Electrical Current Levels Research Articles

Adjustments of the amplitude mapping function: Sensitivity of cochlear implant users and effects on subjective preference and speech recognition

Objective: In sound processors of cochlear implant (CI) users, input sound signals are analysed in multiple frequency channels. The amplitude mapping function (AMF) is the output compression function dictating the conversion from (acoustical) channel output levels to (electrical) current levels used for electrode stimulation. This study focused on the detectability of AMF adjustments by CI users and the effects of detectable AMF adjustments on subjective preference and performance. Design: Just noticeable differences (JNDs) for AMF settings were measured for pre-processed sentences at 60 dB SPL in quiet and noise. Three AMF settings, ranging twice the JND, were used during a take-home trial period of 12 days. Subjective ratings were collected and speech recognition in quiet and noise was measured. Study sample: JND measurements: 17 CI users. Field experiment: 15 CI users. Results: JNDs for AMF settings varied among subjects and were similar in quiet and noise. A steeper AMF in the lower part was advantageous for speech recognition in quiet at soft levels. Subjective ratings showed limited agreement with speech recognition, both in quiet and noise. Conclusions: CI users may benefit from different AMF settings in different listening situations regarding subjective preference and speech perception, especially for speech in quiet.

Real-time single-molecule electronic DNA sequencing by synthesis using polymer-tagged nucleotides on a nanopore array

DNA sequencing by synthesis (SBS) offers a robust platform to decipher nucleic acid sequences. Recently, we reported a single-molecule nanopore-based SBS strategy that accurately distinguishes four bases by electronically detecting and differentiating four different polymer tags attached to the 5'-phosphate of the nucleotides during their incorporation into a growing DNA strand catalyzed by DNA polymerase. Further developing this approach, we report here the use of nucleotides tagged at the terminal phosphate with oligonucleotide-based polymers to perform nanopore SBS on an α-hemolysin nanopore array platform. We designed and synthesized several polymer-tagged nucleotides using tags that produce different electrical current blockade levels and verified they are active substrates for DNA polymerase. A highly processive DNA polymerase was conjugated to the nanopore, and the conjugates were complexed with primer/template DNA and inserted into lipid bilayers over individually addressable electrodes of the nanopore chip. When an incoming complementary-tagged nucleotide forms a tight ternary complex with the primer/template and polymerase, the tag enters the pore, and the current blockade level is measured. The levels displayed by the four nucleotides tagged with four different polymers captured in the nanopore in such ternary complexes were clearly distinguishable and sequence-specific, enabling continuous sequence determination during the polymerase reaction. Thus, real-time single-molecule electronic DNA sequencing data with single-base resolution were obtained. The use of these polymer-tagged nucleotides, combined with polymerase tethering to nanopores and multiplexed nanopore sensors, should lead to new high-throughput sequencing methods.

Improved Repeatability in Planar Water-gated Field Effect Transistor (WG-FET) with 16-nm-thick Single Crystalline Si Film

Repeatable operation of a water-gated field effect transistor (WG-FET) with 16-nm-thick single crystalline silicon (Si) film is reported for the first time. For devices with fluidic interface, repeatability is highly important, especially when they are used for microfluidic applications such as biomedical sensors or lab-on-a-chip implementations. Previous devices have shown almost an order of magnitude decrease in electrical current levels after the first operation. In this work, stable results are obtained for at least ten days after the first operation by insulating silicon oxide (SiO2) region surrounding the active area.

INFLUENCE OF MINERAL ACCRETION INDUCED BY ELECTRIC CURRENT ON THE SETTLEMENT AND GROWTH OF THE SCLERACTINIAN CORAL POCILLOPORA DAMICORNIS (CNIDARIA, ANTHOZOA, HEXACORALLIA)

The effect of mineral accretion induced by electric current on settlement, growth, and survival of planula larvae and juvenile corals of Pocillopora damicornis was examined by both laboratory and field experiments. The laboratory experiment showed that the numbers of larvae settling on tiles with coralline algae and steel plates encrusted with limestone under no electric current condition were higher than that of other conditions. In the field, the highest survival rates of juvenile corals occurred under the lowest electric current density. However, there was no difference on the growth of juvenile corals between different electric current levels. The mineral accretion could potentially be used to enhance survival of juvenile corals for coral rehabilitation purpose.

Evaluation of children presenting to the emergency room after electrical injury.

To evaluate children who presented to the Pediatric Emergency Department with electrical injury and to discuss the follow-up of these cases and potential precautions that can be taken. A total of 36 patients presented to the Pediatric Emergency Department with electrical injury between May 2010 and May 2013, and these cases were investigated retrospectively. The patients' age and sex, location and form of exposure to electric current, seasonal distribution, length of hospital stay, musculoskeletal and cardiovascular system complications, renal damage, and treatments were recorded. The majority of the patients were exposed to low-voltage electrical current at home. When the patients were evaluated based on the type of electric current, alanine transaminase, aspartate transaminase, creatine kinase, and creatine kinase-myocardial isoenzyme levels were found to be significantly higher among patients who were exposed to high-voltage electric current. None of the patients died, and the mean length of hospital stay was 2.50 ± 1.06 days. Electrical injuries can present with a wide variety of problems, ranging from a simple injury to life-threatening severe multiple organ injury. Even simple precautions can prevent possible morbidity and mortality. We think that the public level of knowledge and awareness should be increased.

The Effects of Driver Speed Prediction-Based Battery Management System on Li-ion Battery Performance for Electric Vehicles

The electric vehicle (EV) technologies have received great attention due to the potential contributions to reducing emissions and energy consumption. The relatively short travel distance and battery lifetime of EV are major concerns for consumers. It is suggested that driver behavior plays important role in determining EV battery’s electric current and heat generation, which have effects on travel distance of EV and its battery lifetime. To address this problem, the current work proposes a Driver Speed Prediction-Based Battery Management System (P-BMS). P-BMS is able to innovatively predict both electric current and temperature of EV battery based on driver behavior, proactively manage and control both electric current and temperature level of the EV battery in order to minimize energy consumption and maximize both travel distance of EV and EV battery lifetime. Results suggest that P-BMS can significantly reduce energy, extend travel distance in one charge and prolong EV battery lifetime.

Deep Hole of AISI P20 Mold Steel Material by Electrical Discharge Machining

This research aimed to study the machining efficiency of AISI P20 steel by Electrical Discharge Machining (EDM) using rod copper electrode to machining material by 50 mm depth of machining was mainly assessed from Materials Removal Rate (MRR) and Electrode Wear Ratio (EWR). From the experiment designed to use Taguchi technique of data analysis and suitable parameter prediction, the highest MRR was at on-time of 150 μs, off-time of 2 μs and electric current level was at 15 A or 0.25 A/mm2. Predicted value was at 19.2395 mm3/min which was equal to real experiment, showing Materials Removal Rate of 19.647 mm3/min (with error of 2.12 percent) .Moreover, it was found that gap would increase with the size of electrode and depth of machining caused by movement of particles removed from side surface of electrode, which cause micro sparks at the side of the material workpiece.

Oil whip-induced wear in journal bearings

This paper investigates the effect of oil whirl and oil whip in fluid film radial bearings due to possible metallic contact. The degree of metallic contact and thereby wear and tear between rotating shafts and bearing bushes is assessed by measuring electric currents through the oil film. The current as well as the voltage varied in accordance with the contact ratio between the shaft and bush in the fluid film radial bearing. The gauge signal thus indicates the degree of metallic contact based on the thickness of the oil film in the load zone. Some experimental results are provided to illustrate that at low normalised loads involving oil whirl and oil whip, no electric current is detected, while high levels of electric current are registered at high load levels when no oil whirl or oil whip occurred. It is therefore concluded that at low loads, oil whirl and oil whip have little influence on wear and tear in a journal bearing.

ELECTROLYSIS OF SWINE MANURE EFFLUENTS USING THREE DIFFERENT ELECTRODES Fe-Fe, Al-Al AND Fe-Al

Swine effluent with high organic strength need to be treated to make it suitable for applying to crop/pasture fields, or discharging to any waterways. Electrocoagulation is a relatively simpler and cheaper technique over biological and chemical treatment methods currently used to treat high-strength industrial and municipal wastewater. The performance of an electrocoagulation system mainly depends on the pH, Electrical Conductivity (EC) of the medium, Chemical Oxygen Demand (COD) loading rates and catalytic activity of the electrodes used. In this research, a study was conducted to compare the pollutant removal efficiencies of three electrodes (Fe-Fe, Al-Al and Fe-Al) with three electric current levels (500, 1000 and 2000 mA) while treating swine manure effluents. The electrochemical cell consisted of two parallel rectangular plates (90×25×1.5 mm) of Iron (Fe-Fe), Aluminum (Al-Al) and Iron-Aluminum (Fe-Al, later on described as hybrid) electrodes; immersed in a beaker with 550 mL swine effluents and powered by a Direct Current (DC) supply. All studies were conducted in batches at room temperature. In general, removal efficiencies were increased with increasing current densities and electrolysis times for electrodes evaluated. Aluminum electrodes outperformed iron and hybrid (iron-aluminum electrodes) in removing Total Phosphorus (TP) at all current density levels tested. Overall, use of hybrid electrodes resulted in better COD removal. For the same treatment times (1200 s) at higher current density (21 mA cm-2), hybrid electrodes removed about 100% COD, which are about 1.9 and 1.3 times higher than those of aluminum and iron electrodes, respectively. Iron electrodes showed the highest removal efficiency (85%) for Total Organic Carbon (TOC) at 21 mA cm-2 current density and 1200 s treatment time. Overall, lower Specific Electrical Energy Consumptions (SEECs) per kg of Pollutants (TP, COD and TOC) were estimated for the aluminum electrodes than the other electrodes combination.

Primary auditory cortical responses to electrical stimulation of the thalamus

Cochlear implant electrical stimulation of the auditory system to rehabilitate deafness has been remarkably successful. Its deployment requires both an intact auditory nerve and a suitably patent cochlear lumen. When disease renders prerequisite conditions impassable, such as in neurofibromatosis type II and cochlear obliterans, alternative treatment targets are considered. Electrical stimulation of the cochlear nucleus and midbrain in humans has delivered encouraging clinical outcomes, buttressing the promise of central auditory prostheses to mitigate deafness in those who are not candidates for cochlear implantation. In this study we explored another possible implant target: the auditory thalamus. In anesthetized cats, we first presented pure tones to determine frequency preferences of thalamic and cortical sites. We then electrically stimulated tonotopically organized thalamic sites while recording from primary auditory cortical sites using a multichannel recording probe. Cathode-leading biphasic thalamic stimulation thresholds that evoked cortical responses were much lower than published accounts of cochlear and midbrain stimulation. Cortical activation dynamic ranges were similar to those reported for cochlear stimulation, but they were narrower than those found through midbrain stimulation. Our results imply that thalamic stimulation can activate auditory cortex at low electrical current levels and suggest an auditory thalamic implant may be a viable central auditory prosthesis.

Alternative Control of an Electrically Assisted Tensile Forming Process Using Current Modulation

Electrically assisted forming is a technique whereby metal is deformed while simultaneously undergoing electric current flow. Using this process, electric current level becomes a new degree of freedom for process control. In this work, we present some alternative control architectures allowing for new avenues of control using such a process. The primary findings are architectures to allow for forming at constant force and forming at constant stress levels by modulating electric current to directly control material strength. These are demonstrated in a tensile forming operation, and found to produce the desired results. Combining these control approaches with previous and contemporary efforts in modeling of the process physics will allow for system identification of material response properties and model-based control of difficult-to-observe process parameters such as real time temperature gradients.

Feasibility study of the magnetic beam self-focusing phenomenon in a stack of conducting foils: Application to TNSA proton beams

AbstractThis paper investigates prospects of utilizing a high-power laser-driven target-normal-sheath-acceleration proton beam for the experimental demonstration of the magnetic self-focusing phenomenon in charged particle beams. In the proposed concept, focusing is achieved by propagating a space-charge dominated ion beam through a stack of thin conducting and grounded foils separated by vacuum gaps. As the beam travels through the system, image charges build up at the foils and generate electric field that counteracts the beam's electrostatic self-field — a dominant force responsible for expansion of a high current beam. Once the electrostatic self-field is “neutralized” by the image charges, the beam currents magnetic self-field will do the focusing. The focal spot size and focal length depends on the choice of a number of foils and distance between foils. Considering the typical electrical current level of a target-normal-sheath-acceleration proton beam, we conclude that it is feasible to focus or collimate a beam within tens of millimeters distance, e.g., using 200–1000 Al foils, 0.5 µm thick each, with foil spacing ranging from 25 µm to 100 µm. These requirements are within technical capabilities of modern target fabrication, thus allowing the first possible demonstration of the pinch effect with heavy ion beams.

A Mobile Test Rig for Micro Gas Turbines Based on a Thermal Power Measurement Approach

It is widely considered that micro gas turbines are potential devices for future energy needs. However, many micro gas turbine development projects have failed, particularly those with a very low power level below 10 kW. The financial and experimental capabilities for micro gas turbine development projects are typically extremely limited; hence, there is a need for low cost mobile test rigs. To close this gap, a robust mobile test rig for turboshaft micro gas turbines was developed and validated. The shaft power can be determined using a thermal measurement approach. This circumvents any issues associated with high voltage and electric current levels. The shaft power can be obtained by a straightforward parameter identification procedure based on simple temperature measurements. This approach is feasible because an analytical expression for the transient temperature field can be obtained. The test rig and thermal power measurement concept were fully validated by a commercial micro gas turbine; good agreement was obtained between the experimental results and the theoretical process data.

Comparative study of RF MEMS micro-contact materials

A systematic comparison between several pairs of contact materials based on an innovative methodology early developed at NOVA MEMS is hereby presented. The technique exploits a commercial nanoindenter coupled with electrical measurements, and test vehicles specially designed to investigate the underlying physics driving the surface-related failure modes. The study provides a comprehensive understanding of micro-contact behavior with respect to the impact of low-to-medium levels of electrical current. The decrease of the contact resistance, when the contact force increases, is measured for contact pairs of soft material (Au/Au contact), harder materials (Ru/Ru and Rh/Rh contacts), and mixed configuration (Au/Ru and Au/Ni contacts). The contact temperatures have been calculated and compared with the theoretical values of softening temperature for each couple of contact materials. No softening behavior has been observed for mixed contact at the theoretical softening temperature of both materials. The enhanced resilience of the bimetallic contacts Au/Ru and Au/Ni is demonstrated.

Energy consumption and constant current operation in membrane capacitive deionization

Membrane capacitive deionization (MCDI) is a water desalination technology based on applying a cell voltage between two oppositely placed porous electrodes sandwiching a spacer channel that transports the water to be desalinated. In the salt removal step, ions are adsorbed at the carbon–water interface within the micropores inside the porous electrodes. After the electrodes reach a certain adsorption capacity, the cell voltage is reduced or even reversed, which leads to ion release from the electrodes and a concentrated salt solution in the spacer channel, which is flushed out, after which the cycle can start over again. Ion-exchange membranes are positioned in front of each porous electrode, which has the advantage of preventing the co-ions from leaving the electrode region during ion adsorption, while also allowing for ion desorption at reversed voltage. Both effects significantly increase the salt removal capacity of the system per cycle. The classical operational mode of MCDI at a constant cell voltage results in an effluent stream of desalinated water of which the salt concentration varies with time. In this paper, we propose a different operational mode for MCDI, whereby desalination is driven by a constant electrical current, which leads to a constant salt concentration in the desalinated stream over long periods of time. Furthermore, we show how the salt concentration of the desalinated stream can be accurately adjusted to a certain setpoint, by either varying the electrical current level and/or the water flow rate. Finally, we present an extensive dataset for the energy requirements of MCDI, both for operation at constant voltage and at constant current, and in both cases also for the related technology in which membranes are not included (CDI). We find consistently that in MCDI the energy consumption per mole of salt removed is lower than that in CDI. Within the range 10–200 mM ionic strength of the water to be treated, we find for MCDI a constant energy consumption of ∼22 kT per ion removed. Results in this work are an essential tool to evaluate the economic viability of MCDI for the treatment of saltwater.

Electrodispersion of a liquid of finite electrical conductivity in an immiscible dielectric liquid

Order-of-magnitude estimates and numerical computations are used to analyze an electrospray operating in the cone-jet mode in a bath of an immiscible dielectric liquid. In agreement with experimental results in the literature, the analysis predicts that the electric current carried by the jet increases as the square root of the flow rate of dispersed liquid in a wide range of conditions of the flow. The characteristics of the current transfer region determining the electric current are estimated taking into account the viscous drag of the dielectric liquid that surrounds the jet. The electric current is predicted to depart from the square root law for small flow rates, when charge relaxation effects become important in the current transfer region, and also when the flow rate increases to values of the order of QM=ϵ0γ2a/μ22K, where ϵ0 and μ2 are the permittivity and viscosity of the dielectric liquid, K is the electrical conductivity of the dispersed liquid, a is the radius of the capillary needle through which this liquid is injected, and γ is the interfacial tension of the liquid pair. When the flow rate becomes of order QM, the meniscus at the tip of the capillary ceases to resemble a Taylor cone, the current transfer region ceases to be short compared to the size of the meniscus, the electric current levels to a constant value, and the stationary jet cannot extend very far downstream of the meniscus.

Coating of tips for electrochemical scanning tunneling microscopy by means of silicon, magnesium, and tungsten oxides

Different combinations of metal tips and oxide coatings have been tested for possible operation in electrochemical scanning tunneling microscopy. Silicon and magnesium oxides have been thermally evaporated onto gold and platinum-iridium tips, respectively. Two different thickness values have been explored for both materials, namely, 40 and 120 nm for silicon oxide and 20 and 60 nm for magnesium oxide. Alternatively, tungsten oxide has been grown on tungsten tips via electrochemical anodization. In the latter case, to seek optimal results we have varied the pH of the anodizing electrolyte between one and four. The oxide coated tips have been first inspected by means of scanning electron microscopy equipped with microanalysis to determine the morphological results of the coating. Second, the coated tips have been electrically characterized ex situ for stability in time by means of cyclic voltammetry in 1 M aqueous KCl supporting electrolyte, both bare and supplemented with K(3)[Fe(CN)(6)] complex at 10 mM concentration in milliQ water as an analyte. Only the tungsten oxide coated tungsten tips have shown stable electrical behavior in the electrolyte. For these tips, the uncoated metal area has been estimated from the electrical current levels, and they have been successfully tested by imaging a gold grating in situ, which provided stable results for several hours. The successful tungsten oxide coating obtained at pH=4 has been assigned to the WO(3) form.

Effects of magnetic field and electric current on the solidification of AZ91D magnesium alloys using an electromagnetic vibration technique

Using an electromagnetic vibration (EMV) technique, we solidified the AZ91D magnesium alloys at different magnetic flux densities and electric current levels when the vibration frequency was kept at 900 Hz so as to find the optimum processing parameters. The microstructure and microtexture of the alloy were examined under various magnetic fields, revealing that with the increase of the magnetic flux density, B 0, the microstructure becomes finer and finer and eventually consists of equiaxed grains with the average diameter approximately 57 μm at the magnetic flux intensity of B 0 = 10 tesla (T). In terms of the effect of the electric current on microstructure formation, the average grain size first decreases when the effective electric current, J e, increases from 10 to 60 ampere (A) and then increases when the electric current is further increased from 80 to 120 A. The grain refinement mechanism is clarified when considering the overall EMV process during solidification. The competition between the Lorentz force due to the imposition of the alternating current and the static magnetic force is also incorporated, which is of great importance in elucidating the microstructure and the microtexture formation.

Response of juvenile scalloped hammerhead sharks to electric stimuli

Sharks can use their electrosensory system to detect electric fields in their environment. Measurements of their electrosensitivity are often derived by calculating the voltage gradient from a model of the charge distribution for an ideal dipole. This study measures the charge distribution around a dipole in seawater and confirms the close correspondence with the model. From this, it is possible to predict how the sharks will respond to dipolar electric fields comprised of differing parameters. We tested these predictions by exposing sharks to different sized dipoles and levels of applied current that simulated the bioelectric fields of their natural prey items. The sharks initiated responses from a significantly greater distance with larger dipole sizes and also from a significantly greater distance with increasing levels of electric current. This study is the first to provide empirical evidence supporting a popular theoretical model and test predictions about how sharks will respond to a variety of different electric stimuli.

Plasma Spraying of Metal Coatings Using CO2-Based Gas Mixtures

Compared to argon, plasmas generated by molecular gases and operated at the same electric current level contain much higher enthalpy. This is because molecular gases must dissociate before ionization, which requires larger energy input. The authors have developed a new DC plasma torch, which operates with a mixture of carbon dioxide (CO2) and methane (CH4). The torch was employed for plasma spray coating with input power in a range of 30 to 45 kW. This paper reports on the effect of CO2/CH4 mixtures on the particle conditions during spraying of nickel alloy powders. Results of gas composition analysis at various distances from the nozzle exit are presented. The particle in-flight conditions, coating microstructure, and deposition efficiency are analyzed.