THE HEATING OF ELECTROLYTES IN HIGH FREQUENCY FIELDS

1930 ◽  
Vol 3 (3) ◽  
pp. 224-240 ◽  
Author(s):  
J. C. McLennan F.R.S. ◽  
A. C. Burton M.A.
Keyword(s):  
Dielectric Constant ◽  
High Frequency ◽  
Electromagnetic Waves ◽  
Skin Effect ◽  
Specific Conductivity ◽  
Wave Length ◽  
Radio Waves ◽  
Selective Heating ◽  
Heating Effects ◽  
Maximum Heating

In this investigation the heating of solutions of simple electrolytes of varying concentrations when irradiated by short electromagnetic waves from 10 to 200 metres in length was measured. It was found that for a given wave-length there is a maximum heating effect produced in a medium, the specific conductivity and dielectric constant of which are connected with the frequency by a simple law. This law, proved theoretically as well as shown experimentally to hold for dilute solutions is [Formula: see text] where C = specific conductivity in absolute units, K = dielectric constant and n = frequency of wave."Skin effect" was shown theoretically and experimentally to be negligible for substances having the low conductivities studied and deep-seated heating effects were shown to be attainable with the radio waves used. The possibility of directed selective heating effects is suggested and illustrated by experiments on blood. The law shown to apply in these experiments was used to evaluate the dielectric constant of water.

SELECTIVE HEATING BY SHORT RADIO WAVES AND ITS APPLICATION TO ELECTROTHERAPY

1931 ◽  
Vol 5 (5) ◽  
pp. 550-566 ◽  
Author(s):  
J. C. McLennan F.R.S. ◽  
A. C. Burton M.A.
Keyword(s):  
High Frequency ◽  
Wave Length ◽  
Theoretical Explanation ◽  
The Body ◽  
Radio Waves ◽  
High Frequencies ◽  
Selective Effect ◽  
Selective Heating ◽  
Determining Factors ◽  
Frequency Oscillator

In the first part of the paper the theoretical basis of the formulas, given in a previous communication, for the generation of heat in a poorly conducting dielectric which is placed in the field of a high-frequency oscillator, is examined in some detail. Its application to the complicated case met with in medical "radiothermy" is made and it is shown that the analysis applies with satisfactory accuracy to this case, though not to that of electrode diathermy. Prediction of the "selective" effect is possible from a knowledge of the characteristic electrical constants of the body-substances at high frequencies, and by proper choice of wave-length the heating of a particular part might be favored over that of neighboring parts.In the second part of the paper, experimental work is described which carries verification of the formulas to shorter wave-lengths. Experiments on the heating of meat demonstrate the selective effect and its dependence upon wave-length. The heating of such substances as liver, heart, and the different parts of an egg, are examined experimentally as examples of the various determining factors that are involved.The theoretical explanation of the effects is considered satisfactory and further developments depend upon the results of in viva experiments with shorter wavelengths than those at present in general use.

The role of natural E-region plasma turbulence in the enhanced absorption of HF radio waves in the auroral ionosphere:Implications for RF heating of the auroral electrojet

1994 ◽  
Vol 12 (4) ◽  
pp. 316-332 ◽  
Author(s):  
T. R. Robinson
Keyword(s):  
Radio Wave ◽  
Electromagnetic Waves ◽  
Auroral Electrojet ◽  
Radio Waves ◽  
Electrostatic Waves ◽  
Enhanced Absorption ◽  
Heating Effects ◽  
Wave Heating ◽  
Radio Wave Absorption ◽  
E Region

Abstract. Physical processes which affect the absorption of radio waves passing through the auroral E-region when Farley-Buneman irregularities are present are examined. In particular, the question of whether or not it is legitimate to include the anomalous wave-enhanced collision frequency, which has been used successfully to account for the heating effects of Farley-Buneman waves in the auroral E-region, in the usual expression for the radio-wave absorption coefficient is addressed. Effects also considered are those due to wave coupling between electromagnetic waves and high-frequency electrostatic waves in the presence of Farley-Buneman irregularities. The implications for radio-wave heating of the auroral electrojet of these processes are also discussed. In particular, a new theoretical model for calculating the effects of high-power radio-wave heating on the electron temperature in an electrojet containing Farley-Buneman turbulence is presented.

The relation between the composition, structure and absorption properties of ultra-high frequency radio waves of poly(vinylidene fluoride)/magnetite nanocomposites

2019 ◽  
Vol 33 (10) ◽  
pp. 1950083 ◽  
Author(s):  
M. A. Ramazanov ◽  
F. V. Hajiyeva ◽  
H. A. Shirinova ◽  
H. M. Mamedov
Keyword(s):  
Polymer Matrix ◽  
High Frequency ◽  
Electromagnetic Waves ◽  
Vinylidene Fluoride ◽  
Molecular Structures ◽  
Radio Waves ◽  
X Ray Diffraction ◽  
Atomic Force ◽  
Poly Vinylidene Fluoride ◽  
Composition Structure

In the presented work, nanocomposites based on poly (vinylidene fluoride) (PVDF) and magnetite Fe3O4 nanoparticles were prepared. The structure and content of nanocomposite materials were studied by using scanning electron microscope (SEM), atomic-force microscope (AFM) and X-Ray diffraction (XRD). Magnetic properties of PVDF[Formula: see text]+[Formula: see text]Fe3O4 nanocomposites have been studied upon increasing nanoparticle content in polymer matrix upto 20%, revealing superparamagnetic behavior as Fe3O4 nanoparticles in polymer matrix act out like single-domain particles. It has also been observed that PVDF[Formula: see text]+[Formula: see text]Fe3O4-based nanocomposites can absorb the electromagnetic waves in the high frequency range 0.1–30 GHz. It has been shown that the absorption of high frequency radio waves by PVDF[Formula: see text]+[Formula: see text]Fe3O4 nanocomposites can be explained by the different molecular structures and also by the scattering of the radio waves at the boundary of nanoparticle-polymer matrix.

scholarly journals THE RELATION OF FREQUENCY TO THE PHYSIOLOGICAL EFFECTS OF ULTRA-HIGH FREQUENCY CURRENTS

1929 ◽  
Vol 49 (2) ◽  
pp. 303-321 ◽  
Author(s):  
Ronald V. Christie ◽  
Alfred L. Loomis
Keyword(s):  
Magnetic Field ◽  
High Frequency ◽  
Electromagnetic Waves ◽  
Biological Effects ◽  
Wave Length ◽  
Living Cells ◽  
Physiological Effects ◽  
Induced Current ◽  
Electro Magnetic Field ◽  
Electro Magnetic

1. Biological effects of electromagnetic waves emitted by a vacuum tube oscillator have been studied at frequencis ranging from 8,300,000 to 158,000,000 cycles per second (1.9 to 38 meters wave-length). 2. The effects produced on animals can be fully explained on the basis of the heat generated by high frequency currents which are induced in them. 3. No evidence was obtained to support the theory that certain wave-lengths have a specific action on living cells. 4. At frequencies below 50,000,000 cycles, the effect of these radiations on animals is proportionate to the intensity of the electro-magnetic field. As the frequency is increased beyond this point, the amount of induced current is diminished and the apparent lethality of the radiation is decreased. This can be explained by changes occurring in the dielectric properties of tissues at low wave-lengths.

scholarly journals The high-frequency resistance of superconducting tin

1940 ◽  
Vol 176 (967) ◽  
pp. 522-533 ◽  
Keyword(s):  
High Frequency ◽  
Skin Effect ◽  
Wave Length ◽  
Low Frequency ◽  
Mean Free Path ◽  
Low Frequencies ◽  
The Mean ◽  
Absolute Measurements ◽  
Eddy Current Heating ◽  
Good Agreement

The high-frequency resistance of tin in the superconducting state was measured at a wave-length of 20.5 cm. by a calorimetric method based on the principle of eddy-current heating. It was found that the resistance decreases gradually when the temperature falls below the transition point in contrast to the sudden drop in resistance peculiar to direct currents. An explanation of such a behaviour is given based on the assumption of the simultaneous presence of normal and superconducting electrons. Good agreement between theory and experiment was found. Absolute measurements of the conductivity in the normal state at low temperatures with both high and low frequencies were carried out, and it was found that at the temperature of liquid helium the conductivity for high frequency is considerably lower than for low frequency. This behaviour is possibly due to the fact that the mean free path of the electrons becomes larger than the penetration depth due to skin effect under the conditions of high conductivity and high frequency.

Development of a Capacitor Probe to Detect Subsurface Deterioration in Concrete

1997 ◽  
Vol 503 ◽  
Author(s):  
B. K. Diefenderfer ◽  
I. L. Al-Qadi ◽  
J. J. Yoho ◽  
S. M. Riad ◽  
A. Loulizi
Keyword(s):  
Dielectric Constant ◽  
Portland Cement ◽  
Electromagnetic Waves ◽  
Low Cost ◽  
Complex Dielectric Constant ◽  
Life Cycle Costs ◽  
Parallel Plates ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Set Up

ABSTRACTPortland cement concrete (PCC) structures deteriorate with age and need to be maintained or replaced. Early detection of deterioration in PCC (e.g., alkali-silica reaction, freeze/thaw damage, or chloride presence) can lead to significant reductions in maintenance costs. However, it is often too late to perform low-cost preventative maintenance by the time deterioration becomes evident. By developing techniques that would enable civil engineers to evaluate PCC structures and detect deterioration at early stages (without causing further damage), optimization of life-cycle costs of the constructed facility and minimization of disturbance to the facility users can be achieved.Nondestructive evaluation (NDE) methods are potentially one of the most useful techniques ever developed for assessing constructed facilities. They are noninvasive and can be performed rapidly. Portland cement concrete can be nondestructively evaluated by electrically characterizing its complex dielectric constant. The real part of the dielectric constant depicts the velocity of electromagnetic waves in PCC. The imaginary part, termed the “loss factor,” describes the conductivity of PCC and the attenuation of electromagnetic waves.Dielectric properties of PCC have been investigated in a laboratory setting using a parallel plate capacitor operating in the frequency range of 0.1 to 40.1MIHz. This capacitor set-up consists of two horizontal-parallel plates with an adjustable separation for insertion of a dielectric specimen (PCC). While useful in research, this approach is not practical for field implementation. A new capacitor probe has been developed which consists of two plates, located within the same horizontal plane, for placement upon the specimen to be tested. Preliminary results show that this technique is feasible and results are promising; further testing and evaluation is currently underway.

Reflection of high-frequency radio waves in inhomogeneous ionospheric layers

Radio Science ◽  
1985 ◽  
Vol 20 (3) ◽  
pp. 303-309 ◽  
Author(s):  
Kenneth Davies ◽  
Charles M. Rush
Keyword(s):  
High Frequency ◽  
Radio Waves

Electrohydrodynamic stability: Taylor–Melcher theory for a liquid bridge suspended in a dielectric gas

2002 ◽  
Vol 452 ◽  
pp. 163-187 ◽  
Author(s):  
C. L. BURCHAM ◽  
D. A. SAVILLE
Keyword(s):  
Surface Tension ◽  
Dielectric Constant ◽  
Electric Fields ◽  
Liquid Bridge ◽  
Numerical Solutions ◽  
Specific Conductivity ◽  
Axisymmetric Deformation ◽  
Aspect Ratios ◽  
The Stability ◽  
Theory And Experiment

A liquid bridge is a column of liquid, pinned at each end. Here we analyse the stability of a bridge pinned between planar electrodes held at different potentials and surrounded by a non-conducting, dielectric gas. In the absence of electric fields, surface tension destabilizes bridges with aspect ratios (length/diameter) greater than π. Here we describe how electrical forces counteract surface tension, using a linearized model. When the liquid is treated as an Ohmic conductor, the specific conductivity level is irrelevant and only the dielectric properties of the bridge and the surrounding gas are involved. Fourier series and a biharmonic, biorthogonal set of Papkovich–Fadle functions are used to formulate an eigenvalue problem. Numerical solutions disclose that the most unstable axisymmetric deformation is antisymmetric with respect to the bridge’s midplane. It is shown that whilst a bridge whose length exceeds its circumference may be unstable, a sufficiently strong axial field provides stability if the dielectric constant of the bridge exceeds that of the surrounding fluid. Conversely, a field destabilizes a bridge whose dielectric constant is lower than that of its surroundings, even when its aspect ratio is less than π. Bridge behaviour is sensitive to the presence of conduction along the surface and much higher fields are required for stability when surface transport is present. The theoretical results are compared with experimental work (Burcham & Saville 2000) that demonstrated how a field stabilizes an otherwise unstable configuration. According to the experiments, the bridge undergoes two asymmetric transitions (cylinder-to-amphora and pinch-off) as the field is reduced. Agreement between theory and experiment for the field strength at the pinch-off transition is excellent, but less so for the change from cylinder to amphora. Using surface conductivity as an adjustable parameter brings theory and experiment into agreement.

Scattering of electromagnetic waves by hybrid waves in a two-electron-temperature plasma

1991 ◽  
Vol 46 (1) ◽  
pp. 99-106 ◽  
Author(s):  
S. K. Sharma ◽  
A. Sudarshan
Keyword(s):  
Growth Rate ◽  
Electron Temperature ◽  
High Frequency ◽  
Electromagnetic Waves ◽  
Low Frequency ◽  
Lower Hybrid ◽  
Stimulated Scattering ◽  
Coupled Modes ◽  
Temperature Plasma ◽  
Electrostatic Perturbation

In this paper, we use the hydrodynamic approach to study the stimulated scattering of high-frequency electromagnetic waves by a low-frequency electrostatic perturbation that is either an upper- or lower-hybrid wave in a two-electron-temperature plasma. Considering the four-wave interaction between a strong high-frequency pump and the low-frequency electrostatic perturbation (LHW or UHW), we obtain the dispersion relation for the scattered wave, which is then solved to obtain an explicit expression for the growth rate of the coupled modes. For a typical Q-machine plasma, results show that in both cases the growth rate increases with noh/noc. This is in contrast with the results of Guha & Asthana (1989), who predicted that, for scattering by a UHW perturbation, the growth rate should decrease with increasing noh/noc.

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