Change In Applied Voltage Research Articles

Cephalopods' Skin-Inspired Design of Nanoscale Electronic Transport Layers for Adaptive Electrochromic Tuning.

Cephalopods can change their skin color by using high-speed electron transduction among receptors, neural networks, and pigmentary effectors. However, it remains challenging to realize a neuroelectrical transmission system like that found in cephalopods, where electrons/ions transmit on nanoscale, which is crucial for fast adaptive electrochromic tuning. Inspired by that, hereby an ideal, rapidly responsive, and multicolor electrochromic biomimetic skin is introduced. Specifically, the biomimetic skin comprises W18O49 nanowires (NWs)that are either colorless or blue, Au nanoparticles@polyaniline (Au NPs@PANI) ranging from green to pink, and a flexible conductive substrate. As the applied voltage changes from 0.4 V to -0.7 V and back to 0V, the color of the biomimetic skin transforms from green to blue and ultimately to pink. This color change is attributed to the electrically induced redox reaction of Au NPs@PANI and W18O49 NWs, triggered by the transfer of electrons and ions. Furthermore, the high versatility and adaptability of electrical stimulus enable the creation of a highly interactive electrochromic biomimetic skin system through the integration of sensitive acoustic sensors, providing a perfect environment-responsive platform. This work provides a biomimetic multicolor electrochromic skin that depends on electron/ion transfer on nanoscale, expands potential uses for camouflage skin.

Measurement of electron injection barriers in OS/Au (OS=phthalocyanine and pentacene) using accumulated charge measurement

Accumulated charge measurement (ACM) is an experimental technique employed for studying the charge injection and extraction process in a capacitor composed of metal 1 (M1), insulator, organic semiconductor (OS), and metal 2 (M2). In this method, the change in the accumulated charge (Qacc) is estimated by integrating the displacement current when the applied voltage changes from Voff to Voff + Va. From the observed data set of Qacc and Va, ΔQ and VOS are derived, where ΔQ is the degree of charge injection and VOS is the voltage drop within the OS layer caused by Va. The injection barrier at the OS/M2 interface can be obtained from the plot of ΔQ as a function of VOS. This study presents a new ACM scheme and discusses its application to pentacene/Au and metal-free phthalocyanine (H2Pc)/Au junctions. In this scheme, a large negative Voff is applied and Va is swept towards the positive direction. Based on this scheme, the band gaps of OSs and the electron injection barriers at the OS/M2 interfaces are determined. In addition, a new measurement technique that directly determines the electron injection barrier from the displacement current measurement is developed. The observed values are generally consistent with those determined by photoelectron spectroscopies for non-oriented films. The existence of the mobility edge due to disorder in H2Pc film is proposed.

Computational study on the discharge dynamics of atmospheric pressure He plasma driven by high frequency AC voltage

A two dimensional self-consistent fluid model has been established to investigate the discharge dynamics of double-ring electrode He atmospheric pressure plasma jet (APPJ) driven by high frequency AC voltage. The difference of the internal stream and external jet and the influence of the change of applied voltage polarity on plasma discharge characteristics has been discussed. It has been discovered that the capacitive breakdown characteristic of the double ring electrode significantly enhances the intensity of the APPJ. The discharge intensity of the external jet is stronger than that of the internal stream and the propagation speed of the external jet is faster than that of the internal stream due to the ionization and Penning ionization of N2 and O2. Therefore, the density of reactive species in the external jet is greater than that in the internal stream. When the negative voltage is applied to the downstream electrode, the propagation direction of the internal stream changes to the downstream electrode. The ionization of the external jet is also concentrated near the downstream electrode and in the streamer head. The radial propagation distance of the external jet on the dielectric surface continues to increase and the peak value of the radial electric field is concentrated at the streamer head. When the applied voltage changes from negative to positive, the propagation direction of the internal stream turns to the upstream electrode and the upstream jet is formed above the electrode. At the beginning of the positive cycle, the radial propagation distance of the external jet is shortened due to the effects of the electron attachment of O2 and the radial electric field. With the increase of applied voltage, the ionization in the streamer head gradually increases, which promoted the radial propagation of external jet.

Microfluidic-Blow-Spinning fabricated sandwiched structural fabrics for All-Season personal thermal management

The concept of personal thermal management (PTM) has successfully been proven in heating and cooling fabrics, which can not only improve human comfort, but also reduce energy consumption. However, it remains a huge challenge to integrate the two opposite functions of heating and cooling in the same fabric by adaptive thermal management. Herein, a sandwiched structural fabric featuring both passive reflection cooling derived from photonic crystals (PCs) layer and active heating rooted in nano-Ag layer are generated by adjusting photonic band gap position and applied voltage changes. The passive reflection cooling of sandwiched structural fabric offers improved effect over the normal cotton, and the high absolute temperature difference reaches 7.9 °C. Besides, when a low voltage of 3 V is applied, the extra heating temperature difference of Joule heating realizes 18.1 °C due to the good electrical conductivity of nano-Ag. Moreover, we have successfully constructed a wearable PTM device to adjust temperature of human body by using this sandwiched structural fabric with excellent flexibility, breathability and high mechanical strength. Therefore, this strategy presents an easy-to-manipulate platform for the fabrication of sandwiched structural fabrics and provides new insights for PTM applications.

Effects of swirler blade angle and actuator applied voltage on combustion characteristics and cooling effectiveness

This paper investigated effects of swirlers with blade angles and applied voltage of plasma actuators on combustion and wall temperature of a Can - type gas turbine combustor. Results show that large blade angle of the swirler is beneficial for the mixing of fuel and air, which improves uniformity of the outlet temperature distribution and reduces CO emission but results in temperature rise of the wall. Pattern factor reflects uniformity of the temperature distribution at the outlet of the combustion chamber, and a small value of the pattern factor means a good distribution uniformity. In this paper, the minimum pattern factor is 0.45 when the blade angle of the swirler is 55°, which means the best uniformity of temperature distribution at combustor outlet. Compared with the worst results with a 40° blade angle, the pattern factor for the blade angle of 55° decreases by 66.4%. CO emission decreases with the increase of the blade angle. Compared with the maximum value of CO emission for a 40° blade angle, reductions of CO emission are 67.6%, 95.9% and 99.6% with the blade angles of 45°, 50° and 55°. It is found that CO emission decreases by 1.3% and pattern factor increases by 2.2%, when the blade angle of the swirler changes from 55° to 60°. When the applied voltage changes from 0 kV to 8 kV and 16 kV, cooling effectiveness increases by 3.2% and 0.7%. Cooling effectiveness decreases by 2.9% when the applied voltage increases from 0 kV to 24 kV.

Thermal and non-thermal equilibrium processes of charge extraction in accumulated charge measurement (ACM)

Accumulated charge measurement (ACM) is an experimental technique for studying the charge-injection and extraction processes in a condenser comprising the following: metal electrode 1, insulator (INS), organic semiconductor (OS), and metal electrode 2 (M2). In this method, the change in the accumulated charge (Qacc) is estimated by integrating the displacement current when the applied voltage changes from Voff to Voff + Va. Voff is the constant offset voltage and Va is the alternating voltage that is changed step-by-step; Qacc is expressed as a function Va. From the observed dataset of Qacc and Va, ΔQ and VOS are derived, where ΔQ is the degree of charge injection and VOS is the voltage drop within the OS layer caused by Va. The injection barrier at the OS/M2 interface can be evaluated from the plot of ΔQ as a function of VOS. In this study, two theoretical models for analyzing ACM data are developed using the Poisson–Boltzmann equation. On the one hand, the thermal equilibrium (TE) model reflects the TE process, in which charge evacuation simultaneously occurs at the INS/OS and OS/M2 boundaries. On the other hand, the non-thermal equilibrium (NTE) model assumes a two-step charge evacuation process at the interfaces: charge evacuation at the OS/M2 boundary occurs in the first step, followed by charge evacuation at the INS/OS boundary in the second step. The ACM data for condensers constituting pentacene and H2Pc are well reproduced by the TE and NTE models, respectively. The different behaviors of the two condensers can be attributed to the difference in their diffusion constants.

Influence of deposition time and applied voltage on the properties of electrophoretically deposited nickel oxide colloidal nanoparticles thin film

ABSTRACT In the present work, nickel oxide nanoparticles (NPs) have been synthesised, using the laser ablation technique in aqueous suspension. By applying the electrophoretic deposition (EPD) method with direct current (DC), the nickel oxide NPs obtained have been deposited on an aluminium substrate. During the EPD process, different films have been produced by a variety of deposition times and applied voltages. The characterisation of the samples, including nickel oxide NPs suspension and nickel oxide deposited thin films, was carried out through different methods, such as X-ray diffractometry (XRD), scanning electron microscopy (SEM), UV–Vis spectroscopy and atomic force microscopy (AFM). The crystalline structure of the samples inspected by XRD showed that nickel oxide existed in NPs suspension and all the thin films. The morphology of the deposited films and dried NPs has been obtained by SEM. By observing the SEM micrographs, it was shown that deposition time and applied voltage change the morphology of the deposited thin films. In addition, AFM results demonstrated that the electrophoretic parameters have an effect on the average particles size, thickness and roughness of the deposited films. The optical properties of the NPs and deposited films have been analysed by UV–Vis–NIR spectroscopy.

Effect of the Electric Field Strength on the Energy Resolution of Cr/CdTe/Pt Detectors

The electrical and spectrometric characteristics of the Cr/cadmium telluride (CdTe)/Pt structure with a metal–semiconductor type rectifying contact, used in X/ $\gamma $ -ray detectors, are investigated. For the detectors fabrication, chlorine-doped CdTe crystals with a resistivity of (3–6) $\times 10^{{9}}\,\,\Omega $ cm at 293 K were used. 137Cs spectra and their modification by applied voltage change were obtained. The reverse bias voltage corresponding to the best energy resolution of the Cr/CdTe/Pt structure is experimentally determined. The concentration of impurities N in the crystal, which determines the thickness of the space-charge region, is estimated. An energy resolution deterioration of the Cr/CdTe/Pt structure with increasing voltage is explained due to the Gunn effect.

Using birefringence colors to evaluate a tunable liquid-crystal q-plate

Q-plates are geometrical phase elements that enable the realization of vector beams in simple and compact optical setups. In this work, we consider a tunable liquid-crystal commercial q-plate operative in the visible and near-IR range and study its spectral and color birefringence properties under broadband illumination. We first characterize the spectral retardance function of the device in a wide range from 400 to 1600 nm and determine how it changes upon applied voltage. Then we evaluate the color transmission characteristics when inserting the q-plate between crossed and parallel linear polarizers. These color properties agree with the trajectory in the CIExy chromaticity diagram as the applied voltage changes. Finally, we demonstrate that a simple visual inspection of the transmitted birefringence color perceived when placing the q-plate between crossed polarizers can be used to obtain a rapid estimation of the q-plate retardance at given wavelength ranges.

Dynamic instability region analysis of sandwich piezoelectric nano-beam with FG-CNTRCs face-sheets based on various high-order shear deformation and nonlocal strain gradient theory

In this research, the dynamic instability region (DIR) of the sandwich nano-beams are investigated based on nonlocal strain gradient elasticity theory (NSGET) and various higher order shear deformation beam theories (HSDBTs). The sandwich piezoelectric nano-beam is including a homogenous core and face-sheets reinforced with functionally graded (FG) carbon nanotubes (CNTs). In present study, three patterns of CNTs are employed in order to reinforce the top and bottom face-sheets of the beam. In addition, different higher-order shear deformation beam theories such as trigonometric shear deformation beam theory (TSDBT), exponential shear deformation beam theory (ESDBT), hyperbolic shear deformation beam theory (HSDBT), and Aydogdu shear deformation beam theory (ASDBT) are considered to extract the governing equations for different boundary conditions. The beam is subjected to thermal and electrical loads while is resting on Visco-Pasternak foundation. Hamilton principle is used to derive the governing equations of motion based on various shear deformation theories. In order to analysis of the dynamic instability behaviors, the linear governing equations of motion are solved using differential quadrature method (DQM). After verification with validated reference, comprehensive numerical results are presented to investigate the influence of important parameters such as various shear deformation theories, nonlocal parameter, strain gradient parameter, the volume fraction of the CNTs, various distributions of the CNTs, different boundary conditions, dimensionless geometric parameters, Visco-Pasternak foundation parameters, applied voltage and temperature change on the dynamic instability characteristics of sandwich piezoelectric nano-beam.

A novel approach for fabricating antibacterial nanofiber/cotton hybrid yarns

Novel antibacterial nanofiber/cotton hybrid yarns was fabricated by an efficient combination of a stepped pyramid stage free surface electrospinning and traditional cotton spinning process. In this study, nanofibers loading as well as the morphology variation of the nanofibers resulted from polymer solution concentration and applied voltage changes were investigated. The results demonstrated that the higher solution concentration led to larger nanofiber diameter, and higher applied voltage increased the loading of nanofibers in the hybrid yarns. Moreover, it was found that resultant nanofiber/cotton hybrid yarns which was contained a small amount of Triclosan, possessed excellent antibacterial activity against both Grampositive Staphylococcus aureus and Gram-negative Escherichia coli bacteria. This novel method is promising for the large scale production of antibacterial nanofiber/cotton hybrid yarns for biomedical and antibacterial textiles applications

Vibroacoustic modeling of an acoustic resonator tuned by dielectric elastomer membrane with voltage control

This paper investigates the acoustic properties of a duct resonator tuned by an electro-active membrane. The resonator takes the form of a side-branch cavity which is attached to a rigid duct and covered by a pre-stretched Dielectric Elastomer (DE) in the neck area. A three-dimensional, analytical model based on the sub-structuring approach is developed to characterize the complex structure-acoustic coupling between the DE membrane and its surrounding acoustic media. We show that such resonator provides sound attenuation in the medium frequency range mainly by means of sound reflection, as a result of the membrane vibration. The prediction accuracy of the proposed model is validated against experimental test. The pre-stretched DE membrane with fixed edges responds to applied voltage change with a varying inner stress and, by the same token, its natural frequency and vibrational response can be tuned to suit particular frequencies of interest. The peaks in the transmission loss (TL) curves can be shifted towards lower frequencies when the voltage applied to the DE membrane is increased. Through simulations on the effect of increasing the voltage level, the TL shifting mechanism and its possible tuning range are analyzed. This paves the way for applying such resonator device for adaptive-passive noise control.

Modulating memristive performance of hexagonal WO3 nanowire by water-oxidized hydrogen ion implantation

In a two-terminal Au/hexagonal WO3 nanowire/Au device, ions drifting or carriers self-trapping under external electrical field will modulate the Schottky barriers between the nanowire and electrodes, and then result in memristive effect. When there are water molecules adsorbed on the surface of WO3 nanowire, hydrogen ions will generate near the positively-charged electrode and transport in the condensed water film, which will enhance the memristive performance characterized by analogic resistive switching remarkably. When the bias voltage is swept repeatedly under high relative humidity level, hydrogen ions will accumulate on the surface and then implant into the lattice of the WO3 nanowire, which leads to a transition from semiconducting WO3 nanowire to metallic HxWO3 nanowire. This insulator-metal transition can be realized more easily after enough electron-hole pairs being excited by laser illumination. The concentration of hydrogen ions in HxWO3 nanowire will decrease when the device is exposed to oxygen atmosphere or the bias voltage is swept in atmosphere with low relative humidity. By modulating the concentration of hydrogen ions, conductive hydrogen tungsten bronze filament might form or rupture near electrodes when the polarity of applied voltage changes, which will endow the device with memristive performance characterized by digital resistive switching.

Integral Imaging Capture System With Tunable Field of View Based on Liquid Crystal Microlenses

In recent years, research on autostereoscopic vision has grown rapidly. One of the most promising technologies in order to capture and reproduce three-dimensional images is integral imaging (InI). Until now, most of the proposed technologies use microlens arrays in order to reproduce and capture this type of images. One disadvantage is the fixed parameters of these devices. In this letter, an InI capture system with a tunable field of view (FOV) is demonstrated. For this, a microlens array based on liquid crystal technology is used in order to have tunability of some important characteristics of the rendered images such as angular vision. The focal length of each microlens ranges from 2 to 0.5 mm when the applied voltage changes from 1.2 to 2.6 $\text{V}_{\mathrm {rms}}$ , respectively. This mutual dependence, between voltage and focal length, also produces a tunable FOV of an InI capture system ranging from 3° to 12°. A numerical reconstruction algorithm is used in order to synthesize several new views of a scene from different viewpoints and demonstrate this effect.

Time-resolved electric field measurements during and after the initialization of a kHz plasma jet—from streamers to guided streamers

This work presents the investigation of a 30 kHz operated atmospheric pressure plasma jet impinging a dielectric BSO-crystal, allowing time-resolved electric field measurements based on the Pockels effect. Observations indicate that from the time the voltage is applied, the plasma first develops through unstable branching before a stable periodic behavior is established. This initialization of the plasma jet suggests the importance of the build-up of leftover ionization, which creates a preferred pathway for the streamer-like discharges. After initialization the time and spatially resolved electric field of guided ionization waves induced in the crystal is obtained, showing a highly periodic charging and discharging at the surface of the crystal. When the ionization wave arrives at the crystal charge is deposited and constant electric fields are generated for approximately 14 μs. Then a (back) discharge will remove the deposited charge at the surface, related to the moment when the applied voltage changes polarity and it agrees with imaging reported on in other literature.

Direct Torque Control of Induction Motor Using Three-Level Neutral Point Clamped Inverter

The direct torque control strategy of squirrel-cage induction motor using three-level neutral point clamped inverter is presented. The strategy used for controlling the torque of induction motor includes the change in applied voltage to the squirrel-cage induction motor .The variable voltage is provided with the help of look up table to the inverter. It is observed that the torque ripples are much in three-level inverter as compared to three level ineverter. This is because of the high dv/dt ratio of the output voltage of inverter. The current ripple produces torque ripples in steady state. The performance of motor in transient state and steady state are shown. The parameters of machine are given and the controlling strategy is performed using MATLAB/Simulink software. The control strategy is simulated on a 5 hp SQIM drive with three-level insulated-gate bipolar transistor (IGBT) inverter in MATLAB/Simulink software.

Adaptive Liquid Lens Actuated by Droplet Movement

In this paper we report an adaptive liquid lens actuated by droplet movement. Four rectangular PMMA (Polymethyl Methacrylate) substrates are stacked to form the device structure. Two ITO (Indium Tin Oxide) sheets stick on the bottom substrate. One PMMA sheet with a light hole is inserted in the middle of the device. A conductive droplet is placed on the substrate and touches the PMMA sheet to form a small closed reservoir. The reservoir is filled with another immiscible non-conductive liquid. The non-conductive liquid can form a smooth concave interface with the light hole. When the device is applied with voltage, the droplet stretches towards the reservoir. The volume of the reservoir reduces, changing the curvature of the interface. The device can thus achieve the function of an adaptive lens. Our experiments show that the focal length can be varied from −10 to −159 mm as the applied voltage changes from 0 to 65 V. The response time of the liquid lens is ~75 ms. The proposed device has potential applications in many fields such as information displays, imaging systems, and laser scanning systems.

Time-Resolved Observation of Self-Organized Pattern in an Atmospheric Pressure Dielectric-Barrier Discharges Plasma Jet

In this paper, a time-resolved study on the evolution process of the plasma channels in an atmospheric pressure plasma jet is performed by using a high-speed camera system and synchronous current-voltage measurement. We have succeeded in observing the plasma channels turn up at the same time, and propagate at the speed of about 4×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> m/s in the air. Once pattern formation is done, discharge channels are fixed at the same locations, even when the polarity of the applied voltage changes.

Application of dual-frequency liquid crystal for tunable selective filtration of infrared radiation

The novel dual-frequency liquid crystal (DFLC) consisting of 4-n-pentyl-4′-cyanobiphenyl (5CB), 4-hexyloxyphenyl ester 4′-hexyloxy-3-nitrobenzoic acid (C2), and 4-n-pentanoyloxy-benzoic acid-4′-hexyloxyphenyl ester (H22) was developed and its basic dielectric characteristics were determined. Transmission spectra of the Al2O3 particles-DFLC system in both the ordinary electrooptical cell and the twist-structure were studied. It was shown that for certain changes in the frequency of the applied electric field, a transmission region maximum of the Al2O3 particles-DFLC ordinary cell switches from one wavenumber to the other. While the twist-structure of the system at low frequencies passes the light at the same wavenumbers but it becomes practically opaque at high frequencies. The experimental results are explained by the optical homogeneity of the system in a narrow wavelength interval when the refractive indices of the particle material and the matrix are close, and also by reorientation of the liquid crystal molecules as the frequency of the applied voltage changes.

Study of transport properties in superconducting junctions of double insulating barrier

Abstract In this work we analyze the Tomasch effect in double barrier insulating superconducting N1ISIN2 (N: normal metal, I: insulator and S: superconductor) junctions. From the solution of the Bogoliubov–de Gennes equations we find that the differential conductance presents resonances when the applied voltage changes. These resonances are originated by the formation of quasibound states in the superconducting region and depend on the symmetry of the pair potential. We develop an analytical model in order to find the quasibound states energies and its lifetimes. This model allows us to calculate the voltage at which each resonance appears and the resonance widths. We calculate and analyze the dependence of the transmission coefficients with the thickness of the superconducting layer.