• Applied Microscopy
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• v.30 no.4
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• pp.337-345
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• 2000

Introduction of the buffer layer and the nitridation of a sapphire substrate were one of the most general methods employed for the reduction of lattice defects in GaN thin films Brown on sapphire by MOCVD. In an effort to improve the initial nucleation and growth condition of the GaN, reactive ion beam (RIB) of nitrogen treatment of the sapphire surface has been attempted. The 10 nm thick, amorphous $AlO_xN_y$ layer was formed by RIB and was partially crystallized alter the main growth of GaN at high temperature, leaving isolated amorphous regions at the interface. The beneficial effect of amorphous layer at interface in relieving the thermal stress between substrate and GaN film was examined by measuring the lattice strain value of the GaN film grown with and without the RIB treatment. Higher order Laue zone pattern (HOLZ) of $[\bar{2}201]$ zone axis was compared with simulated patterns and lattice strain was estimated It was confirmed that the great reduction of thermal strain was achieved by RIB process and the amount of thermal stress was 6 times higher in the GaN film grown by conventional method without the RIB treatment.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.35 no.3
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• pp.229-233
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• 2009

20 species of plants were extracted with Methanol and were investigated for DPPH radical scavenging activity and ABTs free radical scavenging activity to quest anti-oxidation ability depending on the proton beam irradiation quantity. In the proton beam irradiation, 15 species's activities increased but among them, Pharbities nil Choisy decreased at 10 KGray and 4 species' activity didn't change at all. In hydrogen ion radical elimination activity, Ulmus macrocarpa (84 %) showed the highest and Pharbitis nil Choisy showed 6 % decreasing at more than 1 KGray. By comparison with untreated $IC_{50}$ value, the beam-treated $IC_{50}$ value increased 6.3 times for Dioscorea batatas Decne. at 1 KGray, 2.1 times for Trichosanthes kirilowii Max., and 2.8 times for Dioscorea batatas Decne. at 5 KGray. In ABTs free radical elimination activity, the activity increased 60 % for Terminalia chebula Retzius compared with untreated one. Besides, the beam-treated $IC_{50}$ value increased 2 times for Gray Ephedra sinica Stapf, 2.5 times for Terminalia chebula Retz. and 2.4 times for Arctium lappa Linne at 1 KGray.

• Journal of radiological science and technology
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• v.33 no.4
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• pp.387-394
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• 2010

In the field of healthcare, the conventional sterilization treatments have been replaced by irradiation methods which are in accordance with internationally well established quality standards. The quality control in radiation sterilization assures that the absorbed dose of the irradiated material is in agreement with its requirements and standards. The electron beam irradiation requires technical assessments of more process parameters than gamma irradiation does. Korea has witnessed wide uses of electron accelerators since early 2000 but there hasn't been research experiences relating to quality system in accordance with international standards. The new large scale e-beam irradiation system with the specification of 10 MeV, 8 kW was installed and operated in 2008 by Seoul Radiology Services Co. It consists of the electron accelerator, product handling system, safety, documentation and control subsystems into an integrated system to meet the requirement of the Good Manufacturing Practice such as process quality assurance and management of product tracking records. To implement the international standard such as EN ISO11137, it is necessary to understand the purposes aimed in the standard and carry out the tests following the procedures required. This study presented the specification of the e-beam facility and showed what its design requirements and features are. The test results on a variety of process parameters were presented and validated it they are within the required limits.

• Radiation Oncology Journal
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• v.19 no.4
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• pp.301-305
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• 2001

Purpose : This study was peformed for the evaluation of the feasibility and toxicity of hypofractionated radiation therapy for early glottic cancer Methods and Materials : From February 1999 to February 2000, 20 patients with Histologically confirmed Stage I, II glottic cancer were enrolled into this study. There were 18 males and 2 females, the median age of the patients was 59 years. The distribution of stage distribution was as fellows; T1aN0-16 patients, T1bN0-1 patient, T2N0-3 patients. Eighteen patients underwent laryngomicroscopic biopsy only, and two patients underwent laser cordectomy. All patients received radical radiation therapy (2.5 Gy per fraction, 24 fractions, total 60 Gy). Median duration of treatment was 36 days (range $31\~45\;days$). Results : Radiation therapy were well tolerated. Most common acute reactions were odynophagia and hoarseness, and these reactions resolved after radiation therapy. There were one case of RTOG grade 3 odynophagia $(5\%)$, six cases of grade 3 hoarseness $(30\%)$. Response of radiation therapy was evaluated one month after completion of treatment. All patients revealed complete response. During follow up, total three cases of treatment failure were detected. two cases were local recurrence in 10 and 13 months of radiation therapy and one case was local recurrence and distant metastasis in 2 months of radiation therapy. Conclusion : This hypofractionated radiation therapy schedule was feasible and effective for control of early glottic cancer But longer follow up time would be required to assess the long-term disease control and the late complication by shortening radiation therapy duration.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.4
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• pp.508-515
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• 2009

In the naval environment, a naval radar has many obstructions of velocity, such as rotation and velocity of ship. In the common situation, the rotations such as roll, pitch and yaw don't influence the velocity of the target. But because the naval radar is located on the top of the mast, there is some influence to the target velocity. When we trace the target, radar controller doesn't use hits whose doppler banks are zero. So, we must compensate the target velocity for the velocity error. This paper suggests a method of velocity compensation of target by the velocity vector and how to apply to the stack beam radar if we don't know the height of the target.

• Journal of the Korean Vacuum Society
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• v.15 no.1
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• pp.97-102
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• 2006

Anodic alumina with self-organized and ordered nano hole arrays can be a good candidate of an irradiation mask to modify the properties of nano-scale region. In order to try using porous anodic alumina as a mask for ion-beam patterning, ion beam transmittance of anodic alumina was tested. 4 Um thick self-standing AAO templates anodized from Al bulk foil with two different aspect ratio, 200:1 and 100:1, were aligned about incident ion beam with finely controllable goniometer. At the best alignment, the transmittance of the AAO with aspect ratio of 200:1 and 100:1 were $10^{-8}\;and\;10^{-4}$, respectively. However transmittance of the thin film AAO with low aspect ratio, 5:1, were remarkably improved to 0.67. The ion beam transmittance of self-standing porous alumina with a thickness larger than $4{\mu}m$ is extremely low owing to high aspect ratio of nano hole and charging effect, even at a precise beam alignment to the direction of nano hole. $SiO_2$ nano dot array was formed by ion irradiation into thin film AAO on $SiO_2$ film. This was confirmed by scanning electron microscopy that the $SiO_2$ nano dot array is similar to AAO hole array.

• Journal of the Korean Vacuum Society
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• v.2 no.3
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• pp.275-281
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• 1993

본 논문은 포항가속기에서 건설 중인 진공 chamger의 용접에 관한 것이다. 저장링에 전자빔을 5시간 이상 저장하기 위하여 10-10torr 이하로 진공도를 유지하도록 설계되어 있기 때문에 초고진공에 적합한 TIG 용접(tungsten inert gas welding)을 하였다. 진공 chamber는 Al 5083-H321이며 flange의 재질은 Al 2219-T852이다. Sector chamber I, II의 총 용접 길이는 각각 27m, 37m이며 진공에 유해한 균열과 virtual leak가 생기지 않도록 하는 용접조건 등을 선정하였다.

• Proceedings of the KAIS Fall Conference
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• 2011.12b
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• pp.481-484
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• 2011

The increasing interest in the laser beam welding is placing stringent demands on the manufacturing techniques and performance requirements, and the manufacture employs the high quality and efficiency laser beam welding technology. This paper covers recent research trends of the laser beam welding technology including the laser beam surfacing and laser beam cladding technology.

• Proceedings of the IEEK Conference
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• 2002.06b
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• pp.53-56
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• 2002

We have developed a Monte Carlo (MC) simulator for electron beam lithography in multi-layer resists and multi-layer substrates in order to fabricate and develop high-speed PHEMT devices for millimeter- wave applications. For the deposited energy calculation to multi-layer resists by electron beam in MC simulation, we modeled newly for multi-layer resists and heterogeneous multi-layer substrates. Using this model, we simulated T-gate or r-gate fabrication process in PHEMT device and showed our results with SEM observations.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.683-684
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• 2009