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91.
92.
A. V. Kravtsov 《Computational Mathematics and Mathematical Physics》2007,47(11):1875-1884
A linear problem of parametric oscillations of a low-viscous two-layer fluid in a closed vessel partially filled with a porous medium is studied. An asymptotic solution is constructed on the basis of combined application of boundary functions and averaging methods. Approximate formulas for boundaries of instability domains in the case of subharmonic and harmonic resonances are derived. 相似文献
93.
成功制备了结构为ITO/PDDOPV/PPQ/Al的异质结聚合物发光二极管。该器件在正反向偏压下均可发光。在正向偏压下的光发射主要来自PDDOPV,但在反向偏压下的光发射则包括来自PPQ的蓝光发射和PDDOPV的黄光发射。蓝光强度与黄光强度的比值随着反向偏压的增加而增加,当反向直流电压分别为22V、24V、26V、28V时,其电致发光光谱中PPQ与PDDOPV的峰高比IPPQ/IPDDOPV分别为1.092、1.329、1.605、2.046。换句话说,该器件的发光颜色是压控可调的,这对实现彩色显示是极为有利的。分析了在反向偏压下的发光机理以及IPPQ/IPDDOPV受电压控制的原因。 相似文献
94.
N. S. Oliveira J. Dorgan J. A. P. Coutinho A. Ferreira J. L. Daridon I. M. Marrucho 《Journal of Polymer Science.Polymer Physics》2007,45(5):616-625
The sorption of carbon dioxide in glassy Poly(lactic acid) (PLA) films was studied by quartz crystal microbalance (QCM) at high pressures. Two thermal treatments, melted and quenched, were performed in PLA with two different L:D contents, 80:20 and 98:2, films and compared with a third thermal protocol, annealed, and used in a previous work. The results obtained show that for pressures higher than 2 MPa, the carbon dioxide solubility is larger in PLA 80:20 than in PLA 98:2, indicating that the L:D plays a dominant role on this property. The thermal treatments only affect the gas solubility in PLA 98:2. Sorption isotherms at temperatures 303, 313, and 323 K, below the glass transition temperature of the polymer, and pressures up to 5 MPa were measured and analyzed with three different models, the dual‐mode sorption model, the Flory–Huggins equation, and a modified dual‐mode sorption model where the Henry's law term was substituted by the Flory–Huggins equation. This last model performs especially well for CO2 in PLA 80:20, due to the convex upward curvature of the solubility isotherms for that system. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 616–625, 2007 相似文献
95.
通过2,5-二溴苯乙烯与对甲酰基苯硼酸的Suzuki偶联反应得到2,5-二(4′-甲酰基苯基)苯乙烯.在催化剂量的冰乙酸存在下,与光学纯的(S)-(-)-α-甲基苄胺或(R)-(+)-α-甲基苄胺发生缩和反应,得到了一对手性非外消旋单体,(+)-2,5-二{4-′[(N-(S)-α-甲基苄亚胺基)次甲基]苯基}苯乙烯和(-)-2,5-二{4′-[(N-(R)-α-甲基苄亚胺基)次甲基]苯基}苯乙烯.以偶氮二异丁腈(AIBN)或过氧化苯甲酰(BPO)为引发剂,经自由基溶液聚合得到光学活性聚合物.比旋光度、紫外-可见吸收光谱以及圆二色光谱研究表明,聚合物主链可能形成了某一方向占优的稳定螺旋构象,且该螺旋构象的旋光方向与单体的旋光方向相反.聚合条件对聚合物的光学活性有很大影响,在极性较大的芳香族溶剂和较高温度下得到的聚合物具有和单体相差更大的比旋光度.侧基的手性基团脱除后,聚合物仍具有一定的旋光性,说明聚合过程中形成的螺旋手性具有一定的记忆效应. 相似文献
96.
We review the unusual structural, transport and magnetic properties of highly conducting polyaniline, doped with boron trifluoride.
Our studies establish the unique conducting state of this system, which is in distinct contrast with the conventional proton-doped
polyaniline samples. 相似文献
97.
Bianchi type-III magnetized cosmological model when the field of gravitation is governed by either a perfect fluid or cosmic
string is investigated in Rosen’s [1] bimetric theory of gravitation. To complete determinate solution, the condition, viz.,
A=(BC)
n
, where n is a constant, between the metric potentials is used. We have assumed different equations of state for cosmic string [2]
for the complete solution of the model. Some physical and geometrical properties of the exhibited model are discussed and
studied. 相似文献
98.
We report viscometric data collected in a Couette rheometry on dilute, single‐solvent polystyrene (PS)/dioctyl phthalate (DOP) solutions over a variety of polymer molecular weights (5.5 × 105 ≤ Mw ≤ 3.0 × 106 Da) and system temperatures (288 K ≤ T ≤ 318 K). In view of the essential viscometric features, the current data may be classified into three categories: The first concerns all the investigated solutions at low shear rates, where the solution properties are found to agree excellently with the Zimm model predictions. The second includes all sample solutions, except for high‐molecular‐weight PS samples (Mw ≥ 2.0 × 106 Da), where excellent time–temperature superposition is observed for the steady‐state polymer viscosity at constant polymer molecular weights. No similar superposition applies at a constant temperature but varied polymer molecular weights, however. The third appears to be characteristic of dilute high‐molecular‐weight polymer solutions, for which the effects of temperature on the viscosity curve are further complicated at high shear rates. The implications concerning the relative importance of hydrodynamic interactions, segmental interactions, and chain extensibility with increasing polymer molecular weight, system temperature, and shear rate are discussed. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 787–794, 2006 相似文献
99.
带有无限到达源的Re-entrant Line的稳定性 总被引:1,自引:0,他引:1
用Foster判别准则,Weiss[13]给出了带有无限到达源的两站三步re-entrant line的稳定性的充分条件.本文用两种不同的方法得到了其稳定性的充分必要条件,即: 二维随机游动方法和Foster判别准则.同时,我们又用流体模型方法得到了系统稳定的充分条件,大大地简化了Weiss[13]的证明. 相似文献
100.
LI Ya-feng~ ** ZHANG Li-mei~ WU Lei-lei~ WANG Sheng-hai~ WANG Hai-lian~ SHANG Xuan-xuan~ . College of Chemistry Molecular Engineering . College of Mathematics Physics Qingdao University of Science & Technology Qingdao P. R. China 《高等学校化学研究》2006,(6)
IntroductionThe interest in polyoxometalates that are widelyused in medical chemistry, catalyst reactions, and ma-terial sciences stems from their complicated aggregatesformed by means of corner-, edge- and face-sha-ring[1—4]. The exploitation of new str… 相似文献