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Structural damage detection using enhanced damage locating vector method with limited wireless sensors

JOURNAL OF SOUND AND VIBRATION 2009年第4-5期328卷 411-427页

作者： Quek, S. T. Tran, V. A. Hou, X. Y. Duan, W. H. Natl Univ Singapore Dept Civil Engn Singapore 117576 Singapore

For detection of damage in structures, the damage locating vector (DLV) method is adapted to account for the different types and variations of internal forces and capacities along the length of each element by using the normalized cumulative energy instead of the normalized cumulative stress. To filter out the actual damaged elements from the identified set of potential damaged elements, an intersection scheme is proposed. A 2-D warehouse structure comprising beam and column elements with constant and varied cross-sectional areas, and truss elements is used to verify the enhancements to the DLV method. With wireless sensors being integrated into damage detection systems, practical issues need to be addressed in conjunction with the detection algorithm employed. For cases where raw signals are transmitted, the intermittent loss of data packets during transmission from the sensor nodes to the base station needs to be addressed. An algorithm to patch the lost data is proposed and when integrated with the DLV damage detection methodology, is experimentally shown to be feasible using a 3-D modular truss structure. (C) 2009 Elsevier Ltd. All rights reserved.

关键词： STRUCTURAL frames STRUCTURAL failures computer algorithms CROSS-sectional method TRUSSES DETECTORS DATA packets & packeting

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Toward scalable real-time messaging

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IBM SYSTEMS JOURNAL 2008年第2期47卷 237-250页

作者： Bauer, D. Garces-Erice, L. Rooney, S. Scotton, P. IBM Res Div Zurich Res Lab CH-8803 Ruschlikon Switzerland

Conventional messaging technologies have been designed for large transactional systems, making the prediction and calibration of their delay impractical. In this paper, we present a minimal messaging system, implemented in Java (TM), that is designed to enable the analysis, modeling, and calibration of the expected performance of these technologies. We describe the algorithms and protocols that underlie this messaging system, show how an analysis can be performed, and give the actual measured performance figures. We show that the system achieves a throughput of more than 100,000 messages per second with less than 120-millisecond maximum latency, in the test environment. At 10,000 messages per second, a maximum latency of 5 milliseconds is measured. The algorithms make use of lock-free data structures, which allow the throughput to scale on multi-core systems.

关键词： ENTERPRISEWIDE computing REAL-time control SCALABILITY (Systems engineering) JAVA (computer program language) computer algorithms computer network protocols computer systems

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An investigation on the application of predictive control for controlling screw position and velocity on an injection molding machine

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POLYMER ENGINEERING AND SCIENCE 2007年第4期47卷 390-399页

作者： Dubay, Rickey Pramujati, Bambang Han, Jianguo Strohmaier, Franz Univ New Brunswick Dept Mech Engn Fredericton NB E3B 5A3 Canada Sepuluh Nopember Inst Technol Dept Mech Engn Surabaya 60111 East Java Indonesia Engel Canada Inc Guelph ON N1K 1C2 Canada

Injection velocity is one of the key parameters in the injection molding process that has significant effect on part quality, influencing common problems, such as flashing and short shots. Different products require specific molding conditions, including mold and melt temperatures, velocity profiles, and polymers, making the injection velocity dynamics vary significantly and difficult for high precision velocity control. Two predictive controllers were developed to control the screw injection velocity. The first approach uses a position sensor as feedback and a simplified predictive controller to track an injection velocity setpoint profile. The controller was developed and implemented utilizing single-step change and multistep change open loop tests. The second strategy uses a multimodel dynamic matrix predictive controller to overcome the nonlinear characteristics of the injection velocity dynamics as the mold is being filled. Velocity feedback is provided by high speed processing of the position analog signal. This approach utilizes several open loop injection velocity profiles to generate corresponding dynamic matrices for the controller. As a result, this controller is modified or retuned automatically when setpoint changes in injection velocity occur, as well as when using different polymers and molds. The close loop results for both simulations and real time control have demonstrated that the two predictive controllers provided good setpoint tracking performance for wide ranging position and velocity profiles.

关键词： DEPENDENT ADAPTIVE CONTROLLER OPTIMAL ANTICIPATORY CONTROL RAM VELOCITY CONTROL ALGORITHM FILLING VELOCITY MODEL VELOCITY PROFILING Injection molding position sensor setpoint Controllers Predictive controllers Predictive control Injections filling velocity RAM VELOCITY OPEN-LOOP computer algorithms

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RAINFLOW COUNTING ALGORITHM FOR VERY LONG STRESS HISTORIES

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INTERNATIONAL JOURNAL OF FATIGUE 1987年第4期9卷 223-228页

作者： GLINKA, G KAM, JCP The authors are with the London Centre for Marine Technology Department of Mechanical Engineering University College London Torrington Place London WC1E 7JE UK

A computer algorithm for rainflow cycle counting of very long stress histories is presented. The procedure enables the rainflow counting to be performed without prior knowledge of the whole stress history being analysed. The stress history can be read and analysed by the computer one block at a time without reading the whole history at once. This will enable small computers to analyse very long stress histories because the length of one block can be adjusted to the computer capabilities. The algorithm does not require any rearrangment of the stress history before the start of counting and the peaks and troughs can be analysed as they were recorded in service.

关键词： rainflow counting computer algorithms stress history analysis

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Virtual Machine Placement Algorithm for Both Energy-Awareness and SLA Violation Reduction in Cloud Data Centers

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SCIENTIFIC PROGRAMMING 2016年第1期2016卷 1-12页

作者： Zhou, Zhou Hu, Zhigang Li, Keqin Cent South Univ Sch Software Changsha 410083 Hunan Peoples R China SUNY Coll New Paltz Dept Comp Sci New Paltz NY 12561 USA

The problem of high energy consumption is becoming more and more serious due to the construction of large-scale cloud data centers. In order to reduce the energy consumption and SLA violation, a new virtual machine (VM) placement algorithm named ATEA (adaptive three-threshold energy-aware algorithm), which takes good use of the historical data from resource usage by VMs, is presented. In ATEA, according to the load handled, data center hosts are divided into four classes: hosts with little load, hosts with light load, hosts with moderate load, and hosts with heavy load. ATEA migrates VMs on heavily loaded or little-loaded hosts to lightly loaded hosts, while the VMs on lightly loaded and moderately loaded hosts remain unchanged. Then, on the basis of ATEA, two kinds of adaptive three-threshold algorithm and three kinds of VMs selection policies are proposed. Finally, we verify the effectiveness of the proposed algorithms by CloudSim toolkit utilizing real-world workload. The experimental results show that the proposed algorithms efficiently reduce energy consumption and SLA violation.

关键词： VIRTUAL machine systems computer algorithms SERVICE level agreements CLOUD computing ENERGY consumption of computers

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A robust Hough transform algorithm for determining the radiation centers of circular and rectangular fields with subpixel accuracy

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PHYSICS IN MEDICINE AND BIOLOGY 2009年第3期54卷 555-567页

作者： Du, Weiliang Yang, James Univ Texas MD Anderson Canc Ctr Dept Radiat Phys Houston TX 77030 USA

Uncertainty in localizing the radiation field center is among the major components that contribute to the overall positional error and thus must be minimized. In this study, we developed a Hough transform (HT)-based computer algorithm to localize the radiation center of a circular or rectangular field with subpixel accuracy. We found that the HT method detected the centers of the test circular fields with an absolute error of 0.037 +/- 0.019 pixels. On a typical electronic portal imager with 0.5 mm image resolution, this mean detection error was translated to 0.02 mm, which was much finer than the image resolution. It is worth noting that the subpixel accuracy described here does not include experimental uncertainties such as linac mechanical instability or room laser inaccuracy. The HT method was more accurate and more robust to image noise and artifacts than the traditional center-of-mass method. Application of the HT method in Winston-Lutz tests was demonstrated to measure the ball-radiation center alignment with subpixel accuracy. Finally, the method was applied to quantitative evaluation of the radiation center wobble during collimator rotation.

关键词： computer algorithms algorithms MATHEMATICAL models MATHEMATICAL analysis

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Denoising of document images based on similarity and connectivity principles

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computerS & ELECTRICAL ENGINEERING 2014年第8期40卷 79-85页

作者： Awad, Ali S. Al Azhar Univ Gaza Fac Engn & Informat Technol Gaza Israel

This paper proposes a highly efficient denoising technique in restoring document images that have been corrupted by impulse noise. The proposed algorithm consists of a number of shells and is based on the connectivity principle;whereby, pixels that have connections with at least one other pixel in each of the consecutive shells are deemed noise-free pixels. Simulation results indicate that the new denoising method is not only useful in eliminating the noise efficiently;it also keeps the fine details of the image. (C) 2014 Elsevier Ltd. All rights reserved.

关键词： Image denoising Document imaging systems Image reconstruction Burst noise computer algorithms Pixels

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Preemptive scheduling on a small number of hierarchical machines

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INFORMATION AND COMPUTATION 2008年第5期206卷 602-619页

作者： Dosa, Gyoergy Epstein, Leah Univ Haifa Dept Math IL-31905 Haifa Israel Univ Pannonia Dept Math Veszprem Hungary

We consider preemptive offline and online scheduling on identical machines and uniformly related machines in the hierarchical model, with the goal of minimizing the makespan. In this model, each job can be assigned to a subset of the machines which is a prefix of the machine set. We design optimal offline and online algorithms for two uniformly related machines, both when the machine of higher hierarchy is faster and when it is slower, as well as for the case of three identical machines. Specifically, for each one of the three variants, we give a simple formula to compute the makespan of an optimal schedule, provide a linear time offline algorithm which computes an optimal schedule and design an online algorithm of the best possible competitive ratio. (c) 2008 Published by Elsevier Inc.

关键词： algorithms ONLINE data processing computer algorithms MULTILEVEL models (Statistics)

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A comparative study of land surface temperature retrieval methods from remote sensing data

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CANADIAN JOURNAL OF REMOTE SENSING 2013年第1期39卷 59-73页

作者： Benmecheta, A. Abdellaoui, A. Hamou, A. UPEC Lab Urba F-94010 Creteil France Univ Oran Fac Sci Lab Chim Polymeres El Menouer 31000 Oran Algeria

The main purpose of this paper is to describe, compare, and analyze the various extraction methods for land surface temperature (LST) in terms of their computational algorithms, their different input parameters, and their relative accuracy to make them more readily usable by a broader cross-section of nontechnical practitioners. Due to the heterogeneity of most natural land surfaces, the atmospheric influence, and a wide variety of satellite sensors, the estimation and validation of LST can be difficult. Furthermore, the large number of algorithms developed to deal with this heterogeneity has led to widespread confusion on how and when to use one algorithm versus another. This paper provides a concise, but thorough, overview of the different algorithms used for the estimation of land surface temperature as well as a comparative list of methods and associated parameters that facilitate, to the general user, the selection and application of the most appropriate method for LST extraction given the situation at hand. We restricted our analysis for the single-channel algorithms to two models. We included a two-channel algorithm (or split-window when it is applied in the region 10-12.5 mu m) according to the literature. The Temperature Emissivity Separation algorithm was also taken into account. The determination of the key parameters needed to execute these algorithms is presented.

关键词： LAND surface temperature RESEARCH computer algorithms DETECTORS EMISSIVITY ATMOSPHERIC temperature -- Research ESTIMATION theory

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Modeling, Identification, and Control of an Unmanned Surface Vehicle

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JOURNAL OF FIELD ROBOTICS 2013年第3期30卷 371-398页

作者： Sonnenburg, Christian R. Woolsey, Craig A. Virginia Tech Dept Aerosp & Ocean Engn Blacksburg VA 24061 USA

This paper describes planar motion modeling for an unmanned surface vehicle (USV), including a comparative evaluation of several experimentally identified models over a wide range of speeds and planing conditions. The modeling and identification objective is to determine a model that is sufficiently rich to enable effective model-based control design and trajectory optimization, sufficiently simple to allow parameter identification, and sufficiently general to describe a variety of hullforms and actuator configurations. We focus, however, on a specific platform: a modified rigid hull inflatable boat with automated throttle and steering. Analysis of experimental results for this vessel indicates that Nomoto's first-order steering model provides the best compromise between simplicity and fidelity at higher speeds. At low speeds, it is helpful to include a first-order lag model for sideslip. Accordingly, we adopt a multiple model approach in which the model structure and parameter values are scheduled based on the nominal forward speed. The speed-scheduled planar motion model may be used to generate dynamically feasible trajectories and to develop trajectory tracking control laws. The paper describes the development, analysis, and experimental implementation of two trajectory tracking control algorithms: a cascade of proportional-derivative controllers and a nonlinear controller obtained through backstepping. Experimental results indicate that the backstepping controller is much more effective at tracking trajectories with highly variable speed and course angle. (c) 2013 Wiley Periodicals, Inc.

关键词： Variable speed Parameter identification Modeling low speed design control trajectory tracking computer algorithms UNMANNED identification and control Model structures Controllers Ground vehicles heading angle

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