Closed-circuit Conditions Research Articles

Kinetic study on the degradation of Acid Red 88 azo dye in a constructed wetland-microbial fuel cell inoculated with Shewanella oneidensis MR-1.

Removal of Acid Red 88 (AR88) as an azo dye from the synthetic type of wastewater was studied in a laboratory-made constructed wetland microbial fuel cell (CW-MFC) inoculated with Shewanella oneidensis MR-1 (SOMR-1). Plant cultivation was implemented using a typical CW plant known as Cyperus alternifolius. The complexity of the SOMR-1 cell membrane having different carriers of electrons and H+ ions gives the microbe special enzymatic ability to participate in the AR88 oxidation link to the O2 reduction. Nernst equation developed based on analyzing the involved redox potential values in these electron exchanges is describable quantitatively in terms of the spontaneity of the catalyzed reaction. Power density (PD) at 100mg/L of the AR88 under closed-circuit conditions in the presence of the plant was 11.83 mW/m2. Reduction of internal resistance positively affected the PD value. In determining degradation kinetics, two approaches were undertaken: chemically in terms of first- and second-order reactions and biochemically in terms of the mathematical equations for rate determination developed on the basis of substrate inhibitory concept. The first-order rate constant was 0.263h-1 without plant cultivation and 0.324h-1 with plant cultivation. The Haldane kinetic model revealed low ks and ki values indicating effective degradation of the AR88. Moreover, the importance of acclimatization in terms of the crucial role of lactate was discussed. These findings suggest that integrating the SOMR-1 electrochemical role with CW-MFC could be a promising approach for the efficient degradation of azo dyes in wastewater treatment.

Electrochemical Oxidation of Glyphosate Using Graphite Rod Electrodes: Impact of Acetic Acid Pretreatment on Degradation Efficiency

The uncontrolled use of herbicides such as glyphosate (GLY) (N-phosphonomethylglycine) in agricultural production has resulted in its presence in water bodies and in negative impacts on the environment and public health. On the frame of understanding the interaction between GLY and graphite rod surfaces, this contribution relies on the study of electrochemical responses of different GLY concentrations by cyclic voltammetry under both open and closed-circuit conditions. Furthermore, the effect of the electrodes’ electrochemical pretreatment with acetic acid on the double-layer capacitance and the subsequent surface functionalization of the graphite rod materials were evaluated. The increment in GLY concentration showed a decrease in the electrochemical oxidation response associated with the adsorption of the contaminant on the surface of the graphite rod electrode and the concomitant blockage of the active sites. Electrochemical pretreatment of the electrodes with acetic acid and GLY concentration play crucial roles in electric double-layer formation due to their ability to interact with both positive and negative electrical charges. By means of optical microscope observations and Fourier Transform Infrared Spectroscopy analysis, it was possible to detect the formation of oxygenated functional groups on the electrode surfaces after the electrochemical pretreatment. Through a 23 factorial design analysis in repetition, the factors significant in the degradation of GLY were identified. The high degradation of GLY with the pretreated electrodes can be attributed to the preferential adsorption of the zwitterionic molecule at the interface, which allowed great direct oxidation of the contaminant on the anode’s surface.

Electrochemical Characteristics of Microbial Fuel Cells Operating with Various Food Industry Wastewaters

In the present work, four different wastewaters from the food industry were used in parallel, in four identical dual-chamber MFCs, with graphite granules as anodic electrodes. Specifically, a mixture of hydrogenogenic reactor effluents (effluents from a dark fermentation reactor fed with cheese whey (CW), for hydrogen production), CW, and a mixture of expired fruit juices and wastewater from the confectionery industry were simultaneously used in MFCs to evaluate the effect of the type of effluent/wastewater on their efficiency. An electrochemical characterization was performed using electrochemical impedance spectroscopy measurements under open- (OCP) and closed-circuit conditions, at the beginning and end of the operating cycle, and the internal resistances were determined and compared. The results showed that the highest OCP value, as well as the highest power density (Pmax) and Coulombic efficiency (εcb) at the beginning of the operating cycle, was exhibited by the MFC, using a sugar-rich wastewater from the confectionery industry as substrate (sugar accounts for almost 92% of the organic content). This can be correlated with the low internal resistance extracted from the Nyquist plot at OCP. In contrast, the use of CW resulted in a lower performance in terms of OCP, εcb and Pmax, which could be correlated to the high internal resistance and the composition of CW, a substrate rich in lactose (disaccharide), and which also contains other substances (sugars account for almost 72% of its organic content, while the remaining 28% is made up of other soluble compounds).

Experimental and computational thermoelectric generator for waste heat recovery for aeronautic application

This study is a comprehensive exploration of a polymer nanocomposite-based Thermoelectric Generator (TEG) developed within the European project InComEss, specifically designed for aeronautical applications. The focus lies on evaluating the TEG's performance under thermal conditions representative of various aircraft flight stages. The TEG module, consisting of four sections with 17 p-n strips each, is constructed from aerospace-grade polycarbonate, exhibiting dimensions of 50 * 1 * 0.3 mm. In the laboratory phase, the TEG's performance is systematically assessed through a series of experiments. Temperature gradients, ranging from −15 °C to 55 °C, emulate conditions experienced during ascending and descending flight stages. The results indicate promising outcomes, showcasing the potential viability of polymer-based TEGs for aeronautical applications. Specifically, temperature gradients of 40–70 °C, representative of atmospheric conditions and wing leading edge skin conditions, are applied across four test trials. The model validation demonstrates creditable agreement between computational outcomes and experimental data. Insights gained from COMSOL Multiphysics simulations includes temperature distribution, electric potential, and flow dynamics. Simulations conducted under varied temperature ranges provide valuable insights into the TEG's performance variability. Key findings include temperature distribution profiles, electric potential outputs under open and closed-circuit conditions, and a detailed flow analysis within a controlled thermal environment. The validated computational model not only enhances understanding of the TEG's behaviour, but also establishes a foundation for optimizing design parameters to enhance thermoelectric efficiency. The error analysis underscores the model's reliability, exhibiting an average error of 5.68 % between computational and experimental results, reinforcing its suitability for scientific investigations of this nature.

In Situ Utilization of Electron-Enhanced Degradation of Azo Dyes in a Constructed Wetland–Microbial Fuel Cell Coupling System

In this study, a constructed wetland was coupled with a microbial fuel cell to establish a coupled system known as the constructed wetland–microbial fuel cell (CW–MFC), utilized for the treatment of X-3B azo dye wastewater at varying concentrations. Experimental results indicated that the anodic region made the primary contributions to the discoloration of azo dyes and COD removal, with a contribution rate of 60.9–75.8% for COD removal and 57.8–83.0% for the effectiveness of discoloration. Additionally, the role of plants in the constructed wetland area could achieve the removal of small molecular substances and further discoloration. In comparison to open-circuit conditions, under closed-circuit conditions the CW–MFC effectively degraded X-3B azo dye wastewater. Under an external resistance of 2000 Ω, a maximum COD removal rate of 60.0% and a maximum discoloration rate of 85.8% were achieved for X-3B azo dye at a concentration of 100 mg/L. Improvements in the treatment efficiency of X-3B dye wastewater were achieved by altering the external resistance. Under an external resistance of 100 Ω and an influent concentration of X-3B of 800 mg/L, the COD removal rate reached 78.6%, and the decolorization rate reached 85.2%. At this point, the CW–MFC exhibited a maximum power density of 0.024 W/m3 and an internal resistance of 99.5 Ω. Spectral analysis and GC–MS results demonstrated the effective degradation of azo dyes within the system, indicating azo bond cleavage and the generation of numerous small molecular substances. Microbial analysis revealed the enrichment of electrogenic microorganisms under low external resistance conditions, where Geobacter and Trichococcus were dominant bacterial genera under an external resistance of 100 Ω, playing crucial roles in power generation and azo dye degradation within the system.

Removal of sulfur and nitrogen pollutants in a sediment microbial fuel cell coupled with Vallisneria natans: Efficiency, microbial community structure, and functional genes

The rapid development of the economy has led to an increase in the sulfur and nitrogen load in surface water, which has the potential to cause river eutrophication and the emission of malodorous gases. A lab-scale sediment microbial fuel cell coupled with Vallisneria natans (P-SMFC) was designed for surface water remediation. The enhancement of pollutant removal performance of P-SMFC was evaluated in contrast to the SMFC system without plants (SMFC), the open-circuit control system with plants (C–P), and the open-circuit control system without plants (C–S), while illustrating the mechanisms of the sulfur and nitrogen transformation process. The results demonstrated that the effluent and sediment of P-SMFC had lower concentrations of sulfide compared to other systems. Furthermore, P-SMFC exhibited higher removal efficiency for COD (73.1 ± 8.7%), NH4+-N (80.5 ± 19.8%), and NO3−-N (88.5 ± 11.8%) compared to other systems. The closed-circuit conditions and growth of Vallisneria natans create a favorable ecological niche for functional microorganisms involved in power generation, sulfur oxidation, and nitrogen transformation. Additionally, metagenomic analysis revealed that multifunctional bacteria possessing both denitrification and sulfur oxidation genes, such as Thiobacillus, Dechloromonas, and Bacillus, may play simultaneous roles in metabolizing sulfur and nitrogen, thus serving as integral factors in maintaining the performance of P-SMFC. In summary, these findings provide a theoretical reference for the concurrent enhancement of sulfur and nitrogen pollutants removal in P-SMFC and will facilitate its practical application in the remediation of contaminated surface water.

Analytical assessment of wave dynamics for natural fibre-reinforced composite plates

This study presents a mathematical modelling to investigate the wave propagation behaviour in laminated natural fibre-reinforced composite plates integrated with surface bonded piezoelectric materials. To model wave dynamics, the constitutive relations, and governing equations of wave motion are derived based on different plate theories and Maxwell's electricity equation due to the surface bonded piezoelectric materials with the closed-circuit electrical boundary condition and transverse poling direction. The influence of natural fibres, as the reinforcing material of the host laminated composite plate, on wave propagation is studied and compared with the effects of synthetic fibres (i.e., carbon, Kevlar, and E-glass). The effects of other factors such as fibre volume fraction, laminate stacking sequence, and the presence of piezoelectric materials on wave dynamics are also investigated. The results of the wave propagation analysis reveal that the impact of different parameters on wave dynamics depends on the range of wavenumbers and wave mode numbers considered. It is found that some parameters may exhibit a noticeable influence on wave velocities, while others may have a negligible effect. The effect of piezoelectric materials on wave velocities in composite plates reinforced with natural fibres e.g., bamboo fibres, may differ from that observed in synthetic fibre-reinforced composite plates.

A novel elastic strip suspension-based bi-directional electromagnetic wind energy harvester designed specifically for wind energy factories

In this study, we propose a novel parallel elastic strips suspended electromagnetic wind energy harvester (ESWEH) based on wind-induced vibration. Profiting galloping phenomena caused by wind flow, the hollow square tube is conceived to generate a significant transverse vibration, and two magnets are equipped on the hollow square tube to generate electrical energy utilizing the electromagnetic induction principle. The symmetrical design of the ESWEH enables it to harvest bi-directional wind energy, while this structure is easy to be assembled into an integrated energy harvesting factory to meet various power supply requirement. A theoretical model is developed to explain the operational mechanism of the proposed electromechanical coupling system. Further, a series of experiments are conducted in a wind tunnel to examine its power generation characteristics (including power-resistance, voltage-resistance) under a closed-circuit condition. The results of the experiments indicate that, when the wind velocity exceeds 2 m/s, the ESWEH equipped with both front and back attached fins produces a continuous and stable current output, with a voltage value exceeding 2.0 V and power exceeding 2.0 mW. Moreover, at an incoming wind velocity of 4 m/s, anaverage power of 7.8 mW is obtained, accompanied by a Root Mean Square (RMS) voltage of 3.2 V when connected to a resistance of 1.2 kΩ. In conclusion, the proposed ESWEH shows good performances in various aspects such as a simplified structure, efficiency-cost, low critical wind velocity and a high-power capacity. The experimental results further indicate that the proposed structure has potential application in construction of a stable power supplying system and wind energy factory for wireless sensors.

LED algal microbial fuel cell stack balancing conception: Electronic voltage reversal blockage, light feed-starvation cycling, and aeration

Stacked algae microbial fuel cells (AMFC) combine the strategic use of light and microbial energy to generate usable electricity. It generates oxygen directly at the electrodes, providing CO2 cycling, algal biomass, and value-added biomolecules. In this work a 12 Liter LED-Algae-Microbial-Fuel-Cell-Stack with maximum power tracking was investigated for voltage balancing and reversal resolution, enabling up to 1200 mV stable stack voltage under closed circuit conditions. The experiment was run in a municipal wastewater treatment plant for 152 days. A new type of data control computer device was used to block voltage reversals and maintaining power with unit resistances between 42 and 99 Ohm. It also allowed the detection of previously unreported light starvation effects in 16 process variants with voltage drops ranging from 14 to 240 mV switching off lights. Algae generated an oxygen concentration of 1.9–3.7 mg/L during power generation. Extending all light-on conditions significantly reduced the voltage reversal frequency. All light-on in combination with assisted oxygenation using 0.25 L/min air bubbling per unit resolved voltage reversals and balanced the AMFC-Stack.The results obtained are relevant to the study of stacked bioelectric systems that use low substrate concentrations and yet aim to generate stable power and minimize voltage reversals.

Electrochemical Promotion of CO2 Hydrogenation Using Rh Catalysts Supported on O2− Conducting Solid Electrolyte

Electrochemical promotion was used to modify the activity and selectivity of a Rh catalyst electrode in the CO2 hydrogenation reaction. The experiments were carried out in a temperature range of 350–430 °C at ambient pressure and at different CO2 to H2 gas feeding ratios (1:2 to 4:1). The only reaction products observed were CO and CH4, both under open- and closed-circuit conditions. The CH4 formation rate was found to increase with both positive and negative potential or current application. The CO formation rate followed the opposite trend. The selectivity to CH4 increased under high values of hydrogen partial pressure and decreased at high pressures of CO2. The results demonstrate how electrochemical promotion can be used to finely tune activity and selectivity for a reaction of high technical and environmental importance.

Effects of porosity distribution and piezoelectric layers on natural frequencies and unsteady aerodynamic pressure of smart thick porous plates

In this paper, the effects of porosity distribution and piezoelectric layers on the natural frequencies and flutter aerodynamic pressure of smart thick porous plates in supersonic airflow are studied. Based on the third-order shear deformation plate theory and first-order piston theory, thick functionally graded porous plates embedded by piezoelectric layers are investigated. The effective porous material properties, such as Young’s modulus and mass density are considered to vary along the thickness direction. The aeroelastic governing equations of motion are obtained using Hamilton’s principle and Maxwell’s equation. By applying Galerkin’s approach, the partial differential governing equations are transformed into a set of ordinary differential equations. The results indicate that the unsteady aerodynamic pressure and natural frequencies decrease as the porosity coefficient increases. Furthermore, the symmetric porosity distribution predicts the highest unsteady aerodynamic pressure and natural frequencies for porous plates. Besides, the results show that the porous plate enclosed by piezoelectric layers in open circuit condition has higher flutter aerodynamic pressure and natural frequencies than the similar plate in closed circuit condition.

3D static bending analysis of functionally graded piezoelectric microplates resting on an elastic medium subjected to electro-mechanical loads using a size-dependent Hermitian C 2 finite layer method based on the consistent couple stress theory

Based on the consistent couple stress theory (CCST), we develop a size-dependent Hermitian C 2 finite layer method (FLM) for carrying out the three-dimensional (3D) static bending analysis of a simply-supported, functionally graded (FG) piezoelectric microplate which is placed under closed-circuit surface conditions. The microplate of interest is assumed to be resting on a Winkler-Pasternak foundation and subjected to either sinusoidal or uniformly distributed electro-mechanical loads. By setting the material length scale parameter at zero and ignoring the piezoelectric and flexoelectric effects, we reduce the formulation of the Hermitian C 2 FLM for analyzing FG piezoelectric microplates to that for analyzing FG piezoelectric macroplates and FG elastic microplates, respectively. The accuracy and the convergence rate of the Hermitian C 2 FLM are assessed by comparing the solutions it produces with the exact and approximate 3D solutions of FG piezoelectric macroplates and FG elastic microplates reported in the literature. Because the Hermitian C 2 FLM requires that the first-order and second-order derivatives of the primary variables must be continuous at each nodal plane, which in turn leads to their solutions converging rapidly and being able to obtain the accurate results of the electric and elastic variables induced in the microplates, especially for the transverse shear and normal stresses and the electric displacements. The effects of piezoelectricity, flexoelectricity, and the material length scale parameter on the deformations and stresses induced in the FG piezoelectric microplates are significant. Highlights A CCST-based Hermitian C 2 finite layer method (FLM) is developed for analyzing functionally graded (FG) piezoelectric microplates. The current FLM can be reduced to that for analyzing FG elastic microplates by ignoring the piezoelectric and flexoelectric effects. The current FLM can be reduced to that for analyzing FG piezoelectric macroplates by setting the material length scale parameter at zero. Implementing the current FLM reveals that its solutions converge rapidly and are in excellent agreement with those obtained using the exact 3D models. The effects of piezoelectricity, flexoelectricity, and the material length scale parameter on the static bending behavior of FG piezoelectric microplates are significant.

Vibration characteristics of smart laminated carbon nanotube-reinforced composite cylindrical shells resting on elastic foundations with open circuit

This study analyzes the vibration of smart laminated carbon nanotube (CNT)-reinforced composite cylindrical shells integrated with piezoelectric materials and resting on elastic foundations. The effect of open circuit electrical boundary condition on vibration characteristics is investigated when a quadratic variation is considered for the electrical potential. Furthermore, the elastic foundations are included in the mathematical modeling to see their effects when the open circuit electrical boundary condition is applied. The first-order shear deformation shell theory and Maxwell’s static electricity equation are employed to derive the governing equations, and natural frequencies are calculated by solving an eigenvalue problem. Vibration characteristics with the open circuit electrical boundary condition are compared with those of closed (short) circuit electrical boundary condition for various mechanical boundary conditions and shell and piezoelectric geometrical parameters. The results demonstrate that the open circuit electrical boundary condition leads to higher frequencies than the closed circuit condition and it must be noticed in the design of smart composite structures with embedded or surface-bonded piezoelectric materials.

Piezoelectric Energy Harvesting Gyroscopes: Comparative Modeling and Effectiveness

Given its versatility in drawing power from many sources in the natural world, piezoelectric energy harvesting (PEH) has become increasingly popular. However, its energy harvesting capacities could be enhanced further. Here, a mathematical model that accurately simulates the dynamic behavior and energy harvested can facilitate further improvements in the performance of piezoelectric devices. One of the goals of this study is to create a dependable reduced-order model of a multi-purpose gyroscope. This model will make it possible to compute the harvested voltage and electrical power in a semi-analytical manner. The harvested voltage is often modeled as an average value across the whole electrode surface in piezoelectric devices. We propose a model which provides practical insights toward optimizing the performance of the system by considering a spatially varying electric field across the electrode surface length. Our framework allows investigation of the limits of applicability of the modeling assumptions across a range of load resistances. The differential quadrature method (DQM) provides the basis for the suggested numerical solution. The model is also employed to examine energy harvesting under various resistance loads. The newly developed spatially varying model is evaluated for open- and closed-circuit conditions and is proved to be accurate for various values of load resistance that have not previously been considered. The results show that using a spatially varying model is more versatile when modeling the performance of the piezoelectric multifunctional energy harvester. The performance may be accurately captured by the model for load resistances ranging between 103 Ω and 108 Ω. At optimum load resistance and near 65 KHz, the maximum power output predicted by the spatially varying (SV) model is 1.3 mV, 1.5 mV for the open-circuit (OC) model, and 2.1 mV for the closed circuit (CE) model. At a high-load resistance, the SV and OC models all predict the maximum power output to be 1.9 mV while the CE model predicted the maximum voltage to be 3 mV.

Optimization of bioenergy generation and chemical oxygen demand reduction in dual-chamber microbial fuel cells using active soil microbes

This study focused on the optimization of a dual-chamber microbial fuel cell (MFC) system using carbon fiber brush and titanium electrodes, meat processing wastewater as substrate, and active soil microbes as biocatalyst. Significant findings revealed promising results on the MFC performance. The active soil microbes contain viable bacteria that worked effectively in the anode chambers. Peak open-circuit voltages (OCV) of the MFCs were as high as 1.05 V using titanium mesh and 1.03 V using carbon fiber brush. In closed-circuit conditions, the current obtained were 1.04 mA and 1.38 mA, and the power densities were 1.22 Wm−2 and 0.34 Wm−2, correspondingly. The power densities were normalized based on the surface areas of the anodes. The bioenergy generation profiles also revealed the MFCs can produce peak potentials of 30.109 kJ and 19.415 kJ using carbon fiber brush and titanium mesh, respectively. Furthermore, the results showed that the reduction in chemical oxygen demand (COD) was highest at 24.32 percent using carbon brush and lowest at 13.34 percent using titanium mesh electrodes.

Refractory azo dye wastewater treatment by combined process of microbial electrolytic reactor and plant-microbial fuel cell

An innovative design of microbial electrolytic reactor (MER) coupled with Ipomoea aquaticaForsk. plant microbial fuel cell (IAF-PMFC) was developed for azo dye wastewater treatment and electricity generation. This study aims to assess the sequential degradation of azo dye and the feasibility of energy self-sufficiency in the MER/IAF-PMFC system. The decomposition of azo dye into aromatic amines and dye decolorization occurred in the MER at high hydraulic loading of 0.28 m3/(m2·d), while dye intermediates were mainly mineralized in the IAF-PMFC at low hydraulic loading of 0.06 m3/(m2·d). The final decolorization efficiency and COD removal of the combined system reached 99.64% and 92.06% respectively, even at influent dye concentration of 1000 mg/L. The effects of open/closed circuit conditions, presence/absence of aquatic plant and different cathode areas on the performance of the IAF-PMFC for treating the effluent of the MER were systematically tested, and the results showed that closed-circuit condition, plant involvement and larger cathode area were more beneficial to decolorization, detoxification and mineralization of dye wastewater, bioelectricity output, plant growth and photosynthetic rate. The power consumption by the MER was 0.0163 kWh/m3 of dye wastewater, while the highest power generation of the IAF-PMFC reached 0.0183 kWh/m3. The current efficiency of the MER for dye decolorization was as high as 942.83%, while the maximum coulombic efficiency of the IAF-PMFC for intermediates metabolism was only 6.30%, which still had much space of bioelectricity generation promotion. The MER/IAF-PMFC technology can simultaneously realize refractory wastewater treatment and balance of electricity production and consumption.

A Hermite-Family C1 Finite Layer Method for the Three-Dimensional Free Vibration Analysis of Exponentially Graded Piezoelectric Microplates Based on the Consistent Couple Stress Theory

Based on the consistent couple stress theory (CCST), we develop a Hermite-family [Formula: see text] finite layer method (FLM) for the three-dimensional (3D) free vibration analysis of a simply-supported, exponentially graded (EG) piezoelectric microplate under open- and closed-circuit surface conditions. In the formulation of the FLM, the microplate is artificially divided into a number of finite microlayers, and Fourier functions and Hermite polynomials are used to interpolate the in-plane and out-of-plane variations of a number of primary variables, respectively, including elastic displacement components and the electric potential variable for each individual layer. The Hermite-family [Formula: see text] FLM for analyzing EG piezoelectric microplates is reduced to the Hermite-family [Formula: see text] FLM for analyzing EG piezoelectric macroscale plates and functionally graded (FG) elastic microplates by assigning a value of zero to the material length scale parameter and by ignoring the piezoelectric and flexoelectric effects in the formulation, respectively. The accuracy and convergence rate of the FLM are assessed by comparing their solutions with the benchmark solutions of both the EG piezoelectric macroplates and the power-law-type FG elastic microplates that are available in the relevant literature. We examine and discuss some key effects on the free vibration characteristics of an EG piezoelectric microplate, including the impact of the material length scale parameter, the material-property gradient index, the length-to-thickness ratio, the piezoelectric effect, and the flexoelectric effect.

Vibration characteristics of sandwich plates with GPLRC core and piezoelectric face sheets with various electrical and mechanical boundary conditions

An analysis is performed in the current investigation to study the vibrations of composite laminated plates integrated with piezoelectric layers. Composite laminated plate is reinforced with graphene platelets (GPLs). Also the amount of GPLs in the layers may be different which results in a piecewise functionally graded (FG) media. Elasticity modulus of the GPLRC media is obtained by means of the Halpin-Tsai rule which contains efficiency parameters to capture the size of reinforcements. First order shear deformation theory of plates and parabolic distribution of electric field through the piezoelectric layers are assumed as the basic assumption. For the piezoelectric layers, both the open circuit and closed circuit conditions are applied. The total strain and kinetic energies of the plate are obtained. After that by means of the general idea of the Ritz method and also Chebyshev polynomials as the basic shape functions, the matrix representation of the equations of motion dealing with free vibration of sandwich plate with piezoelectric face sheets are obtained. Results of this study are first compared with the available data in the open literature. After that novel results are given to explore the effects of different parameters such as the electrical and mechanical boundary conditions, plate geometry, GPL weight fraction and GPL distribution profile. It is shown that with introduction of GPLs, frequencies of the plate may be enhanced for both closed circuit and open circuit conditions.

Unified polarizable electrode models for open and closed circuits: Revisiting the effects of electrode polarization and different circuit conditions on electrode-electrolyte interfaces.

A precise understanding of the interfacial structure and dynamics is essential for the optimal design of various electrochemical devices. Herein, we propose a method for classical molecular dynamics simulations to deal with electrochemical interfaces with polarizable electrodes under the open circuit condition. Less attention has been given to electrochemical circuit conditions in computation despite being often essential for a proper assessment, especially comparison between different models. The present method is based on the chemical potential equalization principle, as is a method developed previously to deal with systems under the closed circuit condition. These two methods can be interconverted through the Legendre transformation so that the difference in the circuit conditions can be compared on the same footing. Furthermore, the electrode polarization effect can be correctly studied by comparing the present method with conventional simulations with the electrodes represented by fixed charges, since both of the methods describe systems under the open circuit condition. The method is applied to a parallel-plate capacitor composed of platinum electrodes and an aqueous electrolyte solution. The electrode polarization effects have an impact on the interfacial structure of the electrolyte solution. We found that the difference in circuit conditions significantly affects the dynamics of the electrolyte solution. The electric field at the charged electrode surface is poorly screened by the nonequilibrium solution structure in the open circuit condition, which accelerates the motion of the electrolyte solution.

Effects of bioelectricity generation processes on methane emission and bacterial community in wetland and carbon fate analysis

Wetlands are an important carbon sink for greenhouse gases (GHGs), and embedding microbial fuel cell (MFC) into constructed wetland (CW) has become a new technology to control methane (CH4) emission. Rhizosphere anode CW–MFC was constructed by selecting rhizome-type wetland plants with strong hypoxia tolerance, which could provide photosynthetic organics as alternative fuel. Compared with non-planted system, CH4 emission flux and power output from the planted CW–MFC increased by approximately 0.48 ± 0.02 mg/(m2·h) and 1.07 W/m3, respectively. The CH4 emission flux of the CW–MFC operated under open-circuit condition was approximately 0.46 ± 0.02 mg/(m2·h) higher than that under closed-circuit condition. The results indicated that plants contributed to the CH4 emission from the CW–MFC, especially under open-circuit mode conditions. The CH4 emission from the CW–MFC was proportional to external resistance, and it increased by 0.67 ± 0.01 mg/(m2·h) when the external resistance was adjusted from 100 to 1000 Ω. High throughput sequencing further showed that there was a competitive relationship between electrogenic bacteria and methanogens. The flora abundance of electrogenic bacteria was high, while methanogens mainly consisted of Methanothrix, Methanobacterium and Methanolinea. The form and content of element C were analysed from solid phase, liquid phase and gas phase. It was found that a large amount of carbon source (TC = 254.70 mg/L) was consumed mostly through microbial migration and conversion, and carbon storage and GHGs emission accounted for 60.38% and 35.80%, respectively. In conclusion, carbon transformation in the CW–MFC can be properly regulated via competition of microorganisms driven by environmental factors, which provides a new direction and idea for the control of CH4 emission from wetlands.Graphical