Nonlinear propagation of high-frequency energy from blast waves

2006 ◽  
Author(s):  
Alexandra Loubeau
Keyword(s):  
High Frequency ◽  
Blast Waves ◽  
Nonlinear Propagation

Nonlinear propagation of high-frequency plasma waves in a magnetized plasma

1977 ◽  
Vol 18 (2) ◽  
pp. 249-256 ◽  
Author(s):  
P. K. Shukla
Keyword(s):  
High Frequency ◽  
Nonlinear Effects ◽  
Plasma Waves ◽  
Electron Plasma ◽  
Magnetized Plasma ◽  
Nonlinear Propagation ◽  
Arbitrary Angle ◽  
High Frequency Plasma ◽  
Frequency Plasma ◽  
Density Perturbations

We study nonlinear effects associated with large amplitude electron plasma waves propagating at an arbitrary angle to the external magnetic field. It is shown that the nonlinear coupling of high-frequency plasma waves with static density perturbations leads to a convective instability. The growth length of the latter is obtained. The evolution of the wave electric field is also investigated.

scholarly journals Construction of an Omnidirectional Parametric Loudspeaker Consisting in a Spherical Distribution of Ultrasound Transducers

Sensors ◽  
2018 ◽  
Vol 18 (12) ◽  
pp. 4317 ◽  
Author(s):  
Marc Arnela ◽  
Oriol Guasch ◽  
Patricia Sánchez-Martín ◽  
Joan Camps ◽  
Rosa Alsina-Pagès ◽  
...  
Keyword(s):  
High Frequency ◽  
Sound Pressure ◽  
Nonlinear Propagation ◽  
Ultrasound Transducers ◽  
Frequency Range ◽  
Carrier Wave ◽  
Sound Sources ◽  
Low Frequencies ◽  
Structural Assembly ◽  
Chamber Measurements

Omnidirectional sound sources are needed to perform a large variety of tests in acoustics. Typically, they consist of conventional speaker drivers arranged in a dodecahedron. However, the directivity of the speaker drivers sharpens with frequency, which induces an intense decrease of the sound pressure levels at the edges of the dodechaedron. In this work, the problem is mitigated by building an Omnidirectional Parametric Loudspeaker (OPL), which contains hundreds of small ultrasound transducers set on a sphere. Each transducer emits an ultrasonic carrier wave modulated by an audible signal. Thanks to nonlinear propagation, the air itself demodulates the signal bringing it back to the audible range. The construction of an OPL prototype is challenging. The structure has been built by 3D-printing a set of pieces that conform to the sphere. Each piece contains the exact location of the transducers, which are aligned in parallels to facilitate the structural assembly and the wiring. The performance of the OPL has been tested in an anechoic chamber. Measurements show that the OPL has a good omnidirectional behavior for most frequencies. It clearly improves the directivity of dodechaedral sources in the high frequency range, but performs worse at low frequencies.

Kinetic theory of transverse plasmons in pair plasmas

2010 ◽  
Vol 77 (2) ◽  
pp. 145-153 ◽  
Author(s):  
S. Q. LIU ◽  
Y. LIU
Keyword(s):  
High Frequency ◽  
Electromagnetic Waves ◽  
Maxwell Equations ◽  
Ponderomotive Force ◽  
Nonlinear Propagation ◽  
Governing Equations ◽  
Filamentary Structure ◽  
Wave Fields ◽  
Propagation Behavior ◽  
Spatially Inhomogeneous

AbstractA set of nonlinear governing equations for interactions of transverse plasmons with pair plasmas is derived from Vlasov–Maxwell equations. It is shown the ponderomotive force induced by high-frequency transverse plasmons will expel the pair particles away, resulting in the formation of density cavity in which transverse plasmons are trapped. Numerical results show the envelope of wave fields will collapse and break into a filamentary structure due to the spatially inhomogeneous growth rate. The results obtained would be useful for understanding the nonlinear propagation behavior of intense electromagnetic waves in pair plasmas.

The Microstructure of Steatite (Protoenstatite)

1985 ◽  
Vol 43 ◽  
pp. 236-237
Author(s):  
W. E. Lee ◽  
A. H. Heuer
Keyword(s):  
High Frequency ◽  
Glass Ceramics ◽  
Magnesium Silicate ◽  
Beam Current ◽  
Glassy Matrix ◽  
Angle Of Incidence ◽  
X Ray ◽  
Mechanical And Electrical Properties ◽  
Argon Ions ◽  
High Temperature Polymorph

IntroductionTraditional steatite ceramics, made by firing (vitrifying) hydrous magnesium silicate, have long been used as insulators for high frequency applications due to their excellent mechanical and electrical properties. Early x-ray and optical analysis of steatites showed that they were composed largely of protoenstatite (MgSiO3) in a glassy matrix. Recent studies of enstatite-containing glass ceramics have revived interest in the polymorphism of enstatite. Three polymorphs exist, two with orthorhombic and one with monoclinic symmetry (ortho, proto and clino enstatite, respectively). Steatite ceramics are of particular interest a they contain the normally unstable high-temperature polymorph, protoenstatite.Experimental3mm diameter discs cut from steatite rods (∼10” long and 0.5” dia.) were ground, polished, dimpled, and ion-thinned to electron transparency using 6KV Argon ions at a beam current of 1 x 10-3 A and a 12° angle of incidence. The discs were coated with carbon prior to TEM examination to minimize charging effects.

Sign in / Sign up

Export Citation Format

Share Document