开孔矩形腔体电磁泄漏特性的解析研究

本文提出了一种用于计算开孔矩形腔体电磁泄漏场的解析理论模型.该理论模型先基于模式展开法求解封闭腔场,进而依据Bethe小孔耦合理论将泄漏场与封闭腔场用等效偶极子关联.该模型可以考虑波频率、场源位置、开孔位置及场强观测点位置等因素的影响,计算结果与全波仿真结果一致.本文计算分析了相关因素对电磁屏蔽效能的影响规律,并给出了物理解释.结果表明近场屏蔽效能小于远场屏蔽效能,且近场区电场屏蔽效能与磁场屏蔽效能并不相同.     

Chemical One Step Method to Prepare Polyaniline Nanofibers with Electromagnetic Function

A “Chemical one step method” (COSM) is proposed to prepare electromagnetic functional composite nanofibers of polyaniline (PANI/γ‐Fe₂O₃) having a diameter of ≈20 nm. In this approach FeCl₃ is acts as the oxidant either for polymerization of aniline or for preparation of γ‐Fe₂O₃ magnets. Besides, it also provides protons produced by the hydrolysis process for doping PANI. It is found that the composite nanofibers have a high conductivity (10⁻¹ ∼ 10⁰ S · cm⁻¹) and super‐paramagnetic properties (M_s = 0.46 ∼ 6.03 emu · g⁻¹ and H_c = 0) at room temperature, where the conductivity is mainly affected by the molar ratio of FeCl₃ to aniline monomer whereas the magnetic properties are dominated by the amount of FeCl₂.

     

Waveguide resonance of subwavelength metallic slits

The transmission characteristics of a metallic film with subwavelength periodic slits are investigated by using the two-dimensional finite-difference time-domain method (2D-FDTD). Two models are constructed to show the dependance of the transmission spectrum on the slit structure. A sandwiched structure is used to exhibit the contribution of the metallic wall inside slits to the extraordinary high transmission. And a filled slit structure is employed to reflect the relation between the average refractive index inside the slits and the transmission spectrum of the structure. The transmission characteristics of two structures can be explained well with the waveguide resonance theory.     

Inhomogeneous Bulk Viscous Fluid Universe with Electromagnetic Field and Variable Λ-Term

Cylindrically symmetric inhomogeneous cosmological model for bulk viscous fluid distribution with electromagnetic field is obtained. The source of the magnetic field is due to an electric current produced along the z-axis. F₁₂ is the non-vanishing component of electromagnetic field tensor. To get the deterministic solution, it has been assumed that the expansion θ in the model is proportional to the shear σ. The values of cosmological constant for these models are found to be small and positive at late time, which are consistent with the results from recent supernovae Ia observations. Physical and geometric aspects of the models are also discussed in presence and absence of magnetic field.     

翼型绕流的电磁力控制

将表面包覆电磁激活板的翼型,按一定的攻角,置于流动的弱电介质溶液中,电磁激活板可产生作用于流体的切向电磁力(Lorentz力),从而改变流体边界层的结构. 在转动水槽中,对翼型绕流及电磁力控制下的绕流形态进行了实验研究. 结果表明,未加电磁力时,前缘涡的脱落点是不确定的,与流场具体条件有关,而后缘涡仅在尖角处脱落. 前缘涡与后缘涡相互影响,并周期性的脱体,在尾部形成涡街. 施加电磁力后,当力的方向与流动方向相同时,可以在一定程度上抑制分离,消除涡街,其效果与减小攻角类似. 加反向电磁力时,则相当于加大攻角,在翼型体的背风面形成涡街.      

Investigation of composite electromagnetic scattering from ship-like target on the randomly rough sea surface using FDTD method

Composite electromagnetic scattering from a two-dimensional (2D) ship-like target on a one-dimensional sea surface is investigated by using the finite-difference time-domain (FDTD) method. A uniaxial perfectly matched layer is adopted for truncation of FDTD lattices. The FDTD updated equations can be used for the total computation domain by choosing the uniaxial parameters properly. To validate the proposed numerical technique, a 2D infinitely long cylinder over the sea surface is taken into account first. The variation of angular distribution of the scattering changing with incident angle is calculated. The results show good agreement with the conventional moment method. Finally, the influence of the incident angle, the polarization, and the size of the ship-like target on the composite scattering coefficient is discussed in detail.     

A Deep Neural Network Method for Arterial Blood Flow Profile Reconstruction

Arterial stenosis will reduce the blood flow to various organs or tissues, causing cardiovascular diseases. Although there are mature diagnostic techniques in clinical practice, they are not suitable for early cardiovascular disease prediction and monitoring due to their high cost and complex operation. In this paper, we studied the electromagnetic effect of arterial blood flow and proposed a method based on the deep neural network for arterial blood flow profile reconstruction. The potential difference and weight matrix are used as inputs to the method, and its output is an estimate of the internal blood flow velocity distribution for arterial blood flow profile reconstruction. Firstly, the weight matrix is input into the convolutional auto-encode (CAE) network to extract its features. Then, the weight matrix features and potential difference are combined to obtain the features of the blood velocity distribution. Finally, the velocity features are reconstructed into blood flow velocity distribution by a convolution neural network (CNN). All data sets are obtained from a model of the carotid artery with different rates of stenosis in a uniform magnetic field by COMSOL. The results show that the average root mean square error of the reconstruction results obtained by the proposed method is 0.0333, and the average correlation coefficient is 0.9721, which is better than the corresponding indicators of the Tikhonov, back propagation (BP) and CNN methods. The simulation results show that the proposed method can achieve high accuracy in blood flow profile reconstruction and is of great significance for the early diagnosis of arterial stenosis and other vessel diseases.     

自组装技术在电磁屏蔽织物加工中的应用

尼龙织物经功能性高分子壳聚糖(CS)预处理后,应用分子自组装技术于其表面自组装钯膜(镀镍前活化).该膜钯微粒为纳米级,比表面较大,催化活性较高.将成膜后的织物化学镀镍磷合金,即可得到屏蔽性能优异的电磁屏蔽织物.正交试验及单因素试验得出CS预处理的最佳工艺条件.SPM、SEM表征活化前后及施镀前后织物表面的形态变化.根据Schelkunoff理论,计算织物的电磁辐射屏蔽效能,其值高于30 dB,相当于屏蔽掉了96.0%以上的电磁波.     

基于Hamilton体系的辛半解析法在各向异性电磁波导中的应用

力学中的Hamilton体系使用对偶变量来描述问题,而电磁场正好有电场和磁场这一对对偶变量。本文将力学中的Hamilton体系应用到电磁波导问题。根据电磁波导的Hamilton体系理论,辛几何可用于任意各向异性材料。将横向的电场和磁场构成对偶向量,基于Hamilton变分原理做半解析横向离散,并保持结构辛体系。本文以各向异性材料电磁波导为例,求解了问题的辛本征值,得到了镜像线的色散曲线。     

电磁感应摆与电磁感应陀螺

根据电磁感应定律和简单的电子线路设计的电磁感应摆与电磁感应陀螺,是一个有趣的演示实验。本文介绍了这两种装置的结构和工作原理。