UHF RFID标签谐振特性非接触测试方法的研究与实现

针对U H F RFID标签贴附在介质表面时,标签的谐振特性用接触式测量方法存在较大的误差问题,通过建立标签的接收功率模型,分析标签芯片获取到的能量与频率之间的关系,提出非接触式测试 U HF RFID谐振特性的方法。详细描述了利用频率和距离关系测试标签谐振特性的原理,说明了非接触式测试方法硬件测试平台的搭建方法和测试软件的编写思想,并完整地实现了该平台。实测实验证明,该测试方法和平台能有效地测试标签的谐振特性。在实际应用中,可以根据标签的谐振特性设计适合不同物体的标签。     

基于FDTD的粗糙地面宽带前向电磁散射研究

采用指数型分布粗糙面模拟实际的粗糙地面,运用FDTD方法研究了超宽带高斯脉冲电磁波入射粗糙地面时的宽带前向电磁散射问题;通过数值计算得到前向散射系数随频率的变化曲线,并与时谐场源激励下的结果进行了对比;分析了不同的粗糙地面高度起伏相关长度、均方根高度,土壤湿度和入射角下前向散射系数随频率的变化关系,得到了指数型分布粗糙地面的宽带前向电磁散射特性。数值计算结果表明各参数的变化对前向电磁散射系数的影响比较明显,入射波不同极化方式下的前向散射系数也有显著变化。     

隔爆型大功率开关磁阻电机仿真分析

采用MAGNET有限元软件对一种双凸极结构,定转子具有可变磁阻回路的开关磁阻电机进行仿真分析,并设计了全压型控制电路对其进行角位置控制联合仿真。     

Effect of graphene oxide on the behavior of poly(amide‐6‐b‐ethylene oxide)/graphene oxide mixed‐matrix membranes in the permeation process

Polyether‐block‐amide (Pebax)/graphene oxide (GO) mixed‐matrix membranes (MMMs) were prepared with a solution casting method, and their gas‐separation performance and mechanical properties were investigated. Compared with the pristine Pebax membrane, the crystallinity of the Pebax/GO MMMs showed a little increase. The incorporation of GO induced an increase in the elastic modulus, whereas the strain at break and tensile strength decreased. The apparent activation energies (E_p) of CO₂, N₂, H₂, and CH₄ permeation through the Pebax/GO MMMs increased because of the greater difficulty of polymer chain rotation. The E_p value of CO₂ changed from 16.5 kJ/mol of the pristine Pebax to 23.7 kJ/mol of the Pebax/GO MMMs with 3.85 vol % GO. Because of the impermeable nature of GO, the gas permeabilities of the Pebax/GO MMMs decreased remarkably with increasing GO content, in particular for the larger gases. The CO₂ permeability of the Pebax/GO MMMs with 3.85 vol % GO decreased by about 70% of that of the pristine Pebax membrane. Rather than the Maxwell model, the permeation properties of the Pebax/GO MMMs could be described successfully with the Lape model, which considered the influence of the geometrical shape and arrangement pattern of GO on the gas transport. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42624.     

Preparation of M@BiFeO3 Nanocomposites (M = Ag,Au) Bowl Arrays with Enhanced Visible Light Photocatalytic Activity

High surface area BiFeO₃ (BFO) bowl arrays photocatalyst loaded with different size noble metal nanoparticles were successfully prepared by combining templates method and thermal evaporation followed by heating. The structural and optical properties of the BiFeO₃ bowl arrays and the composite M@BFO bowl arrays (M = Ag, Au) were comparatively characterized. The composite M@BFO bowl arrays showed much higher photocatalytic performance than the pure BFO bowl arrays. The enhanced photocatalytic property of the composite structure could be ascribed to the enhanced near‐field amplitudes of localized surface plasmon of the noble metal nanoparticles which boost the separation of electron–hole pairs and the transfer mechanism of electrons.     

Design and Synthesis of CdWO4:Sb3+ Phosphor Based on sp Energy Level Regularities of Sb3+ Ion

Sb³⁺‐activated CdWO₄ phosphors were designed according to sp energy levels regularities of Sb³⁺ ion in some inorganic compounds. The sp energy levels regularities of Sb³⁺ in dozens of compounds were established with the aid of the dielectric theory of the chemical bond for complex crystals: E_A = 6.2187?1.7584h_e, E_B = 7.019?1.957h_e, E_C = 7.259?1.964h_e. Environmental factor h_e of Cd site was calculated to be 1.6583 with the refined crystal structure and refractive index of CdWO₄:Sb³⁺. Sb³⁺‐doped CdWO₄ was synthesized through a precipitation method and its structure was refined with the General Structure Analysis System. The transition energy of A band of Sb³⁺ in CdWO₄ can be predicted to be 3.312 eV (374 nm), according to the relationship equation between E_A and environmental factor h_e. By monitoring the 521 nm emission band, the excitation spectrum gives a weak excitation band peaking at 355 nm, which was assigned to the ¹S₀–³P₁ transition of Sb³⁺ according to our prediction. Thus, Sb³⁺‐doped CdWO₄ phosphor was designed and synthesized successfully based on sp energy levels regularities of Sb³⁺ ion. This work is a great help to understand the spectroscopy of Sb³⁺ ion and will be useful for the design and development of Sb³⁺‐doped phosphors for applications.