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We explore the dependence of power losses on average plastic energy densities as rays propagate along deformed polymer optical fibers (POFs). The variation of power losses in deformed POFs with different bend radii and elongations are measured and analyzed. Three-dimensional elastic-plastic finite-element models are used to calculate average plastic energy densities in deformed POFs. The results indicate that the average plastic energy density introduced in a deformed POF can be considered a key index with which to study the power loss. Based on the experimental results, a curve-fitted equation is proposed for estimating the power loss by using the average plastic energy density for various bend radii. 相似文献
94.
The effects of thermionic emission on dust-acoustic solitons with a very small but finite amplitude in a dustelectron plasma are studied using the reductive perturbation technique. The self-consistent variation of dust charge is taken into account. It is shown that the thermionic emission could significantly increase the dust positive charge. The dependences of the phase velocity, amplitude, and width of such solitons on the dust temperature and the dust work function of dust material are plotted and discussed. 相似文献
95.
Barrier Enhancement Effect of Postannealing in Oxygen Ambient on Ni/AIGaN Schottky Contacts
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Al0.2 Ga0.8N/GaN samples are grown by metalorganic chemical vapour deposition (MOCVD) method on (0001) sapphire substrates. A 10nm-thick Ni layer is deposited on AlGaN as the transparent Schottky contact. The effect of postannealing in oxygen ambient on the electrical properties of Ni/AlGaN is studied by current-voltage- temperature (I-V-T) measurement. The annealing at a relatively low temperature of 300℃ for 90 s results in a decrease of the ideality factor from 2.03 to 1.30 and an increase of the Schottky barrier height from 0.77eV to 0.954 e V. The I-V-T analysis confirms the improvement originated from the formation of NiO, a layer with higher resistance, which could passivate the surface states of AlGaN and suppress the tunnelling current. Furthermore, the annealing also leads to an increase of the transmittance of the contacts from 57.5% to 78.2%, which would be favourable for A1GaN-based photodetectors. 相似文献
96.
An efficient and inexpensive catalyst system for the aza-Michael reactions of enones with carbamates
A new strategy which uses very cheap FeCl3 as an effective catalyst in the presence of Me3SiCl has been developed for the conjugate addition of enones and chalcone with unactivated weakly nucleophilic carbamates. 相似文献
97.
A new kind of functionalized Janus dendrimer has been synthesized via a liquid-phase approach, which could easily be purified using a simple precipitation method without the need for chromatographic separation. Their use for liquid-phase organic synthesis has been achieved in the Pd-catalyzed Suzuki coupling reactions, giving biaryl products in excellent yields after cleavage. 相似文献
98.
电化学沉积羟基磷灰石过程晶体生长行为 总被引:9,自引:0,他引:9
采用恒电流电化学沉积方法从含钙与磷盐水溶液中直接在纯金属钛电极表面沉积纳米羟基磷灰石涂层,运用EDS、SEM、XRD、FTIR等方法对其进行表征. 重点考察了一种典型制备条件下钙磷沉积层的形貌、结构及组分随沉积时间的变化,进而探讨相应条件下电化学沉积羟基磷灰石涂层晶体生长过程的基本规律. 研究表明电化学沉积法可用于在医用金属表面直接涂覆含钙离子缺陷的纳米羟基磷灰石涂层,典型条件下涂层的生长规律为: (1)沉积过程中羟基磷灰石晶粒以c轴方向沿沉积面法线方向择优生长,且这一趋势延续整个沉积过程; (2)内层晶粒的生长受到外层晶粒生长的抑制, 对于同层的晶粒,当晶粒分布密集时,晶粒生长可能发生相互制约; (3)随沉积时间的延长,沉积量增加,而膜层的化学组成基本不发生变化. 相似文献
99.
利用传输矩阵理论和TFCalc薄膜设计软件分析了分布布拉格反射镜和垂直腔面发射激光器(VCSEL)的反射率谱特性,对比了从谐振腔入射与从表面入射时反射率谱的差异,为白光反射谱表征VCSEL外延片提供了依据.利用Crosslight软件模拟了InGaAs/AlGaAs应变量子阱的增益谱随温度的变化特性及VCSEL器件内部温度分布,设计了增益-腔模调谐的VCSEL.采用金属有机物化学气相淀积设备外延生长了顶发射VCSEL,制作了氧化孔径为7.5μm的氧化限制型VCSEL器件,测试了器件的直流特性、光谱特性和眼图特性;6 mA,2.5 V偏置条件下输出光功率达5 mW,4级脉冲幅度调制传输速率达50 Gbit/s. 相似文献
100.
Dr. Kong-Qiu Hu Dr. Peng-Xiang Qiu Li-Wen Zeng Prof. Shu-Xian Hu Dr. Lei Mei Dr. Shu-Wen An Zhi-Wei Huang Xiang-He Kong Dr. Jian-Hui Lan Dr. Ji-Pan Yu Prof. Zhi-Hui Zhang Dr. Zhong-Fei Xu Prof. John K. Gibson Prof. Zhi-Fang Chai Prof. Yun-Fei Bu Prof. Wei-Qun Shi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(46):20847-20852
Herein we present a new viologen-based radical-containing metal–organic framework (RMOF) Gd-IHEP-7, which upon heating in air undergoes a single-crystal-to-single-crystal transformation to generate Gd-IHEP-8. Both RMOFs exhibit excellent air and water stability as a result of favorable radical-radical interactions, and their long-lifetime radicals result in wide spectral absorption in the range 200–2500 nm. Gd-IHEP-7 and Gd-IHEP-8 show excellent activity toward solar-driven nitrogen fixation, with ammonia production rates of 128 and 220 μmol h−1 g−1, respectively. Experiments and theoretical calculations indicate that both RMOFs have similar nitrogen fixation pathways. The enhanced catalytic efficiency of Gd-IHEP-8 versus Gd-IHEP-7 is attributed to intermediates stabilized by enhanced hydrogen bonding. 相似文献