Chiral媒质旋波性的物理机制

本文从旋光晶体微观结构入手，将其旋光性同其结构的手征性相联系。简述了旋波理论的几种提法，结合单螺旋散射模型导出其本构关系参数，使之对Ｃｈｉｒａｌ媒质的本质加深理解。     

一种基于神经网络提取旋波材料参数的新方法

提出了一种从测试的S参数中提取旋波材料参数的新方法——神经网络法。针对旋波材料参数的自由空间测试方法,本文采用BP神经网络来构建映射模型,利用不同算法对网络进行训练,从而获得所需的网络。结果表明,该方法计算速度快、精度高,解决了求解非线性方程组解的模糊性问题,确保了测试结果的可靠性。该方法所构建的网络可用于材料测试后旋波材料参数的快速提取。     

电磁波垂直入射到平面多层旋波媒质的反射

本文首先给出旋波媒质基本公式，然后从传输线理论出发，用阻抗法解决了线极化平面波垂直入射到多层平面旋波媒质的反射问题，处理方法简单方便，且易理解，文中最后给出了一些数值模拟计算结果，并将其与别外的方法进行了比较，结果吻合得很好。     

填充旋波媒质矩形波导电磁场的解析求解

提出了一种获得填充旋波媒质矩形波导电磁场解析解的新方法.从旋波媒质本构方程和麦克斯韦方程出发,讨论了电磁波在旋波媒质中的传播特性.经过矢量变换,将难以解析求解的波动方程化简为常规的波动方程,并对其进行了求解.利用矢量变换关系和场矢量的边界条件,求得了电磁场分量表达式和求解传播常数的特征方程组.     

多层旋波媒质平板的反射与透射

本文先利用电磁场的边界条件导出平面电磁波垂直入射于多层平板旋波媒质的透射场表达式。然后用传输线理论中的阻抗法,解决了多层平板旋波媒质的反射问题。最后对多层旋波媒质平板的一特例－双层结构型旅波吸波材料进行了计算机辅助设计分析,分析表明,双层代替单层可以在一定程度上改善涂层的吸波特性。     

用磁矢势并矢格林函数研究旋波媒质中的电波辐射

运用磁矢势并格林函数,研究旋波媒质中的电波辐射性质,结果表明,旋波媒质中本征电磁模式为左、右旋圆极化波,电磁辐射性质与旋波因子密切相关,周转媒质的螺旋性质改变了辐射场的极化状态,增大了天线辐射电阻,增强了辐射能力。     

电磁波垂直入射到平面多层旋波煤质的反射

本文首先给出旋波煤质基本公式，然后从传输线理论出发，用阻抗法解决了线极化平面被垂直和入射到多层平面旋波媒质的反射向题，处理方法简单方便，且易理解。文中最后给出了一些数值模拟计算结果，并将其与另外的方法进行了比较．结果吻合得很好。     

电导率对旋波介质吸波性能的影响

旋波介质的吸波性能与介质的手性参量有关,而手性参量又与介质的电导率有关。制备了4种不同电导率基底的旋波介质,根据自由空间测量旋波介质手性参量的方法,通过测量两次复反射系数、透射偏转角和椭偏率,计算得到介质的手性参量和吸波性能。结果表明,改变旋波介质基底的电导率,可以调节旋波介质的电磁性能和吸波性能,当基底的电导率为4.2×10–2 S/cm时,旋波介质的吸波效果最好,其反射系数的最小值达–24 dB。     

分层媒质复介电常数测量的一种方法

本文给出一种测量分层媒质复介电常数的方法,经过多次测量复反射系数并建立恰当的目标函数,采用遗传算法求解这一优化问题可得到分层媒质的参数。测量结果表明,对于层数校少的媒质,在各分层厚度未知的民政部下仍可测得各分层的复介电常数,同时测得分层厚度。     

手性非晶玻璃的合成及其极化特性

利用溶胶 -凝胶低温合成非晶态技术 ,以正硅酸乙酯和乙醇为前驱体 ,将手性分子灰黄霉素均匀地掺入到溶胶 -凝胶体系中 ,首次成功地研制出手性非晶态玻璃材料 ,并对其光学极化特性及材料的热稳定性进行了测试。测试结果表明 ,手性非晶态玻璃的旋光率为 - 1.4 5°/ cm,计算所得的手征参数为 2 .37× 10 - 7。     

基于Freeman分解的植被参数反演新方法

基于极化Freeman分解的极化协方差矩阵参数,极化干涉SAR互协方差矩阵可简化建模为植被高度、消光系数和地面干涉相位的函数。基于此,该文建立了以极化干涉SAR互协方差矩阵估算值与互协方差矩阵观测值之差为目标函数、以3个植被参数为未知量的优化模型,提出了基于Freeman分解的植被参数反演新方法。该方法避免了三阶段植被参数估计方法所面临的体相关系数确定问题,提供了一种独立于三阶段植被参数估计的新思路。仿真结果验证了新方法的有效性。     

A Thermoresponsive Membrane for Chiral Resolution

A novel thermoresponsive membrane for chiral resolution with high performance has been developed. The membrane exhibits chiral selectivity based on molecular recognition of beta‐cyclodextrin (β‐CD) and thermosensitivity based on the phase transition of poly(N‐isopropylacrylamide) (PNIPAM). Linear PNIPAM chains were grafted onto porous nylon‐6 membrane substrates by using a plasma‐graft pore‐filling polymerization method; the chains thus acted as microenvironmental adjustors for β‐CD molecules. β‐CD moieties were introduced into the linear PNIPAM chains by a chemical grafting polymerization method and acted as chiral selectors. The phase transition of grafted PNIPAM chains affects the microenvironment of β‐CD molecules and, thus, the association between β‐CD and guest molecules. The chiral selectivity of the prepared thermoresponsive membranes in chiral resolution operated at temperature below the lower critical solution temperature (LCST) of PNIPAM is higher than that of membranes with no thermosensitivity. Furthermore, the decomplexation ratio of enantiomer‐loaded thermoresponsive membranes in decomplexation at temperatures above the LCST is much higher than that of membranes with no thermosensitivity. Thus, by simply changing the operation temperature, high, selective chiral resolution and efficient membrane regeneration are achieved. The proposed membrane provides a new and efficient way to solve the difficult decomplexation problem of chiral solid membranes, which is highly attractive for chiral resolution.     

手征材料涂覆导体目标电磁散射特性的PO分析

从Maxwell方程出发 ,推导出平面波照射下手征介质涂覆导体目标表面等效电磁流的一般表达式 ,并基于切平面近似 ,给出了计算手征介质涂覆导体目标电磁散射的物理光学 (PO)解。在此基础上 ,计算了T形结构及锥柱结构的散射特性 ,分析了手征材料参数对电磁散射的影响 ,得到了一些有益的结果。为电大尺寸手征介质涂覆导体目标电磁散射特性的快速估计提供了一种有效的手段     

Photoinduced Chiral Nematic Organization in an Achiral Glassy Nematic Azopolymer

A liquid crystalline homopolymer that has photoisomerizable methoxyazobenzene groups in the side chain has been synthesized and characterized. Thin films of the nematic glassy phase of this polymer have been processed in order to study the absorption spectra and the vibrational and electronic circular dichroism responses by irradiation with 488 nm circularly polarized light (CPL). Selective reflection of visible light demonstrates that the irradiation of this glassy nematic azopolymer induces a helix as a consequence of the chiral arrangement of the azobenzene units. Moreover, a wedge cell with an aligning layer for planar orientation was filled with the polymer with the aim of investigating the change in the macroscopic optical properties and optical textures of the azopolymer on irradiation with CPL. The transfer of chirality from CPL to azopolymer through chiral conformations is proposed as a model for explaining the supramolecular chirality.     

Enantioselective Crystallization on Chiral Polymeric Microspheres

In this article, a new approach to chiral resolution based on enantioselective crystallization on chiral polymeric microspheres is presented. To demonstrate the approach, a new synthetic method is developed for the preparation of porous and hollow chiral polymeric microspheres. Chiral microspheres based on poly(N‐vinyl α‐L ‐phenylalanine) (PV‐L ‐Phe) are synthesized from uniform polystyrene (PS) microsphere templates by a single‐step swelling process. The chiral microspheres display a narrow size distribution, and their properties, especially the porosity, can be controlled by varying the synthesis conditions. The chiral discrimination ability of these chiral microspheres is studied for D L ‐valine crystallization, as a model system for chiral racemic crystallization. X‐ray diffraction (XRD) and differential scanning calorimetry (DSC) provide evidence for the crystallization of enantiopure crystals on the chiral polymeric microspheres. Optical rotation measurements during crystallization show an enatiomeric excess of ca. 25 % for L ‐valine in the chiral microspheres. Although this excess is not yet very high, the basic principle of chiral discrimination by enantioselective crystallization on chiral microspheres is demonstrated.     

一种分析可用于手征媒质测量的准光谐振系统中电磁波传播的数值方法

用有限差分法的箱式差分格式分析了可用于手征媒质测量的准光谐振系统中的电磁波传播，采用求解抛物化波动方程方法可以得到整个系统中各个不同位置处的场值，同时也给出了几个典型算例，并与解析方法进行了比较。     

一种用于求压电材料复参数的快速迭代算法

要精确地描述压电材料的性能,必须把压电材料的参数作为复数考虑。文章提出一种新的自动迭代算法,通过测量压电陶瓷的４种标准型振子谐振峰附近的阻抗（或导纳）,即可由程序自动求出压电陶瓷的全部材料系数。与常用的迭代法相比,本文迭代法巧妙的初值选取方法及选代频率点的选择,使得算法精度高,迭代次数少。     

A Frequency Response Method for Determining the Parameters of High-Performance DC Motors

This paper introduces a technique for measuring the parameters of high-performance dc motors. A second-order motor model, under certain conditions, is shown to be equivalent to a series resonant electrical circuit. Frequency response measurements of the motor, when treated as an electrical impedance, form the basis of a measurement technique which has certain practical advantages. Results are compared to measurements made using conventional methods.