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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

Photoconductivity of High Voltage Space Insulating Materials: Measurements with Metal Electrodes.  

National Technical Information Service (NTIS)

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 determine...

H. T. Coffey J. E. Nanevicz

1975-01-01

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

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

PubMed Central

Summary 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.

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

2012-01-01

5

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

6

Comparison of Potential Step and Triangular Voltage Sweep Methods of Double Layer Capacitance Measurements. III. Porous Zinc Electrodes.  

National Technical Information Service (NTIS)

The double layer capacitance (DLC) of porous zinc electrodes in 31 percent KOH was measured by both the potential step method and the potential sweep method at -40C. The methods yielded similar results, but the potential step method provides additional us...

W. H. Steuernagel

1972-01-01

7

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

8

Properties of electrode used in electrodermal measurement  

Microsoft Academic Search

Various types of electrodes frequently used in electrodermal measurements are shown to have properties which might contribute sizeable errors to the measurements obtained. Electrical resistance of the skin is shown to be an inverse function of the effective electrode area and to be constant for 5 voltages ranging from 1.5 to 7.5 and for 5 currents in the range of

D. T. Lykken

1959-01-01

9

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

10

Measuring electrode assembly  

SciTech Connect

A pH measuring electrode assembly for immersion in a solution includes an enclosed cylindrical member having an aperture at a lower end thereof. An electrolyte is located in the cylindrical member above the level of the aperture and an electrode is disposed in this electrolyte. A ring formed of an ion porous material is mounted relative to the cylindrical member so that a portion of this ring is rotatable relative to and is covering the aperture in the cylindrical member. A suitable mechanism is also provided for indicating which one of a plurality of portions of the ring is covering the aperture and to keep track of which portions of the ring have already been used and become clogged. Preferably, the electrode assembly also includes a glass electrode member in the center thereof including a second electrolyte and electrode disposed therein. The cylindrical member is resiliently mounted relative to the glass electrode member to provide for easy rotation of the cylindrical member relative to the glass electrode member for changing of the portion of the ring covering the aperture.

Bordenick, John E. (West Mifflin, PA)

1989-01-01

11

Measuring electrode assembly  

DOEpatents

A pH measuring electrode assembly for immersion in a solution includes an enclosed cylindrical member having an aperture at a lower end thereof. An electrolyte is located in the cylindrical member above the level of the aperture and an electrode is disposed in this electrolyte. A ring formed of an ion porous material is mounted relative to the cylindrical member so that a portion of this ring is rotatable relative to and is covering the aperture in the cylindrical member. A suitable mechanism is also provided for indicating which one of a plurality of portions of the ring is covering the aperture and to keep track of which portions of the ring have already been used and become clogged. Preferably, the electrode assembly also includes a glass electrode member in the center thereof including a second electrolyte and electrode disposed therein. The cylindrical member is resiliently mounted relative to the glass electrode member to provide for easy rotation of the cylindrical member relative to the glass electrode member for changing of the portion of the ring covering the aperture. 2 figs.

Bordenick, J.E.

1988-04-26

12

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.

Williamson, Rodney L. (Albuquerque, NM); Zanner, Frank J. (Sandia Park, NM); Grose, Stephen M. (Glenwood, WV)

1998-01-01

13

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

14

Evaluation of Niobium as Candidate Electrode Material for DC High Voltage Photoelectron Guns  

NASA Technical Reports Server (NTRS)

The field emission characteristics of niobium electrodes were compared to those of stainless steel electrodes using a DC high voltage field emission test apparatus. A total of eight electrodes were evaluated: two 304 stainless steel electrodes polished to mirror-like finish with diamond grit and six niobium electrodes (two single-crystal, two large-grain, and two fine-grain) that were chemically polished using a buffered-chemical acid solution. Upon the first application of high voltage, the best large-grain and single-crystal niobium electrodes performed better than the best stainless steel electrodes, exhibiting less field emission at comparable voltage and field strength. In all cases, field emission from electrodes (stainless steel and/or niobium) could be significantly reduced and sometimes completely eliminated, by introducing krypton gas into the vacuum chamber while the electrode was biased at high voltage. Of all the electrodes tested, a large-grain niobium electrode performed the best, exhibiting no measurable field emission (< 10 pA) at 225 kV with 20 mm cathode/anode gap, corresponding to a field strength of 18:7 MV/m.

BastaniNejad, M.; Mohamed, Abdullah; Elmustafa, A. A.; Adderley, P.; Clark, J.; Covert, S.; Hansknecht, J.; Hernandez-Garcia, C.; Poelker, M.; Mammei, R.; Surles-Law, K.; Williams, P.

2012-01-01

15

Evaluation of niobium as candidate electrode material for dc high voltage photoelectron guns  

NASA Astrophysics Data System (ADS)

The field emission characteristics of niobium electrodes were compared to those of stainless steel electrodes using a DC high voltage field emission test apparatus. A total of eight electrodes were evaluated: two 304 stainless steel electrodes polished to mirrorlike finish with diamond grit and six niobium electrodes (two single-crystal, two large-grain, and two fine-grain) that were chemically polished using a buffered-chemical acid solution. Upon the first application of high voltage, the best large-grain and single-crystal niobium electrodes performed better than the best stainless steel electrodes, exhibiting less field emission at comparable voltage and field strength. In all cases, field emission from electrodes (stainless steel and/or niobium) could be significantly reduced and sometimes completely eliminated, by introducing krypton gas into the vacuum chamber while the electrode was biased at high voltage. Of all the electrodes tested, a large-grain niobium electrode performed the best, exhibiting no measurable field emission (<10pA) at 225 kV with 20 mm cathode/anode gap, corresponding to a field strength of 18.7MV/m.

BastaniNejad, M.; Mohamed, Md. Abdullah; Elmustafa, A. A.; Adderley, P.; Clark, J.; Covert, S.; Hansknecht, J.; Hernandez-Garcia, C.; Poelker, M.; Mammei, R.; Surles-Law, K.; Williams, P.

2012-08-01

16

Source electrode evolution of a low voltage power MOSFET under avalanche cycling  

Microsoft Academic Search

This paper presents the impact of high current repetitive avalanche pulses on a low voltage vertical power MOSFET at high temperature. Measurements show that RDSon decreases with the number of avalanche cycles whereas other electrical parameters stay constant. A simple model proposed in this paper shows that RDSon measurements are linked to MOSFET source electrode evolution. Also once source electrode

B. Bernoux; R. Escoffier; P. Jalbaud; J. M. Dorkel

2009-01-01

17

Plasma source ion implantation of high voltage electrodes  

NASA Astrophysics Data System (ADS)

Field emission and breakdown characteristics of high voltage, large area electrodes determine the performance of many vacuum-based electron sources. A corroborative project with the Thomas Jefferson National Accelerator Facility involves studying the behavior of such electrodes after nitrogen ion implantation. A Plasma Source Ion Implantation (PSII) facility is designed and constructed at William and Mary, and used to treat stainless steel electrodes. PSII is a novel implantation technique developed at the University of Wisconsin-Madison. A workpiece is submerged in a quiescent plasma of the species to be implanted. A series of high, negative voltages (30--100 kV) is applied to the workpiece to accelerate the ions in the plasma, implanting them to depths of several hundred Angstroms. To characterize the response of the modified electrodes to high field gradients, fields as high as 20 MV/m are applied between parallel electrodes in a VG ESCALab MKII surface analysis system. XPS, AES, and SEM are used to characterize the surface of the cathodes. The pre-breakdown current from implanted electrodes is compared to that of thin film coated, polished, electron beam treated, and untreated electrodes. Current models to explain anomalous field emission are reviewed and considered as explanation of observed effects.

Venhaus, Thomas Joseph

18

Measuring Breakdown Voltage.  

ERIC Educational Resources Information Center

The article discusses an aspect of conductivity, one of the electrical properties subdivisions, and describes a tester that can be shop-built. Breakdown voltage of an insulation material is specifically examined. Test procedures, parts lists, diagrams, and test data form are included. (MF)

Auer, Herbert J.

1978-01-01

19

Technique eliminates high voltage arcing at electrode-insulator contact area  

NASA Technical Reports Server (NTRS)

Coating the electrode-insulator contact area with silver epoxy conductive paint and forcing the electrode and insulator tightly together into a permanent connection, eliminates electrical arcing in high-voltage electrodes supplying electrical power to vacuum facilities.

Mealy, G.

1967-01-01

20

Ion peak narrowing by applying additional AC voltage (ripple voltage) to FAIMS extractor electrode.  

PubMed

The use of a non-uniform electric field in a high-field asymmetric waveform ion mobility spectrometry (FAIMS) analyzer increases sensitivity but decreases resolution. The application of an additional AC voltage to the extractor electrode ("ripple" voltage, U(ripple)) can overcome this effect, which decreases the FAIMS peak width. In this approach, the diffusion ion loss remains minimal in the non-uniform electric field in the cylindrical part of the device, and all ion losses under U(ripple) occur in a short portion of their path. Application of the ripple voltage to the extractor electrode is twice as efficient as the applying of U(ripple) along the total length of the device. PMID:19819165

Pervukhin, Viktor V; Sheven, Dmitriy G

2010-01-01

21

Effect of Built-in Potential under Drain Electrodes on Threshold Voltage of Organic Field-Effect Transistors  

Microsoft Academic Search

The effect of source and drain electrode species on threshold voltage was investigated using top-contact pentacene organic field-effect transistors (OFETs) with several different types of metals as source and drain electrodes. Threshold voltage mainly depended on drain electrode species and not on source electrode species. Most devices showed that threshold voltage did not depend on channel length (L) for L

Kouji Suemori; Sei Uemura; Manabu Yoshida; Satoshi Hoshino; Takehito Kodzasa; Toshihide Kamata

2007-01-01

22

Evaluation of Niobium as Candidate Electrode Material for DC High Voltage Photoelectron Guns  

Microsoft Academic Search

The field emission characteristics of niobium electrodes were compared to those of stainless steel electrodes using a DC high voltage field emission test apparatus. A total of eight electrodes were evaluated: two 304 stainless steel electrodes polished to mirror-like finish with diamond grit and six niobium electrodes (two single-crystal, two large-grain and two fine-grain) that were chemically polished using a

M. BastaniNejad; A. A Elmustafa; P. Adderley; J. Clark; S. Covert; J. Hansknecht; C. Hernandez--Garcia; M. Poelker; R. Mammei; K. Surles-Law; P. Williams

2012-01-01

23

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

24

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

25

Readout electrode assembly for measuring biological impedance  

NASA Technical Reports Server (NTRS)

The invention comprises of a pair of readout ring electrodes which are used in conjunction with apparatus for measuring the electrical impedance between different points in the body of a living animal to determine the amount of blood flow therebetween. The readout electrodes have independently adjustable diameters to permit attachment around different parts of the body between which it is desired to measure electric impedance. The axial spacing between the electrodes is adjusted by a pair of rods which have a first pair of ends fixedly attached to one electrode and a second pair of ends slidably attached to the other electrode. Indicia are provided on the outer surface of the ring electrodes and on the surface of the rods to permit measurement of the circumference and spacing between the ring electrodes.

Montgomery, L. D.; Moody, D. L., Jr. (inventors)

1976-01-01

26

Measuring breakdown voltage for objectively detecting ignition in fire research  

NASA Astrophysics Data System (ADS)

This paper presents a method intended for detecting the initiation of combustion and the presence of smoke in confined or open spaces by continuously applying an intermittent high-voltage pulse between the electrodes. The method is based on an electrical circuit which generates an electrical discharge measuring simultaneously the breakdown voltage between the electrodes. It has been successfully used for the detection of particle-laden aerosols and flames. However, measurements in this study showed that detecting pyrolysis products with this methodology is challenging and arduous. The method presented here is robust and exploits the necessity of having an ignition system which at the same time can automatically discern between clean air, flames or particle-laden aerosols and can be easily implemented in the existing cone calorimeter with very minor modifications.

Ochoterena, R.; Försth, M.; Elfsberg, Mattias; Larsson, Anders

2013-10-01

27

Total Electrode Fall Measurement in a Parallel-Plate Magnetoplasmadynamic Thruster  

NASA Astrophysics Data System (ADS)

The total electrode fall voltage in a channel of magnetoplasmadynamic (MPD) thruster was determined by using "zero-limit approximating method", which is one of the classical methods widely used in the arc welding field. A new five-channel parallel-plate MPDT was designed and operated in a quasi-steady mode. This paper presents the measurement of the discharge voltage vs. the electrode gap for gaps from 1 mm to 4 mm. The extrapolated zero-gap intercept resulted in 18 V, which was considered as the total electrode-fall voltage. The electrode-fall voltage did not depend on the discharge current unless the discharge current exceeded onset threshold. It is considered that most of the electrode fall is deposited on the cathode side since the space potential at the inter-electrode region was almost equal to the anode potential.

Nakata, Daisuke; Toki, Kyoichiro; Shimizu, Yukio; Funaki, Ikkoh; Kuninaka, Hitoshi; Arakawa, Yoshihiro

28

Optimal Pulse Voltage Waveform for a Xenon Barrier Discharge Lamp using both an Inner Electrode and an External Electrode  

NASA Astrophysics Data System (ADS)

When applying a pulsed voltage to a discharge tube using dielectric barrier discharge, discharge occurs two times in a pulse at a rising and a falling edge of a voltage pulse. The timing of the second discharge can be changed by controlling the pulse width. In this study the influence of the pulse width on the luminance of the barrier discharge lamp with an inner electrode is investigated. The lamp used in this study has two electrodes, one is set in the lamp and the other is set on the outside surface of the lamp. Internal electrode is connected to the high voltage side and the external electrode is connected to the ground side. Luminance is observed under the condition of pulse repetition frequency of 10 kHz, peak voltage from 1 kV to 3 kV and pulse width from 2 ?s to 98 ?s. Luminance took almost same value from 30 ?s to 90 ?s, whereas it decreased by both deceasing the pulse width less than 30 ?s and increasing it more than 90 ?s. It means that the higher luminance is obtained by avoiding the overlap of the two radiations at rising and falling edge of applied voltage.

Jinno, Masafumi; Taniuchi, Hidefumi; Watanabe, Masashi; Motomura, Hideki

29

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

NASA Astrophysics Data System (ADS)

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.

Shuto, Mitsutoshi; Tomino, Fukumi; Ohmi, Hiromasa; Kakiuchi, Hiroaki; Yasutake, Kiyoshi

2013-05-01

30

Calibrated single-plunge bipolar electrode array for mapping myocardial vector fields in three dimensions during high-voltage transthoracic defibrillation  

Microsoft Academic Search

Mapping of the myocardial scalar electric potential during defibrillation is normally performed with unipolar electrodes connected to voltage dividers and a global potential reference. Unfortunately, vector potential gradients that are calculated from these data tend to exhibit a high sensitivity to measurement errors. This paper presents a calibrated single-plunge bipolar electrode array (EA) that avoids the error sensitivity of unipolar

O. Carlton Deale; Kwong T. Ng; Ellen J. Kim-Van Housen; Bruce B. Lerman

2001-01-01

31

Design and fabrication of a tuning fork shaped voltage controlled resonator for low-voltage applications with additional tuning electrodes  

NASA Astrophysics Data System (ADS)

In this work a silicon voltage controlled microelectromechanical tuning fork resonator with electrostatic actuation and separate frequency tuning electrodes is presented. The released device is fabricated using a silicon-on-insulator wafer by a two-step process involving only focused ion beam masking and cryogenic deep reactive ion etching. This process is ideal for rapid prototyping, as the time to turn a design into the final device is only a few hours. The design of the resonator is optimized to accommodate the restrictions of the fabrication process, to maximize the frequency tuning range and to minimize the biasing voltage. Separating tuning and driving electrodes enables the resonance frequency adjustment by over 70 000 ppm (fcenter > 1.5?MHz, quality factor Q ? 2000) with a tuning voltage of 29 V in an open loop mode.

Gronicz, J.; Chekurov, N.; Kosunen, M.; Tittonen, I.

2013-11-01

32

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

33

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

34

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

35

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

NASA Astrophysics Data System (ADS)

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/Ni3S2 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 here 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.

36

Silica nanoparticle dispersion size measurement using dielectrophoresis on a microfabricated electrode array  

Microsoft Academic Search

In this article, we report a technique that uses dielectrophoresis to measure particle size distribution information of silica nanoparticle dispersions using a microfabricated periodic interdigitated electrode array. An AC voltage is applied to the electrode array, producing a non-uniform electric field. Depending on their relative permittivity with respect to the dispersion solution, nanoparticles aggregate at either electric field maxima or

Yi Qiao; Jack Lai; Dave Hofeldt

2009-01-01

37

Shaker force measurements using voltage and current.  

National Technical Information Service (NTIS)

In a previous paper (Smallwood and Coleman, 1993), equations were developed which would allow the force into a test item during a vibration test to be measured using voltage and current measurements from the input to an electrodynamic shaker. To accomplis...

D. O. Smallwood

1996-01-01

38

The influence of electrode erosion on the air arc in a low-voltage circuit breaker  

NASA Astrophysics Data System (ADS)

This paper focuses on the numerical research of the influence of electrode erosion on the arc behavior during opening process of low-voltage circuit breakers. The mathematical model of three-dimensional air arc plasma considering electrode erosion is built based on magnetic hydrodynamics. The mass fraction equation of copper vapor is introduced to the model on the basis of traditional mass, momentum, and energy balance equations. The influence of copper vapor on the thermodynamic and transport properties of the gas mixture is considered in this paper. The distributions of temperature field, gas flow field, and mass fraction of copper vapor in the arc chamber are simulated. The arc root displacements and arc voltage, which takes account of the influence of electrode erosion, are calculated. The simulation results indicate that the immobility time of both moving contact and stationary contact is much longer considering electrodes erosion. The calculated voltage of the arc column during arc motion considering erosion is smaller because of the change in the electrical conductivity of air-copper vapor mixtures. Except for the numerical investigation on the arc motion considering electrode erosion, the experiment work is also carried out to support the simulation work.

Rong, Mingzhe; Ma, Qiang; Wu, Yi; Xu, Tiejun; Murphy, Anthony B.

2009-07-01

39

Calibrated single-plunge bipolar electrode array for mapping myocardial vector fields in three dimensions during high-voltage transthoracic defibrillation.  

PubMed

Mapping of the myocardial scalar electric potential during defibrillation is normally performed with unipolar electrodes connected to voltage dividers and a global potential reference. Unfortunately, vector potential gradients that are calculated from these data tend to exhibit a high sensitivity to measurement errors. This paper presents a calibrated single-plunge bipolar electrode array (EA) that avoids the error sensitivity of unipolar electrodes. The EA is triaxial, uses a local potential reference, and simultaneously measures all three components of the myocardial electric field vector. An electrode spacing of approximately 500 microm allows the EA to be direct-coupled to high-input-impedance, isolated, differential amplifiers and eliminates the need for voltage dividers. Calibration is performed with an electrolytic tank in which an accurately measured, uniform electric field is produced. For each EA, unique calibration matrices are determined which transform potential difference readings from the EA to orthogonal components of the electric field vector. Elements of the matrices are evaluated by least squares multiple regression analysis of data recorded during rotation of the electric field. The design of the electrolytic tank and electrode holder allows the electric field vector to be rotated globally with respect to the electrode axes. The calibration technique corrects for both field perturbation by the plunge electrode body and deviations from orthogonality of the electrode axes. A unique feature of this technique is that it eliminates the need for mechanical measurement of the electrode spacing. During calibration, only angular settings and voltages are recorded. For this study, ten EAs were calibrated and their root-mean-square (rms) errors evaluated. The mean of the vector magnitude rms errors over the set of ten EAs was 0.40% and the standard deviation 0.07%. Calibrated EAs were also tested for multisite mapping in four dogs during high-voltage transthoracic shocks. PMID:11499527

Deale, O C; Ng, K T; Kim-Van Housen, E J; Lerman, B B

2001-08-01

40

Florida Current volume transports from voltage measurements  

SciTech Connect

The volume transport of the Florida Current is determined from the motionally induced voltage difference between Florida and Grand Bahama Island. Simultaneous measurements of potential differences and of volume transport by velocity profiling have a correlation of 0.97. The calibration factor is 25 +/- 0.7 sverdrups per volt, and the root-mean square discrepancy is 0.7 sverdrup. The induced voltage is about one-half the open-circuit value, implying that the conductance of the sediments and lithosphere is about equal to that of the water column. 11 references, 2 figures.

Larsen, J.C.; Sanford, T.B.

1985-01-18

41

The Influence of Electrode Surface Mercury Film Deformation on the Breakdown Voltage of a Sub-Nanosecond Pulse Discharge Tube  

NASA Astrophysics Data System (ADS)

A sub-nanosecond pulse discharge tube is a gas discharge tube which can generate a rapid high-voltage pulse of kilo-volts in amplitude and sub-nanoseconds in width. In this paper, the sub-nanosecond pulse discharge tube and its working principles are described. Because of the phenomenon that the deformation process of the mercury film on the electrode surface lags behind the charging process, the mercury film deformation process affects the dynamic breakdown voltage of the tube directly. The deformation of the mercury film is observed microscopically, and the dynamic breakdown voltage of the tube is measured using an oscillograph. The results show that all the parameters in the charging process, such as charging resistance, charging capacitance and DC power supply, affect the dynamic breakdown voltage of the tube. Based on these studies, the output pulse amplitude can be controlled continuously and individually by adjusting the power supply voltage. When the DC power supply is adjusted from 7 kV to 10 kV, the dynamic breakdown voltage ranges from 6.5 kV to 10 kV. According to our research, a kind of sub-nanosecond pulse generator is made, with a pulse width ranging from 0.5 ns to 2.5 ns, a rise time from 0.32 ns to 0.58 ns, and a pulse amplitude that is adjustable from 1.5 kV to 5 kV.

Weng, Ming; Xu, Weijun; Wang, Rui

2012-11-01

42

Magneto-resistance effect element with magnetism sensitive region controlled by voltage applied to gate electrode  

US Patent & Trademark Office Database

A magneto-resistance effect element of the present invention allows detection of a micro-bit signal with a high sensitivity. The magneto-resistance effect element is provided with a first magnetic substance layer, a spacer layer stacked on the first magnetic substance layer, a second magnetic substance layer stacked on the spacer, an insulating layer positioned adjacent to a stacked structure comprising the first magnetic substance layer, the spacer layer and the second magnetic substance layer, a gate electrode positioned adjacent to the insulating layer, and a magnetism sensitive region controlled by a voltage applied to the gate electrode.

2006-07-11

43

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

44

Measurement of noise and impedance of dry and wet textile electrodes, and textile electrodes with hydrogel.  

PubMed

Textile sensors, when embedded into clothing, can provide new ways of monitoring physiological signals, and improve the usability and comfort of such monitoring systems in the areas of medical, occupational health and sports. However, good electrical and mechanical contact between the electrode and the skin is very important, as it often determines the quality of the signal. This paper introduces a study where the properties of dry textile electrodes, textile electrodes moistened with water, and textile electrodes covered with hydrogel were studied with five different electrode sizes. The aim was to study how the electrode size and preparation of the electrode (dry electrode/wet electrode/electrode covered with hydrogel membrane) affect the measurement noise, and the skin-electrode impedance. The measurement noise and skin-electrode impedance were determined from surface biopotential measurements. These preliminary results indicate that noise level increases as the electrode size decreases. The noise level is high in dry textile electrodes, as expected. Yet, the noise level of wet textile electrodes is quite low and similar to that of textile electrodes covered with hydrogel. Hydrogel does not seem to improve noise properties, however it may have effects on movement artifacts. Thus, it is feasible to use textile embedded sensors in physiological monitoring applications when moistening or hydrogel is applied. PMID:17946734

Puurtinen, Merja M; Komulainen, Satu M; Kauppinen, Pasi K; Malmivuo, Jaakko A V; Hyttinen, Jari A K

2006-01-01

45

Voltage breakdown between closely spaced electrodes over polymeric insulator surfaces in air  

Microsoft Academic Search

Voltage breakdowns of some narrow gap electrodes [2–10 mil (0.05–0.25 mm)] on polymeric insulator surfaces (epoxy-glass and triazine) have been examined over the pressure range from atmospheric pressure to 127 Torr and are shown to be an air breakdown modified by the presence of the insulator. Breakdown values as a function of the number of the breakdown and discharge energy

Eoin W. Gray; Daniel J. Harrington

1982-01-01

46

Current-Voltage Characteristics of Pentacene Films: Effect of UV/Ozone Treatment on Au Electrodes  

NASA Astrophysics Data System (ADS)

In relation to a metal/organic interface, the effect of an ozone treatment on the electrical properties of a metal surface was investigated by surface potential and current-voltage (I-V) measurements. With a UV/ozone treatment on a gold (Au) surface, the surface potential formed across a vacuum-evaporated pentacene film (100 nm thickness) on a Au substrate varied from -200 mV to 350 mV. The variation in the surface potential is possibly a result of a change in the apparent work function of the Au surface. The results obtained by photoemission spectroscopy support the deepening of the Fermi level of the Au surface with the UV/ozone treatment. The I-V characteristics of a [Au (top)/pentacene/Au (bottom)] structure showed that the rectifying property reverses with the UV/ozone treatment of the bottom Au electrode. These results are discussed based on the potential barrier at the Au/pentacene interface due to the space charge.

Suzue, Yuuma; Manaka, Takaaki; Iwamoto, Mitsumasa

2005-01-01

47

A consistent approach to estimate the breakdown voltage of high voltage electrodes under positive switching impulses  

NASA Astrophysics Data System (ADS)

The main propose of this paper is to present a physical model of long air gap electrical discharges under positive switching impulses. The development and progression of discharges in long air gaps are attributable to two intertwined physical phenomena, namely, the leader channel and the streamer zone. Experimental studies have been used to develop empirical and physical models capable to represent the streamer zone and the leader channel. The empirical ones have led to improvements in the electrical design of high voltage apparatus and insulation distances, but they cannot take into account factors associated with fundamental physics and/or the behavior of materials. The physical models have been used to describe and understand the discharge phenomena of laboratory and lightning discharges. However, because of the complex simulations necessary to reproduce real cases, they are not in widespread use in the engineering of practical applications. Hence, the aim of the work presented here is to develop a model based on physics of the discharge capable to validate and complement the existing engineering models. The model presented here proposes a new geometrical approximation for the representation of the streamer and the calculation of the accumulated electrical charge. The model considers a variable streamer region that changes with the temporal and spatial variations of the electric field. The leader channel is modeled using the non local thermo-equilibrium equations. Furthermore, statistical delays before the inception of the first corona, and random distributions to represent the tortuous nature of the path taken by the leader channel were included based on the behavior observed in experimental tests, with the intention of ensuring the discharge behaved in a realistic manner. For comparison purposes, two different gap configurations were simulated. A reasonable agreement was found between the physical model and the experimental test results.

Arevalo, L.; Wu, D.; Jacobson, B.

2013-08-01

48

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

49

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

50

Change in the open-circuit voltage during storage of models containing mercuric oxide and cadmium electrodes  

Microsoft Academic Search

In order to establish the correlation between the conservation of the charge in the system containing mercuric oxide and cadmium electrodes and the dynamics of the open-circuit voltage (OCV), the authors have investigated the influence of storage on models made up of the above-mentioned electrodes (MCM). Storage of MCM leads to a linear decrease in OCV which is strictly related

V. K. Kleshchuk; V. A. Nikolskii; I. N. Legkii

1988-01-01

51

Lab-on-a-Chip device with laser-patterned polymer electrodes for high voltage application and contactless conductivity detection.  

PubMed

A laser-patterned microchip electrophoresis device with integrated polymer electrodes for DC high voltages and AC capacitively-coupled contactless conductivity detection was developed. Electrophoresis separations comparable to devices with metal electrodes were obtained, at approximately 20 times lower cost. PMID:22875011

Henderson, Rowan D; Guijt, Rosanne M; Andrewartha, Lee; Lewis, Trevor W; Rodemann, Thomas; Henderson, Alan; Hilder, Emily F; Haddad, Paul R; Breadmore, Michael C

2012-09-25

52

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

53

Factors affecting the open-circuit voltage and electrode kinetics of some iron/titanium/redox flow cells  

NASA Technical Reports Server (NTRS)

The effect of acid concentration on the performance of the iron-titanium redox flow cell was studied. When the acidity was increased, open-circuit voltages decreased on the titanium side but load voltages increased due to decreased polarization. The best load voltage occurs when there is high acidity on the titanium side coupled with low acidity on the iron side, but such cells show voltage losses with repeated cycling because of the diffusion of acid through the membrane. No membrane tested has been found capable of maintaining the differences in acidity. Chelating agents show some promise in reducing polarization at the Ti electrode and thus improving energy efficiency.

Reid, M. A.; Gahn, R. F.

1977-01-01

54

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

55

Optical high voltage measurement using Pockels microsingle crystal  

NASA Astrophysics Data System (ADS)

A new optical high voltage sensor using a Pockels microsingle crystal in a longitudinal modulation arrangement is presented. A prototype of the sensor is assembled and shows an advantage of directly measuring voltage levels up to 50 kV without any potential divider in a wide frequency bandwidth of direct current to 116 MHz. In conventional Pockels sensors, acoustic resonance driven by piezoelectric effect introduces oscillatory components to signals obtained from measurements of lightning impulse voltages. In the new sensor, the measured signal is free from the oscillatory components. An accuracy of 1.9% in good agreement with predicted values is obtained from the lightning impulse voltage measurement.

Santos, Josemir Coelho; Taplamacioglu, Muslum Cengiz; Hidaka, Kunihiko

1999-08-01

56

Optical high voltage measurement transformer using white light interferometry  

Microsoft Academic Search

A new approach to perform measurement of potentials in high voltage levels using electrooptical Pockels sensors is presented here. This paper describes an application of the White Light Interferometry technique to a high voltage optical fiber measurement system. In this system the information is encoded in the spectrum of the light, allowing the measurement to be independent of the optical

Luiz Pinheiro; Josemir Coelho Santos; A. L. Côrtes; K. Hidaka; Escola de Engenharia

2002-01-01

57

Effects of electrode geometry and cell location on single-cell impedance measurement.  

PubMed

Measurements on single cells provide more accurate and in-depth information about electrical properties than those on pathological tissues. The relationship between electrode geometry and the location of a cell on microfluidic devices greatly affects the accuracy of single-cell impedance measurement. Accordingly, this study presents numerical solutions from the FEM simulation of the COMSOL multiphysics package and experimental measurements to analyze the effects of electrode geometry and cell location on microfluidic devices. An equivalent electrical circuit model is developed to obtain the impedance and sensitivity of various cell locations on various electrode geometries using FEM simulation. According to the simulation results, the parallel electrodes have the largest sensing area (39 microm(2)) and the highest sensitivity (0.976) at a voltage of 0.1 V and a frequency of 100 kHz. Increasing the width of electrodes provides a large sensing area but reduces sensitivity, whereas decreasing the gap between electrodes increases both sensing area and sensitivity. In experiments, the results demonstrate that the magnitude is inversely proportional to the overlap area of the cell and electrodes. Moreover, the impedance of single HeLa cells measured at various cell locations can be modified using equations determined from the modeling and experimental results. PMID:19926465

Wang, Ji-Wei; Wang, Min-Haw; Jang, Ling-Sheng

2010-02-15

58

Universality in the low-voltage transport response of molecular wires physisorbed onto graphene electrodes  

NASA Astrophysics Data System (ADS)

We analyze the low-voltage transport response of large molecular wires bridging graphene electrodes, where the molecules are physisorbed onto the graphene sheets by planar anchor groups. In our study, the sheets are pulled away to vary the gap length and the relative atomic positions. The molecular wires are also translated in directions parallel and perpendicular to the sheets. We show that the energy position of the Breit-Wigner molecular resonances is universal for a given molecule, in the sense that it is independent of the details of the graphene edges, gaps lengths, or of the molecule positions. We discuss the need to converge carefully the k sampling to provide reasonable values of the conductance.

García-Suárez, V. M.; Ferradás, R.; Carrascal, D.; Ferrer, J.

2013-06-01

59

Floating Electrode Transistor based on Single-walled Carbon Nanotube Networks for High Source--drain Voltage Operation  

NASA Astrophysics Data System (ADS)

Thin film transistors (TFTs) based on single-walled carbon nanotubes (swCNTs) were reported to exhibit extraordinary characteristics in terms of their conductivity, transparency and flexibility. However, until now, most studies have focused on CNT-TFTs for an operation at a relatively low source--drain voltage below ˜ 10 V, while, for some applications such as LCD displays, one needs a rather high source--drain bias voltage. However, such a high voltage bias on source and drain electrodes may reduce the gating effect of conventional CNT-TFT devices by lowering the Schottky barrier and degrade its overall device performance. Herein, we developed floating electrode thin-film transistors (F-TFTs) based on semiconducting swCNT networks for a high source-drain voltage operation. In this device structure, the swCNT network channel was divided into a number of channels connected by floating metallic electrodes. At a high source-drain voltage, the F-TFTs showed a much higher on--off ratio than conventional swCNT-TFTs. This work should provide an important guideline in designing CNT-TFTs for high voltage applications.

Kim, Jeongsu; Lee, Juhyung; Lee, Hyungwoo; Kim, Taekyeong; Jin, Hye Jun; Shin, Juyeon; Shin, Youngki; Park, Sangho; Khang, Yoonho; Hong, Seunghun

2013-03-01

60

Calibration of high voltage transducers for power quality measurements  

Microsoft Academic Search

Transmission and distribution networks are increasingly affected by sensitive loads, considering the increase of power electronics based equipment and devices. For keeping under control power quality parameters, for instance, harmonics, sags, swells, flicker, reliable measurements performed at high voltage level are necessary. This kind of measurement is performed using high voltage transducers. Considering present technical standards on this subject, for

HÉDIO TATIZAWA; ERASMO SILVEIRA NETO; GERALDO F. BURANI; ANTÔNIO A. C. ARRUDA; KLEIBER T. SOLETTO; NELSON M. MATSUO

2009-01-01

61

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.

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

2010-01-01

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

Dielectric measurements using novel three-electrode technique  

Microsoft Academic Search

The polarization impedance at electrode surfaces can be particularly troublesome when dielectric measurements on high-conductivity fluids or semi-solids, including biological tissues, are attempted. For much biological work, where surface-penetrating measurements are required, relatively rugged dielectric probes are necessary. In such applications, electrode distance-variation or other compensation is too time-consuming. A highly practical solution to the problem uses three electrodes of

W. M. Arnold

1998-01-01

64

Derivation of Theoretical Formulas and an Investigation on Measured Results of Grounding Electrode Transient Responses  

NASA Astrophysics Data System (ADS)

This paper has derived analytical formulas of a voltage and a current on a grounding electrode by adopting a simple model circuit composed of R, L and C elements. Based on the formulas, its transient characteristic is discussed, and approximate formulas of the surge impedance and the propagation velocity are proposed. Also, this paper summarizes measured results of transient responses on grounding electrodes with horizontal and vertical arrangements. The characteristics of the measured results are estimated based on the analytical formulas derived in the paper. It becomes clear that most of the measured results show either an inductive or a resistive characteristic as far as the investigated cases in the paper are concerned. In the capacitive case, the transient resistance is not much different from the steady-state resistance. Also, it has been shown that measured steady-state resistances agree well with those evaluated by Sunde's formula for a horizontal electrode.

Ametani, Akihiro; Morii, Hiroshi; Kubo, Takashi

65

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

66

Simple and compact capacitive voltage probe for measuring voltage impulses up to 0.5 MV  

NASA Astrophysics Data System (ADS)

The paper describes a simple and compact 0.5 MV high-voltage capacitive probe developed in common by Université de Pau (France) and Loughborough University (UK). Design details are provided, together with a simple and straightforward methodology developed to assess the characteristics of high-voltage probes. The technique uses a 4 kV pulsed arrangement combined with results from a 2D electric field solver and a thorough PSpice circuit analysis. Finally, a practical example of high-voltage measurement performed using such a probe during the development phase of a high power microwave generator is provided.

Pecquois, R.; Pecastaing, L.; de Ferron, A.; Rivaletto, M.; Pignolet, P.; Novac, B. M.; Smith, I. R.; Adler, R. J.

2012-03-01

67

A Field Instrument for Measurement of AC Voltage Fluctuations.  

National Technical Information Service (NTIS)

The patent application relates to a device for measuring the AC voltage fluctuation and, more particularly, to a high accuracy, high resolution, fast response field device which stores and displays the sag and surge voltage values of an AC source for X-ra...

J. L. Silberberg

1974-01-01

68

Low circumferential voltage gradient self supporting electrode for solid oxide fuel cells  

DOEpatents

The porous, self-supporting, elongated electrode is made, having at least two chambers through its axial length, the chambers separated by an electronically conductive member. This electrode can be an air electrode of a fuel cell, having a superimposed solid electrolyte and fuel electrode.

Reichner, Philip (Plum Boro, PA)

1989-01-01

69

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

70

Measurement of Serum Ionic Calcium Using a Specific Ion Electrode.  

National Technical Information Service (NTIS)

A recently developed calcium ion electrode was evaluated for use in the routine measurement of serum ionic calcium. The electrode, used in conjunction with an expanded scale pH meter, permits the direct and accurate assay of ionic calcium in fresh serum s...

D. E. Arnold M. J. Stansell H. H. Malvin

1967-01-01

71

Potentiodynamic measurements at semiconductor electrodes. Indium antimonide  

SciTech Connect

The electrochemical behavior and electrophysical surface parameters of InSb electrodes were investigated using the complex field effect in aqueous electrolytes. The effect of special features in the population (degeneracy of the electron or hole gas in the conduction and valence band) and distribution (nonparabolic shape of the conduction band) of the electronic states of allowed bands was demonstrated for the first time. Changes in the density spectrum of fast surface states in the band gap and at the edges of the conduction and valence band which occur as a result of controllable changes in chemical nature of the InSb electrode surface are also discussed. It was established that the structural and chemical anisotropy along the direction in InSb becomes manifest in a variety of electrochemical and electrophysical characteristics of the InSbelectrolyte system. The results obtained demonstrate that the general structural, physical and chemical approach to an interpretation of semiconductor-oxide-electrolyte systems must be developed further. By studying the electrochemical and electrophysical characteristics of the narrow-band InSb electrode in aqueous electrolytes of different pH over a wide range of electrode potentials with the aid of the complex field effect in aqueous electrolytes, it is possible to describe its original surface state in the presence of superthin intrinsic oxide for the first time.

Romanov, O.V.; Sokolov, M.A.

1985-04-01

72

Measurement of threshold voltage in organic thin film transistors  

NASA Astrophysics Data System (ADS)

Conventional method used for measurement of linearly extrapolated threshold voltage from the slope of ISD vs. VGS characteristics in organic thin film transistors (OTFTs) suffers from the influence of gate dependence of field mobility and its use for comparing different devices can result in anomalous trends. In the present work, an improved method is described, which eliminates the effects of mobility and yields a unique value of threshold voltage. Experimental results obtained with pentacene OTFTs with two different dielectric materials are presented, which show that actual threshold voltage can be very different than the values estimated using the conventional technique.

Kumar Singh, Vinay; Mazhari, Baquer

2013-06-01

73

Improved electrode paste provides reliable measurement of galvanic skin response  

NASA Technical Reports Server (NTRS)

High-conductivity electrode paste is used in obtaining accurate skin resistance or skin potential measurements. The paste is isotonic to perspiration, is nonirritating and nonsensitizing, and has an extended shelf life.

Day, J. L.

1966-01-01

74

Improvement of pixel electrode circuit for active-matrix OLED by application of reversed-biased voltage  

Microsoft Academic Search

In this paper, an improved ac pixel electrode circuit for active-matrix organic light-emitting display (AMOLED) has been proposed by adding a thin-film transistor. This circuit can provide an ac driving mode for AMOLED and makes the OLED in a reversed-biased voltage during the reverse cycle. And a circuit design for understanding ac driving mode was presented. The circuit simulation results

Yujuan Si; Liuqi Lang; Yi Zhao; Xinfa Chen; Shiyong Liu

2005-01-01

75

A simple arc column model that accounts for the relationship between voltage, current and electrode gap during VAR  

SciTech Connect

Mean arc voltage is a process parameter commonly used in vacuum arc remelting (VAR) control schemes. The response of this parameter to changes in melting current (I) and electrode gap (g{sub e}) at constant pressure may be accurately described by an equation of the form V = V{sub 0} + c{sub 1}g{sub e}I + c{sub 2}g{sub e}{sup 2} + c{sub 3}I{sup 2}, where c{sub 1}, c{sub 2} and c{sub 3} are constants, and where the non-linear terms generally constitute a relatively small correction. If the non-linear terms are ignored, the equation has the form of Ohm`s law with a constant offset (V{sub 0}), c{sub 1}g{sub e} playing the role of resistance. This implies that the arc column may be treated approximately as a simple resistor during constant current VAR, the resistance changing linearly with g{sub e}. The VAR furnace arc is known to originate from multiple cathode spot clusters situated randomly on the electrode tip surface. Each cluster marks a point of exist for conduction electrons leaving the cathode surface and entering the electrode gap. Because the spot clusters re highly localized on the cathode surface, each gives rise to an arc column that may be considered to operate independently of other local arc columns. This approximation is used to develop a model that accounts for the observed arc voltage dependence on electrode gap at constant current. Local arc column resistivity is estimated from elementary plasma physics and used to test the model for consistency by using it to predict local column heavy particle density. Furthermore, it is shown that the local arc column resistance increases as particle density increases. This is used to account for the common observation that the arc stiffens with increasing current, i.e. the arc voltage becomes more sensitive to changes in electrode gap as the melting current is increased. This explains why arc voltage is an accurate electrode gap indicator for high current VAR processes but not low current VAR processes.

Williamson, R.L. [Sandia National Labs., Albuquerque, NM (United States). Liquid Metal Processing Lab.

1997-02-01

76

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

SciTech Connect

Bubble size distributions (BSD) near a reference electrode (RE) in aqueous glycerol solutions of an electrolyte NaCl have been investigated under various gas superficial velocities (Us). BSD and RE voltage were measured by using a high-speed digital camera and a pH/voltage meter, respectively. Self-similarity is seen in the normalized cumulative number distribution through BSD. The percent relative difference (PRD) based on the baseline voltage shows that bubble size (b) has a strong impact on PRD at low liquid viscosity and both PRD and b increase at diverging rates as Us increases. An analysis on bubble rising velocity reveals that the system is in an intermediate region. A fundamental equation for spherical bubble formation is developed via Newton’s second law of motion and is linked to an electrochemical principle in the practical application.

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

2006-10-01

77

Application of infrared spectroscopy to monitoring gas insulated high-voltage equipment: electrode material-dependent SF(6) decomposition.  

PubMed

Sulfur hexafluoride is a chemically inert gas which is used in gas insulated substations (GIS) and other high-voltage equipment, leading to a significant enhancement of apparatus lifetime and reductions in installation size and maintenance requirements compared to conventional air insulated substations. However, component failures due to aging of the gas through electrical discharges may occur, and on-site monitoring for risk assessment is needed. Infrared spectroscopy was used for the analysis of gaseous by-products generated from electrical discharges in sulfur hexafluoride gas. An infrared monitoring system was developed using a micro-cell coupled to an FTIR spectrometer by silver halide fibers. Partial least-squares calibration was applied by using a limited number of optimally selected spectral variables. Emphasis was placed on the determination of main decomposition products, such as SOF(2), SOF(4), and SO(2)F(2). Besides the different electrical conditions, the material of the plane counter electrode of the discharge chamber was also varied between silver, aluminum, copper, tungsten, or tungsten/copper alloy. For the spark experiments the point electrode was the same material as chosen for the plane electrode, whereas for partial discharges a stainless steel needle was employed. Complementary investigations on the chemical composition within the solid counter electrode material by secondary neutral mass spectrometry (SNMS) were also carried out. Under sparking conditions, the electrode material plays an important role in the decomposition rates of the gas-phase, but no relevant material dependence could be observed under partial discharge conditions. PMID:12185577

Kurte, R; Beyer, C; Heise, H M; Klockow, D

2002-08-01

78

Withstand voltage testing in combination with PD measurements of XLPE cables under damped alternating voltage on-site  

Microsoft Academic Search

As an after-laying test, withstand voltages and PD measurements of XLPE cables on-site have been finished respectively for many years. Standard test procedures using continuous AC voltages are very cost intensive due to the high capacitive power demand of the cables and the resulting large sizes of the test sets. The contribution paper presents that withstand voltage testing in combination

Sun Zhenquan; Zhao Xuefeng; Li Jisheng; Li Yanming

2009-01-01

79

Gating behaviour of sodium currents in adult mouse muscle recorded with an improved two-electrode voltage clamp  

PubMed Central

The availability of knock-in mutant mouse models for channelopathies of skeletal muscle has generated the need for improved methods to record ionic currents under voltage clamp in fully differentiated adult muscle fibres. A two-electrode voltage clamp has been optimized for recording Na+ currents in small fibres dissociated from the footpad. Clamp speed and spatial homogeneity were achieved by using short fibres (<600 ?m) that were detubulated with hyperosmolar glycerol. Series resistance errors were reduced by limiting current amplitude with low [Na+]. The quality of the voltage clamp was explored with computer simulations of a finite cable model with active conductances. Simulations quantitatively defined the range of conditions for which clamp control can be maintained, and provided estimates for the errors in the determination of gating parameters from standard pulse protocols. Sodium currents recorded from short fast-twitch muscles revealed a hyperpolarized shift in the voltage dependence of activation (V1/2?52 mV) and fast inactivation (V1/2?88 mV) compared to expression studies of NaV1.4 in mammalian cell lines. Slow inactivation occurred at depolarized potentials (V1/2?69 mV) relative to fast inactivation. These data reveal a marked divergence in the voltage dependence of fast and slow inactivation and provide normative values of Na+ channel behaviour for mouse skeletal muscle that will serve as a reference for the investigation of muscle ion channelopathies using genetically engineered mice or computer simulation.

Fu, Yu; Struyk, Arie; Markin, Vladislav; Cannon, Stephen

2011-01-01

80

Capacitance measurements for AlGaN/GaN photoelectrochemical electrode by using electrolyte contact and by metal contact  

NASA Astrophysics Data System (ADS)

A semiconductor photo electrochemical electrode that contains heterostructure at the surface vicinity is attractive as a corrosion-tolerant electrode. In order to clarify its basic characteristics, the differences of Schottky junctions were evaluated using semiconductor capacitance dependent on voltage. The Mott-Schottky relationship of thin AlGaN layer on GaN was different from that of GaN bulk semiconductor. The Schottky junctions were formed not only by using metal electrode, but also by using electrolytecontact in order to evaluate the effects of the semiconductor-electrolyte interface on the behavior of Schottky junction. Although diffusions of ions and solvents exist in th electrolyte, the Mott-Schottky plot which was measured in electrolyte system showed a voltage dependence similar to that measured with metal contact. It would be probablethat an electrolyte has a limited effect on the depletion behavior of the semiconductor-heterojunction electrode: only the offset of voltage exists at the semiconductor/electrolyte interface and the offset is insensitive to the applied voltage.

Nakamura, Akihiro; Sugiyama, Masakazu; Fujii, Katsushi; Nakano, Yoshiaki

2013-12-01

81

Electronic transport in oligo-para-phenylene junctions attached to carbon nanotube electrodes: Transition-voltage spectroscopy and chirality  

SciTech Connect

We have investigated, by means of a nonequilibrium Green's function method coupled to density functional theory, the electronic transport properties of molecular junctions composed of oligo-para-phenylene (with two, three, four, and five phenyl rings) covalently bridging the gap between metallic carbon nanotubes electrodes. We have found that the current is strongly correlated to a purely geometrical chiral parameter, both on-resonance and off-resonance. The Fowler-Nordheim plot exhibits minima, V{sub min}, that occur whenever the tail of a resonant transmission peak enters in the bias window. This result corroborates the scenario in which the coherent transport model gives the correct interpretation to transition voltage spectroscopy (TVS). We have shown that V{sub min} corresponds to voltages where a negative differential resistance (NDR) occurs. The finding that V{sub min} corresponds to voltages that exhibit NDR, which can be explained only in single-molecule junctions within the coherent transport model, further confirms the applicability of such models to adequately interpret TVS. The fact that the electrodes are organic is at the origin of differences in the behavior of V{sub min} if compared to the case of molecular junctions with nonorganic contacts treated so far.

Brito Silva, C. A. Jr. [Pos-Graduacao em Engenharia Eletrica, Universidade Federal do Para, 66075-900, Belem, PA (Brazil); Faculdade de Ciencias Naturais, Universidade Federal do Para, 68800-000, Breves, PA (Brazil); Silva, S. J. S. da; Leal, J. F. P. [Pos-Graduacao em Fisica, Universidade Federal do Para, 66075-110, Belem, PA (Brazil); Pinheiro, F. A. [Instituto de Fisica, Universidade Federal do Rio de Janeiro, 21941-972, Rio de Janeiro, RJ (Brazil); Del Nero, J. [Departamento de Fisica, Universidade Federal do Para, 66075-110, Belem, PA (Brazil); Departement de Physique, Ecole Normale Superieure, F-75231, Paris (France)

2011-06-15

82

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.

Ramlo, Susan

83

Progress in measurements with the ETF voltage balance  

Microsoft Academic Search

The results of two series of measurements with the ETF-84 voltage balance carried out in 1987 and 1988, using the classical method of weighting, were previously presented by the authors (1988) with the proviso that some systematic errors had not been accounted for. Detailed analyses of these errors are not in progress, as are numerous experiments to determine the possible

Vojislav Bego; K. Poljancic; J. Butorac; G. Gasljevic

1993-01-01

84

Spark gap with low breakdown voltage jitter  

DOEpatents

Novel spark gap devices and electrodes are disclosed. The novel spark gap devices and electrodes are suitable for use in a variety of spark gap device applications. The shape of the electrodes gives rise to local field enhancements and reduces breakdown voltage jitter. Breakdown voltage jitter of approximately 5% has been measured in spark gaps according the invention. Novel electrode geometries and materials are disclosed. 13 figs.

Rohwein, G.J.; Roose, L.D.

1996-04-23

85

Spark gap with low breakdown voltage jitter  

DOEpatents

Novel spark gap devices and electrodes are disclosed. The novel spark gap devices and electrodes are suitable for use in a variety of spark gap device applications. The shape of the electrodes gives rise to local field enhancements and reduces breakdown voltage jitter. Breakdown voltage jitter of approximately 5% has been measured in spark gaps according the invention. Novel electrode geometries and materials are disclosed.

Rohwein, Gerald J. (Albuquerque, NM); Roose, Lars D. (Albuquerque, NM)

1996-01-01

86

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

87

Radiation protection and measurement for low-voltage neutron generators  

SciTech Connect

This report is concerned with neutron generators that operate at voltages below a few hundred kilovolts and produce neutrons chiefly by the T(d,n) reaction. The report provides information on the radiation protection problems in the use of these generators and the means available for dealing with these problems. It is intended to serve as a guide to good practice and bring together in one place, a number of recommendations relevant to the use of low voltage neutron generators that have appeared in other NCRP documents. The report surveys the radiations produced by low voltage neutron generators and their measurement. It then addresses the fundamentals of radiation protection, including shielding and physical safeguards. Guidance is given on radioactive waste resulting from the use of neutron generators and information is provided on non-radiation hazards and licensing. 91 references, 4 figures, 7 tables.

Not Available

1983-11-01

88

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

89

DC voltage-voltage method to measure the interface traps in sub-micron MOSTs  

NASA Astrophysics Data System (ADS)

A dc voltage-voltage technique for the measurement of stress-generated interface traps in submicron MOSTs is demonstrated. This method uses the source-bulk-drain of a submicron MOST as an effective lateral bipolar transistor when the channel region is out of inversion under the control of the gate voltage Vgb. The emitter injects the minority carriers to the base region and the collector is open. The Vcb versus Vgb spectrum can be explained quantitatively in the spirit of the extended Ebers-Moll equations and interface trap SRH recombination. The spectrum shows clear information on stress-generated interface traps located at the collector-junction region. The new method has the advantages of simplicity, high sensitivity and wide application range to different device structures. A single effective interface trap at the source or drain side could be detected, and interface traps at the source side can be separated from those at the drain side by the new method. Moreover, we propose an improved gated-diode method to separate interface traps at the source side from those at the drain side.

Jie, B. B.; Li, M. F.; Chim, W. K.; Chan, D. S. H.; Lo, K. F.

1999-07-01

90

Numerical simulation of particle dynamics in an orifice-electrode system. Application to counting and sizing by impedance measurement.  

PubMed

This paper describes how to numerically tackle the problem of counting and sizing particles by impedance measurement in an orifice-electrode system. The model allows to simulate the particle dynamics submitted to strong hydrodynamic stresses through a microorifice and to compute the voltage pulses generated by the modification of the inner dielectric medium. This approach gives important information about particles size distribution and allows to quantify the role of trajectory and orientation of particles on the size measurement. PMID:23349148

Isèbe, Damien; Nérin, Philippe

2013-04-01

91

Measurement of pseudoephedrine hydrochloride dissolution using chloride-ion electrode.  

PubMed

Experiments were performed to determine the suitability of using a chloride-ion electrode for the measurement of pseudoephedrine hydrochloride dissolution from commercially available compressed tablets. Dissolution experiments were carried out in 500 ml of distilled water using the USP paddle method at 100 rpm. Both chloride ion and pseudoephedrine (UV spectrophotometry) were measured at six different sampling times. Percent dissolved versus time values were linearized on a log-normal probability basis. The slopes of individual lines obtained from the chloride and pseudoephedrine measurements were compared using a Student t test and did not differ significantly (t = 0.415, df = 5, p greater than 0.05). In addition to providing an efficient, inexpensive, and simple method for measuring pseudoephedrine hydrochloride dissolution rates, the chloride-ion electrode could be used in the measurement of dissolution rates for a wide variety of drugs available as hydrochloride salts. PMID:7299681

Chen, S T; Thompson, R C; Poust, R I

1981-11-01

92

Developing barbed microtip-based electrode arrays for biopotential measurement.  

PubMed

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

93

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

94

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

95

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.

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

2012-01-01

96

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

97

Elimination of high-voltage field effects in end column electrochemical detection in capillary electrophoresis by use of on-chip microband electrodes.  

PubMed

The influence of the separation voltage on end column electrochemical detection (EC) in capillary electrophoresis (CE) has been investigated using an electrochemical detector chip based on an array of microband electrodes. It is shown, both theoretically and experimentally, that the effect of the CE electric field on the detection can be practically eliminated, without using a decoupler, by positioning the reference electrode sufficiently close to the working electrode. In the present study, this was demonstrated by using an experimental setup in which neighboring microband electrodes on a chip, positioned 30 microns from the end of the CE capillary, were used as working and reference electrodes, respectively. The short distance (i.e., 10 microns) between the working and reference electrode ensured that both of the electrodes were very similarly affected by the presence of the CE electric field. With this experimental setup, no significant influence of the CE voltage on the peak potentials for gold oxide reduction could be seen for CE voltages up to +30 kV. The detector noise level was also found to be reduced. PMID:11338610

Klett, O; Björefors, F; Nyholm, L

2001-04-15

98

A four-electrode low frequency impedance spectroscopy measurement system using the AD5933 measurement chip.  

PubMed

This paper presents the design of a four electrode impedance measurement circuit dedicated to bioimpedance embedded applications. It extends the use of the AD5933 measurement chip to allow it to operate in a four electrode configuration in order to limit the effects of the parasitic impedances between the medium under test and the electrodes. The circuit has shown a good measurement accuracy on various test circuits. In association with a four microband electrode system it has been successfully used to characterize small physiological samples (50 ?l) with conductivities ranging from 0.14 to 1.2 S m(-1). It can be used as an alternative bioimpedance measurement approach for embedded applications operating in the four electrode configuration. PMID:23481406

Margo, C; Katrib, J; Nadi, M; Rouane, A

2013-04-01

99

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

100

Luminous flux improvement of xenon fluorescent lamps by applying synchronized high-voltage pulse to the auxiliary external electrode  

NASA Astrophysics Data System (ADS)

As the environmental awareness of people becomes stronger, the demand for mercury-free light sources also becomes stronger. The authors have been developing cold cathode fluorescent lamps in which xenon gas is filled as an ultraviolet radiator instead of mercury. Previously the authors reported the luminous flux enhancement method using a grounded auxiliary external electrode (AEE). In this paper, in order to improve the luminous flux much more, a positive voltage pulse which was synchronized to the main driving negative voltage pulse was applied to the AEE. As a result, the maximum input power increased under which the positive column did not constrict and the luminous flux improved by 70% at the xenon filling pressure of 6.7 kPa. It is proved that the positive voltage pulse application to the AEE with the amplitude of more than 2 kV expands the positive column in the radial direction. It is attributed to the phenomenon that the residual ions and electrons, which are generated by dielectric barrier discharge between the AEE and the anode during the falling edge of the negative pulse to the cathode, spread the discharge path from the anode towards the AEE during the cold cathode discharge mode. By increasing the xenon filling pressure, luminous efficacy was improved to 25 lm W-1.

Motomura, Hideki; Oka, Kojiro; Sogabe, Toru; Jinno, Masafumi

2011-06-01

101

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

102

Determination of the diagnostic x-ray tube practical peak voltage (PPV) from average or average peak voltage measurements.  

PubMed

The practical peak voltage (PPV) has been adopted as the reference measuring quantity for the x-ray tube voltage. However, the majority of commercial kV-meter models measure the average peak, ?(P), the average, ?, the effective, U(eff) or the maximum peak, U(P) tube voltage. This work proposed a method for determination of the PPV from measurements with a kV-meter that measures the average ? or the average peak, ?(p) voltage. The kV-meter reading can be converted to the PPV by applying appropriate calibration coefficients and conversion factors. The average peak k(PPV,kVp) and the average k(PPV,Uav) conversion factors were calculated from virtual voltage waveforms for conventional diagnostic radiology (50-150 kV) and mammography (22-35 kV) tube voltages and for voltage ripples from 0% to 100%. Regression equation and coefficients provide the appropriate conversion factors at any given tube voltage and ripple. The influence of voltage waveform irregularities, like 'spikes' and pulse amplitude variations, on the conversion factors was investigated and discussed. The proposed method and the conversion factors were tested using six commercial kV-meters at several x-ray units. The deviations between the reference and the calculated-according to the proposed method-PPV values were less than 2%. Practical aspects on the voltage ripple measurement were addressed and discussed. The proposed method provides a rigorous base to determine the PPV with kV-meters from ?(p) and ? measurement. Users can benefit, since all kV-meters, irrespective of their measuring quantity, can be used to determine the PPV, complying with the IEC standard requirements. PMID:21403184

Hourdakis, C J

2011-04-01

103

Phase-measurement interferometric microscopy of microlithographically fabricated platinum electrodes  

SciTech Connect

Phase-measurement interferometric microscopy (PMIM) was used to measure the topography of Pt microelectrodes fabricated on silicon wafers. Disk (10 {mu}m radius) and band (10 {mu}m {times} 1,000 {mu}m) electrodes were prepared by deposition and lithographic patterning of a 0.2 {mu}m thick SiO{sub 2} layer on a 0.05 {mu}m thick Pt film. Quantitative topographical images of the resulting electrodes are obtained from PMIM by accounting for the complex refractive index of Pt and for multiple reflections of light which occur within the transparent SiO{sub 2} layer. In situ, quantitative measurement of microelectrode topography in water is also demonstrated.

Smith, C.P.; Kennedy, H.L.; Kragt, H.J.; White, H.S. (Univ. of Minnesota, Minneapolis (USA)); Biegen, J.F. (ZYGO Corporation, Middlefield, CT (USA))

1990-06-01

104

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

105

Direct Ion Energy Measurements at the RF Biased Electrode in Noble and Hydrocarbon Gas Discharges  

NASA Astrophysics Data System (ADS)

We report direct measurements of ion energy distributions at the biased substrate electrode in a RF ICP discharge using a mass-energy analyser thus allowing exploration of greater bias voltage and frequency ranges. IEDs for pure Ar, He and He:Ar or Ar:C2H2 mixtures for pressures up to 90mTorr, mean bias voltages up to 150V and bias frequencies up to 27MHz, are compared with existing single and multi-species [1] IED models. With associated Langmuir probe, ion flux probe and sheath width measurements we observe that lighter ion IEDs deviate from the model and this also affects interpretation of the multiple-species IED model. At high biases we also note deviation from models, probably due to additional capacitively-coupled power input at the substrate electrode. We have mapped the IED spread and peak intensity variation across frequency and pressure ranges, respectively, in order to exploit IED tailoring for technological applications, particularly for the deposition of high integrity carbon based films. In Ar:C2H2 narrow spread IEDs were achieved, required for new diamond-like carbon deposition and growth modeling. Mean energies up to 100eV were obtained with 15% - 20% spread, depending on gas ratio, pulsed bias and frequency. [1] Sobolewski M A et. al. J. Appl. Phys. 91(2002) 6303.

Baby, A.; Mahony, C. M. O.; Maguire, P. D.

2008-10-01

106

Battery Impedance Measurement by Laplace Transformation of Charge or Discharge Current/Voltage  

NASA Astrophysics Data System (ADS)

Impedance spectroscopy of Z(?) is often used in the electrochemical field to analyze electrode reactions and to calculate transient responses. Our previous study measured the overpotential resistance for our thermal behavior model to calculate the temperature rise of Nickel/metal-hydride battery or Lithium-ion battery during charge and discharge cycles. However, the Z(?) measured by AC impedance meter did not agreed with the ones induced by charge/discharge characteristics. Therefore, we focus on the impedance measurement method by Takano et al, who obtained Z(?) for Lithium-ion battery at wide frequency region by the Laplace transformation of both signals of the voltage-step input and its current response. We have extended this method to the Laplace transformation of current-step or current-pulse input signal and its voltage response signal to get Z(?) for any charge/discharge current of Nickel/metal-hydride battery or Lithium-ion battery. We can get almost the same Z(?) by the three different methods, and the measured Z(?) does not depend on both charge/discharge current and the state of charge or the charge input. Moreover, Z(?) including Warlbulg impedance at low frequencies gets near the overpotential resistance that can estimate well the battery temperature rise in our battery thermal behavior model.

Nakayama, Masato; Fukuda, Kenichi; Ohmori, Yoshitake; Wakahara, Kenji; Araki, Takuto; Onda, Kazuo

107

Evaluating object and region of concentric electrode in bio-electrical impedance measurement  

Microsoft Academic Search

Concentric electrode is easy to use and used widely for measuring bio-electrical impedance. But, its evaluating region was not investigated in detail. Then, the characteristics of concentric electrode were studied from various points of view. In case of use without electrode paste, impedance is determined with the contacting condition between electrode and skin surface over all frequency range. In case

Yoshitake YAMAMOTO; Kiyoko SHIRAI; Noriko GODA; Takao NAKAMURA; Toshimasa KUSUHARA; Hiroyuki OKUDA

2003-01-01

108

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

109

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

110

Measurement of Thermopower and Current-Voltage Characteristics of Molecular Junctions to Identify Orbital Alignment  

SciTech Connect

We report an experimental technique that concurrently measures the Seebeck coefficient and the current-voltage (I-V) characteristics of a molecular junction to determine the identity and the effective energetic separation of the molecular orbital closest to the electrodes’ Fermi level. Junctions created by contacting a gold-coated atomic force microscope tip with a monolayer of molecules assembled on a gold substrate were found to have a Seebeck coefficient of (+16.9±1.4) ?V/K. This positive value unambiguously shows that the highest occupied molecular orbital (HOMO) dominates charge transport. Further, by analyzing the (I-V) characteristics, the HOMO level is estimated to be ? 0.69?eV with respect to the Fermi level.

Tan, Aaron; Sadat, Seid; Reddy, Pramod

2010-01-01

111

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

112

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

113

Electrode-nanoparticle collisions: The measurement of the sticking coefficient of silver nanoparticles on a glassy carbon electrode  

NASA Astrophysics Data System (ADS)

In this communication, we combine anodic particle coulometry (APC) with anodic stripping voltammetry, to find the proportion of NP impacts that result in adsorbed NPs, using AgNPs in collision with glassy carbon electrode. Sticking coefficients are reported for AgNP radii of 14, 29, and 45 nm, measured at electrode biases ranging from OCV to -0.2 to -1.2 V (vs. Ag/AgCl). No significant systematic trends were found in either case. We suggest that this methodology may be widely applicable to measuring the sticking coefficient of any oxidisable metal nanoparticle on an electrode surface in solution.

Zhou, Yi-Ge; Rees, Neil V.; Compton, Richard G.

2011-10-01

114

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

115

Two-electrode voltage-clamp analysis of Na,K-ATPase asparagine 776 mutants.  

PubMed

Steady-state and pre-steady-state currents of Asn(776) mutants of Na,K-ATPase are presented. The stationary current generated by N776Q strongly depends on the membrane potential, but has a negative slope, opposite to that of the wild-type enzyme. The apparent rate constant of the reaction sequence E(1)P(Na(+)) <--> E(2)P + Na(+) of this mutant is rather independent of the membrane potential and is at resting and depolarizing membrane potential higher than that of the wild-type enzyme. Thus, the voltage-dependent increase of the rate coefficient of the wild type that is associated with extracellular Na(+) rebinding is almost absent in the N776Q mutant. These findings indicate that dislocating the carboxamide group of Asn(776) decreases the affinity of sodium at its extracellular binding site. PMID:12763788

Koenderink, Jan B; Geibel, Sven; Grabsch, Eva; De Pont, Jan Joep H H M; Bamberg, Ernst; Friedrich, Thomas

2003-04-01

116

Boron-doped diamond electrodes and microelectrode-arrays for the measurement of sulfate and peroxodisulfate  

Microsoft Academic Search

Measurements of sulfate and peroxodisulfate concentrations with boron-doped diamond (BDD) electrodes and microelectrode array electrodes have been performed in various media. Diamond electrodes allow the measurement of sulfate on the anodic side of the electrochemical window through its oxidation into peroxodisulfate, and detection of peroxodisulfate on the cathodic side through the reverse reduction reaction. In all cases, current density was

Christophe Provent; Werner Haenni; Eduardo Santoli; Philippe Rychen

2004-01-01

117

Comparison of Potential Step and Triangular Voltage Sweep Methods of Double-Layer Capacitance Measurements.  

National Technical Information Service (NTIS)

A comparison was made of the potential step and triangular voltage sweep methods for obtaining the double-layer capacitance of a porous electrode. Electrolytic capacitors varying from 2000 to 27,800 microfarads were used as standards. The effects of farad...

W. H. Steuernagel

1969-01-01

118

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

119

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

120

Silica nanoparticle dispersion size measurement using dielectrophoresis on a microfabricated electrode array  

NASA Astrophysics Data System (ADS)

In this article, we report a technique that uses dielectrophoresis to measure particle size distribution information of silica nanoparticle dispersions using a microfabricated periodic interdigitated electrode array. An AC voltage is applied to the electrode array, producing a non-uniform electric field. Depending on their relative permittivity with respect to the dispersion solution, nanoparticles aggregate at either electric field maxima or minima due to dielectrophoresis, forming a periodic density grating. We probe the nanoparticle density grating with a laser beam to generate a diffraction pattern, and then monitor how fast the nanoparticle density grating decays due to diffusion after the electric field is turned off. Particle size information is derived from the diffusion rate. The advantages of the technique include: a) able to operate over a wide range of concentrations and purity levels, b) relatively insensitive to outlier particles in the tail ends of the size distribution, and c) relatively fast (on the order of seconds) measurement response. These characteristics make the method suitable for industrial samples and real time process monitoring.

Qiao, Yi; Lai, Jack; Hofeldt, Dave

2009-08-01

121

Measurement of electrical properties of electrode materials for the bakelite Resistive Plate Chambers  

NASA Astrophysics Data System (ADS)

Single gap (gas gap = 2 mm) bakelite Resistive Plate Chamber (RPC) modules of various sizes from 10 cm × 10 cm to 1 m × 1 m have been fabricated, characterized and optimized for efficiency and time resolution. Thin layers of different grades of silicone compound are applied to the inner electrode surfaces to make them smooth and also to reduce the surface resistivity. In the silicone coated RPCs an efficiency ~ 96% and time resolution ~ 2 ns (FWHM) have been obtained for both the streamer and the avalanche modes of operation. Before fabrication of detectors the electrical properties such as bulk resistivity and surface resistivity of the electrode materials are measured carefully. Effectiveness of different silicone coating in modifying the surface resistivity was evaluated by an instrument developed for monitoring the I-V curve of a high resistive surface. The results indicate definite correlation of the detector efficiency for the atmospheric muons and the RPC noise rates with the surface resistivity and its variation with the applied bias voltage. It was also found that the surface resistivity varies for different grades of silicone material applied as coating, and the results are found to be consistent with the detector efficiency and noise rate measurements done with these RPCs.

Meghna, K. K.; Banerjee, A.; Biswas, S.; Bhattacharya, S.; Bose, S.; Chattopadhyay, S.; Das, G.; Marick, C.; Saha, S.; Viyogi, Y. P.

2012-10-01

122

A high-precision voltage source for EIT.  

PubMed

Electrical impedance tomography (EIT) utilizes electrodes placed on the surface of a body to determine the complex conductivity distribution within the body. EIT can be performed by applying currents through the electrodes and measuring the electrode voltages or by applying electrode voltages and measuring the currents. Techniques have also been developed for applying the desired currents using voltage sources. This paper describes a voltage source for use in applied-voltage EIT that includes the capability of measuring both the applied voltage and applied current. A calibration circuit and calibration algorithm are described which enables all voltage sources in an EIT system to be calibrated to a common standard. The calibration minimizes the impact of stray shunt impedance, passive component variability and active component non-ideality. Simulation data obtained using PSpice are used to demonstrate the effectiveness of the circuits and calibration algorithm. PMID:16636413

Saulnier, Gary J; Ross, Alexander S; Liu, Ning

2006-05-01

123

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

124

Time-resolved voltage measurements in terawatt magnetically insulated transmission lines  

Microsoft Academic Search

We have developed two voltage diagnostics that circumvent many of the difficulties of measuring voltage in magnetically insulated transmission lines driven by terawatt (megavolt and megampere) electrical pulsers. Two versions of simple vacuum capacitive probes use strong magnetic fields to deflect electrons from the anode-mounted displacement current collector. We then introduce the electron launching voltage monitor as a novel way

M. E. Savage; C. W. Mendel Jr.; T. W. Grasser; W. W. Simpson; D. M. Zagar

1990-01-01

125

Power quality measurements performed on a low-voltage grid equipped with two wind turbines  

Microsoft Academic Search

The power quality of a low-voltage grid with two wind turbines is investigated. Slow voltage variations as well as transients and harmonics are measured and analysed. Furthermore, the spectrum of the power is determined so that the presence of periodic power components can be investigated. Although periodic power fluctuations reaching 10% of the rated power are registered, voltage variations are

T. Thiringer

1996-01-01

126

Comparing the influence of electrode materials in electrokinetic experiments: Evidence from literature and laboratory measurements  

Microsoft Academic Search

In the laboratory, commonly two types of electrodes are used to measure electrokinetic effects like streaming potentials in clays and other earth materials. On the one hand, reversible Ag\\/AgCl electrodes are used, whereas in other studies, noble metal oxidation-reduction electrodes like platinum or gold are employed. This paper shortly outlines the different types of electrodes and their application in earlier

Katja Heister; Pieter J. Kleingeld; Gustav Loch

127

Origin of Different Dependences of Open-Circuit Voltage on the Electrodes in Layered and Bulk Heterojunction Organic Photovoltaic Cells  

Microsoft Academic Search

Experimental results show that the V OC of layered heterojunction (HJ) organic photovoltaic (PV) cells behaves with a very weak dependence on the electrodes. However, the V OC of bulk HJ PV cells behaves with a strong dependence on the electrodes. In this paper, an explanation for the different behaviors of V OC on the electrodes is proposed. It is

Chunfu Zhang; Shi-Wun Tong; Chang-Yun Jiang; En-Tang Kang; Daniel S. H. Chan; Chunxiang Zhu

2010-01-01

128

Characterization of gold electrodes in phosphate buffered saline solution by impedance and noise measurements for biological applications.  

PubMed

Impedance spectroscopy and noise measurements have been used to study gold electrodes of three different surface areas in phosphate buffered saline (PBS) solution. The gold-PBS solution interface can be modeled by a charge transfer resistance in parallel with an interfacial constant phase element (CPE) which are in series with the solution resistance. The voltage noise fluctuations were analyzed using the fast Fourier transform (FFT) method. It is found that the voltage noise power is characterized by a 1/f(alpha) spectrum in the low frequency range. The value of alpha is observed to be double that of the CPE coefficient beta. The authors suggest a link between the interface impedance and the measured noise. PMID:17946639

McAdams, E T; Jossinet, J; Subramanian, R; McCauley, R G E

2006-01-01

129

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

130

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

131

Ab initio calculation of the intercalation voltage of lithium-transition-metal oxide electrodes for rechargeable batteries  

Microsoft Academic Search

A first-principle's method to predict the intercalation voltage for lithium in metal oxides is presented. Although the intercalation voltage for lithium is often related to aspects of the electronic structure, this voltage can only be accurately calculated from the lithium chemical potential in the anode and cathode. Using the pseudopotential technique the average intercalation voltage of LiMO2 cathodes is computed

M. K. Aydinol; A. F. Kohan; G. Ceder

1997-01-01

132

Time-resolved voltage measurements in terawatt magnetically insulated transmission lines  

SciTech Connect

We have developed two voltage diagnostics that circumvent many of the difficulties of measuring voltage in magnetically insulated transmission lines driven by terawatt (megavolt and megampere) electrical pulsers. Two versions of simple vacuum capacitive probes use strong magnetic fields to deflect electrons from the anode-mounted displacement current collector. We then introduce the electron launching voltage monitor as a novel way to measure voltage. This device uses a relationship between anode electric field and electron current launched from a cathode-mounted perturbation. The electron launching voltage monitor has a large number of advantages over methods commonly used to measure voltage, including large signal level, tolerance to poor vacuum, and nanosecond temporal response. This article shows designs for all these monitors, and presents data from experiments done on the SuperMite pulser at Sandia National Laboratories.

Savage, M.E.; Mendel, C.W. Jr.; Grasser, T.W.; Simpson, W.W.; Zagar, D.M. (Sandia National Laboratories, Albuquerque, NM (USA))

1990-12-01

133

depth measurement temperature measurement pressure measurement conductivity measurement (Salinity measurement TDS measurement) Oxygen Concentration measurement (Oxygen saturation measurement) pH-value measurement Red-ox-potential ORP measurement turbidity measurement (TSS measurement) measurement ion selective electrode (nitrate chloride ammonium potassium calcium sodium fluoride gas ammonia) fluorescence measurements (chlorophyll a cyanobacteria rhodamine ) optical oxygen measurements.  

EPA Pesticide Factsheets

Did you mean: depth measurement temperature measurement pressure measurement conductivity measurement (Salinity measurement TDS measurement) Oxygen Concentration measurement (Oxygen saturation measurement) pH-value measurement Red-ox-potential ORP measurement turbidity measurement (TSS measurement) measurement ion selective electrode (nitrate chloride ammonium potassium calcium sodium fluoride gas ammonia) fluorescence measurements (chlorophyll a cyanobacteria rhodamine ) optical oxygen measurements. ?

134

Measurements and modeling of recombination from nanoparticle TiO2 electrodes.  

PubMed

Electron-transfer reactions from nanoparticle TiO(2) films to outer-sphere redox shuttles were investigated. Steady-state dark current density versus applied potential and open circuit voltage decay measurements were employed to determine the rates of recombination to cobalt(III) tris(4,4'-dimethyl-2,2'-bipyridyl), [Co(Me(2)bpy)(3)](3+), and ruthenium(III) bis(2,2'-bipyridyl)-bis(N-methylimidozole), [Ru(bpy)(2)(MeIm)(2)](3+). A striking difference in the magnitude as well as the shape of the electron lifetimes for TiO(2) electrodes in contact with these two redox shuttles is observed. A model based on Marcus theory is developed to describe recombination, including contributions from conduction band electrons and surface states. Excellent agreement was found between the modeled and measured lifetimes. The model allows for identification of each contributing component of electron transfer to the measured lifetimes. Comparison of the different components of the modeled lifetimes to the measured lifetimes provides clear evidence for recombination mediated through surface states. PMID:21561078

Ondersma, Jesse W; Hamann, Thomas W

2011-06-01

135

Influence of RMS variation measurement protocols on electrical system performance indices for voltage sags and swells  

Microsoft Academic Search

This paper presents an evaluation study for measurement protocols of characteristic parameters related to short duration voltage variations (SDVs). The evaluation of possible differences in the magnitude and the duration of SDVs produced by different protocols is of great importance, for the electrical system performance indices related to voltage sags and swells are in practice obtained by measuring instruments. The

N. Kagan; E. L. Ferrari; N. M. Matsuo; S. X. Duarte; A. Sanommiya; J. L. Cavaretti; U. F. Castellano; A. Tenorio

2000-01-01

136

Improved optical sensor for high voltage measurement using white light interferometry  

Microsoft Academic Search

A new approach to perform measurement of potentials in high voltage levels using electrooptical Pockets sensors is presented. This paper describes an application of the White Light Interferometry (WLI) technique to a high voltage optical fiber measurement system. Making use of a characteristic of WLI systems, in which the information is encoded in the spectrum of the light, a compensation

J. C. Santos; K. Hidaka; A. L. Cortes; L. P. C. da Silva

2003-01-01

137

Production Engineering Measure for Voltage-Tunable Magnetrons.  

National Technical Information Service (NTIS)

The work performed on two types of voltage-tunable magnetron packages is summarized. The two types of packages are the G-E Developmental Types ZM-6103 and ZM-6104, formerly designated as the Z-5364 and ZM-6001, respectively. The product review performed o...

W. M. Piwnica E. G. Soulier

1964-01-01

138

Low-Threshold-Voltage HfOxN p-Channel Metal-Oxide-Semiconductor Field-Effect Transistors with Partially Silicided Platinum Gate Electrode  

NASA Astrophysics Data System (ADS)

HfOxN p-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) with a low threshold voltage (|Vth|) were successfully fabricated using a partially silicided (PASI) platinum gate electrode for scaled complementary MOS (CMOS). The PASI platinum (PASI-PtSi) gate electrode is composed of a monoclinic-Pt3Si phase in the vicinity of a HfOxN dielectric. The reduced silicon content of the PASI gate electrodes is effective in suppressing the Fermi-level pinning on the Hf-based gate dielectrics which induces a significant |Vth| shift in p-channel MOSFETs. It is shown that the |Vth| of HfOxN p-channel MOSFETs with the PASI-PtSi gate electrode is sufficiently low and applicable to low-standby-power devices. The mobility of the holes at 0.8 MV/cm is as high as about 90% of the universal mobility. It is concluded that the PASI technology in which the gate electrode has a reduced silicon content is useful for scaled CMOSs.

Kadoshima, Masaru; Nabatame, Toshihide; Iwamoto, Kunihiko; Mise, Nobuyuki; Ota, Hiroyuki; Ogawa, Arito; Takahashi, Masashi; Ikeda, Minoru; Satake, Hideki; Toriumi, Akira

2006-08-01

139

Voltage-dependent Membrane Displacements Measured by Atomic Force Microscopy  

PubMed Central

Cells use polar molecules in the membrane to sense changes in the transmembrane potential. The opening of voltage-gated ion channels and membrane bending due to the inverse flexoelectric effect are two examples of such electromechanical coupling. We have looked for membrane motions in an electric field using atomic (or scanning) force microscopy (AFM) with the intent of studying voltage-dependent conformational changes of ion channels. Voltage-clamped HEK293 cells were either untransfected controls or transfected with Shaker K+ channels. Using a ± 10-mV peak–peak AC carrier stimulus, untransfected cells moved 0.5–15 nm normal to the plane of the membrane. These movements tracked the voltage at frequencies >1 kHz with a phase lead of 60–120°, as expected of a displacement current. The movement was outward with depolarization, but the holding potential only weakly influenced the amplitude of the movement. In contrast, cells transfected with a noninactivating mutant of Shaker K+channels showed similar movements, but these were sensitive to the holding potential; decreasing with depolarization between ?80 and 0 mV. Searching for artifactual origins of these movements, we used open or sealed pipettes and AFM cantilever placements just above the cells. These results were negative, suggesting that the observed movements were produced by the cell membrane rather than by movement of the patch pipette, or by acoustic or electrical interactions of the membrane with the AFM tip. In control cells, the electrical motor may arise from the flexoelectric effect, where changes in potential induce changes in curvature. In transfected cells, it appears that channel-specific movements also occurred. These experiments demonstrate that the AFM may be able to exploit voltage-dependent movements as a source of contrast for imaging membrane components. The electrically induced motility will cause twitching during action potentials, and may have physiological consequences.

Mosbacher, J.; Langer, M.; Horber, J.K.H.; Sachs, F.

1998-01-01

140

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

141

Measurement of electrode-tissue interface impedance for improvement of a transcutaneous data transmission using human body as transmission medium.  

PubMed

The electrical property between an electrode and skin or tissue is one of the important issues for communication performance of the transcutaneous communication system (TCS) using a human body as a conductive medium.In this study, we used a simple method to measure interface resistance between the electrode and skin on the surface of the body. The electrode-electrode impedance was measured by a commercially available LCR meter with changes in the distance between two electrodes on an arm of a healthy male subject, and we obtained the tissue resistivity and electrode-skin interface resistance using the cross-sectional area of the arm.We also measured transmission gain of the TCS on the surface of the body, and we investigated the relationship between electrode-skin interface resistance and transmission gain. We examined four kinds of electrodes: a stainless steel electrode, a titanium electrode, an Ag-AgCl electrode and an Ag-AgCl paste electrode. The stainless steel electrode, which had lower electrode-skin resistance, had higher transmission gain.The results indicate that an electrode that has lower electrode-skin resistance will contribute to improvement of the performance of the TCS and that electrode-skin interface resistance is one of valuable evaluation parameters for selecting an optimum electrode for the TCS. PMID:24948457

Okamoto, Eiji; Kato, Yoshikuni; Kikuchi, Sakiko; Mitamura, Yoshinori

2014-01-01

142

A fluid model of the current-voltage characteristics of an electron emitting electrode immersed in a two electron temperature plasma  

NASA Astrophysics Data System (ADS)

The current voltage characteristics of a negatively biased electron emitting electrode immersed in a two-electron temperature plasma are analyzed by a simple one dimensional fluid model. Based on the assumption that the electron density in the pre-sheath region obeys the Boltzmann law the Bohm criterion is derived in the form of a transcendental equation for the Mach number, which can have up to 3 solutions. According to these solutions the ion velocity at the sheath edge can be determined either by the hot or by the cool electron temperature. When it is determined by the cool electron temperature and the hot electron temperature is high enough the critical electron emission current from the collector can have a very pronounced local maximum and a minimum when regarded as a function of the electrode potential. Because of that the current voltage characteristics of the electrode may exhibit up to 3 different floating potentials. This result is in good agreement with the experimental observations reported in [J. Appl. Phys. 63, 5674 (1988)].

Gyergyek, T.; ?er?ek, M.

2007-06-01

143

Flexible electrode belt for EIT using nanofiber web dry electrodes.  

PubMed

Efficient connection of multiple electrodes to the body for impedance measurement and voltage monitoring applications is of critical importance to measurement quality and practicality. Electrical impedance tomography (EIT) experiments have generally required a cumbersome procedure to attach the multiple electrodes needed in EIT. Once placed, these electrodes must then maintain good contact with the skin during measurements that may last several hours. There is usually also the need to manage the wires that run between the electrodes and the EIT system. These problems become more severe as the number of electrodes increases, and may limit the practicality and portability of this imaging method. There have been several trials describing human-electrode interfaces using configurations such as electrode belts, helmets or rings. In this paper, we describe an electrode belt we developed for long-term EIT monitoring of human lung ventilation. The belt included 16 embossed electrodes that were designed to make good contact with the skin. The electrodes were fabricated using an Ag-plated PVDF nanofiber web and metallic threads. A large contact area and padding were used behind each electrode to improve subject comfort and reduce contact impedances. The electrodes were incorporated, equally spaced, into an elasticated fabric belt. We tested the electrode belt in conjunction with the KHU Mark1 multi-frequency EIT system, and demonstrate time-difference images of phantoms and human subjects during normal breathing and running. We found that the Ag-plated PVDF nanofiber web electrodes were suitable for long-term measurement because of their flexibility and durability. Moreover, the contact impedance and stability of the Ag-plated PVDF nanofiber web electrodes were found to be comparable to similarly tested Ag/AgCl electrodes. PMID:22945587

Oh, Tong In; Kim, Tae Eui; Yoon, Sun; Kim, Kap Jin; Woo, Eung Je; Sadleir, Rosalind J

2012-10-01

144

Voltage Clamp Fluorometric Measurements on a Type II Na+-coupled Pi Cotransporter: Shedding Light on Substrate Binding Order  

PubMed Central

Voltage clamp fluorometry (VCF) combines conventional two-electrode voltage clamp with fluorescence measurements to detect protein conformational changes, as sensed by a fluorophore covalently attached to the protein. We have applied VCF to a type IIb Na+-coupled phosphate cotransporter (NaPi-IIb), in which a novel cysteine was introduced in the putative third extracellular loop and expressed in Xenopus oocytes. Labeling this cysteine (S448C) with methanethiosulfonate (MTS) reagents blocked cotransport function, however previous electrophysiological studies (Lambert G., I.C. Forster, G. Stange, J. Biber, and H. Murer. 1999. J. Gen. Physiol. 114:637–651) suggest that substrate interactions with the protein can still occur, thus permitting study of a limited subset of states. After labeling S448C with the fluorophore tetramethylrhodamine MTS, we detected voltage- and substrate-dependent changes in fluorescence (?F), which suggested that this site lies in an environment that is affected by conformational change in the protein. ?F was substrate dependent (no ?F was detectable in 0 mM Na+) and showed little correlation with presteady-state charge movements, indicating that the two signals provide insight into different underlying physical processes. Interpretation of ion substitution experiments indicated that the substrate binding order differs from our previous model (Forster, I., N. Hernando, J. Biber, and H. Murer. 1998. J. Gen. Physiol. 112:1–18). In the new model, two (rather than one) Na+ ions precede Pi binding, and only the second Na+ binding transition is voltage dependent. Moreover, we show that Li+, which does not drive cotransport, interacts with the first Na+ binding transition. The results were incorporated in a new model of the transport cycle of type II Na+/Pi cotransporters, the validity of which is supported by simulations that successfully predict the voltage and substrate dependency of the experimentally determined fluorescence changes.

Virkki, Leila V.; Murer, Heini; Forster, Ian C.

2006-01-01

145

The influence of subgap features in the electromodulation and built-in voltage measurements of polyfluorene blue light-emitting diodes with anodic charge injection layers  

NASA Astrophysics Data System (ADS)

We report on electroabsorption (EA) and built-in voltage (VBI) measurements of polymer light-emitting diodes with the general structure ITO/PEDOT:PSS/emitting polymer/LiF/Ca/Al where ITO is indium tin oxide, PEDOT:PSS is poly(3,4-ethylene dioxythiophene) doped with poly(styrene sulfonate), and the emitting polymer is either poly(9,9-dioctylfluorene), poly(9, 9-dioctyl-fluorene-alt-bis-N,N'-(4-butyl-phenyl)-bis-N, N'-phenyl-1, 4-phenylenediamine), or poly(9,9-dioctylfluorene-alt-N-(4-butylphenyl)-diphenylamine). We find that the EA nulling voltage, i.e., the dc bias at which the EA signal vanishes, depends on the frequency of the ac voltage and on the incident photon wavelength. Such dependence poses a problem for accurate measurement of the built-in voltage (VBI), which is the voltage generated between the electrodes upon equilibration of the Fermi levels through the heterostructure. We find that the EA signal is mixed with a smaller intensity signal which can be ascribed to excited state absorption (ESA). We propose a method for separating the excited state absorption signal and producing accurate VBI measurements. We also demonstrate that in our devices the ESA contribution to the electromodulated (?T/T) signal is negligible with respect to the accuracy with which VBI can be determined from the nulling voltage of ?T/T and can thus be safely ignored.

Bodrozic, Vladimir; Roberts, M.; Phillips, N.; Burroughes, J. H.; Mian, Shabbir; Cacialli, Franco

2007-04-01

146

Realization of the kilogram by measuring at 100 kV with the voltage balance ETF  

Microsoft Academic Search

The possibilities for adapting the existing electrostatic device known as the voltage balance ETF-84, to work with a voltage of 100 kV and a weight of 1 kg, are considered. A few theoretical analyses, experiments, and computer simulations have been carried out to define the measurement procedure needed at the required level of uncertainty of 1 part in 108. These

Vojislav Bego; Josip Butorac; D. Ilic

1999-01-01

147

Rotor position sensing in switched reluctance motor drives by measuring mutually induced voltages  

Microsoft Academic Search

This paper describes a new method of indirect rotor position sensing for switched reluctance motor (SRM) drives. The principle is based on measuring the mutually induced voltage in an inactive phase which is either adjacent or opposite to the energized phase of an SRM. The mutual voltage in the “off” phase, induced due to the current in the active phase,

Iqbal Husain; Mehrdad Ehsani

1994-01-01

148

Expanded electrochemical capabilities of the electrospray ion source using porous flow-through electrodes as the upstream ground and emitter high-voltage contact.  

PubMed

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. PMID:16351154

Van Berkel, Gary J; Kertesz, Vilmos

2005-12-15

149

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

150

Simultaneous multi-site recordings of neural activity with an inline multi-electrode array and optical measurement in rat hippocampal slices  

Microsoft Academic Search

Understanding neuronal network function requires multi-site recording. An optical imaging method using voltage-sensitive dyes (VSD) is one such suitable method. It is also important to complement this technique with methods that measure other physiological parameters of neuronal network activity. We aimed to develop a multi-channel electrode method that would easily permit the simultaneous optical imaging of neural activity in vitro.

Takashi Tominaga; Yoko Tominaga; Michinori Ichikawa

2001-01-01

151

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

152

Direct current dielectric barrier discharges under voltages below the ionization potential of neutrals in electrode systems with one-dimensional nanostructures  

SciTech Connect

We experimentally investigate the characteristics of dielectric barrier discharges in an electrode system with one-dimensional nanostructures of gap size at micrometer scale. Evidence of quasistationary direct current discharges in air has been observed under the applied voltage several times lower than the first ionization potential of O{sub 2}. The results qualitatively agree with the hypothesis on the ionization mechanism of stepwise inelastic collisions within a metastable pool, which is populated through field excitation and inelastic impact between the neutrals and the nanostructures.

Hou Zhongyu; Wang Yanyan; Cai Bingchu [National Key Laboratory of Micro/Nano Fabrication Technology, Key Laboratory for Thin Film and Microfabrication of Ministry of Education, Research Institute of Micro/Nano Science and Technology, Shanghai Jiao Tong University, Shanghai 200030 (China); Zhou Weimin [Shanghai Nanotechnology Promotion Center, Shanghai 200237 (China)

2011-02-07

153

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

154

Gravimetric Electrochemical Voltage Spectroscopy: In Situ Mass Measurements during Electrochemical Doping of the Conducting Polymer Polypyrrole  

NASA Astrophysics Data System (ADS)

A new technique is described for direct measurement of mass changes of a conducting polymer electrode during electrochemical cycling. A quartz microbalance is used, with one of its contacts serving as the working electrode. Its high sensitivity permits resolution of mass changes less than 100 ng/cm2. The results demonstrate that on reduction of poly(pyrrole perchlorate), charge compensation is achieved by diffusion of the lithium cation into the polymer and not the perchlorate anion into solution.

Kaufman, J. H.; Kanazawa, K. Keiji; Street, G. B.

1984-12-01

155

Improvement in low-voltage performance of surface-electrode soft-X-ray detectors composed of undoped homoepitaxial CVD/HPHT Ib diamond layers  

NASA Astrophysics Data System (ADS)

We have successfully fabricated diamond soft-X-ray (SXR) detectors with interdigitated surface electrodes that significantly improve the low-voltage performance using high-quality chemical-vapour-deposited (CVD) diamond films homoepitaxially grown on high-pressure/high-temperature-synthesised (HPHT) diamond Ib substrates. In the present study, the collection efficiencies of photon-excited carriers were evaluated using monochromatised SXRs at applied voltages ?12 V for two types of diamond detectors with different stacking structures of the CVD layers. We found that the diamond detectors with an electrically floating B-doped layer sandwiched between two undoped CVD layers yield significantly larger carrier collection efficiencies compared to those without an inserted B-doped layer, even under the no-applied-voltage condition; moreover, the carrier collection efficiencies only slightly increase with increases in applied voltages below 12 V. This result indicates that the inserted B-doped layer can work independently (without electrical connection to any external circuit) as a potential barrier against carrier diffusions to a HPHT diamond substrate with much poorer quality than CVD diamond film of a photon absorption layer. The detector performances are discussed relative to the potential distribution formed in the active undoped diamond layer and the crystalline quality, which is based on the cathodoluminescence intensity of exciton emissions at room temperature.

Kanasugi, M.; Iwakaji, Y.; Yamamoto, T.; Maida, O.; Takeda, Y.; Saitoh, Y.; Ito, T.

2010-09-01

156

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

NASA Astrophysics Data System (ADS)

The performance of interdigitated electrodes for impedance measurements in a microfluidic assay chamber is dependent upon the geometric design of the electrode pattern and can be significantly impacted by variability or defects in manufacturing or materials. For processes which rely on precise electrode performance, it is necessary to minimize variation through robust design and quality control. An interdigitated electrode design was investigated to identify design strategies which maximize electrode sensitivity and minimize performance variability in produced parts, while potentially reducing the complexity of quality testing. Several configurations were developed to address these goals by increasing the sensing region for a specified electrode area and creating designs which can be easily manufactured with low variability. Design modifications included alterations to interdigitated finger orientation, finger geometry, and gap width. Test findings indicate that optimal designs contain narrow gap widths with electrode fingers parallel to the longest dimension of the electrode. These benefits may be further enhanced by replacing straight finger edges with geometrical features, such as scalloped edges. The design changes identified can be used to improve interdigitated electrode performance for an array of applications and to reduce performance variability caused by variation in the manufacturing process.

Donoghue, Linda; Anthony, Brian W.

2012-02-01

157

Demonstration of the two-chamber approach for high-voltage measurements using collinear laser spectroscopy  

NASA Astrophysics Data System (ADS)

An electronic measurement of high-voltages of several ten kV with accuracy as required for precision experiments is currently only feasible using highly sophisticated voltage dividers. Collinear laser spectroscopy can provide a direct and precise measurement of high-voltages using the Doppler shift of accelerated ions. Although proposed already in 1982, a measurement with relative accuracy better than 10-4 was not reported so far. To improve this accuracy, a dedicated new setup for high-voltage measurements will be installed at the Technische Universität Darmstadt. A two-chamber approach will be used to remove uncertainties due to the insufficiently known starting potential inside the ion source. Here we present a demonstration of the pump-and-probe technique performed in preparatory studies at the TRIGA-LASER experiment in Mainz.

Will, Elisa; Ullmann, Johannes; Frömmgen, Nadja; Geppert, Christopher; Gorges, Christian; Hammen, Michael; Kaufmann, Simon; Krieger, Andreas; Nörtershäuser, Wilfried

2014-06-01

158

Demonstration of the two-chamber approach for high-voltage measurements using collinear laser spectroscopy  

NASA Astrophysics Data System (ADS)

An electronic measurement of high-voltages of several ten kV with accuracy as required for precision experiments is currently only feasible using highly sophisticated voltage dividers. Collinear laser spectroscopy can provide a direct and precise measurement of high-voltages using the Doppler shift of accelerated ions. Although proposed already in 1982, a measurement with relative accuracy better than 10-4 was not reported so far. To improve this accuracy, a dedicated new setup for high-voltage measurements will be installed at the Technische Universität Darmstadt. A two-chamber approach will be used to remove uncertainties due to the insufficiently known starting potential inside the ion source. Here we present a demonstration of the pump-and-probe technique performed in preparatory studies at the TRIGA-LASER experiment in Mainz.

Will, Elisa; Ullmann, Johannes; Frömmgen, Nadja; Geppert, Christopher; Gorges, Christian; Hammen, Michael; Kaufmann, Simon; Krieger, Andreas; Nörtershäuser, Wilfried

2014-04-01

159

>750 mV open circuit voltage measured on 50 ?m thick silicon heterojunction solar cell  

NASA Astrophysics Data System (ADS)

This paper presents experimental evidence that silicon solar cells can achieve >750 mV open circuit voltage at 1 Sun illumination providing very good surface passivation is present. 753 mV local open circuit voltage was measured on a 50 ?m thick non-metalized silicon heterojunction solar cell. The paper also considers a recombination model at open circuit based on the recent Auger and radiative recombination parameterization and the measured surface saturation current density. The loss mechanisms at open circuit and several practical pathways to achieve >760 mV open circuit voltage in silicon heterojunction solar cells are discussed.

Herasimenka, Stanislau Y.; Dauksher, William J.; Bowden, Stuart G.

2013-07-01

160

Flash X-Ray (FXR) Accelerator Optimization - Beam-induced Voltage Simulation and TDR Measurements  

SciTech Connect

Lawrence Livermore National Laboratory (LLNL) is evaluating design alternatives to improve the voltage regulation in our Flash X-Ray (FXR) accelerator cell and pulse-power system. The goal is to create a more mono-energetic electron beam that will create an x-ray source with a smaller spot-size. Studying the interaction of the beam and accelerator cell will generate improved designs for high-current accelerators at Livermore and elsewhere. When an electron beam crosses the energized gap of an accelerator cell, the electron energy is increased. However, the beam with the associated electromagnetic wave also looses a small amount of energy because of the increased impedance seen across the gap. The phenomenon is sometimes called beam loading. It can also be described as a beam-induced voltage at the gap which is time varying. This creates beam energy variations that we need to understand and control. A high-fidelity computer simulation of the beam and cell interaction has been completed to quantify the time varying induced voltage at the gap. The cell and pulse-power system was characterized using a Time-domain Reflectometry (TDR) measurement technique with a coaxial air-line to drive the cell gap. The beam-induced cell voltage is computed by convoluting the cell impedance with measured beam current. The voltage was checked against other measurements to validate the accuracy. The simulation results predicted that there are significant beam-induced gap voltage variations. Beam-induced voltages from different current profiles and cell impedances were simulated and compared. This allows us to predict the effect on voltage regulation for different design alternatives before making hardware changes and high-voltage testing. The beam-induced voltages are incorporated into a larger accelerator system-model to quantify their effect on total beam energy variations.

Ong, M M; Vogtlin, G E

2004-04-07

161

Kerr Cell System for the Measurement of High Voltage Transient Pulses  

NASA Astrophysics Data System (ADS)

An optical method using the Kerr effect is reported for the measurement of high voltage transient pulses with benzonitrile, acrylonitrile, propionitrile, butyronitrile and m-nitrotoluene for the first time along with nitrobenzene and acetone that are well known. These investigations have been performed using high voltage pulse fields ranging from 5×105 vm-1 to 107 vm-1. The experimentally measured values of the electric field from the Kerr signals are found to be in excellent agreement with applied field.

Rajagopal, Krishnamurthy; Rao, Tetali

1995-10-01

162

Evaluating the reliability and sensitivity of the Kerr electro-optic field mapping measurements with high-voltage pulsed transformer oil  

NASA Astrophysics Data System (ADS)

Transformer oil is the most widely used dielectric liquid for high voltage insulation. Measurements of the electric field distribution in high voltage pulsed transformer oil are of both practical and theoretical interests. Due to its low Kerr constant, previous electro-optic measurements with transformer oil rely on a technique called ac modulation, which works only for dc steady-state electric field mapping. With the help of a high-sensitivity charge-coupled device, we directly measure the Kerr electro-optic effect between parallel electrodes in transformer oil stressed by high voltage pulses. This work aims at demonstrating the reliability and evaluating the sensitivity of the measurements for three cases with identical electrodes: space-charge free, uniform electric field in the mid-region of the gap; space-charge free, non-uniform fringing electric field; and space charge distorted electric field in the mid-region of the gap. Future directions to improve accuracy by identifying and handling various sources of error and noise are suggested.

Zhang, X.; Nowocin, J. K.; Zahn, M.

2013-08-01

163

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

164

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

NASA Astrophysics Data System (ADS)

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 ?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.

2007-07-01

165

Relationship between Work Function of Hole Collection Electrode and Temperature Dependence of Open-Circuit Voltage in Multilayered Organic Solar Cells  

NASA Astrophysics Data System (ADS)

We have investigated the photovoltaic properties of multilayered organic photovoltaic devices consisting of indium tin oxide (ITO)/(NiO)/donor/C60/bathocuproine (BCP)/Al structures. Open circuit voltage (VOC) increases with the decrease in temperature between 40 and 350 K. The VOC was, however, pinned at approximately 0.6 V for the device without NiO, probably owing to the insufficient work-function difference between ITO and Al electrodes. The hole injection was also markedly suppressed at the ITO/donor interface in the device with large IP donor materials without the buffer layer and abnormal S-shaped current density--voltage (J--V) characteristics were observed. On the other hand, the value of VOC increases with the increase in ionization potential (IP) of donor materials in the device with NiO buffer layers owing to the enhanced work-function difference of about 1 eV, and the S-shaped curves disappeared at the high temperatures above 200 K. The VOC is further improved to nearly 1.2 V by the UV--ozone treatment of the NiO surface. We have therefore concluded that the increment of work function of the anode caused by the insertion of an oxide buffer layer and the surface treatment of the electrode by UV--ozone treatment are essentially important for the improvement of VOC and charge transport/injection properties in the multilayered organic solar cell applications.

Itoh, Eiji; Shirotori, Toshiki

2012-02-01

166

Zeptomole voltammetric detection and electron-transfer rate measurements using platinum electrodes of nanometer dimensions.  

PubMed

The characterization of quasi-hemispherical Pt electrodes of nanometer dimensions (radius 2-150 nm), prepared by electrophoretic coating of etched Pt wires with poly-(acrylic acid), is described. The goals of these experiments are to estimate the accuracy of using steady-state voltammetric limiting currents (i(lim)) in determining the true electrode area and to develop new electrochemical methods for rapidly screening individual electrodes for non-ideal geometries. Electrochemical active areas were determined by measuring the electrical charge (Q) associated with oxidation of adsorbed bis(2,2'-bipyridine)chloro(4,4'-trimethylenedipyridine)osmium(II) in fast-scan voltammetric measurements (scan rate 1000 V/s). Voltammetric peaks corresponding to oxidation of as few as approximately 7000 molecules (approximately 11 zmol) at individual electrodes are reported, allowing precise measurement of electrode areas as small as approximately 10(-10) cm2. A plot of i(lim) (for a soluble redox species) versus Q1/2 (for an adsorbed redox species), constructed from i(lim)-Q1/2 data pairs obtained as a function of the electrode radius, is shown to be linear if the electrode geometry is independent of electrode radius; departure of experimental values from the straight-line plot is a diagnostic indicator of a nonideal electrode geometry. The results indicate that approximately 50% of the electrodes prepared by the electrophoretic polymer-coating procedure are quasi-hemispherical, the remaining being recessed slightly below the polymer coating. The heterogeneous electron-transfer rate constant for the oxidation of the ferrocenylmethyltrimethylammonium cation in H2O/ 0.2 M KCl was also determined from steady-state voltammetry using the method of Mirkin and Bard and found to be 4.(8) +/- 3.(2) cm/s with alpha = 0.6(4) +/- 0.1(5). PMID:14632106

Watkins, John J; Chen, Jinyuan; White, Henry S; Abruña, Héctor D; Maisonhaute, Emmanuel; Amatore, Christian

2003-08-15

167

Pinch dynamics deduced from terminal current and voltage measurements in a Dense Plasma Focus  

NASA Astrophysics Data System (ADS)

Terminal measurements of current and voltage in a dense plasma focus (DPF) are used with a circuit model to deduce the dynamical evolution of the plasma inductance. This inductance in turn gives the dynamical impedance and hence the peak voltage at the pinch, which is found to be ˜50kV or higher, for a ˜10kV bank voltage. Measurements are described of pinches in a 130kA and a 300kA DPF, with various gases. The dynamical inductance also measures the evolution of the radius of the current carrying region of the imploding pinch. The high pinch voltages and small pinch radii shed light on the neutron production mechanism in such DPFs.

Krishnan, Mahadevan; Bures, Brian; Madden, Robert

2010-11-01

168

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

169

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

170

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

171

Selection of the Optimum Electrospray Voltage for Gradient Elution LC-MS Measurements  

SciTech Connect

Changes in liquid composition during gradient elution liquid chromatography (LC) and mass spectrometry (MS) analyses affect the electrospray operation. To establish methodologies for judicious selection of the electrospray voltage, we monitored in real-time the effect of the LC gradient on the spray current. The optimum range of the electrospray voltage shifted to lower values as the concentration of organic solvent in the eluent increased during reversed-phase LC analyses. These results provided the means to rationally select the voltage that ensured successful electrospray operation throughout gradient elution LC-MS experiments. A small run-to-run drift in the spray current was observed for electrosprays operated at constant voltage. This could be the result of fouling or degradation of the electrospray emitter, which affected the electric field driving the electrospray. Algorithms using feedback from spray current measurements to maintain the electrospray voltage within the optimum operating range throughout gradient elution LC-MS were evaluated. The electrospray operation with voltage regulation and at constant, judiciously selected voltage during gradient elution LC-MS measurements produced data with similar reproducibility.

Marginean, Ioan; Kelly, Ryan T.; Moore, Ronald J.; Prior, David C.; Lamarche, Brian L.; Tang, Keqi; Smith, Richard D.

2009-04-01

172

Plastic pH electrodes for the measurement of gastrointestinal pH.  

PubMed Central

Plastic electrodes have been developed for measuring pH in the human gastrointestinal tract. The electrodes have a plastic hydrogen ion sensitive membrane sealed to a length of fluid filled PVC tubing. Two recently developed hydrogen ion sensitive ligands have been examined. Their operational characteristics have been described. These electrodes have an electrical response of 52 to 58 mV/pH unit change in the range pH 4-9, with a diminished response outwith this range. They have a low resistance value and a fast response time of one second to reach 90% of their maximum response. The electrodes can be passed down the biopsy channel of an endoscope to obtain mucosal pH readings under direct vision. Readings obtained in this way using plastic electrodes are comparable to those obtained with glass electrodes. Alternatively, these electrodes can be joined to a Crosby capsule, allowing continuous recording of mucosal pH through to the jejunum during jejunal biopsy procedures. These electrodes can be used repeatedly or may be acceptable as inexpensive disposable items for sterile clinical use. Images Fig. 1

Rawlings, J M; Lucas, M L

1985-01-01

173

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

174

Development of apparatus for performing rapid capacitance-voltage measurements on MIS structures. Technical memo  

Microsoft Academic Search

This report discusses the design of a complete experimental system for the observation of radiation effects in metal-insulator-semiconductor (MIS) capacitors by use of a rapid, repetitive capacitance-voltage (C-V) measurement technique. The apparatus includes trigger and control-signal generators, bias voltage sources, a sample holder with temperature control and radiation dosimetry, and a high-speed sample capacitance monitor. In typical operation, this apparatus

Boesch; H. E. Jr

1976-01-01

175

Development of apparatus for performing rapid capacitance-voltage measurements on MIS structures  

Microsoft Academic Search

This report discusses the design of a complete experimental system for the observation of radiation effects in metal-insulator-semiconductor (MIS) capacitors by use of a rapid, repetitive capacitance-voltage (C-V) measurement technique. The apparatus includes trigger and control-signal generators, bias voltage sources, a sample holder with temperature control and radiation dosimetry, and a high-speed sample capacitance monitor. In typical operation, this apparatus

H. E. Boesch Jr.

1976-01-01

176

Development of Low-Frequency AC Voltage Measurement System Using Single-Junction Thermal Converter  

NASA Astrophysics Data System (ADS)

Accurate measurement of low-frequency AC voltage using a digital multimeter at frequencies of 4-200Hz is a challenge in the mechanical engineering industry. At the National Metrology Institute of Japan, we developed a low-frequency AC voltage measurement system for calibrating digital multimeters operating at frequencies down to 1 Hz. The system uses a single-junction thermal converter and employs a theoretical model and a three-parameter sine wave fitting algorithm based on the least-square (LS) method. We calibrated the AC voltage down to 1Hz using our measurement system and reduced the measurement time compared with that using thin-film thermal converters. Our measurement results are verified by comparison with those of a digital sampling method using a high-resolution analog-to-digital converter; our data are in agreement to within a few parts in 105. Our proposed method enables us to measure AC voltage with an uncertainty of 25 ?V/V (k = 1) at frequencies down to 4 Hz and a voltage of 10 V.

Amagai, Yasutaka; Nakamura, Yasuhiro

177

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

178

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

179

In vivo measurements of structure/electrode position changes during respiration for Electrical Impedance Tomography  

NASA Astrophysics Data System (ADS)

For pulmonary applications of 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 change tend to introduce artifacts to EIT images of the thorax. Since EIT reconstruction is an ill-posed inverse problem, any inaccurate assumptions of object may cause large artifacts in reconstructed images. Accurate information on structure/electrode position changes is necessary to understand factors contributing to the measured resistivity changes and to improve EIT reconstruction algorithm. In this study, in vivo structure/electrode position changes from a healthy male volunteer are investigated during respiration cycle at two levels, the nipple line level and the level approximately 5 cm below. For each level, sixteen fiduciary markers are equally spaced around the surface, the same as the electrode placement for EIT measurements. A MR scanner with respiration-gated ability is used to acquire images of the thorax. MR thoracic images are prospectively acquired corresponding temporally to specific time periods within respiration cycle (FRC, mid tidal volume, tidal volume). The chest expansions in anterior-posterior and lateral directions and inside tissue/organ position changes are then analyzed. The electrode position changes corresponding to different phases of respiration cycle are also measured.

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

2010-04-01

180

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

181

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

182

Electron trapping, storing, and emission in nanocrystalline Si dots by capacitance-voltage and conductance-voltage measurements  

Microsoft Academic Search

Temperature and frequency dependent electrical properties of SiO2\\/nanocrystalline Si (nc-Si)\\/SiO2 sandwich structures have been studied. A clear shift of the capacitance-voltage and conductance-voltage characteristics toward positive gate voltage suggests electron trapping in an nc-Si dot. The role of interface states and deep traps in our devices has also been thoroughly examined and shown to be unimportant on the overall device

Shaoyun Huang; Souri Banerjee; Raymond T. Tung; Shunri Oda

2003-01-01

183

Effects of electrode geometry and cell location on single-cell impedance measurement  

Microsoft Academic Search

Measurements on single cells provide more accurate and in-depth information about electrical properties than those on pathological tissues. The relationship between electrode geometry and the location of a cell on microfluidic devices greatly affects the accuracy of single-cell impedance measurement. Accordingly, this study presents numerical solutions from the FEM simulation of the COMSOL multiphysics package and experimental measurements to analyze

Ji-Wei Wang; Min-Haw Wang; Ling-Sheng Jang

2010-01-01

184

Optimizing Electrode Configuration for Electrical Impedance Measurements of Muscle via the Finite Element Method  

PubMed Central

Electrical impedance myography (EIM) is a technique for the evaluation of neuromuscular diseases, including amyotrophic lateral sclerosis and muscular dystrophy. In this study, we evaluated how alterations in the size and conductivity of muscle and thickness of subcutaneous fat impact the EIM data, with the aim of identifying an optimized electrode configuration for EIM measurements. Finite element models were developed for the human upper arm based on anatomic data; material properties of the tissues were obtained from rat and published sources. The developed model matched the frequency-dependent character of the data. Of the three major EIM parameters, resistance, reactance, and phase, the reactance was least susceptible to alterations in the subcutaneous fat thickness, regardless of electrode arrangement. For example, a quadrupling of fat thickness resulted in a 375% increase in resistance at 35 kHz but only a 29% reduction in reactance. By further optimizing the electrode configuration, the change in reactance could be reduced to just 0.25%. For a fixed 30 mm distance between the sense electrodes centered between the excitation electrodes, an 80 mm distance between the excitation electrodes was found to provide the best balance, with a less than 1% change in reactance despite a doubling of subcutaneous fat thickness or halving of muscle size. These analyses describe a basic approach for further electrode configuration optimization for EIM.

Jafarpoor, Mina; Li, Jia; White, Jacob K.; Rutkove, Seward B.

2014-01-01

185

Electrochemical impedance measurement of prostate cancer cells using carbon nanotube array electrodes in a microfluidic channel  

NASA Astrophysics Data System (ADS)

Highly aligned multi-wall carbon nanotubes were synthesized in the shape of towers and embedded into fluidic channels as electrodes for impedance measurement of LNCaP human prostate cancer cells. Tower electrodes up to 8 mm high were grown and easily peeled off a silicon substrate. The nanotube electrodes were then successfully soldered onto patterned printed circuit boards and cast into epoxy under pressure. After polishing the top of the tower electrodes, RF plasma was used to enhance the electrocatalytic effect by removing excess epoxy and activating the open end of the nanotubes. Electrodeposition of Au particles on the plasma-treated tower electrodes was done at a controlled density. Finally, the nanotube electrodes were embedded into a polydimethylsiloxane (PDMS) channel and electrochemical impedance spectroscopy was carried out with different conditions. Preliminary electrochemical impedance spectroscopy results using deionized water, buffer solution, and LNCaP prostate cancer cells showed that nanotube electrodes can distinguish the different solutions and could be used in future cell-based biosensor development.

Heung Yun, Yeo; Dong, Zhongyun; Shanov, Vesselin N.; Schulz, Mark J.

2007-11-01

186

Determination of HID electrode falls in a model lamp I: Pyrometric measurements  

NASA Astrophysics Data System (ADS)

To verify models describing the near-electrode regions electrodes of pure and doped tungsten for high intensity discharge lamps are investigated in a special model lamp. It can be operated with arc currents of 1 A to 10 A, DC or AC with arbitrary waveforms up to a few kHz. Argon and xenon, at pressures from 0.1 MPa to 1 MPa, are used as fill gases. A large variety of electrodes can be inserted. To perform spatially resolved measurements they are displaced reproducibly within the discharge tube during lamp operation. Spatially resolved pyrometric measurements of the electrode surface temperature in the case of DC operation are presented. From the temperature distribution the power loss of the electrodes by thermal radiation and heat conduction is determined. It increases almost linearly with the arc current at the anode and less than linear at the cathode. A relation is deduced between the cathode fall and the power fed into the cathode setting up the power balance of the cathodic current transfer zone. The resulting cathode falls show a strong dependence on the electrode diameter. Electrical measurements of separate cathode and anode falls are given in a subsequent paper. The outcomes of both methods and of modelling are compared in a third paper.

Dabringhausen, L.; Nandelstädt, D.; Luhmann, J.; Mentel, J.

2002-07-01

187

Optical dc current and voltage measurement by superposing ac magnetic or electric field  

Microsoft Academic Search

Optical DC current and voltage measurement using Faraday or Pockels effect necessitates the compensation of light intensity variation with some methods, because it is possible the intensity variation may give rise to a measuring error. We have proposed a method which suggests superposing AC magnetic field on linearly polarized light or AC electric field on elliptically polarized light and compensating

Masaru Higaki; Kunio Fujii; Shizuo Yamaguchi

1999-01-01

188

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

189

On the design of capacitive sensors using flexible electrodes for multipurpose measurements.  

PubMed

This article evaluates the potential of capacitive measurements using flexible electrodes to access various physical quantities. These electrodes are made of a thin metallic film, typical thickness 0.2 microm, evaporated on a plastic substrate. Their large flexibility enables them to be mounted in complex geometries such as curved surfaces. In the configuration of planar condensers, using a very sensitive commercial capacitive bridge and a three-terminal measurement method, several measurements are presented. A relative resolution of 10(-8) for the thermal expansion of samples is obtained at low temperature in a differential configuration. The same technique adopted for pressure gauge measurements at low temperature led to a typical 0.1 Pa resolution over a dynamic range of 10(4) Pa. In the configuration of interleaved electrodes, condensers have been used to measure wetting by either bulk liquid helium or by thin continuous helium films in a cylindrical pipe. Both experimental and numerical evidence is provided, showing that the close proximity of a reference ground potential significantly increases the relative sensitivity to fluid wetting. Further, interleaved electrodes can be used to access both the area that is covered by a liquid film but also to determine the thickness of this film, provided it is comparable to the periodicity of the electrode pattern. PMID:17477677

Thibault, Pierre; Diribarne, Pantxo; Fournier, Thierry; Perraud, Sylvain; Puech, Laurent; Wolf, P-Etienne; Rousset, Bernard; Vallcorba, Roser

2007-04-01

190

Measurements of H- Density and Work Function of a Plasma Electrode in a Negative Ion Source  

NASA Astrophysics Data System (ADS)

The correlation between the work function of the plasma electrode of a H- ion source and H- density was investigated in H2 plasma, which contains the vapor of an alkali metal (cesium or rubidium). For the work function measurement, the photoelectric current was measured with laser irradiation to the plasma electrode, while the negative ion signal was measured by the laser photodetachment technique simultaneously with an electrostatic probe. As the work function of the plasma electrode was reduced due to alkali metal adsoption, the ratio of H- density to electron density, n-/ne, increased gradually. The n-/ne ratio became the maximum value when the work function reached the minimum value. The measured work function was well correlated with the n-/ne ratio. The dependence of plasma parameters on the discharge current is compared between pure H2 and H2 + (Rb/Cs) mixture discharge.

Nishiura, M.; Sasao, M.; Wada, M.

2002-11-01

191

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

192

Flash X-Ray (FXR) Accelerator Optimization Beam-induced Voltage Simulation and TDR Measurements  

SciTech Connect

Lawrence Livermore National Laboratory (LLNL) is evaluating design alternatives to improve the voltage regulation in our Flash X-Ray (FXR) accelerator cell and pulse-power system. The goal is to create a more mono-energetic electron beam. When an electron beam crosses the energized gap of an accelerator cell, the electron energy is increased. However, the beam with the associated electromagnetic wave also looses a small amount of energy because of the increased impedance seen across the gap. The beam-induced voltage at the gap is time varying. This creates beam energy variations that we need to understand and control. A high-fidelity computer simulation of the beam and cell interaction has been completed to quantify the time varying induced voltage at the gap. The cell and pulse-power system was characterized using a Time-domain Reflectometry (TDR) measurement technique with a coaxial air-line to drive the cell gap. The beam-induced cell voltage is computed by convoluting the cell impedance with measured beam current. The voltage was checked against other measurements to validate the accuracy.

Ong, M M; Vogtlin, G E

2005-05-12

193

In situ TEM study of platinum electrode catalysts with 80kV-1MV accelerating voltage  

NASA Astrophysics Data System (ADS)

We perform transmission electron microscopy (TEM) at different accelerating voltages for analysis of complex nano-structures of platinum (Pt) nanoparticle catalysts synthesized on titanium dioxide. TEM images obtained at 80, 200, 300, and 1000kV are carefully compared. The particle size, density and volume of the Pt nanoparticles deposited under different conditions are evaluated using electron tomography. The atomic structures of Pt nanoparticles on the TiO2 and amorphous carbon a surfaces are also investigated using spherical aberration corrected TEM in order to study the diffusion of these Pt nanoparticles and atoms.

Yoshida, K.; Carlsson, A.; Jinschek, J. R.; Stokes, D. J.; Gai, P. L.; Arai, S.; Saitoh, K.; Tanaka, N.

2012-07-01

194

Battery Impedance Measurement by Laplace Transformation of Charge or Discharge Current\\/Voltage  

Microsoft Academic Search

Impedance spectroscopy of Z(omega) is often used in the electrochemical field to analyze electrode reactions and to calculate transient responses. Our previous study measured the overpotential resistance for our thermal behavior model to calculate the temperature rise of Nickel\\/metal-hydride battery or Lithium-ion battery during charge and discharge cycles. However, the Z(omega) measured by AC impedance meter did not agreed with

Masato Nakayama; Kenichi Fukuda; Yoshitake Ohmori; Kenji Wakahara; Takuto Araki; Kazuo Onda

2005-01-01

195

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...

196

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

197

A method for measuring displacement and deformation of electrodes during resistance spot welding  

NASA Astrophysics Data System (ADS)

A new method for measuring the time-dependent displacement and deformation of electrodes during resistance spot welding (RSW) is described. The method allows assessment of the non-stationary thermal expansion of the electrodes. By measuring the electrode indentation close to the weld-piece surface, the method enables a better estimation of indentation than the present methods that rely on measurement of the displacement of the outside part of the electrodes or their holders. The method is based on using a digital video camera to acquire image sequences of electrode caps in the RSW process. A regular pattern of shallow bores is drilled into the caps to enhance the contrast of the acquired images and facilitate image processing. The distances between the bores are analyzed from the image sequences to determine the temporally and spatially resolved displacement and deformation of the caps. The analysis revealed that the cap deformations in some welding regimes can reach up to 20% of the maximum cap displacements, which are approximately 200 µm. The employed image processing algorithms are presented as well as examples of results that demonstrate the applicability of the method.

Kuš?er, Lovro; Polajnar, Ivan; Diaci, Janez

2011-06-01

198

Measurements of the fracture energy of lithiated silicon electrodes of Li-ion batteries.  

PubMed

We have measured the fracture energy of lithiated silicon thin-film electrodes as a function of lithium concentration. To this end, we have constructed an electrochemical cell capable of testing multiple thin-film electrodes in parallel. The stress in the electrodes is measured during electrochemical cycling by the substrate curvature technique. The electrodes are disconnected one by one after delithiating to various states of charge, that is, to various concentrations of lithium. The electrodes are then examined by optical microscopy to determine when cracks first form. All of the observed cracks appear brittle in nature. By determining the condition for crack initiation, the fracture energy is calculated using an analysis from fracture mechanics. In the same set of experiments, the fracture energy at a second state of charge (at small concentrations of lithium) is measured by determining the maximum value of the stress during delithiation. The fracture energy was determined to be ? = 8.5 ± 4.3 J/m(2) at small concentrations of lithium (~Li0.7Si) and have bounds of ? = 5.4 ± 2.2 J/m(2) to ? = 6.9 ± 1.9 J/m(2) at larger concentrations of lithium (~Li2.8Si). These values indicate that the fracture energy of lithiated silicon is similar to that of pure silicon and is essentially independent of the concentration of lithium. Thus, lithiated silicon demonstrates a unique ability to flow plastically and fracture in a brittle manner. PMID:24099504

Pharr, Matt; Suo, Zhigang; Vlassak, Joost J

2013-11-13

199

Identification of quench origins in a superconductor with acoustic emission and voltage measurements  

SciTech Connect

The acoustic emission and voltage measurements were used to identify quench sources in a current-carrying superconductor. The sources identified were (i) conductor motion, (ii) epoxy cracking, and (iii) pure joule heating resulting from the conductor reaching critical current. The combination of these two techniques appears to be a promising diagnostic tool in probing premature quenches in superconductors and superconducting magnets.

Tsukamoto, O.; Maguire, J.; Bobrov, E.; Iwasa, Y.

1981-07-15

200

Agonist and Voltage-Gated Calcium Entry in Cultured Mouse Spinal Cord Neurons Under Voltage Clamp Measured Using Arsenazo Ill  

Microsoft Academic Search

Spinal cord neurons in dissociated cell culture were loaded with the calcium indicator arsenazo Ill using the whole-cell patch-clamp recording technique. Under voltage-clamp, de- polarizing voltage steps evoked transient increases in ab- sorbance at 660 nm, with no change at 570 nm, the isosbestic wavelength for calcium-arsenazo Ill complexes. The optical response occurred with a threshold depolarization to -30 mV,

Mark L. Mayer; Amy B. MacDermott; Gary L. Westbrook; Stephen J. Smith; Jeffery L. Barker

1987-01-01

201

Lifetime measurements by open circuit voltage decay in GaAs and InP diodes  

NASA Technical Reports Server (NTRS)

Minority carrier lifetimes in the base of solar cells made on GaAs and InP were measured by the open-circuit voltage decay method. The measurement technique and the conditions under which the minority carrier lifetimes can be measured are described. Minority carrier lifetimes ranging from 1.6 to 34 ns in InP of different doping concentrations were measured. A minority carrier lifetime of 6 ns was measured in n-type GaAs, which agrees well with the lifetime of 5.7 ns measured by transient microwave reflection.

Bhimnathwala, H. G.; Tyagi, S. D.; Bothra, S.; Ghandhi, S. K.; Borrego, J. M.

1990-01-01

202

"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

203

Measurements of current-voltage-induced heating in the Al\\/SrTiO3-xNy\\/Al memristor during electroformation and resistance switching  

Microsoft Academic Search

Heating of the Al\\/SrTiO3-xNy\\/Al memristor is characterized during electroformation and switching of the resistances. The electrode with the higher voltage potential is heated to higher temperatures than the electrode with the lower potential, suggesting a reversible (nonstable) displacement of the anions in a low voltage region (|V|=+\\/-3 V) facilitates migration of anions to the anode interface and increases the local

A. Shkabko; M. H. Aguirre; I. Marozau; T. Lippert; A. Weidenkaff

2009-01-01

204

OXYGEN TENSION MEASUREMENT BY A METHOD OF TIME SELECTION USING THE STATIC PLATINUM ELECTRODE WITH ALTERNATING POTENTIAL  

PubMed Central

1. The possibility of obtaining sustained and reproducible results in the analysis of dissolved oxygen with simple platinum electrodes by means of the application of a periodic potential pattern was explored over a wide range of frequencies and with a variety of wave forms. 2. Satisfactory results were obtained by the application in the frequency range of 5 to 10 C.P.M. of a square wave consisting of a positive and a negative pulse with interposed shorting periods and observing the current flowing at the end of each successive negative pulse. This was found to be linearly proportional to O2 concentration for a pulse duration of the order of 1 second when the RC constant of the circuit was sufficiently small. 3. An instrument was developed to provide the required wave form and record the terminal currents of the negative pulses. The instrument provides either for recording of current voltage curves (polarograms) or for continuous recording at a fixed voltage of diffusion limited current values. 4. Typical measurements of oxygen uptake with yeast suspensions illustrate the application of the technique to problems requiring frequent determinations during short intervals. 5. Applications of this technique to biological and other problems are indicated with its limitations.

Olson, Rodney A.; Brackett, Frederick S.; Crickard, Robert G.

1949-01-01

205

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.  

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

1998-01-01

206

Kelvin probe electrode for contactless potential measurement on concrete-properties and applications  

NASA Astrophysics Data System (ADS)

The practical feasibility of using a Kelvin Probe as a novel reference electrode in the measurement of both potential and polarization pulse response of reinforcing steel in concrete is demonstrated. Potential values measured using a KP reflect greater stability and repeatability than can typically be attained with conventional reference electrodes. Duplicate reinforced concrete beam test specimens with well-differentiated centrally corroding rebar segments were analyzed using both the Kelvin Probe (KP) and a conventional Saturated Calomel Electrode (SCE). Potential profile maps were developed using potential values recorded under static conditions with both the SCE and the KP. Nominal polarization resistance was obtained using potential values recorded under dynamic polarization in both the active and passive regions using the KP and the SCE in conjunction with a customized counter electrode that applied a small galvanostatic polarizing current. In all cases the observed static potential values and dynamic potential response and recovery curves observed using the KP were consistent in shape and magnitude with those observed using conventional reference electrodes.

Walsh, Michael T.

207

Output Voltage Characteristics of Eddy Current Displacement Sensor for Various Heat Treatments of Measuring Objects  

NASA Astrophysics Data System (ADS)

The output voltage of an eddy current displacement sensor (EC displacement sensor) depends on the heat treatment of the measuring object. The EC displacement sensor must detect a displacement of several tens of ?m to allow the examination of the change in output voltage due to the heat treatment of the measuring object. Thus, we measure the relative permeability and resistivity of four objects made of chromium molybdenum steel that have undergone different heat treatments (initial condition (INT), salt quenching (SAQ), annealing (ANL), and vacuum furnace cooling (VFC)). In addition, we examine the relationship between the heat treatment of the measuring objects and the output voltage characteristics of the sensor at a displacement between the measuring object and the sensor of 1 mm. The result shows that the relative permeability of measuring object varies between 35 and 80, and resistivity varies between 0.18 ??m and 0.35 ??m due to different heat treatment conditions. The sensitivities of the sensor after SAQ and VFC treatments of the measuring object are 82.0 V/m and 73.0 V/m, respectively; thus, the difference is -11%.

Mizuno, Tsutomu; Enoki, Shigemi; Asahina, Takashi; Suzuki, Takayuki; Maeda, Hiroyuki; Asahi, Takafumi; Shinagawa, Hiroki

208

Quantitative characterization of the spin-orbit torque using harmonic Hall voltage measurements  

NASA Astrophysics Data System (ADS)

Solid understanding of current induced torques is a key to the development of current and voltage controlled magnetization dynamics in ultrathin magnetic heterostructures. To evaluate the size and direction of such torques, or effective fields, a number of methods have been employed. Here, we examine the adiabatic (low-frequency) harmonic Hall voltage measurement that has been used to study the effective field. We derive an analytical formula for the harmonic Hall voltages to evaluate the effective field for both out of plane and in-plane magnetized systems. The formula agrees with numerical calculations based on a macrospin model. Two different in-plane magnetized films, Pt|CoFeB|MgO and CuIr|CoFeB|MgO are studied using the formula developed. The effective field obtained for the latter system shows relatively good agreement with that estimated using spin torque switching phase diagram measurements reported previously. Our results illustrate the versatile applicability of harmonic Hall voltage measurement for studying current induced torques in magnetic heterostructures.

Hayashi, Masamitsu; Kim, Junyeon; Yamanouchi, Michihiko; Ohno, Hideo

2014-04-01

209

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.

Goldman, Y; Morad, M

1977-01-01

210

Improved lithium-ion battery performance of LiNi0.5Mn1.5-xTixO4 high voltage spinel in full-cells paired with graphite and Li4Ti5O12 negative electrodes  

NASA Astrophysics Data System (ADS)

The effect of Ti-substitution on the electrochemical properties of LiNi0.5Mn1.5-xTixO4 was investigated by using half-cells paired with lithium metal, and full-cells paired with either graphite or Li4Ti5O12 (LTO) negative electrodes. In half-cells, Ti-substitution increased the operation voltage, but reduced the specific capacity. While some improvements in performance, such as higher operation voltage and less self-discharge, could be measured in the half-cells, the critical advantages of the Ti-substitution were readily observed in full-cell cycling. Compared with Ti-free LiNi0.5Mn1.5O4, the LiNi0.5Mn1.5-xTixO4 electrodes delivered improved full-cell performance whether paired with graphite or LTO negative electrodes; greater cycle life, higher cell operating voltage, and lower voltage polarization on charging/discharging. Based on relatively low self-discharge and high Coulombic efficiency, it is suggested that the Ti-substitution in LiNi0.5Mn1.5-xTixO4 retards electrolyte oxidation. In addition, scanning electron microscopy (SEM) images revealed that cycle-aged LiNi0.5Mn1.2Ti0.3O4 particle surfaces remained relatively clean compared with those of LiNi0.5Mn1.5O4 particles. These results are consistent with the hypothesis that Ti-substitution reduces electrolyte oxidation and retards or prevents some of the degradative parasitic reactions at the electrode/electrolyte interfaces during battery cell operation.

Kim, Jung-Hyun; Pieczonka, Nicholas P. W.; Sun, Yang-Kook; Powell, Bob R.

211

Contamination of current-clamp measurement of neuron capacitance by voltage-dependent phenomena  

PubMed Central

Measuring neuron capacitance is important for morphological description, conductance characterization, and neuron modeling. One method to estimate capacitance is to inject current pulses into a neuron and fit the resulting changes in membrane potential with multiple exponentials; if the neuron is purely passive, the amplitude and time constant of the slowest exponential give neuron capacitance (Major G, Evans JD, Jack JJ. Biophys J 65: 423–449, 1993). Golowasch et al. (Golowasch J, Thomas G, Taylor AL, Patel A, Pineda A, Khalil C, Nadim F. J Neurophysiol 102: 2161–2175, 2009) have shown that this is the best method for measuring the capacitance of nonisopotential (i.e., most) neurons. However, prior work has not tested for, or examined how much error would be introduced by, slow voltage-dependent phenomena possibly present at the membrane potentials typically used in such work. We investigated this issue in lobster (Panulirus interruptus) stomatogastric neurons by performing current clamp-based capacitance measurements at multiple membrane potentials. A slow, voltage-dependent phenomenon consistent with residual voltage-dependent conductances was present at all tested membrane potentials (?95 to ?35 mV). This phenomenon was the slowest component of the neuron's voltage response, and failure to recognize and exclude it would lead to capacitance overestimates of several hundredfold. Most methods of estimating capacitance depend on the absence of voltage-dependent phenomena. Our demonstration that such phenomena make nonnegligible contributions to neuron responses even at well-hyperpolarized membrane potentials highlights the critical importance of checking for such phenomena in all work measuring neuron capacitance. We show here how to identify such phenomena and minimize their contaminating influence.

White, William E.

2013-01-01

212

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

213

Impedance measurements of self-assembled lipid bilayer membranes on the tip of an electrode  

Microsoft Academic Search

Supported lipid membranes were self-assembled on the tip of a freshly cleaved silver wire, in the presence of an appropriate polarization voltage, to facilitate, during the membrane formation, the organization of the lipids into an ordered structure. Radiowave impedance spectroscopy measurements have been carried out to provide information on the relaxation properties of the system. We have measured the conductometric

F. Bordi; C. Cametti; A. Gliozzi

2002-01-01

214

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

215

A study on electrode for amperometric measurement of human stress with flow injection analysis biosensing system  

Microsoft Academic Search

This paper presents a study on electrode for the amperometric detection of human stress based on salivary alpha amylase, emulated with different concentration of glucose, with the flow injection analysis biosensing system. Amperometric detection is an electrochemical voltammetric measurement approach, where the current intensity in a detection cell is regarded as a function of the concentration of the analyte. Flow

Lee Yoot Khuan; M. Hurairah Adha b Kamaruddin; Mohd Firdaus Abdullah; N. K. Madzhi; Anuar Ahmad

2010-01-01

216

Measurements of proton conductivity in the active layer of PEM fuel cell gas diffusion electrodes  

Microsoft Academic Search

This paper reports further studies to understand and optimize the Membrane and Electrode Assembly (MEA) structure in Polymer Electrolyte Membrane Fuel Cells (PEMFCs). The effective proton conductivity in the active catalyst layer was measured as a function of its composition, which consisted of platinum catalyst on carbon support (E-Tek) and Nafion® polymer electrolyte (DuPont de Nemours). The conductivity was calculated

C. Boyer; S. Gamburzev; O. Velev; S. Srinivasan; A. J. Appleby

1998-01-01

217

Effect of Y Content in (TaC)1-xYx Gate Electrodes on Flatband Voltage Control for Hf-Based High-k Gate Stacks  

NASA Astrophysics Data System (ADS)

The effects of varying the yttrium (Y) level in a (TaC)1-xYx gate electrode on the structural and electrical properties of a hafnium (Hf)-based high-k metal--oxide--semiconductor (MOS) capacitor, including flatband voltage (Vfb), were evaluated. The composition of (TaC)1-xYx was controlled by the power of pure TaC and Y targets in magnetron sputtering. The structure of the formed (TaC)1-xYx film was that of either a face-center cubic (fcc) at all compositions of x? 0.4 or amorphous at x? 0.5 after annealing at temperatures below 600 °C. X-ray photoelectron spectroscopy (XPS) analysis revealed that the TaC and (TaC)1-xYx films all contained about 10% oxygen. The resistivity of the (TaC)1-xYx films was invariant for all compositions of x? 0.5, but it increased with increasing annealing temperature up to 600 °C for compositions of x? 0.68. In the as-deposited case, the effective work function, which was estimated from the relationship between Vfb and the equivalent oxide thickness of the HfO2 film, clearly changed from 4.8 to 4.3 eV as x increased. The Vfb of HfO2 and HfSiOx dielectrics could be controlled within 0.5 V after annealing at 500 °C by changing the composition of the (TaC)1-xYx film (in terms of x). Based on the experimental data, it is clear that (TaC)1-xYx composites are candidate materials for n-metal gate electrodes in the gate-last process.

Homhuan, Pattira; Nabatame, Toshihide; Chikyow, Toyohiro; Tungasmita, Sukkaneste

2011-10-01

218

International Comparison Test in Asia-Pacific Region for Impulse Voltage Measurements  

NASA Astrophysics Data System (ADS)

The national standard class divider for the lightning impulse voltage measurements in Japan was developed in 1998. After three years, the standard impulse voltage calibrator was manufactured, too. These standard equipment are used as an industrial standard, and the performance had been evaluated annually supported by Ministry of Economy, Trade and Industry (METI). The standard impulse measuring system including the standard divider participated in the worldwide comparison test and its good performance was confirmed in 1999. Another international comparison test was carried out among three countries in the Asia-Pacific region in 2004 again and the standard measuring system participated in the test. In this paper, the details and the results of the international comparison tests in 2004 are described.

Wakimoto, Takayuki; Ishii, Masaru; Goshima, Hisashi; Hino, Etsuhiro; Shimizu, Hiroyuki; Li, Yi; Ik-Soo, Kim

219

Voltage Sensor  

NASA Technical Reports Server (NTRS)

Under a Lewis Research Center Small Business Innovation Research contract, SRICO, Inc. developed a fiber optic voltage sensor to measure voltage in electronic systems in spacecraft. The sensor uses glass and light to sense and transmit electricity, and is relatively safe and accurate. SRICO then commercialized the sensor for measurement of electric field and voltage in applications such as electric power systems and hazardous environments, lightning detection, and fiber optic communication systems.

1996-01-01

220

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 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 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.

Vail, III, William B. (Bothell, WA)

1996-01-01

221

A new method for noninvasive measurement of multilayer tissue conductivity and structure using divided electrodes.  

PubMed

This paper outlines a new method for measuring multilayer tissue conductivity and structure by using divided electrodes, in which current electrodes are divided into several parts. Our purpose is to estimate the multilayer tissue structure and the conductivity distribution in a cross section of the local tissue by using bioresistance data measured noninvasively. The effect of the new method is assessed by computer simulations using a typical two-dimensional (2-D) model. In this paper, the conductivity distribution in the model is analyzed based on a finite difference method (FDM) and a steepest descent method (SDM). Simulation results show that the conductivity values of skin, fat, and muscle layers can be estimated with an error of less than 0.1%. When random noise at various levels is added to the measured resistance values, estimates of the conductivity values for skin, fat, and muscle layers are still reasonably precise: their root mean square errors are about 1.06%, 1.39%, and 1.61% for 10% noise. In a 2-D model, increasing the number of divided electrodes permits simultaneous estimates of tissue structure and conductivity distribution. Optimal configuration for divided electrodes is examined in terms of dividing pattern. PMID:14765709

Zhao, Xueli; Kinouchi, Y; Yasuno, E; Gao, D; Iritani, T; Morimoto, T; Takeuchi, M

2004-02-01

222

Glass and polymeric membrane electrodes for the measurement of pH in milk and cheese.  

PubMed

While there is a considerable interest in the food industry in determining various analytes using ion-selective electrodes (ISEs), only few reports describe their use for direct measurements in food. In this study, the suitability of glass electrodes and ionophore-based solvent polymeric ISEs for the determination of pH in Process cheese, Cheddar cheese and milk was investigated. The liquid junction potential between a 3M KCl bridge electrolyte and diluted as well as undiluted Process cheese was found to be negligible. Reference electrodes with ceramic plug and sleeve-type junctions performed well, although precautions needed to be taken to prevent plugging at the junctions. While the protein rennet casein posed no problems in pH measurements, the extraction of neutral lipophilic compounds or hydrophobic peptides into solvent polymeric membranes was evident, resulting in some loss of selectivity for monovalent cations upon exposure to cheese. However, it was found that ISEs based on tridodecylamine (R(3)N) as ionophore and o-nitrophenyl octyl ether (oNPOE) as plasticizer can be used to accurately measure the pH of milk and, after desensitization of the electrodes in a cheese emulsion, of diluted Process cheese. Since pH measurements with a glass electrode showed that emulsions of cheese moderately diluted to a cheese content of 70% have the same pH as undiluted cheeses, it is possible to determine the pH in cheese with ionophore-based ISEs. R(3)N membranes also performed well in undiluted milk. PMID:18969412

Upreti, Praveen; Metzger, Lloyd E; Bühlmann, Philippe

2004-05-10

223

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

NASA Astrophysics Data System (ADS)

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.; Kuraica, Milorad M.

2014-05-01

224

Simultaneous Measurements of Pressure and Voltage at the Basilar Membrane Inform Theories of Amplification  

NASA Astrophysics Data System (ADS)

A feature of cochlear mechanics is local amplification, in which the response at a given frequency is amplified over a relatively narrow longitudinal extent of the cochlea. The basis for the place-frequency tuning of the amplifier has been explored in cochlear theories, and many models predict realistic level-dependent tuning in BM motion. Modern observations of in vivo active cochlear mechanics also include measurements of local driving pressure, and local extra-cellular voltage. These quantities have been predicted by theories of active cochlear mechanics, and thus the data provide useful modeling constraints. In particular, experimental observations argue against an amplifier that results in highly tuned and nonlinear relationships between pressure:velocity:voltage. These observations are consistent with predictions of some but not all cochlear models. Thus, simultaneous measurements of several cochlear quantities can be very useful in guiding concepts of how cochlear tuning and amplification work.

Olson, Elizabeth S.; Dong, Wei; Neely, Stephen T.

2011-11-01

225

An optically isolated hybrid two-stage current transformer for measurements at high voltage  

Microsoft Academic Search

The development of a high-voltage (HV) current measurement system for on-site\\/in-situ calibrations in power systems is described in the paper. The system is based on an optically isolated hybrid two-stage current transformer with electronic circuitry that performs A\\/D conversion. It uses a fiber optic link for data transmission to a ground station and a laser-driven fiber optic link for supplying

Branislav Djokic; Eddy So

2006-01-01

226

Considerations on the measurement of practical peak voltage in diagnostic radiology  

Microsoft Academic Search

An evaluation of the non-invasive measurement of the practical peak voltage (PPV) in the quality control of X-ray units used in diagnostic radiology was carried out. Two instruments were employed: the PTW Diavolt Universal Tester with readings in PPV and the Waveform Tester for X-rays (WATEX) prototype proposed here, which uses a PIN structure (P-type diffusion, Intrinsic region, N-type diffusion)

F J Ramirez-Jimenez; J S BENITEZ-READ; J O PACHECO-SOTELO

2004-01-01

227

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

228

Temperature measurements at thoriated tungsten electrodes in a model lamp and their interpretation by numerical simulation  

NASA Astrophysics Data System (ADS)

An atmospheric pressure argon arc is operated with dc currents of different amplitudes in a model lamp between electrodes made of pure and thoriated tungsten. Temperature measurements are performed at these electrodes with a CCD camera being calibrated at ? = 890 nm in absolute units of surface radiance and an interference filter for this wavelength. Temperature distributions are deduced from the CCD camera records of the electrodes assuming that they are grey body radiators. The records show a diffuse mode of attachment at the cathode. Doping the electrode with ThO2 causes a reduction in the cathode temperature by an amount of the order of 1000 K. On the other hand the anode temperature is weakly increased by a doping with ThO2. A reduction in the work function ? of the cathode from 4.55 to 3 eV is found by a comparison with cathode temperatures obtained by a numerical simulation of the diffuse mode of arc attachment with a well established cathode boundary layer model. Moreover, it is noted that the reduction is independent of the amount of ThO2 by which the electrode material is doped indicating that the work function of thoriated cathodes is the result of a self adjustment to the work function minimum at a thorium coverage of ? ? 0.5. The weak influence of ThO2 on the anode temperature shows that the average work function of the anode does not depend on the thorium content of the electrode. The results are explained by a thorium ion current, by which evaporated thorium is repatriated to the cathode surface. The paper is dedicated to the memory of the late Dr G M J F Luijks in appreciation of his outstanding pioneering work on high pressure discharge lamps, particularly his contribution to an understanding of the gas phase emitter effect in these lamps in cooperation with us.

Bergner, A.; Westermeier, M.; Ruhrmann, C.; Awakowicz, P.; Mentel, J.

2011-12-01

229

Measured voltages and currents internal to closed metal cylinders due to diffusion of simulated lightning currents  

SciTech Connect

One mechanism for the penetration of lightning energy into the interior of a weapon is by current diffusion through the exterior metal case. Tests were conducted in which simulated lightning currents were driven over the exteriors of similar aluminum and ferrous steel cylinders of 0.125-in wall thickness. Under conditions in which the test currents were driven asymmetrically over the exteriors of the cylinders, voltages were measured between various test points in the interior as functions of the amplitude and duration of the applied current. The maximum recorded open-circuit voltage, which occurred in the steel cylinder, was 1.7 V. On separate shots, currents flowing on a low impedance shorting conductor between the same set of test points were also measured, yielding a maximum current of 630 A, again occurring across the interior of the steel cylinder. Under symmetrical exterior drive current conditions, a maximum end-to-end internal voltage of 4.1 V was obtained, also in the steel cylinder, with a corresponding current of 480 A measured on a coaxial conductor connected between the two end plates of the cylinder. Data were acquired over a range of input current amplitudes between about 40 and 100 kA. These data provide the experimental basis for validating models that can subsequently be applied to real weapons and other objects of interest.

Schnetzer, G.H.; Fisher, R.J.

1994-08-01

230

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

231

A lithography-independent and fully confined fabrication process of phase-change materials in metal electrode nanogap with 16-?A threshold current and 80-mV SET voltage  

NASA Astrophysics Data System (ADS)

In this paper,we fabricate a lateral phase change memory device composed of a Ge2Sb2Te5 nanowire (GST NW) fully confined in a tungsten electrode nanogap. A SiNx spacer is used not only as etch mask for the fabrication of the GST NW, but also as sacrificial layer for the lift-off process, which makes it feasible to fully confine the GST NW in the metal electrode nanogap. Electrical characterization shows that the device has unprecedentedly low threshold current and SET voltage of only 16 ?A and 80 mV, respectively.

Fu, Yingchun; Wang, Xiaofeng; Zhang, Jiayong; Wang, Xiaodong; Chang, Chun; Ma, Huili; Cheng, Kaifang; Chen, Xiaogang; Song, Zhitang; Feng, Songlin; Ji, An; Yang, Fuhua

2013-01-01

232

A Decision Method for LDC Parameters of a SVR and Voltage Control Algorithm using Measurement Data of a Distribution System  

NASA Astrophysics Data System (ADS)

A method for determining line drop compensation (LDC) parameters and a control method for a step voltage regulator (SVR) using measurement data of a distribution system was proposed. Active and reactive power through the SVR and the voltage of each node of the distribution line were analyzed by multiple regression analysis to determine the optimum parameters of the LDC. The analysis results show that the SVR operated with the optimum parameters improves the voltage quality of the distribution line.

Matsuda, Katsuhiro; Futakami, Takafumi; Horikoshi, Kazuhiro; Seto, Toshiyuki; Watanabe, Masahiro; Murakoshi, Jun; Takahashi, Reiji

233

[Flow of high-voltage current in coal electrodes of arc furnaces as a source of noise of special nature].  

PubMed

The noise level for working arc furnace has been measured. Arc furnaces were found to be the source of infrasounds and acoustic field. The sound pressure levels for infrasounds range from 55 to 77 dB. It has been showed that particular noise level includes the onethird-octave band with middle frequency 100 Hz. The sound pressure levels in this band range from 105 to 110 dB. PMID:6472092

Polanowska, R

1984-01-01

234

Memory effect in organic transistor: Controllable shifts in threshold voltage  

NASA Astrophysics Data System (ADS)

A silver nanoparticles self-assembled monolayer was incorporated in pentacene field-effect transistors and their memory effects were investigated using the current-voltage measurement. The results showed that there was a significant shift in threshold voltage under different writing and erasing voltages applied on the gate electrode and the memory window changed accordingly with mentioned applied voltage bias. Charge retention time was estimated up to 2000 s even under different biased voltages. On the other hand, the reference OFETs without a nanoparticle layer exhibited no memory effects. Further, accelerated aging study of the organic transistors with nanoparticles revealed the conservation of memory window.

Lee, Keanchuan; Weis, Martin; Taguchi, Dai; Manaka, Takaaki; Iwamoto, Mitsumasa

2012-11-01

235

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

236

Impedance studies of Ni/Cd and Ni/H2 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 flightweight 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 voltages of the cell cases with respect to the individual electrodes differ from cell to cell even at the same overall cell voltage, but they remains 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.

1989-01-01

237

Electrolyte measurement device and measurement procedure  

DOEpatents

A method and apparatus for measuring the through-thickness resistance or conductance of a thin electrolyte is provided. The method and apparatus includes positioning a first source electrode on a first side of an electrolyte to be tested, positioning a second source electrode on a second side of the electrolyte, positioning a first sense electrode on the second side of the electrolyte, and positioning a second sense electrode on the first side of the electrolyte. current is then passed between the first and second source electrodes and the voltage between the first and second sense electrodes is measured.

Cooper, Kevin R. (Southern Pines, NC); Scribner, Louie L. (Southern Pines, NC)

2010-01-26

238

Fault Location for Parallel Transmission Lines with Limited Voltage and Current Measurements  

NASA Astrophysics Data System (ADS)

This article presents a novel fault location algorithm for parallel transmission lines for scenarios where only limited synchronized voltage and current measurements are available. Existing methods usually request measurements at the faulted line to be available. However, this may not always be the case due to the limited number of recording devices placed in a power system. The proposed method makes the most of available measurements and does not require the measurements to be captured from the faulted line. The pre-fault and during-fault bus impedance matrices for the positive-sequence network are derived. Synchronized bus voltages and branch currents are then expressed as a function of fault location and line parameters. As a result, fault location can be estimated using the obtained measurements. The distributed parameter line model is adopted to fully consider the shunt capacitances of the line. To eliminate the influence of bad measurements, optimal estimation theory is adopted for enhanced accuracy of the fault location estimate. Simulation studies have been carried out based on a 27-bus power system, and encouraging results have been achieved.

Xiu, Wanjing; Liao, Yuan

2013-06-01

239

Degradation studies of transparent conductive electrodes on electroactive poly(vinylidene fluoride) for uric acid measurements  

NASA Astrophysics Data System (ADS)

Biochemical analysis of physiological fluids using, for example, lab-on-a-chip devices requires accurate mixing of two or more fluids. This mixing can be assisted by acoustic microagitation using a piezoelectric material, such as the ?-phase of poly(vinylidene fluoride) (?-PVDF). If the analysis is performed using optical absorption spectroscopy and ?-PVDF is located in the optical path, the material and its conductive electrodes must be transparent. Moreover, if, to improve the transmission of the ultrasonic waves to the fluids, the piezoelectric transducer is placed inside the fluidic structures, its degradation must be assessed. In this paper, we report on the degradation properties of transparent conductive oxides, namely, indium tin oxide (ITO) and aluminum-doped zinc oxide, when they are used as electrodes for providing acoustic microagitation. The latter promotes mixing of chemicals involved in the measurement of uric acid concentration in physiological fluids. The results are compared with those for aluminum electrodes. We find that ?-PVDF samples with ITO electrodes do not degrade either with or without acoustic microagitation.

Cardoso, Vanessa F.; Martins, Pedro; Botelho, Gabriela; Rebouta, Luis; Lanceros-Méndez, Senentxu; Minas, Graca

2010-08-01

240

Improved chemically amplified photoresist characterization using interdigitated electrode sensors: photoacid diffusivity measurements  

NASA Astrophysics Data System (ADS)

The ability of interdigitated electrodes to serve as novel chemically amplified resist characterization tools has recently been demonstrated through their ability to measure the Dill C kinetic rate constant for photoacid generation. The work presented in this paper attempts to further extend the capabilities of the interdigitated electrode (IDE) sensors by investigating their potential use as a measurement tool for photoacid diffusion coefficients. Impedance spectroscopy of chemically amplified photoresist coated interdigitated electrodes is used to calculate the bulk ionic conductivity of the resist film. The ionic conductivity is subsequently utilized in the Nernst-Einstein equation to calculate the diffusion coefficient of the photoacid, assuming that it is the major charge carrying species in the film. A detailed description of the measurement and data analysis processes required to calculate the diffusion coefficient of triphenylsulfonium triflate in poly(p-hydroxystyrene) is provided. In addition, the effect of varying the relative humidity of the measurement environment upon the impedance data collected has been examined. It has been observed that the presence of water within the resist film, typically as a result of absorption of water from the humid ambient environment, dramatically changes the conductivity of the resist coated IDE. This change is apparently the result of changes in the proton conduction mechanism within the resist as a function of film water content. A discussion of several possible causes of this phenomena and its impact on the interpretation of the electrical data and the calculation and meaning of an acid diffusion coefficient are presented.

Berger, Cody M.; Henderson, Clifford L.

2004-05-01

241

Note: Adhesive stamp electrodes using spider silk masks for electronic transport measurements of supra-micron sized samples  

NASA Astrophysics Data System (ADS)

A procedure for fabricating adhesive stamp electrodes based on gold coated adhesive tape used to measure electronic transport properties of supra-micron samples in the lateral range 10-100 ?m and thickness >1 ?m is described. The electrodes can be patterned with a ~4 ?m separation by metal deposition through a mask using Nephila clavipes spider dragline silk fibers. Ohmic contact is made by adhesive lamination of a sample onto the patterned electrodes. The performance of the electrodes with temperature and magnetic field is demonstrated for the quasi-one-dimensional organic conductor (TMTSF)2PF6 and single crystal graphite, respectively.

Steven, E.; Jobiliong, E.; Eugenio, P. M.; Brooks, J. S.

2012-04-01

242

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

243

New apparatus for the measurement of the self-discharge of the nickel hydroxide electrode  

NASA Astrophysics Data System (ADS)

In this report a new method of measurement and equipment [1, 2] are described, that allow easy determination of the activation energy value of the self-decomposition process of the charged Ni(OH) 2/NiOOH electrode. A theoretical description of the method is given and its experimental practicability is demonstrated in addition to preliminary results obtained on differently doped nickel hydroxide samples.

Winsel, August; Fischer, Christian

244

Resistivity Measurement of a Small-Volume Sample Using Two Planar Disc Electrodes and a New Geometric Factor  

Microsoft Academic Search

In this work, we derive a new geometric factor in oblate spheroidal coordinates for conductivity or resistivity measurements using two planar disc electrodes based on the electromagnetic field theory and neglecting the electrode polarization effects. The experiments were conducted on saline solutions contained in a grounded metallic bath to validate the obtained values of the derived geometric factor. The effect

Yoke-Lin Tan; Chee-Earn Chong

2008-01-01

245

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

246

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

247

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

248

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

249

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

250

Finite element modeling of electrode-skin contact impedance in electrical impedance tomography.  

PubMed

In electrical impedance tomography (EIT), we inject currents through and measure voltages from an array of surface electrodes. The measured voltages are sensitive to electrode-skin contact impedance because the contact impedance and the current density through this contact impedance are both high. We used large electrodes to provide a more uniform current distribution and reduce the contact impedance. A large electrode differs from a point electrode in that it has shunting and edge effects which cannot be modeled by a single resistor. We used the finite element method (FEM) to study the electric field distributions underneath an electrode, and developed three models: a FEM model, a simplified FEM model and a weighted load model. We showed that the FEM models considered both shunting and edge effects and matched closely the experimental measurements. FEM models for electrodes can be used to improve the performance of an electrical impedance tomography reconstruction algorithm. PMID:8375870

Hua, P; Woo, E J; Webster, J G; Tompkins, W J

1993-04-01

251

Adsorptive stripping measurements of chromium and uranium at iridium-based mercury electrodes  

SciTech Connect

Iridium-based mercury electrodes are shown to be very suitable for adsorptive stripping measurements of chromium and uranium in the presence of the DTPA and propyl gallate complexing agents. The well-adhered mercury hemispherical electrode offers remarkable durability to withstand various manipulations expected under field deployment and the `pure` mercury surface essential for efficient adsorptive accumulation of the corresponding metal chelates. An electrochemical `cleaning` step ensures complete removal of the adsorbed metal chelate at the end of each run. The same hemispherical surface is thus used over a prolonged period of over five weeks, performing hundreds of runs with RSDs lower than 10%. Detection limits of 0.4 {mu}g/L uranium and 0.5 {mu}/L chromium are obtained following a 10 min adsorptive accumulation. The electrode responds rapidly to the `switching` between solutions of low and high concentrations of chromium or uranium. Proper choice of the constant current used for stripping potentiometric measurement of the uranium-propyl gallate complex results in an effective elimination of the oxygen background contribution. Various experimental parameters relevant to the mercury plating, adsorptive accumulation, and surface `cleaning` steps are explored and optimized. Applicability to groundwater and soil samples is demonstrated. 17 refs., 5 figs.

Wang, J.; Wang, J.; Tian, B.; Jiang, M. [New Mexico State Univ., Las Cruces, NM (United States)] [New Mexico State Univ., Las Cruces, NM (United States)

1997-04-15

252

High performance cermet electrodes  

DOEpatents

Disclosed is a method of increasing the operating cell voltage of a solid oxide electrochemical cell having metal electrode particles in contact with an oxygen-transporting ceramic electrolyte. The metal electrode is heated with the cell, and oxygen is passed through the oxygen-transporting ceramic electrolyte to the surface of the metal electrode particles so that the metal electrode particles are oxidized to form a metal oxide layer between the metal electrode particles and the electrolyte. The metal oxide layer is then reduced to form porous metal between the metal electrode particles and the ceramic electrolyte.

Isenberg, Arnold O. (Forest Hills Boro, PA) [Forest Hills Boro, PA; Zymboly, Gregory E. (Penn Hills, PA) [Penn Hills, PA

1986-01-01

253

Normalization of Voltage-Sensitive Dye Signal with Functional Activity Measures  

PubMed Central

In general, signal amplitude in optical imaging is normalized using the well-established ?F/F method, where functional activity is divided by the total fluorescent light flux. This measure is used both directly, as a measure of population activity, and indirectly, to quantify spatial and spatiotemporal activity patterns. Despite its ubiquitous use, the stability and accuracy of this measure has not been validated for voltage-sensitive dye imaging of mammalian neocortex in vivo. In this report, we find that this normalization can introduce dynamic biases. In particular, the ?F/F is influenced by dye staining quality, and the ratio is also unstable over the course of experiments. As methods to record and analyze optical imaging signals become more precise, such biases can have an increasingly pernicious impact on the accuracy of findings, especially in the comparison of cytoarchitechtonic areas, in area-of-activation measurements, and in plasticity or developmental experiments. These dynamic biases of the ?F/F method may, to an extent, be mitigated by a novel method of normalization, ?F/?Fepileptiform. This normalization uses as a reference the measured activity of epileptiform spikes elicited by global disinhibition with bicuculline methiodide. Since this normalization is based on a functional measure, i.e. the signal amplitude of “hypersynchronized” bursts of activity in the cortical network, it is less influenced by staining of non-functional elements. We demonstrate that such a functional measure can better represent the amplitude of population mass action, and discuss alternative functional normalizations based on the amplitude of synchronized spontaneous sleep-like activity. These findings demonstrate that the traditional ?F/F normalization of voltage-sensitive dye signals can introduce pernicious inaccuracies in the quantification of neural population activity. They further suggest that normalization-independent metrics such as waveform propagation patterns, oscillations in single detectors, and phase relationships between detector pairs may better capture the biological information which is obtained by high-sensitivity imaging.

Dann, Benjamin; Wanger, Tim; Ohl, Frank W.

2008-01-01

254

New Tetrapolar Method for Complex Bioimpedance Measurement: Theoretical Analysis and Circuit Realization  

Microsoft Academic Search

This paper describes the theory and practical implementation of a new tetrapolar (four-electrode) method for measuring complex bioimpedance of local tissue. The new tetrapolar method adopts three independent voltages VIN+, VIN-, VR respectively from the two voltage electrodes and the sample resistor R, which is connected in serial with one of the two current electrodes. Theoretical analysis shows that the

Yuxiang Yang; Jue Wang

2005-01-01

255

Electronic measurement of the Boltzmann constant with a quantum-voltage-calibrated Johnson noise thermometer  

NASA Astrophysics Data System (ADS)

Currently, the CODATA value of the Boltzmann constant is dominated by a single gas-based thermometry measurement with a relative standard uncertainty of 1.8×10 [P.J. Mohr, B.N. Taylor, D.B. Newell, CODATA recommended values of the fundamental physical constants: 2006, Rev. Mod. Phys. 80 (2008) 633-730]. This article describes an electronic approach to measuring the Boltzmann constant that compares Johnson noise from a resistor at the water triple point with a pseudo-random noise generated using quantized ac-voltage synthesis. Measurement of the ratio of the two power spectral densities links Boltzmann's constant to Planck's constant. Recent experiments and detailed uncertainty analysis indicate that Boltzmann's constant can presently be determined using Johnson noise with a relative standard uncertainty below 10×10, which would support both historic and new determinations. To cite this article: S. Benz et al., C. R. Physique 10 (2009).

Benz, Samuel; White, D. Rod; Qu, JiFeng; Rogalla, Horst; Tew, Weston

2009-11-01

256

Reference Electrodes  

NASA Astrophysics Data System (ADS)

In most electrochemical measurements, it is necessary to keep one of the electrodes in an electrochemical cell at a constant potential. This so-called reference electrode allows control of the potential of a working electrode (e.g. in voltammetry) or the measurement of an indicator electrode (e.g. in potentiometry, see Chap. II.9). The standard hydrogen electrode plays the role of a basic reference element in electrochemical devices; however, in practice, it is difficult to handle. Therefore, secondary reference electrodes are preferred in most experiments. A secondary reference electrode must fulfil the following criteria: (i) it should be chemically and electrochemically reversible, i.e. its potential is governed by the Nernst equation and does not change in time; (ii) the potential must remain almost constant when a small current passes through the electrode and reverse to its original value after such small current flow (i.e. a non-polarisable electrode); and (iii) the thermal coefficient of potential should be small.

Kahlert, Heike

257

A wireless passive pH sensor based on pH electrode potential measurement  

Microsoft Academic Search

We present a wireless coupled-coil passive pH sensor for high-resolution remote pH monitoring. The sensor is based on a passive LC coil resonator whose resonant frequency is monitored remotely by measuring the impedance of an interrogator coil coupled to the sensor coil. The sensor consists of an inductive coil connected in parallel with a varactor (voltage dependent capacitor) and a

S. Bhadra; G. E. Bridges; D. J. Thomson; M. S. Freund

2010-01-01

258

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.

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

2013-01-01

259

Voltammetric Membrane Chlorine Dioxide Electrode.  

National Technical Information Service (NTIS)

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 ...

R. Dormond-Herrera K. H. Mancy

1980-01-01

260

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. 4 figs.

Kronberg, J.W.

1994-05-31

261

A dry release of polyimide electrodes using Kapton film and application to EEG signal measurements  

Microsoft Academic Search

We describe here a simple and novel method to fabricate polyimide (PI) electrodes without a complex process to release completed\\u000a PI electrodes from the substrates after full-curing process. We separated the PI electrodes from the Si-wafer prior to full-curing\\u000a process, and these non full-cured electrodes were placed between the Kapton films, and we performed full-curing process with\\u000a these sandwiched electrodes.

Dong-Hyun Baek; Jin-hee Moon; Yoon Young Choi; Mina Lee; Jee Hyun Choi; James Jungho Pak; Sang-Hoon Lee

2011-01-01

262

Comparison of temperature and work function measurements obtained with different GTA electrodes  

Microsoft Academic Search

This work was carried out on one standard electrode (W-ThO2,) and other electrodes developed by additions of La2O3, CeO2, and Y2O3,. The effect of rare-earth metal oxides on GTAW electrode phenomena, concerning electrode temperature, emissivity, and work function, was analyzed and compared from the point of view of those oxides' behavior during arcing. The experimental results indicate that the electrode

Masao Ushio; Alber A. Sadek; Fukuhisa Matsuda

1991-01-01

263

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

264

Small vertical movement of a K+ channel voltage sensor measured with luminescence energy transfer  

Microsoft Academic Search

Voltage-gated ion channels open and close in response to voltage changes across electrically excitable cell membranes. Voltage-gated potassium (Kv) channels are homotetramers with each subunit constructed from six transmembrane segments, S1-S6 (ref. 2). The voltage-sensing domain (segments S1-S4) contains charged arginine residues on S4 that move across the membrane electric field, modulating channel open probability. Understanding the physical movements of

David J. Posson; Pinghua Ge; Christopher Miller; Francisco Bezanilla; Paul R. Selvin

2005-01-01

265

Stable voltage source for Penning trap experiments  

SciTech Connect

A voltage reference has been developed to bias ring electrodes of two Penning traps between -90 and 0 V. For output voltages near -90 V, the Allan deviation of the system's voltage instability is less than 1 part in 10{sup 8} over all time scales shorter than 10{sup 4} s. For averaging times longer than several seconds, the system's stability is determined almost completely by the noise, drift, and aging of the zener diodes in the array of voltage reference integrated circuits. For shorter averaging times, active filters built into the new system significantly reduce the intrinsic noise of the zener diodes. The system makes it possible to continuously adjust the ring voltages for frequency locking the axial motion in the two Penning traps. By keeping electrical noise highly correlated between the two traps, measurement uncertainty should be reduced for precision experiments such as Penning trap mass spectrometry.

Pinegar, David B.; Blaum, Klaus [Division of Stored and Cooled Ions, Max-Planck-Institut fuer Kernphysik, P.O. Box 103980, 69029 Heidelberg (Germany); Biesiadzinski, Tomasz P.; Zafonte, Steven L.; Van Dyck, Robert S. Jr. [Department of Physics, University of Washington, PAB 351560, Seattle, Washington 98195 (United States)

2009-06-15

266

Stable voltage source for Penning trap experiments.  

PubMed

A voltage reference has been developed to bias ring electrodes of two Penning traps between -90 and 0 V. For output voltages near -90 V, the Allan deviation of the system's voltage instability is less than 1 part in 10(8) over all time scales shorter than 10(4) s. For averaging times longer than several seconds, the system's stability is determined almost completely by the noise, drift, and aging of the zener diodes in the array of voltage reference integrated circuits. For shorter averaging times, active filters built into the new system significantly reduce the intrinsic noise of the zener diodes. The system makes it possible to continuously adjust the ring voltages for frequency locking the axial motion in the two Penning traps. By keeping electrical noise highly correlated between the two traps, measurement uncertainty should be reduced for precision experiments such as Penning trap mass spectrometry. PMID:19566217

Pinegar, David B; Blaum, Klaus; Biesiadzinski, Tomasz P; Zafonte, Steven L; Van Dyck, Robert S

2009-06-01

267

a Study of Deep Levels in COPPER-INDIUM-SELENIUM(2) by Current-Voltage Capacitance-Voltage and Capacitance Transient Measurements on Cadmium-Sulfide -SELENIUM(2)  

NASA Astrophysics Data System (ADS)

A study was made of the deep levels in CuInSe _ 2 thin films by Current-Voltage, Capacitance-Voltage, Capacitance-Temperature, and Capacitance Transient measurements on CdS/CuInSe_ 2 solar cells. To accomplish this study, a semi -automated system for Current-Voltage (I-V), Capacitance -Voltage (C-V), and Deep Level Transient Spectroscopy (DLTS) has been developed for the study of semiconductor devices. I -V, C-V, and DLTS measurements can be taken over a wide temperature range, from 100 K up to 450 K. Software for processing the data obtained has also been developed. This thesis presents the first reported successful measurements of deep levels in CuInSe_ 2 by DLTS measurements. The results indicate the presence in the p-type CuInSe_ 2 films of a majority-carrier (hole) trap located 0.70 eV above the valence band edge and a minority-carrier (electron) trap located 0.35 eV below the conduction band edge. Simulation studies show that the width and shape of the DLTS spectra for the hole trap can be explained only by assuming that the traps are distributed in energy around 0.70 eV. Our results are consistent with traps distributed from 0.65 to 0.75 eV, but it is not possible to determine uniquely the exact distribution. The electron trap at 0.35 eV does is not distributed in energy. There is strong evidence from the C-V, C-T, and I-V measurements, and indirectly from the DLTS measurements, that there is a large hole trap concentration in the CuInSe _ 2 layer close to the interface with the CdS. These interface states have a concentration of approximately 5 times 10 ^{15} cm^{ -3}, compared to a doping density in the CuInSe _ 2 layer of 1 times 10^{15} cm ^{-3}, a hole trap concentration of 5 times 10^{14 } cm^{-3}, and an electron trap concentration of 0.5 times 10^{14} cm ^{-3}. The I-V measurements are consistent with charge transport via an interface recombination/tunneling mechanism, where the tunneling is assisted by the interface states.

Christoforou, Nicholas

268

Voltage measurement based on the electrostrictive effect with simultaneous temperature measurement using a 3 × 3 fiber-optic coupler and low coherence interferometric interrogation  

Microsoft Academic Search

A fiber-optic interferometric method for remote voltage measurement with simultaneous temperature measurement is presented. A PMN electrostrictive transducer is employed as a voltage-to-displacement converter. The displacement is then interferometrically measured by the passive demodulation technique based on a 3 × 3 fiber-optic coupler. The third 3 × 3 coupler’s port and the same low coherence light source (LCS) are used

M. C. Tomic; J. M. Elazar; Z. V. Djinovic

2004-01-01

269

Thermoelectric voltage measurements of atomic and molecular wires using microheater-embedded mechanically-controllable break junctions.  

PubMed

We developed a method for simultaneous measurements of conductance and thermopower of atomic and molecular junctions by using a microheater-embedded mechanically-controllable break junction. We find linear increase in the thermoelectric voltage of Au atomic junctions with the voltage added to the heater. We also detect thermopower oscillations at several conductance quanta reflecting the quantum confinement effects in the atomic wire. Under high heater voltage conditions, on the other hand, we observed a peculiar behaviour in the conductance dependent thermopower, which was ascribed to a disordered contact structure under elevated temperatures. PMID:24930503

Morikawa, Takanori; Arima, Akihide; Tsutsui, Makusu; Taniguchi, Masateru

2014-06-26

270

Average Voltage Measurements of Periodic Blocking Oscillation in Resistive Superconducting Quantum Interference Device Connected to Josephson Transmission Line  

NASA Astrophysics Data System (ADS)

Blocking oscillation (BO) is a unique operation mode of resistive superconducting quantum interference devices (RSQUIDs). The author presents experimental measurements of periodic BO by means of the average voltage method. Test circuits are fabricated using a Nb/AlOx/Nb integration process. The input/output voltage ratio in an RSQUID, of which the output is connected to a Josephson transmission line (JTL), becomes 2 under appropriate operation conditions. Since the voltage ratio is exactly proportional to the input/output switching frequency ratio, the results demonstrate the periodic BO, in which the numbers of switching during one period are 2 and 1 in the input and output junction, respectively.

Mizugaki, Yoshinao

2012-03-01

271

A note on the impedance response of Li\\/LiCl\\/solid electrode system  

Microsoft Academic Search

The influence of solid electrodes such as lithium, platinum and conductive paints (silver print and conductive carbon cement) on the overall impedance response of a Li(parent electrode)\\/LiCl(polycrystalline)\\/solid electrode system is reported. The impedance response is measured as a function of d.c. voltage bias. The observed changes in impedance spectra are compared to the corresponding measurements in systems involving liquid solutions

D. Kek; M. Gaberš?ek; S. Pejovnik

1996-01-01

272

Electrode displacement measurement dynamics in monitoring of small scale resistance spot welding  

NASA Astrophysics Data System (ADS)

Small-scale resistance spot welding (SSRSW) process is widely used in medical and electronic devices manufacturing, where it is used to join thin foils and fine wires. Although tremendous work has been focused on traditional RSW process monitoring and control, SSRSW has received less attention, one reason being the process variables that are used in monitoring and control are very small in magnitude. A good example of a process variable that presents this difficulty is electrode displacement, which is generally regarded as one of the variables that can provide real-time information useful for monitoring and controlling RSW process quality. However, in SSRSW production, it is difficult to measure the displacement because its magnitude is very small. In this work, a fibre optic sensor was used for displacement monitoring. It was discovered that the implementation of the sensor introduced extraneous transient fluctuations into the measured signature. To develop techniques to improve the accuracy of the fibre optic sensor displacement measurements, more reliable electrode movement data were obtained using a high-speed video set-up. It was found that the displacement obtained by the fibre optic sensor had a delay and oscillatory feature compared to true displacement. Although it is a valuable research tool, the high-speed video system is not practical for online monitoring and control, while the fibre optic sensor has more potential for real-time monitoring and control implementation. Therefore, attempts were made to recover true displacement from the contaminated fibre optic displacement. A number of dynamic models in state-space form were identified to decode and predict the true displacement from fibre optic sensor measurement. Model parameters were estimated from two sets of known displacement data with fibre optic sensor displacement as input and high-speed video displacement as output. A fifth order innovations form model optimized by the subspace method was found to have the best accuracy compared to high-speed video measurement. Compared to uncorrected fibre optic and high-speed video displacement, fibre optic measurements corrected by this model are promising for real-time monitoring and control algorithms that use electrode displacement measurements.

Chen, J. Z.; Farson, D. F.

2004-12-01

273

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

274

A timing detector with pulsed high-voltage power supply for mass measurements at CSRe  

NASA Astrophysics Data System (ADS)

Accuracy of nuclear mass measurements in storage rings depends critically on the accuracy with which the revolution times of stored ions can be obtained. In such experiments, micro-channel plates (MCP) are used as timing detectors. Due to large phase space of injected secondary beams, a large number of ions cannot be stored in the ring and is lost within the first few revolutions. However, these ions interact with the detector and can saturate the MCP and thus deteriorate its performance. In order to eliminate such effects, a fast, pulsed high-voltage power supply (PHVPS) has been employed which keeps the detector switched-off during the first few revolutions. The new detector setup was taken into operation at the Experimental Cooler-Storage-Ring CSRe in Lanzhou and resulted in a significant improvement of the detector amplitude and efficiency characteristics.

Zhang, W.; Tu, X. L.; Wang, M.; Zhang, Y. H.; Xu, H. S.; Litvinov, Yu. A.; Blaum, K.; Chen, X. C.; Hu, Z. G.; Huang, W. J.; Ma, X. W.; Mao, R. S.; Mei, B.; Shuai, P.; Sun, B. H.; Yamaguchi, T.; Xia, J. W.; Xiao, G. Q.; Xu, X.; Yan, X. L.; Yang, J. C.; Yuan, Y. J.; Zhou, X. H.; Zhao, H. W.; Zhao, T. C.

2014-08-01

275

Prediction and measurements of a current derivative sensor response for voltage pulses applied to induction machines  

NASA Astrophysics Data System (ADS)

Current derivative sensors (CDI's) can advantageously be used in modern drives to determine the position of the rotor or flux in induction machines if no sensor at the shaft is available or to realize an effective condition monitoring of the drive. This is achieved by exploiting the transient current slope of the machine due to voltage pulses impressed by the switching of the inverter. To enable a CDI optimization with reference to the demands given by the drive application, a simulation model is presented which describes the nonlinear dependence on the history of the magnetic field and magnetization in ferromagnetic materials by statistical domain behavior using phenomenological parameters. In addition, measurements and simulations of the developed sensor output signals are presented which are used in a 15 kW induction machine drive. The optimized CDI sensitivity is S=0.35 ??s and the bandwidth exceeds the characteristic of standard current sensors by five times.

Wolbank, Thomas M.; Machl, Juergen L.; Hauser, H.

2003-05-01

276

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

277

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

278

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

Microsoft Academic Search

Objective: A system for electrode placement is described. It is designed for studies on topography and source analysis of spontaneous and evoked EEG activity.Method: The proposed system is based on the extended International 10–20 system which contains 74 electrodes, and extends this system up to 345 electrode locations.Results: The positioning and nomenclature of the electrode system is described, and a

Robert Oostenveld; Peter Praamstra

2001-01-01

279

Transport number and current–voltage of a cation exchange membrane equilibrated in aqueous and organic solutions  

Microsoft Academic Search

A physical-chemistry study of a Nafion 117 membrane is undertaken and a correlation between the transport number and current–voltage data of this cation exchange membrane is established. The current–voltage characteristics of the membrane are obtained with the voltamperometric technique, by means of two feed platinised titanium electrodes and two measuring silver–silver chloride electrodes. Previous measurements show that the membrane presents

H. Hamani; R. Bouamrane; M. Kameche; C. Innocent; Z. Derriche

2012-01-01

280

Continuous measurement of ethanol production by aerobic yeast suspensions with an enzyme electrode  

Microsoft Academic Search

An alcohol electrode was constructed which consisted of an oxygen probe onto which alcohol oxidase was immobilized. This enzyme electrode was used, in combination with a reference oxygen electrode, to study the short-term kinetics of alcoholic fermentation by aerobic yeast suspensions after pulsing with glucose. The results demonstrate that this device is an excellent tool in obtaining quantitative data on

Cornelis Verduyn; Timotheus P. L. Zomerdijk; Johannes P. van Dijken; W. Alexander Scheffers

1984-01-01

281

Measurements of air concentrations of thorium during grinding and welding operations using thoriated tungsten electrodes  

Microsoft Academic Search

An evaluation was performed to determine whether thorium was present in concentrations above the derived air concentration during grinding and welding operations using thoriated tungsten electrodes. A few of the advantages of using thoriated tungsten electrodes in industry include easier arc starting, greater stability, and reduced weld metal contamination. The electrodes used in this evaluation contained 2% thoria (thorium oxide)

E. M. Crim; T. D. Bradleyt

1995-01-01

282

Analyzing Photo Induced Internal Electric Field in Pentacene/C60 Double-Layer Organic Solar Cells under Various External Voltages by Electric-Field-Induced Optical Second Harmonic Generation Measurement  

NASA Astrophysics Data System (ADS)

By using electric-field-induced optical second-harmonic generation (EFISHG) measurement, we investigated interfacial carrier behavior in pentacene/C60 double-layer organic solar cells (OSCs). At various external DC biasing conditions, photoinduced electric field in the OSCs was directly probed by the EFISHG measurements. A potential drop was generated by photoillumination, in a manner like a potential difference across an external resistance, while applying an external DC voltage to the OSCs enables us to examine the carrier behaviors over the entire region of the external voltage Vex. Results showed that only organic double-layer interface charging was induced under positive DC biasing by photoillumination, while interface and electrode charging were induced under negative DC biasing. Analyzing the pentacene/C60 double layer OSCs based on a Maxwell--Wagner model, we showed that the dielectric nature of the organic layers was responsible for the asymmetric charging processes.

Chen, Xiangyu; Taguchi, Dai; Weis, Martin; Manaka, Takaaki; Iwamoto, Mitsumasa

2012-04-01

283

Comparative study of statistical breakdown in mineral, synthetic and natural ester oils under AC voltage  

Microsoft Academic Search

This paper reports on a comparative study of statistical Breakdown Voltage (BDV) in mineral oils, natural esters (vegetable oils) issued from different origins, and one synthetic ester through the measurements of 32 BDV using spherical electrode under AC voltage according to main lines of IEC 60156 specifications. The Normal and Weibull distribution functions are used to analyze and estimate the

Viet-Hung Dang; A. Beroual; C. Perrier

2011-01-01

284

Electrochemical measurements of anisotropic diffusion in thin lyotropic liquid crystal films using interdigitated array electrodes  

SciTech Connect

A new application of interdigitated array (IDA) electrodes is described for diffusion measurements of electrochemical probes dissolved in thin, lyotropic liquid crystalline films. The liquid crystal is a solution of 32% (w/w) lithium 4-trans-n-pentyl cyclohexanoate (Li5CH) in water, which can be prepared as well-ordered films of thickness less than ca. 12 {mu}m. Apparent diffusion coefficients (D{sub APP}) of the electrochemical probes are calculated from steady-state currents of generator/collector voltammograms. The diffusional anisotropy, measured parallel and perpendicular to the liquid crystal director, increases with increasing hydrophobicity of the probes. A simplified model has been developed to explain the diffusional anisotropy of hydrophobic probes in the ordered film. The transition temperature of the liquid crystal is determined from an activation plot of D{sub APP} for 1,1{prime}-dimethylferrocene. 32 refs., 6 figs., 1 tab.

Chen, C.H.; Postlethwaite, T.A.; Hutchison, J.E.; Samulski, E.T.; Murray, R.W. [Univ. of North Carolina, Chapel Hill, NC (United States)

1995-05-25

285

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

286

Needle Electrode-Based Electromechanical Reshaping of Cartilage  

PubMed Central

Electromechanical reshaping (EMR) of cartilage provides an alternative to the classic surgical techniques of modifying the shape of facial cartilages. The original embodiment of EMR required surface electrodes to be in direct contact with the entire cartilage region being reshaped. This study evaluates the feasibility of using needle electrode systems for EMR of facial cartilage and evaluates the relationships between electrode configuration, voltage, and application time in effecting shape change. Flat rabbit nasal septal cartilage specimens were deformed by a jig into a 90° bend, while a constant electric voltage was applied to needle electrodes that were inserted into the cartilage. The electrode configuration, voltage (0–7.5 V), and application time (1–9 min) were varied systematically to create the most effective shape change. Electric current and temperature were measured during voltage application, and the resulting specimen shape was assessed in terms of retained bend angle. In order to demonstrate the clinical feasibility of EMR, the most effective and practical settings from the septal cartilage experimentation were used to reshape intact rabbit and pig ears ex vivo. Cell viability of the cartilage after EMR was determined using confocal microscopy in conjunction with a live/dead assay. Overall, cartilage reshaping increased with increased voltage and increased application time. For all electrode configurations and application times tested, heat generation was negligible (<1 °C) up to 6 V. At 6 V, with the most effective electrode configuration, the bend angle began to significantly increase after 2 min of application time and began to plateau above 5 min. As a function of voltage at 2 min of application time, significant reshaping occurred at and above 5 V, with no significant increase in the bend angle between 6 and 7.5 V. In conclusion, electromechanical reshaping of cartilage grafts and intact ears can be effectively performed with negligible temperature elevation and spatially limited cell injury using needle electrodes.

Manuel, Cyrus T.; Foulad, Allen; Protsenko, Dmitriy E.; Sepehr, Ali

2010-01-01

287

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

288

Amplifier spurious input current components in electrode-electrolyte interface impedance measurements  

PubMed Central

Background In Impedance Microbiology, the time during which the measuring equipment is connected to the bipolar cells is rather long, usually between 6 to 24 hrs for microorganisms with duplication times in the order of less than one hour and concentrations ranging from 101 to 107 [CFU/ml]. Under these conditions, the electrode-electrolyte interface impedance may show a slow drift of about 2%/hr. By and large, growth curves superimposed on such drift do not stabilize, are less reproducible, and keep on distorting all over the measurement of the temporal reactive or resistive records due to interface changes, in turn originated in bacterial activity. This problem has been found when growth curves were obtained by means of impedance analyzers or with impedance bridges using different types of operational amplifiers. Methods Suspecting that the input circuitry was the culprit of the deleterious effect, we used for that matter (a) ultra-low bias current amplifiers, (b) isolating relays for the selection of cells, and (c) a shorter connection time, so that the relays were maintained opened after the readings, to bring down such spurious drift to a negligible value. Bacterial growth curves were obtained in order to test their quality. Results It was demonstrated that the drift decreases ten fold when the circuit remained connected to the cell for a short time between measurements, so that the distortion became truly negligible. Improvement due to better-input amplifiers was not as good as by reducing the connection time. Moreover, temperature effects were insignificant with a regulation of ± 0.2 [°C]. Frequency did not influence either. Conclusion The drift originated either at the dc input bias offset current (Ios) of the integrated circuits, or in discrete transistors connected directly to the electrodes immersed in the cells, depending on the particular circuit arrangement. Reduction of the connection time was the best countermeasure.

Felice, Carmelo J; Madrid, Rossana E; Valentinuzzi, Max E

2005-01-01

289

A Test Method of a PEFC Single Cell with Reference Electrodes  

NASA Astrophysics Data System (ADS)

A test method of a PEFC single cell with reference electrodes for obtaining correct polarization curves is proposed, where the anode polarization curves of H2/O2 and H2/Air should be approximately equal. Measured anode polarization curves are usually linear to the current density but not ohmic. Leak current between cathode and reference electrode causes voltage shift on the anode polarization curve. In order to obtain the ohmic anode polarization, the measured anode polarization curve should be moved vertically up to overlap with the base point. Configuration of the electrode edge adjacent to the reference electrode gives a significant effect on the anode and cathode potential. Polarization of a electrode which is 0.5mm nearer to the reference electrode than the other electrode does not include the ohmic loss of the membrane. Polarization of the other electrode includes the ohmic loss of the membrane instead.

Tsutsumi, Yasuyuki; Ono, Seiichirou; Eguchi, Mika

290

Field Measurements on Wind Turbines: a Voltage Dip Characterization under the Spanish Grid Code  

Microsoft Academic Search

Abstract—Voltage dips are short interruptions of rms voltage. These interruptions can produce interferences in the correct operation of most of the devices connected to the grid such as inverters. To minimize the impact of these events, the transmis- sion system operators with grids containing a large ammount of windpower are imposing requirements for uninterrupted gener- ation throughout power system disturbances.

J. A. Fuentes; A. Molina-Garc ´ õa

291

Interpretation of conduit voltage measurements on the poloidal field insert sample using the CUDI CICC numerical code  

NASA Astrophysics Data System (ADS)

The results of simulations with the CUDI-CICC code on the poloidal field insert sample (PFIS) tested in the SULTAN test facility are presented. The interpretations are based on current distribution analysis from self-field measurements with Hall sensor arrays and current sharing measurements. The possible variation in voltage-current ( VI) curves among the sub-cables in the PFIS caused by the cable self-field and joint non-uniformity is a principal issue for the evaluation of the strand-to-cable performance. The cable transverse voltages, initiated by current non-uniformity in a cabled conductor, can affect the shape of the longitudinal VI curve. The basic cable data are obtained by petal-to-conduit contact resistance and conduit resistivity measurements under transverse cyclic load in the Twente Cryogenic Cable Press. We assessed the impact of the conduit, the sub-cable resistive barrier wraps and the location of the voltage taps on the measured voltage, and some comparisons were carried out with experimental runs on the PFIS. The outcome confirms that the transverse voltages, caused by current redistribution, do affect the shape of the VI transition. This effect seems particularly important in short sample tests. Moreover, it is demonstrated that the location of the voltage taps can affect the experimentally obtained VI curve and solutions for most accurate measurement of the VI are discussed in the paper. The numerical model, CUDI-CICC covers the final cabling stage of inter-petal interactions only, by which the possible role of intra-petal non-uniformities is ignored, although recognized as potentially relevant.

Ilyin, Y.; Nijhuis, A.; ten Kate, H. H. J.

2006-07-01

292

Study of the adsorbed layer on a solid electrode surface by specular reflection measurement  

NASA Astrophysics Data System (ADS)

Specular reflection measurements were carried out to study the adsorbed layers of certain heterocyclic compounds such as adenine, barbital, 2'-deoxyadenosine, phenobarbital, pyridine and thymine. When pyridine was present in 0.1M NaClO 4, a marked decrease in the reflectivity of a gold electrode was observed. In the potential range near the point of zero charge on the reflectivity-potential curve, the decrease was due to the adsorption of pyridine. Assuming the reflectivity change to be proportional to the surface coverage, the potential and concentration dependence of pyridine adsorption was determined and analysed on the basis of a Langmuir-type adsorption isotherm. The refractive indices and extinction coefficients for the adsorbed layers of the compounds investigated were evaluated using the observed reflectivity change, according to relations proposed by McIntyre and Aspnes.

Kusu, Fumiyo; Takamura, Kiyoko

1985-07-01

293

Electrochemically self-assembled ZnO/dye electrodes: preparation and time-resolved photoelectrochemical measurements  

NASA Astrophysics Data System (ADS)

Dye-modified ZnO thin films were prepared by electrochemically induced crystallization from aqueous mixtures of zinc nitrate and water-soluble dyes. A direct crystallization of semiconductor/ dye composites without heat treatment is seen as a significant advantage of this method. Moreover, characterization of these materials has revealed ordered growth of ZnO crystallites as well as formation of ordered dye assemblies, thus characterizing this method as electrochemical self-assembly. The photoelectrochemical properties of these unique ZnO-dye thin film electrodes were investigated in photocurrent transient measurements in the ms-regime and by steady- state voltammetric measurements. Two sets of electrodes are discussed, employing either metal complexes of tetrasulfophthalocyanines (TSPcMt; Mt = Zn, Al, Si) or the xanthene dye Eosin Y. For aggregates of TSPcMt on ZnO, efficient charge-transfer to the electrolyte is found, leading to low surface charging and low surface recombination of photogenerated holes with electrons from the ZnO, at however, rather low injection efficiencies of electrons into the conduction band of ZnO. This efficiency was higher for adsorbed monomers of TSPcMt leading to a considerably higher quantum efficiency of the photocurrent in spite of increased surface charging and recombination of holes. Higher photocurrents were observed for ZnO sensitized with monomers of Eosin Y caused by both, efficient electron transfer from the dye to ZnO as well as hole transfer from the dye to the electrolyte. Not only dye molecules which were directly accessible from the electrolyte, but also those which were enclosed within matrix cavities proved to be photoelectrochemically active.

Schlettwein, Derck; Oekermann, Torsten; Yoshida, Tsukasa; Sugiura, Takashi; Minoura, Hideki; Wohrle, Dieter

2002-11-01

294

A new possible mechanism of lithium insertion and extraction in low-temperature pyrolytic carbon electrode  

Microsoft Academic Search

Lithium\\/carbon (Li\\/C) cells have been assembled with phenolic resin, pyrolyzed at 650°C for 2 h, as the working electrodes. By measuring the Raman spectra of the carbon electrodes discharged and charged to various equilibrium voltages and the discharge\\/charge curves of the Li\\/C cell, it is found that the intensity of the G-band of the discharged\\/charged pyrolytic carbon electrode in the

Zhaoxiang Wang; Xuejie Huang; Rongjian Xue; Liquan Chen

1999-01-01

295

Vacuum breakdown strength of vacuum-degassed oxygen-free copper electrodes  

Microsoft Academic Search

Using an in situ electrode surface cleaning system, the vacuum breakdown strength of vacuum degassed oxygen free copper (VDOFC) electrodes satisfying ASTM-F-68 Class 1, 3, and 5 purity specifications was measured. Breakdown experiments reveal that the breakdown field (breakdown voltage\\/gap length) depends on the purity of the VDOFC electrodes. The initial breakdown strengths are 1.96×107 V\\/m for Class 1 copper,

S. Kobayashi; Y. Saito; Y. Nagai; Y. Yamamoto

1993-01-01

296

Improvement of an enzyme electrode by poly(vinyl alcohol) coating for amperometric measurement of phenol  

Microsoft Academic Search

A poly(vinyl alcohol) film cross-linked with glutaraldehyde (PVA–GA) was introduced to the surface of a tyrosinase-based carbon paste electrode. The coated PVA–GA film was beneficial in terms of increasing the stability and reproducibility of the enzyme electrode. The electrode showed a sensitive current response to the reduction of the o-quinone, which was the oxidation product of phenol, by the tyrosinase,

Gha-Young Kim; Nguyen Manh Cuong; Seung-Hee Cho; Joonmok Shim; Jung-Je Woo; Seung-Hyeon Moon

2007-01-01

297

Feasibility of using respiratory correlated mega voltage cone beam computed tomography to measure tumor motion.  

PubMed

The purpose of this study was to test the feasibility of using respiratory correlated mega voltage cone-beam computed tomography (MVCBCT), taken during patient localization, to quantify the size and motion of lung tumors. An imaging phantom was constructed of a basswood frame embedded with six different-sized spherical pieces of paraffin wax. The Quasar respiratory motion phantom was programmed to move the imaging phantom using typical respiratory motion. The moving imaging phantom was scanned using various MVCBCT imaging parameters, including two beam line types, two protocols with different ranges of rotation and different imaging doses. A static phantom was also imaged as a control. For all the 3D volumetric images, the contours of the six spherical inserts were measured manually. Compared with the nominal sphere diameter, the average relative error in the size of the respiratory correlated MVCBCT spheres ranged from 5.3% to 12.6% for the four largest spheres, ranging in size from 3.6 cc to 29 cc. Larger errors were recorded for the two smallest inserts. The average relative error in motion was 5.1% smaller than the programmed amplitude of 3.0 cm. We are able to conclude that it is feasible to use respiratory correlated MVCBCT to quantify tumor motion for lung cancer patients. PMID:21587196

Chen, Mingqing; Siochi, R Alfredo

2011-01-01

298

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

299

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

300

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

301

Temperature dependent capacitance-voltage measurement of Al/Al2O3/PVA:n-CdSe MIS diode  

NASA Astrophysics Data System (ADS)

This paper presents the temperature dependent capacitance-voltage (C-V) characteristics of the Al/Al2O3/PVA:n-CdSe MIS diode. The different parameters like Built-in-voltage, Fermi energy, Density of States, Donor Concentration and Depletion layer width has been calculated from C-V measurement. The barrier height and depletion layer width decreases with increase in temperature while the donor concentration increases with increase in temperature. C-V-T characteristics confirm that diode parameters strongly influence the properties of MIS structure.

Sharma, Mamta; Tripathi, S. K.

2014-04-01

302

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

303

Sheath voltage ratio for asymmetric rf discharges  

SciTech Connect

Spherical and cylindrical many-particle models are used to simulate rf (radio frequency) discharges in which the rf powered and the grounded electrodes have different areas. This asymmetry determines the magnitude of the average plasma-to-electrode voltage {ital V}{sub {ital a}} (the ion bombarding energy) at the smaller powered electrode, which is a critical process parameter. A collisionless uniform ionization discharge model predicts that the voltage ratio {ital V}{sub {ital a}}/{ital V}{sub {ital b}} scales as the fourth power of the electrode area ratio {ital A}{sub {ital b}}/{ital A}{sub {ital a}}, where {ital V}{sub {ital b}} is the potential drop at the other electrode. However, measurements indicate a much weaker dependence of {ital V}{sub {ital a}}/{ital V}{sub {ital b}} on the area ratio, which is also observed in our simulations. Over a limited range of area ratios it was found that the power dependence was close to one, in agreement with a local ionization discharge model. The simulation codes used are PDC1 (plasma device cylindrical one-dimensional) and PDS1 (plasma device spherical one-dimensional).

Alves, M.V.; Lieberman, M.A.; Vahedi, V.; Birdsall, C.K. (Department of Electrical Engineering and the Electronics Research Laboratory, University of California, Berkeley, California 94720 (USA) Department of Computer Sciences and the Electronics Research Laboratory, University of California, Berkeley, California 94720 (USA))

1991-04-01

304

Nerve Growth Factor Dependent Changes in Electrophysiology Measured in a Neurotrophic Electrode.  

National Technical Information Service (NTIS)

We describe here neurotrophic electrode designed to improve long-term reliability and signal-to-noise in brain-device interface. Our electrode consists of fine microwire inside polyimide tube. The polyimide tube is filled with nerve growth factor (NCF) in...

S. H. Tillery P. J. Rousche K. Hausmann D. Hall M. Beaumont

2001-01-01

305

Tyrosinase biosensor based on modified screen printed electrodes: measurements of total phenol content  

Microsoft Academic Search

A disposable tyrosinase biosensor has been developed for the analysis of phenols and polyphenols, by modifying screen printed electrodes (SPEs) with addition of suitable mediators of redox processes directly into the conductive pastes. The percent ratio of mediator in the pastes was chosen depending on the electrochemical sensitivity either in batch or standard flow conditions. Ferrocene modified carbon electrodes have

Maria Rita Montereali; Walter Vastarella; Livia Della Seta; Roberto Pilloton

2005-01-01

306

Retention of ionizable compounds on HPLC. 6. pH measurements with the glass electrode in methanol–water mixtures  

Microsoft Academic Search

The relationship, ? values, between the two rigorous pH scales, sspH (pH measured in a methanol–water mixture and referred to the same mixture as standard state) and swpH (pH measured in a methanol–water mixture but referred to water as standard state), in several methanol–water mixtures was determined (?=swpH?sspH). ? values were measured using a combined glass electrode and a wide

Immaculada Canals; Fadoua Z. Oumada; Mart?? Rosés; Elisabeth Bosch

2001-01-01

307

12.5 pm/V hybrid silicon and lithium niobate optical microring resonator with integrated electrodes.  

PubMed

We present a silicon microring resonator with a lithium niobate top cladding and integrated tuning electrodes. Submicrometer thin films of z-cut lithium niobate are bonded to silicon microring resonators via benzocyclobutene. Integrated electrodes are incorporated to confine voltage controlled electric fields within the lithium niobate thin film. The electrode design utilizes thin film metal electrodes and an optically transparent electrode wherein the silicon waveguide core serves as both an optical waveguide medium and as a conductive electrode medium. The hybrid material system combines the electro-optic functionality of lithium niobate with the high index contrast of silicon waveguides, enabling compact low tuning voltage microring resonators. Optical characterization of fabricated devices results in a measured loaded quality factor of 11,500 and a free spectral range of 7.15 nm in the infrared. The demonstrated tunability is 12.5 pm/V, which is over an order of magnitude greater than electrode-free designs. PMID:24216923

Chen, Li; Wood, Michael G; Reano, Ronald M

2013-11-01

308

MEASURING SULFIDE ACCUMULATION IN DIFFUSIVE GRADIENTS IN THIN FILMS BY MEANS OF PURGE AND TRAP FOLLOWED BY IONSELECTIVE ELECTRODE  

Microsoft Academic Search

A procedure for measuring in situ sulfide concentrations by coupling diffusive gradients in thin films (DGT) to solid- state ion-selective electrodes (ISE) is described and evaluated. Laboratory tests were performed to evaluate the coupling of these techniques, and these results were compared to the previously used methods of computer imaging densitometry (CID) and methylene blue. An average elution efficiency of

Michael S. Rearick; Cynthia C. Gilmour; Andrew Heyes; Robert P. Mason

2005-01-01

309

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

310

Absolute Standard Hydrogen Electrode Potential Measured by Reduction of Aqueous Nanodrops in the Gas Phase  

PubMed Central

In solution, half-cell potentials are measured relative to those of other half cells, thereby establishing a ladder of thermochemical values that are referenced to the standard hydrogen electrode (SHE), which is arbitrarily assigned a value of exactly 0 V. Although there has been considerable interest in, and efforts toward, establishing an absolute electrochemical half-cell potential in solution, there is no general consensus regarding the best approach to obtain this value. Here, ion-electron recombination energies resulting from electron capture by gas-phase nanodrops containing individual [M(NH3)6]3+, M = Ru, Co, Os, Cr, and Ir, and Cu2+ ions are obtained from the number of water molecules that are lost from the reduced precursors. These experimental data combined with nanodrop solvation energies estimated from Born theory and solution-phase entropies estimated from limited experimental data provide absolute reduction energies for these redox couples in bulk aqueous solution. A key advantage of this approach is that solvent effects well past two solvent shells, that are difficult to model accurately, are included in these experimental measurements. By evaluating these data relative to known solution-phase reduction potentials, an absolute value for the SHE of 4.2 ± 0.4 V versus a free electron is obtained. Although not achieved here, the uncertainty of this method could potentially be reduced to below 0.1 V, making this an attractive method for establishing an absolute electrochemical scale that bridges solution and gas-phase redox chemistry.

Donald, William A.; Leib, Ryan D.; O'Brien, Jeremy T.; Bush, Matthew F.; Williams, Evan R.

2008-01-01

311

Atmospheric pressure plasma jets beyond ground electrode as charge overflow in a dielectric barrier discharge setup  

SciTech Connect

With a proper combination of applied voltage and the width of ground electrode, atmospheric pressure plasma jets extending beyond the ground electrode, whether it sits on the downstream or the upstream side, can be equally obtained with a dielectric barrier discharge setup, which can be ascribed to the overflow of deposited charges [J. Appl. Phys. 106, 013308 (2009)]. Here, we show that, by using narrower ground electrodes, such an overflow jet can be successfully launched at a much reduced voltage (down to below 10 kV). Moreover, by using transparent and triadic ground electrodes, development of charge overflow beneath the ground electrode was temporally and spatially resolved. Temporal evolution of discharge currents measured on the severed ground electrode helps establish the propagation dynamics of discharges along the dielectric surface beneath ground electrode, and also reinforces the conception that the streamer's head is in connection to the active electrode via a conducting channel. A small propagation velocity of 3.3x10{sup 3} m/s was measured for the ''overflow'' jet inside the dielectric tube. The availability of such overflow jets is enormously advantageous concerning their application to living bodies, to which the high voltage at active electrode is lethally dangerous.

Jiang Nan; Ji Ailing; Cao Zexian [Beijing National Laboratory for Condensed Matters, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190 (China)

2010-08-15

312

Semiconductor Measurement Technology: Differential Capacity-Voltage Profiling of Schottky Barrier Diodes for Measuring Implanted Depth Distributions in Silicon.  

National Technical Information Service (NTIS)

This report discusses experimental and analytical aspects of differential capacitance-voltage profiling of ion-implanted carrier depth distributions using reverse-biased Schottky barrier diodes and the associated accuracies, experimental errors, and range...

R. G. Wilson D. M. Jamba

1982-01-01

313

Characterization of 4H-SiC surfaces by non-destructive techniques based on capacitance voltage measurements  

NASA Astrophysics Data System (ADS)

Two recently developed characterization techniques for doping density profiling of SiC structures are introduced and compared. One is the in situ mercury contact capacitance–voltage (C–V) method realized without surface preparation, the other is the corona charge–voltage technique (Q–V) which is not only no-preparation but non-contact as well. It is shown that accurate measurements can be performed by both techniques even in the absence of any passivation layer (bare surface). While in the case of the C–V technique the standard measurement routine and evaluation process is applicable and provides a satisfactory result for SiC, a significantly revised and modified method is used for the Q–V measurement based on the long lasting, stable deep-depletion state of the SiC surface due to the very low intrinsic carrier concentration and thus a very long generation lifetime.

Mizsei, J.; Czett, A.

2014-05-01

314

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

315

Electrode immersion depth determination and control in electroslag remelting furnace  

DOEpatents

An apparatus and method for controlling an electroslag remelting furnace comprising adjusting electrode drive speed by an amount proportional to a difference between a metric of electrode immersion and a set point, monitoring impedance or voltage, and calculating the metric of electrode immersion depth based upon a predetermined characterization of electrode immersion depth as a function of impedance or voltage.

Melgaard, David K. (Albuquerque, NM); Beaman, Joseph J. (Austin, TX); Shelmidine, Gregory J. (Tijeras, NM)

2007-02-20

316

High Voltage Properties of Insulating Materials Measured in the Ultra Wideband  

Microsoft Academic Search

Numerous dielectrics have been developed for various high-voltage high-power microwave applications. The primary goals for HPM insulation are to provide adequate insulation over the lifetime of the device, provide high dielectric strength at low volume and weight, and function with minimal maintenance and ancillary components. Current testing methods for dielectric materials are antiquated processes developed around the 60 Hz machine

M. G. Mayes; J. R. Mayes; M. B. Lara; L. L. Altgilbers

2005-01-01

317

A test and measurement technique for determining possible lightning-induced voltages in aircraft electrical circuits  

NASA Technical Reports Server (NTRS)

Transient analyzer consists of four 0.5 microfarads capacitors chargeable by self-contained solid state 50 KV dc power supply operating from standard 110 Vac line voltage. Unit can circulate unidirectional current impulses of up to 500 amperes through aircraft at waveshapes similar to those of natural lightning strokes.

Plumer, J. A.; Walko, L. C.

1975-01-01

318

Atomic scale movement of the voltage-sensing region in a potassium channel measured via spectroscopy  

Microsoft Academic Search

Voltage-gated ion channels are transmembrane proteins that are essential for nerve impulses and regulate ion flow across cell membranes in response to changes in membrane potential. They are made up of four homologous domains or subunits, each of which contains six transmembrane segments. Studies of potassium channels have shown that the second (S2) and fourth (S4) segments contain several charged

Albert Cha; Gregory E. Snyder; Paul R. Selvin; Francisco Bezanilla

1999-01-01

319

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

320

Extraction of a strongly focusing He+ beam from three-stage concave electrodes for alpha particle measurement system in ITER.  

PubMed

A strongly focusing He(+) ion beam source equipped with concave multi-aperture electrodes was developed for production of He(-) through a charge exchange cell. The beam was extracted at a voltage less than 20 kV from 301 apertures distributed in an area of 100 mm ?, and focused at 750 mm distance. The beam current and the beam size of 2 A and 20 mm in diameter, respectively, were achieved with an arc power less than 10 kW. The optimum perveance was obtained at 0.02 A?kV(1.5) at the beam energy less than 20 keV which is suitable for the conversion to He(-) in an alkali vapor cell. PMID:22380277

Kobuchi, T; Sasao, M; Kisaki, M; Tsumori, K; Tanaka, N; Okamoto, A; Kitajima, S; Kaneko, O; Shinto, K; Wada, M

2012-02-01

321

In situ measurements of electrode work functions in free-burning arcs during operation at atmospheric pressure  

NASA Astrophysics Data System (ADS)

A method of in situ measurement of electrode work functions in free-burning argon arcs during operation is presented. This technique is based on the photoelectric effect ocurring at the surface of a tungsten cathode with the use of a pulse laser system consisting of a Nd-YAG laser and a dye laser. Three types of tungsten electrode, namely, pure W, W-2% ThO2 and W-2% La2O3 are used in this work. Free-burning arcs are operated in argon at atmospheric pressure at currents of 100 A and 200 A. The effective work functions of pure W, W-2% ThO2 and W-2% La2O3 electrodes during operation at a current of 200 A are found to be, respectively, 4.6, 2.8 and 3.0 eV from in situ measurements. These results are very close to the work functions of pure W, ThO2 and La2O3 obtained from the literature. The in situ measurements, however, show that the effective work functions of pure W, W-2% ThO2 and W-2% La2O3 electrodes for an 100 A arc are, respectively, 2.9 eV, 2.6 eV and 2.0 eV. It is shown that each effective work function for an 100 A arc clearly becomes lower than that for a 200 A arc for all types of tungsten electrodes.

Tanaka, Manabu; Ushio, Masao; Ikeuchi, Mitsuru; Kagebayashi, Yoshiro

2005-01-01

322

Flat band potential measurements of naked and viologen-modified n-WS[sub 2] electrodes in aqueous iodide and triiodide solutions  

SciTech Connect

The flat band potentials, E[sub FB], of naked n-WS[sub 2] electrodes and cationic viologen polymer-modified n-WS[sub 2] electrodes have been determined in KI and KI[sub 3] solutions by differential capacitance measurements. The E[sub FB] values for naked n-WS[sub 2] electrodes are shifted negatively in electrolyte media containing I[sup [minus

Huang, J.; Wrighton, M.S. (Massachusetts Institute of Technology, Cambridge, MA (United States))

1994-09-15

323

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

324

Nonlinear and linearized algorithms for the Young's modulus extraction of thin films through the capacitance-voltage measurement of microstructures  

Microsoft Academic Search

Two high-precision algorithms, based on nonlinear and linearized models, for the Young's modulus extraction of thin films through the wafer-level capacitance-voltage (C-V) measurement of microstructures are developed and compared with each other. Two microcantilever beams made of single crystalline silicon are used to verify the present methodologies since the Young's modulus of single crystalline silicon has been well defined. The

Yuh-Chung Hu; Wei-Hsiang Tu

2005-01-01

325

21 CFR 882.1560 - Skin potential measurement device.  

Code of Federal Regulations, 2010 CFR

...device. (a) Identification. A skin potential measurement device is a general diagnostic device used to measure skin voltage by means of surface skin electrodes. (b) Classification. Class II (performance...

2010-04-01

326

21 CFR 882.1560 - Skin potential measurement device.  

Code of Federal Regulations, 2010 CFR

...device. (a) Identification. A skin potential measurement device is a general diagnostic device used to measure skin voltage by means of surface skin electrodes. (b) Classification. Class II (performance...

2009-04-01

327

Elucidation of a Peculiar Phenomenon of Voltage Measuring at a Substation  

NASA Astrophysics Data System (ADS)

An automatic fault-recorder installed in a substation of Chubu Electric Power Company detected a peculiar phenomenon that bus-bar voltage fell to around 20-30% of the nominal value for a short time (about 8-10 cycles) though electric current didn't change during the period. The phenominon was recorded several times. In this paper, we analyzed the origin of this phenomenon and conducted simulations by EMTP. As a result, we estimated that this phenomenon occurred by the saturation of VT (voltage transformer), and this saturation caused by lightning strokes to the transmission line with line arresters, which have been increasingly installed in recent years. Moreover, we evaluated the influence of the phenomenon to protection relays.

Takafuji, Kouya; Satou, Takashi; Itou, Hisanori; Kouda, Isao; Haba, Toshiaki; Satake, Atushi; Haginomori, Eiichi

328

Flash X-Ray (FXR) Accelerator Optimization Beam-Induced Voltage Simulation and TDR Measurements  

Microsoft Academic Search

Lawrence Livermore National Laboratory (LLNL) is evaluating design alternatives to improve the voltage regulation in our Flash X-Ray (FXR) accelerator cell and pulse-power system. The goal is to create a more mono-energetic electron beam. When an electron beam crosses the energized gap of an accelerator cell, the electron energy is increased. However, the beam with the associated electromagnetic wave also

M. M. Ong; G. E. Vogtlin

2005-01-01

329

Measurements of motionally induced voltage in the coastal zone of the Throat of the White Sea  

Microsoft Academic Search

The theoretical relationship between non-local motionally induced voltages (MIV) and tidal currents is validated with observations of natural low-frequency electric field at the coast of the Throat of the White Sea (northwestern Russia). The Throat of the White Sea is a strait of 50-km width and about 500-km length with depths varying from 20 to 50 m connecting semi-closed White

N. A. Palshin; L. L. Vanyan; A. M. Poray-Koshits; V. A. Matyushenko; P. Kaikkonen; J. Tiikkainen

2002-01-01

330

Interaction of DL-threonine with NaCl and NaNO 3in aqueous solutions: e.m.f. measurements with ion-selective electrodes  

Microsoft Academic Search

The interactions betweenDL-threonine and NaCl or NaNO3, atT=(298.15±0.02) K, have been investigated by measuring e.m.f. values, with ion-selective electrodes (ISE), in electrochemical cells. The electrochemical cell employed consisted of two ion-selective electrodes, a cation and an anion ion-selective electrode, against a double junction reference electrode. The e.m.f. values thus obtained were used to calculate the activity coefficients ofDL-threonine in aqueous

Ana M. Soto-Campos; Mohammad K. Khoshkbarchi; Juan H. Vera

1997-01-01

331

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

332

Measurements of air concentrations of thorium during grinding and welding operations using thoriated tungsten electrodes.  

PubMed

An evaluation was performed to determine whether thorium was present in concentrations above the derived air concentration during grinding and welding operations using thoriated tungsten electrodes. A few of the advantages of using thoriated tungsten electrodes in industry include easier are starting, greater stability, and reduced weld metal contamination. The electrodes used in this evaluation contained 2% thoria (thorium oxide) and were either 2.4 mm or 3.9 mm in diameter. Personal breathing zone and area air samples were collected for the experienced welders participating in this evaluation during grinding operations. The results during the grinding operations for personal and area air samples were generally below the derived air concentration (DAC) for 232Th for solubility class Y of 0.04 Bq m-3 (1 x 10(-12) microCi mL-1) as per 10 CFR 20. The area samples collected during welding operations were below the DAC. PMID:7730071

Crim, E M; Bradley, T D

1995-05-01

333

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

334

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

PubMed

We report the first direct measurement of the extent of the spontaneous non-electrochemically driven reaction between a lithium ion battery electrode surface (Si) and a liquid electrolyte (1.2 M LiPF6-3?:?7 wt% ethylene carbonate?:?dimethyl carbonate). This layer is estimated to be 35 Å thick with a SLD of ? 4 × 10(-6) Å(-2) and likely originates from the consumption of the silicon surface. PMID:24513965

Veith, Gabriel M; Baggetto, Loïc; Sacci, Robert L; Unocic, Raymond R; Tenhaeff, Wyatt E; Browning, James F

2014-03-21

335

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

NASA Astrophysics Data System (ADS)

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.

di Vacri, M. L.; Nisi, S.; Balata, M.

2013-08-01

336

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

337

Design and geometry optimization of a conductivity probe with a vertical multiple electrode array for measuring volume fraction and axial velocity of two-phase flow  

Microsoft Academic Search

This paper presents the design and geometry optimization of a conductivity probe with a vertical multiple electrode array (VMEA), which can be used to measure the volume fraction and axial velocity of two-phase flow. The designed VMEA electrodes are axially flush mounted on the inside wall of an insulating duct. On the basis of a finite element analysis method, some

N D Jin; Z Xin; J Wang; Z Y Wang; X H Jia; W P Chen

2008-01-01

338

Nanowire electrodes for high-density stimulation and measurement of neural circuits.  

PubMed

Brain-machine interfaces (BMIs) that can precisely monitor and control neural activity will likely require new hardware with improved resolution and specificity. New nanofabricated electrodes with feature sizes and densities comparable to neural circuits may lead to such improvements. In this perspective, we review the recent development of vertical nanowire (NW) electrodes that could provide highly parallel single-cell recording and stimulation for future BMIs. We compare the advantages of these devices and discuss some of the technical challenges that must be overcome for this technology to become a platform for next-generation closed-loop BMIs. PMID:23486552

Robinson, Jacob T; Jorgolli, Marsela; Park, Hongkun

2013-01-01

339

Nanowire electrodes for high-density stimulation and measurement of neural circuits  

PubMed Central

Brain-machine interfaces (BMIs) that can precisely monitor and control neural activity will likely require new hardware with improved resolution and specificity. New nanofabricated electrodes with feature sizes and densities comparable to neural circuits may lead to such improvements. In this perspective, we review the recent development of vertical nanowire (NW) electrodes that could provide highly parallel single-cell recording and stimulation for future BMIs. We compare the advantages of these devices and discuss some of the technical challenges that must be overcome for this technology to become a platform for next-generation closed-loop BMIs.

Robinson, Jacob T.; Jorgolli, Marsela; Park, Hongkun

2013-01-01

340

Spatially resolved in situ measurements of the ion distribution near the surface of electrode in a steady-state diffusion in an electrolytic tank with confocal micro X-ray fluorescence.  

PubMed

Confocal micro-X-ray fluorescence (MXRF) technology based on a polycapillary focusing X-ray lens and a polycapillary parallel X-ray lens was used to carry out element-resolved and in situ analysis of ion distribution near the surface of the electrode in a steady-state diffusion in an electrolytic tank. The standard curve of the Cu K? fluorescence intensity corresponding to the concentration of CuCl2 was measured to quantitatively determine the ion distribution near the surface of the electrode in a steady-state diffusion. The distribution of the electrolytic ions around the surface of the electrode in the electrolytic tank was measured in situ, and the effects of the concentration of the electrolyte and the bath voltage on the shape of the layer with a nonuniform distribution of the Cu(2+) ions near the cathode surface in a steady state were analyzed with the confocal MXRF. The confocal MXRF has potential applications in spatially resolved analysis of the liquid mass transfer in electrolytic tanks in situ. PMID:24354283

Peng, Song; Liu, Zhiguo; Sun, Tianxi; Ma, Yongzhong; Ding, Xunliang

2014-01-01

341

Low voltage electrophoresis on a CMOS chip  

Microsoft Academic Search

Electrophoresis is a valuable technique for the separation and analysis of chemical and biological specimens. Typically, an electric field is established between two electrodes that induces charged particles to move and separate. Instead of using only one electrode at each end of the separation area, this paper presents a very small, low voltage system that utilizes electrodes beneath the entire

Heather A. Wake; Martin A. Brooke

2007-01-01

342

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

343

Benchmarking of 3D space charge codes using direct phase space measurements from photoemission high voltage dc gun  

NASA Astrophysics Data System (ADS)

We present a comparison between space charge calculations and direct measurements of the transverse phase space of space charge dominated electron bunches from a high voltage dc photoemission gun followed by an emittance compensation solenoid magnet. The measurements were performed using a double-slit emittance measurement system over a range of bunch charge and solenoid current values. The data are compared with detailed simulations using the 3D space charge codes GPT and Parmela3D. The initial particle distributions were generated from measured transverse and temporal laser beam profiles at the photocathode. The beam brightness as a function of beam fraction is calculated for the measured phase space maps and found to approach within a factor of 2 the theoretical maximum set by the thermal energy and the accelerating field at the photocathode.

Bazarov, Ivan V.; Dunham, Bruce M.; Gulliford, Colwyn; Li, Yulin; Liu, Xianghong; Sinclair, Charles K.; Soong, Ken; Hannon, Fay

2008-10-01

344

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

345

Eight electrode optical readout gap  

DOEpatents

A protective device for a plurality of electrical circuits includes a pluity of isolated electrodes forming a gap with a common electrode. An output signal, electrically isolated from the circuits being monitored, is obtained by a photosensor viewing the discharge gap through an optical window. Radioactive stabilization of discharge characteristics is provided for slowly changing voltages and carbon tipped dynamic starters provide desirable discharge characteristics for rapidly varying voltages. A hydrogen permeation barrier is provided on external surfaces of the device.

Boettcher, Gordon E. (Albuquerque, NM); Crain, Robert W. (Albuquerque, NM)

1985-01-01

346

Eight electrode optical readout gap  

DOEpatents

A protective device for a plurality of electrical circuits includes a plurality of isolated electrodes forming a gap with a common electrode. An output signal, electrically isolated from the circuits being monitored, is obtained by a photosensor viewing the discharge gap through an optical window. Radioactive stabilization of discharge characteristics is provided for slowly changing voltages and carbon tipped dynamic starters provide desirable discharge characteristics for rapidly varying voltages. A hydrogen permeation barrier is provided on external surfaces of the device.

Boettcher, G.E.; Crain, R.W.

1984-01-01

347

Remote gate capacitance-voltage studies for noninvasive surface characterization  

NASA Technical Reports Server (NTRS)

A measurement technique has been developed which allows noncontact capacitance-voltage measurements to be made using a gate electrode located remote from the semiconductor surface under study. With gate electrodes about 0.5 mm in diameter and gate to semiconductor separations of about 1500 A, it was possible to generate data entirely comparable to that obtained with integrated MIS structures but with the advantage that there was access directly to the free-semiconductor surface. This technique was applied to bulk single-crystal Si and InP samples.

Chang, R. R.; Lile, D. L.; Gann, R.

1987-01-01

348

Subpicovolt Resolution Measurements of the Current-Voltage Characteristics of Twinned Crystalline YBa2Cu3O7-x: New Evidence for a Vortex-Glass Phase  

Microsoft Academic Search

We present an improved contactless technique that allows measurement of the current-voltage \\\\(I-V\\\\) curves of YBa2Cu3O7-x single crystals in large magnetic fields with 5 orders of magnitude improved voltage resolution compared to conventional transport measurements. The crystals are shaped in the form of rings. The I-V curves are obtained by applying a small triangular oscillation of magnetic field and measuring

M. Charalambous; R. H. Koch; T. Masselink; T. Doany; C. Feild; F. Holtzberg

1995-01-01

349

Characterization of charge carrier injection in organic and hybrid organic/inorganic semiconductor devices by capacitance-voltage measurements  

NASA Astrophysics Data System (ADS)

Organic and hybrid organic / inorganic semiconductor heterostructures offer great potential as key technology for cost-efficient electro-photonic devices. To exploit their full potential, fundamental understanding of charge carrier injection is essential. Therefore we use current-luminance-voltage (I-L-V) and capacitance-voltage (C-V) measurements to analyze the injection characteristics of monochrome OLED test structures and hybrid organic / inorganic (HOI) pentacene / n-GaN and Alq3 / n-GaN heterostructures processed by organic vapor phase deposition (OVPD) and metal organic chemical vapor deposition (MOCVD), respectively. In a first step, we fundamentally analyze the specific C-V characteristics of OLED test structures. The multilayer devices show additional features in the C-V profile as compared to the bilayer OLED investigated by Brütting et al.1,2. We attribute this behavior to the additional organic / organic interfaces and the resulting energetic barriers in multilayer devices. In addition, we compared the C-V measurements of pristine and degraded OLED test structures. Here we conclude that a deterioration of hole injection in degraded devices is dominant, whereas electron injection remains largely unaffected. Furthermore, in pristine and degraded OLED, increased temperatures generally lead to improved charge injection as well as a reduced impact of the additional barriers in multilayer stacks. By analyzing I-V and C-V measurements of HOI heterostructures, we find ambipolar currents in pentacene-based diodes with electrons from n-GaN being injected at lower bias than the onset of hole injection from the gold anode contacts. Generally, I-V measurements of both types of HOI heterostructures show an onset of charge injection at very low bias voltage. Accordingly, n-GaN offers superior electron injection characteristics recommending n-GaN as cathode contact e.g. in fully transparent OLED microdisplays.

Weingarten, M.; Slawinski, M.; Urbain, F.; Fahle, D.; Bertram, D.; Heuken, M.; Kalisch, H.; Vescan, A.

2012-09-01

350

How well do cochlear implant intraoperative impedance measures predict postoperative electrode function?  

PubMed Central

Objective Objectives were to: 1) evaluate the incidence of abnormal cochlear implant electrode impedance intraoperatively and at the initial activation, 2) identify the percentage of abnormalities that resolve by the initial activation, and 3) determine the incidence of normal intraoperative impedances that present as abnormal at the initial activation. Study Design Retrospective records review of intraoperative and postoperative cochlear implant electrode impedances. Setting Tertiary referral center. Patients Records were examined for 194 devices implanted in 165 pediatric and adult patients. Results Results indicate at least 1 open (OC) or short circuit (SC) in 12.4% (24/194) of devices intraoperatively, decreasing to 8.2% (16/194) postoperatively. OCs were more prevalent than SCs for intraoperative (92% vs. 8%) and postoperative (94% vs. 6%) intervals. Of the 3430 total electrodes, 78 had abnormal impedance intraoperatively. Sixty-four of those (82%) resolved by the postoperative interval (62 OC, 2 SC) while 14/78 (18%) remained abnormal postoperatively (12 OC, 2 SC). Six of 3430 (0.17%) electrodes had normal impedance intraoperatively but were abnormal postoperatively. Conclusions The incidence of SCs in the present study is likely underestimated due to poor sensitivity of monopolar coupling for detecting SCs. Intraoperative OCs have a high probability of resolving by the initial activation, particularly when contiguous electrodes are affected, and suggests limited need for the use of a backup device in these cases. Surgical technique and/or complications such as explant/reimplant or perilymphatic gushers may result in increased incidence of bubbles in the cochlea, and may play a role in abnormal intraoperative impedance results.

Goehring, Jenny L.; Hughes, Michelle L.; Baudhuin, Jacquelyn L.; Lusk, Rodney P.

2012-01-01

351

Fully Integrated CMOS Microsystem for Electrochemical Measurements on 32 × 32 Working Electrodes at 90 Frames Per Second.  

PubMed

Microelectrode arrays offer the potential to electrochemically monitor concentrations of molecules at high spatial resolution. However, current systems are limited in the number of sensor sites, signal resolution, and throughput. Here, we present a fully integrated complementary metal oxide semiconductor (CMOS) system with an array of 32 × 32 working electrodes to perform electrochemical measurements like amperometry and voltammetry. The array consists of platinum electrodes with a center-to-center distance of 100 ?m and electrode diameters of 5 to 50 ?m. Currents in the range from 10 ?A down to pA can be measured. The current is digitized by sigma-delta converters at a maximum resolution of 13.3 bits. The integrated noise is 220 fA for a bandwidth of 100 Hz, allowing for detection of pA currents. Currents can be continuously acquired at up to 1 kHz bandwidth, or the whole array can be read out rapidly at a frame rate of up to 90 Hz. The results of the electrical characterization meet the requirements of a wide range of electrochemical methods including cyclic voltammograms and amperometric images of high spatial and temporal resolution. PMID:24941330

Rothe, Joerg; Frey, Olivier; Stettler, Alexander; Chen, Yihui; Hierlemann, Andreas

2014-07-01

352

Carbon nanotube multi-electrode array chips for noninvasive real-time measurement of dopamine, action potentials, and postsynaptic potentials.  

PubMed

Multi-electrode arrays (MEAs) can be used for noninvasive, real-time, and long-term recording of electrophysiological activity and changes in the extracellular chemical microenvironment. Neural network organization, neuronal excitability, synaptic and phenotypic plasticity, and drug responses may be monitored by MEAs, but it is still difficult to measure presynaptic activity, such as neurotransmitter release, from the presynaptic bouton. In this study, we describe the development of planar carbon nanotube (CNT)-MEA chips that can measure both the release of the neurotransmitter dopamine as well as electrophysiological responses such as field postsynaptic potentials (fPSPs) and action potentials (APs). These CNT-MEA chips were fabricated by electroplating the indium-tin oxide (ITO) microelectrode surfaces. The CNT-plated ITO electrode exhibited electrochemical response, having much higher current density compared with the bare ITO electrode. Chronoamperometric measurements using these CNT-MEA chips detected dopamine at nanomolar concentrations. By placing mouse striatal brain slices on the CNT-MEA chip, we successfully measured synaptic dopamine release from spontaneous firings with a high S/N ratio of 62. Furthermore, APs and fPSPs were measured from cultured hippocampal neurons and slices with high temporal resolution and a 100-fold greater S/N ratio. Our CNT-MEA chips made it possible to measure neurotransmitter dopamine (presynaptic activities), postsynaptic potentials, and action potentials, which have a central role in information processing in the neuronal network. CNT-MEA chips could prove useful for in vitro studies of stem cell differentiation, drug screening and toxicity, synaptic plasticity, and pathogenic processes involved in epilepsy, stroke, and neurodegenerative diseases. PMID:23774164

Suzuki, Ikuro; Fukuda, Mao; Shirakawa, Keiichi; Jiko, Hideyasu; Gotoh, Masao

2013-11-15

353

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

354

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

355

Nanoscale measurements of conducting domains and current-voltage characteristics of chemically deposited polyaniline films.  

PubMed

Spatial variations in electric conductivity and evolutions of band structures of polyaniline (PANI) films have been studied by use of a so-called current-sensing atomic force microscope (CS-AFM) or atomic force microscope current image tunneling spectroscopy (AFM-CITS). PANI films were deposited chemically onto indium-tin oxide- (ITO-) glass substrates, and their thickness and doping levels were controlled by polymerization and acid-doping conditions. The conducting uniformity of the PANI films depends on their doping level and thickness. Conducting domains were observed in fully doped PANI film, even when the bias voltage was reduced to as small as 30 mV. High current flowing regions gradually disappeared when conducting PANI films were partially dedoped. The point-contact current-voltage (I-V) characteristics of conducting tip-polymer/ITO systems were investigated on PANI films with different thickness and degree of doping. Various types of I-V curves representing metallic, semiconducting, and insulating states were obtained depending on the aggregation of polymer chains and doping level of the polymer film. The band gap energies (estimated from the I-V or dI/dV-V curves) of emeraldine base (EB) (undoped polyaniline) films are all higher than 3.8 eV, and a wide distribution of the band gap energies (0-1.1 eV and 0.75-1.8 eV for fully and partially doped PANI thin films, respectively) was found in a single polymer film. PMID:16866448

Wu, Chun-Guey; Chang, Su-San

2005-01-20

356

[Desulphurization with multi-needle-water film electrodes by corona discharge].  

PubMed

The study of this paper adopted stainless steel multi-needle as a high voltage electrode system, and water film as low voltage electrode. The electrodes were supplied with negative DC high voltage. Polluted gas containing sulfur dioxide (SO2) flowed into the corona discharge field from the center of the high voltage electrode system in an axis direction, then get across the water surface. Under the effect of corona discharge plasma and water absorption, SO2 was removed by converting it into sulfuric acid. The effect of the three factors which were the applied voltage, SO2 inlet concentration and duration of the exposure to the corona discharge on desulphurization efficiency has been studied mostly. Moreover, the concentrations of SO3(2-) and SO4(2-) ions in the water were measured and the mechanism of desulphurization was analyzed. The results showed that there was a synergistic effect on the removal of SO2 when combining corona discharge and water absorption, and both the desulphurization efficiency and the amount of sulfuric acid increased evidently. As the applied voltage and the duration increased, the desulphurization efficiency increased. Also, the SO2 inlet concentration had effect on desulphurization efficiency. When the SO2 inlet concentration was 430 x 10(-6), the voltage was 14.5 kV and the duration was 7.5 s, a desulphurization efficiency of more than 90% could be attained. PMID:19068659

Huang, Xu-ran; Li, Guo-feng; Li, Jie; Wu, Yan

2008-09-01

357

Standard deviation of the mean and other time series properties of voltages measured with a digital lock-in amplifier  

NASA Astrophysics Data System (ADS)

We investigate some statistical properties of ac voltages from a white noise source measured with a digital lock-in amplifier equipped with finite impulse response output filters which introduce correlations between successive voltage values. The main goal of this work is to propose simple solutions to account for correlations when calculating the standard deviation of the mean (SDM) for a sequence of measurement data acquired using such an instrument. The problem is treated by time series analysis based on a moving average model of the filtering process. Theoretical expressions are derived for the power spectral density (PSD), the autocorrelation function, the equivalent noise bandwidth and the Allan variance; all are related to the SDM. At most three parameters suffice to specify any of the above quantities: the filter time constant, the time between successive measurements (both set by the lock-in operator) and the PSD of the white noise input, h0. Our white noise source is a resistor so that the PSD is easily calculated; there are no free parameters. Theoretical expressions are checked against their respective sample estimates and, with the exception of two of the bandwidth estimates, agreement to within 11% or better is found.

Witt, Thomas J.; Fletcher, N. E.

2010-10-01

358

Mass measurements using isotopically labeled solvents reveal the extent of solvent transport during redox in thin films on electrodes  

SciTech Connect

Transport of solvent during the redox reactions of thin films on electrodes has been identified as a possible influence on both the thermodynamic and kinetic aspects of their electrochemical responses. A variety of methods has been used in attempts to measure solvent content of these films, including ellipsometry and profilimetry. However, those techniques which rely on measurement of thickness suffer from inability to deconvolute the contributions to swelling (or deswelling) from ion and solvent transport. Thus, the situation remains one in which speculation abounds, but accurate measurements are unavailable. In this communication, the authors report on the application of the quartz crystal microbalance (QCM) technique to the determination of solvent transport during redox in thin films of nickel ferrocyanide (the nickel analogue of Prussian Blue) by comparing the difference in the total mass change (comprised of contributions from both ion and solvent transport) which results from use of isotopically substituted solvent. To their knowledge, these experiments represent the first accurate, unambiguous measurements of solvent transport in thin films on electrodes. It is especially significant that these measurements are made in the presence of simultaneous ion transport.

Lasky, S.J.; Buttry, D.A.

1988-08-31

359

Photovoltaic response of symmetric sandwich polymer cells with identical electrodes  

NASA Astrophysics Data System (ADS)

The photovoltaic response of symmetric sandwich polymer cells based on poly[5-(2'-ethylhexyloxy)-2-methoxy-1,4-phenylene vinylene] (MEH-PPV) and MEH-PPV:fullerene blends has been investigated. Identical, semitransparent gold, silver, aluminum, and calcium are used as top and bottom electrodes. Most of the nominally symmetric sandwich cells exhibit pronounced photovoltaic (PV) response. The PV parameters are strongly dependent on the direction of illumination, the active layer thickness, and the evaporation rate of top electrode. Open-circuit voltage as high as 0.7 V has been measured in silver/MEH-PPV/silver cells. The addition of fullerene leads to reduced open-circuit voltage and higher short-circuit current. The photovoltaic response observed in these nominally symmetric sandwich cells is attributed to their different top and bottom electrode interfaces.

Alem, Salima; Gao, Jun; Wantz, Guillaume

2009-08-01

360

Area dependence of breakdown strength of polymer films: automatic measurement method  

Microsoft Academic Search

An automatic method for determining the breakdown strength of thin polymer films was evaluated. The equipment consists of a scanning electrode arm with which the breakdown voltage over the film sample is measured. The measurement electrodes were of solid brass and the ground electrode was of thin aluminum foil. Five different electrode areas between 0.045 and 9.3 cm2 were used

S. J. Laihonen; A. Gustafsson; U. Gafvert; T. Schutte; U. W. Gedde

2007-01-01

361

An electrochemical method for the measurements of substrate-oxidizing activity of acetic acid bacteria using a carbon-paste electrode modified with immobilized bacteria  

Microsoft Academic Search

In order to measure the substrate-oxidizing activity of intact cells of Acetobacter pasteurianus no.?2, a given amount of the bacterial cells was immobilized on a carbon-paste electrode, and the current at the electrode\\u000a was measured in a buffer solution. When Fe(CN)3?\\u000a 6 was added to the buffer solution, an anodic current was observed at 0.5?V (against Ag\\/AgCl). Further, when ethanol

T. Kondo; T. Ikeda

1999-01-01

362

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

363

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.

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

2001-01-01

364

Fabrication of Two-Layered Channel System with Embedded Electrodes to Measure Resistance Across Epithelial and Endothelial Barriers  

PubMed Central

This manuscript describes a straightforward fabrication process for embedding Ag/AgCl electrodes within a two-layer PDMS microfluidic chip where an upper and a lower channel are separated by a semi-porous membrane. This system allows for the reliable real-time measurement of trans-endothelial and trans-epithelial electrical resistance (TEER), an accepted quantification of cell monolayer integrity, across cells cultured on membranes inside the microchannels using impedance spectroscopy. The technique eliminates the need for costly or specialized microelectrode fabrication, enabling commercially available wire electrodes to easily be incorporated into PDMS microsystems for measuring TEER under microfluidic environments. The capability of measuring impedance across a confluent cell monolayer is confirmed using (i) brain-derived endothelial cells (bEND.3), (ii) Madin Darby Canine Kidney Cells (MDCK-2), and mouse myoblast (C2C12) (all from ATCC, Manassas, VA). TEER values as a function of cell type and cell culture time were measured and both agree with previously published values from macro-scale culture techniques. This system opens new opportunities for conveniently resolving both trans-endothelial and trans-epithelial electrical resistance to monitor cell function in real-time in microfluidic cell cultures.

Douville, Nicholas J.; Tung, Yi-Chung; Li, Ran; Wang, Jack Dong; El-Sayed, Mohamed E.H.; Takayama, Shuichi

2010-01-01

365

Application of Carbon Nanotubes As Electrodes in Gas Discharge Tubes  

NASA Astrophysics Data System (ADS)

Gas-tube protector units are used in telecom network interface device boxes and central office switching gears to provide protection from lightning and AC power cross facults on the telecom network. Current gas discharge tube (GDT) protector units are unreliable from the standpoint of mean turn-on voltage and run-to-run variability. Molybdenum electrodes with various interlayer materials were coated with single-walled carbon nanotubes and analyzed for both electron field emission and discharge properties. A mean DC breakdown voltage of 448.5V and a standard deviation of 4.8V over 100 surges were observed in nanotube-based GDTs with 1mm gap spacing between the electrodes. The breakdown reliability is a factor of 4-20 better and the breakdown voltage is 30% lower the commercial products measured. The enhanced performance shows that nanotube-based GDTs are attractive overvoltage protection units in advanced telecom networks.

Rosen, Rachel; Simendinger, William; Debbault, Chris; Shimoda, Hideo; Fleming, Les; Stoner, Brian; Zhou, Otto

2000-03-01

366

Application of carbon nanotubes as electrodes in gas discharge tubes  

NASA Astrophysics Data System (ADS)

Gas-tube protector units are used in telecom network interface device boxes and central office switching gears to provide protection from lightning and alternating current power cross faults on the telecom network. Current gas discharge tube (GDT) protector units are unreliable from the standpoint of mean turn-on voltage and run-to-run variability. Molybdenum electrodes with various interlayer materials were coated with single-walled carbon nanotubes and analyzed for both electron field emission and discharge properties. A mean direct current breakdown voltage of 448.5 V and a standard deviation of 4.8 V over 100 surges were observed in nanotube-based GDTs with 1 mm gap spacing between the electrodes. The breakdown reliability is a factor of 4-20 better and the breakdown voltage is ~30% lower than the two commercial products measured. The enhanced performance shows that nanotube-based GDTs are attractive overvoltage protection units in advanced telecom networks.

Rosen, R.; Simendinger, W.; Debbault, C.; Shimoda, H.; Fleming, L.; Stoner, B.; Zhou, O.

2000-03-01

367

Unusual behaviour of current-voltage relations in an unbalanced grid-assisted magnetron sputtering system  

NASA Astrophysics Data System (ADS)

Current-voltage relations were measured in an unbalanced grid-assisted magnetron sputtering system at different inter-electrode distances and magnetic field configurations. The intensity and configuration of the magnetic field were adjusted through an electromagnetic coil placed at the magnetron centre. This scheme allows observation of the current-voltage relations under conditions of weak and strong plasma confinement. Surprisingly, for some inter-electrode distances, a decreasing discharge current with increased magnetic field was observed. This unusual behaviour in grid-assisted magnetron discharges can be useful for a better understanding of abnormal glow discharges assisted by a magnetic field.

Sagás, J. C.; Duarte, D. A.; Fontana, L. C.

2012-12-01

368

A Simple Method for the Calibration of Traditional and Electronic Measurement Current and Voltage Transformers  

Microsoft Academic Search

The calibration of measurement transformers represents a classical task in the practice of electrical measurements. Most commercial instruments that are expressly designed for this purpose found their working principle on a scheme that is based on the idea of Kusters and Moore. Although they can assure very high accuracy, the need to employ a high-performance electromagnetic circuit makes them very

Arnaldo Brandolini; Marco Faifer; Roberto Ottoboni

2009-01-01

369

Some Studies into Electrical Discharge Machining of Nimonic75 Super Alloy Using Rotary Copper Disk Electrode  

NASA Astrophysics Data System (ADS)

The present study reports the rotary disk electrical discharge machining of Nimonic75 super alloy, extensively used in aerospace industries. The experiments have been performed using Taguchi's orthogonal array L18 (21 × 35) with copper disk electrode. The control factors considered were, viz., peak current, pulse on time, pulse off-time, gap voltage, and rotational speed of disk electrode with three levels each, and aspect ratio (AR) of the disk electrode having two levels, as noise factor. The novel approach of this article is to study the effect of the AR of the disk electrode on the performance measures, viz., material removal rate, disk electrode wear rate, and surface roughness. The results based on Taguchi's analysis show that among the considered process parameters, the AR and peak current significantly affect the machining characteristics. Furthermore, the rotating disk electrode easily flushes off the debris, resulting in better machining and reducing the chances of re-solidified layer formation.

Singh, S.; Pandey, A.

2013-05-01

370

Multi-transient DC resistivity measurements  

US Patent & Trademark Office Database

A method for measuring resistivity variations in the earth comprising passing a transient current between two source electrodes; measuring the transient current at the source electrodes; measuring the resultant transient voltage between at least one pair of receiver electrodes; estimating one or more processing functions for applying to the measured input current to provide a step current profile, and applying the same one or more processing functions to the measured voltage to provide an estimate of the step response voltage between the receivers, using both the step current and the estimated step response voltage to determine the resulting apparent earth resistance, and using the apparent earth resistance to determine the resistivity of the earth.

2012-09-25

371

Electrode-nanoparticle collisions: The measurement of the sticking coefficients of gold and nickel nanoparticles from aqueous solution onto a carbon electrode  

NASA Astrophysics Data System (ADS)

We present experimental results to determine the proportion of nanoparticle (NP) impacts that result in adsorbed NPs, using gold and nickel nanoparticles (AuNPs/NiNPs) in collision with a glassy carbon electrode. Results are given for NP radii of 10 nm (Au) and 26 nm (Ni), as well as a range of electrode potentials. No significant systematic trends were found in either case, and the sticking coefficients were found to be s = 0.19 ± 0.03 for Au and s < 0.01 for Ni.

Zhou, Yi-Ge; Stuart, Emma J. E.; Pillay, Jeseelan; Vilakazi, Sibulelo; Tshikhudo, Robert; Rees, Neil V.; Compton, Richard G.

2012-11-01

372

A Test Method of a PEFC Single Cell with Reference Electrodes  

Microsoft Academic Search

A test method of a PEFC single cell with reference electrodes for obtaining correct polarization curves is proposed, where the anode polarization curves of H2\\/O2 and H2\\/Air should be approximately equal. Measured anode polarization curves are usually linear to the current density but not ohmic. Leak current between cathode and reference electrode causes voltage shift on the anode polarization curve.

Yasuyuki Tsutsumi; Seiichirou Ono; Mika Eguchi

2008-01-01

373

A method for measuring high resistances with negligible leakage effect using one voltage source and one voltmeter  

NASA Astrophysics Data System (ADS)

We present a method for measuring high resistances using one voltage source and one voltmeter. With this method, there exist two techniques. One is to measure a high resistance with a much lower resistance and the other is to cancel the leakage effect effectively using two nominally equal resistances without an auxiliary guarding apparatus. To demonstrate the method's validity, a 1 G? resistance was measured using the two techniques replacing a dummy 1 G? resistance as a leakage resistance; the measurement results agree well with the theoretical results within the measurement uncertainty of 3 × 10?6 (k = 2) level. We used the method to determine 10 M?, 1 G? and 1 T? resistances with an active-guard type and a T-type. The best expanded uncertainties at k = 2 from the results were estimated as 0.3 × 10?6, 0.8 × 10?6 and 20 × 10?6, respectively. We also show that while the expanded uncertainty of 70 × 10?6 is obtained using an 81/2 digit digital multimeter, it is improved to 20 × 10?6 using an electrometer with high-input resistance, low bias current and high resolution when the second technique is used to measure high resistances.

Yu, Kwang Min; Kim, Wan Seop; Lee, Sang Hwa; Han, Kwon Soo; Kang, Jeon Hong

2014-07-01

374

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.

Lee, Chi-Yuan; Chan, Pin-Cheng; Lee, Chung-Ju

2010-01-01

375

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

376

Electrochemical microstructuring with short voltage pulses.  

PubMed

The application of short (nanosecond) voltage pulses between a tool electrode and a work piece immersed in an electrolyte solution allows the three-dimensional machining of electrochemically active materials with submicrometer resolution. The method is based on the finite charging time constant of the double-layer capacitance, which varies approximately linearly with the local separation between the electrode surfaces. Hence, the polarization of the electrodes during short pulses and subsequent electrochemical reactions are confined to regions where the electrodes are in sufficiently close proximity. This Minireview describes the principles behind electrochemical micro-structuring with short voltage pulses, and its current achievements and limitations. PMID:17111455

Schuster, Rolf

2007-01-01

377

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

378

Evaluation of the electrode method for measuring H/sub 2/S vapor pressure over alkanolamine solutions  

SciTech Connect

A new electrode method for measuring the equilibrium vapor pressure of H/sub 2/S over any sulfide solution was tested. The method relates the electropotential difference produced between pH and silver/sulfide ion specific electrodes to the H/sub 2/S equilibrium vapor pressure of solution. The experimental technique is simple and time efficient. In this work, H/sub 2/S equilibrium vapor pressures were measured from 10/sup -4/ kPa to 10 kPa at 25/sup 0/C in aqueous solutions of monoethanolamine-MEA (2.5 N), diethanolamine-DEA (2.0N), and methyldiethanolamine-MDEA (1.0 N and 4.28 N). The H/sub 2/S vapor-liquid equilibria (VLE) of 4.28 N MDEA was also examined at 40/sup 0/C. The results indicate that the addition of MEA to a MDEA solution reduces the H/sub 2/S vapor pressure only at low H/sub 2/S loadings.

Austgen, D.M.; Rochelle, G.T.

1987-01-01

379

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.

Ferrell, Nicholas; Desai, Ravi R.; Fleischman, Aaron J.; Roy, Shuvo; Humes, H. David; Fissell, William H.

2014-01-01

380

Interferometric measurement of the internal field of lithium niobate without high-voltage electric field poling  

NASA Astrophysics Data System (ADS)

A simple interferometric technique for measurement of the internal field (IF) in a ferroelectric crystal has been proposed. This technique has several advantages over the other methods used previously for evaluation of IFs in ferroelectric crystals. Here, the electro-optic property of lithium niobate is exploited for quantitative analysis of its IF. The strength of IF obtained using this technique lies within the range given in the literature. However, at frustrated domain inversion state, the measured value of IF shows a reduced value. A possible reason for this reduction based on the defect model has been discussed.

Das, Ranjit; Chakraborty, Rajib

2014-05-01

381

Measurement of the Energy Supply for Low Voltage Wire Bridge Igniters.  

National Technical Information Service (NTIS)

Methods used to investigate the power required to ignite primers, electrical detonators, and electro-explosive devices in general are discussed. The measuring method must be chosen according to the kind of energy source. It makes a difference if the elect...

M. Held

1972-01-01

382

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

383

Changes in biphasic electrode impedance with protein adsorption and cell growth  

NASA Astrophysics Data System (ADS)

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 polarization 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 µg cm-2, 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 that cell cover mainly contributes to the access resistance of the electrodes. Only a small increase in the polarization component of impedance was seen with cell cover.

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

2010-10-01

384

Partial discharge measuring system for on-line condition monitoring of high voltage equipment  

Microsoft Academic Search

A partial-discharge (PD) measuring and monitoring system utilizing current transducers based on the Rogowski-coil principle and a fast digitizer has been developed. The tests carried out so far using the system show that the Rogowski-coil sensors and a fast digitizer can be effectively used to sense, acquire, and analyze PD signals. The Rogowski coil has the advantage of being nonintrusive

S. Shihab; S. Moorthy; X. Cheng; V. Rao

1992-01-01

385

High performance GaN-based flip-chip LEDs with different electrode patterns.  

PubMed

A high-performance flip-chip light-emitting diode (FCLED) with a Ni/Ag metallic film as high reflectivity mirror (92.67%) of p-type electrode was successfully fabricated. The effect of geometric electrode patterns on the blue InGaN/GaN LEDs was investigated and analyzed qualitatively its current spreading in the active region. With different electrode patterns, these devices were experimented and simulated by simple electrical circuits in order to confirm its current-voltage characteristics and light emission pattern. It was found that the forward voltages of these FCLEDs were about 3.6 V (@350 mA). The light output power of FCLEDs with circle-round type electrode was 368 mW at an injection current of 700 mA. From these optoelectronic measurement and thermal infrared images, we proposed some design methodologies for improved current spreading, light output power, droop efficiency and thermal performance. PMID:24922399

Horng, Ray-Hua; Chuang, Shih-Hao; Tien, Ching-Ho; Lin, Sin-Cyuan; Wuu, Dong-Sing

2014-05-01

386

Liquid Nitrogen as Fast High Voltage Switching Medium  

NASA Astrophysics Data System (ADS)

Compact pulsed power systems require new switching technologies. For high voltages, liquid nitrogen seems to be a suitable switching medium, with high hold-off voltage, low dielectric constant, and no need for pressurized systems as in high pressure gas switches. The discharge behavior in liquid nitrogen, such as breakdown voltages, formative times, current rise as function of voltage, recovery, etc. are virtually unknown, however. The phenomenology of breakdown in liquid nitrogen is investigated with high speed (temporal resolution < 1 ns) electrical and optical diagnostics, in a coaxial system with 50-Ohm impedance. Discharge current and voltage are determined with transmission line type current sensors and capacitive voltage dividers. The discharge luminosity is measured with photomultiplier tubes. Preliminary results of self-breakdown investigations (gap 1 mm, breakdown voltage 44 kV, non-boiling supercooled nitrogen) show a fast (2 ns) transition from an unknown current level to several mA, a long-duration (100 ns) phase with constant current superimposed by ns-spikes, and a final fast transition to the impedance limited current during several nanoseconds. The optical measurements will be expanded toward spectroscopy and high speed photography with the aim of clarifying the overall breakdown mechanisms, including electronic initiation, bubble formation, bubble dynamics, and their role in breakdown, for different electrode geometries (different macroscopic field enhancements).

Dickens, J.; Neuber, A.; Haustein, M.; Krile, J.; Krompholz, H.

2002-12-01

387

Application of reduced graphene oxide and carbon nanotube modified electrodes for measuring the enzymatic activity of alcohol dehydrogenase.  

PubMed

An electrochemical method was developed to measure the enzymatic activity of alcohol dehydrogenase (ADH) by monitoring the amount of reduced nicotinamide adenine dinucleotide (NADH) generated in the catalysed oxidation of ethanol by ADH. The concentration of NADH was determined by amperometric measurements, which recorded the oxidation current of NADH versus time on reduced graphene oxide and functionalised multi-walled carbon nanotube modified electrodes. The initial reaction rates and the apparent Michaelis constants of the enzymatic reaction were obtained in the absence and presence of Al(3+) and nanometre-sized tridecameric aluminium polycationic (nano-Al(13)) species. The results showed that Al(3+) and nano-Al(13) exhibited inhibitory effect on the enzymatic activity of ADH. Fluorescence and circular dichroism spectra indicated the inhibitory effect was likely caused by the conformational changes of ADH and/or NADH induced by Al(3+) and nano-Al(13). PMID:23497876

Wang, Xianlong; Li, Li; Wang, Yanping; Xu, Chongzheng; Zhao, Bo; Yang, Xiaodi

2013-06-15

388

Voltresistometry of noble metals and extension of measuring capability of the contact electroresistance method by using iridium reference electrodes  

NASA Astrophysics Data System (ADS)

The potential dependence of the contact electroresistance (CER) of Ag, Au, Pt and Ir has been investigated in borate buffer solution (pH 9.4). The oxidation potentials of these metals were defined and the CER of its oxides were measured. The CER of Ir at pH 1-14 was shown to have anomalous low values. This made it possible to use Ir as the reference specimen (electrode) for measuring high CER values of the oxides of such metals like Ti, Zr and Cr. The CER of oxidized metal surfaces was found to be of non-ohmic nature. A new method has been proposed for an evaluation in situ of the specific area of defects in oxide films on metals.

Marichev, V. A.; Charny, L. A.

1996-02-01

389

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) [Albuquerque, NM; Maroone, James P. (Albuquerque, NM) [Albuquerque, NM; Tipping, Donald W. (Albuquerque, NM) [Albuquerque, NM; Zanner, Frank J. (Sandia Park, NM) [Sandia Park, NM

1986-01-01

390

Wide-aperture plasma-electrode pockels cell  

SciTech Connect

The results of experimental investigations of wide-aperture (100 Multiplication-Sign 100 mm) plasma-electrode Pockels are presented. Time characteristics, contrast, transmission factor, and optical uniformity of the cell are measured. It has been found that the half-wave effective voltage of the cell is 10 kV, the duration of the transmission window can vary from 250 to 550 ns, its leading and trailing edges are 40-50 and 70-100 ns in duration, respectively, and the time of the cell plasma electrode formation is 40 {+-} 5 ns.

Andreev, N. F.; Babin, A. A.; Davydov, V. S.; Matveev, A. Z. [Russian Academy of Sciences, Institute of Applied Physics (Russian Federation); Garanin, S. G.; Dolgopolov, Yu. V.; Kulikov, S. M.; Sukharev, S. A.; Tyutin, S. V. [All-Russian Federal Nuclear Center (VNIIEF) (Russian Federation)

2011-12-15

391

Lightweight Fibrous Ni Electrodes For Ni/H2 Batteries  

NASA Technical Reports Server (NTRS)

Fibrous nickel plaque electrode material reduces weight of nickel/hydrogen batteries by 40 percent. Discharge voltage and discharge time of fibrous electrode greater than those of equivalent standard sintered-powder electrode. Expected to lead to improvements in performances, increases in energy densities, and decreases in costs of nickel electrodes.

Britton, Doris L.

1991-01-01

392

Experimental evaluation of actual delivered dose using mega-voltage cone-beam CT and direct point dose measurement.  

PubMed

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&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&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&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. PMID:23266165

Matsubara, Kana; Kohno, Ryosuke; Nishioka, Shie; Shibuya, Toshiyuki; Ariji, Takaki; Akimoto, Tetsuo; Saitoh, Hidetoshi

2013-01-01

393

High voltage engineering  

Microsoft Academic Search

This book presents a comprehensive treatment of high voltage engineering fundamentals at the introductory and intermediate levels. It covers: techniques used for generation and measurement of high direct, alternating and surge voltages for general application in industrial testing and selected special examples found in basic research; analytical and numerical calculation of electrostatic fields in simple practical insulation systems; basic ionisation

Kuffel

1984-01-01

394

A miniature high voltage plasma interaction flight experiment - Project MINX. [for measuring solar cell array parasitic current drain  

NASA Technical Reports Server (NTRS)

A miniature high-voltage array was fabricated, incorporating the multi-junction edge illuminated (MJC) cell technique. The array consists of 32 2x2.2 cm MJCs, series connected, capable of 1600 V open circuit at 1 AMO and 1.2 mA short circuit. A solid state, high-voltage relay is connected across each 4-cell subgroup of the array. It was built to test plasma current drain on space systems using high voltage as might occur when a high-voltage solar array is operated from low to synchronous orbit.

Riley, T. J.; Triner, J. E.; Sater, B. L.; Cohen, D.; Somberg, H.

1974-01-01

395

Development of membrane-based biosensors: Measurement of current from photocycling bacteriorhodopsin on patch clamp electrodes  

SciTech Connect

Our initial work toward developing membrane protein-based biosensors has involved use of bacteriorhodopsin (BR) as a model membrane protein. BR was incorporated into liposomes of a polymerizable lecithin, and was shown to pump protons in response to illumination both before and after polymerization of the lipids. In the work described in this paper, BR was first reincorporated in liposomes of asolectin by consonication with purple membrane. The liposomes, which sustained the function of the protein, were used to form a monolayer at the air-water interface. This monolayer was transferred as a bilayer onto patch electrode. When illuminated with a pulse of 514.5-nm light the lipid/protein patch produced a current spike into the pipette corresponding to events no later than the generation of the 412-nm intermediate, probably caused by pumping of protons across the patch membrane. The experiment demonstrates not only the extreme sensitivity of amperometric detection, but also a small tendency for membrane proteins to preferentially orient in this configuration.

Yager, P.

1988-01-01

396

Flow injection catalase activity measurement based on gold nanoparticles/carbon nanotubes modified glassy carbon electrode.  

PubMed

Amperometric flow injection method of hydrogen peroxide analysis was developed based on catalase enzyme (CAT) immobilization on a glassy carbon electrode (GC) modified with electrochemically deposited gold nanoparticles on a multiwalled carbon nanotubes/chitosan film. The resulting biosensor was applied to detect hydrogen peroxide with a linear response range 1.0×10(-7)-2.5×10(-3)M with a correlation coefficient 0.998 and response time less than 10s. The optimum conditions of film deposition such as potential applied, deposition time and pH were tested and the flow injection conditions were optimized to be: flow rate of 3ml/min, sample volume 75?l and saline phosphate buffer of pH 6.89. Catalase enzyme activity was successfully determined in liver homogenate samples of rats, raised under controlled dietary plan, using a flow injection analysis system involving the developed biosensor simultaneously with spectrophotometric detection, which is the common method of enzymatic assay. PMID:22817944

El Nashar, Rasha Mohamed

2012-07-15

397

Topographical and electrochemical nanoscale imaging of living cells using voltage-switching mode scanning electrochemical microscopy.  

PubMed

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

2012-07-17

398

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

399

Note: Electrical modeling and characterization of voltage gradient in liquid crystal microlenses  

NASA Astrophysics Data System (ADS)

In this work, a novel equivalent electric circuit for modeling liquid crystal microlenses is proposed. This model is focused on explaining a lens behavior at the micrometric scale, using its manufacturing parameters. It suggests an approach to predict the solution of the voltage gradient distribution across a microlens. An interesting feature of the model is that it provides an analytical solution for microlenses with modal and hole-patterned electrode schemes, by a simple software tool. The model flexibility allows lens designers to apply complex waveform signals with different harmonics. The voltage distribution has been tested. The simulated and measured voltage profiles are fairly in agreement.

Urruchi, V.; Algorri, J. F.; Marcos, C.; Sánchez-Pena, J. M.

2013-11-01

400

Electro-Hydrodynamic (EHD) Thrust Analysis in Wire-Cylinder Electrode Arrangement  

NASA Astrophysics Data System (ADS)

The thrust generation by electro-hydrodynamic (EHD) effect has been studied for a wire-cylinder arrangement under high DC voltage. Series of measurements have been conducted in order to determine the relationship between generated thrust and corona discharge current, as well as its dependence on geometrical characteristics of the electrodes, e.g. electrode gap, wire and cylinder radii. The experimental investigation has shown a linear relationship between the generated thrust and the discharge current, while parametric analysis showed that increased electrode gap and emitter radius reduces the thrust. On the other hand, large gaps favor the thrust per unit power ratio.

Konstantinos, N. Kiousis; Antonios, X. Moronis; Wolf, G. Fruh

2014-04-01

401

Electrochemical thermodynamic measurement system  

DOEpatents

The present invention provides systems and methods for accurately characterizing thermodynamic and materials properties of electrodes and electrochemical energy storage and conversion systems. Systems and methods of the present invention are configured for simultaneously collecting a suite of measurements characterizing a plurality of interconnected electrochemical and thermodynamic parameters relating to the electrode reaction state of advancement, voltage and temperature. Enhanced sensitivity provided by the present methods and systems combined with measurement conditions that reflect thermodynamically stabilized electrode conditions allow very accurate measurement of thermodynamic parameters, including state functions such as the Gibbs free energy, enthalpy and entropy of electrode/electrochemical cell reactions, that enable prediction of important performance attributes of electrode materials and electrochemical systems, such as the energy, power density, current rate and the cycle life of an electrochemical cell.

Reynier, Yvan (Meylan, FR) [Meylan, FR; Yazami, Rachid (Los Angeles, CA) [Los Angeles, CA; Fultz, Brent T. (Pasadena, CA) [Pasadena, CA

2009-09-29

402

New developments for in situ ultrasonic measurement of transient temperature distributions at the tip of a copper resistance spot weld electrode  

Microsoft Academic Search

This paper presents the new development of a joint thermal simulation and ultrasonic time of flight (TOF) measurement technique for the In situ measurement of transient temperature distributions. A coupled finite element model, using conductive media DC and heat transfer by conduction, was used to simulate the expected transient temperature distributions within the copper electrode during welding. Simulated temperature distributions

A. C. Karloff; A. M. Chertov; J. Kocimski; P. Kustron; R. Gr. Maev

2010-01-01

403

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

404

A method for measuring the volume of transdermally extracted interstitial fluid by a three-electrode skin resistance sensor.  

PubMed

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

405

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

406

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.

Li, Dachao; Wang, Ridong; Yu, Haixia; Li, Guoqing; Sun, Yue; Liang, Wenshuai; Xu, Kexin

2014-01-01

407

Comparison of two electrode arrays for liner leakage location at landfills  

Microsoft Academic Search

High voltage direct current electrical method is very effective in landfill leakage detection and location by measuring the potential distribution patterns in the material under the liner. Different effects of two kinds of detecting electrode laying modes, namely, the honeycomb and the grid, on leak location are compared in a little simulative single-liner landfill. Two algorithms are respectively applied to

S. P. Guan; Y. W. Wang; C. X. Nai; L. Dong

2009-01-01

408

Surface potential measurement of organic thin film on metal electrodes by dynamic force microscopy using a piezoelectric cantilever  

NASA Astrophysics Data System (ADS)

We describe applications of a cantilever with a lead zirconate titanate (PZT) piezoelectric film as self-sensing to dynamic force microscopy (DFM) combined with Kelvin probe force microscopy (KFM). We adopted a frequency modulation (FM) detection method not only to stabilize the imaging conditions in our DFM but also to enhance the sensitivity for the detection of electrostatic forces in KFM measurement. We deposited Alq3 [tris (8-hydroxyquinolinato) aluminum] thin films and aluminum (Al) electrode patterns on an indium tin oxide (ITO)/glass substrate by vacuum evaporation using shadow masks. The surface structures and local surface potential of Alq3 films on metals were investigated using our DFM/KFM instrument to study the local electrical properties at the molecule-metal interface. The photosensitive organic material sample can be in a completely dark environment because no optics are required for cantilever deflection sensing in our experimental setup.

Satoh, Nobuo; Katori, Shigetaka; Kobayashi, Kei; Watanabe, Shunji; Fujii, Toru; Matsushige, Kazumi; Yamada, Hirofumi

2011-06-01

409

An Improvement on the Junction Temperature Measurement of Light-Emitting Diodes by using the Peak Shift Method Compared with the Forward Voltage Method  

NASA Astrophysics Data System (ADS)

The junction temperature of red, green and blue high power light emitting diodes (LEDs) is measured by using the emission peak shift method and the forward voltage method. Both the emission peak shift and the forward voltage decrease show a linear relationship relative to junction temperature. The linear coefficients of the red, green and blue LEDs for the peak shift method and the forward voltage method range from 0.03 to 0.15 nm/°C and from 1.33 to 3.59 mV/°C, respectively. Compared with the forward voltage method, the peak shift method is almost independent of bias current and sample difference. The variation of the slopes is less than 2% for the peak shift method and larger than 30% for the forward voltage method, when the LEDs are driven by different bias currents. It is indicated that the peak shift method gives better stability than the forward voltage method under different LED working conditions.

He, Su-Ming; Luo, Xiang-Dong; Zhang, Bo; Fu, Lei; Cheng, Li-Wen; Wang, Jin-Bin; Lu, Wei

2012-12-01

410

Time-resolved photoelectrochemical measurements and photovoltaic efficiency of electrochemically self-assembled ZnO-dye electrodes  

NASA Astrophysics Data System (ADS)

Dye-modified ZnO thin films were prepared by electrochemically induced crystallization from aqueous mixtures of zinc nitrate and water-soluble dyes. A direct crystallization of semiconductor/ dye composites without heat treatment is seen as a significant advantage of this method. Moreover, characterization of these materials has revealed ordered growth of ZnO crystallites as well as formation of ordered dye assemblies, thus characterizing this method as electrochemical self-assembly. The photoelectrochemical properties of these unique ZnO-dye thin film electrodes were investigated in photocurrent transient measurements in the ms-regime and by steady- state voltammetric measurements. Two sets of electrodes are discussed, employing either metal complexes of tetrasulfophthalocyanines (TSPcMt; Mt = Zn, Al, Si) or the xanthene dye Eosin Y. For aggregates of TSPcMt on ZnO, efficient charge-transfer to the electrolyte is found, leading to low surface charging and low surface recombination of photogenerated holes with electrons from the ZnO, at however, rather low injection efficiencies of electrons into the conduction band of ZnO. This efficiency was higher for adsorbed monomers of TSPcMt leading to a considerably higher quantum efficiency of the photocurrent in spite of increased surface charging and recombination of holes. Higher photocurrents were observed for ZnO sensitized with monomers of Eosin Y caused by both, efficient electron transfer from the dye to ZnO as well as hole transfer from the dye to the electrolyte. Not only dye molecules which were directly accessible from the electrolyte, but also those which were enclosed within matrix cavities proved to be photoelectrochemically active.

Schlettwein, Derck; Oekermann, Torsten; Tsukasa, Yoshida; Sugiura, Takashi; Minoura, Hideki; Woehrle, Dieter

2002-02-01

411

Effect of intratumoral heterogeneity in oxygenation status on FMISO PET, autoradiography, and electrode PO {sub 2} measurements in murine tumors  

SciTech Connect

Purpose: To explore conflicting results obtained when tumor hypoxia is assessed with Eppendorf electrode PO {sub 2} measurements and with positron emission tomography (PET) by use of [{sup 18}F]fluoromisonidazole (FMISO). Methods and Materials: We compared the 2 methods in conjunction with 2-[{sup 18}F]fluoro-2-deoxy-D-glucose (FDG) PET, dual-tracer ex vivo autoradiography (FMISO and 2-deoxy-D-[1-{sup 14}C]glucose (2DG)), and histology in 2 murine tumor models, the C3H mammary carcinoma and the SCCVII squamous cell carcinoma. Results: 2-[{sup 18}F]fluoro-2-deoxy-D-glucose (FDG)-PET showed tumor-to-reference tissue ratios of 3.5 in both tumor models after 2 hours. C3H mammary carcinoma reached an FMISO PET ratio of 11 after 3.5 hours. Autoradiography showed large confluent areas of FMISO and 2DG uptake. Median PO {sub 2} was 7 mm Hg and necrotic fraction was 10% to 30%. SCCVII squamous-cell carcinoma reached an FMISO PET tumor-to-reference tissue ratio of 2 after 2.5 hours. Autoradiography showed homogeneous 2DG uptake and scattered foci of high FMISO uptake. Median PO {sub 2} was 1 mm Hg and necrotic fraction was below 5%. Conclusions: Ex vivo dual-tracer autoradiography documented the ability of in vivo FMISO PET to distinguish between confluent areas of either viable tissue or necrosis. Electrode PO {sub 2} measurements could not be ascribed to specific areas in the tumors. Less uptake of FMISO in SCCVII squamous-cell carcinoma than in C3H mammary carcinoma could be caused by scattered foci versus confluent areas of viable hypoxic tissue in the 2 tumors, respectively.

Sorensen, Michael [PET Center, Aarhus University Hospital, Aarhus (Denmark)]. E-mail: michael@pet.auh.dk; Horsman, Michael R. [Department of Experimental Clinical Oncology, Aarhus University Hospital, Aarhus (Denmark); Cumming, Paul [PET Center, Aarhus University Hospital, Aarhus (Denmark); Munk, Ole Lajord [PET Center, Aarhus University Hospital, Aarhus (Denmark); Keiding, Susanne [PET Center, Aarhus University Hospital, Aarhus (Denmark); Department of Medicine V, Aarhus University Hospital, Aarhus (Denmark)

2005-07-01

412

Built-in voltage of organic bulk heterojuction p-i-n solar cells measured by electroabsorption spectroscopy  

NASA Astrophysics Data System (ADS)

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 C60, 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.; Lyssenko, V. G.; Fischer, J.; Tietze, M.; Brueckner, R.; Schwarze, M.; Vandewal, K.; Ray, D.; Riede, M.; Leo, K.

2014-04-01

413

Plasma treatment on electrode surfaces of bifacial silicon solar cells  

Microsoft Academic Search

To lower the fabrication cost of silicon solar cells, a surface treatment using a dielectric barrier discharge (DBD) instead of a wet cleaning technique was examined on electrode surfaces on silicon solar cells. The fill factor obtained through measuring current–voltage characteristics was evaluated, and the treated surface state was characterized by energy-dispersive X-ray. It was found that the DBD effectively

Tatsuya Sakoda; Youl-Moon Sung; Kunihiro Matsukuma

2006-01-01

414

A four-electrode microconstant direct current resistance detector for ion chromatography applying ion-exchange membrane and porous electrode.  

PubMed

A four-electrode microconstant direct current resistance detector for ion chromatography not sensitive to the effects of electrode polarization, capacitance, and electrolysis by-products is proposed. A constant current of microampere magnitude is applied across the current electrodes of the four-electrode device, and the voltage responses between the detection probes are directly picked up by a high input impedance instrumentation amplifier. The ion-exchange membranes, which separate the detection chamber from the electrolysis chambers, enable the measurement of solution resistance free of the interference of electrolysis by-products. Two resin beds in the detection chamber serve as ion conductors while reduce the dead volume of the detector. Recycled detection effluent supplies water for the electrolysis reactions at the current electrodes to sustain constant current in solution. The porous detection probes provide microchannel for the flowing solution while indicating signals. Owing to the constant current excitation, the electronics setup becomes simple. The cell configuration, operating principle, electronics, and error analysis of this detection mode are discussed along with their use for suppressed anion chromatography. Experimental data show that this four-electrode direct current detection mode is comparable to conventional two-electrode alternating current method. PMID:20801342

Huang, Weixiong; Chen, Huabin; Su, Yuhua; Hu, Rongzong

2010-09-15

415

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

416

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

417

The characterization of liposomal glucose oxidase electrodes for the measurement of glucose  

Microsoft Academic Search

Many biosensors have been described for the measurement of glucose in order to monitor diabetic patients. Glucose oxidase has been used commonly in the construction of glucose sensors but the performance of this enzyme is limited by enzyme saturation kinetics, which restrict the measurement of clinically relevant glucose concentrations (0 to 25 mM). Diffusion limiting membranes have been described that

Séamus P. J. Higson

1995-01-01

418

Magnetic flux and gate voltage modulation of the current in a superconducting loop of ultra-small tunnel junctions  

Microsoft Academic Search

We have measured the current-voltage (I-V) characteristics of a loop of four superconducting tunnel junctions at low temperatures (T~50mK). In each branch of the loop, tunneling occurs through a small capacitance island (C?~1fF). In this geometry we can vary the magnetic flux Phi in the loop and the voltage Vg on gate electrodes, which have capacitance Cg to the small

Y. Harada; D. B. Haviland; C. D. Chen; P. Delsing; T. Claeson

1994-01-01

419

Needle electrode-based electromechanical reshaping of rabbit septal cartilage: a systematic evaluation.  

PubMed

Electromechanical reshaping (EMR) provides a means of producing shape change in cartilage by initiating oxidation-reduction reactions in mechanically deformed specimens. This study evaluates the effect of voltage and application time on specimen shape change using needle electrodes. Rabbit septal cartilage specimens (20 x 8 x 1 mm, n = 200) were bent 90 degrees in a precision-machined plastic jig. Optimal electrode placement and the range of applied voltages were estimated using numerical modeling of the initial electric field within the cartilage sample. A geometric configuration of three platinum needle electrodes 2 mm apart from each other and inserted 6 mm from the bend axis on opposite ends was selected. One row of electrodes served as the anode and the other as the cathode. Constant voltage was applied at 1, 2, 4, 6, and 8 V for 1, 2, and 4 minutes, followed by rehydration in phosphate buffered saline. Samples were then removed from the jig and bend angle was measured. In accordance with previous studies, bend angle increased with increasing voltage and application time. Below a voltage threshold of 4 V, 4 minutes, no clinically significant reshaping was observed. The maximum bend angle obtained was 35.7 ± 1.7 º at 8 V, 4 minutes. PMID:21606017

Wu, Edward C; Protsenko, Dmitriy E; Khan, Adam Z; Dubin, Sterling; Karimi, Koohyar; Wong, Brian J F

2011-08-01

420

Micro-structured electrode arrays  

Microsoft Academic Search

Micro-structured electrode (MSE) arrays allow to generate large-area uniform glow discharges over a wide pressure range up to atmospheric pressure. The electrode dimensions in the ?m-range realized by means of modern micro-machining and galvanic techniques are small enough to generate sufficiently high electric field strengths to ignite gas discharges applying only moderate radio frequency (RF, 13.56MHz) voltages (80–390V in Ne,

Lutz Baars-Hibbe; Christian Schrader; Philipp Sichler; Thorben Cordes; Karl-Heinz Gericke; Stephanus Büttgenbach; Siegfried Draeger

2004-01-01

421

Would an endosteal CI-electrode make sense? Comparison of the auditory nerve excitability from different stimulation sites using ESRT measurements and mathematical models.  

PubMed

Regarding potential endosteal cochlear implant electrodes, the primary goal of this paper is to compare different intra- and extra-cochlear stimulation sites in terms of current strengths needed for stimulating the auditory nerve. Our study was performed during routine cochlear implantation using needle electrodes for electric stimulation and by visually recording electrically elicited stapedius reflexes (ESRT) as a measure for the stimulus transfer. Of course this rather simple setup only allows rough estimations, which, however, may provide further arguments whether or not to proceed with the concept of an endosteal electrode. In addition, a mathematical model is being developed. In a pilot study, intra-operative electric stimuli were applied via a needle electrode commonly used for the promontory stimulation test. Thus, stapedius reflex thresholds (ESRTs), electrically elicited via the needle from different points inside and outside the cochlea served as indicators for the suitability of different electrode positions towards the modiolus. Tests were performed on 11 CI-recipients. In addition, the extension of electrical fields from different stimulation sites is simulated in a mathematical cochlea model. In most patients ESRT measurements could be performed and evaluated. Thus an "endosteal" stimulation seems possible, although the current intensities must be higher than at intraluminal stimulation sites. Moreover, our model calculations confirm that the extension of electric fields is less favourable with increasing distance from the electrode to the ganglion nerve cells. In terms of hearing, the concept of an endosteal electrode should only be promoted, if its superiority for hearing preservation can be proven, e.g. in animal experiments. However, for other indications like the electric suppression of tinnitus, further research seems advisable. Levels of evidence: N/A. PMID:23657576

Pau, Hans Wilhelm; Grünbaum, Annekathrin; Ehrt, Karsten; Dahl, Rüdiger; Just, Tino; van Rienen, Ursula

2014-06-01

422

Measurement of the densities of Cu and Ag vapours in a low-voltage switch using the hook method  

NASA Astrophysics Data System (ADS)

In a research model of a low-voltage circuit breaker with fixed contacts and windows for optical access, arcs powered by either a high-current transformer or a capacitor bank were initiated by the explosion of tungsten wires. Air at atmospheric pressure was the switching medium. The number densities of neutral silver and copper vapours from contacts and arc runners were measured simultaneously by the hook method using a Mach-Zehnder interferometer combined with a 1 m spectrograph and a gated intensified CCD camera. When an arc current was flowing, a substantial fraction of the metal vapour was ionized, and thus not amenable to a density measurement with the technique chosen. To nevertheless obtain approximate density values, the arc current was forced to zero within 8 to 10 µs at a preset time and measurements were carried out 100 µs after extinction of the arc. At that time the metal vapour was expected to have recombined to a large extent but not yet diffused to the walls in significant amounts. Depending on the current amplitude reached within the arc duration the arc remained anchored to the silver contacts or commutated to the copper arc runners. At