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Search Results: 1 - 10 of 22897 matches for " Ning Xiang "
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Computationally Efficient Iterative Pose Estimation for Space Robot Based on Vision
Xiang Wu,Ning Wu
Journal of Robotics , 2013, DOI: 10.1155/2013/692838
Abstract:
Computationally Efficient Iterative Pose Estimation for Space Robot Based on Vision
Xiang Wu,Ning Wu
Journal of Robotics , 2013, DOI: 10.1155/2013/692838
Abstract: In postestimation problem for space robot, photogrammetry has been used to determine the relative pose between an object and a camera. The calculation of the projection from two-dimensional measured data to three-dimensional models is of utmost importance in this vision-based estimation however, this process is usually time consuming, especially in the outer space environment with limited performance of hardware. This paper proposes a computationally efficient iterative algorithm for pose estimation based on vision technology. In this method, an error function is designed to estimate the object-space collinearity error, and the error is minimized iteratively for rotation matrix based on the absolute orientation information. Experimental result shows that this approach achieves comparable accuracy with the SVD-based methods; however, the computational time has been greatly reduced due to the use of the absolute orientation method. 1. Introduction Vision based methods have been applied to estimate the pose of space robot since 1990s. In these methods, the relative position and orientation between a camera and a robot target are determined with a set of feature points expressed in the three dimensional (3D) object coordinates and their two dimensional (2D) projection in the camera coordinate. The error in position and orientation is usually optimized using the noniterative or iterative algorithms. The noniterative algorithms give an analytical solution for the optimization [1–3], and a typical example of these algorithms includes the method to represent feature points as a linear combination of four virtual control points based on their coordinates [4]. The noniterative methods are generally less time consuming than the iterative methods with acceptable accuracy; however, they are sensitive to observation noise such as image noise, different lighting conditions, and even occlusion by outliers. The iterative approaches, however, achieve better accuracy than the noniterative methods by solving the rotation matrix with a nonlinear least-square method iteratively. A typical iterative method is the Levenberg-Marquardt (L-M) algorithm [5–7], and it has been widely used and accepted as a standard algorithm for least-square problem in photogrammetry. The L-M method is in essentially the combination of the steepest descent method and the Gauss-Newton method in different optimization stages. The steepest descent method is used at the early stage of optimization when the current value of error is still far from the minimum, while the Gauss-Newton method is used at
Evidence for the involvement of NGF in human sperm motility  [PDF]
Cui-Ge Shi, Kai Lin, Xiang-Bo Xu, Shu-Cheng Zhang, Ning Wang, Ming Fan
Journal of Biomedical Science and Engineering (JBiSE) , 2012, DOI: 10.4236/jbise.2012.59066
Abstract: Motility is an important physiological characteristic of a mature sperm. Nerve growth factor (NGF) is a key protein for the survival, maintenance and development of the central and peripheral nervous systems. It has been shown that NGF and its receptors TrkA and p75 are widely expressed in the testis, accessory reproductive organ, and the epididymal sperms. These observation have shifted the attention to the role of NGF on male reproductive physiology. In the present study, we found that NGF remarkably increased testicular coefficient in rats subjected to unpredictable chronic mild stress. Furthermore, we investigated the role of NGF on human sperm motility in vitro by CASA. The results showed that the parameters of sperm motility after NGF treatment had significantly increased, the means of VAP, VSL, VCL, BCF and LIN were significantly increased 32% than those of NGF absence, the means of MAD, STR, ALH and WOB had no notable difference. In addition, NGF promotes the sperm motility in a time- and dose-dependent manner. Taken together, our findings suggest that NGF plays a promoted role in sperm motility.
Modification of Low Molecular Weight Polysaccharides from Tremella Fuciformis and Their Antioxidant Activity in Vitro
Qiong Wu,Cheng Zheng,Zheng-Xiang Ning,Bao Yang
International Journal of Molecular Sciences , 2007, DOI: 10.3390/i8070670
Abstract: In this study, sulfated low molecular-weight Tremella fuciformis polysaccharides(SLTP) with different sulfate contents were synthesized and their antioxidant activities,including superoxide anion radical, 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical andhydroxyl radical scavenging activities were investigated. The results indicated that,compared to natural Tremella fuciformis polysaccharide (TP) and low molecular weightTremella fuciformis polysaccharide (LTP), sulfated LTP (SLTP) exhibited strongerscavenging activity towards superoxide anion, DPPH and hydroxyl radicals. In all the casesthe effect was found to be dose dependent. The scavenging activity of SLTP was found tobe in parallel with the degree of sulfation of SLTP.
Numerical Simulation of Temperature Field of Die Casting Dies

Xiang XUE,Zhiliang NING,Bide ZHOU,Chunhui Zhang,

材料科学技术学报 , 2001,
Abstract: In this study, the Solidworks was used as pre-processor, which performed the three- dimensional solid construction and automatic enmeshment. The COSMOS was adopted as post- processor to display the temperature distribution and further to simulate the thermal stress distribution of dies. A software package for three-dimensional temperature fields of complicated die casting and its dies was developed and the temperature distributions of a fan cover casting were simulated by the software.
Scintillation Index of a Gaussian Schell-Model Beam on Slant Atmospheric Turbulence
Ning-Jing Xiang;Zhen-Sen Wu
PIER M , 2013,
Abstract: Based on the altitude-dependent model of the ITU-R slant atmospheric turbulence structure constant model, we present scintillation index calculations for a partially coherent Gaussian Schell-model (GSM) beam under all irradiance fluctuation conditions. The longitudinal and radial components of the scintillation index are treated separately. Our results correctly reduce to the result of the horizontal path with atmospheric structure constant fixed; and simplify to a fully coherent Gaussian beam with source coherence parameter ζ representing unit. The numerical conclusions indicate that within specific source and parameter ranges, a partially coherent GSM beam is capable of offering less scintillation in comparison with the full coherent Gaussian beam. Before the maximum value of the scintillation, the scintillation index of the partially coherent GSM beam will decrease with the increased altitude. However the off axis radial scintillation index will vanish when the Rytov variance is infinity.
Poly[dinitrato[μ3-2,4,6-tris(4-pyridyl)-1,3,5-triazine]cobalt(II)]
Ya-Ping Wang,Ning Zhang,Xiang He,Min Shao
Acta Crystallographica Section E , 2011, DOI: 10.1107/s1600536811017661
Abstract: The solvothermal reaction of Co(NO3)2 and 2,4,6-tris(4-pyridyl)-1,3,5-triazine in dimethylformamide/ethanol mixed solvent afforded the title coordination polymer, [Co(NO3)2(C18H12N6)]n, in which the CoII atom is seven-coordinated by pyridyl groups of three different ligands and two chelating nitrate anions. The complex displays a nano-sized porous metal–organic framework that belongs to a (10,3) topological network.
catena-Poly[[diaquanickel(II)]-bis(μ-pyridine-4-sulfinato)-κ2N,O;κ2O,N]
Zhong-Xiang Du,Su-Ning Ji
Acta Crystallographica Section E , 2009, DOI: 10.1107/s1600536809024258
Abstract: In the title coordination polymer, [Ni(C5H4NO2S)2(H2O)2]n, the NiII ion is located on an inversion centre and is octahedrally coordinated by two N and two O atoms of four symmetry-related and deprotonated pyridine-4-sulfinate (ps) ligands together with two water molecules in axial positions. The ps anions, acting as μ2-bridging ligands, link neighbouring NiII ions into a chain structure along the c axis. These polymeric chains are extended into a three-dimensional framework via intermolecular O—H...O hydrogen bonds with participation of the water molecules.
Function Vector Synchronization of Uncertain Chaotic Systems with Parameters Variable
Ning Li,Heng Liu,Wei Xiang,Hui Lv
Information Technology Journal , 2012,
Abstract: In this study, a state variable Function Vector Synchronization (FVS) of two non-identical chaotic systems with both varying parameters and delay is investigated. Based on feedback principle and Lyapunov stability theory, the adaptive fuzzy controller is constructed. The synchronization for the state variable function vector of systems can be reached by using the proposed controller. The control is robust for varying parameters and disturbance of systems. Compared with the traditional synchronization, aided by appropriate state variable function vectors of master and slave systems instead of state variables, signal transmission security can be improved. The simulation results shows the effectiveness of the method.
Energy-Efficient Relaying Strategy with Network Coding in Two-Way Parallel Channels
Ning Hu,Xiang Chen,Xiaofeng Zhong,Ben Slimane
ISRN Communications and Networking , 2011, DOI: 10.5402/2011/186783
Abstract:
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