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치밀층으로 코팅된 다공성 엔지니어링 세라믹스에서의 접촉응력에 의한 균열 거동
김상겸,김태우,김도경,이기성,Kim, Sang-Kyum,Kim, Tae-Woo,Kim, Do-Kyung,Lee, Kee-Sung 한국세라믹학회 2005 한국세라믹학회지 Vol.42 No.8
The engineering ceramic needs the properties of high strength, hardness, corrosion-resistance and heat-resistance in order to withstand thermal shock or applied nonuniform stresses without failure. The densely coated porous ceramics can be used for machine component, electromagnetic component, bio-system component and energy-system component by their high-performances from superior coating properties and light-weight characteristics due to the structure including pore by itself. In this study we controlled the porosity of silica and alumina, $8.2\~25.4\%$ and $23.4\~36.0\%$, respectively, by the control of sintering temperature and starting powder size. We made bilayer structures, consisting of a transparent glass coating layer bonded to a thick substrate of different porous ceramics by a thin layer of epoxy adhesive, facilitated observations of crack initiation and propagation. The elastic modulus mismatch could be controlled using different porous ceramics as the substrate layer. Then we applied 150 N force using WC sphere with a radius of 3.18 mm by Hertzian indentation. As a result, the crack initiation in the coating layer was delayed at lower porosity in the substrate layer, and the damage in the coating layer was relatively smaller at the bilayer structure coated on higher elastic substrate.
인슐린 매개성 Microsomal Epoxide Hydrolase의 발현증가에서 Akt의 역할
김상겸,김봉희,오정민,윤강욱,김충현,강건욱,Kim, Sang-Kyum,Kim, Bong-Hee,Oh, Jung-Min,Yun, Kang-Uk,Kim, Chung-Hyeon,Kang, Keon-Wook 대한약학회 2007 약학회지 Vol.51 No.5
The present study examines the effect of dominant-negative Akt on the insulin-mediated microsomal epoxide hydrolase (mEH) induction in rat hepatocytes. We also assessed the role of insulin in the expression of soluble epoxide hydrrolase (sEH). Insulin increased mEH levels and the enzyme activities, whereas sEH protein expression was unaffected by insulin. The specific PI3K inhibitors or p70 S6 kinase inhibitor ameliorated the insulin-mediated increase in mEH protein levels. Infection with adenovirus expressing dominant-negative and kinase-dead mutant of Akt1 effectively inhibited the insulin-mediated increase in mEH expression and mEH activity. These results suggest that mEH and sEH are differentially regulated by insulin and PI3K/Akt/p70S6K are active in the insulin-mediated regulation of mEH expression.
알루미나에 YSZ가 나노코팅된 층상형 시스템의 인덴테이션 특성평가
김상겸,김태우,김철,신태호,한인섭,우상국,이기성,Kim, Sang-Kyum,Kim, Tae-Woo,Kim, Chul,Shin, Tae-Ho,Han, In-Sub,Woo, Sang-Kuk,Lee, Kee-Sung 한국세라믹학회 2005 한국세라믹학회지 Vol.42 No.1
전자 범 물리적 증착법(Electron Beam Physical Vaper Deposition, EB-PVD)으로 알루미나 상용기판 위에 나노 크기의 YSZ입자를 포함하고 있는 층을 코팅하여 층상형 시스템을 제조하였으며, 이때 기판층의 온도를 600, 700, $800^{circ}C$로 변화시켜 증착되는 YSZ층이 서로 다른 미세구조가 형성되도록 제어하여, 코팅층 미세구조의 변화에 따른 인덴데이션 거동을 고찰하였다 인덴테이션 거동으로는 비커스 인덴테이션과 헤르찌안 인덴테이션으로 피라미드형 압자 혹은 초경 구를 압입하였으며 압입 하중 및 코링층 구조에 따른 경도와 인덴테이션 응력-변형률 곡선을 구하였고, 미세구조와 하중의 증가에 따른 손상 및 파괴거동을 고찰하였다. 기판층의 온도가 향상됨에 따라 증착된 입자의 크기가 보다 증가하고 각진 입자가 형성됨을 알 수 있었고, 서로 다른 미세구조가 인덴테이션 거동에 영향을 주어, $800^{circ}C$에서 증착된 YSZ/A12달 구조가 상대적으로 우수한 특성을 나타내었다. YSZ layer containing nano-sized particles has been deposited on the commercial A1203 substrate by Electron Beam Physical Vapor Deposition (EB-PVD). The role of coating rnjcrostructures of YSZ to indentation damage is studied. The different coating microsouctures are prepared by varying the substrate temperatures from $600^{circ}C$ to $800^{circ}C$ during the deposition. Microhardness test and Hertzian indentation are conducted on the $YSZ/Al_{2}O_{3}$ layered systems. The damage and flilure behaviors have been investigated according to the effect of microstructures and indentation loads. With increasing the substrate temperature during EB-PVD, the overall grain sizes are coarser and more faceted, which microsoucture ultimately influences on the indentation behavior, thus, YSZ/Al_{2}O_{3}$ layered system prepared at the substrate temperature of $800^{circ}C$ shows relatively higher damage tolerance.
김상겸,Kim, Sang-Kyum 대한약학회 2009 약학회지 Vol.53 No.2
Food deprivation decreases hepatic glutathione (GSH) levels, which is ascribed to alterations in availability of hepatic cysteine, a rate limiting factor for the GSH synthesis. The present study examines the effects of food deprivation on hepatic metabolism of sulfur amino acid in male rats. In rats fasted for 24 or 48 hours, hepatic GSH levels were decreased from $6.70{\pm}0.16{\mu}mol/g$ liver to $4.02{\pm}0.20$ or $4.06{\pm}0.07{\mu}mol/g$ liver, respectively. Hepatic S-adenosylmethionine levels were also decreased in fasted rats, but S-adenosylhomocysteine levels were increased. Hepatic methionine levels were not changed by food deprivation for 48 hours. On the other hand, hepatic cysteine or taurine levels were increased from $106.2{\pm}4.1$ to $130.0{\pm}2.7$ nmol/g liver or from $2.45{\pm}0.43$ to $5.07{\pm}0.78{\mu}mol/g$ liver, respectively, in 48-hour fasted rats. Activity of cystathionine beta-synthase catalyzed homocysteine to cystathionine, was markedly decreased, but activity of betaine homocysteine methyltransferase was increased in fasted rats, indicating that methylation of homocysteine to methionine is activated. Also activity of cysteine dioxygenase, involved in taurine synthesis, was increased. These results suggested that hepatic methionine levels were maintained in rats fasted for 48 hours through increase in homocysteine methylation, and hepatic GSH may serve as a cysteine supplier reservoir in fasting state.
마우스 간의 황함유 아미노산 대사에 미치는 베타인의 용량의존성 영향
김상겸,Kim, Sang-Kyum 대한약학회 2009 약학회지 Vol.53 No.2
Acute betaine treatment induces time-dependent changes in the hepatic glutathione (GSH), cysteine and S-adenosylmethionine (SAM) levels. Our previous study demonstrated that betaine administered $1{\sim}4$ hours prior to sacrifice decreased hepatic GSH levels, but these levels were increased when measured 24 hours following the treatment. The present study was aimed to determine dose-dependent effects of betaine on hepatic metabolism of sulfur amino acid in mice. Mice were sacrificed 2.5 or 24 hours after intraperitoneal treatment with betaine at different dose levels ranging from 50 to 1000 mg/kg. The concentrations of methionine and SAM were increased by a betaine dose of 100 mg/kg, and the concentrations of GSH and cysteine were decreased by a betaine dose of 200 mg/kg at 2.5 hours. These changes were augmented with increasing doses of betaine. At 24 hours following betaine treatment, increased GSH and decreased taurine levels were observed from dose levels of 400 mg/kg. Changes in hepatic activities of cystathionine beta-synthase, gammaglutamylcysteine ligase and cysteine dioxygenase were observed from dose levels of $200{\sim}400$ mg/kg of betaine administered 24 hours prior to sacrifice.
유압 구동방식 타이어 롤러를 위한 유압 시스템 회로분석 및 모델링에 관한 연구
김상겸,박춘식,김정하,Kim, Sang-Gyum,Park, Chun-Shic,Kim, Jung-Ha 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.4
In this research, we are trying to develop the new hydraulic driven tire roller which is conventionally operated by mechanical transmission system. The reason why we would like to develop it is that tire roller is one of the most useful machine for the road construction site and also imported totally from overseas. In this paper, we conceptualize the new hydraulic system and derive the equations of motion for dynamic analysis. And we investigate system modeling by using DAQ system. Finally, we will design the controller, which can manage the hydraulic circuit of steering and traction mechanism system. The advent of modern high-speed computers coupled with the application of high-fidelity simulation technology can be used to create “virtual prototypes of construction equipment. Tests conducted on these virtual prototypes may be used to augment actual machine testing, thereby lowering costs and shortening time to production. So, we studied tire roller to integrate development technology. In System Analysis, We formulate hydraulic driving system model and hydraulic steering system model. Also, We integrate DAQ system to acquire experimental result in real tire roller equipment.
치밀층/다공층 세라믹 충상재료의 구형압자 인덴테이션에 의한 손상거동 연구
김상겸(Sang Kyum Kim),이기성(Kee Sung Lee),김철(Chul Kim),김태우(Tae Woo Kim) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
Advanced components are being developed to exhibit a high strength as well as reduce weight for high fuel-efficiency. The ceramic materials such as Alumina(Al₂O₃) and Silica(SiO₂) can be successfully used for the light-weight materials of comparatively excellent strength. In this study, we investigated to seek the proper conditions of a reliable dense/porous layer structure against contact load condition. We varied the porosities and the resulting elastic modulus in the porous substrate layer. A tungsten carbide spherical indenter was used to induce the contact damage on the surface of the dense coating layer. Finally the contact damages were investigated as a function of the porosity in the substrate layer and/or elastic modulus mismatch between the layers.
김상겸(Sanggyum Kim),김창만(Changman Kim),유환신(Hwansin Yun),임하영(Hayoung Lim),김정하(Jungha Kim) 한국자동차공학회 2003 한국자동차공학회 Symposium Vol.2003 No.8
In this paper, we describe a method of the vehicle control and lane tracking for the unmanned vehicle. Vehicle control and lane tracking arc considered one of the important technologies in an unmanned vehicle. The current position and condition of the vehicle arc calculated from an image processing method by a CCD camera. Images are transmitted to a main computer though wireless video module. A main computer finds information of lane in road images. And it calculates control value of vehicle. In this paper, specially, vehicle control is included in the road model and lateral and longitudinal controls. And the image processing method deals with the lane detection method, image processing algorithm, and filtering method. Finally. we used median filtering method to removal of noise and used characteristic part of road image for advanced of processing time<br/>