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An iterative algorithm for the stability analysis of dynamic interval systems

APPLIED NUMERICAL MATHEMATICS 2013年 69卷 73-77页

作者： Leng, Huinan Zhang, Qi E China Univ Sci & Technol Dept Math Shanghai 200237 Peoples R China Fudan Univ Sch Math Sci Shanghai 200433 Peoples R China

In this paper, a new iterative algorithm is proposed to analyze the stability of dynamic interval systems. Compared with existing researches, this algorithm takes much less computation time to obtain the superior of maximal eigenvalues and the inferior of minimal eigenvalues of a real interval matrix with real eigenvalues, under given precision. As a result, the stability of a dynamic interval system, which is determined by eigenvalues of its corresponding interval matrix, can be judged within a shorter time period. Furthermore, if the dynamic interval system is concluded to be stable, the output of our iterative algorithm also indicates the accurate maximal stability margin of this system. Finally, three numerical examples are given to demonstrate the applicability and effectiveness of this algorithm. (C) 2013 IMACS. Published by Elsevier B.V. All rights reserved.

关键词： Stability analysis Dynamic interval systems Interval matrices iterative algorithm Stability margin

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Reconstruction of Compressed Sensing MRI: An Experimental Review among Priors- and Deep Learning- based algorithms 2

Reconstruction of Compressed Sensing MRI: An Experimental Re...

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2nd International Conference on Sustainable Technologies for Industry 4.0 (STI)

作者： Islam, Rafiqul Dhaka Univ Engn & Technol Dept Comp Sci & Engn Gazipur Bangladesh

ISBN: (纸本)9781665404891

Magnetic resonance imaging (MRI) is the most effective and reliable imaging process to visualize the internal organs of the human body for clinical purposes and medical research. Although MRI does not use any radiation effect, it takes a long time to acquire an MRI image that makes discomfort to the patients, especially children and persons who have anxiety. Compressed sensing (CS) is a recently used technique for allowing faster acquisition of MRI. Since CS generates random under-sampling k-space measurements due to allowing faster acquisition, a non-linear algorithm is required for reconstructing a perfect MRI image. In this work, a comparative study is performed among single priors-, combined priors-, and deep learning-based non-linear algorithms for the reconstruction of MRI from CS measurements. Experiments are conducted to perform a comparative study that shows the significant aspects of the algorithms in terms of visual quality and quantitative measurements compared with each other. The results of the experiment proved the superiority of the combined priors-based method when compared with the single priors- and deep learning-based method.

关键词： Compressed Sensing Magnetic Resonance Imaging Regularization Prior iterative algorithm Image reconstruction Deep Learning

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RnR: A Software-Assisted Record-and-Replay Hardware Prefetcher 53

RnR: A Software-Assisted Record-and-Replay Hardware Prefetch...

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53rd Annual IEEE/ACM International Symposium on Microarchitecture (MICRO)

作者： Zhang, Chao Zeng, Yuan Shalf, John Guo, Xiaochen Lehigh Univ Bethlehem PA 18015 USA Lawrence Berkeley Natl Lab Berkeley CA USA

ISBN: (纸本)9781728173832

Applications with irregular memory access patterns do not benefit well from the memory hierarchy as applications that have good locality do. Relatively high miss ratio and long memory access latency can cause the processor to stall and degrade system performance. Prefetching can help to hide the miss penalty by predicting which memory addresses will be accessed in the near future and issuing memory requests ahead of the time. However, software prefetchers add instruction overhead, whereas hardware prefetchers cannot efficiently predict irregular memory access sequences with high accuracy. Fortunately, in many important irregular applications (e.g., iterative solvers, graph algorithms, and sparse matrix-vector multiplication), memory access sequences repeat over multiple iterations or program phases. When the patterns are long, a conventional spatial-temporal prefetcher can not achieve high prefetching accuracy, but these repeating patterns can be identified by programmers. In this work, we propose a software-assisted hardware prefetcher that focuses on repeating irregular memory access patterns for data structures that cannot benefit from conventional hardware prefetchers. The key idea is to provide a programming interface to record cache miss sequence on the first appearance of a memory access pattern and prefetch through replaying the pattern on the following repeats. The proposed Record-and-Replay (RnR) prefetcher provides a lightweight software interface so that the programmers can specify in the application code: 1) which data structures have irregular memory accesses, 2) when to start the recording, and 3) when to start the replay (prefetching). This work evaluated three irregular workloads with different inputs. For the evaluated workloads and inputs, the proposed RnR prefetcher can achieve on average 2.16x speedup for graph applications and 2.91 x speedup for an iterative solver with a sparse matrix-vector multiplication kernel. By leveraging the knowledge f

关键词： hardware prefetcher irregular memory access iterative algorithm

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Polar Code-Aided Frequency Offset Estimation algorithm in Satellite Covert Communication Carrier Synchronization 4

Polar Code-Aided Frequency Offset Estimation Algorithm in Sa...

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4th IEEE Information Technology, Networking, Electronic and Automation Control Conference (ITNEC)

作者： Wu, Jiayi Chen, Chaofan Bu, Xiangyuan Beijing Inst Technol Sch Informat & Elect Beijing Peoples R China

ISBN: (纸本)9781728143903

At present, covert satellite communication has become one of the most important application scenarios in the communication field. Due to various interferences and detections in space communication environment, satellite covert communications usually adopt short codes for channel coding, such as polar codes. However, polar coding method is highly sensitive to carrier synchronization error, and the performance of the satellite covert communication will degrade severely with the presence of carrier frequency offset. Therefore, carrier synchronization is a critical issue in the field of covert satellite communication. Existing carrier synchronization algorithms are mostly based on pilot assistance and have low spectrum utilization. To cope with the challenge of limit of spectrum in satellite communication and at the same time to guarantee a high communication quality, we propose a polar code-aided frequency offset estimation (PCAFOE) algorithm model in this paper. Based on the estimation indicator of RMSE, Monte Carlo simulations and corresponding analysis are presented. Compared with the traditional carrier synchronization algorithm, PCAFOE algorithm is demonstrated with higher estimation accuracy, which is able to effectively improve the carrier synchronization performance of covert satellite communication systems.

关键词： covert satellite communication carrier synchronization polar codes iterative algorithm

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Implementation and Numerical Evaluation for Multiplicative Algebraic Reconstruction Techniques 6

Implementation and Numerical Evaluation for Multiplicative A...

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Conference on Optical System Alignment, Tolerancing, and Verification XIII

作者： Aoyagi, Tomohiro Ohtsubo, Kouichi Aoyagi, Nobuo Toyo Univ Fac Informat Sci & Arts 2100 Kujirai Saitama 3508585 Japan

ISBN: (纸本)9781510638495;9781510638501

Multiplicative algebraic reconstruction techniques (MART) is one of the method of projections onto convex sets (POCS) for solving a system of simultaneous equation. The image reconstruction problem can be discretized and depends on seeking the inverse of some matrix. We apply the MART to image reconstruction problems and evaluate the image quality in computer simulations. It is showed that the error decreases with increasing the number of projections and the number of iterations. It is also showed that the error decreases with increasing the value of initial data.

关键词： image reconstruction MART POCS iterative algorithm tomography

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Numerical simulation for train-track-bridge dynamic interaction considering damage constitutive relation of concrete tracks

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ARCHIVES OF CIVIL AND MECHANICAL ENGINEERING 2021年第3期21卷 116-116页

作者： Xu, Lei Yu, Zhiwu Shan, Zhi Cent South Univ Sch Civil Engn Shaoshan Rd 22 Changsha 410075 Peoples R China Natl Engn Lab High Speed Railway Construct Changsha 410075 Peoples R China

In this work, a novel and practical method is developed to depict the track slab damage and residual strain evolution, where the concrete damage constitutive relation of track slabs is considered within the train-track-bridge dynamics framework. A three-step strain method is presented to judge the load/unloading, compression/tension status of track slab elements ergodically, so that the damage condition and residual strain of track slabs can be determined. To improve the computational accuracy and efficiency, the combination of the matrix augment method and iterative solution algorithm is elucidated in detail. To validate the present model, the solutions among incremental solution, iterative solution, and non-iterative solution are firstly illustrated, and then experimental studies are performed to declare the effectiveness of this model in characterising strain/stress relation of concrete no matter in compression state or in tension state, and finally, other model results are also introduced to prove the effectiveness of this model. In the numerical studies, the damage distributions of track slabs in the longitudinal and lateral direction are presented, where the influence of track irregularities and track slab positions on the bridge is clarified, besides, the evolution of the damage and residual strain of a track slab subject to a moving train is revealed.

关键词： Train-track-bridge dynamic interaction Damage constitutive relation Stress strain status iterative algorithm

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Accurate Calculation of the Settling Time of a Linear System Using New Expressions and iterative algorithms

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CIRCUITS SYSTEMS AND SIGNAL PROCESSING 2018年第1期37卷 408-431页

作者： Chagra, Wassila Univ Tunis El Manar Lab Analyse Conception & Commande Syst Inst Preparatoire Etud Ingn El Manar LR11ES20Ecole Natl Ingn Tunis BP 37 Tunis 1002 Tunisia

The purpose of this paper is to achieve an exhaustive and generalized method for the accurate calculation of the linear system settling time. Thus, the classical settling time expressions for the second-order linear systems are reviewed. Then, new expressions are proposed and developed for the step response of the second-order and for higher-order under-damped and over-damped linear systems. The proposed expressions are different from all the existing ones, and they are more accurate. In addition, iterative algorithms that can be easily implemented are proposed in order to achieve accurate calculation of the settling time. The accuracy of the new expressions and the proposed iterative algorithms are illustrated by several numerical simulation examples.

关键词： Settling time Accurate calculation Fixed point method iterative algorithm Higher-order linear systems

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High-Performance Blind Spectrum Sensing: An iterative Unsupervised Learning Approach 5

High-Performance Blind Spectrum Sensing: An Iterative Unsupe...

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5th International Conference on Information Science, Computer Technology and Transportation (ISCTT)

作者： Gao, Shishun Zhao, Haitao Zhang, Jiao Wang, Haijun Wei, Jibo Natl Univ Def Technol Coll Elect Sci Changsha 410073 Peoples R China

ISBN: (纸本)9781728185750

In the research of blind spectrum sensing, unsupervised learning has been regarded as a promising technology to detect spectrum status without any prior knowledge or labeled signals. However, the detection performance of the existing unsupervised sensing methods is usually far below that of supervised sensing methods. In order to overcome this problem, we propose an iterative unsupervised learning based cooperative spectrum sensing (CSS) algorithm, where the concept of iteration is introduced to improve detection performance. Specifically, in each iteration, i) The CSS technology is first used to make global labels by combining the local labels of the individual detectors constructed in the last iteration;ii) And then, individual detectors are constructed by utilizing supervised learning to fit the mapping from local sample set to the current global labels. During above iterative process, the global labels contribute to improving individual detectors, while these improved individual detectors can cooperatively make more accurate global labels, which will be utilized in next iteration. Finally, with the increase of the number of iterations, these individual detectors can be used to online cooperatively detect spectrum status when there are only slight changes in global labels. Simulation results show that the proposed algorithm can achieve comparable individual and cooperative detection performance with the existing supervised sensing methods over a wide signal-to-noise ratio (SNR) region.

关键词： Cooperative spectrum sensing unsupervised learning iterative algorithm cognitive radio

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Reducing the Noise Impact of Small Aircraft through Indirect Trajectory Optimization

Reducing the Noise Impact of Small Aircraft through Indirect...

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AIAA Aviation Forum

作者： Galles, Matthew B. Newman, Brett NASA Langley Res Ctr Struct Acoust Branch MS 463 Hampton VA 23681 USA Old Dominion Univ Dept Mech & Aerosp Engn Norfolk VA 23529 USA

ISBN: (数字)9781624105982

ISBN: (纸本)9781624105982

This research examined the feasibility of incorporating an acoustic metric into the optimization of an aircraft trajectory to reduce the noise experienced by an observer. The method investigated a perturbed path of an unmanned aerial system with specified boundary conditions on position and velocity while maintaining a nominal flight speed. An acoustic model based on Gutin's work was developed to estimate propeller noise as a function of flight parameters, propulsion characteristics, and spatial location. A trajectory was then optimized a priori to reduce the noise experienced by an observer. Multiple simulations were performed and results showed that integrating an acoustic metric into the path planning process could be used to reduce the noise impact on an observer with no perturbation to the nominal flight speed.

关键词： Pontryagin's Maximum Principle Aircrafts Propeller Noise Real Time Path Planning Aircraft Trajectory Unmanned Aerial Systems Overall Sound Pressure Level Flight Control System iterative algorithm Flight Trajectory

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A nonlinear subiteration strategy for improved robustness of pseudo-transient continuation methods

A nonlinear subiteration strategy for improved robustness of...

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AIAA Aviation Forum

作者： Plouviez, Leon Wolff, Eric Wukiet, Nathan A. Schrock, Christopher Def Sci & Technol Lab Grad Dev Scheme Fareham Hants England Ohio Aerosp Inst Dayton OH USA Air Force Res Lab Wright Patterson AFB OH USA Multidisciplinary Sci & Technol Ctr Dayton OH USA

ISBN: (数字)9781624105982

ISBN: (纸本)9781624105982

Newton's method for solving nonlinear systems of equations have historically been augmented with pseudo-transient continuation (PTC) methods as a strategy for constructing a globally convergent nonlinear iterative algorithm. The PTC-Newton algorithm is often combined with other globalisation approaches such as line searches and residual smoothing to improve overall convergence and robustness of the method [1]. In this work a nonlinear subiteration strategy is applied to the steps of the PTC procedure to improve the robustness of the overall nonlinear iterative method. This method is compared against a baseline PTC-Newton algorithm and a residual smoothing procedure proposed by Mavriplis et al. [2]. Two problems are studied in order to quantify differences in robustness and convergence properties between the methods. These problems are: a simulation of subsonic, turbulent flow over a Joukowski aerofoil using the Reynolds-Averaged Navier-Stokes (RANS) equations and a simulation of inviscid, supersonic flow in a ramp channel using the Euler equations with artificial viscosity for shock capturing. Results indicate the subiteration strategy can ameliorate convergence challenges that might traditionally result in backtracking failure or stagnation. The subiteration strategy is shown to converge in cases where both PTC-Newton and residual smoothing methods encounter failure, and this robustness is then leveraged to enable stronger CFL ramping. Significant robustness and efficiency benefits are shown in both cases

关键词： Courant Friedrichs Lewy Reynolds Averaged Navier Stokes Discontinuous Galerkin Method Aerofoil Supersonic Flow Nonlinear Systems Viscosity iterative algorithm Euler Equations Spalart Allmaras Turbulence Model

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