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891.
Seungjin Kim Jung Han Park Gunol Kojasoy Joseph M. Kelly Shawn O. Marshall 《Nuclear Engineering and Design》2007,237(20-21):2105-2113
Present study investigates the geometric effects of flow obstruction on the distribution of local two-phase flow parameters and their transport characteristics in horizontal bubbly flow. The round glass tubes of 50.3 mm in inner diameter are employed as test sections, along which a 90-degree Elbow is located at L/D = 206.6 from the two-phase mixture inlet. In total, 15 different flow conditions are examined within the air–water bubbly flow regime. The detailed local two-phase flow parameters are acquired by the double-sensor conductivity probe at four different axial locations. The effect of elbow is found to be evident in both the distribution of local parameters and their development. The elbow clearly promotes bubble interactions resulting in significant changes in interfacial area concentration. It is also found that the elbow-effect propagates to be more significant further downstream (L/D = 250) than immediate downstream (L/D = 225) of the elbow. Furthermore, it is shown that the elbow induces significant oscillations in the flow in both vertical and horizontal directions of the tube cross-section. Characteristic geometric effects due to the existence of elbow are also shown clearly in the transport of one-dimensional interfacial area concentration and void fraction along the flow. 相似文献
892.
Nanda Gopal Sahoo Yong Chae Jung Jae Whan Cho 《Materials and Manufacturing Processes》2007,22(4):419-423
We report the electroactive shape memory composites obtained by shape memory polyurethane block copolymer (PU) and multi-walled carbon nanotubes (MWNTs), and polypyrrole (PPy). An addition of combined MWNTs and PPy contributed to an enhancement in conductivity of PU-MWNTs composites. PU containing 2.5% MWNTs showed better mechanical and thermal properties than other composites, but conductivity was not sufficient for showing the shape memory effect by applying electrical voltages. However, when the composite was lightly coated by PPy (2.5%), its conductivity was the highest than other composites. Such the conductivity of this composite was enough to show electroactive shape recovery by heating above transition temperature of 40-48°C due to melting of polycaprolactone soft segment domain. The good shape recovery of 90-96% could be obtained in the shape recovery test when an electric field of 25 V was applied. 相似文献
893.
We report the characteristics of AlN:Er films that were co-deposited by using AlN, Er, and SiO2 targets. The PL emission spectra show strong green emissions of Er3+ ions in AlN:Er films annealed at an optimal temperature of 750 °C, which is attributed to the intra-4f Er3+ transitions of 2H11/2 → 4I15/2 and 4F7/2 → 4I15/2. This optimal temperature can activate Er species as an efficient visible luminescence center. High-resolution transmission electron microscopy (HREM) observations showed that the AlN:Er film annealed at 750 °C exhibits the microstructure of AlN nanocrystallites embedded in the amorphous matrix. The occurrence of strong Er3+ emissions in the amorphous-nanocrystalline AlN:Er films by thermal annealing might contribute to an increased number of excitation Er3+ centers and the presence of oxygen related to Er3+ excitation and recombination processes. A distinct visible bluish green emission is also confirmed from the EL device with an amorphous-nanocrystalline AlN:Er active layer. 相似文献
894.
We fabricated a dye sensitized solar cells (DSCs) using TiO2 coated multi-wall carbon nanotubes (TiO2-CNTs). Carbon nanotubes (CNTs) have excellent electrical conductivity and good chemical stability. We introduced CNTs in DSCs to improve solar cell performance through reduction of series resistance. TiO2-CNTs were obtained by Sol-Gel method. Compared with a conventional TiO2 cell, the TiO2-CNTs content (0.1 wt.%) cell showed ∼ 50% increase in conversion efficiency, which is attributed to the increase in short circuit current density (Jsc). The enhancement in Jsc occurs due to improvement in interconnectivity between the TiO2 particles and the TiO2-CNTs in the porous TiO2 film. 相似文献
895.
High-Performance Optical 3R Regeneration for Scalable Fiber Transmission System Applications 总被引:1,自引:0,他引:1
Zuqing Zhu Funabashi M. Zhong Pan Paraschis L. Harris D.L. Yoo S.J.B. 《Lightwave Technology, Journal of》2007,25(2):504-511
This paper proposes and demonstrates optical 3R regeneration techniques for high-performance and scalable 10-Gb/s transmission systems. The 3R structures rely on monolithically integrated all-active semiconductor optical amplifier-based Mach-Zehnder interferometers (SOA-MZIs) for signal reshaping and optical narrowband filtering using a Fabry-Peacuterot filter (FPF) for all-optical clock recovery. The experimental results indicate very stable operation and superior cascadability of the proposed optical 3R structure, allowing error-free and low-penalty 10-Gb/s [pseudorandom bit sequence (PRBS) 223-1 ] return-to-zero (RZ) transmission through a record distance of 1 250 000 km using 10 000 optical 3R stages. Clock-enhancement techniques using a SOA-MZI are then proposed to accommodate the clock performance degradations that arise from dispersion uncompensated transmission. Leveraging such clock-enhancement techniques, we experimentally demonstrate error-free 125 000-km RZ dispersion uncompensated transmission at 10 Gb/s (PRBS 223-1) using 1000 stages of optical 3R regenerators spaced by 125-km large-effective-area fiber spans. To evaluate the proposed optical 3R structures in a relatively realistic environment and to investigate the tradeoff between the cascadability and the spacing of the optical 3R, a fiber recirculation loop is set up with 264- and 462-km deployed fiber. The field-trial experiment achieves error-free 10-Gb/s RZ transmission using PRBS 223-1 through 264 000-km deployed fiber across 1000 stages of optical 3R regenerators spaced by 264-km spans 相似文献
896.
An adaptive linear image interpolation method based on the least-squares technique is proposed. A generic adaptive interpolation framework is introduced to provide a simple closed-form formula for adaptive image interpolation. Experimental results indicate that the proposed interpolation method outperforms existing methods in terms of objective and subjective image quality 相似文献
897.
n+/p+ Gate Bulk FinFETs With Locally Separated Channel Structure for Sub-50-nm DRAM Cell Transistors
Han-A-Reum Jung Ki-Heung Park Jong-Ho Lee 《Electron Device Letters, IEEE》2007,28(12):1126-1128
We proposed a new p+/n+ poly-Si gate bulk fin-type field-effect transistor that has two channel fins separated locally by a shallow trench filled with oxide or p+ polygate. Key device characteristics were investigated by changing the n+ poly-Si gate length La, the material filling the trench, and the width and length of the trench at a given gate length Lg. It was shown that the trench filled with p+ poly-Si gate should not be contacted with the source/drain diffusion region to achieve an excellent Ion/Ioff (> 1010) that is suitable for sub-50-nm dynamic random access memory cell transistors. Based on the aforementioned device structure, we designed reasonable Ls/Lg and channel fin width Wcfin at given Lg 's of 30, 40, and 50 nm. 相似文献
898.
The interfacial reactions and ball shear properties of ball grid array (BGA) solder joints aged at 170 °C for up to 21 days were investigated with different displacement rates. Two different kinds of solders, Sn–37Pb and Sn–3.5Ag (all wt.%), and an electroplated Ni/Au BGA substrate were employed in this work. A continuous Ni3Sn4 intermetallic compound (IMC) layer was formed at the interfaces between both the Sn–37Pb and Sn–3.5Ag solders and the substrate during reflow. After aging, two different reaction layers, consisting of (AuxNi1−x)Sn4 IMC and Pb-rich phase, were additionally observed between the Sn–37Pb solder and the Ni3Sn4 IMC layer. The thicknesses of these interfacial reaction layers increased with increasing aging time. After reflow, all the fractures occurred inside the bulk solder. The fracture location of the Sn–37Pb solder joints was shifted toward the solder/Ni interface with increasing aging time and displacement rate, whereas the fracture of the Sn–3.5Ag solder joints mainly occurred inside the bulk solder, irrespective of the aging time and displacement rate. Consequently, the shear properties of the Sn–37Pb solder joints significantly decreased with increasing aging time, whereas those of the Sn–3.5Ag solder joints slightly decreased. The tendency toward brittle fracture of the Sn–37Pb solder joints was intensified with increasing displacement rate. The shear properties of the ductile solder joints increased with increasing displacement rate, while the displacement until fracture, deformation energy and displacement rate sensitivity of the brittle solder joints significantly decreased with increasing displacement rate. 相似文献
899.
Hyun-Do Jung Monroy I.T. Koonen A.M.J. Tangdiongga E. 《Photonics Technology Letters, IEEE》2007,19(22):1777-1779
We propose and demonstrate a new structure of a Data Vortex switch node for all-optical routing of wavelength-division-multiplexing (WDM) 10-Gb/s optical packets. The proposed node consists of two Mach-Zehnder interferometers with integrated semiconductor optical amplifier: an optical and gate and a high-speed optical switch. In the experiment, WDM 10-Gb/s data packets are successfully routed with 1-dB power penalty at a bit-error rate of 10-9. 相似文献
900.
In this letter, a Balun-bandpass filter (BPF) is proposed by using a dual-mode ring resonator. The Balun-BPF is not a simply combined or integrated component of a BPF and a Balun but a single BPF with the balun function. We obtained the proper balanced outputs and two-pole BPF characteristic by symmetrically placing the output ports at lambda/2 distance from each other on the dual-mode ring resonator. The fabricated Balun-BPF has a bandwidth of 40 MHz and an insertion loss of 2.4 dB at a center frequency of 2.45 GHz. The differences between the two outputs are 180-184deg in phase and within 1dB in magnitude. The measured frequency responses agree well with simulated ones. 相似文献