scholarly journals A New Approximate Method for Lightning-Radiated ELF/VLF Ground Wave Propagation over Intermediate Ranges

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Wenhao Hou ◽  
Qilin Zhang ◽  
Jinbo Zhang ◽  
Lei Wang ◽  
Yuan Shen
Keyword(s):  
Wave Propagation ◽  
Approximate Method ◽  
Low Frequency ◽  
Airy Functions ◽  
Complex Differential Equation ◽  
Comparison Results ◽  
Field Peak ◽  
Ground Conductivity ◽  
Ground Wave ◽  
Peak Value

A new approximate method for lightning-radiated extremely low-frequency (ELF) and very low-frequency (VLF) ground wave propagation over intermediate ranges is presented in this paper. In our approximate method, the original field attenuation function is divided into two factors in frequency domain representing the propagation effect of the ground conductivity and Earth’s curvature, and both of them have clearer formulations and can more easily be calculated rather than solving a complex differential equation related to Airy functions. The comparison results show that our new approximate method can predict the lightning-radiated field peak value over the intermediate range with a satisfactory accuracy within maximum errors of 0.0%, −3.3%, and −8.7% for the earth conductivity of 4 S/m, 0.01 S/m, and 0.001 S/m, respectively. We also find that Earth’s curvature has much more effect on the field propagation at the intermediate ranges than the finite ground conductivity, and the lightning-radiated ELF/VLF electric field peak value (V/m) at the intermediate ranges yields a propagation distance d (km) dependence of d−1.32.

Elastic Wave Propagation in Inhomogeneous Bars of Several Sections

1973 ◽  
Vol 40 (4) ◽  
pp. 1050-1054 ◽  
Author(s):  
J. E. Wade ◽  
P. J. Torvik
Keyword(s):  
Wave Propagation ◽  
Elastic Wave ◽  
Approximate Method ◽  
Cross Sections ◽  
Low Frequency ◽  
Frequency Spectra ◽  
Frequency Wave ◽  
Angle Section ◽  
Wave Trains ◽  
Inhomogeneous Composite

An approximate method is given for analyzing the propagation of low-frequency wave trains in prismatic bars of cross sections which can be approximated through subdivision into rectangular elements. The method may be applied to inhomogeneous (composite) bars, for it is not required that each such element have the same properties. Results from the new method compare favorably with results previously obtained for a rectangular bar. Frequency spectra for several composite bars, including a bar of thick angle section, are given.

scholarly journals Ground-Wave Propagation Across a Land/Sea Boundary: 300-m. Waves

Nature ◽  
1949 ◽  
Vol 164 (4159) ◽  
pp. 114-116 ◽  
Author(s):  
N. ELSON
Keyword(s):  
Wave Propagation ◽  
Ground Wave

Numerical Simulation of the Buried Object Detection Based on Underwater Plasma Acoustic Source

2011 ◽  
Vol 105-107 ◽  
pp. 80-83
Author(s):  
Jun Zhang ◽  
Xin Wu Zeng ◽  
Yi Bo Wang ◽  
Zhen Fu Zhang ◽  
Dan Chen
Keyword(s):  
Wave Propagation ◽  
Object Detection ◽  
Pulse Length ◽  
Low Frequency ◽  
Basic Mechanism ◽  
Propagation Model ◽  
Staggered Grid ◽  
Acoustic Source ◽  
Buried Objects ◽  
Buried Object

Detection and classification of buried objects is of great importance in underwater counterterrorism and archaeology. To penetrate the sediment, a low frequency intensive acoustic source is needed. Underwater plasma acoustic source (UPAS) with high voltage discharge has the advantage of adjustable pulse length, high source level output and no pollution to the environment, which can satisfy these needs. In this paper, we introduced the UPAS, including its basic mechanism, structure and pressure output. Then we build up an elastic wave propagation model, solved it with finite difference and staggered grid methods, and combined with certain source and boundary condition, we simulated and analyzed the pressure wave propagation in time domain with an aluminum cylinder buried in sediment, from the results we validated the effectiveness of UPAS in the application of buried object detection.

Boron-Doped Nanocrystalline Diamond Films Deposited By Using DC Arc Plasma Jet CVD

2010 ◽  
Vol 426-427 ◽  
pp. 30-34
Author(s):  
Bing Kun Xiang ◽  
Dun Wen Zuo ◽  
Xiang Feng Li ◽  
Feng Xu ◽  
M. Wang
Keyword(s):  
Diamond Film ◽  
Boron Concentration ◽  
Low Frequency ◽  
Nanocrystalline Diamond ◽  
Boron Doped ◽  
Nano Crystalline ◽  
Diamond Peak ◽  
Dc Arc ◽  
Afm Observation ◽  
Peak Value

Boron-doped micro-nanocrystalline diamond coating may be successfully prepared on Mo substrate with DC arc plasmas jet deposition device. Along with the increase of doped-boron concentration in the film, two-point resistance measurement indicates that film resistance presents exponential decrease; Raman spectrum test shows that, the characteristic peak value of diamond 1332cm-1 in the spectrum moves toward low frequency, the semi-height width of diamond peak, peak D and peak G, etc. in the spectrum is expanded, and the component of non-diamond bonds such as sp2, etc. in the film is increased; SEM and AFM observation shows that, increasing the doped-boron concentration could further subdivide the crystal grains in the film, and is beneficial for the growth of nano- or ultra-nano-crystalline diamond film; film annealing test shows that, micro-nanocrystalline diamond film with higher doped-boron concentration has better thermal stability than the micro-nanocrystalline diamond film without doped boron.

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