Constant Current Conditions Research Articles

Deep learning for pH prediction in water desalination using membrane capacitive deionization

The pH of a solution has a large influence on the ion removal efficiency of the membrane capacitive deionization (MCDI) process, an electrochemical ion separation process. We developed a convolutional neural network linked with a long short-term memory (CNN-LSTM) model based on an artificial intelligence algorithm to predict the effluent pH of MCDI, as effluent pH is difficult to predict using conventional numerical modeling. The model accurately predicted effluent pH (R2≥0.998) based on the analysis of five input variables (current, voltage, influent conductivity and pH, and effluent conductivity) under standard operating conditions of MCDI using either constant-current or constant-voltage conditions. The developed model predicted effluent pH using only limited input variables, current and voltage, with high accuracy (R2≥0.997). Thus, the CNN-LSTM model can be used in practical applications as only the current and voltage of MCDI cells are often monitored in field applications.

Electrophotocatalytic Si–H Activation Governed by Polarity-Matching Effects

Electrophotocatalytic Si–H Activation Governed by Polarity-Matching Effects

Electrochemical Synthesis of Fluorinated Ketones from Enol Acetates and Sodium Perfluoroalkyl Sulfinates.

The electrochemical synthesis of fluorinated ketones from enol acetates and RfSO2Na in an undivided cell under constant current conditions was developed. The electrosynthesis proceeded via perfluoroalkyl radical generation from sodium perfluoroalkyl sulfinate followed by addition to the enol acetate and transformation of the resulting C radical to a fluorinated ketone. The method is applicable to a wide range of enol acetates and results in the desired products in yields of 20 to 85%.

Growth behavior of tantalum oxide nanotubes during constant current anodization

The standard method for growing tantalum oxide (Ta2O5) nanotubes is the constant voltage anodization mode. Although the constant current anodization mode is another feasible approach, the corresponding mechanism is not yet clear. In the present work, Ta2O5 nanotubes have been prepared by constant current anodization in an electrolyte containing HF. The results show that Ta2O5 nanotubes ~ 18 μm in length can be obtained with a very rapid growth rate within 2 min at a current density of 125 mA cm−2. In addition, the effects of current density, anodizing time, concentration of F− ions and electrolyte temperature on the morphology and growth rate of Ta2O5 nanotubes were studied. This work proposes an effective way of preparing tantalum oxide nanotubes under constant current anodic oxidation conditions, and paves the way toward large-scale production of Ta2O5 nanotubes.

Battery State of Health Estimation with Improved Generalization Using Parallel Layer Extreme Learning Machine

The online estimation of battery state of health (SOH) is crucial to ensure the reliability of the energy supply in electric and hybrid vehicles. An approach for enhancing the generalization of SOH estimation using a parallel layer extreme learning machine (PL-ELM) algorithm is analyzed in this paper. The deterministic and stable PL-ELM model is designed to overcome the drift problem that is associated with some conventional machine learning algorithms; hence, extending the application of a single SOH estimation model over a large set of batteries of the same type. The PL-ELM model was trained with selected features that characterize the SOH. These features are acquired as the discrete variation of indicator variables including voltage, state of charge (SOC), and energy releasable by the battery. The model training was performed with an experimental battery dataset collected at room temperature under a constant current load condition at discharge phases. Model validation was performed with a dataset of other batteries of the same type that were aged under a constant load condition. An optimum performance with low error variance was obtained from the model result. The root mean square error (RMSE) of the validated model varies from 0.064% to 0.473%, and the mean absolute error (MAE) error from 0.034% to 0.355% for the battery sets tested. On the basis of performance, the model was compared with a deterministic extreme learning machine (ELM) and an incremental capacity analysis (ICA)-based scheme from the literature. The algorithm was tested on a Texas F28379D microcontroller unit (MCU) board with an average execution speed of 93 μs in real time, and 0.9305% CPU occupation. These results suggest that the model is suitable for online applications.

Exciter–Quadrature–Repeater Transmitter for Wireless Electric Vehicle Charging With High Lateral Misalignment Tolerance and Low EMF Emission

In this article, an exciter–quadrature–repeater transmitter pad is proposed in order to achieve high lateral misalignment tolerance and low leakage flux emission in electric vehicle wireless charging applications. In the proposed WPT system, a single half-bridge inverter unit is needed to energize the exciter coil, which is magnetically coupled to two larger quadrature repeater coils. The currents in the two repeater coils naturally adjust based on the lateral misalignment of the receiver pad to reduce the leakage flux density around the charging zone. The system can maintain zero phase shift between excitation voltage and current and achieve constant current charging conditions with fixed compensation capacitors in the ±150-mm lateral misalignment range. In order to verify the attributes of the proposed wireless power transfer (WPT) system, a 3-kW experiment setup with a 200-mm vertical gap was built and compared to a three-coil WPT system, which consists of a small transmitter coil, a single large repeater coil, and a receiver coil. According to the experiment results, even under extreme 150-mm lateral misalignment, the proposed WPT system has 90.7% coil-to-coil transmission efficiency. Furthermore, it achieves a 30% reduction of leakage flux density compared to the three-coil system in the 150-mm lateral misalignment case.

Fractal Dimension and lacunarity based microscopic image texture characterization of coated and non-coated metallic substrates

ABSTRACT The degree of surface roughness as measured using Fractal Dimension and Lacunarity can serve as quality measures of the coating process. The smoothness of the surface before and after coating is an important characteristic frequently used in surface engineering, to obtain well-polished and smoothened surface finish. We have used Brass plates and coated it with Nickel using electroless and electroplating methods. The images of the coated surfaces were taken using an optical microscope before and after coating. Fractal Dimension (FD) and Lacunarity (λ) of the surface image before and after coating is calculated for comparison using Differential Box-Counting algorithm. Electro-cleaning of the samples in an alkaline degreasing solution is done. Electroplating is carried out in respective electrolytic bath under constant current and temperature conditions. Electroless coating is carried out with a separate Nickel bath at constant temperature of 85° C. The experimental data was validated, which revealed that FD and λ values decreased after coating in all the cases. The lower value of FD and λ after coating suggests more regularity in the surface patterns or smoothness. Hence, we conclude that FD and λ serve as relevant parameters depicting the quality of coating surface at significance level of 0.05.

Electrochemical Synthesis of Benzimidazoles via Dehydrogenative Cyclization of Amidines.

The development of efficient and sustainable methodologies for the synthesis of N-heterocycles is a constant focus of organic synthesis. Herein an electrochemical method is reported for the synthesis of benzimidazoles through dehydrogenative cyclization of easily available N-aryl amidines. The reactions were conducted under simple constant current conditions in an undivided cell without need for catalysts, chemical oxidants, or additives, and produced H2 as the only theoretical byproduct.

Effect of PAC on the Behavior of Dynamic Membrane Bioreactor Filtration Layer Based on the Analysis of Mixed Liquid Properties and Model Fitting.

Recently, dynamic membrane bioreactor (DMBR) has gradually gained the interest of researchers for the development of membrane technology. In this paper, we set up parallel experiments to investigate the effect of powder activated carbon (PAC) on organic matter removal, transmembrane pressure, and filter cake layer characterization to make an overall performance assessment of DMBR. The results showed that DMBR has a good removal effect on organic matter removal, and with a chemical oxygen demand removal rate over 85%. Protein was found to be the main membrane fouling substance. Due to the electric double-layer effect, membrane fouling tended to be alleviated when the PN/PS value was low. Using a filtration model under constant current conditions, the filtration process through the cake layer was observed to be consistent with cake-intermediate model.

Self-sustained oscillations in the potential of a CO-poisoned PEM fuel cell: A model based on physical principles

A dynamic 1-D model for the simulation of the oscillatory behavior in the anode potential of a PEM fuel cell under constant current conditions and the presence of CO impurities in the H2 inlet is presented. The model is built upon electrostatic, chemical kinetic and thermodynamic principles, featuring a probabilistic treatment of dipole interactions between several chemical species in the compact layer. Model predictions are validated with available experimental data in the literature. The model is able to capture the phenomenon of the oscillatory behavior. This phenomenon occurs when the CO molar fraction in the feed exceeds 8 × 10−5. A parametric sensitivity study for CO-electrooxidation and OH-adsorption kinetic rates is also performed. The CO-electrooxidation rate has a noticeable effect on the oscillation frequency, and damped oscillations are observed for a kinetic rate of 6 × 10−3 mol m−2s−1, while OH-adsorption and desorption rates have a moderate effect on system dynamics.

An assessment of microstructure and mechanical properties of inconel 601/ 304 stainless steel dissimilar weld

The microstructure and the mechanical properties of dissimilar joints between Inconel 601 superalloy and 304 austenitic stainless steel were investigated in this work. For this purpose, gas tungsten arc welding (GTAW) process was performed using an austenitic (ER304) stainless steel filler metal in two modes of pulsed and constant current conditions in pure (99.999%) argon gas. Furthermore, an autogenous welding (without filler metal) procedure was also carried out for comparison. The microstructure of weldments was investigated using optical and scanning electron microscopy. Tensile tests and microhardness measurements were carried out to evaluate the mechanical properties. High vacuum FE-SEM investigations revealed that no segregation has occurred in the weld metal. It was found that a decrease in heat input led to a significant grain refinement in the welds, which improved the mechanical properties. Among the welds fabricated with filler metals, welding with pulsed current resulted in superior mechanical properties. Finally, an excellent strength ductility matching (UTS = 485 MPa and Elongation = 39%) was obtained by autogenous welding procedure.

Evaluation and observability analysis of an improved reduced-order electrochemical model for lithium-ion battery

The accurate modeling of lithium-ion battery is helpful for deserves developing advanced battery management system (BMS) and monitoring battery states. Despite the electrochemical model (EM) of a battery cell has gradually become a main candidate for advanced BMS, the EM-based estimators still face a big problem regarding to the weak observability. To address this issue, this paper proposes an improved reduced-order electrochemical model (iROEM) with guaranteed observability. First, the solid phase equations are reconstructed by combing Padé approximation and polynomial fitting method, and the electrolyte concentration equations are reduced by using volume averaging technique, which ultimately contributes the development of the iROEM. Second, the observability analysis of the proposed iROEM is conducted to facilitate the control applications in BMS. Finally, the designed iROEM is evaluated by performing a comparative study of the electrolyte concentration distributions and battery terminal voltages with respect to the pseudo two-dimensional model under the constant current and dynamic working conditions. The results demonstrate that the iROEM with guaranteed observability has high model fidelity and less computational complexity, which contributes to the resultant estimators for the lithium-ion battery electrochemical model.

Direct Electrochemical Defluorinative Carboxylation of gem-Difluoroalkenes with Carbon Dioxide.

We report a facile and economical synthesis of α-fluoroacrylic acids via direct electrochemical defluorinative carboxylation of gem-difluoroalkenes with CO2. By using a platinum plate as the working cathode and a cheap nickel plate as the anode in a user-friendly undivided cell under constant current conditions, the reactions proceed smoothly under room temperature, without the use of expensive transition metal catalysts, ligands, external base or reductant, affording the desired adducts in up to 83% yield and 20:1 Z/E ratio, with good functional group tolerance. A cyclic voltammetry study was conducted and suggested a novel ECEC process.

Analytical modeling of solution-phase diffusion in porous composite electrodes under time-dependent flux boundary conditions using Green’s function method

Mathematical modeling of species transport in a Li-ion cell is important for understanding and optimizing the performance of Li-ion cells in a wide variety of energy conversion and storage processes. Specifically, solid- and liquid-phase diffusion in the electrodes is an important process that governs cell performance. Most analytical and numerical models developed in the past have focused on a constant current boundary condition. However, time-dependent boundary conditions may be important in many applications, where the applied charging or discharging current changes with time. This paper presents an analytical solution for the solution-phase diffusion limitation problem for a composite electrode operating under time-dependent flux boundary condition and arbitrary initial conditions using the Green’s function approach. Results based on the analytical solution show good agreement with past work for constant current boundary conditions, as well as numerical simulation results. The results are used to predict the concentration distribution for linear, periodic, and step-function variations in current density as a function of time. Results from the step-function boundary condition address practical applications where sudden changes in the magnitude and direction of the imposed current may occur. Results derived for periodic functions are also of practical significance since other current profiles can be represented by series comprising periodic functions. This work expands the theoretical understanding of diffusion in Li-ion cells, and provides the basis for understanding and optimizing important charge/discharge processes in Li-ion cells.

A lithium-ion battery electrochemical–thermal model for a wide temperature range applications

The internal temperature of lithium-ion battery affects the battery parameters during discharge and charge process, and the low-temperature environment has a particularly significant impact on the performance of the lithium-ion battery. In this paper, a simplified discrete electrochemical model adapts to a wide temperature range is developed. Based on Pseudo-Two-Dimension (P2D) model, we simplify the governing equation to describe the solid and solution diffusion by fitting the lithium-ion concentration in the form of parabolas. Analysis of the heat generation and dissipation conditions of lithium-ion batteries is conducted, and a concentrated mass thermal model is established to describe the internal temperature changes of batteries. The parameters involved in the electrochemical model are also updated accordingly. Finally, an electrochemical–thermal coupling model is established. In order to verify the cell potential difference simulation accuracy of the model, the constant current discharge conditions, DST (Dynamic Stress Test) in the ambience above 0 °C and the multi-stage current discharge conditions in the ambience below 0 °C is carried out. The results show that the model with parameters update significantly improves the accuracy of simulation, especially at low temperature (−20 °C, −10 °C, 0 °C). What's more, the model with parameter update can simulate the potential difference's ‘trough’ phenomenon in the constant current phase of the pulse discharge at -20°C better than the model without parameter update.

Origin of relaxation frequency shift in blue organic light-emitting diodes

Recent technological innovations in organic light-emitting diodes (OLEDs) have enabled their applicability to be expanded to not only displays but also the lighting industry. In addition, the high scalability and flexibility of OLEDs render them promising candidates for next-generation displays. However, their insufficient lifetime and low uniformity/stability are challenging issues, mainly because of inadequate understanding regarding the fundamental degradation mechanism of OLEDs owing to their complex device structure. Herein, based on impedance spectroscopy (IS), we report the origin of the relaxation frequency (fR) shift in blue OLEDs as a function of electrical stress time for up to 1000 h with a constant current stress condition of 1 mA. These experimental conditions allow us to separately study the degradation mechanisms of the emission and transport layer (TPL) interfaces. On the basis of thorough understanding of the theoretical expression of fR, we mainly attribute the variation in fR at the charge-balancing voltage to the degradation of the TPL interface; this is further rationalized by the negligible difference between fR values obtained from IS and the equivalent circuit theory. This strong correlation consequently renders fR a powerful degradation indicator for the TPL interface. Our results provide a basis for the realization of highly reliable blue OLEDs with a sufficient lifetime.

Miniemulsion switchable electrolysis under constant current conditions

Troxerutin, a naturally occurring flavonoid glycoside, has a variety of beneficial activities characteristic for flavonols, such as strong antioxidant and anti‐inflammatory properties. Besides the beneficial effects of troxerutin, limitations such as bioavailability have disrupted its application and prompt scientists to look for effective modification methods. This work presents the synthesis of troxerutin‐based macromolecules with lipophilic poly(n‐butyl acrylate) (PnBA) star arms via “core‐first” procedure in a two‐step synthetic route. Troxerutin as a polyphenol structure with ubiquitous reactive hydroxyl groups was for the first time modified with α‐bromoisobutyryl bromide to receive an atom transfer radical polymerization (ATRP) initiator with 10 brominated initiation sites. The further step involved the synthesis of novel star‐like macromolecules with troxerutin core and PnBA star arms by simplified electrochemically mediated ATRP (seATRP) in an environmentally friendly reaction medium—miniemulsion. Electrolysis under constant current conditions with temporal control was implemented, resulting in well‐defined star‐like polymers with complete preservation of chain‐end functionality after restarting the synthesis. Hydrophobic properties of received troxerutin‐based macromolecules were investigated by contact angles (Θ) measurements, followed by the free surface energy (FSE) calculations.

Remaining useful life prediction for lithium-ion battery by combining an improved particle filter with sliding-window gray model

Dependable and accurate battery remaining useful life (RUL) prediction is essential for ensuring the safety and reliability of battery systems. To improve the dynamic traceability of the battery degradation process for RUL prediction under different loading profiles, this paper presents an improved RUL prediction method, which is established from the combination of the linear optimization resampling particle filter (LORPF) with the sliding-window gray model (SGM). Major innovations are presented as follows: (1) To increase the accuracy of RUL prediction, a linear optimization combination is proposed to overcome the particle diversity deficiency in the resampling process of the standard PF, i.e. the LORPF; (2) To improve the traceability of the LORPF in predicting degradation trajectory, the SGM is employed to update the state variables of the state–space model in the LORPF. Additionally, an SGM-LORPF framework is constructed for RUL prediction. The performance of the SGM-LORPF is synthetically verified by data from two types of batteries under different loading profiles. Prediction test results indicate that the SGM-LORPF can achieve accurate RUL prediction under both constant current discharge conditions (relative error within 7.20%) and dynamic current discharge conditions (relative error within 2.75%). Moreover, using only a small amount of historical data, the proposed SGM-LORPF framework can acquire accurate results. The experimental outcome indicates that the SGM-LORPF has considerable efficiency and a wide range of practicality.

The role of a nonconductive film (NCF) on Cu/Ni/Sn-Ag microbump interconnect reliability

The use of a nonconductive film (NCF) to establish and enhance the stability of microbumps is crucial. Even though it is normal to apply NCF to microbump interconnection layers, understanding the behavior of microbump stability without the protection from a NCF is important. A free standing structure without a NCF can be used to determine the mechanical response of a single microbump. This information can be used to design robust interconnect structures. Electromigration (EM) tests were performed at 150 ℃ and 1.3 × 105 A/cm2 to investigate the effect of a NCF on the electrical reliability of Cu/Ni/Sn-Ag microbumps. The EM test results show different failure times and failure modes for Cu/Ni/Sn-Ag microbumps with the NCF and without the NCF. The microbump test samples with the NCF had a time to failure that was three times longer than that without the NCF. At a constant current density condition, the contribution of temperature-induced accelerated degradation and mechanical deformation factors were considered. A series of finite element and electron backscattered diffraction analyses revealed that the NCF restricted solder deformation and led to an increase in the back stress, which prolonged the EM lifetime.

Ignition characteristics of energetic nichrome bridge initiator based on Al/CuO reactive multilayer films under capacitor discharge and constant current conditions

Four types of Al/CuO energetic nichrome bridges (ENCBs) initiators are reported, prepared by integrating Al/CuO reactive multilayer films (RMFs) on different V-shaped nichrome bridges (NCBs) through magnetron sputtering technology. V-type angles of NCBs are 150°, 136°, 120° and 90°. The fabrication, electrical explosive characteristics of these ENCBs initiators under capacitor discharge, as well as its firing process under constant current conditions are systematically described. The results reveal a ‘stagflation’ phenomenon in high-speed photograph of ENCBs at low discharge voltage, which is consistent with the result of optical microscope images. It is noted the electric explosion delay time decreases with an increase in the discharged voltages, while the critical ignition energy has no relationship with discharged voltages. Moreover, among the four ENCBs, the one with V-angle of 90° exhibits the shortest electric explosion delay time and lowest critical burst energy. This suggests that the electrical explosion performance of ESCBs can be adjusted by optimising the V-shaped angle and the discharge voltage. At last, the high combustion efficiency of ENCB is proved by comparative test with NCB at 0.6 A. And ENCBs have better heating efficiency than nichrome wire with the same resistance at 0.4A and 0.6A.