Electrical Potential Difference Research Articles

On a Method for Calculating Bending and Shear Vibrations of a Porous Piezoelement in the Low-Frequency Region

Introduction. Devices for collecting and storing energy from the external environment are low-power sources of electric energy that are actively used. The autonomous devices for monitoring the damaged condition of various structures include them as well. The working element of these devices is a piezoelectric generator (PEG) — a converter of mechanical energy into electrical energy. The design of PEG is associated with the preliminary construction of their mathematical and computer models, with the help of which the calculation and optimization of structures is carried out. One of the ways to model and calculate PEG is to develop approximate calculation methods based on applied theories. The applied theories for calculating bending vibrations of multilayer piezoactive plates are known and previously developed in the literature. However, in the scientific literature there is not enough information about bending and shear vibrations as a tool for improving the efficiency of engineering calculations of the described structures. The objective of this work was to develop an applied method for calculating bending and shear vibrations of piezoceramic plates, including porous ones.Materials and Methods. Piezoceramics PZT-4, including porous ones, were used as the piezoactive material of the plate. When using porous ceramics, the rigidity of the structure decreased to a greater extent than the piezoelectric modules, which made it possible to obtain a more effective PEG under mechanical action. The mathematical formulation was carried out within the framework of the linear theory of electroelasticity with plate polarization in thickness. The sides of the plate were electrodated, the right side was fixed, and a smooth contact in the vertical wall was set on the left side. Steady-state vibrations of the plate were caused by pressure on the front surfaces of the plate or the difference in electrical potentials at the electrodes. To calculate the characteristics of PEG, the authors proposed an applied theory based on hypotheses about the distribution of characteristics of the stress-strain state and the electric field.Results. Transverse vibrations of a piezoceramic plate in the low-frequency region (below the first bending-shear resonance) were studied. Due to the fact that the mathematical formulation was considered within the framework of the linear theory of elasticity, the problem was divided into the sum of two. The first one took into account the mechanical effect: a distributed load and a transverse force at the left end acted on the front surfaces of the plate, and the potentials at the electrodes were zero. In the second task, there were no mechanical loads, but the potential difference was set at the electrodes. Based on hypotheses about the distribution of deformations, mechanical stresses and electric potential, both problems were reduced to a system of ordinary differential equations and boundary conditions. Comparison with the results of calculations by the finite element method in the ACELAN package showed the adequacy of the proposed applied theory in the low-frequency region.Discussion and Conclusion. Since the formulation of the problem was considered in the linear theory of electroelasticity, and the low-frequency region was studied, the work succeeded in dividing the problem of bending-shear vibrations of a porous piezoceramic plate into two: bending — with mechanical action at zero potentials, and shear — when setting the potential difference and zero mechanical action. The corresponding hypotheses about bending and shear were used. Two systems of ordinary differential equations and boundary conditions, which were solved analytically without the use of “heavy” finite element packages, were constructed. To compare the results and confirm the adequacy of the proposed method, the finite element modeling of such tasks was carried out in a specialized ACELAN package. The comparison showed that the error in determining displacements and electric potential when using this approach, in the case of setting mechanical loads and potential differences, did not exceed 6%. The method developed in the paper can be applied in the design of piezoelectric generators for energy storage in the low-frequency region.

Delineating leachate-groundwater interaction at Gyadi-Gyadi dumpsite, Kano, using natural electromagnetic (EM) field detector and Vertical Electrical Sounding (VES)

Geophysical investigations are mostly used for hydrogeological studies, mining, geotechnical investigation and environmental surveys. Geophysical investigation of groundwater within the dumpsite is highly critical because the extent of interaction between leachate plume/contaminated zone and aquifer zones could significantly reduce groundwater quality. The textural complexity and clay content of soils could change their electrical properties, thus reflecting inconsistent resistivity values using the resistivity method. This research investigates the extent of leachate infiltration from waste dumpsite into groundwater at Gyadi-Gyadi Kano State, using natural Electromagnetic (EM) field and Vertical Electrical Sounding (VES) methods. Six natural EM profiles were obtained in various locations within the study area using PQWT-TC 150 model. Six VES data points were occupied along the EM profile lines using SAS 1000 ABEM resistivity meter. The two techniques employed revealed some intercalations of low resistivity (conductive) as well as very low electrical potential differences in the study area. The low resistivity media are mixtures of leachates into groundwater units, thereby creating formations from the surface to a depth of about 40 m. The first and second layers have experience leachate-aquifer interaction in the northern, southern and eastern parts of the study area to about 40 m depth, and the leachate-aquifer interaction has extended to the deep aquifer of about 70 m depth at the western part. Shallow aquifer has not been infiltrated by leachate at about >100 m away from the waste dumpsite. Therefore, for potable groundwater exploitation in this area, it is advised that boreholes should be sited >100 m away from the dumpsite, where leachate-aquifer interaction has attenuated. The natural EM field detector is evidently constrained by issues of over-generalization and summation of potential values, probably due to its relatively low resolution. Hence it might not be capable of precisely delineating varying geological units. In contrast, the resistivity method is able to delineate and discretize the subsurface into sub-units of different resistive zones. This implies that VES is better suited for accurately defining the true subsurface geology, while the NEF detector is effective for determining the extent of a leachate plume.

Exploring deeper groundwater in a dolomite aquifer using telluric electric frequency selection method geophysical approach

Several Telluric Electric Frequency Selection Method (TEFSM) geophysical equipment is now available for groundwater exploration. However, case studies on its application in different hydrogeological settings are limited. This study investigates the TEFSM geophysical approach's application to identify groundwater potential sites for drilling production boreholes in a dolomite aquifer in South Africa. Field tests comprised geophysical surveys using the TEFSM approach to collect vertical and horizontal electrical potential difference profile data from four sites. Evaluation of the potential difference profile data before borehole drilling indicated that two sites had groundwater potential. Two sites were therefore prepared for drilling. Corroboration of the survey data and drilling lithology show that the TEFSM investigated up to 230 m depth and delineated the thickness of the dolomite aquifer from 170 m to 210 m. The dolomite aquifer was delineated based on low EPD contrast ranging from 0.042 to 0.083 mV. The ability of the TEFSM to delineate the dolomite aquifer at a depth of 170–210 m highlights the technical capability of the approach in exploring deeper aquifers that are important to meet the rising demand for freshwater. More research is necessary to establish the EPD ranges of aquifer lithology in different hydrogeological settings. It will assist in the interpretation of the data by field practitioners to optimise the application of this TEFSM technology in groundwater investigations.

Analytical description of the ionic relaxation in the presence of surface adsorption

The temporal evolution of the surface electric field in a cell in the presence of ionic adsorption is investigated. The analysis is performed in the framework of the Poisson–Nernst–Planck model, based on the conservation of particles and the equation of Poisson for the actual electric potential across the cell, assuming that only the ions of a given sign are mobile. The adsorption is described using a kinetic equation of Langmuir’s type. The simple case of small adsorption is considered, in which the saturation effect can be neglected, and the fundamental equations of the model can be linearized. In this framework, the effective relaxation time describing the dynamics of the system is evaluated, as well as the profiles of the ions and the electric field. The case in which the sample is a half-space is first considered. A more realistic situation where the sample is a slab of thickness d, limited by two identical or different electrodes, is analyzed too. The difference in electric potential due to the adsorption phenomenon between the electrodes is determined. Our analysis shows that its time dependence, when the electrodes have different adsorption properties, is not monotonic.

Acute intracardiac electrogram changes and their relation to pulsed field ablation dose in porcine left ventricle

Abstract Background Pulsed field ablation (PFA) is an emerging cardiac ablation modality based on irreversible electroporation with promising preclinical and clinical results. Acute reduction of intracardiac electrograms (bipolar iEGMs) is consistently observed, similar to other ablation modalities, e.g. radiofrequency ablation. We and others have previously reported lesion size dependence on PFA dosing. However, the relevance of iEGM changes and their dependence on the PFA dose is not established. Furthermore, our study shows that unipolar iEGM signals may contain additional information about the effects of PFA in cardiac tissue. Purpose To quantify the effect of different PFA dosing on changes observed in bipolar and unipolar iEGMs within 5 minutes after the ablation. Methods In total, PFA was applied endocardially at 40 sites in the left ventricles of 8 pigs via a 5 mm tip catheter using a modified decapolar catheter in the inferior vena cava for current return (all electrodes). The following PFA doses (voltage and number of pulse trains) were used: 1000 V, 4 trains; 1300 V, 4 trains; 1500 V, 1 train; 1500 V, 4 trains; 1500 V, 8 trains; and 1500 V, 16 trains. For standard bipolar iEGMs (30 Hz – 500 Hz) the reduction in peak-to-peak amplitude after PFA was considered as a measure of the effect. In addition, unipolar iEGMs (0.5 Hz – 500 Hz) were decomposed into non-overlapping frequency sub-bands with Daubechies order 6 discrete wavelet transform (Figure 1A) allowing separate analysis in high-frequency (HF) and low-frequency (LF) ranges (63 Hz – 500 Hz and 0.5 Hz – 8 Hz, respectively). Results In total, 30 standard bipolar and 35 unipolar iEGMs (with at least 3.5 minutes of artefact-free post-ablation duration) were analysed. No dose dependency was observed for standard bipolar iEGMs within 5 minutes post-ablation (data not shown). However, the HF and LF content of unipolar iEGMs revealed opposing effects: a decrease in the HF and an increase in the LF content. Correlation with the dose was clearer in the LF content 3.5 minutes post-ablation, the difference being significant (p<0.05) between the lowest and the highest doses (Figure 1B and C). Discussion The decrease in HF content could reflect electrical silencing, ie. stunning of locally affected cardiomyocytes, most likely caused by irreversibly electroporated (ablated) cells located close to the catheter tip and by reversibly electroporated or otherwise temporarily silenced cells in adjacent tissue. The increase in LF content could reflect the current-of-injury effect, which is a broader area phenomenon derived from electrical potential differences between affected (reversibly and irreversibly electroporated) and non-affected regions. Conclusion Unipolar iEGMs acquired with a broadened frequency range and decomposed into HF and LF content provide new insight into the effects of PFA and correlate with PFA dosing in this pre-clinical porcine model.

Numerical analysis of electrothermoconvection of a dielectric nanofluid in a heated cavity

A numerical analysis of electrohydrodynamic (EHD) flow and heat transfer of nanofluid in a heated rectangular cavity is presented. A two-dimensional (2D) rectangular cavity heated from the bottom is considered. An electric potential difference is applied vertically, with the bottom wall acting as a high-voltage electrode, and the top wall is grounded. TiO2-25 # transformer oil nanofluid with nanoparticle volume fraction ranging from 0–5% is considered. The numerical model for EHD flow and heat transfer of nanofluid is implemented in the finite-volume method (FVM) based numerical framework of OpenFOAM. A single-phase approach based on the effective properties is adopted to model the nanofluids. A two-way coupled EHD flow model is employed to consider mutual interactions of flow and electric field variables. The flow and heat transfer behavior of nanofluids in the presence of an electric field is quantified with reference to the key parameters, electric Rayleigh number (T), and the nanoparticle volume fraction ϕ. The addition of nanoparticles increased the viscosity and marginally reduced the natural convective flow and heat transfer. However, EHD flow induced by the electric field aided in overcoming the weak natural convection flow in nanofluids. Results confirm that nanofluids’ net effective heat transfer rates are notably increased in the presence of the electric field. For the parameters under consideration, combining electric fields with nanofluids led to a significant heat transfer enhancement of up to 32.3%. The present study showcases the feasibility of combining passive heat transfer enhancement using nanoparticles and active heat transfer enhancement using EHD flow.

Influence of the Dielectric Constant on the Ionic Current Rectification of Bipolar Nanopores.

In this paper, we investigate how the dielectric constant, ϵ, of an electrolyte solvent influences the current rectification characteristics of bipolar nanopores. It is well recognized that bipolar nanopores with two oppositely charged regions rectify current when exposed to an alternating electric potential difference. Here, we consider dilute electrolytes with NaCl only and with a mixture of NaCl and charged nanoparticles. These systems are studied using two levels of description, all-atom explicit water molecular dynamics (MD) simulations and coarse-grained implicit solvent MD simulations. The charge density and electric potential profiles and current-voltage relationship predicted by the implicit solvent simulations with ϵ = 11.3 show good agreement with the predictions from the explicit water simulations. Under nonequilibrium conditions, the predictions of the implicit solvent simulations with a dielectric constant closer to the one of bulk water are significantly different from the predictions obtained with the explicit water model. These findings are closely aligned with experimental data on the dielectric constant of water when confined to nanometric spaces, which suggests that ϵ decreases significantly compared to its value in the bulk. Moreover, the largest electric current rectification is observed in systems containing nanoparticles when ϵ = 78.8. Using enhanced sampling, we have shown that this larger rectification arises from the presence of a significantly deeper minimum in the free energy of the system with a larger ϵ, and when a negative voltage bias is applied. Since implicit solvent models and mean-field continuum theories are often used to design Janus membranes based on bipolar nanopores, this work highlights the importance of properly accounting for the effects of confinement on the dielectric constant of the electrolyte solvent. The results presented here indicate that the dielectric constant in implicit solvent simulations may be used as an adjustable parameter to approximately account for the effects of nanometric confinement on aqueous electrolyte solvents.

Electrode Spacing Effects on the Capacitance of Glassy Carbon Electrodes in Aqueous Electrolytes

Matched glassy carbon electrodes in aqueous K2SO4 electrolytes were used to examine the effects of opposing electrode spacing on capacitive performance. Planar non-porous glassy carbon electrodes were used to avoid complications with porosity and roughness. Electrode spacing effects were examined in terms of device and individual electrode performance, using cyclic voltammetry, coupled with its deconvolution into residual, diffusional, and capacitive processes. Decreasing the spacing between electrodes led to a decrease in capacitive contributions, and a relative increase in diffusional and residual contributions, implying that individual electrodes were influencing the behaviour of each other. This is also consistent with the use of more dilute electrolytes. Electrode behaviour was modelled using the Poisson-Boltzmann equation, together with its integrated outputs of electric field and potential difference. For electrodes with the same amount of charge and a similar diffuse layer thickness, the electric field and potential drop was diminished because of their charge interaction. Conversely, it is shown that for a similar potential drop across the electrodes, the variable controlled in a cyclic voltammetry experiment, more charge accumulation is needed at the electrode-electrolyte interface to compensate for the counter charge generate from the opposing electrode.

Magnetic field based finite element method for magneto-static problems with discontinuous electric potential distributions

We introduce two finite element formulations to approximate magneto-static problems with discontinuous electric potential based respectively on the electrical scalar potential and the magnetic field. This work is motivated by our interest in Liquid Metal Batteries (LMBs), a promising technology for storing intermittent renewable sources of energy in large scale energy storage devices. LMBs consist of three liquid layers stably stratified and immiscible, with a light liquid metal on top (negative electrode), a molten salt in the middle (electrolyte) and a heavier liquid metal on bottom (positive electrode). Energy is stored in electrical potential differences that can be modeled as jumps at each electrode-electrolyte interface. This paper focuses on introducing new finite element methods for computing current and potential distributions, which account for internal voltage jumps in liquid metal batteries. Two different formulations that use as primary unknowns the electrical potential and magnetic field, respectively, are presented. We validate them using various manufactured test cases, and discuss their applications for simulating the current distribution during the discharge phase in a liquid metal battery.

Effect of hydrostatic pressure on the anodic dissolution process of X80 steel

Based on the fact that hydrostatic pressure affects chemical potentials of reaction species and the structure evolution of electric double layer (EDL), the authors propose a generalized-BV equation to analyze the anodic dissolution process of X80 steel in deep-sea environment. Combined with the results of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests, the following conclusions can be drawn: hydrostatic pressure can compress the electric double layer non-uniformly. The CHCD (CD: capacitance of diffused layer; CH: capacitance of compact layer) value increases first and then decreases with increasing hydrostatic pressure and reaches its maximum at 15 MPa, which is sure to influence the difference in electrical potential that drives chemical reaction at interface. Ultimately, the anodic dissolution current increases and then decreases with rising hydrostatic pressure at the same anodic polarized potential. Besides, low hydrostatic pressure may contribute to forming a dense corrosion product film and inducing a good inhibiting effect on further dissolution of X80 steel; However, when the hydrostatic pressure exceeds the critical value of 20Mpa, too high anodic dissolution rate along with promoted Cl− adsorption will deteriorate the protection performance of corrosion product film, and exacerbate local corrosion process.

Investigation of leachate infiltration on groundwater using georesistivity and natural electric field method around Ojoou-Olayanju’s dumpsite, Ada, southwestern Nigeria

The investigation of groundwater within the dumpsite environment is highly important in geophysical study. This is because the extent of interaction between the aquiferous medium and the contaminated zone could pose a serious threat to the end users especially humans when consumed. This research aimed at investigating leachate infiltration and its potential influence on groundwater at Ojoou Olayanju's Dumpsite using combining geo-resistivity and natural electric field (NEF) methods. In this study, five dipole-dipole and five NEF measurements were obtained using the Omega resistivity meters and PQWT-150 equipment respectively. The dipole-dipole method was deployed to obtain a 2D near-surface pseudo-section, and the NEF method was used to obtain the frequency curve and profile maps of electric potential difference. The dipoledipole results revealed the lateral variation in the resistivity along the traverses, suggesting that the materials within this near-surface are heterogeneous, and the closely spaced contours' varying gradients indicate fracture, which would facilitate potential leachate filtration. The NEF results revealed curves, and a subsurface image with respect to depth and profile distance. The points of convergence signals on the frequency model correspond to a medium with low resistivity on the profile map. The conductive medium is seen as being saturated with leachate, which suggests that very large portion of the study area around the dumpsite has been contaminated by leachate. Conclusively, it was revealed that leachate filtration is evidence especially at the topsoil and due to the presence of fractured zones, the groundwater quality is at risk of contamination by continuous filtration of leachate

Study on electric erosion in grease lubrication using optical interference method

Protecting bearings from electrical environments is crucial as modern industry evolves. With increasing exposure to electrical conditions, the risk of bearing failure due to electric erosion becomes a significant concern. To better understand how lubrication interacts with electric discharge in rolling bearings, an optical ball-on-disc tribometer was modified to measure film thickness under elastohydrodynamic lubrication (EHL) with electric discharge. The results of the study revealed that an electrical potential difference between the surfaces separated by the lubrication film leads to a reduction in film thickness, which can be attributed to the generation of Joule heating. As the electrical potential difference increases, the film thickness decreases even further, ultimately resulting in destructive electric discharge. Interestingly, sporadic discharge was observed in the region of minimum film thickness as the entrainment velocities increased prior to the occurrence of destructive discharge. In addition, the study also investigated the use of grease with a conductive additive, a double trifluoro-sulfonate ionic liquid. It was found that incorporating this ionic liquid into the grease can decrease the energy during discharge, thereby mitigating bearing electric erosion.

Fabrication of Microelectrodes, Suction Electrodes, and Focal Electrodes for Electrophysiological Recording in Drosophila.

Electrophysiological recording is a group of techniques used to record electrical field potentials generated by cells. These techniques rely on several types of electrodes, which can be manufactured in the laboratory. In intracellular recording, glass microelectrodes are used to pierce the cell membrane, and then to measure the electrical potential difference between the inside and the outside of the cell. Another technique, called loose patch or focal recording, is similar to intracellular recording but the electrode tip does not pierce into the cell membrane. Rather, the electrode tip is placed near a nerve or the postsynaptic side of the neuromuscular junction (NMJ) to record extracellular changes in local potentials. A third technique involves a suction electrode, which is used to draw part of the motor nerve into the electrode so that electrical pulses can be applied to elicit action potentials of the nerve. Suction electrodes are specifically used to evoke synaptic potentials at the Drosophila larval NMJ. This protocol details some basic methods for manufacturing microelectrodes used for intracellular recording and two-electrode voltage-clamp and loose patch electrodes used for focal recording. In addition, a method is provided for manufacturing homemade suction electrodes used for nerve stimulation.

Inactivation of microorganisms in foods by electric field processing: A review

The inactivation of microorganisms is critical for ensuring the safety of food products. Currently, emerging electrotechnologies have attracted considerable attention. These non-conventional technologies for food processing rely on thermal effects, non-thermal effects, or a combination of them to achieve this goal. Conventional pasteurization requires a heat transfer medium. It is often performed at high temperatures, leadinging to food quality degradation and flavour distortion. Electrotechnologies contain ohmic heating (OH), pulsed electric field (PEF), and induced electric field (IEF) treatment, which utilize both electric potential difference and current. Compared to conventional heating, they can reduce inactivation temperature thresholds and duration while retaining nutritional value, having a minimal negative impact on food quality, flavor, and color. Since the main purpose of food processing is based on microorganism inactivation to ensure food safety and storability, it is worthwhile to pay attention to the current application of electric field technologies. This paper reviews the research progress on the inactivation of microorganisms by OH, PEF, and IEF treatment. Additionally, it presents the generation characteristics of electrotechnologies and an outlook on future development.

Highly efficient elimination of organic contaminants by boron-doped biochar modified dual-cathode electro-Fenton system

Electro-Fenton (EF) process stands out as an energy-efficient and highly promising advanced oxidation technology for organic contaminants degradation. However, achieving optimal heterogeneous catalytic conditions for simultaneous H2O2 generation and spontaneous Fe2+ regeneration poses difficulties in conventional EF. This is due to the electric potential difference between H2O2 generation and Fe2+ regeneration at a single cathode. Therefore, the boron doped biochar modified dual-cathode EF (DCEF) system was designed in this work to overcome the defect of conventional EF system, which not only demonstrated outstanding accumulation of H2O2 (>300 mg L-1) but also exhibited a remarkable capability of degradation (>90 %). Furthermore, the system could also adapt to a broad pH range of 3–11. The superior doxycycline (DOX) degradation efficiency of DCEF system could be attributed to the dominant role played by C=O and BCO2 groups in the activation of H2O2 and subsequently generating reactive oxygen species (ROSs), as revealed by XPS analysis and DFT calculation. In addition, the DCEF system achieved an impressive TOC removal efficiency of 70.5 % and a minimal energy consumption (EC) of 0.32 kWh (g TOC)-1. Therefore, this work introduced a DCEF system to address the challenges of conventional EF system, which shed light on the design of wastewater treatment technology and lied the groundwork for a strategy of resource utilization.

Equivalent circuits in nanopore-based electrochemical systems

Single-nanopore membranes constitute physical models for biological ion channels and are also central to electrochemical energy transducers, logical circuits in sensors and actuators, and converters in bioelectrical interfaces. The membrane potential, defined as the electrical potential difference established between two different ionic solutions separated by the membrane, is crucial for the electrical coupling of nanofluidic concentration cells to electronic components such as load capacitors and resistors. Here we analyze, theoretically and experimentally, the validity of basic principles governing electric circuit theory such as the Thévenin equivalent circuit, the additivity of voltages and resistances, and the Millman theorem in nanopore-based concentration cells. To this end, we consider a wide range of practical conditions with respect to salt concentrations, nanopore asymmetry, electrical capacitances, and series and parallel arrangements. Additionally, we investigate the scaling of the single pore results to the multipore case. The results obtained suggest that basic circuit models offer approximate tools to guide the analysis of the nanofluidic concentration cells.

Stable photothermal conversion in single-walled carbon nanotube device with pn-junction under uniform sunlight irradiation

N-type single-walled carbon nanotube (SWCNT) films with high air stabilities have attracted significant attention for their potential application in SWCNT devices featuring pn-junctions for power generation. However, SWCNT devices must be locally heated or formed into suspended structures to generate a temperature difference and produce output power. In this study, pn-junction SWCNT films were fabricated via vacuum filtration and subsequently attached to a polyimide substrate, enabling the creation of SWCNT devices without the need for suspended structures. Upon uniform irradiation with artificial sunlight, the SWCNT device produced a stable output voltage and short-circuit photocurrent. A thermographic image showed the emergence of a temperature gradient originating from the center of the SWCNT film and extending to the edge of the polyimide substrate. This phenomenon can be attributed to the higher optical absorption of SWCNT films compared to that of polyimide substrates. Consequently, the diffusion of carriers within the device generated an electric potential difference. Therefore, the SWCNT device generated a temperature gradient and yielded output power under uniform sunlight irradiation. These findings may aid in the development of facile and flexible optical devices, including photodetectors and hybrid devices integrating solar cells.

Thermodynamic analysis of nano-electrospray induced gas jets

Nano-electrospray (nES) produces a plume of charged liquid droplets which have drag interactions with the surrounding gas after they are emitted from a source capillary. The resulting induced gas flow has often been considered unimportant, but we have demonstrated that a gas microjet of significant velocity up to 10s of m/s can be produced. In this work we present a thermodynamic framework that enables analysis of gas jet generation from electrosprays and introduce the important metrics for such analysis, effectiveness (a measure of momentum transfer from the electrosprayed aerosol to gas) and efficiency (a measure of energy conversion from electrical energy generating the electrospray to gas kinetic energy). This analytical framework is applicable to any two-phase flows consisting of discrete conservative-force-driven particles which exchange momentum with an inert, otherwise quiescent fluid medium to yield a co-flowing two-phase jet. We apply this framework to sprays of water from nano-electrospray emitters to demonstrate that increasing the applied electrical potential difference, increasing liquid mass flowrate, and decreasing droplet size all can increase electrospray induced gas jet strength, but only the latter two do so while also increasing the momentum transfer effectiveness and energy conversion efficiency.

Applying module analysis to the Brief Electricity and Magnetism Assessment

The Brief Electricity and Magnetism Assessment (BEMA) is a multiple-choice instrument commonly used to measure introductory undergraduate students’ conceptual understanding of electricity and magnetism. This study used a network analysis technique called modified module analysis-partial (MMA-P) to identify clusters of correlated responses, also known as communities, within 12214 BEMA responses. MMA-P identifies both communities related to the structure of the instrument and communities related to incorrect student reasoning. Every community resulting from MMA-P came from blocked items; groups of items that all refer to the same physical system. The most prevalent and consistently selected incorrect answers involved the relation of the electric field to the electric potential difference. The community structure identified in the Conceptual Survey of Electricity and Magnetism (CSEM) by a prior MMA-P study on items shared by the CSEM and BEMA differed because of the different incorrect responses available in the two instruments. One pair of items in the BEMA involving the induced electric field by a changing magnetic field showed evidence of students applying a variety of incorrect models; the scores on these items indicate their inclusion in the instrument should be reconsidered. Published by the American Physical Society 2024

Harmonic and anharmonic studies on THz spectra of two vanillin polymorphs

Polymorphism commonly exists in organic molecular crystals. The fingerprint features in low-frequency vibrational range are important information reflecting different intermolecular interactions of polymorphs. Interpreting these features is very helpful to understand vibrational property of polymorphs and reveal the thermodynamic stability. In this work, the low-frequency vibrations of form I and II of vanillin are investigated using terahertz time-domain spectroscopy. Static DFT calculation and ab initio molecular dynamics (AIMD) are employed to interpret their low-frequency vibrations of both forms in harmonic and anharmonic ways, respectively. Their low-frequency vibration characteristics in harmonic calculations are discussed, and anharmonic mode couplings between OH bond stretch and the stretching and bending motion of hydrogen bonds are uncovered. Moreover, the thermodynamic energies including electronic potential energy and vibrational/kinetic energy arising from nuclear motions are calculated. The result reveals that the stability order of the two forms is mainly dependent on their electric potential energy difference.