Om Gandhi - Academia.edu (original) (raw)
Papers by Om Gandhi
IETE Journal of Research, 1965
ABSTRACTA new type of crossed field gun utilizing a tapered magnetic field in the gun region is d... more ABSTRACTA new type of crossed field gun utilizing a tapered magnetic field in the gun region is discussed. A closed form space charge model is presented that avoids the singularity at ωcτ = 2π and allows pseudo-parabolic trajectories. The shapes of the gun electrodes are derived by analytic continuation of the space-charge potential off the beam peripheries. The possibility of obtaining high convergence, low noise, laminar beams using this type of gun is discussed.
Journal of Microwave Power, 1983
IETE Journal of Research, 1967
ABSTRACTIn this paper a crossed field gun with small component of magnetic field normal to the ca... more ABSTRACTIn this paper a crossed field gun with small component of magnetic field normal to the cathode plane in addition to the usual magnetic field is proposed for low noise operation. The small extra component of magnetic field would bring about the reduction of randomness of emission velocity in x-direction and decrease the rate of growth of fluctuations in gun region, thereby reducing the noise in the beam.
Encyclopedia of RF and Microwave Engineering, 2005
IEEE Transactions on Electron Devices, 1966
IEEE Transactions on Electron Devices, 1974
Numerical methods have matured to a level that they are being increasingly used by many laborator... more Numerical methods have matured to a level that they are being increasingly used by many laboratories for dosimetric calculations for important and meaningful bioelectromagnetic problems. For certification of mobile telephones to be within the ANSI/IEEE C95.1-1992 RF Safety Guidelines, the approach discussed in this paper may be quite useful. We should also be able to use the numerical approach outlined here to understand coupling of power-frequency high-magnetic-field sources such as hair dryers, hair clippers, electric shavers, etc., to the human head. Of particular-interest would be the induced EMFs and current densities for the pineal gland which has been alleged to be involved in the biological effects of power-frequency FMFs. With the resolution of the present models being on the order of 11.7 milligrams of tissue for each of the cells of dimension 1.974 × 1.974 × 3 mm, it is possible to define even small glands, such as the pineal, with a great deal of precision. The numerical...
: The broad purpose of the research activity reported herein is to extend the useful frequency sp... more : The broad purpose of the research activity reported herein is to extend the useful frequency specttrum into the range from microwave frequencies to optical frequencies and to improve existing devices and techniques in the microwave spectrum. At present this objective is being pursued by studies of electron beam devices, quantum electronic devices, plasmas, and solid-state devices. (Author)
Journal of Microwave Power, 1979
Electricity and Magnetism in Biology and Medicine, 1999
Microwave dosimetry has frequently relied on the used of phantoms to measure microwave dose for b... more Microwave dosimetry has frequently relied on the used of phantoms to measure microwave dose for biological exposures. Here we report the use a homogeneous rhesus monkey phantom, the “green monkey”, to verify the results of a FD-TD computer model. The same techniques previously used to develop heterogeneous models of rat, goat and rhesus monkey from whole-body MRI scans1 were used to create a model of the “green monkey.” A phantom was prepared and subjected to a complete MRI scan. The resulting images were used to construct an accurate computer model of the phantom. FD-TD runs were performed at a range of frequencies using the geometry of the coded phantom. Local SAR values from the FD-TD output were used to select locations for local temperature measurements in the phantom.
IETE Journal of Research, 1967
IETE Journal of Research, 1964
ABSTRACTAn L-band Y-junction Stripline Circulator having a wide bandwidth is developed. The step-... more ABSTRACTAn L-band Y-junction Stripline Circulator having a wide bandwidth is developed. The step-by-step procedure leading to the design of the circulator is indicated. The magnetic field for optimum circulation at different frequencies is measured and is found to increase linearly with increasing frequency—a result previously obtained by Yoshida1 with several circulators designed for operation at different frequencies.This circulator can also be made to operate with a bandwidth of several hundred megacycles at C-band, with a biasing magnetic field of below-resonance value.
IETE Journal of Research, 1965
ABSTRACTThis paper describes the design and development of a semiconductor diode parametric ampli... more ABSTRACTThis paper describes the design and development of a semiconductor diode parametric amplifier at L-band. It is a single-port device operating in the quasi-degenerate mode. Results are given for a single-tuned amplifier, with two different diodes. Also described are the effects on the bandwidth by the inclusion of one additional resonator in the signal circuit. The parametric amplifier has a gain bandwidth product which is as good as for other amplifiers in L-band, reported in the literature.
1975 5th European Microwave Conference, 1975
... In order to increase the sensitivity of the probe to measure field inten-sities below 10 mW/c... more ... In order to increase the sensitivity of the probe to measure field inten-sities below 10 mW/cm2, it is necessary to use liquid crystal mixtures which have a narrow temperature range. ... of the IEEE,60(6), 382 Page 6. 692 (1972). (2) McRee, D. I. and Pendergrass, F. T., "Interaction of ...
MTT-S International Microwave Symposium Digest
A miniaturized microwave probe has been developed using the microwave-caused heating of a thin co... more A miniaturized microwave probe has been developed using the microwave-caused heating of a thin coating of a resistive material and the resulting change in the color of a miniscule amount of liquid crystal in intimate contact. The probe can be inserted in animals for microwave biological effects research and is isotropic in its sensitivity to different polarizations of the fields.
Bulletin of the New York Academy of Medicine, 1979
Journal of cyclic nucleotide research, 1977
Techniques of in-vivo microwave irradiation to inactivate brain enzymes in rats were varied as to... more Techniques of in-vivo microwave irradiation to inactivate brain enzymes in rats were varied as to exposure configuration and output power. The rate at which metabolism was stopped was studied in various regions of the rat brain, using changes in levels of cyclic AMP and phosphodiesterase activity. Exposure times required to obtain stabilized levels of cyclic AMP varied in different brain regions, i.e., hypothalamus, cortex and cerebellum. Levels of cyclic AMP in selective regions of the brain decreased as more rapid inactivation was achieved. The authors identify important sources of variability of present microwave inactivation systems and the need for improved control of signficant microwave parameters.
Review of Scientific Instruments, 1982
A laser synchronization circuit, applicable to (optical) sum or difference frequency generation s... more A laser synchronization circuit, applicable to (optical) sum or difference frequency generation systems, is described. The laser synchronizer has yielded excellent results in preventing damage to the mixing crystal of an infrared-to-visible parametric upconverter.
International Journal of Electronics, 1965
ABSTRACT
IETE Journal of Research, 1965
ABSTRACTA new type of crossed field gun utilizing a tapered magnetic field in the gun region is d... more ABSTRACTA new type of crossed field gun utilizing a tapered magnetic field in the gun region is discussed. A closed form space charge model is presented that avoids the singularity at ωcτ = 2π and allows pseudo-parabolic trajectories. The shapes of the gun electrodes are derived by analytic continuation of the space-charge potential off the beam peripheries. The possibility of obtaining high convergence, low noise, laminar beams using this type of gun is discussed.
Journal of Microwave Power, 1983
IETE Journal of Research, 1967
ABSTRACTIn this paper a crossed field gun with small component of magnetic field normal to the ca... more ABSTRACTIn this paper a crossed field gun with small component of magnetic field normal to the cathode plane in addition to the usual magnetic field is proposed for low noise operation. The small extra component of magnetic field would bring about the reduction of randomness of emission velocity in x-direction and decrease the rate of growth of fluctuations in gun region, thereby reducing the noise in the beam.
Encyclopedia of RF and Microwave Engineering, 2005
IEEE Transactions on Electron Devices, 1966
IEEE Transactions on Electron Devices, 1974
Numerical methods have matured to a level that they are being increasingly used by many laborator... more Numerical methods have matured to a level that they are being increasingly used by many laboratories for dosimetric calculations for important and meaningful bioelectromagnetic problems. For certification of mobile telephones to be within the ANSI/IEEE C95.1-1992 RF Safety Guidelines, the approach discussed in this paper may be quite useful. We should also be able to use the numerical approach outlined here to understand coupling of power-frequency high-magnetic-field sources such as hair dryers, hair clippers, electric shavers, etc., to the human head. Of particular-interest would be the induced EMFs and current densities for the pineal gland which has been alleged to be involved in the biological effects of power-frequency FMFs. With the resolution of the present models being on the order of 11.7 milligrams of tissue for each of the cells of dimension 1.974 × 1.974 × 3 mm, it is possible to define even small glands, such as the pineal, with a great deal of precision. The numerical...
: The broad purpose of the research activity reported herein is to extend the useful frequency sp... more : The broad purpose of the research activity reported herein is to extend the useful frequency specttrum into the range from microwave frequencies to optical frequencies and to improve existing devices and techniques in the microwave spectrum. At present this objective is being pursued by studies of electron beam devices, quantum electronic devices, plasmas, and solid-state devices. (Author)
Journal of Microwave Power, 1979
Electricity and Magnetism in Biology and Medicine, 1999
Microwave dosimetry has frequently relied on the used of phantoms to measure microwave dose for b... more Microwave dosimetry has frequently relied on the used of phantoms to measure microwave dose for biological exposures. Here we report the use a homogeneous rhesus monkey phantom, the “green monkey”, to verify the results of a FD-TD computer model. The same techniques previously used to develop heterogeneous models of rat, goat and rhesus monkey from whole-body MRI scans1 were used to create a model of the “green monkey.” A phantom was prepared and subjected to a complete MRI scan. The resulting images were used to construct an accurate computer model of the phantom. FD-TD runs were performed at a range of frequencies using the geometry of the coded phantom. Local SAR values from the FD-TD output were used to select locations for local temperature measurements in the phantom.
IETE Journal of Research, 1967
IETE Journal of Research, 1964
ABSTRACTAn L-band Y-junction Stripline Circulator having a wide bandwidth is developed. The step-... more ABSTRACTAn L-band Y-junction Stripline Circulator having a wide bandwidth is developed. The step-by-step procedure leading to the design of the circulator is indicated. The magnetic field for optimum circulation at different frequencies is measured and is found to increase linearly with increasing frequency—a result previously obtained by Yoshida1 with several circulators designed for operation at different frequencies.This circulator can also be made to operate with a bandwidth of several hundred megacycles at C-band, with a biasing magnetic field of below-resonance value.
IETE Journal of Research, 1965
ABSTRACTThis paper describes the design and development of a semiconductor diode parametric ampli... more ABSTRACTThis paper describes the design and development of a semiconductor diode parametric amplifier at L-band. It is a single-port device operating in the quasi-degenerate mode. Results are given for a single-tuned amplifier, with two different diodes. Also described are the effects on the bandwidth by the inclusion of one additional resonator in the signal circuit. The parametric amplifier has a gain bandwidth product which is as good as for other amplifiers in L-band, reported in the literature.
1975 5th European Microwave Conference, 1975
... In order to increase the sensitivity of the probe to measure field inten-sities below 10 mW/c... more ... In order to increase the sensitivity of the probe to measure field inten-sities below 10 mW/cm2, it is necessary to use liquid crystal mixtures which have a narrow temperature range. ... of the IEEE,60(6), 382 Page 6. 692 (1972). (2) McRee, D. I. and Pendergrass, F. T., "Interaction of ...
MTT-S International Microwave Symposium Digest
A miniaturized microwave probe has been developed using the microwave-caused heating of a thin co... more A miniaturized microwave probe has been developed using the microwave-caused heating of a thin coating of a resistive material and the resulting change in the color of a miniscule amount of liquid crystal in intimate contact. The probe can be inserted in animals for microwave biological effects research and is isotropic in its sensitivity to different polarizations of the fields.
Bulletin of the New York Academy of Medicine, 1979
Journal of cyclic nucleotide research, 1977
Techniques of in-vivo microwave irradiation to inactivate brain enzymes in rats were varied as to... more Techniques of in-vivo microwave irradiation to inactivate brain enzymes in rats were varied as to exposure configuration and output power. The rate at which metabolism was stopped was studied in various regions of the rat brain, using changes in levels of cyclic AMP and phosphodiesterase activity. Exposure times required to obtain stabilized levels of cyclic AMP varied in different brain regions, i.e., hypothalamus, cortex and cerebellum. Levels of cyclic AMP in selective regions of the brain decreased as more rapid inactivation was achieved. The authors identify important sources of variability of present microwave inactivation systems and the need for improved control of signficant microwave parameters.
Review of Scientific Instruments, 1982
A laser synchronization circuit, applicable to (optical) sum or difference frequency generation s... more A laser synchronization circuit, applicable to (optical) sum or difference frequency generation systems, is described. The laser synchronizer has yielded excellent results in preventing damage to the mixing crystal of an infrared-to-visible parametric upconverter.
International Journal of Electronics, 1965
ABSTRACT