High Peak Currents Research Articles

The Morphologies of Pt Decorated on PANI Membrane and Effects on Glucose Biosensor

This paper mainly studies on the morphologies of Platinum(Pt) nanoparticles decorated on polyanilene(PANI)and their influence on the sensitivity of glucose biosensor. Seldom researches were carried on the morphologies of Pt nanoparticles and the optimization of parameters. Compared by scanning electron microscopy(SEM), cyclic voltammetry(CV) and glucose current response, Pt completely wrapped PANI nanofibers shows better electrochemical stability, sensitivity and larger catalytic area than different kinds of Pt decorated PANI membranes. Pt completely wrapped PANI nanofibers are provided by electrochemical deposition Pt nanoparticles on PANI nanofibers under a special voltage. The average diameter of nanofibers which form porous Pt/PANI membrane is 100 nm. CVs of this membrane become stable in seven circles and provide a higher current peak which indicates larger catalytic area. The sensitivity indicated by current-time glucose response is several times of the other membranes.

Modulation of electrochemical hydrogen evolution rate by araliphatic thiol monolayers on gold

Electroreductive desorption of a highly ordered self-assembled monolayer (SAM) formed by the araliphatic thiol (4-(4-(4-pyridyl)phenyl)phenyl)methanethiol leads to a concurrent rapid hydrogen evolution reaction (HER). The desorption process and resulting interfacial structure were investigated by voltammetric techniques, in situ spectroscopic ellipsometry, and in situ vibrational sum-frequency-generation (SFG) spectroscopy. Voltammetric experiments on SAM-modified electrodes exhibit extraordinarily high peak currents, which differ between Au(111) and polycrystalline Au substrates. Association of reductive desorption with HER is shown to be the origin of the observed excess cathodic charges. The studied SAM preserves its two-dimensional order near Au surface throughout a fast voltammetric scan even when the vertex potential is set several hundred millivolt beyond the desorption potential. A model is developed for the explanation of the observed rapid HER involving ordering and pre-orientation of water present in the nanometer-sized reaction volume between desorbed SAM and the Au electrode, by the structurally extremely stable monolayer, leading to the observed catalysis of the HER.

Sequential Variable Bilevel Driving Approach Suitable for Use in High-Color-Precision LED Display Panels

A bilevel driving approach was proposed in the literature for mitigating the energy wastage associated with driving LEDs at high peak current. The main idea is to introduce two drive parameters, i.e., high/low PWM current levels and duty cycles, that give rise to a 2-D luminosity control capability. The same idea was later generalized to an n-level driving approach for maximizing the electrical-to-light conversion efficiency of LEDs. Although previous uses of the n-level driving approach have been focusing on improving the luminous efficacy of LEDs, it is shown in this paper that its 2-D luminosity control feature can also lead to a significant improvement in color resolution when applied to driving RGB LEDs, hence making it well suited for applications in large-area LED display panels. In comparison to the first prototype driver proposed by the inventor of the driving approach, a more practical implementation of the complex 2-D driving approach with digital microcontroller is demonstrated. The various technical aspects of the driving approach, including luminous efficacy, color resolution, and color stability over dimming, are discussed in this paper with the aid of experimental results.

Electrochemical and electrical properties of novel mono and ball-type phthalocyanines

New mononuclear Co(II) phthalocyanine 3 and ball-type homobinuclear Cu(II)–Cu(II) and Zn(II)–Zn(II) phthalocyanines, 4 and 5 respectively, were synthesized using the corresponding metal salts and the 4,4′-(methane-5-methyl-3-(1-methylcyclohexyl)-2,2′-phenoxy)diphthalonitrile ligand 2, which was prepared from the reaction of 4-nitrophthalonitrile with bis[2-hydroxy-5-methyl-3-(1-methylcyclohexyl)phenyl]methane (1). The novel compounds 3–5 have been characterized using their elemental analysis data and UV–Vis, IR, 1H NMR and MALDI-TOF mass spectra. The redox properties of the complexes were investigated by cyclic voltammetry in a non-aqueous medium. The electrochemical measurements showed that complex 5 forms a mixed-valence reduction species, due to the strong intramolecular interactions between the two phthalocyanine rings. Complex 4 displayed Pc ring-based redox signals with very high peak currents, which were attributed to the adsorption of the complex on the working electrode. Dc and ac electrical properties of films of 3, 4 and 5 were also investigated as a function of temperature (295–523K) and frequency (40–105Hz). From the dc conductivity measurements, activation energy values of the films were found, being 0.70, 0.66 and 0.68eV for films of 3, 4 and 5, respectively. From impedance spectroscopy measurements, it was observed that the bulk resistance decreases with increasing temperature, indicating semiconductor properties.

Current is better than energy as predictor of success for biphasic defibrillatory shocks in a porcine model of ventricular fibrillation

ObjectiveThe evidence that monophasic defibrillation success is mainly determined by current is secure. However, modern defibrillators use biphasic waveforms. The aim of this study was to compare energy, peak voltage and peak current in predicting biphasic shock success in a porcine model of ventricular fibrillation (VF) where the impedance varies within a wide of ranges. MethodsIn 14 domestic male pigs weighing between 27 and 38kg, VF was electrically induced and untreated for 15s. Animals were randomized to receive defibrillation attempts from one of two defibrillators with different impedance compensation methods. A grouped up-and-down defibrillation threshold testing protocol was used to maintain the average success rate in the neighborhood of 50%. After a recovery interval of 5min, the testing sequence was repeated for a total of 60 test shocks for each animal. ResultsA high defibrillation success was observed when high peak current was delivered. The area under ROC curve for predicting shock success was 0.681 for peak current, 0.585 for peak voltage and 0.562 for energy. The odds ratio revealed that peak current was a better predictor (OR=1.321, p<0.001) for defibrillation outcome compared with energy (OR=0.979, p<0.001) and peak voltage (OR=1.000, p=0.69) when multivariable logistic regression was conducted. ConclusionIn this porcine model of VF within a wide range of transthoracic impedance, peak current was a better indicator for shock success than the currently used energy for biphasic defibrillatory shocks. This finding may encourage design of new current-based biphasic defibrillators.

Electric fields changes produced by positives cloud-to-ground lightning flashes

Positive flashes correspond to approximately only 10% of the total number of flashes produced by a thunderstorm. However, strokes with high peak currents and long continuing currents are usually present in positive flashes. Therefore, positive flashes are responsible for more intense damage than the negative ones. Positive flashes often are preceded by significant and long duration intracloud (IC) discharge activity. We observe in detail the electric field variations produced by 80 cloud-to-ground lightning flashes in 9 different storms in S. Paulo, Brazil during the summers of 2009–2011. Intracloud discharges preceding the positive cloud-to-ground flashes and some characteristics of the electric field changes produced by the return stroke that occurred at ranges of 3–80km from the site of the electric field measurements were analyzed. All flashes presented breakdown pulses prior to the return stroke. The mean time interval between the preliminary breakdown pulse (PBP) and return stroke was 157ms. The pulse train duration have a mean value of 3.1ms. Only 6 out of 80 cases analyzed did not present pulse trains but only one single bipolar breakdown pulse before the return stroke. In 95% of cases the initial breakdown pulse presented the same initial polarity of the succeeding return stroke. Time interval between pulses in a pulse train had a mean value of 280μs. The mean values of pulse width is 25.2μs. The mean values of zero-to-peak risetimes and of the 10–90% risetimes for 72 return strokes electric field waveforms are 9.5 and 5.7μs respectively. The AM value of peak amplitudes of the positive return strokes fields normalized to 100km is 17.0V/m.

Voltammetric detection of the α-dicarbonyl compound: Methylglyoxal as a flavoring agent in wine and beer

A simple, rapid and highly selective method for the determination of the most abundant α-dicarbonyl compound in wine and beer has been developed for the first time by employing square wave voltammetry. A novel electrochemical sensor, based on the electrodeposition of platinum nanoparticles onto single wall carbon nanotubes that were cast on a glassy carbon electrode (GCE) substrate, is presented in this paper. This modified electrode exhibited excellent catalytic activity in the electroreduction of methylglyoxal, showing much higher peak currents than those measured on an unmodified GCE. The effects of different experimental and instrumental parameters, such as solution pH and square wave frequency, were examined. The reduction peak current showed a linear range of from 0.1×10−6 to 100×10−6M with a 0.9979 correlation coefficient; and a low detection limit of 2.8×10−9M was also obtained. The proposed methodology was successfully applied to the quantitative analysis of methylglyoxal in wine and beer samples. The developed sensor possesses advantageous properties such as a high active surface area, stability, and rapid electron transfer rate, which cumulatively demonstrate high performance toward the electrocatalytic reduction and detection of methylglyoxal.

Electrochemical behavior of graphite anode during anode effect in cryolite molten salts

Anodic electrochemical behavior was studied on graphite anode at 1000°C in cryolite-alumina molten salt by means of cyclic voltammetry. The high current peak in a typical cyclic voltammogram was discussed. It is considered that a type of oxyfluoroaliminate complex anions reacts with carbon to form a high-resistance CF film on the anode surface at a high potential. The passivation potential is 3.28 V in 0.5% alumina-containing electrolyte, and the passivation potential increases with alumina content increasing which indicates that the alumina content determines the anodic process in the cryolite-alumina molten salt system.

Investigation on carbon nanotube growth using one-pulse discharge with shield

In contrast to earlier micro-electro discharge and typical carbon nanotube preparation methods, the one-pulse discharge method can be used to prepare carbon nanotubes on graphite by using a peak current ( Ip = 2.5 A) and a pulse duration (τ=1400µs) under an atmospheric environment without requiring high peak current. In this study, the one-pulse discharge system and electrode shield were used to prepare carbon nanotubes. The effect of the processing parameters, including the applied peak current and pulse duration, were investigated. The results show that for Ip = 2.5 A, τ = 1400 µs and with an electrode shield, the mass and high density carbon nanotubes grew on the discharge point. Furthermore, a reduced peak current and discharge point size are more efficient than a high peak current without an electrode shield.

Double resonant isolated converter for battery charger with fast switching semiconductors used in hybrid electric shunting locomotive

This paper presents the study and experimental validation of a 9kW lead-acid battery charger used to feed the 72V DC-Bus inside a hybrid electric locomotive demonstrator realized in the frame of the French research project PLATHEE (energy-efficient and environmentally friendly train platform). The role of the converter is to supply the 72V DC consumers and charge the battery. The proposed topology for the battery charger is a DC/AC/DC step-down converter structure using high frequency transformer and double resonant series-parallel dipole. Main advantages of this topology are losses minimization due to soft switching operation, reduction of passive component weight and easy system integration. However, development and testing of the converter remain complex owing to high frequency constraints. Anti-parallel diodes of DC/AC half-bridge dissipate losses in excess during switching sequences and their reverse recovery energy leads to constraining high current peaks. A solution consists in using fast Insulated Gate Bipolar Transistor (IGBT)/diode technology well suited to high frequency switching, and able to limit diode peak-current amplitude during switch-off. Electro-thermal endurance tests have been performed in order to characterize the thermal behavior of the semiconductor module and control its case temperature raising. The battery charger working has been first validated on laboratory test-bench using a battery emulator, and then implemented in the hybrid locomotive for electrical couplings tests.

Evaluation of Bipolar Permaloc™ Electrodes for Direct Bladder Stimulation

Purpose: A bladder control system for spinal cord injured (SCI) patients is needed that can be implanted with minimally invasive methods. New Permaloc bipolar electrodes consisting of 6 mm helical, wire, stimulating surfaces separated by 3 mm and a polypropylene securing barb (Synapse Biomedical Inc) were developed for this application. They are implanted on the bladder wall with a 16 gauge needle, a minimally invasive method. Methods: Seven swines were anesthetized, the lower urinary tract exposed and instrumented with pressure transducers. Four Permaloc TM electrodes were implanted following identification of effective bladder wall stimulation sites next to the ureters and dorsal neurovascular bundle. Bladder stimulation to induce high pressures was conducted at 40 Hz, 400 � s pulses, 5 s stimulation periods and a high stimulating current of 40 mA. Results: At the high stimulating current peak bladder pressures were low, ranging from 12±2 to15±3 cm H20, insufficient to induce urination. Urethral sphincter contractions occurred during high bladder pressure. A spinal reflex role for high sphincter pressures during stimulation was shown by similar high pressures recorded during a bladder squeeze test without stimulation. Conclusions: Stimulation with Permaloc TM bipolar electrodes at high currents produced insufficient bladder pressures for urination. Further modifications of the electrode such as greater separation of the bipolar stimulating surfaces or changes in the testing methods such as alternative animal models are needed to induce high bladder pressures without side effects.

Oxidized Graphene in Ionic Liquids for Assembling Chemically Modified Electrodes: A Structural and Electrochemical Characterization Study

Dispersions of graphene oxide (GO) nanoribbons in ionic liquids, ILs (either 1-butyl-3-methylimidazolium chloride (BMIM-Cl-) or 1-butylpyridinium chloride (-Bupy-Cl-)) have been used to assemble modified screen printed electrodes (SPEs). The graphene oxide/ionic liquid dispersions have been morphologically and structurally characterized by the use of several techniques: X-ray photoelectron spectroscopy (XPS), Fourier transform-infrared (FT-IR) spectroscopy, high-resolution-transmission electron microscopy (HR-TEM). The assembled modified SPEs have then been challenged with various compounds and compared to several electro-active targets. In all cases high peak currents were detected, as well as significant potential shifts, especially in the detection of catecholamines and NADH, compared with the bare SPE and the conventional electrodes, such as glassy carbon (GC) and highly oriented pyrolitic graphite (HOPG). This opens the way to the assembly of new types of sensors and biosensors. The enhanced performances observed are attributed to electrocatalytic effects related to the high electrode surface area, to oxygen-assisted electron transfer, as well as to the disordering effect of the ILs, this latter related to the favorable π-π interactions with the ILs and the GO plane.

전기자동차용 PTC 히터 구동을 위한 입력 필터를 갖는 벅 컨버터의 특성 분석 및 성능 평가

Recently, the market of Electric Vehicle(EV) is increasing more and more than before. Thus a new heater for the EV is required. The PTC devices may be used the heater for the EV. In this paper, a simple DC-DC Converter is proposed as the PTC Heater for the EV. The proposed circuit was optimally desired to decrease the stress of the power devices and reduce the current ripples. To apply the result of the test in the laboratory to the actual EV system with the high DC voltage, ripple current, average current and output peak current are predicted by using the least-squares method. Finally, the proposed circuit is validated, by various experiments.

Hierarchical gold micro-nanostructures based on three-dimensional networks of carbon nanotubes fabricated by using electrochemical deposition

Three-dimensional (3D) hierarchical gold electrodes were fabricated using suspended 3D networks of carbon nanotubes (CNTs) on Si pillar templates using electrochemical deposition (ECD) in KAu(CN)2 solutions. The Pt-coated networks of CNTs played an important role in providing electrical paths for ECD through discontinuous Pt layers, resulting in a vertically uniform deposition of gold on micropillars and 3D networks of CNTs connected with adjacent micropillars. The structural characteristics of the 3D hierarchical gold electrodes were superior, and their cyclic voltammograms exhibited higher peak currents and lower peak separations than those of a plain gold electrode.

A Study of Plasma Parameters in a Capillary Discharge With Calculations Using Ideal and Nonideal Plasma Models for Comparison With Experiment

A study of the plasma parameters in a capillary discharge was conducted using an experimental electrothermal plasma facility. The experimental results are compared to calculations using ideal and nonideal formulas of the Coulomb logarithm in the plasma electrical conductivity model to determine the nature of the plasma regime. Calculations are compared to the measured ablated mass, the measured electrical conductivity. Other calculated parameters are compared to results from similar and typical discharges. The measured ablated mass falls in between the ideal and nonideal calculations suggesting that the plasma is neither ideal nor nonideal; however, the linear fit of the experimental and calculated values shows divergence in the ideal calculations at higher peak currents. Measured plasma electrical conductivity is close to the ideal model predictions at lower values of the peak discharge current and approaches the nonideal model predictions at higher peak currents; the shape of the measured conductivity follows that of the nonideal model.

Diatomite-Assisted Synthesis of Ordered Mesoporous Carbon and Its Application in Fuel Cells

Ordered mesoporous carbon has the promising development and potential in catalysis, because of its large amount of uniform pore size and high surface area. In this paper, ordered mesoporous carbon has been successfully synthesized via evaporation-induced self-assembly (EISA) method, using triblock copolymer Pluronic F127 as a soft template, resol as a carbon precursor and diatomaceous earth as the transient scaffolds. Diatomite is a kind of special biomaterial with 3D precision of tens of nanometers and of low price. Diatomite shells not only maintain the intact structure of the ordered mesoporous carbon, but also increase its aperture diameter and surface area to a certain degree, during the carbonization between 600 °C to 800 °C. When the samples were calcined in nitrogen, the features of diatomite could effectively reduce shrinkage ratio of sample structure, keeping the precursor fluid firmly adsorbed on the surface of diatom shells. The resulting materials were characterized by X-ray diffraction, transmission electron microscopy and N2 adsorption-desorption, etc. The results showed all the samples had highly ordered mesoporous structure. Under the support of diatomite, both of the specific surface area (717~773 m•g) and pore sizes (3.9~11.3 nm) of the mesoporous carbon have become much larger, which could be controlled by adjusting the ratio of diatomite to resol. The influence of the diatomite on the structure of the mesoporous carbon was discussed in the paper. Furthermore, we used the as-prepared ordered mesoporous carbon to load Pt nanoparticles. The Pt/carbon catalysts were prepared by microwave-assisted heating process with ethylene glycol as reductant. The electrocatalytic activity of carbon supported Pt nanoparticles was verified by cyclic voltammetry in CH3OH solution. We found the carbon materials with much larger specific surface areas had higher electrocatalytic activity. When the ratio of diatomite to resol was 0.5, the specific surface area of the sample was the largest, and the corresponding Pt/carbon showed the highest peak current of methanol oxidation.

Low power digital TTL command for 1 bit 60 GHz RF MEMS phase shifter

This paper presents a circuit used to actuate Radio Frequency MicroElectroMechanical Systems (RF MEMS) based phase shifters for 60GHz beam forming. Wireless transmission in the 60GHz band show a dramatic free space loss, thus making it mandatory to use antennas with high gain in a desired direction. Beam forming is then necessary to optimize the link budget between communicating nodes. Antenna arrays can be used for beam forming. The work done at LAAS was aiming to provide RF MEMS based phase shifters working with a standard digital command. RF MEMS commonly have high actuation voltages usually obtained with charge pumps. This paper presents a full 1bit phase shifter with a digital translation part, an analog DC–DC converter, and an RF MEMS based loaded line phase shifter for 60GHz signals. This converter is built using boost converters as an alternative to the use of charge pumps for driving RF MEMS in the field of wireless communications. Boost converters, despite relatively high current peaks, allow shorter settling times compared to charge pumps.

Integrated Differential-Mode and Common-Mode Filter to Mitigate the Effects of Long Motor Leads on AC Drives

Pulsewidth-modulated (PWM) ac drives generate high differential-mode (DM) motor voltages due to the reflected wave phenomenon. The common-mode (CM) voltage produced by a PWM inverter also has fast transitions that result in high peak currents to ground. For low-power ac drives, this can present several issues, such as pump-up of the dc bus and failure of the power module due to high instantaneous currents that are often undetected because of the typical sampling algorithm used. In this paper, existing drive output filter solutions are reviewed, and a new filter design is presented, which has integrated DM and CM impedance with damping matched to typical cable surge impedance. This eliminates reflections of both DM and CM traveling waves and also reduces peak cable charging currents. Experimental results are provided to demonstrate that the new filter has improved performance to reduce motor DM and CM voltages and drive output CM current, thus mitigating the issues specifically seen with low-power ac drives. Complete design details for the filter and a particular implementation of the integrated DM and CM reactor are also presented.

Transient performance of SiC MOSFETs as a function of temperature

This research was completed to study the effects of extreme transient conditions on Silicon Carbide MOSFET devices. Two different transient conditions that are common in power converters were studied in this paper. The first is effects of voltage rise time, or dV/dt, on these devices. The second is the effects of current pulses with short pulse width and high peak currents. Both of these tests were conducted at temperatures of 150 °C to determine the performance of these devices in high stress environments. For both of these experiments, testing apparatus had to be designed and built to create these specific conditions.

Surface treatment by electric discharge machining of Ti–6Al–4V alloy for potential application in orthopaedics

This study investigated the properties of Ti–6Al–4V alloy after surface treatment by the electric discharge machining (EDM) process. The EDM process with high peak currents proved to induce surface macro-roughness and to cause chemical changes to the surface. Evaluations were made of the mechanical properties by means of tensile tests, and of surface roughness for different peak currents of the EDM process. The EDM process with peak current of 29 A was found to induce sufficient surface roughness, and to have a low adverse effect on tensile properties. The chemical changes were studied by scanning electron microscopy equipped with an energy dispersive X-ray analyser (EDX). The surface of the benchmark samples was obtained by plasma-spraying a titanium dioxide coating. An investigation of the biocompatibility of the surface-treated Ti–6Al–4V samples in cultures of human osteoblast-like MG 63 cells revealed that the samples modified by EDM provided better substrates for the adhesion, growth and viability of MG 63 cells than the TiO2 coated surface. Thus, EDM treatment can be considered as a promising surface modification to orthopaedic implants, in which good integration with the surrounding bone tissue is required.