Direct Current Signal Research Articles

Compact semi‐lumped dual‐ and tri‐wideband bandpass filters

This study presents a novel design approach of semi-lumped dual-wideband bandpass filters (DWB-BPF) and tri-wideband-BPF (TWB-BPF). One or two pairs of λ/4 uniform-impedance open stubs first generate the desired transmission zeros (TZs) to divide the lowpass frequency response based on radial stub loaded high-impedance microstrip line (RSHIML) into a dual- or tri-band lowpass-bandpass frequency response. Then, a pair of lumped-element capacitors are series to the input and output ports to suppress the direct current signal, so as to transform the lowpass passband to the bandpass passband. Moreover, the other RSHIML is also introduced not only to produce a TZ located at the lower transition band of the first passband to improve its passband selectivity, but also to enhance the passband flatness. As examples, a semi-lumped DWB-BPF and a semi-lumped TWB-BPF are designed and fabricated, which exhibit the merits of wide passbands, low insertion loss and compact size.

Comparison between the AC and DC measurement of electrodermal activity.

Recording electrodermal activity is a well-accepted physiological measurement for clinical approaches and research. Historically, applying a DC (direct current) signal to the skin to measure the conductance is the most common practice for exogenous recordings. However, this method can be subject to error due to electrode polarization even with "nonpolarizing" electrodes-a problem that can be eliminated with alternating current (AC) methodology. For that reason, Boucsein et al. () called for research demonstrating an AC method that is validated by comparison to standard DC methodology. Additionally, the complex structure of human skin has electrical properties that include both resistance and capacitance, and AC recording enables the measurement of skin susceptance (associated with current flow through capacitors). Finally, AC recording permits the simultaneous recording of the endogenous skin potential. In this paper, the results from a direct comparison between both methods are presented, which has not been reported previously. The results demonstrated excellent agreement between a 20 Hz AC method and a standard DC method, supporting the validity of the AC recording methodology employed. The results also showed that an applied voltage of 0.2 V is sufficient for DC recordings.

The application of Hilbert–Huang transform energy spectrum in brushless direct current motor vibration signals monitoring of unmanned aerial vehicle

Due to the characteristics of structure, brushless direct current motor has a long lifetime, which makes it more difficult to obtain failure data. Accordingly, valid degeneration characteristics are required in life prediction. In this article, a novel method of condition monitoring and comparing is presented, which contributes to life prediction. Experiments were conducted for hundreds of hours to get degradation data of brushless direct current motor used in rotor of unmanned aerial vehicle. Furthermore, the vibration characteristics were analyzed by Hilbert–Huang transform to get energy spectrum. And, the differences in energy spectrum between two groups of sample collected were quantified by Euclidean distance. According to the scan under microscope, the oxidation was observed on surface of the used bearing, which leads to the changes in energy spectrum. The experimental results demonstrate that Hilbert–Huang transform energy spectrum can be effectively applied to monitor and evaluate the status of brushless direct current motor.

Direct current signal measurement invariant to non-coherent harmonic interferences

This paper describes solution of a topical problem of direct current signal measurement against the background of harmonic interferences. The result is achieved using fissionable sets of measurement signal samples, a method originally developed in ICS RAS. Consideration involves an example of non-coherent harmonic interferences. The efficiency of the obtained results is roughly estimated and their application domains are outlined. And finally, further research directions are identified.

The effects of high frequency current ripple on electric vehicle battery performance

The power electronic subsystems within electric vehicle (EV) powertrains are required to manage both the energy flows within the vehicle and the delivery of torque by the electrical machine. Such systems are known to generate undesired electrical noise on the high voltage bus. High frequency current oscillations, or ripple, if unhindered will enter the vehicle’s battery system. Real-world measurements of the current on the high voltage bus of a series hybrid electric vehicle (HEV) show that significant current perturbations ranging from 10Hz to in excess of 10kHz are present. Little is reported within the academic literature about the potential impact on battery system performance and the rate of degradation associated with exposing the battery to coupled direct current (DC) and alternating currents (AC). This paper documents an experimental investigation that studies the long-term impact of current ripple on battery performance degradation. Initial results highlight that both capacity fade and impedance rise progressively increase as the frequency of the superimposed AC current increases. A further conclusion is that the spread of degradation for cells cycled with a coupled AC–DC signal is considerably more than for cells exercised with a traditional DC waveform. The underlying causality for this degradation is not yet understood. However, this has important implications for the battery management system (BMS). Increased variations in cell capacity and impedance will cause differential current flows and heat generation within the battery pack that if not properly managed will further reduce battery life and degrade the operation of the vehicle.

Phase-to-Phase Communication Scheme for Downhole Monitoring Tool Design in Electrical Submersible Pump Systems

Electrical submersible pumps (ESPs) are commonly used artificial lift method in deep wells in oil industry. To monitor ESP systems operation, downhole monitoring tools are used to transmit data representing the physical condition of the downhole such as temperature, pressure, and vibration to the surface. The most common communication method for downhole monitoring tools in the field is to use a direct current (dc) signal over three phases of the main power cable, and the ground serves as a return path. However, this method cannot operate in the event of a single-line-to-ground (SLG) fault, although the ESP is still in operation due to ungrounded practice in its downhole zone. This method is also prone to failure in the presence of voltage unbalance. To overcome issues in the existing downhole monitoring tool design, a new phase-to-phase communication scheme is proposed in this paper. Intentional disturbances are applied to the ESP system and used as means of binary communication. In this paper, theoretical formulas of the proposed method are derived, and its performance is evaluated using simulation through case and sensitivity studies.

Relaxing the maximum dc input amplitude vs. consumption trade‐off in differential‐input band‐pass biquad filters

SummaryThis paper shows that an important part of the power consumption of a biquad band‐pass filter is associated with the feedback loop that fixes the high‐pass frequency and blocks the direct current (dc) input signals. The dc input amplitude that can be blocked is related to the maximum output current that one of the transconductors can provide, hence impacting on the required consumption through this effect. Then, a technique that efficiently blocks the dc input signal and fixes the high‐pass frequency is introduced and analyzed in depth. Moreover, an architecture for ultra‐low‐power differential‐input biquads is fully presented. The proposed architecture enables lowering the power consumption or blocking higher levels of dc input without jeopardizing the power consumption. Results show that the proposed architecture, compared with a traditional one, presents a 30% reduction in power consumption and more than doubles the dc input that can be blocked. Copyright © 2016 John Wiley & Sons, Ltd.

A surface acoustic wave biofilm sensor integrated with a treatment method based on the bioelectric effect

Bacterial biofilms have an extensive impact on quality of life, ranging from severe infections in the clinical field to water facility contamination in environmental science. Biofilms are comprised of diverse bacteria that produce an extracellular matrix which prevents drug diffusion through them. Hence traditional antibiotic therapies require 500–5000 times the concentration used to eliminate non-biofilm-associated infections. Early biofilm detection is critical for effective eradication. Moreover, developing an alternative biofilm treatment method that utilizes low doses of antibiotics is desired. In this paper, a real-time microsystem is shown to detect growth of biofilms as well as their removal through integrated treatment. Detection of biofilms is achieved using a surface acoustic wave (SAW) sensor that monitors the total biomass by measuring the resonant frequency of the system. Biofilm treatment is based on the bioelectric effect (BE), a combination of low-dose antibiotics with application of both alternating and direct current signals. The detection limit of the SAW system is approximately 166pg, corresponding to a bacterial population on the order of hundreds of bacteria. The system is used to observe an 80% reduction of total biomass when treated by the BE as compared to traditional antibiotics. Through system integration of the BE with the SAW sensor, simultaneous biofilm detection and treatment is achieved. The system consumes 194μW of power, with the sensor and treatment consuming 100μW and 94μW, respectively. The integrated sensing and treatment capabilities of this system advance the development of an innovative biofilm control method.

An adaptable multiple power source for mass spectrometry and other scientific instruments.

An Adaptable Multiple Power Source (AMPS) system has been designed and constructed. The AMPS system can provide up to 16 direct current (DC) (±400 V; 5 mA), 4 radio frequency (RF) (two 500 VPP sinusoidal signals each, 0.5-5 MHz) channels, 2 high voltage sources (±6 kV), and one ∼40 W, 250 °C temperature-regulated heater. The system is controlled by a microcontroller, capable of communicating with its front panel or a computer. It can assign not only pre-saved fixed DC and RF signals but also profiled DC voltages. The AMPS system is capable of driving many mass spectrometry components and ancillary devices and can be adapted to other instrumentation/engineering projects.

Parametric System Identification Using Quantized Data

The estimation of signal parameters using quantized data is a recurrent problem in electrical engineering. As an example, this includes the estimation of a noisy constant value and of the parameters of a sinewave, that is, its amplitude, initial record phase, and offset. Conventional algorithms, such as the arithmetic mean, in the case of the estimation of a constant, are known not to be optimal in the presence of quantization errors. They provide biased estimates if particular conditions regarding the quantization process are not met, as it usually happens in practice. In this paper, a quantile-based estimator is presented, which is based on the Gauss-Markov theorem. The general theory is first described and the estimator is then applied to both direct current and alternate current input signals with unknown characteristics. Using simulations and experimental results, it is shown that the new estimator outperforms conventional estimators in both problems, by removing the estimation bias.

Modified balanced ratio metric detection system used for high sensitive vapor detection

A modified balanced ratio metric detection (BRD) system was proposed and applied in trace measurement of water vapor. Three features, including proportion of alternating current (AC) and direct current (DC) signals, environment temperature and light intensity ratio have been stated. Their influences on measured result have been analyzed. Meanwhile, techniques including adding filter, using integrated transistor and light intensity ratio adjustment and their effects for measurement improvement have been discussed. The absorption line was chosen at 1368.597nm and the path length was 10cm. With application of the above techniques, an accuracy of 5ppm for water vapor concentration has been achieved.

Self-calibrated trajectory estimation and signal correction method for robust radial imaging using GRAPPA operator gridding.

In radial imaging, projections may become "miscentered" due to gradient errors such as delays and eddy currents. These errors may result in image artifacts and can disrupt the reliability of direct current (DC) navigation. The proposed parallel imaging-based technique retrospectively estimates trajectory error from miscentered radial data without extra acquisitions, hardware, or sequence modification. After phase correction, self-calibrated GRAPPA operator gridding (GROG) weights are iteratively applied to shift-miscentered projections toward the center of k-space. A search algorithm identifies the shift that aligns the peak k-space signals by maximizing the sum-of-squares DC signal estimate of each projection. The algorithm returns a trajectory estimate and a corrected radial k-space signal. Data from a spherical phantom, the head, and the heart demonstrate that image reconstruction with the estimated trajectory restores image quality and reduces artifacts such as streaks and signal voids. The DC signal level is increased and variability is reduced. Retrospective phase correction and iterative application of GROG can be used to successfully estimate the trajectory error in two-dimensional radial acquisitions for improved image reconstruction without requiring extra data acquisition or sequence modification.

Self-Commissioning of Permanent Magnet Synchronous Machine Drives at Standstill Considering Inverter Nonlinearities

Offline parameter identification of permanent magnet synchronous machines (PMSMs) is essential for proper tuning of the controller and position observer for general-purpose drives with sensorless control. This paper proposes a self-commissioning method of electrical machine parameters at standstill only using a voltage source inverter fed drive. The influence of inverter nonlinearities including the effect of parasitic capacitance, which may cause estimation error, is analyzed. And an error model of inductance identification considering different rotor positions is established. Along with high-frequency sinusoidal signal, a supplementary direct current signal is injected into the estimated direct-axis to attenuate the inductance identification error. In addition, a compensation strategy based on the error model is adopted to enhance the accuracy of inductance identification. For stator resistance identification, the linear regression method is adopted to overcome the influence of inverter nonlinearities by injecting the linearly increasing current signal. The proposed method is promising and robust to extract the resistance information from the gradient coefficient of the voltage variation. The effectiveness of the proposed self-commissioning scheme is validated on a 22-kW PMSM drive.

SElf-gated Non-Contrast-Enhanced FUnctional Lung imaging (SENCEFUL) using a quasi-random fast low-angle shot (FLASH) sequence and proton MRI.

Obtaining functional information on the human lung is of tremendous interest in the characterization of lung defects and pathologies. However, pulmonary ventilation and perfusion maps usually require contrast agents and the application of electrocardiogram (ECG) triggering and breath holds to generate datasets free of motion artifacts. This work demonstrates the possibility of obtaining highly resolved perfusion-weighted and ventilation-weighted images of the human lung using proton MRI and the SElf-gated Non-Contrast-Enhanced FUnctional Lung imaging (SENCEFUL) technique. The SENCEFUL technique utilizes a two-dimensional fast low-angle shot (FLASH) sequence with quasi-random sampling of phase-encoding (PE) steps for data acquisition. After every readout, a short additional acquisition of the non-phase-encoded direct current (DC) signal necessary for self-gating was added. By sorting the quasi-randomly acquired data according to respiratory and cardiac phase derived from the DC signal, datasets of representative respiratory and cardiac cycles could be accurately reconstructed. By application of the Fourier transform along the temporal dimension, functional maps (perfusion and ventilation) were obtained. These maps were compared with dynamic contrast-enhanced (DCE, perfusion) as well as standard Fourier decomposition (FD, ventilation) reference datasets. All datasets were additionally scored by two experienced radiologists to quantify image quality. In addition, one initial patient examination using SENCEFUL was performed. Functional images of healthy volunteers and a patient diagnosed with hypoplasia of the left pulmonary artery and left-sided pulmonary fibrosis were successfully obtained. Perfusion-weighted images corresponded well to DCE-MRI data; ventilation-weighted images offered a significantly better depiction of the lung periphery compared with standard FD. Furthermore, the SENCEFUL technique hints at a potential clinical relevance by successfully detecting a perfusion defect in the patient scan. It can be concluded that SENCEFUL enables highly resolved ventilation- and perfusion-weighted maps of the human lung to be obtained using proton MRI, and might be interesting for further clinical evaluation.

Understand the AC induced pitting corrosion on pipelines in both high pH and neutral pH carbonate/bicarbonate solutions

In this work, the alternating current (AC) induced corrosion and pitting corrosion of X65 pipeline steel was studied in both high pH and neutral pH carbonate/bicarbonate solutions. A real-time AC/DC (direct current) signal data acquisition technique coupled with polarization curve measurements and surface characterization was used for mechanistic studies. Pitting corrosion can be initiated on the steel at sufficiently high AC current densities in both solutions. Mechanistic models are proposed to illustrate the pitting initiation in the presence of AC, where AC can affect passive film or corrosion product layer formed on the steel as well as the charge distribution in double layer charge. In the high and neutral pH solutions, the critical AC current densities to initiate pitting are approximately 0.03A/cm2 and 0.02A/cm2, respectively.

Design of Digital Single-Phase Full-Bridge Invert Controller Based on TMS320F28027

This paper elaborates a method to realize the single phase full bridge inverter digital controller based on DSP TMS320F28027 and gives the design scheme of both its hardware and its software. In accordance with SPWM duty ratio parameter calculated with DSP algorithm, utilizing the EPWM module on DSP, it finally attains the inverting control from direct current signal to sine wave signal. Compared with traditional method, this new method improves the output waveform effectively and shows stable performance.

Electromechanical tuning of nanoscale MIM diodes by nanoindentation

Abstract

A Bioelectrochemical Method for the Quantitative Description of the Hofmeister Effect of Ionic Liquids in Aqueous Solution

It is imperative to establish a simple, efficient, and practical method to investigate the Hofmeister effect of ionic liquids (ILs) on the behavior of proteins (enzymes). In this study, the effects of the cations and anions of different ILs in aqueous media on the structural stability of horseradish peroxidase (HRP), a model oxidoreductase, were systematically investigated using electrochemical methods. It is found that without ILs no direct electron transfer current signals of HRP appear at bare glassy carbon electrode (GCE) in phosphate buffer (pH 7.0) even after incubation and accumulation at a negative potential. In the presence of ILs, however, a current signal occurs at GCE, depending on the structure of the IL and its concentration. A linear relationship between the peak currents and the scan rates demonstrates that the direct electron transfer is a surface-confined thin-layer electrochemical process. The redox signal at GCE is from the heme of HRP. An IL has a perturbing effect on the HRP structure. The anodic peak current of HRP at GCE, the catalytic activity of HRP, and the secondary structure of HRP are well correlated. Different cations or anions at varied concentrations have different effects on the structural stability of HRP, resulting in different current signals at GCE. Thus, the anodic peak current of HRP at GCE can be used as an indicator to quantitatively characterize the effect of ILs on the structural stability of HRP. The present Hofmeister series for cations and anions is in good agreement with that reported elsewhere. To our knowledge, this is a first attempt to establish a simple and practical electrochemical method to correlate Hofmeister effects with characteristics of ions and solvents. The present investigation not only deepens our understanding of the complex electrochemical behavior of proteins in ILs media but also offers a practical guidance to designing "green" and biocompatible ILs for protein (enzyme) separation, purification, and enzymatic catalysis and conversion.

Development of a real-time AC/DC data acquisition technique for studies of AC corrosion of pipelines

In this work, the alternating current (AC), 60Hz in frequency, corrosion of 16Mn pipeline steel was studied in a simulated soil solution by weight loss and polarization curve measurements, real-time AC/DC (direct current) signal data acquisition (DAQ), and surface characterization. The developed DAQ is capable of separating the DC and AC voltage components from the recorded total reading, providing mechanistic information about the steel corrosion in the presence of AC interference. The corrosion of steel is enhanced by the applied AC current density from 0 to 400A/m2. With the further increase to 600A/m2 and 800A/m2, the corrosion rate of the steel decreases, which is attributed to the formation of a compact corrosion product layer on the steel surface at sufficiently high AC current densities, and a compact film is formed on the steel surface. While AC could enhance corrosion of the steel, only a very small percentage of AC current is involved in the steel dissolution (acts as Faradaic current). The vast majority of AC either participates in the charging–discharging process (acts as non-Faradaic current) of the double-charge layer or gets involved in the redox reaction of water.

Bi‐directional flow induced by an AC electroosmotic micropump with DC voltage bias

This paper discusses the principle of biased alternating current electroosmosis (ACEO) and its application to move the bulk fluid in a microchannel, as an alternative to mechanical pumping methods. Previous EO-driven flow research has looked at the effect of electrode asymmetry and transverse traveling wave forms on the performance of electroosmotic pumps. This paper presents an analysis that was conducted to assess the effect of combining an AC signal with a DC (direct current) bias when generating the electric field needed to impart electroosmosis (EO) within a microchannel. The results presented here are numerical and experimental. The numerical results were generated through simulations performed using COMSOL 3.5a. Currently available theoretical models for EO flows were embedded in the software and solved numerically to evaluate the effects of channel geometry, frequency of excitation, electrode array geometry, and AC signal with a DC bias on the flow imparted on an electrically conducting fluid. Simulations of the ACEO flow driven by a constant magnitude of AC voltage over symmetric electrodes did not indicate relevant net flows. However, superimposing a DC signal over the AC signal on the same symmetric electrode array leads to a noticeable net forward flow. Moreover, changing the polarity of electrical signal creates a bi-directional flow on symmetrical electrode array. Experimental flow measurements were performed on several electrode array configurations. The mismatch between the numerical and experimental results revealed the limitations of the currently available models for the biased EO. However, they confirm that using a symmetric electrode array excited by an AC signal with a DC bias leads to a significant improvement in flow rates in comparison to the flow rates obtained in an asymmetric electrode array configuration excited just with an AC signal.