In dynamic laser light scattering (LLS), for a given plydisperse sample, a line-width distribution G(Γ) or the translational diffusion coefficient distributionG(D) can be obtained from the measured time correlation f...In dynamic laser light scattering (LLS), for a given plydisperse sample, a line-width distribution G(Γ) or the translational diffusion coefficient distributionG(D) can be obtained from the measured time correlation function. For rigid colloid particles,G(Γ) can be directly related to the hydrodynamic size distribution. However, for flexible polymer chains, G (Γ) depends not only on the chain length distribution, but also on the relaxation of the chain conformation; that is, even for a monodisperse polymer sample there still exists a chain conformation distribution. If the time scale of the chain conformation relaxation is comparable to that of the translational diffusion, such as in the case of a very long polymer chain, the conformation relaxation might lead to an additional broadening in G(Γ). This ‘conformation broadening’ has been directly observed for the first time by comparing twoG(Γ)s obtained from a ply(N-iso-propyl-acrylamide) solution at ~25°C: and ~ 32°C at which the solution is thermodynamically stable, where the fact is utilized that the PNIPAM chain can change from an extended and flexible coil at ~25°C into a highly collapsed and compact globule at ~ 32°C at which pint the polymer chain conformation distribution has diminished.展开更多
针对多电平移相全数字发信机(All Digital Transmitter,ADTx)架构中脉冲波形幅度不平衡误差问题,开展了误差机理分析和数值仿真研究。提出了一个基于ADTx硬件电路不理想性引起的脉冲幅度不平衡误差非线性失真模型,并推导分析了脉冲幅度...针对多电平移相全数字发信机(All Digital Transmitter,ADTx)架构中脉冲波形幅度不平衡误差问题,开展了误差机理分析和数值仿真研究。提出了一个基于ADTx硬件电路不理想性引起的脉冲幅度不平衡误差非线性失真模型,并推导分析了脉冲幅度不平衡误差对输出信号时域波形的畸变机制。通过数值仿真研究了脉冲幅度不平衡误差对发信机线性性能的影响。实验结果表明,脉冲幅度不平衡误差会显著恶化误差矢量幅度(Error Vector Magnitude,EVM)、邻信道功率比(Adjacent Channel Power Ratio,ACPR)以及三次谐波抑制性能等关键性能指标。深入分析该幅度不平衡误差对于准确评估并消除误差、提升多电平ADTx系统性能具有重要的理论和实践意义。展开更多
研究地下内衬岩洞(Lined Rock Caverns,LRC)储气库的衬砌开裂特征,为该类储气库的设计和工程应用提供参考。通过应用ABAQUS有限元软件建立地下大罐式内衬高压储气库模型,使用显示动力分析研究横向配筋率、纵向配筋率、埋深、储气压力等...研究地下内衬岩洞(Lined Rock Caverns,LRC)储气库的衬砌开裂特征,为该类储气库的设计和工程应用提供参考。通过应用ABAQUS有限元软件建立地下大罐式内衬高压储气库模型,使用显示动力分析研究横向配筋率、纵向配筋率、埋深、储气压力等参数对衬砌开裂特征的影响。结果表明:衬砌外表面最大裂缝宽度大于内表面,而衬砌内表面存在更多的细小裂缝;随着横向配筋率的提高,混凝土衬砌中内外表面裂缝宽度逐渐减小,贯穿性裂缝数量减小,裂缝平均间距减小。但当横向配筋率超过0.16%,裂缝宽度变化不再显著;埋深越大,地应力越大,衬砌产生的环向拉应力越小,衬砌裂缝宽度越小。建议适当增大横向配筋率和储气库埋深,减小储气压力来抑制衬砌裂缝的开展,而纵向钢筋按构造配筋即可。展开更多
基金Supported by the Climbing Project of the Chinese National Basic Project--Macromolecule Condensed State, the Research Grants Council (RGC) of Hong Kong Government Earmarked Grants 1997/98 (CUHK4181/97P, 2160082, RGC/96-97/03)the National Distinguish
文摘In dynamic laser light scattering (LLS), for a given plydisperse sample, a line-width distribution G(Γ) or the translational diffusion coefficient distributionG(D) can be obtained from the measured time correlation function. For rigid colloid particles,G(Γ) can be directly related to the hydrodynamic size distribution. However, for flexible polymer chains, G (Γ) depends not only on the chain length distribution, but also on the relaxation of the chain conformation; that is, even for a monodisperse polymer sample there still exists a chain conformation distribution. If the time scale of the chain conformation relaxation is comparable to that of the translational diffusion, such as in the case of a very long polymer chain, the conformation relaxation might lead to an additional broadening in G(Γ). This ‘conformation broadening’ has been directly observed for the first time by comparing twoG(Γ)s obtained from a ply(N-iso-propyl-acrylamide) solution at ~25°C: and ~ 32°C at which the solution is thermodynamically stable, where the fact is utilized that the PNIPAM chain can change from an extended and flexible coil at ~25°C into a highly collapsed and compact globule at ~ 32°C at which pint the polymer chain conformation distribution has diminished.
文摘针对多电平移相全数字发信机(All Digital Transmitter,ADTx)架构中脉冲波形幅度不平衡误差问题,开展了误差机理分析和数值仿真研究。提出了一个基于ADTx硬件电路不理想性引起的脉冲幅度不平衡误差非线性失真模型,并推导分析了脉冲幅度不平衡误差对输出信号时域波形的畸变机制。通过数值仿真研究了脉冲幅度不平衡误差对发信机线性性能的影响。实验结果表明,脉冲幅度不平衡误差会显著恶化误差矢量幅度(Error Vector Magnitude,EVM)、邻信道功率比(Adjacent Channel Power Ratio,ACPR)以及三次谐波抑制性能等关键性能指标。深入分析该幅度不平衡误差对于准确评估并消除误差、提升多电平ADTx系统性能具有重要的理论和实践意义。
文摘研究地下内衬岩洞(Lined Rock Caverns,LRC)储气库的衬砌开裂特征,为该类储气库的设计和工程应用提供参考。通过应用ABAQUS有限元软件建立地下大罐式内衬高压储气库模型,使用显示动力分析研究横向配筋率、纵向配筋率、埋深、储气压力等参数对衬砌开裂特征的影响。结果表明:衬砌外表面最大裂缝宽度大于内表面,而衬砌内表面存在更多的细小裂缝;随着横向配筋率的提高,混凝土衬砌中内外表面裂缝宽度逐渐减小,贯穿性裂缝数量减小,裂缝平均间距减小。但当横向配筋率超过0.16%,裂缝宽度变化不再显著;埋深越大,地应力越大,衬砌产生的环向拉应力越小,衬砌裂缝宽度越小。建议适当增大横向配筋率和储气库埋深,减小储气压力来抑制衬砌裂缝的开展,而纵向钢筋按构造配筋即可。
