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Simulation and Experiment of Injection Molding Process for Superalloy Feedstock
Jung, Im Doo,Kim, Youngmoo,Park, Seong Jin The Korean Powder Metallurgy Institute 2015 한국분말재료학회지 (KPMI) Vol.22 No.1
Powder injection molding is an important manufacturing technology to mass produce superalloy components with complex shape. Injection molding step is particularly important for realizing a desired shape, which requires much time and efforts finding the optimum process condition. Therefore computer aided engineering can be very useful to find proper injection molding conditions. In this study, we have conducted a finite element method based simulation for the spiral mold test of superalloy feedstock and compared the results with experimental ones. Sensitivity analysis with both of simulation and experiment reveals that the melt temperature of superalloy feedstock is the most important factor for the full filling of mold cavity. The FEM based simulation matches well the experimental results. This study contributes to the optimization of superalloy powder injection molding process.
Modeling of magnetic particle orientation in magnetic powder injection molding
Jung, Im Doo,Kang, Tae Gon,Shin, Da Seul,Park, Seong Jin IOP 2018 Journal of Physics. D, Applied Physics Vol.51 No.11
<P>The magnetic micro powder orientation under viscous shear flow has been analytically understood and characterized into a new analytical orientation model for a powder injection molding process. The effects of hydrodynamic force from the viscous flow, external magnetic force and internal dipole–dipole interaction were considered to predict the orientation under given process conditions. Comparative studies with a finite element method proved the calculation validity with a partial differential form of the model. The angular motion, agglomeration and magnetic chain formation have been simulated, which shows that the effect of dipole–dipole interaction among powders on the orientation state becomes negligible at a high Mason number condition and at a low <I>λ</I> condition (the ratio of external magnetic field strength and internal magnetic moment of powder). Our developed model can be very usefully employed in the process analysis and design of magnetic powder injection molding.</P>
Spark Plasma Sintering Behaviors of M-type Barium Hexaferrite Nano Powders
Jung, Im Doo,Kim, Youngmoo,Hong, Yang-Ki,Park, Seong Jin The Korean Powder Metallurgy Institute 2014 한국분말재료학회지 (KPMI) Vol.21 No.4
A magnetic powder, M-type barium hexaferrite (BaFe12O19), was consolidated with the spark plasma sintering process. Three different holding temperatures, $850^{\circ}C$, $875^{\circ}C$ and $900^{\circ}C$ were applied to the spark plasma sintering process with the same holding times, heating rates and compaction pressure of 30 MPa. The relative density was measured simultaneously with spark plasma sintering and the convergent relative density after cooling was found to be proportional to the holding temperature. The full relative density was obtained at $900^{\circ}C$ and the total sintering time was only 33.3 min, which was much less than the conventional furnace sintering method. The higher holding temperature also led to the higher saturation magnetic moment (${\sigma}_s$) and the higher coercivity ($H_c$) in the vibrating sample magnetometer measurement. The saturation magnetic moment (${\sigma}_s$) and the coercivity ($H_c$) obtained at $900^{\circ}C$ were 56.3 emu/g and 541.5 Oe for each.
Im, Hyeon-Gyun,Jeong, Seonju,Jin, Jungho,Lee, Jaemin,Youn, Doo-Young,Koo, Won-Tae,Kang, Sin-Bi,Kim, Hyo-Joong,Jang, Junho,Lee, Daewon,Kim, Han-Ki,Kim, Il-Doo,Lee, Jung-Yong,Bae, Byeong-Soo Nature Publishing Group 2016 NPG Asia Materials Vol.8 No.-
<P>Here, we propose crystalline indium tin oxide/metal nanowire composite electrode (c-ITO/metal NW-GFRHybrimer) films as a robust platform for flexible optoelectronic devices. A very thin c-ITO overcoating layer was introduced to the surface-embedded metal nanowire (NW) network. The c-ITO/metal NW-GFRHybrimer films exhibited outstanding mechanical flexibility, excellent optoelectrical properties and thermal/chemical robustness. Highly flexible and efficient metal halide perovskite solar cells were fabricated on the films. The devices on the c-ITO/AgNW- and c-ITO/CuNW-GFRHybrimer films exhibited power conversion efficiency values of 14.15% and 12.95%, respectively. A synergetic combination of the thin c-ITO layer and the metal NW mesh transparent conducting electrode will be beneficial for use in flexible optoelectronic applications.</P>
Relaxation Effect of Synthetic Ceramide Analogues in Cat Esophageal Smooth Muscle Cells
Doo Won Lee,Sun Young Park,Jung Su Ryu,Sung Hyo Kim,Chae Uk Im,Su Hang Choi,Se Eun Lee,Sung Kwon Ko,Uy Dong Sohn 대한생리학회-대한약리학회 2008 The Korean Journal of Physiology & Pharmacology Vol.12 No.4
Ceramide has emerged as a novel second messenger for intracellular signalling. It is produced from sphingomyelin and is involved in the control of cell differntiation, proliferation, and apoptosis. C<sub>2</sub>- ceramide, short chain ceramide, plays a role in mediating contraction of cat esophageal smooth muscle cells. We examined the effect of synthesized ceramide analogues on the C<sub>2</sub>-ceramide and ACh-induced contraction in esophageal smooth muscle cells isolated with collagenase. CY3523, CY3525, or CY3723 inhibited C<sub>2</sub>-ceramide induced contraction, in a time dependent manne. Each analogue also inhibited the contraction in concentration dependent manners. CY 3523, CY 3525, and CY 3723 had no effect to the contraction induced by PMA. The inhibition with CY3523, CY3525 and CY3723 on the C<sub>2</sub>- ceramide induced contraction was recovered by PMA. These analogues decreased the density of MAPK bands (p44/42 or p38) in the western blot. These results suggest that ceramide analogues can inhibit C<sub>2</sub>-ceramide induced contraction via PKC and MAPK dependent pathway.