• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.2
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• pp.519-528
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• 1994

Degradation problem due to long term service in machine or structure is now one of important problems in whole industrial field. In this study, pressure vessel steel, Cr-Mo steel, which was used more than 60,000 hours, was surface-modified by laser beam radiation for the improvement of fatigue strength. To find out optimum radiation condition, hardness, residual stress measurement and fatigue tests were carried out with the specimen of different radiation conditions. Experimental results show that micro-hardness values on the surface of the radiated specimens were approximately 2.2 times higher than those of un-radiated ones. In the depth direction of the specimen, hardness on the surface showed maximum value and was decreased at the inside the specimen. Different hardness values are due to the energy density Q which was absorbed by the specimen. Fatigue tests show that fatigue life was improved by the compressive residual stress after laser beam radiation. However, some specimens with differednt conditions show the shorter fatigue life. It means that laser beam radiation with optimum parameter can improve thae fatigue strength.

• Progress in Medical Physics
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• v.32 no.4
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• pp.159-164
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• 2021

Purpose: We investigated the properties of CLEANBOLUS based on silicone with suitable characteristics for clinical use. Methods: We evaluated the characteristics of CLEANBOLUS and compared the results with the commercial product (Super-Flex bolus). Also, we conducted physical evaluations, including shore hardness, element composition, and elongation break. Transparency was investigated through the measured absorbance within the visible region (400-700 nm). Also, dosimetric characteristics were investigated with surface dose and beam quality. Finally, the volume of unwanted air gap was investigated based on computed tomography images for breast, chin, and nose using Super-Flex bolus and CELANBOLUS. Results: CLEANBOLUS showed excellent physical properties for a low shore hardness (000-35) and elongation break (>1,000%). Additionally, it was shown that CLEANBOLUS is more transparent than Super-Flex bolus. Dosimetric results obtained through measurement and calculation have an electron density similar to water in CLEANBOLUS. Finally, CLEANBOLUS showed that the volume of unwanted air gap between the phantom and each bolus is smaller than Super-Flex bolus for breast, chin, and nose. Conclusions: The physical properties of CLEANBOLUS, including excellent adhesive strength and lower shore hardness, reduce unwanted air gaps and ensure accurate dose distribution. Therefore, it would be an alternative to other boluses, thus improving clinical use efficiency.

• Journal of the East Asian Society of Dietary Life
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• v.17 no.6
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• pp.816-821
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• 2007

The physical properties and sensory characteristics of acorn starch gels (Dotori Mook), which were gamma-irradiated up to 3 kGy, were evaluated during storage at $4^{\circ}C$. Even at the dose of 2 kGy, the gamma irradiation decreased total bacteria in the Dotori Mook during 5 days of storage, to lower than the detection limit $(10^2CFU/g)$. The hardness of the control sample increased according to the days of storage, while the gamma irradiated samples had decreased hardness according to the irradiation dose. The sample irradiated at 3 kGy maintained the same hardness as the control at day 0 of storage. Irradiation did not affect the Hunter color values. No significant differences were observed in off-odor, color, springiness, and overall acceptability (p<0.05) at the irradiation dose of 2 kGy. It can be concluded that the irradiation of Dotori Mook, up to 2 kGy, does not affect the quality of the Mook during storage, with regard to texture and sensory characteristics. Moreover, the irradiated Mook was superior in maintaining hardness and had prolonged shelf-life time by sanitation.

• Food Science of Animal Resources
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• v.30 no.5
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• pp.780-786
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• 2010

This study compared the effects of autoclaving (AC; $121^{\circ}C$ for 15 min), gamma (GR), and electron beam irradiation (EB; 0-20 kGy) on the microbial, physicochemical, and sensory properties of ready-to-eat bulgogi during storage at $35^{\circ}C$ for 90 d. No viable cells were observed (p<0.05) upon AC, GR or EB at more than 15 kGy. However, adverse effects such as tenderization and deterioration of sensory properties were induced in bulgogi upon AC and high dose irradiation. Especially, the hardness and sensory qualities (texture and taste) of the AC-treated samples were extremely deteriorated (p<0.05). These results indicate that use of GR and EB (15 kGy) can ensure the microbial safety of bulgogi without compromising the hardness and sensory properties (texture, taste and flavor).

• Nuclear Engineering and Technology
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• v.51 no.1
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• pp.190-197
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• 2019

W-K-TiC alloys with different titanium carbide concentrations (0.05, 0.1, 0.25, 0.5, 1, 2) wt.% were fabricated through Mechanical Alloying and Spark Plasma Sintering. The effects of the addition of nano-scaled TiC particles on the relative density, Vickers micro-hardness, microstructure, crystal information, thermal shock resistance, and tensile strength were investigated. It is revealed that the doped TiC nano-particles located at the grain boundaries. The relative density and Vickers micro-hardness of W-K-TiC alloys was enhanced with TiC addition and the highest Vickers micro-hardness is 731.55. As the TiC addition increased from 0.05 to 2 wt%, the room-temperature tensile strength raised from 141 to 353 MPa. The grain size of the W-K-TiC alloys decreased sharply from $2.56{\mu}m$ to 330 nm with the enhanced TiC doping. The resistance to thermal shock damage of W-K-TiC alloys was improved slightly with the increased TiC addition.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.9
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• pp.1351-1358
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• 2017

In this work, we investigated radiation hardness of GaN-based transistors which are strong candidates for next-generation power electronics. Field effect transistors with three types of gate structures including metal Schottky gate, recessed gate, and p-AlGaN layer gate were fabricated on AlGaN/GaN heterostructure on Si substrate. The devices were irradiated with energetic protons and alpha-particles. The irradiated transistors exhibited the reduction of on-current and the shift of threshold voltage which were attributed to displacement damage by incident energetic particles at high fluence. However, FET operation was still maintained and leakage characteristics were not degraded, suggesting that GaN-based FETs possess high potential for radiation-hardened electronics.

• Food Science and Biotechnology
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• v.17 no.4
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• pp.751-754
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• 2008

Texture analysis, sensory evaluation, and scanning electronic microscopic (SEM) observation were conducted to evaluate the effects of different calcium salts (calcium lactate, calcium acetate, and calcium chloride) and vitamin C on the textural properties of kimchi, gamma-irradiated at 25 kGy. Increase of the hardness and sensory score were observed in the kimchi pretreated with calcium salt or vitamin C as compared with the untreated and irradiated kimchi. And the hardness and sensory quality of the co-pretreated sample with 0.01% of calcium lactate and 0.3% of vitamin C were the highest after 30 days at $35^{\circ}C$, which indicates that the co-pretreatment is effective in preventing a decrease of the texture and sensory qualities of kimchi by gamma irradiation. Also, this result was supported by the SEM observation.

• Journal of Semiconductor Engineering
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• v.2 no.1
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• pp.119-124
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• 2021

Along with the needs for feasibility in the field of space applications, interests in radiation-hardened electronics is growing rapidly. Gallium nitride (GaN)-based devices have been widely researched so far owing to superb radiation resistance. Among them, research on the most abundant protons in low earth orbit (LEO) is essential. In this paper, proton irradiation effects on parameter changes, degradation mechanism, and correlation with reliability of GaN-based devices are summarized.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.5
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• pp.129-136
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• 2012

On this study, $CO_2$ gas, net of Ar gas, and mixed gas in solid wire(AWS ER 70S-6) and flux cored wire(AWS E71T-1) were used to weld on Mild steel(SS400). After the progress, the status changes of the welds in Mild steel(SS400) were investigated with compositional changes. For stable experiments, welding was conducted using the automatic feeder. Radiation testing, hardness testing, chemical composition analysis and penetrated cross-section were measured. Through these experiments, shapes of penetrated cross-section, chemical composition changes, and weld defects according to the variation of welding gas were known. Weld defects and weld cross-sectional shapes by the variation of the welding voltage were also detected.

• Food Science and Preservation
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• v.15 no.1
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• pp.37-42
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• 2008

This study investigated the effects of green tea powder (GTP) on the quality characteristics of Yukwa during storage, to improve shelf-stability and sensory quality. The crude lipid contents of Yukwa decreased with increasing levels of GTP, but significant changes in moisture contents were not found. 'The blowhole size and expansion rate of Yukwa decreased with increases in GTP. The hardness of Yukwa samples with over 2% (w/v) GTP significantly increased, but no notable changes in hardness during storage were found. Sensory evaluation tests indicated that all sensory characteristics decreased with increasing GTP levels, but there was no significant difference in overall acceptability between Yukwa samples with 1% (w/v) GTP and control. Antioxidant activity increased as the concentration of GTP increased 'The results indicate that addition of 1% (w/v) G1P yielded optimal quality of Yukwa during storage.