scholarly journals SIMULATION ON THE CONDITIONS AFFECTING PARTIAL DISCHARGE INITIATION IN MICROBUBBLE IMMERSED IN DIELECTRIC LIQUID

2018 ◽  
Vol 80 (6) ◽  
Author(s):  
Azharudin Mukhtaruddin ◽  
Muzamir Isa ◽  
Mazlee Mohd Noor ◽  
Mohd Rafi Adzman ◽  
Baharuddin Ismail ◽  
...  
Keyword(s):  
Computer Simulation ◽  
Electric Field ◽  
Partial Discharge ◽  
Prolate Spheroid ◽  
Liquid Dielectric ◽  
Dielectric Liquid ◽  
The Other ◽  
B Values ◽  
Other Hand ◽  
Different Gases

Microbubble floating in liquid dielectric and subjected to an electric field may initiate partial discharge (PD). This paper studies the parameters that affect the initiation through a computer simulation. This study inspects how the type of gas inside the microbubble, the size of the microbubble, distance from an electric field, Eo, source and, the magnitude of source’s voltage affect the start of PD. For a prolate spheroid shape, there is an important parameter called ‘c’. This ratio is between the radius of the microbubble polar (‘a’) and the radius of the equator (‘b’). At constant Eo and c, different gases will initiate PD at different distances from source due to differences in a localised electric field inside the microbubble (Emax). Emax is one of the important factors for PD initiation. It is interesting to report that if the ‘a’ and ‘b’ values are chosen so that ‘c’ will be constant, changes in Emax are insignificant. On the other hand, changes in ‘c’ will result in significant changes in Emax. Finally, changes in source’s voltage certainly affect the Emax.

scholarly journals Luminous vapour from the mercury arc and the progressive changes in its spectrum

1925 ◽  
Vol 108 (746) ◽  
pp. 262-279 ◽  
Keyword(s):  
Glow Discharge ◽  
Electric Field ◽  
Arc Discharge ◽  
The Other ◽  
Line Spectrum ◽  
Mercury Vapour ◽  
Band Spectrum ◽  
Other Hand ◽  
Continuous Band

It was observed originally by Stark that a stream of mercury vapour allowed to distil away from the arc or glow discharge in vacuo remains luminous. It may be said to carry the luminosity away with it, and in the case of the arc discharge there is no difficulty in detecting the luminosity for 50 cm. or so from the source. Stark found that when a glow discharge was used, which developed the continuous band spectrum, this spectrum could be detected in the distilled vapour, along with the line spectrum. When the glow was passed through an electric field, the line spectrum was found to be quenched, leaving the band spectrum unaffected. The arc discharge, on the other hand, gave only the line spectrum in his experiments.

scholarly journals Detection of partial discharge acoustic emission in power transformer

2019 ◽  
Vol 9 (6) ◽  
pp. 4573 ◽  
Author(s):  
Yomna Omran Shaker
Keyword(s):  
Acoustic Emission ◽  
Acoustic Wave ◽  
Arrival Time ◽  
Power Transformer ◽  
Partial Discharge ◽  
The Other ◽  
Health Index ◽  
High Attenuation ◽  
Other Hand ◽  
Emission Detection

<span>Partial discharge is one the most important factor that leads to deteroration and failure of the power transformer transformer. Acoustic emission detection is effective method to evaluate the health index of the power transformer.      Using acoustic emission (AE) sensors for partial discharge (PD) measurement is considered as one of the most promising techniques to detect and localize PD activities inside the transformer tank. On the other hand, AE waves suffer from high attenuation and reflections while traveling from the PD source to the AE sensor. The modeling of the AE wave can help to understand the behavior of the AE PD signal during its travel. In this paper, the AE PD signal is assumed to be composed of different frequencies. This work aims to investigate the influence of the frequency value on the attenuation and arrival time of the acoustic wave.</span>

Studying on Auxiliary Gradient Rings for the Collecting Area of Electrospinning

2011 ◽  
Vol 201-203 ◽  
pp. 726-729 ◽  
Author(s):  
Da Li Liu ◽  
Xiao Yu Zhao ◽  
Hai Guang Zhang ◽  
Yuan Yuan Liu ◽  
Qing Xi Hu
Keyword(s):  
Electric Field ◽  
Maximum Intensity ◽  
The Other ◽  
Experimental Result ◽  
Mechanism Analysis ◽  
Bone Scaffold ◽  
Other Hand ◽  
Key Factor ◽  
Electric Filed

When electrospinning has been used as a special technology of regenerative bone scaffold, for raising the efficiency of electrospinning and decreasing collecting area, the mechanism of bending instability was analyzed and concluded that the force of electric field is a key factor. Auxiliary gradient rings have been added to electric field, which changed the environment of electric filed. Then, it was verified that additive gradient rings could reduce the collecting area. On the other hand, Maxwell was used to analyze the strength and structure of electric field. The maximum intensity of electric field existed in the position of nozzle. The farther apart from nozzle, the rapidly intensity decreased. When auxiliary gradient rings had been added, the intensity of instability stage showed increased trend. Mechanism analysis and experimental result were confirmed by the simulation effectively.

Ground-Space Observations of Pc5 Poleward Moving Auroral Arc Pulsations and Field-Line Resonances in the Post-Midnight Sector: THEMIS Observations

2020 ◽  
Author(s):  
Natsuo Sato ◽  
Akira Sessai Yukimatu ◽  
Yoshimasa Tanaka ◽  
Tomoaki Tomoaki ◽  
Akira Kadokura
Keyword(s):  
Electric Field ◽  
Field Line ◽  
Solar Wind Speed ◽  
Time History ◽  
Oscillation Period ◽  
The Other ◽  
Lower Latitude ◽  
Other Hand ◽  
Magnetic Pulsations ◽  
Latitude Region

Abstract We investigate the Pc5 poleward moving auroral arc (PMAA) pulsations (~ 4–5 min period) using the ground-based all-sky imager network and the Time History of Events and Macroscale Interactions during Substorms (THEMIS) A, D, and E satellites, whose footprints were located near the PMAA in the post-midnight sector. The Pc5 PMAA pulsations considered herein occurred in conjunction with the enhancement of the magnetic and electric field oscillations observed near the equatorial plane of the magnetosphere. The magnetospheric oscillation signal displayed three-cycle oscillations, which correspond primarily to the PMAA pulsations. The value of coherence between the magnetospheric oscillations and the luminosity pulsations was higher than 0.9. Based on these observations, it is suggested that the PMAA pulsations and the magnetospheric field oscillations are initiated by the same physical mechanism and thus oscillate concurrently by the magnetosphere-ionosphere (M-I) coupling. The satellite data indicated a longer period of magnetospheric oscillations at the higher latitude site. On the other hand, the measured period of the PMAA pulsation was almost constant in the lower latitude region (~ 68.5°-70.0° MLAT), whereas in the higher latitude region (~ 70.0°-70.5° MLAT) it increased with increasing latitude. This signature demonstrates that the oscillations on the lower latitudinal side of the PMAA conformed with the monochromatic frequency field-line resonance (FLR) where the oscillation period was constant and independent of latitude, whereas the higher latitude side of the PMAA presented a multi-frequency FLR region where the period lengthened with increasing latitude. The Pc5 magnetic pulsations observed on the ground neither exhibited a clear coincidence with the PMAA pulsations nor with the magnetospheric magnetic oscillations. On the other hand, the H component of magnetic pulsations demonstrated a rather similar behavior to that of the ion pressure variation within the magnetosphere. The solar wind speed was significantly high, approximately 650 km/s, during this event. The magnetospheric magnetic and electric field oscillations could be triggered simultaneously in a wide region by an impulse such as rapid convection changes caused by the sudden variations of the interplanetary magnetic field (IMF) Bz, which was observed by the SuperDARN radar and the Geotail satellite.

A Class of E xact Solutions for the Vlasov-Turbulence

1969 ◽  
Vol 24 (5) ◽  
pp. 711-715
Author(s):  
Pitter Gräff
Keyword(s):  
Electric Field ◽  
Correlation Length ◽  
The Other ◽  
Homogeneous Turbulence ◽  
Statistical Character ◽  
Other Hand ◽  
Closure Conditions ◽  
Finite Correlation

Abstract The admissible closure conditions can be completely determined in the limit of vanishing cor­ relation length. In this case the Lundgren hierarchy can be solved, since this irregular state persists in the course of time. The electric field on the other hand loses its statistical character. - The results can be extended to examples of homogeneous turbulence with a finite correlation length.

An electrostatics paradox

2021 ◽  
Vol 57 (2) ◽  
pp. 023001
Author(s):  
Rod Cross
Keyword(s):  
Electric Field ◽  
Electric Charge ◽  
The Other ◽  
Apparent Contradiction ◽  
Other Hand ◽  
Third Law ◽  
A Charge ◽  
Outside The Box

Abstract An electric charge located outside a closed metal box does not produce an electric field inside the box. On the other hand, an electric charge located inside the box can generate an electric field outside the box. A charge inside the box can therefore exert a force on a charge outside the box, but not vice-versa, in apparent contradiction of Newton’s third law.

A study of cometary eruptions through OH radio-lines

1999 ◽  
Vol 173 ◽  
pp. 249-254
Author(s):  
A.M. Silva ◽  
R.D. Miró
Keyword(s):  
Short Duration ◽  
Growth Curves ◽  
The Other ◽  
Initial Mass ◽  
Radio Lines ◽  
Other Hand ◽  
Sudden Rise

AbstractWe have developed a model for theH2OandOHevolution in a comet outburst, assuming that together with the gas, a distribution of icy grains is ejected. With an initial mass of icy grains of 108kg released, theH2OandOHproductions are increased up to a factor two, and the growth curves change drastically in the first two days. The model is applied to eruptions detected in theOHradio monitorings and fits well with the slow variations in the flux. On the other hand, several events of short duration appear, consisting of a sudden rise ofOHflux, followed by a sudden decay on the second day. These apparent short bursts are frequently found as precursors of a more durable eruption. We suggest that both of them are part of a unique eruption, and that the sudden decay is due to collisions that de-excite theOHmaser, when it reaches the Cometopause region located at 1.35 × 105kmfrom the nucleus.

Closing the GAP—A 5Å Scanning Microscope

1969 ◽  
Vol 27 ◽  
pp. 6-7
Author(s):  
A. V. Crewe
Keyword(s):  
Normal Form ◽  
The Other ◽  
Resolving Power ◽  
Scanning Microscope ◽  
Conventional Microscope ◽  
Other Hand ◽  
Closing The Gap ◽  
Thermal Sources ◽  
Better Than ◽  
Transmission Microscope

We have become accustomed to differentiating between the scanning microscope and the conventional transmission microscope according to the resolving power which the two instruments offer. The conventional microscope is capable of a point resolution of a few angstroms and line resolutions of periodic objects of about 1Å. On the other hand, the scanning microscope, in its normal form, is not ordinarily capable of a point resolution better than 100Å. Upon examining reasons for the 100Å limitation, it becomes clear that this is based more on tradition than reason, and in particular, it is a condition imposed upon the microscope by adherence to thermal sources of electrons.

Life Beyond 1MeV

1980 ◽  
Vol 38 ◽  
pp. 30-33
Author(s):  
K.H. Westmacott
Keyword(s):  
Electron Microscopy ◽  
Past Experience ◽  
The Other ◽  
Good Case ◽  
Other Hand ◽  
The U.S

Life beyond 1MeV – like life after 40 – is not too different unless one takes advantage of past experience and is receptive to new opportunities. At first glance, the returns on performing electron microscopy at voltages greater than 1MeV diminish rather rapidly as the curves which describe the well-known advantages of HVEM often tend towards saturation. However, in a country with a significant HVEM capability, a good case can be made for investing in instruments with a range of maximum accelerating voltages. In this regard, the 1.5MeV KRATOS HVEM being installed in Berkeley will complement the other 650KeV, 1MeV, and 1.2MeV instruments currently operating in the U.S. One other consideration suggests that 1.5MeV is an optimum voltage machine – Its additional advantages may be purchased for not much more than a 1MeV instrument. On the other hand, the 3MeV HVEM's which seem to be operated at 2MeV maximum, are much more expensive.

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