External DC Research Articles

I-V characteristic behavior of BSCCO-2223 superconductor under low intensity DC magnetic fields a Home-Made Experiment

Electrical characterization of superconductor materials exposed to external magnetic field play a important role for many technological applications. In this paper, the electrical characterization of Bi-2223 pellet prepared by conventional route was performed. The electrical resistance temperaturedependence (RxT), showed a superconductor transition at around 105 K. The current-voltage (I-V) behavior under magnetic field and temperature has been investigated, the results point to a powerlaw dependence between the electrical current (I) and applied voltage (V), at different conditions, as described by the literature. The external DC magnetic field, was produced by a simple home-made apparatus, where a simple copper coil was used to produce an external DC magnetic field between 2,0 mT and 8,0 mT. Then, the dependence of the critical current (Ic) on magnetic field and temperature has been studied, revealing a double step behavior DOI:http://dx.doi.org/10.30609/JETI.2018-2.5682

A Wideband Multifunctional Multilayer Switchable Linear Polarization Metasurface

In this letter, a wideband multifunctional and switchable linear polarizer has been presented based on an active metasurface for the X-band. The proposed structure consists of three metallic layers and two dielectric spacers. The switchable function is obtained by embedding PIN diodes, which are controlled by four independent sets of external dc bias networks on the top and bottom metallic layers. Two main functions (polarization conversion and polarization separator) and four working states are exhibited by combining four independent sources. As a polarization rotator, the proposed structure converts electromagnetic (EM) waves to cross-polarization from 5.2 to 16.7 GHz with the polarization conversion ratio beyond 90%, while as a polarization separator, the copolarization EM waves can be transmitted and the cross-polarization waves reflected with isolation over 10 dB from 8 to 14.3 GHz. The numerical and experimental results are in a good agreement, which demonstrates the excellent and stable performance of the proposed structure.

Oxidative Dehydrogenation of Liquefied Petroleum Gas on Copper, Zinc and Iron Oxide Impregnated on MFI Zeolite Assisted by Electric Power

Olefin was produced with a non-conventional method using an electric field exerted on zeolites. The lattice oxygen mobility increases with a decrease in band gap, leading to an increase in olefin yield. By impregnating the transition metal, an increase in carrier concentration occurs. The external electric field changes the Fermi level. In this research, HZSM-5 was placed in an external DC electric field with strength appropriate for studying its catalytic performance. The Fermi level changed with the metal type and the external electric field. The increase in permittivity with temperature extracts higher energy from the external electric field. In catalytic reactions assisted by the external DC electric field, at 510 °C, the yield was approximately equal to the yield in a conventional reaction at 650 °C. With regard to TGA, in the catalytic reaction assisted by the external DC electric field, the produced coke declined. The results showed that the maximum yield value (50.54%) and conversion (92.81%) were be obtained at 650 °C with an input electrical current of 12 mA, a gap distance of 10 mm and a metal loading of 4 wt. % over FeHZSM-5.

Modeling of dielectric elastomer oscillators for soft biomimetic applications

Biomimetic, entirely soft robots with animal-like behavior and integrated artificial nervous systems will open up totally new perspectives and applications. However, until now, most presented studies on soft robots were limited to only partly soft designs, since all solutions at least needed conventional, stiff electronics to sense, process signals and activate actuators. We present a novel approach for a set up and the experimental validation of an artificial pace maker that is able to drive basic robotic structures and act as artificial central pattern generator. The structure is based on multi-functional dielectric elastomers (DEs). DE actuators, DE switches and DE resistors are combined to create complex DE oscillators (DEOs). Supplied with only one external DC voltage, the DEO autonomously generates oscillating signals that can be used to clock a robotic structure, control the cyclic motion of artificial muscles in bionic robots or make a whole robotic structure move. We present the basic functionality, derive a mathematical model for predicting the generated signal waveform and verify the model experimentally.

Interface-induced spin-orbit interaction in silicon quantum dots and prospects for scalability

We identify the presence of monoatomic steps at the Si/SiGe or Si/SiO$_2$ interface as a dominant source of variations in the dephasing time of Si quantum dot (QD) spin qubits. First, using atomistc tight-binding calculations we show that the g-factors and their Stark shifts undergo variations due to these steps. We compare our theoretical predictions with experiments on QDs at a Si/SiO$_2$ interface, in which we observe significant differences in Stark shifts between QDs in two different samples. We also experimentally observe variations in the $g$-factors of one-electron and three-electron spin qubits realized in three neighboring QDs on the same sample, at a level consistent with our calculations. The dephasing times of these qubits also vary, most likely due to their varying sensitivity to charge noise, resulting from different interface conditions. More importantly, from our calculations we show that by employing the anisotropic nature of the spin-orbit interaction (SOI) in a Si QD, we can minimize and control these variations. Ultimately, we predict that the dephasing times of the Si QD spin qubits will be anisotropic and can be improved by at least an order of magnitude, by aligning the external DC magnetic field towards specific crystal directions.

Effect of a dc magnetic field on the anomalous dispersion of localized Josephson plasma modes in layered superconductors

We study theoretically the propagation of Josephson plasma waves (JPWs) localized on a slab of layered superconductor in the presence of an external dc magnetic field. The slab is sandwiched between two dielectric half-spaces and the wave modes propagate across the layers. We derive analytic expressions for the dispersion relations of the localized JPWs and present the numerical simulation for the effect of the external dc magnetic field on the dispersion. The anomalous dispersion of localized JPWs is predicted for a wide range of frequencies, wave vectors, and dc fields. Also, we discuss the possibility of the internal reflection of the localized modes in the inhomogeneous dc magnetic field. This phenomenon can find application in the terahertz electronics for the control of the localized mode propagation.

Quantum measurement of a rapidly rotating spin qubit in diamond.

A controlled qubit in a rotating frame opens new opportunities to probe fundamental quantum physics, such as geometric phases in physically rotating frames, and can potentially enhance detection of magnetic fields. Realizing a single qubit that can be measured and controlled during physical rotation is experimentally challenging. We demonstrate quantum control of a single nitrogen-vacancy (NV) center within a diamond rotated at 200,000 rpm, a rotational period comparable to the NV spin coherence time T2. We stroboscopically image individual NV centers that execute rapid circular motion in addition to rotation and demonstrate preparation, control, and readout of the qubit quantum state with lasers and microwaves. Using spin-echo interferometry of the rotating qubit, we are able to detect modulation of the NV Zeeman shift arising from the rotating NV axis and an external DC magnetic field. Our work establishes single NV qubits in diamond as quantum sensors in the physically rotating frame and paves the way for the realization of single-qubit diamond-based rotation sensors.

The Effect of External DC Electric Field on the Atmospheric Corrosion Behaviour of Zinc under a Thin Electrolyte Layer

The Effect of External DC Electric Field on the Atmospheric Corrosion Behaviour of Zinc under a Thin Electrolyte Layer

Local electromechanical characterization of Pr doped BiFeO3 ceramics

Local electromechanical (EM) measurements were performed in Pr doped BiFeO3 (BPFO) ceramics via piezoresponse force microscopy (PFM). The results revealed that local EM response was different from the macroscopic one due to the large contribution of the leakage current. The locally measured response was used to evaluate effective piezoelectric coefficient d33 of the material. The multi-frequency PFM mode with additional compensation of the cantilever-surface Coulomb interaction under application of the external DC bias provided the most accurate values of the effective d33 coefficient and allowed studying its surface distribution and residual depolarization field distribution across the surface of BPFO ceramics.

Investing in Green Infrastructure and Protecting Utility Finances

Journal AWWAVolume 110, Issue 3 p. 12-13 Letters to the Editor Investing in Green Infrastructure and Protecting Utility Finances Daniel Kaplan, Daniel Kaplan Financial Service Administrator Wastewater Treatment Division, King County, Seattle, Wash. US Environmental Protection Agency Environmental Financial Advisory BoardSearch for more papers by this authorJohn Lisle, John Lisle Chief of External Affairs DC WaterSearch for more papers by this author Daniel Kaplan, Daniel Kaplan Financial Service Administrator Wastewater Treatment Division, King County, Seattle, Wash. US Environmental Protection Agency Environmental Financial Advisory BoardSearch for more papers by this authorJohn Lisle, John Lisle Chief of External Affairs DC WaterSearch for more papers by this author First published: 09 March 2018 https://doi.org/10.1002/awwa.1028Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume110, Issue3March 2018Pages 12-13 RelatedInformation

Electromagnetic properties of Fe-Co granular composite materials containing acicular nanoparticles

Electromagnetic properties of acicular (needle-like) Fe76Co24 nanoparticle composite materials have been studied in microwave frequency range up to 20 GHz. The Fe76Co24 particles are commercially available acicular Fe76Co24 nanoparticles with an approximate length and diameter of 100 and 25 nm, respectively. The Fe76Co24 nanocomposites were prepared by embedding the Fe76Co24 nanoparticle in an appropriate resin. Since the metallic Fe76Co24 nanoparticles have an oxidized surface, even high particle content composites at 78 vol.%, which is in the percolated state, does not show metallic conduction; a low frequency plasmonic state with the negative permittivity spectrum was not observed. Meanwhile, the negative permeability spectrum caused by the magnetic resonance in Fe76Co24 alloy was obtained in the high particle content composites. From the measurement of the complex permeability spectra under the external dc magnetic field, it was clarified that the gyromagnetic spin rotation mainly contributes to the permeability spectrum of nanocomposites due to extremely small quantity of domain walls in the acicular nanoparticles. This result suggests that the negative permeability spectrum was caused by the gyromagnetic spin resonance. By the comparison of the complex permeability spectrum between the acicular Fe76Co24 nanocomposite and the spherical Fe50Co50 microcomposite, the gyromagnetic spin resonance frequency of the acicular nanocomposite tends to locate higher than that of the spherical microcomposite owing to the demagnetizing field effect. Therefore, it can be concluded that the negative permeability frequency band of the acicular nanocomposite is higher than that of the spherical microcomposite at the same particle content.

224 Electrical Actuation of a Penile Prosthesis

Shape memory alloys (SMA) can revert to “memorized” shapes under appropriate conditions. We have been exploring the use of SMAs in the development of penile prosthesis using a lasercut Nitinol extruded tube that expands and becomes rigid when activated to simulate an erection. We hypothesized that electrical current can act as an alternative method to activate SMA prostheses. We used an external current DC generator and commercially available electrical wires attached at the ends of a bent SMA prosthesis, measuring 17 cm in length and 1 cm in diameter, and passed increasing amounts of electrical current through the prosthesis. The current was set at increasing values with 1 ampere intervals. Temperature was recorded at the centre with the use of thermocouples. Mechanical changes were measured in terms of decreased angulation towards “memorized” straight configuration. Perpendicular force to bend the prosthesis was measured with a Dillon handheld force meter. After bench tests, a SMA prosthesis was implanted in the corpora cavernosa of a cadaver with electrical leads connected to an external DC generator and activated.

On the magnetism of the C14 Nb0.975Fe2.025 Laves phase compound: Determination of the H-T phase diagram

A C14 Nb0.975Fe2.025 Laves phase compound was investigated aimed at determining the H-T magnetic phase diagram. Magnetization, M, and AC magnetic susceptibility measurement were performed. Concerning the former field-cooled and zero-field-cooled M-curves were recorded in the temperature range of 2–200 K and in applied magnetic field, H, up to 1000 Oe, isothermal M(H) curves at 2 K, 5 K, 50 K, 80 K and 110 K as well as hysteresis loops at several temperatures over the field range of ±10 kOe were measured. Regarding the AC susceptibility, χ, both real and imaginary components were registered as a function of increasing temperature in the interval of 2 K-150 K at the frequencies of the oscillating field, f, from 3 Hz up to 999 Hz. An influence of the external DC magnetic field on the temperature dependence of χ was investigated, too. The measurements clearly demonstrated that the magnetism of the studied sample is weak, itinerant and has a reentrant character. Based on the obtained results a magnetic phase diagram has been constructed in the H-T coordinates.

The effects of magnetic field and polarization on the permeability and permittivity of (1 – x)Ni0.4Zn0.6Fe2O4+xPb(Zr0.53Ti0.47)O3 composites at high frequency

(1 – x)Ni0.4Zn0.6Fe2O4+xPb(Zr0.53Ti0.47)O3 (x = 0–1) multiferroic composite materials were prepared by a conventional sintering process. The magnetic permeability and permittivity were researched at high frequency in detail. The permittivity ε′ decreases slightly with the frequency and the permittivity ε″ shows a peak in the 3 MHz–1 GHz range. The permeability displays a relaxation resonance within the 3 MHz–1 GHz frequency range. The magnetic resonances of the domain wall and spin rotation were excited by the external dc magnetic field in the microwave frequency. The resonance peaks in the imaginary permeability move to high frequency with the magnetic field, but shift to low frequency in the composite samples. The permittivity spectra exhibit two resonance peaks after polarization. The changes of the permittivity and permeability under magnetic field or/and after polarization confirm the interaction between ferromagnetism and ferroelectricity in the microwave frequency. The observed phenomena were understood by employing a resonance equation for the domain wall motion and a Landau–Gilbert equation for the spin rotation. The results indicate that permittivity and permeability can be adjusted by the magnetic field or electric field.

Energy spectrum of ideal quantum dots controlled by an external electric field

We have constructed a theoretical model describing the energy spectrum and autoionisation probability for an ideal quantum dot in the external DC and AC electric fields, free of using the delta-potential approximation and perturbation theory. The wave functions of the electron quasi-stationary states under these conditions are calculated. To this end, we have elaborated a new method for regularising the Gamov wave function used to calculate the complex electron energy, describing both the energy spectrum of the system and the probability of the state decay (autoionisation). The oscillations of the Stark shift and the energy level width due to the DC electric field are found. It is shown that these oscillations essentially affect the energy spectrum of the quantum dot and principally cannot be described within the frameworks of perturbative approaches.

Frequency response characterization of ironless inductive position sensors with long cables

The two linear position sensors used to determine the position of the European Organization for Nuclear Research; Large Hadron Collider collimator’s jaws with respect to the beam are the linear variable differential transformer and the ironless inductive position sensor. The latter was designed as an alternative to the former since the linear variable differential transformer exhibits a position error in magnetic environments. The ironless inductive position sensor is an air cored, high-precision linear position sensor, which is by design immune to external DC or slowly varying magnetic fields. Since the ironless inductive position sensor is required to have no on-board electronics, the raw signal has to be carried through long cable lengths and this may lead to performance degradation. This paper focuses on a set of experimental measurements conducted to assess the ironless inductive position sensor’s sensitivity at different frequencies with long cable lengths. This is critical for the sensor`s correct operation in the Large Hadron Collider`s collimators. Furthermore, to gain a better understanding, the ironless inductive position sensor’s frequency response is compared with a commercial off-the-shelf linear variable differential transformer.

Research on Control System of Three - phase Brushless DC Motor for Electric Vehicle

In order to study the three-phase brushless motor control system of electric vehicle, Freescale9S12XS128 chip is used as the control core, and the power MOSFET is used as the inverter device. The software is compiled by Codewarrior software. The speed control link adopts open-loop control, and the control chip collects the external sensor signal voltage Change control PWM signal output control three-phase brushless DC motor speed. The whole system consists of Hall position detection module, current detection module, power drive module and voltage detection module. The basic functions of three-phase brushless DC motor drive control are realized.

Electro-optically Induced and Manipulated Terahertz Waves from Fe-doped InGaAs Surfaces

We demonstrate the presence of dual simultaneous nonlinear mechanisms: field-induced optical rectification (FIOR) and field-induced surge current (FISC) for the generation of terahertz (THz) pulses from p-type and n-type Fe:In0.53Ga0.47As surfaces upon excitation with femtosecond laser pulses centered at 800 nm wavelength. Experimental investigations of the dependence of the generated THz waves on the incident angular optical polarization, optical irradiance, and the direction and magnitude of applied electric DC fields give confirming results to the proposed THz generation mechanisms. Applying external DC electric fields in the plane of the incident optical field shows efficient capability in manipulating the direction and phase of the generated THz waves, and controlling the refractive index of Fe:In0.53Ga0.47As material in the THz range, in addition to enhancing the emitted THz power up to two orders of magnitude. The fast and reliable response of Fe:In0.53Ga0.47As to the changes in the direction and magnitude of the optical and electrical fields suggests its use in amplitude and phase modulators, and ultrafast optoelectronic systems.

Effect of orientational ordering of magnetic nanoemulsions immobilized in agar gel on magnetic hyperthermia

Magnetic nanoemulsions of droplet size ∼200 nm, loaded with single domain superparamagnetic nanoparticles (MNP), are potential candidates for multimodal hyperthermia due to availability of large loading volume and enhanced permeation and retention (EPR) in the cancerous tissues. In such nanoemulsions, radio frequency alternating magnetic field induced heating occur at two entirely different length scales, viz. Neel-Brown relaxation of the dispersed MNP and Brownian relaxation of emulsion droplets. Here we study the effects of orientation ordering or texturing of droplets, immobilized in a tissue mimicking agar matrix, on the field induced heating efficiency. A higher specific absorption rate (maximum ∼73 ± 2 W/gFe) is observed for droplets orientated parallel to the direction of the alternating magnetic field because of the enhancement of effective uniaxial anisotropy energy density and increased effective relaxation time. For identical and non-interacting MNP oriented parallel to the external DC magnetic field, a threefold increase in the effective uniaxial anisotropy energy density and ∼20–30% increased specific absorption rate are observed as compared to those oriented perpendicular to the magnetic field. Magnetic force microscopy images showed that the spherical morphology of the droplets remains intact even after orientational ordering and average topographic height of the droplets are found to be ∼220 (±17) nm, which is in good agreement with the most probable size obtained from dynamic light scattering. The residual volume magnetization of the emulsion droplets is found to be 1.1 × 10−6 emu/cc, indicating the superparamagnetic nature of the droplets in tissue equivalent environment. The observed increase in heating efficiency of the immobilized and oriented emulsion droplets shows promising applications in multimodal hyperthermia therapy because of the requirement of lower dose of MNP and shorter treatment time.

Observation and manipulation of magnetic domains in sol gel derived thin films of spinel ferrites

Thin films of spinel ferrites, namely zinc substituted nickel, cobalt ferrite, and manganese substituted cobalt ferrite, were synthesized using sol-gel derived spin-coating techniques. The films were characterized using x-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy and Raman spectroscopy techniques for the analysis of structural, morphological and vibrational band transition properties, which confirm the spinel phase formation of the films. The magnetic force microscopy (MFM) technique was used to observe the magnetic domain structure present in the synthesized films. Further, the films were subjected to an external DC magnetic field of 2 kG to orient the magnetic domains and analyzed using an ex situ MFM technique.