scholarly journals A method for separating O-wave and X-wave and its application in digital ionosonde

2014 ◽  
Vol 56 (5) ◽  
Author(s):  
Wang Shun ◽  
Chen Ziwei ◽  
Zhang Feng ◽  
Gong Zhaoqian ◽  
Li Jutao ◽  
...  
Keyword(s):  
Image Recognition ◽  
Initial Phase ◽  
Phase Shifters ◽  
New Method ◽  
Digital Method ◽  
Electrical Method ◽  
Circularly Polarized ◽  
Automatic Scaling ◽  
Polarized Waves ◽  
Phase 0

<p><strong><em></em></strong>Separation for O wave and X wave is a very important job in interpretation of ionograms, which is premise for automatic scaling. In this paper, a new digital method for separating O wave and X wave is presented, based on a numerical synthesizing technique, which is different from using image recognition to separate trace O and trace X in the ionograms, and from using the electrical method to synthesize and detect circularly polarized waves. By replacing analog phase shifters and switches in existing ionosonde with digital phase shifters with different initial phase, 0°, +90°, −90°, circularly polarized waves are synthesized digitally within the range of 1-30 MHz, which eliminates the nonlinearity and expands the bandwidth of the ionosonde, and there is no need to switch the analog switches continuously. The new method has been successfully applied to CAS-DIS ionosonde and testing results show that the new digital method is capable of separating O wave and X wave well.</p>

One Extended OTSU Flame Image Recognition Method Using RGBL and Stripe Segmentation

2011 ◽  
Vol 121-126 ◽  
pp. 2141-2145 ◽  
Author(s):  
Wei Gang Yan ◽  
Chang Jian Wang ◽  
Jin Guo
Keyword(s):  
Image Segmentation ◽  
Water Vapor ◽  
Image Recognition ◽  
Recognition Accuracy ◽  
New Method ◽  
Recognition Method ◽  
Otsu’S Method ◽  
Flame Shape ◽  
Image Segmentation Algorithm ◽  
Rgb Image

This paper proposes a new image segmentation algorithm to detect the flame image from video in enclosed compartment. In order to avoid the contamination of soot and water vapor, this method first employs the cubic root of four color channels to transform a RGB image to a pseudo-gray one. Then the latter is divided into many small stripes (child images) and OTSU is employed to perform child image segmentation. Lastly, these processed child images are reconstructed into a whole image. A computer program using OpenCV library is developed and the new method is compared with other commonly used methods such as edge detection and normal Otsu’s method. It is found that the new method has better performance in flame image recognition accuracy and can be used to obtain flame shape from experiment video with much noise.

Parametric excitation in an inhomogeneous plasma

1971 ◽  
Vol 5 (1) ◽  
pp. 107-113 ◽  
Author(s):  
C. S. Chen
Keyword(s):  
Electric Field ◽  
Parametric Excitation ◽  
Growth Rates ◽  
Inhomogeneous Plasma ◽  
Electron Plasma ◽  
Transverse Waves ◽  
Circularly Polarized ◽  
Polarized Waves ◽  
Oscillating Electric Field ◽  
Unmagnetized Plasma

An infinite, inhomogeneous electron plasma driven by a spatially uniform oscillating electric field is investigated. The multi-time perturbation method is used to analyze possible parametric excitations of transverse waves and to evaluate their growth rates. It is shown that there exist subharmonic excitations of: (1) a pair of transverse waves in an unmagnetized plasma and (2) a pair of one right and one left circularly polarized wave in a magnetoplasma. Additionally, parametric excitation of two right or two left circularly polarized waves with different frequencies can exist in a magnetoplasma. The subharmonic excitations are impossible whenever the density gradient and the applied electric field are perpendicular. However, parametric excitation is possible with all configurations.

The Microwave Permeability of a Ferrite-Filled Parallel-Plate Transmission Structure

1973 ◽  
Vol 51 (23) ◽  
pp. 2495-2497
Author(s):  
C. K. Campbell
Keyword(s):  
Parallel Plate ◽  
Effective Permeability ◽  
Phase Shifter ◽  
Permeability Tensor ◽  
Ferrite Phase ◽  
Circularly Polarized ◽  
Polarized Waves ◽  
Transmission Structure ◽  
Microwave Permeability

With the aid of a phasor diagram it is shown that the scalar effective permeability μe = (μ2 − K2)/μ of a parallel-plate longitudinally magnetized microwave ferrite phase shifter may be simply obtained in terms of four circularly polarized waves relating to the permeability tensor eigenvalues μ + K and μ − K.

Metrology of degree of coherence of circularly polarized optical waves

2011 ◽  
Vol 19 (3) ◽  
Author(s):  
C. Zenkova ◽  
M. Gorsky ◽  
N. Gorodynska
Keyword(s):  
Spatial Distribution ◽  
Polarization Modulation ◽  
Circularly Polarized ◽  
Optical Waves ◽  
Field Polarization ◽  
Polarized Waves ◽  
Degree Of Coherence

AbstractThe use of the method of field polarization modulation for defining the degree of coherence of circularly polarized waves is offered. The role of the reference circularly polarized wave in transforming the spatial distribution of polarization into the depth of visibility modulation of the resulting distribution, which can be metrologically estimated and analyzed, is demonstrated.

Optical activity and enantiomorphism

2004 ◽  
Author(s):  
Robert E. Newnham
Keyword(s):  
Optical Activity ◽  
Polarized Light ◽  
Polarization Vector ◽  
Optically Active ◽  
Crystal Thickness ◽  
Helical Structures ◽  
Active Materials ◽  
Circularly Polarized ◽  
Space Groups ◽  
Polarized Waves

When plane-polarized light enters a crystal it divides into right- and lefthanded circularly polarized waves. If the crystal possesses handedness, the two waves travel with different speeds, and are soon out of phase. On leaving the crystal, the circularly polarized waves recombine to form a plane polarized wave, but with the plane of polarization rotated through an angle αt. The crystal thickness t is in mm, and α is the optical activity coefficient expressed in degrees/mm. The polarization vector of the combined wave can be visualized as a helix, turning α ◦/mm path length in the optically-active medium. Because of the low symmetry of a helix, optical activity is not observed in many high symmetry crystals. Point groups possessing a center of symmetry are inactive. In relating α to crystal chemistry it is convenient to divide optically-active materials into two categories: Those which retain optical activity in liquid form, and those which do not. It has long been known that optically-active solutions crystallize to give optically-active solids. This follows from the fact that molecules lacking mirror or inversion symmetry can never crystallize in a pattern containing such symmetry elements. Thus one way of obtaining optically-active materials is to begin with optically-active molecules, as in Rochelle salt, tartaric acid and cane sugar. Few of these crystals are very stable, however, and the optical activity coefficients are usually small, typically 2◦/mm. The same is true of many inorganic solids, though they are seldom optically active in the liquid state. For NaClO3 and MgSO4·7H2O, α is about 3◦/mm. Quartz and selenium, however, have coefficients an order of magnitude larger, showing the importance of helical structures to optical activity. Both compounds crystallize as right- and left-handed forms in space groups P312 and P322, with helices spiraling around the trigonal screw axes. Quartz contains nearly regular SiO4 tetrahedra with Si–O distances of 1.61 Å. Levorotatory quartz belongs to space group P312 and contains right-handed helices; enantiomorphic dextrorotatory quartz crystallizes in P322. Trigonal selenium also contains helical chains.

Energy transport of circularly polarized waves in bi-kappa distributed plasmas

2020 ◽  
Vol 74 (5) ◽  
Author(s):  
Tajammal H. Khokhar ◽  
Imran A. Khan ◽  
Hassan A. Shah ◽  
Ghulam Murtaza
Keyword(s):  
Energy Transport ◽  
Circularly Polarized ◽  
Polarized Waves
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