TiCl~4-Ga还原体系中芳基三卤甲烷的还原偶联反应

研究了在低价钛(TiCl~4-Ga)试剂作用下,α,α,α-三卤甲基芳烃的还原偶联反应,得到了脱卤偶联产物-二卤代烯烃、炔烃。     

激光成像系统中高耦合效率单模光纤耦合器设计

在三维激光成像系统中,其性能表现绝大部分决定于器件接收背反射光能幅度的大小,以及耦合器中空间光到光纤纤芯的光耦合效率的高低.为了增加耦合器中激光能量到纤芯内的耦合效率,提出了一种新型非球面透镜到锥形光纤头的耦合器的设计,得到了该耦合器中耦合效率的解析表达式.通过优化耦合透镜的倒相对孔径,对应波长为1 310 nm和1 ...     

Study of intensity-dependent nonlinear optical coefficients of GaP optical crystal at 800 nm by femtosecond pump-probe experiment

The intensity-dependent two-photon absorption and nonlinear refraction coefficients of GaP optical crystal at 800 nm were measured with time-resolved femtosecond pump-probe technique. A nonlinear refraction coefficient of 1.7×10-17 m2/W and a two-photon absorption coefficient of 1.5×10-12 m/W of GaP crystal were obtained at a pump intensity of 3.5×1012 W/m2. The nonlinear refraction coefficient saturates at 3.5×1012 W/m2, while the two-photon absorption coefficient keeps linear increase at 6×1012 W/m2. Furthermore, fifth-order nonlinear refraction of the GaP optical crystal was revealed to occur above pump intensity of 3.5×1012 W/m2.     

OFDM技术在Beyond3G中的应用

目前,继3G 之后的下一代移动通信系统“Beyond 3G ”或“4G ”的技术研究和标准建议工作正在紧张展开,预计下一代移动通信系统的速率可达到20M bit/s ,最高速率可达100M bit/s,国际电信联盟已经着手有关标准的制定工作。正交频分复用(O FD M )技术因其网络结构高度可扩展,具有良好的抗噪声性能和抗干扰能力以及频谱利用率高而被普遍认为是下一代移动通信系统必不可少的技术。 一、Beyond 3G 系统的特点[1,2] Beyond 3G 将是一种全IP 的网络结构(包括各种接入网与核心网),各种针对不同业务的接入系统连接到基于IP 的核心网中,形成…     

子阵平滑对小快拍数下CAB算法的改善

研究了子阵空间平滑自适应阵列方法对CAB算法性能的改进。数字波束形成是DBF雷达实现的关键技术。在诸多数字波束形成算法中，由于CAB算法在较高信干噪比条件下具有较快的收敛速度，因此具有较强的优势。但是该算法在较少的快拍数情况下不能保证在输出SINR收敛并趋向于最优值的同时保持较低的自适应旁瓣电平。因此，采用空间子阵平滑方法并利用子阵级自适应处理结构来等效提高CAB算法的快拍数，从而抑制干扰和噪声。仿真结果证明了该方法的有效性。     

Phase Controlled Laser Interference for Tunable Phase Gratings in Dye-Doped Nematic Liquid Crystals

A phase controlled multi-beam interference is applied to excite the doped liquid crystals. Control of the phase difference between the exciting beams allows the external control of the interference pattern inside the liquid crystal. The dynamic variation of the grating is made possible with a time-dependent phase change to derive the nonlinear refractive index as well as the responding speed of the material. The induced grating structure is numerically modelled with reorientational phase gratings in the liquid crystal, and the diffraction dynamics is found to be in good agreement between theoretical and experimental results.     

Research on cross-chain and interoperability for blockchain system

At present, there is an urgent need for blockchain interoperability technology to realize interconnection between various blockchains, data communication and value transfer between blockchains, so as to break the ‘ value silo’ phenomenon of each blockchain. Firstly, it lists what people understand about the concept of interoperability. Secondly, it gives the key technical issues of cross-chain, including cross-chain mechanism, interoperability, eventual consistency, and universality. Then, the implementation of each cross-chain key technology is analyzed, including Hash-locking, two-way peg, notary schemes, relay chain scheme, cross-chain protocol, and global identity system. Immediately after that, five typical cross-chain systems are introduced and comparative analysis is made. In addition, two examples of cross-chain programmability and their analysis are given. Finally, the current state of cross-chain technology is summarized from two aspects: key technology implementation and cross-chain application enforcement. The cross-chain technology as a whole has formed a centralized fixed mechanism, as well as a trend of modular design, and some of the solutions to mature applications were established in the relevant standards organizations, and the cross-chain technology architecture tends to be unified, which is expected to accelerate the evolution of the open cross-chain network that supports the real needs of the interconnection of all chains.     

基于编码拆分的跨网通信技术优化研究

现有的WEBee系统可通过模拟接收器的标准时域波形在物理层面实现WiFi到ZigBee的跨网通信,但该系统存在单次传输帧接收率不高,符号错误率较大等局限.针对该局限,本文提出了一种基于循环前缀前的编码拆分优化方案,主要思想是对ZigBee前导码中的同步码序列进行编码拆分,可有效降低循环前缀操作时出现的错误,提高帧接收率.结果表明该方案优化系统单次传输的帧接收率可达65.2％,相比原系统提高了8.1％,且单次传输的符号错误率从2.7％降低至1.8％.