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Deconvolution of Wave-Number-Frequency Spectra of Wall Pressure Fluctuations

AIAA JOURNAL 2020年第1期58卷 164-173页

作者： Prigent, Simon L. Salze, Edouard Bailly, Christophe Univ Lyon Cent Sch Lyon LMFA UMR 5509 F-69134 Ecully France

The wave-number-frequency spectra of a pressure field beneath a turbulent boundary layer is considered, with the aim of removing the effect of the measuring device. A rotating antenna of aligned microphones has been used in previous studies, and the measured spectra are shown to be a convolution of the true spectra with the transfer function of said antenna. Deconvolution algorithms that were previously developed for other fields of studies are presented. Test cases and processing of experimental data are used to assess their applicability. A hybrid approach of both deconvolution and interpolation, to artificially refine the azimuthal discretization, is found to be best at estimating both narrowband and broadband components of the spectra.

关键词： Antennas Turbulent Boundary Layer iterative algorithm Spectral Density Structural Vibration Numerical Simulation Anechoic Chambers Vibroacoustics Hydrodynamics Aeroacoustics

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A Solution algorithm for a Modified Bouc-Wen Model Capable of Simulating Cyclic Softening and Pinching Phenomena

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IFAC-PapersOnLine 2022年第20期55卷 319-324页

作者： Raffaele Capuano Nicolò Vaiana Davide Pellecchia Luciano Rosati

The paper illustrates an extension of a solution algorithm required to evaluate the output variable of a modified Bouc-Wen model, namely a differential model capable of simulating generalized force-displacement hysteresis loops exhibiting cyclic softening and/or pinching. The proposed solution scheme has been derived by adopting the Backward Euler Method in conjunction with the Newton-Raphson iterative procedure. In order to demonstrate the accuracy and the computational efficiency of the proposed algorithm, the results of numerical simulations are compared to those obtained by employing the widely used MATLAB ode45 solver.

关键词： Hysteresis Bouc-Wen model cyclic softening pinching iterative algorithm

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Digital Predistortion for MIMO Transmitters Using Multi-Channel Error Feedback Adaptation

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IEEE ACCESS 2020年 8卷 209345-209355页

作者： Liu, Ying Zhang, Libin Xia, Xiangjie Quan, Xin Shao, Shihai Tang, Youxi Univ Elect Sci & Technol China Natl Key Lab Sci & Technol Commun Chengdu 611731 Peoples R China Beijing Inst Aerosp Syst Engn Beijing 100076 Peoples R China Southwest Jiaotong Univ Sch Informat Sci & Technol Chengdu 611756 Peoples R China

Digital predistortion (DPD) is known as an efficient solution to suppress nonlinear distortion of power amplifiers (PAs) in wireless transmitters to achieve both high linearity and power efficiency. In multiple input and multiple output (MIMO) applications, the power gains of multiple transmitting channels are usually different. Meanwhile, the channel crosstalk cannot be ignored, given the isolations between the physical channels are limited. Accordingly, the linearization performances of the conventional DPD methods are usually degraded. In this article, we propose a novel DPD method for MIMO transmitters, where both the crosstalk and different power gains of multiple channels are considered. In this method, the expected predistorted signals, which would be used to train the DPD model, are firstly obtained by an iterative algorithm derived from the contraction mapping theorem. Then, the coefficients of a MIMO-DPD model are extracted by fitting the DPD model to the obtained predistorted signal. Experimental results verify that the extracted coefficients can achieve an improved linearization performance for the MIMO transmitter with crosstalk between the channels, especially in the case where the channel gains are different. Specifically, for a 2 x 2 MIMO transmitter with -20 dB crosstalk and 1.2 dB difference between the two channel gains, the proposed DPD improves the adjacent channel power ratio (ACPR) from -31.4 dBc to -47.1 dBc, which outperforms the conventional DPD by 6.8 dB.

关键词： MIMO transmitter crosstalk digital predistortion (DPD) iterative algorithm nonlinear distortion

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Reliability Analysis of Stiffened Aircraft Panels Using Adjusting Mean Value Method

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AIAA JOURNAL 2020年第12期58卷 5448-5458页

作者： Keshtegar, Behrooz Xiao, Mi Kolahchi, Reza Trung, Nguyen-Thoi Ton Duc Thang Univ Fac Civil Engn Inst Computat Sci Div Computat Math & Engn Ho Chi Minh City 758307 Vietnam Huazhong Univ Sci & Technol State Key Lab Digital Mfg Equipment & Technol Wuhan 430074 Peoples R China Duy Tan Univ Fac Civil Engn Inst Res & Dev Da Nang 550000 Vietnam

With regard to real-world engineering structures, an adjusting mean value called the self-adjusting mean value (SMV) is proposed for improving the efficiency and robustness of a maximum performance target point for evaluating the reliable performance of stiffened aircraft panel. A self-adaptive step size is presented using a merit function by a sufficient criterion, which is determined by using the results of the advanced mean value and the SMV. The abilities of the SMV are compared with several existing reliability methods through two nonlinear structural/mechanical examples. In particular, a practical aircraft panel example is investigated. Furthermore, the influence of self-adaptive parameters in the SMV is discussed on abilities the proposed SMV method for reliability analysis of aircraft panel example. The results demonstrate that the SMV is a robust algorithm for complex structural/mechanical examples, and it is slightly more efficient than the improved versions of reliability methods, which is significant for the reliability assessment of an aerospace structure.

关键词： Aircrafts iterative algorithm Trusses Elastic Modulus Cumulative Distribution Function Finite Element Modeling Particle Swarm Optimization Artificial Neural Network Surrogate Model Computing

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A fast algorithm for the adaptive discretization of 3D parametric curves

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ENGINEERING COMPUTATIONS 2020年第5期37卷 1663-1682页

作者： Zhang, Jianming Ju, Chuanming Chi, Baotao Hunan Univ State Key Lab Adv Design & Mfg Vehicle Body Changsha Hunan Peoples R China

Purpose The purpose of this paper is to present a fast algorithm for the adaptive discretization of three-dimensional parametric curves. Design/methodology/approach The proposed algorithm computes the parametric increments of all segments to obtain the parametric coordinates of all discrete nodes. This process is recursively applied until the optimal discretization of curves is obtained. The parametric increment of a segment is inversely proportional to the number of sub-segments, which can be subdivided, and the sum of parametric increments of all segments is constant. Thus, a new expression for parametric increment of a segment can be obtained. In addition, the number of sub-segments, which a segment can be subdivided is calculated approximately, thus avoiding Gaussian integration. Findings The proposed method can use less CPU time to perform the optimal discretization of three-dimensional curves. The results of curves discretization can also meet requirements for mesh generation used in the preprocessing of numerical simulation. Originality/value Several numerical examples presented have verified the robustness and efficiency of the proposed algorithm. Compared with the conventional algorithm, the more complex the model, the more time the algorithm saves in the process of curve discretization.

关键词： Computer-aided engineering Meshing Curve discretization iterative algorithm Mesh Computer graphics

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Simultaneous dual-wavelength phase-shifting interferometry for surface topography measurement

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OPTICS AND LASERS IN ENGINEERING 2020年 124卷

作者： Liu, Qian Li, Lulu Zhang, Hui Huang, Wen Yue, Xiaobin China Acad Engn Phys Inst Machinery Mfg Technol 64th Mianshan Rd Mianyang 621000 Sichuan Peoples R China

To deal with vibration disturbance in interferometric measurement of surface topography, we present a simultaneous dual-wavelength phase-shifting interferometry (SDWPSI). SDWPSI collects phase-shifting interferograms of two wavelengths simultaneously with two cameras to accelerate data collection. The optical phases are retrieved from dual-wavelength interferograms with an iterative algorithm that is tolerant of phase-shifting error caused by vibration. And then the measured surface topography is reconstructed by fusing the phases of two wavelengths. Simulations and experiments verify that SDWPSI has a lower measurement noise than single-wavelength interferometry and extends the discontinuity limit to several micrometres. SDWPSI has advantages of high speed, vibration resistance, and low cost, and could be applied to in-workshop and on-machine measurement.

关键词： Phase-shifting interferometry Dual-wavelength interferometry iterative algorithm Vibration resistance

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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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Should competing firms offer 'Buy n times, get one free' loyalty programs? A game-theoretic analysis

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JOURNAL OF THE OPERATIONAL RESEARCH SOCIETY 2020年第2期71卷 280-300页

作者： Bazargan, Amirhossein Zolfaghari, Saeed Karray, Salma Ryerson Univ Dept Mech & Ind Engn 350 Victoria St Toronto ON M5B 2K3 Canada UOIT Fac Business & Informat Technol Oshawa ON Canada

This study investigates the profitability of 'Buy n, get one free' loyalty programs (LPs) for competing firms deciding on whether to offer such LP. We use a game-theoretic approach and obtain the equilibrium by considering four subgames;two symmetric ones where both firms either offer or do not offer a LP, and two asymmetric ones where only one firm offers a LP. We derive the demand using an analytical choice model. Then, we obtain the firms' optimal decision variables (prices and reward periods) and profits for each subgame under different combinations of behavioral parameters of time and reward valuations for both symmetric and asymmetric production cost for the firms. The results show that when customers highly value reward but not time, offering loyalty programs is a dominant strategy. However, under different market conditions, firms face a prisoner dilemma or find that not offering a LP is a dominant equilibrium.

关键词： OR in marketing iterative algorithm multinomial logit models loyalty programs game theory

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A survey on the algorithm and development of multiple sequence alignment

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BRIEFINGS IN BIOINFORMATICS 2022年第3期23卷 bbac069页

作者： Zhang, Yongqing Zhang, Qiang Zhou, Jiliu Zou, Quan Chengdu Univ Informat Technol Sch Comp Sci Chengdu Peoples R China Univ Elect Sci & Technol China Inst Fundamental & Frontier Sci Chengdu 610054 Peoples R China

Multiple sequence alignment (MSA) is an essential cornerstone in bioinformatics, which can reveal the potential information in biological sequences, such as function, evolution and structure. MSA is widely used in many bioinformatics scenarios, such as phylogenetic analysis, protein analysis and genomic analysis. However, MSA faces new challenges with the gradual increase in sequence scale and the increasing demand for alignment accuracy. Therefore, developing an efficient and accurate strategy for MSA has become one of the research hotspots in bioinformatics. In this work, we mainly summarize the algorithms for MSA and its applications in bioinformatics. To provide a structured and clear perspective, we systematically introduce MSA's knowledge, including background, database, metric and benchmark. Besides, we list the most common applications of MSA in the field of bioinformatics, including database searching, phylogenetic analysis, genomic analysis, metagenomic analysis and protein analysis. Furthermore, we categorize and analyze classical and state-of-the-art algorithms, divided into progressive alignment, iterative algorithm, heuristics, machine learning and divide-and-conquer. Moreover, we also discuss the challenges and opportunities of MSA in bioinformatics. Our work provides a comprehensive survey of MSA applications and their relevant algorithms. It could bring valuable insights for researchers to contribute their knowledge to MSA and relevant studies.

关键词： multiple sequence alignment progressive alignment iterative algorithm heuristic

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Progressive Colorization via iterative Generative Models

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IEEE SIGNAL PROCESSING LETTERS 2020年 27卷 2054-2058页

作者： Zhou, Jinjie Hong, Kai Deng, Tao Wang, Yuhao Liu, Qiegen Nanchang Univ Dept Elect Informat Engn Nanchang 330031 Jiangxi Peoples R China

Colorization is the process of coloring monochrome images. It has been widely used in photo processing and scientific illustration. However, colorizing grayscale images is an intrinsic ill-posed and ambiguous problem, with multiple plausible solutions. To address this issue, we develop a novel progressive automatic colorization via iterative generative models (iGM) that can produce satisfactory colorization in an unsupervised manner. In particular, the generative model is exploited in multi-color spaces (e.g., RGB, YCbCr) jointly and enforced with linearly autocorrelative constraint. This is regarded as the key prior information to pave the way for producing the most probable colorization in high-dimensional space. Experiments on indoor and outdoor scenes reveal that iGM produces more realistic and finer results, compared to state-of-the-arts.

关键词： Colorization generative model unsupervised learning multi-color spaces iterative algorithm

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