A constant modulus algorithm for blind equalization in α-stable noise

Channel noise is often assumed to be Gaussian in most of the existing channel equalization algorithms. The performance of these algorithms will degrade seriously when the noise is non-Gaussian. This paper deals with the problem of blind channel equalization in impulsive noise environment that is modeled as α-stable process. A modified adaptive error-constrained constant modulus algorithm (MAECCMA) is proposed by soft-limiting the amplitude of the equalizer input and transforming the error signal of the original adaptive error-constrained constant modulus algorithm (AECCMA) nonlinearly to suppress the influence of α-stable noise. Computer simulation results of two underwater acoustic channels show that, MAECCMA has almost the same performance as AECCMA and they both have faster convergence rate than constant modulus algorithm (CMA) and normalized least mean absolute deviation (NLMAD) algorithm in Gaussian noise, while MAECCMA provides the best performance of those four algorithms in α-stable noise.     

Normal structure and some geometric parameters related to the modulus of U-convexity in banach spaces

We present a short and simple proof of the recent result of Yang and Wang [12]. Stimulated by their idea, two geometric parameters U~ax(ε) and βx (ε), both related to Gao’s modulus of U-convexity of a Banach space X, are introduced. Their properties and the relationships with normal structure are studied. Some existing results involving normal structure and fixed points for non-expansive mappings in Banach spaces are improved.     

The James constant for the <Emphasis Type="Italic">l</Emphasis><Subscript>3</Subscript> − <Emphasis Type="Italic">l</Emphasis><Subscript>1</Subscript> space

In this note, the exact value of the James constant for the l₃-l₁ space is obtained, J(l₃-l₁)=1.5573…. This result improves the known inequality, J(l₃-l₁)≤4/³√10, which was given by Dhompongsa, Piraisangjun and Saejung.     

利用海洋环境噪声估计浅海海底表层声速

为提高反演效率,提出一种快速估计浅海海底表层声速的方法。根据噪声能流理论,垂直阵接收的海洋环境噪声数据能够用于无源提取海底反射损失,反射损失曲线中具有明显的临界角效应,从而接估计海底表层声速。以射线模型为基础,推导了噪声提取的反射损失与理论值之间的差异,并讨论实际阵列波束形成在不同角度和频率下的性能。考虑到非等声速环境下声线会发生弯曲,需对角度进行修正以提高方法的广泛适用性。不同频率的临界角与有效深度之间存在对应关系,黄海某海区数据处理结果表明,在临界角不变的有效深度内,海底表层可以视为等声速层,该海区海底表层0.5 m内声速估计结果为1547 m/s,与有源反演结果相近。     

Gurarii的凸性模与正规结构

本文研究了Gurarii的凸性模与正规结构的联系.利用关于该模的不等式得出了如果存在ε,1≤ε≤2,使得β(ε)＞ε-1.则空间X具有一致正规结构.     

短程透镜的损耗

本文讨论了引起短程透镜损耗的各种因素,用最优边缘卷边曲率半径和表面抛光的方法成功地降低了短程透镜的损耗,给出了短程透镜的损耗测量值.     

Surface Acoustic Wave Characterization of Equivalent Young's Moduli for Patterned Films北大核心CSCD

Based on the equivalent elasticity theory for layered materials, the micro-mechanics equivalent models for single and dual damascene structures were established. The equivalent elastic constant of the patterned structure was introduced, to establish the propagation model for the surface acoustic waves propagating in the layered structure of the patterned film/ substrate, and the theoretical dispersion curves of the surface acoustic waves were calculated with Green’s function and the matrix method. The finite element method was used to calculate 24 numerical examples of damascene structures with different volume ratios, and the results were compared with those of the strain energy method. The results show that, the average relative errors of the equivalent Young’s moduli of the 300 nm-thick dual damascene film and the 100 nm-thick single damascene film are 2.06% and 2.27%, respectively. The research verifies the correctness of the equivalent patterned structure model and the feasibility of the surface acoustic wave method to characterize the mechanical properties of patterned films, and provides a reference for the development of suitable chemico-mechanical polishing technologies for patterned films under low pressure. © 2023 Editorial Office of Applied Mathematics and Mechanics. All rights reserved.     

CaCu3Ti4O12 陶瓷介电模量响应特性的研究

由于CaCu₃Ti₄O₁₂巨介电常数陶瓷的低频区直流电导较大, 本文采用模量 M"-f频谱表征与分析了低频和高频的两个松弛极化过程. 研究认为, 这两个特征峰属于晶界区Schottky 势垒耗尽层边缘深陷阱的电子松弛过程, 其中高频松弛峰起源于晶粒本征缺陷的电子松弛过程, 而低频松弛峰则为与氧空位有关的松弛极化过程. 对于CaCu₃Ti₄O₁₂这类低频下具有高直流电导的陶瓷材料, 采用模量频谱能更有效地分析研究其损耗极化机理. 关键词： 3Ti₄O₁₂陶瓷')" href="#">CaCu₃Ti₄O₁₂陶瓷 模量 松弛过程 电导     

Effects of annealing and additions on dynamic mechanical properties of SnSb quenched alloy

The elastic modulus, internal friction and stiffness values of quenched SnSb bearing alloy have been evaluated using the dynamic resonance technique. Annealing for 2 and 4 h at 120, 140 and 160 °C caused variations in the elastic modulus, internal friction and stiffness values. This is due to structural changes in the SnSb matrix during isothermal annealing such as coarsening in the phases (Sn, Sb or intermetallic compounds), recrystallization and stress relief. In addition, adding a small amount (1 wt.%) of Cu or Ag improved the bearing mechanical properties of the SnSb bearing alloy. The SnSbCu₁ alloy has the best bearing mechanical properties with thermo-mechanical stability for long time at high temperature.     

二元Ni-Al合金极端条件下的弹性和热力学性能：全电子准谐波近似 cited: 1)

通过在原子尺度上建模来研究Al、NiAl和Ni₃Al合金在极端高温和高压下的点阵常数、弹性常数、弹性模量、泊松比和弹性各向异性因子等性质．计算得到的弹性常数均满足相应的力学稳定条件．由于NiAl和Ni₃Al具有较高的B=G值,在0～30 GPa内都属于延展性材料．通过包含电子热运动对体系吉布斯自由能贡献的全电子准谐近似方法,得到了高温高压下Al、NiAl和Ni₃Al合金的热膨胀系数、体积模量、热容和熵等．计算值与已有的实验值和理论值符合较好