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791.
The catalysts of un‐doped, single‐doped and co‐doped mesoporous titanium dioxide (MTiO2) were prepared by a template method with tetrabutyltitanate (Ti(OC4H9)4) as a Ti source material and Pluronic P123 as a template. The photo‐absorbance of the obtained catalysts was measured by UV‐vis absorption spectroscopy, and the photocatalytic activities of the prepared samples under UV and visible light were estimated by measuring the degradation rate of methyl orange (MO) (50 mg/L) in an aqueous solution. It was shown that the co‐doped MTiO2 could be activated by visible light and could thus be used as an effective catalyst in photo‐oxidation reactions. The effect of Fe and Ce co‐dopants on the material properties was investigated by X‐ray diffraction (XRD), scanning electron microscopy (SEM) and N2 adsorption‐desorption isotherm measurement. The characterizations indicated that the photocatalysts possessed a homogeneous pore diameter of ca. 10 nm with high surface area of ca. 150 m2/g. The photocatalytic activity of MTiO2 co‐doped with Fe and Ce was markedly improved due to the synergistic actions of the two dopants. 相似文献
792.
Huihong Huang Jiayan Li Lihui Liao Jinhu Li Lixin Wu Chaoke Dong Peibao Lai Daojun Liu 《European Polymer Journal》2012,48(4):696-704
Star-block copolymers PEI-g-(PLG-b-PEG), which consist of a hyperbranched polyethylenimine (PEI) core, a poly(l-glutamic acid) (PLG) inner shell, and a poly(ethylene glycol) (PEG) outer shell, were synthesised and evaluated as nanocarriers for cationic drugs. The synthesised star-block copolymers were characterised by 1H NMR, gel permeation chromatography (GPC), dynamic light scattering (DLS), and transmission electron microscopy (TEM). Crystal violet (CV), as a model cationic dye, and doxorubicin hydrochloride (DOX), as a model anticancer drug, could be efficiently entrapped by the synthesised star-block copolymers at physiological pH as a result of electrostatic interactions between the cationic guest molecules and the negatively charged PLG segments in the PEI-g-(PLG-b-PEG) host. The drug–polymer complexes showed relatively high temporal stability at physiological pH and sustained release of the encapsulated drugs was observed. The entrapped model compounds demonstrated accelerated release as the pH was gradually decreased. 相似文献
793.
794.
给出了HR分解的分量型和范数型的一阶扰动界.对于范数型,新的精化扰动界至少优于已有结果,特别的,新的关于R因子的扰动界远远优于已有的扰动界. 相似文献
795.
In this paper, bifurcations of limit cycles at three fine focuses for a class of Z 2-equivariant non-analytic cubic planar differential systems are studied. By a transformation, we first transform nonanalytic systems into analytic systems. Then sufficient and necessary conditions for critical points of the systems being centers are obtained. The fact that there exist 12 small amplitude limit cycles created from the critical points is also proved. Henceforth we give a lower bound of cyclicity of Z 2-equivariant non-analytic cubic differential systems. 相似文献
796.
Dehui Yuan Xiaoling Liu Shengyun Yang Guoming Lai 《Journal of Applied Mathematics and Computing》2012,40(1-2):383-397
In this paper, we deal with multiobjective programming problems involving functions which are not necessarily differential. A new concept of generalized convexity, which is called (G,C,??)-convexity, is introduced. We establish not only sufficient but also necessary optimality conditions for multiobjective programming problems from a viewpoint of the new generalized convexity. When the sufficient conditions are utilized, the corresponding duality theorems are derived for general Mond-Weir type dual program. 相似文献
797.
建立了三原子分子离予XYZ+(XY2^+)解离产生多种离子产物时Eα和Eβ两个解离通道之间竞争的理论模型.实验测量出碎片产物分支比和对两束解离光光强比的依赖关系后,由理论公式对数据进行拟合获得拟合参数,可以计算出两个激发解离通道α和β的激发截面分支比. 相似文献
798.
799.
In this study, an integrated flow simulation and aeroacoustics prediction methodology is applied to testing a sound control
technique using porous inserts in an open cavity. Large eddy simulation (LES) combined with a three-dimensional Ffowcs Williams–Hawkings
(FW–H) acoustic analogy is employed to predict the flow field, the acoustic sources and the sound radiation. The Darcy pressure
– velocity law is applied to conceptually mimic the effect of porous media placed on the cavity floor and/or rear wall. Consequently,
flow in the cavity could locally move in or out through these porous walls, depending on the local pressure differences. LES
with “standard” subgrid-scale models for compressible flow is carried out to simulate the flow field covering the sound source
and near fields, and the fully three-dimensional FW–H acoustic analogy is used to predict the sound field. The numerical results
show that applying the conceptual porous media on cavity floor and/or rear wall could decrease the pressure fluctuations in
the cavity and the sound pressure level in the far field. The amplitudes of the dominant oscillations (Rossiter modes) are
suppressed and their frequencies are slightly modified. The dominant sound source is the transverse dipole term, which is
significantly reduced due to the porous walls. As a result, the sound pressure in the far field is also suppressed. The preliminary
study reveals that using porous-inserts is a promising technology for flow and sound radiation control. 相似文献
800.
Lai SC Mayer-Kress G Newell KM 《Nonlinear dynamics, psychology, and life sciences》2008,12(3):241-259
This study investigated the mutual information in the trajectories of discrete aiming movements on a computer controlled graphics tablet where movement time ( 300 - 2050 ms) was manipulated in a given distance (100 mm) and movement distance (15-240 mm) in 2 given movement times (300 ms and 800 ms ). For the distance-fixed conditions, there was higher mutual information in the slower movements in the 0 vs. 80-100% trajectory point comparisons, whereas the mutual information was higher for the faster movements when comparing within the 80 and 100% points of the movement trajectory. For the time-fixed conditions, the spatial constraints led to a decreasing pattern of the mutual information throughout the points of the trajectory, with the highest mutual information found in the 80 vs. 100% comparison. Overall, the pattern of mutual information reveals systematic modulation of the trajectories between the attractive fixed point of the target as a function of movement condition. These mutual information patterns are postulated to be the consequence of the different relative contributions of feedforward and feedback control processes in trajectory formation as a function of task constraints. 相似文献