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A ROBUST REDUCED-ORDER OBSERVERS DESIGN APPROACH FOR LINEAR DISCRETE PERIODIC SYSTEMS

JOURNAL OF INDUSTRIAL AND MANAGEMENT OPTIMIZATION 2020年第6期16卷 2799-2812页

作者： Lv, Lingling He, Wei Liu, Xianxing Zhang, Lei North China Univ Water Resources & Elect Power Inst Elect Power Zhengzhou 450011 Peoples R China Henan Univ Key Lab Big Data Anal & Proc Henan Prov Zhengzhou 450011 Peoples R China

This paper investigates the problem of designing reduced-order observers for linear discrete-time periodic (LDP) systems. In case that the linear discrete-time periodic system is observable, an algebraic equivalent system is obtained by non-singular linear transformation, and the partial states to be observed are separated simultaneously. Then the considered problem is transformed into the problem of solving a class of periodic Sylvester matrix equation and an iterative algorithm for periodic reduced-order state observers design is derived. In addition, robust consideration based on periodic reduced-order state observers for LDP systems is also conducted. At last, one numerical example is worked out to illustrate the effectiveness of the proposed approaches.

关键词： Linear discrete-time periodic (LDP) system reduced-order observers iterative algorithm robustness

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Texture and colour region separation based image retrieval using probability annular histogram and weighted similarity matching scheme

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IET IMAGE PROCESSING 2020年第7期14卷 1303-1315页

作者： Pradhan, Jitesh Kumar, Sumit Pal, Arup Kumar Banka, Haider Indian Inst Technol Indian Sch Mines Dept Comp Sci & Engn Dhanbad 826004 Jharkhand India

Content-based image retrieval (CBIR) uses primitive image features for retrieval of similar images from a dataset. Generally, researchers extract these visual features from the whole image. Therefore, the extracted features contain overlapped information of texture, colour, and shape features, and it is a critical challenge in the field of CBIR. This problem can be overcome by extracting the colour features from the colour as well as shape and texture features from the intensity dominant part only. In this study, the authors have proposed an iterative algorithm to separate colour and texture dominant part of the image into two different images. Here, a combination of edge maps and gradients has been used to achieve separate colour and texture images. Further, scale-invariant feature transform and 2D dual-tree complex wavelet transform has been realised to extract unique shape and texture features from the texture image. Simultaneously, a probability-based semantic centred annular histogram has been suggested to extract unique colour features from the colour image. Finally, a novel weighted distance-based feature comparison scheme has been proposed for similarity matching and retrieval. All the image retrieval experiments have been carried out on seven standard datasets and demonstrated significant improvements over other state-of-arts CBIR systems

关键词： wavelet transforms trees (mathematics) image texture image colour analysis feature extraction content-based retrieval probability image retrieval shape recognition image matching edge detection iterative methods colour region separation based image retrieval content-based image retrieval system CBIR primitive image visual features colour dominant part texture feature intensity dominant part iterative algorithm texture dominant part probability-based semantic centred annular histogram unique colour features weighted distance-based feature comparison scheme shape feature similarities query image database images image retrieval experiments texture image datasets retrieval performances unique shape feature extraction weighted similarity matching scheme scale-invariant feature transform two-dimensional dual-tree complex wavelet transform edge maps

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Frictional receding contact problem of a functionally graded layer resting on a homogeneous coated half-plane

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ARCHIVE OF APPLIED MECHANICS 2020年第9期90卷 2113-2131页

作者： Comez, Isa El-Borgi, Sami Yildirim, Bora Karadeniz Tech Univ Dept Civil Engn TR-61080 Trabzon Turkey Texas A&M Univ Qatar Mech Engn Program Engn BldgPOB 23874 Doha Qatar Hacettepe Univ Mech Engn Dept Ankara Turkey

This paper investigates the frictional receding contact problem between a functionally graded (FG) layer resting on a homogeneous coated half-plane when the system indented by a rigid cylindrical punch. The shear modulus of the upper graded layer is assumed to vary exponentially in the depth direction. Upon loading, the advancing contact and receding contact occur between the FG layer and rigid punch and between the FG layer and coating, respectively. Under the assumptions of sliding contact, the shear and normal contact stresses are related through Coulomb's law of friction. The contact problem is converted analytically using Fourier integral transforms and the proper boundary conditions into a system of two singular integral equations. The unknowns of these integral equations consist of the contact stresses under the punch and between the FG layer and coating as well as the dimensions of the contact zones. The Gauss-Jacobi quadrature collocation method is then employed to transform the singular integral equations into a system of nonlinear equations which are solved using an appropriate iterative algorithm to compute the contact stresses and the dimensions of the contact areas. The main purpose of this paper is to examine the influence of several parameters on the upper and lower contact stresses, which include the material inhomogeneity parameter, friction coefficient, punch radius, applied load, thickness of homogeneous layer, shear modulus of homogeneous layer and shear modulus of homogeneous half-plane. One of the most important conclusions from this study is that the contact stresses and contact areas can be controlled with the addition of the homogeneous layer.

关键词： Graded layer Receding frictional contact Homogeneous layer Singular integral equations iterative algorithm

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A Set of Point-Targets-Based Polarimetric Calibration Methods Based on General Polarimetric System Model

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IEEE JOURNAL OF SELECTED TOPICS IN APPLIED EARTH OBSERVATIONS AND REMOTE SENSING 2020年 13卷 2502-2519页

作者： Liang, Weibin Chinese Acad Sci Key Lab Technol Geospatial Informat Proc & Applic Inst Elect Beijing 100190 Peoples R China

Freeman proposed a general polarimetric system model in 1991 for the characterization and calibration of fully polarimetric synthetic aperture radar (SAR) systems. The model contains three-channel imbalance parameters and four cross-talk parameters, which together describe the polarimetric distortion in a practical imaging radar more accurately than the conventional six-parameter model by including a third imbalance parameter, namely gamma. This parameter is independent of the others and represents the ratio of the product of the transfer functions of the copolarized channels to the product of the transfer functions of the cross-polarized channels. Nonnegligible errors may arise if this parameter is not estimated and corrected, but since this parameter was proposed, there has been very little research into calibration methods that account for gamma. In this article, based on the general polarimetric system model in the 2 x 2 matrix form, we propose a gamma-factor estimation method based on an active radar calibrator (ARC) or a dihedral corner reflector. We also propose a universal iterative polarimetric calibration algorithm based on three pieces of calibration equipment, which can be all ARCs, all corner reflectors (CRs), or a combination of ARCs and CRs. The convergence of this iterative algorithm is proven mathematically. These alternatives provide a variety of practical calibration method options for polarimetric SAR calibration under different conditions. Finally, the simple calibration method based on a single piece of calibration equipment and the iterative algorithm based on three pieces of calibration equipment are verified by the polarimetric calibration experiment data from the GaoFen-3 satellite.

关键词： Calibration Radar polarimetry Distortion Spaceborne radar Synthetic aperture radar Transfer functions Calibration iterative algorithm GaoFen-3 polarimetric SAR polarimetric calibration polarimetric system model synthetic aperture radar (SAR)

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Blind atmospheric turbulence deconvolution

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IET IMAGE PROCESSING 2020年第14期14卷 3422-3432页

作者： Deledalle, Charles-Alban Gilles, Jerome Univ Calif San Diego Elect & Comp Engn Dept 9500 Gilman Dr La Jolla CA 92093 USA San Diego State Univ Dept Math & Stat 5500 Campanile Dr San Diego CA 92182 USA

A new blind image deconvolution technique is developed for atmospheric turbulence deblurring to overcome limitations of 'generic' blind deconvolution algorithms that do not take into account the complicated physics of the turbulence. The originality of the proposed approach relies on an actual physical model, known as the Fried kernel, that quantifies the impact of the atmospheric turbulence on the optical resolution of images. While the original expression of the Fried kernel can seem cumbersome at first sight, the authors show that it can be reparameterised in a much simpler form. This simple expression allows to efficiently embed this kernel in the proposed blind atmospheric turbulence deconvolution (BATUD) algorithm. BATUD is an iterative algorithm that alternately performs deconvolution and estimates the Fried kernel by jointly relying on a Gaussian mixture model prior to natural image patches and controlling for the square Euclidean norm of the Fried kernel. Numerical experiments show that the proposed blind deconvolution algorithm behaves well in different simulated turbulence scenarios, as well as on real images. Not only BATUD outperforms state-of-the-art approaches used in atmospheric turbulence deconvolution in terms of image quality metrics but is also faster.

关键词： atmospheric turbulence deconvolution image restoration iterative methods Gaussian processes iterative algorithm Fried kernel natural image patches BATUD image quality metrics blind image deconvolution technique atmospheric turbulence deblurring generic blind deconvolution algorithms complicated physics actual physical model blind atmospheric turbulence deconvolution algorithm simulated turbulence scenarios Gaussian mixture model

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Variational inequalities for lattice-valued fuzzy relations with applications

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JOURNAL OF INTELLIGENT & FUZZY SYSTEMS 2020年第1期39卷 145-153页

作者： Kim, Jong Kyu Mehmood, Nayyar Rawashdeh, Ahmed Al Kyungnam Univ Dept Math Educ Chang Won 51767 Gyeongnam South Korea Int Islamic Univ Dept Math & Stat H-10 Islamabad Pakistan UAE Univ Coll Sci Dept Math Sci Al Ain U Arab Emirates

In this article, we study the notion of the variational inequalities for lattice-valued fuzzy relations. In this context, a variational inequality problem has been proposed that generalizes many results in the literature. The conditions for the existence of solutions of the proposed problem have been discussed. It has been shown that the proposed variational inequality problem is equivalent to a fixed point problem. This fixed point formulation allows us to present an iterative algorithm to approximate solution of the variational inequality problem. For applications, first the existence result for the solutions of an L-fuzzy Caputo-Fabrizio fractional differential inclusion initial value problem involving a projection operator has been proved. Then the solutions of an obstacle boundary value variational inequality problem in function spaces has been obtained.

关键词： L-fuzzy relations fixed points variational inequalities iterative algorithm

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Multilevel minimum cross entropy thresholding: A comparative study

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APPLIED SOFT COMPUTING 2020年 96卷 106588-106588页

作者： Lei, Bo Fan, Jiulun Xian Univ Posts & Telecommun Sch Commun & Informat Engn Xian 710121 Peoples R China Xian Univ Posts & Telecommun Ctr Image & Informat Proc Xian 710121 Peoples R China

Multilevel thresholding method is one of the most popular techniques in image segmentation. However, the multilevel thresholding method is time-consuming, its time complexity increases exponentially with the number of threshold levels. In this paper, in order to improve the computation efficiency of the multilevel minimum cross entropy thresholding, the iterative formula of the multilevel cross entropy thresholding algorithm is proposed and compared with the modern meta-heuristic optimization algorithms. The iterative multilevel cross entropy thresholding algorithm can find the thresholds close to the global optimums with less time. The computation cost of the iterative multilevel cross entropy thresholding algorithm is linear in the number of the threshold levels. We prove the convergence of the iterative algorithm and compare the iterative multilevel cross entropy thresholding algorithm with multilevel cross entropy thresholding methods combined with the state-of-the-art meta-heuristic optimization techniques including particle swarm optimization (PSO), cuckoo search algorithm (CS), differential evolution (DE), crow search algorithm (CSA) and genetic algorithm (GA). Experimental results show that the iterative multilevel cross entropy thresholding algorithm is efficient and effective. Therefore, iterative algorithm for the multilevel cross entropy thresholding is an effective method to improve the computation efficiency. (C) 2020 Elsevier B.V. All rights reserved.

关键词： Image segmentation Multilevel thresholding Cross entropy iterative algorithm Meta-heuristic optimization

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A finite difference scheme for the nonlinear time-fractional partial integro-differential equation

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MATHEMATICAL METHODS IN THE APPLIED SCIENCES 2020年第6期43卷 3392-3412页

作者： Guo, Jing Xu, Da Qiu, Wenlin Hunan Normal Univ Sch Math & Stat Minist Educ Key Lab Comp & Stochast Math Changsha 410081 Hunan Peoples R China

In this paper, a finite difference scheme is proposed for solving the nonlinear time-fractional integro-differential equation. This model involves two nonlocal terms in time, ie, a Caputo time-fractional derivative and an integral term with memory. The existence of numerical solutions is shown by the Leray-Schauder theorem. And we obtain the discrete L-2 stability and convergence with second order in time and space by the discrete energy method. Then the uniqueness of numerical solutions is derived. Moreover, an iterative algorithm is designed for solving the derived nonlinear system. Numerical examples are presented to validate the theoretical findings and the efficiency of the proposed algorithm.

关键词： existence and uniqueness finite difference scheme iterative algorithm nonlinear time-fractional integro-differential equation stability and convergence

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Resource allocation algorithm for downlink MIMO-OFDMA based cognitive radio networks in spectrum underlay scenario

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IET COMMUNICATIONS 2020年第11期14卷 1812-1821页

作者： Mohammadi, Mahla Hosseini Andargoli, Seyed Mehdi Babol Noshirvani Univ Technol Dept Elect & Comp Engn Babol Sar Mazandaran Iran

In this study, the sum throughput maximisation problem for cognitive radio networks (CRNs) based on the multiple-input multiple-output orthogonal frequency division multiple access (MIMO-OFDMA) structure has been investigated. Hence, the intention is to maximise the downlink sum throughput of the CRN in a way that the sum power of the cognitive base station (CBS) remains below the given power limit and the induced interference on each subcarrier guarantees the interference threshold level predefined by primary users. Here, due to combinatorial constraints, the complex problem should be resolved. Hence, the core purpose of this study is to prepare a novel resource assignment algorithm that tries to fulfil these combinatorial constraints simultaneously. Therefore, this study makes progress towards solving the problem theoretically based on convex optimisation framework. An optimal solution has been implemented by proposing the iterative algorithm in which an optimal level of Lagrangian coefficients is obtained. Then, because of the optimal algorithm intricacy, the two low complicated algorithms are further suggested based on the solutions of two simplified versions of the original problem. Numerical results demonstrate that the suggested algorithms improve sum throughput considerably in comparison with classical algorithm. The proposed simplified algorithms converge to the optimal solutions' performance while their complexities are desirable for practical implementation.

关键词： radio networks radiofrequency interference iterative methods cognitive radio MIMO communication OFDM modulation frequency division multiple access convex programming resource allocation radio spectrum management resource allocation algorithm cognitive radio networks spectrum underlay scenario maximisation problem cognitive base station combinatorial constraints complex problem resource assignment algorithm iterative algorithm optimal algorithm intricacy low complicated algorithms induced interference threshold level multiple-input multiple-output orthogonal frequency division multiple access structure downlink MIMO-OFDMA structure CBS convex optimisation framework sum throughput maximisation problem CRN Lagrangian coefficients CBS

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Fault detection observer design for periodic piecewise linear systems

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INTERNATIONAL JOURNAL OF SYSTEMS SCIENCE 2020年第9期51卷 1622-1636页

作者： Fan, Chenchen Lam, James Xie, Xiaochen Univ Hong Kong Dept Mech Engn Hong Kong Peoples R China

This article deals with the problem of fault detection observer design for continuous-time periodic piecewise linear systems. Mixed H-/H-infinity performance index is introduced, which results in a trade-off between robustness to unknown input and sensitivity to a fault. Based on a class of Lyapunov functions with time-varying Lyapunov matrices, sufficient conditions are developed to investigate the existence of periodic piecewise fault detection observer with weighted H-/H-infinity performance. A tractable iterative algorithm is proposed to establish the desired periodic piecewise fault detection observer. Finally, a numerical example is provided to illustrate the effectiveness of the proposed approach.

关键词： Fault detection H-/H-infinity observer iterative algorithm periodic piecewise systems

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