High-Frequency and Low-Frequency Oscillations in a Plasma in a Magnetic Field

1966 ◽  
Vol 21 (11) ◽  
pp. 2421-2421
Author(s):  
Kiyoe Kato ◽  
Takaya Kawabe ◽  
Mikiko Koganei ◽  
Eiich Kawasaki
Keyword(s):  
Magnetic Field ◽  
High Frequency ◽  
Low Frequency ◽  
Low Frequency Oscillations

Nonrandom variability in respiratory cycle parameters of humans during stage 2 sleep

1990 ◽  
Vol 69 (2) ◽  
pp. 630-639 ◽  
Author(s):  
M. Modarreszadeh ◽  
E. N. Bruce ◽  
B. Gothe
Keyword(s):  
High Frequency ◽  
Minute Ventilation ◽  
Power Spectra ◽  
Low Frequency ◽  
Neural Mechanism ◽  
Normal Subjects ◽  
Feedback Loops ◽  
Low Frequency Oscillations ◽  
Stage 2 Sleep ◽  
Correlated Components

We analyzed breath-to-breath inspiratory time (TI), expiratory time (TE), inspiratory volume (VI), and minute ventilation (Vm) from 11 normal subjects during stage 2 sleep. The analysis consisted of 1) fitting first- and second-order autoregressive models (AR1 and AR2) and 2) obtaining the power spectra of the data by fast-Fourier transform. For the AR2 model, the only coefficients that were statistically different from zero were the average alpha 1 (a1) for TI, VI, and Vm (a1 = 0.19, 0.29, and 0.15, respectively). However, the power spectra of all parameters often exhibited peaks at low frequency (less than 0.2 cycles/breath) and/or at high frequency (greater than 0.2 cycles/breath), indicative of periodic oscillations. After accounting for the corrupting effects of added oscillations on the a1 estimates, we conclude that 1) breath-to-breath fluctuations of VI, and to a lesser extent TI and Vm, exhibit a first-order autoregressive structure such that fluctuations of each breath are positively correlated with those of immediately preceding breaths and 2) the correlated components of variability in TE are mostly due to discrete high- and/or low-frequency oscillations with no underlying autoregressive structure. We propose that the autoregressive structure of VI, TI, and Vm during spontaneous breathing in stage 2 sleep may reflect either a central neural mechanism or the effects of noise in respiratory chemical feedback loops; the presence of low-frequency oscillations, seen more often in Vm, suggests possible instability in the chemical feedback loops. Mechanisms of high-frequency periodicities, seen more often in TE, are unknown.

scholarly journals ANALYSIS OF HIGH-FREQUENCY C-CORE MAGNETIC FLUX LEAKAGES FOR BONE TUMOR WITH INDUCTION HEATING BY USING MULTI-COIL

2019 ◽  
Author(s):  
Metharak Jokpudsa ◽  
Supawat Kotchapradit ◽  
Chanchai Thongsopa ◽  
Thanaset Thosdeekoraphat
Keyword(s):  
Magnetic Field ◽  
High Frequency ◽  
Tumor Tissue ◽  
Low Frequency ◽  
Heat Energy ◽  
High Frequencies ◽  
Frequency Magnetic Field ◽  
High Frequency Magnetic Field ◽  
The Magnetic Field ◽  
Flux Leakage

High-frequency magnetic field has been developed pervasively. The induction of heat from the magnetic field can help to treat tumor tissue to a certain extent. Normally, treatment by the low-frequency magnetic field needed to be combined with magnetic substances. To assist in the induction of magnetic fields and reduce flux leakage. However, there are studies that have found that high frequencies can cause heat to tumor tissue. In this paper present, a new magnetic application will focus on the analysis of the high-frequency magnetic nickel core with multi-coil. In order to focus the heat energy using a high-frequency magnetic field into the tumor tissue. The magnetic coil was excited by 915 MHz signal and the combination of tissues used are muscle, bone, and tumor. The magnetic power on the heating predicted by the analytical model, the power loss density (2.98e-6 w/m3) was analyzed using the CST microwave studio.

Oscillations in a Collapsed-Tube Analog of the Brachial Artery Under a Sphygmomanometer Cuff

1989 ◽  
Vol 111 (3) ◽  
pp. 185-191 ◽  
Author(s):  
C. D. Bertram ◽  
C. J. Raymond ◽  
K. S. A. Butcher
Keyword(s):  
High Frequency ◽  
Flow Characteristics ◽  
Low Frequency ◽  
Collapsible Tube ◽  
Tube Size ◽  
Low Frequency Oscillations ◽  
Central Segment ◽  
Experimental Parameters ◽  
Aqueous Flow ◽  
Low Frequency Mode

To determine whether self-excited oscillations in a Starling resistor are relevant to physiological situations, a collapsible tube conveying an aqueous flow was externally pressurized along only a central segment of its unsupported length. This was achieved by passing the tube through a shorter and wider collapsible sleeve which was mounted in Starling resistor fashion in a pressure chamber. The tube size and material, and all other experimental parameters, were as used in our previous Starling resistor studies. Both low- and high-frequency self-excited oscillations were observed, but the low-frequency oscillations were sensitive to the sleeve type and length relative to unsupported distance. Pressure-flow characteristics showed multiple oscillatory modes, which differed quantitatively from those observed in comparable Starling resistors. Slow variation of driving pressure gave differing behavior according to whether the pressure was rising or falling, in accord with the hysteresis noted on the characteristics and in the tube law. The results are discussed in terms of the various possible mechanisms of collapsible tube instability, and reasons are presented for the absence of the low-frequency mode under most physiological circumstances.

Interaction between High Frequency Oscillations and Low Frequency Oscillations in Beam-Plasma System

1967 ◽  
Vol 23 (6) ◽  
pp. 1430-1431 ◽  
Author(s):  
Takaya Kawabe ◽  
Yoshinobu Kawai ◽  
Kazuo Takayama ◽  
Shoji Kojima
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Plasma System ◽  
High Frequency Oscillations ◽  
Low Frequency Oscillations ◽  
Beam Plasma

A parametric study of the vertical electric source

Geophysics ◽  
1995 ◽  
Vol 60 (1) ◽  
pp. 43-52 ◽  
Author(s):  
Louise Pellerin ◽  
Gerald W. Hohmann
Keyword(s):  
Magnetic Field ◽  
High Frequency ◽  
Host Response ◽  
Low Frequency ◽  
Signal Strength ◽  
Phase Response ◽  
Vertical Magnetic Field ◽  
Electric Source ◽  
Measured Response ◽  
Quadrature Response

Measurement of the vertical magnetic field caused by a vertical electric source (VES) is an attractive exploration option because the measured response is caused by only 2-D and 3-D structures. The absence of a host response markedly increases the detectability of confined structures. In addition, the VES configuration offers advantages such as alleviating masking resulting from conductive overburden and the option of having a source functioning in a collapsed borehole. Applications of the VES, as in mineral exploration, seafloor exploration, and process monitoring such as enhanced oil recovery, are varied, but we limit this study to a classic mining problem—the location of a confined, conductive target at depth in the vicinity of a borehole. By analyzing the electromagnetic responses of a thin, vertical prism, a horizontal slab and an equidimensional body, we investigate the resolving capabilities, identify survey design problems, and provide interpretational insight for vertical magnetic field responses arising from a VES. Data acquisition problems, such as electrode contact within a borehole, are not addressed. Current channeling is the dominant mechanism by which a 2-D or 3-D target is excited. The response caused by currents induced in the target is relatively unimportant compared to that of channeled currents. At low frequencies, the in‐phase response results from galvanic currents from the source electrodes channeled through the target. The quadrature response, at all frequencies, results from currents induced in the host and channeled through the target. At high frequencies, in‐phase currents are also induced in the host and channeled through the target. Hence, the quadrature response and the high‐frequency in‐phase response are quite sensitive to the host resistivity. Time‐domain magnetic field responses show the same behavior as the quadrature component. Interpretation of low‐frequency vertical magnetic field measurements is straightforward for a source placed along strike of the target and a profile line traversing the target. The target is located under a sign reversal or null in the field for a flat‐lying or vertical target. A dipping target has an asymmetrical response, with reduced amplitude on the downdip lobe. The target is located between the maximum lobe and the null. Although the vertical magnetic field caused by a VES for a 2-D or 3-D structure is purely anomalous, the host layering can affect signal strength by more than an order of magnitude. A general knowledge of the location of the target and host layering is helpful in maximizing signal strength. In practice boreholes are not vertical. An angled source can introduce a response because of the horizontal component that can overwhelm the VES response. For low‐frequency, in‐phase, or magnetometric resistivity (MMR) measurements made with a source angled at less than 30 degrees from the vertical, the host response caused by a horizontal electric source (HES) is negligible, and the free space response is easily computed and removed from the total response leaving a response that can be interpreted as that being caused by a VES. The high‐frequency, in‐phase response and the quadrature response at any frequency caused by a HES are strongly dependent on the host resistivity and dominate the scattered response. The measured response, therefore, must be interpreted using sophisticated techniques that take source geometry and host resistivity into account.

Filamentation and collapse of Langmuir waves in a weak magnetic field

1982 ◽  
Vol 28 (1) ◽  
pp. 19-36 ◽  
Author(s):  
P. Rolland ◽  
S. G. Tagare
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Small Angle ◽  
Nonlinear Interaction ◽  
High Frequency ◽  
Weak Magnetic Field ◽  
Low Frequency ◽  
Langmuir Waves ◽  
The Magnetic Field

The filamentation and collapse of Langmuir waves in a weak magnetic field are analysed in two particular cases of low-frequency acoustic perturbations: (i) adiabatic perturbations which correspond to subsonic collapse, and (ii) nonadiabatic perturbations which correspond to supersonic collapse. Here the existence of Langmuir filaments and Langmuir collapse in a weak magnetic field are due to nonlinear interaction of high-frequency Langmuir waves (which make small angle with the external magnetic field) with low-frequency acoustic perturbations along the magnetic field.

Low-frequency oscillations of plasma rotating in a magnetic field

1972 ◽  
Vol 10 (5) ◽  
pp. 822-824
Author(s):  
V. G. Andropov ◽  
G. S. Lopatskii ◽  
G. D. Petrov ◽  
V. I. Chernysh ◽  
�. F. Yurchuk
Keyword(s):  
Magnetic Field ◽  
Low Frequency ◽  
Low Frequency Oscillations

Observation of Turbulent Waves in a Helium Plasma by Optical Spectroscopy

1975 ◽  
Vol 30 (10) ◽  
pp. 1271-1278
Author(s):  
W. R. Rutgers
Keyword(s):  
Energy Density ◽  
Field Strength ◽  
High Frequency ◽  
Low Frequency ◽  
Turbulent Plasma ◽  
Helium Plasma ◽  
High Frequency Oscillations ◽  
Low Frequency Oscillations ◽  
Frequency Domains ◽  
Turbulent Heating

Abstract From the combined Stark-Zeeman pattern of helium allowed and forbidden optical lines the frequency spectrum, the field strength and the dominant polarization of microfields were determined in a turbulent plasma. Two frequency domains of oscillations were found in a turbulent heating experiment: low-frequency oscillations with dominant polarization perpendicular to the current direction and high-frequency oscillations (f~fpe) with random polarization. The r.m.s. field strength of the oscillations is between 2 kV/cm and 10 kV/cm. The energy density of turbulent microfields amounts to 1‰ of the thermal energy density.

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