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New Algorithm for Constructing and Computing Scale Invariants of 3D Tchebichef Moments

MATHEMATICAL PROBLEMS IN ENGINEERING 2013年第1期2013卷 1-8页

作者： Wu, Haiyong Coatrieux, Jean Louis Shu, Huazhong Southeast Univ Sch Comp Sci & Engn Lab Image Sci & Technol Nanjing 210096 Jiangsu Peoples R China INSERM U1099 F-35000 Rennes France Univ Rennes 1 Lab Traitement Signal & Image F-35000 Rennes France Ctr Rech Informat Biomed Sino Francais CRIBs Nanjing 210096 Jiangsu Peoples R China

Scale invariants of Tchebichef moments are usually achieved by a linear combination of corresponding invariants of geometric moments or via an iterative algorithm to eliminate the scale factor. According to the properties of Tchebichef polynomials, we propose a new approach to construct scale invariants of Tchebichef moments. An algorithm based on matrix multiplication is also provided to efficiently compute the 3D moments and invariants. Several experiments are carried out to validate the effectiveness of our descriptors and algorithm.

关键词： computer algorithms SCALE invariance (Statistical physics) LINEAR systems GEOMETRIC analysis ITERATIVE methods (Mathematics) POLYNOMIALS MATRIX multiplications

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Low-Frequency Acoustic-Structure Analysis Using Coupled FEM-BEM Method

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MATHEMATICAL PROBLEMS IN ENGINEERING 2013年第1期2013卷 1-8页

作者： Feng, Jinlong Zheng, Xiaoping Wang, Haitao Wang, HongTao Zou, Yuanjie Liu, Yinghua Yao, Zhenhan Tsinghua Univ Sch Aerosp Beijing 100084 Peoples R China Tsinghua Univ Inst Nucl & New Energy Technol Beijing 100084 Peoples R China China Acad Space Technol Beijing 100094 Peoples R China

A numerical algorithm based on finite element method (FEM) and boundary element method (BEM) is proposed for the analyses of acoustic-structure coupled problems. By this algorithm, the structural domain and the acoustic domain are modelled by FEM and BEM, respectively, which are coupled with each other through the consideration of the appropriate compatibility and equilibrium conditions on the interface of the two domains. To improve the computational efficiency, the adaptive cross approximation (ACA) approach is incorporated into the proposed algorithm to deal with the nonsymmetric and fully populated matrices resulting from the coupling of the FEM and BEM. The validity and the high efficiency of the present approach are demonstrated by two examples.

关键词： BOUNDARY element methods FINITE element method NUMERICAL analysis computer algorithms APPROXIMATION theory

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Robust Iterative Learning Control for a Class of Linear Systems with Data Dropouts

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MATHEMATICAL PROBLEMS IN ENGINEERING 2013年第1期2013卷 1-9页

作者： Wang Rui Ma Xinghe Bu Xuhui Henan Polytech Univ Sch Elect Engn & Automat Jiaozuo 454000 Peoples R China

A robust iterative learning control algorithm is proposed for a class of intermittent systems with disturbances and uncertain initial conditions. Based on the contraction mapping approach, the convergence condition for the proposed algorithm is first given, and then the bounds on control input and output trajectories can be obtained. It is shown that these bounds depend on bounds on the initial condition errors and disturbances, and the bounds are zero in the absence of these disturbances. A numerical example is also given to verify the theoretical result.

关键词： ROBUST control ITERATIVE methods (Mathematics) MACHINE learning computer algorithms BOUNDS (Mathematics) NUMERICAL analysis

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A Work-Demand Analysis Compatible with Preemption-Aware Scheduling for Power-Aware Real-Time Tasks

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MATHEMATICAL PROBLEMS IN ENGINEERING 2013年第1期2013卷 1-16页

作者： Chen, Da-Ren Chen, Mu-Yen Chen, You-Shyang Chen, Lin-Chih Natl Taichung Univ Sci & Technol Dept Informat Management Taichung 404 Taiwan Hwa Hsia Inst Technol Dept Informat Management New Taipei City 235 Taiwan Natl Dong Hwa Univ Dept Informat Management Shoufeng 97401 Hualien Taiwan

Due to the importance of slack time utilization for power-aware scheduling algorithms, we propose a work-demand analysis method called parareclamation algorithm (PRA) to increase slack time utilization of the existing real-time DVS algorithms. PRA is an online scheduling for power-aware real-time tasks under rate-monotonic (RM) policy. It can be implemented and fully compatible with preemption-aware or transition-aware scheduling algorithms without increasing their computational complexities. The key technique of the heuristics method doubles the analytical interval and turns the deferrable workload out the potential slack time. Theoretical proofs show that PRA guarantees the task deadlines in a feasible RM schedule and takes linear time and space complexities. Experimental results indicate that the proposed method combining the preemption-aware methods seamlessly reduces the energy consumption by 14% on average over their original algorithms.

关键词： POWER aware computing REAL-time computing computer algorithms computer scheduling HEURISTIC algorithms ENERGY consumption

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Motion Control of Four-Wheel Independently Actuated Electric Ground Vehicles considering Tire Force Saturations

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MATHEMATICAL PROBLEMS IN ENGINEERING 2013年第1期2013卷 1-8页

作者： Wang, Rongrong Karimi, Hamid Reza Chen, Nan Yin, Guodong Wang, Jinxiang SE Univ Sch Mech Engn Nanjing 211189 Jiangsu Peoples R China Univ Agder Fac Sci & Engn Dept Engn N-4898 Grimstad Norway

A vehicle stability control approach for four-wheel independently actuated (FWIA) electric vehicles is presented. The proposed control method consists of a higher-level controller and a lower-level controller. An adaptive control-based higher-level controller is designed to yield the vehicle virtual control efforts to track the desired vehicle motions due to the possible modeling inaccuracies and parametric uncertainties. The lower-level controller considering tire force saturation is given to allocate the required control efforts to the four in-wheel motors for providing the desired tire forces. An analytic method is given to distribute the high-level control efforts, without using the numerical-optimization-based control allocation algorithms. Simulations based on a high-fidelity, CarSim, and full-vehicle model show the effectiveness of the control approach.

关键词： FOUR-wheel driving ELECTRIC vehicles ADAPTIVE control system stability ELECTRIC actuators MOTION control devices computer algorithms

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Factorized Point Based Global Illumination

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computer GRAPHICS FORUM 2013年第4期32卷 117-123页

作者： Wang, Beibei Huang, Jing Buchholz, Bert Meng, Xiangxu Boubekeur, Tamy Telecom ParisTech CNRS Paris France Shandong Univ Jinan Peoples R China NYU Polytech Inst New York NY 10003 USA

The Point-Based Global Illumination (PBGI) algorithm is composed of two major steps: a caching step and a multiview rasterization step. At caching time, a dense point-sampling of the scene is shaded and organized in a spatial hierarchy, with internal nodes approximating the radiance of their subtrees using spherical harmonics. At rasterization time, a microbuffer is instantiated at the unprojected position of each image pixel (receiver). Then, a view-adaptive level-of-detail of the scene is extracted in the form of a tree cut and rasterized in the receiver's microbuffer, solving for visibility using a local variant of the z-buffer. Finally, the pixel color is computed by convolving its filled microbuffer with the surface BRDF. This noise-free indirect lighting method is widely used in the industry and captures several critical lighting effects, including ambient occlusion, color bleeding, (indirect) soft-shadows and environment lighting. However, we observe a large redundancy in this algorithm, both in cuts and receivers'microbuffers, which stems from their relatively low resolution. In this paper, we propose an evolution of PBGI which exploits spatial coherence to reduce these redundant computations. Starting from a similarity-based variational clustering of the receivers, we compute a single tree cut and rasterize a single microbuffer for each cluster. This per-cluster microbuffer provides a faithful approximation of the incident radiance for distant nodes and is composited over a receiver-specific microbuffer rasterizing only the closest nodes of the cluster's cut. This factorized approach is easy to integrate in any existing PBGI implementation and offers a significant rendering speed-up for a negligible and controllable approximation error.

关键词： GLOBAL illumination algorithms APPROXIMATION error SPHERICAL harmonics computer graphics computer algorithms

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Online Manifold Regularization by Dual Ascending Procedure

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MATHEMATICAL PROBLEMS IN ENGINEERING 2013年第1期2013卷 1-16页

作者： Sun, Boliang Li, Guohui Jia, Li Zhang, Hui Natl Univ Def Technol Dept Informat Syst & Management Changsha 410073 Hunan Peoples R China

We propose a novel online manifold regularization framework based on the notion of duality in constrained optimization. The Fenchel conjugate of hinge functions is a key to transfer manifold regularization from offline to online in this paper. Our algorithms are derived by gradient ascent in the dual function. For practical purpose, we propose two buffering strategies and two sparse approximations to reduce the computational complexity. Detailed experiments verify the utility of our approaches. An important conclusion is that our online MR algorithms can handle the settings where the target hypothesis is not fixed but drifts with the sequence of examples. We also recap and draw connections to earlier works. This paper paves a way to the design and analysis of online manifold regularization algorithms.

关键词： MANIFOLDS (Mathematics) DUALITY (Logic) CONSTRAINT satisfaction (Artificial intelligence) MATHEMATICAL optimization computer algorithms COMPUTATIONAL complexity

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Driving Control Research for Longitudinal Dynamics of Electric Vehicles with Independently Driven Front and Rear Wheels

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MATHEMATICAL PROBLEMS IN ENGINEERING 2013年第1期2013卷 1-17页

作者： Liu, Wei He, Hongwen Peng, Jiankun Beijing Inst Technol Natl Engn Lab Elect Vehicles Beijing 100081 Peoples R China

This paper takes the electric off-road vehicle with separated driven axles as the research object. To solve the longitudinal dynamics driving control problems, vehicle dynamics model, and control strategies were studied and the corresponding simulation was carried out. An 8-DOF vehicle dynamics model with separated driven axles was built. The driving control strategies on the typical roads were put forward. The recognition algorithm of the typical road surfaces based on the wheels' slip rates was proposed. And the two control systems were designed including the pedal opening degree adjustment control system based on PI algorithm and the interaxle torque distribution control system based on sliding mode control algorithm. The driving control flow of the proposed vehicle combining the pedal adjustment control system with the interaxle torque distribution control system was developed. And the driven control strategies for the typical roads were simulated. Simulation results show that the proposed drive control strategies can adapt to different typical road surfaces, limit the slip rates of the driving wheels within the stable zone, and ensure the vehicle driving safely and stably in accordance with the driver's intention.

关键词： AUTOMOBILE driving LONGITUDINAL method ELECTRIC vehicles TORQUE computer algorithms

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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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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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