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Chinese Control and Decision Conference, CCDC

作者： Dengfeng Chen Qichun Ji Hongcai Zhang Information and Control Engineering School Xi''an University of Architecture and Technology Xi'an China College of Automation Control Northwestern Polytechnical University Xi'an China

Based on the studies of the manufacturing procedure of the cement industries, a self-optimizing load-based control strategy for the material pulverization system was proposed. Both the hardware and the software implem... 详细信息

关键词： Conferences Control systems Power demand Productivity

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Autonomous Integrated Navigation Plan for Space Transfer Vehicle

Autonomous Integrated Navigation Plan for Space Transfer Veh...

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International Symposium on Systems and Control in Aerospace and Astronautics (ISSCAA)

作者： Weihua Ma Yajun Xu Yong Bao Bo Yang College ofAstronautics Northwestern Polytechnical University Xi'an China Aero Engineering Institute Civil Aviation Flight University of China Sichuan China

Space transfer vehicle (STV), which performs missions such as servicing, repairing and rescuing in space without the ground tracking or communication, creates the requirement for the development of an autonomous navigation capability. The navigation sensors should have autonomous characteristics. Strapdown inertial navigation system (SINS), Global Positioning System (GPS) and star sensors (SS) are selected as the navigation sensors for STV. Models of SINS navigation and error for STV are described, but some matrix parameter in models is re-derived. Attitude of SINS is modified as a more intuitionistic mode, too. The extend Kalman filter(EKF) of the SINS/GPS/SS is constructed. Simulations show SINS/GPS/SS could supply the better estimation of position, velocity and attitude during STV orbit changing mission.

关键词： Navigation Remotely operated vehicles Space vehicles Mobile robots Silicon compounds Global Positioning System Sensor phenomena and characterization Space missions Sensor systems Land vehicles

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Bivariate evaluation of cylinder implant diameter and length: A three-dimensional finite element analysis

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Journal of Prosthodontics 2008年第4期17卷 286-293页

作者： Kong, Liang Sun, Yingying Hu, Kaijin Li, Dehua Hou, Rui Yang, Jin Liu, Baolin Department of Oral and Maxillofacial Surgery School of Stomatology Fourth Military Medical University Xi'an China Department of Implantology School of Stomatology Fourth Military Medical University Xi'an China Department of Civil Engineering Northwestern Polytechnical University Xi'an China Department of Implantology College of Stomatology Fourth Military Medical University Xi'an 710032 Changlexi Street 145 China

Purpose: To evaluate continuous and simultaneous variations of implant diameter and length for an experimental cylinder implant. Materials and Methods: A finite element model of a mandible segment with implant was created. The range of implant diameter (D) was set from 2.5 to 5.0 mm, and that of implant length (L) from 6.0 to 16.0 mm. The maximum Von Mises stresses in the mandible were evaluated, and the sensitivity of the stresses in the mandible to the variables was also evaluated. Results: Under axial load, the maximum von Mises stresses in cortical and cancellous bones decreased by 73.3% and 69.4%, respectively, with D and L increasing. Under buccolingual load, those decreased 83.8% and 79.2%, respectively. When D exceeded 3.9 mm and L exceeded 10.0 mm, the tangent slope rate of the maximum von Mises stress response curve ranged from -1 to 0. The variation of the maximum von Mises stresses in the mandible was more sensitive to D than to L. Conclusions: Buccolingual force is apt to be influenced by the two implant parameters;implant diameter and length favor stress distribution in cortical bone and cancellous bone, respectively. Implant diameter exceeding 3.9 mm and implant length exceeding 10.0 mm are the optimal choice for type B/2 bone in a cylinder implant. The implant diameter is more important than length in reducing bone stress. © 2008 by The American College of Prosthodontists.

关键词： Bivariate Dental implant Implant diameter Implant length Stress Three-dimensional finite element analysis

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Error Restricted Piecewise Linear Representation of Time Series Based on Special Points

Error Restricted Piecewise Linear Representation of Time Ser...

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World Congress on Intelligent Control and Automation (WCICA)

作者： Pengtao Jia Huacan He Tao Sun School of Computer Science Northwestern Polytechnical University Xi'an China Department of Computer Science Xi''an University of Science and Technology Xi'an China School of Architecture and Civil Engineering Xi''an University of Science and Technology Xi'an China

Time series composed of a series of data observed according to time sequence. There are large numbers of time series in the field of automatic control. Usually time series data is massive. Sometimes, it is inefficient or impractical to mine the original time series data directly. So time series should be represented on higher level. Piecewise Linear Representation is perhaps the most frequently used representation with lower dimensions of index structure and the faster speed of calculation. But PLR needs a parameter k given by users and to make certain k is not easy for the users. We put forward an algorithm of error restricted piecewise linear representation based on special points that can give the number of fitting lines automatically according to a given error e. And it has lower time complexity than other error restricted algorithm, such as sliding windows, Bottom-Up, Top-Down. According to experiments our algorithm leads to less fitting error and better performance than other algorithms. So it would be more efficient in the real application of control fields.

关键词： Time series analysis Approximation algorithms Fitting Approximation methods Complexity theory Piecewise linear approximation Algorithm design and analysis

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A Reverse Numerical Approach to Determine Elastic-plastic Properties of Multi-layer Material Systems with Flat Cylindrical Indenters

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Journal of Materials Science & Technology 2007年第5期23卷 707-712页

作者： Baoxing XU Zhufeng YUE School of Mechanics Civil Engineering and Architecture Northwestern Polytechnical University Xi＇an 710072 China

In the present study, the indentation testing with a flat cylindrical indenter on typical multi-layer material systems was simulated successfully by finite element method. The emphasis was put on the methods of extracting the yield stresses and strain-hardening modulus of upper and middle-layers of three-layer material systems from the indentation testing. The slope of the indentation depth to the applied indentation stress curve was found to have a turning point, which can be used to determine the yield stress of the upper-layer. Then, a different method was also presented to determine the yield stress of the middle-layer. This method was based on a set of assumed applied indentation stresses which were to be intersected by the experimental results in order to meet the requirement of having the experimental indentation depth. At last, a reverse numerical algorithm was explored to determine the yield stresses of upper and middle-layers simultaneously by using the indentation testing with two different size indenters. This method assumed two ranges of yield stresses to simulate the indentation behavior. The experimental depth behavior was used to intersect the simulated indentation behavior. And the intersection corresponded to the values of yield stresses of upper and middle-layers. This method was also used further to determine the strain-hardening modulus of upper and middle-layers simultaneously.

关键词： Multi-layer material systems Indentation testing Finite element method （FEM） Yield stress Strain-hardening modulus

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A Numerical Method for Cavity Identification in Beams on an Elastic Foundation

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Tsinghua Science and Technology 2007年第5期12卷 540-545页

作者：葛洪海许金余 School of Mechanics Civil Engineering and Architecture Northwestern Polytechnical University

An analytical solution for the natural frequencies of a beam containing a cavity on an elastic foundation is presented. Based on the analytical solution, a numerical method for identifying cavities in the foundation is developed. The position and size of the cavities are identified by minimizing an objective function, which is formulated according to the difference between the computed and measured natural frequencies of the system. The conjugate gradient algorithm is adopted for minimizing the objective function. Some numerical examples are presented to demonstrate the applicability of the presented cavity determination method. The results show that the presented method can be used to identify the cavity position and size conveniently and efficiently.

关键词： pavement-subgrade system beam on an elastic foundation cavity identification natural frequency conjugate gradient algorithm

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Multi-symplectic methods for membrane free vibration equation

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Applied Mathematics and Mechanics(English Edition) 2007年第9期28卷 1181-1189页

作者：胡伟鹏邓子辰李文成 School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnincal University School of Science Northwestern Polytechnical University

In this paper, the multi-symplectic formulations of the membrane free vibration equation with periodic boundary conditions in Hamilton space are considered. The complex method is introduced and a semi-implicit twenty-seven-points scheme with certain discrete conservation laws-a multi-symplectic conservation law （CLS）, a local energy conservation law （ECL） as well as a local momentum conservation law （MCL） --is constructed to discrete the PDEs that are derived from the membrane free vibration equation. The results of the numerical experiments show that the multi-symplectic scheme has excellent long-time numerical behavior,

关键词： multi-symplectic complex discretization Runge-Kutta methods

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Assessment of Structural Damage Condition Based on Fuzzy Pattern Recognition

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International Journal of Plant engineering and Management 2008年第1期000卷

作者： WU Zi-yan ZHANG Yu School of Mechanics Civil Engineering and Architecture Northwestern Polytechnical University Xi'an 710072 P.R.China

This paper presents a new method of damage condition assessment that allows accommodating other types of uncertainties due to ambiguity, vagueness, and fuzziness that are statistically non-describable. In this method, healthy observations are used to construct a fuzzy set representing sound performance characteristics. Additionally, the bounds on the similarities among the structural damage states are prescribed by using the state similarity matrix. Thus, an optimal group fuzzy sets representing damage states such as little, moderate, and severe damage can be inferred as an inverse problem from healthy observations only. The optimal group of damage fuzzy sets is used to classify a set of observations at any unknown state of damage using the principles of fuzzy pattern recognition based on an approximate principle. This method can be embedded into the system of Structural Health Monitoring (SHM) to give advice about structural maintenance and life prediction. Finally, a case study, which comes from Reference [9] for damage pattern recognition is presented and discussed. The compared result illustrates our method is more effective and general, so it is very practical in engineering.

关键词： damage condition assessment fuzzy pattern recognition state similarity matrix approximate principle structural health monitoring

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ZnO thin film grown on glass by metal-organic chemical vapor deposition

ZnO thin film grown on glass by metal-organic chemical vapor...

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IEEE International Nanoelectronics Conference (INEC)

作者： X.M. Ma X.T. Yang C. Wang J. Yang X.H. Gao J.E Liu H. Jing G.T. Du B.Y. Liu K. Ma Changchun Institute of Optics Fine Mechanics and Physics Graduate School of Chinese Academy of Sciences Jilin Institute of Architectural and Civil Engineering China Jilin Institute of Architecture and Civil Engineering China Changchun Institute of Optics Fine Mechanics and Physics Chinese Academy and Sciences China Jilin University China Northwestern University USA

ZnO thin film was deposited on the substrate of Corning glass by metal-organic chemical vapor deposition (MOCVD) [X. Wang et al., 2002; J. Wang et al., 2002; X. Wang et al., 2001] with a buffer layer of SiN x grown by plasma enhanced chemical vapor deposition. The quality of ZnO film was studied by X-ray diffraction and photoluminescence measurement. We found strong diffraction (0 0 2) peak at 34.50deg, indicating that the ZnO film was strongly C-oriented. The full-width at half maximum of (0 0 2) peak was 0.179deg.

关键词： Nanoelectronics Conferences

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Fault Diagnosis of an Intelligent Building Facility Using Bayesian Networks

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International Journal of Plant engineering and Management 2008年第1期000卷

作者： ZHANG Qi-ding XU Jin-yu BAI Er-lei School of Mechanics Civil Engineering and Architecture Northwestern Polytechnical University Xi'an 710072 P.R.China School of Mechanics Civil Engineering and Architecture Northwestern Polytechnical University Xi'an 710072 P.R.China The Engineering Institute Air Force Engineering University Xi'an 710038 P.R.China The Engineering Institute Air Force Engineering University Xi'an 710038 P.R.China

There is great significance to diagnose the fault of an intelligent building facility for fault controlling, repairing, eliminating and preventing. As an example, this paper established a Bayesian networks model for fault diagnosis of the refrigeration system of an intelligent building facility, gave the networks parameters, and analyzed the reasoning mechanism. Based on the model, some data was analyzed and diagnosed by adopting Bayesian networks reasoning platform GeNIe. The result shows that the diagnosis effect is more comprehensive and reasonable than the other method.

关键词： intelligent building facility refrigeration system fault diagnosis Bayesian networks

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