Effect of pyrolytic polyacrylonitrile on electrochemical performance of Si/graphite composite anode for lithium-ion batteries

The silicon/graphite (Si/G) composite was prepared using pyrolytic polyacrylonitrile (PAN) as carbon precursor, which is a nitrogen-doped carbon that provides efficient pathway for electron transfer. The combination of flake graphite and pyrolytic carbon layer accommodates the large volume expansion of Si during discharge-charge process. The Si/G composite was synthesized via cost-effective liquid solidification followed by carbonization process. The effect of PAN content on electrochemical performance of composites was investigated. The composite containing 40 wt% PAN exhibits a relatively better rate capability and cycle performance than others. It exhibits initial reversible specific capacity of 793.6 mAh g^?1 at a current density of 100 mA g^?1. High capacity of 661 mAh g^?1 can be reached after 50 cycles at current density of 500 mA g^?1.     

光谱成像技术无损鉴别西洋参饮片的研究

应用电可控液晶光谱成像装置,测定不同市售来源的西洋参饮片,以期为其质量控制提供新的方法。系统光谱分辨率5nm,光谱覆盖范围为405～680nm,空间分辨率50lp·mm-1。从成像光谱立方体中提取特征光谱曲线,构建饮片指纹图谱;采用主成分等聚类分析方法解析其指纹图谱,用于饮片真伪鉴别与质量判定。结果与性状,显微及理化鉴定结果相吻合。表明光谱成像分析技术可用于中药指纹图谱的构建和质量评价,操作方法简便、快速、无损。     

First principles simulation technique for characterizing single event effects

This paper develops a new simulation technique to characterize single event effects on semiconductor devices. The technique used to calculate the single event effects is developed according to the physical interaction mechanism of a single event effect. An application of the first principles simulation technique is performed to predict the ground-test single event upset effect on field-programmable gate arrays based on 0.25 μm advanced complementary metal-oxide-semiconductor technology. The agreement between the single event upset cross section accessed from a broad-beam heavy ion experiment and simulation shows that the simulation technique could be used to characterize the single event effects induced by heavy ions on a semiconductor device.     

LD side-pumped 41 W high beam quality acousto-optical Q-switched single-rod Nd:YAG laser

We report a LD side-pumped high beam quality (M _x ² = 1.20 and M _y ² = 1.19) acousto-optic (AO) Q-switched single-rod Nd:YAG laser with a TEM₀₀-mode dynamic stable cavity. At the pump power of 600 W, 41 W TEM₀₀-mode 1064 nm laser was achieved with electro-optical conversion efficiency of 7%. The repetition rate and pulse width were 30 kHz and 102 ns, respectively with pulse energy of 1.4 mJ and peak power of 13 kW. Up to 24 W of 532 nm green laser was generated by external frequency doubling, corresponding to 59% optical conversion efficiency.     

碲化铋取向纳米柱状薄膜热导率测量

将热电材料制作成纳米柱状薄膜结构是一种理论上能有效降低热导率、从而大幅提升热电优值的操控手段。但是随之而来的问题是纳米柱状薄膜热导率的精确获取困难,因为常规的热物性测试手段已无法适用于该类表面多孔、厚度为微米量级结构热输运特性的表征。本文提出利用3ω方法可实现Bi_2Te_3取向纳米柱状薄膜热导率实验表征的测量结构,并且获得了纳米柱状薄膜的热导率和热扩散率值。该方法有望用于微米厚纳米柱状薄膜结构热输运性能的实验评价。     

利用固体物理LED发光原理测量普朗克常数

普朗克常数是物理学中一个重要的常数,利用二极管的量子特性探讨运用发光二极管来测量普朗克常数。通过测量二极管的伏安曲线,确定其阈值电压,根据相关量子理论,间接得出普朗克常数,通过与光电效应法测量普朗克常数的测量结果相比较,结果表明此误差略大,但作为一种新型的实验方法探索,对于开拓学生的综合素养还是非常有益的。     

Wide-band circular polarization-keeping reflection mediated by metasurface

In this paper,we show that circular polarization-keeping reflection can be achieved using reflective metasurfaces.The underlying physical mechanism of the polarization-keeping reflection is analyzed using a reflection matrix.A wideband circular polarization-keeping reflector is demonstrated using N-shaped resonators.Both the simulation and experiment results show that the polarization-keeping reflection can be achieved with a high efficiency larger than 98%over the frequency range from 9.2 GHz to 17.7 GHz for both incident left-and right-handed circularly polarized waves.Under oblique incidence,the bandwidth increases as the incident angle varies from 0°to 80°. Moreover,the co-polarization reflection is independent of the incident azimuth angles.