Field limit for ion evaporation from charged thermospray droplets

Electro-coalescence of two charged droplets under pulsed direct current electric fields with various waveforms: A molecular dynamics study

We examine a time-dependent, three-dimensional rotation of magnetic ellipsoidal particles in a two-dimensional, simple shear flow and a uniform magnetic field. We consider that the particles have paramagnetic and ferromagnetic properties, and we compare their rotational dynamics due to the strengths and directions of the applied uniform magnetic field. We determine the critical magnetic field strength that can pin the particles’ rotations. Above the critical field strength, the particles’ stable steady angles were determined. In a weak magnetic regime (below the critical field strength), a paramagnetic particle’s polar angle will oscillate toward the magnetic field plane while its azimuthal angle will execute periodic rotations. A ferromagnetic particle’s rotation depends on its initial angles and the magnetic field strength and direction. Even when it is exposed to a critical magnetic field strength, its rotational dynamics will either be pinned in or out of the magnetic field plane. In a weak magnetic regime, a ferromagnetic particle will either execute out-of-plane rotations or will oscillate toward the magnetic field plane and perform periodic rotations. For both particles, we analytically determine the peaks and troughs of their oscillations and study their time-dependent rotations through analytical and numerical analyses.

The phenomenon of partial discharge of soil that occurs when a lightning current enters the ground through a ground electrode poses a threat to the safety of personnel and equipment. The strength of partial discharge and the formation of soil discharge channels are closely related to the magnitude of the critical breakdown field strength. Therefore, how to accurately obtain the variation law of the critical breakdown field strength of typical soil is the key to realize the safe operation of the grounding device and the cable in the ground and ensure the safety of personnel and equipment. In this paper, a simulation experiment of soil impact characteristics is used to study the variation law of typical soil critical breakdown field strength with soil properties. X-ray transmission imaging technology is used to obtain the morphology of the discharge channel, and its non-intrusive observation method will not disturb the discharge channel itself, making the measurement more accurate. This paper first selects a variety of typical soils to study the influence of soil moisture, salt content, compactness and other factors on the discharge channel morphology, and then studies the calculation method of the critical breakdown field strength of the soil under different discharge channel morphologies. And further explore the reasons for the influence of typical soil media factors on the critical breakdown field strength. The experimental results show that under the same conditions, the relationship between the critical breakdown field strength values of different soils is: Ec of sandy soil <; Ec of loam soil <; Ec of pastoral soil; It is precisely because of the different reasons that different factors of the soil medium affect the critical breakdown field strength, the content of water and air inside the soil and the conductivity of the soil are different, so that the variation law of the critical breakdown field strength is different.

One of the most effective precipitation methods for submicrometer particles is the charged droplet scrubber. The dust collection in the charged droplet scrubber is considered to consist of some processes with respect to the interaction between charged dust particles and a charged water droplet. That is, the charged dust particles are attracted to, collide with, adhere to, penetrate into, rebound from, accumulate on, and reentrain from a charged water droplet. The direct observation of the collection process for dust particles by a charged water droplet was conducted by using the experimental setup designed by the authors. It was found from the experiments that particles with good wettability were captured inside the water droplet, particles with poor wettability floated at regular intervals on the droplet surface, and particles with medium wettability were trapped on or inside the water droplet. When particles were trapped on the droplet surface the growth of dendritic depositions was found, and their behavior was very distinct from those obtained on the fibrous filter due to the fluidity of the droplet surface. The deposition mechanisms of charged particles on the charged water droplet are discussed qualitatively.

The galvanotaxis response of neural crest cells that had migrated out of the neural tube of a 56-hr-old quail embryo onto glass coverslips was observed using time-lapse video microscopy. These cells exhibit a track velocity of about 7 microns/min and actively translocate toward the negative pole of an imposed DC electric field. This nonrandom migration could be detected for fields as low as 7 mV/mm (0.4 mV/cell length). We find that this directional migration is independent of the speed of migration and have generated a rather simple mathematical equation that fits these data. We find that the number of cells that translocate at a given angle, phi, with respect to the field is given by the equation N(phi) = exp(a0 + a1cos phi), where a1 is linearly proportional to the electric field strength for fields less than 390 mV/mm with a constant of proportionality equal to KG, the galvanotaxis constant. We show that KG = (150 mV/mm)-1, and at this field strength the cellular response is approximately half maximal. This approach to cellular translocation data analysis is generalizable to other directed movements such as chemotaxis and allows the direct comparison of different types of directed movements This analysis requires that the response of every cell, rather than averages of cellular responses, is reported. Once an equation for N(phi) is derived, several characteristics of the cellular response can be determined. Specifically, we describe 1) the critical field strength (390 mV/mm) below which the cellular response exhibits a simple, linear dependence on field strength (for larger field strengths, an inhibitory constant can be used to fit the data, suggesting that larger field strengths influence a second cellular target that inhibits the first); and 2) the amount of information the cell must obtain in order to generate the observed asymmetry in the translocation distribution (for a field strength of 100 mV/mm, 0.3 bits of information is required).

The external field induced paranematic–nematic phase separation of hard spherocylinder systems is studied using the Onsager and Parsons free-energy functionals. A bifurcation analysis is carried out in the context of the Onsager theory at an infinitesimal external field. The bifurcation concentration is found to decrease with increasing field strength. Below the critical field strength, van der Waals-like loops are found. The molecular aspect ratio dependence of the phase coexistence curves of hard spherocylinders also is investigated. The critical field strength is found to decrease with decreasing aspect ratio. The external field dependence of the order parameter along the paranematic–nematic phase equilibrium curve is also studied.

Dielectrical and electro-mechanical behavior of NBR at high electric field strength

Active control of viscous fingering (VF) is of critical importance for many industrial and experimental systems. Here, we numerically study the electrokinetic control of miscible VF using an externally applied electric field. Simulations for three intrinsically hydrodynamically unstable mobility ratios are carried out using two different configurations for each: case I where the high-viscosity resident fluid has higher electroosmotic mobility than the invading low-viscosity fluid and case II where the resident fluid has a lower electroosmotic mobility than the invading fluid. For both cases, the theoretical critical electric field value required to (de)-stabilize the interface is computed and electric fields around this value are applied in simulations. Qualitative results show that VF can be fully suppressed if an electric field is applied with an absolute value above the critical field strength. For case I, this means an electric field in the direction of the pressure-driven flow, while for case II, a field in opposite direction is required. Our quantitative analysis using interfacial and mixing lengths was used to support the qualitative findings. Even though any field strength applied in the right direction will reduce the instability, full suppression is only achieved if the absolute field strength is higher than the required critical field strength. The results from this work provide useful insights that can be applied to electrokinetically enhanced oil recovery, spreading of pollution zones in aquifers, band broadening in liquid chromatography, and electrokinetic soil remediation.

The transport of water molecules through nanopores is not only crucial to biological activities but also useful for designing novel nanofluidic devices. Despite considerable effort and progress that has been made, a controllable and unidirectional water flow is still difficult to achieve and the underlying mechanism is far from being understood. In this paper, using molecular dynamics simulations, we systematically investigate the effects of an external electric field on the transport of single-file water molecules through a carbon nanotube (CNT). We find that the orientation of water molecules inside the CNT can be well-tuned by the electric field and is strongly coupled to the water flux. This orientation-induced water flux is energetically due to the asymmetrical water-water interaction along the CNT axis. The wavelike water density profiles are disturbed under strong field strengths. The frequency of flipping for the water dipoles will decrease as the field strength is increased, and the flipping events vanish completely for the relatively large field strengths. Most importantly, a critical field strength E(c) related to the water flux is found. The water flux is increased as E is increased for E ≤ E(c), while it is almost unchanged for E > E(c). Thus, the electric field offers a level of governing for unidirectional water flow, which may have some biological applications and provides a route for designing efficient nanopumps.

The electric self‐heating and conduction behaviors of a high‐density polyethylene/carbon black composite at the electric–thermal equilibrium state are studied. An equation describing the current density/electric‐field strength (J–E) characteristic is derived on the basis of an equation proposed for the self‐heating temperature as a function of the field strength. The conduction is related to the electronic tunneling and the resistor breakdown due to self‐heating that dominate the nonlinear J–E characteristic below and above a critical field strength corresponding to the J maximum, respectively. The influences of the initial structure of the percolation network and the physical state of the matrix on the conduction are also discussed on the basis of scaling arguments of the self‐heating and the nonlinear J–E characteristic with respect to the initial resistivity at various ambient temperatures from 19 to 120 °C. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2484–2492, 2005

Flash sintering of zirconia: Effect of field strength on the incubation stage before densification

The SF6/N2 gas mixture is a key eco-friendly alternative to SF6 in power equipment. However, its insulation and decomposition behaviors under realistic conditions of varying pressure and electric field non-uniformity remain insufficiently studied. This study establishes an experimental platform to systematically investigate the power–frequency breakdown and decomposition characteristics of a 3:7 SF6/N2 mixture. Breakdown tests and critical field strength calculations were conducted under different pressures and electric field uniformities, followed by gas composition analysis. Results demonstrate that the proposed critical breakdown field strength method effectively predicts the mixture’s breakdown voltage. Furthermore, a range of decomposition products, including NF3, SOF2, CO2, and C2F6, were identified, whose concentrations generally decreased with rising pressure. These findings provide valuable experimental data and a predictive tool for optimizing the insulation design and condition monitoring of SF6/N2 gas-insulated equipment.

During brushing, friction between the brush and solid wood causes surfaces to become electrically charged through triboelectric effects. Wood, being a semi-conductive material, has its electrical conductivity influenced by factors such as moisture content, density, and anatomical structure. This study investigates the extent of triboelectric activation on wood surfaces using a wood brushing machine, with continuous detection of triboelectric surface field strengths. The effects of various wood modification technologies were assessed by comparing untreated control samples of two wood species, beech and poplar, to samples subjected to (1) densification, (2) steaming, and (3) thermal treatment at 120 °C and 180 °C. Positive triboelectric field strengths were recorded across all samples, with both nylon and steel wire brushes. The highest mean field strengths, 29.33 kV/m with the nylon brush and 7.86 kV/m with the steel brush, were observed in thermally treated at 180 °C and steamed poplar wood. Although surface field strength could not be directly correlated to density, a dependency on moisture content was established. These findings suggest that tailoring surface charges by controlling triboelectric effects could offer new opportunities for technical applications, such as chemistry-free primer modifications prior to wood coating.

Electrophoresis of a highly charged dielectric fluid droplet in electrolyte solutions

A mass spectrometer system which is capable of sampling ions directly from an atmospheric pressure source has been constructed and used to investigate ions which are evaporated from the surface of highly charged water droplets. Solutions of electrolytes are sprayed into the air, and a large charge imparted to the droplets by induction; an electric field applied across the plume of evaporating spray extracts small ions, probably already clustered with solvent molecules, which are drawn through a 25 μm orifice into the vacuum chamber. Differential pumping is applied and the ions are focused into a quadrupole mass filter. Approximately 30 univalent anions and cations of various sizes and structures have been tested, and almost all have been observed to evaporate; significant exceptions are Ag+, Tl+, and Cu+. Furthermore, certain molecules such as urea and acetanilide, when present as neutrals in the sprayed water, are observed to remain attached to the ions when these evaporate. The experimental results are discussed: ion mass spectra are interpreted in terms of ion evaporation (or field emission) and ion–molecule reactions in gas phase, and the potential value of the process for ion research and analytical applications is considered. The main features of the experimental results are consistent with the predictions of the theory developed in a previous paper by the authors.