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1

Photoconductivity of high voltage space insulating materials: Measurements with metal electrodes  

NASA Technical Reports Server (NTRS)

The electrical conductivities of high voltage insulating materials were measured in the dark and under various intensities of illumination. The materials investigated included FEP Teflon, Kapton-H, fused quartz, and parylene. Conductivities were determined as functions of temperature between 22 and 100 C and light intensity between 0 and 2.5 kW/m2. The thickness dependence of the conductivity was determined for Teflon and Kapton, and the influence of spectral wavelengths on the conductivity was determined in several cases. All measurements were made in a vacuum to simulate a space environment, and all samples had metallic electrodes. The conductivity of Kapton was permanently increased by exposure to light; changes as great as five orders of magnitude were observed after six hours of illumination.

Coffey, H. T.; Nanevicz, J. E.

1975-01-01

2

Switched single-electrode voltage-clamp amplifiers allow precise measurement of gap junction conductance.  

PubMed

Measurement of gap junction conductance (gj) with patch-clamp amplifiers can, due to series resistance problems, be subject to considerable errors when large currents are measured. Formulas developed to correct for these errors unfortunately depend on exact estimates of series resistance, which are not always easy to obtain. Discontinuous single-electrode voltage-clamp amplifiers (DSEVCs) were shown to overcome series resistance problems in single whole cell recording. With the use of two synchronized DSEVCs, the simulated gj in a model circuit can be measured with a maximum error of <5% in all recording situations investigated (series resistance, 5-47 MOmega; membrane resistance, 20-1,000 MOmega; gj, 1-100 nS). At a very low gj of 100 pS, the error sometimes exceeded 5% (maximum of 15%), but the error was always <5% when membrane resistance was >100 MOmega. The precision of the measurements is independent of series resistance, membrane resistance, and gj. Consequently, it is possible to calculate gj directly from Ohm's law, i.e., without using correction formulas. Our results suggest that DSEVCs should be used to measure gj if large currents must be recorded, i.e., if cells are well coupled or if membrane resistance is low. PMID:10199830

Müller, A; Lauven, M; Berkels, R; Dhein, S; Polder, H R; Klaus, W

1999-04-01

3

Current-voltage characteristics of single-molecule diarylethene junctions measured with adjustable gold electrodes in solution.  

PubMed

We report on an experimental analysis of the charge transport through sulfur-free photochromic molecular junctions. The conductance of individual molecules contacted with gold electrodes and the current-voltage characteristics of these junctions are measured in a mechanically controlled break-junction system at room temperature and in liquid environment. We compare the transport properties of a series of molecules, labeled TSC, MN, and 4Py, with the same switching core but varying side-arms and end-groups designed for providing the mechanical and electrical contact to the gold electrodes. We perform a detailed analysis of the transport properties of TSC in its open and closed states. We find rather broad distributions of conductance values in both states. The analysis, based on the assumption that the current is carried by a single dominating molecular orbital, reveals distinct differences between both states. We discuss the appearance of diode-like behavior for the particular species 4Py that features end-groups, which preferentially couple to the metal electrode by physisorption. We show that the energetic position of the molecular orbital varies as a function of the transmission. Finally, we show for the species MN that the use of two cyano end-groups on each side considerably enhances the coupling strength compared to the typical behavior of a single cyano group. PMID:23365792

Briechle, Bernd M; Kim, Youngsang; Ehrenreich, Philipp; Erbe, Artur; Sysoiev, Dmytro; Huhn, Thomas; Groth, Ulrich; Scheer, Elke

2012-01-01

4

Determining resistivity of a formation adjacent to a borehole having casing by generating constant current flow in portion of casing and using at least two voltage measurement electrodes  

DOEpatents

Methods of operation of different types of multiple electrode apparatus vertically disposed in a cased well to measure information related to the resistivity of adjacent geological formations from within the cased well are described. The multiple electrode apparatus has a minimum of two spaced apart voltage measurement electrodes that electrically engage a first portion of the interior of the cased well and that provide at least first voltage information. Current control means are used to control the magnitude of any selected current that flows along a second portion of the interior of the casing to be equal to a predetermined selected constant. The first portion of the interior of the cased well is spaced apart from the second portion of the interior of the cased well. The first voltage information and the predetermined selected constant value of any selected current flowing along the casing are used in part to determine a magnitude related to the formation resistivity adjacent to the first portion of the interior of the cased well. Methods and apparatus having a plurality of voltage measurement electrodes are disclosed that provide voltage related information in the presence of constant currents flowing along the casing which is used to provide formation resistivity.

Vail, III, William Banning (Bothell, WA)

2000-01-01

5

Direct measurement of cyclic current-voltage responses of integral membrane proteins at a self-assembled lipid-bilayer-modified electrode: Cytochrome f and cytochrome c oxidase  

SciTech Connect

Direct cyclic voltage-current responses, produced in the absence of redox mediators, for two detergent-solubilized integral membrane proteins, spinach cytochrome f and beef heart cytochrome c oxidase, have been obtained at an optically transparent indium oxide electrode modified with a self-assembled lipid-bilayer membrane. The results indicate that both proteins interact with the lipid membrane so as to support quasi-reversible electron transfer redox reactions at the semiconductor electrode. The redox potentials that were obtained from analysis of the cyclic [open quotes]voltammograms,[close quotes] 365 mV for cytochrome f and 250 and 380 mV for cytochrome c oxidase (vs. normal hydrogen electrode), compare quite well with the values reported by using conventional titration methods. The ability to obtain direct electrochemical measurements opens up another approach to the investigation of the properties of integral membrane redox proteins. 63 refs., 2 figs., 1 tab.

Salamon, Z.; Hazzard, J.T.; Tollin, G. (Univ. of Arizona, Tucson (United States))

1993-07-15

6

Methods for testing high voltage connectors in vacuum, measurements of thermal stresses in encapsulated assemblies, and measurement of dielectric strength of electrodes in encapsulants versus radius of curvature  

NASA Technical Reports Server (NTRS)

Internal embedment stress measurements were performed, using tiny ferrite core transformers, whose voltage output was calibrated versus pressure by the manufacturer. Comparative internal strain measurements were made by attaching conventional strain gages to the same type of resistors and encapsulating these in various potting compounds. Both types of determinations were carried out while temperature cycling from 77 C to -50 C.

Bever, R. S.

1976-01-01

7

Arc voltage distribution skewness as an indicator of electrode gap during vacuum arc remelting  

DOEpatents

The electrode gap of a VAR is monitored by determining the skewness of a distribution of gap voltage measurements. A decrease in skewness indicates an increase in gap and may be used to control the gap. 4 figs.

Williamson, R.L.; Zanner, F.J.; Grose, S.M.

1998-01-13

8

Application of active electrode compensation to perform continuous voltage-clamp recordings with sharp microelectrodes  

NASA Astrophysics Data System (ADS)

Objective. Electrophysiological recordings of single neurons in brain tissues are very common in neuroscience. Glass microelectrodes filled with an electrolyte are used to impale the cell membrane in order to record the membrane potential or to inject current. Their high resistance induces a high voltage drop when passing current and it is essential to correct the voltage measurements. In particular, for voltage clamping, the traditional alternatives are two-electrode voltage-clamp technique or discontinuous single electrode voltage-clamp (dSEVC). Nevertheless, it is generally difficult to impale two electrodes in a same neuron and the switching frequency is limited to low frequencies in the case of dSEVC. We present a novel fully computer-implemented alternative to perform continuous voltage-clamp recordings with a single sharp-electrode. Approach. To reach such voltage-clamp recordings, we combine an active electrode compensation algorithm (AEC) with a digital controller (AECVC). Main results. We applied two types of control-systems: a linear controller (proportional plus integrative controller) and a model-based controller (optimal control). We compared the performance of the two methods to dSEVC using a dynamic model cell and experiments in brain slices. Significance. The AECVC method provides an entirely digital method to perform continuous recording and smooth switching between voltage-clamp, current clamp or dynamic-clamp configurations without introducing artifacts.

Gómez-González, J. F.; Destexhe, A.; Bal, T.

2014-10-01

9

The effect of electrode temperature on the sparking voltage of short spark gaps  

NASA Technical Reports Server (NTRS)

This report presents the results of an investigation to determine what effect the temperature of spark plug electrodes might have on the voltage at which a spark occurred. A spark gap was set up so that one electrode could be heated to temperatures up to 700 degrees C., while the other electrode and the air in the gap were maintained at room temperature. The sparking voltages were measured both with direct voltage and with voltage impulse from ignition coil. It was found that the sparking voltage of the gap decreased materially with increase of temperature. This change was more marked when the hot electrode was of negative polarity. The phenomena observed can be explained by the ionic theory of gaseous conduction, and serve to account for certain hitherto unexplained actions in the operation of internal combustion engines. These results indicate that the ignition spark will pass more readily when the spark-plug design is such as to make the electrodes run hot. This possible gain is, however, very closely limited by the danger of producing preignition. These experiments also show that sparking is somewhat easier when the hot electrode (which is almost always the central electrode) is negative than when the polarity is reversed.

Silsbee, F B

1924-01-01

10

High Voltage Cathode Temperature Measurement  

Microsoft Academic Search

The problem of making accurate measurement of temperature of a high voltage cathode in an emission microscope is discussed. Temperatures to 1300°C with voltages to 50 kV were measured within approximately ±5°C. Radiation sensing measurement schemes were dismissed, primarily on the basis of limited accuracy due to emissivity variations. In the developed system the entire temperature measurement and control system

R. L. Forgacs; B. A. Parafin; E. Eichen

1965-01-01

11

Cell voltage versus electrode potential range in aqueous supercapacitors.  

PubMed

Supercapacitors with aqueous electrolytes and nanostructured composite electrodes are attractive because of their high charging-discharging speed, long cycle life, low environmental impact and wide commercial affordability. However, the energy capacity of aqueous supercapacitors is limited by the electrochemical window of water. In this paper, a recently reported engineering strategy is further developed and demonstrated to correlate the maximum charging voltage of a supercapacitor with the capacitive potential ranges and the capacitance ratio of the two electrodes. Beyond the maximum charging voltage, a supercapacitor may still operate, but at the expense of a reduced cycle life. In addition, it is shown that the supercapacitor performance is strongly affected by the initial and zero charge potentials of the electrodes. Further, the differences are highlighted and elaborated between freshly prepared, aged under open circuit conditions, and cycled electrodes of composites of conducting polymers and carbon nanotubes. The first voltammetric charging-discharging cycle has an electrode conditioning effect to change the electrodes from their initial potentials to the potential of zero voltage, and reduce the irreversibility. PMID:25897670

Dai, Zengxin; Peng, Chuang; Chae, Jung Hoon; Ng, Kok Chiang; Chen, George Z

2015-01-01

12

Improving membrane voltage measurements  

E-print Network

as fluorescence resonance energy transfer (FRET) donor and acceptor to develop a voltage sensor, named Mermaid activities in cultured excitable cells. Notably, Mermaid has fast on-off kinetics at warm (B33 1C

Cai, Long

13

Electrodic voltages accompanying stimulated bioremediation of a uraniumcontaminated aquifer  

E-print Network

Click Here for Full Article Electrodic voltages accompanying stimulated bioremediation microbial activity during stimulated bioremediation has limited its implementation. We used spatiotemporal bioremediation of a uraniumcontaminated aquifer, J. Geophys. Res., 115, G00G05, doi:10.1029/2009JG001142. 1

Hubbard, Susan

14

Streamer initiation in mineral oil. Part I: electrode surface effect under impulse voltage  

Microsoft Academic Search

Presents a study of streamer inception in mineral transformer oil, in point-plane and rod-plane geometry under impulse voltage. The measurements performed with points and rods over a wide range of tip radii show a marked decrease of initiation fields when the electrode radius is increased. The initiation field is divided by 30 over the investigated range (from 1 ?m points

O. Lesaint; T. V. Top

2002-01-01

15

Field Emission Measurements from Niobium Electrodes  

SciTech Connect

Increasing the operating voltage of a DC high voltage photogun serves to minimize space charge induced emittance growth and thereby preserve electron beam brightness, however, field emission from the photogun cathode electrode can pose significant problems: constant low level field emission degrades vacuum via electron stimulated desorption which in turn reduces photocathode yield through chemical poisoning and/or ion bombardment and high levels of field emission can damage the ceramic insulator. Niobium electrodes (single crystal, large grain and fine grain) were characterized using a DC high voltage field emission test stand at maximum voltage -225kV and electric field gradient > 10MV/m. Niobium electrodes appear to be superior to diamond-paste polished stainless steel electrodes.

M. BastaniNejad, P.A. Adderley, J. Clark, S. Covert, J. Hansknecht, C. Hernandez-Garcia, R. Mammei, M. Poelker

2011-03-01

16

Electrodic voltages accompanying stimulated bioremediation of a uranium-contaminated aquifer  

SciTech Connect

The inability to track the products of subsurface microbial activity during stimulated bioremediation has limited its implementation. We used spatiotemporal changes in electrodic potentials (EP) to track the onset and persistence of stimulated sulfate-reducing bacteria in a uranium-contaminated aquifer undergoing acetate amendment. Following acetate injection, anomalous voltages approaching -900 mV were measured between copper electrodes within the aquifer sediments and a single reference electrode at the ground surface. Onset of EP anomalies correlated in time with both the accumulation of dissolved sulfide and the removal of uranium from groundwater. The anomalies persisted for 45 days after halting acetate injection. Current-voltage and current-power relationships between measurement and reference electrodes exhibited a galvanic response, with a maximum power density of 10 mW/m{sup 2} during sulfate reduction. We infer that the EP anomalies resulted from electrochemical differences between geochemically reduced regions and areas having higher oxidation potential. Following the period of sulfate reduction, EP values ranged from -500 to -600 mV and were associated with elevated concentrations of ferrous iron. Within 10 days of the voltage decrease, uranium concentrations rebounded from 0.2 to 0.8 {mu}M, a level still below the background value of 1.5 {mu}M. These findings demonstrate that EP measurements provide an inexpensive and minimally invasive means for monitoring the products of stimulated microbial activity within aquifer sediments and are capable of verifying maintenance of redox conditions favorable for the stability of bioreduced contaminants, such as uranium.

Williams, K.H.; N'Guessan, A.L.; Druhan, J.; Long, P.E.; Hubbard, S.S.; Lovley, D.R.; Banfield, J.F.

2009-11-15

17

Measurements of Plasma Potential Distribution in Segmented Electrode Hall Thruster  

SciTech Connect

Use of a segmented electrode placed at the Hall thruster exit can substantially reduce the voltage potential drop in the fringing magnetic field outside the thruster channel. In this paper, we investigate the dependence of this effect on thruster operating conditions and segmented electrode configuration. A fast movable emissive probe is used to measure plasma potential in a 1 kW laboratory Hall thruster with semented electrodes made of a graphite material. Relatively small probe-induced perturbations of the thruster discharge in the vicinity of the thruster exit allow a reasonable comparison of the measured results for different thruster configurations. It is shown that the plasma potential distribution is almost not sensitive to changes of the electrode potential, but depends on the magnetic field distribution and the electrode placement.

Y. Raitses; D. Staack; N.J. Fisch

2001-10-16

18

Electrode-less measurement of cell layers impedance.  

PubMed

This paper is devoted to yet unpublished electrode-less methods (ELM) of cell layers impedance measurement based on transformer principle. The main advantage of ELM is elimination uncertainties caused by interface between electrodes and measured electrolyte. The method of avoiding distortion caused by non-ideal transformer transfer function ("deconvolution") and errors caused by residual voltage is described. The modification of original transformer based method allowing to measure an impedance of inserted object is proposed. Results of several calibration measurements confirming the proper function of ELM including example of transepithelial resistance of cells layer are presented. Crucial parts of measuring system and recommendation for their realization are included. PMID:25157656

Kr?šek, J; ?a?o, S

2014-01-01

19

High voltage and high specific capacity dual intercalating electrode Li-ion batteries  

NASA Technical Reports Server (NTRS)

The present invention provides high capacity and high voltage Li-ion batteries that have a carbonaceous cathode and a nonaqueous electrolyte solution comprising LiF salt and an anion receptor that binds the fluoride ion. The batteries can comprise dual intercalating electrode Li ion batteries. Methods of the present invention use a cathode and electrode pair, wherein each of the electrodes reversibly intercalate ions provided by a LiF salt to make a high voltage and high specific capacity dual intercalating electrode Li-ion battery. The present methods and systems provide high-capacity batteries particularly useful in powering devices where minimizing battery mass is important.

West, William C. (Inventor); Blanco, Mario (Inventor)

2010-01-01

20

Voltage distribution over capacitively coupled plasma electrode for atmospheric-pressure plasma generation  

PubMed Central

When capacitively coupled plasma (CCP) is used to generate large-area plasma, the standing wave effect becomes significant, which results in the hindering of the uniform plasma process such as in a plasma etcher or plasma chemical vapor deposition. In this study, the transmission line modeling method is applied to calculate the voltage distribution over atmospheric-pressure CCP electrodes with the size of 1 m × 0.2 m. The measured plasma impedance in our previous study was used in the present calculation. The results of the calculations clearly showed the effects of excitation frequency and the impedance of the plasma on the form of the voltage distribution caused by the standing wave effect. In the case of 150 MHz frequency, the standing wave effect causes a drastic change in the voltage distribution via plasma ignition; however, the change is small for 13.56 MHz. It was also clarified that the power application position is important for obtaining a uniform voltage distribution. PMID:23634893

2013-01-01

21

PEDOT-CNT coated electrodes stimulate retinal neurons at low voltage amplitudes and low charge densities.  

PubMed

Objective. The aim of this study was to compare two different microelectrode materials-the conductive polymer composite poly-3,4-ethylenedioxythiophene (PEDOT)-carbon nanotube(CNT) and titanium nitride (TiN)-at activating spikes in retinal ganglion cells in whole mount rat retina through stimulation of the local retinal network. Stimulation efficacy of the microelectrodes was analyzed by comparing voltage, current and transferred charge at stimulation threshold. Approach. Retinal ganglion cell spikes were recorded by a central electrode (30 ?m diameter) in the planar grid of an electrode array. Extracellular stimulation (monophasic, cathodic, 0.1-1.0 ms) of the retinal network was performed using constant voltage pulses applied to the eight surrounding electrodes. The stimulation electrodes were equally spaced on the four sides of a square (400 × 400 ?m). Threshold voltage was determined as the pulse amplitude required to evoke network-mediated ganglion cell spiking in a defined post stimulus time window in 50% of identical stimulus repetitions. For the two electrode materials threshold voltage, transferred charge at threshold, maximum current and the residual current at the end of the pulse were compared. Main results. Stimulation of retinal interneurons using PEDOT-CNT electrodes is achieved with lower stimulation voltage and requires lower charge transfer as compared to TiN. The key parameter for effective stimulation is a constant current over at least 0.5 ms, which is obtained by PEDOT-CNT electrodes at lower stimulation voltage due to its faradaic charge transfer mechanism. Significance. In neuroprosthetic implants, PEDOT-CNT may allow for smaller electrodes, effective stimulation in a safe voltage regime and lower energy-consumption. Our study also indicates, that the charge transferred at threshold or the charge injection capacity per se does not determine stimulation efficacy. PMID:25588201

Samba, R; Herrmann, T; Zeck, G

2015-02-01

22

PEDOT–CNT coated electrodes stimulate retinal neurons at low voltage amplitudes and low charge densities  

NASA Astrophysics Data System (ADS)

Objective. The aim of this study was to compare two different microelectrode materials—the conductive polymer composite poly-3,4-ethylenedioxythiophene (PEDOT)–carbon nanotube(CNT) and titanium nitride (TiN)—at activating spikes in retinal ganglion cells in whole mount rat retina through stimulation of the local retinal network. Stimulation efficacy of the microelectrodes was analyzed by comparing voltage, current and transferred charge at stimulation threshold. Approach. Retinal ganglion cell spikes were recorded by a central electrode (30 ?m diameter) in the planar grid of an electrode array. Extracellular stimulation (monophasic, cathodic, 0.1–1.0 ms) of the retinal network was performed using constant voltage pulses applied to the eight surrounding electrodes. The stimulation electrodes were equally spaced on the four sides of a square (400 × 400 ?m). Threshold voltage was determined as the pulse amplitude required to evoke network-mediated ganglion cell spiking in a defined post stimulus time window in 50% of identical stimulus repetitions. For the two electrode materials threshold voltage, transferred charge at threshold, maximum current and the residual current at the end of the pulse were compared. Main results. Stimulation of retinal interneurons using PEDOT–CNT electrodes is achieved with lower stimulation voltage and requires lower charge transfer as compared to TiN. The key parameter for effective stimulation is a constant current over at least 0.5 ms, which is obtained by PEDOT–CNT electrodes at lower stimulation voltage due to its faradaic charge transfer mechanism. Significance. In neuroprosthetic implants, PEDOT–CNT may allow for smaller electrodes, effective stimulation in a safe voltage regime and lower energy-consumption. Our study also indicates, that the charge transferred at threshold or the charge injection capacity per se does not determine stimulation efficacy.

Samba, R.; Herrmann, T.; Zeck, G.

2015-02-01

23

Senderovich 1 Electrode Design Adjustments to a High Voltage Electron Gun  

E-print Network

Senderovich 1 Electrode Design Adjustments to a High Voltage Electron Gun Igor Senderovich Abstract, a very high voltage electron gun needs to be designed.1 To these ends, several geometric parameters were analyzed computationally in order to isolate a feasible design. Attempting to provide a practical lifetime

Hoffstaetter, Georg

24

Thermoelectric corrections to quantum voltage measurement  

NASA Astrophysics Data System (ADS)

A generalization of Büttiker's voltage probe concept for nonzero temperatures is an open third terminal of a quantum thermoelectric circuit. An explicit analytic expression for the thermoelectric correction to an ideal quantum voltage measurement in linear response is derived and interpreted in terms of local Peltier cooling/heating within the nonequilibrium system. The thermoelectric correction is found to be large (up to ±24 % of the peak voltage) in a prototypical ballistic quantum conductor (graphene nanoribbon). The effects of measurement nonideality are also investigated. Our findings have important implications for precision local electrical measurements.

Bergfield, Justin P.; Stafford, Charles A.

2014-12-01

25

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

DOEpatents

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.

Vail, III, William Banning (Bothell, WA); Momii, Steven Thomas (Seattle, WA)

2001-01-01

26

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

DOEpatents

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.

Vail III, William Banning; Momii, Steven Thomas

2003-06-10

27

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

DOEpatents

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.

Vail, III, William Banning (Bothell, WA); Momii, Steven Thomas (Seattle, WA)

2000-01-01

28

Current-voltage characteristics of organic semiconductors: Interfacial control between organic layers and electrodes  

NASA Astrophysics Data System (ADS)

Current-voltage (I-V) characteristics of organic molecular glasses and solution processable materials embedded between two electrodes were studied to find materials possessing high charge-carrier mobilities and to design organic memory devices. The comparison studies between TOF, FET and SCLC measurements confirm the validity of using analyses of I-V characteristics to determine the mobility of organic semiconductors. Hexaazatrinaphthylene derivatives tri-substituted by electron withdrawing groups were characterized as potential electron transporting molecular glasses. The presence of two isomers has important implications for film morphology and effective mobility. The statistical isomer mixture of hexaazatrinaphthylene derivatized with pentafluoro-phenylmethyl ester is able to form amorphous films, and electron mobilities with the range of 10--2 cm2/Vs are observed in their I-V characteristics. Single-layer organic memory devices consisting of a polymer layer embedded between an Al electrode and ITO modified with Ag nanodots (Ag-NDs) prepared by a solution-based surface assembly demonstrated a potential capability as nonvolatile organic memory device with high ON/OFF switching ratios of 10 4. This level of performance could be achieved by modifying the ITO electrodes with some Ag-NDs that act as trapping sites, reducing the current in the OFF state. Based upon the observed electrical characteristics, the currents of the low-resistance state can be attributed to a tunneling through low-resistance pathways of metal particles originating from the metal top electrode in the organic layer and that the high-resistance state is controlled by charge trapping by the metal particles including Ag-NDs. In an alternative approach, complex films of AgNO3: hexaazatrinaphthylene derivatives were studied as the active layers for all-solution processed and air-stable organic memory devices. Rewritable memory effects were observed in the devices comprised of a thin polymer dielectric layer deposited on the bottom electrode, the complex film, and a conducting polymer film as the top electrode. The electrical characteristics indicate that the accumulation of Ag+ ions at the interface of the complex film and the top electrode may contribute to the switching effect.

Kondo, Takeshi

2007-12-01

29

Improving the performance of stainless-steel DC high voltage photoelectron gun cathode electrodes via gas conditioning with helium or krypton  

SciTech Connect

Gas conditioning was shown to eliminate field emission from cathode electrodes used inside DC high voltage photoelectron guns, thus providing a reliable means to operate photoguns at higher voltages and field strengths. Measurements and simulation results indicate that gas conditioning eliminates field emission from cathode electrodes via two mechanisms: sputtering and implantation, with the benefits of implantation reversed by heating the electrode. We have studied five stainless steel electrodes (304L and 316LN) that were polished to approximately 20 nm surface roughness using diamond grit, and evaluated inside a high voltage apparatus to determine the onset of field emission as a function of voltage and field strength. The field emission characteristics of each electrode varied significantly upon the initial application of voltage but improved to nearly the same level after gas conditioning using either helium or krypton, exhibiting less than 10 pA field emission at ?225 kV bias voltage with a 50 mm cathode/anode gap, corresponding to a field strength of ~13 MV/m. Field emission could be reduced with either gas, but there were conditions related to gas choice, voltage and field strength that were more favorable than others.

Bastaninejad, Mahzad [ODU; Elmustafa, Abdelmageed [ODU; Forman, Eric I. [JLAB; Clark, James [JLAB; Covert, Steven R. [JLAB; Grames, Joseph M. [JLAB; Hansknecht, John C. [JLAB; Hernandez-Garcia, Carlos [JLAB; Poelker, Bernard [JLAB; Suleiman, Riad S. [JLAB

2014-10-01

30

Josephson device for voltage measurement  

NASA Astrophysics Data System (ADS)

This paper describes a new Josephson device with microwave integrated circuit for voltage standard. The circuit is essentially made of a resonator (Nb), the Josephson junction (Nb, NbOx, Pb-In) and a capacitive microstrip section (Pb-In) which ends the rf part; the dc connections are through Cauer Filters (Nb or Pb-In). A niobium film is deposited on the opposite side of the fused quartz substrate as a ground plane. The circuit is enclosed in a special package with outside dc and rf connections. The technology ensures very good cyclability and lifetime with storage at room temperature. In liquid helium (4.2 K) with a very weak rf power less than 0.5 milliwatts at the frequency resonance (11.5 GHz), 100 ? A high current steps were obtained near a polarization of 4.5 mV. These devices allows a precision of 1 × 10 -7 on the volt standard when used with a series-parallel divider of fixed value (ratio 225). The precise adjustment of the voltages is made by a slight drift of the rf frequency of the source, allowed by the high rf coupling factor of the device and the band width of its resonance.

Régent, A.; Villegier, J. C.; Angénieux, G.; Monllor, C.; Delahaye, F.

31

Sheath expansion of two-dimensional grid electrodes subjected to short pulses of negative high-voltage  

NASA Astrophysics Data System (ADS)

Sheath expansion was investigated for two-dimensional (2D) grid electrodes which consist of a periodic array of cylindrical electrodes when short pulses of negative high-voltage were applied to the electrodes immersed in plasmas. In the sheath expansion model, a geometric function which describes the electrode system is crucial to numerically calculate the temporal evolution of a sheath boundary. In this paper, the 2D geometric function of grid electrodes was obtained by using XOOPIC (particle-in-cell) simulation. When the ratio between the diameter of cylindrical electrodes and grid spacing is fixed, we found that the geometric functions and the temporal evolutions of the sheath boundary for grid electrodes are identical in normalized coordinates. The numerical calculation results of the temporal evolutions of the sheath boundary showed reasonable agreements with the experimental measurements carried out in argon plasmas produced by hot filament discharges with neutral gas pressure of ˜0.4 mTorr and plasma density in the order of 1010 cm?3 in a multi-dipole device.

Yi, Changho; Lee, Huijea; Park, Byungjae; Namkung, Won; Cho, Moohyun

2015-02-01

32

Characterization of voltage losses during high-intensity current pulses in reactive, porous electrodes of molten salt cells  

SciTech Connect

A technique for the rapid characterization of the power-related properties of porous electrodes of molten salt cells has been developed. In this method, the electrode properties were investigated under one-dimensional current-distribution conditions in small test cells of 0.3 to 1.5 Ah capacity. The electrode potential was measured against a Ni/Ni/sub 3/S/sub 2/ or Li-Al reference electrode located so that the IR-voltage drop was eliminated. At different states of charge, galvanostatic discharge or charge current pulses of different intensity and duration were applied to the electrode by high-precision power sources. The state of charge for the electrode was determined from the quantity of the coulombs passed in galvanostatic cycling and is indicated in this paper by the numeric value of x in the generic formula of the active material (e.g., x in FeS/sub x/). Electrode materials iron sulfide, nickel sulfide, Li-Al and Li-Si alloys in LiCl-KCl and LiF-LiCl-LiBr molten salt electrolytes were investigated.

Redey, L.

1984-01-01

33

Rapidly prototyped multi-scale electrodes to minimize the voltage requirements for bacterial cell lysis.  

PubMed

Lab-on-a-chip systems used for nucleic acid based detection of bacteria rely on bacterial lysis for the release of cellular material. Although electrical lysis devices can be miniaturized for on-chip integration and reagent-free lysis, they often suffer from high voltage requirements, and rely on the use of off-chip voltage supplies. To overcome this barrier, we developed a rapid prototyping method for creating multi-scale electrodes that are structurally tuned for lowering the voltage needed for electrical bacterial lysis. These three-dimensional multi-scale electrodes - with micron scale reaction areas and nanoscale features - are fabricated using benchtop methods including craft cutting, polymer-induced wrinkling, and electrodeposition, which enable a lysis device to be designed, fabricated, and optimized in a matter of hours. These tunable electrodes show superior behaviour compared to lithographically-prepared electrodes in terms of lysis efficiency and voltage requirement. Successful extraction of nucleic acids from bacterial samples processed by these electrodes demonstrates the potential for these rapidly prototyped devices to be integrated within practical lab-on-a-chip systems. PMID:25597363

Gabardo, Christine M; Kwong, Aaron M; Soleymani, Leyla

2015-03-01

34

High-Voltage Measurements and Isolation  

NSDL National Science Digital Library

This tutorial is part of the National Instruments Measurement Fundamentals series. Each tutorial in this series teaches you a specific topic of common measurement applications by explaining theoretical concepts and providing practical examples. There are many issues to consider when measuring high voltage. When specifying a data acquisition (DAQ) system, the first question one should ask is whether the system will be safe. Making high-voltage measurements can be hazardous to the equipment, to the unit under test, and to you and your colleagues. This tutorial covers the concept of isolation, as well as discussing National Instruments' isolated products. A PDF of the material is available for download as well.

35

Transition voltages of vacuum-spaced and molecular junctions with Ag and Pt electrodes  

NASA Astrophysics Data System (ADS)

The transition voltage of vacuum-spaced and molecular junctions constructed with Ag and Pt electrodes is investigated by non-equilibrium Green's function formalism combined with density functional theory. Our calculations show that, similarly to the case of Au-vacuum-Au previously studied, the transition voltages of Ag and Pt metal-vacuum-metal junctions with atomic protrusions on the electrode surface are determined by the local density of states of the p-type atomic orbitals of the protrusion. Since the energy position of the Pt 6p atomic orbitals is higher than that of the 5p/6p of Ag and Au, the transition voltage of Pt-vacuum-Pt junctions is larger than that of both Ag-vacuum-Ag and Au-vacuum-Au junctions. When one moves to analyzing asymmetric molecular junctions constructed with biphenyl thiol as central molecule, then the transition voltage is found to depend on the specific bonding site for the sulfur atom in the thiol group. In particular agreement with experiments, where the largest transition voltage is found for Ag and the smallest for Pt, is obtained when one assumes S binding at the hollow-bridge site on the Ag/Au(111) surface and at the adatom site on the Pt(111) one. This demonstrates the critical role played by the linker-electrode binding geometry in determining the transition voltage of devices made of conjugated thiol molecules.

Wu, Kunlin; Bai, Meilin; Sanvito, Stefano; Hou, Shimin

2014-07-01

36

Transition voltages of vacuum-spaced and molecular junctions with Ag and Pt electrodes  

SciTech Connect

The transition voltage of vacuum-spaced and molecular junctions constructed with Ag and Pt electrodes is investigated by non-equilibrium Green's function formalism combined with density functional theory. Our calculations show that, similarly to the case of Au-vacuum-Au previously studied, the transition voltages of Ag and Pt metal-vacuum-metal junctions with atomic protrusions on the electrode surface are determined by the local density of states of the p-type atomic orbitals of the protrusion. Since the energy position of the Pt 6p atomic orbitals is higher than that of the 5p/6p of Ag and Au, the transition voltage of Pt-vacuum-Pt junctions is larger than that of both Ag-vacuum-Ag and Au-vacuum-Au junctions. When one moves to analyzing asymmetric molecular junctions constructed with biphenyl thiol as central molecule, then the transition voltage is found to depend on the specific bonding site for the sulfur atom in the thiol group. In particular agreement with experiments, where the largest transition voltage is found for Ag and the smallest for Pt, is obtained when one assumes S binding at the hollow-bridge site on the Ag/Au(111) surface and at the adatom site on the Pt(111) one. This demonstrates the critical role played by the linker-electrode binding geometry in determining the transition voltage of devices made of conjugated thiol molecules.

Wu, Kunlin; Bai, Meilin; Hou, Shimin, E-mail: smhou@pku.edu.cn [Key Laboratory for the Physics and Chemistry of Nanodevices, Department of Electronics, Peking University, Beijing 100871 (China); Sanvito, Stefano [School of Physics, AMBER and CRANN Institute, Trinity College, Dublin 2 (Ireland)

2014-07-07

37

Fiber-optic voltage measuring system  

NASA Astrophysics Data System (ADS)

A new fibre optic voltage measuring system has been developed based on the electrooptic effect of bismuth germanium oxide (Bi4Ge3O12)crystal. It uses the LED as the light source. The light beam emitted from the light source is transmitted to the sensor through the optic fibre and the intensity of the output beam is changed by the applied voltage. This optic signal is transmitted to the PIN detector and converted to an electric signal which is processed by the electronic circuit and 8098 single chip microcomputer the output voltage signal obtained is directly proportional to the applied voltage. This paper describes the principle the configuration and the performance parameters of the system. Test results are evaluated and discussed.

Ye, Miaoyuan; Nie, De-Xin; Li, Yan; Peng, Yu; Lin, Qi-Qing; Wang, Jing-Gang

1993-09-01

38

Flexible viologen electrochromic devices with low operational voltages using reduced graphene oxide electrodes.  

PubMed

Reduced graphene oxide (RGO) films have been electrodeposited on indium tin oxide-coated polyethylene terephthalate (ITO-PET) substrates from graphene oxide (GO) solutions, and the resulting flexible transparent electrodes have been used in electrochromic devices of ethyl viologen (EtV(2+)). The electrochromic performance of devices with bare ITO-PET electrodes and ITO-PET coated with RGO has been compared. Under continuous cycling tests up to large voltages, the RGO film was oxidized and dispersed in the electrochromic mixture. The resulting devices, which contained GO and RGO in the electrochromic mixture, showed lower switching voltages between the colored and bleached states. This electrocatalytic activity of the solution-phase GO/RGO pair toward the electrochemical reaction of the electrochromic redox couple (the dication EtV(2+) and the radical cation EtV(+•)) allowed devices with an optical contrast higher than the contrast of those free of GO at the same applied voltage. PMID:25090050

Palenzuela, Jesús; Viñuales, Ana; Odriozola, Ibon; Cabañero, Germán; Grande, Hans J; Ruiz, Virginia

2014-08-27

39

Using fast moving electrode to achieve overvoltage breakdown of gas switch stressed with high direct voltages  

NASA Astrophysics Data System (ADS)

A small-scale fast risetime gas switch attached to a 50 ? pulse forming line is tested. It includes a fast moving electrode and a fixed electrode. For the applied direct voltages, such as 2.8 kV, 2.0 kV, and 1.0 kV, the risetimes of this switch are tested to be ˜3.8 ns, ˜2.3 ns, and ˜1.1 ns, respectively, while the risetimes of a switch with two fixed electrodes are about ˜10.1 ns, ˜9.0 ns, and ˜3.6 ns. The results of high-speed photography and laser interferometry reveal that the moving electrode will obviously shorten discharge spark length but almost will not change the inter-electrodes gas pressure. The reason of shortening spark length is the existence of the discharge time delay of gas switch. After moving to the static breakdown spacing, the fast moving electrode will move on for an additional distance within the discharge time delay, which makes gas switch achieve overvoltage breakdown under high direct voltages and therefore leads to shorter spark length and faster switch risetime.

Zou, X. B.; Shi, H. T.; Xie, H.; Wang, Xinxin; Zhang, Guixin

2015-03-01

40

Engineering the metal gate electrode for controlling the threshold voltage of organic transistors  

NASA Astrophysics Data System (ADS)

For practical applications of organic field-effect transistors (OFETs), the control of threshold voltage (VTH) is important as different circuits require different electrical characteristics. Here, we demonstrate two types of gate electrode structures to achieve this control, namely, via dual-metal gates and bilayer metal gates. The first approach uses different metallic materials, titanium, and platinum, while the second approach uses different thicknesses in a metal bilayer composed of aluminum and platinum. Our results show that the VTH is varied by more than 20% of the supply voltage without affecting the field-effect mobility values for both pentacene p-channel and C60 n-channel OFETs.

Chung, Yoonyoung; Johnson, Olasupo; Deal, Michael; Nishi, Yoshio; Murmann, Boris; Bao, Zhenan

2012-08-01

41

Voltage assisted magnetic switching in Co50Fe50 interdigitated electrodes on piezoelectric substrates  

NASA Astrophysics Data System (ADS)

We report on the properties of 10 nm thick Co50Fe50 interdigitated electrodes deposited on lead zirconate titanate (PZT) substrates to achieve low power dynamic tuning of magnetic properties. The actuation of this combination relies on magnetoelectric coupling through the shear mode deformation of the PZT: numerical simulations confirmed that both uniaxial tensile and compressive strain can be achieved either by applying a bias voltage on the appropriate set of electrodes or by reversing the polarity of the bias voltage. Reversible electric field induced changes in the coercive field of more than 10% and a 0.08% change in the resistance were obtained for an applied electrical field of 5 kV/cm.

Boukari, H.; Cavaco, C.; Eyckmans, W.; Lagae, L.; Borghs, G.

2007-03-01

42

Low voltage charge-balanced capacitance-voltage conversion circuit for one-side-electrode-type fluid-based inclination sensor  

Microsoft Academic Search

Low voltage detection circuit for capacitance sensor is important to connect low voltage digital circuit interface. We demonstrated two configuration types of charge-balanced capacitance-voltage (C-V) conversion circuit by using operational-amplifier (op-amp) and inverter-amplifier (inv-amp). These circuits were packaged with one-side-electrode-type fluid- based inclination sensor on ceramic substrate. Performances of these circuits were evaluated. This inclination sensor system could be combined

A. Bin Abd Manaf; Y. Matsumoto

2007-01-01

43

Influence of electrode mismatch on Cole parameter estimation from total right side electrical bioimpedance spectroscopy measurements.  

PubMed

Applications based on measurements of Electrical Bioimpedance (EBI) spectroscopy analysis, like assessment of body composition, have proliferated in the past years. Currently Body Composition Assessment (BCA) based in Bioimpedance Spectroscopy (BIS) analysis relays on an accurate estimation of the Cole parameters R(0) and R(?). A recent study by Bogonez-Franco et al. has proposed electrode mismatch as source of remarkable artefacts in BIS measurements. Using Total Right Side BIS measurements from the aforementioned study, this work has focused on the influence of electrode mismatch on the estimation of R(0) and R(?) using the Non-Linear Least Square curve fitting technique on the modulus of the impedance. The results show that electrode mismatch on the voltage sensing electrodes produces an overestimation of the impedance spectrum leading to a wrong estimation of the parameters R(0) and R(?), and consequently obtaining values around 4% larger that the values obtained from BIS without electrode mismatch. The specific key factors behind electrode mismatch or its influence on the analysis of single and spectroscopy measurements have not been investigated yet, no compensation or correction technique is available to overcome the deviation produced on the EBI measurement. Since textile-enabled EBI applications using dry textrodes, i.e. textile electrodes with dry skin-electrode interfaces and potentially large values of electrode polarization impedance are more prone to produce electrode mismatch, the lack of a correction or compensation technique might hinder the proliferation of textile-enabled EBI applications for personalized healthcare monitoring. PMID:22738873

Buendía, Rubén; Bogónez-Franco, Paco; Nescolarde, Lexa; Seoane, Fernando

2012-09-01

44

dc step response of induced-charge electro-osmosis between parallel electrodes at large voltages  

NASA Astrophysics Data System (ADS)

Induced-charge electro-osmosis (ICEO) is important since it can be used for realizing high performance microfluidic devices. Here, we analyze the simplest problem of ion relaxation around a circular polarizable cylinder between parallel blocking electrodes in a closed cell by using a multiphysics coupled simulation technique. This technique is based on a combination of the finite-element method and finite-volume method for the Poisson-Nernst-Planck (PNP) equations having a flow term and the Stokes equation having an electric stress term. Through this analysis, we successfully demonstrate that on application of dc voltages, quadorapolar ICEO vortex flows grow during the charging time of the cylinder for both unbounded and bounded problems and decay during the charging time of the parallel electrodes only for the bounded problem using blocking electrodes. Further, by proposing a simple model that considers the two-dimensional (2D) PNP equations analytically, we successfully explain the step response time of the ICEO flow for the both unbounded and bounded problems. Furthermore, at low applied voltages, we find analytical formulations on steady diffused-ion problems and steady ICEO-flow problems and examine that our numerical results agree well with the analytical results. Moreover, by considering an ion-conserving condition with 2D Poisson-Boltzmann equations, we explain significant decrease of the maximum slip velocity at large applied voltages fairly well. We believe that our analysis will contribute greatly to the realistic designs of prospective high-performance microfluidic devices.

Sugioka, Hideyuki

2014-07-01

45

dc Step response of induced-charge electro-osmosis between parallel electrodes at large voltages.  

PubMed

Induced-charge electro-osmosis (ICEO) is important since it can be used for realizing high performance microfluidic devices. Here, we analyze the simplest problem of ion relaxation around a circular polarizable cylinder between parallel blocking electrodes in a closed cell by using a multiphysics coupled simulation technique. This technique is based on a combination of the finite-element method and finite-volume method for the Poisson-Nernst-Planck (PNP) equations having a flow term and the Stokes equation having an electric stress term. Through this analysis, we successfully demonstrate that on application of dc voltages, quadorapolar ICEO vortex flows grow during the charging time of the cylinder for both unbounded and bounded problems and decay during the charging time of the parallel electrodes only for the bounded problem using blocking electrodes. Further, by proposing a simple model that considers the two-dimensional (2D) PNP equations analytically, we successfully explain the step response time of the ICEO flow for the both unbounded and bounded problems. Furthermore, at low applied voltages, we find analytical formulations on steady diffused-ion problems and steady ICEO-flow problems and examine that our numerical results agree well with the analytical results. Moreover, by considering an ion-conserving condition with 2D Poisson-Boltzmann equations, we explain significant decrease of the maximum slip velocity at large applied voltages fairly well. We believe that our analysis will contribute greatly to the realistic designs of prospective high-performance microfluidic devices. PMID:25122369

Sugioka, Hideyuki

2014-07-01

46

Origin of voltage decay in high-capacity layered oxide electrodes  

NASA Astrophysics Data System (ADS)

Although Li-rich layered oxides (Li1+xNiyCozMn1?x?y?zO2 > 250 mAh g?1) are attractive electrode materials providing energy densities more than 15% higher than today’s commercial Li-ion cells, they suffer from voltage decay on cycling. To elucidate the origin of this phenomenon, we employ chemical substitution in structurally related Li2RuO3 compounds. Li-rich layered Li2Ru1?yTiyO3 phases with capacities of ~240 mAh g?1 exhibit the characteristic voltage decay on cycling. A combination of transmission electron microscopy and X-ray photoelectron spectroscopy studies reveals that the migration of cations between metal layers and Li layers is an intrinsic feature of the charge–discharge process that increases the trapping of metal ions in interstitial tetrahedral sites. A correlation between these trapped ions and the voltage decay is established by expanding the study to both Li2Ru1?ySnyO3 and Li2RuO3; the slowest decay occurs for the cations with the largest ionic radii. This effect is robust, and the finding provides insights into new chemistry to be explored for developing high-capacity layered electrodes that evade voltage decay.

Sathiya, M.; Abakumov, A. M.; Foix, D.; Rousse, G.; Ramesha, K.; Saubanère, M.; Doublet, M. L.; Vezin, H.; Laisa, C. P.; Prakash, A. S.; Gonbeau, D.; Vantendeloo, G.; Tarascon, J.-M.

2015-02-01

47

Origin of voltage decay in high-capacity layered oxide electrodes.  

PubMed

Although Li-rich layered oxides (Li1+xNiyCozMn1-x-y-zO2 > 250 mAh g(-1)) are attractive electrode materials providing energy densities more than 15% higher than today's commercial Li-ion cells, they suffer from voltage decay on cycling. To elucidate the origin of this phenomenon, we employ chemical substitution in structurally related Li2RuO3 compounds. Li-rich layered Li2Ru1-yTiyO3 phases with capacities of ~240 mAh g(-1) exhibit the characteristic voltage decay on cycling. A combination of transmission electron microscopy and X-ray photoelectron spectroscopy studies reveals that the migration of cations between metal layers and Li layers is an intrinsic feature of the charge-discharge process that increases the trapping of metal ions in interstitial tetrahedral sites. A correlation between these trapped ions and the voltage decay is established by expanding the study to both Li2Ru1-ySnyO3 and Li2RuO3; the slowest decay occurs for the cations with the largest ionic radii. This effect is robust, and the finding provides insights into new chemistry to be explored for developing high-capacity layered electrodes that evade voltage decay. PMID:25437258

Sathiya, M; Abakumov, A M; Foix, D; Rousse, G; Ramesha, K; Saubanère, M; Doublet, M L; Vezin, H; Laisa, C P; Prakash, A S; Gonbeau, D; VanTendeloo, G; Tarascon, J-M

2015-02-01

48

New methods for measuring mechanical properties of thin films in micromachining: Beam pull-in voltage ( V PI) method and long beam deflection (LBD) method  

Microsoft Academic Search

New stress-measurement methods for determining both tensile and compressive stress and Young's modulus in surface micromachining are presented. The investigation is concentrated on the development of two techniques: (1) beam pull-in voltage (VPI) and (2) long beam deflection (LBD). The VPI method is based on the pulling down of the upper electrode (beam) when the voltage between two electrodes exceeds

Quanbo Zou; Zhijian Li; Litian Liu

1995-01-01

49

Electrochemical dealloying using pulsed voltage waveforms and its application for supercapacitor electrodes  

NASA Astrophysics Data System (ADS)

Dealloying is an important industrial technique for generating nanoporous metallic structures by selectively leaching out the more reactive metal component from an alloy material. A constant voltage is often applied to facilitate the dealloying process. Here we report the first study on dealloying with the application of a voltage waveform-specifically, pulsed voltage waveforms are applied for dealloying Ni-Cu alloys. It is found that pulsed dealloying voltage waveforms can exert a strong impact on the dealloying process by 1) significantly lowering the compositional threshold of the more reactive metal component for the dealloying reaction to take place, 2) more thoroughly removing the more reactive metal component and thus producing a porous metal of higher purity and higher porosity (volume fraction of voids), and 3) greatly affecting the morphology of the generated porous metal structure (e.g., leading to significantly thinner ligaments). The nanoporous metallic materials obtained by the pulsed voltage waveform enable supercapacitor electrodes of significantly better performance than the counterpart dealloyed with a constant voltage.

Zhang, Jie; Zhan, Yawen; Bian, Haidong; Li, Zhe; Tsang, Chun-Kwan; Lee, Chris; Cheng, Hua; Shu, Shiwei; Li, Yang Yang; Lu, Jian

2014-07-01

50

A Selective Voltage Measurement System for Series Connected Battery Packs  

Microsoft Academic Search

A method has been developed to measure the voltages of individual batteries used in hybrid electric vehicle (HEV) battery packs using a new selective battery measurement system. This system consists of a voltage measurement circuit that measures battery voltages using a set of electromechanical relays connected in a matrix formation. A sixteen-bit microcontroller was used for controlling the operation of

Abhiman Hande; Sukumar Kamalasadan; Anurag Srivastava

2006-01-01

51

Electronic circuit for measuring series connected electrochemical cell voltages  

DOEpatents

An electronic circuit for measuring voltage signals in an energy storage device is disclosed. The electronic circuit includes a plurality of energy storage cells forming the energy storage device. A voltage divider circuit is connected to at least one of the energy storage cells. A current regulating circuit is provided for regulating the current through the voltage divider circuit. A voltage measurement node is associated with the voltage divider circuit for producing a voltage signal which is proportional to the voltage across the energy storage cell.

Ashtiani, Cyrus N. (West Bloomfield, MI); Stuart, Thomas A. (Toledo, OH)

2000-01-01

52

Measurement and Analysis of Gas Bubbles near a Reference Electrode in  

Microsoft Academic Search

Bubble size distributions (BSDs) near a reference electrode (RE) in aqueous glycerol solutions of an electrolyte NaCl have been investigated under various gas superficial velocities (Us). BSD and voltage reading of the solution were measured by using a high-speed digital camera and a pH\\/voltage meter, respectively. The results show that bubble size (b) increases with liquid viscosity (Ìc) and Us.

Supathorn Phongikaroon; Steven D. Herrmann; Shelly X. Li; Michael F. Simpson

53

Experimental validation of a high voltage pulse measurement method.  

SciTech Connect

This report describes X-cut lithium niobate's (LiNbO3) utilization for voltage sensing by monitoring the acoustic wave propagation changes through LiNbO3 resulting from applied voltage. Direct current (DC), alternating current (AC) and pulsed voltage signals were applied to the crystal. Voltage induced shift in acoustic wave propagation time scaled quadratically for DC and AC voltages and linearly for pulsed voltages. The measured values ranged from 10 - 273 ps and 189 ps - 2 ns for DC and non-DC voltages, respectively. Data suggests LiNbO3 has a frequency sensitive response to voltage. If voltage source error is eliminated through physical modeling from the uncertainty budget, the sensor's U95 estimated combined uncertainty could decrease to ~0.025% for DC, AC, and pulsed voltage measurements.

Cular, Stefan; Patel, Nishant Bhupendra; Branch, Darren W.

2013-09-01

54

Study of a guarded electrode system in the dc conductivity measurement of insulating liquid  

NASA Astrophysics Data System (ADS)

The design and choice of an electrode system is important in dc conductivity measurement of insulating liquid. In this paper, the electric field distribution of an electrode system which consists of two parallel circular metallic electrodes and a guard electrode has been studied using Comsol Multiphysics software. A new parameter, which is not yet involved in current standards, the edge radius, has been mentioned in the literature formerly and is currently discussed in a CIGRE working group. In this paper, the influence of this parameter has been investigated by means of field calculation. As seen from the simulating result, there are regions in the vicinity of the edges of the guard and measuring electrode that are under high electric field. If the edges of these two electrodes are sharp, the maximum electric field in the test cell will be much higher than the average field between the measuring electrode and the high voltage electrode. An empirical equation has been proposed to calculate this maximum field. The classic correction expression for an effective radius has been re-evaluated with the edge radius being taken into account. Experimental work has been performed to confirm this conclusion. Three kinds of mineral oils with different ageing times have been tested under the dc field using a guarded electrode system and the electric strengths of these oils have been estimated. A recommendation has been made to current standards in insulating liquid measurement.

Zhou, Yuan; Hao, Miao; Chen, George; Wilson, Gordon; Jarman, Paul

2014-07-01

55

Atomic layer deposition encapsulated activated carbon electrodes for high voltage stable supercapacitors.  

PubMed

Operating voltage enhancement is an effective route for high energy density supercapacitors. Unfortunately, widely used activated carbon electrode generally suffers from poor electrochemical stability over 2.5 V. Here we present atomic layer deposition (ALD) encapsulation of activated carbons for high voltage stable supercapacitors. Two-nanometer-thick Al2O3 dielectric layers are conformally coated at activated carbon surface by ALD, well-maintaining microporous morphology. Resultant electrodes exhibit excellent stability at 3 V operation with 39% energy density enhancement from 2.5 V operation. Because of the protection of surface functional groups and reduction of electrolyte degradation, 74% of initial voltage was maintained 50 h after full charge, and 88% of capacitance was retained after 5000 cycles at 70 °C accelerated test, which correspond to 31 and 17% improvements from bare activated carbon, respectively. This ALD-based surface modification offers a general method to enhance electrochemical stability of carbon materials for diverse energy and environmental applications. PMID:25548826

Hong, Kijoo; Cho, Moonkyu; Kim, Sang Ouk

2015-01-28

56

Non-intrusive high voltage measurement using slab coupled optical sensors  

NASA Astrophysics Data System (ADS)

We present an optical fiber non-intrusive sensor for measuring high voltage transients. The sensor converts the unknown voltage to electric field, which is then measured using slab-coupled optical fiber sensor (SCOS). Since everything in the sensor except the electrodes is made of dielectric materials and due to the small field sensor size, the sensor is minimally perturbing to the measured voltage. We present the details of the sensor design, which eliminates arcing and minimizes local dielectric breakdown using Teflon blocks and insulation of the whole structure with transformer oil. The structure has a capacitance of less than 3pF and resistance greater than 10 G?. We show the measurement of 66.5 kV pulse with a 32.6?s time constant. The measurement matches the expected value of 67.8 kV with less than 2% error.

Stan, Nikola; Chadderdon, Spencer; Selfridge, Richard H.; Schultz, Stephen M.

2014-03-01

57

Analysis of NSTX TF Joint Voltage Measurements  

SciTech Connect

This report presents findings of analyses of recorded current and voltage data associated with 72 electrical joints operating at high current and high mechanical stress. The analysis goal was to characterize the mechanical behavior of each joint and thus evaluate its mechanical supports. The joints are part of the toroidal field (TF) magnet system of the National Spherical Torus Experiment (NSTX) pulsed plasma device operating at the Princeton Plasma Physics Laboratory (PPPL). Since there is not sufficient space near the joints for much traditional mechanical instrumentation, small voltage probes were installed on each joint and their voltage monitoring waveforms have been recorded on sampling digitizers during each NSTX ''shot''.

R, Woolley

2005-10-07

58

Current-voltage characteristics of organic photovoltaic cells following deposition of cathode electrode  

PubMed Central

The current-voltage characteristics of benzoporphine-fullerene solar cells were measured subsequent to the deposition of Al as a cathode material. Even in vacuum, a shift in the open circuit voltage was observed at 20 min after Al deposition. Moreover, the displacement of inert gases (N2or Ar) in the evaporation chamber enhanced the photovoltaic parameters. The power conversion efficiency was increased by 24% over the initial characteristics (from 1.04% to 1.29%), which indicates that the structure of the organic-metal interface changed rapidly after Al deposition, even if the process was performed in an air-free glovebox. PMID:21151322

Saeki, Hiroyuki; Hirohara, Kazuto; Koshiba, Yasuko; Horie, Satoshi; Misaki, Masahiro; Takeshita, Kimiya; Ishida, Kenji; Ueda, Yasukiyo

2010-01-01

59

Organic dicarboxylate negative electrode materials with remarkably small strain for high-voltage bipolar batteries.  

PubMed

As advanced negative electrodes for powerful and useful high-voltage bipolar batteries, an intercalated metal-organic framework (iMOF), 2,6-naphthalene dicarboxylate dilithium, is described which has an organic-inorganic layered structure of ?-stacked naphthalene and tetrahedral LiO4 units. The material shows a reversible two-electron-transfer Li intercalation at a flat potential of 0.8?V with a small polarization. Detailed crystal structure analysis during Li intercalation shows the layered framework to be maintained and its volume change is only 0.33%. The material possesses two-dimensional pathways for efficient electron and Li(+) transport formed by Li-doped naphthalene packing and tetrahedral LiO3C network. A cell with a high potential operating LiNi(0.5)Mn(1.5)O4 spinel positive and the proposed negative electrodes exhibited favorable cycle performance (96% capacity retention after 100 cycles), high specific energy (300?Wh?kg(-1)), and high specific power (5?kW?kg(-1)). An 8?V bipolar cell was also constructed by connecting only two cells in series. PMID:25196994

Ogihara, Nobuhiro; Yasuda, Tomomi; Kishida, Yoshihiro; Ohsuna, Tetsu; Miyamoto, Kaito; Ohba, Nobuko

2014-10-20

60

B#: Hex to Dec, Dec to Hex Conversion 1. Measured Voltage (Hex2Dec)  

E-print Network

B#: Hex to Dec, Dec to Hex Conversion 1. Measured Voltage (Hex2Dec) Reference voltage low: 0V Reference voltage high: 5V Resolution: 10bit Offset: TBD Dec Voltage Value = Hex2 Dec (Hex Voltage Value Reference Voltage Range: 1.23V~12.40V 2. Emulated Voltage (Dec2Hex) Resolution: 12bit Output Voltage Range

Shinozuka, Masanobu

61

Measurement of high voltage using Rutherford backscattering spectrometry  

E-print Network

A novel variation of Rutherford Backscattering Spectrometry (RBS) has been utilized to measure a high voltage collected on an aluminum target by Direct Energy Conversion. The maximum high voltage on the target was measured to be 97.5 kV +/- 2 k...

Abrego, Celestino Pete

2007-04-25

62

Frequency response measurements in battery electrodes  

NASA Technical Reports Server (NTRS)

Electrical impedance spectroscopy was used to investigate the behavior of porous zinc, silver, cadmium, and nickel electrodes. State of charge could be correlated with impedance data for all but the nickel electrodes. State of health was correlated with impedance data for two AgZn cells, one apparently good and the other bad. The impedance data was fit to equivalent circuit models.

Thomas, Daniel L.

1992-01-01

63

satellite surface potential survey. [Kapton voltage measurement  

NASA Technical Reports Server (NTRS)

Results of Kapton differential voltage charging of the satellite surface potential monitor Kapton samples are presented for the first 100 days of P78-2 operations. Daily charging occurrences are plotted in magnetic local time and L-shell (altitude and magnetic latitude) space as a function of magnetic activity. Most of the low level charging occurs well into the dawn local time sector whereas the highest voltage levels occur in the premidnight local time sector. The probabilities of differential charging are extremely dependent on the local time sector, the altitude (or L-shell) and of course, the magnetic activity.

Mizera, P. F.; Boyd, G. M.

1980-01-01

64

Measurement uncertainties arising from unpowered shipment of dc voltage references  

Microsoft Academic Search

We have measured the hysteresis in output voltage arising from loss of power for three Fluke 732B dc voltage references. Continuously powering the internal temperature-controlled oven provides the best accuracy with such Zener-diode-based dc voltage references. Batteries are used to provide power continuity when shipping between laboratories. We have shown that for these particular instruments, an apparent hysteresis induced by

Laurie A. Christian; Sze Wey Chua; Tian Yeong Sim; Ling Xiang Liu

2001-01-01

65

Measuring Helical FCG Voltage with an Electric Field Antenna  

SciTech Connect

A method of measuring the voltage produced by a helical explosive flux compression generator using a remote electric field antenna is described in detail. The diagnostic has been successfully implemented on several experiments. Measured data from the diagnostic compare favorably with voltages predicted using the code CAGEN, validating our predictive modeling tools. The measured data is important to understanding generator performance, and is measured with a low-risk, minimally intrusive approach.

White, A D; Anderson, R A; Javedani, J B; Reisman, D B; Goerz, D A; Ferriera, A J; Speer, R D

2011-08-01

66

Method for linearizing deflection of a MEMS device using binary electrodes and voltage modulation  

DOEpatents

A micromechanical device comprising one or more electronically movable structure sets comprising for each set a first electrode supported on a substrate and a second electrode supported substantially parallel from said first electrode. Said second electrode is movable with respect to said first electrode whereby an electric potential applied between said first and second electrodes causing said second electrode to move relative to said first electrode a distance X, (X), where X is a nonlinear function of said potential, (V). Means are provided for linearizing the relationship between V and X.

Horenstein, Mark N. (West Roxbury, MA) [West Roxbury, MA

2008-06-10

67

Floating input, optically isolated, high-voltage measurement probe  

Microsoft Academic Search

A simple, floating input, high-voltage measurement probe is described. The divider is purely capacitive and is completely isolated from earth. Optical fibers are used to transmit information to the recording instruments which can be operated at earth potential. The probe can easily be constructed in a laboratory and is adaptable to a wide range of voltages up to 1 MV.

C. A. Bleys

1976-01-01

68

An electrode polarization impedance based flow sensor for low water flow measurement  

NASA Astrophysics Data System (ADS)

This note describes an electrode polarization impedance based flow sensor for low water flow measurement. It consists of two pairs of stainless steel electrodes set apart and inserted into a non-conductive flow tube with each pair of electrodes placed diametrically at the opposite sides. The flow sensor is modeled as a typical four-electrode system of which two electrodes are current-carrying and the other two serve as output pick ups. The polarization impedances of the two current carrying electrodes are affected by water flows resulting in changes of differential potential between the two pick-up electrodes which are separated by the same fluid. The interrogation of the two excitation electrodes with dc biased ac signals offers significantly higher sensor sensitivities to flow. The prototype flow sensor constructed for a 20 mm diameter pipeline was able to measure water flow rate as low as tested at 1.06 l h-1 and remained sensitive at a flow rate of 25.18 l h-1 when it was driven with a sinusoidal voltage at 1000 Hz with a peak ac amplitude of 2 V and a dc offset of +8 V. The nonlinear characteristics of the sensor response indicate that the sensor is more sensitive at low flows and will not be able to measure at very high flows. Additional experiments are needed to evaluate the influences of impurities, chemical species, ions constituents, conductivity and temperature over a practical range of residential water conditions, the effects of fluctuating ground signals, measurement uncertainty, power consumption, compensation of effects and practical operations. The flow sensor (principle) presented may be used as (in) a secondary sensor in combination with an existing electronic water meter to extend the low end of measurement range in residential water metering.

Yan, Tinghu; Sabic, Darko

2013-06-01

69

Determination of HID electrode falls in a model lamp II: Langmuir-probe measurements  

NASA Astrophysics Data System (ADS)

A special measuring method with Langmuir probes was established which yields the plasma potential in high-pressure plasmas to determine separate cathode and anode falls of HID electrodes. The probes consist of two tungsten wires which are inserted via side arms into the discharge tube of a model lamp. Their bended ends form together a full circle which surrounds the arc at its boundary. One probe is operated at floating potential with the other one a current-voltage characteristic of the probe is recorded. Its shape corresponds to that taken with a plane probe in a low-pressure plasma. Taking into account the radial voltage drop between the axis and the boundary of the arc, it was shown that the inflection point between the retarded electron current and electron saturation current represents the plasma potential in the arc axis. The electrode falls were determined by an extrapolation of the plasma potential which was measured along the arc axis towards the electrodes. Cathode and anode fall measurements at tungsten electrodes of different diameters are presented which were performed with an arc in argon at 0.26 MPa at currents between 1.5 and 6 A.

Luhmann, J.; Lichtenberg, S.; Langenscheidt, O.; Benilov, M. S.; Mentel, J.

2002-07-01

70

STUDY OF AN ELECTROOPTIC SENSOR FOR HIGH-VOLTAGE MEASUREMENTS  

Microsoft Academic Search

In the recent years, several optical potential transformers (OPT) have been developed and applied to perform high-voltage measurements in electrical power systems. Such devices offer very attractive advantages, compared to conventional transformers, such as, fast transitory response, low susceptibility to electromagnetic interference, high signal\\/noise ratio, reduced size and weight, and provide complete electric isolation between high-voltage system and measurement equipment.

J. C. SANTOS; L. PINHEIRO C. SILVA; J. C. J. ALMEIDA; J. RUBINI JR; N. M. ABE; A. PASSARO

2006-01-01

71

Voltage-controlled liquid-crystal terahertz phase shifter with indium-tin-oxide nanowhiskers as transparent electrodes.  

PubMed

Indium-tin-oxide nanowhiskers were employed as transparent electrodes in a liquid-crystal terahertz phase shifter. Transmittance of the device was as high as ?75%. Phase shift exceeding ?/2 at 1.0 THz is achieved in a ?500???m-thick cell. The driving voltage required for the device operating as a quarter-wave plate was as low as 17.68 V (rms), an improvement of nearly an order of magnitude over previous work. PMID:24979031

Yang, Chan-Shan; Tang, Tsung-Ta; Chen, Po-Han; Pan, Ru-Pin; Yu, Peichen; Pan, Ci-Ling

2014-04-15

72

Measuring the displacement of the movable guard electrode in the new vertical calculable capacitor at NIM  

NASA Astrophysics Data System (ADS)

A new type vertical calculable capacitor has been built at National Institute of Metrology (NIM) cooperated with National Measurement Institute of Australia (NMIA). The calculable capacitor is the highest accuracy equipment apparatus except the quantum voltage and the quantum resistance in the electromagnetic metrological field. In order to measure the capacitance precisely, the accurate displacement measurement among the two guard electrodes in the calculable capacitor is a pivotal part. This paper describes a method of measuring the displacement of a Fabry-Perot interferometer, and this interferometer is component of two mirrors in two guard electrodes of the calculable capacitor at NIM. One concave reflective mirror, with 5 m radius and 70% reflectivity, is on the top of the bottom fixed guards electrodes. The other planar mirror is placed at the end of the moveable guard electrodes. This Fabry-Perot interferometer employs a home-made lamb-dip stabilization He-Ne laser at 633 nm to measure the displacement of the movable guard electrode. The internal modulation, which is used for laser stabilization, is also employed for locking the Fabry-Perot interferometer. The displacement of the movable guard electrode could be measured, when the Fabry-Perot interferometer is locked to the stabilization laser at two positions respectively. An iodine stabilization He-Ne laser at 633 nm is employed to simultaneously calibrate the wavelength of lamb-dip working laser. A reproducibility of 1.43×10-8(k=3) for the range of 205 mm can be obtained at present, and that is estimated from the experimental results of calculable capacitor.

Wang, Jianbo; Qian, Jin; Liu, Zhongyou; Liu, Xiuying; Lu, Zhuliang; Huang, Lu; Yin, Cong; Li, Tongbao

2014-11-01

73

Open circuit voltage temperature coefficients vs. concentration: Theory, indoor measurements, and outdoor measurements  

NASA Astrophysics Data System (ADS)

Current-voltage characteristics of multijunction III-V solar cells from several different vendors were measured at different light concentrations and temperatures. Measurements were taken indoors using flash lamp solar simulators and outdoors under natural sunlight. The change in open-circuit voltage with temperature was measured. Modeled results, indoor measurements, and outdoor measurements are compared.

Bagienski, Will; Kinsey, Geoffrey S.; Liu, Mingguo; Nayak, Adi; Garboushian, Vahan

2012-10-01

74

Digital measurement system for the LHC klystron high voltage modulator.  

E-print Network

Accelerating voltage in the Large Hadron Collider (LHC) is created by a means of 16 superconducting standing wave RF cavities, each fed by a 400MHz/300kW continuous wave klystron amplifier. Part of the upgrade program for the LHC long shutdown one is to replace the obsolete analogue current and voltage measurement circuitry located in the high voltage bunkers by a new, digital system, using ADCs and optical fibres. A digital measurement card is implemented and integrated into the current HV modulator oil tank (floating at -58kV) and interfaced to the existing digital VME boards collecting the data for several klystrons at the ground potential. Measured signals are stored for the logging, diagnostics and post-mortem analysis purposes.

Mikkelsen, Anders

75

A two electrode apparatus for electrical impedance measurements  

NASA Astrophysics Data System (ADS)

A two electrode cell for complex impedance measurements on core samples in the range 1 mHz - 0.3 kHz is described. Two electrode cells are more convenient than four electrode cells but some restrictions need to be observed. I will show that the contact impedance between the electrodes and the sample can be controlled and reduced to less than fifty ohms in most cases. The contact impedance is repeatable, with a peak phase near 10 Hz of less than one degree and a maximum change in impedance magnitude of less than fifty ohm. A model for the contact impedance is used to correct impedance measurements, leaving an un-modeled contact impedance of a few ohms. There is typically a drift of about 100 ohm during a measurement sequence due to diffusion between the ceramic frits at the ends of the sample. This is corrected by repeat measurements at 100 Hz. Un-modeled impedance changes due to drift are about ten ohm. The un-modeled impedance changes mean that the relative error on conductive samples is greater than on resistive samples. Repeat measurements on a sandstone sample with conductive pore water (0.14 S/m) yield a mean of 492 ohms with a standard deviation of 20 ohm, or about five percent. Measurements on mineralized core and on cells constructed from mixtures of silica sand and polarizable minerals demonstrate that the two electrode set up can be used even on heavily mineralized samples.

Merriam, J. B.

2009-12-01

76

Heating rate and electrode charging measurements in a scalable, microfabricated, surface-electrode ion trap  

E-print Network

We characterise the performance of a surface-electrode ion "chip" trap fabricated using established semiconductor integrated circuit and micro-electro-mechanical-system (MEMS) microfabrication processes which are in principle scalable to much larger ion trap arrays, as proposed for implementing ion trap quantum information processing. We measure rf ion micromotion parallel and perpendicular to the plane of the trap electrodes, and find that on-package capacitors reduce this to heating rate for a single trapped ion. The performance of this trap is found to be comparable with others of the same size scale.

D. T. C. Allcock; T. P. Harty; H. A. Janacek; N. M. Linke; C. J. Ballance; A. M. Steane; D. M. Lucas; R. L. Jarecki Jr.; S. D. Habermehl; M. G. Blain; D. Stick; D. L. Moehring

2011-05-24

77

Means to remove electrode contamination effect of Langmuir probe measurement in space  

SciTech Connect

Precaution to remove the serious effect of electrode contamination in Langmuir probe experiments has not been taken in many space measurements because the effect is either not understood or ignored. We stress here that one should pay extra attention to the electrode contamination effect to get accurate and reliable plasma measurements so that the long time effort for sounding rocket/satellite missions does not end in vain or becomes less fruitful. In this paper, we describe two main features of voltage-current characteristic curves associated with the contaminated Langmuir probe, which are predicted from the equivalent circuit model, which we proposed in 1970's. We then show that fast sweeping dc Langmuir probes can give reliable results in the steady state regime. The fast sweeping probe can also give reliable results in transient situations such as satellite moves through plasma bubble in the ionosphere where the electron density drastically changes. This fact was first confirmed in our laboratory experiment.

Oyama, K.-I.; Lee, C. H.; Fang, H. K.; Cheng, C. Z. [Plasma and Space Science Center, National Cheng Kung University, No.1 Ta-Hsueh Rd., Tainan 70101, Taiwan (China)

2012-05-15

78

Means to remove electrode contamination effect of Langmuir probe measurement in space.  

PubMed

Precaution to remove the serious effect of electrode contamination in Langmuir probe experiments has not been taken in many space measurements because the effect is either not understood or ignored. We stress here that one should pay extra attention to the electrode contamination effect to get accurate and reliable plasma measurements so that the long time effort for sounding rocket/satellite missions does not end in vain or becomes less fruitful. In this paper, we describe two main features of voltage-current characteristic curves associated with the contaminated Langmuir probe, which are predicted from the equivalent circuit model, which we proposed in 1970's. We then show that fast sweeping dc Langmuir probes can give reliable results in the steady state regime. The fast sweeping probe can also give reliable results in transient situations such as satellite moves through plasma bubble in the ionosphere where the electron density drastically changes. This fact was first confirmed in our laboratory experiment. PMID:22667663

Oyama, K-I; Lee, C H; Fang, H K; Cheng, C Z

2012-05-01

79

Linearisation of ?DNA molecules by instantaneous variation of the trapping electrode voltage inside a micro-channel  

NASA Astrophysics Data System (ADS)

Because long DNA molecules usually exist in random coil states due to the entropic effect, linearisation is required for devices equipped with nanopores where electrical sequencing is necessary during single-file translocation. We present a novel technique for linearising DNA molecules in a micro-channel. In our device, electrodes are embedded in the bottom surface of the channel. The application of a voltage induces the trapping of ?DNA molecules on the positive electrode. An instantaneous voltage drop is used to put the ?DNA molecules in a partly released state and the hydrodynamic force of the solution induces linearisation. Phenomena were directly observed using an optical microscopy system equipped with a high-speed camera and the linearisation principle was explored in detail. Furthermore, we estimate the tensile characteristics produced by the flow of the solution through a numerical model of a tethered polymer subject to a Poiseuille flow. The mean tensile force is in the range of 0.1–1 pN. This is sufficiently smaller than the structural transition point of ?DNA but counterbalances the entropic elasticity that causes the random coil shape of ?DNA molecules in solution. We show the important role of thermal fluctuation in the manipulation of molecules in solution and clarify the tensile conditions required for DNA linearisation using a combination of solution flow and voltage variation in a microchannel.

Hanasaki, Itsuo; Yukimoto, Naoya; Uehara, Satoshi; Shintaku, Hirofumi; Kawano, Satoyuki

2015-04-01

80

Control of threshold voltage in organic thin-film transistors by modifying gate electrode surface with MoOX aqueous solution and inverter circuit applications  

NASA Astrophysics Data System (ADS)

We controlled the threshold voltage of organic thin-film transistors (TFTs) by treating only the gate electrode surface with a MoOX aqueous solution and used them to build inverter circuits. The threshold voltage was changed by varying the concentration of the MoOX aqueous solution. A strong correlation between the work function of the gate electrode and the threshold voltage was observed. The threshold voltage of one of the two organic TFT devices in the inverter circuit was selectively changed by +2.3 V by reducing the concentration of the MoOx solution. We controlled the switching voltage of p-type organic inverter circuits and obtained excellent inverter characteristics. These results indicate that using a MoOx aqueous solution to control the threshold voltage is very useful for integrated circuits applications.

Shiwaku, Rei; Yoshimura, Yudai; Takeda, Yasunori; Fukuda, Kenjiro; Kumaki, Daisuke; Tokito, Shizuo

2015-02-01

81

Measuring voltage and current in a DC circuit  

NSDL National Science Digital Library

These exercises target student misconceptions about how to properly measure voltage and current in simple DC circuits by letting them investigate different meter arrangements without fear of damaging equipment. These activities also are designed to lead to other investigations about simple DC circuits.

Susan Ramlo

82

A HIGH CURRENT, HIGH VOLTAGE SOLID-STATE PULSE GENERATOR FOR THE NIF PLASMA ELECTRODE POCKELS CELL  

SciTech Connect

A high current, high voltage, all solid-state pulse modulator has been developed for use in the Plasma Electrode Pockels Cell (PEPC) subsystem in the National Ignition Facility. The MOSFET-switched pulse generator, designed to be a more capable plug-in replacement for the thyratron-switched units currently deployed in NIF, offers unprecedented capabilities including burst-mode operation, pulse width agility and a steady-state pulse repetition frequency exceeding 1 Hz. Capable of delivering requisite fast risetime, 17 kV flattop pulses into a 6 {Omega} load, the pulser employs a modular architecture characteristic of the inductive adder technology, pioneered at LLNL for use in acceleration applications, which keeps primary voltages low (and well within the capabilities of existing FET technology), reduces fabrication costs and is amenable to rapid assembly and quick field repairs.

Arnold, P A; Barbosa, F; Cook, E G; Hickman, B C; Akana, G L; Brooksby, C A

2007-07-27

83

Nanoscopic electrode molecular probes  

DOEpatents

The present invention relates to a method and apparatus for enhancing the electron transport property measurements of a molecule when the molecule is placed between chemically functionalized carbon-based nanoscopic electrodes to which a suitable voltage bias is applied. The invention includes selecting a dopant atom for the nanoscopic electrodes, the dopant atoms being chemically similar to atoms present in the molecule, and functionalizing the outer surface and terminations of the electrodes with the dopant atoms.

Krstic, Predrag S. (Knoxville, TN); Meunier, Vincent (Knoxville, TN)

2012-05-22

84

Simultaneous measurement of changes in current and tracer flux in voltage-clamped squid giant axon.  

PubMed

A method is described for the simultaneous measurement of changes in membrane current and unidirectional radiotracer flux in internally dialyzed voltage-clamped squid giant axons. The small currents that are produced by electrogenic transport processes or steady-state ionic currents can be resolved using this method. Because the use of grounded guard electrodes in the end pools is not, by itself, an adequate means of eliminating end-effects, two ancillary end pool clamp circuits are described to eliminate extraneous current flow from the ends of the axon. The end pool voltage-clamp circuits serve to minimize net current flow between the end pools and center pool, and employ stable, low-impedance calomel electrodes to monitor the potentials of the end and center pools. The adequacy of the method is demonstrated by experiments in which unidirectional 22Na efflux and current, flowing through tetrodotoxin (TTX)-sensitive Na channels into Na-free seawater, under K-free conditions, are shown to be equal. The equality of unidirectional TTX-sensitive flux and current is maintained over the entire range of membrane potentials examined (-60 to +20 mV). The method has been applied to a series of experiments in which the voltage dependence and stoichiometry of the Na/K pump have been measured (Rakowski et al., 1989), and can be applied in general to the simultaneous measurement of changes in current and flux of other electrogenic transport processes, and of currents through ionic channels that open under steady-state conditions. PMID:2720065

Rakowski, R F

1989-04-01

85

Measuring skin conductivity --designed amplifier circuit to measure the voltage difference across two  

E-print Network

Measuring skin conductivity -- designed amplifier circuit to measure the voltage difference across for skin conductivity and pulse rate signals (both in DC voltage) with sampling rate of 1kHz Algorithms -- Updating heart rate at each heart beat and determine the average of skin conductivity at the same time

Hero, Alfred O.

86

Modeling and measurement of piezoelectric fibers and interdigitaded electrodes for the optimization of piezofibre composites  

NASA Astrophysics Data System (ADS)

Commercially available PZT-5A composition fibres fabricated using four production methods were incorporated into 1-3 composites with fibre volume fractions ranging from 0.02 to 0.72. Measurements of the piezoelectric induced strain constants (d33 and d31), relative dielectric constants (e33), longitudinal coupling factors (k33) and stiffness' (s33) of the varying volume fraction composites are compared to analytical expressions in order to extract the fibre properties. Results show 1-3 composite data accurately follows the analytical trends. The Viscous Plastic Process (VPP) fibres are found to exhibit optimum material properties, which approach bulk material values. Reduced piezoelectric activity in extruded fibres is thought to be associated with a small grain size and high porosity. A second study, an optimisation of interdigitated electrode design, was performed using the finite element software ANSYS. The effect of the IDE geometry (electrode width and spacing) and PZT substrate thickness on the strain output of bulk PZT substrates was modelled. Results show optimal actuation occurs at electrode widths equal to half the substrate thickness, and for thin substrates the electrode finger spacing can be reduced to enable lower driving voltages.

Nelson, Luke; Bowen, Chris; Stevens, Ron; Cain, Markys; Stewart, Mark

2003-08-01

87

Developing Barbed Microtip-Based Electrode Arrays for Biopotential Measurement  

PubMed Central

This study involved fabricating barbed microtip-based electrode arrays by using silicon wet etching. KOH anisotropic wet etching was employed to form a standard pyramidal microtip array and HF/HNO3 isotropic etching was used to fabricate barbs on these microtips. To improve the electrical conductance between the tip array on the front side of the wafer and the electrical contact on the back side, a through-silicon via was created during the wet etching process. The experimental results show that the forces required to detach the barbed microtip arrays from human skin, a polydimethylsiloxane (PDMS) polymer, and a polyvinylchloride (PVC) film were larger compared with those required to detach microtip arrays that lacked barbs. The impedances of the skin-electrode interface were measured and the performance levels of the proposed dry electrode were characterized. Electrode prototypes that employed the proposed tip arrays were implemented. Electroencephalogram (EEG) and electrocardiography (ECG) recordings using these electrode prototypes were also demonstrated. PMID:25014098

Hsu, Li-Sheng; Tung, Shu-Wei; Kuo, Che-Hsi; Yang, Yao-Joe

2014-01-01

88

Unraveling the voltage fade mechanism in layer Li-Mn-rich electrode: formation of the tetrahedral cations for spinel conversion  

SciTech Connect

Discovery of high-voltage layered lithium-and manganese-rich (LMR) composite oxide electrode has dramatically enhanced the energy density of current Li-ion energy storage systems. However, practical usage of these materials is currently not viable because of their inability to maintain a consistent voltage profile (voltage fading) during subsequent charge-discharge cycles. This report rationalizes the cause of this voltage fade by providing the evidence of layer to spinel-like (LSL) structural evolution pathways in the host Li1.2Mn0.55Ni0.15Co0.1O2 LMR composite oxide. By employing neutron powder diffraction, and temperature dependent magnetic susceptibility, we show that LSL structural rearrangement in LMR oxide occurs through a tetrahedral cation intermediate via: i) diffusion of lithium atoms from octahedral to tetrahedral sites of the lithium layer [(LiLioct LiLitet] which is followed by the dispersal of the lithium ions from the adjacent octahedral site of the metal layer to the tetrahedral sites of lithium layer [LiTM oct LiLitet]; and ii) migration of Mn from the octahedral sites of the transition metal layer to the permanent octahedral site of lithium layer via tetrahedral site of lithium layer [MnTMoct MnLitet MnLioct)]. The findings opens the door to the potential routes to mitigate this atomic restructuring in the high-voltage LMR composite oxide cathodes by manipulating the composition/structure for practical use in high-energy-density lithium-ion batteries.

Mohanty, Debasish [ORNL; Li, Jianlin [ORNL; Abraham, Daniel P [Argonne National Laboratory (ANL); Huq, Ashfia [ORNL; Payzant, E Andrew [ORNL; Wood III, David L [ORNL; Daniel, Claus [ORNL

2014-01-01

89

Technical Development on Partial Discharge Measurement and Electrical Insulation Techniques for Low Voltage Motors Driven by Voltage Inverters  

Microsoft Academic Search

This paper reviews the up-to-date research activities on electrical insulation techniques under repetitive surge voltages with steep wavefront for low voltage inverter-fed motors. Partial discharge (PD) inception, propagation, ageing and breakdown characteristics of magnet wires, including recently developed PD-resistant wires such as nanocomposite enameled wires, are described. PD measurement techniques under the steep-front voltages and IEC activity toward their standardization

Hitoshi Okubo; Naoki Hayakawa; Gian Carlo Montanari

2007-01-01

90

Improved Uniform-Field Electrode Profiles for TEA Laser and High-Voltage Applications  

Microsoft Academic Search

Simple analytic formulas that can be used to design a finite width uniform-field electrode for any desired aspect ratio and field uniformity are derived. The resulting profile is superior to those of Rogowski, Bruce, and Harrison in its smoothness, compactness, and field uniformity. A procedure for designing a three-dimensional profile is also given.

T. Y. Chang

1973-01-01

91

Optically-initiated silicon carbide high voltage switch with contoured-profile electrode interfaces  

DOEpatents

An improved photoconductive switch having a SiC or other wide band gap substrate material with opposing contoured profile cavities which have a contoured profile selected from one of Rogowski, Bruce, Chang, Harrison, and Ernst profiles, and two electrodes with matching contoured-profile convex interface surfaces.

Sullivan, James S.; Hawkins, Steven A.

2012-09-04

92

Robust signatures in the current-voltage characteristics of DNA molecules oriented between two graphene nanoribbon electrodes  

NASA Astrophysics Data System (ADS)

In this work we numerically calculate the electric current through three kinds of DNA sequences (telomeric, ?-DNA, and p53-DNA) described by different heuristic models. A bias voltage is applied between two zig-zag edged graphene contacts attached to the DNA segments, while a gate terminal modulates the conductance of the molecule. The calculation of current is performed by integrating the transmission function (calculated using the lattice Green's function) over the range of energies allowed by the chemical potentials. We show that a telomeric DNA sequence, when treated as a quantum wire in the fully coherent low-temperature regime, works as an excellent semiconductor. Clear steps are apparent in the current-voltage curves of telomeric sequences and are present independent of lengths and sequence initialisation at the contacts. The current-voltage curves suggest the existence of stepped structures independent of length and sequencing initialisation at the contacts. We also find that the molecule-electrode coupling can drastically influence the magnitude of the current. The difference between telomeric DNA and other DNA, such as ?-DNA and DNA for the tumour suppressor p53, is particularly visible in the length dependence of the current.

Paez, Carlos; Schulz, Peter; Roemer, Rudolf; Wilson, Neil

2013-03-01

93

Measurement and Analysis of Gas Bubbles Near a Reference Electrode in Aqueous Solutions  

SciTech Connect

Bubble size distributions (BSDs) near a reference electrode (RE) in aqueous glycerol solutions of an electrolyte NaCl have been investigated under various gas superficial velocities (U{sub S}). BSD and voltage reading of the solution were measured by using a high-speed digital camera and a pH/voltage meter, respectively. The results show that bubble size (b) increases with liquid viscosity ({mu}{sub c}) and U{sub S}. Self-similarity is seen and can be described by the log-normal form of the continuous number frequency distribution. The result shows that b controls the voltage reading in each solution. As b increases, the voltage increases because of gas bubbles interrupting their electrolyte paths in the solutions. An analysis of bubble rising velocity reveals that Stokes Law should be used cautiously to describe the system. The fundamental equation for bubble formation was developed via Newton's second law of motion and shown to be the function of three dimensionless groups--Weber number, Bond number, and Capillary number. After linking an electrochemical principle in the practical application, the result indicates that the critical bubble size is {approx}177 {micro}m. Further analysis suggests that there may be 3000 to 70,000 bubbles generated on the anode surface depending on the size of initial bubbles and provides the potential cause of the efficiency drop observed in the practical application.

Supathorn Phongikaroon; Steve Herrmann; Shelly Li; Michael Simpson

2005-10-01

94

Measurement of Microchannel Fluidic Resistance with a Standard Voltage Meter  

PubMed Central

A simplified method for measuring the fluidic resistance (Rfluidic) of microfluidic channels is presented, in which the electrical resistance (Relec) of a channel filled with a conductivity standard solution can be measured and directly correlated to Rfluidic using a simple equation. Although a slight correction factor could be applied in this system to improve accuracy, results showed that a standard voltage meter could be used without calibration to determine Rfluidic to within 12% error. Results accurate to within 2% were obtained when a geometric correction factor was applied using these particular channels. When compared to standard flow rate measurements, such as meniscus tracking in outlet tubing, this approach provided a more straightforward alternative and resulted in lower measurement error. The method was validated using 9 different fluidic resistance values (from ~40 – 600 kPa s mm?3) and over 30 separately fabricated microfluidic devices. Furthermore, since the method is analogous to resistance measurements with a voltage meter in electrical circuits, dynamic Rfluidic measurements were possible in more complex microfluidic designs. Microchannel Relec was shown to dynamically mimic pressure waveforms applied to a membrane in a variable microfluidic resistor. The variable resistor was then used to dynamically control aqueous-in-oil droplet sizes and spacing, providing a unique and convenient control system for droplet-generating devices. This conductivity-based method for fluidic resistance measurement is thus a useful tool for static or real-time characterization of microfluidic systems. PMID:23245901

Godwin, Leah A.; Deal, Kennon S.; Hoepfner, Lauren D.; Jackson, Louis A.; Easley, Christopher J.

2012-01-01

95

Measurement of microchannel fluidic resistance with a standard voltage meter.  

PubMed

A simplified method for measuring the fluidic resistance (R(fluidic)) of microfluidic channels is presented, in which the electrical resistance (R(elec)) of a channel filled with a conductivity standard solution can be measured and directly correlated to R(fluidic) using a simple equation. Although a slight correction factor could be applied in this system to improve accuracy, results showed that a standard voltage meter could be used without calibration to determine R(fluidic) to within 12% error. Results accurate to within 2% were obtained when a geometric correction factor was applied using these particular channels. When compared to standard flow rate measurements, such as meniscus tracking in outlet tubing, this approach provided a more straightforward alternative and resulted in lower measurement error. The method was validated using 9 different fluidic resistance values (from ?40 to 600kPa smm(-3)) and over 30 separately fabricated microfluidic devices. Furthermore, since the method is analogous to resistance measurements with a voltage meter in electrical circuits, dynamic R(fluidic) measurements were possible in more complex microfluidic designs. Microchannel R(elec) was shown to dynamically mimic pressure waveforms applied to a membrane in a variable microfluidic resistor. The variable resistor was then used to dynamically control aqueous-in-oil droplet sizes and spacing, providing a unique and convenient control system for droplet-generating devices. This conductivity-based method for fluidic resistance measurement is thus a useful tool for static or real-time characterization of microfluidic systems. PMID:23245901

Godwin, Leah A; Deal, Kennon S; Hoepfner, Lauren D; Jackson, Louis A; Easley, Christopher J

2013-01-01

96

Low-voltage circuit breaker arcs—simulation and measurements  

NASA Astrophysics Data System (ADS)

As one of the most important electrical components, the low-voltage circuit breaker (LVCB) has been widely used for protection in all types of low-voltage distribution systems. In particular, the low-voltage dc circuit breaker has been arousing great research interest in recent years. In this type of circuit breaker, an air arc is formed in the interrupting process which is a 3D transient arc in a complex chamber geometry with splitter plates. Controlling the arc evolution and the extinction are the most significant problems. This paper reviews published research works referring to LVCB arcs. Based on the working principle, the arcing process is divided into arc commutation, arc motion and arc splitting; we focus our attention on the modelling and measurement of these phases. In addition, previous approaches in papers of the critical physical phenomenon treatment are discussed, such as radiation, metal erosion, wall ablation and turbulence in the air arc. Recommendations for air arc modelling and measurement are presented for further investigation.

Yang, Fei; Wu, Yi; Rong, Mingzhe; Sun, Hao; Murphy, Anthony B.; Ren, Zhigang; Niu, Chunping

2013-07-01

97

New ways of measuring the pull-in voltage and transient behavior of parallel-plate capacitive MEMS transducers  

NASA Astrophysics Data System (ADS)

In this paper we introduce two new ways of measuring the pull-in voltage and the transient behavior of parallel-plate capacitive microelectromechanical systems (MEMS) transducers. The advantages in the measurement speed and resolution of the so-called fast MEMS test will be discussed. Also an enhanced method, the time-resolved dynamic measurement, will be shown. With the second method, we can visualize the integral displacement of a membrane while measuring the voltage drop of a high-frequency signal over a shunt resistor/capacitor. With a more advanced charge amplifier circuit, also a force-free resonance measurement of the membrane and electrode is possible in one step. All this offers a robust and cheap option for tracing moving structures without the need of an optical line of sight.

Glacer, C.; Dehé, A.; Nawaz, M.; Kolb, C.; Laur, R.

2013-08-01

98

Monitoring and intelligent control of electrode wear based on a measured electrode displacement curve in resistance spot welding  

NASA Astrophysics Data System (ADS)

Advanced high strength steels are being increasingly used in the automotive industry to reduce weight and improve fuel economy. However, due to increased physical properties and chemistry of high strength steels, it is difficult to directly substitute these materials into production processes currently designed for mild steels. New process parameters and process-related issues must be developed and understood for high strength steels. Among all issues, endurance of the electrode cap is the most important. In this paper, electrode wear characteristics of hot-dipped galvanized dual-phase (DP600) steels and the effect on weld quality are firstly analysed. An electrode displacement curve which can monitor electrode wear was measured by a developing experimental system using a servo gun. A neuro-fuzzy inference system based on the electrode displacement curve is developed for minimizing the effect of a worn electrode on weld quality by adaptively adjusting input variables based on the measured electrode displacement curve when electrode wear occurs. A modified current curve is implemented to reduce the effects of electrode wear on weld quality using a developed neuro-fuzzy system.

Zhang, Y. S.; Wang, H.; Chen, G. L.; Zhang, X. Q.

2007-03-01

99

[Portable ECG measuring system with non-contact electrode].  

PubMed

Heart disease is the major disease that threaten human health. ECG is an important tool for the diagnosis of cardiac disease. As traditional ECG measurement devices have many disadvantages, a non-contact ECG measurement system was designed. With the non-contact electrode based on capacitive coupling, the signals were collected and then they were amplified and filtered. The conditioned analog signal was converted to digital data which was sent to the mobile terminal through bluetooth. Finally, the ECG data was analyzed to extract the key ECG parameters. The results showed that the precise ECG signals can be got with the non-contact electrode and the key ECG parameters can be acquired accurately. PMID:25241508

Zhang, Xudong; Liu, Chen; Cui, Qiangqiang

2014-05-01

100

Enhanced open-circuit voltage in visible quantum dot photovoltaics by engineering of carrier-collecting electrodes.  

PubMed

Colloidal quantum dots (CQDs) enable multijunction solar cells using a single material programmed using the quantum size effect. Here we report the systematic engineering of 1.6 eV PbS CQD solar cells, optimal as the front cell responsible for visible-wavelength harvesting in tandem photovoltaics. We rationally optimize each of the device's collecting electrodes-the heterointerface with electron-accepting TiO(2) and the deep-work-function hole-collecting MoO(3) for ohmic contact-for maximum efficiency. We report an open-circuit voltage of 0.70 V, the highest observed in a colloidal quantum dot solar cell operating at room temperature. We report an AM1.5 solar power conversion efficiency of 3.5%, the highest observed in >1.5 eV bandgap CQD PV device. PMID:21936534

Wang, Xihua; Koleilat, Ghada I; Fischer, Armin; Tang, Jiang; Debnath, Ratan; Levina, Larissa; Sargent, Edward H

2011-10-01

101

Prediction of partial discharge and breakdown voltages in CF4 for arbitrary electrode geometries  

NASA Astrophysics Data System (ADS)

In literature a model was described for the simulation of the breakdown behaviour of SF6. As input parameters, results from swarm experiments—the critical field strength and the effective ionization coefficient—and thermodynamic properties are sufficient. Recently it was shown that it is possible to transfer this model to another strongly attaching gas. In this contribution the model is applied to tetrafluoromethane (CF4), which has a smaller critical field strength and is less attaching than SF6. Furthermore, the breakdown field strengths of alternating and lightning impulse voltages of different field configurations—from homogeneous to inhomogeneous fields—are predicted for CF4. A comparison to experimental results from the literature shows good agreement. Thus, the model is applicable not only to predict partial discharges and breakdown voltages in strongly attaching gases but also to gases less attaching than SF6.

Koch, M.; Franck, C. M.

2015-02-01

102

Molds and Resists Studies for Nanoimprint Lithography of Electrodes in Low-Voltage Polymer Thin-Film Transistors  

NASA Astrophysics Data System (ADS)

A low-cost patterning of electrodes was investigated looking forward to replacing conventional photolithography for the processing of low-operating voltage polymeric thin-film transistors. Hard silicon, etched by sulfur hexafluoride and oxygen gas mixture, and flexible polydimethylsiloxane imprinting molds were studied through atomic force microscopy (AFM) and field emission gun scanning electron microscopy. The higher the concentration of oxygen in reactive ion etching, the lower the etch rate, sidewall angle, and surface roughness. A concentration around 30 % at 100 mTorr, 65 W and 70 sccm was demonstrated as adequate for submicrometric channels, presenting a reduced etch rate of 176 nm/min. Imprinting with positive photoresist AZ1518 was compared to negative SU-8 2002 by optical microscopy and AFM. Conformal results were obtained only with the last resist by hot embossing at 120 °C and 1 kgf/cm2 for 2 min, followed by a 10 min post-baking at 100 °C. The patterning procedure was applied to define gold source and drain electrodes on oxide-covered substrates to produce bottom-gate bottom-contact transistors. Poly(3-hexylthiophene) (P3HT) devices were processed on high-? titanium oxynitride (TiO x N y ) deposited by radiofrequency magnetron sputtering over indium tin oxide-covered glass to achieve low-voltage operation. Hole mobility on micrometric imprinted channels may approach amorphous silicon (˜0.01 cm2/V s) and, since these devices operated at less than 5 V, they are not only suitable for electronic applications but also as sensors in aqueous media.

Cavallari, Marco Roberto; Zanchin, Vinicius Ramos; Pojar, Mariana; Seabra, Antonio Carlos; de Assumpção Pereira-da-Silva, Marcelo; Fonseca, Fernando Josepetti; de Andrade, Adnei Melges

2014-05-01

103

Pressure-independent point in current-voltage characteristics of coplanar electrode microplasma devices operated in neon  

SciTech Connect

We introduce the idea of a pressure-independent point (PIP) in a group of current-voltage curves for the coplanar electrode microplasma device (CEMPD) at neon pressures ranging from 15 to 95 kPa. We studied four samples of CEMPDs with different sizes of the microcavity and observed the PIP phenomenon for each sample. The PIP voltage depends on the area of the microcavity and is independent of the height of the microcavity. The PIP discharge current, I{sub PIP}, is proportional to the volume (Vol) of the microcavity and can be expressed by the formula I{sub PIP}=I{sub PIP0}+DxVol. For our samples, I{sub PIP0} (the discharge current when Vol is zero) is about zero and D (discharge current density) is about 3.95 mA mm{sup -3}. The error in D is 0.411 mA mm{sup -3} (less than 11% of D). When the CEMPD operates at V{sub PIP}, the discharge current is quite stable under different neon pressures.

Meng Lingguo; Lin Zhaojun [School of Physics, Shandong University, Jinan 250100 (China); Xing Jianping [School of Information Science and Engineering, Shandong University, Jinan 250100 (China); Liang Zhihu; Liu Chunliang [Key Laboratory of Physical Electronics and Devices of the Ministry of Education, Xi'an Jiaotong University, Xi'an 710049 (China)

2010-05-10

104

Robust signatures in the current-voltage characteristics of DNA molecules oriented between two graphene nanoribbon electrodes  

NASA Astrophysics Data System (ADS)

In this work, we numerically calculate the electric current through three kinds of DNA sequences (telomeric, ?-DNA and p53-DNA) described by different heuristic models. A bias voltage is applied between two zigzag edged graphene contacts attached to the DNA segments, while a gate terminal modulates the conductance of the molecule. Calculation of the current is performed by integrating the transmission function (calculated using the lattice Green's function) over the range of energies allowed by the chemical potentials. We show that a telomeric DNA sequence, when treated as a quantum wire in the fully coherent low-temperature regime, works as an excellent semiconductor. Clear steps are apparent in the current-voltage curves of telomeric sequences and are present independent of length and sequence initialization at the contacts. We also find that the molecule-electrode coupling can drastically influence the magnitude of the current. The difference between telomeric DNA and other DNAs, such as ?-DNA and DNA for the tumour suppressor p53, is particularly visible in the length dependence of the current.

Páez, Carlos J.; Schulz, Peter A.; Wilson, Neil R.; Römer, Rudolf A.

2012-09-01

105

Electrooptic matched filter controlled by independent voltages applied to multiple sets of electrodes  

E-print Network

V3 V4 V5 V6 V7 V8 ? ? ? ? ? ? ? ? ? ? ? LiNbO3 Ti:LiNbO3 lc lp? ? 26 Fig. 12. Selection of voltages in the structure of a single sideband..._ngr=0.08; period=21; lc=(179+3/4)*period; lp=(20+1/4)*period; L=lc*8+lp*7; lambda0=period*(n3-n1); lambdaj=lambda0-0.0016; npoints=2000; S=pi/(2*1.51*10^4); for int=1:npoints lambda = 1.37+0.0001*int; delta=2*pi*(n3-n1)*(1/lambda-1...

Kim, Changdong

2006-04-12

106

Electric and magnetic field measurements in a high voltage center.  

PubMed

This paper investigates the electric and magnetic fields inside a large high voltage center constituted both of 400/150 and 150/20 kV substation areas. Results of previous field measurements and calculations in substations, made by the authors of this paper or other researchers, are presented first. The basic data distinguishing the examined center from previously examined substations follow. The main results of the field measurements in the areas of the above-mentioned center are presented in relevant diagrams. General conclusions arising from the comparison of the measured field values with relevant reference levels in force for safe public and occupational exposure as well as with the results of previous research are finally given. PMID:21917821

Safigianni, Anastasia S; Spyridopoulos, Anastasios I; Kanas, Vasilis L

2012-01-01

107

Estimating the optimal number of membrane electrode assembly catalyst layers for proton exchange membrane fuel cell by considering open circuit voltage and polarization  

Microsoft Academic Search

This paper reports on a thin polymer membrane with a self-humidifying membrane electrode assembly (MEA) using water generated from the cathode. However, the open circuit voltage was low because the activation and diffusion polarizations were high. Therefore, a multilayered MEA was prepared for a proton exchange membrane fuel cell by the screen-printing method to reduce the two polarizations and improve

Daisuke Tashima; Yujiro Sakaguchi; Hiroaki Hidaka; Masahisa Otsubo

2010-01-01

108

Design of a micro-interdigitated electrode for impedance measurement performance in a biochemical assay  

E-print Network

The performance of interdigitated electrodes for impedance measurements is dependent upon the geometric design of the electrode pattern and can be significantly impacted by manufactured variability or defects. For processes ...

Donoghue, Linda (Linda Marie)

2011-01-01

109

Laser interferometric measurement of ion electrode shape and charge exchange erosion  

NASA Technical Reports Server (NTRS)

A novel projected fringe profilometry system was applied to surface contour measurements of an accelerator electrode from an ion thruster. The system permitted noncontact, nondestructive evaluation of the fine and gross structure of the electrode. A 3D surface map of a dished electrode was generated without altering the electrode surface. The same system was used to examine charge exchange erosion pits near the periphery of the electrode to determine the depth, location, and volume of material lost. This electro-optical measurement system allowed rapid nondestructive digital data acquisition coupled with automated computer data-processing. In addition, variable sensitivity allowed both coarse and fine measurements of objects having various surface finishes.

Macrae, Gregory S.; Mercer, Carolyn R.

1991-01-01

110

Laser interferometric measurement of ion electrode shape and charge exchange erosion  

NASA Technical Reports Server (NTRS)

A projected fringe profilometry system was applied to surface contour measurements of an accelerator electrode from an ion thrustor. The system permitted noncontact, nondestructive evaluation of the fine and gross structure of the electrode. A 3-D surface map of a dished electrode was generated without altering the electrode surface. The same system was used to examine charge exchange erosion pits near the periphery of the electrode to determine the depth, location, and volume of material lost. This electro-optical measurement system allowed rapid, nondestructive, digital data acquisition coupled with automated computer data processing. In addition, variable sensitivity allowed both coarse and fine measurements of objects having various surface finishes.

Macrae, Gregory S.; Mercer, Carolyn R.

1991-01-01

111

System for improving measurement accuracy of transducer by measuring transducer temperature and resistance change using thermoelectric voltages  

NASA Technical Reports Server (NTRS)

A constant current loop measuring system measures a property including the temperature of a sensor responsive to an external condition being measured. The measuring system includes thermocouple conductors connected to the sensor, sensing first and second induced voltages responsive to the external condition. In addition, the measuring system includes a current generator and reverser generating a constant current, and supplying the constant current to the thermocouple conductors in forward and reverse directions generating first and second measured voltages, and a determining unit receiving the first and second measured voltages from the current generator and reverser, and determining the temperature of the sensor responsive to the first and second measured voltages.

Anderson, Karl F. (inventor); Parker, Allen R., Jr. (inventor)

1993-01-01

112

Measuring Vitamin C Content of Commercial Orange Juice Using a Pencil Lead Electrode  

ERIC Educational Resources Information Center

A pencil lead successfully served as an electrode for the determination of ascorbic acid in commercial orange juice. Cyclic voltammetry was used as an electrochemical probe to measure the current produced from the oxidation of ascorbic acid with a variety of electrodes. The data demonstrate that the less expensive pencil lead electrode gives…

King, David; Friend, Jeffrey; Kariuki, James

2010-01-01

113

Measurement of ohmic voltage losses in individual cells of a PEMFC stack  

Microsoft Academic Search

The ohmic voltage loss in a fuel cell can be determined with the current interruption method. The method was utilized to measure the ohmic voltage loss in an individual cell of a fuel cell stack. This was achieved by producing voltage transients and monitoring them with a digital oscilloscope connected in parallel with the individual cell. In this study, the

Tuomas Mennola; Mikko Mikkola; Matti Noponen; Tero Hottinen; Peter Lund

2002-01-01

114

Ionization detector, electrode configuration and single polarity charge detection method  

DOEpatents

An ionization detector, an electrode configuration and a single polarity charge detection method each utilize a boundary electrode which symmetrically surrounds first and second central interlaced and symmetrical electrodes. All of the electrodes are held at a voltage potential of a first polarity type. The first central electrode is held at a higher potential than the second central or boundary electrodes. By forming the first and second central electrodes in a substantially interlaced and symmetrical pattern and forming the boundary electrode symmetrically about the first and second central electrodes, signals generated by charge carriers are substantially of equal strength with respect to both of the central electrodes. The only significant difference in measured signal strength occurs when the charge carriers move to within close proximity of the first central electrode and are received at the first central electrode. The measured signals are then subtracted and compared to quantitatively measure the magnitude of the charge. 10 figs.

He, Z.

1998-07-07

115

Ionization detector, electrode configuration and single polarity charge detection method  

DOEpatents

An ionization detector, an electrode configuration and a single polarity charge detection method each utilize a boundary electrode which symmetrically surrounds first and second central interlaced and symmetrical electrodes. All of the electrodes are held at a voltage potential of a first polarity type. The first central electrode is held at a higher potential than the second central or boundary electrodes. By forming the first and second central electrodes in a substantially interlaced and symmetrical pattern and forming the boundary electrode symmetrically about the first and second central electrodes, signals generated by charge carriers are substantially of equal strength with respect to both of the central electrodes. The only significant difference in measured signal strength occurs when the charge carriers move to within close proximity of the first central electrode and are received at the first central electrode. The measured signals are then subtracted and compared to quantitatively measure the magnitude of the charge.

He, Zhong (Ann Arbor, MI)

1998-01-01

116

Membrane reference electrode  

DOEpatents

A reference electrode utilizes a small thin, flat membrane of a highly conductive glass placed on a small diameter insulator tube having a reference material inside in contact with an internal voltage lead. When the sensor is placed in a non-aqueous ionic electrolytic solution, the concentration difference across the glass membrane generates a low voltage signal in precise relationship to the concentration of the species to be measured with high spatial resolution.

Redey, Laszlo (Downers Grove, IL); Bloom, Ira D. (Bolingbrook, IL)

1989-01-01

117

Membrane reference electrode  

DOEpatents

A reference electrode utilizes a small thin, flat membrane of a highly conductive glass placed on a small diameter insulator tube having a reference material inside in contact with an internal voltage lead. When the sensor is placed in a non-aqueous ionic electrolytic solution, the concentration difference across the glass membrane generates a low voltage signal in precise relationship to the concentration of the species to be measured, with high spatial resolution. 2 figs.

Redey, L.; Bloom, I.D.

1988-01-21

118

Low voltage charge-balanced capacitance–voltage conversion circuit for one-side-electrode-type fluid-based inclination sensor  

Microsoft Academic Search

A low voltage detection circuit for a capacitance sensor is important for connection to a low voltage digital circuit interface. We studied two different charge-balanced capacitance–voltage (C–V) conversion circuits configurations; the operational amplifier and the inverter amplifier. Both capacitance detection circuits were designed using 0.35?m CMOS circuitry technology. Both amplifiers used in the detection circuits were not affected by offset

Asrulnizam Bin Abd Manaf; Yoshinori Matsumoto

2009-01-01

119

A Cu-Plate-Bonded System-in-Package (SiP) With Low Spreading Resistance of Topside Electrodes for Voltage Regulators  

Microsoft Academic Search

This paper presents a system-in-package (SiP) with Cu-plate bonding for voltage regulators. The SiP reduces the power loss by 23% and the thermal resistance by 44% compared to those of a SiP with wire bonding. Copper plates reduce the spreading resistance of the topside electrodes in the MOSFETs, leading to lower power loss. They also act as heat spreaders, leading

Takayuki Hashimoto; Tomoaki Uno; Masaki Shiraishi; Tetsuya Kawashima; Noboru Akiyama; Nobuyoshi Matsuura; Hirofumi Akagi

2010-01-01

120

The use of virtual ground to control transmembrane voltages and measure bilayer currents in serial arrays of droplet interface bilayers  

NASA Astrophysics Data System (ADS)

The droplet interface bilayer (DIB) is a simple technique for constructing a stable lipid bilayer at the interface of two lipid-encased water droplets submerged in oil. Networks of DIBs formed by connecting more than two droplets constitute a new form of modular biomolecular smart material, where the transduction properties of a single lipid bilayer can affect the actions performed at other interface bilayers in the network via diffusion through the aqueous environments of shared droplet connections. The passive electrical properties of a lipid bilayer and the arrangement of droplets that determine the paths for transport in the network require specific electrical control to stimulate and interrogate each bilayer. Here, we explore the use of virtual ground for electrodes inserted into specific droplets in the network and employ a multichannel patch clamp amplifier to characterize bilayer formation and ion-channel activity in a serial DIB array. Analysis of serial connections of DIBs is discussed to understand how assigning electrode connections to the measurement device can be used to measure activity across all lipid membranes within a network. Serial arrays of DIBs are assembled using the regulated attachment method within a multi-compartment flexible substrate, and wire-type electrodes inserted into each droplet compartment of the substrate enable the application of voltage and measurement of current in each droplet in the array.

Sarles, Stephen A.

2013-09-01

121

Single Cell Measurement of Dopamine Release with Simultaneous Voltage-clamp and Amperometry  

PubMed Central

After its release into the synaptic cleft, dopamine exerts its biological properties via its pre- and post-synaptic targets1. The dopamine signal is terminated by diffusion2-3, extracellular enzymes4, and membrane transporters5. The dopamine transporter, located in the peri-synaptic cleft of dopamine neurons clears the released amines through an inward dopamine flux (uptake). The dopamine transporter can also work in reverse direction to release amines from inside to outside in a process called outward transport or efflux of dopamine5. More than 20 years ago Sulzer et al. reported the dopamine transporter can operate in two modes of activity: forward (uptake) and reverse (efflux)5. The neurotransmitter released via efflux through the transporter can move a large amount of dopamine to the extracellular space, and has been shown to play a major regulatory role in extracellular dopamine homeostasis6. Here we describe how simultaneous patch clamp and amperometry recording can be used to measure released dopamine via the efflux mechanism with millisecond time resolution when the membrane potential is controlled. For this, whole-cell current and oxidative (amperometric) signals are measured simultaneously using an Axopatch 200B amplifier (Molecular Devices, with a low-pass Bessel filter set at 1,000 Hz for whole-cell current recording). For amperometry recording a carbon fiber electrode is connected to a second amplifier (Axopatch 200B) and is placed adjacent to the plasma membrane and held at +700 mV. The whole-cell and oxidative (amperometric) currents can be recorded and the current-voltage relationship can be generated using a voltage step protocol. Unlike the usual amperometric calibration, which requires conversion to concentration, the current is reported directly without considering the effective volume7. Thus, the resulting data represent a lower limit to dopamine efflux because some transmitter is lost to the bulk solution. PMID:23207721

Saha, Kaustuv; Swant, Jarod; Khoshbouei, Habibeh

2012-01-01

122

Voltage dependent capacitance -- a measure of energy level bending in naphthalene-tetra-carboxylic- di-imide based transistors  

NASA Astrophysics Data System (ADS)

We demonstrate transient capacitance measurements using charge extraction by a linearly increasing voltage (CELIV) on the small molecule naphthalene-tetra-carboxylic- di-imide (NTCDI) based organic transistors. The OFETs use Aluminum (Al) and Aluminum Oxide (AlOx) as bottom gate and dielectric, with gold (Au) source and drain electrodes. The Al/AlOx gate is modified using two different self assembled monolayers, triethoxy(octyl)silane and perfluorooctyltriethoxysilane, in order to tune the turn-on voltage. We have clarified the voltage dependent capacitance in diode structures and found that when the transistor is in the fully on state a charge reservoir is formed at the AlOx interface and a saturation of the steady-state capacitance is seen, equaling the capacitance of the AlOx layer. When the transistor is in the fully off state the steady state capacitance saturates to the capacitance of the semiconductor bulk. We interpret this as a build-up of a charge reservoir in the semi conductor bulk when going from the off to the on state making it possible to charge the AlOx capacitance. By going from the on state towards the off state using a linearly increasing voltage pulse the dynamics of the depletion of the reservoir gives information about the energy level bending in the bulk.

Nyman, Mathias; Sandberg, Oskar; Martinez Hardigree, Josue; Kola, Srinivas; Katz, Howard; Osterbacka, Ronald

2013-03-01

123

A new gate current extraction technique for measurement of on-state breakdown voltage in HEMTs  

Microsoft Academic Search

We present a new simple three-terminal technique for measuring the on-state breakdown voltage in HEMTs. The gate current extraction technique involves grounding the source, and extracting a constant current from the gate. The drain current is then ramped from the off-state to the on-state, and the locus of drain voltage is measured. This locus of drain current versus drain voltage

Mark H. Somerville; Roxann Blanchard; J. A. del Alamo; G. Duh; P. C. Chao

1998-01-01

124

Electrode and Langmuir probe tools used for flow damping studies in the Helically Symmetric Experiment  

Microsoft Academic Search

A system of electrodes and Langmuir probes has been developed for the measurement of plasma flow damping in the Helically Symmetric Experiment (HSX) stellarator. A biased electrode is used to apply a J×B torque to the plasma. The fast switching electrode power supply allows the electrode voltage to be applied in ?1 ?s, which is much faster than any of

S. P. Gerhardt; D. T. Anderson; F. S. B. Anderson; J. N. Talmadge

2004-01-01

125

Electrode and Langmuir probe tools used for flow damping studies in the Helically Symmetric Experiment  

Microsoft Academic Search

A system of electrodes and Langmuir probes has been developed for the measurement of plasma flow damping in the Helically Symmetric Experiment (HSX) stellarator. A biased electrode is used to apply a J×B torque to the plasma. The fast switching electrode power supply allows the electrode voltage to be applied in ~1 mus, which is much faster than any of

S. P. Gerhardt; D. T. Anderson; F. S. B. Anderson; J. N. Talmadge

2004-01-01

126

Measuring surfactant concentration in plating solutions  

DOEpatents

An arrangement for measuring the concentration of surfactants in a electrolyte containing metal ions includes applying a DC bias voltage and a modulated voltage to a counter electrode. The phase angle between the modulated voltage and the current response to the modulated voltage at a working electrode is correlated to the surfactant concentration.

Bonivert, William D. (Livermore, CA); Farmer, Joseph C. (Livermore, CA); Hachman, John T. (Stockton, CA)

1989-01-01

127

Voltage Stability Analysis of a Multiple-Infeed Load Center Using Phasor Measurement Data  

Microsoft Academic Search

Voltage stability is a security concern for modern power systems. It can be analyzed using detailed or equivalent models. In this paper a new approach is presented for voltage stability analysis using synchronized phasor measurement data. Simple equivalent models of the interconnected system and load side at a measurement point are estimated from the data, and then used for calculating

Mostafa Parniani; Joe H. Chow; Luigi Vanfretti; Bharat Bhargava; Armando Salazar

2006-01-01

128

Measurement of serum lipase activity with the oxygen electrode.  

PubMed

We describe the measurement of lipase (triacylglycerol lipase; EC 3.1.1.3) in serum by continuous monitoring of relative rates of oxygen consumption with a polarographic oxygen electrode. The reactions described by Proelss and Wright (Clin. Chem. 23: 522-531, 1977) are used: trilinolein, with lipase catalysis, yields linoleic acid, which reacts with oxygen in the presence of lipoxygenase. Lipase activity is measured by comparing the zero order reaction rate of the specimen with that obtained with linoleic acid standards. Results for lipase (y) correlated well with those by the copper-soap method of Myrtle and Zell (x) (Clin. Chem. 21: 1469-1473, 1975); y = 0.33x - 11; r = 0.98; n = 34. Results are unaffected by specimen dilution, and the standard curve is linear to 520 U/L. Day-to-day precision (CV) is 10.4% for normal activities, 6.1% for above-normal activities. We believe the method offers a precise, practical approach to lipase analysis. PMID:7449101

Griebel, R J; Knoblock, E C; Koch, T R

1981-01-01

129

Measurement of effective piezoelectric coefficients of PZT thin films for energy harvesting application with interdigitated electrodes.  

PubMed

Interdigitated electrode (IDE) systems with lead zirconate titanate (PZT) thin films play an increasingly important role for two reasons: first, such a configuration generates higher voltages than parallel plate capacitor-type electrode (PPE) structures, and second, the application of an electric field leads to a compressive stress component in addition to the overall stress state, unlike a PPE structure, which results in tensile stress component. Because ceramics tend to crack at relatively moderate tensile stresses, this means that IDEs have a lower risk of cracking than PPEs. For these reasons, IDE systems are ideal for energy harvesting of vibration energy, and for actuators. Systematic investigations of PZT films with IDE systems have not yet been undertaken. In this work, we present results on the evaluation of the in-plane piezoelectric coefficients with IDE systems. Additionally, we also propose a simple and measurable figure of merit (FOM) to analyze and evaluate the relevant piezoelectric parameter for harvesting efficiency without the need to fabricate the energy harvesting device. Idealized effective coefficients e(IDE) and h(IDE) are derived, showing its composite nature with about one-third contribution of the transverse effect, and about two-thirds contribution of the longitudinal effect in the case of a PZT film deposited on a (100)-oriented silicon wafer with the in-plane electric field along one of the <011> Si directions. Randomly oriented 1-?m-thick PZT 53/47 film deposited by a sol-gel technique, was evaluated and yielded an effective coefficient e(IDE) of 15 C·m(-2). Our FOM is the product between effective e and h coefficient representing twice the electrical energy density stored in the piezoelectric film per unit strain deformation (both for IDE and PPE systems). Assuming homogeneous fields between the fingers, and neglecting the contribution from below the electrode fingers, the FOM for IDE structures with larger electrode gap is derived to be twice as large as for PPE structures, for PZT-5H properties. The experiments yielded an FOM of the IDE structures of 1.25 × 10(10) J/m(3) and 14 mV/? strain. PMID:22899110

Chidambaram, Nachiappan; Mazzalai, Andrea; Muralt, Paul

2012-08-01

130

Measurements of the volt-ampere characteristics and the breakdown voltages of direct-current helium and hydrogen discharges in microgaps  

SciTech Connect

The discharge phenomena for micro meter gap sizes include many interesting problems from engineering and physical perspectives. In this paper, the authors deal with the experimental and theoretical results of the breakdown voltage and current-voltage characteristics of the direct-current helium and hydrogen discharges. The measurements were performed at a constant pressure of around one atmosphere, while varying the gap size between two parallel plane tungsten electrodes between 1??m and 100??m. From the measured breakdown voltage curves, the effective yields and the ionization coefficients were derived for both gases. Present data for the ionization coefficients correlate with the data obtained for the breakdown voltage curves measured for fixed 100??m interelectrode separation. The current-voltage characteristics were plotted for the various gap sizes illustrating the role of the field emission effects in the microgaps. Based on the Fowler-Nordheim theory, the enhancement factors were determined. The gap spacing dependence of the field emission current can be explained by the introduction of two ideas, the first being a space charge effect by emitted electrons, and the second a change in the breakdown mechanism. Experimental results, presented here, demonstrate that Townsend phenomenology breaks down when field emission becomes the key mechanism affecting the breakdown and deforming the left hand side of the breakdown voltage curves.

Klas, M.; Matej?ik, Š. [Department of Experimental Physics, Comenius University, Mlynskadolina F2, 84248 Bratislava (Slovakia); Radjenovi?, B.; Radmilovi?-Radjenovi?, M. [Institute of Physics, University of Belgrade, P.O. Box 57, 11080 Belgrade (Serbia)

2014-10-15

131

Measurements of the volt-ampere characteristics and the breakdown voltages of direct-current helium and hydrogen discharges in microgaps  

NASA Astrophysics Data System (ADS)

The discharge phenomena for micro meter gap sizes include many interesting problems from engineering and physical perspectives. In this paper, the authors deal with the experimental and theoretical results of the breakdown voltage and current-voltage characteristics of the direct-current helium and hydrogen discharges. The measurements were performed at a constant pressure of around one atmosphere, while varying the gap size between two parallel plane tungsten electrodes between 1 ?m and 100 ?m. From the measured breakdown voltage curves, the effective yields and the ionization coefficients were derived for both gases. Present data for the ionization coefficients correlate with the data obtained for the breakdown voltage curves measured for fixed 100 ?m interelectrode separation. The current-voltage characteristics were plotted for the various gap sizes illustrating the role of the field emission effects in the microgaps. Based on the Fowler-Nordheim theory, the enhancement factors were determined. The gap spacing dependence of the field emission current can be explained by the introduction of two ideas, the first being a space charge effect by emitted electrons, and the second a change in the breakdown mechanism. Experimental results, presented here, demonstrate that Townsend phenomenology breaks down when field emission becomes the key mechanism affecting the breakdown and deforming the left hand side of the breakdown voltage curves.

Klas, M.; Matej?ik, Š.; Radjenovi?, B.; Radmilovi?-Radjenovi?, M.

2014-10-01

132

Measurement uncertainties arising from unpowered shipment of DC voltage references  

Microsoft Academic Search

Continuously powering the internal temperature-controlled oven provides best accuracy with Zener-diode-based DC voltage references. The hysteresis uncertainties arising from loss of power for two Fluke 732Bs are quantified. This establishes that these instruments can be shipped without battery power between national laboratories without adding significant uncertainty to a comparison

L. A. Christian; S. W. Chua; T. Y. Sim; L. X. Liu

2000-01-01

133

Development and Demonstration of Measurement-Time Efficient Methods for Impedance Spectroscopy of Electrode and Sensor Arrays  

PubMed Central

The development of impedance-based array devices is hindered by a lack of robust platforms and methods upon which to evaluate and interrogate sensors. One aspect to be addressed is the development of measurement-time efficient techniques for broadband impedance spectroscopy of large electrode arrays. The objective of this work was to substantially increase the low frequency impedance measurement throughput capability of a large channel count array analyzer by developing true parallel measurement methods. The goal was achieved by Fourier transform-based analysis of simultaneously-acquired multi-channel time-based current and voltage data. Efficacy and quantitative analysis of the parallel approach at frequencies less than ca. 10 Hz as well as a combined sequential + parallel approach for efficient broadband impedance spectroscopy over 5-orders of magnitude in frequency is demonstrated through complex impedance measurement of arrays consisting of up to 100 elements.

Cooper, Kevin R.; Smith, Matthew; Johnson, Derek

2008-01-01

134

Preparation and measurement of air electrodes for alkaline fuel cells  

NASA Astrophysics Data System (ADS)

The optimum structure and materials for the gas diffusion layer of air electrodes for alkaline fuel cells was studied. These electrodes contain carbon black, pretreated in different ways (e.g., boiling in nitric acid, heat treatment in different atmospheres) and polytetrafluorethylene as a hydrophobic binder. The samples were studied by different methods; air permeability, electrical conductivity, and porosity. Heat-treated cobolttetra methoxyphenyl porphyrine was used as a catalyst in the active layer.

Kivisaari, J.; Lamminen, J.; Lampinen, M. J.; Viitanen, M.

135

Preparation and measurement of air electrodes for alkaline fuel cells  

NASA Astrophysics Data System (ADS)

The optimum structure and materials for the gas diffusion layer of air electrodes for alkaline fuel cells were studied. These electrodes contain carbon black, pretreated in different ways ( e.g., boiling nitric acid, heat treatment in different atmospheres), and polytetrafluorethylene as a hydrophobic binder. The samples prepared were studied by different methods, e.g., air permeability, electrical conductivity and porosity. Heat-treated cobalttetramethoxyphenylporphyrine was used as catalyst in the active layer.

Kivisaari, Juhani; Lamminen, Jaakko; Lampinen, Markku J.; Viitanen, Minna

136

Time-resolved voltage measurements of Z-pinch radiation sources with a vacuum voltmeter  

SciTech Connect

A vacuum-voltmeter (VVM) was fielded on the Saturn pulsed power generator during a series of argon gas-puff Z-pinch shots. Time-resolved voltage and separately measured load current are used to determine several dynamic properties as the load implodes, namely, the inductance, L(t), net energy coupled to the load, E{sub coupled}(t), and the load radius, r(t). The VVM is a two-stage voltage divider, designed to operate at voltages up to 2 MV. The VVM is presently being modified to operate at voltages up to 6 MV for eventual use on the Z generator.

Murphy, D. P.; Allen, R. J.; Weber, B. V.; Commisso, R. J.; Apruzese, J. P. [Plasma Physics Division, Naval Research Laboratory, 4555 Overlook Ave. SW, Code 6770 Washington, DC 20375 (United States); Phipps, D. G.; Mosher, D. [L3 Communications/Titan Group, Reston, Virginia 20910 (United States)

2008-10-15

137

Generation of large-scale, barrier-free diffuse plasmas in air at atmospheric pressure using array wire electrodes and nanosecond high-voltage pulses  

SciTech Connect

This paper introduces a method to generate large-scale diffuse plasmas by using a repetition nanosecond pulse generator and a parallel array wire-electrode configuration. We investigated barrier-free diffuse plasmas produced in the open air in parallel and cross-parallel array line-line electrode configurations. We found that, when the distance between the wire-electrode pair is small, the discharges were almost extinguished. Also, glow-like diffuse plasmas with little discharge weakening were obtained in an appropriate range of line-line distances and with a cathode-grounding cross-electrode configuration. As an example, we produced a large-scale, stable diffuse plasma with volumes as large as 18?×?15?×?15?cm{sup 3}, and this discharge region can be further expanded. Additionally, using optical and electrical measurements, we showed that the electron temperature was higher than the gas temperature, which was almost the same as room temperature. Also, an array of electrode configuration with more wire electrodes had helped to prevent the transition from diffuse discharge to arc discharge. Comparing the current waveforms of configurations with 1 cell and 9 cells, we found that adding cells significantly increased the conduction current and the electrical energy delivered in the electrode gaps.

Teng, Yun; Li, Lee, E-mail: leeli@mail.hust.edu.cn; Liu, Yun-Long; Liu, Lun; Liu, Minghai [State Key Laboratory of AEET, School of Electric and Electronic Engineering, HuaZhong University of Science and Technology (HUST), Wuhan 430074 (China)

2014-10-15

138

Generation of large-scale, barrier-free diffuse plasmas in air at atmospheric pressure using array wire electrodes and nanosecond high-voltage pulses  

NASA Astrophysics Data System (ADS)

This paper introduces a method to generate large-scale diffuse plasmas by using a repetition nanosecond pulse generator and a parallel array wire-electrode configuration. We investigated barrier-free diffuse plasmas produced in the open air in parallel and cross-parallel array line-line electrode configurations. We found that, when the distance between the wire-electrode pair is small, the discharges were almost extinguished. Also, glow-like diffuse plasmas with little discharge weakening were obtained in an appropriate range of line-line distances and with a cathode-grounding cross-electrode configuration. As an example, we produced a large-scale, stable diffuse plasma with volumes as large as 18 × 15 × 15 cm3, and this discharge region can be further expanded. Additionally, using optical and electrical measurements, we showed that the electron temperature was higher than the gas temperature, which was almost the same as room temperature. Also, an array of electrode configuration with more wire electrodes had helped to prevent the transition from diffuse discharge to arc discharge. Comparing the current waveforms of configurations with 1 cell and 9 cells, we found that adding cells significantly increased the conduction current and the electrical energy delivered in the electrode gaps.

Teng, Yun; Li, Lee; Liu, Yun-Long; Liu, Lun; Liu, Minghai

2014-10-01

139

Expanded Electrochemical Capabilities of the Electrospray Ion Source using Porous Flow-Through Electrodes as the Upstream Ground and Emitter High Voltage Contact  

SciTech Connect

Use of a porous flow-through electrode at the upstream ground contact or at both the upstream ground contact and the high-voltage emitter contact in an electrospray ion source was shown to provide for new types of electrochemical experiments utilizing only the electrochemistry inherent to electrospray. The normal stainless steel bore-through union serving as the upstream grounding point in a floated electrospray emitter system was replaced with a high surface area porous flow-through electrode assembly to achieve effective electrochemical reduction of analytes at this point in positive ion mode, and effective electrochemical oxidation of analytes in negative ion mode. This was demonstrated by the oxidation of 3,4-dihydroxybenzoic acid and reserpine in negative ion mode and by the reduction of thionine in positive ion mode. In the case of reversible oxidation (3,4-dihydroxybenzoic acid) and reduction (thionine) processes, partial rereduction and reoxidation of the products due to reaction with products generated by cathodic and anodic processes at the emitter were observed, respectively. By implementing two high surface area porous flow-through electrodes in the system, one as the upstream grounding point and the other as the emitter electrode, a multiple-step reaction scheme was achieved that included consecutive electrochemical reduction and oxidation reactions and a following chemical reaction as demonstrated by the hydroquinone tagging of an initially disulfide-linked peptide.

Van Berkel, Gary J [ORNL; Kertesz, Vilmos [ORNL

2005-01-01

140

Voltage-probe-position dependence and magnetic-flux contribution to the measured voltage in ac transport measurements: which measuring circuit determines the real losses?  

SciTech Connect

The voltage V{sub ab} measured between two voltage taps a and b during magnetic flux transport in a type-II superconductor carrying current I is the sum of two contributions, the line integral from a to b of the electric field along an arbitrary path C{sub s} through the superconductor and a term proportional to the time rate of change of magnetic flux through the area bounded by the path C{sub s} and the measuring circuit leads. When the current I(t) is oscillating with time t, the apparent ac loss (the time average of the product IV{sub ab}) depends upon the measuring circuit used. Only when the measuring-circuit leads are brought out far from the surface does the apparent power dissipation approach the real (or true) ac loss associated with the length of sample probed. Calculations showing comparisons between the apparent and real ac losses in a flat strip of rectangular cross section will be presented, showing the behavior as a function of the measuring-circuit dimensions. Corresponding calculations also are presented for a sample of elliptical cross section.

Pe, T.; McDonald, J.; Clem, J.R.

1995-12-31

141

Optimization of the multi-electrode electrostatic sensor for velocity distribution measurement  

NASA Astrophysics Data System (ADS)

Measuring the velocity distribution of dilute gas-solid two-phase flow is necessary for industrial process monitor and control. However, in order to get correct measurement of the velocity distribution, the effective correlation calculation by non-corresponding side electrode couples of the electrostatic sensor was needed. By introducing the principle of electrostatic correlation based velocity distribution measurement method, the importance of the effective correlation calculation by non-corresponding side electrode couples was emphasized in this paper. In order to ensure effective correlation calculation by non-corresponding side electrode couples was emphasized in this paper. In order to ensure effective correlation calculation by non-corresponding side electrode couples, effective correlation analysis of multi-electrode electrostatic sensor was carried out and effective correlation analysis method was proposed. According to this method, the structure of multi-electrode electrostatic sensor was optimized. Finally, experimental results show that correlation calculation of non-corresponding side electrode couples could be done effectively by the optimized multi-electrode electrostatic sensor. This result lays a foundation for further research on velocity distribution measurement.

Wang, Chao; Zhang, Wenbiao; Wu, Weiping

2014-04-01

142

Comparison of dry-textile electrodes for electrical bioimpedance spectroscopy measurements  

NASA Astrophysics Data System (ADS)

Textile Electrodes have been widely studied for biopotentials recordings, specially for monitoring the cardiac activity. Commercially available applications, such as Adistar T-shirt and Textronics Cardioshirt, have proved a good performance for heart rate monitoring and are available worldwide. Textile technology can also be used for Electrical Bioimpedance Spectroscopy measurements enabling home and personalized health monitoring applications however solid ground research about the measurement performance of the electrodes must be done prior to the development of any textile-enabled EBI application. In this work a comparison of the measurement performance of two different types of dry-textile electrodes and manufacturers has been performed against standardized RedDot 3M Ag/AgCl electrolytic electrodes. 4-Electrode, whole body, Ankle-to-Wrist EBI measurements have been taken with the Impedimed spectrometer SFB7 from healthy subjects in the frequency range of 3kHz to 500kHz. Measurements have been taken with dry electrodes at different times to study the influence of the interaction skin-electrode interface on the EBI measurements. The analysis of the obtained complex EBI spectra shows that the measurements performed with textile electrodes produce constant and reliable EBI spectra. Certain deviation can be observed at higher frequencies and the measurements obtained with Textronics and Ag/AgCl electrodes present a better resemblance. Textile technology, if successfully integrated it, may enable the performance of EBI measurements in new scenarios allowing the rising of novel wearable monitoring applications for home and personal care as well as car safety.

Márquez, J. C.; Seoane, F.; Välimäki, E.; Lindecrantz, K.

2010-04-01

143

Determination of the inductance of imploding wire array Z-pinches using measurements of load voltage  

NASA Astrophysics Data System (ADS)

The inductance of imploding cylindrical wire array z-pinches has been determined from measurements of load voltage and current. A thorough analysis method is presented that explains how the load voltage of interest is found from raw signals obtained using a resistive voltage divider. This method is applied to voltage data obtained during z-pinch experiments carried out on the MAGPIE facility (1.4 MA, 240 ns rise-time) in order to calculate the load inductance and thereafter the radial trajectory of the effective current sheath during the snowplough implosion. Voltage and current are monitored very close to the load, allowing these calculations to be carried out without the need for circuit modelling. Measurements give a convergence ratio for the current of between 3.1 and 5.7 at stagnation of the pinch.

Burdiak, G. C.; Lebedev, S. V.; Hall, G. N.; Harvey-Thompson, A. J.; Suzuki-Vidal, F.; Swadling, G. F.; Khoory, E.; Pickworth, L.; Bland, S. N.; de Grouchy, P.; Skidmore, J.

2013-03-01

144

Mirror Langmuir probe: A technique for real-time measurement of magnetized plasma conditions using a single Langmuir electrode  

SciTech Connect

A new method for the real-time evaluation of the conditions in a magnetized plasma is described. The technique employs an electronic ''mirror Langmuir probe'' (MLP), constructed from bipolar rf transistors and associated high-bandwidth electronics. Utilizing a three-state bias wave form and active feedback control, the mirror probe's I-V characteristic is continuously adjusted to be a scaled replica of the ''actual'' Langmuir electrode immersed in a plasma. Real-time high-bandwidth measurements of the plasma's electron temperature, ion saturation current, and floating potential can thereby be obtained using only a single electrode. Initial tests of a prototype MLP system are reported, proving the concept. Fast-switching metal-oxide-semiconductor field-effect transistors produce the required three-state voltage bias wave form, completing a full cycle in under 1 {mu}s. Real-time outputs of electron temperature, ion saturation current, and floating potential are demonstrated, which accurately track an independent computation of these values from digitally stored I-V characteristics. The MLP technique represents a significant improvement over existing real-time methods, eliminating the need for multiple electrodes and sampling all three plasma parameters at a single spatial location.

LaBombard, B.; Lyons, L. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2007-07-15

145

Effects of Impulse Voltage Polarity, Peak Amplitude, and Rise Time on Streamers Initiated From a Needle Electrode in Transformer Oil  

E-print Network

An electrothermal hydrodynamic model is presented to evaluate effects of the applied lightning impulse voltage parameters such as polarity, magnitude, and rise time on the initiation and propagation of the streamers formed ...

Jadidian, Jouya

146

Calibration & measurement facilities for AC high current & high voltage ratio standards at NPL  

Microsoft Academic Search

Regular calibration of the Instrument Transformers (ITs) is very essential for the accurate measurement of power and energy\\u000a at high voltages. ITs are also used in the measurement of high currents & high voltages at power frequencies. The nominal\\u000a transformation of an IT depends only on the number of turns of its windings but due to various losses there are

S. R. Gupta

2009-01-01

147

High voltage coaxial switch  

DOEpatents

A coaxial high voltage, high current switch having a solid cylindrical cold cathode coaxially surrounded by a thin hollow cylindrical inner electrode and a larger hollow cylindrical outer electrode. A high voltage trigger between the cathode and the inner electrode causes electrons to be emitted from the cathode and flow to the inner electrode preferably through a vacuum. Some of the electrons penetrate the inner electrode and cause a volumetric discharge in the gas (which may be merely air) between the inner and outer electrodes. The discharge provides a low impedance path between a high voltage charge placed on the outer electrode and a load (which may be a high power laser) coupled to the inner electrode. For high repetition rate the gas between the inner and outer electrodes may be continuously exchanged or refreshed under pressure.

Rink, John P. (Los Alamos, NM)

1983-07-19

148

High voltage coaxial switch  

DOEpatents

A coaxial high voltage, high current switch having a solid cylindrical cold cathode coaxially surrounded by a thin hollow cylindrical inner electrode and a larger hollow cylindrical outer electrode. A high voltage trigger between the cathode and the inner electrode causes electrons to be emitted from the cathode and flow to the inner electrode preferably through a vacuum. Some of the electrons penetrate the inner electrode and cause a volumetric discharge in the gas (which may be merely air) between the inner and outer electrodes. The discharge provides a low impedance path between a high voltage charge placed on the outer electrode and a load (which may be a high power laser) coupled to the inner electrode. For high repetition rate the gas between the inner and outer electrodes may be continuously exchanged or refreshed under pressure. 3 figs.

Rink, J.P.

1983-07-19

149

Electrode-Skin contact impedance: In vivo measurements on an ovine model  

NASA Astrophysics Data System (ADS)

The problem of electrical impedance between the skin and the electrode is an on-going challenge in bio-electronics. This is particularly true in the case of Electrical Impedance Tomography (EIT), which uses a large number of skin-contact electrodes and is very sensitive to noise. In the present article, contact impedance is measured and compared for a range of electrodes placed on the thorax of an ovine model. The study has been approved by the Westmead Hospital Animal Ethics Committee. The electrode models that were employed in the research are Ag/AgCl electrodes (E1), commonly used for ECG and EIT measurements in both humans and animal models, stainless steel crocodile clips (E2), typically used on animal models, and novel multi-point dry electrodes in two modifications: bronze plated (E3) and nickel plated (E4). Further, since the contact impedance is mostly attributed to the acellular outer layer of the skin, in our experiment, we attempted to study the effect of this layer by comparing the results when the skin is intact and when electrodes are introduced underneath the skin through small cuts. This boundary effect was assessed by comparison of measurements obtained during E2 skin surface contact, and sub-cutaneous contact (E5). Twelve gauge intradermal needles were also tested as an electrode (E6). The full impedance spectrum, from 500 Hz to 300 kHz, was recorded, analysed and compared. As expected, the contact impedance in the more invasive cases, i.e the electrodes under the skin, is significantly lower than in the non-invasive cases. At the frequency of 50 kHz which is commonly used in lung EIT acquisition, electrodes E3, E4 and E6 demonstrated contact impedance of less than 200 ?, compared to more than 400 ? measured for electrodes E1, E2 and E5. In conclusion, the novel multipoint electrodes proved to be best suited for EIT purposes, because they are non-invasive and have lower contact impedance than Ag/AgCl and crocodile clips, in both invasive and non-invasive cases. This further prompted us to design a flexible electrode belt using the novel multi-point electrodes for lung EIT on animal models.

Nguyen, D. T.; Kosobrodov, R.; Barry, M. A.; Chik, W.; Jin, C.; Oh, T. I.; Thiagalingam, A.; McEwan, A.

2013-04-01

150

Cavitation in the vicinity of the high-voltage electrode as a key step of nanosecond breakdown in liquids  

NASA Astrophysics Data System (ADS)

Fast shadowgraphy of nanosecond discharge in liquids with different dielectric permittivity, namely in water, ethanol and n-pentane, has been performed. Formation of a gas cavity at a nanosecond time scale was observed as a pre-breakdown phenomenon at amplitudes of the high-voltage pulse close to the breakdown threshold. This phenomenon is considered as a possible key step of high-voltage breakdown in polar liquids.

Marinov, I.; Guaitella, O.; Rousseau, A.; Starikovskaia, S. M.

2013-08-01

151

Stark broadening measurement of the electron density in an atmospheric pressure argon plasma jet with double-power electrodes  

SciTech Connect

Characteristics of a double-power electrode dielectric barrier discharge of an argon plasma jet generated at the atmospheric pressure are investigated in this paper. Time-averaged optical emission spectroscopy is used to measure the plasma parameters, of which the excitation electron temperature is determined by the Boltzmann's plot method whereas the gas temperature is estimated using a fiber thermometer. Furthermore, the Stark broadening of the hydrogen Balmer H{sub {beta}} line is applied to measure the electron density, and the simultaneous presence of comparable Doppler, van der Waals, and instrumental broadenings is discussed. Besides, properties of the jet discharge are also studied by electrical diagnosis. It has been found that the electron densities in this argon plasma jet are on the order of 10{sup 14} cm{sup -3}, and the excitation temperature, gas temperature, and electron density increase with the applied voltage. On the other hand, these parameters are inversely proportional to the argon gas flow rate.

Qian Muyang; Ren Chunsheng; Wang Dezhen; Zhang Jialiang; Wei Guodong [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China)

2010-03-15

152

A new measurement method for electrode gain in an orthogonally symmetric beam position monitor  

NASA Astrophysics Data System (ADS)

The new beam position monitor (BPM) system of the injector at the upgrade project of the Hefei Light Source (HLS II) has 19 stripline beam position monitors. Most consist of four orthogonally symmetric stripline electrodes. Differences in electronic gain and mismachining tolerance can cause changes in the beam response of the BPM electrodes. This variation will couple the two measured horizontal positions, resulting in measuring error. To alleviate this effect, a new technique to measure the relative response of the four electrodes has been developed. It is independent of the beam charge, and the related coefficient can be calculated theoretically. The effect of electrode coupling on this technique is analyzed. The calibration data is used to fit the gain for all 19 injector beam position monitors. The results show the standard deviation of the distribution of measured gains is about 5%.

Zou, Jun-Ying; Wu, Fang-Fang; Yang, Yong-Liang; Sun, Bao-Gen; Zhou, Ze-Ran; Luo, Qing; Lu, Ping; Xu, Hong-Liang

2014-12-01

153

Electrode size and boundary condition independent measurement of the effective piezoelectric coefficient of thin films  

NASA Astrophysics Data System (ADS)

The determination of the piezoelectric coefficient of thin films using interferometry is hindered by bending contributions. Using finite element analysis (FEA) simulations, we show that the Lefki and Dormans approximations using either single or double-beam measurements cannot be used with finite top electrode sizes. We introduce a novel method for characterising piezoelectric thin films which uses a differential measurement over the discontinuity at the electrode edge as an internal reference, thereby eliminating bending contributions. This step height is shown to be electrode size and boundary condition independent. An analytical expression is derived which gives good agreement with FEA predictions of the step height.

Stewart, M.; Lepadatu, S.; McCartney, L. N.; Cain, M. G.; Wright, L.; Crain, J.; Newns, D. M.; Martyna, G. J.

2015-02-01

154

Megavolt range voltage measurement in vacuum through a short-circuited line  

SciTech Connect

Method of voltage measurement at a vacuum load by means of homogeneous short-circuited vacuum-isolated line was considered. Prior to appearance of a measured high-voltage pulse, a magnetic field is formed in the line due to the bias current. Biasing provides fulfillment of magnetic electron isolation conditions and strong pressing of an electron layer down to the cathode already at the voltage wave front. As a result, a weak change of the ''hot'' line wave impedance is achieved during a pulse. Theoretical consideration and numerical simulation of the measuring line operation in the presence of bias current basing the applicability of the method was carried out. The method was used to determine the plasma-filled diode voltage at a megavolt voltage level. The absence of electron leakages at the voltage wave propagation of the amplitude {approx_equal}1 MV along the measuring line of the length 2.3 m with the wave impedance of 136 {Omega} and initial bias current of {approx_equal}6 kA was realized.

Belomyttsev, S. Ya.; Grishkov, A. A.; Kovalchuk, B. M.; Pedin, N. N.; Zherlitsyn, A. A. [Institute of High Current Electronics, 2/3 Academichesky Avenue, 634055 Tomsk (Russian Federation)

2011-10-15

155

Dielectric-wall linear accelerator with a high voltage fast rise time switch that includes a pair of electrodes between which are laminated alternating layers of isolated conductors and insulators  

DOEpatents

A dielectric-wall linear accelerator is improved by a high-voltage, fast rise-time switch that includes a pair of electrodes between which are laminated alternating layers of isolated conductors and insulators. A high voltage is placed between the electrodes sufficient to stress the voltage breakdown of the insulator on command. A light trigger, such as a laser, is focused along at least one line along the edge surface of the laminated alternating layers of isolated conductors and insulators extending between the electrodes. The laser is energized to initiate a surface breakdown by a fluence of photons, thus causing the electrical switch to close very promptly. Such insulators and lasers are incorporated in a dielectric wall linear accelerator with Blumlein modules, and phasing is controlled by adjusting the length of fiber optic cables that carry the laser light to the insulator surface. 12 figs.

Caporaso, G.J.; Sampayan, S.E.; Kirbie, H.C.

1998-10-13

156

Dielectric-wall linear accelerator with a high voltage fast rise time switch that includes a pair of electrodes between which are laminated alternating layers of isolated conductors and insulators  

DOEpatents

A dielectric-wall linear accelerator is improved by a high-voltage, fast rise-time switch that includes a pair of electrodes between which are laminated alternating layers of isolated conductors and insulators. A high voltage is placed between the electrodes sufficient to stress the voltage breakdown of the insulator on command. A light trigger, such as a laser, is focused along at least one line along the edge surface of the laminated alternating layers of isolated conductors and insulators extending between the electrodes. The laser is energized to initiate a surface breakdown by a fluence of photons, thus causing the electrical switch to close very promptly. Such insulators and lasers are incorporated in a dielectric wall linear accelerator with Blumlein modules, and phasing is controlled by adjusting the length of fiber optic cables that carry the laser light to the insulator surface.

Caporaso, George J. (Livermore, CA); Sampayan, Stephen E. (Manteca, CA); Kirbie, Hugh C. (Dublin, CA)

1998-01-01

157

Oxidation of S(IV) in Seawater by Pulsed High Voltage Discharge Plasma with TiO2/Ti Electrode as Catalyst  

NASA Astrophysics Data System (ADS)

Oxidation of S(IV) to S(VI) in the effluent of a flue gas desulfurization(FGD) system is very critical for industrial applications of seawater FGD. This paper reports a pulsed corona discharge oxidation process combined with a TiO2 photocatalyst to convert S(IV) to S(VI) in artificial seawater. Experimental results show that the oxidation of S(IV) in artificial seawater is enhanced in the pulsed discharge plasma process through the application of TiO2 coating electrodes. The oxidation rate of S(IV) using Ti metal as a ground electrode is about 2.0×10-4 mol · L-1 · min-1, the oxidation rate using TiO2/Ti electrode prepared by annealing at 500°C in air is 4.5×10-4 mol · L-1 · min-1, an increase with a factor 2.25. The annealing temperature for preparing TiO2/Ti electrode has a strong effect on the oxidation of S(IV) in artificial seawater. The results of in-situ emission spectroscopic analysis show that chemically active species (i.e. hydroxyl radicals and oxygen radicals) are produced in the pulsed discharge plasma process. Compared with the traditional air oxidation process and the sole plasma-induced oxidation process, the combined application of TiO2 photocatalysts and a pulsed high-voltage electrical discharge process is useful in enhancing the energy and conversion efficiency of S(IV) for the seawater FGD system.

Gong, Jianying; Zhang, Xingwang; Wang, Xiaoping; Lei, Lecheng

2013-12-01

158

Series asymmetric supercapacitors based on free-standing inner-connection electrodes for high energy density and high output voltage  

NASA Astrophysics Data System (ADS)

Asymmetric supercapacitors (ASCs) based on free-standing membranes with high energy density and high output voltage are reported. MnO2 nanowire/carbon nanotube (CNT) composites and MoO3 nanobelt/CNT composites are selected as the anode and the cathode materials of the devices, respectively. The ASC has a high volumetric capacitance of 50.2 F cm-3 at a scan rate of 2 mV s-1 and a high operation voltage window of 2.0 V. Especially, after a middle layer with an inner-connection structure was inserted between the anode and the cathode, the output voltage of the whole device can achieve 4.0 V. The full cell of series ASCs (SASC) with an inner-connection middle layer has a high energy density of 28.6 mW h cm-3 at a power density of 261.4 mW cm-3, and exhibits excellent cycling performance of 99.6% capacitance retention over 10 000 cycles. This strategy of designing the hybridized structure for SASCs provides a promising route for next-generation SCs with high energy density and high output voltage.Asymmetric supercapacitors (ASCs) based on free-standing membranes with high energy density and high output voltage are reported. MnO2 nanowire/carbon nanotube (CNT) composites and MoO3 nanobelt/CNT composites are selected as the anode and the cathode materials of the devices, respectively. The ASC has a high volumetric capacitance of 50.2 F cm-3 at a scan rate of 2 mV s-1 and a high operation voltage window of 2.0 V. Especially, after a middle layer with an inner-connection structure was inserted between the anode and the cathode, the output voltage of the whole device can achieve 4.0 V. The full cell of series ASCs (SASC) with an inner-connection middle layer has a high energy density of 28.6 mW h cm-3 at a power density of 261.4 mW cm-3, and exhibits excellent cycling performance of 99.6% capacitance retention over 10 000 cycles. This strategy of designing the hybridized structure for SASCs provides a promising route for next-generation SCs with high energy density and high output voltage. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr04819a

Tao, Jiayou; Liu, Nishuang; Rao, Jiangyu; Ding, Longwei; Al Bahrani, Majid Raissan; Li, Luying; Su, Jun; Gao, Yihua

2014-11-01

159

Method of glass melter electrode length measurement using time domain reflectometry (TDR)  

SciTech Connect

The present invention overcomes the drawbacks inherent in the prior art and solves the problems inherent in conventional Joule-heated vitrification melters, where the melter preferably comprises a vessel having a refractory liner and an opening for receiving material which is converted into molten vitreous material in the vessel. The vessel has an outlet port for removing molten vitreous material from the vessel. A plurality of electrodes is disposed in the vessel and electrical energy is passed between electrode pairs through feed material and molten vitreous material in the vessel. Typically, the electrodes erode and wear in time, and this invention seeks to monitor and evaluate the length and condition of the electrodes. The present invention uses time domain reflectometry (TDR) methods to accurately measure the length of an electrode that is subject to wear and electrolytic decomposition due to the extreme conditions in which the electrode is required to operate. Specifically, TDR would be used to measure the length and effects of erosion of molybdenum electrodes used in Joule-heated vitrification melter. Of course, the inventive concept should not be limited to this preferred environment.

Tarpley, James M.; Zamecnik, John R.

2000-02-28

160

A High-Resolution Hybrid Digital Wattmeter for Measurements at High Voltage  

Microsoft Academic Search

A development of a high-voltage high-resolution digital sampling wattmeter system for on-site\\/in-situ calibrations of metering systems for high-voltage power\\/energy measurements is described in the paper. The current input uses an optically isolated hybrid two-stage current transformer with electronic circuitry that performs A\\/D conversion. Data is transmitted to a ground station through a fiber optic link. Another laser-driven fiber optic link

Branislav Djokic; E. So

2008-01-01

161

Measurements of transient electrical noise on low voltage distribution systems  

Microsoft Academic Search

Electrical noise measurements which were undertaken in preparation of designing a low-frequency (below 100 kHz) carrier current system for use in protective relaying are discussed. Steady-state measurements were made to assess the fluctuating noise level on a 600 V bus over a 24 hour period, and transient measurements were taken to discover the extent of the electrical noise generated in

PETER T. ASHTON; GLENN W. SWIFT

1990-01-01

162

Improvement of Electrical Stimulation Protocol for Simultaneous Measurement of Extracellular Potential with On-Chip Multi-Electrode Array System  

NASA Astrophysics Data System (ADS)

Cardiotoxicity testing with a multi-electrode array (MEA) system requires the stable beating of cardiomyocytes for the measurement of the field potential duration (FPD), because different spontaneous beating rates cause different responses of FPD prolongation induced by drugs, and the beating rate change effected by drugs complicates the FPD prolongation assessment. We have developed an on-chip MEA system with electrical stimulation for the measurement of the FPD during the stable beating of human embryonic stem (ES) cell-derived cardiomyocyte clusters. Using a conventional bipolar stimulation protocol, we observed such large artifacts in electrical stimulation that we could not estimate the FPD quantitatively. Therefore, we improved the stimulation protocol by using sequential rectangular pulses in which the positive and negative stimulation voltages and number of pulses could be changed flexibly. The balanced voltages and number of pulses for sequential rectangular pulses enabled the recording of small negative artifacts only, which hardly affected the FPD measurement of human-ES-cell-derived cardiomyocyte clusters. These conditions of electrical stimulation are expected to find applications for the control of constant beating for cardiotoxicity testing.

Kaneko, Tomoyuki; Nomura, Fumimasa; Hattori, Akihiro; Yasuda, Kenji

2012-06-01

163

Potentiometric measurement of polymer-membrane electrodes based on lanthanum  

NASA Astrophysics Data System (ADS)

Quantitative analysis of rare earth elements which are considered as the standard method that has a high accuracy, and detection limits achieved by the order of ppm is inductively coupled plasma atomic emission spectroscopy (ICPAES). But these tools are expensive and valuable analysis of the high cost of implementation. In this study be made and characterized selective electrode for the determination of rare earth ions is potentiometric. Membrane manufacturing techniques studied is based on immersion (liquid impregnated membrane) in PTFE 0.5 pore size. As ionophores to be used tri butyl phosphate (TBP) and bis(2-etylhexyl) hydrogen phosphate. There is no report previously that TBP used as ionophore in polymeric membrane based lanthanum. Some parameters that affect the performance of membrane electrode such as membrane composition, membrane thickness, and types of membrane materials studied in this research. Manufacturing of Ion Selective Electrodes (ISE) Lanthanum (La) by means of impregnation La membrane in TBP in kerosene solution has been done and showed performance for ISE-La. FTIR spectrum results for PTFE 0.5 pore size which impregnated in TBP and PTFE blank showed difference of spectra in the top 1257 cm-1, 1031 cm-1 and 794.7 cm-1 for P=O stretching and stretching POC from group -OP =O. The result showed shift wave number for P =O stretching of the cluster (-OP=O) in PTFE-TBP mixture that is at the peak of 1230 cm-1 indicated that no interaction bond between hydroxyl group of molecules with molecular clusters fosforil of TBP or R3P = O. The membrane had stable responses in pH range between 1 and 9. Good responses were obtained using 10-3 M La(III) internal solution, which produced relatively high potential. ISE-La showed relatively good performances. The electrode had a response time of 29±4.5 second and could be use for 50 days. The linear range was between 10-5 and 10-1 M.

Saefurohman, Asep; Buchari, Noviandri, Indra; Syoni

2014-03-01

164

A new geometric factor for in situ resistivity measurement using four slender cylindrical electrodes.  

PubMed

The four-electrode method is commonly used for in situ measurement of the electrical resistivity of biological tissues. In this paper, a new geometric factor between the resistivity and measured resistance using the four-electrode interface is derived in the prolate spheroidal coordinates and experimentally validated. Evaluation of the experimental results shows that the resistivities determined using both the derived geometric factor and a commercial conductivity meter are in close agreement even when the length of the immersed electrodes becomes long with respect to the inter-electrode spacing. The evaluation also shows the effect of the relative size of the sample volume when the limitation to semi-infinite volume begins to result in poor accuracy. PMID:18269995

Chong, Chee-Earn; Tan, Yoke-Lin

2008-02-01

165

Effect of current compliance and voltage sweep rate on the resistive switching of HfO2/ITO/Invar structure as measured by conductive atomic force microscopy  

NASA Astrophysics Data System (ADS)

The electrical characterization of HfO2/ITO/Invar resistive switching memory structure was studied using conductive atomic force microscopy (AFM) with a semiconductor parameter analyzer, Agilent 4156C. The metal alloy Invar was used as the metal substrate to ensure good ohmic contact with the substrate holder of the AFM. A conductive Pt/Ir AFM tip was placed in direct contact with the HfO2 surface, such that it acted as the top electrode. Nanoscale current-voltage (I-V) characteristics of the HfO2/ITO/Invar structure were measured by applying a ramp voltage through the conductive AFM tip at various current compliances and ramp voltage sweep rates. It was found that the resistance of the low resistance state (RLRS) decreased with increasing current compliance value, but resistance of high resistance state (RHRS) barely changed. However, both the RHRS and RLRS decreased as the voltage sweep rate increased. The reasons for this dependency on current compliance and voltage sweep rate are discussed.

Wu, You-Lin; Liao, Chun-Wei; Ling, Jing-Jenn

2014-06-01

166

Practical nitric oxide measurement employing a nitric oxide-selective electrode  

NASA Astrophysics Data System (ADS)

An NO-selective electrode was developed as an easily applicable tool for a real-time nitric oxide (NO) measurement. The working electrode (0.2 mm diam) was made from Pt/Ir alloy coated with a three-layered membrane. The counterelectrode was made from a carbon fiber. When a stable NO donor, S-nitroso-N-acetyl-dl-penicillamine, was applied, the electrode current increased in a dose-dependent fashion. The current and calculated NO concentration showed a linear relationship in the range from 0.2 nM (S/N=1) to 1 ?M of NO. The response of the electrode was 1.14±0.09 s. The effects of temperature, pH, and chemicals other than NO on the electrode current were also evaluated. Electrodes which were placed in the luminal side of rat aortic rings exhibited 30 pA of current due to NO generation induced by the addition of 10-6 M of acetylcholine. The current was eliminated in the presence of 50 ?M NG-monomethyl-L-arginine, an inhibitor of NO synthase. Thus, this NO-selective electrode is applicable to real-time NO assay in biological systems.

Ichimori, K.; Ishida, H.; Fukahori, M.; Nakazawa, H.; Murakami, E.

1994-08-01

167

The Coefficient of the Voltage Induced Frequency Shift Measurement on a Quartz Tuning Fork  

PubMed Central

We have measured the coefficient of the voltage induced frequency shift (VIFS) of a 32.768 KHz quartz tuning fork. Three vibration modes were studied: one prong oscillating, two prongs oscillating in the same direction, and two prongs oscillating in opposite directions. They all showed a parabolic dependence of the eigen-frequency shift on the bias voltage applied across the fork, due to the voltage-induced internal stress, which varies as the fork oscillates. The average coefficient of the VIFS effect is as low as several hundred nano-Hz per millivolt, implying that fast-response voltage-controlled oscillators and phase-locked loops with nano-Hz resolution can be built. PMID:25414971

Hou, Yubin; Lu, Qingyou

2014-01-01

168

Measuring bi-directional current through a field-effect transistor by virtue of drain-to-source voltage measurement  

DOEpatents

A method and apparatus for measuring current, and particularly bi-directional current, in a field-effect transistor (FET) using drain-to-source voltage measurements. The drain-to-source voltage of the FET is measured and amplified. This signal is then compensated for variations in the temperature of the FET, which affects the impedance of the FET when it is switched on. The output is a signal representative of the direction of the flow of current through the field-effect transistor and the level of the current through the field-effect transistor. Preferably, the measurement only occurs when the FET is switched on.

Turner, Steven Richard

2006-12-26

169

A miniature all-solid-state calcium electrode applied to in situ seawater measurement  

NASA Astrophysics Data System (ADS)

An all-solid-state miniature calcium ion selective electrode (ISE) based on poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonate) (PEDOT(PSS)) for continuous in situ measurement in seawater was studied. The electrode substrate was a platinum (Pt) wire of 0.5 mm diameter and PEDOT(PSS) was electropolymerized on one end of the Pt wire to act as the solid contact of this calcium ISE. The PEDOT(PSS) layer was covered with a calcium-selective poly(vinyl chloride) membrane, which contained ETH129 as calcium ionophore, potassium tetrakis-(p-chlorophenyl)borate as lipophilic anion and bis(2-ethylhexyl) sebacate as the plasticizer. Experiments using electrochemical impedance spectroscopy and reversed chronopotentiometry illustrated that electropolymerized PEDOT(PSS) decreased the resistance and improved the stability of the electrode. The sensors can work stably in the calcium ion concentration range of 10-6-10-1 mol L-1 with the slope of 27.7 mV/decade. Also Na+, K+ and Mg2+ can hardly interfere with the performance of the electrode. This electrode was applied to measure the calcium ion concentration of seawater samples. The experimental data showed that the electrode can resist the corrosion of seawater and its reproducibility was good (SD < 0.1 mM kg-1). The lifetime of such an electrode was at least six months. Because of the wire-shape and the small size of such a liquid junction free calcium electrode, it is pressure-resistant and easy to package and seal, therefore it is suitable for use in underwater equipment for in situ seawater measurement.

Xu, Hui; Wang, You; Luo, Zhiyuan; Pan, Yiwen

2013-12-01

170

Front-end-of-line quadrature-clocked voltage-dependent capacitance measurement  

Microsoft Academic Search

We report on Front-End-Of-Line Quadrature-clocked Voltage-dependent Capacitance Measurement (QVCM), a charge based capacitance measurement technique applicable to modern logic CMOS technologies with leaky gate oxides. QVCM test structures are designed using only first level of metal and support parallel test of multiple devices. Results for 45 nm SOI FETs illustrate the power of the developed technique.

Stas Polonsky; Paul Solomon; Jiun-hsin Liao; Lou Medina; Mark Ketchen

2011-01-01

171

Effect of test conditions and sample configuration on the AMTEC electrode/electrolyte characteristics measurements in the Sodium Exposure Test Cell experiment  

E-print Network

/electrolyte configurations. Temperature at the electrode 562 C. Temperature in the sodium pool 193 . . 80 4. Parameters measured in SETC for two different electrode/electrolyte configurations. Temperature at the electrode 698 C. Temperature in the sodium pool 230 C . 80... 5. Parameters measured in SETC for two different electrode/electrolyte configurations. Temperature at the electrode 811 C. Temperature in the sodium pool 271 C . 80 6. Parameters measured in SETC for two different electrode...

Azimov, Ulughbek Bakhadirovich

2001-01-01

172

Advanced Ring-Shaped Microelectrode Assay Combined with Small Rectangular Electrode for Quasi-In vivo Measurement of Cell-to-Cell Conductance in Cardiomyocyte Network  

NASA Astrophysics Data System (ADS)

To predict the risk of fatal arrhythmia induced by cardiotoxicity in the highly complex human heart system, we have developed a novel quasi-in vivo electrophysiological measurement assay, which combines a ring-shaped human cardiomyocyte network and a set of two electrodes that form a large single ring-shaped electrode for the direct measurement of irregular cell-to-cell conductance occurrence in a cardiomyocyte network, and a small rectangular microelectrode for forced pacing of cardiomyocyte beating and for acquiring the field potential waveforms of cardiomyocytes. The advantages of this assay are as follows. The electrophysiological signals of cardiomyocytes in the ring-shaped network are superimposed directly on a single loop-shaped electrode, in which the information of asynchronous behavior of cell-to-cell conductance are included, without requiring a set of huge numbers of microelectrode arrays, a set of fast data conversion circuits, or a complex analysis in a computer. Another advantage is that the small rectangular electrode can control the position and timing of forced beating in a ring-shaped human induced pluripotent stem cell (hiPS)-derived cardiomyocyte network and can also acquire the field potentials of cardiomyocytes. First, we constructed the human iPS-derived cardiomyocyte ring-shaped network on the set of two electrodes, and acquired the field potential signals of particular cardiomyocytes in the ring-shaped cardiomyocyte network during simultaneous acquisition of the superimposed signals of whole-cardiomyocyte networks representing cell-to-cell conduction. Using the small rectangular electrode, we have also evaluated the response of the cell network to electrical stimulation. The mean and SD of the minimum stimulation voltage required for pacing (VMin) at the small rectangular electrode was 166+/-74 mV, which is the same as the magnitude of amplitude for the pacing using the ring-shaped electrode (179+/-33 mV). The results showed that the addition of a small rectangular electrode into the ring-shaped electrode was effective for the simultaneous measurement of whole-cell-network signals and single-cell/small-cluster signals on a local site in the cell network, and for the pacing by electrical stimulation of cardiomyocyte networks.

Nomura, Fumimasa; Kaneko, Tomoyuki; Hamada, Tomoyo; Hattori, Akihiro; Yasuda, Kenji

2013-06-01

173

Electrical measurement of a high-frequency, high-capacitance piezoceramic resonator with resistive electrodes.  

PubMed

In a thin and large area PZT-ceramics piezoresonator (PR) with relatively low resonance impedance, caused by high-frequency resonance and high PR capacitance, the effect of electrode resistivity and parasitic resistive and inductive elements in the measurement fixture results in significant distortion of the measured thickness-mode (longitudinal TL, shear TS) resonance response-resonance frequency shifts and characteristics deformation. This distortion may not allow the precise measurement of the PR characteristic frequencies, quality factor, and electromechanical coupling coefficient so essential to a complete PR and material characterization. A theoretical description of the "energy-trap" phenomena in a thickness-vibrating PR with resistive electrodes is presented. To interpret electrical measurements, the electromechanical model, including for completeness both the PR with resistive electrodes (as a system with distributed parameters) and the measurement fixture, is developed. The method of two contact points on the electrode provides deep sharpening and exact determination of the PR resonance. For the optimal disposition of the contact fingers, the resonance bandwidth of a real PR with resistive electrodes is even more pointed than that for the ideal PR. PMID:16245592

Mezheritsky, Alex V

2005-08-01

174

Current-Voltage Measurements in a 2G YBCO Coil  

SciTech Connect

Abstract- The Oak Ridge National Laboratory in collaboration with American Superconductor Corporation and Cryomagnetics Inc. has designed, fabricated, and tested an HTS coil wound with second-generation (2G) YBCO coated conductor tape. The purpose of the HTS coil project was to study the quench characteristics in 2G YBCO coils at 77 K and lower temperatures (~ 30-45 K). These quench characteristics were investigated in both a pool boiling LN2 environment and in a conduction cooled configuration at ~ 30 K and 45 K. Transport critical current (Ic) measurements taken on the very first thermal cycle of the YBCO coil in pool boiling LN2 showed an Ic ~ 31 A corresponding to a central magnetic field of 0.32 T. The measured Ic value was consistent with the calculated value using the calculated maximum perpendicular B-field component and the measured short sample Ic at 77 K. Subsequent Ic measurements taken in the conduction cooling configuration at 34 K and 45 K, showed a steady-state Ic ~ 45-49 A and 38-44 A, respectively. These Ic values were significantly lower than the calculated value assuming a literature derived temperature dependent Ic of the 2G YBCO tape. A steady degradation was observed in the Ic of the coil with each successive thermal cycle. In addition, the coil was also pulse tested up to 1-T in non-steady state transient conditions and for ramp rates varying between 0.01 and 5 A/s. The problems and limitations encountered during testing of this new type of 2G coil is briefly discussed.

Rey, Christopher M [ORNL; Duckworth, Robert C [ORNL

2007-01-01

175

"Analysis of SOFCs using reference electrodes?  

SciTech Connect

Reference electrodes are frequently applied to isolate the performance of one electrode in a solid oxide fuel cell. However, reference electrode simulations raise doubt to veracity of data collected using reference electrodes. The simulations predict that the reported performance for the one electrode will frequently contain performance of both electrodes. Nonetheless, recent reports persistently treat data so collected as ideally isolated. This work confirms the predictions of the reference electrode simulations on two SOFC designs, and to provides a method of validating the data measured in the 3-electrode configuration. Validation is based on the assumption that a change in gas composition to one electrode does not affect the impedance of the other electrode at open circuit voltage. This assumption is supported by a full physics simulation of the SOFC. Three configurations of reference electrode and cell design are experimentally examined using various gas flows and two temperatures. Impedance data are subjected to deconvolution analysis and equivalent circuit fitting and approximate polarization resistances of the cathode and anode are determined. The results demonstrate that the utility of reference electrodes is limited and often wholly inappropriate. Reported impedances and single electrode polarization values must be scrutinized on this basis.

Finklea, Harry; Chen,Xiaoke; Gerdes,Kirk; Pakalapati, Suryanarayana; Celik, Ismail

2013-07-01

176

Iridium Oxide Nanotube Electrodes for Highly Sensitive and Prolonged Intracellular Measurement of Action Potentials  

PubMed Central

Intracellular recording of action potentials is important to understand electrically-excitable cells. Recently, vertical nanoelectrodes have been developed to achieve highly sensitive, minimally invasive, and large scale intracellular recording. It has been demonstrated that the vertical geometry is crucial for the enhanced signal detection. Here we develop nanoelectrodes made up of nanotubes of iridium oxide. When cardiomyocytes are cultured upon those nanotubes, the cell membrane not only wraps around the vertical tubes but also protrudes deep into the hollow center. We show that this geometry enhances cell-electrode coupling and results in measuring much larger intracellular action potentials. The nanotube electrodes afford much longer intracellular access and are minimally invasive, making it possible to achieve stable recording up to an hour in a single session and more than 8 days of consecutive daily recording. This study suggests that the electrode performance can be significantly improved by optimizing the electrode geometry. PMID:24487777

Lin, Ziliang Carter; Xie, Chong; Osakada, Yasuko; Cui, Yi; Cui, Bianxiao

2014-01-01

177

Complete electrode model in EEG: relationship and differences to the point electrode model  

NASA Astrophysics Data System (ADS)

In electroencephalography (EEG) source analysis, a primary current density generated by the neural activity of the brain is reconstructed from external electrode voltage measurements. This paper focuses on accurate and effective simulations of EEG through the complete electrode model (CEM). The CEM allows for the incorporation of the electrode size, shape and effective contact impedance into the forward simulation. Both neural currents in the brain and shunting currents between the electrodes and the skin can affect the measured voltages in the CEM. The goal of this study was to investigate the CEM by comparing it with the point electrode model (PEM), which is the current standard electrode model for EEG. We used a three-dimensional, realistic and high-resolution finite element head model as the reference computational domain in the comparison. The PEM could be formulated as a limit of the CEM, in which the effective impedance of each electrode goes to infinity and the size tends to zero. Numerical results concerning the forward and inverse errors and electrode voltage strengths with different impedances and electrode sizes are presented. Based on the results obtained, limits for extremely high and low impedance values of the shunting currents are suggested.

Pursiainen, S.; Lucka, F.; Wolters, C. H.

2012-02-01

178

The effect of electrode geometry on electrochemical properties measured in saline.  

PubMed

The impedance, cyclic voltammetry, and charge-injection properties of rectangular, sputtered iridium oxide (SIROF) electrodes have been measured in buffered physiological saline over a range of geometric surface areas (GSA) and perimeter-to-area ratios (P/A). Electrodes with a higher P/A are expected to have a lower impedance and higher charge injection capacity (Q(inj)), and both these effects were evident for SIROF electrodes with a GSA in the range 0.0023-0.0031 mm(2). However, the magnitude of the effect was modest. The increase in Q(inj) for rectangular electrodes with a P/A ranging from 94 to 255 mm(-1) was 21-26% depending on pulse width. There was a corresponding decrease in impedance (0.1 to 10(5) Hz) with increasing P/A and an increase in the SIROF charge storage capacity calculated from cyclic voltammetry. To assess the full usefulness of high P/A electrodes for increasing the reversible Q(inj) of an electrode, measurements should now be extended to chronic in vivo preparations. PMID:25571570

Cogan, Stuart F; Ehrlich, Julia; Plante, Timothy D

2014-01-01

179

Measurements of Coulomb blockade with a noninvasive voltage probe  

NASA Astrophysics Data System (ADS)

We have investigated the behavior of a laterally confined quantum dot in close proximity to a one-dimensional channel in a separate electrical circuit. When this channel is biased in the tunneling regime the resistance is very sensitive to electric fields, and therefore is sensitive to the potential variations on the dot when it is showing Coulomb blockade oscillations. This effect can be calibrated directly, allowing the Coulomb charging energy to be measured. We also found the activation energy of transport through the dot is much lower than expected.

Field, M.; Smith, C. G.; Pepper, M.; Ritchie, D. A.; Frost, J. E. F.; Jones, G. A. C.; Hasko, D. G.

1993-03-01

180

A test technique for measuring lightning-induced voltages on aircraft electrical circuits  

NASA Technical Reports Server (NTRS)

The development of a test technique used for the measurement of lightning-induced voltages in the electrical circuits of a complete aircraft is described. The resultant technique utilizes a portable device known as a transient analyzer capable of generating unidirectional current impulses similar to lightning current surges, but at a lower current level. A linear relationship between the magnitude of lightning current and the magnitude of induced voltage permitted the scaling up of measured induced values to full threat levels. The test technique was found to be practical when used on a complete aircraft.

Walko, L. C.

1974-01-01

181

Method and apparatus for remote tube crevice detection by current and voltage probe resistance measurement  

DOEpatents

A method and apparatus for determining the extent of contact between an electrically conducting tube and an electrically conductive tubesheet surrounding the tube, based upon the electrical resistance of the tube and tubesheet. A constant current source is applied to the interior of the electrically conducting tube by probes and a voltmeter is connected between other probes to measure the voltage at the point of current injection, which is inversely proportional to the amount of contact between the tube and tubesheet. Namely, the higher the voltage measured by the voltmeter, the less contact between the tube and tubesheet. 4 figs.

Kikta, T.J.; Mitchell, R.D.

1992-11-24

182

High-resolution dc-voltage-biased ac conductance bridge for tunnel junction measurements  

Microsoft Academic Search

A simple, low-cost conductance bridge circuit, which provides high-resolution measurements of dI\\/dV and d2I\\/dV2 for a voltage-biased load, is presented. A resolution in dI\\/dV for a 90-Omega tunnel junction of several parts in 105 has been measured using a 35-muV-rms modulation level and a 1-s postdetection time constant (Bn=0.25 Hz). The output impedance of the voltage source and the error

M. V. Moody; J. L. Paterson; R. L. Ciali

1979-01-01

183

High-resolution dc-voltage-biased ac conductance bridge for tunnel junction measurements  

Microsoft Academic Search

A simple, low-cost conductance bridge circuit, which provides high-resolution measurements of dI\\/dV and d2I\\/dV2 for a voltage-biased load, is presented. A resolution in dI\\/dV for a 90-? tunnel junction of several parts in 105 has been measured using a 35-?V-rms modulation level and a 1-s postdetection time constant (Bn=0.25 Hz). The output impedance of the voltage source and the error

M. V. Moody; J. L. Paterson; R. L. Ciali

1979-01-01

184

AN EVALUATION OF ELECTRODE INSERTION TECHNIQUES FOR MEASUREMENT OF REDOX POTENTIAL IN ESTUARINE SEDIMENTS  

EPA Science Inventory

Eh measurements by electrodes are commonly used to characterize redox status of sediments in freshwater, marine and estuarine studies, due to the relative ease and rapidity of data collection. In our studies of fine-grained estuarine seabeds, we observed that Eh values measured i...

185

Catalase activity measured with a micro oxygen electrode in a pressurized reaction vessel. [Mice, rats  

Microsoft Academic Search

The assembly and the use of a simple airtight pressurized reaction vessel are described for the measurement of catalase activity with a micro oxygen electrode in an optically heterogenous medium. The oxygen concentration is expressed as the ratio of observed current to the current in an air-saturated solution. Thus, an individual standard can be obtained for each measurement and the

Halbach

1977-01-01

186

Variable-RL-cancel circuit for precise J C measurement using third-harmonic voltage method  

Microsoft Academic Search

A precise and reliable non-destructive measurement technique is required for evaluation of critical current density, JC, and electric field E vs. current density J characteristics in the recently developed large-area or long-length high temperature superconducting films. Here, we measured E–J characteristics of a 2-in. ? Y-123 film with an inductive measurement system using the third-harmonic voltage, V3, and adopted a

H. Yamada; T. Minakuchi; D. Itoh; T. Yamamoto; S. Nakagawa; K. Kanayama; K. Hirachi; Y. Mawatari; H. Yamasaki

2007-01-01

187

Dark current-voltage measurements on photovoltaic modules as a diagnostic or manufacturing tool  

Microsoft Academic Search

Dark current-voltage (dark I-V) measurements are commonly used to analyze the electrical characteristics of solar cells, providing an effective way to determine fundamental performance parameters without the need for a solar simulator. The dark I-V measurement procedure does not provide information regarding short-circuit current, but is more sensitive than light I-V measurements in determining the other parameters (series resistance, shunt

D. L. King; B. R. Hansen; J. A. Kratochvil; M. A. Quintana

1997-01-01

188

Role of measurement voltage on hysteresis loop shape in Piezoresponse Force Microscopy  

SciTech Connect

The dependence of on-field and off-field hysteresis loop shape in Piezoresponse Force Microscopy (PFM) on driving voltage, Vac, is explored. A nontrivial dependence of hysteresis loop parameters on measurement conditions is observed. The strategies to distinguish between paraelectric and ferroelectric states with small coercive bias and separate reversible hysteretic and non-hysteretic behaviors are suggested. Generally, measurement of loop evolution with Vac is a necessary step to establish the veracity of PFM hysteresis measurements.

Kim, Yunseok [ORNL; Yang, J.-C. [University of California, Berkeley; Chu, Ying Hao [National Chiao Tung University, Hsinchu, Taiwan; Yu, Pu [University of California, Berkeley; Lu, X. [Xidian University, China; Jesse, Stephen [ORNL; Kalinin, Sergei V [ORNL

2012-01-01

189

Determining resistivity of a formation adjacent to a borehole having casing using multiple electrodes and with resistances being defined between the electrodes  

DOEpatents

Methods of operation are disclosed for different types of multiple electrode apparatus vertically disposed in a cased well to measure information related to the resistivity of adjacent geological formations from inside the cased well. The multiple electrode apparatus have a minimum of three spaced-apart voltage measurement electrodes that electrically engage the interior of the cased well. Measurement information is obtained related to current which is caused to flow from the cased well into the adjacent geological formation. First compensation information is obtained related to a first casing resistance between a first pair of the spaced-apart voltage measurement electrodes. Second compensation information is obtained related to a second casing resistance between a second pair of the spaced-apart voltage measurement electrodes. The measurement information, and first and second compensation information are used to determine a magnitude related to the adjacent formation resistivity. 13 figs.

Vail, W.B. III

1996-10-29

190

Isolation amplifier for high voltage measurement using a resonant control loop  

Microsoft Academic Search

Some papers describe a novel pulse width modulation, which makes enter converter's current control loop in a resonant mode and permits an accurate tracking of the reference. Here, we investigate an analog high voltage measurement board, which implements an isolation amplifier using this modulation strategy. Thus, the isolation amplifier involves an analog-to-digital converter whose operating mode depends on this modulation

J. C. Le Claire; L. Menager; J. C. Olivier; N. Ginot

2005-01-01

191

Characterization of ion implanter electron flood guns using charge pumping and threshold voltage measurements  

Microsoft Academic Search

In this paper, three successive generations of ion implant electron flood devices are compared with regard to their wafer charging characteristics. Gate oxide damage of CMOS antenna transistors is used as a relative indicator to quantify the degree of implant charging. Charge pumping and threshold voltage measurements are used as parametric damage indicators. Our results show that the largest charging

W. D. Sawyer; P. W. Mason; R. S. Santiesteban; E. J. Persson

1999-01-01

192

Variable-RL-cancel circuit for precise JC measurement using third-harmonic voltage method  

NASA Astrophysics Data System (ADS)

A precise and reliable non-destructive measurement technique is required for evaluation of critical current density, JC, and electric field E vs. current density J characteristics in the recently developed large-area or long-length high temperature superconducting films. Here, we measured E- J characteristics of a 2-in. ? Y-123 film with an inductive measurement system using the third-harmonic voltage, V3, and adopted a tunable-RL-cancel circuit to decrease harmonic-voltage noise. First, we measured coil current I0 dependences of V3 voltage and obtained the threshold coil current, I0 = Ith, when a certain V3 voltage suddenly arose. And we also measured self inductance of the drive coil, Ld, with changing pressure between the drive coil and film in the range of 0.1-0.6 MPa. The Ld and Ith saturated to constant values at coil pressures above 0.2 MPa, and the saturated Ld value was almost equivalent to the simulated Ld of 134 ?H. With application of an adequate coil pressure of 0.25 MPa, we measured Ith with varying drive frequency f from 0.2 to 5 kHz. Harmonic voltage noise was sufficiently eliminated below 1 mV using the variable-cancel circuit. If a constant criterion of third-harmonic inductance V3/( fI0) = 3 ?H was applied to define the Ith, obtained E- J curves showed a good fit to the theoretical power-law dependence of E = aJn. The average n value obtained from each E- J curve at five different positions in the film was 21.0, which was slightly lower than the value of 23.5 obtained from transport E- J characteristics.

Yamada, H.; Minakuchi, T.; Itoh, D.; Yamamoto, T.; Nakagawa, S.; Kanayama, K.; Hirachi, K.; Mawatari, Y.; Yamasaki, H.

2007-01-01

193

Preventive measures reduce exposure to polycyclic aromatic hydrocarbons at a graphite electrode plant  

PubMed Central

OBJECTIVE: This study assessed the efficacy of preventive measures in a graphite electrode plant aimed at reducing occupational exposure to polycyclic aromatic hydrocarbons (PAHs). METHODS: Electrode workers (n = 146) answered a questionnaire and provided an end of shift urine sample. Urinary 1-hydroxypyrene (1-hpur), a biological marker of exposure to PAHs, was measured by high performance liquid chromatography coupled with: (a) fluorescence detection. 1- Hydroxypyrene concentrations were compared with the concentrations measured before implementing the preventive measures; and (b) those of a control group of 54 men not occupationally exposed to PAHs. RESULTS: After implementation of preventive measures, median concentrations 1- hpur were significantly reduced in some groups of workers: by -24%, - 37% and -30% in workers at the green electrode unit, one baking impregnation unit, and the laboratory, respectively. In workers at a second baking impregnation unit, in end product finishing and in the power station 1-hpur concentrations were unchanged. Urinary 1-hp concentrations were still significantly higher in each group of workers than in the control group (p < 0.001 for any comparison). Concentrations in the workers varied with the type of job, the highest values being found in workers engaged in the power station, in the two baking impregnation units and in the green electrode unit. CONCLUSIONS: Implementing preventive measures significantly reduced exposure to PAHs at a graphite electrode plant. The reduction in median and peak concentrations of 1-hpur, which reflects total exposure to, and internal dose of PAHs, was most evident in workers employed in the units where preventive measures had been taken. Despite an overall reduction, further preventive measures are needed to minimise exposure to PAHs and consequently the risk of adverse health effects.   PMID:9764100

dell'Omo, M.; Muzi, G.; Marchionna, G.; Latini, L.; Carrieri, P.; Paolemili, P.; Abbritti, G.

1998-01-01

194

Measurement of contact voltage drop and resistance in organic solar cells  

NASA Astrophysics Data System (ADS)

Bulk heterojunction organic solar cells based on poly[4,7-bis(3-dodecylthiophene-2-yl) benzothiadiazole-co-benzothiadiazole] and [6,6]-phenyl C71-butyric acid methyl ester are investigated. A prominent kink is observed in the fourth quadrant of the current density-voltage (J-V) response. Annealing the active layer prior to cathode deposition eliminates the kink. The kink is attributed to an extraction barrier. The J-V response in these devices is well described by a power law. This behavior is attributed to an imbalance in charge carrier mobility. An expected photocurrent for the device displaying a kink in the J-V response is determined by fitting to a power law. The difference between the expected and measured photocurrent allows for the determination of a voltage drop within the device. Under simulated 1 sun irradiance, the peak voltage drop and contact resistance at short circuit are 0.14 V and 90 ?, respectively.

Williams, Evan L.; Ooi, Zien; Sonar, Prashant; Dodabalapur, Ananth

2012-12-01

195

Differential pH measurements of metabolic cellular activity in nl culture volumes using microfabricated iridium oxide electrodes  

Microsoft Academic Search

In this paper we describe a new approach to measure pH differences in microfluidic devices and demonstrated acidification rate measurements in on-chip cell culture systems with nl wells. We use two miniaturized identical iridium oxide (IrOx) thin film electrodes (20?m×400?m), one as a quasi-reference electrode, the other as a sensing electrode, placed in two confluent compartments on chip. The IrOx

Igor A. Ges; Borislav L. Ivanov; Andreas A. Werdich; Franz J. Baudenbacher

2007-01-01

196

Measurement of transmembrane potential and current in cardiac muscle: a new voltage clamp method.  

PubMed Central

1. A single sucrose gap voltage clamp technique was developed to correct for artifacts of 'leakage' corrent and extracellular resistance making possible improved measurement of membrane current and membrane potential in cardiac muscle. 2. A fourth compartment termed 'guard gap' was added to the sucrose gap. The guard gap is maintained at the same potential as the Reinger pool, so that no extracellular leakage current can flow into the Ringer pool. Comparison of experimental results with the predictions of an idealized cable model indicates that the guard gap is effective in trapping leakage current. 3. The slow charging of membrane capacitance due to extracellular series resistance was accelerated by applying a 'pre-pulse' of the command potential past the final voltage clamp value. 4. A second technique, termed 'chopped current pulse clamp', was used to compensate for the extracellular resistance throughout the voltage clamp step. The applied current was turned on and off at a frequency of 0-5-2 kHz. The membrane potential sampled during the zero current phase was fed back through the clamp loop. 5. With either of these compensation techniques, the voltage and current traces settle to effectively constant values within 2-4 msec after initiation of a hyperpolarizing voltage clamp step from rest. 6. The membrane conductance measured by the prepulse and chopped current-pulse technique are equal and confirm a higher conductance at rest than during the plateau of the action potential. 7. The 'instantaneous' current-voltage relation of the membrane is linear during the plateau of the frog ventricular action potential. PMID:301933

Goldman, Y; Morad, M

1977-01-01

197

Online partial discharge measurement of a high-voltage direct current converter wall-bushing  

Microsoft Academic Search

An online Partial Discharge (PD) measurement performed on a High Voltage Direct Current (HVDC) wall bushing successfully identified the presence of internal discharges. The wall bushing is a sulfur hexafluoride gas-insulated bushing, rated for 500kVdc and terminated on a thyristor controlled HVDC converter bridge. The measurement of PD within the HVDC station environment is particularly challenging due to the high

N. D. Jacob; W. M. McDermid; B. Kordi

2010-01-01

198

Impedance studies of nickel/cadmium and nickel/hydrogen cells using the cell case as a reference electrode  

NASA Technical Reports Server (NTRS)

Impedance measurements have been made on several Ni/Cd and Ni/H2 flight-weight cells using the case as a reference electrode. For these measurements, the voltage of the case with respect to the anode or cathode is unimportant provided that it remains stable during the measurement of the impedance. In the cells measured so far, the voltage of the cell cases with respect to the individual electrodes differ from cell to cell, even at the same overall cell voltage, but they remain stable with time. The measurements can thus be used to separate the cell impedance into the contributions of each electrode, allowing improved diagnosis of cell problems.

Reid, Margaret A.

1990-01-01

199

Activity coefficients of aqueous potassium chloride measured with a potassium-sensitive glass electrode  

USGS Publications Warehouse

Values of ????KCI temperature and molality ranges of 10?? to 50??C and 0.01 to 1.0 molal were determined with an electromotive-force cell: potasslum-sensitive glass electrode, KCl (molality), Ag-AgCl. A more satisfactory method than is commonly employed was devised for treating the experimental measurements of potential.

Hostetler, P.B.; Truesdell, A.H.; Christ, C.L.

1967-01-01

200

Activity coefficients of aqueous sodium chloride from 15?? to 50??C measured with a glass electrode  

USGS Publications Warehouse

Values of the mean activity coefficient of sodium chloride at 15??, 25??, 38?? and 50??C were determined for aqueous NaCl solutions of 0.01 to 1.0 molal from electromotive force measurements on the cell: (sodium-sensitive glass electrode, aqueous sodium chloride, silver chloride-silver).

Truesdell, A.H.

1968-01-01

201

Human CT Measurements of Structure/Electrode Position Changes During Respiration with Electrical Impedance Tomography.  

PubMed

For pulmonary applications of Electrical Impedance Tomography (EIT) systems, the electrodes are placed around the chest in a 2D ring, and the images are reconstructed based on the assumptions that the object is rigid and the measured resistivity change in EIT images is only caused by the actual resistivity change of tissue. Structural changes are rarely considered. Previous studies have shown that structural changes which result in tissue/organ and electrode position changes tend to introduce artefacts to EIT images of the thorax. Since EIT reconstruction is an ill-posed inverse problem, any small inaccurate assumptions of object may cause large artefacts in reconstructed images. Accurate information on structure/electrode position changes is a need to understand factors contributing to the measured resistivity changes and to improve EIT reconstruction algorithm. Our previous study using MRI technique showed that chest expansion leads to electrode and tissue/organ movements but not significant as proposed. The accuracy of the measurements by MRI may be limited by its relatively low temporal and spatial resolution. In this study, structure/electrode position changes during respiration cycle in patients who underwent chest CT scans are further investigated. For each patient, sixteen fiduciary markers are equally spaced around the surface, the same as the electrode placement for EIT measurements. A CT scanner with respiration-gated ability is used to acquire images of the thorax. CT thoracic images are retrospectively reconstructed corresponding temporally to specific time periods within respiration cycle (from 0% to 90%, every 10%). The average chest expansions are 2 mm in anterior-posterior and -1.6 mm in lateral directions. Inside tissue/organ move down 9.0±2.5 mm with inspiration of tidal volume (0.54±0.14 liters), ranging from 6 mm to 12 mm. During normal quiet respiration, electrode position changes are smaller than expected. No general patterns of electrode position changes are observed. The results in this study provide guidelines for accommodating the motion that may introduce artefacts to EIT images. PMID:24339836

Zhang, Jie; Qin, Lihong; Allen, Tadashi; Patterson, Robert P

2013-01-01

202

Single-Molecule Electronic Measurements with Metal Electrodes  

ERIC Educational Resources Information Center

A review of concepts like tunneling through a metal-molecule-metal-junction, contrast with electrochemical and optical-charge injection, strong-coupling limit, calculations of tunnel transport, electron transfer through Redox-active molecules is presented. This is followed by a discussion of experimental approaches for single-molecule measurements.

Lindsay, Stuart

2005-01-01

203

Prototype for automatable, dielectrophoretically-accessed intracellular membrane-potential measurements by metal electrodes.  

PubMed

Functional access to membrane proteins, for example, ion channels, of individual cells is an important prerequisite in drug discovery studies. The highly sophisticated patch-clamp method is widely used for electrogenic membrane proteins, but is demanding for the operator, and its automation remains challenging. The dielectrophoretically-accessed, intracellular membrane-potential measurement (DAIMM) method is a new technique showing high potential for automation of electrophysiological data recording in the whole-cell configuration. A cell suspension is brought between a mm-scaled planar electrode and a ?m-scaled tip electrode, placed opposite to each other. Due to the asymmetric electrode configuration, the application of alternating electric fields (1-5 MHz) provokes a dielectrophoretic force acting on the target cell. As a consequence, the cell is accelerated and pierced by the tip electrode, hence functioning as the internal (working) electrode. We used the light-gated cation channel Channelrhodopsin-2 as a reporter protein expressed in HEK293 cells to characterize the DAIMM method in comparison with the patch-clamp technique. PMID:22994967

Terpitz, Ulrich; Sukhorukov, Vladimir L; Zimmermann, Dirk

2013-02-01

204

Wavelength stabilisation of a DFB laser diode using measurement of junction voltage  

NASA Astrophysics Data System (ADS)

Laser diode wavelength stability is vital for applications such as spectroscopy and data communication, and the emitted wavelength is a function of temperature. In a conventional system, the laser diode temperature is controlled using a Peltier element with a temperature-sensing thermistor, the latter placed at a short distance from the laser diode chip. Despite the use of good thermal design and a case, a change in ambient temperature may cause a change to internal thermal gradients, resulting in a systematic error in the laser diode wavelength. In this paper we describe a novel system to measure the temperature of the laser diode junction via measurement of the junction voltage. The method has been applied to a 1651 nm DFB laser diode for use in tunable diode laser spectroscopy (TDLS) of methane. The wavelength stability of both thermistor- and voltage- control systems are compared over a period of 30 minutes and with different ambient temperatures. Over 30 min at constant ambient temperature, thermistor control provided a precision of +/- 0.4 pm (40 MHz) and junction voltage control gave a similar +/- 0.6 pm (70 MHz). For an ambient temperature change of 20°C, conventional thermistor control suffered a wavelength change of 76 pm (8.4 GHz), whereas junction voltage control reduced this to 0.6 pm (70 MHz), at or below the level of long-term wavelength precision.

Asmari, A.; Hodgkinson, J.; Chehura, E.; Staines, S. E.; Tatam, R. P.

2014-05-01

205

Forward voltage short-pulse technique for measuring high power laser array junction temperature  

NASA Technical Reports Server (NTRS)

The present invention relates to a method of measuring the temperature of the P-N junction within the light-emitting region of a quasi-continuous-wave or pulsed semiconductor laser diode device. A series of relatively short and low current monitor pulses are applied to the laser diode in the period between the main drive current pulses necessary to cause the semiconductor to lase. At the sufficiently low current level of the monitor pulses, the laser diode device does not lase and behaves similar to an electronic diode. The voltage across the laser diode resulting from each of these low current monitor pulses is measured with a high degree of precision. The junction temperature is then determined from the measured junction voltage using their known linear relationship.

Meadows, Byron L. (Inventor); Amzajerdian, Frazin (Inventor); Barnes, Bruce W. (Inventor); Baker, Nathaniel R. (Inventor)

2012-01-01

206

Measurement of electrode overpotentials for direct hydrocarbon conversion fuel cells  

Microsoft Academic Search

Cathodic and anodic overpotentials were measured using current interruption and AC impedance spectroscopy for two separate solid oxide fuel cells (SOFCs). The fuel cells used yttria-stabilized zirconia (YSZ) as the electrolyte, strontium-doped lanthanum manganite (LSM) as the cathode, and a porous YSZ layer impregnated with copper and ceria as the anode. The Cu\\/CeO2\\/YSZ anode is active for the direct conversion

Venkatesan V. Krishnan; Steven McIntosh; Raymond J. Gorte; John M. Vohs

2004-01-01

207

Measurement of tg? and C of single-phase electrical apparatus with capacitive insulation under operating voltage  

Microsoft Academic Search

The authors describe a method of measuring tg? (loss tangent) and C (capacitance) of a single-phase apparatus with capacitive insulation by using an ordinary Schering bridge which takes the secondary voltage of a same-phase power transformer as the voltage of the standard arm and suppresses interference. Examples are given to illustrate how to analyze the results of measurement. The proposed

G. Zhu; J. Wang

1988-01-01

208

Current Control for AC Motor Drives Using a Single DC-Link Current Sensor and Measurement Voltage Vectors  

Microsoft Academic Search

A new algorithm using a single dc-link current sensor to reconstruct all three inverter phase currents has been proposed that overcomes problems caused by the presence of regions in the voltage vector plane where the phase currents are not conveniently measurable. The measurement vector insertion method (MVIM) achieves this objective by applying additional active voltage vectors for brief intervals only

Hongrae Kim; Thomas M. Jahns

2006-01-01

209

in the lipid bilayer Distance measurements reveal a common topology of prokaryotic voltage-gated ion channels  

E-print Network

in the lipid bilayer Distance measurements reveal a common topology of prokaryotic voltage.pnas.org/misc/reprints.shtml To order reprints, see: Notes: #12;Distance measurements reveal a common topology of prokaryotic voltage conformations in a mem- brane environment. The validity of the crystal structure for the prokaryotic K channel

Bezanilla, Francisco

210

Voltage-dependent gating and gating charge measurements in the Kv1.2 potassium channel.  

PubMed

Much has been learned about the voltage sensors of ion channels since the x-ray structure of the mammalian voltage-gated potassium channel Kv1.2 was published in 2005. High resolution structural data of a Kv channel enabled the structural interpretation of numerous electrophysiological findings collected in various ion channels, most notably Shaker, and permitted the development of meticulous computational simulations of the activation mechanism. The fundamental premise for the structural interpretation of functional measurements from Shaker is that this channel and Kv1.2 have the same characteristics, such that correlation of data from both channels would be a trivial task. We tested these assumptions by measuring Kv1.2 voltage-dependent gating and charge per channel. We found that the Kv1.2 gating charge is near 10 elementary charges (eo), ?25% less than the well-established 13-14 eo in Shaker. Next, we neutralized positive residues in the Kv1.2 S4 transmembrane segment to investigate the cause of the reduction of the gating charge and found that, whereas replacing R1 with glutamine decreased voltage sensitivity to ?50% of the wild-type channel value, mutation of the subsequent arginines had a much smaller effect. These data are in marked contrast to the effects of charge neutralization in Shaker, where removal of the first four basic residues reduces the gating charge by roughly the same amount. In light of these differences, we propose that the voltage-sensing domains (VSDs) of Kv1.2 and Shaker might undergo the same physical movement, but the septum that separates the aqueous crevices in the VSD of Kv1.2 might be thicker than Shaker's, accounting for the smaller Kv1.2 gating charge. PMID:25779871

Ishida, Itzel G; Rangel-Yescas, Gisela E; Carrasco-Zanini, Julia; Islas, León D

2015-04-01

211

A coated-wire ion-selective electrode for ionic calcium measurements  

NASA Technical Reports Server (NTRS)

A coated-wire ion-selective electrode for measuring ionic calcium was developed, in collaboration with Teknektron Sensor Development Corporation (TSDC). This coated wire electrode sensor makes use of advanced, ion-responsive polyvinyl chloride (PVC) membrane technology, whereby the electroactive agent is incorporated into a polymeric film. The technology greatly simplifies conventional ion-selective electrode measurement technology, and is envisioned to be used for real-time measurement of physiological and environment ionic constituents, initially calcium. A primary target biomedical application is the real-time measurement of urinary and blood calcium changes during extended exposure to microgravity, during prolonged hospital or fracture immobilization, and for osteoporosis research. Potential advanced life support applications include monitoring of calcium and other ions, heavy metals, and related parameters in closed-loop water processing and management systems. This technology provides a much simplified ionic calcium measurement capability, suitable for both automated in-vitro, in-vivo, and in-situ measurement applications, which should be of great interest to the medical, scientific, chemical, and space life sciences communities.

Hines, John W.; Arnaud, Sara; Madou, Marc; Joseph, Jose; Jina, Arvind

1991-01-01

212

Correlation between measured voltage and observed wavelength in commercial AlGaInP laser diode  

SciTech Connect

Temperature of a commercial AlGaInP/GaInP quantum well laser diode (LD) is measured using two methods: peak wavelength shift and the diode voltage drop caused by working current. Time evolutions of temperature obtained by the two methods during the LD self-heating are measured and compared. No significant difference between the thus obtained temperature evolutions is obtained. Correlation between the LD voltage drop and the laser radiation frequency is established using a simple four-level semiconductor laser scheme and the LD gap energy is estimated. The LD gap energy decreases from 1.66?eV to 1.56?eV for temperature increase of 21?K, at close to room temperature. It is found that LD's frequency decrease is caused by the gap energy decrease.

Iskrenovi?, Predrag S.; Krsti?, Ivan B.; Obradovi?, Bratislav M., E-mail: obrat@ff.bg.ac.rs; Kuraica, Milorad M. [Faculty of Physics, University of Belgrade, 11000 Belgrade (Serbia)

2014-05-14

213

A novel approach to high voltage substation surveillance using radio frequency interference measurement  

Microsoft Academic Search

The deployment of radio frequency interference (RFI) measurement has gained increasing acceptance as a front line, non-invasive technique to assess the condition of individual high-voltage (HV) electrical equipment items as part of a substation surveillance program. However, successful detection and discrimination of low-repetition rate discharges that typically accompany electrical deterioration is constrained by the capabilities and limitations of the field

A. Nesbitt; B. G. Stewart; S. G. McMeekin; S. Conner; J. C. Gamio; K. Liebech-Lien; H. O. Kristiansen; S. Krakenes

2009-01-01

214

A new approach to high-speed flow measurements using constant voltage anemometry  

NASA Technical Reports Server (NTRS)

The paper addresses the basic features of conventional instrumentation, such as the constant temperature (CTA) and the constant current (CCA) anemometers, their limitations, and describes a totally new approach to high-speed dynamic measurements using a constant voltage anemometer (CVA). The paper describes the design features of a newly developed CVA and compares preliminary results obtained with CVA and conventional anemometry in low- and high-speed flows.

Mangalam, S. M.; Sarma, G. R.; Kuppa, S.; Kubendran, L. R.

1992-01-01

215

SPEAR-1: An experiment to measure current collection in the ionosphere by high voltage biased conductors  

NASA Technical Reports Server (NTRS)

An experiment is described in which a high electrical potential difference, up to 45 kV, was applied between deployed conducting spheres and a sounding rocket in the ionosphere. Measurements were made of the applied voltage and the resulting currents for each of 24 applications of different high potentials. In addition, diagnostic measurements of optical emissions in the vicinity of the spheres, energetic particle flow to the sounding rocket, dc electric field and wave data were made. The ambient plasma and neutral environments were measured by a Langmuir probe and a cold cathode neutral ionization gauge, respectively. The payload is described and examples of the measured current and voltage characteristics are presented. The characteristics of the measured currents are discussed in terms of the diagnostic measurements and the in-situ measurements of the vehicle environment. In general, it was found that the currents observed were at a level typical of magnetically limited currents from the ionospheric plasma for potentials less than 12 kV, and slightly higher for larger potentials. However, due to the failure to expose the plasma contactor, the vehicle sheath modified the sphere sheaths and made comparisons with the analytic models of Langmuir-Blodgett and Parker-Murphy less meaningful. Examples of localized enhancements of ambient gas density resulting from the operation of the attitude control system thrusters (cold nitrogen) were obtained. Current measurements and optical data indicated localized discharges due to enhanced gas density that reduced the vehicle-ionosphere impedance.

Raitt, W. John; Myers, Neil B.; Roberts, Jon A.; Thompson, D. C.

1990-01-01

216

Dopant profiling and surface analysis of silicon nanowires using capacitance-voltage measurements.  

PubMed

Silicon nanowires are expected to have applications in transistors, sensors, resonators, solar cells and thermoelectric systems. Understanding the surface properties and dopant distribution will be critical for the fabrication of high-performance devices based on nanowires. At present, determination of the dopant concentration depends on a combination of experimental measurements of the mobility and threshold voltage in a nanowire field-effect transistor, a calculated value for the capacitance, and two assumptions--that the dopant distribution is uniform and that the surface (interface) charge density is known. These assumptions can be tested in planar devices with the capacitance-voltage technique. This technique has also been used to determine the mobility of nanowires, but it has not been used to measure surface properties and dopant distributions, despite their influence on the electronic properties of nanowires. Here, we measure the surface (interface) state density and the radial dopant profile of individual silicon nanowire field-effect transistors with the capacitance-voltage technique. PMID:19421217

Garnett, Erik C; Tseng, Yu-Chih; Khanal, Devesh R; Wu, Junqiao; Bokor, Jeffrey; Yang, Peidong

2009-05-01

217

Thoracic impedance measures tissue characteristics in the vicinity of the electrodes, not intervening lung water: implications for heart failure monitoring.  

PubMed

The rationale for intrathoracic impedance (Z) detection of worsening heart failure (HF) presupposes that changes in Z reflect changes in pulmonary congestion, but is confounded by poor specificity in clinical trials. We therefore tested the hypothesis that Z is primarily affected by tissue/water content in proximity to electrodes rather than by lung water distribution between electrodes through the use of a new computational model for deriving the near-field impedance contributions from the various electrodes. Six sheep were implanted with a left atrial pressure (LAP) monitor and a cardiac resynchronization therapy device which measured Z from six vectors comprising of five electrodes. The vector-based Z was modelled as the summation of the near-field impedances of the two electrodes forming the vector. During volume expansion an acute increase in LAP resulted in simultaneous reductions in the near-field impedances of the intra-cardiac electrodes, while the subcutaneous electrode showed several hours of lag (all p<0.001). In contrast, during the simulated formation of device-pocket edema (induced by fluid injection) the near-field impedance of the subcutaneous electrode had an instantaneous response, while the intra-cardiac electrodes had a minimal inconsistent response. This study suggests that the primary contribution to the vector based Z is from the tissue/water in proximity to the individual electrodes. This novel finding may help explain the limited utility of Z for detecting worsening HF. PMID:24619657

Charles, Christopher J; Rademaker, Miriam T; Melton, Iain C; Gutfinger, Dan; Eigler, Neal L; Qu, Fujian; Troughton, Richard W

2015-02-01

218

Drilling electrode for real-time measurement of electrical impedance in bone tissues.  

PubMed

In order to prevent possible damages to soft tissues, reliable monitoring methods are required to provide valuable information on the condition of the bone being cut. This paper describes the design of an electrical impedance sensing drill developed to estimate the relative position between the drill and the bone being drilled. The two-electrode method is applied to continuously measure the electrical impedance during a drill feeding movement: two copper wire brushes are used to conduct electricity in the rotating drill and then the drill is one electrode; a needle is inserted into the soft tissues adjacent to the bone being drilled and acts as another electrode. Considering that the recorded electrical impedance is correlated with the insertion depth of the drill, we theoretically calculate the electrode-tissue contact impedance and prove that the rate of impedance change varies considerably when the drill bit crosses the boundary between two different bone tissues. Therefore, the rate of impedance change is used to determine whether the tip of the drill is located in one of cortical bone, cancellous bone, and cortical bone near a boundary with soft tissue. In vitro experiments in porcine thoracic spines were performed to demonstrate the feasibility of the impedance sensing drill. The experimental results indicate that the drill, used with the proposed data-processing method, can provide accurate and reliable breakthrough detection in the bone-drilling process. PMID:24254254

Dai, Yu; Xue, Yuan; Zhang, Jianxun

2014-03-01

219

Liquid electrode  

DOEpatents

A dropping electrolyte electrode for use in electrochemical analysis of non-polar sample solutions, such as benzene or cyclohexane. The liquid electrode, preferably an aqueous salt solution immiscible in the sample solution, is introduced into the solution in dropwise fashion from a capillary. The electrolyte is introduced at a known rate, thus, the droplets each have the same volume and surface area. The electrode is used in making standard electrochemical measurements in order to determine properties of non-polar sample solutions.

Ekechukwu, Amy A. (Augusta, GA)

1994-01-01

220

Gold Electrodes Modified with Self-Assembled Monolayers for Measuring L-Ascorbic Acid: An Undergraduate Analytical Chemistry Laboratory Experiment  

ERIC Educational Resources Information Center

This article describes an undergraduate electrochemistry laboratory experiment in which the students measure the L-ascorbic acid content of a real sample. Gold electrodes modified with self-assembled monolayers (SAMs) of thioctic acid and cysteamine are prepared to study the effects of surface modification on the electrode reaction of L-ascorbic…

Ito, Takashi; Perera, D. M. Neluni T.; Nagasaka, Shinobu

2008-01-01

221

New frequency/voltage converters for ac-electrogravimetric measurements based on fast quartz crystal microbalance  

SciTech Connect

A better understanding of the mechanisms located at the solid/electrolyte interface is becoming essential to the development of new applications in the electrochemical fields. The fast quartz crystal microbalance is an attractive and powerful gravimetric sensor which can be used in the dynamic regime to determine a mass/potential transfer function. The principle is equivalent to classical electrochemical impedance measurements; the only difference is the determination of mass changes given by the quartz crystal microbalance rather than current changes following sine wave modulations of the applied potential. This function appears very well adapted to characterize ionic exchanges at the electrochemical interface. Frequency/voltage converters are the key devices in translating the microbalance frequency response in terms of a continuous voltage change. The latter allows the transfer function to be obtained via a frequency response analyzer. Different converters were tested in this work in order to improve the performances of the experimental setup.

Gabrielli, C.; Perrot, H.; Rose, D.; Rubin, A.; Toque, J. P.; Pham, M. C.; Piro, B. [LISE--UPR 15 du CNRS, Universite Pierre et Marie Curie-Paris 6, 4, place Jussieu (case 133), 75252 Paris Cedex 05 (France); LISE-UPR 15 du CNRS, Universite Pierre et Marie Curie-Paris 6, 4, place Jussieu (case 133), 75252 Paris Cedex 05, France and ITODYS, Universite Denis Diderot-Paris 7, 1, rue Guy de la Brosse, 75005 Paris (France); LISE-UPR 15 du CNRS, Universite Pierre et Marie Curie-Paris 6, 4, place Jussieu (case 133), 75252 Paris Cedex 05 (France); ITODYS, Universite Denis Diderot-Paris 7, 1, rue Guy de la Brosse, 75005 Paris (France)

2007-07-15

222

In vivo measurement of electrical parameters with alumina-covered stainless steel electrodes.  

PubMed

An experimental method has been developed for in vivo measurement of electrical parameters. It is thus possible to evaluate not only the instantaneous corrosion rate of implants but also their susceptibility to pitting corrosion. It has also been shown that when the method is applied to stainless steel/ceramic electrodes, these remain in the passive condition. If an eventual breakdown of the passivating film occurs, it will quickly regenerate itself. PMID:3719038

Escudero, M L; Ruiz, J; González, J A; Ruiz, J

1986-05-01

223

Proton conductivity of Nafion 117 as measured by a four-electrode AC impedance method  

Microsoft Academic Search

Nafion 117{reg_sign} is a proton conducting ion-exchange membrane which is now receiving much attention due to its use as an electrolyte in the polymer-electrolyte-membrane fuel cell (PEMFC), which is of great interest for electric vehicle propulsion. The proton conductivity of Nafion 117 was measured under various conditions of humidity and temperature using a four-electrode ac impedance method. The conductivity of

Yoshitsugu Sone; P. Ekdunge; D. Simonsson

1996-01-01

224

A very low noise, high accuracy, programmable voltage source for low frequency noise measurements.  

PubMed

In this paper an approach for designing a programmable, very low noise, high accuracy voltage source for biasing devices under test in low frequency noise measurements is proposed. The core of the system is a supercapacitor based two pole low pass filter used for filtering out the noise produced by a standard DA converter down to 100 mHz with an attenuation in excess of 40 dB. The high leakage current of the supercapacitors, however, introduces large DC errors that need to be compensated in order to obtain high accuracy as well as very low output noise. To this end, a proper circuit topology has been developed that allows to considerably reduce the effect of the supercapacitor leakage current on the DC response of the system while maintaining a very low level of output noise. With a proper design an output noise as low as the equivalent input voltage noise of the OP27 operational amplifier, used as the output buffer of the system, can be obtained with DC accuracies better that 0.05% up to the maximum output of 8 V. The expected performances of the proposed voltage source have been confirmed both by means of SPICE simulations and by means of measurements on actual prototypes. Turn on and stabilization times for the system are of the order of a few hundred seconds. These times are fully compatible with noise measurements down to 100 mHz, since measurement times of the order of several tens of minutes are required in any case in order to reduce the statistical error in the measured spectra down to an acceptable level. PMID:24784633

Scandurra, Graziella; Giusi, Gino; Ciofi, Carmine

2014-04-01

225

Measuring Ca(2+) binding to short chain fatty acids and gluconate with a Ca(2+) electrode: role of the reference electrode.  

PubMed

Many organic anions bind free Ca(2+), the total concentration of which must be adjusted in experimental solutions. Because published values for the apparent dissociation constant (Kapp) describing the Ca(2+) affinity of short chain fatty acids (SCFAs) and gluconate are highly variable, Ca(2+) electrodes coupled to either a 3M KCl or a Na(+) selective electrode were used to redetermine Kapp. All solutions contained 130mM Na(+), whereas the concentration of the studied anion was varied from 15 to 120mM, replacing Cl(-) that was decreased concomitantly to maintain osmolarity. This induces changes in the liquid junction potential (LJP) at the 3M KCl reference electrode, leading to a systematic underestimation of Kapp if left uncorrected. Because the Na(+) concentration in all solutions was constant, a Na(+) electrode was used to directly measure the changes in the LJP at the 3 M KCl reference, which were under 5mV but twice those predicted by the Henderson equation. Determination of Kapp either after correction for these LJP changes or via direct reference to a Na(+) electrode showed that SCFAs do not bind Ca(2+) and that the Kapp for the binding of Ca(2+) to gluconate at pH 7.4, ionic strength 0.15M, and 23°C was 52.7mM. PMID:24835426

Stumpff, Friederike; McGuigan, John A S

2014-08-15

226

An unattended device for high-voltage sampling and passive measurement of thoron decay products.  

PubMed

An integrating measurement device for the concentration of airborne thoron decay products was designed and calibrated. It is suitable for unattended use over up to several months also in inhabited dwellings. The device consists of a hemispheric capacitor with a wire mesh as the outer electrode on ground potential and the sampling substrates as the inner electrode on +7.0 kV. Negatively charged and neutral thoron decay products are accelerated to and deposited on the sampling substrates. As sampling substrates, CR39 solid-state nuclear track detectors are used in order to record the alpha decay of the sampled decay products. Nuclide discrimination is achieved by covering the detectors with aluminum foil of different thickness, which are penetrated only by alpha particles with sufficient energy. Devices of this type were calibrated against working level monitors in a thoron experimental house. The sensitivity was measured as 9.2 tracks per Bq/m(3) × d of thoron decay products. The devices were used over 8 weeks in several houses built of earthen material in southern Germany, where equilibrium equivalent concentrations of 1.4-9.9 Bq/m(3) of thoron decay products were measured. PMID:24593339

Gierl, Stefanie; Meisenberg, Oliver; Haninger, Thomas; Wielunski, Marek; Tschiersch, Jochen

2014-02-01

227

An unattended device for high-voltage sampling and passive measurement of thoron decay products  

SciTech Connect

An integrating measurement device for the concentration of airborne thoron decay products was designed and calibrated. It is suitable for unattended use over up to several months also in inhabited dwellings. The device consists of a hemispheric capacitor with a wire mesh as the outer electrode on ground potential and the sampling substrates as the inner electrode on +7.0 kV. Negatively charged and neutral thoron decay products are accelerated to and deposited on the sampling substrates. As sampling substrates, CR39 solid-state nuclear track detectors are used in order to record the alpha decay of the sampled decay products. Nuclide discrimination is achieved by covering the detectors with aluminum foil of different thickness, which are penetrated only by alpha particles with sufficient energy. Devices of this type were calibrated against working level monitors in a thoron experimental house. The sensitivity was measured as 9.2 tracks per Bq/m{sup 3} × d of thoron decay products. The devices were used over 8 weeks in several houses built of earthen material in southern Germany, where equilibrium equivalent concentrations of 1.4–9.9 Bq/m{sup 3} of thoron decay products were measured.

Gierl, Stefanie; Meisenberg, Oliver, E-mail: oliver.meisenberg@helmholtz-muenchen.de; Wielunski, Marek; Tschiersch, Jochen [Helmholtz Zentrum München, German Research Center for Environmental Health, Institute of Radiation Protection, Ingolstädter Landstr. 1, 85764 Neuherberg (Germany)] [Helmholtz Zentrum München, German Research Center for Environmental Health, Institute of Radiation Protection, Ingolstädter Landstr. 1, 85764 Neuherberg (Germany); Haninger, Thomas [Helmholtz Zentrum München, German Research Center for Environmental Health, Auswertungsstelle für Strahlendosimeter, Otto-Hahn-Ring 6, 81739 München (Germany)] [Helmholtz Zentrum München, German Research Center for Environmental Health, Auswertungsstelle für Strahlendosimeter, Otto-Hahn-Ring 6, 81739 München (Germany)

2014-02-15

228

Teaching pH Measurements with a Student-Assembled Combination Quinhydrone Electrode  

ERIC Educational Resources Information Center

A simple combination pH electrode consisting of a solid-state quinhydrone sensor and a solid-state quinhydrone reference electrode is described. Both electrodes are essentially rubber stoppers that are inserted into a special doublewalled holder.

Scholz, Fritz; Steinhardt, Tim; Kahlert, Heike; Porksen, Jens R.; Behnert, Jurgen

2005-01-01

229

Small-Scale and Low Cost Electrodes for "Standard" Reduction Potential Measurements  

ERIC Educational Resources Information Center

The construction of three simple and inexpensive electrodes, hydrogen, and chlorine and copper electrode is described. This simple method will encourage students to construct their own electrode and better help in understanding precipitation and other electrochemistry concepts.

Eggen, Per-Odd; Kvittingen, Lise

2007-01-01

230

In-line inspection resistance mapping using quantitative measurement of voltage contrast in SEM images  

NASA Astrophysics Data System (ADS)

We developed an in-line inspection method for partial-electrical measurement of contact resistance, which is quantitatively estimated from the voltage contrast formed in an SEM image of an incomplete-contact defect. At first, standard calibration wafers were manufactured for the voltage-contrast calibration. The contact resistance of systematically formed defects was varied from 10 8 to 10 17 ohms. We quantitatively analyzed the grayscale of these defect images captured by a review SEM. Then, the relationship between the grayscales of the defect images captured from these standard calibration wafers and the contact resistances of the defects was studied. We obtained a uniform, stable grayscale of the SEM images of each standard calibration wafer. As a result, calibration curves for estimating the contact resistance of the incomplete-contact defect were obtained at a probe current condition of 80 pA and charging voltages of 1 and 2 V. The estimated contact resistance under these inspection conditions was between 10 10 and 10 16 ohms. Using this in-line inspection method, we demonstrated wafer mapping of contact resistances calibrated from grayscales of defect patterns. We could not determine whether contact resistances on a wafer widely varied unless we used this method.

Matsui, Miyako; Anan, Yoshihiro; Odaka, Takayuki; Nagaishi, Hiroshi; Sakurai, Koichi

2008-03-01

231

Measurements of voltage current characteristics of a plasma needle and its effect on plant cells  

NASA Astrophysics Data System (ADS)

In this paper we present voltage-current-power characteristics of a plasma needle operating in the flow of helium at atmospheric pressure. In addition, we show some examples of how such a plasma affects plant tissues. In the characterization of the plasma needle, current and voltage waveforms were recorded by two derivative probes. These two probes are similar to the probes previously used by Puac et al for measuring transmitted power in low pressure CCP rf discharge. The instantaneous power was calculated from current and voltage waveforms and U-I characteristics of the discharge were determined. Regimes of operation with and without the grounding ring at the tip of the needle were considered. We have chosen two model systems to study the effect of the plasma needle on plant cells and tissues: sweet fern gametophyte (prothallus) and calli produced in vitro. Since the prothallus consists of a single layer of cells, the cytological effects could be easily examined. In addition, calli and prothallus are easy to manipulate and in vitro culture provides a possibility to work under constant and controlled conditions.

Puac, N.; Petrovic, Z. Lj; Malovic, G.; Dordevic, A.; Zivkovic, S.; Giba, Z.; Grubisic, D.

2006-08-01

232

A finite-element study of the effects of electrode position on the measured impedance change in impedance cardiography.  

PubMed

Traditional impedance cardiography (ICG) technique uses band electrodes both for delivering current to and measuring impedance change in the thorax. The use of spot electrodes increases the ease of electrode placement and comfort level for patients. Research has shown that changes in thoracic impedance can have multiple causes. In this study, we used finite element modeling to investigate the sources of impedance change for both band-electrode and spot-electrode ICG, and focused on how differences in electrode location affect the contribution of different sources to changes in impedance. The ultimate purpose is to identify the optimal electrode type and placement for the sensing of stroke volume (SV). Our models were built on sets of end-diastolic and end-systolic magnetic resonance images of a healthy human subject. The results showed that the effect of ventricular contraction is opposite to that of the other changes in systole: the expansion of major vessels, decrease in blood resistivity due to increased blood flow velocity, and decrease in lung resistivity due to increased blood perfusion. Ventricular contraction, the only factor that tends to increase systolic impedance, has a larger effect than any of the other factors. When spot electrodes are placed on the anterior chest wall near the heart, ventricular contraction is so dominant that the measured impedance increases from end-diastole to end-systole, and the change represents 82% of the contribution from ventricular contraction. When using the common band-electrode configuration, the change in measured impedance is a more balanced combination of the four effects, and ventricular contraction is overcome by the other three factors so that the impedance decreases. These results suggest that the belief that ICG can be used to directly measure SV based on the change in the whole thoracic impedance may be invalid, and that spot electrodes may be more useful for understanding local physiological events such as ventricular volume change. These findings are supported by previously reported experimental observations. PMID:11759920

Wang, Y; Haynor, D R; Kim, Y

2001-12-01

233

High-voltage space-plasma interactions measured on the PASP Plus test arrays  

NASA Technical Reports Server (NTRS)

The Photovoltaic Array Space Power Plus Diagnostics (PASP Plus) experiment was developed by the Air Force's Phillips Laboratory with support from NASA's Lewis Research Center. It was launched on the Advanced Photovoltaic and Electronics EXperiments (APEX) satellite on August 3, 1994 into a 70 degree inclination, 363 km by 2550 km elliptical orbit. This orbit allows the investigation of space plasma effects on high-voltage operation (leakage current at positive voltages and arcing at negative voltages) in the perigee region. PASP Plus is testing twelve solar arrays. There are four planar Si arrays: an old standard type (used as a reference), the large-cell Space Station Freedom (SSF) array, a thin 'APSA' array, and an amorphous Si array. Next are three GaAs on Ge planar arrays and three new material planar arrays, including InP and two multijunction types. Finally, there are two concentrator arrays: a reflective-focusing Mini-Cassegrainian and a Fresnel-lens focusing Mini-Dome. PASP Plus's diagnostic sensors include: Langmuir probe to measure plasma density, an electrostatic analyzer (ESA) to measure the 30 eV to 30 KeV electron/ion spectra and determine vehicle negative potential during positive biasing, and a transient pulse monitor (TPM) to characterize the arcs that occur during the negative biasing. Through positive biasing of its test arrays, PASP Plus investigated the snapover phenomenon, which took place over the range of +100 to +300 V. It was found that array configurations where the interconnects are shielded from the space plasma (i.e., the concentrators or arrays with 'wrap-through' connectors) have lower leakage current. The concentrators exhibited negligible leakage current over the whole range up to +500 V. In the case of two similar GaAs on Ge arrays, the one with 'wrap-through' connectors had lower leakage current than the one with conventional interconnects. Through negative biasing, PASP Plus investigated the arcing rates of its test arrays. The standard Si array, with its old construction (exposed rough-surface interconnects), arced significantly over a wide voltage and plasma-density range. The other arrays arced at very low rates, mostly at voltages greater than -350 V and plasma densities near or greater than 10(exp 5)/cm(exp -3). AS expected according to theory, arcing was more prevalent when array temperatures were cold (based on biasing in eclipse).

Guidice, Donald A.

1995-01-01

234

High frequency reference electrode  

DOEpatents

A high frequency reference electrode for electrochemical experiments comprises a mercury-calomel or silver-silver chloride reference electrode with a layer of platinum around it and a layer of a chemically and electrically resistant material such as TEFLON around the platinum covering all but a small ring or "halo" at the tip of the reference electrode, adjacent to the active portion of the reference electrode. The voltage output of the platinum layer, which serves as a redox electrode, and that of the reference electrode are coupled by a capacitor or a set of capacitors and the coupled output transmitted to a standard laboratory potentiostat. The platinum may be applied by thermal decomposition to the surface of the reference electrode. The electrode provides superior high-frequency response over conventional electrodes.

Kronberg, James W. (Aiken, SC)

1994-01-01

235

Measurements of High Voltage across the Vacuum Diode of a High-Current Generator by Using Photoneutron Reactions  

NASA Astrophysics Data System (ADS)

A new method is proposed for measuring the voltage across the vacuum diode of a high-current generator by determining the high-energy edge of bremsstrahlung from an electron beam with the help of photoneutron reactions. The method is approved in the RS-20 facility with a plasma opening switch in the voltage range2.5+4.5 MV. The results obtained by using this technique are in good agreement with the data from electrotechnical measurements.

Dan'ko, Seregej A.; Dolgachev, Georgy I.; Kalinin, Yury G.; Maslennikov, Dmitry D.

2002-12-01

236

In vivo impedance spectroscopy of deep brain stimulation electrodes  

NASA Astrophysics Data System (ADS)

Deep brain stimulation (DBS) represents a powerful clinical technology, but a systematic characterization of the electrical interactions between the electrode and the brain is lacking. The goal of this study was to examine the in vivo changes in the DBS electrode impedance that occur after implantation and during clinically relevant stimulation. Clinical DBS devices typically apply high-frequency voltage-controlled stimulation, and as a result, the injected current is directly regulated by the impedance of the electrode-tissue interface. We monitored the impedance of scaled-down clinical DBS electrodes implanted in the thalamus and subthalamic nucleus of a rhesus macaque using electrode impedance spectroscopy (EIS) measurements ranging from 0.5 Hz to 10 kHz. To further characterize our measurements, equivalent circuit models of the electrode-tissue interface were used to quantify the role of various interface components in producing the observed electrode impedance. Following implantation, the DBS electrode impedance increased and a semicircular arc was observed in the high-frequency range of the EIS measurements, commonly referred to as the tissue component of the impedance. Clinically relevant stimulation produced a rapid decrease in electrode impedance with extensive changes in the tissue component. These post-operative and stimulation-induced changes in impedance could play an important role in the observed functional effects of voltage-controlled DBS and should be considered during clinical stimulation parameter selection and chronic animal research studies.

Lempka, Scott F.; Miocinovic, Svjetlana; Johnson, Matthew D.; Vitek, Jerrold L.; McIntyre, Cameron C.

2009-08-01

237

Rapid pH change due to bacteriorhodopsin measured with a tin-oxide electrode.  

PubMed Central

The photocurrent transient generated by bacteriorhodopsin (bR) on a tin-oxide electrode is due to pH change and not to charge displacement as previously assumed. Films of either randomly oriented or highly oriented purple membranes were deposited on transparent electrodes made of tin-oxide-coated glass. The membranes contained either wild-type or D96N-mutant bR. When excited with yellow light through the glass, the bR pumps protons across the membrane. The result is a rapid local pH change as well as a charge displacement. Experiments with these films show that it is the pH change rather than the displacement that produces the current transient. The calibration for the transient pH measurement is given. The sensitivity of a tin-oxide electrode to a transient pH change is very much larger than its sensitivity to a steady-state pH change. PMID:7787036

Robertson, B; Lukashev, E P

1995-01-01

238

Membrane potential measurements of isolated neurons using a voltage-sensitive dye.  

PubMed

The ability to monitor changes in membrane potential is a useful tool for studying neuronal function, but there are only limited options available at present. Here, we have investigated the potential of a commercially available FLIPR membrane potential (FMP) dye, developed originally for high throughput screening using a plate reader, for imaging the membrane potential of cultured cells using an epifluorescence-based single cell imaging system. We found that the properties of the FMP dye make it highly suitable for such imaging since 1) its fluorescence displayed a high signal-to-noise ratio, 2) robust signals meant only minimal exposure times of around 5 ms were necessary, and 3) bidirectional changes in fluorescence were detectable resulting from hyper- or depolarising conditions, reaching equilibrium with a time constant of 4-8 s. Measurements were possible independently of whether membrane potential changes were induced by voltage clamping, or manipulating the ionic distribution of either Na(+) or K(+). Since FMP behaves as a charged molecule which accumulates in the cytosol, equations based on the Boltzmann distribution were developed determining that the apparent charge of FMP which represents a measure of the voltage sensitivity of the dye, is between -0.62 and -0.72. Finally, we demonstrated that FMP is suitable for use in a variety of neuronal cell types and detects membrane potential changes arising from spontaneous firing of action potentials and through stimulation with a variety of excitatory and inhibitory neurotransmitters. PMID:23516458

Fairless, Richard; Beck, Andreas; Kravchenko, Mykola; Williams, Sarah K; Wissenbach, Ulrich; Diem, Ricarda; Cavalié, Adolfo

2013-01-01

239

Membrane Potential Measurements of Isolated Neurons Using a Voltage-Sensitive Dye  

PubMed Central

The ability to monitor changes in membrane potential is a useful tool for studying neuronal function, but there are only limited options available at present. Here, we have investigated the potential of a commercially available FLIPR membrane potential (FMP) dye, developed originally for high throughput screening using a plate reader, for imaging the membrane potential of cultured cells using an epifluorescence-based single cell imaging system. We found that the properties of the FMP dye make it highly suitable for such imaging since 1) its fluorescence displayed a high signal-to-noise ratio, 2) robust signals meant only minimal exposure times of around 5 ms were necessary, and 3) bidirectional changes in fluorescence were detectable resulting from hyper- or depolarising conditions, reaching equilibrium with a time constant of 4–8 s. Measurements were possible independently of whether membrane potential changes were induced by voltage clamping, or manipulating the ionic distribution of either Na+ or K+. Since FMP behaves as a charged molecule which accumulates in the cytosol, equations based on the Boltzmann distribution were developed determining that the apparent charge of FMP which represents a measure of the voltage sensitivity of the dye, is between ?0.62 and ?0.72. Finally, we demonstrated that FMP is suitable for use in a variety of neuronal cell types and detects membrane potential changes arising from spontaneous firing of action potentials and through stimulation with a variety of excitatory and inhibitory neurotransmitters. PMID:23516458

Fairless, Richard; Beck, Andreas; Kravchenko, Mykola; Williams, Sarah K.; Wissenbach, Ulrich; Diem, Ricarda; Cavalié, Adolfo

2013-01-01

240

Focused ion beam processing to fabricate ohmic contact electrodes on a bismuth nanowire for Hall measurements.  

PubMed

Ohmic contact electrodes for four-wire resistance and Hall measurements were fabricated on an individual single-crystal bismuth nanowire encapsulated in a cylindrical quartz template. Focused ion beam processing was utilized to expose the side surfaces of the bismuth nanowire in the template, and carbon and tungsten electrodes were deposited on the bismuth nanowire in situ to achieve electrical contacts. The temperature dependence of the four-wire resistance was successfully measured for the bismuth nanowire, and a difference between the resistivities of the two-wire and four-wire methods was observed. It was concluded that the two-wire method was unsuitable for estimation of the resistivity due to the influence of contact resistance, even if the magnitude of the bismuth nanowire resistance was greater than the kilo-ohm order. Furthermore, Hall measurement of a 4-?m-diameter bismuth microwire was also performed as a trial, and the evaluated temperature dependence of the carrier mobility was in agreement with that for bulk bismuth, which indicates that the carrier mobility was successfully measured using this technique. PACS: 81.07.Gf. PMID:24070421

Murata, Masayuki; Hasegawa, Yasuhiro

2013-01-01

241

Focused ion beam processing to fabricate ohmic contact electrodes on a bismuth nanowire for Hall measurements  

PubMed Central

Ohmic contact electrodes for four-wire resistance and Hall measurements were fabricated on an individual single-crystal bismuth nanowire encapsulated in a cylindrical quartz template. Focused ion beam processing was utilized to expose the side surfaces of the bismuth nanowire in the template, and carbon and tungsten electrodes were deposited on the bismuth nanowire in situ to achieve electrical contacts. The temperature dependence of the four-wire resistance was successfully measured for the bismuth nanowire, and a difference between the resistivities of the two-wire and four-wire methods was observed. It was concluded that the two-wire method was unsuitable for estimation of the resistivity due to the influence of contact resistance, even if the magnitude of the bismuth nanowire resistance was greater than the kilo-ohm order. Furthermore, Hall measurement of a 4-?m-diameter bismuth microwire was also performed as a trial, and the evaluated temperature dependence of the carrier mobility was in agreement with that for bulk bismuth, which indicates that the carrier mobility was successfully measured using this technique. PACS 81.07.Gf PMID:24070421

2013-01-01

242

Access resistance of stimulation electrodes as a function of electrode proximity to the retina  

NASA Astrophysics Data System (ADS)

Objective. Epiretinal prostheses seek to effectively stimulate the retina by positioning electrode arrays close to its surface so current pulses generate narrow retinal electric fields. Our objective was to evaluate the use of the electrical impedance of insulated platinum electrodes as a measure of the proximity of insulated platinum electrodes to the inner surface of the retina. Approach. We examined the impedance of platinum disk electrodes, 0.25 mm in diameter, insulated with two widths (0.8 and 1.6 mm outer diameter) of transparent fluoropolymer in a rabbit retinal eyecup preparation. Optical coherence tomography measured the electrode’s proximity to the retinal surface which was correlated with changes in the voltage waveform at the electrode. Electrode impedance changes during retinal deformation were also studied. Main results. When the 1.6 mm diameter insulated electrodes advanced towards the retinal surface from 1000 ?m, their voltage step at current pulse onset increased, reflecting an access resistance increase of 3880 ± 630 ?, with the 50% midpoint averaging 30 ?m, while thin 0.8 mm insulated electrode advancement showed an access resistance increase 50% midpoint averaging 16 ?m. Using impedance spectroscopy, electrode–retina proximity differences were seen in the 1.6 mm insulated electrode impedance modulus between 1 and 100 kHz and the waveform phase angle at 0.3–10 kHz, while thin 0.8 mm insulated electrode advancement produced smaller impedance modulus changes with retinal proximity between 3 and 100 kHz. These impedance changes with retinal proximity may reflect different sized zones of eye wall being coupled in series with the insulated platinum electrode. Significance. The proximity of stimulus electrodes to neural tissue in fluid-filled spaces can be estimated from access resistance changes in the stimulus pulse waveform. Because many prosthetic devices allow back telemetry communication of the stimulus electrode waveform, it is possible these series resistance increases observed with retinal proximity could be used as a metric of stimulus electrode placement.

Majdi, Joseph A.; Minnikanti, Saugandhika; Peixoto, Nathalia; Agrawal, Anant; Cohen, Ethan D.

2015-02-01

243

Voltage measurements over the CAM-1 submarine cable between Madeira Island and Portugal mainland  

NASA Astrophysics Data System (ADS)

Data of electrical voltage measured between the ends of the CAM-1 cable, during fifteen months, have been analysed in order to determine the electrical stability of the cable and to obtain some preliminary information related to water transport. The monthly average of the potential measured during days with low geomagnetic activity suggests a periodicity of 120 days that was tentatively interpreted as having origin in water flow. These results show a small trend that is compatible with no drift in the cable. The mean electric field estimated from quiet days is 0.206 ± 0.022 mV/km. If the variations of this potential are attributable to ocean water transport a total water flow of ±0.09 cm/s is estimated. This value represents a maximum value for temporal variations of the spatially averaged water-flow velocity.

Monteiro Santos, F. A.; Soares, A.; Trindade, L.; Nolasco, R.; Rodrigues, H.; Iso-3D Team

2002-04-01

244

Oil-Water Interface Level Sensor Based on an Electrode Array  

Microsoft Academic Search

A novel liquid interface level sensor is presented that is able to determine the position of the interface between a conductive and an insulating liquid. The sensor consists of an array of equally spaced electrodes, two of which are used to inject a current into the conductive liquid and the remaining electrodes are used to measure the drop in voltage

Ramon Casanella; Óscar Casas; Ramon Pallàs-Areny

2006-01-01

245

All-printed low-voltage organic transistors  

Microsoft Academic Search

All-printed low-voltage organic transistors were manufactured on a plastic substrate and measured in normal room atmosphere. All electrodes were ink-jet printed, while the homogeneous semiconductor and insulator layers were subsequently applied by the reverse gravure coating technique. No destructive effects from the rough plastic substrate or the printed silver source and drain electrodes were observed. Changes in the transistor characteristics

D. Tobjörk; N. J. Kaihovirta; T. Mäkelä; F. S. Pettersson; R. Österbacka

2008-01-01

246

A new drain-current injection technique for the measurement of off-state breakdown voltage in FETs  

Microsoft Academic Search

A simple three-terminal technique for measuring the off-state breakdown voltage of FETs is presented. With the source grounded, current is injected into the drain of the on-state device. The gate is then ramped down to shut the device off. In this process, the drain-source voltage rises to a peak and then drops. This peak represents an unambiguous definition of three-terminal

Sandeep R. Bahl; Jeslis A. del Alamo

1993-01-01

247

Emulsion stability measurements by single electrode capacitance probe (SeCaP) technology  

NASA Astrophysics Data System (ADS)

This paper describes a new and novel method for the determination of the stability of emulsions. The method is based on the single electrode capacitance technology (SeCaP). A measuring system consisting of eight individual measuring cells, each with a volume of approximately 10 ml, is described in detail. The system has been tested on an emulsion system based on whey proteins (WPC80), oil and water. Xanthan was added to modify the emulsion stability. The results show that the new measuring system is able to quantify the stability of the emulsion in terms of a differential variable. The whole separation process is observed much faster in the SeCaP system than in a conventional separation column. The complete separation process observed visually over 30 h is seen in less than 1.4 h in the SeCaP system.

Schüller, R. B.; Løkra, S.; Salas-Bringas, C.; Egelandsdal, B.; Engebretsen, B.

2008-08-01

248

In situ spatially and temporally resolved measurements of salt concentration between charging porous electrodes for desalination by capacitive deionization.  

PubMed

Capacitive deionization (CDI) is an emerging water desalination technique. In CDI, pairs of porous electrode capacitors are electrically charged to remove salt from brackish water present between the electrodes. We here present a novel experimental technique allowing measurement of spatially and temporally resolved salt concentration between the CDI electrodes. Our technique measures the local fluorescence intensity of a neutrally charged fluorescent probe which is collisionally quenched by chloride ions. To our knowledge, our system is the first to measure in situ and spatially resolved chloride concentration in a laboratory CDI cell. We here demonstrate good agreement between our dynamic measurements of salt concentration in a charging, millimeter-scale CDI system to the results of a modified Donnan porous electrode transport model. Further, we utilize our dynamic measurements to demonstrate that salt removal between our charging CDI electrodes occurs on a longer time scale than the capacitive charging time scales of our CDI cell. Compared to typical measurements of CDI system performance (namely, measurements of outflow ionic conductivity), our technique can enable more advanced and better-controlled studies of ion transport in CDI systems, which can potentially catalyze future performance improvements. PMID:24433022

Suss, Matthew E; Biesheuvel, P M; Baumann, Theodore F; Stadermann, Michael; Santiago, Juan G

2014-02-01

249

Spatiotemporal electrochemical measurements across an electric double layer capacitor electrode with application to aqueous sodium hybrid batteries  

NASA Astrophysics Data System (ADS)

This paper presents in-situ spatiotemporal measurements of the electrolyte phase potential within an electric double layer capacitor (EDLC) negative electrode as envisaged for use in an aqueous hybrid battery for grid-scale energy storage. The ultra-thick electrodes used in these batteries to reduce non-functional material costs require sufficiently fast through-plane mass and charge transport to attain suitable charging and discharging rates. To better evaluate the through-plane transport, we have developed an electrode scaffold (ES) for making in situ electrolyte potential distribution measurements at discrete known distances across the thickness of an uninterrupted EDLC negative electrode. Using finite difference methods, we calculate local current, volumetric charging current and charge storage distributions from the spatiotemporal electrolyte potential measurements. These potential distributions provide insight into complex phenomena that cannot be directly observed using other existing methods. Herein, we use the distributions to identify areas of the electrode that are underutilized, assess the effects of various parameters on the cumulative charge storage distribution, and evaluate an effectiveness factor for charge storage in EDLC electrodes.

Tully, Katherine C.; Whitacre, Jay F.; Litster, Shawn

2014-02-01

250

Shielded button electrodes for time-resolved measurements of electron cloud buildup  

NASA Astrophysics Data System (ADS)

We report on the design, deployment and signal analysis for shielded button electrodes sensitive to electron cloud buildup at the Cornell Electron Storage Ring. These simple detectors, derived from a beam-position monitor electrode design, have provided detailed information on the physical processes underlying the local production and the lifetime of electron densities in the storage ring. Digitizing oscilloscopes are used to record electron fluxes incident on the vacuum chamber wall in 1024 time steps of 100 ps or more. The fine time steps provide a detailed characterization of the cloud, allowing the independent estimation of processes contributing on differing time scales and providing sensitivity to the characteristic kinetic energies of the electrons making up the cloud. By varying the spacing and population of electron and positron beam bunches, we map the time development of the various cloud production and re-absorption processes. The excellent reproducibility of the measurements also permits the measurement of long-term conditioning of vacuum chamber surfaces.

Crittenden, J. A.; Billing, M. G.; Li, Y.; Palmer, M. A.; Sikora, J. P.

2014-06-01

251

Effect of current compliance and voltage sweep rate on the resistive switching of HfO{sub 2}/ITO/Invar structure as measured by conductive atomic force microscopy  

SciTech Connect

The electrical characterization of HfO{sub 2}/ITO/Invar resistive switching memory structure was studied using conductive atomic force microscopy (AFM) with a semiconductor parameter analyzer, Agilent 4156C. The metal alloy Invar was used as the metal substrate to ensure good ohmic contact with the substrate holder of the AFM. A conductive Pt/Ir AFM tip was placed in direct contact with the HfO{sub 2} surface, such that it acted as the top electrode. Nanoscale current-voltage (I-V) characteristics of the HfO{sub 2}/ITO/Invar structure were measured by applying a ramp voltage through the conductive AFM tip at various current compliances and ramp voltage sweep rates. It was found that the resistance of the low resistance state (RLRS) decreased with increasing current compliance value, but resistance of high resistance state (RHRS) barely changed. However, both the RHRS and RLRS decreased as the voltage sweep rate increased. The reasons for this dependency on current compliance and voltage sweep rate are discussed.

Wu, You-Lin, E-mail: ylwu@ncnu.edu.tw; Liao, Chun-Wei [Department of Electrical Engineering, National Chi Nan University, Puli, Nantou, Taiwan (China); Ling, Jing-Jenn [Department of Applied Materials and Optoelectronic Engineering, National Chi Nan University, Puli, Nantou, Taiwan (China)

2014-06-16

252

Access resistance of stimulation electrodes as a function of electrode proximity to the retina.  

PubMed

Objective. Epiretinal prostheses seek to effectively stimulate the retina by positioning electrode arrays close to its surface so current pulses generate narrow retinal electric fields. Our objective was to evaluate the use of the electrical impedance of insulated platinum electrodes as a measure of the proximity of insulated platinum electrodes to the inner surface of the retina. Approach. We examined the impedance of platinum disk electrodes, 0.25 mm in diameter, insulated with two widths (0.8 and 1.6 mm outer diameter) of transparent fluoropolymer in a rabbit retinal eyecup preparation. Optical coherence tomography measured the electrode's proximity to the retinal surface which was correlated with changes in the voltage waveform at the electrode. Electrode impedance changes during retinal deformation were also studied. Main results. When the 1.6 mm diameter insulated electrodes advanced towards the retinal surface from 1000 ?m, their voltage step at current pulse onset increased, reflecting an access resistance increase of 3880 ± 630 ?, with the 50% midpoint averaging 30 ?m, while thin 0.8 mm insulated electrode advancement showed an access resistance increase 50% midpoint averaging 16 ?m. Using impedance spectroscopy, electrode-retina proximity differences were seen in the 1.6 mm insulated electrode impedance modulus between 1 and 100 kHz and the waveform phase angle at 0.3-10 kHz, while thin 0.8 mm insulated electrode advancement produced smaller impedance modulus changes with retinal proximity between 3 and 100 kHz. These impedance changes with retinal proximity may reflect different sized zones of eye wall being coupled in series with the insulated platinum electrode. Significance. The proximity of stimulus electrodes to neural tissue in fluid-filled spaces can be estimated from access resistance changes in the stimulus pulse waveform. Because many prosthetic devices allow back telemetry communication of the stimulus electrode waveform, it is possible these series resistance increases observed with retinal proximity could be used as a metric of stimulus electrode placement. PMID:25474329

Majdi, Joseph A; Minnikanti, Saugandhika; Peixoto, Nathalia; Agrawal, Anant; Cohen, Ethan D

2015-02-01

253

Measurements of induced voltages and currents in a distribution power line and associated atmospheric parameters  

NASA Technical Reports Server (NTRS)

The frequency and intensity of thunderstorms around the Kennedy Space Center (KSC) has affected scheduled launch, landing, and other ground operations for many years. In order to protect against and provide safe working facilities, KSC has performed and hosted several studies on lightning phenomena. For the reasons mentioned above, KSC has established the Atmospheric Science Field Laboratory (ASFL). At these facilities KSC launches wire-towing rockets into thunderstorms to trigger natural lightning to the launch site. A program named Rocket Triggered Lightning Program (RTLP) is being conducted at the ASFL. This report calls for two of the experiments conducted in the summer 1988 Rocket Triggered Lightning Program. One experiment suspended an electric field mill over the launching areas from a balloon about 500 meters high to measure the space charges over the launching area. The other was to connect a waveform recorder to a nearby distribution power line to record currents and voltages wave forms induced by natural and triggered lightning.

Santiago-Perez, Julio

1988-01-01

254

Measurements of induced voltages and currents in a distribution power line and associated atmospheric parameters  

NASA Astrophysics Data System (ADS)

The frequency and intensity of thunderstorms around the Kennedy Space Center (KSC) has affected scheduled launch, landing, and other ground operations for many years. In order to protect against and provide safe working facilities, KSC has performed and hosted several studies on lightning phenomena. For the reasons mentioned above, KSC has established the Atmospheric Science Field Laboratory (ASFL). At these facilities KSC launches wire-towing rockets into thunderstorms to trigger natural lightning to the launch site. A program named Rocket Triggered Lightning Program (RTLP) is being conducted at the ASFL. This report calls for two of the experiments conducted in the summer 1988 Rocket Triggered Lightning Program. One experiment suspended an electric field mill over the launching areas from a balloon about 500 meters high to measure the space charges over the launching area. The other was to connect a waveform recorder to a nearby distribution power line to record currents and voltages wave forms induced by natural and triggered lightning.

Santiago-Perez, Julio

1988-10-01

255

High-voltage space-plasma interactions measured on the PASP Plus test arrays  

SciTech Connect

The Photovoltaic Array Space Power Plus Diagnostics (PASP Plus) experiment was developed by the Air Force`s Phillips Laboratory with support from NASA`s Lewis Research Center. It was launched on the Advanced Photovoltaic and Electronics EXperiments (APEX) satellite on August 3, 1994 into a 70 degree inclination, 363 km by 2550 km elliptical orbit. This orbit allows the investigation of space plasma effects on high-voltage operation (leakage current at positive voltages and arcing at negative voltages) in the perigee region. PASP Plus is testing twelve solar arrays. There are four planar Si arrays: an old standard type (used as a reference), the large-cell Space Station Freedom (SSF) array, a thin `APSA` array, and an amorphous Si array. Next are three GaAs on Ge planar arrays and three new material planar arrays, including InP and two multijunction types. Finally, there are two concentrator arrays: a reflective-focusing Mini-Cassegrainian and a Fresnel-lens focusing Mini-Dome. PASP Plus`s diagnostic sensors include: Langmuir probe to measure plasma density, an electrostatic analyzer (ESA) to measure the 30 eV to 30 KeV electron/ion spectra and determine vehicle negative potential during positive biasing, and a transient pulse monitor (TPM) to characterize the arcs that occur during the negative biasing. Through positive biasing of its test arrays, PASP Plus investigated the snapover phenomenon, which took place over the range of +100 to +300 V. It was found that array configurations where the interconnects are shielded from the space plasma (i.e., the concentrators or arrays with `wrap-through` connectors) have lower leakage current. The concentrators exhibited negligible leakage current over the whole range up to +500 V. In the case of two similar GaAs on Ge arrays, the one with `wrap-through` connectors had lower leakage current than the one with conventional interconnects. Through negative biasing, PASP Plus investigated the arcing rates of its test arrays.

Guidice, D.A.

1995-10-01

256

Liquid electrode  

DOEpatents

A dropping electrolyte electrode is described for use in electrochemical analysis of non-polar sample solutions, such as benzene or cyclohexane. The liquid electrode, preferably an aqueous salt solution immiscible in the sample solution, is introduced into the solution in dropwise fashion from a capillary. The electrolyte is introduced at a known rate, thus, the droplets each have the same volume and surface area. The electrode is used in making standard electrochemical measurements in order to determine properties of non-polar sample solutions. 2 figures.

Ekechukwu, A.A.

1994-07-05

257

In vivo and In vitro Differences in the Charge-injection and Electrochemical Properties of Iridium Oxide Electrodes  

Microsoft Academic Search

The electrochemical response of activated iridium oxide (AIROF) electrodes implanted acutely in the subretinal space of the rabbit is compared with in vitro measurements in model electrolytes. Voltage transients during current pulsing, cyclic voltammetry, impedance spectroscopy and open-circuit potential measurements were compared. Subretinal charge injection by constant current pulsing required significantly greater driving voltages due to both higher access resistances

Stuart F. Cogan

2006-01-01

258

Hysteresis observed in quasi open-circuit voltage measurements of lithium insertion in hydrogen-containing carbons  

Microsoft Academic Search

High capacities with large hysteresis were observed during lithium insertion in hydrogen-containing carbons heated at temperatures near 700 °C. Quasi open-circuit voltage (OCV) measurements were used to study these materials. Using a simple model developed previously [1], we can qualitatively model the result of the OCV measurement. It is believed that the lithium atoms bind near aromatic hydrogen at edge

Tao Zheng; J. R. Dahn

1997-01-01

259

Influence of barrier on partial discharge activity by a conducting particle in liquid nitrogen under AC voltages adopting UHF technique  

NASA Astrophysics Data System (ADS)

The UHF signals are generated due to PD formed by particle movement in liquid nitrogen under AC voltages. The levitation voltage of a particle in liquid nitrogen measured through UHF technique and by conventional PD measurement technique is the same, confirming the sensitivity of UHF technique for identification of PD activity. The frequency content of UHF signal generated due to particle movement in liquid nitrogen, under AC voltages, lies in the range 0.5-1.5 GHz. The characteristics of UHF signal generated due to particle movement between the barrier and high voltage/ground electrode is much similar to the signal generated by particle movement in clean electrode gap. Pseudo resonance phenomena can occur in liquid nitrogen due to particle movement. It is also observed that the partial discharge magnitude, in general, be high when the particle moves between the barrier and high voltage electrode when compared to the barrier and the ground electrode. Percentage of clay in epoxy nanocomposites has not altered the levitation voltage of the particle in the electrode gap. Zero span analysis clearly indicates that pseudo resonance occurs when particle moves (in a short gap) between the barrier and high voltage/ground electrode.

Sarathi, R.; Giridhar, A. V.; Sethupathi, K.

2011-02-01

260

Simultaneous measurements of wire electrode surface contamination and corona discharge characteristics in an air-cleaning electrostatic precipitator  

SciTech Connect

Contamination of the corona wire in a wire-to-plate type air-cleaning electrostatic precipitator is studied experimentally. In order to enhance the contamination of wire, air containing dusts is directly supplied to a part of the wire electrode. Spores of Lycopodium and cigarette smoke particles are used as test dusts. Simultaneous measurements of wire electrode optical images and corona discharge modes are carried out during contamination processes. Results show that corona discharge modes and optical emission from the wire electrode change with time due to the surface contamination. In the case of cigarette smoke, after a time elapsed, streamer coronas appear due to the buildup of smoke particles on the wire surface. After the first streamer generation, the corona current fluctuates with time because the formation and diminution of the projections occur alternately at the different parts on the wire electrode surface.

Kanazawa, Seiji; Ohkubo, Toshikazu; Nomoto, Yukiharu; Adachi, Takayoshi [Oita Univ. (Japan). Dept. of Electrical and Electronic Engineering] [Oita Univ. (Japan). Dept. of Electrical and Electronic Engineering; Chang, J.S. [McMaster Univ., Hamilton, Ontario (Canada). Dept. of Engineering Physics] [McMaster Univ., Hamilton, Ontario (Canada). Dept. of Engineering Physics

1997-01-01

261

Time varying voltage combustion control and diagnostics sensor  

DOEpatents

A time-varying voltage is applied to an electrode, or a pair of electrodes, of a sensor installed in a fuel nozzle disposed adjacent the combustion zone of a continuous combustion system, such as of the gas turbine engine type. The time-varying voltage induces a time-varying current in the flame which is measured and used to determine flame capacitance using AC electrical circuit analysis. Flame capacitance is used to accurately determine the position of the flame from the sensor and the fuel/air ratio. The fuel and/or air flow rate (s) is/are then adjusted to provide reduced flame instability problems such as flashback, combustion dynamics and lean blowout, as well as reduced emissions. The time-varying voltage may be an alternating voltage and the time-varying current may be an alternating current.

Chorpening, Benjamin T. (Morgantown, WV); Thornton, Jimmy D. (Morgantown, WV); Huckaby, E. David (Morgantown, WV); Fincham, William (Fairmont, WV)

2011-04-19

262

An electric field in nanosecond surface dielectric barrier discharge at different polarities of the high voltage pulse: spectroscopy measurements and numerical modeling  

NASA Astrophysics Data System (ADS)

The ratio of emission intensities of the second positive N2(C3?u, v? = 0) ? N2(B3?g, v = 0), 337.1 nm and first negative \\text{N}2+ (B2?g+,v\\prime =0) ? \\text{N}2+ (X2?g+,v=0) , 391.4 nm systems of nitrogen have been measured in a nanosecond surface dielectric barrier discharge (SDBD). The measurements were carried out in synthetic air for a pressure range 1–3 bar for different polarities of the high-voltage (HV) pulse. For all the investigated conditions, the ratio of emission intensities at the wavelengthes 391.4 and 337.1 nm, measured experimentally, R391/337\\text{exp} is systematically higher for the positive polarity of HV electrodes. To analyze the spatial distribution of N2(C3?u) and \\text{N}2+ (B2?g+) emissions, comprehensive two-dimensional numerical modeling for P = 1 bar has been performed. The details of the formation of a narrow gap between the dielectric surface and the streamer channel in the case of positive polarity of HV electrodes are discussed. The ratio of integrated over space calculated emission intensities, R391/337\\text{th} , has been analyzed and compared with obtained experimental data. A good agreement was obtained for a negative polarity SDBD. For a positive polarity discharge, R391/337\\text{exp}\\gg R391/337\\text{th} for all the considered conditions. Explanation for the observed effect is suggested.

Stepanyan, S. A.; Soloviev, V. R.; Starikovskaia, S. M.

2014-12-01

263

A Simple Hydrogen Electrode  

ERIC Educational Resources Information Center

This article describes the construction of an inexpensive, robust, and simple hydrogen electrode, as well as the use of this electrode to measure "standard" potentials. In the experiment described here the students can measure the reduction potentials of metal-metal ion pairs directly, without using a secondary reference electrode. Measurements

Eggen, Per-Odd

2009-01-01

264

Dielectric spectroscopy of thin films by dual-channel impedance measurements on differential interdigitated electrode arrays  

NASA Astrophysics Data System (ADS)

We report a new approach to measuring the dielectric behavior of thin films by means of differential interdigitated electrode (IDE) cells coupled with a dual-channel impedance measurement setup. The differential IDE cell consists of two identical IDE's on a common substrate. With one IDE loaded with sample and the other one empty, the complex permittivities of both capacitors are measured simultaneously by means of a dual-channel impedance measurement setup. The net dielectric response of the material under study is then obtained by the difference of the two permittivities, which corrects for the substrate contribution. The applicability of this approach is examined with bulk glycerol and a 600 nm indomethacin film and is evidenced by the results being consistent with those measured by conventional methods. The main advantages of this new approach include a simplified preparation technique for thin film samples and a straightforward correction for the substrate contribution by subtracting the empty IDE signal obtained at the same temperature and thermal history.

Chen, Z.; Sepúlveda, A.; Ediger, M. D.; Richert, R.

2012-08-01

265

Real-time management of faulty electrodes in electrical impedance tomography.  

PubMed

Completely or partially disconnected electrodes are a fairly common occurrence in many electrical impedance tomography (EIT) clinical applications. Several factors can contribute to electrode disconnection: patient movement, perspiration, manipulations by clinical staff, and defective electrode leads or electronics. By corrupting several measurements, faulty electrodes introduce significant image artifacts. In order to properly manage faulty electrodes, it is necessary to: 1) account for invalid data in image reconstruction algorithms and 2) automatically detect faulty electrodes. This paper presents a two-part approach for real-time management of faulty electrodes based on the principle of voltage-current reciprocity. The first part allows accounting for faulty electrodes in EIT image reconstruction without a priori knowledge of which electrodes are at fault. The method properly weights each measurement according to its compliance with the principle of voltage-current reciprocity. Results show that the algorithm is able to automatically determine the valid portion of the data and use it to calculate high-quality images. The second part of the approach allows automatic real-time detection of at least one faulty electrode with 100% sensitivity and two faulty electrodes with 80% sensitivity enabling the clinical staff to fix the problem as soon as possible to minimize data loss. PMID:19272943

Hartinger, Alzbeta E; Guardo, Robert; Adler, Andy; Gagnon, Hervé

2009-02-01

266

Proton conductivity of Nafion 117 as measured by a four-electrode AC impedance method  

SciTech Connect

Nafion 117{reg_sign} is a proton conducting ion-exchange membrane which is now receiving much attention due to its use as an electrolyte in the polymer-electrolyte-membrane fuel cell (PEMFC), which is of great interest for electric vehicle propulsion. The proton conductivity of Nafion 117 was measured under various conditions of humidity and temperature using a four-electrode ac impedance method. The conductivity of this membrane without heat-treatment was ca. 7.8 {times} 10{sup {minus}2} S/cm at ambient temperature and 100% relative humidity; it varied strongly with the humidity and heat-treatment of the membrane. After heat-treatment, the membrane showed a slight dependence of conductivity on temperature. From 21 to 45 C, its conductivity at a given relative humidity decreased with increasing temperature, while from 45 to 80 C it increased with temperature.

Sone, Y.; Ekdunge, P.; Simonsson, D. [Royal Inst. of Tech., Stockholm (Sweden)

1996-04-01

267

A voltage-doubling (2-kV) pulser for biomedical ultrasound measurements  

NASA Astrophysics Data System (ADS)

High-voltage pulsers offer advantages in some biomedical ultrasound measurement applications, such as driving focused transducers for bioeffects studies, or transiently exciting plane, thick transducers for broadband measurements of attenuation or frequency response of receiving transducers. Because the duty cycle is low (typically less than 0.1%), bulky, expensive pulsers having large temporal-average power capability are not required. In the present design integrated gate bipolar transistors (IGBTs) are used to energize the ultrasound transducer. This solid-state switching device can handle large currents, has a low on-resistance, and can be turned off as well as on by its gate signal. However, widely available devices are limited to 1200-V peak. Therefore, the present design charges two capacitors in parallel and then uses two IGBTs to connect them in series to produce the output pulse. With a 1200-V supply this approach produces a pulse of 2100 V into a 50-? load at a 200-Hz repetition rate. The length of the output pulse is determined by the controlling input TTL pulse unless small capacitors are used, in which case a decaying exponential pulse is obtained. This design is readily reproduced and the components, exclusive of the power supply, cost less than $100.

Gammell, Paul M.; Harris, Gerald R.

2003-04-01

268

Radio frequency cavity analysis, measurement, and calibration of absolute Dee voltage for K-500 superconducting cyclotron at VECC, Kolkata  

NASA Astrophysics Data System (ADS)

Variable Energy Cyclotron Centre has commissioned a K-500 superconducting cyclotron for various types of nuclear physics experiments. The 3-phase radio-frequency system of superconducting cyclotron has been developed in the frequency range 9-27 MHz with amplitude and phase stability of 100 ppm and ±0.20, respectively. The analysis of the RF cavity has been carried out using 3D Computer Simulation Technology (CST) Microwave Studio code and various RF parameters and accelerating voltages ("Dee" voltage) are calculated from simulation. During the RF system commissioning, measurement of different RF parameters has been done and absolute Dee voltage has been calibrated using a CdTe X-ray detector along with its accessories and known X-ray source. The present paper discusses about the measured data and the simulation result.

Som, Sumit; Seth, Sudeshna; Mandal, Aditya; Paul, Saikat; Duttagupta, Anjan

2013-02-01

269

Radio frequency cavity analysis, measurement, and calibration of absolute Dee voltage for K-500 superconducting cyclotron at VECC, Kolkata.  

PubMed

Variable Energy Cyclotron Centre has commissioned a K-500 superconducting cyclotron for various types of nuclear physics experiments. The 3-phase radio-frequency system of superconducting cyclotron has been developed in the frequency range 9-27 MHz with amplitude and phase stability of 100 ppm and ±0.2(0), respectively. The analysis of the RF cavity has been carried out using 3D Computer Simulation Technology (CST) Microwave Studio code and various RF parameters and accelerating voltages ("Dee" voltage) are calculated from simulation. During the RF system commissioning, measurement of different RF parameters has been done and absolute Dee voltage has been calibrated using a CdTe X-ray detector along with its accessories and known X-ray source. The present paper discusses about the measured data and the simulation result. PMID:23464200

Som, Sumit; Seth, Sudeshna; Mandal, Aditya; Paul, Saikat; Duttagupta, Anjan

2013-02-01

270

Radio frequency cavity analysis, measurement, and calibration of absolute Dee voltage for K-500 superconducting cyclotron at VECC, Kolkata  

SciTech Connect

Variable Energy Cyclotron Centre has commissioned a K-500 superconducting cyclotron for various types of nuclear physics experiments. The 3-phase radio-frequency system of superconducting cyclotron has been developed in the frequency range 9-27 MHz with amplitude and phase stability of 100 ppm and {+-}0.2{sup 0}, respectively. The analysis of the RF cavity has been carried out using 3D Computer Simulation Technology (CST) Microwave Studio code and various RF parameters and accelerating voltages ('Dee' voltage) are calculated from simulation. During the RF system commissioning, measurement of different RF parameters has been done and absolute Dee voltage has been calibrated using a CdTe X-ray detector along with its accessories and known X-ray source. The present paper discusses about the measured data and the simulation result.

Som, Sumit; Seth, Sudeshna; Mandal, Aditya; Paul, Saikat; Duttagupta, Anjan [Variable Energy Cyclotron Centre, Kolkata (India)

2013-02-15

271

Measurement and prediction of microshock currents and voltages in an HV laboratory  

Microsoft Academic Search

Microshocks are the low current, continuous discharges experienced by people capacitively coupled to high voltage equipment. The situations in which these discharges occur are complicated by the size and complexity of the high voltage equipment and the sensitivity of the person concerned. A simple model has been constructed in the commercial software package CDEGS. This has been used to model

Y. Ahmed; S. M. Rowland

2007-01-01

272

Charge-pump voltage converter  

DOEpatents

A charge-pump voltage converter for converting a low voltage provided by a low-voltage source to a higher voltage. Charge is inductively generated on a transfer rotor electrode during its transit past an inductor stator electrode and subsequently transferred by the rotating rotor to a collector stator electrode for storage or use. Repetition of the charge transfer process leads to a build-up of voltage on a charge-receiving device. Connection of multiple charge-pump voltage converters in series can generate higher voltages, and connection of multiple charge-pump voltage converters in parallel can generate higher currents. Microelectromechanical (MEMS) embodiments of this invention provide a small and compact high-voltage (several hundred V) voltage source starting with a few-V initial voltage source. The microscale size of many embodiments of this invention make it ideally suited for MEMS- and other micro-applications where integration of the voltage or charge source in a small package is highly desirable.

Brainard, John P. (Albuquerque, NM); Christenson, Todd R. (Albuquerque, NM)

2009-11-03

273

Three-electrode plasma reactor for the removal of toxic gases  

NASA Astrophysics Data System (ADS)

Electrical and spectroscopic measurement for the characterization of a novel three- electrode plasma reactor for the treatment of toxic gases is presented. The three-electrode discharge consists in a dielectric barrier discharge (DBD) combined with a corona discharge (CD). The DBD is generated by applying an alternating high voltage signal between two circular aluminium plate electrodes attached to opposite sides of a disk made of dielectric material. The CD is generated applying a continuous negative high voltage to an external cylindrical mesh electrode, coaxial with the DBD electrode system. The gap between the edge of the DBD system and the mesh electrode is approximately 20 mm wide. Up to five DBD electrode systems can be connected in parallel inside the reactor, axially separated from each other by 30 mm. The electrical characterization consisted in the measurement of the current between the DBD system and the external mesh, and the voltages of the electrodes. In order to understand the dynamics of the streamers, a theoretical determination of the laplacian electric field generated by the biased electrodes was done. Optical emission spectroscopy was performed in the range of wavelengths 280-480 nm, containing the typical spectral bands 2nd positive and 1st negative systems of molecular nitrogen.

Gallego, J. L.; Giuliani, L.; Grondona, D.; Minotti, F.

2015-03-01

274

Secondary electron energy spectra emitted from radio frequency biased plasma electrodes  

NASA Astrophysics Data System (ADS)

The ion-induced secondary electron energy spectra from a radio frequency biased (13.56 MHz) electrically insulating (Al2O3) plasma electrode surface immersed in a separately powered inductively coupled plasma are studied both experimentally and theoretically. Radio frequency (rf) electrode bias voltages of 140 and 285 V (peak to ground) are employed and the complete electron energy spectra emitted from the electrode and accelerated by the rf sheath are measured 14 cm from the rf biased electrode using a differentially pumped retarding potential analyzer. A collisionless radio frequency Child-Langmuir sheath model is used to explain the experimentally measured electron energy spectra.

Shaw, D. M.; Watanabe, M.; Uchiyama, H.; Collins, G. J.

1999-07-01

275

Development of New Electrode System for High Field Dielectric Properties Measurement Using Evaporated Polypropylene Thin Guard Film  

NASA Astrophysics Data System (ADS)

Non-polar polymers such as polyethylene (PE) and polypropylene (PP) are widely used as very important electrical insulating and dielectric materials. They are used in the increasingly high AC electric field strength region approaching to the limit of electrical breakdown strength of the materials. Therefore the study of high-field dielectric property is very important in terms of understanding the AC breakdown mechanism of materials. A three-terminals electrode system with a guard film (new type electrode system) was developed in our laboratory for the precise measurement of high-field tan?, where the guard film was used to reduce the disturbance of electric field around the edge of a main electrode. However, minute air sometimes steals between a sample film and the guard film. The air sometimes generates partial discharge in the high electric field region. Therefore, when the sample had minute air, the new type electrode system was limited under 100kVrms/mm application that didn't reach to an intrinsic breakdown strength of the 30?m-thick sample. We tried to improve the new electrode system without minute air between a sample film and the guard film. We also tried to make very thin guard film to reduce the field disturbance at the edge of main electrode. In this paper a PP-guard film on a biaxially oriented polypropylene (BOPP) film was made by evaporation. This improvement of the electrode system using the evaporated PP-guard film was in success so that high-field dielectric properties of BOPP film could be measured up to near the intrinsic breakdown field of the sample.

Fujii, Masayuki; Tohyama, Kazuyuki; Tokoro, Tetsuro; Mizuno, Yukio; Nagao, Masayuki; Kosaki, Masamitsu

276

The ve percent electrode system for high-resolution EEG and ERP measurements  

E-print Network

that a standard method of placement of electrodes used in electroencephalography (EEG) was needed. Possible- national Federation of Societies for Electroencephalography and Clinical Neurophysiology (Nuwer et al

Daunizeau, Jean

277

Use of vacuum tubes in test instrumentation for measuring characteristics of fast high-voltage semiconductor devices  

NASA Technical Reports Server (NTRS)

Circuits are described that permit measurement of fast events occurring in power semiconductors. These circuits were developed for the dynamic characterization of transistors used in inductive-load switching applications. Fast voltage clamping using vacuum diodes is discussed, and reference is made to a unique circuit that was built for performing nondestructive, reverse-bias, second-breakdown tests on transistors.

Berning, D.

1981-01-01

278

Phase Current Reconstruction for AC Motor Drives Using a DC Link Single Current Sensor and Measurement Voltage Vectors  

Microsoft Academic Search

Three-phase current measurement using only a single current sensor in the inverter dc link is appealing for ac motor drives because it minimizes the number of current sensors, thereby reducing sensor cost, weight, and volume. However, the basic dc link single current sensor technique poses special challenges because the duration of the active voltage vectors must be long enough to

Hongrae Kim; Thomas M. Jahns

2006-01-01

279

The correlation of capacitance-voltage hysteresis measurements with performance during accelerated lifetime testing of polycrystalline thin film solar cells  

Microsoft Academic Search

Cell performance, or efficiency, ?% is the most used, if not most important metric for evaluating different solar cell technologies. Efficiency in turn is determined directly by the product of open-circuit voltage, Voc, short-circuit current density, Jsc, and fill-factor, FF. From numerous studies involving the measurement of ?% as a function of stress, it has been determined that ?% can

David S. Albin

2010-01-01

280

Development of a system for measuring lightning voltage waveforms on insulator strings for 500KV overhead transmission lines  

Microsoft Academic Search

This paper describes the development of a system for measuring lightning voltage waveforms on insulator strings during a lightning strokes on a power transmission line now used in commercial service. The system uses a quick response noise-immune optoelectronic sensor. The majority of lightning faults affecting overhead transmission lines involve back flashovers across the insulators that support the towers and line

T. Iwanma; Y. Sumiya; R. Kimata; T. Kawamura

1990-01-01

281

Comparison of clinical and physical measures of image quality in chest and pelvis computed radiography at different tube voltages  

SciTech Connect

The aim of this work was to study the dependence of image quality in digital chest and pelvis radiography on tube voltage, and to explore correlations between clinical and physical measures of image quality. The effect on image quality of tube voltage in these two examinations was assessed using two methods. The first method relies on radiologists' observations of images of an anthropomorphic phantom, and the second method was based on computer modeling of the imaging system using an anthropomorphic voxel phantom. The tube voltage was varied within a broad range (50-150 kV), including those values typically used with screen-film radiography. The tube charge was altered so that the same effective dose was achieved for each projection. Two x-ray units were employed using a computed radiography (CR) image detector with standard tube filtration and antiscatter device. Clinical image quality was assessed by a group of radiologists using a visual grading analysis (VGA) technique based on the revised CEC image criteria. Physical image quality was derived from a Monte Carlo computer model in terms of the signal-to-noise ratio, SNR, of anatomical structures corresponding to the image criteria. Both the VGAS (visual grading analysis score) and SNR decrease with increasing tube voltage in both chest PA and pelvis AP examinations, indicating superior performance if lower tube voltages are employed. Hence, a positive correlation between clinical and physical measures of image quality was found. The pros and cons of using lower tube voltages with CR digital radiography than typically used in analog screen-film radiography are discussed, as well as the relevance of using VGAS and quantum-noise SNR as measures of image quality in pelvis and chest radiography.

Sandborg, Michael; Tingberg, Anders; Ullman, Gustaf; Dance, David R.; Alm Carlsson, Gudrun [Department of Radiation Physics, Faculty of Health Sciences, Linkoeping University, SE-581 85 Linkoeping (Sweden); Department of Radiation Physics, Malmoe University Hospital, SE-205 02 Malmoe (Sweden); Department of Radiation Physics, Faculty of Health Sciences, Linkoeping University, SE-581 85 Linkoeping (Sweden); Joint Department of Physics, Royal Marsden NHS Trust and Institute of Cancer Research, Fulham Road, London SW3 6JJ (United Kingdom); Department of Radiation Physics, Faculty of Health Sciences, Linkoeping University, SE-581 85 Linkoeping (Sweden)

2006-11-15

282

Comparison of clinical and physical measures of image quality in chest and pelvis computed radiography at different tube voltages.  

PubMed

The aim of this work was to study the dependence of image quality in digital chest and pelvis radiography on tube voltage, and to explore correlations between clinical and physical measures of image quality. The effect on image quality of tube voltage in these two examinations was assessed using two methods. The first method relies on radiologists' observations of images of an anthropomorphic phantom, and the second method was based on computer modeling of the imaging system using an anthropomorphic voxel phantom. The tube voltage was varied within a broad range (50-150 kV), including those values typically used with screen-film radiography. The tube charge was altered so that the same effective dose was achieved for each projection. Two x-ray units were employed using a computed radiography (CR) image detector with standard tube filtration and antiscatter device. Clinical image quality was assessed by a group of radiologists using a visual grading analysis (VGA) technique based on the revised CEC image criteria. Physical image quality was derived from a Monte Carlo computer model in terms of the signal-to-noise ratio, SNR, of anatomical structures corresponding to the image criteria. Both the VGAS (visual grading analysis score) and SNR decrease with increasing tube voltage in both chest PA and pelvis AP examinations, indicating superior performance if lower tube voltages are employed. Hence, a positive correlation between clinical and physical measures of image quality was found. The pros and cons of using lower tube voltages with CR digital radiography than typically used in analog screen-film radiography are discussed, as well as the relevance of using VGAS and quantum-noise SNR as measures of image quality in pelvis and chest radiography. PMID:17153395

Sandborg, Michael; Tingberg, Anders; Ullman, Gustaf; Dance, David R; Alm Carlsson, Gudrun

2006-11-01

283

Design of an Integrated Thermoelectric Generator Power Converter for Ultra-Low Power and Low Voltage Body Energy Harvesters aimed at EEG/ECG Active Electrodes  

NASA Astrophysics Data System (ADS)

This paper describes a design procedure for an efficient body thermal energy harvesting integrated power converter. This procedure is based on loss examination for a selfpowered medical device. All optimum system parameters are calculated respecting the transducer constraints and the application form factor. It is found that it is possible to optimize converter's working frequency with proper design of its pulse generator circuit. At selected frequency, it has been demonstrated that wide area voltage doubler can be eliminated at the expense of wider switches. With this method, more than 60% efficiency is achieved in simulation for just 20mV transducer output voltage and 30% of entire chip area is saved.

Ataei, Milad; Robert, Christian; Boegli, Alexis; Farine, Pierre-André

2014-11-01

284

Methanol-air fuel cell with hydrophilic air electrodes  

Microsoft Academic Search

A methanol-air fuel cell system with alkaline electrolyte and hydrophilic air electrodes was built and tested. Heat and fuel losses as well as auxiliary system power demand have been measured. Information is gained about attainable temperatures and voltage efficiencies as a function of the number of cells delivering a given electrical output. The effects of some stack imperfections are discussed.

C. L. Sylwan

1977-01-01

285

Quantitative measurement of voltage contrast in SEM images for in-line resistance inspection of incomplete contact  

NASA Astrophysics Data System (ADS)

An in-line inspection method for estimating defect resistances from the grayscale of voltage contrast in SEM images of manufactured patterns was developed. This method applies a circuit simulator to calculate the intensity of the secondary electrons according to an equivalent-circuit model considering the charge-up voltage on the patterns. To accurately estimate the resistance of defects formed in a device, first, the simulator was improved by taking the variation of defect resistance into account, which strongly depends on the differential voltage between the plug surfaces and the backside wafer. The defect resistances were obtained from the measured I-V characteristics of the deliberately formed defect on the standard calibration wafers, in which some incomplete-contact defects were systematically formed. Next, to consider the effect of the electronic characteristics of the pattern under the normal plugs on the grayscale, the I-V characteristics of the normal plugs were measured. The equivalent circuit of the simulator was improved by taking into account the measured I-V characteristics. The calibration curve for the inspected patterns was calculated from the improved circuit simulator. Finally, the inspection method was applied to estimate the resistance of defects formed on an SRAM pattern. The calculated calibration curve was used to accurately estimate the defect resistance (with an accuracy of about an order of magnitude) from the voltage contrast formed on the defects in the inspected SRAM patterns.

Matsui, Miyako; Yano, Tasuku; Odaka, Takayuki

2011-03-01

286

Measurement of voltage and current in continuous and pulsed RF and DC glow discharges  

NASA Astrophysics Data System (ADS)

Electrical measurements are an important tool for the characterisation of glow discharges and have proved to be useful for a variety of needs in fundamental studies and as control parameter. Therefore, extensive hardware developments and studies of I-U characteristics in continuous and pulsed, dc and rf modes have been made (Wilken et al. 2007) and will be presented together with new results. In continuous dc mode, the I-U curves are non-linear and may be characterised by a threshold voltage U_0 and saturation current I_max (both cathode material and pressure dependent). On the other hand P-U curves are to a large extent linear and very similar in the continuous rf mode (Hoffmann et al. 1998). The ionic part of time resolved I-U curves of rf discharges however shows almost a linear behaviour and the capacitive component is small. No saturation current exists. This led to the assumption that gas heating is responsible for the non-linearity between U and I in continuous dc discharges. Consistent with this assumption, a dependence of the U-I curves of pulsed discharges on the duty cycle was found. The comparison of the curves with those at low duty cycle (cold) led to a rough estimation of the gas temperature. Owing to the large changes of current in a very short time, the measurement of the electronic part of the U-I curve in rf mode is far more difficult. If conducting samples are analysed, this electronic part contains extra information. For pulsed rf discharges the hysteresis of electronic part increased with decreasing duty cycle (lower gas temperature). In a study of the effect of the addition of small amounts of H_2 to the Ar discharge gas similar changes in the electronic part of the U-I curve were observed whereas the ionic part was identical. Further investigation and cooperation with modelling groups is needed and planned to explain these results.

Hoffmann, V.; Efimova, V. V.; Voronov, M. V.; Smid, P.; Steers, E. B. M.; Eckert, J.

2008-07-01

287

Direct measurement of the chemical reactivity of silicon electrodes with LiPF6-based battery electrolytes  

SciTech Connect

We report the first direct measurement of the chemistry and extent of reactivity between a lithium ion battery electrode surface (Si) and a liquid electrolyte (1.2M LiPF6-3:7 wt% ethylene carbonate:dimethyl carbonate). This layer is estimated to be 3.6 nm thick and partially originates from the consumption of the silicon surface.

Veith, Gabriel M [ORNL] [ORNL; Baggetto, Loic [ORNL] [ORNL; Sacci, Robert L [ORNL] [ORNL; Unocic, Raymond R [ORNL] [ORNL; Tenhaeff, Wyatt E [ORNL] [ORNL; Browning, Jim [ORNL] [ORNL

2014-01-01

288

Nonwoven Fabric Active Electrodes for Biopotential Measurement During Normal Daily Activity  

Microsoft Academic Search

Body movement is responsible for most of the interference during physiological data acquisition during normal daily activities. In this paper, we introduce nonwoven fabric active electrodes that provide the comfort required for clothing while robustly recording physiological data in the presence of body movement. The nonwoven fabric active electrodes were designed and fabricated using both hand- and screen-printing thick-film techniques.

Tae-Ho Kang; Carey R. Merritt; Edward Grant; Behnam Pourdeyhimi; H. Troy Nagle

2008-01-01

289

Development of Reliable Three-Electrode Impedance Measurements in Plastic Li-Ion Batteries  

Microsoft Academic Search

The electrochemical impedance spectroscopy ~EIS! is a well- developed technique used to predict the behavior of batteries, and to determine the factors limiting the performance of an electrode, in- cluding its conductivity, charge-transfer properties, properties of the passivation layer, etc. Numerous recent studies have been published on various aspects of the insertion electrodes used in lithium-ion cells as researchers attempt

Mickae?l Dolle?; Franc?ois Orsini; Antoni S. Gozdz; Jean-Marie Tarascona

2001-01-01

290

Conductive polymer foam surface improves the performance of a capacitive EEG electrode.  

PubMed

In this paper, a new conductive polymer foam-surfaced electrode was proposed for use as a capacitive EEG electrode for nonintrusive EEG measurements in out-of-hospital environments. The current capacitive electrode has a rigid surface that produces an undefined contact area due to its stiffness, which renders it unable to conform to head curvature and locally isolates hairs between the electrode surface and scalp skin, making EEG measurement through hair difficult. In order to overcome this issue, a conductive polymer foam was applied to the capacitive electrode surface to provide a cushioning effect. This enabled EEG measurement through hair without any conductive contact with bare scalp skin. Experimental results showed that the new electrode provided lower electrode-skin impedance and higher voltage gains, signal-to-noise ratios, signal-to-error ratios, and correlation coefficients between EEGs measured by capacitive and conventional resistive methods compared to a conventional capacitive electrode. In addition, the new electrode could measure EEG signals, while the conventional capacitive electrode could not. We expect that the new electrode presented here can be easily installed in a hat or helmet to create a nonintrusive wearable EEG apparatus that does not make users look strange for real-world EEG applications. PMID:22961261

Baek, Hyun Jae; Lee, Hong Ji; Lim, Yong Gyu; Park, Kwang Suk

2012-12-01

291

Transparent electrode for optical switch  

DOEpatents

A low pressure gas electrode utilizing ionized gas in a glow discharge regime forms a transparent electrode for electro-optical switches. The transparent electrode comprises a low pressure gas region on both sides of the crystal. When the gas is ionized, e.g., by a glow discharge in the low pressure gas, the plasma formed is a good conductor. The gas electrode acts as a highly uniform conducting electrode. Since the plasma is transparent to a high energy laser beam passing through the crystal, the electrode is a transparent electrode. A crystal exposed from two sides to such a plasma can be charged up uniformly to any desired voltage. The plasma can be created either by the main high voltage pulser used to charge up the crystal or by auxiliary discharges or external sources of ionization. A typical configuration utilizes 10 torr argon in the discharge region adjacent to each crystal face.

Goldhar, Julius (San Ramon, CA); Henesian, Mark A. (Livermore, CA)

1986-01-01

292

Integrated high-voltage\\/Low-voltage MOS devices  

Microsoft Academic Search

A new high voltage device structure and a corresponding fabrication process have been developed. The device has a planar, integrable, closed geometry structure that utilizes a highly resistive polysilicon field relief electrode (field plate) to control device breakdown voltage and transconductance. The active device area is totally covered by polysilicon or metal, contributing to long term stability and reliability. The

Steven A. Buhler; David L. Heald; Ram R. Ronen; Terry Gannon; Patricia Elkins

1981-01-01

293

Carrier transport and collection in fully depleted semiconductors by a combined action of the space charge field and the field due to electrode voltages  

DOEpatents

A semiconductor charge transport device and method for making same, characterized by providing a thin semiconductor wafer having rectifying junctions on its opposing major surfaces and including a small capacitance ohmic contact, in combination with bias voltage means and associated circuit means for applying a predetermined voltage to effectively deplete the wafer in regions thereof between the rectifying junctions and the ohmic contact. A charge transport device of the invention is usable as a drift chamber, a low capacitance detector, or a charge coupled device each constructed according to the methods of the invention for making such devices. Detectors constructed according to the principles of the invention are characterized by having significantly higher particle position indicating resolution than is attainable with prior art detectors, while at the same time requiring substantially fewer readout channels to realize such high resolution.

Rehak, Pavel (Patchogue, NY); Gatti, Emilio (Lesmo, IT)

1987-01-01

294

Carrier transport and collection in fully depleted semiconductors by a combined action of the space charge field and the field due to electrode voltages  

DOEpatents

A semiconductor charge transport device and method for making same, characterized by providing a thin semiconductor wafer having rectifying functions on its opposing major surfaces and including a small capacitance ohmic contact, in combination with bias voltage means and associated circuit means for applying a predetermined voltage to effectively deplete the wafer in regions thereof between the rectifying junctions and the ohmic contact. A charge transport device of the invention is usable as a drift chamber, a low capacitance detector, or a charge coupled device each constructed according to the methods of the invention for making such devices. Detectors constructed according to the principles of the invention are characterized by having significantly higher particle position indicating resolution than is attainable with prior art detectors, while at the same time requiring substantially fewer readout channels to realize such high resolution.

Rehak, P.; Gatti, E.

1984-02-24

295

A multi-electrode biomimetic electrolocation sensor  

NASA Astrophysics Data System (ADS)

We present the concept of an active multi-electrode catheter inspired by the electroreceptive system of the weakly electric fish, Gnathonemus petersii. The skin of this fish exhibits numerous electroreceptor organs which are capable of sensing a self induced electrical field. Our sensor is composed of a sending electrode and sixteen receiving electrodes. The electrical field produced by the sending electrode was measured by the receiving electrodes and objects were detected by the perturbation of the electrical field they induce. The intended application of such a sensor is in coronary diagnostics, in particular in distinguishing various types of plaques, which are major causes of heart attack. For calibration of the sensor system, finite element modeling (FEM) was performed. To validate the model, experimental measurements were carried out with two different systems. The physical system was glass tubing with metal and plastic wall insertions as targets. For the control of the experiment and for data acquisition, the software LabView designed for 17 electrodes was used. Different parameters of the electric images were analyzed for the prediction of the electrical properties and size of the inserted targets in the tube. Comparisons of the voltage modulations predicted from the FEM model and the experiments showed a good correspondence. It can be concluded that this novel biomimetic method can be further developed for detailed investigations of atherosclerotic lesions. Finally, we discuss various design strategies to optimize the output of the sensor using different simulated models to enhance target recognition.

Mayekar, K.; Damalla, D.; Gottwald, M.; Bousack, H.; von der Emde, G.

2012-04-01

296

Noninvasive measurement of torque development in the rat foot: measurement setup and results from stimulation of the sciatic nerve with polyimide-based cuff electrodes.  

PubMed

In neural rehabilitation, selective activation of muscles after electrical stimulation is mandatory for control of paralyzed limbs. For an evaluation of electrode selectivity, a setup to noninvasively measure the force development after electrical stimulation in the rat foot was developed. The setup was designed in accordance to the anatomical features of the rat model to test the isometric torque development at given ankle positions in an intact leg. In this paper, the setup design and development is presented and discussed. In a first study, the selectivity of small nerve cuffs with 12 electrodes implanted around the rat sciatic nerve was investigated. Special attention was drawn to the performance of the torque measurement setup in comparison to electrophysiological data obtained from compound muscle action potential recordings. Using one cuff around the nerve, electrical stimulation on different electrode tripoles led to plantarflexion and dorsiflexion of the foot without an a priori alignment of the cuff. PMID:14960120

Stieglitz, Thomas; Schuettler, Martin; Schneider, Andreas; Valderrama, Elena; Navarro, Xavier

2003-12-01

297

Effect of electrode configuration and electronic conductivity on current density distribution measurements in PEM fuel cells  

E-print Network

of commercially available gas diffusion layers. Both galvanostatic and potentiostatic discharge modes were employed. Irrespective of the type of gas diffusion layer, when a common electrode was employed, significant performance variations were encountered between...

Natarajan, Dilip; Van Nguyen, Trung

2004-09-03

298

Studies of the vacuum breakdown behavior using refractory-metal thin film coated electrodes  

NASA Astrophysics Data System (ADS)

A reliable operation of ICRF antennas in fusion devices is often limited by its breakdown threshold. Surface conditions of electrodes during high voltage operations have played a key role in affecting breakdowns. In this work, the effects of coating electrodes with refractory-metal thin films to improve on the reliability and power delivered by ICRF antennas have been investigated. Using the Surface Plasma Arcs by Radiofrequency - Control Study (SPARCS) facility at the Center for Plasma-Material Interactions which is designed as a DC system, the current and voltage breakdown patterns and the measured energy in the arc at an electric field of up to 150 MW/m were studied. Experiments with electrodes coated with W, Mo and Ta operated at high temperature of 600 ^oC and above were explored. Surface studies were also conducted on the electrodes to determine the electrode conditions and other surface reactions after the breakdown.

Flauta, Randolph; Kionka, John; Neumann, Martin John; Ruzic, David; Caughman, John

2009-11-01

299

Longitudinal vascular dynamics following cranial window and electrode implantation measured with speckle variance optical coherence angiography  

PubMed Central

Speckle variance optical coherence angiography (OCA) was used to characterize the vascular tissue response from craniotomy, window implantation, and electrode insertion in mouse motor cortex. We observed initial vasodilation ~40% greater than original diameter 2-3 days post-surgery (dps). After 4 weeks, dilation subsided in large vessels (>50 µm diameter) but persisted in smaller vessels (25-50 µm diameter). Neovascularization began 8-12 dps and vessel migration continued throughout the study. Vasodilation and neovascularization were primarily associated with craniotomy and window implantation rather than electrode insertion. Initial evidence of capillary re-mapping in the region surrounding the implanted electrode was manifest in OCA image dissimilarity. Further investigation, including higher resolution imaging, is required to validate the finding. Spontaneous lesions also occurred in many electrode animals, though the inception point appeared random and not directly associated with electrode insertion. OCA allows high resolution, label-free in vivo visualization of neurovascular tissue, which may help determine any biological contribution to chronic electrode signal degradation. Vascular and flow-based biomarkers can aid development of novel neural prostheses. PMID:25136505

Hammer, Daniel X.; Lozzi, Andrea; Abliz, Erkinay; Greenbaum, Noah; Agrawal, Anant; Krauthamer, Victor; Welle, Cristin G.

2014-01-01

300

Longitudinal vascular dynamics following cranial window and electrode implantation measured with speckle variance optical coherence angiography.  

PubMed

Speckle variance optical coherence angiography (OCA) was used to characterize the vascular tissue response from craniotomy, window implantation, and electrode insertion in mouse motor cortex. We observed initial vasodilation ~40% greater than original diameter 2-3 days post-surgery (dps). After 4 weeks, dilation subsided in large vessels (>50 µm diameter) but persisted in smaller vessels (25-50 µm diameter). Neovascularization began 8-12 dps and vessel migration continued throughout the study. Vasodilation and neovascularization were primarily associated with craniotomy and window implantation rather than electrode insertion. Initial evidence of capillary re-mapping in the region surrounding the implanted electrode was manifest in OCA image dissimilarity. Further investigation, including higher resolution imaging, is required to validate the finding. Spontaneous lesions also occurred in many electrode animals, though the inception point appeared random and not directly associated with electrode insertion. OCA allows high resolution, label-free in vivo visualization of neurovascular tissue, which may help determine any biological contribution to chronic electrode signal degradation. Vascular and flow-based biomarkers can aid development of novel neural prostheses. PMID:25136505

Hammer, Daniel X; Lozzi, Andrea; Abliz, Erkinay; Greenbaum, Noah; Agrawal, Anant; Krauthamer, Victor; Welle, Cristin G

2014-08-01

301

Near-electrode imager  

DOEpatents

An apparatus, near-electrode imager, for employing nuclear magnetic resonance imaging to provide in situ measurements of electrochemical properties of a sample as a function of distance from a working electrode. The near-electrode imager uses the radio frequency field gradient within a cylindrical toroid cavity resonator to provide high-resolution nuclear magnetic resonance spectral information on electrolyte materials.

Rathke, Jerome W. (Lockport, IL); Klingler, Robert J. (Westmont, IL); Woelk, Klaus (Wachtberg, DE); Gerald, II, Rex E. (Brookfield, IL)

2000-01-01

302

Nonequilibrium Thermodynamics of Porous Electrodes  

E-print Network

We reformulate and extend porous electrode theory for non-ideal active materials, including those capable of phase transformations. Using principles of non-equilibrium thermodynamics, we relate the cell voltage, ionic ...

Ferguson, Todd Richard

303

Design of a platinum resistance thermometer temperature measuring transducer and improved accuracy of linearizing the output voltage  

SciTech Connect

An improved method is presented for designing a temperature measuring transducer, the electrical circuit of which comprises an unbalanced bridge, in one arm of which is a platinum resistance thermometer, and containing a differential amplifier with feedback. Values are given for the coefficients, the minimum linearization error is determined, and an example is also given of the practical design of the transducer, using the given coefficients. A determination is made of the limiting achievable accuracy in linearizing the output voltage of the measuring transducer, as a function of the range of measured temperature.

Malygin, V.M.

1995-06-01

304

Measurement of high-voltage and radiation-damage limitations to advanced solar array performance  

NASA Technical Reports Server (NTRS)

A description is given of the reconfigured Photovoltaic Array Space Power (PASP) Plus experiment: its objectives, solar-array complement, and diagnostic sensors. Results from a successful spaceflight will lead to a better understanding of high-voltage and radiation-damage limitations in the operation of new-technology solar arrays.

Guidice, D. A.; Severance, P. S.; Keinhardt, K. C.

1991-01-01

305

Electrode measurements of the oxidation reduction potential in the Gotland Deep using a moored profiling instrumentation  

NASA Astrophysics Data System (ADS)

The Gotland Deep Environmental Sampling Station (GODESS) operating between 30 m and 185 m was used to assess the variation of in situ redox potential (Eh) in the stratified water column of the central Baltic Sea, for a period of 56 days (November 2010-January 2011). The aim of this study was to acquire in-depth understanding of redox variations with the overall objective to identify the processes controlling Eh. At an interval of 8 h basic hydro-physical parameters were registered, including the oxidation-reduction potential, dissolved oxygen, chlorophyll a fluorescence, turbidity, temperature and conductivity. In total 170 profiles of all parameters were obtained. The measured Eh (with respect to standard hydrogen electrode, SHE) ranged from -0.055 V to 0.167 V. After temperature and pH correction of the standard reduction potentials, a comparison of the measured Eh with that calculated for the particular redox couples was carried out by applying the Nernst-equation. Furthermore, the concentrations of the most important redox elements such as Fe, Mn, N, O, C and S used for comparison were estimated by using empirical functions or were based on measurements of discrete water samples, taken at the time of deployment and recovery of the mooring. The obtained results reveal that the reduction of Fe(III) and O2 may be the main processes controlling the Eh potential in the Gotland basin. Below the redoxcline the reduction of hematite and then ferric oxyhydroxide could be related to the redox potential and somewhat deeper Fe(III)/Fe(II) was found to be the dominant redox couple. Although mixed potential theory could have been applied, the Fe couples appear to dominate over many other possible redox equilibria. This may be explained by the relatively high exchange current of Fe and by high Fe concentrations (up to 1.5 ?M). Finally, a close correspondence to the Eh potentials measured in the oxic/hypoxic part of the water column was found considering the O2/O2-· and the O2-·/H2O2 couples. This suggests that one-electron transfer reactions determined the Eh under oxic/hypoxic conditions.

Meyer, David; Prien, Ralf D.; Dellwig, Olaf; Waniek, Joanna J.; Schulz–Bull, Detlef E.

2014-03-01

306

Characteristics of distributed-type inorganic electroluminescence panels with comb-shaped electrodes  

NASA Astrophysics Data System (ADS)

We deposited comb electrodes with narrow gaps between the teeth on a glass substrate, thus realizing a high electric field intensity that cannot be achieved with conventional structures. Au electrodes are deposited to form a comb shape and then spin-coated with a phosphor layer obtained by mixing ZnS phosphor particles with resins in a certain ratio. An AC voltage was applied to the gaps between the teeth of the comb electrode to emit light, from which the luminance was measured for different electric field intensities. The luminance was not affected by the transmittance of the electrodes themselves when measured from the phosphor layer side. Therefore, it may be possible to produce a display that does not require transparent electrodes by using the phosphor layer side of a device with comb electrodes made of metals, such as Au, for the display.

Yamamoto, Shin-Ichi; Uraoka, Yukiharu; Taguchi, Nobuyoshi; Nonaka, Toshihiro

2013-09-01

307

Electrodes for microfluidic applications  

DOEpatents

An electrode device for high pressure applications. These electrodes, designed to withstand pressure of greater than 10,000 psi, are adapted for use in microfluidic devices that employ electrokinetic or electrophoretic flow. The electrode is composed, generally, of an outer electrically insulating tubular body having a porous ceramic frit material disposed in one end of the outer body. The pores of the porous ceramic material are filled with an ion conductive polymer resin. A conductive material situated on the upper surface of the porous ceramic frit material and, thus isolated from direct contact with the electrolyte, forms a gas diffusion electrode. A metal current collector, in contact with the gas diffusion electrode, provides connection to a voltage source.

Crocker, Robert W. (Fremont, CA); Harnett, Cindy K. (Livermore, CA); Rognlien, Judith L. (Livermore, CA)

2006-08-22

308

Signal enhancement of electron magnetic circular dichroism by ultra-high-voltage TEM, toward quantitative nano-magnetism measurements.  

PubMed

Electron magnetic circular dichroism (EMCD) has been known as the transmission electron microscopy (TEM) counterpart of X-ray magnetic circular dichroism (XMCD). XMCD is already widely used for the characterization of magnetic materials with synchrotron radiation. There have been common difficulties encountered in quantitative analysis of the EMCD signal measured by medium-voltage TEMs, such as a small signal fraction and the low signal-to-noise ratio of the EMCD signal. Theoretical calculations of EMCD considering many-beam dynamical diffraction effects showed improved net magnetic signal fractions at an accelerating voltage of 1 MV compared with 200 kV, which is in agreement with the present experiment. PMID:24503161

Tatsumi, Kazuyoshi; Muto, Shunsuke; Rusz, Ján; Kudo, Tomohiro; Arai, Shigeo

2014-06-01

309

Iridium oxide nanotube electrodes for sensitive and prolonged intracellular measurement of action potentials  

NASA Astrophysics Data System (ADS)

Intracellular recording of action potentials is important to understand electrically-excitable cells. Recently, vertical nanoelectrodes have been developed to achieve highly sensitive, minimally invasive and large-scale intracellular recording. It has been demonstrated that the vertical geometry is crucial for the enhanced signal detection. Here we develop nanoelectrodes of a new geometry, namely nanotubes of iridium oxide. When cardiomyocytes are cultured upon those nanotubes, the cell membrane not only wraps around the vertical tubes but also protrudes deep into the hollow centre. We show that this nanotube geometry enhances cell-electrode coupling and results in larger signals than solid nanoelectrodes. The nanotube electrodes also afford much longer intracellular access and are minimally invasive, making it possible to achieve stable recording up to an hour in a single session and more than 8 days of consecutive daily recording. This study suggests that the nanoelectrode performance can be significantly improved by optimizing the electrode geometry.

Lin, Ziliang Carter; Xie, Chong; Osakada, Yasuko; Cui, Yi; Cui, Bianxiao

2014-02-01

310

Iridium oxide nanotube electrodes for sensitive and prolonged intracellular measurement of action potentials.  

PubMed

Intracellular recording of action potentials is important to understand electrically-excitable cells. Recently, vertical nanoelectrodes have been developed to achieve highly sensitive, minimally invasive and large-scale intracellular recording. It has been demonstrated that the vertical geometry is crucial for the enhanced signal detection. Here we develop nanoelectrodes of a new geometry, namely nanotubes of iridium oxide. When cardiomyocytes are cultured upon those nanotubes, the cell membrane not only wraps around the vertical tubes but also protrudes deep into the hollow centre. We show that this nanotube geometry enhances cell-electrode coupling and results in larger signals than solid nanoelectrodes. The nanotube electrodes also afford much longer intracellular access and are minimally invasive, making it possible to achieve stable recording up to an hour in a single session and more than 8 days of consecutive daily recording. This study suggests that the nanoelectrode performance can be significantly improved by optimizing the electrode geometry. PMID:24487777

Lin, Ziliang Carter; Xie, Chong; Osakada, Yasuko; Cui, Yi; Cui, Bianxiao

2014-01-01

311

Measurement of low radioactivity background in a high voltage cable by high resolution inductively coupled plasma mass spectrometry  

SciTech Connect

The measurement of naturally occurring low level radioactivity background in a high voltage (HV) cable by high resolution inductively coupled plasma mass spectrometry (HR ICP MS) is presented in this work. The measurements were performed at the Chemistry Service of the Gran Sasso National Laboratory. The contributions to the radioactive background coming from the different components of the heterogeneous material were separated. Based on the mass fraction of the cable, the whole contamination was calculated. The HR ICP MS results were cross-checked by gamma ray spectroscopy analysis that was performed at the low background facility STELLA (Sub Terranean Low Level Assay) of the LNGS underground lab using HPGe detectors.

Vacri, M. L. di; Nisi, S.; Balata, M. [Gran Sasso National Laboratory, Chemistry Service, SS 17bis km 18.910, 67100 Assergi (Aq) (Italy)] [Gran Sasso National Laboratory, Chemistry Service, SS 17bis km 18.910, 67100 Assergi (Aq) (Italy)

2013-08-08

312

Study on Method to Detect Loss of Synchronism Using Bus Voltage and Line Current Measured on a Line Using Power System Simulator  

NASA Astrophysics Data System (ADS)

A severe fault may cause loss of synchronism of a small number of generators. And it may make many generators out of service resulting in wide area blackout. When two groups of generators lose synchronism, the magnitudes of voltage on some lines becomes zero. Therefore an approach that lines with zero voltage are opened has been employed actually in order to prevent loss of synchronism from extension. This paper presents a new method using voltage and current measured on a line during disturbance to detect the line with zero voltage at the instant when loss of synchronism takes place. A method to detect loss of synchronism using voltage and current measured on a line was already proposed. This paper presents results of the tests performed by using power system simulator which is composed of a DC-motor, a synchronous generator, artificial transmission line, circuit breaker equipments and so on. The validity of proposed methods was verified by finding loss of synchronism correctly.

Takaoka, Masaomi; Kiuchi, Toru; Sato, Masahiro

313

VOLTAMMETRIC MEMBRANE CHLORINE DIOXIDE ELECTRODE  

EPA Science Inventory

A voltammetric membrane electrode system has been modified and applied to the in situ measurement of chlorine dioxide. The electrode system consisted of a gold cathode, a silver/silver chloride reference electrode, and a gold counter electrode. Different membrane materials were t...

314

Amplifier for measuring low-level signals in the presence of high common mode voltage  

NASA Technical Reports Server (NTRS)

A high common mode rejection differential amplifier wherein two serially arranged Darlington amplifier stages are employed and any common mode voltage is divided between them by a resistance network. The input to the first Darlington amplifier stage is coupled to a signal input resistor via an amplifier which isolates the input and presents a high impedance across this resistor. The output of the second Darlington stage is transposed in scale via an amplifier stage which has its input a biasing circuit which effects a finite biasing of the two Darlington amplifier stages.

Lukens, F. E. (inventor)

1985-01-01

315

High voltage DC power supply  

DOEpatents

A high voltage DC power supply having a first series resistor at the output for limiting current in the event of a short-circuited output, a second series resistor for sensing the magnitude of output current, and a voltage divider circuit for providing a source of feedback voltage for use in voltage regulation is disclosed. The voltage divider circuit is coupled to the second series resistor so as to compensate the feedback voltage for a voltage drop across the first series resistor. The power supply also includes a pulse-width modulated control circuit, having dual clock signals, which is responsive to both the feedback voltage and a command voltage, and also includes voltage and current measuring circuits responsive to the feedback voltage and the voltage developed across the second series resistor respectively. 7 figs.

Droege, T.F.

1989-12-19

316

High voltage DC power supply  

DOEpatents

A high voltage DC power supply having a first series resistor at the output for limiting current in the event of a short-circuited output, a second series resistor for sensing the magnitude of output current, and a voltage divider circuit for providing a source of feedback voltage for use in voltage regulation is disclosed. The voltage divider circuit is coupled to the second series resistor so as to compensate the feedback voltage for a voltage drop across the first series resistor. The power supply also includes a pulse-width modulated control circuit, having dual clock signals, which is responsive to both the feedback voltage and a command voltage, and also includes voltage and current measuring circuits responsive to the feedback voltage and the voltage developed across the second series resistor respectively.

Droege, Thomas F. (Batavia, IL)

1989-01-01

317

Consistent time-of-flight mobility measurements and polymer light-emitting diode current{endash}voltage characteristics  

SciTech Connect

We present time-of-flight mobility measurements and measured and calculated current{endash}voltage (I{endash}V) characteristics of structures fabricated using a soluble poly({ital p}-phenylene vinylene) derivative. Time-of-flight measurements were used to determine the electric field dependent hole mobility. This mobility was then used, without adjustable parameters, to calculate the I{endash}V characteristics of space-charge-limited, hole only devices. The measured and calculated I{endash}V characteristics are in good agreement over five orders of magnitude in current. These results demonstrate that an electric field dependent mobility, without invoking trapping effects, provides an accurate description of hole transport in this polymer. {copyright} {ital 1999 American Institute of Physics.}

Campbell, I.H.; Smith, D.L. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Neef, C.J.; Ferraris, J.P. [The University of Texas at Dallas, Richardson, Texas 75083 (United States)] [The University of Texas at Dallas, Richardson, Texas 75083 (United States)

1999-05-01

318

[29] It was not possible to measure the adsorption of DMAP stabilized gold nanoparticles onto bare (gold-coated) QCM electrodes, as the gold sur-  

E-print Network

[29] It was not possible to measure the adsorption of DMAP stabilized gold nanoparticles onto bare (gold-coated) QCM electrodes, as the gold sur- face destabilized the nanoparticle solution and caused

319

Electrode independent chemoresistive response for cobalt phthalocyanine in the space charge limited conductivity regime.  

PubMed

The electrical properties of 50 nm thick metallophthalocyanine films, prepared by organic molecular beam epitaxy (OMBE) on interdigitated electrodes, were studied with DC current-voltage measurements and impedance spectroscopy. The transition from Ohmic behavior at low voltages to space-charge-limited conductivity (SCLC) at higher voltages depends on the metal electrode (Pt, Pd, and Au), but does not correlate with the work function of the electrode. Impedance spectroscopy studies show the coexistence of low- and high-frequency traps in the thin film devices, and the contribution of low-frequency traps associated with Ohmic behavior diminishes at higher bias. Although device resistances are strongly influenced by the electrode material, and vary by a factor of over 300, the relative chemical sensor responses on exposure to dimethyl methylphosphonate (DMMP), methanol, water, or toluene vapors are similar for CoPc on Pt, Pd, and Au electrodes when these devices are operated in the SCLC regime at room temperature. When the devices are operated at voltages where the low-frequency interfacial traps are filled, the sensor response to analyte becomes uniform and reliable regardless of the specific interfacial electrode contact. PMID:16471543

Miller, Karla A; Yang, Richard D; Hale, Michael J; Park, Jeongwon; Fruhberger, Bernd; Colesniuc, Corneliu N; Schuller, Ivan K; Kummel, Andrew C; Trogler, William C

2006-01-12

320

Multiple-needle corona electrodes for electrostatic processes application  

Microsoft Academic Search

Corona from high-voltage electrodes is employed in various electrostatic installations, such as ozonizers, air filters, powder sprayers and separators. Multiple-needle electrode designs are preferred whenever low corona onset voltage and good resistance to mechanical shocks are required. This paper aims at identifying a simple solution to overcome the main drawback of this type of electrode, the nonuniformity of the generated

Lucian Dascalescu; Adrian Samuila; Dan Rafiroiu; Alexandru Iuga; Roman Morar

1999-01-01

321

Impedances of electrochemically impregnated nickel electrodes as functions of potential, KOH concentration, and impregnation method  

NASA Technical Reports Server (NTRS)

Impedances of fifteen electrodes form each of the four U.S. manufactures were measured at 0.200 V vs. the Hg/HgO reference electrode. This corresponds to a voltage of 1.145 for a Ni/H2 cell. Measurements were also made of a representative sample of these at 0.44 V. At the higher voltage, the impedances were small and very similar, but at the lower voltage there were major differences between manufacturers. Electrodes from the same manufacturers showed only small differences. The impedances of electrodes from two manufacturers were considerably different in 26 percent KOH from those in 31 percent KOH. These preliminary results seen to correlate with the limited data from earlier life testing of cells from these manufacturers. The impedances of cells being tested for Space Station Freedom are being followed, and more impendance measurements of electrodes are being performed as functions of manufacturer, voltage, electrolyte concentration, and cycle history in hopes of finding better correlations of impedance with life.

Reid, Margaret A.

1989-01-01

322

Experimental measurements of the plasma sheath around pinhole defects in a simulated high-voltage solar array  

NASA Technical Reports Server (NTRS)

An emissive Langmuir probe was used to measure the potentials within the plasma sheath developed around a hole in a simulated solar array at voltages between 50 and 450 V. The hole sizes were larger than actual pinhole defects; the plasma density was in the 10,000 per cu cm range, which is considerably lower than the density of 1,000,000 per cu cm found at low-earth-orbit altitudes. Despite these inadequacies in the simulation, the experiments indicate that this type of probe is a useful diagnostic technique for investigating the plasma sheaths developing around pinhole defects.

Gabriel, S. B.; Garner, C.; Kitamura, S.

1983-01-01

323

Measurement of the electro-optic properties of poled polymers at lambda=1.55 mum by means of sandwich structures with zinc oxide transparent electrode  

Microsoft Academic Search

We report on the measurement of the electro-optic properties of poled polymers at lambda=1.55 mum via the Teng and Man technique. Measurements of the electro-optic coefficient obtained for two different sandwich structures, using either indium tin oxide (ITO) or aluminum doped zinc oxide (ZnO:Al) semitransparent electrodes, are compared. The experimental results show that the use of ITO electrodes can lead

F. Michelotti; A. Belardini; M. C. Larciprete; M. Bertolotti; A. Rousseau; A. Ratsimihety; G. Schoer; J. Mueller

2003-01-01

324

Calibration of bridge-, charge- and voltage amplifiers for dynamic measurement applications  

NASA Astrophysics Data System (ADS)

Measuring amplifiers are used for transducer output signal conditioning in many dynamic measurement applications. For a traceable measurement, a calibration of all components of the measuring chain—and therefore of the conditioning amplifiers, too—is mandatory. In this paper methods for a dynamic calibration of different types of conditioning amplifiers are presented. Measurement uncertainties and calibration results for typical amplifiers are discussed.

Klaus, Leonard; Bruns, Thomas; Volkers, Henrik

2015-02-01

325

Determining resistivity of a formation adjacent to a borehole having casing with an apparatus having all current conducting electrodes within the cased well  

DOEpatents

Methods of operation of different types of multiple electrode apparatus vertically disposed in a cased well to measure information useful to determine the resistivity of adjacent geological formations from within the cased well are described. The multiple electrode apparatus has a plurality of spaced apart voltage measurement electrodes that electrically engage a portion of the interior of the cased well. During measurements of information useful to determine formation resistivity, current is conducted between a first current conducting electrode in electrical contact with the interior of the cased well to a second current conducting electrode that is also in electrical contact with the interior of the cased well. The first and second current conducting electrodes are separated by a distance sufficient so that at least a portion of the current conducted between the first and second current conducting electrodes is conducted through the geological formation of interest.

Vail, III, William Banning (Bothell, WA)

2001-01-01

326

Quantitative measurement of voltage contrast in SEM images for in-line resistance inspection of wafers manufactured for SRAM  

NASA Astrophysics Data System (ADS)

An in-line inspection method for partial-electrical measurement of defect resistance, which is quantitatively estimated from the voltage contrast formed in an SEM image of an incomplete-contact defect, was developed. This inspection method was applied to wafers manufactured for an SRAM device. That is, the gray scales of the defect images captured on an SRAM plug pattern were quantitatively analyzed. Accordingly, the gray scales of defective plugs formed for shared contact patterns were classified as two levels. The higher contrasts, which were calculated from the grayscales of the darker defects, were about 100%; the lower contrasts, which were calculated from the grayscales of the other defects, were from 38% to 60%. The resistances of these defects were estimated from a calibration curve obtained from the grayscales of the SEM images and the resistances of deliberately formed failures on standard wafers for voltage-contrast estimation. The estimated resistances of the lower-contrast defects (with an accuracy of about an order of magnitude) agree well with the resistances measured by nano-prober. It is concluded that this in-line inspection method for partial-electrical measurement is a useful technique for defect classification based on defect resistance and defect mode.

Matsui, Miyako; Odaka, Takahiro; Nagaishi, Hiroshi; Sakurai, Koichi

2009-03-01

327

Detection of viable Salmonella typhimurium by impedance measurement of electrode capacitance and medium resistance  

Microsoft Academic Search

Three-electrode electrochemical impedance technique was investigated for detection of Salmonella typhimurium by monitoring the growth of bacteria in selenite cystine (SC) broth supplemented with trimethylamine oxide hydrochloride (TMAO·HCl) and mannitol (M). The change in the system impedance during the growth of bacteria was studied using frequency spectral scanning. It was found that the impedance at low frequencies (10 kHz), the

Liju Yang; Chuanmin Ruan; Yanbin Li

2003-01-01

328

Flexible gold electrode array for multiplexed immunoelectrochemical measurement of three protein biomarkers for prostate cancer.  

PubMed

In this work, we report a simple and novel electrochemical multiplexed immunosensor on a flexible polydimethylsiloxane (PDMS) slice deposited with 8 × 8 nano-Au film electrodes for simultaneous detection of prostate specific antigen (PSA), prostate specific membrane antigen (PSMA), and interleukin-6 (IL-6). Primary antibodies linked with magnetic beads (Ab1-MBs) were modified on the nano-Au film electrodes via magnetic force. In the presence of corresponding antigen, horse radish peroxidase-secondary antibody-conjugated gold nanorods (HRP-Ab2-gold NRs) were brought into the surface of electrodes, generating obvious electrochemical signals of H2O2 reduction reactions. Based on this, the designed immunosensor provide good performance in sensitivity and specificity during the detection of above three biomarkers for prostate cancer. The electrochemical multiplexed immunosensor was verified for selective and accurate detection of complex samples in human serum. Data suggested that the reported multiplexed immunosensing strategy holds great promise for applications in clinical assay and diseases diagnosis. PMID:25333408

Liu, Jing; Lu, Cai-Yu; Zhou, Hong; Xu, Jing-Juan; Chen, Hong-Yuan

2014-11-26

329

Process for measuring degradation of sulfur hexafluoride in high voltage systems  

DOEpatents

This invention is a method of detecting the presence of toxic and corrosive by-products in high voltage systems produced by electrically induced degradation of SF/sub 6/ insulating gas in the presence of certain impurities. It is an improvement over previous methods because it is extremely sensitive, detecting by-products present in parts per billion concentrations, and because the device employed is of a simple design and takes advantage of the by-products natural affinity for fluoride ions. The method employs an ion-molecule reaction cell in which negative ions of the by-products are produced by fluorine attachment. These ions are admitted to a negative ion mass spectrometer and identified by their spectra. This spectrometry technique is an improvement over conventional techniques because the negative ion peaks are strong and not obscured by a major ion spectra of the SF/sub 6/ component as is the case in positive ion mass spectrometry.

Sauers, I.

1985-04-23

330

Process for measuring degradation of sulfur hexafluoride in high voltage systems  

DOEpatents

This invention is a method of detecting the presence of toxic and corrosive by-products in high voltage systems produced by electrically induced degradation of SF.sub.6 insulating gas in the presence of certain impurities. It is an improvement over previous methods because it is extremely sensitive, detecting by-products present in parts per billion concentrations, and because the device employed is of a simple design and takes advantage of the by-products natural affinity for fluoride ions. The method employs an ion-molecule reaction cell in which negative ions of the by-products are produced by fluorine attachment. These ions are admitted to a negative ion mass spectrometer and identified by their spectra. This spectrometry technique is an improvement over conventional techniques because the negative ion peaks are strong and not obscured by a major ion spectra of the SF.sub.6 component as is the case in positive ion mass spectrometry.

Sauers, Isidor (Knoxville, TN)

1986-01-01

331

Aquifer and Vadose Zone Pollution Determined From Geoelectrical Measurements With Multi- Electrode Wells and Surface Multi-Profiling  

NASA Astrophysics Data System (ADS)

During the last three years we are developing hydrobiogeological researches to quantitatively describe the underground contamination of a 4.0 km2 area, including two landfill deposits and a tannery industry of Alagoinhas city, Bahia state, Brazil. We used electrical geophysics, geological, geochemical and biological analysis to gain a general understanding of the complex interactions between organic and inorganic pollutants and their environmental impacts. A geological reconnaissance work and a geoelectrical survey using vertical electrical soundings were made around the area to detect and to delineate the extent of the underground contamination plume. The results pointed out the presence of a strong conductive anomaly within the aquifer resulting from invasive fluids both from the landfills and from the surface disposal lagoons from the tannery. Water samples collected at available wells and along the Sauipe river, have shown drastic changes in the total dissolved solids, total chromium, inorganic macro-components, biochemical oxygen demand, chemical oxygen demand, nutrients and bacterial content. As a complimentary work, apparent resistivity and chargeability data were measured as a function of depth along three new multi-electrode wells, and as a function of electrode spacing along five double semi-Schlumberger subsurface profiles. A multi-electrode well is a special monitoring well where we externally install copper electrodes as thin metallic rings spaced by 0.50 m, along its entire filter and casing length. Such electrodes are connected through insulated cables to the ground surface and may be combined into different arrays. Two-side semi-Schlumberger soundings expanded up to 200 m AB/2 spacing and with centers spaced by 50 m along special transverse centered at the plume were inverted using 1D and 2D models. Both techniques were used to detail the groundwater contamination around the Alagoinhas landfills. The electrical measurements performed at the earth surface and within wells, were used both to characterize the plume and to estimate changes in water saturation and water chemistry bellow the water table and throughout the upper vadose section of the Marizal- São Sebastião aquifer system. Well data were acquired during three different campaigns of 2004-2006 years, covering a complete seasonal cycle. The results are quantitativelyinterpreted using the volume conductivity approach described by Lima et al. (2005) extended for condiction of partial water saturation.

de Lima, O. A.; Pereira, P. D.

2007-05-01

332

Highly selective water channel activity measured by voltage clamp: Analysis of planar lipid bilayers reconstituted with purified AqpZ  

PubMed Central

Aquaporins are membrane channels selectively permeated by water or water plus glycerol. Conflicting reports have described ion conductance associated with some water channels, raising the question of whether ion conductance is a general property of the aquaporin family. To clarify this question, a defined system was developed to simultaneously measure water permeability and ion conductance. The Escherichia coli water channel aquaporin-Z (AqpZ) was studied, because it is a highly stable tetramer. Planar lipid bilayers were formed from unilamellar vesicles containing purified AqpZ. The hydraulic conductivity of bilayers made from the total extract of E. coli lipids increased 3-fold if reconstituted with AqpZ, but electric conductance was unchanged. No channel activity was detected under voltage-clamp conditions, indicating that less than one in 109 transport events is electrogenic. Microelectrode measurements were simultaneously undertaken adjacent to the membrane. Changes in sodium concentration profiles accompanying transmembrane water flow permitted calculation of the activation energies: 14 kcal/mol for protein-free lipid bilayers and 4 kcal/mol for lipid bilayers containing AqpZ. Neither the water permeability nor the electric conductivity exhibited voltage dependence. This sensitive system demonstrated that AqpZ is permeated by water but not charged ions and should permit direct analyses of putative electrogenic properties of other aquaporins. PMID:11493683

Pohl, Peter; Saparov, Sapar M.; Borgnia, Mario J.; Agre, Peter

2001-01-01

333

Highly selective water channel activity measured by voltage clamp: analysis of planar lipid bilayers reconstituted with purified AqpZ.  

PubMed

Aquaporins are membrane channels selectively permeated by water or water plus glycerol. Conflicting reports have described ion conductance associated with some water channels, raising the question of whether ion conductance is a general property of the aquaporin family. To clarify this question, a defined system was developed to simultaneously measure water permeability and ion conductance. The Escherichia coli water channel aquaporin-Z (AqpZ) was studied, because it is a highly stable tetramer. Planar lipid bilayers were formed from unilamellar vesicles containing purified AqpZ. The hydraulic conductivity of bilayers made from the total extract of E. coli lipids increased 3-fold if reconstituted with AqpZ, but electric conductance was unchanged. No channel activity was detected under voltage-clamp conditions, indicating that less than one in 10(9) transport events is electrogenic. Microelectrode measurements were simultaneously undertaken adjacent to the membrane. Changes in sodium concentration profiles accompanying transmembrane water flow permitted calculation of the activation energies: 14 kcal/mol for protein-free lipid bilayers and 4 kcal/mol for lipid bilayers containing AqpZ. Neither the water permeability nor the electric conductivity exhibited voltage dependence. This sensitive system demonstrated that AqpZ is permeated by water but not charged ions and should permit direct analyses of putative electrogenic properties of other aquaporins. PMID:11493683

Pohl, P; Saparov, S M; Borgnia, M J; Agre, P

2001-08-14

334

Changes in biphasic electrode impedance with protein adsorption and cell growth  

PubMed Central

This study was undertaken to assess the contribution of protein adsorption and cell growth to increases in electrode impedance that occur immediately following implantation of cochlear implant electrodes and other neural stimulation devices. An in vitro model of the electrode-tissue interface was used. Radiolabelled albumin in phosphate buffered saline was added to planar gold electrodes and electrode impedance measured using a charge-balanced biphasic current pulse. The polarisation impedance component increased with protein adsorption, while no change to access resistance was observed. The maximum level of protein adsorbed was measured at 0.5 ?g/cm2, indicating a tightly packed monolayer of albumin molecules on the gold electrode and resin substrate. Three cell types were grown over the electrodes, macrophage cell line J774, dissociated fibroblasts and epithelial cell line MDCK, all of which created a significant increase in electrode impedance. As cell cover over electrodes increased, there was a corresponding increase in the initial rise in voltage, suggesting cell cover mainly contributes to the access resistance of the electrodes. Only a small increase in the polarisation component of impedance was seen with cell cover. PMID:20841637

Newbold, Carrie; Richardson, Rachael; Millard, Rodney; Huang, Christie; Milojevic, Dusan; Shepherd, Robert; Cowan, Robert

2012-01-01

335

Development of PDMS-based flexible dry type SEMG electrodes by micromachining technologies  

NASA Astrophysics Data System (ADS)

The authors developed PDMS (polydimethylsiloxane)-based dry type surface electromyography (SEMG) electrodes for myoelectric prosthetic hands. The SEMG electrodes were strongly recommended to be fabricated on a flexible substrate to be compatible with the surface of skin. In this study, the authors designed a bar-shaped dry-type flexible SEMG electrodes comprised of two input electrodes and a reference electrode on a flexible PDMS substrate to measure EMG signals. The space distance between each electrode with a size of 10 mm × 2 mm was chosen to 18 mm to get optimal result according to the simulation result with taking into consideration the conduction velocity and the median frequency of EMG signals. Raw EMG signals were measured from Brachioradialis, Biceps brachii, deltoideus, and pectoralis major muscles, to drive the application of the myoelectric hand prosthesis. Measured raw EMG signals were transformed to root mean square (RMS) EMG signals using Acqknowledge4.2. The experimental peak voltage values of RMS EMG signals from Brachioradialis, Biceps brachii, deltoideus, and pectoralis major muscles were 2.96 V, 4.45 V, 1.74 V, and 2.62 V, respectively. Values from the dry type flexible SEMG electrodes showed higher peak values than a commercially available wet type Ag-AgCl electrode. The study shows that the PDMS-based flexible electrode devised for measuring myoelectric signals from the surface of skin is more useful for prosthetic hands because of its greater sensitivity and flexibility.

Jung, Jung Mo; Cha, Doo Yeol; Kim, Deok Su; Yang, Hee Jun; Choi, Kyo Sang; Choi, Jong Myoung; Chang, Sung Pil

2014-09-01

336

Application of HFCT and UHF Sensors in On-Line Partial Discharge Measurements for Insulation Diagnosis of High Voltage Equipment.  

PubMed

Partial discharge (PD) measurements provide valuable information for assessing the condition of high voltage (HV) insulation systems, contributing to their quality assurance. Different PD measuring techniques have been developed in the last years specially designed to perform on-line measurements. Non-conventional PD methods operating in high frequency bands are usually used when this type of tests are carried out. In PD measurements the signal acquisition, the subsequent signal processing and the capability to obtain an accurate diagnosis are conditioned by the selection of a suitable detection technique and by the implementation of effective signal processing tools. This paper proposes an optimized electromagnetic detection method based on the combined use of wideband PD sensors for measurements performed in the HF and UHF frequency ranges, together with the implementation of powerful processing tools. The effectiveness of the measuring techniques proposed is demonstrated through an example, where several PD sources are measured simultaneously in a HV installation consisting of a cable system connected by a plug-in terminal to a gas insulated substation (GIS) compartment. PMID:25815452

Álvarez, Fernando; Garnacho, Fernando; Ortego, Javier; Sánchez-Urán, Miguel Ángel

2015-01-01

337

Measurement of oxygen tension in the ischemic myocardium using encased polargraphic oxygen electrodes.  

PubMed

The ability to continuously monitor the delicate balance between blood flow and oxygen consumption would be a great asset in the study of myocardial ischemia. The present study was performed, in anesthetized dogs, to validate the use of encased polargraphic oxygen electrodes in the study of myocardial ischemia. Polargraphic oxygen electrodes were placed in the area to be rendered ischemic at fixed tissue depths of 3 mm (epicardium) and 9 mm (endocardium). Endocardial and epicardial oxygen tensions as well as the ratio of endocardial to epicardial oxygen tension and left circumflex coronary flow were monitored. Ischemia was induced by decreasing left circumflex coronary flow by 50%. Upon completion of a 20-min poststenotic period, endocardial pO2, endocardial/epicardial ratio, and coronary flow were significantly decreased (59 +/- 7, 52 +/- 7, and 55 +/- 4%, respectively) whereas epicardial pO2 was slightly decreased. Nitroglycerin (10 micrograms/kg, i.v.) markedly increased endocardial pO2 and endocardial/epicardial ratio above poststenotic control (13 +/- 5 mmHg and 64 +/- 10%, respectively) whereas epicardial pO2 was not significantly decreased. The increases in endocardial pO2 occurred at a point where coronary flow and mean arterial pressure were not significantly changed. Conversely, dipyridamole (125 micrograms/kg, i.v.) significantly increased coronary flow (26 +/- 2 ml/min/100 g) although it did not appreciably alter endocardial or epicardial pO2. It is concluded that encased polargraphic oxygen electrodes provide a quantitative method for determination of oxygen tension in the ischemic myocardium. PMID:3086625

Barrett, J A; Lynch, V D; Balkon, J; Wolf, P S

1986-06-01

338

Direct current measurement of ohmic resistance of high conductivity solutions by means of polarized electrodes  

E-print Network

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Artecona, Victor Manuel

1959-01-01

339

Use of multi-functional flexible micro-sensors for in situ measurement of temperature, voltage and fuel flow in a proton exchange membrane fuel cell.  

PubMed

Temperature, voltage and fuel flow distribution all contribute considerably to fuel cell performance. Conventional methods cannot accurately determine parameter changes inside a fuel cell. This investigation developed flexible and multi-functional micro sensors on a 40 ?m-thick stainless steel foil substrate by using micro-electro-mechanical systems (MEMS) and embedded them in a proton exchange membrane fuel cell (PEMFC) to measure the temperature, voltage and flow. Users can monitor and control in situ the temperature, voltage and fuel flow distribution in the cell. Thereby, both fuel cell performance and lifetime can be increased. PMID:22163545

Lee, Chi-Yuan; Chan, Pin-Cheng; Lee, Chung-Ju

2010-01-01

340

Use of Multi-Functional Flexible Micro-Sensors for in situ Measurement of Temperature, Voltage and Fuel Flow in a Proton Exchange Membrane Fuel Cell  

PubMed Central

Temperature, voltage and fuel flow distribution all contribute considerably to fuel cell performance. Conventional methods cannot accurately determine parameter changes inside a fuel cell. This investigation developed flexible and multi-functional micro sensors on a 40 ?m-thick stainless steel foil substrate by using micro-electro-mechanical systems (MEMS) and embedded them in a proton exchange membrane fuel cell (PEMFC) to measure the temperature, voltage and flow. Users can monitor and control in situ the temperature, voltage and fuel flow distribution in the cell. Thereby, both fuel cell performance and lifetime can be increased. PMID:22163545

Lee, Chi-Yuan; Chan, Pin-Cheng; Lee, Chung-Ju

2010-01-01

341

An approach to the diagnosis of metabolic syndrome by the multi-electrode impedance method  

NASA Astrophysics Data System (ADS)

It is well known that metabolic syndrome can induce myocardial infarction and cerebral infarction. So, it is very important to measure the visceral fat volume. In the electric impedance method, information in the vicinity of the electrodes is strongly reflected. Therefore, we propose a new multi-electrode arrangement method based on the impedance sensitivity theorem to measure the visceral fat volume. This electrode arrangement is designed to enable high impedance sensitivity in the visceral and subcutaneous fat regions. Currents are simultaneously applied to several current electrodes on the body surface, and one voltage electrode pair is arranged on the body surface near the organ of interest to obtain the visceral fat information and another voltage electrode pair is arranged on the body surface near the current electrodes to obtain the subcutaneous fat information. A simulation study indicates that by weighting the impedance sensitivity distribution, as in our method, a high-sensitivity region in the visceral and the subcutaneous fat regions can be formed. In addition, it was confirmed that the visceral fat volume can be estimated by the measured impedance data.

Furuya, N.; Sakamoto, K.; Kanai, H.

2010-04-01

342

Measuring neural coupling from non-Gaussian power spectra of voltage traces taken from awake behaving animals  

NASA Astrophysics Data System (ADS)

Brains consist of complex networks of neurons possessing highly non-linear interactions, suggesting that neural systems will show cooperative dynamics. Previous studies of the non-Gaussian statistics of 1/f noise in spin glasses and amorphous semiconductors have revealed important information concerning interaction kinetics not available through other techniques. Five male Brown-Norway-Cross rats were chronically implanted with arrays of microwire electrodes from which local field potentials (LFPs) were recorded from the dorsocentral striatum as the animals performed complex navigational tasks. The power spectra displayed a frequency dependence significantly different from 1/f. The correlation coefficients of the Fourier transform of the LFPs from striatum showed significant non-zero correlations between frequencies separated by less than three octaves. This novel technique may be useful in measuring functional interactions in neural systems.

Masimore, Beth; Kakalios, James; Redish, A. David

2003-05-01

343

Measurement of Ba-densities close to the electrode in an HPS-lamp by broadband absorption spectroscopy with a UHP-lamp  

NASA Astrophysics Data System (ADS)

Within this work, the emitter-effect of barium is investigated in a high-pressure-sodium (HPS) lamp. The emitter-effect reduces the thermal stress of the lamp electrode by a reduction in the effective work-function of the tungsten material. The investigated HPS-lamp has a special design of the Ba-emitter storage: it is deposited during lamp production in a tungsten coil around the electrode rod with a certain distance to the electrode tip. During lamp operation the Ba-emitter diffuses along the electrode surface to the electrode tip. To optimize the Ba-diffusion along the electrode, a measurement of the Ba-vapour density close to the electrode is executed by means of a broadband absorption spectroscopy (BBAS) at a Ba resonance line. An ultra-high-pressure (UHP) lamp is used as an absorption backlight source. It provides a high radiance at the measuring wavelength and operates very stably over time. An approximately linear decrease in the Ba-vapour density close to the electrode rod from 1.5 × 1012 to 0.5 × 1012 cm-3 is measured between the coil and the tip. The UHP-broadband absorption measurement at the Ba resonance line yields results which are independent of the plasma temperature. It can be applied to any arbitrary position within the HPS-lamp. Thus, the presented BBAS by means of a UHP-lamp is a very flexible but simple alternative to laser-absorption spectroscopy or to emission spectroscopy.

Westermeier, M.; Reinelt, J.; Luijks, G.; Mentel, J.; Awakowicz, P.

2010-03-01

344

On the possibility of determining the energy-distribution function of nonlocal penning electrons by measuring the current to wall electrode in afterglow plasma  

NASA Astrophysics Data System (ADS)

The results of numerical simulation of the afterglow plasma of pulsed discharge in a nonlocal regime confirm the possibility of determining the energy-distribution function (EDF) of nonlocal penning electrons by measuring their current to a wall electrode. It is shown that the EDF of nonlocal Penning electrons is proportional to the first derivative of the electron-current density with respect to potential on the wall electrode.

Saifutdinov, A. I.; Kapustin, K. D.; Kudryavtsev, A. A.

2014-11-01

345

Modeling gating charge and voltage changes in response to charge separation in membrane proteins  

PubMed Central

Measurements of voltage changes in response to charge separation within membrane proteins can offer fundamental information on mechanisms of charge transport and displacement processes. A recent example is provided by studies of cytochrome c oxidase. However, the interpretation of the observed voltage changes in terms of the number of charge equivalents and transfer distances is far from being trivial or unique. Using continuum approaches to describe the voltage generation may involve significant uncertainties and reliable microscopic simulations are not yet available. Here, we attempt to solve this problem by using a coarse-grained model of membrane proteins, which includes an explicit description of the membrane, the electrolytes, and the electrodes. The model evaluates the gating charges and the electrode potentials (c.f. measured voltage) upon charge transfer within the protein. The accuracy of the model is evaluated by a comparison of measured voltage changes associated with electron and proton transfer in bacterial photosynthetic reaction centers to those calculated using our coarse-grained model. The calculations reproduce the experimental observations and thus indicate that the method is of general use. Interestingly, it is found that charge-separation processes with different spatial directions (but the same distance perpendicular to the membrane) can give similar observed voltage changes, which indicates that caution should be exercised when using simplified interpretation of the relationship between charge displacement and voltage changes. PMID:25049404

Kim, Ilsoo; Chakrabarty, Suman; Brzezinski, Peter; Warshel, Arieh

2014-01-01

346

Drop short control of electrode gap  

DOEpatents

During vacuum consumable arc remelting the electrode gap between a consumable electrode and a pool of molten metal is difficult to control. The present invention monitors drop shorts by detecting a decrease in the voltage between the consumable electrode and molten pool. The drop shorts and their associated voltage reductions occur as repetitive pulses which are closely correlated to the electrode gap. Thus, the method and apparatus of the present invention controls electrode gap based upon drop shorts detected from the monitored anode-cathode voltage. The number of drop shorts are accumulated, and each time the number of drop shorts reach a predetermined number, the average period between drop shorts is calculated from this predetermined number and the time in which this number is accumulated. This average drop short period is used in a drop short period electrode gap model which determines the actual electrode gap from the drop short. The actual electrode gap is then compared with a desired electrode gap which is selected to produce optimum operating conditions and the velocity of the consumable error is varied based upon the gap error. The consumable electrode is driven according to any prior art system at this velocity. In the preferred embodiment, a microprocessor system is utilized to perform the necessary calculations and further to monitor the duration of each drop short. If any drop short exceeds a preset duration period, the consumable electrode is rapidly retracted a predetermined distance to prevent bonding of the consumable electrode to the molten remelt.

Fisher, Robert W. (Albuquerque, NM); Maroone, James P. (Albuquerque, NM); Tipping, Donald W. (Albuquerque, NM); Zanner, Frank J. (Sandia Park, NM)

1986-01-01

347

Restraint Method of Voltage Total Harmonic Distortion in Distribution Network by Power Conditioner Systems using Measured Data from IT Switches  

NASA Astrophysics Data System (ADS)

Recently, the amount of distributed generation (DG) such as photovoltaic system and wind power generator system installed in a distribution system has been increasing because of reduction of the effects on the environment. However, the harmonic troubles in the distribution system are apprehended in the background of the increase of connection of DGs through the inverters and the spread of power electronics equipment. In this paper, the authors propose a restraint method of voltage total harmonic distortion (THD) in a whole distribution network by active filter (AF) operation of plural power conditioner systems (PCS). Moreover, the authors propose a determination method of the optimal gain of AF operation so as to minimize the maximum value of voltage THD in the distribution network by the real-time feedback control with measured data from the information technology (IT) switches. In order to verify the validity of the proposed method, the numerical calculations are carried out by using an analytical model of distribution network interconnected DGs with PCS.

Kawasaki, Shoji; Shimoda, Kazuki; Tanaka, Motohiro; Taoka, Hisao; Matsuki, Junya; Hayashi, Yasuhiro

348

Tunneling spectroscopy of clean and adsorbate-covered gold surfaces in humid air, measured with fast bias voltage ramps  

NASA Astrophysics Data System (ADS)

The noise level of tunneling spectroscopic data can be significantly reduced by averaging the tunneling current over a large number of short bias voltage ramps, instead of recording over a single slow ramp. This effect is demonstrated for tunneling spectra of Au(111) by averaging over 200 consecutive bias voltage ramps, each 500 ?s long. We attribute the improvement of the data quality to the frequency dependence of the current noise spectral density. Due to mechanical vibrations and tip instabilities the noise density is usually much higher for low frequencies ca. < 1 kHz than for the high frequencies relevant for measuring with fast bias ramps. The high data quality allowed for the routine detection of the Au(111) surface state and the investigation of the influence of steps in humid air, i.e., with a water-covered tunneling gap. For a CN covered Au surface in the presence of water we unexpectedly found additional electronic density of states at positive energies, around 0.6 eV, i.e., for unoccupied states. STS spectra of a (?{ 3} ×?{ 3}) R 30 ° Cu-UPD layer, formed by adsorbed sulfate and Cu species, indicate tunneling via the sulfate electronic density of states.

Rösch, Raphael; Schuster, Rolf

2015-01-01

349

Topographical and electrochemical nanoscale imaging of living cells using voltage-switching mode scanning electrochemical microscopy  

PubMed Central

We describe voltage-switching mode scanning electrochemical microscopy (VSM-SECM), in which a single SECM tip electrode was used to acquire high-quality topographical and electrochemical images of living cells simultaneously. This was achieved by switching the applied voltage so as to change the faradaic current from a hindered diffusion feedback signal (for distance control and topographical imaging) to the electrochemical flux measurement of interest. This imaging method is robust, and a single nanoscale SECM electrode, which is simple to produce, is used for both topography and activity measurements. In order to minimize the delay at voltage switching, we used pyrolytic carbon nanoelectrodes with 6.5–100 nm radii that rapidly reached a steady-state current, typically in less than 20 ms for the largest electrodes and faster for smaller electrodes. In addition, these carbon nanoelectrodes are suitable for convoluted cell topography imaging because the RG value (ratio of overall probe diameter to active electrode diameter) is typically in the range of 1.5–3.0. We first evaluated the resolution of constant-current mode topography imaging using carbon nanoelectrodes. Next, we performed VSM-SECM measurements to visualize membrane proteins on A431 cells and to detect neurotransmitters from a PC12 cells. We also combined VSM-SECM with surface confocal microscopy to allow simultaneous fluorescence and topographical imaging. VSM-SECM opens up new opportunities in nanoscale chemical mapping at interfaces, and should find wide application in the physical and biological sciences. PMID:22611191

Takahashi, Yasufumi; Shevchuk, Andrew I.; Novak, Pavel; Babakinejad, Babak; Macpherson, Julie; Unwin, Patrick R.; Shiku, Hitoshi; Gorelik, Julia; Klenerman, David; Korchev, Yuri E.; Matsue, Tomokazu

2012-01-01

350

A Microfluidic Bioreactor With Integrated Transepithelial Electrical Resistance (TEER) Measurement Electrodes for Evaluation of Renal Epithelial Cells  

PubMed Central

We have developed a bilayer microfluidic system with integrated transepithelial electrical resistance (TEER) measurement electrodes to evaluate kidney epithelial cells under physiologically relevant fluid flow conditions. The bioreactor consists of apical and basolateral fluidic chambers connected via a transparent microporous membrane. The top chamber contains microfluidic channels to perfuse the apical surface of the cells. The bottom chamber acts as a reservoir for transport across the cell layer and provides support for the membrane. TEER electrodes were integrated into the device to monitor cell growth and evaluate cell–cell tight junction integrity. Immunofluorescence staining was performed within the microchannels for ZO-1 tight junction protein and acetylated ?-tubulin (primary cilia) using human renal epithelial cells (HREC) and MDCK cells. HREC were stained for cytoskeletal F-actin and exhibited disassembly of cytosolic F-actin stress fibers when exposed to shear stress. TEER was monitored over time under normal culture conditions and after disruption of the tight junctions using low Ca2+ medium. The transport rate of a fluorescently labeled tracer molecule (FITC-inulin) was measured before and after Ca2+ switch and a decrease in TEER corresponded with a large increase in paracellular inulin transport. This bioreactor design provides an instrumented platform with physiologically meaningful flow conditions to study various epithelial cell transport processes. PMID:20552673

Ferrell, Nicholas; Desai, Ravi R.; Fleischman, Aaron J.; Roy, Shuvo; Humes, H. David; Fissell, William H.

2014-01-01

351

Low-voltage-tunable nanobeam lasers immersed in liquid crystals.  

PubMed

A low-voltage-tunable one-dimensional nanobeam laser is realized by employing lithographically defined lateral electrodes. An InGaAsP nanobeam with a sub-micrometer width is transfer-printed in the middle of two electrodes using a polydimethylsiloxane stamp. Spectral tuning is achieved by controlling the molecular alignment of the surrounding liquid crystals (LCs). From ?m-scale-gap structures, a total wavelength shift that exceed 6 nm is observed at a low voltage of less than 10 V. A measured spectral tuning rate of 0.87 nm/V, which is the largest value ever reported to our knowledge among LC-tuned photonic crystal lasers, was also noted. PMID:25607018

Kim, Sejeong; Kim, Hwi-Min; Son, Jaehyun; Kim, Yun-Ho; Ok, Jong Min; Kim, Ki Soo; Jung, Hee-Tae; Min, Bumki; Lee, Yong-Hee

2014-12-15

352

Current-to-voltage amplifier with a high voltage isolated input  

NASA Astrophysics Data System (ADS)

The measurement of very low currents collected on electrodes held at high voltages is a commonly encountered experimental problem, since a commercial electrometer's input can usually be floated only at a few tens of volts. In order to solve it, a current-to-voltage (transresistance) amplifier whose input can be floated up to + or - 2000 V, while providing a ground-referenced low-impedance output capable of driving a voltmeter or chart recorder is designed, built, and tested. This very flexible instrument can measure currents in the 10 to the -12th - 10 to the -7th-A range, has a 1-Hz bandwidth, and it can be built at a cost of a few hundred dollars.

Jaduszliwer, B.; Kahla, C. M.

1989-06-01

353

Image processing for non-ratiometric measurement of membrane voltage using fluorescent reporters and pulsed laser illumination.  

PubMed

The measurement of transmembrane voltages induced by pulsed electric field exposure can be achieved by using fluorescent dyes like ANNINE-6. Such approach requires a quantitative determination of the fluorescence intensity along the cell's membrane by image processing. When high temporal resolution is required, the illumination source is frequently a dye-laser which causes high fluctuations in the intensity of illumination which in turn affects the fluorescence intensity and thus the quality of the results. We propose an image processing technique that allows to overcome the fluctuations and to produce quantitative data. It uses the optical background noise as a correcting factor. Standard deviation in the fluctuations is thus efficiently reduced by at least a factor of 2.5. Additionally we draw attention to the fact that the parasitic component of the laser radiation (ASE) can also suppress fluctuations although it deteriorates wavelength precision. PMID:25091458

Silve, Aude; Rocke, Sarah; Frey, Wolfgang

2015-06-01

354

Constant voltage electro-slag remelting control  

DOEpatents

A system for controlling electrode gap in an electro-slag remelt furnace has a constant regulated voltage and an electrode which is fed into the slag pool at a constant rate. The impedance of the circuit through the slag pool is directly proportional to the gap distance. Because of the constant voltage, the system current changes are inversely proportional to changes in gap. This negative feedback causes the gap to remain stable. 1 fig.

Schlienger, M.E.

1996-10-22

355

Sensitivities of Key Parameters in the Preparation of Silver/Silver Chloride Electrodes Used in Harned Cell Measurements of pH  

PubMed Central

A questionnaire was completed by fourteen world leading national metrology institutes to study the influence of several variables in the preparation of Ag/AgCl electrodes on the accuracy of Harned cell measurements of pH. The performance of each institute in the last decade has been assessed based on their results in eight key comparisons, organized by the Bureau International des Poids et Measures Consultative Committee for Amount of Substance, involving the measurement of pH of phosphate, phthalate, carbonate, borate and tetroxalate buffer solutions. The performance of each laboratory has been correlated to the results of the questionnaire to determine the critical parameters in the preparation of Ag/AgCl electrodes and their sensitivities with respect to the accuracy of pH measurement. This study reveals that the parameters most closely correlated to performance in comparisons are area of electrode wire exposed to the electrolyte, diameter and porosity of the Ag sphere prior to anodisation, amount of Ag converted to AgCl during anodisation, stability times employed for electrodes to reach equilibrium in solution prior to measurement, electrode rejection criteria employed and purity of reagents. PMID:22164063

Brewer, Paul J.; Stoica, Daniela; Brown, Richard J. C.

2011-01-01

356

Output trends, characteristics, and measurements of three mega-voltage radiotherapy linear accelerators  

PubMed Central

The purpose of this study is to characterize and understand the long term behavior of the output from megavoltage radiotherapy linear accelerators. Output trends of nine beams from three linear accelerators over a period of more than three years are reported and analyzed. Output taken during daily warm-up forms the basis of this study. The output is measured using devices having ion-chambers. These are not calibrated by accredited dosimetry laboratory but are baseline compared against monthly output which are measured using calibrated ion-chambers. We consider the output from the daily check devices as it is and sometimes normalized them by the actual output measured during the monthly calibration of the Linacs. The data shows noisy quasi-periodic behavior. The output variation if normalized by monthly measured “real’ output, is bounded between ±3%. Beams of different energies from the same Linac are correlated with a correlation coefficient as high as 0.97 for one particular Linac and as low as 0.44 for another. These maximum and minimum correlations drop to 0.78 and 0.25 when daily output is normalized by the monthly measurements. These results suggest that the origin of these correlations are both the Linacs and the daily output check devices. Beams from different Linacs, independent of their energies, have lower correlation coefficient with a maximum of about 0.50 and a minimum of almost zero. The maximum correlation drops to almost zero if the output is normalized by the monthly measured output. Some scatter plots of pairs of beam-output from the same Linac show band-like structures. These structures are blurred when the output is normalized by the monthly calibrated output. Fourier decomposition of the quasi periodic output is consistent with a 1/f power law. The output variation appears to come from a distorted normal distribution with a mean of slightly greater than unity. The quasi-periodic behavior is manifested in the seasonally averaged output showing annual variability with negative variations in the winter and positive in the summer. This trend is weakened when the daily output is normalized by the monthly calibrated output indicating that the variation of the periodic component may be intrinsic to both the Linacs and the daily measurement devices. Actual Linac output was measured monthly. It is needed to be adjusted once every 3-6 months for our tolerance and action levels. If these adjustments are artificially removed then there is an increase in output of about 2-4% per year. PMID:25207404

Hossain, Murshed

2015-01-01

357

A DSP based real time power quality measurement system with voltage distortion improvement capability  

E-print Network

TMS320C30 FFT time benchmarks . . 26 3 Simulation results from the C30MS 38 4 Experimental results for balanced three phase nonlinear loads 39 6 Experimental results for measuring the neutral current 40 6 Relationship between Fourier transform... out real time measurement with low cost and mcreased flexibility. In the proposed PQMS, a 32 bit DSP processor TMS320C30 is used. The key features of the processor a. re listed as follows, (i) 32 bit floating point DSP processor (ii) 60 ns single...

Gou, Jian

1992-01-01

358

Filter-fluorescer measurement of low-voltage simulator x-ray energy spectra  

SciTech Connect

X-ray energy spectra of the Maxwell Laboratories MBS and Physics International Pulserad 737 were measured using an eight-channel filter-fluorescer array. The PHOSCAT computer code was used to calculate channel response functions, and the UFO code to unfold spectrum.

Baldwin, G.T.; Craven, R.E.

1986-01-01

359

New frequency\\/voltage converters for ac-electrogravimetric measurements based on fast quartz crystal microbalance  

Microsoft Academic Search

A better understanding of the mechanisms located at the solid\\/electrolyte interface is becoming essential to the development of new applications in the electrochemical fields. The fast quartz crystal microbalance is an attractive and powerful gravimetric sensor which can be used in the dynamic regime to determine a mass\\/potential transfer function. The principle is equivalent to classical electrochemical impedance measurements; the

C. Gabrielli; H. Perrot; D. Rose; A. Rubin; J. P. Toqué; M. C. Pham; B. Piro

2007-01-01

360

Voltage Drop  

NSDL National Science Digital Library

The first site with information on voltage drop is provided by Power and System Innovations on their Frequently Asked Questions: Voltage Drop (1) page. Visitors can read what voltage drop is, what causes it, what happens as a result of it, and what the maximum recommended voltage drop is. The second site, Basics of Electricity (2), is part of General Electric's Lighting for Business Web site. Through descriptions and illustrations, the site explains what voltage drop is and gives examples of how it is calculated using Ohm's law. The next site is a lab worksheet that is part of a class from the Electrical and Computer Engineering Department of Montana State University called Voltage Drop in Cables (3). The objective of the lesson is to determine the internal resistance of an extension cord and choose the proper wire size for a particular application. Students are given an explanation of the procedure and a number of questions to answer related to the exercise. The Oregon Building Congress offers the Lesson Plans (4) Web site and the downloadable Voltage Drop educational activity. The lesson, which is suggested to be contained within a unit on formulas and solving literal equations, explores the concept of voltage drop that is encountered in basic wiring. The fifth site entitled Explanation of Voltage Drop in a Series Circuit (5) is offered by the Horizons Electronic Lesson Plan Resource. The page describes voltage drop as an electronic concept, gives a formula determining voltage drop, provides a schematic that helps illustrate the concept, and offers a quiz and answer sheet. Next, from electrician.com, is the online Voltage Drop Calculator (6). Users input the type and size of wire being used, the voltage and phase, circuit length, and amp load to calculate voltage drop and several other parameters. The seventh site, entitled The Hazards of Voltage Drop (7), is provided within the Electrical Construction Maintenance Web site. The page describes how electrical equipment can overheat or even power down if it operates below its voltage rating. It also provides a thorough explanation of how to determine the load's operating voltage. The last site, maintained by Williamson Labs (8), is a comprehensive learning site called Elementary Electricity. Visitors will find a wealth of information here, including fun descriptions, graphics, and animations on all aspects of electricity including voltage drop.

361

Characterizing voltage contrast in photoelectron emission microscopy.  

PubMed

A non-destructive technique for obtaining voltage contrast information with photoelectron emission microscopy is described. Samples consisting of electrically isolated metal lines were used to quantify voltage contrast in photoelectron emission microscopy. The voltage contrast behaviour is characterized by comparing measured voltage contrast with calculated voltage contrast from two electrostatic models. Measured voltage contrast was found to agree closely with the calculated voltage contrast, demonstrating that voltage contrast in photoelectron emission microscopy can be used to probe local voltage information in microelectronic devices in a non-intrusive fashion. PMID:20579259

Sangwan, V K; Ballarotto, V W; Siegrist, K; Williams, E D

2010-06-01

362

Near-uv photon efficiency in a TiO2 electrode - Application to hydrogen production from solar energy  

NASA Technical Reports Server (NTRS)

An n-type (001) TiO2 electrode irradiated at 365 nm was tested under anodic polarization. A saturation current independent of pH and proportional to light intensity has been observed. Accurate measurements of the incident power lead to a 60 per cent photon efficiency. A photoelectrochemical cell built with such an electrode, operated under solar irradiation without concentration, produced an electrolysis current of 0.7 mA/sq cm without applied voltage.

Desplat, J.-L.

1976-01-01

363

Digital wireless data acquisition system for measurement in high voltage substations  

Microsoft Academic Search

This paper describes a new digital wireless data acquisition system that can be used to measure electromagnetic interference (EMI) in power stations or other similar harsh environments. It comprises of a remote acquisition unit (RAU), a wireless data communication network (WDCN) and a PC-based control platform as a front end of the field-distributed-data-acquisition system, RAU captures, digitizes and stores the

Y. Wang; F. A. M. Mir; W. H. Siew

2006-01-01

364

Building a Low-Cost, Six-Electrode Instrument to Measure Electrical Properties of Self-Assembled Monolayers of Gold Nanoparticles  

ERIC Educational Resources Information Center

The development of a new low-cost, six-electrode instrument for measuring the electrical properties of the self-assembled monolayers of gold particles is being described. The system can also be used to measure conductive liquids, except for those that contain aqua region.

Gerber, Ralph W.; Oliver-Hoyo, Maria

2007-01-01

365

Electrohydrodynamic flow in a wire-plate non-thermal plasma reactor measured by 3D PIV method  

NASA Astrophysics Data System (ADS)

This work was aimed at measurements of the electrohydrodynamic (EHD) secondary flow in a non-thermal plasma reactor using three-dimensional particle image velocimetry (3D PIV) method. The wide-type non-thermal plasma reactor used in this work was an acrylic box with a wire discharge electrode and two plate collecting electrodes. The positive DC voltage was applied to the wire electrode through a 10 M? resistor. The collecting electrodes were grounded. The voltage applied to the wire electrode was 28 kV. Air flow seeded with a cigarette smoke was blown along the reactor duct with an average velocity of 0.6 m/s. The 3D PIV velocity fields measurements were carried out in four parallel planes stretched along the reactor duct, perpendicularly to the wire electrode and plate electrodes. The measured flow velocity fields illustrate complex nature of the EHD induced secondary flow in the non-thermal plasma reactor.

Podlinski, J.; Niewulis, A.; Mizeraczyk, J.

2009-08-01

366

Experimental evaluation of actual delivered dose using mega-voltage cone-beam CT and direct point dose measurement  

SciTech Connect

Radiation therapy in patients is planned by using computed tomography (CT) images acquired before start of the treatment course. Here, tumor shrinkage or weight loss or both, which are common during the treatment course for patients with head-and-neck (H and N) cancer, causes unexpected differences from the plan, as well as dose uncertainty with the daily positional error of patients. For accurate clinical evaluation, it is essential to identify these anatomical changes and daily positional errors, as well as consequent dosimetric changes. To evaluate the actual delivered dose, the authors proposed direct dose measurement and dose calculation with mega-voltage cone-beam CT (MVCBCT). The purpose of the present study was to experimentally evaluate dose calculation by MVCBCT. Furthermore, actual delivered dose was evaluated directly with accurate phantom setup. Because MVCBCT has CT-number variation, even when the analyzed object has a uniform density, a specific and simple CT-number correction method was developed and applied for the H and N site of a RANDO phantom. Dose distributions were calculated with the corrected MVCBCT images of a cylindrical polymethyl methacrylate phantom. Treatment processes from planning to beam delivery were performed for the H and N site of the RANDO phantom. The image-guided radiation therapy procedure was utilized for the phantom setup to improve measurement reliability. The calculated dose in the RANDO phantom was compared to the measured dose obtained by metal-oxide-semiconductor field-effect transistor detectors. In the polymethyl methacrylate phantom, the calculated and measured doses agreed within about +3%. In the RANDO phantom, the dose difference was less than +5%. The calculated dose based on simulation-CT agreed with the measured dose within±3%, even in the region with a high dose gradient. The actual delivered dose was successfully determined by dose calculation with MVCBCT, and the point dose measurement with the image-guided radiation therapy procedure.

Matsubara, Kana, E-mail: matsubara-kana@hs.tmu.ac.jp [Graduate School of Human Health Sciences, Tokyo Metropolitan University, Arakawa-ku Tokyo (Japan); Kohno, Ryosuke [National Cancer Center Hospital East, Chiba (Japan); National Cancer Center Research Institute, Chiba (Japan); Nishioka, Shie; Shibuya, Toshiyuki; Ariji, Takaki; Akimoto, Tetsuo [National Cancer Center Hospital East, Chiba (Japan); Saitoh, Hidetoshi [Graduate School of Human Health Sciences, Tokyo Metropolitan University, Arakawa-ku Tokyo (Japan)

2013-07-01

367

Considerations for Estimating Electrode Performance in Li-Ion Cells  

NASA Technical Reports Server (NTRS)

Advanced electrode materials with increased specific capacity and voltage performance are critical to the development of Li-ion batteries with increased specific energy and energy density. Although performance metrics for individual electrodes are critically important, a fundamental understanding of the interactions of electrodes in a full cell is essential to achieving the desired performance, and for establishing meaningful goals for electrode performance. This paper presents practical design considerations for matching positive and negative electrodes in a viable design. Methods for predicting cell-level discharge voltage, based on laboratory data for individual electrodes, are presented and discussed.

Bennett, William R.

2012-01-01

368

A Method for Measuring the Volume of Transdermally Extracted Interstitial Fluid by a Three-Electrode Skin Resistance Sensor  

PubMed Central

It is difficult to accurately measure the volume of transdermally extracted interstitial fluid (ISF), which is important for improving blood glucose prediction accuracy. Skin resistance, which is a good indicator of skin permeability, can be used to determine the volume of extracted ISF. However, it is a challenge to realize in vivo longitudinal skin resistance measurements of microareas. In this study, a three-electrode sensor was presented for measuring single-point skin resistance in vivo, and a method for determining the volume of transdermally extracted ISF using this sensor was proposed. Skin resistance was measured under static and dynamic conditions. The correlation between the skin resistance and the permeation rate of transdermally extracted ISF was proven. The volume of transdermally extracted ISF was determined using skin resistance. Factors affecting the volume prediction accuracy of transdermally extracted ISF were discussed. This method is expected to improve the accuracy of blood glucose prediction, and is of great significance for the clinical application of minimally invasive blood glucose measurement. PMID:24759111

Li, Dachao; Wang, Ridong; Yu, Haixia; Li, Guoqing; Sun, Yue; Liang, Wenshuai; Xu, Kexin

2014-01-01

369

A nine-electrode probe for simultaneous measurement of all terms in the ideal radial Ohm's law  

SciTech Connect

A Nine-Electrode Probe (NEP) has been developed for simultaneous measurement of all terms in the ideal Ohm's law E+UxB=0 in the radial (r) direction in cylindrical geometry, where E is the electric field, U is the plasma flow velocity, and B is the magnetic field. The probe consists of two pairs of directional Langmuir probes ('Mach' probes) to measure the axial (z) and azimuthal ({theta}) plasma flows, two pairs of floating Langmuir probes at different radial positions to measure the radial electric field, and two B-dot coils to measure the axial and azimuthal magnetic field. The measurement is performed in the Flowing Magnetized Plasma (FMP) experiment. Two flow patterns are identified in the FMP experiment by the NEP. The peak-to-peak values of radial electric field fluctuation is 1.5-4 times of the mean values. Comparisons of UxBvertical bar{sub r} and E{sub r} show that E{sub r}+ UxBvertical bar{sub r} is not zero within some periods of discharge. This deviation suggests non-ideal effects in Ohm's law can not be neglected.

Si, Jiahe; Wang, Zhehui [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2006-10-15

370

Effects of skin blood flow and temperature on skin--electrode impedance and offset potential: measurements at low alternating current density.  

PubMed

Skin--electrode impedance was determined at 100 Hz and 1 kHz between two disposable electrodes, 5 cm apart, at current densities < 65 microA.cm-2. Measurements were made on the volar skin of the forearm during cooling on cardiopulmonary bypass, and on the dorsum of the foot in the absence of skin blood flow during aortic aneurysm repair. Both the resistive and reactive components of the skin-electrode impedence showed an inverse linear relationship to temperature between 26 and 36 degrees C. The magnitude of the impedance change was different for each patient studied; resistance changes ranged from 0.03 to 23.2 k omega. Degrees C-1 at 100 Hz and from 0.03 to 2.7 k omega. Degrees C-1 at 1 kHz, while reactance changes ranged from 0.4 to 2.1 k omega. Degrees C-1 at 100 Hz and from 0.04 to 0.18 k omega. Degrees C-1 at 1 kHz. Changes in skin-electrode impedance were not due to changes in skin blood flow. There was no consistent change in offset potential with temperature. Although the skin-electrode impedance increases as temperature falls, it is concluded that temperature effects at the skin-electrode interface are not responsible for the observed failure of evoked electromyography during clinical monitoring of neuromuscular function. PMID:1404312

Smith, D C

1992-01-01

371

Electrode compositions  

DOEpatents

An electrode composition for use as an electrode in a non-aqueous battery system. The electrode composition contains an electrically active powder in a solid polymer and, as a dispersant, a C.sub.8 -C.sub.15 alkyl capped oligomer of a hexanoic acid that is electrochemically inert at 2.5-4.5 volts.

Block, Jacob (Rockville, MD); Fan, Xiyun (Orange, TX)

1998-01-01

372

Electrode compositions  

DOEpatents

An electrode composition is described for use as an electrode in a non-aqueous battery system. The electrode composition contains an electrically active powder in a solid polymer and, as a dispersant, a C{sub 8}-C{sub 15} alkyl capped oligomer of a hexanoic acid that is electrochemically inert at 2.5--4.5 volts.

Block, J.; Fan, X.

1998-10-27

373

Current-voltage characteristics of dc corona discharges in air between coaxial cylinders  

NASA Astrophysics Data System (ADS)

This paper presents the experimental measurement and numerical analysis of the current-voltage characteristics of dc corona discharges in air between coaxial cylinders. The current-voltage characteristics for both positive and negative corona discharges were measured within a specially designed corona cage. Then the measured results were fitted by different empirical formulae and analyzed by the fluid model. The current-voltage characteristics between coaxial cylinders can be expressed as I = C(U - U0)m, where m is within the range 1.5-2.0, which is similar to the point-plane electrode system. The ionization region has no significant effect on the current-voltage characteristic under a low corona current, while it will affect the distribution for the negative corona under a high corona current. The surface onset fields and ion mobilities were emphatically discussed.

Zheng, Yuesheng; Zhang, Bo; He, Jinliang

2015-02-01

374

Electrode and Langmuir probe tools used for flow damping studies in the Helically Symmetric Experiment  

SciTech Connect

A system of electrodes and Langmuir probes has been developed for the measurement of plasma flow damping in the Helically Symmetric Experiment (HSX) stellarator. A biased electrode is used to apply a JxB torque to the plasma. The fast switching electrode power supply allows the electrode voltage to be applied in {approx}1 {mu}s, which is much faster than any of the plasma time scales; the electrode current is terminated on a similar time scale at the end of the electrode pulse. A pair of multitipped Mach probes have been designed to measure the plasma flows in a magnetic surface with good spatial and time resolution ({delta}t>20 {mu}s). The unmagnetized model by Hutchinson is used to analyze the Mach probe data, and radial force balance is found to be well satisfied during electrode bias. These probes allow for measurements of the transient response of the plasma flows and floating potential when the electrode is energized. An example of using the system for the estimation of viscous damping times in HSX is provided.

Gerhardt, S.P.; Anderson, D.T.; Anderson, F.S.B.; Talmadge, J.N. [Department of Electrical and Computer Engineering, University of Wisconsin, Madison, Wisconsin 53703 (United States)

2004-11-01

375

Contactless measurement of electrical parameters and estimation of current-voltage characteristics of Si solar cells using the illumination intensity dependence of lock-in carrierography (photoluminescence) images  

NASA Astrophysics Data System (ADS)

A combined theoretical and experimental approach is reported using spectrally windowed lock-in carrierography imaging (lock-in photoluminescence) under variable illumination intensity to provide quantitative contactless measurements of key electrical parameters (photogenerated current density, Jg, open circuit voltage, VOC, and maximum power voltage, Vm) of multicrystalline silicon (m-Si) solar cells in very good agreement with standard electrical measurements. The method is based on a recently developed photocarrier radiative recombination current flux relation which links the optical and electrical characteristics of solar cells. In addition, this approach is shown to yield non-contact all-optical estimates of the solar-cell current-voltage characteristics with the conventional variable load resistance replaced by variable laser intensity.

Liu, Junyan; Melnikov, Alexander; Mandelis, Andreas

2013-09-01

376

Contact impedance of grounded and capacitive electrodes  

NASA Astrophysics Data System (ADS)

The contact impedance of electrodes determines how much current can be injected into the ground for a given voltage. If the ground is very resistive, capacitive electrodes may be an alternative to galvanic coupling. The impedance of capacitive electrodes is often estimated with the assumption that the halfspace is an ideal conductor. Over resistive ground at high frequencies, however, the contact impedance will depend on the electrical properties, i.e. electrical conductivity and permittivity, of the subsurface. Here, we review existing equations for the resistance of a galvanically coupled, spherical electrode in a fullspace, and extend the theory to the general case of a sphere in a spherically layered fullspace. We then develop a method to calculate the impedance of a spherical disc over a homogeneous halfspace. We carry out modelling studies to demonstrate the consistency of the algorithms and to assess under which conditions the determination of the electrical parameters from the impedance may be feasible. For a capacitively coupled electrode, the common assumption of an ideally conducting fullspace (or halfspace) breaks down if the displacement currents in the fullspace become as large as the conduction currents. For a moderately resistive medium with 1000 ?m this is the case for frequencies larger than 100 kHz. The transition from a galvanically coupled disc to a disc in the air is continuous as function of distance. However, depending on the electrical parameters and frequency, the impedance may vary by several orders of magnitude within a few nanometers distance or less. We derive a simple equation to assess under which conditions the impedance is independent of the electrode height, which may be important for determining subsurface permittivity and conductivity in cases where control on the exact geometry is difficult. Our theory is consistent with measured data obtained in a sandbox in the laboratory.

Hördt, Andreas; Weidelt, Peter; Przyklenk, Anita

2013-04-01

377

Performance enhancement of ITO/oxide/semiconductor MOS-structure silicon solar cells with voltage biasing  

PubMed Central

In this study, we demonstrate the photovoltaic performance enhancement of a p-n junction silicon solar cell using a transparent-antireflective ITO/oxide film deposited on the spacing of the front-side finger electrodes and with a DC voltage applied on the ITO-electrode. The depletion width of the p-n junction under the ITO-electrode was induced and extended while the absorbed volume and built-in electric field were also increased when the biasing voltage was increased. The photocurrent and conversion efficiency were increased because more photo-carriers are generated in a larger absorbed volume and because the carriers transported and collected more effectively due to higher biasing voltage effects. Compared to a reference solar cell (which was biased at 0 V), a conversion efficiency enhancement of 26.57% (from 12.42% to 15.72%) and short-circuit current density enhancement of 42.43% (from 29.51 to 42.03 mA/cm2) were obtained as the proposed MOS-structure solar cell biased at 2.5 V. In addition, the capacitance-volt (C-V) measurement was also used to examine the mechanism of photovoltaic performance enhancement due to the depletion width being enlarged by applying a DC voltage on an ITO-electrode. PMID:25593550

2014-01-01

378

Multifunctional reference electrode  

DOEpatents

A multifunctional, low mass reference electrode of a nickel tube, thermocouple means inside the nickel tube electrically insulated therefrom for measuring the temperature thereof, a housing surrounding the nickel tube, an electrolyte having a fixed sulfide ion activity between the housing and the outer surface of the nickel tube forming the nickel/nickel sulfide/sulfide half-cell are described. An ion diffusion barrier is associated with the housing in contact with the electrolyte. Also disclosed is a cell using the reference electrode to measure characteristics of a working electrode.

Redey, L.; Vissers, D.R.

1981-12-30

379

Multifunctional reference electrode  

DOEpatents

A multifunctional, low mass reference electrode of a nickel tube, thermocouple means inside the nickel tube electrically insulated therefrom for measuring the temperature thereof, a housing surrounding the nickel tube, an electrolyte having a fixed sulfide ion activity between the housing and the outer surface of the nickel tube forming the nickel/nickel sulfide/sulfide half-cell. An ion diffusion barrier is associated with the housing in contact with the electrolyte. Also disclosed is a cell using the reference electrode to measure characteristics of a working electrode.

Redey, Laszlo (Lisle, IL); Vissers, Donald R. (Naperville, IL)

1983-01-01

380

Influence of superoxide on myeloperoxidase kinetics measured with a hydrogen peroxide electrode.  

PubMed Central

Stimulated neutrophils discharge large quantities of superoxide (O2.-), which dismutates to form H2O2. In combination with Cl-, H2O2 is converted into the potent oxidant hypochlorous acid (HOCl) by the haem enzyme myeloperoxidase. We have used an H2O2 electrode to monitor H2O2 uptake by myeloperoxidase, and have shown that in the presence of Cl- this accurately represents production of HOCl. Monochlorodimedon, which is routinely used to assay production of HOCl, inhibited H2O2 uptake by 95%. This result confirms that monochlorodimedon inhibits myeloperoxidase, and that the monochlorodimedon assay grossly underestimates the activity of myeloperoxidase. With 10 microM-H2O2 and 100 mM-Cl-, myeloperoxidase had a neutral pH optimum. Increasing the H2O2 concentration to 100 microM lowered the pH optimum to pH 6.5. Above the pH optimum there was a burst of H2O2 uptake that rapidly declined due to accumulation of Compound II. High concentrations of H2O2 inhibited myeloperoxidase and promoted the formation of Compound II. These effects of H2O2 were decreased at higher concentrations of Cl-. We propose that H2O2 competes with Cl- for Compound I and reduces it to Compound II, thereby inhibiting myeloperoxidase. Above pH 6.5, O2.- generated by xanthine oxidase and acetaldehyde prevented H2O2 from inhibiting myeloperoxidase, increasing the initial rate of H2O2 uptake. O2.- allowed myeloperoxidase to function optimally with 100 microM-H2O2 at pH 7.0. This occurred because, as previously demonstrated, O2.- prevents Compound II from accumulating by reducing it to ferric myeloperoxidase. In contrast, at pH 6.0, where Compound II did not accumulate, O2.- retarded the uptake of H2O2. We propose that by generating O2.- neutrophils prevent H2O2 and other one-electron donors from inhibiting myeloperoxidase, and ensure that this enzyme functions optimally at neutral pH. PMID:2557013

Kettle, A J; Winterbourn, C C

1989-01-01

381

Electrodeposition of Nanoporous Nickel Layers Using Inductive Voltage Pulses  

NASA Astrophysics Data System (ADS)

We used inductive voltage pulses for electro-deposition of porous nickel thin film onto steel electrode. Short pulses (tp<1 ?s) with variable amplitude (to ensure electro-deposition current density in region 124-224 A/dm2) were applied to electrode and resulting coating were analyzed with electrochemical and microscopic methods. At lower current densities only smooth nickel coatings growth, while at higher current densities the bubbles appear and porous layer was formed. Electrochemical impedance spectra of smooth and porous layers are measured in deionized water and in 1M KOH solution. The capacity in equivalent scheme is proportional to electrode surface, and from impedance spectra it is calculated that porous layer has 20 times larger active surface comparing to smooth layer (in KOH solution). From electrochemical measurements it is estimated that more efficient hydrogen evolution reaction occurs on electrode with porous nickel layer obtained at 223 A/dm2. It is shown in this work that inductive short pulse method can be used to obtain nano-porous nickel coatings on electrodes for efficient electrolysis cell.

Vanags, Martins; Kleperis, Janis; Bajars, Gunars; Nemcevs, Vladimirs

2013-12-01

382

Electrodes as social glue: measuring heart rate promotes giving in the trust game.  

PubMed

While physiological measures are increasingly used to help us understand the workings of interpersonal trust (and related behaviors), we know very little about the effects of such measures on trust. We examined the effects of a classic measure, the measurement of heart rate using a standard protocol, on behavioral trust in dyads of women who did not know each other. Behavioral trust was assessed in the trust game, in which the trustor decides how much money from their subject payment to give to a trustee, while knowing that the experimenter triples that amount before giving it to the trustee, after which the trustee decides how much money to return to the trustor. As predicted, we found greater levels of behavioral trust in the trust game, as well as greater returns by the trustees (which were accounted for by trustor's giving), in the heart rate (HR) than in no heart rate (NHR) measurement condition. Parallel findings were observed for self-reported trust. Findings are discussed in terms of the idea that the elusive effects of a protocol for measuring heart rate can cause pronounced effects on subsequent social interactions via enhanced interpersonal trust. PMID:21420448

Van Lange, Paul A M; Finkenauer, Catrin; Popma, Arne; van Vugt, Mark

2011-06-01

383

Voltage Controlled Voltage Source (VCVS)  

NSDL National Science Digital Library

Hosted by Clarkson University, this applet demonstrates a circuit that contains a voltage controlled voltage source (VCVS). The gain may be modified using the scroll bar. Even though brief, this resource can be used in a variety of different technical education classrooms.

Dorf, Richard C.

384

Experimental Investigation of the Low-Voltage Arc in Noble Gases  

Microsoft Academic Search

An experimental investigation of the low-voltage arc mode of the hot-cathode discharge has been carried out in a diode utilizing planar electrode geometry. The investigation consisted predominantly of Langmuir-probe measurements of the discharge in a neon atmosphere. Measurements were also obtained in argon, xenon, and hydrogen and hydrogen-neon and argon-neon mixtures. The probes were of planar, guard-ringed geometry. The volt-ampere

R. J. Martin; J. E. Rowe

1968-01-01

385

Time-resolved photoluminescence measurements for determining voltage-dependent charge-separation efficiencies of subcells in triple-junction solar cells  

NASA Astrophysics Data System (ADS)

Conventional external quantum-efficiency measurement of solar cells provides charge-collection efficiency for approximate short-circuit conditions. Because this differs from actual operating voltages, the optimization of high-quality tandem solar cells is especially complicated. Here, we propose a contactless method, which allows for the determination of the voltage dependence of charge-collection efficiency for each subcell independently. By investigating the power dependence of photoluminescence decays, charge-separation and recombination-loss time constants are obtained. The upper limit of the charge-collection efficiencies at the operating points is then obtained by applying the uniform field model. This technique may complement electrical characterization of the voltage dependence of charge collection, since subcells are directly accessible.

Tex, David M.; Ihara, Toshiyuki; Akiyama, Hidefumi; Imaizumi, Mitsuru; Kanemitsu, Yoshihiko

2015-01-01

386

Characterization of dry biopotential electrodes.  

PubMed

Driven by the increased interest in wearable long-term healthcare monitoring systems, varieties of dry electrodes are proposed based on different materials with different patterns and structures. Most of the studies reported in the literature focus on proposing new electrodes and comparing its performance with commercial electrodes. Few papers are about detailed comparison among different dry electrodes. In this paper, printed metal-plate electrodes, textile based electrodes, and spiked electrodes are for the first time evaluated and compared under the same experimental setup. The contact impedance and noise characterization are measured. The in-vivo electrocardiogram (ECG) measurement is applied to evaluate the overall performance of different electrodes. Textile electrodes and printed electrodes gain comparable high-quality ECG signals. The ECG signal obtained by spiked electrodes is noisier. However, a clear ECG envelope can be observed and the signal quality can be easily improved by backend signal processing. The features of each type of electrodes are analyzed and the suitable application scenario is addressed. PMID:24109978

Xie, Li; Yang, Geng; Xu, Linlin; Seoane, Fernando; Chen, Qiang; Zheng, Lirong

2013-01-01

387

Micro-Electrode Signal Degradation as an Indicator of the Biological Processes Involved in the Foreign Body Response  

E-print Network

and/or surface treatments on the electrodes to alter the foreign body response. Selection of Micro directly in the frequency domain by applying a single- frequency voltage to the interface and measuring the phase shift and amplitude (real & imaginary parts) of the resulting current at that frequency

388

Through-the-electrode model of a proton exchange membrane fuel cell with independently measured parameters  

SciTech Connect

A one dimensional model for a proton exchange membrane fuel cell was developed which makes use of independently measured parameters for predicting single cell performance. Optimization of catalyst layer formulation and properties are explored. Impact of temperature and cathode pressure upon system performance was investigated.

Weisbrod, K.R.; Grot, S.A.; Vanderborgh, N.E.

1995-05-01

389

Through-the-electrode model of a proton exchange membrane fuel cell with independently measured parameters  

SciTech Connect

A one dimensional model for a proton exchange membrane fuel cell was developed which makes use of independently measured parameters for predicting single cell performance. Optimization of catalyst layer formulation and properties are explored. Impact of temperature and cathode pressure upon system performance is investigated.

Weisbrod, K.R.; Grot, S.A.; Vandergborgh, N.E.

1995-09-01

390

Micro-electrode measurement of skin pH in humans during ischaemia, hypoxia and local hypothermia.  

PubMed Central

1. The extracellular pH value in the dermis of human skin (skin pH) was measured in vivo using glass micro-electrodes. They were found to be both reliable and accurate. 2. The mean value of skin pH measured in the legs of forty different volunteers was found to be pH 7.54 +/- 0.09 (S.D.). No difference in skin pH was observed between males and females, or in different regions of the limb. 3. Local reductions in skin surface temperature in ten subjects caused an increase of pH 0.023 +/- 0.007 per degree C fall. 4. A 20 min period of tourniquet ischaemia in twenty volunteers induced a fall in skin pH of 0.13 +/- 0.05 units. 5. Hyperventilation during a 10 min period of breathing 10% O2 in N2 caused an increase of pH 0.04 +/- 0.02 in the skin of healthy subjects. 6. Skin pH fell to a value 0.02 +/- 0.02 units below normal 10 min after the hypoxic period, suggesting the presence of excess lactate. 7. Skin pH results compared well with blood gases and pH values of arterialized samples taken during hypoxia. 8. It was concluded that the system was suitable for clinical trials. PMID:39164

Harrison, D K; Walker, W F

1979-01-01

391

A new dry biomedical electrode  

NASA Technical Reports Server (NTRS)

Electronic circuitry contains new operational amplifier which incorporates monolithic super-gain transistors. Electrode does not provide voltage amplification; instead, it acts as current amplifier to make it possible to pick up electrical potentials from surface of highly resistant dry skin.

Luce, R. S.; Cleveland, G. J.

1973-01-01

392

A prototype 64-electrode stimulator in 65 nm CMOS process towards a high density epi-retinal prosthesis.  

PubMed

This paper presents a highly flexible 64-electrode stimulator using 65 nm CMOS process fabricated as a stage towards a 1024-electrode epi-retinal prosthesis, which aims to restore partial vision in patients suffering from eye diseases such as retinitis pigmentosa (RP) and age-related macular degradation (AMD). The stimulator drives 64 electrodes with many flexible features, which are necessary before making a complete 1024-electrode implant chip. Each electrode driver can provide a bi-phasic stimulus current with fully programmable parameters such as amplitude, pulse duration, inter-phase gap, and stimulation rate. The electrode driver operates in an alternately pull-push manner with only one current source working at a time, which helps reduce headroom voltage while controlling charge balance at the active electrode. The stimulator varies both stimulus current amplitude and stimulation rate to represent phosphene brightness. The stimulus current amplitude starts from the tissue depolarization threshold with 64 different levels. The selection of active and return electrodes is arbitrary, any electrodes and any number of them can be selected at any time. The power consumption of the stimulator is 400 ?W excluding the stimulus power. Measurement results verify correct operation. The stimulator is easily scaled up to drive 1024 electrodes. PMID:22255883

Tran, N; Skafidas, E; Yang, J; Bai, S; Fu, M; Ng, D; Halpern, M; Mareels, I

2011-01-01

393

Automatic frequency control of voltage-controlled oscillators  

NASA Technical Reports Server (NTRS)

Optical-capacitive coupling is used for isolation of control voltages, such as the high-voltage level of a klystron control electrode that is not referenced to ground, to serve as error voltages referenced to system ground so that the magnitude and sense of correction may be transferred.

Kolbly, R. B.

1969-01-01

394

Modeling defibrillation electrode performance.  

PubMed

A Boundary Element (BE) model was developed of the electric potential field in the heart arising from electric potentials applied on implanted defibrillator electrodes. The model solved Laplace's equation for potential and was implemented using the BE method with realistic torso structures. An efficient out-of-core solver was developed, allowing any size problem to be solved, subject only to computer speed and time available. A method was also developed that allowed matrices calculated in one problem to be used in other, similar problems, often reducing calculation times by an order of magnitude. Model validation included comparison with myocardial potentials from a finite element model and clinically found voltage and resistance at defibrillation threshold from 29 patients. The model was used in investigations of transvenous electrode configurations, with potential found for reduction in defibrillation voltage and energy. The BE model was successful in modelling the electric field in the torso, in predicting implantable defibrillator performance and in finding application in electrode performance studies. PMID:17281079

Gale, Timothy

2005-01-01

395

Multilevel Cascade H-bridge Inverter DC Voltage Estimation Through Output Voltage Sensing  

E-print Network

at the output of the inverter to eliminate all the dc voltage sensors measuring the individual source voltagesMultilevel Cascade H-bridge Inverter DC Voltage Estimation Through Output Voltage Sensing Faete to determine the input voltage value of each cell in a cascade H-bridge multilevel inverter using a sensor

Tolbert, Leon M.

396

High voltage solar array experiments  

NASA Technical Reports Server (NTRS)

The interaction between the components of a high voltage solar array and a simulated space plasma is studied to obtain data for the design of a high voltage solar array capable of 15kW at 2 to 16kV. Testing was conducted in a vacuum chamber 1.5-m long by 1.5-m diameter having a plasma source which simulated the plasma conditions existing in earth orbit between 400 nautical miles and synchronous altitude. Test samples included solar array segments pinholes in insulation covering high voltage electrodes, and plain dielectric samples. Quantitative data are presented in the areas of plasma power losses, plasma and high voltage induced damage, and dielectric properties. Limitations of the investigation are described.

Kennerud, K. L.

1974-01-01

397

Electrooptic polymer voltage sensor and method of manufacture thereof  

NASA Technical Reports Server (NTRS)

An optical voltage sensor utilizing an electrooptic polymer is disclosed for application to electric power distribution systems. The sensor, which can be manufactured at low cost in accordance with a disclosed method, measures voltages across a greater range than prior art sensors. The electrooptic polymer, which replaces the optical crystal used in prior art sensors, is sandwiched directly between two high voltage electrodes. Voltage is measured by fiber optical means, and no voltage division is required. The sample of electrooptic polymer is fabricated in a special mold and later mounted in a sensor housing. Alternatively, mold and sensor housing may be identical. The sensor housing is made out of a machinable polymeric material and is equipped with two opposing optical windows. The optical windows are mounted in the bottom of machined holes in the wall of the mold. These holes provide for mounting of the polarizing optical components and for mounting of the fiber optic connectors. One connecting fiber is equipped with a light emitting diode as a light source. Another connecting fiber is equipped with a photodiode as a detector.

Gottsche, Allan (Inventor); Perry, Joseph W. (Inventor)

1993-01-01

398

Multi-Electrode Impedance Method for Detection of Regional Ventilation  

NASA Astrophysics Data System (ADS)

By means of computer simulation and experiment, we investigated the feasibility of simultaneously measuring the transfer impedance changes in the right apex, left apex, right base and left base of the lungs using the multi-electrode impedance method. To obtain the transfer impedance in each region, while suppressing the effects of other regions, changing the amplitude and polarity of the applied current must localize the high sensitivity areas in the interest region. Twelve current and eight voltage electrodes were equidistantly arranged on the anterior and posterior chest walls. The amplitudes and polarities of the currents that were simultaneously applied to the current electrodes, and which provided the appropriate sensitivity distribution, were theoretically obtained. The effects of the localized sensitivity distribution were verified by comparing the simulation results of the investigated method with the results of the conventional four-electrode method. From the results of the computer simulation, we developed a multi-electrode impedance pneumography and applied it to healthy adult volunteers who were both in sitting position and in left decubitus. We found that the measurement results were physiologically reasonable.

Furuya, Norio; Sakamoto, Katsuyuki

2013-04-01

399

Effect of a floating electrode on a plasma jet  

SciTech Connect

Two kinds of floating electrode, floating dielectric barrier covered electrode (FDBCE) and floating pin electrode (FPE), which can enhance the performance of plasma jet are reported. The intense discharge between the floating electrode and power electrode decreased the voltage to trigger the plasma jet substantially. The transition of plasma bullet from ring shape to disk shape in the high helium concentration region happened when the floating electrode was totally inside the powered ring electrode. The enhanced electric field between propagating plasma bullet and ground electrode is the reason for this transition. The double plasma bullets happened when part of the FDBCE was outside the powered ring electrode, which is attributed to the structure and surface charge of FDBCE. As part of the FPE was outside the powered ring electrode, the return stroke resulted in a single intensified plasma channel between FPE and ground electrode.

Hu, J. T.; Wang, J. G.; Liu, X. Y.; Liu, D. W.; Lu, X. P. [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, WuHan, HuBei 430074 (China)] [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, WuHan, HuBei 430074 (China); Shi, J. J. [College of Science, Donghua University, Shanghai 201620 (China)] [College of Science, Donghua University, Shanghai 201620 (China); Ostrikov, K. [Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, P. O. Box 218, Lindfield, New South Wales 2070 (Australia)] [Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, P. O. Box 218, Lindfield, New South Wales 2070 (Australia)

2013-08-15

400

Built-in voltage of organic bulk heterojuction p-i-n solar cells measured by electroabsorption spectroscopy  

SciTech Connect

We investigate the influence of the built-in voltage on the performance of organic bulk heterojuction solar cells that are based on a p-i-n structure. Electrical doping in the hole and the electron transport layer allows to tune their work function and hence to adjust the built-in voltage: Changing the doping concentration from 0.5 to 32 wt% induces a shift of the work function towards the transport levels and increases the built-in voltage. To determine the built-in voltage, we use electroabsorption spectroscopy which is based on an evaluation of the spectra caused by a change in absorption due to an electric field (Stark effect). For a model system with a bulk heterojunction of BF-DPB and C{sub 60}, we show that higher doping concentrations in both the electron and the hole transport layer increase the built-in voltage, leading to an enhanced short circuit current and solar cell performance.

Siebert-Henze, E., E-mail: ellen.siebert@iapp.de; Lyssenko, V. G.; Fischer, J.; Tietze, M.; Brueckner, R.; Schwarze, M.; Vandewal, K.; Ray, D.; Riede, M.; Leo, K. [Institut für Angewandte Photophysik, Technische Universität Dresden, D-01062 Dresden (Germany)] [Institut für Angewandte Photophysik, Technische Universität Dresden, D-01062 Dresden (Germany)

2014-04-15

401

Nonlinearity of Cardiac Pacemaker Electrodes  

Microsoft Academic Search

Nonlinear properties of electrodes immersed in saline were studied in the time domain and frequency domain. Three electrode materials were tested: platinum-iridium, Elgiloy, and stainless steel. For time domain measurements, current pulses of 1.0 to 2.0 ms duration and varying amplitudes were applied to the electrodes. Frequency domain measurements of polarization impedance were made with an impedance bridge, utilizing sinusoidal

Dov Jaron; Stanley A. Briller; Herman P. Schwan; David B. Geselowitz

1969-01-01

402

Switching properties of VAN LCoS devices with ultra-microscale electrodes  

NASA Astrophysics Data System (ADS)

Nanolithographic fabrication techniques may soon enable electrically-driven LCoS devices to be manipulated using ultra-nanoscale CMOS transistors. However, questions as to the switching properties of such LCoS devices arise due to the diminishing dimensions of their transistors. Thus, experimental investigations into the response times and the onset-threshold voltages for LCoS devices were embarked upon. Such measurements were obtained for various electrode dimensions and cell gaps. Furthermore, an interdigitated (IDT) electrode pattern was used to drive the homeotropically-aligned NLC material in a direction parallel to the bounding planes of the cell. Experimental findings revealed that faster response times were achieved when the electrode spacings were decreased. Such results have shown that a 10?m-thick device with an electrode pitch of 2?m can achieve a switch-on time of < 5ms. In addition, decreasing the electrode spacing results in the threshold voltage to drop. The results therefore indicate that improvements in a LCoS device's switching properties can be realised by using smaller electrode dimensions.

Ghannam, R.; Collings, N.; Crossland, W.; James, R.; Day, S.; Fernandez, A.

2007-09-01

403

NREL Develops Technique to Measure Membrane Thickness and Defects in Polymer Electrode Membrane Fuel Cells (Fact Sheet)  

SciTech Connect

This fact sheet describes NREL's accomplishments in fuel cell membrane electrode assembly research and development. Work was performed by the Hydrogen Technologies and Systems Center and the National Center for Photovoltaics.

Not Available

2010-11-01

404

A flexible electrode array for muscle impedance measurements in the mouse hind limb: A tool to speed research in neuromuscular disease  

NASA Astrophysics Data System (ADS)

Electrical impedance myography (EIM) is a bioelectrical impedance technique focused on the assessment of neuromuscular diseases using tetrapolar surface arrays. Recently, we have shown that reproducible and sensitive EIM measurements can be made on the gastrocnemius muscle of the mouse hind limb and that these are sensitive to disease alterations. A dedicated array would help speed data acquisition and provide additional sensitivity to disease-induced alterations. A flexible electrode array was developed with electrode sizes of 1mm × 1mm by Parlex, Inc. Tetrapolar electrode sets were arranged both parallel to (longitudinal) and orthogonally to (transverse) the major muscle fiber direction of the gastrocnemius muscle. Measurements were made with a dedicated EIM system. A total of 11 healthy animals and 7 animals with spinal muscular atrophy (a form of motor neuron disease) were evaluated after the fur was completely removed with a depilatory agent from the hind limb. Standard electrophysiologic testing (compound motor action potential amplitude and motor unit number estimation) was also performed. The flexible electrode array demonstrated high repeatability in both the longitudinal and transverse directions in the healthy and diseased animals (with intraclass correlation coefficients of 0.94 and 0.89, respectively, for phase angle measured transversely). In addition, differences between healthy and diseased animals were identifiable. For example, the 50 kHz transverse phase angle was higher in the healthy as compared to the SMA animals (16.8° ± 0.5 vs. 14.3° ± 0.7, respectively) at 21 weeks of age (p = 0.01). Differences in anisotropy were also identifiable. Correlations to several standard neurophysiologic parameters also appeared promising. This novel flexible tetrapolar electrode array can be used on the mouse hind limb and provides multidirectional data that can be used to assess muscle health. This technique has the potential of finding widespread use in the evaluation of drug therapies in neuromuscular animal disease models.

Li, J.; Rutkove, S. B.

2013-04-01

405

Electric field in transformer oil measured with the Kerr-effect technique  

Microsoft Academic Search

The electric field distribution in transformer insulating oil was measured as a function of time, both after application of a DC step voltage and after polarity change of the DC voltage, using a highly sensitive advanced Kerr electro-optic technique. The lower limit of the applied electric field intensity was 100 V\\/cm in insulating oil with an electrode length of 8

Y. Nonaka; H. Sato; T. Maeno; T. Takada

1991-01-01

406

Electrode measurements of the oxidation-reduction potential in the Gotland Deep using medium-term moored profiling instrumentation  

NASA Astrophysics Data System (ADS)

The variation of in situ redox potential (Eh) was studied in the stratified water column (30 - 185 m) of the central Baltic Sea, for a period of 56 days (November, 2010 - January, 2011) using the Gotland Deep Environmental Sampling Station (GODESS) in order to identify the processes that control Eh. During the deployment of the mooring 170 profiles of hydro-physical parameters were registered, including the oxidation-reduction potential, pH, dissolved oxygen, chlorophyll a fluorescence, turbidity, temperature and conductivity. In general, the measured Eh (with respect to standard hydrogen electrode, SHE) ranged from - 55 to 167 mV. A comparison of the measured Eh with that calculated for the particular redox couples was carried out by applying the Nernst-equation. The standard reduction potentials were corrected for temperature and pH. Furthermore, the concentrations of the most important redox components such as Fe, Mn, N, O, C and S used for comparison were estimated by using empirical functions or were based on measurements of discrete water samples, taken at the time of deployment and recovery of the mooring. The results reveal that the reduction of Fe(III) essentially controls the electrode potential of the redox sensor in most parts of the anoxic waters. Below the redoxcline the reduction of hematite and then ferric oxyhydroxid could be related to the redox potential and somewhat deeper Fe(III)/Fe(II) was found to be the dominant redox couple. Theoretically a mixed potential theory should have been applied because in natural waters a variety of redox pairs is present but Fe couples appear to dominate all the other redox equlibria. This could be explained by the relatively high exchange current of Fe and by the high concentrations (up to 1.5 µM) present at those depths in the study area. However, there are still gaps in our knowledge about the cycling of redox-sensitive elements and long-term moored profiling instrumentations may help to improve our understanding. Thus, we are pursuing the use of in situ analyzers for electro active compounds on moored systems in the future. In this case, analyzer data would be associated with chemical and physical parameters measured with high resolution in time and space, giving information on mixing processes and reaction kinetics. This approach is required to assess the relevance, for instance, of intrusions of oxygenated waters, vertical eddy-diffusion and fluctuations caused by internal waves on the cycle of redox-sensitive elements. This is particularly important as lateral transport appears to play a dominant role along isopycnal surfaces, especially in medium-sized stratified basins and yet have not been investigated extensively in the Baltic Sea with respect to the cycles of the most electro-active compounds.

Meyer, David; Prien, Ralf; Dellwig, Olaf; Schulz-Bull, Detlef

2013-04-01

407

DRAMATIC REDUCTION OF DC FIELD EMISSION FROM LARGE AREA ELECTRODES BY PLASMA-SOURCE ION IMPLANTATION*  

E-print Network

to 125 kV. The cathode electrode is biased at high voltage, and the anode is electrically isolated and cathode-anode voltages well above the present state- of-the-art. Such electron sources could provide high and high cathode-anode voltage. Field emission from the cathode electrode and its support structure

408

Laboratory experiments on current flow between stationary and moving electrodes in magnetoplasmas  

NASA Technical Reports Server (NTRS)

Laboratory experiments were performed in order to investigate the basic physics of current flow between tethered electrodes in magnetoplasmas. The major findings are summarized. The experiments are performed in an effectively very large laboratory plasma in which not only the nonlinear current collection is addressed but also the propagation and spread of currents, the formation of current wings by moving electrodes, the current closure, and radiation from transmission lines. The laboratory plasma consists of a pulsed dc discharge whose Maxwellian afterglow provides a quiescent, current-free uniform background plasma. Electrodes consisting of collectors and electron emitters are inserted into the plasma and a pulsed voltage is applied between two floating electrodes via insulated transmission lines. Besides the applied current in the wire, the total current density in the plasma is obtained from space and time resolved magnetic probe measurements via Maxwell's law. Langmuir probes yield the plasma parameters.

Stenzel, Reiner L.; Urrutia, J. M.

1990-01-01

409

Superposition of borehole-to-surface voltage residuals for Vadose Zone plume delineation.  

PubMed

An injected tracer field experiment was conducted at the University of Idaho Ground Water Field Laboratory to evaluate the application of borehole-to-surface voltage measurements for delineation of the tracer distribution in partially saturated, fractured basalt. A tap water tracer was injected into a fracture-dominated, salt-water plume formed during a previous salt-water injection experiment. The tap water tracer was injected into a central injection well under constant hydraulic head for 34 days. The injection well was surrounded by seven test boreholes. Each borehole contained several copper wire electrodes for borehole-to-surface potential measurements between a surface grid of 224 copper sulfate, porous pot electrodes. Eight pole-pole, borehole-to-surface voltage data sets were acquired during each measurement period by energization of a selected electrode in each of the eight boreholes. Predicted voltages for a uniform earth (homogeneous and isotropic) potential model (finite difference) were subtracted from each data set (for its respective current source location), and the voltage residuals superposed to create new data sets with greater measurement sensitivity and coverage, to aid in interpretation. These data sets were collected over four measurement periods during tap water injection and four measurement periods during the subsequent 64-day drainage phase. The data were interpreted with the use of three-dimensional models and by comparisons with other electrical and hydrological observations. Results indicate that superposition of multiple data sets of voltage residuals significantly improved the lateral resolution of subsurface bulk resistivity changes that occurred over time. PMID:16298016

Osiensky, James L; Belknap, Willard J; Donaldson, Paul R

2006-01-10

410

H- density profile and response to applied bias and extraction voltages in H- source  

NASA Astrophysics Data System (ADS)

Characteristics of negative-hydrogen ion (H-) density in the vicinity of plasma grid (PG) which is a boundary electrode between plasma and beam were experimentally investigated in cesium-seeded H- source. The H- density was measured with Cavity Ring Down method (CRD). Our CRD system has been upgraded from fixed line measurement to movable one which provides a profile measurement of the H- density. The H- density above the PG aperture is lower than that above the PG metal surface, and this density structure become to disappear in further region from the PG surface. The H- density decreases with positive bias voltage where an arc discharge chamber is higher potential than the PG. On the other hand, the H- density does not largely change with negative bias voltage. Reduction of the H- density was observed when a beam extraction voltage is applied. The reduction occurs in the case of lower bias voltage close to plasma potential. The extraction voltage influences H- density to a greater degree than bias voltage in low bias voltage region.

Nakano, H.; Tsumori, K.; Kisaki, M.; Ikeda, K.; Nagaoka, K.; Osakabe, M.; Kaneko, O.; Asano, E.; Kondo, T.; Sato, M.; Shibuya, M.; Komada, S.; Sekiguchi, H.; Takeiri, Y.

2013-02-01

411

Method of making biocompatible electrodes  

DOEpatents

A process of improving the sensing function of biocompatible electrodes and the product so made are disclosed. The process is designed to alter the surfaces of the electrodes at their tips to provide increased surface area and therefore decreased contact resistance at the electrode-tissue interface for increased sensitivity and essentially includes rendering the tips atomically clean by exposing them to bombardment by ions of an inert gas, depositing an adhesion layer on the cleaned tips, forming a hillocked layer on the adhesion layer by increasing the temperature of the tips, and applying a biocompatible coating on the hillocked layer. The resultant biocompatible electrode is characterized by improved sensitivity, minimum voltage requirement for organ stimulation and a longer battery life for the device in which it is employed.

Wollam, John S. (Acton, MA)

1992-01-01

412

Voltage-induced swelling and deswelling of weak polybase brushes.  

PubMed

We have investigated a novel method of remotely switching the conformation of a weak polybase brush using an applied voltage. Surface-grafted polyelectrolyte brushes exhibit rich responsive behavior and show great promise as "smart surfaces", but existing switching methods involve physically or chemically changing the solution in contact with the brush. In this study, high grafting density poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes were grown from silicon surfaces using atom transfer radical polymerization. Optical ellipsometry and neutron reflectivity were used to measure changes in the profiles of the brushes in response to DC voltages applied between the brush substrate and a parallel electrode some distance away in the surrounding liquid (water or D(2)O). Positive voltages were shown to cause swelling, while negative voltages in some cases caused deswelling. Neutron reflectometry experiments were carried out on the INTER reflectometer (ISIS, Rutherford Appleton Laboratory, UK) allowing time-resolved measurements of polymer brush structure. The PDMAEMA brushes were shown to have a polymer volume fraction profile described by a Gaussian-terminated parabola both in the equilibrium and in the partially swollen states. At very high positive voltages (in this study, positive bias means positive voltage to the brush-bearing substrate), the brush chains were shown to be stretched to an extent comparable to their contour length, before being physically removed from the interface. Voltage-induced swelling was shown to exhibit a wider range of brush swelling states in comparison to pH switching, with the additional advantages that the stimulus is remotely controlled and may be fully automated. PMID:21793596

Weir, Michael P; Heriot, Sasha Y; Martin, Simon J; Parnell, Andrew J; Holt, Stephen A; Webster, John R P; Jones, Richard A L

2011-09-01

413

Measurements and Modeling of Noise on 22.9kV Medium-Voltage Underground Power Line for Broadband Power Line Communication  

Microsoft Academic Search

\\u000a This paper proposed the measurements and modeling of noise on the 22.9-kV Medium-Voltage (MV) underground power distribution\\u000a cable for Broadband Power Line Communication (BPLC). The proposed measurement system was composed of inductive coupler and\\u000a Digital Phosphor Oscilloscope (DPO). The measurement noise data was obtained from thirty-two pad mounted transformers in the\\u000a test field located in Choji area of Ansan city.

Seungjoon Lee; Donghwan Shin; Yonghwa Kim; Jaejo Lee; Kihwan Eom

2010-01-01

414

A comparative study of charge trapping effects in LDD surface-channel and buried-channel pMOS transistors using charge profiling and threshold voltage shift measurements  

Microsoft Academic Search

Extracted charge profiles of lightly-doped drain (LDD) surface-channel and buried-channel pMOS devices stressed under hot-carrier injection conditions reveal predominant electron trapping near the gate edge at the drain region in both cases. From threshold voltage measurements, there is some evidence of hole trapping after long stress times in surface-channel pMOSFETs, but not in buried-channel devices

C. K. Kok; W. C. Chew; W. K. Chim; D. S. H. Chan; S. E. Leang

1999-01-01

415

Internal voltages in GaInP\\/GaInAs\\/Ge multijunction solar cells determined by electroluminescence measurements  

Microsoft Academic Search

We analyze electroluminescence spectra of a GaInP\\/GaInAs\\/Ge triple-junction solar cell at different injection currents. Using the reciprocity theorem between electroluminescent emission and external quantum efficiency of solar cells allows us to derive the current\\/voltage curves and the diode quality factors of all individual subcells.

Thomas Kirchartz; Uwe Rau; Martin Hermle; Andreas W. Bett; Anke Helbig; Jürgen H. Werner

2008-01-01

416

Characterization of Resistive Switching Behaviors of RF Sputtered Si Oxide Resistive Random Access Memories with Ti-Based Electrodes  

NASA Astrophysics Data System (ADS)

We have fabricated metal-insulator-metal (MIM) diodes with a radio frequency (RF) sputtered Si oxide (SiOx) dielectric layer and studied the impact of three kinds of top electrodes (Ti, TiN, and Pt) on the resistive switching characteristics of the MIM diodes by current-voltage (I-V) measurements. For the MIM diodes with Ti-based electrodes, a significant increase in the initial current level and a decrease in the ON/OFF resistance rate were observed as compared to those of the reference MIM diodes with the Pt top electrodes. To gain a better understanding of the changes in the current levels with the top electrodes, the chemical bonding features in the region near the interface between the top electrode and SiOx layer were investigated using hard X-ray photoemission spectroscopy (HAXPES) under synchrotron radiation (h?= 7939 eV). From HAXPES analyses, it was found that the SiOx surface partially reacted with the Ti and TiN top electrodes during the deposition. Due to the formation of a TiOx barrier layer at the interface between the TiN top electrode and SiOx layer, distinct bi-polar type resistive switching with lower operation voltages below 2.0 V has been achieved.

Ohta, Akio; Fukusima, Motoki; Makihara, Katsunori; Murakami, Hideki; Higashi, Seiichiro; Miyazaki, Seiichi

2013-11-01

417

Effect of voltage waveform on dielectric barrier discharge ozone production efficiency  

NASA Astrophysics Data System (ADS)

Dielectric barrier discharges (DBDs) are commonly used for gas effluent cleanup and ozone generation. For these applications, the energy efficiency of the discharge is a major concern. This paper reports on investigations carried out on the voltage shape applied to DBD reactor electrodes, aiming to evaluate a possible energy efficiency improvement for ozone production. Two DBD reactor geometries were used: pin-to-pin and cylinder-to-cylinder, both driven either by a bi-directional power supply (voltage rise rate 1 kV/?s) or by a pulsed power supply (voltage rise rate 1 kV/ns). Ozone formed in dry air was measured at the reactor outlet. Special attention was paid to discharge input power evaluation using different methods including instantaneous current-voltage product and transferred charge-applied voltage figures. The charge transferred by the discharges was also correlated to the ozone production. It is shown that, in the case of the DBD reactors under investigation, the applied voltage shape has no influence on the ozone production efficiency. For the considered voltage rise rate, the charge deposit on the dielectric inserted inside the discharge gap is the important factor (as opposed to the voltage shape) governing the efficiency of the discharge - it does this by tailoring the duration of the current peak into the tens of nanosecond range.

Mericam-Bourdet, N.; Kirkpatrick, M. J.; Tuvache, F.; Frochot, D.; Odic, E.

2012-03-01

418

A systematic study of BNL's 3D-Trench Electrode detectors  

NASA Astrophysics Data System (ADS)

New types of silicon pixel detectors have been proposed because of the need for more radiation hard semiconductor devices for the high luminosity tracking detector upgrades at the Large Hadron Collider. A novel type of 3D Si pixel detectors is proposed, with each cell of the 3D-Trench Electrode pixel detector featuring a concentric trench electrode surrounding the central collecting column electrode. The pixel sensor is an array of those individual cells. Systematic 3D simulations using Silvacos TCAD programs have been carried out to study the characteristics of this novel 3D pixel design and to compare to the traditional 3D column electrode pixel design. The 3D simulations show a much lower depletion voltage and a more uniform electric field in the new 3D-Trench Electrode pixel detectors as compared to the traditional 3D column Electrode detectors. The first prototype 3D-Trench Electrode pixel detectors have been manufactured at the Centro Nacional De Microelectronica. Preliminary electrical measurements are discussed and charge collection efficiency measurements are presented.

Montalbano, A.; Bassignana, D.; Li, Z.; Liu, S.; Lynn, D.; Pellegrini, G.; Tsybychev, D.

2014-11-01

419

Electrode structure and methods of making same  

DOEpatents

A method of making an electrode structure is provided. The method includes disposing an electrocatalytic material on an electrode, applying heat to the electrocatalytic material to form a volatile oxide of the electrocatalytic material, and applying a voltage to the electrode to reduce the volatile oxide to provide a number of nano-sized electrocatalytic particles on or proximate to a triple phase boundary, where the number of nano-sized electrocatalytic particles is greater on or proximate to the triple phase boundary than in an area that is not on or proximate to the triple phase boundary, and where the triple phase boundary is disposed on the electrode.

Ruud, James Anthony; Browall, Kenneth Walter; Rehg, Timothy Joseph; Renou, Stephane; Striker, Todd-Michael

2010-04-06

420

Ion behavior and interelectrode breakdown voltage of a drift tube  

E-print Network

We experimentally studied ion behavior and interelectrode breakdown voltage. The ion behavior of a drift tube directly influences the detection of ion intensity, and then influences the detection sensitivity of a system. Interelectrode voltage and pressure directly influence the ion behavior. Gas discharge between electrodes influences the adjustments required for interelectrode voltage. The experimental results show: ion intensity increases exponentially with the increment of voltage between drift electrodes; ion intensity decreases exponentially as pressure increases; with the increment of pressure, the breakdown voltage at first decreases, and then increases; ion injection has a significant influence on breakdown voltage, and this influence depends on the pressure and shapes of the electrodes. We explain the results above through assumptions and by mathematical methods.

Geng, Hao; Duan, Yixiang

2015-01-01

421

Field-enhanced electrodes for additive-injection non-thermal plasma (NTP) processor  

DOEpatents

The present invention comprises a field enhanced electrode package for use in a non-thermal plasma processor. The field enhanced electrode package includes a high voltage electrode and a field-enhancing electrode with a dielectric material layer disposed in-between the high voltage electrode and the field-enhancing electrode. The field-enhancing electrode features at least one raised section that includes at least one injection hole that allows plasma discharge streamers to occur primarily within an injected additive gas.

Rosocha, Louis A. (Los Alamos, NM); Ferreri, Vincent (Westminster, CO); Kim, Yongho (Los Alamos, NM)

2009-04-21

422

Measuring of electrical changes induced by in situ combustion through flow-through electrodes in a laboratory sample of core material  

DOEpatents

Method and apparatus are provided for obtaining accurate dynamic measurements for passage of phase fronts through a core sample in a test fixture. Flow-through grid structures are provided for electrodes to permit data to be obtained before, during and after passage of a front there through. Such electrodes are incorporated in a test apparatus for obtaining electrical characteristics of the core sample. With the inventive structure a method is provided for measurement of instabilities in a phase front progressing through the medium. Availability of accurate dynamic data representing parameters descriptive of material characteristics before, during and after passage of a front provides a more efficient method for enhanced recovery of oil using a fire flood technique. 12 figs.

Lee, D.O.; Montoya, P.C.; Wayland, J.R. Jr.

1986-12-09

423

Measuring of electrical changes induced by in situ combustion through flow-through electrodes in a laboratory sample of core material  

DOEpatents

Method and apparatus are provided for obtaining accurate dynamic measurements for passage of phase fronts through a core sample in a test fixture. Flow-through grid structures are provided for electrodes to permit data to be obtained before, during and after passage of a front therethrough. Such electrodes are incorporated in a test apparatus for obtaining electrical characteristics of the core sample. With the inventive structure a method is provided for measurement of instabilities in a phase front progressing through the medium. Availability of accurate dynamic data representing parameters descriptive of material characteristics before, during and after passage of a front provides a more efficient method for enhanced recovery of oil using a fire flood technique.

Lee, David O. (Albuquerque, NM); Montoya, Paul C. (Albuquerque, NM); Wayland, Jr., James R. (Albuquerque, NM)

1986-01-01

424

Memristor-integrated voltage-stabilizing supercapacitor system.  

PubMed

Voltage-stabilized supercapacitors: A single supercapacitor formed with PCBM/Pt/IPS nanorod-array electrodes is designed and delivers enhanced areal capacitance, capacitance retention, and excellent electrical stability under bending, while a significant voltage-decrease is observed during the discharging process. Once integrated with the memristor, the memristor-integrated supercapacitor systems deliver an extremely low voltage-drop, indicating greatly enhanced voltage-stabilizing features. PMID:24805149

Liu, Bin; Liu, Boyang; Wang, Xianfu; Wu, Xinghui; Zhao, Wenning; Xu, Zhimou; Chen, Di; Shen, Guozhen

2014-08-01

425

Electrode contamination effects of retarding potential analyzer.  

PubMed

The electrode contamination in electrostatic analyzers such as Langmuir probes and retarding potential analyzers (RPA) is a serious problem for space measurements. The contamination layer acts as extra capacitance and resistance and leads to distortion in the measured I-V curve, which leads to erroneous measurement results. There are two main effects of the contamination layer: one is the impedance effect and the other is the charge attachment and accumulation due to the capacitance. The impedance effect can be reduced or eliminated by choosing the proper sweeping frequency. However, for RPA the charge accumulation effect becomes serious because the capacitance of the contamination layer is much larger than that of the Langmuir probe of similar dimension. The charge accumulation on the retarding potential grid causes the effective potential, that ions experience, to be changed from the applied voltage. Then, the number of ions that can pass through the retarding potential grid to reach the collector and, thus, the measured ion current are changed. This effect causes the measured ion drift velocity and ion temperature to be changed from the actual values. The error caused by the RPA electrode contamination is expected to be significant for sounding rocket measurements with low rocket velocity (1-2 km/s) and low ion temperature of 200-300 K in the height range of 100-300 km. In this paper we discuss the effects associated with the RPA contaminated electrodes based on theoretical analysis and experiments performed in a space plasma operation chamber. Finally, the development of a contamination-free RPA for sounding rocket missions is presented. PMID:24517809

Fang, H K; Oyama, K-I; Cheng, C Z

2014-01-01

426

Subdural Electrodes  

PubMed Central

Subdural electrodes are frequently used to aid in the neurophysiological assessment of patients with intractable seizures. We review the indications for these, their uses for localizing epileptogenic regions and for localizing cortical regions supporting movement, sensation, and language. PMID:20573543

Lesser, Ronald P.; Crone, Nathan E.; Webber, W.R.S.

2010-01-01

427

Microfabrication of Surface Electrode Ion Traps for Quantum Information Experiments  

NASA Astrophysics Data System (ADS)

Surface electrode ion traps, while promising for large-scale quantum computation, have long been challenged by ion heating rates which increase rapidly as trap length scales are reduced. Through a series of measurements on over fifteen traps, we show that ion heating rates are surprisingly sensitive to electrode material and morphology, and in particular, to details of the fabrication procedure. For example, one 75 ?m size trap, made of chemically etched silver on a single crystal quartz substrate, showed a minimum heating rate of ˜40 quanta/second, when prepared by annealing at 760^oC in vacuum for one hour. This annealing smooths sharp edges, and significantly reduces breakdown voltage. However, if the annealing temperature is lowered to 720^oC, leaving the breakdown voltage still robustly high, the heating rate jumps to ˜1000 quanta/second. With electroplated gold, on a silver seed layer, a record low heating rate of ˜2 quanta/second is obtained. We present details of the fabrication procedures, evaluate alternative electrode materials such as niobium nitride, and explain how these measurements were obtained with an ion trap operated at 6 Kelvin, containing a single strontium ion, sideband cooled to its quantum ground state of motion.

Ge, Yufei; Labaziewicz, Jaroslaw; Antohi, Paul; Chuang, Isaac

2008-03-01

428

Methods and apparatus for measurement of electronic properties of geological formations through borehole casing  

DOEpatents

Methods and apparatus are provided for measuring electronic properties of geological formations and cement layers adjacent to cased boreholes including resistivities, polarization phenomena and dielectric constants. 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. At least three voltage measuring electrodes in electrical contact with the interior of the casing measure the voltage at various points thereon. The voltage differences between discrete pairs of the voltage measuring electrodes provide a measurement of the differential current conducted into the formation in the vicinity of those electrodes. These measurements facilitate calculation of the resistivities of the adjacent geological formations as well as an indication of whether cement is present. Measurements of the differential voltage response to transient currents provide a measurement of the polarization phenomena in formation as well as the capacitance of the casing in contact with the formation which is useful for determining whether oil and gas are present. Lithological characteristics of the formation such as the presence or absence of clay can also be determined. A calibration procedure is provided for minimizing errors induced by variations in the casing. The device also may be placed within the pipe attached to a drill bit while drilling open holes. 48 figures.

Vail, W.B. III.

1991-08-27

429

Methods and apparatus for measurement of electronic properties of geological formations through borehole casing  

DOEpatents

Methods and apparatus are provided for measuring electronic properties of geological formations and cement layers adjacent to cased boreholes including resistivities, polarization phenomena and dielectric constants. 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. At least three voltage measuring electrodes in electrical contact with the interior of the casing measure the voltage at various points thereon. The voltage differences between discrete pairs of the voltage measuring electrodes provide a measurement of differential current conducted into formation in the vicinity of those electrodes. These measurements facilitate calculation of the resistivities of the adjacent geological formations as well as an indication of whether cement is present. Measurements of the differential voltage response to transient currents provide a measurement of the polarization phenomena in formation as well as the capacitance of the casing in contact with the formation which is useful for determining whether oil and gas are present. Lithological characteristics of the formation such as the presence or absence of clay can also be determined. A calibration procedure is provided for minimizing errors induced by variations in the casing. The device also may be placed within the pipe attached to a drill bit while drilling open holes. 48 figs.

Vail, W.B. III.

1989-11-21

430

Methods and apparatus for measurement of electronic properties of geological formations through borehole casing  

DOEpatents

Methods and apparatus are provided for measuring electronic properties of geological formations and cemen