Deformation analysis of vesicles in an alternating-current electric field.

PubMed

Tang, Yu-Gang; Liu, Ying; Feng, Xi-Qiao

2014-08-01

In this paper the shape equation for axisymmetric vesicles subjected to an ac electric field is derived on the basis of the liquid-crystal model. The equilibrium morphology of a lipid vesicle is determined by the minimization of its free energy in coupled mechanical and ac electric fields. Besides elastic bending, the effects of the osmotic pressure difference, surface tension, Maxwell pressure, and flexoelectric and dielectric properties of phospholipid membrane as well are taken into account. The influences of elastic bending, osmotic pressure difference, and surface tension on the frequency-dependent behavior of a vesicle membrane in an ac electric field are examined. The singularity of the ac electric field is also investigated. Our theoretical results of vesicle deformation agree well with previous experimental and numerical results. The present study provides insights into the physical mechanisms underpinning the frequency-dependent morphological evolution of vesicles in the electric and mechanical fields.

Direct current uninterruptible power supply method and system

DOEpatents

Sinha, Gautam

2003-12-02

A method and system are described for providing a direct current (DC) uninterruptible power supply with the method including, for example: continuously supplying fuel to a turbine; converting mechanical power from the turbine into alternating current (AC) electrical power; converting the AC electrical power to DC power within a predetermined voltage level range; supplying the DC power to a load; and maintaining a DC load voltage within the predetermined voltage level range by adjusting the amount of fuel supplied to the turbine.

Electrical voltages and resistances measured to inspect metallic cased wells and pipelines

DOEpatents

Vail, III, William Banning; Momii, Steven Thomas

2001-01-01

A cased well in the earth is electrically energized with A.C. current. Voltages are measured from three voltage measurement electrodes in electrical contact with the interior of the casing while the casing is electrically energized. In a measurement mode, A.C. current is conducted from a first current carrying electrode within the cased well to a remote second current carrying electrode located on the surface of the earth. In a calibration mode, current is passed from the first current carrying electrode to a third current carrying electrode located vertically at a different position within the cased well, where the three voltage measurement electrodes are located vertically in between the first and third current carrying electrodes. Voltages along the casing and resistances along the casing are measured to determine wall thickness and the location of any casing collars present so as to electrically inspect the casing. Similar methods are employed to energize a pipeline to measure the wall thickness of the pipeline and the location of pipe joints to electrically inspect the pipeline.

Electrical voltages and resistances measured to inspect metallic cased wells and pipelines

DOEpatents

Vail III, William Banning; Momii, Steven Thomas

2003-06-10

A cased well in the earth is electrically energized with A.C. current. Voltages are measured from three voltage measurement electrodes in electrical contact with the interior of the casing while the casing is electrically energized. In a measurement mode, A.C. current is conducted from a first current carrying electrode within the cased well to a remote second current carrying electrode located on the surface of the earth. In a calibration mode, current is passed from the first current carrying electrode to a third current carrying electrode located vertically at a different position within the cased well, where the three voltage measurement electrodes are located vertically in between the first and third current carrying electrodes. Voltages along the casing and resistances along the casing are measured to determine wall thickness and the location of any casing collars present so as to electrically inspect the casing. Similar methods are employed to energize a pipeline to measure the wall thickness of the pipeline and the location of pipe joints to electrically inspect the pipeline.

Photovoltaic system with improved AC connections and method of making same

DOEpatents

Cioffi, Philip Michael; Todorovic, Maja Harfman; Herzog, Michael Scott; Korman, Charles Steven; Doherty, Donald M.; Johnson, Neil Anthony

2018-02-13

An alternating current (AC) harness for a photovoltaic (PV) system includes a wire assembly having a first end and a second end, the wire assembly having a plurality of lead wires, and at least one AC connection module positioned at a location along a length of the wire assembly between the first end and the second end. Further, the at least one AC connection module includes a first connection terminal electrically coupled to the plurality of lead wires of the wire assembly and constructed to electrically couple the wire assembly with an output of a first PV module of the PV system. The at least one AC connection module also includes a second connection terminal electrically coupled to the plurality of lead wires of the wire assembly and constructed to electrically couple the wire assembly with an output of a second PV module of the PV system.

Thermal and ac electrical properties of N-methylanthranilic acid below room temperature

NASA Astrophysics Data System (ADS)

Abdel-Kader, M. M.; Basha, M. A. F.; Ramzy, G. H.; Aboud, A. I.

2018-06-01

In this study, we investigated the thermal and alternating current (ac) electrical properties of N-methylanthranilic acid. Based on data obtained by differential scanning calorimetry, we detected two endothermic transitions at ≈ 213 K and ≈265.41 K. The weakening of hydrogen bonds as the temperature increased appeared to be the main cause of these phase transitions. We also recorded the melting point at about 475.5 K. Both the ac conductivity (σac) and complex dielectric constant (ε∗ = ε ' - jε ' ') were studied as functions of temperature over the frequency range from 1 kHz to 100 kHz. We observed significant variations in the thermal and electrical properties before and after the transition temperature at 265.41 K. The conduction mechanism responsible for the ac electrical properties before this transition was due to overlapping large polarons. These novel results are expected to have impacts on the application of organic semiconductors and dielectrics.

Static Measurements on HTS Coils of Fully Superconducting AC Electric Machines for Aircraft Electric Propulsion System

NASA Technical Reports Server (NTRS)

Choi, Benjamin B.; Hunker, Keith R.; Hartwig, Jason; Brown, Gerald V.

2017-01-01

The NASA Glenn Research Center (GRC) has been developing the high efficiency and high-power density superconducting (SC) electric machines in full support of electrified aircraft propulsion (EAP) systems for a future electric aircraft. A SC coil test rig has been designed and built to perform static and AC measurements on BSCCO, (RE)BCO, and YBCO high temperature superconducting (HTS) wire and coils at liquid nitrogen (LN2) temperature. In this paper, DC measurements on five SC coil configurations of various geometry in zero external magnetic field are measured to develop good measurement technique and to determine the critical current (Ic) and the sharpness (n value) of the super-to-normal transition. Also, standard procedures for coil design, fabrication, coil mounting, micro-volt measurement, cryogenic testing, current control, and data acquisition technique were established. Experimentally measured critical currents are compared with theoretical predicted values based on an electric-field criterion (Ec). Data here are essential to quantify the SC electric machine operation limits where the SC begins to exhibit non-zero resistance. All test data will be utilized to assess the feasibility of using HTS coils for the fully superconducting AC electric machine development for an aircraft electric propulsion system.

Soap-film flow induced by electric fields in asymmetric frames

NASA Astrophysics Data System (ADS)

Mollaei, S.; Nasiri, M.; Soltanmohammadi, N.; Shirsavar, R.; Ramos, A.; Amjadi, A.

2018-04-01

Net fluid flow of soap films induced by (ac or dc) electric fields in asymmetric frames is presented. Previous experiments of controllable soap film flow required the simultaneous use of an electrical current passing through the film and an external electric field or the use of nonuniform ac electric fields. Here a single voltage difference generates both the electrical current going through the film and the electric field that actuates on the charge induced on the film. The film is set into global motion due to the broken symmetry that appears by the use of asymmetric frames. If symmetric frames are used, the film flow is not steady but time dependent and irregular. Finally, we study numerically these film flows by employing the model of charge induction in ohmic liquids.

Soap-film flow induced by electric fields in asymmetric frames.

PubMed

Mollaei, S; Nasiri, M; Soltanmohammadi, N; Shirsavar, R; Ramos, A; Amjadi, A

2018-04-01

Net fluid flow of soap films induced by (ac or dc) electric fields in asymmetric frames is presented. Previous experiments of controllable soap film flow required the simultaneous use of an electrical current passing through the film and an external electric field or the use of nonuniform ac electric fields. Here a single voltage difference generates both the electrical current going through the film and the electric field that actuates on the charge induced on the film. The film is set into global motion due to the broken symmetry that appears by the use of asymmetric frames. If symmetric frames are used, the film flow is not steady but time dependent and irregular. Finally, we study numerically these film flows by employing the model of charge induction in ohmic liquids.

Bead-on-string structure printed by electrohydrodynamic jet under alternating current electric field

NASA Astrophysics Data System (ADS)

Liu, Juan; Lin, Yihuang; Jiang, Jiaxin; Liu, Haiyan; Zhao, Yang; Zheng, Gaofeng

2016-09-01

Electrohydrodynamic printing (EHDP) under alternating current (AC) electric field provides a novel way for the precise micro-/nano-droplet printing. The AC electric field induces the free charge to reciprocate along the EHDP jet and changes the electric field force on the jet periodically. The stability of jet can be enhanced by increasing the voltage frequency, and the regular bead-on-string structure is direct-written along the trajectory of collector. The deposition frequency of bead structure increases with the increasing of voltage frequency, due to the short period of AC electric field. As the voltage frequency is increased from 10 to 60 Hz, the diameter of bead structure decreases from 200 to 110 µm. As the duty ration increased from 10 to 60 %, the diameter of bead structure increased from 100 to 140 µm. This work would accelerate the development and the application of micro-/nano-printing technology in the fields of flexible electronic and micro-/nano-system.

Simultaneous distribution of AC and DC power

DOEpatents

Polese, Luigi Gentile

2015-09-15

A system and method for the transport and distribution of both AC (alternating current) power and DC (direct current) power over wiring infrastructure normally used for distributing AC power only, for example, residential and/or commercial buildings' electrical wires is disclosed and taught. The system and method permits the combining of AC and DC power sources and the simultaneous distribution of the resulting power over the same wiring. At the utilization site a complementary device permits the separation of the DC power from the AC power and their reconstruction, for use in conventional AC-only and DC-only devices.

Test plan for performance testing of the Eaton AC-3 electric vehicle

NASA Astrophysics Data System (ADS)

Crumley, R.; Heiselmann, H. W.

1985-04-01

An alternating current (ac) propulsion system for an electric vehicle was developed and tested. The test bed vehicle is a modified 1981 Mercury Lynx. The test plan was prepared specifically for the third modification to this test bed and identified as the Eaton AC-3. The scope of the testing done on the Eaton AC-3 includes coastdown and dynamometer tests but does not include environmental, on-road, or track testing. Coastdown testing is performed in accordance with SAE J-1263 (SAE Recommended Practice for Road Load Measurement and Dynamometer Simulation Using Coastdown Techniques).

Influence of electrical fields (AC and DC) on phytoremediation of metal polluted soils with rapeseed (Brassica napus) and tobacco (Nicotiana tabacum).

PubMed

Bi, Ran; Schlaak, Michael; Siefert, Eike; Lord, Richard; Connolly, Helen

2011-04-01

The combined use of electrokinetic remediation and phytoremediation to decontaminate soil polluted with heavy metals has been demonstrated in a laboratory-scale experiment. The plants species selected were rapeseed and tobacco. Three kinds of soil were used: un-contaminated soil from forest area (S1), artificially contaminated soil with 15mgkg(-1) Cd (S2) and multi-contaminated soil with Cd, Zn and Pb from an industrial area (S3). Three treatment conditions were applied to the plants growing in the experimental vessels: control (no electrical field), alternating current electrical field (AC, 1Vcm(-1)) and direct current electrical field (DC, 1Vcm(-1)) with switching polarity every 3h. The electrical fields were applied for 30d for rapeseed and 90d for tobacco, each experiment had three replicates. After a total of 90d growth for rapeseed and of 180d for tobacco, the plants were harvested. The pH variation from anode to cathode was eliminated by switching the polarity of the DC field. The plants reacted differently under the applied electrical field. Rapeseed biomass was enhanced under the AC field and no negative effect was found under DC field. However, no enhancement of the tobacco biomass under the AC treatment was found. The DC field had a negative influence on biomass production on tobacco plants. In general, Cd content was higher in both species growing in S2 treated with AC field compared to the control. Metal uptake (Cd, Cu, Zn and Pb) per rapeseed plant shoot was enhanced by the application of AC field in all soils. Copyright © 2010 Elsevier Ltd. All rights reserved.

Evaluation of semiconductor devices for Electric and Hybrid Vehicle (EHV) ac-drive applications, volume 1

NASA Technical Reports Server (NTRS)

Lee, F. C.; Chen, D. Y.; Jovanovic, M.; Hopkins, D. C.

1985-01-01

The results of evaluation of power semiconductor devices for electric hybrid vehicle ac drive applications are summarized. Three types of power devices are evaluated in the effort: high power bipolar or Darlington transistors, power MOSFETs, and asymmetric silicon control rectifiers (ASCR). The Bipolar transistors, including discrete device and Darlington devices, range from 100 A to 400 A and from 400 V to 900 V. These devices are currently used as key switching elements inverters for ac motor drive applications. Power MOSFETs, on the other hand, are much smaller in current rating. For the 400 V device, the current rating is limited to 25 A. For the main drive of an electric vehicle, device paralleling is normally needed to achieve practical power level. For other electric vehicle (EV) related applications such as battery charger circuit, however, MOSFET is advantageous to other devices because of drive circuit simplicity and high frequency capability. Asymmetrical SCR is basically a SCR device and needs commutation circuit for turn off. However, the device poses several advantages, i.e., low conduction drop and low cost.

Photovoltaic system with improved DC connections and method of making same

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cioffi, Philip Michael; Todorovic, Maja Harfman; Herzog, Michael Scott

A micro-inverter assembly includes a housing having an opening formed in a bottom surface thereof, and a direct current (DC)-to-alternating current (AC) micro-inverter disposed within the housing at a position adjacent to the opening. The micro-inverter assembly further includes a micro-inverter DC connector electrically coupled to the DC-to-AC micro-inverter and positioned within the opening of the housing, the micro-inverter DC connector having a plurality of exposed electrical contacts.

Power dissipation in HTS coated conductor coils under the simultaneous action of AC and DC currents and fields

NASA Astrophysics Data System (ADS)

Shen, Boyang; Li, Chao; Geng, Jianzhao; Zhang, Xiuchang; Gawith, James; Ma, Jun; Liu, Yingzhen; Grilli, Francesco; Coombs, T. A.

2018-07-01

This paper presents a comprehensive alternating current (AC) loss study of a circular high temperature superconductor (HTS) coated conductor coil. The AC losses from a circular double pancake coil were measured using the electrical method. A 2D axisymmetric H -formulation model using the FEM package in COMSOL Multiphysics has been established to match the circular geometry of the coil used in the experiment. Three scenarios have been analysed: Scenario 1 with AC transport current and DC magnetic field (experiment and simulation); Scenario 2 with DC transport current and AC magnetic field (simulation); and Scenario 3 with AC transport current and AC magnetic field (simulation and experimental data support). The angular dependence analysis on the coil under a magnetic field with different orientation angle θ has been carried out for all three scenarios. For Scenario 3, the effect of the relative phase difference Δφ between the AC current and the AC field on the total AC loss of the coil has been investigated. In summary, a current/field/angle/phase dependent AC loss ( I , B , θ, Δφ) study of a circular HTS coil has been carried out. The obtained results provide useful indications for the future design and research of HTS AC systems.

Improved transistorized AC motor controller for battery powered urban electric passenger vehicles

NASA Technical Reports Server (NTRS)

Peak, S. C.

1982-01-01

An ac motor controller for an induction motor electric vehicle drive system was designed, fabricated, tested, evaluated, and cost analyzed. A vehicle performance analysis was done to establish the vehicle tractive effort-speed requirements. These requirements were then converted into a set of ac motor and ac controller requirements. The power inverter is a three-phase bridge using power Darlington transistors. The induction motor was optimized for use with an inverter power source. The drive system has a constant torque output to base motor speed and a constant horsepower output to maximum speed. A gear shifting transmission is not required. The ac controller was scaled from the base 20 hp (41 hp peak) at 108 volts dec to an expanded horsepower and battery voltage range. Motor reversal was accomplished by electronic reversal of the inverter phase sequence. The ac controller can also be used as a boost chopper battery charger. The drive system was tested on a dynamometer and results are presented. The current-controlled pulse width modulation control scheme yielded improved motor current waveforms. The ac controller favors a higher system voltage.

Instantaneous velocity measurement of AC electroosmotic flows by laser induced fluorescence photobleaching anemometer with high temporal resolution

NASA Astrophysics Data System (ADS)

Zhao, Wei; Yang, Fang; Qiao, Rui; Wang, Guiren; Rui Qiao Collaboration

2015-11-01

Understanding the instantaneous response of flows to applied AC electric fields may help understand some unsolved issues in induced-charge electrokinetics and enhance performance of microfluidic devices. Since currently available velocimeters have difficulty in measuring velocity fluctuations with frequency higher than 1 kHz, most experimental studies so far focus only on the average velocity measurement in AC electrokinetic flows. Here, we present measurements of AC electroosmotic flow (AC-EOF) response time in microchannels by a novel velocimeter with submicrometer spatial resolution and microsecond temporal resolution, i.e. laser-induced fluorescence photobleaching anemometer (LIFPA). Several parameters affecting the AC-EOF response time to the applied electric signal were investigated, i.e. channel length, transverse position and solution conductivity. The experimental results show that the EOF response time under a pulsed electric field decreases with the reduction of the microchannel length, distance between the detection position to the wall and the conductivity of the solution. This work could provide a new powerful tool to measure AC electrokinetics and enhance our understanding of AC electrokinetic flows.

Alternating-Current Motor Drive for Electric Vehicles

NASA Technical Reports Server (NTRS)

Krauthamer, S.; Rippel, W. E.

1982-01-01

New electric drive controls speed of a polyphase as motor by varying frequency of inverter output. Closed-loop current-sensing circuit automatically adjusts frequency of voltage-controlled oscillator that controls inverter frequency, to limit starting and accelerating surges. Efficient inverter and ac motor would give electric vehicles extra miles per battery charge.

Popular Science Recognizes Innovative Solar Technologies

Science.gov Websites

photovoltaic (solar electric) modules to produce standard household current are listed among the magazine's photovoltaic module that produces standard household, or alternating current (AC). Ascension Technology's SunSineTM 300 AC photovoltaic module has a built-in microinverter that eliminates the need for direct

A method for determining electrophoretic and electroosmotic mobilities using AC and DC electric field particle displacements.

PubMed

Oddy, M H; Santiago, J G

2004-01-01

We have developed a method for measuring the electrophoretic mobility of submicrometer, fluorescently labeled particles and the electroosmotic mobility of a microchannel. We derive explicit expressions for the unknown electrophoretic and the electroosmotic mobilities as a function of particle displacements resulting from alternating current (AC) and direct current (DC) applied electric fields. Images of particle displacements are captured using an epifluorescent microscope and a CCD camera. A custom image-processing code was developed to determine image streak lengths associated with AC measurements, and a custom particle tracking velocimetry (PTV) code was devised to determine DC particle displacements. Statistical analysis was applied to relate mobility estimates to measured particle displacement distributions.

Electroosmotic flow in microchannels with arbitrary geometry and arbitrary distribution of wall charge.

PubMed

Xuan, Xiangchun; Li, Dongqing

2005-09-01

General solutions are developed for direct current (DC) and alternating current (AC) electroosmotic flows in microfluidic channels with arbitrary cross-sectional geometry and arbitrary distribution of wall charge (zeta potential). The applied AC electric field can also be of arbitrary waveform. By proposing a nondimensional time scale varpi defined as the ratio of the diffusion time of momentum across the electric double-layer thickness to the period of the applied electric field, we demonstrate analytically that the Helmholtz-Smoluchowski electroosmotic velocity is an appropriate slip condition for AC electroosmotic flows in typical microfluidic applications. With this slip condition approach, electroosmotic flows in rectangular and asymmetric trapezoidal microchannels with nonuniform wall charge, as examples, are investigated. The unknown constants in the proposed general solutions are numerically determined with a least-squares method through matching the boundary conditions. We find that the wall charge affects significantly the electroosmotic flow while the channel geometry does not. Moreover, the flow feature is characterized by another nondimensional time scale Omega defined as the ratio of the diffusion time of momentum across the channel hydraulic radius to the period of the applied electric field. The onset of phase shift between AC electroosmotic velocity and applied electric field is also examined analytically.

Compensation for Harmonic Currents and Reactive Power in Wind Power Generation System using PWM Inverter

NASA Astrophysics Data System (ADS)

Shinohara, Katsuji; Shinhatsubo, Kurato; Iimori, Kenichi; Yamamoto, Kichiro; Saruban, Takamichi; Yamaemori, Takahiro

In recent year, consciousness of environmental problems is enhancing, and the price of the electric power purchased by an electric power company is established expensive for the power plant utilizing the natural energy. So, the introduction of the wind power generation is promoted in Japan. Generally, squirrel-cage induction machines are widely used as a generator in wind power generation system because of its small size, lightweight and low-cost. However, the induction machines do not have a source of excitation. Thus, it causes the inrush currents and the instantaneous voltage drop when the generator is directly connected to a power grid. To reduce the inrush currents, an AC power regulator is used. Wind power generations are frequently connected to and disconnected from the power grid. However, when the inrush currents are reduced, harmonic currents are caused by phase control of the AC power regulator. And the phase control of AC power regulator cannot control the power factor. Therefore, we propose the use of the AC power regulator to compensate for the harmonic currents and reactive power in the wind power generation system, and demonstrate the validity of its system by simulated and experimental results.

Module Twelve: Series AC Resistive-Reactive Circuits; Basic Electricity and Electronics Individualized Learning System.

ERIC Educational Resources Information Center

Bureau of Naval Personnel, Washington, DC.

The module covers series circuits which contain both resistive and reactive components and methods of solving these circuits for current, voltage, impedance, and phase angle. The module is divided into six lessons: voltage and impedance in AC (alternating current) series circuits, vector computations, rectangular and polar notation, variational…

Method and system for a gas tube switch-based voltage source high voltage direct current transmission system

DOE Office of Scientific and Technical Information (OSTI.GOV)

She, Xu; Chokhawala, Rahul Shantilal; Zhou, Rui

A voltage source converter based high-voltage direct-current (HVDC) transmission system includes a voltage source converter (VSC)-based power converter channel. The VSC-based power converter channel includes an AC-DC converter and a DC-AC inverter electrically coupled to the AC-DC converter. The AC-DC converter and a DC-AC inverter include at least one gas tube switching device coupled in electrical anti-parallel with a respective gas tube diode. The VSC-based power converter channel includes a commutating circuit communicatively coupled to one or more of the at least one gas tube switching devices. The commutating circuit is configured to "switch on" a respective one of themore » one or more gas tube switching devices during a first portion of an operational cycle and "switch off" the respective one of the one or more gas tube switching devices during a second portion of the operational cycle.« less

Printing of highly conductive solution by alternating current electrohydrodynamic direct-write

NASA Astrophysics Data System (ADS)

Jiang, Jiaxin; Zheng, Gaofeng; Wang, Xiang; Zheng, Jianyi; Liu, Juan; Liu, Yifang; Li, Wenwang; Guo, Shumin

2018-03-01

Electrohydrodynamic Direct-Write (EDW) is a novel technology for the printing of micro/nano structures. In this paper, Alternating Current (AC) electrical field was introduced to improve the ejection stability of jet with highly conductive solution. By alternating the electrical field, the polarity of free charges on the surface of jet was changed and the average density of charge, as well as the repulsive force, was reduced to stabilize the jet. When the frequency of AC electrical field increased, the EDW process became more stable and the shape of deposited droplets became more regular. The diameter of printed droplets decreased and the deposition frequency increased with the increase of voltage frequency. The phenomenon of corona discharge was overcome effectively as well. To further evaluate the performance of AC EDW for highly conductive solution, more NaCl was added to the solution and the conductivity was increased to 2810μs/cm. With such high conductivity, the problem of serious corona discharge could still be prevented by AC EDW, and the diameter of printed droplets decreased significantly. This work provides an effective way to accelerate industrial applications of EDW.

Effect of neodymium substitution on the electric and dielectric properties of Mn-Ni-Zn ferrite

NASA Astrophysics Data System (ADS)

Agami, W. R.

2018-04-01

Ferrite samples of Mn0.5Ni0.1Zn0.4NdxFe2-xO4 (x = 0.0, 0.01, 0.02, 0.05, 0.075 and 0.1) have been prepared by usual ceramic method. The temperature and composition dependences of the dc electric resistivity (ρdc) were studied. The frequency and composition dependences of the ac electric resistivity (ρac) and dielectric parameters (dielectric constant ε' and dielectric loss ε'') have been investigated. ρdc was found to decrease with temperature for all samples while it increases with increasing Nd3+ concentration. On the other hand, ρac and the dielectric properties were found to decrease with increasing the frequency while ρac increases and both ε' and ε'' decrease with increasing Nd3+ concentration. These results were explained by the Maxwell-Wagner two-layer model and Koops's theory. The improvement in dc and ac electric resistivities shows that these prepared materials are valid for decreasing the eddy current losses at high frequencies, so they can be used in the fabrication of multilayer chip inductor (MLCI) devices.

AC Loss Measurements on a 2G YBCO Coil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rey, Christopher M; Duckworth, Robert C; Schwenterly, S W

2011-01-01

The Oak Ridge National Laboratory (ORNL) is collaborating with Waukesha Electric Systems (WES) to continue development of HTS power transformers. For compatibility with the existing power grid, a commercially viable HTS transformer will have to operate at high voltages in the range of 138 kV and above, and will have to withstand 550-kV impulse voltages as well. Second-generation (2G) YBCO coated conductors will be required for an economically-competitive design. In order to adequately size the refrigeration system for these transformers, the ac loss of these HTS coils must be characterized. Electrical AC loss measurements were conducted on a prototype highmore » voltage (HV) coil with co-wound stainless steel at 60 Hz in a liquid nitrogen bath using a lock-in amplifier technique. The prototype HV coil consisted of 26 continuous (without splice) single pancake coils concentrically centered on a stainless steel former. For ac loss measurement purposes, voltage tap pairs were soldered across each set of two single pancake coils so that a total of 13 separate voltage measurements could be made across the entire length of the coil. AC loss measurements were taken as a function of ac excitation current. Results show that the loss is primarily concentrated at the ends of the coil where the operating fraction of critical current is the highest and show a distinct difference in current scaling of the losses between low current and high current regimes.« less

Systems and methods for commutating inductor current using a matrix converter

DOEpatents

Ransom, Ray M; Kajouke, Lateef A; Perisic, Milun

2012-10-16

Systems and methods are provided for delivering current using a matrix converter in a vehicle. An electrical system comprises an AC interface, a first conversion module coupled to the AC interface, an inductive element coupled between the AC interface and the first conversion module, and a control module coupled to the first conversion module. The control module is configured to operate the first conversion module in a bidirectional operating mode to commutate current bidirectionally. When a magnitude of the current through the inductive element is greater than a first threshold value, the control module operates the conversion module in a unidirectional operating mode, wherein current is commutated unidirectionally.

Module Two: Voltage; Basic Electricity and Electronics Individualized Learning System.

ERIC Educational Resources Information Center

Bureau of Naval Personnel, Washington, DC.

In this module the student will study and learn what voltage is, how it is generated, what AC (alternating current) and DC (direct current) are and why both kinds are needed, and how to measure voltages. The module is divided into six lessons: EMF (electromotive force) from chemical action, magnetism, electromagnetic induction, AC voltage, the…

Demodulation circuit for AC motor current spectral analysis

DOEpatents

Hendrix, Donald E.; Smith, Stephen F.

1990-12-18

A motor current analysis method for the remote, noninvasive inspection of electric motor-operated systems. Synchronous amplitude demodulation and phase demodulation circuits are used singly and in combination along with a frequency analyzer to produce improved spectral analysis of load-induced frequencies present in the electric current flowing in a motor-driven system.

AC Loss Analysis of MgB2-Based Fully Superconducting Machines

NASA Astrophysics Data System (ADS)

Feddersen, M.; Haran, K. S.; Berg, F.

2017-12-01

Superconducting electric machines have shown potential for significant increase in power density, making them attractive for size and weight sensitive applications such as offshore wind generation, marine propulsion, and hybrid-electric aircraft propulsion. Superconductors exhibit no loss under dc conditions, though ac current and field produce considerable losses due to hysteresis, eddy currents, and coupling mechanisms. For this reason, many present machines are designed to be partially superconducting, meaning that the dc field components are superconducting while the ac armature coils are conventional conductors. Fully superconducting designs can provide increases in power density with significantly higher armature current; however, a good estimate of ac losses is required to determine the feasibility under the machines intended operating conditions. This paper aims to characterize the expected losses in a fully superconducting machine targeted towards aircraft, based on an actively-shielded, partially superconducting machine from prior work. Various factors are examined such as magnet strength, operating frequency, and machine load to produce a model for the loss in the superconducting components of the machine. This model is then used to optimize the design of the machine for minimal ac loss while maximizing power density. Important observations from the study are discussed.

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

PubMed

Islam, Nazmul; Reyna, Jairo

2012-04-01

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. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electrical conductivity and dielectric relaxation of 2-(antipyrin-4-ylhydrazono)-2-(4-nitrophenyl)acetonitrile

NASA Astrophysics Data System (ADS)

El-Menyawy, E. M.; Zedan, I. T.; Nawar, H. H.

2014-03-01

The electrical and dielectric properties of the synthesized 2-(antipyrin-4-ylhydrazono)-2-(4-nitrophenyl)acetonitrile (AHNA) have been studied. The direct and alternating current (DC and AC) conductivities and complex dielectric constant were investigated in temperature range 303-403 K. The AC conductivity and dielectric properties of AHNA were investigated over frequency range 100 Hz-5 MHz. From DC and AC measurements, electrical conduction is found to be a thermally activated process. The frequency-dependent AC conductivity obeys Jonscher's universal power law in which the frequency exponent decreases with increasing temperature. The correlated barrier hopping (CBH) is the predominant model for describing the charge carrier transport in which the electrical parameters are evaluated. The activation energy is found to decrease with increasing frequency. The behaviors of dielectric and dielectric loss are discussed in terms of a polarization mechanism. The dielectric loss shows frequency power law from which the maximum barrier height is determined as 0.19 eV in terms of the Guintini model.

Discharging a DC bus capacitor of an electrical converter system

DOEpatents

Kajouke, Lateef A; Perisic, Milun; Ransom, Ray M

2014-10-14

A system and method of discharging a bus capacitor of a bidirectional matrix converter of a vehicle are presented here. The method begins by electrically shorting the AC interface of the converter after an AC energy source is disconnected from the AC interface. The method continues by arranging a plurality of switching elements of a second energy conversion module into a discharge configuration to establish an electrical current path from a first terminal of an isolation module, through an inductive element, and to a second terminal of the isolation module. The method also modulates a plurality of switching elements of a first energy conversion module, while maintaining the discharge configuration of the second energy conversion module, to at least partially discharge a DC bus capacitor.

A hybrid air conditioner driven by a hybrid solar collector

NASA Astrophysics Data System (ADS)

Al-Alili, Ali

The objective of this thesis is to search for an efficient way of utilizing solar energy in air conditioning applications. The current solar Air Conditioners (A/C)s suffer from low Coefficient of Performance (COP) and performance degradation in hot and humid climates. By investigating the possible ways of utilizing solar energy in air conditioning applications, the bottlenecks in these approaches were identified. That resulted in proposing a novel system whose subsystem synergy led to a COP higher than unity. The proposed system was found to maintain indoor comfort at a higher COP compared to the most common solar A/Cs, especially under very hot and humid climate conditions. The novelty of the proposed A/C is to use a concentrating photovoltaic/thermal collector, which outputs thermal and electrical energy simultaneously, to drive a hybrid A/C. The performance of the hybrid A/C, which consists of a desiccant wheel, an enthalpy wheel, and a vapor compression cycle (VCC), was investigated experimentally. This work also explored the use of a new type of desiccant material, which can be regenerated with a low temperature heat source. The experimental results showed that the hybrid A/C is more effective than the standalone VCC in maintaining the indoor conditions within the comfort zone. Using the experimental data, the COP of the hybrid A/C driven by a hybrid solar collector was found to be at least double that of the current solar A/Cs. The innovative integration of its subsystems allows each subsystem to do what it can do best. That leads to lower energy consumption which helps reduce the peak electrical loads on electric utilities and reduces the consumer operating cost since less energy is purchased during the on peak periods and less solar collector area is needed. In order for the proposed A/C to become a real alternative to conventional systems, its performance and total cost were optimized using the experimentally validated model. The results showed that for an electricity price of 0.12 $/kW-hr, the hybrid solar A/C's cumulative total cost will be less than that of a standard VCC after 17.5 years of operation.

Fibrillar disruption by AC electric field induced oscillation: A case study with human serum albumin.

PubMed

Sen, Shubhatam; Chakraborty, Monojit; Goley, Snigdha; Dasgupta, Swagata; DasGupta, Sunando

2017-07-01

The effect of oscillation induced by a frequency-dependent alternating current (AC) electric field to dissociate preformed amyloid fibrils has been investigated. An electrowetting-on-dielectric type setup has been used to apply the AC field of varying frequencies on preformed fibrils of human serum albumin (HSA). The disintegration potency has been monitored by a combination of spectroscopic and microscopic techniques. The experimental results suggest that the frequency of the applied AC field plays a crucial role in the disruption of preformed HSA fibrils. The extent of stress generated inside the droplet due to the application of the AC field at different frequencies has been monitored as a function of the input frequency of the applied AC voltage. This has been accomplished by assessing the morphology deformation of the oscillating HSA fibril droplets. The shape deformation of the oscillating droplets is characterized using image analysis by measuring the dynamic changes in the shape dependent parameters such as contact angle and droplet footprint radius and the amplitude. It is suggested that the cumulative effects of the stress generated inside the HSA fibril droplets due to the shape deformation induced hydrodynamic flows and the torque induced by the intrinsic electric dipoles of protein due to their continuous periodic realignment in presence of the AC electric field results in the destruction of the fibrillar species. Copyright © 2017. Published by Elsevier B.V.

An "Off-the-Shelf" System for Intraprocedural Electrical Current Evaluation and Monitoring of Irreversible Electroporation Therapy.

PubMed

Neal, Robert E; Kavnoudias, Helen; Thomson, Kenneth R

2015-06-01

Irreversible electroporation (IRE) ablation uses a series of brief electric pulses to create nanoscale defects in cell membranes, killing the cells. It has shown promise in numerous soft-tissue tumor applications. Larger voltages between electrodes will increase ablation volume, but exceeding electrical limits may risk damage to the patient, cause ineffective therapy delivery, or require generator restart. Monitoring electrical current for these conditions in real-time enables managing these risks. This capacity is not presently available in clinical IRE generators. We describe a system using a Tektronix TCP305 AC/DC Current Probe connected to a TCPA300 AC/DC Current Probe Amplifier, which is read on a computer using a Protek DSO-2090 USB computer-interfacing oscilloscope. Accuracy of the system was tested with a resistor circuit and by comparing measured currents with final outputs from the NanoKnife clinical electroporation pulse generator. Accuracy of measured currents was 1.64 ± 2.4 % relative to calculations for the resistor circuit and averaged 0.371 ± 0.977 % deviation from the NanoKnife. During clinical pulse delivery, the system offers real-time evaluation of IRE procedure progress and enables a number of methods for identifying approaching issues from electrical behavior of therapy delivery, facilitating protocol changes before encountering therapy delivery issues. This system can monitor electrical currents in real-time without altering the electric pulses or modifying the pulse generator. This facilitates delivering electric pulse protocols that remain within the optimal range of electrical currents-sufficient strength for clinically relevant ablation volumes, without the risk of exceeding safe electric currents or causing inadequate ablation.

The radiation impedance of an electrodynamic tether with end connectors

NASA Technical Reports Server (NTRS)

Hastings, Daniel E.; Wang, J.

1987-01-01

Electrodynamic tethers are wires deployed across the earth's geomagnetic field through which a current is flowing. The radiation impedance of a tether with end connectors carrying an ac current is computed from classical antenna theory. This simulates the use of a tether on a space structure. It is shown that the current flow pattern at the tether connector is critical to determining the overall radiation impedance. If the tether makes direct electrical contact with the ionosphere then radiation impedances of the order of several thousand Ohms can be expected. If the only electrical contact is through the end connectors then the impedance is only a few Ohms for a dc current rising to several tens of Ohms for an ac current with frequencies in the whistler range.

CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Characteristics of alternating current hopping conductivity in DNA sequences

NASA Astrophysics Data System (ADS)

Ma, Song-Shan; Xu, Hui; Wang, Huan-You; Guo, Rui

2009-08-01

This paper presents a model to describe alternating current (AC) conductivity of DNA sequences, in which DNA is considered as a one-dimensional (1D) disordered system, and electrons transport via hopping between localized states. It finds that AC conductivity in DNA sequences increases as the frequency of the external electric field rises, and it takes the form of øac(ω) ~ ω2 ln2(1/ω). Also AC conductivity of DNA sequences increases with the increase of temperature, this phenomenon presents characteristics of weak temperature-dependence. Meanwhile, the AC conductivity in an off-diagonally correlated case is much larger than that in the uncorrelated case of the Anderson limit in low temperatures, which indicates that the off-diagonal correlations in DNA sequences have a great effect on the AC conductivity, while at high temperature the off-diagonal correlations no longer play a vital role in electric transport. In addition, the proportion of nucleotide pairs p also plays an important role in AC electron transport of DNA sequences. For p < 0.5, the conductivity of DNA sequence decreases with the increase of p, while for p >= 0.5, the conductivity increases with the increase of p.

Application of low-frequency alternating current electric fields via interdigitated electrodes: effects on cellular viability, cytoplasmic calcium, and osteogenic differentiation of human adipose-derived stem cells.

PubMed

McCullen, Seth D; McQuilling, John P; Grossfeld, Robert M; Lubischer, Jane L; Clarke, Laura I; Loboa, Elizabeth G

2010-12-01

Electric stimulation is known to initiate signaling pathways and provides a technique to enhance osteogenic differentiation of stem and/or progenitor cells. There are a variety of in vitro stimulation devices to apply electric fields to such cells. Herein, we describe and highlight the use of interdigitated electrodes to characterize signaling pathways and the effect of electric fields on the proliferation and osteogenic differentiation of human adipose-derived stem cells (hASCs). The advantage of the interdigitated electrode configuration is that cells can be easily imaged during short-term (acute) stimulation, and this identical configuration can be utilized for long-term (chronic) studies. Acute exposure of hASCs to alternating current (AC) sinusoidal electric fields of 1 Hz induced a dose-dependent increase in cytoplasmic calcium in response to electric field magnitude, as observed by fluorescence microscopy. hASCs that were chronically exposed to AC electric field treatment of 1 V/cm (4 h/day for 14 days, cultured in the osteogenic differentiation medium containing dexamethasone, ascorbic acid, and β-glycerol phosphate) displayed a significant increase in mineral deposition relative to unstimulated controls. This is the first study to evaluate the effects of sinusoidal AC electric fields on hASCs and to demonstrate that acute and chronic electric field exposure can significantly increase intracellular calcium signaling and the deposition of accreted calcium under osteogenic stimulation, respectively.

Proposal and Development of a High Voltage Variable Frequency Alternating Current Power System for Hybrid Electric Aircraft

NASA Technical Reports Server (NTRS)

Sadey, David J.; Taylor, Linda M.; Beach, Raymond F.

2017-01-01

The development of ultra-efficient commercial vehicles and the transition to low-carbon emission propulsion are seen as strategic thrust paths within NASA Aeronautics. A critical enabler to these paths comes in the form of hybrid electric propulsion systems. For megawatt-class systems, the best power system topology for these hybrid electric propulsion systems is debatable. Current proposals within NASA and the Aero community suggest using a combination of alternating current (AC) and direct current (DC) for power generation, transmission, and distribution. This paper proposes an alternative to the current thought model through the use of a primarily high voltage AC power system, supported by the Convergent Aeronautics Solutions (CAS) Project. This system relies heavily on the use of doubly-fed induction machines (DFIMs), which provide high power densities, minimal power conversion, and variable speed operation. The paper presents background on the activity along with the system architecture, development status, and preliminary results.

Temperature dependence of critical current and transport current losses of 4 mm YBCO coated conductors manufactured using nonmagnetic substrate

NASA Astrophysics Data System (ADS)

Kvitkovic, J.; Hatwar, R.; Pamidi, S. V.; Fleshler, S.; Thieme, C.

2015-12-01

The temperature dependence of the critical current and AC losses were measured on American Superconductor Corporation's (AMSC) second generation high temperature superconducting (2G HTS) wire produced by Rolling Assisted Biaxially Textured Substrate (RABiTS) and Metal Organic Deposition (MOD) process. Wires manufactured with two types of substrates were characterized. The magnetic substrate with composition Ni5a%W exhibits a magnetic signature and has non-negligible AC losses in AC power applications. A new nonmagnetic substrate with an alloy composition Ni9a%W has been developed by AMSC to address the AC losses in 2G HTS. The data presented show that the performance of the new conductor is identical to the conductor with magnetic substrate in terms of critical current density. The data on AC losses demonstrate the absence of ferromagnetic loss component in the new conductor and significantly reduced AC losses at low to moderate values of I/Ic. The reduced losses will translate into reduced capital costs and lower operating costs of superconducting electrical devices for AC applications.

Testing of a 1.25-m HTS Cable Made from YBCO Tapes

NASA Astrophysics Data System (ADS)

Gouge, M. J.; Lue, J. W.; Demko, J. A.; Duckworth, R. C.; Fisher, P. W.; Daumling, M.; Lindsay, D. T.; Roden, M. L.; Tolbert, J. C.

2004-06-01

Ultera and Oak Ridge National Laboratory (ORNL) have jointly designed, built, and tested a 1.25-m-long, prototype high-temperature superconducting (HTS) power cable made from 1-cm-wide, second-generation YBa2Cu3Ox (YBCO)-coated conductor tapes. Electrical tests of this cable were performed in boiling liquid nitrogen at 77 K. DC testing of the 1.25-m cable included determination of the V-I curve, with a critical current of 4200 A. This was consistent with the properties of the 24 individual YBCO tapes. AC testing of the cable was conducted at currents up to 2500 Arms. The ac losses were measured calorimetrically by measuring the response of a calibrated temperature sensor placed on the former and electrically by use of a Rogowski coil with a lock-in amplifier. AC losses of about 2 W/m were measured at a cable ac current of 2000 Arms. Overcurrent testing was conducted at peak current values up to 12 kA for pulse lengths of 0.1-0.2 s. The cable temperature increased to 105 K for a 12 kA, 0.2 s overcurrent pulse, and the cable showed no degradation after the sequence of overcurrent testing. This commercial-grade HTS cable demonstrated the feasibility of second-generation YBCO tapes in an ac cable application.

Hall-Effect Based Semi-Fast AC On-Board Charging Equipment for Electric Vehicles

PubMed Central

Milanés-Montero, María Isabel; Gallardo-Lozano, Javier; Romero-Cadaval, Enrique; González-Romera, Eva

2011-01-01

The expected increase in the penetration of electric vehicles (EV) and plug-in hybrid electric vehicles (PHEV) will produce unbalanced conditions, reactive power consumption and current harmonics drawn by the battery charging equipment, causing a great impact on the power quality of the future smart grid. A single-phase semi-fast electric vehicle battery charger is proposed in this paper. This ac on-board charging equipment can operate in grid-to-vehicle (G2V) mode, and also in vehicle-to-grid (V2G) mode, transferring the battery energy to the grid when the vehicle is parked. The charger is controlled with a Perfect Harmonic Cancellation (PHC) strategy, contributing to improve the grid power quality, since the current demanded or injected has no harmonic content and a high power factor. Hall-effect current and voltage transducers have been used in the sensor stage to carry out this control strategy. Experimental results with a laboratory prototype are presented. PMID:22163697

Hall-effect based semi-fast AC on-board charging equipment for electric vehicles.

PubMed

Milanés-Montero, María Isabel; Gallardo-Lozano, Javier; Romero-Cadaval, Enrique; González-Romera, Eva

2011-01-01

The expected increase in the penetration of electric vehicles (EV) and plug-in hybrid electric vehicles (PHEV) will produce unbalanced conditions, reactive power consumption and current harmonics drawn by the battery charging equipment, causing a great impact on the power quality of the future smart grid. A single-phase semi-fast electric vehicle battery charger is proposed in this paper. This ac on-board charging equipment can operate in grid-to-vehicle (G2V) mode, and also in vehicle-to-grid (V2G) mode, transferring the battery energy to the grid when the vehicle is parked. The charger is controlled with a Perfect Harmonic Cancellation (PHC) strategy, contributing to improve the grid power quality, since the current demanded or injected has no harmonic content and a high power factor. Hall-effect current and voltage transducers have been used in the sensor stage to carry out this control strategy. Experimental results with a laboratory prototype are presented.

Inhibition of motor cortex excitability with 15Hz transcranial alternating current stimulation (tACS).

PubMed

Zaghi, Soroush; de Freitas Rezende, Larissa; de Oliveira, Laís Machado; El-Nazer, Rasheda; Menning, Sanne; Tadini, Laura; Fregni, Felipe

2010-08-02

There remains a lack of solid evidence showing whether transcranial stimulation with weak alternating current (transcranial alternating current stimulation, tACS) can in fact induce significant neurophysiological effects. Previously, a study in which tACS was applied for 2 and 5min with current density=0.16-0.25A/m(2) was unable to show robust effects on cortical excitability. Here we applied tACS at a significantly higher current density (0.80A/m(2)) for a considerably longer duration (20min) and were indeed able to demonstrate measurable changes to cortical excitability. Our results show that active 15Hz tACS of the motor cortex (electrodes placed at C3 and C4) significantly diminished the amplitude of motor evoked potentials and decreased intracortical facilitation (ICF) as compared to baseline and sham stimulation. In addition, we show that our method of sham tACS is a reliable control condition. These results support the notion that AC stimulation with weak currents can induce significant changes in brain excitability; in this case, 15Hz tACS led to a pattern of inhibition of cortical excitability. We propose that tACS may have a dampening effect on cortical networks and perhaps interfere with the temporal and spatial summation of weak subthreshold electric potentials. Copyright 2010 Elsevier Ireland Ltd. All rights reserved.

Trade Electricity. Motors & Controls--Level 3. Standardized Curriculum.

ERIC Educational Resources Information Center

New York City Board of Education, Brooklyn, NY. Office of Occupational and Career Education.

This curriculum guide consists of seven modules on motors and controls, one of the three divisions of the standardized trade electricity curriculum in high schools in New York City. The seven modules cover the following subjects: energy conservation wiring, direct current (DC) motor repair and rewinding, DC motor controls, alternating current (AC)…

Proposal and Development of a High Voltage Variable Frequency Alternating Current Power System for Hybrid Electric Aircraft

NASA Technical Reports Server (NTRS)

Sadey, David J.; Taylor, Linda M.; Beach, Raymond F.

2016-01-01

The development of ultra-efficient commercial vehicles and the transition to low-carbon emission propulsion are seen as thrust paths within NASA Aeronautics. A critical enabler to these paths comes in the form of hybrid-electric propulsion systems. For megawatt-class systems, the best power system topology for these hybrid-electric propulsion systems is debatable. Current proposals within NASA and the Aero community suggest using a combination of AC and DC for power transmission. This paper proposes an alternative to the current thought model through the use of a primarily high voltage AC power generation, transmission, and distribution systems, supported by the Convergent Aeronautics Solutions (CAS) Project. This system relies heavily on the use of dual-fed induction machines, which provide high power densities, minimal power conversion, and variable speed operation. The paper presents background on the project along with the system architecture, development status and preliminary results.

Fault current limiter

DOEpatents

Darmann, Francis Anthony

2013-10-08

A fault current limiter (FCL) includes a series of high permeability posts for collectively define a core for the FCL. A DC coil, for the purposes of saturating a portion of the high permeability posts, surrounds the complete structure outside of an enclosure in the form of a vessel. The vessel contains a dielectric insulation medium. AC coils, for transporting AC current, are wound on insulating formers and electrically interconnected to each other in a manner such that the senses of the magnetic field produced by each AC coil in the corresponding high permeability core are opposing. There are insulation barriers between phases to improve dielectric withstand properties of the dielectric medium.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aeloiza, Eddy C.; Burgos, Rolando P.

A step-down AC/AC converter for use in an electric distribution system includes at least one chopper circuit for each one of a plurality of phases of the AC power, each chopper circuit including a four-quadrant switch coupled in series between primary and secondary sides of the chopper circuit and a current-bidirectional two-quadrant switch coupled between the secondary side of the chopper circuit and a common node. Each current-bidirectional two-quadrant switch is oriented in the same direction, with respect to the secondary side of the corresponding chopper circuit and the common node. The converter further includes a control circuit configured tomore » pulse-width-modulate control inputs of the switches, to convert a first multiphase AC voltage at the primary sides of the chopper circuits to a second multiphase AC voltage at the secondary sides of the chopper circuits, the second multiphase AC voltage being lower in voltage than the first multiphase AC voltage.« less

Solution pH change in non-uniform alternating current electric fields at frequencies above the electrode charging frequency

PubMed Central

An, Ran; Massa, Katherine

2014-01-01

AC Faradaic reactions have been reported as a mechanism inducing non-ideal phenomena such as flow reversal and cell deformation in electrokinetic microfluidic systems. Prior published work described experiments in parallel electrode arrays below the electrode charging frequency (fc), the frequency for electrical double layer charging at the electrode. However, 2D spatially non-uniform AC electric fields are required for applications such as in plane AC electroosmosis, AC electrothermal pumps, and dielectrophoresis. Many microscale experimental applications utilize AC frequencies around or above fc. In this work, a pH sensitive fluorescein sodium salt dye was used to detect [H+] as an indicator of Faradaic reactions in aqueous solutions within non-uniform AC electric fields. Comparison experiments with (a) parallel (2D uniform fields) electrodes and (b) organic media were employed to deduce the electrode charging mechanism at 5 kHz (1.5fc). Time dependency analysis illustrated that Faradaic reactions exist above the theoretically predicted electrode charging frequency. Spatial analysis showed [H+] varied spatially due to electric field non-uniformities and local pH changed at length scales greater than 50 μm away from the electrode surface. Thus, non-uniform AC fields yielded spatially varied pH gradients as a direct consequence of ion path length differences while uniform fields did not yield pH gradients; the latter is consistent with prior published data. Frequency dependence was examined from 5 kHz to 12 kHz at 5.5 Vpp potential, and voltage dependency was explored from 3.5 to 7.5 Vpp at 5 kHz. Results suggest that Faradaic reactions can still proceed within electrochemical systems in the absence of well-established electrical double layers. This work also illustrates that in microfluidic systems, spatial medium variations must be considered as a function of experiment time, initial medium conditions, electric signal potential, frequency, and spatial position. PMID:25553200

Non-oxidized porous silicon-based power AC switch peripheries.

PubMed

Menard, Samuel; Fèvre, Angélique; Valente, Damien; Billoué, Jérôme; Gautier, Gaël

2012-10-11

We present in this paper a novel application of porous silicon (PS) for low-power alternating current (AC) switches such as triode alternating current devices (TRIACs) frequently used to control small appliances (fridge, vacuum cleaner, washing machine, coffee makers, etc.). More precisely, it seems possible to benefit from the PS electrical insulation properties to ensure the OFF state of the device. Based on the technological aspects of the most commonly used AC switch peripheries physically responsible of the TRIAC blocking performances (leakage current and breakdown voltage), we suggest to isolate upper and lower junctions through the addition of a PS layer anodically etched from existing AC switch diffusion profiles. Then, we comment the voltage capability of practical samples emanating from the proposed architecture. Thanks to the characterization results of simple Al-PS-Si(P) structures, the experimental observations are interpreted, thus opening new outlooks in the field of AC switch peripheries.

Ozone and dinitrogen monoxide production in atmospheric pressure air dielectric barrier discharge plasma effluent generated by nanosecond pulse superimposed alternating current voltage

NASA Astrophysics Data System (ADS)

Takashima, Keisuke; Kaneko, Toshiro

2017-06-01

The effects of nanosecond pulse superposition to alternating current voltage (NS + AC) on the generation of an air dielectric barrier discharge (DBD) plasma and reactive species are experimentally studied, along with measurements of ozone (O3) and dinitrogen monoxide (N2O) in the exhausted gas through the air DBD plasma (air plasma effluent). The charge-voltage cycle measurement indicates that the role of nanosecond pulse superposition is to induce electrical charge transport and excess charge accumulation on the dielectric surface following the nanosecond pulses. The densities of O3 and N2O in NS + AC DBD are found to be significantly increased in the plasma effluent, compared to the sum of those densities generated in NS DBD and AC DBD operated individually. The production of O3 and N2O is modulated significantly by the phase in which the nanosecond pulse is superimposed. The density increase and modulation effects by the nanosecond pulse are found to correspond with the electrical charge transport and the excess electrical charge accumulation induced by the nanosecond pulse. It is suggested that the electrical charge transport by the nanosecond pulse might result in the enhancement of the nanosecond pulse current, which may lead to more efficient molecular dissociation, and the excess electrical charge accumulation induced by the nanosecond pulse increases the discharge coupling power which would enhance molecular dissociation.

The AC/DCs of Electricity.

ERIC Educational Resources Information Center

Calhoun, Michael J.

1994-01-01

Describes an activity that allows students to use a rectifier circuit to convert alternating current into direct current. Also informs teachers of how to obtain most of the equipment needed for free. (ZWH)

Effects of a parallel resistor on electrical characteristics of a piezoelectric transformer in open-circuit transient state.

PubMed

Chang, Kuo-Tsai

2007-01-01

This paper investigates electrical transient characteristics of a Rosen-type piezoelectric transformer (PT), including maximum voltages, time constants, energy losses and average powers, and their improvements immediately after turning OFF. A parallel resistor connected to both input terminals of the PT is needed to improve the transient characteristics. An equivalent circuit for the PT is first given. Then, an open-circuit voltage, involving a direct current (DC) component and an alternating current (AC) component, and its related energy losses are derived from the equivalent circuit with initial conditions. Moreover, an AC power control system, including a DC-to-AC resonant inverter, a control switch and electronic instruments, is constructed to determine the electrical characteristics of the OFF transient state. Furthermore, the effects of the parallel resistor on the transient characteristics at different parallel resistances are measured. The advantages of adding the parallel resistor also are discussed. From the measured results, the DC time constant is greatly decreased from 9 to 0.04 ms by a 10 k(omega) parallel resistance under open output.

Systems and methods for deactivating a matrix converter

DOEpatents

Ransom, Ray M.

2013-04-02

Systems and methods are provided for deactivating a matrix conversion module. An electrical system comprises an alternating current (AC) interface, a matrix conversion module coupled to the AC interface, an inductive element coupled between the AC interface and the matrix conversion module, and a control module. The control module is coupled to the matrix conversion module, and in response to a shutdown condition, the control module is configured to operate the matrix conversion module to deactivate the first conversion module when a magnitude of a current through the inductive element is less than a threshold value.

46 CFR 129.120 - Alternative standards.

Code of Federal Regulations, 2010 CFR

2010-10-01

... or less may meet the following requirements of the American Yacht and Boat Council Projects, where applicable, instead of § 129.340 of this part: (1) E-1, Bonding of Direct Current Systems. (2) E-8, AC Electrical Systems on Boats. (3) E-9, DC Electrical Systems on Boats. (b) An OSV with an electrical...

Hybrid-secondary uncluttered induction machine

DOEpatents

Hsu, John S.

2001-01-01

An uncluttered secondary induction machine (100) includes an uncluttered rotating transformer (66) which is mounted on the same shaft as the rotor (73) of the induction machine. Current in the rotor (73) is electrically connected to current in the rotor winding (67) of the transformer, which is not electrically connected to, but is magnetically coupled to, a stator secondary winding (40). The stator secondary winding (40) is alternately connected to an effective resistance (41), an AC source inverter (42) or a magnetic switch (43) to provide a cost effective slip-energy-controlled, adjustable speed, induction motor that operates over a wide speed range from below synchronous speed to above synchronous speed based on the AC line frequency fed to the stator.

AUTOMOTIVE DIESEL MAINTENANCE 2. UNIT XVI, LEARNING ABOUT AC GENERATOR (ALTERNATOR) PRINCIPLES (PART I).

ERIC Educational Resources Information Center

Human Engineering Inst., Cleveland, OH.

THIS MODULE OF A 25-MODULE COURSE IS DESIGNED TO DEVELOP AN UNDERSTANDING OF THE OPERATING PRINCIPLES OF ALTERNATING CURRENT GENERATORS USED ON DIESEL POWERED EQUIPMENT. TOPICS ARE REVIEWING ELECTRICAL FUNDAMENTALS, AND OPERATING PRINCIPLES OF ALTERNATORS. THE MODULE CONSISTS OF A SELF-INSTRUCTIONAL PROGRAMED TRAINING FILM "AC GENERATORS…

ac propulsion system for an electric vehicle

NASA Technical Reports Server (NTRS)

Geppert, S.

1980-01-01

It is pointed out that dc drives will be the logical choice for current production electric vehicles (EV). However, by the mid-80's, there is a good chance that the price and reliability of suitable high-power semiconductors will allow for a competitive ac system. The driving force behind the ac approach is the induction motor, which has specific advantages relative to a dc shunt or series traction motor. These advantages would be an important factor in the case of a vehicle for which low maintenance characteristics are of primary importance. A description of an EV ac propulsion system is provided, taking into account the logic controller, the inverter, the motor, and a two-speed transmission-differential-axle assembly. The main barrier to the employment of the considered propulsion system in EV is not any technical problem, but inverter transistor cost.

Simulation study on transient electric shock characteristics of human body under high voltage ac transmission lines

NASA Astrophysics Data System (ADS)

Huang, Tao; Zou, Yanhui; Lv, Jianhong; Yang, Jinchun; Tao, Li; Zhou, Jianfei

2017-09-01

Human body under high-voltage AC transmission lines will produce a certain induced voltage due to the electrostatic induction. When the human body contacts with some grounded objects, the charges transfer from the body to the ground and produce contact current which may cause transient electric shock. Using CDEGS and ATP/EMTP, the paper proposes a method for quantitatively calculating the transient electric shock characteristics. It calculates the human body voltage, discharge current and discharge energy under certain 500kV compact-type transmission lines and predicts the corresponding human feelings. The results show that the average root value of discharge current is less than 10mA when the human body is under the 500kV compact-type transmission lines and the human body is overall safe if the transmission lines satisfy the relevant design specifications. It concludes that the electric field strength above the ground should be limited to 4kV/m through the residential area for the purpose of reducing the electromagnetic impact.

Effect of the type of metal on the electrical conductivity and thermal properties of metal complexes: The relation between ionic radius of metal complexes and electrical conductivity

NASA Astrophysics Data System (ADS)

Morgan, Sh. M.; El-Ghamaz, N. A.; Diab, M. A.

2018-05-01

Co(II) complexes (1-4) and Ni(II) complexes (5-8) were prepared and characterized by elemental analysis, IR spectra and thermal analysis data. Thermal decomposition of all complexes was discussed using thermogravimetric analysis. The dielectric properties and alternating current conductivity were investigated in the frequency range 0.1-100 kHz and temperature range 300-660 K. The thermal activation energies of electrical conductivity (ΔE1 and ΔE2) values for complexes were calculated and discussed. The values of ΔE1 and ΔE2 for complexes (1-8) were found to decrease with increasing the frequency. Ac electrical conductivity (σac) values increases with increasing temperatures and the values of σac for Co(II) complexes are greater than Ni(II) complexes. Co(II) complexes showed a higher conductivity than other Ni(II) complexes due to the higher crystallinity as confirmed by X-ray diffraction analysis.

Single channel double-duct liquid metal electrical generator using a magnetohydrodynamic device

DOEpatents

Haaland, C.M.; Deeds, W.E.

1999-07-13

A single channel double-duct liquid metal electrical generator using a magnetohydrodynamic (MHD) device. The single channel device provides useful output AC electric energy. The generator includes a two-cylinder linear-piston engine which drives liquid metal in a single channel looped around one side of the MHD device to form a double-duct contra-flowing liquid metal MHD generator. A flow conduit network and drive mechanism are provided for moving liquid metal with an oscillating flow through a static magnetic field to produce useful AC electric energy at practical voltages and currents. Variable stroke is obtained by controlling the quantity of liquid metal in the channel. High efficiency is obtained over a wide range of frequency and power output. 5 figs.

Single channel double-duct liquid metal electrical generator using a magnetohydrodynamic device

DOEpatents

Haaland, Carsten M.; Deeds, W. Edward

1999-01-01

A single channel double-duct liquid metal electrical generator using a magnetohydrodynamic (MHD) device. The single channel device provides useful output AC electric energy. The generator includes a two-cylinder linear-piston engine which drives liquid metal in a single channel looped around one side of the MHD device to form a double-duct contra-flowing liquid metal MHD generator. A flow conduit network and drive mechanism are provided for moving liquid metal with an oscillating flow through a static magnetic field to produce useful AC electric energy at practical voltages and currents. Variable stroke is obtained by controlling the quantity of liquid metal in the channel. High efficiency is obtained over a wide range of frequency and power output.

Electrodeformation of multi-bilayer spherical concentric membranes by AC electric fields

NASA Astrophysics Data System (ADS)

Lira-Escobedo, J.; Arauz-Lara, J.; Aranda-Espinoza, H.; Adlerz, K.; Viveros-Mendez, P. X.; Aranda-Espinoza, S.

2017-09-01

It is now well established that external stresses alter the behaviour of cells, where such alterations can be as profound as changes in gene expression. A type of stresses of particular interest are those due to alternating-current (AC) electric fields. The effect of AC fields on cells is still not well understood, in particular it is not clear how these fields affect the cell nucleus and other organelles. Here, we propose that one possible mechanism is through the deformation of the membranes. In order to investigate the effect of AC fields on the morphological changes of the cell organelles, we modelled the cell as two concentric bilayer membranes. This model allows us to obtain the deformations induced by the AC field by balancing the elastic energy and the work done by the Maxwell stresses. Morphological phase diagrams are obtained as a function of the frequency and the electrical properties of the media and membranes. We demonstrate that the organelle shapes can be changed without modifying the shape of the external cell membrane and that the organelle deformation transitions can be used to measure, for example, the conductivity of the nucleus.

Rapid immunocytochemistry based on alternating current electric field using squash smear preparation of central nervous system tumors.

PubMed

Moriya, Jun; Tanino, Mishie Ann; Takenami, Tomoko; Endoh, Tomoko; Urushido, Masana; Kato, Yasutaka; Wang, Lei; Kimura, Taichi; Tsuda, Masumi; Nishihara, Hiroshi; Tanaka, Shinya

2016-01-01

The role of intraoperative pathological diagnosis for central nervous system (CNS) tumors is crucial for neurosurgery when determining the surgical procedure. Especially, treatment of carmustine (BCNU) wafers requires a conclusive diagnosis of high-grade glioma proven by intraoperative diagnosis. Recently, we demonstrated the usefulness of rapid immunohistochemistry (R-IHC) that facilitates antigen-antibody reaction under alternative current (AC) electric field in the intraoperative diagnosis of CNS tumors; however, a higher proportion of water and lipid in the brain parenchyma sometimes leads to freezing artifacts, resulting in poor quality of frozen sections. On the other hand, squash smear preparation of CNS tumors for cytology does not affect the frozen artifacts, and the importance of smear preparation is now being re-recognized as being better than that of the tissue sections. In this study, we established the rapid immunocytochemistry (R-ICC) protocol for squash smears of CNS tumors using AC electric field that takes only 22 min, and demonstrated its usefulness for semi-quantitative Ki-67/MIB-1 labeling index and CD 20 by R-ICC for intraoperative diagnosis. R-ICC by AC electric field may become a substantial tool for compensating R-IHC and will be applied for broad antibodies in the future.

Non-invasive Brain Stimulation: A Paradigm Shift in Understanding Brain Oscillations.

PubMed

Vosskuhl, Johannes; Strüber, Daniel; Herrmann, Christoph S

2018-01-01

Cognitive neuroscience set out to understand the neural mechanisms underlying cognition. One central question is how oscillatory brain activity relates to cognitive processes. Up to now, most of the evidence supporting this relationship was correlative in nature. This situation changed dramatically with the recent development of non-invasive brain stimulation (NIBS) techniques, which open up new vistas for neuroscience by allowing researchers for the first time to validate their correlational theories by manipulating brain functioning directly. In this review, we focus on transcranial alternating current stimulation (tACS), an electrical brain stimulation method that applies sinusoidal currents to the intact scalp of human individuals to directly interfere with ongoing brain oscillations. We outline how tACS can impact human brain oscillations by employing different levels of observation from non-invasive tACS application in healthy volunteers and intracranial recordings in patients to animal studies demonstrating the effectiveness of alternating electric fields on neurons in vitro and in vivo . These findings likely translate to humans as comparable effects can be observed in human and animal studies. Neural entrainment and plasticity are suggested to mediate the behavioral effects of tACS. Furthermore, we focus on mechanistic theories about the relationship between certain cognitive functions and specific parameters of brain oscillaitons such as its amplitude, frequency, phase and phase coherence. For each of these parameters we present the current state of testing its functional relevance by means of tACS. Recent developments in the field of tACS are outlined which include the stimulation with physiologically inspired non-sinusoidal waveforms, stimulation protocols which allow for the observation of online-effects, and closed loop applications of tACS.

Driving Force of Plasma Bullet in Atmospheric-Pressure Plasma

NASA Astrophysics Data System (ADS)

Yambe, Kiyoyuki; Masuda, Seiya; Kondo, Shoma

2018-06-01

When plasma is generated by applying high-voltage alternating current (AC), the driving force of the temporally and spatially varying electric field is applied to the plasma. The strength of the driving force of the plasma at each spatial position is different because the electrons constituting the atmospheric-pressure nonequilibrium (cold) plasma move at a high speed in space. If the force applied to the plasma is accelerated only by the driving force, the plasma will be accelerated infinitely. The equilibrium between the driving force and the restricting force due to the collision between the plasma and neutral particles determines the inertial force and the drift velocity of the plasma. Consequently, the drift velocity depends on the strength of the time-averaged AC electric field. The pressure applied by the AC electric field equilibrates with the plasma pressure. From the law of conservation of energy, the pressure equilibrium is maintained by varying the drift velocity of the plasma.

Proposal for conversion of end use equipment and service from AC to DC for enhanced benefits from photovoltaics and fuel cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wicks, F.

1998-07-01

The need to produce electricity either more fuel efficiently or without need for consuming fuel is well recognized. Fuel cells are typically suggested for higher efficiency and photovoltaics can produce electricity directly from the sun. However, both of these devices produce direct current which is not compatible with the existing ac power system. The typical options of installing AC to DC inverters and the dedication of this DC generation to DC loads and storage are costly and inefficient. Thus, the author suggests it would be better in terms of energy conservation and public policy to convert end use service tomore » DC for direct compatibility with this DC generation, as a first step toward conversion to a new and better type of electric power system that can be described as a solid state power electronics based multiple voltage DC power system.« less

Spatially variant red blood cell crenation in alternating current non-uniform fields.

PubMed

An, Ran; Wipf, David O; Minerick, Adrienne R

2014-03-01

Alternating-current (AC) electrokinetics involve the movement and behaviors of particles or cells. Many applications, including dielectrophoretic manipulations, are dependent upon charge interactions between the cell or particle and the surrounding medium. Medium concentrations are traditionally treated as spatially uniform in both theoretical models and experiments. Human red blood cells (RBCs) are observed to crenate, or shrink due to changing osmotic pressure, over 10 min experiments in non-uniform AC electric fields. Cell crenation magnitude is examined as functions of frequency from 250 kHz to 1 MHz and potential from 10 Vpp to 17.5 Vpp over a 100 μm perpendicular electrode gap. Experimental results show higher peak to peak potential and lower frequency lead to greater cell volume crenation up to a maximum volume loss of 20%. A series of experiments are conducted to elucidate the physical mechanisms behind the red blood cell crenation. Non-uniform and uniform electrode systems as well as high and low ion concentration experiments are compared and illustrate that AC electroporation, system temperature, rapid temperature changes, medium pH, electrode reactions, and convection do not account for the crenation behaviors observed. AC electroosmotic was found to be negligible at these conditions and AC electrothermal fluid flows were found to reduce RBC crenation behaviors. These cell deformations were attributed to medium hypertonicity induced by ion concentration gradients in the spatially nonuniform AC electric fields.

Avoiding 100 new power plants by increasing efficiency of room air conditioners in India: opportunities and challenges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Phadke, Amol; Abhyankar, Nikit; Shah, Nihar

Electricity demand for room ACs is growing very rapidly in emerging economies such as India. We estimate the electricity demand from room ACs in 2030 in India considering factors such as weather and income growth using market data on penetration of ACs in different income classes and climatic regions. We discuss the status of the current standards, labels, and incentive programs to improve the efficiency of room ACs in these markets and assess the potential for further large improvements in efficiency and find that efficiency can be improved by over 40% cost effectively. The total potential energy savings from Roommore » AC efficiency improvement in India using the best available technology will reach over 118 TWh in 2030; potential peak demand saving is found to be 60 GW by 2030. This is equivalent to avoiding 120 new coal fired power plants of 500 MW each. We discuss policy options to complement, expand and improve the ongoing programs to capture this large potential.« less

AC power generation from microbial fuel cells

NASA Astrophysics Data System (ADS)

Lobo, Fernanda Leite; Wang, Heming; Forrestal, Casey; Ren, Zhiyong Jason

2015-11-01

Microbial fuel cells (MFCs) directly convert biodegradable substrates to electricity and carry good potential for energy-positive wastewater treatment. However, the low and direct current (DC) output from MFC is not usable for general electronics except small sensors, yet commercial DC-AC converters or inverters used in solar systems cannot be directly applied to MFCs. This study presents a new DC-AC converter system for MFCs that can generate alternating voltage in any desired frequency. Results show that AC power can be easily achieved in three different frequencies tested (1, 10, 60 Hz), and no energy storage layer such as capacitors was needed. The DC-AC converter efficiency was higher than 95% when powered by either individual MFCs or simple MFC stacks. Total harmonic distortion (THD) was used to investigate the quality of the energy, and it showed that the energy could be directly usable for linear electronic loads. This study shows that through electrical conversion MFCs can be potentially used in household electronics for decentralized off-grid communities.

Measurements and calculations of transport AC loss in second generation high temperature superconducting pancake coils

NASA Astrophysics Data System (ADS)

Yuan, Weijia; Coombs, T. A.; Kim, Jae-Ho; Han Kim, Chul; Kvitkovic, Jozef; Pamidi, Sastry

2011-12-01

Theoretical and experimental AC loss data on a superconducting pancake coil wound using second generation (2 G) conductors are presented. An anisotropic critical state model is used to calculate critical current and the AC losses of a superconducting pancake coil. In the coil there are two regions, the critical state region and the subcritical region. The model assumes that in the subcritical region the flux lines are parallel to the tape wide face. AC losses of the superconducting pancake coil are calculated using this model. Both calorimetric and electrical techniques were used to measure AC losses in the coil. The calorimetric method is based on measuring the boil-off rate of liquid nitrogen. The electric method used a compensation circuit to eliminate the inductive component to measure the loss voltage of the coil. The experimental results are consistent with the theoretical calculations thus validating the anisotropic critical state model for loss estimations in the superconducting pancake coil.

TECHNOLOGICAL CHANGE AND THE JOURNEYMAN ELECTRICIAN, AN EXPERIMENTAL STUDY IN CONTINUING EDUCATION. VOLUME II, COURSE AND SUPPLEMENTARY MATERIALS.

ERIC Educational Resources Information Center

BUSHNELL, DAVID S.

A SURVEY OF THE MEMBERS OF LOCAL 617, INTERNATIONAL BROTHERHOOD OF ELECTRICAL WORKERS, SAN MATEO COUNTY, CALIFORNIA, REVEALED THAT THE ELECTRICIANS FELT THEY NEEDED--(1) A REVIEW OF THE FUNDAMENTALS OF ELECTRICITY AND ELECTRIC CIRCUIT THEORY, BOTH FOR AC AND DC CURRENTS, (2) NEW APPLICATIONS AND USE OF ELECTRICAL TEST EQUIPMENT, (3) THE ABILITY TO…

Analytical theory and possible detection of the ac quantum spin Hall effect

DOE PAGES

Deng, W. Y.; Ren, Y. J.; Lin, Z. X.; ...

2017-07-11

Here, we develop an analytical theory of the low-frequency ac quantum spin Hall (QSH) effect based upon the scattering matrix formalism. It is shown that the ac QSH effect can be interpreted as a bulk quantum pumping effect. When the electron spin is conserved, the integer-quantized ac spin Hall conductivity can be linked to the winding numbers of the reflection matrices in the electrodes, which also equal to the bulk spin Chern numbers of the QSH material. Furthermore, a possible experimental scheme by using ferromagnetic metals as electrodes is proposed to detect the topological ac spin current by electrical means.

Current-voltage hysteresis and dielectric properties of PVA coated MWCNT film

NASA Astrophysics Data System (ADS)

Das, Amit Kumar; Meikap, Ajit Kumar

2017-12-01

In this work, we have prepared polyvinyl alcohol (PVA) coated multiwall carbon nanotube (MWCNT) film by an in situ chemical oxidative preparation technique. The thermogravimetric analysis clearly explains the thermal degradation of pure polymer and polymer nanocomposite film. We have studied the AC electrical transport properties and current-voltage (I-V) characteristic of PVA-MWCNT composites within the temperature range 300 ≤ T ≤ 423 K and frequency range 150 Hz ≤ f ≤ 2 MHz. It is observed that the dielectric constant of the composite film increases significantly. The frequency variation of AC conductivity follows the power law ( ωS ) and a sharp transition from small polaron tunneling to correlated barrier hopping model is found. The imaginary part of electric modulus shows non-Debye type asymmetric behaviour. The impedance spectroscopy shows the negative temperature coefficient of resistance of the composite film. Nyquist plot of the composite film at different temperatures is established from impedance measurement. The current-voltage characteristic (under ± 20 V) shows hysteresis behaviour and field dependent resistance. We simulate the experimentally observed current density-electric field data with the established theory.

Current-voltage hysteresis and dielectric properties of PVA coated MWCNT film

NASA Astrophysics Data System (ADS)

Das, Amit Kumar; Meikap, Ajit Kumar

2018-06-01

In this work, we have prepared polyvinyl alcohol (PVA) coated multiwall carbon nanotube (MWCNT) film by an in situ chemical oxidative preparation technique. The thermogravimetric analysis clearly explains the thermal degradation of pure polymer and polymer nanocomposite film. We have studied the AC electrical transport properties and current-voltage (I-V) characteristic of PVA-MWCNT composites within the temperature range 300 ≤ T ≤ 423 K and frequency range 150 Hz ≤ f ≤ 2 MHz. It is observed that the dielectric constant of the composite film increases significantly. The frequency variation of AC conductivity follows the power law ( ωS ) and a sharp transition from small polaron tunneling to correlated barrier hopping model is found. The imaginary part of electric modulus shows non-Debye type asymmetric behaviour. The impedance spectroscopy shows the negative temperature coefficient of resistance of the composite film. Nyquist plot of the composite film at different temperatures is established from impedance measurement. The current-voltage characteristic (under ± 20 V) shows hysteresis behaviour and field dependent resistance. We simulate the experimentally observed current density-electric field data with the established theory.

Endogenous Cortical Oscillations Constrain Neuromodulation by Weak Electric Fields

PubMed Central

Schmidt, Stephen L.; Iyengar, Apoorva K.; Foulser, A. Alban; Boyle, Michael R.; Fröhlich, Flavio

2014-01-01

Background Transcranial alternating current stimulation (tACS) is a non-invasive brain stimulation modality that may modulate cognition by enhancing endogenous neocortical oscillations with the application of sine-wave electric fields. Yet, the role of endogenous network activity in enabling and shaping the effects of tACS has remained unclear. Objective We combined optogenetic stimulation and multichannel slice electrophysiology to elucidate how the effect of weak sine-wave electric field depends on the ongoing cortical oscillatory activity. We hypothesized that the structure of the response to stimulation depended on matching the stimulation frequency to the endogenous cortical oscillation. Methods We studied the effect of weak sine-wave electric fields on oscillatory activity in mouse neocortical slices. Optogenetic control of the network activity enabled the generation of in vivo like cortical oscillations for studying the temporal relationship between network activity and sine-wave electric field stimulation. Results Weak electric fields enhanced endogenous oscillations but failed to induce a frequency shift of the ongoing oscillation for stimulation frequencies that were not matched to the endogenous oscillation. This constraint on the effect of electric field stimulation imposed by endogenous network dynamics was limited to the case of weak electric fields targeting in vivo-like network dynamics. Together, these results suggest that the key mechanism of tACS may be enhancing but not overriding of intrinsic network dynamics. Conclusion Our results contribute to understanding the inconsistent tACS results from human studies and propose that stimulation precisely adjusted in frequency to the endogenous oscillations is key to rational design of non-invasive brain stimulation paradigms. PMID:25129402

Dephasing effects on ac-driven triple quantum dot systems

NASA Astrophysics Data System (ADS)

Maldonado, I.; Villavicencio, J.; Contreras-Pulido, L. D.; Cota, E.; Maytorena, J. A.

2018-05-01

We analyze the effect of environmental dephasing on the electrical current in an ac-driven triple quantum dot system in a symmetric Λ configuration. The current is explored by solving the time evolution equation of the density matrix as a function of the frequency and amplitude of the driving field. Two characteristic spectra are observed depending on the field amplitude. At the resonance condition, when the frequency matches the interdot energy difference, one spectrum shows a distinctive Fano-type peak, while the other, occurring at larger values of the field amplitude, exhibits a strong current suppression due to dynamic localization. In the former case we observe that the current maximum is reduced due to dephasing, while in the latter it is shown that dephasing partially alleviates the localization. In both cases, away from resonance, we observe current oscillations which are dephasing-enhanced for a wide range of frequencies. These effects are also discussed using Floquet theory, and analytical expressions for the electrical current are obtained within the rotating wave approximation.

Roebel assembled coated conductor cables (RACC): Ac-Losses and current carrying potential

NASA Astrophysics Data System (ADS)

Frank, A.; Heller, R.; Goldacker, W.; Kling, A.; Schmidt, C.

2008-02-01

Low ac-loss HTS cables for transport currents well above 1 kA are required for application in transformers and generators and are taken into consideration for future generations of fusion reactor coils. Coated conductors (CC) are suitable candidates for high field application at an operation temperature in the range 50-77 K. Ac-field applications require cables with low ac-losses and hence twisting of the individual strands. We solved this problem using the Roebel technique. Short lengths of Roebel bar cables were prepared from industrial DyBCO and YBCO-CC. Meander shaped tapes of 4 or 5 mm width with twist pitches of 123 or 127 mm were cut from the 10 or 12 mm wide CC tapes using a specially designed tool. Eleven or twelve of these strands were assembled to a cable. The electrical and mechanical connection of the tapes was achieved using a silver powder filled conductive epoxy resin. Ac-losses of a short sample in an external ac-field were measured as a function of frequency and field amplitude as well as the coupling current decay time constant. We discuss the results in terms of available theories and compare measured time constants in transverse field with measured coupling losses. Finally the potential of this cable type for ac-use is discussed with respect to ac-losses and current carrying capability.

Alternating current (AC) iontophoretic transport across human epidermal membrane: effects of AC frequency and amplitude.

PubMed

Yan, Guang; Xu, Qingfang; Anissimov, Yuri G; Hao, Jinsong; Higuchi, William I; Li, S Kevin

2008-03-01

As a continuing effort to understand the mechanisms of alternating current (AC) transdermal iontophoresis and the iontophoretic transport pathways in the stratum corneum (SC), the objectives of the present study were to determine the interplay of AC frequency, AC voltage, and iontophoretic transport of ionic and neutral permeants across human epidermal membrane (HEM) and use AC as a means to characterize the transport pathways. Constant AC voltage iontophoresis experiments were conducted with HEM in 0.10 M tetraethyl ammonium pivalate (TEAP). AC frequencies ranging from 0.0001 to 25 Hz and AC applied voltages of 0.5 and 2.5 V were investigated. Tetraethyl ammonium (TEA) and arabinose (ARA) were the ionic and neutral model permeants, respectively. In data analysis, the logarithm of the permeability coefficients of HEM for the model permeants was plotted against the logarithm of the HEM electrical resistance for each AC condition. As expected, linear correlations between the logarithms of permeability coefficients and the logarithms of resistances of HEM were observed, and the permeability data were first normalized and then compared at the same HEM electrical resistance using these correlations. Transport enhancement of the ionic permeant was significantly larger than that of the neutral permeant during AC iontophoresis. The fluxes of the ionic permeant during AC iontophoresis of 2.5 V in the frequency range from 5 to 1,000 Hz were relatively constant and were approximately 4 times over those of passive transport. When the AC frequency decreased from 5 to 0.001 Hz at 2.5 V, flux enhancement increased to around 50 times over passive transport. While the AC frequency for achieving the full effect of iontophoretic enhancement at low AC frequency was lower than anticipated, the frequency for approaching passive diffusion transport at high frequency was higher than expected from the HEM morphology. These observations are consistent with a transport model of multiple barriers in series and the previous hypothesis that the iontophoresis pathways across HEM under AC behave like a series of reservoirs interconnected by short pore pathways.

Antiferromagnetic spin current rectifier

NASA Astrophysics Data System (ADS)

Khymyn, Roman; Tiberkevich, Vasil; Slavin, Andrei

2017-05-01

It is shown theoretically, that an antiferromagnetic dielectric with bi-axial anisotropy, such as NiO, can be used for the rectification of linearly-polarized AC spin current. The AC spin current excites two evanescent modes in the antiferromagnet, which, in turn, create DC spin current flowing back through the antiferromagnetic surface. Spin diode based on this effect can be used in future spintronic devices as direct detector of spin current in the millimeter- and submillimeter-wave bands. The sensitivity of such a spin diode is comparable to the sensitivity of modern electric Schottky diodes and lies in the range 102-103 V/W for 30 ×30 nm2 structure.

Alternating Current Driven Organic Light Emitting Diodes Using Lithium Fluoride Insulating Layers

PubMed Central

Liu, Shang-Yi; Chang, Jung-Hung; -Wen Wu, I.; Wu, Chih-I

2014-01-01

We demonstrate an alternating current (AC)-driven organic light emitting diodes (OLED) with lithium fluoride (LiF) insulating layers fabricated using simple thermal evaporation. Thermal evaporated LiF provides high stability and excellent capacitance for insulating layers in AC devices. The device requires a relatively low turn-on voltage of 7.1 V with maximum luminance of 87 cd/m2 obtained at 10 kHz and 15 Vrms. Ultraviolet photoemission spectroscopy and inverse photoemission spectroscopy are employed simultaneously to examine the electronic band structure of the materials in AC-driven OLED and to elucidate the operating mechanism, optical properties and electrical characteristics. The time-resolved luminance is also used to verify the device performance when driven by AC voltage. PMID:25523436

Microfabricated AC impedance sensor

DOEpatents

Krulevitch, Peter; Ackler, Harold D.; Becker, Frederick; Boser, Bernhard E.; Eldredge, Adam B.; Fuller, Christopher K.; Gascoyne, Peter R. C.; Hamilton, Julie K.; Swierkowski, Stefan P.; Wang, Xiao-Bo

2002-01-01

A microfabricated instrument for detecting and identifying cells and other particles based on alternating current (AC) impedance measurements. The microfabricated AC impedance sensor includes two critical elements: 1) a microfluidic chip, preferably of glass substrates, having at least one microchannel therein and with electrodes patterned on both substrates, and 2) electrical circuits that connect to the electrodes on the microfluidic chip and detect signals associated with particles traveling down the microchannels. These circuits enable multiple AC impedance measurements of individual particles at high throughput rates with sufficient resolution to identify different particle and cell types as appropriate for environmental detection and clinical diagnostic applications.

Evaluation of constant current alternating current iontophoresis for transdermal drug delivery.

PubMed

Yan, Guang; Li, S Kevin; Higuchi, William I

2005-12-10

Previous studies in our laboratory have demonstrated that alternating current (AC) iontophoresis can significantly decrease skin electric resistance and enhance the transport of charged permeants across skin. Flux variability of neutral permeants during AC iontophoresis was also found to be less than that of conventional direct current (DC) iontophoresis. The objectives of the present study were to evaluate flux enhancement of constant current AC transdermal iontophoresis and compare the AC flux with that of constant current DC iontophoresis. Iontophoresis studies of AC amplitude of 1, 2, and 5 mA were conducted in side-by-side diffusion cells with donor solution of 0.015, 0.15, and 1.0 M tetraethylammonium (TEA) chloride and receiver solution of phosphate buffered saline (PBS) using human epidermal membrane (HEM). Conventional constant current DC iontophoresis of 0.2 mA was also performed under similar conditions. TEA and mannitol were the model permeants. The following are the major findings in the present study. The flux of TEA increased proportionally with the AC current for all three TEA chloride concentrations and at the AC frequency used in the present study. When the permeant and its counter ion were the only ionic species in the donor chamber, the fluxes during DC iontophoresis were weakly dependent of its donor concentration. The fluxes of TEA during constant current AC iontophoresis were moderately related to the donor concentration with the highest TEA flux observed under the 1.0 M TEA chloride condition although the relationship between flux and donor concentration was not linear. A trend of decreasing electroosmotic transport with increasing donor TEA chloride concentration was observed with significant sample-to-sample variability during DC iontophoresis. Mannitol permeability was also observed to decrease with increasing TEA chloride concentration in the donor under the AC conditions, but data variability under AC was significantly smaller than that under DC. The results in the present study indicate that constant current AC iontophoresis under conditions tolerable to human (2 and 5 mA) can provide predictable fluxes that were lower than but of comparable magnitude as those of conventional constant current DC iontophoresis (0.2 mA).

Influences of internal resistance and specific surface area of electrode materials on characteristics of electric double layer capacitors

NASA Astrophysics Data System (ADS)

Suda, Yoshiyuki; Mizutani, Akitaka; Harigai, Toru; Takikawa, Hirofumi; Ue, Hitoshi; Umeda, Yoshito

2017-01-01

We fabricated electric double layer capacitors (EDLCs) using particulate and fibrous types of carbon nanomaterials with a wide range of specific surface areas and resistivity as an active material. The carbon nanomaterials used in this study are carbon nanoballoons (CNBs), onion-like carbon (OLC), and carbon nanocoils (CNCs). A commercially used activated carbon (AC) combined with a conductive agent was used as a comparison. We compared the EDLC performance using cyclic voltammetry (CV), galvanostatic charge/discharge testing, and electrochemical impedance spectroscopy (EIS). OLC showed a poor EDLC performance, although it has the lowest resistivity among the carbon nanomaterials. CNB, which has a 1/16 lower specific surface area than AC but higher specific surface area than CNC and OLC, had a higher specific capacitance than CNC and OLC. Moreover, at current densities of 1.5 Ag-1 and larger, the specific capacitance of the EDLC using CNB was almost the same as that using AC. Electrochemical impedance spectroscopy of the EDLCs revealed that the CNB and CNC electrodes had a much lower internal resistance than the AC electrode, which correlated with a low capacitance maintenance factor as the current density increased.

Analysis of Electric Vehicle DC High Current Conversion Technology

NASA Astrophysics Data System (ADS)

Yang, Jing; Bai, Jing-fen; Lin, Fan-tao; Lu, Da

2017-05-01

Based on the background of electric vehicles, it is elaborated the necessity about electric energy accurate metering of electric vehicle power batteries, and it is analyzed about the charging and discharging characteristics of power batteries. It is needed a DC large current converter to realize accurate calibration of power batteries electric energy metering. Several kinds of measuring methods are analyzed based on shunts and magnetic induction principle in detail. It is put forward power batteries charge and discharge calibration system principle, and it is simulated and analyzed ripple waves containing rate and harmonic waves containing rate of power batteries AC side and DC side. It is put forward suitable DC large current measurement methods of power batteries by comparing different measurement principles and it is looked forward the DC large current measurement techniques.

Electric-Field-Directed Parallel Alignment Architecting 3D Lithium-Ion Pathways within Solid Composite Electrolyte.

PubMed

Liu, Xueqing; Peng, Sha; Gao, Shuyu; Cao, Yuancheng; You, Qingliang; Zhou, Liyong; Jin, Yongcheng; Liu, Zhihong; Liu, Jiyan

2018-05-09

It is of great significance to seek high-performance solid electrolytes via a facile chemistry and simple process for meeting the requirements of solid batteries. Previous reports revealed that ion conducting pathways within ceramic-polymer composite electrolytes mainly occur at ceramic particles and the ceramic-polymer interface. Herein, one facile strategy toward ceramic particles' alignment and assembly induced by an external alternating-current (AC) electric field is presented. It was manifested by an in situ optical microscope that Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 particles and poly(ethylene glycol) diacrylate in poly(dimethylsiloxane) (LATP@PEGDA@PDMS) assembled into three-dimensional connected networks on applying an external AC electric field. Scanning electron microscopy revealed that the ceramic LATP particles aligned into a necklacelike assembly. Electrochemical impedance spectroscopy confirmed that the ionic conductivity of this necklacelike alignment was significantly enhanced compared to that of the random one. It was demonstrated that this facile strategy of applying an AC electric field can be a very effective approach for architecting three-dimensional lithium-ion conductive networks within solid composite electrolyte.

Integration of regenerative shock absorber into vehicle electric system

NASA Astrophysics Data System (ADS)

Zhang, Chongxiao; Li, Peng; Xing, Shaoxu; Kim, Junyoung; Yu, Liangyao; Zuo, Lei

2014-03-01

Regenerative/Energy harvesting shock absorbers have a great potential to increase fuel efficiency and provide suspension damping simultaneously. In recent years there's intensive work on this topic, but most researches focus on electricity extraction from vibration and harvesting efficiency improvement. The integration of electricity generated from regenerative shock absorbers into vehicle electric system, which is very important to realize the fuel efficiency benefit, has not been investigated. This paper is to study and demonstrate the integration of regenerative shock absorber with vehicle alternator, battery and in-vehicle electrical load together. In the presented system, the shock absorber is excited by a shaker and it converts kinetic energy into electricity. The harvested electricity flows into a DC/DC converter which realizes two functions: controlling the shock absorber's damping and regulating the output voltage. The damping is tuned by controlling shock absorber's output current, which is also the input current of DC/DC converter. By adjusting the duty cycles of switches in the converter, its input impedance together with input current can be adjusted according to dynamic damping requirements. An automotive lead-acid battery is charged by the DC/DC converter's output. To simulate the working condition of combustion engine, an AC motor is used to drive a truck alternator, which also charges the battery. Power resistors are used as battery's electrical load to simulate in-vehicle electrical devices. Experimental results show that the proposed integration strategy can effectively utilize the harvested electricity and power consumption of the AC motor is decreased accordingly. This proves the combustion engine's load reduction and fuel efficiency improvement.

Comparison of Three Non-Invasive Transcranial Electrical Stimulation Methods for Increasing Cortical Excitability.

PubMed

Inukai, Yasuto; Saito, Kei; Sasaki, Ryoki; Tsuiki, Shota; Miyaguchi, Shota; Kojima, Sho; Masaki, Mitsuhiro; Otsuru, Naofumi; Onishi, Hideaki

2016-01-01

Transcranial direct current stimulation (tDCS) is a representative non-invasive brain stimulation method (NIBS). tDCS increases cortical excitability not only in healthy individuals, but also in stroke patients where it contributes to motor function improvement. Recently, two additional types of transcranial electrical stimulation (tES) methods have been introduced that may also prove beneficial for stimulating cortical excitability; these are transcranial random noise stimulation (tRNS) and transcranial alternating current stimulation (tACS). However, comparison of tDCS with tRNS and tACS, in terms of efficacy in cortical excitability alteration, has not been reported thus far. We compared the efficacy of the three different tES methods for increasing cortical excitability using the same subject population and same current intensity. Fifteen healthy subjects participated in this study. Similar stimulation patterns (1.0 mA and 10 min) were used for the three conditions of stimulation (tDCS, tRNS, and tACS). Cortical excitability was explored via single-pulse TMS elicited motor evoked potentials (MEPs). Compared with pre-measurements, MEPs significantly increased with tDCS, tACS, and tRNS ( p < 0.05). Compared with sham measurements, significant increases in MEPs were also observed with tRNS and tACS ( p < 0.05), but not with tDCS. In addition, a significant correlation of the mean stimulation effect was observed between tRNS and tACS ( p = 0.019, r = 0.598). tRNS induced a significant increase in MEP compared with the Pre or Sham at all time points. tRNS resulted in the largest significant increase in MEPs. These findings suggest that tRNS is the most effective tES method and should be considered as part of a treatment plan for improving motor function in stroke patients.

Performance-Enhanced Activated Carbon Electrodes for Supercapacitors Combining Both Graphene-Modified Current Collectors and Graphene Conductive Additive.

PubMed

Wang, Rubing; Qian, Yuting; Li, Weiwei; Zhu, Shoupu; Liu, Fengkui; Guo, Yufen; Chen, Mingliang; Li, Qi; Liu, Liwei

2018-05-15

Graphene has been widely used in the active material, conductive agent, binder or current collector for supercapacitors, due to its large specific surface area, high conductivity, and electron mobility. However, works simultaneously employing graphene as conductive agent and current collector were rarely reported. Here, we report improved activated carbon (AC) electrodes (AC@G@NiF/G) simultaneously combining chemical vapor deposition (CVD) graphene-modified nickel foams (NiF/Gs) current collectors and high quality few-layer graphene conductive additive instead of carbon black (CB). The synergistic effect of NiF/Gs and graphene additive makes the performances of AC@G@NiF/G electrodes superior to those of electrodes with CB or with nickel foam current collectors. The performances of AC@G@NiF/G electrodes show that for the few-layer graphene addition exists an optimum value around 5 wt %, rather than a larger addition of graphene, works out better. A symmetric supercapacitor assembled by AC@G@NiF/G electrodes exhibits excellent cycling stability. We attribute improved performances to graphene-enhanced conductivity of electrode materials and NiF/Gs with 3D graphene conductive network and lower oxidation, largely improving the electrical contact between active materials and current collectors.

Performance-Enhanced Activated Carbon Electrodes for Supercapacitors Combining Both Graphene-Modified Current Collectors and Graphene Conductive Additive

PubMed Central

Wang, Rubing; Qian, Yuting; Li, Weiwei; Zhu, Shoupu; Liu, Fengkui; Guo, Yufen; Chen, Mingliang; Li, Qi; Liu, Liwei

2018-01-01

Graphene has been widely used in the active material, conductive agent, binder or current collector for supercapacitors, due to its large specific surface area, high conductivity, and electron mobility. However, works simultaneously employing graphene as conductive agent and current collector were rarely reported. Here, we report improved activated carbon (AC) electrodes (AC@G@NiF/G) simultaneously combining chemical vapor deposition (CVD) graphene-modified nickel foams (NiF/Gs) current collectors and high quality few-layer graphene conductive additive instead of carbon black (CB). The synergistic effect of NiF/Gs and graphene additive makes the performances of AC@G@NiF/G electrodes superior to those of electrodes with CB or with nickel foam current collectors. The performances of AC@G@NiF/G electrodes show that for the few-layer graphene addition exists an optimum value around 5 wt %, rather than a larger addition of graphene, works out better. A symmetric supercapacitor assembled by AC@G@NiF/G electrodes exhibits excellent cycling stability. We attribute improved performances to graphene-enhanced conductivity of electrode materials and NiF/Gs with 3D graphene conductive network and lower oxidation, largely improving the electrical contact between active materials and current collectors. PMID:29762528

Power processing and control requirements of dispersed solar thermal electric generation systems

NASA Technical Reports Server (NTRS)

Das, R. L.

1980-01-01

Power Processing and Control requirements of Dispersed Receiver Solar Thermal Electric Generation Systems are presented. Kinematic Stirling Engines, Brayton Engines and Rankine Engines are considered as prime movers. Various types of generators are considered for ac and dc link generations. It is found that ac-ac Power Conversion is not suitable for implementation at this time. It is also found that ac-dc-ac Power Conversion with a large central inverter is more efficient than ac-dc-ac Power Conversion using small dispersed inverters. Ac-link solar thermal electric plants face potential stability and synchronization problems. Research and development efforts are needed in improving component performance characteristics and generation efficiency to make Solar Thermal Electric Generation economically attractive.

Observer-based higher order sliding mode control of power factor in three-phase AC/DC converter for hybrid electric vehicle applications

NASA Astrophysics Data System (ADS)

Liu, Jianxing; Laghrouche, Salah; Wack, Maxime

2014-06-01

In this paper, a full-bridge boost power converter topology is studied for power factor control, using output higher order sliding mode control. The AC/DC converters are used for charging the battery and super-capacitor in hybrid electric vehicles from the utility. The proposed control forces the input currents to track the desired values, which can control the output voltage while keeping the power factor close to one. Super-twisting sliding mode observer is employed to estimate the input currents and load resistance only from the measurement of output voltage. Lyapunov analysis shows the asymptotic convergence of the closed-loop system to zero. Multi-rate simulation illustrates the effectiveness and robustness of the proposed controller in the presence of measurement noise.

Converter topologies for common mode voltage reduction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rodriguez, Fernando

An inverter includes a three-winding transformer, a DC-AC inverter electrically coupled to the first winding of the transformer, a cycloconverter electrically coupled to the second winding of the transformer, and an active filter electrically coupled to the third winding of the transformer. The DC-AC inverter is adapted to convert the input DC waveform to an AC waveform delivered to the transformer at the first winding. The cycloconverter is adapted to convert an AC waveform received at the second winding of the transformer to the output AC waveform having a grid frequency of the AC grid. The active filter is adaptedmore » to sink and source power with one or more energy storage devices based on a mismatch in power between the DC source and the AC grid. At least two of the DC-AC inverter, the cycloconverter, or the active filter are electrically coupled via a common reference electrical interconnect.« less

Vertical motion of a charged colloidal particle near an AC polarized electrode with a nonuniform potential distribution: theory and experimental evidence.

PubMed

Fagan, Jeffrey A; Sides, Paul J; Prieve, Dennis C

2004-06-08

Electroosmotic flow in the vicinity of a colloidal particle suspended over an electrode accounts for observed changes in the average height of the particle when the electrode passes alternating current at 100 Hz. The main findings are (1) electroosmotic flow provides sufficient force to move the particle and (2) a phase shift between the purely electrical force on the particle and the particle's motion provides evidence of an E2 force acting on the particle. The electroosmotic force in this case arises from the boundary condition applied when faradaic reactions occur on the electrode. The presence of a potential-dependent electrode reaction moves the likely distribution of electrical current at the electrode surface toward uniform current density around the particle. In the presence of a particle the uniform current density is associated with a nonuniform potential; thus, the electric field around the particle has a nonzero radial component along the electrode surface, which interacts with unbalanced charge in the diffuse double layer on the electrode to create a flow pattern and impose an electroosmotic-flow-based force on the particle. Numerical solutions are presented for these additional height-dependent forces on the particle as a function of the current distribution on the electrode and for the time-dependent probability density of a charged colloidal particle near a planar electrode with a nonuniform electrical potential boundary condition. The electrical potential distribution on the electrode, combined with a phase difference between the electric field in solution and the electrode potential, can account for the experimentally observed motion of particles in ac electric fields in the frequency range from approximately 10 to 200 Hz.

System and method for motor speed estimation of an electric motor

DOEpatents

Lu, Bin [Kenosha, WI; Yan, Ting [Brookfield, WI; Luebke, Charles John [Sussex, WI; Sharma, Santosh Kumar [Viman Nagar, IN

2012-06-19

A system and method for a motor management system includes a computer readable storage medium and a processing unit. The processing unit configured to determine a voltage value of a voltage input to an alternating current (AC) motor, determine a frequency value of at least one of a voltage input and a current input to the AC motor, determine a load value from the AC motor, and access a set of motor nameplate data, where the set of motor nameplate data includes a rated power, a rated speed, a rated frequency, and a rated voltage of the AC motor. The processing unit is also configured to estimate a motor speed based on the voltage value, the frequency value, the load value, and the set of nameplate data and also store the motor speed on the computer readable storage medium.

Electroporation of cells using EM induction of ac fields by a magnetic stimulator

NASA Astrophysics Data System (ADS)

Chen, C.; Evans, J. A.; Robinson, M. P.; Smye, S. W.; O'Toole, P.

2010-02-01

This paper describes a method of effectively electroporating mammalian cell membranes with pulsed alternating-current (ac) electric fields at field strengths of 30-160 kV m-1. Although many in vivo electroporation protocols entail applying square wave or monotonically decreasing pulses via needles or electrode plates, relatively few have explored the use of pulsed ac fields. Following our previous study, which established the effectiveness of ac fields for electroporating cell membranes, a primary/secondary coil system was constructed to produce sufficiently strong electric fields by electromagnetic induction. The primary coil was formed from the applicator of an established transcranial magnetic stimulation (TMS) system, while the secondary coil was a purpose-built device of a design which could eventually be implanted into tissue. The effects of field strength, pulse interval and cumulative exposure time were investigated using microscopy and flow cytometry. Results from experiments on concentrated cell suspensions showed an optimized electroporation efficiency of around 50%, demonstrating that electroporation can be practicably achieved by inducing such pulsed ac fields. This finding confirms the possibility of a wide range of in vivo applications based on magnetically coupled ac electroporation.

Avoiding 100 New Power Plants by Increasing Efficiency of Room Air Conditioners in India: Opportunities and Challenges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Phadke, Amol; Abhyankar, Nikit; Shah, Nihar

Electricity demand for room ACs is growing very rapidly in emerging economies such as India. We estimate the electricity demand from room ACs in 2030 in India considering factors such as weather and income growth using market data on penetration of ACs in different income classes and climatic regions. We discuss the status of the current standards, labels, and incentive programs to improve the efficiency of room ACs in these markets and assess the potential for further large improvements in efficiency and find that efficiency can be improved by over 40percent cost effectively. The total potential energy savings from Roommore » AC efficiency improvement in India using the best available technology will reach over 118 TWh in 2030; potential peak demand saving is found to be 60 GW by 2030. This is equivalent to avoiding 120 new coal fired power plants of 500 MW each. We discuss policy options to complement, expand and improve the ongoing programs to capture this large potential.« less

ELECTRICAL AND ELECTRONIC INDUSTRIAL CONTROL. A-C CONVENTIONAL MAGNETIC MOTOR CONTROL, PART I, UNIT 5, ASSIGNMENTS.

ERIC Educational Resources Information Center

SUTTON, MACK C.

THIS GUIDE IS FOR INDIVIDUAL STUDENT USE IN STUDYING ALTERNATING CURRENT CONVENTIONAL MAGNETIC MOTOR CONTROL IN ELECTRICAL-ELECTRONIC PROGRAMS. IT WAS DEVELOPED BY AN INSTRUCTIONAL MATERIALS SPECIALIST AND ADVISERS. EACH OF THE 10 ASSIGNMENT SHEETS PROVIDES THE LESSON SUBJECT, PURPOSE, INTRODUCTORY INFORMATION, STUDY REFERENCES, SUPPLEMENTARY…

Integration of HTS Cables in the Future Grid of the Netherlands

NASA Astrophysics Data System (ADS)

Zuijderduin, R.; Chevtchenko, O.; Smit, J. J.; Aanhaanen, G.; Melnik, I.; Geschiere, A.

Due to increasing power demand, the electricity grid of the Netherlands is changing. The future transmission grid will obtain electrical power generated by decentralized renewable sources, together with large scale generation units located at the coastal region. In this way electrical power has to be distributed and transmitted over longer distances from generation to end user. Potential grid issues like: amount of distributed power, grid stability and electrical loss dissipation merit particular attention. High temperature superconductors (HTS) can play an important role in solving these grid problems. Advantages to integrate HTS components at transmission voltages are numerous: more transmittable power together with less emissions, intrinsic fault current limiting capability, lower ac loss, better control of power flow, reduced footprint, less magnetic field emissions, etc. The main obstacle at present is the relatively high price of HTS conductor. However as the price goes down, initial market penetration of several HTS components (e.g.: cables, fault current limiters) is expected by year 2015. In the full paper we present selected ways to integrate EHV AC HTS cables depending on a particular future grid scenario in the Netherlands.

System for automatically switching transformer coupled lines

NASA Technical Reports Server (NTRS)

Dwinell, W. S. (Inventor)

1979-01-01

A system is presented for automatically controlling transformer coupled alternating current electric lines. The secondary winding of each transformer is provided with a center tap. A switching circuit is connected to the center taps of a pair of secondary windings and includes a switch controller. An impedance is connected between the center taps of the opposite pair of secondary windings. The switching circuit has continuity when the AC lines are continuous and discontinuity with any disconnect of the AC lines. Normally open switching means are provided in at least one AC line. The switch controller automatically opens the switching means when the AC lines become separated.

Certain applied electrical signals during EPG cause negative effects on stylet probing behaviors by adult Lygus lineolaris (Hemiptera: Miridae).

PubMed

Backus, Elaine A; Cervantes, Felix A; Godfrey, Larry; Akbar, Waseem; Clark, Thomas L; Rojas, Maria G

This study is the first to fully evaluate whether electrical signals applied to large insects during electropenetrography (EPG; also called electrical penetration graph) negatively affect insect behavior. During EPG, electrical signals are applied to plants, and thus to the gold-wire-tethered insects feeding on them. The insect completes an electrical circuit whose changes in voltage reflect the insect's stylet probing/penetration behaviors, recorded as waveform output. For nearly 50 years of EPG science, evidence has supported that there are no or negligible effects on tiny insects from applied electricity during EPG. Recently however, EPG studies of large-bodied hemipterans such as heteropterans and sharpshooter leafhoppers have been published. The wider stylet diameters of such large insects cause them to have lower inherent resistances to applied signals compared with smaller insects, conveying more electrical current. The present study asked whether such increased currents would affect insect stylet probing, by comparing Lygus lineolaris behaviors on pin-head cotton squares using an AC-DC electropenetrograph. Effects of AC or DC applied signals were separately examined in two factorial studies, each comparing four input resistor (Ri) levels (10 6 , 10 7 , 10 8 and 10 9  Ω) and four applied voltage levels (2, 60, 150 and 250 mV). Results showed that changes in both probing and non-probing behaviors were indeed caused by changing signal type, Ri level, or applied voltage. Negative effects on feeding were numerically greater overall for DC than AC applied signals, perhaps due to muscular tetany from DC; however, AC versus DC could not be statistically tested. Results strongly support the need for flexible Ri and applied voltage levels and types, to tailor instrument settings to the size and special needs of each insect subject. Our findings will facilitate further EPG studies of Lygus spp., such as host plant resistance or insecticidal assays/bioassays to assess mode of action and appropriate dosage. It is hoped that this study will also inform EPG studies of similar, large heteropterans in the future. Published by Elsevier Ltd.

Electrokinetic enhancement on phytoremediation in Zn, Pb, Cu and Cd contaminated soil using potato plants.

PubMed

Aboughalma, Hanssan; Bi, Ran; Schlaak, Michael

2008-07-01

The use of a combination of electrokinetic remediation and phytoremediation to decontaminate soil polluted with heavy metals has been demonstrated in a laboratory-scale experiment. Potato tubers were planted in plastic vessels filled with Zn, Pb, Cu and Cd contaminated soil and grown in a greenhouse. Three of these vessels were treated with direct current electric field (DC), three with alternative current (AC) and three remained untreated as control vessels. The soil pH varied from anode to cathode with a minimum of pH 3 near the anode and a maximum of pH 8 near the cathode in the DC treated soil profile. There was an accumulation of Zn, Cu and Cd at about 12 cm distance from anode when soil pH was 5 in the DC treated soil profile. There was no significant metal redistribution and pH variation between anode and cathode in the AC soil profile. The biomass production of the plants was 72% higher under AC treatment and 27% lower under DC treatment compared to the control. Metal accumulation was generally higher in the plant roots treated with electrical fields than the control. The overall metal uptake in plant shoots was lower under DC treatment compared to AC treatment and control, although there was a higher accumulation of Zn and Cu in the plant roots treated with electrical fields. The Zn uptake in plant shoots under AC treatment was higher compared to the control and DC treatment. Zn and Cu accumulation in the plant roots under AC and DC treatment was similar, and both were higher comparing to control. Cd content in plant roots under all three treatments was found to be higher than that in the soil. The Pb accumulation in the roots and the uptake into the shoots was lower compared to its content in the soil.

DC and AC Electric Field Measurements by Spin-Plane Double Probes Onboard MMS

NASA Astrophysics Data System (ADS)

Lindqvist, P. A.; Marklund, G. T.; Khotyaintsev, Y. V.; Ergun, R. E.; Goodrich, K.; Torbert, R. B.; Argall, M. R.; Nakamura, R.

2015-12-01

The four spacecraft of the NASA Magnetospheric Multiscale mission (MMS) were launched on 12 March 2015 into a 1.2 x 12 Re equatorial orbit to study energy conversion processes in Earth's magnetosphere. After a 5-month commissioning period the first scientific phase starts on 1 September as the orbit enters the dusk magnetopause region. The Spin-plane Double Probe electric field instrument (SDP), part of the electric and magnetic fields instrument suite FIELDS, measures the electric field in the range 0.3 - 500 mV/m with a continuous time resolution up to 8192 samples/s. The instrument features adjustable bias currents and guard voltages to optimize the measurement performance. SDP also measures the spacecraft potential, which can be controlled by the Active Spacecraft Potential Control (ASPOC) ion emitter, and under certain conditions can be used to determine plasma density. We present observations of DC and AC electric fields in different plasma regions covered by MMS since launch including the night side flow braking region, reconnection regions at the dusk and dayside magnetopause, and in the magnetosheath. We compare the electric field measurements by SDP to other, independent determinations of the electric field, in particular by the Electron Drift Instrument (EDI), in order to assess the accuracy of the electric field measurement under different plasma conditions. We also study the influence of the currents emitted by ASPOC and EDI on the SDP measurements.

Hair growth-promotion effects of different alternating current parameter settings are mediated by the activation of Wnt/β-catenin and MAPK pathway.

PubMed

Sohn, Ki Min; Jeong, Kwan Ho; Kim, Jung Eun; Park, Young Min; Kang, Hoon

2015-12-01

Electrical stimulation is being used in variable skin therapeutic conditions. There have been clinical studies demonstrating the positive effect of electrical stimuli on hair regrowth. However, the underlying exact mechanism and optimal parameter settings are not clarified yet. To investigate the effects of different parameter settings of electrical stimuli on hair growth by examining changes in human dermal papilla cells (hDPCs) in vitro and by observing molecular changes in animal tissue. In vitro, cultured hDPCs were electrically stimulated with different parameter settings at alternating current (AC). Cell proliferation was measured by MTT assay. The Ki67 expression was measured by immunofluorescence. Hair growth-related gene expressions were measured by RT-PCR. In animal model, different parameter settings of AC were applied to the shaved dorsal skin of rabbit for 8 weeks. Expression of hair-related genes in the skin of rabbit was examined by RT-PCR. At low voltage power (3.5 V) and low frequency (1 or 2 MHz) with AC, in vitro proliferation of hDPCs was successfully induced. A significant increase in Wnt/β-catenin, Ki67, p-ERK and p-AKT expressions was observed under the aforementioned settings. In animal model, hair regrowth was observed in the entire stimulated areas under individual conditions. Expression of hair-related genes in the skin significantly increased on the 6th week of treatment. There are optimal conditions for electrical stimulated hair growth, and they might be different in the cells, animals and human tissues. Electrical stimuli induce mechanisms such as the activation of Wnt/β-catenin and MAPK pathway in hair follicles. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Power transmission cable development for the Space Station Freedom electrical power system

NASA Technical Reports Server (NTRS)

Schmitz, Gregory V.; Biess, John J.

1989-01-01

Power transmission cable is presently being evaluated under a NASA Lewis Research Center advanced development contract for application in the Space Station Freedom (SSF) electrical power system (EPS). Evaluation testing has been performed by TRW and NASA Lewis Research Center. The results of this development contract are presented. The primary cable design goals are to provide (1) a low characteristic inductance to minimize line voltage drop at 20 kHz, (2) electromagnetic compatibility control of the 20-kHz ac power current, (3) a physical configuration that minimizes ac resistance and (4) release of trapped air for corona-free operation.

Alternate current conductivity in BSb films prepared by PLD technique: Electron transport processes in low-temperature range (10-275 K)

NASA Astrophysics Data System (ADS)

Das, Shirsendu; Bhunia, Ritamay; Hussain, Shamima; Bhar, Radhaballabh; Kumar Pal, Arun

2017-04-01

This study is focused on the measurement of alternate current (a.c.) electrical conductivity of BSb films, deposited on fluorine-doped tin oxide (FTO)-coated glass substrates at 673K by the pulsed laser deposition (PLD) technique. The frequency-dependent a.c. conductivity is measured as a function of temperature (10-275K) and frequency (100Hz-100kHz). The transport processes governing the electrical conduction processes in this material are analyzed critically. It is observed from FESEM micrograph that the film is composed of small discrete grain with sizes varying in the range 6-12nm. It is interesting to notice from \\lnσ_ac versus 1000/T plot that there are three distinct zones: i) Semiconductor zone at high temperature from 275 to 150K, ii) Insulator zone at low temperature from 70 to 10K and iii) an abrupt change of the \\lnσ_ac versus 1000/T plot at ˜ 75 indicating MIS transition occurring in this BSb film. We found that the activation energy for the BSb films in the lower-temperature range was quite low ˜ 6 to 41neV, while that in the higher-temperature range was 20 to 50meV.

A critical comparison of electrical methods for measuring spin-orbit torques

NASA Astrophysics Data System (ADS)

Zhang, Xuanzi; Hung, Yu-Ming; Rehm, Laura; Kent, Andrew D.

Direct (DC) and alternating current (AC) transport measurements of spin-orbit torques (SOTs) in heavy metal-ferromagnet heterostructure with perpendicular magnetic anisotropy have been proposed and demonstrated. A DC method measures the change of perpendicular magnetization component while an AC method probes the first and second harmonic magnetization oscillation in responses to an AC current (~1 kHz). Here we conduct both types of measurements on β-Ta/CoFeB/MgO in the form of patterned Hall bars (20 μm linewidth) and compare the results. Experiments results are qualitatively in agreement with a macro spin model including Slonzewski-like and a field-like SOTs. However, the effective field from the ac method is larger than that obtained from the DC method. We discuss the possible origins of the discrepancy and its implications for quantitatively determining SOTs. Research supported by the SRC-INDEX program, NSF-DMR-1309202 and NYU-DURF award.

Electrical Experiments. VT-214-12-2. Part II. A-C Across the Line Control.

ERIC Educational Resources Information Center

Connecticut State Dept. of Education, Hartford. Div. of Vocational Education.

Designed for high school electronics students, this second document in a series of six electrical learning activity packages focuses on alternating current across-the-line control. An introductory section gives the objective for the activities, an introduction, and an outline of the content. The remainder of the activity book is comprised of…

Frequency-dependent laminar electroosmotic flow in a closed-end rectangular microchannel.

PubMed

Marcos; Yang, C; Ooi, K T; Wong, T N; Masliyah, J H

2004-07-15

This article presents an analysis of the frequency- and time-dependent electroosmotic flow in a closed-end rectangular microchannel. An exact solution to the modified Navier-Stokes equation governing the ac electroosmotic flow field is obtained by using the Green's function formulation in combination with a complex variable approach. An analytical expression for the induced backpressure gradient is derived. With the Debye-Hückel approximation, the electrical double-layer potential distribution in the channel is obtained by analytically solving the linearized two-dimensional Poisson-Boltzmann equation. Since the counterparts of the flow rate and the electrical current are shown to be linearly proportional to the applied electric field and the pressure gradient, Onsager's principle of reciprocity is demonstrated for transient and ac electroosmotic flows. The time evolution of the electroosmotic flow and the effect of a frequency-dependent ac electric field on the oscillating electroosmotic flow in a closed-end rectangular microchannel are examined. Specifically, the induced pressure gradient is analyzed under effects of the channel dimension and the frequency of electric field. In addition, based on the Stokes second problem, the solution of the slip velocity approximation is presented for comparison with the results obtained from the analytical scheme developed in this study. Copyright 2004 Elsevier Inc.

Modeling AC ripple currents in HTS coated conductors by integral equations

NASA Astrophysics Data System (ADS)

Grilli, Francesco; Xu, Zhihan

2016-12-01

In several HTS applications, the superconducting tapes experience the simultaneous presence of DC and AC excitations. For example in high-current DC cables, where the transport current is not perfectly constant, but it exhibits some ripples at different frequencies introduced by the rectification process (AC-DC conversion). These ripples give rise to dissipation, whose magnitude and possible influence on the device's cooling requirements need to be evaluated. Here we report a study of the AC losses in a HTS coated conductor subjected to DC currents and AC ripples simultaneously. The modeling approach is based on an integral equation method for thin superconductors: the superconducting tape is modeled as a 1-D object with a non-linear resistivity, which includes the dependence of the critical current density Jc on the magnetic field. The model, implemented in a commercial finite-element program, runs very fast (the simulation of one AC cycle typically takes a few seconds on standard desktop workstation): this allows simulating a large number of cycles and estimating when the AC ripple losses stabilize to a constant value. The model is used to study the influence of the flux creep power index n on the stabilization speed and on the AC loss values, as well as the effect of using a field-dependent Jc instead of a constant one. The simulations confirm that the dissipation level should not be a practical concern in HTS DC cables. At the same time, however, they reveal a strong dependence of the results upon the power index n and the form of Jc , which spurs the question whether the power-law is the most suitable description of the superconductor's electrical behavior for this kind of analysis.

AC losses in horizontally parallel HTS tapes for possible wireless power transfer applications

NASA Astrophysics Data System (ADS)

Shen, Boyang; Geng, Jianzhao; Zhang, Xiuchang; Fu, Lin; Li, Chao; Zhang, Heng; Dong, Qihuan; Ma, Jun; Gawith, James; Coombs, T. A.

2017-12-01

This paper presents the concept of using horizontally parallel HTS tapes with AC loss study, and the investigation on possible wireless power transfer (WPT) applications. An example of three parallel HTS tapes was proposed, whose AC loss study was carried out both from experiment using electrical method; and simulation using 2D H-formulation on the FEM platform of COMSOL Multiphysics. The electromagnetic induction around the three parallel tapes was monitored using COMSOL simulation. The electromagnetic induction and AC losses generated by a conventional three turn coil was simulated as well, and then compared to the case of three parallel tapes with the same AC transport current. The analysis demonstrates that HTS parallel tapes could be potentially used into wireless power transfer systems, which could have lower total AC losses than conventional HTS coils.

High Voltage Hybrid Electric Propulsion - Multilayered Functional Insulation System (MFIS) NASA-GRC

NASA Technical Reports Server (NTRS)

Lizcano, M.

2017-01-01

High power transmission cables pose a key challenge in future Hybrid Electric Propulsion Aircraft. The challenge arises in developing safe transmission lines that can withstand the unique environment found in aircraft while providing megawatts of power. High voltage AC, variable frequency cables do not currently exist and present particular electrical insulation challenges since electrical arcing and high heating are more prevalent at higher voltages and frequencies. Identifying and developing materials that maintain their dielectric properties at high voltage and frequencies is crucial.

Low AC Loss YBCO Coated Conductor Geometry by Direct Inkjet Printing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rupich, Martin, Dr.; Duckworth, Robert, Dr.

The second generation (2G) high temperature superconductors (HTS) wire offers potential benefits for many electric power applications, including ones requiring filamentized conductors with low ac loss, such as transformers and fault current limiters. However, the use of 2G wire in these applications requires the development of both novel multi-filamentary conductor designs with lower ac losses and the development of advanced manufacturing technologies that enable the low-cost manufacturing of these filamentized architectures. This Phase I SBIR project focused on testing inkjet printing as a potential low-cost, roll-to-roll manufacturing technique to fabricate potential low ac loss filamentized architectures directly on the 2Gmore » template strips.« less

Heat-coping strategies and bedroom thermal satisfaction in New York City.

PubMed

Lee, W Victoria; Shaman, Jeffrey

2017-01-01

There has been little research into the thermal condition of the sleeping environment. Even less well documented and understood is how the sleeping thermal environment is affected by occupant behaviors such as the use of air-conditioning (AC) and electric fans, or window operations. In this paper we present results from a questionnaire survey administered to assess summertime bedroom thermal satisfaction and heat-coping strategies among New York City (NYC) residents. Specifically, we investigated current AC usage in bedrooms and examined alternate cooling strategies, cooling appliance usage patterns, and the motivations that drove these patterns during the 2015 summer. Among survey respondents (n=706), AC was the preferred heat-coping strategy, and for 30% of respondents was the only strategy used. Electric fan use and window opening were deemed ineffective for cooling by many respondents. Indeed, less than a quarter of all respondents ever opened windows to alleviate heat in their bedrooms. In general, people utilized strategies that modify the environment more than the individual person. Unsurprisingly, the frequency and overall use of AC were significantly associated with greater bedroom thermal satisfaction; however, setting AC to a lower temperature provided no additional benefit. In contrast, more frequent use of electric fans was associated with lower thermal satisfaction. In addition, 14.7% of all respondents did not have AC in their sleeping environment and 5.8% were without any AC at home. Despite the high penetration of AC ownership, usage cost was still a major concern for most. This work contributes to a better understanding of bedtime heat-coping strategies, cooling appliance usage patterns, and associated thermal satisfaction in NYC. The findings of this study suggest resident AC usage patterns may not be optimized for thermal satisfaction. Potential alternative cooling approaches could be explored to better balance maximizing thermal comfort while reducing energy consumption and environmental impact. Copyright © 2016 Elsevier B.V. All rights reserved.

An MRI-Compatible High Frequency AC Resistive Heating System for Homeothermic Maintenance in Small Animals

PubMed Central

Gomes, Ana L.; Kinchesh, Paul; Kersemans, Veerle; Allen, Philip D.; Smart, Sean C.

2016-01-01

Purpose To develop an MRI-compatible resistive heater, using high frequency alternating current (AC), for temperature maintenance of anaesthetised animals. Materials and Methods An MRI-compatible resistive electrical heater was formed from narrow gauge wire connected to a high frequency (10–100 kHz) AC power source. Multiple gradient echo images covering a range of echo times, and pulse-acquire spectra were acquired with the wire heater powered using high frequency AC or DC power sources and without any current flowing in order to assess the sensitivity of the MRI acquisitions to the presence of current flow through the heater wire. The efficacy of temperature maintenance using the AC heater was assessed by measuring rectal temperature immediately following induction of general anaesthesia for a period of 30 minutes in three different mice. Results Images and spectra acquired in the presence and absence of 50–100 kHz AC through the wire heater were indistinguishable, whereas DC power created field shifts and lineshape distortions. Temperature lost during induction of anaesthesia was recovered within approximately 20 minutes and a stable temperature was reached as the mouse’s temperature approached the set target. Conclusion The AC-powered wire heater maintains adequate heat input to the animal to maintain body temperature, and does not compromise image quality. PMID:27806062

The mechanism of detection of air pollution by an ionization chamber.

PubMed

Novković, D; Vukanac; Milosević, Z

2000-01-01

The mechanism of detection of chemical vapors in air by an ionization chamber supplied by DC and AC voltage has been described. The theoretical explanation is based on numerical solutions of the differential equations of the cylindrical ionization chamber. The current of the ionization chamber operating in the AC regime has two components: a conductive component, caused by the ions drifts, and a capacitive component, caused by the distortion of the electric field. The ionization chamber operating in the DC regime has only the first component; hence the AC supplied chamber has larger response than the DC supplied chamber.

Friends, not foes: Magnetoencephalography as a tool to uncover brain dynamics during transcranial alternating current stimulation.

PubMed

Neuling, Toralf; Ruhnau, Philipp; Fuscà, Marco; Demarchi, Gianpaolo; Herrmann, Christoph S; Weisz, Nathan

2015-09-01

Brain oscillations are supposedly crucial for normal cognitive functioning and alterations are associated with cognitive dysfunctions. To demonstrate their causal role on behavior, entrainment approaches in particular aim at driving endogenous oscillations via rhythmic stimulation. Within this context, transcranial electrical stimulation, especially transcranial alternating current stimulation (tACS), has received renewed attention. This is likely due to the possibility of defining oscillatory stimulation properties precisely. Also, measurements comparing pre-tACS with post-tACS electroencephalography (EEG) have shown impressive modulations. However, the period during tACS has remained a blackbox until now, due to the enormous stimulation artifact. By means of application of beamforming to magnetoencephalography (MEG) data, we successfully recovered modulations of the amplitude of brain oscillations during weak and strong tACS. Additionally, we demonstrate that also evoked responses to visual and auditory stimuli can be recovered during tACS. The main contribution of the present study is to provide critical evidence that during ongoing tACS, subtle modulations of oscillatory brain activity can be reconstructed even at the stimulation frequency. Future tACS experiments will be able to deliver direct physiological insights in order to further the understanding of the contribution of brain oscillations to cognition and behavior. Copyright © 2015. Published by Elsevier Inc.

Friends, not foes: Magnetoencephalography as a tool to uncover brain dynamics during transcranial alternating current stimulation

PubMed Central

Neuling, Toralf; Ruhnau, Philipp; Fuscà, Marco; Demarchi, Gianpaolo; Herrmann, Christoph S.; Weisz, Nathan

2015-01-01

Brain oscillations are supposedly crucial for normal cognitive functioning and alterations are associated with cognitive dysfunctions. To demonstrate their causal role on behavior, entrainment approaches in particular aim at driving endogenous oscillations via rhythmic stimulation. Within this context, transcranial electrical stimulation, especially transcranial alternating current stimulation (tACS), has received renewed attention. This is likely due to the possibility of defining oscillatory stimulation properties precisely. Also, measurements comparing pre-tACS with post-tACS electroencephalography (EEG) have shown impressive modulations. However, the period during tACS has remained a blackbox until now, due to the enormous stimulation artifact. By means of application of beamforming to magnetoencephalography (MEG) data, we successfully recovered modulations of the amplitude of brain oscillations during weak and strong tACS. Additionally, we demonstrate that also evoked responses to visual and auditory stimuli can be recovered during tACS. The main contribution of the present study is to provide critical evidence that during ongoing tACS, subtle modulations of oscillatory brain activity can be reconstructed even at the stimulation frequency. Future tACS experiments will be able to deliver direct physiological insights in order to further the understanding of the contribution of brain oscillations to cognition and behavior. PMID:26080310

Boosting the LTP-like plasticity effect of intermittent theta-burst stimulation using gamma transcranial alternating current stimulation.

PubMed

Guerra, Andrea; Suppa, Antonio; Bologna, Matteo; D'Onofrio, Valentina; Bianchini, Edoardo; Brown, Peter; Di Lazzaro, Vincenzo; Berardelli, Alfredo

2018-03-24

Transcranial Alternating Current Stimulation (tACS) consists in delivering electric current to the brain using an oscillatory pattern that may entrain the rhythmic activity of cortical neurons. When delivered at gamma frequency, tACS modulates motor performance and GABA-A-ergic interneuron activity. Since interneuronal discharges play a crucial role in brain plasticity phenomena, here we co-stimulated the primary motor cortex (M1) in healthy subjects by means of tACS during intermittent theta-burst stimulation (iTBS), a transcranial magnetic stimulation paradigm known to induce long-term potentiation (LTP)-like plasticity. We measured and compared motor evoked potentials before and after gamma, beta and sham tACS-iTBS. While we delivered gamma-tACS, we also measured short-interval intracortical inhibition (SICI) to detect any changes in GABA-A-ergic neurotransmission. Gamma, but not beta and sham tACS, significantly boosted and prolonged the iTBS-induced after-effects. Interestingly, the extent of the gamma tACS-iTBS after-effects correlated directly with SICI changes. Overall, our findings point to a link between gamma oscillations, interneuronal GABA-A-ergic activity and LTP-like plasticity in the human M1. Gamma tACS-iTBS co-stimulation might represent a new strategy to enhance and prolong responses to plasticity-inducing protocols, thereby lending itself to future applications in the neurorehabilitation setting. Copyright © 2018 Elsevier Inc. All rights reserved.

AC induction field heating of graphite foam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klett, James W.; Rios, Orlando; Kisner, Roger

A magneto-energy apparatus includes an electromagnetic field source for generating a time-varying electromagnetic field. A graphite foam conductor is disposed within the electromagnetic field. The graphite foam when exposed to the time-varying electromagnetic field conducts an induced electric current, the electric current heating the graphite foam. An energy conversion device utilizes heat energy from the heated graphite foam to perform a heat energy consuming function. A device for heating a fluid and a method of converting energy are also disclosed.

Fractional Modeling of the AC Large-Signal Frequency Response in Magnetoresistive Current Sensors

PubMed Central

Arias, Sergio Iván Ravello; Muñoz, Diego Ramírez; Moreno, Jaime Sánchez; Cardoso, Susana; Ferreira, Ricardo; de Freitas, Paulo Jorge Peixeiro

2013-01-01

Fractional calculus is considered when derivatives and integrals of non-integer order are applied over a specific function. In the electrical and electronic domain, the transfer function dependence of a fractional filter not only by the filter order n, but additionally, of the fractional order α is an example of a great number of systems where its input-output behavior could be more exactly modeled by a fractional behavior. Following this aim, the present work shows the experimental ac large-signal frequency response of a family of electrical current sensors based in different spintronic conduction mechanisms. Using an ac characterization set-up the sensor transimpedance function Zt(if) is obtained considering it as the relationship between sensor output voltage and input sensing current, Zt(jf)=Vo,sensor(jf)/Isensor(jf). The study has been extended to various magnetoresistance sensors based in different technologies like anisotropic magnetoresistance (AMR), giant magnetoresistance (GMR), spin-valve (GMR-SV) and tunnel magnetoresistance (TMR). The resulting modeling shows two predominant behaviors, the low-pass and the inverse low-pass with fractional index different from the classical integer response. The TMR technology with internal magnetization offers the best dynamic and sensitivity properties opening the way to develop actual industrial applications. PMID:24351648

Magnetic storm effects in electric power systems and prediction needs

NASA Technical Reports Server (NTRS)

Albertson, V. D.; Kappenman, J. G.

1979-01-01

Geomagnetic field fluctuations produce spurious currents in electric power systems. These currents enter and exit through points remote from each other. The fundamental period of these currents is on the order of several minutes which is quasi-dc compared to the normal 60 Hz or 50 Hz power system frequency. Nearly all of the power systems problems caused by the geomagnetically induced currents result from the half-cycle saturation of power transformers due to simultaneous ac and dc excitation. The effects produced in power systems are presented, current research activity is discussed, and magnetic storm prediction needs of the power industry are listed.

The Effects of Low Atmosphere Stunning and Deboning Time on Broiler Breast Meat Quality

USDA-ARS?s Scientific Manuscript database

A randomized complete block design with 3 replications (n = 432, 72 broilers per treatment) was used to evaluate the effects of electrical (ES) and vacuum stunning (VS) on broiler breast meat quality. Electrical stunning was performed by applying 11.5 V, <0.05 mA, AC to DC current for 3 s for each b...

Nature of Dielectric Properties, Electric Modulus and AC Electrical Conductivity of Nanocrystalline ZnIn2Se4 Thin Films

NASA Astrophysics Data System (ADS)

El-Nahass, M. M.; Attia, A. A.; Ali, H. A. M.; Salem, G. F.; Ismail, M. I.

2018-02-01

The structural characteristics of thermally deposited ZnIn2Se4 thin films were indexed utilizing x-ray diffraction as well as scanning electron microscopy techniques. Dielectric properties, electric modulus and AC electrical conductivity of ZnIn2Se4 thin films were examined in the frequency range from 42 Hz to 106 Hz. The capacitance, conductance and impedance were measured at different temperatures. The dielectric constant and dielectric loss decrease with an increase in frequency. The maximum barrier height was determined from the analysis of the dielectric loss depending on the Giuntini model. The real part of the electric modulus revealed a constant maximum value at higher frequencies and the imaginary part of the electric modulus was characterized by the appearance of dielectric relaxation peaks. The AC electrical conductivity obeyed the Jonscher universal power law. Correlated barrier hopping model was the appropriate mechanism for AC conduction in ZnIn2Se4 thin films. Estimation of the density of states at the Fermi level and activation energy, for AC conduction, was carried out based on the temperature dependence of AC electrical conductivity.

AC Glow Discharge Plasma in N2O

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yousif, F. B.; Martinez, H.; Robledo-Martinez, A.

2006-12-04

This paper considers the optical and electrical characterization of AC glow discharge plasma in the abnormal glow mode used for optical emission spectroscopy. The total discharge current and applied voltage are measured using conventional techniques. The electrical characteristics of the planer-cathode glow discharge confirmed that the plasma is operating at abnormal discharge mode characterized by the increases in the operating voltage as the current was raised under given pressure. Optical emission spectroscopy was used to determine the main emission lines of the glow discharge plasma of N2O at pressures between 0.5 and 4.0 Torr. It shows that the discharge emissionmore » range is mainly within 300-400 nm. The emission lines correspond to NO, O2, and O{sub 2}{sup +} are the dominant lines in the glow discharge plasma in the present study. Intensity of the emission lines show linear increase with the discharge current up to 0.4 A followed by saturation at higher currents. No emission lines were observed in this work corresponding to atomic oxygen or nitrogen.« less

Investigation on discharge characteristics of a coaxial dielectric barrier discharge reactor driven by AC and ns power sources

NASA Astrophysics Data System (ADS)

Qian, WANG; Feng, LIU; Chuanrun, MIAO; Bing, YAN; Zhi, FANG

2018-03-01

A coaxial dielectric barrier discharge (DBD) reactor with double layer dielectric barriers has been developed for exhaust gas treatment and excited either by AC power or nanosecond (ns) pulse to generate atmospheric pressure plasma. The comparative study on the discharge characteristics of the discharge uniformity, power deposition, energy efficiency, and operation temperature between AC and ns pulsed coaxial DBD is carried out in terms of optical and electrical characteristics and operation temperature for optimizing the coaxial DBD reactor performance. The voltages across the air gap and dielectric layer and the conduction and displacement currents are extracted from the applied voltages and measured currents of AC and ns pulsed coaxial DBDs for the calculation of the power depositions and energy efficiencies through an equivalent electrical model. The discharge uniformity and operating temperature of the coaxial DBD reactor are monitored and analyzed by optical images and infrared camera. A heat conduction model is used to calculate the temperature of the internal quartz tube. It is found that the ns pulsed coaxial DBD has a much higher instantaneous power deposition in plasma, a lower total power consumption, and a higher energy efficiency compared with that excited by AC power and is more homogeneous and stable. The temperature of the outside wall of the AC and ns pulse excited coaxial DBD reaches 158 °C and 64.3 °C after 900 s operation, respectively. The experimental results on the comparison of the discharge characteristics of coaxial DBDs excited by different powers are significant for understanding of the mechanism of DBDs, reducing energy loss, and optimizing the performance of coaxial DBD in industrial applications.

New perspectives on the dynamics of AC and DC plasma arcs exposed to cross-fields

NASA Astrophysics Data System (ADS)

Abdo, Youssef; Rohani, Vandad; Cauneau, François; Fulcheri, Laurent

2017-02-01

Interactions between an arc and external fields are crucially important for the design and the optimization of modern plasma torches. Multiple studies have been conducted to help better understand the behavior of DC and AC current arcs exposed to external and ‘self-induced’ magnetic fields, but the theoretical foundations remain very poorly explored. An analytical investigation has therefore been carried out in order to study the general behavior of DC and AC arcs under the effect of random cross-fields. A simple differential equation describing the general behavior of a planar DC or AC arc has been obtained. Several dimensionless numbers that depend primarily on arc and field parameters and the main arc characteristics (temperature, electric field strength) have also been determined. Their magnitude indicates the general tendency pattern of the arc evolution. The analytical results for many case studies have been validated using an MHD numerical model. The main purpose of this investigation was deriving a practical analytical model for the electric arc, rendering possible its stabilization and control, and the enhancement of the plasma torch power.

Influence of the carrier mobility distribution on the Hall and the Nernst effect measurements in n-type InSb

DOE Office of Scientific and Technical Information (OSTI.GOV)

Madon, B.; Wegrowe, J.-E.; Drouhin, H.-J.

2016-01-14

In this study, we report magneto-resistance measurements on an n-doped InSb film, to separate the contributions of the electrical currents from the heat currents. We have demonstrated a prototype for a magnetic field sensor which is powered by heat currents and does not require any electrical current. We fabricated two Hall bars, where a low frequency (f = 0.05 Hz) AC current, was applied between the two contacts in one of the Hall bars. Separating the f and 2f components of the voltage measured across the second Hall bar was used to distinguish between the electrical and the heat contributions to the electronmore » currents. Our observations can be modeled using a Gaussian distribution of mobility within the sample.« less

Alternating current breakdown voltage of ice electret

NASA Astrophysics Data System (ADS)

Oshika, Y.; Tsuchiya, Y.; Okumura, T.; Muramoto, Y.

2017-09-01

Ice has low environmental impact. Our research objectives are to study the availability of ice as a dielectric insulating material at cryogenic temperatures. We focus on ferroelectric ice (iceXI) at cryogenic temperatures. The properties of iceXI, including its formation, are not clear. We attempted to obtain the polarized ice that was similar to iceXI under the applied voltage and cooling to 77 K. The polarized ice have a wide range of engineering applications as electronic materials at cryogenic temperatures. This polarized ice is called ice electret. The structural difference between ice electret and normal ice is only the positions of protons. The effects of the proton arrangement on the breakdown voltage of ice electret were shown because electrical properties are influenced by the structure of ice. We observed an alternating current (ac) breakdown voltage of ice electret and normal ice at 77 K. The mean and minimum ac breakdown voltage values of ice electret were higher than those of normal ice. We considered that the electrically weak part of the normal ice was improved by applied a direct electric field.

Comparative studies of the structure, morphology and electrical conductivity of polyaniline weakly doped with chlorocarboxylic acids

NASA Astrophysics Data System (ADS)

Gmati, Fethi; Fattoum, Arbi; Bohli, Nadra; Dhaoui, Wadia; Belhadj Mohamed, Abdellatif

2007-08-01

We report the results of studies on two series of polyaniline (PANI), doped with dichloroacetic (DCA) and trichloroacetic (TCA) acids, respectively, at various doping rates and obtained by the in situ polymerization method. Samples were characterized by x-ray diffraction, scanning electron microscopy and conductivity measurements. The direct current (dc) and alternating current (ac) electrical conductivities of PANI salts have been investigated in the temperature range 100-310 K and frequency range 7-106 Hz. The results of this study indicate better chain ordering and higher conductivity for PANI doped with TCA. The dc conductivity of all samples is suitably fitted to Mott's three-dimensional variable-range hopping (VRH) model. Different Mott parameters such as characteristic temperature T0, density of states at the Fermi level (N(EF)), average hopping energy (W) and the average hopping distance (R) have been evaluated. The dependence of such values on the dopant acid used is discussed. At high frequencies, the ac conductivity follows the power law σac(ω,T) = A(T)ωs(T,ω), which is characteristic for charge transport in disordered materials by hopping or tunnelling processes. The observed increase in the frequency exponent s with temperature suggests that the small-polaron tunnelling model best describes the dominant ac conduction mechanism. A direct correlation between conductivity, structure and morphology was obtained in our systems.

Preliminary investigation of the effects of γ-tACS on working memory in schizophrenia.

PubMed

Hoy, Kate E; Whitty, Dean; Bailey, Neil; Fitzgerald, Paul B

2016-10-01

Working memory impairment in schizophrenia has been strongly associated with abnormalities in gamma oscillations within the dorsolateral prefrontal cortex (DLFPC). We recently published the first ever study showing that anodal transcranial direct current stimulation (tDCS) to the left DLPFC was able to significantly improve working memory in schizophrenia and did so seemingly via restoring normal gamma oscillatory function. Transcranial alternating current stimulation (tACS) is a form of electrical brain stimulation that delivers stimulation at a specific frequency and has been shown to entrain endogenous cortical oscillations. Therefore, gamma (γ) tACS may be even more effective than tDCS in improving working memory in schizophrenia. In a randomized repeated-measures study we compared the effects of γ-tACS, tDCS and sham stimulation on the performance of the two back working memory tasks in ten patients with schizophrenia. There was a significant time by stimulation interaction, with tDCS and sham showing trend-level improvements in working memory, while γ-tACS, contrary to our hypothesis, showed no change. The results are discussed in light of posited divergent effects of tACS and tDCS on the pathophysiology of working memory impairment in schizophrenia.

Dielectric Breakdown Characteristics of Oil-pressboard Insulation System against AC/DC Superposed Voltage

NASA Astrophysics Data System (ADS)

Ebisawa, Yoshihito; Yamada, Shin; Mori, Shigekazu; Ikeda, Masami

This paper describes breakdown characteristics of an oil-pressboard insulation system to a superposition voltage of AC and DC voltages. Although AC electric field is decided by the ratio of the relative permittivity of a pressboard and insulating oil, DC electric field is decided by ratio α of volume resistivities. From the measurement in this study, 13—78 and 1.8—5.7 are obtained as the volume resistivity ratios α at temperature of 30°C and 80°C, respectively. The breakdown voltages against AC, DC, and those superposition voltages are surveyed to insulation models. In normal temperature, the breakdown voltage to the superposition voltage of AC and DC is determined by AC electric field applied to the oil duct. Since the α becomes as low as 2-3 at temperature of 80°C, AC and DC voltages almost equally contribute to the electric field of the oil duct as a result. That is, it became clear that superposed DC voltage boosts the electric field across oil ducts at operating high temperature.

Electronic Energy Meter Based on a Tunnel Magnetoresistive Effect (TMR) Current Sensor.

PubMed

Vidal, Enrique García; Muñoz, Diego Ramírez; Arias, Sergio Iván Ravelo; Moreno, Jaime Sánchez; Cardoso, Susana; Ferreira, Ricardo; Freitas, Paulo

2017-09-26

In the present work, the design and microfabrication of a tunneling magnetoresistance (TMR) electrical current sensor is presented. After its physical and electrical characterization, a wattmeter is developed to determine the active power delivered to a load from the AC 50/60 Hz mains line. Experimental results are shown up to 1000 W of power load. A relative uncertainty of less than 1.5% with resistive load and less than 1% with capacitive load was obtained. The described application is an example of how TMR sensing technology can play a relevant role in the management and control of electrical energy.

Electronic Energy Meter Based on a Tunnel Magnetoresistive Effect (TMR) Current Sensor

PubMed Central

García Vidal, Enrique; Ravelo Arias, Sergio Iván; Sánchez Moreno, Jaime; Ferreira, Ricardo; Freitas, Paulo

2017-01-01

In the present work, the design and microfabrication of a tunneling magnetoresistance (TMR) electrical current sensor is presented. After its physical and electrical characterization, a wattmeter is developed to determine the active power delivered to a load from the AC 50/60 Hz mains line. Experimental results are shown up to 1000 W of power load. A relative uncertainty of less than 1.5% with resistive load and less than 1% with capacitive load was obtained. The described application is an example of how TMR sensing technology can play a relevant role in the management and control of electrical energy. PMID:28954425

Enhancement of crystal homogeneity of protein crystals under application of an external alternating current electric field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koizumi, H.; Uda, S.; Fujiwara, K.

X-ray diffraction rocking-curve measurements were performed on tetragonal hen egg white (HEW) lysozyme crystals grown with and without the application of an external alternating current (AC) electric field. The crystal quality was assessed by the full width at half maximum (FWHM) value for each rocking curve. For two-dimensional maps of the FWHMs measured on the 440 and the 12 12 0 reflection, the crystal homogeneity was improved under application of an external electric field at 1 MHz, compared with that without. In particular, the significant improvement of the crystal homogeneity was observed for the 12 12 0 reflection.

Alternating current loss characteristics in (bismuth,lead)SCCO and yttrium barium copper oxide superconducting tapes

NASA Astrophysics Data System (ADS)

Nguyen, Doan Ngoc

Alternating current (AC) loss and current carrying capacity are two of the most crucial considerations in large-scale power applications of high temperature superconducting (HTS) conductors. AC losses result in an increased thermal load for cooling machines, and thus increased operating costs. Furthermore, AC losses can stimulate quenching phenomena or at least decrease the stability margin for superconducting devices. Thus, understanding AC losses is essential for the development of HTS AC applications. The main focus of this dissertation is to make reliable total AC loss measurements and interpret the experimental results in a theoretical framework. With a specially designed magnet, advanced total AC loss measurement system in liquid nitrogen (77 K) has been successfully built. Both calorimetric and electromagnetic methods were employed to confirm the validity of the measured results and to have a more thorough understanding of AC loss in HTS conductors. The measurement is capable of measuring total AC loss in HTS tapes over a wide range of frequency and amplitude of transport current and magnetic field. An accurate phase control technique allows measurement of total AC loss with any phase difference between the transport current and magnetic field by calorimetric method. In addition, a novel total AC loss measurement system with variable temperatures from 30 K to 100 K was successfully built and tested. Understanding the dependence of AC losses on temperature will enable optimization of the operating temperature and design of HTS devices. As a part of the dissertation, numerical calculations using Brandt's model were developed to study electrodynamics and total AC loss in HTS conductors. In the calculations, the superconducting electrical behavior is assumed to follow a power-law model. In general, the practical properties of conductors, including field-dependence of critical current density Jc, n-value and non-uniform distribution of Jc, can be accounted for in the numerical calculations. The numerical calculations are also capable of investigating eddy current loss in the stabilizer and ferromagnetic loss in the substrate of YBa2Cu3O 7-delta (YBCO) coated conductor. AC loss characteristics and electrodynamics in several (Bi,Pb)2 Sr2Ca2Cu3Ox (Bi-2223) and YBCO tapes were studied experimentally and numerically. It was found that AC loss behavior Ax in HTS tapes is strongly affected by the sample parameters such as cross-section, structure, dimensions, critical current distribution as well as by operation parameters including temperature, frequency, the phase difference between transport current and magnetic field, the orientation of magnetic field. The Ni-5%W substrate in YBCO conductors generates some ferromagnetic loss but this loss component is significantly reduced by a small parallel DC magnetic field. At a given AC magnetic field B0, there is a temperature Tmax at which the magnetization loss is maximum. The design of HTS devices needs to be optimized to avoid operating at that temperature. In general, the total AC loss in HTS tapes is still high for many power device applications, especially for those that present a rather high AC applied magnetic field. The development of low loss conductors is therefore crucial for HTS large-scale applications.

Evaluation of DC electric field distribution of PPLP specimen based on the measurement of electrical conductivity in LN2

NASA Astrophysics Data System (ADS)

Hwang, Jae-Sang; Seong, Jae-Kyu; Shin, Woo-Ju; Lee, Jong-Geon; Cho, Jeon-Wook; Ryoo, Hee-Suk; Lee, Bang-Wook

2013-11-01

High temperature superconducting (HTS) cable has been paid much attention due to its high efficiency and high current transportation capability, and it is also regarded as eco-friendly power cable for the next generation. Especially for DC HTS cable, it has more sustainable and stable properties compared to AC HTS cable due to the absence of AC loss in DC HTS cable. Recently, DC HTS cable has been investigated competitively all over the world, and one of the key components of DC HTS cable to be developed is a cable joint box considering HVDC environment. In order to achieve the optimum insulation design of the joint box, analysis of DC electric field distribution of the joint box is a fundamental process to develop DC HTS cable. Generally, AC electric field distribution depends on relative permittivity of dielectric materials but in case of DC, electrical conductivity of dielectric material is a dominant factor which determines electric field distribution. In this study, in order to evaluate DC electric field characteristics of the joint box for DC HTS cable, polypropylene laminated paper (PPLP) specimen has been prepared and its DC electric field distribution was analyzed based on the measurement of electrical conductivity of PPLP in liquid nitrogen (LN2). Electrical conductivity of PPLP in LN2 has not been reported yet but it should be measured for DC electric field analysis. The experimental works for measuring electrical conductivity of PPLP in LN2 were presented in this paper. Based on the experimental works, DC electric field distribution of PPLP specimen was fully analyzed considering the steady state and the transient state of DC. Consequently, it was possible to determine the electric field distribution characteristics considering different DC applying stages including DC switching on, DC switching off and polarity reversal conditions.

Systems and methods for reducing transient voltage spikes in matrix converters

DOEpatents

Kajouke, Lateef A.; Perisic, Milun; Ransom, Ray M.

2013-06-11

Systems and methods are provided for delivering energy using an energy conversion module that includes one or more switching elements. An exemplary electrical system comprises a DC interface, an AC interface, an isolation module, a first conversion module between the DC interface and the isolation module, and a second conversion module between the AC interface and the isolation module. A control module is configured to operate the first conversion module to provide an injection current to the second conversion module to reduce a magnitude of a current through a switching element of the second conversion module before opening the switching element.

Power Delivery from an Actual Thermoelectric Generation System

NASA Astrophysics Data System (ADS)

Kaibe, Hiromasa; Kajihara, Takeshi; Nagano, Kouji; Makino, Kazuya; Hachiuma, Hirokuni; Natsuume, Daisuke

2014-06-01

Similar to photovoltaic (PV) and fuel cells, thermoelectric generators (TEGs) supply direct-current (DC) power, essentially requiring DC/alternating current (AC) conversion for delivery as electricity into the grid network. Use of PVs is already well established through power conditioning systems (PCSs) that enable DC/AC conversion with maximum-power-point tracking, which enables commercial use by customers. From the economic, legal, and regulatory perspectives, a commercial PCS for PVs should also be available for TEGs, preferably as is or with just simple adjustment. Herein, we report use of a PV PCS with an actual TEG. The results are analyzed, and proper application for TEGs is proposed.

Converter topologies and control

DOEpatents

Rodriguez, Fernando; Qin, Hengsi; Chapman, Patrick

2018-05-01

An inverter includes a transformer that includes a first winding, a second winding, and a third winding, a DC-AC inverter electrically coupled to the first winding of the transformer, a cycloconverter electrically coupled to the second winding of the transformer, an active filter electrically coupled to the third winding of the transformer. The DC-AC inverter is adapted to convert the input DC waveform to an AC waveform delivered to the transformer at the first winding. The cycloconverter is adapted to convert an AC waveform received at the second winding of the transformer to the output AC waveform having a grid frequency of the AC grid. The active filter is adapted to sink and source power with one or more energy storage devices based on a mismatch in power between the DC source and the AC grid.

Electrically and spatially controllable PDLC phase gratings for diffraction and modulation of laser beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hadjichristov, Georgi B., E-mail: georgibh@issp.bas.bg; Marinov, Yordan G.; Petrov, Alexander G.

2016-03-25

We present a study on electrically- and spatially-controllable laser beam diffraction, electrooptic (EO) phase modulation, as well as amplitude-frequency EO modulation by single-layer microscale polymer-dispersed liquid crystal (PDLC) phase gratings (PDLC SLPGs) of interest for device applications. PDLC SLPGs were produced from nematic liquid crystal (LC) E7 in photo-curable NOA65 polymer. The wedge-formed PDLC SLPGs have a continuously variable thickness (2–25 µm). They contain LC droplets of diameters twice as the layer thickness, with a linear-gradient size distribution along the wedge. By applying alternating-current (AC) electric field, the PDLC SLPGs produce efficient: (i) diffraction splitting of transmitted laser beams; (ii)more » spatial redistribution of diffracted light intensity; (iii) optical phase modulation; (iv) amplitude-frequency modulation, all controllable by the driven AC field and the droplet size gradient.« less

Experiments on pumping of liquids using arrays of microelectrodes subjected to travelling wave potentials

NASA Astrophysics Data System (ADS)

García-Sánchez, P.; Ramos, A.; Green, Nicolas G.; Morgan, H.

2008-12-01

Net fluid flow of electrolytes driven on an array of microelectrodes subjected to a travelling-wave potential is presented. Two sizes of platinum microelectrodes have been studied. In both arrays, at low voltages the liquid flows according to the prediction given by ac electroosmotic theory. At voltages above a threshold the fluid flow is reversed. Measurements of the electrical current when the microelectrode array is pumping the liquid are also reported. Transient behaviours in both electrical current and fluid velocity have been observed.

Infrared signal generation from AC induction field heating of graphite foam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klett, James W.; Rios, Orlando

A magneto-energy apparatus includes an electromagnetic field source for generating a time-varying electromagnetic field. A graphite foam conductor is disposed within the electromagnetic field. The graphite foam when exposed to the time-varying electromagnetic field conducts an induced electric current, the electric current heating the graphite foam to produce light. An energy conversion device utilizes light energy from the heated graphite foam to perform a light energy consuming function. A device for producing light and a method of converting energy are also disclosed.

High bandwidth magnetically isolated signal transmission circuit

NASA Technical Reports Server (NTRS)

Repp, John Donald (Inventor)

2005-01-01

Many current electronic systems incorporate expensive or sensitive electrical components. Because electrical energy is often generated or transmitted at high voltages, the power supplies to these electronic systems must be carefully designed. Power supply design must ensure that the electrical system being supplied with power is not exposed to excessive voltages or currents. In order to isolate power supplies from electrical equipment, many methods have been employed. These methods typically involve control systems or signal transfer methods. However, these methods are not always suitable because of their drawbacks. The present invention relates to transmitting information across an interface. More specifically, the present invention provides an apparatus for transmitting both AC and DC information across a high bandwidth magnetic interface with low distortion.

Electrical Behavior of Copper Mine Tailings During EKR with Modified Electric Fields.

PubMed

Rojo, Adrian; Hansen, Henrik K; Monárdez, Omara; Jorquera, Carlos; Santis, Paulina; Inostroza, Paula

2017-03-01

Electro-kinetic remediation (EKR) with sinusoidal electric field obtained simultaneously with DC/AC voltage reduce the polarization of the EKR with DC voltage. The DC voltage value defines the presence of a periodic polarity reversal of the cell and the electrical charge for electro-kinetic transport. In this case, the AC frequency favors the breaking of polarization conditions resulting from the EKR with DC voltage. However, with high frequencies a negative effect occurs where the tailings behave as a filter circuit, discriminating frequencies of an electric signal. The goal of this work is to analyse the electrical behaviour of tailings in EKR experiments. The conditions selected were: DC/AC voltages: 10/15 and 20/25 V (peak values), and AC voltage frequencies 50-2000 Hz. When the AC frequency reaches 2000 Hz, the copper removal tends to zero, indicating that the tailing behaves as a high-pass filter in which the DC voltage was filtered out.

Space Charge Modulated Electrical Breakdown

PubMed Central

Li, Shengtao; Zhu, Yuanwei; Min, Daomin; Chen, George

2016-01-01

Electrical breakdown is one of the most important physical phenomena in electrical and electronic engineering. Since the early 20th century, many theories and models of electrical breakdown have been proposed, but the origin of one key issue, that the explanation for dc breakdown strength being twice or higher than ac breakdown strength in insulating materials, remains unclear. Here, by employing a bipolar charge transport model, we investigate the space charge dynamics in both dc and ac breakdown processes. We demonstrate the differences in charge accumulations under both dc and ac stresses and estimate the breakdown strength, which is modulated by the electric field distortion induced by space charge. It is concluded that dc breakdown initializes in the bulk whereas ac breakdown initializes in the vicinity of the sample-electrode interface. Compared with dc breakdown, the lower breakdown strength under ac stress and the decreasing breakdown strength with an increase in applied frequency, are both attributed to the electric field distortion induced by space charges located in the vicinity of the electrodes. PMID:27599577

Measurement of electromagnetic properties of powder and solid metal materials for additive manufacturing

NASA Astrophysics Data System (ADS)

Todorov, Evgueni Iordanov

2017-04-01

The lack of validated nondestructive evaluation (NDE) techniques for examination during and after additive manufacturing (AM) component fabrication is one of the obstacles in the way of broadening use of AM for critical applications. Knowledge of electromagnetic properties of powder (e.g. feedstock) and solid AM metal components is necessary to evaluate and deploy electromagnetic NDE modalities for examination of AM components. The objective of this research study was to develop and implement techniques for measurement of powder and solid metal electromagnetic properties. Three materials were selected - Inconel 625, duplex stainless steel 2205, and carbon steel 4140. The powder properties were measured with alternate current (AC) model based eddy current technique and direct current (DC) resistivity measurements. The solid metal properties were measured with DC resistivity measurements, DC magnetic techniques, and AC model based eddy current technique. Initial magnetic permeability and electrical conductivity were acquired for both powder and solid metal. Additional magnetic properties such as maximum permeability, coercivity, retentivity, and others were acquired for 2205 and 4140. Two groups of specimens were tested along the build length and width respectively to investigate for possible anisotropy. There was no significant difference or anisotropy when comparing measurements acquired along build length to those along the width. A trend in AC measurements might be associated with build geometry. Powder electrical conductivity was very low and difficult to estimate reliably with techniques used in the study. The agreement between various techniques was very good where adequate comparison was possible.

Non-Invasive Electrical Brain Stimulation Montages for Modulation of Human Motor Function.

PubMed

Curado, Marco; Fritsch, Brita; Reis, Janine

2016-02-04

Non-invasive electrical brain stimulation (NEBS) is used to modulate brain function and behavior, both for research and clinical purposes. In particular, NEBS can be applied transcranially either as direct current stimulation (tDCS) or alternating current stimulation (tACS). These stimulation types exert time-, dose- and in the case of tDCS polarity-specific effects on motor function and skill learning in healthy subjects. Lately, tDCS has been used to augment the therapy of motor disabilities in patients with stroke or movement disorders. This article provides a step-by-step protocol for targeting the primary motor cortex with tDCS and transcranial random noise stimulation (tRNS), a specific form of tACS using an electrical current applied randomly within a pre-defined frequency range. The setup of two different stimulation montages is explained. In both montages the emitting electrode (the anode for tDCS) is placed on the primary motor cortex of interest. For unilateral motor cortex stimulation the receiving electrode is placed on the contralateral forehead while for bilateral motor cortex stimulation the receiving electrode is placed on the opposite primary motor cortex. The advantages and disadvantages of each montage for the modulation of cortical excitability and motor function including learning are discussed, as well as safety, tolerability and blinding aspects.

Electrical power system WP-04

NASA Astrophysics Data System (ADS)

Nored, Donald L.

Viewgraphs on Space Station Freedom Electrical Power System (EPS) WP-40 are presented. Topics covered include: key EPS technical requirements; photovoltaic power module systems; solar array assembly; blanket containment box and box positioning subassemblies; solar cell; bypass diode assembly; Kapton with atomic oxygen resistant coating; sequential shunt unit; gimbal assembly; energy storage subsystem; thermal control subsystem; direct current switching unit; integrated equipment assembly; PV cargo element; PMAD system; and PMC and AC architecture.

Electrical power system WP-04

NASA Technical Reports Server (NTRS)

Nored, Donald L.

1990-01-01

Viewgraphs on Space Station Freedom Electrical Power System (EPS) WP-40 are presented. Topics covered include: key EPS technical requirements; photovoltaic power module systems; solar array assembly; blanket containment box and box positioning subassemblies; solar cell; bypass diode assembly; Kapton with atomic oxygen resistant coating; sequential shunt unit; gimbal assembly; energy storage subsystem; thermal control subsystem; direct current switching unit; integrated equipment assembly; PV cargo element; PMAD system; and PMC and AC architecture.

Property and microstructural nonuniformity in the yttrium-barium-copper-oxide superconductor determined from electrical, magnetic, and ultrasonic measurements. Ph.D. Thesis - Case Western Reserve Univ.

NASA Technical Reports Server (NTRS)

Roth, Don J.

1991-01-01

The purpose of this dissertation was the following: (1) to characterize the effect of pore fraction on a comprehensive set of electrical and magnetic properties for the yttrium-barium-copper-oxide (YBCO) high temperature ceramic superconductor; and (2) to determine the viability of using a room-temperature, nondestructive characterization method to aid in the prediction of superconducting (cryogenic) properties. The latter involved correlating ultrasonic velocity measurements at room temperature with property-affecting pore fraction and oxygen content variations. The use of ultrasonic velocity for estimating pore fraction in YBCO is presented, and other polycrystalline materials are reviewed, modeled, and statistically analyzed. This provides the basis for using ultrasonic velocity to interrogate microstructure. The effect of pore fraction (0.10-0.25) on superconductor properties of YBCO samples was characterized. Spatial (within-sample) variations in microstructure and superconductor properties were investigated, and the effect of oxygen content on elastic behavior was examined. Experimental methods used included a.c. susceptibility, electrical, and ultrasonic velocity measurements. Superconductor properties measured included transition temperature, magnetic transition width, transport and magnetic critical current density, magnetic shielding, a.c. loss, and sharpness of the voltage-current characteristics. An ultrasonic velocity image constructed from measurements at 1mm increments across a YBCO sample revealed microstructural variations that correlated with variations in magnetic shielding and a.c. loss behavior. Destructive examination using quantitative image analysis revealed pore fraction to be the varying microstructural feature.

“Beating speckles” via electrically-induced vibrations of Au nanorods embedded in sol-gel

PubMed Central

Ritenberg, Margarita; Beilis, Edith; Ilovitsh, Asaf; Barkai, Zehava; Shahmoon, Asaf; Richter, Shachar; Zalevsky, Zeev; Jelinek, Raz

2014-01-01

Generation of macroscopic phenomena through manipulating nano-scale properties of materials is among the most fundamental goals of nanotechnology research. We demonstrate cooperative “speckle beats” induced through electric-field modulation of gold (Au) nanorods embedded in a transparent sol-gel host. Specifically, we show that placing the Au nanorod/sol-gel matrix in an alternating current (AC) field gives rise to dramatic modulation of incident light scattered from the material. The speckle light patterns take form of “beats”, for which the amplitude and frequency are directly correlated with the voltage and frequency, respectively, of the applied AC field. The data indicate that the speckle beats arise from localized vibrations of the gel-embedded Au nanorods, induced through the interactions between the AC field and the electrostatically-charged nanorods. This phenomenon opens the way for new means of investigating nanoparticles in constrained environments. Applications in electro-optical devices, such as optical modulators, movable lenses, and others are also envisaged. PMID:24413086

Investigation of ac-magnetic field stimulated nanoelectroporation of magneto-electric nano-drug-carrier inside CNS cells.

PubMed

Kaushik, Ajeet; Nikkhah-Moshaie, Roozbeh; Sinha, Raju; Bhardwaj, Vinay; Atluri, Venkata; Jayant, Rahul Dev; Yndart, Adriana; Kateb, Babak; Pala, Nezih; Nair, Madhavan

2017-04-04

In this research, we demonstrate cell uptake of magneto-electric nanoparticles (MENPs) through nanoelectroporation (NEP) using alternating current (ac)-magnetic field stimulation. Uptake of MENPs was confirmed using focused-ion-beam assisted transmission electron microscopy (FIB-TEM) and validated by a numerical simulation model. The NEP was performed in microglial (MG) brain cells, which are highly sensitive for neuro-viral infection and were selected as target for nano-neuro-therapeutics. When the ac-magnetic field optimized (60 Oe at 1 kHz), MENPs were taken up by MG cells without affecting cell health (viability > 92%). FIB-TEM analysis of porated MG cells confirmed the non-agglomerated distribution of MENPs inside the cell and no loss of their elemental and crystalline characteristics. The presented NEP method can be adopted as a part of future nanotherapeutics and nanoneurosurgery strategies where a high uptake of a nanomedicine is required for effective and timely treatment of brain diseases.

Investigation of ac-magnetic field stimulated nanoelectroporation of magneto-electric nano-drug-carrier inside CNS cells

PubMed Central

Kaushik, Ajeet; Nikkhah-Moshaie, Roozbeh; Sinha, Raju; Bhardwaj, Vinay; Atluri, Venkata; Jayant, Rahul Dev; Yndart, Adriana; Kateb, Babak; Pala, Nezih; Nair, Madhavan

2017-01-01

In this research, we demonstrate cell uptake of magneto-electric nanoparticles (MENPs) through nanoelectroporation (NEP) using alternating current (ac)-magnetic field stimulation. Uptake of MENPs was confirmed using focused-ion-beam assisted transmission electron microscopy (FIB-TEM) and validated by a numerical simulation model. The NEP was performed in microglial (MG) brain cells, which are highly sensitive for neuro-viral infection and were selected as target for nano-neuro-therapeutics. When the ac-magnetic field optimized (60 Oe at 1 kHz), MENPs were taken up by MG cells without affecting cell health (viability > 92%). FIB-TEM analysis of porated MG cells confirmed the non-agglomerated distribution of MENPs inside the cell and no loss of their elemental and crystalline characteristics. The presented NEP method can be adopted as a part of future nanotherapeutics and nanoneurosurgery strategies where a high uptake of a nanomedicine is required for effective and timely treatment of brain diseases. PMID:28374799

Sham transcranial electrical stimulation and its effects on corticospinal excitability: a systematic review and meta-analysis.

PubMed

Dissanayaka, Thusharika D; Zoghi, Maryam; Farrell, Michael; Egan, Gary F; Jaberzadeh, Shapour

2018-02-23

Sham stimulation is used in randomized controlled trials (RCTs) to assess the efficacy of active stimulation and placebo effects. It should mimic the characteristics of active stimulation to achieve blinding integrity. The present study was a systematic review and meta-analysis of the published literature to identify the effects of sham transcranial electrical stimulation (tES) - including anodal and cathodal transcranial direct current stimulation (a-tDCS, c-tDCS), transcranial alternating current stimulation (tACS), transcranial random noise stimulation (tRNS) and transcranial pulsed current stimulation (tPCS) - on corticospinal excitability (CSE), compared to baseline in healthy individuals. Electronic databases - PubMed, CINAHL, Scopus, Science Direct and MEDLINE (Ovid) - were searched for RCTs of tES from 1990 to March 2017. Thirty RCTs were identified. Using a random-effects model, meta-analysis of a-tDCS, c-tDCS, tACS, tRNS and tPCS studies showed statistically non-significant pre-post effects of sham interventions on CSE. This review found evidence for statically non-significant effects of sham tES on CSE.

Hybrid power system intelligent operation and protection involving distributed architectures and pulsed loads

NASA Astrophysics Data System (ADS)

Mohamed, Ahmed

Efficient and reliable techniques for power delivery and utilization are needed to account for the increased penetration of renewable energy sources in electric power systems. Such methods are also required for current and future demands of plug-in electric vehicles and high-power electronic loads. Distributed control and optimal power network architectures will lead to viable solutions to the energy management issue with high level of reliability and security. This dissertation is aimed at developing and verifying new techniques for distributed control by deploying DC microgrids, involving distributed renewable generation and energy storage, through the operating AC power system. To achieve the findings of this dissertation, an energy system architecture was developed involving AC and DC networks, both with distributed generations and demands. The various components of the DC microgrid were designed and built including DC-DC converters, voltage source inverters (VSI) and AC-DC rectifiers featuring novel designs developed by the candidate. New control techniques were developed and implemented to maximize the operating range of the power conditioning units used for integrating renewable energy into the DC bus. The control and operation of the DC microgrids in the hybrid AC/DC system involve intelligent energy management. Real-time energy management algorithms were developed and experimentally verified. These algorithms are based on intelligent decision-making elements along with an optimization process. This was aimed at enhancing the overall performance of the power system and mitigating the effect of heavy non-linear loads with variable intensity and duration. The developed algorithms were also used for managing the charging/discharging process of plug-in electric vehicle emulators. The protection of the proposed hybrid AC/DC power system was studied. Fault analysis and protection scheme and coordination, in addition to ideas on how to retrofit currently available protection concepts and devices for AC systems in a DC network, were presented. A study was also conducted on the effect of changing the distribution architecture and distributing the storage assets on the various zones of the network on the system's dynamic security and stability. A practical shipboard power system was studied as an example of a hybrid AC/DC power system involving pulsed loads. Generally, the proposed hybrid AC/DC power system, besides most of the ideas, controls and algorithms presented in this dissertation, were experimentally verified at the Smart Grid Testbed, Energy Systems Research Laboratory. All the developments in this dissertation were experimentally verified at the Smart Grid Testbed.

Generation and electric control of spin-valley-coupled circular photogalvanic current in WSe2

NASA Astrophysics Data System (ADS)

Yuan, Hongtao; Hwang, Harold Y.; Cui, Yi

2015-03-01

Compared to the weak spin-orbit-interaction (SOI) in graphene, layered transitionmetal chalcogenides MX2 have heavy 4d/5d elements with strong atomic SOI, providing a unique way to extend functionalities of novel spintronics and valleytronics devices. Such a valley polarization achieved via valley-selective circular dichroism has been predicted theoretically and demonstrated with optical experiments in MX2 systems. Despite the exciting progresses, the generation of a valley/spin current by valley polarization in MX2 remains elusive and a great challenge. A spin/valley current in MX2 compounds caused by such a valley polarization has never been observed, nor its electric-field control. In this talk, we demonstrated, within an electric-double-layer transistor based on WSe2, the manipulation of a spin-coupled valley photocurrent whose direction and magnitude depend on the degree of circular polarization of the incident radiation and can be further greatly modulated with an external electric field. Such room temperature generation and electric control of valley/spin photocurrent provides a new property of electrons in MX2 systems, thereby enabling new degrees of control for quantum-confined spintronics devices. (In collaboration with S.C. Zhang, Y.L. Chen, Z.X. Shen, B Lian, H.J. Zhang, G Xu, Y Xu, B Zhou, X.Q. Wang, B Shen X.F. Fang) Acknowledge the support from DoE, BES, Division of MSE under contract DE-AC02-76SF00515. Acknowledge the support from DoE, BES, Division of MSE under contract DE-AC02-76SF00515.

Macroscopic kinematics of the Hall electric field under influence of carrier magnetic moments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sakai, Masamichi, E-mail: sakai@fms.saitama-u.ac.jp

2016-06-15

The relativistic effect on electromagnetic forces yields two types of forces which depend on the velocity of the relevant particles: (i) the usual Lorentz force exerted on a moving charged particle and (ii) the apparent Lorentz force exerted on a moving magnetic moment. In sharp contrast with type (i), the type (ii) force originates due to the transverse field induced by the Hall effect (HE). This study incorporates both forces into a Drude-type equation with a fully spin-polarized condition to investigate the effects of self-consistency of the source and the resultant fields on the HE. We also examine the self-consistencymore » of the carrier kinematics and electromagnetic dynamics by simultaneously considering the Drude type equation and Maxwell equations at low frequencies. Thus, our approach can predict both the dc and ac characteristics of the HE, demonstrating that the dc current condition solely yields the ordinary HE, while the ac current condition yields generation of both fundamental and second harmonic modes of the HE field. When the magnetostatic field is absent, the simultaneous presence of dc and ac longitudinal currents generates the ac HE that has both fundamental frequency and second harmonic.« less

Inactivation of bacteria by electric current in the presence of carbon nanotubes embedded within a polymeric membrane.

PubMed

Zhu, Anna; Liu, Harris K; Long, Feng; Su, Erzheng; Klibanov, Alexander M

2015-01-01

Uniform conductive composite membranes were prepared using a phase inversion method by blending carboxyl-functionalized multi-walled carbon nanotubes (CNTs) with a polysulfone polymer. At 6 % of the embedded CNTs, the membrane pore size measured by transmission electron microscopy (TEM) was approximately 50 nm. Electric current in the presence of the composite membranes markedly inactivated the model pathogenic bacteria Escherichia coli and Staphylococcus aureus, with the extent of bacterial inactivation rising when the current was increased. Over 99.999 % inactivation of both bacteria was observed in deionized water after 40 min at 5 mA direct current (DC); importantly, no appreciable inactivation occurred in the absence of either the electric field or the CNTs within the membranes under otherwise the same conditions. A much lower, although still pronounced, inactivation was seen with alternating current (AC) in a 25 mM NaCl aqueous solution.

AC Application of HTS Conductors in Highly Dynamic Electric Motors

NASA Astrophysics Data System (ADS)

Oswald, B.; Best, K.-J.; Setzer, M.; Duffner, E.; Soell, M.; Gawalek, W.; Kovalev, L. K.

2006-06-01

Based on recent investigations we design highly dynamic electric motors up to 400 kW and linear motors up to 120 kN linear force using HTS bulk material and HTS tapes. The introduction of HTS tapes into AC applications in electric motors needs fundamental studies on double pancake coils under transversal magnetic fields. First theoretical and experimental results on AC field distributions in double-pancake-coils and corresponding AC losses will be presented. Based on these results the simulation of the motor performance confirms extremely high power density and efficiency of both types of electric motors. Improved characteristics of rare earth permanent magnets used in our motors at low temperatures give an additional technological benefit.

Droplet condensation on superhydrophobic surfaces with enhanced dewetting under a tangential AC electric field

NASA Astrophysics Data System (ADS)

Yan, Xinzhu; Li, Jian; Li, Licheng; Huang, Zhengyong; Wang, Feipeng; Wei, Yuan

2016-10-01

In this Letter, the dewetting behavior of superhydrophobic condensing surfaces under a tangential AC electric field is reported. The surface coverage of condensed droplets only exhibits a negligible increase with time. The jumping frequency of droplets is enhanced. The AC electric field motivates the dynamic transition of droplets from stretch to recoil, resulting in the counterforce propelling droplet jumping. The considerable horizontal component of jumping velocity facilitates droplet departure from superhydrophobic surfaces. Both the amplitude and frequency of AC voltage are important factors for droplet departure and dewetting effect. Thereby, the tangential electric field provides a unique and easily implementable approach to enhance droplet removal from superhydrophobic condensing surfaces.

Dynamic microparticle manipulation with an electroosmotic flow gradient in low-frequency alternating current dielectrophoresis.

PubMed

Gencoglu, Aytug; Olney, David; LaLonde, Alexandra; Koppula, Karuna S; Lapizco-Encinas, Blanca H

2014-02-01

In this study, the potential of low-frequency AC insulator-based DEP (iDEP) was explored for the separation of polystyrene microparticles and yeast cells. An EOF gradient was generated by employing an asymmetrical, 20 Hz AC electrical signal in an iDEP device consisting of a microchannel with diamond-shaped insulating posts. Two types of samples were analyzed, the first sample contained three types of polystyrene particles with different diameters (0.5, 1.0, and 2.0 μm) and the second sample contained two types of polystyrene particles (1.0 and 2 μm) and yeast cells (6.3 μm). This particular scheme uses a tapered AC signal that allows for all particles to be trapped and concentrated at the insulating post array, as the signal becomes asymmetrical (more positive), particles are selectively released. The smallest particles in each sample were released first, since they require greater dielectrophoretic forces to remain trapped. The largest particles in each sample were released last, when the applied signal became cyclical. A dielectropherogram, which is analogous to a chromatogram, was obtained for each sample, demonstrating successful separation of the particles by showing "peaks" of the released particles. These separations were achieved at lower applied potentials than those reported in previous studies that used solely direct current electrical voltages. Additionally, mathematical modeling with COMSOL Multiphysics was carried out to estimate the magnitude of the dielectrophoretic and EOF forces acting on the particles considering the low-frequency, asymmetrical AC signal used in the experiments. The results demonstrated the potential of low-frequency AC-iDEP systems for handling and separating complex mixtures of microparticles and biological cells. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Analysis of Electrokinetic Mixing Using AC Electric Field and Patchwise Surface Heterogeneities

NASA Astrophysics Data System (ADS)

Luo, Win-Jet; Yarn, Kao-Feng; Hsu, Shou-Ping

2007-04-01

In this paper, the authors investigate the use of an applied AC electric field and microchannel surface heterogeneities to carry out the microfluidic mixing of two-dimensional, time-dependent electroosmotic flows. The time-dependent flow fields within the microchannel are simulated using the backwards-Euler time-stepping numerical method. The mixing efficiencies obtained in microchannels with two different patchwise surface heterogeneity patterns are investigated. In general, the results show that the application of an AC electric field significantly reduces the required mixing length compared with the use of a DC electric field. Furthermore, the presence of oppositely charged surface heterogeneities on the microchannel walls results in the formation of localized flow circulation regions within the bulk flow. These circulation regions grow and decay periodically in accordance with the periodic variation of the AC electric field intensity and provide an effective means of enhancing species mixing in the microchannel. Consequently, the use of an AC electric field together with patchwise surface heterogeneities permits a significant reduction in both the mixing channel length and the retention time required to attain a homogeneous solution.

Comparative study of superconducting fault current limiter both for LCC-HVDC and VSC-HVDC systems

NASA Astrophysics Data System (ADS)

Lee, Jong-Geon; Khan, Umer Amir; Lim, Sung-Woo; Shin, Woo-ju; Seo, In-Jin; Lee, Bang-Wook

2015-11-01

High Voltage Direct Current (HVDC) system has been evaluated as the optimum solution for the renewable energy transmission and long-distance power grid connections. In spite of the various advantages of HVDC system, it still has been regarded as an unreliable system compared to AC system due to its vulnerable characteristics on the power system fault. Furthermore, unlike AC system, optimum protection and switching device has not been fully developed yet. Therefore, in order to enhance the reliability of the HVDC systems mitigation of power system fault and reliable fault current limiting and switching devices should be developed. In this paper, in order to mitigate HVDC fault, both for Line Commutated Converter HVDC (LCC-HVDC) and Voltage Source Converter HVDC (VSC-HVDC) system, an application of resistive superconducting fault current limiter which has been known as optimum solution to cope with the power system fault was considered. Firstly, simulation models for two types of LCC-HVDC and VSC-HVDC system which has point to point connection model were developed. From the designed model, fault current characteristics of faulty condition were analyzed. Second, application of SFCL on each types of HVDC system and comparative study of modified fault current characteristics were analyzed. Consequently, it was deduced that an application of AC-SFCL on LCC-HVDC system with point to point connection was desirable solution to mitigate the fault current stresses and to prevent commutation failure in HVDC electric power system interconnected with AC grid.

Alternating current electroosmotic flow in polyelectrolyte-grafted nanochannel.

PubMed

Li, Fengqin; Jian, Yongjun; Chang, Long; Zhao, Guangpu; Yang, Liangui

2016-11-01

In this work, we investigate the time periodic electroosmotic flow (EOF) of an electrolyte solution through a slit polyelectrolyte-grafted (PE-grafted) nanochannel under applied alternating current (AC) electrical field. The PE-grafted nanochannel is represented by a rigid surface covered by a polyelectrolyte layer (PEL) in a brush-like configuration. Under Debye-Hückel approximation, we obtain analytical solutions of electrical potential in decoupled regime of PE-grafted nanochannel, where the thickness of PEL is independent of the electrostatic effects triggered by polyelectrolyte charges. Based upon the electrical potential obtained above, we calculate EOF velocities with uniform and non-uniform drag coefficients for PE-grafted nanochannel and compare their results. The effects of pertinent dimensionless parameters on EOF velocity amplitude are discussed in detail. Moreover, the amplitude of EOF velocity in a PE-grafted nanochannel is compared with that in a rigid one. It is shown that larger EOF velocity and volume flow rate are found for a PE-grafted nanochannel. In addition, AC EOF velocity is further investigated. The oscillation of velocity reduces and is restricted within the region near the PEL-electrolyte interface for higher oscillating Reynolds number Re. Copyright © 2016 Elsevier B.V. All rights reserved.

Emerging techniques for assisting and accelerating food freezing processes: A review of recent research progresses.

PubMed

Cheng, Lina; Sun, Da-Wen; Zhu, Zhiwei; Zhang, Zi

2017-03-04

Freezing plays an important role in food preservation and the emergence of rapid freezing technologies can be highly beneficial to the food industry. This paper reviews some novel food freezing technologies, including high-pressure freezing (HPF), ultrasound-assisted freezing (UAF), electrically disturbed freezing (EF) and magnetically disturbed freezing (MF), microwave-assisted freezing (MWF), and osmo-dehydro-freezing (ODF). HPF and UAF can initiate ice nucleation rapidly, leading to uniform distribution of ice crystals and the control of their size and shape. Specifically, the former is focused on increasing the degree of supercooling, whereas the latter aims to decrease it. Direct current electric freezing (DC-EF) and alternating current electric freezing (AC-EF) exhibit different effects on ice nucleation. DC-EF can promote ice nucleation and AC-EF has the opposite effect. Furthermore, ODF has been successfully used for freezing various vegetables and fruit. MWF cannot control the nucleation temperature, but can decrease supercooling degree, thus decreasing the size of ice crystals. The heat and mass transfer processes during ODF have been investigated experimentally and modeled mathematically. More studies should be carried out to understand the effects of these technologies on food freezing process.

Digital ac monitor

DOEpatents

Hart, George W.; Kern, Jr., Edward C.

1987-06-09

An apparatus and method is provided for monitoring a plurality of analog ac circuits by sampling the voltage and current waveform in each circuit at predetermined intervals, converting the analog current and voltage samples to digital format, storing the digitized current and voltage samples and using the stored digitized current and voltage samples to calculate a variety of electrical parameters; some of which are derived from the stored samples. The non-derived quantities are repeatedly calculated and stored over many separate cycles then averaged. The derived quantities are then calculated at the end of an averaging period. This produces a more accurate reading, especially when averaging over a period in which the power varies over a wide dynamic range. Frequency is measured by timing three cycles of the voltage waveform using the upward zero crossover point as a starting point for a digital timer.

Digital ac monitor

DOEpatents

Hart, G.W.; Kern, E.C. Jr.

1987-06-09

An apparatus and method is provided for monitoring a plurality of analog ac circuits by sampling the voltage and current waveform in each circuit at predetermined intervals, converting the analog current and voltage samples to digital format, storing the digitized current and voltage samples and using the stored digitized current and voltage samples to calculate a variety of electrical parameters; some of which are derived from the stored samples. The non-derived quantities are repeatedly calculated and stored over many separate cycles then averaged. The derived quantities are then calculated at the end of an averaging period. This produces a more accurate reading, especially when averaging over a period in which the power varies over a wide dynamic range. Frequency is measured by timing three cycles of the voltage waveform using the upward zero crossover point as a starting point for a digital timer. 24 figs.

A pre-heating method based on sinusoidal alternating current for lithium-ion battery

NASA Astrophysics Data System (ADS)

Fan, Wentao; Sun, Fengchun; Guo, Shanshan

2018-04-01

In this paper, a method of low temperature pre-heating of sinusoidal alternating current (SAC) is proposed. Generally, the lower the frequency of the AC current, the higher the heat generation rate. Yet at low frequency, there is a risk of lithium-ion deposition during the half cycle of charging. This study develops a temperature-adaptive, deposition-free AC pre-heating method. a equivalent electric circuit(EEC) model is established to predict the heat generation rate and temperature status, whose parameters are calibrated from the EIS impedance measurements. The effects of current frequency and amplitude on the heating effect are investigated respectively. A multistep temperature-adaptive amplitude strategy is proposed and the cell can be heated from -20°C to 5°C within 509s at 100Hz frequency with this method.

30% CPV Module Milestone

NASA Astrophysics Data System (ADS)

Gordon, Robert; Kinsey, Geoff; Nayaak, Adi; Garboushian, Vahan

2010-10-01

Concentrating Photovoltaics has held out the promise of low cost solar electricity for now several decades. Steady progress towards this goal in the 80's and 90's gradually produced more efficient and reliable systems. System efficiency is regarded as the largest factor in lowering the electricity cost and the relatively recent advent of the terrestrial multi-junction solar cell has pressed this race forward dramatically. CPV systems are now exhibiting impressive AC field efficiencies of 25% and more, approximately twice that of the best flat plate systems available today. Amonix inc. has just tested their latest generation multi-junction module design, achieving over 31% DC efficiency at near PVUSA test conditions. Inculcating this design into their next MegaModule is forthcoming, but the expected AC system field efficiency should be significantly higher than current 25% levels.

SERVOMOTOR CONTROL SYSTEM

DOEpatents

MacNeille, S.M.

1958-12-01

Control systems for automatic positioning of an electric motor operated vapor valve are described which is operable under the severe conditions existing in apparatus for electro-magnetlcally separating isotopes. In general, the system includes a rotor for turning the valve comprising two colls mounted mutually perpendicular to each other and also perpendicular to the magnetic field of the isotope separating apparatus. The coils are furnished with both a-c and d- c current by assoclate control circuitry and a position control is provided for varying the ratlo of the a-c currents in the coils and at the same time, but in an inverse manner, the ratio between the d-c currents in the coils is varied. With the present system the magnitude of the motor torque is constant for all valves of the rotor orientatlon angle.

AC electric field induced dipole-based on-chip 3D cell rotation.

PubMed

Benhal, Prateek; Chase, J Geoffrey; Gaynor, Paul; Oback, Björn; Wang, Wenhui

2014-08-07

The precise rotation of suspended cells is one of the many fundamental manipulations used in a wide range of biotechnological applications such as cell injection and enucleation in nuclear transfer (NT) cloning. Noticeably scarce among the existing rotation techniques is the three-dimensional (3D) rotation of cells on a single chip. Here we present an alternating current (ac) induced electric field-based biochip platform, which has an open-top sub-mm square chamber enclosed by four sidewall electrodes and two bottom electrodes, to achieve rotation about the two axes, thus 3D cell rotation. By applying an ac potential to the four sidewall electrodes, an in-plane (yaw) rotating electric field is generated and in-plane rotation is achieved. Similarly, by applying an ac potential to two opposite sidewall electrodes and the two bottom electrodes, an out-of-plane (pitch) rotating electric field is generated and rolling rotation is achieved. As a prompt proof-of-concept, bottom electrodes were constructed with transparent indium tin oxide (ITO) using the standard lift-off process and the sidewall electrodes were constructed using a low-cost micro-milling process and then assembled to form the chip. Through experiments, we demonstrate rotation of bovine oocytes of ~120 μm diameter about two axes, with the capability of controlling the rotation direction and the rate for each axis through control of the ac potential amplitude, frequency, and phase shift, and cell medium conductivity. The maximum observed rotation rate reached nearly 140° s⁻¹, while a consistent rotation rate reached up to 40° s⁻¹. Rotation rate spectra for zona pellucida-intact and zona pellucida-free oocytes were further compared and found to have no effective difference. This simple, transparent, cheap-to-manufacture, and open-top platform allows additional functional modules to be integrated to become a more powerful cell manipulation system.

Ac-loss measurement of a DyBCO-Roebel assembled coated conductor cable (RACC)

NASA Astrophysics Data System (ADS)

Schuller, S.; Goldacker, W.; Kling, A.; Krempasky, L.; Schmidt, C.

2007-10-01

Low ac-loss HTS cables for transport currents well above 1 kA are required for application in transformers and generators and are taken into consideration for future generations of fusion reactor coils. Coated conductors (CC) are suitable candidates for high field application at an operation temperature around 50-77 K, which is a crucial precondition for economical cooling costs. We prepared a short length of a Roebel bar cable made of industrial DyBCO coated conductor (Theva Company, Germany). Meander shaped tapes of 4 mm width with a twist pitch of 122 mm were cut from 10 mm wide CC tapes using a specially designed tool. Eleven of these strands were assembled to a cable. The electrical and mechanical connection of the tapes was achieved using a silver powder filled conductive epoxy resin. Ac-losses of a short sample in an external ac field were measured as a function of frequency and field amplitude in transverse and parallel field orientations. In addition, the coupling current time constant of the sample was directly measured.

AC Conductivity and Dielectric Properties of Borotellurite Glass

NASA Astrophysics Data System (ADS)

Taha, T. A.; Azab, A. A.

2016-10-01

Borotellurite glasses with formula 60B2O3-10ZnO-(30 - x)NaF- xTeO2 ( x = 0 mol.%, 5 mol.%, 10 mol.%, and 15 mol.%) have been synthesized by thermal melting. X-ray diffraction (XRD) analysis confirmed that the glasses were amorphous. The glass density ( ρ) was determined by the Archimedes method at room temperature. The density ( ρ) and molar volume ( V m) were found to increase with increasing TeO2 content. The direct-current (DC) conductivity was measured in the temperature range from 473 K to 623 K, in which the electrical activation energy of ionic conduction increased from 0.27 eV to 0.48 eV with increasing TeO2 content from 0 mol.% to 15 mol.%. The dielectric parameters and alternating-current (AC) conductivity ( σ ac) were investigated in the frequency range from 1 kHz to 1 MHz and temperature range from 300 K to 633 K. The AC conductivity and dielectric constant decreased with increasing TeO2 content from 0 mol.% to 15 mol.%.

Cortical inhibition and excitation by bilateral transcranial alternating current stimulation.

PubMed

Cancelli, Andrea; Cottone, Carlo; Zito, Giancarlo; Di Giorgio, Marina; Pasqualetti, Patrizio; Tecchio, Franca

2015-01-01

Transcranial electric stimulations (tES) with amplitude-modulated currents are promising tools to enhance neuromodulation effects. It is essential to select the correct cortical targets and inhibitory/excitatory protocols to reverse changes in specific networks. We aimed at assessing the dependence of cortical excitability changes on the current amplitude of 20 Hz transcranial alternating current stimulation (tACS) over the bilateral primary motor cortex. We chose two amplitude ranges of the stimulations, around 25 μA/cm2 and 63 μA/cm2 from peak to peak, with three values (at steps of about 2.5%) around each, to generate, respectively, inhibitory and excitatory effects of the primary motor cortex. We checked such changes online through transcranial magnetic stimulation (TMS)-induced motor evoked potentials (MEPs). Cortical excitability changes depended upon current density (p = 0.001). Low current densities decreased MEP amplitudes (inhibition) while high current densities increased them (excitation). tACS targeting bilateral homologous cortical areas can induce online inhibition or excitation as a function of the current density.

Frequency-dependent failure mechanisms of nanocrystalline gold interconnect lines under general alternating current

NASA Astrophysics Data System (ADS)

Luo, X. M.; Zhang, B.; Zhang, G. P.

2014-09-01

Thermal fatigue failure of metallization interconnect lines subjected to alternating currents (AC) is becoming a severe threat to the long-term reliability of micro/nanodevices with increasing electrical current density/power. Here, thermal fatigue failure behaviors and damage mechanisms of nanocrystalline Au interconnect lines on the silicon glass substrate have been investigated by applying general alternating currents (the pure alternating current coupled with a direct current (DC) component) with different frequencies ranging from 0.05 Hz to 5 kHz. We observed both thermal fatigue damages caused by Joule heating-induced cyclic strain/stress and electromigration (EM) damages caused by the DC component. Besides, the damage formation showed a strong electrically-thermally-mechanically coupled effect and frequency dependence. At lower frequencies, thermal fatigue damages were dominant and the main damage forms were grain coarsening with grain boundary (GB) cracking/voiding and grain thinning. At higher frequencies, EM damages took over and the main damage forms were GB cracking/voiding of smaller grains and hillocks. Furthermore, the healing effect of the reversing current was considered to elucidate damage mechanisms of the nanocrystalline Au lines generated by the general AC. Lastly, a modified model was proposed to predict the lifetime of the nanocrystalline metal interconnect lines, i.e., that was a competing drift velocity-based approach based on the threshold time required for reverse diffusion/healing to occur.

Laser-guided energetic discharges over large air gaps by electric-field enhanced plasma filaments

NASA Astrophysics Data System (ADS)

Théberge, Francis; Daigle, Jean-François; Kieffer, Jean-Claude; Vidal, François; Châteauneuf, Marc

2017-01-01

Recent works on plasma channels produced during the propagation of ultrashort and intense laser pulses in air demonstrated the guiding of electric discharges along the laser path. However, the short plasma lifetime limits the length of the laser-guided discharge. In this paper, the conductivity and lifetime of long plasma channels produced by ultrashort laser pulses is enhanced efficiently over many orders of magnitude by the electric field of a hybrid AC-DC high-voltage source. The AC electric pulse from a Tesla coil allowed to stimulate and maintain the highly conductive channel during few milliseconds in order to guide a subsequent 500 times more energetic discharge from a 30-kV DC source. This DC discharge was laser-guided over an air gap length of two metres, which is more than two orders of magnitude longer than the expected natural discharge length. Long plasma channel induced by laser pulses and stimulated by an external high-voltage source opens the way for wireless and efficient transportation of energetic current pulses over long air gaps and potentially for guiding lightning.

Laser-guided energetic discharges over large air gaps by electric-field enhanced plasma filaments

PubMed Central

Théberge, Francis; Daigle, Jean-François; Kieffer, Jean-Claude; Vidal, François; Châteauneuf , Marc

2017-01-01

Recent works on plasma channels produced during the propagation of ultrashort and intense laser pulses in air demonstrated the guiding of electric discharges along the laser path. However, the short plasma lifetime limits the length of the laser-guided discharge. In this paper, the conductivity and lifetime of long plasma channels produced by ultrashort laser pulses is enhanced efficiently over many orders of magnitude by the electric field of a hybrid AC-DC high-voltage source. The AC electric pulse from a Tesla coil allowed to stimulate and maintain the highly conductive channel during few milliseconds in order to guide a subsequent 500 times more energetic discharge from a 30-kV DC source. This DC discharge was laser-guided over an air gap length of two metres, which is more than two orders of magnitude longer than the expected natural discharge length. Long plasma channel induced by laser pulses and stimulated by an external high-voltage source opens the way for wireless and efficient transportation of energetic current pulses over long air gaps and potentially for guiding lightning. PMID:28053312

Electromechanically generating electricity with a gapped-graphene electric generator

NASA Astrophysics Data System (ADS)

Dressen, Donald; Golovchenko, Jene

2015-03-01

We demonstrate the fabrication and operation of a gapped-graphene electric generator (G-GEG) device. The G-GEG generates electricity from the mechanical oscillation of droplets of electrolytes and ionic liquids. The spontaneous adsorption of ionic species on graphene charges opposing electric double-layer capacitors (EDLCs) on each half of the device. Modulating the area of contact between the droplet and graphene leads to adsorption/desorption of ions, effectively charging/discharging each EDLC and generating a current. The flow of current supports a potential difference across the G-GEG due to the device's internal impedance. Both the magnitude and polarity of the induced current and voltage show a strong dependence on the type of ionic species used, suggesting that certain ions interact more strongly with graphene than others. We find that a simple model circuit consisting of an AC current source in series with a resistor and a time-varying capacitor accurately predicts the device's dynamic behavior. Additionally, we discuss the effect of graphene's intrinsic quantum capacitance on the G-GEG's performance and speculate on the utility of the device in the context of energy harvesting.

The role of optoelectronic feedback on Franz-Keldysh voltage modulation of transistor lasers

NASA Astrophysics Data System (ADS)

Chang, Chi-Hsiang; Chang, Shu-Wei; Wu, Chao-Hsin

2016-03-01

Possessing both the high-speed characteristics of heterojunction bipolar transistors (HBTs) and enhanced radiative recombination of quantum wells (QWs), the light-emitting transistor (LET) which operates in the regime of spontaneous emissions has achieved up to 4.3 GHz modulation bandwidth. A 40 Gbit/s transmission rate can be even achieved using transistor laser (TL). The transistor laser provides not only the current modulation but also direct voltage-controlled modulation scheme of optical signals via Franz-Keldysh (FK) photon-assisted tunneling effect. In this work, the effect of FK absorption on the voltage modulation of TLs is investigated. In order to analyze the dynamics and optical responses of voltage modulation in TLs, the conventional rate equations relevant to diode lasers (DLs) are first modified to include the FK effect intuitively. The theoretical results of direct-current (DC) and small-signal alternating-current (AC) characteristics of optical responses are both investigated. While the DC characteristics look physical, the intrinsic optical response of TLs under the FK voltage modulation shows an AC enhancement with a 20 dB peak, which however is not observed in experiment. A complete model composed of the intrinsic optical transfer function and an electrical transfer function fed back by optical responses is proposed to explain the behaviors of voltage modulation in TLs. The abnormal AC peak disappears through this optoelectronic feedback. With the electrical response along with FK-included photon-carrier rate equations taken into account, the complete voltage-controlled optical modulation response of TLs is demonstrated.

Direct Current as an Integrating Platform for ZNE Buildings with EVs and Storage: DC Direct Systems – A Bridge to a Low Carbon Future?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Karl; Vossos, Vagelis; Kloss, Margarita

2016-09-01

Cost effective zero net energy (ZNE) schemes exist for many types of residential and commercial buildings. Yet, today’s alternating current (AC) based ZNE designs may be as much as 10% to 20% less efficient, more costly, and more complicated than a design based on direct current (DC) technologies. An increasing number of research organizations and manufacturers are just starting the process of developing products and conducting research and development (R&D) efforts. These early R&D efforts indicate that the use of DC technologies may deliver many energy and non-energy benefits relative to AC-based typologies. DC ZNE schemes may provide for anmore » ideal integrating platform for natively DC-based onsite generation, storage, electric vehicle (EV) charging and end-use loads. Emerging empirical data suggest that DC end-use appliances are more efficient, simpler, more durable, and lower cost. DC technologies appear to provide ratepayers a lower cost pathway to achieve resilient ZNE buildings, and simultaneously yield a plethora of benefits. This paper draws from the current research effort entitled "Direct Current as an Integrating and Enabling Platform," co-led by the Lawrence Berkeley National Laboratory (LBNL), the California Institute for Energy and the Environment (CIEE), the Electric Power Research Institute (EPRI) and funded under the California Energy Commission’s Energy Program Investment Charge (CEC EPIC). The first phase of this EPIC research is focused on assembling and summarizing known global performance information on DC and DC-AC hybrid end-use appliances and power systems. This paper summarizes the information and insights gained from this research effort.« less

Nanopore with Transverse Nanoelectrodes for Electrical Characterization and Sequencing of DNA

PubMed Central

Gierhart, Brian C.; Howitt, David G.; Chen, Shiahn J.; Zhu, Zhineng; Kotecki, David E.; Smith, Rosemary L.; Collins, Scott D.

2009-01-01

A DNA sequencing device which integrates transverse conducting electrodes for the measurement of electrode currents during DNA translocation through a nanopore has been nanofabricated and characterized. A focused electron beam (FEB) milling technique, capable of creating features on the order of 1 nm in diameter, was used to create the nanopore. The device was characterized electrically using gold nanoparticles as an artificial analyte with both DC and AC measurement methods. Single nanoparticle/electrode interaction events were recorded. A low-noise, high-speed transimpedance current amplifier for the detection of nano to picoampere currents at microsecond time scales was designed, fabricated and tested for future integration with the nanopore device. PMID:19584949

Nanopore with Transverse Nanoelectrodes for Electrical Characterization and Sequencing of DNA.

PubMed

Gierhart, Brian C; Howitt, David G; Chen, Shiahn J; Zhu, Zhineng; Kotecki, David E; Smith, Rosemary L; Collins, Scott D

2008-06-16

A DNA sequencing device which integrates transverse conducting electrodes for the measurement of electrode currents during DNA translocation through a nanopore has been nanofabricated and characterized. A focused electron beam (FEB) milling technique, capable of creating features on the order of 1 nm in diameter, was used to create the nanopore. The device was characterized electrically using gold nanoparticles as an artificial analyte with both DC and AC measurement methods. Single nanoparticle/electrode interaction events were recorded. A low-noise, high-speed transimpedance current amplifier for the detection of nano to picoampere currents at microsecond time scales was designed, fabricated and tested for future integration with the nanopore device.

Limited output transcranial electrical stimulation (LOTES-2017): Engineering principles, regulatory statutes, and industry standards for wellness, over-the-counter, or prescription devices with low risk.

PubMed

Bikson, Marom; Paneri, Bhaskar; Mourdoukoutas, Andoni; Esmaeilpour, Zeinab; Badran, Bashar W; Azzam, Robin; Adair, Devin; Datta, Abhishek; Fang, Xiao Hui; Wingeier, Brett; Chao, Daniel; Alonso-Alonso, Miguel; Lee, Kiwon; Knotkova, Helena; Woods, Adam J; Hagedorn, David; Jeffery, Doug; Giordano, James; Tyler, William J

We present device standards for low-power non-invasive electrical brain stimulation devices classified as limited output transcranial electrical stimulation (tES). Emerging applications of limited output tES to modulate brain function span techniques to stimulate brain or nerve structures, including transcranial direct current stimulation (tDCS), transcranial alternating current stimulation (tACS), and transcranial pulsed current stimulation (tPCS), have engendered discussion on how access to technology should be regulated. In regards to legal regulations and manufacturing standards for comparable technologies, a comprehensive framework already exists, including quality systems (QS), risk management, and (inter)national electrotechnical standards (IEC). In Part 1, relevant statutes are described for medical and wellness application. While agencies overseeing medical devices have broad jurisdiction, enforcement typically focuses on those devices with medical claims or posing significant risk. Consumer protections regarding responsible marketing and manufacture apply regardless. In Part 2 of this paper, we classify the electrical output performance of devices cleared by the United States Food and Drug Administration (FDA) including over-the-counter (OTC) and prescription electrostimulation devices, devices available for therapeutic or cosmetic purposes, and devices indicated for stimulation of the body or head. Examples include iontophoresis devices, powered muscle stimulators (PMS), cranial electrotherapy stimulation (CES), and transcutaneous electrical nerve stimulation (TENS) devices. Spanning over 13 FDA product codes, more than 1200 electrical stimulators have been cleared for marketing since 1977. The output characteristics of conventional tDCS, tACS, and tPCS techniques are well below those of most FDA cleared devices, including devices that are available OTC and those intended for stimulation on the head. This engineering analysis demonstrates that with regard to output performance and standing regulation, the availability of tDCS, tACS, or tPCS to the public would not introduce risk, provided such devices are responsibly manufactured and legally marketed. In Part 3, we develop voluntary manufacturer guidance for limited output tES that is aligned with current regulatory standards. Based on established medical engineering and scientific principles, we outline a robust and transparent technical framework for ensuring limited output tES devices are designed to minimize risks, while also supporting access and innovation. Alongside applicable medical and government activities, this voluntary industry standard (LOTES-2017) further serves an important role in supporting informed decisions by the public. Copyright © 2017 Elsevier Inc. All rights reserved.

Motor Controllers

NASA Technical Reports Server (NTRS)

1984-01-01

Kollmorgen Corporation's Mermaid II two person submersible is propeller-driven by a system of five DC brushless motors with new electronic controllers that originated in work performed in a NASA/DOE project managed by Lewis Research Center. A key feature of the system is electric commutation rather than mechanical commutation for converting AC current to DC.

Performance assessment of the PNM Prosperity electricity storage project

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roberson, Dakota; Ellison, James F.; Bhatnagar, Dhruv

2014-05-01

The purpose of this study is to characterize the technical performance of the PNM Prosperity electricity storage project, and to identify lessons learned that can be used to improve similar projects in the future. The PNM Prosperity electricity storage project consists of a 500 kW/350 kWh advanced lead-acid battery with integrated supercapacitor (for energy smoothing) and a 250 kW/1 MWh advanced lead-acid battery (for energy shifting), and is co-located with a 500 kW solar photovoltaic (PV) resource. The project received American Reinvestment and Recovery Act (ARRA) funding. The smoothing system is e ective in smoothing intermittent PV output. The shiftingmore » system exhibits good round-trip efficiencies, though the AC-to-AC annual average efficiency is lower than one might hope. Given the current utilization of the smoothing system, there is an opportunity to incorporate additional control algorithms in order to increase the value of the energy storage system.« less

Conduction in In 2O 3/YSZ heterostructures: Complex interplay between electrons and ions, mediated by interfaces

DOE PAGES

Veal, B. W.; Eastman, J. A.

2017-03-01

Thin film In 2O 3/YSZ heterostructures exhibit significant increases in electrical conductance with time when small in-plane electric fields are applied. Contact resistances between the current electrodes and film, and between current electrodes and substrate are responsible for the behavior. With an in-plane electric field, different field profiles are established in the two materials, with the result that oxygen ions can be driven across the heterointerface, altering the doping of the n-type In 2O 3. Furthermore, a low frequency inductive feature observed in AC impedance spectroscopy measurements under DC bias conditions was found to be due to frequency-dependent changes inmore » the contact resistance.« less

Electrical Characteristics, Electrode Sheath and Contamination Layer Behavior of a Meso-Scale Premixed Methane-Air Flame Under AC/DC Electric Fields

NASA Astrophysics Data System (ADS)

Chen, Qi; Yan, Limin; Zhang, Hao; Li, Guoxiu

2016-05-01

Electrical characteristics of a nozzle-attached meso-scale premixed methane-air flame under low-frequency AC (0-4300 V, 0-500 Hz) and DC (0-3300 V) electric fields were studied. I-V curves were measured under different experimental conditions to estimate the magnitude of the total current 100-102 μA, the electron density 1015-1016 m-3 and further the power dissipation ≤ 0.7 W in the reaction zone. At the same time, the meso-scale premixed flame conductivity 10-4-10-3 Ω-1·m-1 as a function of voltage and frequency was experimentally obtained and was believed to represent a useful order-of magnitude estimate. Moreover, the influence of the collision sheath relating to Debye length (31-98 μm) and the contamination layer of an active electrode on measurements was discussed, based on the combination of simulation and theoretical analysis. As a result, the electrode sheath dimension was evaluated to less than 0.5 mm, which indicated a complex effect of the collision sheath on the current measurements. The surface contamination effect of an active electrode was further analyzed using the SEM imaging method, which showed elements immigration during the contamination layer formation process. supported by National Natural Science Foundation of China (No. 51376021), and the Fundamental Research Fund for Major Universities (No. 2013JBM079)

Measured losses in superconductor magnets for 60-Hertz ac operation.

NASA Technical Reports Server (NTRS)

Hamlet, I. L.; Kilgore, R. A.

1971-01-01

Results of an experimental study of electrical losses in superconductor magnets. Preliminary 60-Hz ac loss data are presented for coils constructed of Nb3Sn ribbon, Nb-Ti cable, and multifilament Nb-Ti. Losses have been measured for different size coils up to approximately 20 cm in diameter. Of the conductor types tested, Nb3Sn ribbon has the lowest losses for ac operation. In Nb3Sn-ribbon coils of different sizes, the loss per unit length of conductor is shown to decrease with a decrease in the rate of change of current and to increase, in general, with increase in coil size. An important aspect of the study is the high degree of repeatability of the data.

Critical frequency for coalescence of emulsions in an AC electric field

NASA Astrophysics Data System (ADS)

Liu, Zhou; Ali, Faizi Hammad; Shum, Ho Cheung

2017-11-01

Applying an electric field to trigger the coalescence of emulsions has been applied in various applications which include crude oil recovery, emulsion stability characterization as well as pico-injection and droplet-based chemical reaction in microfluidics. In this work, we systematically investigated the responses of surfactant-stabilized emulsions to a controlled AC electric field using a customer-built chip. At a given amplitude of the AC voltage, we found a critical frequency beyond which the emulsions remain stable. When the frequency is decreased to below the critical value, emulsions coalesce immediately. Such critical frequency is found to be dependent of amplitude of the AC voltage, viscosity of the fluids, concentration and type of the surfactant as well as the electric conductivity of the droplet phase. Using a model based on the drainage of thin film, we have explored the mechanism behind and interpret this phenomenon systematically. Our work extends the understanding of the electro-coalescence of emulsions and can be beneficial for any applications involve the coalescence of droplets in an AC electric field.

Combined AC electroosmosis and dielectrophoresis for controlled rotation of microparticles

PubMed Central

Walid Rezanoor, Md.; Dutta, Prashanta

2016-01-01

Electrorotation is widely used for characterization of biological cells and materials using a rotating electric field. Generally, multiphase AC electric fields and quadrupolar electrode configuration are needed to create a rotating electric field for electrorotation. In this study, we demonstrate a simple method to rotate dielectrophoretically trapped microparticles using a stationary AC electric field. Coplanar interdigitated electrodes are used to create a linearly polarized nonuniform AC electric field. This nonuniform electric field is employed for dielectrophoretic trapping of microparticles as well as for generating electroosmotic flow in the vicinity of the electrodes resulting in rotation of microparticles in a microfluidic device. The rotation of barium titanate microparticles is observed in 2-propanol and methanol solvent at a frequency below 1 kHz. A particle rotation rate as high as 240 revolutions per minute is observed. It is demonstrated that precise manipulation (both rotation rate and equilibrium position) of the particles is possible by controlling the frequency of the applied electric field. At low frequency range, the equilibrium positions of the microparticles are observed between the electrode edge and electrode center. This method of particle manipulation is different from electrorotation as it uses induced AC electroosmosis instead of electric torque as in the case of electrorotation. Moreover, it has been shown that a microparticle can be rotated along its own axis without any translational motion. PMID:27014394

Combined AC electroosmosis and dielectrophoresis for controlled rotation of microparticles.

PubMed

Walid Rezanoor, Md; Dutta, Prashanta

2016-03-01

Electrorotation is widely used for characterization of biological cells and materials using a rotating electric field. Generally, multiphase AC electric fields and quadrupolar electrode configuration are needed to create a rotating electric field for electrorotation. In this study, we demonstrate a simple method to rotate dielectrophoretically trapped microparticles using a stationary AC electric field. Coplanar interdigitated electrodes are used to create a linearly polarized nonuniform AC electric field. This nonuniform electric field is employed for dielectrophoretic trapping of microparticles as well as for generating electroosmotic flow in the vicinity of the electrodes resulting in rotation of microparticles in a microfluidic device. The rotation of barium titanate microparticles is observed in 2-propanol and methanol solvent at a frequency below 1 kHz. A particle rotation rate as high as 240 revolutions per minute is observed. It is demonstrated that precise manipulation (both rotation rate and equilibrium position) of the particles is possible by controlling the frequency of the applied electric field. At low frequency range, the equilibrium positions of the microparticles are observed between the electrode edge and electrode center. This method of particle manipulation is different from electrorotation as it uses induced AC electroosmosis instead of electric torque as in the case of electrorotation. Moreover, it has been shown that a microparticle can be rotated along its own axis without any translational motion.

AC current rectification in Nb films with or without symmetrical Nb/Ni periodic pinning arrays in perpendicular magnetic field

NASA Astrophysics Data System (ADS)

Pryadun, Vladimir

2005-03-01

Rectification of AC current has been observed in plain superconducting Nb films and in Nb/Ni films with symmetric periodic pinning centers. The rectified DC voltage appears for various sample geometries (cross or strip) both along and transverse to the alternating current direction, is nearly anti-symmetric with perpendicular magnetic field and strongly dependent on temperature below Tc. Analyses of the data at different temperatures, drive frequencies from 100kHz to 150MHz and at the different sample sides [1] shows that not far below Tc the rectification phenomena can be understood in terms of generation of electric fields due to local excess of critical current. Further below Tc anisotropic pinning effects could also contribute to the rectification. [1] F.G.Aliev, et al., Cond. Mat.405656. Supported by Comunidad Autonoma de Madrid -CAM/07N/0050/2002

The effect of surface grain reversal on the AC losses of sintered Nd-Fe-B permanent magnets

NASA Astrophysics Data System (ADS)

Moore, Martina; Roth, Stefan; Gebert, Annett; Schultz, Ludwig; Gutfleisch, Oliver

2015-02-01

Sintered Nd-Fe-B magnets are exposed to AC magnetic fields in many applications, e.g. in permanent magnet electric motors. We have measured the AC losses of sintered Nd-Fe-B magnets in a closed circuit arrangement using AC fields with root mean square-values up to 80 mT (peak amplitude 113 mT) over the frequency range 50 to 1000 Hz. Two magnet grades with different dysprosium content were investigated. Around the remanence point the low grade material (1.7 wt% Dy) showed significant hysteresis losses; whereas the losses in the high grade material (8.9 wt% Dy) were dominated by classical eddy currents. Kerr microscopy images revealed that the hysteresis losses measured for the low grade magnet can be mainly ascribed to grains at the sample surface with multiple domains. This was further confirmed when the high grade material was subsequently exposed to DC and AC magnetic fields. Here a larger number of surface grains with multiple domains are also present once the step in the demagnetization curve attributed to the surface grain reversal is reached and a rise in the measured hysteresis losses is evident. If in the low grade material the operating point is slightly offset from the remanence point, such that zero field is not bypassed, its AC losses can also be fairly well described with classical eddy current theory.

Effects of surface chemical properties of activated carbon modified by amino-fluorination for electric double-layer capacitor.

PubMed

Jung, Min-Jung; Jeong, Euigyung; Cho, Seho; Yeo, Sang Young; Lee, Young-Seak

2012-09-01

The surface of phenol-based activated carbon (AC) was seriatim amino-fluorinated with solution of ammonium hydroxide and hydrofluoric acid in varying ratio to fabricate electrode materials for use in an electric double-layer capacitor (EDLC). The specific capacitance of the amino-fluorinated AC-based EDLC was measured in a 1 M H(2)SO(4) electrolyte, in which it was observed that the specific capacitances increased from 215 to 389 Fg(-1) and 119 and 250 Fg(-1) with the current densities of 0.1 and 1.0 Ag(-1), respectively, in comparison with those of an untreated AC-based EDLC when the amino-fluorination was optimized via seriatim mixed solution of 7.43 mol L(-1) ammonium hydroxide and 2.06 mol L(-1) hydrofluoric acid. This enhancement of capacitance was attributed to the synergistic effects of an increased electrochemical activity due to the formation of surface N- and F-functional groups and increased, specific surface area, and mesopore volumes, all of which resulted from the amino-fluorination of the electrode material. Copyright © 2012 Elsevier Inc. All rights reserved.

Preparation and physical properties of polycrystalline (Bi1-xPbx)2Sr2Ca2Cu3Oy high T c superconductors

NASA Astrophysics Data System (ADS)

Awan, M. S.; Maqsood, M.; Mirza, S. A.; Yousaf, M.; Maqsood, A.

1995-02-01

(Bi1-xPbx:)2Sr2Ca2Cu3Oy ( x = 0.3) high critical transition temperature ( T c) superconductors are synthesized by the solid-state reaction method in polycrystalline form. X-ray diffraction (XRD) studies, direct current (dc) electrical resistivity measurements, scanning electron microscopic (SEM) studies, critical current density measurements, and zero-field alternating current (ac) susceptibility measurements are performed to investigate the physical changes, structural changes, and magnetic behavior of the superconducting samples. X-ray diffraction studies show that a high T c phase exists with orthorhombic symmetry in the specimen. According to the XRD data, the lattice parameters of the high T c phase were determined as a = 0.537(1) nm, b = 0.539(1) nm, and c = 3.70(1) nm. The compound exhibits a superconducting transition at 106 ±1 K for zero resistance. The ac susceptibility measurements in zero field confirm the dc electrical resistivity results; hence both support the XRD results. The particle size and structural changes as a function of the cold-pressing and aging effect are also reported.

Assessing summertime urban air conditioning consumption in a semiarid environment

NASA Astrophysics Data System (ADS)

Salamanca, F.; Georgescu, M.; Mahalov, A.; Moustaoui, M.; Wang, M.; Svoma, B. M.

2013-09-01

Evaluation of built environment energy demand is necessary in light of global projections of urban expansion. Of particular concern are rapidly expanding urban areas in environments where consumption requirements for cooling are excessive. Here, we simulate urban air conditioning (AC) electric consumption for several extreme heat events during summertime over a semiarid metropolitan area with the Weather Research and Forecasting (WRF) model coupled to a multilayer building energy scheme. Observed total load values obtained from an electric utility company were split into two parts, one linked to meteorology (i.e., AC consumption) which was compared to WRF simulations, and another to human behavior. WRF-simulated non-dimensional AC consumption profiles compared favorably to diurnal observations in terms of both amplitude and timing. The hourly ratio of AC to total electricity consumption accounted for ˜53% of diurnally averaged total electric demand, ranging from ˜35% during early morning to ˜65% during evening hours. Our work highlights the importance of modeling AC electricity consumption and its role for the sustainable planning of future urban energy needs. Finally, the methodology presented in this article establishes a new energy consumption-modeling framework that can be applied to any urban environment where the use of AC systems is prevalent.

Electrodeless RF Plasma Thruster Using m = 0 Coil

NASA Astrophysics Data System (ADS)

Nishimura, Shuichi; Arai, Daisuke; Kuwahara, Daisuke; Shinohara, Shunjiro

2016-10-01

In order to realize a deep space exploration in the future, we have been developing a next generation electrodeless electric propulsion system by electromagnetic acceleration of high-density helicon plasma. A new proposed method by m = 0 coil plasma acceleration (m is an azimuthal mode number) is based on the Lorentz force: a product of the induced azimuthal current by supplying an AC current to the m = 0 coil and the radial component of the externally applied magnetic field (divergent field configuration). Here, we have investigated the dependences of an ion velocity and an electron density on the external parameters, leading to optimized conditions, using the SHD device. By increasing AC current on the order of 100 A, we could see the increase of ion velocity and electron density by a factor of 2.5 and 3, respectively.

Low Insertion HVDC Circuit Breaker: Magnetically Pulsed Hybrid Breaker for HVDC Power Distribution Protection

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

2012-01-09

GENI Project: General Atomics is developing a direct current (DC) circuit breaker that could protect the grid from faults 100 times faster than its alternating current (AC) counterparts. Circuit breakers are critical elements in any electrical system. At the grid level, their main function is to isolate parts of the grid where a fault has occurred—such as a downed power line or a transformer explosion—from the rest of the system. DC circuit breakers must interrupt the system during a fault much faster than AC circuit breakers to prevent possible damage to cables, converters and other grid-level components. General Atomics’ high-voltagemore » DC circuit breaker would react in less than 1/1,000th of a second to interrupt current during a fault, preventing potential hazards to people and equipment.« less

Design and evaluation of 66 kV-class HTS power cable using REBCO wires

NASA Astrophysics Data System (ADS)

Ohya, M.; Yumura, H.; Masuda, T.; Amemiya, N.; Ishiyama, A.; Ohkuma, T.

2011-11-01

Sumitomo Electric (SEI) has been involved in the development of 66 kV-class HTS cables using REBCO wires. One of the technical targets in this project is to reduce the AC loss to less than 2 W/m/phase at 5 kA. SEI has developed a clad-type of textured metal substrate with lower magnetization loss compared with a conventional NiW substrate. In addition, 30 mm-wide REBCO tapes were slit into 4 mm-wide strips, and these strips were wound spirally on a former with small gaps. The AC loss of a manufactured 4-layer cable conductor was 1.5 W/m at 5 kA at 64 K. Given that the AC loss in a shield layer is supposed to be one-fourth of a whole cable core loss, our cables are expected to achieve the AC loss target of less than 2 W/m/phase at 5 kA. Another important target is to manage a fault current. A cable core was designed and fabricated based on the simulation findings, and over-current tests (max. 31.5 kA, 2 s) were conducted to check its performance. The critical current value of the cable cores were measured before and after the over-current tests and verified its soundness. A 5 kA-class current lead for the cable terminations was also developed. The current loading tests were conducted for the developed current leads. The temperature distribution of the current leads reached to the steady-state within less than 12 h, and it was confirmed that the developed current lead has enough capacity of 5 kA loading.

Fiber-optic sensors for aerospace electrical measurements: An update

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Rose, A. H.; Tang, D.; Day, G. W.

1991-01-01

Fiber-optic sensors are being developed for electrical current, voltage, and power measurements in aerospace applications. These sensors are presently designed to cover ac frequencies from 60 Hz to 20 kHz. The current sensor, based on the Faraday effect in optical fiber, is in advanced development after some initial testing. Concentration is on packaging methods and ways to maintain consistent sensitivity with changes in temperature. The voltage sensor, utilizing the Pockels effect in a crystal, has excelled in temperature tests. This paper reports on the development of these sensors, the results of evaluation, improvements now in progress, and the future direction of the work.

Construction and characterization of spherical Si solar cells combined with SiC electric power inverter

NASA Astrophysics Data System (ADS)

Oku, Takeo; Matsumoto, Taisuke; Hiramatsu, Kouichi; Yasuda, Masashi; Shimono, Akio; Takeda, Yoshikazu; Murozono, Mikio

2015-02-01

Spherical silicon (Si) photovoltaic solar cell systems combined with an electric power inverter using silicon carbide (SiC) field-effect transistor (FET) were constructed and characterized, which were compared with an ordinary Si-based converter. The SiC-FET devices were introduced in the direct current-alternating current (DC-AC) converter, which was connected with the solar panels. The spherical Si solar cells were used as the power sources, and the spherical Si panels are lighter and more flexible compared with the ordinary flat Si solar panels. Conversion efficiencies of the spherical Si solar cells were improved by using the SiC-FET.

A new approach for AC loss reduction in HTS transformer using auxiliary windings, case study: 25 kA HTS current injection transformer

NASA Astrophysics Data System (ADS)

Heydari, Hossein; Faghihi, Faramarz; Aligholizadeh, Reza

2008-01-01

AC loss is one of the important parameters in HTS (high temperature superconducting) AC devices. Among the HTS AC power devices, the transformer is an essential part in the electrical power system. The AC losses in an HTS tape depend on the magnetic field. One of the techniques usually adopted to mitigate the unwanted magnetic field is using a system of coils that produce a magnetic field opposite to the incident one, reducing the total magnetic field. In this paper adding two auxiliary windings to the HTS transformer to produce this opposite magnetic field is proposed. The proper use of these auxiliary windings could reduce the leakage flux and, therefore, the AC loss. A mathematical model is used to describe the behaviour of a transformer operating with auxiliary windings, based on the theory of electromagnetic coupled circuits. The influence of the auxiliary windings on the leakage field is studied by the finite element method (FEM) and the AC loss of an HTS transformer was calculated. Also, the simulation results show that employing auxiliary windings will improve the HTS transformer efficiency.

Nickel-cadmium battery system for electric vehicles

NASA Astrophysics Data System (ADS)

Klein, M.; Charkey, A.

A nickel-cadmium battery system has been developed and is being evaluated for electric vehicle propulsion applications. The battery system design features include: (1) air circulation through gaps between cells for thermal management, (2) a metal-gas coulometric fuel gauge for state-of-charge and charge control, and (3) a modified constant current ac/dc power supply for the charger. The battery delivers one and a half to two times the energy density of comparable lead-acid batteries depending on operating conditions.

Electrical safety for high voltage arrays

NASA Technical Reports Server (NTRS)

Marshall, N. A.

1983-01-01

A number of key electrical safety requirements for the high voltage arrays of central station photovoltaic power systems are explored. The suitability of representative industrial DC power switchgear for control and fault protection was evaluated. Included were AC/DC circuit breakers, electromechanical contactors and relays, load interruptors, cold disconnect devices, sectionalizing switches, and high voltage DC fuses. As appropriate, steady state and transient characteristics were analyzed. Failure modes impacting upon operation and maintenance safety were also identified, as were the voltage withstand and current interruption levels.

Modulation of electric brain responses evoked by pitch deviants through transcranial direct current stimulation.

PubMed

Royal, Isabelle; Zendel, Benjamin Rich; Desjardins, Marie-Ève; Robitaille, Nicolas; Peretz, Isabelle

2018-01-31

Congenital amusia is a neurodevelopmental disorder, characterized by a difficulty detecting pitch deviation that is related to abnormal electrical brain responses. Abnormalities found along the right fronto-temporal pathway between the inferior frontal gyrus (IFG) and the auditory cortex (AC) are the likely neural mechanism responsible for amusia. To investigate the causal role of these regions during the detection of pitch deviants, we applied cathodal (inhibitory) transcranial direct current stimulation (tDCS) over right frontal and right temporal regions during separate testing sessions. We recorded participants' electrical brain activity (EEG) before and after tDCS stimulation while they performed a pitch change detection task. Relative to a sham condition, there was a decrease in P3 amplitude after cathodal stimulation over both frontal and temporal regions compared to pre-stimulation baseline. This decrease was associated with small pitch deviations (6.25 cents), but not large pitch deviations (200 cents). Overall, this demonstrates that using tDCS to disrupt regions around the IFG and AC can induce temporary changes in evoked brain activity when processing pitch deviants. These electrophysiological changes are similar to those observed in amusia and provide causal support for the connection between P3 and fronto-temporal brain regions. Copyright © 2017 Elsevier Ltd. All rights reserved.

Alternating current transport and dielectric relaxation of nanocrystalline graphene oxide

NASA Astrophysics Data System (ADS)

Zedan, I. T.; El-Menyawy, E. M.

2018-07-01

Graphene oxide (GO) has been synthesized from natural graphite using modified Hummer's method and is subjected to sonication for 1 h. X-ray diffraction (XRD) showed that the prepared GO has nanocrystalline structure with particle size of about 5 nm and high-resolution transmission electron microscope showed that it had a layered structure. The nanocrystalline GO powder was pressed as a disk and the alternating current (AC) electrical conductivity, σAC, and dielectric properties have been investigated in the frequency range 50Hz-5 MHz and temperature range 298-523K using parallel plate spectroscopic technique. Analysis of σ AC as a function of frequency shows that the relation follows Jonscher's universal law with frequency exponent decreases with increasing temperature in which the correlated barrier hopping model is applicable to describe the behavior. The dielectric constant and dielectric loss are studied as functions of frequency and temperature. The dielectric modulus formalism is used for describing the relaxation process in which the relaxation time and its activation energy were evaluated.

Electroosmotic Flow Driven by DC and AC Electric Fields in Curved Microchannels

NASA Astrophysics Data System (ADS)

Chen, Jia-Kun; Luo, Win-Jet; Yang, Ruey-Jen

2006-10-01

The purpose of this study is to investigate electroosmotic flows driven by externally applied DC and AC electric fields in curved microchannels. For the DC electric driving field, the velocity distribution and secondary flow patterns are investigated in microchannels with various curvature ratios. We use the Dean number to describe the curvature effect of the flow field in DC electric field. The result implies that the effect of curvatures and the strength of the secondary flows become get stronger when the curvature ratio of C/A (where C is the radius of curvature of the microchannel and A is the half-height of rectangular curved tube.) is smaller. For the AC electric field, the velocity distribution and secondary flow patterns are investigated for driving frequencies in the range of 2.0 kHz (\\mathit{Wo}=0.71) to 11 kHz (\\mathit{Wo}=1.66). The numerical results reveal that the velocity at the center of the microchannel becomes lower at higher frequencies of the AC electric field and the strength of the secondary flow decreases. When the applied frequency exceeds 3.0 kHz (\\mathit{Wo}=0.87), vortices are no longer observed at the corners of the microchannel. Therefore, it can be concluded that the secondary flow induced at higher AC electric field frequencies has virtually no effect on the axial flow field in the microchannel.

Self-oscillations in field emission nanowire mechanical resonators: a nanometric dc-ac conversion.

PubMed

Ayari, Anthony; Vincent, Pascal; Perisanu, Sorin; Choueib, May; Gouttenoire, Vincent; Bechelany, Mikhael; Cornu, David; Purcell, Stephen T

2007-08-01

We report the observation of self-oscillations in a bottom-up nanoelectromechanical system (NEMS) during field emission driven by a constant applied voltage. An electromechanical model is explored that explains the phenomenon and that can be directly used to develop integrated devices. In this first study, we have already achieved approximately 50% dc/ac (direct to alternating current) conversion. Electrical self-oscillations in NEMS open up a new path for the development of high-speed, autonomous nanoresonators and signal generators and show that field emission (FE) is a powerful tool for building new nanocomponents.

Single Phase Passive Rectification Versus Active Rectification Applied to High Power Stirling Engines

NASA Technical Reports Server (NTRS)

Santiago, Walter; Birchenough, Arthur G.

2006-01-01

Stirling engine converters are being considered as potential candidates for high power energy conversion systems required by future NASA explorations missions. These types of engines typically contain two major moving parts, the displacer and the piston, in which a linear alternator is attached to the piston to produce a single phase sinusoidal waveform at a specific electric frequency. Since all Stirling engines perform at low electrical frequencies (less or equal to 100 Hz), space explorations missions that will employ these engines will be required to use DC power management and distribution (PMAD) system instead of an AC PMAD system to save on space and weight. Therefore, to supply such DC power an AC to DC converter is connected to the Stirling engine. There are two types of AC to DC converters that can be employed, a passive full bridge diode rectifier and an active switching full bridge rectifier. Due to the inherent line inductance of the Stirling Engine-Linear Alternator (SE-LA), their sinusoidal voltage and current will be phase shifted producing a power factor below 1. In order to keep power the factor close to unity, both AC to DC converters topologies will implement power factor correction. This paper discusses these power factor correction methods as well as their impact on overall mass for exploration applications. Simulation results on both AC to DC converters topologies with power factor correction as a function of output power and SE-LA line inductance impedance are presented and compared.

Electric discharge during electrosurgery

PubMed Central

Shashurin, Alexey; Scott, David; Zhuang, Taisen; Canady, Jerome; Beilis, Isak I.; Keidar, Michael

2015-01-01

Electric discharge utilized for electrosurgery is studied by means of a recently developed method for the diagnostics of small-size atmospheric plasma objects based on Rayleigh scattering of microwaves on the plasma volume. Evolution of the plasma parameters in the near-electrode sheaths and in the positive column is measured and analyzed. It is found that the electrosurgical system produces a glow discharge of alternating current with strongly contracted positive column with current densities reaching 103 A/cm2. The plasma electron density and electrical conductivities in the channel were found be 1016 cm−3 and (1-2) Ohm−1cm−1, respectively. The discharge interrupts every instance when the discharge-driving AC voltage crosses zero and re-ignites again every next half-wave at the moment when the instant voltage exceeds the breakdown threshold. PMID:25880721

Electric discharge during electrosurgery.

PubMed

Shashurin, Alexey; Scott, David; Zhuang, Taisen; Canady, Jerome; Beilis, Isak I; Keidar, Michael

2015-04-16

Electric discharge utilized for electrosurgery is studied by means of a recently developed method for the diagnostics of small-size atmospheric plasma objects based on Rayleigh scattering of microwaves on the plasma volume. Evolution of the plasma parameters in the near-electrode sheaths and in the positive column is measured and analyzed. It is found that the electrosurgical system produces a glow discharge of alternating current with strongly contracted positive column with current densities reaching 10(3) A/cm(2). The plasma electron density and electrical conductivities in the channel were found be 10(16) cm(-3) and (1-2) Ohm(-1) cm(-1), respectively. The discharge interrupts every instance when the discharge-driving AC voltage crosses zero and re-ignites again every next half-wave at the moment when the instant voltage exceeds the breakdown threshold.

Using WRF-Urban to Assess Summertime Air Conditioning Electric Loads and Their Impacts on Urban Weather in Beijing

NASA Astrophysics Data System (ADS)

Xu, Xiaoyu; Chen, Fei; Shen, Shuanghe; Miao, Shiguang; Barlage, Michael; Guo, Wenli; Mahalov, Alex

2018-03-01

The air conditioning (AC) electric loads and their impacts on local weather over Beijing during a 5 day heat wave event in 2010 are investigated by using the Weather Research and Forecasting (WRF) model, in which the Noah land surface model with multiparameterization options (Noah-MP) is coupled to the multilayer Building Effect Parameterization and Building Energy Model (BEP+BEM). Compared to the legacy Noah scheme coupled to BEP+BEM, this modeling system shows a better performance, decreasing the root-mean-square error of 2 m air temperature to 1.9°C for urban stations. The simulated AC electric loads in suburban and rural districts are significantly improved by introducing the urban class-dependent building cooled fraction. Analysis reveals that the observed AC electric loads in each district are characterized by a common double peak at 3 p.m. and at 9 p.m. local standard time, and the incorporation of more realistic AC working schedules helps reproduce the evening peak. Waste heat from AC systems has a smaller effect ( 1°C) on the afternoon 2 m air temperature than the evening one (1.5 2.4°C) if AC systems work for 24 h and vent sensible waste heat into air. Influences of AC systems can only reach up to 400 m above the ground for the evening air temperature and humidity due to a shallower urban boundary layer than daytime. Spatially varying maps of AC working schedules and the ratio of sensible to latent waste heat release are critical for correctly simulating the cooling electric loads and capturing the thermal stratification of urban boundary layer.

Experimentally determined transport and magnetization ac losses of small cable models constructed from YBCO coated conductors

NASA Astrophysics Data System (ADS)

Šouc, J.; Vojenčiak, M.; Gömöry, F.

2010-04-01

Several short cable models were constructed from YBCO coated conductor (YBCO CC) to study their basic dc and ac electrical properties. They were prepared using superconducting tapes helically wound on fiberglass former of different diameter (5, 8 and 10 mm) with different twist pitch (from 1.7 up to 2.4 cm). The number of parallel-connected tapes ranged from 1 up to 6. The standard length of the models was 11 cm. In one case a 35 cm long model has been manufactured in order to perform a bending test. We observed that the critical currents of the models were proportional to the number of tapes used for their construction. Transport and magnetization ac loss were measured at 36 and 72 Hz.

Polaron conductivity mechanism in oxalic acid dihydrate: ac conductivity experiment

NASA Astrophysics Data System (ADS)

Levstik, Adrijan; Filipič, Cene; Bobnar, Vid; Levstik, Iva; Hadži, Dušan

2006-10-01

The ac electrical conductivity of the oxalic acid dihydrate ( α -POX) was investigated as a function of the frequency and temperature. The real part of the complex ac electrical conductivity was found to follow the universal dielectric response σ'∝νs , indicating that hopping or tunneling of localized charge carriers governs the electrical transport. A detailed analysis of the temperature dependence of the exponent s revealed that in a broad temperature range 50-200K the tunneling of polarons is the dominating charge transport mechanism.

Analytical Analysis and Case Study of Transient Behavior of Inrush Current in Power Transformer for Designing of Efficient Circuit Breakers

NASA Astrophysics Data System (ADS)

Harmanpreet, Singh, Sukhwinder; Kumar, Ashok; Kaur, Parneet

2010-11-01

Stability & security are main aspects in electrical power systems. Transformer protection is major issue of concern to system operation. There are many mall-trip cases of transformer protection are caused by inrush current problems. The phenomenon of transformer inrush current has been discussed in many papers since 1958. In this paper analytical analysis of inrush current in a transformer switched on dc and ac supply has been done. This analysis will help in design aspects of circuit breakers for better performance.

Does transcranial electrical stimulation enhance corticospinal excitability of the motor cortex in healthy individuals? A systematic review and meta-analysis.

PubMed

Dissanayaka, Thusharika; Zoghi, Maryam; Farrell, Michael; Egan, Gary F; Jaberzadeh, Shapour

2017-08-01

Numerous studies have explored the effects of transcranial electrical stimulation (tES) - including anodal transcranial direct current stimulation (a-tDCS), cathodal transcranial direct current stimulation (c-tDCS), transcranial alternative current stimulation (tACS), transcranial random noise stimulation (tRNS) and transcranial pulsed current stimulation (tPCS) - on corticospinal excitability (CSE) in healthy populations. However, the efficacy of these techniques and their optimal parameters for producing robust results has not been studied. Thus, the aim of this systematic review was to consolidate current knowledge about the effects of various parameters of a-tDCS, c-tDCS, tACS, tRNS and tPCS on the CSE of the primary motor cortex (M1) in healthy people. Leading electronic databases were searched for relevant studies published between January 1990 and February 2017; 126 articles were identified, and their results were extracted and analysed using RevMan software. The meta-analysis showed that a-tDCS application on the dominant side significantly increases CSE (P < 0.01) and that the efficacy of a-tDCS is dependent on current density and duration of application. Similar results were obtained for stimulation of M1 on the non-dominant side (P = 0.003). The effects of a-tDCS reduce significantly after 24 h (P = 0.006). Meta-analysis also revealed significant reduction in CSE following c-tDCS (P < 0.001) and significant increases after tRNS (P = 0.03) and tPCS (P = 0.01). However, tACS effects on CSE were only significant when the stimulation frequency was ≥140 Hz. This review provides evidence that tES has substantial effects on CSE in healthy individuals for a range of stimulus parameters. © 2017 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Frequency and voltage dependent profile of dielectric properties, electric modulus and ac electrical conductivity in the PrBaCoO nanofiber capacitors

NASA Astrophysics Data System (ADS)

Demirezen, S.; Kaya, A.; Yerişkin, S. A.; Balbaşı, M.; Uslu, İ.

In this study, praseodymium barium cobalt oxide nanofiber interfacial layer was sandwiched between Au and n-Si. Frequency and voltage dependence of ε‧, ε‧, tanδ, electric modulus (M‧ and M″) and σac of PrBaCoO nanofiber capacitor have been investigated by using impedance spectroscopy method. The obtained experimental results show that the values of ε‧, ε‧, tanδ, M‧, M″ and σac of the PrBaCoO nanofiber capacitor are strongly dependent on frequency of applied bias voltage. The values of ε‧, ε″ and tanδ show a steep decrease with increasing frequency for each forward bias voltage, whereas the values of σac and the electric modulus increase with increasing frequency. The high dispersion in ε‧ and ε″ values at low frequencies may be attributed to the Maxwell-Wagner and space charge polarization. The high values of ε‧ may be due to the interfacial effects within the material, PrBaCoO nanofibers interfacial layer and electron effect. The values of M‧ and M″ reach a maximum constant value corresponding to M∞ ≈ 1/ε∞ due to the relaxation process at high frequencies, but both the values of M‧ and M″ approach almost to zero at low frequencies. The changes in the dielectric and electrical properties with frequency can be also attributed to the existence of Nss and Rs of the capacitors. As a result, the change in the ε‧, ε″, tanδ, M‧, M″ and ac electric conductivity (σac) is a result of restructuring and reordering of charges at the PrBaCoO/n-Si interface under an external electric field or voltage and interface polarization.

Electric power processing, distribution and control for advanced aerospace vehicles.

NASA Technical Reports Server (NTRS)

Krausz, A.; Felch, J. L.

1972-01-01

The results of a current study program to develop a rational basis for selection of power processing, distribution, and control configurations for future aerospace vehicles including the Space Station, Space Shuttle, and high-performance aircraft are presented. Within the constraints imposed by the characteristics of power generation subsystems and the load utilization equipment requirements, the power processing, distribution and control subsystem can be optimized by selection of the proper distribution voltage, frequency, and overload/fault protection method. It is shown that, for large space vehicles which rely on static energy conversion to provide electric power, high-voltage dc distribution (above 100 V dc) is preferable to conventional 28 V dc and 115 V ac distribution per MIL-STD-704A. High-voltage dc also has advantages over conventional constant frequency ac systems in many aircraft applications due to the elimination of speed control, wave shaping, and synchronization equipment.

Electromagnetic augmentation for casting of thin metal sheets

DOEpatents

Hull, J.R.

1987-10-28

Thin metal sheets are cast by magnetically levitating molten metal deposited in a model within a ferromagnetic yoke and between AC conducting coils and linearly displacing the magnetically levitated liquid metal while it is being cooled by the water-cooled walls of the mold to form a solid metal sheet. A conducting shield is electrically coupled to the molten metal sheet to provide a return path for eddy currents induced in the metal sheet by the current in the AC conducting coils. In another embodiment, a DC conducting coil is coupled to the metal sheet for providing a direct current therein which interacts with the magnetic field to levitate the moving metal sheet. Levitation of the metal sheet in both molten and solid forms reduces its contact pressure with the mold walls while maintaining sufficient engagement therebetween to permit efficient conductive cooling by the mold through which a coolant fluid may be circulated. 8 figs.

Motor torque compensation of an induction electric motor by adjusting a slip command during periods of supposed change in motor temperature

DOEpatents

Kelledes, William L.; St. John, Don K.

1992-01-01

The present invention maintains constant torque in an inverter driven AC induction motor during variations in rotor temperature. It is known that the torque output of a given AC induction motor is dependent upon rotor temperature. At rotor temperatures higher than the nominal operating condition the rotor impedance increases, reducing the rotor current and motor torque. In a similar fashion, the rotor impedance is reduced resulting in increased rotor current and motor torque when the rotor temperature is lower than the nominal operating condition. The present invention monitors the bus current from the DC supply to the inverter and adjusts the slip frequency of the inverter drive to maintain a constant motor torque. This adjustment is based upon whether predetermined conditions implying increased rotor temperature or decreased rotor temperature exist for longer that a predetermined interval of time.

Development of AC-coupled, poly-silicon biased, p-on-n silicon strip detectors in India for HEP experiments

NASA Astrophysics Data System (ADS)

Jain, Geetika; Dalal, Ranjeet; Bhardwaj, Ashutosh; Ranjan, Kirti; Dierlamm, Alexander; Hartmann, Frank; Eber, Robert; Demarteau, Marcel

2018-02-01

P-on-n silicon strip sensors having multiple guard-ring structures have been developed for High Energy Physics applications. The study constitutes the optimization of the sensor design, and fabrication of AC-coupled, poly-silicon biased sensors of strip width of 30 μm and strip pitch of 55 μm. The silicon wafers used for the fabrication are of 4 inch n-type, having an average resistivity of 2-5 k Ω cm, with a thickness of 300 μm. The electrical characterization of these detectors comprises of: (a) global measurements of total leakage current, and backplane capacitance; (b) strip and voltage scans of strip leakage current, poly-silicon resistance, interstrip capacitance, interstrip resistance, coupling capacitance, and dielectric current; and (c) charge collection measurements using ALiBaVa setup. The results of the same are reported here.

The metallic sphere in a uniform ac magnetic field: A simple and precise experiment for exploring eddy currents and non-destructive testing

NASA Astrophysics Data System (ADS)

Honke, Michael L.; Bidinosti, Christopher P.

2018-06-01

We describe a very simple experiment that utilizes standard laboratory equipment to measure the electromagnetic response of a metallic sphere exposed to a uniform ac magnetic field. Measurements were made for a variety of non-magnetic and magnetic metals, and in all cases the results fit very well with theory over the four orders of frequency (25 Hz to 102 kHz) explored here. Precise values of magnetic permeability and electrical conductivity can be extracted from fits to the data given the sphere radius only. The same apparatus is also used to explore the effects of geometry on eddy current generation as well as to demonstrate non-destructive testing through measurements on coins of different composition.

Nonlinear spin current generation in noncentrosymmetric spin-orbit coupled systems

NASA Astrophysics Data System (ADS)

Hamamoto, Keita; Ezawa, Motohiko; Kim, Kun Woo; Morimoto, Takahiro; Nagaosa, Naoto

2017-06-01

Spin current plays a central role in spintronics. In particular, finding more efficient ways to generate spin current has been an important issue and has been studied actively. For example, representative methods of spin-current generation include spin-polarized current injections from ferromagnetic metals, the spin Hall effect, and the spin battery. Here, we theoretically propose a mechanism of spin-current generation based on nonlinear phenomena. By using Boltzmann transport theory, we show that a simple application of the electric field E induces spin current proportional to E2 in noncentrosymmetric spin-orbit coupled systems. We demonstrate that the nonlinear spin current of the proposed mechanism is supported in the surface state of three-dimensional topological insulators and two-dimensional semiconductors with the Rashba and/or Dresselhaus interaction. In the latter case, the angular dependence of the nonlinear spin current can be manipulated by the direction of the electric field and by the ratio of the Rashba and Dresselhaus interactions. We find that the magnitude of the spin current largely exceeds those in the previous methods for a reasonable magnitude of the electric field. Furthermore, we show that application of ac electric fields (e.g., terahertz light) leads to the rectifying effect of the spin current, where dc spin current is generated. These findings will pave a route to manipulate the spin current in noncentrosymmetric crystals.

Control of effect on the nucleation rate for hen egg white lysozyme crystals under application of an external ac electric field.

PubMed

Koizumi, H; Uda, S; Fujiwara, K; Nozawa, J

2011-07-05

The effect of an external ac electric field on the nucleation rate of hen egg white lysozyme crystals increased with an increase in the concentration of the precipitant used, which enabled the design of an electric double layer (EDL) formed at the inner surface of the drop in the oil. This is attributed to the thickness of the EDL controlled by the ionic strength of the precipitant used. Control of the EDL formed at the interface between the two phases is important to establishing this novel technique for the crystallization of proteins under the application of an external ac electric field. © 2011 American Chemical Society

Nonlinear system identification of the reduction nickel oxide smelting process in electric arc furnace

NASA Astrophysics Data System (ADS)

Gubin, V.; Firsov, A.

2018-03-01

As the title implies the article describes the nonlinear system identification of the reduction smelting process of nickel oxide in electric arc furnaces. It is suggested that for operational control ratio of components of the charge must be solved the problem of determining the qualitative composition of the melt in real time. The use of 0th harmonic of phase voltage AC furnace as an indirect measure of the melt composition is proposed. Brief description of the mechanism of occurrence and nature of the non-zero 0th harmonic of the AC voltage of the arc is given. It is shown that value of 0th harmonic of the arc voltage is not function of electrical parameters but depends of the material composition of the melt. Processed industrial data are given. Hammerstein-Wiener model is used for description of the dependence of 0th harmonic of the furnace voltage from the technical parameters of melting furnace: the melt composition and current. Recommendations are given about the practical use of the model.

Device for removing foreign objects from anatomic organs

NASA Technical Reports Server (NTRS)

Angulo, Earl D. (Inventor)

1992-01-01

A device is disclosed for removing foreign objects from anatomic organs such as the ear canal or throat. It has a housing shaped like a flashlight, an electrical power source such as a battery or AC power from a wall socket, and a tip extending from the housing. The tip has at least one wire loop made from a shape-memory-effect alloy, such as Nitinol, switchably connected to the electrical power source such that when electric current flows through the wire loop the wire loop heats up and returns to a previously programmed shape such as a curet or tweezers so as to facilitate removal of the foreign object.

``Dissection'' of a Hair Dryer

NASA Astrophysics Data System (ADS)

Eisenstein, Stan; Simpson, Jeff

2008-12-01

The electrical design of the common hair dryer is based almost entirely on relatively simple principles learned in introductory physics classes. Just as biology students dissect a frog to see the principles of anatomy in action, physics students can "dissect" a hair dryer to see how principles of electricity are used in a real system. They can discover how engineers solve problems such as how to vary between low and high heat and fan speed by simply moving the position of a single switch. Principles of alternating versus direct current, series and parallel circuits, electrical safety, voltage dividing, ac rectification, power, and measurement of resistance and continuity all come in to play.

Experimental prototype of an electric elevator

NASA Astrophysics Data System (ADS)

Gaiceanu, M.; Epure, S.; Ciuta, S.

2016-08-01

The main objective is to achieve an elevator prototype powered by a three-phase voltage system via a bidirectional static power converter ac-ac with regenerating capability. In order to diminish the power size of the electric motor up to 1/3 of rated power, the elevator contains two carriages of the same weight, one serving as the payload, and the other as counterweight. Before proper operation of the static power converter, the capacitor must be charged at rated voltage via a precharge circuit. At the moment of stabilizing the DC voltage at nominal value, the AC-AC power converter can operates in the proper limits. The functions of the control structure are: the load control task, speed and torque controls. System includes transducers for current measuring, voltage sensors and encoder. As reserve power sources the hybrid battery-photovoltaic panels are used. The control voltage is modulated by implementing four types of pulse width modulations: sinusoidal, with reduced commutation, third order harmonic insertion, and the space vector modulation. Therefore, the prototype could operates with an increased efficiency, in spite of the existing ones. The experimental results confirm the well design of the chosen solution. The control solution assures bidirectional power flow control, precharge control, and load control and it is implemented on a digital signal processor. The elevator capacity is between 300-450 kg, and it is driven by using a 1.5 kW three-phase asynchronous machine.

Detection of γ-radiation and heavy metals using electrochemical bacterial-based sensor

NASA Astrophysics Data System (ADS)

Al-Shanawa, M.; Nabok, A.; Hashim, A.; Smith, T.; Forder, S.

2013-06-01

The main aim of this work is to develop a simple electrochemical sensor for detection of γ-radiation and heavy metals using bacteria. A series of DC and AC electrical measurements were carried out on samples of two types of bacteria, namely Escherichia coli and Deinococcus radiodurans. As a first step, a correlation between DC and AC electrical conductivity and bacteria concentration in solution was established. The study of the effect of γ-radiation and heavy metal ions (Cd2+) on DC and AC electrical characteristics of bacteria revealed a possibility of pattern recognition of the above inhibition factors.

Particle Segregation in a Flowing Suspension Subject to High-Gradient Strong Electric Fields

NASA Technical Reports Server (NTRS)

Acrivos, Andreas; Qiu, Zhiyong; Khusid, Boris; Markarian, Nikolai

2002-01-01

The widespread use of electro-hydrodynamic devices and processes emphasizes a critical need for developing a comprehensive predictive theory capable of improving our fundamental understanding of the behavior of a suspension subject to an AC electric field and shear, and of facilitating the design and optimization of such devices. The currently favored approach to the qualitative interpretation of the AC field driven manipulation of suspensions is based on a model which considers only the force exerted on a single particle by an external field and neglects the field-induced and hydrodynamic interparticle interactions both being inversely proportional to the interparticle distance raised to the power three. On the other hand, the purpose of the field-induced separation is to concentrate particles in certain regions of a device. This clearly raises the fundamental question regarding the extent to which we can neglect these slow decaying electrical and hydrodynamic collective interactions and rely on the predictions of a single-particle model. Another important issue that still remains open is how to characterize the polarization of a particle exposed to a strong electric field. The presentation will address both these questions. Experiments were conducted in a parallel-plate channel in which a 10(exp -3) (v/v) suspension of heavy, positively polarized Al2O3 spheres was exposed to an AC field under conditions such that the field lines were arranged in the channel cross-section perpendicular to the streamlines of the main flow. To reduce the effects of the gravitational settling of the particles, the channel was slowly rotated (4 rpm) around a horizontal axis. Following the application of a high-gradient strong AC field (approx. kV/mm), the particles were found to move towards both the high-voltage (HV) and grounded (GR) electrodes and to form 'bristles' along their edges.

Electrical power generation by mechanically modulating electrical double layers.

PubMed

Moon, Jong Kyun; Jeong, Jaeki; Lee, Dongyun; Pak, Hyuk Kyu

2013-01-01

Since Michael Faraday and Joseph Henry made their great discovery of electromagnetic induction, there have been continuous developments in electrical power generation. Most people today get electricity from thermal, hydroelectric, or nuclear power generation systems, which use this electromagnetic induction phenomenon. Here we propose a new method for electrical power generation, without using electromagnetic induction, by mechanically modulating the electrical double layers at the interfacial areas of a water bridge between two conducting plates. We find that when the height of the water bridge is mechanically modulated, the electrical double layer capacitors formed on the two interfacial areas are continuously charged and discharged at different phases from each other, thus generating an AC electric current across the plates. We use a resistor-capacitor circuit model to explain the results of this experiment. This observation could be useful for constructing a micro-fluidic power generation system in the near future.

Enhanced cell trapping throughput using DC-biased AC electric field in a dielectrophoresis-based fluidic device with densely packed silica beads.

PubMed

Lewpiriyawong, Nuttawut; Xu, Guolin; Yang, Chun

2018-03-01

This paper presents the use of DC-biased AC electric field for enhancing cell trapping throughput in an insulator-based dielectrophoretic (iDEP) fluidic device with densely packed silica beads. Cell suspension is carried through the iDEP device by a pressure-driven flow. Under an applied DC-biased AC electric field, DEP trapping force is produced as a result of non-uniform electric field induced by the gap of electrically insulating silica beads packed between two mesh electrodes that allow both fluid and cells to pass through. While the AC component is mainly to control the magnitude of DEP trapping force, the DC component generates local electroosmotic (EO) flow in the cavity between the beads and the EO flow can be set to move along or against the main pressure-driven flow. Our experimental and simulation results show that desirable trapping is achieved when the EO flow direction is along (not against) the main flow direction. Using our proposed DC-biased AC field, the device can enhance the trapping throughput (in terms of the flowrate of cell suspension) up to five times while yielding almost the same cell capture rates as compared to the pure AC field case. Additionally, the device was demonstrated to selectively trap dead yeast cells from a mixture of flowing live and dead yeast cells. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

26. Port side of engine room looking forward from aft ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

26. Port side of engine room looking forward from aft bulkhead. This area contains mostly electrical equipment. Two single-cylinder steam-driven dynamos are located near the engine bed, one at right foreground, the other in background. At left in image are a motor-generator set installed to convert DC current (from dynamos) to AC current. Edge-on view of control panel appears near center of image. - Ferry TICONDEROGA, Route 7, Shelburne, Chittenden County, VT

Experimental quantification of the true efficiency of carbon nanotube thin-film thermophones.

PubMed

Bouman, Troy M; Barnard, Andrew R; Asgarisabet, Mahsa

2016-03-01

Carbon nanotube thermophones can create acoustic waves from 1 Hz to 100 kHz. The thermoacoustic effect that allows for this non-vibrating sound source is naturally inefficient. Prior efforts have not explored their true efficiency (i.e., the ratio of the total acoustic power to the electrical input power). All previous works have used the ratio of sound pressure to input electrical power. A method for true power efficiency measurement is shown using a fully anechoic technique. True efficiency data are presented for three different drive signal processing techniques: standard alternating current (AC), direct current added to alternating current (DCAC), and amplitude modulation of an alternating current (AMAC) signal. These signal processing techniques are needed to limit the frequency doubling non-linear effects inherent to carbon nanotube thermophones. Each type of processing affects the true efficiency differently. Using a 72 W(rms) input signal, the measured efficiency ranges were 4.3 × 10(-6) - 319 × 10(-6), 1.7 × 10(-6) - 308 × 10(-6), and 1.2 × 10(-6) - 228 × 10(-6)% for AC, DCAC, and AMAC, respectively. These data were measured in the frequency range of 100 Hz to 10 kHz. In addition, the effects of these processing techniques relative to sound quality are presented in terms of total harmonic distortion.

High-Voltage, High-Power Gaseous Electronics Switch For Electric Grid Power Conversion

NASA Astrophysics Data System (ADS)

Sommerer, Timothy J.

2014-05-01

We are developing a high-voltage, high-power gas switch for use in low-cost power conversion terminals on the electric power grid. Direct-current (dc) power transmission has many advantages over alternating current (ac) transmission, but at present the high cost of ac-dc power interconversion limits the use of dc. The gas switch we are developing conducts current through a magnetized cold cathode plasma in hydrogen or helium to reach practical current densities > 1 A/cm2. Thermal and sputter damage of the cathode by the incident ion flux is a major technical risk, and is being addressed through use of a ``self-healing'' liquid metal cathode (eg, gallium). Plasma conditions and cathode sputtering loss are estimated by analyzing plasma spectral emission. A particle-in-cell plasma model is used to understand various aspects of switch operation, including the conduction phase (where plasma densities can exceed 1013 cm-3), the switch-open phase (where the high-voltage must be held against gas breakdown on the left side of Paschen's curve), and the switching transitions (especially the opening process, which is initiated by forming an ion-matrix sheath adjacent to a control grid). The information, data, or work presented herein was funded in part by the Advanced Research Projects Agency-Energy (ARPA-E), U.S. Department of Energy, under Award Number DE-AR0000298.

AC Electroosmotic Pumping in Nanofluidic Funnels.

PubMed

Kneller, Andrew R; Haywood, Daniel G; Jacobson, Stephen C

2016-06-21

We report efficient pumping of fluids through nanofluidic funnels when a symmetric AC waveform is applied. The asymmetric geometry of the nanofluidic funnel induces not only ion current rectification but also electroosmotic flow rectification. In the base-to-tip direction, the funnel exhibits a lower ion conductance and a higher electroosmotic flow velocity, whereas, in the tip-to-base direction, the funnel has a higher ion conductance and a lower electroosmotic flow velocity. Consequently, symmetric AC waveforms easily pump fluid through the nanofunnels over a range of frequencies, e.g., 5 Hz to 5 kHz. In our experiments, the nanofunnels were milled into glass substrates with a focused ion beam (FIB) instrument, and the funnel design had a constant 5° taper with aspect ratios (funnel tip width to funnel depth) of 0.1 to 1.0. We tracked ion current rectification by current-voltage (I-V) response and electroosmotic flow rectification by transport of a zwitterionic fluorescent probe. Rectification of ion current and electroosmotic flow increased with increasing electric field applied to the nanofunnel. Our results support three-dimensional simulations of ion transport and electroosmotic transport through nanofunnels, which suggest the asymmetric electroosmotic transport stems from an induced pressure at the junction of the nanochannel and nanofunnel tip.

Measurements and tests of HTS bulk material in resistive fault current limiters

NASA Astrophysics Data System (ADS)

Noe, M.; Juengst, K.-P.; Werfel, F. N.; Elschner, S.; Bock, J.; Wolf, A.; Breuer, F.

2002-08-01

The application of superconducting fault current limiters (SCFCL) depends highly on their technical and economical benefits. Therefore it is obvious that the main requirements on the SCFCL are a reliable, fail-safe and rapid current limitation, low losses, and an inexpensive production. As a potential candidate material we have investigated HTS bulk material in resistive fault current limiters. Our report focuses on the E- j-curves, the AC-losses and the quench behaviour of melt cast processed-BSCCO 2212 and melt textured polycrystalline-YBCO 123. Within a temperature range from 64 to 80 K E- j-curves and AC losses of HTS elements were measured. The measurement results show that HTS bulk material meets the SCFCL specifications. In order to avoid hot spots during limitation and to improve mechanical stability a metallic bypass is needed. First test results of the quench behaviour of HTS bulk material with metallic bypass demonstrate safe limitation up to the specified electrical field of 100 V/m.

4-aminopyridine in scala media reversibly alters the cochlear potentials and suppresses electrically evoked oto-acoustic emissions.

PubMed

Kirk, D L; Yates, G K

1998-01-01

Iontophoresis of 4-aminopyridine into scala media of the guinea pig cochlea caused elevation of the thresholds of the compound action potential of the auditory nerve, loss of amplitude of the extracellular cochlear microphonic response (CM), increase in the endocochlear potential (EP) and reduction in the amplitude of electrically evoked oto-acoustic emissions (EEOAEs). These changes were reversible over 10-20 min. The reciprocity of the changes in the CM and the EP was consistent with an interruption of both DC and AC currents through outer hair cells (OHCs), probably by blockade of mechano-electrical transduction (MET) channels in OHCs. Reductions in EEOAEs were consistent with the extrinsically applied generating current entering the OHC via the MET channels. Implications for the activation of OHC electromotility in vivo are discussed.

Graphene-coated coupling coil for AC resistance reduction

DOEpatents

Miller, John M

2014-03-04

At least one graphene layer is formed to laterally surround a tube so that the basal plane of each graphene layer is tangential to the local surface of the tube on which the graphene layer is formed. An electrically conductive path is provided around the tube for providing high conductivity electrical path provided by the basal plane of each graphene layer. The high conductivity path can be employed for high frequency applications such as coupling coils for wireless power transmission to overcome skin depth effects and proximity effects prevalent in high frequency alternating current paths.

The Analysis of a Vortex Type Magnetohydrodynamic Induction Generator

NASA Technical Reports Server (NTRS)

Lengyel, L. L.

1962-01-01

Consideration it is given to the performance to the characteristics of an AC magnetohydrodynamic power generator, A rotating magnetic field is imposed on the vortex flow of an electrically conducting fluid, which is injected tangentially into an annulus formed by two nonconducting concentric cylinders and two nonconducting end plates. A perturbation technique is used to determine the two dimensional velocity and three dimensional electromagnetic field and current distributions. Finally, the generated power, the ohmic losses, the effective power and the electrical efficiency of the converter system are calculated.

Rydberg wave packets in static electric fields initiated with far infrared pulses

NASA Astrophysics Data System (ADS)

Robicheaux, F.; Lankhuijzen, G. M.; Rella, C.; Noordam, L. D.

1998-05-01

We perform experimental and theoretical studies of transitions from bound atomic Rydberg Stark states in a static electric field to autoionizing states. The transitions are induced by a broadband, tunable free electron laser pulse (1-5 ps width). The systematics of the wave packet properties are investigated when the initial state is the lowest energy state or highest energy state of the n-manifold. We show that the recently proposed electron gun is realized for Rb giving an AC electron current with a 20 ps period.

Transient electroosmotic flow induced by AC electric field in micro-channel with patchwise surface heterogeneities.

PubMed

Luo, Win-Jet

2006-03-15

This paper investigates two-dimensional, time-dependent electroosmotic flow driven by an AC electric field via patchwise surface heterogeneities distributed along the micro-channel walls. The time-dependent flow fields through the micro-channel are simulated for various patchwise heterogeneous surface patterns using the backwards-Euler time stepping numerical method. Different heterogeneous surface patterns are found to create significantly different electrokinetic transport phenomena. The transient behavior characteristics of the generated electroosmotic flow are then discussed in terms of the influence of the patchwise surface heterogeneities, the direction of the applied AC electric field, and the velocity of the bulk flow. It is shown that the presence of oppositely charged surface heterogeneities on the micro-channel walls results in the formation of localized flow circulations within the bulk flow. These circulation regions grow and decay periodically in phase with the applied periodic AC electric field intensity. The location and rotational direction of the induced circulations are determined by the directions of the bulk flow velocity and the applied electric field.

Improved SCR ac Motor Controller for Battery Powered Urban Electric Vehicles

NASA Technical Reports Server (NTRS)

Latos, T. S.

1982-01-01

An improved ac motor controller, which when coupled to a standard ac induction motor and a dc propulsion battery would provide a complete electric vehicle power train with the exception of the mechanical transmission and drive wheels was designed. In such a system, the motor controller converts the dc electrical power available at the battery terminals to ac electrical power for the induction motor in response to the drivers commands. The performance requirements of a hypothetical electric vehicle with an upper weight bound of 1590 kg (3500 lb) were used to determine the power rating of the controller. Vehicle acceleration capability, top speed, and gradeability requisites were contained in the Society of Automotive Engineers (SAE) Schedule 227a(d) driving cycle. The important capabilities contained in this driving cycle are a vehicle acceleration requirement of 0 to 72.4 kmph (0 to 45 mph) in 28 seconds a top speed of 88.5 kmph (55 mph), and the ability to negotiate a 10% grade at 48 kmph (30 mph). A 10% grade is defined as one foot of vertical rise per 10 feet of horizontal distance.

AC Electric Field Communication for Human-Area Networking

NASA Astrophysics Data System (ADS)

Kado, Yuichi; Shinagawa, Mitsuru

We have proposed a human-area networking technology that uses the surface of the human body as a data transmission path and uses an AC electric field signal below the resonant frequency of the human body. This technology aims to achieve a “touch and connect” intuitive form of communication by using the electric field signal that propagates along the surface of the human body, while suppressing both the electric field radiating from the human body and mutual interference. To suppress the radiation field, the frequency of the AC signal that excites the transmitter electrode must be lowered, and the sensitivity of the receiver must be raised while reducing transmission power to its minimally required level. We describe how we are developing AC electric field communication technologies to promote the further evolution of a human-area network in support of ubiquitous services, focusing on three main characteristics, enabling-transceiver technique, application-scenario modeling, and communications quality evaluation. Special attention is paid to the relationship between electro-magnetic compatibility evaluation and regulations for extremely low-power radio stations based on Japan's Radio Law.

Theoretical and experimental study of AC electrical conduction mechanism in the low temperature range of p-CuIn3Se5

NASA Astrophysics Data System (ADS)

Essaleh, L.; Amhil, S.; Wasim, S. M.; Marín, G.; Choukri, E.; Hajji, L.

2018-05-01

In the present work, an attempt has been made to study theoretically and experimentally the AC electrical conduction mechanism in disordered semiconducting materials. The key parameter considered in this analysis is the frequency exponent s(ω , T) =( ∂ln(σAC(ω , T))/∂ ln(ω)T , where σAC is the AC electrical conductivity that depends on angular frequency ω and temperature T. In the theoretical part of this work, the effect of the barrier hopping energy, the polaron radius and the characteristic relaxation time is considered. The theoretical models of Quantum Mechanical Tunneling (QMT), Non overlapping Small Polaron Tunneling (NSPT), Overlapping Large Polaron Tunneling (OLPT) and Correlated Barrier Hopping (CBH) are considered to fit experimental data of σAC in p-CuIn3Se5 (p-CIS135) in the low temperature range up to 96 K. Some important parameters, as the polaron radius, the localization length and the barrier hopping energies, are estimated and their temperature and frequency dependence discussed.

AC electrical conductivity and dielectric relaxation studies on n-type organic thin films of N, N‧-Dimethyl-3,4,9,10-perylenedicarboximide (DMPDC)

NASA Astrophysics Data System (ADS)

Qashou, Saleem I.; Darwish, A. A. A.; Rashad, M.; Khattari, Z.

2017-11-01

Both Alternating current (AC) conductivity and dielectric behavior of n-type organic thin films of N, N‧-Dimethyl-3,4,9,10-perylenedicarboximide (DMPDC) have been investigated. Fourier transformation infrared (FTIR) spectroscopy is used for identifying both powder and film bonds which confirm that there are no observed changes in the bonds between the DMPDC powder and evaporated films. The dependence of AC conductivity on the temperature for DMPDC evaporated films was explained by the correlated barrier hopping (CBH) model. The calculated barrier height using CBH model shows a decreasing behavior with increasing temperature. The mechanism of dielectric relaxation was interpreted on the basis of the modulus of the complex dielectric. The calculated activation energy of the relaxation process was found to be 0.055 eV.

electric dipole superconductor in bilayer exciton system

NASA Astrophysics Data System (ADS)

Sun, Qing-Feng; Jiang, Qing-Dong; Bao, Zhi-Qiang; Xie, X. C.

Recently, it was reported that the bilayer exciton systems could exhibit many new phenomena, including the large bilayer counterflow conductivity, the Coulomb drag, etc. These phenomena imply the formation of exciton condensate superfluid state. On the other hand, it is now well known that the superconductor is the condensate superfluid state of the Cooper pairs, which can be viewed as electric monopoles. In other words, the superconductor state is the electric monopole condensate superfluid state. Thus, one may wonder whether there exists electric dipole superfluid state. In this talk, we point out that the exciton in a bilayer system can be considered as a charge neutral electric dipole. And we derive the London-type and Ginzburg-Landau-type equations of electric dipole superconductivity. From these equations, we discover the Meissner-type effect (against spatial variation of magnetic fields), and the dipole current Josephson effect. The frequency in the AC Josephson effect of the dipole current is equal to that in the normal (monopole) superconductor. These results can provide direct evidence for the formation of exciton superfluid state in the bilayer systems and pave new ways to obtain the electric dipole current. We gratefully acknowledge the financial support by NBRP of China (2012CB921303 and 2015CB921102) and NSF-China under Grants Nos. 11274364 and 11574007.

AC-electric field dependent electroformation of giant lipid vesicles.

PubMed

Politano, Timothy J; Froude, Victoria E; Jing, Benxin; Zhu, Yingxi

2010-08-01

Giant vesicles of larger than 5 microm, which have been of intense interest for their potential as drug delivery vehicles and as a model system for cell membranes, can be rapidly formed from a spin-coated lipid thin film under an electric field. In this work, we explore the AC-field dependent electroformation of giant lipid vesicles in aqueous media over a wide range of AC-frequency from 1 Hz to 1 MHz and peak-to-peak field strength from 0.212 V/mm to 40 V/mm between two parallel conducting electrode surfaces. By using fluorescence microscopy, we perform in-situ microscopic observations of the structural evolution of giant vesicles formed from spin-coated lipid films under varied uniform AC-electric fields. The real-time observation of bilayer bulging from the lipid film, vesicle growth and fusing further examine the critical role of AC-induced electroosmotic flow of surrounding fluids for giant vesicle formation. A rich AC-frequency and field strength phase diagram is obtained experimentally to predict the AC-electroformation of giant unilamellar vesicles (GUVs) of l-alpha-phosphatidylcholine, where a weak dependence of vesicle size on AC-frequency is observed at low AC-field voltages, showing decreased vesicle size with a narrowed size distribution with increased AC-frequency. Formation of vesicles was shown to be constrained by an upper field strength of 10 V/mm and an upper AC-frequency of 10 kHz. Within these parameters, giant lipid vesicles were formed predominantly unilamellar and prevalent across the entire electrode surfaces. Copyright 2010 Elsevier B.V. All rights reserved.

A comparative study of electric power distribution systems for spacecraft

NASA Technical Reports Server (NTRS)

Stuart, Thomas A.; King, Roger J.

1990-01-01

The electric power distribution systems for spacecraft are compared concentrating on two interrelated issues: the choice between dc and high frequency ac, and the converter/inverter topology to be used at the power source. The relative merits of dc and ac distribution are discussed. Specific converter and inverter topologies are identified and analyzed in detail for the purpose of detailed comparison. Finally, specific topologies are recommended for use in dc and ac systems.

Design and implementation of co-operative control strategy for hybrid AC/DC microgrids

NASA Astrophysics Data System (ADS)

Mahmud, Rasel

This thesis is mainly divided in two major sections: 1) Modeling and control of AC microgrid, DC microgrid, Hybrid AC/DC microgrid using distributed co-operative control, and 2) Development of a four bus laboratory prototype of an AC microgrid system. At first, a distributed cooperative control (DCC) for a DC microgrid considering the state-of-charge (SoC) of the batteries in a typical plug-in-electric-vehicle (PEV) is developed. In DC microgrids, this methodology is developed to assist the load sharing amongst the distributed generation units (DGs), according to their ratings with improved voltage regulation. Subsequently, a DCC based control algorithm for AC microgrid is also investigated to improve the performance of AC microgrid in terms of power sharing among the DGs, voltage regulation and frequency deviation. The results validate the advantages of the proposed methodology as compared to traditional droop control of AC microgrid. The DCC-based control methodology for AC microgrid and DC microgrid are further expanded to develop a DCC-based power management algorithm for hybrid AC/DC microgrid. The developed algorithm for hybrid microgrid controls the power flow through the interfacing converter (IC) between the AC and DC microgrids. This will facilitate the power sharing between the DGs according to their power ratings. Moreover, it enables the fixed scheduled power delivery at different operating conditions, while maintaining good voltage regulation and improved frequency profile. The second section provides a detailed explanation and step-by-step design and development of an AC/DC microgrid testbed. Controllers for the three-phase inverters are designed and tested on different generation units along with their corresponding inductor-capacitor-inductor (LCL) filters to eliminate the switching frequency harmonics. Electric power distribution line models are developed to form the microgrid network topology. Voltage and current sensors are placed in the proper positions to achieve a full visibility over the microgrid. A running average filter (RAF) based enhanced phase-locked-loop (EPLL) is designed and implemented to extract frequency and phase angle information. A PLL-based synchronizing scheme is also developed to synchronize the DGs to the microgrid. The developed laboratory prototype runs on dSpace platform for real time data acquisition, communication and controller implementation.

Electrical modulus and dielectric behavior of Cr3+ substituted Mg-Zn nanoferrites

NASA Astrophysics Data System (ADS)

Mansour, S. F.; Abdo, M. A.

2017-04-01

The dielectric parameters and ac electrical conductivity of Mg0.8Zn0.2CrxFe2-xO4; (0≤x≤0.025) nanoferrites synthesized citrate-nitrate auto-combustion method were studied using the complex impedance technique in the frequency and temperature ranges 4 Hz-5 MHz and 303-873 K respectively. Hopping of charge carriers plus interfacial polarization could interpret the behaviors of dielectric constant (ε‧), dielectric loss tangent (tanδ) and ac electrical conductivity (σac) with frequency, temperatures and composition. The up-normal behavior observed in tanδ trend with temperatures confirms the presence of relaxation loss (dipoles losses). Correlated barrier hopping (CBH) of electron is the conduction mechanism of the investigated nanoferrites. Cole-Cole plots at different temperatures emphasize the main role of grain and grain boundaries in the properties of the investigated nanoferrites. Cr3+ substitution can control the dielectric parameters and ac electrical conductivity of Mg-Zn nanoferrites making it candidates for versatile applications.

A study of some features of ac and dc electric power systems for a space station

NASA Technical Reports Server (NTRS)

Hanania, J. I.

1983-01-01

This study analyzes certain selected topics in rival dc and high frequency ac electric power systems for a Space Station. The interaction between the Space Station and the plasma environment is analyzed, leading to a limit on the voltage for the solar array and a potential problem with resonance coupling at high frequencies. Certain problems are pointed out in the concept of a rotary transformer, and further development work is indicated in connection with dc circuit switching, special design of a transmission conductor for the ac system, and electric motors. The question of electric shock hazards, particularly at high frequency, is also explored. and a problem with reduced skin resistance and therefore increased hazard with high frequency ac is pointed out. The study concludes with a comparison of the main advantages and disadvantages of the two rival systems, and it is suggested that the choice between the two should be made after further studies and development work are completed.

The electrical and dielectric properties of the Au/Ti/HfO2/n-GaAs structures

NASA Astrophysics Data System (ADS)

Karabulut, Abdulkerim; Türüt, Abdulmecit; Karataş, Şükrü

2018-04-01

In this work, temperature dependent electrical and dielectric properties of the Au/Ti/HfO2/n-GaAs structures were investigated using capacitance-voltage (C-V) and conductance-voltage (G-V) measurements in the temperature range of 60-320 K by steps of 20 K at 1 MHz. The dielectric constant (ε‧), dielectric loss (ε″), dielectric loss tangent (tanδ) and ac electrical conductivities (σac) have been calculated as a function of temperature. These values of the ε‧, ε″, tanδ and σac have been found to be 2.272, 5.981, 2.631 and 3.32 × 10-6 (Ω-1cm-1) at 80 K, respectively, 1.779, 2.315, 1.301 and 1.28 × 10-6 (Ω-1cm-1), respectively at 320 K. These decrease of the dielectric parameters (ε‧, ε″, tanδ and σac) have been observed at high temperatures. The experimental results show that electrical and dielectric properties are strongly temperature and bias voltage dependent.

Rigor and reproducibility in research with transcranial electrical stimulation: An NIMH-sponsored workshop.

PubMed

Bikson, Marom; Brunoni, Andre R; Charvet, Leigh E; Clark, Vincent P; Cohen, Leonardo G; Deng, Zhi-De; Dmochowski, Jacek; Edwards, Dylan J; Frohlich, Flavio; Kappenman, Emily S; Lim, Kelvin O; Loo, Colleen; Mantovani, Antonio; McMullen, David P; Parra, Lucas C; Pearson, Michele; Richardson, Jessica D; Rumsey, Judith M; Sehatpour, Pejman; Sommers, David; Unal, Gozde; Wassermann, Eric M; Woods, Adam J; Lisanby, Sarah H

Neuropsychiatric disorders are a leading source of disability and require novel treatments that target mechanisms of disease. As such disorders are thought to result from aberrant neuronal circuit activity, neuromodulation approaches are of increasing interest given their potential for manipulating circuits directly. Low intensity transcranial electrical stimulation (tES) with direct currents (transcranial direct current stimulation, tDCS) or alternating currents (transcranial alternating current stimulation, tACS) represent novel, safe, well-tolerated, and relatively inexpensive putative treatment modalities. This report seeks to promote the science, technology and effective clinical applications of these modalities, identify research challenges, and suggest approaches for addressing these needs in order to achieve rigorous, reproducible findings that can advance clinical treatment. The National Institute of Mental Health (NIMH) convened a workshop in September 2016 that brought together experts in basic and human neuroscience, electrical stimulation biophysics and devices, and clinical trial methods to examine the physiological mechanisms underlying tDCS/tACS, technologies and technical strategies for optimizing stimulation protocols, and the state of the science with respect to therapeutic applications and trial designs. Advances in understanding mechanisms, methodological and technological improvements (e.g., electronics, computational models to facilitate proper dosing), and improved clinical trial designs are poised to advance rigorous, reproducible therapeutic applications of these techniques. A number of challenges were identified and meeting participants made recommendations made to address them. These recommendations align with requirements in NIMH funding opportunity announcements to, among other needs, define dosimetry, demonstrate dose/response relationships, implement rigorous blinded trial designs, employ computational modeling, and demonstrate target engagement when testing stimulation-based interventions for the treatment of mental disorders. Published by Elsevier Inc.

Rigor and reproducibility in research with transcranial electrical stimulation: An NIMH-sponsored workshop

PubMed Central

Bikson, Marom; Brunoni, Andre R.; Charvet, Leigh E.; Clark, Vincent P.; Cohen, Leonardo G.; Deng, Zhi-De; Dmochowski, Jacek; Edwards, Dylan J.; Frohlich, Flavio; Kappenman, Emily S.; Lim, Kelvin O.; Loo, Colleen; Mantovani, Antonio; McMullen, David P.; Parra, Lucas C.; Pearson, Michele; Richardson, Jessica D.; Rumsey, Judith M.; Sehatpour, Pejman; Sommers, David; Unal, Gozde; Wassermann, Eric M.; Woods, Adam J.; Lisanby, Sarah H.

2018-01-01

Background Neuropsychiatric disorders are a leading source of disability and require novel treatments that target mechanisms of disease. As such disorders are thought to result from aberrant neuronal circuit activity, neuromodulation approaches are of increasing interest given their potential for manipulating circuits directly. Low intensity transcranial electrical stimulation (tES) with direct currents (transcranial direct current stimulation, tDCS) or alternating currents (transcranial alternating current stimulation, tACS) represent novel, safe, well-tolerated, and relatively inexpensive putative treatment modalities. Objective This report seeks to promote the science, technology and effective clinical applications of these modalities, identify research challenges, and suggest approaches for addressing these needs in order to achieve rigorous, reproducible findings that can advance clinical treatment. Methods The National Institute of Mental Health (NIMH) convened a workshop in September 2016 that brought together experts in basic and human neuroscience, electrical stimulation biophysics and devices, and clinical trial methods to examine the physiological mechanisms underlying tDCS/tACS, technologies and technical strategies for optimizing stimulation protocols, and the state of the science with respect to therapeutic applications and trial designs. Results Advances in understanding mechanisms, methodological and technological improvements (e.g., electronics, computational models to facilitate proper dosing), and improved clinical trial designs are poised to advance rigorous, reproducible therapeutic applications of these techniques. A number of challenges were identified and meeting participants made recommendations made to address them. Conclusions These recommendations align with requirements in NIMH funding opportunity announcements to, among other needs, define dosimetry, demonstrate dose/response relationships, implement rigorous blinded trial designs, employ computational modeling, and demonstrate target engagement when testing stimulation-based interventions for the treatment of mental disorders. PMID:29398575

Simultaneous measurement of skin potential and conductance in electrodermal response monitoring

NASA Astrophysics Data System (ADS)

Jabbari, A.; Johnsen, B.; Grimnes, S.; Martinsen, Ø. G.

2010-04-01

Measurement of electrodermal activity (EDA) has been an important tool in psychophysiological research. The emotional sweat activity is very sensitive to psychological stimuli or conditions. The changes are easily detected by means of electrical measurements and since the sweat ducts are predominantly resistive, a low-frequency conductance measurement is appropriate for measurement of skin conductance in electrodermal response. The main purpose of this study was to develop a measuring system where DC current was replaced by a small AC current in a system so the DC potential and AC conductance could be measured simultaneously at the same skin site. A small, battery operated, PDA based instrument has been developed. The preliminary results of this ongoing study show that there is additional information in the DC potential channel and that different stimuli seem to produce slightly different response patterns.

Investigation of pumping mechanism for non-Newtonian blood flow with AC electrothermal forces in a microchannel by hybrid boundary element method and immersed boundary-lattice Boltzmann method.

PubMed

Ren, Qinlong

2018-02-10

Efficient pumping of blood flow in a microfluidic device is essential for rapid detection of bacterial bloodstream infections (BSI) using alternating current (AC) electrokinetics. Compared with AC electro-osmosis (ACEO) phenomenon, the advantage of AC electrothermal (ACET) mechanism is its capability of pumping biofluids with high electrical conductivities at a relatively high AC voltage frequency. In the current work, the microfluidic pumping of non-Newtonian blood flow using ACET forces is investigated in detail by modeling its multi-physics process with hybrid boundary element method (BEM) and immersed boundary-lattice Boltzmann method (IB-LBM). The Carreau-Yasuda model is used to simulate the realistic rheological behavior of blood flow. The ACET pumping efficiency of blood flow is studied in terms of different AC voltage magnitudes and frequencies, thermal boundary conditions of electrodes, electrode configurations, channel height, and the channel length per electrode pair. Besides, the effect of rheological behavior on the blood flow velocity is theoretically analyzed by comparing with the Newtonian fluid flow using scaling law analysis under the same physical conditions. The results indicate that the rheological behavior of blood flow and its frequency-dependent dielectric property make the pumping phenomenon of blood flow different from that of the common Newtonian aqueous solutions. It is also demonstrated that using a thermally insulated electrode could enhance the pumping efficiency dramatically. Besides, the results conclude that increasing the AC voltage magnitude is a more economical pumping approach than adding the number of electrodes with the same energy consumption when the Joule heating effect is acceptable. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development of 66 kV class REBCO superconducting cable

NASA Astrophysics Data System (ADS)

Ohya, M.; Masuda, T.; Amemiya, N.; Ishiyama, A.; Ohkuma, T.

Sumitomo Electric Industries (SEI) has been involved in the development of 66 kV/5 kA-class HTS cables using REBCO wires. One of the technical targets was to reduce the AC loss to less than 2 W/m/phase at 5 kA. SEI developed a clad-type textured metal substrate with lower magnetization loss than NiW substrates. REBCO wires of 30 mm wide were slit into 4 mm-wide strips, and these strips were wound spirally on a former with small gaps. The measured AC loss of the manufactured cable was 1.8 W/m/phase at 5 kA, achieving the AC loss goal. Another important target was to manage fault current. The copper protection layers were designed based on simulation findings. Fault current tests (max. 31.5 kA, 2 sec) showed that the designed HTS cable has the required withstanding performance. The development of the elemental technologies was finished on schedule, and a 15 m-long HTS cable system will be constructed to demonstrate that it meets all the required specifications.

Study of dielectric relaxation and AC conductivity of InP:S single crystal

NASA Astrophysics Data System (ADS)

El-Nahass, M. M.; Ali, H. A. M.; El-Shazly, E. A.

2012-07-01

The dielectric relaxation and AC conductivity of InP:S single crystal were studied in the frequency range from 100 to 5.25 × 105 Hz and in the temperature range from 296 to 455 K. The dependence of the dielectric constant (ɛ1) and the dielectric loss (ɛ2) on both frequency and temperature was investigated. Since no peak was observed on the dielectric loss, we used a method based on the electric modulus to evaluate the activation energy of the dielectric relaxation. Scaling of the electric modulus spectra showed that the charge transport dynamics is independent of temperature. The AC conductivity (σAC) was found to obey the power law: Aωs. Analysis of the AC conductivity data and the frequency exponent showed that the correlated barrier hopping (CBH) model is the dominant mechanism for the AC conduction. The variation of AC conductivity with temperature at different frequencies showed that σAC is a thermally activated process.

Strength Testing in the Air Force: Current Processes and Suggestions for Improvements

DTIC Science & Technology

2014-01-01

Electrical Power Production 4Y0X1 Dental Assistant 3E1X1 Heating, Ventilation, AC, & Refrigeration 4Y0X2 Dental Laboratory 3E2X1 Pavements and...MAFS AFE SF AFU-AS EOD Push 29 -- 22 -- 113 72 111 62 Pull 22 -- 21 -- -- -- 82 -- Cary 19 57 20 -- 188 120 77 -- Hold -- -- -- -- -- -- 64

Transcranial electrical stimulation of the occipital cortex during visual perception modifies the magnitude of BOLD activity: A combined tES-fMRI approach.

PubMed

Alekseichuk, Ivan; Diers, Kersten; Paulus, Walter; Antal, Andrea

2016-10-15

The aim of this study was to investigate if the blood oxygenation level-dependent (BOLD) changes in the visual cortex can be used as biomarkers reflecting the online and offline effects of transcranial electrical stimulation (tES). Anodal transcranial direct current stimulation (tDCS) and 10Hz transcranial alternating current stimulation (tACS) were applied for 10min duration over the occipital cortex of healthy adults during the presentation of different visual stimuli, using a crossover, double-blinded design. Control experiments were also performed, in which sham stimulation as well as another electrode montage were used. Anodal tDCS over the visual cortex induced a small but significant further increase in BOLD response evoked by a visual stimulus; however, no aftereffect was observed. Ten hertz of tACS did not result in an online effect, but in a widespread offline BOLD decrease over the occipital, temporal, and frontal areas. These findings demonstrate that tES during visual perception affects the neuronal metabolism, which can be detected with functional magnetic resonance imaging (fMRI). Copyright © 2016 Elsevier Inc. All rights reserved.

Simple circuit monitors "third wire" in ac lines

NASA Technical Reports Server (NTRS)

Kojima, T. T.; Stuck, D. E.

1980-01-01

Device detects interruption of ground connection in three-wire electrical equipment and shuts off ac power to prevent shock hazard. Silicon-controlled rectifiers detect floating ground, and deenergize optoelectric relays thereby breaking power connections. Circuit could be incorporated into hand tools, appliances, and other electrical equipment.

Eddy current modeling in linear and nonlinear multifilamentary composite materials

NASA Astrophysics Data System (ADS)

Menana, Hocine; Farhat, Mohamad; Hinaje, Melika; Berger, Kevin; Douine, Bruno; Lévêque, Jean

2018-04-01

In this work, a numerical model is developed for a rapid computation of eddy currents in composite materials, adaptable for both carbon fiber reinforced polymers (CFRPs) for NDT applications and multifilamentary high temperature superconductive (HTS) tapes for AC loss evaluation. The proposed model is based on an integro-differential formulation in terms of the electric vector potential in the frequency domain. The high anisotropy and the nonlinearity of the considered materials are easily handled in the frequency domain.

Hardware Model Of A Shipboard Zonal Electrical Distribution System (ZEDS): Alternating Current/Direct Current (AC/DC)

DTIC Science & Technology

2010-06-01

essential to fostering the loyalty , dedication and pride that enables the diverse student population within your department to be the very best systems...that I have enjoyed in my short time with you. Without you in my life, to share my success, I could not have ever achieved the level of satisfaction ...used. A typical wall mounted light switch is a single pole single throw switch. A common industrial motor start switch is a three pole single throw

Hardware Model of a Shipboard Zonal Electrical Distribution System (ZEDS): Alternating Current/Direct Current (AC/DC)

DTIC Science & Technology

2010-06-01

perfect example on how to lead, manage and strive for excellence in every aspect of your life. Your leadership is essential to fostering the loyalty ...share my success, I could not have ever achieved the level of satisfaction and enjoyment that I have. You will never understand how helpful the...A typical wall mounted light switch is a single pole single throw switch. A common industrial motor start switch is a three pole single throw switch

Characterizing fiber-reinforced composite structures using AC-impedance spectroscopy (AC-IS)

NASA Astrophysics Data System (ADS)

Woo, Leta Y.

Property enhancement in composites depends largely on the reinforcement. For fiber-reinforced composites, the distribution of fibers is crucial in determining the electrical and mechanical performance. Image analysis methods for characterization can be time-consuming and/or destructive. This work explores the capability of AC-impedance spectroscopy (AC-IS), an electrical measurement technique, to serve as a rapid, non-destructive tool for characterizing composite microstructure. The composite requirements include a filler that is electrically conducting or semi-conducting with higher conductivity than the matrix, and a high-impedance interface or coating between the filler and the matrix. To establish an AC-IS characterization method, cement-matrix composites with steel reinforcement were employed as both a technologically important and a model system to investigate how fibers affect the electrical response. Beginning with spherical particulates and then fibers, composites were examined using composite theory and an "intrinsic conductivity" approach. The intrinsic conductivity approach applies to composites with low volume fractions of fibers (i.e., in the dilute regime) and relates how the composite conductivity varies relative to the matrix as a function of volume fraction. A universal equivalent circuit model was created to understand the AC-IS response of composites based on the geometry and volume fraction of the filler. Deviation from predicted behavior was assessed using a developed f-function, which quantifies how fibers contribute to the overall electrical response of the composite. Using the f-function, an AC-IS method for investigating fiber dispersion was established to characterize alignment, settling/segregation, and aggregation. Alignment was investigated using measurements made in three directions. A point-probe technique characterized settling and/or large-scale inhomogeneous mixing in samples. Aggregation was quantified using a "dispersion factor" that compared theoretical with measured values and served as an upper limit for how well the fibers were dispersed. The AC-IS method was then extended to two different cement-matrix composite systems, low resistivity fresh-paste cement composites (confirmed by time domain reflectometry) and high resistivity cement composites, both of which required additional analysis to apply the AC-IS characterization method.

Multiple piezo-patch energy harvesters on a thin plate with respective AC-DC conversion

NASA Astrophysics Data System (ADS)

Aghakhani, Amirreza; Basdogan, Ipek

2018-03-01

Piezoelectric patch energy harvesters can be directly integrated to plate-like structures which are widely used in automotive, marine and aerospace applications, to convert vibrational energy to electrical energy. This paper presents two different AC-DC conversion techniques for multiple patch harvesters, namely single rectifier and respective rectifiers. The first case considers all the piezo-patches are connected in parallel to a single rectifier, whereas in the second case, each harvester is respectively rectified and then connected in parallel to a smoothing capacitor and a resistive load. The latter configuration of AC-DC conversion helps to avoid the electrical charge cancellation which is a problem with the multiple harvesters attached to different locations of the host plate surface. Equivalent circuit model of the multiple piezo-patch harvesters is developed in the SPICE software to simulate the electrical response. The system parameters are obtained from the modal analysis solution of the plate. Simulations of the voltage frequency response functions (FRFs) for the standard AC input - AC output case are conducted and validated by experimental data. Finally, for the AC input - DC output case, numerical simulation and experimental results of the power outputs of multiple piezo-patch harvesters with multiple AC-DC converters are obtained for a wide range of resistive loads and compared with the same array of harvesters connected to a single AC-DC converter.

Single-Walled Carbon Nanotubes Probed with Insulator-Based Dielectrophoresis

PubMed Central

2017-01-01

Single-walled carbon nanotubes (SWNTs) offer unique electrical and optical properties. Common synthesis processes yield SWNTs with large length polydispersity (several tens of nanometers up to centimeters) and heterogeneous electrical and optical properties. Applications often require suitable selection and purification. Dielectrophoresis is one manipulation method for separating SWNTs based on dielectric properties and geometry. Here, we present a study of surfactant and single-stranded DNA-wrapped SWNTs suspended in aqueous solutions manipulated by insulator-based dielectrophoresis (iDEP). This method allows us to manipulate SWNTs with the help of arrays of insulating posts in a microfluidic device around which electric field gradients are created by the application of an electric potential to the extremities of the device. Semiconducting SWNTs were imaged during dielectrophoretic manipulation with fluorescence microscopy making use of their fluorescence emission in the near IR. We demonstrate SWNT trapping at low-frequency alternating current (AC) electric fields with applied potentials not exceeding 1000 V. Interestingly, suspended SWNTs showed both positive and negative dielectrophoresis, which we attribute to their ζ potential and the suspension properties. Such behavior agrees with common theoretical models for nanoparticle dielectrophoresis. We further show that the measured ζ potentials and suspension properties are in excellent agreement with a numerical model predicting the trapping locations in the iDEP device. This study is fundamental for the future application of low-frequency AC iDEP for technological applications of SWNTs. PMID:29131586

Transcranial electric stimulation for the investigation of speech perception and comprehension

PubMed Central

Zoefel, Benedikt; Davis, Matthew H.

2017-01-01

ABSTRACT Transcranial electric stimulation (tES), comprising transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS), involves applying weak electrical current to the scalp, which can be used to modulate membrane potentials and thereby modify neural activity. Critically, behavioural or perceptual consequences of this modulation provide evidence for a causal role of neural activity in the stimulated brain region for the observed outcome. We present tES as a tool for the investigation of which neural responses are necessary for successful speech perception and comprehension. We summarise existing studies, along with challenges that need to be overcome, potential solutions, and future directions. We conclude that, although standardised stimulation parameters still need to be established, tES is a promising tool for revealing the neural basis of speech processing. Future research can use this method to explore the causal role of brain regions and neural processes for the perception and comprehension of speech. PMID:28670598

Performance Analysis of a Static Synchronous Compensator (STATCOM)

NASA Astrophysics Data System (ADS)

Kambey, M. M.; Ticoh, J. D.

2018-02-01

Reactive power and voltage are some of the problems in electric power supply and A Gate Turn Off (GTO) Static Synchronous Compensator (STATCOM) is one of the type of FACTS with shunt which can supply variable reactive power and regulate the voltage of the bus where it is connected. This study only discuss about the performance characteristic of the three phase six-pulse STATCOM by analysing the current wave flowing through DC Capacitor which depend on switching current and capacitor voltage wave. Simulation methods used in this research is started with a mathematical analysis of the ac current, dc voltage and current equations that pass STATCOM from a literature. The result shows the presence of the capacitor voltage ripple also alters the ac current waveform, even though the errors to be not very significant and the constraint of the symmetry circuit is valid if the source voltages have no zero sequence components and the impedances in all the three phases are identical. There for to improve STATCOM performance it is necessary to use multi-pulse 12, 24, 36, 48 or more, and/or with a multilevel converter.

Neural Network Analysis of Musculoskeletal Responses to Electrical AC-Stimulus

DTIC Science & Technology

2001-10-25

FAM, SOM I. INTRODUCTION Various kinds of electrical measurements have been used to investigate the human body, including the mechanical or chemical...measurements were obtained from five points; namely, the patients’ wrists, ankles and back. The electrodes of an IF Electrotherapy unit [5] were attached...musculoskeletal responses to electrical AC-stimulus M. Hannula1, E. Alasaarela2 , J. Laitinen1 1Institute of Technology , Oulu Polytechnic, Oulu, Finland

Introducing AC Inductive Reactance with a Power Tool

ERIC Educational Resources Information Center

Bryant, Wesley; Baker, Blane

2016-01-01

The concept of reactance in AC electrical circuits is often non-intuitive and difficult for students to grasp. In order to address this lack of conceptual understanding, classroom exercises compare the predicted resistance of a power tool, based on electrical specifications, to measured resistance. Once students discover that measured resistance…

Exposure of unionid mussels to electric current: Assessing risks associated with electrofishing

USGS Publications Warehouse

Holliman, F.M.; Kwak, T.J.; Cope, W.G.; Levine, Jay F.

2007-01-01

Electric current is routinely applied in freshwater for scientific sampling of fish populations (i.e., electrofishing). Freshwater mussels (families Margaritiferidae and Unionidae) are distributed worldwide, but their recent declines in diversity and abundance constitute an imperilment of global significance. Freshwater mussels are not targeted for capture by electrofishing, and any exposure to electric current is unintentional. The effects of electric shock are not fully understood for mussels but could disrupt vital physiological processes and represent an additional threat to their survival. In a controlled laboratory environment, we examined the consequences of exposure to two typical electrofishing currents, 60-Hz pulsed DC and 60-Hz AC, for the survival of adult and early life stages of three unionid species; we included fish as a quality control measure. The outcomes suggest that electrical exposure associated with typical electrofishing poses little direct risk to freshwater mussels. That is, adult mussel survival and righting behaviors (indicators of sublethal stress) were not adversely affected by electrical exposure. Glochidia (larvae that attach to and become parasites on fish gills or fins) showed minimal immediate reduction in viability after exposure. Metamorphosis from glochidia to free-living juvenile mussels was not impaired after electric current simulated capture-prone behaviors (stunning) in infested host fish. In addition, the short-term survival of juvenile mussels was not adversely influenced by exposure to electric current. Any minimal risk to imperiled mussels must be weighed at the population level against the benefits gained by using the gear for scientific sampling of fish in the same waters. However, scientists sampling fish by electrofishing should be aware of mussel reproductive periods and processes in order to minimize the harmful effects to host fish, especially in areas where mussel conservation is a concern. ?? Copyright by the American Fisheries Society 2007.

The Design of Operational Amplifier for Low Voltage and Low Current Sound Energy Harvesting System

NASA Astrophysics Data System (ADS)

Fang, Liew Hui; Rahim, Rosemizi Bin Abd; Isa, Muzamir; Idris Syed Hassan, Syed; Ismail, Baharuddin Bin

2018-03-01

The objective of this paper is to design a combination of an operational amplifier (op-amp) with a rectifier used in an alternate current (ac) to direct current (dc) power conversion. The op-amp was designed to specifically work at low voltage and low current for a sound energy harvesting system. The goal of the op-amp design with adjustable gain was to control output voltage based on the objectives of the experiment conducted. The op-amp was designed for minimum power dissipation performance, with the means of increasing the output current when receiving a large amount of load. The harvesting circuits which designed further improved the power output efficiency by shortening the fully charged time needed by a supercapacitor bank. It can fulfil the long-time power demands for low power device. Typically, a small amount of energy sources were converted to electricity and stored in the supercapacitor bank, which was built by 10 pieces of capacitors with 0.22 F each, arranged in parallel connection. The highest capacitance was chosen based on the characteristic that have the longest discharging time to support the applications of a supercapacitor bank. Testing results show that the op-amp can boost the low input ac voltage (∼3.89 V) to high output dc voltage (5.0 V) with output current of 30 mA and stored the electrical energy in a big supercapacitor bank having a total of 2.2 F, effectively. The measured results agree well with the calculated results.

Requirements for a Hydrogen Powered All-Electric Manned Helicopter

NASA Technical Reports Server (NTRS)

Datta, Anubhav

2012-01-01

The objective of this paper is to set propulsion system targets for an all-electric manned helicopter of ultra-light utility class to achieve performance comparable to combustion engines. The approach is to begin with a current two-seat helicopter (Robinson R 22 Beta II-like), design an all-electric power plant as replacement for its existing piston engine, and study performance of the new all-electric aircraft. The new power plant consists of high-pressure Proton Exchange Membrane fuel cells, hydrogen stored in 700 bar type-4 tanks, lithium-ion batteries, and an AC synchronous permanent magnet motor. The aircraft and the transmission are assumed to remain the same. The paper surveys the state of the art in each of these areas, synthesizes a power plant using best available technologies in each, examines the performance achievable by such a power plant, identifies key barriers, and sets future technology targets to achieve performance at par with current internal combustion engines.

DC bias effect on alternating current electrical conductivity of poly(ethylene terephthalate)/alumina nanocomposites

NASA Astrophysics Data System (ADS)

Nikam, Pravin N.; Deshpande, Vineeta D.

2016-05-01

Polymer nanocomposites based on metal oxide (ceramic) nanoparticles are a new class of materials with unique properties and designed for various applications such as electronic device packaging, insulation, fabrication and automotive industries. Poly(ethylene terephthalate) (PET)/alumina (Al2O3) nanocomposites with filler content between 1 wt% and 5 wt% were prepared by melt compounding method using co-rotating twin screw extruder and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and precision LCR meter techniques. The results revealed that proper uniform dispersion at lower content up to 2 wt% of nano-alumina observed by using TEM. Aggregation of nanoparticles was observed at higher content of alumina examined by using SEM and TEM. The frequency dependences of the alternating current (AC) conductivity (σAC) of PET/alumina nanocomposites on the filler content and DC bias were investigated in the frequency range of 20Hz - 1MHz. The results showed that the AC and direct current (DC) conductivity increases with increasing DC bias and nano-alumina content upto 3 wt%. It follows the Jonscher's universal power law of solids. It revealed that σAC of PET/alumina nanocomposites can be well characterized by the DC conductivity (σDC), critical frequency (ωc), critical exponent of the power law (s). Roll of DC bias potential led to an increase of DC conductivity (σDC) due to the creation of additional conducting paths with the polymer nanocomposites and percolation behavior achieved through co-continuous morphology.

The ac propulsion system for an electric vehicle, phase 1

NASA Astrophysics Data System (ADS)

Geppert, S.

1981-08-01

A functional prototype of an electric vehicle ac propulsion system was built consisting of a 18.65 kW rated ac induction traction motor, pulse width modulated (PWM) transistorized inverter, two speed mechanically shifted automatic transmission, and an overall drive/vehicle controller. Design developmental steps, and test results of individual components and the complex system on an instrumented test frame are described. Computer models were developed for the inverter, motor and a representative vehicle. A preliminary reliability model and failure modes effects analysis are given.

The ac propulsion system for an electric vehicle, phase 1

NASA Technical Reports Server (NTRS)

Geppert, S.

1981-01-01

A functional prototype of an electric vehicle ac propulsion system was built consisting of a 18.65 kW rated ac induction traction motor, pulse width modulated (PWM) transistorized inverter, two speed mechanically shifted automatic transmission, and an overall drive/vehicle controller. Design developmental steps, and test results of individual components and the complex system on an instrumented test frame are described. Computer models were developed for the inverter, motor and a representative vehicle. A preliminary reliability model and failure modes effects analysis are given.

Optimal management of batteries in electric systems

DOEpatents

Atcitty, Stanley; Butler, Paul C.; Corey, Garth P.; Symons, Philip C.

2002-01-01

An electric system including at least a pair of battery strings and an AC source minimizes the use and maximizes the efficiency of the AC source by using the AC source only to charge all battery strings at the same time. Then one or more battery strings is used to power the load while management, such as application of a finish charge, is provided to one battery string. After another charge cycle, the roles of the battery strings are reversed so that each battery string receives regular management.

EV drivetrain inverter with V/HZ optimization

DOEpatents

Gritter, David J.; O'Neil, Walter K.

1986-01-01

An inverter (34) which provides power to an A.C. machine (28) is controlled by a circuit (36) employing PWM control strategy whereby A.C. power is supplied to the machine at a preselectable frequency and preselectable voltage. This is accomplished by the technique of waveform notching in which the shapes of the notches are varied to determine the average energy content of the overall waveform. Through this arrangement, the operational efficiency of the A.C. machine is optimized. The control circuit includes a micro-computer which calculates optimized machine control data signals from various parametric inputs and during steady state load conditions, seeks a best V/HZ ratio to minimize battery current drawn (system losses) from a D.C. power source (32). In the preferred embodiment, the present invention is incorporated within an electric vehicle (10) employing a 144 VDC battery pack and a three-phase induction motor (18).

Unidirectional oxide hetero-interface thin-film diode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Youngmin; Lee, Eungkyu; Lee, Jinwon

2015-10-05

The unidirectional thin-film diode based on oxide hetero-interface, which is well compatible with conventional thin-film fabrication process, is presented. With the metal anode/electron-transporting oxide (ETO)/electron-injecting oxide (EIO)/metal cathode structure, it exhibits that electrical currents ohmically flow at the ETO/EIO hetero-interfaces for only positive voltages showing current density (J)-rectifying ratio of ∼10{sup 5} at 5 V. The electrical properties (ex, current levels, and working device yields) of the thin-film diode (TFD) are systematically controlled by changing oxide layer thickness. Moreover, we show that the oxide hetero-interface TFD clearly rectifies an AC input within frequency (f) range of 10{sup 2} Hz < f < 10{sup 6} Hz, providing amore » high feasibility for practical applications.« less

Superconductor disks and cylinders in an axial magnetic field: II. Nonlinear and linear ac susceptibilities

NASA Astrophysics Data System (ADS)

Brandt, Ernst Helmut

1998-09-01

The ac susceptibility χ=χ'-iχ'' of superconductor cylinders of finite length in a magnetic field applied along the cylinder axis is calculated using the method developed in the preceding paper, part I. This method does not require any approximation of the infinitely extended magnetic field outside the cylinder or disk but directly computes the current density J inside the superconductor. The material is characterized by a general current-voltage law E(J), e.g., E(J)=Ec[J/Jc(B)]n(B), where E is the electric field, B=μ0H the magnetic induction, Ec a prefactor, Jc the critical current density, and n>=1 the creep exponent. For n>1, the nonlinear ac susceptibility is calculated from the hysteresis loops of the magnetic moment of the cylinder, which is obtained by time integration of the equation for J(r,t). For n>>1 these results go over into the Bean critical state model. For n=1, and for any linear complex resistivity ρac(ω)=E/J, the linear ac susceptibility is calculated from an eigenvalue problem which depends on the aspect ratio b/a of the cylinder or disk. In the limits b/a<<1 and b/a>>1, the known results for thin disks in a perpendicular field and long cylinders in a parallel field are reproduced. For thin disks in a perpendicular field, at large frequencies χ(ω) crosses over to the behavior of slabs in parallel geometry since the magnetic field lines are expelled and have to flow around the disk. The results presented may be used to obtain the nonlinear or linear resistivity from contact-free magnetic measurements on superconductors of realistic shape.

Molecular wires acting as quantum heat ratchets.

PubMed

Zhan, Fei; Li, Nianbei; Kohler, Sigmund; Hänggi, Peter

2009-12-01

We explore heat transfer in molecular junctions between two leads in the absence of a finite net thermal bias. The application of an unbiased time-periodic temperature modulation of the leads entails a dynamical breaking of reflection symmetry, such that a directed heat current may emerge (ratchet effect). In particular, we consider two cases of adiabatically slow driving, namely, (i) periodic temperature modulation of only one lead and (ii) temperature modulation of both leads with an ac driving that contains a second harmonic, thus, generating harmonic mixing. Both scenarios yield sizable directed heat currents, which should be detectable with present techniques. Adding a static thermal bias allows one to compute the heat current-thermal load characteristics, which includes the ratchet effect of negative thermal bias with positive-valued heat flow against the thermal bias, up to the thermal stop load. The ratchet heat flow in turn generates also an electric current. An applied electric stop voltage, yielding effective zero electric current flow, then mimics a solely heat-ratchet-induced thermopower ("ratchet Seebeck effect"), although no net thermal bias is acting. Moreover, we find that the relative phase between the two harmonics in scenario (ii) enables steering the net heat current into a direction of choice.

Effect of ac electric field on the dynamics of a vesicle under shear flow in the small deformation regime

NASA Astrophysics Data System (ADS)

Sinha, Kumari Priti; Thaokar, Rochish M.

2018-03-01

Vesicles or biological cells under simultaneous shear and electric field can be encountered in dielectrophoretic devices or designs used for continuous flow electrofusion or electroporation. In this work, the dynamics of a vesicle subjected to simultaneous shear and uniform alternating current (ac) electric field is investigated in the small deformation limit. The coupled equations for vesicle orientation and shape evolution are derived theoretically, and the resulting nonlinear equations are handled numerically to generate relevant phase diagrams that demonstrate the effect of electrical parameters on the different dynamical regimes such as tank treading (TT), vacillating breathing (VB) [called trembling (TR) in this work], and tumbling (TU). It is found that while the electric Mason number (Mn), which represents the relative strength of the electrical forces to the shear forces, promotes the TT regime, the response itself is found to be sensitive to the applied frequency as well as the conductivity ratio. While higher outer conductivity promotes orientation along the flow axis, orientation along the electric field is favored when the inner conductivity is higher. Similarly a switch of orientation from the direction of the electric field to the direction of flow is possible by a mere change of frequency when the outer conductivity is higher. Interestingly, in some cases, a coupling between electric field-induced deformation and shear can result in the system admitting an intermediate TU regime while attaining the TT regime at high Mn. The results could enable designing better dielectrophoretic devices wherein the residence time as well as the dynamical states of the vesicular suspension can be controlled as per the application.

Spectrophotometric and electrical properties of imperatorin: an organic molecule

NASA Astrophysics Data System (ADS)

Mir, Feroz A.

2015-09-01

Imperatorin (molecular formula = C16H14O4, molecular mass = 270) an organic molecule was isolated from ethyl acetate extract of the root parts of the plant Prangos pabularia. The optical study was carried out by ultraviolet-visible spectroscopy, and this compound showed an indirect allowed transition. The optical band gap ( E g ) was found around 3.75 eV. Photoluminescence shows various good emission bands. The frequency-dependent real part of the complex ac conductivity was found to follow the universal dielectric response: σ ac ( ω) α ω s [where σ ac ( ω) is the frequency-dependent total conductivity, ω is the frequency, and s is the frequency exponent]. From ac conductivity data analysis, correlated barrier hopping charge-transport mechanism is the dominant electrical transport process shown by this compound. The good emission, less absorption, wide band gap and good electrical properties shown by this compound project them as a bright choice for organic electronic devices.

Performance Analysis of Three-Phase Induction Motor with AC Direct and VFD

NASA Astrophysics Data System (ADS)

Kumar, Dinesh

2018-03-01

The electrical machine analysis and performance calculation is a very important aspect of efficient drive system design. The development of power electronics devices and power converters provide smooth speed control of Induction Motors by changing the frequency of input supply. These converters, on one hand are providing a more flexible speed control that also leads to problems of harmonics and their associated ailments like pulsating torque, distorted current and voltage waveforms, increasing losses etc. This paper includes the performance analysis of three phase induction motor with three-phase AC direct and variable frequency drives (VFD). The comparison has been concluded with respect to various parameters. MATLAB-SIMULINKTM is used for the analysis.

Measuring Multiple Resistances Using Single-Point Excitation

NASA Technical Reports Server (NTRS)

Hall, Dan; Davies, Frank

2009-01-01

In a proposed method of determining the resistances of individual DC electrical devices connected in a series or parallel string, no attempt would be made to perform direct measurements on individual devices. Instead, (1) the devices would be instrumented by connecting reactive circuit components in parallel and/or in series with the devices, as appropriate; (2) a pulse or AC voltage excitation would be applied at a single point on the string; and (3) the transient or AC steady-state current response of the string would be measured at that point only. Each reactive component(s) associated with each device would be distinct in order to associate a unique time-dependent response with that device.

Similarity between the superconductivity in the graphene with the spin transport in the two-dimensional antiferromagnet in the honeycomb lattice

NASA Astrophysics Data System (ADS)

Lima, L. S.

2017-02-01

We have used the Dirac's massless quasi-particles together with the Kubo's formula to study the spin transport by electrons in the graphene monolayer. We have calculated the electric conductivity and verified the behavior of the AC and DC currents of this system, that is a relativistic electron plasma. Our results show that the AC conductivity tends to infinity in the limit ω → 0 , similar to the behavior obtained for the spin transport in the two-dimensional frustrated antiferromagnet in the honeycomb lattice. We have made a diagrammatic expansion for the Green's function and we have not gotten significative change in the results.

Cyclotron resonance of the magnetic ratchet effect and second harmonic generation in bilayer graphene

NASA Astrophysics Data System (ADS)

Kheirabadi, Narjes; McCann, Edward; Fal'ko, Vladimir I.

2018-02-01

We model the magnetic ratchet effect in bilayer graphene in which a dc electric current is produced by an ac electric field of frequency ω in the presence of a steady in-plane magnetic field and inversion-symmetry breaking. In bilayer graphene, the ratchet effect is tunable by an external metallic gate which breaks inversion symmetry. For zero in-plane magnetic field, we show that trigonal warping and inversion-symmetry breaking are able to produce a large dc valley current, but not a nonzero total dc charge current. For the magnetic ratchet in a tilted magnetic field, the perpendicular field component induces cyclotron motion with frequency ωc and we find that the dc current displays cyclotron resonance at ωc=ω , although this peak in the current is actually smaller than its value at ωc=0 . Second harmonic generation, however, is greatly enhanced by resonances at ωc=ω and ωc=2 ω for which the current is generally much larger than at ωc=0 .

Highly conductive porous Na-embedded carbon nanowalls for high-performance capacitive deionization

NASA Astrophysics Data System (ADS)

Chang, Liang; Hu, Yun Hang

2018-05-01

Highly conductive porous Na-embedded carbon nanowalls (Na@C), which were recently invented, have exhibited excellent performance for dye-sensitized solar cells and electric double-layer capacitors. In this work, Na@C was demonstrated as an excellent electrode material for capacitive deionization (CDI). In a three-electrode configuration system, the specific capacity of the Na@C electrodes can achieve 306.4 F/g at current density of 0.2 A/g in 1 M NaCl, which is higher than that (235.2 F/g) of activated carbon (AC) electrodes. Furthermore, a high electrosorption capacity of 8.75 mg g-1 in 100 mg/L NaCl was obtained with the Na@C electrodes in a batch-mode capacitive deionization cell. It exceeds the electrosorption capacity (4.08 mg g-1) of AC electrodes. The Na@C electrode also showed a promising cycle stability. The excellent performance of Na@C electrode for capacitive deionization (CDI) can be attributed to its high electrical conductivity and large accessible surface area.

The investigation of an electric arc in the long cylindrical channel of the powerful high-voltage AC plasma torch

NASA Astrophysics Data System (ADS)

Rutberg, Ph G.; Popov, S. D.; Surov, A. V.; Serba, E. O.; Nakonechny, Gh V.; Spodobin, V. A.; Pavlov, A. V.; Surov, A. V.

2012-12-01

The comparison of conductivity obtained in experiments with calculated values is made in this paper. Powerful stationary plasma torches with prolonged period of continuous work are popular for modern plasmachemical applications. The maximum electrode lifetime with the minimum erosion can be reached while working on rather low currents. Meanwhile it is required to provide voltage arc drop for the high power achievement. Electric field strength in the arc column of the high-voltage plasma torch, using air as a plasma-forming gas, does not exceed 15 V/cm. It is possible to obtain the high voltage drop in the long arc stabilized in the channel by the intensive gas flow under given conditions. Models of high voltage plasma torches with rod electrodes with power up to 50 kW have been developed and investigated. The plasma torch arcs are burning in cylindrical channels. Present investigations are directed at studying the possibility of developing long arc plasma torches with higher power. The advantage of AC power supplies usage is the possibility of the loss minimization due to the reactive power compensation. The theoretical maximum of voltage arc drop for power supplies with inductive current limitations is about 50 % of the no-load voltage for a single-phase circuit and about 30 % for the three-phase circuit. Burning of intensively blown arcs in the long cylindrical channel using the AC power supply with 10 kV no-load voltage is experimentally investigated in the work. Voltage drops close to the maximum possible had been reached in the examined arcs in single-phase and three-phase modes. Operating parameters for single-phase mode were: current -30 A, voltage drop -5 kV, air flow rate 35 g/s; for three-phase mode: current (40-85) A, voltage drop (2.5-3.2) kV, air flow rate (60-100) g/s. Arc length in the installations exceeded 2 m.

Transcranial Alternating Current Stimulation: A Potential Risk for Genetic Generalized Epilepsy Patients (Study Case)

PubMed Central

San-Juan, Daniel; Sarmiento, Carlos Ignacio; Hernandez-Ruiz, Axel; Elizondo-Zepeda, Ernesto; Santos-Vázquez, Gabriel; Reyes-Acevedo, Gerardo; Zúñiga-Gazcón, Héctor; Zamora-Jarquín, Carol Marina

2016-01-01

Transcranial alternating current stimulation (tACS) is a re-emergent neuromodulation technique that consists in the external application of oscillating electrical currents that induces changes in cortical excitability. We present the case of a 16-year-old female with pharmaco-resistant juvenile myoclonic epilepsy to 3 antiepileptic’s drugs characterized by 4 myoclonic and 20 absence seizures monthly. She received tACS at 1 mA at 3 Hz pulse train during 60 min over Fp1–Fp2 (10–20 EEG international system position) during 4 consecutive days using an Endeavor™ IOM Systems device® (Natus Medical Incorporated, Middleton, WI, USA). At the 1-month follow-up, she reported a 75% increase in seizures frequency (only myoclonic and tonic–clonic events) and developed a 24-h myoclonic status epilepticus that resolved with oral clonazepam and intravenous valproate. At the 2-month follow-up, the patient reported a 15-day seizure-free period. PMID:27965623

Aligned Immobilization of Proteins Using AC Electric Fields.

PubMed

Laux, Eva-Maria; Knigge, Xenia; Bier, Frank F; Wenger, Christian; Hölzel, Ralph

2016-03-01

Protein molecules are aligned and immobilized from solution by AC electric fields. In a single-step experiment, the enhanced green fluorescent proteins are immobilized on the surface as well as at the edges of planar nanoelectrodes. Alignment is found to follow the molecules' geometrical shape with their longitudinal axes parallel to the electric field. Simultaneous dielectrophoretic attraction and AC electroosmotic flow are identified as the dominant forces causing protein movement and alignment. Molecular orientation is determined by fluorescence microscopy based on polarized excitation of the proteins' chromophores. The chromophores' orientation with respect to the whole molecule supports X-ray crystal data. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electrorotation of novel electroactive polymer composites in uniform DC and AC electric fields

NASA Astrophysics Data System (ADS)

Zrinyi, Miklós; Nakano, Masami; Tsujita, Teppei

2012-06-01

Novel electroactive polymer composites have been developed that could spin in uniform DC and AC electric fields. The angular displacement as well as rotation of polymer disks around an axis that is perpendicular to the direction of the applied electric field was studied. It was found that the dynamics of the polymer rotor is very complex. Depending on the strength of the static DC field, three regimes have been observed: no rotation occurs below a critical threshold field intensity, oscillatory motion takes place just above this value and continuous rotation can be observed above the critical threshold field intensity. It was also found that low frequency AC fields could also induce angular deformation.

The Dynamics of Oblate Drop Between Heterogeneous Plates Under Alternating Electric Field. Non-uniform Field

NASA Astrophysics Data System (ADS)

Kashina, M. A.; Alabuzhev, A. A.

2018-02-01

The dynamics of the incompressible fluid drop under the non-uniform electric field are considered. The drop is bounded axially by two parallel solid planes and the case of heterogeneous plates is investigated. The external electric field acts as an external force that causes motion of the contact line. We assume that the electric current is alternative current and the AC filed amplitude is a spatially non-uniform function. In equilibrium, the drop has the form of a circular cylinder. The equilibrium contact angle is 0.5 π. In order to describe this contact line motion the modified Hocking boundary condition is applied: the velocity of the contact line is proportional to the deviation of the contact angle and the speed of the fast relaxation processes, which frequency is proportional to twice the frequency of the electric field. The Hocking parameter depends on the polar angle, i.e. the coefficient of the interaction between the plate and the fluid (the contact line) is a function of the plane coordinates. This function is expanded in a series of the Laplace operator eigenfunctions.

Mathematical model for the dc-ac inverter for the Space Shuttle

NASA Technical Reports Server (NTRS)

Berry, Frederick C.

1987-01-01

The reader is informed of what was done for the mathematical modeling of the dc-ac inverter for the Space Shuttle. The mathematical modeling of the dc-ac inverter is an essential element in the modeling of the electrical power distribution system of the Space Shuttle. The electrical power distribution system which is present on the Space Shuttle is made up to 3 strings each having a fuel cell which provides dc to those systems which require dc, and the inverters which convert the dc to ac for those elements which require ac. The inverters are units which are 2 wire structures for the main dc inputs and 2 wire structures for the ac output. When 3 are connected together a 4 wire wye connection results on the ac side. The method of modeling is performed by using a Least Squares curve fitting method. A computer program is presented for implementation of the model along with graphs and tables to demonstrate the accuracy of the model.

Stirling Convertor Control for a Concept Rover at NASA Glenn Research Center

NASA Technical Reports Server (NTRS)

Blaze-Dugala, Gina M.

2009-01-01

The U.S. Department of Energy (DOE), Lockheed Martin Space Systems Company (LMSSC), Sunpower Inc., and NASA Glenn Research Center (GRC) have been developing an Advanced Stirling Radioisotope Generator (ASRG) for potential use as an electric power system for space science missions. This generator would make use of the free-piston Stirling cycle to achieve higher conversion efficiency than currently used alternatives. NASA GRC initiated an experiment with an ASRG simulator to demonstrate the functionality of a Stirling convertor on a mobile application, such as a rover. The ASRG simulator made use of two Advanced Stirling Convertors to convert thermal energy from a heat source to electricity. The ASRG simulator was designed to incorporate a minimum amount of support equipment, allowing integration onto a rover powered directly by the convertors. Support equipment to provide control was designed including a linear AC regulator controller, constant power controller, and Li-ion battery charger controller. The ASRG simulator is controlled by a linear AC regulator controller. The rover is powered by both a Stirling convertor and Li-ion batteries. A constant power controller enables the Stirling convertor to maintain a constant power output when additional power is supplied by the Li-ion batteries. A Li-ion battery charger controller limits the charging current and cut off current of the batteries. This paper discusses the design, fabrication, and implementation of these three controllers.

A Touch Sensing Technique Using the Effects of Extremely Low Frequency Fields on the Human Body

PubMed Central

Elfekey, Hatem; Bastawrous, Hany Ayad; Okamoto, Shogo

2016-01-01

Touch sensing is a fundamental approach in human-to-machine interfaces, and is currently under widespread use. Many current applications use active touch sensing technologies. Passive touch sensing technologies are, however, more adequate to implement low power or energy harvesting touch sensing interfaces. This paper presents a passive touch sensing technique based on the fact that the human body is affected by the surrounding extremely low frequency (ELF) electromagnetic fields, such as those of AC power lines. These external ELF fields induce electric potentials on the human body—because human tissues exhibit some conductivity at these frequencies—resulting in what is called AC hum. We therefore propose a passive touch sensing system that detects this hum noise when a human touch occurs, thus distinguishing between touch and non-touch events. The effectiveness of the proposed technique is validated by designing and implementing a flexible touch sensing keyboard. PMID:27918416

A Touch Sensing Technique Using the Effects of Extremely Low Frequency Fields on the Human Body.

PubMed

Elfekey, Hatem; Bastawrous, Hany Ayad; Okamoto, Shogo

2016-12-02

Touch sensing is a fundamental approach in human-to-machine interfaces, and is currently under widespread use. Many current applications use active touch sensing technologies. Passive touch sensing technologies are, however, more adequate to implement low power or energy harvesting touch sensing interfaces. This paper presents a passive touch sensing technique based on the fact that the human body is affected by the surrounding extremely low frequency (ELF) electromagnetic fields, such as those of AC power lines. These external ELF fields induce electric potentials on the human body-because human tissues exhibit some conductivity at these frequencies-resulting in what is called AC hum. We therefore propose a passive touch sensing system that detects this hum noise when a human touch occurs, thus distinguishing between touch and non-touch events. The effectiveness of the proposed technique is validated by designing and implementing a flexible touch sensing keyboard.

A novel interface circuit for triboelectric nanogenerator

NASA Astrophysics Data System (ADS)

Yu, Wuqi; Ma, Jiahao; Zhang, Zhaohua; Ren, Tianling

2017-10-01

For most triboelectric nanogenerators (TENGs), the electric output should be a short AC pulse, which has the common characteristic of high voltage but low current. Thus it is necessary to convert the AC to DC and store the electric energy before driving conventional electronics. The traditional AC voltage regulator circuit which commonly consists of transformer, rectifier bridge, filter capacitor, and voltage regulator diode is not suitable for the TENG because the transformer’s consumption of power is appreciable if the TENG output is small. This article describes an innovative design of an interface circuit for a triboelectric nanogenerator that is transformerless and easily integrated. The circuit consists of large-capacity electrolytic capacitors that can realize to intermittently charge lithium-ion batteries and the control section contains the charging chip, the rectifying circuit, a comparator chip and switch chip. More important, the whole interface circuit is completely self-powered and self-controlled. Meanwhile, the chip is widely used in the circuit, so it is convenient to integrate into PCB. In short, this work presents a novel interface circuit for TENGs and makes progress to the practical application and industrialization of nanogenerators. Project supported by the National Natural Science Foundation of China (No. 61434001) and the ‘Thousands Talents’ Program for Pioneer Researchers and Its Innovation Team, China.

21 CFR 880.5500 - AC-powered patient lift.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false AC-powered patient lift. 880.5500 Section 880.5500... Devices § 880.5500 AC-powered patient lift. (a) Identification. An AC-powered lift is an electrically powered device either fixed or mobile, used to lift and transport patients in the horizontal or other...

21 CFR 880.5500 - AC-powered patient lift.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false AC-powered patient lift. 880.5500 Section 880.5500... Devices § 880.5500 AC-powered patient lift. (a) Identification. An AC-powered lift is an electrically powered device either fixed or mobile, used to lift and transport patients in the horizontal or other...

Controller for controlling operation of at least one electrical load operating on an AC supply, and a method thereof

DOEpatents

Cantin, Luc; Deschenes, Mario; D'Amours, Mario

1995-08-15

A controller is provided for controlling operation of at least one electrical load operating on an AC supply having a typical frequency, the AC supply being provided via power transformers by an electrical power distribution grid. The controller is associated with the load and comprises an input interface for coupling the controller to the grid, a frequency detector for detecting the frequency of the AC supply and producing a signal indicative of the frequency, memory modules for storing preprogrammed commands, a frequency monitor for reading the signal indicative of the frequency and producing frequency data derived thereof, a selector for selecting at least one of the preprogrammed commands with respect to the frequency data, a control unit for producing at least one command signal representative of the selected preprogrammed commands, and an output interface including a device responsive to the command signal for controlling the load. Therefore, the load can be controlled by means of the controller depending on the frequency of the AC supply.

Effect of Dimension and Shape of Magnet on the Performance AC Generator with Translation Motion

NASA Astrophysics Data System (ADS)

Indriani, A.; Dimas, S.; Hendra

2018-02-01

The development of power plants using the renewable energy sources is very rapid. Renewable energy sources used solar energy, wind energy, ocean wave energy and other energy. All of these renewable energy sources require a processing device or a change of motion system to become electrical energy. One processing device is a generator which have work principle of converting motion (mechanical) energy into electrical energy with rotary shaft, blade and other motion components. Generator consists of several types of rotation motion and linear motion (translational). The generator have components such as rotor, stator and anchor. In the rotor and stator having magnet and winding coil as an electric generating part of the electric motion force. Working principle of AC generator with linear motion (translation) also apply the principle of Faraday that is using magnetic induction which change iron magnet to produce magnetic flux. Magnetic flux is captured by the stator to be converted into electrical energy. Linear motion generators consist of linear induction machine, wound synchronous machine field, and permanent magnet synchronous [1]. Performance of synchronous generator of translation motion is influenced by magnet type, magnetic shape, coil winding, magnetic and coil spacing and others. In this paper focus on the neodymium magnet with varying shapes, number of coil windings and gap of magnetic distances. This generator work by using pneumatic mechanism (PLTGL) for power plants system. Result testing of performance AC generator translation motion obtained that maximum voltage, current and power are 63 Volt for diameter winding coil 0.15 mm, number of winding coil 13000 and distance of magnet 20 mm. For effect shape of magnet, maximum voltage happen on rectangle magnet 30x20x5 mm with 4.64 Volt. Voltage and power on effect of diameter winding coil is 14.63 V and 17.82 W at the diameter winding coil 0.7 and number of winding coil is 1260 with the distance of magnet 25 mm.

Aggregation of model amyloid insulin protein in crowding environments and under ac-electric fields

NASA Astrophysics Data System (ADS)

Zheng, Zhongli; Jing, Benxin; Murray, Brian; Sorci, Mirco; Belfort, Georges; Zhu, Y.

2013-03-01

In vitro experiments have been widely used to characterize the misfolding/unfolding pathway characteristic of amylodogenic proteins. Conversion from natively folded amyloidogenic proteins to oligomers via nucleation is the accepted path to fibril formation upon heating over a certain lag time period. In this work, we investigate the effect of crowing environment and external electric fields on the pathway and kinetics of insulin, a well-established amyloid model protein by single fluorescence spectroscopy and imaging. With added co-solutes, such as glycerol and polyvinylpyrrolidone (PVP), to mimic the cellular crowding environments, we have observed that the lag time can be significantly prolonged. The lag time increases with increasing co-solute concentration, yet showing little dependence on solution viscosity. Conversely, applied ac-electric fields can considerably shorten the lag timewhen a critical ac-voltage is exceeded. The strong dependence of lag time on ac-frequency over a narrow range of 500 Hz-5 kHz indicates the effect of ac-electroosmosis on the diffusion controlled process of insulin nucleation. Yet, no conformational structure is detected with insulin under applied ac-fields, suggesting the equivalence of ac-polarization to the conventional thermal activation process for insulin aggregation. These finding suggest that at least the aggregation kinetics of insulin can be altered by local solution condition or external stimuli, which gives new insight to the treatment of amyloid related diseases.

Dielectric behavior of AC aged polyethylene in humid environment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scarpa, P.C.N.; Das-Gupta, D.K.; Bulinski, A.T.

1996-12-31

The present paper reports the results of a study of electrical aging of low density polyethylene (LDPE) aged in humid environment (0.1M NaCl) at an AC stress of 6kV/mm, 1kHz, at room temperature (RT) and at 65 C, and cross-linked polyethylene (XLPE) AC aged in humid environment (water) at an AC stress of 6kV/mm, 50Hz, at RT, for an extended period of time. For this study the dielectric spectroscopy data in the frequency range of 10{sup {minus}5}Hz to 10{sup 6}Hz and their comparative analysis, have been used to provide electrical analog models of the aging.

ACS experiment for atmospheric studies on "ExoMars-2016" Orbiter

NASA Astrophysics Data System (ADS)

Korablev, O. I.; Montmessin, F.; Fedorova, A. A.; Ignatiev, N. I.; Shakun, A. V.; Trokhimovskiy, A. V.; Grigoriev, A. V.; Anufreichik, K. A.; Kozlova, T. O.

2015-12-01

ACS is a set of spectrometers for atmospheric studies (Atmospheric Chemistry Suite). It is one of the Russian instruments for the Trace Gas Orbiter (TGO) of the Russian-European "ExoMars" program. The purpose of the experiment is to study the Martian atmosphere by means of two observations regimes: sensitive trace gases measurements in solar occultations and by monitoring the atmospheric state during nadir observations. The experiment will allow us to approach global problems of Mars research such as current volcanism, and the modern climate status and its evolution. Also, the experiment is intended to solve the mystery of methane presence in the Martian atmosphere. Spectrometers of the ACS set cover the spectral range from the near IR-range (0.7 μm) to the thermal IR-range (17 μm) with spectral resolution λ/Δλ reaching 50000. The ACS instrument consists of three independent IR spectrometers and an electronics module, all integrated in a single unit with common mechanical, electrical and thermal interfaces. The article gives an overview of scientific tasks and presents the concept of the experiment.

Classification of methods in transcranial electrical stimulation (tES) and evolving strategy from historical approaches to contemporary innovations.

PubMed

Guleyupoglu, Berkan; Schestatsky, Pedro; Edwards, Dylan; Fregni, Felipe; Bikson, Marom

2013-10-15

Transcranial Electrical Stimulation (tES) encompasses all methods of non-invasive current application to the brain used in research and clinical practice. We present the first comprehensive and technical review, explaining the evolution of tES in both terminology and dosage over the past 100 years of research to present day. Current transcranial Pulsed Current Stimulation (tPCS) approaches such as Cranial Electrotherapy Stimulation (CES) descended from Electrosleep (ES) through Cranial Electro-stimulation Therapy (CET), Transcerebral Electrotherapy (TCET), and NeuroElectric Therapy (NET) while others like Transcutaneous Cranial Electrical Stimulation (TCES) descended from Electroanesthesia (EA) through Limoge, and Interferential Stimulation. Prior to a contemporary resurgence in interest, variations of transcranial Direct Current Stimulation were explored intermittently, including Polarizing current, Galvanic Vestibular Stimulation (GVS), and Transcranial Micropolarization. The development of these approaches alongside Electroconvulsive Therapy (ECT) and pharmacological developments are considered. Both the roots and unique features of contemporary approaches such as transcranial Alternating Current Stimulation (tACS) and transcranial Random Noise Stimulation (tRNS) are discussed. Trends and incremental developments in electrode montage and waveform spanning decades are presented leading to the present day. Commercial devices, seminal conferences, and regulatory decisions are noted. We conclude with six rules on how increasing medical and technological sophistication may now be leveraged for broader success and adoption of tES. Copyright © 2013 Elsevier B.V. All rights reserved.

Classification of methods in transcranial Electrical Stimulation (tES) and evolving strategy from historical approaches to contemporary innovations

PubMed Central

Guleyupoglu, Berkan; Schestatsky, Pedro; Edwards, Dylan; Fregni, Felipe; Bikson, Marom

2013-01-01

Transcranial Electrical Stimulation (tES) encompasses all methods of non-invasive current application to the brain used in research and clinical practice. We present the first comprehensive and technical review, explaining the evolution of tES in both terminology and dosage over the past 100 years of research to present day. Current transcranial Pulsed Current Stimulation (tPCS) approaches such as Cranial Electrotherapy Stimulation (CES) descended from Electrosleep (ES) through Cranial Electro-stimulation Therapy (CET), Transcerebral Electrotherapy (TCET), and NeuroElectric Therapy (NET) while others like Transcutaneous Cranial Electrical Stimulation (TCES) descended from Electroanesthesia (EA) through Limoge, and Interferential Stimulation. Prior to a contemporary resurgence in interest, variations of trans-cranial Direct Current Stimulation were explored intermittently, including Polarizing current, Galvanic Vestibular Stimulation (GVS), and Transcranial Micropolarization. The development of these approaches alongside Electroconvulsive Therapy (ECT) and pharmacological developments are considered. Both the roots and unique features of contemporary approaches such as transcranial Alternating Current Stimulation (tACS) and transcranial Random Noise Stimulation (tRNS) are discussed. Trends and incremental developments in electrode montage and waveform spanning decades are presented leading to the present day. Commercial devices, seminal conferences, and regulatory decisions are noted. We conclude with six rules on how increasing medical and technological sophistication may now be leveraged for broader success and adoption of tES. PMID:23954780

Electric dipole spin resonance in a quantum spin dimer system driven by magnetoelectric coupling

NASA Astrophysics Data System (ADS)

Kimura, Shojiro; Matsumoto, Masashige; Akaki, Mitsuru; Hagiwara, Masayuki; Kindo, Koichi; Tanaka, Hidekazu

2018-04-01

In this Rapid Communication, we propose a mechanism for electric dipole active spin resonance caused by spin-dependent electric polarization in a quantum spin gapped system. This proposal was successfully confirmed by high-frequency electron spin resonance (ESR) measurements of the quantum spin dimer system KCuCl3. ESR measurements by an illuminating linearly polarized electromagnetic wave reveal that the optical transition between the singlet and triplet states in KCuCl3 is driven by an ac electric field. The selection rule of the observed transition agrees with the calculation by taking into account spin-dependent electric polarization. We suggest that spin-dependent electric polarization is effective in achieving fast control of quantum spins by an ac electric field.

Introducing AC inductive reactance with a power tool

NASA Astrophysics Data System (ADS)

Bryant, Wesley; Baker, Blane

2016-09-01

The concept of reactance in AC electrical circuits is often non-intuitive and difficult for students to grasp. In order to address this lack of conceptual understanding, classroom exercises compare the predicted resistance of a power tool, based on electrical specifications, to measured resistance. Once students discover that measured resistance is smaller than expected, they are asked to explain these observations using previously studied principles of magnetic induction. Exercises also introduce the notion of inductive reactance and impedance in AC circuits and, ultimately, determine self-inductance of the motor windings within the power tool.

Hybrid immersed interface-immersed boundary methods for AC dielectrophoresis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hossan, Mohammad Robiul; Department of Engineering and Physics, University of Central Oklahoma, Edmond, OK 73034-5209; Dillon, Robert

2014-08-01

Dielectrophoresis, a nonlinear electrokinetic transport mechanism, has become popular in many engineering applications including manipulation, characterization and actuation of biomaterials, particles and biological cells. In this paper, we present a hybrid immersed interface–immersed boundary method to study AC dielectrophoresis where an algorithm is developed to solve the complex Poisson equation using a real variable formulation. An immersed interface method is employed to obtain the AC electric field in a fluid media with suspended particles and an immersed boundary method is used for the fluid equations and particle transport. The convergence of the proposed algorithm as well as validation of themore » hybrid scheme with experimental results is presented. In this paper, the Maxwell stress tensor is used to calculate the dielectrophoretic force acting on particles by considering the physical effect of particles in the computational domain. Thus, this study eliminates the approximations used in point dipole methods for calculating dielectrophoretic force. A comparative study between Maxwell stress tensor and point dipole methods for computing dielectrophoretic forces are presented. The hybrid method is used to investigate the physics of dielectrophoresis in microfluidic devices using an AC electric field. The numerical results show that with proper design and appropriate selection of applied potential and frequency, global electric field minima can be obtained to facilitate multiple particle trapping by exploiting the mechanism of negative dielectrophoresis. Our numerical results also show that electrically neutral particles form a chain parallel to the applied electric field irrespective of their initial orientation when an AC electric field is applied. This proposed hybrid numerical scheme will help to better understand dielectrophoresis and to design and optimize microfluidic devices.« less

Electrical and magnetic properties of conductive Cu-based coated conductors

NASA Astrophysics Data System (ADS)

Aytug, T.; Paranthaman, M.; Thompson, J. R.; Goyal, A.; Rutter, N.; Zhai, H. Y.; Gapud, A. A.; Ijaduola, A. O.; Christen, D. K.

2003-11-01

The development of YBa2Cu3O7-δ (YBCO)-based coated conductors for electric power applications will require electrical and thermal stabilization of the high-temperature superconducting (HTS) coating. In addition, nonmagnetic tape substrates are an important factor in order to reduce the ferromagnetic hysteresis energy loss in ac applications. We report progress toward a conductive buffer layer architecture on biaxially textured nonmagnetic Cu tapes to electrically couple the HTS layer to the underlying metal substrate. A protective Ni overlayer, followed by a single buffer layer of La0.7Sr0.3MnO3, was employed to avoid Cu diffusion and to improve oxidation resistance of the substrate. Property characterizations of YBCO films on short prototype samples revealed self-field critical current density (Jc) values exceeding 2×106 A/cm2 at 77 K and good electrical connectivity. Magnetic hysteretic loss due to Ni overlayer was also investigated.

Resonance of scroll rings with periodic external fields in excitable media

NASA Astrophysics Data System (ADS)

Pan, De-Bei; Li, Qi-Hao; Zhang, Hong

2018-06-01

By direct numerical simulations of a chemical reaction-diffusion system coupled to a periodic external AC electric field with frequency equal to double frequency of the scroll wave rotation, we find that scroll rings resonate with the electric field and exhibit various dynamical behaviors, for example, their reversals, collapses, or growths, depending both on the initial phase of AC electric fields and on the initial phase of scroll rings. A kinematical model characterizing the drift velocity of the scroll rings along their radial directions as well as that of the scroll rings along their symmetry axes is proposed, which can effectively account for the numerical observations and predict the behaviors of the scroll rings. Besides, the existence of the equilibrium state of a scroll ring under the AC electric fields is predicted by the kinematical model and the predictions agree well with the simulations.

Biasing and fast degaussing circuit for magnetic materials

DOEpatents

Dress, Jr., William B.; McNeilly, David R.

1984-01-01

A dual-function circuit is provided which may be used to both magnetically bias and alternately, quickly degauss a magnetic device. The circuit may be magnetically coupled or directly connected electrically to a magnetic device, such as a magnetostrictive transducer, to magnetically bias the device by applying a d.c. current and alternately apply a selectively damped a.c. current to the device to degauss the device. The circuit is of particular value in many systems which use magnetostrictive transducers for ultrasonic transmission in different propagation modes over very short time periods.

Biasing and fast degaussing circuit for magnetic materials

DOEpatents

Dress, W.B. Jr.; McNeilly, D.R.

1983-10-04

A dual-function circuit is provided which may be used to both magnetically bias and alternately, quickly degauss a magnetic device. The circuit may be magnetically coupled or directly connected electrically to a magnetic device, such as a magnetostrictive transducer, to magnetically bias the device by applying a dc current and alternately apply a selectively damped ac current to the device to degauss the device. The circuit is of particular value in many systems which use magnetostrictive transducers for ultrasonic transmission in different propagation modes over very short time periods.

Application field and ways to control alternating-current plasma torch with rail electrodes

NASA Astrophysics Data System (ADS)

Kuznetsov, V. E.; Safronov, A. A.; Vasilieva, O. B.; Shiryaev, V. N.; Dudnik, Yu D.; Pavlov, A. V.; Kuchina, Yu A.

2018-01-01

The paper deals with the investigation of parameters of the high voltage alternating-current plasma torch with rail electrodes. Usage of the injector and its variation allows controlling of operation of the ac plasma torch with rail electrodes. Also the possibility to protect the electric arc chamber without protective gas has been studied. It was found that increasing in the injector power causes the repeated breakdown at lower voltage and hence the arc dimensions decreases. The results of experiments are presented in the paper.

Plasma injector for a three-phase plasma torch with rail electrodes and some results of its investigation

NASA Astrophysics Data System (ADS)

Dudnik, Yu D.; Borovskoy, A. M.; Shiryaev, V. N.; Safronov, A. A.; Kuznetsov, V. E.; Vasilieva, O. B.; Pavlov, A. V.; Ivanov, D. V.

2018-01-01

Plasma injector made on the basis of the alternating-current plasma torch designed for the three-phase ac plasma torch with 100-500 kWrail electrodes is studied. The construction of the plasma injector is examined. Different materials for manufacture of injector electrodes are investigated. Current-voltage characteristics of the injector are obtained. Investigations of the plasma jet are carried out, and the jet temperature dependence versus the gas flow rate and electric power of the injector is measured.

Frequency-specific insight into short-term memory capacity.

PubMed

Feurra, Matteo; Galli, Giulia; Pavone, Enea Francesco; Rossi, Alessandro; Rossi, Simone

2016-07-01

The digit span is one of the most widely used memory tests in clinical and experimental neuropsychology for reliably measuring short-term memory capacity. In the forward version, sequences of digits of increasing length have to be reproduced in the order in which they are presented, whereas in the backward version items must be reproduced in the reversed order. Here, we assessed whether transcranial alternating current stimulation (tACS) increases the memory span for digits of young and midlife adults. Imperceptibly weak electrical currents in the alpha (10 Hz), beta (20 Hz), theta (5 Hz), and gamma (40 Hz) range, as well as a sham stimulation, were delivered over the left posterior parietal cortex, a cortical region thought to sustain maintenance processes in short-term memory through oscillatory brain activity in the beta range. We showed a frequency-specific effect of beta-tACS that robustly increased the forward memory span of young, but not middle-aged, healthy individuals. The effect correlated with age: the younger the subjects, the greater the benefit arising from parietal beta stimulation. Our results provide evidence of a short-term memory capacity improvement in young adults by online frequency-specific tACS application. Copyright © 2016 the American Physiological Society.

Rabi-Bloch oscillations in spatially distributed systems: Temporal dynamics and frequency spectra

NASA Astrophysics Data System (ADS)

Levie, Ilay; Kastner, Raphael; Slepyan, Gregory

2017-10-01

We consider one-dimensional chains of two-level quantum systems coupled via tunneling. The chain is driven by the superposition of dc and ac fields in the strong coupling regime. Based on the fundamental principles of electrodynamics and quantum theory, we have developed a generalized model of quantum dynamics for such interactions, free of rotating-wave approximation. The system of equations of motion was studied numerically. We analyzed the dynamics and spectra of the inversion density, dipole current density, and tunneling current density. In the case of resonant interaction with the ac component, the particle dynamics exhibits itself in the oscillatory regime, which may be interpreted as a combination of Rabi and Bloch oscillations with their strong mutual influence. Such scenario for an obliquely incident ac field dramatically differs from the individual picture of both types of oscillations due to the interactions. This effect is counterintuitive because of the existence of markedly different frequency ranges for such two types of oscillations. These dynamics manifest themselves in multiline spectra in different combinations of Rabi and Bloch frequencies. The effect is promising as a framework of a new type of spectroscopy in nanoelectronics and electrical control of nanodevices.

Basic and functional effects of transcranial Electrical Stimulation (tES)-An introduction.

PubMed

Yavari, Fatemeh; Jamil, Asif; Mosayebi Samani, Mohsen; Vidor, Liliane Pinto; Nitsche, Michael A

2018-02-01

Non-invasive brain stimulation (NIBS) has been gaining increased popularity in human neuroscience research during the last years. Among the emerging NIBS tools is transcranial electrical stimulation (tES), whose main modalities are transcranial direct, and alternating current stimulation (tDCS, tACS). In tES, a small current (usually less than 3mA) is delivered through the scalp. Depending on its shape, density, and duration, the applied current induces acute or long-lasting effects on excitability and activity of cerebral regions, and brain networks. tES is increasingly applied in different domains to (a) explore human brain physiology with regard to plasticity, and brain oscillations, (b) explore the impact of brain physiology on cognitive processes, and (c) treat clinical symptoms in neurological and psychiatric diseases. In this review, we give a broad overview of the main mechanisms and applications of these brain stimulation tools. Copyright © 2017 Elsevier Ltd. All rights reserved.

75 FR 33515 - Federal Motor Vehicle Safety Standards; Electric-Powered Vehicles; Electrolyte Spillage and...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-06-14

..., and made a simple comparison. Based on the IEC report, the human body can withstand up to four times....\\3\\ The flow of this amount of AC through the human body may result in perception of the current and... considered to be safe) corresponds to 8 mA of DC (that is also considered to be safe for the human body).\\4...

Alternating current electric fields of varying frequencies: effects on proliferation and differentiation of porcine neural progenitor cells.

PubMed

Lim, Ji-Hey; McCullen, Seth D; Piedrahita, Jorge A; Loboa, Elizabeth G; Olby, Natasha J

2013-10-01

Application of sinusoidal electric fields (EFs) has been observed to affect cellular processes, including alignment, proliferation, and differentiation. In the present study, we applied low-frequency alternating current (AC) EFs to porcine neural progenitor cells (pNPCs) and investigated the effects on cell patterning, proliferation, and differentiation. pNPCs were grown directly on interdigitated electrodes (IDEs) localizing the EFs to a region accessible visually for fluorescence-based assays. Cultures of pNPCs were exposed to EFs (1 V/cm) of 1 Hz, 10 Hz, and 50 Hz for 3, 7, and 14 days and compared to control cultures. Immunocytochemistry was performed to evaluate the expression of neural markers. pNPCs grew uniformly with no evidence of alignment to the EFs and no change in cell numbers when compared with controls. Nestin expression was shown in all groups at 3 and 7 days, but not at 14 days. NG2 expression was low in all groups. Co-expression of glial fibrillary acidic protein (GFAP) and TUJ1 was significantly higher in the cultures exposed to 10- and 50-Hz EFs than the controls. In summary, sinusoidal AC EFs via IDEs did not alter the alignment and proliferation of pNPCs, but higher frequency stimulation appeared to delay differentiation into mature astrocytes.

Numerical modelling of dynamic resistance in high-temperature superconducting coated-conductor wires

NASA Astrophysics Data System (ADS)

Ainslie, Mark D.; Bumby, Chris W.; Jiang, Zhenan; Toyomoto, Ryuki; Amemiya, Naoyuki

2018-07-01

The use of superconducting wire within AC power systems is complicated by the dissipative interactions that occur when a superconductor is exposed to an alternating current and/or magnetic field, giving rise to a superconducting AC loss caused by the motion of vortices within the superconducting material. When a superconductor is exposed to an alternating field whilst carrying a constant DC transport current, a DC electrical resistance can be observed, commonly referred to as ‘dynamic resistance.’ Dynamic resistance is relevant to many potential high-temperature superconducting (HTS) applications and has been identified as critical to understanding the operating mechanism of HTS flux pump devices. In this paper, a 2D numerical model based on the finite-element method and implementing the H -formulation is used to calculate the dynamic resistance and total AC loss in a coated-conductor HTS wire carrying an arbitrary DC transport current and exposed to background AC magnetic fields up to 100 mT. The measured angular dependence of the superconducting properties of the wire are used as input data, and the model is validated using experimental data for magnetic fields perpendicular to the plane of the wire, as well as at angles of 30° and 60° to this axis. The model is used to obtain insights into the characteristics of such dynamic resistance, including its relationship with the applied current and field, the wire’s superconducting properties, the threshold field above which dynamic resistance is generated and the flux-flow resistance that arises when the total driven transport current exceeds the field-dependent critical current, I c( B ), of the wire. It is shown that the dynamic resistance can be mostly determined by the perpendicular field component with subtle differences determined by the angular dependence of the superconducting properties of the wire. The dynamic resistance in parallel fields is essentially negligible until J c is exceeded and flux-flow resistance occurs.

Influence of Electric Fields and Conductivity on Pollen Tube Growth assessed via Electrical Lab-on-Chip

PubMed Central

Agudelo, Carlos; Packirisamy, Muthukumaran; Geitmann, Anja

2016-01-01

Pollen tubes are polarly growing plant cells that are able to rapidly respond to a combination of chemical, mechanical, and electrical cues. This behavioural feature allows them to invade the flower pistil and deliver the sperm cells in highly targeted manner to receptive ovules in order to accomplish fertilization. How signals are perceived and processed in the pollen tube is still poorly understood. Evidence for electrical guidance in particular is vague and highly contradictory. To generate reproducible experimental conditions for the investigation of the effect of electric fields on pollen tube growth we developed an Electrical Lab-on-Chip (ELoC). Pollen from the species Camellia displayed differential sensitivity to electric fields depending on whether the entire cell or only its growing tip was exposed. The response to DC fields was dramatically higher than that to AC fields of the same strength. However, AC fields were found to restore and even promote pollen growth. Surprisingly, the pollen tube response correlated with the conductivity of the growth medium under different AC frequencies—consistent with the notion that the effect of the field on pollen tube growth may be mediated via its effect on the motion of ions. PMID:26804186

Electromechanical systems with transient high power response operating from a resonant AC link

NASA Technical Reports Server (NTRS)

Burrows, Linda M.; Hansen, Irving G.

1992-01-01

The combination of an inherently robust asynchronous (induction) electrical machine with the rapid control of energy provided by a high frequency resonant AC link enables the efficient management of higher power levels with greater versatility. This could have a variety of applications from launch vehicles to all-electric automobiles. These types of systems utilize a machine which is operated by independent control of both the voltage and frequency. This is made possible by using an indirect field-oriented control method which allows instantaneous torque control in all four operating quadrants. Incorporating the AC link allows the converter in these systems to switch at the zero crossing of every half cycle of the AC waveform. This zero loss switching of the link allows rapid energy variations to be achieved without the usual frequency proportional switching loss. Several field-oriented control systems were developed by LeRC and General Dynamics Space Systems Division under contract to NASA. A description of a single motor, electromechanical actuation system is presented. Then, focus is on a conceptual design for an AC electric vehicle. This design incorporates an induction motor/generator together with a flywheel for peak energy storage. System operation and implications along with the associated circuitry are addressed. Such a system would greatly improve all-electric vehicle ranges over the Federal Urban Driving Cycle (FUD).

DC bias effect on alternating current electrical conductivity of poly(ethylene terephthalate)/alumina nanocomposites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nikam, Pravin N., E-mail: pravinya26@gmail.com; Deshpande, Vineeta D., E-mail: drdeshpandevd@gmail.com

Polymer nanocomposites based on metal oxide (ceramic) nanoparticles are a new class of materials with unique properties and designed for various applications such as electronic device packaging, insulation, fabrication and automotive industries. Poly(ethylene terephthalate) (PET)/alumina (Al{sub 2}O{sub 3}) nanocomposites with filler content between 1 wt% and 5 wt% were prepared by melt compounding method using co-rotating twin screw extruder and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and precision LCR meter techniques. The results revealed that proper uniform dispersion at lower content up to 2 wt% of nano-alumina observed by using TEM. Aggregation of nanoparticles was observedmore » at higher content of alumina examined by using SEM and TEM. The frequency dependences of the alternating current (AC) conductivity (σ{sub AC}) of PET/alumina nanocomposites on the filler content and DC bias were investigated in the frequency range of 20Hz - 1MHz. The results showed that the AC and direct current (DC) conductivity increases with increasing DC bias and nano-alumina content upto 3 wt%. It follows the Jonscher’s universal power law of solids. It revealed that σ{sub AC} of PET/alumina nanocomposites can be well characterized by the DC conductivity (σ{sub DC}), critical frequency (ω{sub c}), critical exponent of the power law (s). Roll of DC bias potential led to an increase of DC conductivity (σ{sub DC}) due to the creation of additional conducting paths with the polymer nanocomposites and percolation behavior achieved through co-continuous morphology.« less

Electric-field-driven Phenomena for Manipulating Particles in Micro-Devices

NASA Technical Reports Server (NTRS)

Khusid, Boris; Acrivos, Andreas

2004-01-01

Compared to other available methods, ac dielectrophoresis is particularly well-suited for the manipulation of minute particles in micro- and nano-fluidics. The essential advantage of this technique is that an ac field at a sufficiently high frequency suppresses unwanted electric effects in a liquid. To date very little has been achieved towards understanding the micro-scale field-and shear driven behavior of a suspension in that, the concepts currently favored for the design and operation of dielectrophoretic micro-devices adopt the approach used for macro-scale electric filters. This strategy considers the trend of the field-induced particle motions by computing the spatial distribution of the field strength over a channel as if it were filled only with a liquid and then evaluating the direction of the dielectrophoretic force, exerted on a single particle placed in the liquid. However, the exposure of suspended particles to a field generates not only the dielectrophoretic force acting on each of these particles, but also the dipolar interactions of the particles due to their polarization. Furthermore, the field-driven motion of the particles is accompanied by their hydrodynamic interactions. We present the results of our experimental and theoretical studies which indicate that, under certain conditions, these long-range electrical and hydrodynamic interparticle interactions drastically affect the suspension behavior in a micro-channel due to its small dimensions.

Thermal treatment of low permeability soils using electrical resistance heating

DOE Office of Scientific and Technical Information (OSTI.GOV)

Udell, K.S.

1996-08-01

The acceleration of recovery rates of second phase liquid contaminants from the subsurface during gas or water pumping operations is realized by increasing the soil and ground water temperature. Electrical heating with AC current is one method of increasing the soil and groundwater temperature and has particular applicability to low permeability soils. Several mechanisms have been identified that account for the enhanced removal of the contaminants during electrical heating. These are vaporization of liquid contaminants with low boiling points, temperature-enhanced evaporation rates of semi-volatile components, and removal of residual contaminants by the boiling of residual water. Field scale studies ofmore » electrical heating and fluid extraction show the effectiveness of this technique and its applicability to contaminants found both above and below the water table and within low permeability soils. 10 refs., 8 figs.« less

Electrical power inverter having a phase modulated, twin-inverter, high frequency link and an energy storage module

DOEpatents

Pitel, Ira J.

1987-02-03

The present invention provides an electrical power inverter method and apparatus, which includes a high frequency link, for converting DC power into AC power. Generally stated, the apparatus includes a first high frequency module which produces an AC voltage at a first output frequency, and a second high frequency inverter module which produces an AC voltage at a second output frequency that is substantially the same as the first output frequency. The second AC voltage is out of phase with the first AC voltage by a selected angular phase displacement. A mixer mixes the first and second output voltages to produce a high frequency carrier which has a selected base frequency impressed on the sidebands thereof. A rectifier rectifies the carrier, and a filter filters the rectified carrier. An output inverter inverts the filtered carrier to produce an AC line voltage at the selected base frequency. A phase modulator adjusts the relative angular phase displacement between the outputs of the first and second high frequency modules to control the base frequency and magnitude of the AC line voltage.

Electrical power inverter having a phase modulated, twin-inverter, high frequency link and an energy storage module

DOEpatents

Pitel, I.J.

1987-02-03

The present invention provides an electrical power inverter method and apparatus, which includes a high frequency link, for converting DC power into AC power. Generally stated, the apparatus includes a first high frequency module which produces an AC voltage at a first output frequency, and a second high frequency inverter module which produces an AC voltage at a second output frequency that is substantially the same as the first output frequency. The second AC voltage is out of phase with the first AC voltage by a selected angular phase displacement. A mixer mixes the first and second output voltages to produce a high frequency carrier which has a selected base frequency impressed on the sidebands thereof. A rectifier rectifies the carrier, and a filter filters the rectified carrier. An output inverter inverts the filtered carrier to produce an AC line voltage at the selected base frequency. A phase modulator adjusts the relative angular phase displacement between the outputs of the first and second high frequency modules to control the base frequency and magnitude of the AC line voltage. 19 figs.

Hyperfine field, electric field gradient, quadrupole coupling constant and magnetic properties of challenging actinide digallide

NASA Astrophysics Data System (ADS)

Khan, Sajid; Yazdani-Kachoei, M.; Jalali-Asadabadi, S.; Ahmad, Iftikhar

2017-12-01

In this paper, we explore the structural and magnetic properties as well as electric field gradient (EFG), hyperfine field (HFF) and quadrupole coupling constant in actinide digallide AcGa2 (Ac = U, Np, Pu) using LDA, GGA, LDA+U, GGA+U and hybrid functional with Wu-Cohen Generalized Gradient approximation HF-WC. Relativistic effects of the electrons are considered by including spin-orbit coupling. The comparison of the calculated structural parameters and magnetic properties with the available experimental results confirms the consistency and hence effectiveness of our theoretical tools. The calculated magnetic moments demonstrate that UGa2 and NpGa2 are ferromagnetic while PuGa2 is antiferromagnetic in nature. The EFG of AcGa2 is reported for the first time. The HFF, EFG and quadrupole coupling constant in AcGa2 (Ac = U, Np, Pu) are mainly originated from f-f and p-p contributions of Ac atom and p-p contribution of Ga atom.

Methods and apparatus for measurement of the resistivity of geological formations from within cased boreholes

DOEpatents

Vail, W.B. III.

1989-04-11

Methods and apparatus are disclosed which allow measurement of the resistivity of a geological formation through borehole casing which may be surrounded by brine saturated cement. A.C. current is passed from an electrode in electrical contact with the interior of the borehole casing to an electrode on the surface of the earth. The A.C. voltage difference is measured between two additional vertically disposed electrodes on the interior of the casing which provides a measure of the resistivity of the geological formation. A calibration and nulling procedure is presented which minimizes the influence of variations in the thickness of the casing. The procedure also minimizes the influence of inaccurate placements of the additional vertically disposed electrodes. 3 figs.

AC motor controller with 180 degree conductive switches

NASA Technical Reports Server (NTRS)

Oximberg, Carol A. (Inventor)

1995-01-01

An ac motor controller is operated by a modified time-switching scheme where the switches of the inverter are on for electrical-phase-and-rotation intervals of 180.degree. as opposed to the conventional 120.degree.. The motor is provided with three-phase drive windings, a power inverter for power supplied from a dc power source consisting of six switches, and a motor controller which controls the current controlled switches in voltage-fed mode. During full power, each switch is gated continuously for three successive intervals of 60.degree. and modulated for only one of said intervals. Thus, during each 60.degree. interval, the two switches with like signs are on continuously and the switch with the opposite sign is modulated.

Methods and apparatus for measurement of the resistivity of geological formations from within cased boreholes

DOEpatents

Vail, III, William B.

1989-01-01

Methods and apparatus are disclosed which allow measurement of the resistivity of a geological formation through borehole casing which may be surrounded by brine saturated cement. A.C. current is passed from an electrode in electrical contact with the interior of the borehole casing to an electrode on the surface of the earth. The A.C. voltage difference is measured between two additional vertically disposed electrodes on the interior of the casing which provides a measure of the resistivity of the geological formation. A calibration and nulling procedure is presented which minimizes the influence of variations in the thickness of the casing. The procedure also minimizes the influence of inaccurate placements of the additional vertically disposed electrodes.

An induction heater device for studies of magnetic hyperthermia and specific absorption ratio measurements

NASA Astrophysics Data System (ADS)

Cano, M. E.; Barrera, A.; Estrada, J. C.; Hernandez, A.; Cordova, T.

2011-11-01

The development of a device for generating ac magnetic fields based on a resonant inverter is presented, which has been specially designed to carry out experiments of magnetic hyperthermia. By determining the electric current in the LC resonant circuit, a maximum intensity of magnetic field around of 15 mT is calculated, with a frequency around of 206 kHz. This ac magnetic field is able to heat powdered magnetic materials embedded in biological systems to be used in biomedical applications. Indeed, in order to evaluate the sensitivity of the device we also present the measurements of the specific absorption rate in phantoms performed with commercially prepared Fe3O4 and distilled water at different concentrations.

Magnetic field tunable ac electrical transport of LaFeO3-wax nanocomposites

NASA Astrophysics Data System (ADS)

Roy, Supratim; Mandal, S. K.; Debnath, Rajesh; Nath, Debajyoti; Dey, P.

2018-04-01

Single phase perovskite LaFeO3 nanoparticles have been prepared through chemical pyrophoric reaction process. It is further grinded with paraffin wax of quantity 0.5 wt% of total composition to obtain an organic composite 99.5%LaFeO3-0.5%Wax. Studies of ac electrical properties viz. complex impedance, dielectric response, loss coefficient have been done in presence of external dc magnetic field, which reveals a good magnetoimpedance (˜221%) and a negative magnetodielectric (˜ 64%). The value of impedance, its real and imaginary part is observed to increase with dc field. The composite exhibits high dielectric constant (˜4760). The ac conductivity is found to decrease with applied field and increase with ac frequency.

Thermoplastic-based conductive composites containing multi-wall carbon nanotubes aligned under the application of external electric fields

NASA Astrophysics Data System (ADS)

Osazuwa, Osayuki

The objective of this thesis is to prepare thermoplastic/multi-wall carbon nanotubes (MWCNTs) and to apply external alternating current (AC) electric fields to achieve enhanced conductivity and dielectric properties. The first part of the thesis focuses on preparing polyolefin-based composites containing welldispersed MWCNTs. MWCNTs are functionalized with a hyperbranched polyethylene (HBPE) using a non-covalent, non-specific functionalization approach and melt compounded with an ethylene-octene copolymer (EOC) matrix. The improved filler dispersion in the functionalized EOC/MWCNT composite results in higher elongation at break compared to the non-functionalized composite. However, the electrical percolation threshold and the ultimate conductivity of the composites are not affected considerably, suggesting that this functionalization approach leaves the inherent properties of the nanotubes intact. EOC/HBPE-functionalized MWCNT composites are further subjected to external AC electric fields (35 -- 212 kV/m), which induce the formation of aligned columnar structures, as evidenced by Scanning Electron Microscopy. Experimentally acquired resistivity data are used to derive correlations between the characteristic insulator-to-conductor transition times of the composites and the electric field strength (E), polymer viscosity (eta) and MWCNT volume fraction (φ). A criterion for the selection of (eta, E, φ) conditions that enable MWCNT assembly under an electric field controlled regime (minimal Brownian motion-driven aggregation effects) is developed. The dielectric properties of the solidified aligned EOC/MWCNT composites are further studied using dielectric spectroscopy. Annealing of the composites at 160 °C results in the formation of interconnected structures, whereas electrification, using AC field of 71 and 212 kV/m induces the formation of aligned columnar structures. The electrified and annealed composites have increased real and imaginary permittivity compared to the as-compounded composite, resulting in improved conductivity and storage capacity. An equivalent circuit model is fitted to the experimentally obtained impedance data in order to correlate the effects of electric field and processing time to the dielectric characteristics of the treated composites. Finally poly(ethylene succinate) (PESu) composites containing well-dispersed MWCNT were prepared by an in-situ polymerization method. Composite electrification results in improvements in the electrical conductivity by up to 12 orders of magnitude, and a retention of high conductivity in the solidified state.

Impact of alternative electrical stunning parameters on the ability of broilers to recover consciousness and meat quality

USDA-ARS?s Scientific Manuscript database

Broilers in the United States are typically electrically stunned using low voltage-high frequency (12-38V, =400Hz) DC or AC water bath stunners. In the European Union, however, broilers are required to be electrocuted using high voltage-low frequency (50-150V, 50-350Hz) AC. Low voltage stunned broil...

Images of Bottomside Irregularities Observed at Topside Altitudes (Postprint)

DTIC Science & Technology

2012-04-04

pairs of 20 m tip-to-tip double probes and a fluxgate magnetometer on a 0.6 m boom [Pfaff et al., 2010]. Vector electric fields are obtained with 16-bit... magnetometer out- puts. AC electric fields are measured by passing VEFI data streams though low (0–6 Hz) and high-pass (3–8,000 Hz) filters. AC magnetic field

Experimental investigation of SDBD plasma actuator driven by AC high voltage with a superimposed positive pulse bias voltage

NASA Astrophysics Data System (ADS)

Qi, Xiao-Hua; Yan, Hui-Jie; Yang, Liang; Hua, Yue; Ren, Chun-Sheng

2017-08-01

In this work, a driven voltage consisting of AC high voltage with a superimposed positive pulse bias voltage ("AC+ Positive pulse bias" voltage) is adopted to study the performance of a surface dielectric barrier discharge plasma actuator under atmospheric conditions. To compare the performance of the actuator driven by single-AC voltage and "AC+ Positive pulse bias" voltage, the actuator-induced thrust force and power consumption are measured as a function of the applied AC voltage, and the measured results indicate that the thrust force can be promoted significantly after superimposing the positive pulse bias voltage. The physical mechanism behind the thrust force changes is analyzed by measuring the optical properties, electrical characteristics, and surface potential distribution. Experimental results indicate that the glow-like discharge in the AC voltage half-cycle, next to the cycle where a bias voltage pulse has been applied, is enhanced after applying the positive pulse bias voltage, and this perhaps is the main reason for the thrust force increase. Moreover, surface potential measurement results reveal that the spatial electric field formed by the surface charge accumulation after positive pulse discharge can significantly affect the applied external electric field, and this perhaps can be responsible for the experimental phenomenon that the decrease of thrust force is delayed by pulse bias voltage action after the filament discharge occurs in the glow-like discharge region. The schlieren images further verify that the actuator-induced airflow velocity increases with the positive pulse voltage.

Electrical transport in lead-free (Na0.5Bi0.5)1-xSrxTiO3 ceramics (x = 0, 0.01 and 0.02)

NASA Astrophysics Data System (ADS)

Dutkiewicz, E. M.; Suchanicz, J.; Konieczny, K.; Czaja, P.; Kluczewska, K.; Czternastek, H.; Antonova, M.; Sternberg, A.

2017-09-01

Lead-free (Na0.5Bi0.5)1xSrxTiO3 (x = 0, 0.01 and 0.02) ceramics were manufactured through a solid-state mixed oxide method and their ac (σac) and dc (σdc) electric conductivity were studied. It is shown that the low-frequency (100 Hz-1 MHz) ac conductivity obeys a power law σac ∼ ωs characteristic for disordered materials. Both the dc and ac conductivities have thermally activated character and possess linear parts with different activation energies. The calculated activation energies are attributed to different mechanism of conductivity. Frequency dependence of σdc and exponent s is reasonably interpreted by a correlated barrier hopping model. The NBT-ST system is expected to be a new promising candidate for lead-free electronic materials.

Direct-current triboelectricity generation by a sliding Schottky nanocontact on MoS2 multilayers

NASA Astrophysics Data System (ADS)

Liu, Jun; Goswami, Ankur; Jiang, Keren; Khan, Faheem; Kim, Seokbeom; McGee, Ryan; Li, Zhi; Hu, Zhiyu; Lee, Jungchul; Thundat, Thomas

2018-02-01

The direct conversion of mechanical energy into electricity by nanomaterial-based devices offers potential for green energy harvesting1-3. A conventional triboelectric nanogenerator converts frictional energy into electricity by producing alternating current (a.c.) triboelectricity. However, this approach is limited by low current density and the need for rectification2. Here, we show that continuous direct-current (d.c.) with a maximum density of 106 A m-2 can be directly generated by a sliding Schottky nanocontact without the application of an external voltage. We demonstrate this by sliding a conductive-atomic force microscope tip on a thin film of molybdenum disulfide (MoS2). Finite element simulation reveals that the anomalously high current density can be attributed to the non-equilibrium carrier transport phenomenon enhanced by the strong local electrical field (105-106 V m-2) at the conductive nanoscale tip4. We hypothesize that the charge transport may be induced by electronic excitation under friction, and the nanoscale current-voltage spectra analysis indicates that the rectifying Schottky barrier at the tip-sample interface plays a critical role in efficient d.c. energy harvesting. This concept is scalable when combined with microfabricated or contact surface modified electrodes, which makes it promising for efficient d.c. triboelectricity generation.

Dynamic Kerr effect in a strong uniform AC electric field for interacting polar and polarizable molecules in the mean field approximation

NASA Astrophysics Data System (ADS)

Deshmukh, Snehal D.; Déjardin, Pierre-Michel; Kalmykov, Yuri P.

2017-09-01

Analytical formulas for the electric birefringence response of interacting polar and anisotropically polarizable molecules due to a uniform alternating electric field are derived using Berne's forced rotational diffusion model [B. J. Berne, J. Chem. Phys. 62, 1154 (1975)] in the nonlinear version described by Warchol and Vaughan [J. Chem. Phys. 71, 502 (1979)]. It is found for noninteracting molecules that the signal consists of a frequency-dependent DC component superimposed on an oscillatory part with a frequency twice that of the AC driving field. However, unlike noninteracting molecules, the AC part strongly deviates from its dilute counterpart. This suggests a possible way of motivating new experimental studies of intermolecular interactions involving electro-optical methods and complementary nonlinear dielectric relaxation experiments.

Electric Fields near RF Heating and Current Drive Antennas in Tore Supra Measured with Dynamic Stark Effect Spectroscopy*

NASA Astrophysics Data System (ADS)

Klepper, C. C.; Martin, E. H.; Isler, R. C.; Colas, L.; Hillairet, J.; Marandet, Y.; Lotte, Ph.; Colledani, G.; Martin, V.; Hillis, D. L.; Harris, J. H.; Saoutic, B.

2011-10-01

Computational models of the interaction between RF waves and the scrape-off layer plasma near ion cyclotron resonant heating (ICRH) and lower hybrid current drive launch antennas are continuously improving. These models mainly predict the RF electric fields produced in the SOL and, therefore, the best measurement for verification of these models would be a direct measurement of these electric fields. Both types of launch antennas are used on Tore Supra and are designed for high power (up to 4MW/antenna) and long pulse (> > 25s) operation. Direct, non-intrusive measurement of the RF electric fields in the vicinity of these structures is achieved by fitting spectral profiles of deuterium Balmer-alpha and Balmer-beta to a model that includes the dynamic, external-field Stark effect, as well as Zeeman splitting and Doppler broadening mechanisms. The measurements are compared to the mentioned, near-field region, RF antenna models. *Work supported in part by the US DOE under Contract No. DE-AC05-00OR22725 with UT-Battelle, LLC.

AC signal characterization for optimization of a CMOS single-electron pump

NASA Astrophysics Data System (ADS)

Murray, Roy; Perron, Justin K.; Stewart, M. D., Jr.; Zimmerman, Neil M.

2018-02-01

Pumping single electrons at a set rate is being widely pursued as an electrical current standard. Semiconductor charge pumps have been pursued in a variety of modes, including single gate ratchet, a variety of 2-gate ratchet pumps, and 2-gate turnstiles. Whether pumping with one or two AC signals, lower error rates can result from better knowledge of the properties of the AC signal at the device. In this work, we operated a CMOS single-electron pump with a 2-gate ratchet style measurement and used the results to characterize and optimize our two AC signals. Fitting this data at various frequencies revealed both a difference in signal path length and attenuation between our two AC lines. Using this data, we corrected for the difference in signal path length and attenuation by applying an offset in both the phase and the amplitude at the signal generator. Operating the device as a turnstile while using the optimized parameters determined from the 2-gate ratchet measurement led to much flatter, more robust charge pumping plateaus. This method was useful in tuning our device up for optimal charge pumping, and may prove useful to the semiconductor quantum dot community to determine signal attenuation and path differences at the device.

Thermal, Structural, AC Conductivity, and Dielectric Properties of Ethyl-2-amino-6-ethyl-5-oxo-4-(3-phenoxyphenyl)-5,6-dihydro-4H-pyrano[3,2-c]quinoline-3-carboxylate Thin Films

NASA Astrophysics Data System (ADS)

El-Shabaan, M. M.

2018-05-01

Thermal, structural, alternating-current (AC) conductivity (σ AC), and dielectric properties of ethyl-2-amino-6-ethyl-5-oxo-4-(3-phenoxyphenyl)-5,6-dihydro-4H-pyrano[3,2-c]quinoline-3-carboxylate (HPQC) thin films have been studied. Thermogravimetry analysis and differential scanning calorimetry confirmed the thermal stability of HPQC over a wide temperature range. Fourier-transform infrared spectroscopy and x-ray diffraction analysis were carried out on HPQC in powder form and as-deposited thin film. The crystal system and space group type were determined for HPQC in powder form. The AC conductivity and dielectric properties were determined in the frequency range from 0.5 kHz to 5 MHz and temperature range from 296 K to 443 K. The AC electrical conduction of HPQC thin film was found to be governed by the small-polaron tunneling mechanism. The polaron hopping energy (W H), tunneling distance (R), and density of states (N) near the Fermi level were determined as functions of temperature and frequency. The dielectric properties of HPQC thin film were studied by analysis of Nyquist diagrams, the dissipation factor (tan δ), and real (ɛ') and imaginary (ɛ″) parts of the dielectric constant.

Differences in receptor-evoked membrane electrical responses in native and mRNA-injected Xenopus oocytes.

PubMed

Oron, Y; Gillo, B; Gershengorn, M C

1988-06-01

Xenopus laevis oocytes are giant cells suitable for studies of plasma membrane receptors and signal transduction pathways because of their capacity to express receptors after injection of heterologous mRNA. We studied depolarizing chloride currents evoked by acetylcholine (AcCho) in native oocytes ("intrinsic AcCho response"), by thyrotropin-releasing hormone (TRH) in oocytes injected with pituitary (GH3) cell RNA ("acquired TRH response"), and by AcCho in oocytes injected with rat brain RNA ("acquired AcCho response"). We found differences in the latencies and patterns of these responses and in the responsiveness to these agonists when applied to the animal or vegetal hemisphere, even though all of the responses are mediated by the same signal transduction pathway. The common intrinsic response to AcCho is characterized by minimal latency (0.86 +/- 0.05 sec), a rapid, transient depolarization followed by a distinct prolonged depolarization, and larger responses obtained after AcCho application at the vegetal rather than the animal hemisphere. By contrast, the acquired responses to TRH and AcCho are characterized by much longer latencies, 9.3 +/- 1.0 and 5.5 +/- 0.8 sec, respectively, and large rapid depolarizations followed by less distinct prolonged depolarizations. The responsiveness on the two hemispheres to TRH and AcCho in mRNA-injected oocytes is opposite to that for the common intrinsic AcCho response in that there is a much greater response when agonist is applied at the animal rather than the vegetal hemisphere. We suggest that the differences in these responses are caused by differences in the intrinsic properties of these receptors. Because different receptors appear to be segregated in the same oocyte in distinct localizations, Xenopus oocytes may be an important model system in which to study receptor sorting in polarized cells.

Facilitatory effect of AC-iontophoresis of lidocaine hydrochloride on the permeability of human enamel and dentine in extracted teeth.

PubMed

Ikeda, Hideharu; Suda, Hideaki

2013-04-01

The objectives of the present study were to quantitatively evaluate chemical permeability through human enamel/dentine using conductometry and to clarify if alternating current (AC) iontophoresis facilitates such permeability. Electrical impedance of different concentrations of lidocaine hydrochloride was measured using a bipolar platinum impedance probe. A quadratic curve closely fitted to the response functions between conductance and lidocaine hydrochloride. For analysis of the passage of lidocaine hydrochloride through human enamel/dentine, eight premolars that were extracted for orthodontic treatment were sectioned at the cemento-enamel junction. The tooth crowns were held between two chambers with a double O-ring. The enamel-side chamber was filled with lidocaine hydrochloride, and the pulp-side chamber was filled with extrapure water. Two platinum plate electrodes were set at the end of each chamber to pass alternating current. A simulated interstitial pulp pressure was applied to the pulp-side chamber. The change in the concentration of lidocaine hydrochloride in the pulp-side chamber was measured every 2min using a platinum recording probe positioned at the centre of the pulp-side chamber. Passive entry without iontophoresis was used as a control. The level of lidocaine hydrochloride that passed through enamel/dentine against the dentinal fluid flow increased with time. Electrical conductance (G, mho) correlated closely to the concentration (x, mmol/L) of lidocaine hydrochloride (G=2.16x(2)+0.0289x+0.000376, r(2)=0.999). Lidocaine hydrochloride can pass through enamel/dentine. Conductometry showed that the level of lidocaine hydrochloride that passed through enamel/dentine was increased by AC iontophoresis. Copyright © 2012 Elsevier Ltd. All rights reserved.

An active homopolar magnetic bearing with high temperature superconductor (HTS) coils and ferromagnetic cores

NASA Technical Reports Server (NTRS)

Brown, G. V.; Dirusso, E.; Provenza, A. J.

1995-01-01

A proof-of-feasibility demonstration showed that high temperature superconductor (HTS) coils can be used in a high-load, active magnetic bearing in liquid nitrogen. A homopolar radial bearing with commercially wound HTS (Bi 2223) bias and control coils produced over 200 lb (890 N) radial load capacity (measured non-rotating) and supported a shaft to 14000 rpm. The goal was to show that HTS coils can operate stably with ferromagnetic cores in a feedback controlled system at a current density similar to that in Cu in liquid nitrogen. Design compromises permitted use of circular coils with rectangular cross section. Conductor improvements will eventually permit coil shape optimization, higher current density and higher bearing load capacity. The bias coil, wound with non-twisted, multifilament HTS conductor, required negligible power to carry its direct current. The control coils were wound with monofilament HTS sheathed in Ag. These dissipated negligible power for direct current (i.e. for steady radial load components). When an alternating current (AC) was added, the AC component dissipated power which increased rapidly with frequency and quadratically with AC amplitude. In fact at frequencies above about 2 hz, the effective resistance of the control coil conductor actually exceeds that of the silver which is in electrical parallel with the oxide superconductor. This is at least qualitatively understandable in the context of a Bean-type model of flux and current penetration into a Type II superconductor. Fortunately the dynamic currents required for bearing stability are of small amplitude. These results show that while twisted multifilament conductor is not needed for stable levitation, twisted multifilaments will be required to reduce control power for sizable dynamic loads, such as those due to unbalance.

Inductive detection of fieldlike and dampinglike ac inverse spin-orbit torques in ferromagnet/normal-metal bilayers

NASA Astrophysics Data System (ADS)

Berger, Andrew J.; Edwards, Eric R. J.; Nembach, Hans T.; Karenowska, Alexy D.; Weiler, Mathias; Silva, Thomas J.

2018-03-01

Functional spintronic devices rely on spin-charge interconversion effects, such as the reciprocal processes of electric field-driven spin torque and magnetization dynamics-driven spin and charge flow. Both dampinglike and fieldlike spin-orbit torques have been observed in the forward process of current-driven spin torque and dampinglike inverse spin-orbit torque has been well studied via spin pumping into heavy metal layers. Here, we demonstrate that established microwave transmission spectroscopy of ferromagnet/normal metal bilayers under ferromagnetic resonance can be used to inductively detect the ac charge currents driven by the inverse spin-charge conversion processes. This technique relies on vector network analyzer ferromagnetic resonance (VNA-FMR) measurements. We show that in addition to the commonly extracted spectroscopic information, VNA-FMR measurements can be used to quantify the magnitude and phase of all ac charge currents in the sample, including those due to spin pumping and spin-charge conversion. Our findings reveal that Ni80Fe20/Pt bilayers exhibit both dampinglike and fieldlike inverse spin-orbit torques. While the magnitudes of both the dampinglike and fieldlike inverse spin-orbit torque are of comparable scale to prior reported values for similar material systems, we observed a significant dependence of the dampinglike magnitude on the order of deposition. This suggests interface quality plays an important role in the overall strength of the dampinglike spin-to-charge conversion.

Hot electrons injection in carbon nanotubes under the influence of quasi-static ac-field

NASA Astrophysics Data System (ADS)

Amekpewu, M.; Mensah, S. Y.; Musah, R.; Mensah, N. G.; Abukari, S. S.; Dompreh, K. A.

2016-07-01

The theory of hot electrons injection in carbon nanotubes (CNTs) where both dc electric field (Ez), and a quasi-static ac field exist simultaneously (i.e. when the frequency ω of ac field is much less than the scattering frequency v (ω ⪡ v or ωτ ⪡ 1, v =τ-1) where τ is relaxation time) is studied. The investigation is done theoretically by solving semi-classical Boltzmann transport equation with and without the presence of the hot electrons source to derive the current densities. Plots of the normalized current density versus dc field (Ez) applied along the axis of the CNTs in the presence and absence of hot electrons reveal ohmic conductivity initially and finally negative differential conductivity (NDC) provided ωτ ⪡ 1 (i.e. quasi- static case). With strong enough axial injection of the hot electrons, there is a switch from NDC to positive differential conductivity (PDC) about Ez ≥ 75 kV / cm and Ez ≥ 140 kV / cm for a zigzag CNT and an armchair CNT respectively. Thus, the most important tough problem for NDC region which is the space charge instabilities can be suppressed due to the switch from the NDC behaviour to the PDC behaviour predicting a potential generation of terahertz radiations whose applications are relevance in current-day technology, industry, and research.

Recovery of consciousness in broilers following combined dc and ac stunning

USDA-ARS?s Scientific Manuscript database

Broilers in the United States are typically electrically stunned using low voltage-high frequency pulsed DC water bath stunners and in the European Union broilers are electrocuted using high voltage-low frequency AC. DC stunned broilers regain consciousness in the absence of exsanguination and AC st...

High Voltage Power Supply Design Guide for Space

NASA Technical Reports Server (NTRS)

Bever, Renate S.; Ruitberg, Arthur P.; Kellenbenz, Carl W.; Irish, Sandra M.

2006-01-01

This book is written for newcomers to the topic of high voltage (HV) in space and is intended to replace an earlier (1970s) out-of-print document. It discusses the designs, problems, and their solutions for HV, mostly direct current, electric power, or bias supplies that are needed for space scientific instruments and devices, including stepping supplies. Output voltages up to 30kV are considered, but only very low output currents, on the order of microamperes. The book gives a brief review of the basic physics of electrical insulation and breakdown problems, especially in gases. It recites details about embedment and coating of the supplies with polymeric resins. Suggestions on HV circuit parts follow. Corona or partial discharge testing on the HV parts and assemblies is discussed both under AC and DC impressed test voltages. Electric field analysis by computer on an HV device is included in considerable detail. Finally, there are many examples given of HV power supplies, complete with some of the circuit diagrams and color photographs of the layouts.

Tobacco Stem-Based Activated Carbons for High Performance Supercapacitors

NASA Astrophysics Data System (ADS)

Xia, Xiaohong; Liu, Hongbo; Shi, Lei; He, Yuede

2012-09-01

Tobacco stem-based activated carbons (TS-ACs) were prepared by simple KOH activation and their application as electrodes in the electrical double layer capacitor (EDLC) performed successfully. The BET surface area, pore volume, and pore size distribution of the TS-ACs were evaluated based on N2 adsorption isotherms at 77 K. The surface area of the obtained activated carbons varies over a wide range (1472.8-3326.7 m2/g) and the mesoporosity was enhanced significantly as the ratio of KOH to tobacco stem (TS) increased. The electrochemical behaviors of series TS-ACs were characterized by means of galvanostatic charging/discharging, cyclic voltammetry, and impedance spectroscopy. The correlation between electrochemical properties and pore structure was investigated. A high specific capacitance value as 190 F/g at 1 mA/cm2 was obtained in 1 M LiPF6-EC/DMC/DEC electrolyte solution. Furthermore, good performance is also achieved even at high current densities. A development of new use for TS into a valuable energy storage material is explored.

Effect of electric field induced alignment and dispersion of functionalized carbon nanotubes on properties of natural rubber

NASA Astrophysics Data System (ADS)

Gao, Jiangshan; He, Yan; Gong, Xiubin

2018-06-01

The original equipment and method for orienting multi-walled carbon nanotubes (MWCNTs) in natural rubber (NR) by alternating current (AC) electric field were reported in the present study. MWCNTs with various volume fractions were dispersed in the mixture latex which composed of natural rubber, additives and methylbenzene. The application of AC electric field during nanocomposites curing process was used to induce the formation of aligned conductive nanotube networks between the electrodes. The aligned MWCNTs in the composites have a better orientation performance and dispersion quality than these of random MWCNTs by analyzing TEM and SEM images. The effects of MWCNTs anisotropy on thermal conductivity, dielectric properties, and dynamic mechanical properties of NR were studied. The mean value of thermal conductivity of composites loading with aligned MWCNTs was 8.67% higher than that of composites with random MWCNTs due to the anisotropy of aligned MWCNTs. The compounds with aligned MWCNTs possessed low dielectric constant, loss tangents and conductivity, namely a good insulativity. The compounds loading with aligned MWCNTs had lower loss modulus and better dynamic mechanical properties than those with random MWCNTs. This method can make full use of the high thermal conductivity of MWCNTs axis, and expand the application areas of natural rubber like conducting heat in a certain direction with a high efficiency.

Measurements of Induced-Charge Electroosmotic Flow Around a Metallic Rod

NASA Astrophysics Data System (ADS)

Beskok, Ali; Canpolat, Cetin

2012-11-01

A cylindrical gold-coated stainless steel rod was positioned at the center of a straight microchannel connecting two fluid reservoirs on either end. The microchannel was filled with 1 mM KCl containing 0.5 micron diameter carboxylate-modified spherical particles. Induced-charge electro-osmotic (ICEO) flow occurred around the metallic rod under a sinusoidal AC electric field applied using two platinum electrodes. The ICEO flows around the metallic rod were measured using micro particle image velocimetry (micro-PIV) technique as functions of the AC electric field strength and frequency. The present study provides experimental data about ICEO flow in the weakly nonlinear limit of thin double layers, in which, the charging dynamics of the double layer cannot be presented analytically. Flow around the rod is quadrupolar, driving liquid towards the rod along the electric field and forcing it away from the rod in the direction perpendicular to the imposed electric field. The measured ICEO flow velocity is proportional to the square of the electric field strength, and depends on the applied AC frequency.

Preparation of Janus Particles and Alternating Current Electrokinetic Measurements with a Rapidly Fabricated Indium Tin Oxide Electrode Array.

PubMed

Chen, Yu-Liang; Jiang, Hong-Ren

2017-06-23

This article provides a simple method to prepare partially or fully coated metallic particles and to perform the rapid fabrication of electrode arrays, which can facilitate electrical experiments in microfluidic devices. Janus particles are asymmetric particles that contain two different surface properties on their two sides. To prepare Janus particles, a monolayer of silica particles is prepared by a drying process. Gold (Au) is deposited on one side of each particle using a sputtering device. The fully coated metallic particles are completed after the second coating process. To analyze the electrical surface properties of Janus particles, alternating current (AC) electrokinetic measurements, such as dielectrophoresis (DEP) and electrorotation (EROT)- which require specifically designed electrode arrays in the experimental device- are performed. However, traditional methods to fabricate electrode arrays, such as the photolithographic technique, require a series of complicated procedures. Here, we introduce a flexible method to fabricate a designed electrode array. An indium tin oxide (ITO) glass is patterned by a fiber laser marking machine (1,064 nm, 20 W, 90 to 120 ns pulse-width, and 20 to 80 kHz pulse repetition frequency) to create a four-phase electrode array. To generate the four-phase electric field, the electrodes are connected to a 2-channel function generator and to two invertors. The phase shift between the adjacent electrodes is set at either 90° (for EROT) or 180° (for DEP). Representative results of AC electrokinetic measurements with a four-phase ITO electrode array are presented.

Lipid rafts sense and direct electric field-induced migration

PubMed Central

Lin, Bo-jian; Tsao, Shun-hao; Chen, Alex; Hu, Shu-Kai; Chao, Ling

2017-01-01

Endogenous electric fields (EFs) are involved in developmental regulation and wound healing. Although the phenomenon is known for more than a century, it is not clear how cells perceive the external EF. Membrane proteins, responding to electrophoretic and electroosmotic forces, have long been proposed as the sensing molecules. However, specific charge modification of surface proteins did not change cell migration motility nor directionality in EFs. Moreover, symmetric alternating current (AC) EF directs cell migration in a frequency-dependent manner. Due to their charge and ability to coalesce, glycolipids are therefore the likely primary EF sensor driving polarization of membrane proteins and intracellular signaling. We demonstrate that detergent-resistant membrane nanodomains, also known as lipid rafts, are the primary response element in EF sensing. The clustering and activation of caveolin and signaling proteins further stabilize raft structure and feed-forward downstream signaling events, such as rho and PI3K activation. Theoretical modeling supports the experimental results and predicts AC frequency-dependent cell and raft migration. Our results establish a fundamental mechanism for cell electrosensing and provide a role in lipid raft mechanotransduction. PMID:28739955

Lipid rafts sense and direct electric field-induced migration.

PubMed

Lin, Bo-Jian; Tsao, Shun-Hao; Chen, Alex; Hu, Shu-Kai; Chao, Ling; Chao, Pen-Hsiu Grace

2017-08-08

Endogenous electric fields (EFs) are involved in developmental regulation and wound healing. Although the phenomenon is known for more than a century, it is not clear how cells perceive the external EF. Membrane proteins, responding to electrophoretic and electroosmotic forces, have long been proposed as the sensing molecules. However, specific charge modification of surface proteins did not change cell migration motility nor directionality in EFs. Moreover, symmetric alternating current (AC) EF directs cell migration in a frequency-dependent manner. Due to their charge and ability to coalesce, glycolipids are therefore the likely primary EF sensor driving polarization of membrane proteins and intracellular signaling. We demonstrate that detergent-resistant membrane nanodomains, also known as lipid rafts, are the primary response element in EF sensing. The clustering and activation of caveolin and signaling proteins further stabilize raft structure and feed-forward downstream signaling events, such as rho and PI3K activation. Theoretical modeling supports the experimental results and predicts AC frequency-dependent cell and raft migration. Our results establish a fundamental mechanism for cell electrosensing and provide a role in lipid raft mechanotransduction.

Structural, electrical, and photoelectric properties of p-NiO/n-CdTe heterojunctions

NASA Astrophysics Data System (ADS)

Parkhomenko, Hryhorii; Solovan, Mykhaylo; Brus, Viktor; Maystruk, Eduard; Maryanchuk, Pavlo

2018-01-01

p-NiO/n-CdTe-photosensitive heterojunctions were prepared by the deposition of nickel oxide thin films onto n-type single-crystal CdTe substrates by DC reactive magnetron sputtering. The analysis of capacitance-voltage (C-V) characteristics, measured at different frequencies of the small amplitude AC signal and corrected by the effect of the series resistance, provided evidence of the presence of electrically charged interface states, which significantly affect the measured capacitance. The dominant current transport mechanisms in the heterojunctions were determined at forward and reverse biases. Using "light" I-V characteristics, we determined the open-circuit voltage Voc=0.42 V, the short-circuit current Isc=57.5 μA/cm2, and the fill factor FF=0.24 under white light illumination with the intensity of 80 mW.

The monitoring of transient regimes on machine tools based on speed, acceleration and active electric power absorbed by motors

NASA Astrophysics Data System (ADS)

Horodinca, M.

2016-08-01

This paper intend to propose some new results related with computer aided monitoring of transient regimes on machine-tools based on the evolution of active electrical power absorbed by the electric motor used to drive the main kinematic chains and the evolution of rotational speed and acceleration of the main shaft. The active power is calculated in numerical format using the evolution of instantaneous voltage and current delivered by electrical power system to the electric motor. The rotational speed and acceleration of the main shaft are calculated based on the signal delivered by a sensor. Three real-time analogic signals are acquired with a very simple computer assisted setup which contains a voltage transformer, a current transformer, an AC generator as rotational speed sensor, a data acquisition system and a personal computer. The data processing and analysis was done using Matlab software. Some different transient regimes were investigated; several important conclusions related with the advantages of this monitoring technique were formulated. Many others features of the experimental setup are also available: to supervise the mechanical loading of machine-tools during cutting processes or for diagnosis of machine-tools condition by active electrical power signal analysis in frequency domain.

HVDC power transmission technology assessment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hauth, R.L.; Tatro, P.J.; Railing, B.D.

1997-04-01

The purpose of this study was to develop an assessment of the national utility system`s needs for electric transmission during the period 1995-2020 that could be met by future reduced-cost HVDC systems. The assessment was to include an economic evaluation of HVDC as a means for meeting those needs as well as a comparison with competing technologies such as ac transmission with and without Flexible AC Transmission System (FACTS) controllers. The role of force commutated dc converters was to be assumed where appropriate. The assessment begins by identifying the general needs for transmission in the U.S. in the context ofmore » a future deregulated power industry. The possible roles for direct current transmission are then postulated in terms of representative scenarios. A few of the scenarios are illustrated with the help of actual U.S. system examples. non-traditional applications as well as traditional applications such as long lines and asynchronous interconnections are discussed. The classical ``break-even distance`` concept for comparing HVDC and ac lines is used to assess the selected scenarios. The impact of reduced-cost converters is reflected in terms of the break-even distance. This report presents a comprehensive review of the functional benefits of HVDC transmission and updated cost data for both ac and dc system components. It also provides some provocative thoughts on how direct current transmission might be applied to better utilize and expand our nation`s increasingly stressed transmission assets.« less

Double-duct liquid metal magnetohydrodynamic engine

DOEpatents

Haaland, Carsten M.

1995-01-01

An internal combustion, liquid metal (LM) magnetohydrodynamic (MHD) engine and an alternating current (AC) magnetohydrodynamic generator, are used in combination to provide useful AC electric energy output. The engine design has-four pistons and a double duct configuration, with each duct containing sodium potassium liquid metal confined between free pistons located at either end of the duct. The liquid metal is forced to flow back and forth in the duct by the movement of the pistons, which are alternatively driven by an internal combustion process. In the MHD generator, the two LM-MHD ducts pass in close proximity through a Hartmann duct with output transformer. AC power is produced by operating the engine with the liquid metal in the two generator ducts always flowing in counter directions. The amount of liquid metal maintained in the ducts may be varied. This provides a variable stroke length for the pistons. The engine/generator provides variable AC power at variable frequencies that correspond to the power demands of the vehicular propulsion. Also the engine should maintain nearly constant efficiency throughout the range of power usage. Automobiles and trucks could be powered by the invention, with no transmission or power converter devices being required.

Double-duct liquid metal magnetohydrodynamic engine

DOEpatents

Haaland, Carsten M.

1997-01-01

An internal combustion, liquid metal (LM) magnetohydrodynamic (MHD) engine and an alternating current (AC) magnetohydrodynamic generator, are used in combination to provide useful AC electric energy output. The engine design has four pistons and a double duct configuration, with each duct containing sodium potassium liquid metal confined between free pistons located at either end of the duct. The liquid metal is forced to flow back and forth in the duct by the movement of the pistons, which are alternatively driven by an internal combustion process. In the MHD generator, the two LM-MHD ducts pass in close proximity through a Hartmann duct with output transformer. AC power is produced by operating the engine with the liquid metal in the two generator ducts always flowing in counter directions. The amount of liquid metal maintained in the ducts may be varied. This provides a variable stroke length for the pistons. The engine/generator provides variable AC power at variable frequencies that correspond to the power demands of the vehicular propulsion. Also the engine should maintain nearly constant efficiency throughout the range of power usage. Automobiles and trucks could be powered by the invention, with no transmission or power converter devices being required.

A Computer Model for Teaching the Dynamic Behavior of AC Contactors

ERIC Educational Resources Information Center

Ruiz, J.-R. R.; Espinosa, A. G.; Romeral, L.

2010-01-01

Ac-powered contactors are extensively used in industry in applications such as automatic electrical devices, motor starters, and heaters. In this work, a practical session that allows students to model and simulate the dynamic behavior of ac-powered electromechanical contactors is presented. Simulation is carried out using a rigorous parametric…

Mixing enhancement by biologically inspired convection in a micro-chamber using alternating current galvanotactic control of the Tetrahymena pyriformis

NASA Astrophysics Data System (ADS)

Kim, Jihoon; Jang, Yonghee; Byun, Doyoung; Hyung Kim, Dal; Jun Kim, Min

2013-09-01

Recently, there has been increasing interest in the swimming behavior of microorganisms and biologically inspired micro-robots. In this study, we investigated biologically induced convection flow with living microorganism using galvanotaxis. We fabricated and evaluated our micro-mixer with motile cells. For the cell based active micro-mixers, two miscible fluids were used to measure the mixing index. Under alternating current (AC) electric fields with varying frequency, a group of motile Tetrahymena pyriformis cells generated reciprocal motion with circulating flows around their pathline, enhancing the mixing ratio.

Electrical conductivity of activated carbon-metal oxide nanocomposites under compression: a comparison study.

PubMed

Barroso-Bogeat, A; Alexandre-Franco, M; Fernández-González, C; Macías-García, A; Gómez-Serrano, V

2014-12-07

From a granular commercial activated carbon (AC) and six metal oxide (Al2O3, Fe2O3, SnO2, TiO2, WO3 and ZnO) precursors, two series of AC-metal oxide nanocomposites were prepared by wet impregnation, oven-drying at 120 °C, and subsequent heat treatment at 200 or 850 °C in an inert atmosphere. Here, the electrical conductivity of the resulting products was studied under moderate compression. The influence of the applied pressure, sample volume, mechanical work, and density of the hybrid materials was thoroughly investigated. The DC electrical conductivity of the compressed samples was measured at room temperature by the four-probe method. Compaction assays suggest that the mechanical properties of the nanocomposites are largely determined by the carbon matrix. Both the decrease in volume and the increase in density were relatively small and only significant at pressures lower than 100 kPa for AC and most nanocomposites. In contrast, the bulk electrical conductivity of the hybrid materials was strongly influenced by the intrinsic conductivity, mean crystallite size, content and chemical nature of the supported phases, which ultimately depend on the metal oxide precursor and heat treatment temperature. The supported nanoparticles may be considered to act as electrical switches either hindering or favouring the effective electron transport between the AC cores of neighbouring composite particles in contact under compression. Conductivity values as a rule were lower for the nanocomposites than for the raw AC, all of them falling in the range of semiconductor materials. With the increase in heat treatment temperature, the trend is toward the improvement of conductivity due to the increase in the crystallite size and, in some cases, to the formation of metals in the elemental state and even metal carbides. The patterns of variation of the electrical conductivity with pressure and mechanical work were slightly similar, thus suggesting the predominance of the pressure effects rather than the volume ones.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lentine, Anthony L.; Kekatpure, Rohan Deodatta; Zortman, William A.

A photonic resonator system is designed to use thermal tuning to adjust the resonant wavelength of each resonator in the system, with a separate tuning circuit associated with each resonator so that individual adjustments may be made. The common electrical ground connection between the tuning circuits is particularly formed to provide thermal isolation between adjacent resonators by including a capacitor along each return path to ground, where the presence of the capacitor's dielectric material provides the thermal isolation. The use of capacitively coupling necessarily requires the use of an AC current as an input to the heater element (conductor/resistor) ofmore » each resonator, where the RMS value of the AC signal is indicative of the amount of heat that is generated along the element and the degree of wavelength tuning that is obtained.« less

Separate Poles Mode for Large-Capacity HVDC System

NASA Astrophysics Data System (ADS)

Zhu, Lin; Gao, Qin

2017-05-01

This paper proposes a novel connection mode, separate poles mode (SPM), for large-capacity HVDC systems. The proposed mode focuses on the core issues of HVDC connection in interconnected power grids and principally aims at increasing effective electric distance between poles, which helps to mitigate the interaction problems between AC system and DC system. Receiving end of bipolar HVDC has been divided into different inverter stations under the mode, and thus significantly alleviates difficulties in power transmission and consumption of receiving-end AC grids. By investigating the changes of multi-feed short-circuit ratio (MISCR), finding that HVDC with SPM shows critical impacts upon itself and other HVDC systems with conventional connection mode, which demonstrates that SPM can make balance between MISCR increase and short-circuit current limit.

Battery charging and discharging research based on the interactive technology of smart grid and electric vehicle

NASA Astrophysics Data System (ADS)

Zhang, Mingyang

2018-06-01

To further study the bidirectional flow problem of V2G (Vehicle to Grid) charge and discharge motor, the mathematical model of AC/DC converter and bi-directional DC/DC converter was established. Then, lithium battery was chosen as the battery of electric vehicle and its mathematical model was established. In order to improve the service life of lithium battery, bidirectional DC/DC converter adopted constant current and constant voltage control strategy. In the initial stage of charging, constant current charging was adopted with current single closed loop control. After reaching a certain value, voltage was switched to constant voltage charging controlled by voltage and current. Subsequently, the V2G system simulation model was built in MATLAB/Simulink. The simulation results verified the correctness of the control strategy and showed that when charging, constant current and constant voltage charging was achieved, the grid side voltage and current were in the same phase, and the power factor was about 1. When discharging, the constant current discharge was applied, and the grid voltage and current phase difference was r. To sum up, the simulation results are correct and helpful.

Optimization of spin-torque switching using AC and DC pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dunn, Tom; Kamenev, Alex; Fine Theoretical Physics Institute, University of Minnesota, Minneapolis, Minnesota 55455

2014-06-21

We explore spin-torque induced magnetic reversal in magnetic tunnel junctions using combined AC and DC spin-current pulses. We calculate the optimal pulse times and current strengths for both AC and DC pulses as well as the optimal AC signal frequency, needed to minimize the Joule heat lost during the switching process. The results of this optimization are compared against numeric simulations. Finally, we show how this optimization leads to different dynamic regimes, where switching is optimized by either a purely AC or DC spin-current, or a combination AC/DC spin-current, depending on the anisotropy energies and the spin-current polarization.

Grid regulation services for energy storage devices based on grid frequency

DOEpatents

Pratt, Richard M; Hammerstrom, Donald J; Kintner-Meyer, Michael C.W.; Tuffner, Francis K

2013-07-02

Disclosed herein are representative embodiments of methods, apparatus, and systems for charging and discharging an energy storage device connected to an electrical power distribution system. In one exemplary embodiment, a controller monitors electrical characteristics of an electrical power distribution system and provides an output to a bi-directional charger causing the charger to charge or discharge an energy storage device (e.g., a battery in a plug-in hybrid electric vehicle (PHEV)). The controller can help stabilize the electrical power distribution system by increasing the charging rate when there is excess power in the electrical power distribution system (e.g., when the frequency of an AC power grid exceeds an average value), or by discharging power from the energy storage device to stabilize the grid when there is a shortage of power in the electrical power distribution system (e.g., when the frequency of an AC power grid is below an average value).

Grid regulation services for energy storage devices based on grid frequency

DOEpatents

Pratt, Richard M.; Hammerstrom, Donald J.; Kintner-Meyer, Michael C. W.; Tuffner, Francis K.

2017-09-05

Disclosed herein are representative embodiments of methods, apparatus, and systems for charging and discharging an energy storage device connected to an electrical power distribution system. In one exemplary embodiment, a controller monitors electrical characteristics of an electrical power distribution system and provides an output to a bi-directional charger causing the charger to charge or discharge an energy storage device (e.g., a battery in a plug-in hybrid electric vehicle (PHEV)). The controller can help stabilize the electrical power distribution system by increasing the charging rate when there is excess power in the electrical power distribution system (e.g., when the frequency of an AC power grid exceeds an average value), or by discharging power from the energy storage device to stabilize the grid when there is a shortage of power in the electrical power distribution system (e.g., when the frequency of an AC power grid is below an average value).

Grid regulation services for energy storage devices based on grid frequency

DOEpatents

Pratt, Richard M; Hammerstrom, Donald J; Kintner-Meyer, Michael C.W.; Tuffner, Francis K

2014-04-15

Disclosed herein are representative embodiments of methods, apparatus, and systems for charging and discharging an energy storage device connected to an electrical power distribution system. In one exemplary embodiment, a controller monitors electrical characteristics of an electrical power distribution system and provides an output to a bi-directional charger causing the charger to charge or discharge an energy storage device (e.g., a battery in a plug-in hybrid electric vehicle (PHEV)). The controller can help stabilize the electrical power distribution system by increasing the charging rate when there is excess power in the electrical power distribution system (e.g., when the frequency of an AC power grid exceeds an average value), or by discharging power from the energy storage device to stabilize the grid when there is a shortage of power in the electrical power distribution system (e.g., when the frequency of an AC power grid is below an average value).

Aging dynamics in the polymer glass of poly(2-chlorostyrene): Dielectric susceptibility and volume

NASA Astrophysics Data System (ADS)

Fukao, Koji; Tahara, Daisuke

2009-11-01

Aging dynamics was investigated in the glassy states of poly(2-chlorostyrene) by measuring the complex electrical capacitance during aging below the glass transition temperature. The variations with time and temperature of the ac dielectric susceptibility and volume could be determined by simply measuring the variation in the complex electrical capacitance. Isothermal aging at a given temperature for several hours after an intermittent stop in constant-rate cooling is stored in the deviations of both the real and imaginary parts of the complex ac dielectric susceptibility and volume. During cooling after isothermal aging, the deviation of the ac dielectric susceptibility from the reference value decreases and almost vanishes at room temperature. By contrast, the deviation in volume induced during isothermal aging remains almost constant during cooling. The simultaneous measurement of ac dielectric susceptibility and volume clearly revealed that the ac dielectric susceptibility exhibits a full rejuvenation effect, whereas the volume does not show any rejuvenation effects. We discuss a plausible model that can reproduce the present experimental results.

High voltage AC plasma torches with long electric arcs for plasma-chemical applications

NASA Astrophysics Data System (ADS)

Surov, A. V.; Popov, S. D.; Serba, E. O.; Pavlov, A. V.; Nakonechny, Gh V.; Spodobin, V. A.; Nikonov, A. V.; Subbotin, D. I.; Borovskoy, A. M.

2017-04-01

Powerful AC plasma torches are in demand for a number of advanced plasma chemical applications, they can provide high enthalpy of the working gas. IEE RAS specialists have developed a number of models of stationary thermal plasma torches for continuous operation on air with the power from 5 to 500 kW, and on mixture of H2O, CO2 and CH4 up to 150 kW. AC plasma torches were tested on the pilot plasmachemical installations. Powerful AC plasma torch with hollow electrodes and the gas vortex stabilization of arc in cylindrical channels and its operation characteristics are presented. Lifetime of its continuous operation on air is 2000 hours and thermal efficiency is about 92%, the electric arc length between two electrodes of the plasma torch exceeds 2 m.

VLF-emissions from ring current electrons. An interpretation of the band of missing emissions

NASA Technical Reports Server (NTRS)

Maeda, K.; Smith, P. H.; Anderson, R. R.

1976-01-01

VLF-emissions associated with the enhancement of ring current electrons during magnetic storms and substorms which were detected by the equatorially orbiting S-A satellite (Explorer 45) are described. The emissions observed near the geomagnetic equator consist of essentially two frequency regimes, i.e., one above the electron gyrofrequency, f sub H at the equator and the other below f sub H. This is indicated as a part of the wide-band data obtained during the main phase of the December 17, 1971 magnetic storm. The upper figure is the ac-magnetic field data measured by the search-coil magnetometer with the upper cutoff of 3kHz and the lower figure is the ac-electric field data obtained by the electric field sensor with the upper cutoff of 10kHz. These figures show the time sequence of the observed emissions along the inbound orbit (No. 101) of the satellite as f sub H changes approximately from 3 kHz at 20 UT to 6 kHz at 21 UT. The emissions above f sub H are electrostatic mode, which peak near the frequencies of (n + 1/2) f sub H where n is positive integer, and sometimes emissions up to n = 10 are observed. The emissions below f sub H are whistler mode, which have a conspicuous gap along exactly half electron gyrofrequency, f sub H/2.

Vehicle performance tests of the Ford/GE first generation single-shaft (ETX-I) alternating current propulsion system

NASA Astrophysics Data System (ADS)

Crumley, R. L.; MacDowall, R. D.; Hardin, J. E.; Burke, A. F.

1989-04-01

This report is concerned with the test and evaluation of the ETX-I electric test vehicle, which is a Mercury LN7 retrofitted with the single-shaft ac electric powertrain developed by Ford and General Electric under contract to the U.S. Department of Energy (DOE) during the period 1982 to 1985. The lead-acid battery used in the ETX-I was developed by Lucas Chloride Electric Vehicle (EV) Systems (LCEVS) as part of the same DOE contract. Extensive tests of the powertrain and battery were done by General Electric and Lucas Chloride before they were integrated into the ETX-I test vehicle by Ford. Ford did limited testing of the ETX-I vehicle on a chassis dynamometer to determine the energy consumption of the powertrain for several driving schedules before the vehicle was shipped to INEL for complete dynamometer testing. Ford also performed track tests with the ETX-I to determine its acceleration performance characteristics.

Self-assembly of metal nanowires induced by alternating current electric fields

NASA Astrophysics Data System (ADS)

García-Sánchez, Pablo; Arcenegui, Juan J.; Morgan, Hywel; Ramos, Antonio

2015-01-01

We describe the reversible assembly of an aqueous suspension of metal nanowires into two different 2-dimensional stable configurations. The assembly is induced by an AC electric field of magnitude around 10 kV/m. It is known that single metal nanowires orientate parallel to the electric field for all values of applied frequency, according to two different mechanisms depending on the frequency. These different mechanisms also govern the mutual interaction between nanowires, which leads to directed-assembly into distinctive structures, the shape of which depends on the frequency of the applied field. We show that for frequencies higher than the typical frequency for charging the electrical double layer at the metal-electrolyte interface, dipole-dipole interaction leads to the formation of chains of nanowires. For lower frequencies, the nanowires form wavy bands perpendicular to the electric field direction. This behavior appears to be driven by the electroosmotic flow induced on the metal surface of the nanowires. Remarkably, no similar structures have been reported in previous studies of nanowires.

Poynting-vector based method for determining the bearing and location of electromagnetic sources

DOEpatents

Simons, David J.; Carrigan, Charles R.; Harben, Philip E.; Kirkendall, Barry A.; Schultz, Craig A.

2008-10-21

A method and apparatus is utilized to determine the bearing and/or location of sources, such as, alternating current (A.C.) generators and loads, power lines, transformers and/or radio-frequency (RF) transmitters, emitting electromagnetic-wave energy for which a Poynting-Vector can be defined. When both a source and field sensors (electric and magnetic) are static, a bearing to the electromagnetic source can be obtained. If a single set of electric (E) and magnetic (B) sensors are in motion, multiple measurements permit location of the source. The method can be extended to networks of sensors allowing determination of the location of both stationary and moving sources.

Superconducting magnetic energy storage for asynchronous electrical systems

DOEpatents

Boenig, Heinrich J.

1986-01-01

A superconducting magnetic energy storage coil connected in parallel between converters of two or more ac power systems provides load leveling and stability improvement to any or all of the ac systems. Control is provided to direct the charging and independently the discharging of the superconducting coil to at least a selected one of the ac power systems.

Cost Performance Estimating Relationships for Hybrid Electric Vehicle Components

DTIC Science & Technology

2003-07-31

Permanent magnet motors are more likely to be used as generators, while AC induction motors are more efficiently used as motors. Inverters/controllers can...than permanent magnet motors . Switched Reluctance motors are also used on hybrid electric vehicles, but are not used as widely as either AC...induction or permanent magnet motors , and are not analyzed here. Methodology The motor estimates are based on power, with kilowatts being the unit of

Frequency and temperature dependence of dielectric and ac electrical properties of NiFe2O4-ZnO multiferroic nanocomposite

NASA Astrophysics Data System (ADS)

Dutta, Papia; Mandal, S. K.; Dey, P.; Nath, A.

2018-04-01

We have presented the ac electrical properties and dielectric studies of 0.5 NiFe2O4 - 0.5 ZnO multiferroic nanocomposites prepared through low temperature "pyrophoric reaction process". Structural characterization has been carried out through X-ray diffraction technique, which shows the co-existence of both the phases of the nanocomposites. The ac electrical properties of nanocomposites have been studied employing impedance spectroscopy technique. The impedance value is found to increase with increase in magnetic field attributing the magnetostriction property of the composites. Dielectric constant is found to decrease with both the increase in magnetic fields and temperatures. Studies of dielectric constant reveal the Maxwell Wagner interfacial polarization at low frequency regime. Relaxation frequency as a function of magnetic fields and temperatures is found to shift towards the high frequency region.

Electrokinetically driven microfluidic mixing with patchwise surface heterogeneity and AC applied electric field

NASA Astrophysics Data System (ADS)

Luo, Win-Jet; Yue, Cheng-Feng

2004-12-01

This paper investigates two-dimensional, time-dependent electroosmotic flows driven by an AC electric field via patchwise surface heterogeneities distributed along the microchannel walls. The time-dependent flow fields through the microchannel are simulated for various patchwise heterogeneous surface patterns using the backwards-Euler time stepping numerical method. Different heterogeneous surface patterns are found to create significantly different electrokinetic transport phenomena. It is shown that the presence of oppositely charged surface heterogeneities on the microchannel walls results in the formation of localized flow circulations within the bulk flow. These circulation regions grow and decay periodically in accordance with the applied periodic AC electric field intensity. The circulations provide an effective means of enhancing species mixing in the microchannel. A suitable design of the patchwise heterogeneous surface pattern permits the mixing channel length and the retention time required to attain a homogeneous solution to be reduced significantly.

dc Arc Fault Effect on Hybrid ac/dc Microgrid

NASA Astrophysics Data System (ADS)

Fatima, Zahra

The advent of distributed energy resources (DER) and reliability and stability problems of the conventional grid system has given rise to the wide spread deployment of microgrids. Microgrids provide many advantages by incorporating renewable energy sources and increasing the reliability of the grid by isolating from the main grid in case of an outage. AC microgrids have been installed all over the world, but dc microgrids have been gaining interest due to the advantages they provide over ac microgrids. However the entire power network backbone is still ac and dc microgrids require expensive converters to connect to the ac power network. As a result hybrid ac/dc microgrids are gaining more attention as it combines the advantages of both ac and dc microgrids such as direct integration of ac and dc systems with minimum number of conversions which increases the efficiency by reducing energy losses. Although dc electric systems offer many advantages such as no synchronization and no reactive power, successful implementation of dc systems requires appropriate protection strategies. One unique protection challenge brought by the dc systems is dc arc faults. A dc arc fault is generated when there is a gap in the conductor due to insulation degradation and current is used to bridge the gap, resulting in an arc with very high temperature. Such a fault if it goes undetected and is not extinguished can cause damage to the entire system and cause fires. The purpose of the research is to study the effect of the dc arc fault at different locations in the hybrid ac/dc microgrid and provide insight on the reliability of the grid components when it is impacted by arc faults at various locations in the grid. The impact of dc arc fault at different locations on the performance of the PV array, wind generation, and constant power loads (CPL) interfaced with dc/dc converters is studied. MATLAB/Simulink is used to model the hybrid ac/dc microgrid and arc fault.

Design and Modelling of a Microfluidic Electro-Lysis Device with Controlling Plates

NASA Technical Reports Server (NTRS)

Jenkins, A.; Chen, C. P.; Spearing, S.; Monaco, L. A.; Steele, A.; Flores, G.

2006-01-01

Many Lab-on-Chip applications require sample pre-treatment systems. Using electric fields to perform cell-lysis in bio-MEMS systems has provided a powerful tool which can be integrated into Lab-on-a-Chip platforms. The major design considerations for electro-lysis devices include optimal geometry and placement of micro-electrodes, cell concentration, flow rates, optimal electric field (e.g. pulsed DC vs. AC), etc. To avoid electrolysis of the flowing solution at the exposed electrode surfaces, magnitudes and the applied voltages and duration of the DC pulse, or the AC frequency of the AC, have to be optimized for a given configuration. Using simulation tools for calculation of electric fields has proved very useful, for exploring alternative configurations and operating conditions for achieving electro cell-lysis. To alleviate the problem associated with low electric fields within the microfluidics channel and the high voltage demand on the contact electrode strips, two "control plates" are added to the microfluidics configuration. The principle of placing the two controlling plate-electrodes is based on the electric fields generated by a combined insulator/dielectric (gladwater) media. Surface charges are established at the insulator/dielectric interface. This paper discusses the effects of this interface charge on the modification of the electric field of the flowing liquid/cell solution.

Effect of proton-conduction in electrolyte on electric efficiency of multi-stage solid oxide fuel cells

PubMed Central

Matsuzaki, Yoshio; Tachikawa, Yuya; Somekawa, Takaaki; Hatae, Toru; Matsumoto, Hiroshige; Taniguchi, Shunsuke; Sasaki, Kazunari

2015-01-01

Solid oxide fuel cells (SOFCs) are promising electrochemical devices that enable the highest fuel-to-electricity conversion efficiencies under high operating temperatures. The concept of multi-stage electrochemical oxidation using SOFCs has been proposed and studied over the past several decades for further improving the electrical efficiency. However, the improvement is limited by fuel dilution downstream of the fuel flow. Therefore, evolved technologies are required to achieve considerably higher electrical efficiencies. Here we present an innovative concept for a critically-high fuel-to-electricity conversion efficiency of up to 85% based on the lower heating value (LHV), in which a high-temperature multi-stage electrochemical oxidation is combined with a proton-conducting solid electrolyte. Switching a solid electrolyte material from a conventional oxide-ion conducting material to a proton-conducting material under the high-temperature multi-stage electrochemical oxidation mechanism has proven to be highly advantageous for the electrical efficiency. The DC efficiency of 85% (LHV) corresponds to a net AC efficiency of approximately 76% (LHV), where the net AC efficiency refers to the transmission-end AC efficiency. This evolved concept will yield a considerably higher efficiency with a much smaller generation capacity than the state-of-the-art several tens-of-MW-class most advanced combined cycle (MACC). PMID:26218470

Improved model of activation energy absorption for different electrical breakdowns in semi-crystalline insulating polymers

NASA Astrophysics Data System (ADS)

Sima, Wenxia; Jiang, Xiongwei; Peng, Qingjun; Sun, Potao

2018-05-01

Electrical breakdown is an important physical phenomenon in electrical equipment and electronic devices. Many related models and theories of electrical breakdown have been proposed. However, a widely recognized understanding on the following phenomenon is still lacking: impulse breakdown strength which varies with waveform parameters, decrease in the breakdown strength of AC voltage with increasing frequency, and higher impulse breakdown strength than that of AC. In this work, an improved model of activation energy absorption for different electrical breakdowns in semi-crystalline insulating polymers is proposed based on the Harmonic oscillator model. Simulation and experimental results show that, the energy of trapped charges obtained from AC stress is higher than that of impulse voltage, and the absorbed activation energy increases with the increase in the electric field frequency. Meanwhile, the frequency-dependent relative dielectric constant ε r and dielectric loss tanδ also affect the absorption of activation energy. The absorbed activation energy and modified trap level synergistically determine the breakdown strength. The mechanism analysis of breakdown strength under various voltage waveforms is consistent with the experimental results. Therefore, the proposed model of activation energy absorption in the present work may provide a new possible method for analyzing and explaining the breakdown phenomenon in semi-crystalline insulating polymers.

Design and Modelling of a Microfluidic Electro-Lysis Device with Controlling Plates

NASA Astrophysics Data System (ADS)

Jenkins, A.; Chen, C. P.; Spearing, S.; Monaco, L. A.; Steele, A.; Flores, G.

2006-04-01

Many Lab-on-Chip applications require sample pre-treatment systems. Using electric fields to perform cell lysis in bio-MEMS systems has provided a powerful tool which can be integrated into Lab-on-a- Chip platforms. The major design considerations for electro-lysis devices include optimal geometry and placement of micro-electrodes, cell concentration, flow rates, optimal electric field (e.g. pulsed DC vs. AC), etc. To avoid electrolysis of the flowing solution at the exposed electrode surfaces, magnitudes and the applied voltages and duration of the DC pulse, or the AC frequency of the AC, have to be optimized for a given configuration. Using simulation tools for calculation of electric fields has proved very useful, for exploring alternative configurations and operating conditions for achieving electro cell-lysis. To alleviate the problem associated with low electric fields within the microfluidics channel and the high voltage demand on the contact electrode strips, two ''control plates'' are added to the microfluidics configuration. The principle of placing the two controlling plate-electrodes is based on the electric fields generated by a combined insulator/dielectric (glass/water) media. Surface charges are established at the insulator/dielectric interface. This paper discusses the effects of this interface charge on the modification of the electric field of the flowing liquid/cell solution.

Effect of proton-conduction in electrolyte on electric efficiency of multi-stage solid oxide fuel cells.

PubMed

Matsuzaki, Yoshio; Tachikawa, Yuya; Somekawa, Takaaki; Hatae, Toru; Matsumoto, Hiroshige; Taniguchi, Shunsuke; Sasaki, Kazunari

2015-07-28

Solid oxide fuel cells (SOFCs) are promising electrochemical devices that enable the highest fuel-to-electricity conversion efficiencies under high operating temperatures. The concept of multi-stage electrochemical oxidation using SOFCs has been proposed and studied over the past several decades for further improving the electrical efficiency. However, the improvement is limited by fuel dilution downstream of the fuel flow. Therefore, evolved technologies are required to achieve considerably higher electrical efficiencies. Here we present an innovative concept for a critically-high fuel-to-electricity conversion efficiency of up to 85% based on the lower heating value (LHV), in which a high-temperature multi-stage electrochemical oxidation is combined with a proton-conducting solid electrolyte. Switching a solid electrolyte material from a conventional oxide-ion conducting material to a proton-conducting material under the high-temperature multi-stage electrochemical oxidation mechanism has proven to be highly advantageous for the electrical efficiency. The DC efficiency of 85% (LHV) corresponds to a net AC efficiency of approximately 76% (LHV), where the net AC efficiency refers to the transmission-end AC efficiency. This evolved concept will yield a considerably higher efficiency with a much smaller generation capacity than the state-of-the-art several tens-of-MW-class most advanced combined cycle (MACC).

Analysis of a piezoelectric power harvester with adjustable frequency by precise electric field method.

PubMed

Wang, Yujue; Lian, Ziyang; Yao, Mingge; Wang, Ji; Hu, Hongping

2013-10-01

A power harvester with adjustable frequency, which consists of a hinged-hinged piezoelectric bimorph and a concentrated mass, is studied by the precise electric field method (PEFM), taking into account a distribution of the electric field over the thickness. Usually, using the equivalent electric field method (EEFM), the electric field is approximated as a constant value in the piezoelectric layer. Charge on the upper electrode (UEC) of the bimorph is often assumed as output charge. However, different output charge can be obtained by integrating on electric displacement over the electrode with different thickness coordinates. Therefore, an average charge (AC) on thickness is often assumed as the output value. This method is denoted EEFM AC. The flexural vibration of the bimorph is calculated by the three methods and their results are compared. Numerical results illustrate that EEFM UEC overestimates resonant frequency, output power, and efficiency. EEFM AC can accurately calculate the output power and efficiency, but underestimates resonant frequency. The performance of the harvester, which depends on concentrated mass weight, position, and circuit load, is analyzed using PEFM. The resonant frequency can be modulated 924 Hz by moving the concentrated mass along the bimorph. This feature suggests that the natural frequency of the harvester can be adjusted conveniently to adapt to frequency fluctuation of the ambient vibration.

Clinician accessible tools for GUI computational models of transcranial electrical stimulation: BONSAI and SPHERES.

PubMed

Truong, Dennis Q; Hüber, Mathias; Xie, Xihe; Datta, Abhishek; Rahman, Asif; Parra, Lucas C; Dmochowski, Jacek P; Bikson, Marom

2014-01-01

Computational models of brain current flow during transcranial electrical stimulation (tES), including transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS), are increasingly used to understand and optimize clinical trials. We propose that broad dissemination requires a simple graphical user interface (GUI) software that allows users to explore and design montages in real-time, based on their own clinical/experimental experience and objectives. We introduce two complimentary open-source platforms for this purpose: BONSAI and SPHERES. BONSAI is a web (cloud) based application (available at neuralengr.com/bonsai) that can be accessed through any flash-supported browser interface. SPHERES (available at neuralengr.com/spheres) is a stand-alone GUI application that allow consideration of arbitrary montages on a concentric sphere model by leveraging an analytical solution. These open-source tES modeling platforms are designed go be upgraded and enhanced. Trade-offs between open-access approaches that balance ease of access, speed, and flexibility are discussed. Copyright © 2014 Elsevier Inc. All rights reserved.

Stable Rotation of Microparticles using a Combination of Dielectrophoresis and Electroosmosis

NASA Astrophysics Data System (ADS)

Dutta, Prashanta; Rezanoor, Walid

2016-11-01

Electric field induced microparticle rotation has become a powerful technique to evaluate cell membrane dielectric properties and cell morphology. In this study, stable rotations of microparticles are demonstrated in a stationary AC electric field created from a set of coplanar interdigitated microelectrodes. The medium, particle size, and material are carefully chosen so that particle can be controlled by dielectrophoretic force, while a sufficiently high AC electroosmotic flow is produced for continuous particle rotation. Stable rotation up to 218 rpm is observed at 30 Vp-p applied sinusoidal potential in the frequency range of 80 - 1000 Hz. The particle spin rate observed from the experimental study is then validated with a numerical model. The model is formulated around complex charge conservation equation to determine the electric potential distribution in the domain. Stokes equation is employed to solve for AC electroosmotic fluid flow in the domain. Complexity arising from nonlinear potential drop across the electric double layer due to the application of a very large electric potential is also addressed by introducing modified capacitance equation which considers steric effect. This work was supported in part by the U.S. National Science Foundation under Grant No. DMS 1317671.

Impedance Spectroscopy and AC Conductivity Studies of Bulk 3-Amino-7-(dimethylamino)-2-methyl-hydrochloride

NASA Astrophysics Data System (ADS)

El-Shabaan, M. M.

2018-02-01

Impedance spectroscopy and alternating-current (AC) conductivity (σ AC) studies of bulk 3-amino-7-(dimethylamino)-2-methyl-hydrochloride (neutral red, NR) have been carried out over the temperature (T) range from 303 K to 383 K and frequency (f) range from 0.5 kHz to 5 MHz. Dielectric data were analyzed using the complex impedance (Z *) and complex electric modulus (M *) for bulk NR at various temperatures. The impedance loss peaks were found to shift towards high frequencies, indicating an increase in the relaxation time (τ 0) and loss in the material, with increasing temperature. For each temperature, a single depressed semicircle was observed at high frequencies, originating from the bulk transport, and a spike in the low-frequency region, resulting from the electrode effect. Fitting of these curves yielded an equivalent circuit containing a parallel combination of a resistance R and constant-phase element (CPE) Q. The carrier transport in bulk NR is governed by the correlated barrier hopping (CBH) mechanism, some parameters of which, such as the maximum barrier height (W M), charge density (N), and hopping distance (r), were determined as functions of both temperature and frequency. The frequency dependence of σ AC at different temperatures indicated that the conduction in bulk NR is a thermally activated process. The σ AC value at different frequencies increased linearly with temperature.

Preliminary power train design for a state-of-the-art electric vehicle

NASA Technical Reports Server (NTRS)

Mighdoll, P.; Hahn, W. F.

1978-01-01

Power train designs which can be implemented within the current state-of-the-art were identified by means of a review of existing electric vehicles and suitable off-the-shelf components. The affect of various motor/transmission combinations on vehicle range over the SAE J227a schedule D cycle was evaluated. The selected, state-of-the-art power train employs a dc series wound motor, SCR controller, variable speed transmission, regenerative braking, drum brakes and radial ply tires. Vehicle range over the SAE cycle can be extended by approximately 20% by the further development of separately excited, shunt wound DC motors and electrical controllers. Approaches which could improve overall power train efficiency, such as AC motor systems, are identified. However, future emphasis should remain on batteries, tires and lightweight structures if substantial range improvements are to be achieved.

Design of bipolar, flowing-electrolyte zinc-bromine electric-vehicle battery systems

NASA Astrophysics Data System (ADS)

Malachesky, P. A.; Bellows, R. J.; Einstein, H. E.; Grimes, P. G.; Newby, K.; Young, A.

1983-01-01

The integration of bipolar, flowing electrolyte zinc-bromine technology into a viable electric vehicle battery system requires careful analysis of the requirements placed on the battery system by the EV power train. In addition to the basic requirement of an appropriate battery voltage and power density, overall battery system energy efficiency must also be considered and parasitic losses from auxiliaries such as pumps and shunt current protection minimized. An analysis of the influence of these various factors on zinc-bromine EV battery system design has been carried out for two types of EV propulsion systems. The first of these is a nominal 100V dc system, while the second is a high voltage (200V dc) system as might be used with an advanced design ac propulsion system. Battery performance was calculated using an experimentally determined relationship which expresses battery voltage as a function of current density and state-of-charge.

Electrical conductivity and dielectric properties of TlInS2 single crystals

NASA Astrophysics Data System (ADS)

El-Nahass, M. M.; Youssef, S. B.; Ali, H. A. M.; Hassan, A.

2011-07-01

TlInS2 single crystals were grown by using Bridgman-Stockbauer technique. Measurements of DC conductivity were carried out in parallel (σ//) and perpendicular (σ⊥) directions to the c-axis over a temperature range from 303 to 463 K. The anisotropic behaviour of the electrical conductivity was also detected. AC conductivity and dielectric measurements were studied as a function of both frequency (102-106 Hz) and temperature (297-375 K). The frequency dependence of the AC conductivity revealed that σac(ω) obeys the universal law: σac(ω) = Aωs. The mechanism of the ac charge transport across the layers of TlInS2 single crystals was referred to the hopping over localized states near the Fermi level in the frequency range >3.5 × 103 Hz. The temperature dependence of σac(ω) for TlInS2 showed that σac is thermally activated process. Both of ɛ1 and ɛ2 decrease by increasing frequency and increase by increasing temperature. Some parameters were calculated as: the density of localized states near the Fermi level NF = 1.5 × 1020 eV-1 cm-3, the average time of charge carrier hoping between localized states τ = 3.79 μs and the average hopping distance R = 6.07 nm.

Flexible nanoporous tunable electrical double layer biosensors for sweat diagnostics.

PubMed

Munje, Rujuta D; Muthukumar, Sriram; Panneer Selvam, Anjan; Prasad, Shalini

2015-09-30

An ultra-sensitive and highly specific electrical double layer (EDL) modulated biosensor, using nanoporous flexible substrates for wearable diagnostics is demonstrated with the detection of the stress biomarker cortisol in synthetic and human sweat. Zinc oxide thin film was used as active region in contact with the liquid i.e. synthetic and human sweat containing the biomolecules. Cortisol detection in sweat was accomplished by measuring and quantifying impedance changes due to modulation of the double layer capacitance within the electrical double layer through the application of a low orthogonally directed alternating current (AC) electric field. The EDL formed at the liquid-semiconductor interface was amplified in the presence of the nanoporous flexible substrate allowing for measuring the changes in the alternating current impedance signal due to the antibody-hormone interactions at diagnostically relevant concentrations. High sensitivity of detection of 1 pg/mL or 2.75 pmol cortisol in synthetic sweat and 1 ng/mL in human sweat is demonstrated with these novel biosensors. Specificity in synthetic sweat was demonstrated using a cytokine IL-1β. Cortisol detection in human sweat was demonstrated over a concentration range from 10-200 ng/mL.

Flexible nanoporous tunable electrical double layer biosensors for sweat diagnostics

NASA Astrophysics Data System (ADS)

Munje, Rujuta D.; Muthukumar, Sriram; Panneer Selvam, Anjan; Prasad, Shalini

2015-09-01

An ultra-sensitive and highly specific electrical double layer (EDL) modulated biosensor, using nanoporous flexible substrates for wearable diagnostics is demonstrated with the detection of the stress biomarker cortisol in synthetic and human sweat. Zinc oxide thin film was used as active region in contact with the liquid i.e. synthetic and human sweat containing the biomolecules. Cortisol detection in sweat was accomplished by measuring and quantifying impedance changes due to modulation of the double layer capacitance within the electrical double layer through the application of a low orthogonally directed alternating current (AC) electric field. The EDL formed at the liquid-semiconductor interface was amplified in the presence of the nanoporous flexible substrate allowing for measuring the changes in the alternating current impedance signal due to the antibody-hormone interactions at diagnostically relevant concentrations. High sensitivity of detection of 1 pg/mL or 2.75 pmol cortisol in synthetic sweat and 1 ng/mL in human sweat is demonstrated with these novel biosensors. Specificity in synthetic sweat was demonstrated using a cytokine IL-1β. Cortisol detection in human sweat was demonstrated over a concentration range from 10-200 ng/mL.

Magnetoelectricity in Multi-Scale Composites and Application in Nanorobotics for Live Cell Manipulation

NASA Astrophysics Data System (ADS)

Betal, Soutik

In this research biomedical and sensor applications of magnetoelectric effect have been broadly explored using magnetoelectric composites. Firstly NiFe2O4/Pb(Zr0.52Ti0.48)O 3/NiFe2O4 layered bulk composite have been studied to achieve high magnetoelectric coefficient for their applications in brain magnetic field detection at room temperature. Magnetic sensors like SQUID (superconducting quantum interference device) nowadays are able to detect pico-Tesla magnetic fields produced outside the brain by the neuronal currents which can be used for diagnostic application, but due to heavy liquid helium cooling and insulation requirements, the technique become quite inefficient in gaining high resolution measurement. At room temperature layered ME samples exhibit high magnetoelectric response in mV/cm.Oe range and hence can transform very low magnetic field into electric signal which can be measured even in femtovolts. Moreover temperature and a.c. frequency dependent studies were done to extensively characterize the layered ME sample for sensor application. Secondly core-shell magnetoelectric nanoparticles (CSMEN) have been fabricated, characterized and their interaction with biological cell in presence of a.c. and d.c. field have been thoroughly analyzed. A magnetically controlled elastically driven electroporation phenomenon, or Magneto-Elasto- Electroporation (MEEP), is discovered while studying interactions between core-shell magneto-electric nanoparticles (CSMEN) and biological cells in the presence of an AC magnetic field. In this research MEEP effect was observed via a series of in-vitro experiments using core (CoFe2O4)-shell (BaTiO3 ) structured magnetoelectric nanoparticles and human epithelial cells (HEP2). Cell electroporation phenomenon and its correlation with the magnetic field modulated CSMEN have been elaborately studied. Potential of CSMEN for application in targeted single cell electroporation have been confirmed by analysing crystallographic phases, multiferroic properties of the fabricated CSMEN , influences of DC and AC magnetic field on the CSMEN and cytotoxicity tests. We also report the mathematical formalism to quantitatively describe the phenomena. The reported findings provide the basis of the underlying MEEP mechanism and demonstrate the utility of CSMEN as electric pulse generating nano-probe in cell electroporation experiments for the potential application towards accurate and efficient targeted cell permeation as well as drug delivery. Thirdly, experiments of fabricated magnetoelectric nanocomposites with biological cells in controlled boundary condition under fluctuating and biased magnetic field excitation revealed the smart nanorobotics characteristics of the nanostructure to achieve remote controlled dynamically targeted live cell manipulation. A remotely controlled dynamic process of manipulating targeted biological live cells using fabricated core-shell magnetoelectric nanocomposites have been fabricated, which comprises of single crystalline ferromagnetic cores (CoFe2O4) coated with crystalline ferroelectric thin film shells (BaTiO3). These nanocomposites are demonstrated as a unique family of inorganic magnetoelectric nanorobots (MENRs), controlled remotely by applied a.c. or d.c. magnetic fields, to perform cell targeting, permeation, patterning and transport. MENRs performs these functions via localized electric periodic pulse generation, local electric-field sensing, or thrust generation and acts as a unique tool for remotely controlled dynamically targeted cellular manipulation. Under a.c. magnetic field excitation (50 Oe, 60 Hz), the MENR acts as a localized periodic electric pulse generator and can permeate a series of misaligned cells, while aligning/patterning them to an equipotential mono-array. Under a.c. magnetic field (40 Oe, 30 Hz) excitation, MENRs can be dynamically driven to a targeted cell, avoiding untargeted cells in the path, irrespective of cell density. D.C. magnetic field (-50 Oe) excitation causes the MENRs to act as thrust generator and exerts motion in a group of cells. Visualization of magnetoelectricity at nanoscale and its application in dynamically targeted live cell manipulation have been presented in this research.

Non-invasive electric current stimulation for restoration of vision after unilateral occipital stroke.

PubMed

Gall, Carolin; Silvennoinen, Katri; Granata, Giuseppe; de Rossi, Francesca; Vecchio, Fabrizio; Brösel, Doreen; Bola, Michał; Sailer, Michael; Waleszczyk, Wioletta J; Rossini, Paolo M; Tatlisumak, Turgut; Sabel, Bernhard A

2015-07-01

Occipital stroke often leads to visual field loss, for which no effective treatment exists. Little is known about the potential of non-invasive electric current stimulation to ameliorate visual functions in patients suffering from unilateral occipital stroke. One reason is the traditional thinking that visual field loss after brain lesions is permanent. Since evidence is available documenting vision restoration by means of vision training or non-invasive electric current stimulation future studies should also consider investigating recovery processes after visual cortical strokes. Here, protocols of repetitive transorbital alternating current stimulation (rtACS) and transcranial direct current stimulation (tDCS) are presented and the European consortium for restoration of vision (REVIS) is introduced. Within the consortium different stimulation approaches will be applied to patients with unilateral occipital strokes resulting in homonymous hemianopic visual field defects. The aim of the study is to evaluate effects of current stimulation of the brain on vision parameters, vision-related quality of life, and physiological parameters that allow concluding about the mechanisms of vision restoration. These include EEG-spectra and coherence measures, and visual evoked potentials. The design of stimulation protocols involves an appropriate sham-stimulation condition and sufficient follow-up periods to test whether the effects are stable. This is the first application of non-invasive current stimulation for vision rehabilitation in stroke-related visual field deficits. Positive results of the trials could have far-reaching implications for clinical practice. The ability of non-invasive electrical current brain stimulation to modulate the activity of neuronal networks may have implications for stroke rehabilitation also in the visual domain. Copyright © 2015 Elsevier Inc. All rights reserved.

Electric-field control of a hydrogenic donor's spin in a semiconductor

NASA Astrophysics Data System (ADS)

de, Amrit; Pryor, Craig E.; Flatté, Michael E.

2009-03-01

The orbital wave function of an electron bound to a single donor in a semiconductor can be modulated by an applied AC electric field, which affects the electron spin dynamics via the spin-orbit interaction. Numerical calculations of the spin dynamics of a single hydrogenic donor (Si) using a real-space multi-band k.p formalism show that in addition to breaking the high symmetry of the hydrogenic donor state, the g-tensor has a strong nonlinear dependence on the applied fields. By explicitly integrating the time dependent Schr"odinger equation it is seen that Rabi oscillations can be obtained for electric fields modulated at sub-harmonics of the Larmor frequency. The Rabi frequencies obtained from sub-harmonic modulation depend on the magnitudes of the AC and DC components of the electric field. For a purely AC field, the highest Rabi frequency is obtained when E is driven at the 2nd sub-harmonic of the Larmor frequency. Apart from suggesting ways to measure g-tensor anisotropies and nonlinearities, these results also suggest the possibility of direct frequency domain measurements of Rabi frequencies.

The electrical characteristics of the dielectric barrier discharges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yehia, Ashraf, E-mail: yehia30161@yahoo.com; Department of Physics, Faculty of Science, Assiut University, Assiut 71516

2016-06-15

The electrical characteristics of the dielectric barrier discharges have been studied in this paper under different operating conditions. The dielectric barrier discharges were formed inside two reactors composed of electrodes in the shape of two parallel plates. The dielectric layers inside these reactors were pasted on the surface of one electrode only in the first reactor and on the surfaces of the two electrodes in the second reactor. The reactor under study has been fed by atmospheric air that flowed inside it with a constant rate at the normal temperature and pressure, in parallel with applying a sinusoidal ac voltagemore » between the electrodes of the reactor. The amount of the electric charge that flows from the reactors to the external circuit has been studied experimentally versus the ac peak voltage applied to them. An analytical model has been obtained for calculating the electrical characteristics of the dielectric barrier discharges that were formed inside the reactors during a complete cycle of the ac voltage. The results that were calculated by using this model have agreed well with the experimental results under the different operating conditions.« less

Electromechanical systems with transient high power response operating from a resonant ac link

NASA Technical Reports Server (NTRS)

Burrows, Linda M.; Hansen, Irving G.

1992-01-01

The combination of an inherently robust asynchronous (induction) electrical machine with the rapid control of energy provided by a high frequency resonant ac link enables the efficient management of higher power levels with greater versatility. This could have a variety of applications from launch vehicles to all-electric automobiles. These types of systems utilize a machine which is operated by independent control of both the voltage and frequency. This is made possible by using an indirect field-oriented control method which allows instantaneous torque control all four operating quadrants. Incorporating the ac link allows the converter in these systems to switch at the zero crossing of every half cycle of the ac waveform. This zero loss switching of the link allows rapid energy variations to be achieved without the usual frequency proportional switching loss. Several field-oriented control systems were developed under contract to NASA.

Advanced AC permanent magnet axial flux disc motor for electric passenger vehicle

NASA Technical Reports Server (NTRS)

Kliman, G. B.

1982-01-01

An ac permanent magnet axial flux disc motor was developed to operate with a thyristor load commutated inverter as part of an electric vehicle drive system. The motor was required to deliver 29.8 kW (40 hp) peak and 10.4 kW (14 hp) average with a maximum speed of 11,000 rpm. It was also required to run at leading power factor to commutate the inverter. Three motors were built.

Electrical Evaluation of RCA MWS5001D Random Access Memory, Volume 4, Appendix C

NASA Technical Reports Server (NTRS)

Klute, A.

1979-01-01

The electrical characterization and qualification test results are presented for the RCA MWS5001D random access memory. The tests included functional tests, AC and DC parametric tests, AC parametric worst-case pattern selection test, determination of worst-case transition for setup and hold times, and a series of schmoo plots. Statistical analysis data is supplied along with write pulse width, read cycle time, write cycle time, and chip enable time data.

Electrical Evaluation of RCA MWS5501D Random Access Memory, Volume 2, Appendix a

NASA Technical Reports Server (NTRS)

Klute, A.

1979-01-01

The electrical characterization and qualification test results are presented for the RCA MWS5001D random access memory. The tests included functional tests, AC and DC parametric tests, AC parametric worst-case pattern selection test, determination of worst-case transition for setup and hold times, and a series of schmoo plots. The address access time, address readout time, the data hold time, and the data setup time are some of the results surveyed.

PHEV-EV Charger Technology Assessment with an Emphasis on V2G Operation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kisacikoglu, Mithat C; Bedir, Abdulkadir; Ozpineci, Burak

2012-03-01

More battery powered electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs) will be introduced to the market in 2011 and beyond. Since these vehicles have large batteries that need to be charged from an external power source or directly from the grid, their batteries, charging circuits, charging stations/infrastructures, and grid interconnection issues are garnering more attention. This report summarizes information regarding the batteries used in PHEVs, different types of chargers, charging standards and circuits, and compares different topologies. Furthermore, it includes a list of vehicles that are going to be in the market soon with information on their chargingmore » and energy storage equipment. A summary of different standards governing charging circuits and charging stations concludes the report. There are several battery types that are available for PHEVs; however, the most popular ones have nickel metal hydride (NiMH) and lithium-ion (Li-ion) chemistries. The former one is being used in current hybrid electric vehicles (HEVs), but the latter will be used in most of the PHEVs and EVs due to higher energy densities and higher efficiencies. The chargers can be classified based on the circuit topologies (dedicated or integrated), location of the charger (either on or off the vehicle), connection (conductive, inductive/wireless, and mechanical), electrical waveform (direct current (dc) or alternating current (ac)), and the direction of power flow (unidirectional or bidirectional). The first PHEVs typically will have dedicated, on-board, unidirectional chargers that will have conductive connections to the charging stations or wall outlets and will be charged using either dc or ac. In the near future, bidirectional chargers might also be used in these vehicles once the benefits of practical vehicle to grid applications are realized. The terms charger and charging station cause terminology confusion. To prevent misunderstandings, a more descriptive term of electric vehicle supply equipment (EVSE) is used instead of charging station. The charger is the power conversion equipment that connects the battery to the grid or another power source, while EVSE refers to external equipment between the grid or other power source and the vehicle. EVSE might include conductors, connectors, attachment plugs, microprocessors, energy measurement devices, transformers, etc. Presently, there are more than 40 companies that are producing EVSEs. There are several standards and codes regarding conductive and inductive chargers and EVSEs from the Society of Automotive Engineers (SAE), the Underwriter Laboratories (UL), the International Electrotechnical Commission (IEC), and the National Electric Code (NEC). The two main standards from SAE describe the requirements for conductive and inductive coupled chargers and the charging levels. For inductive coupled charging, three levels are specified: Level 1 (120 V and 12 A, single-phase), Level 2 (208 V-240 V and 32 A, single-phase), and Level 3 (208-600 V and 400 A, three-phase) . The standard for the conductive-coupled charger also has similar charging ratings for Levels 1 and 2, but it allows higher current ratings for Level 2 charging up to 80 A. Level 3 charging for this standard is still under development and considers dc charging instead of three-phase ac. More details in these areas and related references can be found in this Oak Ridge National Laboratory (ORNL) report on PHEV-EV charger technology assessment.« less

AC propulsion system for an electric vehicle, phase 2

NASA Astrophysics Data System (ADS)

Slicker, J. M.

1983-06-01

A second-generation prototype ac propulsion system for a passenger electric vehicle was designed, fabricated, tested, installed in a modified Mercury Lynx vehicle and track tested at the Contractor's site. The system consisted of a Phase 2, 18.7 kw rated ac induction traction motor, a 192-volt, battery powered, pulse-width-modulated, transistorized inverter packaged for under rear seat installation, a 2-axis, 2-speed, automatically-shifted mechanical transaxle and a microprocessor-based powertrain/vehicle controller. A diagnostics computer to assist tuning and fault finding was fabricated. Dc-to-mechanical-system efficiency varied from 78% to 82% as axle speed/torque ranged from 159 rpm/788 nm to 65 rpm/328 nm. Track test efficiency results suggest that the ac system will be equal or superior to dc systems when driving urban cycles. Additional short-term work is being performed under a third contract phase (AC-3) to raise transaxle efficiency to predicted levels, and to improve starting and shifting characteristics. However, the long-term challenge to the system's viability remains inverter cost. A final report on the Phase 2 system, describing Phase 3 modifications, will be issued at the conclusion of AC-3.

AC propulsion system for an electric vehicle, phase 2

NASA Technical Reports Server (NTRS)

Slicker, J. M.

1983-01-01

A second-generation prototype ac propulsion system for a passenger electric vehicle was designed, fabricated, tested, installed in a modified Mercury Lynx vehicle and track tested at the Contractor's site. The system consisted of a Phase 2, 18.7 kw rated ac induction traction motor, a 192-volt, battery powered, pulse-width-modulated, transistorized inverter packaged for under rear seat installation, a 2-axis, 2-speed, automatically-shifted mechanical transaxle and a microprocessor-based powertrain/vehicle controller. A diagnostics computer to assist tuning and fault finding was fabricated. Dc-to-mechanical-system efficiency varied from 78% to 82% as axle speed/torque ranged from 159 rpm/788 nm to 65 rpm/328 nm. Track test efficiency results suggest that the ac system will be equal or superior to dc systems when driving urban cycles. Additional short-term work is being performed under a third contract phase (AC-3) to raise transaxle efficiency to predicted levels, and to improve starting and shifting characteristics. However, the long-term challenge to the system's viability remains inverter cost. A final report on the Phase 2 system, describing Phase 3 modifications, will be issued at the conclusion of AC-3.

Differential polarization of cortical pyramidal neuron dendrites through weak extracellular fields

PubMed Central

Obermayer, Klaus

2018-01-01

The rise of transcranial current stimulation (tCS) techniques have sparked an increasing interest in the effects of weak extracellular electric fields on neural activity. These fields modulate ongoing neural activity through polarization of the neuronal membrane. While the somatic polarization has been investigated experimentally, the frequency-dependent polarization of the dendritic trees in the presence of alternating (AC) fields has received little attention yet. Using a biophysically detailed model with experimentally constrained active conductances, we analyze the subthreshold response of cortical pyramidal cells to weak AC fields, as induced during tCS. We observe a strong frequency resonance around 10-20 Hz in the apical dendrites sensitivity to polarize in response to electric fields but not in the basal dendrites nor the soma. To disentangle the relative roles of the cell morphology and active and passive membrane properties in this resonance, we perform a thorough analysis using simplified models, e.g. a passive pyramidal neuron model, simple passive cables and reconstructed cell model with simplified ion channels. We attribute the origin of the resonance in the apical dendrites to (i) a locally increased sensitivity due to the morphology and to (ii) the high density of h-type channels. Our systematic study provides an improved understanding of the subthreshold response of cortical cells to weak electric fields and, importantly, allows for an improved design of tCS stimuli. PMID:29727454

Precision Tests of a Quantum Hall Effect Device DC Equivalent Circuit Using Double-Series and Triple-Series Connections

PubMed Central

Jeffery, A.; Elmquist, R. E.; Cage, M. E.

1995-01-01

Precision tests verify the dc equivalent circuit used by Ricketts and Kemeny to describe a quantum Hall effect device in terms of electrical circuit elements. The tests employ the use of cryogenic current comparators and the double-series and triple-series connection techniques of Delahaye. Verification of the dc equivalent circuit in double-series and triple-series connections is a necessary step in developing the ac quantum Hall effect as an intrinsic standard of resistance. PMID:29151768

Next Generation Inverter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Zilai; Gough, Charles

The goal of this Cooperative Agreement was the development of a Next Generation Inverter for General Motors’ electrified vehicles, including battery electric vehicles, range extended electric vehicles, plug-in hybrid electric vehicles and hybrid electric vehicles. The inverter is a critical electronics component that converts battery power (DC) to and from the electric power for the motor (AC).

Nonlinear theory of the narrow-band generation and detection of terahertz radiation in resonant tunneling heterostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kapaev, V. V., E-mail: kapaev@lebedev.ru

The nonlinear regime of high-frequency response for resonant tunneling structures in a time-periodic electric field has been investigated using a technique for solving the time-dependent Schrödinger equation based on a Floquet mode expansion of the wave functions. The dependences of current harmonic amplitudes on ac signal amplitude have been calculated and the limiting values of the generated field have been determined for singleand double-well resonant tunneling structures. The dynamic Stark effect is shown to play an important role in the formation of response. It leads to a quadratic (in ac field amplitude) shift in the positions of resonances E{sub r}more » in single-well structures and in double-well ones in the nonresonant case and to a splitting at resonance hν ≈ E{sub r2}–E{sub r1} (ν is the signal frequency, E{sub r1} and E{sub r2} are the energies of the size-quantization levels) in double-well structures proportional to the ac signal amplitude. The phenomenon of ac signal detection by resonant tunneling structures has been investigated. The effect of resonant direct-current amplification in double-well structures has been detected at a signal frequency satisfying the condition hν ≈ E{sub r2}–E{sub r1}. In asymmetric systems, detection is shown to be possible in the absence of a dc bias, which allows zero-biased detectors based on them to be created.« less

Electrokinetic framework of dielectrophoretic deposition devices

NASA Astrophysics Data System (ADS)

Burg, Brian R.; Bianco, Vincenzo; Schneider, Julian; Poulikakos, Dimos

2010-06-01

Numerical modeling and experiments are performed investigating the properties of a dielectrophoresis-based deposition device, in order to establish the electrokinetic framework required to understand the effects of applied inhomogeneous electric fields while moving particles to desired locations. By capacitively coupling electrodes to a conductive substrate, the controlled large-scale parallel dielectrophoretic assembly of nanostructures in individually accessible devices at a high integration density is accomplished. Thermal gradients in the solution, which give rise to local permittivity and conductivity changes, and velocity fields are solved by coupling electric, thermal, and fluid-mechanical equations. The induced electrothermal flow (ETF) causes vortices above the electrode gap, attracting particles, such as single-walled carbon nanotubes (SWNTs), before they are trapped by the dielectrophoretic force and deposit across the electrodes. Long-range carbon nanotube transport is governed by hydrodynamic effects, while local trapping is dominated by dielectrophoretic forces in low concentration SWNT dispersions. Results show that by decreasing the ac frequency ac electroosmosis on the metallic electrodes occurs due to the emergence of an electric double layer, disturbing the initial flow pattern of the system. By superimposing a dc potential offset, a generated tangential electroosmotic fluid flow in the dielectric electrode gap also disrupts the ETF. Capacitive coupling is most efficient in the high frequency regime where it is the dominating impedance contribution. Understanding the occurrence and interaction of these different effects, including a self-limiting integration mechanism for individual nanostructures, allows an increased deposition yield at overall lower electric field strengths through a prudent choice of electric field parameters. The findings provide important avenues toward gentler particle handling, without direct current throughput, a relevant aspect for limiting process effects during device fabrication, all while increasing dielectrophoretic deposition efficiency in nanostructured networks.

Optical devices having flakes suspended in a host fluid to provide a flake/fluid system providing flakes with angularly dependent optical properties in response to an alternating current electric field due to the dielectric properties of the system

DOEpatents

Kosc, Tanya Z [Rochester, NY; Marshall, Kenneth L [Rochester, NY; Jacobs, Stephen D [Pittsford, NY

2006-05-09

Optical devices utilizing flakes (also called platelets) suspended in a host fluid have optical characteristics, such as reflective properties, which are angular dependent in response to an AC field. The reflectivity may be Bragg-like, and the characteristics are obtained through the use of flakes of liquid crystal material, such as polymer liquid crystal (PLC) materials including polymer cholesteric liquid crystal (PCLC) and polymer nematic liquid crystal (PNLC) material or birefringent polymers (BP). The host fluid may be propylene carbonate, poly(ethylene glycol) or other fluids or fluid mixtures having fluid conductivity to support conductivity in the flake/host system. AC field dependent rotation of 90.degree. can be obtained at rates and field intensities dependent upon the frequency and magnitude of the AC field. The devices are useful in providing displays, polarizers, filters, spatial light modulators and wherever switchable polarizing, reflecting, and transmission properties are desired.

AC Electric-Field-Induced Fluid Flow in Microelectrodes.

PubMed

Ramos; Morgan; Green; Castellanos

1999-09-15

During the AC electrokinetic manipulation of particles in suspension on microelectrode structures, strong frequency-dependent fluid flow is observed. The fluid movement is predominant at frequencies below the reciprocal charge relaxation time, with a reproducible pattern occurring close to and across the electrode surface. This paper reports measurements of the fluid velocity as a function of frequency and position across the electrode. Evidence is presented indicating that the flow occurs due to electroosmotic stress arising from the interaction of the electric field and the electrical double layer on the electrodes. The electrode polarization plays a significant role in controlling the frequency dependence of the flow. Copyright 1999 Academic Press.

Antiferromagnetic resonance excited by oscillating electric currents

NASA Astrophysics Data System (ADS)

Sluka, Volker

2017-12-01

In antiferromagnetic materials the order parameter exhibits resonant modes at frequencies that can be in the terahertz range, making them interesting components for spintronic devices. Here, it is shown that antiferromagnetic resonance can be excited using the inverse spin-Hall effect in a system consisting of an antiferromagnetic insulator coupled to a normal-metal waveguide. The time-dependent interplay between spin torque, ac spin accumulation, and magnetic degrees of freedom is studied. It is found that the dynamics of the antiferromagnet affects the frequency-dependent conductivity of the normal metal. Further, a comparison is made between spin-current-induced and Oersted-field-induced excitation under the condition of constant power injection.

Evolution of Structural and Electrical Properties of Carbon Films from Amorphous Carbon to Nanocrystalline Graphene on Quartz Glass by HFCVD.

PubMed

Zhai, Zihao; Shen, Honglie; Chen, Jieyi; Li, Xuemei; Jiang, Ye

2018-05-23

Direct growth of graphene films on glass is of great importance but has so far met with limited success. The noncatalytic property of glass results in the low decomposition ability of hydrocarbon precursors, especially at reduced temperatures (<1000 °C), and therefore amorphous carbon (a-C) films are more likely to be obtained. Here, we report the hydrogen influence on the structural and electrical properties of carbon films deposited on quartz glass at 850 °C by hot-filament chemical vapor deposition (HFCVD). The results revealed that the obtained a-C films were all graphitelike carbon films. Structural transition of the deposited films from a-C to nanocrystalline graphene was achieved by raising the hydrogen dilution ratios from 10 to over 80%. On the basis of systematic structural and chemical characterizations, a schematic process with three steps including sp 2 chain aggregation, aromatic ring formation, and sp 3 bond etching was proposed to interpret the structural evolution. The nanocrystalline graphene films grown on glass by HFCVD exhibited good electrical performance with a carrier mobility of 36.76 cm 2 /(V s) and a resistivity of 5.24 × 10 -3 Ω cm over an area of 1 cm 2 . Temperature-dependent electrical characterizations revealed that the electronic transport in carbon films was dominated by defect, localized, and extended states, respectively, when increasing the temperature from 75 to 292 K. The nanocrystalline graphene films presented higher carrier mobility and lower carrier concentration than those of a-C films, which was mainly attributed to their smaller conductive activation energy. The present investigation provides an effective way for direct growth of graphene films on glass at reduced temperatures and also offers useful insights into the understanding of structural and electrical relationship between a-C and graphene.

Modulation and control of matrix converter for aerospace application

NASA Astrophysics Data System (ADS)

Kobravi, Keyhan

In the context of modern aircraft systems, a major challenge is power conversion to supply the aircraft's electrical instruments. These instruments are energized through a fixed-frequency internal power grid. In an aircraft, the available sources of energy are a set of variable-speed generators which provide variable-frequency ac voltages. Therefore, to energize the internal power grid of an aircraft, the variable-frequency ac voltages should be converted to a fixed-frequency ac voltage. As a result, an ac to ac power conversion is required within an aircraft's power system. This thesis develops a Matrix Converter to energize the aircraft's internal power grid. The Matrix Converter provides a direct ac to ac power conversion. A major challenge of designing Matrix Converters for aerospace applications is to minimize the volume and weight of the converter. These parameters are minimized by increasing the switching frequency of the converter. To design a Matrix Converter operating at a high switching frequency, this thesis (i) develops a scheme to integrate fast semiconductor switches within the current available Matrix Converter topologies, i.e., MOSFET-based Matrix Converter, and (ii) develops a new modulation strategy for the Matrix Converter. This Matrix Converter and the new modulation strategy enables the operation of the converter at a switching-frequency of 40kHz. To provide a reliable source of energy, this thesis also develops a new methodology for robust control of Matrix Converter. To verify the performance of the proposed MOSFET-based Matrix Converter, modulation strategy, and control design methodology, various simulation and experimental results are presented. The experimental results are obtained under operating condition present in an aircraft. The experimental results verify the proposed Matrix Converter provides a reliable power conversion in an aircraft under extreme operating conditions. The results prove the superiority of the proposed Matrix Converter technology for ac to ac power conversion regarding the existing technologies of Matrix Converters.

An active magnetic bearing with high T(sub c) superconducting coils and ferromagnetic cores

NASA Technical Reports Server (NTRS)

Brown, G. V.; Dirusso, E.; Provenza, A. J.

1995-01-01

A proof-of-feasibility demonstration showed that high-T(sub c) superconductor (HTS) coils can be used in a high-load, active magnetic bearing in LN2. A homopolar radial bearing with commercially wound HTS (Bi 2223) bias and control coils produced over 890 N (200 lb) radial load capacity (measured non-rotatings) and supported a shaft to 14,000 rpm. The goal was to show that HTS coils can operate stably with ferromagnetic cores in a feedback controlled system at a current density similar to that for Cu in LN2. The bias coil, wound with non-twisted, multifilament HTS conductor, dissipated negligible power for its direct current. The control coils, wound with monofilament HTS sheathed in Ag, dissipated negligible power for direct current. AC losses increased rapidly with frequency and quadratically with AC amplitude. Above about 2 Hz, the effective resistance of the control coils exceeds that of the silver which is in electrical parallel with the oxide superconductor. These results show that twisted multifilament conductor is not needed for stable levitation but may be desired to reduce control power for sizable dynamic loads.

High-frequency carbon supercapacitors from polyfurfuryl alcohol

NASA Astrophysics Data System (ADS)

Ruiz, V.; Pandolfo, A. G.

Porous carbons with controllable and narrow pore-size distributions are prepared from the chemical activation of polyfurfuryl alcohol (PFA). High apparent BET surface areas, up to 2600 m 2 g -1 (2611 m 2 g -1 by Density Functional Theory (DFT)), and good electrical conductivities (up to ∼130 S cm -1) are obtained. By varying the potassium hydroxide: carbon precursor ratio, the preparation of carbons with different proportions of micro- and fine mesoporosity (<5 nm) can be tailored to provide an ideal electronic and ionic pore structure for electrochemical energy-storage devices, such as electrical double-layer capacitors. High specific capacitance values are obtained up to 147 F g -1 in a voltage window of 2.5 V using 1 M tetraethyl ammonium tetrafluoroborate in acetonitrile. Moreover, excellent high-current and high-frequency performance is demonstrated: 100 F g -1 at 225 A g -1 (10 Hz) and ∼30 F g -1 at 100 Hz. When comparing the performance with commercial activated carbons (ACs) of similar textural properties, the PFA-derived ACs demonstrated better performance in terms of higher capacitance values and improved rate capabilities. There is a 125% increase in capacitance values at 1 kHz.

What is the origin of anomalous dielectric response in 2D organic dimer Mott insulators κ-(BEDT-TTF)2Cu[N(CN)2]Cl and κ-(BEDT-TTF)2Cu2(CN)3

NASA Astrophysics Data System (ADS)

Pinterić, M.; Ivek, T.; Čulo, M.; Milat, O.; Basletić, M.; Korin-Hamzić, B.; Tafra, E.; Hamzić, A.; Dressel, M.; Tomić, S.

2015-03-01

Novel forms of the low-temperature phases in the two-dimensional molecular solids with competing interactions between charges, spins and lattice, in particular those featuring anomalous dielectric relaxation, have been the focus of intense activity in recent years. Open issues concern the nature of collective charge excitations as well as their coupling to applied ac and dc electric fields. The charge response is reasonably well understood by now in the charge-ordered phase with the formation of ferroelectric-like domains below the metal-to-insulator phase transition. Conversely, the dielectric response observed in dimer Mott insulator phases with no complete evidence for charge ordering is rather intriguing. We overview our recent results of anisotropic complex conductivity (dc - MHz) in the magnetic phase of κ-(BEDT - TTF) 2 Cu [ N(CN)2 ] Cl and in the spin-liquid phase of κ-(BEDT - TTF) 2Cu2(CN)3. We discuss possible explanations for the observed dynamics within current theoretical models and compare them with the well-known fingerprints of the spin density wave response to ac electric fields.

AC conductivity and dielectric behavior of bulk Furfurylidenemalononitrile

NASA Astrophysics Data System (ADS)

El-Nahass, M. M.; Ali, H. A. M.

2012-06-01

AC conductivity and dielectric behavior for bulk Furfurylidenemalononitrile have been studied over a temperature range (293-333 K) and frequency range (50-5×106 Hz). The frequency dependence of ac conductivity, σac, has been investigated by the universal power law, σac(ω)=Aωs. The variation of the frequency exponent (s) with temperature was analyzed in terms of different conduction mechanisms, and it was found that the correlated barrier hopping (CBH) model is the predominant conduction mechanism. The temperature dependence of σac(ω) showed a linear increase with the increase in temperature at different frequencies. The ac activation energy was determined at different frequencies. Dielectric data were analyzed using complex permittivity and complex electric modulus for bulk Furfurylidenemalononitrile at various temperatures.

Enhanced sub-micron colloidal particle separation with interdigitated microelectrode arrays using mixed AC/DC dielectrophoretic scheme.

PubMed

Swaminathan, Vikhram V; Shannon, Mark A; Bashir, Rashid

2015-04-01

Dielectrophoretic separation of particles finds a variety of applications in the capture of species such as cells, viruses, proteins, DNA from biological systems, as well as other organic and inorganic contaminants from water. The ability to capture particles is constrained by poor volumetric scaling of separation force with respect to particle diameter, as well as the weak penetration of electric fields in the media. In order to improve the separation of sub-micron colloids, we present a scheme based on multiple interdigitated electrode arrays under mixed AC/DC bias. The use of high frequency longitudinal AC bias breaks the shielding effects through electroosmotic micromixing to enhance electric fields through the electrolyte, while a transverse DC bias between the electrode arrays enables penetration of the separation force to capture particles from the bulk of the microchannel. We determine the favorable biasing conditions for field enhancement with the help of analytical models, and experimentally demonstrate the improved capture from sub-micron colloidal suspensions with the mixed AC/DC electrostatic excitation scheme over conventional AC-DEP methods.

Unity power factor converter

NASA Technical Reports Server (NTRS)

Wester, Gene W. (Inventor)

1980-01-01

A unity power factor converter capable of effecting either inversion (dc-to-dc) or rectification (ac-to-dc), and capable of providing bilateral power control from a DC source (or load) through an AC transmission line to a DC load (or source) for power flow in either direction, is comprised of comparators for comparing the AC current i with an AC signal i.sub.ref (or its phase inversion) derived from the AC ports to generate control signals to operate a switch control circuit for high speed switching to shape the AC current waveform to a sine waveform, and synchronize it in phase and frequency with the AC voltage at the AC ports, by selectively switching the connections to a series inductor as required to increase or decrease the current i.

Effect of electrical energy on the efficacy of biofilm treatment using the bioelectric effect

PubMed Central

Kim, Young Wook; Subramanian, Sowmya; Gerasopoulos, Konstantinos; Ben-Yoav, Hadar; Wu, Hsuan-Chen; Quan, David; Carter, Karen; Meyer, Mariana T; Bentley, William E; Ghodssi, Reza

2015-01-01

Background/Objectives: The use of electric fields in combination with small doses of antibiotics for enhanced treatment of biofilms is termed the ‘bioelectric effect’ (BE). Different mechanisms of action for the AC and DC fields have been reported in the literature over the last two decades. In this work, we conduct the first study on the correlation between the electrical energy and the treatment efficacy of the bioelectric effect on Escherichia coli K-12 W3110 biofilms. Methods: A thorough study was performed through the application of alternating (AC), direct (DC) and superimposed (SP) potentials of different amplitudes on mature E. coli biofilms. The electric fields were applied in combination with the antibiotic gentamicin (10 μg/ml) over a course of 24 h, after the biofilms had matured for 24 h. The biofilms were analysed using the crystal violet assay, the colony-forming unit method and fluorescence microscopy. Results: Results show that there is no statistical difference in treatment efficacy between the DC-, AC- and SP-based BE treatment of equivalent energies (analysis of variance (ANOVA) P>0.05) for voltages <1 V. We also demonstrate that the efficacy of the BE treatment as measured by the crystal violet staining method and colony-forming unit assay is proportional to the electrical energy applied (ANOVA P<0.05). We further verify that the treatment efficacy varies linearly with the energy of the BE treatment (r2 =0.984). Our results thus suggest that the energy of the electrical signal is the primary factor in determining the efficacy of the BE treatment, at potentials less than the media electrolysis voltage. Conclusions: Our results demonstrate that the energy of the electrical signal, and not the type of electrical signal (AC or DC or SP), is the key to determine the efficacy of the BE treatment. We anticipate that this observation will pave the way for further understanding of the mechanism of action of the BE treatment method and may open new doors to the use of electric fields in the treatment of bacterial biofilms. PMID:28721233

A PWM transistor inverter for an ac electric vehicle drive

NASA Technical Reports Server (NTRS)

Slicker, J. M.

1981-01-01

A prototype system consisting of closely integrated motor, inverter, and transaxle has been built in order to demonstrate the feasibility of a three-phase ac transistorized inverter for electric vehicle applications. The microprocessor-controlled inverter employs monolithic power transistors to drive an oil-cooled, three-phase induction traction motor at a peak output power of 30 kW from a 144 V battery pack. Transistor safe switching requirements are discussed, and a circuit is presented for recovering trapped snubber inductor energy at transistor turn-off.

9 CFR 307.7 - Safety requirements for electrical stimulating (EST) equipment.

Code of Federal Regulations, 2012 CFR

2012-01-01

... requirements for electrical stimulating (EST) equipment. (a) General. Electrical stimulating (EST) equipment is... of facilitating blood removal. These provisions do not apply to electrical equipment used to stun and... generate pulsed DC or AC voltage for stimulation and is separate from the equipment used to apply the...

9 CFR 307.7 - Safety requirements for electrical stimulating (EST) equipment.

Code of Federal Regulations, 2014 CFR

2014-01-01

... requirements for electrical stimulating (EST) equipment. (a) General. Electrical stimulating (EST) equipment is... of facilitating blood removal. These provisions do not apply to electrical equipment used to stun and... generate pulsed DC or AC voltage for stimulation and is separate from the equipment used to apply the...

Electrical and dielectric properties of PVdF-HFP - PMMA - (PC + DEC)- LiClO4 based gel polymer electrolyte

NASA Astrophysics Data System (ADS)

Gohel, Khushbu; Kanchan, D. K.; Maheshwaran, C.

2018-04-01

In the present paper, AC impedance studies have been measured to evaluate ion conduction behavior of (PVdF-HFP - PMMA) + (PC-DEC) + LiClO4 gel polymer electrolyte system prepared by solution casting method. Structural characterization and morphology has been carried out using XRD and SEM respectively. The AC conductivity and dielectric permittivity, electric modulus and relaxation mechanism have been studied. The variation of ac conductivity with frequency obeys Jonscher power law. Maximum value of dielectric constant ɛ' in the lower frequency region has been observed for the gel polymer electrolyte containing 7.5 wt% LiClO4. The highest conducting sample shows the shortest relaxation time.

Activated carbon/manganese dioxide hybrid electrodes for high performance thin film supercapacitors

NASA Astrophysics Data System (ADS)

Jang, Yunseok; Jo, Jeongdai; Jang, Hyunjung; Kim, Inyoung; Kang, Dongwoo; Kim, Kwang-Young

2014-06-01

We combine the activated carbon (AC) and the manganese dioxide (MnO2) in a AC/MnO2 hybrid electrode to overcome the low capacitance of activated carbon and MnO2 by exploiting the large surface area of AC and the fast reversible redox reaction of MnO2. An aqueous permanganate (MnO4 -) is converted to MnO2 on the surface of the AC electrode by dipping the AC electrode into an aqueous permanganate solution. The AC/MnO2 hybrid electrode is found to display superior specific capacitance of 290 F/g. This shows that supercapacitors classified as electric double layer capacitors and pseudocapacitors can be combined together.

Combined Effect of Alternating Current Interference and Cathodic Protection on Pitting Corrosion and Stress Corrosion Cracking Behavior of X70 Pipeline Steel in Near-Neutral pH Environment.

PubMed

Wang, Liwei; Cheng, Lianjun; Li, Junru; Zhu, Zhifu; Bai, Shuowei; Cui, Zhongyu

2018-03-22

Influence of alternating current (AC) on pitting corrosion and stress corrosion cracking (SCC) behavior of X70 pipeline steel in the near-neutral pH environment under cathodic protection (CP) was investigated. Both corrosion and SCC are inhibited by -0.775 V SCE CP without AC interference. With the superimposition of AC current (1-10 mA/cm²), the direct current (DC) potential shifts negatively under the CP of -0.775 V SCE and the cathodic DC current decreases and shifts to the anodic direction. Under the CP potential of -0.95 V SCE and -1.2 V SCE , the applied AC current promotes the cathodic reaction and leads to the positive shift of DC potential and increase of cathodic current. Local anodic dissolution occurs attributing to the generated anodic current transients in the positive half-cycle of the AC current, resulting in the initiation of corrosion pits (0.6-2 μm in diameter). AC enhances the SCC susceptibility of X70 steel under -0.775 V SCE CP, attributing to the promotion of anodic dissolution and hydrogen evolution. Even an AC current as low as 1 mA/cm² can enhance the SCC susceptibility.

Holographic Floquet states I: a strongly coupled Weyl semimetal

NASA Astrophysics Data System (ADS)

Hashimoto, Koji; Kinoshita, Shunichiro; Murata, Keiju; Oka, Takashi

2017-05-01

Floquet states can be realized in quantum systems driven by continuous time-periodic perturbations. It is known that a state known as the Floquet Weyl semimetal can be realized when free Dirac fermions are placed in a rotating electric field. What will happen if strong interaction is introduced to this system? Will the interaction wash out the characteristic features of Weyl semimetals such as the Hall response? Is there a steady state and what is its thermodynamic behavior? We answer these questions using AdS/CFT correspondence in the N = 2 supersymmetric massless QCD in a rotating electric field in the large N c limit realizing the first example of a "holographic Floquet state". In this limit, gluons not only mediate interaction, but also act as an energy reservoir and stabilize the nonequilibrium steady state (NESS). We obtain the electric current induced by a rotating electric field: in the high frequency region, the Ohm's law is satisfied, while we recover the DC nonlinear conductivity at low frequency, which was obtained holographically in a previous work. The thermodynamic properties of the NESS, e.g., fluctuation-dissipation relation, is characterized by the effective Hawking temperature that is defined from the effective horizon giving a holographic meaning to the "periodic thermodynamic" concept. In addition to the strong (pump) rotating electric field, we apply an additional weak (probe) electric field in the spirit of the pump-probe experiments done in condensed matter experiments. Weak DC and AC probe analysis in the background rotating electric field shows Hall currents as a linear response, therefore the Hall response of Floquet Weyl semimetals survives at the strong coupling limit. We also find frequency mixed response currents, i.e., a heterodyning effect, characteristic to periodically driven Floquet systems.

AC/DC Power Systems with Applications for future Lunar/Mars base and Crew Exploration Vehicle

NASA Technical Reports Server (NTRS)

Chowdhury, Badrul H.

2005-01-01

ABSTRACT The Power Systems branch at JSC faces a number of complex issues as it readies itself for the President's initiative on future space exploration beyond low earth orbit. Some of these preliminary issues - those dealing with electric power generation and distribution on board Mars-bound vehicle and that on Lunar and Martian surface may be summarized as follows: Type of prime mover - Because solar power may not be readily available on parts of the Lunar/Mars surface and also during the long duration flight to Mars, the primary source of power will most likely be nuclear power (Uranium fuel rods) with a secondary source of fuel cell (Hydrogen supply). The electric power generation source - With nuclear power being the main prime mover, the electric power generation source will most likely be an ac generator at a yet to be determined frequency. Thus, a critical issue is whether the generator should generate at constant or variable frequency. This will decide what type of generator to use - whether it is a synchronous machine, an asynchronous induction machine or a switched reluctance machine. The type of power distribution system - the distribution frequency, number of wires (3- wire, 4-wire or higher), and ac/dc hybridization. Building redundancy and fault tolerance in the generation and distribution sub-systems so that the system is safe; provides 100% availability to critical loads; continues to operate even with faulted sub-systems; and requires minimal maintenance. This report descril_es results of a summer faculty fellowship spent in the Power Systems Branch with the specific aim of investigating some of the lessons learned in electric power generation and usage from the terrestrial power systems industry, the aerospace industry as well as NASA's on-going missions so as to recommend novel surface and vehicle-based power systems architectures in support of future space exploration initiatives. A hybrid ac/dc architecture with source side and load side redundancies and including emergency generators on both ac and dc sides is proposed. The generation frequency is 400 Hz mostly because of the technology maturity at this frequency in the aerospace industry. Power will be distributed to several ac load distribution buses through solid state variable speed, constant frequency converters on the ac side. A segmented dc ring bus supplied from ac/dc converters and with the capability of connecting/disconnecting the segments will supply power to multiple de load distribution buses. The system will have the capability of reverse flow from dc to ac side in the case of an extreme emergency on the main ac generation side.

Intersociety Energy Conversion Engineering Conference, 20th, Miami Beach, FL, August 18-23, 1985, Proceedings. Volumes 1, 2, & 3

NASA Astrophysics Data System (ADS)

1985-12-01

Topics related to aerospace power are discussed, taking into account trends and issues of military space power systems technology, space station power system advanced development, the application and use of nuclear power for future spacecraft, the current status of advanced solar array technology development, the application of a parabolic trough concentrator to space station power needs, life test results of the Intelsat-V nickel-cadmium battery, and metal hydride hydrogen storage in nickel hydrogen batteries. Other subjects explored are concerned with alternative fuels, biomass energy, biomedical power, coal gasification, electric power cycles, and electric propulsion. Attention is given to an advanced terrestrial vehicle electric propulsion systems assessment, fuel cells as electric propulsion power plants, a sinewave synthesis for high efficiency dc-ac conversion, steam desulfurization of coal, leadless transfer of energy into the body to power implanted blood pumps, oil production via entrained flow pyrolysis of biomass, and a New Zealand synthetic gasoline plant.

Alternating current long range alpha particle detector

DOEpatents

MacArthur, Duncan W.; McAtee, James L.

1993-01-01

An alpha particle detector, utilizing alternating currents, whcih is capable of detecting alpha particles from distinct sources. The use of alternating currents allows use of simpler ac circuits which, in turn, are not susceptible to dc error components. It also allows the benefit of gas gain, if desired. In the invention, a voltage source creates an electric field between two conductive grids, and between the grids and a conductive enclosure. Air containing air ions created by collision with alpha particles is drawn into the enclosure and detected. In some embodiments, the air flow into the enclosure is interrupted, creating an alternating flow of ions. In another embodiment, a modulated voltage is applied to the grid, also modulating the detection of ions.

Alternating current long range alpha particle detector

DOEpatents

MacArthur, D.W.; McAtee, J.L.

1993-02-16

An alpha particle detector, utilizing alternating currents, which is capable of detecting alpha particles from distinct sources. The use of alternating currents allows use of simpler ac circuits which, in turn, are not susceptible to dc error components. It also allows the benefit of gas gain, if desired. In the invention, a voltage source creates an electric field between two conductive grids, and between the grids and a conductive enclosure. Air containing air ions created by collision with alpha particles is drawn into the enclosure and detected. In some embodiments, the air flow into the enclosure is interrupted, creating an alternating flow of ions. In another embodiment, a modulated voltage is applied to the grid, also modulating the detection of ions.

Capacitive Neutralization Dialysis for Direct Energy Generation.

PubMed

Liu, Yue; Zhang, Yi; Ou-Yang, Wei; Bastos Sales, Bruno; Sun, Zhuo; Liu, Fei; Zhao, Ran

2017-08-15

Capacitive neutralization dialysis energy (CNDE) is proposed as a novel energy-harvesting technique that is able to utilize waste acid and alkaline solutions to produce electrical energy. CNDE is a modification based on neutralization dialysis. It was found that a higher NaCl concentration led to a higher open-circuit potential when the concentrations of acid and alkaline solutions were fixed. Upon closing of the circuit, the membrane potential was used as a driving force to move counter ions into the electrical double layers at the electrode-liquid interface, thereby creating an ionic current. Correspondingly, in the external circuit, electrons flow through an external resistor from one electrode to the other, thereby generating electrical energy directly. The influence of external resistances was studied to achieve greater energy extraction, with the maximum output of 110 mW/m 2 obtained by employing an external resistance of 5 Ω together with the AC-coated electrode.

Measurement of changes in impedance of DNA nanowires due to radiation induced structural damage. A novel approach for a DNA-based radiosensitive device

NASA Astrophysics Data System (ADS)

Heimbach, Florian; Arndt, Alexander; Nettelbeck, Heidi; Langner, Frank; Giesen, Ulrich; Rabus, Hans; Sellner, Stefan; Toppari, Jussi; Shen, Boxuan; Baek, Woon Yong

2017-08-01

The ability of DNA to conduct electric current has been the topic of numerous investigations over the past few decades. Those investigations indicate that this ability is dependent on the molecular structure of the DNA. Radiation-induced damages, which lead to an alteration of the molecular structure, should therefore change the electrical impedance of a DNA molecule. In this paper, the damage due to ionising radiation is shown to have a direct effect on the electrical transport properties of DNA. Impedance measurements of DNA samples were carried out by an AC impedance spectrometer before, during and after irradiation. The samples comprised of DNA segments, which were immobilized between gold electrodes with a gap of 12 μm. The impedance of all DNA samples exhibited rising capacitive behaviour with increasing absorbed dose.

Optimal Transmission Line Switching under Geomagnetic Disturbances

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Mowen; Nagarajan, Harsha; Yamangil, Emre

Recently, there have been increasing concerns about how geomagnetic disturbances (GMDs) impact electrical power systems. Geomagnetically-induced currents (GICs) can saturate transformers, induce hot spot heating and increase reactive power losses. These effects can potentially cause catastrophic damage to transformers and severely impact the ability of a power system to deliver power. To address this problem, we develop a model of GIC impacts to power systems that includes 1) GIC thermal capacity of transformers as a function of normal Alternating Current (AC) and 2) reactive power losses as a function of GIC. We also use this model to derive an optimizationmore » problem that protects power systems from GIC impacts through line switching, generator dispatch, and load shedding. We then employ state-of-the-art convex relaxations of AC power flow equations to lower bound the objective. We demonstrate the approach on a modified RTS96 system and UIUC 150-bus system and show that line switching is an effective means to mitigate GIC impacts. We also provide a sensitivity analysis of decisions with respect to GMD direction.« less

A simulation-based efficiency comparison of AC and DC power distribution networks in commercial buildings

DOE PAGES

Gerber, Daniel L.; Vossos, Vagelis; Feng, Wei; ...

2017-06-12

Direct current (DC) power distribution has recently gained traction in buildings research due to the proliferation of on-site electricity generation and battery storage, and an increasing prevalence of internal DC loads. The research discussed in this paper uses Modelica-based simulation to compare the efficiency of DC building power distribution with an equivalent alternating current (AC) distribution. The buildings are all modeled with solar generation, battery storage, and loads that are representative of the most efficient building technology. A variety of paramet ric simulations determine how and when DC distribution proves advantageous. These simulations also validate previous studies that use simplermore » approaches and arithmetic efficiency models. This work shows that using DC distribution can be considerably more efficient: a medium sized office building using DC distribution has an expected baseline of 12% savings, but may also save up to 18%. In these results, the baseline simulation parameters are for a zero net energy (ZNE) building that can island as a microgrid. DC is most advantageous in buildings with large solar capacity, large battery capacity, and high voltage distribution.« less

Optimal Transmission Line Switching under Geomagnetic Disturbances

DOE PAGES

Lu, Mowen; Nagarajan, Harsha; Yamangil, Emre; ...

2017-10-11

Recently, there have been increasing concerns about how geomagnetic disturbances (GMDs) impact electrical power systems. Geomagnetically-induced currents (GICs) can saturate transformers, induce hot spot heating and increase reactive power losses. These effects can potentially cause catastrophic damage to transformers and severely impact the ability of a power system to deliver power. To address this problem, we develop a model of GIC impacts to power systems that includes 1) GIC thermal capacity of transformers as a function of normal Alternating Current (AC) and 2) reactive power losses as a function of GIC. We also use this model to derive an optimizationmore » problem that protects power systems from GIC impacts through line switching, generator dispatch, and load shedding. We then employ state-of-the-art convex relaxations of AC power flow equations to lower bound the objective. We demonstrate the approach on a modified RTS96 system and UIUC 150-bus system and show that line switching is an effective means to mitigate GIC impacts. We also provide a sensitivity analysis of decisions with respect to GMD direction.« less

Impact of electromagnetic fields on human vestibular system and standing balance: pilot results and future developments

NASA Astrophysics Data System (ADS)

Allen, A.; Villard, S.; Corbacio, M.; Goulet, D.; Plante, M.; Souques, M.; Deschamps, F.; Ostiguy, G.; Lambrozo, J.; Thomas, A. W.; Legros, A.

2016-03-01

Although studies have found that extremely low-frequency (ELF, < 300 Hz) magnetic fields (MF) can modulate human standing balance, the acute effects of electromagnetic fields on standing balance have not been systematically investigated. This work aims to establish the threshold for acute standing balance modulation during ELFMF exposure. One hundred volunteers will be exposed to transcranial electric stimulations (Direct Current - DC and Alternating Current - AC, 1 mA) and ELFMF (0 to 160 Hz, 0 to 100 mT). The displacement of their center of pressure will be collected and analyzed as an indicator of vestibular performance. During pilot testing (n=6), we found increased lateral sway with DC, and to a lesser extent, AC exposure. The ELFMF exposure system still needs to be adapted to allow meaningful results. Future protocol design will test for possible effects due to exposures in the radiofrequency range (i.e. above 3 kHz). These results will contribute to the literature documenting exposure guidelines aiming to protect workers and the general public.

A simulation-based efficiency comparison of AC and DC power distribution networks in commercial buildings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gerber, Daniel L.; Vossos, Vagelis; Feng, Wei

Direct current (DC) power distribution has recently gained traction in buildings research due to the proliferation of on-site electricity generation and battery storage, and an increasing prevalence of internal DC loads. The research discussed in this paper uses Modelica-based simulation to compare the efficiency of DC building power distribution with an equivalent alternating current (AC) distribution. The buildings are all modeled with solar generation, battery storage, and loads that are representative of the most efficient building technology. A variety of paramet ric simulations determine how and when DC distribution proves advantageous. These simulations also validate previous studies that use simplermore » approaches and arithmetic efficiency models. This work shows that using DC distribution can be considerably more efficient: a medium sized office building using DC distribution has an expected baseline of 12% savings, but may also save up to 18%. In these results, the baseline simulation parameters are for a zero net energy (ZNE) building that can island as a microgrid. DC is most advantageous in buildings with large solar capacity, large battery capacity, and high voltage distribution.« less

Numerical and theoretical evaluations of AC losses for single and infinite numbers of superconductor strips with direct and alternating transport currents in external AC magnetic field

NASA Astrophysics Data System (ADS)

Kajikawa, K.; Funaki, K.; Shikimachi, K.; Hirano, N.; Nagaya, S.

2010-11-01

AC losses in a superconductor strip are numerically evaluated by means of a finite element method formulated with a current vector potential. The expressions of AC losses in an infinite slab that corresponds to a simple model of infinitely stacked strips are also derived theoretically. It is assumed that the voltage-current characteristics of the superconductors are represented by Bean's critical state model. The typical operation pattern of a Superconducting Magnetic Energy Storage (SMES) coil with direct and alternating transport currents in an external AC magnetic field is taken into account as the electromagnetic environment for both the single strip and the infinite slab. By using the obtained results of AC losses, the influences of the transport currents on the total losses are discussed quantitatively.

Department of Energy Semiannual Regulatory Agenda

Federal Register 2010, 2011, 2012, 2013, 2014

2010-12-20

... Water Heaters; and (2) Energy Efficiency Standards for Certain Commercial and Industrial Electric Motors... Standards for Certain Commercial and Industrial Electric Motors..... 1904-AC28 Energy Efficiency and... FOR CERTAIN COMMERCIAL AND INDUSTRIAL ELECTRIC MOTORS Legal Authority: 42 USC 6313(b)(4)(B) Abstract...

75 FR 79759 - Regulatory Agenda

Federal Register 2010, 2011, 2012, 2013, 2014

2010-12-20

... Efficiency Standards for Certain Commercial and Industrial Electric Motors. The Plan appears in both the... Commercial and Industrial Electric Motors..... 1904-AC28 Energy Efficiency and Renewable Energy--Completed... COMMERCIAL AND INDUSTRIAL ELECTRIC MOTORS Legal Authority: 42 USC 6313(b)(4)(B) Abstract: The Energy Policy...

Development of software to improve AC power quality on large spacecraft

NASA Technical Reports Server (NTRS)

Kraft, L. Alan

1991-01-01

To insure the reliability of a 20 kHz, alternating current (AC) power system on spacecraft, it is essential to analyze its behavior under many adverse operating conditions. Some of these conditions include overloads, short circuits, switching surges, and harmonic distortions. Harmonic distortions can become a serious problem. It can cause malfunctions in equipment that the power system is supplying, and, during distortions such as voltage resonance, it can cause equipment and insulation failures due to the extreme peak voltages. To address the harmonic distortion issue, work was begun under the 1990 NASA-ASEE Summer Faculty Fellowship Program. Software, originally developed by EPRI, called HARMFLO, a power flow program capable of analyzing harmonic conditions on three phase, balanced, 60 Hz AC power systems, was modified to analyze single phase, 20 kHz, AC power systems. Since almost all of the equipment used on spacecraft power systems is electrically different from equipment used on terrestrial power systems, it was also necessary to develop mathematical models for the equipment to be used on the spacecraft. The modelling was also started under the same fellowship work period. Details of the modifications and models completed during the 1990 NASA-ASEE Summer Faculty Fellowship Program can be found in a project report. As a continuation of the work to develop a complete package necessary for the full analysis of spacecraft AC power system behavior, deployment work has continued through NASA Grant NAG3-1254. This report details the work covered by the above mentioned grant.

Electricity generation from real industrial wastewater using a single-chamber air cathode microbial fuel cell with an activated carbon anode.

PubMed

Mohamed, Hend Omar; Obaid, M; Sayed, Enas Taha; Liu, Yang; Lee, Jinpyo; Park, Mira; Barakat, Nasser A M; Kim, Hak Yong

2017-08-01

This study introduces activated carbon (AC) as an effective anode for microbial fuel cells (MFCs) using real industrial wastewater without treatment or addition of external microorganism mediators. Inexpensive activated carbon is introduced as a proper electrode alternative to carbon cloth and carbon paper materials, which are considered too expensive for the large-scale application of MFCs. AC has a porous interconnected structure with a high bio-available surface area. The large surface area, in addition to the high macro porosity, facilitates the high performance by reducing electron transfer resistance. Extensive characterization, including surface morphology, material chemistry, surface area, mechanical strength and biofilm adhesion, was conducted to confirm the effectiveness of the AC material as an anode in MFCs. The electrochemical performance of AC was also compared to other anodes, i.e., Teflon-treated carbon cloth (CCT), Teflon-treated carbon paper (CPT), untreated carbon cloth (CC) and untreated carbon paper (CP). Initial tests of a single air-cathode MFC display a current density of 1792 mAm -2 , which is approximately four times greater than the maximum value of the other anode materials. COD analyses and Coulombic efficiency (CE) measurements for AC-MFC show the greatest removal of organic compounds and the highest CE efficiency (60 and 71%, respectively). Overall, this study shows a new economical technique for power generation from real industrial wastewater with no treatment and using inexpensive electrode materials.

Electrical conductivity and modulus formulation in zinc modified bismuth boro-tellurite glasses

NASA Astrophysics Data System (ADS)

Dhankhar, Sunil; Kundu, R. S.; Dult, Meenakshi; Murugavel, S.; Punia, R.; Kishore, N.

2016-09-01

The ac conductivity of zinc modified tellurium based quaternary glasses having composition 60 TeO2-10 B2O3-(30 - x) Bi2O3-x ZnO; x = 10, 15, 20, 25 and 30 has been investigated in the frequency range 10-1-105 Hz and in temperature range 483-593 K. Frequency and temperature dependent ac conductivity found to obey Jonscher power law modified by Almond-West. DC conductivity, crossover frequency and frequency exponent have been estimated from the fitting of the experimental data of conductivity with Jonscher power law modified by Almond-West. The ac conductivity and its frequency exponent have been analyzed by various theoretical models. In presently studied glasses ac conduction takes place via tunneling of overlapping large polaron tunneling. Activation energy is found to be increased with increase in zinc content and dc conduction takes place via variable range hopping proposed by Mott with some modification suggested by Punia et al. The value of the stretched exponent ( β) obtained by fitting of M^' ' }} reveals the presence of non-Debye type relaxation. Scaling spectra of ac conductivity and electric modulus collapse into a single master curve for all compositions and temperatures, reveals the presence of composition and temperature independent conduction and relaxation process in these glasses. Activation energy of conduction ( W) and electric modulus ( E R ) are nearly equal, indicating that polaron have to overcome the same energy barrier during conduction as well as relaxation processes.

High-Frequency Nanocapacitor Arrays: Concept, Recent Developments, and Outlook.

PubMed

Lemay, Serge G; Laborde, Cecilia; Renault, Christophe; Cossettini, Andrea; Selmi, Luca; Widdershoven, Frans P

2016-10-18

We have developed a measurement platform for performing high-frequency AC detection at nanoelectrodes. The system consists of 65 536 electrodes (diameter 180 nm) arranged in a sub-micrometer rectangular array. The electrodes are actuated at frequencies up to 50 MHz, and the resulting AC current response at each separately addressable electrode is measured in real time. These capabilities are made possible by fabricating the electrodes on a complementary metal-oxide-semiconductor (CMOS) chip together with the associated control and readout electronics, thus minimizing parasitic capacitance and maximizing the signal-to-noise ratio. This combination of features offers several advantages for a broad range of experiments. First, in contrast to alternative CMOS-based electrical systems based on field-effect detection, high-frequency operation is sensitive beyond the electrical double layer and can probe entities at a range of micrometers in electrolytes with high ionic strength such as water at physiological salt concentrations. Far from being limited to single- or few-channel recordings like conventional electrochemical impedance spectroscopy, the massively parallel design of the array permits electrically imaging micrometer-scale entities with each electrode serving as a separate pixel. This allows observation of complex kinetics in heterogeneous environments, for example, the motion of living cells on the surface of the array. This imaging aspect is further strengthened by the ability to distinguish between analyte species based on the sign and magnitude of their AC response. Finally, we show here that sensitivity down to the attofarad level combined with the small electrode size permits detection of individual 28 nm diameter particles as they land on the sensor surface. Interestingly, using finite-element methods, it is also possible to calculate accurately the full three-dimensional electric field and current distributions during operation at the level of the Poisson-Nernst-Planck formalism. This makes it possible to validate the interpretation of measurements and to optimize the design of future experiments. Indeed, the complex frequency and spatial dependence of the data suggests that experiments to date have only scratched the surface of the method's capabilities. Future iterations of the hardware will take advantage of the higher frequencies, higher electrode packing densities and smaller electrode sizes made available by continuing advances in CMOS manufacturing. Combined with targeted immobilization of targets at the electrodes, we anticipate that it will soon be possible to realize complex biosensors based on spatial- and time-resolved nanoscale impedance detection.

The AC photovoltaic module is here!

NASA Astrophysics Data System (ADS)

Strong, Steven J.; Wohlgemuth, John H.; Wills, Robert H.

1997-02-01

This paper describes the design, development, and performance results of a large-area photovoltaic module whose electrical output is ac power suitable for direct connection to the utility grid. The large-area ac PV module features a dedicated, integrally mounted, high-efficiency dc-to-ac power inverter with a nominal output of 250 watts (STC) at 120 Vac, 60 H, that is fully compatible with utility power. The module's output is connected directly to the building's conventional ac distribution system without need for any dc wiring, string combiners, dc ground-fault protection or additional power-conditioning equipment. With its advantages, the ac photovoltaic module promises to become a universal building block for use in all utility-interactive PV systems. This paper discusses AC Module design aspects and utility interface issues (including islanding).

Power And Propulsion Systems For Mobile Robotic Applications

NASA Astrophysics Data System (ADS)

Layuan, Li; Haiming, Zou

1987-02-01

Choosing the best power and propulsion systems for mobile robotic land vehicle applications requires consideration of technologies. The electric power requirements for onboard electronic and auxiliary equipment include 110/220 volt 60 Hz ac power as well as low voltage dc power. Weight and power are saved by either direct dc power distribution, or high frequency (20 kHz) ac power distribution. Vehicle control functions are performed electronically but steering, braking and traction power may be distributed electrically, mechanically or by fluid (hydraulic) means. Electric drive is practical, even for small vehicles, provided that advanced electric motors are used. Such electric motors have demonstrated power densities of 3.1 kilowatts per kilogram with devices in the 15 kilowatt range. Electric motors have a lower torque, but higher power density as compared to hydraulic or mechanical transmission systems. Power density being comparable, electric drives were selected to best meet the other requirements for robotic vehicles. Two robotic vehicle propulsion system designs are described to illustrate the implementation of electric drive over a vehicle size range of 250-7500 kilograms.

Frequency- and doping-level influence on electric and dielectric properties of PolySi/SiO2/cSi (MOS) structures

NASA Astrophysics Data System (ADS)

Doukhane, N.; Birouk, B.

2018-03-01

The electric and dielectric characteristics of PolySi/SiO2/cSi (MOS) structure, such as series resistance ( R s), dielectric constants ( ɛ') and ( ɛ″), dielectric losses (tan δ), and the ac electric conductivity ( σ ac), were studied in the frequency range 100 kHz-1 MHz for various doping levels and two thicknesses for the polysilicon layer (100 and 175 nm). The experimental results show that the C and G/ ω characteristics are very sensitive to the frequency due to the presence of interface states. Series resistance R s is deduced from C and G/ ω measurements and is plotted as a function of the frequency for various doping levels. It is found to decrease with frequency and doping level. To determine {ɛ ^' }, ɛ″, tan δ, and {σ _{{ac}}}, the admittance technique was used. An interesting behavior of the constants, {ɛ ^' } and ɛ″, was noticed. The {ɛ ^' } values fit led to relations between {ɛ ^' } and the frequency, on one hand, and between {ɛ ^' } and the electric conductivity of the polysilicon layers on the other. These relations make it possible to interpolate directly between two experimental points for a given frequency. The analysis of the results shows that the values of {ɛ ^' }, ɛ″, and tan δ decrease with increasing frequency. This is due to the fact that in the region of low frequencies, interfacial polarization occurs easily, and the interface states between Si and SiO2 contribute to the improvement of the dielectric properties of the PolySi/SiO2/cSi structures. The study also emphasizes that the ac electric conductivity increases with the increase in frequency and doping level; this causes to the reduction in series resistance.

Tailoring particle translocation via dielectrophoresis in pore channels

PubMed Central

Tanaka, Shoji; Tsutsui, Makusu; Theodore, Hu; Yuhui, He; Arima, Akihide; Tsuji, Tetsuro; Doi, Kentaro; Kawano, Satoyuki; Taniguchi, Masateru; Kawai, Tomoji

2016-01-01

Understanding and controlling electrophoretic motions of nanoscopic objects in fluidic channels are a central challenge in developing nanopore technology for molecular analyses. Although progress has been made in slowing the translocation velocity to meet the requirement for electrical detections of analytes via picoampere current measurements, there exists no method useful for regulating particle flows in the transverse directions. Here, we report the use of dielectrophoresis to manipulate the single-particle passage through a solid-state pore. We created a trap field by applying AC voltage between electrodes embedded in a low-aspect-ratio micropore. We demonstrated a traffic control of particles to go through center or near side surface via the voltage frequency. We also found enhanced capture efficiency along with faster escaping speed of particles by virtue of the AC-mediated electroosmosis. This method is compatible with nanopore sensing and would be widely applied for reducing off-axis effects to achieve single-molecule identification. PMID:27527126

Controlled Trapping of Onion-Like Carbon (OLC) via Dielectrophoresis

NASA Astrophysics Data System (ADS)

Olariu, Marius; Arcire, Alexandru; Plonska-Brzezinska, Marta E.

2017-01-01

Manipulation of onion-like carbon (OLC), also known as carbon nano-onions (CNOs), at the level of various arrays of microelectrodes is vital in practical applications such as biological and chemical sensing, ultracapacitors (supercapacitors), electromagnetic shielding, catalysis, tribology, optical limiting and molecular junctions in scanning tunneling microscopy, and field-effect transistors. In spite of technological developments in this area, rigorous handling of carbon nano-onions towards desired locations within a device remains a challenge, and the quantity of OLC required significantly influences the price of the final electrical or electronic device. We present herein an experimental study on electromanipulation and trapping of onion-like carbon (OLC) at the level of gold-patterned interdigitated microelectrodes through dielectrophoresis. The influence of the magnitude as well as frequency of the alternating-current (AC) voltage employed for OLC trapping is discussed in detail. The effects of tuning the AC field strength and frequency on the OLC trapping behavior are also considered.

Performance criteria guideline for three explosion protection methods of electrical equipment rated up to 15,000 volts AC

NASA Technical Reports Server (NTRS)

Linley, L. J.; Luper, A. B.; Dunn, J. H.

1982-01-01

The Bureau of Mines, U.S. Department of the Interior, is reviewing explosion protection methods for use in gassy coal mines. This performance criteria guideline is an evaluation of three explosion protection methods of machines electrically powered with voltages up to 15,000 volts ac. A sufficient amount of basic research has been accomplished to verify that the explosion proof and pressurized enclosure methods can provide adequate explosion protection with the present state of the art up to 15,000 volts ac. This routine application of the potted enclosure as a stand alone protection method requires further investigation or development in order to clarify performance criteria and verification certification requirements. An extensive literature search, a series of high voltage tests, and a design evaluation of the three explosion protection methods indicate that the explosion proof, pressurized, and potted enclosures can all be used to enclose up to 15,000 volts ac.

Method and apparatus for reducing the harmonic currents in alternating-current distribution networks

DOEpatents

Beverly, Leon H.; Hance, Richard D.; Kristalinski, Alexandr L.; Visser, Age T.

1996-01-01

An improved apparatus and method reduce the harmonic content of AC line and neutral line currents in polyphase AC source distribution networks. The apparatus and method employ a polyphase Zig-Zag transformer connected between the AC source distribution network and a load. The apparatus and method also employs a mechanism for increasing the source neutral impedance of the AC source distribution network. This mechanism can consist of a choke installed in the neutral line between the AC source and the Zig-Zag transformer.

Method and apparatus for reducing the harmonic currents in alternating-current distribution networks

DOEpatents

Beverly, L.H.; Hance, R.D.; Kristalinski, A.L.; Visser, A.T.

1996-11-19

An improved apparatus and method reduce the harmonic content of AC line and neutral line currents in polyphase AC source distribution networks. The apparatus and method employ a polyphase Zig-Zag transformer connected between the AC source distribution network and a load. The apparatus and method also employs a mechanism for increasing the source neutral impedance of the AC source distribution network. This mechanism can consist of a choke installed in the neutral line between the AC source and the Zig-Zag transformer. 23 figs.

Spacecraft attitude control for a solar electric geosynchronous transfer mission

NASA Technical Reports Server (NTRS)

Leroy, B. E.; Regetz, J. D., Jr.

1975-01-01

A study of the Attitude Control System (ACS) is made for a solar electric propulsion geosynchronous transfer mission. The basic mission considered is spacecraft injection into a low altitude, inclined orbit followed by low thrust orbit changing to achieve geosynchronous orbit. Because of the extended thrusting time, the mission performance is a strong function of the attitude control system. Two attitude control system design options for an example mission evolve from consideration of the spacecraft configuration, the environmental disturbances, and the probable ACS modes of operation. The impact of these design options on other spacecraft subsystems is discussed. The factors which must be considered in determining the ACS actuation and sensing subsystems are discussed. The effects of the actuation and sensing subsystems on the mission performance are also considered.

AC electric field for rapid assembly of nanostructured polyaniline onto microsized gap for sensor devices.

PubMed

La Ferrara, Vera; Rametta, Gabriella; De Maria, Antonella

2015-07-01

Interconnected network of nanostructured polyaniline (PANI) is giving strong potential for enhancing device performances than bulk PANI counterparts. For nanostructured device processing, the main challenge is to get prototypes on large area by requiring precision, low cost and high rate assembly. Among processes meeting these requests, the alternate current electric fields are often used for nanostructure assembling. For the first time, we show the assembly of nanostructured PANI onto large electrode gaps (30-60 μm width) by applying alternate current electric fields, at low frequencies, to PANI particles dispersed in acetonitrile (ACN). An important advantage is the short assembly time, limited to 5-10 s, although electrode gaps are microsized. That encouraging result is due to a combination of forces, such as dielectrophoresis (DEP), induced-charge electrokinetic (ICEK) flow and alternate current electroosmotic (ACEO) flow, which speed up the assembly process when low frequencies and large electrode gaps are used. The main achievement of the present study is the development of ammonia sensors created by direct assembling of nanostructured PANI onto electrodes. Sensors exhibit high sensitivity to low gas concentrations as well as excellent reversibility at room temperature, even after storage in air. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Influence of Ag, Cd or Pb Addition on Electrical and Dielectric Properties of Bulk Glassy Se-Ge

NASA Astrophysics Data System (ADS)

El-Metwally, E. G.; Shakra, A. M.

2018-05-01

Bulk glassy samples of Se0.7Ge0.3 and Se0.7Ge0.25 X 0.05 (X = Ag, Cd or Pb) chalcogenide glass have been prepared by melt-quenching method. The studied compositions were examined in powder form by x-ray diffraction analysis. The direct-current (dc) conductivity σ_{{dc}} was measured for bulk samples in the temperature range from 303 K to 433 K, revealing enhancement with temperature for all samples. The results indicate two values of activation energy ( Δ E_{{σ1 }} and Δ E_{{σ2 }} ) due to two conduction mechanisms. Measurements of the alternating-current (ac) conductivity σ_{{ac}} ( ω ) and dielectric properties for bulk samples were carried out in the temperature range from 303 K to 433 K and frequency range from 1 kHz to 1 MHz. The ac conductivity σ_{{ac}} ( ω ) was temperature dependent and proportional to ωS , where S is the frequency exponent, which reduced with rising temperature, and ω is the angular frequency. These results are discussed based on a correlated barrier hopping model. The calculated values of the maximum height of the barrier W_{{M}} for each composition are consistent with carrier hopping over a potential barrier. The density of localized states N( {E_{{F}} } ) at the Fermi level lay in the range from 1019 eV-1 cm-3 to 1020 eV-1 cm-3, and increased with temperature. The dielectric constant ɛ1 ( ω ) and loss ɛ2 ( ω ) increased with temperature but decreased with frequency. The values of σ_{{dc}} , σ_{{ac}} ( ω ) , ɛ1 ( ω ) , and ɛ2 ( ω ) increased with temperature and with addition of Ag, Cd or Pb. The observed increase was greater for Se0.7Ge0.25Pb0.05 than for Se0.7Ge0.25Cd0.05, which was greater than for Se0.7Ge0.25Ag0.05.

Volume and Mass Estimation of Three-Phase High Power Transformers for Space Applications

NASA Technical Reports Server (NTRS)

Kimnach, Greg L.

2004-01-01

Spacecraft historically have had sub-1kW(sub e), electrical requirements for GN&C, science, and communications: Galileo at 600W(sub e), and Cassini at 900W(sub e), for example. Because most missions have had the same order of magnitude power requirements, the Power Distribution Systems (PDS) use existing, space-qualified technology and are DC. As science payload and mission duration requirements increase, however, the required electrical power increases. Subsequently, this requires a change from a passive energy conversion (solar arrays and batteries) to dynamic (alternator, solar dynamic, etc.), because dynamic conversion has higher thermal and conversion efficiencies, has higher power densities, and scales more readily to higher power levels. Furthermore, increased power requirements and physical distribution lengths are best served with high-voltage, multi-phase AC to maintain distribution efficiency and minimize voltage drops. The generated AC-voltage must be stepped-up (or down) to interface with various subsystems or electrical hardware. Part of the trade-space design for AC distribution systems is volume and mass estimation of high-power transformers. The volume and mass are functions of the power rating, operating frequency, the ambient and allowable temperature rise, the types and amount of heat transfer available, the core material and shape, the required flux density in a core, the maximum current density, etc. McLyman has tabulated the performance of a number of transformers cores and derived a "cookbook" methodology to determine the volume of transformers, whereas Schawrze had derived an empirical method to estimate the mass of single-phase transformers. Based on the work of McLyman and Schwarze, it is the intent herein to derive an empirical solution to the volume and mass estimation of three-phase, laminated EI-core power transformers, having radiated and conducted heat transfer mechanisms available. Estimation of the mounting hardware, connectors, etc. is not included.

AC/DC current ratio in a current superimposition variable flux reluctance machine

NASA Astrophysics Data System (ADS)

Kohara, Akira; Hirata, Katsuhiro; Niguchi, Noboru; Takahara, Kazuaki

2018-05-01

We have proposed a current superimposition variable flux reluctance machine for traction motors. The torque-speed characteristics of this machine can be controlled by increasing or decreasing the DC current. In this paper, we discuss an AC/DC current ratio in the current superimposition variable flux reluctance machine. The structure and control method are described, and the characteristics are computed using FEA in several AC/DC ratios.

Preliminary design of a Primary Loop Pump Assembly (PLPA), using electromagnetic pumps

NASA Technical Reports Server (NTRS)

Moss, T. A.; Matlin, G.; Donelan, L.; Johnson, J. L.; Rowe, I.

1972-01-01

A preliminary design study of flight-type dc conduction-permanent magnetic, ac helical induction, and ac linear induction pumps for circulating 883 K (1130 F) NaK at 9.1 kg/sec (20 lb/sec) is described. Various electromagnetic pump geometrics are evaluated against hydraulic performance, and the effects of multiple windings and numbers of pumps per assembly on overall reliability were determined. The methods used in the electrical-hydraulic, stress, and thermal analysis are discussed, and the high temperature electrical materials selected for the application are listed.

Working Towards Net Zero Energy at Fort Irwin, CA

DTIC Science & Technology

2010-09-01

capacity factor for the solar photovoltaic analysis was based on simu- lations conducted by National Renewable Energy Laboratory (NREL) for Las Vegas, NV...kWhAC/kWhDC) x 8760 hrs = 5240 kWhAC/yr Savings for annual electricity savings are: 5240 kWh x 8.3 cents/kWh = $435/yr The capacity factor for the...43,668 kWh/yr Annual electricity savings are: 43,668 kWh x 8.3 cents/kWh = $3624/yr The capacity factor for the solar photovoltaic analysis was

Mathematical modeling and measurement of electric fields of electrode-based through-the-earth (TTE) communication

NASA Astrophysics Data System (ADS)

Yan, Lincan; Zhou, Chenming; Reyes, Miguel; Whisner, Bruce; Damiano, Nicholas

2017-06-01

There are two types of through-the-earth (TTE) wireless communication in the mining industry: magnetic loop TTE and electrode-based (or linear) TTE. While the magnetic loop systems send signal through magnetic fields, the transmitter of an electrode-based TTE system sends signal directly through the mine overburden by driving an extremely low frequency (ELF) or ultralow frequency (ULF) AC current into the earth. The receiver at the other end (underground or surface) detects the resultant current and receives it as a voltage. A wireless communication link between surface and underground is then established. For electrode-based TTE communications, the signal is transmitted through the established electric field and is received as a voltage detected at the receiver. It is important to understand the electric field distribution within the mine overburden for the purpose of designing and improving the performance of the electrode-based TTE systems. In this paper, a complete explicit solution for all three electric field components for the electrode-based TTE communication was developed. An experiment was conducted using a prototype electrode-based TTE system developed by National Institute for Occupational Safety and Health. The mathematical model was then compared and validated with test data. A reasonable agreement was found between them.

Mathematical modeling and measurement of electric fields of electrode-based through-the-earth (TTE) communication.

PubMed

Yan, Lincan; Zhou, Chenming; Reyes, Miguel; Whisner, Bruce; Damiano, Nicholas

2017-07-12

There are two types of through-the-earth (TTE) wireless communication in the mining industry: magnetic loop TTE and electrode-based (or linear) TTE. While the magnetic loop systems send signal through magnetic fields, the transmitter of an electrode-based TTE system sends signal directly through the mine overburden by driving an extremely low frequency (ELF) or ultralow frequency (ULF) AC current into the earth. The receiver at the other end (underground or surface) detects the resultant current and receives it as a voltage. A wireless communication link between surface and underground is then established. For electrode-based TTE communications, the signal is transmitted through the established electric field and is received as a voltage detected at the receiver. It is important to understand the electric field distribution within the mine overburden for the purpose of designing and improving the performance of the electrode-based TTE systems. In this paper, a complete explicit solution for all three electric field components for the electrode-based TTE communication was developed. An experiment was conducted using a prototype electrode-based TTE system developed by National Institute for Occupational Safety and Health. The mathematical model was then compared and validated with test data. A reasonable agreement was found between them.

Mathematical modeling and measurement of electric fields of electrode-based through-the-earth (TTE) communication

PubMed Central

Yan, Lincan; Zhou, Chenming; Reyes, Miguel; Whisner, Bruce; Damiano, Nicholas

2017-01-01

There are two types of through-the-earth (TTE) wireless communication in the mining industry: magnetic loop TTE and electrode-based (or linear) TTE. While the magnetic loop systems send signal through magnetic fields, the transmitter of an electrode-based TTE system sends signal directly through the mine overburden by driving an extremely low frequency (ELF) or ultralow frequency (ULF) AC current into the earth. The receiver at the other end (underground or surface) detects the resultant current and receives it as a voltage. A wireless communication link between surface and underground is then established. For electrode-based TTE communications, the signal is transmitted through the established electric field and is received as a voltage detected at the receiver. It is important to understand the electric field distribution within the mine overburden for the purpose of designing and improving the performance of the electrode-based TTE systems. In this paper, a complete explicit solution for all three electric field components for the electrode-based TTE communication was developed. An experiment was conducted using a prototype electrode-based TTE system developed by National Institute for Occupational Safety and Health. The mathematical model was then compared and validated with test data. A reasonable agreement was found between them. PMID:28845062

Physiological processes non-linearly affect electrophysiological recordings during transcranial electric stimulation.

PubMed

Noury, Nima; Hipp, Joerg F; Siegel, Markus

2016-10-15

Transcranial electric stimulation (tES) is a promising tool to non-invasively manipulate neuronal activity in the human brain. Several studies have shown behavioral effects of tES, but stimulation artifacts complicate the simultaneous investigation of neural activity with EEG or MEG. Here, we first show for EEG and MEG, that contrary to previous assumptions, artifacts do not simply reflect stimulation currents, but that heartbeat and respiration non-linearly modulate stimulation artifacts. These modulations occur irrespective of the stimulation frequency, i.e. during both transcranial alternating and direct current stimulations (tACS and tDCS). Second, we show that, although at first sight previously employed artifact rejection methods may seem to remove artifacts, data are still contaminated by non-linear stimulation artifacts. Because of their complex nature and dependence on the subjects' physiological state, these artifacts are prone to be mistaken as neural entrainment. In sum, our results uncover non-linear tES artifacts, show that current techniques fail to fully remove them, and pave the way for new artifact rejection methods. Copyright © 2016 Elsevier Inc. All rights reserved.

Unified Model of the rf Plasma Sheath, Part II

NASA Astrophysics Data System (ADS)

Riley, Merle

1996-10-01

By developing an approximation to the first integral of the Poisson equation, one can obtain solutions for the current-voltage characteristics of an rf plasma sheath that are valid over the whole range of inertial response of the ions to an imposed rf voltage or current. (M.E.Riley, 1995 GEC, abstract QA5, published in Bull. Am. Phys. Soc., 40, 1587 (1995).) The theory has been shown to adequately reproduce current-voltage characteristics of two extreme cases (M.A. Lieberman, IEEE Trans. Plasma Sci. 16, 638 (1988). A. Metze, D.W. Ernie, and H.J.Oskam, J.Appl.Phys., 60, 3081 (1986).) of ion response. In this work I show the effect of different conventions for connecting the sheath model to the bulk plasma. Modifications of the Mach number and a finite electric field at the Bohm point are natural choices. The differences are examined for a sheath in a high density Ar plasma and are found to be insignificant. A theoretical argument favors the electric field modification. *Work performed at Sandia National Labs and supported by US DoE under contract DE-AC04-94AL85000.

Dc and ac electrical response of MOCVD grown GaN in p-i-n structure, assessed through I-V and admittance measurement

NASA Astrophysics Data System (ADS)

Ayarcı Kuruoğlu, Neslihan; Özdemir, Orhan; Bozkurt, Kutsal; Sundaram, Suresh; Salvestrini, Jean-Paul; Ougazzaden, Abdallah; Gaimard, Quentin; Belahsene, Sofiane; Merghem, Kamel; Ramdane, Abderrahim

2017-12-01

The electrical response of gallium nitride (GaN), produced through metal-organic chemical vapor deposition in a p-i-n structure was investigated through temperature-dependent current-voltage (I-V) and admittance measurement. The I-V curves showed double diode behavior together with several distinct regions in which trap-assisted tunnelling current has been identified at low and moderate forward/reverse direction and space charge limited current (SCLC) at large forward/reverse bias. The value of extracted energy (˜200 meV in forward and  ˜70 meV in reverse direction) marked the tunnelling entity as electron and heavy hole in the present structure. These values were also obtained in space charge limited regime and considered as minority carriers which might originate the experimentally observed negative capacitance issue at low frequencies over the junction under both forward and reverse bias directions. Analytically derived expression for the admittance in the revised versions of SCLC model was also applied to explain the inductance effect, yielding good fits to the experimentally measured admittance data.

ac response of thin superconductors in the flux-creep regime

NASA Astrophysics Data System (ADS)

Gurevich, A.; Brandt, E. H.

1997-05-01

We calculate both analytically and numerically the ac susceptibility χ(ω) and the nonlinear electromagnetic response of thin superconductor strips and disks of constant thickness in a perpendicular time-dependent magnetic field Ba(t)=B0cos ωt, taking account of the strong nonlinearity of the voltage-current characteristics below the irreversibility line. We consider integral equations of nonlinear nonlocal flux diffusion for a wide class of thermally activated creep models. It is shown that thin superconductors, despite being fully in the critical state, exhibit a universal Meissner-like electromagnetic response in the dissipative flux-creep regime. The expression for the linear ac susceptibility during flux creep appears to be similar to the susceptibility of Ohmic conductors, but with the relaxation time constant replaced by the time t elapsed after flux creep has started. This result is independent of any material parameter or temperature or dc field. For ωt>>:1, we obtain χ(ω)~-1+pln (qiωt)/(iωt), where p and q are constants. Above a critical ac amplitude B0=Bl, the local response of the electric field becomes nonlinear, and there are two distinctive nonlinear regimes at B0>Bl, where Bl~s(d/a)1/2Bp, Bp is a characteristic field of full flux penetration, s(T,B)=\\|dln j/dln t\\| is the dimensionless flux-creep rate and d and a are the sample thickness and width, respectively. For BlBh(ω) the ac field causes hysteresis dissipation due to a periodic remagnetization of the critical state that gives rise to the hysteretic magnetic response of the Bean model at B0>>:Bh. Here Bh(ω) weakly depends on ω and is of order (d/a)1/2Bp for a very wide frequency range, well below the irreversibility field, where s(T,B)<<1. Magnetization and ac losses at B0>>:Bh are calculated accounting for the nonlinearity of E(J) at J

Spatial redistribution of nano-particles using electrokinetic micro-focuser

NASA Astrophysics Data System (ADS)

Garcia, Daniel E.; Silva, Aleidy; Ho, Chih-Ming

2007-09-01

Current microfabrication technologies rely on top-down, photolithographic techniques that are ultimately limited by the wavelength of light. While systems for nanofabrication do exist, they frequently suffer from high costs and slow processing times, creating a need for a new manufacturing paradigm. The combination of top-down and bottom-up fabrication approaches in device construction creates a new paradigm in micro- and nano-manufacturing. The pre-requisite for the realization of the manufacturing paradigm relies on the manipulation of molecules in a deterministic and controlled manner. The use of AC electrokinetic forces, such as dielectrophoresis (DEP) and AC electroosmosis, is a promising technology for manipulating nano-sized particle in a parallel fashion. A three-electrode micro-focusing system was designed to expoit this forces in order to control the spatial distribution of nano-particles in different frequency ranges. Thus far, we have demonstrated the ability to concentrate 40 nm and 300 nm diameter particles using a 50 μm diameter focusing system. AC electroosmotic motion of the nano-particles was observed while using low frequencies (in a range of 30 Hz - 1 KHz). By using different frequencies and changing the ground location, we have manipulated the nano-particles into circular band structures with different width, and focused the nanoparticles into circular spots with different diameters. Currently, we are in the progress of optimizing the operation parameters (e.g. frequency and AC voltages) by using the technique of particle image velocimetry (PIV). In the future, design of different electrode geometries and the numerical simulation of electric field distribution will be carried out to manipulate the nano-particles into a variety of geometries.