The effect of dielectric exclusion on the rejection performance of inhomogeneously charged polyamide nanofiltration membranes

Journal of Nanoparticle Research - A green bioreduction method was used to prepare highly efficient supported TiO2 photocatalysts with bimetallic (Au-Ag) nanoparticles at room temperature using...     

Vibration analysis of a new polymer quartz piezoelectric crystal sensor for detecting characteristic materials of volatility liquid

We present a new polymer quartz piezoelectric crystal sensor that takes a quartz piezoelectric crystal as the basal material and a nanometer nonmetallic polymer thin film as the surface coating based on the principle of quartz crystal microbalance (QCM). The new sensor can be used to detect the characteristic materials of a volatile liquid. A mechanical model of the new sensor was built, whose structure was a thin circle plate composing of polytef/quartz piezoelectric/polytef. The mechanical model had a diameter of 8 mm and a thickness of 170 μ. The vibration state of the model was simulated by software ANSYS after the physical parameters and the boundary condition of the new sensor were set. According to the results of experiments, we set up a frequency range from 9.995850 MHz to 9.997225 MHz, 17 kinds of frequencies and modes of vibration were obtained within this range. We found a special frequency f_sp of 9.996358 MHz. When the resonant frequency of the new sensor’s mechanical model reached the special frequency, a special phenomenon occurred. In this case, the amplitude of the center point O on the mechanical model reached the maximum value. At the same time, the minimum absolute difference between the simulated frequency based on the ANSYS software and the experimental measured stable frequency was reached. The research showed that the design of the new polymer quartz piezoelectric crystal sensor perfectly conforms to the principle of QCM. A special frequency value f_sp was found and subsequently became one of the most important parameters in the new sensor design.     

改进的双曲等效法用于双站合成孔径雷达前视成像

双站合成孔径雷达(SAR)前视成像有着很多的潜在应用,比如在能见度很低的天气实现飞机的导航和盲降,提高飞机飞行的安全度等.然而实现双站SAR前视成像的难点在于其距离历程的双根式性,直接采用驻定相位原理对其分解将得到复杂的解析式,从而后续算法的推导变得困难.现有的双曲等效法可以将双根式距离历程等效为单根式,但由于该方法为距离历程的二阶近似,当用于双站SAR前视成像时,由于其较大的前视角,未完全等效的距离历程高次项造成的误差已经超出可以接受的范围.针对以上问题,本文首先提出了一种改进的双曲等效法,该方法通过引入新的补偿变量来提高距离历程的等效精度;然后在此基础上推导回波信号的二维频谱解析式,并给出了一种适用于双站SAR前视成像的距离多普勒算法;最后通过仿真实验,将原双曲等效法与改进方法的等效误差以及成像结果做对比,验证了本文算法的有效性和优越性.     

Improvement on ‘Cryptanalysis and Improvement of a Multiparty Quantum Direct Secret Sharing of Classical Messages with Bell States and Bell Measurements’

Recently, Liu (Int J Theor Phys: pp.1–6, 2018) pointed out that Song et al.’s multiparty quantum direct secret sharing protocol (Int J Theor Phys: 57, 1559, 2018) suffers from several attacks and then an improved quantum direct secret sharing protocol was hence proposed. However, this study shows that Liu’s protocol still suffers from an intercept-resend attack. To solve this problem, a modification is proposed here.

     

双电子复合过程在激光在Au靶耦合物理中的作用

 描述了考虑双电子复合过程的平均原子模型,通过与流体力学耦合计算,对双电子复合过程在激光－Au靶耦合物理中的作用进行了总体计算,结果表明,双电子复合对等离子体状态及X光转换等有明显影响,特别表现在晕区电子温度、电离度的降低,激光－X光的转换效率的提高以及X光的发光区域变宽等。     

北京谱仪Ds物理研究新进展

简要介绍了北京谱仪Ｄｓ物理研究的背景,北京谱仪和北京正负电子地撞机已取得的几项物理结果的内容,及其对国际粒子物理研究的贡献。     

光学分数傅里叶变换及其应用

介绍了分数傅里叶变换的定义及其性质,给出了分数傅里叶变换的光学实验结构,并对分数傅里叶变换在光学信息处理领域中的应用进行了综述。     

Measurement of the optical transmission modes and losses of the poled guest–host polymer NAEC/PEK-c planar waveguides

The polyetherketone (PEK-c) guest–host polymer planar waveguides doped with (4′-nitro)-3-azo-9-ethyl-carbazole (NAEC) were prepared. The waveguide films were poled by corona-onset poling at elevated temperature (COPET), and the corona poling setup includes a grid voltage making the surface-charge distribution uniform. By using the prism-in coupling method, the dark-line spectrum given by the reflected intensity versus the angle of incidence have been obtained, and the optical transmission losses of mth modes have been measured for the poled polymer waveguides at λ=632.8 nm. The measurement result showed that the optical loss of the fundamental mode is less than 0.7 dB cm⁻¹ for the TE polarization.     

Bi2S3纳米复合材料的非线性光学性质

利用单光束 Z扫描技术 ,在波长为 1 .0 64μm、脉宽为 38ps条件下测定了不同热处理条件下表面包覆纳米 Bi2 S3 掺杂有机改性硅酸盐材料的三阶光学非线性。结果发现室温下自然干燥的样品和在 N2 气氛下 1 50℃加热处理 2小时后的样品的三阶光学非线性极化系数分别为5.8× 1 0 -1 3 esu和 3.7× 1 0 -1 2 esu。后者的三阶光学非线性极化系数比前者几乎大一个数量级。显然 ,适当的热处理能增强样品的三阶光学非线性。对此现象进行了分析和讨论。     

Evolution of domain structure in Fe_3GeTe_2

Two-dimensional(2D)magnets provide an ideal platform to explore new physical phenomena in fundamental magnetism and to realize the miniaturization of magnetic devices.The study on its domain structure evolution with thickness is of great significance for better understanding the 2D magnetism.Here,we investigate the magnetization reversal and domain structure evolution in 2D ferromagnet Fe₃GeTe₂(FGT)with a thickness range of 11.2-112 nm.Three types of domain structures and their corresponding hysteresis loops can be obtained.The magnetic domain varies from a circular domain via a dendritic domain to a labyrinthian domain with increasing FGT thickness,which is accompanied by a transition from squared to slanted hysteresis loops with reduced coercive fields.These features can be ascribed to the total energy changes from exchange interaction-dominated to dipolar interaction-dominated with increasing FGT thickness.Our finding not only enriches the fundamental magnetism,but also paves a way towards spintronics based on 2D magnet.