Measurement Of Current Flow Research Articles

Characterization of Mechanical Oscillations in Bismuth Selenide Nanowires at Low Temperatures.

A single transistor preamplifier circuit was designed to facilitate electrical detection of mechanical oscillations in nanoelectromechanical systems (NEMSs) at low temperatures. The amplifier was integrated in the close vicinity of the nanowire inside the cryostat to minimize cabling load and interference. The function of the circuit was impedance conversion for current flow measurements in NEMSs with a high internal resistance. The circuit was tested to operate at temperatures as low as 5 K and demonstrated the ability to detect oscillations in double-clamped bismuth selenide nanowires upon excitation by a 0.1 MHz-10 MHz AC signal applied to a mechanically separated gate electrode. A strong resonance frequency dependency on temperature was observed. A relatively weak shift in the oscillation amplitude and resonance frequency was measured when a DC bias voltage was applied to the gate electrode at a constant temperature.

Compatible Phase Current Reconstruction Scheme for Fault-Tolerant Five-Leg Dual-Inverter Fed Open-Winding Permanent Magnet Synchronous Motor

In this paper, a novel phase current reconstruction strategy for a Five-Leg Dual-Inverter (FL-DI) fed Open-Winding Permanent Magnet Synchronous Motor (OW-PMSM) drive is put forward. Benefiting from the doubling of the power legs, the OW-PMSM drive is endowed with outstanding fault-tolerant ability. When an open-circuit fault occurs, the OW-PMSM automatically turns to the post-fault Two-Phase (2-ph) operation. By reconfiguring the wiring method, the fault-tolerant FL-DI topology is obtained, and the post-fault Three-Phase (3-ph) operation is realized. However, the current flow path changes and measurement vectors become unavailable in post-fault operation processes, making the existing current reconstruction schemes unusable. To prevent the system collapse caused by the current reconstruction failure, a novel current reconstruction strategy is proposed, which can be applied in the case of the open-circuit fault in any leg. In addition, the proposed current reconstruction strategy is compatible with the specific Zero-Sequence Current (ZSC) suppression for the FI-DI fed OW-PMSM drive, which ensures better system performance in the post-fault operation. The reconstructed current is of high accuracy, where the relative reconstruction error is 7.8% at low load and 5.3% at heavy load. Finally, experimental results are presented to verify the feasibility and effectiveness of the proposed strategy.

Apparatus for measurement of thermoelectric properties of a single leg under large temperature differences.

Thermoelectric (TE) devices operate under large temperature differences, but material property measurements are typically accomplished under small temperature differences. Because of the issues associated with forming proper contact between the test sample and the electrodes and the control of heat flux, there are very few reports on large temperature difference measurements. Therefore, practically relevant performance parameters of a device, namely, power output and efficiency, are estimated by temperature averaging of material properties, whose accuracy is rarely validated by experimental investigations. To overcome these issues, we report an apparatus that has been designed and assembled to measure the TE properties-Seebeck coefficient, electrical conductivity, thermal conductivity, and power output and efficiency of a single thermoelectric material sample over large temperature gradients. The sample holder-a unique feature of this design-lowers the contact resistance between the sample and the electrodes, allowing for more accurate estimates of the sample's properties. Measurements were performed under constant temperature differences ranging from 50 to 300K with the hot side reaching 673K on a metallized Mg2Si0.3Sn0.7 leg synthesized in the laboratory. To simulate practical operating conditions of a continuously loaded generator, continuous current flow measurements were also performed under large temperature differences. The temperature-averaged TE properties from standard low temperature difference measurements and the experimental TE properties agree with each other, indicating that the designed setup is reliable for measuring various thermoelectric generator properties of single TE legs when subjected to temperature gradients between 50 and 300K.

EDNA and Acoustic Tag Monitoring Reveal Congruent Overwintering Distributions of Striped Bass in a Hydrologically Complex Estuarine Environment

After collapsing in the late 1990s, the southern Gulf of St. Lawrence population of striped bass (Morone saxatilis) is recovering. Here, we evaluate the use of under-ice eDNA sampling to monitor the population and confirm overwintering locations. From 2018 to 2020, water samples were collected from transects spanning 35 km of the Miramichi River system, accounting for the effects of sampling site, month, sampling depth and tidal influence on eDNA concentration. We examined the distribution of eDNA in a complex tidal river system with a time series consisting of 12 h of continuous sampling throughout a tidal cycle, in conjunction with the use of artificial DNA tracers and acoustic Doppler current profiler flow measurements. The eDNA distribution correctly identified overwintering grounds based on acoustic tag data, including a perceptible upstream shift in 2020. Overall, there was no significant effect of year, sampling month (February or March), sampling depth or tidal phase on eDNA concentrations. The tidal time series revealed only weak patterns of eDNA recirculation. Monitoring eDNA concentration and distribution allows for a relative comparison of population size and location between years, and has the potential to be expanded to other river systems more easily than traditional acoustic fish tags and surveys.

Study on Flow Velocity Distribution in Open Channel With Flexible Vegetation

Ecological management of river channels is a hot topic for current sustainable development and flow measurement of ecological river is an important part. In this article, a flow velocity distribution model of the channel containing flexible vegetation is constructed from the vegetation riverbed theory and the bursting phenomenon to reveal the microscopic mechanism of the flow velocity distribution in the upper layer of vegetation. In the vegetation riverbed law, the effect of flexible vegetation is evaluated by the mixed length formula. The bursting phenomenon law considers the influence of the channel sidewalls on the flow and a two-dimensional velocity model is established by introducing the concept of average turbulence structure. The mechanism of the downward shift of the maximum flow velocity point on the channel sidewall is explained. The verification of the calculated velocity profiles is carried out based on data obtained in laboratory experiments. The results show that the combination of the two models can well describe the velocity distribution of the whole channel. At the end, the phenomenon of flow velocity zoning in open channel is discussed, which provides a solution for flow measurement in ecological channel.

Technical note: Novel triple O<sub>2</sub> sensor aquatic eddy covariance instrument with improved time shift correction reveals central role of microphytobenthos for carbon cycling in coral reef sands

Abstract. The aquatic eddy covariance technique stands out as a powerful method for benthic O2 flux measurements in shelf environments because it integrates effects of naturally varying drivers of the flux such as current flow and light. In conventional eddy covariance instruments, the time shift caused by spatial separation of the measuring locations of flow and O2 concentration can produce substantial flux errors that are difficult to correct. We here introduce a triple O2 sensor eddy covariance instrument (3OEC) that by instrument design eliminates these errors. This is achieved by positioning three O2 sensors around the flow measuring volume, which allows the O2 concentration to be calculated at the point of the current flow measurements. The new instrument was tested in an energetic coastal environment with highly permeable coral reef sands colonised by microphytobenthos. Parallel deployments of the 3OEC and a conventional eddy covariance system (2OEC) demonstrate that the new instrument produces more consistent fluxes with lower error margin. 3OEC fluxes in general were lower than 2OEC fluxes, and the nighttime fluxes recorded by the two instruments were statistically different. We attribute this to the elimination of uncertainties associated with the time shift correction. The deployments at ∼ 10 m water depth revealed high day- and nighttime O2 fluxes despite the relatively low organic content of the coarse sediment and overlying water. High light utilisation efficiency of the microphytobenthos and bottom currents increasing pore water exchange facilitated the high benthic production and coupled respiration. 3OEC measurements after sunset documented a gradual transfer of negative flux signals from the small turbulence generated at the sediment–water interface to the larger wave-dominated eddies of the overlying water column that still carried a positive flux signal, suggesting concurrent fluxes in opposite directions depending on eddy size and a memory effect of large eddies. The results demonstrate that the 3OEC can improve the precision of benthic flux measurements, including measurements in environments considered challenging for the eddy covariance technique, and thereby produce novel insights into the mechanisms that control flux. We consider the fluxes produced by this instrument for the permeable reef sands the most realistic achievable with present-day technology.

Measurement of critical current flow and connectivity in systems of joined square superconducting plates

A method to measure the electrical connectivity between square superconducting plates joined by weak link interfaces is presented. It is based on observation of lines where the flow of critical current abruptly changes direction due to the presence of weak links, and the confinement created by the shape of the sample. The method is demonstrated using magneto-optical imaging (MOI) of systems consisting of up to 2×2 plates joined to form a larger square. The samples used in this study are Nb films with weak links created by focused ion beam machining. Common features are found in the current flow patterns, which allow to measure the electrical connectivity between the plates by observing an angle between pairs of lines indicating where the current abruptly changes flow direction, so-called discontinuity, or d-lines.

Measurement of Electroconvulsive Therapy Current Flow on Cadaver Head by Different Electrode Placements

Electroconvulsive Therapy (ECT) has been the golden standard treatment for refractory depression. There have been three electrode placements including bilateral, right unilateral and bifrontal that are widely used so far. While some of those electrode placements have superior efficacy, they also had more memory impairments. Our aim is to explore flow currents of different electrode placements including a novel electrode placement

Assessment of pressure field and performance parameter reconstruction from velocity data for ramjet inlet

The current flow measurement devices for ramjet inlet still have many limitations in the supersonic internal flow, such as the qualitative feature of schlieren and the low resolution of pressure tap/probe. In this paper, a non-intrusive measurement scheme for the internal pressure field and performance parameters of ramjet inlet based on particle image velocimetry (PIV) data is established and quantitatively evaluated by using a typical model. This scheme is combined with two important PIV-based pressure reconstruction approaches, namely, the spatial integration in conservative form and the MacCormack method, which are especially suitable for the supersonic flows with shock waves. The feasibility of this scheme is firstly confirmed by using a numerical velocity field, and the turbulence contribution is concluded to be negligible. Then, a simulated PIV experiment is conducted to achieve a synthetic velocity field with various theoretical measurement errors for the comprehensive analyses of the accuracy and robustness of this measurement method. Compared with the traditional equipment, the PIV-based method can obtain the high-resolution velocity and pressure distributions of whole flow field without interference, and the performance parameters are also available along the flow path. The good reconstruction results show the great advantage and attraction of this non-intrusive method in the future wind tunnel test for ramjet inlet.

Stable Photoelectrochemical Hydrogen Evolution for 1000 Hours at 14% Efficiency in a Monolithic Device

The development of a fully-integrated, photoelectrochemical (PEC) device coupling water oxidation to hydrogen evolution using a III-V triple-junction photovoltaic (PV) embedded in a Nafion membrane is reported. This architecture is genuinely monolithic, with wireless catalyst integration being achieved via compression of metal sputter-coated, carbon electrodes against the front and back PV contacts. The resulting MEA-type, sandwich structure minimizes the path length for proton conduction through the membrane ionomer, while simultaneously preventing PV light attenuation by the catalyst layer, a common issue for monolithic PEC structures. While the wireless nature of monolithic PEC devices typically prevents the measurement of current flow and faradaic efficiencies, we circumvent this complication through the placement of an electrical shunt between the PV and the cathode catalyst layer, rerouting charge generated at the PV through a potentiostat prior to cathodic proton reduction. Using this device architecture, we demonstrate significant enhancements in device stability and longevity, by transitioning from a liquid-water to water-vapor anode. Our use of a gas-fed anode enables 1000 hours of cumulative device operation at a peak solar-to-hydrogen efficiency of 14%, during simulated, solar illumination at 1 sun and outdoor, diurnal cycling. Vapor-fed water oxidation is shown to reduce drops in device performance by mitigating the corrosion effects that are commonly associated with full-aqueous immersion of the electrochemical and photovoltaic elements in PEC devices. Causes for observed fluctuations in device performance are determined through the collection of real-time, current-voltage data, paired with an analytical method, permitting the deconvolution of PV- and catalyst-driven performance losses. Figure 1

Stable Photoelectrochemical Hydrogen Evolution for 1000 Hours at 14% Efficiency in a Monolithic Device

The development of a fully-integrated, photoelectrochemical (PEC) device coupling water oxidation to hydrogen evolution using a III-V triple-junction photovoltaic (PV) embedded in a Nafion membrane is reported. This architecture is genuinely monolithic, with wireless catalyst integration being achieved via compression of metal sputter-coated, carbon electrodes against the front and back PV contacts. The resulting MEA-type, sandwich structure minimizes the path length for proton conduction through the membrane ionomer, while simultaneously preventing PV light attenuation by the catalyst layer, a common issue for monolithic PEC structures. While the wireless nature of monolithic PEC devices typically prevents the measurement of current flow and faradaic efficiencies, we circumvent this complication through the placement of an electrical shunt between the PV and the cathode catalyst layer, rerouting charge generated at the PV through a potentiostat prior to cathodic proton reduction. Using this device architecture, we demonstrate significant enhancements in device stability and longevity, by transitioning from a liquid-water to water-vapor anode. Our use of a gas-fed anode enables 1000 hours of cumulative device operation at a peak solar-to-hydrogen efficiency of 14%, during simulated, solar illumination at 1 sun and outdoor, diurnal cycling. Vapor-fed water oxidation is shown to reduce drops in device performance by mitigating the corrosion effects that are commonly associated with full-aqueous immersion of the electrochemical and photovoltaic elements in PEC devices. Causes for observed fluctuations in device performance are determined through the collection of real-time, current-voltage data, paired with an analytical method permitting the deconvolution of PV-driven and catalyst-driven performance losses. Figure 1

Comparing the results of field modelling to physiological measurements and MR-based current flow measurements

Spatial targeting is often still only loosely controlled in TES studies, which can weaken the conclusions drawn about the brain areas that underlie the physiological and behavioral stimulation effects. Targeting control can be improved using electric field calculations based on Finite-Element Methods (FEM) and anatomically realistic head models. We highlight the relevance of FEM-based targeting control and optimization by summarizing recent key findings from simulation studies that characterized the field distributions generated by established single- and dual-site TACS montages.

Editors' Choice—A Monolithic Photoelectrochemical Device Evolving Hydrogen in Pure Water

We report the development of a fully-integrated, photoelectrochemical (PEC) device coupling water oxidation to hydrogen evolution using a III-V triple-junction photovoltaic (PV) embedded in a Nafion membrane. This architecture is genuinely monolithic, with wireless catalyst integration being achieved via compression of metal sputter-coated carbon electrodes against the front and back PV contacts. The resulting MEA-type, sandwich structure minimizes the path length for proton conduction through the membrane ionomer, while simultaneously preventing PV light attenuation by the catalyst layer, a common issue for monolithic PEC structures. Simulated, solar illumination of this construct, when operating in neutral-pH water, yields a peak solar-to-hydrogen efficiency of 12.6% during a four-day trial. While the wireless nature of monolithic PEC devices typically prevents the measurement of current flow and faradaic efficiencies, we circumvent this complication through the placement of an electrical shunt between the PV and the cathode catalyst layer, rerouting charge generated at the PV through a potentiostat prior to cathodic proton reduction. Using this configuration, we also show evidence of a corrosion current competing with anodic oxygen evolution under acidic conditions, highlighting the importance of quantifying product generation in monolithic devices.

ASSESSMENT OF HYDRO-ENVIRONMENTAL CONDITION USING NUMERICAL MODELING IN DIBAWAH LAKE, WESTERN SUMATRA, INDONESIA

This study investigates the hydro-environmental condition of Dibawah Lake, Province of WesternSumatra, Indonesia, using a finite element model called the Surface-water Modeling System (SMS). The aimis to present the parameters distribution in the existing condition and a year later. Field measurements arecarried out to supply data for the domain input, boundary conditions, and model validation. The fieldmeasurements are lake-bed elevation, water level, current flow, and contaminant quantity measurements. Thecontaminant measurements are carried out to collect biochemical oxygen demand (BOD), sulfide, and totalsuspended sediment (TSS). The existing flow model is validated by current flow and water elevation field data.The validation shows a decent agreement. The result of water quality modeling, using the water quality moduleof SMS called RMA4, shows that after a year the BOD content is still in an acceptable proportion, which isless than 2 mg/liter. However, it is found that the sulfide content exceeds the limit defined by the governmentregulation, at over 0.002 mg/liter. In the sedimentation model generated by the module in SMS called SED2D,the maximum bed change obtained is around 15 cm, located at the inlet of two rivers connected to the lake.The proposed mitigation of the current research findings is to control the use of fertilizer around the lakewatershed area with the aim of lowering the sulfide content and to maintain the lake bed elevation by routinedredging, particularly in the river inlets.

Improved sulfide mitigation in sewers through on-line control of ferrous salt dosing

Water utilities worldwide spend annually billions of dollars to control sulfide-induced corrosion in sewers. Iron salts chemically oxidize and/or precipitate dissolved sulfide in sewage and are especially used in medium- and large-size sewers. Iron salt dosing rates are defined ad hoc, ignoring variation in sewage flows and sulfide levels. This often results in iron overdosing or poor sulfide control. Online dosing control can adjust the chemical dosing rates to current (and future) state of the sewer system, allowing high-precision, stable and cost-effective sulfide control. In this paper, we report a novel and robust online control strategy for the dosing of ferrous salt in sewers. The control considers the fluctuation of sewage flow, pH, sulfide levels and also the perturbation from rainfall. Sulfide production in the pipe is predicted using auto–regressive models (AR) based on current flow measurements, which in turn can be used to determine the dose of ferrous salt required for cost-effective sulfide control. Following comprehensive model-based assesment, the control was successfully validated and its effectiveness demonstrated in a 3-week field trial. The online control algorithm controlled sulfide below the target level (0.5 mg S/L) while reducing chemical dosing up to 30%.

Development of an Automated Three-Phase Distribution Box System

Most electrical appliances require continuous power supply. For domestic use, crucial appliances such as refrigerator, aquarium and alarm system highly depend upon the continuity of power supply. However, if they are left without electricity due to power outage or blackouts caused by internal or external disturbance, the discontinuity of power supply could be a critical issue to some involving party. Blackouts may be due to short circuit, fault or the overloading of electricity mains. During power outage, Residual Current Device (RCD) detects fault currents from live to the neutral wire within circuit and will trip to prevent shock. This circumstance can increase safety when a house is left unoccupied. Be that as it may, the power will remain switched off until manually reset by man. Thus, this paper presented a new concept of Three-Phase distribution box system in order to overcome tripping problem. This system will be able to identify and isolate the fault using measurement of current flow into each Miniature Circuit Breaker (MCB) of appliances and current flowing out from each of the load. The measured current value will be compared and the maximum allowable difference is 30mA. If the current difference exceeds the maximum limit then the fault MCB will be detected. Hence RCD will be automatically close the circuit after determining the fault location via the motor operation to make sure of power stability and evade any property loss.

A detached eddy simulation model for the study of lateral separation zones along a large canyon‐bound river

AbstractLateral flow separation occurs in rivers where banks exhibit strong curvature. In canyon‐bound rivers, lateral recirculation zones are the principal storage of fine‐sediment deposits. A parallelized, three‐dimensional, turbulence‐resolving model was developed to study the flow structures along lateral separation zones located in two pools along the Colorado River in Marble Canyon. The model employs the detached eddy simulation (DES) technique, which resolves turbulence structures larger than the grid spacing in the interior of the flow. The DES‐3D model is validated using Acoustic Doppler Current Profiler flow measurements taken during the 2008 controlled flood release from Glen Canyon Dam. A point‐to‐point validation using a number of skill metrics, often employed in hydrological research, is proposed here for fluvial modeling. The validation results show predictive capabilities of the DES model. The model reproduces the pattern and magnitude of the velocity in the lateral recirculation zone, including the size and position of the primary and secondary eddy cells, and return current. The lateral recirculation zone is open, having continuous import of fluid upstream of the point of reattachment and export by the recirculation return current downstream of the point of separation. Differences in magnitude and direction of near‐bed and near‐surface velocity vectors are found, resulting in an inward vertical spiral. Interaction between the recirculation return current and the main flow is dynamic, with large temporal changes in flow direction and magnitude. Turbulence structures with a predominately vertical axis of vorticity are observed in the shear layer becoming three‐dimensional without preferred orientation downstream.

Dynamics of ion beam charge neutralization by ferroelectric plasma sources

Ferroelectric Plasma Sources (FEPSs) can generate plasma that provides effective space-charge neutralization of intense high-perveance ion beams, as has been demonstrated on the Neutralized Drift Compression Experiment NDCX-I and NDCX-II. This article presents experimental results on charge neutralization of a high-perveance 38 keV Ar+ beam by a plasma produced in a FEPS discharge. By comparing the measured beam radius with the envelope model for space-charge expansion, it is shown that a charge neutralization fraction of 98% is attainable with sufficiently dense FEPS plasma. The transverse electrostatic potential of the ion beam is reduced from 15 V before neutralization to 0.3 V, implying that the energy of the neutralizing electrons is below 0.3 eV. Measurements of the time-evolution of beam radius show that near-complete charge neutralization is established ∼5 μs after the driving pulse is applied to the FEPS and can last for 35 μs. It is argued that the duration of neutralization is much longer than a reasonable lifetime of the plasma produced in the sub-μs surface discharge. Measurements of current flow in the driving circuit of the FEPS show the existence of electron emission into vacuum, which lasts for tens of μs after the high voltage pulse is applied. It is argued that the beam is neutralized by the plasma produced by this process and not by a surface discharge plasma that is produced at the instant the high-voltage pulse is applied.

Three-dimensional deformation of a large circular flexible sea cage in high currents: Field experiment and modeling

This paper presents the full-scale measurements of the deformation and current reduction of a large-scale fish sea cage submitted to high currents. Pressure tags were used to measure the cage deformation and the vertical displacement of the bottom ring, while an Acoustic Doppler Current Profiler (ADCP) and Acoustic Doppler Velocimeter (ADV) were used to measure the current reduction. The results show a reduction of 30% of the cage volume for current velocity above 0.6m/s. The measured current reduction in the cage was 21.5%. A simulation model based on super-elements describing the cage shape was applied, and the results show good agreement with the cage deformations. Also the current flow measurements show the interaction between the sea cage and the bathymetry chart.

Water flow measurements in Turkey's rivers and evaluation of alternative methods

The accuracy and sustainability in the flow measurement of rivers has a great importance for the water management, planning of water storage structures and prediction of floods. Flow measurements include some difficulty due to the variability of many hydrologic factors. Current rivers flow measurement in Turkey is generally based on the use of limnograph and discharge rating curve and, advances has mostly been made the improvement of reading of limnograph. In this study, at the stage of the discharge measurement, giving priority to the improvement in the measurements of flow velocity and cross-section has been emphasized. Then, while obtaining discharge rating curve, it was expressed that not only the depth of water but also flow velocity values have to be taken into account for the preparing and using the discharge rating curve. A field study conducted by the acoustic method sampled for the assessments that were made. From findings, It was concluded that the use of flow velocity values for the discharge rating curve gives better estimate results.