The Corona breakdown of aerials in air at low pressures

1963 ◽  
Vol 271 (1347) ◽  
pp. 551-564 ◽  
Keyword(s):  
Field Strength ◽  
Electric Field ◽  
Radio Frequency ◽  
Critical Field ◽  
Diffusion Theory ◽  
Reduced Pressure ◽  
Radiated Power ◽  
Diffusion Controlled ◽  
Experimental Values ◽  
Low Pressures

Radio-frequency corona breakdown of the air surrounding a transmitting aerial operating under conditions of reduced pressure occurs for a comparatively low radiated power. In this paper the theory of diffusion-controlled breakdown is discussed and used to deduce the critical field strength for breakdown at the tip of a prolate spheroidal unipole aerial. Two independent methods are used to determine the electric field strength at the tip of the unipole. In one of these the voltage on the coaxial transmission line feeding the unipole is measured at a distance of three-quarters of a wavelength from the base of the unipole. In this way the current entering the base of the unipole can be found, and hence the electric field at the tip can be calculated. The other method makes use of a small microphone actuated by the attractive force of the electric field. When this method is used, the radio-frequency oscillator is square-wave modulated. The two methods give satisfactory agreement. In the breakdown experiments two unipoles of different base diameter were used. For each of these experimental values of the critical field strengths for onset of corona are compared with the values deduced from the diffusion theory of breakdown.

scholarly journals The influence of pressure on the boiling points of metals

1910 ◽  
Vol 83 (565) ◽  
pp. 483-491 ◽  
Keyword(s):  
Atmospheric Pressure ◽  
Boiling Point ◽  
High Vacuum ◽  
Similar Type ◽  
Exact Relation ◽  
Reduced Pressure ◽  
Boiling Points ◽  
Experimental Values ◽  
Low Pressures ◽  
Very High

Part I. — Pressures below 760 mm . In a previous communication (‘Proc.’, A, vol. 82, 1909, p. 396) the approximate boiling points of a number of metals were determined at atmospheric pressure. Apart from the question of finding the exact relation between the boiling point and pressure, it is an important criterion of any method for fixing the temperatures of ebullition to demonstrate that the experimental values obtained are dependent on the pressure. It is specially desirable when dealing with substances boiling at temperatures above 2000° to have some evidence that the points indicated are true boiling points. Previous work on the vaporisation of metals at different pressures has been confined to experiments in a very high vacuum except for metals like bismuth, cadmium, and zinc, which boil at relatively low temperatures under atmospheric pressure. The observations were limited to very low pressures on account of the difficulty of obtaining any material capable of withstanding a vacuum at temperatures over 1400° and the consequent necessity for keeping the boiling point below this limit by using very low pressures. Moreover in the case of the majority of the metals, e. g. , copper, tin, ebullition under reduced pressure has never been observed. The difficulties indicated above were avoided by using a similar type of apparatus to that previously described, and arranging the whole furnace inside a vacuum enclosure, thus permitting of the use of graphite crucibles to contain the metal.

Experimental Study on the Movement of Conducting Spheroidal Particles under Electric Field in Air

2015 ◽  
Vol 781 ◽  
pp. 351-354
Author(s):  
Tatchawin Sangsri ◽  
Viet Quoc Huynh ◽  
Boonchai Techaumnat
Keyword(s):  
Electric Field ◽  
Critical Field ◽  
Contact Point ◽  
Uniform Electric Field ◽  
Prolate Spheroidal ◽  
Voltage Polarity ◽  
Insulation Systems ◽  
Conducting Particle ◽  
Experimental Values ◽  
Measured Particle

Study on the movement of conducting particle is useful for managing particles in gas insulation systems. The authors observed the movement of conducting prolate spheroidal particles under uniform electric field in air. From the experimental results we found three patterns of the movement. The critical electric field results in particle rotating or lifting. The particles rotated about the contact point before lifting in most cases. The measured particle-rotating field was lower than the analytical ones by 6 and 21% for 9 and 18 mm gaps, respectively. From the experiment, the size of the particles and the gap distance affect the critical field. The voltage polarity has no effect on the critical field for particle movement because of little difference between the experimental values of positive and negative polarities.

scholarly journals Electron Swarm Parameters and Dielectric Properties of the Superconducting Binary Mixtures of He-H2

2021 ◽  
Vol 36 (1) ◽  
pp. 420-432
Author(s):  
Mohammad M. Othman ◽  
Sherzad A. Taha ◽  
Saeed O. Ibrahim
Keyword(s):  
Distribution Function ◽  
Boltzmann Equation ◽  
Field Strength ◽  
Electric Field ◽  
Dielectric Strength ◽  
Ionization Coefficient ◽  
Experimental Values ◽  
Attachment Coefficient ◽  
Term Approximation ◽  
Effective Ionization

In this study, the electron energy distribution function EEDF, the electron swarm parameters, the effective ionization coefficients, and the critical field strength (dielectric strength) in binary He-H2 gas mixture which used as cryogenic for high-temperature superconducting power application, are evaluated by using two-term approximation of the Boltzmann equation over the range of E/N ( the electric field to gas density) from 1 to 100 Td ( 1 Td=10-17 Vcm2) at temperature 77 K and pressure 2MPa, taking into account elastic and inelastic cross-section. Using the calculated EEDF, the electron swarm parameters (electron drift velocity, mean electron energy, diffusion coefficient, electron mobility, ionization and attachment coefficient) are calculated. At low reduced electric field E/N, the EEDF close Maxwellian distribution, at high E/N, due to vibrational excitation of H2 the calculated distribution function is non-Maxwellian. Besides, in the He-H2 mixture, it is found that increasing small amount of H2 enhances to shift the tail of EEDF to the lower energy region, the reduced ionization coefficient α/N. reduced effective ionization coefficient (α-η)/N) decreases, while, reduced attachment coefficient η/N, reduced critical electric field strength (E/N)crt. and critical electric field Ecrt. Increases, because of hydrogen’s large ionization cross-sections. The dielectric strength of 5% H2 in mixture is in good agreement with experimental values, it is found that dielectric strength depend on pressure and temperature. The electron swarm parameters in pure gaseous helium (He) and hydrogen (H2), in satisfying agreement with previous available theoretical and experimental values. The validity of the calculated values has been confirmed by two-term approximation of the Boltzmann equation analysis.

Inactivation of Saccharomyces cerevisiae with Radio Frequency Electric Fields†

2003 ◽  
Vol 66 (9) ◽  
pp. 1712-1715 ◽  
Author(s):  
DAVID J. GEVEKE ◽  
CHRISTOPHER BRUNKHORST
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Field Strength ◽  
Electric Field ◽  
Radio Frequency ◽  
Electric Fields ◽  
Flow Rate ◽  
Low Temperatures ◽  
Thermal Inactivation ◽  
Rf System ◽  
Radio Frequency Electric Fields

The application of radio frequency (RF) electric fields as a nonthermal alternative to thermal inactivation of microorganisms in liquids was investigated. A novel RF system producing frequencies in the range of 20 to 60 kHz was developed. Electric field strengths of 20 and 30 kV/cm were applied to suspensions of Saccharomyces cerevisiae in water over a temperature range of 35 to 55°C. The flow rate was 1.2 liters/min. The S. cerevisiae population was reduced by 2.1 ± 0.1 log units following exposure to a 30-kV/cm field at 40°C. The results of the present study provide the first evidence that strong RF electric fields inactivate microorganisms at moderately low temperatures. Increasing the field strength, the number of treatments, and the temperature enhanced inactivation. Frequency had no effect on inactivation over the range of frequencies studied.

Height and Angle Characteristics of Point Source Transmitting Power of Wireless Avionics Intra-Communication Systems Based on FDTD Analysis

2021 ◽  
Vol 35 (11) ◽  
pp. 1274-1275
Author(s):  
Shunichi Futatsumori ◽  
Kazuyuki Morioka ◽  
Takashi Hikage ◽  
Tetsuya Sekiguchi ◽  
Manabu Yamamoto ◽  
...  
Keyword(s):  
Electromagnetic Field ◽  
Field Strength ◽  
Electric Field ◽  
Point Source ◽  
Communication Systems ◽  
Large Scale ◽  
Three Dimensional ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Radiated Power

The equivalent isotopically radiated power (EIRP) of a wireless avionics intra-communication (WAIC) system is limited to 6 dBm/MHz at the geometrical center of the aircraft, to avoid interference with aircraft radio altimeters, which are operated at the same frequency band between 4,200–4,400 MHz. In this paper, the height and angle characteristics of the point source EIRP of a WAIC system are analyzed based on the large scale FDTD analysis. Firstly, the strength of the electric field (E-field) around the three-dimensional model of Airbus A320-200 is analyzed. Then, the point source EIRP is calculated based on the analyzed E-field strength. Finally, the height and angle characteristics are analyzed to estimate the electromagnetic field characteristics of the aircraft.

Optical Measurement of the Electric Field Strength in a Gel Insulator

2016 ◽  
Vol 136 (10) ◽  
pp. 1420-1421
Author(s):  
Yusuke Tanaka ◽  
Yuji Nagaoka ◽  
Hyeon-Gu Jeon ◽  
Masaharu Fujii ◽  
Haruo Ihori
Keyword(s):  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Optical Measurement

Effect of external magnetic field on lane formation in driven pair-ion plasmas

2021 ◽  
Vol 87 (2) ◽  
Author(s):  
Swati Baruah ◽  
U. Sarma ◽  
R. Ganesh
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Coupling Parameter ◽  
Critical Parameters ◽  
Coulomb Coupling ◽  
Lane Formation ◽  
Parameter Values

Lane formation dynamics in externally driven pair-ion plasma (PIP) particles is studied in the presence of external magnetic field using Langevin dynamics (LD) simulation. The phase diagram obtained distinguishing the no-lane and lane states is systematically determined from a study of various Coulomb coupling parameter values. A peculiar lane formation-disintegration parameter space is identified; lane formation area extended to a wide range of Coulomb coupling parameter values is observed before disappearing to a mixed phase. The different phases are identified by calculating the order parameter. This and the critical parameters are calculated directly from LD simulation. The critical electric field strength value above which the lanes are formed distinctly is obtained, and it is observed that in the presence of the external magnetic field, the PIP system requires a higher value of the electric field strength to enter into the lane formation state than that in the absence of the magnetic field. We further find out the critical value of electric field frequency beyond which the system exhibits a transition back to the disordered state and this critical frequency is found as an increasing function of the electric field strength in the presence of an external magnetic field. The movement of the lanes is also observed in a direction perpendicular to that of the applied electric and magnetic field directions, which reveals the existence of the electric field drift in the system under study. We also use an oblique force field as the external driving force, both in the presence and absence of the external magnetic field. The application of this oblique force changes the orientation of the lane structures for different applied oblique angle values.

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