Charged Plates Research Articles

A linear shaped charge cutting model for brittle flat plates

The dynamic response and damage fracture of brittle materials under explosive cutting have always been important research issues in the fields of military, aerospace, and other engineering fields. In this paper, a linear shaped charge cutting model for explosive cutting of brittle materials is proposed. This model suggests that explosive cutting is caused by the combined effects of jet penetration, spallation, and impact fracture. Theoretical calculation models for jet penetration, spallation, and impact fracture were constructed, and the concept of impact strength was introduced to establish dynamic mechanical performance parameters for brittle materials. A calculation program for explosive cutting of brittle materials was developed using the Python language, which can calculate the jet penetration depth, spallation thickness, and impact fracture thickness by inputting parameters such as the size and mechanical properties of the linear shaped charge and target plate, and determine whether the target plate can be successfully cut. Subsequently, a series of explosion cutting experiments and numerical simulations for brittle target plates were conducted to verify the accuracy of the calculation program. The results indicate a high degree of consistency between simulation, experimentation, and program calculation results. This work can provide guidance and promotion for the design and application of explosive energy harvesting cutters.

A model for zwitterionic polymers and their capacitance applications.

Zwitterions have been shown experimentally to enhance the dielectric constant of ionic media, owing to their large molecular dipole. Many studies since explored the enhancement of ionic conductivity with zwitterion additives as well as bulk behavior of zwitterions. Here, we examine the capacitance behavior of zwitterions between charged parallel plates using a mean-field theory. Employing only chain connectivity of a cation and anion with neutral monomers in between with mean-field electrostatics, we show that our model captures the high-dielectric behavior of zwitterions. We also predict an optimum in the capacitance of zwitterionic media as a function of chain length. To address the issue of zwitterion screening near charged surfaces, we demonstrate that zwitterions simultaneously partially screen charged walls and act as a pure dielectric that propagates the electric field far from the surface. Moreover, we show that salt solutions with zwitterionic additives outperform the energy density of both salt-only and zwitterion-only capacitors. We find that salt-only capacitors perform better at low applied potential, whereas salt capacitors with zwitterionic additives perform better at high applied potential.

Nonlinear Poisson-Boltzmann solutions for charged parallel plates: When opposite charges repel.

I present an exact solution of the Poisson-Boltzmann equation for two parallel plates and discuss the solution properties. I discuss in more detail plates with opposite charges: In this case, there are two critical separations, Lc,1 < Lc,2. For separations less than Lc,1, the force between plates is repulsive. It switches to attractive at Lc,1, but with the electric potential having the same signon both plates. For L > Lc,2, the force remains attractive, and the potential at the plates has the same signas the charge on each plate. I also describe charge regulation, determined by pKa, and provide formulas for both the critical distance where oppositely charged plates repel and their charging process. The implications of these results for the nanoparticle assembly, as driven by electrostatic interactions, are also discussed.

Strong-coupling effective-field theory for asymmetrically charged plates with counterions only.

We are interested in rationalizing the phenomenon of like-charge attraction between charged bodies, such as a pair of colloids, in the strong coupling regime. The two colloids are modelled as uniformly charged parallel plates, neutralized by mobile counterions. In an earlier work [Palaia etal., J. Phys. Chem. B 126, 3143 (2022)1520-610610.1021/acs.jpcb.2c00028], we developed an effective-field theory for symmetric plates, stemming from the ground-state description that holds at infinite couplings. Here, we generalize the approach to the asymmetric case, where the plates bear charges of the same sign, but of different values. In the symmetric situation, the mobile ions, which are localized in the vicinity of the two plates, share equally between both of them. Here, the sharing is nontrivial, depending both on the coupling parameter and the distance between the plates. We thus introduce a counterion occupation parameter that is determined variationally to ensure minimum of the free energy. The analytical results for the pressure as a function of the plate-plate distance d agree well with our Monte Carlo data, in a large interval of strong and intermediate coupling constants Ξ. We show in particular that within this description there exists a range of large distances at which the attractive pressure features a 1/d^{2} behavior.

Strange property of physical quantities of some petal shape objects

We study various physical quantities of objects with petal shapes. N-petal shapes exhibit N-fold rotational symmetry. Furthermore, they might have an additional characteristic: the equation defining their boundaries could be represented by F(N θ). We will show that physical quantities of objects with these characteristics may show strange properties. By ‘physical quantities’, we refer to aspects such as electric potential and electric field due to a charged petal-shaped plate or cylinder on the rotation axis, their mass and moment of inertia. We are going to show that for such objects, these physical observables do not depend on the number of petals, N. This intriguing result has a simple reason.

Concentrated aqueous solutions of multivalent macroions enhance the electrical double layer capacitance and differential capacitance of a planar supercapacitor

The electrostatic properties of the ionic cloud, or electrical double layer, neutralizing a charged electrode are relevant to improve the storage of electrical energy and the efficiency of supercapacitors and/or batteries using coulombic fluids. In this work, we study the microscopic profiles of charged particles, integrated surface charge density, and the mean electrostatic potential associated to a pair of infinite parallel plates uncharged or, else, with opposite charge, in the presence of a salt-free aqueous solution constituted by big positive macroions and small anions, which interact via an explicit electrostatic coulombic potential and are dissolved in an implicit solvent. The particle profiles and the integrated surface charge density associated to Monte Carlo simulations and integral equations theory display an oscillatory or non-monotonic behaviour producing the phenomena of charge inversion and charge reversal. These phenomena are not predicted by the non-linear Poisson-Boltzmann equation, which highlights the importance of ion correlations and ionic volume excluded effects. The phenomenon of surface charge amplification is observed near the point of zero charge, which is yielded by the particle size-asymmetry. For a fixed concentration of macroions, a monotonic increase of the mean electrostatic potential difference between the charged parallel plates is predicted by simulations and theories as a function of the electrodes' charge. For a fixed surface charge density, the capacitance of the parallel plates capacitor increases when the ionic strength of the macroion's solution increases. A concavity inversion and an augment of the differential capacitance is also observed for an electrode near the point of zero charge as function of the macroion's concentration.

Accurate approximations for the shape-dependent electrostatic energy of a uniformly charged rectangular plate

We consider a simple approach to calculate approximately the stored electrostatic energy of a uniformly charged rectangular plate. It is expected that the method may work reasonably well when one dimension of the rectangular plate is considerably larger than the other one (for instance, when length of rectangular plate is much larger than its width). However, to our surprise, we find out that the results obtained are not only simple and accurate, but they also apply to any arbitrary shape of the rectangular plate including the square shape.

Effect of stacking position on drying rate during radio-frequency vacuum combined with mechanical press drying of Douglas-fir and Radiata pine

In this study, the effect of stacking position in the dryer on the drying rate during radio-frequency vacuum combined with mechanical press (RF/VP) drying was investigated for Douglas-fir and Radiata pine. Drying test was performed at a temperature of 40 °C using RF/VP dryer with approximately 3 m3. The results showed that the stacking position has a significant effect on the drying rate, with a more pronounced decrease in drying rate as the stacking position of specimens approaches the ground plate. Previous moisture content was an important factor in determining the drying rate in both species. The MC distribution of specimens in the dryer before drying was very irregular, but over time, specimens stacked on the RF charge plate side in the dryer tended to have lower MC distributions than those stacked on the ground plate side, which was serious at the specimens in contact with the upper ground plate. In addition, as the MC decreases below the fiber saturation point during RF/VP drying, the difference in MC distribution within the dryer according to the stacking position became clearer. These findings provide new insights into the effect of stacking position on drying rate during the RF/VP drying and are expected to improve RF/VP drying technology.

Clay micromechanics: Numerical modelling of electrical double-layer interactions to develop particle-based models for clay

Discrete element modelling of clays requires defining the interaction energy between two particles. The Derjaguin, Landau, Verwey and Overbeek (DLVO) theory combining the effect of the van der Waals forces and the Coulombic forces due to the double layer of counterions provides a widely accepted framework to characterise the pair potential energy. Solutions of the Poisson-Boltzmann (PB) equation to quantify the Coulombic forces are only available for the case of infinitely extended and uniformly charged facing plates (1D conditions). However, these assumptions are not representative of a clay particle system. Particles should be represented by platelets of finite size and finite thickness, with different charges between the edge and the basal planes. This paper addresses the problem of deriving the Coulombic interaction forces for plates of finite size and thickness in 3D configuration by solving the Poisson-Boltzmann equation numerically via the Finite Element Method (FEM). It is shown that 2D particles (plates of infinitesimal thickness) provide an adequate representation of Coulombic interaction as long as the particles are uniformly charged. The advantage of 2D particles is to reconcile numerical modelling with analytical solutions available in the literature. The use of 2D particles is questionable when considering different charges between basal planes and edges.

Operando analysis of the positive active mass of lead batteries by neutron diffraction

We have analysed, through neutron diffraction experiments with the volume-gauge technique, the operando performance of lead cells composed of industrial positive and negative electrodes, previously tank formed in the manufacturing plant. The cells, 6.7 cm × 11.5 cm in surface, comprised a 3.4 mm thick positive electrode sandwiched between two 2.3 mm thick negative electrodes. The electrolyte was sulphuric acid diluted in water, both deuterated, and the separators were industrial grade absorptive glass mat (AGM). The experiments, carried out using the VULCAN instrument at the Oak Ridge National Laboratory (TN, USA), showed the evolution of α-PbO2, β-PbO2 and PbSO4 phases in the positive active mass during charge/discharge cycling, comparing the behaviour of fresh and cycled cells. No evidence of PbSO4 phase in fully charged plates or PbO in any state of charge were found above 1% by weight. Significant inhomogeneity of phase distribution and transition rates inside the positive electrode was observed. The experiments allowed estimation of the energy efficiency by comparing the external energy provided to the cell with the energy stored in the PbSO4 to PbO2 transformations.

A recurrent neural network model for structural response to underwater shock

Simulating the dynamic response of structures to shock involves numerical models that can require significant effort and computational resources to create and solve. This can make accurate naval platform vulnerability analyses involving a large number of simulations impractical and motivates the development of efficient surrogate models for shock and blast effects. This paper presents a novel approach to predicting the response of a floating structure to underwater shock based on machine learning (ML). Velocity time-series for a rigid floating plate subjected to underwater shock and cavitation effects are calculated for a range of charge mass, standoff distance and plate mass per unit area values using a coupled Eulerian–Lagrangian (CEL) numerical model. The computed motions are used to train a recurrent neural network (RNN) to predict the plate response including the effect of reloading due to the cavitation closure pulse. The RNN predicts plate responses from a test set of CEL model instances with a mean value of mean-squared errors between the ML and CEL model velocities, normalized with respect to the velocity ranges, of 1.5 × 10-4.

Exact analytical results for the electrostatic potential due to a uniformly charged finite rectangular plate

We explain a general mathematical method that allows one to calculate the electrostatic potential created by a uniformly charged rectangular plate with arbitrary length and width at an arbitrary point in space. Exact analytical results for the electrostatic potential due to a uniformly charged finite rectangular plate are shown for special cases in order to illustrate the implementation of the formalism. Results of this nature are very important to various problems in physical sciences, applied mathematics, and potential theory.

Mesoscopic theory for ionic liquids and concentrated electrolytes in a slit with charged walls

Concentrated electrolytes and ionic liquids confined between parallel charged plates are studied within a theory combining density functional and field-theoretic methods, extended in this work to the slit geometry. We obtain charge- and density profiles, as well as the excess grand potential as a function of the slit width L in the self-consistent Gaussian approximation. For large density of ions, the obtained disjoining pressure exhibits oscillatory asymptotic decay for increasing L, with the decay length that agrees with the results of recent experiments. On a general level, we show that if the charge density decays with a distance from a charged surface in the oscillatory way, then the electrostatic energy of the slit with charged walls also decays with L in an oscillatory way with the same characteristic lengths. The oscillatory decay disagrees with the asymptotic repulsion obtained in the surface force balance experiments. We argue that in the experiment, the lack of the attraction between the confining surfaces for large L may follow from slow ordering of the isotropic fluid absorbed in the expanding slit into layers with alternating charge.

An investigation into shale swelling inhibition properties of dodecyltrimethylammonium chloride (DTAC) for water-based drilling fluids

Shale formations adsorb water and swell when they are in contact with water-based drilling fluids due to the content of active clay minerals. Shale swelling in the well wall is one of the main challenges of drilling operations and causes many problems and damages. Modifying drilling mud with shale swelling inhibitors is one of the solutions to this challenge. Recently, amines and their derivatives have been considered by researchers due to their ability to control the swelling of shale layers and the range of properties that can be adapted to any drilling conditions. In this study, Dodecyltrimethylammonium Chloride (DTAC) was investigated as a new shale stabilizer and swelling inhibitor. Various tests such as bentonite sedimentation, bentonite inhibition, shale sample recovery and dynamic linear swelling were used for this study. Wettability, zeta potential, isothermal water adsorption and thermogravimetric analysis (TGA) tests were performed to evaluate the mechanism of action of this amine-based shale swelling inhibitor. Based on the results, DTAC shows good inhibition power in controlling and reducing the swelling of shale and bentonite samples at both low and high temperatures, even at low concentrations. DTAC is well-compatible with other common additives in drilling fluids. On the other hand, this amine shows a relatively stronger function than Cetyltrimethyl Ammonium Bromide (CTAB) and Ammonium Chloride (NH4Cl). Adsorption of DTAC molecules on the surface of charged plates of bentonite particles reduces the negative charges of these plates, makes inaccessible places available on the plates of water molecules, increases their hydrophobicity and finally reduces the sensitivity of surfaces to adsorption of water molecules, which leads to stabilization of shale samples and bentonite particles against contact with aqueous media.

Identification of Compounds Preventing A. fumigatus Biofilm Formation by Inhibition of the Galactosaminogalactan Deacetylase Agd3.

The opportunistic fungus Aspergillus fumigatus causes a set of diseases ranging from allergy to lethal invasive mycosis. Within the human airways, A. fumigatus is embedded in a biofilm that forms not only a barrier against the host immune defense system, but also creates a physical barrier protecting the fungi from chemicals such as antifungal drugs. Novel therapeutic strategies aim at combining drugs that inhibit biofilm synthesis or disrupt existing biofilm with classical antimicrobials. One of the major constituents of A. fumigatus biofilm is the polysaccharide galactosaminogalactan (GAG) composed of α1,4-linked N-acetylgalactosamine, galactosamine, and galactose residues. GAG is synthesized on the cytosolic face of the plasma membrane and is extruded in the extracellular space, where it is partially deacetylated. The deacetylase Agd3 that mediates this last step is essential for the biofilm formation and full virulence of the fungus. In this work, a previously described enzyme-linked lectin assay, based on the adhesion of deacetylated GAG to negatively charged plates and quantification with biotinylated soybean agglutinin was adapted to screen microbial natural compounds, as well as compounds identified in in silico screening of drug libraries. Actinomycin X2, actinomycin D, rifaximin, and imatinib were shown to inhibit Agd3 activity in vitro. At a concentration of 100 µM, actinomycin D and imatinib showed a clear reduction in the biofilm biomass without affecting the fungal growth. Finally, imatinib reduced the virulence of A. fumigatus in a Galleria mellonella infection model in an Agd3-dependent manner.

Polyoxometalate ionic liquid between graphene oxide surfaces as a new membrane in the desalination process: a molecular dynamics study.

In this study, the performance of the positioning of polyoxometalate ionic liquid ([Keggin][emim]3 IL) between graphene oxide (GO) plates with different concentrations (nIL-GO (n = 1-4)) were examined in the desalination process at different external pressures using molecular dynamics (MD) simulations. The use of Keggin anions with charged GO layers was also investigated in the desalination process. The potential of the mean force, average number of hydrogen bonds, self-diffusion coefficient, and angle distribution function were calculated and discussed. The results showed that although the presence of polyoxometalate ILs between the GO plates decreases water flux, they efficiently increase salt rejection. The positioning of one IL increases salt rejection to two times at lower pressure and increases it up to four times at higher pressure. Moreover, the positioning of four ILs results in almost complete salt rejection at all pressures. The use of only Keggin anions between the charged GO plates (n[Keggin]-GO+3n) presents more water flux and a smaller salt rejection rate than the nIL-GO systems. However, the n[Keggin]-GO+3n systems show a nearly complete salt rejection at high concentrations of Keggin anions. These systems also have a smaller risk of the contamination of the desalinated water by the probable escape of cations from the nanostructure to the desalinated water at very high pressures.

Target-Size-Dependent Application of Electrostatic Techniques for Pest Management in Greenhouses

Two new electrostatic devices were developed to manage greenhouse insect pests. One was an electrostatic insect catcher (EIC) to trap small flying pests, and the other was an arc-discharge zapper (ADZ) to kill larger insects emerging from soil beds. The EIC consisted of negatively charged insulated conductor plates (NIPs) and grounded conductor plates (GCPs), which were alternately arrayed in parallel at defined intervals. The ADZ had the same framework as the EIC, except that the NIPs were replaced with negatively charged non-insulated iron plates (NNPs). The EIC formed a non-discharging electric field between the NIP and GCP to create an attractive force to capture insects. By contrast, the ADZ formed a discharge-generating electric field between the NNP and GCP that killed insects. The EIC was effectively applied to small pests, such as whiteflies, thrips, leaf miners, winged aphids, and shore flies, that can pass through the conventional insect-proof nets installed on greenhouse windows. The ADZ was effective for adult houseflies emerging from pupae in soil beds. Our electrostatic devices are useful for controlling insect pests of different sizes.

Graphene Nanoribbon Bending (Nanotubes): Interaction Force between QDs and Graphene

Carbon materials in different shapes—such as fullerene molecules (0D), nanotubes and graphene nanoribbons (1D), graphene sheets (2D), and nanodiamonds (3D)—each have distinct electrical and optical properties. All graphene-based nanostructures are expected to exhibit extraordinary electronic, thermal, and mechanical properties. Moreover, they are therefore promising candidates for a wide range of nanoscience and nanotechnology applications. In this work, we theoretically studied and analyzed how an array of quantum dots affects a charged graphene plate. To that end, the array of quantum dots was embedded on the graphene plate. Then, considering the interaction between QDs and graphene nanoribbons, we transformed the charged plate of a graphene capacitor into a nanotube using the bipolar-induced interaction and the application of an external electromagnetic field. In this work, the dimensions of the graphene plate were 40 nm × 3100 nm. The bending process of a charged graphene plate is controlled by the induced force due to the applied electromagnetic field and the electric field induced by the quantum dots. Finally, using the predetermined frequency and amplitude of the electromagnetic field, the graphene nanoribbon was converted into a graphene nanotube. Since the electrical and optical properties of nanotubes are different from those of graphene plates, this achievement has many practical potential applications in the electro-optical industry.

Separation behavior of sieved endosperm-enriched oat fractions via tribo-electrostatic approach

Endosperm-enriched oat fraction passed through 106-μm aperture size sieving of oat groats was further processed by dry and chemical-free tribo-electrostatic separation approach for protein enrichment. The sieved oat flour consisting of both bran and endosperm particles was fluidized in dry air to be tribo-charged in a polytetrafluoroethylene (PTFE) tube before being separated under an external electric field into protein-rich and protein-depleted fractions. The effects of airflow rate and electric field strength were assessed by conducting fifteen tribo-electrostatic separations at five different plate voltages of ±1, ±3, ±7, ±12, and ± 15 kV, as well as three different airflow rates of 7, 10, and 14 l per minute (LPM), providing laminar, transient, and turbulent conditions in the tribo-charger tube, respectively. All fractions attracted to the negatively charged plate (i.e., NCP fraction) were enriched in protein. However, the fractions absorbed on the positively charged plate (PCP fraction) or collected by gravity at the bottom of the separation chamber (i.e., CB fraction) were all depleted of proteins. Higher protein enrichments were observed for NCP fractions at laminar airflow rate, where the lowest yields and protein separation efficiencies were obtained. Increasing plate voltages slightly reduced the NCP fractions' protein content but significantly improved their yields and protein separation efficiencies. Therefore, a laminar airflow rate of 7 LPM and a high plate voltage of ±12 kV was selected as the best separation conditions for sieved oat flour. The SEM images of the NCP fraction obtained at 7 LPM and ± 12 kV showed the presence of bran and endosperm particles, while the PCP and CB fractions were depleted of bran particles. The full compositional analysis of the fractions produced at 7 LPM and ± 12 kV conditions showed the highest percentage of dietary fiber content in the PCP fraction. A negative correlation was observed between the protein content and mean particle size (D50) of the electrostatically separated fractions at the laminar and transient airflow rates. However, the protein-rich NCP fractions had the largest particle sizes at the turbulent airflow rate due to particle agglomeration and intense particle-particle interactions. An indirect offline approach was adapted to assess the charging behavior of all electrostatically separated fractions as functions of their protein content and particle sizes. All NCP fractions acquired higher charge density values than other fractions, which could be attributed to their higher protein contents. An online tribo-charge analysis method should be developed to assess the particle-particle interactions in the tribo-charger tube during electrostatic separation.

Theory of Ionic Diffusion in Water-saturated Porous Solid with Surface Charge

The theory of ionic diffusion in water-saturated porous solids with surface electric charges has been constructed by using the general theory of diffusion, Gauss’s law, and the condition of electrical neutrality. The theory derives the diffusion rate of ions not from the gradient of the ionic concentration but from the gradient of the chemical potential of ions. The chemical potential is obtained by rigorously solving the Poisson-Boltzmann equation that is derived by connecting the general theory of diffusion and the condition of electrical neutrality with Gauss’s law. Application of the theory to the ionic diffusion from an outer solution into a pore solution surrounded by two parallel charged plates indicates that the maximum concentration of ions penetrable into the pore solution is lower than that of the outer solution, though the penetration rate is not much affected by the surface charge. A simple approximation method of calculating the diffusion rate without solving the Poisson-Boltzmann equation is presented.