scholarly journals Finite Element Based Comparative Analysis of Positive Streamers in Multi Dispersed Nanoparticle Based Transformer Oil

2021 ◽  
Vol 12 (1) ◽  
pp. 29-44
Author(s):  
Mihir Bhatt ◽  
Praghnesh Bhatt
Keyword(s):  
Electron Density ◽  
Dielectric Strength ◽  
Space Charge Density ◽  
Transformer Oil ◽  
Ionization Region ◽  
Streamer Propagation ◽  
Positive Streamers ◽  
Al2o3 Nps ◽  
The Impact ◽  
Positive Streamer

The dispersion of dissimilar nanoparticles (NPs) in transformer oil (TO) has a major impact on fast propagating positive streamers. This work investigates the positive streamer dynamics in TO modified by dispersing both Fe3O4 and Al2O3 NPs at a homogenous concentration. The hydrodynamic drift diffusion model of positive streamer evolution and propagation are solved using the commercial software package COMSOL Multiphysics. The impact of multiple NPs (MNPs) has been analysed for streamer propagation, electric field intensity, electron density, and space charge density of modified TO. MNPs successfully reduce streamer propagation velocity by 50%, 17%, and 37.5% comparing to pure oil, Fe3O4 based nanodielectric fluids (NDFs), and Al2O3 based NDFs, respectively. The spatial distribution of electron density reveals the loss of electrons from the ionization region until the saturation of NPs. A comparative study demonstrates that MNPs significantly alter the streamer dynamics and augment the dielectric strength of TO compared to individual NPs.

scholarly journals Streamer Propagation in a Long Gap in Model Liquids

2018 ◽  
Author(s):  
N.V. Dung ◽  
H.K. Høidalen ◽  
D. Linhjell ◽  
L.E. Lundgaard ◽  
M. Unge
Keyword(s):  
Ionization Potential ◽  
Transformer Oil ◽  
Experimental Conditions ◽  
Reduced Pressure ◽  
Long Gap ◽  
Electron Scavenger ◽  
Streamer Propagation ◽  
Positive Streamers

<p>A summary of streamer propagation in Exxsol-D140 and Marcol-52 under various experimental conditions is given. The results are compared to those of cyclohexane and mineral transformer oil. Streamer propagation is polarity and liquid dependent. The breakdown and acceleration voltages are also governed by liquid chemistry. Reduced pressure largely enhances streamer propagation of both polarities. A low ionization potential additive significantly affects positive streamers while an electron scavenger markedly impacts negative streamers. Adding a low ionization potential additive caused positive streamers to behave like those in mineral transformer oil while adding an electron scavenger had the same influence on negative streamers. Processes at the streamer heads are suggested to be responsible for streamer propagation.</p>

scholarly journals Effect of Fe3O4 nanoparticles on positive streamer propagation in transformer oil

AIP Advances ◽  
2016 ◽  
Vol 6 (3) ◽  
pp. 035110 ◽  
Author(s):  
Yuzhen Lv ◽  
Qi Wang ◽  
You Zhou ◽  
Chengrong Li ◽  
Yang Ge ◽  
...  
Keyword(s):  
Fe3o4 Nanoparticles ◽  
Transformer Oil ◽  
Streamer Propagation ◽  
Positive Streamer

Measurement of Dysprosium Stark Width and the Electron Impact Width Parameter

2018 ◽  
Vol 73 (2) ◽  
pp. 203-213 ◽  
Author(s):  
Jhonatha R. dos Santos ◽  
Jonas Jakutis Neto ◽  
N. Rodrigues ◽  
M.G. Destro ◽  
José W. Neri ◽  
...  
Keyword(s):  
Electron Density ◽  
Impact Parameter ◽  
Plasma Temperature ◽  
Spectral Lines ◽  
Emission Lines ◽  
Spectroscopic Methods ◽  
Species Concentration ◽  
The Impact ◽  
Stark Width

In this work, we suggest a methodology to determine the impact parameter for neutral dysprosium emission lines from the characterization of the plasma generated by laser ablation in a sealed chamber filled with argon. The procedure is a combination of known consistent spectroscopic methods for plasma temperature determination, electron density, and species concentration. With an electron density of 3.1 × 1018 cm–3 and temperature close to 104 K, we estimated the impact electron parameter for nine spectral lines of the neutral dysprosium atom. The gaps in the impact parameter data in the literature, mainly for heavy elements, stress the importance of the proposed method.

scholarly journals A comparison of Galactic electron density models using PyGEDM

2021 ◽  
Vol 38 ◽  
Author(s):  
D. C. Price ◽  
C. Flynn ◽  
A. Deller
Keyword(s):  
Electron Density ◽  
Large Scale ◽  
Galactic Halo ◽  
Application Programming Interface ◽  
Dispersion Measure ◽  
Radio Pulsars ◽  
Distribution Models ◽  
Distance Measurements ◽  
Application Programming ◽  
The Impact

Abstract Galactic electron density distribution models are crucial tools for estimating the impact of the ionised interstellar medium on the impulsive signals from radio pulsars and fast radio bursts. The two prevailing Galactic electron density models (GEDMs) are YMW16 (Yao et al. 2017, ApJ, 835, 29) and NE2001 (Cordes & Lazio 2002, arXiv e-prints, pp astro–ph/0207156). Here, we introduce a software package PyGEDM which provides a unified application programming interface for these models and the YT20 (Yamasaki & Totani 2020, ApJ, 888, 105) model of the Galactic halo. We use PyGEDM to compute all-sky maps of Galactic dispersion measure (DM) for YMW16 and NE2001 and compare the large-scale differences between the two. In general, YMW16 predicts higher DM values towards the Galactic anticentre. YMW16 predicts higher DMs at low Galactic latitudes, but NE2001 predicts higher DMs in most other directions. We identify lines of sight for which the models are most discrepant, using pulsars with independent distance measurements. YMW16 performs better on average than NE2001, but both models show significant outliers. We suggest that future campaigns to determine pulsar distances should focus on targets where the models show large discrepancies, so future models can use those measurements to better estimate distances along those line of sight. We also suggest that the Galactic halo should be considered as a component in future GEDMs, to avoid overestimating the Galactic DM contribution for extragalactic sources such as FRBs.

scholarly journals Factors Impacting σ- and π-Hole Regions as Revealed by the Electrostatic Potential and Its Source Function Reconstruction: The Case of 4,4′-Bipyridine Derivatives

Molecules ◽  
2020 ◽  
Vol 25 (19) ◽  
pp. 4409
Author(s):  
Carlo Gatti ◽  
Alessandro Dessì ◽  
Roberto Dallocchio ◽  
Victor Mamane ◽  
Sergio Cossu ◽  
...  
Keyword(s):  
Electron Density ◽  
Electrostatic Potential ◽  
Source Function ◽  
Noncovalent Interactions ◽  
Conformational Search ◽  
Atomic Group ◽  
Group Contributions ◽  
Conformational Freedom ◽  
Molecular Patterns ◽  
The Impact

Positive electrostatic potential (V) values are often associated with σ- and π-holes, regions of lower electron density which can interact with electron-rich sites to form noncovalent interactions. Factors impacting σ- and π-holes may thus be monitored in terms of the shape and values of the resulting V. Further precious insights into such factors are obtained through a rigorous decomposition of the V values in atomic or atomic group contributions, a task here achieved by extending the Bader–Gatti source function (SF) for the electron density to V. In this article, this general methodology is applied to a series of 4,4′-bipyridine derivatives containing atoms from Groups VI (S, Se) and VII (Cl, Br), and the pentafluorophenyl group acting as a π-hole. As these molecules are characterized by a certain degree of conformational freedom due to the possibility of rotation around the two C–Ch bonds, from two to four conformational motifs could be identified for each structure through conformational search. On this basis, the impact of chemical and conformational features on σ- and π-hole regions could be systematically evaluated by computing the V values on electron density isosurfaces (VS) and by comparing and dissecting in atomic/atomic group contributions the VS maxima (VS,max) values calculated for different molecular patterns. The results of this study confirm that both chemical and conformational features may seriously impact σ- and π-hole regions and provide a clear analysis and a rationale of why and how this influence is realized. Hence, the proposed methodology might offer precious clues for designing changes in the σ- and π-hole regions, aimed at affecting their potential involvement in noncovalent interactions in a desired way.

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