基于模糊PI控制的超声波换能器谐振频率跟踪系统仿真

对于超声波换能器谐振系统,利用传统谐振频率跟踪方法动态性能不甚理想,故而采用模糊控制与PI控制相结合的模糊PI控制方法.首先对超声波发生器系统进行建模,再由模糊规则表、模糊化、反模糊化以及在线仿真整定,确定PI控制器参数,最后以相位差作为模糊PI控制器的输入量,进而得到新的驱动频率控制量,新的驱动频率信号驱动逆变器得到换能器此时所需要的控制频率,即换能器谐振频率.计算机仿真结果表明,模糊PI控制方法使整个系统具有更好的动态和静态性能,能有效地使换能器工作在谐振频率.     

Structure and magnetic properties of Ni50Mn35In15 thin film

Thin film of Ni50Mn35In15 Heusler alloy was prepared on Mg O(001) substrate by epitaxial growth in an ultra-high vacuum(UHV) chamber by a Pulsed Laser Deposition(PLD) method. The epitaxial growth process was monitored by in situ reflection high energy electron diffraction(RHEED) and the structure of the film was checked by ex situ X-ray diffraction(XRD), which indicates that high quality Ni50Mn35In15 single crystal film with a face-centered-cubic(fcc) structure could be stabilized on Mg O(001). Magnetic property measurement was also conducted at various temperatures by using physical property measurement system(PPMS). A significant exchange bias was observed for Ni50Mn35In15 film,and the strength of the exchange bias field(HEB) increases with the decrease of temperature. Such a behavior can be ascribed to the fact that the interfacial spin interaction between ferromagnetic(FM) and antiferromagnetic(AFM) cluster is enhanced with the decrease of temperature.     

复合添加炭黑对低碳铝碳材料显微结构与性能的影响

以板状刚玉颗粒、活性氧化铝微粉、Si粉为主要原料,以N220或N990炭黑为碳源,以热固性酚醛树脂为结合剂,在埋炭条件下制备低碳铝碳材料,研究添加不同炭黑对所制得试样显微结构、抗折强度及热震稳定性的影响。结果表明,添加N220炭黑有利于促进材料的致密化和有效发挥纳米炭黑粒子对热应力的吸收作用,降低热冲击对材料结构的破坏,而添加N990炭黑有助于改善铝碳材料的孔结构,有利于试样在高温下形成长径比更大的碳化硅晶须,从而提高材料的力学性能;复合添加N220、N990炭黑能提高低碳铝碳材料试样的强度和抗热震性。材料热震后的抗折强度为7.44 MPa、残余强度保持率为53%~62%。     

基于智能手机Tango传感器的室内三维场景实时感知

室内三维场景实时感知是室内增强现实、三维测图和机器人自主定位与导航的关键技术之一。利用智能手机Tango传感器搭载的单目摄像头和深度相机,根据实时获取的彩色图像和深度信息,研究并提出了一种实时的室内三维场景感知方法;该方法首先根据智能手机Tango传感器获取的彩色图像存在的问题,采用多项式函数对彩色相机进行校正。接着,使用ORB(oriented FAST and rotated BRIEF)算子对彩色图像进行特征提取,利用RANSAC算法剔除误匹配点;并根据优化后的匹配点对采用ICP算法对手机姿态进行初步估计。最后,基于融合空间关系的视觉词典(SDBo W2)对感知的初步室内场景进行闭环检测;并通过图优化得到实时感知的室内三维场景模型。实验表明,方法能利用Tango传感器高效地获取室内场景完整的三维结构信息与纹理。     

用可编程控制器实现的重型平台运输车转向控制系统

根据 1 30t升降平台运输车对转向系统的特殊要求 ,通过分析转向驱动机构的传动特性 ,采用C2 0 0HG可编程控制器为核心设计了该车的转向控制系统 ,编制了控制软件 在以PID为基础的控制算法中结合车轮的不同位置和偏转方向进行计算修正 ,达到了车轮在所处的任意位置向左或向右偏转时 ,转向系统的工作速度特性都基本保持一致 从而使转向过程中各车轮组之间的偏转关系始终满足车辆转向特性要求 ,实现转向控制系统的准确、稳定和快速灵敏     

High concentration retene and methylretene in Silurian carbonate of Michigan Basin

Retene and methylretene have been identified by gas chromatography-mass spectrometry in aromatic hydrocarbon fractions of Silurian carbonate extracts of the Michigan Basin. Retene identified in pre-Devonian carbonates indicates that the compound not only is the biomarker of higher plants but also derived from alga or bacterium. The geochemical significance of methylretene has been discussed.     

Induction of human β-defensin-2 in airway epithelial cells by Streptococcus pneumoniae:involvement of IP3-dependent intracellular calcium release and NF-jB

Human β-definsin-2(hBD-2)is mainly induced by bacterial factors and pro-inflammation mediators in epithelial cells.As the major cause of community-acquired pneumonia,whether Streptococcus pneumoniae(S.pneumoniae)stimulation induces hBD-2 expression in airway epithelial cells is elusive.In this study,we found that S.pneumoniae stimulation induced hBD-2 expression in a time-and concentration-dependent manner in primary human airway epithelial cells.To further reveal the mechanism of S.pneumoniae inducing hBD-2,we found that S.pneumoniae stimulation activated NF-jB signaling pathway.Specific NF-jB inhibitor,PDTC,could reverse the induction of hBD-2 by S.pneumoniae.We also found that cellular inner Ca2+ signaling is involved in the S.pneumoniae-induced hBD-2.Taken together,our findings indicated that S.pneumoniae can stimulate the expression of hBD-2 in airway epithelial cells and NF-jB and inositol triphosphate-dependent intracellular calcium release is involved in this induction.     

第五方物流的GIMIS对讲调度平台

综述了第五方物流及其相关技术发展,研究基于第五方物流的GIMIS中间件,提出基于第五方物流的GIMIS对讲调度运营平台.     

大颗粒细水雾测量中光学系统布局的数值实验研究

本文通过计算模拟和实验研究，用三维ＡＰＶ（ＡｄａｐｔｉｖｅＰｈａｓｅ／ＤｏｐｐｌｅｒＶｅｌｏｃｉｍｅｔｅｒ）系统对雾场中大粒子的特性参数进行了测量，对三维ＡＰＶ的光路系统进行了选择设定。     

α类蛋白的构建模式及拓扑结构预测

给出了α类蛋白的构建规则，指出了螺旋片段的长短是决定相邻两个片段取向的重要原因．讨论了４螺旋束的构建及理论模式，对α类蛋白的分类进行了补充，给出了区分平行和垂直拓扑结构的简明预测规则