取代二苯多烯和取代聚二乙炔的三阶非线性光学性质

为了设计新的具有较高非线性极化率和光损耗小的有机非线性光学（ＮＬＯ）材料，需要了解不同的有机结构对分子非线性的影响。在此基础之上，建议用平行对比的方法来近似估算取代二苯多烯和聚二乙炔（ＰＤＡ）的三阶非线性光学极化率。     

通信接收机的抗信道干扰问题

接收机产生干扰的机理分析是提高其抗干扰性能的基础和前提,为此文中对其作了详细阐述,并对降低接收机共信道干扰的改善措施也作了简明分析研究。本文为从事通信工作者理解与应用有关内容提供一轮廓性依据。     

基于数据的GSM系统天馈线干扰快速排查法

天馈线系统产生的无源互调干扰有其独特性,实践中多采用测试仪表现场排查方法,存在效率低下、准确率低等问题。针对这些问题,提出了利用基站系统作为互调检测硬件平台的天馈线干扰非现场排查法,可以通过干扰频谱数值对比,从复合干扰中分离出由天馈系统引发的互调干扰并对其进行定性,因而提高了检测排查的效率和准确性。     

基于三阶超螺旋滑模观测器算法的机器人力矩估计方法

本文研究了六自由度(6-DOF)机器人关节力矩估计问题.为了提高机器人关节力矩估计精度,本文设计了一种三阶超螺旋滑模关节力矩观测器.在对观测器系统进行稳定性分析时,本文设计了一种新的Lyapunov函数证明了观测器闭环系统的稳定性.与已有的机器人力矩观测器结果不同,该力矩观测器仅以机器人关节角度作为观测器输入信号,减少了对机器人系统信息的依赖.最后,以6-DOF工业机器人为对象,开展实验验证.实验结果表明,与传统线性力矩观测器相比,本文提出的滑模力矩观测器估计误差小,验证理论的正确性.     

Exploring the potential of boron-doped nanographene as efficient charge transport and nonlinear optical material: A first-principles study

Owing to their excellent electrochemical properties, graphenes found applications in several fields ranging from semiconductors, solar cells, field effect transistors, and nanoscale electronic devices as well as in nonlinear optical (NLO) applications. The structural features, electro-optical, charge transport and nonlinear optical properties of the boron-doped graphene (BG) compound 1 were studied using density functional theory methods The BG compound comprises a central electron deficient site of boron atoms, which can serve as electron acceptor while terminal alkoxy groups as donors leading to powerful donor-π-acceptor (D-π-A) configuration. The experimental crystal structure was successfully reproduced by optimized ground state geometry at PBE0/6-311G* level of theory for isolated molecule. The experimental lattice parameters, geometries, crystal presentation and alignment of molecules in the unit cells as well as their packing orientation of BG compound 1 was also efficiently reproduced by applying periodic boundary conditions (PBC) at PBE level. The comprehensive intramolecular charge transfer (CT) was realized from terminal rings of the HOMO to the electron deficient sites of boron atoms of the LUMO. The nature of BG compound 1 might be more towards hole transport even though its hole reorganization energy is twice than that of the electron one due to the significant higher hole transfer integral values. The superior hole transfer integrals and intrinsic mobility values of the BG compound 1 might lead remarkable hole transport contender as compared to many other organic materials. The narrow band gap, density of states profile, dielectric function, uniform conductivity functions and noteworthy electronic as well as CT properties revealed that the BG compound 1 might be proficient optoelectronic contestant having intermolecular CT as well as intramolecular CT with optimal stability. A comparison of static third-order polarizability <γ> of BG compound 1, as calculated in present investigation, was also performed with some standard NLO molecules as well as graphene nanoflakes. Moreover, longitudinal component γ_zzzz of parent compound has been found 12 and 4 times larger than those of previously reported open-shell poly aromatic hydrocarbons (PAH). Interestingly, by increasing the donor ability, i.e., introduction of C₂H₂PhNH₂ groups in place of OC₄H₉ groups (BG compound 3) at terminal positions boosts the <γ> amplitude ∼ 8 times than that of its parent BG compound 1.     

Modeling power and intermodulation behavior of microwave transistors with unified small‐signal/large‐signal neural network models

This article presents a detailed procedure to learn a nonlinear model and its derivatives to as many orders as desired with multilayer perceptron (MLP) neural networks. A modular neural network modeling a nonlinear function and its derivatives is introduced. The method has been used for the extraction of the large‐signal model of a power MESFET device, modeling the nonlinear relationship of drain‐source current I_ds as well as gate and drain charge Q_g and Q_d with respect to intrinsic voltages V_gs and V_ds over the whole operational bias region. The neural models have been implemented into a user‐defined nonlinear model of a commercial microwave simulator to predict output power performance as well as intermodulation distortion. The accuracy of the device model is verified by harmonic load‐pull measurements. This neural network approach has demonstrated to predict nonlinear behavior with enough accuracy even if based only on first‐order derivative information. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 276–284, 2003.     

Nonlinear optical responses of erbium-doped YAG ceramics

By performing the Z-scan measurements with ultrafast femtosecond laser centered at 800 nm wavelength, we can unambiguously distinguish the real and imaginary part of the third-order optical nonlinearity of the erbium-doped YAG ceramics. The reverse saturable absorption of the erbium-doped YAG ceramics has been observed experimentally, and the nonlinear refractive index of the ceramics is estimated to be about 10⁻²¹ m²/W. The experimental results may provide design guidelines for the high power laser design and its applications.     

无线电测控装备互调分析方法研究

在大型试验、演练中,靶场多台大型测控装备分别布设在陆基和海基不同站点,各装备相对于被测控目标的方位、俯仰不同,为达到合理布站、更好地完成测控任务,需要对装备进行合理的组网和互调分析。对互调理论应用于靶场试验中的方法进行了分析,对频率分配、装备布站、电磁兼容性等进行了研究,给出了计算模型和参数取值原则。