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101.
ZHAO Xuehui ) HUANG Kelong) JIAO Feipeng) LI Zhiaojian) and PENG Xiahui) ) College of Chemistry Chemical Engineering Central South University Changsha China ) Chemistry Department Hunan Technology BOE Science University Zhuzhou China 《稀有金属(英文版)》2006,(2)
1. Introduction Rare earth elements have an important function inlife process. The fluorescence enhancement of lan-thanides in aqueous solutions has therefore becomean area of active study in trace-level estimation oflanthanides using spectrofluorimetry [1]. Its possiblemechanism and application as fluorescence probesin biological systems have also attracted attention inrecent years [2]. Generally, fluorescence enhance-ment can be achieved through ligand sensitization.Various ligands have bee… 相似文献
102.
The fluorescence of terbium (Ⅲ) was enhanced by about three orders of magnitude in the presence of trimellitic acid (benzene-l, 2, 4-tricarboxylic acid (TLA)) in aqueous solution at pH 6. The fluorescence intensity could be greatly increased when the system of Tb3+-TLA was treated with La3+ (or Gd3+) and TritonX- 100. The addition of La3+ (or Gd3+) enhances the fluorescence of the system by about two orders of magnitude due to cofluorescence, and the TritonX-100 micellar medium plays an important role for stabilization of the system. Both the intermolecular energy transfer mode and intramolecular energy transfer mode are responsible for the mechanism of fluorescence enhancement. In the optimum conditions, the fluorescence intensity is a linear function of Tb3+ concentration in the range of 7.8 × 10-9-3.6 × 10-6 mol/L for the system Tb3+-La3+-TLA and 1.0 × 10-8-4.7 × 10-6 mol/L for the system Tb3+-Gd3+-TLA, and the limits of detection are 4.6 ×10-10 mol/L and 6.0 × 10-10 mol/L, respectively. 相似文献
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104.
Tae-Sik Kim Young-Je An Kwang Ho Kim Won-Sub Chung Young-Rae Cho 《Metals and Materials International》2006,12(4):339-343
The effect of the dielectric constant (k) of bonding materials in a screen-printed carbon nanotube (CNT) cathode on the field
enhancement factor was investigated for high-efficiency CNT cathodes using the ANSYS software. The values obtained by a simulation
study were compared to the experimental results obtained for screen-printed CNT cathodes. The field enhancement factor increased
as the dielectric constant decreased, reaching a maximum value at a dielectric constant of 1, the value for a vacuum. The
findings indicate that the larger sheet resistance of the bonding materials, after the firing process, can be attributed to
the larger emission current of the CNT cathode. From these results, it was concluded that the best bonding materials for screen-printed
CNT cathodes should have a low dielectric constant and a high sheet resistance. This finding can be used as criteria for selecting
bonding materials for use in CNT pastes for highly efficient CNT cathodes. 相似文献
105.
106.
为提高强噪声环境下语音信号的信噪比,增强语音通信的质量,以DSP为平台,构建一个基于自适应滤波技术的单通道语音增强系统。该系统以TMS320F2812为核心,结合其多通道缓冲串口(McBSP)与扩展音频接口芯片TLV320AIC23实现了语音信号的高速采集及输出;同时,利用箕舌线函数更新自适应滤波步长因子并引入解相关运算进行语音降噪处理,有效改善了传统算法适应性差,收敛速度慢,稳态误差大等问题。实验结果表明该算法降噪性能好,能明显提高语音清晰度,且系统稳定性强。 相似文献
107.
In this work, the issues of bandwidth enhancement of planar antennas and the relevance of precise and automated response control through numerical optimization have been investigated. Using an example of a planar antenna with parasitic radiator we illustrate possible effects of even minor modifications of the antenna geometry (here, applied to the ground plane) on its reflection performance. In particular, a proper handling of geometry parameters may lead to considerable broadening of the antenna bandwidth. For the sake of computational efficiency, the adjustment of geometry parameters is carried out using surrogate‐based optimization methods exploiting coarse‐discretization EM simulations as the underlying low‐fidelity antenna model. Additionally, suitably defined penalty function allows us to precisely control the maximum in‐band reflection so that sufficient margin to accommodate possible manufacturing tolerances can be achieved. The optimized designs of the two antenna structures considered in this work exhibit over 1.75 GHz (>31%) and 2.15 GHz (>38%) bandwidth, respectively, for the center frequency of 5.6 GHz. Simulation results are validated using measurements of the fabricated prototypes. Comparison with state‐of‐the‐art designs is also provided. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:653–659, 2016. 相似文献
108.
Profile miniaturization and performance improvement of a rectangular patch antenna using magnetic metamaterial substrates
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The idea of profile miniaturization and performance improvement of a rectangular patch antenna using a metamaterial substrate with large values in the real part of effective relative permeability is proposed in microwave frequency range. The volume profile of the antenna is minimized by tuning the effective relative permeability and thickness of the substrate material. The specific type of metamaterial which can be used as substrate material for the antenna miniaturization purpose is suggested. The proposed idea is validated through finite‐difference time‐domain (FDTD) simulations for sample rectangular patch antennas with metamaterial substrates at the frequency about 10 GHz. Improvement of the power directivity is found for the metamaterial substrate with large value in the real part of effective permeability. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:254–261, 2016. 相似文献
109.
基于人机交互的实际应用场景,提出了一种交互目标声源三维定位与语音增强算法。该算法首先在广义相关法的基础上提出一种声达时延差的估计方法,通过由6个麦克风构成的平行均匀线阵接收模型,实现对目标声源的三维定位;然后在交互目标声源定位的基础上,通过调整时延波束叠加的权值,实现对目标语音的增强。仿真实验结果表明,文中提出的算法能够准确定位目标声源并对目标语音进行有效增强。在信噪比大于1.5 dB 的环境中,该算法可使目标声源达到98%以上定位精度,5 dB 以上信噪比改善,同时算法运算量小且易于硬件实现。 相似文献
110.