Calibration method for a photoelastic modulator with a peak retardation of less than a half-wavelength

A new calibration method for a photoelastic modulator is proposed. The calibration includes a coarse calibration and a fine calibration. In the coarse calibration, the peak retardation of the photoelastic modulator is set near 1.841 rad. In the fine calibration, the value of the zeroth Bessel function is obtained. The zeroth Bessel function is approximated as a linear equation to directly calculate the peak retardation. In experiments, the usefulness of the calibration method is verified and the calibration error is less than 0.014 rad. The calibration is immune to the intensity fluctuation of the light source and independent of the circuit parameters. The method specially suits the calibration of a photoelastic modulator with a peak retardation of less than a half-wavelength.     

Facile synthesis of carbon coated LiFePO4 nanocomposite with excellent electrochemical performance through in situ formed lithium stearate pyrolysis route

Carbon coated LiFePO₄ (LiFePO₄/C) nanocomposite is successfully synthesized at a comparatively low temperature (400 °C) via a pyrolysis process of in situ formed lithium stearate. The obtained products are characterized by X-ray diffraction, electron microscopy, thermogravimetry, infrared and X-ray photoelectron spectroscopy. Experimental results indicate that the in situ formed lithium stearate can decompose at ∼290 °C, which is beneficial for the formation of carbon coating and reduction of Fe³⁺ species, and then the crystallized LiFePO₄/C nanocomposite can be formed at 400 °C without other intermediate products. As cathode material of Li-ion battery, the obtained LiFePO₄/C nanocomposite exhibits a good rate and cycling performance with a high discharge capacity of ∼160 mAh g⁻¹ (>94% theoretical capacity of LiFePO₄) at a current density of 1 C (170 mA g⁻¹), and ∼96% of its initial capacity can be retained after 200 charging/discharging cycles. Even at a high current density (10 C), the LiFePO₄/C nanocomposite still presents a discharge capacity as high as ∼100 mAh g⁻¹. The excellent electrochemical performances of the present LiFePO₄/C nanocomposite mainly originate from the good crystallinity, small particles and enhanced electronic conductivity of the materials coated and linked by carbon layers.     

基于互联网的扫描探针显微镜远程控制研究

在Ｉｎｔｅｒｎｅｔ信息传输的基础上,实现了数字化ＳＰＭ的远程控制。用户首先在连接ＳＰＭ的服务器上远程登陆,并取得不同的控制权。在得到主要操作人,协作者或旁观者的权力后,分别能远程直接控制ＳＰＭ的全部参数,部分参数,或不能控制参数。该系统已经在北京与上海两城市间进行了演示。     

Integrated liquid crystal optical switch based on double teeth-shaped structure at telecom wavelengths

The characteristics of a double teeth-shaped plasmonic optical switch are analyzed. Based on the metal–insulator–metal waveguide consisting of double rectangular teeth, a nanoscale liquid crystal optical switch is proposed and numerically simulated by using the finite difference time domain method with a perfectly matched layer absorbing boundary condition. It is found that the double teeth-shaped structure filled with liquid crystal can realize the function of a switch. The modulation depth of the double teeth-shaped structure is larger than 50?dB.     

Piezo‐Phototronic Effect on Selective Electron or Hole Transport through Depletion Region of Vis–NIR Broadband Photodiode

Silicon underpins nearly all microelectronics today and will continue to do so for some decades to come. However, for silicon photonics, the indirect band gap of silicon and lack of adjustability severely limit its use in applications such as broadband photodiodes. Here, a high‐performance p‐Si/n‐ZnO broadband photodiode working in a wide wavelength range from visible to near‐infrared light with high sensitivity, fast response, and good stability is reported. The absorption of near‐infrared wavelength light is significantly enhanced due to the nanostructured/textured top surface. The general performance of the broadband photodiodes can be further improved by the piezo‐phototronic effect. The enhancement of responsivity can reach a maximum of 78% to 442 nm illumination, the linearity and saturation limit to 1060 nm light are also significantly increased by applying external strains. The photodiode is illuminated with different wavelength lights to selectively choose the photogenerated charge carriers (either electrons or holes) passing through the depletion region, to investigate the piezo‐phototronic effect on electron or hole transport separately for the first time. This is essential for studying the basic principles in order to develop a full understanding about piezotronics and it also enables the development of the better performance of optoelectronics.     

直接法合成三烷氧基硅烷的研究进展

综述了直接法合成三烷氧基硅烷反应机理、所用原料、溶剂、催化剂以及分离纯化工艺.并对其发展前景进行了展望.     

BDCP:一个有效的相关任务调度算法

表调度算法ＢＤＣＰ采用动态关键路径技术并均衡考虑关键路径结点和非关键路径结点,使得对相关任务图调度长度影响最大的就绪得结点能够被优先调度,从而极大地缩短了调度长度。分析和实验结果表明,该算法要明显优于ＭＣＰ和ＥＴＦ算法。     

聚合物/MXene柔性力敏材料制备及应用研究进展

MXene作为一种新型的二维纳米材料,拥有优良的导电性,在柔性力敏材料领域有广泛的应用前景。为了构筑柔性力敏材料,通常将MXene与柔性聚合物或多孔聚合物相结合,从而实现柔性及大形变。柔性力敏材料中,MXene的分布、导电网络结构与形态由制备方法决定,进而决定传感器的类型和应用类型及场合。文中从MXene柔性力敏材料的制备策略角度出发,总结了浸渍法、喷涂法、真空过滤法、冰模板法及其它方法对MXene柔性力敏材料性能的影响,同时归纳了MXene柔性力敏材料在生理信号、细微人体动作、关节运动信号监测以及对信号进行示踪等方面的应用进展。     

Dendrite‐Free Lithium Deposition via a Superfilling Mechanism for High‐Performance Li‐Metal Batteries

Uncontrollable Li dendrite growth and low Coulombic efficiency severely hinder the application of lithium metal batteries. Although a lot of approaches have been developed to control Li deposition, most of them are based on inhibiting lithium deposition on protrusions, which can suppress Li dendrite growth at low current density, but is inefficient for practical battery applications, with high current density and large area capacity. Here, a novel leveling mechanism based on accelerating Li growth in concave fashion is proposed, which enables uniform and dendrite‐free Li plating by simply adding thiourea into the electrolyte. The small thiourea molecules can be absorbed on the Li metal surface and promote Li growth with a superfilling effect. With 0.02 m thiourea added in the electrolyte, Li | Li symmetrical cells can be cycled over 1000 cycles at 5.0 mA cm^?2, and a full cell with LiFePO₄ | Li configuration can even maintain 90% capacity after 650 cycles at 5.0 C. The superfilling effect is also verified by computational chemistry and numerical simulation, and can be expanded to a series of small chemicals using as electrolyte additives. It offers a new avenue to dendrite‐free lithium deposition and may also be expanded to other battery chemistries.