Q‐factor approximation of electromagnetic fields for high‐frequency sounding in the 300 kHz to 30 MHz range over layered media

Geophysics ◽  
1995 ◽  
Vol 60 (4) ◽  
pp. 1253-1258 ◽  
Author(s):  
Walter L. Anderson
Keyword(s):  
Closed Form ◽  
Half Space ◽  
Electromagnetic Fields ◽  
High Frequency ◽  
Analytic Solution ◽  
Layered Media ◽  
New Method ◽  
Earth Model ◽  
Q Factor ◽  
Layered Earth

A new method for rapid approximation of electromagnetic (EM) fields for high‐frequency sounding (HFS) over a layered earth is presented in this paper. The essence of this method uses a Q‐factor correction for extending a closed‐form, half‐space analytic solution to a layered earth model. Use of the Q‐factor in this context was first studied by Wait (1953, 1962). Kraichman (1976) also discusses the problem of when the Q‐factor method can be used to provide a good approximation to an exact layered earth solution.

To: “Q‐factor approximation of electromagnetic fields for high‐frequency sounding in the 300 kHz to 30 kHz range over layered media,” by Walter L. Anderson (July–August 1995, GEOPHYSICS, 60, p. 1253–1258).

Geophysics ◽  
1995 ◽  
Vol 60 (6) ◽  
pp. 1949-1949
Keyword(s):  
Electromagnetic Fields ◽  
High Frequency ◽  
Layered Media ◽  
Q Factor

The last bracketed term [Formula: see text] in equation (1) should appear in the denominator; i.e., a “/” symbol should be inserted immediately before this term in equation (1), exactly as before the last bracketed term in equation (3). The title letters “b)” and “c)” in the sub‐figures of Figure 4 should be interchanged, which would then correspond to the existing caption of Figure 4 and the text in the last paragraph on page 1255.

Response of a layered earth to the Crone pulse electromagnetic system

Geophysics ◽  
1982 ◽  
Vol 47 (1) ◽  
pp. 63-70 ◽  
Author(s):  
S. K. Verma ◽  
S. S. Rai
Keyword(s):  
Half Space ◽  
Single Channel ◽  
Time Derivative ◽  
Measuring System ◽  
Difference Approximation ◽  
Earth Model ◽  
Theoretical Formulation ◽  
Electromagnetic System ◽  
Layered Earth ◽  
Derivative Formula

The response of a layered earth to the Crone pulse electromagnetic (PEM) system, which measures the decay of the time derivative [Formula: see text] has been computed. The transient vertical magnetic field component [Formula: see text] due to a vertical magnetic dipole is obtained by applying a Fourier series summation approach and using digital linear filters to compute the response at individual frequencies. Oscillations in [Formula: see text] due to Gibb’s phenomena are suppressed with Lanczos weights, and the derivative [Formula: see text] is computed numerically by using a linear difference approximation over five points. Decay curves for various half‐spaces are found to cross each other at different values of time. Thus, a single channel response cannot be used to estimate the half‐space resistivity uniquely. This can be achieved, however, by making use of responses at two different channels. Conductivity‐aperture diagrams for half‐space models are plotted for both [Formula: see text] and [Formula: see text]. For [Formula: see text], all the channel amplitudes show well‐defined peaks in the range of 0.3 to 5 ω-m, whereas for [Formula: see text] these peaks lie in the range of 0.7 to 20 Ω-m. This supports the finding by earlier workers that for higher conductivities a total field measuring system responds better than a derivative measuring system. A theoretical formulation is presented to compute the Crone PEM response of an n‐layered earth model. After checking the accuracy of the program, some results are presented for models with different numbers of layers. However, detailed investigation is reported for two‐layered earth only. It is found that overburden parameters can be determined by utilizing responses at two different channels. Nomograms to determine these parameters are presented. There nomograms reveal that for the resistive basement case the best discrimination can be done for the overburden resistivities in the range of 3 to 10 Ω-m and for thicknesses in the range of 0.5 L to 1.5 L (L being the coil separation). For the conductive basement situation the corresponding values are 3 to 15 Ω-m and 0.25 L to 1 L.

Method of high frequency therapy at cows' mastitis during machine milking

2020 ◽  
pp. 9-12
Author(s):  
Viktor E. Lyubimov ◽  
Keyword(s):  
Dairy Cows ◽  
Electromagnetic Fields ◽  
High Frequency ◽  
High Efficiency ◽  
Environmentally Friendly ◽  
Ultrahigh Frequency ◽  
Machine Milking ◽  
High Frequency Electromagnetic Field ◽  
Milking Machine ◽  
Methods Of Treatment

Health of dairy cows ensures human health, so it is important that dairy products do not contain antibiotics that are used to treat any inflammation, including mastitis. In Russia at present, the problem of mastitis in cows exists with both attached and loose housing of cows. Mastitis of dairy cows are the great problem in milking husbandry. Losses from mastitis in milk yield can reach 15-20%. The main reasons for the occurrence of nonspecific mastitis of cows are the shortcomings of the working components of the milking machine: the degree of deterioration of the nipple rubber and the violation of machine milking technology (the reduction in pre-milking time and vacuum fluctuations account for 70% of all causes). Treatment of mastitis with antibiotics is effective, but not environmentally friendly and unacceptable. For the treatment of inflammation of the udder, it is necessary to use more environmentally friendly methods of treatment, one of which is the exposure to ultra-high frequency electromagnetic field tested by medicine. Use of three types of medical-mobile milking machines with the same method of exposure to ultrahigh-frequency electromagnetic fields on cow's nipples through electrodes in milking cups: LPDA-1-UHF, LPDA-2-UHF and LPDA-UHF-30 M, is described in the article. Author proved that cows with subclinical forms of mastitis recovered faster during milking with exposure to the ultrahigh frequency than when treated by antibiotics, and milking with the ultrahigh frequency device helps to recover 82% of the affected quarters with clinical forms and 100% of cows with subclinical forms of mastitis or with udder irritation. The high efficiency of the method of exposure to electromagnetic fields of the ultrahigh frequency during machine milking by means of medical-mobile milking machines LPDA-UHF for the prevention and treatment of mastitis of cows was shown.

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