综合传动装置起动扭矩测试试验研究

低温环境起动性能是表征车辆动力性能的一项重要指标。对液力机械传动车辆而言,由于综合传动装置自身技术特点,改善车辆起动性能除应当考虑发动机自身起动阻力外,还应当考虑综合传动装置的起动阻力。在系统分析综合传动装置技术特点和功率流向的基础上,总结了发动机起动过程的主要特征,提出采用稳态试验与动态试验相结合的台架试验方法进行综合传动装置起动扭矩测试。以某高速履带车辆为研究对象,进行了综合传动装置起动扭矩测试。试验结果表明,传动油温的变化和各类油泵的功率消耗是决定综合传动装置起动扭矩大小的关键因素,为改进车辆总体设计和提高车辆起动性能提供了依据。     

Orientations of ZnO grown on GaN

On semipolar epitaxial ZnO grown by chemical vapor deposition consists of two distinct orientations as evidenced by transmission electron microscopy and X‐ray diffraction. The initially grown ZnO on GaN follows the GaN lattice with the epitaxial relationship of // and The other oriented ZnO domains then grow on faceted with and with good coherency with the ‐oriented grains. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Nonlinear properties of the lattice network-based nonlinear CRLH transmission lines

The nonlinear properties of lattice network-based(LNB) composite right-/left-handed transmission lines(CRLH TLs)with nonlinear capacitors are experimentally investigated.Harmonic generation,subharmonic generation,and parametric excitation are clearly observed in an unbalanced LNB CRLH TL separately.While the balanced design of the novel nonlinear TL shows that the subharmonic generation and parametric processes can be suppressed,and almost the same power level of the higher harmonics can be achieved over a wide bandwidth range,which are difficult to find in conventional CRLH TLs.     

PbTiO3/SrTiO3(010)异质界面上的周期性失配位错及电子富集

It is important to determine the effects of misfit dislocations and other defects on the domain structure, ferroelectricity, conductivity, and other physical properties of ferroelectric thin films to understand their ferroelectric and piezoelectric behaviors. Much attention has been given to ferroelectric PbTiO₃/SrTiO₃ or PbZr_0.2Ti_0.8O₃/SrTiO₃ heterointerfaces, at which improper ferroelectricity, a spin-polarized two-dimensional electron gas, and other physical phenomena have been found. However, those heterointerfaces were all (001) planes, and there has been no experimental studies on the growth of (010) PbTiO₃/SrTiO₃ heterointerface due to the 6.4% misfit between two materials. In this study, we selected an atomically flat (010) PbTiO₃/SrTiO₃ heterointerface grown using a two-step hydrothermal method as the research subject, and this is the first experimental report on that interface. Interfacial dislocations can play a significant role in causing dramatic changes in the Curie temperature and polarization distribution near the dislocation cores, especially when the size of a ferroelectric thin film is scaled down to the nanoscale. The results of previous studies on the effects of interfacial dislocations on the physical properties of ferroelectric thin films have been contradictory. Thus, this issue needs to be explored more deeply in the future. This study used aberration corrected scanning transmission electron microscopy (STEM) to study the atomic structure of a (010) PbTiO₃/SrTiO₃ heterointerface and found periodic misfit dislocations with a Burgers vector of a[001]. The extra planes at the dislocation cores could relieve the misfit strain between the two materials in the [001] direction and thus allowed the growth of such an atomically sharp heterointerface. Moreover, monochromated electron energy-loss spectroscopy with an atomic scale spatial resolution and high energy resolution was used to explore the charge distribution near the periodic misfit dislocation cores. The fine structure of the Ti L edge was quantitatively analyzed by linearly fitting the experimental spectra recorded at various locations near and at the misfit dislocation cores with the Ti³⁺ and Ti⁴⁺ reference spectra. Therefore, the accurate valence change of Ti could be determined, which corresponded to the charge distribution. The probable existence of an aggregation of electrons was found near the a[001] dislocation cores, and the density of the electrons calculated from the valence change was 0.26 electrons per unit cell. Based on an analysis of the fine structure of the oxygen K edge, it could be argued that the electrons aggregating at the dislocation cores came from the oxygen vacancies in the interior regions of the PbTiO₃. This aggregation of electrons will probably increase the electron conductivity along the dislocation line. The physics of two-dimensional charge distributions at oxide interfaces have been intensively studied, however, little attention had been given to the one-dimensional charge distribution. Therefore, the results of this study can stimulate research interest in exploring the influence of the interfacial dislocations on the physics of ferroelectric heterointerfaces.     

用转移矩阵法数值研究二维正方介质柱光子晶体的传输特性

利用转移矩阵方法对二维正方介质柱光子晶体的传输特性进行了研究,数值计算研究了不同晶格、同一晶格柱体截面面积不同、放置方位角不同时光子晶体的传输特性。数值结果表明光子禁带的宽度与中心频率和晶格结构有很大关系,正方晶格更易形成平坦光子禁带,柱体截面面积大,则形成的禁带较宽,在其他因素相同的条件下柱体放置的方位角对光子禁带有重要影响。数值研究表明在正方介质柱下设计宽平坦光子禁带时,可以首先考虑正方晶格结构,其次设法使柱体截面尽量大一些,最后可通过柱体放置方位角来微调光子禁带的宽度与中心频率以达到设计要求。     

h-BN型超晶格等离子体光子晶体能带特性研究

六方氮化硼(h-BN)晶格结构是一种类六方对称复式超晶格结构。具有h-BN晶格构型的光子晶体以其宽光子带隙特点受到国内外学者的广泛关注。本文利用不同尺度低压气体放电管与Al₂O₃介质棒周期性排列,构建了新型h-BN型超晶格等离子体光子晶体,实现其空间结构和等离子体参数的动态调控。利用微波透射谱对比研究了h-BN型超晶格与简单三角晶格等离子体光子晶体禁带位置、宽度和数目。分析了放电电流、介质棒阵列数对不同频段光子带隙的影响,以及电磁波入射角度对电磁传输特性的影响。结果表明：等离子体的引入不仅能够形成新的光子带隙,而且可以选择性地使部分禁带位置发生移动;相对于简单三角晶格,h-BN型超晶格等离子体光子晶体呈现出更多光子带隙;Al₂O₃介质棒阵列数对等离子体光子晶体禁带位置、宽度和数目均具有重要影响。电磁波入射角度变化越大,电磁传输特性差别越显著,透射谱相关性越差。本文所设计的新型h-BN型超晶格等离子体光子晶体为制作可调谐光子晶体提供了新的思路,在微波和太赫兹波控制领域具有潜在应用价值。     

光斜入射时偏振器作用的表述

对偏振器特性的分析表明,当光斜入射时,振动方向与偏振器透光轴不平行的光也能通过偏振器,只要该方向与系统光轴与透光轴构成的平面平行。提出了透光平面的概念。利用欧拉角表示光波坐标系和偏振器坐标系之间的变换,得到透过偏振器后偏振光的振动方向及其大小的数学表述,给出了简化表达式及其使用条件。表达式具有一般性,可以直接使用。     

透过率起伏光谱分析法测粒技术

提出的透过率起伏光谱分析法是一种新的颗粒测量方法。采用一细小光束照射匀速流动的颗粒系统,通过采集透射光起伏信号,经统计处理得到透过率的平均值与起伏谱。通过求解逆问题,从透过率的起伏谱中得到颗粒粒径分布信息,再结合透过率的平均值得到颗粒的体积分数信息。给出了关于单层颗粒透过率的平均值与起伏谱的理论表达式,并推广到三维单分散和多分散的颗粒系统。对粒径在32~425μm内的稀薄颗粒系进行了部分实验测试和模拟计算,结果表明该方法可同时对颗粒粒径分布和体积分数进行有效测量。     

随机生长误差对双腔型平顶法布里-珀罗滤波器的影响

在光网络中平顶滤波器可以有效地提高信道光检测的快速性和准确性。利用两个法布里珀罗腔间的串联耦合,可以构建出具有平顶透射特性的双腔型法布里珀罗滤波器。采用传输矩阵的方法,研究了随机生长误差对双腔型平顶滤波器透射特性的影响。模拟分析表明,当两个法布里珀罗腔的物理厚度差超过一个纳米时,在透射谱中就会出现两个高度不同的透射峰;解释了实测器件的透射谱中的双峰不对称性;用界面起伏的概念解释了实测滤波器带宽大于理论值的原因。理论分析与实验结果取得了较好的一致。