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Restoration of Face-Centered Cubic Metals Subjected to Kinetic Spraying
Kicheol Kang,Gyuyeol Bae,이창희 대한금속·재료학회 2013 METALS AND MATERIALS International Vol.19 No.2
Deformation mode and restoration of face-centered cubic (FCC) metal (Al, Ni, and Cu) particles subjected to kinetic spraying (KS) were investigated. The FCC metal particles were accelerated to supersonic velocity by high pressure process gas, and collided with substrates or previously deposited coating layer. The high velocity impact of in-flight particles and their successive deposition leads to severe plastic deformation at ultra-high strain rate and the dissipation of heat energy from the plasticity. Accordingly, highly strained interface undergoes restoration to stabilize strained area during KS. Although Al, Ni, and Cu have equivalent slip systems {111} <110>, the different physical and metallurgical properties of the FCC metals differentiate the deformation mode and lead to variations in static recovery and recrystallization rates. The deformation and restoration behavior of KS FCC metals are discussed, taking into account the physical and metallurgical factors such as stacking fault energy, dislocation mobility, diffusivity, and melting point.
Kang, Kicheol,Bae, Gyuyeol,Lee, Changhee Cambridge University Press (Materials Research Soc 2012 Journal of materials research Vol.27 No.18
<▼1><B>Abstract</B><P/></▼1><▼2><P>Multiwalled carbon nanotube (MWCNT)-reinforced copper (Cu) nanocomposite coatings were consolidated using kinetic spraying. Nanocomposite particles colliding with supersonic velocity led to severe plastic deformation and deposition and resulted in bimodal structural evolution by grain refinement and work hardening. These microstructural factors contributed to the remarkable strengthening of the nanocomposites in conjunction with Orowan looping of MWCNTs. In this study, the microstructural and physical metallurgical analyses were performed to understand the strengthening mechanisms of MWCNT/Cu nanocomposites consolidated by kinetic spraying.</P></▼2>
고속 화염 용사를 통하여 형성된 다중벽 탄소 나노튜브 알루미늄 복합소재 코팅의 특성 평가
강기철(Kicheol Kang),박형권(Hyungkwon Park),이창희(Changhee Lee) 한국표면공학회 2012 한국표면공학회지 Vol.45 No.1
Multi-walled carbon nanotube (MWCNT) aluminum composite powders were deposited to form coatings using a high velocity oxygen fuel (HVOF) spraying process. High thermal energy and contact with atmospheric oxygen were supplied as the MWCNT aluminum composite particles were exposed to a gas flow field at high temperature (~3.0 × 10<SUP>3</SUP> K) during HVOF spraying. As a result, the particles underwent full or partial melting and rapid solidification due to the high thermal energy, and the exposure to oxygen induced the interfacial reaction of MWCNTs within the particle. The electrical and mechanical properties of MWCNT aluminum composite coatings were evaluated based on microstructure analysis. Electrical resistivity, elastic modulus, and micro-hardness, of the MWCNT aluminum composite coatings were higher than those of pure aluminum coating. The contribution of MWCNTs to the aluminum matrix can be attributed to their high electrical conductivity, dispersion hardening and anchoring effects. The relationship among the properties and the interaction of the MWCNTs with the aluminum matrix is discussed.
Digital Background Self-calibration for High Resolution Analog to Digital Converters
Kicheol Kim,Sungho Kang 대한전자공학회 2009 ITC-CSCC :International Technical Conference on Ci Vol.2009 No.7
A new self-calibration scheme of a high resolution ADC compensating offset and non-linearity errors is presented. The scheme uses redundant bits of a high resolution ADC for calibrating main characteristic parameters such as offset and non?linearity. The proposed self-calibration circuitry consists of a small adder, a shifter, a subtractor and memory. The experimental results using MATLAB verify the performance of the methodology.
Enflurane, 아산화질소, Thiopental과 소량의 Fentanyl을 이용한 마취유도시 기관삽관에 의한 빈맥과 수축기고혈압을 막기위한 Esmolol의 ED95
강기철,양병이 대한마취과학회 1999 Korean Journal of Anesthesiology Vol.36 No.2
Background: Esmolol has been used combined with small dose of fentanyl to prevent tachycardia and hypertension induced by tracheal intubation, but there has been few studies about the appropriate doses of esmolol when used combined with fentanyl. Methods: According to esmolol dose, 140 patients were randomly allocated to 7 groups of 20 patients. After 2 μg/kg of fentanyl, 4 mg/kg of thiopental and 0.12 mg/kg of vecuronium were intravenously administered, mask ventilation for 3 minutes with enflurane, nitrous oxide and oxygen was followed. Then one of the doses of esmolol, 0, 0.2, 0.3, 0.45, 0.6, 0.8 or 1.0 mg/kg was administered. Ninty seconds later, tracheal intubation by direct laryngoscopy was performed. After then heart rate was monitored continuously and blood pressure was measured 5 times with 1 minute interval. The highest heart rate and systolic blood pressure were recorded. We calculated the doses of esmolol which reduce the incidence of tachycardia (increased above 100 bpm or by more than 40% ofpreinduction level) and systolic hypertension (increased above 170 mmHg or by more than 40% of preinduction level) below 5% respectively. Results: The ED95 of esmolol for prevention of tachycardia induced by tracheal intubation was 0.56 mg/kg (95% CI: 0.44∼0.81 mg/kg). But the incidence of systolic hypertension was so low even without esmolol injection that the esmolol dose was not significant factor. Conclusions: In anesthetic induction and tracheal intubation with enflurane, nitrous oxide, thiopental, vecuronium, and fentanyl 2 μg/kg, esmolol 0.56 mg/kg was ED95 of preventing tachycardia. But the incidence of systolic hypertension was acceptably low even without esmolol injection. (Korean J Anesthesiol 1999; 36: 225∼231)
Serial Changes of Heat Shock Protein 70 and Interleukin-8 in Burn Blister Fluid
( Kicheol Yoo ),( Kang Yeol Suh ),( Gi Hun Choi ),( In-suk Kwak ),( Dong Kook Seo ),( Dohern Kym ),( Hyeon Yoon ),( Yong Se Cho ),( Hye One Kim ) 대한피부과학회 2017 Annals of Dermatology Vol.29 No.2
Background: It has been reported that heat shock protein 70 (HSP70) and interleukin-8 (IL-8) play an important role in cells during the wound healing process. However, there has been no report on the effect of HSP70 and IL-8 on the blisters of burn patients. Objective: This study aimed to evaluate the serial quantitative changes of HSP70 and IL-8 in burn blisters. Methods: Twenty-five burn patients were included, for a total of 36 cases: twenty cases on the first day, six cases on the sec-ond, five cases on the third, three cases on the fourth, and two cases on the fifth. A correlation analysis was performed to de-termine the relationship between the concentration of HSP70 and IL-8 and the length of the treatment period. Results: The HSP70 concentration was the highest on the first day, after which it decreased down to near zero. Most HSP70 was generated during the first 12 hours after the burn accident. There was no correlation between the concen-tration of HSP70 on the first day and the length of the treat-ment period. No measurable concentration of IL-8 was de-tected before 5 hours, but the concentration started to in-crease after 11 hours. The peak value was measured on the fourth day. Conclusion: While HSP70 increased in the first few hours and decreased afterwards, IL-8 was produced after 11 hours and increased afterward in burn blister fluid. These findings provide new evidence on serial changes of in-flammatory mediators in burn blister fluid. (Ann Dermatol 29(2) 194∼199, 2017)
Kang, Chang-Ho,Shin, YuJin,Kim, WooRi,Kim, YongGyeong,Song, KiCheol,Oh, Eun-Gyoung,Kim, SuKyung,Yu, HongSik,So, Jae-Seong Springer-Verlag 2016 Environmental Science and Pollution Research Vol.23 No.1
<P>Vibrio parahaemolyticus is the most prevalent gastroenteritis-causing pathogen in Korea and in some other Asian countries. It is frequently found in oysters and other seafood. This study monitored changes in the prevalence of V. parahaemolyticus and environmental parameters in oyster aquaculture environments in Korea. From June to October 2014, we tested oysters (Crassostrea gigas) from shellfish-harvesting areas off the west coast of Korea. These 71 isolates were the sum of 16 (22.5 %), 19 (26.8 %), 23 (32.4 %), and 13 (18.3 %) isolates collected in July, August, September, and October, respectively. These 71 isolates had the following profiles of resistance against 16 antibiotics: all isolates were resistant to ampicillin and vancomycin, and 52.2, 50.7, and 50.7 % of isolates exhibited resistance to cephalothin, rifampin, and streptomycin, respectively. PCR analysis for the presence of the species-specific toxR gene confirmed that 38 (53.5 %) of the total 71 isolated strains were positive for V. parahaemolyticus. In PCR analysis for virulence of V. parahaemolyticus, of the 71 isolates tested in the present study, only 38 (53.5 %) were positive for the trh virulence gene and 71 (100 %) was negative for the tdh virulence gene.</P>