a尺度正交的多尺度函数的构造

给出α尺度正交多尺度函数一种新的构造方法。α尺度正交的多尺度函数可由任意α尺度正交的单尺度函数及滤波器组构造出来的。由于α尺度单正交尺度函数选取的任意性和用于构造的滤波器组具有相当大的自由度，从而使得有可能构造出大量的具有很好性质的α尺度的多尺度函数，进而得到良好性质的多小波。     

全局最优正交小波滤波器设计

在应用中通常希望正交小波滤波组在具有完美重建和一定阶消失矩的同时,也具备最优的频谱特征。为达到这双重目的,提出一种新的基于多项式优化理论的正交小波滤波器组设计方法,该方法可以保证计算出的滤波器组具有获得全局最优频率特征,并且设计出的滤波器与等长的Daubechies正交小波滤波器相比较具有更快速的过渡带滚降。     

构造对称和反对称M带正交小波滤波器的新方法

本文给出了构造M带对称和反对称的正交小波滤波器的新方法。该方法优点是计算简单,只需要解一些二次方程组。最后,得到了对称和反对称M带正交小波实系数滤波器组和复系数滤波器组。     

基于滤波器组分解的周期性振动冲击信号解调方法及其应用

针对离散小波包变换用于振动信号解调分析存在的不足,构造了一种具有线性相位的两通道正交镜像对称滤波器组(QMF)用于信号解调分析;与同阶的小波滤波器相比,此QMF滤波器不仅滤波性能更优,而且其滤波系数的求取更加便捷.为了解决常规两通道滤波器组分解算法中存在的子带信号组频带错位问题,引入了无频带错位的QMF滤波器组分解算法.基于此分解算法,提出了一种用于早期故障自动检测的振动信号解调新方法.该方法在考虑各组子带信号能量大小的基础上,按修正的归一化峭度(MKv)最大化准则自动选择一组含有丰富故障信息的子带信号进行Hil-ben包络谱分析提取故障特征.利用该方法对仿真和实际轴承故障信号进行了解调分析,分析结果表明,该方法可以有效地检测出轴承故障.     

多项式正交滤波器与共轭正交滤波器组

主要讨论了多项式正交滤波器和共轭正交滤波器组的构造方法，首先利用Riesz引理和特殊的余弦三角形多项式，给出了一种多项式正交滤波器的构造算法，该算法可以构造出一系列特性各异的紧支撑正交小波基；还给出了由一个矩阵CQFs派生多个新的矩阵CQFs的共轭正交滤波器组算法,包括由低阶矩阵CQFs构造高阶矩阵CQFs。     

EMD和二进正交小波分解对旋转机械振动信号处理效果的研究

二进正交小波分解通过一组高、低通正交镜像滤波器，以二分频形式把信号分解到各个频段中，经验模式分解（EMD）具有类似性质。但由于分解原理问的差异，对同一信号有不同处理效果。以故障滚动轴承振动信号处理为例，对比分析两种方法的处理效果，表明对于旋转机械，由于故障信号往往表现为调幅形式，而且相互间具有不同的载波与调制波频率，EMD方法是以信号的真实物理意义实现自适应二分频分解，能完整保留各个调幅信号，二进正交小波变换严格按照数学意义分解信号，势必破坏调幅信号完整性，影响故障定位，对比处理效果，EMD提取故障特征频率的效果要比二进正交小波分解好。     

信号解调的正交滤波器方法

信号的解调分析是通讯领域和机械故障诊断的常用方法。本文从数字滤波器的角度出发,提出了实现信号解调的正交滤波器法,即基于 Ｆ Ｉ Ｒ 正交滤波器方法和基于正交小波函数的正交滤波器方法。正交滤波器方法将带通滤波和希尔伯特变换的过程和功能有合二为一,实现过程方便。针对 Ｆ Ｉ Ｒ 正交滤波器方法的缺点,本文根据函数逼近理论,在理论上,证明了正交小波函数可以最佳一致逼近理想滤波器。并在具体应用上,介绍了采用正交小波函数构造正交滤波器时,参数的选择和信号解调分析的具体实施方法。采用正交小波函数设计的正交滤波器方法,带宽选择方便,相位的线性度高,正交性好,而且滤波器的滤波性能更优。可根据要求很方便地实现多通带信号滤波和多通带信号的解调分析     

基于一种特殊变换的多小波构造

本文引入一种矩阵滤波器的特殊变换。任一紧支撑正交多尺度函数都可由一个简单的矩阵滤波器通过这种变换得到。由此给出一种由多尺度函数构造相应紧支撑正交多小波的算法。与传统方法相比,这种方法既不需要对罗朗多项式矩阵逐行降次,也不需要将多项矩阵分解成特殊的形式,并且不受滤波器长度的限制。可以利用该方法构造出GHM正交多小波。     

具有矩阵的小波包

本文推广了Ｃｏｉｆｍａｎ与Ｍｅｙｅｒ引入的正交小波包及崔锦泰与李淳引入的非正交小波包。给出了相应的分解与再构造算法。本文引入的具有矩阵的小波包使Ｌ＾２（Ｒ）的分解更具有灵活性。     

滤波器组多载波系统的高精度符号定时估计

针对滤波器组多载波(FBMC)系统的传统定时同步算法精度较低的问题,研究了其发送信号统计特性,从理论上量化分析了受数据符号重叠影响部分和非重叠部分的同步训练数据的特性,在此基础上提出了一种适用的高精度符号定时估计算法.该算法通过传输一串长度大于滤波器重叠因子的连续相同的训练符号,使得时域合成信号具有多重延迟冗余特性.仿...     

从变通思维到同构创意图形的探讨

通过探讨同构创意图形的几种组合形式和变通思维之间内在本质的联系,了解两者之间可以相互转换,思维的转换可以创造出同构创意图形,同构创意图形让人产生思维的转换,不断提高变通思维能力从而创造出更多的同构创意图形.     

Exponential stability in thermoelasticity with microtemperatures

This article is concerned with a linear theory for elastic materials with inner structure, whose particles in addition to the classical displacement, possess microtemperatures. In the main part of the paper we restrict our attention to the one-dimensional problem. First, we prove the slow decay of solutions for the one-dimensional problem of micromorphic elastic solids with the usual thermal effects. Then, we prove the exponential stability of the solutions when we consider the theory with microtemperatures. The anti-plane distributions of microtemperatures are considered later.     

纤维丛上的Poisson结构

在文[1]的基础上。将纤维丛理论与广义Hamilton系统理论相结合,得到了Poisson丛,进而讨论了Poison丛的一些性质。     

Parallel Krylov methods and the application to 3-d simulations of a triphasic porous media model in soil mechanics

We introduce a general parallel model for solving coupled nonlinear and time-dependent problems in soil mechanics, where we employ general purpose linear solvers with specially adjusted preconditioners. In particular, we present a parallel realization of the GMRES method applied to a triphasic porous media model in soil mechanics, where we compute the deformation of unsaturated soil together with the pore-fluid flow of water and air in the soil. Therefore, we propose a pointwise preconditioner coupling all unknowns at the nodal points. In two large-scale numerical experiments we finally present an extended evaluation of our parallel model for demanding configurations of the triphasic model.     

精密铂电阻温度计的校准方法

介绍了精密铂电阻温度计的特性及0~660.323℃温度范围内精密铂电阻温度计的校准方法。提出对测量上限温度高于450℃的精密铂电阻温度计可参考使用说明书要求进行上限温度退火,进行定点法校准时,可采用熔化点温坪替代凝固点温坪,对于无法进行定点法校准的精密铂电阻温度计,可采用比较法校准及采用简化公式计算各项参数的可行性,同时指出自热效应对测量的影响。     

用于复合式柔性触觉传感器的导电复合材料研究

根据目前不同导电填料的导电橡胶导电机理的分析,理论分析了填加炭黑和石墨的导电橡胶所具有的压阻效应与电阻温度效应,由GEM模型获得填加炭黑的导电橡胶压阻计算模型,由层积模型获得填加石墨的导电橡胶电阻温度计算模型,并对其理论模型进行了验证。通过实验得出以炭黑和石墨作为主要导电填料的导电橡胶可用于复合式柔性触觉传感器的压力与温度的检测。     

Asymptotic study of transverse conductivity in superconducting multifilamentary composites

This paper deals with superconducting multifilamentary composites with periodic structure in the presence of a weak electromagnetic field. We study the magnetic induction and establish an approximation result when the period is small (in the framework of homogenization theory). Then we determine some physical constants of an “equivalent” homogeneous conductor, and thus transverse conductivity can be obtained. For various proportions of superconductor, we compute both the values of transverse conductivity proposed by different physicists and the mathematical value obtained in this paper (we use finite elements and an overrelaxation method); we compare them between themselves and with recent experimental results; we note that our results are in very good agreement with Carr's formula and with the experimental measures of Davoust.     

First principles simulations of kink defects on the SP 90° partial dislocation in silicon

In this paper we study kink defects on the single period (SP) reconstructed 90° partial dislocation in silicon. First, we use the Tersoff potential in order to determine how to set up the supercells we are employing so that we can extract meaningful results. In particular, we consider the elastic interactions between all dislocation segments and their effect on the energetics of the cells. We have identified a new long-range elastic field associated with the SP structure and we model it as arising from a dipolar line of force along the dislocation line. We also study the effect of this field on kink energies. With this information we then perform first principles simulations. Our results indicate that the only stable kink defects are those that separate regions of the dislocation with opposite reconstruction senses. We study the structure of these defects or complexes, as they are called, and we obtain the formation energy of a complex pair. We also investigate the changes in electronic structure and the rebonding that take place during the motion of these defects. We obtain the energy of migration of a single complex. Using a tight binding approach, we obtain the bandstructures associated with the complexes both at stable positions and at the migration saddle point and we discuss their role in the dislocation dopant effect.     

Modelling hierarchical structure in functional brain networks

In this work, we focus on a complex-network approach for the study of the brain. In particular, we consider functional brain networks, where the vertices represent different anatomical regions and the links their functional connectivity. First, we build these networks using data obtained with functional magnetic resonance imaging. Then, we analyse the main characteristics of these complex networks, including degree distribution, the presence of modules and hierarchical structure. Finally, we present a network model with dynamical nodes and adaptive links. We show that the model allows for the emergence of complex networks with characteristics similar to those observed in functional brain networks.     

Sliding beams,Part II: time integration

In this paper we obtain solutions for the discretized incremental system equations, as obtained in Part I, under certain initial and boundary conditions and/or specified applied loads, using the variable domain beam element. As a check on the validity of implementation, we first limit ourselves to linear analysis and obtain results for the axially inextensible sliding beams which we compare with the results reported in the literature. Second we set the axial velocity to zero and solve some special cases when the length of the beam is constant. In this case, we check the formulation and its implementation for non-linearities in the system due to large displacements. Finally, we solve the sliding beam problem for small amplitude oscillations, with a non-linear solver and compare the results with those obtained by the linear solver used for inextensible sliding beams. With these preliminary tests completed, we obtain the transient response of the free and forced large amplitude vibrations of the flexible sliding beam and demonstrate the need for using a non-linear analysis for this complex system. Finally, we consider the stability of the motion of periodically time varying flexible sliding beams and show that in the case of parametric resonance, the unstable regions obtained in the linear analysis, which imply unbounded amplitudes, are indeed stable and bounded when non-linear terms are taken into account. © 1998 John Wiley & Sons, Ltd.