基于FPGA的时延辅助定位FBG传感系统的研究与设计

由于受光源谱宽和光纤Bragg光栅传感波长移动范 围的限制,FBG传感系统中可复用的FBG数量 受到很大限制。为了解决这种限制问题,提出通过传感信号的时间延迟对传感FBG进行定位 的方法。 设计出基于FPGA的时延辅助定位FBG传感系统,用Fabry-Peror(F-P)腔和时延定位结合的 方式对传感信息进 行解调,用FPGA进行数据处理。搭建了实验系统,进行了简单的实验。实验结果表明, 本文系统增加可复用FBG数量的方法实用性强,精度高。     

Vehicle active steering control research based on two-DOF robust internal model control

Because of vehicle’s external disturbances and model uncertainties, robust control algorithms have obtained popularity in vehicle stability control. The robust control usually gives up performance in order to guarantee the robustness of the control algorithm, therefore an improved robust internal model control(IMC) algorithm blending model tracking and internal model control is put forward for active steering system in order to reach high performance of yaw rate tracking with certain robustness. The proposed algorithm inherits the good model tracking ability of the IMC control and guarantees robustness to model uncertainties. In order to separate the design process of model tracking from the robustness design process, the improved 2 degree of freedom(DOF) robust internal model controller structure is given from the standard Youla parameterization. Simulations of double lane change maneuver and those of crosswind disturbances are conducted for evaluating the robust control algorithm, on the basis of a nonlinear vehicle simulation model with a magic tyre model. Results show that the established 2-DOF robust IMC method has better model tracking ability and a guaranteed level of robustness and robust performance, which can enhance the vehicle stability and handling, regardless of variations of the vehicle model parameters and the external crosswind interferences. Contradiction between performance and robustness of active steering control algorithm is solved and higher control performance with certain robustness to model uncertainties is obtained.     

“Dark hole” cure in Ba4.2Nd9.2Ti18O54 microwave dielectric ceramics

Large size Ba_4.2Nd_9.2Ti₁₈O₅₄ (BNT) ceramics doped with MnCO₃, CuO and CoO were prepared by the conventional solid-state method. Only a single BaNd₂Ti₄O₁₂ phase was formed in all samples. No second phase was found in the XRD patterns. The bulk density increases slightly because of the dopants. The SEM results showed that the grain size of Mn²⁺and Cu²⁺-doped BNT ceramics became larger with the increasing amount of dopants. The permittivity of all samples stays the same. However, the Q×f value of BNT ceramics increases by doping, especially with Mn²⁺ ions. The conductivity of BNT ceramic doped with Mn²⁺(0.5 mol‰) under high temperature is lower than that without doping. There are fewer defects in Mn²⁺-doped BNT ceramics. The XPS results indicated that Ti reduction was suppressed in BNT ceramics doped with 0.5 mol‰ Mn²⁺. BNT ceramics doped with 0.5 mol‰ Mn²⁺ ions sintered at 1320 °C for 2 h exhibited good microwave dielectric properties, with ε_r=88.67, Q×f=7408 GHz and τf = 82.98 ppm/°C.     

Preparation and electrical properties of (1−x)SrBi2Nb2O9−xBiFeO3 lead-free piezoelectric ceramics

Lead-free piezoelectric ceramics, (1−x)SrBi₂Nb₂O₉−xBiFeO₃ [(1−x)SBN−xBFO] (x=0.0, 0.03, 0.05, 0.07, 0.10) were prepared by a conventional solid-state reaction method. The crystal structure, microstructure and electrical properties were systematically investigated. All compositions formed layered perovskite structure without any detectable secondary phases. Plate-like morphology of the grains which is characteristic for layer-structure Aurivillius compounds was clearly observed. The excellent electrical properties (e.g., d₃₃~19 pC/N, 2P_r~18.8 μC/cm²) and a high Curie temperature (e.g., T_c~449 °C) were simultaneously obtained in the ceramics with x=0.05. Additionally, thermal annealing studies indicated that the BFO modified SBN ceramics system possessed stable piezoelectric properties, demonstrating that the modified SBN-based ceramics are the promising candidates for high-temperature applications.     

Structural,dielectric and piezoelectric properties of (Bi0.5Na0.5)TiO3–(Bi0.5K0.5)TiO3–Bi(Zn0.5Ti0.5)O3 thin films prepared by sol–gel method

Lead free (1−x)(0.8Bi_0.5Na_0.5Ti_0.5O₃–0.2Bi_0.5K_0.5TiO₃)–xBiZn_0.5Ti_0.5O₃ (x=0–0.06) (BNT–BKT–BZT) thin films were deposited on Pt(111)/Ti/SiO₂/Si(100) substrates by a sol–gel processing technique. The effects of BZT content on the structural, dielectric, ferroelectric and piezoelectric properties of the BNT–BKT–BZT thin films were investigated systematically. The BNT–BKT–BZT thin films undergo a transition from ferroelectric to relaxor phase with increasing temperature. The phase transition temperature decreases with the increase of BZT content. The BNT–BKT–BZT thin film with x=0.04 exhibits the best ferroelectric properties (P_max=40 µC/cm² and P_r=10 µC/cm²), largest dielectric constant (ε=560) and piezoelectric constant (d₃₃=40 pm/V). This finding demonstrates that the BNT–BKT–BZT thin film has an excellent potential for demanding high piezoelectric properties in lead free films.     

毛细管电泳脉冲安培法测定二氯苯酚的离解常数

基于毛细管电泳三脉冲安培检测技术,利用毛细管电泳中不同pH值条件下有效淌度(μeff)与缓冲溶液中[H ]的非线性关系,以及1／μeff缓冲溶液中[H ]的线性关系,测定了2,4-二氯苯酚(DCP)的离解常数。考察了三脉冲电位及时间、电解液的浓度、酸度、电泳电压及进样时间对测定的影响,得到了最优测定条件。以微盘铂电极为工作电极,Ag/AgCl为参比电极,三脉冲电位为:C1-300mV, t1200ms;E2600mV,t2100ms;E31000mV,t3100ms。该方法具有简单、快速、准确等特点。测得二氯苯酚的pK,为7.91。     

基于核心概念集的多语言Ontology

随着Web资源的日益丰富,人们需要跨语言的知识共享和信息检索。一个多语言Ontology可以用来刻画不同语言相关领域的知识,克服不同文化和不同语言带来的障碍。对现有的构建多语言Ontology方法进行分析和比较,提出一种基于核心概念集的多语言Ontology的构建方法,用一个独立于特定语言的Ontology以及来自不同自然语言的定义和词汇的同义词集来描述相关领域的概念。用该方法构建的Ontology具有良好的扩展能力、表达能力和推理能力,特别适合分布式环境下大型Ontology的创建。     

Free electron laser based on the Smith-Purcell radiation

The electromagnetic radiation is sti mulated when anelectron beampasses a metallic periodic structure like adiffraction grating at a fixed distance close to the sur-face.This phenomenon is known as the Smith-Purcelleffect .The radiation mechanism was pred…     

The luminescence of magnesium tungstate dihydrate,MgWO4·2H2O

The luminescence of MgWO₄.2H₂O contains two emission bands, one due to the tungstate tetrahedron, and another one related to the hydrate group. The former is compared with the tungstate luminescence of anhydrous MGWO₄.     

甲基蓝体系共振瑞利散射法测定蛋白质

在pH2.36的BR介质中,甲基蓝与蛋白质相互作用生成复合物,使最大波长350nm的共振光散射光谱得到增强,增强程度与蛋白质浓度成正比。据此建立了测定蛋白质的新方法。人血清白蛋白、牛血清白蛋白的线性范围分别为0～2.4mg/L、0～2.8mg/L,相应检出限分别为39.3、43.4μg/L。方法的稳定性好,灵敏度高,用于牛奶、豆浆、人血清、尿液中总蛋白质的测定,结果与考马斯亮蓝法一致。