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951.
952.
The surface and interfacial properties of polymers are important for their applications. In one of our previous articles, we discussed the relationship between the dispersive surface tension component and the density and molecular weight of solvents and polymers to seek a simple and easy method to estimate the rationality of surface tension results of polymers. We found that for 30 organic solvents and 12 polymers, there was a good relationship between the dispersive surface tension and the experiential parameter 1/ρ2 M 0.2 w . In this article, the existence of the squared density term is simply deduced from the general molecular interaction energy equation and is proved with four pairs of polymer/monomer; these are polystyrene/styrene, polyisoprene/isoprene, polymethyl methacrylate/methyl methacrylate, and polyvinyl acetate/vinyl acetate. 相似文献
953.
The mechanical and damping properties of blends of ethylene-vinyl acetate rubber (VA content >40% wt) (EVM)/ethylene-propylene-diene copolymer (EPDM) and EVM/nitrile butadiene rubber (NBR), both with 1.4 phr BIPB (bis (tert-butyl peroxy isopropyl) benzene) as curing agent, were investigated by dynamic mechanical analysis (DMA). The effect of added polyvinyl chloride (PVC), amido donor N-cyclohexyl-2-benzothiazole sulfonamide (CZ), and dicumyl peroxide (DCP) as a substitute curing agent, on the damping and mechanical properties of both rubber blends were studied. The results showed that in EVM/EPDM/PVC blends, EPDM was immiscible with EVM and could not expand the damping range of EVM at low temperature. PVC was miscible with EVM and dramatically improved the damping property of EVM at high temperature while keeping good mechanical performance. In EVM/NBR/PVC blends, PVC was partially miscible with EVM/NBR blends and remarkably widened the effective damping temperature range (EDTR) from 41.1°C for EVM/NBR to 62.4°C. Curing agents BIPB and DCP had a similar influence on EVM/EPDM blends. DCP, however, dramatically raised the height of tan δ peak of EVM/NBR = 80/20 and expanded its EDTR to 64.9°C. CZ had no obvious influence on the EVM/EPDM blends cured with BIPB. However, a small content of CZ enlarged the tan δ peak of EVM/NBR = 80/20 in both height and width, but at the cost of a deterioration of mechanical performance. 相似文献
954.
ABSTRACTA direct dynamic study on the reactions of CH3O2?+?CH2O was carried out over the temperature range of 300–1500?K. All stationary points were calculated with the M06-2X/6-311++G(d,p) level of theory and identified for local minimum. The energetic parameters were refined at QCISD (T)/cc-pVTZ and CCSD (T)/cc-pVTZ levels of theory. Three channels were explored and a reaction of hydrogen abstraction from CH2O by CH3O2 was identified as dominant channel which involves the formation of a prereactive complex in the entrance channel. The rate coefficient of the dominant channel was calculated with TST and TST/Eck and the Eckart tunnelling effect is only important over the lower temperature region. The calculated rate coefficient of the dominant channel has positive temperature dependence and agrees reasonably with the available literature data. 相似文献
955.
We report a photoluminescence observation of the coupling of donor-bound excitons and longitudinal optical phonons in high-quality ZnO crystals at 5 K. The first-order phonon Stockes line of donor-bound excitons exhibits a distinct asymmetric line shape with a clear dip at its higher energy side, suggesting that quantum mechanical interference occurs during the annihilation of donor-bound excitons. The donor binding energy is determined to be 49.3 meV from spectral featural. 相似文献
956.
基于RBF神经网络的较低浓度下同步荧光光谱的溢油鉴别 总被引:1,自引:0,他引:1
针对海面溢油样品的含量难以确定,同时考虑到海水掺杂及风化等问题的影响,提出了在较低非线性浓度范围内采集溢油嫌疑样品的同步荧光光谱,获取其训练样本集,利用主成分分析法(Principal com-ponent analysis,PCA)提取其特征光谱,结合径向基函数(Radial basis function,RBF)神经网络对肇事样本和嫌疑样本进行模式识别的方法。通过对相近油源原油样品分类识别研究表明:该方法仅需单次对肇事样本同步光谱测量,再借助数据分析,就可以很好区分相近油源溢油样品,外扰对识别率影响也不大。RBF神经网络算法识别率在92%左右。该结论对海洋环境中溢油的实时检测及油指纹数据信息库的建立有重要意义。 相似文献
957.
嫦娥一号干涉成像光谱仪(IIM)2C级数据信息提取 总被引:2,自引:0,他引:2
通过分析Chang’E-1卫星所获取的高光谱数据的太阳高度角因素,选取了太阳高度角较高的IIM2C数据进行光谱定标。采用邻域平均法及邻域加权均值法对原始数据进行了杂点、条带修复。由于干涉成像光谱仪CCD阵列增益畸变以及它的自身问题使得干涉影像存在横向响应不均一性,提出采用基于子空间最大特征值法进行校正,结果影像亮度统计其强度表现均一,符合自然图像特征,并采用自编程序进行几何校正。运用国际上较为成熟的经验线性法对Chang’E-1IIM 2C数据进行绝对定标;与此同时,为了修正线性定标的偏置系数及降低数据噪声,首次采用自适应小波变换法对辐射定标后数据进行后处理,确定了IIM2C数据可用波段。通过对比国际标准定标点数据,制订了嫦娥IIM2C数据分析方案,完成了第一幅完整的Chang’E-1IIM 2C月球正面反射率影像。 相似文献
958.
Efficient continuous-wave eye-safe region signal output from intra-cavity singly resonant optical parametric oscillator 下载免费PDF全文
We report an efficient continuous-wave (CW) tunable intra-cavity singly resonant optical parametric oscillator based on the multi-period periodically poled lithium niobate and using a laser diode (LD) end-pumped CW 1064 nm Nd:YVO4 laser as the pump source. A highly efficiency CW operation is realized through a careful cavity design for mode matching and thermal stability. The signal tuning range is 1401-1500 nm obtained by varying the domain period. The maximum output power of 2.2 W at 1500 nm is obtained with a 17.1 W 808 nm LD power and the corresponding conversion efficiency is 12.9%. 相似文献
959.
采用内收缩多参考组态相互作用(MRCI)方法和包含Davidson修正(+Q) 的MRCI方法结合相关一致基aug-cc-pV5Z研究了PH (X3Σ-, a1Δ和A3∏)分子的势能曲线. 在同位素质量识别的基础上对势能曲线进行拟合, 得到PH, PD和PT分子各个电子态的光谱常数(Te, Re, ωe, ωexe, αe和 Be). 通过与已有实验数据的比较发现, 本文的结果与实验结果非常一致. 对于PH, PD和PT分子的Σ-电子态, 计算得到了J = 0时的前12个振动态. 对于每一个振动态, 还分别计算了它的振动能级、惯性转动常数和离心畸变常数. 与其他理论结果和实验数据进行比较可知, 本文的结果更精确、更完整. 文中PD和PT分子的光谱常数和分子常数均属首次报导. 相似文献
960.
X. J. Cheng B. X. Jiang L. Li J. L. Wang Zh. G. Yang W. B. Cheng X. Ch. Shi Y. B. Pan 《Laser Physics》2012,22(4):652-655
Lasers from Yb:YAG ceramic at different temperature were reported in this paper. The Yb:YAG ceramic laser with active-mirror structure was end-pumped by a laser diode whose central wavelength was 940 nm. At 80 K, with doping concentration of 5 at % Yb:YAG ceramic slab, output energy of 0.68 J at 10 Hz repetition rate was obtained under the pump energy of 2.49 J, corresponding to a slope efficiency of 40% and a conversion efficiency of 27.3%, respectively. 相似文献