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1

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

2

Single electrode voltage clamp by iteration.  

PubMed

A technique for providing conditions of voltage clamp which differs considerably from other voltage clamp schemes has been developed. The feedback network which determines the current which will clamp the cell to the desired voltage does not operate in real time. Instead, the system uses a form of discontinuous feedback. The event to be clamped, which must be one which can be made to repeat itself without change, is elicited and allowed to run to completion without the intervention of feedback. During each repetition of the event, a current waveform is injected whose shape is based on the foregoing trials (iterations). Successive repetitions of this process develop a current waveform which ever more closely clamps the voltage to the desired value. Implementation involves a means of converting the intracellular voltage signal to digital form (a transient recorder), a means of processing the digitalized voltage signal (a digital computer), and a means of delivering the clamping current back to the preparation. The system has two advantages over other voltage clamp techniques. First, that the feedback loop is open in real time confers great stability. This advantage is exploited in the use of iterative voltage clamp in single electrode preparations. Secondly, iterative voltage clamp is essentially unlimited in the speed with which it can respond to transients. This would make the technique of interest even in preparations such as squid giant axon, where two electrodes are used and very fast responsiveness is desired. PMID:7218855

Park, M R; Leber, W; Klee, M R

1981-02-01

3

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

4

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

5

An electret transducer for impulse voltage measurements  

SciTech Connect

It is known that lightning produces impulse voltages and currents in transmission and distribution lines. A low-cost method for measuring peak currents is to use devices such as magnetic links and magnetic tapes. In this paper, a new method for detecting impulse voltages that uses an electret as the element of transduction is proposed. The new sensor consists of two metallic electrodes separated by a piece of dielectric (Teflon FEP) and an air gap. The impulse voltage produces an electric discharge in the gap and charges are transferred from the electrode to the dielectric surface, forming the electret.

Altafim, R.A.C. (Escola de Engenharia de Sao Carlos, Univ. de Sao Carlos, Sao Paulo (Brazil)); Giacometti, J.A. (Inst. de Fisica e Quimica de Sao Carlos, Univ. de Sao Paulo, Sao Carlos (Brazil)); Janiszewski, J.M. (Escola Politecnica-PEL, Univ. de Sao Paulo, Sao Paulo (Brazil))

1992-10-01

6

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.

Bordenick, John E. (West Mifflin, PA)

1989-01-01

7

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

8

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

9

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

10

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

11

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

12

Improving membrane voltage measurements  

E-print Network

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

Cai, Long

13

Electrodic voltages accompanying stimulated bioremediation of a uraniumcontaminated aquifer  

E-print Network

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

Hubbard, Susan

14

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

15

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

Microsoft Academic Search

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

O. Lesaint; T. V. Top

2002-01-01

16

Charge voltage maximums in alkaline storage cells with silver electrode  

SciTech Connect

A study has been made of the voltage spikes that arise during charging silver-zinc storage cells at the instant of transition from the lower charge step of silver electrode (Ag{sub 2}O formation) to the upper charge step (AgO formation). The amplitude and duration of spikes depend on the charge current, the depth of preceding discharge, the time of charged-electrode storage, and the temperature. The effect of copper oxide additives, which are introduced into the active mass of silver electrode for lowering the spikes, is associated with redistribution of charge current among the grains of silver oxide Ag{sub 2}O and copper oxide at the instant of spike; the redistribution leads to the reduction of local current density during the formation of crystallization nuclei of oxide AgO. The effect of lead addition to the electrode is associated with the formation of phase Ag{sub 5}Pb{sub 2}O{sub 6} that also consumes a part of charge current in the transient region and, in addition, reduces the resistance of active mass assisting the reaction zone expansion.

Yablokova, I.E.; Udalova, E.V.; Kazakevich, G.Z. [KVANT State Research and Production Enterprise, Moscow (Russian Federation)

1995-04-01

17

Electrodic voltages accompanying stimulated bioremediation of a uranium-contaminated aquifer  

NASA Astrophysics Data System (ADS)

The inability to track the products of subsurface microbial activity during stimulated bioremediation has limited its implementation. We used spatiotemporal changes in electrodic potentials (EP) to track the onset and persistence of stimulated sulfate-reducing bacteria in a uranium-contaminated aquifer undergoing acetate amendment. Following acetate injection, anomalous voltages approaching -900 mV were measured between copper electrodes within the aquifer sediments and a single reference electrode at the ground surface. Onset of EP anomalies correlated in time with both the accumulation of dissolved sulfide and the removal of uranium from groundwater. The anomalies persisted for 45 days after halting acetate injection. Current-voltage and current-power relationships between measurement and reference electrodes exhibited a galvanic response, with a maximum power density of 10 mW/m2 during sulfate reduction. We infer that the EP anomalies resulted from electrochemical differences between geochemically reduced regions and areas having higher oxidation potential. Following the period of sulfate reduction, EP values ranged from -500 to -600 mV and were associated with elevated concentrations of ferrous iron. Within 10 days of the voltage decrease, uranium concentrations rebounded from 0.2 to 0.8 ?M, a level still below the background value of 1.5 ?M. These findings demonstrate that EP measurements provide an inexpensive and minimally invasive means for monitoring the products of stimulated microbial activity within aquifer sediments and are capable of verifying maintenance of redox conditions favorable for the stability of bioreduced contaminants, such as uranium.

Williams, Kenneth H.; N'guessan, A. Lucie; Druhan, Jennifer; Long, Philip E.; Hubbard, Susan S.; Lovley, Derek R.; Banfield, Jillian F.

2010-06-01

18

Non-contact measurement of dc voltages using nonlinear elements  

NASA Astrophysics Data System (ADS)

In this work, it is shown that dc voltages may be measured via a capacitive interface, provided that the capacitance between the measurement system and the dc voltage source being measured is nonlinearized. This nonlinearization is achieved by the addition of a nonlinear capacitor in series with the coupling capacitance. Two types of nonlinear capacitor are used—multilayer ceramics and varicap diodes. Currently available multilayer ceramics have a larger value than desired but prove the concept, while the small capacitance of the varicap diode allows measurement on real wires. Results show that over a low voltage range (-8 V to +8 V), the voltage on a conductor can be measured if the coupling capacitance between source and electrode is larger than 20 pF, which equates to an electrode length of 5 cm when wire compliant with MIL-W-81044-22 is used. Detection is performed by momentarily applying a voltage at a node within the measurement system, then measuring the time it takes for this voltage to decay to a threshold level—the capacitive nonlinearity causes this time delay to be dependent upon the dc input voltage whose value is being measured.

McKenzie, G.; Record, P.

2012-04-01

19

Field Emission Measurements from Niobium Electrodes  

Microsoft Academic Search

Increasing the operating voltage of a DC high voltage photogun serves to minimize space charge induced emittance growth and thereby preserve electron beam brightness, however, field emission from the photogun cathode electrode can pose significant problems: constant low level field emission degrades vacuum via electron stimulated desorption which in turn reduces photocathode yield through chemical poisoning and\\/or ion bombardment and

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

2011-01-01

20

Measurements of EHD flow patterns in ESP with DC+Pulsed voltage hybrid power supply  

NASA Astrophysics Data System (ADS)

Results of Particle Image Velocimetry (PIV) measurements in an electrostatic precipitator (ESP) supplied with high voltage pulses superimposed on DC voltage are presented in this paper. The ESP had a stainless-steel wire discharge electrode placed between two grounded, stainless-steel plate collecting electrodes. The DC high voltage (0-20 kV) with superimposed voltage pulses (0-30 kV), either positive or negative polarity, was applied to the wire electrode. We found no effect of the applied voltage pulses upon the flow patterns when there was no DC voltage. However, when the high voltage pulses were superimposed on DC high voltage, the flow patterns were affected significantly.

Podli?ski, Janusz; Kocik, Marek; Mizeraczyk, Jerzy

2008-12-01

21

Optical wideband high-voltage measurement system  

Microsoft Academic Search

A wideband fiber-optic system for the measurement of ac high voltages is presented. The system is based on a capacitively coupled Pockels cell which works as a passive voltage sensor. The lower frequency limit is a few Hz and the upper is 150–230 MHz depending on the application. Other system characteristics are excellent electrical noise suppression, large voltage range, high

H. M. Hertz; P. Thomsen

1987-01-01

22

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

23

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

24

An electrically tunable-focusing liquid crystal lens with a low voltage and simple electrodes.  

PubMed

An electrically tunable focusing LC lens with a low voltage and simple planar electrodes is demonstrated. The inhomogeneous electric field of the LC lens without any hole-patterned-electrode is generated by using an embedded polymeric layer with a gradient distribution of dielectric constants (or relative permittivity). LC directors in the LC layer experience spatially inhomogeneous voltages even though a single voltage is applied to the planar electrodes. Such a LC lens has a low voltage (~2.6 V(rms)) and simple design of electrodes. The gradient distribution of dielectric constants of polymeric layer is discussed and the performance of the LC lens is investigated. The applications of such a LC lens are cell phones, webcam, and pico projectors. PMID:22330445

Lin, Hung-Chun; Lin, Yi-Hsin

2012-01-30

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

Measurement and Analysis of Voltage Events  

Microsoft Academic Search

This chapter describes the main issues related to the measurement and analysis of voltage events in\\u000a power systems. Section 4.1 describes the definitions and the different magnitude and duration thresholds\\u000a used in the main power-quality standards to distinguish between the different types of voltage events. Section\\u000a 4.2 describes the performance of the standard method for detection and analysis of voltage

Julio Barros; Enrique Pérez; Ramón I. Diego

27

A novel electrode power profiler for dimmable ballasts using DC link voltage and switching frequency controls  

Microsoft Academic Search

A novel electrode power profiler for dimmable ballasts using series-resonant parallel-loaded inverter is presented. Dimming of the fluorescent lamp is primarily based on reducing the dc link voltage. Variations of the electrode power (due to the decrease in the lamp current) during dimming is compensated by changing the switching frequency of the inverter, so that the resonant tank circuit current

Stephen T. S. Lee; Henry Shu-Hung Chung; S. Y. R. Hui

2004-01-01

28

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

29

Charge Injection Capacity of TiN Electrodes for an Extended Voltage Range  

PubMed Central

Many applications of neural stimulation demand a high current density from the electrodes used for stimulus delivery. New materials have been searched that can provide such large current and charge densities where the traditional noble metal and capacitor electrodes are inadequate. Titanium nitride, which has been used in cardiac pacemaker leads for many years, is one of these materials recently considered for neural stimulation. In this short report, we investigated the charge injection capacity of TiN electrodes for an extended range of cathodic voltages. The injected charge increased first slowly as a function of the electrode voltage, and then at a faster rate beyond ?1.6 V. The maximum charge was 4.45 mC/cm2 (n=6) for a cathodic voltage peak of ?3.0 V and a bias voltage of ?0.8 V. There was no evidence of bubble generation under microscopic observation. The unrecoverable charges remained under 7% of the total injected charge for the largest cathodic voltage tested. These large values of charge injection capacity and relatively small unrecoverable charges warrant further investigation of the charge injection mechanism in TiN interfaces at this extended range of electrode voltages. PMID:17946870

Patan, Mustafa; Shah, Tosha; Sahin, Mesut

2011-01-01

30

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

31

The relation of electrode voltages to charge position in SLC arc and final focus beam position monitors  

SciTech Connect

The position of a charged particle beam can be measured with a Beam Position Monitor (BPM) by converting the voltages induced on its array of electrodes into a position offset from the array's center. Most of the BPMs in the Arcs and Final Focus of the SLC use four stripline electrodes arranged symmetrically around the beam; normalized voltage differences are calculated as the difference divided by the sum of voltages on opposite electrode pairs. The resulting number is multiplied by a conversion factor, denoted in this paper as S{sub b}, to give the offset (in millimeters) of the charge from the center of the BPM. Prior to installation in the beam line, the BPMs were calibrated with a charge pulse on a rod. Owing to geometric effects which will be discussed later, a different conversion factor had to be used for calibration. It will be denoted here by S{sub r}. This paper gives the results of calculations and measurements of S{sub r} and S{sub b} for Arc and Final Focus BPMs. This paper also describes the relevant physical properties of the several types of BPMs and calculations of the expected scale factors, the measurement methods used, and gives the results of measurements, which are compared with the theoretical expectations. 2 refs., 18 figs., 7 tabs.

Fordham, C.

1989-11-02

32

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

NASA Astrophysics Data System (ADS)

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

BastaniNejad, M.; Elmustafa, A. A.; Forman, E.; Clark, J.; Covert, S.; Grames, J.; Hansknecht, J.; Hernandez-Garcia, C.; Poelker, M.; Suleiman, R.

2014-10-01

33

Fiber-optic voltage measuring system  

NASA Astrophysics Data System (ADS)

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

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

1993-09-01

34

Two-electrode voltage clamp of Xenopus oocytes under high hydrostatic pressure.  

PubMed

Functional assays of cloned ion channels and other transport systems under various hydrostatic pressures provide information on the apparent changes in protein volume occurring during conformational rearrangements. Thus, they are valuable tools in the detailed study of the molecular steps underlying the functioning of such proteins. Here we present details of a set-up which can be used for two-electrode voltage-clamp experiments on Xenopus oocytes, commonly used for heterologous protein expression, at hydrostatic (oil) pressures as high as 60 MPa (approximately 600 atm.). The advantages of this set-up over pneumatic systems include the minimization of compression/decompression-induced temperature changes, and an increased safety of handling due to the small volume (< 10 ml) of compression medium (oil) required. The performance of the system is illustrated using experimental data on the effects of high pressure on currents recorded from oocytes expressing a Shaker potassium channel mutant. This set-up is suitable for the investigation of all electrically measurable transport systems expressed in Xenopus oocytes. PMID:9696303

Schmalwasser, H; Neef, A; Elliott, A A; Heinemann, S H

1998-06-01

35

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

36

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

37

Acoustoelectric Voltage Measurements for Semiconductor Material Characterization  

NASA Astrophysics Data System (ADS)

Transverse Acoustoelectric Voltage (TAV) measurements were used to characterize the electrical and optical properties of semiconducting materials. A modified theoretical expression for the acoustoelectric voltage was obtained and utilized to evaluate the change of TAV as a function of external perturbations, such as applied bias, incident photon energy, temperature and SAW power. The change in TAV due to applied bias voltage was utilized to evaluate the density of defect states at semiconductor/insulator interfaces. The heterostructure interface between ZnSe and the Semi Insulating GaAs substrate was investigated using TAV spectroscopy on samples with different ZnSe film thickness. From these measurements the bandgap energies of ZnSe (2.663 eV) and GaAs (1.425 eV) were evaluated along with the conduction and valence band offsets between the two materials, (Delta E_{rm c} = 0.12 eV, DeltaE_ {rm v} = 1.118 eV). For pseudomorphic ZnSe films on GaAs, a reduction of one order of magnitude in the surface recombination velocity was found. As the thickness of the ZnSe films increased above 0.15 mum, an increase in surface recombination velocity was measured, which seem to indicate the presence of a large number of misfit dislocations due to the strain induced by the lattice mismatch between ZnSe and GaAs crystal structures. The theory for the TAV in a combined medium structure was developed and used to obtain a new method for determining the impurity doping profile of the transport channel of surface acoustic wave devices on piezoelectric semiconductors. This allows testing to be performed in-situ without altering or damaging the device. The doping profile and the impurity levels of a GaAs epilayer (epi) grown on a semi-insulating (SI) GaAs substrate were obtained measuring the TAV as a function of applied bias and sample temperature. From the temperature data, we have obtained three impurity levels with activation energies of 0.03, 0.19 and 0.40 eV and relative density of 4 times 10 ^{rm 11}, 1.4 times 10^{rm 13} and 3 times 10^{ rm 14} cm^{rm -3}, respectively. These levels have been associated to the presence of Te in the growth system. The fall time of the TAV signal was related to the transient behavior of free carriers in the semiconductor. The optical cross sections of the EL2 level in GaAs was evaluated by measuring the TAV fall time as a function of incident photon energy. The thermal cross section for the EL2 level was also evaluated from the measurement performed in the dark; the value obtained was sigma_ {rm n} = 7.22 times 10^{rm -14} cm^2.

Abbate, Agostino

1993-01-01

38

Performance measurements of advanced AMTEC electrodes  

Microsoft Academic Search

These results are from sodium exposure test cell experiments with advanced AMTEC electrodes performed at Texas A&M University. The majority of the results are for metal electrodes; the minority of the results are for ceramic electrodes. Initial results for iridium and titanate electrodes have been good, but degrade with time. .

Michael Schuller; Brad Fiebig; Patricia Hudson; Imran Kakwan

2000-01-01

39

Analysis of NSTX TF Joint Voltage Measurements  

SciTech Connect

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

Woolley R

2005-10-07

40

Studies of calcium channels in rat clonal pituitary cells with patch electrode voltage clamp  

PubMed Central

1. The properties of the Ca channel in tissue cultured clonal cells (GH3) isolated from a rat anterior pituitary tumour were studied with the patch electrode voltage-clamp technique. 2. To isolate the current through the Ca channel, the currents through the Na channel, the delayed K channel and the Ca2+ induced K channel were minimized by replacing the external Na+ with TEA+ and adding EGTA to the K-free solution inside the patch electrode. 3. The selectivity ratios through the Ca channel with different cations were 2·7 (Ba2+):1·6 (Sr2+):1·0 (Ca2+) and the m2 form of the activation kinetics and the relationships between the time constant and the membrane potential were common to the three divalent cations. 4. The amplitude of the Ba2+ current increased linearly with [Ba2+]o up to 25 mM and thereafter tended to show saturation. 5. The current—voltage relation showed a positive shift along the voltage axis as [Ba2+]o increased, probably due to the screening effect of Ba2+ on the negative surface charges. 6. The time constant of activation as a function of the membrane potential showed a parallel shift as [Ba2+]o was increased, suggesting that the activation kinetics were independent of the permeant ion concentration. 7. The time constant of the tail current was consistent with m2 kinetics for opening and closing of the Ca channel. 8. The extrapolated `instantaneous' tail current rapidly increased as the activating membrane potential became more positive and reached an apparent saturation at membrane potentials substantially more positive than the potential that gave the maximum peak inward current, and suggested that the single channel has a sigmoidal current—voltage relationship. 9. The power density spectrum obtained during the steady-state inward Ba2+ current had a cut-off frequency which was nearly voltage independent; this is expected if the fluctuation of the current originates from m2 activation kinetics. 10. The results of noise analysis suggest that the amplitude of the single Ca channel current was about 0·2 pA at 25 mM-Ba2+ and 0·7 pA at 100 mM-Ba2+ for membrane potentials in the vicinity of the maximum inward current. PMID:6296367

Hagiwara, Susumu; Ohmori, Harunori

1982-01-01

41

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

42

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

43

A torsional sensor for MEMS-based RMS voltage measurements  

Microsoft Academic Search

RF voltage measurement based on electrostatic RMS voltage-to-force conversion is an alternative method in comparison to the conventional thermal power dissipation method. It is based on a mechanical force induced by an RF voltage applied to a micro-mechanical system. For a theoretically adequate resolution and high precision measurements, the necessary geometrical dimensions of the sensor require the application of micro

J. Dittmer; R. Judaschke; S. Büttgenbach

2008-01-01

44

Real-time measurement of electrode impedance during intracochlear electrode insertion  

PubMed Central

Objectives This pilot study details the use of a software tool that uses continuous impedance measurement during electrode insertion, with the eventual potential to assess and optimize electrode position and reduce insertional trauma. Study Design Software development and experimental study with human cadaveric cochleae and two live surgeries. Methods A prototype program to measure intracochlear electrode impedance and display it graphically in real time has been developed. The software was evaluated in human cadaveric temporal bones while simultaneously making real time fluoroscopic recordings, and in two live surgeries during intracochlear electrode insertion. Results Impedance changes were observed with various scalar positions, and values were consistent with those obtained using clinically available software. Using Contour Advance™ electrodes, impedance values increased after stylet removal, particularly when using the monopolar mode. Conclusion Impedance values seem systematically affected by electrode position, with higher values being associated with proximity to the cochlear wall. The new software is capable of acquiring impedance measurements during electrode insertion and this data may be useful to guide surgeons to achieve optimal and atraumatic electrode insertion, to guide robotic electrode insertion, and to provide insights about electrode position in the cochlea. PMID:23529884

Tan, Chin-Tuan; Svirsky, Mario; Anwar, Abbas; Kumar, Shaun; Caessens, Bernie; Carter, Paul; Treaba, Claudiu; Roland, J. Thomas

2013-01-01

45

Insulator and electrode mass erosion and surface voltage holdoff recovery for transient, high current surface discharges  

NASA Astrophysics Data System (ADS)

Several polymeric insulator materials commonly used as sidewall insulators in EM accelerators are subjected to repetitive, high current transient surface discharges. The insulator materials tested include the thermosetting polymers G-9, G-10, and G-11 (i.e., fiberglass reinforced melamine and epoxy) and the thermoplastic polymers Lexan (i.e, polycarbonate) and Delrin (i.e., polyacetyl). Empirical scaling relationships are given that relate the total amount of insulator and electrode (i.e., molybdenum) mass erosion versus the total amount of arc energy transferred. Scaling relationships are also given that relate the 'lifetime' of the given polymer as a function of the initial discharge current. The 'lifetime' of an insulator material is defined as the number of discharges required to reduce the initial surface holdoff voltage to its half-power level for three consecutive discharges, and is a useful parameter when specifying insulator materials to be used in high power switching devices.

Engel, T. G.; Dickens, J. C.; Kristiansen, M.

1993-01-01

46

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

NASA Technical Reports Server (NTRS)

Performance of the iron-titanium redox flow cell was studied as a function of acid concentration. Anion permeable membranes separated the compartments. Electrodes were graphite cloth. Current densities ranged up to 25 mA/square centimeter. Open-circuit and load voltages decreased as the acidity was increased on the iron side as predicted. On the titanium side, open-circuit voltages decreased as the acidity was increased in agreement with theory, but load voltages increased due to decreased polarization with increasing acidity. High acidity on the titanium side coupled with low acidity on the iron side gives the best load voltage, but such cells show voltage losses as they are repeatedly cycled. Analyses show that the bulk of the voltage losses are due to diffusion of acid through the membrane.

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

1977-01-01

47

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

PubMed

As advanced negative electrodes for powerful and useful high-voltage bipolar batteries, an intercalated metal-organic framework (iMOF), 2,6-naphthalene dicarboxylate dilithium, is described which has an organic-inorganic layered structure of ?-stacked naphthalene and tetrahedral LiO4 units. The material shows a reversible two-electron-transfer Li intercalation at a flat potential of 0.8?V with a small polarization. Detailed crystal structure analysis during Li intercalation shows the layered framework to be maintained and its volume change is only 0.33?%. The material possesses two-dimensional pathways for efficient electron and Li(+) transport formed by Li-doped naphthalene packing and tetrahedral LiO3 C network. A cell with a high potential operating LiNi0.5 Mn1.5 O4 spinel positive and the proposed negative electrodes exhibited favorable cycle performance (96?% capacity retention after 100 cycles), high specific energy (300?Wh?kg(-1) ), and high specific power (5?kW?kg(-1) ). An 8?V bipolar cell was also constructed by connecting only two cells in series. PMID:25196994

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

2014-10-20

48

Three electrode measurements on solid electrolytes  

SciTech Connect

AC impedance spectroscopy and chronopotentiometry have been used to study solid-state ionic conductors. Results obtained using three electrodes are compared to those using a two-electrode configuration. The uncompensated resistance was shown to depend strongly on the geometric placement of the electrodes. The optimal configuration for minimized uncompensated resistance effects is similar to the Luggin capillary arrangement in the liquid phase. The effect of non-negligible geometric capacitance on interpretation of results is discussed.

Pham, A.Q.; Glass, R.S.

1995-12-01

49

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

PubMed Central

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

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

2010-01-01

50

Simple linearization of measurement based on photovoltaic voltage  

NASA Astrophysics Data System (ADS)

Based on the logarithmic relationship between photovoltaic voltage and incident light intensity of a photo-detector, a simple and low-cost method is proposed to linearize the measurement of nonlinear variables related to light intensity. Theoretical analysis shows that this linear measurement method is feasible in a large measurement range if we choose a proper load resistance for the photodiode. Based on the Lambert-Beer law and the photovoltaic voltage-based measurement method, the linear measurements of liquid level and liquor concentration have been achieved experimentally by directly detecting the output voltage of a solar cell, and their nonlinearities are both less than 2.0%.

Li, Changsheng

2008-10-01

51

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

PubMed

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. PMID:22462950

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

2012-03-01

52

High-speed metal-insulator transition in vanadium dioxide films induced by an electrical pulsed voltage over nano-gap electrodes  

NASA Astrophysics Data System (ADS)

We report the fabrication of VO2-based two terminal devices with ˜125-nm gaps between the two electrodes, using a simple, cost-effective method employing optical lithography and shadow evaporation. Current-voltage characteristics of the obtained devices show a main abrupt metal-insulator transition (MIT) in the VO2 film with voltage threshold values of several volts, followed by secondary MIT steps due to the nanostructured morphology of the layer. By applying to the two-terminal device a pulsed voltage over the MIT threshold, the measured switching time was as low as 4.5 ns and its value does not significantly change with device temperature, supporting the evidence of an electronically driven MIT.

Leroy, J.; Crunteanu, A.; Bessaudou, A.; Cosset, F.; Champeaux, C.; Orlianges, J.-C.

2012-05-01

53

RESEARCH ON SPUTTERING PHENOMENA, SURFACE STABILITY AND VOLTAGE BREAKDOWN FOR ALKALI-COATED REFRACTORY ELECTRODES. Quarterly Report No. 2, August 1, 1961October 31, 1961  

Microsoft Academic Search

Studies of voltage breakdown in ion propulsion systems are described. ; Results of microscopic examinations of Cs deposited on W electrodes indicate that ; under ion propulsion conditions, Cs intercepted by the electrodes can accumulate ; and apread readily from the point of impact, thus enhancing the breakdown ; likelinood by spreading on the electrode support insulation. Plans for examining

R. L. Strayer; F. M. Charbonnier; E. C. Cooper

1963-01-01

54

A microsystem of low-voltage-driven electrophoresis on microchip with array electrode pairs for the separation of amino acids.  

PubMed

In this paper, a new approach for the separation of amino acids on the electrophoresis chip-based low-voltage-driven electrophoresis was reported in detail. This low-voltage-driven electrophoresis process could be realized by powering directly the arrayed electrode pairs with low direct current (DC) voltage to generate a moving electric field along the separation microchannel, which could maintain enough electric field strength for electrophoresis. The proposed microfluidic electrophoresis chip was bonded directly with silicon-on-insulator (SOI) substrate and polydimethylsiloxane (PDMS) cover plate at room temperature. The microfluidic channels and the arrayed electrodes were etched on SOI wafer by silicon microelectromechanical system technology. A specially integrated circuit was proposed to power a 30-60-V DC voltage to particular sets of these electrode pairs in a controlled sequence such that the moving electric field could be formed, and the low-voltage-driven electrophoresis could be realized in the microchannel. In the experiments, with 10(-4) mol/L phenylalanine and lysine as analytes, the separation of amino acids on the low-voltage-driven electrophoresis microchip was conducted by homemade integrated control circuit; a method for separating amino acids was well established. It was also shown that the phenylalanine and lysine mixture was effectively separated in less than 7 min and with a resolution of 2.0. To the best of our knowledge, the low-voltage-driven microchip electrophoresis device could be of potential prospective in the fields of integrated and miniaturized biochemical analysis system. PMID:19543715

Xu, Yi; Hu, Xiaoguo; Liang, Jing; Sun, Jianxin; Gu, Wenwen; Zhao, Tianming; Wen, Zhiyu

2009-08-01

55

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

E-print Network

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

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

2011-05-24

56

Kerr electro-optic field mapping measurements in water using parallel cylindrical electrodes  

Microsoft Academic Search

An extensive set of Kerr electro-optic field mapping measurements are reported for highly purified water over the temperature range of 8.8–29.5 °C. The Kerr constant is independent of temperature over this range and equals B&bartil;3.4×10?14 m\\/V2. Pulsed high voltages up to 140 kV across parallel cylindrical electrodes with a 1-cm gap are applied on millisecond time scales. For early times,

Markus Zahn; Tatsuo Takada; Steven Voldman

1983-01-01

57

Beam based measurement of beam position monitor electrode gains  

NASA Astrophysics Data System (ADS)

Low emittance tuning at the Cornell Electron Storage Ring (CESR) test accelerator depends on precision measurement of vertical dispersion and transverse coupling. The CESR beam position monitors (BPMs) consist of four button electrodes, instrumented with electronics that allow acquisition of turn-by-turn data. The response to the beam will vary among the four electrodes due to differences in electronic gain and/or misalignment. This variation in the response of the BPM electrodes will couple real horizontal offset to apparent vertical position, and introduce spurious measurements of coupling and vertical dispersion. To alleviate this systematic effect, a beam based technique to measure the relative response of the four electrodes has been developed. With typical CESR parameters, simulations show that turn-by-turn BPM data can be used to determine electrode gains to within ˜0.1%.

Rubin, D. L.; Billing, M.; Meller, R.; Palmer, M.; Rendina, M.; Rider, N.; Sagan, D.; Shanks, J.; Strohman, C.

2010-09-01

58

Stand for investigation properties of arrays of ion-selective electrodes for multiparameter measurements  

NASA Astrophysics Data System (ADS)

This paper describes the measurement system used for measuring properties of the ion selective electrodes and for multi parameter measurement. The measurement system can be used for research of dynamic properties of the ion selective electrodes and electrode arrays.

Kozyra, Andrzej

2001-08-01

59

Effect of number of electrodes, electrode displacement, and RMS measurement noise on the localization accuracy of ECG inverse problem  

Microsoft Academic Search

The effect of the number of electrodes, electrode displacement and RMS measurement noise was evaluated using an anatomically-detailed computer model of the thorax as a volume conductor. The body surface potential distributions due to cardiac dipole sources were calculated by applying five different electrode montages: the eight electrodes representing the independent leads of the standard 12-lead electrocardiogram (ECG), a modified

H. G. Puurtinen; J. Hyttinen; P. Laarne; N. Takano; J. Malmivuo

2001-01-01

60

A novel ultra sensitive method for voltage noise measurements  

Microsoft Academic Search

Ultra low noise measurements often require the application of signal processing and correction techniques to go beyond the noise performances of front-end amplifiers. In this paper, we propose a new method for the measurement of a voltage noise source that allows, at least in principle, the complete elimination of the noise introduced by the amplifiers used for the measurements. This

Felice Crupi; Gino Giusi; Carmine Ciofi; Calogero Pace

2005-01-01

61

Enhanced sensitivity cross-correlation method for voltage noise measurements  

Microsoft Academic Search

Ultralow noise measurements often require the application of signal processing and correction techniques to go beyond the noise performances of front-end amplifiers. In this paper, a new method for the voltage noise measurement is proposed, which allows, at least in principle, the complete elimination of the noise introduced by the amplifiers used for the measurements. This is obtained by resorting

Felice Crupi; Gino Giusi; Carmine Ciofi; Calogero Pace

2006-01-01

62

Capacitance-voltage measurement in memory devices using ferroelectric polymer  

NASA Astrophysics Data System (ADS)

Application of thin polymer film as storing mean for non-volatile memory devices is investigated. Capacitance-voltage (C-V) measurement of metal-ferroelectric-metal device using ferroelectric copolymer P(VDF-TrFE) as dielectric layer shows stable 'butter-fly' curve. The two peaks in C-V measurement corresponding to the largest capacitance are coincidental at the coercive voltages that give rise to zero polarization in the polarization hysteresis measurement. By comparing data of C-V and P-E measurement, a correlation between two types of hysteresis is established in which it reveals simultaneous electrical processes occurring inside the device. These processes are caused by the response of irreversible and reversible polarization to the applied electric field that can be used to present a memory window. The memory effect of ferroelectric copolymer is further demonstrated for fabricating polymeric non-volatile memory devices using metal-ferroelectric-insulator-semiconductor structure (MFIS). By applying different sweeping voltages at the gate, bidirectional flat-band voltage shift is observed in the ferroelectric capacitor. The asymmetrical shift after negative sweeping is resulted from charge accumulation at the surface of Si substrate caused by the dipole direction in the polymer layer. The effect is reversed for positive voltage sweeping.

Nguyen, Chien A.; Lee, Pooi See

2006-01-01

63

A multichannel meter for measuring root-mean-square voltage  

Microsoft Academic Search

There are two operational regimes, viz., measurement of the root-mean-square input voltages and calibration of the measuring channels. In the first regime, after feeding the 'Start of measurement' pulse with an uncertainty of duration that is equal to the half-period (half-cycle) of the 'Synchronization' signal, processing of the information starts at the output of the measuring channels using the analog-to-digital

A. I. Erygin; Yu. A. Litvinov; I. A. Nikol'nikov; A. L. Semenov

1993-01-01

64

Effect on plasma and etch-rate uniformity of controlled phase shift between rf voltages applied to powered electrodes in a triode capacitively coupled plasma reactor  

SciTech Connect

The influence of the phase shift between rf voltages applied to the powered electrodes on plasma parameters and etch characteristics was studied in a very high-frequency (VHF) capacitively coupled plasma (CCP) triode reactor. rf voltages at 100 MHz were simultaneously applied to the top and bottom electrodes having a controlled phase shift between them, which could be varied between 0 deg. and 360 deg. Several plasma and process characteristics were measured as a function of the phase shift: (i) radial profiles of plasma-emission intensity, (ii) line-of-sight averaged plasma-emission intensity, and (iii) radial profiles of blanket SiO{sub 2} etching rate over a 300 mm wafer. Radial profiles of plasma emission were obtained using the scanning optical probe. It has been shown that all the measured characteristics strongly depend on the phase shift: (i) plasma-emission intensity is minimal at phase shift equal to 0 deg. and maximal at 180 deg. for all radial positions, while the emission radial profile changes from bell-shaped distribution with considerable nonuniformity at 0 deg. to a much more flattened distribution at 180 deg.; (ii) line-of-sight averaged plasma-emission intensity shows a similar dependence on the phase shift with minimum and maximum at 0 deg. and 180 deg., respectively; and (iii) the etch-rate radial profile at 180 deg. shows a much better uniformity as compared to that at 0 deg. Some of these results can be qualitatively explained by the redistribution of plasma currents that flow between the electrodes and also from the electrodes to the grounded wall with the phase shift. We suggest that the phase-shift effect can be used to improve the plasma and etch-rate spatial uniformity in VHF-CCP triode reactors.

Sung, Dougyong; Jeong, Sangmin; Park, Youngmin; Volynets, Vladimir N.; Ushakov, Andrey G.; Kim, Gon-Ho [Mechatronics and Manufacturing Technology Center, Samsung Electronics Co. Ltd., 416 Maetan-3 dong, Yeongtong-Gu, Suwon, Gyeonggi-Do, 443-742 (Korea, Republic of); Department of Nuclear Engineering, Seoul National University, Seoul, 151-744 (Korea, Republic of)

2009-01-15

65

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

Microsoft Academic Search

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, UP, the average, U, the effective, Ueff or the maximum peak, UP tube voltage. This work proposed a method for determination of the PPV from measurements with a kV-meter that measures

C. J. Hourdakis

2011-01-01

66

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

67

Measurements of Electrode Skin Impedances using Carbon Rubber Electrodes - First Results  

NASA Astrophysics Data System (ADS)

Non-invasive bioimpedance measurement as a tool in biomedical engineering and life sciences allows conclusions about condition and composition of living tissue. For interfacing the electronic conduction of the instrumentation and the ionic conduction of the tissue, electrodes are needed. A crucial point is the uncertainty arising from the unknown, time-varying and current density depend Electrode Skin Impedance (ESI). This work presents ESI measurements using carbon rubber electrodes on different human test subjects. The measurements for this work are carried out by employing a high accuracy Bioimpedance Measurement System (BMS) developed by the authors group, which is based on a Field Programmable Gate Array (FPGA) System on Chip (SoC). The system is able to measure magnitude and phase of complex impedances using a two- or four-electrode setup, with excitation currents from 60 ?A to 5 mA in a frequency range from about 10 kHz to 300 kHz. Achieved overall measurement uncertainties are below 1%.

Kaufmann, Steffen; Ardelt, Gunther; Ryschka, Martin

2013-04-01

68

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

69

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

70

Generated Voltage Measurement of Poly(3-Hexylthiophene) LB Films  

NASA Astrophysics Data System (ADS)

The electrical conductivity of a bulky polythiophene or a bulky gold has high value. If the electrical conductivity of nanometer scale films of polythiophene or gold has high value, it is very interesting that the molecular devices are combined with these polythiophene. The Langmuir-Blodgett (LB) films were synthesized from poly(3-hexylthiophene) (P3HT), and the LB films of P3HT were doped by the electrochemical method in present study. Samples of Al/P3HT LB films/Au generated the voltage. The time dependence of the voltage generated from the Al/P3HT LB films/Au was measured. The electrochemical doping caused the generated voltage of the samples to increase.

Kushida, Masahito; Koide, Tetsuya; Hino, Koji

71

Root-Mean-Square Measurement of Distinct Voltage Signals  

Microsoft Academic Search

A circuit for measuring the root-mean-square (RMS) value of N distinct voltage signals, which employs two second-generation current conveyors and 2N + 1 metal-oxide-semiconductor transistors, is presented. The proposed circuit can find applications in measuring the RMS value of the output error signal of an artificial neural network (ANN). The presented network can also be used for realizing half-and full-wave

Erkan Yüce; Shahram Minaei; Sezai Tokat

2007-01-01

72

Current-voltage characteristics and breakdown mechanism in one-dimensional band and mott insulators attached to electrodes  

NASA Astrophysics Data System (ADS)

The current-voltage characteristics and mechanism of bias-induced breakdown in one-dimensional models for band and Mott insulators are investigated theoretically by using nonequilibrium Green's functions. We attach the models to metallic electrodes, the effects of which are incorporated into the self-energy. For the models of both the band and the Mott insulators with lengths L C , the bias voltage induces a breakdown of the insulating state, and the breakdown mechanism shows a crossover depending on L C . When L C is smaller than the correlation length ? = W/?, the threshold is determined basically by the bias V th ˜ ?, where W and ? are the bandwidth and the energy gap, respectively. For systems with L C ? ?, the threshold is governed by the electric field, V th/ L C , which is consistent with a Landau-Zener-type breakdown V th/ L C ? ?2/ W.

Tanaka, Yasuhiro; Yonemitsu, Kenji

2013-06-01

73

Structure of the near-electrode dissociation-recombination charged layers at various low-voltage conductivities of a low-conducting liquid  

NASA Astrophysics Data System (ADS)

The current passage through a low-conducting liquid is simulated for a system of electrodes with a highly nonuniform electric-field distribution at voltages lower and higher than the threshold of appearance of electrohydrodynamic flows. The structure of the near-electrode dissociation-recombination charged layers is considered in terms of the following two-charge formation models: constant dissociation in the volume but without injection and injection from an electrode and constant dissociation in the volume. The change in the polarity of the near-electrode charged layer caused by an increase in the voltage or a change in the low-voltage conductivity of the liquid is analyzed. Two types of electrohydrodynamic flows, which appear in real electrohydrodynamic devices and have opposite directions, are obtained using one mathematical model.

Stishkov, Yu. K.; Chirkov, V. A.

2013-12-01

74

Effect of applied voltage, initial concentration and natural organic matter on sequential reduction/oxidation of nitrobenzene by graphite electrodes  

PubMed Central

Carbon electrodes are proposed in reactive sediment caps for in situ treatment of contaminants. The electrodes produce reducing conditions and H2 at the cathode and oxidizing conditions and O2 at the anode. Emplaced perpendicular to seepage flow, the electrodes provide the opportunity for sequential reduction and oxidation of contaminants. The objectives of this study are to demonstrate degradation of nitrobenzene (NB) as a probe compound for sequential electrochemical reduction and oxidation, and to determine the effect of applied voltage, initial concentration and natural organic matter on the degradation rate. In H-cell reactors with graphite electrodes and buffer solution, NB was reduced stoichiometrically to aniline (AN) at the cathode with nitrosobenzene (NSB) as the intermediate. AN was then removed at the anode, faster than the reduction step. No common AN oxidation intermediate was detected in the system. Both the first order reduction rate constants of NB (kNB) and NSB (kNSB) increased with applied voltage between 2V and 3.5 V (when the initial NB concentration was 100 µM, kNB=0.3 d?1 and kNSB=0.04 d?1at 2V; kNB=1.6 d?1 and kNSB=0.64 d?1at 3.5 V) but stopped increasing beyond the threshold of 3.5V. When initial NB concentration decreased from 100 to 5 µM, kNB and kNSB became 9 and 5 times faster, respectively, suggesting that competition for active sites on the electrode surface is an important factor in NB degradation. Presence of natural organic matter (in forms of either humic acid or Anacostia River sediment porewater) decreased kNB while slightly increased kNSB, but only to a limited extent (~factor of 3) for dissolved organic carbon content up to 100 mg/l. These findings suggest that electrode-based reactive sediment capping via sequential reduction/oxidation is a potentially robust and tunable technology for in situ contaminants degradation. PMID:22571797

Sun, Mei; Reible, Danny D.; Lowry, Gregory V.; Gregory, Kelvin B.

2012-01-01

75

Effects of electrode curvature, distance from glass insulator, and addition of hydrogen on field-emission currents and breakdown voltage in vacuum  

Microsoft Academic Search

Measurements of the prebreakdown currents have been made for highly polished stainless-steel electrodes in an ultrahigh vacuum (UHV) at 10-9 Torr as a function of electrode separation in the range 0.5-3.81 mm. Three sets of electrodes are employed to investigate the dependence of the prebreakdown current on the radius of curvature of the electrodes and the electrodes-insulator distance. The breakdown

R. Hackam; S. K. Salman

1974-01-01

76

Measuring the electrical breakdown of air for very small electrode separations  

NASA Astrophysics Data System (ADS)

Understanding the basic principles of electrical breakdown in air for small electrode separations is becoming very important in the design and operation of microscale devices such as MEMS sensors and actuators. This work presents a new method [1] for measuring the value of breakdown voltage in air for electrode separations from 400 nm to 45 ?m. The method consists of bringing 2 evaporated Au electrodes on sapphire together in a parallel plate geometry. Amongst the improvements of our method are the measurement of plate separation and the very small surface roughness ( average of 6 nm ). We demonstrate the ability to deduce the value of the separation of the plates by the value of the capacitance. We analyze the data for small separations, using the theory of standard field emission and field amplification on the surface of a conductor. We come to a prediction about the geometry and size of the electrode surface protrusions that would produce the observed emission. For the first time, we look for these predicted protrusions using an AFM. We find several reasons why the standard theory does not appear to explain our data. [1] Rev. Sci. Instrum. 77, 034702 (2006)

Hourdakis, Emmanouel; Bryant, Garnett W.; Zimmerman, Neil M.

2006-10-01

77

Evaluation of different stimulation and measurement patterns based on internal electrode: application in cardiac impedance tomography.  

PubMed

The conductivity distribution around the thorax is altered during the cardiac cycle due to the blood perfusion, heart contraction and lung inflation. Previous studies showed that these bio-impedance changes are appropriate for non-invasive cardiac function imaging using Electrical Impedance Tomography (EIT) techniques. However, the spatial resolution is presently low. One of the main obstacles in cardiac imaging at the heart location is the large impedance variation of the lungs by respiration and muscles on the dorsal and posterior side of the body. In critical care units there is a potential to insert an internal electrode inside the esophagus directly behind the heart in the same plane of the external electrodes. The aim of the present study is to evaluate different current stimulation and measurement patterns with both external and internal electrodes. Analysis is performed with planar arrangement of 16 electrodes for a simulated 3D cylindrical tank and pig thorax model. In our study we evaluated current injection patterns consisting of adjacent, diagonal, trigonometric, and radial to the internal electrode. The performance of these arrangements was assessed using quantitative methods based on distinguishability, sensitivity and GREIT (Graz consensus Reconstruction algorithm for Electrical Impedance Tomography). Our evaluation shows that an internal electrode configuration based on the trigonometric injection patterns has better performance and improves pixel intensity of the small conductivity changes related to heart near 1.7 times in reconstructed images and also shows more stability with different levels of added noise. For the internal electrode, when we combined radial or adjacent injection with trigonometric injection pattern, we found an improvement in amplitude response. However, the combination of diagonal with trigonometric injection pattern deteriorated the shape deformation (correlation coefficient r=0.344) more than combination of radial and trigonometric injection (correlation coefficient r=0.836) for the perturbations in the area close to the center of the cylinder. We also find that trigonometric stimulation pattern performance is degraded in a realistic thorax model with anatomical asymmetry. For that reason we recommend using internal electrodes only for voltage measurements and as a reference electrode during trigonometric stimulation patterns in practical measurements. PMID:23017828

Nasehi Tehrani, J; Oh, T I; Jin, C; Thiagalingam, A; McEwan, A

2012-11-01

78

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

SciTech Connect

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

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

2014-01-01

79

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

80

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

81

Developing Barbed Microtip-Based Electrode Arrays for Biopotential Measurement  

PubMed Central

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

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

2014-01-01

82

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

83

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

NASA Astrophysics Data System (ADS)

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, Ueff or the maximum peak, UP 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 kPPV,kVp and the average kPPV,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.

Hourdakis, C. J.

2011-04-01

84

Leakage current measurements of high voltage ceramic capacitors  

NASA Astrophysics Data System (ADS)

Leakage currents of NOVACAP Company NPO surface mount high voltage multilayer ceramic capacitors, type LS1808N102K302NX080, were measured before and after irradiation by 200MeV protons at a fluence of 5 × 1014/cm2. Two banks of 20 capacitors showed that the leakage current was < 1 × 10-11 ampere. As we see from the results, the average current was very close to zero and the measurement accuracy was limited by the equipment sensitivity and the experimental setup noise.

Atac, M.; Arndt, K.; Gobbi, B.; Los, S.; Parashar, N.; Sellberg, G.; Spencer, E.

2006-08-01

85

Motional induction voltage measurements in estuarine environments: the Ria de Aveiro Lagoon (Portugal)  

NASA Astrophysics Data System (ADS)

Electromagnetic fluctuations in the ocean have external sources like ionospheric-magnetospheric current systems, and purely internal oceanic sources associated with interaction between water velocity fields and the geomagnetic field, that is, the motionally induced voltage (MIV). During the last decade techniques based on MIV have proven to provide reliable information when applied to the flow monitoring at large oceanic channels. In this paper analysis of data resulting from the implementation of these techniques in a small-scale system, that is, the Ria de Aveiro lagoon (Portugal), is presented. A submarine cable crossing the channel at the entrance of the lagoon (Barra channel) allows the measurement of the potential difference between two electrodes located on both sides of the channel. Spectral analysis of these data reveals that measured voltages are dominated by semidiurnal M2, S2/K2 frequencies. Comparison between the sum of the four main constituents determined by harmonic analysis and the sea surface elevation measured at a tide gauge located at the lagoon mouth reveal that the measured potential difference is proportional to the water flow. To estimate the water flow in this location from the MIV measurements the data collected using this methodology were compared with numerical results obtained from a previously calibrated hydrodynamic model. A value of 720 m3 s-1 mV-1 was estimated for the coefficient relating voltage and water transport at Barra. Taking this value into account a sediment layer of about 20 m is estimated, at Barra. The results show that it is possible to indirectly measure the water transport (by tidal and residual flows) through the channel by measuring the differences of electrical potential. This demonstrates the applicability of the MIV method to a small-scale system.

Nolasco, Rita; Soares, António; Dias, João M.; Monteiro Santos, Fernando A.; Palshin, N. A.; Represas, Patricia; Vaz, Nuno

2006-07-01

86

Nanoscopic electrode molecular probes  

DOEpatents

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

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

2012-05-22

87

Capacitance-Voltage Measurement of Transporting Function at Cell Membrane  

NASA Astrophysics Data System (ADS)

In this paper, we report the detection of transporting function at cell membrane using capacitance-voltage (CV) measurement. The detection principle of our devices is based on the field-effect of electrostatic interaction between charged species at cell membrane in solution and surface electrons in silicon crystal through the gate insulator of Si3N4/SiO2 thin double-layer. We designed an oocyte-based field-effect capacitor, on which a Xenopus laevis oocyte was fixed. The transporter of human organic anion transporting peptide C (hOATP-C) was expressed at oocyte membrane by induction of cRNA. The electrical phenomena such as ion or molecular charge flux at the interface between cell membrane and gate surface could be detected as the change of flat band voltage in CV characteristics. The flat band voltage shift decreased with incubation time after introduction of substrate into the oocyte-based field-effect capacitor. The electrical signal is due to the change of charge flux from the oocyte at the gate surface inspired by transporter-substrate binding. The platform based on the oocyte-based field-effect capacitor is suitable for a simple and non-invasive detection system in order to analyze function of transporters related to drug efficacy.

Sakata, Toshiya; Miyahara, Yuji

88

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

89

Effect of the high-voltage electrode polarity and wire preheating on the energy characteristics of electric explosion of fine tungsten wires in vacuum  

Microsoft Academic Search

Results are presented from experiments on the explosion of 30.5-?m tungsten wires at a current density of up to 140 MA\\/cm2 and resistive-heating time of 40–100 ns. The experiments were performed both with and without preheating of wires and at\\u000a different polarities of the high-voltage electrode. The effect of plasma production at the electrodes on the initiation of\\u000a breakdown along

A. G. Russkikh; R. B. Baksht; A. Yu. Labetski?; P. R. Levashov; S. I. Tkachenko; K. V. Khishchenko; A. V. Shishlov; A. V. Fedyunin; S. A. Cha?kovski?

2006-01-01

90

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

91

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

NASA Astrophysics Data System (ADS)

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

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

2007-03-01

92

Electrochemical measurements on lightweight composite nickel-graphite battery electrodes  

SciTech Connect

Graphite mat fibers and nickel metal composite electrodes are superior to sintered carbonyl-nickel powder electrodes in nickel-cadmium cells. The composite electrode functions as a thin electrode and can be utilized in nickel-cadmium, nickel-iron, nickel-zinc, and nickel-hydrogen electrochemical systems. 4 refs.

Sutula, R.A.; Crowe, C.R.

1980-12-01

93

Traceability of pH measurements by glass electrode cells: performance characteristic of pH electrodes by multi-point calibration  

Microsoft Academic Search

Routine pH measurements are carried out with pH meter-glass electrode assemblies. In most cases the glass and reference electrodes are thereby fashioned into a single probe, the so-called 'combination electrode' or simply 'the pH electrode'. The use of these electrodes is subject to various effects, described below, producing uncertainties of unknown magnitude. Therefore, the measurement of pH of a sample

R. Naumann; Ch. Alexander-Weber; R. Eberhardt; J. Giera; P. Spitzer

2002-01-01

94

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

E-print Network

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

Donoghue, Linda (Linda Marie)

2011-01-01

95

Simultaneous Measurement of Dopamine and Ascorbic Acid at Cnt Electrode  

NASA Astrophysics Data System (ADS)

Electrochemical behaviors of dopamine and ascorbic acid have been studied at the carbon nanotube electrode using cyclic voltammetry. Electrocatalysis has been found for dopamine redox reactions at the carbon nanotube electrode in comparison with the glassy carbon electrode. A well-defined oxidative peak for ascorbic acid was observed at the carbon nanotube electrode with the peak potential negative shift versus the glassy carbon electrode. The important discover was that the carbon nanotube electrode can be used to detect low level of dopamine selectively with high sensitivity in the presence of a large excess of ascorbic acid in the acidic media and in the physiological pH buffer solution as well.

Hu, C. G.; Wang, W. L.; Feng, B.; Wang, H.

96

An Accurate Voltage Measurement System Based on DSP and Optical Fiber Transmission  

Microsoft Academic Search

\\u000a Accurate voltage measurement is very important for power energy measurement. To reduce the total error of power energy measurement,\\u000a a novel voltage measurement system is designed in this paper. The system uses Digital Signal Processor (DSP) to accomplish\\u000a signal acquisition and processing, and uses optical fiber to realize zero voltage drops in long distance transmission. The\\u000a results of expriment show

Qiufeng Shang; Hao Li

97

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

98

Measurement of the Direct-Current (Faradic) Resistance of the Electrode-Electrolyte Interface for Commonly Used Electrode Materials  

Microsoft Academic Search

The direct-current (Faradic) resistance is important because it is the highest impedance that an electrode-electrolyte interface can attain. In this study, the Faradic resistance (Rf) of identical pairs of 0.5 cm2 electrodes of bare and chlorided silver, tin and chlorided tin, nickel–silver, copper, and carbon was measured in contact with 0.9% saline at room temperature. It was found that for

L. A. Geddes; R. Roeder

2001-01-01

99

[Dielectric measurements on the rabbit cornea using a surface electrode].  

PubMed

Using a concentric surface electrode, we measured in situ electrical impedance in the 10 kHz-100 MHz range for the anterior portion of eyeballs isolated from white rabbits. Replacement of fluid in the anterior chamber with an equal volume of air led to decreases in conductivity, resulting in a marked alteration of impedance behavior as expressed in a loss tangent plot. Eyeballs either with corneal erosin induced through mechanical abrasion or with endothelial injury caused by a 70% ethanol replacement in the anterior chamber were subjected to impedance measurements. Dielectric analysis based on the two-term Cole-Cole equation revealed that the observed overall dielectric dispersion could be divided into two subdispersions. Of these, the first dispersion, occurring at low frequencies was associated with the endothelial layer and the second, higher-frequency dispersion was due to the epithelial layer of the cornea. PMID:8337961

Watanabe, M; Mokudai, Y; Ueno, H; Ando, M; Irimajiri, A

1993-05-01

100

Method for Determining the Faradaic Impedance of an Electrode Reaction: Application to Metal Corrosion Rate Measurements  

Microsoft Academic Search

A method was developed to determine the faradaic impedance (Z[sub t]) of an electrode reaction on the basis of a measurement of the electrode impedance (Z). Neither the reaction mechanism nor the equivalent electric circuit needed to be known. Z[sub f] was determined by a method based on determination of the minimum of the length of the electrode admittance diagram

F. Berthier; C. Montella; J.-P. Diard; B. Le Gorrec

1995-01-01

101

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

102

Semiconductor Measurement Technology: Suppression of Premature Dielectric Breakdown for High-Voltage Capacitance Measurements.  

National Technical Information Service (NTIS)

Surface-initiated premature dielectric breakdown is encountered in extended-range MIS C(V) measurements at applied-bias voltages above some sample-dependent threshold value, e.g., 3 to 5 kV across a 150-micrometer-thick wafer of sapphire. It is necessary ...

A. M. Goodman

1977-01-01

103

Stimulation characteristics of a steroid-eluting electrode compared with three conventional electrodes.  

PubMed

Stimulation thresholds of a steroid-eluting electrode (Medtronic CapSure 4003, 9 patients) were compared with three conventional electrodes (carbon-tipped lead, Siemens-Elema 423 S/60, 10 patients; Elgiloy-tipped lead, Cordis Encor, 10 patients; platinum-tipped lead, Telectronix Laserdish 030-276, 9 patients). Voltage thresholds were determined during implantation, 1-3 days, 6 weeks, and 6 months postimplantation. No significant difference among the four electrodes was found in regard to stimulation and sensing behavior during implantation. Compared to intraoperative measurements, mean increase in voltage threshold and absolute voltage thresholds were substantially less for the steroid-eluting electrode than for the other tested electrodes 6 weeks and 6 months after implantation. The rheobasechronaxie product, a parameter of the stimulation performance of electrodes, underlined the superior pacing characteristics of the steroid-eluting electrode. To achieve low chronic stimulation threshold by pharmacological means is an attractive direction for future electrode technology. PMID:1689827

Klein, H H; Steinberger, J; Knake, W

1990-02-01

104

An energy based security measure for assessing vulnerability to voltage collapse  

Microsoft Academic Search

A security measure is defined to indicate vulnerability to voltage collapse based on an energy function for system models that includes voltage variation and reactive loads. The system dynamic model, the energy function, and the security measure are first illustrated in a simple radial system. Application of the security measure and its computational aspects are then examined in a standard

C. L. DeMarco; T. J. Overbye

1990-01-01

105

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

Microsoft Academic Search

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

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

1998-01-01

106

Electrically evoked compound action potential measures for virtual channels versus physical electrodes  

PubMed Central

Objectives The number of distinct pitch percepts for cochlear implant (CI) listeners is somewhat limited by the number of physical electrodes in the array. Newer-generation CIs have the capability to potentially increase this number by stimulating areas of the cochlea between the physical electrodes. Currently this is achieved by electrically coupling adjacent electrodes or by simultaneously activating two electrodes with independent current sources (i.e., “current steering”). Presumably, either type of dual-electrode stimulation will generate neural excitation patterns that are intermediate to those generated by either physical electrode alone (henceforth termed virtual channel). However, it is not clear whether virtual-channel stimulation yields neural recruitment patterns with similar shapes and rates of growth as compared with each physical electrode alone. The purpose of this study was to compare basic electrically evoked compound action potential (ECAP) measures for physical electrodes and virtual channels to determine whether properties of the respective excitation patterns were similar. Design Data were collected for 12 adult CI recipients (N = 6 Nucleus Freedom CI24RE, N = 2 Advanced Bionics HiResolution 90K, N = 4 Advanced Bionics CII). ECAP responses were measured for a set of three adjacent physical electrodes and two corresponding intermediate virtual channels (e.g., physical electrodes 4, 5, and 6 and virtual channels 4+5 and 5+6) at three positions along the electrode array (basal, middle, and apical). Virtual channels for Nucleus subjects were produced via electrical coupling of adjacent electrode pairs (“dual-electrode mode”). For AB subjects, virtual channels were produced via simultaneous, in-phase stimulation of adjacent electrode pairs with 50 % of the total current delivered to each electrode in the pair. Specific ECAP measures were: (1) threshold and slope of the input/output (I/O) functions, (2) amplitude for a masker-probe interval of 1500 ?sec (measure of refractory recovery), and (3) the relative location of spread-of-excitation (SOE) functions among virtual channels and adjacent physical electrodes. Measures for virtual channels were compared with those for the flanking physical electrodes using a multivariate analysis of variance. Results There were no statistically significant differences between physical electrodes and virtual channels for ECAP thresholds, slope of the I/O function, or refractory recovery. On average, SOE functions for the virtual channels were spatially located approximately halfway between SOE functions for the adjacent physical electrodes. Conclusions Results from this study suggest that virtual channels produce neural recruitment patterns with properties similar to those elicited by the adjacent physical electrodes. PMID:21187752

Hughes, Michelle L.; Goulson, Adam M.

2011-01-01

107

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

108

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

109

Characterization of automotive high voltage networks for EMI measurements  

Microsoft Academic Search

One major task in developing electric cars is to control electromagnetic interferences (EMI) of their power train. Fast slew rates in power electronics increase efficiency, but also emitted radio frequency (RF) disturbances. One main approach to reduce EMI within automotive systems is a complete shielding of its high voltage (HV) power network. The shielding of HV power networks changes the

M. Reuter; S. Tenbohlen; W. Kohler

2010-01-01

110

Membrane reference electrode  

DOEpatents

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

Redey, L.; Bloom, I.D.

1988-01-21

111

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

112

Dynamic correlations in sliding charge-density waves probed by spatially resolved measurements of voltage oscillations  

NASA Astrophysics Data System (ADS)

In sliding charge-density wave (CDW) conductors such as NbSe3, voltage oscillations at a frequency proportional to the local CDW velocity accompany CDW motion and can furnish many insights into the dynamics of these systems. We have used high-performance cryogenic differential amplifiers to make position-dependent measurements of voltage oscillations in the quasisteady state. These measurements yield voltage-voltage and velocity-velocity correlations and the temperature dependence of the CDW's longitudinal and transverse velocity coherence.

Geil, E. C.; Thorne, R. E.

2014-11-01

113

Quantum measurement of an electron in a disordered potential: Delocalization versus measurement voltages  

NASA Astrophysics Data System (ADS)

Quantum point contact (QPC), one of the typical mesoscopic transport devices, has been suggested to be an efficient detector for quantum measurement. In the context of two-state charge qubit, our previous studies showed that the QPC’s measurement back-action cannot be described by the conventional Lindblad quantum master equation. In this work, we study the measurement problem of a multistate system, say, an electron in disordered potential, subject to the quantum measurement of the mesoscopic detector QPC. The effect of measurement back-action and the detector’s readout current are analyzed, where particular attention is focused on some new features and the underlying physics associated with the measurement-induced delocalization versus the measurement voltages.

Hu, Xue-Ning; Li, Xin-Qi

2006-01-01

114

Establishment of traceability for strain measuring data acquisition system in terms of voltage  

Microsoft Academic Search

This paper emphasizes on establishment of traceability for the strain measuring data acquisition system in terms of voltage.\\u000a If this amplifier’s output voltage is not calibrated then traceability chain breaks. To complete the traceability chain, the\\u000a amplifier’s output voltage has been calibrated for corresponding strain. The sensitivity is calculated using calibration results\\u000a and further used to feed in data acquisition

Bijendra Pal; Anil Kumar; Sunidhi Madan; Saood Ahmad; A. K. Govil

2010-01-01

115

Sensitivity of performance and degradation measurements on AMTEC electrodes in sodium exposure test cells to experiment conditions  

Microsoft Academic Search

In this paper we discuss performance and degradation measurements made on AMTEC electrodes in sodium exposure test cells. We measured electrode temperatures, sodium pool temperatures, and apparent charge transfer resistance values, from which we derived normalized exchange current density (B) values for WRh, MoRe, Re, and Ir electrodes. Electrode temperatures ranged from 600°C to 900°C, while sodium pool temperatures ranged

Michael Schuller; B. Fiebig; Patricia Hudson; Alicia Williams

2000-01-01

116

The electrically noncontacting ECG measurement on the toilet seat using the capacitively-coupled insulated electrodes  

Microsoft Academic Search

The studies of ECG measurement on the toilet seat have been performed specifically for the ubiquitous health care. Instead of the mainly used dry electrodes having several problems such as the electrical safety or the environmental stability, we used the capacitively-coupled insulated electrodes, which were composed of the Cu plate and the PTFE film for the measurement. The biosignal sensed

Ko Keun Kim; Yong Kyu Lim; Kwang Suk Park

2004-01-01

117

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

118

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

119

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

120

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

121

High voltage dielectric frequency response measurements on polyethylene samples during water tree ageing  

Microsoft Academic Search

High voltage dielectric frequency response measurements have been performed on laboratory aged polyethylene samples with special attention for studying non-linear effects during water tree ageing. A measurement set-up for making high voltage and high sensitive measurements on disc shaped samples in the range of 10 pF is presented. Prior to ageing, the samples were vacuum treated and then equipped with

P. Tharning; U. Gafvert

1995-01-01

122

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

123

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

Microsoft Academic Search

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

Pattira Homhuan; Toshihide Nabatame; Toyohiro Chikyow; Sukkaneste Tungasmita

2011-01-01

124

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

125

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

126

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

E-print Network

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

Jadidian, Jouya

127

Studying the Performance of Conductive Polymer Films as Textile Electrodes for Electrical Bioimpedance Measurements  

NASA Astrophysics Data System (ADS)

With the goal of finding novel biocompatible materials suitable to replace silver in the manufacturing of textile electrodes for medical applications of electrical bioimpedance spectroscopy, three different polymeric materials have been investigated. Films have been prepared from different polymeric materials and custom bracelets have been confectioned with them. Tetrapolar total right side electrical bioimpedance spectroscopy (EBIS) measurements have been performed with polymer and with standard gel electrodes. The performance of the polymer films was compared against the performance of the gel electrodes. The results indicated that only the polypropylene 1380 could produce EBIS measurements but remarkably tainted with high frequency artefacts. The influence of the electrode mismatch, stray capacitances and large electrode polarization impedance are unclear and they need to be clarified with further studies. If sensorized garments could be made with such biocompatible polymeric materials the burden of considering textrodes class III devices could be avoided.

Cunico, F. J.; Marquez, J. C.; Hilke, H.; Skrifvars, M.; Seoane, F.

2013-04-01

128

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

129

Realization of the SI Unit Volt by Means of a Voltage Balance  

Microsoft Academic Search

A description is given of the measuring system set up at the PTB for the realization of the SI volt and the determination of the conversion factor Kv by means of a voltage balance. The voltage balance comprises two cylindrical electrodes to generate the electrostatic force from the measuring voltage of 10.186 kV, and a substitution balance to measure the

V. Sienknecht; T. Funck

1986-01-01

130

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

SciTech Connect

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

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

2007-07-15

131

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

132

Electrode arrays for measuring groundwater flow direction and velocity  

Microsoft Academic Search

The movement of 2,000 liters of salt water after injection into groundwater within gravels a few meters below the ground surface at three injection sites was traced by six different resistivity monitoring arrays; the resistivity rectangle, Schlumberger sounding, Wenner sounding, Wenner fixed-spacing, mise-a-la-masses and downhole electrode array. Five of the arrays indicated ground water flow direction and seepage velocity. As

P. A. White

1994-01-01

133

Simple light guide for measuring irradiance in an aqueous oxygen electrode chamber  

Microsoft Academic Search

The light-dependent reactions of photosynthesis are often measured with Clark-type oxygen electrodes yet the irradiance level\\u000a inside aqueous oxygen electrode reaction vessels is seldom reported due to the difficulty of measuring light inside a small\\u000a volume chamber. We describe a simple light guide terminating in a 90° prism that can be inserted into a reaction vessel. Incoming\\u000a irradiation is directed

Jeff Vogtschaller; Robert Wise

2004-01-01

134

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

Microsoft Academic Search

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

Branislav Djokic; E. So

2008-01-01

135

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

136

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 PMID:3967838

Rawlings, J M; Lucas, M L

1985-01-01

137

A photoelectric relay for measuring voltages of low frequency  

Microsoft Academic Search

Summary  A device is described, which can be used for amplifying and measuring the a.c. output of slow responding detectors (e.g. bolometers),\\u000a receiving signals of constant but low frequency (~1 Hz). This device, based on frequency conversion, which in principle is\\u000a insensitive to drift-effects, consists of a primary galvanometer, a rotating disk, chopping the lightbeam reflected by the\\u000a moving mirror of

J. M. W. Milatz; H. J. J. van Boort; J. van Laar; C. T. J. Alkemade

1955-01-01

138

A photoelectric relay for measuring voltages of low frequency  

Microsoft Academic Search

Summary  A device is described, which can be used for amplifying and measuring the a.c. output of slow responding detectors (e.g. bolometers),\\u000a receiving signals of constant but low frequency (?1 Hz). This device, based on frequency conversion, which in principle is\\u000a insensitive to drift-effects, consists of a primary galvanometer, a rotating disk, chopping the lightbeam reflected by the\\u000a moving mirror of

J. M. W. Milatz; H. J. J. van Boort; J. van Laar; C. T. J. Alkemade

1953-01-01

139

Control of current and voltage oscillations in a short dc discharge making use of external auxiliary electrode  

E-print Network

Control of current and voltage oscillations in a short dc discharge making use of external.1063/1.4757111 View Table of Contents: http://rsi.aip.org/resource/1/RSINAK/v83/i10 Published by the American plasma in a Hall thruster Phys. Plasmas 19, 113508 (2012) Consideration of the electron energy

Kaganovich, Igor

140

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

PubMed

Asymmetric supercapacitors (ASCs) based on free-standing membranes with high energy density and high output voltage are reported. MnO2 nanowire/carbon nanotube (CNT) composites and MoO3 nanobelt/CNT composites are selected as the anode and the cathode materials of the devices, respectively. The ASC has a high volumetric capacitance of 50.2 F cm(-3) at a scan rate of 2 mV s(-1) and a high operation voltage window of 2.0 V. Especially, after a middle layer with an inner-connection structure was inserted between the anode and the cathode, the output voltage of the whole device can achieve 4.0 V. The full cell of series ASCs (SASC) with an inner-connection middle layer has a high energy density of 28.6 mW h cm(-3) at a power density of 261.4 mW cm(-3), and exhibits excellent cycling performance of 99.6% capacitance retention over 10?000 cycles. This strategy of designing the hybridized structure for SASCs provides a promising route for next-generation SCs with high energy density and high output voltage. PMID:25367363

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

2014-12-21

141

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

142

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

143

The coefficient of the voltage induced frequency shift measurement on a quartz tuning fork.  

PubMed

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

Hou, Yubin; Lu, Qingyou

2014-01-01

144

A new method for measuring the threshold voltage of small-geometry MOSFETs from subthreshold conduction  

NASA Astrophysics Data System (ADS)

A new method for measuring the threshold voltage of small geometry MOS devices is presented. Based on the drain current equation in the subthreshold region, the threshold voltage ( VTH), defined as the gate voltage required for a surface band-bending of 2 ?F, can be accurately determined experimentally by the Quasi-Constant-Current (QCC) method. Compared with some other commonly used methods, this technique has the advantages of better fitting accuracy in subthreshold region, extracting the VTH with a unique value, and being suitable for small geometry devices over a wide range of voltage biases, temperatures, and process parameter variations. It can be used either for circuit simulation like the MOS3 model in SPICE, or as a routine monitor of processing like channel doping profile, gate oxide thickness or source and drain junction depths.

Deen, M. J.; Yan, Z. X.

1990-05-01

145

Constant voltage stress induced current in Ta2O5 stacks and its dependence on a gate electrode  

NASA Astrophysics Data System (ADS)

Response of 8 nm Ta2O5 stacks with different gates (Al, W and Au) to voltage stress at gate injection is studied by probing under various voltage/time conditions at room temperature and at 100 °C. A stress-induced leakage current (SILC) is detected in all samples and reveals gate dependence. It is established that the pre-existing traps actually govern this response, and the impact of gate-induced defects is stronger. The Au-gated devices are the most susceptible to the stress degradation. Two processes—electron trapping at pre-existing traps and positive charge build-up—are suggested to be responsible for generation of SILC. It is concluded that despite some gate effects, the origin of CVS degradation in this particular high-k dielectric is different from that in SiO2.

Atanassova, E.; Stojadinovic, N.; Paskaleva, A.; Spassov, D.; Vracar, L.; Georgieva, M.

2008-07-01

146

Transcatheter measurement of myocardium electrical impedance: 2 versus 3 electrode method  

Microsoft Academic Search

We are interested in the use of electrical impedance spectroscopy for on-line in-situ monitorization of the state of the myocardium tissue using a transcatheter method. In this study we evaluate a new 3 electrode measurement method (3EM) in comparison with the standard two electrode method (2EM). We analyze the effect of the tip distance to the myocardium wall and the

Y. Salazar; R. Bragos; J. Rosell

2003-01-01

147

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

148

Sensitive immunodetection through impedance measurements onto gold functionalized electrodes.  

PubMed

This article deals with a direct electrochemical method of detecting antigens using new methods of functionalization of gold electrodes. Based on the reacting ability of gold with sulfhydryl groups, three protocols for the fixation of antibodies have been explored. They are based on either the self-assembling properties of functional thiols bearing long alkyl chains or the possibility of a direct coupling of antibody moieties. Coverage rates as high as 97% can be reached. The analysis of the electrochemical impedance behavior of such layers can lead to a sensitive method for the direct detection of the antibody/antigen interaction. The addition of a redox couple in the tested solution, acting as an amplifier, allowed detection limits for the antigens as low as a few picograms/milliliter to be reached. PMID:11209460

Ameur, S; Martelet, C; Jaffrezic-Renault, N; Chovelon, J M

2000-01-01

149

Practical nitric oxide measurement employing a nitric oxide-selective electrode  

NASA Astrophysics Data System (ADS)

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

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

1994-08-01

150

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

151

Measurement scheme of kicker impedances via beam-induced voltages of coaxial cables  

NASA Astrophysics Data System (ADS)

A new theory, which satisfies the causality condition, is developed to describe impedances of kicker magnets with coaxial cables. The theoretical results well describe measurement results, which are obtained by standard wire methods. On the other hand, when beams pass through the kicker, voltages are induced at the terminals of coaxial cables. In other words, by analyzing the voltages, the kicker impedance for the beams can be obtained. The observed impedances are consistent with the theoretical results. The theory describes the impedance for non-relativistic beams, as well. The theoretical, simulation and measurement results indicate that the horizontal kicker impedance is drastically reduced by the non-relativistic effect.

Shobuda, Yoshihiro; Irie, Yoshiro; Toyama, Takeshi; Kamiya, Junichiro; Watanabe, Masao

2013-06-01

152

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

153

Voltage transformer frequency response. Measuring harmonics in Norwegian 300 kV and 132 kV power systems  

Microsoft Academic Search

Measuring harmonics in high voltage power systems with inductive and in particular capacitive voltage transformers, CVTs, may cause large errors. Test carried out by The Norwegian National Grid Company (Statnett), Bergenshalvoens Kommunale Kraftselskap (BKK) and The Norwegian Electric Power Research Institute (now SINTEF Energy Research) revealed errors from 80% to +1200% (0,2-12 pu) of correct values. Inductive voltage transformers did

H. Seljeseth; E. A. Saethre; T. Ohnstad; I. Lien

1998-01-01

154

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

PubMed Central

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

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

2014-01-01

155

Compact 132 kV combined optical voltage and current measurement system  

Microsoft Academic Search

This paper presents details of a compact 132 kV insulator arrangement developed for use with unlinked optical voltage and current transducers (OCT and OVT). The measured temperature characteristics of terbium gallium garnet, the Faraday rotator in the OCT, is given and compared to previously published results. The application of this data to a temperature compensation system for the OCT is

Andrew Cruden; Zachery J. Richardson; James R. McDonald; Ivan Andonovic; William Laycock; Alan Bennett

1998-01-01

156

Compact 132 kV combined optical voltage and current measurement system  

Microsoft Academic Search

This paper presents details of a compact 132 kV insulator arrangement developed for use with unlinked optical voltage and current transducers (OCT and OVT). The measured temperature characteristics of terbium gallium garnet, the Faraday rotator in the OCT, are given and compared to previously published results. The application of this data to a temperature compensation system for the OCT is

A. Cruden; Z. J. Richardson; J. R. McDonald; I. Andonovic; W. Laycock; A. Bennett

1997-01-01

157

Acoustic measurement of the arc voltage applicable to arc welding and arc furnaces  

Microsoft Academic Search

A new technique is proposed for determining the time evolution of the voltage in the column of an electric arc. It is based on measurement of the sound wave produced by the arc, which is shown to depend on the rate of change of the electrical power fed to the arc column. There is no electrical connection to the arc

M. G. Drouet; F. Nadeau

1982-01-01

158

Nature Macmillan Publishers Ltd 1998 function between two traces which are measured at bias voltages  

E-print Network

Nature � Macmillan Publishers Ltd 1998 8 function between two traces which are measured at bias BAB; this means that by increas- ing the bias voltage by 5 V a minimum GAB is turned into a maximum-excitable media Sa� ndor Ka� da� r,

Showalter, Kenneth

159

Measuring the root-mean-square values of random voltages with tube voltmeters  

Microsoft Academic Search

The above examples indicate that in using standard tube voltmeters for measuring root-mean-square values of noise voltages it is necessary to take into account the distribution laws of their instantaneous values. Otherwise substantial errors can be made. By using the above technique it is possible to find the required corrections for every type of voltmeter and any kind of distribution

V. N. Kuz'michev; V. F. Nesteruk

1970-01-01

160

Measurement and simulation of conductive dielectric two-layer materials with a multiple electrodes sensor  

Microsoft Academic Search

Impedance spectroscopy has been shown to provide a great potential as a measuring technique for monitoring human blood glucose. The two major potential benefits are the ability to perform non-invasive and continuous measurements. Previous work has outlined the range of challenges of such an impedance based technique. Our impedance sensor is composed of several capacitive fringing field electrodes with various

F. Dewarrat; L. Falco; A. Caduff; M. S. Talary; Y. Feldman; A. Puzenko

2008-01-01

161

Electrode Structure Optimum for Impedance Measurement of Intraoperative Breast Cancer Focus  

Microsoft Academic Search

The impedance measuring method may be used to assess the margin of breast cancer focus in the process of operation. This rapid measurement can shorten the waiting time and lighten patients' pain in partial mastectomy. In order to satisfy the requirements of margin assessment, the design of electrodes structure is studied in this paper. Through simulation analyses on three types

WANG Chao CHEN; Hong-bin Chen; Da-li Du; Ya-su Xiao; Hong-jun Sun

2008-01-01

162

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

Microsoft Academic Search

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

Halbach

1977-01-01

163

Renewable pencil electrodes for highly sensitive stripping potentiometric measurements of DNA and RNA.  

PubMed

Renewable graphite pencil electrodes are demonstrated to be excellent materials for adsorptive stripping measurements of trace nucleic acids. While displaying an attractive stripping performance, comparable to that of conventional carbon paste electrodes, the pencil electrode offers a convenient (mechanical) renewal, with each stripping potentiogram recorded at a fresh surface. Various pencil lead materials and lengths have been examined and experimental variables of the pretreatment and measurement procedures have been explored and optimized. The extremely low detection limits (e.g., 3 micrograms l-1 tRNA with 10 min accumulation) are coupled to a good surface-to-surface reproducibility (RSD of 6.4% for 14 repetitive measurements of 1 mg l-1 ssDNA). PMID:10885061

Wang, J; Kawde, A N; Sahlin, E

2000-01-01

164

The Effects of Preheating of a Fine Tungsten Wire and the Polarity of a High-Voltage Electrode on the Energy Characteristics of an Electrically Exploded Wire in Vacuum  

Microsoft Academic Search

Results obtained from experimental and numerical studies of tungsten wires electrical explosion in vacuum are presented. The experiments were performed both with and without preheating of the wires using positive or negative polarity of a high-voltage electrode. Preheating is shown to increase energy deposition in the wire core due to a longer resistive heating stage. The effect was observed both

Alexander G. Rousskikh; Rina B. Baksht; Stanislav A. Chaikovsky; Anatoly V. Fedunin; Konstantin V. Khishchenko; A. Yu. Labetsky; P. R. Levashov; A. V. Shishlov; S. I. Tkachenko

2006-01-01

165

Measurement of contact voltage drop and resistance in organic solar cells  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

166

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

167

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

168

Simple light guide for measuring irradiance in an aqueous oxygen electrode chamber.  

PubMed

The light-dependent reactions of photosynthesis are often measured with Clark-type oxygen electrodes yet the irradiance level inside aqueous oxygen electrode reaction vessels is seldom reported due to the difficulty of measuring light inside a small volume chamber. We describe a simple light guide terminating in a 90 degrees prism that can be inserted into a reaction vessel. Incoming irradiation is directed to a commercially available quantum sensor positioned at the other end of the light guide. Both materials for and construction of the device are inexpensive. PMID:16151875

Vogtschaller, Jeff; Wise, Robert

2004-01-01

169

Improvement in microscope photometry by voltage to frequency conversion: analogue measurement and digital processing.  

PubMed

A system for digital measurement of microscope photometric signals, based on Voltage to Frequency Conversion (VFC) and suitable for automatic data processing, has been devised. Advantages and disadvantages are illustrated with special emphasis on the comparison between photocurrent measuring and photon counting techniques. A statistical analysis of the results allows the calibration of VFC net counts versus detected photons. A biological application is reported; this shows the suitability of the system even to low light levels. PMID:6172589

Freitas, M I; Giordano, P A; Bottiroli, G

1981-11-01

170

Transmembrane potential measurements on plant cells using the voltage-sensitive dye ANNINE-6.  

PubMed

The charging of the plasma membrane is a necessary condition for the generation of an electric-field-induced permeability increase of the plasmalemma, which is usually explained by the creation and the growth of aqueous pores. For cells suspended in physiological buffers, the time domain of membrane charging is in the submicrosecond range. Systematic measurements using Nicotiana tabacum L. cv. Bright Yellow 2 (BY-2) protoplasts stained with the fast voltage-sensitive fluorescence dye ANNINE-6 have been performed using a pulsed laser fluorescence microscopy setup with a time resolution of 5 ns. A clear saturation of the membrane voltage could be measured, caused by a strong membrane permeability increase, commonly explained by enhanced pore formation, which prevents further membrane charging by external electric field exposure. The field strength dependence of the protoplast's transmembrane potential V (M) shows strong asymmetric saturation characteristics due to the high resting potential of the plants plasmalemma. At the pole of the hyperpolarized hemisphere of the cell, saturation starts at an external field strength of 0.3 kV/cm, resulting in a measured transmembrane voltage shift of ?V(M) = -150 mV, while on the cathodic (depolarized) cell pole, the threshold for enhanced pore formation is reached at a field strength of approximately 1.0 kV/cm and ?V(M) = 450 mV, respectively. From this asymmetry of the measured maximum membrane voltage shifts, the resting potential of BY-2 protoplasts at the given experimental conditions can be determined to V(R) = -150 mV. Consequently, a strong membrane permeability increase occurs when the membrane voltage diverges |V(M)| = 300 mV from the resting potential of the protoplast. The largest membrane voltage change at a given external electric field occurs at the cell poles. The azimuthal dependence of the transmembrane potential, measured in angular intervals of 10° along the circumference of the cell, shows a flattening and a slight decrease at higher fields at the pole region due to enhanced pore formation. Additionally, at the hyperpolarized cell pole, a polarization reversal could be observed at an external field range around 1.0 kV/cm. This behavior might be attributed to a fast charge transfer through the membrane at the hyperpolarized pole, e.g., by voltage-gated channels. PMID:20309592

Flickinger, Bianca; Berghöfer, Thomas; Hohenberger, Petra; Eing, Christian; Frey, Wolfgang

2010-11-01

171

Broadband electromagnetic characterization of a 100? traveling-wave electrode by measuring scattering parameters  

NASA Astrophysics Data System (ADS)

The Single Bunch Selector (SBS) will be used on the Spiral2 linear accelerator to reduce the rate of high energy bunches reaching the target with, in principle, no residual particles from the suppressed bunches. For this purpose, a pulsed electromagnetic wave will travel along the 100? microstrip meander line electrode of the SBS. In this work we describe the broadband accurate characterization of the electrode electromagnetic features. The method applied here leads to the analytical determination of complex characteristic impedance, propagation constant, and group velocity from a measurement of the 50? scattering parameters on the meander transmission line. Particular care is given to the de-embedding phase of the transitions required to connect the meander electrode to the measurement device.

Consoli, Fabrizio; Balleyguier, Pascal; Di Giacomo, Marco

2013-07-01

172

Modification of DNA towards high conductance and transport measurements with mechanically controllable break junction electrodes  

NASA Astrophysics Data System (ADS)

The DNA molecule is proposed to be used as building block for molecular electronic devices by virtue of its unique recognition and self-assembling properties. However, electron transport properties of DNA are still not well established mainly because poor binding between DNA and gold electrodes. Here, we synthesized new DNA samples with terminal bases modified with a thiol group on its C5 atom and protected with Me3Si for better binding with gold electrodes and better conductivity because of better electron overlap. Its transport properties were measured with mechanically controlled break junction. Conductance with a current of 700 nA in 0.25V were obtained, which is higher than most of the former reports. We also measured conductance through DNA G-quadruple instead of double-stranded structure., which shows a more stable conductance when the distance between electrodes reversibly varied over a several nm.

Liu, Shoupeng; Bornemann, Benjamin; Weisbrod, Samuel; Tang, Zhuo; Marx, Andreas; Erbe, Artur; Scheer, Elke

2011-03-01

173

A portable transfer chamber for electrochemical measurements on electrodes prepared in ultra-high vacuum  

NASA Astrophysics Data System (ADS)

This paper describes a versatile, light weight, and portable chamber dedicated to the transfer of electrodes from ultra-high vacuum (UHV) to atmospheric pressure and the liquid phase. This chamber can be connected to a liquid-phase reaction cell to perform electrochemical measurements and transfer back the electrode to the UHV environment. The experimental set-up can also be turned in order to make the electrode the bottom of the electrochemical cell. The validity and the efficiency of the experimental set-up were tested with a Pt(111) surface that provides unique electrochemical features in acidic sulphate-containing solution. This transfer chamber concept provides the surface science community with a new and versatile tool, complementary to existing systems, which allows fast electrolyte purging or electrochemical measurements under well-controlled mass transport conditions.

El-Jawad, M.; Chemin, J.-L.; Gilles, B.; Maillard, F.

2013-06-01

174

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

PubMed Central

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

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

1998-01-01

175

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.

176

A high-DC-voltage GaAs photoemission gun: Transverse emittance and momentum spread measurements  

SciTech Connect

We have built a high-DC-voltage photoemission gun and a diagnostic beamline permitting us to measure rms transverse emittance ({epsilon}{sub x}) and rms momentum spread ({delta}) of short-duration electron pulses produced by illuminating the cathode with light from a mode-locked, frequency-doubled Nd:YLF laser. The electron gun is a GaAs photocathode source designed to operate at 500kV. We have measured {epsilon}{sub x} and {delta} for conditions ranging from emittance-dominated to space-charge-dominated. We report these measurements as functions of microbunch charge for different beam radii, pulse lengths, and voltages/field gradients at the cathode, and compare them with PARMELA calculations.

Engwall, D.; Bohn, C.; Cardman, L. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)] [and others

1997-06-01

177

Measurement of Dielectric Permittivity and Conductivity of Samples Using Guarded Electrodes.  

NASA Astrophysics Data System (ADS)

A laboratory apparatus is designed to measure the complex dielectric permittivity of both liquid and solid samples in the frequency range 2 to 13 MHz. This device uses a guarded electrode sample holder to eliminate the fringing effects. A synthetic focusing method is utilized to ensure that the potentials at both the main and the guard electrodes are equal. Extensive measurements on NaCl solutions of different salinities are made to study the accuracy of the guarded electrode method. It is found that the measured complex permittivities are in good agreement with those reported in the literature. Furthermore, various measurements have been conducted on Berea sandstones, and glass beads which are saturated with saline water. Two independent apparatus, namely, the guarded electrode holder and the parallel-disk holder, are used to investigate the variation of the complex permittivity of soil with amount of diesel contaminant. A mixing law is selected to compare the measured data with the theory. Finally, the effect of the gap that inevitably exists between a solid sample and the parallel-plate capacitor is studied using computer simulation. Procedures to correct for the gap are developed.

Darayan, Shahryar

178

An instrumentation amplifier as a front-end for a four-electrode bioimpedance measurement.  

PubMed

The performance of a monolithic instrumentation amplifier used as an interface for a four-electrode bioimpedance measurement is examined with a commercially available impedance meter based on an auto-balancing bridge. The errors due to particularities in the input stage of the impedance meter, when used without a front-end, were several orders of magnitude higher than the measured quantity. The analysis was performed on an electrical circuit model of the skin and electrodes over a frequency range of 20 Hz to 1 MHz. The achieved accuracy with balanced electrode impedances for the frequencies up to 100 kHz can be below 0.2% for impedance magnitude and 0.1 degrees for impedance phase, which is within the specified basic accuracy range of the LCR-meter used for the measurements. At frequencies above 100 kHz the errors are increasing and are higher than the LCR-meter's basic accuracy. This study indicates that use of an instrumentation amplifier as a front-end with the particular LCR-meter can significantly improve the measurement accuracy of the four-electrode bioimpedance measurement at low frequencies. PMID:17664668

Zagar, T; Krizaj, D

2007-08-01

179

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

180

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

181

Measurements of stray antenna capacitance in the STEREO/ WAVES instrument: Comparison of the measured voltage  

E-print Network

is the quasi-thermal noise spectroscopy, which uses the voltage fluctuation spectrum on an electric antenna velocity distributions in the frame of the antenna. In the absence of a static magnetic field that the resulting shot noise spectrum in the solar wind dominates the power at lower frequencies. The shot noise

California at Berkeley, University of

182

Polyimide-based multi-channel arrayed electrode for measuring EEG signal on the skull of mouse.  

PubMed

In this paper, we have developed 40 channel multiple electrodes mounted on the surface of mouse's skull using polyimide substrate and tested its performance by measuring EEG signals. The recording site of the electrode was electroplated by Pt to enhance both contact impedance and adhesive strength by applying proper current, cleaning surface and removing H(2) gas bubbles. For in vivo test, the electrode was placed on the skull of F1 mouse and EEG signals were measured. We observed the suitability of electrode for measuring EEG signals from multiple areas on the skull. The spectrum of EEG signal to change was observed by urethane administration. PMID:19964191

Baek, Dong-Hyun; Lee, Eun-Joong; Moon, Jin-Hee; Choi, Jee Hyun; Pak, James Jungho; Lee, Sang-Hoon

2009-01-01

183

The isolated anterior stomach of larval mosquitoes (Aedes aegypti): voltage-clamp measurements with a tubular epithelium.  

PubMed

The anterior stomach of larval Aedes aegypti was isolated and perfused via two pipettes. For transepithelial voltage (V(te)) measurement, the inflow pipette and the bath were connected via agar bridges to calomel electrodes. For voltage-clamping, the lumen of the tissue contained an Ag/AgCl wire held by the outflow pipette, and the preparation was placed in a bath within a spiral of Ag/AgCl wire. After equilibrating the tissue in mosquito saline on both sides, a V(te) of -8+/-1 mV was measured (+/-S.E.M., N=32). Current-voltage curves (+/-100 mV) demonstrated ohmic behaviour of the epithelium. Short-circuiting resulted in a current (I(sc)) of 103+/-16 microA cm(-2) and a mean transepithelial conductance (G(te)) of 11.8+/-1.3 mS cm(-2) (+/-S.E.M., N=32). A Yonath-Civan plot of G(te) of individual preparations over the corresponding I(sc) resulted in a straight line (r(2)=0.8422), indicating that the difference in I(sc) of individual preparations is mainly based on different transcellular conductances (G(c)). This analysis allowed to estimate the mean leak conductance (G(l) approximately 3.9 mS cm(-2)) and the mean transcellular electromotive force (E(c) approximately 13 mV). After administering 0.2 micromol L(-1) serotonin, I(sc) and G(te) significantly increased, to 457+/-49 microA cm(-2) and to 21.3+/-2.3 mS cm(-2) (+/-S.E.M., N=31, P<0.05), respectively. The Yonath-Civan plot after serotonin resulted again in a straight line (r(2)=0.8219), indicating a mean G(l) of about 1 mS cm(-2) and a mean E(c) of about 22 mV. Dinitrophenol (2.5 mmol L(-1)) almost abolished I(sc) and significantly reduced G(te) (N=6). Concanamycin A (100 micromol L(-1)) reduced I(sc) by more than 90% without significantly affecting G(te). PMID:16310390

Onken, Horst; Moffett, Stacia B; Moffett, David F

2006-01-01

184

Testing of an ammonia ion selective electrode for ammonia nitrogen measurement in the methanogenic sludge  

Microsoft Academic Search

The ammonia ion selective electrode method was the most practical and the most convenient one for measuring the ammonia nitrogen in methanogenic sludge. This is because of its simplicity, rapidity, high precision and accuracy, freedom from interference, small sample size, and possibility for continuous monitoring.

Anh LeDuy; Rejean Samson

1982-01-01

185

Ion selective electrodes for measurement of sodium and chloride in salinity experiments  

Microsoft Academic Search

A method of measuring sodium (Na) and chloride (Cl) content of plant tissue and root uptake of these ions using ion selective electrodes (ISE) was developed and tested. Peach [Prunus persica (L.) Batsch.] and barley (Hordeum vulgare L.) plants were grown for 52 days in solution culture with up to 50 and 100 mM NaCl added, respectively. During this time,

Mark Rieger; Paula Litvin

1998-01-01

186

Measurements of the Fracture Energy of Lithiated Silicon Electrodes of Li-Ion Batteries  

E-print Network

decreases from 5 to 1.5 GPa and the elastic modulus decreases from 92 to 12 GPa in transitioning from,11 Hertzberg et al. used nanoindentation methods to measure the hardness and elastic modulus of lithiated the biaxial elastic modulus of thin-film silicon electrodes as a function of lithium concentration using

Suo, Zhigang

187

An Inexpensive Electrode and Cell for Measurement of Oxygen Uptake in Chemical and Biochemical Systems.  

ERIC Educational Resources Information Center

The continuous measurement of oxygen consumption in an enzymatic reaction is a frequent experimental fact and extremely important in the enzymatic activity of oxygenase. An electrochemical system, based on a polarographic method, has been developed to monitor the oxygen uptake. The system developed and electrode used are described. (JN)

Brunet, Juan E.; And Others

1983-01-01

188

Comparison of dry-textile electrodes for electrical bioimpedance spectroscopy measurements  

Microsoft Academic Search

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

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

2010-01-01

189

Measurement of dielectric constant and conductivity of samples using guarded electrodes  

NASA Astrophysics Data System (ADS)

A laboratory apparatus is designed to measure the complex permittivity of both liquid and solid samples in the frequency range from 2 to 13 MHz. This device uses a guarded-electrode sample holder to significantly reduce fringe effects. A synthetic focusing method is utilized to ensure that the potentials at both the main and the guard electrodes are equal. Extensive measurements on NaCl solutions of different salinities are made to study the accuracy of the guarded-electrode method. The measured complex permittivities are in good agreement with those reported in the literature. The deviation is less than 3% for the conductivity measurement and depends on the salinity of the solution for the dielectric constant measurement. Various measurements conducted on Berea sandstones and glass beads saturated with saline water showed the accuracy and feasibility of the experimental set up. This measurement method might be used to obtain accurate values for the conversion of measured data from the measurement while drilling (MWD) resistivity tool.

Darayan, Shahryar; Shattuck, David P.; Shen, Liang C.; Liu, Richard C.

1996-11-01

190

Measurement of Component Cell Current-Voltage Characteristics in a Tandem-JunctionTwo-Terminal Solar Cell  

E-print Network

Measurement of Component Cell Current-Voltage Characteristics in a Tandem- JunctionTwo-Terminal Solar Cell Chandan Das, Xianbi Xiang and Xunming Deng Department of Physics and Astronomy, University of Toledo, Toledo, Ohio 43606 Abstract A new method for measuring component cell current-voltage (I

Deng, Xunming

191

Spectroscopic measurements on a titanium plasma gun with hydrogenated electrodes  

Microsoft Academic Search

The plasma produced by a plasma gun which consists of concentric titanium and tantalum washers has been observed in the plasma gun as well as in a drift tube in which the plasma particles have been injected. Axial drift velocities of hydrogen and impurities have been determined in the drift tube by optical time-of-flight measurements. Maximum hydrogen velocities between 9·106

H.-W. Drawin

1963-01-01

192

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

PubMed Central

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

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

2013-01-01

193

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

PubMed

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

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

2013-01-01

194

Note: A quartz cell with Pt single crystal bead electrode for electrochemical scanning tunneling microscope measurements.  

PubMed

In this paper, we provide and demonstrate a design of a unique cell with Pt single crystal bead electrode for electrochemical scanning tunneling microscope (ECSTM) measurements. The active metal Pt electrode can be protected from air contamination during the preparation process. The transparency of the cell allows the tip and bead to be aligned by direct observation. Based on this, a new and effective alignment method is introduced. The high-quality bead preparations through this new cell have been confirmed by the ECSTM images of Pt (111). PMID:25273789

Xia, Zhigang; Wang, Jihao; Hou, Yubin; Lu, Qingyou

2014-09-01

195

Note: A quartz cell with Pt single crystal bead electrode for electrochemical scanning tunneling microscope measurements  

NASA Astrophysics Data System (ADS)

In this paper, we provide and demonstrate a design of a unique cell with Pt single crystal bead electrode for electrochemical scanning tunneling microscope (ECSTM) measurements. The active metal Pt electrode can be protected from air contamination during the preparation process. The transparency of the cell allows the tip and bead to be aligned by direct observation. Based on this, a new and effective alignment method is introduced. The high-quality bead preparations through this new cell have been confirmed by the ECSTM images of Pt (111).

Xia, Zhigang; Wang, Jihao; Hou, Yubin; Lu, Qingyou

2014-09-01

196

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

197

An Optically Isolated Hybrid Two-Stage Current Transformer for Measurements at High Voltage  

Microsoft Academic Search

The development of a high-voltage reference 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 features a fiber optic link for data transmission to a ground station, and a laser-driven fiber optic link for supplying

Branislav Djokic; Eddy So

2005-01-01

198

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

199

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

NASA Astrophysics Data System (ADS)

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

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

1992-07-01

200

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

201

Breakdown Streamers in Coronas with Heated Discharge Electrode  

Microsoft Academic Search

Experiments have been carried out on a wire-tube corona apparatus to measure the breakdown voltage and the maximum prebreakdown corona current with and without heating the discharge electrode. Positive and negative polarities were employed on discharge electrodes of different diameters in clean air at room temperature. The results showed that the triggering of the break- down streamers, and hence the

M. B. Awad; G. S. P. Castle

1977-01-01

202

Voltage biasing, cyclic voltammetry, & electrical impedance spectroscopy for neural interfaces.  

PubMed

Electrical impedance spectroscopy (EIS) and cyclic voltammetry (CV) measure properties of the electrode-tissue interface without additional invasive procedures, and can be used to monitor electrode performance over the long term. EIS measures electrical impedance at multiple frequencies, and increases in impedance indicate increased glial scar formation around the device, while cyclic voltammetry measures the charge carrying capacity of the electrode, and indicates how charge is transferred at different voltage levels. As implanted electrodes age, EIS and CV data change, and electrode sites that previously recorded spiking neurons often exhibit significantly lower efficacy for neural recording. The application of a brief voltage pulse to implanted electrode arrays, known as rejuvenation, can bring back spiking activity on otherwise silent electrode sites for a period of time. Rejuvenation alters EIS and CV, and can be monitored by these complementary methods. Typically, EIS is measured daily as an indication of the tissue response at the electrode site. If spikes are absent in a channel that previously had spikes, then CV is used to determine the charge carrying capacity of the electrode site, and rejuvenation can be applied to improve the interface efficacy. CV and EIS are then repeated to check the changes at the electrode-tissue interface, and neural recordings are collected. The overall goal of rejuvenation is to extend the functional lifetime of implanted arrays. PMID:22395095

Wilks, Seth J; Richner, Tom J; Brodnick, Sarah K; Kipke, Daryl R; Williams, Justin C; Otto, Kevin J

2012-01-01

203

On-chip amperometric measurement of quantal catecholamine release using transparent indium tin oxide electrodes.  

PubMed

Carbon-fiber amperometry has been extensively used to monitor the time course of catecholamine release from cells as individual secretory granules discharge their contents during the process of quantal exocytosis, but microfabricated devices offer the promise of higher throughput. Here we report development of a microchip device that uses transparent indium tin oxide (ITO) electrodes to measure quantal exocytosis from cells in microfluidic channels. ITO films on a glass substrate were patterned as 20-mum-wide stripes using photolithography and wet etching and then coated with polylysine to facilitate cell adherence. Microfluidic channels (100 mum wide by 100 mum deep) were formed by molding poly(dimethylsiloxane) (PDMS) on photoresist and then reversibly sealing the PDMS slab to the ITO-glass substrate. Bovine adrenal chromaffin cells were loaded into the microfluidic channel and adhered to the ITO electrodes. Cells were stimulated to secrete by perfusing a depolarizing "high-K" solution while monitoring oxidation of catecholamines on the ITO electrode beneath the cell using amperometry. Amperometric spikes with charges ranging from 0.1 to 1.5 pC were recorded with a signal-to-noise ratio comparable to that of carbon-fiber electrodes. Further development of this approach will enable high-throughput measurement of quantal catecholamine release simultaneously with optical cell measurements such as fluorescence. PMID:16615759

Sun, Xiuhua; Gillis, Kevin D

2006-04-15

204

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

205

Ion currents involved in early Nod factor response in Medicago sativa root hairs: a discontinuous single-electrode voltage-clamp study.  

PubMed

Nod factor [NodRm-IV(Ac,S)], isolated from the bacterium Rhizobium meliloti, induces a well-known depolarization in Medicago sativa (cv Sitel) root hairs. Analysis of this membrane response using the discontinuous single-electrode voltage-clamp technique (dSEVC) shows that anion channel, K+ channel and H+-ATPase pump currents are involved in young growing root hairs. The early Nod-factor-induced depolarization is due to increase of the inward ion current and inhibition of the H+ pump. It involved an instantaneous inward anion current (IIAC) and/or a time-dependent inward K+ current (IRKC). These two ion currents are then down-regulated while the H+ pump is stimulated, allowing long-term rectification of the membrane potential (Em). Our results support the idea that the regulation of inward current plays a primary role in the Nod-factor-induced electrical response, the nature of the ions carried by these currents depending on the activated anion and/or K+ channels at the plasma membrane. PMID:10792816

Kurkdjian, A; Bouteau, F; Pennarun, A M; Convert, M; Cornel, D; Rona, J P; Bousquet, U

2000-04-01

206

Effect of metallic buffer at electrode-oxide interface on current-voltage characteristics of resistive random access memories (ReRAMs): A first-principles study  

NASA Astrophysics Data System (ADS)

We present the electric current (I)-voltage (V) characteristics (-1.0 eV < V < +1.0 eV) for a model of ReRAM devices with metal-oxide-metal structures, based on first principles nonequilibrium Green's function (NEGF) theory [1]. We choose TiN and hafnia (HfO2) for the electrode and oxide materials, respectively, because this combination has been widely known in literature. We investigate the I-V characteristics for two different compositions of the TiN/HfO2 interface, (a) with and (b) without the Ta buffer layer between TiN and HfO2. We assume cubic HfO2 layers for simplicity. For case (a), a clear distinction between the ``ON" and ``OFF" states appears depending on the occurrence and absence of the oxygen vacancies (VOs), respectively. For case (b), however, little electric current flows even when the VOs exist in hafnia. In the latter, the O atoms abstracted from hafnia are strongly bound to N, leading to substantial separation of TiN from HfO2. In contrast, in the former, the Ta buffer not only absorbs the O atoms but also bridges TiN and HfO2 to secure the occurrence of the ``ON" state. [1] H. Nakamura et al., J. Phys. Chem. C 115, 19931 (2011).

Miyazaki, Takehide; Nakamura, Hisao; Nishio, Kengo; Shima, Hisashi; Akinaga, Hiroyuki; Asai, Yoshihiro

2013-03-01

207

Voltage transient measurements in a distribution network correlated with data from lightning location system and from sequence of events recorders  

Microsoft Academic Search

Measurement units of high-frequency voltage transients have been specifically developed and installed at three different busses of an Italian medium voltage (MV) feeder, mainly composed by overhead lines and located in a rural region characterized by a high ground flash density (4flashes\\/km2\\/yr). Several of the recorded voltage transients in the period from March 2007 to August 2008 are correlated with

F. Napolitano; A. Borghetti; M. Paolone; M. Bernardi

2011-01-01

208

Interarea Model Estimation for Radial Power System Transfer Paths With Intermediate Voltage Control Using Synchronized Phasor Measurements  

Microsoft Academic Search

In this paper we develop measurement-based methods for estimating a two-machine reduced model to represent the interarea dynamics of a radial, two-area power system with intermediate dynamic voltage control. Two types of voltage control equipment are considered, namely, a static VAr compensator (SVC), and a synchronous condenser. The methods use synchronized bus voltage phasor data at several buses including the

Aranya Chakrabortty; Joe H. Chow; Armando Salazar

2009-01-01

209

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

210

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

211

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

PubMed

A better understanding of the mechanisms located at the solid/electrolyte interface is becoming essential to the development of new applications in the electrochemical fields. The fast quartz crystal microbalance is an attractive and powerful gravimetric sensor which can be used in the dynamic regime to determine a mass/potential transfer function. The principle is equivalent to classical electrochemical impedance measurements; the only difference is the determination of mass changes given by the quartz crystal microbalance rather than current changes following sine wave modulations of the applied potential. This function appears very well adapted to characterize ionic exchanges at the electrochemical interface. Frequency/voltage converters are the key devices in translating the microbalance frequency response in terms of a continuous voltage change. The latter allows the transfer function to be obtained via a frequency response analyzer. Different converters were tested in this work in order to improve the performances of the experimental setup. PMID:17672777

Gabrielli, C; Perrot, H; Rose, D; Rubin, A; Toqué, J P; Pham, M C; Piro, B

2007-07-01

212

Combined in situ EC-AFM and CV measurement study on lead electrode for lead–acid batteries  

Microsoft Academic Search

An electrochemical atomic force microscope (EC-AFM) was used to study the reaction of a lead electrode in sulfuric acid electrolyte, when the reaction corresponding to what occurs at the negative electrode of a lead–acid battery took place. At first, the AFM was applied to observation of the lead electrode during cyclic-voltammetry (CV) measurement, and was found to be useful to

Yoshiaki Yamaguchi; Masashi Shiota; Yasuhide Nakayama; Nobumitsu Hirai; Shigeta Hara

2001-01-01

213

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

PubMed

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

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

2014-02-01

214

Development of an automated AC-DC transfer measurement system for voltage and current at low frequencies  

Microsoft Academic Search

National Physical Laboratory India (NPLI) is the premier research & development center and the National Metrology Institute, which provides traceability in measurements by calibration throughout the country. Low Frequency voltage and current are very important quantities in electrical metrology. The standards for LF voltage and current are established by assigning AC-DC transfer difference to Thermal Converters (TCs) worldwide. The range

A. K. Govil; S. Ahmad; B. Pal; P. C. Kothari

2008-01-01

215

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

216

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

PubMed

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

Dai, Yu; Xue, Yuan; Zhang, Jianxun

2014-03-01

217

Rotating Disk Electrode Voltammetric Measurements of Serotonin Transporter Kinetics in Synaptosomes  

PubMed Central

Altered serotonin (5-HT) signaling is implicated in several neuropsychiatric disorders, including depression, anxiety, obsessive-compulsive disorder, and autism. The 5-HT transporter (SERT) modulates 5-HT neurotransmission strength and duration. This is the first study using rotating disk electrode voltammetry (RDEV) to measure 5-HT clearance. SERT kinetics were measured in whole brain synaptosomes. Uptake kinetics of exogenous 5-HT were measured using glassy carbon electrodes rotated in 500 uL glass chambers containing synaptosomes from SERT-knockout (?/?), heterozygous (+/?), or wild-type (+/+) mice. RDEV detected 5-HT concentrations of 5 nM and higher. Initial velocities were kinetically resolved with Km and Vmax values of 99 ± 35 standard error of regression (SER) nM and 181 ± 11 SER fmol / (s x mg protein), respectively in wild-type synaptosomes. The method enables control over drug and chemical concentrations, facilitating interpretation of results. Results are compared in detail to other techniques used to measure SERT kinetics, including tritium labeled assays, chronoamperometry, and fast scan cyclic voltammetry. RDEV exhibits decreased 5-HT detection limits, decreased vulnerability to 5-HT oxidation products that reduce electrode sensitivity, and also overcomes diffusion limitations via forced convection by providing a continuous, kinetically resolved signal. Finally, RDEV distinguishes functional differences between genotypes, notably, between wild-type and heterozygous mice, an experimental problem with other experimental approaches. PMID:20713085

Hagan, Catherine E.; Neumaier, John F.; Schenk, James O.

2010-01-01

218

APS linac klystron and accelerating structure gain measurements and klystron PFN voltage regulation requirements  

SciTech Connect

This note details measurements of the APS positron linac klystron and accelerating structure gain and presents an analysis of the data using fits to simple mathematical models. The models are used to investigate the sensitivity of the energy dependence of the output positron beam to klystron parameters. The gain measurements are separated into two parts: first, the energy gains of the accelerating structures of the positron linac are measured as a function of output power of the klystron; second, the klystron output power is measured as a function of input drive power and pulse forming network (PFN) voltage. This note concentrates on the positron linac rf and its performance as it directly affects the energy stability of the positron beam injected into the positron accumulator ring (PAR). Ultimately it is important to be able to minimize beam energy variations to maximize the PAR accumulation efficiency.

Sereno, N.S.

1997-07-01

219

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

NASA Technical Reports Server (NTRS)

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

Guidice, Donald A.

1995-01-01

220

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

NASA Astrophysics Data System (ADS)

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

Guidice, Donald A.

1995-10-01

221

D.C. voltammetry of ionic liquid-based capacitors: effects of Faradaic reactions, electrolyte resistance and voltage scan speed investigated using an electrode of carbon nanotubes in EMIM-EtSO4.  

PubMed

Carbon nanotube (CNT) electrodes in combination with ionic liquid (IL) electrolytes are potentially important for energy storage systems. We report electrochemical investigation of such a system involving a paper-electrode of multi-wall CNT (MWCNT) in the IL of 1-ethyl-3-methyl imidazolium ethylsulfate (EMIM-EtSO(4)). Our study concentrates on the analytical aspects of cyclic voltammetry (CV) to probe the double layer capacitance of these relatively unconventional systems (that involve rather large charge-discharge time constants). Both theoretical and experimental aspects of CV for such systems are discussed, focusing in particular, on the effects of Faradaic side-reactions, electrolyte resistance and voltage scan speeds. The results are analyzed using an electrode equivalent circuit (EEC) model, demonstrating a method to account for the typical artifacts expected in CV of CNT-IL interfaces. PMID:19269472

Zheng, J P; Pettit, C M; Goonetilleke, P C; Zenger, G M; Roy, D

2009-05-15

222

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

223

Measuring the solubilities of ionic liquids in water using ion-selective electrodes  

Microsoft Academic Search

Polyvinyl chloride-plasticized membrane ion-selective electrodes (ISE) based on conventional ion-exchangers have been proposed as a cheap universal tool to measure the solubilities of ionic liquids (ILs) in water. They are applicable for ILs with a wide range of solubilities in water, since the linear range of a potentiometric response spans several orders of magnitude. As an example, we have fabricated

Natalia V. Shvedene; Svetlana V. Borovskaya; Victor V. Sviridov; Erika R. Ismailova; Igor V. Pletnev

2005-01-01

224

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

225

System for unconstrained ECG measurement on a toilet seat using capacitive coupled electrodes : the efficacy and practicality.  

PubMed

Home healthcare is a common matter of concern to modern people. For the successful home healthcare, unconstrained bio-signal monitoring is important. Previously, unconstrained lavatory typed ECG measurement system was developed. It is enough to measure subject's ECG signal non-intrusively, but not practical because of moist environment of toilet. In this study, capacitive coupled electrode was employed for overcome above disadvantages. ECG was obtained by capacitive coupled electrode and compared with ECGs obtained from conventional Ag/AgCl electrode. Possible motion artifacts were investigated. Experimental results showed that toilet based capacitive coupled ECG signal was measured successfully. PMID:19163167

Baek, Hyun Jae; Kim, Jung Soo; Kim, Ko Keun; Park, Kwang Suk

2008-01-01

226

Membrane transport mechanisms probed by capacitance measurements with megahertz voltage clamp.  

PubMed Central

We have used capacitance measurements with a 1-microsecond voltage clamp technique to probe electrogenic ion-transporter interactions in giant excised membrane patches. The hydrophobic ion dipicrylamine was used to test model predictions for a simple charge-moving reaction. The voltage and frequency dependencies of the apparent dipicrylamine-induced capacitance, monitored by 1-mV sinusoidal perturbations, correspond to single charges moving across 76% of the membrane field at a rate of 9500 s-1 at 0 mV. For the cardiac Na,K pump, the combined presence of cytoplasmic ATP and sodium induces an increase of apparent membrane capacitance which requires the presence of extracellular sodium. The dependencies of capacitance changes on frequency, voltage, ATP, and sodium verify that phosphorylation enables a slow, 300- to 900-s-1, pump transition (the E1-E2 conformational change), which in turn enables fast, electrogenic, extracellular sodium binding reactions. For the GAT1 (gamma-aminobutyric acid,Na,Cl) cotransporter, expressed in Xenopus oocyte membrane, we find that chloride binding from the cytoplasmic side, and probably sodium binding from the extracellular side, results in a decrease of membrane capacitance monitored with 1- to 50-kHz perturbation frequencies. Evidently, ion binding by the GAT1 transporter suppresses an intrinsic fast charge movement which may originate from a mobility of charged residues of the transporter binding sites. The results demonstrate that fast capacitance measurements can provide new insight into electrogenic processes closely associated with ion binding by membrane transporters. Images Fig. 2 Fig. 3 Fig. 4 PMID:7479969

Lu, C C; Kabakov, A; Markin, V S; Mager, S; Frazier, G A; Hilgemann, D W

1995-01-01

227

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

228

Numerical analysis and demonstration of a 2-DOF large-size micromirror with sloped electrodes  

NASA Astrophysics Data System (ADS)

We report on the numerical analysis and demonstration of a two-degree-of-freedom (2-DOF) micromirror with a large mirror plate and a reduced actuation voltage. The micromirror consists of two layers, namely, a top layer and a bottom layer. In the top layer, the flat reflection surface is comprised of single crystalline silicon, while the bottom layer has sloped electrodes allowing for a decrease in the actuation voltage. The sloped electrodes are fabricated by time-delayed electroplating using nickel. Two different types of electrodes, a cone-type electrode and a wedge-type electrode, are designed for the mirror plate actuation and for the frame actuation, respectively. The mirror size is 1.5 mm × 1.5 mm, and the distance between the top and bottom layers is 65 µm. The slope angle of the bottom electrode is 10.3° for the cone-type electrode and 11.3° for the wedge-type electrode. The mechanical maximum tilt angles are measured at 2.7° with 127 V and 3.1° with 120 V for the cone-type electrode and wedge-type electrode, respectively. The cone-type electrode and the wedge-type electrode provide decreased actuation voltages of 49.3% and 62.1%, respectively, compared to a parallel-type electrode. This design is useful for building large-size mirrors actuated by electrostatic forces.

Jin, Joo-Young; Park, Jae-Hyoung; Yoo, Byung-Wook; Jang, Yun-Ho; Kim, Yong-Kweon

2011-09-01

229

Numerical Electric Field Analysis of Power Status Sensor Observing Power Distribution System Taking into Account Voltage Divider Measurement Circuit  

NASA Astrophysics Data System (ADS)

We have proposed and preproducted the voltage-current waveform sensor of resin molded type for measuring the power factor and harmonics in power distribution systems. We have executed numerical electromagnetic analyses using the finite element method to estimate the characteristics and behaviours of the sensor. Although the magnetic field analyses for the current sensor have involved the measurement circuit, the electric field analyses have not included the measurement circuit for measuring voltage waveforms of power lines. In this paper, we describe the electric field analyses with the measurement circuit and prove the insulating strength of the proposed sensor permissible to the use in 22kV power distribution systems.

Kubo, Takuro; Furukawa, Tatsuya; Itoh, Hideaki; Fukumoto, Hisao; Wakuya, Hiroshi; Ohchi, Masashi

230

A neural-network-based local-field-effect correction scheme for quantitative voltage contrast measurements in the scanning electron microscope  

NASA Astrophysics Data System (ADS)

A local-field-effect correction scheme, using a neural-network-based approach, is proposed for quantitative voltage contrast measurements (QVCM) in the scanning electron microscope (SEM). This technique showed some (though modest) improvement over an iterative correction scheme proposed previously. The correction technique also gives reasonably accurate voltage measurements on a multi-electrode test structure, even under low-extraction-field conditions for which local field effects are especially serious. The neural network employed is a back-propagation network with an adaptive learning rate to decrease the training time of the correction scheme. A momentum constant is also added to the back-propagation learning rule to minimize the chances of the network becoming stuck in a local minima of the error surface curve. The addition of momentum has a low-pass filtering effect on noise in the training data set and this could possibly account for the modest improvement in performance of this approach over the earlier iterative approach.

Chim, W. K.

1996-06-01

231

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

PubMed Central

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

Robertson, B; Lukashev, E P

1995-01-01

232

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

2014-07-21

233

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

234

High frequency reference electrode  

DOEpatents

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

Kronberg, James W. (Aiken, SC)

1994-01-01

235

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

236

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

PubMed Central

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

2013-01-01

237

A novel, remote-controlled suspension device for brain tissue PO2 measurements with multiwire surface electrodes.  

PubMed

A new device was developed for rapid assessment of PO2 values in viable tissue, such as the brain, using a multiwire surface electrode. The instrument utilizes a phonograph-like construction with weightless suspension of the electrode which thus minimizes surface pressure and allows for compensation of brain movements. The new and original component of the present device is the motor-driven, servo-controlled rotation of the PO2 electrode around its vertical axis. This enables PO2 measurements from precisely defined locations. From values measured on rabbit brain surface a PO2 histogram was constructed. The mean PO2 and distribution histogram were similar to those obtained with a needle electrode. The novel device, therefore, enables accurate and fast tissue PO2 measurements with minimal risk of brain damage. PMID:8183646

Murr, R; Berger, S; Schürer, L; Peter, K; Baethmann, A

1994-02-01

238

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

Microsoft Academic Search

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

Sandeep R. Bahl; Jeslis A. del Alamo

1993-01-01

239

Broadband Root-Mean-Square Detector in CMOS for On-Chip Measurements of Millimeter-Wave Voltages  

Microsoft Academic Search

A root-mean-square Schottky diode detector for estimating millimeter-wave (80–110 GHz) signal voltage using dc or low-frequency measurements for debugging and self-testing is demonstrated. The detector is realized in a 45-nm CMOS process without any process modifications. The detector gain at 30-$ \\\\hbox{mV}_{\\\\rm rms}$ input voltage is 11 $\\\\hbox{V}^{-1}$ . The insertion loss is less than 0.2 dB, and the flatness

Chuan Lee; Wooyeol Choi; Ruonan Han; Hisashi Shichijo; Kenneth K. O

2012-01-01

240

Temperature-dependent property measurements on multi-electroded thin-layer dielectrics  

SciTech Connect

A measurement system was designed and assembled for the automatic collection of electrical data for thin-layer dielectrics as a function of temperature. The dielectrics were deposited on platinized silicon by sol-gel processing, and the dielectric thickness was 0.2--0.4 [mu]m. Many ([gt]25) surface electrodes were formed by sputtering gold through a shadow mark, with a typical electrode size of 210[times]210 [mu]m[sup 2]. The measurement equipment was computer controlled, with three-axis digital stepping motors that could scan multi-electroded capacitors and collect statistically meaningful data. The temperature-dependent properties were measured between [minus]100 and 300 [degree]C as a function of frequency (100 Hz to 1 MHz) and applied field strength (0--50 MV/m). Data are reported for sol-gel-derived BaTiO[sub 3], PbZrO[sub 3], and (Pb,La)(Zr,Ti)O[sub 3] (i.e., PLZT) thin-layer capacitors. Capacitance values were typically 500--1000 pF, and the dielectric constant could be determined within a standard deviation of [plus minus]1.3%. Nanocrystalline BaTiO[sub 3] was found to have a dielectric constant of 210 at room temperature with no ferroelectric properties or dielectric anomalies between [minus]80 and 200 [degree]C. Antiferroelectric PbZrO[sub 3] had characteristic field-forced phase transformation behavior to the ferroelectric state with increasing bias. The field-induced polarization was approximately 300 mC/m[sup 2] and the coercive field was 22--28 MV/m. PLZT 8/65/35 had a dielectric constant of 556[plus minus]7 at 25 [degree]C, 100 KHz, and 50 mV.

Tani, T.; Xu, Z.; Moses, P.; Payne, D.A. (Department of Materials Science and Engineering, Materials Research Laboratory, and Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States))

1994-06-01

241

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

242

Enthalpy probe measurements and three-dimensional modelling on air plasma jets generated by a non-transferred plasma torch with hollow electrodes  

NASA Astrophysics Data System (ADS)

Thermal flow characteristics of air plasma jets generated by a non-transferred plasma torch with hollow electrodes are experimentally and numerically investigated in order to provide more reliable scientific and technical information, which has been insufficient for their practical applications to material and environmental industries. In this work, a thermal plasma torch of hollow electrode type is first designed and fabricated, and similarity criteria for predicting operational conditions for the scale-up to high-power torches are derived from the arc voltage characteristics measured with various operating and geometry conditions of the torch. The thermal flow characteristics of air plasma jets ejected from the torch are measured by enthalpy probe diagnostics and turn out to have relatively low temperatures of around 3000-7000 K, but show features of other unique properties, such as high energy flux, broad high temperature region and long plasma jet with moderate axial velocity, which are promising for their applications to material syntheses and hazardous waste treatments. Such high enthalpy at a relatively low temperature of air thermal plasma compared with the argon one is due to the high thermal energy residing in the vibrational and rotational states and oxygen dissociation, besides the translational states in monatomic gases such as argon. It is expected that this high specific enthalpy of the air plasma will enable material and environmental industries to treat a large amount of precursors and waste materials effectively at a lower temperature for a longer residence time by the low plasma velocity. It is also found from the measurements that the turbulence intensity influenced by the size of the electrode diameter has a significant effect on the axial and radial profiles of plasma jet properties and that a longer plasma jet is more readily achievable with a larger electrode diameter reducing the turbulence intensity in the external region of the torch. In the numerical studies based on magnetohydrodynamics (MHD) theory, a precise three-dimensional transient numerical model for the internal arc discharge plasma of the torch has been developed along with a practical two-dimensional stationary one for the external thermal plasma jet by considering highly localized distributions of arc roots with circumferential non-uniformity on the electrode wall surfaces, so that more reliable and realistic descriptions on the arc thermal plasma properties become feasible both inside and outside the torch. The numerical calculation results are compared with the experimental data obtained from the probe measurements and found to be in good agreement with them.

Kim, Keun Su; Park, Jin Myung; Choi, Sooseok; Kim, Jongin; Hong, Sang Hee

2008-03-01

243

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

244

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

NASA Astrophysics Data System (ADS)

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

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

2008-08-01

245

Dependence of hydrogen arcjet operation on electrode geometry  

NASA Technical Reports Server (NTRS)

The dependence of 2 kW hydrogen arcjet performance on cathode to anode electrode spacing was evaluated at specific impulses of 900 and 1000 s. Less than 2 absolute percent change in efficiency was measured for the spacings tested which did not repeat the 14 absolute percent variation reported in earlier work with similar electrode designs. A different nozzle configuration was used to quantify the variation in hydrogen arcjet performance over an extended range of electrode spacing. Electrode gap variation resulted in less than 3 absolute percent change in efficiency. These null results suggested that electrode spacing is decoupled from hydrogen arcjet performance considerations over the ranges tested. Initial studies were conducted on hydrogen arcjet ignition. The dependence of breakdown voltage on mass flow rate and hydrogen arcjet ignition on rates of pulse repetition and pulse voltage rise were also included for comparison with previous results obtained using simulated hydrazine.

Pencil, Eric J.; Sankovic, John M.; Sarmiento, Charles J.; Hamley, John A.

1992-01-01

246

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

247

RF Currents Produced from AC Arcs with Asymmetrical Electrodes  

Microsoft Academic Search

The RF current (0-20MHz) produced by an air arc with asymmetrical (graphite-copper) electrodes was investigated for 120Vac 60Hz over a current range of 1.2Arms to 45Arms. Time resolved spectral signatures of measured RF currents showed amplitude dependence on 60 Hz arc current level, voltage polarity, electrode material, and circuit impedance. For most conditions, RF currents were measured only when the

John J. Shea; Xin Zhou

2010-01-01

248

Mapping corrosion kinetics using the wire beam electrode in conjunction with electrochemical noise resistance measurements  

SciTech Connect

A wire beam electrode (WBE) has been used, in conjunction with the electrochemical noise resistance method, to determine the kinetics of nonuniform corrosion of mild steel in a carbon dioxide saturated brine. Local electrochemical parameters including corrosion potential, galvanic current, and electrochemical noise resistance were measured from local areas of a WBE surface. These parameters were used to calculate the kinetics of local electrochemical corrosion processes. A map showing instantaneous corrosion rate distribution over a WBE surface has been produced. Corrosion depths were calculated, based on instantaneous corrosion rate data, at various stages of the corrosion exposure period, and these were summed up to produce an accumulated corrosion depth map. This accumulated corrosion depth map was found to be quantitatively comparable with a microscopically observed corrosion depth map. This work shows that electrochemical corrosion kinetics can be determined using kinetic equations previously derived based on the WBE concept. This work also shows that the WBE is a novel electrode design which is suitable for performing electrochemical noise resistance measurement and that the WBE is applicable to practical corrosion conditions.

Tan, Y.J.; Bailey, S.; Kinsella, B.; Lowe, A.

2000-02-01

249

The Effects of Preheating of a Fine Tungsten Wire and the Polarity of a High-Voltage Electrode on the Energy Characteristics of an Electrically Exploded Wire in Vacuum  

E-print Network

Results obtained from experimental and numerical studies of tungsten wires electrical explosion in vacuum are presented. The experiments were performed both with and without preheating of the wires, using positive or negative polarity of a high-voltage electrode. Preheating is shown to increase energy deposition in the wire core due to a longer resistive heating stage. The effect was observed both in single wire and wire array experiments. The evolution of the phase state of the wire material during explosion was examined by means of one-dimensional numerical simulation using a semiempirical wide-range equation of state describing the properties of tungsten with allowance made for melting and vaporization.

Rousskikh, A G; Chaikovsky, S A; Fedunin, A V; Khishchenko, K V; Labetsky, A Y; Levashov, P R; Shishlov, A V; Tkachenko, S I

2006-01-01

250

Characterization of an Ion Sensitive Field Effect Transistor and Chloride Ion Selective Electrodes for pH Measurements in Seawater.  

PubMed

Characterization of several potentiometric cells without a liquid junction has been carried out in universal buffer, aqueous HCl, and artificial seawater media. The electrodes studied include Ion Sensitive Field Effect Transistor (ISFET) pH electrodes, and Chloride-Ion Selective Electrodes (Cl-ISE) directly exposed to the solution. These electrodes were compared directly to the conventional hydrogen electrode and silver-silver chloride electrode in order to report the degree to which they obey ideal Nernstian laws. These data provide a foundation for operating the ISFET|Cl-ISE pair in seawater as a pH sensor. In order to obtain the highest quality pH measurements from this sensor, its response to changes in pH and salinity must be properly characterized. Our results indicate near-ideal Nernstian response for both electrodes over a wide range of pH (2-12) and Cl(-) molality (0.01-1). We conclude that the error due to sub-Nernstian response of the cell ISFET|seawater|Cl-ISE over the range of seawater pH and salinity is negligible (<0.0001 pH). The cross sensitivity of the Cl-ISE to Br(-) does not seem to be a significant source of error (<0.003 pH) in seawater media in the salinity range 20-35. PMID:25325617

Takeshita, Yuichiro; Martz, Todd R; Johnson, Kenneth S; Dickson, Andrew G

2014-11-18

251

Detection of DNA hybridization and extension reactions by an extended-gate field-effect transistor: characterizations of immobilized DNA-probes and role of applying a superimposed high-frequency voltage onto a reference electrode.  

PubMed

As we have already shown in a previous publication [Kamahori, M., Ihige, Y., Shimoda, M., 2007. Anal. Sci. 23, 75-79], an extended-gate field-effect transistor (FET) sensor with a gold electrode, on which both DNA probes and 6-hydroxyl-1-hexanethiol (6-HHT) molecules are immobilized, can detect DNA hybridization and extension reactions by applying a superimposed high-frequency voltage to a reference electrode. However, kinetic parameters such as the dissociation constant (K(d)(s)) and the apparent DNA-probe concentration (C(probe)(s)) on a surface were not clarified. In addition, the role of applying the superimposed high-frequency voltage was not considered in detail. In this study, the values of K(d)(s) and C(probe)(s) were estimated using a method involving single-base extension reaction combined with bioluminescence detection. The value of K(d)(s) on the surface was 0.38 microM, which was about six times that in a liquid phase. The value of C(probe)(s), which expressed the upper detection limit for the solid phase reaction, was 0.079 microM at a DNA-probe density of 2.6 x 10(12)molecules/cm(2). We found that applying the superimposed high-frequency voltage accelerated the DNA molecules to reach the gold surface. Also, the distance between the DNA-probes immobilized on the gold surface was controlled to be over 6 nm by applying a method of competitive reaction with DNA probes and 6-HHT molecules. This space was sufficient to enable the immobilized DNA-probes to lie down on the 6-HHT monolayer in the space between them. Thus, the FET sensor could detect DNA hybridization and extension reactions by applying a superimposed high-frequency voltage to the DNA-probes density-controlling gold surface. PMID:18054478

Kamahori, Masao; Ishige, Yu; Shimoda, Maki

2008-02-28

252

Chronic measurement of the stimulation selectivity of the flat interface nerve electrode  

Microsoft Academic Search

The flat interface nerve electrode (FINE) is an attempt to improve the stimulation selectivity of extraneural electrodes. By reshaping peripheral nerves into elliptical cylinders, central fibers are moved closer to the nerve-electrode interface, and additional surface area is created for contact placement. The goals of this study were to test the hypothesis that greater nerve reshaping leads to improved selectivity

Daniel K. Leventhal; Dominique M. Durand

2004-01-01

253

3D PIV measurements of the EHD flow patterns in a narrow lectrostatic precipitator with wire-plate or wire-flocking electrodes  

NASA Astrophysics Data System (ADS)

The results of 3-dimensional (3D) Particle Image Velocimetry (PIV) measurements of the electrohydrodynamic (EHD) flow patterns in a narrow electrostatic precipitator (ESP) are presented in this paper. The ESP was an acrylic parallelepiped with a wire discharge electrode and two plane collecting electrodes. In contrary to typical ESPs the wire electrode was placed along the gas flow, in the ESP centre, in the halfway between collecting electrodes. Either two smooth stainless steel plates or two stainless steel meshes with nylon flocks were used as the collecting electrodes. They were placed on the top and bottom of the ESP. The PIV measurements were carried out in two parallel planes, placed perpendicularly to the collecting electrodes and parallel to the wire electrode. The obtained results showed some similarities and differences of a 3D particle flow in the ESP with plate or flocking electrodes.

Podli?ski, J.; Kocik, M.; Barbucha, R.; Niewulis, A.; Mizeraczyk, J.; Mizuno, A.

2006-10-01

254

Multi-resolution wavelet analysis for chopped impulse voltage measurements and feature extraction  

Microsoft Academic Search

In this study, an application of the wavelet transform based on the multi-resolution analysis (MRA) is aimed for evaluation of amplitude and time parameters of the chopped impulse voltage. In terms of getting data set, three types of the chopped lightning impulse voltages with different chopping times are considered and MRA is applied to these data as different case studies.

Emel Onal; Ozcan Kalenderli; Serhat Seker

2008-01-01

255

Calculating depletion region carrier concentrations with capacitance-voltage measurements and etching  

NASA Astrophysics Data System (ADS)

Methods were developed for finding the charge carrier concentrations within the initial depletion region of n-type semiconductors. These methods combine the capacitance-voltage (C-V) technique with the etching of layers from the semiconductor surface. After each etch, the depletion region is made to end at the same location within the semiconductor. This location is used as a common reference and is arbitrarily chosen at a distance deep below the original unetched surface. For each etch depth, the voltage which extends the depletion region to the common reference distance is found. The voltage drop from an etch depth to the deeper common reference distance is the same as it would be if the semiconductor was not etched. This voltage drop is the sum of the applied voltage and the built-in potential. The built-in potential depends on the barrier potential at the semiconductor surface and the concentration at the common reference distance.

Gainer, Gordon H., Jr.

1987-12-01

256

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

257

Electromechanical characterisation of dielectric elastomer planar actuators: comparative evaluation of different electrode materials and different counterloads  

Microsoft Academic Search

This work intends to extend the electromechanical characterisation of dielectric elastomer actuators. Planar actuators were realised with a 50?m-thick film of an acrylic elastomer coated with compliant electrodes. The isotonic transverse strain, the isometric transverse stress and the driving current, due to a 2s high voltage impulse, were measured for four electrode materials (thickened electrolyte solution, graphite spray, carbon grease

Federico Carpi; Piero Chiarelli; Alberto Mazzoldi; Danilo De Rossi

2003-01-01

258

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

PubMed

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

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

2013-02-01

259

Calculated and measured battery voltages - thermodynamics aids in identifying electrochemical reactions. Final report, March-June 1984  

SciTech Connect

Both the open- and closed-circuit voltages of a battery depend on the thermodynamic conditions inside the cell. When the actual electrochemical reaction of a particular battery is unknown, thermodynamic calculations can help to identify it. Using thermodynamics data, the open-circuit voltages for alternatively electrochemical reactions can be calculated. When accurate data are available, the calculated voltage for the correct electrochemical reaction will agree to within millivolts with the measured value. For the Cl/sub 2/-Li molten salt system, the calculated and measured values are both 3.612V. For alkaline zinc batteries, the data indicate that Zn0 is the discharge product at the anode under ambient conditions. For the acid Mn02-Zn system, under the thermodynamic conditions, a two-electron reduction of MnO/sub 2/ occurs. Initially, in the alkaline MnO/sub 2/-Zn system. Mn(OH)/sub 4/ is the discharge product at the cathode.

DeVries, L.E.

1985-02-01

260

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

SciTech Connect

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

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

2013-02-15

261

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

262

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

263

Comparison of three accurate methods to measure AC voltage at low frequencies  

Microsoft Academic Search

Three methods for the determination of the RMS value of AC voltage at low frequencies are compared: the step calibration of a digitally synthesized source, the optimized sampling method, and the AC-DC voltage transfer with a multijunction thermal converter. The three methods agree within 1×10-6 with an uncertainty of 2.5×10-8 in the frequency range from 10 to 100 Hz

Marian Kampik; Héctor Laiz; Manfred Klonz

2000-01-01

264

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

265

Metal Electrode Formation on Organic Film Using Xe-Buffer-Layer-Assisted Deposition for Efficient Measurement of Inelastic Tunneling Spectroscopy  

NASA Astrophysics Data System (ADS)

We demonstrate that, by using a Xe-buffer-layer-assisted deposition, a metal electrode can be formed on an organic film without altering the chemical properties of the molecules. A new efficient measurement of inelastic tunneling spectroscopy (IETS) was demonstrated by attaching the scanning tunneling microscopy (STM) tip to the Au cluster. Au electrode was formed on a Xe buffer layer condensed on an alkanethiol self-assembled monolayer (SAM), in which the Xe layer prevents direct interaction between hot metal atoms and molecules in the film. An IETS measurement executed with the new method revealed the robustness of the molecules at the metal-film interface.

Rahim, Abdur; Liu, Jie; Fakruddin Shahed, Syed Mohammad; Komeda, Tadahiro

2013-10-01

266

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

267

Technological Aspects: High Voltage  

E-print Network

This paper covers the theory and technological aspects of high-voltage design for ion sources. Electric field strengths are critical to understanding high-voltage breakdown. The equations governing electric fields and the techniques to solve them are discussed. The fundamental physics of high-voltage breakdown and electrical discharges are outlined. Different types of electrical discharges are catalogued and their behaviour in environments ranging from air to vacuum are detailed. The importance of surfaces is discussed. The principles of designing electrodes and insulators are introduced. The use of high-voltage platforms and their relation to system design are discussed. The use of commercially available high-voltage technology such as connectors, feedthroughs and cables are considered. Different power supply technologies and their procurement are briefly outlined. High-voltage safety, electric shocks and system design rules are covered.

Faircloth, D C

2013-01-01

268

Electronic transport, transition-voltage spectroscopy, and the Fano effect in single molecule junctions composed of a biphenyl molecule attached to metallic and semiconducting carbon nanotube electrodes.  

PubMed

We have investigated electronic transport in a single-molecule junction composed of a biphenyl molecule attached to a p-doped semiconductor and metallic carbon nanotube leads. We find that the current-voltage characteristics are asymmetric as a result of the different electronic natures of the right and left leads, which are metallic and semiconducting, respectively. We provide an analysis of transition voltage spectroscopy in such a system by means of both Fowler-Nordheim and Lauritsen-Millikan plots; this analysis allows one to identify the positions of resonances and the regions where the negative differential conductance occurs. We show that transmittance curves are well described by the Fano lineshape, for both direct and reverse bias, demonstrating that the frontier molecular orbitals are effectively involved in the transport process. This result gives support to the interpretation of transition voltage spectroscopy based on the coherent transport model. PMID:25109887

Brito da Silva Júnior, Carlos Alberto; Leal, José Fernando Pereira; Aleixo, Vicente Ferrer Pureza; Pinheiro, Felipe A; Del Nero, Jordan

2014-09-28

269

Ion selectivity and water dissociation in polymer bipolar membranes studied by membrane potential and current–voltage measurements  

Microsoft Academic Search

A polymer bipolar ion-exchange membrane consists of a layered structure involving one cation and one anion ion-exchange layer joined together in series. In this study, the ionic selectivity and water dissociation rate of six commercial bipolar membranes was evaluated from the measurements of the membrane potential in a concentration cell and the current–voltage curve in a four-point measuring cell. Bipolar

A. Alcaraz; P. Ram??rez; S. Mafeb; H. Holdikc; B. Bauerd

2000-01-01

270

Application of a Josephson quantum voltage source to the measurement of microsecond timescale settling time on the Agilent 3458A 8\\frac{1}{2} digit voltmeter  

NASA Astrophysics Data System (ADS)

The voltage waveform measurement characteristics due to finite settling time on the microsecond timescale are investigated for the Agilent 3458A 8\\frac{1}{2} digit voltmeter in DCV mode. A quantum-accurate voltage synthesizer based on the Josephson effect produces a change in test voltage in less than 1 ?s and the voltage reported by the voltmeter is measured as a function of two timing parameters, aperture delay and duration. A model is presented and the level of agreement is discussed in the context of optimizing the configuration of the instrument for both high measurement throughput and accuracy.

Henderson, D.; Williams, J. M.; Yamada, T.

2012-12-01

271

Measuring mercury ion concentration with a carbon nano tube paste electrode using the cyclic voltammetry method  

Microsoft Academic Search

A simply prepared carbon nano tube paste electrode (CNTPE) was utilized for monitoring mercury ion concentration using the cyclic voltammetry (CV) method and the square wave anodic stripping voltammetric (SWASV) method. The CNTPE was compared with various conventional electrodes. The CNTPE method was applied to determine the concentration of trace levels of Hg(II) in several water samples, which yielded a

Suw Young LY; Sung Kuk Kim; Tae Hyun Kim; Young Sam Jung; Sang Min Lee

2005-01-01

272

The effect of leakage on micro-electrode measurements of intracellular sodium activity in crab muscle fibres.  

PubMed Central

The effect of lowering extracellular Na (Nao) on the intracellular Na activity has been measured in single muscle fibres from the crab Carcinus maenas using Na+-sensitive glass micro-electrodes. Measurements have been made with recessed-tip micro-electrodes inserted radially into intact fibres, and with axial electrodes in cannulated fibres. Reducing Nao to one-tenth normal caused local contractions in intact fibres. The apparent steady-state internal Na (Nai) and the fall in Nai when Nao was reduced were found to vary considerably not only between different fibres but also when measured with different electrodes in the same fibre. The steady-state Nai, and the extent and rate of its decrease when Nao was reduced, could be reduced by pushing the Na+-sensitive electrode deeper into the fibre. Cannulated fibres generally had higher internal Na activities than intact fibres, but at comparable levels of Nai the rate of fall recorded from cannulated fibres when Nao was reduced was much slower than with intact fibres. In both intact and cannulated fibres the decrease in Nai was reduced by ouabain. The level of Nai recorded in cannulated fibres was sensitive to depolarization. Depolarizations from -50 to -30 mV resulted in a rise in Nai while further depolarization to 0 mV resulted in a fall in Nai. We conclude that both our results and those of Vaughan-Jones (1977) on undissected fibres are contaminated by leakage into the fibre round the micro-electrode. The true internal Na activity is probably much lower than previously reported. PMID:6747900

Taylor, P S; Thomas, R C

1984-01-01

273

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

PubMed

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

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

2009-02-01

274

Microwave complex permittivity of voltage-tunable nematic liquid crystals measured in high resistivity silicon transducers  

NASA Astrophysics Data System (ADS)

A split post dielectric resonator is used to determine the effect of AC bias voltage on the microwave complex permittivity of nematic liquid crystals. High resistivity silicon transducers separated by 100 ?m are bridged by nematic liquid crystals and their properties determined. The in-plane permittivity of liquid crystals can be effectively tuned (change of effective permittivity of up to 8%) by increasing the AC bias voltage from 0 to 6 V. Using high resistivity silicon allowed us to obtain tunable dielectric stacks with relatively small dielectric losses at microwave frequencies.

Kowerdziej, Rafa?; Krupka, Jerzy; Nowinowski-Kruszelnicki, Edward; Olifierczuk, Marek; Parka, Janusz

2013-03-01

275

Ammonia measurement with a pH electrode in the ammonia/urea-SCR process  

NASA Astrophysics Data System (ADS)

The selective catalytic reduction of nitrogen oxides with ammonia (ammonia SCR) and urea (urea SCR), respectively, is a widespread process to clean flue and diesel exhaust gases due to its simplicity and efficiency. The main challenge of the process is to minimize the ammonia emissions downstream of the SCR catalyst. We found that ammonia emissions of >10 ppm can reliably be detected with a simple pH electrode in the presence of CO2, SOx, NOx, and moderately weak organic acids. 10-20 ppm of ammonia in the exhaust gas are sufficient to neutralize the acids and to increase the pH value from 3 to 6. On this basis a continuous measuring method for ammonia was developed, which was used to control the dosage of urea in the SCR process. While keeping the ammonia emissions after the SCR catalyst at 5-30 ppm an average NOx removal efficiency (DeNOx) of >95% were achieved at a diesel test rig. The method can also be applied for exhaust gases with higher acid contents, if a basic pre-filter is added adsorbing the acidic exhaust components. Compared to water as absorption solution, more precise ammonia measurements are possible, if a 0.1 M NH4Cl absorption solution is applied, whose pH value is changing as a Nernst function of the ammonia concentration.

Kröcher, Oliver; Elsener, Martin

2007-03-01

276

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

DOEpatents

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

Rehak, P.; Gatti, E.

1984-02-24

277

Transfection of mammalian cells with connexins and measurement of voltage sensitivity of their gap junctions  

Microsoft Academic Search

Vertebrate gap junction channels are formed by a family of more than 20 connexin proteins. These gap junction proteins are expressed with overlapping cellular and tissue specificity, and coding region mutations can cause human hereditary diseases. Here we present a summary of what has been learned from voltage clamp studies performed on cell pairs either endogenously expressing gap junctions or

Cristiane del Corsso; Miduturu Srinivas; Marcia Urban-Maldonado; Alonso P Moreno; Alfredo G Fort; Glenn I Fishman; David C Spray

2006-01-01

278

Positive electrode materials with high operating voltage for lithium batteries: LiCr yMn 2 ? yO 4 (0 ? y ? 1)  

Microsoft Academic Search

Reversible lithium deintercalation of chromium-substituted spinel manganese oxides LiCryMn2 ? yO4 (0 ? y ? 1) in the voltage range 3.4–5.4 V versus Li, occurs in two main steps for 0 < y < 1: one at about 4.9 V and the other at about 4 V. The 4.9 V process capacity increases with the chromium content while the 4

C. Sigala; D. Guyomard; A. Verbaere; Y. Piffard; M. Tournoux

1995-01-01

279

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

280

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

281

Using Concha Electrodes to Measure Cochlear Microphonic Waveforms and Auditory Brainstem Responses  

PubMed Central

During electrocochleography, that is, ECochG or ECoG, a recording electrode can be placed in the ear canal lateral to the tympanic membrane. We designed a concha electrode to record both sinusoidal waveforms of cochlear microphonics (CMs) and auditory brainstem responses (ABRs). The amplitudes of CM waveforms and Wave I or compound action potentials (CAPs) recorded at the concha were greater than those recorded at the mastoid but slightly lower than those recorded at the ear canal. Wave V amplitudes recorded at the concha were greater than those recorded at the ear canal but lower than those recorded at the mastoid. There was not a significant difference between the amplitudes recorded at the concha and at the ear canal. For CM and Wave I or CAP, the latency recorded at the concha was longer than at the canal but shorter than at the mastoid; for Wave V, the reverse was true. However, these differences were not statistically significant and may be due to the distance to response generators. Aside from the advantages that the regular ECoG has over otoacoustic emission (OAE) testing, the concha electrode was also easier and safer to place and may be suitable for children, newborn screening, participants with canal conditions, and remote clinics which could have concerns with the availability and cost of a canal electrode. Using concha electrodes, we also experienced fewer postauricular artifacts than when using a mastoid electrode. PMID:21131635

Zhang, Ming

2010-01-01

282

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

283

Effect of addition of main ion to carrier solution in potentiometric flow-injection measurements with solid state ion-selective electrodes  

Microsoft Academic Search

Summary  Flow-injection measurements were performed using chloride, fluoride, iodide and copper(II)-selective electrodes. A pronounced effect of addition of main ion to the carrier solution was observed for the fluoride- and iodide-selective electrode. Super-Nernstian slope observed for the fluoride- and copper(II)-selective electrode in the absence of the sensed ion in the carrier solution decreased to Nernstian values in the presence of the

Liliana Ilcheva; Marek Trojanowicz; Tadeusz Krawczynski vel Krawczyk

1987-01-01

284

Activity coefficients of DL-valine in aqueous solutions of KCl at 25°C. Measurement with ion selective electrodes and modelling  

Microsoft Academic Search

Electrochemical cells with two ion selective electrodes, a cation and an anion ion selective electrode, versus a double junction reference electrode were used to measure the activity coefficients of DL-valine at 298.15 K, up to 0.5 molality, in aqueous solutions of KCl up to 1.0 molality. The results obtained in this work are compared with those reported before for the

Mohammad K. Khoshkbarchi; Juan H. Vera

1996-01-01

285

Phase transition in porous electrodes.  

PubMed

It is shown by Monte Carlo simulation that electrochemical thermodynamics of electrolytes in a porous electrode is qualitatively different from that in the bulk with a planar electrode. In particular, first order phase transitions occur in porous electrodes when the pore size is comparable to the ion size of the electrolytes: as the voltage is increased from zero, the surface charge density and the ion density in the porous electrodes discontinuously change at a specific voltage. The critical points for those phase transitions are identified. PMID:21513411

Kiyohara, Kenji; Sugino, Takushi; Asaka, Kinji

2011-04-21

286

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. PMID:18288835

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

2008-01-01

287

Evaluation of carrier distributions in a depletion region of semiconductor measured by a capacitance-voltage profile method  

NASA Astrophysics Data System (ADS)

It is well known that carrier depth profiles obtained by the capacitance-voltage (C-V) measurement method provide carrier information only beyond the initial semiconductor depletion region. A novel new method has been developed within the depletion approximation for obtaining carrier depth profiles inside the initial depletion region of a semiconductor through the combined use of the layer-removal technique and C-V profile measurements. This method has been successfully demonstrated through simulated C-V profile data created from a known Gaussian distribution of Si-implanted GaAs.

Yeo, Y. K.; Gainer, G. H., Jr.; Kim, Jong Hyun; Hengehold, R. L.

1990-01-01

288

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

289

Dynamic Analysis of Mcfc Porous Electrode  

NASA Astrophysics Data System (ADS)

The intent of this work is to develop AC impedance measurements, in combination with other methods, as a tool to determine the relative importance of various resistance sources in the multi-step process occurring at a gas-diffusion porous electrode. In particular, the case of a MCFC cathode is studied. The goals of this study are: (1) elucidation of electrode mechanism; (2) analysis of the porous electrode performance for the purpose of optimizing design; and (3) developing the capabilities of AC impedance as an index of long-term cell performance decay. The oxygen reduction reaction of molten carbonate fuel cell and the corresponding kinetic as well as transport parameters were tried to be estimated by using impedance techniques combining with other electrochemical methods from flag, wire and rotating disk electrodes in pot cell as well as porous electrode in lab cell. The dominant pathway for oxygen reduction in 62%Li _2CO_3/38%K _2CO_3 melt at 650^circC is via superoxide ions. This follows from flag electrode impedance results indicating that O_sp{2}{ -}/CO_2 mixed diffusion is the dominant source of resistance. The polarization behavior of gas-diffusion porous electrodes has been analyzed in terms of individual voltage loss and overall voltage loss. In most cases, the optimal electrolyte filling will be obtained when the dominant source of voltage loss switches from ohmic or mass transfer resistances to kinetic activation resistance, and similar behavior for optimal electrode thickness. Pressurized operation is favorable for performance if the reaction mechanism follows the superoxide mechanism, but not if the peroxide path dominates. A distributed-network approach has been developed and it is concluded that a digital simulation of AC-superimposed -on-DC impedance of a porous electrode is possible and helpful. Kinetic activation and mass transfer resistances are extracted separate and conclude that both peroxide and superoxide contribute the oxygen reduction around rest potential, but the superoxide will be the dominant reduction species under current load. CO_2 can somewhat reacts with (O)^- to form CO _sp{3}{=}, this leads CO_2 has a near zero reaction order for porous electrode. The capabilities of using AC impedance techniques for monitoring the long term cell performance is promising but needs further development.

Lee, Gwo-Lin Kevin

1992-01-01

290

Determining the Mobility of Ions by Transient Current Measurements at High Voltages  

NASA Astrophysics Data System (ADS)

We present polarization and transient current experiments that allow an independent determination of the charge carrier density and the mobility of ions in polymer electrolytes at low charge carrier density. The method relies on a complete depletion of ions in the bulk electrolyte achieved by applying high voltages. Based on a qualitative model for the charge dynamics in this nonlinear regime, the method is exemplarily applied to a system of polymethylmethacrylate doped with small amounts of a lithium salt. The independently obtained values for the ionic mobility, the charge carrier density, and the conductivity are consistent for all salt concentrations studied. Criteria for the applicability of the method are discussed.

Kohn, Peter; Schröter, Klaus; Thurn-Albrecht, Thomas

2007-08-01

291

A multi-electrode biomimetic electrolocation sensor  

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

292

Near-Electrode Imager  

SciTech Connect

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 use 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.; Klingler, Robert J.; Woelk, Klaus; Gerald, Rex E.,II

1999-05-01

293

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

294

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

295

Nonwoven fabric active electrodes for biopotential measurement during normal daily activity.  

PubMed

Body movement is responsible for most of the interference during physiological data acquisition during normal daily activities. In this paper, we introduce nonwoven fabric active electrodes that provide the comfort required for clothing while robustly recording physiological data in the presence of body movement. The nonwoven fabric active electrodes were designed and fabricated using both hand- and screen-printing thick-film techniques. Nonstretchable nonwoven (Evolon 100) was chosen as the flexible fabric substrate and a silver filled polymer ink (Creative Materials CMI 112-15) was used to form a transducer layer and conductive lines on the nonwoven fabrics. These nonwoven fabric active electrodes can be easily integrated into clothing for wearable health monitoring applications. Test results indicate that nonwoven textile-based sensors show considerable promise for physiological data acquisition in wearable healthcare monitoring applications. PMID:18232361

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

2008-01-01

296

In line measurement of chemical oxygen demand by means of multipulse amperometry at a rotating Pt ring — Pt\\/PbO 2 disc electrode  

Microsoft Academic Search

In this paper an amperometric method that makes use of a the rotating ring-disc electrode (RRDE) configuration is described for the determination of the chemical oxygen demand (COD). It is shown that the strong oxidant necessary in COD measurements can be generated by an electrolytic in situ formation of an aggressive species, at the disc part of the ring-disc electrode,

P Westbroek; E Temmerman

2001-01-01

297

X-Ray Measurement and Enhancement of SBUPF1 Plasma Focus Device in Different Ar Pressures and Operating Voltages  

NASA Astrophysics Data System (ADS)

In this paper, best condition of filling gas pressure and operating voltage for SBUPF1 plasma focus device to have maximum intensity of hard and soft X-ray emission has been reported. For time resolved X-ray detection, PIN detector and fast plastic Scintillator detector with appropriate filters have been used and for time integrated X-ray emission measurement, radiography films with appropriate filter masks have been used. Rogowski coil has been used for pinch detection. The highest hard X-ray emission has been observed at the pressure of 0.45 mbar of Argon and discharge voltage about 23.5 kV. The highest Soft X-ray emission has been observed at the pressure of 0.35 mbar of Argon and discharge voltage about 23.5 kV. For enhancement of hard X-ray emission intensity, lead disk was placed in copper anode tip and measurements were repeated. Results have shown that hard X-ray emission has been enhanced about 23% and soft X-ray emission has been enhanced about 33% with inserting a high atomic number metal disk like lead. Results from integral X-ray measurement have shown presence of dominant peaks in ranges 13.2-15, 21-21.9 and 23.4-24.3 keV with significant spectral components in the range of 0-50 keV. Pinch size has measured with pin hole camera and it is about 0.6 mm × 2.12 mm. Captured images with SBUPF1 have confirmed that it is a suitable source for introspective imaging with capability of showing very fine details.

Darestani Farahani, Nikoo; Abbasi Davani, Fereydoon; Shahbazi Rad, Zahra

2011-12-01

298

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

299

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

300

Electrode effects of a cellulose-based electro-active paper energy harvester  

NASA Astrophysics Data System (ADS)

The possibility of cellulose-based electro-active paper (EAPap) as a vibrational energy transducer was investigated in this paper. Thin cellulose EAPap film specimens were prepared by the regenerating process. Three different metal electrodes of gold, silver and aluminum were deposited on a 50 × 50 mm2 cellulose film using a thermal evaporator. An aluminum cantilever beam was used as a vibrational bender and EAPap was attached close to the root of the cantilever beam. The voltage output of the EAPap was measured under harmonic base excitation of the cantilever beam. The EAPap with aluminum electrode provided the largest open circuit voltage output compared to those with gold or silver electrodes. The output voltages of the EAPap increased linearly with increase of the area of the electrodes. The output voltages also increased with increasing input acceleration but became saturated at a certain magnitude. From the experimental results, we conclude that EAPap with metal electrodes can be used as a flexible energy harvesting transducer by external mechanical stress, and the output voltage is related to the electrode material due to its work function.

Abas, Zafar; Kim, Heung Soo; Zhai, Lindong; Kim, Jaehwan; Kim, Joo-Hyung

2014-07-01

301

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

302

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

303

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

304

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

305

Blood flow rate, temperature, oxygen tension and consumption in the skin of adults measured by a heated microcathode oxygen electrode.  

PubMed

Reliable transcutaneous measurements of arterial oxygen tension are based on a maximum skin blood flow rate which is created by heating the skin, typically at an electrode temperature of 44 to 45 degrees C. This increase in skin blood flow rate creates an arterialization of the oxygen tension in the capillaries and the surrounding tissue. The heat conducted to the skin surface is removed by a combination of convection (skin perfusion) and conduction to the deeper layers of the skin. This heat transport to and through the skin surface causes a measurable temperature profile from the electrode surface to the capillary layer. By a blood flow cessation it is possible to change the temperature profile because the convective part of the heat consumption is eliminated and the conductive part can then be measured and subtracted. Using the forearm as measuring area and a heated tc-PO2 electrode several observations were made. The mean temperature gradient over epidermis down to the capillary layer at an electrode temperature of 43, 44, and 45 degrees C was 2.1, 2.4 and 2.7 degrees C, respectively. The change in temperature profile caused by the blood flow cessation enabled primarily an estimation of the skin blood flow rate by temperature measurements, ranging from 0.07 to 0.24 ml.cm-2.min-1. Increasing blood flow rates correlated to increasing tc-PO2 values. By means of a dynamically, thermally shielded tc-PO2 electrode it was possible to determine the skin blood flow rates in the same arbitrary units computed on the basis of the heat dissipation to the skin surface. Furthermore, it was possible to correlate these blood flow estimations to the cutaneous blood flow rates measured by 133Xe washout technique. By increasing the electrode temperature the cutaneous blood flow rates increased from 12 to 50 ml.(100 g)-1.min-1. It was possible to calculate a conversion factor on the basis of the correlation between the heat determinations of the skin blood flow rate and the 133Xe measurements. Using this conversion factor the highest blood flow rate did not exceed 55 ml.(100 g)-1.min-1. The subcutaneous blood flow rate increased accordingly with increasing electrode temperature. It was concluded that the measured heat consumption of the skin is effected by the heat removing capacity of the cutaneous as well as the subcutaneous blood flow. The cutaneous blood flow, however, was considered predominant in the transport of heat from the skin surface. By 50 times of stripping the skin surface, the cornified epidermal membrane was removed. This procedure increased the tc-PO2 values by on an average 3.6 kPa (27.1 mmHg).(ABSTRACT TRUNCATED AT 400 WORDS) PMID:3048920

Jaszczak, P

1988-08-01

306

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. PMID:23295726

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

2012-01-01

307

Dry electrodes for electrocardiography.  

PubMed

Patient biopotentials are usually measured with conventional disposable Ag/AgCl electrodes. These electrodes provide excellent signal quality but are irritating for long-term use. Skin preparation is usually required prior to the application of electrodes such as shaving and cleansing with alcohol. To overcome these difficulties, researchers and caregivers seek alternative electrodes that would be acceptable in clinical and research environments. Dry electrodes that operate without gel, adhesive or even skin preparation have been studied for many decades. They are used in research applications, but they have yet to achieve acceptance for medical use. So far, a complete comparison and evaluation of dry electrodes is not well described in the literature. This work compares dry electrodes for biomedical use and physiological research, and reviews some novel systems developed for cardiac monitoring. Lastly, the paper provides suggestions to develop a dry-electrode-based system for mobile and long-term cardiac monitoring applications. PMID:24137716

Meziane, N; Webster, J G; Attari, M; Nimunkar, A J

2013-09-01

308

ESR Process Instabilities while Melting Pipe Electrodes  

SciTech Connect

With the demonstration of the viability of using the electroslag remelting process for the decontamination of radionuclides, interest has increased in examining the unique aspects associated with melting steel pipe electrodes. These electrodes consist of several nested pipes, welded concentrically to atop plate. Since these electrodes can be half as dense as a solid electrode, they present unique challenges to the standard algorithms used in controlling the melting process. Naturally the electrode must be driven down at a dramatically increased speed. However, since the heat transfer is greatly influenced and enhanced with the increased area to volume ratio, considerable variation in the melting rate of the pipes has been found. Standard control methods can become unstable as a result of the variation at increased speeds, particularly at shallow immersion depths. The key to good control lies in the understanding of the melting process. Several experiments were conducted to observe the characteristics of the melting using two different control modes. By using a pressure transducer to monitor the pressure inside the pipes, the venting of the air trapped inside the electrode was observed. The measurements reveal that for a considerable amount of time. the pipes are not completely immersed in the slag, allowing the gas inside to escape without the formation of bubbles. This result has implications for the voltage swing as well as for the decontamination reactions.

Melgaard, D.K.; Shelmidine, G.J.

1999-01-06

309

Direct subnanosecond voltage monitors  

SciTech Connect

Advanced system development in the subnanosecond time frame increasingly demands high-resolution voltage measurements for both single-shot and repetitive operation. Voltage monitors having capabilities up to the hundred kilovolt level have been developed for direct measurements in discrete and transmission line geometries. Resolutions of 100 ps at 100 kV to 30 ps at 20 kV have been achieved. Detailed test data is presented and ultimate voltage scaling limits are discussed.

Barth, J.E.; Sajeant, W.J.

1981-01-01

310

High voltage DC power supply  

DOEpatents

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

Droege, Thomas F. (Batavia, IL)

1989-01-01

311

High voltage DC power supply  

DOEpatents

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

Droege, T.F.

1989-12-19

312

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

PubMed Central

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

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

2001-01-01

313

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

E-print Network

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

314

Assessment of hand held ion selective electrode technology for direct measurement of soil chemical properties  

Microsoft Academic Search

Access to real-time information on soil chemistry would assist farmers in making decisions about nutrient management. Hand held Ion Selective Electrodes (ISE) are commercially available for testing pH, sodium (Na), potassium (K), and nitrate-nitrogen (NO3-N). To date, there has been some success in adapting hand held ISE devices for testing plant sap nutrient levels. The objective of our study was

J. R. Davenport; J. D. Jabro

2001-01-01

315

Dominating redox systems in lakes and rivers; thermodynamic interpretation of in-situ measurements with a platinum electrode.  

PubMed

Thorough studies of 28 water bodies, predominantly lakes from the younger moraine area of Schleswig-Holstein, Northern Germany but also some peat bog waters in Niedersachsen, Northern Germany and lake Balaton in Hungary, showed the presence of at least six redox systems: NO3-/NO2-; NO3-/NH4+; NO2-/NH4+; So/HS-; So/H2S; and probably Fe(OH)3/Fe2+. Depending on the physico-chemical conditions one of these becomes the dominant system determining the electric potential measured with the platinum electrode. The platinum electrode does not respond to any oxygen dominated redox system. The corresponding theoretical redox equations seem to apply to almost all water bodies such as freshwater lakes, rivers, brackish water bodies, sea water and sometimes even humus rich water bodies from peat bogs and black water streams, hydromorphic soils, sediments and sewage sludge. The equations were found not to be valid for some heavily polluted effluents from lakes. The following points are discussed on the basis of these findings: the redox systems to which the normal platinum electrode reacts under natural conditions; equations of redox systems relevant in natural waters; methods of determination of the dominating redox system. PMID:3797630

David, R

1986-01-01

316

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

317

Effect of Silver Annealing Conditions on the Performance of Electrolytic Silver/Silver Chloride Electrodes used in Harned Cell Measurements of pH  

PubMed Central

We have studied the long and short term stability of electrolytic Ag/AgCl electrodes fabricated from Ag wire that has been subjected to a range of different annealing conditions. At elevated temperatures, the presence of oxygen during the annealing process has been shown to be detrimental to the performance of electrodes produced. This phenomenon has been attributed to the dissolution of oxygen in the Ag lattice leading to structural changes in the Ag/AgCl electrode material. Electrodes prepared from Ag wire annealed in the absence of oxygen have shown no appreciable change in performance throughout the temperature range employed. This work has resulted in an improved understanding of the optimum annealing conditions required for Ag used in the preparation of electrolytic Ag/AgCl reference electrodes. This work has positive implications for the accuracy of Harned cell measurements of pH. PMID:22294923

Brewer, Paul. J.; Brown, Richard. J. C.

2010-01-01

318

KEY COMPARISON: Final report on CCEM.RF-K4.CL comparison: RF-voltage measurements up to 1 GHz  

NASA Astrophysics Data System (ADS)

We report the results of an international comparison of measurements of radio frequency voltage in the frequency range 1 MHz to 1 GHz. This comparison was performed as a Key Comparison under the auspices of the Consultative Committee for Electricity and Magnetism (CCEM) of the International Committee for Weights and Measures (CIPM). Participating laboratories were the designated national metrology institutes (NMIs) for their respective countries. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

de Vreede, Jan P. M.; Randa, James

2010-01-01

319

Influence and modification of coupling device on low voltage power network channel characterization measurement  

Microsoft Academic Search

Channel characterization measurements of power line are often carried out when the power system is operation actively. So the coupling device is adopted to isolate the power frequency signal. Due to the impedance mismatch between the output of coupling device and power network, the energy of carrier signal will be attenuated, which causes much influence on the accuracy of measurement

Zheng Tao; Yang Xiaoxian; Zhang Baohui

2005-01-01

320

Making hexagonal electrodes on Nafion for deformable mirrors applications  

NASA Astrophysics Data System (ADS)

In this paper, a fabrication of IPMC (Ionic Polymer Metal Composites) films with hexagonal electrodes for deformable mirrors applications has been described. With the array of hexagonal electrodes on one side of IPMC membrane, we can control the contour of IPMC by driving voltage selectively. Our fabrication process involves ion-exchange, lithography, and electroless plating steps. A positive photoresist in photolithography is used as the mask in the electroless plating process to selectively grow platinum electrodes in IPMC regions. We have measured the surface resistance of the IPMC. The surface resistance of the hexagonal electrodes is about 5?, which is small enough to enable the IPMC to be actuated by low voltage. The other side of the IPMC membrane is smooth and can be used as reflection surface. We have generated deformation on our IPMCs (5 cm X 5 cm) under a low actuation voltage less than 5 volts successfully. The maximum stroke of the IPMC deformable mirror is about 25 um. Due to the low driving voltage of IPMCs, the deformable mirrors made of IPMCs is promising.

Huang, Po-Jung; Su, Guo-Dung J.

2014-09-01

321

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. PMID:20178370

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

2010-01-01

322

Effect of Electrode Thickness for Reducing Ozone Generation in Electrostatic Precipitator  

NASA Astrophysics Data System (ADS)

The influence of electrode thickness on ozone generation in the electrostatic precipitator(ESP) was experimentally investigated. The experimental ESP was two-stage-type which composed of a prechager, followed by the collecting section. The precharger consists of high voltage electrodes and grounded electrodes. The thickness of high voltage electrode was selected as 0.1, 0.2, 0.5 and 0.8 mm and the grounded electrodes was 1.0mm. The collecting electrode section had parallel-plates configuration. The gases emitted from the diesel engine were diluted with air and introduced into ESP in order to measure the particle counts were attributed to saw type electrode. In the present study, the electric field distribution was caluculated using the commercial coad called “Ansys”. The relationship between the ozone generation and collection efficiency was investigated. As a result, the ozone concentration decreased with decreasing the electrode thickness maintaining the same collection efficiency. This result is attributed to decreasing the dissociation area of O2 in the vicinity of the electrodes.

Yasumoto, Koji; Zukeran, Akinori; Takagi, Yasuhiro; Ehara, Yoshiyasu; Takahashi, Takeo; Yamamoto, Toshiaki

323

Thermo- and photoinduced voltages in Ag heterodimensional junctions  

NASA Astrophysics Data System (ADS)

Macroscopic-long Ag nanowires have been synthesized through an improved solid-state ionics method and characterized at different spatial scales. Using a bundle of as-fabricated Ag nanowires to connect with two bulk Ag electrodes, two Ag heterodimensional junctions are formed into an electrical circuit. Thermo- and photoinduced electromotive forces are observed and the corresponding voltages are measured in the circuit on the macroscale. For the photoinduced voltage, the fast dynamic response of the circuit, irradiated locally by 532nm and 10.6?m lasers, is exhibited. The studied low-dimensional effects need to be taken into account in future applications of Ag nanowires.

Xu, Jia; Sun, Jia-Lin; Zhu, Jia-Lin

2007-10-01

324

Electrochemical performance of platinum electrodes within the multi-electrode spiral nerve cuff.  

PubMed

In this study, the electrochemical performance of platinum electrodes within a multi-electrode spiral cuff to be used for selective nerve stimulation was investigated. The original cuff, simplified into a half-cuff, contained a single row of nine electrodes (0.5 × 2 mm) at a distance of 2 mm from its inner surface. Cyclic voltammetry was used to investigate the electrochemical reactions at the electrode-electrolyte interface, to define a potential window within which the electrode could be safely used in selective nerve stimulation, to calculate the charge injection capacity and cathodal charge storage capacity. Voltage transients retrieved during excitation with quasitrapezoidal biphasic current pulses, tested by selective nerve stimulation of the isolated porcine left cervical vagus nerve segment, were used to determine the maximum polarization across the electrode-electrolyte interface and to calculate cathodic charge injection capacity of the electrode. The results show that the most negative and most positive potentials across the electrode-electrolyte interface reached -0.54 and 0.59 V; these did not exceed the safe potential limits for water electrolysis. Furthermore, the time integral of the cathodic current by cyclic voltammetry measured over the potential range of water electrolysis, actually representing the cathodal charge storage capacity, was approximately -4 mC cm(-2). The charge injection capacity, representing the maximum charge density injected in a current stimulation pulse, using only reversible processes, however, was around 75 µC cm(-2). In conclusion, both, the tested stimulation pulse and electrode are suitable for efficient and safe selective nerve stimulation. PMID:24938675

Rozman, Janez; Pe?lin, Polona; Mehle, Andraž; Sala, Martin

2014-09-01

325

Effect of the reference electrode size on the ionization instability in the plasma sheath of a small positively biased electrode  

SciTech Connect

It is well known that additional ionization in the vicinity of a positively biased electrode immersed into a weakly ionized plasma is responsible for a hysteresis in the electrode current-voltage characteristics and the current self-oscillations rise. Here we show both experimentally and theoretically that under certain conditions these phenomena cannot be correctly interpreted once considered separately from the reference electrode current-voltage characteristics. It is shown that small electrodes can be separated into three groups according to the relation between the electrode and the reference electrode areas. Each group is characterized by its own dependence of the collected current on the bias voltage.

Bliokh, Y. P.; Brodsky, Yu. L.; Chashka, Kh. B.; Felsteiner, J.; Slutsker, Ya. Z. [Department of Physics, Technion, 32000 Haifa (Israel)

2011-06-01

326

Real-time, Noninvasive Monitoring of Ion Energy at Insulating Electrodes  

NASA Astrophysics Data System (ADS)

The dc self bias voltage is often monitored during plasma processing to provide a rough estimate of ion bombardment energies. However, many plasma reactors use electrostatic chucks, which have a large dc impedance that makes dc bias measurements impossible. A chuck may also have a large rf impedance that produces a significant rf voltage drop across the chuck. In this study chuck impedance effects were investigated in an inductively coupled plasma reactor by incorporating insulating structures into the rf-biased lower electrode. Measurements were made to characterize the capacitive impedance of the insulating electrode itself and the combined impedance of the electrode plus the wafer. This impedance was included in a numerical model of the plasma and its sheaths and the combined model was used to analyze measured rf bias current and voltage waveforms. This approach allows a real-time, noninvasive monitoring technique developed for bare metallic electrodes to be extended to insulating electrodes, including electrostatic chucks. The technique not only determines the dc self bias voltage but also the total ion current and ion energy distributions at the wafer or chuck surface.

Sobolewski, Mark

2006-10-01

327

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

328

A high speed, medium voltage pulse amplifier for diode reverse transient measurements  

NASA Astrophysics Data System (ADS)

A dc-coupled nonlinear pulse amplifier circuit is presented. The circuit presented can produce 40 V peak-to-peak pulses with 3 ns rise and fall times. This speed is obtained by using class D transistor amplifier stages. This circuit is shown to be useful for measuring the reverse recovery transients of fast switching diodes such as the 1N4148, and fast recovery power rectifiers.

Chudobiak, Michael J.

1995-11-01

329

Comparative analysis of vacuum and SF6 as high voltage insulations  

Microsoft Academic Search

Compares experimental measurements of the electroinsulation properties of a vacuum insulation system with those of the same system filled with SF6. The influence of the following factors of the condition of the two insulation systems on the electron strength at AC voltage was examined: conditioning, kind of electrode material, level of pressure, the degree of nonuniformity of macroscopic and microscopic

W. Opydo; J. Opydo

1991-01-01

330

A Microfluidic Bioreactor With Integrated Transepithelial Electrical Resistance (TEER) Measurement Electrodes for Evaluation of Renal Epithelial Cells  

PubMed Central

We have developed a bilayer microfluidic system with integrated transepithelial electrical resistance (TEER) measurement electrodes to evaluate kidney epithelial cells under physiologically relevant fluid flow conditions. The bioreactor consists of apical and basolateral fluidic chambers connected via a transparent microporous membrane. The top chamber contains microfluidic channels to perfuse the apical surface of the cells. The bottom chamber acts as a reservoir for transport across the cell layer and provides support for the membrane. TEER electrodes were integrated into the device to monitor cell growth and evaluate cell–cell tight junction integrity. Immunofluorescence staining was performed within the microchannels for ZO-1 tight junction protein and acetylated ?-tubulin (primary cilia) using human renal epithelial cells (HREC) and MDCK cells. HREC were stained for cytoskeletal F-actin and exhibited disassembly of cytosolic F-actin stress fibers when exposed to shear stress. TEER was monitored over time under normal culture conditions and after disruption of the tight junctions using low Ca2+ medium. The transport rate of a fluorescently labeled tracer molecule (FITC-inulin) was measured before and after Ca2+ switch and a decrease in TEER corresponded with a large increase in paracellular inulin transport. This bioreactor design provides an instrumented platform with physiologically meaningful flow conditions to study various epithelial cell transport processes. PMID:20552673

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

2014-01-01

331

Voltage Drop  

NSDL National Science Digital Library

The first site with information on voltage drop is provided by Power and System Innovations on their Frequently Asked Questions: Voltage Drop (1) page. Visitors can read what voltage drop is, what causes it, what happens as a result of it, and what the maximum recommended voltage drop is. The second site, Basics of Electricity (2), is part of General Electric's Lighting for Business Web site. Through descriptions and illustrations, the site explains what voltage drop is and gives examples of how it is calculated using Ohm's law. The next site is a lab worksheet that is part of a class from the Electrical and Computer Engineering Department of Montana State University called Voltage Drop in Cables (3). The objective of the lesson is to determine the internal resistance of an extension cord and choose the proper wire size for a particular application. Students are given an explanation of the procedure and a number of questions to answer related to the exercise. The Oregon Building Congress offers the Lesson Plans (4) Web site and the downloadable Voltage Drop educational activity. The lesson, which is suggested to be contained within a unit on formulas and solving literal equations, explores the concept of voltage drop that is encountered in basic wiring. The fifth site entitled Explanation of Voltage Drop in a Series Circuit (5) is offered by the Horizons Electronic Lesson Plan Resource. The page describes voltage drop as an electronic concept, gives a formula determining voltage drop, provides a schematic that helps illustrate the concept, and offers a quiz and answer sheet. Next, from electrician.com, is the online Voltage Drop Calculator (6). Users input the type and size of wire being used, the voltage and phase, circuit length, and amp load to calculate voltage drop and several other parameters. The seventh site, entitled The Hazards of Voltage Drop (7), is provided within the Electrical Construction Maintenance Web site. The page describes how electrical equipment can overheat or even power down if it operates below its voltage rating. It also provides a thorough explanation of how to determine the load's operating voltage. The last site, maintained by Williamson Labs (8), is a comprehensive learning site called Elementary Electricity. Visitors will find a wealth of information here, including fun descriptions, graphics, and animations on all aspects of electricity including voltage drop.

332

MICROCONTROLLER-BASED LOW-COST DATA-ACQUISITION SYSTEM WITH A DOUBLE ADAPTIVE POLAROGRAPHIC ELECTRODE FOR MEASURING DISSOLVED OXYGEN IN WINE  

Microsoft Academic Search

A microcontroller based low-cost data-acquisition system has been developed to measure dissolved oxygen in fluids, applied to wine, using polarographic electrodes in a Clark cell. The prototype consists of a sophisticated adaptation system to amplify correctly the low current that this type of sensor provides. The system compensates for the temperature effect in the measurement. This measurement system supports any

A. Abarca; P. Casanova-Peláez; M. de la Fuente; J. M. Abril; y F. Pérez-Ocón

2012-01-01

333

Direct current measurement of ohmic resistance of high conductivity solutions by means of polarized electrodes  

E-print Network

polar~on pon~ at oa" 4 electrode, ~~aaciy, ln auy elsccr&yctc ceU ci~ cn . piete circ~t . vtII tnchaio four pote:~ values: le Ills IB?prossod potx'at'~cg across nr! ":Iq. 2. The cathode p~atial, 1. . :. . N, p:Isricat(on ~V~I d~ tc, hydro.... iR ~ i": ?. E + iR cell cath an col (4) Now, according to Tsfel' lsw: E th ~ c i dlogi/A cath cath (5) ~ c', d' log i/A su sn wbsrs c, d, c', d' are constants, and A~ snd A are effectbre ursus of cathode and anode respectively. 5ubstituting...

Artecona, Victor Manuel

2012-06-07

334

Measurement of Fast Voltage Transients in High-Performance Nb3Sn Magnets  

SciTech Connect

The Superconducting Magnet group at Lawrence Berkeley National Laboratory has been developing Nb{sub 3}Sn high-field accelerator magnet technology for the last fifteen years. In order to support the magnet R&D effort, we are developing a diagnostic system that can help identify the causes of performance limiting quenches by recording small flux-changes within the magnet prior to quench-onset. These analysis techniques were applied to the test results from recent Nb{sub 3}Sn magnets. This paper will examine various types of events and their distinguishing characteristics. The present measurement techniques are discussed along with the design of a new data acquisition system that will substantially improve the quality of the recorded signals.

Lietzke, A. F.; Sabbi., G. L.; Ferracin, P.; Caspi, S.; Zimmerman, S.; Joseph, J.; Doering, D.; Lizarazo, J.

2008-06-01

335

Objective Measures of Electrode Discrimination with Electrically-Evoked Auditory Change Complex and Speech Perception Abilities in Children with Auditory Neuropathy Spectrum Disorder  

PubMed Central

Objective: This study aimed to 1) determine the sensitivity of the electrically evoked auditory change complex (eACC) to changes in stimulating electrode position; and 2) investigate the association between results of eACC measures and behavioral electrode discrimination and their association with speech-perception performance in pediatric cochlear implant (CI) users who have auditory neuropathy spectrum disorder (ANSD). Design: Fifteen children with ANSD ranging in age between 5.4 and 18.6 yrs participated in this study. All subjects used Cochlear Nucleus devices. For each subject, open-set speech perception ability was assessed using the Phonetically Balanced Kindergarten (PBK) word lists presented at 60 dB SPL using monitored live voice in a sound booth. Behavioral and objective measures of electrode discrimination were made in a non-clinical test environment. The stimuli used to elicit these measures were 800-ms biphasic pulse trains delivered by a direct interface to the cochlear implant. Data were collected from two basic stimulation conditions. In the standard condition, the entire pulse train was delivered to a mid-array electrode (electrode 11 or 12) at the maximum comfortable level (C level). In the change condition, the stimulus was split into two 400-ms pulse train segments presented sequentially on two different electrodes. The stimulation level of the second 400-ms pulse train was loudness balanced to the C level of the mid-array electrode used in the standard condition. The separation between the pair of stimulating electrodes was systematically varied. For behavioral electrode discrimination measures, each subject was required to determine whether they heard one or two sounds for stimuli presented in different stimulation conditions. For the eACC measures, two replicates of 100 artifact-free sweeps were recorded for each stimulation condition. Results: The eACC in response to changes in stimulating electrode position was recorded from all subjects with ANSD using direct electrical stimulation. Electrode discrimination thresholds determined with the eACC and behavioral measures were consistent. Children with ANSD using cochlear implants who showed poorer speech performance also required larger separations between the stimulating electrode pair to reliably elicit the eACC than subjects with better speech-perception performance. There was a robust correlation between electrode discrimination capacities and speech-perception performances in subjects tested in this study. The effect of electrode separation on eACC amplitudes was not monotonic. Conclusions: These results demonstrate the feasibility of using the eACC to evaluate electrode discrimination capacities in children with ANSD. These results suggest that the eACC elicited by changes in stimulating electrode position holds great promise as an objective tool for evaluating spectral pattern detection in this population, which may be predictive of their potential speech-perception performance. PMID:24231629

He, Shuman; Grose, John H.; Teagle, Holly F.B.; Buchman, Craig A.

2014-01-01

336

Changes in biphasic electrode impedance with protein adsorption and cell growth  

PubMed Central

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

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

2012-01-01

337

Evaluation of uncertainty in the inductive measurement of critical current densities of superconducting films using third-harmonic voltages  

NASA Astrophysics Data System (ADS)

Several techniques can be used for inductive measurement of the critical current density Jc of large-area superconducting thin films used in microwave devices and fault-current limiters. The most popular of these methods employs the third-harmonic voltages V3. We have proposed a standard method using V3 for determining Jc under a criterion of electric field E. Here, the uncertainty in the standard method is evaluated. Since the measured Jc is directly proportional to the magnetic field at the upper surface of the superconducting film, the most significant systematic effect is the deviation of the coil-to-film distance Z1 from the prescribed value. The principal origins of this deviation of Z1 are (1) inadequate pressing of the coil onto the film and (2) ice layers occasionally forming between the coil and the protective polyimide film. If these effects are eliminated, uncertainty of Jc originates mainly from (a) uncertainty of the experimental coil coefficient k', which is dominated by uncertainty of the transport Jc, and (b) underestimation of the induced electric field E when using a simple Bean model. For a typical DyBa2Cu3O7 film specimen, the relative combined standard uncertainty in the standard method was evaluated as ˜5%. The effect of the film edge on Jc measurements is also described.

Yamasaki, H.; Mawatari, Y.; Nakagawa, Y.; Yamada, H.

2012-10-01

338

Environmentally friendly disposable sensors with microfabricated on-chip planar bismuth electrode for in situ heavy metal ions measurement  

Microsoft Academic Search

This paper presents an environmentally friendly disposable heavy metal ion sensor for in situ and online monitoring in the nature and physiological systems. The miniaturized sensor chip consists of a non-toxic microfabricated bismuth (Bi) working electrode that replaces the conventional mercury electrodes, an integrated Ag\\/AgCl reference electrode, a gold counter electrode, and microfluidic channels. In this work, the electrochemical behavior

Zhiwei Zou; Am Jang; Eric MacKnight; Pei-Ming Wu; Paul L. Bishop; Chong H. Ahn

2008-01-01

339

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

340

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

SciTech Connect

Radiation therapy in patients is planned by using computed tomography (CT) images acquired before start of the treatment course. Here, tumor shrinkage or weight loss or both, which are common during the treatment course for patients with head-and-neck (H and N) cancer, causes unexpected differences from the plan, as well as dose uncertainty with the daily positional error of patients. For accurate clinical evaluation, it is essential to identify these anatomical changes and daily positional errors, as well as consequent dosimetric changes. To evaluate the actual delivered dose, the authors proposed direct dose measurement and dose calculation with mega-voltage cone-beam CT (MVCBCT). The purpose of the present study was to experimentally evaluate dose calculation by MVCBCT. Furthermore, actual delivered dose was evaluated directly with accurate phantom setup. Because MVCBCT has CT-number variation, even when the analyzed object has a uniform density, a specific and simple CT-number correction method was developed and applied for the H and N site of a RANDO phantom. Dose distributions were calculated with the corrected MVCBCT images of a cylindrical polymethyl methacrylate phantom. Treatment processes from planning to beam delivery were performed for the H and N site of the RANDO phantom. The image-guided radiation therapy procedure was utilized for the phantom setup to improve measurement reliability. The calculated dose in the RANDO phantom was compared to the measured dose obtained by metal-oxide-semiconductor field-effect transistor detectors. In the polymethyl methacrylate phantom, the calculated and measured doses agreed within about +3%. In the RANDO phantom, the dose difference was less than +5%. The calculated dose based on simulation-CT agreed with the measured dose within±3%, even in the region with a high dose gradient. The actual delivered dose was successfully determined by dose calculation with MVCBCT, and the point dose measurement with the image-guided radiation therapy procedure.

Matsubara, Kana, E-mail: matsubara-kana@hs.tmu.ac.jp [Graduate School of Human Health Sciences, Tokyo Metropolitan University, Arakawa-ku Tokyo (Japan); Kohno, Ryosuke [National Cancer Center Hospital East, Chiba (Japan); National Cancer Center Research Institute, Chiba (Japan); Nishioka, Shie; Shibuya, Toshiyuki; Ariji, Takaki; Akimoto, Tetsuo [National Cancer Center Hospital East, Chiba (Japan); Saitoh, Hidetoshi [Graduate School of Human Health Sciences, Tokyo Metropolitan University, Arakawa-ku Tokyo (Japan)

2013-07-01

341

The electrochemical measurements were conducted using a three-electrode cell at 25 C. A Pt wire and an Ag/AgCl (in saturated KCl) were used as the  

E-print Network

The electrochemical measurements were conducted using a three-electrode cell at 25 C. A Pt wire in Millipore water (18 MX cm). The working electrode was brushed with a cata- lyst ink as described previously.1±0.6 V versus NHE (NHE = nor- mal hydrogen electrode) to identify the properties of the Pt-based catalyst

Gao, Hongjun

342

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

PubMed Central

We describe voltage-switching mode scanning electrochemical microscopy (VSM-SECM), in which a single SECM tip electrode was used to acquire high-quality topographical and electrochemical images of living cells simultaneously. This was achieved by switching the applied voltage so as to change the faradaic current from a hindered diffusion feedback signal (for distance control and topographical imaging) to the electrochemical flux measurement of interest. This imaging method is robust, and a single nanoscale SECM electrode, which is simple to produce, is used for both topography and activity measurements. In order to minimize the delay at voltage switching, we used pyrolytic carbon nanoelectrodes with 6.5–100 nm radii that rapidly reached a steady-state current, typically in less than 20 ms for the largest electrodes and faster for smaller electrodes. In addition, these carbon nanoelectrodes are suitable for convoluted cell topography imaging because the RG value (ratio of overall probe diameter to active electrode diameter) is typically in the range of 1.5–3.0. We first evaluated the resolution of constant-current mode topography imaging using carbon nanoelectrodes. Next, we performed VSM-SECM measurements to visualize membrane proteins on A431 cells and to detect neurotransmitters from a PC12 cells. We also combined VSM-SECM with surface confocal microscopy to allow simultaneous fluorescence and topographical imaging. VSM-SECM opens up new opportunities in nanoscale chemical mapping at interfaces, and should find wide application in the physical and biological sciences. PMID:22611191

Takahashi, Yasufumi; Shevchuk, Andrew I.; Novak, Pavel; Babakinejad, Babak; Macpherson, Julie; Unwin, Patrick R.; Shiku, Hitoshi; Gorelik, Julia; Klenerman, David; Korchev, Yuri E.; Matsue, Tomokazu

2012-01-01

343

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

344

Fiber-optic voltage sensor  

Microsoft Academic Search

A fiber-optic voltage sensor is described which includes a source of light, a reference fiber for receiving a known percentage of the light and an electrostrictive element having terminals across which is applied, and a voltage to be measured. The electrostrictive element is responsive to the applied voltage to assume an altered physical state. A measuring fiber also receives a

C. B. Wood

1990-01-01

345

Modeling gating charge and voltage changes in response to charge separation in membrane proteins.  

PubMed

Measurements of voltage changes in response to charge separation within membrane proteins can offer fundamental information on mechanisms of charge transport and displacement processes. A recent example is provided by studies of cytochrome c oxidase. However, the interpretation of the observed voltage changes in terms of the number of charge equivalents and transfer distances is far from being trivial or unique. Using continuum approaches to describe the voltage generation may involve significant uncertainties and reliable microscopic simulations are not yet available. Here, we attempt to solve this problem by using a coarse-grained model of membrane proteins, which includes an explicit description of the membrane, the electrolytes, and the electrodes. The model evaluates the gating charges and the electrode potentials (c.f. measured voltage) upon charge transfer within the protein. The accuracy of the model is evaluated by a comparison of measured voltage changes associated with electron and proton transfer in bacterial photosynthetic reaction centers to those calculated using our coarse-grained model. The calculations reproduce the experimental observations and thus indicate that the method is of general use. Interestingly, it is found that charge-separation processes with different spatial directions (but the same distance perpendicular to the membrane) can give similar observed voltage changes, which indicates that caution should be exercised when using simplified interpretation of the relationship between charge displacement and voltage changes. PMID:25049404

Kim, Ilsoo; Chakrabarty, Suman; Brzezinski, Peter; Warshel, Arieh

2014-08-01

346

Drop short control of electrode gap  

DOEpatents

During vacuum consumable arc remelting the electrode gap between a consumable electrode and a pool of molten metal is difficult to control. The present invention monitors drop shorts by detecting a decrease in the voltage between the consumable electrode and molten pool. The drop shorts and their associated voltage reductions occur as repetitive pulses which are closely correlated to the electrode gap. Thus, the method and apparatus of the present invention controls electrode gap based upon drop shorts detected from the monitored anode-cathode voltage. The number of drop shorts are accumulated, and each time the number of drop shorts reach a predetermined number, the average period between drop shorts is calculated from this predetermined number and the time in which this number is accumulated. This average drop short period is used in a drop short period electrode gap model which determines the actual electrode gap from the drop short. The actual electrode gap is then compared with a desired electrode gap which is selected to produce optimum operating conditions and the velocity of the consumable error is varied based upon the gap error. The consumable electrode is driven according to any prior art system at this velocity. In the preferred embodiment, a microprocessor system is utilized to perform the necessary calculations and further to monitor the duration of each drop short. If any drop short exceeds a preset duration period, the consumable electrode is rapidly retracted a predetermined distance to prevent bonding of the consumable electrode to the molten remelt.

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

1986-01-01

347

Modeling, fabrication and demonstration of an electrostatic actuator with a coplanar pre-charged electrode  

NASA Astrophysics Data System (ADS)

We present the modeling, fabrication and measurement results of a novel electrostatic actuator with a coplanar pre-charged electrode. Different from the conventional electrostatic actuator, the pull-in voltage of the proposed actuator can be freely controlled even after fabrication by inducing charges prior to use in the auxiliary electrode right next to the actuation electrode. To investigate the static and dynamic characteristics of the proposed actuator, analytical models were first developed on the basis of a parallel-plate capacitor model. We then successfully designed, fabricated, and evaluated a micro-switch with a fixed-fixed beam and a coplanar pre-charged electrode. By properly introducing a dimple structure, the pull-in voltage of the fabricated micro-switch was reduced from 71.2 V to 6.8 V when pre-charged by 58.8 V. The resonant frequency of the fabricated micro-switch was 84.8% of the initial resonant frequency when the reduced pull-in voltage of the device was half of the original pull-in voltage. These measurement results were compared with those from the analytical models and FEM simulation, showing deviations of less than 12%. This work can favorably be adapted and used in designing an electrostatic micro-switch since the proposed switch can remarkably reduce the pull-in voltage as desired without notable performance degradation.

Yang, Hyun-Ho; Choi, Dong-Hoon; Oen Lee, Jeong; Yoon, Jun-Bo

2011-08-01

348

An approach to the diagnosis of metabolic syndrome by the multi-electrode impedance method  

NASA Astrophysics Data System (ADS)

It is well known that metabolic syndrome can induce myocardial infarction and cerebral infarction. So, it is very important to measure the visceral fat volume. In the electric impedance method, information in the vicinity of the electrodes is strongly reflected. Therefore, we propose a new multi-electrode arrangement method based on the impedance sensitivity theorem to measure the visceral fat volume. This electrode arrangement is designed to enable high impedance sensitivity in the visceral and subcutaneous fat regions. Currents are simultaneously applied to several current electrodes on the body surface, and one voltage electrode pair is arranged on the body surface near the organ of interest to obtain the visceral fat information and another voltage electrode pair is arranged on the body surface near the current electrodes to obtain the subcutaneous fat information. A simulation study indicates that by weighting the impedance sensitivity distribution, as in our method, a high-sensitivity region in the visceral and the subcutaneous fat regions can be formed. In addition, it was confirmed that the visceral fat volume can be estimated by the measured impedance data.

Furuya, N.; Sakamoto, K.; Kanai, H.

2010-04-01

349

Measurement of GABA-evoked conductance changes of lobster muscle fibres by a three-microelectrode voltage clamp technique.  

PubMed

The effective membrane conductance and capacity of lobster muscle fibres was measured by a three-intracellular-microelectrode voltage clamp technique. Conductance values agreed well with those determined under current clamp, by means of the 'short' cable equations. Reversible increases in conductance evoked by gamma-aminobutyric acid (GABA) were reflected by differences (delta V) in electrotonic potential amplitude recorded at the centre, and midway between the centre and fibre end respectively. GABA dose--conductance curves derived from cable theory or from delta V measurements were virtually identical. The effective capacity (ceff), determined from the area beneath the 'on' delta V capacity transient, yielded values of the membrane time constant consistently lower than those obtained by the graphical method of E. Stefani & A.B. Steinbach (J. Physiol., London. 203, 383-401 (1969)); one possible explanation for this discrepancy is discussed. In the presence of GABA, the effective capacity was reduced in a dose-related manner. The results were interpreted in terms of an equivalent circuit in which surface membrane was arranged in parallel with cleft-tubular membrane of finite conductance, charged through an access resistance. GABA was though to be decreasing ceff by selectively increasing the conductance of the cleft-tubular membranes. PMID:6127711

Constanti, A; Smart, T G

1982-06-22

350

Experimental measurement of shaft voltage and bearing current in an inverter fed three phase induction motor drive  

Microsoft Academic Search

With Pulse Width Modulation (PWM) inverter driven induction motors (IM) both internally and externally sourced bearing currents may exists (1). Currents flowing through induction motor bearings have the potential of creating premature bearing failures. IM powered by using PWM voltage source inverters (VSI) will generate high frequency noise voltage with respect to ground (gnd). Due to fast switching action of

B. Muralidhara; A. Ramachandran; R. Srinivasan; M. C. Reddy

2011-01-01

351

Junction-temperature measurements in GaN UV light-emitting diodes using the diode forward voltage  

Microsoft Academic Search

A theoretical model for the dependence of the diode forward voltage (Vf) on junction temperature (T) is developed. A new expression for dVf\\/dT is derived that takes into account all relevant contributions to the temperature dependence of the forward voltage including the intrinsic carrier concentration, the bandgap energy, and the effective density of states. Experimental results on the junction temperature

Y. Xi; E. F. Schubert

2004-01-01

352

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

353

Organic bistable devices with high switching voltage  

Microsoft Academic Search

Electrical bistable device with high switching voltage is developed. The device structure is Al electrode layer\\/ metal dispersed layer\\/ organic material layer\\/ Au electrode layer, whose thickness is 60\\/30\\/80\\/60nm, respectively. The organic material is a type of bisquinomethane, 2, 5-bis {(3\\

Haruo Kawakami; Hisato Kato; Keisuke Yamashiro; Nobuyuki Sekine; Masami Kuroda

2004-01-01

354

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

355

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

356

Determination of the threshold-energy surface for copper using in-situ electrical-resistivity measurements in the high-voltage electron microscope  

Microsoft Academic Search

A detailed study of the anisotropy of the threshold energy for Frenkel-pair production in copper was carried out experimentally, using in-situ electrical-resistivity measurements in the high-voltage electron microscope. These electrical-resistivity measurements, which are sensitive to small changes in point-defect concentration, were used to determine the damage or defect production rate. Damage-rate measurements in copper single crystals were carried out for

Wayne E. King; K. L. Merkle; M. Meshii

1981-01-01

357

Comparative studies of self-discharge by potential decay and float-current measurements at C double-layer capacitor and battery electrodes  

NASA Astrophysics Data System (ADS)

Charged electrochemical capacitors and battery electrodes are in a state of high Gibbs energy in relation to that of their discharged states; hence there is a thermodynamic "driving force" for their self-discharge on open-circuit. Several mechanisms for self-discharge can be envisaged and diagnostically distinguished. They must take place by mixed cathodic/anodic electrochemical processes (as in corrosion) or, in some cases, by a surface-chemical process. Self-discharge can be characterized by two procedures: (a) measurement of open-circuit decline of electrode potential or state-of-charge with time or (b) by establishing the polarizing currents, so-called float-currents, at various potentials in the self-discharge process that are required just to maintain those respective potentials constant. The importance, for either case, of characterizing the self-discharge behavior individually for each electrode of a cell pair (using a third electrode as a reference) is stressed. Experimental data are presented for potentiostatic float-current measurements at porous C-cloth and glassy-C electrodes, and related to digital potential-decay measurements under the same conditions in aqueous H 2SO 4 below the decomposition potential of the solution. Treatment of an equivalent circuit model enables the time dependence of components of double-layer charging and self-discharge under potentiostatic float conditions to be understood and evaluated.

Niu, Jianjun; Conway, Brian E.; Pell, Wendy G.

358

Voltage Controlled Voltage Source (VCVS)  

NSDL National Science Digital Library

Hosted by Clarkson University, this applet demonstrates a circuit that contains a voltage controlled voltage source (VCVS). The gain may be modified using the scroll bar. Even though brief, this resource can be used in a variety of different technical education classrooms.

Dorf, Richard C.; Svoboda, James A.

2008-11-27

359

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

360

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

361

Tunneling between carbon nanofiber and gold electrodes  

NASA Astrophysics Data System (ADS)

In a carbon nanofiber (CNF)-metal system such as a bridge between two gold electrodes, passing high current (current stressing) reduces the total resistance of the system (CNF resistance RCNF plus contact resistance Rc) by orders of magnitude. The role of current stressing is modeled as a reduction in the interfacial tunneling gap with transport characteristics attributed to tunneling between Au and CNF. The model predicts a reduction in Rc and gradual disappearance of the nonlinearity in the current-voltage (I-V) characteristics as Rc decreases. These results are consistent with measured I-V behavior.

Yamada, Toshishige; Saito, Tsutomu; Suzuki, Makoto; Wilhite, Patrick; Sun, Xuhui; Akhavantafti, Navid; Fabris, Drazen; Yang, Cary Y.

2010-02-01

362

A Solid Fe2O3 Based Carbon-Epoxy Electrode For Potentiometric Measurements of pH  

Microsoft Academic Search

A solid of Fe2O3 based carbon-epoxy composite electrode was investigated for use as a potentiometric pH sensor. The electrode was constructed with a mixture of sulfated iron(III) oxide, carbon power and epoxy resin that was deposited directly onto a glass tube. The effect of composition (Fe2O3, carbon and epoxy resin) on the electrode response and its calibration curve (mV\\/pH) were

M. F. S. Teixeira; L. A. Ramos; E. A. Neves; E. T. G. Cavalheiro

2002-01-01

363

A Solid Fe 2 O 3 Based Carbon–Epoxy Electrode for Potentiometric Measurements of pH  

Microsoft Academic Search

A solid Fe2O3 based carbon-epoxy composite electrode was investigated for use as a potentiometric pH sensor. The electrode was constructed using a mixture of sulfated iron(III) oxide, carbon power, and epoxy resin, which was deposited directly onto a glass tube. The effect of composition (Fe2O3?, carbon and epoxy resin) on the electrode response and its calibration curve (mV\\/pH) were investigated.

M. F. S. Teixeira; L. A. Ramos; E. A. Neves; E. T. G. Cavalheiro

2002-01-01

364

Influence of fabrication process steps on Pd-IPMC electrode morphologies and mechano-electrical properties  

NASA Astrophysics Data System (ADS)

The electrode of Ionic polymer-metal composites (IPMCs) is the key to understand their working mechanisms and mechano-electrical properties; however, there is little experimental report on the electrode morphologies and their forming mechanisms. In this paper, several typical IPMC samples with different electrode morphologies are fabricated by combining various process steps. The influence of the process steps, such as roughing treatment, immersing reduction and chemical plating, on the electrode surface and cross-section morphologies is investigated by SEM study, where the reaction principles are employed to explain that how the metal particles generate and grow at different directions of the electrode. The current and deformation responses of the samples are measured at the present of a voltage to characterize the mechano-electrical properties. Then it is concluded that immersing reduction is only suitable as a pre-deposition process step, and chemical plating is necessary for IPMC with desirable performance.

Zhu, Zicai; Chen, Hualing; Chang, Longfei; Li, Bo; Wang, Yongquan

2011-04-01

365

Millimeter thick ionic polymer membrane-based IPMCs with bimetallic Pd-Pt electrodes  

NASA Astrophysics Data System (ADS)

Ionic polymer metal composites (IPMC) are a low-voltage driven Electroactive Polymers (EAP) that can be used as actuators or sensors. This paper presents a comparative study of millimeter thick ionic polymer membrane-based IPMCs with high-performance Pd-Pt electrodes and conventional Pt electrodes. IPMCs assembled with different electrodes are characterized in terms of electromechanical, -chemical and mechanolelectrical properties. The SEM and energy dispersive X-ray (EDS) analysis are used to investigate the distribution of deposited electrode metals in the cross-section of Pd-Pt IPMCs. The study shows that IPMCs assembled with millimeter thick ionic polymer membranes and bimetallic Pd-Pt electrodes are superior in mechanoelectrical sensing and, also, show considerably higher blocking forces compared to the conventional type of IPMCs. Blocking forces more than 30 grams are measured under 4V DC. However, the actuation response is slower than conventional IPMCs having approximately 0.2-0.3 mm thickness.

Palmre, Viljar; Kim, Sung Jun; Kim, Kwang

2011-04-01

366

Electrocatalytic Measurement Methodology of Oxide Catalysts Using a Thin-Film Rotating Disk Electrode  

E-print Network

Transition-metal oxides can exhibit high electrocatalytic activity for reactions such as the oxygen reduction reaction (ORR) in alkaline media. It is often difficult to measure and compare the activities of oxide catalysts ...

Suntivich, Jin

367

Considerations for Estimating Electrode Performance in Li-Ion Cells  

NASA Technical Reports Server (NTRS)

Advanced electrode materials with increased specific capacity and voltage performance are critical to the development of Li-ion batteries with increased specific energy and energy density. Although performance metrics for individual electrodes are critically important, a fundamental understanding of the interactions of electrodes in a full cell is essential to achieving the desired performance, and for establishing meaningful goals for electrode performance. This paper presents practical design considerations for matching positive and negative electrodes in a viable design. Methods for predicting cell-level discharge voltage, based on laboratory data for individual electrodes, are presented and discussed.

Bennett, William R.

2012-01-01

368

Discrepancies between sodium concentrations measured by the Kodak Ektachem 700 and by dilutional and direct ion-selective electrode analyzers.  

PubMed

We have identified rare (approximately 0.2% of all samples), but clinically significant, discrepancies between serum or plasma sodium concentrations measured with the Kodak Ektachem 700's direct ion-selective electrode (ISE) method and concentrations measured with two other analyzers: the Beckman Synchron CX3's dilutional ISE instrument and the Radiometer KNA2 instrument for sodium-potassium analysis by the direct ISE method. The differences do not appear to be related to any previously identified sources of discrepancy, such as variations in triglycerides, bicarbonate, total protein, albumin, or gamma-globulin, the presence of paraproteins, or interference by benzalkonium chloride from heparinized catheters. They occurred despite the use of Gen 04 reference fluid on the Ektachem. We could not identify any drug or family of drugs that the patients had taken in common and that might influence the results. Until this problem is resolved, Ektachem users should be aware of the potential for discrepancies of > 6 mmol/L in measurements of sodium concentrations. PMID:1458577

Stone, J A; Moriguchi, J R; Notto, D R; Murphy, P E; Dass, C J; Wessels, L M; Freier, E F

1992-12-01

369

Electrohydrodynamic flow in a wire-plate non-thermal plasma reactor measured by 3D PIV method  

NASA Astrophysics Data System (ADS)

This work was aimed at measurements of the electrohydrodynamic (EHD) secondary flow in a non-thermal plasma reactor using three-dimensional particle image velocimetry (3D PIV) method. The wide-type non-thermal plasma reactor used in this work was an acrylic box with a wire discharge electrode and two plate collecting electrodes. The positive DC voltage was applied to the wire electrode through a 10 M? resistor. The collecting electrodes were grounded. The voltage applied to the wire electrode was 28 kV. Air flow seeded with a cigarette smoke was blown along the reactor duct with an average velocity of 0.6 m/s. The 3D PIV velocity fields measurements were carried out in four parallel planes stretched along the reactor duct, perpendicularly to the wire electrode and plate electrodes. The measured flow velocity fields illustrate complex nature of the EHD induced secondary flow in the non-thermal plasma reactor.

Podlinski, J.; Niewulis, A.; Mizeraczyk, J.

2009-08-01

370

Working Electrodes  

NASA Astrophysics Data System (ADS)

In electrochemistry an electrode is an electronic conductor in contact with an ionic conductor. The electronic conductor can be a metal, or a semiconductor, or a mixed electronic and ionic conductor. The ionic conductor is usually an electrolyte solution; however, solid electrolytes and ionic melts can be used as well. The term "electrode" is also used in a technical sense, meaning the electronic conductor only. If not specified otherwise, this meaning of the term "electrode" is the subject of the present chapter. In the simplest case the electrode is a metallic conductor immersed in an electrolyte solution. At the surface of the electrode, dissolved electroactive ions change their charges by exchanging one or more electrons with the conductor. In this electrochemical reaction both the reduced and oxidized ions remain in solution, while the conductor is chemically inert and serves only as a source and sink of electrons. The technical term "electrode" usually also includes all mechanical parts supporting the conductor (e.g., a rotating disk electrode or a static mercury drop electrode). Furthermore, it includes all chemical and physical modifications of the conductor, or its surface (e.g., a mercury film electrode, an enzyme electrode, and a carbon paste electrode). However, this term does not cover the electrolyte solution and the ionic part of a double layer at the electrode/solution interface. Ion-selective electrodes, which are used in potentiometry, will not be considered in this chapter. Theoretical and practical aspects of electrodes are covered in various books and reviews [1-9].

Komorsky-Lovri?, Šebojka

371

Through-the-electrode model of a proton exchange membrane fuel cell with independently measured parameters  

SciTech Connect

A one dimensional model for a proton exchange membrane fuel cell was developed which makes use of independently measured parameters for predicting single cell performance. Optimization of catalyst layer formulation and properties are explored. Impact of temperature and cathode pressure upon system performance is investigated.

Weisbrod, K.R.; Grot, S.A.; Vandergborgh, N.E.

1995-09-01

372

Multifunctional reference electrode  

DOEpatents

A multifunctional, low mass reference electrode of a nickel tube, thermocouple means inside the nickel tube electrically insulated therefrom for measuring the temperature thereof, a housing surrounding the nickel tube, an electrolyte having a fixed sulfide ion activity between the housing and the outer surface of the nickel tube forming the nickel/nickel sulfide/sulfide half-cell. An ion diffusion barrier is associated with the housing in contact with the electrolyte. Also disclosed is a cell using the reference electrode to measure characteristics of a working electrode.

Redey, Laszlo (Lisle, IL); Vissers, Donald R. (Naperville, IL)

1983-01-01

373

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

SciTech Connect

A system of electrodes and Langmuir probes has been developed for the measurement of plasma flow damping in the Helically Symmetric Experiment (HSX) stellarator. A biased electrode is used to apply a JxB torque to the plasma. The fast switching electrode power supply allows the electrode voltage to be applied in {approx}1 {mu}s, which is much faster than any of the plasma time scales; the electrode current is terminated on a similar time scale at the end of the electrode pulse. A pair of multitipped Mach probes have been designed to measure the plasma flows in a magnetic surface with good spatial and time resolution ({delta}t>20 {mu}s). The unmagnetized model by Hutchinson is used to analyze the Mach probe data, and radial force balance is found to be well satisfied during electrode bias. These probes allow for measurements of the transient response of the plasma flows and floating potential when the electrode is energized. An example of using the system for the estimation of viscous damping times in HSX is provided.

Gerhardt, S.P.; Anderson, D.T.; Anderson, F.S.B.; Talmadge, J.N. [Department of Electrical and Computer Engineering, University of Wisconsin, Madison, Wisconsin 53703 (United States)

2004-11-01

374

Detection of crevice corrosion under an O-ring by polarization resistance measurements using electrodes embedded in the O-ring  

SciTech Connect

An electrochemical sensor which incorporates a counter electrode (CE) and a reference electrode (RE) into an O-ring has been developed for in situ monitoring of crevice corrosion initiation and propagation. It is applicable to crevice corrosion situations where the crevice is created by a gasket or an O-ring and the attack occurs in that crevice. It is shown that polarization resistance (R{sub p}) values calculated from in situ electrochemical impedance measurements correlate with the onset of crevice attack and with its propagation for crevice corrosion of alloy 625 (UNS N06625) in 3.5% NaCl and in 10% FeCl{sub 3} solutions.

Inman, M.; Rawat, A.K.; Taylor, E.J. [Faraday Technology, Inc., Dayton, OH (United States); Moran, P.J. [Naval Academy, Annapolis, MD (United States). Mechanical Engineering Dept.

1997-12-01

375

Device and method for the measurement of depth of interaction using co-planar electrodes  

DOEpatents

A device and method for measuring a depth of interaction of an ionizing event and improving resolution of a co-planar grid sensor (CPG) are provided. A time-of-occurrence is measured using a comparator to time the leading edge of the event pulse from the non-collecting or collecting grid. A difference signal between the grid signals obtained with a differential amplifier includes a pulse with a leading edge occurring at the time-of-detection, measured with another comparator. A timing difference between comparator outputs corresponds to the depth of interaction, calculated using a processor, which in turn weights the difference grid signal to improve spectral resolution of a CPG sensor. The device, which includes channels for grid inputs, may be integrated into an Application Specific Integrated Circuit. The combination of the device and sensor is included. An improved high-resolution CPG is provided, e.g., a gamma-ray Cadmium Zinc Telluride CPG sensor operating at room temperature.

DeGeronimo, Gianluigi (Syosset, NY)

2007-09-18

376

High-voltage pulsed generator for dynamic fragmentation of rocks.  

PubMed

A portable high-voltage (HV) pulsed generator has been designed for rock fragmentation experiments. The generator can be used also for other technological applications. The installation consists of low voltage block, HV block, coaxial transmission line, fragmentation chamber, and control system block. Low voltage block of the generator, consisting of a primary capacitor bank (300??F) and a thyristor switch, stores pulse energy and transfers it to the HV block. The primary capacitor bank stores energy of 600 J at the maximum charging voltage of 2 kV. HV block includes HV pulsed step up transformer, HV capacitive storage, and two electrode gas switch. The following technical parameters of the generator were achieved: output voltage up to 300 kV, voltage rise time of ?50?ns, current amplitude of ?6?kA with the 40?? active load, and ?20?kA in a rock fragmentation regime (with discharge in a rock-water mixture). Typical operation regime is a burst of 1000 pulses with a frequency of 10 Hz. The operation process can be controlled within a wide range of parameters. The entire installation (generator, transmission line, treatment chamber, and measuring probes) is designed like a continuous Faraday's cage (complete shielding) to exclude external electromagnetic perturbations. PMID:21034090

Kovalchuk, B M; Kharlov, A V; Vizir, V A; Kumpyak, V V; Zorin, V B; Kiselev, V N

2010-10-01

377

High voltage solar array experiments  

NASA Technical Reports Server (NTRS)

The interaction between the components of a high voltage solar array and a simulated space plasma is studied to obtain data for the design of a high voltage solar array capable of 15kW at 2 to 16kV. Testing was conducted in a vacuum chamber 1.5-m long by 1.5-m diameter having a plasma source which simulated the plasma conditions existing in earth orbit between 400 nautical miles and synchronous altitude. Test samples included solar array segments pinholes in insulation covering high voltage electrodes, and plain dielectric samples. Quantitative data are presented in the areas of plasma power losses, plasma and high voltage induced damage, and dielectric properties. Limitations of the investigation are described.

Kennerud, K. L.

1974-01-01

378

Multi Frequency Phase Fluorimetry (MFPF) for Oxygen Partial Pressure Measurement: Ex Vivo Validation by Polarographic Clark-Type Electrode  

PubMed Central

Background Measurement of partial pressure of oxygen (PO2) at high temporal resolution remains a technological challenge. This study introduces a novel PO2 sensing technology based on Multi-Frequency Phase Fluorimetry (MFPF). The aim was to validate MFPF against polarographic Clark-type electrode (CTE) PO2 measurements. Methodology/Principal Findings MFPF technology was first investigated in N?=?8 anaesthetised pigs at FIO2 of 0.21, 0.4, 0.6, 0.8 and 1.0. At each FIO2 level, blood samples were withdrawn and PO2 was measured in vitro with MFPF using two FOXY-AL300 probes immediately followed by CTE measurement. Secondly, MFPF-PO2 readings were compared to CTE in an artificial circulatory setup (human packed red blood cells, haematocrit of 30%). The impacts of temperature (20, 30, 40°C) and blood flow (0.8, 1.6, 2.4, 3.2, 4.0 L min?1) on MFPF-PO2 measurements were assessed. MFPF response time in the gas- and blood-phase was determined. Porcine MFPF-PO2 ranged from 63 to 749 mmHg; the corresponding CTE samples from 43 to 712 mmHg. Linear regression: CTE?=?15.59+1.18*MFPF (R2?=?0.93; P<0.0001). Bland Altman analysis: meandiff 69.2 mmHg, rangediff -50.1/215.6 mmHg, 1.96-SD limits -56.3/194.8 mmHg. In artificial circulatory setup, MFPF-PO2 ranged from 20 to 567 mmHg and CTE samples from 11 to 575 mmHg. Linear regression: CTE?=??8.73+1.05*MFPF (R2?=?0.99; P<0.0001). Bland-Altman analysis: meandiff 6.6 mmHg, rangediff -9.7/20.5 mmHg, 1.96-SD limits -12.7/25.8 mmHg. Differences between MFPF and CTE-PO2 due to variations of temperature were less than 6 mmHg (range 0–140 mmHg) and less than 35 mmHg (range 140–750 mmHg); differences due to variations in blood flow were less than 15 mmHg (all P-values>0.05). MFPF response-time (monoexponential) was 1.48±0.26 s for the gas-phase and 1.51±0.20 s for the blood-phase. Conclusions/Significance MFPF-derived PO2 readings were reproducible and showed excellent correlation and good agreement with Clark-type electrode-based PO2 measurements. There was no relevant impact of temperature and blood flow upon MFPF-PO2 measurements. The response time of the MFPF FOXY-AL300 probe was adequate for real-time sensing in the blood phase. PMID:23565259

Boehme, Stefan; Duenges, Bastian; Klein, Klaus U.; Hartwich, Volker; Mayr, Beate; Consiglio, Jolanda; Baumgardner, James E.; Markstaller, Klaus; Basciani, Reto; Vogt, Andreas

2013-01-01

379

Ionized calcium measurement in serum and plasma by ion selective electrodes: comparison of measured and calculated parameters.  

PubMed

To determine the concentration of ionized calcium (iCa) collected in lithium heparin and gel tubes and to correlate the measured iCa with calculated iCa. Anaerobic fasting blood samples were simultaneously collected from healthy laboratory workers in lithium-heparin and gel tubes. iCa, pH, total calcium (CaT), total protein and albumin were measured. Ionized Ca was calculated with albumin and globulin values using an appropriate formula. Mean iCa in gel tubes showed a positive constant bias of 0.08 mmol/L (p < 0.001) when compared to lithium heparin results. The mean pH of blood taken in lithium heparin and gel tubes was non-significant (p = 0.3). Measured iCa poorly correlated with CaT (r = 0.2, p = 0.1) and calculated iCa (r = 0.2, p = 0.2). To evaluate the calcium status direct measurement of iCa must be done rather than using the formulae for iCa determination. In addition serum is recommended as the choice of sample for iCa determination in comparison to plasma samples. PMID:24966481

Jafri, Lena; Khan, Aysha Habib; Azeem, Saba

2014-07-01

380

The use of multiple EBIC curves and low voltage electron microscopy in the measurement of small diffusion lengths  

NASA Technical Reports Server (NTRS)

Accurate evaluations of diffusion lengths for heavily to moderately doped III-V semiconductors and/or radiation damaged solar cells have been made possible by using experimental and numerical techniques. The techniques employed were electron beam induced current and low voltage electron microscopy.

Leon, R. P.

1987-01-01

381

A Gibbs-ensemble based technique for Monte Carlo simulation of electric double layer capacitors (EDLC) at constant voltage.  

PubMed

Current methods for molecular simulations of Electric Double Layer Capacitors (EDLC) have both the electrodes and the electrolyte region in a single simulation box. This necessitates simulation of the electrode-electrolyte region interface. Typical capacitors have macroscopic dimensions where the fraction of the molecules at the electrode-electrolyte region interface is very low. Hence, large systems sizes are needed to minimize the electrode-electrolyte region interfacial effects. To overcome these problems, a new technique based on the Gibbs Ensemble is proposed for simulation of an EDLC. In the proposed technique, each electrode is simulated in a separate simulation box. Application of periodic boundary conditions eliminates the interfacial effects. This in addition to the use of constant voltage ensemble allows for a more convenient comparison of simulation results with experimental measurements on typical EDLCs. PMID:24811628

Punnathanam, Sudeep N

2014-05-01

382

A hydrogen peroxide electrode assay to measure thiol peroxidase activity for organoselenium and organotellurium drugs.  

PubMed

Molecular mimics of the enzyme glutathione peroxidase (GPx) are increasingly being evaluated as redox active drugs. Their molecular mechanism of action parallels that of the native enzyme; however, a major distinction is that GPx mimics can use alternative thiol substrates to glutathione. This generic thiol peroxidase activity implies that it is necessary to assess a GPx mimic's recognition of a range of cellular thiols in order to determine its potential therapeutic effects. We report an electrochemical assay that, by measuring the rate of decrease of the peroxide substrate, allows the activity of GPx mimics to be directly compared against an array of thiols. The derived pseudo zero-order rate constants, k(obs), for representative GPx mimics range between 0 and 6.6 min(-1) and can vary by more than an order of magnitude depending on the thiol electron donor. An additional advantage of the assay is that it enables synergistic interactions between GPx mimics and cellular proteins to be evaluated. Here we report that glutathione disulfide reductase, which is commonly used to evaluate GPx mimic activity, recognizes the GPx mimic ebselen as a substrate, increasing its apparent k(obs). Therefore, reports relying on glutathione disulfide reductase to evaluate GPx mimic activity may exaggerate drug antioxidant action. PMID:22813709

Giles, Niroshini M; Kumari, Sweta; Stamm, Rosemary A; Patel, Siddharth; Giles, Gregory I

2012-10-15

383

The LMF triaxial MITL voltage adder system  

SciTech Connect

The light-ion microfusion driver design consists of multiple accelerating modules fired in coincidence and sequentially in order to provide the desired ion energy, power pulse shape and energy deposition uniformity on an Inertial Confinement Fusion (ICF) target. The basic energy source is a number of Marx generators which, through the appropriate pulse power conditioning, provide the necessary voltage pulse wave form to the accelerating gaps or feeds of each module. The cavity gaps are inductively isolated, and the voltage addition occurs in the center conductor of the voltage adder which is the positive electrode while the electrons of the sheath flow closer to the outer cylinder which is the magnetically insulated cathode electrode. Each module powers a separate two-stage extraction diode which provides a low divergence ion beam. In order to provide the two separate voltage pulses required by the diode, a triaxial adder system is designed for each module. The voltage addition occurs in two separate MITLs. The center hollow cylinder (anode) of the second MITL also serves as the outer cathode electrode for the extension of the first voltage adder MITL. The voltage of the second stage is about twice that of the first stage. The cavities are connected in series to form the outer cylinder of each module. The accelerating modules are positioned radially in a symmetrical way around the fusion chamber. A preliminary conceptual design of the LMF modules with emphasis on the voltage adders and extension MITLs will be presented and discussed.

Mazarakis, M.G.; Smith, D.L.; Bennett, L.F.; Lockner, T.R.; Olson, R.E.; Poukey, J.W.

1992-12-31

384

An automated system for rapid evaluation of high-density electrode arrays in neural prostheses  

NASA Astrophysics Data System (ADS)

The success of high-density electrode arrays for use in neural prostheses depends on efficient impedance monitoring and fault detection. Conventional methods of impedance testing and fault detection are time consuming and not always suited for in vivo assessment of high-density electrode arrays. Additionally, the ability to evaluate impedances and faults such as open and short circuits, both in vitro and in vivo, are important to ensure safe and effective stimulation. In this work we describe an automated system for the rapid evaluation of high-density electrode arrays. The system uses a current pulse similar to that used to stimulate neural tissue and measures the voltage across the electrode in order to calculate the impedance. The switching of the system was validated by emulating a high-density electrode array using light-emitting diodes and a resistor-capacitor network. The system was tested in vitro and in vivo using a range of commercially available and in-house developed electrode arrays. The system accurately identified faults in an 84-electrode array in less than 20 s and reliably measured impedances up to 110 k? using a 200 µA, 250 µs per phase current pulse. This system has direct application for screening high-density electrode arrays in both clinical and experimental settings.

John, Sam E.; Shivdasani, Mohit N.; Leuenberger, James; Fallon, James B.; Shepherd, Robert K.; Millard, Rodney E.; Rathbone, Graeme D.; Williams, Chris E.

2011-06-01

385

Electrooptic polymer voltage sensor and method of manufacture thereof  

NASA Technical Reports Server (NTRS)

An optical voltage sensor utilizing an electrooptic polymer is disclosed for application to electric power distribution systems. The sensor, which can be manufactured at low cost in accordance with a disclosed method, measures voltages across a greater range than prior art sensors. The electrooptic polymer, which replaces the optical crystal used in prior art sensors, is sandwiched directly between two high voltage electrodes. Voltage is measured by fiber optical means, and no voltage division is required. The sample of electrooptic polymer is fabricated in a special mold and later mounted in a sensor housing. Alternatively, mold and sensor housing may be identical. The sensor housing is made out of a machinable polymeric material and is equipped with two opposing optical windows. The optical windows are mounted in the bottom of machined holes in the wall of the mold. These holes provide for mounting of the polarizing optical components and for mounting of the fiber optic connectors. One connecting fiber is equipped with a light emitting diode as a light source. Another connecting fiber is equipped with a photodiode as a detector.

Gottsche, Allan (Inventor); Perry, Joseph W. (Inventor)

1993-01-01

386

An instrument for the operational measurement of the current strength in the conductor of a high-voltage active transmission line  

Microsoft Academic Search

The results of an estimate of an algorithm for constructing a mobile instrument for the operational measurement of phase-current\\u000a strength with an error of 0.2% in high-voltage (greater than 10 kV) circuits without disturbing the couplings in the phase\\u000a conductors are presented. The problems involved in designing such instruments and possible technical solutions are considered.

V. M. Gevorkyan; S. V. Gevorkyan; Yu. A. Kazantsev; S. N. Mikhalin; I. A. Yashin

2011-01-01

387

Quantum States Probed By Temperature Dependence Capacitance-Voltage Measurements For InP/GaAs Type-II Ultrathin Quantum Well  

SciTech Connect

We report on the temperature dependent capacitance-voltage measurements on InP/GaAs ultrathin quantum well (QW). We observe a peak in apparent carrier distribution (ACD) profile at around the geometrical position of the QW. Peak value of the ACD profile increases, while it's width decreases with reducing temperature indicating that the peak in ACD is due to the accumulation of two dimensional electrons occupying the quantum states in ultrathin QW.

Singh, S. D.; Dixit, V. K.; Khamari, Shailesh K.; Ganguli, Tapas; Oak, S. M.

2011-07-15

388

Anode electrode for plasmatron structure  

US Patent & Trademark Office Database

A plasmatron operating efficiently within a wider range of gas flows and capable of sustaining a stable arc voltage. The plasmatron generates an electric arc at the tip of a cathode electrode and transfers the arc along an arc chamber and into the bore of an anode electrode located at the downstream end of the arc chamber. A plurality of arc root attachment surfaces are defined on an inner surface of the anode by a plurality of ring members, causing the electric arc to attach with its root to the arc root attachment surfaces and therefore the axial movement of the arc root is confined substantially to the anode electrode. The arc voltage variations are limited and controlled substantially by the arc root movement between two adjacent arc root attachment surfaces. When used within a plasma-spraying torch, the plasma stream generated by the plasmatron has improved characteristics and induces improved plasma spray coatings.

2000-09-05

389

Development of a method of measuring relative phase difference between sending and receiving voltage on a power line  

E-print Network

of Measuri np, Relative Phase Difference Between Sending ~nd Receiving Voltage on ~ Power Line. Conclusions. 4. Bibliography 29 FIGURFS 1. Two Machine System 2. Magnetic Cylinder Shunt for Current Transformer 4. Phase Shift Meter Network 5. Standard... Westinghouse Phase Angle Meter . . . 10 6. Schematic of a Standard Phase Angle Meter . 17 7. Schematic of Converted Phase Angle Meter . . 18 8. Meter As Normally Connected To Power Line . 20 9 . Laboratory Circuit 10. Laboratorv Set Up 21 22 11. 9raph...

Rackley, Benton Tiburce

2012-06-07

390

Charge and fluence lifetime measurements of a dc high voltage GaAs photogun at high average current  

SciTech Connect

GaAs-based dc high voltage photoguns used at accelerators with extensive user programs must exhibit long photocathode operating lifetime. Achieving this goal represents a significant challenge for proposed high average current facilities that must operate at tens of milliamperes or more. This paper describes techniques to maintain good vacuum while delivering beam, and techniques that minimize the ill effects of ion bombardment, the dominant mechanism that reduces photocathode yield of a GaAs-based dc high voltage photogun. Experimental results presented here demonstrate enhanced lifetime at high beam currents by: (a) operating with the drive laser beam positioned away from the electrostatic center of the photocathode, (b) limiting the photocathode active area to eliminate photoemission from regions of the photocathode that do not support efficient beam delivery, (c) using a large drive laser beam to distribute ion damage over a larger area, and (d) by applying a relatively low bias voltage to the anode to repel ions created within the downstream beam line. A combination of these techniques provided the best total charge extracted lifetimes in excess of 1000 C at dc beam currents up to 9.5 mA, using green light illumination of bulk GaAs inside a 100 kV photogun.

J. Grames, R. Suleiman, P.A. Adderley, J. Clark, J. Hansknecht, D. Machie, M. Poelker, M.L. Stutzman

2011-04-01

391

Multi-Electrode Impedance Method for Detection of Regional Ventilation  

NASA Astrophysics Data System (ADS)

By means of computer simulation and experiment, we investigated the feasibility of simultaneously measuring the transfer impedance changes in the right apex, left apex, right base and left base of the lungs using the multi-electrode impedance method. To obtain the transfer impedance in each region, while suppressing the effects of other regions, changing the amplitude and polarity of the applied current must localize the high sensitivity areas in the interest region. Twelve current and eight voltage electrodes were equidistantly arranged on the anterior and posterior chest walls. The amplitudes and polarities of the currents that were simultaneously applied to the current electrodes, and which provided the appropriate sensitivity distribution, were theoretically obtained. The effects of the localized sensitivity distribution were verified by comparing the simulation results of the investigated method with the results of the conventional four-electrode method. From the results of the computer simulation, we developed a multi-electrode impedance pneumography and applied it to healthy adult volunteers who were both in sitting position and in left decubitus. We found that the measurement results were physiologically reasonable.

Furuya, Norio; Sakamoto, Katsuyuki

2013-04-01

392

New Low Contact Resistance Electrode  

Microsoft Academic Search

STUDY was made of the contact resistance developed at a ferrite-electrode interface using for comparative purposes a variety of different electrode materials and methods of application. In this study individual samples measuring 0.565 in.XO.31O in. XO.065 in. were sectioned from a high-density homogeneous nickel ferrite ceramic body. Samples were cleaned in acetone immedi­ ately prior to application of electrodes. Measured

S. S. Flaschen; L. G. van Uitert

1956-01-01

393

Phase transitions detection by means of a contact electrode  

NASA Astrophysics Data System (ADS)

We investigate theoretically and next experimentally a new possibility to detect critical temperatures of solids by means of a very simple electrical circuit consisting of an analyzed sample (exhibiting phase transitions) and a contact electrode (hereafter reference electrode) where the constant voltage is applied only to the latter one. The measured system is placed into a thermostat and the electric current flow through the reference electrode is measured as function of temperature. By assuming a model Hamiltonian for the probed sample describing ferromagnetic, superconducting or reentrant phase transitions and a one-band model for the contact electrode we calculate d.c. conductivity of the reference electrode. The temperature dependence of the conductivity of this electrode clearly indicates (in the form of kinks) the transition temperatures connected with phase transitions occurring in the investigated material. This is due to the fact that the chemical potential of the whole system in contact should equal at equilibrium. Our considerations suggest straightforward application of such a circuit in a direct laboratory praxis, especially because (beyond simplicity) the applied method possesses unlimited temperature range and can be considered as noninvasive with respect to the investigated sample. To verify the effect experimentally we have used as an investigated sample an antiferromagnetic Cr material and Cu as the reference electrode. The measurements of the resistivity R(Cr + Cu) and R(Cu) alone as functions of temperature made a possibility to plot the difference R(Cr + Cu) - R(Cu) vs temperature. This plot enabled to identify the critical Neel temperature of the Cr sample corresponding to the profound minimum in this curve.

Matlak, M.; Pietruszka, M.

2004-01-01

394

Strain-optic voltage monitor  

SciTech Connect

A voltage monitor which uses the shift in absorption edge of crystalline material to measure strain resulting from electric field-induced deformation of piezoelectric or electrostrictive material, providing a simple and accurate means for measuring voltage applied either by direct contact with the crystalline material or by subjecting the material to an electric field.

Weiss, J.D.

1995-12-31

395

Water desalination using capacitive deionization with microporous carbon electrodes.  

PubMed

Capacitive deionization (CDI) is a water desalination technology in which salt ions are removed from brackish water by flowing through a spacer channel with porous electrodes on each side. Upon applying a voltage difference between the two electrodes, cations move to and are accumulated in electrostatic double layers inside the negatively charged cathode and the anions are removed by the positively charged anode. One of the key parameters for commercial realization of CDI is the salt adsorption capacity of the electrodes. State-of-the-art electrode materials are based on porous activated carbon particles or carbon aerogels. Here we report the use for CDI of carbide-derived carbon (CDC), a porous material with well-defined and tunable pore sizes in the sub-nanometer range. When comparing electrodes made with CDC with electrodes based on activated carbon, we find a significantly higher salt adsorption capacity in the relevant cell voltage window of 1.2-1.4 V. The measured adsorption capacity for four materials tested negatively correlates with known metrics for pore structure of the carbon powders such as total pore volume and BET-area, but is positively correlated with the volume of pores of sizes <1 nm, suggesting the relevance of these sub-nanometer pores for ion adsorption. The charge efficiency, being the ratio of equilibrium salt adsorption over charge, does not depend much on the type of material, indicating that materials that have been identified for high charge storage capacity can also be highly suitable for CDI. This work shows the potential of materials with well-defined sub-nanometer pore sizes for energy-efficient water desalination. PMID:22329838

Porada, S; Weinstein, L; Dash, R; van der Wal, A; Bryjak, M; Gogotsi, Y; Biesheuvel, P M

2012-03-01

396

Charge Lifetime Measurements at High Average Current Using a K{sub 2}CsSb Photocathode inside a DC High Voltage Photogun  

SciTech Connect

Two K{sub 2}CsSb photocathodes were manufactured at Brookhaven National Lab and delivered to Jefferson Lab within a compact vacuum apparatus at pressure ~ 10{sup -11} Torr. These photocathodes were evaluated using a dc high voltage photogun biased at voltages up to 200 kV, and illuminated with laser light at wavelengths 440 or 532 nm, to generate dc electron beams at currents up to 20 mA. Some conditions produced exceptionally large photocathode charge lifetimes, without measurable quantum efficiency (QE) decay, even from the center of the photocathode where operation using GaAs photocathodes is precluded due to ion bombardment. Under other conditions the charge lifetime was poor, suggesting a complex QE decay mechanism likely related to chemistry and localized heating via the laser beam. Following beam delivery, the photocathodes were evaluated using a scanning electron microscope with energy dispersive x-ray spectroscopy capability, to determine surface morphology and chemical composition.

Mammei, Russell; Feingold, Joshua; Adderley, Philip; Clark, James; Covert, Steven; Grames, Joseph; Hansknecht, John; Machie, Danny; Poelker, Benard; Rao, Triveni; Smedley, John; Walsh, John; McCarter, James

2013-03-01

397

Charge lifetime measurements at high average current using a K2CsSb photocathode inside a dc high voltage photogun  

NASA Astrophysics Data System (ADS)

Two K2CsSb photocathodes were manufactured at Brookhaven National Lab and delivered to Jefferson Lab within a compact vacuum apparatus at pressure ˜10-11Torr. These photocathodes were evaluated using a dc high voltage photogun biased at voltages up to 200 kV, and illuminated with laser light at wavelengths 440 or 532 nm, to generate dc electron beams at currents up to 20 mA. Some conditions produced exceptionally large photocathode charge lifetimes, without measurable quantum efficiency decay, even from the center of the photocathode where operation using GaAs photocathodes is precluded due to ion bombardment. Under other conditions the charge lifetime was poor due to extensive ion bombardment under severely degraded vacuum conditions, and as a result of localized heating via the laser beam. Following beam delivery, the photocathodes were evaluated using a scanning electron microscope to determine surface morphology.

Mammei, R. R.; Suleiman, R.; Feingold, J.; Adderley, P. A.; Clark, J.; Covert, S.; Grames, J.; Hansknecht, J.; Machie, D.; Poelker, M.; Rao, T.; Smedley, J.; Walsh, J.; McCarter, J. L.; Ruiz-Osés, M.

2013-03-01

398

Measuring of electrical changes induced by in situ combustion through flow-through electrodes in a laboratory sample of core material  

DOEpatents

Method and apparatus are provided for obtaining accurate dynamic measurements for passage of phase fronts through a core sample in a test fixture. Flow-through grid structures are provided for electrodes to permit data to be obtained before, during and after passage of a front therethrough. Such electrodes are incorporated in a test apparatus for obtaining electrical characteristics of the core sample. With the inventive structure a method is provided for measurement of instabilities in a phase front progressing through the medium. Availability of accurate dynamic data representing parameters descriptive of material characteristics before, during and after passage of a front provides a more efficient method for enhanced recovery of oil using a fire flood technique.

Lee, David O. (Albuquerque, NM); Montoya, Paul C. (Albuquerque, NM); Wayland, Jr., James R. (Albuquerque, NM)

1986-01-01

399

Measuring of electrical changes induced by in situ combustion through flow-through electrodes in a laboratory sample of core material  

DOEpatents

Method and apparatus are provided for obtaining accurate dynamic measurements for passage of phase fronts through a core sample in a test fixture. Flow-through grid structures are provided for electrodes to permit data to be obtained before, during and after passage of a front there through. Such electrodes are incorporated in a test apparatus for obtaining electrical characteristics of the core sample. With the inventive structure a method is provided for measurement of instabilities in a phase front progressing through the medium. Availability of accurate dynamic data representing parameters descriptive of material characteristics before, during and after passage of a front provides a more efficient method for enhanced recovery of oil using a fire flood technique. 12 figs.

Lee, D.O.; Montoya, P.C.; Wayland, J.R. Jr.

1986-12-09

400

Superposition of borehole-to-surface voltage residuals for Vadose Zone plume delineation.  

PubMed

An injected tracer field experiment was conducted at the University of Idaho Ground Water Field Laboratory to evaluate the application of borehole-to-surface voltage measurements for delineation of the tracer distribution in partially saturated, fractured basalt. A tap water tracer was injected into a fracture-dominated, salt-water plume formed during a previous salt-water injection experiment. The tap water tracer was injected into a central injection well under constant hydraulic head for 34 days. The injection well was surrounded by seven test boreholes. Each borehole contained several copper wire electrodes for borehole-to-surface potential measurements between a surface grid of 224 copper sulfate, porous pot electrodes. Eight pole-pole, borehole-to-surface voltage data sets were acquired during each measurement period by energization of a selected electrode in each of the eight boreholes. Predicted voltages for a uniform earth (homogeneous and isotropic) potential model (finite difference) were subtracted from each data set (for its respective current source location), and the voltage residuals superposed to create new data sets with greater measurement sensitivity and coverage, to aid in interpretation. These data sets were collected over four measurement periods during tap water injection and four measurement periods during the subsequent 64-day drainage phase. The data were interpreted with the use of three-dimensional models and by comparisons with other electrical and hydrological observations. Results indicate that superposition of multiple data sets of voltage residuals significantly improved the lateral resolution of subsurface bulk resistivity changes that occurred over time. PMID:16298016

Osiensky, James L; Belknap, Willard J; Donaldson, Paul R

2006-01-10

401

Enhanced performance of sulfone-based electrolytes at lithium ion battery electrodes, including the LiNi0.5Mn1.5O4 high voltage cathode  

E-print Network

Enhanced performance of sulfone-based electrolytes at lithium ion battery electrodes, including o Article history: Received 21 January 2014 Received in revised form 10 March 2014 Accepted 20 March 2014 Available online 27 March 2014 Keywords: Lithium ion battery Sulfone-based electrolytes High

Angell, C. Austen

402

Method of making biocompatible electrodes  

DOEpatents

A process of improving the sensing function of biocompatible electrodes and the product so made are disclosed. The process is designed to alter the surfaces of the electrodes at their tips to provide increased surface area and therefore decreased contact resistance at the electrode-tissue interface for increased sensitivity and essentially includes rendering the tips atomically clean by exposing them to bombardment by ions of an inert gas, depositing an adhesion layer on the cleaned tips, forming a hillocked layer on the adhesion layer by increasing the temperature of the tips, and applying a biocompatible coating on the hillocked layer. The resultant biocompatible electrode is characterized by improved sensitivity, minimum voltage requirement for organ stimulation and a longer battery life for the device in which it is employed.

Wollam, John S. (Acton, MA)

1992-01-01

403

High-Voltage Droplet Dispenser  

NASA Technical Reports Server (NTRS)

An apparatus that is extremely effective in dispensing a wide range of droplets has been developed. This droplet dispenser is unique in that it utilizes a droplet bias voltage, as well as an ionization pulse, to release a droplet. Apparatuses that deploy individual droplets have been used in many applications, including, notably, study of combustion of liquid fuels. Experiments on isolated droplets are useful in that they enable the study of droplet phenomena under well-controlled and simplified conditions. In this apparatus, a syringe dispenses a known value of liquid, which emerges from, and hangs onto, the outer end of a flat-tipped, stainless steel needle. Somewhat below the needle tip and droplet is a ring electrode. A bias high voltage, followed by a high-voltage pulse, is applied so as to attract the droplet sufficiently to pull it off the needle. The voltages are such that the droplet and needle are negatively charged and the ring electrode is positively charged.

Eichenberg, Dennis J.

2003-01-01

404

Silver-coated TiO2 electrodes for high performance dye-sensitized solar cells  

NASA Astrophysics Data System (ADS)

Silver-coated TiO2 electrodes were prepared by photodeposition with different light durations. Comparing with the dye-sensitized solar cells (DSSCs) using conventional TiO2 electrode, the conversion efficiency of DSSCs fabricated with silver-coated TiO2 electrodes was improved from 5.97% to 6.86%. The Ag layer could reflect incident light and lengthen the optical path in electrodes, and also appropriate Ag particles absorbed on the TiO2 surface slowed down the electron recombination. The recombination mechanisms of DSSCs were analyzed by open circuit voltage decay (OCVD) measurements, which provide evidence that the charge transfer from the surface state was strongly suppressed by the silver coating.

Peng, Wei; Zeng, Yun; Gong, Hao; Leng, Yong-qing; Yan, Yong-hong; Hu, Wei

2013-11-01

405

Carbon nanotube counter electrode for high-efficient fibrous dye-sensitized solar cells  

NASA Astrophysics Data System (ADS)

High-efficient fibrous dye-sensitized solar cell with carbon nanotube (CNT) thin films as counter electrodes has been reported. The CNT films were fabricated by coating CNT paste or spraying CNT suspension solution on Ti wires. A fluorine tin oxide-coated CNT underlayer was used to improve the adherence of the CNT layer on Ti substrate for sprayed samples. The charge transfer catalytic behavior of fibrous CNT/Ti counter electrodes to the iodide/triiodide redox pair was carefully studied by electrochemical impedance and current-voltage measurement. The catalytic activity can be enhanced by increasing the amount of CNT loading on substrate. Both the efficiencies of fibrous dye-sensitized solar cells using paste coated and sprayed CNT films as counter electrodes are comparative to that using Pt wires, indicating the feasibility of CNT/Ti wires as fibrous counter electrode for superseding Pt wires.

Huang, Shuqing; Sun, Huicheng; Huang, Xiaoming; Zhang, Quanxin; Li, Dongmei; Luo, Yanhong; Meng, Qingbo

2012-04-01

406

Linear inductive voltage adders (IVA) for advanced hydrodynamic radiography  

SciTech Connect

The electron beam which drifts through the multiple cavities of conventional induction linacs (LIA) is replaced in an IVA by a cylindrical metal conductor which extends along the entire length of the device and effectuates the addition of the accelerator cavity voltages. In the approach to radiography, the linear inductive voltage adder drives a magnetically immersed electron diode with a millimeter diameter cathode electrode and a planar anode/bremsstrahlung converter. Both anode and cathode electrodes are immersed in a strong (15--50 T) solenoidal magnetic field. The electron beam cross section is approximately of the same size as the cathode needle and generates a similar size, very intense x-ray beam when it strikes the anode converter. An IVA driven diode can produce electron beams of equal size and energy as a LIA but with much higher currents (40--50 kA versus 4--5 kA), simpler hardware and thus lower cost. The authors present here first experimental validations of the technology utilizing HERMES 3 and SABRE IVA accelerators. The electron beam voltage and current were respectively of the order of 10 MV and 40 kA. X-ray doses of up to 1 kR {at} 1 m and spot sizes as small as 1.7 mm (at 200 R doses) were measured.

Mazarakis, M.G.; Boyes, J.D.; Johnson, D.L. [and others

1998-09-01

407

Differential-output B-dot and D-dot monitors for current and voltage measurements on a 20-MA, 3-MV pulsed-power accelerator  

NASA Astrophysics Data System (ADS)

We have developed a system of differential-output monitors that diagnose current and voltage in the vacuum section of a 20-MA 3-MV pulsed-power accelerator. The system includes 62 gauges: 3 current and 6 voltage monitors that are fielded on each of the accelerator’s 4 vacuum-insulator stacks, 6 current monitors on each of the accelerator’s 4 outer magnetically insulated transmission lines (MITLs), and 2 current monitors on the accelerator’s inner MITL. The inner-MITL monitors are located 6 cm from the axis of the load. Each of the stack and outer-MITL current monitors comprises two separate B-dot sensors, each of which consists of four 3-mm-diameter wire loops wound in series. The two sensors are separately located within adjacent cavities machined out of a single piece of copper. The high electrical conductivity of copper minimizes penetration of magnetic flux into the cavity walls, which minimizes changes in the sensitivity of the sensors on the 100-ns time scale of the accelerator’s power pulse. A model of flux penetration has been developed and is used to correct (to first order) the B-dot signals for the penetration that does occur. The two sensors are designed to produce signals with opposite polarities; hence, each current monitor may be regarded as a single detector with differential outputs. Common-mode-noise rejection is achieved by combining these signals in a 50-? balun. The signal cables that connect the B-dot monitors to the balun are chosen to provide reasonable bandwidth and acceptable levels of Compton drive in the bremsstrahlung field of the accelerator. A single 50-? cable transmits the output signal of each balun to a double-wall screen room, where the signals are attenuated, digitized (0.5-ns/sample), numerically compensated for cable losses, and numerically integrated. By contrast, each inner-MITL current monitor contains only a single B-dot sensor. These monitors are fielded in opposite-polarity pairs. The two signals from a pair are not combined in a balun; they are instead numerically processed for common-mode-noise rejection after digitization. All the current monitors are calibrated on a 76-cm-diameter axisymmetric radial transmission line that is driven by a 10-kA current pulse. The reference current is measured by a current-viewing resistor (CVR). The stack voltage monitors are also differential-output gauges, consisting of one 1.8-cm-diameter D-dot sensor and one null sensor. Hence, each voltage monitor is also a differential detector with two output signals, processed as described above. The voltage monitors are calibrated in situ at 1.5 MV on dedicated accelerator shots with a short-circuit load. Faraday’s law of induction is used to generate the reference voltage: currents are obtained from calibrated outer-MITL B-dot monitors, and inductances from the system geometry. In this way, both current and voltage measurements are traceable to a single CVR. Dependable and consistent measurements are thus obtained with this system of calibrated diagnostics. On accelerator shots that deliver 22 MA to a low-impedance z-pinch load, the peak lineal current densities at the stack, outer-MITL, and inner-MITL monitor locations are 0.5, 1, and 58MA/m, respectively. On such shots the peak currents measured at these three locations agree to within 1%.

Wagoner, T. C.; Stygar, W. A.; Ives, H. C.; Gilliland, T. L.; Spielman, R. B.; Johnson, M. F.; Reynolds, P. G.; Moore, J. K.; Mourning, R. L.; Fehl, D. L.; Androlewicz, K. E.; Bailey, J. E.; Broyles, R. S.; Dinwoodie, T. A.; Donovan, G. L.; Dudley, M. E.; Hahn, K. D.; Kim, A. A.; Lee, J. R.; Leeper, R. J.; Leifeste, G. T.; Melville, J. A.; Mills, J. A.; Mix, L. P.; Moore, W. B. S.; Peyton, B. P.; Porter, J. L.; Rochau, G. A.; Rochau, G. E.; Savage, M. E.; Seamen, J. F.; Serrano, J. D.; Sharpe, A. W.; Shoup, R. W.; Slopek, J. S.; Speas, C. S.; Struve, K. W.; van de Valde, D. M.; Woodring, R. M.

2008-10-01

408

Differential B-dot and D-dot monitors for current and voltage measurements on a 20-MA 3-MV pulsed-power accelerator.  

SciTech Connect

We have developed a system of differential-output monitors that diagnose current and voltage in the vacuum section of a 20-MA 3-MV pulsed-power accelerator. The system includes 62 gauges: 3 current and 6 voltage monitors that are fielded on each of the accelerator's 4 vacuum-insulator stacks, 6 current monitors on each of the accelerator's 4 outer magnetically insulated transmission lines (MITLs), and 2 current monitors on the accelerator's inner MITL. The inner-MITL monitors are located 6 cm from the axis of the load. Each of the stack and outer-MITL current monitors comprises two separate B-dot sensors, each of which consists of four 3-mm-diameter wire loops wound in series. The two sensors are separately located within adjacent cavities machined out of a single piece of copper. The high electrical conductivity of copper minimizes penetration of magnetic flux into the cavity walls, which minimizes changes in the sensitivity of the sensors on the 100-ns time scale of the accelerator's power pulse. A model of flux penetration has been developed and is used to correct (to first order) the B-dot signals for the penetration that does occur. The two sensors are designed to produce signals with opposite polarities; hence, each current monitor may be regarded as a single detector with differential outputs. Common-mode-noise rejection is achieved by combining these signals in a 50-{Omega} balun. The signal cables that connect the B-dot monitors to the balun are chosen to provide reasonable bandwidth and acceptable levels of Compton drive in the bremsstrahlung field of the accelerator. A single 50-{omega} cable transmits the output signal of each balun to a double-wall screen room, where the signals are attenuated, digitized (0.5-ns/sample), numerically compensated for cable losses, and numerically integrated. By contrast, each inner-MITL current monitor contains only a single B-dot sensor. These monitors are fielded in opposite-polarity pairs. The two signals from a pair are not combined in a balun; they are instead numerically processed for common-mode-noise rejection after digitization. All the current monitors are calibrated on a 76-cm-diameter axisymmetric radial transmission line that is driven by a 10-kA current pulse. The reference current is measured by a current-viewing resistor (CVR). The stack voltage monitors are also differential-output gauges, consisting of one 1.8-cm-diameter D-dot sensor and one null sensor. Hence, each voltage monitor is also a differential detector with two output signals, processed as described above. The voltage monitors are calibrated in situ at 1.5 MV on dedicated accelerator shots with a short-circuit load. Faraday's law of induction is used to generate the reference voltage: currents are obtained from calibrated outer-MITL B-dot monitors, and inductances from the system geometry. In this way, both current and voltage measurements are traceable to a single CVR. Dependable and consistent measurements are thus obtained with this system of calibrated diagnostics. On accelerator shots that deliver 22 MA to a low-impedance z-pinch load, the peak lineal current densities at the stack, outer-MITL, and inner-MITL monitor locations are 0.5, 1, and 58 MA/m, respectively. On such shots the peak currents measured at these three locations agree to within 1%.

Shoup, Roy Willlam (ITT Industries, Albuquerque, NM); Gilliland, Terrance Leo (Ktech Corporation, Albuquerque, NM); Lee, James R.; Speas, Christopher Shane; Kim, Alexandre A. (High Current Electronic Institute, Russian Academy of Sciences, Tomsk, Russia); Struve, Kenneth William; York, Mathew William; Leifeste, Gordon T.; Rochau, Gregory Alan; Sharpe, Arthur William; Stygar, William A.; Porter, John Larry Jr.; Wagoner, Tim C. (Ktech Corporation, Albuquerque, NM); Reynolds, Paul Gerard (Team Specialty Products Corporation, Albuquerque, NM); Slopek, Jeffrey Scott (Ktech Corporation, Albuquerque, NM); Moore, William B. S.; Dinwoodie, Thomas Albert (Ktech Corporation, Albuquerque, NM); Woodring, R. M. (Ktech Corporation, Albuquerque, NM); Broyles, Robin Scott (Ktech Corporation, Albuquerque, NM); Mills, Jerry Alan; Melville, J. A. (Prodyn Technologies Incorporated, Albuquerque, NM); Dudley, M. E. (Ktech Corporation, Albuquerque, NM); Androlewicz, K. E. (Ktech Corporation, Albuquerque, NM); Mourning, R. W. (Ktech Corporation, Albuquerque, NM); Moore, J. K. (Ktech Corporation, Albuquerque, NM); Serrano, Jason Dimitri (Ktech Corporation, Albuquerque, NM); Ives, H. C. (EG& G, Albuquerque, NM); Johnson, M. F. (Team Specialty Products Corporation, Albuquerque, NM); Peyton, B. P. (Ktech Corporation, Albuquerque, NM); Leeper, Ramon Joe; Savage, Mark Edward; Donovan, Guy Louis; Spielman, R. B. (Ktech Corporation, Albuquerque, NM); Seamen, Johann F.

2007-12-01

409

Theoretical and experimental study of Differential Pulse Voltammetry at spherical electrodes: Measuring diffusion coefficients and formal potentials  

Microsoft Academic Search

Rigorous and approximate analytical expressions are deduced for Differential Pulse Voltammetry at spherical electrodes of any size, including microelectrodes, when the electrogenerated species is soluble in the electrolytic solution. From these, we examine the utility of DPV for the determination of diffusion coefficients and formal potentials, establishing the optimum conditions for this purpose. The experimental validation of the theoretical results

Ángela Molina; Eduardo Laborda; Emma I. Rogers; Francisco Martínez-Ortiz; Carmen Serna; Juan G. Limon-Petersen; Neil V. Rees; Richard G. Compton

2009-01-01

410

Comparative determination of actual thermal plasma characteristics by modeling and measurements for a nontransferred plasma torch with hollow electrodes  

Microsoft Academic Search

Summary form only given, as follows. Thermal plasma characteristics of a nontransferred plasma torch with hollow electrodes are numerically and experimentally investigated in the atmospheric condition, and a more accurate determination method of their actual distributions is suggested by comparison between numerical modeling and experiments. The plasma torch designed and fabricated consists of a cylindrical cathode with one end closed,

M. Hur; S. H. Hong

2001-01-01

411

Electrode contamination effects of retarding potential analyzer.  

PubMed

The electrode contamination in electrostatic analyzers such as Langmuir probes and retarding potential analyzers (RPA) is a serious problem for space measurements. The contamination layer acts as extra capacitance and resistance and leads to distortion in the measured I-V curve, which leads to erroneous measurement results. There are two main effects of the contamination layer: one is the impedance effect and the other is the charge attachment and accumulation due to the capacitance. The impedance effect can be reduced or eliminated by choosing the proper sweeping frequency. However, for RPA the charge accumulation effect becomes serious because the capacitance of the contamination layer is much larger than that of the Langmuir probe of similar dimension. The charge accumulation on the retarding potential grid causes the effective potential, that ions experience, to be changed from the applied voltage. Then, the number of ions that can pass through the retarding potential grid to reach the collector and, thus, the measured ion current are changed. This effect causes the measured ion drift velocity and ion temperature to be changed from the actual values. The error caused by the RPA electrode contamination is expected to be significant for sounding rocket measurements with low rocket velocity (1-2 km/s) and low ion temperature of 200-300 K in the height range of 100-300 km. In this paper we discuss the effects associated with the RPA contaminated electrodes based on theoretical analysis and experiments performed in a space plasma operation chamber. Finally, the development of a contamination-free RPA for sounding rocket missions is presented. PMID:24517809

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

2014-01-01

412

Field-enhanced electrodes for additive-injection non-thermal plasma (NTP) processor  

DOEpatents

The present invention comprises a field enhanced electrode package for use in a non-thermal plasma processor. The field enhanced electrode package includes a high voltage electrode and a field-enhancing electrode with a dielectric material layer disposed in-between the high voltage electrode and the field-enhancing electrode. The field-enhancing electrode features at least one raised section that includes at least one injection hole that allows plasma discharge streamers to occur primarily within an injected additive gas.

Rosocha, Louis A. (Los Alamos, NM); Ferreri, Vincent (Westminster, CO); Kim, Yongho (Los Alamos, NM)

2009-04-21

413

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 eletrode 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.

Schlienger, Max E. (Albuquerque, NM)

1996-01-01

414

High-performance carbon counter electrode for dye-sensitized solar cells  

Microsoft Academic Search

Here, we reported that a new carbon electrode prepared with an activated carbon was superior to a Pt sputtered electrode as the counter electrode of dye-sensitized solar cells. The photovoltaic performance was largely influenced by the roughness factor of carbon electrode. The open-circuit voltage increased by about 60mV using the carbon counter electrode compared to the Pt counter electrode because

Kiyoaki Imoto; Kohshin Takahashi; Takahiro Yamaguchi; Teruhisa Komura; Jun-ichi Nakamura; Kazuhiko Murata

2003-01-01

415

Electron launching voltage monitor  

SciTech Connect

An electron launching voltage monitor measures MITL voltage using a relationship between anode electric field and electron current launched from a cathode-mounted perturbation. An electron launching probe extends through and is spaced from the edge of an opening in a first MITL conductor, one end of the launching probe being in the gap between the MITL conductor, the other end being adjacent a first side of the first conductor away from the second conductor. A housing surrounds the launching probe and electrically connects the first side of the first conductor to the other end of the launching probe. A detector detects the current passing through the housing to the launching probe, the detected current being representative of the voltage between the conductors.

Mendel, Clifford W. (Albuquerque, NM); Savage, Mark E. (Albuquerque, NM)

1992-01-01

416

Electron launching voltage monitor  

SciTech Connect

An electron launching voltage monitor measures MITL voltage using a relationship between anode electric field and electron current launched from a cathode-mounted perturbation. An electron launching probe extends through and is spaced from the edge of an opening in a first MITL conductor, one end of the launching probe being in the gap between the MITL conductor, the other end being adjacent a first side of the first conductor away from the second conductor. A housing surrounds the launching probe and electrically connects the first side of the first conductor to the other end of the launching probe. A detector detects the current passing through the housing to the launching probe, the detected current being representative of the voltage between the conductors. 5 figs.

Mendel, C.W.; Savage, M.E.

1992-03-17

417

A large deflection model of silicon membranes for testing intrinsic stress of MEMS microphones by measuring pull-In voltage  

NASA Astrophysics Data System (ADS)

Mechanical parameters, especially mechanical stress of membranes used in silicon microphones strongly depend on the manufacturing process. As a result, deviations during this process can result in sensitivity variations of the microphone. Therefore, the stress should be well controlled within a certain tensile level. This paper describes a method to test devices electrically using the MEMS related pull-in phenomenon with respect to the mechanical compliance of microphone membranes. Using this method, out of specification chips can be detected at an early stage within the manufacturing process instead of determination at a system functionality test after packaging. Therefore, the adequacy for the intended use of the pull-in voltage and its dependency on varying tensile stress due to manufacturing tolerance is evaluated.

Oesterle, Florian; Fink, Franz; Kuhn, Harald; Dehé, Alfons; Weigel, Robert; Koelpin, Alexander

2013-05-01

418

"Wormhole" geometry for entrapping topologically protected qubits in non-abelian quantum hall states and probing them with voltage and noise measurements.  

PubMed

We study a tunneling geometry defined by a single point-contact constriction that brings to close vicinity two points sitting at the same edge of a quantum Hall liquid, shortening the trip between the otherwise spatially separated points along the normal chiral edge path. This wormhole-like geometry allows for entrapping bulk quasiparticles between the edge path and the tunnel junction, possibly realizing a topologically protected qubit if the quasiparticles have non-Abelian statistics. We show how either noise or simpler voltage measurements along the edge can probe the non-Abelian nature of the trapped quasiparticles. PMID:17155280

Hou, Chang-Yu; Chamon, Claudio

2006-10-01

419

Fiber Optic High Voltage Probe  

SciTech Connect

We developed a fiber coupled sensor to measure High Voltage directly using only light as the probe. We use the Pockles effect in lithium niobate crystal which will induce a phase shift in a laser beam that varies according to applied voltage. This can then be transformed into a modulation of beam intensity by polarizers, interferometery, or waveguide coupling. No voltage dividers are necessary, nor is any physical connection. This is accompanied by taking advantage of the structure of the power system itself, using voltage planes and dielectric insulation already present as the capacitive voltage divider. We hypothesize a bandwidth from GHz to DC. Such a system could be used in any application that calls for isolated and unobtrusive voltage sensing.

Matthew J. Heino

1999-08-01

420

Methods and apparatus for measurement of electronic properties of geological formations through borehole casing  

DOEpatents

Methods and apparatus are provided for measuring electronic properties of geological formations and cement layers adjacent to cased boreholes including resistivities, polarization phenomena and dielectric constants. Current is passed from an electrode in electrical contact with the interior of the borehole casing to an electrode on the surface of the earth. At least three voltage measuring electrodes in electrical contact with the interior of the casing measure the voltage at various points thereon. The voltage differences between discrete pairs of the voltage measuring electrodes provide a measurement of the differential current conducted into formation in the vicinity of those electrodes. These measurements facilitate calculation of the resistivities of the adjacent geological formations as well as an indication of whether cement is present. Measurements of the differential voltage response to transient currents provide a measurement of the polarization phenomena in formation as well as the capacitance of the casing in contact with the formation which is useful for determining whether oil and gas present. Lithological characteristics of the formation such as the pressence or absence of clay can also be determined. A calibration procedure is provided for minimizing errors induced by variations in the casing. The device also may be placed within the pipe attached to a drill bit while drilling open holes.

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

1991-01-01

421

Methods and apparatus for measurement of electronic properties of geological formations through borehole casing  

DOEpatents

Methods and apparatus are provided for measuring electronic properties of geological formations and cement layers adjacent to cased boreholes including resistivities, polarization phenomena and dielectric constants. Current is passed from an electrode in electrical contact with the interior of the borehole casing to an electrode on the surface of the earth. At least three voltage measuring electrodes in electrical contact with the interior of the casing measure the voltage at various points thereon. The voltage differences between discrete pairs of the voltage measuring electrodes provide a measurement of differential current conducted into formation in the vicinity of those electrodes. These measurements facilitate calculation of the resistivities of the adjacent geological formations as well as an indication of whether cement is present. Measurements of the differential voltage response to transient currents provide a measurement of the polarization phenomena in formation as well as the capacitance of the casing in contact with the formation which is useful for determining whether oil and gas are present. Lithological characteristics of the formation such as the presence or absence of clay can also be determined. A calibration procedure is provided for minimizing errors induced by variations in the casing. The device also may be placed within the pipe attached to a drill bit while drilling open holes.

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

1989-01-01

422

Effect of buffer layer on the voltage responsivity of the pyroelectric thermal sensors prepared with PZT ceramics  

NASA Astrophysics Data System (ADS)

The pyroelectric thermal detectors were prepared with lead zirconate titanate (PZT) ceramics, where a signal electrode had a structure of Au/metallic buffer/(PZT ceramic). The effect of buffer layer on the voltage responsivity was investigated with a response to step signal, taken by dynamic pyroelectric measurement. Pyroelectric ceramic wafer was prepared by mixed oxide technique. Au layer (thickness: 50 nm) and metallic buffers (thickness: 0 - 20 nm) of Cr, NiCr (80/20), and Ti were prepared by dc magnetron sputtering. In order to improve the light absorptivity, an Au-black was coated on Au signal electrode by thermal evaporation. At steady state, the output voltage (Vo) was decreased with increasing chopping frequency in the range of 1 - 100 Hz. A sensor without buffer showed the severe time-drift and instability in the output signal. However, the sensors with buffer layer showed the stable outputs. For step radiations, rising time (tp), peak voltage (Vp), and initial slope (k) of the output voltage were dependent upon the thickness and materials of buffer layer. The mechanical and electrical contacts between Au electrode and PZT ceramics were improved by inserting the metallic buffer layer. Considering the characteristics of the output voltage, the optimum thickness of buffer layer was about 15 - 20 nm, and the sensors with Ti buffer of 15 - 20 nm in thickness showed the good detectivity. Therefore, the stability and reliability of the thermal sensors could be improved by use of appropriate buffer layer.

Lee, Moon-Ho; Hwang, Ha R.; Bae, Seong-Ho

1997-08-01

423

Fiber optic high voltage probe  

Microsoft Academic Search

The authors developed a fiber coupled sensor to measure high voltages (~45 kV) directly using only light as the probe. They use the Pockels effect in lithium niobate crystals which induces a phase shift in a laser beam that varies according to applied voltage. This can then be transformed into a modulation of beam intensity by polarizers, interferometery or waveguide

Matthew J. Heino; Vasco Suite

1999-01-01

424

Electrode surface rf harmonics generated by the nonlinear sheath in a coaxial capacitive rf discharge  

SciTech Connect

rf harmonics of the 13.56 MHz excitation signal have been measured on the electrode surface in a large coaxial capacitive discharge. These are seen to have from 10% of the fundamental amplitude for the second harmonic to between 1% and 4% for the third and fourth harmonics. There is evidence that these modes propragate as TEM surface waves (Gould-Trivelpiece modes) along the length of the electrode. The Telegrapher's equations can be written for the system with non-constant shunt capacitance and admittance. The resulting nonlinear equation for the sheath voltage is solved for the harmonics to yield approximate agreement with their observed magnitudes.

Savas, S.E. (Applied Materials, Santa Clara, CA (USA))

1989-07-01

425

Biomass-modified carbon paste electrodes for monitoring dissolved metal ions  

Microsoft Academic Search

Electrodes were prepared by incorporating dried, nonliving biomass of a common lichen, Ramalina stenospora, and Sphagnum (peat) moss in carbon paste. The electrodes were tested on solutions containing Pb(II) and Cu(II) ions by immersing the electrode in the solution for selected periods of time to accumulate ions. Following this the electrode was connected to a potentiostat and the applied voltage

Hua Yao; Gerald J Ramelow

1998-01-01