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"Charge distribution"
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Electricity : investigating the presence and flow of electric charge
This book traces scientists and their discoveries about electricity from 271 CE to 2007.
Book
Numerical Solution to Poisson’s Equation for Estimating Electrostatic Properties Resulting from an Axially Symmetric Gaussian Charge Density Distribution: Charge in Free Space
Poisson’s equation frequently emerges in many fields, yet its exact solution is rarely feasible, making the numerical approach notably valuable. This study aims to provide a tutorial-level guide to numerically solving Poisson’s equation, focusing on estimating the electrostatic field and potential resulting from an axially symmetric Gaussian charge distribution. The Finite Difference Method is utilized to discretize the desired spatial domain into a grid of points and approximate the derivatives using finite difference approximations. The resulting system of linear equations is then tackled using the Successive Over-Relaxation technique. Our results suggest that the potential obtained from the direct integration of the distance-weighted charge density is a reasonable choice for Dirichlet boundary conditions. We examine a scenario involving a charge in free space; the numerical electrostatic potential is estimated to be within a tolerable error range compared to the exact solution.
Journal Article
Power Definitions and the Physical Mechanism of Power Flow
Professor Emanuel uses clear presentation to compare and facilitate understanding of two seminal standards, The IEEE Std. 1459 and The DIN 40110-2:2002-11. Through critical analysis of the most important and recent theories and review of basic concepts, a highly accessible guide to the essence of the standards is presented. <p><b>Key features:</b></p> <ul> <li>Explains the physical mechanism of energy flow under different conditions: single- and three-phase, sinusoidal and nonsinusoidal, balanced and unbalanced systems</li> <li>Starts at an elementary level and becomes more complex, with six core chapters and six appendices to clarify the mathematical aspects</li> <li>Discusses and recommends power definitions that played a significant historical role in paving the road for the two standards</li> <li>Provides a number of original unsolved problems at the end of each chapter</li> <li>Introduces a new nonactive power; the Randomness power.</li> </ul> <p><i>Power Definitions and the Physical Mechanism of Power Flow</i> is useful for electrical engineers and consultants involved in energy and power quality. It is also helpful to engineers dealing with energy flow quantification, design and manufacturing of metering instrumentation; consultants working with regulations related to renewable energy courses and the smart grid; and electric utility planning and operation engineers dealing with energy bill structure. The text is also relevant to university researchers, professors, and advanced students in power systems, power quality and energy related courses.</p>
eBook
Regulating band structure, charge transfer and separation, oxygen adsorption and activation by surface ion modification
As a most promising environmental technology, the substantial enhancement of photocatalytic efficiency is still a big challenge for practical applications. In this work, the surface of Bi
2
O
2
CO
3
(BOC) nanotubes are modified by Cl and I. The as-obtained samples at different hydrothermal temperatures (
T
) are designated as
T
-X-BOC (X = Cl, I). X-ray diffraction (XRD), energy dispersive X-ray (EDX) spectroscopy and X-ray photoelectron spectroscopy (XPS) prove that Cl and I merely chemically adsorb on the BOC surface, rather than dope into the crystal lattice. The surface modification of Cl and I slightly increases light absorption range, while significantly promotes the photoelectron migration from bulk to the surface that greatly enhances the carrier separation efficiency. Density functional theory (DFT) calculations further prove that surface Cl and I have adjusted band structure and surface charge distribution. Besides, the surface Cl and I favor the O
2
adsorption and trap the surface photoelectrons, thus promoting the formation of •O
2
–
; while the surface Cl and I impede the surface adsorption of H
2
O, thus refraining the generation of •OH. In the degradation of rhodamine B (RhB), holes and •O
2
−
radicals play the crucial role. Under ultraviolet light irradiation (λ < 420 nm) for 45 min, the RhB degradation ratios over 150-Cl-BOC (94%) and 150-I-BOC (85%) are 4.2 and 3.7 times higher than that of original BOC (18%), respectively. This work demonstrates that the simple surface halogenation modification greatly improves the photocatalytic activity.
Journal Article
Identifying the origin of porous evolution of microsized bismuth in potassium-ion batteries
Microsized bismuth (Bi) with
in-situ
constructed three-dimensional (3D) porous network has been considered as a promising anode for high-performance potassium-ion batteries (PIBs). However, the mechanism of the
in-situ
porous evolution of microsized Bi during the charge/discharge process is still mysterious. Herein, various electrolytes are employed to disclose the origin of porous evolution of microsized Bi in PIBs. Experimentally and theoretically, the 3D porous network originates from the uniform interfacial charge distribution on the Bi surface in the linear ether-based electrolyte. In addition, the universality of the interfacial charge distribution mechanism was verified by microsized Sn and Sb. The
in-situ
constructed 3D porous network of Bi enables a superior potassium storage performance in a wide temperature range from −40 to 40 °C. More importantly, the K
0.9
Mn
0.7
Ni
0.3
O
2
∥Bi full cell delivers excellent cycling stability (a high capacity retention of 88.44% even after 2,000 cycles) and good temperature tolerance. This work gives a distinct clarification of the origin of the porous evolution of microsized Bi during cycling, which is critical for developing high-performance PIBs.
Journal Article
Electrostatic pair-potentials based on the Poisson equation
Electrostatic pair-potentials within molecular simulations are often based on empirical data, cancellation of derivatives or moments, or statistical distributions of image-particles. In this work we start with the fundamental Poisson equation and show that no truncated Coulomb pair-potential, unsurprisingly, can solve the Poisson equation. For any such pair-potential the Poisson equation gives two incompatible constraints, yet we find a single unique expression which, pending two physically connected smoothness parameters, can obey either one of these. This expression has a general form which covers several recently published pair-potentials. For sufficiently large degree of smoothness we find that the solution implies a Gaussian distribution of the charge, a feature which is frequently assumed in pair-potential theory. We end up by recommending a single pair-potential based both on theoretical arguments and empirical evaluations of non-thermal lattice- and thermal water-systems. The same derivations have also been made for the screened Poisson equation, i.e. for Yukawa potentials, with a similar solution.
Journal Article
On the Filtration Efficiency of Composite Media Composed of Multiple Layers of Electret Media
This study aimed to explain the discrepancy reported in previous studies between the observed and the calculated filtration efficiencies of a composite formed of multiple electret medium layers. After measuring the composite’s filtration efficiency using particles divided by size and electrical charge status, viz., those possessing no charge, a single charge, and a stationary charge according to the Boltzmann distribution, we traced the discrepancy to the latter attribute. Hence, to accurately predict the filtration efficiency of multi-layered electret media, we must account for the test particles’ electrical charge distribution.
Journal Article
Quantifying Output Power and Dynamic Charge Distribution in Sliding Mode Freestanding Triboelectric Nanogenerator
The general concept of dielectric polarization density (P) is a macroscopic description of the underlying microscopic structure in the presence of an external electric field and polarized materials itself. A time‐dependent polarization PS induced by a non‐electric field also exists in practice due to the mechanically driven relative motion of media owing to the effects of contact electrification or piezoelectricity. In this work, the starting point is to consider the difference between P and PS, and how PS enters into the governing equations, since it describes the dielectric polarization density without an applied electric field, finally modifying the constitutive relations, Faraday's law, and Maxwell's equations. On this background, a 3D mathematical‐physical model for the sliding mode freestanding triboelectric nanogenerators (TENGs) is established that is taken as an example to confirm the relationship of free charge distribution and dynamics of output power. What needs to be emphasized is that the method of segmented uniform charge distribution is effective and the physical basis for modeling construction and analysis. Finally, we summarized the mathematical‐physical models of TENGs in rectangular coordinates, cylindrical coordinates, and spherical coordinates, building a bridge to reveal the underlying principle behind the microscopic polarization and energy conversion. The difference between P and PS, and how PS enters into the governing equations of triboelectric nanogenerator is considered. A 3D mathematical‐physical model for the sliding mode freestanding TENGs is established to confirm the relationship between free charge distribution and dynamics of output power. The mathematical‐physical models of TENGs in rectangular coordinates, cylindrical coordinates, and spherical coordinates are summarized.
Journal Article
What Protein Charging (and Supercharging) Reveal about the Mechanism of Electrospray Ionization
Understanding the charging mechanism of electrospray ionization is central to overcoming shortcomings such as ion suppression or limited dynamic range, and explaining phenomena such as supercharging. Towards that end, we explore what accumulated observations reveal about the mechanism of electrospray. We introduce the idea of an intermediate region for electrospray ionization (and other ionization methods) to account for the facts that solution charge state distributions (CSDs) do not correlate with those observed by ESI-MS (the latter bear more charge) and that gas phase reactions can reduce, but not increase, the extent of charging. This region incorporates properties (e.g., basicities) intermediate between solution and gas phase. Assuming that droplet species polarize within the high electric field leads to equations describing ion emission resembling those from the equilibrium partitioning model. The equations predict many trends successfully, including CSD shifts to higher
m/z
for concentrated analytes and shifts to lower
m/z
for sprays employing smaller emitter opening diameters. From this view, a single mechanism can be formulated to explain how reagents that promote analyte charging (“supercharging”) such as
m-
NBA, sulfolane, and
3
-nitrobenzonitrile increase analyte charge from “denaturing” and “native” solvent systems. It is suggested that additives’ Brønsted basicities are inversely correlated to their ability to shift CSDs to lower
m/z
in positive ESI, as are Brønsted acidities for negative ESI. Because supercharging agents reduce an analyte’s
solution
ionization, excess spray charge is bestowed on evaporating ions carrying
fewer opposing charges.
Brønsted basicity (or acidity) determines how much ESI charge is lost to the agent (unavailable to evaporating analyte).
Graphical Abstract
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Journal Article
Robust ZnS interphase for stable Zn metal anode of high-performance aqueous secondary batteries
Although Zn metal is an ideal anode candidate for aqueous batteries owing to its high theoretical capacity, lower cost, and safety, its service life and efficiency are damaged by severe hydrogen evolution reaction, self-corrosion, and dendrite growth. Herein, a thickness-controlled ZnS passivation layer was fabricated on the Zn metal surface to obtain Zn@ZnS electrode through oxidation—orientation sulfuration by the liquid- and vapor-phase hydrothermal processes. Benefiting from the chemical inertness of the ZnS interphase, the as-prepared Zn@ZnS electrode presents an excellent anti-corrosion and undesirable hydrogen evolution reaction. Meanwhile, the thickness-optimized ZnS layer with an unbalanced charge distribution represses dendrite growth by guiding Zn plating/stripping, leading to long service life. Consequently, the Zn@ZnS presented 300 cycles in the symmetric cells with a 42 mV overpotential, 200 cycles in half cells with a 78 mV overpotential, and superb rate performance in Zn∥NH
4
V
4
O
10
full cells.
Journal Article