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排序方式: 共有173条查询结果,搜索用时 15 毫秒
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激光二极管泵浦单频连续工作的Nd:YAG激光器 总被引:5,自引:2,他引:3
在国内首次报道了激光二极管泵浦单频连续工作的Nd:YAG激光器,采用扭摆模腔技术方法,在808nm激光二极管连续泵浦下,取得1064nm连续单频工作,输出功率55mW的结果,泵浦阈值276mW,斜率效率23%,线宽小于25MHz(受仪器测量精度限制)。 相似文献
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Three flavonoid glycosides including orientin, vitexin, quercetin-3-O-neohesperidoside and one unknown compound were isolated and purified by high-speed counter-current chromatography (HSCCC) and semi-preparative HPLC from Trollius ledebouri Reichb., a traditional Chinese medicine. Preparative HSCCC with a two-phase solvent system composed of ethyl acetate-n-butanol-water (2:1:3, v/v/v) was successfully performed by increasing the flow-rate of the mobile phase from 1.5 to 2.5 ml/min after 190 min. Consequently, 95.8 mg orientin, 11.6 mg vitexin, 9.3 mg unknown compound with purities of over 97% and one partially purified peak fraction (contained quercetin-3-O-neohesperidoside at 85.1% purity) were obtained from 500 mg of the crude extract. Then the partially purified fraction was further purified by reversed-phase semi-preparative high-performance liquid chromatography. The structure identification of all pure fractions was carried out by UV, MS, 1H NMR and 13C NMR. 相似文献
5.
Wei Lin Xizhe Li Zhengming Yang Juan Wang Shengchun Xiong Yutian Luo Guoming Wu 《Transport in Porous Media》2017,120(1):227-238
In order to further improve the accuracy of digital core modeling, a new hybrid method was proposed to construct the dual pore 3-D digital core with high precision. First of all, 3-D macro-pore digital cores were constructed by micro-CT. Secondly, based on the high-resolution 2-D scanning electron microscopy images of rock cores, micro-pore digital cores were constructed by simulated annealing method. And then, a superposition method was used to construct the digital core which could describe different pore characteristics. Finally, pore structures of digital cores were compared, and lattice Boltzmann method was used to analyze the percolation properties. The results show that the carbonate dual pore digital core constructed by the new hybrid method has a high accuracy, which can capture the pore properties of both macro-pore and micro-pore, and whose permeability simulation results are in good agreement with the experimental measurements. In addition, the new hybrid method is not only accurate and reliable, but also high efficient and economic, and can be applied to all kinds of reservoir modeling. 相似文献
6.
The effect of microstructure on the rheology of clay/polymer nanocomposites is investigated using dispersions of organically
treated clay in nearly Newtonian poly(dimethylsiloxane). Degree of dispersion and floc size are altered by using two different
dispersion procedures and by changing the shear history. The scaling for dynamic moduli of attractive colloids applies, except
for a possible relaxation mechanism at very low frequencies. The time to reach the crossover at a given frequency is found
to be extremely sensitive to the dispersion procedure used. Hydrodynamic and elastic components of the steady state stress,
on the other hand, evolve in a very similar fashion for the different systems. Although the relaxation times of the elastic
stress components change drastically with flow-induced changes in structure, the dispersion process hardly has an effect at
all. Intermittent start-up flows in the forward and reverse directions show that anisotropy persists long after the flow has
been arrested, even at shear rates where no large reversible flocs are present. The degree of dispersion only had a limited
effect on the anisotropy. Finally, the effect of shear on structure recovery has been studied. Very low shear rates are found
to increase the rate of recovery, even for small strains. 相似文献
7.
Hongbo Lu Yutian Chu Shuaicheng Jing Guobing Zhang Juntao Hu Guoqiang Lv 《Liquid crystals》2017,44(3):437-443
In reverse-mode polymer-stabilised cholesteric texture (PSCT), the dynamic response is derived from local director reorientation governed by dielectric coupling effect/self-assembly and polymer network deformation. A double exponential rise/decay model is proposed to investigate the underlying physical mechanisms. Through simulation of the transient rise and decay processes, the polymer network deformation in PSCT can be quantitatively evaluated. Less deformation and faster restoration speed of the polymer network can suppress hysteresis. These results provide useful guidelines for future PSCT fabrication and performance optimisation. 相似文献
8.
Silver meso- and rac-tartrate and silver squarate have been synthesized, and the crystal structure of a new polymorph of the latter is reported.
Three reaction products of these silver salts with pyrazine have been obtained and structurally characterized: From silver
squarate, a chain polymer with linear coordination of Ag(I) by two pyrazine ligands is formed, whereas the silver tartrates
yield solids in which the inner coordination sites around the metal are only partially occupied by N donors; in contrast to
expectation, oxygen coordination prevails. All the four new Ag(I) coordination compounds reported show high packing coefficients
in the range between 0.789 and 0.885. In order to put these results into a meaningful context, packing coefficients for the
crystal structures of almost 30,000 compounds retrieved from the Cambridge Structural Database have been determined. Tartrates
pack significantly closer than pyrazine complexes or metal-containing compounds in general. The exceptionally high packing
coefficient of the new polymorph of silver squarate is due to stacking of anions and concomitant Ag···Ag contacts, both along
the shortest lattice parameter which amounts to only 3.3990(9) ?. 相似文献
9.
Chen Wang Yaju Pan Guorong Fan Yifeng Chai Yutian Wu 《Biomedical chromatography : BMC》2010,24(3):235-244
This study presents an efficient strategy based on microwave‐assisted extraction (MAE), HPLC‐DAD‐MS/MS and high‐speed counter‐current chromatography (HSCCC) for the rapid extraction, identification, separation and purification of active components from the traditional Chinese medicine Fructus Aurantii Immaturus. An LC‐DAD‐MS/MS method was applied for the screening and structural identification of main components in crude extract, and five components were preliminarily identified as neoeriocitrin, narirutin, naringin, hesperidin and neohesperidin according to their UV and mass spectra. An efficient MAE method for the extraction of the three most abundant components (narirutin, naringin and neohesperidin) was optimized by the combination of univariate and multivariate approaches. The crude extract was then separated and purified by HSCCC and a total of 61.6 mg of narirutin, 207.3 mg of naringin and 159.5 mg of neohesperidin at high purities of 98.1, 97.2 and 99.5%, respectively, were obtained from 1.42 g of crude extract. The recoveries of these compounds were 86, 93 and 89%, respectively. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
10.
The behavior of radial minimizers for a Ginzburg-Landau type functional is considered. The weak convergence of minimizers in W1,n is improved to the strong convergence in W1,n. Some estimates of the rate of the convergence for the module of minimizers are presented. 相似文献