单驱动变曲率单晶硅反射镜的研究

为了解决高能激光器输出光束的光束质量随时间蜕变的问题,提出了一种主动光学元件的结构,只使用一个驱动器使反射镜的曲率产生可控制的改变,用以补偿高能激光器中增益介质或光学元件因热效应而产生的球差。通过理论模拟计算和实验研究对比验证,这种结构能够使单晶硅基底的反射镜产生微小变形,通过精确控制驱动器,可以使反射镜产生所需要的曲率变化。结果表明,这种主动光学元件可以用于谐振腔内补偿高能激光器中热效应产生的球差项的影响。     

Improving sound diffusion in a reverberation tank using a randomly fluctuating surface

Underwater reverberation environments that satisfy the conditions of uniformity and isotropy of the diffuse field can be used to measure the acoustic characteristics of underwater targets. This study combines two practical indicators — the standard deviation of the absolute sound pressure field (to indicate uniformity) and the analysis of the wavenumber spectrum in the spherical harmonics domain (to indicate isotropy) — for an accurate evaluation of the diffusion of the sound field in a reverberation tank. A method is proposed that can improve the narrow-band diffusion of the sound field by employing a randomly fluctuating surface. An acoustic experiment was performed in a reverberation water tank (1.2 m×1 m×0.8 m), where a randomly fluctuating surface was generated by making waves. The experimental results show that as the wave motion contributes effectively to the random reflection of sound rays in all directions, the uniformity and isotropy are improved significantly when the surface is fluctuating randomly. This work helps to ensure accurate measurements of the characteristics of underwater targets in reverberation tanks.     

利用起伏界面改善非消声水池中的声功率测量

针对非消声水池的声学测量应用,提出了一种在界面起伏的非消声水池中测量水下声源辐射声功率的方法。基于数值方法分析了在非消声水池中利用起伏界面改善低频声源辐射声功率测量的可行性,进一步在一个尺寸为1.2 m×1.0 m×0.8 m的非消声水池中开展实验研究,测量了水声换能器的辐射声功率。实验表明,相对于界面静止的水池,利用造波装置生成随机起伏界面后,声场扩散性明显改善:(1)水池的Schroeder频率从10015 Hz降低到8370 Hz,辐射声功率的测量范围向低频扩展;(2)结合空间平均技术测得的频响曲线起伏程度减小,与自由场值更接近,辐射声功率的测量结果更为准确。所提方法有助于提高非消声水池中水下目标声学特性的测量能力。     

高效叠层OLED白光器件进展

叠层有机发光二极管（Organic Light-Emitting Diode,OLED）白光器件具备低功耗、高亮度、高色域等性能优势。然而,由于效率、寿命及驱动电压等性能仍有较大改进空间,叠层结构的材料及电学结构仍需进一步优化。本文重点介绍叠层OLED白光器件的最新研究进展,总结了三类电荷产生层（Charge Generation Layer,CGL）在工程化应用中存在的问题以及其非破坏性检测方法;综述高效叠层OLED白光器件的“全磷光体系”、“并行通道激子收集”及“混合磷光热活性型延迟荧光（Thermally Activated Delayed Fluorescence,TADF）体系”最新研究成果,对器件寿命问题进行总结,探讨分析“分级掺杂”、“四色混合TADF体系”等从结构方面提出优化方案,并针对不同发光材料体系中的CGL材料及结构综述叠层OLED白光器件实现较低工作电压的技术方法,最后对叠层OLED白光器件的材料和结构提出改进建议。     

随机共振法估计二水听器时延差

针对二元阵航船目标方位估计问题,提出了一种基于随机共振滤波的航船辐射噪声双水听器时延差估计方法。设计了一种随机共振滤波器,提取航船螺旋桨旋转噪声在水听器接收信号中出现的本地时间,并通过滤波结果的互相关来估计目标辐射噪声分别到达两个水听器的时延差。在5 dB的输入信噪比下进行200次仿真,提出方法时延估计的归一化均方误差要低于互谱方法一个数量级。对于海试中的非合作航船,提出的方法可以在1 km距离下准确估计出目标辐射噪声到达双水听器的时延差,从而为在二元阵上实现对航船目标的准确测向提供基础。     

最佳雇主的标准是什么?

最佳雇主看重员工满意度,但满意的员工就是敬业的员工吗?员工满意度高的企业是否就是经营状况好的企业今年5月,全球知名咨询公司翰威特公布了“亚洲最佳雇主”名单,引起了业界和媒体     

人物电视专题片的创作技巧研究

如何创作出优秀的人物电视专题片、将现实生活中典型的人物形象塑造成情感丰富、血肉饱满的电视人物形象等问题,是当前很多人物电视专题片创作者所共同关心的问题.笔者从“人物选题”“前期的采访和拍摄”“确定片子的结构和撰写解说词”以及“把握细节”四个部分简要阐述了人物电视专题片的创作技巧,以期对相关的专题片创作者有所帮助.     

Investigation on threshold voltage of p-channel GaN MOSFETs based on p-GaN/AlGaN/GaN heterostructure

The threshold voltage (V_th) of the p-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) is investigated via Silvaco-Atlas simulations. The main factors which influence the threshold voltage of p-channel GaN MOSFETs are barrier height Φ_1,p, polarization charge density σ_b, and equivalent unite capacitance C_oc. It is found that the thinner thickness of p-GaN layer and oxide layer will acquire the more negative threshold voltage V_th, and threshold voltage |V_th| increases with the reduction in p-GaN doping concentration and the work-function of gate metal. Meanwhile, the increase in gate dielectric relative permittivity may cause the increase in threshold voltage |V_th|. Additionally, the parameter influencing output current most is the p-GaN doping concentration, and the maximum current density is 9.5 mA/mm with p-type doping concentration of 9.5×10¹⁶ cm^-3 at V_GS = -12 V and V_DS = -10 V.