The Experts below are selected from a list of 252 Experts worldwide ranked by ideXlab platform

Yuyang Pan - One of the best experts on this subject based on the ideXlab platform.

  • Spatiotemporal distribution of surface charges in Square-grid state in a dielectric barrier discharge
    Physics of Plasmas, 2018
    Co-Authors: Fang Hao, Lifang Dong, Weili Fan, Du Tian, Ying Liu, Yuyang Pan
    Abstract:

    The spatiotemporal distribution of surface charges in the Square-grid state in a dielectric barrier discharge system is investigated at the sub-microsecond time scale using a spectrograph combined with a high-speed framing camera. With increasing driving parameter, the Square-grid state transforms from a Square Pattern into one composed of three sub-lattices: a core sub-lattice with Square symmetry and two marginal lattices with lower symmetry. In essence, this breaks the symmetry of the Square-grid state—a highly symmetric state. From this perspective, the Square Pattern trifurcates to a Square-grid state of lower symmetry. The electron density of the Square-grid state changes periodically, both temporally and spatially, resulting in a periodic distribution of surface charges over the dielectric layer. The calculation of the surface-charge field further verifies that the surface charges have a significant influence on the formation of the Square-grid state consistent with the experimental results.

T. Armstrong - One of the best experts on this subject based on the ideXlab platform.

  • Neutron measurements of the vortex lattice in YBa2Cu3O7 (invited)
    Journal of Applied Physics, 1993
    Co-Authors: Herbert A. Mook, Mohana Yethiraj, G. D. Wignall, E. M. Forgan, Stephen Lee, Robert Cubitt, D. Mck. Paul, T. Armstrong
    Abstract:

    Neutron diffraction has been used to measure the vortex lattice scattering for YBa2Cu3O7. A Square Pattern is found when the field is applied along the c axis, while a triangular Pattern is found when the field is applied well away from the c axis. High‐resolution measurements for the Square Pattern show that the vortex lattice has long‐range orientational order but only short‐range positional order. The temperature dependence of the penetration depth is not that expected for a superconductor with a conventional s‐wave BCS‐type gap. Preliminary measurements for temperatures near the irreversibility line are consistent with the occurrence of melting of the vortex lattice or glass phase.

  • Neutron measurements of the vortex lattice in YBa{sub 2}Cu{sub 3}O{sub 7}
    1992
    Co-Authors: Herbert A. Mook, Mohana Yethiraj, G. D. Wignall, E. M. Forgan, Stephen Lee, Robert Cubitt, D. Mck. Paul, T. Armstrong
    Abstract:

    Neutron diffraction has been used to measure the vortex lattice scattering for YBa[sub 2]Cu[sub 3]O[sub 7]. A Square Pattern is found when the field is applied along the c axis, while a triangular Pattern is found when the field is applied well away from the c axis. High-resolution measurements for the Square Pattern show that the vortex lattice has long-range orientational order but only short-range positional order. The temperature dependence of the penetration depth is not that expected for a superconductor with a conventional s-wave BCS type gap. Preliminary measurements for temperatures near the irreversibility line are consistent with the occurrence of melting of the vortex lattice or glass phase.

Narayanan C. Sathiya - One of the best experts on this subject based on the ideXlab platform.

  • prediction of limiting strains for Square Pattern Square hole perforated commercial pure aluminium sheets
    Advanced Materials Research, 2012
    Co-Authors: G. Venkatachalam, S. Narayanan, Narayanan C. Sathiya
    Abstract:

    Forming limit diagram (FLD) is the most appropriate tool used to obtain the safe strain region in sheet metal forming industries. This FLD is based on limiting values of major and minor strains. This Limiting strain is the strain at the onset of fracture / necking in a sheet metal. It is influenced by the material / condition of the material, strain condition in geometrical features of a sheet metal. In this paper, Square Pattern – Square holed, perforated commercial aluminium sheets are considered for the study. The limiting strain for the above perforated sheet metals is predicted using finite element analysis. It is found that the limiting strain is controlled by percentage of open area, ligament ratio and hole size.

  • Prediction of Limiting Strains for Square Pattern – Square Hole Perforated Commercial Pure Aluminium Sheets
    Advanced Materials Research, 2012
    Co-Authors: G. Venkatachalam, S. Narayanan, Narayanan C. Sathiya
    Abstract:

    Forming limit diagram (FLD) is the most appropriate tool used to obtain the safe strain region in sheet metal forming industries. This FLD is based on limiting values of major and minor strains. This Limiting strain is the strain at the onset of fracture / necking in a sheet metal. It is influenced by the material / condition of the material, strain condition in geometrical features of a sheet metal. In this paper, Square Pattern – Square holed, perforated commercial aluminium sheets are considered for the study. The limiting strain for the above perforated sheet metals is predicted using finite element analysis. It is found that the limiting strain is controlled by percentage of open area, ligament ratio and hole size.

Lifang Dong - One of the best experts on this subject based on the ideXlab platform.

  • Spatiotemporal distribution of surface charges in Square-grid state in a dielectric barrier discharge
    Physics of Plasmas, 2018
    Co-Authors: Fang Hao, Lifang Dong, Weili Fan, Du Tian, Ying Liu, Yuyang Pan
    Abstract:

    The spatiotemporal distribution of surface charges in the Square-grid state in a dielectric barrier discharge system is investigated at the sub-microsecond time scale using a spectrograph combined with a high-speed framing camera. With increasing driving parameter, the Square-grid state transforms from a Square Pattern into one composed of three sub-lattices: a core sub-lattice with Square symmetry and two marginal lattices with lower symmetry. In essence, this breaks the symmetry of the Square-grid state—a highly symmetric state. From this perspective, the Square Pattern trifurcates to a Square-grid state of lower symmetry. The electron density of the Square-grid state changes periodically, both temporally and spatially, resulting in a periodic distribution of surface charges over the dielectric layer. The calculation of the surface-charge field further verifies that the surface charges have a significant influence on the formation of the Square-grid state consistent with the experimental results.

  • Investigation of plasma parameters of the Square Pattern with two kinds of spatiotemporal symmetry in dielectric barrier discharge
    Guang pu xue yu guang pu fen xi = Guang pu, 2014
    Co-Authors: Yong-jie Wang, Lifang Dong, Long-hu Zhao, Weibo Liu, Xinpu Zhang, Chao Zhang
    Abstract:

    Two kinds of Square Patterns with different spatiotemporal symmetry were observed in dielectric barrier discharge, and their plasma parameters were measured by using optical emission spectra. It was found that the spatiotemporal symmetry of the Square Pattern at lower gas pressure is different from the one at higher gas pressure. Six spectral lines in the emission spectrum of the N2 second positive band were chosen to estimate the vibrational temperature, and the ratio of I391.4/I394.1 was used to represent the average electron energy. The excitation temperature was determined by the ratio of I763.2/I772.1. Furthermore, the width and shift of Ar I 696.54 nm were used to estimate the electron density. The results show that the vibrational temperature, excitation temperature and electron energy of the Square Pattern at lower gas pressure are higher than those at higher gas pressure, while the electron density is lower than that at higher gas pressure.

  • Analysis of the Transition from Hexagon to Square Pattern in Dielectric Barrier Discharge
    2008 Congress on Image and Signal Processing, 2008
    Co-Authors: Lifang Dong, Han Yue, Hong Xiao, Weili Fan
    Abstract:

    Several spatiotemporal Patterns: random spots, hexagon Pattern, coexistences of hexagon and Square Pattern, and Square Pattern are obtained in dielectric barrier discharge system while increasing the voltage with other parameters fixed. By using image processing including spatial correlation function and Fourier spectrum, the structures of Patterns and the bifurcation scenario are studied. It is shown that the structures of hexagon and Square Patterns are both perfect, and the spatial periodicity increases with the voltage increasing, whereas the mean distance between the neighboring filaments decreases. Moreover, the development of the modes excited from the system in this transition is investigated in detail. Both the two methods are in agreement with each other.

  • Study on the photo-electrical characteristics of different Patterns in dielectric barrier discharge by using photoelectricity method
    Optical Design and Testing III, 2007
    Co-Authors: Lifang Dong, Zengchao Zhao
    Abstract:

    A dielectric barrier discharge apparatus with two liquid electrodes and a photoelectric detection system are specially designed to study the photo-electrical characteristic of different Patterns. A series of filamentary Patterns, in which the filaments can be fixed for a long time, have been generated from filaments moving stochastically by increasing applied voltage. It follows the sequence of Square Pattern, Square superlattice Pattern and hexagon Pattern. The studies of optical and electrical characteristics, including discharge current, light signals, the voltage drop across discharge gap, transported charges, and Lissajous figures of these different Patterns are realized by the photo-electrical detection method. From the light signals and waveforms of current, it is found that the Square Pattern has two discharge pulses, the Square superlattice has three and the hexagon has several pulses in each half cycle of the applied voltage. The voltage drop across discharge gap and transported charges increase with the increasing of applied voltage. The dissipated power obtained by the charge-voltage Lissajous figures also increases with the increasing of applied voltage.

  • Square Pattern formation in a gas discharge system
    Thin Solid Films, 2003
    Co-Authors: Lifang Dong, Zengqian Yin, Long Wang, Zhifang Chai
    Abstract:

    The Square Pattern is observed in dielectric barrier discharge in argon for the first time. The hexagon Pattern and the mixture of hexagon and Square structure are also observed. The Square Pattern can remain stable for several tens of minutes. The spatio-temporal dynamics of Square Pattern formation is investigated by optical method. The measurement results show that the Square Pattern is an interleaving of two Square Patterns, which is the reason of the stability of Square Pattern.

Guannan Li - One of the best experts on this subject based on the ideXlab platform.

  • A flexible calibration method using the planar target with a Square Pattern for line structured light vision system
    PLoS ONE, 2014
    Co-Authors: Qiucheng Sun, Yueqian Hou, Qingchang Tan, Guannan Li
    Abstract:

    A flexible calibration approach for line structured light vision system is proposed in this paper. Firstly a camera model is established by transforming the points from the 2D image plane to the world coordinate frame, and the intrinsic parameters of camera can be obtained accurately. Then a novel calibration method for structured light projector is presented by moving a planar target with a Square Pattern randomly, and the method mainly involves three steps: first, a simple linear model is proposed, by which the plane equation of the target at any orientations can be determined based on the Square's geometry information; second, the pixel coordinates of the light stripe center on the target images are extracted as the control points; finally, the points are projected into the camera coordinate frame with the help of the intrinsic parameters and the plane equations of the target, and the structured light plane can be determined by fitting these three-dimensional points. The experimental data show that the method has good repeatability and accuracy.