Note: This page contains sample records for the topic voltage measurement electrodes from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: November 12, 2013.
1

HIGH VOLTAGE ELECTRODES  

Microsoft Academic Search

S>This patent relates to electrode structure for creating an intense ; direct current electric field which may have a field strength of the order of two ; to three times that heretofore obtained, with automatic suppression of arcing. ; The positive electrode is a conventional conductive material such as copper while ; the negative electrode is made from a special

1963-01-01

2

HIGH VOLTAGE ELECTRODES  

DOEpatents

S>This patent relates to electrode structure for creating an intense direct current electric field which may have a field strength of the order of two to three times that heretofore obtained, with automatic suppression of arcing. The positive electrode is a conventional conductive material such as copper while the negative electrode is made from a special material having a resistivity greater than that of good conductors and less than that of good insulators. When an incipient arc occurs, the moderate resistivity of the negative electrode causes a momentary, localized decrease in the electric field intensity, thus suppressing the flow of electrons and avoiding arcing. Heated glass may be utilized for the negative electrode, since it provides the desired combination of resistivity, capacity, dielectric strength, mechani-cal strength, and thermal stability. (AEC)

Murray, J.J.

1963-04-23

3

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

National Technical Information Service (NTIS)

The electrical conductivities of high voltage insulating materials were measured in the dark and under various intensities of illumination. The materials investigated included FEP Teflon, Kapton-H, fused quartz, and parylene. Conductivities were determine...

H. T. Coffey J. E. Nanevicz

1975-01-01

4

Measurement of Radiated Electromagnetic Field due to Low Voltage ESD with Spherical Electrode in 1-3GHz Frequency Bandwidth  

NASA Astrophysics Data System (ADS)

The micro-gap discharge as the low voltage ESD shows very fast transition-duration of about 32 ps or less. Furthermore, the breakdown field strength in the gap was very high of about 80 MV/m in low voltage discharging of below 400V. The relationship between the breakdown field strength in the gap and the amplitude of radiated electromagnetic field was examined in experimental study. The amplitude of radiated electromagnetic field was proportion to the breakdown field strength at the gap in the resonance experimental system using the discharge electrode with dipole configuration. In this time, we present an improved experimental system to measure the amplitude of radiated electromagnetic filed in more wideband region using spherical electrodes and a horn antenna. As a result, the amplitude of radiated electromagnetic field is proportion to the discharge voltage from 300V to 620V, and the amplitude of radiated electromagnetic field was according to the diameter of spherical electrode in 1-3GHz frequency bandwidth.

Kawamata, Ken; Minegishi, Shigeki; Fujiwara, Osamu

5

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

PubMed Central

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

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

2012-01-01

6

Design of a single electrode voltage clamp.  

PubMed

The detailed schematic diagrams and construction techniques are presented for a single microelectrode voltage clamp. The devices is used to study the membrane processes of small cells not able to be penetrated with the traditional two microelectrode system. The technique utilizes the same microelectrode alternately for current injection and membrane potential sampling on a time-sharing basis controlled by electronic switching circuitry. Current is injected in pulses and the membrane potential is sampled after an individual current pulse discharges from the microelectrode capacitance to the true membrane potential. The device can either measure the voltage response to an injected current waveform (current injection mode) or the membrane currents generated during a controlled change in membrane potential (voltage clamp mode). In voltage clamp mode, the membrane potential reaches steady-state within 2 msec (maximum time) in response to a 40 mV step command. The single electrode voltage clamp is potentially very important to the investigation of slow current processes within electrically excitable cells too small to be previously studied with traditional voltage clamp technology. PMID:7329092

Merickel, M

1980-02-01

7

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

8

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

9

Feedback control of electrode offset voltage during functional electrical stimulation.  

PubMed

Control of the electrode offset voltage is an important issue related to the processes of functional electrical stimulation because excess charge accumulation over time damages both the tissue and the electrodes. This paper proposes a new feedback control scheme to regulate the electrode offset voltage to a predetermined reference value. The electrode offset voltage was continuously monitored using a sample-and-hold (S/H) circuit during stimulation and non-stimulation periods. The stimulation current was subsequently adjusted using a proportional-integral (PI) controller to minimise the error between the reference value and the electrode offset voltage. During the stimulation period, the electrode offset voltage was maintained through the S/H circuit, and the PI controller did not affect the amplitude of the stimulation current. In contrast, during the non-stimulation period, the electrode offset voltage was sampled through the S/H circuit and rapidly regulated through the PI controller. The experimental results obtained using a nerve cuff electrode showed that the electrode offset voltage was successfully controlled in terms of the performance specifications, such as the steady- and transient-state responses and the constraint of the controller output. Therefore, the proposed control scheme can potentially be used in various nerve stimulation devices and applications requiring control of the electrode offset voltage. PMID:23685268

Chu, Jun-Uk; Song, Kang-Il; Shon, Ahnsei; Han, Sungmin; Lee, Soo Hyun; Kang, Ji Yoon; Hwang, Dosik; Suh, Jun-Kyo Francis; Choi, Kuiwon; Youn, Inchan

2013-05-16

10

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  

Microsoft Academic Search

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

R. S. Bever

1976-01-01

11

Measuring electrode assembly  

DOEpatents

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

Bordenick, John E. (West Mifflin, PA)

1989-01-01

12

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

DOEpatents

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

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

1998-01-13

13

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

National Technical Information Service (NTIS)

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...

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

2012-01-01

14

Electrodic voltages accompanying stimulated bioremediation of a uranium-contaminated aquifer  

Microsoft Academic Search

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

K. H. Williams; A. L. NGuessan; J. Druhan; P. E. Long; S. S. Hubbard; D. R. Lovley; J. F. Banfield

2009-01-01

15

Electrodic voltages accompanying stimulated bioremediation of a uranium-contaminated aquifer  

Microsoft Academic Search

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

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

2010-01-01

16

Electrodic voltages accompanying stimulated bioremediation of a uranium-contaminated aquifer  

Microsoft Academic Search

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

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

2010-01-01

17

Crosstalk current measurements using multi-electrode arrays in saline.  

PubMed

This paper investigates how the configuration of return electrodes in an electrode array affects the amount of current crosstalk when electrodes are driven simultaneously in saline. Two pairs of electrodes in different return configurations were stimulated with different-amplitude biphasic currents. Stimulating electrodes were controlled by current sinks and current sources while return electrodes were connected to supply voltage or ground. Measurement results show that no matter what return configuration was used, the return current was almost equally distributed amongst the return electrodes, which is problematic in bipolar concurrent stimulation, at least in saline. This result is due to the fact that the spreading impedance of saline solution is small compared to the electrode-electrolyte impedance, which makes the saline solution have almost the same potential. This result suggests that monopolar stimulation using a common remote return electrode be used in simultaneous stimulation to avoid crosstalk. PMID:23366561

Tran, N; Halpern, M; Bai, S; Skafidas, E

2012-01-01

18

Grounding resistance of buried electrodes in multi-layer earth predicted by simple voltage measurements along earth surface -- A theoretical discussion  

Microsoft Academic Search

The earth is modeled as inhomogeneous conducting medium with multiple horizontal layers. For known layer conductivities and thickness, the voltage distribution and grounding resistance have been computed efficiently using an equivalent image method. In this paper, the reverse sequence is proposed. Without explicitly knowing the layer conductivities, thickness and number of layers, the equivalent images are determined by the voltage

Y. L. Chow; J. J. Yang; K. D. Srivastava

1995-01-01

19

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

20

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

21

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

22

Field Emission Measurements from Niobium Electrodes  

SciTech Connect

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

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

2011-03-01

23

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

Microsoft Academic Search

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

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

2012-01-01

24

Measuring membrane voltage with microbial rhodopsins.  

PubMed

Membrane voltage (Vm) is a fundamental biological parameter that is essential for neuronal communication, cardiac activity, transmembrane transport, regulation of signaling, and bacterial motility. Optical measurements of Vm promise new insights into how voltage propagates within and between cells, but effective optical contrast agents have been lacking. Microbial rhodopsin-based fluorescent voltage indicators are exquisitely sensitive and fast, but very dim, necessitating careful attention to experimental procedures. This chapter describes how to make optical voltage measurements with microbial rhodopsins. PMID:24052383

Cohen, Adam E; Hochbaum, Daniel R

2014-01-01

25

High-voltage oil gap tests using parallel-plane electrodes  

Microsoft Academic Search

A paraffinic-base insulating oil, PB, and a naphthenic-base insulating oil, NH, were evaluated using two electrode systems. The uniform field electrodes represented a method to easily test relatively large volumes of oil and showed the paraffinic-base oil, PB, had somewhat lower breakdown voltages on both 60-Hz tests and 1.2- X 50-microsecond impulse voltage tests. The rod to plane electrode system

T. K. Sloat; W. J. Carter; H. R. Moore

1979-01-01

26

Imaging and estimation of human abdominal fat by electrical impedance tomography using multiple voltage measurement patterns.  

PubMed

A measuring device for human abdominal fat from the conductivity image derived by electrical impedance tomography (EIT) is rarely found. This study was aimed to reconstruct precise conductivity images from multiple voltage measurements in different patterns of the combination of current and voltage electrodes. We examined two voltage measuring patterns using electrodes located at upper and lower levels around the abdomen of a subject. In the experiment, after 1024 voltage data were taken from one specified voltage measurement pattern, another 1024 data were also taken continuously using another pattern. The reconstruction of conductivity image was made using entire data. As a result, the tomography image was improved compared with the image obtained from single voltage measurement pattern. We then obtained the histogram of the conductivities and estimated the area of abdominal fat. The present method using multiple voltage measurement patterns would be effective, if the measuring time can be much reduced through future modification of the tomography device. PMID:24110433

Yamaguchi, Tohru F; Katashima, Mitsuhiro; Wang, Li-Qun; Kuriki, Shinya

2013-07-01

27

Impedance measurements on button electrodes  

SciTech Connect

In the Advanced Light Source, there will be about 400 capacitance button electrodes in the beam position monitor (BPM) system, hence the contribution of each button to the machine beam impedance must be very small. We have measured the impedance of a single button as sensed by a coax connected directly to the button surface. This method is very sensitive and did not require a model of the total beam chamber as would the usual wire method. The measurements covered the range 0.1--20 GHz. The proportionality factor between the button impedance and the beam impedance depends upon geometry and frequency and was obtained from the measured sensitivity of a developmental BPM at low frequency. Discontinuities in the connection of the coax to the face of the button introduce parasitic effects that must be accounted for in interpreting the data. Below 5 GHz the results compare very well with responses computed from mechanical dimensions of the electrode. Above 15 GHz corrections for the parasitic elements become more uncertain, but the accuracy of the method is still adequate. The results show multiple resonances, a prominent example being for one button a beam impedance peak of /approximately/1 ohm with a Q of 500 at 16 GHz. 2 refs., 7 figs.

Jacob, A.; Lambertson, G.R.

1989-03-01

28

Breakdown voltage of electrode arrangements in vacuum circuit breakers  

Microsoft Academic Search

The prediction of HV strength of electrode arrangements in vacuum is complex. A comparison of experimental results from different labs is quite difficult, because they are influenced by a wide range of parameters like electrode material, surface finish, surface area, conditioning state of the surface and the geometry of the electrode arrangement. The aim of this work is to find

Ulf Schümann; Stefan Giere; Michael Kurrat

2003-01-01

29

Measuring breakdown voltage for objectively detecting ignition in fire research  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

30

Single-Electrode Voltage Clamp in Mammalian Electrophysiology.  

National Technical Information Service (NTIS)

Voltage clamping is a very important technique in neurophysiology. It provides a direct method of studying both intrinsic membrane currents and transmitter- or drug-induced currents. Until recently, many cells were unavailable for voltage clamping because...

T. Pellmar

1986-01-01

31

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

32

Novel high-voltage power lateral MOSFET with adaptive buried electrodes  

NASA Astrophysics Data System (ADS)

A new high-voltage and low-specific on-resistance (Ron,sp) adaptive buried electrode (ABE) silicon-on-insulator (SOI) power lateral MOSFET and its analytical model of the electric fields are proposed. The MOSFET features are that the electrodes are in the buried oxide (BOX) layer, the negative drain voltage Vd is divided into many partial voltages and the output to the electrodes is in the buried oxide layer and the potentials on the electrodes change linearly from the drain to the source. Because the interface silicon layer potentials are lower than the neighboring electrode potentials, the electronic potential wells are formed above the electrode regions, and the hole potential wells are formed in the spacing of two neighbouring electrode regions. The interface hole concentration is much higher than the electron concentration through designing the buried layer electrode potentials. Based on the interface charge enhanced dielectric layer field theory, the electric field strength in the buried layer is enhanced. The vertical electric field EI and the breakdown voltage (BV) of ABE SOI are 545 V/?m and -587 V in the 50 ?m long drift region and the 1 ?m thick dielectric layer, and a low Ron,sp is obtained. Furthermore, the structure also alleviates the self-heating effect (SHE). The analytical model matches the simulation results.

Zhang, Wen-Tong; Wu, Li-Juan; Qiao, Ming; Luo, Xiao-Rong; Zhang, Bo; Li, Zhao-Ji

2012-07-01

33

Measuring Multi-Megavolt Diode Voltages  

NASA Astrophysics Data System (ADS)

The voltage in high-power diodes can be determined by measuring the Compton electrons generated by the diode's bremsstrahlung radiation. This technique is implemented with a Compton-Hall (C-H) voltmeter that collimates the bremsstrahlung onto a Compton target and bends the emitted Compton electron orbits off to the side with an applied magnetic field off to Si pin diode detectors. Voltage is determined from the ratio of the Compton electron dose to the forward x-ray dose. The instrument's calibration and response are determined from coupled electron/photon transport calculations. The applicable voltage range is tuned by adjusting the position of the electron detector relative to the Compton target or by varying the magnetic field strength. The instrument was used to obtain time-dependent voltage measurements for a pinched-beam diode whose voltage is enhanced by an upstream opening switch. In this case, plasmas and vacuum electron flow from the opening switch make it difficult to determine the voltage accurately from electrical measurements. The C-H voltmeter gives voltages that are significantly higher than those obtained from electrical measurements but are consistent with measurements of peak voltage based on nuclear activation of boron-nitride targets.

Pereira, N. R.; Swanekamp, S. B.; Weber, B. V.; Commisso, R. J.; Hinshelwood, D. D.; Stephanakis, S. J.

2002-12-01

34

Characteristics of Corona Discharge in an Icicle\\/Iced-plate Electrode System under Negative DC Voltage  

Microsoft Academic Search

This paper presents the results of a series of experiments on the corona discharges occurring at icicle tips under negative DC voltage, using an icicle-iced-plate electrode system. The corona discharge development processes and the responding discharge current pulses were recorded. The influences of the gap distance, the icicle surface state and the freezing water conductivity on the corona inception voltage

M. Farzanehl; J. Zhang; D. Yu; C. Sun; W. Sima; L. Shu

2006-01-01

35

Acoustoelectric Voltage Measurements for Semiconductor Material Characterization  

Microsoft Academic Search

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

Agostino Abbate

1993-01-01

36

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

37

Anode-fall and cathode-fall voltages of air arc in atmosphere between silver electrodes  

Microsoft Academic Search

A method for estimating an anode-fall and a cathode-fall voltages of an arc discharge was proposed. By using this method, the separate estimation of the anode-fall and the cathode-fall voltages was performed for an air arc in atmosphere burning between silver electrodes. The derived anode-fall and cathode-fall voltages proved to be about 4.5 V and 14 V, respectively. It was

Rei Hemmi; Yasunobu Yokomizu; Toshiro Matsumura

2003-01-01

38

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.

Patan, Mustafa; Shah, Tosha; Sahin, Mesut

2011-01-01

39

Breakdown voltage measurements in alkali-metal-seeded rare gases at elevated temperatures and atmospheric pressure  

Microsoft Academic Search

The results of breakdown voltage measurements in various rare-gas - alkali-metal mixtures at atmospheric pressure and elevated temperature are given, the diluent gases being helium, neon and argon, and the seed metals, caesium, potassium and sodium. The breakdown voltage is shown to increase linearly as the electrode spacing rises from 1 to 15 mm, and to show little systematic variation

H. I. Ellington

1968-01-01

40

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

NASA Astrophysics Data System (ADS)

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

Kondo, Takeshi

41

Harmonic measurements: current and voltage transducers  

Microsoft Academic Search

An overview of the development of special current and voltage transducers at the National Research Council of Canada for accurate measurements of harmonics in power systems will be presented. The transducers include two-stage and electronically-aided instrument transformers, openable-core AC and AC\\/DC current transformers, multi-stage clamp-on current transformers, and current-comparator-based current and voltage transducers.

Eddy So

2003-01-01

42

Florida Current Volume Transports from Voltage Measurements  

Microsoft Academic Search

The volume transport of the Florida Current is determined from the motionally induced voltage difference between Florida and Grand Bahama Island. Simultaneous measurements of potential differences and of volume transport by velocity profiling have a correlation of 0.97. the calibration factor is 25 ± 0.7 sverdrups per volt, and the root-mean-square discrepancy is 0.7 sverdrup. The induced voltage is about

Jimmy C. Larsen; Thomas B. Sanford

1985-01-01

43

Florida Current volume transports from voltage measurements  

Microsoft Academic Search

The volume transport of the Florida Current is determined from the motionally induced voltage difference between Florida and Grand Bahama Island. Simultaneous measurements of potential differences and of volume transport by velocity profiling have a correlation of 0.97. The calibration factor is 25 +\\/- 0.7 sverdrups per volt, and the root-mean square discrepancy is 0.7 sverdrup. The induced voltage is

J. C. Larsen; T. B. Sanford

1985-01-01

44

Measurement of secondary ionization coefficient of CaO film electrode  

NASA Astrophysics Data System (ADS)

The secondary ionization coefficient ? of a CaO film electrode is investigated taking into account the difference in breakdown voltage obtained by repeated voltage applications. Such measurement is performed under a sinusoidal voltage of 0.5 Hz. If the CaO film electrode acts as the cathode, breakdown voltage gradually decreases and converges to an almost constant value after several breakdowns. From the obtained results, the ? of the CaO film electrode is determined for each breakdown using Townsend's criterion. The ? in the first breakdown is lower than those in subsequent breakdowns, particularly in the steady state. The difference in ? is considered to originate from accumulated charges on the CaO film electrode. Contribution to the Topical Issue "13th International Symposium on High Pressure Low Temperature Plasma Chemistry (Hakone XIII)", Edited by Nicolas Gherardi, Henryca Danuta Stryczewska and Yvan Ségui.

Suzuki, Susumu; Kashiwagi, Yasuhide; Itoh, Haruo

2013-02-01

45

Influence of High Voltage Needle Electrode Material on Hydrogen Peroxide Formation and Electrode Erosion in a Hybrid Gas–Liquid Series Electrical Discharge Reactor  

Microsoft Academic Search

Formation rates of hydrogen peroxide and electrode erosion rates for a range of different electrode materials were determined\\u000a in a gas–liquid pulsed electrical discharge reactor with a high voltage electrode needle in the liquid and a ground electrode\\u000a suspended in the gas over the liquid. It was found that the H2O2 formation rates and efficiencies did not depend on the

Frank Holzer; Bruce R. Locke

2008-01-01

46

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

NASA Astrophysics Data System (ADS)

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

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

2009-07-01

47

Instrument for Measuring True-RMS AC Voltage and AC Voltage Fluctuations.  

National Technical Information Service (NTIS)

This invention relates to devices for measuring fluctuations in alternating current voltage, and more particularly to instruments for measuring true-RMS line voltages, frequency and percent regulation in connection with measurements required in the testin...

J. L. Silbergerg

1980-01-01

48

Comparison of three current sources for single-electrode capacitance measurement  

NASA Astrophysics Data System (ADS)

The capacitance of a single electrode is usually measured by injecting a current to the electrode and measuring the resultant voltage on the electrode. In this case, a voltage-controlled current source with a high bandwidth is needed because the impedance is inversely proportional to the excitation frequency. In this design note, three different current sources are discussed: (1) the Howland current source, (2) a modified Howland current source, and (3) a dual op-amp current source. The principle and dynamic performances are presented and compared. Simulation and experimental results show that although the Howland current source has the lowest (i.e., worst) output impedance, its output is the most stable among the three current sources when the frequency changes. Therefore, it is suitable for single-electrode capacitance measurement. Initial tests have proven the feasibility of single-electrode capacitance sensor with the Howland current source.

Chen, D. X.; Deng, X.; Yang, W. Q.

2010-03-01

49

Loss measurement in high voltage thyristor valves  

SciTech Connect

No measuring method is presently available for direct and sufficiently accurate evaluation of power losses in thyristor valves used in HVDC converter stations and Static VAR controllers. This paper presents a measuring method to be used during the valve type tests with the intention to verify the guaranteed loss characteristic. The method was validated under laboratory conditions by comparison to a sophisticated calorimetric technique. An uncertainty of 1% was achieved at conditions simulating full load operation. Voltage across and current through the valve are recorded in discrete steps and digitized. The loss is then calculated as their product. Special current and voltage sensors were developed to cover a very high dynamic range of the measured quantities. A high resolution, multichannel digital recorder was used for simultaneous registration of two voltage and two current signals. The method is of a general application, since the valve is treated as a two port circuit. Therefore, it can be used to measure loss in other non-linear components and apparatus, where large dynamic changes of the measured quantities preclude application of conventional techniques.

Cepek, M.; Douville, J.; Fecteau, G. (Hydro-Quebec Research Inst., Montreal, Quebec (Canada)); Malewski, R.

1994-07-01

50

Harmonic measurements: current and voltage transducers  

Microsoft Academic Search

Summary form only given. At the National Research Council of Canada, special current and voltage transducers have been developed to accurately measure harmonics in power systems. An overview of the development of these special transducers with a wide dynamic and frequency range of operation are presented. The transducers include two-stage and electronically-aided instrument transformers, openable-core AC and AC\\/DC current transformers,

Eddy So

1999-01-01

51

Retarding field analyzer for ion energy distribution measurements at a radio-frequency biased electrode  

SciTech Connect

A retarding field energy analyzer designed to measure ion energy distributions impacting a radio-frequency biased electrode in a plasma discharge is examined. The analyzer is compact so that the need for differential pumping is avoided. The analyzer is designed to sit on the electrode surface, in place of the substrate, and the signal cables are fed out through the reactor side port. This prevents the need for modifications to the rf electrode--as is normally the case for analyzers built into such electrodes. The capabilities of the analyzer are demonstrated through experiments with various electrode bias conditions in an inductively coupled plasma reactor. The electrode is initially grounded and the measured distributions are validated with the Langmuir probe measurements of the plasma potential. Ion energy distributions are then given for various rf bias voltage levels, discharge pressures, rf bias frequencies - 500 kHz to 30 MHz, and rf bias waveforms - sinusoidal, square, and dual frequency.

Gahan, D.; Hopkins, M. B. [National Centre for Plasma Science and Technology, Dublin City University, Glasnevin, Dublin 9 (Ireland); Dolinaj, B. [Impedans Ltd., Invent Centre, Dublin City University, Glasnevin, Dublin 9 (Ireland)

2008-03-15

52

Retarding field analyzer for ion energy distribution measurements at a radio-frequency biased electrode.  

PubMed

A retarding field energy analyzer designed to measure ion energy distributions impacting a radio-frequency biased electrode in a plasma discharge is examined. The analyzer is compact so that the need for differential pumping is avoided. The analyzer is designed to sit on the electrode surface, in place of the substrate, and the signal cables are fed out through the reactor side port. This prevents the need for modifications to the rf electrode--as is normally the case for analyzers built into such electrodes. The capabilities of the analyzer are demonstrated through experiments with various electrode bias conditions in an inductively coupled plasma reactor. The electrode is initially grounded and the measured distributions are validated with the Langmuir probe measurements of the plasma potential. Ion energy distributions are then given for various rf bias voltage levels, discharge pressures, rf bias frequencies--500 kHz to 30 MHz, and rf bias waveforms--sinusoidal, square, and dual frequency. PMID:18377005

Gahan, D; Dolinaj, B; Hopkins, M B

2008-03-01

53

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

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

54

Non-contact bias voltage measurement using the electro-optic probing technique  

NASA Astrophysics Data System (ADS)

The traditional non-contact electro-optic (EO) probing technique is further extended to measure quasi-dc bias voltages. We propose a special external LiTaO3 probe equipped with a grounded side-electrode (GSE) and a power supply modulation (PSM) method. The GSE can improve the voltage measurement sensitivity and error due to the tip position variation. The PSM can make all bias voltages chopped and readily picked up by using a high sensitivity lock-in amplifier. Test results on model circuits demonstrated that the proposed new EO probing system can obtain voltage measurement results that are in good agreement with known values. With this extension function this new system can perform ac high frequency and dc bias voltage measurements as well.

Kuo, Wen-Kai; Kuo, Jen-Yu; Wu, Chien-Jang; Juang, Fuh-Shyang

2008-08-01

55

The Effect of the Earthed Electrode Size on the Ignition Voltage of Low-Pressure RF Capacitive Discharge in Argon  

NASA Astrophysics Data System (ADS)

The effect of the grounded electrode diameter on the ignition voltage using 13.56 MHz in argon gas is studied experimentally. The results indicate a systematic decrease of the breakdown voltage with increasing electrode area for the same pd value. No multi-valued breakdown voltages are observed. The Paschen minimum is not affected by the electrode diameter as long as the parallel plane approximation is valid. A modified Paschen equation which takes into account indirect discharge via the chamber walls at high pd values gives reasonable fits to the experimental data.

A. Azooz, A.; A. Ahmad, M.

2013-09-01

56

High-voltage plasma generators of alternating current with rod electrodes stationary operating on oxidizing media  

Microsoft Academic Search

The stationary plasma generators of alternating current with rod electrodes and power from 5 kW up to 50 kW have been developed in IEE RAS.The generators are used in plasmachemical installations intended for various practical applications including waste destruction and processing with synthesis-gas production.These are single-phase and three-phase high-voltage lasma generators, which prime property is ability to work on oxidizing

Ph. G. Rutberg; I. I. Kumkova; V. E. Kuznetsov; S. D. Popov; A. Ph. Rutberg; A. A. Safronov; V. N. Shiryaev; A. V. Surov

2007-01-01

57

High-Voltage Plasma Generators of Alternating Current with Rod Electrodes Stationary Operating on Oxidizing Media  

Microsoft Academic Search

Summary form only given. The stationary plasma generators of alternating current with rod electrodes and power from 5 kW up to 50 kW have been developed in IEE RAS. The generators are used in plasmachemical installations intended for various practical applications including waste destruction and processing with synthesis-gas production. These are single-phase and three-phase high-voltage plasma generators, which prime property

P. G. Rutberg; I. I. Kumkova; V. E. Kuznetsov; S. D. Popov; A. P. Rutberg; A. A. Safronov; V. N. Shiryaev; A. V. Surov

2007-01-01

58

Electronic circuit for measuring series connected electrochemical cell voltages  

DOEpatents

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

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

2000-01-01

59

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

60

Electrode polarization in dielectric measurements: a review  

NASA Astrophysics Data System (ADS)

In this review, we present an overview of the state of the art concerning the fundamental properties of electrode polarization (EP) of interest in the measurement of high conductivity samples and its implications for both dielectric (DS) and impedance spectroscopy (IS). Initially a detailed description of what constitutes EP is provided and the problems that it induces. Then, we review some of the more popular models that have been used to describe the physical phenomena behind the formation of the ionic double layer. Following this we shall enumerate the common strategies used historically to correct its influence on the measured signals in DS or in IS. Finally we also review recent attempts to employ fractal electrodes to bypass the effects of EP and to offer some physical explanation as to the limitations of their use.

Ben Ishai, Paul; Talary, Mark S.; Caduff, Andreas; Levy, Evgeniya; Feldman, Yuri

2013-10-01

61

Spark gap electrode erosion  

NASA Astrophysics Data System (ADS)

The results of a one-year contract on electrode erosion phenomena are summarized. The arc voltage drop in a spark gap was measured for various electrode, gas, and pressure combinations. A previously developed model of self breakdown voltage distribution was extended. A jet model for electrode erosion was proposed and an experimental arrangement for testing the model was constructed. The effects of inhomogeneities and impurities in the electrodes were investigated. Some of the work described here is scheduled for completion in 1985 under a current grant (AFOSR 84-0032). The areas of investigation described here include: (1) Self breakdown voltage distributions; (2) Electrode erosion; (3) Spark gap voltage recovery.

Krompholz, H.; Kristiansen, M.

1984-12-01

62

First-principles Simulation of Electrochemical Systems at Fixed Applied Voltage: Vibrational Stark Effect for CO on Platinum Electrodes  

Microsoft Academic Search

Chemisorbed molecules at a fuel-cell electrode are a very sensitive probe of the surrounding electrochemical environment, and one that can be accurately monitored with different spectroscopic techniques. We calculate from first principles the dependence of vibrational frequencies as a function of the electrode voltage (the vibrational Stark effect) for chemisorbed CO molecules, finding excellent agreement with electrochemical spectroscopic experiments and

Ismaila Dabo; Eric Cances; Yanli Li; Nicola Marzari

2010-01-01

63

Can undersea voltage measurements detect tsunamis?  

NASA Astrophysics Data System (ADS)

The movement of electrically conducting ocean water in the ambient geomagnetic field induces secondary electric and magnetic fields in the oceans. Ocean water transport is now routinely inferred from undersea cable voltage data. We try to answer the question whether the method could also be useful to detect tsunami. A barotropic shallow water model along with a three-dimensional electromagnetic induction code was used to predict the electric fields induced by the Indian Ocean Tsunami occurred on December 26, 2004. We show that the ocean flow related to the Indian Ocean Tsunami must have induced electric voltages of the order of ±500 mV across the existing submarine cables in the Indian Ocean. The electric fields induced by the Tsunami flow have strength within the range of ±10 mV/km, with enhancements along the main flow region and near the coasts and islands. Thus, making use of the in-service or retired submarine cables to measure the electric potential across oceans, it may be possible to detect water movement related to tsunami.

Manoj, C.; Kuvshinov, A.; Neetu, S.; Harinarayana, T.

2010-03-01

64

The electrode system in impedance-based ventilation measurement  

Microsoft Academic Search

The authors determined which electrode types, sizes, and locations were best suited for impedance-based ventilation measurement. They compared 14 electrodes from two main groups: adhesive-gel and conductive rubber electrodes. Adhesive-gel electrodes were easy to apply, made good body contact, and did not slip during the course of the experiment. Higher signal-to-motion artifact ratios (SARs) were obtained when electrode area was

Shen Luo; Valtino X. Afonso; John G. Webster; Willis J. Tompkins

1992-01-01

65

Phasor measurement application for power system voltage stability monitoring  

Microsoft Academic Search

Monitoring voltage stability is an important task for ensuring secure operation of electrical power networks. In this paper, a phasor measurement based voltage stability monitoring scheme is proposed. By using phasor measurement units and transformer tap position changes, voltage stability indices can be computed at load supply points in the operational time scale. Because this scheme is only based on

Le Fu; Bikash C. Pal; Brian J. Cory

2008-01-01

66

Wall-shaped electrodes for reducing the operation voltage of polymer-stabilized blue phase liquid crystal displays  

NASA Astrophysics Data System (ADS)

Polymer-stabilized blue phase liquid crystal displays based on the Kerr effect are emerging due to their submillisecond response time, wide view and simple fabrication process. However, the conventional in-plane switching device exhibits a relatively high operating voltage because the electric fields are restricted in the vicinity of the electrode surface. To overcome this technical barrier, we propose a partitioned wall-shaped electrode configuration so that the induced birefringence is uniform between electrodes throughout the entire cell gap. Consequently, the operating voltage is reduced by ~ 2.8× with two transistors. The responsible physical mechanisms are explained.

Kim, Miyoung; Kim, Min Su; Kang, Byeong Gyun; Kim, Mi-Kyung; Yoon, Sukin; Lee, Seung Hee; Ge, Zhibing; Rao, Linghui; Gauza, Sebastian; Wu, Shin-Tson

2009-12-01

67

Performance measurements of advanced AMTEC electrodes  

NASA Astrophysics Data System (ADS)

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. .

Schuller, Michael; Fiebig, Brad; Hudson, Patricia; Kakwan, Imran

2000-01-01

68

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

69

High precision voltage ratio measurements using digital voltmeters and resistive voltage divider  

Microsoft Academic Search

This paper presents a method to accurately measure voltage ratios from 1:2 to 1:10 with a calibrated digital voltmeter at voltage ranges of 1V and 10V using a simple resistive voltage divider. The divider can be used as an absolute divider or as a Hamon divider. The achieved accuracy is better than 10-7, comparable to those reported with measurements with

Roman MalariC; I. Lenicek; K. Malaric

2004-01-01

70

Voltage ratio measurements using two digital voltmeters and resistive voltage divider  

Microsoft Academic Search

This paper presents a method to accurately measure voltage ratios from 1:2 to 1:10 with a calibrated digital voltmeter (DVM) at voltage ranges of 1-10 V using a simple resistive-voltage divider. The divider can be used as an absolute divider or as a Hamon divider. The achieved accuracy is better than 10-7, comparable to those reported with measurements with Josephson

Roman Malaric; Ivan Lenicek; Kresimir Malaric

2006-01-01

71

A high voltage source with digital control for dielectric measurements  

Microsoft Academic Search

An improvement in the rigorous control of high voltages for dielectric measurements is achieved by employing digital techniques in the development of a low-voltage controller for a generator of either the oscillator or electrostatic type. Principal advantages over a method previously described are the provision of a highly stable hold mode and the capability for very slow rates of voltage

A. R. Reichert; G. M. Rhodes; J. E. Brignell

1972-01-01

72

In situ measurements of electron-beam-induced surface voltage of highly resistive materials  

NASA Astrophysics Data System (ADS)

This study presents the development, calibration, characterization, and use of new instrumentation for in situ measurements of electron-beam-induced surface voltage. The instrument capabilities allow for measurements of a full range of insulating materials that are of concern to NASA spacecraft charging experts. These measurements are made using moveable capacitive sensor electrodes that can be swept across the sample using an in vacu stepper motor. Testing has shown a voltage range of more than ±30 kV with a low-voltage resolution of 0.2 V. The movable sensors allow for a radial measurement of surface voltage with spatial resolution as low as 1.5 mm. The instrumentation has response time of ˜7 s from the time the beam is shut off until the probe is in position to take data and uses computer automation to stabilize the system and acquire data over the period of several days or longer. Three types of measurements have been made on two prototypical polymeric spacecraft materials, Low-density Polyethylene (LDPE) and polyimide (Kapton™ HN), to illustrate the research capabilities of the new system. Surface voltage measurements were made periodically during the charging process using a pulsed electron beam and subsequently as the surface voltage discharged to a grounded substrate; these were used to obtain information about the material's electron yields and bulk resistivity. The spatial profile of the voltage across the sample surface was also measured by sweeping the electrode across the surface. Subsequent measurements monitored the time evolution of the magnitude and spatial charge distribution as charge dispersed radially across the sample surface. The results of these measurements are present and compared to literature values validating the instrument's effectiveness.

Hodges, Joshua

73

Two types of potassium currents seen in isolated Necturus enterocytes with the single-electrode voltage-clamp technique.  

PubMed Central

1. The ionic permeability of Necturus maculosus small intestine epithelial cells was investigated using intracellular microelectrodes to measure membrane potential in intact tissue or by the single-electrode voltage-clamp technique in isolated cells. 2. The basolateral membrane of enterocytes appears to be K+ selective as demonstrated by the dependence of membrane potential and fractional serosal resistance measured in the intact epithelium on serosal K+ concentration. 3. Isolated cells had membrane potentials similar to those measured in the intact tissue. Voltage-clamp experiments in a physiological Ringer solution showed the presence of both large outward and inward currents. 4. Removal of Cl- from the bathing medium, linear subtraction or the use of a Cl- channel blocker revealed outwardly rectifying currents. The quasi-linear component was also revealed following K+ channel inhibition; it reversed near ECl, suggesting that the charge carrier was Cl-. 5. Outwardly rectifying currents could be kinetically resolved into two components. A fast component (tau for activation < 4 ms) accounted for 60-80% of the total current at positive potentials. A slowly activating component appeared at voltages positive to 50 mV with tau for activation of > 25 ms. 6. The slow outward current showed strong voltage dependence of both activation and relaxation, which were faster at more depolarized potentials. 7. Both fast and slow outward currents seem to be carried by K+ as they were blocked by Ba2+ and tetraethylammonium (TEA). Tail current analysis of the slow component indicated a reversal potential very similar to EK. 8. Fast outward currents were half-activated at about -40 mV whereas slow outward currents were only apparent at more positive potentials. It is proposed that the fast outward K+ current plays a role, together with Cl- currents, in determining the resting membrane potential of Necturus enterocytes.

Valverde, M A; Sheppard, D N; Giraldez, F; Sepulveda, F V

1991-01-01

74

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

75

Small onset voltages in negative corona discharges using the edges of gold and aluminum foils as nano-structured electrodes  

NASA Astrophysics Data System (ADS)

Gold and aluminum foils with nano-structured edges were investigated as electrodes for corona discharges in nitrogen and ambient air. Low onset voltages were observed due to the field enhancement near the edges of the foil. The lowest onset voltage was determined to be about 1.2 kV in ambient air and about 1.1 kV in nitrogen for a 5 mm inter-electrode spacing. This is significantly smaller than the values reported in the literature for sharp tips with similar electrode spacing. The foil-based electrode tips are extremely simple to produce, making them candidates for low-cost, low power consumption and easily available corona-discharge technology.

Eifert, A.; Baier, T.; Hardt, S.

2013-07-01

76

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

77

High voltage automotive EMC component measurements using an artificial network  

Microsoft Academic Search

This paper investigates the adaptation of the standard 12V automotive conducted emissions component EMC measurement method, as defined in CISPR 25, to the ever increasing high voltage automotive components seen in hybrid electric, fuel cell, and the alike vehicles. Due to significantly higher voltages and currents and variations in shielding strategies, conventional automotive measurement methods do not always produce vehicle

Jody J. Nelson; William Goodwin; Mark Steffka; William Ivan; Markus Kopp

2007-01-01

78

Characterization of textile electrodes and conductors using standardized measurement setups.  

PubMed

Textile electrodes and conductors are being developed and used in different monitoring scenarios, such as ECG or bioimpedance spectroscopy measurements. Compared to standard materials, conductive textile materials offer improved wearing comfort and enable long-term measurements. Unfortunately, the development and investigation of such materials often suffers from the non-reproducibility of the test scenarios. For example, the materials are generally tested on human skin which is difficult since the properties of human skin differ for each person and can change within hours. This study presents two test setups which offer reproducible measurement procedures for the systematic analysis of textile electrodes and conductors. The electrode test setup was designed with a special skin dummy which allows investigation of not only the electrical properties of textile electrodes but also the contact behavior between electrode and skin. Using both test setups, eight textile electrodes and five textile conductors were analyzed and compared. PMID:20086274

Beckmann, L; Neuhaus, C; Medrano, G; Jungbecker, N; Walter, M; Gries, T; Leonhardt, S

2010-01-20

79

Measuring Helical FCG Voltage with an Electric Field Antenna  

SciTech Connect

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

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

2011-08-01

80

Membrane voltage, resistance, and channel switching in isolated mouse fibroblasts (L cells): a patch-electrode analysis.  

PubMed Central

The whole-cell patch-electrode technique of Fenwick, Marty & Neher (1982) has been applied to single suspension-cultured mouse fibroblasts. Seals in the range of 10-50 G omega were obtained without special cleaning of the cell membranes. Rupture of the membrane patch inside the electrode was accompanied by a shift of measured potential into the range -10 to -25 mV, but in most cases with little change in the recorded resistance. The latter fact implied that the absolute resistance of the cell membrane must be in the same range as the seal resistance and the recorded potential is a poor measure of actual cell membrane potential. Steady-state current-voltage curves (range -160 mV to +80 mV) were generated before and after rupture of the membrane patch, and the difference between these gave (zero-current) membrane potentials of -50 to -75 mV, which represents a leak-corrected estimate of the true cell-membrane potential. The associated slope conductivity of the cell membrane was 5-15 microS/cm2 (assumed smooth-sphere geometry, cells 13-15 microns in diameter) and was K+-dominated. With 0.1 mM (or more) free Ca2+ filling the patch electrode, membrane potentials in the range -60 to -85 mV were observed following patch rupture, with associated slope conductivities of 200-400 microS/cm2, also K+-dominated. Similar voltages and conductivities were observed at the peak of pulse-induced 'hyperpolarizing activation' (Nelson, Peacock, & Minna, 1972), and the two phenomena probably reflect the behaviour of Ca2+-activated K+ channels. Both the pulse-induced conductance and the Ca2+-activated conductance spontaneously decayed, the latter over periods of 5-15 min following patch rupture. Sr2+, Ba2+, and Co2+ could also activate the putative K+ channels, but only Sr2+ really mimicked Ca2+. Co2+ and Ba2+ activated with a delay of several minutes following patch rupture, and deactivated quickly with a small decrease of conductance and a large decrease of membrane potential. Evidently, Co2+ and Ba2+ affect channel specificity as well as channel opening and closing kinetics.

Hosoi, S; Slayman, C L

1985-01-01

81

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

82

Power system voltage stability assessment employing phasor measurement units  

Microsoft Academic Search

Employing Phasor Measurement Units in wide area monitoring and control of power systems and the availability of phase angles, a new look at the voltage stability indices is performed in this paper. A systematic approach for comparing these indices is presented, where the behavior of different indices to a step load change, for studying long term voltage stability, is compared.

H. Mesgarnejad; S. M. Shahrtash

2010-01-01

83

Measurement errors in multifrequency bioelectrical impedance analyzers with and without impedance electrode mismatch.  

PubMed

The purpose of this study is to compare measurement errors in two commercially available multi-frequency bioimpedance analyzers, a Xitron 4000B and an ImpediMed SFB7, including electrode impedance mismatch. The comparison was made using resistive electrical models and in ten human volunteers. We used three different electrical models simulating three different body segments: the right-side, leg and thorax. In the electrical models, we tested the effect of the capacitive coupling of the patient to ground and the skin-electrode impedance mismatch. Results showed that both sets of equipment are optimized for right-side measurements and for moderate skin-electrode impedance mismatch. In right-side measurements with mismatch electrode, 4000B is more accurate than SFB7. When an electrode impedance mismatch was simulated, errors increased in both bioimpedance analyzers and the effect of the mismatch in the voltage detection leads was greater than that in current injection leads. For segments with lower impedance as the leg and thorax, SFB7 is more accurate than 4000B and also shows less dependence on electrode mismatch. In both devices, impedance measurements were not significantly affected (p > 0.05) by the capacitive coupling to ground. PMID:19491458

Bogónez-Franco, P; Nescolarde, L; Bragós, R; Rosell-Ferrer, J; Yandiola, I

2009-06-03

84

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

DOEpatents

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

Horenstein, Mark N. (West Roxbury, MA)

2008-06-10

85

Real time measurement of transients and electrode edge effects for plasma charging induced damage  

Microsoft Academic Search

Plasma charging behavior is monitored in-situ by a newly developed wafer charging probe. Both charging voltage measurements and damage studies show that more charging is evident near the electrode edge even without the presence of any magnetic fields. Moreover, plasma charging is seen to consist of both transient and steady state components. Both plasma turn-on and turn-off can cause short

Shawming Ma; J. P. McVittie

1994-01-01

86

[Applicability of the two-compartment coaxial cylindrical model for ambulatory measuring of cardiac output with spot-electrodes].  

PubMed

The principle of ambulatory cardiac output (CO) measuring technique is introduced in this paper. Experimental studies about the applicability of the two-compartment coaxial cylindrical model for ambulatory measurement of cardiac output with spot-electrodes have been carried out with using our newly-developed multi-channel impedance mapping system. The key factors using a spot-electrode array instead of a conventional band-electrode array for non-invasive CO) measurement are elaborated. The variations of the electric impedance pulsatile component (deltaZ waveform) and the two kinds of typical modes of deltaZ distributions measured by six electrodes on the midsternal (midian) line from the medial portion at the level of clavicle to the portion above the xiphisternum are discussed. The applicability of the two-compartment coaxial cylindrical model for ambulatory measurement of CO with spot-electrodes is analyzed. Synthesizing the deltaZ distributions and their typical changing models on the midsternal (midian) line during blood inflowing into aorta is the optimal positions of a pair of spot-electrodes for voltage pick-up at the level of clavicle for the upper electrode and the position at the level of nipple for the lower electrode when spot-electrode is being used to measure non-invasive CO. PMID:24059037

Song, Yilin; Gao, Shumei; Ikrashi, Akira; Yamakoshi, Ken-ichi

2013-08-01

87

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

88

Traveling electric field probed by a fine particle above voltage-modulated strips in a striped electrode device  

SciTech Connect

It is described that the distribution of the horizontal electric field above a striped electrode can be inferred from the trajectory of a single fine particle with known mass and diameter. The striped electrode consists of 100 segmented stainless steel strips, each electrically insulated. A traveling periodic potential profile is produced above the striped electrode by modulating the voltage signals on the strips. When the voltage modulation is on, the fine particle, which is originally levitated in the sheath region above the striped electrode, experiences a periodic oscillation along both the vertical and the horizontal directions because of the periodic electric force arising from the modulation voltages. Tracking the motion of the fine particles, the electric force is obtained from the momentum equation including the gravity and the neutral gas friction. With the particle charge estimated by the vertical oscillation method, the electric field can be derived. The horizontal electric field obtained by this method is in agreement with the result predicted by a collisional particle-in-cell simulation.

Li Yangfang; Jiang Ke; Thomas, H. M.; Morfill, G. E. [Max-Planck-Institute for Extraterrestrial Physics, Garching 85748 (Germany); Zhang Wengui; Ma, J. X. [Department of Modern Physics, CAS Key Laboratory of Basic Plasma Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China)

2010-03-15

89

Flexible electrode belt for EIT using nanofiber web dry electrodes  

Microsoft Academic Search

Efficient connection of multiple electrodes to the body for impedance measurement and voltage monitoring applications is of critical importance to measurement quality and practicality. Electrical impedance tomography (EIT) experiments have generally required a cumbersome procedure to attach the multiple electrodes needed in EIT. Once placed, these electrodes must then maintain good contact with the skin during measurements that may last

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

2012-01-01

90

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

PubMed

Muscle contraction is triggered by the spread of an action potential along the fibre. The ionic current to generate the action potential is conducted through voltage-activated sodium channels, and mutations of these channels are known to cause several human muscle disorders. Mouse models have been created by introducing point mutations into the sodium channel gene. This achievement has created the need for a high-fidelity technique to record sodium currents from intact mouse muscle fibres. We have optimized a two-electrode voltage clamp, using sharp microelectrodes to preserve the myoplasmic contents. The voltage-dependent behaviour of sodium channel activation, inactivation and slow-inactivation were characterized. The voltage range for these gating behaviours was remarkably hyperpolarized, in comparison to studies in artificial expression systems. These results provide normative data for sodium channels natively expressed in mouse muscle and illustrate the need to modify model simulations of muscle excitability to account for the hyperpolarized shift. PMID:21135045

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

2010-12-06

91

LiNiO 2 electrode modified by plasma chemical vapor deposition for higher voltage performance  

Microsoft Academic Search

Surface modification of the electrode improved the performance of the LiNiO2 electrode charged to 4.6V. An amorphous carbon thin film was uniformly deposited on the electrode surface using dc plasma chemical vapor deposition. This surface treatment suppressed electrolyte decomposition during the charge process. When a coin-type cell using this electrode was charged to 4.6V, the charge–discharge efficiency was 84% in

Eishi Endo; Toshikazu Yasuda; Kiyoshi Yamaura; Akinori Kita; Koji Sekai

2001-01-01

92

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

NASA Astrophysics Data System (ADS)

A dc discharge with a hot cathode is subject to current and voltage plasma oscillations, which have deleterious effects on its operation. The oscillations can be inhibited by installing an auxiliary electrode, placed outside of anode. By collecting a modest current through a small opening in anode, we show that the discharge becomes stable, in a certain pressure range. This method of avoiding current oscillations can be used, for example, for high current stabilizers.

Mustafaev, A. S.; Demidov, V. I.; Kaganovich, I.; Adams, S. F.; Koepke, M. E.; Grabovskiy, A.

2012-10-01

93

Dielectrophoretic capture voltage spectrum for measurement of dielectric properties and separation of cancer cells.  

PubMed

In this paper, a new dielectrophoresis (DEP) method based on capture voltage spectrum is proposed for measuring dielectric properties of biological cells. The capture voltage spectrum can be obtained from the balance of dielectrophoretic force and Stokes drag force acting on the cell in a microfluidic device with fluid flow and strip electrodes. The method was demonstrated with the measurement of dielectric properties of human colon cancer cells (HT-29 cells). From the capture voltage spectrum, the real part of Clausius-Mossotti factor of HT-29 cells for different frequencies of applied electric field was obtained. The dielectric properties of cell interior and plasma membrane were then estimated by using single-shell dielectric model. The cell interior permittivity and conductivity were found to be insensitive to changes in the conductivity of the medium in which the cells are suspended, but the measured permittivity and conductivity of cell membrane were found to increase with the increase of medium conductivity. In addition, the measurement of capture voltage spectrum was found to be useful in providing the optimum operating conditions for separating HT-29 cells from other cells (such as red blood cells) using dielectrophoresis. PMID:22662097

Wu, Liqun; Lanry Yung, Lin-Yue; Lim, Kian-Meng

2012-03-01

94

Dielectrophoretic capture voltage spectrum for measurement of dielectric properties and separation of cancer cells  

PubMed Central

In this paper, a new dielectrophoresis (DEP) method based on capture voltage spectrum is proposed for measuring dielectric properties of biological cells. The capture voltage spectrum can be obtained from the balance of dielectrophoretic force and Stokes drag force acting on the cell in a microfluidic device with fluid flow and strip electrodes. The method was demonstrated with the measurement of dielectric properties of human colon cancer cells (HT-29 cells). From the capture voltage spectrum, the real part of Clausius–Mossotti factor of HT-29 cells for different frequencies of applied electric field was obtained. The dielectric properties of cell interior and plasma membrane were then estimated by using single-shell dielectric model. The cell interior permittivity and conductivity were found to be insensitive to changes in the conductivity of the medium in which the cells are suspended, but the measured permittivity and conductivity of cell membrane were found to increase with the increase of medium conductivity. In addition, the measurement of capture voltage spectrum was found to be useful in providing the optimum operating conditions for separating HT-29 cells from other cells (such as red blood cells) using dielectrophoresis.

Wu, Liqun; Lanry Yung, Lin-Yue; Lim, Kian-Meng

2012-01-01

95

Electrochemical impedance measurement of a carbon nanotube probe electrode  

NASA Astrophysics Data System (ADS)

We measured and analyzed the electrochemical impedance of carbon nanotube (CNT) probe electrodes fabricated through the physical separation of insulated CNT bridges. The fabricated CNT electrodes were free-standing CNTs that were completely covered with an insulator, except for their tips. Typical dimensions of the nanoelectrodes were 1-10 nm in CNT diameter, 80-300 nm in insulator diameter, 0.5-4 ?m in exposed CNT length and 1-10 ?m in probe length. The electrochemical impedance at frequencies ranging from 40 Hz to 1 MHz was measured in physiological saline. The measured impedance of the CNT electrode was constant at 32 M? at frequencies below 1 kHz and was inversely proportional to frequency at frequencies above 10 kHz. By means of comparison with the parasitic capacitive impedance of the insulator membrane, we confirmed that the electrode was sufficiently insulated such that the measured constant impedance was given by the exposed CNT tip. Consequently, we can use the CNT electrode for highly localized electrochemical impedance measurements below 1 kHz. Considering an equivalent circuit and the nanoscopic dimensions of the CNT electrode, we demonstrated that the constant impedance was governed by diffusion impedance, whereas the solution resistance, charge-transfer resistance and double-layer capacitance were negligible.

Inaba, Akira; Takei, Yusuke; Kan, Tetsuo; Matsumoto, Kiyoshi; Shimoyama, Isao

2012-12-01

96

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

97

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

2006-12-01

98

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

SciTech Connect

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

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

1997-02-01

99

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

100

A high voltage, constant current stimulator for electrocutaneous stimulation through small electrodes  

Microsoft Academic Search

A high-voltage stimulator has been designed to allow transcutaneous stimulation of tactile fibers of the fingertip. The stimulator's output stage was based upon an improved Howland current pump topology, modified to allow high load impedances and small currents, The compliance voltage of approximately 800 V is achieved using commercially available high-voltage operational amplifiers. The output current accuracy is better than

Christopher J. Poletto; Clayton L. Van Doren

1999-01-01

101

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

NASA Astrophysics Data System (ADS)

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 ?10 nm in amplitude. We also 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.

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

2012-06-01

102

Microfabricated Patch Clamp Electrodes for Improved Ion Channel Protein Measurements  

NASA Astrophysics Data System (ADS)

Ion channels are trans-membrane proteins that underlie many cell functions including hormone and neurotransmitter release, muscle contraction and cell signaling cascades. Ion channel proteins are commonly characterized via the patch clamp method in which an extruded glass tube containing ionic solution, manipulated by an expert technician, is brought into contact with a living cell to record ionic current through the cell membrane. Microfabricated planar patch electrodes, micromolded in the silicone elastomer poly-dimethylsiloxane (PDMS) from microlithographically patterned structures, have been developed that improve on this method. Microfabrication techniques allow arrays of patch electrodes to be fabricated, increasing the throughput of the measurement technique. Planar patch electrodes readily allow the automation of cell sealing, further increasing throughput. Microfabricated electrode arrays may be readily integrated with microfluidic structures to allow fast, in situ solution exchange. Miniaturization of the electrode geometry should increase both the signal to noise and the bandwidth of the measurement. Microfabricated patch electrode arrays have been fabricated and measurements have been taken.

Klemic, James; Klemic, Kathryn; Reed, Mark; Sigworth, Frederick

2002-03-01

103

Measurement Accuracy Maintenance of a High-voltage Measuring System and the Trend of the Latest IEC Standard  

NASA Astrophysics Data System (ADS)

High-voltage measurement is evaluated using a measurement system built combining a voltage divider, a measuring instrument, etc. A measurement system is calibrated as compared with a reference measurement system, and is maintaining accuracy. The IEC standard about high-voltage measurement is going to be revised, and especially the evaluation method of impulse voltage is changed greatly.

Koyama, Hiroshi; Hoshina, Yoshikazu

104

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

PubMed Central

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

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

2011-01-01

105

High-Voltage Oil GAP Tests Using Parallel-Plane Electrodes.  

National Technical Information Service (NTIS)

A paraffinic-base insulating oil, PB, and a naphthenic-base insulating oil, NH, were evaluated using two electrode systems. The uniform field electrodes represented a method to easily test relatively large volumes of oil and showed the paraffinic-base oil...

T. K. Sloat W. J. Carter H. R. Moore

1979-01-01

106

Development of the optical instrument transformer for DC voltage measurement  

NASA Astrophysics Data System (ADS)

The optical instruments based on the Pockels effect for DC voltage measurement show great advantages in comparison with the traditional type voltage transformers, but the development is impeded due to the presence of the space charge and the charge drift effect in DC voltage measurement. In this paper, the author will analyze the reason of the space drift phenomena and the errors to the measurement accuracy. A method using the octagonal LiNbO3 crystal with a polyurethane ring with ?r=3.4 to suppress the space charge is proposed in the paper. A better result of the electrical field distribution is obtained from the simulation with the ANSOFT software. It can improve the measurement accuracy and sensitivity. At the same time, a new method in which the chopped DC voltage applied to the crystal is also introduced. It can suppress the charge drift effectively with the appropriate frequency. We will show the theoretical analysis and simulation result, and can find the new method can provide a better result, the new instruments are to be more stable and accurate.

Zhu, Pingping; Zhang, Guixin

2007-03-01

107

The design of voltage measuring system of TCR  

Microsoft Academic Search

TCR is one type of reactive power compensation equipment which is popular used in power system nowadays. Its precision of compensation affects the quality of electrical energy. As the data source, the data acquisition section's performance will impact the function of control system directly, so as to affect the compensation effect. The paper designs a suit of voltage measuring system

Chen Yang; Zai-lin Piao; Xu-wang Sun; Yang Wang

2010-01-01

108

Comparison of DC Voltage Reference Measuring Systems of HUT and NPL. Euromet Project 495. Comparison of Voltage Measurement at DC Voltages up to 100 kv.  

National Technical Information Service (NTIS)

The work was executed in frameworks EUROMET, project No 495. The purpose of the project was to compare the reference standards and measurement techniques of the participants in the area of high voltages up to 100 kV. The HUT measurements were carried out ...

C. Juri H. Jari P. Jukka

2000-01-01

109

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

SciTech Connect

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

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

2011-06-15

110

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

NASA Astrophysics Data System (ADS)

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

Brito Silva, C. A., Jr.; da Silva, S. J. S.; Leal, J. F. P.; Pinheiro, F. A.; Del Nero, J.

2011-06-01

111

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

SciTech Connect

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

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

2012-05-15

112

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

PubMed

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

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

2012-05-01

113

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

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

114

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

SciTech Connect

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

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

2007-07-27

115

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

PubMed Central

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

Rakowski, R F

1989-01-01

116

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.

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

2012-01-01

117

Measurement of external pressures generated by nerve cuff electrodes  

Microsoft Academic Search

When external pressures are applied to a peripheral nerve, tissue damage can occur via compression and blood flow occlusion, resulting in degeneration and demyelination of axons. Although many types of nerve electrodes have been designed to avoid or minimize this pressure during stimulation of the nerve or recording of its activity, the measurement of the pressure exerted by these cuffs

Frank A. Cuoco; Dominique M. Durand

2000-01-01

118

Measurement of wire electrode temperature in WEDM  

Microsoft Academic Search

Wire temperature is an important parameter in the wire electro-discharge machining (WEDM) process because overheating of the\\u000a wire can cause the wire to break. It is difficult, however, to measure the wire temperature directly under the condition that\\u000a the wire is emerged in water and surrounded by the workpiece. Only mathematical analyses by now have been reported to determine\\u000a such

Fuzhu Han; Gang Cheng; Zhijing Feng; Isago Soichiro

2009-01-01

119

Voltage Versus Magnetic Field Measurements on Nb3Sn Wires  

NASA Astrophysics Data System (ADS)

We measured voltage versus magnetic field (V-H) on commercial Nb3Sn wires. Typically voltage-current (V-I) at constant field is measured to determine the critical current (Ic). Recently, V-H at constant or ramping current is being measured to assess the relative stability of Nb3Sn wires. Our low-noise measurements were made with the same equipment, apparatus, and sample mount as used in Ic measurements. High-performance Nb3Sn wires exhibit flux-jump instabilities at low magnetic fields, and low-noise V-H curves on these wires show indications of flux jumps. Two nominal 0.8 mm diameter Nb3Sn wires were measured: a high-performance wire with an Ic of 750 A at 12 T and a stable wire with an Ic of 150 A at 12 T. V-H measurements also reveal that less stable wires will quench (abrupt and irreversible transition to the normal state) at currents much smaller than Ic at the lower magnetic fields. The measured V-H curves and quench currents of these two wires are contrasted.

Goodrich, L. F.

2006-03-01

120

Low-voltage circuit breaker arcs—simulation and measurements  

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

121

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

2011-03-14

122

Electrode systems for measuring cardiac impedances using optical transmembrane potential sensors and interstitial electrodes-theoretical design  

Microsoft Academic Search

The cardiac electrical substrate is a challenge to direct measurement of its properties. Optical technology together with the capability to fabricate small electrodes at close spacings opens new possibilities. Here, those possibilities are explored from a theoretical viewpoint. It appears that with careful measurements from a well-designed set of electrodes one can obtain structural conductivities, separating intracellular from interstitial values,

Roger C. Barr; Robert Plonsey

2003-01-01

123

Measurement of specific contact resistivity using scanning voltage probes  

NASA Astrophysics Data System (ADS)

Specific contact resistivity measurements have conventionally been heavy in both fabrication and simulation/calculation in order to account for complicated geometries and other effects such as parasitic resistance. We propose a simpler geometry to deliver current and the use of a scanning voltage probe to sense the potential variation along the sample surface, from which the specific contact resistivity can be straightforwardly deduced. We demonstrate an analytical example in the case where both materials are thin films. Experimental data with a scanning Kelvin probe measurement on graphene from the literature corroborate our model calculation.

Wang, Weigang; Beasley, Malcolm R.

2013-04-01

124

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

2013-03-13

125

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

126

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

NASA Astrophysics Data System (ADS)

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

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

2011-06-01

127

Voltage Divider  

NSDL National Science Digital Library

This voltage divider produces an output voltage, Vo, that is proportional to the input voltage, Vs. The output voltage is measured using a voltmeter. The input voltage is the voltage of the voltage source. The constant of proportionality is called the gain of the voltage divider. The value of the gain of the voltage divider is determined by the resistances, R1 and R2, of the two resistors that comprise the voltage divider.

2008-11-24

128

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

129

Decision Tree-Based Online Voltage Security Assessment Using PMU Measurements  

Microsoft Academic Search

Voltage collapse is a critical problem that impacts power system operational security. Timely and accurate assessment of voltage security is necessary to detect post-contingency voltage problems in order to prevent a large scale blackout. This paper presents an online voltage security assessment scheme using synchronized phasor measurements and periodically updated decision trees (DTs). The DTs are first trained offline using

Ruisheng Diao; Kai Sun; Vijay Vittal; Robert J. O'Keefe; Michael R. Richardson; Navin Bhatt; Dwayne Stradford; Sanjoy K. Sarawgi

2009-01-01

130

Frequency response measurements of integrated-optic electrodes  

SciTech Connect

The frequency response of electro-optic waveguides can be determined using a variety of testing methods. In this paper, we compare and contrast three measurement techniques used to test our LiNbO{sub 3} devices for improving packages and electrode designs. Each method is described and accompanied by typical results and the experimental setup. Finally, we summarize the advantages and disadvantages of each method.

Hugenberg, K.F; Sargis, P.D.; McConaghy, C.F.

1994-07-01

131

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

PubMed

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

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

2011-09-27

132

Instantaneous Temperature Measurements using Constant-Voltage Anemometry  

NASA Astrophysics Data System (ADS)

Up to now, cold wires have been operated by constant-current anemometers, with a classic thermal inertia correction based on the mean value of the cold wire time constant [Lemay, Bena"issa & Antonia, Exp. Thermal & Fluid Sci, 2003, 27,133-143] or with a new correction method making use of the instantaneous value of the cold wire thermal lag [Berson, Poignand, Blanc-Benon & Comte-Bellot, Rev. Sci. Instrum. 2010, 81, 015102]. The latter correction method is applied to the constant-voltage anemometer and temperature measurements are presented for the first time with such a device. Two constant-voltage anemometers are used for the instantaneous measurement of temperature fluctuations in unsteady flows. The first one is a new prototype elaborated by Tao Systems Inc. and adapted to fine wires with a resistance between 30 and 100 ohms. It operates a cold wire whose resistance varies with the temperature of the surrounding fluid. The second anemometer is a commercial system by the same company. It operates a hot wire, from which the instantaneous effect of the thermal inertia of the cold wire is determined. Results are presented for two flows: (i) a heated turbulent jet and (ii) an acoustic standing wave inside a resonator where flow reversal occurs.

Comte-Bellot, Genevieve; Berson, Arganthael; Blanc-Benon, Philippe; Jondeau, Emmanuel

2011-11-01

133

Lowering of operational voltage of organic electroluminescent devices by coating indium-tin-oxide electrodes with a thin CuOx layer  

NASA Astrophysics Data System (ADS)

We devised a method of modifying indium-tin-oxide (ITO) electrodes for organic electroluminescent devices. It consists of deposition of a nanometer-thick Cu layer on the ITO electrode and an oxygen plasma treatment. By this modification, the surface of the ITO substrate is covered with a partly oxidized Cu layer (CuOx). The CuOx-coated ITO electrode possesses strong hole-injection ability, which leads to lowered operational voltage and high luminance from the devices consisting of tris(8-quinolinato)aluminum and diamine hole-transport layers. The hole-injection ability of the CuOx-coated ITO electrode is better than that of the ITO electrode modified by conventional methods, such as insertion of a Cu-phthalocyanine buffer layer. Moreover, the CuOx layer is effective to improve the durability of the devices.

Hu, Wenping; Manabe, Kaoru; Furukawa, Takumi; Matsumura, Michio

2002-04-01

134

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

SciTech Connect

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

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

2010-05-10

135

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

136

New approach to electrode kinetic measurements in square-wave voltammetry: amplitude-based quasireversible maximum.  

PubMed

The influence of the potential pulse height of square-wave voltammetry (SWV) (i.e., the SW amplitude) is studied for a variety of quasireversible electrode mechanisms, including a simple solution-phase electrode reaction at a planar or spherical electrode, a solution phase electrode reaction coupled with a reversible follow-up chemical reaction, and a diffusionless surface confined electrode reaction. The electrode kinetics of all the electrode mechanisms depends critically on the SW amplitude, and the quasireversible kinetic region is a function of both frequency-related electrode kinetic parameters and the SW amplitude. Thus, a novel methodology for electrode kinetics measurements is proposed by altering the SW amplitude only, at a fixed frequency of the SW potential modulation, that is, at a constant scan rate of the voltammetric experiment. Electrode kinetic measurements at a constant SW frequency are of exceptional importance especially when complex electrode mechanisms are studied, which depend on several frequency-related kinetic parameters. The electrode kinetic measurements are based on a novel feature termed the "amplitude-based quasireversible maximum", manifested as a parabolic dependence of the amplitude-normalized net SW peak current versus the SW amplitude. The position of the amplitude-based quasireversible maximum depends on the standard rate constant of the electrode reaction, enabling estimation of this important kinetic parameter in a simple and fast procedure. The novel quasireversible maximum is attributed to all studied electrode mechanisms, implying that it is a general feature of most electrode mechanisms under conditions of SWV. PMID:23642036

Mirceski, Valentin; Laborda, Eduardo; Guziejewski, Dariusz; Compton, Richard G

2013-05-23

137

Measurement of low impedances with digital techniques for current and voltage compensation  

Microsoft Academic Search

The introduced measuring system determines low impedances by comparing the current and voltage values of two impedances. The voltages are measured by digital voltage compensators. The currents are determined by compensating the magnetic field of two currents in a magnetic coil. Digital signal synthesis is used for the coherent sources

Raymond Wicht

2000-01-01

138

Antimony electrodes  

Microsoft Academic Search

Antimony electrodes are clinically useful because of their low cost and simple construction; they have no glass to break. There is only a few hundred ohms resistance between an antimony pH electrode and the reference electrode so that the voltage generated can be recorded with simple low-impedance recorders linked to microcomputers. We used antimony pH electrodes with silver-silver chloride electrodes

Antone R. Opekun; J. Lacey Smith; David Y. Graham

1990-01-01

139

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.

140

An assessment of comparaqtive methods for approaching electrode polarization in dielectric permittivity measurements  

SciTech Connect

We examine the validity of three common methods for analysis and correction of the electrode polarization (EP) effect in dielectric spectroscopy measurements of conductive liquid samples. The methods considered are (i) algorithmic treatment by modeling the EP behavior at constant phase angle, (ii) varying the size of the electrode gap, and (iii) polypyrrole (PPyPss) layered electrodes. The latter is a relatively recent innovation suggested to be an efficient solution. We demonstrate that PPyPss coated electrodes do not diminish the effect of EP, and even add relaxation processes of its own. Our conclusion is that these polymer coated electrodes are not suitable for the correction of electrode polarization.

Ben Ishai, Paul [ORNL; Sobol, Z [The Hebrew University of Jerusalem, Jerusalem ISRAEL; Nickels, Jonathan D [ORNL; Agapov, Alexander L [ORNL; Sokolov, Alexei P [ORNL

2012-01-01

141

A high-precision voltage source for EIT  

PubMed Central

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

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

2006-01-01

142

Clarification and measurements of high frequency harmonic resonance by a voltage sourced converter  

Microsoft Academic Search

This work presents the clarification and measurements of a high-order harmonic resonance phenomenon for voltage sourced converters. When a voltage sourced converter is connected to a power system through a cable, there is a possibility that small, high frequency, harmonic voltages due to the converter are magnified by series and parallel resonances. The cause of the high-order harmonic resonance is

Koji Temma; Fujio Ishiguro; Naohiro Toki; Isao Iyoda; John J. Paserba

2005-01-01

143

Clarification and Measurements of High Frequency Harmonic Resonance by a Voltage Sourced Converter  

Microsoft Academic Search

Summary form only given. This paper presents the clarification and measurements of a high-order harmonic resonance phenomenon for voltage sourced converters. When a voltage sourced converter is connected to a power system through a cable, there is a possibility that small, high frequency, harmonic voltages due to the converter are magnified by series and parallel resonances. The cause of the

K. Temma; F. Ishiguro; N. Toki; I. Iyoda; J. Paserba

2006-01-01

144

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

145

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

NASA Astrophysics Data System (ADS)

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

Qiao, Yi; Lai, Jack; Hofeldt, Dave

2009-08-01

146

High-Voltage Pulse Measurement with a Precision Capacitive Voltage Divider  

Microsoft Academic Search

The capacitive voltage divider can be designed to have an accurately known division ratio over a wide range of operating frequencies. A coaxial, guard-ring type geometry is described, and an analysis of possible errors due to geometrical anomalies and temperature variations is given. Due to the particular method of construction used, the division ratio of the divider itself is essentially

M. M. Brady; K. G. Dedrick

1962-01-01

147

Design Aspects of Electrochemical Noise Measurements for Uncoated Metals: Electrode Size and Sampling Rate  

Microsoft Academic Search

Observed and simulated electrochemical noise (EN) from general and localized corrosion on uncoated metals was used to test theoretical concepts regarding the relation of electrode area and corrosion rate to noise. Electrode area influences noise resistance, which emphasized the importance of the choice of electrode area in design of noise measurements. The possibility of obtaining mechanistic information by spectral analysis

P. C. Pistorius

1997-01-01

148

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

149

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

Microsoft Academic Search

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 mum 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

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

2008-01-01

150

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

151

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

NASA Astrophysics Data System (ADS)

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

Sarles, Stephen A.

2013-09-01

152

Silver\\/silver chloride electrodes for measurement of potential difference in human bronchi  

Microsoft Academic Search

BACKGROUNDAn easy and reliable method to measure potential difference (PD) in the lower airways would be of interest in the field of cystic fibrosis. We have developed silver\\/silver chloride (Ag\\/AgCl) electrodes to measure PD in the lower airways.METHODSTo validate this technique the nasal PD measured with Ag\\/AgCl electrodes and with conventional perfused electrodes was compared in 16 patients. The range

Isabelle Fajac; Jacques Lacronique; Alain Lockhart; Josette Dall’Ava-Santucci; Daniel J Dusser

1998-01-01

153

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

Microsoft Academic Search

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

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

2010-01-01

154

Nonlinear inversion of electrode-type resistivity measurements  

SciTech Connect

This paper deals with the inversion of low-frequency electrode-type resistivity measurements for the conductivity distribution in a two-dimensional axisymmetric medium. It is well known that the inversion of such transverse magnetic (TM) measurements is much more nonlinear than that of TE (transverse electric) measurements. The distorted Born iterative method (DBIM) is applied to solve the nonlinear inverse problem. In each iteration of the DBIM, an efficient numerical mode-matching (NMM) method is used as a forward solver. In addition to its efficiency in solving for the predicted data, the NMM method gives a semianalytic expression for the partial derivatives of the Green's function required in the inversion. Several numerical results are presented to demonstrate the applications of the DBIM, and to address several practical issues related to the performance of the nonlinear inversion scheme. Because of the fast forward modeling and semianalytic Green's function available due to the NMM method, the inversion is fast and is practical for the interpretation of measurement data.

Liu, Q.H. (Schlumberger-Doll Research, Ridgefield, CT (United States))

1994-05-01

155

Ionization detector, electrode configuration and single polarity charge detection method  

DOEpatents

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

He, Zhong (Ann Arbor, MI)

1998-01-01

156

Module Four: Measuring Current and Voltage in Series Circuits; Basic Electricity and Electronics Individualized Learning System.  

ERIC Educational Resources Information Center

|The module covers the characteristics of series circuits, how to use the multimeter as an ammeter and voltmeter, and how to make current and voltage measurements in series circuits. This module is divided into three lessons: measuring current in a series circuit, voltage in a series circuit, and using the multimeter as a voltmeter. Each lesson…

Bureau of Naval Personnel, Washington, DC.

157

System for precision ac-dc difference measurements based on a Programmable Josephson Voltage Standard  

Microsoft Academic Search

A system designed for precision measurement of AC-DC difference of thermal voltage converters in terms of a Programmable Josephson Voltage Standard is under development at the National Measurement Institute, Australia (NMIA), in collaboration with the National Institute of Advanced Industrial Science and Technology (AIST), Japan. The agreement between the new system and the calculable thermal converters is presently better than

I. Budovsky; D. Georgakopoulos; T. Hagen

2010-01-01

158

Module Four: Measuring Current and Voltage in Series Circuits; Basic Electricity and Electronics Individualized Learning System.  

ERIC Educational Resources Information Center

The module covers the characteristics of series circuits, how to use the multimeter as an ammeter and voltmeter, and how to make current and voltage measurements in series circuits. This module is divided into three lessons: measuring current in a series circuit, voltage in a series circuit, and using the multimeter as a voltmeter. Each lesson…

Bureau of Naval Personnel, Washington, DC.

159

Features of the measurement of high-frequency ac voltage with electronic voltmeters  

Microsoft Academic Search

The features of the measurement of a high-frequency ac voltage with electronic voltmeters are considered for cases when the\\u000a measured ac voltage is normalized at the input of the electronic-voltmeter probe or at the input of a special connector to\\u000a which the voltmeter probe is connected.

V. V. Krestovskii; G. P. Telitchenko; V. I. Shevtsov

2011-01-01

160

Electrochemical cell and electrode designs for high-temperature/high-pressure kinetic measurements  

SciTech Connect

Many corrosion processes of interest to the nuclear power industry occur in high-temperature/high-pressure aqueous systems. The investigation of the kinetics of the appropriate electrode reactions is a serious experimental challenge, partially because of the high temperatures and pressures and partially because many of these reactions are very rapid, requiring fast relaxation measurements. An electrochemical measuring system is described which is suitable for measurements of the kinetics of fast electrode reactions at temperatures extending to at least 300C and pressures to at least 10 MPa (100 atmospheres). The system includes solution preparation and handling equipment, the electrochemical cell, and several electrode designs. One of the new designs is a coaxial working electrode-counter electrode assembly; this electrode can be used with very fast-rising pulses, and it provides a well defined, repeatedly-polishable working surface. Low-impedance reference electrodes are also described, based on electrode concepts responding to the pH or the redox potential of the test solution. Additionally, a novel, long-life primary reference electrode design is reported, based on a modification of the external, pressure-balanced Ag/AgCl reference electrode.

Nagy, Z.; Yonco, R.M.

1987-05-01

161

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

162

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

PubMed

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

Chidambaram, Nachiappan; Mazzalai, Andrea; Muralt, Paul

2012-08-01

163

Measurement of Direct Current Voltage Causing Electrical Pitting  

NASA Astrophysics Data System (ADS)

It is widely known that electrical pitting occurs when an electrical current is passed through a ball or roller bearing. The authors have investigated critical electrical current density causing electrical pitting and have shown that it occurs in a ball bearing even at an extremely low current. In this paper we present the results of an experiment in which a small ball bearing was supplied with a direct current (DC) voltage to determine the voltage required to induce a current. A film of grease acts as the insulator on an antifriction bearing used, and the thickness of this film is an important consideration and the current must pass through this film. Four types of grease were used on the bearing, which was rotated at various speed during 500 hours. A potential of 1.3V to 1.5V was necessary to induce the flow of current. The results indicate that the voltage supplied by typical dry cell batteries is sufficient to drive a currents through a small bearing, and that the experimental conditions had little effect on the magnitude of the flowing current.

Noguchi, Shoji; Kakinuma, Shin-Nosuke; Kanada, Tohru

164

Dependence of measured ionized calcium on protein concentration as measured by three ion-selective electrodes.  

PubMed

A positive effect of protein on the measurement of ionized calcium in serum by ion-selective electrodes (ISEs) has been previously reported and the present study confirms this finding. Ionized calcium in serum was measured in the presence of increasing protein concentrations induced by venous stasis in 17 healthy volunteer subjects. Ionized calcium was measured using two commercial analysers, a Radiometer ICA2 analyser and a Baker Analyte+2 analyser, and a calcium cell devised by Covington for the calcium reference method (CRM). Both commercial analysers used charged ionophores and the CRM used a neutral carrier ionophore in the selective membrane. A small but significant rise in ionized calcium with increasing protein was measured on all analysers. Substitution of isotonic KCl for saturated KCl in the reference electrode of the CRM resulted in significantly reduced values for ionized calcium in paired serum samples when measured using the isotonic salt bridge. This study supports the premise that the positive effect of protein is related to the salt bridge concentration of the reference electrode rather than the ISE membrane composition. PMID:1642453

McEnroe, E; McKenna, M J; Diamond, D; Covington, A K; Freaney, R

1992-07-01

165

Measurement of the performance of nerve cuff electrodes for recording  

Microsoft Academic Search

New designs of cuff electrodes for the recording of signals from peripheral nerves are typically tested in acute animal experiments\\u000a before long-term evaluation takes place. A reproducible, cost-effective and fast method is presented for evaluating cuff electrodes\\u000a with respect to signal amplitude, noise rejection, and, in some cases, selectivity, as an alternative to acute in vivo experiments.\\u000a Comparisons with a

L. N. S. Andreasen; J. J. Struijk; S. Lawrence

2000-01-01

166

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

NASA Astrophysics Data System (ADS)

Optical DC current and voltage measurement using Faraday or Pockels effect necessitates the compensation of light intensity variation with some methods, because it is possible the intensity variation may give rise to a measuring error. We have proposed a method which suggests superposing AC magnetic field on linearly polarized light or AC electric field on elliptically polarized light and compensating light intensity variation by detecting AC components caused by constant AC magnetic or electric field. Experiments of long term stability for DC current and voltage measurement were carried out by using flint glass for DC current measurement and B12SiO20 (BSO) crystals for DC voltage measurement. An experimental result of DC current measurement where DC current of 1.0 A was passed under AC current of 1 kHz 1.5 Arms showed that the modulation depth without compensation through AC magnetic field varied largely with time because of the temperature rise of the flint glass, but that with compensation through AC magnetic field hardly varied with time and the effectiveness of AC magnetic field superposition was confirmed. The same compensation method was applied to optical DC voltage measurement using Pockels effect. An experimental result of DC voltage measurement where DC voltage of 500 V was applied under AC voltage of 5 kHz 50 Vrms clarified that the time variation of the modulation depth with compensation through AC electric field was small compared with that without compensation through AC electric field.

Higaki, Masaru; Fujii, Kunio; Yamaguchi, Shizuo

1999-05-01

167

Flexible electrode belt for EIT using nanofiber web dry electrodes.  

PubMed

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

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

2012-09-04

168

Transient-boundary voltage method for measurement of equivalent circuit components of rechargeable batteries  

Microsoft Academic Search

A method is presented for measuring the equivalent circuit components of rechargeable batteries. The temporal discharge–rest–charge–rest sequence of a rechargeable battery is described, using the principles of transient circuit analysis, to derive equations for the battery voltage as a function of time during voltage transients and at the boundaries at transitions between transient phases. The equations lead to a new

K. H. Norian

169

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

170

Comparison of non-polarising electrode designs for measuring electrical properties in biogeophysics experiments  

NASA Astrophysics Data System (ADS)

An increasing number of laboratory studies are investigating the link between microbial biogeochemical processes, such as the bioreduction of Fe(III) and sulfate, and geophysical responses. Self Potential (SP) and Induced Polarization (IP) studies both use non-polarisable electrodes to measure these responses. Commonly used electrodes include Ag with AgCl coating, in direct contact with the solution chemistry of the experiment being performed. However, this arrangement can lead to alteration and degradation of the AgCl coating, for example by formation of AgS, resulting in signals from a galvanic response. In this contribution, we directly compare the performance of two alternative electrode arrangements for monitoring SP and IP in laboratory column experiments. The first arrangement uses inexpensive, plastic-bodied, commercially available Ag/AgCl reference electrodes in a KCl gel, offering ease of use. The second arrangement uses miniaturized, laboratory-constructed Pb/PbCl2 “Petiau” electrodes. Petiau electrodes are commonly used in field SP investigations and their dimensions can be tailored for specific laboratory experiment requirements. The performance of these electrodes in aqueous solutions of known conductivity was compared. The measured SP between electrode pairs in the same conductive solution, which should theoretically be zero, was < 2 mV for Petiau electrodes and < 1.2 mV for Ag/AgCl electrodes. However, Petiau electrodes showed greater accuracy and reproducibility when used for conductivity (IP) measurements. The results from the use of both types of electrodes in column experiments with biologically active sediments will be reported.

West, L. J.; Hubbard, C. G.; Morris, K.; Shaw, S.

2009-12-01

171

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

SciTech Connect

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

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

2005-01-01

172

Impact of bipolar electrodes contact on fractionation index measurement.  

PubMed

Signals such as Complex Fractionated Atrial Electrograms (CFAE) are tracked during ablation procedures to locate the arrhythmical substrate regions. Most of CFAE classification tools use fractionation indexes. However, recordings from intracardiac catheter depend on electrode contact quality. This paper investigates the impact of electrode contact area on fractionation indexes. It is assessed through three kinds of arrhythmical activations resulting from a numerical simulation of a small piece of the cardiac tissue. Bipolar electrograms are extracted corresponding to 25 different contact areas and fractionation indexes (Shannon entropy, non linear energy operator and maximum peak ratio) are computed. Results yield that the Shannon entropy offers a good potential discrimination between arrhythmic scenarios and is less sensitive to the electrode contact variation. PMID:24110661

Navoret, Nicolas; Jacquir, Sabir; Laurent, Gabriel; Binczak, Stephane

2013-07-01

173

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

SciTech Connect

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

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

2011-02-07

174

Improved surface EMG electrode for measuring genioglossus muscle activity  

Microsoft Academic Search

Activation of the genioglossus (GG) muscles is necessary to maintain the patency of the upper airway. In the condition of obstructive sleep apnea (OSA) this mechanism fails and the possible role of fatigue in its pathogenesis is still not fully understood. In this paper, a new electrode design for recording the genioglossus surface electromyogram (sEMG) is presented. The new design

Ciara M. O’Connor; Madeleine M. Lowery; Liam S. Doherty; Michael McHugh; Cormac O’Muircheartaigh; John Cullen; Philip Nolan; Walter T. McNicholas; Mark J. O’Malley

2007-01-01

175

Improved surface EMG electrode for measuring genioglossus muscle activity.  

PubMed

Activation of the genioglossus (GG) muscles is necessary to maintain the patency of the upper airway. In the condition of obstructive sleep apnea (OSA) this mechanism fails and the possible role of fatigue in its pathogenesis is still not fully understood. In this paper, a new electrode design for recording the genioglossus surface electromyogram (sEMG) is presented. The new design differs from a widely used GG surface electrode in both electrode configuration (unilateral rather than bilateral) and electrode material (Ag-AgCl rather than stainless steel (SS)). The separate effects of these factors were evaluated during force-varying and fatiguing contractions on normal human subjects and using GG sEMG model simulations. Unilateral sEMG was found to have lower amplitude, lower frequency content and a different rate of change of median frequency during fatiguing contractions. It was shown to overcome several disadvantages posed by the bilateral configuration and be more selective. Ag-AgCl has more favorable impedance characteristics and resulted in greater signal amplitudes. It was concluded that the new design is more suitable for detecting GG sEMG and allows more reliable interpretation of changes in sEMG due to physiological mechanisms, thus providing a new methodology for studying GG function and the role of fatigue in OSA. PMID:17707698

O'Connor, Ciara M; Lowery, Madeleine M; Doherty, Liam S; McHugh, Michael; O'Muircheartaigh, Cormac; Cullen, John; Nolan, Philip; McNicholas, Walter T; O'Malley, Mark J

2007-05-24

176

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

177

Droplet sensing by measuring the capacitance between coplanar electrodes in a digital microfluidic system.  

PubMed

In this paper, we report a novel method of droplet sensing in a two-plate digital microfluidic system (DMS) based on coplanar capacitance measurement. The total capacitance between the two adjacent electrodes on the lower plate depends on the position of the droplet. Both numerical and experimental results show that the capacitance is maximal at the midpoint between two electrodes. The value of maximum capacitance increases with the volume of the droplet. Further, the measured capacitance is a function of the gaps between the electrodes as well as the plates. This new method of droplet sensing adds to the functionality of DMSs by allowing single plate measurement. PMID:22930258

Bhattacharjee, Biddut; Najjaran, Homayoun

2012-11-01

178

Radio Noise Measurements on High Voltage Lines from 2.4 to 345 kV  

Microsoft Academic Search

This paper is based on radio noise measurements made near overhead power lines operating at voltages from 2.4 kV to 345 kV inclusive. Some of the measurements made are discussed and analyzed and used in a radio noise prediction technique for determining the location of communication and electronic sites with respect to high voltage overhead power lines. This paper is

W. E. Pakala; E. R. Taylor; R. T. Harrold

1968-01-01

179

Precision AC–DC Difference Measurement System Based on a Programmable Josephson Voltage Standard  

Microsoft Academic Search

A system designed for precision measurement of ac-dc difference of thermal voltage converters in terms of a pro- grammable Josephson voltage standard is under development at the National Measurement Institute, Australia, in collaboration with the National Institute of Advanced Industrial Science and Technology, Japan. The agreement between the new system and calculable thermal converters is presently better than 0.5 ?V\\/V

Ilya Budovsky; Dimitrios Georgakopoulos; Thomas Hagen; Hitoshi Sasaki; Hirotake Yamamori

2011-01-01

180

A measurement of the gate-emitter voltage waveform of IGBT in a motor driver circuit  

Microsoft Academic Search

A fiber optic isolation system is introduced for the measurement of active gate-emitter voltage waveform of IGBT(Insulated Gate Bipolar Transistor) in a motor driver circuit. The system is designed for this kind of floating measurement which requires large common-mode rejection ratio(CMRR) at high frequency and common-mode slew-rate(dV\\/dt). The required performance is analysed by the convolution of the emitter voltage waveform

A. Nara

1994-01-01

181

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

182

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

183

High Quality Nanogap Electrodes for Electronic Transport Measurements of Single Molecules  

NASA Astrophysics Data System (ADS)

Electromigrated metal electrodes and resulting devices have shown great promise in moving towards the realization of single molecule-based electronic devices holding the potential for a wide range of electronic applications. At present, a major concern is that the electronic behavior of such devices may be greatly influenced by residual nanoscale metal particles. We have developed a computer controlled electromigration (CCE) process for creating nanogaps at room temperature which allows us to characterize a bare nanogap before putting a molecule into the nanogap.^1 This is very different from other approaches used in the field where nanogaps are formed at low temperature with molecules already attached to the nanowire by employing a simple ramp up in voltage. Among the bare nanogaps we produced using CCE, tunneling behavior is observed with no indication of transport signatures associated with metal particle formation. Details of molecular measurements utilizing these clean gaps will be discussed. This work was supported by the National Science Foundation (NIRT Grant No. 0304531 and MRSEC award DMR05-20020). ^1D. R. Strachan, D. E. Smith, D. E. Johnston et al., Appl. Phys. Lett. 86 043109 (2005).

Johnston, Danvers E.; Strachan, Douglas R.; Guiton, Beth S.; Davies, Peter K.; Park, Tae Hong; Therien, Michael J.; Johnson, A. T. Charlie

2007-03-01

184

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

PubMed Central

Changes in liquid composition during gradient elution liquid chromatography (LC) coupled to mass spectrometry (MS) analyses affect the electrospray operation. To establish methodologies for judicious selection of the electrospray voltage, we monitored in real-time the effect of the LC gradient on the spray current. The optimum range of the electrospray voltage decreased as the concentration of organic solvent in the eluent increased during reversed-phase LC analyses. These results provided the means to rationally select the voltage so as to ensure effective electrospray operation throughout gradient-elution LC separations. For analyses in which the electrospray was operated at constant voltage, a small run-to-run variation in the spray current was observed, indicating a changing electric field due to fouling or degradation of the emitter. Algorithms using feedback from spray current measurements to maintain the electrospray voltage within the optimum operating range throughout gradient elution LC-MS were evaluated. The electrospray operation with voltage regulation and at a constant, judiciously selected voltage during gradient elution LC-MS measurements produced data with similar reproducibility. SYNOPSIS Electrospray current measurements during gradient elution liquid chromatography analyses provide reliable feedback for monitoring, understanding, and improving performance.

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

2009-01-01

185

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

186

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

PubMed

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 mus. 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. PMID:17672759

LaBombard, B; Lyons, L

2007-07-01

187

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

188

Effect of a spherical object in 4 electrode Focused Impedance Method (FIM): measurement and simulation  

NASA Astrophysics Data System (ADS)

Focused Impedance Method (FIM) gives enhanced localized sensitivity at the centre of a zone defined by a simple system of electrodes, of which a 4-electrode version with electrodes at the corners of a square region has been studied in detail in the present work. The present work studies the effect of a large sphere whose diameter almost equals the dimensions of the central focused zone, or, the Focused Impedance. The sphere is placed at different positions with respect to the centre of the system at the electrode plane. The study has been made using a phantom in which the electrodes are fixed on a side wall while an insulating ball is hung at various positions inside the saline and moved with respect to the electrodes in their vicinity. The same was then simulated by providing appropriate parameters in COMSOL multiphysics, a software package utilizing Finite Element Method, by providing appropriately matching parameters. The measured impedance decreases as the ball is moved away from the centre in the electrode plane or along the depth. The sensitivity also decreases with an increase in electrode spacing. Although the behaviours were similar in both the studies, simulated values by COMSOL deviated from the measured values significantly. It suggests that COMSOL may not give accurate simulations for large objects.

Abir, R.; Pettersen, F. J.; Martinsen, O. G.; Rabbani, K. S.

2013-04-01

189

Needle Enzyme Electrode for Lactate Measurement In Vivo  

Microsoft Academic Search

Electrochemical lactate needle enzyme electrodes were fabricated based on lactate oxidase with a conventional hydrogen peroxide detection regimen with a linear range up to 7 mM, response time ~ 3 min, and sensitivity ~ 1 nA\\/mM. A negatively charged inner (sulphonated polyether ether sulphone-polyether sulphone) membrane was applied for ensuring selectivity by limiting oxidazible anion diffusion to the Pt working

Zimei Rong; Eugenia Leitao; Jonathan Popplewell; BurÇak Alp; Pankaj Vadgama

2008-01-01

190

Measurement of space-charge distributions in solid insulators under rapidly varying voltage using the high-voltage, high-speed pulsed electro-acoustic (PEA) apparatus  

NASA Astrophysics Data System (ADS)

A new high-voltage, high-speed pulsed electro-acoustic (PEA) apparatus for real-time measurements of space-charge distribution in solid insulators subjected to rapidly varying voltages is described. Very high-rate PEA measurement is accomplished with the use of a high-speed real-time data acquisition module known as the `Eclipse' unit and a purpose-built high-voltage FET switch pulse generator. Real-time space-charge measurements with good phase resolving capability can be made under time varying applied stresses, e.g. voltage transients or ac conditions. The high-field PEA system has been used to investigate the space-charge dynamics in polyethylene samples stressed by 0.2 and 50 Hz sinusoidal ac voltages.

See, A.; Fothergill, J. C.; Dissado, L. A.; Alison, J. M.

2001-08-01

191

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

SciTech Connect

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

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

2009-04-01

192

Analysis of high voltage TDDB measurements on Ta2O5 \\/SiO2 stack  

Microsoft Academic Search

Time-dependent dielectric breakdown measurements on a SiO2 \\/Ta2O5 (1.4\\/6 nm) stack are analyzed. After comparing current\\/voltage-curves, statistical distribution and time-to-breakdown values of this stack with SiO2-layers, it is concluded that the high voltage breakdown of the stack is completely determined by the interfacial SiO2-layer. Simple extrapolation of the time-to-breakdown to low voltages will yield incorrect reliability predictions

R. Degraeve; B. Kaczer; M. Houssa; G. Groeseneken; M. Heyns; J. S. Jeon; A. Halliyal

1999-01-01

193

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

194

A new method for measuring the Faradic resistance of a single electrode-electrolyte interface.  

PubMed

A new method is described for measuring the Faradic resistance of a single electrode-electrolyte interface. The method employs a test (monopolar) electrode, a potential-sensing electrode and a large reference (indifferent) electrode, along with a constant-current source capable of providing a step function of current. The method was used to measure the Faradic resistance of a 0.1 cm2 platinum electrode in contact with saline (p = 150 ohm-cm) at room temperature. It was found that for both a positive and negative current pulse, the Faradic resistance decreased almost hyperbolically with increasing current density. When the reciprocal of the Faradic resistance (Gf) was plotted versus current density and the data were fit to a polynomial curve, the results showed that for the positive pulse Gf = 0.009 + 0.05J - 0.0001J2; (SEE = 0.117); for the negative pulse, Gf = 0.007 + 0.067J - 0.0001J2; (SEE = 0.028); where Gf is in millisiemens and J is in mA/cm2 for this 0.1 cm2 electrode. These relationships permit estimating the Faradic resistance (Rf) for zero current density. For the positive pulse, Rf = 111 kilohms and for the negative pulse Rf = 143 kilohms. The method is applicable to the measurement of the Faradic resistance of a wide variety of metal electrodes. PMID:1575647

Mayer, S; Geddes, L A; Bourland, J D; Ogborn, L

1992-03-01

195

Factors Affecting the Open-Circuit Voltage and Electrode Kinetics of Some Iron/Titanium Redox Flow Cells.  

National Technical Information Service (NTIS)

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/cm exp 2 . Open-circuit and load v...

M. A. Reid R. F. Gahn

1977-01-01

196

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

197

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

198

Adverse effects of near current-electrode placement in non-invasive bio-impedance measurements.  

PubMed

A major problem confronting application of impedance techniques to studies of disease is the extraction of intrinsic properties of the tissue from the measured impedances, which unavoidably involve geometric factors as well. Amongst the foremost are the sizes and locations of the measuring electrode arrays, and this paper addresses one of these, the location of current injecting electrodes. Tetrapolar impedance measurements on a 17.5 cm segment of the thigh gave R and X values three to four times larger when the current injecting electrodes were placed 2.5 cm from the sensing electrodes than when very distant placement was used. The frequency dependences of R and X were affected as well, though the X versus R plots still showed virtually perfect depressed-center semicircles, as in the Cole model. R(f) and X(f) for the set of contiguous 2.5 cm wide sub-segments show that these behaviors can be explained by a combination of the transverse orientation of current flow lines near the injecting electrodes and the anisotropy of the resistivity associated with the bundled fiber structure of muscle tissue. The measured impedance was found to be a separable function of geometric and intrinsic tissue variables, but far more complicated than is implicit in the usual cylindrical models. The results also suggest that many full and segmental body composition studies in the literature may be prone to substantial errors due to too close placement of the current injecting electrodes. PMID:24149840

Shiffman, C A

2013-10-22

199

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

NASA Astrophysics Data System (ADS)

For pulmonary applications of EIT systems, the electrodes are placed around the chest in a 2D ring, and the images are reconstructed based on the assumptions that the object is rigid and the measured resistivity change in EIT images is only caused by the actual resistivity change of tissue. Structural changes are rarely considered. Previous studies have shown that structural changes which result in tissue/organ and electrode position change tend to introduce artifacts to EIT images of the thorax. Since EIT reconstruction is an ill-posed inverse problem, any inaccurate assumptions of object may cause large artifacts in reconstructed images. Accurate information on structure/electrode position changes is necessary to understand factors contributing to the measured resistivity changes and to improve EIT reconstruction algorithm. In this study, in vivo structure/electrode position changes from a healthy male volunteer are investigated during respiration cycle at two levels, the nipple line level and the level approximately 5 cm below. For each level, sixteen fiduciary markers are equally spaced around the surface, the same as the electrode placement for EIT measurements. A MR scanner with respiration-gated ability is used to acquire images of the thorax. MR thoracic images are prospectively acquired corresponding temporally to specific time periods within respiration cycle (FRC, mid tidal volume, tidal volume). The chest expansions in anterior-posterior and lateral directions and inside tissue/organ position changes are then analyzed. The electrode position changes corresponding to different phases of respiration cycle are also measured.

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

2010-04-01

200

Measurements of electric and magnetic stray fields produced by various electrodes of 27-MHz diathermy equipment  

NASA Astrophysics Data System (ADS)

The present paper describes the results of measurements of electric and magnetic stray fields around three types of commercially available diathermy units with four very typical electrodes in six routine therapeutic treatments. The aim of the survey was to investigate the exposure to the physiotherapist and the exposure to unprescribed tissues. Field strengths were measured at 15 points close to the patient's body. At a distance of 0.6 m from the diathermy units the power density was less than 10 W/m2. With respect to stray fields the results showed that the diathermy devices are very similar but there are great differences between the electrodes during specific treatments. The results assist in selecting proper electrodes for various therapeutic treatments, as they indicate which electrodes would have minimal stray fields.

Kalliomaki, P. L.; Hietanen, M.; Kalliomaki, K.; Koistinen, O.; Valtonen, E.

201

Influence of measurement noise and electrode mislocalisation on EEG dipole-source localisation  

Microsoft Academic Search

Measurement noise in the electro-encephalogram (EEG) and inaccurate formation about the locations of the EEG electrodes on\\u000a the head induce localisation errors in the results of EEG dipole source analysis. These errors are studied by performing dipole\\u000a source localisation for simulated electrode potentials in a spherical head model, for a range of different dipole locations\\u000a and for two different numbers

G. Van Hoey; B. Vanrumste; M. D'Havé; R. Van de Walle; I. Lemahieu; P. Boon

2000-01-01

202

In situ conductance measurement to investigate roles of conductive additives in lithium ion battery electrodes  

Microsoft Academic Search

Electrical dc conductance of a composite electrode for a lithium-ion battery was monitored in situ during successive charge\\/discharge cycles, in order to investigate functions of conductive additives. Such measurement was achieved by means of an interdigitated microarray electrode with a bipotentiostat. The composite films of mesocarbon microbeads (MCMBs) heat-treated at 1000°C were studied with conductive additives of acetylene black or

Matsuhiko Nishizawa; Hiromichi Koshika; Takashi Itoh; Mohamed Mohamedi; Takayuki Abe; Isamu Uchida

1999-01-01

203

Optical Micro-current Transducer for the Measurement of Corona Discharge Current Under High Voltage Environment  

Microsoft Academic Search

Measuring corona discharge current directly on the high voltage side is essential for the discharge mechanism research of test object. The corona discharge is so weak that the amplitude of the current is in the level of muA and its frequency ranges from DC to MHz. An optical micro-current transducer used for the measurement of this current is described in

Peng Wang; Guixin Zhang; Jun Zhou; Chen Gu

2007-01-01

204

A New Modeling of Inductive Sensors for Current Measuring at High Voltage  

Microsoft Academic Search

Inductive sensors are used in electric equipment like current measuring insulators and metal detectors. Modeling of these sensors will raise their accuracy and consequently will lead to developing of high precision current measuring devices. The idea of expressing the voltage induced in the sensor in terms of current passing through the line and geometrical parameters is the goal of this

HASHEM ORAEE MIRZAMANI; AZIM LOTFJOU CHOOBARI; Mohammad Hadi Varahram

205

Spark protection circuit for measuring current in high-voltage circuits  

Microsoft Academic Search

A circuit has been designed to protect electrometers and other sensitive instrumentation from damage by electrical sparks. Measuring current is necessary in a variety of high-voltage applications, including the evaluation of ionizers designed to eliminate static charge. The currents are often small, perhaps only several microamperes (?A) or less. Instruments designed to accurately measure such small currents are expensive and

Kelly S. Robinson; John J. Coleman

2005-01-01

206

Electrochemical measurements for marine atmospheric corrosion studies using Kelvin probe reference electrode  

NASA Astrophysics Data System (ADS)

A Kelvin probe was used as reference in this study on electrochemical measurements of a simulated marine atmospheric corrosion system (electrode covered by a very thin electrolyte layer). The experimental setups for improved measurements proved satisfactory for the conventional steady—state electrochemical measurements in atmospheric studies.

Wang, Jia

1996-09-01

207

Measurement of water concentration in oil\\/water dispersions by a single-electrode capacitance probe  

Microsoft Academic Search

A- - A new measurement mghod called SeCaP, has been used to measure the water content in OiVwater dispersions The measuring principle is based on an oscillator working at approximately 20 MHG The dielectric property of the medium adjacent to one single free electrode affects the frequency of the oscillator. The dispersion was produced by means of recirculation through a

R. B. Schuller; B. Engebretsen; M. Halleraker

2003-01-01

208

Low-voltage pulsed plasma discharges inside water using a bubble self-generating parallel plate electrode with a porous ceramic  

NASA Astrophysics Data System (ADS)

Characteristics of pulsed bubbles discharges in water were investigated using parallel punched plate electrodes with a porous thin ceramic plate inserted between two metal plates. The micro-bubbles were generated just beneath the porous ceramic plate by flowing gas through it. The transition from spiky dielectric barrier discharges to pulsed glow discharges enables efficient bubble discharges at a relatively low voltage of 1.8 ~ 4.0 kV of the 5 kHz square-waves with a pulse-width of about 750 ns. With 80% Ar and 20% O2 mixture gas at 4.0 kV, the 50 mg/l Indigo Carmine aqueous solution was efficiently decolorized within about 3 min.

Muradia, Sonia; Nagatsu, Masaaki

2013-04-01

209

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

DOEpatents

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

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

1992-11-24

210

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

DOEpatents

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

Kikta, Thomas J. (Pittsburgh, PA); Mitchell, Ronald D. (Pittsburgh, PA)

1992-01-01

211

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

Microsoft Academic Search

Traditional impedance cardiography (ICG) technique uses band electrodes both for delivering current to and measuring impedance change in the thorax. The use of spot electrodes increases the ease of electrode placement and comfort level for patients. Research has shown that changes in thoracic impedance can have multiple causes. In this study, we used finite element modeling to investigate the sources

Yanqun Wang; David R. Haynor; Yongmin Kim

2001-01-01

212

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

PubMed

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

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

2007-04-01

213

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

NASA Astrophysics Data System (ADS)

This article evaluates the potential of capacitive measurements using flexible electrodes to access various physical quantities. These electrodes are made of a thin metallic film, typical thickness 0.2 ?m, evaporated on a plastic substrate. Their large flexibility enables them to be mounted in complex geometries such as curved surfaces. In the configuration of planar condensers, using a very sensitive commercial capacitive bridge and a three-terminal measurement method, several measurements are presented. A relative resolution of 10-8 for the thermal expansion of samples is obtained at low temperature in a differential configuration. The same technique adopted for pressure gauge measurements at low temperature led to a typical 0.1 Pa resolution over a dynamic range of 104 Pa. In the configuration of interleaved electrodes, condensers have been used to measure wetting by either bulk liquid helium or by thin continuous helium films in a cylindrical pipe. Both experimental and numerical evidence is provided, showing that the close proximity of a reference ground potential significantly increases the relative sensitivity to fluid wetting. Further, interleaved electrodes can be used to access both the area that is covered by a liquid film but also to determine the thickness of this film, provided it is comparable to the periodicity of the electrode pattern.

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

2007-04-01

214

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

215

Spectroscopic measurements with a silicon drift detector having a continuous implanted drift cathode-voltage divider  

NASA Astrophysics Data System (ADS)

A silicon drift detector (SDD) prototype where the drift electrode also plays the role of a high-voltage divider has been realised and characterised for spectroscopic applications at near-room temperatures. Among the advantages of this design, is the absence of metal on the sensitive surface which makes this detector interesting for soft X-rays. The detector prototype has a large sensitive area (2×130mm2) and the charge is collected by two anodes (butterfly-like detector). The energy resolution of a such a detector has been investigated at near-room temperatures using a commercial, hybrid, low-noise charge-sensitive preamplifier. The results obtained for the X-ray lines from 55Fe and 241Am are presented.

Bonvicini, V.; Burger, P.; D'Acunto, L.; Franck, D.; Gregorio, A.; Pihet, P.; Rashevsky, A.; Vacchi, A.; Vinogradov, L.; Zampa, N.

2000-01-01

216

Measurements of electrical conductivity of ceramics under electron irradiation in a high voltage electron microscope  

Microsoft Academic Search

A specimen holder for in-situ measurements of electrical conductivity in a high voltage electron microscope (HVEM) was developed. The performance of newly developed holder was checked by measuring the temperature dependence of the electrical conductivity in ZrO23mol%Y2O3 (YSZ) and the radiation induced conductivity was subsequently measured in YSZ, ?-Al2O3 and MgAl2O4 during irradiation with 1 MeV electrons. The electrical conductivity

Kenichi Shiiyama; Tadahiro Izu; Chiken Kinoshita; Masanori Kutsuwada

1996-01-01

217

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

SciTech Connect

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

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

2012-01-01

218

Measurements of body composition in limbs and trunk using a eight contact electrodes impedancemeter  

Microsoft Academic Search

Regional body composition measurements may be achieved in a single operation with impedancemeters equipped with four plantar and four hand electrodes. By measuring sequentially the resistances of five current lines connecting the hands and feet and solving a system of five linear equations, it is possible to calculate the resistances of each limb and the trunk. The impedancemeter used in

Michel Y. Jaffrin; Hélène Morel

2009-01-01

219

A High-Resolution Prototype System for Automatic Measurement of Standard Cell Voltage  

Microsoft Academic Search

The conceptual requirements, the design, and the initial performance of the prototype switching for connecting standard cells to an automatic measurement system are described. Features of the design include random selection of two cells at a time, inversion of connection polarity on command, modular construction for expansion, and less than 10-nV residual uncompensated error voltage. Also described briefly are controllers

David W. Braudaway; Robert E. Kleimann

1974-01-01

220

Measurement of magnetic fields in an outdoor high voltage power substation  

Microsoft Academic Search

Human exposure to magnetic fields generated by distribution substations and power lines is one of the growing health concerns that has drawn much attention from Qatar General Electricity & Water Corporation (also called Kahramaa) and Qatar ministry of environment. This paper presents the results of magnetic field measurements in an outdoor high voltage 132\\/66kV power substation, located in the residential

Khaled Ellithy; Abdulaziz Al Shafai; Fahad Al Assiry

2009-01-01

221

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

Microsoft Academic Search

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

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

1999-01-01

222

Bidirectional electrowetting actuation with voltage polarity dependence  

NASA Astrophysics Data System (ADS)

This work presents an electrowetting system in which the actuation direction depends on the polarity of the applied voltage. Since electrowetting response depends on the voltage squared, it is typically independent of voltage sign to first order. However, the introduction of an electrochemical diode into the equivalent electrical circuit permits polarity-dependent behavior. Electrochemical diodes were created by making holes in the dielectric. The aluminum electrodes passivate and prevent current flow in one direction, creating diodelike electrical behavior with high breakdown voltage. The resulting actuation forces were directly measured and are of comparable magnitude for both actuation directions.

Crane, Nathan B.; Volinsky, Alex A.; Mishra, Pradeep; Rajgadkar, Ajay; Khodayari, Mehdi

2010-03-01

223

Surface potential determination in irradiated MOS transistors combining current-voltage and charge pumping measurements  

SciTech Connect

A method combining charge pumping and current-voltage measurements is presented for determining the surface potential versus gate voltage relationship in irradiated MOS transistors. This technique uses parameter optimization and simple numerical equations. It can be applied even for a high interface state density and for a non-uniform distribution in the silicon bandgap. This makes the method attractive for all studies concerning interface trap characterization or accurate modeling of MOS transistors in subthreshold regime. In this study, this new approach is applied to n-channel transistors irradiated up to 10 Mrad (SiO{sub 2}).

Masson, P. [INSA de Lyon, Villeurbanne (France)]|[ENSERG, Grenoble (France); Autran, J.L.; Raynaud, C. [INSA de Lyon, Villeurbanne (France); Flament, O.; Paillet, P. [CEA Centre d`Etudes, Bruyeres-le-Chatel (France); Chabrerie, C. [Thomson CSF Communications, Colombes (France)

1998-06-01

224

Textile electrode straps for wrist-to-ankle bioimpedance measurements for Body Composition Analysis. Initial validation & experimental results  

Microsoft Academic Search

Electrical Bioimpedance (EBI) is one of the non-invasive monitoring technologies that could benefit from the emerging textile based measurement systems. If reliable and reproducible EBI measurements could be done with textile electrodes, that would facilitate the utilization of EBI-based personalized healthcare monitoring applications. In this work the performance of a custom-made dry-textile electrode prototype is tested. Four-electrodes ankle-to-wrist EBI measurements

J. C. Marquez; J. Ferreira; F. Seoane; R. Buendia; K. Lindecrantz

2010-01-01

225

A Very Simple Low Noise Voltage Preamplifier For High Sensitivity Noise Measurements  

NASA Astrophysics Data System (ADS)

An ultra low noise voltage preamplifier is presented that, while characterized by excellent noise performances, is based on a very simple topology. Indeed, the choice has been made of maintaining the component count to a minimum and of avoiding, by design, that any trimming or calibration step be required. This was done in order to make the realization of this piece of instrumentation as simple as possible for any researcher interested in noise measurements. The amplifier is AC coupled with a low corner frequency below 100 mHz and a useful bandwidth in the order of a few kHz. The voltage gain is 80 dB and the equivalent input voltage noise is 14, 1.4 and less than 1 nV/Hz at 100 mHz, 1 Hz and for f>10 Hz, respectively.

Cannatà, G.; Scandurra, G.; Ciofi, C.

2009-04-01

226

Firing and sustaining discharge characteristics in alternate current micro-discharge cell with three electrodes  

Microsoft Academic Search

In this paper, the firing and sustaining characteristics in the AC micro-discharge cell with three electrodes are examined based on the variations in the distances among the three electrodes. In particular, the firing and sustaining voltages are measured as a parameter of the width of the discharge gap among the three electrodes. In addition, the difference between the firing and

Hyun Kim; Heung-Sik Tae

2003-01-01

227

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

PubMed Central

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

Goldman, Y; Morad, M

1977-01-01

228

Measurement of Sparkover Voltage and Time Lag Characteristics in SF6-N2 Gas Mixtures by using Steep-front Square Voltage  

NASA Astrophysics Data System (ADS)

A square pulse voltage is useful for studying electrical discharge physics and/or very fast transient overvoltage issues. This paper describes sparkover voltages and time lag (V-t) characteristics of SF6-N2 gas mixtures in a very short time range below a microsecond, which are measured by using a steep-front square voltage with a rise time of 16 nanoseconds and a peak value of 200 kilovolts. SF6-N2 gas mixture, which contains nitrogen gas at a ratio of 60 % or less, has equivalent dielectric strength to pure SF6 gas even in the short time range around 10 nanoseconds. Sparkover voltage and time lag characteristics are evaluated by using the equal area criterion even in the short time range below a microsecond.

Toyota, Hiroyuki; Matsuoka, Shigeyasu; Hidaka, Kunihiko

229

Electrode size dependence of piezoelectric response of lead zirconate titanate thin films measured by double beam laser interferometry  

NASA Astrophysics Data System (ADS)

The electrode size dependence of the effective large signal piezoelectric response coefficient (d33,f) of lead zirconate titanate (PZT) thin films is investigated by using double beam laser interferometer measurements and finite element modeling. The experimentally observed electrode size dependence is shown to arise from a contribution from the substrate. The intrinsic PZT contribution to d33,f is independent of electrode size and is equal to the theoretical value derived assuming a rigid substrate. The substrate contribution is strongly dependent on the relative size of the electrode with respect to the substrate thickness. For electrode sizes larger than the substrate thickness, the substrate contribution is positive and for electrode sizes smaller than the substrate thickness, the substrate contribution is negative. In the case of silicon substrates, if the electrode size is equal to the substrate thickness, the substrate contribution vanishes, and the measured value of d33,f is equal to the theoretical value under the rigid substrate assumption.

Sivaramakrishnan, S.; Mardilovich, P.; Mason, A.; Roelofs, A.; Schmitz-Kempen, T.; Tiedke, S.

2013-09-01

230

Evaluation of the catalytic performance of gas-evolving electrodes using local electrochemical noise measurements.  

PubMed

Characterization of gas evolution reactions at the electrode/electrolyte boundary is often difficult due to the dynamic behavior of interfacial processes. Electrochemical noise measurements determined by scanning electrochemical microscopy were used to characterize Cl(2) evolution at gas-evolving electrodes (GEEs). Analysis of the electrochemical noise is a powerful method to evaluate the efficiency of the catalyst layer at a GEE. The high sensitivity of the developed measurement system enabled accurate monitoring of the current fluctuations caused by gas-bubble detachment from the electrode surface. Fourier transform analysis of the obtained current responses allows extraction of the characteristic frequency, which is the main parameter of the macrokinetics of GEEs. The characteristic frequency was used as part of a methodology to evaluate the catalyst performance and, in particular, to estimate the fraction of the catalyst layer that is active during the gas evolution reaction. PMID:23001744

Zeradjanin, Aleksandar R; Ventosa, Edgar; Bondarenko, Alexander S; Schuhmann, Wolfgang

2012-09-23

231

Measurement and research of channel noise distributed characterization in low voltage networks  

Microsoft Academic Search

In this paper, measurement and research of noise characterizations in three-phase four-wire low voltage power network channels are carried out. The power networks have overhead conductor structures. Measurement frequency is from 1 kHz to 1 MHz. The studies include noise classification and load characterizations, noise distribution characterization along the power lines and noise distribution characterization when coupling across different phases.

Yang Xiaoxian; Zheng Tao; Zhang Baohui

2005-01-01

232

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

PubMed Central

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

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

1998-01-01

233

Measurements of 1/f noise in Josephson junctions at zero voltage: Implications for decoherence in superconducting quantum bits  

NASA Astrophysics Data System (ADS)

Critical current fluctuations with a 1/f spectral density (f is frequency) are potentially a limiting source of intrinsic decoherence in superconducting quantum bits (qubits) based on Josephson tunnel junctions. Prior measurements of this noise were made at nonzero voltages whereas qubits are operated in the zero voltage state. We report measurements of 1/f noise in a dc superconducting quantum interference device first, coupled to a resonant tank circuit and operated in a dispersive mode at zero voltage, and, second, operated conventionally with a current bias in the voltage regime. Both measurements yield essentially the same magnitude of critical current 1/f noise.

Mück, Michael; Korn, Matthias; Mugford, C. G. A.; Kycia, J. B.; Clarke, John

2005-01-01

234

A mostly-digital analog scan-out chain for low bandwidth voltage measurement for analog IP test  

Microsoft Academic Search

A method of precise measurement of on-chip analog voltages in a mostly-digital manner, with minimal overhead, is presented. A pair of clock signals is routed to the node of an analog voltage. This analog voltage controls the delay between this pair of clock signals, which is then measured in an all-digital manner using the technique of sub-sampling. This sub-sampling technique,

Rajath Vasudevamurthy; Pratap Kumar Das; Bharadwaj Amrutur

2011-01-01

235

High-speed measurement of free spectral range voltage of tunable filters.  

PubMed

A new technique to measure the frequency response of a fiber-optic tunable filter (TF) is proposed and demonstrated. This technique is based on the linearity of the sinusoidal function in the vicinity of mpi, where m is an integer. The free spectral range (FSR) voltage, V(FSR), is evaluated fast and accurately by measuring the time interval corresponding to the bandwidth of TF. The time interval is obtained by adjusting the dc offset of the driving signal to locate the transmission peak of TF at the maximum slope of the driving signal of <1V(p-p). The measured FSR voltages range from 500 mV to 100 V over the frequency up to 200 kHz. PMID:19109637

Yeh, Yunhae; Park, DoHyun; Park, Se Hoon

2009-01-01

236

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

Microsoft Academic Search

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

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

2007-01-01

237

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

Microsoft Academic Search

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

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

2000-01-01

238

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

Microsoft Academic Search

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

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

1998-01-01

239

Measurement of the Electrical Conductivity and Dielectric Constant without Contacting Electrodes  

Microsoft Academic Search

A method is developed whereby electrical conductivity and dielectric constant of semiconducting and dielectric materials without contacting electrodes can be measured. The principle of this method is that a specimen suspended in a rotating field with a fine fiber is rotated by the torque proportional to the electrical conductivity or the imaginary part of its complex dielectric constant, and the

Tomoya Ogawa

1961-01-01

240

Determination of electrode kinetics by corrosion potential measurements: Zinc corrosion by bromine  

Microsoft Academic Search

An attractive way of determining the electrode kinetics of very fast dissolution reactions is that of measuring the corrosion potential in flowing solutions. This study analyses a critical aspect of the corrosion potential method, i.e., the effect of nonuniform corrosion distribution, which is very common in flow systems. The analysis is then applied to experimental data for zinc dissolution by

S. L. Chiu; J. R. Selman

1992-01-01

241

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

242

Design of surface electrode array for measuring conduction velocity in the human genioglossus muscle.  

PubMed

A new appliance, incorporating linear arrays of pin electrodes for genioglossus (GG) surface electromyography measurement, is presented. This design enables the estimation of GG muscle fiber conduction velocity, which decreases with fatigue. The performance of the device was evaluated for ten healthy human subjects during fatiguing and force varying contractions. PMID:17278591

O'Connor, Ciara M; van der Merwe, Lize; der van Merwe, Lize; Langran, Simon; O'Sullivan, Michael; Nolan, Philip; Vaughan, Christopher L; O'Malley, Mark J

2007-02-01

243

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

Microsoft Academic Search

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

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

2010-01-01

244

An investigation of breakdown voltage in AMTECs  

NASA Astrophysics Data System (ADS)

Experiments are conducted to investigate the DC electrical breakdown voltage in cesium vapor between two planner molybdenum electrodes, 1.6 cm in diameter, separated by a 0.5 mm gap, and relate the results to the potential electrical breakdown on the cathode side of Alkali Metal Thermal-to-Electric Converters (AMTECs). In the first set of experiments, in which the electrodes are kept at 560 and 650 K, while varying the cesium pressure from 0.71 to 29 Pa, when the cooler electrode is positively biased, breakdown occurs at ~500 V, but at 700 V when the cooler electrode is negatively biased. In the second set of experiments, in which the electrodes are held at 625 and 1100 K and the cesium pressure varied from 1.7 to 235 Pa, when the cooler electrode is positively biased, breakdown voltage is <4 V, but in excess of 400 V when the cooler electrode is negatively biased. Since the first ionization potential and the ionization rate constant of cesium are lower and higher, respectively, than for the sodium (5.14 V) and potassium (4.34 V) vapors in AMTECs, the DC electrical breakdown voltage in an AMTEC is expected to be higher than measured in this work for cesium vapor. .

Momozaki, Yoichi; El-Genk, Mohamed S.

2002-01-01

245

Detection of bottom ferromagnetic electrode oxidation in magnetic tunnel junctions by magnetometry measurements  

SciTech Connect

Surface oxidation of the bottom ferromagnetic (FM) electrode, one of the major detrimental factors to the performance of a magnetic tunnel junction (MTJ), is difficult to avoid during the fabrication process of the MTJ's tunnel barrier. Since Co rich alloys are commonly used for the FM electrodes in MTJs, overoxidation of the tunnel barrier results in the formation of a CoO antiferromagnetic (AF) interface layer which couples with the bottom FM electrode to form a typical AF/FM exchange bias (EB) system. In this work, surface oxidation of the CoFe and CoFeB bottom electrodes was detected via magnetometry measurements of EB characterizations including the EB field, training effect, uncompensated spin density, and enhanced coercivity. Variations in these parameters were found to be related to the surface oxidation of the bottom electrode, among them the change in coercivity is most sensitive. Annealed samples show evidence for an oxygen migration back to the MgO tunnel barrier by annealing.

Chen Wei [Department of Physics, University of Virginia, Charlottesville, Virginia 22904 (United States); Nam, Dao N. H.; Lu, Jiwei [Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States); Wolf, Stuart A. [Department of Physics, University of Virginia, Charlottesville, Virginia 22904 (United States); Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States)

2010-12-01

246

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

Microsoft Academic Search

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

Hongrae Kim; Thomas M. Jahns

2006-01-01

247

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

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

248

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

2012-02-24

249

Robust adaptive voltage-fed permanent magnet step motor control without current measurements  

Microsoft Academic Search

In this paper, a robust adaptive nonlinear dynamic controller is designed to achieve practical stabilization for position tracking error of a voltage-fed permanent-magnet stepper motor. The control design is an output-feedback design that utilizes only rotor position and velocity measurements. Currents are not available for feedback. Adaptations are utilized so that no knowledge of motor parameters is required except for

P. Krishnamurthy; F. Khorrami

2003-01-01

250

Time-resolved voltage measurements of imploding radiation sources at 6 MA with a vacuum voltmeter  

Microsoft Academic Search

A vacuum-voltmeter[ 1 ] (VVM) was fielded on the Saturn pulsed-power generator during a series of 12-MA short-circuit, 6-MA aluminum wire-array z-pinch, and 6 MA argon Plasma Radiation Source (PRS) shots. The VVM was connected to the convolute structure in the vacuum chamber above the load. This arrangement permitted the VVM to directly measure the time-resolved voltage between the ground

D. P. Murphy; B. V. Weber; R. J. Commisso; J. P. Apruzese; D. Mosher

2007-01-01

251

Time-Resolved Voltage Measurements of Imploding Radiation Sources with a Vacuum Voltmeter at 6 MA  

Microsoft Academic Search

A vacuum-voltmeter (WM) was fielded on the Saturn pulsed-power generator during a series of 12-MA short-circuit, 6-MA aluminum wire-array z-pinch, and 6-MA argon Plasma Radiation Source (PRS) shots. The WM was mounted inside the conical, magnetically-insulated-transmission-line (MITL) structure, in the vacuum chamber above the load. This arrangement permitted the WM to directly measure the time-resolved voltage between the ground side

D. P. Murphy; B. V. Weber; R. J. Commisso; J. P. Apruzese; D. Mosher

2007-01-01

252

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

253

Measurement of kinetically resolved vesicular dopamine uptake and efflux using rotating disk electrode voltammetry  

Microsoft Academic Search

The vesicular monoamine transporter-2 (VMAT-2) sequesters cytoplasmic dopamine (DA) into vesicles for storage and subsequent release. VMAT-2 activity has traditionally been measured in small synaptic vesicles isolated from rat striatum by monitoring [3H] DA uptake and in cellular expression systems using fast scan cyclic voltammetry. This is the first report using rotating disk electrode (RDE) voltammetry to measure VMAT-2 DA

Trent J. Volz; Glen R. Hanson; Annette E. Fleckenstein

2006-01-01

254

Non-invasive measurement of the input-output properties of peripheral nerve stimulating electrodes  

Microsoft Academic Search

A non-invasive method was developed to determine the input-output (IO) properties of peripheral nerve stimulating electrodes. An apparatus was fabricated to measure the 3-dimensional (3-D) isometric torque generated at the cat ankle joint by electrical activation of the sciatic nerve. The performance of the apparatus was quantified, and the utility of the method was demonstrated by measuring the recruitment properties

Warren M. Grill; J. Thomas Mortimer

1996-01-01

255

Electrode position and size in electrical impedance myography  

Microsoft Academic Search

ObjectiveLinear-electrical impedance myography (EIM) is a non-invasive technique for the evaluation of muscle, in which high-frequency alternating current is injected into the body via two surface electrodes, and the resulting voltage pattern over a selected muscle is measured using a second, larger set of electrodes. The precise location and size of the electrodes can be critical to the data obtained,

Seward B. Rutkove; Ramon A. Partida; Gregory J. Esper; Ronald Aaron; Carl A. Shiffman

2005-01-01

256

The optimization of needle electrode number and placement for irreversible electroporation of hepatocellular carcinoma  

PubMed Central

Background Irreversible electroporation (IRE) is a novel ablation tool that uses brief high-voltage pulses to treat cancer. The efficacy of the therapy depends upon the distribution of the electric field, which in turn depends upon the configuration of electrodes used. Methods We sought to optimize the electrode configuration in terms of the distance between electrodes, the depth of electrode insertion, and the number of electrodes. We employed a 3D Finite Element Model and systematically varied the distance between the electrodes and the depth of electrode insertion, monitoring the lowest voltage sufficient to ablate the tumor, VIRE. We also measured the amount of normal (non-cancerous) tissue ablated. Measurements were performed for two electrodes, three electrodes, and four electrodes. The optimal electrode configuration was determined to be the one with the lowest VIRE, as that minimized damage to normal tissue. Results The optimal electrode configuration to ablate a 2.5 cm spheroidal tumor used two electrodes with a distance of 2 cm between the electrodes and a depth of insertion of 1 cm below the halfway point in the spherical tumor, as measured from the bottom of the electrode. This produced a VIRE of 3700 V. We found that it was generally best to have a small distance between the electrodes and for the center of the electrodes to be inserted at a depth equal to or deeper than the center of the tumor. We also found the distance between electrodes was far more important in influencing the outcome measures when compared with the depth of electrode insertion. Conclusions Overall, the distribution of electric field is highly dependent upon the electrode configuration, but the optimal configuration can be determined using numerical modeling. Our findings can help guide the clinical application of IRE as well as the selection of the best optimization algorithm to use in finding the optimal electrode configuration.

Adeyanju, Oyinlolu O.; Al-Angari, Haitham M.; Sahakian, Alan V.

2012-01-01

257

Electrolyte measurement device and measurement procedure  

DOEpatents

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

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

2010-01-26

258

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

SciTech Connect

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

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

2007-07-15

259

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

NASA Astrophysics Data System (ADS)

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

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

2007-07-01

260

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

Microsoft Academic Search

The aim of this work was to study the dependence of image quality in digital chest and pelvis radiography on tube voltage, and to explore correlations between clinical and physical measures of image quality. The effect on image quality of tube voltage in these two examinations was assessed using two methods. The first method relies on radiologists' observations of images

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

2006-01-01

261

Calculation of Lightning-Induced Voltages with RUSCK's Method in EMTP Part I: Comparison with Measurements and Agrawal's Coupling Model  

Microsoft Academic Search

This paper discusses the computation of lightning-induced voltages on a transmission line with a phase and neutral conductor, using an implementa tion of Rusck's theory in the Electromagnetic Transients Program EMTP. The results obtained are compared with measurements and with equations for the estimation of the maximum induced voltage, for an experimental distribution line subjected to rocket triggered lightning flashes.

J. P. Silva; A. E. A. Araújo; J. O. S. Paulino; H. W. Dommel

262

Simple PVC-PPy electrode for pH measurement and titrations.  

PubMed

Cobaltabis(dicarbollide) [3,3'-Co(1,2-C2B9H11)](-)-doped polypyrrole (PPy) films have been prepared galvanostatically on glassy carbon electrodes in acetonitrile solution. The potential response behavior of the film of this new material has been investigated in some common pH buffers and in acid-base titrations. The potentiometric characteristics of the resulting films are indicative of a quasi-Nernstian response (approximately 50 mV/pH unit), a linearity range from pH 12 to 3 and correlation coefficients (r2) of approximately 0.98. The electrode is suitable for pH measurements and for monoprotic titrations of strong alkalis with strong acids, and weak bases with strong acids, but the long response time hinders the use of this electrode for multiprotic titrations. The time response has been dramatically improved by reducing the film thickness by using the template effect of a non-conducting polymer (PVC) cast over the graphite surface before PPy deposition. PPy polymerization occurs in the free channels of PVC leading to the formation of PPy wires. The morphological change of PPy does not affect the slope or linearity range. The response of the PVC-PPy electrochemical sensor is rapid and the sensor is easy to prepare, at low cost, and its performance is comparable with that of commercial glass electrodes. PMID:11939624

Masalles, C; Borrós, S; Viñas, C; Teixidor, F

2002-01-11

263

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

NASA Astrophysics Data System (ADS)

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

Berger, Cody M.; Henderson, Clifford L.

2004-05-01

264

Modeling the measurements of cellular fluxes in microbioreactor devices using thin enzyme electrodes  

PubMed Central

An analytic approach to the modeling of stop-flow amperometric measurements of cellular metabolism with thin glucose oxidase and lactate oxidase electrodes would provide a mechanistic understanding of the various factors that affect the measured signals. We divide the problem into two parts: (1) analytic formulas that provide the boundary conditions for the substrate and the hydrogen peroxide at the outer surface of the enzyme electrode layers and the electrode current expressed through these boundary conditions, and (2) a simple diffusion problem in the liquid compartment with the provided boundary conditions, which can be solved analytically or numerically, depending on the geometry of the compartment. The current in an amperometric stop-flow measurement of cellular glucose or lactate consumption/excretion is obtained analytically for two geometries, corresponding to devices developed at the Vanderbilt Institute for Integrative Biosystems Research and Education: a multianalyte nanophysiometer with effective one-dimensional diffusion and a multianalyte microphysiometer, for which plentiful data for metabolic changes in cells are available. The data are calibrated and fitted with the obtained time dependences to extract several cellular fluxes. We conclude that the analytical approach is applicable to a wide variety of measurement geometries and flow protocols.

Velkovsky, Momchil; Snider, Rachel; Wikswo, John P.

2013-01-01

265

Measurement of low frequency relative permittivity of room temperature molten salts by triangular waveform voltage  

NASA Astrophysics Data System (ADS)

We present a low-cost experimental method for measuring cell resistance and capacitance independently. In this technique a triangular waveform voltage excitation is adopted. Conductivity calibration is straightforward. However, it is demonstrated that a specific calibration procedure needs to be followed to obtain correct relative permittivity values for highly conductive liquids. It is also required to measure conductivity in order to measure relative permittivity for highly conductive liquids. Using this technique, the relative permittivities of room temperature molten salt 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4) and 1-butyl-3-methylimidazolium tetrafluoroborate (BMImBF4) were measured. To our knowledge, this is the first ever directly measured low frequency relative permittivity value of highly conducting EMImBF4 and BMImBF4.

Wu, Jianping; Stark, John P. W.

2006-04-01

266

Dependence of hydrogen arcjet operation on electrode geometry  

NASA Astrophysics Data System (ADS)

The dependence of 2kW 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 ignition. The dependence of breakdown voltage on mass flow rate and electrode agreed with Paschen curves for hydrogen. Preliminary characterization of the dependence of 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.

1992-07-01

267

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

268

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

Microsoft Academic Search

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

Yoshitsugu Sone; P. Ekdunge; D. Simonsson

1996-01-01

269

Electrical properties of platinum electrodes: Impedance measurements and time-domain analysis  

Microsoft Academic Search

The impedance of small platinum electrodes has been measured as a function of frequency. In the range of 0·1 Hz to 10 kHz,\\u000a this impedance Z can be described accurately as K\\/(i2?f)m. The value of K is about 2·5 M? for a surface are of 0·05 mm2. The values for m are in the order of 0·75. Various step responses

R. W. de Boer; A. van Oosterom

1978-01-01

270

Design of 1-kbit antifuse OTP memory IP using dual program voltage and its measurement  

Microsoft Academic Search

In this paper, we design a l-kbit antifuse OTP (one time programmable) memory IP which is used for power management ICs. A conventional antifuse OTP cell using a single VPP (positive program voltage) has a problem about applying a higher voltage than the breakdown voltage to thin gate oxides and securing the reliability of MV (medium voltage) devices which are

Ji-Hye Jang; Huiling Yang; Liyan Jin; Pan-Bong Ha; Young-Hee Kim

2011-01-01

271

Acetylene - Argon Plasmas Measured at a Biased Substrate Electrode for Diamond-Like Carbon Deposition. Part 2: Ion Energy Distributions  

Microsoft Academic Search

Ion energy distributions have been determined at the rf-bias electrode in an\\u000ainductively-coupled acetylene-argon plasma for various substrate bias voltages\\u000aand frequencies under conditions suitable for film deposition. These are\\u000acompared with those obtained at the grounded wall of a capacitively coupled\\u000aplasma. In the former, for pressures up to 25 mTorr, the IEDs exhibit bimodal\\u000astructures with peak separation

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

2008-01-01

272

Acetylene - Argon Plasmas Measured at a Biased Substrate Electrode for Diamond-Like Carbon Deposition. Part 2: Ion Energy Distributions  

Microsoft Academic Search

Ion energy distributions have been determined at the rf-bias electrode in an inductively-coupled acetylene-argon plasma for various substrate bias voltages and frequencies under conditions suitable for film deposition. These are compared with those obtained at the grounded wall of a capacitively coupled plasma. In the former, for pressures up to 25 mTorr, the IEDs exhibit bimodal structures with peak separation

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

2008-01-01

273

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

PubMed

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

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

1993-04-01

274

Teaching pH Measurements with a Student-Assembled Combination Quinhydrone Electrode  

ERIC Educational Resources Information Center

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

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

2005-01-01

275

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

ERIC Educational Resources Information Center

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

Eggen, Per-Odd; Kvittingen, Lise

2007-01-01

276

Teaching pH Measurements with a Student-Assembled Combination Quinhydrone Electrode  

ERIC Educational Resources Information Center

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

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

2005-01-01

277

Downhole steam quality measurement  

SciTech Connect

A method is described for measuring the quality of steam flowing through a conduit containing a pair of spaced electrodes comprising calibrating the system by: filling the conduit with steam samples of known qualities; applying an AC frequency across the electrodes; measuring the capacitance between the electrodes as a function of frequency for each steam sample; determining a frequency range where measured capacitance is a linear function of steam quality; and injecting an unknown sample of steam into the conduit; applying an alternating voltage at a selected frequency within the frequency range to the electrodes; measuring the capacitance between the electrodes at the selected frequency; and determining steam quality from the capacitance measurement.

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

1987-04-14

278

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

279

High performance cermet electrodes  

DOEpatents

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

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

1986-01-01

280

Adsorptive Stripping Voltammetric Measurements of Trace Uranium at the Bismuth Film Electrode  

SciTech Connect

Bismuth-coated carbon-fiber electrodes have been successfully applied for adsorptive-stripping voltammetric measurements of trace uranium in the presence of cupferron. The new protocol is based on the accumulation of the uranium-cupferron complex at a preplated bismuth film electrode held at –0.30 V (vs. Ag/AgCl), followed by a negatively-sweeping square-wave voltammetric waveform. Factors influencing the stripping performance, including the film preparation, solution pH, cupferron concentration, adsorption potential and time have been optimized. The resulting performance compares well with that observed for analogous measurements at mercury film electrodes. A detection limit of 0.3 ?g/L is obtained in connection to a 10 min adsorption time. The response is linear up to 50 ?g/L and the relative standard deviation at 50 ?g/L uranium is 3.8% (n=10; 2 min adsorption). Potential interferences are examined. Applicability to sea water samples is demonstrated. The attractive behavior of the new “mercury-free” uranium sensor holds great promise for on-site environmental and industrial monitoring of uranium.

Lin, L.; Thongngamdee, Sompong; Wang, Joseph; Lin, Yuehe; Sadik, O. A.; Ly, Suw-Young

2005-04-11

281

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)

1997-04-15

282

Precision Differential Sampling Measurements of Low-Frequency Synthesized Sine Waves With an AC Programmable Josephson Voltage Standard  

Microsoft Academic Search

We have developed a precision technique to measure sine-wave sources with the use of a quantum-accurate AC programmable Josephson voltage standard. This paper describes a differential method that uses an integrating sampling voltmeter to precisely determine the amplitude and phase of high-purity and low-frequency (a few hundred hertz or less) sine-wave voltages. We have performed a variety of measurements to

Alain Rüfenacht; Charles J. Burroughs; Samuel P. Benz; Paul D. Dresselhaus; Bryan C. Waltrip; Thomas L. Nelson

2009-01-01

283

The electrochemical impedance measurements of carbon nanotubes  

Microsoft Academic Search

The two types of carbon nanotube electrodes have been studied as a function of frequency and the open circuit cell voltage. Nyquist plots measured from the closed carbon nanotubes electrodes at different potentials include only one semicircle that is attributed the adsorption phenomenon at the surface only. However, the Nyquist plots measured from the opened carbon nanotubes electrodes at different

Zhan-hong Yang; Hao-qing Wu

2001-01-01

284

Influence of electrode temperature on the metastable atom concentration in an argon-filled diode  

Microsoft Academic Search

The influence of electrode temperature on the time delay of electrical breakdown in an argon-filled (13.3 mbar) diode at electrode temperatures of 300, 523 and 673K has been investigated by measuring the electrical breakdown time delay (td) dependence on both the time interval between two successive measurements ( tau ) ('memory curves') and the applied voltages (Uw). The results obtained

M. M. Pejovic; Dj A. Bosan

1981-01-01

285

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

PubMed Central

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

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

2013-01-01

286

A comparison between two methods for measuring limb resistances with wrist and ankle electrodes.  

PubMed

Segmental measurements of limb resistances permit to evaluate the regional distribution of fat-free-mass (FFM). As shown by Organ et al. (J Appl Physiol 1994;77:98-112) "virtual" limb resistances can be measured with only peripheral electrodes at ankle and wrist, which is faster and does not require undressing. This paper presents a different method for obtaining "virtual" limb resistances from peripheral electrodes and compares it with that of Organ et al. and with segmental measurements using same protocol. It is found that virtual arm resistances of both methods were overestimated as compared to segmental values, by 6.8% in men and 5.8% in women for our method and by 7.4% and 8% for Organ et al. one. Virtual leg resistances were found, for both methods, to be slightly lower than segmental leg resistances measured with proximal waist electrodes, which were a little overestimated. But after correcting this overestimation using Organ et al. data, we evaluated the overestimation of virtual leg resistances to be 2.3% in men and 2.8% in women by our method versus 4.4% and 5.9%, respectively, for Organ et al. one. An important finding was the strong correlation between virtual resistances of both methods and segmental ones, as their ratio had a small standard deviation between 0.019 and 0.024 for arms and legs. Thus, the overestimation of limb resistance is automatically corrected when FFM is determined by an equation calibrated with DXA segmental measurements. PMID:21481627

Jaffrin, Michel Y; Bousbiat, Sana; Dongmo, Edwige

2011-04-09

287

Holographic Method for the Measurement of the Sagitta of a Thin Electrode of a Parallel Plate Counter.  

National Technical Information Service (NTIS)

An holographic method for the measurement of the sagitta of the thin electrode of a position sensitive parallel plate counter is presented. The method is simple but very sensitive (about 1 mu m). (Atomindex citation 19:033428)

C. Guidi R. Bellazzini A. Brez M. M. Massai M. R. Torquati

1986-01-01

288

Reference Electrodes  

NASA Astrophysics Data System (ADS)

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

Kahlert, Heike

289

Construction and in vitro test of a new electrode for dentin resistance measurement.  

PubMed

Abstract It is necessary to reduce the tooth substance before treating a tooth with a dental crown. The preparation often requires reduction of the dentin. This results in a dentin wound and a thinner substance over the pulp, increases the risk of inflammation, and could result in necrosis of the pulp. To give the dentist information about the amount of dentin over the pulp during preparation, the Prepometer was developed. The function of this device is based on the measurement of the electric resistance of the tooth substance. The measuring behavior of the first-generation Prepometer is characterized by smaller values of electric resistance before reaching full contact of the measuring head to the dentin surface and the actual value RT. This measuring behavior can mislead inexperienced therapists with inaccurate values that suggest thinner dentin than the reality. In this study, a new electrode based on the technology of active guard drive was constructed to overcome this issue. The results show that improvement in the measuring behavior of the new electrode could be achieved, eliminating the earlier disadvantage of the Prepometer. PMID:24021589

Stein, Steffen; Gente, Michael

2013-10-01

290

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

PubMed

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

1995-04-01

291

Channel length scaling in graphene field-effect transistors studied with pulsed current-voltage measurements.  

PubMed

We investigate current saturation at short channel lengths in graphene field-effect transistors (GFETs). Saturation is necessary to achieve low-output conductance required for device power gain. Dual-channel pulsed current-voltage measurements are performed to eliminate the significant effects of trapped charge in the gate dielectric, a problem common to all oxide-based dielectric films on graphene. With pulsed measurements, graphene transistors with channel lengths as small as 130 nm achieve output conductance as low as 0.3 mS/?m in saturation. The transconductance of the devices is independent of channel length, consistent with a velocity saturation model of high-field transport. Saturation velocities have a density dependence consistent with diffusive transport limited by optical phonon emission. PMID:21271736

Meric, Inanc; Dean, Cory R; Young, Andrea F; Baklitskaya, Natalia; Tremblay, Noah J; Nuckolls, Colin; Kim, Philip; Shepard, Kenneth L

2011-01-27

292

Impact of self-heating in LF noise measurements with voltage amplifiers  

NASA Astrophysics Data System (ADS)

Voltage Amplifiers have been used to characterize the low-frequency noise of Heterojunction Bipolar Transistors (HBTs). They generally feature not only a lower noise floor, but also have less impact on simultaneous (two-port) measurements than Transimpedance Amplifiers, when moderate to high DC current regimes are considered. However, when the Device Under Test (DUT) is characterized under these regimes, common concepts such as unilateralism and frequency-independent small-signal parameters are no longer valid due to the frequency-dependent thermal response of the DUT (self-heating). It will be shown that depending on the conditions under which the measurements are carried out, the experimental data may vary for some orders of magnitude, leading to an incorrect characterization if the effect is disregarded.

Lisboa de Souza, A. A.; Nallatamby, J.-C.; Prigent, M.; Obregon, J.

2007-07-01

293

Voltammetric Membrane Chlorine Dioxide Electrode.  

National Technical Information Service (NTIS)

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

R. Dormond-Herrera K. H. Mancy

1980-01-01

294

High frequency reference electrode  

DOEpatents

A high frequency reference electrode for electrochemical experiments comprises a mercury-calomel or silver-silver chloride reference electrode with a layer of platinum around it and a layer of a chemically and electrically resistant material such as TEFLON around the platinum covering all but a small ring or halo' at the tip of the reference electrode, adjacent to the active portion of the reference electrode. The voltage output of the platinum layer, which serves as a redox electrode, and that of the reference electrode are coupled by a capacitor or a set of capacitors and the coupled output transmitted to a standard laboratory potentiostat. The platinum may be applied by thermal decomposition to the surface of the reference electrode. The electrode provides superior high-frequency response over conventional electrodes. 4 figs.

Kronberg, J.W.

1994-05-31

295

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, J.W.

1991-03-05

296

Voltage stability constrained load curtailment procedure to evaluate power system reliability measures  

Microsoft Academic Search

This paper reports a method to evaluate composite power system reliability indices incorporating the voltage stability margin criteria. To compute the load curtailment evaluation, an optimal power flow (OPF) computation algorithm, considering the steady state voltage stability margin constraint is developed. A steady state voltage stability indicator is first discussed for its applicability as a suitable indicator for representing stability

G. M. Huang; Nirmal-Kumar C Nair

2002-01-01

297

Stability of Measurement of Heterojunction Bipolar Transistors Current-Voltage Characteristics with Thermal Effect  

NASA Astrophysics Data System (ADS)

To obtain a reliable design, a careful determination of model parameters is needed. In this study, the thermally stable time of collector current (IC) of heterojunction bipolar transistors (HBTs) operated at different biasing points is observed. It is observed that the stable time of IC is different with different biasing points. The maximum thermally stable time is about 72 ms in this study. For the conventional measurement method, the default biasing time of current-voltage (IC-VCE) curves at each bias point is about 20 ms. The calculated thermal resistance and junction temperature obtained by the conventional measurement are quite different from those obtained by thermally stable measurement. In this work, we found that the thermal resistance obtained by thermally stable measurement (i.e. sufficiently long biasing time) is smaller than that obtained by conventional measurement. Moreover, the junction temperature estimated from the former is smaller than that from the latter. It is obvious that the biasing time of every measurement point must be ascertained by using the curve of IC versus biasing time with the operation VCE.

Wei, Sun-Chin; Su, Yan-Kuin; Wang, Ruey-Lue

2002-12-01

298

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

299

Longitudinal impedance of capacitive pick-up electrodes: Calculations and comparison with measurements  

SciTech Connect

In order to obtain high sensitivity over a broad frequency range, split cylinder capacitive pick-up electrodes have been adopted as the beam position monitors (BPMs) for the AGS booster. Numerical simulation and prototype measurements have been employed to find the coupling impedance of a BPM. The impedance was calculated using the MAFIA computer codes, and measurements were made using a coaxial wire. We found that the measured impedance depended strongly on external electronics, which could not be modeled using the computer code. Additionally, the calculated impedance is a function of beam velocity, which was not studied in the measurements. Only by using both could a reliable bound on the shunt impedance be obtained. We find that the longitudinal impedance of the BPMs is negligible for normal operating conditions in the booster.

Blaskiewicz, M.; Luccio, A.; Ratti, A.; Shea, T.J.

1992-09-01

300

Longitudinal impedance of capacitive pick-up electrodes: Calculations and comparison with measurements  

SciTech Connect

In order to obtain high sensitivity over a broad frequency range, split cylinder capacitive pick-up electrodes have been adopted as the beam position monitors (BPMs) for the AGS booster. Numerical simulation and prototype measurements have been employed to find the coupling impedance of a BPM. The impedance was calculated using the MAFIA computer codes, and measurements were made using a coaxial wire. We found that the measured impedance depended strongly on external electronics, which could not be modeled using the computer code. Additionally, the calculated impedance is a function of beam velocity, which was not studied in the measurements. Only by using both could a reliable bound on the shunt impedance be obtained. We find that the longitudinal impedance of the BPMs is negligible for normal operating conditions in the booster.

Blaskiewicz, M.; Luccio, A.; Ratti, A.; Shea, T.J.

1992-01-01

301

Feasibility of potentiometric oxygen gas sensor based on perovskite and sodium titanate measuring electrode  

Microsoft Academic Search

A new solid potentiometric sensor for the oxygen gas detection using NASICON as solid electrolyte is proposed and tested in the range 300–700°C for a feasibility study. The measuring electrode is a mixture of Na2Ti3O7–Na2Ti6O13 and La1?xSrxMnO3±? (LSM) as mixed electronic and ionic conductors. A system based on Ni-NiO\\/Na2Ti3O7–Na2Ti6O13 is used as solid internal reference. A linear relationship was observed

J. Ram??rez-Salgado; P. Fabry

2002-01-01

302

Measurement of calcium influx under voltage clamp in molluscan neurones using the metallochromic dye arsenazo III.  

PubMed Central

1. The metallochromic indicator dye, arsenazo III, was injected into somata of molluscan neurones from Archidoris monteryensis. Membrane current and dye absorbance change were simultaneously monitored under voltage clamp. 2. Absorbance measured at 660 nm increased during positive-going voltage steps large enough to activate membrane conductances. In situ idifference spectra were qualitatively similar to dye, dye-calcium difference spectra recorded in vitro. The absorbance change was abolished by either a thorough removal of external calcium or internal chelation of calcium by EGTA. It was concluded that the absorbance increase primarily reflected changing internal calcium concentration and that the calcium entered from the outside. 3. Dye absorbance increased in a nearly linear fashion during voltage clamp pulses of 100--300 msec duration. This is in qualitative agreement with electrical stuidies which demonstrated only fractional inactivation of calcium conductance during such periods. Plots of absorbance change vs. Vm peaked at +30 to +40 mV and fell off sharply until approximately +70 mV where the slope became less steep. A null or reversal of the absorbance change was generally observed aroung +110 mV. Evidence is presented that calcium influx was in some cases sufficient to cause sizeable changes in its equilibrium potential. 4. During multisecond voltage clamps the slope of the absorbance change showed a large decline. Where barium substituted for calcium as the influx species in identical clamps, the absorbance at 660 nm also increased but in a much more linear fashion. Except for a slight effect on the initial few pulses, the absorbance signal did not recover after a period of barium influx. These results suggest that part of the slope decline might result from processes related to calcium uptake and not to membrane conductance decrease. 5. Dye absorbance changes during normal and TEA action potentials were measured. Comparison of these changes with voltage clamp records indicated that calcium influx during a spike was capable of raising concentration by roughly 2 X 10(-7) M if the cell were considered to be a uniform sphere with no buffering capacity. Calcium influx during action potentials was increased dramatically by TEA, primarily as a result of a prolonged plateau phase. The existence and duration of the plateau was controlled mainly by potassium conductance systems, however. There was no evidence found for facilitation of the calcium conductance. 6. Following a moderate influx of calcium it required 20--60 sec, depending on the neurone, for the dye absorbance to return to base line (at 9 degrees C). The recovery time course showed a marked difference when examined at different wavelengths. For lambda = 660 nm there was an initial period in which the absorbance decreased rapidly, followed by a slower phase which generally carried the absorbance below the initial (prepulse) value...

Ahmed, Z; Connor, J A

1979-01-01

303

Reticle programmed defect size measurement using low-voltage SEM and pattern recognition techniques  

NASA Astrophysics Data System (ADS)

The use of programmed defect test reticles to characterize automatic defect inspection equipment has long been an established practice in the maskmaking industry. Measurement of the defect sizes on these programmed defect test masks is not necessary if one only desires to qualitatively investigate differences in system performance. However, more meaningful comparisons in inspection system performance require a calibrated programmed defect test mask. Historically, commercially available programmed defect test reticles have not had traceable or well-documented defect sizing methods nor was information regarding the precision of these measurements provided. This paper describes the methods used and results obtained from the work performed to address these issues. Using a low voltage scanning electron microscope as an image acquisition system, defect sizing is accomplished using automated pattern recognition software. The software reports defect size metrics such as maximum inscribed circle diameter and area. Measurement precision better than 30 nm has been demonstrated for the maximum inscribed circle method. The correlation of SEM based measurements to historical optical metrology measurements ia also discussed.

Zurbrick, Larry S.; Khanna, Steve; Lee, Jay; Greed, James J.; Laird, Ellen R.; Blanquies, Rene M.

2000-02-01

304

Normalization of voltage-sensitive dye signal with functional activity measures.  

PubMed

In general, signal amplitude in optical imaging is normalized using the well-established DeltaF/F method, where functional activity is divided by the total fluorescent light flux. This measure is used both directly, as a measure of population activity, and indirectly, to quantify spatial and spatiotemporal activity patterns. Despite its ubiquitous use, the stability and accuracy of this measure has not been validated for voltage-sensitive dye imaging of mammalian neocortex in vivo. In this report, we find that this normalization can introduce dynamic biases. In particular, the DeltaF/F is influenced by dye staining quality, and the ratio is also unstable over the course of experiments. As methods to record and analyze optical imaging signals become more precise, such biases can have an increasingly pernicious impact on the accuracy of findings, especially in the comparison of cytoarchitechtonic areas, in area-of-activation measurements, and in plasticity or developmental experiments. These dynamic biases of the DeltaF/F method may, to an extent, be mitigated by a novel method of normalization, DeltaF/DeltaF(epileptiform). This normalization uses as a reference the measured activity of epileptiform spikes elicited by global disinhibition with bicuculline methiodide. Since this normalization is based on a functional measure, i.e. the signal amplitude of "hypersynchronized" bursts of activity in the cortical network, it is less influenced by staining of non-functional elements. We demonstrate that such a functional measure can better represent the amplitude of population mass action, and discuss alternative functional normalizations based on the amplitude of synchronized spontaneous sleep-like activity. These findings demonstrate that the traditional DeltaF/F normalization of voltage-sensitive dye signals can introduce pernicious inaccuracies in the quantification of neural population activity. They further suggest that normalization-independent metrics such as waveform propagation patterns, oscillations in single detectors, and phase relationships between detector pairs may better capture the biological information which is obtained by high-sensitivity imaging. PMID:19116673

Takagaki, Kentaroh; Lippert, Michael Thomas; Dann, Benjamin; Wanger, Tim; Ohl, Frank W

2008-12-24

305

Development of Low Noise Active Electrode for High-Resolution EEG  

Microsoft Academic Search

\\u000a In this paper the design and testing of an active electrode are presented. The purpose was to design a low noise small sized\\u000a active electrode that can be used to measure electroencephalography (EEG) and increase the signal-to-noise ratio of the measured\\u000a signal. During the design process a unity gain active electrode was developed. It acts as a voltage follower and

Sari Ahokas; Jaakko Malmivuo; Pasi Kauppinen

306

In vivo impedance spectroscopy of deep brain stimulation electrodes  

NASA Astrophysics Data System (ADS)

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

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

2009-08-01

307

In vivo impedance spectroscopy of deep brain stimulation electrodes  

PubMed Central

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

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

2010-01-01

308

Measurement of junction temperature in GaN-based laser diodes using voltage-temperature characteristics  

NASA Astrophysics Data System (ADS)

With increasing demands for the development of high power GaN-based blue-violet laser diodes (LDs), thermal management has become an important issue. We present a new method to determine junction temperature of GaN-based LDs for simple, fast, and reliable characterization of thermal performances. The large change of forward operation voltage with temperature is advantageously used to measure junction temperature. Using this method, we compare junction temperature of LD structures with different substrates and chip mounting methods. It is found that the junction temperature can be reduced considerably by employing GaN substrates or epi-down bonding. For epi-down bonded LDs, as much as two-fold reduction in junction temperature is achieved compared to epi-up bonded ones and temperature increase in this case is only about 13 degrees for more than 100 mW-output power.

Ryu, Han-Youl; Ha, Kyoung-Ho; Chae, Jung-Hye; Nam, Ok-Hyun; Park, Yong-Jo

2005-04-01

309

Dependence of hydrogen arcjet operation on electrode geometry  

NASA Astrophysics Data System (ADS)

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.

1992-09-01

310

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

311

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

312

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

NASA Astrophysics Data System (ADS)

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 Sea basin with the Barents Sea. Strong tidal currents providing a reference signal for calibrating coastal measurements of non-local MIV characterize the Throat. The measurements were carried out simultaneously by means of two horizontal receiving on-land and land-sea antennas. Tidally driven MIV dominates in all time series obtained in the coastal zone of the Throat of the White Sea. Monitoring of non-local MIV within the coastal zone could be used for studies of wind tides, residual tidal circulation and temporal variability of a quasi-stationary current. MIV measurements offer an important advantage over traditional oceanographic methods (currents meters, etc.), because it works also in winter period (about 6 months) when the White Sea is covered by ice. The main disadvantage of this technique is a necessity to calibrate non-local MIV with some other oceanographic direct or remote measurements.

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

2002-05-01

313

The Measurement of the Erosion Rate at the Electrodes of an Arc Rotated by a Transverse Magnetic Field  

Microsoft Academic Search

The measurement of the erosion at the electrodes of an arc rotated between water-cooled nonrefractory coaxial electrodes in an axial magnetic field has been made in air at atmospheric pressure. Values of erosion rate an order-of-magnitude less than those previously reported have been obtained. The effect of variation in axial magnetic flux density, arc velocity, rotational frequency, cooling-water flow-rate, and

J. E. Harry

1969-01-01

314

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

315

The electrode resistance of ZrO2---Y2O3(Bi2O3) solid electrolytes with Pt electrodes  

Microsoft Academic Search

The electrode resistance (Re1) at low over-voltages has been determined for Bi2O3 free and Bi2O3 doped yttria-stabilized zirconia with sputtered platinum electrodes. The anode and cathode resistances are measured separately and are equal. Bi2O3 causes a decrease of the electrode resistance at small overvoltage and with 5 × 10?4 < PO2 less-than-or-equals, slant 1 atm. The rate determining step for

A. J. A. Winnubst; A. H. A. Scharenborg; A. J. Burggraaf

1984-01-01

316

Destruction of living cells by pulsed high-voltage application  

Microsoft Academic Search

Destruction of living cells in liquid has been formed by pulsed high-voltage application to the liquid. S. cerevsaie (yeast cell) or Bacillus natto, dispersed in deionized water and one- and three-percent NaCl solution, were used in this experiment. Four different electrodes (plate-plate, needle-plate wire-cylinder, and rod-rod electrode) were tested. The survival rate of cells was measured against peak electric field

A. Mizuno; Y. Hori

1988-01-01

317

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

Microsoft Academic Search

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

Robert Oostenveld; Peter Praamstra

2001-01-01

318

Extraction of Cu diffusivities in dielectric materials by numerical calculation and capacitance-voltage measurement  

NASA Astrophysics Data System (ADS)

A rigorous method of obtaining the Cu diffusivities in various SiO2-based dielectric materials is proposed. The diffusion profile of Cu ions in a dielectric material is first simulated and the resulting flatband voltage shift (?VFB) is compared with the experimental results obtained by C-V measurements after bias-temperature stressing (BTS). The evolution of the Cu concentration in dielectric materials is evaluated using a one-dimensional finite differential method with two unknown parameters, the diffusivity, and the maximum solid solubility of Cu ions in the dielectric material. C-V measurements are conducted at 1 MHz to measure the ?VFB value of Cu/SiO2/Si capacitors before and after BTS at an electric field of +1.0 MV/cm and in the temperature range between 200 and 275 °C. With this process, the Cu diffusivities in thermally grown SiO2, oxynitride and SiO2 deposited by plasma-enhanced chemical vapor deposition, and methyl-doped SiO2 are found to be 2.22×10-3 exp(-1.54 eV/kT), 3.09×10-5 exp(-1.34 eV/kT), 2.59×10-5 exp(-1.18eV/kT), and 6.07×10-9 exp(-0.71 eV/kT), respectively.

Kim, Ki-Su; Joo, Young-Chang; Kim, Ki-Bum; Kwon, Jang-Yeon

2006-09-01

319

Experimental and numerical studies on voltage distribution in capacitively coupled very high-frequency plasmas  

NASA Astrophysics Data System (ADS)

A non-uniform voltage distribution across a driven electrode results in inhomogeneous film deposition in large-area, very high-frequency (VHF) plasma reactors. Here we perform experimental and numerical studies on the voltage distribution across the electrode. Two kinds of dedicated vacuum chambers are prepared for one- and two-dimensional observations of the voltage and the plasma distributions. A comparison between the measured voltage and the plasma distribution clearly shows a good agreement between the two. In principle the plasma distribution is governed by the standing wave of the voltage on the driven electrode for an at least one-dimensional electrode. A numerical model based on transmission-line modelling is presented for calculating the voltage distribution. The influence of plasma conditions such as the electron density and the sheath length included in the model on the voltage distribution is investigated through comparison of the model predictions with the experimental results. The correlation between the plasma conditions and the propagation constant of the model suggests that the sheath length dominates the wavelength; in contrast, the electron density dominates the decay of the wave propagation. Using the parameters of the plasma conditions estimated from the experimental results, the model can predict the voltage distribution across a ladder electrode of size 45 cm × 55 cm in a large-area VHF plasma reactor.

Satake, Koji; Yamakoshi, Hideo; Noda, Matsuhei

2004-08-01

320

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

321

Operational features and air plasma characteristics of a thermal plasma torch with hollow electrodes  

Microsoft Academic Search

The operational features and thermal plasma characteristics of a plasma torch with hollow electrodes are investigated based on their dependence on input current, gas flow rate and electrode diameter when air is used as a plasma gas. A plasma torch with a hollow cathode and anode has been designed and fabricated, and the arc voltages and thermal efficiencies are measured

Min Hur; Keun Su Kim; Sang Hee Hong

2003-01-01

322

Frequency Characteristics Measurement of Overhead High-Voltage Power-Line in Low Radio-Frequency Range  

Microsoft Academic Search

This paper presents measurement results of frequency characteristics of the high-voltage power line in low radio-frequency range: amplitude and phase characteristic, group delay, and input impedance. Measurement results for the 400-kV overhead power-line under operation are presented together with the developed measurement methodology. The methodology provides a method to measure amplitude and phase characteristics, group delay and the return loss

M. Zajc; N. Suljanovic; A. Mujcic; J. F. Tasic

2007-01-01

323

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; Chang, J.S. [McMaster Univ., Hamilton, Ontario (Canada). Dept. of Engineering Physics

1997-01-01

324

Properties of voltage-gated Ca2+ currents measured from mouse pancreatic beta-cells in situ.  

PubMed

We used the single-microelectrode voltage-clamp technique to record ionic currents from pancreatic beta-cells within intact mouse islets of Langerhans at 37 degrees C, the typical preparation for studies of glucose-induced "bursting" electrical activity. Cells were impaled with intracellular microelectrodes, and voltage pulses were applied in the presence of tetraethylammonium. Under these conditions, a voltage-dependent Ca2+ current (I(Cav)), containing L-type and non-L-type components, was observed. The current measured in situ was larger than that measured in single cells with whole-cell patch clamping, particularly at membrane potentials corresponding to the action potentials of beta-cell electrical activity. The temperature dependence of I(Cav) was not sufficient to account for the difference in size of the currents recorded with the two methods. During prolonged pulses, the voltage-dependent Ca2+ current measured in situ displayed both rapid and slow components of inactivation. The rapid component was Ca2+-dependent and was inhibited by the membrane-permeable Ca2+ chelator, BAPTA-AM. The effect of BAPTA-AM on beta-cell electrical activity then demonstrated that Ca2+-dependent inactivation of I(Cav) contributes to action potential repolarization and to control of burst frequency. Our results demonstrate the utility of voltage clamping beta-cells in situ for determining the roles of ion channels in electrical activity and insulin secretion. PMID:17106582

Mears, David; Rojas, Eduardo

2006-11-07

325

The role of charge traps in inducing hysteresis: Capacitance-voltage measurements on top gated bilayer graphene  

NASA Astrophysics Data System (ADS)

Understanding the origin of hysteresis in the channel resistance from top gated graphene transistors is important for transistor applications. Capacitance-voltage measurements across the gate oxide on top gated bilayer graphene show hysteresis with a charging and discharging time constant of ~100 ?s. However, the measured capacitance across the graphene channel does not show any hysteresis but shows an abrupt jump at a high channel voltage due to the emergence of an order, indicating that the origin of hysteresis between gate and source is due to charge traps present in the gate oxide and graphene interface.

Kalon, Gopinadhan; Jun Shin, Young; Giang Truong, Viet; Kalitsov, Alan; Yang, Hyunsoo

2011-08-01

326

The Effect of Electrode Construction in Breakdown Time Lag of Impulse Breakdown in Mineral Oil  

NASA Astrophysics Data System (ADS)

A breakdown time lag of uniform and nonuniform electric fields using point-plane and sphere-sphere electrodes in mineral oil was measured. The stainless-steel spherical electrode was 12.5 mm in diameter. The needle electrode was made of iron and its tip was electrolytically polished. The copper plate electrode measured 10 mm×20 mm×1 mm. The effect on breakdown time lag wielded of differences in the distance between electrodes and applied impulse voltage revealed that the time lag was proportional to the applied voltage and the breakdown time lag of a nonuniform electric field was shorter than that of a uniform electric field. It was found that the breakdown phenomena in point-plane and sphere-sphere electrodes were respectively similar to a streamer-type breakdown and a streamer breakdown structure.

Hirai, Naoshi; Akumu, Aloys; Arii, Kiyomitsu

1998-09-01

327

Liquid electrode  

DOEpatents

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

Ekechukwu, A.A.

1994-07-05

328

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

329

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

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

330

X-ray spectroscopy in mammography with a silicon PIN photodiode with application to the measurement of tube voltage  

SciTech Connect

In this work a silicon PIN photodiode was employed in mammographic x-ray spectroscopy under clinical and nonclinical conditions. Measurements have been performed at a constant potential tungsten anode tube, adapted in this work with molybdenum filters to produce a beam like that used in mammography, and at a clinical equipment with a molybdenum anode tube by using an additional aluminum filtration. The corrected x-ray spectra were in full agreement with those generated by theoretical models published in the literature and agree well with those measured with a CdZnTe detector for tube voltages less than 30 kV. The half value layer and the relative exposure values calculated from the corrected silicon PIN photodiode spectra were in agreement with those measured with an ionization chamber. These results indicate that a silicon PIN photodiode are very suitable for mammographic x-ray spectroscopy. As an application, the voltage (kV) applied to mammographic x-ray equipment has been measured through the evaluation of the spectra high energy cut off. Uncertainties evaluated for the voltage values calculated from the measured spectra are less than 0.13% for voltages in the range 20-35 kV. The low uncertainties associated with the obtained results in this work point out that the method employed can be accurately used for calibration of noninvasive mammographic kVp meters.

Kuenzel, Roseli; Herdade, Silvio Bruni; Terini, Ricardo Andrade; Costa, Paulo Roberto [Instituto de Fisica, Universidade de Sao Paulo, Rua do Matao, Travessa R, 187, Cidade Universitaria, CEP 05508-900, Sao Paulo, Sao Paulo (Brazil); Departamento de Fisica, Pontificia Universidade Catolica de Sao Paulo, R. Marques de Paranagua, 111, Consolacao, CEP 01303-050, Sao Paulo, Sao Paulo (Brazil); Secao Tecnica de Desenvolvimento Tecnologico em Saude, Instituto de Electrotecnica e Energia, Universidade de Sao Paulo, Avenida Professor Luciano Gualberto, 1289, Cidade Universitaria, CEP 05508-010, Sao Paulo (Brazil)

2004-11-01

331

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

PubMed

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 and tested ISEs for widely used alkylimidazolium ionic liquids. The aqueous solubilities of four typical ILs have been determined at 21 degrees C: 0.075 +/- 0.001 mol l(-1) (1-butyl-3-methylimidazolium, BMIm, hexafluorophosphate); 0.018 +/- 0.001 mol l(-1) (BMIm bis(triflylimide)); 0.054 +/- 0.007 mol l(-1) (1-butyl-2,3-dimethylimidazolium, BDMIm, hexafluorophosphate); 0.014 +/- 0.001 mol l(-1) (BDMIm bis(triflylimide)). PMID:15662509

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

2005-01-21

332

Contribution of Oxygen Reduction to Charge Injection on Platinum and Sputtered Iridium Oxide Neural Stimulation Electrodes  

Microsoft Academic Search

The extent to which oxygen reduction occurs on sputtered iridium oxide (SIROF) and platinum neural stimulation electrodes was quantified by cyclic voltammetry and voltage-transient measurements in oxygen-saturated physiological saline. Oxygen reduction was the dominant charge-admittance reaction on platinum electrodes during slow-sweep-rate cyclic voltammetry, contributing ~12 mC\\/cm2 (88% of total charge) to overall cathodal charge capacity. For a 300-nm-thick SIROF electrode,

Stuart F. Cogan; Julia Ehrlich; Timothy D. Plante; Marcus D. Gingerich; Douglas B. Shire

2010-01-01

333

Current-Voltage Measurements for DC Microplasmas with Gap Sizes Less Than 10 ?m  

NASA Astrophysics Data System (ADS)

Direct current (DC) microplasmas have been of great interest to the scientific community for the past decade because of their non-equilibrium characteristics and stability at atmospheric pressures. Owing to their large surface-to-volume ratio, processes occurring at the cathode surface can play a dominant role in determining many of the thermodynamic properties of a DC microplasma. Better understanding of these processes can lead to better control of thermodynamic properties, such as the electron energy distribution function. The departure from typical Paschen pressurexdistance pd-scaling for breakdown in gap sizes d < 5?m indicates that processes other than traditional secondary emission are producing electron current at the cathode, and ion-enhanced field emission has been identified as the main process leading to the so-called modified Paschen's curve. However, it is still unclear what other properties ion-enhanced field emission affects in addition to breakdown and its ultimate role in sustaining the microplasma. Using a classic, one-dimensional, parallel plate setup, current-voltage (iV) curves are measured for gap sizes less than 10 ?m in both pure argon and nitrogen with pressures ranging from 1 to 750 torr. Distinct features of these iV curves provide insight to the different processes occurring in DC microplasmas that separate them from their meso- (˜100 ?ms) and macroscale counterparts (> 1 mm).

Rumbach, Paul; Go, David

2011-11-01

334

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

PubMed

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

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

2006-11-01

335

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

SciTech Connect

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

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

2006-11-15

336

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

Microsoft Academic Search

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

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

1990-01-01

337

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

Microsoft Academic Search

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

Hongrae Kim; Thomas M. Jahns

2006-01-01

338

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

Microsoft Academic Search

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

Stuart F. Cogan

2006-01-01

339

Sources and effects of electrode impedance during deep brain stimulation  

Microsoft Academic Search

ObjectiveClinical impedance measurements for deep brain stimulation (DBS) electrodes in human patients are normally in the range 500–1500?. DBS devices utilize voltage-controlled stimulation; therefore, the current delivered to the tissue is inversely proportional to the impedance. The goals of this study were to evaluate the effects of various electrical properties of the tissue medium and electrode-tissue interface on the impedance

Christopher R. Butson; Christopher B. Maks; Cameron C. McIntyre

2006-01-01

340

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

341

Voltage-dependent quantum efficiency measurements of amorphous silicon multi-junction mini-modules  

Microsoft Academic Search

Multi-junction solar cells have the potential to provide higher efficiencies than single junction devices and to reduce the impact of Staebler–Wronski degradation on amorphous silicon (a-Si) devices. They could, therefore, reduce the cost of solar electricity. However, their characterization presents additional challenges over that of single junction devices. Achieving acceptable accuracy of any current–voltage calibration requires correction of the current–voltage

C. J. Hibberd; F. Plyta; C. Monokroussos; M. Bliss; T. R. Betts; R. Gottschalg

2011-01-01

342

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

NASA Astrophysics Data System (ADS)

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

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

2008-07-01

343

Application of a contact mode AFM for spatially resolved electrochemical impedance spectroscopy measurements of a Nafion membrane electrode assembly.  

PubMed

A Nafion fuel cell membrane is investigated by means of electrochemical atomic force microscopy in different gas atmospheres. From chronoamperometric experiments with a point contact electrode spatially resolved electrochemical impedance spectra are obtained from which information about electrode processes and proton transport in the membrane is derived. In the first part the oxygen reduction reaction is investigated. Due to the absence of diffusion limitation, which is partly a result of the small electrode size, a low frequency inductive loop is observed, which is normally masked in macroscopic electrochemical impedance spectra. The influence of water formation from the oxygen reduction reaction at the cathode is discussed. The second part focuses on a hydrogen/oxygen fuel cell setup. A qualitative explanation is given for the necessity of an applied voltage in addition to the electrochemical potential. Electrochemical impedance spectra obtained at two different positions are compared and fitted based on a Randles-like equivalent circuit. A strongly inhomogeneous performance is observed which is attributed to the properties of the Nafion membrane. The electrolyte resistance and the Nernst impedance are restrictive parameters which describe the diffusion through the membrane. PMID:23080435

Hink, Steffen; Roduner, Emil

2013-02-01

344

Automated Targeting of Cells to Electrochemical Electrodes Using a Surface Chemistry Approach for the Measurement of Quantal Exocytosis  

PubMed Central

Here, we describe a method to fabricate a multichannel high-throughput microchip device for the measurement of quantal transmitter release from individual cells. Instead of bringing carbon-fiber electrodes to cells, the device uses a surface chemistry approach to bring cells to an array of electrochemical microelectrodes. The microelectrodes are small and cytophilic in order to promote adhesion of a single cell, whereas all other areas of the chip are covered with a thin cytophobic film to block cell attachement and facilitate the movement of cells to electrodes. This cytophobic film also insulates unused areas of the conductive film; thus, the alignment of cell docking sites to working electrodes is automatic. Amperometric spikes resulting from single-granule fusion events were recorded on the device and had amplitudes and kinetics similar to those measured using carbon-fiber microelectrodes. Use of this device will increase the pace of basic neuroscience research and may also find applications in drug discovery or validation.

2010-01-01

345

Current-voltage-temperature characteristics of DNA origami  

Microsoft Academic Search

The temperature dependences of the current-voltage characteristics of a sample of triangular DNA origami deposited in a 100 nm gap between platinum electrodes are measured using a probe station. Below 240 K, the sample shows high impedance, similar to that of the substrate. Near room temperature the current shows exponential behavior with respect to the inverse of temperature. Sweep times

Edson P. Bellido; Alfredo D. Bobadilla; Norma L. Rangel; Hong Zhong; Michael L. Norton; Alexander Sinitskii; Jorge M. Seminario

2009-01-01

346

Current–voltage–temperature characteristics of DNA origami  

Microsoft Academic Search

The temperature dependences of the current–voltage characteristics of a sample of triangular DNA origami deposited in a 100 nm gap between platinum electrodes are measured using a probe station. Below 240 K, the sample shows high impedance, similar to that of the substrate. Near room temperature the current shows exponential behavior with respect to the inverse of temperature. Sweep times

Edson P Bellido; Alfredo D Bobadilla; Norma L Rangel; Hong Zhong; Michael L Norton; Alexander Sinitskii; Jorge M Seminario

2009-01-01

347

Measurement of kinetically resolved vesicular dopamine uptake and efflux using rotating disk electrode voltammetry.  

PubMed

The vesicular monoamine transporter-2 (VMAT-2) sequesters cytoplasmic dopamine (DA) into vesicles for storage and subsequent release. VMAT-2 activity has traditionally been measured in small synaptic vesicles isolated from rat striatum by monitoring [3H] DA uptake and in cellular expression systems using fast scan cyclic voltammetry. This is the first report using rotating disk electrode (RDE) voltammetry to measure VMAT-2 DA uptake and efflux in small synaptic vesicles. DA uptake profiles followed mixed order kinetics with apparent zero order kinetics for the first 25 s and apparent first order kinetics thereafter. Vesicular DA uptake was temperature- and ATP-dependent and was blocked by the VMAT-2 inhibitor tetrabenazine. Initial velocities of DA uptake were kinetically resolved and displayed Michaelis-Menten kinetics with a Km and Vmax of 289 +/- 59 nM and 1.9 +/- 0.2 fmol/(s microg protein), respectively. Methamphetamine-induced DA efflux was blocked by tetrabenazine and kinetically resolved with an initial velocity of 0.54 +/- 0.08 fmol/(s microg protein). These results suggest that RDE voltammetry can be used to make kinetically resolved measurements of vesicular DA uptake and efflux and will allow the design of experiments that could reveal important information about the kinetics of VMAT-2 activity and its inhibition. PMID:16480775

Volz, Trent J; Hanson, Glen R; Fleckenstein, Annette E

2006-02-09

348

A Simple Hydrogen Electrode  

ERIC Educational Resources Information Center

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

Eggen, Per-Odd

2009-01-01

349

Floating electrode dielectrophoresis.  

PubMed

In practice, dielectrophoresis (DEP) devices are based on micropatterned electrodes. When subjected to applied voltages, the electrodes generate nonuniform electric fields that are necessary for the DEP manipulation of particles. In this study, electrically floating electrodes are used in DEP devices. It is demonstrated that effective DEP forces can be achieved by using floating electrodes. Additionally, DEP forces generated by floating electrodes are different from DEP forces generated by excited electrodes. The floating electrodes' capabilities are explained theoretically by calculating the electric field gradients and demonstrated experimentally by using test-devices. The test-devices show that floating electrodes can be used to collect erythrocytes (red blood cells). DEP devices which contain many floating electrodes ought to have fewer connections to external signal sources. Therefore, the use of floating electrodes may considerably facilitate the fabrication and operation of DEP devices. It can also reduce device dimensions. However, the key point is that DEP devices can integrate excited electrodes fabricated by microtechnology processes and floating electrodes fabricated by nanotechnology processes. Such integration is expected to promote the use of DEP devices in the manipulation of nanoparticles. PMID:17117384

Golan, Saar; Elata, David; Orenstein, Meir; Dinnar, Uri

2006-12-01

350

ELECTRODE MEASUREMENT OF REDOX POTENTIAL IN ANAEROBIC FERRIC/FERROUS CHLORIDE SYSTEMS  

EPA Science Inventory

The behaviour of two inert redox electrodes (Pt and wax-impregnated graphite) was investigated in anaerobic ferrous and ferric chloride solutions in order to establish if these electrodes respond to the Fe3+/Fe2+ couple in a Nernstian manner. A new method fo...

351

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

352

Electrical conductivity of fluidized bed electrodes: its significance and some experimental measurements  

Microsoft Academic Search

By applying a mathematical model (developed by Newman and Tobias for porous electrodes) to a fluidized bed electrode it can be concluded that the effective electrical conductivity of the bed is a key parameter affecting bed performance. Poor current and power efficiencies and operational difficulties are predicted for beds with low electrical conductivities and it is suggested that high conductivities

B. J. Sabacky; J. W. Evans

1978-01-01

353

The electrical conductivity of fluidized bed electrodes---its significance and some experimental measurements  

Microsoft Academic Search

By applying a mathematical model (developed by Newman and Tobias for porous electrodes) to a fluidized bed electrode it can be concluded that the effective electrical conductivity of the bed is a key parameter affecting bed performance. Poor current and power efficiencies and operational difficulties are predicted for beds with low electrical conductivities and it is suggested that high conductivities

B. J. Sabacky; J. W. Evans

1977-01-01

354

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

Microsoft Academic Search

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

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

2001-01-01

355

Measurement of water concentration in oil\\/water dispersions with a circular single-electrode capacitance probe  

Microsoft Academic Search

A new measurement method, called SeCaP, has been used to measure the water content in oil\\/water dispersions. The measuring principle is based on an oscillator working at approximately 20 MHz. The dielectric property of the medium adjacent to one single free electrode affects the frequency of the oscillator. The dispersion was produced by means of recirculation through a colloid mill.

Reidar Barfod Schüller; Tore Gundersen; Morten Halleraker; Bjørn Engebretsen

2004-01-01

356

Analysis of cell impedance measured on the LiMn 2O 4 film electrode by PITT and EIS with Monte Carlo simulation  

Microsoft Academic Search

Cell impedance measured on a LiMn2O4 film electrode was analyzed by using the potentiostatic intermittent titration technique (PITT) and electrochemical impedance spectroscopy (EIS) with Monte Carlo simulation. The plot of the resistance of the absorption–desorption of lithium ions at the electrolyte?electrode interface vs. the electrode potential measured by EIS coincided well with the plot of the cell impedance versus the

Sung-Woo Kim; Su-Il Pyun

2002-01-01

357

Four versus two-electrode measurement strategies for cell growing and differentiation monitoring using electrical impedance spectroscopy.  

PubMed

The aim of this work is to provide optimization tools for cell and tissue engineering processes through continuous monitoring of cell cultures. Structural cell properties can be obtained from non-destructive electrical measurements by using electrical impedance spectroscopy (EIS). EIS measurements on monolayer animal cell cultures are usually performed using a two-electrode strategy. Because of this, the measurement is very sensitive to the electrode covering ratio and to the degree of adherence of cells. Of course, these parameters give useful information but can mask the behaviour of the cell layer above the electrodes. In a previous work, preliminary measurements with commercial microelectrode structures were performed with simulated grow processes using the settlement of cell suspensions with two and four microelectrode strategies to validate the technique. In this work, real cell growths of Vero cells are described and the resulting EIS biomass density estimators are compared to cell counts. The four-electrode impedance spectra are fitted to the Cole-Cole impedance model and the time course of their parameters are extracted and studied. PMID:17946497

Bragós, R; Sarro, E; Fontova, A; Soley, A; Cairó, J; Bayés-Genís, A; Rosell, J

2006-01-01

358

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

SciTech Connect

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

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

2010-08-15

359

The theoretical current-voltage dependence of a non-degenerate disordered organic material obtained with conductive atomic force microscopy  

NASA Astrophysics Data System (ADS)

We develop a simple continuum model for the current voltage characteristics of a material as measured by the conducting atomic force microscopy, including space charge effects. We address the effect of the point contact on the magnitude of the current and on the transition voltages between the different current regimes by comparing these with the corresponding expressions obtained with planar electrodes.

Woellner, Cristiano F.; Freire, José A.; Guide, Michele; Nguyen, Thuc-Quyen

2011-08-01

360

Voltage polarity dependent low-power and high-speed resistance switching in CoO resistance random access memory with Ta electrode  

NASA Astrophysics Data System (ADS)

Structural and resistance switching properties were investigated in the CoO resistance random access memory (RRAM) with the Ta electrode. The intermediate layer consisting of Co and Ta oxides was confirmed at the interface by the transmission electron microscopy and electron energy loss spectroscopy. The great affinity with oxygen in Ta together with a high resistivity of the Ta oxide improves the operational performance of RRAM. The controllability of the resistance after forming and the low-current operation property were substantially improved by using the load resistor connected in series with CoO RRAM with the Ta electrode. The reset current less than 0.2 mA and the switching speed faster than 20 ns were demonstrated.

Shima, Hisashi; Takano, Fumiyoshi; Muramatsu, Hidenobu; Akinaga, Hiro; Tamai, Yukio; Inque, Isao H.; Takagi, Hidenori

2008-09-01

361

Photoemission current-spacecraft voltage relation: Key to routine, quantitative low-energy plasma measurements  

NASA Astrophysics Data System (ADS)

Measurements of the floating potential and plasma return current on the GGS-Polar spacecraft are used to determine the equilibrium photoemission current, J?v, as a function of the spacecraft's (S/C) "floating potential," ??S/C. The photoemission current function is found to be time independent using nearly 10 months of GGS-Polar data from April 1996 to March 1997 including 1.6 million separate spectra from the Hydra (hot plasma) and EFI (electric field) instruments. The photoemission current density leaving the spacecraft at positive floating potentials ??S/C < 50 V is well fit by a sum of two exponentials of the form: J?v(?A/m2) = A exp ( -??S/C/B) + C exp (-??S/C/D), where best fit estimates A ? 152 ± 57 ?A/m2, B ? 1.7 ± 0.2 eV, C ? 0.86 ± 0.29 ?A/m2, and D ? 9.5 ± 1.0 eV. In equilibrium this photoemission current density is determined from the ratio of sunlit to spacecraft areas and the plasma current density, JRC, collected by the spacecraft. For the Polar spacecraft this ratio of areas is not constant in time, and the observed return current voltage relation is time dependent. After correction for the orbitally induced time-dependent ratio of areas, the photoemission curve reported above is obtained and is essentially time independent. After correcting for the different procedures used the present results are illustrated to be consistent with early results with less resolution reported by Pedersen [1995]. When the sensing of the floating potential by EFI on the spacecraft is interrupted, the photoemission-voltage relationship is essential for the assignment of the ambient kinetic energy of the detected particle fluxes. We demonstrate a method using the plasma data and the statistical return current relationship that recovers the floating potential of the spacecraft with a typical precision that is the larger of 0.5 V and 0.1??S/C We also demonstrate that the ion and electron densities determined by numerical integration over distributions corrected with opposite energy shifts implied by the potential enhances their routine agreement, a further check on the absolute precision of the potential inferences. The "systematic" departures of 40% of the data from the statistically defined J?v(??S/C) curve reported above are time varying and organized in radius and with L shell. These data are inferred to be the signature of missing ambient plasma currents to the spacecraft that are not directly detected by the Hydra instrumentation (cf. X. Cao et al., Properties of very cold (Te ? 0.1 eV) electrons within the magnetosphere, submitted to Journal of Geophysical Research, 1999).

Scudder, J. D.; Cao, Xuejun; Mozer, F. S.

2000-09-01

362

Digital multirate algorithms for measurement of voltage, current, power and flicker  

Microsoft Academic Search

Digital multirate processing, i.e, signal processing that involves more than one sample rate, permits computationally efficient estimation of several electrical quantities. The new multirate algorithms for active power, voltage and current do not require periodicity of the input signals or synchronous sampling and give excellent accuracy. They replace the integration or summation of conventional methods with digital low pass filtering,

L. Toivonen; J. Morsky

1994-01-01

363

Digital multirate algorithms for measurement of voltage, current, power and flicker  

Microsoft Academic Search

Digital multirate processing, i.e., signal processing that involves more than one sample rate, permits computationally efficient estimation of several electrical quantities. The new multirate algorithms for active power, voltage and current do not require periodicity of the input signals or synchronous sampling and give excellent accuracy. They replace the integration or summation of conventional methods with digital low pass filtering,

L. Toivonen; J. Moersky

1995-01-01

364

Some Comments on Energy Loss Measurements Made with a High Voltage Electron Microscope  

Microsoft Academic Search

There is a distinct possibility that chromatic aberration may be a deciding factor in determining the specimen thickness that can be usefully penetrated with high voltage electron microscopes. In this paper a simple model of multiple inelastic scattering is considered, and method of calculating the most probable loss is discussed. The theoretical loss profiles so obtained are compared with Kamiya's

A. J. F. Metherell

1968-01-01

365

High Voltage Properties of Insulating Materials Measured in the Ultra Wideband  

Microsoft Academic Search

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

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

2005-01-01

366

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 are disclosed, characterized by providing a thin semiconductor wafer having rectifying junctions on its opposing major surfaces and including a small capacitance ohmic contact, in combination with bias voltage means and associated circuit means for applying a predetermined voltage to effectively deplete the wafer in regions thereof between the rectifying junctions and the ohmic contact. A charge transport device of the invention is usable as a drift chamber, a low capacitance detector, or a charge coupled device each constructed according to the methods of the invention for making such devices. Detectors constructed according to the principles of the invention are characterized by having significantly higher particle position indicating resolution than is attainable with prior art detectors, while at the same time requiring substantially fewer readout channels to realize such high resolution. 16 figs.

Rehak, P.; Gatti, E.

1987-08-18

367

Voltammetric measurement of ultraslow diffusion rates in polymeric media with microdisk electrodes  

SciTech Connect

Cyclic voltammetry and chronoamperometry were used in conjunction with microdisk electrodes in polymeric solvents to measure diffusion coefficients of ferrocene redox solutes down to 10{sup {minus}12} cm{sup 2}/s. Experimental manipulation of the parameter {tau} ({tau} = 4Dt/r{sup 2}) results in diffusion profiles dominated by radial diffusion, linear diffusion, or a combination of the two. In the former two cases, adherence to the steady-state current equation for a a microdisk and the Cottrell equation, respectively, was observed. Under conditions of mixed contribution, evaluation of diffusion coefficients was based on comparison of experimental and simulated current-time curves. Generally, diffusion coefficients >10{sup {minus}7} cm{sup 2}/s were evaluated from steady-state potential sweeps. Diffusion coefficients <10{sup {minus}11} cm{sup 2}/s could be evaluated by a standard Cottrell analysis. Values in the transition region were evaluated from the slope of nonzero intercept Cottrell plots. A numerical guideline, based on {tau}, is presented.

Longmire, M.L.; Watanabe, M.; Zhang, H.; Wooster, T.T.; Murray, R.W. (Univ. of North Carolina, Chapel Hill (USA))

1990-04-01

368

An area-efficient 55 nm 10-bit 1-MS/s SAR ADC for battery voltage measurement  

NASA Astrophysics Data System (ADS)

An area-efficient CMOS 1-MS/s 10-bit charge-redistribution SAR ADC for battery voltage measurement in a SoC chip is proposed. A new DAC architecture presents the benefits of a low power approach without applying the common mode voltage. The threshold inverter quantizer (TIQ)-based CMOS Inverter is used as a comparator in the ADC to avoid static power consumption which is attractive in battery-supply application. Sixteen level-up shifters aim at converting the ultra low core voltage control signals to the higher voltage level analog circuit in a 55 nm CMOS process. The whole ADC power consumption is 2.5 mW with a maximum input capacitance of 12 pF in the sampling mode. The active area of the proposed ADC is 0.0462 mm2 and it achieves the SFDR and ENOB of 65.6917 dB and 9.8726 bits respectively with an input frequency of 200 kHz at 1 MS/s sampling rate.

Hongming, Chen; Yueguo, Hao; Long, Zhao; Yuhua, Cheng

2013-09-01

369

Computer Measurements of Hippocampal Fast Activity in Cats with Chronically Implanted Electrodes.  

National Technical Information Service (NTIS)

An evoked potential technique is described for implanting bipolar electrodes that straddle the dorsal hippocampal pyramical cell layer. Recordings from cats chronically implanted with this technique exhibited large amplitude theta and beta wave spontaneou...

J. C. Boudreau

1965-01-01

370

Breakdown Voltage of CO2 at Temperatures around 4000K and in Range from 300 to 700K  

NASA Astrophysics Data System (ADS)

The breakdown voltage of high temperature CO2 was measured at temperatures around 4000K and in the temperature from 300 to 700K at an absolute pressure of 0.1MPa. A voltage was applied to the high temperature CO2 through a set of two rod electrodes made of stainless steel with a diameter of 2mm. The gap length between the electrodes was adjusted to be of 1mm. The breakdown voltage of the hot CO2 proved to decrease in inverse proportion to the increase in temperature, in the range from 300 to 700K. Further increase in temperature of the CO2 reduced the breakdown voltage more markedly. For example, at 4000 K the breakdown voltage was measured to be of 55V. This breakdown voltage is only 1.1% of that at room temperature.

Matsumura, Toshiro; Yokomizu, Yasunobu; Almiron, Pablo C.; Yamamoto, Kazuma; Ohta, Daisuke; Shibuya, Masatoyo

371

The electrical conductivity of fluidized bed electrodes—its significance and some experimental measurements  

Microsoft Academic Search

By applying a mathematical model (developed by Newman and Tobias for porous electrodes) to a fluidized bed electrode it can\\u000a be concluded that the effective electrical conductivity of the bed is a key parameter affecting bed performance. Poor current\\u000a and power efficiencies and operational difficulties are predicted for beds with low electrical conductivities and it is suggested\\u000a that high conductivities

B. J. Sabacky; J. W. Evans

1977-01-01

372

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

PubMed

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

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

2012-02-01

373

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

SciTech Connect

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

Malygin, V.M.

1995-06-01

374

Transparent electrode for optical switch  

DOEpatents

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

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

1986-01-01

375

Measurement and Analysis of Electromagnetic Radiation of 110KV High-Voltage Lines in One Urban Location in Chongqing P.R. China  

Microsoft Academic Search

Objective To understand electromagnetic radiation field strength and its influencing factors of certain 110KV high-voltage lines in one urban area of Chongqing by measuring110KV high-voltage line's electromagnetic radiation level. Methods According to the methodology as determined by the National Hygienic Standards, we selected certain adjacent residential buildings, high-voltage lines along a specific street and selected different distances around its vertical

Qin Qi-zhong; Chen Yu; Fu Ting-ting; Ding Li; Li Jian-chao; Han Ling-li

2010-01-01

376

Special Aspects of High-Voltage and High-Current Measurements. Post Graduate Seminar of High-Voltage Engineering S-18.148.  

National Technical Information Service (NTIS)

Voltage dividers in HV laboratories are used for DC, AC, switching/lightning impulse and chopped impulse applications. Calibration procedures are prescribed by the currently revised IEC 60. Different scale factors for different applications are allowed. V...

G. C. Damstra M. Aro P. Wallin Z. Matyaes

2000-01-01

377

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

PubMed

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

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

2012-09-03

378

Adaptive Scheme for Minimal Load Shedding Utilizing Synchrophasor Measurements to Ensure Frequency and Voltage Stability  

Microsoft Academic Search

This article presents a new scheme for load curtailment in the power system under critical contingencies that may pose a threat to the frequency and voltage stability of the system. The proposed scheme is based on a two-stage load-shedding strategy. In the first stage, disturbances have been classified based on the computed value of the disturbance power, and the load-shedding

K. Seethalekshmi; S. N. Singh; S. C. Srivastava

2010-01-01

379

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

380

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

381

Effects of electrode degradation and solvent evaporation on the performance of ionic-polymer-metal composite sensors  

NASA Astrophysics Data System (ADS)

An ionic-polymer-metal composite (IPMC) consists of an ionic polymer membrane and metallic electrodes plated on both surfaces. When it bends, a voltage is generated between the two electrodes across the membrane. Since it works not only in aqueous solution similar to in vivo but also in air, it can be used for embedded biomedical as well as surface-mounted sensors. The present study investigates the effect of solvent evaporation and mechanisms of electrode degradation of an IPMC when it is operated as a sensor. The output voltages and electrode resistances were measured with several cyclic bending motions applied on the sensor in both aqueous solution and air. There was a good correlation between the sensor voltage and the bending angle when the sensor was tested in aqueous solution. The sensor worked for a long time without attenuation in the output voltage in an aqueous solution. The output voltage, however, decreased rapidly when the sensor was operated in air. The results of resistance measurement showed that the electrode on the compressive side deformed more and generated more cracks than on the tensile side. Optical microscopic images taken on the electrode surfaces validated the results. The results provided very useful information needed to understand electrode degradation and solvent evaporation and to improve the performance of IPMC sensors.

Park, Kiwon; Yoon, Myung-Keun; Lee, Sangbok; Choi, Jinho; Thubrikar, Mano

2010-07-01

382

Voltage-dependent calcium channels in skeletal muscle transverse tubules. Measurements of calcium efflux in membrane vesicles  

SciTech Connect

Transverse tubule membranes isolated from rabbit skeletal muscle consist mainly of sealed vesicles that are oriented primarily inside out. These membranes contain a high density of binding sites for 1,4-dihydropyridine calcium channel antagonists. The presence of functional voltage-dependent calcium channels in these membranes has been demonstrated by their ability to mediate {sup 45}Ca2+ efflux in response to changes in membrane potential. Fluorescence changes of the voltage-sensitive dye, 3,3'-dipropyl-2,2'-thiadicarbocyanine, have shown that transverse tubule vesicles may generate and maintain membrane potentials in response to establishing potassium gradients across the membrane in the presence of valinomycin. A two-step procedure has been developed to measure voltage-dependent calcium fluxes. Vesicles loaded with {sup 45}Ca2+ are first diluted into a buffer designed to generate a membrane potential mimicking the resting state of the cell and to reduce the extravesicular Ca2+ to sub-micromolar levels. {sup 45}Ca2+ efflux is then measured upon subsequent depolarization. Flux responses are modulated with appropriate pharmacological specificity by 1,4-dihydropyridines and are inhibited by other calcium channel antagonists such as lanthanum and verapamil.

Dunn, S.M. (Univ. of Iowa, Iowa City (USA))

1989-07-05

383

Validation of improved recording site to measure phrenic conduction from surface electrodes in humans.  

PubMed

Phrenic nerve stimulation, electrical (ES) or from cervical magnetic stimulation (CMS), allows one to assess the diaphragm contractile properties and the conduction time of the phrenic nerve (PNCT) through recording of an electromyographic response, traditionally by using surface electrodes. Because of the coactivation of extradiaphragmatic muscles, signal contamination can jeopardize the determination of surface PNCTs. To address this, we compared PNCTs with ES and CMS from surface and needle diaphragm electrodes in five subjects (10 phrenic nerves). At a modified recording site, lower and more anterior than usual (lowest accessible intercostal space, costochondral junction) with electrodes 2 cm apart, surface and needle PNCTs were similar (CMS: 6.0 +/- 0.25 ms surface vs. 6.2 +/- 0.13 ms needle, not significant). Electrodes recording the activity of the most likely sources of signal contamination, i.e., the serratus anterior and pectoralis major, showed distinct responses from that of the diaphragm, their earlier occurrence strongly arguing against contamination. With ES and CMS, apparently uncontaminated signals could be consistently recorded from surface electrodes. PMID:11842028

Verin, Eric; Straus, Christian; Demoule, Alexandre; Mialon, Philippe; Derenne, Jean-Philippe; Similowski, Thomas

2002-03-01

384

A low-cost approach for measuring electrical conductivity and relative permittivity of liquids by triangular waveform voltage at low frequencies  

Microsoft Academic Search

We present a novel low-cost experimental method for measuring the electrical conductivity and relative permittivity of liquids at low frequencies. Based on the different relationship between the resistive and capacitive currents with an applied voltage, the resistance and capacitance of fluid test cell can be obtained independently from different time regions of a triangular waveform voltage (TWV). The electrical conductivity

Jianping Wu; J. P. W. Stark

2005-01-01

385

Variability of electrode positions using electrode caps.  

PubMed

We investigated the variability of electrode positions for a multi-channel, custom electrode cap placed onto participants' heads without taking scalp measurements. The electrode positions were digitized in a three-dimensional space for 10 young adult participants on three separate occasions. Positional variability was determined for 15 selected electrodes within the three-dimensional preauricular-nasion (PAN) coordinate system and from this system, angular coordinate variability was also determined. The standard deviations of the 15 selected electrodes ranged from 3.0 to 12.7 mm in the PAN system. These data resulted in a variability of 2.0 degrees to 10.4 degrees among the angular coordinates. The measurements indicated slightly greater variability of electrode positions compared to studies when electrodes were placed using scalp measurements. The implication of this study is that the use of electrode caps may not be appropriate when electroencephalographic (EEG) or evoked potential (EP) techniques depend on accurate electrode placement. Additionally, if a longitudinal study is performed, electrode locations should be checked to ensure that they conform with previous sessions. PMID:17929157

Atcherson, Samuel R; Gould, Herbert Jay; Pousson, Monique A; Prout, Tina M

2007-10-11

386

Measurement of the neutral vapour density decay following the extinction of a high-current vacuum arc between copper electrodes  

Microsoft Academic Search

The decay of neutral copper vapour density which follows the extinction of a high current (2-11 kA) vacuum arc between copper electrodes has been measured. The results show that during the period 1-8 ms from current zero the vapour density decays at least an order of magnitude slower than expected on the assumption that vapour atoms generated by the arc

J. E. Jenkins; J. C. Sherman; R. Webster; R. Holmes

1975-01-01

387

Surface chemical activation of quartz crystal microbalance gold electrodes — analysis by frequency changes, contact angle measurements and grazing angle FTIR  

Microsoft Academic Search

A hydroxyalkanethiol, HS(CH2)12OH was deposited onto the gold electrodes of quartz crystal microbalances and gold-coated quartz microscope slides in order to aid in subsequent immobilization of antibodies. FTIR and contact angle measurements confirm the presence of thiol on the fresh gold substrates. In contrast, the change in frequency of the quartz crystal during thiol adsorption indicates an apparent decrease in

N. J. Geddes; E. M. Paschinger; D. N. Furlong; F. Caruso; C. L. Hoffmann; J. F. Rabolt

1995-01-01

388

Uncertainty of measurement for the determination of fluoride in water and wastewater by direct selective electrode potentiometry  

Microsoft Academic Search

A procedure to estimate the uncertainty of measurement applied to the fluoride determination of waters and wastewaters matrices\\u000a by selective electrode potentiometry was implemented based on Eurachem Guide. The major sources of uncertainty were identified\\u000a as the calibration standard solutions, fluoride concentration obtained by potential interpolation of the regression line and\\u000a the precision. However the relative uncertainties depend on the

Ana R. Sousa; Maria A. Trancoso

2005-01-01

389

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

2013-03-12

390

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

NASA Astrophysics Data System (ADS)

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

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

2008-10-01

391

[Evaluation of reports on environmental measurements of electromagnetic fields generated by high voltage transmission lines and substations].  

PubMed

This paper presents some situations, in which measurements of electromagnetic fields generated by transmission lines and substations should be performed. The range of measurements may differ, but maximum values of electric and magnetic fields and flux density must be identified in all situations. The area with electric field exceeding 1 kV/m should be identified as well. The author also presents basic requirements to be met by the measurement technique. These requirements are specified according to the national standard. Special attention should be paid to the identification of the spatial distribution of electric field and flux density generated in the vicinity of high voltage transmission lines. To verify the measurement results, it is necessary to calculate the distribution of both aforesaid field components. For environmental protection purposes, it is also proposed that the report should include measurements of electromagnetic fields of 50 Hz along with calculated results presented in tables and diagrams. PMID:17926507

Szuba, Marek

2007-01-01

392

Stabilizing the ferroelectric phase of KNO3 thin films using substrate electrodes  

NASA Astrophysics Data System (ADS)

In this study, polarization-voltage (P-V) and current density-voltage (J-V) measurements were utilized to investigate the effect of nickel (Ni), 304 austenitic stainless steel (SS) and tantalum (Ta) substrate electrodes on the ferroelectric phase stability of KNO3 thin films. P-V loops and J-V switching peaks were obtained to suggest the intriguing possibility of attaining ferroelectric phase stability in KNO3 films by means of an appropriate substrate electrode. SS substrate electrode stabilized the ferroelectric phase to room temperature (28 °C) while Ni substrate electrodes stabilized the phase close to room temperature. On the other hand, Ta substrate electrodes severely degraded the ferroelectric phase of the deposited films. A strong agreement was found between the appearance of the P-V hysteresis loop and the occurrence of the J-V switching peaks confirming polarization switching to be responsible for the observed ferroelectric properties exhibited by the thin film samples.

Donkor, M. K. E.; Boakye, F.; Nkum, R. K.; Britwum, A.

2012-11-01

393

Acetylene-argon plasmas measured at an rf-biased substrate electrode for diamond-like carbon deposition: II. Ion energy distributions  

Microsoft Academic Search

Ion energy distributions (IEDs) have been determined at the radio frequency (rf)-biased electrode in an inductively coupled acetylene-argon plasma for various substrate bias voltages and frequencies under conditions suitable for diamond-like carbon (DLC) and polymer-like film deposition. These are compared with those obtained at a capacitively coupled plasma grounded wall. In the former, for pressures <25 mTorr, the IEDs exhibit

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

2011-01-01

394

Wide-Range Threshold Voltage Controllable Silicon on Thin Buried Oxide Integrated with Bulk Complementary Metal Oxide Semiconductor Featuring Fully Silicided NiSi Gate Electrode  

NASA Astrophysics Data System (ADS)

A fully depleted silicon-on-insulator (FD SOI) device having an ultrathin buried oxide (BOX) with a 45-nm fully silicided (FUSI) NiSi gate, and a hybrid SOI/bulk complementary metal oxide semiconductor (CMOS) integration process have been developed. The optimal threshold voltage (Vth) for low stand-by power (LSTP) applications in FUSI gate silicon on thin BOX (SOTB) MOSFETs was achieved while keeping a lightly doped channel. By using back-gate bias, we have demonstrated the optimization of device power and performance and a reduction in Vth variation after device fabrication. We have also shown that the characteristics of the integrated hybrid bulk transistor are comparable to those of conventional bulk transistors.

Ishigaki, Takashi; Tsuchiya, Ryuta; Morita, Yusuke; Sugii, Nobuyuki; Kimura, Shinichiro; Iwamatsu, Toshiaki; Ipposhi, Takashi; Inoue, Yasuo; Hiramoto, Toshiro

2008-04-01

395

Two components of voltage-dependent calcium influx in mouse neuroblastoma cells. Measurement with arsenazo III  

PubMed Central

N1E-115 mouse neuroblastoma cells were injected with the calcium indicator dye arsenazo III. Optical absorbance changes during voltage- clamp depolarization were used to examine the properties of the two calcium currents present in these cells. The rapidly inactivating calcium current (Moolenar and Spector, 1979b, Journal of Physiology, 292:307-323) inactivates by a voltage-dependent mechanism. The slowly inactivating calcium current is dominant in raising intracellular calcium during depolarizations to greater than -20 mV. Lowering the extracellular calcium concentration affects the two calcium currents unequally, with the slowly inactivating current being reduced more. Intracellular calcium falls very slowly (tau greater than 1 min) after a depolarization. The rapidly inactivating calcium current is responsible for a calcium action potential under physiological conditions. In contrast, it is unlikely that the slowly inactivating calcium current has an important electrical role. Rather, its function may be to add a further increment of calcium influx over and above the calcium influx through the rapidly inactivating calcium channels.

1986-01-01

396

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

397

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

398

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

399

Design considerations for optimum impedance probes with planar electrodes for bioimpedance measurements  

Microsoft Academic Search

This paper describes the key issues for designing optimum impedance probes for bioimpedance monitoring. The geometrical specification of a silicon-based probe is described and experimental obtained results are also reported. A new model for probes with non-constant inter-electrode distance is also analyzed

A. Ivorra; J. Aguilo; J. Millan

2001-01-01

400

Selective ion electrode measurements of chloride concentrations in the determination of cation exchange capacities of soils  

Microsoft Academic Search

The determination of chloride ion in soil extracts for cation exchange capacity in the presence of ammonium ions of nearly equal concentration (5 x 10 M) and excess sodium sulphate (0.5 M) by an Orion solid state selective ion electrode is reported. Ammonium ions were found to interfere by reducing the determined value of the chloride ion by up to

R. St. C. Smart; A. D. Thomas; D. P. Drover

1974-01-01

401

Change in open-circuit voltage of rechargeable cells based on silver (II) oxide and cadmium during storage in the charged state  

Microsoft Academic Search

During storage in the charged state, chemical sources of current undergo profound changes, with consequent changes in the open-circuit voltage (OCV), capacity, voltage, etc. The authors will examine the effects of storage of initially charged SKG-15 rechargable cells in terms of changes in the OCV and individual electrode potentials. The potential measurements were performed by means of an R-379 potentiometer

V. K. Kleshchuk

1992-01-01

402

High-Voltage Testing and Measuring Techniques On-site Including Condition Monitoring and Diagnostics. Application of Digital Techniques in High-Voltage Testing. Post Graduate Seminar of High-voltage Engineering S-18.148. Held in Sjoekulla, Finland on October 13, 1999.  

National Technical Information Service (NTIS)

Contents: High-voltage insulation co-ordination; Computer assisted evalution of test results of HV power transformers; Computer assisted evaluation of test results partial discharges measurements; On-site tests and insulation assessment of HV power and in...

M. Aro

1999-01-01

403

Process for measuring degradation of sulfur hexafluoride in high voltage systems  

DOEpatents

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

Sauers, I.

1985-04-23

404

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

405

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

PubMed

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

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

2008-09-01

406

Fabrication of amperometric electrodes.  

PubMed

Carbon fiber electrodes are crucial for the detection of catecholamine release from vesicles in single cells for amperometry measurements. Here, we describe the techniques needed to generate low noise (<0.5 pA) electrodes. The techniques have been modified from published descriptions by previous researchers (1,2). Electrodes are made by preparing carbon fibers and threading them individually into each capillary tube by using a vacuum with a filter to aspirate the fiber. Next, the capillary tube with fiber is pulled by an electrode puller, creating two halves, each with a fine-pointed tip. The electrodes are dipped in hot, liquid epoxy mixed with hardener to create an epoxy-glass seal. Lastly, the electrodes are placed in an oven to cure the epoxy. Careful handling of the electrodes is critical to ensure that they are made consistently and without damage. This protocol shows how to fabricate and cut amperometric electrodes for recording from single cells. PMID:19415069

Pike, Carolyn M; Grabner, Chad P; Harkins, Amy B

2009-05-04

407

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:23969948

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

2013-08-23

408

Measurement of axonal membrane conductances and capacity by means of a varying potential control voltage clamp.  

PubMed

A new mode of voltage clamping in the squid giant axon is introduced and its advantages are analyzed, tested, and utilized to investigate membrane conductances and capacity. This method replaces the constant command potentials of the standard voltage clamp with potentials which vary with time. Some of the advantages in using the varying potential clamp are: (1) slowly varying potentials generate practically pureI K ; (2) rapidly varying potentials generate practically pureI Na; (3) triangular waves generate, under proper conditions, pure capacity currents and easy-to-analyze leakage currents; (4) the method gives direct, on-line display of sodium or potassium I-V characteristics within milliseconds; (5) it enables rapid and accurateE Na andE K determinations; and (6) it enables simple and accurate determination ofC m. The method was utilized to study the effects of various ions on membrane conductances and the effects of ionic composition, ionic strength, and temperature on membrane capacity. Membrane capacity was found to be practically independent of frequency in the 200 to 2,000 Hz range. Replacement of external sodium by Ca(++), by impermeable Tris(+), or even by dextrose or sucrose (low ionic-strength solutions) had negligible effects onC m.C m showed a small, positive temperature coefficient of 1.39% per °C in the 3 to 21°C range, and little change with temperature in the 20 to 40°C range. Above 40°C, bothC m andg L increased considerably with temperature. PMID:24174059

Palti, Y; Adelman, W J

1969-12-01

409

Change in open-circuit voltage of rechargeable cells based on silver (II) oxide and cadmium during storage in the charged state  

SciTech Connect

During storage in the charged state, chemical sources of current undergo profound changes, with consequent changes in the open-circuit voltage (OCV), capacity, voltage, etc. The authors will examine the effects of storage of initially charged SKG-15 rechargable cells in terms of changes in the OCV and individual electrode potentials. The potential measurements were performed by means of an R-379 potentiometer with an accuracy of {+-}0.01 mV. The reproducibility of measurements of individual electrode potentials was poorer ({+-}0.05 mV), which is explained by nonuniformity in the oxidation of different sections of the electrode surfaces. 7 refs., 3 figs., 3 tabs.

Kleshchuk, V.K.; Nikol`skii, V.A.

1992-06-20

410

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

PubMed

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

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

2013-05-25

411

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

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

412

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

NASA Astrophysics Data System (ADS)

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

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

2009-03-01

413

Measurement of the amount of liquid and vapour created by an electric arc on an electrode - case of Ag and AgSnO2 electrodes  

Microsoft Academic Search

In this paper an original experimental device is presented. It allowed to obtain, for the first time, the total amount of liquid and vapour of metal created on the electrode surface by a non stationary electric arc (600 A\\/20 ms) burning in air at atmospheric pressure. The results are presented for two different materials Ag and AgSnO2 and for electrode

Ph. Teste; R. Andlauer; T. Leblanc

2011-01-01

414

A feedback pulse-lengthener circuit for the peak voltage measurement of a single shot pulse as narrow as 2.5 nsec  

Microsoft Academic Search

A circuit capable of measuring the peak voltage of a single shot pulse as narrow as 2.5 nsec is described. The circuit uses a pulse-lengthener circuit that has an amplifier in its negative feedback path. The amplifier reduces the charging time constant of the pulse-lengthener circuit to improve its speed capability. The measurable peak voltage of a single shot pulse

Masami Uno; Ryuichi Koike

1974-01-01

415

Trace measurements of plasmid DNAs by adsorptive stripping potentiometry at carbon paste electrodes  

Microsoft Academic Search

Supercoiled, linear and denatured forms of plasmid pUC19 DNA can be adsorbed at carbon paste (CPE) and pyrolytic graphite (PGE) electrodes and detected by constant current chronopotentiometric stripping analysis (PSA) at low bulk concentrations. The determination is based on the PSA peak at about 1.0 V (against Ag|AgCl) due to the oxidation of guanine residues in the DNA. In agreement

Xiaohua Cai; Gustavo Rivas; Percio A. M. Farias; Haruki Shiraishi; Joseph Wang; Miroslav Fojta; Emil Pale?ek

1996-01-01

416

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

417

Traceability and Mutual Recognizability of Impulse Voltage Measurements. Report of Results of First Round.  

National Technical Information Service (NTIS)

This report presents the results of the first round of a worldwide international lightning impulse comparison measurement. Five laboratories out of 27 made the comparison measurements on the first round; results were received from four and they are presen...

J. Haellstroem M. Aro

2001-01-01

418

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

419

Electrode Potentials of a Silver-Silver Chloride Electrode vs. Temperature for Biosensors  

NASA Astrophysics Data System (ADS)

The aim of this study is to make clear the effect of temperature on the potentials of silver-silver chloride(Ag-AgCl) electrodes in potassium chloride(KCl) and sodium chloride(NaCl) solutions for micro biosensor applications. Non-isothermal coefficients, or thermal coefficient of Ag-AgCl electrodes in the concentrations of 0.1 to 1.0[mol/kg] were experimentally measured in the range of 15 to 45[°C]. The electrode was prepared by electrolytical process in KCl or NaCl solutions. The length and diameter of the electrode are 20[mm] and 3[mm], respectively. The coefficients in KCl solutions were 0.42[mV/°C] in 0.1[mol/kg] and 0.26[mV/°C] in 1.0[mol/kg] and almost the same in NaCl solutions. Isothermal coefficients were also measured. Although the coefficients must theoretically be zero by definition for all temperatures, the difference of potentials between a pair of electrodes which is called as offset voltage appears practically. They were 3?4[?V/°C] in 0.1[mol/kg] and 0.3[?V/°C] in 1[mol/kg] at the steady state of temperature. The values were depending on the degree of the uniformity of electrode surface.

Dendo, Isao; Seki, Kana

420

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

421

VOLTAMMETRIC MEMBRANE CHLORINE DIOXIDE ELECTRODE  

EPA Science Inventory

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

422

Blotting with plate electrodes.  

PubMed

Since its introduction by Towbin et al. (1), electro-blotting has become one of the most valuable analytical procedures in protein research. Conventionally, the gel and the immobilizing matrix are sandwiched between porous pads and inserted between two electrodes in a buffer tank. Electrodes of platinum wire are mounted in such a way that, with a minimum amount of material, they still generate a uniform electrical field in the center of the buffer chamber, with the minimum amount of material. On the other hand, transfer efficiency is largely dependent of the voltage gradient between the two electrodes. High voltages generate high currents and high temperatures, whereas reducing the distance between wire electrodes seriously disturbs the electrical field (2). Plate electrodes yield essentially homogeneous electrical fields, even when they are moved close together. Vaessen et al. (3) were the first to experiment with plate electrodes. Kyhse-Andersen (4) introduced horizontal semidry blotting in which the transfer takes place in a stack of buffer-saturated filter papers, inserted between two graphite plates. PMID:21400178

Peferoen, M

1988-01-01

423

Measuring neural coupling from non-Gaussian power spectra of voltage traces taken from awake behaving animals  

NASA Astrophysics Data System (ADS)

Brains consist of complex networks of neurons possessing highly non-linear interactions, suggesting that neural systems will show cooperative dynamics. Previous studies of the non-Gaussian statistics of 1/f noise in spin glasses and amorphous semiconductors have revealed important information concerning interaction kinetics not available through other techniques. Five male Brown-Norway-Cross rats were chronically implanted with arrays of microwire electrodes from which local field potentials (LFPs) were recorded from the dorsocentral striatum as the animals performed complex navigational tasks. The power spectra displayed a frequency dependence significantly different from 1/f. The correlation coefficients of the Fourier transform of the LFPs from striatum showed significant non-zero correlations between frequencies separated by less than three octaves. This novel technique may be useful in measuring functional interactions in neural systems.

Masimore, Beth; Kakalios, James; Redish, A. David

2003-05-01

424

Use of an iridium electrode for direct measurements of pI of proteins after isoelectric focusing in polyacrylamide gel.  

PubMed

The use of an iridium microelectrode 0.5 mm in diameter is proposed for measuring the pH gradient in polyacrylamide gels after isoelectric focusing. The electrode exhibits a perfectly linear potential/pH relationship; thus it can be used directly in conjunction with a pH meter using the pH scale for readings. pH equilibrium values are rapidly reached (10-15 s) and pI determinations are obtainable with good accuracy (better than 0.1 pH). PMID:11823

Papeschi, G; Bordi, S; Beni, C; Ventura, L

1976-11-26

425

Simple PVC-PPy electrode for pH measurement and titrations  

Microsoft Academic Search

Cobaltabis(dicarbollide) [3,3'-Co(1,2-C2B9H11)]--doped polypyrrole (PPy) films have been prepared galvanostatically on glassy carbon electrodes in acetonitrile solution. The potential response behavior of the film of this new material has been investigated in some common pH buffers and in acid-base titrations. The potentiometric characteristics of the resulting films are indicative of a quasi-Nernstian response (approximately 50 mV\\/pH unit), a linearity range from

C. Masalles; S. Borrós; C. Viñas; F. Teixidor

2002-01-01

426

Effect of Surface Charge Control on DC Corona Onset Voltages  

NASA Astrophysics Data System (ADS)

A dielectric disc with a thickness of 0.1 cm placed on the plane electrode in a rod to plane room air gap of 2 cm long is charged by DC corona discharges with the positive and negative polarities. The dielectric discs made of acryl PMMA have six kinds of radii from 2 to 16 cm. The surface potentials induced from the accumulated surface charges are measured by a vibrating capaciting voltage meter which can be controlled in the direction of X and Y, and the effect of surface potential on the corona onset voltage is also investigated from both the laser-induced measurement of electric field and the theoretical calculation of surface potential and electric field. In order to make clear the effect of surface charge on the corona onset voltage under the same gap condition, we measure the onset voltage by using the applied voltage of same or inversed polarity to the polarity of surface charge just after the charge deposition was achieved on the dielectric disc. In the case of same polarity, the corona onset voltages increase with increasing the amount of surface charge. However, in the case of inverse polarity the corona onset voltages remarkably decrease in increase of the amount of the charge and are much lower than those without the surface charge. Also, it is surprising that in spite of short gap length 2 cm, the charging area spreads more than that with a radius of 16 cm around the disc center.

Nishijima, Kiyoto; Furuie, Shigemasa; Izawa, Yasuji

427

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

NASA Astrophysics Data System (ADS)

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

Singh, S.; Pandey, A.

2013-05-01

428

Ignition of a welding arc during a short-circuit of melted electrodes  

NASA Astrophysics Data System (ADS)

It is shown that an arc discharge in a welding process with fusible electrodes (gas-metal arc welding) starts before a short-circuit bridge, made by a metal drop between the electrodes, is broken. The possibility of this premature ignition is proved by voltage and current measurements, by analysis of the electrical field near the neck of the drop and also by simulation of the increase in current in an electrical discharge.

Hajossy, R.; Pastva, P.; Morva, I.

1999-05-01

429

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

NASA Astrophysics Data System (ADS)

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.

2011-06-01

430

Radio frequency glow discharge source with integrated voltage and current probes used for sputtering rate and emission yield measurements at insulating samples.  

PubMed

Radio frequency glow discharge optical emission spectroscopy (RF-GD-OES) is routinely used for the chemical analysis of solid samples. Two independent electrical signals from the discharge are required for quantification. When sputtering insulating samples, the voltage over the discharge is not directly measurable. The coupling capacity of the sample is required in order to calculate the discharge voltage. A procedure is outlined where the coupling capacity is determined using an electrical measurement without discharge. The calculated time-dependent discharge voltage and current are evaluated using a plasma equivalent circuit. An insulating sample is sputtered at constant cathode voltage and current. The emission yield for an aluminium line is comparable to that of conducting reference material. PMID:15952004

Wilken, L; Hoffmann, V; Wetzig, K

2005-10-19

431

Accurate on wafer measurement of phase and amplitude of the spectral components of incident and scattered voltage waves at the signal ports of a nonlinear microwave device  

Microsoft Academic Search

A measurement setup and calibration procedure are described allowing the accurate on wafer measurement of phases and amplitudes of the spectral components of incident and scattered voltage waves at the signal ports of a nonlinear microwave device. A comparison is made between measurements performed with the setup and simulations based on a Root-model

Jan Verspecht; Peter Debie; Alain Barel; Luc Martens

1995-01-01

432

Electrode polarization measurements in the Fe|SrCe 0.95Yb 0.05O 2.975|Au proton conducting solid electrolyte cell  

Microsoft Academic Search

The effect of hydrogen partial pressure (1.3–5.8 kPa) and cell temperature (600–800 °C) on the kinetics and mechanism of the charge transfer electrode reaction taking place at the three phase boundary H2–Fe–SCY (SCY=SrCe0.95Yb0.05O2.975), was thoroughly examined by performing electrode polarization measurements. A three electrode single chamber proton conducting solid electrolyte cell of the type Fe–SCY–Au, was used in order to conduct the

G. Pekridis; K. Kalimeri; N. Kaklidis; C. Athanasiou; G. Marnellos

2007-01-01

433

Excitatory Amino Acid Regulation of Intracellular Ca*+ in Isolated Catfish Cone Horizontal Cells Measured under Voltage and Concentration-Clamp Conditions  

Microsoft Academic Search

(Ca2+li was measured using fura-*-loaded isolated catfish horizontal cells in the presence of L-glutamate and the glu- tamate analogs kainate (KA), quisqualate (QA), and NMDA. Caffeine was used to release Ca*+ from intracellular stores. Cell membrane potential was controlled with a voltage clamp to prevent activation of voltage-dependent Ca2+ channels in the presence of agonist. All excitatory amino acid agonists

C. P. Linn; B. N. Christensen

1992-01-01

434

Sensitive Enzyme Electrodes  

Microsoft Academic Search

Conventional enzyme electrodes are relatively insensitive devices capable of measuring analytes in the micromolar range. Inhibited enzyme electrodes work by measuring the inhibition of an enzyme turning over undersaturated conditions. This increased turnover gives greater sensitivity. The detection limits are controlled either by the thermodynamic amplitude or by the kinetic discrimination. Software has been developed to analyse the current time

W. John Albery; Martyn G. Boutelle; Sally L. T. Durrant; Marrianne Fillenz; Andrew R. Hopkins; Bernard P. Mangold

1990-01-01

435

Investigation of impurities in type-II InAs/GaSb superlattices via capacitance-voltage measurement  

NASA Astrophysics Data System (ADS)

Capacitance-voltage measurement was utilized to characterize impurities in the non-intentionally doped region of Type-II InAs/GaSb superlattice p-i-n photodiodes. Ionized carrier concentration versus temperature dependence revealed the presence of a kind of defects with activation energy below 6 meV and a total concentration of low 1015 cm-3. Correlation between defect characteristics and superlattice designs was studied. The defects exhibited a p-type behavior with decreasing activation energy as the InAs thickness increased from 7 to 11 monolayers, while maintaining the GaSb thickness of 7 monolayers. With 13 monolayers of InAs, the superlattice became n-type and the activation energy deviated from the p-type trend.

Chen, G.; Hoang, A. M.; Bogdanov, S.; Haddadi, A.; Bijjam, P. R.; Nguyen, B.-M.; Razeghi, M.

2013-07-01

436

Measurement of the amount of liquid and vapour created by an electric arc on an electrode - case of Ag and AgSnO2 electrodes  

NASA Astrophysics Data System (ADS)

In this paper an original experimental device is presented. It allowed to obtain, for the first time, the total amount of liquid and vapour of metal created on the electrode surface by a non stationary electric arc (600 A/20 ms) burning in air at atmospheric pressure. The results are presented for two different materials Ag and AgSnO2 and for electrode gap values in the range 1-10 mm. The amount of liquid and vapour created under the arc action is compared with usual erosion rate in the same experimental conditions. In the case of Ag electrodes the amount of liquid metal created on the anode may be 3 to 5 times higher than on the cathode although the usual erosion rates are more important at the cathode. For the anode, the usual erosion may represent a very low percentage (<10%) of the total amount of metal liquid created showing then that a very small part of the liquid created during the arc is ejected. In the case of AgSnO2 electrodes the amount of liquid metal is smaller. The usual erosion rates at the cathode are higher than for the anode and the usual erosion represent 10 to 50% of the amount of liquid and vapour created.

Teste, Ph.; Andlauer, R.; Leblanc, T.

2011-07-01

437

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

National Technical Information Service (NTIS)

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

M. Held

1972-01-01

438

An on-chip NBTI sensor for measuring PMOS threshold voltage degradation  

Microsoft Academic Search

Negative Bias Temperature Instability (NBTI) is one of the most critical device reliability issues facing scaled CMOS technology. In order to better understand the characteristics of this mechanism, accurate and efficient means of measuring its effects must be explored. In this work, we describe an on-chip NBTI degradation sensor using two delay-locked loops (DLL). The increase in PMOS transistor threshold

John Keane; Tae-hyoung Kim; Chris H. Kim

2007-01-01

439

Reticle programmed defect size measurement using low-voltage SEM and pattern recognition techniques  

Microsoft Academic Search

The use of programmed defect test reticles to characterize automatic defect inspection equipment has long been an established practice in the maskmaking industry. Measurement