scholarly journals The Impact of Cross-Linking Effect on the Space Charge Characteristics of Cross-Linked Polyethylene with Different Degrees of Cross-Linking under Strong Direct Current Electric Field

Polymers ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1149 ◽  
Author(s):  
Shuchao Wang ◽  
Quan Zhou ◽  
Ruijin Liao ◽  
Lai Xing ◽  
Nengcheng Wu ◽  
...  
Keyword(s):  
Field Strength ◽  
Electric Field ◽  
Space Charge ◽  
Direct Current ◽  
Cross Linking ◽  
Average Charge ◽  
Electrical Field ◽  
Electrical Field Strength ◽  
The Cross ◽  
The Impact

Cross-linked polyethylene (XLPE) obtained by the crossing-linking reaction of polyethylene (PE) can greatly enhance the mechanical properties and other properties of PE, which makes XLPE widely applied in the field of electric power engineering. However, the space charges can distort the distribution of the electrical field strength in the XLPE applied in the insulation materials, which can shorten the service life of the insulation materials. Therefore, the space charge characteristics of XLPE under the strong direct current (DC) electric field have been the focus of scholars and engineers all over the world. This article has studied the impact of the cross-linking effect on the space charge characteristics of XLPE with different degrees of cross-linking. For this issue, we used dicumyl peroxide (DCP) as the cross-linking agent and low-density polyethylene (LDPE) as the base material for the preparation of samples. Besides, the space charge distribution was measured by the pulsed electro-acoustic method (PEA). In addition, the average charge density as a characteristic parameter was introduced into the experiment, which was used to quantitatively analyze the impact of the cross-linking effect on the space charge characteristics of XLPE with different degrees of cross-linking. Meanwhile, we also explained the impact of the cross-linking effect on XLPE with different degrees of cross-linking from a microscopic point of view. Ultimately, some important conclusions can be obtained. For instance, the cross-linking effect significantly increases the threshold electrical field strength of XLPE, and as the content of cross-linking agent increases, the threshold electrical field strength increases at first and then decreases, and the threshold electrical field strength reaches the maximum value when the content of the cross-linking agent is 1.0% or 2.1%. Besides, the cross-linking effect introduces negative charge traps into the LDPE and increases the densities of the deeper charge traps, and so on. In addition, we have also analyzed the average charge density, and we have summarized the theoretical model of the average charge decay, namely, Q ( t ) = Q 0 + α e − t β , which is very effective for explaining the dissipation characteristics (more conclusive contents can be seen in the conclusion section of this article).

Estimation of the Local Electric field inside an Isotropic Mixture.

1994 ◽  
Vol 347 ◽  
Author(s):  
Georges Roussy ◽  
Jean-Marie Thiebaut ◽  
Med Madi
Keyword(s):  
Field Strength ◽  
Electric Field ◽  
Ceramic Material ◽  
Microwave Sintering ◽  
Effective Permittivity ◽  
Heterogeneous Mixture ◽  
Electrical Field ◽  
Two Phase ◽  
Electrical Field Strength ◽  
Phase Mixture

ABSTRACTAs a consequence of the BERGMAN - MILTON theory, which expresses the effective permittivity of a two phase mixture with an integral of a density function, it has been possible to evaluate the local electrical field strength inside a heterogeneous mixture. The developed formula can be used advantageously for modeling the local temperature inside a ceramic material during its microwave sintering.

Untersuchung der Plasmagrenzschidht in einer Niederdruckentladung

1962 ◽  
Vol 17 (11) ◽  
pp. 962-967 ◽  
Author(s):  
Werner Ott
Keyword(s):  
Field Strength ◽  
Charge Density ◽  
Space Charge ◽  
Debye Length ◽  
Linear Increase ◽  
Space Charge Density ◽  
Zero Field ◽  
Linear Extrapolation ◽  
Electrical Field ◽  
Electrical Field Strength

The electrical field in the space charge sheath between a Hg low-pressure plasma and an insulated plane wall was measured with an electron beam probe. Near the wall, the field strength was observed to increase linearly. Linear extrapolation to zero field strength is used here to define the thickness of the sheath which turned out to be 3 to 5 times the DEBYE length. On the other hand, the potential, the electrical field strength, and the space charge density in the sheath were, now, calculated (using BOHM'S criterion). Also theoretically, a (approximately) linear increase of field strength is found. A linear extrapolation of the theoretical values gives a boundary layer thickness about 6.7 to 6.9 times the DEBYE length, if the wall is at floating potential. Some differences are found between the experimental and the theoretical values of the wall potential and the space charge density in the sheath.

scholarly journals Multi-Region Brain Stimulation Optimization Using Transcranial Direct Current Stimulation

2019 ◽  
Author(s):  
Ziliang Xu ◽  
Jinbo Sun ◽  
Yao Chen ◽  
Yang Yu ◽  
Xuejuan Yang ◽  
...  
Keyword(s):  
Field Strength ◽  
Direct Current ◽  
Brain Stimulation ◽  
Transcranial Direct Current Stimulation ◽  
Brain Region ◽  
Optimization Scheme ◽  
Electrical Field ◽  
Electrical Field Strength ◽  
Single Target ◽  
Optimization Schemes

AbstractTranscranial direct current stimulation (tDCS) is a type of noninvasive transcranial electrical brain stimulation. By optimizing the current distribution of each electrode on the scalp, the stimulation can be guided to a target brain region using a tDCS dense electrode array system. However, previous studies have yielded simple results using optimization schemes in single target stimulation cases. The detailed parameter settings for each optimization scheme and the associated simulation results have not been comprehensively assessed. In this study, we investigated parameter settings of optimization schemes in detail in both single target and multi-target cases. Two optimization schemes, minimum least squares (MLS) and maximum electrical field strength (ME), were examined in this study. MLS minimizes the squared errors between the expected electrical field and the estimated electrical field, whereas ME maximizes the electrical field strength in the target region. We constructed a five layer finite-element head model with 64 electrodes placed on the scalp according to the EEG 10/10 system for simulation. We evaluated the effects of stimulation using these two schemes under three conditions, 1) single target stimulation, 2) multi-target stimulation, and 3) multi-target stimulation under specific task activation, which shown that directly using MLS and ME scheme in multi-target stimulation case may lead to a wrong result. We also reported the improved results fixed by our proposed weighted MLS and weighted ME schemes which take detailed parameter settings into consideration. Our results indicate that the parameter settings in each optimization scheme greatly affected the final stimulation results, especially in the case of multi-target stimulation, and thus, indicate that the parameter settings of each optimization scheme should be carefully considered according to the expected stimulation mode. Our results also suggest that, by calculating the parameters through our proposed methods, the weighted ME and weighted MLS scheme can precisely distribute energy into each target brain region.

scholarly journals Investigation of the functional network modifier loading on the stoichiometric ratio of epoxy resins and their dielectric properties

2021 ◽  
Author(s):  
Istebreq A. Saeedi ◽  
Sunny Chaudhary ◽  
Thomas Andritsch ◽  
Alun S. Vaughan
Keyword(s):  
Glass Transition ◽  
Dielectric Properties ◽  
Electrical Properties ◽  
Epoxy Resins ◽  
Functional Network ◽  
Cross Linking ◽  
Network Modifier ◽  
Epoxy Resin System ◽  
The Cross ◽  
The Impact

AbstractReactive molecular additives have often been employed to tailor the mechanical properties of epoxy resins. In addition, several studies have reported improved electrical properties in such systems, where the network architecture and included function groups have been modified through the use of so-called functional network modifier (FNM) molecules. The study reported here set out to investigate the effect of a glycidyl polyhedral oligomeric silsesquioxane (GPOSS) FNM on the cross-linking reactions, glass transition, breakdown strength and dielectric properties of an amine-cured epoxy resin system. Since many previous studies have considered POSS to act as an inorganic filler, a key aim was to consider the impact of GPOSS addition on the stoichiometry of curing. Fourier transform infrared spectroscopy revealed significant changes in the cross-linking reactions that occur if appropriate stoichiometric compensation is not made for the additional epoxide groups present on the GPOSS. These changes, in concert with the direct effect of the GPOSS itself, influence the glass transition temperature, dielectric breakdown behaviour and dielectric response of the system. Specifically, the work shows that the inclusion of GPOSS can result in beneficial changes in electrical properties, but that these gains are easily lost if consequential changes in the matrix polymer are not appropriately counteracted. Nevertheless, if the system is appropriately optimized, materials with pronounced improvements in technologically important characteristics can be designed.

Electrohydrodynamic Printing via Spinneret with Conductive Probe

2013 ◽  
Vol 562-565 ◽  
pp. 1155-1160
Author(s):  
Yi Hong Lin ◽  
Guang Qi He ◽  
Hai Yan Liu ◽  
Jin Wei ◽  
Jian Yi Zheng ◽  
...  
Keyword(s):  
Field Strength ◽  
Applied Voltage ◽  
Industrial Application ◽  
Control Level ◽  
Direct Write ◽  
Electrical Field ◽  
Nano Structure ◽  
Electrical Field Strength ◽  
Electrohydrodynamic Printing ◽  
The Stability

Stability jet ejection and precision deposition are the two keys for industrial application of electrohydrodynamic printing. In this paper, inserted conductive probe is utilized to gain stability jet, which would increase the electrical field strength, reduce the back flow, onset and sustaining voltage. Lower applied voltage would enhance the stability of electrospun jet, in which fine jet can be used to direct-write orderly Micro/Nano-structure. With the guidance and constrain of inserted probe, the oscillating angle range of electrohydrodynamic jet is decreased to 3°from 15°, and the width of printed structures is 21μm in average that is much narrower than that printed from spinneret without probe (74μm in average). Spinneret with tip provides a good way to improve the control level of electrohydrodynamic printing, which would accelerate the industrial application of electrohydrodynamic printed Micro/Nano structure.

Fully Developed Flow of Power-Law Fluid Through a Cylindrical Microfluidic Pipe: Pressure Drop and Electroviscous Effects

2008 ◽  
Author(s):  
Ram P. Bharti ◽  
Dalton J. E. Harvie ◽  
Malcolm R. Davidson
Keyword(s):  
Pressure Drop ◽  
Field Strength ◽  
Charge Density ◽  
Power Law ◽  
Maximum Velocity ◽  
Shear Thickening ◽  
Shear Thinning ◽  
Electrical Field ◽  
Electrical Field Strength ◽  
Fluid Behaviour

Pressure drop and electroviscous effects in the axisymmetric, steady, fully developed, pressure-driven flow of incompressible power-law fluids through a cylindrical microchannel at low Reynolds number (Re = 0.01) have been investigated. The Poisson-Boltzmann equation (describing the electrical potential) and the momentum equations in conjunction with electrical force and power-law fluid rheology have been solved numerically using the finite difference method. The pipe wall is considered to have uniform surface charge density (S = 4) and the liquid is assumed to be a symmetric electrolyte solution. In particular, the influence of the dimensionless inverse Debye length (K = 2, 20) and power-law flow behaviour index (n = 0.2, 1, 1.8) on the EDL potential, ion concentrations and charge density profiles, induced electrical field strength, velocity and viscosity profiles and pressure drop have been studied. As expected, the local EDL potential, local charge density and electrical field strength increases with decreasing K and/or increasing S. The velocity profiles cross-over away from the charged pipe wall with increasing K and/or decreasing n. The maximum velocity at the center of the pipe increases with increasing n and/or increasing S and/or decreasing K. The shear-thinning fluid viscosity is strongly dependent on K and S, whereas the shear-thickening viscosity is very weakly dependent on K and S. For fixed K, as the fluid behaviour changes from Newtonian (n = 1) to shear-thinning (n < 1), the induced electrical field strength increases and maximum velocity reduces. On the other hand, the change in fluid behaviour from Newtonian (n = 1) to shear-thickening (n > 1) decreases the electrical field strength and increases the maximum velocity. The non-Newtonian effects on maximum velocity and pressure drop are stronger in shear-thinning fluids at small K and large S, the shear-thickening fluids show opposite influence. Electroviscous effects enhance with decreasing K and/or increasing S. The electroviscous effects show complex dependence on the non-Newtonian tendency of the fluids. The shear-thickening (n > 1) fluids and/or smaller K show stronger influence on the pressure drop and thus, enhance the electroviscous effects than that in shear-thinning (n < 1) fluids and/or large K where EDL is very thin.

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