快速发光二极管的性能与分析

本文叙述了用于光通信快速、高辐射度GaAs/GaAlAs双异质结发光管的性能.其电带宽大于60MHz,光带宽在100MHz以上.在200mA辐射度为1017W/cm2·sr.尾纤输出超过160μw(NA=0.2).分析和讨论了影响辐射输出和调制能力的诸因素,并选取了最佳折衷方案.     

关于自同构作用下的不变元

文章主要讨论了代数（环）、（双）Ｈｏｐｆ代数中自同构作用下不变元素的性质，得到一些新的结果：设Ａ是有限维半单代数，则ＡｕｔＡ作用下的不变元属于中心，并且举出反例说明这个性质不能一般化到有限维代数、有限维半单（双）Ｈｏｐｆ代数．     

FNR-Ⅰ核磁共振波谱仪

基于自旋回波的原理研制成功了一台专用于分析磁性材料的核磁共振波谱仪。其工作频率为25-80MHz;输出功率10W,可用它在77-300°k范围测量铁磁材料的共振谱线,增强因数和自旋-自旋弛豫时间T₂;它也可用于测量非磁性固体的宽核磁共振谱线。     

Multi-reference lens-less Fourier-transform holography with a Greek-ladder sieve array

Lens-less Fourier-transform holography has been actively studied because of its simple optical structure and its single-shot recording.However,a low-contrast interferogram between the reference and object waves limits its signal to noise ratio.Here,multi-reference lens-less Fourier-transform holography with a Greek-ladder sieve array is proposed in the experiment and demonstrated effectively to improve the signal to noise ratio.The key technique in our proposed method is a Greek-ladder sieve array,which acts as not only a wave-front modulator but also a beam splitter.With advantages of the common path,single shot,and no need for a lens,this system has enormous potential in imaging and especially in extreme ultraviolet and soft X-ray holography.     

介电球体和无限长圆柱体沉浸在另一介质中的极化模和色散关系

本文导出了介电球体和无限长圆柱体沉浸在另一极性或非极性介质中的极化本征模矢量和色散关系。计算表明,每一介面振动对应两个振动频率,它们分别局限在两种介质的TO频率(ωTo)和LO频率(ωLO)之间。但是,当介质球沉浸在另一非晶介质中时,每一个介面振动只对应一个振动频率,位于内球介质的ωTo和ωLO之间。我们还将Cds微晶无规地分布在另一非晶介质中的实验结果同计算值进行了比较,两者是基本符合的。     

1.3 GHz超导腔磁通排出效应研究

设计并搭建了一套高精度的磁场测量和补偿系统,并结合中国科学院高能物理研究所（IHEP）的2K超导腔垂直测试平台对1.3 GHz 单加速间隙超导腔的磁通排出效应开展了实验研究：利用研制的磁场测量和补偿系统能够精密地测量超导腔赤道位置磁场,并能够将磁场补偿至小于5.0×10⁻⁸ T;并对超导腔不同表面温度梯度下的磁通排出效应进行了测量分析;对钉扎了磁场的超导腔进行了射频性能测试,研究了超导腔电阻对磁通钉扎的敏感度,以及在不同电场梯度下超导腔的表面电阻变化情况。结果表明,研制的高精度磁场测量和补偿系统能够满足超导腔磁通排出研究的需求;高的超导腔表面温度梯度有利于磁通的排出;磁通钉扎电阻的敏感度随着加速电场梯度的增加而增大,导致超导腔的性能下降。此实验研究也为后续超导腔的研制奠定了一定基础。     

Fast Liquid Phase Epitaxial Growth for Perovskite Single Crystals

Semiconductors grown by the solution-processed method have shown low-cost,facile fabrication process and comparable performance.However,there are many reasons why it is difficult to achieve high quality films.For example,lattice constant mismatch is one of the problems when photovoltaic devices made of organ metallic perovskites.In this work,MAPbBr^{MA=CH3NH3^+}perovskites single crystals grown on the surface of MAPbBr2.5 CI0.5 perovskites single crystals via liquid epitaxial growth method is demonstrated.It is found that when the lattice constants of the two perovskite single crystals are matched,another crystal can be grown on the surface of one crystal by epitaxial growth.The whole epitaxy growth process does not require high heating temperature and long heating time.X-ray diffraction method is used to prove the lattice plane of the substrate and the epitaxial grown layer.A scanning electron microscope is used to measure the thickness of the epitaxial layer.Compared with perovskite-based photodetectors without epitaxial growth layer,perovskite-based photodetectors with epitaxial growth layer have lower dark current density and higher optical responsibility.     

Influence of external load on friction coefficient of Fe-polytetrafluoroethylene

A coarse-grained molecular dynamics simulation model was developed in this study to investigate the friction process occurring between Fe and polytetrafluoroethylene(PTFE).We investigated the effect of an external load on the friction coefficient of Fe–PTFE using the molecular dynamics simulations and experimental methods.The simulation results show that the friction coefficient decreases with the external load increasing,which is in a good agreement with the experimental results.The high external load could result in a larger contact area between the Fe and PTFE layers,severer springback as a consequence of the deformed PTFE molecules,and faster motion of the PTFE molecules,thereby affecting the friction force and normal force during friction and consequently varying the friction coefficient.     

G波段500 W带状注扩展互作用速调管设计研究

针对太赫兹频段实现高功率面临物理机制上的难题,设计了一个G波段带状注速调管,展示了基于非相对论带状电子注和扩展互作用技术所能达到的功率水平以及影响性能的物理因素。文中设计基于电压24.5 kV、电流0.6 A,1 mm×0.15 mm的椭圆电子注,以及与之相匹配的互作用系统,即横向过尺寸哑铃型多间隙谐振腔,可以实现高功率和高增益。三维PIC仿真结果显示,在考虑实际腔体损耗的情况下,能够获得超过500 W的功率,电子效率和增益分别达到3.65%和38.2 dB。研究发现,输出功率和效率的提升很大程度上受到多间隙腔模式稳定性以及电路欧姆损耗的制约;输出腔的欧姆损耗对输出功率影响尤为显著,工程设计需要特别考虑。本文的研究为高频段带状注扩展互作用器件的研发打下了良好的基础。