Charged Drops Research Articles

The Coalescence of Charged and Uncharged Drops Under Electric Field

The Coalescence of Charged and Uncharged Drops Under Electric Field

A Priori Estimates for the Motion of Charged Liquid Drop: A Dynamic Approach via Free Boundary Euler Equations

We study the motion of charged liquid drop in three dimensions where the equations of motions are given by the Euler equations with free boundary with an electric field. This is a well-known problem in physics going back to the famous work by Rayleigh. Due to experiments and numerical simulations one may expect the charged drop to form conical singularities called Taylor cones, which we interpret as singularities of the flow. In this paper, we study the well-posedness of the problem and regularity of the solution. Our main theorem is a criterion which roughly states that if the flow remains C1,α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$C^{1,\\alpha }$$\\end{document}-regular in shape and the velocity remains Lipschitz-continuous, then the flow remains smooth, i.e., C∞\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$C^\\infty $$\\end{document} in time and space, assuming that the initial data is smooth. Our main focus is on the regularity of the shape of the drop. Indeed, due to the appearance of Taylor cones, which are singularities with Lipschitz-regularity, we expect the C1,α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$C^{1,\\alpha }$$\\end{document}-regularity assumption to be optimal. We also quantify the C∞\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$C^\\infty $$\\end{document}-regularity via high order energy estimates which, in particular, implies the well-posedness of the problem.

Fission valleys and favored isotopes emitted from 310\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{310}$$\\end{document}126

The decay channels for the superheavy nucleus 310\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{310}$$\\end{document}126 are studied under the binary macroscopic–microscopic method. The macroscopic part is calculated as the heavy-light interacting charged liquid drops, linked through the finite range Yukawa-plus-exponential force. The microscopic energy is calculated based on the spheroidally deformed two-center shell model. The proton and neutron single-particle levels are introduced in the binary Strutinsky procedure. The resulting shell corrections are added to the macroscopic part to obtain the fission barriers. The dynamical part follows by introducing the Werner–Wheeler inertia. The final lifetimes are calculated for all possible isotopic channels around the most favored heavy-light fragment pairs.

Control of spontaneous charging of sliding water drops by plasma-surface treatment

Slide electrification is the spontaneous separation of electric charges at the rear of water drops sliding over solid surfaces. This study delves into how surfaces treated with a low-pressure plasma impact water slide electrification. Ar, O2, and N2 plasma treatment reduced the drop charge and contact angles on glass, quartz, and SU-8 coated with 1H,1H,2H,2H-perfluoroctyltrichlorosilane (PFOTS), and polystyrene. Conversely, 64% higher drop charge was achieved using electrode-facing treatment in plasma chamber. Based on the zeta potential, Kelvin potential, and XPS measurements, the plasma effects were attributed to alterations of the topmost layer's chemistry, such as oxidation and etching, and superficially charge deposition. The surface top layer charges were less negative after electrode-facing and more negative after bulk plasma treatment. As a result, the zeta potential was less negative after electrode-facing and more negative after bulk plasma treatment. Although the fluorinated layer was applied after plasma activation, we observed a discernible impact of plasma-glass treatment on drop charging. Plasma surface modification offers a means to adjust drop charges: electrode-facing treatment of the fluorinated layer leads to an enhanced drop charge, while plasma treatment on the substrate prior to fluorination diminishes drop charges, all without affecting contact angles or surface roughness.

Dual-ROS-scavenging and dual-lingering nanozyme-based eye drops alleviate dry eye disease

Efficiently removing excess reactive oxygen species (ROS) generated by various factors on the ocular surface is a promising strategy for preventing the development of dry eye disease (DED). The currently available eye drops for DED treatment are palliative, short-lived and frequently administered due to the short precorneal residence time. Here, we developed nanozyme-based eye drops for DED by exploiting borate-mediated dynamic covalent complexation between n-FeZIF-8 nanozymes (n-Z(Fe)) and poly(vinyl alcohol) (PVA) to overcome these problems. The resultant formulation (PBnZ), which has dual-ROS scavenging abilities and prolonged corneal retention can effectively reduce oxidative stress, thereby providing an excellent preventive effect to alleviate DED. In vitro and in vivo experiments revealed that PBnZ could eliminate excess ROS through both its multienzyme-like activity and the ROS-scavenging activity of borate bonds. The positively charged nanozyme-based eye drops displayed a longer precorneal residence time due to physical adhesion and the dynamic borate bonds between phenyboronic acid and PVA or o-diol with mucin. The in vivo results showed that eye drops could effectively alleviate DED. These dual-function PBnZ nanozyme-based eye drops can provide insights into the development of novel treatment strategies for DED and other ROS-mediated inflammatory diseases and a rationale for the application of nanomaterials in clinical settings.Graphical

Surface properties of schwertmannite with different sulfate contents and its effect on Cr(VI) adsorption

Sulfate is a critical component of schwertmannite. However, the sulfate content of schwertmannite decreases with the increase in AMD-polluted river pH value, and its impact on the surface properties and Cr(VI) adsorption of schwertmannite remains unclear. To address this issue, different methods, including batch adsorption, N2 physisorption, scanning electron microscopy (SEM), potentiometric titration, X-ray photoelectron spectroscopy (XPS), attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR) in combination with two-dimensional correlation spectroscopy (2D-COS) analysis, and surface complexation modeling (SCM) were employed. Our results showed that sulfate existed as both non-protonated bidentate-binuclear complexes and non-protonated outer-sphere complexes in schwertmannite. The surface morphology and particle size of schwertmannite were unaffected by the sulfate content. However, a decrease in sulfate content resulted in a drop in the negative charge on the surface of schwertmannite, which is conducive to particle aggregation. An increase in pH, on the other hand, raised the negative charge and encouraged the dispersion of the particles. And then, reducing the sulfate content of schwertmannite led to a decrease in acid-base buffer and Cr(VI) adsorption capacity of schwertmannite. The adsorption process of Cr(VI) by schwertmannite can be divided into two stages. In the first stage, Cr(VI) was adsorbed primarily through anion exchange reactions with the sulfate; however, the contribution of surface complexation gradually increased as the initial sulfate content decreased because of a reduced likelihood of anion exchange and an increase in the specific surface area of schwertmannite. Additionally, the behavior of sulfate and Cr(VI) in this stage could be predicted based on the initial sulfate content of schwertmannite. In the second stage, surface complexation with hydroxyl sites became the predominant mechanism of adsorption, which still exhibited great potential at higher Cr(VI) concentrations. Finally, the aforementioned hypothesis was used to establish a CD-MUSIC model, and the fitting results demonstrated that the density and Cr(VI) adsorption capacity of the sulfate site dropped as the sulfate content decreased, while the hydroxyl site was less impacted. The findings have provided insights into further understanding the properties of schwertmannite and its adsorption of Cr(VI).

Electrical effects on droplet behaviour

The effect of charge on water droplets modulates various aspects of their behaviour. These include the droplet stability, evaporation, and lifetime. Microphysical models have been developed such that a reasonably good understanding of these processes has been achieved. However, the specific effects of charge deserve further scrutiny as they are an intrinsic component of the factors controlling droplet characteristics. Describing the effects of these requires an understanding of the electrostatic pressure present in the droplet and its surface tension. One way to test these effects and assess droplet response to charge is to take an experimental approach to make observations directly. In this study, individual droplets are levitated in an acoustic wave to allow isolated measurements to be taken. The droplets are monitored using a CCD camera with a microscope objective lens. In some cases, with sufficient charge present, effects on droplet stability can be observed as Rayleigh explosions, where a sudden drop in mass is seen superimposed on the evaporation profile. These events also allow the charge on the droplet to be calculated, which is then compared with the droplet evaporation. Another factor that plays a part in droplet behaviour is droplet composition. Different substances have different surface tension, and this is explored by performing some experiments on sulphuric acid droplets. Theory predicts that the more highly charged a droplet is, the more resistant to evaporation it becomes. Experimental data collected during this study agrees with this, with more highly charged droplets observed to have slower evaporation rates. However, highly charged drops were also observed to periodically become unstable during evaporation and undergo Rayleigh explosions. Each instability of a highly charged drop removes mass, reducing the overall droplet lifetime regardless of the slower evaporation rate. The sulphuric acid droplets were observed to be much more resistant to evaporation and no Rayleigh instabilities were observed.

Evaluation of Sort Recovery via Rmax.

Cell sorting performance can be evaluated in regard to the purity and recovery of the sorted fractions. The purity provides checks on sample quality, acquisition settings, gating strategy, and the sort decisions made by the instrument, but alone it is not sufficient to evaluate sorting performance. Recovery, defined here as the number of target particles sorted relative to the number of original target particles to be sorted, is a key metric of sort fitness and performance but is often neglected due to difficulties in its measurement. Both purity and recovery require re-sampling of the sorted fraction, but unlike determining purity, calculating recovery calls for the absolute counting of particles in the sorted fraction that comes with large errors, and may not be feasible for rare populations or precious samples. Here, we describe a recently developed metric and method for calculating sort recovery called Rmax, representing the maximum expected recovery for a particular set of instrument settings. Rmax calculation avoids re-sampling of the total sorted fraction and absolute counting, being instead based on the ratios of target and non-target populations in the original pre-sort sample and in the waste stream or center stream catch. The Rmax method is ideal to evaluate and troubleshoot the optimum drop-charge delay of the sorter or any instrument-related failures that will affect sort performance. It can be used as a daily quality control check but can be particularly useful to assess instrument fitness before single-cell or rare population sorts. Because the sorted fraction is not perturbed, we can calculate Rmax during the sort run. © 2024 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Evaluating sorter setup with Rmax Basic Protocol 2: Finding the maximum Rmax: scanning over the drop charge delay Alternate Protocol: Finding the maximum Rmax for cells: scanning over the drop charge delay Basic Protocol 3: Estimating sorted cell number with Rmax.

Analysis of the level of battery drop in electric bikes with different night parking options

The study analyzed the level of drop in battery charge of electric bikes under different options for night parking during the summer operating season. An analysis was made of the level of charge drop in the battery of electric bikes under different options for night parking with three storage options (home storage, garage storage, street storage) providing different temperature conditions for the electric bicycle battery. The data obtained reflect the level of drop in battery charge of electric bikes for different options for night parking during the summer operating season. These studies can be used when conducting research aimed at optimizing the level of battery charge loss for electric bikes under different options for night parking in urban conditions.

Dynamic Surface Tension of a Charged Spherical Water Drop

In the asymptotic calculations of the first order of smallness by the dimensionless amplitude of oscillations of the water drop, the effect of the dynamic surface tension on the parameters of oscillations was investigated on the model of an ideal uncompressible liquid. It was shown that the effect of the dynamic surface tension is significantly manifested at the frequencies of the external influence of the order inverse to the water relaxation time. At such frequencies, under the influence of the external influences, the double electric layer is destroyed (there is a violation of the order of water molecules in the near-surface layer), the free energy of the surface increases, and, with it, the value of the surface tension of the liquid. The dynamic surface tension affects the acoustic radiation from the droplet through a change in the value of the surface tension coefficient. The contribution to electromagnetic radiation of the oscillating droplet is associated with the destruction of the ordering of the near-surface water molecules in the double electric layer.

Microwave Diagnostics of Electrical Discharges in an Artificial Cloud of Charged Water Drops

Microwave Diagnostics of Electrical Discharges in an Artificial Cloud of Charged Water Drops

Bifurcation and stability for charged drops

In this paper, we investigate the Laplace’s equation for the electrical potential of charge drops on exterior domain, and overdetermined boundary conditions are prescribed. We determine the local bifurcation structure with respect to the surface tension coefficient as bifurcation parameter. Furthermore, we establish the stability and the instability near the bifurcation point.

TEMPERATURE DYNAMICS OF THE MICRODROPLET FRACTION OF METAL PLASMA IN PLASMA-OPTICAL DEVICES WITH FAST ELECTRONS

The computer simulation of a plasma filter with fast electrons shows that the main source of droplet heating is thermal electrons, while the role of fast electrons is reduced mainly to transferring energy to slow electrons. The processes of drop charging in the presence of an electron beam and the effective emission of electrons due are also considered.

Appraising Jackson-based unrestorability to competence to stand trial: The demonstration model.

Under United States law, criminal prosecution may not proceed against a defendant who is incompetent to participate in this process. The vast majority of defendants who are adjudicated incompetent to stand trial (IST) will subsequently regain sufficient capacities to be adjudicated competent to stand trial (CST). However, a small subgroup of defendants do not show sufficient improvement in clinical functioning and functional-legal capacities to regain CST. Under Jackson v. Indiana (1972), such individuals should be adjudicated unrestorably IST, with associated actions (e.g., dropping of criminal charges, civil commitment, transfer to a less restrictive environment or released) specified under the particular jurisdictional statutes. But the present practices associated with the evaluation of unrestorability do not appear well supported by research. In particular, statutorily specified evaluative procedures are overly dependent on prediction in some instances and allow an unnecessarily long restoration period in others. In the present article, we propose and describe an alternative approach-the Demonstration Model-that would address both challenges, providing a more consistent and standard approach to assessing CST and the possibility that a defendant may not recover needed capacities within the foreseeable future. Implementation of this approach can potentially guide restoration planning and intervention, decrease unsupported reliance upon prediction in favor of observing and documenting the results of selected interventions, and provide legal decision-makers with clearer and more transparent evidence, while acknowledging the liberty interests of IST defendants set forth in Jackson. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Molecular dynamics simulation of the cone-jet electrospray: Role of surfactants

Electrospray in the cone-jet regime could produce highly charged and fine monodisperse drops, and further disintegrates into nanoscale drops, even ions due to synergism of Rayleigh instability and evaporation. The jet and its breakup instability into drops are significantly affected by liquid properties including surface tension, conductivity, density and others. Surfactants may play important roles on gas-liquid interface and are usually added in solution to vary liquid property and may further affect electrospray behaviors. In present work, the ethanol containing surfactants is atomized in the cone-jet to discuss the synergistic effect of surfactant types, concentrations and surfactant-salt on the jet evolution behaviors under direct current electric fields using molecular dynamics (MD) method. It is found that the jet length of ethanol solution with Span-80 is the longest (Span-80, SDS, CTAB and TX-100), while it has excellent dispersion. The addition of CTAB could make ethanol solution transform from continuous jet into dripping. SDS interacts most violently with ethanol due to the presence of sodium ions. As surfactant concentration increasing, the number of solution molecules sprayed remarkably increases, while the interaction generated from ethanol decreases. The number of molecular clusters (composed of three or more ethanol molecules) in the cone-jet electrospray increases with increasing Span-80 concentration. It is also found that the addition of Span-80 slightly changes the average bond angle of ethanol and bond angle distribution. The ethanol atomization morphology transforms to spindle becasue of the synergistic effect of surfactant and salt ions. The interaction generated between ethanol molecules plays a dominating role and decreases due to the generation of spindle-shaped drops. The hydrogen bond generated from ethanol decreases with increasing conductivity and surface tension. The conclusions of this paper will be latent value for the optimization of physical parameters in electrospray.

Tailoring the Charge Carrier Lifetime Distribution of 10 kV SiC PiN Diodes by Physical Simulations

In this paper, Shockley-Read-Hall (SRH) lifetime depth profiles in the drift layer of 10 kV SiC PiN diodes are calculated after MeV proton implantation. It is assumed that the carbon vacancy will be the domination trap for charge carrier recombination and the SRH lifetime is calculated with defect parameters from the literature and proton-induced defect distributions deduced from SRIM calculations. The lifetime profiles are imported to Sentaurus TCAD and static and dynamic simulations using tailored lifetime profiles are carried out to study the electrical effect of proton implantation parameters. The results are compared to measurements, specializing on optimization of the trade off between on-state and turn-off losses, represented by the forward voltage drop, VT, and reverse recovery charge, Qrr, respectively. Both the simulated and measured IV characteristics show that increasing proton dose, or energy, has the effect on increasing forward voltage drop and on-state losses, while simultaneously, the localized SRH lifetime drop decreases the plasma level, increases the speed of recombination and decreases reverse recovery charge. Finally, TCAD simulations with different combinations of proton energies and fluences are used to optimize the trade-off between static and dynamic performances. Reverse recovery charge and forward voltage drops of these groups of diodes are plotted together, showing that a medium energy which induces the most defects in the depletion region relatively close to the anode gives the best dynamic performances, with a minimum cost of static performance.

Shape, stability and dynamics of a charged drop falling on a substrate

The stability of charged droplets emanating from a jet is paramount in electrostatic jet-based applications, such as colloid thruster, electroprinting, electrospinning, electrostatic atomization and spray deposition. Among the number of factors governing the stability, the drop–substrate interaction is imperative as the droplets ultimately settle onto a surface. In this study we numerically investigate the shape, stability and dynamics of a charged droplet falling normal to a ground conducting substrate. The boundary element method (BEM) is used to solve electrostatics and hydrodynamics of an inherently charged droplet as it approaches the surface at different conditions. The numerical results imply several previously unreported behaviors of a charged drop caused by the interplay between its dynamics, the flow fields and the electrostatics. The study emphasizes the influence of fall distance (s0), net charge at drop surface (Q), Bond number (Bo) and viscosity (μ) on the drop shape, its kinetics and stability limits. The observations suggest that the critical charge limit (QC) of a settling drop is governed by the fall distance (s0), Bond number and the shape perturbations. Interestingly the QC can be larger or smaller than the Rayleigh critical charge limit depending on the governing parameters. The breakup modes of a droplet above critical charge limit are identical; however, the stable droplets exhibit peculiar shape-transitions, not seen in charged droplets levitated near wall or in infinite space. The observations reported here highlight the profound effect of nozzle position from substrate in the abovementioned applications, in addition to the electrical and physical properties of the systems.

Методы расчета и оценки термоэмиссионного плазменно-капельного генератора с магнитной сепарацией заряда

The development of design solutions and preliminary calculation substantiation of the characteristics of a high-voltage plasma-drop generator with magnetic charge separation have been completed. The aim of the study was to confirm the possibility of creating a current source with an operating voltage of about 107 V. The proposed energy conversion method is based on the separation of charged drops from dusty plasma in a gradient magnetic field. Droplets are charged due to thermal emission from their surface. A schematic description of the generator is presented and an elementary calculation model is proposed. This model is divided into 4 blocks that describe the various processes taking place in the device. The assumptions and simplifications necessary for the evaluation are discussed. Preliminary calculation data on the efficiency of a plasma-drop generator with magnetic charge separation have been obtained under conditions close to those actually achievable by manufacturing technologies. The main parameters for evaluation were power, efficiency, voltage and magnetic field induction. As a result of the calculations performed, the fundamental possibility of creating a workable plasma-drop generator based on the proposed solutions is shown. The results obtained are not accurate and require further improvement of the model and study of the processes taking place in the generator.

A SiC asymmetric cell trench MOSFET with a split gate and integrated p+-poly Si/SiC heterojunction freewheeling diode

A new SiC asymmetric cell trench metal–oxide–semiconductor field effect transistor (MOSFET) with a split gate (SG) and integrated p+-poly Si/SiC heterojunction freewheeling diode (SGHJD-TMOS) is investigated in this article. The SG structure of the SGHJD-TMOS structure can effectively reduce the gate-drain capacitance and reduce the high gate-oxide electric field. The integrated p+-poly Si/SiC heterojunction freewheeling diode substantially improves body diode characteristics and reduces switching losses without degrading the static characteristics of the device. Numerical analysis results show that, compared with the conventional asymmetric cell trench MOSFET (CA-TMOS), the high-frequency figure of merit (HF-FOM, R on,sp × Q gd,sp) is reduced by 92.5%, and the gate-oxide electric field is reduced by 75%. In addition, the forward conduction voltage drop (V F) and gate-drain charge (Q gd) are reduced from 2.90 V and 63.5 μC/cm2 in the CA-TMOS to 1.80 V and 26.1 μC/cm2 in the SGHJD-TMOS, respectively. Compared with the CA-TMOS, the turn-on loss (E on) and turn-off loss (E off) of the SGHJD-TMOS are reduced by 21.1% and 12.2%, respectively.

Self-generated electrostatic forces of drops rebounding from hydrophobic surfaces

We study the charge separation of drops rebounding from hydrophobic surfaces. Based on high-speed video imaging and the deflection of drops by electric fields, we reproducibly detected the amount of charge. Here, we show that the charge separation of bouncing drops can be 2 orders of magnitude higher on hydrophobic than superhydrophobic surfaces. We observed the existence of self-generated electrostatic forces between the drop and the surface. These forces affect the maximum rebounding height and slow down the retraction motion of drops. We additionally calculated the electrostatic forces using an energy conservation approach. Our results indicate that electrostatic forces on hydrophobic surfaces can be even stronger than gravity, reducing the restitution coefficients up to 50%. This new approach becomes advantageous compared with other methods that require more complicated setups for drop charge detection.