Two-dimensional stability and orthogonal polynomials on the hypercircle

This paper is concerned with a possible extension of a well-known stabilization technique for one-variable recursive digital filters to the two-dimensional case, as recently conjectured. It is shown that this problem is equivalent to considering a new class of orthogonal polynomials, the two-variable orthogonal polynomials on the hypercircle, the properties of which are investigated. As a result, the zeros of these polynomials are proved not to lie necessarily in an appropriate region compatible with the proposed conjecture, which therefore turns out to be in error.     

Stability of multidimensional scalar and matrix polynomials

A comprehensive study of multidimensional stability and related problems of scalar and matrix polynomials is presented in this survey paper. In particular, applications of this study to stability of multidimensional recursive digital and continuous filters, to synthesis of network with commensurate and noncommensurate transmission lines, and to numerical stability of stiff differential equations are enumerated. A novel approach to the multidimensional stability study is the classification of various regions of analyticity. Various computational tests for checking these regions are presented. These include the classical ones based on inners and symmetric matrix approach, table form, local positivity, Lyapunov test, the impulse response tests, the cepstral method and the graphical ones based on Nyquist-like tests. A thorough discussion and comparison of the computational complexities which arise in the various tests are included. A critical view of the progress made during the last two decades on multidimensional stability is presented in the conclusions. The latter also includes some research topics for future investigations. An extensive list of references constitutes a major part of this survey.     

On the stability of real exponential polynomials with interval-valued delays

We consider the family ? of exponential polynomials. $$f_T (z): = f_0 (z) + f_1 (z)e^{ - zT_1 } + f_2 (z)e^{ - T_2 } + \cdots + f_n (z)e^{ - zT_n } ,T : = T_1 \times T_2 \times \cdots \times T_n ,$$ where thef _k(z),k=0(1)n, are real polynomials under the degree restriction deg(f ₀)>deg(f _k),k=1(1)n, and theT _k,k=1(1)n, are intervals inR ₊. The functions in ? are characteristic functions of linear, retarded dynamical systems with constant coefficients and finitely many interval-valued discrete delays. A stability criterion for ? is expounded; ? is stable if (a) ? contains a stable member and (b) a certain functionalT:S(y) →; {0, 1} vanishes fory in a compact interval inR ₊. Here,S(y) is the boundary of a circular are regionS(y) in the complex plane derived fromf _T. Tools needed for a computer implementation are compiled.     

Scattering and transmission matrix representations of multiguidejunctions

The scattering and transmission matrix representations of the mode-matching technique are generalized for multiguide junctions with arbitrarily shaped coupling apertures. A comparison between both representations is given with respect to the CPU time. The relative convergence phenomenon arising in cascaded discontinuities of multiguide junctions is investigated. A numerical criterion for choosing the correct mode ratio among the guides is presented. Also studied is the application to a kind of multiguide junction between a circular waveguide and a coaxial waveguide with hollow inner conductor     

Multiparameter discrete transforms based on discrete orthogonal polynomials and their application to image watermarking

Applications of discrete orthogonal polynomials (DOPs) in image processing have been recently emerging. In particular, Krawtchouk, Chebyshev, and Charlier DOPs have been applied as bases for image analysis in the frequency domain. However, fast realizations and fractional-type generalizations of DOP-based discrete transforms have been rarely addressed. In this paper, we introduce families of multiparameter discrete fractional transforms via orthogonal spectral decomposition based on Krawtchouk, Chebyshev, and Charlier DOPs. The eigenvalues are chosen arbitrarily in both unitary and non-unitary settings. All families of transforms, for varieties of eigenvalues, are applied in image watermarking. We also exploit recently introduced fast techniques to reduce complexity for the Krawtchouk case. Experimental results show the robustness of the proposed transforms against watermarking attacks.     

基于独立分量分析的实正交空时分组码盲识别

提出一种基于独立分量分析的正交空时分组码(OSTBC)盲识别方法。首先给出了接收信号模型,利用独立分量分析得到含有编码矩阵的虚拟信道矩阵,然后利用编码矩阵特性,证明得到正交空时分组码的虚拟信道矩阵的相关矩阵为对角矩阵;最后提出用于正交空时分组码识别的2个特征参数:稀疏度和方差。仿真结果表明,所提出方法能够较好地识别正交空时分组码。     

Directional lapped orthogonal transform: theory and design

This paper proposes a directional design method of 2-D nonseparable linear-phase paraunitary filter banks. The proposed method is based on a lattice structure consisting of the 2-D separable DCT block and nonseparable support extension processes. Because of the nonseparability, the bases are allowed to be directional with the critically fixed subsampling, overlapping, orthogonal, symmetric, real-valued, and compact support properties. First, a novel vanishing moment (VM) condition is introduced as a suitable directional constraint, where the moment is referred to as the trend VM. The condition forces wavelet filters, i.e., high-pass and bandpass filters, to annihilate trend-surface components. Second, some theoretical properties of TVMs are discussed for general 2-D paraunitary systems, and then, the properties are applied to the lattice parameters. In order to verify the significance, several design examples are shown, the trend-surface annihilation properties are numerically confirmed, and the denoising capability is evaluated for images through shrinkage. It is shown that our proposed transforms yield perceptually preferable results.     

Scattering matrix approach for the design of microwave filters

A synthesis procedure, based on a distributed parameter model, for the design of microwave filters is presented in this paper. The frequency response of the filter is described in terms of the characteristic polynomial T₂₁=S₁₁/S₂₁ where S₁₁ and S₂₁ are the scattering parameters of the filter. Starting from the desired polynomial T₂₁, the design scheme directly yields the scattering parameters of the various junctions, which can be realized by any kind of discontinuity. The capability of synthesizing an arbitrary frequency response allows one to introduce the concept of a “predistorted” characteristic polynomial in order to compensate for the degradations caused by multimodal interactions, frequency dispersion, etc. Comparison with measured data of a Chebyshev-like eight-pole E-plane filter confirms the validity of the method also in the presence of losses     

A note on the relationship between the conjugate gradient method and polynomials orthogonal over the spectrum of a linear operator

The relationship between the conjugate gradient method and polynomials orthogonal over the spectrum of a linear operator is discussed. It is shown that as a byproduct of the conjugate gradient construction, two sets of polynomials are generated which are orthogonal with respect to a positive real measure over the spectrum of a self-adjoint operator. The roots of these polynomials can, under certain circumstances, be used to track the eigenvalues or singular values of the relevant operator.     

一种基于Walsh矩阵的正交多相码设计方法

借助Walsh矩阵严格正交性,通过类Walsh矩阵构造和随机列重排生成多相码严格正交性空间域,利用遗传算法从中选取低相关旁瓣量信号组.该方法保证了设计的信号间严格正交性,降低了遗传算法搜索空间.遗传算法代价函数选取为自相关峰值旁瓣量、互相关峰值量以及“和信号”(所有发射信号空间叠加之和)相关峰值旁瓣量之和,“和信号”相关输出为实际信号处理的综合输出,其旁瓣量的高低直接影响雷达对目标的检测性能.仿真结果验证了该方法在保证低自相关旁瓣量和低互相关量的同时,能够设计出信号间符合严格正交性和低综合输出旁瓣量的信号组.     

Strip and line path integrals with a square pixel matrix: a unified theory for computational CT projections

Calculated forward projection techniques have been used for various purposes in computerized tomography applications, and several models have been proposed to simulate the tomography projection process. Since the area weighted strip integral is one of the best models, methods to facilitate the computation of strip integrals would be very useful. In particular, a triangular subtraction technique with a reduced number of weighting factors is proposed for the calculation of the strip integral. A unified path integral theory is also proposed to bridge various models and to clarify the integral interaction when a line or a strip passes through a square pixel matrix.     

基于线激光正交扫描的电感微裂纹热成像检测

在检测铁氧体电感表面微裂纹时,传统机器视觉检测存在裂纹成像信噪比不高、准确率低等问题。为此文中搭建了一套基于线激光正交扫描的微裂纹热成像检测系统。通过热像仪记录试样表面温度变化并成像;采用次最大值滤波消除热成像图的非均匀性和边缘轮廓干扰,再利用多方向扇形滤波得到试样在不同方向上的灰度图;最后通过BP神经网络和形态学处理实现对电感表面微裂纹的定性检测。结果表明:基于两种规格共610个样品测试,所有裂纹和隐裂均正确成像;自动识别算法误检率5%,裂纹漏检率6%,隐裂漏检率10%。系统每5 s检测20~35个电感,可应用于生产中自动化品质检测。     

Spectral estimation for the transmission line matrix method

The transmission line matrix (TLM) method for microwave circuit analysis calculates the time-domain variation of the electromagnetic fields in response to an arbitrarily chosen excitation. Spectral estimation for the TLM method by use of the discrete fourier transform and fast Fourier transform is reviewed. Error bounds are given and checked by means of a numerical example. A spectral estimation method based on Prony's method for use with TLM is presented. A numerical example shows that the method allows an order of magnitude reduction in the number of iterations in the TLM method for equal accuracy     

Assessment of domestic photovoltaic systems based on real options theory

In the last decade, the financial attractiveness of photovoltaic (PV) systems has been increasing due to the rapid and constant improvements of PV technologies and the introduction of renewable energy support mechanisms. Under these circumstances, residential electricity consumers can benefit from investments in domestic PV systems. Investment decisions in PV systems can be assessed with well‐known discounted cash flows criteria such as the cost of energy and the net present value. These types of analyses either recommend abandoning the project or investing immediately. However, due to fast improvements in PV technologies, especially in the last few years, options to postpone investments in PV systems can be valuable. These options can be assessed with real options theory. This paper proposes a real options methodology for the assessment of domestic PV systems, considering the expected evolution of PV technologies and the option to delay investment. The methodology employs a normalization technique to illustrate, in a simple and intuitive manner, the convenience of the delay option. Two case studies based on real aggregated data for the UK are presented. The first case study illustrates the methodology, whereas the second is an extensive study meant to provide insights about investments in domestic PV systems in the UK. The results indicate the circumstances that drive and disincentivize investments in different PV technologies. Additionally, it is shown that the option to delay investment is a potential driver for investments in emerging organic‐based PV technologies. Copyright © 2012 John Wiley & Sons, Ltd.     

基于内积运算和正交矩阵的并行扩频传输新方案

为了提高并行解扩的频谱效率和功率效率,提出了以内积运算为数学理论基础,以线性算子扩频、结合律并行扩频传输、分配律并行解扩为特征的IOR并行扩频传输方案,较经典并行扩频相关解扩和经典并行扩频匹配滤波解扩的频谱效率和功率效率分别提高了2096128倍和1048576倍。在8×randn(1,length(b))干扰下,并行扩频传输64比特,其100000次大样本检验结果表明统计平均误码率和标准差分别为0.0000和0.0007。     

使用传输线理论的硅通孔电参数提取方法

针对三维集成电路中的关键技术硅通孔的电特性,使用传输线理论提取了其单位长度RL-GC参数。将硅通孔等效为传输线,利用HFSS仿真结果并结合传输线理论给出了具体的参数提取方法。计算结果表明,硅通孔单位长度RLGC 参数呈现较强的频变特性,当频率从1 MHz增加到20 GHz时,单位长度的电阻和导纳分别从0.45 mΩ/μm和2.5μS/μm增加到2.5 mΩ/μm和17μS/μm,而单位长度电感和电容分别从8.7 pH/μm和8.8 fF/μm减小至7.5 pH/μm和0.2 fF/μm。与传统的阻抗矩阵和导纳矩阵提取方法相比,该方法具有结果绝对收敛和适用频率高等诸多优点,可进一步应用于三维集成电路的仿真设计。     

颗粒浓度及粒度的光散射在线测量

介绍一种在线监测颗粒浓度及粒度变化的光散射方法。着重提出消除观察窗玻璃污染物对测量结果影响的办法。给出了部分现场实测结果。     

Scattering matrix integral equation analysis for the design of awaveguide Rotman lens

An integral-equation-based procedure is developed for determining the scattering parameters of a multiport Rotman lens device. The device is intended for use at millimeter-wave frequencies and incorporates rectangular waveguide feeds. The integral equation model takes higher order modes in the feed apertures into account and incorporates mutual coupling between neighboring ports. A prototype lens was designed using the integral equation model and fabricated. The lens S-parameters were measured and modified with an ideal -40 dB (n=3) Taylor weighting function. The resulting beam sidelobe level is better than -30 dB