Unveiling the presence of mixed oxidation states of Europium in Li7+δEuxLa3−δZr2−δO12−δ garnet and its impact on the Li-ion conductivity

Recently, lanthanides have been employed by researchers to examine their impact on the structure and properties of Li₇La₃Zr₂O₁₂ (LLZO) garnets. In this regard, we developed Europium oxide (Eu₂O₃) doped LLZO (Li_7+δEu_xLa_3−δZr_2−δO_12−δ) solid electrolyte which demonstrates a cubic phase with the symmetry of Iad (No.230) at room temperature. In this investigation, different concentrations of Eu ranging from 0.1 to 0.6 atoms per formula unit (pfu) were doped into Li₇La₃Zr₂O₁₂ to evaluate the impact of Eu on the stability of the cubic phase and thereby the ionic conductivity. The results unveiled that upon doping Eu³⁺ ions, the Eu²⁺ state is also formed and is then self-doped into the structure in which Rietveld refinement coupled with XPS, EPR, and solid-state NMR suggests that Eu³⁺ ions most probably partially occupy Zr⁴⁺ (16a) site, the Eu²⁺ ions occupy La³⁺ (24d) site, and the Li⁺ ions occupy two different sites (24d and 96h). It was further found that such a site preference induces distortion at LaO₈ polyhedrons opening up the neck for Li-ions diffusion, thereby enhancing the ionic conductivity. Moreover, it was revealed that Li-ions probably hop from 96h to 24d and then to 96h site to generate the Li-ion movement. Overall, by introducing Eu ions into the LLZO structure, an enhanced bulk ionic conductivity of 0.30 × 10⁻³ S/cm at 298 K with a minimum electronic conductivity of 2.547 × 10⁻⁹ S/cm at 298 K was achieved.     

基于CITAF-HAF的立方调频信号参数估计

针对立方调频（Cubic Frequency Modulated,CFM）信号的参数估计问题,提出了一种基于高阶模糊函数（High order Ambiguity Function,HAF）和相参积累三阶自相关函数（Coherently Integrated Trilinear Autocorrelation Function,CITAF）的参数估计方法。利用HAF将立方相位信号降阶为二次调频（Quadratic Frequency Modulated,QFM）信号,再利用CITAF完成参数估计。由于CITAF能够在时域和时延域完成信号能量的二维相参积累,其实现过程利用复乘、傅里叶变换和加法操作即可完成,因此该方法能够提高参数估计的分辨率和抗噪声干扰能力,并保持较低的计算量。实验结果证实了该算法的有效性和性能上的优越性。     

ISAR Imaging of Fluctuating Ship Target Based on a Novel Approach for Cubic Chirplet Decomposition with Local Polynomial Wigner Distribution

基于局域多项式魏格纳分布的三次Chirplet分解新方法及其在舰船目标逆合成孔径雷达成像中的应用

王勇,高建军

(哈尔滨工业大学 电子与信息工程学院)

创新点说明：

1） 本文提出一种三次Chirplet分解的新方法。通过计算散射点回波信号的局域多项式魏格纳分布,可获得三次Chirplet基函数的参数估计。解决了传统参数估计方法存在的算法复杂、计算量大等问题。

2） 本文提出一种基于三次Chirplet分解的舰船目标逆合成孔径雷达成像新方法,解决了舰船目标复杂运动情况下,传统的成像方法成像质量下降的问题。本文方法可获得舰船目标高质量的成像结果。

研究目的：

本文的写作目的主要是为了解决舰船目标复杂运动情况下如何提高成像质量的问题。同时提出新的信号参数估计方法,解决传统方法存在的算法复杂、计算量大等问题。

研究方法：

1） 基于局域多项式魏格纳分布的三次Chirplet分解的新方法。通过峰值搜索,可获得三次Chirplet基函数三次相位系数的估计,进而通过解调频等技术获得其它信号参数的估计。对于多分量信号,可通过洁净技术逐一估计出不同信号分量的参数。

2） 舰船目标复杂运动情况下,散射点回波信号可用多分量多项式相位信号模型来进行刻画。通过对多项式相位信号进行三次Chirplet分解,可获得其内在结构信息。进而采用距离——瞬时多普勒成像算法,可获得舰船目标高质量的成像结果。

仿真数据和外场实测数据成像结果验证了本文方法的有效性。

结果：

1） 文中构造了三维摆动的舰船目标及其回波信号模型,如文中图2所示。相应的成像结果如文中图4所示。此时获得了舰船目标高质量的成像结果。

2）文中选取舰船目标的外场实测数据,相应的成像结果如文中图6和图7所示,进一步说明了本文算法的适应性。

结论：

基于局域多项式魏格纳分布的三次Chirplet分解的新方法,可获得三次Chirplet基函数的高精度参数估计结果。将该方法应用于复杂运动舰船目标的逆合成孔径雷达成像中,可获得舰船目标高质量的成像结果。

关键词：三次Chirplet分解;局域多项式魏格纳分布;逆合成孔径雷达成像

     

ISAR imaging algorithm for targets with the complex motion based on the high-order ambiguity function-Lv's distribution

In ISAR imaging for targets with the complex motion, since the azimuth high order phase terms caused by the time-varying rotation vector will deteriorate the azimuth focusing quality, the traditional RD algorithm and LFM model are not appropriate. Thereby, in the case when the received signal can be modeled as cubic phase signals (CPSs), this paper proposes an ISAR imaging algorithm based on HAF-LVD (high-order ambiguity function-Lv's distribution). First, this algorithm defines a novel double lag parametric instantaneous autocorrelation function, and then applies the scaling operator to remove the coupling and utilizes FFT to achieve the energy accumulation. Finally, the non-searching estimation of the moving parameter and the ISAR images for targets are accomplished by the obtained HAF-LVD. Because of the introduction of the scaling factor, this algorithm can flexibly deal with more changeful and hostile ISAR environment without loss of the anti-noise performance and computational efficiency. Simulation results validate the effectiveness of the ISAR imaging approach.     

椭圆曲线 y^2＝px（x^2＋4）的正整数点

设p是奇素数,本文证明了,当p≠5时,椭圆曲线y^2＝px（ x^2＋4）至多有1组正整数点（x,y）;p ＝5时恰有2组正整数点（1,5）,（4,20）。     

基于三次B样条有限元法的BBMB方程数值解

对空间和时间坐标分别采用三次B样条有限法和Crank-Nicolson差分法求得非线性BBMB方程的数值解,应用Von-Neumann稳定性理论证明了此方法的无条件稳定性,并且通过两个例子验证了该方法的有效性与可行性.     

合成工艺参数对金刚石质量影响的研究

本文较系统地在6×8MN型和6×10MN型压机上，研究了φ23mm腔体合成工艺参数对金刚石质量的影响。批量试验结果表明，平均单产达1．68g（8．4克拉），＞60目的达77％，＞120N的达41．3％，锤耗9kg／万克拉。     

渐开线螺旋花键的滚压加工

阐述了渐开线螺旋花键的滚压原理、坯料计算、工装设计及材料的选择，对滚压加工进行了很好的研究。实践表明，采用滚压技术加工的渐开线螺旋花健，不仅极大地提高了生产效率，且制件的质量也大为提高。     

CYCLIC DEFORMATION OF FACE CENTERED CUBIC CRYSTALS AND ITS DISLOCATION INTERACTION MODEL——Ⅱ.DISLOCATION INTERACTION MODEL OF CYCLIC DEFORMATION

A dislocation interaction model has been proposed for cyclic deformation of fcc crystals.Ac-cording to this model,cyclic stress-strain responses and saturation dislocation structures of acrystal are associated with the modes and intensities of dislocation interactions between slipsystems active in the crystal; and,hence,may be predicted by the location of its tensile axis inthe crystallographic triangle.This model has successfully explained the different behaviours ofdouble-slip crystals and multi-slip behaviours of some crystals with orientations usually con-sidered as single-slip ones.     

活性元素Ti在CBN与钎料结合界面的特征

通过扫描电镜、能谱仪、X射线衍射仪研究了Ag-Cu-Ti钎料中的活性元素Ti在钎料与立方氮化硼（CBN）磨粒高温钎焊结合界面的扩散现象，并运用动力学分析对界面反应层的生长过程及反应激活能进行了探讨。结果表明：钎焊过程中，钎料中的活性元素Ti明显向磨粒侧扩散偏聚并发生化学反应，实现了磨粒与基体材料的牢固结合；钎焊CBN磨粒表面生成的TiB2和TiN化合物形貌接近平衡状态下生长的理想形貌；界面反应层在钎焊温度1153K～1193K，保温时间5min～20min之间依据抛物线生长法则所得扩散激活能值表明其生长过程主要受新生TiN影响。