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Now showing items 1 - 13 of 13

  • Wo xiang zongli shuo shihua (I Told the Truth to the Premier)by Li Changping

    Review by: Mobo Gao  

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  • Estimating Leaf Area Density of Individual Trees Using the Point Cloud Segmentation of Terrestrial LiDAR Data and a Voxel-Based Model

    Li Shihua   Dai Leiyu   Wang Hongshu   Wang Yong   He Ze   Lin Sen  

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  • Wo xiang zongli shuo shihua (I Told the Truth to the Premier)by Li Changping

    Review by: Mobo Gao  

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  • Research on Screws System Dependency under Different Space Geometrical Condition

    Li Shihua   Liu Yanmin   Ma Ning  

    By projective geometry theory, the dependency of screw system which is constituted by three line vectors and three couples, or four line vectors and two couples, or five line vectors and one couples, is discussed. The lines in the P3 will be mapped to the points in the P5 by using the Klein mapping representation and the homogeneous Pl眉cker coordinates, the dependency of screw system is determined, criterions of dependency are given, and the dependency on different geometrical conditions are listed. All of the results are useful for some problem, such as parallel manipulator degrees of freedom and voluntarily input selecting.<
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  • Development and characterization of the replicon system of Japanese encephalitis live vaccine virus SA14-14-2.

    Li ShiHua   Li XiaoFeng   Zhao Hui   Deng YongQiang   Yu XueDong   Zhu ShunYa   Jiang Tao   Ye Qing   Qin EDe   Qin ChengFeng  

    Background: Viral self-replicating sub-genomic replicons represent a powerful tool for studying viral genome replication, antiviral screening and chimeric vaccine development. Many kinds of flavivirus replicons have been developed with broad applications. Findings: The replicon system of JEV live vaccine strain SA14-14-2 was successfully developed in this study. Two kinds of replicons that express enhanced green fluorescent protein (EGFP) and Renilla luciferase (R.luc) were constructed under the control of SP6 promoter, respectively. Robust EGFP and R.luc signals could be detected in the replicon-transfected BHK-21 cells. Furthermore, the potential effects of selected amino acids in the C-terminal of envelope protein on replication were characterized using the replicon system. Conclusions: Our results provide a useful platform not only for the study of JEV replication, but also for antiviral screening and chimeric vaccine development.
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  • Position Analysis of a Novel 3-5R Parallel Platform Mechanism Using Continuation Method

    Li Shihua   Du Chongjie   Huang Zhen  

    By adopting a continuation approach, the position analyses of a novel 3-5R parallel mechanism, which has three translation degrees of freedom, are conducted. Next, an equation system of the mechanism structure constraint and an initial equation system are established. Next, a versatile software for solving polynomial equation system is compiled. As giving one displacement, all inverse kinematics are obtained from this software.
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  • Synthesis of Branched Chains with Actuation Redundancy for Eliminating Interior Singularities of 3T1R Parallel Mechanisms

    Li Shihua   Liu Yanmin   Cui Hongliu   Niu Yunzhan   Zhao Yanzhi  

    Although it is common to eliminate the singularity of parallel mechanism by adding the branched chain with actuation redundancy, there is no theory and method for the configuration synthesis of the branched chain with actuation redundancy in parallel mechanism. Branched chains with actuation redundancy are synthesized for eliminating interior singularity of 3-translational and 1-rotational(3T1R) parallel mechanisms. Guided by the discriminance method of hybrid screw group according to Grassmann line geometry, all the possibilities are listed for the occurrence of interior singularities in 3T1R parallel mechanism. Based on the linear relevance of screw system and the principles of eliminating parallel mechanism singularity with actuation redundancy, different types of branched chains with actuation redundancy are synthesized systematically to indicate the layout and the number of the branched chainsinterior with actuation redundancy. A general method is proposed for the configuration synthesis of the branched chains with actuation redundancy of the redundant parallel mechanism, and it builds a solid foundation for the subsequent performance optimization of the redundant actuation parallel mechanism.
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  • Set Stabilization of Nonholonomic Mobile Robots

    Jie, Yang   Li Shihua  

    Conventional stabilizing controllers for the nonholonomic systems stabilize the closed loop system to a target point. In this paper; considering the kinematic model of nonholonomic mobile robots; a design approach based on set stabilizing control is proposed. The proposed control laws can stabilize the closed loop system asymptotically to a set of given target points. First; for the one-order subsystem of the heading angle; a state feedback control law is designed to guarantee that the state of the closed loop subsystem is asymptotically stabilized to a set of target points. Second; for the second-order subsystem of the planar coordinates of the mass center; a state feedback control law is designed to guarantee that the states of the closed loop subsystem are both asymptotically stabilized to zero. Simulation results show the effectiveness of our method.
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  • Apparent reflectance and its applications using resourcesat-1 remote sensing data - art. no. 64190D

    Li Shihua   Niu Zheng  

    Resourcesat-1 (IRS-P6) was built by Indian Space Research Organisation and launched in October, 2003. Resourcesat-1 carries three imaging sensors-a moderate resolution camera Advanced Wide Field Sensor (AWFS), a moderate resolution Linear Imaging Self Scanning-III device (LISS-III) and a high resolution Linear Imaging Self Scanning-IV device (LISS-IV) to get different spatial resolution image. Apparent reflectance of LISS-III image is calculated in Poyang Lake, south of China. The mean Digital Number (DN) in Red Band image of part of this district is 108.9, and Stdev is 62.72. The mean apparent reflectance of this image is 0.17, and Stdev is 0.093. Apparent reflectance can be used in the normalized difference vegetation index (NDVI) calculation, atmospheric correction, and others. NDVI value which is calculated by apparent reflectance can represent surface status accurately.
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  • Design and analysis of A 3-DOF micromanipulator driven by piezoelectric actuators

    Cao Shumeng   Feng Yanting   Ju Yanru   Li Shihua  

    Based on 3-RRRRR parallel mechanism; a novel 3-DOF micromanipulator which is driven by piezoelectric actuators has been put forward. From the aspect of micromanipulator; spatial parallel mechanism possesses the advantages of high stiffness; compact structure and so on; and overcomes the disadvantage of small workspace. All the flexible hinges of the 3-RRRRR parallel mechanism are revolute pairs; so it is easy to be machininged and has high precision. In this paper; the static stiffness analysis of the micromanipulator is given. The dimension of the platforms and flexible hinges and the arrangement of the chains are designed. The PZT and the material of the flexure mechanism are chosen. The safety check of the flexure mechanism is done. The merits of parallel mechanism and piezoelectric actuators are reflected in the mechanism.
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  • A Two-order Active Disturbance Rejection Control Algorithm for Permanent Magnetic Synchronus Motor

    Zhigang, Liu   Li Shihua  

    When designing the controller by using active disturbance rejection control (ADRC) techniques for the permanent magnetic synchronous motor (PMSM) speed-regulation system; the speed controller is designed to be a one-order ADRC according to the speed output equation. This design employs the output of the speed regulator; i.e.; the input of the current regulator; to approximately replace the real q-axis stator current. The one-order ADRC can not compensate this approximation; which makes it difficult for the closed loop system to obtain excellent performance. Considering this problem; a new two-order ADRC scheme is proposed in this paper based on the analysis of speed output equation. Simulation results indicate that under this scheme the closed loop system can have stronger anti-disturbance ability; more smooth speed response and less overshoots..
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  • Global smooth time-varying exponential stabilization of nonholonomic chained form systems

    Tian Yu-Ping   Li Shihua  

    It is well known that nonholonomic chained form systems cannot be stabilized by continuous pure state feedback. The solutions include time-varying feedback stabilization and discontinuous time-invariant feedback stabilization. Most of the existing time-varying control results suffer from the drawback that the designed control laws are very complex. Moreover, the control laws using smooth time-varying feedback do not stabilize the system with exponential convergence rate. It is pointed out that controlling nonholonomic chained form systems with discontinuous controls may be difficult to implement. In this paper smooth time-varying feedback control laws, which globally stabilize the system with exponential convergence rate, are developed. Besides the advantage of design simplicity, the convergence rate of each state can be specified in a prior. The method has no constraints on the initial value of states. The simulation results show the efficiency of this method
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  • Composite control method for stabilizing spacecraft attitude in terms of Rodrigues parameters

    Sun Haibin   Li Shihua  

    In this paper, the attitude stabilization problem of a rigid spacecraft described by Rodrigues parameters is investigated via a composite control strategy, which combines a feedback control law designed by a finite time control technique with a feedforward compensator based on a linear disturbance observer (DOB) method. By choosing a suitable coordinate transformation, the spacecraft dynamics can be divided into three second-order subsystems. Each subsystem includes a certain part and an uncertain part. By using the finite time control technique, a continuous finite time controller is designed for the certain part. The uncertain part is considered to be a lumped disturbance, which is estimated by a DOB, and a corresponding feedforward design is then implemented to compensate the disturbance. Simulation results are employed to confirm the effectiveness of the proposed approach. (C) 2013 Production and hosting by Elsevier Ltd. on behalf of CSAA & BUAA.
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