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41.
The hydrothermal aging of poly(ethylene terephthalate)(PET) was investigated at 70 95 °C. A new method to investigate the hydrolysis degree of PET by Fourier transform infrared spectroscopy(FTIR) was proposed. The spectra during the hydrothermal aging were measured using attenuated total reflection accessory(ATR). Peak resolving of carbonyl regions was performed, and the ratio of two groups of bands representing carboxylic acids and esters respectively were calculated to show the hydrolysis degree of ester groups in PET. The acid/ester ratio shows exactly the same trend as the average chain scission number per unit mass at various temperatures and thus can be used as a parameter to characterize the hydrolysis and random chain scission of PET. This method related to the hydrolysis mechanism directly, is simple, fast and convenient compared to the traditional methods such as viscometry, end-group titration and size exclusion chromatography(SEC). It may also be useful in hydrolysis characterization of other polyesters. 相似文献
42.
针对无限大n-型压电半导体板,论文理论研究了其在初应力作用下水平剪切波的传播特性。基于压电半导体三维宏观理论和边界条件得到色散关系,结合数值算例,系统分析了边界条件、初始载流子浓度、板的厚度和初应力大小对SH波传播特性的影响。此外,讨论了初应力下两种不同材料中的SH波传播。研究显示:较小的初应力对相速度影响很小可忽略,当初应力达到一定值时波速急剧下降;类似地,初应力足够大时衰减才会逐渐加强。计算结果对压电半导体器件设计具有一定的理论指导意义。 相似文献
43.
The effect of configuration complex on dielectronic recombination process in highly ionized plasmas 下载免费PDF全文
This paper analyses the effect of configuration complex on dielectronic recombination (DR) process in highly ionized plasmas (Xe^26+, Dy^38+, W^46+) by using the multiconfiguration relativistic Hartree-Fock method. Resonant and nonresonant radiative stabilizing transitions and decays to autoionizing levels followed by radiative cascades are included. Collisional transitions following electron capture are neglected. The remarkable difference between the isoelectronic trend of the rate coefficients for DR through 3d^94l4l′ and through 3d^94l5l′ is emphasized. The trend of DR through 3d^94l4l′ shows irregularities at relatively low temperature due to the progressive closing of DR channels as atomic number Z increases. 相似文献
44.
On the differentiability of depth distribution function of deposited energy, momentum and ion range 下载免费PDF全文
Based on the translational invariance of a medium,a new theorem has been proposed and proved rigorously:the depth distributions of the deposited energy,momentum and ion range must be infinitely differentiable functions in amorphous or polycrystalline infinite targets by ion bombardment,if these functions exist.The origin of the “discontinuity”,derived by Dr Glazov in 1995 in J.Phys.:Condens.Matter 7 6365,has been analysed in detail.For the power cross section,neglecting electronic stopping,the linear transport equations determining the depth distribution functions of the deposited energy and monentum (by taking the threshold enerkgy into account )have been solved asymptotically.An important formula derived by Dr Glazov has been confirmed and generalized.The results agree with the new theorem. 相似文献
45.
研究墙体对微波脉冲的衰减特性,测量了微波脉冲垂直入射墙体后的脉冲信号,经过计算得到普通砖混墙、普通钢筋混凝土墙、钢筋网混凝土墙对窄带微波和超宽带微波的衰减值;分析了微波脉冲穿越不同墙体的频谱变化。研究结果表明,普通钢筋混凝土墙和普通砖混墙对窄带微波脉冲的衰减为0.342~0.699 dB/cm,对超宽带信号的衰减为0.134~0.183 dB/cm。钢筋网混凝土墙(厚65 cm)对超宽带信号的衰减较大(29.07~45.79 dB),同时使穿透墙体的超宽带信号频率分布向高频位移。 相似文献
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在二维正方Heisenberg铁磁系统的基础上建立了磁振子-声子相互作用模型. 利用松原格林函数理论研究了系统的声子衰减,计算了布里渊区的主要对称点线上的声子衰减曲线. 发现在第一布里渊区,在Δ线上,横向声频支声子无衰减,在Z线上,纵向声频支声子无衰减;横向声频支声子衰减比纵向声频支声子衰减至少大一个数量级,并讨论了各项参数的变化对横向声频支声子衰减与纵向声频支声子衰减的影响. 根据声子衰减与声子寿命的关系,声子衰减与声子态密度的关系,可以讨论横向声频支声子与纵向声频支声子的寿命与态密度.
关键词:
磁振子-声子相互作用
横向声频支声子衰减
纵向声频支声子衰减
声子寿命 相似文献
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Mourad Bellassoued 《数学学报(英文版)》2008,24(7):1175-1192
In this paper, we shall investigate the decay property of the solutions to the initial-boundary value problem for the elastic wave equation with a local time-dependent nonlinear damping. We give some decay rate of the energy when the damping term is effective only in a neighborhood of a suitable subset of the boundary. The results obtained in this paper extend, in particular, the known results for the scalar wave equation. 相似文献