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Search Results: 1 - 10 of 61257 matches for " Young-Jun Kim "
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Enhancement in Elastic Modulus of GFRP Bars by Material Hybridization  [PDF]
Dong-Woo Seo, Ki-Tae Park, Young-Jun You, Hyeong-Yeol Kim
Engineering (ENG) , 2013, DOI: 10.4236/eng.2013.511105

Fiber reinforced polymer (FRP) reinforcing bars for concrete structure has been extensively investigated for last two decades and a number of FRP bars are commercially available. However, one of shortcomings of the existing FRP bars is its low elastic modulus, if glass fibers are used (i.e., GFRP). The main objective of this study using the concept of material hybridization is to develop a viable hybrid FRP bar for concrete structures, especially for marine and port con- crete structures. The purposes of hybridization are to increase the elastic modulus of GFRP bar with acceptable tensile strength. Two types of hybrid GFRP bar were considered in the development: GFRP crust with steel core and GFRP bar with steel wires dispersed over the cross-section. Using E-glass fibers and unsaturated polyester resins, the hybrid GFRP bar samples of 13 mm in diameter were pultruded and tested for tensile properties. The effect of hybridization on tensile properties of GFRP bars was evaluated by comparing the results of tensile test with those of non-hybrid GFRP bars. The results of this study indicated that the elastic modulus of the hybrid GFRP bar was increased by up to 270 percent by the material hybridization. The results of the test and the future recommendations are summarized in this paper. To ensure long-term durability of the hybrid GFRP bars in waterfront structure applications, the individual and combined effects of environmental conditions on hybrid GFRP rebar itself as well as on the interface between rebar and concrete should be accessed.

A Practical Cooperative Multicell MIMO-OFDMA Network Based on Rank Coordination
Bruno Clerckx,Heunchul Lee,Young-Jun Hong,Gil Kim
Mathematics , 2013,
Abstract: An important challenge of wireless networks is to boost the cell edge performance and enable multi-stream transmissions to cell edge users. Interference mitigation techniques relying on multiple antennas and coordination among cells are nowadays heavily studied in the literature. Typical strategies in OFDMA networks include coordinated scheduling, beamforming and power control. In this paper, we propose a novel and practical type of coordination for OFDMA downlink networks relying on multiple antennas at the transmitter and the receiver. The transmission ranks, i.e.\ the number of transmitted streams, and the user scheduling in all cells are jointly optimized in order to maximize a network utility function accounting for fairness among users. A distributed coordinated scheduler motivated by an interference pricing mechanism and relying on a master-slave architecture is introduced. The proposed scheme is operated based on the user report of a recommended rank for the interfering cells accounting for the receiver interference suppression capability. It incurs a very low feedback and backhaul overhead and enables efficient link adaptation. It is moreover robust to channel measurement errors and applicable to both open-loop and closed-loop MIMO operations. A 20% cell edge performance gain over uncoordinated LTE-A system is shown through system level simulations.
Tuning the graphene work function by electric field effect
Young-Jun Yu,Yue Zhao,Sunmin Ryu,Louis E. Brus,Kwang S. Kim,Philip Kim
Physics , 2009, DOI: 10.1021/nl901572a
Abstract: We report variation of the work function for single and bi-layer graphene devices measured by scanning Kelvin probe microscopy (SKPM). Using the electric field effect, the work function of graphene can be adjusted as the gate voltage tunes the Fermi level across the charge neutrality point. Upon biasing the device, the surface potential map obtained by SKPM provides a reliable way to measure the contact resistance of individual electrodes contacting graphene.
Subharmonicity of the variations of K?hler-Einstein metrics on pseudoconvex domains
Young-Jun Choi
Mathematics , 2015,
Abstract: This paper is a sequel to \cite{Choi} in Math. Ann. In that paper we studied the subharmonicity of K\"ahler-Einstein metrics on strongly pseudoconvex domains of dimension greater than or equal to $3$. In this paper, we study the variations K\"ahler-Einstein metrics on bounded strongly pseudoconvex domains of dimension $2$. In addition, we discuss the previous result with general bounded pseudoconvex domain and local triviality of a family of bounded strongly pseudoconvex domains.
Semi-positivity of fiberwise Ricci-flat metrics on Calabi-Yau fibrations
Young-Jun Choi
Mathematics , 2015,
Abstract: Let $X$ be a K\"ahler manifold which is fibered over a complex manifold $Y$ such that every fiber is a Calabi-Yau manifold. Let $\omega$ be a fixed K\"ahler form on $X$. By the theorem due to Yau, there exists a unique Ricci-flat K\"ahler form $\rho\vert_{X_y}$ for each fiber, which is cohomologous to $\omega\vert_{X_y}$. This family of Ricci-flat K\"ahler forms $\rho\vert_{X_y}$ induce a smooth $(1,1)$-form $\rho$ on $X$. In this paper, we prove that $\rho$ is semi-positive on the total space $X$. We also discuss several byproducts, among them the local triviality of families of Calabi-Yau manifolds.
A Rapid Colorimetric Loop-Mediated Isothermal Amplification Assay for the Detection of Lawsonia intracellularis in Pigs
Nag-Jin Choi,Byoung-Yong Park,Chul Park,Young-Jun Kim,Ho-Seong Cho
Journal of Animal and Veterinary Advances , 2012, DOI: 10.3923/javaa.2012.4258.4262
Abstract: A colorimetric Loop-mediated isothermal Amplification (LAMP) assay with hydroxy naphthol blue was designed for the detection of Lawsonia (L.) intracellularis which is an important pathogenic bacteria that causes animal diseases. A set of six primers was designed to target the aspartate ammonia-lyase (aspA) gene. Serial 10 fold dilutions of cultured L. intracellularis and spiked feces were used for LAMP optimization. The lower limit of the linear range of the assay in L. intracellularis was 101 L. intracellularis which is ten times more sensitive than conventional PCR. Based on testing in 210 porcine fecal samples using LAMP and conventional PCR, the agreement quotients between LAMP and conventional PCR was 0.92. These results suggest that colorimetric LAMP is a simple method for L. intracellularis detection in porcine fecal samples.
Atmospheric Oxygen Binding and Hole Doping in Deformed Graphene on a SiO2 Substrate
Sunmin Ryu,Li Liu,Stephane Berciaud,Young-Jun Yu,Haitao Liu,Philip Kim,George W. Flynn,Louis E. Brus
Physics , 2010, DOI: 10.1021/nl1029607
Abstract: Using micro-Raman spectroscopy and scanning tunneling microscopy, we study the relationship between structural distortion and electrical hole doping of graphene on a silicon dioxide substrate. The observed upshift of the Raman G band represents charge doping and not compressive strain. Two independent factors control the doping: (1) the degree of graphene coupling to the substrate, and (2) exposure to oxygen and moisture. Thermal annealing induces a pronounced structural distortion due to close coupling to SiO2 and activates the ability of diatomic oxygen to accept charge from graphene. Gas flow experiments show that dry oxygen reversibly dopes graphene; doping becomes stronger and more irreversible in the presence of moisture and over long periods of time. We propose that oxygen molecular anions are stabilized by water solvation and electrostatic binding to the silicon dioxide surface.
Water-Gated Charge Doping of Graphene Induced by Mica Substrates
Jihye Shim,Chun Hung Lui,Taeg Yeoung Ko,Young-Jun Yu,Philip Kim,Tony F. Heinz,Sunmin Ryu
Physics , 2012, DOI: 10.1021/nl2034317
Abstract: We report on the existence of water-gated charge doping of graphene deposited on atomically flat mica substrates. Molecular films of water in units of ~0.4 nm-thick bilayers were found to be present in regions of the interface of graphene/mica hetero-stacks prepared by micromechanical exfoliation of kish graphite. The spectral variation of the G and 2D bands, as visualized by Raman mapping, shows that mica substrates induce strong p-type doping in graphene, with hole densities of $(9 \pm 2) \times 1012 cm${-2}$. The ultrathin water films, however, effectively block interfacial charge transfer, rendering graphene significantly less hole-doped. Scanning Kelvin probe microscopy independently confirmed a water-gated modulation of the Fermi level by 0.35 eV, in agreement with the optically determined hole density. The manipulation of the electronic properties of graphene demonstrated in this study should serve as a useful tool in realizing future graphene applications.
The effect of dimiristoylphosphatidylethanol on the rotational mobility of n-(9-Anthroyloxy) stearic acid in neuronal and model membranes  [PDF]
Young-Sik Park, No-Soo Park, Jun-Bong Seo, Soo-Kyoung Bae, You-Kwang kim, Ki-Soo Seong, Young-Jun Kim, Ju-Won Park, Joung-Moung Shin, Young-Chan Jeon, In-Kyo Chung, Moon-Kyoung Bae, Hye-Ock Jang, Il Yun
Journal of Biophysical Chemistry (JBPC) , 2010, DOI: 10.4236/jbpc.2010.13016
Abstract: The aim of this study was to provide a basis for examining the molecular mechanism for the pharmacological action of ethanol. We studied di¬myristoyl¬phosphatidylethanol (DMPEt)’s effects on specific locations of n-(9-anthroyloxy) palmitic acid or stearic acid (n-AS) within phos¬pholipids of synaptosomal plasma membrane vesicles isolated from bovine cerebral cortex (SPMV) and liposomes of total lipids (SPMVTL) and phospholipids (SPMVPL) extracted from SPMV. DMPEt increased rotational mobility (increased disordering) of hydrocarbon interior, but it decreased mobility (increased ordering) of membrane interface, in native and model membranes. The degree of rotational mobility in accordance with the carbon atom numbers of phospholipids comprising neuronal membranes was in the order at the 16, 12, 9, 6 and 2 position of aliphatic chain present in phospholipids. The sensitivity of increasing or decreasing effect of rotational mobility of hydrocarbon interior or surface region by DMPEt differed depending on the neuronal and model membranes in the descending order of SPMV, SPMVPL and SPMVTL.
Self-Assembled Wire Arrays and ITO Contacts for Silicon Nanowire Solar Cell Applications

YANG Cheng,ZHANG Gang,LEE Dae-Young,LI Hua-Min,LIM Young-Dae,YOO Won Jong,PARK Young-Jun,KIM Jong-Min,

中国物理快报 , 2011,
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