RADIATION FROM ELEMENTARY FLUID-MECHANICAL SOURCES IN AN UNBOUNDED ELECTRON PLASMA

1964 ◽  
Vol 42 (8) ◽  
pp. 1573-1586 ◽  
Author(s):  
S. R. Seshadri
Keyword(s):  
Line Source ◽  
Uniform Magnetic Field ◽  
Electron Plasma ◽  
The Other ◽  
Frequency Range ◽  
Entire Frequency Range ◽  
Fluid Flux ◽  
Radiation Characteristics ◽  
Transverse Waves ◽  
Infinite Extent

The radiation characteristics of a line source of fluid flux and a line source of force, embedded in a homogeneous electron plasma of infinite extent, are investigated for the case in which a uniform magnetic field is impressed externally throughout the medium in the direction of the source. It is found that there are two propagating modes which are strictly coupled longitudinal and transverse waves. However, one of the modes is predominantly transverse in the entire frequency range of propagation and the other is predominantly transverse in the lower, and predominantly longitudinal in the higher ranges of frequency of propagation. It is shown that the elementary fluid-mechanical sources considered in this paper radiate significant amounts of power only in the longitudinal-type waves.

scholarly journals A Multiband Arrow Shaped Patch Antenna Based on Apollonian Gasket and Soddy’s circle for Application in LTE and UWB range

2019 ◽  
Vol 9 (2) ◽  
pp. 2276-2282
Keyword(s):  
Wireless Communications ◽  
Frequency Response ◽  
Patch Antenna ◽  
Impedance Matching ◽  
Impedance Bandwidth ◽  
Frequency Range ◽  
Ground Structure ◽  
Entire Frequency Range ◽  
Radiation Characteristics ◽  
Overall Performance

A novel arrow shaped planar multiband antenna based on apollonian gasket and Soddy’s circle with Defective Ground Structure (DGS) is described in this paper. The structure is designed on an FR4_epoxy substrate (εr=4.4).The performance is evaluated using HFSS software. The antenna displays multiband behaviour in the frequency range from 3 to 10 GHz which is suitable for wireless communications applications.The antenna gives tri-frequency response in LTE range(600 MHz6GHz):1.17 GHz, 3.44 GHz and 6 GHz;and tetra frequency response in the UWB frequency range(3 GHz to 10 GHz): 8.1 GHz, 9.5 GHz, 11.8 GHz & 13.5 GHz which could be used in wireless and radar communications.The overall performance of the antenna demonstrates an average impedance bandwidth(IBW) of 300 MHz with a good impedance matching (S11< -10 dB).The proposed antenna has the satisfactory radiation characteristics throughout its operating band. The measured highest gain differs from 1 dBi to 1.9 dBi inthe entire frequency range.

RADIATION FROM A PHASED LINE SOURCE IN A MAGNETOIONIC MEDIUM

1965 ◽  
Vol 43 (9) ◽  
pp. 1636-1648
Author(s):  
H. S. Tuan ◽  
S. R. Seshadri
Keyword(s):  
Electric Current ◽  
Current Distribution ◽  
Free Space ◽  
Line Source ◽  
Propagation Constant ◽  
Electron Plasma ◽  
Radiation Characteristics ◽  
Magnetostatic Field ◽  
Phase Constant ◽  
Special Case

The radiation characteristics of a phased line source of electric current immersed in a magnetoionic medium are analyzed. The line source is assumed to be parallel to the direction of the external magnetostatic field and the phase constant for the current distribution is assumed to be given by k0/β, where k0 is the propagation constant of free space and β is a dimensionless phase parameter. In general, it is found that two modes are excited. The frequency ranges of propagation of these so-called ordinary and extraordinary modes are examined by means of a construction in the Ω2–R2 parameter space for the case [Formula: see text], where Ω = ω/ωp, R = ωc/ωp, and ω, ωp and ωc are the source, the electron plasma, and the gyromagnetic frequency respectively. The dispersion relations and the frequency spectrum are evaluated. It is found that β = 1 is a special case for which only one mode is excited.

Radiation of a line source mounted between two dielectric substrates

1990 ◽  
Vol 68 (12) ◽  
pp. 1486-1491 ◽  
Author(s):  
Ioanna Diamandi ◽  
Costas Mertzianidis ◽  
John N. Sahalos
Keyword(s):  
Remote Sensing ◽  
Antenna Arrays ◽  
Line Source ◽  
Finite Thickness ◽  
Dielectric Substrate ◽  
Microstrip Antennas ◽  
The Other ◽  
Bottom Surface ◽  
Radiation Characteristics ◽  
Dielectric Substrates

The radiation characteristics of a line source lying on the bottom surface of a dielectric substrate that is mounted on the top of another one are presented. The pattern is calculated for two different cases. One is for infinite thickness of the second substrate and the other is for finite thickness. Some interesting considerations useful for applications in remote sensing, microstrip antennas, and antenna arrays are made.

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.

Damping and Inertia Coefficients for a Rolling or Swaying Vertical Strip

1963 ◽  
Vol 7 (04) ◽  
pp. 19-23
Author(s):  
J. Kotik
Keyword(s):  
Wave Amplitude ◽  
Added Mass ◽  
Frequency Range ◽  
Entire Frequency Range ◽  
Vertical Strip ◽  
Amplitude Coefficient

Ursell's exact expression3 for the wave-amplitude coefficient for a swaying or rolling vertical strip is evaluated numerically over the entire frequency range. The added-mass and inertia coefficients are then obtained numerically, also over the entire frequency range, via the Kramers-Kronig relations.

The relationship between group velocity and phase velocity for finite, discrete observations

1977 ◽  
Vol 67 (5) ◽  
pp. 1249-1258
Author(s):  
Douglas C. Nyman ◽  
Harsh K. Gupta ◽  
Mark Landisman
Keyword(s):  
Phase Velocity ◽  
Group Velocity ◽  
The Other ◽  
Frequency Range ◽  
Finite Frequency ◽  
Discrete Observations ◽  
Practical Situation ◽  
Order Polynomial ◽  
Observational Errors ◽  
The Relationship

abstract The well-known relationship between group velocity and phase velocity, 1/u = d/dω (ω/c), is adapted to the practical situation of discrete observations over a finite frequency range. The transformation of one quantity into the other is achieved in two steps: a low-order polynomial accounts for the dominant trends; the derivative/integral of the residual is evaluated by Fourier analysis. For observations of both group velocity and phase velocity, the requirement that they be mutually consistent can reduce observational errors. The method is also applicable to observations of eigenfrequency and group velocity as functions of normal-mode angular order.

Respiratory input impedance in anesthetized paralyzed patients

1990 ◽  
Vol 69 (4) ◽  
pp. 1372-1379 ◽  
Author(s):  
D. Navajas ◽  
R. Farre ◽  
J. Canet ◽  
M. Rotger ◽  
J. Sanchis
Keyword(s):  
Mechanical Model ◽  
Forced Oscillation ◽  
Respiratory Resistance ◽  
Frequency Range ◽  
Entire Frequency Range ◽  
Peripheral Airways ◽  
Distal Branch ◽  
Low Amplitude ◽  
Gas Compressibility ◽  
Central Airway

Respiratory impedance (Zrs) was measured between 0.25 and 32 Hz in seven anesthetized and paralyzed patients by applying forced oscillation of low amplitude at the inlet of the endotracheal tube. Effective respiratory resistance (Rrs; in cmH2O.l-1.s) fell sharply from 6.2 +/- 2.1 (SD) at 0.25 Hz to 2.3 +/- 0.6 at 2 Hz. From then on, Rrs decreased slightly with frequency down to 1.5 +/- 0.5 at 32 Hz. Respiratory reactance (Xrs; in cmH2O.l-1.s) was -22.2 +/- 5.9 at 0.25 Hz and reached zero at approximately 14 Hz and 2.3 +/- 0.8 at 32 Hz. Effective respiratory elastance (Ers = -2pi x frequency x Xrs; in cmH2O/1) was 34.8 +/- 9.2 at 0.25 Hz and increased markedly with frequency up to 44.2 +/- 8.6 at 2 Hz. We interpreted Zrs data in terms of a T network mechanical model. We represented the proximal branch by central airway resistance and inertance. The shunt pathway accounted for bronchial distensibility and alveolar gas compressibility. The distal branch included a Newtonian resistance component for tissues and peripheral airways and a viscoelastic component for tissues. When the viscoelastic component was represented by a Kelvin body as in the model of Bates et al. (J. Appl. Physiol. 61: 873-880, 1986), a good fit was obtained over the entire frequency range, and reasonable values of parameters were estimated. The strong frequency dependence of Rrs and Ers observed below 2 Hz in our anesthetized paralyzed patients could be mainly interpreted in terms of tissue viscoelasticity. Nevertheless, the high Ers we found with low volume excursions suggests that tissues also exhibit plasticlike properties.

TWO FAMILIES OF EXACT DISKS WITH A CENTRAL BLACK HOLE

1996 ◽  
Vol 05 (01) ◽  
pp. 53-63 ◽  
Author(s):  
JOSÉ P.S. LEMOS ◽  
PATRICIO S. LETELIER
Keyword(s):  
Black Hole ◽  
Topological Defect ◽  
Rotational Velocity ◽  
The Other ◽  
Central Black Hole ◽  
Counter Rotation ◽  
Infinite Extent ◽  
Self Similar ◽  
Physical Effects ◽  
Many Particles

The gravitational field of a configuration formed by a static disk and a Schwarzschild black hole is analysed for two families of disks. The matter of the disks is made of counter-rotating particles with as many particles rotating to one side as to the other, in such a way that the net angular momentum is zero and the disk is static. The first family consists of peculiar disks, in the sense that they are generated by two opposite dipoles. The particles of the disk have no pressure or centrifugal support. However, when there is a central black hole, centrifugal balance in the form of counter-rotation appears. The second family is a one parameter family of self-similar disks which includes at one end a Newtonian disk, and at the other a topological defect of spacetime. The presence of the black hole impresses more rotational velocity to the particles. These two families are of infinite extent. Some interesting physical effects are studied.

scholarly journals A.C conductivity and dielectric properties of (PVA/ PEO) blends doped with MWCNTs

2019 ◽  
Vol 14 (30) ◽  
pp. 64-72
Author(s):  
Ahmad A. Hasan
Keyword(s):  
Electrical Conductivity ◽  
Dielectric Properties ◽  
The Other ◽  
Poly Vinyl Alcohol ◽  
Conductivity Measurements ◽  
Frequency Range ◽  
Maximum Value ◽  
Multi Walled Carbon Nanotube ◽  
Poly Ethylene Oxide ◽  
Poly Ethylene

A.C electrical conductivity and dielectric properties for poly(vinyl alcohol) (PVA) /poly (ethylene oxide) (PEO) blends undopedand doped with multi-walled carbon nanotube (MWCNTs) withdifferent concentrations (1, and 3 wt %) in the frequency range(25x103 - 5x106 Hz) were investigated. Samples of (PVA/PEO)blends undoped and doped with MWCNTs were prepared usingcasting technique. The electrical conductivity measurements showedthat σA.C is frequency dependent and obey the relation σA.C =Aωs forundoped and doped blends with 1% MWCNTs, while it is frequencyindependent with increases of MWCNTs content to 3%. Theexponent s showed proceeding increase with the increase of PEOratio (≥50%) for undoped blends samples, while s value for dopedblends exhibits to change in different manner, i.e. s increases andreach maximum value at 50/50 PVA/PEO, then decreases forresidual doped blends samples with 1% MWCNTs on the other handthe exponent s decrease and reach minimum value at 50/50PVA/PEO for samples doped with 3% MWCNTs, then return toincrease. The results explained in different terms.

scholarly journals Elastic Properties of Magnetorheological Elastomers in a Heterogeneous Uniaxial Magnetic Field

2018 ◽  
Vol 19 (10) ◽  
pp. 3045 ◽  
Author(s):  
Takehito Kikuchi ◽  
Yusuke Kobayashi ◽  
Mika Kawai ◽  
Tetsu Mitsumata
Keyword(s):  
Magnetic Field ◽  
Elastic Properties ◽  
Uniform Magnetic Field ◽  
Large Strain ◽  
Small Strain ◽  
Experimental Results ◽  
The Other ◽  
Magnetorheological Elastomers ◽  
Other Hand ◽  
Strain Model

Magnetorheological elastomers (MREs) are stimulus-responsive soft materials that consist of polymeric matrices and magnetic particles. In this study, large-strain response of MREs with 5 vol % of carbonyl iron (CI) particles is experimentally characterized for two different conditions: (1) shear deformation in a uniform magnetic field; and (2), compression in a heterogeneous uniaxial magnetic field. For condition (1), dynamic viscoelastic measurements were performed using a rheometer with a rotor disc and an electric magnet that generated a uniform magnetic field on disc-like material samples. For condition (2), on the other hand, three permanent magnets with different surface flux densities were used to generate a heterogeneous uniaxial magnetic field under cylindrical material samples. The experimental results were mathematically modeled, and the relationship between them was investigated. We also used finite-element method (FEM) software to estimate the uniaxial distributions of the magnetic field in the analyzed MREs for condition (2), and developed mathematical models to describe these phenomena. By using these practicable techniques, we established a simple macroscale model of the elastic properties of MREs under simple compression. We estimated the elastic properties of MREs in the small-strain regime (neo–Hookean model) and in the large-strain regime (Mooney–Rivlin model). The small-strain model explains the experimental results for strains under 5%. On the other hand, the large-strain model explains the experimental results for strains above 10%.

Sign in / Sign up

Export Citation Format

Share Document