表面喷砂对有机玻璃沿面闪络性能影响

绝缘子表面粗糙处理是提升其沿面闪络性能的重要途径,表面粗糙化处理方式不当,极易带来表面结构不均匀,难以获得稳定耐压性能的绝缘材料。为提升绝缘子表面粗糙处理的均匀性,本文利用表面喷砂技术对圆柱形有机玻璃（PMMA）绝缘子进行了粗糙化处理研究,以球形二氧化硅（SiO₂）颗粒为工作介质,研究了不同喷砂粒径、氢氟酸后处理等因素对绝缘材料表面形貌和组分的影响,并利用短脉冲高压测试平台对喷砂处理前后有机玻璃绝缘子样品进行了真空沿面闪络性能测试。研究结果表明,喷砂处理在有机玻璃表面形成了较为均匀的凹坑,HF酸能够有效去除表面残留的SiO₂颗粒,具有表面喷砂粗糙结构的绝缘子沿面闪络电压得到了稳定提升,相较于未处理的绝缘子闪络电压提升了约80%。     

Multicaloric and coupled-caloric effects

The multicaloric effect refers to the thermal response of a solid material driven by simultaneous or sequential application of more than one type of external field.For practical applications,the multicaloric effect is a potentially interesting strategy to improve the efficiency of refrigeration devices.Here,the state of the art in multi-field driven multicaloric effect is reviewed.The phenomenology and fundamental thermodynamics of the multicaloric effect are well established.A number of theoretical and experimental research approaches are covered.At present,the theoretical understanding of the multicaloric effect is thorough.However,due to the limitation of the current experimental technology,the experimental approach is still in progress.All these researches indicated that the thermal response and effective reversibility of multiferroic materials can be improved through multicaloric cycles to overcome the inherent limitations of the physical mechanisms behind single-field-induced caloric effects.Finally,the viewpoint of further developments is presented.     

Double Andreev reflections at surface states of the topological insulators with hexagonal warping

We study the Andreev reflection(AR)at the interface of the topological insulator with hexagonal warping and superconductor junction.Due to the hexagonal warping effect,the double ARs are found in a certain range of the incident angle,where for one incident electron beam,two beams of holes are reflected back.Interestingly,both the beams of holes are reflected as retro-AR on the same side of the normal line of the interface but with different reflection angles,different from the previously reported double AR with one retro-AR and one specular-AR.The double reflections owing to the warping effect show the optics-like property of the Dirac fermion and can stimulate the double reflections of light in anisotropic crystals.In addition,we find that the double ARs are dependent on the hexagonal warping parameter nonmonotonically,and in an intermediate strength the double AR phenomenon is prominent,providing a possibility to explore the warping parameter of topological insulators.     

Image Displaying Method of Ground-Based Millimeter Wave Radiometric Imaging System

The image displaying methods used in a millimeter wave radiometric imaging system have great influence on its imaging quality. In order to obtain high quality millimeter wave radiometric images, intensive studies on the image displaying methods are needed. This paper describes the image displaying method of Ground-based 8mm Millimeter Wave Radiometric Imaging (GMWRI) system and compares two different image displaying methods. The experimental results prove the unequal size element arc displaying method fits GMWRI system better.     

Improving nonlinearity tolerance of 112-Gb/s PDM OFDM systems with coherent detection using BLAST algorithm

A novel long wavelength photodetector with dual-wavelength spectral response is designed and fabricated using a step-shaped Fabry-Prot (F-P) filter structure.The step-shaped GaAs/AlGaAs distributed Bragg reflectors and the InP PIN photodetector are grown on a GaAs substrate using low pressure metal organic chemical vapor deposition.High quality GaAs/InP heteroepitaxy is realized by employing a thin low temperature buffer layer.The photodetector structure is optimized by theoretical simulation.This device has a dual-peak distance of 19 nm (1 558 and 1 577 nm).The 3-dB bandwidth of 16 GHz is simultaneously obtained with peak quantum efficiencies of 8.5% and 8.6% around 1 558 and 1 577 nm,respectively.     

High-reflectivity non-periodic sub-wavelength gratings with small-angle beam-steering ability and its application in Fabry–Perot cavity

We report a high-reflectivity non-periodic sub-wavelength gratings (SWGs) mirror with small-angle beam-steering ability for reflect light. It presents a distinctive characteristic of flexibly controlling the width of oscillation optical field for the improved Fabry–Perot (F–P) cavity. We propose a detailed principle analysis of the improved cavity. By finding out a set of SWGs with the designed structural parameters, both high reflectivity (>?93%) and beam steering (1°) can be implemented. By setting beam-steering angle and cavity length, we can control the width of oscillation optical field in the improved cavity. Beam steering ability and property of controlling the oscillation width are numerically investigated by finite element method. Simulation results prove that cavity length and steering angle can effectively control the main width of oscillation optical field, and the width is linearly associated with the cavity length.     

玻璃-橡胶混合颗粒体系的弹性行为研究

废旧橡胶制品颗粒与砂土颗粒混合物作为建筑填充材料具有环保、轻质、减震效果好等特点.软硬组分的混合比例可以调制体系力学性能从而实现兼顾材料柔韧性与强度的需求,但细观层面上材料性能改变的原因尚不明确.本文主要研究玻璃-橡胶混合颗粒体系的弹性行为及其微观机制.利用飞行时间法测量混合材料等效动弹性模量,发现随着橡胶颗粒增加,体系逐渐从类玻璃刚性行为转变为类橡胶柔性行为.离散元模拟结果与实验结果类似.此外,模拟显示低橡胶颗粒占比样品内主要由玻璃颗粒构成主力链结构,而橡胶颗粒基本不参与强力链的构成.当橡胶颗粒占比较大时,玻璃颗粒和橡胶颗粒共同构成主力链网络结构,但颗粒间法向接触力分布相对更为均匀,可视为玻璃颗粒悬浮于橡胶颗粒中.基于上述结果,提出了改进的等效介质理论,用于描述混合颗粒体系的弹性行为.研究认为:橡胶颗粒占比较小时内部颗粒的变形相对均匀,材料近似满足等应变假设,视为并联弹簧模型;橡胶颗粒占比较大时混合材料近似满足等应力假设,视为串联弹簧模型.两种模型得到的结果与模拟结果一致.上述结果有利于从微观角度揭示混合颗粒材料弹性行为的变化机制.     

Self-referenced continuous-variable measurement-device-independent quantum key distribution

We propose a scheme to remove the demand of transmitting a high-brightness local oscillator (LO) in continuous-variable measurement-device-independent quantum key distribution (CV-MDI QKD) protocol, which we call as the self-referenced (SR) CV-MDI QKD. We show that our scheme is immune to the side-channel attacks, such as the calibration attacks, the wavelength attacks and the LO fluctuation attacks, which are all exploiting the security loopholes introduced by transmitting the LO. Besides, the proposed scheme waives the necessity of complex multiplexer and demultiplexer, which can greatly simplify the QKD processes and improve the transmission efficiency. The numerical simulations under collective attacks show that all the improvements brought about by our scheme are only at the expense of slight transmission distance shortening. This scheme shows an available method to mend the security loopholes incurred by transmitting LO in CV-MDI QKD.