Direct Current Signal Research Articles

Droplet three-dimension manipulation in parallel liquid-infused membrane plates configuration

Abstract In this paper, we demonstrated the droplets three-dimension (3D) manipulation between a pair of parallel liquid-infused membrane plates with patterned electrodes by programmably controlling electrical direct current signals. The asymmetric electrowetting behaviors of droplet between the parallel slippery liquid-infused porous surface (SLIPS) plates configuration were investigated firstly. The droplet tends to move from the higher potential plate to the lower potential plate. The transport of the deionized water droplet in the vertical direction with electrostatic force was investigated in detail subsequently. A model was developed to study the dynamic transport behavior of the droplet movement in the vertical direction. It is found the droplet velocity increases with time, while tends to a maximum value due to the increase of drag force. We also experimentally demonstrated the droplet was driven accelerated from the higher potential plate to the lower one, and the transport time exponentially decreases with the increase of applied voltage. However, note that the excessive applied voltage would cause irregularly jumping of droplets between two plates. The applied voltage range for driving a 0.5 μl droplet was determined experimentally with various parallel-plate spacings. Finally, we demonstrated the 3D manipulation of one droplet and two droplets in two parallel plates configuration with patterned electrodes by the hybrid forces, namely, by asymmetric electrowetting force in the horizontal direction and by electrostatic force in the vertical direction. The 3D droplet manipulation on SLIPS provides a promising solution for high-throughput analysis and integrated device with high density on the digital microfluidic chip.

Acoustoelectric drag current in vanadium oxide films

Two different Mott insulator wires, vanadium dioxide and vanadium sesquioxide, were prepared on the piezoelectric LiNbO3 substrates. Coupling of acoustic waves propagating in LiNbO3 with free carriers in vanadium oxide gives rise to the acoustoelectric effect that manifests itself as the generation of direct electric current by the acoustic wave. According to a phenomenological model, the value of the effect strongly depends on the wires conductivity, which, for the vanadium-oxide films, changes by a few orders of magnitude. We demonstrated that this yields a significant enhancement of the direct current (DC) current generated in the wires at the metal–insulator transition temperatures. The sign of the generated DC voltage is different for excitations by surface and bulk acoustic wave modes, which may happen due to reverse wave propagation at the substrate surface. For each resonance mode, polarities of the generated DC signal are the same in both wires, despite the signs of charge carriers being different for these materials. It was shown that two complementary techniques (acoustoelectric and Hall effect measurements) yield opposite signs of charge carriers in VO2.

Novel NiCo2O4/MWCNTs nanocomposite with flake-like architecture as room temperature capacitive-type NH3 gas sensor

In this study, a facile hydrothermal method, which was employed as a simple and inexpensive technique, was proposed to prepare flake-like NiCo2O4/multi-walled carbon nanotubes (MWCNTs) sensor. The direct current signal measurements were performed at a frequency of 10–100 kHz at room temperature. NiCo2O4 (7.46 pF) and NiCo2O4/MWCNTs (24.75 pF) were observed to have the highest capacitances at 10 kHz. Our results showed that the NiCo2O4/MWCNTs nanocomposite-based sensor potentially exhibited excellent sensitivity for the detection of ammonia (NH3) gas room temperature.

A high-accuracy non-contact online measurement method of the rotor-stator axial gap based on the microwave heterodyne structure

Rotor-stator axial gap is a key design parameter that affects the efficiency and safety of large rotating machines. An optimal axial gap value should be determined so that the rotating machines could work at the highest efficiency. To realize active clearance control (ACC) of rotating machines, high-accuracy non-contact online measurement of the axial gap must be carried out. However, direct current (DC) offset signals in absolute distance measurement, limited working space of sensors, and extremely harsh working environment all pose challenges to the realization of high-accuracy, non-contact, and online performance required by the axial gap measurement. Therefore, no mature measurement method exists at present. In this paper a rotor-stator axial gap measurement method was proposed based on the phase difference ranging principle. The structure of microwave heterodyne could effectively eliminate the errors caused by DC noise during absolute distance measurement. To break through the bottleneck of axial gap measurement accuracy, an axial gap measurement error model was established, and a signal carrier frequency error processing method along with a phase measurement error processing method based on spatial distance scanning were proposed. A platform modeled on the rotating machines’ structure of edge labyrinth gas seal was built in the laboratory to carry out room temperature rotor-stator axial gap measurement. A prototype of the axial gap measurement based on a microstrip type sensor was developed, and the system’s calibration and measurement performance evaluation experiments were carried out. Experimental results verified the effectiveness and accuracy of the proposed method. The measurement accuracy is better than 30 μm (at 0.5–3 mm) and better than 1% (at 3–18.5 mm).

Step‐on versus step‐off signals in time‐domain controlled source electromagnetic methods using a grounded electric dipole

ABSTRACTThe time‐domain controlled source electromagnetic method is a geophysical prospecting tool applied to image the subsurface resistivity distribution on land and in the marine environment. In its most general set‐up, a square‐wave current is fed into a grounded horizontal electric dipole, and several electric and magnetic field receivers at defined offsets to the imposed current measure the electromagnetic response of the Earth. In the marine environment, the application often uses only inline electric field receivers that, for a 50% duty‐cycle current waveform, include both step‐on and step‐off signals. Here, forward and inverse 1D modelling is used to demonstrate limited sensitivity towards shallow resistive layers in the step‐off electric field when transmitter and receivers are surrounded by conductive seawater. This observation is explained by a masking effect of the direct current signal that flows through the seawater and primarily affects step‐off data. During a step‐off measurement, this direct current is orders of magnitude larger than the inductive response at early and intermediate times, limiting the step‐off sensitivity towards shallow resistive layers in the seafloor. Step‐on data measure the resistive layer at times preceding the arrival of the direct current signal leading to higher sensitivity compared to step‐off data. Such dichotomous behaviour between step‐on and step‐off data is less obvious in onshore experiments due to the lack of a strong overlying conductive zone and corresponding masking effect from direct current flow. Supported by synthetic 1D inversion studies, we conclude that time‐domain controlled source electromagnetic measurements on land should apply both step‐on and step‐off data in a combined inversion approach to maximize signal‐to‐noise ratios and utilize the sensitivity characteristics of each signal. In an isotropic marine environment, step‐off electric fields have inferior sensitivity towards shallow resistive layers compared to step‐on data, resulting in an increase of non‐uniqueness when interpreting step‐off data in a single or combined inversion.

Electromagnetic-triboelectric-hybrid energy tile for biomechanical green energy harvesting

Since the invention of Piezoelectric Nanogenerator in 2006, nanogenerators has become an attractive technology to the researchers for scavenging mechanical energy from the ambient environment for real life applications. Hybridization of these nanogenerators has been one of the effective techniques to maximize its output performance. In this work, a Triboelectric Nanogenerator (TENG) and Electro Magnetic Generator (EMG) based hybrid floor-tile has been developed to utilize the biomechanical energy from human footsteps. The TENG consists of oppositely charged layers of conductive aluminum and high-polarized Kapton with a layer of MoS2 as electron acceptor. On the other hand, the EMG is composed of copper coils and neodymium magnets. The output open circuit voltage and short circuit current of the device was tested at variable load (50 l b, 100 l b and 200 l b) and frequency of footsteps (60BPM, 90BPM, 120BPM). The device was further integrated with a bridge rectifier to test its capability to convert Alternative Current (AC) signal into Direct Current (DC) signal. The maximum open circuit voltage and short-circuit current was noted as 1200 V and 5 mA respectively. The output power of this energy harvesting device can be high as 6 W. This hybrid nanogenerator produces 25 times more open-circuit voltage and 20% more power in comparison to a commercially sold energy-harvester floor tile, Pavegen. The developed hybrid NG based floor-tile allows for cost-effective, green, and sustainable energy conversion and promotes sustainable development.

A Single‐Material Multi‐Source Energy Harvester, Multifunctional Sensor, and Integrated Harvester–Sensor System—Demonstration of Concept

Single‐source energy harvesters that convert solar, thermal, or kinetic energy into electricity for small‐scale smart electronic devices and wireless sensor networks have been under development for decades. When an individual energy source is insufficient for the required electricity generation, multi‐source energy harvesting is indicated. Current technology usually combines different individual harvesters to achieve the capability of harvesting multiple energy sources simultaneously. However, this increases the overall size of the multi‐source harvester, but in microelectronics miniaturization is a critical consideration. Herein, an advanced approach is demonstrated to solve this issue. A single‐material energy harvesting/sensing device is fabricated using a (K0.5Na0.5)NbO3‐Ba(Ni0.5Nb0.5)O3–Δ (KNBNNO) ceramic as the sole energy‐conversion component. This single‐material component is able simultaneously to harvest or sense solar (visible light), thermal (temperature fluctuation), and kinetic (vibration) energy sources by incorporating its photovoltaic, pyroelectric, and piezoelectric effects, respectively. The interactions between different energy conversion effects, e.g., the influence of dynamic behavior on the photovoltaic effect and alternating current–direct current (AC–DC) signal trade‐offs, are assessed and discussed. This research is expected to stimulate energy‐efficient design of electronic devices by integrating both harvesting and sensing functions in the same material/component.

Double layer carbon-nanoparticle-based flexible pressure sensor with high precision and stability

Recently, the development of electronic skin and smart wearable sensor have put forward high requirements for flexible sensor with excellent performance. As for a flexible sensor, precision and stability are also significant parameters besides the sensitivity and measuring range. Flexible piezoresistive sensors based on nanomaterial/nanostructure have been reported to possess the high sensitivity. Precision and stability are also important for a sensor, hence we focused on promoting them in this paper. Furthermore, a mechanism for random error generated by a nano-based piezoresistive sensor was proposed. Based on the mechanism, a certain high frequency testing signal was used instead of the direct current signal to promote the precision of the sensor. The relative random error of the sensor decrease greatly above 800 kHz (by three order at low pressure range), which increase the precision greatly. Long-term stability was tested using a total of 12 000 consecutive compression tests. After a 250 s aging process, the sensor remained incredibly stable and only 0.08% change occurred which is much better than those of reported sensors. The sensor also possessed a sensitivity of 0.24 kPa−1 and a linear measuring range of 0–4 kPa. Some applications, including respiratory/arterial pulse measurement and gait recognition, were demonstrated finally.

Power-Recycling Microwave Mixer With Wide Linear Instantaneous Bandwidth

A self-embedded power-recycling technique in microwave mixers is proposed and presented for radio frequency (RF) and microwave multiple-input multiple-output (MIMO) systems. The novelty of the proposed power-recycling technique stems from a distinct concept of harnessing direct current (dc) signal rectified by mixing elements in the course of a frequency translation. The large-signal model of a nonlinear mixing element coupled with electromagnetic simulations is used to understand and examine the contribution of the dc signal in the overall transceiver energy efficiency. A single-balanced (SB) diode-switching mixer integrated with a diplexer bank is prototyped using off-the-shelf components to validate the power-recycling technique, which can be extended for an IC implementation. The measurement results show that about 30% of the driving signal power is directly present in the form of a dc signal at the power-recycling port under the maximum conversion efficiency condition. Furthermore, wide linear instantaneous bandwidth performance is shown with a resistive termination of sum–product signal in a downconverter.

A Novel Piezoelectric Inchworm Actuator Driven by One Channel Direct Current Signal

A novel piezoelectric inchworm actuator driven by one channel dc signal is developed in this article to simplify excitation signal of the inchworm actuators, and the clamping force of the developed actuator is generated by a dc motor and two permanent magnets. The piezoelectric stack is excited by a sensing signal, which is generated by the separate photoelectric sensor to detect the position of the rotational permanent magnets. A mathematical model is established to predict the motion of the slider. The prototype of the proposed piezoelectric actuator is fabricated, and mechanical output performance is measured. At a voltage of 75 V and frequency of 3.2 Hz, the average output step is 0.241 μm under no-load conditions. The proposed inchworm actuator can be operated by just one channel dc signal and the output displacement is stable, which provides a new idea for the integration design of the piezoelectric actuators in the future.

Application of VMD and Hilbert Transform Algorithms on Detection of the Ripple Components of the DC Signal

Accurate detection of ripple components of the direct-current (DC) signals is essential for evaluating DC power quality. In this study, the combination algorithm based on variational mode decomposition (VMD) and Hilbert transform (HT) is applied to detect and analyze the characteristics of the ripple components of the DC disturbance signals. Firstly, the optimal modal number of VMD algorithms is comprehensively determined by observing the center frequencies of the mode components and the Index of Orthogonality (IO) of mode components. Through utilizing the VMD algorithm, the DC disturbance signal is accurately decomposed into a series of amplitude modulation-frequency modulation (AM-FM) functions. Then, the HT algorithm is applied to each AM-FM function to obtain the corresponding instantaneous amplitude and frequency, and the characteristics of DC disturbance signal are determined. Some case studies are implemented to analyze the ripple components of the DC disturbance signal with the VMD-HT and empirical mode decomposition (EMD) algorithm. Finally, the experiment results of Gree Photovoltaic Cabin have verified the feasibility and effectiveness of the proposed combination VMD-HT algorithm by comparison with EMD and the window interpolation fast Fourier transform (WIFFT) algorithms.

In Vivo Assessment of a Hydroxyapatite/κ-Carrageenan-Maleic Anhydride-Casein/Doxorubicin Composite-Coated Titanium Bone Implant.

Here, we focus on the fabrications of an osteosarcoma implant for bone repair via the development of a hydroxyapatite/κ-carrageenan-maleic anhydride/casein with doxorubicin (HAP/κ-CA-MA-CAS/DOX) composite-deposited titanium (Ti) plate. The HAP/κ-CA-MA-CAS/DOX material was coated on the Ti plate through the EPD method (electrophoretic deposition), applying direct current (DC) signals to deposit the composite on the surface of the Ti plate. The physicochemical and morphological possessions and biocompatibility in vitro of the prepared nanocomposite were examined to assess its prospective effectiveness for purposes of bone regeneration. Excellent biocompatibility and elevated osteoconductivity were confirmed using MG63 osteoblast-like cells. In vivo studies were performed at tibia sites in Wistar rats, and rapid bone regeneration was detected at four weeks in defective bone. Overall, the studies demonstrate that the HAP/κ-CA-MA-CAS/DOX composite enhances the biocompatible and cell-stimulating biointerface of Ti metallic implants. As such, HAP/κ-CA-MA-CAS/DOX implants are viable prospects for osteosarcoma-affected bone regeneration.

Improved Linear Active Disturbance Rejection Controller Control Considering Bus Voltage Filtering in Permanent Magnet Synchronous Generator

In the permanent magnet direct drive wind power generation system, the direct current (DC) bus voltage signal of the converter is usually used as the feedback of the voltage outer loop. Because of the existence of random white noise and the measurement error when the sensor collects the DC bus voltage signal, it is necessary to filter the bus voltage signal through the first-order inertial link. The time constant of the first order inertial link is usually 10ms-15ms. In the traditional voltage external loop second-order active disturbance rejection controller (ADRC) system, the influence of the bus voltage filter is not considered in the design of ADRC, which results in the phase lag and amplitude offset between the feedback of the controller and the real bus voltage. This will make the performance of the system affected by the time constant of the first-order inertial link. In this paper, an improved ADRC considering the bus voltage filter is proposed. The filtered bus voltage is expanded into a new state variable. The voltage before the filter is estimated by using the fourth-order linear expansion state observer (LESO) and used as the feedback. The simulation results show that the improved ADRC system has better control performance.

Design and simulation of techniques for mitigation of harmonic distortion in a three-phase rectifier

Rectifiers are electrical devices that receive an alternating signal and deliver a direct current signal at their output, this process by which they transform one type of energy to another is known as rectification. This type of device incorporates a phenomenon called harmonic distortion into the electrical network, which consists of malformations presented in the waveform of the alternating signal from which it feeds, which generate unwanted effects on electrical systems. Because of this, this work presents the combination of two harmonic distortion mitigation strategies (12-pulse multilevel converter and harmonic frequency tuned filtering stage) in order to reduce total harmonic distortion levels generated by a three-phase rectifier.

Flexible and Printed Microwave Plasmonic Sensor for Noninvasive Measurement

The printed electrodes for detecting direct current signal changes of human vital signs have been fully investigated. Here a flexible and printed microwave plasmonic sensor for detecting liquid solutions is proposed and demonstrated. The sensor for noninvasive measurement at microwave frequencies is based on the spoof localized surface plasmons resonator, which is composed of a metal corrugated ring fabricated on the flexible PET substrate using the inkjet printing technology. The winding-shaped polydimethylsiloxane (PDMS) microfluidic channel is interleaved with the corrugated ring to simulate the complicated blood vessel. The simulated results agree well with the experimental measurements. It shows that the measured resonance frequency offset of 147 MHz has been achieved when the microfluidic channel is filled with deionized water, which indicates that the flexible microwave biological sensor is feasible. The calculated figure of merit is as high as 1178. The sensor can find wider applications in the flexible and wearable device field for continuous health monitoring.

The Invariant to Direct Current Signal Non-Coherent Harmonic Alternating Current Signals Vectors Sets Measurement

A high-accuracy fast-acting simple in implementation and invariant to interferences in the form of direct current signal method of non-coherent harmonic alternating current signals vectors sets measurement is described. The solution of stated in the general view problem is gained on the base of so called the splitting sets of samples method and invariant theory approach to measurement process organization. The implementation of the method is illustrated on example of a synthesis of the measurement algorithm for the case of three harmonic signals. The analysis of the gained results is given.

Joint Modulation Format Identification and Frequency Offset Estimation Based on Superimposed LFM Signal and FrFT

We propose a novel technique for joint modulation format identification and frequency offset (FO) estimation. The linear frequency modulation signal which is obtained by a direct current signal and Fractional Fourier Transform (FrFT) is superimposed on the data symbols to mark and identify the modulation formats. Simulation results demonstrate our method can identify the DPBPSK, DPQPSK, DP8PSK, DP16QAM, DP32QAM and DP64QAM modulation formats correctly before chromatic dispersion compensation even the optical signal to noise ratio is extremely low. Additionally, due to the excellent time and frequency analysis properties of FrFT, the FO estimation range is greatly extended compared with the traditional Viterbi-Viterbi method.

A Direct Current Measurement Method Based on Terbium Gallium Garnet Crystal and a Double Correlation Detection Algorithm.

When applying an optical current transformer (OCT) to direct current measurement, output signals exhibit a low signal-to-noise ratio and signal-to-noise band overlap. Sinusoidal wave modulation is used to solve this problem. A double correlation detection algorithm is used to extract the direct current (DC) signal, remove white noise and improve the signal-to-noise ratio. Our sensing unit uses a terbium gallium garnet crystal in order to increase the output signal-to-noise ratio and measurement sensitivity. Measurement errors of single correlation and double correlation detection algorithms are compared, and experimental results showed that this measurement method can control measurement error to about 0.3%, thus verifying its feasibility.

Magneto-Impedance Sensor Driven by 400 MHz Logarithmic Amplifier.

A thin-film magnetic field sensor is useful for detecting foreign matters and nanoparticles included in industrial and medical products. It can detect a small piece of tool steel chipping or breakage inside the products nondestructively. An inspection of all items in the manufacturing process is desirable for the smart manufacturing system. This report provides an impressive candidate for realizing this target. A thin-film magneto-impedance sensor has an extremely high sensitivity, especially, it is driven by alternatiing current (AC) around 500 MHz. For driving the sensor in such high frequency, a special circuit is needed for detecting an impedance variation of the sensor. In this paper, a logarithmic amplifier for detecting a signal level of 400 MHz output of the sensor is proposed. The logarithmic amplifier is almost 5 mm × 5 mm size small IC-chip which is widely used in wireless devices such as cell phones for detecting high-frequency signal level. The merit of the amplifier is that it can translate hundreds of MHz signal to a direct current (DC) voltage signal which is proportional to the radio frequency (RF)signal by only one IC-chip, so that the combination of a chip Voltage Controlled Oscillator (VCO), a magneto-impedance (MI) sensor and the logarithmic amplifier can compose a simple sensor driving circuit.

Modeling and computation of double drift region transit time diode performance based on graphene‐SiC

AbstractWe have proposed a double drift region (DDR) Impact Avalanche Transit Time (IMPATT) diode based on graphene‐silicon carbide (SiC) substrate. Due to attractive and extensive electronics properties of graphene materials, for the first time, we have modeled and designed the diode on epitaxially grown graphene deposited on the silicon face of SiC. The direct current (DC) characteristics and small signal performance of the modeled diode are computed with the help of COMSOL Multi Physics and MATLAB software tools. Performance is evaluated at the frequency regime of Ka band. The proposed diode is validated through the boundary conditions. Profiles of electric field distribution, density of mobile space charge, conversion efficiency, power density, susceptance‐conductance, and voltage drops at different zones are obtained. The graphene‐SiC–based DDR IMPATT is giving better DC and small signal performances.