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101.
Baijun Liu Gilles P. Robertson Michael D. Guiver Yi‐Ming Sun Yin‐Ling Liu Juin‐Yih Lai Serguei Mikhailenko Serge Kaliaguine 《Journal of Polymer Science.Polymer Physics》2006,44(16):2299-2310
A series of sulfonated poly(aryl ether ether ketone ketone)s statistical copolymers with high molecular weights were synthesized via an aromatic nucleophilic substitution polymerization. The sulfonation content (SC), defined as the number of sulfonic acid groups contained in an average repeat unit, could be controlled by the feed ratios of monomers. Flexible and strong membranes in sodium sulfonate form could be prepared by the solution casting method, and readily transformed to their proton forms by treating them in 2 N sulfuric acid. The polymers showed high Tgs, which increased with an increase in SC. Membranes prepared from the present sulfonated poly(ether ether ketone ketone) copolymers containing the hexafluoroisopropylidene moiety (SPEEKK‐6F) and copolymers containing the pendant 3,5‐ditrifluoromethylphenyl moiety (SPEEKK‐6FP) had lower water uptakes and lower swelling ratios in comparison with previously prepared copolymers containing 6F units. All of the polymers possessed proton conductivities higher than 1 × 10?2 S/cm at room temperature, and proton conductivity values of several polymers were comparable to that of Nafion at high relative humidity. Their thermal stability, oxidative stability, and mechanical properties were also evaluated. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2299–2310, 2006 相似文献
102.
Positive Steady States of a Prey-predator Model with Diffusion and Non-monotone Conversion Rate 总被引:1,自引:0,他引:1
Rui PENG Ming Xin WANG Wen Van CHEN 《数学学报(英文版)》2007,23(4):749-760
In this paper, we study the positive steady states of a prey-predator model with diffusion throughout and a non-monotone conversion rate under the homogeneous Dirichlet boundary condition. We obtain some results of the existence and non-existence of positive steady states. The stability and uniqueness of positive steady states are also discussed. 相似文献
103.
Two novel dithienylethenes with ferrocene units were synthesized by Wittig reaction. The structure of 2a has been established by X‐ray diffraction studies. They could reversibly interconvert between two thermally stable forms, an open and a closed one, using light of different wavelengths as triggers. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
104.
Phase-Locked Fibre Array for Coherent Combination and Atmosphere Aberration Compensation 总被引:1,自引:0,他引:1
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We report a fibre amplifier array that not only achieves coherent beam combination by compensation of phase noises of fibre amplifier, but also accomplishes correction of atmosphere aberration. It is of master-oscillatormultiple-amplifier (MOPA) configuration, which can be phase-locked by the multidither principle or heterodyne detection principle. First laboratory experiments of atmosphere aberration compensation of a three-element fibre amplifier array are reported. The atmosphere aberration is created by a phase screen in the experiment. The phase changes of the beam, which are introduced by the fibre amplifier and the phase screen, are both detected by the heterodyne detection method. Phase modulators are controlled to compensate for the phase in the three paths. No matter whether there is a phase screen producing atmosphere aberration or not, the dim dynamic interference fringes in the far field turn to a clear and stable pattern, and the peak intensity is maximized. It is indicated that the fibre amplifier array is phase-locked, and coherent combination of the three beams is achieved. It can be used not only to obtain high power fibre laser array but also in laser space communication. 相似文献
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107.
电流控阈技术及二值I~2L施密特电路设计黄瑞祥,杭国强(杭州大学电子工程系杭州310028)在数字电路中,以往对施密特电路的分析与研究大多局限于用电压信号来表示逻辑值的电路,例如TTL、CMOS、ECL等电路[1-3].然而,对于以电流为信号的电流型?.. 相似文献
108.
Stevenson NR Schubank RB Shin YM Amaudruz P Delheij PP Healey DC Jennings BK Ottewell DF Sheffer G Smith GR Wait GD Brack JT Feltham A Hanna M Johnson RR Rozon FM Sossi V Vetterli D Weber P Grion N Rui R Kohler M Ristinen RA Mathie EL Tacik R Yeomans M Gossett CA Wagner GJ 《Physical review letters》1990,65(16):1987-1990
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110.
聚合物电致发光材料研究进展 总被引:5,自引:0,他引:5
本文较详细地综述了聚合物电致发光材料的研究进展,重点介绍了聚对苯撑乙烯(PPV),并提出了有关聚合物电致发光材料及器件构造研究的一些观点。 相似文献