealed by rapid thermal anneal(RTA), using Hall measurement, photoluminescence, and transmission electron microscopy (TEM). According to intensity and full-width at half maximum maintained stable at the same energy level, the quantized energy level in $Al_{0.25}Ga_{0.75}As/In_{0.2}Ga_{0.8}As$ quantum wells was independent of the RTA conditions. However, the Hall mobility was decreased from $6,326cm^2/V.s\;to\;2,790cm^2/V.s\;and\;2,078cm^2/V.s$ after heat treatment respectively at $500^{\circ}C\;and\;600^{\circ}C$. The heat treatment which is indispensable during the fabrication procedure would cause catastrophic degradation in electrical transport properties. TEM observation revealed atomically non-uniform interfaces, but no dislocations were generated or propagated. From theoretical consideration about the mobility changes owing to inter-diffusion, the degraded mobility could be directly correlated to the interface scattering as long as samples were annealed below $600^{\circ}C$ lot 1 min.

• Applied Chemistry for Engineering
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• v.16 no.3
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• pp.449-455
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• 2005

Electron beam (EB) and ultraviolet (UV) curable monomers (AF-1 with mono functionality and AF-2 with tetra functionality) containing hydroxy and acrylate group for anti-fogging coating were synthesized and applied to EB and UV-curable coating systems. The synthesized reactive AF-1 and AF-2 monomers were first formulated into UV-curable system and the optimization of film properties for anti-fogging coating was investigated. The 5:17.5 ratio for AF-1 and AF-2 was found to be the best optimized formulation for anti-fogging coating without destroying the other essential properties such as hardness, solvent resistance, and adhesion. The optimized formulation was applied to the EB-curable system, and EB and UV-curable systems were compared. The results demonstrated that both EB and UV-cured films coated on PC sheet showed excellent anti-fogging properties; however, the EB-cured film exhibited better hardness, adhesion, and water repellent properties than the UV-cured film.

• Korean Journal of Poultry Science
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• v.42 no.3
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• pp.215-221
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• 2015

Chicken breast meat samples were injected with marinade solution (salt, sugar, phosphate, monosodium glutamate, and nucleic acid) with or without 2% citrus peel extract (CPE), and then a subset were irradiated with a 1 or 2 kGy electron beam (EB) and/or subjected to high-pressure (HP) at 300 or 400 MPa. The initial total aerobic bacterial (TAB) count of the control sample was 4.57 log CFU/g and reached 7.17 log CFU/g after 3 days of storage at $4^{\circ}C$. The 2 kGy EB reduced the TAB count to 4.61 log CFU/g after 7 days. The 400 MPa HP treatment was also effective in reducing the TAB count, but the effect was slightly less than that noted with the 2 kGy EB. The CPE, in combination with the EB and HP, decreased the TAB count by 1.71 and 1.32 log CFU/g at the initial stage and further decreased the count during storage. The 2 kGy EB and the HP (300 and 400 MPa) increased the thiobarbituric acid-reactive substances value, whereas the CPE did not show an antioxidative effect. The EB and HP caused no difference in the sensory qualities. In contrast, the CPE decreased all sensory qualities tested. Sensory panelists commented that the samples with CPE were not in the "rejection" category but were "unfamiliar" for chicken breast meat. In conclusion, the EB was more effective than HP in improving the microbial quality of marinated chicken breast meat. The use of CPE in the marinade solution may synergistically increase the shelf life; however, it is necessary to develop an appropriate formulation to ensure that the sensory qualities are maintained.

• Journal of the Korean Magnetics Society
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• v.9 no.4
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• pp.210-216
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• 1999

The objective of this paper is to investigate corrosion behaviors of CoCrTa/CrNi thin film and post heat-treatment effect. An electron beam evaporator was used for films deposition. After evaporation, post heat-treatment was carried out under $5.0{\times}10^3$ Torr vacuum condition. Annealing temperature and time were 400 $^{\circ}C$ and 30 min, respectively. To understand the effect of annealing on corrosion behavior of CoCrTa/CrNi, potentiodynamic polarization technique and accelerated corrosion chamber test were undertaken. Corrosion potential is higher for the annealed samples (CoCrTa 400$\AA$/CrNi 1000$\AA$) than for as-deposited one. This is attributed to an enrichment of Cr in the surface layer of the thinfilm resulting in a more corrosion resistant material.

• Journal of the Korean Society for Heat Treatment
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• v.21 no.5
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• pp.235-243
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• 2008

Ni-C composite films were prepared using a combination of microwave plasma CVD and ion beam sputtering deposition working in a codeposition way. The structure of these films was characterized by energy-dispersive X-ray diffraction (EDXRD), transmission electron microscopy (TEM) and Raman spectroscopy. It was found that a nickel carbide phase, $Ni_3C$ (hcp), formed as very fine crystallites over a wide temperature range when Ni-C films were deposited at low $CH_4$ flow rates. The thermal stability of this nonequilibrium carbide $Ni_3C$ was also studied. As a result, the $Ni_3C$ carbide was found to decompose into nickel and graphite at around $400^{\circ}C$. With high $CH_4$ flow rates (> 0.2 sccm), the structure of the Ni-C films became amorphous. The formation behavior of the carbide and amorphous Ni-C phases are discussed in relation to the electrical resistivity of the films.