大型推土机推土刀板模态分析

本文采用随机锤击法进行激励，对大型推土机刀板进行模态试验，并用正交分量法识别模态参数，获取了刀板作业状态下的固有频率，因有振型，模态阻尼比等动态特性。这些参数可用来进一步计算刀板的动态响应及动态应力。     

Excitation dynamics of cerium in niobate crystals

Transient gratings have been observed in Ce³⁺-doped SBN(Sr_xBa_1−xNb₂O₆) and KNSBN (potassium–sodium SBN) niobate crystals by picosecond-pulse, two-photon excitation using degenerate four-wave-mixing (DFWM) in the case where the C-axis is perpendicular to the grating vector. The charge-carriers produced in the conduction band are responsible for the observed coherent signal associated with the third-order nonlinearity, while a post-coherent, slow signal is due to the temporal lattice distortion associated with formation of Nb⁴⁺-hole polarons. Following excitation of the niobate host, energy transfer between host and rare-earth ions occurred, resulting in the excited state of cerium ions being populated and cross-luminescence from host to Ce³⁺ being observed. This excitation mechanism was also verified by a fluorescence study.     

The evaluation of transition matrix elements for atomic excitations by a screened Coulomb potential

We have developed a FORTRAN code for calculating screened potential matrix elements for transitions between atomic bound states. In the applied procedure, the target wave functions can be arbitrarily chosen, and a wide class of screening potentials can be applied. The program includes subroutines for the calculation of the modified Bessel functions of fractional order and their derivatives for a broad range of argument and order.     

Evaluation of excitation function by TALYS code for producing ^109Cd with different ion beams

ion of millicurries of the radioisotope with incident beam energy less 15 MeV using low energy accelerator.     

Studies on NaLn(WO_4)_2 Single Crystals(Ln=La,Pr,Nd)

The crystals of NaLn(WO4)_2(Ln=La,Pr,Nd)are grown from a melt of LiCl-Na_2WO_4 flux by slowcooling method.The chemical analysis data show that the crystals are NaLa(WO_4)_2,NaPr(WO4)_2 andNaNd(WO_4)_2 respectively.The structures of the crystals are ascertained that they belong to scheelite structureof the tetragonal system with a space group of 14_1/a.The lattice parameters of the crystals have beencalculated.It is found that the cell volume of NaLn(WO_4)_2 crystals decrease with a decrease of Ln~(3 )radius.The bond distances and their angles in NaLa(WO_4)_2 and NaNd(WO_4)_2 are given.It is found that inaccordance with the decrease of ionic radii of Ln~(3 )due to increase of atomic number,the bond distances betweenLn-O,Ln-Ln and W-O decrease regularly.The infrared spectra of NaLn(WO_4)_2 are measured.Thetetrahedra characteristic absorptions of WO_4~(2-)are shown.The sensitization of host lattice is observed from theexcitation and fluorescent spectra of NaLa(WO_4)_2 and NaPr(WO_4)_2.     

基于双闭环励磁电调矿用电铲电控系统研究

目前矿用电铲常见的是采用磁性触发器进行控制,存在系统动态响应慢、动态指标欠佳、电铲特性不理想、结构复杂等缺陷,采用电流内环和电压外环的双闭环励磁电调方案,设计了一种先进的电子集成电铲电控系统,详细介绍了系统电路结构,尤其是电压、电流调节器及其反馈电路与特性适配电路的基本原理和功能特点。在实际应用中,该系统具有结构简单、技术指标性能好、动态响应快等优点,较好地满足了现场控制和实际生产的要求。     

同步发电机励磁系统电压模式下并网策略研究

发电机机端电压平滑并网对于电网及发电机本身的稳定性而言至关重要。本文首先建立了同步发电机励磁控制系统电压调节模式下的控制系统模型,并应用新型高精度数模混合仿真软件Saber Designer对该模型进行理论分析与仿真验证,对励磁控制系统的起励、并网切换及改善电力系统工作稳定性的控制策略进行了研究。实验结果表明本文采用的并网策略能够实现发电机平滑并网,有助于设计出高性能的全数字化励磁控制系统。     

铁东变电所1号主变复式比率差动保护动作事件分析

针对铁东变电所1号主变复式比率差动保护动作事件发生背景、经过、现象及处理措施进行了介绍。根据该事件的现象、保护整定值和励磁涌流的特点，对此次事件进行了详细分析。     

Dynamic Behavior of Nonlinear Cable System. IV

A suitable filter response is defined that allows studies of the effects of excitation bandwidth on the responses of geometrically nonlinear dynamic systems. For such a random excitation, as the bandwidth approaches zero, the mean square displacement response of a linear single-degree-of-freedom (SDOF) system approaches the mean square response to harmonic excitation. Studies of mean square responses of a nonlinear SDOF model of a cable system are presented. The set of nonlinear equations for the response moments are truncated using Gaussian closure and solved using continuation techniques as implemented in the program AUTO. Surfaces of turning point loci are computed in the parameter space of excitation bandwidth, excitation central frequency, and system damping. These surfaces provide values of the three parameters that separate regions with multiple mean square responses from regions with unique mean square responses. Response time histories are computed by simulation to illustrate system behavior in regions with multiple stable mean square responses.     

发电机励磁、汽门理电阻挚动的非线性协调控制

利用非线性状态PI控制能直接对非线性确定对象进行控制的特点,设计了发电机励磁、汽门电阻挚动的非线性状态PI协调控制器。该协调控制器先根据等面积法测设计出电阻挚动的控制策略。然后将电阻挚动的制作用视为发电机励磁与汽门协调控制的外部扰动,根据非线性状态PI控制器能将系统的外扰和不确定性等不确定因素进行实时补偿的特点,实现发电机励磁、汽门与电阻挚动的协调控制。仿真计算表明发电机励磁、汽门与电阻挚动的非线性状态PI协调器能够有效地提高系统的暂态稳定性。