Electric Current Research Articles

Performance evaluation of bridgeless isolated SEPIC-Luo converter for EV battery charging using PI and ANN controller

Electric vehicle (EV) rechargeable battery packs that employ traditional power factor correction (PFC) circuit design have performance limitations due to their substantial conductivity loss that ensures at the input of a diode bridge rectifier (DBR). This study suggests a bridgeless (BL) isolated single ended primary inductance converter (SEPIC) - Luo converter to address the problem. As a result, the input current exhibits a power factor operation of unity throughout the charging process. DBR elimination and current conduction through a remarkably small number of circuits both significantly reduce conduction losses. The use of an artificial neural network (ANN) and proportional integral (PI) controller enhances the converter's performance with a stable DC link voltage. The suggested converter overall operation is thoroughly described in terms of variety of operating modes and simulation-based effectiveness. Here, with the assistance of the hysteresis current controller (HCC), the input current disruptions are reduced. Constant current and voltage management is used to successfully charge the EV battery, resulting in improved efficacy and inherent PFC. By utilizing simulation outcomes achieved from MATLAB, the performance of proposed BL isolated SEPIC-Luo in boosting the power quality of EV charger system is examined.

Discrete element model for effective electrical conductivity of spark plasma sintered porous materials

AbstractThis paper aims to analyse electrical conduction in partially sintered porous materials using an original resistor network model within discrete element framework. The model is based on sintering geometry, where two particles are connected via neck. Particle-to-particle conductance depends on neck size in sintered materials. Therefore, accurate evaluation of neck size is essential to determine conductance. The neck size was determined using volume preservation criterion. Additionally, grain boundary correction factor was introduced to compensate for any non-physical overlaps between particles, particularly at higher densification. Furthermore, grain boundary resistance was added to account for the porosity within necks. For numerical analysis, the DEM sample was generated using real particle size distribution, ensuring a heterogeneous and realistic microstructure characterized by a maximum-to-minimum particle diameter ratio of 15. The DEM sample was subjected to hot press simulation to obtain geometries with different porosity levels. These representative geometries were used to simulate current flow and determine effective electrical conductivity as a function of porosity. The discrete element model (DEM) was validated using experimentally measured electrical conductivities of porous NiAl samples manufactured using spark plasma sintering (SPS). The numerical results were in close agreement with the experimental results, hence proving the accuracy of the model. The model can be used for microscopic analysis and can also be coupled with sintering models to evaluate effective properties during the sintering process.

Study of conduction mechanisms of InSeSb nano-chalcogenide alloys

The electrical conduction mechanisms for bulk samples of In0.1Se0.9−x Sb x (x = 0, 0.04, 0.08 and 0.12) nano-chalcogenide system, synthesized by the melt-quenching technique are investigated through current–voltage (I–V) characteristics. For the detailed study of conduction mechanism pellets of bulk samples are prepared. A thorough examination of electrical conductivity is done in the temperature range of 295–318 K and 0–50 V voltage range. From I–V measurements it is observed that samples are showing ohmic nature at lower field and non-ohmic nature at relatively higher field values. The temperature dependence of DC conductivity is analyzed using the Arrhenius relationship which is found to increase with Sb content. The value of activation energy and pre-exponential factor are calculated, which revealed that the conduction is due to the hopping of charge carriers among the localized states. Different parameters of Mott’s variable range hopping such as degree of disorder T 0, density of localized states N(E F), hopping distance (R hop), and hopping energy (W) are calculated. For the high field conduction process Poole–Frenkel, and Schottky processes are studied.

Understanding how junction resistances impact the conduction mechanism in nano-networks

Networks of nanowires, nanotubes, and nanosheets are important for many applications in printed electronics. However, the network conductivity and mobility are usually limited by the resistance between the particles, often referred to as the junction resistance. Minimising the junction resistance has proven to be challenging, partly because it is difficult to measure. Here, we develop a simple model for electrical conduction in networks of 1D or 2D nanomaterials that allows us to extract junction and nanoparticle resistances from particle-size-dependent DC network resistivity data. We find junction resistances in porous networks to scale with nanoparticle resistivity and vary from 5 Ω for silver nanosheets to 24 GΩ for WS2 nanosheets. Moreover, our model allows junction and nanoparticle resistances to be obtained simultaneously from AC impedance spectra of semiconducting nanosheet networks. Through our model, we use the impedance data to directly link the high mobility of aligned networks of electrochemically exfoliated MoS2 nanosheets (≈ 7 cm2 V−1 s−1) to low junction resistances of ∼2.3 MΩ. Temperature-dependent impedance measurements also allow us to comprehensively investigate transport mechanisms within the network and quantitatively differentiate intra-nanosheet phonon-limited bandlike transport from inter-nanosheet hopping.

Structure–polaronic conductivity relationship in vanadate–phosphate glasses

AbstractThis work provides new insights into the nature of the polaronic transport in xV2O5–(100−x)P2O5, 41 ≤ x ≤ 89 mol% glasses from analysis of their conductivity over a wide range of frequencies and temperatures, and correlation of the electrical parameters to the structural models of these materials. The results show that the linear increase in direct current (DC) conductivity with the increase in V2O5 could be related to the formation of a vanadate subnetwork, which is characterized by a length distribution of V–O bonds and variations in linkages between different vanadate units. Such a structurally complex network offers multiple conduction pathways which are favorable for polaron hopping. The Summerfield scaling of conductivity spectra reveals a temperature‐invariant mechanism of polaron transport for all glasses and the same local structural environment of polarons at higher V2O5 contents due to the same ratio of vanadate units present in the network. Also, this study highlights the similarities and differences in the nature of the polaronic transport of vanadate–phosphate glasses and other polaronically conducting phosphate glasses containing WO3, MoO3, and Fe2O3, and pins down a pivotal role of the glass structure in electrical processes in these materials.

FFF print defect characterization through in-situ electrical resistance monitoring

Fused filament fabrication is a popular fabrication technique. Currently there is a need for in-situ monitoring modalities to gather real-time information on prints, both for quality control and closed-loop control. Despite current advancements, effective and affordable in-situ monitoring techniques for non-destructive defect detection of voids and bonding quality are still limited. This work demonstrates in-situ monitoring of fused filament fabrication through electrical resistance measurements as an alternative to thermal and optical methods. A new, easy-to-implement setup is demonstrated which measures the electrical resistance of a conductively doped filament between the nozzle and single or multi-electrodes on the bed. Defects can be located in an unprecedented way with the use of encoded axes in combination with the observed resistance variations throughout the part. A model of the anisotropic electrical conduction is used to interpret the measurements, which matches well with the data. Warping, inter-layer adhesion, under-extrusion and overhang sagging print defects can be observed in the measurements of parts with a complex geometry, which would be difficult to measure otherwise. Altogether in-situ electrical resistance monitoring offers a tool for optimising prints by online studying the influence of the print parameters for quality assessment and it opens up possibilities for closed-loop control.

Quantifying local cardiac substrate heterogeneity from high density recordings: an experimental study

Abstract Background and Purpose High-density (HD) grid catheters offer enhanced local electrical conduction characterization, owing to their unique grid arrangement. This arrangement enables the generation of orientation-independent EGMs, termed omnipolar EGMs (oEGMs), overcoming limitations associated with traditional unipolar and bipolar EGMs. This innovation holds potential for differentiating healthy tissue from scarred or arrhythmogenic areas. In this study, we introduce a novel metric, the Vector Field Heterogeneity (VFH), designed to quantify the heterogeneity of propagation wavefronts in local vector maps derived from oEGMs. Methods We developed and validated the VFH metric through a combination of simulations and experiment conducted on Langendorff-perfused rabbit hearts. Simulations involved creating a model that generated 100,000 simulated maps exhibiting various levels of disorganization. For experimental data, 68 propagation maps were utilized, including 29 from basal recordings, 39 from recordings with stimulation (4 or 6Hz), from five Langendorff-perfused rabbit hearts at 37ºC, using a multielectrode mapping catheter with 128 electrodes spaced 1mm apart. The VFH metric, based on vector field theory (see figure 2), was computed and compared to the widely adopted the Spatial Inhomogeneity Index (SI) from Statistical analysis was then performed to assess the distribution of heterogeneity values. Results The analysis of the VFH metric through simulations revealed a linear increase in VFH values with disorganization up to a 45º angle, followed by a plateau. Different catheter grid sizes demonstrated that larger grids reduced the standard deviation, with the VFH metric converging to a lower value of approximately 0.62 for larger grids. Experimental data indicated that for a 4x4 grid, VFH values averaged 0.35 without stimulation and decreased to 0.11 with stimulation. The VFH metric consistently outperformed the SI index in binary classification of basal vs stimulated conditions, as evidenced by higher Area Under Curve (AUC) values in both Receiver Operating Characteristic (ROC) and Precision-Recall (PR) analyses across various catheter sizes. For example, in the 4x4 grid, the AUROC for the VFH metric was 0.9752 compared to 0.8311 for the SI index, showcasing the VFH metric’s superior accuracy in assessing cardiac wavefront heterogeneity (see figure 2). Conclusion Vector Field Heterogeneity (VFH) emerges as an effective tool for characterizing cardiac tissue. It successfully differentiates between stimulated and non-stimulated tissue, accurately representing progressive disorganization in simulated maps. The VFH metric demonstrates superiority over the established Spatial Inhomogeneity (SI) index, making it a reliable parameter for assessing cardiac heterogeneity, especially on small high-density grids. It holds promise for clinical use in studying and understanding the cardiac substrate during arrhythmic conditions.Figure 1.Abstract Figure.Figure 2.Methods and Results.

To Determine the Accuracy and Reliability of Broselow Tape in Comparison with Actual Weight and Advance Pediatric Life Support Formula Weight Assessment among the Pediatric Population Presenting to Emergency Department of a Low Income Setting

Background: Near precise weight assessment among sick pediatric patients remains a dilemma and conventionally accepted weight assessment methods, in busy ED might be inaccurate or unreliable. Children have different weights at different ages, and accurate/precise weight measurement is of utmost importance for weight-related dose calculation of drugs/fluids, equipment sizes, an accurate dose of electrical currents during cardiac shock, etc. Several weight estimation methods are available and are dependent on the child's age, length, or both. However, length or length-and-age-based methods may have greater accuracy than merely age-based, still precise weight measurement while children are recumbent (length) has its own challenges. Objective: We determined the accuracy and reliability of BT by comparing it with actual weight and advanced pediatric life support formula (APLS) among the pediatric population presenting to the emergency department. Methods: This was a single-center, cross-sectional study design. This study was conducted at pediatric emergency of an urban tertiary care hospital after ethics committee approval and written consent from parents/caregivers during July 2021- June 22. Pediatric patients aged 1 month to 12 years, weight 3-36 kg, and height 46.5-142.5 cm on BT were included. Actual weight was measured on a standard weighing machine. We use Broselow pediatric emergency tape (2017 edition), APLS formula was also used to measure the estimated weight by using the age provided by parents. Descriptive analysis, mean and standard deviation were calculated, frequencies and percentages were calculated for categorical variables. Cronbach’s alpha and Passing-Bablok regression analysis was applied to assess the reliability and identify systematic biases between actual body weights with estimated BT. Bland–Altman analysis was also performed to measure the precision, accuracy, and bias. Results: 250 children were included with equal gender distribution and were divided in to three categories as per the weight estimation by BT in to <10 kg (n=58, 23.2%), 10-18 kg (n=151, 60.4%) and >18 kg (n=41, 16.4%). The mean age was 5.26 (±2.37) years, majority of children were below 5 years of age (n=144, 58%). Positive agreement between BT weight with actual weight and other formulas in weight category of <10 kg, however as weight increases from 10 kg, onward results are not significant. Passing and Bablok Regression analysis showed a positive correlation between the estimated and actual (AW) body weight (r=0.9280, p<0.001) and accuracy (r2=0.929), and the accuracy of BT weight decreases with the increasing weight of children. Similarly, 95% agreement limit and mean biased was 0.465 to 1.113 and 0.789±2.602 between BT and APLS, BT with AW was -0.50 to -0.28 and -0.39±0.885. Comparing and correlating weight assessment of APLS formula vs LF and TF didn't show significance with a p-value of 0.041 and 0.034 respectively. Bland-Altman plot between BT measurement with AW demonstrates a bias equal to 1.096 kg with a limit of 0.870 to 1.815. Conclusion: BT may be an accurate and time bound method of weight measurement as compared to other methods of weight estimation, however the accuracy of BT may be adversely affected with age exceeding 95 months and weight >26 kg. BT may be safely used in the younger pediatric population. Health care professionals may consider this information while using BT to estimate weight for pediatric resuscitation, however, this is a single center hospital based study with limited cases, we recommend to have a large scale community based study or a census before to generalize these results to general population.

Longitudinal Retrospective Study of a Wearable NMES System to Determine the Effects on Arm Usage in Hemiparetic and Hemiplegic Patients

ABSTRACT Introduction Brain disorders such as traumatic brain injury (TBI), stroke, cerebral palsy (CP), and surgical interventions can result in aberrant motor function in the contralateral limbs, resulting in paralysis, weakness, and/or spasticity. It is known that, in the short term, neuromuscular electrical stimulation (NMES), the application of low-level electrical currents to motor nerves to induce muscle contractions in paralyzed muscles, can stimulate affected muscle groups and increase arm mobility. However, there remains a paucity of longitudinal evidence examining NMES-mediated improvements of arm usage. Objective The aim of this study was to determine the effectiveness of a long-term BioSleeve intervention on the recovery of arm mobility in hemiparetic patients. Study Design The design of this study is a retrospective cohort study. Methods We examined self-reported arm usage in patients with 1) TBI, 2) stroke, 3) hemispherectomy, or 4) CP who wore Axiobionics’ BioSleeve NMES device and compared this to arm usage achieved from years of conventional therapy. Results The device was well-tolerated. Patients reported an average increase in arm usage from 9.9% to 43.5%, with the TBI subcohort reporting a consistent increase in arm usage of 5.7% per year over the treatment period. Conclusions This study supports the literature suggesting that longitudinal NMES can be used to increase arm usage in hemiplegic patients. Clinical Relevance Statement This study supports the use of wearable NMES intervention in the treatment of arm hemiparesis.

Perspectives on Optimized Transcranial Electrical Stimulation Based on Spatial Electric Field Modeling in Humans

Background: Transcranial electrical stimulation (tES) generates an electric field (or current density) in the brain through surface electrodes attached to the scalp. Clinical significance has been demonstrated, although with moderate and heterogeneous results partly due to a lack of control of the delivered electric currents. In the last decade, computational electric field analysis has allowed the estimation and optimization of the electric field using accurate anatomical head models. This review examines recent tES computational studies, providing a comprehensive background on the technical aspects of adopting computational electric field analysis as a standardized procedure in medical applications. Methods: Specific search strategies were designed to retrieve papers from the Web of Science database. The papers were initially screened based on the soundness of the title and abstract and then on their full contents, resulting in a total of 57 studies. Results: Recent trends were identified in individual- and population-level analysis of the electric field, including head models from non-neurotypical individuals. Advanced optimization techniques that allow a high degree of control with the required focality and direction of the electric field were also summarized. There is also growing evidence of a correlation between the computationally estimated electric field and the observed responses in real experiments. Conclusion: Computational pipelines and optimization algorithms have reached a degree of maturity that provides a rationale to improve tES experimental design and a posteriori analysis of the responses for supporting clinical studies.

Impact of zinc oxide on dielectric properties of forsterite coated titanium based medical implants

Zinc oxide-doped forsterite solutions are synthesized through the sol-gel approach by varying the weight percentage of zinc oxide. These solutions are then applied to titanium (Ti) substrates to form zinc oxide-doped forsterite coated Ti substrate samples using the dip-coating method. The structural and surface morphology analyses of the samples are conducted using x-ray Diffraction (XRD) and Scanning Electron Microscope (SEM). Dielectric properties, encompassing dielectric constant, dielectric loss, alternating current conductivity, loss tangent, and relaxation time are explored at room temperature over a frequency range of 200 MHz to 20 GHz utilizing a Vector Network Analyzer (VNA) setup. The impact of zinc oxide on the structure, morphology, and dielectric properties of the samples, particularly in medical implant applications, is extensively discussed. The results indicate that samples with a higher weight percentage of zinc oxide demonstrate superior dielectric characteristics.

Josephson diode effect in junctions of superconductors with band asymmetric metals

At interfaces connecting two superconductors (SCs) separated by a metallic layer, an electric current is induced when there is a disparity in the phases of the two superconductors. We elucidate this phenomenon based on the weights of the Andreev bound states associated with the states carrying currents in forward and reverse directions. Typically, current phase relation (CPR) in Josephson junctions is an odd function. When time reversal and inversion symmetries are broken at the junction, CPR ceases to be an odd function and the system may exhibit Josephson diode effect. This phenomenon has been studied in spin orbit coupled systems under an external Zeeman field wherein the magnetochiral anisotropy is responsible for the Josephson diode effect. Recently introduced the band asymmetric metal (BAM) model presents a novel avenue, featuring an asymmetric band structure. We investigate DC Josephson effect in SC-BAM-SC junctions and find that band asymmetry can lead to Josephson diode effect and anomalous Josephson effect. We explain the mechanism behind these effects based on interference of plane wave modes within the Bogoliubov de-Genne formalism. We calculate diode effect coefficient for different values of the parameters.

The effect of electrical current on lubricant film thickness in boundary and mixed lubrication contacts measured with ultrasound

AbstractThis work explores experimentally the effects of DC electrical currents on lubricant film thickness alteration in lubricated sliding steel contacts in the boundary and mixed regime as measured by ultrasound. The experiments were performed in a two-electrode cell-based pin-on-disk tester instrumented with ultrasonic transducers. Unelectrified and electrified tribological tests were conducted on steel flat-on-flat contacts under various speeds and loads using both a mineral base oil and a gear oil. Film thickness, coefficient of friction (CoF), and electrical contact resistance (ECR) were measured during short experiments (30 s) in unelectrified and electrified (1.5 and 3 A) conditions. The results suggest that film thickness, CoF, and all ECR are altered by passing DC currents through the contact. In particular, film thickness increased and decreased, respectively, by applying electricity at the different speeds and loads tested. These alterations were majorly ascribed to oil viscosity decrease by local heat and surface oxidation caused by electrical discharge and break down at the interface.

Direct Monitoring of Whole‐Brain Electrodynamics via High‐Spatiotemporal‐Resolution Photoacoustics with Voltage‐Sensitive Dye

AbstractBrain voltage plays a crucial role in indicating internal functions or diseases, and optical voltage imaging has gained intensive attention in recent years. Despite encouraging progress, current implementations encounter limitations pertaining to penetration depth, field of view (FOV), and photostability of indicators. To mitigate these challenges, a robust voltage‐sensitive dye (VSD)‐based whole‐field photoacoustic brain detection (WF‐PABD) platform is proposed, enabling direct evaluation of voltage dynamics across the whole brain, forming as PA‐VSD. WF‐PABD is equipped with a 512‐element ring‐array ultrasound detector capable of 360‐degree scanning, providing a large FOV (≈5 cm), high spatial resolution (≈110 µm), and rapid imaging acquisition. The proposed VSD remained ≈75% photostability after 30 min laser exposure, much greater than most calcium sensors. The optical voltage‐response mechanisms are validated and the capability of PA‐VSD to directly screen seizures is established. It is demonstrated that investigating connectivity among different brain regions allows to identify the precise location of active epileptic foci as well as the electrical conduction pathways and their directionality through fast temporal visualization. In summary, this study not only addresses the need for non‐invasive, high‐resolution, long‐term, and direct monitoring of brain voltage but also empowers exciting venues for PA applications in neuroscience.

#3050 Hemodynamic study of hypertensive disorders in pregnancy using cardiothoracic bioimpedance

Abstract Background and Aims Hypertensive disorders in pregnancy (HDP) are a major cause of maternal and perinatal morbidity and mortality. There is still a need for the development of biomarkers for early diagnosis of the severity of the condition. Thoracic electrical bioimpedance (TEB) is a non-invasive hemodynamic technique based on the resistance to the flow of electrical current. We investigated hemodynamic changes in pregnant/postpartum women with HDP using TEB. Method A retrospective observational study was conducted in pregnant and postpartum women with hypertension monitored by TEB. Indirect changes were analyzed in: cardiac work, left cardiac work index (LCWI kg⋅m/m2) and calculated cardiac output (CO ml/min=systolic volume -SV ml- × heart rate -HR bpm-); fluid status, thoracic fluid content index (TFCI l/kOhm/m2); and resistances, systemic vascular resistance index (SVRI dyn.s.cm-5.m2). Normality of variables was assessed by Shapiro-Wilk test and correlation analysis was performed by Pearson/Spearman tests. Statistical inference between the hypertension-preeclampsia and pregnancy-postpartum groups was performed using Student's/Mann-Whitney U tests. Analysis was performed using STATA 12. Results Fifty-five patients were included with a mean age of 36.5 years (SD 4.54), 69% were older than 35 years. Pregnant women accounted for 86% of the TEB evaluations, the majority (93.6%) in the third trimester. There was chronic hypertension in 7.27% and pre-eclampsia in 18.18% of previous pregnancies. The diagnoses were: pre-eclampsia (56.36%), gestational hypertension (40%) and HELLP syndrome (3.64%). The mean blood pressure was 144/89 (SD 16/11) mmHg. Mean proteinuria was 363.2 (range: 10.3-23220) mg/g. The median values were as follow: LCWI: 5.05 (IQR: 1.4) kg⋅m/m2; CO: 6352 (IQR: 2345) ml/min; TFCI: 17.9 (IQR: 6.3) l/kOhm/m2; SVRI: 2167.63 (SD: 462.87) dyn.s.cm-5.m2. LCWI showed a weak positive correlation with systolic blood pressure (SBP) and a strong correlation with diastolic blood pressure (DBP) (Rho 0.2899 and 0.5176, respectively). There was also a positive and moderate correlation between SVRI and SBP and DBP (r 0.4265 and 0.4019, respectively). There was no correlation between CO or TFCI and SBP or DBP. No statistically significant differences in hemodynamic parameters were found between gestational hypertension and pre-eclampsia, nor between pregnant and postpartum women. Conclusion Increased blood pressure in the setting of HDP correlates with increased LCWI and systemic resistance independent of fluid retention. An increase in systemic vascular resistance measured by TEB (which decreases in normal pregnancy) may be an early diagnostic marker of HDP. These findings require further validation in a larger cohort, including a control group of pregnant women without hypertension.

Analysis of Leakage Current in Dynamic Wireless Power Transfer Systems Based on LCC-S Architecture

This paper investigates the issue of leakage current at the transmitter in the Dynamic Wireless Power Transfer (DWPT) system for electric vehicles and puts forward a novel bilateral resonant compensation topology structure based on the conventional LCC-S architecture. Based on the LCC-S framework, a circuit model was developed for traditional (unilateral)/bilateral resonant compensation topologies. The Fourier series voltage-to-earth expansions for the power supply rail were deduced for both topologies. Subsequently, the voltage-to-earth waveforms for the power supply rail were obtained by utilizing the Fourier series expansions of the voltage-to-earth and the corresponding circuit simulation models. The results demonstrate the efficacy of the bilateral resonant compensation topology in mitigating higher-order harmonics of the voltage to earth on the power supply rail by effectively suppressing the distortion in the leakage current and minimizing its conduction. The effectiveness of the double-ended resonant compensation topology in suppressing leakage current conduction has been verified through experimental tests and waveform comparisons of the voltage to earth and leakage current on the power supply rail under two different topologies. Through experimental testing, during which the unilateral/bilateral resonant compensation topologies were compared, an analysis was conducted on the waveforms of the voltage to earth and leakage current of the power supply rail. The results verified the effectiveness of the bilateral resonant compensation topology in mitigating the conduction of leakage current. This study provides empirical evidence supporting the use of the bilateral resonant compensation topology for suppressing leakage current in power rail applications.

Simple circuit and experimental proposal for the detection of gauge-waves

Abstract Aharonov-Bohm electrodynamics predicts the existence of traveling waves of pure potentials, with zero electromagnetic fields, denoted as gauge waves, or g-waves for short. In general, these waves cannot be shielded by matter since their lack of electromagnetic fields prevents the material from reacting to them. However, a not-locally-conserved electric current present in the material does interact with the potentials in the wave, giving the possibility of its detection. In [F.M.,G.M.,Eur.Phys.J. C 83, 1086 (2023)] the basic theoretical description of a detecting circuit was presented, based on a phenomenological theory of materials that can sustain not-locally-conserved electric currents. In the present work we discuss how that circuit can be built in practice, and used for the effective detection of g-waves.

Br-Vacancies Induced Variable Ranging Hopping Conduction in High-Order Topological Insulator Bi4Br4.

The defects have a remarkable influence on the electronic structures and the electric transport behaviors of the matter, providing the additional means to engineering their physical properties. In this work, a comprehensive study on the effect of Br-vacancies on the electronic structures and transport behaviors in the high-order topological insulator Bi4Br4 is performed by the combined techniques of the scanning tunneling microscopy (STM), angle-resolved photoemission spectroscopy (ARPES), and physical properties measurement system along with the first-principle calculations. The STM results show the defects on the cleaved surface of a single crystal and reveal that the defects are correlated to the Br-vacancies with the support of the simulated STM images. The role of the Br-vacancies in the modulation of the band structures has been identified by ARPES spectra and the calculated energy-momentum dispersion. The relationship between the Br-vacancies and the semiconducting-like transport behaviors at low temperature has been established, implying a Mott variable ranging hopping conduction in Bi4Br4. The work not only resolves the unclear transport behaviors in this matter, but also paves a way to modulate the electric conduction path by the defects engineering.

Design of adaptive hybrid MPPT controllers with universal input voltage DC–DC converter for RES’s

At present, conventional energy production is absent because of the more hazardous gases released into the environment, the high effect on human health, more cost required for maintenance, plus less usefulness for highly populated areas. So, the Renewable Energy Sources are more focused for the present automotive industry application. In this work, the Proton Exchange Membrane Fuel Stack is considered for analyzing the proposed DC–DC converter circuit. The advantages of this fuel stack are high energy density, fast functioning nature, more robustness, and more usefulness for the various water membrane conditions of the fuel stack. However, the disadvantages of the fuel stack are excessive current generation, plus more current conduction losses. So, the wide voltage supply single switch power converter is introduced in this work for optimizing the current production of the fuel stack network. The merits of this converter circuit are high stability, good reliability, low voltage appearing across the switches, plus a uniform power supply. Here, the converter switching pulses are obtained by proposing the Modified Continuous Step Change Adaptive Fuzzy Logic with Grey Wolf Optimization hybrid controller. This controller provides high maximum power extraction efficiency from the fuel stack which is equal to 99.421%. Also, this controller's Maximum Power Point Tracking time is 0.0285 s.

Rapid low-temperature densification of Ag2Se bulk material: mass transfer through the dissociative adsorption reaction of Ag protrusions and Se saturated vapor

In materials science, the impact of density on a material’s capabilities is profound. Conventional sintering requires high temperatures and is energy-demanding, propelling the pursuit of less intensive, low-temperature densification methods. Electric field-assisted sintering has recently gained attention for its simplicity and effectiveness, offering a new frontier in low-temperature densification. In this study, dense bulk materials were produced by subjecting monophasic Ag2Se powders to electric field-assisted sintering, where a direct current with an average value of 4 A was applied, achieving a peak temperature of 344 K. The novel low-temperature densification mechanism unfolds thus: nanoscale silver protrusions, stimulated by electrical current, engage in a dissociative adsorption reaction with the ambient saturated selenium vapor. This process swiftly engenders the formation of fresh silver selenide (Ag2Se) compounds, initiating nucleation and subsequent growth. Consecutively, these compounds seamlessly occupy and expand, perpetually bridging the interstices amidst the powders. In a scant 8 s, the density swiftly surpassed 99%, yielding a bulk material that exhibited a ZT value of 1.07 at 390 K. This investigation not only attains an unparalleled density at low temperatures but also charts a pioneering course for material densification in such conditions.