Maximum Potential Drop Research Articles

Enhancing photocathodic protection with Ti3C2-Decorated BiVO4 microspheres

In order to solve the problem of low carrier separation efficiency and large electron-transmission loss in transfer process of BiVO4; therefore, this study considered titanium carbide (Ti3C2) as a photoelectron-transfer agent for use in photocathodic protection (PCP) applications. Frist, SEM characterization proved that the typical accordion structure of Ti3C2 could be controlled by adjusting the etching time (36 h) and temperature (50 ℃). As-prepared Ti3C2 could reduced the volume resistivity of epoxy resin by four orders of magnitude and has excellent hydrophilicity. Second, different mass ratios of Ti3C2 to BiVO4 were also tested. When the ratio of BiVO4 to Ti3C2 was 1:2, the mixture self-assembled into BiVO4/Ti3C2 microspheres owing to the electrostatic adsorption of functional groups on the Ti3C2 surface. Third, the PEC test demonstrated that 304SS coupled with BiVO4/Ti3C2 (B:T = 1:2) photoanode showed an enhanced photocurrent density (154 μA•cm−2) and maximum potential drop (799 mV), which were equivalent to 3.5 times and 2.18 times that of the bare BiVO4, respectively. Mechanism study illustrated that enhanced performance of the BiVO4/Ti3C2 photoanode was attributed to Ti3C2 increased the hydrophilicity and conductivity, promoting the differentiation of the photocurrent in composite microspheres, and the interconnection structure helped maintain long-term stability.

Pulsar death line revisited – II. ‘The death valley’

ABSTRACTIn this paper, which is the second in a series of papers, we analyse what parameters can determine the width of the radio pulsar ‘death valley’ in the P–${\dot{P}}$ diagram. Using exact expression for the maximum potential drop, which can be realized over magnetic polar caps and the corresponding threshold for the secondary plasma production determined in Paper I, we analyse in detail the observed distribution of pulsars taking into account all the possible parameters (radius R and moment of inertia of a neutron star Ir, high-energy tail in the γ-quanta energy distribution giving rise to secondary particles, etc.) which could broaden ‘the death line’. We show that the consistent allowance for all these effects leads to a sufficiently wide of ‘the death valley’ containing all the observed pulsars even for dipole magnetic field of a neutron star. We emphasize that the main goal of this work is to demonstrate that the original Ruderman–Sutherland idea of the death line (dipole magnetic field, vacuum gap) is in good agreement with observations. The comparison with other models is beyond the scope of this paper.

Enhancing photoelectrochemical cathodic protection performance by facile tuning sulfur redox state in sacrificial agents

Photocathodic protection (PCP) performance is restricted by the photogenerated charges separation efficiency. This study reported a facile approach to enhance PCP performance. Na2S, Na2SO3, Na2S2O3, Na2SO4, and NaCl was selected as sacrificial agents, in which the PCP performance is characterized by coupling TiO2 and TiO2/ZnSe composites with 304 stainless steel. TiO2/ZnSe photoanode presented the best PCP performance in Na2S media. The maximum potential drop is 466.7 mV, which is about 3.5 times higher than that of in NaCl media. The corresponding photocurrent density is 270.7 μA/cm2, which is about 10 times higher than that of in NaCl media. Based on circle voltammetry and ultraviolet photo-electron spectroscopy characterization, it was found that the redox potential of the sacrificial reagent governs the migration and consumption of photogenerated holes of the photoanode.

Fabrication of pyramid-BiVO4/CdSe composite with controlled surface oxygen vacancies boosting efficient carriers’ separation for photocathodic protection

• A novel pyramid-BiVO 4 /CdSe photoanode with enriched oxygen vacancies was prepared. • Pyramid-BiVO 4 /CdSe heterojunction promotes solar harvesting and carrier separation. • The pyramid-BiVO 4 /CdSe photoanode exhibits superior PEC performance and stability. • The corrosion potential of 304SS coupled with 8V-BC photoanode drop 708 mV. In order to solve the bottleneck problem of weak efficiency of carriers’ separation and transfer in BiVO 4 photocatalyst, a novel pyramid-BiVO 4 with sufficient oxygen vacancies was successfully synthesized via a low-temperature solvothermal method. By adjusting solution pH and adding SDBS surfactant, the prepared samples could have a variety of controllable morphologies and exposed {0 0 1} facets, which were determined by SEM, XRD, and BET methods. XPS O1s peak and ESR signals indicated that pyramid-BiVO 4 exhibited higher oxygen vacancies concentration than others. Besides, CdSe quantum dots (QDs) were introduced to construct BiVO 4 /CdSe heterojunctions composite based photoanode to further promote solar harvesting and carrier separation. The photoelectrochemical experimental results showed that 304 stainless steel (304SS) coupled with 8V-BC photoanode showed an enhanced photocurrent density (608 μA·cm −2 ) and maximum potential drop (708 mV), which were equivalent to 5.06 times and 2.10 times that of the original BiVO 4 , respectively. Mechanism study illustrated that the ultra-high performance of the 8V-BC photoanode was attributed to the synergistic effect of enriched oxygen vacancies, exposed {0 0 1} facets, enlarged visible light absorption and larger specific surface area.

Nonlinear dependence of plasma potential and ion impinging energy on energy loss of edge localized modes

Particle-in-cell (PIC) modelling has been performed to investigate the impact of energy loss during edge localized modes (ELMs) on the plasma potential and ion impinging energy on the divertor target. A double-peak structure of the ion impinging energy has been identified under JET-relevant ELM conditions. The ELM burst leads to a strong increase in the potential drop in front of the target plate, which accelerates the cold ions from the downstream divertor and accordingly causes a peak value of ion impinging energy. Moreover, the great potential drop helps confine the fast electrons and leads to a reduction in the potential drop and ion impinging energy. The arrival of the upstream hot ions results in the second peak value of ion impinging energy. The maximum potential drop and ion impact energy show a linear dependence on the pedestal temperature. Further, a nonlinear dependence of the peak potential drop and ion impact energy on the ELM energy loss can be ascertained based on the PIC simulations.

What Can We Learn About the Average Treatment Effect of Retirement on Consumption?

We present a nonparametric bounds analysis of the Average Treatment Effect (ATE) of retirement on domestic expenditure. We consider identification under a wide catalogue of assumptions which restrict either the potential outcomes or the process of selection into treatment. We put forward new assumptions that exploit the longitudinal information in panels to refine existing results regarding the partial identification of ATEs. The tightest identification region suggest that retirement could lead to a drop of up to 7% in expenditure. However, the sign of the actual effect is not identified unless one restricts the variation in potential outcomes across households or one assumes that, on average, retirement is detrimental for consumption. The latter assumption might be suitable only in environments like the United States or the United Kingdom, where the pension replacement rate are low. We find that savings and education have mitigating effects on the magnitude of the maximum potential drop in expenditure.

Impact of sheath evolution on ion impinging energy on the target during edge localized modes

The impact of the sheath evolution during edge localized modes (ELMs) on the ion impinging energy on the divertor target is studied by particle-in-cell simulation. A significant increase of the ion impact energy is obtained at the beginning of ELM. The arrival of the upstream bulk plasma leads to a suppression of the potential drop in front of the divertor target. The peak value of the ion impact energy emerges after the maximum potential drop in front of the divertor target. It is found that the peak value of the ion impact energy is increased by about 30% compared to the ion initial energy, which is induced by the potential drop during ELMs.

Effect of thickness on the maximum potential drop of current collectors

The basic principle for achieving high-power capability on an electrochemical energy storage cell is minimizing the overall resistance. The resistance due to current collecting systems has not received sufficient attention in the past, presumably because it was not considered of significance for low-power batteries and supercapacitors. However, the necessity of high-power cells has reduced other sources of the inner resistance, and the current collector potential drop has become more important. Moreover, the miniaturization of energy storage devices could increase the ohmic loses in current collectors. In this work, we have developed an electrical model to assess the effect of the current collector thickness on the maximum potential drop. We have found that the thickness of current collectors is a critical parameter that can increase the maximum potential drop drastically. Indeed, the maximum potential drop of current collectors remains almost constant for thicknesses greater than 500 μm, but below this value, there is an inverse relationship between the maximum potential drop and the thickness. We have also analyzed the effect of the material and tab position in the maximum potential drop.

Simulation and Measurement of the Current Density Distribution in Lithium-Ion Batteries by a Multi-Tab Cell Approach

A single-layered NMC/graphite pouch cell is investigated by means of differential local potential measurements during various operation scenarios. 44 tabs in total allow for a highly resolved potential measurement along the electrodes whilst the single layer configuration guarantees the absence of superimposed thermal gradients. By applying a multi-dimensional model framework to this cell, the current density and SOC distribution are analyzed quantitatively. The study is performed for four C-rates (0.1C, 0.5C, 1C, 2C) at three temperatures (5°C, 25°C, 40°C). The maximum potential drop as well the corresponding SOC deviation are characterized. The results indicate that cell inhomogeneity is positively coupled to temperature, i.e. the lower the temperature, the more uniform the electrodes will be utilized.

Electron-Positron Pairs Related to Alfven Waves on the Magnetar Surface

The phenomena of electron-positron pairs production through the polar cap region of a magnetar is studied. Assuming the distances of electron-positron pair regions from the magnetar centre to be the height scales of magnetic deformed regions and hence determine by adopting the Alfven waves propagation. The maximum potential drop on the magnetar surface and the potential differences in the confined regions are obtained by using Lorentz factor. The attempt is made to find out the curvature photon energy through the polar cap region of magnetar that is greater than critical energy and verify the conversion into electron-positron pairs via synchrotron radiation with their characteristic photon energy. Further, an estimate is made to flow the charged particles per second through the polar cap region.

Efficient network-matrix architecture for general flow transport inspired by natural pinnate leaves.

Networks embedded in three dimensional matrices are beneficial to deliver physical flows to the matrices. Leaf architectures, pervasive natural network-matrix architectures, endow leaves with high transpiration rates and low water pressure drops, providing inspiration for efficient network-matrix architectures. In this study, the network-matrix model for general flow transport inspired by natural pinnate leaves is investigated analytically. The results indicate that the optimal network structure inspired by natural pinnate leaves can greatly reduce the maximum potential drop and the total potential drop caused by the flow through the network while maximizing the total flow rate through the matrix. These results can be used to design efficient networks in network-matrix architectures for a variety of practical applications, such as tissue engineering, cell culture, photovoltaic devices and heat transfer.

High Energy Emission from Magnetar Due to Giant Flare

We propose a theoretical model for magnetar giant flare to explain the flaring activity on 2004 December 27 from SGR1806-20 comprehensively. A global rearrangement is expected by the magnetic reconnection that requires explaining the giant SGR flares. In this paper we propose two regions of flares: preflare on the surface of magnetar and main burst at a distance of light cylinder radius. Acquiring the maximum potential drop on the magnetar surface, adopting space charge limited flow model, and using magnetic field B ≈ 1015 G, the luminosities of flare energies release for the preflare phase and main burst phase are found to be in the order of 1041 erg·sˉ1 and 1044 erg·sˉ1 respectively, conforming to magnetar burst energy and flare temperature is determined by considering black body radiation.

Temporal evolution and electric potential structure of the auroral acceleration region from multispacecraft measurements

Bright aurorae can be excited by the acceleration of electrons into the atmosphere in violation of ideal magnetohydrodynamics. Modeling studies predict that the accelerating electric potential consists of electric double layers at the boundaries of an acceleration region but observations suggest that particle acceleration occurs throughout this region. Using multispacecraft observations from Cluster, we have examined two upward current regions on 14 December 2009. Our observations show that the potential difference below C4 and C3 changed by up to 1.7 kV between their respective crossings, which were separated by 150 s. The field‐aligned current density observed by C3 was also larger than that observed by C4. The potential drop above C3 and C4 was approximately the same in both crossings. Using a novel technique of quantitively comparing the electron spectra measured by Cluster 1 and 3, which were separated in altitude, we determine when these spacecraft made effectively magnetically conjugate observations, and we use these conjugate observations to determine the instantaneous distribution of the potential drop in the AAR. Our observations show that an average of 15% of the potential drop in the AAR was located between C1 at 6235 km and C3 at 4685 km altitude, with a maximum potential drop between the spacecraft of 500 V, and that the majority of the potential drop was below C3. Assuming a spatial invariance along the length of the upward current region, we discuss these observations in terms of temporal changes and the vertical structure of the electrostatic potential drop and in the context of existing models and previous single‐ and multispacecraft observations.

Studies of the effect of variation of blend ratio on permselectivity and heterogeneity of ion-exchange membranes

Heterogeneous ion-exchange membranes (both cationic and anionic types) have been synthesized by solution casting techniques using polyvinyl chloride (PVC) as binder and ion-exchange resin (−300+400 mesh). The binder:resin ratio varied from 60:40 to 30:70. The transport behavior of the membranes has been evaluated chronopotentiometrically in sodium chloride (NaCl) solutions of different concentrations. The different parameters E 0 (potential drop across the membrane at the instant of application of current I), E max (maximum potential drop across the membrane after the application of current I), Δ E (magnitude of the potential jump across the membrane at transition time τ), Iτ 1/2, τ, etc., have been evaluated. The isoconductance points were determined and based on the microheterogeneous model proposed by Zabolotsky and Nikonenko (J. Membrane Sci. 79 (1993) 181) the distribution factors β has been evaluated for both types of ion exchange membranes. The electroconductivity of the joint gel ( κ ̄ ) and pure gel phases ( κ ̄ ′ ) has been determined. At any particular solution concentration the transport number as well as the permselectivity of membranes increases with increased resin content of the membrane. The microheterogeneity factor β exhibits synchronization among the each set of four different membranes for both the cationic and anionic type.

Potential Distribution in Semiconductor Particles

The potential distribution inside spherical semiconductor particles with arbitrary doping profiles has been derived. Both polynomial and exponential‐graded doping densities have been considered. With the derived expressions, the maximum attainable potential drop within a single particle can be calculated. For a highly defected surface, this maximum potential drop appears to be much larger than usually is assumed.

Pulsed sheath dynamics in a small cylindrical bore

The temporal evolution of the plasma sheath in small cylindrical bores and planar gaps is calculated for zero-rise-time voltage pulses. The ions are modeled as a cold, collisionless fluid, and the problem is reduced to the solution of two coupled, first-order, ordinary differential equations. These equations are solved analytically for the planar case, and numerically for the cylindrical case. The maximum ion impact energies are 50% and 36.8% of the maximum potential drop in the planar and cylindrical cases, respectively. Ion impact energy decreases with the square of the radius of the bore.

Monte Carlo study of photogenerated carrier transport in GaAs surface space-charge fields

A self-consistent ensemble Monte Carlo particle model to simulate the dynamics of photogenerated carrier transport in GaAs surface space-charge fields is presented. Dependence of transport parameters, such as relaxation processes, carrier screening, and velocity overshoot, on pulse width, injection level, and excitation energy is investigated and related to the experimentally observable potential drop across the surface space-charge region. In the present study, the high-field conditions are produced by charged surface states, and are to be modified by the redistribution of injected carriers. The photocarrier-induced change in the electric field, which can be measured using electro-optic sampling techniques, is found to be due to the spatial separation of the electron-hole pairs. The simulation results show that at a high injection level a maximum potential drop would result due to complete carrier screening of the surface charge field. The rate of change of this potential drop also would increase with increasing level of injection. These results are in good qualitative agreement with experimental observations. The simulation predicts an enhanced degree of velocity overshoot at decreasing injection energies and, at below L-minima excitation, a second increase in the potential resulting from the redistribution of carriers in the bulk. In this way, it is indicated that the study of the onset of photoconductivity can be used to probe such transport properties in GaAs.

On the Acceleration of Energetic Cosmic Particles by Electrostatic Double Layers

The capability of electrostatic double layers of accelerating charged particles to high energies is investigated. Starting from a one-dimensional relativistic double-layer model a two-dimensional relativistic double layer in a current filament is studied. It is found that the filamentary double layer has a maximum potential drop that depends both on the magnitude of the filamentary current and on the composition of the layer. The results are applied to two cosmic double layers-one in a solar electric circuit and another in a galactic circuit. If the layers are composed of protons and electrons, these particles may be accelerated to 1011 eV in the solar layer and to 1014 eV in the galactic layer. It is suggested that the solar double layer may account for the acceleration of solar cosmic rays while the galactic layer may contribute to the generation of cosmic radiation.