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排序方式: 共有156条查询结果,搜索用时 31 毫秒
101.
102.
在传统光纤激光器工作原理的基础上,考虑光子晶体光纤(PCF)模场分布特征,给出了连续泵浦情况下单模PCF激光器的速率方程和功率传输方程。利用该方程对掺镱单模PCF激光器的性能进行了数值模拟研究。结果表明:虽然空气占空比大小对PCF激光器的输出功率、泵浦阈值和斜率效率等影响不显著,但对拉曼非线性阈值影响却很大。当泵浦功率小于拉曼非线性阈值时,激光器主要输出信号激光;当超过拉曼阈值且在较宽的范围内,激光器同时输出功率相近的信号激光和拉曼光。基于这种效应,提出一种由泵浦功率控制的双波长光纤激光器的新思路。考虑到PCF非线性系数的可调控特性,采用不同光纤有可能在较宽的功率范围获得双波长激光振荡。 相似文献
103.
Two β-glucosidase/xylosidase genes, Rubg3A and Rubg3B, were cloned from yak rumen uncultured microorganisms by metagenome method and function-based screening. Recombinant RuBG3A
and RuBG3B purified from Escherichia coli were characterized for enzymatic properties, and they exhibited activity against 4-nitrophenyl-β-d-glucopyranoside and 4-nitrophenyl-β-d-xylopyranoside, suggesting bifunctional β-glucosidase/xylosidase activity. Chromatography analysis showed that they could
effectively hydrolyze cellooligosaccharide substrates, indicating the facilitation in saccharification of cellulose. RuBG3A
and RuBG3B can also increase the reducing sugar released in xylan hydrolysis to 218% and 169%, respectively, through synergism
with xylanase, suggesting their application in hemicellulose saccharification. Molecular modeling and substrate docking showed
that there should be one active center responsible for the bifunctional activity in each enzyme, since the active site pocket
is substantially wide to allow the entry of both β-glucosidic or β-xylosidic substrates, which elucidated the structure–function
relationship in substrate specificities. Therefore, the enzymatic properties, the participation in hydrolysis of cellooligosaccharides,
and the synergism with xylanase make RuBG3A and RuBG3B very interesting candidates for saccharification of both cellulose
and hemicellulose. 相似文献
104.
We develop a simple dry wrapping method to fabricate a tungsten oxide (WO(3))/carbon nanotube (CNT) cable, in which WO(3) layers act as an electrochromic component while aligned CNTs as the core provide mechanical support and an anisotropic, continuous electron transport pathway. Interestingly, the resultant cable material exhibits an obvious gradient electrochromic phenomenon. 相似文献
105.
We develop a global Hopf bifurcation theory for a system of functional differential equations with state-dependent delay. The theory is based on an application of the homotopy invariance of S1-equivariant degree using the formal linearization of the system at a stationary state. Our results show that under a set of mild conditions the information about the characteristic equation of the formal linearization with frozen delay can be utilized to detect the local Hopf bifurcation and to describe the global continuation of periodic solutions for such a system with state-dependent delay. 相似文献
106.
In this paper, we consider the dynamical behavior of delayed Cohen–Grossberg neural networks with discontinuous activation functions. Some sufficient conditions are derived to guarantee the existence, uniqueness and global stability of the equilibrium point of the neural network. Convergence behavior for both state and output is discussed. The constraints imposed on the interconnection matrices, which concern the theory of M-matrices, are easily verifiable and independent of the delay parameter. The obtained results improve and extend the previous results. Finally, we give an numerical example to illustrate the effectiveness of the theoretical results. 相似文献
107.
Gagner J Johnson H Watkins E Li Q Terrones M Majewski J 《Langmuir : the ACS journal of surfaces and colloids》2006,22(26):10909-10911
Single bilayer membranes of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) were formed on micron thin-films of hydrophilized carbon nanotubes (CNT) by fusion of small unilamellar vesicles. The structure of the membrane was investigated using neutron reflectivity (NR). The underlying thin film of CNT was formed by chemical vapor deposition (CVD) in the presence of Fe catalyst, followed by reaction with 5 M nitric acid to render the film hydrophilic. We demonstrate that this platform lends support to homogeneous and continuous bilayer membranes that have promising applications in the fields of biomaterials, biosensors, and biophysics. 相似文献
108.
109.
Wen X Deng Q Guo J 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,79(5):1941-1945
In this work, room temperature ionic liquid (RTIL) 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim]PF6) was used as extractant in single drop microextraction (SDME). The traditionally volatile organic extractants were substituted by this green reagent, which changed SDME preconcentration into environmentally friendly method, relatively. After this pretreatment, ultra-trace copper in water and food samples could be accurately detected by spectrophotometer. This study was focused on the improvement of the analytical performance of spectrophotometric determination, expanding its applications. The influence factors relevant to IL-SDME, such as absorption spectra of complex, drop volume of RTIL, stirring rate and time, concentration of chelating agent, pH, and salt effect were studied systematically. Under the optimal conditions, the limit of detection (LOD) was 0.15 μg L(-1) with an enhancement factor (EF) of 33. The proposed method was green, simple, rapid, sensitive, and cost-efficient. 相似文献
110.
杨长森 《数学物理学报(A辑)》2005,25(1):21-26
该文首先证明了具有负指数的Furta型不等式等价于Tanahashi的不等式,其次证明了该不等式可以推广为一个保序不等式 相似文献