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1

Continuous-function ground conductivity model for the determination of electric railway earth conductance  

SciTech Connect

A method is described for the determination of ground conductivity as a continuous function of depth and frequency for applications along spatially linear structures such as railway tracks. The technique involves measurements of mutual resistance using a modified dipole array excited with AC currents up to audio frequency. After representation of the experimental data by analytic functions, the ground conductivity-depth variation is obtained as a degenerate hypergeometric function. The determined ground conductivity is utilized to model the self and mutual conductance of and between the running rails in a single-track railway. The result is verified by experimental measurement.

Carpenter, D.C. (Vector Fields Ltd., Kidlington, Oxford (United Kingdom)); Hill, R.J. (Univ. of Bath, Claverton Down (United Kingdom). School of Electronic and Electrical Engineering)

1993-09-01

2

Electrical Conductivity.  

ERIC Educational Resources Information Center

Explains how electrical conductivity (EC) can be used to measure ion concentration in solutions. Describes instrumentation for the measurement, temperature dependence and EC, and the EC of common substances. (PR)

Hershey, David R.; Sand, Susan

1993-01-01

3

Electrical Conductivity Protocol  

NSDL National Science Digital Library

The purpose of this resource is to measure the conductivity of water at a freshwater hydrology site. Students calibrate and take electrical conductivity measurements using an electrical conductivity meter. Students estimate the total dissolved solids from the electrical conductivity measurements.

The GLOBE Program, UCAR (University Corporation for Atmospheric Research)

2003-08-01

4

Electrically continuous graphene from single crystal copper verified by terahertz conductance spectroscopy and micro four-point probe.  

PubMed

The electrical performance of graphene synthesized by chemical vapor deposition and transferred to insulating surfaces may be compromised by extended defects, including for instance grain boundaries, cracks, wrinkles, and tears. In this study, we experimentally investigate and compare the nano- and microscale electrical continuity of single layer graphene grown on centimeter-sized single crystal copper with that of previously studied graphene films, grown on commercially available copper foil, after transfer to SiO2 surfaces. The electrical continuity of the graphene films is analyzed using two noninvasive conductance characterization methods: ultrabroadband terahertz time-domain spectroscopy and micro four-point probe, which probe the electrical properties of the graphene film on different length scales, 100 nm and 10 ?m, respectively. Ultrabroadband terahertz time-domain spectroscopy allows for measurement of the complex conductance response in the frequency range 1-15 terahertz, covering the entire intraband conductance spectrum, and reveals that the conductance response for the graphene grown on single crystalline copper intimately follows the Drude model for a barrier-free conductor. In contrast, the graphene grown on commercial copper foil shows a distinctly non-Drude conductance spectrum that is better described by the Drude-Smith model, which incorporates the effect of preferential carrier backscattering associated with extended, electronic barriers with a typical separation on the order of 100 nm. Micro four-point probe resistance values measured on graphene grown on single crystalline copper in two different voltage-current configurations show close agreement with the expected distributions for a continuous 2D conductor, in contrast with previous observations on graphene grown on commercial copper foil. The terahertz and micro four-point probe conductance values of the graphene grown on single crystalline copper shows a close to unity correlation, in contrast with those of the graphene grown on commercial copper foil, which we explain by the absence of extended defects on the microscale in CVD graphene grown on single crystalline copper. The presented results demonstrate that the graphene grown on single crystal copper is electrically continuous on the nanoscopic, microscopic, as well as intermediate length scales. PMID:25317778

Buron, Jonas D; Pizzocchero, Filippo; Jessen, Bjarke S; Booth, Timothy J; Nielsen, Peter F; Hansen, Ole; Hilke, Michael; Whiteway, Eric; Jepsen, Peter U; Bøggild, Peter; Petersen, Dirch H

2014-11-12

5

Electrically conductive cellulose composite  

DOEpatents

An electrically conductive cellulose composite includes a cellulose matrix and an electrically conductive carbonaceous material incorporated into the cellulose matrix. The electrical conductivity of the cellulose composite is at least 10 .mu.S/cm at 25.degree. C. The composite can be made by incorporating the electrically conductive carbonaceous material into a culture medium with a cellulose-producing organism, such as Gluconoacetobacter hansenii. The composites can be used to form electrodes, such as for use in membrane electrode assemblies for fuel cells.

Evans, Barbara R.; O'Neill, Hugh M.; Woodward, Jonathan

2010-05-04

6

Polymers that Conduct Electricity.  

ERIC Educational Resources Information Center

Although polymers are regarded as electrical insulators, it was discovered that they can be made to conduct electricity. This discovery has opened vast new practical and theoretical areas for exploration by physicists and chemists. Research studies with these conducting polymers and charge-transfer salts as well as possible applications are…

Edelson, Edward

1983-01-01

7

Electrically conductive composite material  

DOEpatents

An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistant pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like.

Clough, Roger L. (Albuquerque, NM); Sylwester, Alan P. (Albuquerque, NM)

1989-01-01

8

Electrically conductive composite material  

DOEpatents

An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistent pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like. 2 figs.

Clough, R.L.; Sylwester, A.P.

1989-05-23

9

Electrical Conduction Activity  

NSDL National Science Digital Library

This resource provides an introductory activity on electrical conduction. As the module states, "electrical conduction, the movement of electrical charges, is a mechanism for passing energy and signals from one place to another." The activity covers concepts such as insulators, conductors, semiconductors, superconductors, and ballistic conduction at nanoscale. This module allows students to test their knowledge as they go. Although a preview of the activity is available, instructors and students are encouraged to sign up with the Electron Technologies site before starting to use these materials.

10

Electrically conductive material  

DOEpatents

An electrically conductive material for use in solid oxide fuel cells, electrochemical sensors for combustion exhaust, and various other applications possesses increased fracture toughness over available materials, while affording the same electrical conductivity. One embodiment of the sintered electrically conductive material consists essentially of cubic ZrO.sub.2 as a matrix and 6-19 wt. % monoclinic ZrO.sub.2 formed from particles having an average size equal to or greater than about 0.23 microns. Another embodiment of the electrically conductive material consists essentially at cubic ZrO.sub.2 as a matrix and 10-30 wt. % partially stabilized zirconia (PSZ) formed from particles having an average size of approximately 3 microns.

Singh, Jitendra P. (Bollingbrook, IL); Bosak, Andrea L. (Burnam, IL); McPheeters, Charles C. (Woodridge, IL); Dees, Dennis W. (Woodridge, IL)

1993-01-01

11

Electrically conductive material  

DOEpatents

An electrically conductive material is described for use in solid oxide fuel cells, electrochemical sensors for combustion exhaust, and various other applications possesses increased fracture toughness over available materials, while affording the same electrical conductivity. One embodiment of the sintered electrically conductive material consists essentially of cubic ZrO[sub 2] as a matrix and 6-19 wt. % monoclinic ZrO[sub 2] formed from particles having an average size equal to or greater than about 0.23 microns. Another embodiment of the electrically conductive material consists essentially at cubic ZrO[sub 2] as a matrix and 10-30 wt. % partially stabilized zirconia (PSZ) formed from particles having an average size of approximately 3 microns. 8 figures.

Singh, J.P.; Bosak, A.L.; McPheeters, C.C.; Dees, D.W.

1993-09-07

12

Electrically conductive ceramic powders  

NASA Astrophysics Data System (ADS)

Electrically conductive ceramic powders were investigated in this project. There are three ways to produce those materials. The first is doping alkali metal into the titanium dioxides in an inert or reducing atmosphere. The second is reducing un-doped titanium dioxide, forming a non-stoichiometric composition in a hydrogen atmosphere. The third is to coat a conductive layer, reduced titanium dioxide, on an insulating core such as alumina. Highly conductive powders have been produced by all these processes. The conductivity of powder compacts ranged between 10-2 and 10° S/cm. A novel doping process was developed. All samples were doped by a solid-vapor reaction instead of a solid state reaction. Titanium dioxide was doped with alkali metals such as Na or Li in this study. The alkali metal atom contributes an electron to the host material (TiO2), which then creates Ti 3+ ion. The conductivity was enhanced by creating the donor level due to the presence of these Ti3+ ions. The conductivity of those alkali doped titanium oxides was dependent on the doping level and charge mobility. Non-stoichiometric titanium oxides were produced by reduction of titanium dioxide in a hydrogen atmosphere at 800°C to 1000°C for 2 to 6 hours. The reduced titanium oxides showed better stability with respect to conductivity at ambient condition when compared with the Na or Li doped samples. Conductive coatings were prepared by coating titanium precursors on insulating core materials like SiO2, Al2O3 or mica. The titania coating was made by hydrolysis of titanyl sulfate (TiOSO 4) followed by a reduction procedure to form reduced titanium oxide. The reduced titanium oxides are highly conductive. A uniform coating of titanium oxides on alumina cores was successfully produced. The conductivity of coated powder composites was a function of coating quantity and hydrolysis reaction temperature. The conductivity of the powder as a function of structure, composition, temperature, frequency and moisture was studied. Three classifications of structure were identified for alkali-doped titanium oxides: (1) Pure titanium dioxide phase with alkali ions located in interstitial positions. (2) The titanium bronze phases. (3) Alkali-doped titanium oxides. Highly conductive powders were obtained in the first and second classifications with conductivity of 10-2 to 10° S/cm. Materials in the third classification had poor conductivity below 10-3 S/cm. The conductivity of a powder was determined mainly by the grain conductivity and the grain contact conductivity. The present results of impedance spectroscopy suggested that the grain contact resistance was a major factor of the electrical resistance of the samples. The aging effect at different moisture conditions was also caused by an increase of the contact resistance. Both sodium-doped and reduced titanium oxides showed re-oxidation at elevated temperature (above 140°C) in air, which is most probably caused by oxidizing the Ti3+ ions under those conditions. Lithium doped titanium oxides did not show this re-oxidation at temperatures up to 200°C. Theoretical models were applied to describe the effects of porosity, contact configuration and grain surface on conductivity of powder compacts. Percolation theory was used in the present study to demonstrate the effect of mixtures of conductive and non-conductive powders, which is one of applications for conductive ceramic powders when they are used as filler materials in paper, paints or plastics.

Lu, Yanxia

1999-11-01

13

Dynamics of electrically conducting fluids  

NASA Astrophysics Data System (ADS)

Electrically conducting fluids are described by the magneto-hydrodynamic (MHD) formalism that combines the classical laws of fluid mechanics and electromagnetism. After a brief review of this formalism, several examples of electrically conducting fluids will be discussed. For instance, liquid metal flows are important in several industrial applications including the steel industry as well as in the description of geophysical flows and laboratory experiments on the dynamo effect. Also, plasmas represent an important class of electrically conductive fluids when they are treated in the limit of continuous media. Plasma physics is relevant in the study of various astrophysical systems as well as in laboratory experiments on magnetic confinement fusion. The importance of MHD effects for the ITER (International Thermonuclear Experimental Reactor) experiment will also be briefly discussed. Numerical simulations of the MHD equations play an increasingly important role in the description of electrically conducting fluids. Recent numerical results will be presented and MHD turbulence will be analyzed in terms of energy transfers, locality functions as well as sub-grid scale modeling in large eddy simulations.

Carati, Daniele

2010-11-01

14

Electrically Conductive Porous Membrane  

NASA Technical Reports Server (NTRS)

The present invention relates to an electrically conductive membrane that can be configured to be used in fuel cell systems to act as a hydrophilic water separator internal to the fuel cell, or as a water separator used with water vapor fed electrolysis cells, or as a water separator used with water vapor fed electrolysis cells, or as a capillary structure in a thin head pipe evaporator, or as a hydrophobic gas diffusion layer covering the fuel cell electrode surface in a fuel cell.

Burke, Kenneth Alan (Inventor)

2014-01-01

15

Electrically conductive anodized aluminum coatings  

NASA Technical Reports Server (NTRS)

A process for producing anodized aluminum with enhanced electrical conductivity, comprising anodic oxidation of aluminum alloy substrate, electrolytic deposition of a small amount of metal into the pores of the anodized aluminum, and electrolytic anodic deposition of an electrically conductive oxide, including manganese dioxide, into the pores containing the metal deposit; and the product produced by the process.

Alwitt, Robert S. (Inventor); Liu, Yanming (Inventor)

2001-01-01

16

Electrically Conductive Anodized Aluminum Surfaces  

NASA Technical Reports Server (NTRS)

Anodized aluminum components can be treated to make them sufficiently electrically conductive to suppress discharges of static electricity. The treatment was conceived as a means of preventing static electric discharges on exterior satin-anodized aluminum (SAA) surfaces of spacecraft without adversely affecting the thermal-control/optical properties of the SAA and without need to apply electrically conductive paints, which eventually peel off in the harsh environment of outer space. The treatment can also be used to impart electrical conductivity to anodized housings of computers, medical electronic instruments, telephoneexchange equipment, and other terrestrial electronic equipment vulnerable to electrostatic discharge. The electrical resistivity of a typical anodized aluminum surface layer lies between 10(exp 11) and 10(exp 13) Omega-cm. To suppress electrostatic discharge, it is necessary to reduce the electrical resistivity significantly - preferably to < or = 10(exp 9) Omega-cm. The present treatment does this. The treatment is a direct electrodeposition process in which the outer anodized surface becomes covered and the pores in the surface filled with a transparent, electrically conductive metal oxide nanocomposite. Filling the pores with the nanocomposite reduces the transverse electrical resistivity and, in the original intended outer-space application, the exterior covering portion of the nanocomposite would afford the requisite electrical contact with the outer-space plasma. The electrical resistivity of the nanocomposite can be tailored to a value between 10(exp 7) and 10(exp 12) Omega-cm. Unlike electrically conductive paint, the nanocomposite becomes an integral part of the anodized aluminum substrate, without need for adhesive bonding material and without risk of subsequent peeling. The electrodeposition process is compatible with commercial anodizing production lines. At present, the electronics industry uses expensive, exotic, electrostaticdischarge- suppressing finishes: examples include silver impregnated anodized, black electroless nickel, black chrome, and black copper. In comparison with these competing finishes, the present nanocomposite finishes are expected to cost 50 to 20 percent less and to last longer.

Nguyen, Trung Hung

2006-01-01

17

Electrical conductivity of compressed argon  

SciTech Connect

The authors report calculations of the electrical conductivity of solid argon as a function of compression within the density functional local density approximation formulation for a norm-conserving pseudopotential using both electron-phonon coupling and molecular dynamics techniques.

Bauer, R. [Univ. Regensburg (Germany); Windl, W.; Collins, L.; Kress, J.; Kwon, I. [Los Alamos National Lab., NM (United States)

1997-10-01

18

Calibration-free electrical conductivity measurements for highly conductive slags  

SciTech Connect

This research involves the measurement of the electrical conductivity (K) for the ESR (electroslag remelting) slag (60 wt.% CaF{sub 2} - 20 wt.% CaO - 20 wt.% Al{sub 2}O{sub 3}) used in the decontamination of radioactive stainless steel. The electrical conductivity is measured with an improved high-accuracy-height-differential technique that requires no calibration. This method consists of making continuous AC impedance measurements over several successive depth increments of the coaxial cylindrical electrodes in the ESR slag. The electrical conductivity is then calculated from the slope of the plot of inverse impedance versus the depth of the electrodes in the slag. The improvements on the existing technique include an increased electrochemical cell geometry and the capability of measuring high precision depth increments and the associated impedances. These improvements allow this technique to be used for measuring the electrical conductivity of highly conductive slags such as the ESR slag. The volatilization rate and the volatile species of the ESR slag measured through thermogravimetric (TG) and mass spectroscopy analysis, respectively, reveal that the ESR slag composition essentially remains the same throughout the electrical conductivity experiments.

MACDONALD,CHRISTOPHER J.; GAO,HUANG; PAL,UDAY B.; VAN DEN AVYLE,JAMES A.; MELGAARD,DAVID K.

2000-05-01

19

Electrically conductive polymer concrete coatings  

DOEpatents

A sprayable electrically conductive polymer concrete coating for vertical d overhead applications is described. The coating is permeable yet has low electrical resistivity (<10 ohm-cm), good bond strength to concrete substrates, and good weatherability. A preferred formulation contains about 60 wt % calcined coke breeze, 40 wt % vinyl ester with 3.5 wt % modified bentonite clay. Such formulations apply evenly and provide enough rigidity for vertical or overhead structures so there is no drip or sag.

Fontana, J.J.; Elling, D.; Reams, W.

1990-03-13

20

Electrically conductive polymer concrete coatings  

DOEpatents

A sprayable electrically conductive polymer concrete coating for vertical d overhead applications is described. The coating is permeable yet has low electrical resistivity (<10 ohm-cm), good bond strength to concrete substrates, and good weatherability. A preferred formulation contains about 60 wt % calcined coke breeze, 40 wt % vinyl ester with 3.5 wt % modified bentonite clay. Such formulations apply evenly and provide enough rigidity for vertical or overhead structures so there is no drip or sag.

Fontana, Jack J. (Shirley, NY); Elling, David (Centereach, NY); Reams, Walter (Shirley, NY)

1990-01-01

21

Electrically conductive polymer concrete coatings  

DOEpatents

A sprayable electrically conductive polymer concrete coating for vertical and overhead applications is described. The coating is permeable yet has low electrical resistivity (<10 ohm-cm), good bond strength to concrete substrates, and good weatherability. A preferred formulation contains about 60 wt% calcined coke breeze, 40 wt% vinyl ester resin with 3.5 wt% modified bentonite clay. Such formulations apply evenly and provide enough rigidity for vertical or overhead structures so there is no drip or sag. 4 tabs.

Fontana, J.J.; Elling, D.; Reams, W.

1988-05-26

22

Electrically conductive polymer concrete overlays  

NASA Astrophysics Data System (ADS)

The use of cathodic protection to prevent the corrosion of reinforcing steel in concrete structures has been well established. Application of a durable, skid-resistant electrically conductive polymer concrete overlay would advance the use of cathodic protection for the highway industry. Laboratory studies indicate that electrically conductive polymer concrete overlays using conductive fillers, such as calcined coke breeze, in conjunction with polyester or vinyl ester resins have resistivities of 1 to 10 ohm-cm. Both multiple-layer and premixed mortar-type overlays were made. Shear bond strengths of the conductive overlays to concrete substrates vary from 600 to 1300 psi, with the premixed overlays having bond strengths 50 to 100% higher than the multiple-layer overlays.

Fontana, J. J.; Webster, R. P.

1984-08-01

23

Conduction of Electricity in Gases  

Microsoft Academic Search

The conduction of electricity through gases has played ubiquitous roles in science and technology. It was responsible for many of the fundamental discoveries in atomic and molecular physics; gas discharge lighting is essential to every night operations; gas discharge lasers are still important in research and manufacturing; and all of advanced microelectronics depends on plasma enhanced processing. To a large

Alan Garscadden

2006-01-01

24

Electrically conductive rigid polyurethane foam  

DOEpatents

A rigid, polyurethane foam comprises about 2-10 weight percent, based on the total foam weight, of a carbon black which is CONDUCTEX CC-40-220 or CONDUCTEX SC, whereby the rigid polyurethane foam is electrically conductive and has essentially the same mechanical properties as the same foam without carbon black added.

Neet, Thomas E. (Grandview, MO); Spieker, David A. (Olathe, KS)

1985-03-19

25

Electrically conductive rigid polyurethane foam  

DOEpatents

A rigid, moldable polyurethane foam comprises about 2 to 10 weight percent, based on the total foam weight, of a carbon black which is CONDUCTEX CC-40-220 or CONDUCTEX SC, whereby the rigid polyurethane foam is electrically conductive and has essentially the same mechanical properties as the same foam without carbon black added.

Neet, T.E.; Spieker, D.A.

1983-12-08

26

Electrical Conductivity in Transition Metals  

ERIC Educational Resources Information Center

The aim of this "Science Note" is to describe how to test the electron-sea model to determine whether it accurately predicts relative electrical conductivity for first-row transition metals. In the electron-sea model, a metal crystal is viewed as a three-dimensional array of metal cations immersed in a sea of delocalised valence…

Talbot, Christopher; Vickneson, Kishanda

2013-01-01

27

Electrically conductive black optical paint  

NASA Technical Reports Server (NTRS)

An electrically conductive flat black paint has been developed for use on the Galileo spacecraft which will orbit Jupiter in the late 1980s. The paint, designed for equipment operating in high-energy radiation fields, has multipurpose functions. Its electrical conductivity keeps differential charging of the spacecraft external surfaces and equipment to a minimum, preventing the buildup of electrostatic fields and arcing. Its flat black aspect minimizes the effects of stray light and unwanted reflectances, when used in optical instruments and on sunshades. Its blackness is suitable, also, for thermal control, when the paint is put on spacecraft surfaces. The paint has good adherence properties, as measured by tape tests, when applied properly to a surface. The electrically conductive paint which was developed has the following characteristics: an electrical resistivity of 5 x 10 to the 7th ohms per square; a visual light total reflectance of approximately 5 percent; an infrared reflectance of 0.13 measured over a spectrum from 10 to the (-5.5) power to 0.001 meter; a solar absorptivity, alpha-s, of 0.93, and a thermal emissivity, epsilon, of 0.87, resulting in an alpha-s/epsilon of 1.07. The formula for making the paint and the process for applying it are described.

Birnbaum, M. M.; Metzler, E. C.; Cleland, E. L.

1983-01-01

28

Electrical conductivity of ice VII  

PubMed Central

It was discovered that a peak appears near a pressure of Pc = 10?GPa in the electrical conductivity of ice VII as measured through impedance spectroscopy in a diamond anvil cell (DAC) during the process of compression from 2?GPa to 40?GPa at room temperature. The activation energy for the conductivity measured in the cooling/heating process between 278?K and 303?K reached a minimum near Pc. Theoretical modelling and molecular dynamics simulations suggest that the origin of this unique peak is the transition of the major charge carriers from the rotational defects to the ionic defects. PMID:25047728

Okada, Taku; Iitaka, Toshiaki; Yagi, Takehiko; Aoki, Katsutoshi

2014-01-01

29

Electrically conductive thermal control coatings  

NASA Technical Reports Server (NTRS)

A coating characterized by low thermal absorption, high thermal emittance and high electrical conductivity comprises: (1) a fired oxide pigment comprising a minor amount of aluminum oxide and a major amount of zinc oxide; (2) sufficient water to provide a mixture suitable for application to a substrate, is presented. The fired oxide pigment may further include a minor amount of cobalt oxide. The resulting coating is particularly useful for coating the surfaces of spacecraft and similar objects.

Shai, M. C. (inventor)

1978-01-01

30

Electrical Conductivity in Sodium Chlorate Crystals  

Microsoft Academic Search

The electrical conductivity, sigma of single crystals of sodium chlorate (m.p. 256 oC) grown from solution is studied in the temperature range 100 to 250 oC. A plot of 1g (sigma T) against 1000\\/T gives a fairly continuous curve. It is resolved into three straight lines by a special graphical procedure. The experimental data can then be represented by sigma

C. Ramasastry; K. Viswanatha Reddy; V. S. Murthy

1971-01-01

31

Electrical Conductivity of Ferritin Proteins by Conductive AFM  

NASA Technical Reports Server (NTRS)

Electrical conductivity measurements were performed on single apoferritin and holoferritin molecules by conductive atomic force microscopy. Conductivity of self-assembled monolayer films of ferritin molecules on gold surfaces was also measured. Holoferritin was 5-25 times more conductive than apoferritin, indicating that for holoferritin most electron-transfer goes through the ferrihydrite core. With 1 V applied, the average electrical currents through single holoferritin and apoferritin molecules were 2.6 PA and 0.19 PA, respectively.

Xu, Degao; Watt, Gerald D.; Harb, John N.; Davis, Robert C.

2005-01-01

32

Electrical Conductivity of Nylon 66  

Microsoft Academic Search

The D.C.-conductivity, absorption current and non-Ohmic behaviour of nylon 66 were examined as a function of the temperature. The existence of three distinct temperature ranges was observed in conduction; 1) below 97°C, 2) 97°C˜250°C (Esigma{=}0.9 eV), 3) above 250°C (Esigma{=}0.8 eV). Below 97°C, the conductivity followed the W.L.F. equation (C1{=}15, C2{=}112), and the rate determining process for conduction seemed to

Seiji Isoda; Hideki Miyaji; Kenjiro Asai

1973-01-01

33

The electrical conductivity and surface conduction of consolidated rock cores.  

PubMed

A fully computerized high-pressure and high-temperature core holder device is simultaneously used to determine the electrical conductivity, zeta potential, and surface conductivity of consolidated rock cores in aqueous and nonaqueous systems. The total electrical conductivity of rock cores was determined by coupling streaming current and potential measurements. This shows that neglecting the surface conductivity Ksigma is crucial to converting the streaming potential into zeta potentials. It is observed that plots of the core total conductivity as a function of the electrolyte conductivity KL exhibit two behaviors. At low ionic strength, the core conductivity clearly depends on the contribution of surface conductivity behind the slip plane, whereas at higher ionic strength, the magnitude of the surface conductivity becomes negligible. The electrical conductivity of rock cores was found to be in good agreement with the O'Brien theory and the Briggs method. The contribution of the stagnant layer to the surface conductivity in nonaqueous systems has been shown to be significant. This shows that the stagnant layer displays significantly different behavior in different nonaqueous systems, depending on the core porosity and the double-layer overlap. The results indicate that the application of electrokinetics in petroleum reservoirs can provide important insights into reservoir fluid flow characterization. PMID:17346731

Alkafeef, Saad F; Alajmi, Abdullah F

2007-05-15

34

Electrical conductivity of pyrolyzed polyacrylonitrile  

SciTech Connect

Using ultrapure samples of polyacrylonitrile (PAN) of 485,000 or 150,000 average molecular weight solution cast in dimethylformamide, the dc conductivity (sigma) of pyrolyzed PAN (PANP) films has been studied for pyrolysis temperatures (T/ sub p/) of 280 to 435/sup 0/C. Conductivity measurements made during pyrolysis indicate the onset of a dramatic increase in sigma for T/sub p/ of 390 to 435/sup 0/C. Conductivities as high as 5 (ohm-cm)/sup -1/ have been observed for T/sub p/ < 435/sup 0/C.

Teoh, H.; Metz, P.D.; Wilhelm, W.G.

1981-01-01

35

Electrically conductive connection for an electrode  

DOEpatents

An electrically conductive connection for an electrode assembly of an electrolyte cell in which aluminum is produced by electrolysis in a molten salt is described. The electrode assembly comprises an electrode flask and a conductor rod. The flask has a collar above an area of minimum flask diameter. The electrically conductive connection comprises the electrode flask, the conductor rod and a structure bearing against the collar and the conductor rod for pulling the conductor rod into compressive and electrical contact with the flask.

Hornack, Thomas R. (Lower Burrell, PA); Chilko, Robert J. (Lower Burrell, PA)

1986-01-01

36

Electrical conduction in fluoropolymer films  

Microsoft Academic Search

Isothermal charging, discharging and transport currents in fluoropolymer films are measured in the temperature range of 50 to 200°C at electric fields to 40 MV\\/m. The currents are measured as a function of time elapsed after the application of steady state voltages in the range of 1 to 104 s. Charging currents increase with time to 103 s, depending upon

Z. Leo Wu; G. R. Govinda Raju

1995-01-01

37

The electrical conductivity of protoplasm  

Microsoft Academic Search

Summary The specific conductance of the protoplasm, apart from the cell membrane ofAmoeba proteus, Euplotes, Spirostomum teres, Frontonia, of the plant cellNitella and the starfish oögonia has been determined.

Samuel Gelfan

1928-01-01

38

Electrically conductive polyimides containing silver trifluoroacetylacetonate  

NASA Technical Reports Server (NTRS)

Polyimides with enhanced electrical conductivity are produced by adding a silver ion-containing additive to the polyamic acid resin formed by the condensation of an aromatic dianhydride with an aromatic diamine. After thermal treatment the resulting polyimides had surface conductivities in the range of 1.7.times.10.sup.-3 4.5 .OMEGA..sup.-1 making them useful in low the electronics industry as flexible, electrically conductive polymeric films and coatings.

Rancourt, James D. (Inventor); Stoakley, Diane M. (Inventor); Caplan, Maggie L. (Inventor); St. Clair, Anne K. (Inventor); Taylor, Larry T. (Inventor)

1996-01-01

39

Combining Optical Transparency with Electrical Conductivity  

E-print Network

1 Combining Optical Transparency with Electrical Conductivity: Challenges and Prospects Julia E: a transparent material is an insulator which possesses completely filled valence and empty conduction bands with optical band gap of about 3 eV. To become a transparent conducting oxide (TCO), these TCO hosts must

Medvedeva, Julia E.

40

Electrically conducting polymers for aerospace applications  

NASA Technical Reports Server (NTRS)

Current research on electrically conducting polymers from 1974 to the present is reviewed focusing on the development of materials for aeronautic and space applications. Problems discussed include extended pi-systems, pyrolytic polymers, charge-transfer systems, conductive matrix resins for composite materials, and prospects for the use of conducting polymers in space photovoltaics.

Meador, Mary Ann B.; Gaier, James R.; Good, Brian S.; Sharp, G. R.; Meador, Michael A.

1991-01-01

41

Electrical and thermal conductivities in dense plasmas  

SciTech Connect

Expressions for the electrical and thermal conductivities in dense plasmas are derived combining the Chester-Thellung-Kubo-Greenwood approach and the Kramers approximation. The infrared divergence is removed assuming a Drude-like behaviour. An analytical expression is obtained for the Lorenz number that interpolates between the cold solid-state and the hot plasma phases. An expression for the electrical resistivity is proposed using the Ziman-Evans formula, from which the thermal conductivity can be deduced using the analytical expression for the Lorenz number. The present method can be used to estimate electrical and thermal conductivities of mixtures. Comparisons with experiment and quantum molecular dynamics simulations are done.

Faussurier, G., E-mail: gerald.faussurier@cea.fr; Blancard, C.; Combis, P.; Videau, L. [CEA, DAM, DIF, F-91297 Arpajon (France)

2014-09-15

42

Electrical and thermal conductivities in dense plasmas  

NASA Astrophysics Data System (ADS)

Expressions for the electrical and thermal conductivities in dense plasmas are derived combining the Chester-Thellung-Kubo-Greenwood approach and the Kramers approximation. The infrared divergence is removed assuming a Drude-like behaviour. An analytical expression is obtained for the Lorenz number that interpolates between the cold solid-state and the hot plasma phases. An expression for the electrical resistivity is proposed using the Ziman-Evans formula, from which the thermal conductivity can be deduced using the analytical expression for the Lorenz number. The present method can be used to estimate electrical and thermal conductivities of mixtures. Comparisons with experiment and quantum molecular dynamics simulations are done.

Faussurier, G.; Blancard, C.; Combis, P.; Videau, L.

2014-09-01

43

Electrically Conductive Polyimide Films Containing Gold Surface  

NASA Technical Reports Server (NTRS)

Polyimide films exhibiting high thermo-oxidative stability and including electrically conductive surface layers containing gold made by casting process. Many variations of basic process conditions, ingredients, and sequence of operations possible, and not all resulting versions of process yield electrically conductive films. Gold-containing layer formed on film surface during cure. These metallic gold-containing polyimides used in film and coating applications requiring electrical conductivity, high reflectivity, exceptional thermal stability, and/or mechanical integrity. They also find commercial potential in areas ranging from thin films for satellite antennas to decorative coatings and packaging.

Caplan, Maggie L.; Stoakley, Diane M.; St. Clair, Anne K.

1994-01-01

44

Laboratory Electrical Conductivity Measurement of Mantle Minerals  

Microsoft Academic Search

Electrical conductivity structures of the Earth’s mantle estimated from the magnetotelluric and geomagnetic deep sounding\\u000a methods generally show increase of conductivity from 10?4–10?2 to 100 S\\/m with increasing depth to the top of the lower mantle. Although conductivity does not vary significantly in the lower\\u000a mantle, the possible existence of a highly conductive layer has been proposed at the base of

Takashi Yoshino

2010-01-01

45

Electrical conductivity imaging using magnetic resonance tomography.  

PubMed

The electrical conductivity of human tissue could be used as an additional diagnostic parameter or might be helpful for the prediction of the local SAR during MR measurements. In this study, the approach "Electric Properties Tomography" (EPT) is applied, which derives the patient's electric conductivity using a standard MR system. To this goal, the spatial transmit sensitivity distribution of the applied RF coil is measured. This sensitivity distribution represents the positive circularly polarized component of the magnetic field. It can be post-processed utilizing Faraday's and Ampere's law, yielding an estimation of the spatial distribution of the patient's electric conductivity. Thus, EPT does not apply externally mounted electrodes, currents, or RF probes. In this study, phantom experiments underline the principle feasibility of EPT. Furthermore, initial conductivity measurements in the brain allow distinguishing cerebro-spinal fluid from the surrounding grey and white matter. PMID:19964612

Katscher, Ulrich; Voigt, Tobias; Findeklee, Christian

2009-01-01

46

Electrically Conductive White Thermal-Control Paint  

NASA Technical Reports Server (NTRS)

Report describes development of white thermal-control paint intended for use on spacecraft. Paint required to exhibit combination of high emittance (equal to or greater than 0.90), low absorptance (equal to or less than 0.20), and electrical conductivity sufficient to prevent charging with static electricity to potentials beyond range of plus or minus 10 V.

Hsieh, Cheng-Hsien; Forsberg, Gustaf A.; O'Donnell, Timothy P.

1995-01-01

47

SOME EXPERIMENTS ON ELECTRICAL CONDUCTION IN VACUUM  

Microsoft Academic Search

The conduction of electricity through a vacuum was investigated in high ; voltage generators using beta emitters as current sources, The voltage attained ; by the generators was limited by vacuum conduction to values of tens to a few ; hundreds of kilovolts. The leakage current responsible for this limitation in ; most cases was found to consist of an

J. W. Kennedy; E. A. Bryant; U. Merten; P. V. Murphy; E. K. Storms

1957-01-01

48

Making Complex Electrically Conductive Patterns on Cloth  

NASA Technical Reports Server (NTRS)

A method for automated fabrication of flexible, electrically conductive patterns on cloth substrates has been demonstrated. Products developed using this method, or related prior methods, are instances of a technology known as 'e-textiles,' in which electrically conductive patterns ar formed in, and on, textiles. For many applications, including high-speed digital circuits, antennas, and radio frequency (RF) circuits, an e-textile method should be capable of providing high surface conductivity, tight tolerances for control of characteristic impedances, and geometrically complex conductive patterns. Unlike prior methods, the present method satisfies all three of these criteria. Typical patterns can include such circuit structures as RF transmission lines, antennas, filters, and other conductive patterns equivalent to those of conventional printed circuits. The present method overcomes the limitations of the prior methods for forming the equivalent of printed circuits on cloth. A typical fabrication process according to the present method involves selecting the appropriate conductive and non-conductive fabric layers to build the e-textile circuit. The present method uses commercially available woven conductive cloth with established surface conductivity specifications. Dielectric constant, loss tangent, and thickness are some of the parameters to be considered for the non-conductive fabric layers. The circuit design of the conductive woven fabric is secured onto a non-conductive fabric layer using sewing, embroidery, and/or adhesive means. The portion of the conductive fabric that is not part of the circuit is next cut from the desired circuit using an automated machine such as a printed-circuit-board milling machine or a laser cutting machine. Fiducials can be used to align the circuit and the cutting machine. Multilayer circuits can be built starting with the inner layer and using conductive thread to make electrical connections between layers.

Chu, Andrew; Fink, Patrick W.; Dobbins, Justin A.; Lin, Greg Y.; Scully, Robert C.; Trevino, Robert

2008-01-01

49

Electrically conductive containment vessel for molten aluminum  

DOEpatents

The present invention is directed to a containment vessel which is particularly useful in melting aluminum. The vessel of the present invention is a multilayered vessel characterized by being electrically conductive, essentially nonwettable by and nonreactive with molten aluminum. The vessel is formed by coating a tantalum substrate of a suitable configuration with a mixture of yttria and particulate metal 10 borides. The yttria in the coating inhibits the wetting of the coating while the boride particulate material provides the electrical conductivity through the vessel. The vessel of the present invention is particularly suitable for use in melting aluminum by ion bombardment.

Holcombe, C.E.; Scott, D.G.

1984-06-25

50

Electrically conductive containment vessel for molten aluminum  

DOEpatents

The present invention is directed to a containment vessel which is particularly useful in melting aluminum. The vessel of the present invention is a multilayered vessel characterized by being electrically conductive, essentially nonwettable by and nonreactive with molten aluminum. The vessel is formed by coating a tantalum substrate of a suitable configuration with a mixture of yttria and particulate metal borides. The yttria in the coating inhibits the wetting of the coating while the boride particulate material provides the electrical conductivity through the vessel. The vessel of the present invention is particularly suitable for use in melting aluminum by ion bombardment.

Holcombe, Cressie E. (Knoxville, TN); Scott, Donald G. (Oak Ridge, TN)

1985-01-01

51

Continuously variable transmission: Assessment of applicability to advance electric vehicles  

NASA Technical Reports Server (NTRS)

A brief historical account of the evolution of continuously variable transmissions (CVT) for automotive use is given. The CVT concepts which are potentially suitable for application with electric and hybrid vehicles are discussed. The arrangement and function of several CVT concepts are cited along with their current developmental status. The results of preliminary design studies conducted on four CVT concepts for use in advanced electric vehicles are discussed.

Loewenthal, S. H.; Parker, R. J.

1981-01-01

52

Towards electrically conductive, self-healing materials  

Microsoft Academic Search

A novel class of organometallic polymers comprising N-heterocyclic carbenes and transition metals was shown to have potential as an electrically conductive, self-healing material. These polymers were found to exhibit conductivities of the order of 10K3 Sc mK1 and showed structurally dynamic characteristics in the solid-state. Thin films of these materials were cast onto silicon wafers, then scored and imaged using

Kyle A. Williams; Andrew J. Boydston; Christopher W. Bielawski

2007-01-01

53

Electrical conductivity and impedance behaviour of hydrogels  

NASA Astrophysics Data System (ADS)

The impedance and electrical conductivity behavior of gellan gum hydrogels containing the conducting fillers poly(3,4- ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) and vapour grown carbon nanofibers (VGCNF) is presented. Impedance analysis showed that an equivalent circuit consisting of a Warburg element in series with a resistor could be used to model the gels' behavior. It is demonstrated that the addition of the conducting fillers PEDOT:PSS and VGCNFs can result in a measurable improvement in the conductivity of hydrogels with high water content and swelling ratios. Incorporation of combinations of these conducting fillers resulted in an improvement of the conductivity of gellan gum-containing hydrogels with water content (swelling ratio) of at least 97.5% (40) from 1.2 +/- 0.1 mS/cm to 4 +/- 0.6 mS/cm.

Warren, Holly; in het Panhuis, Marc

2014-08-01

54

Global Electrical Conductivity Magnetic Satellite Induction Studies  

E-print Network

km. Skin depth can be a very useful indicator of energy penetration, but be careful! 2nd induction to measure Earth conductivity: · Magnetotelluric (MT) method Measure electric and magnetic fields · Geomagnetic depth sounding (GDS) method Measure horizontal and vertical magnetic fields 2nd

Constable, Steve

55

On the Electrical Conductivity of Metals  

Microsoft Academic Search

The exact formula for the electrical conductivity of a metal, derived by Kubo, Greenwood, and others, is evaluated using Van Hove's methods for quantum mechanical transport problems. The evaluation is restricted to the case of elastic scattering by impurities or lattice vibrations, but completely avoids the use of the customary random phase assumption. In the limit of weak coupling our

G. V. Chester; A. Thellung

1959-01-01

56

Thermal and electrical contact conductance studies  

NASA Technical Reports Server (NTRS)

Prediction of electrical and thermal contact resistance for pressed, nominally flat contacts is complicated by the large number of variables which influence contact formation. This is reflected in experimental results as a wide variation in contact resistances, spanning up to six orders of magnitude. A series of experiments were performed to observe the effects of oxidation and surface roughness on contact resistance. Electrical contact resistance and thermal contact conductance from 4 to 290 K on OFHC Cu contacts are reported. Electrical contact resistance was measured with a 4-wire DC technique. Thermal contact conductance was determined by steady-state longitudinal heat flow. Corrections for the bulk contribution ot the overall measured resistance were made, with the remaining resistance due solely to the presence of the contact.

Vansciver, S. W.; Nilles, M.

1985-01-01

57

Continuous Improvement in Electrical Engineering Student Outcomes  

NSDL National Science Digital Library

Continuous improvement in the sophomore-level electrical engineering course outcomes and junior-level entrance exam outcomes has been studied at Western New England College. Data has been tracked over a four year period and continuous improvement of students knowledge retention between the sophomore and junior-level years has been demonstrated. This paper addresses the methods and curricular changes implemented to affect the improvement. The effects of the curricular changes made in the sophomore-level electrical engineering courses are also analyzed and presented.

Burke, John.

58

Electrical conduction control of carbon nanowalls  

SciTech Connect

The electrical conduction behavior of carbon nanowalls (CNWs) has been evaluated by Hall measurement. CNWs, which comprise stacks of graphene sheets standing on the substrate, are fabricated by fluorocarbon/hydrogen plasma enhanced chemical vapor deposition. We have investigated the effect of N{sub 2} addition to C{sub 2}F{sub 6}/H{sub 2} system on the electrical properties of CNWs. The CNWs grown with the C{sub 2}F{sub 6}/H{sub 2} plasma exhibit p-type conduction. As a result of the nitrogen inclusion in the CNWs, the conduction type of the CNWs changes to n type. The carrier concentration is controllable by changing the flow rate of the additional N{sub 2} during the CNW growth process.

Takeuchi, Wakana; Ura, Masato; Hori, Masaru [Department of Electrical Engineering and Computer Science, Nagoya University, Chikusa, Nagoya 468-8603 (Japan); Hiramatsu, Mineo [Department of Electrical and Electronic Engineering, Meijo University, Tempaku, Nagoya 468-8502 (Japan); Tokuda, Yutaka [Department of Electrical and Electronics Engineering, Aichi Institute of Technology, Yakusa, Toyota 470-0392 (Japan); Kano, Hiroyuki [NU Eco-Engineering Co., Ltd., Kurozasa, Miyoshi, Nishikamo 470-0201 (Japan)

2008-05-26

59

Electrical conduction of a XLPE nanocomposite  

NASA Astrophysics Data System (ADS)

The resistivity, breakdown strength, and formation of space charges are very important factors for insulation design of HVDC cable. It is known that a nano-sized metal-oxide inorganic filler reduces the formation of space charges in the polymer nanocomposite. Electrical conduction of cross-linked polyethylene(XLPE) nanocomposite insulating material is investigated in this paper. The conduction currents of two kinds of XLPE nanocomposites and XLPE without nano-filler were measured at temperature of 303 ~ 363 K under the applied electric fields of 10 ~ 50 kV/mm. The current of the nanocomposite specimen is smaller than that of XLPE specimen without nano-filler. The conduction mechanism may be explained in terms of Schottky emission and multi-core model.

Park, Yong-Jun; Sim, Jae-Yong; Lim, Kee-Joe; Nam, Jin-Ho; Park, Wan-Gi

2014-07-01

60

Advanced continuously variable transmissions for electric and hybrid vehicles  

NASA Technical Reports Server (NTRS)

A brief survey of past and present continuously variable transmissions (CVT) which are potentially suitable for application with electric and hybrid vehicles is presented. Discussion of general transmission requirements and benefits attainable with a CVT for electric vehicle use is given. The arrangement and function of several specific CVT concepts are cited along with their current development status. Lastly, the results of preliminary design studies conducted under a NASA contract for DOE on four CVT concepts for use in advanced electric vehicles are reviewed.

Loewenthal, S. H.

1980-01-01

61

Synthesis and characterization of electrical conducting nanoporous carbon structures  

NASA Astrophysics Data System (ADS)

Nanoporous organic xerogel compounds were prepared by sol-gel method from pyrogallol-formaldehyde (PF) mixtures in water using perchloric acid as catalyst. The preparation conditions of electrical conducting carbon (ECC) structures were explored by changing the pyrolysis temperature. The effect of this preparation parameters on the structural and electrical properties of the obtained ECCs were studied, respectively, by thermogravimetric analysis (TGA), nitrogen adsorption isotherms, IR spectroscopy and electrical conductivity measurements. The analysis of the obtained results revealed that, the polymeric insulating phase was transformed progressively with pyrolysis temperature into carbon conducting phase; this means the formation of long continuous conducting path for charge carriers when the carbon microparticles inside the structure agglomerated with thermal treatment and the samples exhibited tangible percolation behaviour where the percolation threshold can be determined by pyrolysis temperature. The temperature-dependent conductivity and the I( V) characteristics of the obtained ECC structures show a non-ohmic behaviour. The results obtained from TGA and differential thermal analyser (DTA) thermograms, scanning electron microscope (SEM) and transmission electron microscope (TEM) micrographs, IR spectroscopy and X-ray diffraction revealed that, the obtained ECC structures consist of amorphous and nanoporous electrical conducting carbon materials.

El Mir, L.; Kraiem, S.; Bengagi, M.; Elaloui, E.; Ouederni, A.; Alaya, S.

2007-05-01

62

Electrically conducting superhydrophobic microtextured carbon nanotube nanocomposite  

NASA Astrophysics Data System (ADS)

We report a simple and inexpensive method of producing an electrically conductive superhydrophobic polymer surface by adding multiwall carbon nanotubes directly into the polymer poly(dimethylsiloxane) (PDMS) matrix and replicating micro/nanotexture using a replication master prepared by ultrafast-laser microtexturing process. No additional coatings on conducting PDMS are required to achieve water contact angles greater than 161°. The conductivity can be controlled by changing the percent MWCNT added to PDMS and at a bulk loading of 4.4 wt% we report a conductivity improvement over pure PDMS by a factor of more than 1011 with electrical resistivity ? = 761 ? cm. This combined behavior of a conductive, superhydrophobic nanocomposite has exciting applications for allowing a new class of enclosures providing EMI shielding, water repellency and sensing to provide built-in temperature feedback. The effect of temperature on the nanocomposite was investigated and a negative temperature coefficient of resistance (-0.037 ?/K) similar to that of a thermistor was observed.

Caffrey, Paul O.; Gupta, Mool C.

2014-09-01

63

Electric conductance of highly selective nanochannels  

NASA Astrophysics Data System (ADS)

We consider electric conductance through a narrow nanochannel in the thick-double-layer limit, where the space-charge Debye layers adjacent to the channel walls overlap. At moderate surface-charge densities the electrolyte solution filling the channel comprises mainly of counterions. This allows to derive an analytic closed-form approximation for the channel conductance, independent of the salt concentration in the channel reservoirs. The derived expression consists of two terms. The first, representing electromigratory transport, is independent of the channel depth. The second, representing convective transport, depends upon it weakly.

Schnitzer, Ory; Yariv, Ehud

2013-05-01

64

Towards electrically conductive, self-healing materials.  

PubMed

A novel class of organometallic polymers comprising N-heterocyclic carbenes and transition metals was shown to have potential as an electrically conductive, self-healing material. These polymers were found to exhibit conductivities of the order of 10(-3) S cm-1 and showed structurally dynamic characteristics in the solid-state. Thin films of these materials were cast onto silicon wafers, then scored and imaged using a scanning electron microscopy (SEM). The scored films were subsequently healed via thermal treatment, which enabled the material to flow via a unique depolymerization process, as determined by SEM and surface profilometry. A method for incorporating these features into a device that exhibits electrically driven, self-healing functions is proposed. PMID:17251165

Williams, Kyle A; Boydston, Andrew J; Bielawski, Christopher W

2007-04-22

65

Electrically conducting polyimide film containing tin complexes  

NASA Technical Reports Server (NTRS)

Disclosed is a thermally-stable SnO.sub.2 -surfaced polyimide film wherein the electrical conductivity of the SnO.sub.2 surface is within the range of about 3.0.times.10.sup.-3 to about 1.times.10.sup.-2 ohms.sup.-1,. Also disclosed is a method of preparing this film from a solution containing a polyamic acid and SnCl.sub.4 (DMSO).sub.2.

St. Clair, Anne K. (Inventor); Ezzell, Stephen A. (Inventor); Taylor, Larry T. (Inventor); Boston, Harold G. (Inventor)

1996-01-01

66

The electrical conductivity of sodium polysulfide melts  

SciTech Connect

The sodium polysulfide melt has been described by a macroscopic model. This model considers the melt to be composed of sodium cations, monosulfide anions, and neutral sulfur solvent. The transport equations of concentrated-solution theory are used to derived the governing equations for this binaryelectrolyte melt model. These equations relate measurable transport properties to fundamental transport parameters. The focus of this research is to measure the electrical conductivity of sodium polysulfide melts and calculate one of fundamental transport parameters from the experimental data. The conductance cells used in the conductivity measurements are axisymmetric cylindrical cells with a microelectrode. The electrode effects, including double-layer capacity, charge transfer resistance, and concentration overpotential, were minimized by the use of the alternating current at an adequately high frequency. The high cell constants of the conductance cells not only enhanced the experimental accuracy but also made the electrode effects negligible. The electrical conductivities of sodium polysulfide Na{sub 2}S{sub 4} and Na{sub 2}S{sub 5} were measured as a function of temperature (range: 300 to 360{degree}C). Variations between experiments were only up to 2%. The values of the Arrhenius activation energy derived from the experimental data are about 33 kJ/mol. The fundamental transport parameter which quantifies the interaction within sodium cations and monosulfide anions are of interest and expected to be positive. Values of it were calculated from the experimental conductivity data and most of them are positive. Some negative values were obtained probably due to the experimental errors of transference number, diffusion coefficient, density or conductivity data.

Meihui Wang.

1992-06-01

67

Testing of techniques for improvement of conductivity of electrically conductive adhesives  

Microsoft Academic Search

The paper presents methods, which have been used for improvement of electrical conductivity of electrically conductive adhesives with isotropical electrical conductivity. Conductivity level depends, among other things, on level of aggregation of filler particles. The research has been focused on improvement of electrical properties by better aggregation of filler particles in adhesive. Following methods have been tested with the goal

P. Mach; L. Richter; Alena Pietrikova

2008-01-01

68

Electrically Conductive Metal Nanowire Polymer Nanocomposites  

NASA Astrophysics Data System (ADS)

This thesis investigates electrically conductive polymer nanocomposites formulated with metal nanowires for electrostatic discharge and electromagnetic interference shielding. Copper nanowires (CuNWs) of an average length of 1.98 mum and diameter of 25 +/- 4 nm were synthesized. The oxidation reaction of the CuNWs in air can be divided into two stages at weight of 111.2% on TGA curves. The isoconversional activation energies determined by Starink method were used to fit the different master plots. Johnson-Mehl-Avrami (JMA) equation gave the best fit. The surface atoms of the CuNWs are the sites for the random nucleation and the crystallite strain in the CuNWs is the driving force for the growth of nuclei mechanism during the oxidation process. To improve the anti-oxidation properties of the CuNWs, silver was coated onto the surface of the CuNWs in Ag-amine solution. The prepared silver coated CuNWs (AgCuNWs) with silver content of 66.52 wt. %, diameter of 28--33 nm exhibited improved anti-oxidation behavior. The electrical resistivity of the AgCuNW/low density polyethylene (LDPE) nanocomposites is lower than that of the CuNW/LDPE nanocomposites with the same volume percentage of fillers. The nanocomposites formulated with CuNWs and polyethylenes (PEs) were compared to study the different interaction between the CuNWs and the different types of PE matrices. The electrical conductivity of the different PE matrices filled with the same concentrations of CuNWs correlated well with the level of the CuNW dispersion. The intermolecular force and entanglement resulting from the different macromolecular structures such as molecular weight and branching played an important role in the dispersion, electrical properties and rheological behaviour of the CuNW/PE nanocomposites. Ferromagnetic polycrystalline nickel nanowires (NiNWs) were synthesized with uniform diameter of ca. 38 nm and an average length of 2.68 mum. The NiNW linear low density polyethylene (LLDPE) nanocomposites exhibited electrical percolation threshold at NiNW volume fraction of 0.005. The power law fitting results imply that the electrical conductivity of the NiNW/LLDPE nanocomposites mainly originated from the contact among individual nanowires.

Luo, Xiaoxiong

69

The deep lunar electrical conductivity profile - Structural and thermal inferences  

NASA Technical Reports Server (NTRS)

Simultaneous lunar surface and orbital magnetometer records are reexamined, to ascertain intervals which may be suitable for measuring lunar inductive response in the solar wind and terrestrial magnetosheath. Power spectral estimates of the response tangent to the lunar surface, defined in terms of transfer and gain functions, are obtained for the 0.0001-0.01 Hz frequency range. The maximum consistency of estimates from different time intervals is found when the initial analysis is limited to the tangential direction of maximum incident power, or that direction in which the ratio of signal to background noise is greatest. Spherically symmetric plasma confinement theory is used in the interpretation of transfer function data, by way of forward model calculations, under the assumption of continuous electrical conductivity increase with depth. Results are presented for internal electrical conductivity profile, metallic core radius, and selenotherm limits.

Hood, L. L.; Herbert, F.; Sonett, C. P.

1982-01-01

70

Photovoltaic device having light transmitting electrically conductive stacked films  

DOEpatents

A light transmitting electrically conductive stacked film, useful as a light transmitting electrode, including a first light transmitting electrically conductive layer, having a first optical thickness, a second light transmitting layer, having a second optical thickness different from the optical thickness of the first layer, and an electrically conductive metallic layer interposed between and in initimate contact with the first and second layers.

Weber, Michael F. (St. Paul, MN); Tran, Nang T. (St. Paul, MN); Jeffrey, Frank R. (St. Paul, MN); Gilbert, James R. (St. Paul, MN); Aspen, Frank E. (St. Paul, MN)

1990-07-10

71

Chapter A6. Section 6.3. Specific Electrical Conductance  

USGS Publications Warehouse

Electrical conductance is a measure of the capacity of a substance to conduct an electrical current. The specific electrical conductance (conductivity) of water is a function of the types and quantities of dissolved substances it contains, normalized to a unit length and unit cross section at a specified temperature. This section of the National Field Manual (NFM) describes U.S. Geological Survey (USGS) guidance and protocols for measurement of conductivity in ground and surface waters.

Radtke, Dean B.; Davis, Jerri V.; Wilde, Franceska D.

2005-01-01

72

Thermal Conductivity and Elastic Constants of PEDOT:PSS with High Electrical Conductivity  

E-print Network

1 Thermal Conductivity and Elastic Constants of PEDOT:PSS with High Electrical Conductivity Jun Liu) and polystyrene sulfonate (PEDOT:PSS) have high electrical conductivity when cast from aqueous suspensions conductivity along multiple directions of thick (>20 µm) drop-cast PEDOT films, that the thermal conductivity

Cahill, David G.

73

Investigation of Mechanical and Electrical Characteristics for Cracked Conductive Particle in Anisotropic Conductive Adhesive (ACA) Assembly  

Microsoft Academic Search

In an anisotropic conductive adhesive (ACA) assembly, the electrical conduction is usually achieved with the conductive particles between the bumps of integrated circuit (IC) and corresponding conductive tracks on the glass substrate. Fully understanding of the mechanical and electrical characteristics of ACA particles can help to optimize the assembly process and improve the reliability of ACA interconnection. Most conductive particles

Bin Xie; X. Q. Shi; Han Ding

2008-01-01

74

Performance comparison of continuous conduction mode (CCM) and discontinuous conduction mode (DCM) flyback converters  

Microsoft Academic Search

This paper presents performance comparison of continuous conduction mode (CCM) and discontinuous conduction mode (DCM) flyback converters. The comparison is conducted through experiment on the 5 V\\/25 W, 50 kHz prototype CCM and DCM flyback converters, which have been designed and built with similar circuit layouts, components, and power ratings. Aspects to be compared are component stress, output voltage regulation

S. Howimanporn; C. Bunlaksananusorn

2003-01-01

75

Magnetic flowmeter for electrically conductive liquid  

DOEpatents

A magnetic flowmeter includes first and second tube sections each having ls of non-magnetic material. The first tube is suitably connected to a process for passing a flow of an electrically conductive fluid to be measured. The second tube is established as a reference containing a still medium and is maintained at the same temperature as the first tube. A rotatable magnet assembly is disposed between the two tubes with at least two magnets attached to radially extending arms from a central shaft. Each magnet includes an air gap suitably sized to pass astraddle the diameter along a portion of the length of each of the two tubes. The magnets are provided in matched pairs spaced 180.degree. apart such that signals will be simultaneously generated in signal leads attached to each of the two tubes. By comparing the signals from the two tubes and varying the rotating speed of the magnet assembly until the signals are equal, or attain a maximum, the flow velocity of the fluid within the first tube can be determined. Through temperature monitoring and appropriate heaters, the two tubes are maintained at the same temperature.

Skladzien, Stanley B. (Elmhurst, IL); Raue, Donald J. (Naperville, IL)

1982-01-01

76

Magnetic flowmeter for electrically conductive liquid  

DOEpatents

A magnetic flowmeter includes first and second tube sections each having walls of non-magnetic material. The first tube is suitably connected to a process for passing a flow of an electrically conductive fluid to be measured. The second tube is established as a reference containing a still medium and is maintained at the same temperature as the first tube. A rotatable magnet assembly is disposed between the two tubes with at least two magnets attached to radially extending arms from a central shaft. Each magnet includes an air gap suitably sized to pass astraddle the diameter along a portion of the length of each of the two tubes. Two magnets are provided in matched pairs spaced 180/sup 0/ apart such that signals will be simultaneously generated in signal leads attached to each of the two tubes. By comparing the signals from the two tubes and varying the rotating speed of the magnet assembly until the signals are equal, or attain a maximum, the flow velocity of the fluid within the first tube can be determined. Through temperature monitoring and appropriate heaters, the two tubes are maintained at the same temperature.

Skladzien, S.B.; Raue, D.J.

1980-08-18

77

Electrical Conductivity in Polymer Blends/ Multiwall Carbon Nanotubes  

NASA Astrophysics Data System (ADS)

Carbon nanotubes (CNT) based polymer composites have emerged as the future multifunctional materials in view of its exceptional mechanical, thermal and electrical properties. One of the major interests is to develop conductive polymer composites preferably at low concentration of CNT utilizing their high aspect ratio (L/D) for numerous applications, which include antistatic devices, capacitors and materials for EMI shielding. In this context, polymer blends have emerged as a potential candidate in lowering the percolation thresholds further by the utilization of `double-percolation' which arises from the synergistic improvements in blend properties associated with the co-continuous morphology. Due to strong inter-tube van der Waals' forces, they often tend to aggregate and uniform dispersion remains a challenge. To overcome this challenge, we exploited sodium salt of 6-aminohexanoic acid (Na-AHA) which was able to assist in debundlling the multiwall carbon nanotubes (MWNT) through `cation-?' interactions during melt-mixing leading to percolative `network-like' structure of MWNT within polyamide6 (PA6) phase in co-continuous PA6/acrylonitrile butadiene styrene (ABS) blends. The composite exhibited low electrical percolation thresholds of 0.25 wt% of MWNT, the lowest reported value in this system so far. Retention of `network-like structure' in the solid state with significant refinement was observed even at lower MWNT concentration in presence Na-AHA, which was assessed through AC electrical conductivity measurements. Reactive coupling was found to be a dominant factor besides `cation-?' interactions in achieving low electrical percolation in PA6/ABS+MWNT composites.

Kulkarni, Ajit R.; Bose, Suryasarathi; Bhattacharyya, Arup R.

2008-10-01

78

Relating relative hydraulic and electrical conductivity in the unsaturated zone  

NASA Astrophysics Data System (ADS)

Numerical modeling was used to generate pore-scale structures with different structural properties. They were partially saturated according to wetting and drainage regimes using morphological operations for a range of saturations. The hydraulic and electrical conductivities of the resulting partially saturated grain packs were numerically computed to produce relative hydraulic conductivity versus saturation and relative electrical conductivity versus saturation curves. The relative hydraulic conductivities were then compared to the relative electrical conductivities for the same saturations and it was found that relative hydraulic conductivity could be expressed as relative electrical conductivity to a power law exponent, ?. This exponent ? was not correlated to porosity, specific surface area, or tortuosity. It did change according to whether the soil was wetting or draining. However, a ? value of 2.1 reproduced relative hydraulic conductivity from relative electrical conductivity with little added error. The effects of surface conduction on the observed power law relationship due to either low fluid electrical conductivity or increased clay content were analyzed. The relationship was found to hold for fluid conductivities typical of groundwater and for clay content of less than 5% if the clays were layered perpendicular to electrical flow. The relationship breaks down for electrical flow parallel to clay layers, which makes the choice of electrode arrangement important in cases where clay may be present. This relationship can be used with secondary pressure or saturation data to characterize a soil's hydraulic conductivity curve.

Mawer, Chloe; Knight, Rosemary; Kitanidis, Peter K.

2015-01-01

79

Dual channel DC-DC converter in continuous conduction mode  

Microsoft Academic Search

The paper presents the CCM (continuous conduction mode) operation of the dual channel resonant DC-DC step down (buck) converter. However, as a result of certain limitations, sometimes the converter cannot be operated in CCM at all. The paper presents the mathematical analysis of CCM operation, explores the basic relations between input, output and control variables for the more general asymmetric

I. Nagy; J. Hamar; K. R. Jardan

1999-01-01

80

Role of Dislocation Movement in the Electrical Conductance of Nanocontacts  

PubMed Central

Dislocation is a lattice imperfection of crystalline materials. Dislocation movement is induced during plastic deformation and influences the mechanical properties. Although the role of dislocation in mechanical properties has been well understood, the role of dislocation in electrical properties is completely lacking. Only Matthiessen's rule addresses the electrical influence of dislocations at the macroscale. Here, we show that the electrical conductance change due to dislocations and show their movements through in situ observation of a gold nanocontact. The density of the dislocations in the gold nanocontact did not affect the electrical conductance. The repeated and discrete dislocation movements resulted in an electrical conductance oscillation. Our results demonstrate how dislocations and their movements affect electric conductance at the nanoscale. This instability issue will cause a big problem for future electric devices such as ultra low power electric devices and nanowire photovoltaic devices. PMID:22953044

Ishida, Tadashi; Kakushima, Kuniyuki; Mizoguchi, Teruyasu; Fujita, Hiroyuki

2012-01-01

81

Electrical conductivity of drying cement paste  

Microsoft Academic Search

Previous research has shown that electrical measurements can be used to monitor moisture movement inside concrete. The interpretation\\u000a of these measurements is frequently based on empirical relationships between moisture changes and electrical properties of\\u000a concrete. As such, these empirical relationships can limit the application of the electrical measurements to a specific material\\u000a or exposure history. To facilitate the development of

Farshad Rajabipour; Jason Weiss

2007-01-01

82

Variable Anisotropic Brain Electrical Conductivities in Epileptogenic Foci  

Microsoft Academic Search

Source localization models assume brain electrical conductivities are isotropic at about 0.33 S\\/m. These assumptions have\\u000a not been confirmed ex vivo in humans. This study determined bidirectional electrical conductivities from pediatric epilepsy\\u000a surgery patients. Electrical conductivities perpendicular and parallel to the pial surface of neocortex and subcortical white\\u000a matter (n = 15) were measured using the 4-electrode technique and compared with clinical

M. Akhtari; M. Mandelkern; D. Bui; N. Salamon; H. V. Vinters; G. W. Mathern

2010-01-01

83

Method of forming an electrically conductive cellulose composite  

DOEpatents

An electrically conductive cellulose composite includes a cellulose matrix and an electrically conductive carbonaceous material incorporated into the cellulose matrix. The electrical conductivity of the cellulose composite is at least 10 .mu.S/cm at 25.degree. C. The composite can be made by incorporating the electrically conductive carbonaceous material into a culture medium with a cellulose-producing organism, such as Gluconoacetobacter hansenii. The composites can be used to form electrodes, such as for use in membrane electrode assemblies for fuel cells.

Evans, Barbara R. (Oak Ridge, TN); O'Neill, Hugh M. (Knoxville, TN); Woodward, Jonathan (Ashtead, GB)

2011-11-22

84

Synthesis and electrical conductivity of multilayer silicene  

SciTech Connect

The epitaxial growth and the electrical resistance of multilayer silicene on the Ag(111) surface has been investigated. We show that the atomic structure of the first silicene layer differs from the next layers and that the adsorption of Si induces the formation of extended silicene terraces surrounded by step bunching. Thanks to the controlled contact formation between the tips of a multiple probe scanning tunneling microscope and these extended terraces, a low sheet resistance, albeit much higher than the electrical resistance of the underlying silver substrate, has been measured, advocating for the electrical viability of multilayer silicene.

Vogt, P., E-mail: patrick.vogt@tu-berlin.de, E-mail: bruno.grandidier@isen.iemn.univ-lille1.fr; Bruhn, T. [Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin (Germany); Capiod, P.; Berthe, M.; Grandidier, B., E-mail: patrick.vogt@tu-berlin.de, E-mail: bruno.grandidier@isen.iemn.univ-lille1.fr [Institut d'Electronique, de Microélectronique et de Nanotechnologies (IEMN), CNRS, UMR 8520 Département ISEN, 41 bd Vauban, 59046 Lille Cedex (France); Resta, A. [Aix-Marseille University, CNRS-CINaM, Campus de Luminy, Case 913, F-13288 Marseille Cedex 09 (France); De Padova, P. [Instituto di Struttura della Materia, Consiglio Nazionale delle Ricerche - ISM, via Fosso del Cavaliere, 00133 Roma (Italy); Le Lay, G. [Aix-Marseille University, CNRS-CINaM, Campus de Luminy, Case 913, F-13288 Marseille Cedex 09 (France); Instituto di Struttura della Materia, Consiglio Nazionale delle Ricerche - ISM, via Fosso del Cavaliere, 00133 Roma (Italy)

2014-01-13

85

Mantle electrical conductivity profile of Niger delta region  

NASA Astrophysics Data System (ADS)

The mantle electrical conductivity-depth profile of the Niger delta region in Nigeria has been determined using solar quiet day ionospheric current (Sq). The magnetometer data obtained in 2010 from geomagnetic stations installed in Lagos by magnetic dataset (MAGDAS) in 2008 and data from magnetometers installed in some parts of Niger delta by Center for Basic Space Science, University of Nigeria, Nsukka, were employed in this study. Gauss spherical harmonic analysis (SHA) method was used to separate the internal and external field contributions to Sq current system. The result depicted that the conductivity profile rose steadily from about 0.032 S/m at a depth of 89 km to 0.041 S/m at 100 km and 0.09 S/m at 221 km. This high conductivity region agreed with the global seismic low velocity region, the asthenosphere. The conductivity profile continued increasing downward until it got to 0.157 S/m at a depth of about 373 km (close to the base of upper mantle), 0.201 S/m at 784 km and reached 0.243 S/m at a depth of 1179 km at the lower mantle.

Obiora, Daniel N.; Okeke, Francisca N.; Yumoto, K.; Agha, Stan O.

2014-06-01

86

Electrically conducting ternary amorphous fully oxidized materials and their application  

NASA Technical Reports Server (NTRS)

Electrically active devices are formed using a special conducting material of the form Tm--Ox mixed with SiO2 where the materials are immiscible. The immiscible materials are forced together by using high energy process to form an amorphous phase of the two materials. The amorphous combination of the two materials is electrically conducting but forms an effective barrier.

Giauque, Pierre (Inventor); Nicolet, Marc (Inventor); Gasser, Stefan M. (Inventor); Kolawa, Elzbieta A. (Inventor); Cherry, Hillary (Inventor)

2004-01-01

87

Electrical conductivity and partial melting of mafic rocks under pressure  

Microsoft Academic Search

We demonstrate the importance of electric conductivity measurements of partially molten mafic rocks by examining of Oman gabbro, Karelia olivinite, Ronda and Spitzbergen peridotites. The electrical conductivities of these rocks were estimated using the impedance spectroscopy at temperatures between 800°C and 1450°C and at pressures between 0.3 and 2 GPa in experiments performed in a piston cylinder apparatus. At temperatures

J. Maumus; N. Bagdassarov; H. Schmeling

2005-01-01

88

Electrical conductivity of. gamma. -irradiated and chemically oxidized wool  

SciTech Connect

Examples of wool fibers were irradiated with gamma rays and chemically oxidized with H/sub 2/O/sub 2/ to study the effect on their electrical conductivity. In both cases, electrical conductivity increased whereas the activation cnergy decreased with increases in diameter, moisture content and intrensic ash content of the wool samples.

Moharram, M.A. (Tanta Univ., Cairo, Egypt); Abou Sekkina, M.M.; Rabie, S.M.

1981-08-01

89

High pressure electrical conductivity studies of acid doped polybenzimidazole  

Microsoft Academic Search

Electrical conductivity studies of acid doped poplybenzimidazole (PBI) and 85% phosphoric acid have been carried out. The PBI contained about 600mol% of 85% phosphoric acid and the electrical conductivity was deduced from complex impedance studies which were made at frequencies from 10 to 107Hz. Measurements were made at pressures up to 0.25 GPa and temperatures of about 25, 50 and

J. J Fontanella; M. C Wintersgill; J. S Wainright; R. F Savinell; M Litt

1998-01-01

90

Synthesis of novel electrically conducting polymers: Potential conducting Langmuir-Blodgett films and conducting polymers on defined surfaces  

NASA Technical Reports Server (NTRS)

Based on previous results involving thiophene derived electrically conducting polymers in which it was shown that thiophene, 3-substituted thiophenes, furans, and certain oligomers of these compounds showed electrical conductivity after polymerization. The conductivity was in the order of up to 500 S/cm. In addition, these polymers showed conductivity without being doped and most of all they were practically inert toward ambient conditions. They even could be used in aqueous media. With these findings as a guide, a number of 3-long-chain-substituted thiophenes and 1-substituted-3-long-chain substituted pyrrols were synthesized as monomers for potential polymeric electrically conducting Langmuir-Blodgett films.

Zimmer, Hans

1993-01-01

91

Photochemical formation of electrically conductive silver nanowires on polymer scaffolds.  

PubMed

A photochemical method has been exploited for the synthesis of electrically conductive silver (Ag) nanowires in a polymer solution in the presence of negatively charged Au seed particles. The synthesis was completed within 8 min of UV-photoirradiation in ambient conditions. The nanowires were fabricated on a PVA template having an average diameter of 135+/-20 nm and a length of 10-20 microm. The current-voltage (I-V) characterization showed that the PVA-Ag nanowires were continuous, having Ohmic behavior with low contact resistance. Results indicate that the PVA acted as a reducing agent, stabilizing agent, and a template for the nucleation and growth of Ag nanowires. The Ag deposition was highly selective and on the PVA only. Our research indicated that the PVA-Ag nanowires might be useful as interconnects in nanoscale integrated circuitry, functional nanodevices, and in optoelectronics. PMID:20138630

Kundu, Subrata; Huitink, David; Wang, Ke; Liang, Hong

2010-04-15

92

Electrical conductivity anisotropy in alkali feldspar at high pressure  

NASA Astrophysics Data System (ADS)

Magnetotelluric studies have shown that electrical conductivity in the crust is highly anisotropic. Knowledge of the anisotropy of crustal minerals, such as feldspar and quartz, is essential to interpreting this phenomenon. Feldspars are the most abundant minerals in the earth's crust, and thus, the electrical conductivity of feldspars may help in understanding of the bulk conductivity of the crust. The electrical conductivities of single-crystal and polycrystalline feldspars have been previously studied, but few studies have considered the electrical conductivity of single alkali feldspars. In this study, we investigated the electrical conductivity of alkali feldspars at different orientations under high temperatures and pressures through several heating and cooling cycles. The starting materials were natural alkali feldspar minerals collected from Beijing, China. The samples contain 65 % potassium-rich host (microcline) and 30 % sodium-rich exsolution lamellae (albite), as well as ~5% minor phases. The impedance spectrum measurements were carried out in a high-pressure cubic-anvil apparatus.All complex impedance measurements were performed at 1 GPa using a Solartron 1260 impedance phase analyzer. Impedance arcs representing crystal conductivity occur in the frequency range of ~10^3-10^6 Hz. The electrical conductivity of alkali feldspars increased with increasing temperature. The highest electrical conductivities in alkali feldspars were measured along the a-axis, with somewhat lower conductivities along the b-axis and the lowest conductivities along the c-axis, suggesting minor anisotropy. The activation enthalpies ranged from 100 to 110 kJ/mol. The electrical conductivity of alkali feldspar is mildly anisotropic, with an anisotropy factor of approximately 2. The minor anisotropy in conductivity for alkali feldspar may not account for the anisotropy of the crust. This work is supported by the Important Field Knowledge Innovation Program (KZCX2-YW-QN608), National Natural Science Foundation of China (No. 40774036)

Wang, D.; Yu, Y.

2013-12-01

93

Electrical Conductivity and Magnetic Susceptibility of Ovalene  

Microsoft Academic Search

OVALENE(C32H14) has the most compact configuration of rings among the condensed aromatic compounds which have so far been obtained. From this point of view, it is of interest to know the electrical and magnetic properties to be attributed to the pi-electrons of this molecule.

Hideo Akamatu; Hiroo Inokuchi; Takashi Handa

1951-01-01

94

Review article Influence of electric conductivity management  

E-print Network

their sugar: acid ratio, and influences the transpiration rate and the water uptake by the plant, which 2001; accepted 26 February 2001) Abstract ­ The osmotic and ionic effects of the electrical growers to modify water availability to the crop and hence improve fruit quality. At some point, however

Boyer, Edmond

95

Defect electrical conduction in SIMOX buried oxides  

Microsoft Academic Search

It is pointed out that the buried oxide (BOX) layers in SIMOX structures exhibit localized defect conduction superimposed on the background (bulk) conduction. Type I defects show a pre-breakdown quasi-linear I-V characteristic with 10-7

George A. Brown; Akos G. Revesz

1993-01-01

96

Models proposed to explain the electrical conductivity of mixtures made of conductive and insulating materials  

Microsoft Academic Search

The electrical conductivity of mixtures of conductive and insulating materials is reviewed. In general, the conductivity of such mixtures increases drastically at a certain concentration of the conductive component, the so-called percolation concentration. Among the parameters influencing the percolation concentration, the filler distribution, filler shape, filler\\/matrix interactions and the processing technique are the most important ones. On the basis of

F. Lux

1993-01-01

97

Structural and Electrical Study of Conducting Polymers  

NASA Astrophysics Data System (ADS)

Pure and oxalic acid doped conducting polymers (polyaniline and polypyrrole) were chemically synthesized using ammonium persulfate (APS) as an oxidant. These samples were characterized through Scanning Electron Microscopy (SEM), which provides information about the surface topography of polymers. I-V characteristics have been recorded at room temperature as well as in the temperature range from 313 K to 463 K. So obtained characteristic curves were found to be linear. Temperature dependence of conductivity suggests a semiconducting nature in polyaniline samples with increase in temperature, whereas oxalic acid doped polypyrrole sample suggests a transition from semiconducting to metallic nature with the increase of temperature.

Shaktawat, Vinodini; Dixit, Manasvi; Saxena, N. S.; Sharma, Kananbala

2010-06-01

98

High temperature electrical conductivity of rigid polyurethane foam  

Microsoft Academic Search

The temperature dependence of the electrical conductivity of three rigid polyurethane foams prepared using different formulations was measured to approx. 320 C. The materials exhibit similar conductivity characteristics, showing a pronounced increase in conductivity with increasing temperature. The insulating characteristics to approx. 200 C are better than that for phenolic materials (glass fabric reinforced), and are similar to those for

R. T. Johnson Jr.; R. T. Jr

1984-01-01

99

EFFECTS OF TRITIUM GAS EXPOSURE ON ELECTRICALLY CONDUCTING POLYMERS  

Microsoft Academic Search

Effects of beta (tritium) and gamma irradiation on the surface electrical conductivity of two types of conducting polymer films are documented to determine their potential use as a sensing and surveillance device for the tritium facility. It was shown that surface conductivity was significantly reduced by irradiation with both gamma and tritium gas. In order to compare the results from

M. Kane; E. Clark; R. Lascola

2009-01-01

100

Effect of electrical double layer on electric conductivity and pressure drop in a pressure-driven microchannel flow.  

PubMed

The effect of an electrical double layer (EDL) on microchannel flow has been studied widely, and a constant bulk electric conductivity is often used in calculations of flow rate or pressure drop. In our experimental study of pressure-driven micropipette flows, the pipette diameter is on the same order of magnitude as the Debye length. The overlapping EDL resulted in a much higher electric conductivity, lower streaming potential, and lower electroviscous effect. To elucidate the effect of overlapping EDL, this paper developed a simple model for water flow without salts or dissolved gases (such as CO(2)) inside a two-dimensional microchannel. The governing equations for the flow, the Poisson, and Nernst equations for the electric potential and ion concentrations and the charge continuity equation were solved. The effects of overlapping EDL on the electric conductivity, velocity distribution, and overall pressure drop in the microchannel were quantified. The results showed that the average electric conductivity of electrolyte inside the channel increased significantly as the EDL overlaps. With the modified mean electric conductivity, the pressure drop for the pressure-driven flow was smaller than that without the influence of the EDL on conductivity. The results of this study provide a physical explanation for the observed decrease in electroviscous effect for microchannels when the EDL layers from opposing walls overlap. PMID:20644673

Ban, Heng; Lin, Bochuan; Song, Zhuorui

2010-01-01

101

Effect of electrical double layer on electric conductivity and pressure drop in a pressure-driven microchannel flow  

PubMed Central

The effect of an electrical double layer (EDL) on microchannel flow has been studied widely, and a constant bulk electric conductivity is often used in calculations of flow rate or pressure drop. In our experimental study of pressure-driven micropipette flows, the pipette diameter is on the same order of magnitude as the Debye length. The overlapping EDL resulted in a much higher electric conductivity, lower streaming potential, and lower electroviscous effect. To elucidate the effect of overlapping EDL, this paper developed a simple model for water flow without salts or dissolved gases (such as CO2) inside a two-dimensional microchannel. The governing equations for the flow, the Poisson, and Nernst equations for the electric potential and ion concentrations and the charge continuity equation were solved. The effects of overlapping EDL on the electric conductivity, velocity distribution, and overall pressure drop in the microchannel were quantified. The results showed that the average electric conductivity of electrolyte inside the channel increased significantly as the EDL overlaps. With the modified mean electric conductivity, the pressure drop for the pressure-driven flow was smaller than that without the influence of the EDL on conductivity. The results of this study provide a physical explanation for the observed decrease in electroviscous effect for microchannels when the EDL layers from opposing walls overlap. PMID:20644673

Ban, Heng; Lin, Bochuan; Song, Zhuorui

2010-01-01

102

Assembly for electrical conductivity measurements in the piston cylinder device  

DOEpatents

An assembly apparatus for measurement of electrical conductivity or other properties of a sample in a piston cylinder device wherein pressure and heat are applied to the sample by the piston cylinder device. The assembly apparatus includes a body, a first electrode in the body, the first electrode operatively connected to the sample, a first electrical conductor connected to the first electrode, a washer constructed of a hard conducting material, the washer surrounding the first electrical conductor in the body, a second electrode in the body, the second electrode operatively connected to the sample, and a second electrical conductor connected to the second electrode.

Watson, Heather Christine (Dublin, CA); Roberts, Jeffrey James (Livermore, CA)

2012-06-05

103

Using electrical impedance tomography to map subsurface hydraulic conductivity  

DOEpatents

The use of Electrical Impedance Tomography (EIT) to map subsurface hydraulic conductivity. EIT can be used to map hydraulic conductivity in the subsurface where measurements of both amplitude and phase are made. Hydraulic conductivity depends on at least two parameters: porosity and a length scale parameter. Electrical Resistance Tomography (ERT) measures and maps electrical conductivity (which can be related to porosity) in three dimensions. By introducing phase measurements along with amplitude, the desired additional measurement of a pertinent length scale can be achieved. Hydraulic conductivity controls the ability to flush unwanted fluid contaminants from the surface. Thus inexpensive maps of hydraulic conductivity would improve planning strategies for subsequent remediation efforts. Fluid permeability is also of importance for oil field exploitation and thus detailed knowledge of fluid permeability distribution in three-dimension (3-D) would be a great boon to petroleum reservoir analysts.

Berryman, James G. (Danville, CA); Daily, William D. (Livermore, CA); Ramirez, Abelardo L. (Pleasanton, CA); Roberts, Jeffery J. (Livermore, CA)

2000-01-01

104

Local electric conductive property of Si nanowire models  

NASA Astrophysics Data System (ADS)

Local electric conductive properties of Si nanowire models are investigated by using two local electric conductivity tensors, {{? }limits^{leftrArr }}_{ext}(r) and {{? }limits^{leftrArr }}_{int}(r), defined in Rigged QED. It is emphasized that {{? }limits^{leftrArr }}_{int}(r) is defined as the response of electric current to the actual electric field at a specific point and does not have corresponding macroscopic physical quantity. For the Si nanowire models, there are regions which show complicated response of electric current density to electric field, in particular, opposite and rotational ones. Local conductivities are considered to be available for the study of a negative differential resistance (NDR), which may be related to this opposite response. It is found that {{? }limits^{leftrArr }}_{int}(r) shows quite different pattern from {{? }limits^{leftrArr }}_{ext}(r), local electric conductivity defined for the external electric field. The effects of impurities are also studied by using the model including a Ge atom, in terms of the local response to electric field. It is found that the difference from the pristine model is found mainly around the Ge atom.

Ikeda, Yuji; Senami, Masato; Tachibana, Akitomo

2012-12-01

105

Microstructure, electrical conductivity, and piezoelectric properties of bismuth titanate  

Microsoft Academic Search

A study was conducted on the effects of microstructure, atmosphere, and several dopants on the electrical conductivity of bismuth titanate (BiâTiâOââ, BIT). Increased grain size increased the conductivity in undoped BIT as did acceptor dopants that substituted for either Bi (Ca and Sr) or Ti(Fe). A donor dopant (Nb) decreased the conductivity in BIT by as much as 3 orders

Holly S. Shulman; Martin Testorf; Dragan Damjanovic; Nava Setter

1996-01-01

106

Software optimization for electrical conductivity imaging in polycrystalline diamond cutters  

SciTech Connect

We previously reported on an electrical conductivity imaging instrument developed for measurements on polycrystalline diamond cutters. These cylindrical cutters for oil and gas drilling feature a thick polycrystalline diamond layer on a tungsten carbide substrate. The instrument uses electrical impedance tomography to profile the conductivity in the diamond table. Conductivity images must be acquired quickly, on the order of 5 sec per cutter, to be useful in the manufacturing process. This paper reports on successful efforts to optimize the conductivity reconstruction routine, porting major portions of it to NVIDIA GPUs, including a custom CUDA kernel for Jacobian computation.

Bogdanov, G.; Ludwig, R. [Department of Electrical and Computer Engineering, Worcester Polytechnic Institute, 100 Institute Rd, Worcester, MA 01609 (United States); Wiggins, J.; Bertagnolli, K. [US Synthetic, 1260 South 1600 West, Orem, UT 84058 (United States)

2014-02-18

107

Thermal conductivity and electrical resistivity of porous materials  

NASA Technical Reports Server (NTRS)

Process for determining thermal conductivity and electrical resistivity of porous materials is described. Characteristics of materials are identified and used in development of mathematical models. Limitations of method are examined.

Koh, J. C. Y.; Fortini, A.

1972-01-01

108

Electrical conductivity of rocks at high pressures and temperatures  

NASA Technical Reports Server (NTRS)

The results of studies of the electrical conductivity in the most widely distributed types of igneous rocks, at temperatures of up to 1200 C, at atmospheric pressure, and also at temperatures of up to 700 C and at pressures of up to 20,000 kg/sq cm are described. The figures of electrical conductivity, of activaation energy and of the preexponential coefficient are presented and the dependence of these parameters on the petrochemical parameters of the rocks are reviewed. The possible electrical conductivities for the depository, granite and basalt layers of the Earth's crust and of the upper mantle are presented, as well as the electrical conductivity distribution to the depth of 200 to 240 km for different geological structures.

Parkhomenko, E. I.; Bondarenko, A. T.

1986-01-01

109

Electrical Circuit Analogues of Thermal Conduction and Diffusion  

ERIC Educational Resources Information Center

After briefly reviewing equations of conduction and diffusion, and voltage and charge in electrical circuits, a simple experiment is given that allows students practical experience in a theoretical realm of physics. (MDR)

Tomlin, D. H.; Fullarton, G. K.

1978-01-01

110

Conductivity  

NSDL National Science Digital Library

Students make a simple conductivity tester using a battery and light bulb. They learn the difference between conductors and insulators of electrical energy as they test a variety of materials for their ability to conduct electricity.

Integrated Teaching and Learning Program,

111

Effect of volatile components on electrical conductivity of mantle materials  

NASA Astrophysics Data System (ADS)

Recent laboratory electrical conductivity measurements of the main mantle constituent minerals have refined our understanding of the effect of water, carbon and iron contents on electrical conductivity. Especially effect of water on electrical conductivity of nominally anhydrous minerals has been substantially investigated. These studies suggested that proton conduction in nominally anhydrous minerals can elevate the electrical conductivity compared to the dry condition. However, if the water exists along grain boundaries, the proton conduction is completely masked by contribution of grain boundary water to the bulk conductivity. This phenomena was confirmed by the conductivity measurement at high temperatures (> 1000 K), leading to higher conductivity due to the grain boundary water generated by dehydration of sample. For nominally anhydrous minerals containing water in its crystal structure, water must partition between crystal and fluid. Thus when certain amount of grain boundary water exists, we cannot directly estimate water content in minerals based on a comparison between laboratory and geophysical data. Volatile components such as water and carbon dioxide in mantle materials can largely reduce the melting temperature. For example, solidus temperature of carbonate-bearing peridotite is below the normal mantle geotherm up to the 330 km depth. Solidus of water-saturated peridotite is low enough to generate partial melting through the upper mantle and the transition zone. Electrical conductivity of partial molten carbonate peridotite showed that the conductivity of the carbonate melt is nearly one order of magnitude higher than those of silicate melt in peridotite. In addition, electrical conductivity of hydrous basalt also show enhancement of the conductivity. Considering the effect of water and carbon on the bulk conductivity, the conductivity of volatile-bearing peridotites could be significantly higher than that of the volatile-free peridotites. Because melts contaning volatile components have smaller temperature dependence (low activation energy), the high conductivity can be accomplished even if temperature is largely lower than the normal mantle geotherm. Therefore, the electrical conductivity of the Earth's mantle would be controlled by the trace amount of volatile components.

Yoshino, T.; Katsura, T.; Shimojuku, A.

2011-12-01

112

Manipulating connectivity and electrical conductivity in metallic nanowire networks.  

PubMed

Connectivity in metallic nanowire networks with resistive junctions is manipulated by applying an electric field to create materials with tunable electrical conductivity. In situ electron microscope and electrical measurements visualize the activation and evolution of connectivity within these networks. Modeling nanowire networks, having a distribution of junction breakdown voltages, reveals universal scaling behavior applicable to all network materials. We demonstrate how local connectivity within these networks can be programmed and discuss material and device applications. PMID:23062152

Nirmalraj, Peter N; Bellew, Allen T; Bell, Alan P; Fairfield, Jessamyn A; McCarthy, Eoin K; O'Kelly, Curtis; Pereira, Luiz F C; Sorel, Sophie; Morosan, Diana; Coleman, Jonathan N; Ferreira, Mauro S; Boland, John J

2012-11-14

113

Which electric fields are realizable in conducting January 8, 2013  

E-print Network

u represents the electric field, while u is the current field according to Ohm's law. AlternativelyWhich electric fields are realizable in conducting materials? January 8, 2013 Marc Brianea , Graeme such that u is a divergence free current field. The construction is shown to be always possible locally in Rd

Paris-Sud XI, Université de

114

DC Electrical Conductivity of Silicon Carbide Ceramics and Composites for Flow Channel Insert Applications  

SciTech Connect

High purity chemically vapor-deposited silicon carbide (SiC) and 2D continuous SiC fiber, chemically vapor-infiltrated SiC matrix composites with pyrocarbon interphases were examined for temperature dependent (RT to 800 C) electrical conductivity and the influence of neutron irradiation on it. In the 2D composites, trans-thickness electrical conductivity was dominated by bypass conduction via interphase network at relatively low temperatures, whereas conduction through SiC constituents dominated at higher temperatures. The Influence of neutron irradiation on electrical properties appeared very strong for SiC, resulting typically in by orders lower ambient conductivity and steeper temperature dependency. Through-thickness electrical conductivity of neutron-irradiated 2D SiC composites with thin PyC interphase will likely in the order of 10 S/m in the typical operating temperature range for flow channel inserts. Mechanisms of electrical conduction in the composites and irradiation-induced modification of electrical conductivity of the composites and their constituents are discussed.

Katoh, Yutai [ORNL; Kondo, Sosuke [ORNL; Snead, Lance Lewis [ORNL

2009-01-01

115

Thermal and Electrical Conductivity Measurements of CDA 510 Phosphor Bronze  

NASA Technical Reports Server (NTRS)

Many cryogenic systems use electrical cables containing phosphor bronze wire. While phosphor bronze's electrical and thermal conductivity values have been published, there is significant variation among different phosphor bronze formulations. The James Webb Space Telescope (JWST) will use several phosphor bronze wire harnesses containing a specific formulation (CDA 510, annealed temper). The heat conducted into the JWST instrument stage is dominated by these harnesses, and approximately half of the harness conductance is due to the phosphor bronze wires. Since the JWST radiators are expected to just keep the instruments at their operating temperature with limited cooling margin, it is important to know the thermal conductivity of the actual alloy being used. We describe an experiment which measured the electrical and thermal conductivity of this material between 4 and 295 Kelvin.

Tuttle, James E.; Canavan, Edgar; DiPirro, Michael

2009-01-01

116

7. VIEW OF THE HOT BED FOR THE CONTINUOUS ELECTRIC ...  

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

7. VIEW OF THE HOT BED FOR THE CONTINUOUS ELECTRIC FURNACE HEAT TREATING LINE AT THE HEAT TREATMENT PLANT OF THE DUQUESNE WORKS. - U.S. Steel Duquesne Works, Heat Treatment Plant, Along Monongahela River, Duquesne, Allegheny County, PA

117

8. QUENCHING MECHANISM FOR THE CONTINUOUS ELECTRIC FURNACE HEAT TREATING ...  

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

8. QUENCHING MECHANISM FOR THE CONTINUOUS ELECTRIC FURNACE HEAT TREATING LINE AT THE HEAT TREATMENT PLANT OF THE DUQUESNE WORKS. - U.S. Steel Duquesne Works, Heat Treatment Plant, Along Monongahela River, Duquesne, Allegheny County, PA

118

Electrostatic Discharge Sensitivity and Electrical Conductivity of Composite Energetic Materials  

SciTech Connect

Composite energetic material response to electrical stimuli was investigated and a correlation between electrical conductivity and ignition sensitivity was examined. The composites consisted of micrometer particle aluminum combined with another metal, metal oxide, or fluoropolymer. Of the nine tested mixtures, aluminum with copper oxide was the only mixture to ignite by electrostatic discharge with minimum ignition energy (MIE) of 25 mJ and an electrical conductivity of 1246.25 nS; two orders of magnitude higher than the next composite. This study showed a similar trend in MIE for ignition triggered by a discharged spark compared with a thermal hot wire source.

Michael A. Daniels; Daniel J. Prentice; Chelsea Weir; Michelle L. Pantoya; Gautham Ramachandran; Tim Dallas

2013-02-01

119

Electrical conductivity anisotropy in partially molten peridotite under shear deformation  

NASA Astrophysics Data System (ADS)

The electrical conductivity of partially molten peridotite was measured during deformation in simple shear at 1 GPa in a DIA type apparatus with a uniaxial deformation facility. To detect development of electrical anisotropy during deformation of partially molten system, the electrical conductivity was measured simultaneously in two directions of three principal axes: parallel and normal to the shear direction on the shear plane, and perpendicular to the shear plane. Impedance spectroscopy measurement was performed at temperatures of 1523 K for Fe-bearing and 1723 K for Fe-free samples, respectively, in a frequency range from 0.1 Hz to 1 MHz. The electrical conductivity of partially molten peridotite parallel to shear direction increased to more than one order of magnitude higher than those normal to shear direction on the shear plane. This conductivity difference is consistent with the magnitude of the conductivity anisotropy observed in the oceanic asthenosphere near the Eastern Pacific Rise. On the other hand, conductivity perpendicular to the shear plane decreased gradually after the initiation of shear and finally achieved a value close to that of olivine. The magnitude and development style of conductivity anisotropy was almost the same for both Fe-bearing and Fe-free melt-bearing systems, and also independent of shear strain. However, such conductivity anisotropy was not developed in melt-free samples during shear deformation, suggesting that the conductivity anisotropy requires a presence of partial melting under shear stress. Microstructural observations of deformed partially molten peridotite samples demonstrated that conductivity anisotropy was attributed to the elongation of melt pockets parallel to the shear direction. Horizontal electrical conductivity anisotropy revealed by magnetotelluric surveys in the oceanic asthenosphere can be well explained by the realignment of partial melt induced by shear stress.

Zhang, Baohua; Yoshino, Takashi; Yamazaki, Daisuke; Manthilake, Geeth; Katsura, Tomoo

2014-11-01

120

ION AND TEMPERATURE DEPENDENCE OF ELECTRICAL CONDUCTANCE FOR NATURAL WATERS  

EPA Science Inventory

Four empirical equations describing the temperature dependence of electrical conductance of aqueous solutions are compared for the case of single electrolytes. The best method uses a modified Walden product where the log of the ratio between the conductances at two temperatures i...

121

Calculation of Electrical and Thermal Conductivities of Metallurgical Plasmas  

E-print Network

) ) Calculation of Electrical and Thermal Conductivities of Metallurgical Plasmas by G. J. Dunn Abstract A simplified road map ofthe plasma physics literature for calculation ofelectrical and thermal of the extensive literature on calculation of plasma elec- trical and thermal conductivities. An attempt is made

Eagar, Thomas W.

122

Kinetics of aggregation in colloidal systems. Electrical conductivity measurements  

Microsoft Academic Search

We report low-frequency measurements of the electrical conductivity of charged colloids in an aqueous solution containing a simple electrolyte as aggregating agent. The measurements are performed as a function of time in a regime where the aggregation is diffusion limited. The results for the relative increase of conductivity can be described in terms of an asymptotic power law in time

C. Cametti; P. Codastefano; P. Tartaglia

1988-01-01

123

Thermal conductivity, electrical conductivity and specific heat of copper-carbon fiber composite  

NASA Technical Reports Server (NTRS)

A new material of copper/carbon fiber composite is developed which retains the properties of copper, i.e., its excellent electrical and thermal conductivity, and the property of carbon, i.e., a small thermal expansion coefficient. These properties of the composite are adjustable within a certain range by changing the volume and/or the orientation of the carbon fibers. The effects of carbon fiber volume and arrangement changes on the thermal and electrical conductivity, and specific heat of the composite are studied. Results obtained are as follows: the thermal and electrical conductivity of the composite decrease as the volume of the carbon fiber increases, and were influenced by the fiber orientation. The results are predictable from a careful application of the rule of mixtures for composites. The specific heat of the composite was dependent, not on fiber orientation, but on fiber volume. In the thermal fatigue tests, no degradation in the electrical conductivity of this composite was observed.

Kuniya, Keiichi; Arakawa, Hideo; Kanai, Tsuneyuki; Chiba, Akio

1988-01-01

124

Electric field enhanced conductivity in strongly coupled dense metal plasma  

SciTech Connect

Experimentation with dense metal plasma has shown that non-negligible increases in plasma conductivity are induced when a relatively low electric field ({approx}6 kV/cm) is applied. Existing conductivity models assume that atoms, electrons, and ions all exist in thermal equilibrium. This assumption is invalidated by the application of an appreciable electric field, where electrons are accelerated to energies comparable to the ionization potential of the surrounding atoms. Experimental data obtained from electrically exploded silver wire is compared with a finite difference hydrodynamic model that makes use of the SESAME equation-of-state database. Free electron generation through both thermal and electric field excitations, and their effect on plasma conductivity are applied and discussed.

Stephens, J.; Neuber, A. [Center for Pulsed Power and Power Electronics, Texas Tech University, Lubbock, Texas 79409 (United States)

2012-06-15

125

UV-induced surface electrical conductivity jump of polymer nanocomposites  

SciTech Connect

A method of improving the electrical conductivity of polymer nanocomposites under UV irradiation was described. An anatase TiO{sub 2}-grafted carbon nanotube could function as a conductive filler and a photocatalyst when it compounds with a poly(L-lactide) to produce a composite. After UV irradiation, the decomposition of the polymer only occurred on the surface of a poly(L-lactide)/TiO{sub 2} grafted carbon nanotube composite and not on bulk, resulting in an electrical conductivity jump as high as six orders of magnitude.

Chen Guangxin [College of Materials Science and Engineering, Beijing University of Chemical Technology, P.O. Box 206, Beijing 100029 (China); Miyauchi, Masahiro; Shimizu, Hiroshi [Nanotechnology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565 (Japan)

2008-05-19

126

Continuous-flow electrophoresis: Membrane-associated deviations of buffer pH and conductivity  

NASA Technical Reports Server (NTRS)

The deviations in buffer pH and conductivity which occur near the electrode membranes in continuous-flow electrophoresis were studied in the Beckman charged particle electrophoresis system and the Hanning FF-5 preparative electrophoresis instrument. The nature of the membranes separating the electrode compartments from the electrophoresis chamber, the electric field strength, and the flow rate of electrophoresis buffer were all found to influence the formation of the pH and conductivity gradients. Variations in electrode buffer flow rate and the time of electrophoresis were less important. The results obtained supported the hypothesis that a combination of Donnan membrane effects and the differing ionic mobilities in the electrophoresis buffer was responsible for the formation of the gradients. The significance of the results for the design and stable operation of continuous-flow electrophoresis apparatus was discussed.

Smolka, A. J. K.; Mcguire, J. K.

1978-01-01

127

Detection of temperature distribution via recovering electrical conductivity in MREIT  

NASA Astrophysics Data System (ADS)

In radiofrequency (RF) ablation or hyperthermia, internal temperature measurements and tissue property imaging are important to control their outputs and assess the treatment effect. Recently, magnetic resonance electrical impedance tomography (MREIT), as a non-invasive imaging method of internal conductivity distribution using an MR scanner, has been developed. Its reconstruction algorithm uses measured magnetic flux density induced by injected currents. The MREIT technique has the potential to visualize electrical conductivity of tissue with high spatial resolution and measure relative conductivity variation according to the internal temperature change based on the fact that the electrical conductivity of biological tissues is sensitive to the internal temperature distribution. In this paper, we propose a method to provide a non-invasive alternative to monitor the internal temperature distribution by recovering the electrical conductivity distribution using the MREIT technique. To validate the proposed method, we design a phantom with saline solution and a thin transparency film in a form of a hollow cylinder with holes to create anomalies with different electrical and thermal conductivities controlled by morphological structure. We first prove the temperature maps with respect to spatial and time resolution by solving the thermal conductivity partial differential equation with the real phantom experimental environment. The measured magnetic flux density and the reconstructed conductivity distributions using the phantom experiments were compared to the simulated temperature distribution. The relative temperature variation of two testing objects with respect to the background saline was determined by the relative conductivity contrast ratio (rCCR,%). The relation between the temperature and conductivity measurements using MREIT was approximately linear with better accuracy than 0.22 °C.

In Oh, Tong; Kim, Hyung Joong; Jeong, Woo Chul; Chauhan, Munish; In Kwon, Oh; Woo, Eung Je

2013-04-01

128

GLOBE Videos: Hydrology Protocols - Electrical Conductivity (9:20 min)  

NSDL National Science Digital Library

The video is a procedural guide to sampling electrical conductivity measurements in water bodies using standardized GLOBE protocols. It provides a step-by-step explanation of the field procedure and features students conducting the investigation and asking questions about measuring electrical conductivity and what these measurements mean with respect to water impurities and dissolved solids. The resource includes a video, transcript, and is supported by the Electrical Conductivity Protocol in the GLOBE Teacher's Guide. This is one of seven videos on hydrology in the 24-part instructional video series describing scientific protocols used by GLOBE (Global Learning and Observation to Benefit the Environment) a worldwide, hands-on, K-12 school-based science education program.

129

The role of acids in electrical conduction through ice  

NASA Astrophysics Data System (ADS)

Electrical conduction through meteoric polar ice is controlled by soluble impurities that originate mostly from sea salt, biomass burning, and volcanic eruptions. The strongest conductivity response is to acids, yet the mechanism causing this response has been unclear. Here we elucidate conduction mechanisms in ice using broadband dielectric spectroscopy of meteoric polar ice cores. We find that conduction through polycrystalline polar ice is consistent with Jaccard theory for migration of charged protonic point defects through single ice crystals, except that bulk DC conduction is impeded by grain boundaries. Neither our observations nor modeling using Archie's Law support the hypothesis that grain-boundary networks of unfrozen acids cause significant electrolytic conduction. Common electrical logs of ice cores (by electrical conductivity measurement [ECM] or dielectric profiling [DEP]) and the attenuation of radio waves in ice sheets thus respond to protonic point defects only. This response implies that joint interpretation of electrical and chemical logs can determine impurity partitioning between the lattice and grain boundaries or inclusions. For example, in the Greenland Ice Core Project (GRIP) ice core from central Greenland, on average more than half of the available lattice-soluble impurities (H+, Cl-, NH4+) create defects. Understanding this partitioning could help further resolve the nature of past changes in atmospheric chemistry.

Stillman, David E.; MacGregor, Joseph A.; Grimm, Robert E.

2013-03-01

130

Studies with sample conductivity, insertion rates, and particle deflection in a continuous flow electrophoresis system  

NASA Technical Reports Server (NTRS)

The continuous flow electrophoresis system makes electrophoresis possible in a free-flowing film of aqueous electrolyte medium. The sample continuously enters the electrolyte at the top of the chamber and is subjected to the action of a lateral dc field. This divides the sample into fractions since each component has a distinctive electrophoretic mobility. Tests were made using monodisperse polystyrene latex microspheres to determine optimum sample conductivity, insertion rates and optimum electric field applications as baseline data for future STS flight experiments. Optimum sample flow rates for the selected samples were determined to be approximately 26 micro-liters/min. Experiments with samples in deionized water yielded best results and voltages in the 20 V/cm to 30 V/cm range were optimum. Deflections of formaldehyde fixed turkey and bovine erythrocytes were determined using the continuous flow electrophoresis system. The effects of particle interactions on sample resolution and migration in the chamber was also evaluated.

Williams, G., Jr.

1982-01-01

131

Thermal conductivity and electrical resistivity of porous material  

NASA Technical Reports Server (NTRS)

Thermal conductivity and electrical resistivity of porous materials, including 304L stainless steel Rigimesh, 304L stainless steel sintered spherical powders, and OFHC sintered spherical powders at different porosities and temperatures are reported and correlated. It was found that the thermal conductivity and electrical resistivity can be related to the solid material properties and the porosity of the porous matrix regardless of the matrix structure. It was also found that the Wiedermann-Franz-Lorenz relationship is valid for the porous materials under consideration. For high conductivity materials, the Lorenz constant and the lattice component of conductivity depend on the material and are independent of the porosity. For low conductivity, the lattice component depends on the porosity as well.

Koh, J. C. Y.; Fortini, A.

1971-01-01

132

Peculiarities of coexistence of phases with different electric conductivities under the influence of an electric current  

E-print Network

of an electric current Yu. Dolinsky* and T. Elperin The Pearlstone Center for Aeronautical Engineering Studies of coexistence of phases under the influence of the electric current, the phase equilibrium curve splits into two lines in a current-carrying system taking into account the difference of electric conductivities

Elperin, Tov

133

Electrically conducting shape memory polymer composites for electroactive actuator  

NASA Astrophysics Data System (ADS)

We have tried to apply electroactive shape memory polymer to smart actuator. Electroactive shape memory can be achieved by applying an electric field to shape memory polymer without any thermal heating as conventional shape memory polymers. For it, electrically conducting shape memory composites were prepared by incorporating carbon nanotube into polymer matrix. A segmented polyurethane block copolymer composed of 4,4'-methylene bis (phenylisocyanate), polycaprolactone, and 1,4-butanediol was synthesized to be used as shape memory polymer, and carbon nanotube was used after surface-modification by an acid. It was found that nanotube-reinforced composites could show high electrical conductivity with increased modulus at only several weight percentages of nanotube, and electroactive shape recovery effect more than 80% could be obtained. Consequently, electric field-stimulated shape memory could be demonstrated through combined composites of polyurethane and nanotube.

Jung, Yong Chae; Goo, Nam Seo; Cho, Jae Whan

2004-07-01

134

Electrically Conductive Crust in Southern Tibet from INDEPTH Magnetotelluric Surveying  

PubMed

The crust north of the Himalaya is generally electrically conductive below depths of 10 to 20 km. This conductive zone approaches the surface beneath the Kangmar dome (dipping north) and extends beneath the Zangbo suture. A profile crossing the northern Yadong-Gulu rift shows that the high conductivity region extends outside the rift, and its top within the rift coincides with a bright spot horizon imaged on the INDEPTH CMP (common midpoint) profiles. The high conductivity of the middle crust is atypical of stable continental regions and suggests that there is a regionally interconnected fluid phase in the crust of the region. PMID:8939855

Chen; Booker; Jones; Wu; Unsworth; Wei; Tan

1996-12-01

135

Electrical and thermal conductivity of hybrid nanocomposites with giant strain  

NASA Astrophysics Data System (ADS)

The prospect of electronic circuits that are stretchable and bendable promises tantalizing applications such as skin-like electronics, conformable sensors, and lightweight solar cells. The optimization of electronic, thermal, and mechanical properties of conductive and extensible materials is necessary for the application of energy device. Here we demonstrate the theoretical prediction for the electrical conductivity of the nanocomposites compared with experimental results. Also, we present the giant dependence of electrical conductivity on strain and the large positive thermal expansion that can be expected for the elastomer matrix. The percolation threshold (26 vol% of Ag, average interparticle distance model) and Poisson's ratio (Vt=0.33, Vw=0.2) of nanocomposites are significant factors that can determine the electrical and thermal conductivity with giant strain. The thermal conductivity for the electronically conducting elastomeric film is relatively high at the zero-strain state, and shows a non-metallic temperature dependence consistent with phonon transport. The observed combinational property of a very small dependence of conductivity on temperature with an exponential dependence can be suitable for for the mechanical strain sensing.

Chun, Kyoung-Yong; Kim, Shi Hyeong; Shin, Min Kyoon; Spinks, Geoffrey M.; Aliev, Ali E.; Baughman, Ray H.; Kim, Seon Jeong

2013-04-01

136

Thermal and Electrical Conductivities of Porous Si Membranes  

NASA Astrophysics Data System (ADS)

The microstructure of materials affects thermal and electrical transport as well as the physical properties. The effects of the microstructure on both thermal and electrical transport in silicon membranes with periodic microporous structures produced from silicon-on-insulator wafers using microfabrication processes were studied. The in-plane thermal and electrical conductivities of the Si membranes were measured simultaneously by using a self-heating method. The measured thermal conductivity was compared with the result from the periodically laser-heating method. The thermal and electrical conductivities were much lower in the porous membranes than in the non-porous membrane. The measured thermal conductivity was much lower than expected based on values determined using classical models. A significant phonon size effect was observed even in microsized structures, and the mean free path for phonons was very long. It was concluded that phonon transport is quasi-ballistic and electron transport is diffuse in microporous Si structures. It was suggested that the microstructure had a different effect on thermal and electrical transport.

Hagino, Harutoshi; Tanaka, Saburo; Tanimura, Naoki; Miyazaki, Koji

2014-06-01

137

Measurement of Electrical Conductivity into Tomato Cultivation Beds using Small Insertion Type Electrical Conductivity Sensor Designed for Agriculture  

NASA Astrophysics Data System (ADS)

Our group has studied on-site monitoring sensor for agricultural field. An electrical conductivity (EC) sensor had been fabricated using Si integrated circuit technology. EC information of solutions shows ion concentrations dissolving in water, and can be used as the index of nutrient concentration for plants. So, it is important to measure EC in real time and on site. Because our EC sensor (5mm×5mm in size) is smaller than other commercial ones (several centimeters), it is easy to insert and achieve measurement in rock wool. In this study, our sensor measured long term EC values in tomato cultivation soil and rock wool medium. At first, we calibrated a relationship between output voltages and EC values on the sensor. The sensor was confirmed about enough EC measurement range from 8 to 969mS/m. In long period measurement, the sensor was confirmed about continuous operation for over five months, and intermittent measurement for over a year. In measurement in the cultivation soil, the sensor indicated that water was kept and diffused in the soil. In contrast, it was found that water diffused without keeping in it in rock wool medium. We confirmed our small EC sensor is useful for on-site monitoring and analysis of solution concentration distribution in several kinds of cultivation bed in real time.

Kawashima, Kazuko; Futagawa, Masato; Ban, Yoshihiro; Asano, Yoshiyuki; Sawada, Kazuaki

138

Electrical conductivity measurements on silicate melts using the loop technique  

NASA Technical Reports Server (NTRS)

A new method is described for measurement of the electrical conductivity of silicate melts under controlled oxygen partial pressure at temperatures to 1550 C. The melt samples are suspended as droplets on platinum-rhodium loops, minimizing iron loss from the melt due to alloying with platinum, and providing maximum surface exposure of the melt to the oxygen-buffering gas atmosphere. The latter provides extremely rapid equilibration of the melt with the imposed oxygen partial pressure. The loop technique involves a minimum of setup time and cost, provides reproducible results to within + or - 5% and is well suited to electrical conductivity studies on silicate melts containing redox cations.

Waff, H. S.

1976-01-01

139

Electrically conductive doped block copolymer of polyacetylene and polyisoprene  

DOEpatents

An electrically conductive block copolymer of polyisoprene and polyacetyl and a method of making the same are disclosed. The polymer is prepared by first polymerizing isoprene with n-butyllithium in a toluene solution to form an active isoprenyllithium polymer. The active polymer is reacted with an equimolar amount of titanium butoxide and subsequently exposed to gaseous acetylene. A block copolymer of polyisoprene and polyacetylene is formed. The copolymer is soluble in common solvents and may be doped with I.sub.2 to give it an electrical conductivity in the metallic regime.

Aldissi, Mahmoud (Los Alamos, NM)

1985-01-01

140

Electrically conducting porphyrin and porphyrin-fullerene electropolymers  

DOEpatents

Compounds with aryl ring(s) at porphyrin meso position(s) bearing an amino group in position 4 relative to the porphyrin macrocycle, and at least one unsubstituted 5 (hydrogen-bearing) meso position with the 10-, 15-, and/or 20-relationship to the aryl ring bearing the amino group, and metal complexes thereof, feature broad spectral absorption throughout the visible region. These compounds are electropolymerized to form electrically conducting porphyrin and porphyrin-fullerene polymers that are useful in photovoltaic applications. The structure of one such electrically conducting porphyrin polymer is shown below. ##STR00001##

Gust, Jr., John Devens; Liddell, Paul Anthony; Gervaldo, Miguel Andres; Bridgewater, James Ward; Brennan, Bradley James; Moore, Thomas Andrew; Moore, Ana Lorenzelli

2014-03-11

141

Thermodynamic properties and electrical conductivity of strongly correlated plasma media  

E-print Network

We study thermodynamic properties and the electrical conductivity of dense hydrogen and deuterium using three methods: classical reactive Monte Carlo (REMC), direct path integral Monte Carlo (PIMC) and a quantum dynamics method in the Wigner representation of quantum mechanics. We report the calculation of the deuterium compression quasi-isentrope in good agreement with experiments. We also solve the Wigner-Liouville equation of dense degenerate hydrogen calculating the initial equilibrium state by the PIMC method. The obtained particle trajectories determine the momentum-momentum correlation functions and the electrical conductivity and are compared with available theories and simulations.

Filinov, V S; Boţan, A V; Bonitz, M; Fortov, V E

2008-01-01

142

Corrosion-protective coatings from electrically conducting polymers  

NASA Technical Reports Server (NTRS)

In a joint effort between NASA Kennedy and LANL, electrically conductive polymer coatings were developed as corrosion protective coatings for metal surfaces. At NASA Kennedy, the launch environment consist of marine, severe solar, and intermittent high acid and/or elevated temperature conditions. Electrically conductive polymer coatings were developed which impart corrosion resistance to mild steel when exposed to saline and acidic environments. Such coatings also seem to promote corrosion resistance in areas of mild steel where scratches exist in the protective coating. Such coatings appear promising for many commercial applications.

Thompson, Karen Gebert; Bryan, Coleman J.; Benicewicz, Brian C.; Wrobleski, Debra A.

1991-01-01

143

Rubber-like electrically conductive polymeric materials with shape memory  

NASA Astrophysics Data System (ADS)

This paper presents a heating-responsive shape memory polymeric material, which is not only rubber-like at room temperature and above its shape recovery temperature, but also electrically conductive. This polymeric material is made of silicone, melting glue (MG), and carbon black (CB). The influence of volume fractions of MG and CB on the elasticity, electrical resistivity, and shape memory effect of the polymeric material is systematically investigated. The feasibility of Joule heating for shape recovery is experimentally demonstrated with an electric power of 31 V.

Cui, H. P.; Song, C. L.; Huang, W. M.; Wang, C. C.; Zhao, Y.

2013-05-01

144

Micromechanical approach for electrical resistivity and conductivity of sandstone  

NASA Astrophysics Data System (ADS)

The objective of this work is to employ the micromechanical approach for the modeling of the electrical resistivity and of the conductivity of sandstone. This type of rock is considered as a mixture of solid mineral and porous space filled fully or partially by conductive water. The Eshelby's solution of a spheroidal inclusion in a homogeneous matrix is employed. The differential effective medium model (DEM) with different concepts of the microstructure is developed for the calculation of the resistivity. The parametric study clarifies the impact of the microscopic parameters on the macroscopic electrical properties. The simulations are compared with the classical empirical and theoretical approaches as well as with the laboratory measurements. The results show a strong impact of the microstructure (the shape of the pore, the presence of non-conductive fluids in the pore space, the connectivity of conductive fluid) on the macroscopic resistivity and conductivity of sandstone. This approach gives a link between the microscopic physical parameters of the rock and the macroscopic electrical parameters such as the cementation exponent and the electrical formation factor.

Nguyen, S. T.

2014-12-01

145

15 CFR 923.133 - Procedure for conducting continuing reviews of approved State CZM programs.  

Code of Federal Regulations, 2013 CFR

...MANAGEMENT PROGRAM REGULATIONS Review of Performance § 923.133 Procedure for conducting continuing reviews of approved State CZM programs...shall conduct a continuing review of the performance of coastal States with...

2013-01-01

146

15 CFR 923.133 - Procedure for conducting continuing reviews of approved State CZM programs.  

Code of Federal Regulations, 2014 CFR

...MANAGEMENT PROGRAM REGULATIONS Review of Performance § 923.133 Procedure for conducting continuing reviews of approved State CZM programs...shall conduct a continuing review of the performance of coastal States with...

2014-01-01

147

15 CFR 923.133 - Procedure for conducting continuing reviews of approved State CZM programs.  

Code of Federal Regulations, 2011 CFR

...MANAGEMENT PROGRAM REGULATIONS Review of Performance § 923.133 Procedure for conducting continuing reviews of approved State CZM programs...shall conduct a continuing review of the performance of coastal States with...

2011-01-01

148

15 CFR 923.133 - Procedure for conducting continuing reviews of approved State CZM programs.  

Code of Federal Regulations, 2012 CFR

...MANAGEMENT PROGRAM REGULATIONS Review of Performance § 923.133 Procedure for conducting continuing reviews of approved State CZM programs...shall conduct a continuing review of the performance of coastal States with...

2012-01-01

149

Experiment of electrical conductivity at low temperature (preliminary measurement)  

SciTech Connect

A muon collider needs very large amount of RF power, how to reduce the RF power consumption is of major concern. Thus the application of liquid nitrogen cooling has been proposed. However, it is known that the electrical conductivity depends on many factors and the data from different sources vary in a wide range, especially the data of conductivity of beryllium has no demonstration in a real application. Therefore it is important to know the conductivity of materials, which are commercially available, and at a specified frequency. Here, the results of the preliminary measurement on the electrical conductivity of copper at liquid nitrogen temperature are summarized. Addressed also are the data fitting method and the linear expansion of copper.

Zhao, Y.; Wang, H.

1998-07-01

150

Carbonatite melts and electrical conductivity in the asthenosphere.  

PubMed

Electrically conductive regions in Earth's mantle have been interpreted to reflect the presence of either silicate melt or water dissolved in olivine. On the basis of laboratory measurements, we show that molten carbonates have electrical conductivities that are three orders of magnitude higher than those of molten silicate and five orders of magnitude higher than those of hydrated olivine. High conductivities in the asthenosphere probably indicate the presence of small amounts of carbonate melt in peridotite and can therefore be interpreted in terms of carbon concentration in the upper mantle. We show that the conductivity of the oceanic asthenosphere can be explained by 0.1 volume percent of carbonatite melts on average, which agrees with the carbon dioxide content of mid-ocean ridge basalts. PMID:19039132

Gaillard, Fabrice; Malki, Mohammed; Iacono-Marziano, Giada; Pichavant, Michel; Scaillet, Bruno

2008-11-28

151

Electrically Joining Mixed Conducting Oxides for High Temperature Applications  

SciTech Connect

Mixed conducting oxides such as lanthanum strontium cobalt ferrite are currently being investigated for potential use as electrochemically active electrodes and catalytic membranes in a number of high temperature devices, including oxygen generators and solid oxide fuel cells (SOFC). However to take full advantage of the unique properties of these materials, reliable joining techniques need to be developed. What complicates joining in these applications is the requirement that the ceramic-to-metal junction be electrically conductive, so that current can either be drawn from the mixed conducting oxide, in the case of SOFC applications, or be carried to the oxide to initate ionic conduction, as required for oxygen separation and electrocatalysis. This paper outlines a new technique that is being developed to electrically join an oxide conductor to a metal current collector for high temperature electrochemical application.

Weil, K. Scott; Hardy, John S.

2003-01-06

152

Self-healable electrically conducting wires for wearable microelectronics.  

PubMed

Electrically conducting wires play a critical role in the advancement of modern electronics and in particular are an important key to the development of next-generation wearable microelectronics. However, the thin conducting wires can easily break during use, and the whole device fails to function as a result. Herein, a new family of high-performance conducting wires that can self-heal after breaking has been developed by wrapping sheets of aligned carbon nanotubes around polymer fibers. The aligned carbon nanotubes offer an effective strategy for the self-healing of the electric conductivity, whereas the polymer fiber recovers its mechanical strength. A self-healable wire-shaped supercapacitor fabricated from a wire electrode of this type maintained a high capacitance after breaking and self-healing. PMID:25044134

Sun, Hao; You, Xiao; Jiang, Yishu; Guan, Guozhen; Fang, Xin; Deng, Jue; Chen, Peining; Luo, Yongfeng; Peng, Huisheng

2014-09-01

153

Electrical resistivity imaging of conductive plume dilution in fractured rock  

Microsoft Academic Search

Electrical resistance tomography (ERT) was used to monitor a conductive plume dilution experiment that was conducted in fractured\\u000a basalt in order to assess its applications in this type of fractured-rock environment. Tap water was injected into an injection\\u000a well for 34 days to dilute a pre-existing potassium chloride (KCl) plume at a site in Idaho, USA. No further fluids were introduced

Robin E. Nimmer; James L. Osiensky; Andrew M. Binley; Kenneth F. Sprenke; Barbara C. Williams

2007-01-01

154

Electrical Conductivity of Serpentinized Rocks to 6 Kilobars  

Microsoft Academic Search

Electrical conductivity of serpentinized rocks from the Indian Ocean ridge is 3-4 orders of magnitude higher than that of serpentine-free peridotitc, hornblende gabbro, and basalt from the same area and from the Tonga trench. The enhanced conduction is apparently characteristic of many but not all serpentine-rich rocks and may be due in part to high porosity and in part to

R. M. Stesky; W. F. Brace

1973-01-01

155

Diffusion and mobility of electrically conducting defects in olivine  

Microsoft Academic Search

Electrical conductivity of lherzolite (65% olivine), measured as a function of time after changes in the oxygen fugacity\\u000a (f\\u000a o2) of the surrounding CO2\\/CO atmosphere, is used to infer the diffusivity of the point defects responsible for conduction in olivine. A total of 63\\u000a equilibration runs at temperatures of 900, 1000, 1100, and 1200??C were fit using nonlinear parameter estimation

S. Constable; A. Duba

2002-01-01

156

Electrical conductivity of ammonia solutions containing rhenium(VII)  

NASA Astrophysics Data System (ADS)

The electrical conductivity of rhenium-containing ammonia solutions is studied by mathematical planning of experiment (rotatable second-order plan). It is shown that the conductivity of the solutions increases with the rhenium(VII) concentration and temperature. The temperature coefficient of conductivity of the rhenium-containing ammonia solutions has been determined. It is shown that the required conductivity of the system under consideration can be provided using solutions containing 10-20 g/L rhenium. In this case, the conductivity of ammonia solutions approaches the conductivity of the well-known electrolytes, such as H2SO4, KCl, and NaCl. The studies performed are related to the physicochemical justification of the electrochemical processing of the metallic wastes of rare refractory metals in ammonia electrolytes.

Levchuk, O. M.; Levin, A. M.

2014-09-01

157

Revisited modeling of Titan’s middle atmosphere electrical conductivity  

NASA Astrophysics Data System (ADS)

The atmospheric electrical conductivity measured by the Permittivity, Wave and Altimetry (PWA) subsystem on board the Huygens probe, during the landing mission on Titan, has been modeled in the present work. Previous modeling studies showed a Galactic Cosmic Ray (GCR) peak of conductivity at a higher altitude and a quantitative overestimation in the altitude range 0-100 km compared to that observed by the PWA instrument. Recently the PWA data was revisited and provided new constraints on the conductivity at altitudes 100-180 km. Because the aerosols in the atmosphere are known to alter the electron concentration, using a detailed distribution of the aerosols at all altitudes, the electron conductivity has been calculated in the altitude range 0-180 km. By using a variable range of photoemission threshold for the aerosols, the present model is able to reasonably predict the altitude at which the GCR peak of conductivity occurs and to meet the new constraints for the conductivity profile.

Mishra, Alabhya; Michael, Marykutty; Tripathi, Sachchida Nand; Béghin, Christian

2014-08-01

158

Electrical conducting properties of proton-conducting terbium-doped strontium cerate membrane  

Microsoft Academic Search

The electrical conduction behavior of SrCe0.95Tb0.05O3?? (SCTb) was investigated in different gases at high temperatures. In air, oxygen or nitrogen SCTb shows small electronic-hole conduction below 800°C and oxygen ionic conduction over 800°C with activation energy about 30 kJ\\/mol and 164–181 kJ\\/mol respectively. SCTb becomes a protonic conductor in hydrogen or methane in 500–900°C, with the proton conductivity in the

Xiwang Qi; Y. S. Lin

1999-01-01

159

A continuous electric kiln for rapid sintering: Final report  

SciTech Connect

Alumina-based spark plug insulators have traditionally been sintered in continuous gas-fired car tunnel kilns with cycle times of thirty to forty hours. Automation of the handling has been difficult, and large amounts of kiln furniture are required to hold the ware as it passes through the kiln. This report describes an electric alternative that drastically shortens the firing cycle while maintaining desired ceramic properties. A fast-fire, electrically-heated, continuous kiln design is proposed which minimizes kiln furniture and promotes automated handling of the insulators.

O'Brien, D.A.; Tanagho, N.F.

1987-09-01

160

Electrical Conduction and Dielectric Properties of Biodegradable Plastics  

Microsoft Academic Search

We examined the electrical conduction and dielectric properties as well as thermal analysis of polylactic acid (PLA) that is biodegradable plastics. From the results of thermal analyses, it was found that the glass transition temperature (Tg) of PLA was about 60°C and the melting point (Tm) was about 166°C. For the temperature dependence of current density (J), J of PLA

Katsuyoshi Shinyama; Shigetaka Fujita

2005-01-01

161

Soil water sensor response to bulk electrical conductivity  

Technology Transfer Automated Retrieval System (TEKTRAN)

Soil water monitoring using electromagnetic (EM) sensors can facilitate observations of water content at high temporal and spatial resolutions. These sensors measure soil dielectric permittivity (Ka) which is largely a function of volumetric water content. However, bulk electrical conductivity BEC c...

162

Physiological Effects of a Conducted Electrical Weapon on Human Subjects  

Microsoft Academic Search

Study objective: Sudden death after a conducted electrical weapon exposure has not been well studied. We examine the effects of a single Taser exposure on markers of physiologic stress in healthy humans. Methods: This is a prospective trial investigating the effects of a single Taser exposure. As part of their police training, 32 healthy law enforcement officers received a 5-second

Gary M. Vilke; Christian M. Sloane; Katie D. Bouton; Fred W. Kolkhorst; Saul D. Levine; Tom S. Neuman; Edward M. Castillo; Theodore C. Chan

2007-01-01

163

Electric and electromagnetic shielding properties of highly conducting polyaniline films  

Microsoft Academic Search

The increasing use of commercial, military, and scientific electrical products and electronic devices has raised the problem of electromagnetic interference (EMI), also called electromagnetic environmental pollution, so there is an increased interest in EMI shielding. By use of mechanical mixing doping method, highly conducting polyaniline (PANI) films were prepared by the variation of dopant (camphor sulphonic acid) loading and solvent

Song Yuexian; Hongli' WENG; Zheng Yuansuo

2002-01-01

164

Electrically conductive polycrystalline diamond and particulate metal based electrodes  

DOEpatents

An electrically conducting and dimensionally stable diamond (12, 14) and metal particle (13) electrode produced by electrodepositing the metal on the diamond is described. The electrode is particularly useful in harsh chemical environments and at high current densities and potentials. The electrode is particularly useful for generating hydrogen, and for reducing oxygen and oxidizing methanol in reactions which are of importance in fuel cells.

Swain, Greg M.; Wang, Jian

2005-04-26

165

Electrical conduction and trapping distributions in tellurium oxide films  

Microsoft Academic Search

The electrical charge transport and trapping distribution was studied in vacuum-deposited tellurium oxide films. The current-voltage characteristics suggested a space-charge-limited conduction process at higher voltage levels. Assuming an exponential type of trapping distribution the density of traps estimated from (log10J)-(1\\/T) curves were (0.5-6.0)×1024 m-3.

Amarjit Singh

1988-01-01

166

Improved Electrical Conductivity of Graphene Films Integrated with Metal Nanowires  

E-print Network

the possibility to replace indium tin oxide (ITO) by graphene as the TCF, particularly for flexible and large-area the transport properties of CVD-grown graphene. Large-area CVD-grown graphene is a polycrystalline materialImproved Electrical Conductivity of Graphene Films Integrated with Metal Nanowires Iskandar N

167

Osteoblast function on electrically conductive electrospun PLA\\/MWCNTs nanofibers  

Microsoft Academic Search

The electrospinning process was utilized successfully to fabricate the random oriented and aligned electrically conductive nanofibers of biodegradable poly-DL-lactide (PLA) in which multiwalled carbon nanotubes (MWCNTs) were embedded. The topographical features of the composite nanofibers were characterized by SEM. The dispersion and alignment of MWCNTs in nanofiber matrix were observed by TEM. The in vitro degradation was characterized in terms

Shijun Shao; Shaobing Zhou; Long Li; Jinrong Li; Chao Luo; Jianxin Wang; Xiaohong Li; Jie Weng

2011-01-01

168

Human cardiovascular effects of a new generation conducted electrical weapon  

Microsoft Academic Search

ObjectivesThe conducted electrical weapon (CEW) is used by law enforcement to control potentially violent people. Much of the research in CEW safety has focused on the TASER X26, which uses a single deployment cartridge. New Generation CEW (NGCEW) technology has been developed that uses a different circuit and multiple cartridges that can be simultaneously deployed. The objective of this study

Jeffrey D. Ho; Donald M. Dawes; Robert F. Reardon; Seth R. Strote; Sebastian N. Kunz; Rebecca S. Nelson; Erik J. Lundin; Benjamin S. Orozco; James R. Miner

2011-01-01

169

www.VadoseZoneJournal.org Electrical Conductivity Imaging  

E-print Network

in an Arctic Ecosystem, through Advanced Inversion of Electromagnetic Induction Data Characterizing the spatial electromagnetic induction (EMI) data with portable tools (e.g., EM38, GEM2, or DUALEM) over large regions, EMI conductivity; EMI, electromagnetic induction; ERT, electrical resistance tomography; MCMC, Markov chain Monte

Hubbard, Susan

170

Electrical conductivity of colloidal systems during irreversible aggregation  

Microsoft Academic Search

The low-frequency electrical conductivity of dielectric colloids (polysterene and silica) and metallic (silver) ones in aqueous solutions shows a power-law behavior in time during the salt-induced cluster-cluster aggregation. We interpret this fact using current theories of heterogeneous dielectric systems. The fractal nature of the clusters, checked by light scattering, determines the exponent of the power law.

F. Bordi; C. Cametti; P. Codastefano; P. Tartaglia

1990-01-01

171

UNCERTAINTY EFFECTS ON ELECTRICAL CONDUCTIVITY AND PERMITTIVITY SPECTRA  

Technology Transfer Automated Retrieval System (TEKTRAN)

Soil permittivity and electrical conductivity values are usually reported without error bars, which limits comparisons among different studies using different equipment. Uncertainty in measured permittivity spectra could be due to the measurement system (hardware) or sample-to-sample variation. Ther...

172

Efficiency of continuous double auctions in the electricity market  

Microsoft Academic Search

Intra-day electricity markets are considered as im- portant mechanisms to reconcile short-term fluctuations of en- ergy production with consumption. This even gains in significance in systems with heavy intermittent production at virtually no variable costs, such as wind energy. In Europe, intra-day markets are often designed as continuous double auctions where bid and ask orders are collected continuously, ranked by

Alexander Weber; Sascha Schroder

2011-01-01

173

Relating Relative Hydraulic Conductivity and Electrical Conductivity in the Unsaturated Zone  

NASA Astrophysics Data System (ADS)

Monitoring flow in the unsaturated zone is an important task, especially for overseeing managed aquifer recharge, tracking contaminant transport, and optimizing agricultural operations. Geophysical data can provide in-situ unsaturated subsurface information with much higher temporal and spatial resolution over a larger areal extent than traditional hydrologic methods. The measurement of electrical conductivity is a geophysical technique of particular interest in the vadose zone because the geophysical parameter that is obtained is highly correlated with saturation. Changes in saturation can then be used to make qualitative inferences on the rate of fluid motion within the unsaturated zone. However, quantitative information on infiltration rates and unsaturated flow rates via saturation is typically hard to find and usually requires a cumbersome hydrologic inversion that cannot be done in real-time. In this work, we used numerical simulations to find a relationship that relates electrical conductivity not to saturation, but to relative hydraulic conductivity, which has been shown to be a useful proxy for direct estimation of infiltration and unsaturated flow rates even under transient conditions. We obtained this relationship through numerical modeling by generating pore-scale soil structures, partially saturating them through morphological operations according to both wetting and draining schemes and calculating their hydraulic and electrical conductivities at a range of saturations. We found that a power law relationship exists between relative hydraulic conductivity (hydraulic conductivity divided by saturated conductivity) and relative electrical conductivity for each of the sixteen tested media. The power law exponent in the relationship changes depending on whether the medium is being wetted or drained as would be expected as hysteresis is evident in both unsaturated hydraulic and electrical conductivity. Parameters that are typically seen to be related to both saturated conductivities, such as tortuosity, porosity and surface area to volume ratio were calculated for each sphere pack and plotted against the exponent. No correlation was seen between the exponent and these parameters for either the wetting or draining curves. However, the exponent was well constrained for the wetting curve to between 2.45 and 3 and the draining curve to between 1.6 and 2.2. The error introduced by using values within these bounds to estimate the hydraulic conductivity of any of the numerical soil packs using electrical conductivity was negligible, meaning that mean values of 2.75 and 1.8 could be used to estimate the hydraulic conductivity for any pack. These results are applicable to media with minimal surface conduction. We went on to analyze the effects of surface conduction via mineralogy and clay on the power law relationship between electrical and hydraulic conductivity via a number of approaches. We found that the power law relationship between hydraulic and electrical conductivity breaks down when clay content exceeds 5%. However, for media with less clay, use of the relationship with the mean values for exponents found for the clean medium results in less than ten percent error.

Mawer, C. M.; Knight, R. J.; Kitanidis, P. K.

2013-12-01

174

Anomalous electrical conduction in carbon fibers at low temperatures  

NASA Astrophysics Data System (ADS)

Electrical conductivity of carbon fibers heat-treated at 1000 or 1200°C has been measured at low temperatures. Both carbon fibers show a large decrease of the conductivity with T - {1}/{2} dependence with decreasing temperature below about 1 K in the absence of magnetic field, while T {1}/{2} dependence of the conductivity is observed in high magnetic fields ( T: temperature). The former seems due to the Kondo effect in the three-dimensional weakly localized regime investigated by Ohkawa and Fukuyama, while the latter is considered as due to the electron-electron interaction effect perceptible after the suppression of the Kondo effect by the magnetic field.

Koike, Y.; Fukase, T.

1987-05-01

175

Toward a unified hydrous olivine electrical conductivity law  

NASA Astrophysics Data System (ADS)

has long been proposed that water incorporation in olivine has dramatic effects on the upper mantle properties, affecting large-scale geodynamics, and triggering high electrical conductivity. But the laboratory-based laws of olivine electrical conductivity predict contrasting effects of water, precluding the interpretation of geophysical data in term of mantle hydration. We review the experimental measurements of hydrous olivine conductivity and conclude that most of data are consistent when errors in samples water contents are considered. We report a new law calibrated on the largest database of measurements on hydrous olivine oriented single crystals and polycrystals. It fits most of measurements within uncertainties, and is compatible with most of geophysical data within petrological constraints on mantle olivine hydration. The conductivity anisotropy of hydrous olivine might be higher than dry olivine, but preferential orientation should produce moderate anisotropy (˜0-0.8 log unit). In the oceanic mantle, the enhancement of olivine conductivity is limited to ˜1 log unit in the maximum range of mantle olivine water concentrations (0-500 wt ppm). Strongest enhancements are expected in colder regions, like cratonic lithospheres and subduction settings. High conductivities in melt-free mantle require great depths and high water concentrations in olivine (>0.1 S/m at >250 km and >200 wt ppm). Thus, the hydration of olivine appears unlikely to produce the highest conductivities of the upper mantle.

Gardés, Emmanuel; Gaillard, Fabrice; Tarits, Pascal

2014-12-01

176

Electrical conduction and polarization of calcite single crystals  

NASA Astrophysics Data System (ADS)

The electrical conductivity and polarization properties of calcite single crystals with three orientations, namely, a (00.1) plane perpendicular to the crystallographic c axis (10.0) plane parallel to the crystallographic c axis, and a (10.4) cleavage plane, were studied by both complex impedance and thermally stimulated depolarization current (TSDC) measurements. Conductivities for (00.1)-, (10.0)-, and (10.4)-oriented single calcite crystals at 400-600 °C were 1.16 × 10-7 - 1.05 × 10-5, 7.40 × 10-8 - 4.27 × 10-6, and 4.27 × 10-7 - 2.86 × 10-5 ?-1 m-1, respectively, and the activation energies for conduction were 112, 103, and 101 kJ mol-1, respectively. The TSDC spectra verified the electrical polarizability of calcite crystals. The activation energy for depolarization, estimated from TSDC spectra, of the (00.1)-, (10.0)-, and (10.4)-oriented calcite substrates were 112, 119, and 114 kJ mol-1, respectively. Considering the correlation between the processes of conduction and electric polarization, we proposed the mechanisms of conduction and polarization in calcite on the assumption of oxide ion transport.

Wada, Norio; Horiuchi, Naohiro; Wang, Wei; Hiyama, Tetsuo; Nakamura, Miho; Nagai, Akiko; Yamashita, Kimihiro

2012-10-01

177

Consequences of electrical conductivity in an orb spider's capture web  

NASA Astrophysics Data System (ADS)

The glue-coated and wet capture spiral of the orb web of the garden cross spider Araneus diadematus is suspended between the dry silk radial and web frame threads. Here, we experimentally demonstrate that the capture spiral is electrically conductive because of necks of liquid connecting the droplets even if the thread is stretched. We examine how this conductivity of the capture spiral may lead to entrapment of charged airborne particles such as pollen, spray droplets and even insects. We further describe and model how the conducting spiral will also locally distort the Earth's ambient electric field. Finally, we examine the hypothesis that such distortion could be used by potential prey to detect the presence of a web but conclude that any effect would probably be too small to allow an insect to take evasive action.

Vollrath, Fritz; Edmonds, Donald

2013-12-01

178

Electrical conductivity and relaxation in mixed alkali tellurite glasses.  

PubMed

The authors have reported the electrical conductivity and the conductivity relaxation in mixed alkali tellurite glasses of compositions of 70TeO2-xNa2O-(30-x)Li2O in the frequency range from 10 Hz to 2 MHz and in the temperature range from room temperature to just below the glass transition temperature. They have analyzed the relaxation data in the framework of different models. They have observed the mixed alkali effect in the dc and ac conductivities, the crossover frequency, and the conductivity relaxation frequency as well as in their respective activation energies in these glasses. They have also observed the mixed alkali effect in the decoupling index. The scaling property of the modulus spectra of these mixed alkali glasses shows that the conductivity relaxation in the mixed alkali tellurite glasses is independent of temperature but depends on the glass compositions. PMID:17508813

Ghosh, S; Ghosh, A

2007-05-14

179

Electrical conductivity of doped polyacrylonitrile (PAN). [Halogen doped polyacrylonitrile  

SciTech Connect

The electrical conductivity and optical absorption spectra of halogen doped PAN have been investigated. When films of PAN previously heated in vacuum to 280/sup 0/C are exposed to bromine or iodine vapor the conductivity rises suddenly. The conductivity is reduced by pumping off the vapor, but upon subsequent reheating the conductivity increases dramatically, with a transition occurring at about 270/sup 0/C. Undoped samples were previously reported to undergo a similar transition above 390/sup 0/C. All samples obey sigma ..cap alpha.. T/sup -1/4/ behavior, suggesting 3-dimensional variable range hopping as the conduction mechanism. The optical and infrared absorption spectra of doped PAN are compared to those previously reported for the undoped material. The stability of doped PAN in air is also discussed. 7 figures.

Teoh, H.; MacInnes, D.; Metz, P.D.

1982-01-01

180

Electrical conductivity and dielectric properties of SiO 2 nanoparticles dispersed in conducting polymer matrix  

Microsoft Academic Search

Electrical and dielectric properties of conducting polypyrrole–wide band gap silica (PPY–SiO2) nanocomposites have been investigated as a function of temperature and frequency for different concentrations of polypyrrole.\\u000a The average grain size of the nanocomposites is in the range of 40–80 nm. Impedance spectra reveal two distorted semicircles\\u000a corresponding to grain and grain boundary effects. The magnitude of conductivity and its temperature

Kousik Dutta; S. K. De

2007-01-01

181

Copper-Filled Electrically Conductive Adhesives with Enhanced Shear Strength  

NASA Astrophysics Data System (ADS)

In this study, the effects of diethyl carbitol (diluent) and tertiary amines on the electrical, mechanical, and rheological properties of the Cu-filled polyurethane-based electrically conductive adhesives (ECAs) were investigated. Significant difference could be observed in the electrical resistivity and shear strength of ECA prepared with different amount of diethyl carbitol. Reduced electrical resistivity was found in ECAs prepared with addition of tertiary amines, but no obvious change was observed in the shear strength of the ECA joint. Rheological property of the ECA paste was investigated in order to understand the correlation of the viscosity of ECA paste and electrical resistivity and shear strength of ECA joint. Results revealed that decrease in viscosity of the ECA paste reduced electrical resistivity and enhanced shear strength of ECA joint. A Cu-filled polyurethane-based ECA with considerably low electrical resistivity at the magnitude order range of 10-3 ? cm, and significantly high shear strength (above 17 MPa) could be achieved.

Ho, Li-Ngee; Nishikawa, Hiroshi

2014-09-01

182

Synthesis of Conductive Nanofillers/Nanofibers and Electrical Properties of their Conductive Polymer Composites  

NASA Astrophysics Data System (ADS)

Thanks to their corrosion resistance, light weight, low cost, and ease of processing, electrically conducting polymer composites (CPCs) have received significant attention for the replacement of metals and inorganic materials for sensors, actuators, supercapacitors, and electromagnetic interference (EMI) shields. In this PhD thesis, high aspect ratio conductive nanofillers namely copper nanowires (CuNWs) and multiwall carbon nanotubes (MWCNTs) were coated with polyaniline (PANi) using solution mixing and in-situ polymerization method, respectively. Transmission electron microscopy (TEM) showed a smooth polyaniline nano-coating between 5--18 nm in thickness on the nanofillers' surface. The coating thickness and; consequently, electrical conductivity was controlled and tuned by polyaniline/aniline concentration in solution. Composites with tunable conductivity may be used as chemisensors, electronic pressure sensors and switches. Coated nanofillers demonstrated better dispersion in polystyrene (PS) and provided lower electrical percolation threshold. Dispersion of nanofillers in PS was investigated using rheological measurements and confirmed with electron micrographs and nano-scale images of CPCs. Polyaniline (PANi), when used as a coating layer, was able to attenuate electromagnetic (EM) waves via absorption and store electrical charges though pseudocapacitance mechanism. The dielectric measurements of MWCNT-PANi/PS composites showed one order of magnitude increase in real electrical permittivity compared to that of MWCNT/PS composites making them suitable for charge storage purposes. Incorporation of PANi also brought a new insight into conductive network formation mechanism in electrospun mats where the orientation of conductive high aspect ratio nanofillers is a major problem. Conductive nanofibers of poly(vinylidene fluoride) (PVDF) filled with coated multiwall carbon nanotubes (MWCNTs) were fabricated using electrospinning. These highly oriented PVDF nanofibers exhibited high beta (beta) crystal content and enhanced piezoelectricity. Moreover, multilayer electrospun nanofibers, in which MWCNTs were located at the shell layer, were fabricated for further decrease in electrical percolation threshold. In addition the PANi coated nanofillers, immiscible polymer blends (poly(methyl methacrylate) (PMMA) and styrene-acrylonitrile copolymer (SAN) blends) were employed to deliver lower percolation threshold via double percolation phenomenon. Conductivity measurements revealed a significant decrease in electrical percolation threshold (0.4 wt%) for PMMA70/SAN30 blends compared with MWCNT-filled SAN and PMMA (ca 0.8 wt%).

Sarvi, Ali

183

Rearrangement of 1D Conducting Nanomaterials towards Highly Electrically Conducting Nanocomposite Fibres for Electronic Textiles.  

PubMed

Nanocarbon-based conducting fibres have been produced using solution- or dry-spinning techniques. Highly conductive polymer-composite fibres containing large amounts of conducting nanomaterials have not been produced without dispersants, however, because of the severe aggregation of conducting materials in high-concentration colloidal solutions. Here we show that highly conductive (electrical conductivity ~1.5 × 10(5)?S m(-1)) polymer-composite fibres containing carbon nanotubes and silver nanowires can be fabricated via a conventional solution-spinning process without any other treatment. Spinning dopes were fabricated by a simple mixing of a polyvinyl alcohol solution in dimethylsulfoxide with a paste of long multi-walled carbon nanotubes dispersed in organic solvents, assisted by quadruple hydrogen-bonding networks and an aqueous silver nanowire dispersion. The high electrical conductivity of the fibre was achieved by rearrangement of silver nanowires towards the fibre skin during coagulation because of the selective favourable interaction between the silver nanowires and coagulation solvents. The prepared conducting fibres provide applications in electronic textiles such as a textile interconnector of light emitting diodes, flexible textile heaters, and touch gloves for capacitive touch sensors. PMID:25792333

Han, Joong Tark; Choi, Sua; Jang, Jeong In; Seol, Seung Kwon; Woo, Jong Seok; Jeong, Hee Jin; Jeong, Seung Yol; Baeg, Kang-Jun; Lee, Geon-Woong

2015-01-01

184

Rearrangement of 1D Conducting Nanomaterials towards Highly Electrically Conducting Nanocomposite Fibres for Electronic Textiles  

PubMed Central

Nanocarbon-based conducting fibres have been produced using solution- or dry-spinning techniques. Highly conductive polymer-composite fibres containing large amounts of conducting nanomaterials have not been produced without dispersants, however, because of the severe aggregation of conducting materials in high-concentration colloidal solutions. Here we show that highly conductive (electrical conductivity ~1.5 × 105?S m?1) polymer-composite fibres containing carbon nanotubes and silver nanowires can be fabricated via a conventional solution-spinning process without any other treatment. Spinning dopes were fabricated by a simple mixing of a polyvinyl alcohol solution in dimethylsulfoxide with a paste of long multi-walled carbon nanotubes dispersed in organic solvents, assisted by quadruple hydrogen-bonding networks and an aqueous silver nanowire dispersion. The high electrical conductivity of the fibre was achieved by rearrangement of silver nanowires towards the fibre skin during coagulation because of the selective favourable interaction between the silver nanowires and coagulation solvents. The prepared conducting fibres provide applications in electronic textiles such as a textile interconnector of light emitting diodes, flexible textile heaters, and touch gloves for capacitive touch sensors. PMID:25792333

Han, Joong Tark; Choi, Sua; Jang, Jeong In; Seol, Seung Kwon; Woo, Jong Seok; Jeong, Hee Jin; Jeong, Seung Yol; Baeg, Kang-Jun; Lee, Geon-Woong

2015-01-01

185

Water chemistry and electrical conductivity database for rivers in Yellowstone National Park, Wyoming  

USGS Publications Warehouse

This study aims to quantify relations between solute concentrations (especially chloride) and electrical conductivity for several rivers in Yellowstone National Park (YNP), by using automated samplers and conductivity meters. Norton and Friedman (1985) found that chloride concentrations and electrical conductivity have a good correlation in the Falls, Snake, Madison, and Yellowstone Rivers. However, their results are based on limited sampling and hydrologic conditions and their relation with other solutes was not determined. Once the correlations are established, conductivity measurements can then be used as a proxy for chloride concentrations, thereby enabling continuous heat-flow estimation on a much finer timescale and at lower cost than is currently possible with direct sampling. This publication serves as a repository for all data collected during the course of the study from May 2010 through July 2011, but it does not include correlations between solutes and conductivity or recommendations for quantification of chloride through continuous electrical conductivity measurements. This will be the object of a future document.

Clor, Laura E.; McCleskey, R. Blaine; Huebner, Mark A.; Lowenstern, Jacob B.; Heasler, Henry P.; Mahony, Dan L.; Maloney, Tim; Evans, William C.

2012-01-01

186

Optimization and Testing of Electrically Conductive Spacecraft Coatings  

NASA Technical Reports Server (NTRS)

This is the final report discussing work done for the Space Environmental Effects (SEE) program in the Materials and Processes Laboratory, on electrically conductive thermal control coatings. These thermal control coatings are being developed to have several orders of magnitude lower electrical resistivity than most available thermal control coatings. Extensive research has taken place over the last few years to develop a variety of spacecraft coatings with the unique property of being able to conduct surface charge to a substrate or grounding system. The ability to conduct surface charge to a safe point, while maintaining optical properties and performance, is highly advantageous in maintaining operational space based systems. Without this mechanism the surface of a spacecraft can accumulate charge to the point that a catastrophic electrical breakdown can occur, resulting in damage to or failure of the spacecraft. Ultimately, use of this type of coating will help mitigate many of the concerns that NASA and the space industry still have for their space based systems. The unique coatings studied here fall into two specific categories: 1) broadband absorber and 2) selective absorber. These coatings have controllable solar absorptance and electrical surface resistivity values over the designated ranges. These coatings were developed under an SBIR program which focused on the development of such constituents and coatings. This project focused on simulated space environmental effects testing with the intent of using this data to help optimize the stability and initial properties of these coatings.

Mell, Richard J.

2001-01-01

187

Spatial-decomposition analysis of electrical conductivity in ionic liquid  

NASA Astrophysics Data System (ADS)

The electrical conductivity of room temperature ionic liquid (IL) is investigated with molecular dynamics simulation. A trajectory of 1 ?s in total is analyzed for the ionic liquid [C4mim][NTf2] (1-n-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and the anion is also called TFSI or TFSA), and the ion motions are examined in direct connection to the conductivity within the framework formulated previously [K.-M. Tu, R. Ishizuka, and N. Matubayasi, J. Chem. Phys. 141, 044126 (2014)]. As a transport coefficient, the computed electrical conductivity is in fair agreement with the experiment. The conductivity is then decomposed into the autocorrelation term of Nernst-Einstein form and the cross-correlation term describing the two-body motions of ions, and the cross-correlation term is further decomposed spatially to incorporate the structural insights on ion configurations into the dynamic picture. It is observed that the ion-pair contribution to the conductivity is not spatially localized and extends beyond the first coordination shell. The extent of localization of the cross-correlation effect in the conductivity is in correspondence to that of the spatial correlation represented by radial distribution function, which persists over nanometer scale.

Tu, Kai-Min; Ishizuka, Ryosuke; Matubayasi, Nobuyuki

2014-12-01

188

Electrical conductivity of olivine: New experimental results and a unified model for hydrogen-assisted conduction  

NASA Astrophysics Data System (ADS)

Although extensive experimental studies have been carried out on the hydrogen-assisted electrical conductivity in olivine, a few important issues remain unclear. We have conducted new experiments (i) on the pressure effects, (ii) on the influence of Fe content, and (iii) on the influence of oxygen fugacity on hydrogen-assisted conductivity to clarify these issues. The pressure effect is important in resolving the difference between Wang et al. (2006) and Yoshino et al. (2009) and also in evaluating the conductivity jump at the 410-km discontinuity. Our new results show only a small effect of pressure indicating that (i) the difference between Wang et al. (2006) and Yoshino et al. (2009) is not due to the pressure effect, and that (ii) there must be a large drop in conductivity at 410-km boundary if the water content in the upper mantle is the same as that of the transition zone. We also conducted a series of experiments to determine the influence of Fe on hydrogen-assisted conductivity. Both Fe and hydrogen enhance conductivity, but their combined effect was not characterized. We found that Fe effect and hydrogen effect are connected: for given hydrogen content, conductivity is higher for a sample with higher Fe content. This implies that the hydrogen mobility is enhanced by Fe. The results have potential applications for Fe-rich planets such as Mars. We are also conducting a series of experiments to see the influence of oxygen fugacity on hydrogen-assisted conductivity. A similar study was made for wadsleyite showing the negative dependence of conductivity on oxygen fugacity showing a simple model of hydrogen-assisted conductivity (i.e., all hydrogen atoms contribute equally to conductivity) does not work. Our new results will provide strong constraints on the mechanism of hydrogen-assisted conduction in olivine. A hybrid model explains a broad range of observations including the discrepancies between diffusion data and electrical conductivity, and predicts that hydrogen-assisted conductivity will be highly anisotropic at high temperatures.

Karato, S.; Dai, L.

2013-12-01

189

Growth of a Long Silver Nanowire and the Electric Conductance  

NASA Astrophysics Data System (ADS)

Electric conductance of metal nanowires is quantized even at room temperature. Ballistic transport of the electrons occurs there. How long can the electrons transmit in the nanowire without diffuse scattering? As long as the ballistic transport occurs, the conductance should be independent of the nanowire length. Is there any upper length limit for the conductance quantization? We have developed a method to grow a long silver nanowire in a UHV- transmission electron microscope combined with an STM system to study the transport mechanism in the long nanowire. An ionic conductor of silver iodide is used as a source of supply of silver atoms to make long silver nanowires. Longer nanowires than twice of the mean-free-path for bulk silver material (about tens of nanometer) have been successfully made, while the diameter is a little thick (10nm or less). Both of the structure and conductance were observed simultaneously.

Tanishiro, Yasumasa; Itoh, Ryoji; Arimoto, Akiko; Takayanagi, Kunio

2004-03-01

190

Enhancement of electrical conductivity of ion-implanted polymer films  

SciTech Connect

The electrical conductivity of ion-implanted films of Nylon 66, Polypropylene (PP), Poly(tetrafluoroethylene) (Teflon) and mainly Poly (ethylene terephthalate) (PET) was determined by DC measurements at voltages up to 4500 V and compared with the corresponding values of pristine films. Measurements were made at 21/sup 0/C +/- 1/sup 0/C and 65 +/- 2% RH. The electrical conductivity of PET films implanted with F/sup +/, Ar/sup +/, or As/sup +/ ions at energies of 50 keV increases by seven orders of magnitude as the fluence increases from 1 x 10/sup 18/ to 1 x 10/sup 20/ ions/m/sup 2/. The conductivity of films implanted with As/sup +/ was approximately one order greater than those implanted with Ar/sup +/, which in turn was approximately one-half order greater than those implanted with F/sup +/. The conductivity of the most conductive film approx.1 S/m) was almost 14 orders of magnitude greater than the pristine PET film. Except for the three PET samples implanted at fluences near 1 x 10/sup 20/ ions/m/sup 2/ with F/sup +/, Ar/sup +/, and As/sup +/ ions, all implanted films were ohmic up to an electric field strength of 600 kV/m. The temperature dependence of the conductivity of the three PET films implanted near a fluence of 1 x 10/sup 20/ ions/m/sup 2/ was measured over the range of 80 K < T < 300 K.

Brock, S.

1985-01-01

191

Evolving concepts on the electrical conductivity of the continental crust  

NASA Astrophysics Data System (ADS)

Several decades of geophysical research have established that the middle and lower crust are typically much more electrically conductive than the upper crust and orders of magnitude more so than either dry crystalline rocks or rock-forming silicate minerals at similar conditions. The high conductivities at depth were originally ascribed to the presence of saline fluids. Two problems with this view have emerged: hot water is far too reactive with surrounding rocks to remain for long in the deep crust, and the permeability of hot, ductile crust is too low to account for the observed conductivities. Another possibility is that graphitic carbon exerts the primary control on deep crustal conductivity. Graphitic carbon can exist in different habits and abundances and influence conductivity on different scales. Buried organic-rich shales form megascopic layers in which carbon is likely to be interconnected over kilometers, but such layers are not common. Graphitic veins formed during metamorphism are probably more common but much less extensive. Carbon also forms films on microfracture surfaces. These have been observed in many crystalline rocks and appear to be ubiquitous; they are also probably extensive and thus may generally account for the crustal conductivity structure. The microcrack network need not be completely interconnected to impart high electrical conductivity. It can exist in series with conductive minor phases such as oxides or sulfides, and it also reduces the size of regions of high resistivity. Regardless of mode of occurrence, that carbonaceous rocks are more abundant in the Phanerozoic than Precambrian records explains why the deep Phanerozoic crust is more conductive than old shield regions. The control of rock conductivity by carbon in the microfracture network implies that conductivity is in part controlled by microstructure and microfabric and by the chemical state of carbon. Observations of rocks from the KTB borehole indicate that microcrack carbon at the bottom of the hole (9.1 km depth) is relatively pure but at shallower levels contains a higher proportion of hydrocarbon. With uplift of the host rocks, carbon may react with fluids to form less conductive hydrocarbons. This retrograde metamorphism of microcrack carbon may be one reason that shallow crust can be less conductive than deep crust.

Mathez, E. A.

2002-12-01

192

The Thermal Electrical Conductivity Probe (TECP) for Phoenix  

NASA Technical Reports Server (NTRS)

The Thermal and Electrical Conductivity Probe (TECP) is a component of the Microscopy, Electrochemistry, and Conductivity Analyzer (MECA) payload on the Phoenix Lander. TECP will measure the temperature, thermal conductivity and volumetric heat capacity of the regolith. It will also detect and quantify the population of mobile H2O molecules in the regolith, if any, throughout the polar summer, by measuring the electrical conductivity of the regolith, as well as the dielectric permittivity. In the vapor phase, TECP is capable of measuring the atmospheric H2O vapor abundance, as well as augment the wind velocity measurements from the meteorology instrumentation. TECP is mounted near the end of the 2.3 m Robotic Arm, and can be placed either in the regolith material or held aloft in the atmosphere. This paper describes the development and calibration of the TECP. In addition, substantial characterization of the instrument has been conducted to identify behavioral characteristics that might affect landed surface operations. The greatest potential issue identified in characterization tests is the extraordinary sensitivity of the TECP to placement. Small gaps alter the contact between the TECP and regolith, complicating data interpretation. Testing with the Phoenix Robotic Arm identified mitigation techniques that will be implemented during flight. A flight model of the instrument was also field tested in the Antarctic Dry Valleys during the 2007-2008 International Polar year. 2

Zent, Aaron P.; Hecht, Michael H.; Cobos, Doug R.; Campbell, Gaylon S.; Campbell, Colin S.; Cardell, Greg; Foote, Marc C.; Wood, Stephen E.; Mehta, Manish

2009-01-01

193

Equation of state and electrical conductivity of expanded Al  

NASA Astrophysics Data System (ADS)

Ab-initio molecular dynamics (AIMD) simulations have been performed for generating equation of state (EOS) data as well as atomic configurations of expanded states of Al. The generated atomic configurations have been used for the calculation of electrical conductivity. AIMD simulations have been performed using the ABINIT code and electrical conductivity has been calculated using the Kubo-Greenwood formula as implemented in ABINIT. The generated equation of state data have been fitted to a three-term EOS model using adjustable parameters of ionic and electronic Gruneisen parameters. This three-term EOS model has been used to estimate critical density, temperature and pressure in the liquid-vapour region. The calculated values of critical density, temperature and pressure show good agreement with results available in the literature.

Mishra, V.; Mehra, V.; Chaturvedi, S.

2012-07-01

194

Nonideal ultrathin mantle cloak for electrically large conducting cylinders.  

PubMed

Based on the concept of the scattering cancellation technique, we propose a nonideal ultrathin mantle cloak that can efficiently suppress the total scattering cross sections of an electrically large conducting cylinder (over one free-space wavelength). The cloaking mechanism is investigated in depth based on the Mie scattering theory and is simultaneously interpreted from the perspective of far-field bistatic scattering and near-field distributions. We remark that, unlike the perfect transformation-optics-based cloak, this nonideal cloaking technique is mainly designed to minimize simultaneously several scattering multipoles of a relatively large geometry around considerably broad bandwidth. Numerical simulations and experimental results show that the antiscattering ability of the metasurface gives rise to excellent total scattering reduction of the electrically large cylinder and remarkable electric-field restoration around the cloak. The outstanding cloaking performance together with the good features of and ultralow profile, flexibility, and easy fabrication predict promising applications in the microwave frequencies. PMID:25401449

Liu, Shuo; Zhang, Hao Chi; Xu, He-Xiu; Cui, Tie Jun

2014-09-01

195

Electrical conductivity for warm, dense aluminum plasmas and liquids.  

PubMed

The electrical conductivity of warm, dense aluminum plasmas and liquids is calculated using ab initio molecular dynamics and the Kubo-Greenwood formula. The density range extends from near solid to one-hundredth of solid density, and the temperature range extends from 6000 K to 30 000 K. This density and temperature range allows direct comparison with experimental results obtained with the tamped exploding wire technique. PMID:12241227

Desjarlais, M P; Kress, J D; Collins, L A

2002-08-01

196

Grain size-dependent electrical conductivity of polycrystalline cerium oxide  

Microsoft Academic Search

The electrical conductivity of polycrystalline cerium oxide was investigated in the nanometer and micrometer size range. Nanocrystalline samples of different grain size were prepared by uniaxial hot-pressing of nanocrystalline powder at various temperatures and pressures. Additional annealing at high temperatures was employed in order to obtain microcrystalline samples. An equivalent-circuit analysis of ac-impedance spectra based on the brick-layer model was

A. Tschöpe; E. Sommer; R. Birringer

2001-01-01

197

Electrically Conductive Thick Film Made from Silver Alkylcarbamates  

NASA Astrophysics Data System (ADS)

A homogeneous electrically conductive silver paste without solid or particle phase was developed using silver alkylcarbamates [(C n H2 n-1NHCOO)2Ag, n ? 4] as the precursor of the functional phase. The silver alkylcarbamates were light insensitive and had a low decomposition temperature (below 200°C). The paste was a non-Newtonian fluid with viscosity significantly depending on the content of the thickening agent ethyl cellulose. Array patterns with a resolution of 20 ?m were obtained using this paste by a micropen direct-writing method. After the paste with about 48 wt.% silver methylcarbamate [(CH3NHCOO)2Ag] precursor was sintered at 180°C for 15 min, an electrically conductive network consisting of more than 95 wt.% silver was formed, and was found to have a volume electrical resistivity on the order of 10-5 ? cm and a sheet electrical resistivity on the order of 10-2-10-3 ?/?. The cohesion strength within the sintered paste and the adhesion strength between the sintered paste layer and the alumina ceramic substrate were tested according to test method B of the American Society for Testing and Materials standard D3359-08. None of the sintered paste layer was detached under the test conditions, and the cohesion and adhesion strengths met the highest grade according to the standard.

Liu, Jianguo; Li, Xiangyou; Wang, Xiaoye; Zeng, Xiaoyan

2010-10-01

198

Electrically Conductive Chitosan/Carbon Scaffolds for Cardiac Tissue Engineering  

PubMed Central

In this work, carbon nanofibers were used as doping material to develop a highly conductive chitosan-based composite. Scaffolds based on chitosan only and chitosan/carbon composites were prepared by precipitation. Carbon nanofibers were homogeneously dispersed throughout the chitosan matrix, and the composite scaffold was highly porous with fully interconnected pores. Chitosan/carbon scaffolds had an elastic modulus of 28.1 ± 3.3 KPa, similar to that measured for rat myocardium, and excellent electrical properties, with a conductivity of 0.25 ± 0.09 S/m. The scaffolds were seeded with neonatal rat heart cells and cultured for up to 14 days, without electrical stimulation. After 14 days of culture, the scaffold pores throughout the construct volume were filled with cells. The metabolic activity of cells in chitosan/carbon constructs was significantly higher as compared to cells in chitosan scaffolds. The incorporation of carbon nanofibers also led to increased expression of cardiac-specific genes involved in muscle contraction and electrical coupling. This study demonstrates that the incorporation of carbon nanofibers into porous chitosan scaffolds improved the properties of cardiac tissue constructs, presumably through enhanced transmission of electrical signals between the cells. PMID:24417502

2015-01-01

199

Electrical studies on silver based fast ion conducting glassy materials  

NASA Astrophysics Data System (ADS)

Among all the available fast ion conductors, silver based glasses exhibit high conductivity. Further, glasses containing silver iodide enhances fast ion conducting behavior at room temperature. Glasses of various compositions of silver based fast ion conductors in the AgI-Ag2O-[(1-x)B2O3-xTeO2] (x=0 to1 mol% in steps of 0.2) glassy system have been prepared by melt quenching method. The glassy nature of the compounds has been confirmed by X-ray diffraction. The electrical conductivity (AC) measurements have been carried out in the frequency range of 1 KHz-3MHz by Impedance Analyzer in the temperature range 303-423K. The DC conductivity measurements were also carried out in the temperature range 300-523K. From both AC and DC conductivity studies, it is found that the conductivity increases and activation energy decreases with increasing the concentration of TeO2 as well as with temperature. The conductivity of the present glass system is found to be of the order of 10-2 S/cm at room temperature. The ionic transport number of these glasses is found to be 0.999 indicating that these glasses can be used as electrolyte in batteries.

Rao, B. Appa; Kumar, E. Ramesh; Kumari, K. Rajani; Bhikshamaiah, G.

2014-04-01

200

Electrical studies on silver based fast ion conducting glassy materials  

SciTech Connect

Among all the available fast ion conductors, silver based glasses exhibit high conductivity. Further, glasses containing silver iodide enhances fast ion conducting behavior at room temperature. Glasses of various compositions of silver based fast ion conductors in the AgI?Ag{sub 2}O?[(1?x)B{sub 2}O{sub 3}?xTeO{sub 2}] (x=0 to1 mol% in steps of 0.2) glassy system have been prepared by melt quenching method. The glassy nature of the compounds has been confirmed by X-ray diffraction. The electrical conductivity (AC) measurements have been carried out in the frequency range of 1 KHz–3MHz by Impedance Analyzer in the temperature range 303–423K. The DC conductivity measurements were also carried out in the temperature range 300–523K. From both AC and DC conductivity studies, it is found that the conductivity increases and activation energy decreases with increasing the concentration of TeO{sub 2} as well as with temperature. The conductivity of the present glass system is found to be of the order of 10{sup ?2} S/cm at room temperature. The ionic transport number of these glasses is found to be 0.999 indicating that these glasses can be used as electrolyte in batteries.

Rao, B. Appa, E-mail: apparao.bojja@gmail.com; Kumar, E. Ramesh, E-mail: apparao.bojja@gmail.com; Kumari, K. Rajani, E-mail: apparao.bojja@gmail.com; Bhikshamaiah, G., E-mail: apparao.bojja@gmail.com [Department of Physics, Osmania University, Hyderabad-500007 (India)

2014-04-24

201

Effect of twist and porosity on the electrical conductivity of carbon nanofiber yarns  

NASA Astrophysics Data System (ADS)

This study focuses on the effect of twist and porosity on the electrical conductivity of carbon nanofiber (CNF) yarns. The process of fabrication of CNF yarns included the synthesis of aligned ribbons of polyacrylonitrile (PAN) nanofibers via electrospinning. The PAN ribbons were twisted into yarns with twist levels ranging from zero twist to high twists of 1300 turn per meter (tpm). The twist imposed on the ribbons substantially improved the interactions between nanofibers and reduced the porosity. The PAN yarns were subsequently stabilized in air, and then carbonized in nitrogen at 1100?° C for 1 h. Compressive stresses developed between the PAN nanofibers as a result of twist promoted interfusion between neighboring nanofibers, which was accelerated by heating the yarns during stabilization to temperatures above the glass transition of PAN. The electrical conductivity of the yarns was measured with a four point probe measurement technique. Although increasing the twist promotes electrical conductivity between nanofibers by forming junctions between them, our results indicate that the electrical conductivity does not continuously increase with increasing twist, but reaches a threshold value after which it starts to decrease. The causes for this behavior were studied through experimental techniques and further explored using a yarn-equivalent electrical circuit model.

Chawla, S.; Naraghi, M.; Davoudi, A.

2013-06-01

202

Method for electrically isolating an electrically conductive member from another such member  

DOEpatents

The invention relates to methods for electrically isolating a first electrically conductive member from another such member by means of an electrically insulating medium. In accordance with the invention, the insulating medium is provided in the form of MgO which contains a dopant selected from lithium, copper, cobalt, sodium, silver, gold and hydrogen. The dopant is present in the MgO in an amount effective to suppress dielectric breakdown of the MgO, even at elevated temperatures and in the presence of electrical fields.

Tsang, K.L.; Chen, Y.

1984-02-09

203

Magnetic resonance electrical impedance tomography for measuring electrical conductivity during electroporation.  

PubMed

The electroporation effect on tissue can be assessed by measurement of electrical properties of the tissue undergoing electroporation. The most prominent techniques for measuring electrical properties of electroporated tissues have been voltage-current measurement of applied pulses and electrical impedance tomography (EIT). However, the electrical conductivity of tissue assessed by means of voltage-current measurement was lacking in information on tissue heterogeneity, while EIT requires numerous additional electrodes and produces results with low spatial resolution and high noise. Magnetic resonance EIT (MREIT) is similar to EIT, as it is also used for reconstruction of conductivity images, though voltage and current measurements are not limited to the boundaries in MREIT, hence it yields conductivity images with better spatial resolution. The aim of this study was to investigate and demonstrate the feasibility of the MREIT technique for assessment of conductivity images of tissues undergoing electroporation. Two objects were investigated: agar phantoms and ex vivo liver tissue. As expected, no significant change of electrical conductivity was detected in agar phantoms exposed to pulses of all used amplitudes, while a considerable increase of conductivity was measured in liver tissue exposed to pulses of different amplitudes. PMID:24844299

Kranjc, M; Bajd, F; Serša, I; Miklav?i?, D

2014-06-01

204

Effects of an Electrically Conducting Inner Core on Planetary and Stellar Dynamos  

NASA Astrophysics Data System (ADS)

The influence of an electrically conducting inner core on the characteristics of kinematic spherical ?2 dynamos is investigated both analytically and numerically. Emphasis is placed on the magnetic coupling between the outer turbulent fluid spherical shell where magnetic fields are generated and the electrically conducting inner core, which can control the way in which the magnetic field in the shell is produced. We illustrate the subtlety of the electromagnetic boundary conditions at the core-shell interface: continuity of the radial magnetic field, continuity of the tangential electric field, and continuity of the tangential magnetic field. In the special cases of zero and infinite core electrical conductivity, the core-shell interface conditions take different explicit forms and in the latter case depend on whether the dynamo is stationary or oscillatory. Dynamo solutions depend on ?, the ratio of inner to outer shell radius; ?, the ratio of core to shell magnetic diffusivity; ?(r), the radially dependent ? function in the outer turbulent fluid spherical shell; and R?, the magnetic Reynolds number of the shell. For small cores, ?<0.5, the ?2 dynamo is always stationary, independent of ?. For larger cores, the dynamo is oscillatory for ?<5.3 and stationary for ?>5.3. Time-dependent dynamo behavior can arise from the ?-effect alone in the presence of a sufficiently large and electrically conducting inner core. This phenomenon could be relevant to the solar dynamo for which ?=0.8 and ?=10-3. It could also be relevant to the dynamos of planets with sufficiently large inner cores; Earth's inner core is too small, however, for the oscillatory phenomenon to be directly applicable to the geodynamo.

Schubert, Gerald; Zhang, Keke

2001-08-01

205

Effects of contact resistance on electrical conductivity measurements of SiC-based materials  

SciTech Connect

A combination 2/4-probe method was used to measure electrical resistances across a pure, monolithic CVD-SiC disc sample with contact resistance at the SiC/metallic electrode interfaces. By comparison of the almost simultaneous 2/4-probe measurements, the specific contact resistance (Rc) and its temperature dependence were determined for two types (sputtered gold and porous nickel) electrodes from room temperature (RT) to ?973 K. The Rc-values behaved similarly for each type of metallic electrode: Rc > ?1000 ? cm2 at RT, decreasing continuously to ?1–10 ? cm2 at 973 K. The temperature dependence of the inverse Rc indicated thermally activated electrical conduction across the SiC/metallic interface with an apparent activation energy of ?0.3 eV. For the flow channel insert application in a fusion reactor blanket, contact resistance potentially could reduce the transverse electrical conductivity by about 50%.

Youngblood, Gerald E.; Thomsen, Edwin C.; Henager, Charles H.

2013-06-30

206

Electrical conductivity of p-type BiOCl nanosheets.  

PubMed

High quality BiOCl nanosheets were fabricated using facile, room temperature hydrolysis of Bi(NO3)3 and HCl. The resulting nanosheets had dimensions of 500 nm with the exposed {001} facet. The band gap of the nanosheets was found to be 3.34 eV with conduction and valence band edges at -3.63 eV and -6.97 eV with respect to vacuum, respectively. The electrical conductivity of drop-cast BiOCl nanosheets was measured between aluminum patterned electrodes as a function of temperature and oxygen partial pressure (pO2). The activation energy for conduction in BiOCl was found to be 862 meV in the temperature range of 300-425 K and below 1000 mbar. The electrical conductivity varied with pO2, indicating ? ? pO2(1/4.05) and ? ? pO2(1/32) for low and sub atmospheric pressures, respectively. A prototypical device for low temperature (425 K) O2 sensing was demonstrated. PMID:25573144

Myung, Yoon; Wu, Fei; Banerjee, Sriya; Park, Jeunghee; Banerjee, Parag

2015-01-29

207

High temperature electrically conducting ceramic heating element and control system  

NASA Technical Reports Server (NTRS)

Improvements were made in both electrode technology and ceramic conductor quality to increase significantly the lifetime and thermal cycling capability of electrically conducting ceramic heater elements. These elements were operated in vacuum, inert and reducing environments as well as oxidizing atmospheres adding to the versatility of the conducting ceramic as an ohmic heater. Using stabilized zirconia conducting ceramic heater elements, a furnace was fabricated and demonstrated to have excellent thermal response and cycling capability. The furnace was used to melt platinum-20% rhodium alloy (melting point 1904 C) with an isothermal ceramic heating element having a nominal working cavity size of 2.5 cm diameter by 10.0 cm long. The furnace was operated to 1940 C with the isothermal ceramic heating element. The same furnace structure was fitted with a pair of main heater elements to provide axial gradient temperature control over a working cavity length of 17.8 cm.

Halbach, C. R.; Page, R. J.

1975-01-01

208

Flake Electrical Conductivity of Few-Layer Graphene  

PubMed Central

The Kubo formula for the electrical conductivity of per stratum of few-layer graphene, up to five, is analytically calculated in both simple and Bernal structures within the tight-binding Hamiltonian model and Green's function technique, compared with the single-layer one. The results show that, by increasing the layers of the graphene as well as the interlayer hopping of the nonhybridized pz orbitals, this conductivity decreases. Although the change in its magnitude varies less as the layer number increases to beyond two,distinguishably, at low temperatures, it exhibits a small deviation from linear behavior. Moreover, the simple bilayer graphene represents more conductivity with respect to the Bernal case. PMID:24550711

2014-01-01

209

Flake electrical conductivity of few-layer graphene.  

PubMed

The Kubo formula for the electrical conductivity of per stratum of few-layer graphene, up to five, is analytically calculated in both simple and Bernal structures within the tight-binding Hamiltonian model and Green's function technique, compared with the single-layer one. The results show that, by increasing the layers of the graphene as well as the interlayer hopping of the nonhybridized p z orbitals, this conductivity decreases. Although the change in its magnitude varies less as the layer number increases to beyond two,distinguishably, at low temperatures, it exhibits a small deviation from linear behavior. Moreover, the simple bilayer graphene represents more conductivity with respect to the Bernal case. PMID:24550711

Mousavi, Hamze; Khodadadi, Jabbar

2014-01-01

210

Using High Resolution Complex Electrical Conductivity Measurements of Heterogeneous Rocks  

NASA Astrophysics Data System (ADS)

The complex electrical resistivity of a slab of Berea sandstone was measured using a four electrode probe in the frequency range of 1 Hz to 1 kHz. The measurements where made in the context of the development of a new high resolution methodology for the laboratory characterization of hydro-geophysical properties on core and field samples. Electrical conductivity maps with millimeter-scale resolution and measured at different pore fluid salinities are used to constrain dual conduction models (e.g. Waxman-Smits, 1968) that allow us to separate the contribution of electrical conduction through the pore fluid from surface conduction along mineral grain surfaces. Measured resistivity variations are observed to be structured in distinct layers at the scale of millimeters to centimeters and are well correlated with fine scale layering observed in thin section. The data is analyzed in conjunction with petrophysical maps of permeability and velocity variations. The maps of permeability, resistivity, and velocity all indicate that Berea sandstone contains measurable structural anisotropy at a variety of scales. The heterogeneities in petrophysical properties are in general rather weak, with permeability varying by a factor of 3 and velocity and resistivity varying by 7% and 19% respectively. Analyzed collectively, the data provides insights into the physical causes of the observed resistivity anomalies and allows us to interpret them as due to localized pore-scale variations in grain size, pore structure, and mineralogy. Correlations among these petrographic variables lead to the discovery that surface conductivity of the rock is negatively correlated with the conductivity due to the free electrolyte. Using this integrated petrophysical data-set, we build a predictive model of the meter-scale petrophysical properties that honors the intrinsic heterogeneity of the sample. The data and models are used as the foundation for a physically-based upscaling approach for understanding how petrophysical properties relate to flow and transport processes at scales difficult to measure in the laboratory. Through application of effective media and numerical models we show that the observed small-scale heterogeneity leads to anisotropy in electrical properties that correlates with anisotropy in relative permeability. The anisotropy is found to be a complex function of scale, salinity, and saturation.

Boitnott, G. N.; Bussod, G. Y.

2009-12-01

211

The bedrock electrical conductivity structure of Northern Ireland  

NASA Astrophysics Data System (ADS)

An airborne geophysical survey of the whole of Northern Ireland has provided over 4.8 M estimates of the bedrock conductivity over the wide range of geological formations present. This study investigates how such data can be used to provide additional knowledge in relation to existing digital geological map information. A by-product of the analysis is a simplification of the spatially aggregated information obtained in such surveys. The methodology used is a GIS-based attribution of the conductivity estimates using a lithological classification of the bedrock formations. A 1:250k geological classification of the data is performed leading to a 56 unit lithological and geostatistical analysis of the conductivity information. The central moments (medians) of the classified data are used to provide a new digital bedrock conductivity map of Northern Ireland with values ranging from 0.32 to 41.36 mS m-1. This baseline map of conductivities displays a strong correspondence with an existing 4 quadrant, chrono-geological description of Northern Ireland. Once defined, the baseline conductivity map allows departures from the norm to be assessed across each specific lithological unit. Bulk electrical conductivity is controlled by a number of petrophysical parameters and it is their variation that is assessed by the procedures employed. The igneous rocks are found to display the largest variability in conductivity values and many of the statistical distributions are multi-modal. A sequence of low-value modes in these data are associated with intrusives within volcanic complexes. These and much older Neoproterzoic rocks appear to represent very low porosity formations that may be the product of rapid cooling during emplacement. By way of contrast, extensive flood basalts (the Antrim lavas) record a well-defined and much higher median value (12.24 mS m-1) although they display complex spatial behaviour in detail. Sedimentary rocks appear to follow the broad behaviours anticipated by standard theoretical descriptions of rock electrical properties that allow for a term due to grain surface conduction (e.g. the presence of clay). Single lithology sedimentary rocks are represented by an increasing set of conductivities through the sequence sandstone (4.91 mS m-1), limestone (8.41 mS m-1) and mudstone (17.85 mS m-1) with argillaceous rocks providing a conductivity of 41.1 mS m-1. In the case of both sandstone and limestone, the single lithology conductivities are significantly less than their mixed lithology counterparts. Mudrocks display a bimodal statistical distribution and an extended analysis of these rocks is carried out across a Carboniferous basin. The results clearly indicate that non-shale mudstones are distinctly less conductive than their shale counterparts. Shale formations display rapid and large movements in conductivity and it is suggested that the observed sensitivity may be due to competing surface conduction effects due to clay and organic material. A study of the variation of conductivity with geological period is also performed. Both a decreasing trend with age and a modulation that peaks in the Triassic period are observed.

Beamish, David

2013-08-01

212

Electric conductivity from the solution of the relativistic Boltzmann equation  

NASA Astrophysics Data System (ADS)

We present numerical results of electric conductivity ?el of a fluid obtained solving the relativistic transport Boltzmann equation in a box with periodic boundary conditions. We compute ?el using two methods: the definition itself, i.e., applying an external electric field, and the evaluation of the Green-Kubo relation based on the time evolution of the current-current correlator. We find a very good agreement between the two methods. We also compare numerical results with analytic formulas in relaxation time approximation (RTA) where the relaxation time for ?el is determined by the transport cross section ?tr , i.e., the differential cross section weighted with the collisional momentum transfer. We investigate the electric conductivity dependence on the microscopic details of the two-body scatterings: isotropic and anisotropic cross section as well as massless and massive particles. We find that the RTA underestimates considerably ?el ; for example, at screening masses mD˜T , such underestimation can be as large as a factor of 2. Furthermore, we study a more realistic case for a quark-gluon system (QGP) considering both a quasiparticle model tuned to lattice QCD (lQCD) thermodynamics, as well as the case of a perturbative QCD (pQCD) gas with running coupling. Also, for these cases more directly related to the description of the QGP system, we find that the RTA significantly underestimates the ?el by about 60%-80%.

Puglisi, A.; Plumari, S.; Greco, V.

2014-12-01

213

Testing and Optimization of Electrically Conductive Spacecraft Coatings  

NASA Technical Reports Server (NTRS)

This is the final report discussing the work done for the Space Environments and Effects (SEE) Program. It discusses test chamber design, coating research, and test results on electrically thermal control coatings. These thermal control coatings are being developed to have several orders of magnitude higher electrical conductivity than most available thermal control coatings. Most current coatings tend to have a range in surface resistivity from 1,011 to 1,013 ohms/sq. Historically, spacecraft have had thermal control surfaces composed of dielectric materials of either polymers (paints and metalized films) or glasses (ceramic paints and optical solar reflectors). Very seldom has the thermal control surface of a spacecraft been a metal where the surface would be intrinsically electrically conductive. The poor thermal optical properties of most metals have, in most cases, stopped them from being used as a thermal control surface. Metals low infrared emittance (generally considered poor for thermal control surfaces) and/or solar absorptance, have resulted in the use of various dielectric coatings or films being applied over the substrate materials in order to obtain the required optical properties.

Mell, R. J.; Wertz, G. E.; Edwards, D. L. (Technical Monitor)

2001-01-01

214

Electric Conductivity from the solution of the Relativistic Boltzmann Equation  

E-print Network

We present numerical results of electric conductivity $\\sigma_{el}$ of a fluid obtained solving the Relativistic Transport Boltzmann equation in a box with periodic boundary conditions. We compute $\\sigma_{el}$ using two methods: the definition itself, i.e. applying an external electric field, and the evaluation of the Green-Kubo relation based on the time evolution of the current-current correlator. We find a very good agreement between the two methods. We also compare numerical results with analytic formulas in Relaxation Time Approximation (RTA) where the relaxation time for $\\sigma_{el}$ is determined by the transport cross section $\\sigma_{tr}$, i.e. the differential cross section weighted with the collisional momentum transfer. We investigate the electric conductivity dependence on the microscopic details of the 2-body scatterings: isotropic and anisotropic cross-section, and massless and massive particles. We find that the RTA underestimates considerably $\\sigma_{el}$; for example at screening masses $m_D \\sim \\,T$ such underestimation can be as large as a factor of 2. Furthermore, we study a more realistic case for a quark-gluon system (QGP) considering both a quasi-particle model, tuned to lQCD thermodynamics, as well as the case of a pQCD gas with running coupling. Also for these cases more directly related to the description of the QGP system, we find that RTA significantly underestimate the $\\sigma_{el}$ by about a $60-80\\%$.

A. Puglisi; S. Plumari; V. Greco

2014-09-08

215

Multifunctional conducting fibres with electrically controlled release of ciprofloxacin.  

PubMed

We hereby present a new method of producing coaxial conducting polymer fibres loaded with an antibiotic drug that can then be subsequently released (or sustained) in response to electrical stimulation. The method involves wet-spinning of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) fibre, which served as the inner core to the electropolymerised outer shell layer of polypyrrole (Ppy). Ciprofloxacin hydrochloride (Cipro) was selected as the model drug and as the dopant in the Ppy synthesis. The release of Cipro in phosphate buffered saline (PBS) from the fibres was controlled by switching the redox state of Ppy.Cipro layer. Released Cipro under passive and stimulated conditions were tested against Gram positive (Streptococcus pyogenes) and Gram negative (Escherichia coli) bacteria. Significant inhibition of bacterial growth was observed against both strains tested. These results confirm that Cipro retains antibacterial properties during fibre fabrication and electrochemically controlled release. In vitro cytotoxicity testing utilising the neural B35 cell line confirmed the cytocompatibility of the drug loaded conducting fibres. Electrical conductivity, cytocompatibility and tuning release profile from this flexible fibre can lead to promising bionic applications such as neuroprosthetics and localised drug delivery. PMID:23379995

Esrafilzadeh, Dorna; Razal, Joselito M; Moulton, Simon E; Stewart, Elise M; Wallace, Gordon G

2013-08-10

216

Miniatuization of the flowing fluid electric conductivity loggingtec hnique  

SciTech Connect

An understanding of both the hydraulic properties of the aquifer and the depth distribution of salts is critical for evaluating the potential of groundwater for conjunctive water use and for maintaining suitable groundwater quality in agricultural regions where groundwater is used extensively for irrigation and drinking water. The electrical conductivity profiles recorded in a well using the flowing fluid electric conductivity logging (FEC logging) method can be analyzed to estimate interval specific hydraulic conductivity and estimates of the salinity concentration with depth. However, irrigation wells that are common in agricultural regions have limited access into them because these wells are still in operation, and the traditional equipment used for FEC logging cannot fit through the small access pipe intersecting the well. A modified, miniaturized FEC logging technique was developed such that this logging method could be used in wells with limited access. In addition, a new method for injecting water over the entire screened interval of the well was developed to reduce the time required to perform FEC logging. Results of FEC logging using the new methodology and miniaturized system in two irrigation wells are also summarized.

Su, Grace W.; Quinn, Nigel W.T.; Cook, Paul J.; Shipp, William

2005-10-19

217

Electrical conductivity investigation of the Corso-Sardinian microplate area  

NASA Astrophysics Data System (ADS)

The analysis of magnetovariational data from an array quasi- simultaneously covering Sardinia (Italy) and Corsica (France), from summer 1988 to spring 1991, indicates the existence of two major conducting bodies, one north of Corsica, the other south of Sardinia. Fourier maps also show local conductivity anomalies along the Campidano Graben (Sardinia), across the Bonifacio Straits and in the northernmost part of Corsica. Two-dimensional (2D) modelling and inversion procedures have been carried out in order to find the optimum conductivity and geometrical characteristics of the conductive bodies deduced from Fourier maps, induction arrows and pseudosections studies. As a result of the 2D inversion, two zones with enhanced electrical conductivity are found, respectively, in the Sardinia Channel and in the Bonifacio Straits. The former can be related to the thermal characteristics of the area; the latter, shallower, can be ascribed to an accumulation of sediments. Some short-period magnetovariational anomalies in northern Corsica can be related to recent reheating processes that occurred there, as well as to the crustal thinning in the Ligurian sea.

Cerv, V.; Bozzo, E.; De Santis, A.; Elena, A.; Gambetta, M.; Mariotti, A.; Meloni, A.; Pek, J.

1993-11-01

218

Development of Tailorable Electrically Conductive Thermal Control Material Systems  

NASA Technical Reports Server (NTRS)

The optical characteristics of surfaces on spacecraft are fundamental parameters in controlling its temperature. Passive thermal control coatings with designed solar absorptance and infrared emittance properties have been developed and been in use for some time. In this total space environment, the coating must be stable and maintain its desired optical properties for the course of the mission lifetime. The mission lifetimes are increasing and in our quest to save weight, newer substrates are being integrated which limit electrical grounding schemes. All of this has already added to the existing concerns about spacecraft charging and related spacecraft failures or operational failures. The concern is even greater for thermal control surfaces that are very large. One way of alleviating such concerns is to design new thermal control material systems (TCMS) that can help to mitigate charging via providing charge leakage paths. The object of this program was to develop two types of passive electrically conductive TCMS.

Deshpande, M. S.; Harada, Y.

1998-01-01

219

Transparent electrical conducting films by activated reactive evaporation  

DOEpatents

Process and apparatus for producing transparent electrical conducting thin films by activated reactive evaporation is disclosed. Thin films of low melting point metals and alloys, such as indium oxide and indium oxide doped with tin, are produced by physical vapor deposition. The metal or alloy is vaporized by electrical resistance heating in a vacuum chamber, oxygen and an inert gas such as argon are introduced into the chamber, and vapor and gas are ionized by a beam of low energy electrons in a reaction zone between the resistance heater and the substrate. There is a reaction between the ionized oxygen and the metal vapor resulting in the metal oxide which deposits on the substrate as a thin film which is ready for use without requiring post deposition heat treatment. 1 fig.

Bunshah, R.; Nath, P.

1982-06-22

220

Transparent electrical conducting films by activated reactive evaporation  

DOEpatents

Process and apparatus for producing transparent electrical conducting thin films by activated reactive evaporation. Thin films of low melting point metals and alloys, such as indium oxide and indium oxide doped with tin, are produced by physical vapor deposition. The metal or alloy is vaporized by electrical resistance heating in a vacuum chamber, oxygen and an inert gas such as argon are introduced into the chamber, and vapor and gas are ionized by a beam of low energy electrons in a reaction zone between the resistance heater and the substrate. There is a reaction between the ionized oxygen and the metal vapor resulting in the metal oxide which deposits on the substrate as a thin film which is ready for use without requiring post deposition heat treatment.

Bunshah, Rointan (Los Angeles, CA); Nath, Prem (Troy, MI)

1982-01-01

221

Electrical Modulation of the Local Conduction at Oxide Tubular Interfaces  

SciTech Connect

Hetero-interfaces between complex oxides have sparked considerable interest due to their fascinating physical properties and offer new possibilities for next-generation electronic devices. The key to realize practical applications is the control through external stimulus. In this study, we take the self-assembled BiFeO3-CoFe2O4 hetero-interface as a model system to demonstrate the non-volatile electric control of the local conduction at the complex oxide tubular interface. The fundamental mechanism behind this modulation was explored based on static and dynamic conducting atomic force microscopy. We found the movement of oxygen vacancies in the BiFeO3-CoFe2O4 heterostructure is the key to drive this intriguing behavior. This study delivers a possibility of designing new device for next-generation electronic devices.

Hsieh, Ying-Hui [National Chiao Tung University, Hsinchu, Taiwan] [National Chiao Tung University, Hsinchu, Taiwan; Strelcov, Evgheni [ORNL] [ORNL; Jia-Ming, Liou [National Cheng Kung University, Tainan, Taiwan] [National Cheng Kung University, Tainan, Taiwan; Chia-Ying, Shen [National Chiao Tung University, Hsinchu, Taiwan] [National Chiao Tung University, Hsinchu, Taiwan; Yi-Chun, Chen [National Cheng Kung University, Tainan, Taiwan] [National Cheng Kung University, Tainan, Taiwan; Kalinin, Sergei V [ORNL] [ORNL; Ying-Hao, Chu [National Chiao Tung University, Hsinchu, Taiwan] [National Chiao Tung University, Hsinchu, Taiwan

2013-01-01

222

Electrical conductivity measurements on disk-shaped samples.  

PubMed

We have developed a sample holder design that allows for electrical conductivity measurements on a disk-shaped sample. The sample holder design is based on and compatible with popular measurement systems that are currently restricted to bar-shaped samples. The geometrical correction factors which account for the adjusted measurement configuration were calculated using finite element modeling for a broad range of sample and measurement geometries. We also show that the modeling results can be approximated by a simple analytical fit function with excellent accuracy. The proposed sample holder design is compatible with a concurrent measurement of the Seebeck coefficient. The chosen sample geometry is furthermore compatible with a thermal conductivity measurement using a laser flash apparatus. A complete thermoelectric characterization without cutting the sample is thus possible. PMID:25085170

de Boor, J; Zabrocki, K; Frohring, J; Müller, E

2014-07-01

223

DNA-templated nanowires: morphology and electrical conductivity  

NASA Astrophysics Data System (ADS)

DNA-templating has been used to create nanowires from metals, compound semiconductors and conductive polymers. The mechanism of growth involves nucleation at binding sites on the DNA followed by growth of spherical particles and then, under favourable conditions, a slow transformation to a smooth nanowire. The final transformation is favoured by restricting the amount of templated material per unit length of template and occurs most readily for materials of low surface tension. Electrical measurements on DNA-templated nanowires can be facilitated using three techniques: (i) standard current-voltage measurements with contact electrodes embedded in a dielectric so that there is a minimal step height at the dielectric/electrode boundary across which nanowires may be aligned by molecular combing, (ii) the use of a dried droplet technique and conductive AFM to determine contact resistance by moving the tip along the length of an individual nanowire and (iii) non-contact assessment of conductivity by scanned conductance microscopy on Si/SiO2 substrates.

Watson, Scott M. D.; Pike, Andrew R.; Pate, Jonathan; Houlton, Andrew; Horrocks, Benjamin R.

2014-03-01

224

Conductance imaging AFM and electrical properties of carbon nanotubes  

NASA Astrophysics Data System (ADS)

This thesis reports the development of a new method for measuring electrical of nanoscale objects, called conductance imaging atomic force microscopy (CIAFM), and reports the results of measurements performed on carbon nanotube networks and nanotube junctions. We introduce CIAFM, a method that combines atomic force microscopy and local conductance measurements. The method is implemented by using a tuning fork as cantilever and a solid metal tip. It excels at taking large amounts of measurements at high data density, making it equally suitable to analyze transitions on the nanometer scale or large systems such as networks. The method is thoroughly characterized. CIAFM is applied to measure the local conductances of a carbon nanotube network on the nanometer scale to characterize current paths through the network. The extent of metallic connections is investigated and found to be the principal contributor to current flow on the macroscopic scale. Finally, we analyze the length scale of conductance decay around carbon nanotube junctions. We find indication for ballistic current and exponential decay of ballistic current over a distance of several microns.

Stadermann, Michael

225

DNA-templated nanowires: morphology and electrical conductivity.  

PubMed

DNA-templating has been used to create nanowires from metals, compound semiconductors and conductive polymers. The mechanism of growth involves nucleation at binding sites on the DNA followed by growth of spherical particles and then, under favourable conditions, a slow transformation to a smooth nanowire. The final transformation is favoured by restricting the amount of templated material per unit length of template and occurs most readily for materials of low surface tension. Electrical measurements on DNA-templated nanowires can be facilitated using three techniques: (i) standard current-voltage measurements with contact electrodes embedded in a dielectric so that there is a minimal step height at the dielectric/electrode boundary across which nanowires may be aligned by molecular combing, (ii) the use of a dried droplet technique and conductive AFM to determine contact resistance by moving the tip along the length of an individual nanowire and (iii) non-contact assessment of conductivity by scanned conductance microscopy on Si/SiO2 substrates. PMID:24614835

Watson, Scott M D; Pike, Andrew R; Pate, Jonathan; Houlton, Andrew; Horrocks, Benjamin R

2014-04-21

226

Synthesis and electrical conductivity of nanocrystalline tetragonal FeS  

NASA Astrophysics Data System (ADS)

A convenient method for synthesis of tetragonal FeS using iron powder as iron source, is reported. Nanocrystalline tetragonal FeS samples were successfully synthesized by reacting metallic iron powder with sodium sulfide in acetate buffer solution. The obtained sample is single-phase tetragonal FeS with lattice parameters a = 0.3767 nm and c = 0.5037 nm, as revealed by X-ray diffraction. The sample consists of flat nanosheets with lateral dimensions from 20 nm up to 200 nm and average thickness of about 20 nm. We found that tetragonal FeS is a fairly good conductor from the electrical resistivity measurement on a pellet of the nanosheets. The temperature dependence of conductivity of the pellet was well fitted using an empirical equation wherein the effect of different grain boundaries was taken into consideration. This study provides a convenient, economic way to synthesize tetragonal FeS in a large scale and reports the first electrical conductivity data for tetragonal FeS down to liquid helium temperature.

Zeng, Shu-Lin; Wang, Hui-Xian; Dong, Cheng

2014-08-01

227

Printability and Electrical Conductivity of UV Curable MWCNT Ink  

NASA Astrophysics Data System (ADS)

Composites reinforced with multiwalled carbon nanotubes (MWCNT) in a photosensitive acrylic matrix were successfully synthesized and their printing, rheological, and electrical behavior was characterized. The shape of the reinforcement MWCNT particles was analyzed by transmission electron microscopy. The MWCNT were mixed in the acrylic polymer at increasing concentrations until the percolation threshold was determined at 2 wt.% with a conductivity of 4.26 × 10-4 S/cm. The large increase in viscosity with addition of MWCNT showed the need for a printing system capable of dispensing solutions of up to 613 × 103 cp. Lines were printed with a precision dispensing system mounted in computer controlled x-y-z stages, while an integrated ultraviolet light emission diode dot with a single wavelength of 385 nm cured seconds after the ink was dispensed. The wetting properties of the composite with respect to polyester, polyethylene terephthalate, polyimide, and paper films were analyzed with a goniometer. The relationship between the contact angle, pattern accuracy, and electrical conductivity was determined for each substrate.

Ortega, Ada; Park, Byungwoo; Kim, Nam Soo

2015-03-01

228

Thermophysical Properties of Liquid Te: Density, Electrical Conductivity, and Viscosity  

NASA Technical Reports Server (NTRS)

The thermophysical properties of liquid Te, namely, density, electrical conductivity, and viscosity, were determined using the pycnometric and transient torque methods from the melting point of Te (723 K) to approximately 1150 K. A maximum was observed in the density of liquid Te as the temperature was increased. The electrical conductivity of liquid Te increased to a constant value of 2.89 x 10(exp 5 OMEGA-1m-1) as the temperature was raised above 1000 K. The viscosity decreased rapidly upon heating the liquid to elevated temperatures. The anomalous behaviors of the measured properties are explained as caused by the structural transitions in the liquid and discussed in terms of Eyring's and Bachiskii's predicted behaviors for homogeneous liquids. The Properties were also measured as a function of time after the liquid was coded from approximately 1173 or 1123 to 823 K. No relaxation phenomena were observed in the properties after the temperature of liquid Te was decreased to 823 K, in contrast to the relaxation behavior observed for some of the Te compounds.

Li, C.; Su, C.; Lehoczky, S. L.; Scripa, R. N.; Ban, H.; Lin, B.

2004-01-01

229

Effect of conductivity and concentration on the sample stream in the transverse axis of a continuous flow electrophoresis chamber  

NASA Technical Reports Server (NTRS)

The resolution of continuous flow electrophoresis systems is generally measured by the spread of the sample bands in the direction of the electrophoretic migration. This paper evaluates the cross section of the sample bands in the plane perpendicular to the flow and shows that the spread in the direction perpendicular to the migration increased significantly with the applied electric field. Concentrated samples of monodisperse latex particles and vinyltoluene T-butylstyrene particles in sample buffers of different electrical conductivities were used to map the shape of the sample bands relative to the zero electric field case. As the electric field was applied, the sample band spread from an initial diameter of only one-third the chamber thickness until it approached the chamber walls where electroosmosis significantly reduced the resolution of separation. It can be shown, however, that it is possible to minimize these distortions by careful sample preparation and experiment design.

Miller, Teresa Y.; Williams, George O.; Snyder, Robert S.

1985-01-01

230

Machining of low electrical conductive materials by wire electrical discharge machining (WEDM)  

Microsoft Academic Search

This theoretical and experimental study of WEDM of low conductive materials demonstrates that total electrical resistance between the workpiece and wire electrode vary during machining depending upon the clamping position. This change in resistance causes a change in material removal rate (MRR) and average surface roughness that leads to poor quality of products. A technique developed in this work minimizes

Jerzy Kozak; Kamlakar P. Rajurkar; Niraj Chandarana

2004-01-01

231

On the electrical conductivity structure of the stable continental crust  

NASA Astrophysics Data System (ADS)

A high conductivity zone (HCZ) exists in many places worldwide in the stable mid- to lower continental crust, at the depth of about 20-30 km, but its origin is enigmatic. At this depth range, the temperatures are constrained between 400 and 600 °C and free fluids are believed to have been consumed by retrograde mineral reactions. Many causes for the HCZ have been considered such as residual fluids and brines, partial melting, serpentine or other hydroxyl-bearing minerals in a state of dehydration, but intergranular carbon films have been the most widely accepted explanation. This view is challenged. Electrical conductivity and dielectric polarization measurements on materials as structurally and chemically diverse as laboratory-grown MgO, upper mantle olivine single crystals, and lower crustal anorthosite rock indicate that, in all of them, highly mobile electronic charge carriers are generated in the 450±50-650±50 °C window. These charge carriers are positive holes, e.g. defect electrons in the O 2p-dominated valence band, chemically equivalent to O - in the O 2- matrix. They form through dissociation of positive hole pairs, PHP, chemically equivalent to peroxy links, O 3X-OO-XO 3 (X=Si 4+, Al 3+ etc.). The PHPs in turn derive from hydroxyl, O 3X-OH, that become incorporated into nominally anhydrous minerals whenever they crystallize in H 2O-laden igneous or metamorphic environments. Upon cooling, O 3X-OH pairs undergo a redox conversion to O 3X-OO-XO 3 plus H 2. Positive hole charge carriers have no problem co-existing with reduced cations under the non-equilibrium conditions that prevail in dry rocks below 600 °C, and they dominate their electrical conductivity in the 400-600 °C temperature range. It is proposed that the HCZ is caused by positive hole charge carriers that are metastably activated in the crust in the 20-30 km depth range.

Freund, Friedemann

2003-04-01

232

Acidosis slows electrical conduction through the atrio-ventricular node  

PubMed Central

Acidosis affects the mechanical and electrical activity of mammalian hearts but comparatively little is known about its effects on the function of the atrio-ventricular node (AVN). In this study, the electrical activity of the epicardial surface of the left ventricle of isolated Langendorff-perfused rabbit hearts was examined using optical methods. Perfusion with hypercapnic Tyrode's solution (20% CO2, pH 6.7) increased the time of earliest activation (Tact) from 100.5 ± 7.9 to 166.1 ± 7.2 ms (n = 8) at a pacing cycle length (PCL) of 300 ms (37°C). Tact increased at shorter PCL, and the hypercapnic solution prolonged Tact further: at 150 ms PCL, Tact was prolonged from 131.0 ± 5.2 to 174.9 ± 16.3 ms. 2:1 AVN block was common at shorter cycle lengths. Atrial and ventricular conduction times were not significantly affected by the hypercapnic solution suggesting that the increased delay originated in the AVN. Isolated right atrial preparations were superfused with Tyrode's solutions at pH 7.4 (control), 6.8 and 6.3. Low pH prolonged the atrial-Hisian (AH) interval, the AVN effective and functional refractory periods and Wenckebach cycle length significantly. Complete AVN block occurred in 6 out of 9 preparations. Optical imaging of conduction at the AV junction revealed increased conduction delay in the region of the AVN, with less marked effects in atrial and ventricular tissue. Thus acidosis can dramatically prolong the AVN delay, and in combination with short cycle lengths, this can cause partial or complete AVN block and is therefore implicated in the development of brady-arrhythmias in conditions of local or systemic acidosis. PMID:25009505

Nisbet, Ashley M.; Burton, Francis L.; Walker, Nicola L.; Craig, Margaret A.; Cheng, Hongwei; Hancox, Jules C.; Orchard, Clive H.; Smith, Godfrey L.

2014-01-01

233

Electrical resistivity imaging of conductive plume dilution in fractured rock  

NASA Astrophysics Data System (ADS)

Electrical resistance tomography (ERT) was used to monitor a conductive plume dilution experiment that was conducted in fractured basalt in order to assess its applications in this type of fractured-rock environment. Tap water was injected into an injection well for 34 days to dilute a pre-existing potassium chloride (KCl) plume at a site in Idaho, USA. No further fluids were introduced artificially during a 62-day monitoring period. Both surface ERT and cross-borehole ERT were used to monitor dilution and displacement of the plume. A square grid of land-surface electrodes was used with the surface ERT. Three-dimensional images of surface ERT delineated areas of increased and decreased resistivities. Increasing resistivities are attributed to dilution/displacement of the KCl solution by tap-water invasion or the influx of seasonal recharge. Decreasing resistivities resulted from redistribution of residual KCl solution. Cross-borehole ERT was conducted between the injection well and each of seven surrounding monitoring wells. Polar plots of the injection-well resistivity data in the direction of each monitoring well delineate specific locations where tap water seeped from the injection well via preferential flow paths determined by time-dependent resistivity increases. Monitoring-well data indicate locations of clustered and isolated regions of resistivity changes.

Nimmer, Robin E.; Osiensky, James L.; Binley, Andrew M.; Sprenke, Kenneth F.; Williams, Barbara C.

2007-08-01

234

The relationship between electric elds, conductances and currents in the high-latitude ionosphere  

E-print Network

The relationship between electric ®elds, conductances and currents in the high-latitude ionosphere between electric ®elds, height-integrated conductivities and electric currents in the high allowing the determination of both ®eld-perpendicular electric current components. Over 1300 h of common

Paris-Sud XI, Université de

235

Simultaneous remote electric and magnetic field measurements of lightning continuing currents  

E-print Network

Simultaneous remote electric and magnetic field measurements of lightning continuing currents Manus in quasi-static electric fields have been most frequently used to remotely measure continuing current of continuing current signatures observed in both the quasi-static electric and magnetic fields from four

Cummer, Steven A.

236

Polymeric salt bridges for conducting electric current in microfluidic devices  

DOEpatents

A "cast-in-place" monolithic microporous polymer salt bridge for conducting electrical current in microfluidic devices, and methods for manufacture thereof is disclosed. Polymeric salt bridges are formed in place in capillaries or microchannels. Formulations are prepared with monomer, suitable cross-linkers, solvent, and a thermal or radiation responsive initiator. The formulation is placed in a desired location and then suitable radiation such as UV light is used to polymerize the salt bridge within a desired structural location. Embodiments are provided wherein the polymeric salt bridges have sufficient porosity to allow ionic migration without bulk flow of solvents therethrough. The salt bridges form barriers that seal against fluid pressures in excess of 5000 pounds per square inch. The salt bridges can be formulated for carriage of suitable amperage at a desired voltage, and thus microfluidic devices using such salt bridges can be specifically constructed to meet selected analytical requirements.

Shepodd, Timothy J. (Livermore, CA); Tichenor, Mark S. (San Diego, CA); Artau, Alexander (Humacao, PR)

2009-11-17

237

System and method for determining velocity of electrically conductive fluid  

NASA Technical Reports Server (NTRS)

A flowing electrically-conductive fluid is controlled between an upstream and downstream location thereof to insure that a convection timescale of the flowing fluid is less than a thermal diffusion timescale of the flowing fluid. First and second nodes of a current-carrying circuit are coupled to the fluid at the upstream location. A current pulse is applied to the current-carrying circuit so that the current pulse travels through the flowing fluid to thereby generate a thermal feature therein at the upstream location. The thermal feature is convected to the downstream location where it is monitored to detect a peak associated with the thermal feature so-convected. The velocity of the fluid flow is determined using a time-of-flight analysis.

Polzin, Kurt A. (Inventor); Korman, Valentin (Inventor); Markusic, Thomas E. (Inventor); Stanojev, Boris Johann (Inventor)

2008-01-01

238

Formulation of electrically conductive thermal-control coatings  

NASA Technical Reports Server (NTRS)

The development and formulation of electrically conductive thermal control coating was undertaken for use on the International Sun Earth Explorer spacecraft. The primary effort was to develop a coating with a bulk resistivity of less than 100,000 ohm/sqm, an optical absorptance of approximately 0.55, and a normal emittance of 0.90. The required stability in space called for a bulk resistivity of less than 100,000 ohm/sq m, an absorptance of less than 0.67, and a normal emittance of 0.90 after exposure to approximately 4 x 10 to the 16th proton/sq cm of solar-wind particles and 5300 equivalent sun-hours. These exposures represent 2 years of ISEE flight conditions. Both the unsuccessful formulation efforts and the successful use of oxide pigments fired at 1448 K are described. Problems relative to the reactivity of specific coating vehicles exposed to high humidity are discussed.

Shai, M. C.

1978-01-01

239

Lunar magnetic permeability, magnetic fields, and electrical conductivity temperature  

NASA Technical Reports Server (NTRS)

In the time period 1969-1972 a total of five magnetometers were deployed on the lunar surface during four Apollo missions. Data from these instruments, along with simultaneous measurements from other experiments on the moon and in lunar orbit, were used to study properties of the lunar interior and the lunar environment. The principal scientific results from analyses of the magnetic field data are discussed. The results are presented in the following main categories: (1) lunar electrical conductivity, temperature, and structure; (2) lunar magnetic permeability, iron abundance, and core size limits; (3) the local remnant magnetic fields, their interaction with the solar wind, and a thermoelectric generator model for their origin. Relevant publications and presented papers are listed.

Parkin, C. W.

1978-01-01

240

Electrically conductive, optically transparent polymer/carbon nanotube composites  

NASA Technical Reports Server (NTRS)

The present invention is directed to the effective dispersion of carbon nanotubes (CNTs) into polymer matrices. The nanocomposites are prepared using polymer matrices and exhibit a unique combination of properties, most notably, high retention of optical transparency in the visible range (i.e., 400-800 nm), electrical conductivity, and high thermal stability. By appropriate selection of the matrix resin, additional properties such as vacuum ultraviolet radiation resistance, atomic oxygen resistance, high glass transition (T.sub.g) temperatures, and excellent toughness can be attained. The resulting nanocomposites can be used to fabricate or formulate a variety of articles such as coatings on a variety of substrates, films, foams, fibers, threads, adhesives and fiber coated prepreg. The properties of the nanocomposites can be adjusted by selection of the polymer matrix and CNT to fabricate articles that possess high optical transparency and antistatic behavior.

Connell, John W. (Inventor); Smith, Jr., Joseph G. (Inventor); Harrison, Joycelyn S. (Inventor); Park, Cheol (Inventor); Watson, Kent A. (Inventor); Ounaies, Zoubeida (Inventor)

2011-01-01

241

D.C. electrical conductivity of Green River oil shales  

NASA Astrophysics Data System (ADS)

Direct-current conductivity measurements have been carried out on Green River oil shales in the temperature range of 25-500 C. The observed electrical behavior of this material is found to be consistent with a two-step decomposition model in which the rate-determining processes are: (1) breakdown of an outershell polar bridge structure with an activation energy of 15 plus or minus 2 kcal/mol (180-350 C) and (2) cleavage of an inner core naphthenic structure also involving polar groups with an activation energy of 35 plus or minus 3 kcal/mol (350-500 C). These structural changes correspond to the chemical transformation of kerogen to liquid and gaseous hydrocarbons through a bitumen intermediate.

Rajeshwar, K.; Das, M.; Dubow, J.

1980-09-01

242

Laboratory derived constraints on electrical conductivity beneath Slave craton  

NASA Astrophysics Data System (ADS)

The depth profile of the electrical conductivity, ?(d), beneath the Central Slave craton (Canada) has been reconstructed with the help of laboratory measurements carried out on peridotite xenoliths. ?(T) of xenoliths was determined in the piston-cylinder apparatus at 1 and 2 GPa and from 600 to 1150 °C. ?(T) of xenoliths follows the Arrhenius dependence with the activation energy, E, varying from 2.10 to 1.44 eV depending on temperature range and the Mg-number. The calculated xenolith geotherm and the suggested lithology beneath the Central Slave have been used to constrain ?(d) as follows: ?(d) in the crust varies between 0.5×10-5 and 10-3 S/m; the lithospheric ?(d) sharply decreases below the Moho at 39.4 km to 0.5×10-8 S/m, which corresponds to 460 °C, and then gradually increases with the depth d to 0.5×10-2 S/m. The modeled MT-response of the constrained ?(d) profile has been compared with MT-observations [Jones, A.G., Lezaeta, P., Ferguson, I.J., Chave, A.D., Evans, R.L., Garcia, X., Spratt J., 2003. The electrical structure of the Slave craton. Lithos, 71, 505-527]. The general trend of the calculated MT-response based on the ?(d) model mimics the MT-inversion of the field data from the Central Slave.

Bagdassarov, Nikolai S.; Kopylova, Maya G.; Eichert, Sandrine

2007-04-01

243

Electrical conductivity anisotropy of partially molten peridotite under shear deformation  

NASA Astrophysics Data System (ADS)

Recent ocean bottom magnetotelluric investigations have revealed a high-conductivity layer (HCL) with high anisotropy characterized by higher conductivity values in the direction parallel to the plate motion beneath the southern East Pacific Rise (Evans et al., 2005) and beneath the edge of the Cocos plate at the Middle America trench offshore of Nicaragua (Naif et al., 2013). These geophysical observations have been attributed to either hydration (water) of mantle minerals or the presence of partial melt. Currently, aligned partial melt has been regarded as the most preferable candidate for explaining the conductivity anisotropy because of the implausibility of proton conduction (Yoshino et al., 2006). In this study, we report development of the conductivity anisotropy between parallel and normal to shear direction on the shear plane in partial molten peridotite as a function of time and shear strain. Starting samples were pre-synthesized partial molten peridotite, showing homogeneous melt distribution. The partially molten peridotite samples were deformed in simple shear geometry at 1 GPa and 1723 K in a DIA-type apparatus with uniaxial deformation facility. Conductivity difference between parallel and normal to shear direction reached one order, which is equivalent to that observed beneath asthenosphere. In contrast, such anisotropic behavior was not found in the melt-free samples, suggesting that development of the conductivity anisotropy was generated under shear stress. Microstructure of the deformed partial molten peridotite shows partial melt tends to preferentially locate grain boundaries parallel to shear direction, and forms continuously thin melt layer sub-parallel to the shear direction, whereas apparently isolated distribution was observed on the section perpendicular to the shear direction. The resultant melt morphology can be approximated by tube like geometry parallel to the shear direction. This observation suggests that the development of conductivity anisotropy is caused by the realignment of partial melt (forming tube-like melt) parallel to shear direction in the silicate matrix. Finally, the high anisotropy of conductivity in the direction of plate motion can be well explained by anisotropic interconnection of melt in partially molten rocks at the top of asthenosphere, but not hydration of nominally anhydrous minerals. Therefore, our results provide the direct experimental evidence for supporting these geophysically observed high-conductivity anisotropy at the LAB and verify the validity of partial melting hypothesis (Yoshino et al., 2006; Naif et al., 2013). References Evans, R. L. et al. Geophysical evidence from the MELT area for compositional controls on oceanic plates. Nature 437, 249-252 (2005). Naif, S., Key, K., Constable, S. & Evans, R. L. Melt-rich channel observed at the lithosphere-asthenosphere boundary. Nature 495, 356-359 (2013). Yoshino, T., Matsuzaki, T., Yamashita, S. & Katsura, T. Hydrous olivine unable to account for conductivity anomaly at the top of the asthenosphere. Nature 443, 973-976 (2006).

Zhang, B.; Yoshino, T.; Yamazaki, D.; Manthilake, G. M.; Katsura, T.

2013-12-01

244

Development of Tailorable Electrically Conductive Thermal Control Material Systems  

NASA Technical Reports Server (NTRS)

The optical characteristics of surfaces on spacecraft are fundamental parameters in controlling its temperature. Passive thermal control coatings with designed solar absorptance and infrared emittance properties have been developed and have been in use for some time. In this total space environment, the coating must be stable and maintain its desired optical properties as well as mechanical properties for the course of the mission lifetime. The mission lifetimes are increasing and in our quest to save weight, newer substrates are being integrated which limit electrical grounding schemes. All of this has added to already existing concerns about spacecraft charging and related spacecraft failures or operational failures. The concern is even greater for thermal control surfaces that are very large. One way of alleviating such concerns is to design new thermal control material systems (TCMS) that can help to mitigate charging via providing charge leakage paths. The objective of this program was to develop two types of passive electrically conductive TCMS. The first was a highly absorbing/emitting black surface and the second was a low (alpha(sub s)/epsilon(sub N)) type white surface. The surface resistance goals for the black absorber was 10(exp 4) to 10(exp 9) Omega/square, and for the white surfaces it was 10(exp 6) to 10(exp 10) Omega/square. Several material system concepts were suggested and evaluated for space environment stability and electrical performance characterization. Our efforts in designing and evaluating these material systems have resulted in several developments. New concepts, pigments and binders have been developed to provide new engineering quality TCMS. Some of these have already found application on space hardware, some are waiting to be recognized by thermal designers, and some require further detailed studies to become state-of-the-art for future space hardware and space structures. Our studies on baseline state-of-the-art materials and conductive concepts have resulted in several important findings that are of interest to all thermal designers and systems integrators.

Deshpande, M. S.; Harada, Y.

1997-01-01

245

Low-drag electrical contact arrangement for maintaining continuity between horizontally movable members  

SciTech Connect

This invention is a low-drag electrical contact arrangement for establishing continuity between upper and lower spaced members which are subject to relative horizontal movement. In one aspect, the invention comprises an electrical commutating arrangement which includes a horizontally disposed linear electrical commutator. A horizontally movable electrically conductive pedestal is positioned below the commutator and defines a clearance therewith. The pedestal is formed with a cavity confronting the commutator. In the cavity is a bead of electrical conductive liquid, the bead being characterized by an upwardly convex meniscus portion which extends across the clearance and contacts the commutator. The surface tension of the bead is sufficient to maintain the bead intact when the commutator and pedestal are displaced horizontally at speeds from zero to at least twelve inches a minute. This arrangement provides a significant advance in highly precise machining processes, such as diamond-turning, where precision is limited by the drag imposed by conventional commutators of the carbon-brush type.

Brown, R.; Gerth, H.L.; Robinson, S.C.

1982-04-20

246

Low-drag electrical contact arrangement for maintaining continuity between horizontally movable members  

SciTech Connect

This invention is a low-drag electrical contact arrangement for establishing continuity between upper and lower spaced members which are subject to relative horizontal movement. In one aspect, the invention comprises an electrical commutating arrangement which includes a horizontally disposed linear electrical commutator. A horizontally movable electrically conductive pedestal is positioned below the commutator and defines a clearance therewith. The pedestal is formed with a cavity confronting the commutator. In the cavity is a bead of electrical conductive liquid, the bead being characterized by an upwardly convex meniscus portion which extends across the clearance and contacts the commutator. The surface tension of the bead is sufficient to maintain the bead intact when the commutator and pedestal are displaced horizontally at speeds from zero to at least twelve inches a minute. This arrangement provides a significant advance in highly precise machining processes, such as diamond-turning, where precision is limited by the drag imposed by conventional commutators of the carbon-brush type.

Brown, R. Jack (Clinton, TN); Gerth, Howard L. (Knoxville, TN); Robinson, Samuel C. (Clinton, TN)

1982-01-01

247

Low-drag electrical-contact arrangement for maintaining continuity between horizontally movable members  

SciTech Connect

This invention is a low-drag electrical contact arrangement for establishing continuity between upper and lower spaced members which are subject to relative horizontal movement. In one aspect, the invention comprises an electrical commutating arrangement which includes a horizontally disposed linear electrical commutator. A horizontally movable electrically conductive pedestal is positioned below the commutator and defines a clearance therewith. The pedestal is formed with a cavity confronting the commutator. In the cavity is a bead of electrical conductive liquid, the bead being characterized by an upwardly convex meniscus portion which extends across the clearance and contacts the commutator. The surface tension of the bead is sufficient to maintain the bead intact when the commutator and pedestal are displaced horizontally at speeds from zero to at least twelve inches a minute. This arrangement provides a significant advance in highly precise machining processes, such as diamond-turning, where precision is limited by the drag imposed by conventional commutators of the carbon-brush type.

Brown, R.J.; Gerth, H.L.; Robinson, S.C.

1981-01-23

248

Nonlinear Dynamics of Electrical Conduction in Extrinsic Photoconductors  

NASA Astrophysics Data System (ADS)

An extensive experimental and theoretical treatment of the role of nonlinear dynamics in describing the electrical conduction properties of extrinsic photoconductors is given. Experiments were carried out at 4.2 K on ultrapure p-type far-infrared (FIR) Ge photo- conductors with shallow ((TURN)10 meV) acceptor levels and B-ion-implanted ohmic electrical contacts. Measured d.c. current-voltage (I-V) characteristics are strongly nonlinear for moderate electric fields >0.1(, )V/cm and frequently reveal the onset of spontaneous current oscillations for threshold fields (TURN)1 to (TURN)2 V/cm. Small signal admittance and transient response measurements demonstrate that Ge photoconductors behave as damped nonlinear oscillators with damped ringing frequency determined by the FIR illumination level in the range (TURN)50 Hz to (TURN)5 kHz. When driven with an additional sinus- oidal bias V(,ac) cos (2(pi)f(,dr)t) Ge photoconductors are found to exhibit nonlinear dynamical phenomena including a period-doubling cas- cade to chaotic oscillation which produces excess "deterministic" broadband noise with observed noise temperatures as high as (TURN)10('9) K; chaotic behavior is also found in the spontaneous current oscillation with no added a.c. bias. In addition to period doubling, observed complex behavior includes quasi-periodic oscillation, intermittent switching between different modes of oscillation with concomitant excess low-frequency noise, and chaos suppression through frequency locking for large drive amplitudes V(,ac). A hierarchy of theoretical models extending from a generally valid set of partial differential equations to a simple driven two-dimensional dynamical system is presented. Most of the experimental data is surprisingly well described in terms of the simplest model with dynamical vari- ables the average hole concentration and electric field and in which chaotic behavior arises due to the nonlinear field-dependence of rates for capture and impact ionization. Numerical spatially- dependent steady state solutions for the most general model as well as analysis of two-region models indicate the importance of space charge trapped near the injecting contact in determining long time scales observed for transient response (TURN)1 sec. Theoretical criteria are derived for the onset of oscillatory instabilities; photoconductor properties necessary for chaotic behavior and suggestions for the design of more stable devices are discussed.

Teitsworth, Stephen Winthrop

249

The Deep Electrical Conductivity Structure of the Dead Sea Basin  

NASA Astrophysics Data System (ADS)

The left-lateral Dead Sea transform (DST) is a major transform fault separating the Arabian plate in the east from the African and Sinai plates in the west. It extends from the Red Sea rift to the Taurus collision zone in eastern Turkey, with a total length of more than 1000 km. During its evolution, the DST formed several deep sedimentary (pull-apart) basins, such as the Gulf of Aqaba / Eilat, the Lake Tiberias and the Dead Sea basin (DSB). The DSB is the largest basin along the transform valley and probably the largest of these structures on earth. The basin is 135km long, 20km wide and according to an interpretation of gravity data the basin's sedimentary fill is assessed to 10km thickness. Within the framework of the multi-disciplinary DESIRE (Dead Sea Integrated Research) project, several geophysical methods were applied to investigate the southern part of the DSB, including magnetotellurics (MT), active reflection and refraction seismic, aero-gravity, and passive seismology. The MT data were acquired at 150 stations in 2006 along a 120 km long, approximately east-west oriented profile. Resistivity models obtained from two-dimensional inversion of the MT data reveal several robust features: Beneath the Dead Sea, extending to a depth of approximately 3 km, we observe extremely low electrical resistivity (0.1- 0.5 ? m). Embedded within this structure and located beneath the Al-Lisan Peninsula we observe a localized high resistivity body (> 100 ? m), which is interpreted as the Al Lisan salt diapir. The lateral boundaries of the DSB are clearly expressed in the resistivity model as abrupt changes from moderately low (~20 ? m) to high resistivity (> 1000 ? m) at depths of 3 and 4 km under the eastern and western segment of the profile, respectively. The locations of the boundaries coincide with the surface traces of the eastern and western border faults. Furthermore, the 2D model images two conductive layers beneath both, the eastern and western segments of the profile at varying depth ranges. Based on hydro-geological information the location and depth extent of these conductive layers appear to coincide with a shallow and a deeper aquifer. With our electrical conductivity model it is possible to delineate the saline/fresh water interface, particularly at the eastern shoreline of the Dead Sea. The border faults appear to prevent cross-fault fluid flow of the Dead Sea brines.

Meqbel, N. M.; Ritter, O.; Weckmann, U.; Becken, M.; Munoz, G.

2008-12-01

250

Electrical conductivity of Cu/graphite composite material as a function of structural characteristics  

SciTech Connect

The electrofriction materials for collectors are exposed to difficult operating conditions such as dry friction processes and high voltage for high current densities. The materials for this application should possess high electrical and thermal conductivity and a low coefficient of friction. Cu/graphite composites have successfully solved this problem. The electrical conductivity of Cu/graphite composites is affected by the existence of a continuous copper network. It was shown that a conductivity break can be caused by the absence of this continuous network, i.e. there exists a break point-threshold in the volume fraction of copper. The aim of this work is to determine the threshold value of the volume fraction of copper for Cu/graphite composites prepared by the powder metallurgical method and to show that the existence of this threshold depends on the structure of Cu/graphite composite, especially on the geometry of copper particles, on their size, shape and orientation. Another aim of this work is to show that the models for transport properties of composites should take the composite structure into the account.

Kovacik, J. [Slovak Academy of Sciences, Bratislava (Slovakia). Inst. of Materials and Machine Mechanics] [Slovak Academy of Sciences, Bratislava (Slovakia). Inst. of Materials and Machine Mechanics; Bielek, J. [Slovak Technical Univ., Bratislava (Slovakia)] [Slovak Technical Univ., Bratislava (Slovakia)

1996-07-15

251

Thermal and electrical conductivity of iron at Earth's core conditions.  

PubMed

The Earth acts as a gigantic heat engine driven by the decay of radiogenic isotopes and slow cooling, which gives rise to plate tectonics, volcanoes and mountain building. Another key product is the geomagnetic field, generated in the liquid iron core by a dynamo running on heat released by cooling and freezing (as the solid inner core grows), and on chemical convection (due to light elements expelled from the liquid on freezing). The power supplied to the geodynamo, measured by the heat flux across the core-mantle boundary (CMB), places constraints on Earth's evolution. Estimates of CMB heat flux depend on properties of iron mixtures under the extreme pressure and temperature conditions in the core, most critically on the thermal and electrical conductivities. These quantities remain poorly known because of inherent experimental and theoretical difficulties. Here we use density functional theory to compute these conductivities in liquid iron mixtures at core conditions from first principles--unlike previous estimates, which relied on extrapolations. The mixtures of iron, oxygen, sulphur and silicon are taken from earlier work and fit the seismologically determined core density and inner-core boundary density jump. We find both conductivities to be two to three times higher than estimates in current use. The changes are so large that core thermal histories and power requirements need to be reassessed. New estimates indicate that the adiabatic heat flux is 15 to 16 terawatts at the CMB, higher than present estimates of CMB heat flux based on mantle convection; the top of the core must be thermally stratified and any convection in the upper core must be driven by chemical convection against the adverse thermal buoyancy or lateral variations in CMB heat flow. Power for the geodynamo is greatly restricted, and future models of mantle evolution will need to incorporate a high CMB heat flux and explain the recent formation of the inner core. PMID:22495307

Pozzo, Monica; Davies, Chris; Gubbins, David; Alfè, Dario

2012-05-17

252

Tokamak electrical conductivity modified by electrostatic trapping in the applied electric field  

SciTech Connect

Passing electrons traveling in the same direction as the applied Ohmic electric field, near the trapped-passing boundary, can get electrostatically trapped by the applied Ohmic potential, reverse their parallel flow direction, and become passing particles traveling in the opposite direction. The number of these electrons is proportional to the applied voltage and is small. But, the amount of change in their time-averaged parallel velocity by reversing their flow direction, is about twice the average parallel velocity of the barely passing electrons and is large. Hence, these electrostatically trapped particles can significantly contribute to the Ohmic electrical current. The new electrical conductivity is calculated in the banana regime using a pitch angle scattering operator, and the values are found to be significantly enhanced from previous neoclassical theories. 4 refs., 2 figs.

Chang, C.S.

1989-07-01

253

Electrical Conductivity, Thermal Stability, and Lattice Defect Evolution During Cyclic Channel Die Compression of OFHC Copper  

NASA Astrophysics Data System (ADS)

Oxygen-free high-conductivity (OFHC) copper samples are severe plastically deformed by cyclic channel die compression (CCDC) technique at room temperature up to an effective plastic strain of 7.2. Effect of straining on variation in electrical conductivity, evolution of deformation stored energy, and recrystallization onset temperatures are studied. Deformation-induced lattice defects are quantified using three different methodologies including x-ray diffraction profile analysis employing Williamson-Hall technique, stored energy based method, and electrical resistivity-based techniques. Compared to other severe plastic deformation techniques, electrical conductivity degrades marginally from 100.6% to 96.6% IACS after three cycles of CCDC. Decrease in recrystallization onset and peak temperatures is noticed, whereas stored energy increases and saturates at around 0.95-1.1J/g after three cycles of CCDC. Although drop in recrystallization activation energy is observed with the increasing strain, superior thermal stability is revealed, which is attributed to CCDC process mechanics. Low activation energy observed in CCDC-processed OFHC copper is corroborated to synergistic influence of grain boundary characteristics and lattice defects distribution. Estimated defects concentration indicated continuous increase in dislocation density and vacancy with strain. Deformation-induced vacancy concentration is found to be significantly higher than equilibrium vacancy concentration ascribed to hydrostatic stress states experienced during CCDC.

Satheesh Kumar, S. S.; Raghu, T.

2015-02-01

254

Design studies of continuously variable transmissions for electric vehicles  

NASA Technical Reports Server (NTRS)

Preliminary design studies were performed on four continuously variable transmission (CVT) concepts for use with a flywheel equipped electric vehicle of 1700 kg gross weight. Requirements of the CVT's were a maximum torque of 450 N-m (330 lb-ft), a maximum output power of 75 kW (100 hp), and a flywheel speed range of 28,000 to 14,000 rpm. Efficiency, size, weight, cost, reliability, maintainability, and controls were evaluated for each of the four concepts which included a steel V-belt type, a flat rubber belt type, a toroidal traction type, and a cone roller traction type. All CVT's exhibited relatively high calculated efficiencies (68 percent to 97 percent) over a broad range of vehicle operating conditions. Estimated weight and size of these transmissions were comparable to or less than equivalent automatic transmission. The design of each concept was carried through the design layout stage.

Parker, R. J.; Loewenthal, S. H.; Fischer, G. K.

1981-01-01

255

Fracture criterion for conductive cracks in soda-lime glass under combined mechanical and electrical loading  

Microsoft Academic Search

Fracture tests of electrically conductive cracks on pre-notched four-point bending soda-lime glass samples were conducted\\u000a under combined mechanical and electrical loading. The experimental results show that the critical stress intensity factor\\u000a at fracture is reduced if an electric field is applied, thereby indicating that the electric field makes contributions to\\u000a the fracture of conductive cracks. Base on the charge-free zone

Dong-Jun Yan; Hai-You Huang; Chi-Wai Cheung; Tong-Yi Zhang

2010-01-01

256

Deformation and breakup of Newtonian and non-Newtonian conducting drops in an electric field  

Microsoft Academic Search

In this article, we considered experimentally the deformation and breakup of Newtonian and non-Newtonian conducting drops in surrounding fluid subjected to a uniform electric field. First, we examined three distinctive cases of Newtonian-fluid pairs with different relative conductivities, namely highly conducting drops, conducting drops and slightly conducting drops. The results on the Newtonian fluids demonstrated that when the conductivity of

Jong-Wook Ha; Seung-Man Yang

2000-01-01

257

Identification of current density distribution in electrically conducting subject with anisotropic conductivity distribution.  

PubMed

Current density imaging (CDI) is able to visualize a three-dimensional current density distribution J inside an electrically conducting subject caused by an externally applied current. CDI may use a magnetic resonance imaging (MRI) scanner to measure the induced magnetic flux density B and compute J via the Ampere law [Formula: see text]. However, measuring all three components of B = (B(x), B(y), B(z)) has a technical difficulty due to the requirement of orthogonal rotations of the subject inside the MRI scanner. In this work, we propose a new method of reconstructing a current density image using only B(z) data so that we can avoid the subject rotation procedure. The method utilizes an auxiliary injection current to compensate the missing information of B(x) and B(y). The major advantage of the method is its applicability to a subject with an anisotropic conductivity distribution. Numerical experiments show the feasibility of the new technique. PMID:15972989

Pyo, Hyun Chan; Kwon, Ohin; Seo, Jin Keun; Woo, Eung Je

2005-07-01

258

The role of electronic and ionic conduction in the electrical conductivity of carbon fiber reinforced cement  

E-print Network

, the electrical con- ductivity allows applications such as electrical grounding, lightning protection, deicing, electromagnetic interference shielding and electrostatic discharge protection. Because of the attractive

Chung, Deborah D.L.

259

High-strength carbon nanotube fibre-like ribbon with high ductility and high electrical conductivity.  

PubMed

Macroscopic fibres made up of carbon nanotubes exhibit properties far below theoretical predictions and even much lower than those for conventional carbon fibres. Here we report improvements of mechanical and electrical properties by more than one order of magnitude by pressurized rolling. Our carbon nanotubes self-assemble to a hollow macroscopic cylinder in a tube reactor operated at high temperature and then condense in water or ethanol to form a fibre, which is continually spooled in an open-air environment. This initial fibre is densified by rolling under pressure, leading to a combination of high tensile strength (3.76-5.53 GPa), high tensile ductility (8-13%) and high electrical conductivity ((1.82-2.24) × 10(4) S cm(-1)). Our study therefore demonstrates strategies for future performance maximization and the very considerable potential of carbon nanotube assemblies for high-end uses. PMID:24964266

Wang, J N; Luo, X G; Wu, T; Chen, Y

2014-01-01

260

Explosive Electric Breakdown due to Conducting-Particle Deposition on an Insulating Substrate  

NASA Astrophysics Data System (ADS)

We introduce a theoretical model to investigate the electric breakdown of a substrate on which highly conducting particles are adsorbed and desorbed with a probability that depends on the local electric field. We find that, by tuning the relative strength q of this dependence, the breakdown can change from continuous to explosive. Precisely, in the limit in which the adsorption probability is the same for any finite voltage drop, we can map our model exactly onto the q-state Potts model and thus the transition to a jump occurs at q=4. In another limit, where the adsorption probability becomes independent of the local field strength, the traditional bond percolation model is recovered. Our model is thus an example of a possible experimental realization exhibiting a truly discontinuous percolation transition.

Oliveira, Cláudio L. N.; Araújo, Nuno A. M.; Andrade, José S.; Herrmann, Hans J.

2014-10-01

261

Optically transparent and electrically conducting epitaxial Ta2O films  

NASA Astrophysics Data System (ADS)

An optically transparent and electrically conducting oxide Ta2O epitaxial thin film has been fabricated and characterized. In our experiments, we grew epitaxial Ta films on r-cut sapphire crystal substrates, which were subsequently oxidized into Ta2O films. The x-ray ?-2? scan peaks match the American Society for Testing and Materials x-ray powder data card for Ta2O (18-1302) with a cubic structure. The x-ray photoelectron spectroscopic measurements indicated Ta 4f peak energy values between those for Ta and TaO whereas the O /Ta atomic ratio is between 0.5 and 1. Resistivity-temperature measurements showed a metallic behavior with resistivity values in the range of (1.5-3.3)×10-4?cm at 293K. Optical measurements on 25-100nm thick films indicated that they are transparent in the range of 400-2000nm and have an energy band gap between 2.04 and 2.17eV. The Hall mobility and carrier density of the films were in the range of 62-110cm2V-1s-1 and (1.9-3.0)×1020cm-3, respectively.

Gnanarajan, S.; Lam, S. K. H.; Foley, C. P.

2007-03-01

262

Hopping conduction in high electric fields: three issues  

SciTech Connect

Three issues concerning phonon-assisted hopping in molecularly doped polymers are considered. The first issue is whether Arrhenius jump rates in the vicinity of room temperature arise from single- phonon or small-polaronic hopping. It is concluded that Arrhenius hopping only occurs above low temperatures through small-polaronic hopping. Second, hopping in molecularly doped polymers is compared with small- polaronic hopping of other systems. Small-polaronic hopping typically occurs between similar chemical structures whose energies are relatively insensitive to their surroundings. Thus, disorder energies experienced by carriers are often modest, values of several hundredths of an eV are common. Nonetheless, the effects of large electric fields on carrier mobilities differ significantly among disordered systems. Data reported for molecularly doped polymers is unlike that for either transition- metal-oxide or chalcogenide glasses. In no case is high-field transport well understood. Finally, I stress that steady-state flow is driven by differences in sites` quasielectrochemical potentials (QECPs). With disorder, differences of QECPs are not simply related to the driving emf. Solution of the (nonlinear) stochastic equations for the QECPs shows that bottlenecks produced by disorder result in nonohmic conduction. Solving the linearized stochastic (disordered resistor network) equations underestimates bottleneck effects. Linearization is inappropriate when interest differences in the QECPs exceed [kappa]T.

Emin, D.

1996-10-01

263

Guar gum based biodegradable, antibacterial and electrically conductive hydrogels.  

PubMed

Guar gum-polyacrylic acid-polyaniline based biodegradable electrically conductive interpenetrating network (IPN) structures were prepared through a two-step aqueous polymerization. Hexamine and ammonium persulfate (APS) were used as a cross linker-initiator system to crosslink the poly(AA) chains on Guar gum (Ggum) backbone. Optimum reaction conditions for maximum percentage swelling (7470.23%) were time (min)=60; vacuum (mmHg)=450; pH=7.0; solvent (mL)=27.5; [APS] (molL(-1))=0.306×10(-1); [AA] (molL(-1))=0.291×10(-3) and [hexamine] (molL(-1))=0.356×10(-1). The semi-interpenetrating networks (semi-IPNs) were converted into IPNs through impregnation of polyaniline chains under acidic and neutral conditions. Fourier transform infra-red spectroscopy (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) techniques were used to characterize the semi-IPNs and IPNs. Synthesized semi-IPNs and IPNs were further evaluated for moisture retention in different soils, antibacterial and biodegradation behavior. PMID:25660656

Kaith, Balbir S; Sharma, Reena; Kalia, Susheel

2015-04-01

264

Electrical conductivity measurements of strongly coupled W plasmas.  

PubMed

Nonideal plasmas of tungsten were produced by vaporizing thin wires of 0.1 mm and 0.3 mm in diameter in small glass capillaries (in air) by means of a short-pulse current from an electrical discharge. For a short period of time, the inner wall of the rigid glass capillary confines the plasma until the induced pressure shock wave disintegrates the capillary. Spectroscopic measurements were carried out on the ejected plasma close to the end of the capillary. The plasma temperature was obtained by fitting a Planck function to the measured continuum spectrum. The resistance was derived from the voltage across the plasma and the current through the plasma. The plasma radius was determined with an intensified charge-coupled device camera and a streak camera and allowed the derivation of the conductivity. Particle densities were of the order of 10(22) particle/cm(3) and electron temperatures were in the range from 10 kK to 22 kK. These measurements are compared with theoretical models and previous work. PMID:11736097

Saleem, S; Haun, J; Kunze, H J

2001-11-01

265

DPL model analysis of non-Fourier heat conduction restricted by continuous boundary interface  

NASA Astrophysics Data System (ADS)

Dual-phase lag (DPL) model is used to describe the non-Fourier heat conduction in a finite medium where the boundary at x=0 is heated by a rectangular pulsed energy source and the other boundary is tightly contacted with another medium and satisfies the continuous boundary condition. Numerical solution of this kind of non-Fourier heat conduction is presented in this paper. The results are compared with those predicted by the hyperbolic heat conduction (HHC) equation.

Jiang, Fangming; Liu, Dengying

2001-03-01

266

Pricing and Firm Conduct in California's Deregulated Electricity Market  

E-print Network

sector to competitive forces by restructuring the method of procuring electricity. Private electric, the organized market broke down, and the state government was required to step in to purchase power. Market

California at Berkeley. University of

267

Electric conductivity of the quark-gluon plasma investigated using a perturbative QCD based parton cascade  

NASA Astrophysics Data System (ADS)

Electric conductivity is sensitive to effective cross sections among the particles of the partonic medium. We investigate the electric conductivity of a hot plasma of quarks and gluons, solving the relativistic Boltzmann equation. In order to extract this transport coefficient, we employ the Green-Kubo formalism and, independently, a method motivated by the classical definition of electric conductivity. To this end we evaluate the static electric diffusion current upon the influence of an electric field. Both methods give identical results. For the first time, we obtain numerically the Drude electric conductivity formula for an ultrarelativistic gas of quarks and gluons employing constant isotropic binary cross sections. Furthermore, we extract the electric conductivity for a system of massless quarks and gluons including screened binary and inelastic, radiative 2 ?3 perturbative QCD scattering. Comparing with recent lattice results, we find an agreement in the temperature dependence of the conductivity.

Greif, Moritz; Bouras, Ioannis; Greiner, Carsten; Xu, Zhe

2014-11-01

268

Electric conductivity of the quark-gluon plasma investigated using a perturbative QCD based parton cascade  

E-print Network

Electric conductivity is sensitive to effective cross sections among the particles of the partonic medium. We investigate the electric conductivity of a hot plasma of quarks and gluons, solving the relativistic Boltzmann equation. In order to extract this transport coefficient, we employ the Green-Kubo formalism and, independently, a method motivated by the classical definition of electric conductivity. To this end we evaluate the static electric diffusion current upon the influence of an electric field. Both methods give identical results. For the first time, we obtain numerically the Drude electric conductivity formula for an ultrarelativistic gas of quarks and gluons employing constant isotropic binary cross sections. Furthermore, we extract the electric conductivity for a system of massless quarks and gluons including screened binary and inelastic, radiative $2\\leftrightarrow 3$ perturbative QCD scattering. Comparing with recent lattice results, we find an agreement in the temperature dependence of the conductivity.

Moritz Greif; Ioannis Bouras; Zhe Xu; Carsten Greiner

2014-11-17

269

Heat Conduction through Surface Structures and Mixtures using Electric Circuits as Analogs  

Microsoft Academic Search

We present a mathematical model using electric analogs to simulate vertical and lateral conductive heat flow in surface layers of planetary bodies with topography. The model can also be used to determine average electric and thermal conductivities of small-scale granular mixtures (as opposed to molecular mixtures). The algorithm is general and applicable to complex compositions. Analogies between thermal and electric

W. F. Huebner; D. C. Boice; J. R. Green

1998-01-01

270

Imparting Electrical Conductivity into Asphalt Composites Using Graphite  

E-print Network

to enable such applications. Previous investigators have used conductive fibers as major conductive additive for asphalt composites, and the sudden transition from the insulated phase to the conductive phase, known as the percolation threshold, is commonly...

Baranikumar, Aishwarya

2013-07-09

271

Growth and percolation of metal nanostructures in electrode gaps leading to conductive paths for electrical DNA analysis.  

PubMed

Metal nanostructures are promising novel labels for microarray-based biomolecular detection. Additional silver deposition on the surface-bound labels strongly enhances the sensitivity of the system and can lead to continuous metal areas, which enable an electrical readout especially for simple and robust point-of-care analyses. In this paper, atomic force microscopy (AFM) was used to study different routes of metal deposition on labelled DNA-DNA duplexes in electrode gaps. Besides the well-established metal-induced silver enhancement, a recently introduced enzymatic silver deposition was applied and proved highly specific. The in situ characterization was especially focused on the nanostructure percolation-the moment at which the nanoparticulate film becomes continuous and electrically conducting. The formation of conducting paths, continuous from one electrode to the other, was followed by complementary electrical measurements. Thereby, a percolation threshold was determined for the surface coverage with metal structures, i.e. the required metallized area to achieve conductance. Complementary graphic simulations of the growth process and graphic 'conductance measurements' were developed and proved suitable to model the metal deposition and electrical detection. This may help to design electrode arrays and identify optimum enhancement parameters (required seed concentration and shell growth) as well as draw quantitative conclusions on the existing label (i.e. analyte) concentration. PMID:21817724

Festag, Grit; Schüler, Thomas; Möller, Robert; Csáki, Andrea; Fritzsche, Wolfgang

2008-03-26

272

Electrical conductivities of three-phase emulsions. 1. Strongly wetting middle phase  

SciTech Connect

Electrical conductivities of steady-state, three-phase (macro)emulsions formed by the top (T), middle (M), and bottom (B) phases of the amphiphile/oil/[open quotes]water[close quotes] (i.e., aqueous 10 mM NaCl) system C[sub 4]H[sub 9]OC[sub 2]H[sub 4]OH/n-decane/water have been measured and compared with the predictions of equations from the literature or that we have proposed. In all cases the continuous phase could be deduced from the combination of experiment and theory, but less information was obtained about dispersed-phase structures. Three new conductivity equations and two new three-phase dispersion morphologies have been proposed. 30 refs., 8 figs., 2 tabs.

Smith, D.H. (Morgantown Energy Technology Center, WV (United States) Univ. of Oklahoma, Norman, OK (United States)); Johnson, G.K. (Morgantown Energy Technology Center, WV (United States)); Wang, Y.H.C.; Lim, K.H. (WASC, Inc., Morgantown, WV (United States))

1994-08-01

273

The Wilkes subglacial basin eastern margin electrical conductivity anomaly  

NASA Astrophysics Data System (ADS)

We have analyzed the deep conductivity structure at the transition between the Transantarctic Mountains (TAM) and the eastern margin of the WSB in NVL, by means of the GDS (Geomagnetic Deep Sounding) technique, in order to constrain the geodynamical interpretation of this antarctic sector. The TAM form the uplifted flank of the Mesozoic and Cenozoic West Antarctic Rift System. Structure of the TAM rift flank has been partially investigated with different geophysical approaches.The Wilkes Subglacial Basin is a broad depression over 400 km wide at the George V Coast and 1200 km long. Geology, lithospheric structure and tectonics of the Basin are only partially known because the Basin is buried beneath the East Antarctic Ice Sheet and is located in a remote region which makes geophysical exploration logistically challenging. Different authors have proposed contrasting hypothesis regarding the origin of the WSB: it could represent a region of rifted continental crust, or it may have a flexural origin or might represent an "extended terrane". Recently aerogeophysical investigations have demonstrated a strong structural control on the margin. Magnetovariational studies carried out at high geomagnetic latitudes are often hampered by source effects, mainly due to the closeness to the Polar Electrojet currents systems (PEJ). Its presence, in fact, makes the uniform magnetic field assumption, on which the magnetovariational methods are based on, often invalid, which outcome is a bias in the GDS transfer functions and to compromise the reliability of the inverted models. Data from the aforementioned campaigns have been then processed under the ISEE project (Ice Sheet Electromagnetic Experiment), aimed at evaluate and mitigate the bias effect of the PEJ on geomagnetic an magnetotelluric transfer functions at high geomagnetic latitudes, by means of suitable processing algorithms, developed upon a statistical analysis study on PEJ effects (Rizzello et al. 2013). Recent results allowed for a new processing of a wide dataset acquired during three different international Antarctic campaigns supported by the Italian Antarctic Project: the BACKTAM, WIBEM and WISE expeditions. The qualitative analysis of the induction arrows, in the period range 20-170 s, reveals an approximately 2D regional electrical conductivity pattern with a clear differentiation between the three Terrains crossed by the GDS transect we have re-analized: the Robertson Bay, the Bowers and the Wilson Terrain. Bi-dimensional conductivity models, jointly with magnetic and gravimetric profiles, suggest a differentiation of the investigated area in three crustal sectors separated by the Daniels Range and the Bowers Mts., in close relation with main known structural lineaments; to the West, a deep conductivity anomaly is associated with the transition to the Wilkes Subglagial Basin. We deem that such anomaly, together with the magnetic and gravimetric signatures, is compatible with an extensional regime in the eastern margin of the WSB. References Rizzello, D., Armadillo, E., Manzella, A."Statistical analysis of the polar electrojet influence on geomagnetic transfer functions estimates, over wide time and space scales". EGU 2013 General Assembly, Wien - poster presentation.

Rizzello, Daniele; Armadillo, Egidio; Ferraccioli, Fausto; Caneva, Giorgio

2014-05-01

274

ELECTRICAL CONDUCTIVITY AND SCATTERING MATRIX FOR DIRAC OPERATORS ON MANIFOLDS WITH CYLINDRICAL CONTACTS  

Microsoft Academic Search

In the static limit of linear response theory, the electrical con- ductivity is a linear operator taking closed electric flelds into closed electric current densities. The induced mapping in cohomology is called the electrical conductance. Using the notion of relative de Rham cohomology of a mani- fold M with boundary, we give a thorough discussion of what is meant by

MATTHIAS LESCH; FLORIAN MERZ; MARTIN R. ZIRNBAUER

275

Magnetic resonance electrical impedance tomography (MREIT) for high-resolution conductivity imaging  

Microsoft Academic Search

Cross-sectional imaging of an electrical conductivity distribution inside the human body has been an active research goal in impedance imaging. By injecting current into an electrically conducting object through surface electrodes, we induce current density and voltage distributions. Based on the fact that these are determined by the conductivity distribution as well as the geometry of the object and the

Eung Je Woo; Jin Keun Seo

2008-01-01

276

Bisphenol A Exposure and Cardiac Electrical Conduction in Excised Rat Hearts  

PubMed Central

Background: Bisphenol A (BPA) is used to produce polycarbonate plastics and epoxy resins that are widely used in everyday products, such as food and beverage containers, toys, and medical devices. Human biomonitoring studies have suggested that a large proportion of the population may be exposed to BPA. Recent epidemiological studies have reported correlations between increased urinary BPA concentrations and cardiovascular disease, yet the direct effects of BPA on the heart are unknown. Objectives: The goal of our study was to measure the effect of BPA (0.1–100 ?M) on cardiac impulse propagation ex vivo using excised whole hearts from adult female rats. Methods: We measured atrial and ventricular activation times during sinus and paced rhythms using epicardial electrodes and optical mapping of transmembrane potential in excised rat hearts exposed to BPA via perfusate media. Atrioventricular activation intervals and epicardial conduction velocities were computed using recorded activation times. Results: Cardiac BPA exposure resulted in prolonged PR segment and decreased epicardial conduction velocity (0.1–100 ?M BPA), prolonged action potential duration (1–100 ?M BPA), and delayed atrioventricular conduction (10–100 ?M BPA). These effects were observed after acute exposure (? 15 min), underscoring the potential detrimental effects of continuous BPA exposure. The highest BPA concentration used (100 ?M) resulted in prolonged QRS intervals and dropped ventricular beats, and eventually resulted in complete heart block. Conclusions: Our results show that acute BPA exposure slowed electrical conduction in excised hearts from female rats. These findings emphasize the importance of examining BPA’s effect on heart electrophysiology and determining whether chronic in vivo exposure can cause or exacerbate conduction abnormalities in patients with preexisting heart conditions and in other high-risk populations. Citation: Posnack NG, Jaimes R III, Asfour H, Swift LM, Wengrowski AM, Sarvazyan N, Kay MW. 2014. Bisphenol A exposure and cardiac electrical conduction in excised rat hearts. Environ Health Perspect 122:384–390;?http://dx.doi.org/10.1289/ehp.1206157 PMID:24487307

Jaimes, Rafael; Asfour, Huda; Swift, Luther M.; Wengrowski, Anastasia M.; Sarvazyan, Narine; Kay, Matthew W.

2014-01-01

277

Microstructural inhomogeneity of electrical conductivity in subcutaneous fat tissue.  

PubMed

Microscopic peculiarities stemming from a temperature increase in subcutaneous adipose tissue (sWAT) after applying a radio-frequency (RF) current, must be strongly dependent on the type of sWAT. This effect is connected with different electrical conductivities of pathways inside (triglycerides in adipocytes) and outside (extra-cellular matrix) the cells and to the different weighting of these pathways in hypertrophic and hyperplastic types of sWAT. The application of the RF current to hypertrophic sWAT, which normally has a strongly developed extracellular matrix with high concentrations of hyaluronan and collagen in a peri-cellular space of adipocytes, can produce, micro-structurally, a highly inhomogeneous temperature distribution, characterized by strong temperature gradients between the peri-cellular sheath of the extra-cellular matrix around the hypertrophic adipocytes and their volumes. In addition to normal temperature effects, which are generally considered in body contouring, these temperature gradients can produce thermo-mechanical stresses on the cells' surfaces. Whereas these stresses are relatively small under normal conditions and cannot cause any direct fracturing or damage of the cell structure, these stresses can, under some supportive conditions, be theoretically increased by several orders of magnitude, causing the thermo-mechanical cell damage. This effect cannot be realized in sWAT of normal or hyperplastic types where the peri-cellular structures are under-developed. It is concluded that the results of RF application in body contouring procedures must be strongly dependent on the morphological structure of sWAT. PMID:25734656

Kruglikov, Ilja L

2015-01-01

278

EOSC 252 Assignment 2 Effective Electrical Conductivity of Rocks  

E-print Network

data are important for the interpretation of natural electromagnetic induction in the seafloor from as artificial sources of electromagnetic induction. Electrical resistivity studies are used widely to prospect

Jellinek, Mark

279

Accelerated osteoblast mineralization on a conductive substrate by multiple electrical stimulation  

Microsoft Academic Search

One of the major benefits of a conductive PPy-based substrate is that the mediated electrical stimulation (ES) can be a stimulating\\u000a factor to promote tissue regeneration. We cultured osteoblast-like Saos-2 cells on a conductive substrate made of biodegradable\\u000a polylactide (95 wt%) and electrically conducting polypyrrole bioactivated with heparin (PPy\\/HE) (5 wt%). Using multi-well\\u000a electrical cell culture plates, the effect of multiple ESs

Shiyun MengZe; Ze Zhang; Mahmoud Rouabhia

280

Electrical conductivity of the lower-mantle ferropericlase across the electronic spin transition  

Microsoft Academic Search

Electrical conductivity of the lower-mantle ferropericlase-(Mg0.75,Fe0.25)O has been studied using designer diamond anvils to pressures over one megabar and temperatures up to 500 K. The electrical conductivity of (Mg0.75,Fe0.25)O gradually rises by an order of magnitude up to 50 GPa but decreases by a factor of approximately three between 50 to 70 GPa. This decrease in the electrical conductivity is

Jung-Fu Lin; Samuel T. Weir; Damon D. Jackson; William J. Evans; Yogesh K. Vohra; Wei Qiu; Choong-Shik Yoo

2007-01-01

281

High thermal conductivity connector having high electrical isolation  

DOEpatents

A method and article for providing a low-thermal-resistance, high-electrical-isolation heat intercept connection. The connection method involves clamping, by thermal interference fit, an electrically isolating cylinder between an outer metallic ring and an inner metallic disk. The connection provides durable coupling of a heat sink and a heat source.

Nieman, Ralph C. (Downers Grove, IL); Gonczy, John D. (Oak Lawn, IL); Nicol, Thomas H. (St. Charles, IL)

1995-01-01

282

Electrical conductivity and density of state of boron nitride nanotubes due to electronic correlation  

NASA Astrophysics Data System (ADS)

The temperature behavior of electrical conductivity of boron nitride nanotubes (6, 0) in the context of Hubbard model at the paramagnetic sector. The effect of electronic correlation on the energy gap of boron nitride nanotube (BNNT) is investigated. Interacting electronic Green's function matrix has been found within GW approximation. Using Kubo formula, electrical conductivity of the system has been calculated. The results show that the band gap in the density of state decreases with Coulomb repulsion strength. Moreover, the increase of electronic correlation leads to decrease electrical conductivity of BNNT. Also the electrical conductivity shows an exponential behavior in terms of temperature at all the values of electron-electron interaction parameter.

Rezania, H.

2014-07-01

283

DPL model analysis of non-Fourier heat conduction restricted by continuous boundary interface  

Microsoft Academic Search

Dual-phase lag (DPL) model is used to describe the non-Fourier heat conduction in a finite medium where the boundary at x=0 is heated by a rectangular pulsed energy source and the other boundary is tightly contacted with another medium and satisfies\\u000a the continuous boundary condition. Numerical solution of this kind of non-Fourier heat conduction is presented in this paper.\\u000a The

Fangming Jiang; Dengying Liu

2001-01-01

284

Subthreshold continuous electrical stimulation facilitates functional recovery of facial nerve after crush injury in rabbit.  

PubMed

We sought to determine whether electrical stimulation (ES) with subthreshold, continuous, low-frequency impulses is a viable clinical method for improving functional recovery after facial nerve crush injury. In 10 rabbits, bilateral crush injuries were made on the facial nerve by compression for 30 s with mosquito forceps, causing complete facial paralysis. Subthreshold continuous direct current ES with 20-Hz square-wave pulses was applied to the proximal stump on one side for 4 weeks. Vibrissae movement returned significantly earlier on the ES side, with a less variable recovery time. Electrophysiologically, the stimulated side had a significantly shorter latency, longer duration, and faster conduction velocity. Light and transmission electron microscopy revealed that the electrical stimulation also markedly decreased Wallerian degeneration. The average numbers of fluorescent, double-labeled nerve cells were significantly different between the ES and non-ES sides. This study shows that subthreshold, continuous, low-frequency ES immediately after a crush injury of the facial nerve results in earlier recovery of facial function and shorter overall recovery time. PMID:21254091

Kim, Jin; Han, Su Jin; Shin, Dong Hyun; Lee, Won-Sang; Choi, Jae Young

2011-02-01

285

Study of electrical conductivity response upon formation of ice and gas hydrates from salt solutions by a second generation high pressure electrical conductivity probe  

NASA Astrophysics Data System (ADS)

We recently reported the development of a high pressure electrical conductivity probe (HP-ECP) for experimental studies of formation of gas hydrates from electrolytes. The onset of the formation of methane-propane mixed gas hydrate from salt solutions was marked by a temporary upward spike in the electrical conductivity. To further understand hydrate formation a second generation of window-less HP-ECP (MkII), which has a much smaller heat capacity than the earlier version and allows access to faster cooling rates, has been constructed. Using the HP-ECP (MkII) the electrical conductivity signal responses of NaCl solutions upon the formation of ice, tetrahydrofuran hydrates, and methane-propane mixed gas hydrate has been measured. The concentration range of the NaCl solutions was from 1 mM to 3M and the driving AC frequency range was from 25 Hz to 5 kHz. This data has been used to construct an "electrical conductivity response phase diagrams" that summarize the electrical conductivity response signal upon solid formation in these systems. The general trend is that gas hydrate formation is marked by an upward spike in the conductivity at high concentrations and by a drop at low concentrations. This work shows that HP-ECP can be applied in automated measurements of hydrate formation probability distributions of optically opaque samples using the conductivity response signals as a trigger.

Sowa, Barbara; Zhang, Xue Hua; Kozielski, Karen A.; Dunstan, Dave E.; Hartley, Patrick G.; Maeda, Nobuo

2014-11-01

286

Physical modeling of electrical conduction in printed circuit board insulation  

E-print Network

This thesis is concerned with understanding the degradation of electrical and electronic components in automobiles due to environmental effects. A special emphasis is placed on understanding the physical processes underlying ...

Sarathy, Vasanth

2005-01-01

287

Phase Diagrams of Electric-Fduced Aggregation in Conducting Colloids  

NASA Technical Reports Server (NTRS)

Under the application of a sufficiently strong electric field, a suspension may undergo reversible phase transitions from a homogeneous random arrangement of particles into a variety of ordered aggregation patterns. The surprising fact about electric-field driven phase transitions is that the aggregation patterns, that are observed in very diverse systems of colloids, display a number of common structural features and modes of evolution thereby implying that a universal mechanism may exist to account for these phenomena. It is now generally believed that this mechanism emanates from the presence of the long-range anisotropic interactions between colloidal particles due to their polarization in an applied field. But, in spite of numerous applications of the electric-field-driven phenomena in biotechnology, separation, materials engineering, chemical analysis, etc. our understanding of these phenomena is far from complete. Thus, it is the purpose of the proposed research to develop a theory and then test experimentally, under normal- and low-gravity conditions, the accuracy of the theoretical predictions regarding the effect of the synergism of the interparticle electric and hydrodynamic interactions on the phase diagram of a suspension. The main results from our theoretical studies performed to-date enable one to trace how the variations of the electrical properties of the constituent materials influence the topology of the suspension phase diagram and then, by using an appropriate phase diagram, to evaluate how the electric-field-induced transformations will depend on the frequency and the strength of the applied field.

Khusid, B.; Acrivos, A.

1999-01-01

288

Electrical and Hydraulic Properties of Humified Bog Peat as a Function of Pore-fluid Conductivity  

NASA Astrophysics Data System (ADS)

The electrical properties of organic sediments and their relationship to physical properties are poorly understood. A simple approach to relate electrical properties to physical properties commonly applied to inorganic sediments is to model the electrolytic conductivity and the surface conductivity as parallel conduction paths. Low-frequency electrical measurements were made in conjunction with hydraulic conductivity measurements on peat samples from an 11 m section collected in a large freshwater peatland. The electrical and hydraulic measurements were made as a function of NaCl concentration and depth of burial. In all cases, the electrical conductivity of the peat was not well modeled by the parallel conduction path model, with the model yielding formation factor values close to one. Sample measurements along the section suggest a slight increase in the formation factor and surface conductivity values with depth. Hydraulic conductivity measured by constant head method shows a marked increase with increasing NaCl concentration, which we believe results from expansion of macropore porosity by chemical dilation as proposed by others. Attempts to return the samples to their original conditions by decreasing the salinity only partially restored the hydraulic conductivity values, indicating a permanent disruption of the hydraulic properties of the peat. The increase of surface electrical conductivity and hydraulic conductivity with depth may indicate a close correlation with the high cation exchange capacity of organic matter and its tendency for chemical dilation as decomposition of organic matter increases with depth. We propose that the electrical conductivity of peat cannot be modeled by an electrolytic and a surface conduction path in parallel. The increase in the electrolytic conduction causes ionic accumulation and dispersion processes, expanding the macropore porosity and hence inducing a decrease in the formation factor values. A proper electrical model for organic materials such as peat needs to include this pore dilation effect caused by the increase in electrolytic conduction.

Comas, X.; Slater, L.

2003-12-01

289

Inductively coupled power transfer for continuously powered electric vehicles  

Microsoft Academic Search

Economic and environmental issues are main motivation for developing efficient and sustainable electrical vehicle for urban transportation. Electrical vehicles (EV) have two main advantages compared to hybrid and gasoline vehicle: eliminated tailpipe emissions and simplified drive-train. However, electric vehicles have a limited range between recharges when fitted with the current state-of-the-art energy storage. To mitigate the limitations of the energy

Zeljko Pantic; Sanzhong Bai; Srdjan M. Lukic

2009-01-01

290

Generation and characterization of a laser-plasma-based electrical conduction pathway in air  

NASA Astrophysics Data System (ADS)

The concurrent reduction of printed wiring board (PWB) features and utilization of many embedded signal layers is rendering the application of mechanical (pin contact) electrical testers obsolete. Laser-based non-contact testing (NCT) can potentially access these structures via a photoionization plasma, which is used to complete the required electrical signal pathways. Applications for this technology include such areas as: bare-board continuity testing, die/component testing, parametric noncontact electrical testing, signal multiplexing by light, noncontact logic overdrive and very high frequency probing. This thesis contains the road map for future NCT system designers. The road map is a summary of the results of the scientific issues explored. These issues include plasma resistance and lifetime, thresholds for breakdown and the point of opacity in air, and the multiphoton processes which occur in air. Theories about the breakdown of air and resulting conduction pathway resistance that have been developed and verified with experiments are highlighted. Values for the minimum Nd:YAG laser pulse energy per unit volume for breakdown and opacity are found to be 1.75 mJ/mm3 and 33 mJ/mm3, respectively. Laser pulse energy and pulsewidth, focal volume and gaseous contributions to the NCT process are also discussed. A model for the resistivity of the pathway is presented as well. The thesis concludes with the steps to follow when designing a system, which incorporates laser-induced, plasma-based noncontact test technology.

Umstadter, Karl Robert

1998-12-01

291

Preparation of Electrically Conductive Polystyrene/Carbon Nanofiber Nanocomposite Films  

ERIC Educational Resources Information Center

A simple and effective approach to prepare conductive polystyrene/carbon nanofiber (PS/CNF) nanocomposite films via a solution dispersion method is presented. Inexpensive CNF, which has a structure similar to multi-walled carbon nanotubes, is chosen as a nanofiller in this experiment to achieve conductivity in PS films. A good dispersion is…

Sun, Luyi; O'Reilly, Jonathan Y.; Tien, Chi-Wei; Sue, Hung-Jue

2008-01-01

292

Electrical conductivity of diopside: evidence for oxygen vacancies  

USGS Publications Warehouse

Impedance spectra for two natural single crystals of diopside were obtained at 800 to 1300??C and 1-bar pressure over the frequency range 0.001 Hz to 100 kHz in a system closed to all components but oxygen. At both higher and lower fO2 values, no fO2 dependence of conductivity was observed, indicating the presence of different conduction mechanisms. At temperatures less than 1000??C, the activation energy is 1.3 eV, also suggesting a different conduction mechanism. Thus, at least four regimes are necessary to describe the conductivity of this diopside in T-fO2 space. The approximately -1/(7 ?? 1) value of d(log ??)/d(log fO2) in a high-temperature geologic region suggests a reaction by which oxygen vacancies control the conductivity. This relatively pure diopside is much less conducting than olivine or orthopyroxene. A second diopside with greater Fe content but otherwise similar in composition to the near-end-member diopside, is more conducting, has a smaller activation energy (1.0 eV) over the range 1050 to 1225??C, and shows only a weak negative fO2 dependence; suggesting that oxygen vacancies are present but are not the dominant defect in controlling the conductivity. -from Authors

Huebner, J.S.; Voigt, D.E.

1988-01-01

293

Soil permittivity response to bulk electrical conductivity for selected soil water sensors  

Technology Transfer Automated Retrieval System (TEKTRAN)

Bulk electrical conductivity can dominate the low frequency dielectric loss spectrum in soils, masking changes in the real permittivity and causing errors in estimated water content. We examined the dependence of measured apparent permittivity (Ka) on bulk electrical conductivity in contrasting soil...

294

Electrical Conductivity and Anisotropy in Pacific Lithosphere: CSEM Results from APPLE  

Microsoft Academic Search

Strain associated with plate formation at mid-ocean ridge spreading centers may influence electrical conductivity at various depths in the lithosphere, and may leave an anisotropic fabric frozen in place. By measuring lithospheric electrical conductivity and anisotropy, insight may be gained regarding the formation and evolution of oceanic crust and mantle. Controlled-source electromagnetic (CSEM) sounding of 35 Ma Pacific lithosphere was

J. Behrens; S. Constable; M. Everett; L. MacGregor

2003-01-01

295

Electrical Conductivity and Anisotropy in Pacific Lithosphere: CSEM Results from APPLE  

Microsoft Academic Search

Emplacement of the sheeted dyke complex and strain associated with plate formation at mid-ocean ridge spreading centers may influence electrical conductivity at various depths in the lithosphere, and may leave an anisotropic fabric frozen in place. By measuring lithospheric electrical conductivity and anisotropy as a function of depth, insight may be gained regarding the formation and evolution of oceanic crust

J. Behrens; S. Constable; L. MacGregor; M. Everett

2002-01-01

296

POTENTIAL IRRIGATION APPLICATIONS USING SENSOR-BASED APPARENT SOIL ELECTRICAL CONDUCTIVITY  

Technology Transfer Automated Retrieval System (TEKTRAN)

Apparent soil electrical conductivity (ECa) is a measure of a soil's ability to conduct an electrical charge and can be obtained quickly for mapping purposes using on-the-go sensors. Several important soil properties, important for irrigation management, have been successfully related to soil ECa. I...

297

Comparison of Electromagnetic Induction and Direct Sensing of Soil Electrical Conductivity  

Microsoft Academic Search

et al. (1989) modeled ECa as a function of soil water content (both the mobile and immobile fractions), the Apparent profile soil electrical conductivity (ECa) can be an indi- electrical conductivity (EC) of the soil water, soil bulk rect indicator of a number of soil physical and chemical properties. Commercially available ECa sensors can be used to efficiently and density,

K. A. Sudduth; N. R. Kitchen; G. A. Bollero; D. G. Bullock; W. J. Wiebold

2003-01-01

298

Relating bulk electrical conduction to litho-textural properties and pore-fluid conductivity within porous alluvial aquifers  

NASA Astrophysics Data System (ADS)

The estimate of hydraulic conductivity from Direct Current methods represents a powerful tool in aquifer characterization as both electrical and hydraulic conductivities depend on connected pore volumes and connected pore surface areas. A crucial, intermediate stage of this process is the assessment of sediments' textures and lithology from DC electrical conductivity as the electrical response of the aquifers' basic building blocks (i.e., hydrofacies) is controlled by the prevailing process of electrical conduction, electrolytic (?EL; pore-volume dominated) vs. "shale" (?SH; pore-surface dominated), determined by pore-space structure, clay distribution and electrical properties of pore fluids (?W). In this work laboratory experiments were conducted and the results were interpreted through the analysis i) of a volume-averaged, macroscopic litho-textural property of alluvial hydrofacies', the coarse-to-fine ratio (C/F), as a "proxy" of the process of electrical conduction within each samples on the basis of the volume proportion between nonconductive, coarse-grained and conductive, shaly textures and ii) of the surface conduction component, produced in fresh-to-salt water environment by clay materials. 8 hydrofacies' samples were collected with an hand-auger within the outcropping alluvial aquifers of the Quaternary meander river belt of the southernmost Lodi plain (northern Italy), represented by loose gravelly-sands to sands (6 samples), fine and sandy-silty clays (2 samples). As a first step, laboratory measurements of the bulk electrical conductivity (?B) of representative sub-samples, totally saturated with water with different salinity (?W from 125 to 1100 ?s/cm), were performed. The experimental apparatus was made up by a series of polycarbonate, cylindrical cells (9cm x 12cm) equipped with external, copper plates as current electrodes and internal, copper squared-grids as potential electrodes. Electrical conductivity of each sample was obtained averaging time-repeated measures during 48 h after the samples' assemblage with a DC resistivity meter. As a second step, texture analysis was performed in order to obtain the textures' volume fractions of each hydrofacies subsamples; C/F threshold equal to 1 identifies coarse-grained litho-textural association (gravelly-sands to sands samples) and fine-grained litho-textural association. Plot of ?B vs. C/F generally shows an increasing conductivity with decreasing C/F ratio and increasing ?W, that is consistent with previous studies perform on field-scale electrical conductivity datasets obtained through DC resistivity soundings calibrated on sediments outcropping the alluvial basin. The distributions of ?B vs. C/F are fitted with a power-law regressions, showing a decreasing R2 with increasing ?W. A conduction model which takes into account C/F and ?W and considers ?B as the sum of two terms, ?EL (pore-volume dominated) and ?SH (pore-surface dominated), where surface conduction is treated as an equivalent shale volume conduction, was adopted. Values of ?EL and ?SH were computed for each sample and for increasing ?W.

Mele, M.; Giudici, M.; Inzoli, S.; Cavalli, E.; Bersezio, R.

2012-04-01

299

Electrical conductivity in directionally solidified lead-9 and -20 wt pct copper alloys  

NASA Technical Reports Server (NTRS)

Composites consisting of aligned copper dendrites in a lead matrix have been produced by directional solidification processing for potential application as grids in lead-acid batteries. To promote a uniform composite of aligned copper dendrites in a protective lead matrix, two alloy compositions, Pb-9 and -20 wt pct Cu, have been directionally solidified through a temperature gradient of 4.5 K/mm at constant growth velocities which ranged from 1 to 100 micron/s. With slow growth rates (below about 10 microns/s), the copper dendrites were generally columnar and continuous along the sample length; at higher velocities (above 60 microns/s), they assumed an intricate and equiaxed morphology. In accordance with copper content and growth rate, the electrical conductivity of the directionally solidified composites was found to be as much as a 2.5 times that of pure lead. The results are compared with that predicted by a model based on a geometrical dendrite.

Kim, Shinwoo; Flanagan, W. F.; Lichter, B. D.; Grugel, R. N.

1993-01-01

300

Reversible temperature regulation of electrical and thermal conductivity using liquid-solid phase transitions.  

PubMed

Reversible temperature tuning of electrical and thermal conductivities of materials is of interest for many applications, including seasonal regulation of building temperature, thermal storage and sensors. Here we introduce a general strategy to achieve large contrasts in electrical and thermal conductivities using first-order phase transitions in percolated composite materials. Internal stress generated during a phase transition modulates the electrical and thermal contact resistances, leading to large contrasts in the electrical and thermal conductivities at the phase transition temperature. With graphite/hexadecane suspensions, the electrical conductivity changes 2 orders of magnitude and the thermal conductivity varies up to 3.2 times near 18 °C. The generality of the approach is also demonstrated in other materials such as graphite/water and carbon nanotube/hexadecane suspensions. PMID:21505445

Zheng, Ruiting; Gao, Jinwei; Wang, Jianjian; Chen, Gang

2011-01-01

301

Reversible temperature regulation of electrical and thermal conductivity using liquid–solid phase transitions  

PubMed Central

Reversible temperature tuning of electrical and thermal conductivities of materials is of interest for many applications, including seasonal regulation of building temperature, thermal storage and sensors. Here we introduce a general strategy to achieve large contrasts in electrical and thermal conductivities using first-order phase transitions in percolated composite materials. Internal stress generated during a phase transition modulates the electrical and thermal contact resistances, leading to large contrasts in the electrical and thermal conductivities at the phase transition temperature. With graphite/hexadecane suspensions, the electrical conductivity changes 2 orders of magnitude and the thermal conductivity varies up to 3.2 times near 18 °C. The generality of the approach is also demonstrated in other materials such as graphite/water and carbon nanotube/hexadecane suspensions. PMID:21505445

Zheng, Ruiting; Gao, Jinwei; Wang, Jianjian; Chen, Gang

2011-01-01

302

Influence of matching solubility parameter of polymer matrix and CNT on electrical conductivity of CNT/rubber composite  

NASA Astrophysics Data System (ADS)

We report a general approach to fabricate elastomeric composites possessing high electrical conductivity for applications ranging from wireless charging interfaces to stretchable electronics. By using arbitrary nine kinds of rubbers as matrices, we experimentally demonstrate that the matching the solubility parameter of CNTs and the rubber matrix is important to achieve higher electrical conductivity in CNT/rubber composite, resulting in continuous conductive pathways leading to electrical conductivities as high as 15 S/cm with 10 vol% CNT in fluorinated rubber. Further, using thermodynamic considerations, we demonstrate an approach to mix CNTs to arbitrary rubber matrices regardless of solubility parameter of matrices by adding small amounts of fluorinated rubber as a polymeric-compatibilizer of CNTs. We thereby achieved electrical conductivities ranging from 1.2 to 13.8 S/cm (10 vol% CNTs) using nine varieties of rubber matrices differing in chemical structures and physical properties. Finally, we investigated the components of solubility parameter of CNT by using Hansen solubility parameters, these findings may useful for controlling solubility parameter of CNTs.

Ata, Seisuke; Mizuno, Takaaki; Nishizawa, Ayumi; Subramaniam, Chandramouli; Futaba, Don N.; Hata, Kenji

2014-12-01

303

Influence of matching solubility parameter of polymer matrix and CNT on electrical conductivity of CNT/rubber composite  

PubMed Central

We report a general approach to fabricate elastomeric composites possessing high electrical conductivity for applications ranging from wireless charging interfaces to stretchable electronics. By using arbitrary nine kinds of rubbers as matrices, we experimentally demonstrate that the matching the solubility parameter of CNTs and the rubber matrix is important to achieve higher electrical conductivity in CNT/rubber composite, resulting in continuous conductive pathways leading to electrical conductivities as high as 15?S/cm with 10 vol% CNT in fluorinated rubber. Further, using thermodynamic considerations, we demonstrate an approach to mix CNTs to arbitrary rubber matrices regardless of solubility parameter of matrices by adding small amounts of fluorinated rubber as a polymeric-compatibilizer of CNTs. We thereby achieved electrical conductivities ranging from 1.2 to 13.8?S/cm (10 vol% CNTs) using nine varieties of rubber matrices differing in chemical structures and physical properties. Finally, we investigated the components of solubility parameter of CNT by using Hansen solubility parameters, these findings may useful for controlling solubility parameter of CNTs. PMID:25434701

Ata, Seisuke; Mizuno, Takaaki; Nishizawa, Ayumi; Subramaniam, Chandramouli; Futaba, Don N.; Hata, Kenji

2014-01-01

304

On the Electrical Conductivity of Violanthrone, Iso-Violanthrone and Pyranthrone  

Microsoft Academic Search

Violanthrone, iso-violanthrone, and pyranthrone have electrical conductance to a certain degree. This is due to the molecular structure of these compounds, which are made of the network planes of carbon atoms, and to the assumption that the ?-electron contribute to the electrical conduction.The electrical resistivity of violanthrone, iso-violanthrone, and pyranthrone was measured. The values at 15°C are as follows; 2.3×1010

Hideo Akamatu; Hiroo Inokuchi

1950-01-01

305

Different clinical electrodes achieve similar electrical nerve conduction block  

NASA Astrophysics Data System (ADS)

Objective. We aim to evaluate the suitability of four electrodes previously used in clinical experiments for peripheral nerve electrical block applications. Approach. We evaluated peripheral nerve electrical block using three such clinical nerve cuff electrodes (the Huntington helix, the Case self-sizing Spiral and the flat interface nerve electrode) and one clinical intramuscular electrode (the Memberg electrode) in five cats. Amplitude thresholds for the block using 12 or 25 kHz voltage-controlled stimulation, onset response, and stimulation thresholds before and after block testing were determined. Main results. Complete nerve block was achieved reliably and the onset response to blocking stimulation was similar for all electrodes. Amplitude thresholds for the block were lowest for the Case Spiral electrode (4 ± 1 Vpp) and lower for the nerve cuff electrodes (7 ± 3 Vpp) than for the intramuscular electrode (26 ± 10 Vpp). A minor elevation in stimulation threshold and reduction in stimulus-evoked urethral pressure was observed during testing, but the effect was temporary and did not vary between electrodes. Significance. Multiple clinical electrodes appear suitable for neuroprostheses using peripheral nerve electrical block. The freedom to choose electrodes based on secondary criteria such as ease of implantation or cost should ease translation of electrical nerve block to clinical practice.

Boger, Adam; Bhadra, Narendra; Gustafson, Kenneth J.

2013-10-01

306

Electrical Conduction Models for the Solution of Water Seepage Problems  

Microsoft Academic Search

A method is described for the construction of electrical models with which to solve problems of the flow of liquids through porous media under the action of gravity. With these models the shape of the free surface and the extent of the surface of seepage are determined simultaneously with the potential distribution within the flow system. Four examples are given

R. D. Wyckoff; D. W. Reed

1935-01-01

307

Electrical Conductance of Bolted Copper Joints for Cryogenic Applications  

NASA Astrophysics Data System (ADS)

We present the results of electric contact resistance measurements at low temperatures on copper-to-copper bolted joints. Our accurate and systematic data display a rather small dispersion, and may be a useful tool for cryogenic applications like pulse-tubes, dilution refrigerators and nuclear refrigerators.

Blondelle, F.; Sultan, A.; Collin, E.; Godfrin, H.

2014-06-01

308

Electrical Resistivity—Hydraulic Conductivity Relationships in Glacial Outwash Aquifers  

NASA Astrophysics Data System (ADS)

Empirical field relationships between the apparent formation factors from surface resistivity soundings and hydraulic conductivity from pumping tests in fresh water granular aquifers usually show positive correlations. These relationships can be adequately explained by theory if consideration is taken of in situ field conditions. A sound theoretical basis for relating apparent formation factor to pertinent hydrogeophysical parameters in homogeneous isotropic sand is a three-phase parallel resistor model which explicity includes parameters of porewater resistivity, grain size and shape, porosity, tortuosity, and intergranular surface conductance. The veracity of the theoretical model is supported by data from laboratory tests. The model demonstrates that intergranular surface conductance is an important factor at small grain sizes and high porewater resistivities, operating to lower the apparent formation factor. The model further shows that direct relationships between hydraulic conductivity and formation factor are weak in the normal range of porewater resistivity, being strongly dependent on porosity. When systematic variation of in situ porosity and aquifer layering effects are considered, a simulated field curve relating the apparent formation factor to hydraulic conductivity is shown to compare favorably with the comparable curve from field data for thirteen pumping test sites in southern Rhode Island. Both theoretical and empirical results demonstrate a useful positive correlation between aquifer apparent formation factor and hydraulic conductivity. Quantitative interpretation, however, is imprecise because of nonuniqueness of interpretation and inherent variation in important aquifer parameters, especially porosity.

Urish, Daniel W.

1981-10-01

309

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

310

Highly Electrically Conductive Nanocomposites Based on PolymerInfused Graphene Sponges  

PubMed Central

Conductive polymer composites require a threedimensional 3D network to impart electrical conductivity. A general method that is applicable to most polymers for achieving a desirable graphene 3D network is still a challenge. We have developed a facile technique to fabricate highly electrical conductive composite using vacuumassisted infusion of epoxy into graphene sponge GS scaffold. Macroscopic GSs were synthesized from graphene oxide solution by a hydrothermal method combined with freeze drying. The GSepoxy composites prepared display consistent isotropic electrical conductivity around 1Sm, and it is found to be close to that of the pristine GS. Compared with neat epoxy, GSepoxy has a 12ordersofmagnitude increase in electrical conductivity, attributed to the compactly interconnected graphene network constructed in the polymer matrix. This method can be extended to other materials to fabricate highly conductive composites for practical applications such as electronic devices, sensors, actuators, and electromagnetic shielding. PMID:24722145

Li, Yuanqing; Samad, Yarjan Abdul; Polychronopoulou, Kyriaki; Alhassan, Saeed M.; Liao, Kin

2014-01-01

311

Highly Electrically Conductive Nanocomposites Based on PolymerInfused Graphene Sponges  

NASA Astrophysics Data System (ADS)

Conductive polymer composites require a threedimensional 3D network to impart electrical conductivity. A general method that is applicable to most polymers for achieving a desirable graphene 3D network is still a challenge. We have developed a facile technique to fabricate highly electrical conductive composite using vacuumassisted infusion of epoxy into graphene sponge GS scaffold. Macroscopic GSs were synthesized from graphene oxide solution by a hydrothermal method combined with freeze drying. The GSepoxy composites prepared display consistent isotropic electrical conductivity around 1Sm, and it is found to be close to that of the pristine GS. Compared with neat epoxy, GSepoxy has a 12ordersofmagnitude increase in electrical conductivity, attributed to the compactly interconnected graphene network constructed in the polymer matrix. This method can be extended to other materials to fabricate highly conductive composites for practical applications such as electronic devices, sensors, actuators, and electromagnetic shielding.

Li, Yuanqing; Samad, Yarjan Abdul; Polychronopoulou, Kyriaki; Alhassan, Saeed M.; Liao, Kin

2014-04-01

312

Electrical conductivity imaging using gradient B\\/sub z\\/ decomposition algorithm in magnetic resonance electrical impedance tomography (MREIT)  

Microsoft Academic Search

In magnetic resonance electrical impedance tomography (MREIT), we try to visualize cross-sectional conductivity (or resistivity) images of a subject. We inject electrical currents into the subject through surface electrodes and measure the z component Bz of the induced internal magnetic flux density using an MRI scanner. Here, z is the direction of the main magnetic field of the MRI scanner.

Ohin Kwon; Eung Je Woo; Jin Keun Seo

2004-01-01

313

Laboratory measurements of electrical conductivities of hydrous and dry Mount Vesuvius melts under pressure  

NASA Astrophysics Data System (ADS)

Quantitative interpretation of MT anomalies in volcanic regions requires laboratory measurements of electrical conductivities of natural magma compositions. The electrical conductivities of three lava compositions from Mount Vesuvius (Italy) have been measured using an impedance spectrometer. Experiments were conducted on both glasses and melts between 400 and 1300°C, at both ambient pressure in air and high pressures (up to 400 MPa). Both dry and hydrous (up to 5.6 wt % H2O) melt compositions were investigated. A change of the conduction mechanism corresponding to the glass transition was systematically observed. The conductivity data were fitted by sample-specific Arrhenius laws on either side of Tg. The electrical conductivity increases with temperature and is higher in the order tephrite, phonotephrite to phonolite. For the three investigated compositions, increasing pressure decreases the conductivity, although the effect of pressure is relatively small. The three investigated compositions have similar activation volumes (?V = 16-24 cm3 mol-1). Increasing the water content of the melt increases the conductivity. Comparison of activation energies (Ea) from conductivity and sodium diffusion and use of the Nernst-Einstein relation allow sodium to be identified as the main charge carrier in our melts and presumably also in the corresponding glasses. Our data and those of previous studies highlight the correlation between the Arrhenius parameters Ea and ?0. A semiempirical method allowing the determination of the electrical conductivity of natural magmatic liquids is proposed, in which the activation energy is modeled on the basis of the Anderson-Stuart model, ?0 being obtained from the compensation law and ?V being fitted from our experimental data. The model enables the electrical conductivity to be calculated for the entire range of melt compositions at Mount Vesuvius and also satisfactorily predicts the electrical response of other melt compositions. Electrical conductivity data for Mount Vesuvius melts and magmas are slightly lower than the electrical anomaly revealed by MT studies.

Pommier, A.; Gaillard, F.; Pichavant, M.; Scaillet, B.

2008-05-01

314

Electrical Characterization and Morphological Studies of Conducting Polymer Nanofibers  

NASA Technical Reports Server (NTRS)

Doped polyaniline blended with poly(ethylene oxide) has been electrospun in air to give fibers with diameters in the range 3 nm 200 nm. These fibers were captured on wafers of degenerately doped Si/SiO2 by placing the wafer in the path of the fiber jet formed during the electrospinning process. Individual fibers were contacted using shadow mask evaporation and were also captured on prepatterned wafers. Fibers having diameters greater than 100 nm show a slight increase in the conductivity as compared to the bulk film, while fibers with diameters less than 30 nm had lower conductivity than the bulk. Data on Scanning Conductance Microscopy along the length of individual fibers will be presented. For fibers where the diameter was not uniform, we found that below a certain diameter ( approx.15 nm) the fiber was less conducting as compared to thicker diameter fibers. Dependence of the fiber conductivity on a gate bias is underway and these results will also be presented.

Pinto, N. J.; Zhou, Y. X.; Freitag, M.; Johnson, A. T.; MacDiarmid, A. G.; Mueller, C. H.; Theofylaktos, N.; Robinson, D. C.; Miranda, F. A.

2003-01-01

315

A CONTINUED INVESTIGATION OF ELECTRICALLY STIMULATED FABRIC FILTRATION  

EPA Science Inventory

The report summarizes three experiments performed by Southern Research Institute under a cooperative agreement with EPA. First was a demonstration of electrostatically stimulated fabric filtration (ESFF) used to collect particulate matter (PM) from fossil fuel electrical power pl...

316

Epoxy Resin\\/Graphite Electrically Conductive Nanosheet Nanocomposite  

Microsoft Academic Search

In this study, graphite nanosheets were prepared by powdering expanded graphite with sonication in aqueous alcoholic solution. Epoxy resin\\/graphite nanosheet nanocomposites were fabricated and their electrical and mechanical properties were investigated. The results revealed that graphite sheets 30–80 nm in thickness could be effectively dispersed within the epoxy resin. The percolation threshold of epoxy resin\\/graphite nanoparticles was about 0.015, much lower

Wei Lu; Jianxin Weng; Dajun Wu; Cuiling Wu; Guohua Chen

2006-01-01

317

Electrical conductivity of rubidium and cesium salts of heteropoly acids  

SciTech Connect

The conductivity of solid heteropoly compounds with the formulas A/sub 3/PM/sub 12/O/sub 40/ .nH/sub 2/O and A/sub 2/HPM/sub 12/O/sub 40/ .nH/sub 2/O, where A=Rb, Cs, and M=Mo, W, is determined by measuring the electrochemical impedance at frequencies ranging from 0.1 to 100 KHz. The salts of heteropoly acids, and in particular the salts of Cs and Rb, are of interest because of their proton conductivity. The amount of Cs and Rb was determined gravimetrically in the form of the tetraphenylborates, following the preliminary dissolution of a weighed sample with gentle heating in a dilute NaOH solution. The authors conclude from this work that the conductivities of the di- and trisubstituted salts of the heteropoly acids are of the same order of magnitude.

Leonova, L.S.; Korosteleva, A.I.; Kovalenko, V.I.; Ukshe, E.A.

1985-06-01

318

Electrical Conductivity of 2D-SiCf/CVI-SiC  

SciTech Connect

Electrical conductivity (EC) data for several plate forms of two-dimensional, silicon carbide composite made with chemical vapor infiltration matrix and with Hi Nicalon{trademark} type S fibers (2D-SiCf/CVI-SiC) were acquired. The composite fibers were coated with pyrocarbon (PyC) of various thicknesses (50 to 310 nm) and an outer thin ({approx}60 {mu}m) SiC 'seal coat' was applied by CVD to the infiltrated plates. The EC was highly anisotropic in the transverse and in-plane directions. In-plane EC ranged from {approx}150 to 1600 S/m, increased slowly with increasing temperature, and depended primarily on the total PyC thickness. High in-plane EC-values occur because it is dominated by conduction along the numerous, continuous PyC fiber coating pathways. Transverse EC ranged from {approx}1 to 60 S/m, and increased strongly with increasing temperature up to 800 C. The transverse EC is controlled by conduction through the interconnections of the carboncoating network within and between fiber bundles, especially at moderate temperatures ({approx}300 to 700 C). Below {approx}300 C, the electrical resistance of the pure SiC seal coat becomes increasingly more important as temperatures are further lowered. Importantly, a '3-layer series' model predicts that transverse EC-values for a standard seal-coated 2DSiCf/ CVI-SiC with a monolayer PyC fiber coating of {approx}50-nm thickness will be <20 S/m for all temperatures up to 800 C, as desired for a flow channel insert in a fusion reactor blanket component.

Youngblood, Gerald E.; Thomsen, Edwin C.; Shinavski, Robert J.

2011-07-11

319

Electrical conductivity of mantle in the North Central region of Nigeria  

NASA Astrophysics Data System (ADS)

The mantle electrical conductivity profile of the North Central region of Nigeria was determined using the quiet day ionospheric current variations (Sq). The employed magnetic averaged hourly data were obtained from Magnetic Data Acquisition System (MAGDAS) ground based observatories at two Nigerian stations located at Ilorin (8°30?N, 4°33?E) and Abuja (8°59?N, 7°23?E) for the year 2009 and 2010. The magnetometer data from Pankshin (9°20?N, 9°27?E) and Katsina-Ala (7°10?N, 9°17?E) for the same years were equally employed. The separation of both the internal and external field contributions to the Sq variations was successfully carried out employing spherical harmonic analysis (SHA). Transfer function was performed in computing the conductivity-depth profile for North Central region of Nigeria from the paired external and internal coefficients of the SHA. The conductivity value of approximately 0.039 S/m was estimated at a depth of 100 km which rose gradually to 0.087 S/m at 207 km depth and 0.142 S/m at 367 km (close to the base of upper mantle). Subsequently, the conductivity profile continued rising to a value of 0.144 S/m at 442 km, 0.164 S/m at 653 km and 0.174 S/m at 710 km. Finally, value of approximately 0.195 S/m at a depth of 881 km and 0.240 S/m at 1100 km depth were recorded at the lower mantle with no indication of leveling off. Some evidence of discontinuities near 100-214 km, 214-420 km, 420-640 km, 640-900 km and 900-1100 km were clearly obvious. The sharp increase in conductivity from about 100 km depth to 230 km was interpreted to correspond to the global seismic low velocity zone - the asthenosphere.

Obiora, Daniel N.; Okeke, Francisca N.; Yumoto, K.

2015-01-01

320

Damage detection and conductivity evolution in carbon nanofiber epoxy via electrical impedance tomography  

NASA Astrophysics Data System (ADS)

Utilizing electrically conductive nanocomposites for integrated self-sensing and health monitoring is a promising area of structural health monitoring (SHM) research wherein local changes in conductivity coincide with damage. In this research we conduct proof of concept investigations using electrical impedance tomography (EIT) for damage detection by identifying conductivity changes and by imaging conductivity evolution in a carbon nanofiber (CNF) filled epoxy composite. CNF/epoxy is examined because fibrous composites can be manufactured with a CNF/epoxy matrix thereby enabling the entire matrix to become self-sensing. We also study the mechanisms of conductivity evolution in CNF/epoxy through electrical impedance spectroscopy (EIS) testing. The results of these tests indicate that thermal expansion is responsible for conductivity evolution in a CNF/epoxy composite.

Tallman, T. N.; Gungor, S.; Wang, K. W.; Bakis, C. E.

2014-04-01

321

Electrical conductivity of quark matter in magnetic field  

E-print Network

Fermion currents in dense quark matter embedded into magnetic field are under intense discussions motivated by Chiral Magnetic Effect. We argue that conductivity of quark matter may be independent of the magnetic field direction and not proportional to the magnetic field strength.

B. Kerbikov; M. Andreichikov

2011-12-05

322

Electrically conductive bulk composites through a contact-connected aggregate.  

PubMed

This paper introduces a concept that allows the creation of low-resistance composites using a network of compliant conductive aggregate units, connected through contact, embedded within the composite. Due to the straight-forward fabrication method of the aggregate, conductive composites can be created in nearly arbitrary shapes and sizes, with a lower bound near the length scale of the conductive cell used in the aggregate. The described instantiation involves aggregate cells that are approximately spherical copper coils-of-coils within a polymeric matrix, but the concept can be implemented with a wide range of conductor elements, cell geometries, and matrix materials due to its lack of reliance on specific material chemistries. The aggregate cell network provides a conductive pathway that can have orders of magnitude lower resistance than that of the matrix material--from 10(12) ohm-cm (approx.) for pure silicone rubber to as low as 1 ohm-cm for the silicone/copper composite at room temperature for the presented example. After describing the basic concept and key factors involved in its success, three methods of implementing the aggregate into a matrix are then addressed--unjammed packing, jammed packing, and pre-stressed jammed packing--with an analysis of the tradeoffs between increased stiffness and improved resistivity. PMID:24349239

Nawroj, Ahsan I; Swensen, John P; Dollar, Aaron M

2013-01-01

323

On the electrical conductivity structure of the stable continental crust  

Microsoft Academic Search

A high conductivity zone (HCZ) exists in many places worldwide in the stable mid- to lower continental crust, at the depth of about 20–30 km, but its origin is enigmatic. At this depth range, the temperatures are constrained between 400 and 600 °C and free fluids are believed to have been consumed by retrograde mineral reactions. Many causes for the HCZ

Friedemann Freund

2003-01-01

324

Detecting Water Stress in Trees Using Stem Electrical Conductivity Measurements  

Microsoft Academic Search

Using time domain refl ectometry (TDR), we studied stem water content (?stem), stem elec- trical conductivity (?stem), and their ratio for 220 d in stressed, installation-cured, living trees of four species. Lysimeter-grown mango (Mangifera indica L.), banana (Musa acuminata Colla), date (Phoenix dactylifera L.), and olive (Olea europaea L.) were subjected to several types of mild (intensity and duration) water

Arie Nadler; Eran Raveh; Uri Yermiyahu; Marcos Lado; Ahmed Nasser; Mordechai Barak; Steve Green

2008-01-01

325

Electrically conductive interpenetrating network composites of polyaniline and carboxymethylcellulose  

Microsoft Academic Search

Conductive polyaniline composite films formed by chemical oxidative polymerization of aniline inside carboxymethylcellulose matrix films have been studied. The composite shows extremely low percolation threshold (fc?1.12×10?3). The UV-visible absorption spectra of the composite materials are affected by acid\\/base treatment in the same manner as pure polyaniline.

Pallab Banerjee

1998-01-01

326

Effects of continuous epidural block on motor nerve conduction velocity in patients with lower spine disorders  

Microsoft Academic Search

Thirty-one patients with severe low back pain were treated by continuous epidural block for 18±3 (mean±SEM) days. Motor nerve\\u000a conduction velocity (MCV) of the common peroneal nerve was measured before and after the treatment. After the treatment, the\\u000a visual analogue scale score (VAS) and straight leg-raising (SLR) test were markedly reduced (PPPP<0.001) between VAS and MCV was demonstrated after treatment.

Sumihisa Aida; Toshiyuki Tobita; Koki Shimoji

1994-01-01

327

Transparent electrically conducting thin films for spacecraft temperature control applications  

NASA Technical Reports Server (NTRS)

Thin transparent films of In2O3 or In2O3 + SnO2 prepared by evaporation or sputtering have been tested for use as surface layers for spacecraft temperature control coatings. The films are intended to prevent nonuniform electric charge buildup on the spacecraft exterior. Film thicknesses of 300 to 500 A were found to be optimal in terms of durability and minimum impact on the solar absorptance and the thermal emissivity of the underlayers. As a verification of their suitability for long-duration space missions, the films were subjected to simulated solar UV plus proton irradiation in a vacuum.

Hass, G.; Heaney, J. B.; Toft, A. R.

1979-01-01

328

Electrical conductivity of lunar surface rocks - Laboratory measurements and implications for lunar interior temperatures  

NASA Technical Reports Server (NTRS)

Results are reported for laboratory measurements of the dc and low-frequency ac electrical conductivity of three lunar rocks with ferrous iron contents of 5 to 26 wt %. The measurements were made at temperatures ranging from 20 to 1000 C, and Mossbauer spectroscopy was used to determine the dependence of electrical conductivity on furnace atmosphere. It is found that the magnitude of electrical conductivity generally increases with increasing iron content. A comparison of the data on these samples with data on terrestrial olivines and pyroxenes shows that the electrical conductivity of anhydrous silicate minerals is influenced primarily by the concentration, oxidation state, and distribution of iron, while the silicate crystal structure is only of secondary importance. Lunar interior temperatures are deduced from experimental lunar conductivity profiles, and the resulting temperature-depth profiles are found to be consistent with those calculated for two different lunar evolutionary models as well as with various experimental constraints.

Schwerer, F. C.; Huffman, G. P.; Fisher, R. M.; Nagata, T.

1974-01-01

329

Continuous glucose monitoring microsensor with a nanoscale conducting matrix and redox mediator  

NASA Astrophysics Data System (ADS)

The major limiting factor in kidney clinical transplantation is the shortage of transplantable organs. The current inability to distinguish viability from non-viability on a prospective basis represents a major obstacle in any attempt to expand organ donor criteria. Consequently, a way to measure and monitor a relevant analyte to assess kidney viability is needed. For the first time, the initial development and characterization of a metabolic microsensor to assess kidney viability is presented. The rate of glucose consumption appears to serve as an indicator of kidney metabolism that may distinguish reversible from irreversible kidney damage. The proposed MetaSense (Metabolic Sensor) microdevice would replace periodic laboratory diagnosis tests with a continuous monitor that provides real-time data on organ viability. Amperometry, a technique that correlates an electrical signal with analyte concentration, is used as a method to detect glucose concentrations. A novel two-electrode electrochemical sensing cell design is presented. It uses a modified metallic working electrode (WE) and a bare metallic reference electrode (RE) that acts as a pseudo-reference/counter electrode as well. The proposed microsensor has the potential to be used as a minimally invasive sensor for its reduced number of probes and very small dimensions achieved by micromachining and lithography. In order to improve selectivity of the microdevice, two electron transfer mechanisms or generations were explored. A first generation microsensor uses molecular oxygen as the electron acceptor in the enzymatic reaction and oxidizes hydrogen peroxide (H2O2) to get the electrical signal. The microsensor's modified WE with conductive polymer polypyrrole (PPy) and corresponding enzyme glucose oxidase (GOx) immobilized into its matrix, constitutes the electrochemical detection mechanism. Photoluminescence spectroscopic analysis confirmed and quantified enzyme immobilized concentrations within the matrix. In vitro testing for glucose shows increasing current with increasing analyte concentration. Testing the glucose microsensor with known concentrations of glucose over a period of 48 hours demonstrated both the potential durability and sensitivity of the device. Unknown/blind in vitro glucose experiments showed the reproducibility and accuracy of the microsensor to detect various glucose levels. Thinner polymer matrix films lead to better sensing performance during in vitro tests (0.6nA/mM lower limit sensitivity and 0.2nA/mM upper limit sensitivity). In vitro experiments using electroactive ascorbic acid (AA) and uric acid (UA) showed the selectivity of the sensor for glucose. In an effort to reduce the sensor's oxidation potential (0.7V) and noise, a second generation electron transfer approach was developed by incorporating into a modified Platinum WE with a nanoscale PPy and GOx matrix, a redox mediator. Ferrocene (Fc) was selected as the artificial electron carrier, substituting molecular oxygen in the enzymatic reaction. The incorporation of Fc into the polymer matrix is done by a simple electrochemical synthesis. Modifications in the microsensor design, materials and fabrication process are presented. Experiments with the new sensor generation resulted in higher sensitivity values (22.8nA/mM lower limit sensitivity and 12.5nA/mM upper limit sensitivity) for glucose and noise was further eliminated by operating the sensor at a lower oxidation potential (0.3V). The final experimental work consisted of preliminary ex vivo tests with the MetaSense microdevice on bovine kidney samples, which showed a qualitatively correlation between glucose consumption trend profile during preservation and viability histology outcome.

Pesantez, Daniel

330

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2013-04-01

336

Electrical conductivity of electrolytes applicable to natural waters from 0 to 100 degrees C  

USGS Publications Warehouse

The electrical conductivities of 34 electrolyte solutions found in natural waters ranging from (10-4 to 1) mol?kg-1 in concentration and from (5 to 90) °C have been determined. High-quality electrical conductivity data for numerous electrolytes exist in the scientific literature, but the data do not span the concentration or temperature ranges of many electrolytes in natural waters. Methods for calculating the electrical conductivities of natural waters have incorporated these data from the literature, and as a result these methods cannot be used to reliably calculate the electrical conductivity over a large enough range of temperature and concentration. For the single-electrolyte solutions, empirical equations were developed that relate electrical conductivity to temperature and molality. For the 942 molar conductivity determinations for single electrolytes from this study, the mean relative difference between the calculated and measured values was 0.1 %. The calculated molar conductivity was compared to literature data, and the mean relative difference for 1978 measurements was 0.2 %. These data provide an improved basis for calculating electrical conductivity for most natural waters.

McCleskey, R. Blaine

2011-01-01

337

Electrical conductivity of cationized ferritin decorated gold nanoshells  

NASA Astrophysics Data System (ADS)

We report on a novel method of controlling the resistance of nanodimensional, gold-coated SiO2 nanoparticles by utilizing biomolecules chemisorbed to the nanoshell surface. Local electronic transport properties of gold-coated nanoshells were measured using scanning conductance microscopy. These results were compared to transport properties of identical gold nanoshells biofunctionalized with cationized ferritin protein both with and without an iron oxide core (apoferritin). Measured resistances were on the order of mega-ohms. White light irradiation effects on transport properties were also explored. The results suggest that the light energy influences the nanoshells' conductivity. A mechanism for assembly of gold nanoshells with cationized ferritin or cationized apoferritin is proposed to explain the resistivity dependence on irradiation.

Cortez, Rebecca; Slocik, Joseph M.; Van Nostrand, Joseph E.; Halas, Naomi J.; Naik, Rajesh R.

2012-06-01

338

Electrical and surface properties of clay-conducting polymer composites  

NASA Astrophysics Data System (ADS)

Organic guests such as aniline, pyrrole and thiophene polymerize on the surface and in the intergallery regions of smectite clays which contain exchangeable transition metal cations such as Cu2+ and Fe3+. We monitor these reactions in thin films of smectite clays using electron spin resonance (ESR) and impedance spectroscopies. Polymers that form on the surface and in the interlayer region are studied by scanning force microscopy (SFM). ESR studies have shown that the transition metal ions are reduced during the polymerization process. Impedance measurements indicate that the formation of conducting polymer in the interlayer region of dry, Cu2+ exchanged hectorite thin films results in a dramatic reduction in observed impedance. SFM scans indicate that the conducting polymers can adopt a variety of morphologies on the surfaces of the films and within the intergalleries of the host framework. These studies have applications in the development of advanced materials including microsensors and novel nanocomposites.

Eastman, M. P.; Hagerman, M. E.; Porter, T. L.; Parnell, R. A.; Attuso, J. L.; Bradley, M.; Thompson, D.

1997-08-01

339

Nanostructured Cu-Cr alloy with high strength and electrical conductivity  

SciTech Connect

The influence of nanostructuring by high pressure torsion (HPT) on strength and electrical conductivity in the Cu-Cr alloy has been investigated. Microstructure of HPT samples was studied by transmission electron microscopy with special attention on precipitation of small chromium particles after various treatments. Effect of dynamic precipitation leading to enhancement of strength and electrical conductivity was observed. It is shown that nanostructuring leads to combination of high ultimate tensile strength of 790–840?MPa, enhanced electrical conductivity of 81%–85% IACS and thermal stability up to 500?°C. The contributions of grain refinement and precipitation to enhanced properties of nanostructured alloy are discussed.

Islamgaliev, R. K., E-mail: saturn@mail.rb.ru; Nesterov, K. M. [Institute of Physics of Advanced Materials, Ufa State Aviation Technical University, Ufa 450000 (Russian Federation); Bourgon, J.; Champion, Y. [ICMPE-CNRS, Université Paris 12, 6-8 rue Henri Dunant, 94320 Thiais, cedex (France); Valiev, R. Z. [Institute of Physics of Advanced Materials, Ufa State Aviation Technical University, Ufa 450000 (Russian Federation); Laboratory for Mechanics of Bulk Nanostructured Materials, Saint Petersburg State University, 198504 Peterhof, Saint Petersburg (Russian Federation)

2014-05-21

340

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2014-04-01

344

Electric conductivity of nanocluster polyoxomolybdates in the solid state and solutions  

NASA Astrophysics Data System (ADS)

The electric conductivity of nanocluster polyoxomolybdates (POMs) Mo132 and Mo72Fe30 with a keplerate structure in aqueous solutions, of these POMs in the solid state, and of Mo138 with a toroidal structure was studied. Data on the concentration dependence of the equivalent electric conductivity in solutions and on the specific conductivity of the solid samples were obtained. Solid Mo132 showed predominantly electron type of conductivity at nearly room temperatures due to the presence of molybdenum at different oxidation levels; Mo72Fe30, which has metal components at the highest oxidation levels, was found to be poor electric conductor; Mo138, which has a lower content of low-valence molybdenum than Mo132, showed intermediate conductivity and a reversible transition between the proton and electron types of conductivity.

Ostroushko, A. A.; Grzhegorzhevskii, K. V.

2014-06-01

345

Iodine doped carbon nanotube cables exceeding specific electrical conductivity of metals  

PubMed Central

Creating highly electrically conducting cables from macroscopic aggregates of carbon nanotubes, to replace metallic wires, is still a dream. Here we report the fabrication of iodine-doped, double-walled nanotube cables having electrical resistivity reaching ?10?7??.m. Due to the low density, their specific conductivity (conductivity/weight) is higher than copper and aluminum and is only just below that of the highest specific conductivity metal, sodium. The cables exhibit high current-carrying capacity of 104?105?A/cm2 and can be joined together into arbitrary length and diameter, without degradation of their electrical properties. The application of such nanotube cables is demonstrated by partly replacing metal wires in a household light bulb circuit. The conductivity variation as a function of temperature for the cables is five times smaller than that for copper. The high conductivity nanotube cables could find a range of applications, from low dimensional interconnects to transmission lines. PMID:22355602

Zhao, Yao; Wei, Jinquan; Vajtai, Robert; Ajayan, Pulickel M.; Barrera, Enrique V.

2011-01-01

346

Assessing the temporal stability of spatial patterns of soil apparent electrical conductivity using geophysical methods  

NASA Astrophysics Data System (ADS)

Cocoa remains in the same field for decades, resulting in plantations dominated with aging trees growing on variable and depleted soils. We determined the spatio-temporal variability of key soil properties in a (5.81 ha) field from the International Cocoa Genebank, Trinidad using geophysical methods. Multi-year (2008-2009) measurements of apparent electrical conductivity at 0-0.75 m (shallow) and 0.75-1.5 m (deep) were conducted. Apparent electrical conductivity at deep and shallow gave the strongest linear correlation with clay-silt content (R = 0.67 and R = 0.78, respectively) and soil solution electrical conductivity (R = 0.76 and R = 0.60, respectively). Spearman rank correlation coefficients ranged between 0.89-0.97 and 0.81- 0.95 for apparent electrical conductivity at deep and shallow, respectively, signifying a strong linear dependence between measurement days. Thus, in the humid tropics, cocoa fields with thick organic litter layer and relatively dense understory cover, experience minimal fluctuations in transient properties of soil water and temperature at the topsoil resulting in similarly stable apparent electrical conductivity at shallow and deep. Therefore, apparent electrical conductivity at shallow, which covers the depth where cocoa feeder roots concentrate, can be used as a fertility indicator and to develop soil zones for efficient application of inputs and management of cocoa fields.

De Caires, Sunshine A.; Wuddivira, Mark N.; Bekele, Isaac

2014-10-01

347

Development of eddy current microscopy for high resolution electrical conductivity imaging using atomic force microscopy  

NASA Astrophysics Data System (ADS)

We present a high resolution electrical conductivity imaging technique based on the principles of eddy current and atomic force microscopy (AFM). An electromagnetic coil is used to generate eddy currents in an electrically conducting material. The eddy currents generated in the conducting sample are detected and measured with a magnetic tip attached to a flexible cantilever of an AFM. The eddy current generation and its interaction with the magnetic tip cantilever are theoretically modeled using monopole approximation. The model is used to estimate the eddy current force between the magnetic tip and the electrically conducting sample. The theoretical model is also used to choose a magnetic tip-cantilever system with appropriate magnetic field and spring constant to facilitate the design of a high resolution electrical conductivity imaging system. The force between the tip and the sample due to eddy currents is measured as a function of the separation distance and compared to the model in a single crystal copper. Images of electrical conductivity variations in a polycrystalline dual phase titanium alloy (Ti-6Al-4V) sample are obtained by scanning the magnetic tip-cantilever held at a standoff distance from the sample surface. The contrast in the image is explained based on the electrical conductivity and eddy current force between the magnetic tip and the sample. The spatial resolution of the eddy current imaging system is determined by imaging carbon nanofibers in a polymer matrix. The advantages, limitations, and applications of the technique are discussed.

Nalladega, V.; Sathish, S.; Jata, K. V.; Blodgett, M. P.

2008-07-01

348

Estimation of the electric conductivity of the quark gluon plasma via asymmetric heavy-ion collisions  

NASA Astrophysics Data System (ADS)

We show that in asymmetric heavy-ion collisions, especially off-central Cu + Au collisions, a sizable strength of electric field directed from Au nucleus to Cu nucleus is generated in the overlapping region, because of the difference in the number of electric charges between the two nuclei. This electric field would induce an electric current in the matter created after the collision, which results in a dipole deformation of the charge distribution. The directed flow parameters v1± of charged particles turn out to be sensitive to the charge dipole and provide us with information about electric conductivity of the quark gluon plasma.

Hirono, Yuji; Hongo, Masaru; Hirano, Tetsufumi

2014-08-01

349

Micellar nanoreactors for hematin catalyzed synthesis of electrically conducting polypyrrole.  

PubMed

Enzymatic synthesis of doped polypyrrole (PPy) complexes using oxidoreductases (specifically peroxidases) is very well established "green" methods for producing conducting polypyrrole. The importance of this approach is realized by the numerous potential opportunities of using PPy in biological applications. However, due to very high costs and low acid stability of these enzymes, there is need for more robust alternate biomimetic catalysts. Hematin, a hydroxyferriprotoporphyrin, has a similar iron catalytic active center like the peroxidases and has previously shown to catalyze polymerization of phenol monomers at pH 12. The insolubility of hematin due to extensive self-aggregation at low pH conditions has prevented its use in the synthesis of conjugated polymers. In this study, we have demonstrated the use of a micellar environment with sodium dodecylbenzenesulfonate (DBSA) for biomimetic synthesis of PPy. The micellar environment helps solubilize hematin, generating nanometer size reactors for the polymerization of pyrrole. The resulting PPy is characterized using UV-visible, Fourier transform infrared, and X-ray photoelectron spectroscopy and reveals the formation of an ordered PPy/DBSA complex with conductivities approaching 0.1 S/cm. PMID:22906396

Ravichandran, Sethumadhavan; Nagarajan, Subhalakshmi; Kokil, Akshay; Ponrathnam, Timothy; Bouldin, Ryan M; Bruno, Ferdinando F; Samuelson, Lynne; Kumar, Jayant; Nagarajan, Ramaswamy

2012-09-18

350

Conducting polymers. VI. Effect of doping with iodine on the dielectrical and electrical conduction properties of polyacrylonitrile  

NASA Astrophysics Data System (ADS)

The effect of doping of polyacrylonitrile (PAN) with iodine on the dielectical properties and ac conductivity as a function of temperature and frequency is investigated. Thermogravimetric analysis, TGA, and FTIR measurements show that PAN undergoes degradation starting at 523 K. Doping PAN with I2 enhances the ac electrical conductivity ?ac in the temperature range under investigation due to oligomerization of the nitrile groups giving a conjugated polyimine. The thermal activation energy, ?E, is calculated for PAN and PAN/I2 and found to be in the range 0.16-1.16 eV at 0.1 kHz. The correlated barrier hopping (CBH) conduction mechanism is found to be the dominant conduction mechanism for PAN and PAN/I2 samples.

El-Ghamaz, N. A.; Diab, M. A.; Zoromba, M. Sh.; El-Sonbati, A. Z.; El-Shahat, O.

2013-10-01

351

Magnetohydrodynamic Simulations of Solar Chromospheric Dynamics Using a Complete Electrical Conductivity Tensor  

NASA Astrophysics Data System (ADS)

A 1.5-dimensional, time-dependent magnetohydrodynamic (MHD) model that includes an energy equation and anisotropic electrical conductivity tensor for a variably ionized, multispecies plasma is presented. The model includes an algorithm that reduces the numerical dissipation rate far below the dissipation rate determined by the conductivity tensor. This is necessary for accurate calculation of resistive heating rates. The model is used to simulate the propagation of Alfvén waves launched near the base of the middle chromosphere. The background state is the FAL CM equilibrium with a vertical magnetic field. The initial magnetic energy of a wave is almost completely damped out in the chromosphere by the time the disturbance propagates a distance of one wavelength. The energy is converted mainly into thermal energy. The remainder is converted into bulk flow kinetic energy and a Poynting flux with nonzero divergence. The thermal energy is generated almost entirely by Pedersen current dissipation. The corresponding heating rates are close to the FAL CM values near the base of the middle chromosphere. Dynamo action is observed. The damping of a continuously driven Alfvén wave train is also simulated, yielding results similar to those of the single wave cases. It is the strong magnetization and weak ionization of the chromosphere that allows for strong heating by Pedersen current dissipation. This distinguishes the chromosphere from the weakly magnetized and weakly ionized photosphere, and the strongly magnetized and strongly ionized corona where Pedersen current dissipation is not significant on the length and timescales simulated.

Kazeminezhad, Farzad; Goodman, Michael L.

2006-10-01

352

Electrical conductivity of a two-dimensional model for a composite material with structural anisotropy  

NASA Astrophysics Data System (ADS)

The electrical conductivity of a structurally anisotropic two-dimensional model for a composite material is considered. The model represents an isotropic matrix with a system of nonconducting inclusions in the form of mutually perpendicular scratches of various lengths. The centers of the scratches are chaotically distributed in plane ( x, y). The approximate effective medium method is used to derive an expression for effective conductivity tensor that satisfactorily describes the electrical conductivity of this model over a wide concentration range. The model conductivity in the critical region is considered in terms of the similarity hypothesis.

Balagurov, B. Ya.

2013-08-01

353

Improvement of thermal conductivity of nano MgO/epoxy composites for electrical insulation materials  

NASA Astrophysics Data System (ADS)

In the present study the dielectric and thermal properties of nano and micro MgO / Epoxy composites were studied with different weight percentage ratios, aiming at the development of electrical insulating materials with high thermal conductivity, this can be achieved by adding a low concentration of thermally conducting but electrically insulating nanofillers such as MgO nanoparticles, the results are discussed by determining the relative permittivity, tan delta and the thermal conductivity of the tested specimens. The obtained results showed improvement in the thermal conductivity values without deteriorating the dielectric properties.

Majeed, Kawakib Jassim

2013-12-01

354

MAGNETIC RESONANCE ELECTRICAL IMPEDANCE TOMOGRAPHY (MR-EIT): A new technique for high resolution conductivity imaging  

E-print Network

MAGNETIC RESONANCE ELECTRICAL IMPEDANCE TOMOGRAPHY (MR-EIT): A new technique for high resolution field measurements are performed by using magnetic resonance imaging techniques. The conductivity resonance imaging (MRI) techniques, if the conductor contains magnetic resonance active nuclei [2

Eyüboðlu, Murat

355

Reversible temperature regulation of electrical and thermal conductivity using liquid–solid phase transitions  

E-print Network

Reversible temperature tuning of electrical and thermal conductivities of materials is of interest for many applications, including seasonal regulation of building temperature, thermal storage and sensors. Here we introduce ...

Zheng, Ruiting

356

Effect of band gap energy on the electrical conductivity in doped ZnO thin film  

NASA Astrophysics Data System (ADS)

The transparent conductive pure and doped zinc oxide thin films with aluminum, cobalt and indium were deposited by ultrasonic spray technique on glass substrate at 350 °C. This paper is to present a new approach to the description of correlation between electrical conductivity and optical gap energy with dopants' concentration of Al, Co and In. The correlation between the electrical and optical properties with doping level suggests that the electrical conductivity of the films is predominantly estimated by the band gap energy and the concentrations of Al, Co and In. The measurement in the electrical conductivity of doped films with correlation is equal to the experimental value, the error of this correlation is smaller than 13%. The minimum error value was estimated in the cobalt-doped ZnO thin films. This result indicates that such Co-doped ZnO thin films are chemically purer and have far fewer defects and less disorder owing to an almost complete chemical decomposition.

Benramache, Said; Belahssen, Okba; Ben Temam, Hachemi

2014-07-01

357

EVIDENCE FOR MICROBIAL ENHANCED ELECTRICAL CONDUCTIVITY IN HYDROCARBON-CONTAMINATED SEDIMENTS  

EPA Science Inventory

Electrical conductivity of sediments during microbial mineralization of diesel was investigated in a mesoscale column experiment consisting of biotic contaminated and uncontaminated columns. Microbial population numbers increased with a clear pattern of depth zonation within the ...

358

Comment on "Calculation of ionization balance and electrical conductivity in nonideal aluminum plasma".  

PubMed

We comment on the use of an inaccurate fitting formula for the energy-average electron-ion momentum transport cross section in the computation of electrical conductivity of nonideal aluminum plasma. PMID:15600571

Zaghloul, Mofreh R

2004-10-01

359

Mixed ionic and electronic conducting electrode studies for an alkali metal thermal to electric converter  

E-print Network

This research focuses on preparation, kinetics, and performance studies of mixed ionic and electronic conducting electrodes (MIEE) applied in an alkali metal thermal to electric converter (AMTEC). Two types of MIEE, metal/sodium titanate and metal...

Guo, Yuyan

2009-05-15

360

Substituent effects on the electrical conductivities of the phenazine derivatives  

NASA Technical Reports Server (NTRS)

The and/or photoconductivities of 16 substituted phenazines having methoxy, hydroxy, chloro, nitro, amino or t-butyl group at 1-, 2-, 1, 6- or 2,7- positions of the phenazine ring measured by using the surface type cells. The energy gaps of the dark conductivities in the range 2.0 to 2.3 were independent of the kinds and the positions of the substituent groups, although the photo-absorption wavelength of the evaporated films changed with them. No correlation between photoconductivity and fluorescence was observed. The photocurrent was affected by the position of the substituents; namely, the photocurrents of the 1,6-di-substituted phenazines. When the substituent at 1,6-positions was hydroxy or amino group, however, the photocurrents decreased. The photocurrents decreased drastically in the presence of oxygen.

Sugimoto, A.; Furuyama, S.; Inoue, H.; Imoto, E.

1984-01-01

361

Electrical conduction and dielectric breakdown in sputter-deposited silicon dioxide films on silicon  

Microsoft Academic Search

Silicon dioxide films, 8–100 nm thick, are sputter deposited in an oxygen-argon atmosphere onto a silicon substrate at 200 °C. Electrical conduction and dielectric breakdown in oxygen-argon sputter-deposited film are measured using metal-oxide-semiconductor capacitors and compared with those in thermal dioxide film. Moreover, their mechanisms are investigated. Thin oxygen-argon sputter-deposited film is found to have the same low electrical conduction

S. Suyama; A. Okamoto; T. Serikawa; H. Tanigawa

1987-01-01

362

Light transmissive electrically conductive oxide electrode formed in the presence of a stabilizing gas  

DOEpatents

A light transmissive, electrically conductive oxide is doped with a stabilizing gas such as H.sub.2 and H.sub.2 O. The oxide is formed by sputtering a light transmissive, electrically conductive oxide precursor onto a substrate at a temperature from 20.degree. C. to 300.degree. C. Sputtering occurs in a gaseous mixture including a sputtering gas and the stabilizing gas.

Tran, Nang T. (Cottage Grove, MN); Gilbert, James R. (Maplewood, MN)

1992-08-04

363

A four-layer model for interpreting electrical conductivity measurements of clay soils near agricultural lagoons  

E-print Network

interpretation model 9 Figure 2. Soil profile used as the basis for the model developed by Brune and Zheng 11 Figure 3. Relative response functions for the EM-34 meter 13 Figure 4. Topographic map of dairy 1 (elevations in meters) 28 Figure 5. Topographic... bulk electrical conductivity must be interpreted to give information on pore water quality. Brune and Zheng (1993) have developed a model for interpreting E M meter readings which produces estimates of pore water electrical conductivity and anion...

Jones, John Richard

1994-01-01

364

Electrical conductivity and equation of state measurements on planetary fluids at high pressures and temperatures  

SciTech Connect

Hugoniot equation-of-state, shock temperature, and electrical conductivity measurements are reported for fluids believed to be the primary constituents of the planets Uranus and Neptune. The equation-of-state results are compared with calculations performed using a statistical mechanical, chemical equilibrium computer code and electrical conductivities are discussed in terms of the recently measured magnetic field of Uranus. 4 refs., 2 figs., 1 tab.

Hamilton, D.C.; Nellis, W.J.; Holmes, N.C.; Radousky, H.B.; Ree, F.H.; Nicol, M.

1987-07-01

365

An evaluation of total body electrical conductivity to estimate body composition of largemouth bass  

E-print Network

AN EVALUATION OF TOTAL BODY ELECTRICAL CONDUCTIVITY TO ESTIMATE BODY COMPOSITION OF LARGEMOUTH BASS A Thesis by DANIEL EUGENE BARZIZA Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment... of the requirements for the degree of MASTER OF SCIENCE August 1998 Major Subject: Nutrition AN EVALUATION OF TOTAL BODY ELECTRICAL CONDUCTIVITY TO ESTIMATE BODY COMPOSITION OF LARGEMOUTH BASS A Thesis by DANIEL EUGENE BARZIZA Submitted to Texas Ak...

Barziza, Daniel Eugene

1998-01-01

366

Ignition Sensitivity and Electrical Conductivity of a Composite Energetic Material with Conductive Nanofillers  

SciTech Connect

The safe handling of powdered composite energetic materials requires an understanding of their response to electrostatic ignition stimuli. A binary composite comprised of Al and polytetrafluoroethylene (PTFE) was tailored for ESD ignition sensitivity with varied concentrations of highly conductive nanofillers. The goal was to control the ESD ignition response of the Al+PTFE with small concentrations of nanofillers that may not significantly affect the overall combustion performance of the mixture. The nanofillers examined include carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs). Adding CNTs created percolation at a lower volumetric percentage than GNPs and were found to be the controlling nanofiller, creating percolation for the mixture containing both CNTs and GNPs. Various mixing methods were examined. Ignition was achieved only for adding nanofillers at a volumetric percentage and mixing method that led to a bulk conductivity of approximately 5x10-3 ?S/cm.

Eric S. Collins; Brandon R. Skelton; Michelle L. Pantoya; Fahmida Irin; Micah J. Green; Michael A. Daniels

2014-12-01

367

Electrical Conduction in Native Deoxyribonucleic Acid: Hole Hopping Transfer Mechanism? Zdravko Kutnjak* and Cene Filipic  

E-print Network

Department of Physics, University of Ljubljana, Jadranska 19, 1000 Ljubljana, Slovenia Lars Nordenskio¨ld-induced superconducting [15] behavior of electric conductivity. The dc current-voltage (I-V) curves point to a remarkably dielectric constant, thus influencing the frequency and temperature dependence of the effective electric

Podgornik, Rudolf

368

Static conductivity imaging using variational gradient Bz algorithm in magnetic resonance electrical impedance tomography  

Microsoft Academic Search

A new image reconstruction algorithm is proposed to visualize static conductivity images of a subject in magnetic resonance electrical impedance tomography (MREIT). Injecting electrical current into the subject through surface electrodes, we can measure the induced internal magnetic flux density B = (Bx, By, Bz) using an MRI scanner. In this paper, we assume that only the z-component Bz is

Eun-Jae Park; Eung Je Woo; Ohin Kwon; Jin Keun Seo

2004-01-01

369

Estimating topsoil water content of clay soils with data from time-lapse electrical conductivity surveys  

Technology Transfer Automated Retrieval System (TEKTRAN)

Spatial estimation of soil water content (') at the field, hillslope, or catchment scale is required in numerous applications. Time-lapse electrical resistivity and electrical conductivity surveys were recognized as the useful source of information about both spatial variations in soil water conten...

370

Temperature and frequency dependence of electric conductivity in nano-grained SiO2 exposed to neutron irradiation  

NASA Astrophysics Data System (ADS)

We studied electric properties of SiO2 nanoparticles exposed to continuous neutron irradiation (2×1013 cm-2 s-1 neutron flux) for different periods up to 20 h and initial states. Electric properties of the samples before and after irradiation were studied in the 0.09 Hz-2.3 MHz frequency and 100-400 K temperature range. In the experiments the samples have been irradiated by up to 20 h. It has been shown that upon increasing irradiation period, electric conductivity of the samples increases. The formation of clusters in three different states and energies at low temperatures under the neutron flux effect has been revealed. In addition, activation energy was calculated from the temperature-dependent dielectric response data using the Arrhenius expression.

Huseynov, Elchin; Garibov, Adil; Mehdiyeva, Ravan

2014-10-01

371

Influence of FeO and H on the electrical conductivity of olivine  

NASA Astrophysics Data System (ADS)

The influence of Fe (iron) and H (hydrogen) on the electrical conductivity of olivine was investigated. Synthetic olivine aggregates with the XFe = Fe/(Fe + Mg) (molar ratio) = 21-64% with the water content of 84-620 ppm wt (Paterson calibration) were prepared and their electrical conductivity was measured at P = 4 GPa and T = 873-1473 K. The impedance spectroscopy was used to calculate the DC electrical conductivity. We found that electrical conductivity of samples increases with increasing FeO content in both anhydrous and hydrous olivine. However, the way in which FeO enhances electrical conductivity is different between anhydrous and hydrous olivine. In anhydrous sample, the activation energy is reduced with FeO content and hence the effect of FeO content is large at low temperatures, but its effect is small at mantle temperatures. In contrast, FeO content does not affect the activation energy in hydrous olivine, and consequently, the magnitude of FeO effect is nearly independent of temperature. For both anhydrous and hydrous olivine, the influence of FeO is only modest at high temperatures (increase in conductivity by a factor of ?2 for the increase in FeO by 20% (e.g., from 10 to 30%)). In contrast, the FeO content has relatively large effects at low temperatures for anhydrous olivine. However, the role of hydrogen is large at low temperatures and hydrogen mechanism dominates under most cases. Therefore the influence of FeO on electrical conductivity is small at all temperatures for a plausible range of water content. We conclude that the water (hydrogen) content in a terrestrial planet can be inferred from observed conductivity without substantial influence of FeO if the temperature is constrained. The present results provide a basis for the interpretation of electrical conductivity model of other planets with different FeO contents.

Dai, Lidong; Karato, Shun-ichiro

2014-12-01

372

Systems Characterization of Temperature, Ph and Electrical Conductivity in Aerobic Biodegradation of Wheat Biomass at Differing Mixing Rates  

NASA Technical Reports Server (NTRS)

The purpose of this preliminary study is to observe and relate the rate of mixing to pH and electrical conductivity in an aerobic, continuously stirred bioreactor. The objective is to use data collected from successive experiments as a means of a system characterization. Tests were conducted to obtain these data using a continuously stirred 20 L Cytostir glass reaction vessel as a bioreactor operated without built-in temperature or pH control. The tests were conducted on the lab bench at ambient temperatures. The substrate in the bioreactor was ground wheat biomass obtained from the Biomass Production Chamber at NASA Kennedy Space Center. In this study, the data reflect characteristics of the native (uninoculated) systems as well as inoculated systems. In the native systems, it was found that pi levels became stable after approximately 2 to 3 days. The electrical conductivity levels for the native systems tended to decrease over time. In contrast, ion activity was increased after the introduction of bacteria into the system. This could be correlated with the release of nutrients, due to the activity of the bacteria. Also, there were slight increases in pH in the inoculated system, a result which is expected for a system with no active pr controls. The data will be used to test a mathematical model in an automated system.

Calhoun, M.; Trotman, A.; Aglan, H.

1998-01-01

373

Effects of temperature and composition on the thermal and electrical conductivities of Ni3Al  

NASA Astrophysics Data System (ADS)

The results of a study of the thermal conductivity, electrical resistivity, and Seebeck coefficient of Ni3Al are described. The thermal and electrical conductivities are sensitive to composition and attain their maximum values in well-ordered, stoichiometric Ni3Al. Nonstoichiometry (antisite defects), and Fe (a substitutional solute) and B (an interstitial solute) contents are all about equally effective in reducing the transport properties. Even for stoichiometric Ni3Al, the temperature variation of the thermal and electrical conductivities resembles that of an alloy, and this is attributed to scattering associated with the loss of ferromagnetic order at ˜60 K. Experimental data and a theoretical analysis show that phonon conduction is an important part of the thermal conductivity and not very sensitive to composition or stoichiometry.

Williams, R. K.; Graves, R. S.; Weaver, F. J.

1987-02-01

374

Electrical Impedance Spectroscopy for Electro-Mechanical Characterization of Conductive Fabrics  

PubMed Central

When we use a conductive fabric as a pressure sensor, it is necessary to quantitatively understand its electromechanical property related with the applied pressure. We investigated electromechanical properties of three different conductive fabrics using the electrical impedance spectroscopy (EIS). We found that their electrical impedance spectra depend not only on the electrical properties of the conductive yarns, but also on their weaving structures. When we apply a mechanical tension or compression, there occur structural deformations in the conductive fabrics altering their apparent electrical impedance spectra. For a stretchable conductive fabric, the impedance magnitude increased or decreased under tension or compression, respectively. For an almost non-stretchable conductive fabric, both tension and compression resulted in decreased impedance values since the applied tension failed to elongate the fabric. To measure both tension and compression separately, it is desirable to use a stretchable conductive fabric. For any conductive fabric chosen as a pressure-sensing material, its resistivity under no loading conditions must be carefully chosen since it determines a measurable range of the impedance values subject to different amounts of loadings. We suggest the EIS method to characterize the electromechanical property of a conductive fabric in designing a thin and flexible fabric pressure sensor. PMID:24892493

Bera, Tushar Kanti; Mohamadou, Youssoufa; Lee, Kyounghun; Wi, Hun; Oh, Tong In; Woo, Eung Je; Soleimani, Manuchehr; Seo, Jin Keun

2014-01-01

375

Electrical impedance spectroscopy for electro-mechanical characterization of conductive fabrics.  

PubMed

When we use a conductive fabric as a pressure sensor, it is necessary to quantitatively understand its electromechanical property related with the applied pressure. We investigated electromechanical properties of three different conductive fabrics using the electrical impedance spectroscopy (EIS). We found that their electrical impedance spectra depend not only on the electrical properties of the conductive yarns, but also on their weaving structures. When we apply a mechanical tension or compression, there occur structural deformations in the conductive fabrics altering their apparent electrical impedance spectra. For a stretchable conductive fabric, the impedance magnitude increased or decreased under tension or compression, respectively. For an almost non-stretchable conductive fabric, both tension and compression resulted in decreased impedance values since the applied tension failed to elongate the fabric. To measure both tension and compression separately, it is desirable to use a stretchable conductive fabric. For any conductive fabric chosen as a pressure-sensing material, its resistivity under no loading conditions must be carefully chosen since it determines a measurable range of the impedance values subject to different amounts of loadings. We suggest the EIS method to characterize the electromechanical property of a conductive fabric in designing a thin and flexible fabric pressure sensor. PMID:24892493

Bera, Tushar Kanti; Mohamadou, Youssoufa; Lee, Kyounghun; Wi, Hun; Oh, Tong In; Woo, Eung Je; Soleimani, Manuchehr; Seo, Jin Keun

2014-01-01

376

Solid State Physics View of Liquid State Chemistry III. Electrical Conductance of Pure and Impure Water  

NASA Astrophysics Data System (ADS)

The ‘abnormally’ high electrical conductivity of pure water was recently studied by us using our protonic bond, trap and energy band model, with five host particles: the positive and negative protons, and the amphoteric protonic trap in three charge states, positive, neutral and negative. Our second report described the electrical charge storage capacitance of pure and impure water. This third report presents the theory of particle density and electrical conductance of pure and impure water, including the impuritons, which consist of an impurity ion bonded to a proton, proton-hole or proton trap and which significantly affect impure waters' properties.

Binbin, Jie; Chihtang, Sah

2014-04-01

377

Electrical conductivity and depth of groundwater at the Pergamino zone (Buenos Aires Province, Argentina) through vertical electrical soundings and geostatistical analysis  

NASA Astrophysics Data System (ADS)

In the humid Pampean region of Argentina, a rich agricultural zone, the periodic occurrence of droughts of different intensity is one of the most important factors in the variability of crop yield. Because complementary irrigation is a highly efficient resource to increase such yields, an understanding of groundwater resources is important. This knowledge is limited in topographically smooth zones by the absence of outcroppings and observation boreholes. Water conductivity is another limitation factor if the goal is to avoid soil degradation by irrigation and negative effects for animal and human consumption. The aquifers of the northeastern zone of the Buenos Aires province have been studied regionally, but information at the local scale is limited to sparse boreholes. In this work, a survey using vertical electrical soundings was carried out to determine the depth, thickness, and continuity of shallower aquifers. Both a mapping of the water table and the electrical conductivity distribution of free aquifers were achieved from well data and geophysical results using geostatistical techniques. Recharge areas of the aquifer were recognized as those areas with low conductivity and topographic highs. The discharge areas, mainly at the bed of the Pergamino River, have higher values of conductivity; two zones north and south of the city of Pergamino have conductivities greater than 2000 ?S cm -1. Isolines of depth to the fresh-salty water interface showed different values over the Pergamino River, with some local maxima at the swamp zone and near Pergamino.

Sainato, Claudia; Galindo, Griselda; Pomposiello, Cristina; Malleville, Horacio; de Abelleyra, Diego; Losinno, B.

2003-06-01

378

Electrical Conductivity Measurement through the Loaded Q Factor of a Resonant Cavity  

E-print Network

Research, P.O. Box 515, S. J. Campos, 12201-970 SP, Brazil Abstract=We present a method for measuring. INTRODUCTION In the method presented here, the electrical conductivity measurement of metallic materials. of the conductor penetrated by the fields due to skin effect. Now if we replace the upper disk (with conductivity R

379

How Well Does Zone Sampling Based On Soil Electrical Conductivity Maps Represent Soil Variability  

Technology Transfer Automated Retrieval System (TEKTRAN)

How Well Does Zone Sampling Based On Soil Electrical Conductivity Maps Represent Soil Variability. Dale L. Shaner A study was conducted determined if ECa-directed zone sampling could predict soil texture and soil organic matter (SOM) patterns of samples taken by a more intensive grid sample method...

380

J. Geomag. Geoelectr., 45, 707728, 1993 Constraints on Mantle Electrical Conductivity  

E-print Network

J. Geomag. Geoelectr., 45, 707­728, 1993 Constraints on Mantle Electrical Conductivity from Field's mantle to depths of at least 1800 km, is obtained by averaging published, single-site response functions in conductivity at the 660 km seismic discontinuity lowers the electrogeotherm to 1600 C at 410 km, while

Constable, Steve

381

Electrical conductivity as an indicator of iron reduction rates in abiotic and biotic systems  

E-print Network

that incorporate the stoichiometry of five different types of reactions: redox, acid-base, sorption, dissolution attributed to microbial activity, b has never been used to infer biogeochemical reaction rates quantitatively. To explore the use of electrical conductivity to measure reaction rates, we conducted iron oxide reduction

Singha, Kamini

382

Indirect Estimates of Soil Electrical Conductivity for Improved Prediction of Wheat Grain Yield  

Microsoft Academic Search

A system of midseason prediction of winter wheat grain yield based on sensed plant growth properties has been established. However, little research has been conducted to determine the relationship of grain yield, sensed plant data, and soil electrical conductivity (EC). This study was carried out to determine if soil EC could be useful in better predicting wheat grain yield. During

M. T. Humphreys; W. R. Raun; K. L. Martin; K. W. Freeman; G. V. Johnson; M. L. Stone

2005-01-01

383

Universal properties of thermal and electrical conductivity of gauge theory plasmas from holography  

E-print Network

We propose that for conformal field theories admitting gravity duals, the thermal conductivity is fixed by the central charges in a universal manner. Though we do not have a proof as yet, we have checked our proposal against several examples. This proposal, if correct, allows us to express electrical conductivity in terms of thermodynamical quantities even in the presence of chemical potential.

Sachin Jain

2010-06-08

384

Preparation and properties of electrically conducting ceramics based on indium oxide-rare earth oxides-hafnium oxides  

SciTech Connect

Electrically conducting refractory oxides based on adding indium oxide to rare earth-stabilized hafnium oxide are being studied for use in magnetohydrodynamic (MHD) generators, fuel cells, and thermoelectric generators. The use of indium oxide generally increases the electrical conductivity. The results of measurements of the electrical conductivity and data on corrosion resistance in molten salts are presented.

Marchant, D.D.; Bates, J.L.

1983-09-01

385

Effective electrical conductivity of carbon nanotube-polymer composites: a simplified model and its validation  

NASA Astrophysics Data System (ADS)

A simplified model is presented to predict the effective electrical conductivity of carbon nanotube(CNT)-polymer composite with different material proportions, which is validated by the experiments of multi-walled CNT/polydimethylsiloxane (PDMS) composites. CNTs are well dispersed in a PDMS matrix, and the mixture is then cured and cast into thin films for electrical characterization. The CNTs are assumed to be statistically uniformly distributed in the PDMS matrix with the three-dimensional (3D) waviness. As the proportion of CNTs increases to a certain level, namely the percolation threshold, the discrete CNTs start to connect with each other, forming a 3D network which exhibits a significant increase of effective electrical conductivity. The eight-chain model has been used to predict the effective electrical conductivity of the composite, in which the contact resistance between CNTs has been considered through the Simmons’ equation. The eight-chain network features can be significantly changed with the modification to mixing process, CNT length and diameter, and CNT clustering and curling. A Gaussian statistics-based formulation is used to calculate the effective length of a single CNT well dispersed in the matrix. The modeling results of effective electrical conductivity agree with the experiments very well, which are highly dependent on a contact resistance between CNTs and the waviness of the CNTs. The effect of inner-nanotube distance and diameter of CNTs on the effective electrical conductivity of the CNT/PDMS composite is also discussed.

Jang, Sung-Hwan; Yin, Huiming

2015-04-01

386

Synthesis, electrical and thermal conductivities, and potential applications of graphite fluoride fibers  

NASA Technical Reports Server (NTRS)

Graphite fluoride fibers can be produced by fluorinating pristine or intercalated graphite fibers. The higher the degree of graphitization of the fibers, the higher the temperature needed to reach the same degree of fluorination. Structural damage during high temperature fluorination can be reduced or eliminated by pretreating the fibers with bromine and/or fluorine. The electrical resistivity of the fibers was in the 0.01 to 10 to the 11th ohm-cm range. The thermal conductivity of these fibers ranged from 5 to 75 W/m-K, which is much larger than the thermal conductivity of glass (1.1 W/m-K), the commonly used fiber in epoxy composites. A composite made from graphite fluoride fibers and epoxy or PTFE may be highly thermally conducting and electrically insulating or semiconducting. The electrically insulating product may be used as heat sinks for electrical or electronic instruments.

Hung, Ching-Cheh; Long, Martin; Stahl, Mark

1988-01-01

387

Electrical conductivity and dielectric properties of PMMA/graphite nanoplatelet ensembles  

NASA Astrophysics Data System (ADS)

Poly(methyl methacrylate) (PMMA)/graphite nanoplatelet (GNP) ensembles were prepared by in situ polymerization of MMA in the presence of GNPs with the aid of sonication and heating. Electrical conductivity and dielectric properties of the ensembles were measured using the four-point probe resistivity measurement method and a Network Analyzer. The results showed that the electrical behavior of PMMA/GNP ensembles can be described well by percolation theory. The electrical conductivity of the ensemble was found to exhibit an insulator-conductor transition at a very low percolation threshold for GNPs. The percolation threshold of PMMA/GNP at room temperature was only about 1 wt% filler content, much lower than that of the ensembles filled with conventional graphite particles. Results showed that the difference in filler geometry (high aspect ratio and surface area) has a very significant effect on forming a conducting network in the PMMA matrix and improves both electrical and dielectric properties.

Xu, Ke; Erricolo, Danilo; Dutta, Mitra; Stroscio, Michael A.

2012-05-01

388

Conduction of Electrical Current to and Through the Human Body: A Review  

PubMed Central

Objective: The objective of this article is to explain ways in which electric current is conducted to and through the human body and how this influences the nature of injuries. Methods: This multidisciplinary topic is explained by first reviewing electrical and pathophysiological principles. There are discussions of how electric current is conducted through the body via air, water, earth, and man-made conductive materials. There are also discussions of skin resistance (impedance), internal body resistance, current path through the body, the let-go phenomenon, skin breakdown, electrical stimulation of skeletal muscles and nerves, cardiac dysrhythmias and arrest, and electric shock drowning. After the review of basic principles, a number of clinically relevant examples of accident mechanisms and their medical effects are discussed. Topics related to high-voltage burns include ground faults, ground potential gradient, step and touch potentials, arcs, and lightning. Results: The practicing physician will have a better understanding of electrical mechanisms of injury and their expected clinical effects. Conclusions: There are a variety of types of electrical contact, each with important characteristics. Understanding how electric current reaches and travels through the body can help the clinician understand how and why specific accidents occur and what medical and surgical problems may be expected. PMID:19907637

Fish, Raymond M.; Geddes, Leslie A.

2009-01-01

389

Field and temperature dependence of the small polaron hopping electrical conductivity in 1D disordered systems.  

PubMed

We investigate the effect of the electric field and the temperature on the electrical conductivity of one-dimensional disordered systems due to phonon assisted hopping of small polarons. The microscopic transport mechanism is treated within the framework of the generalized molecular crystal model and the Kubo formula, while percolation theoretical arguments lead to analytical expressions for the macroscopic behavior of the electrical conductivity at high (multi-phonon assisted hopping) and low (few-phonon assisted hopping) temperatures under the influence of moderate electric fields. The theoretical results are successfully applied to recent experimental findings for a wide temperature range and from low up to moderate electric fields. Comparison is made with other theories. PMID:21832371

Triberis, G P; Dimakogianni, M

2009-09-23

390

Increasing the electrical conductivity of poly(vinylidene fluoride) by KrF excimer laser irradiation  

SciTech Connect

This letter describes the increase in electrical conductivity of poly(vinylidene fluoride) induced by excimer laser irradiation with {lambda}=248 nm. The electrical conductivity was found to increase from 10{sup -13} to 10{sup -4} {omega}{sup -1} cm{sup -1}. As a result, experiments produced a transition in the property of the material from an insulator to a conductor. Optimal conditions for laser irradiation were determined in terms of the laser energy density, the repetition frequency, and the total number of laser shots. This letter also discusses the micromechanics of increasing conductivity in the light of Raman spectroscopy and x-ray photoelectron spectroscopy.

Ji Yaling; Jiang Yijian [National Center for Laser Technology, Beijing University of Technology, Beijing 100022 (China)

2006-11-27

391

Vapor sensing mechanism of acid on copper phthalocyanine thin films studied by electrical conductivity  

NASA Astrophysics Data System (ADS)

The electrical conductivity of thin films of iron phthalocyanine on glass substrates by thermal evaporation technique have been investigated. The electrical conductivity of thin films of these complexes changes when exposed to oxidizing and reducing gases such as halogens, ammonia, water and NOX. Thermal activation energy in the intrinsic region and impurity scattering region can be calculated by using Arrhenius plot. The dark conductivity and photoconductivity have been taken at different temperatures in the range 312-389 K. These films have been studied as chemical sensors for dilute sulphuric acid.

Singh, Sukhwinder; Saini, G. S. S.; Tripathi, S. K.

2013-06-01

392

Electrical conductivity of high-pressure liquid hydrogen by quantum Monte Carlo methods.  

PubMed

We compute the electrical conductivity for liquid hydrogen at high pressure using Monte Carlo techniques. The method uses coupled electron-ion Monte Carlo simulations to generate configurations of liquid hydrogen. For each configuration, correlated sampling of electrons is performed in order to calculate a set of lowest many-body eigenstates and current-current correlation functions of the system, which are summed over in the many-body Kubo formula to give ac electrical conductivity. The extrapolated dc conductivity at 3000 K for several densities shows a liquid semiconductor to liquid-metal transition at high pressure. Our results are in good agreement with shock-wave data. PMID:20366267

Lin, Fei; Morales, Miguel A; Delaney, Kris T; Pierleoni, Carlo; Martin, Richard M; Ceperley, D M

2009-12-18

393

The effect of pressure on the electrical conductivity of olivine under the hydrogen-rich conditions  

NASA Astrophysics Data System (ADS)

The influence of pressure on the hydrogen-assisted electrical conductivity in olivine has been studied under conditions of 4-10 GPa and 873-1273 K. Synthetic polycrystalline olivine samples with the water content of 160 ppm wt (Paterson calibration) were used and the electrical conductivity was determined from the results of the impedance spectroscopy. We found that the pressure reduces the hydrogen-assisted electrical conductivity, but its magnitude is small: between 4 and 10 GPa, the difference is a factor of ?2.5 for the same water content and temperature. The pressure dependence is characterized by a negative activation volume and the negative dependence of the pre-exponential factor on pressure. Such anomalous behavior is explained by a model where hydrogen-related defect is considered as a weak inclusion in a strong matrix. We use these new data to calculate the electrical conductivity contrast at the 410-km discontinuity. We found that if the water content of the mantle does not change with depth, there should be a large (a factor of ?10) drop in conductivity from above to below the 410-km discontinuity. In contrast, geophysically inferred electrical conductivity increases at 410-km suggesting the increase in water content from above to below the 410-km discontinuity. The present results are used to compare several previous results obtained at different pressures. It was shown that our results agree well with most of previous studies but not with (Yoshino et al., 2009). Possible causes for this discrepancy are discussed.

Dai, Lidong; Karato, Shun-ichiro

2014-07-01

394

Effect of strain on the electrical conductivity of a styrene-butadiene rubber  

NASA Astrophysics Data System (ADS)

When the carbon black-filled rubbers are stretched, the electrical resistivity increases at lower extension ranges, and then it decreases with further extension. This complex behavior is attributed to the morphology changes of carbon black particles during extension, i.e., breaking and forming conducting paths. In this study, highly conductive carbon blacks were compounded with high styrene content SBR matrix with contents varying from 5phr, 10phr, 15phr and 20phr. All the compounds measured the electrical resistance at room temp., 40°C, 80°C, respectively. The electrical resistances are decreased as the conductive carbon blacks are higher and temperature is increased. The electrical resistivity and tensile behaviors were investigated as a function of stretching at 80°C. The conductive carbon black-filled a styrene-butadiene rubber vulcanizate showed much higher conductivity and the electrical resistivity is more stable by increase of contents. In tensile behaviors, as the contents of conductive carbon blacks increase, it shows the increase of strength.

Kim, Young Hee; Lim, Jee Young; Jose, Jobin; Kim, Jae Young; Lee, Gi-Bbeum; Gent, Alan N.; Nah, Changwoon

2010-04-01

395

The static electrical conductivity of water-in-oil microemulsions below percolation threshold  

NASA Astrophysics Data System (ADS)

We study the static electric conductivity in water-in-oil microemulsion systems both in the droplet phase and in the vicinity of a percolation transition in the non-percolating region. We discuss the mechanisms of conduction in the two regimes. In particular, we interpret the behavior of conductivity far from percolation in terms of charge fluctuations and close to percolation in terms of collection of relaxation times connected to the presence of a polydisperse set of independent fractal clusters.

Bordi, F.; Cametti, C.; Chen, S. H.; Rouch, J.; Sciortino, F.; Tartaglia, P.

1996-02-01

396

Electrical conductivities of aluminum, copper, and tungsten observed by an underwater explosion  

SciTech Connect

Conductivities of dense aluminum, copper, and tungsten are evaluated using exploding wire discharges in water. Evolutions of the radius and the electrical resistance of exploding wire are measured together with direct pyrometric estimation of the temperature. The conductivities are evaluated based on the measurements and their density dependence is compared with theoretical predictions at a fixed temperature. The results indicate that regardless of materials, the conductivity has a minimum around 3% of solid density at temperature of 5000 K.

Sasaki, Toru [Department of Electrical Engineering, Nagaoka University of Technology, Kamitomioka 1603-1, Nagaoka, Niigata 940-2188 (Japan); Nakajima, Mitsuo; Kawamura, Tohru; Horioka, Kazuhiko [Department of Energy Sciences, Tokyo Institute of Technology, Nagatsuta 4259, Midori-ku, Yokohama 226-8502 (Japan)

2010-08-15

397

Enhancement of energy density in organic redox capacitor by improvement of electric conduction network  

NASA Astrophysics Data System (ADS)

Organic compounds have attracted attention as inexpensive and environmentally friendly active materials for energy storage devices. Among them, quinonic compounds can achieve high power capabilities because of their fast redox reactions. To utilize the organic compounds, which have a poor electrical conductivity and which are soluble in the electrolyte, the construction of electric conductive network to hold the organic compounds is necessary. In this study, we enhanced the capacity in aqueous redox-capacitors with quinonic and hydroquinonic organic compounds supported in nanoporous carbon by adding a small amount of another highly conductive carbon. The improvement of the electric conduction path enabled a high loading ratio of organic active material to nanoporous carbon (>70 wt%) in the electrode with a high utilization rate. It also achieved the high energy density of 30 Wh kg-1 in the organic redox capacitor.

Komatsu, Daiki; Tomai, Takaaki; Honma, Itaru

2015-01-01

398

Relationship between the hydraulic conductivity and electric properties for investigating the alluvium aquifer  

NASA Astrophysics Data System (ADS)

In this study, to understand relationship between hydraulic conductivity and electrical properties in alluvial aquifer, some indoor experiments and field electrical surveys were conducted. Soil sampled from alluvial aquifer and various size of quartz sand particles were saturated in NaCl solution which had 100 ohm-m. Then their porosity, hydraulic conductivity, time domain induced polarization and spectral induced polarization were measured. As a result, hydraulic conductivity and resistivity of quartz sand had proportional relation but, chargeability and phase difference of it showed small value also, hydraulic conductivity did not show clear tendency. Through this experiment, it was possible to identify which quartz sand had almost no response from induced polarization survey. Moreover, for silty sand, hydraulic conductivity and resistivity had proportional relation, hydraulic conductivity and chargeability had inverse proportional relation and hydraulic conductivity and phase difference had proportional relation. Through this experiment, silty sand showed correlation between hydraulic conductivity and electrical property. When field resistivity survey was conducted at alluvial aquifer, it showed wider range of values than the values from indoor experiment. Therefore, it is difficult to estimate accurate hydraulic conductivity of alluvial aquifer by applying hydraulic conductivity-resistivity interaction formula from indoor experiment to field resistivity survey. However, through comparison between resistivity survey result and borehole data, it was acknowledged that parts with low resistivity were clayey stratum and parts with high resistivity were gravel stratum. Consequently, estimating relative hydraulic conductivity distribution was able to be determined. However, followed by result of time domain induced polarization survey, clayey sand stratum did not have high chargeability. Through this field induced polarization survey experiment, it looks difficult to estimate hydraulic conductivity distribution.

Park, Samgyu; Kim, Soodong; Hamm, Se-Yeong

2014-05-01

399

Investigating Electricity: Testing for Electrical Conductivity (Conductors and Insulators) Using a Variety of Materials  

NSDL National Science Digital Library

In this lab, the students will test a variety of materials to discover which items are conductors and which items are insulators. They will discuss, classify, record data, and develop new questions relating to electricity.

400

Ac Conductivity and Electrical Relaxation in ion conducting Li4Nb1-x Zn2.5xP3O12 glasses  

NASA Astrophysics Data System (ADS)

We report the electrical relaxation in ion conducting Li4Nb1-xZn 2.5xP3O12. These glasses were prepared by conventional melt quenching method. The electrical relaxation has been investigated both in ac conductivity as well as electric modulus formalisms. The conductivity isotherms show a transition from frequency independent dc region to dispersive region where the conductivity increases with increasing frequency. The power law dispersion of the ac conductivity scales regardless of the variation of x in TTSP scheme, and therefore suggests that relaxation in these glasses is independent of the temperature and composition..

Rathan, S. Vinoth; Shah, Aashaq Hussain; Govindaraj, G.

2011-07-01

401

Laboratory and Field Measurements of Soil Bulk Electrical Conductivity Using Time Domain Reflectometry  

NASA Astrophysics Data System (ADS)

As the increasing of contamination in soil and groundwater, there is a demand for fast, accurate, and cost-effective techniques for contaminated site investigation. Time domain reflectometry (TDR) is a nondestructive geophysical method that allows, in real time, simultaneous estimation of both the dielectric constant and the bulk soil electrical conductivity (EC). On such bases, TDR is a technique that could potentially be adapted for continuous monitoring of solute contaminants in soil and water. The objective of this study is to assess the performance of TDR for estimating the EC and the solute concentration through the laboratory experiments and then applied it to a field of mercury contamination in the sediments. Measurement of EC using TDR is based on the attenuation of the applied voltage as it traverses the medium of interest. Once the geometric constant of the probe can be determined and the mismatch of the TDR instrument can be corrected during the experimental setup, EC can easily be accurately evaluated through a single TDR measurement on the considered sample. The results obtained from the laboratory experiments showed the good agreement between the TDR measurement and conductivity meter, and the linear relationship between EC and solute concentration is also validated. Given a specific concentration of solution, the decrease of EC with the decrease of water content followed Archie's law. Experiments with releasing a pulse and continuous potassium nitrate solutions into a soil column were conducted to demonstrate the TDR capability of real time monitoring. The results showed that the breakthrough curve (BC) can be accurately and clearly delineated by the TDR measurement. In this study, the TDR application was also extended to a contaminated site in southern Taiwan. The mercury contaminated sediments were deposited at the bottom of saline lakes and the TDR probes were modified to overcome the measurement under the water. The field work showed that the spatial distribution of relative-high mercury concentrations could be identified by TDR. Although the absolute mercury concentration is still undetermined, but the feasibility of using TDR as a reference tool for contaminant site investigation and self-assessment of remediation was successfully demonstrated.

Hsu, S.; Chiu, Y.

2013-12-01

402

Towards practical application of paper based printed circuits: capillarity effectively enhances conductivity of the thermoplastic electrically conductive adhesives.  

PubMed

Direct printing nanoparticle-based conductive inks onto paper substrates has encountered difficulties e.g. the nanoparticles are prone to penetrate into the pores of the paper and become partially segmented, and the necessary low-temperature-sintering process is harmful to the dimension-stability of paper. Here we prototyped the paper-based circuit substrate in combination with printed thermoplastic electrically conductive adhesives (ECA), which takes the advantage of the capillarity of paper and thus both the conductivity and mechanical robustness of the printed circuits were drastically improved without sintering process. For instance, the electrical resistivity of the ECA specimen on a pulp paper (6 × 10(-5)? · cm, with 50 wt% loading of Ag) was only 14% of that on PET film than that on PET film. This improvement has been found directly related to the sizing degree of paper, in agreement with the effective medium approximation simulation results in this work. The thermoplastic nature also enables excellent mechanical strength of the printed ECA to resist repeated folding. Considering the generality of the process and the wide acceptance of ECA technique in the modern electronic packages, this method may find vast applications in e.g. circuit boards, capacitive touch pads, and radio frequency identification antennas, which have been prototyped in the manuscript. PMID:25182052

Wu, Haoyi; Chiang, Sum Wai; Lin, Wei; Yang, Cheng; Li, Zhuo; Liu, Jingping; Cui, Xiaoya; Kang, Feiyu; Wong, Ching Ping

2014-01-01

403

Towards Practical Application of Paper based Printed Circuits: Capillarity Effectively Enhances Conductivity of the Thermoplastic Electrically Conductive Adhesives  

NASA Astrophysics Data System (ADS)

Direct printing nanoparticle-based conductive inks onto paper substrates has encountered difficulties e.g. the nanoparticles are prone to penetrate into the pores of the paper and become partially segmented, and the necessary low-temperature-sintering process is harmful to the dimension-stability of paper. Here we prototyped the paper-based circuit substrate in combination with printed thermoplastic electrically conductive adhesives (ECA), which takes the advantage of the capillarity of paper and thus both the conductivity and mechanical robustness of the printed circuitsweredrastically improved without sintering process. For instance, the electrical resistivity of the ECA specimen on a pulp paper (6 × 10-5?.cm, with 50 wt% loading of Ag) was only 14% of that on PET film than that on PET film. This improvement has been found directly related to the sizing degree of paper, in agreement with the effective medium approximation simulation results in this work. The thermoplastic nature also enables excellent mechanical strength of the printed ECA to resist repeated folding. Considering the generality of the process and the wide acceptance of ECA technique in the modern electronic packages, this method may find vast applications in e.g. circuit boards, capacitive touch pads, and radio frequency identification antennas, which have been prototyped in the manuscript.

Wu, Haoyi; Chiang, Sum Wai; Lin, Wei; Yang, Cheng; Li, Zhuo; Liu, Jingping; Cui, Xiaoya; Kang, Feiyu; Wong, Ching Ping

2014-09-01

404

Towards Practical Application of Paper based Printed Circuits: Capillarity Effectively Enhances Conductivity of the Thermoplastic Electrically Conductive Adhesives  

PubMed Central

Direct printing nanoparticle-based conductive inks onto paper substrates has encountered difficulties e.g. the nanoparticles are prone to penetrate into the pores of the paper and become partially segmented, and the necessary low-temperature-sintering process is harmful to the dimension-stability of paper. Here we prototyped the paper-based circuit substrate in combination with printed thermoplastic electrically conductive adhesives (ECA), which takes the advantage of the capillarity of paper and thus both the conductivity and mechanical robustness of the printed circuitsweredrastically improved without sintering process. For instance, the electrical resistivity of the ECA specimen on a pulp paper (6 × 10?5?·cm, with 50?wt% loading of Ag) was only 14% of that on PET film than that on PET film. This improvement has been found directly related to the sizing degree of paper, in agreement with the effective medium approximation simulation results in this work. The thermoplastic nature also enables excellent mechanical strength of the printed ECA to resist repeated folding. Considering the generality of the process and the wide acceptance of ECA technique in the modern electronic packages, this method may find vast applications in e.g. circuit boards, capacitive touch pads, and radio frequency identification antennas, which have been prototyped in the manuscript. PMID:25182052

Wu, Haoyi; Chiang, Sum Wai; Lin, Wei; Yang, Cheng; Li, Zhuo; Liu, Jingping; Cui, Xiaoya; Kang, Feiyu; Wong, Ching Ping

2014-01-01

405

Intracranial Electrical Impedance Tomography: A Method of Continuous Monitoring in an Animal Model of Head Trauma  

PubMed Central

Background Electrical impedance tomography (EIT) is a method that can render continuous graphical cross-sectional images of the brain’s electrical properties. Because these properties can be altered by variations in water content, shifts in Na+ concentration, bleeding, and mass deformation, EIT has promise as a sensitive instrument for head injury monitoring to improve early recognition of deterioration, and to observe the benefits of therapeutic intervention. This study presents a swine model of head injury used to determine the detection capabilities of an inexpensive bed side EIT monitoring system with a novel intracranial pressure (ICP)/EIT electrode combination sensor on induced intraparenchymal mass effect, intraparenchymal hemorrhage, and cessation of brain blood flow. Conductivity difference images are shown in conjunction with ICP data, confirming the effects. Methods Eight domestic piglets (3–4 weeks old, mean 10kg), under general anesthesia, were subjected to four injuries: induced intraparenchymal mass effect using an inflated, and later, deflated 0.15mL Fogarty catheter; hemorrhage by intraparenchymal injection of 1mL arterial blood; and ischemia/infarction by euthanasia. EIT and ICP data were recorded 10 minutes prior to inducing the injury until 10 minutes post-injury. Continuous EIT and ICP monitoring were facilitated by a ring of circumferentially disposed cranial Ag/AgCl electrodes and one intraparenchymal ICP/EIT sensor-electrode combination. Data were recorded at 100 Hz. Two-dimensional tomographic conductivity difference (??) images, rendered using data before and after an injury, were displayed in real-time on an axial circular mesh. Regions of interest (ROI) within the images were automatically selected as the upper or lower 5% of conductivity data depending upon the nature of the injury. Mean ?? within the ROIs and background were statistically analyzed. ROI ?? was compared to the background ?? after an injury event using an unpaired, unequal variance t-test. Conductivity change within an ROI post- injury was likewise compared to the same ROI prior to the injury utilizing unpaired t-tests with unequal variance. Results Eight animal subjects were studied, each undergoing four injury events including euthanasia. Changes in conductivity due to injury showed expected pathophysiologic effects in an ROI identified within the middle of the left hemisphere; this localization is reasonable given the actual site of injury (left hemisphere) and spatial warping associated with estimating a 3D conductivity distribution in two dimensional space. Results are shown as mean ± 1 SD. When averaged across all eight animals, balloon inflation caused the mean ?? within the ROI to shift by ?11.4 ± 10.9 mS/m; balloon deflation by +9.4 ± 8.8 mS/m; blood injection by +19.5 ± 11.5 mS/m; death by ?12.6 ± 13.2 mS/m. All induced injuries were detectable to statistical significance (p < 0.0001). Conclusion This study confirms that the bed-side EIT system with ICP/EIT combination sensor can detect induced trauma. Such a technique may hold promise for further research in the monitoring and management of traumatically brain-injured individuals. PMID:23842194

Manwaring, Preston K.; Moodie, Karen L.; Hartov, Alexander; Manwaring, Kim H.; Halter, Ryan J.

2013-01-01

406

Electrical conductivity images of Quaternary faults and Tertiary detachments in the California Basin and Range  

NASA Astrophysics Data System (ADS)

Comparison of an electrical resistivity section derived from magnetotelluric (MT) data to a geologic section extending eastward from the Sierra Nevada near latitude 36°20'N shows that the crust is dominated by steeply dipping conductive features that correlate with active strike-slip faults. While there is a subhorizontal conductor at a depth ˜20 km beneath some of the profile, it is broken by vertical structures associated with the active strike-slip faults. The continuous subhorizontal anomalies in the lower crust typically observed in extensional regions are therefore absent in the resistivity section. The present-day strike-slip tectonic regime as indicated by geodetic data in this part of the Basin and Range is not producing features that could be inferred to indicate subhorizontal shear zones resulting from lateral crustal flow during extension. Because the Miocene tectonic regime resulted in the formation of metamorphic core complexes and thus was accompanied by such flow, the present regime appears to represent a fundamental transition in the mode of crustal deformation in the region. A serendipitous result of our study was the identification on resistivity sections of carbonate aquifers in the upper crust. Comparison of resistivities from the MT section to measured fluid resistivities from springs and boreholes suggests that the aquifers must be heterogeneous, with more saline brines occupying the deepest portions of the carbonates.

Park, Stephen K.; Wernicke, Brian

2003-08-01

407

The electrical conductivities of candidate beam-waveguide antenna shroud materials  

NASA Technical Reports Server (NTRS)

The shroud on the beam-waveguide (BWG) antenna at DSS 13 is made from highly magnetic American Society for Testing and Materials (ASTM) A36 steel. Measurements at 8.42 GHz showed that this material (with paint) has a very poor electrical conductivity that is 600 times worse than aluminum. In cases where the BWG mirrors might be slightly misaligned, unintentional illumination and poor electrical conductivity of the shroud walls can cause system noise temperature to be increased significantly. This potential increase of noise temperature contribution can be reduced through the use of better conductivity materials for the shroud walls. An alternative is to attempt to improve the conductivity of the currently used ASTM A36 steel by means of some type of plating, surface treatment, or high-conductivity paints. This article presents the results of a study made to find improved materials for future shrouds and mirror supports.

Otoshi, T. Y.; Franco, M. M.

1994-01-01

408

Electrical conductivity and phase transition studies of TiO2-BaO system  

NASA Astrophysics Data System (ADS)

The solid solution of BaTiO3 was prepared by conventional solid state reaction. The electrical conductivity of TiO2-BaO system has been studied at different temperatures for various molar ratios. The isothermal conductivity increases with BaO concentration due to the vacancy migration phenomenon. It has been found that the electrical conductivity after attaining a maximum value at 240°C decreases with increase in temperature due to the collapse of the fluorite framework. A second rise in conductivity in the temperature range 470-540°C indicates the phase transition of TiO2 from anatase to rutile. AC Impedance measurements proved that the oxide ion conductivity predominantly arises from the grain contribution. The sample characterization and the study of phase transition changes were done by using XRD, FT-IR and DSC measurements. On increasing the concentration of BaO the transition temperature shifts towards higher side.

Beg, Saba; Haneef, Sadaf

2015-01-01

409

High and highly anisotropic electrical conductivity of the asthenosphere due to hydrogen diffusion in olivine  

NASA Astrophysics Data System (ADS)

Experimental studies on electrical conductivity in hydrated olivine had been made only at relatively low temperatures. The extrapolation of these data to asthenosphere temperatures shows that explaining high and highly anisotropic conductivity by hydrogen is difficult. We present new experimental results on the electrical conductivity in hydrated olivine single crystals measured under a broader temperature range than before (T (temperature) = 573-1373 K at P (pressure) = 4 GPa). The new results agree well with the previous results at low temperatures (T < 900 K), whereas at higher temperatures (T > 1000 K) substantial deviations from the previous results are observed: (i) anisotropy in conductivity increases with temperature, and (ii) activation energies at high temperature regime are substantially higher than those at lower T. The high temperature behavior is consistent with a model invoking diffusion of two-protons at M-site vacancy, whereas the low temperature behavior suggests conduction by more mobile species such as free proton. The present results (i) explain the discrepancy between different previous studies conducted under different temperature regimes, and (ii) show that most of geophysical observations on the electrical conductivity in the asthenosphere including the high and highly anisotropic conductivity can be explained by high water content in the asthenosphere that is consistent with the geochemical model. Combining with a previous model of low seismic wave velocity of the asthenosphere, a subsolidus model invoking the role of hydrogen provides a unified explanation for the geophysical anomalies of the asthenosphere.

Dai, Lidong; Karato, Shun-ichiro

2014-12-01

410

The Electrical and Thermal Conductivity of Woven Pristine and Intercalated Graphite Fiber-Polymer Composites  

NASA Technical Reports Server (NTRS)

A series of woven fabric laminar composite plates and narrow strips were fabricated from a variety of pitch-based pristine and bromine intercalated graphite fibers in an attempt to determine the influence of the weave on the electrical and thermal conduction. It was found generally that these materials can be treated as if they are homogeneous plates. The rule of mixtures describes the resistivity of the composite fairly well if it is realized that only the component of the fibers normal to the equipotential surface will conduct current. When the composite is narrow with respect to the fiber weave, however, there is a marked angular dependence of the resistance which was well modeled by assuming that the current follows only along the fibers (and not across them in a transverse direction), and that the contact resistance among the fibers in the composite is negligible. The thermal conductivity of composites made from less conductive fibers more closely followed the rule of mixtures than that of the high conductivity fibers, though this is thought to be an artifact of the measurement technique. Electrical and thermal anisotropy could be induced in a particular region of the structure by weaving together high and low conductivity fibers in different directions, though this must be done throughout all of the layers of the structure as interlaminar conduction precludes having only the top layer carry the anisotropy. The anisotropy in the thermal conductivity is considerably less than either that predicted by the rule of mixtures or the electrical resistivity.

Gaier, James R.; Vandenburg, Yvonne Yoder; Berkebile, Steven; Stueben, Heather; Balagadde, Frederick

2002-01-01

411

Electrical conductivity measurement of excised human metastatic liver tumours before and after thermal ablation  

PubMed Central

We measured the ex vivo electrical conductivity of eight human metastatic liver tumours and six normal liver tissue samples from six patients using the four electrode method over the frequency range 10 Hz to 1 MHz. In addition, in a single patient we measured the electrical conductivity before and after the thermal ablation of normal and tumour tissue. The average conductivity of tumour tissue was significantly higher than normal tissue over the entire frequency range (from 4.11 versus 0.75 mS cm?1 at 10 Hz, to 5.33 versus 2.88 mS cm?1 at 1 MHz). We found no significant correlation between tumour size and measured electrical conductivity. While before ablation tumour tissue had considerably higher conductivity than normal tissue, the two had similar conductivity throughout the frequency range after ablation. Tumour tissue conductivity changed by +25% and ?7% at 10 Hz and 1 MHz after ablation (0.23?0.29 at 10 Hz, and 0.43?0.40 at 1 MHz), while normal tissue conductivity increased by +270% and +10% at 10 Hz and 1 MHz (0.09?0.32 at 10 Hz and 0.37?0.41 at 1 MHz). These data can potentially be used to differentiate tumour from normal tissue diagnostically. PMID:19349647

Haemmerich, Dieter; Schutt, David J; Wright, Andrew W; Webster, John G; Mahvi, David M

2009-01-01

412

Electrical conductivity of fluid-bearing quartzite at high pressure and high temperature  

NASA Astrophysics Data System (ADS)

It has been reported that the electrical conductivities determined by magnetotelluric methods are much higher than those determined by dry laboratory sample of crustal rocks (e.g., Shankland and Ander, 1983). The possible reasons of the high-conductivity anomaly regions are interconnected graphite films, partial melt, and aqueous fluid (e.g., Glover and Vine, 1994). Because the solubility of silicate component in the aqueous fluid should increase with increasing pressure, the electrical conductivity of fluid-bearing rocks can be higher at pressure of the lower crust even if there is no brine. To clarify the effect of the soluble ionic species in aqueous fluid on the bulk rock conductivity, we measured the electrical conductivity of fluid-bearing quartzite as functions of temperature and fluid content at high pressure. Based on the result, we discuss the fluid content in the crust. High-pressure experiments were conducted using a DIA-type high-pressure apparatus. Pressure medium is pyrophyllite and heater is graphite. The starting materials were mixture of quartz powder plus silicic acid, or quartz aggregate synthesized using Piston-cylinder apparatus plus silicic acid. Electrical conductivity was determined by impedance spectroscopy method. To prevent a loss of water during the electrical conductivity measurements, we used a diamond single crystal capsule. The pressure is 1 GPa, and temperature range is 700-1100K. The texture of the recovered samples was observed using field-emission scanning electron microscope, and the fluid content was measured from the obtained SEM images. The electrical conductivity of fluid-bearing quartzite (fluid fraction=0.29) is about 4 orders of magnitude higher than that of dry quartzite at 1000K. Our result suggests that the observational electrical conductivity at Tohoku, Japan (Ogawa et al. 2001) and New Zealand (Wannamaker et al. 2009) in the middle crust is unable to account for quartz plus H2O. Therefore, plausible explanations of high-conductivity anomaly are presence of saline fluid and/or the other ionic species.

Shimojuku, A.; Yoshino, T.; Yamazaki, D.

2010-12-01

413

Using Specific Electrical Conductance to Compare Rainfall Runoff in NH Urban and Rural Catchments  

NASA Astrophysics Data System (ADS)

Chemical hydrograph separation has typically relied on specific solutes or isotopic tracers however, the use of specific electrical conductance (EC) from simple water sensors is more rare. This is surprising given how common high temporal resolution EC data are. We used a two-component hydrograph separation during rain events in different watersheds throughout New Hampshire, U.S.A. to test the performance of EC as a tracer of storm events across different watershed types, and to compare runoff generation in these different systems. The area of the watersheds varied from 0.4 sq. km to 2644 sq. km. All watersheds were dominated by forested land cover with varying levels of development and agricultural use. The water EC was used as a continuous tracer of 'new' water during the storm hydrographs. We hypothesized that earlier and higher new water peaks could be the result of infiltration excess runoff and that urban areas, with higher percent impervious surface, would exhibit faster and greater amplitude response to rain events. While other studies have used EC as a water tracer, none have tested these methods on such a large and diverse scale. Water isotopes, oxygen-18 (18O) and deuterium (2H) were used to compare hydrograph separation results with those of the specific conductance. The two tracers produced slightly different results, with EC generally predicting greater new water contributions to peak runoff. This raises questions about the accuracy of EC-derived estimates of new water contributions to storm runoff, however the EC results will still be useful in cross-site comparisons of watershed controls on streamflow generation.

Hyde, E. A.; Green, M.; Boyer, J. N.; Volitis, E.

2013-12-01

414

Reinforced carbon nanotubes as electrically conducting and flexible films for space applications.  

PubMed

Chemical vapor deposition (CVD)-grown entangled carbon nanotube (CNT) sheets are characterized by high electrical conductivity and durability to bending and folding. However, since freestanding CNT sheets are mechanically weak, they cannot be used as stand-alone flexible films. In this work, polyimide (PI) infiltration into entangled cup-stacked CNT (CSCNT) sheets was studied to form electrically conducting, robust, and flexible films for space applications. The infiltration process preserved CNTs' advantageous properties (i.e., conductivity and flexibility), prevented CNT agglomeration, and enabled CNT patterning. In particular, the CNT-PI films exhibited ohmic electrical conductance in both the lateral and vertical directions, with a sheet resistivity as low as 122 ?/?, similar to that of as-grown CNT sheets, with minimal effect of the insulating matrix. Moreover, this high conductivity was preserved under mechanical and thermal manipulations. These properties make the reported CNT-PI films excellent candidates for applications where flexibility, thermal stability, and electrical conductivity are required. Particularly, the developed CNT-PI films were found to be durable in space environment hazards such as high vacuum, thermal cycling, and ionizing radiation, and hence they are suggested as an alternative for the electrostatic discharge (ESD) protection layer in spacecraft thermal blankets. PMID:25366559

Atar, Nurit; Grossman, Eitan; Gouzman, Irina; Bolker, Asaf; Hanein, Yael

2014-11-26

415

Surface electrical conductivity of single crystal spinel in cesium vapor. Final report  

SciTech Connect

The operation of a thermionic fuel element (TFE) requires the maintenance of good electrical resistance between the anode and cathode, and between the electrodes and the TFE body. A program of research was established as part of the TOPAZ International Program (TIP) with the purpose of investigating the degradation of TFE electrical insulators. The major emphasis of this research has been on the interactions of oxide ceramics with cesium (Cs) vapor, and the resurfacing decrease of surface resistivity. Previous work has studied the surface electrical conductivity of sapphire exposed to Cs. In this report the authors describe the results of an experimental investigation of the surface electrical conductivity of single crystal magnesium aluminate spinel at temperatures ranging from 573K to 923K, in the presence of cesium vapor at pressures up to 1 Torr. The interest in spinel has arisen in view of its apparent resistance to radiation damage.

Agnew, P.; Ing, J.L.

1995-04-02

416

Electrical conductivity modeling and research of polypropylene composites filled with carbon black  

NASA Astrophysics Data System (ADS)

Composites of polypropylene filled with carbon black (PP/CB composite) at different concentrations were prepared by melt mixing followed by compression molding. The dependence of electrical resistance on the filler mass fraction was experimentally received. It was shown that the received dependence had the threshold character. The composite kept dielectric properties at the filler concentration below the threshold and at the concentration above the threshold the electrical resistance decreased more than on 8-10 orders. The theoretical description of electrical conductivity of the composite was offered. Experimental data of the dependence between electrical resistance and the filler mass fraction agreed with the theoretical. The process of conductivity in the PP/CB composite was simulated by means of the Monte-Carlo method for threshold mass fraction estimation.

Stepashkina, A. S.; Tsobkallo, E. S.; Alyoshin, A. N.

2014-12-01

417

Mechanical properties and electrical conductivity of Al 6101 and 6201 alloys processed by hydro-extrusion  

NASA Astrophysics Data System (ADS)

The aim of this work was to produce a material with high strength and electrical conductivity. Two aluminium alloys: Al 6101 and 6201 were used for investigation. Improvement of mechanical properties was obtained by severe plastic deformation, using Hydrostatic Extrusion (HE). To examine mechanical properties of the materials microhardness and tensile tests were carried out. Furthermore, the microstructure analysis was carried out using TEM and light microscopy. Electrical conductivity of materials was measured by 4-wire method. It was found that in the material processed by HE tensile strength and microhardness increased about twice. The biggest strength of 356 MPa was obtained for alloy 6201 after HE. In this case the reduction of a diameters from 20 to 5 mm was used. Examination of the microstructure revealed that as a result of HE grain size refinement to 0.5 micrometer occurred. It was also found that the material has the electric conductivity of about 52% IACS.

Pakiela, Z.; Ludwichowska, K.; Ferenc, J.; Kulczyk, M.

2014-08-01

418

Mechanically robust, electrically conductive ultralow-density carbon nanotube-based aerogels  

DOEpatents

A method of making a mechanically robust, electrically conductive ultralow-density carbon nanotube-based aerogel, including the steps of dispersing nanotubes in an aqueous media or other media to form a suspension, adding reactants and catalyst to the suspension to create a reaction mixture, curing the reaction mixture to form a wet gel, drying the wet gel to produce a dry gel, and pyrolyzing the dry gel to produce the mechanically robust, electrically conductive ultralow-density carbon nanotube-based aerogel. The aerogel is mechanically robust, electrically conductive, and ultralow-density, and is made of a porous carbon material having 5 to 95% by weight carbon nanotubes and 5 to 95% carbon binder.

Worsley, Marcus A; Baumann, Theodore F; Satcher, Jr., Joe H

2014-04-01

419

Quantum transport in strongly disordered crystals: Electrical conductivity with large negative vertex corrections  

NASA Astrophysics Data System (ADS)

We propose a renormalization scheme of the Kubo formula for the electrical conductivity with multiple backscatterings contributing to the electron-hole irreducible vertex derived from the asymptotic limit to high spatial dimensions. We use this vertex to represent the two-particle Green function via a symmetrized Bethe-Salpeter equation in momentum space. We further utilize the dominance of a pole in the irreducible vertex to an approximate diagonalization of the Bethe-Salpeter equation and a non-perturbative representation of the electron-hole correlation function. The latter function is then used to derive a compact representation for the electrical conductivity at zero temperature without the necessity to evaluate separately the Drude term and vertex corrections. The electrical conductivity calculated in this way remains nonnegative also in the strongly disordered regime where the localization effects become significant and the negative vertex corrections in the standard Kubo formula overweight the Drude term.

Janiš, Václav; Pokorný, Vladislav

2012-12-01

420

Modeling electric conduction in composite materials based on polypropylene and carbon black  

NASA Astrophysics Data System (ADS)

We have created a composite material based on polypropylene (PP) with carbon black as the filler. The dependence of the electric resistivity of the composite on the filler mass fraction has been experimentally studied. It is established that this dependence has a threshold character and the material retains dielectric properties at filler concentrations below the percolation threshold. Above the threshold, the resistivity drops by from eight to ten orders of magnitude. A theoretical description of the electric conduction of the composite is proposed, and it is shown that theoretical values of the conductivity quite satisfactorily coincide with experimental data. The process of electric conduction of the composite material has been simulated in order to determine the percolation threshold by the Monte Carlo method.

Stepashkina, A. S.; Tsobkallo, E. S.; Moskalyuk, O. A.; Aleshin, A. N.

2015-01-01

421

Numerical investigation of entropy generation in unsteady MHD generalized Couette flow with variable electrical conductivity.  

PubMed

The thermodynamic second law analysis is utilized to investigate the inherent irreversibility in an unsteady hydromagnetic generalized Couette flow with variable electrical conductivity in the presence of induced electric field. Based on some simplified assumption, the model nonlinear governing equations are obtained and solved numerically using semidiscretization finite difference techniques. Effects of various thermophysical parameters on the fluid velocity, temperature, current density, skin friction, the Nusselt number, entropy generation number, and the Bejan number are presented graphically and discussed quantitatively. PMID:23956691

Chinyoka, T; Makinde, O D

2013-01-01

422

Critical review of electrical conductivity measurements and charge distribution analysis of magnesium oxide  

Microsoft Academic Search

The electrical conductivity sigma of MgO single crystals shows a sharp increase at 500-800°C, in particular of sigma surface, generally attributed to surface contamination. Charge Distribution Analysis (CDA), a new technique providing information on fundamental properties that was previously unavailable, allows for the determination of surface charges, their sign and associated internal electric field. Data on 99.99% purity, arc-fusion grown

Friedemann Freund; Minoru M. Freund; François Batllo

1993-01-01

423

Numerical Investigation of Entropy Generation in Unsteady MHD Generalized Couette Flow with Variable Electrical Conductivity  

PubMed Central

The thermodynamic second law analysis is utilized to investigate the inherent irreversibility in an unsteady hydromagnetic generalized Couette flow with variable electrical conductivity in the presence of induced electric field. Based on some simplified assumption, the model nonlinear governing equations are obtained and solved numerically using semidiscretization finite difference techniques. Effects of various thermophysical parameters on the fluid velocity, temperature, current density, skin friction, the Nusselt number, entropy generation number, and the Bejan number are presented graphically and discussed quantitatively. PMID:23956691

Chinyoka, T.; Makinde, O. D.

2013-01-01

424

Hygrothermal Stability of Electrical Contacts Made from Silver and Graphite Electrically Conductive Pastes  

E-print Network

, University at Buffalo, State University of New York, Buffalo, NY14260-4400, USA. 2.--E-mail: ddlchung@buffalo in water at 15°C and 40°C. The pastes are silver paint, silver paint with a nonconductive epoxy overcoat is even less durable than silver epoxy, due to its being water based. Key words: Electrical contact

Chung, Deborah D.L.

425

Natural rubber electrical conduction mechanism in high and low electric fields  

Microsoft Academic Search

The services in energized lines become more and more indispensable and its efficiency depends on the electrical worker who is involved in such activity. The efficiency of such work highly depends on the worker's safety, which is protected by tools such as gloves, sleeves, blankets and flexible coverings among other manufactured natural-rubber goods. Use, storage and maintenance of these tools

E. L. Kowalski; R. Robert; J. Tomioka; Teixeira Junior; J. C. Tosin; R. E. Clerise; O. E. Filho

2005-01-01

426

The electrical conductivity during incipient melting in the oceanic low velocity zone  

PubMed Central

A low viscosity layer in the upper mantle, the Asthenosphere, is a requirement for plate tectonics1. The seismic low velocities and the high electrical conductivities of the Asthenosphere are attributed either to sub-solidus water-related defects in olivine minerals2-4 or to a few volume percents of partial melt5-8 but these two interpretations have shortcomings: (1) The amount of H2O stored in olivine is not expected to be higher than 50 ppm due to partitioning with other mantle phases9, including pargasite amphibole at moderate temperatures10, and partial melting at high temperatures9; (2) elevated melt volume fractions are impeded by the too cold temperatures prevailing in the Asthenosphere and by the high melt mobility that can lead to gravitational segregation11,12. Here we determined the electrical conductivity of CO2-H2O-rich melts, typically produced at the onset of mantle melting. Electrical conductivity modestly increases with moderate amounts of H2O and CO2 but it dramatically increases as CO2 content exceeds 6 wt% in the melt. Incipient melts, long-expected to prevail in the asthenosphere10,13-15, can therefore trigger its high electrical conductivities. Considering depleted and enriched mantle abundances in H2O and CO2 and their effect on the petrology of incipient melting, we calculated conductivity profiles across the Asthenosphere for various plate ages. Several electrical discontinuities are predicted and match geophysical observations in a consistent petrological and geochemical framework. In moderately aged plates (>5Ma), incipient melts most likely trigger both the seismic low velocities and the high electrical conductivities in the upper part of the asthenosphere, whereas for young plates4, where seamount volcanism occurs6, higher degree of melting is expected. PMID:24784219

Sifré, David; Gardés, Emmanuel; Massuyeau, Malcolm; Hashim, Leila; Hier-Majumder, Saswata; Gaillard, Fabrice

2014-01-01

427

Electrical conductivity during incipient melting in the oceanic low-velocity zone.  

PubMed

The low-viscosity layer in the upper mantle, the asthenosphere, is a requirement for plate tectonics. The seismic low velocities and the high electrical conductivities of the asthenosphere are attributed either to subsolidus, water-related defects in olivine minerals or to a few volume per cent of partial melt, but these two interpretations have two shortcomings. First, the amount of water stored in olivine is not expected to be higher than 50 parts per million owing to partitioning with other mantle phases (including pargasite amphibole at moderate temperatures) and partial melting at high temperatures. Second, elevated melt volume fractions are impeded by the temperatures prevailing in the asthenosphere, which are too low, and by the melt mobility, which is high and can lead to gravitational segregation. Here we determine the electrical conductivity of carbon-dioxide-rich and water-rich melts, typically produced at the onset of mantle melting. Electrical conductivity increases modestly with moderate amounts of water and carbon dioxide, but it increases drastically once the carbon dioxide content exceeds six weight per cent in the melt. Incipient melts, long-expected to prevail in the asthenosphere, can therefore produce high electrical conductivities there. Taking into account variable degrees of depletion of the mantle in water and carbon dioxide, and their effect on the petrology of incipient melting, we calculated conductivity profiles across the asthenosphere for various tectonic plate ages. Several electrical discontinuities are predicted and match geophysical observations in a consistent petrological and geochemical framework. In moderately aged plates (more than five million years old), incipient melts probably trigger both the seismic low velocities and the high electrical conductivities in the upper part of the asthenosphere, whereas in young plates, where seamount volcanism occurs, a higher degree of melting is expected. PMID:24784219

Sifré, David; Gardés, Emmanuel; Massuyeau, Malcolm; Hashim, Leila; Hier-Majumder, Saswata; Gaillard, Fabrice

2014-05-01

428

Electrical conductivity during incipient melting in the oceanic low-velocity zone  

NASA Astrophysics Data System (ADS)

The low-viscosity layer in the upper mantle, the asthenosphere, is a requirement for plate tectonics. The seismic low velocities and the high electrical conductivities of the asthenosphere are attributed either to subsolidus, water-related defects in olivine minerals or to a few volume per cent of partial melt, but these two interpretations have two shortcomings. First, the amount of water stored in olivine is not expected to be higher than 50 parts per million owing to partitioning with other mantle phases (including pargasite amphibole at moderate temperatures) and partial melting at high temperatures. Second, elevated melt volume fractions are impeded by the temperatures prevailing in the asthenosphere, which are too low, and by the melt mobility, which is high and can lead to gravitational segregation. Here we determine the electrical conductivity of carbon-dioxide-rich and water-rich melts, typically produced at the onset of mantle melting. Electrical conductivity increases modestly with moderate amounts of water and carbon dioxide, but it increases drastically once the carbon dioxide content exceeds six weight per cent in the melt. Incipient melts, long-expected to prevail in the asthenosphere, can therefore produce high electrical conductivities there. Taking into account variable degrees of depletion of the mantle in water and carbon dioxide, and their effect on the petrology of incipient melting, we calculated conductivity profiles across the asthenosphere for various tectonic plate ages. Several electrical discontinuities are predicted and match geophysical observations in a consistent petrological and geochemical framework. In moderately aged plates (more than five million years old), incipient melts probably trigger both the seismic low velocities and the high electrical conductivities in the upper part of the asthenosphere, whereas in young plates, where seamount volcanism occurs, a higher degree of melting is expected.

Sifré, David; Gardés, Emmanuel; Massuyeau, Malcolm; Hashim, Leila; Hier-Majumder, Saswata; Gaillard, Fabrice

2014-05-01

429

Reconstruction of apparent orthotropic conductivity tensor image using magnetic resonance electrical impedance tomography  

NASA Astrophysics Data System (ADS)

Magnetic resonance electrical impedance tomography visualizes current density and/or conductivity distributions inside an electrically conductive object. Injecting currents into the imaging object along at least two different directions, induced magnetic flux density data can be measured using a magnetic resonance imaging scanner. Without rotating the object inside the scanner, we can measure only one component of the magnetic flux density denoted as Bz. Since the biological tissues such as skeletal muscle and brain white matter show strong anisotropic properties, the reconstruction of anisotropic conductivity tensor is indispensable for the accurate observations in the biological systems. In this paper, we propose a direct method to reconstruct an axial apparent orthotropic conductivity tensor by using multiple Bz data subject to multiple injection currents. To investigate the anisotropic conductivity properties, we first recover the internal current density from the measured Bz data. From the recovered internal current density and the curl-free condition of the electric field, we derive an over-determined matrix system for determining the internal absolute orthotropic conductivity tensor. The over-determined matrix system is designed to use a combination of two loops around each pixel. Numerical simulations and phantom experimental results demonstrate that the proposed algorithm stably determines the orthotropic conductivity tensor.

Sajib, Saurav Z. K.; Kim, Ji Eun; Jeong, Woo Chul; Kim, Hyung Joong; Kwon, Oh In; Woo, Eung Je

2015-03-01

430

Effects of Extremity Elevation and Health Factors On Soft Tissue Electrical Conductivity  

NASA Astrophysics Data System (ADS)

Two clinical studies were completed using an auto-tuned induction coil conductivity sensor (ICCS) to determine the effects of a variety of factors on the electrical conductivity of soft tissue. In addition to fifteen "subject variables" such as blood pressure and others, we have specifically focused on considering the role of such factors as gender, age, BMI, smoking and elevation of extremities. Measurements were made at seven sites on either side of the body for a total of fourteen. Higher conductivities were obtained for women than men at all sites. At five sites, where age was a significant factor, conductivity was found to decline with increased age. Interestingly, smokers as a group tended to have reduced conductivity, suggesting that aging and smoking have similar effects on the microvasculature of soft tissue. Generally speaking, electrical conductivity is observed to increase in response to increased elevation at sites located on extremities. Considering just healthy adults, a definite pattern of elevation-induced electrical conductivity displacement emerges when subjects are flagged according to high, low or moderate blood pressure. We suggest that violations of this pattern may provide a method for identifying those individuals in an early stage of peripheral vascular disease.

Feldkamp, J. R.; Heller, J.

2009-01-01

431

Breakdown characteristics of an isolated conducting object in a uniform electric field  

NASA Technical Reports Server (NTRS)

A laboratory experiment was conducted to determine the physical processes involved in the electrical breakdown of a particular spark gap arrangement. The gap consists of an isolated conducting ellipsoid located midway between two large flat electrodes. Gradual increase of the applied electric field, E, in the gap produces corona on the ellipsoid tips followed by flashover in a leader-arc sequence. The leader phase consists of the abrupt formation of ionized channels which partially bridge the gap and then decay prior to the arc. Measurements of dE/dt and of current were made, and photographs were taken with an image converter. Experimental parameters are listed.

Grothaus, M. G.; Trost, T. F.

1986-01-01

432

Velocity, temperature, and electrical conductivity profiles in hydrogen-oxygen MHD duct flows  

NASA Technical Reports Server (NTRS)

This paper presents results of two-dimensional duct flow computations for radial distributions of velocity, temperature, and electrical conductivity. Calculations were carried out for the flow conditions representative of NASA Lewis hydrogen-oxygen combustion driven MHD duct. Results are presented for two sets of computations: (1) profiles of developing flow in a smooth duct, and (2) profiles of fully developed pipe flow with a specified streamwise shear stress distribution. The predicted temperature and electrical conductivity profiles for the developing flows compared well with available experimental data.

Greywall, M. S.; Pian, C. C. P.

1978-01-01

433

Length and temperature dependence of electrical conduction through dithiolated porphyrin arrays  

NASA Astrophysics Data System (ADS)

We present an investigation of electrical transport through fused and orthogonal dithiolated porphyrin arrays of different molecular lengths. Length dependence measurements show that conductance decreases much more slowly with molecular length than the exponential dependence expected for a coherent tunneling process. It suggests that the electrical conduction through porphyrin arrays is mainly due to the thermally activated hopping transport. From the temperature dependence of ISD- VSD curves, the thermal activation energy Ea is estimated to be about 0.35 eV at zero-bias voltage, independently of molecular conformation and length.

Kang, Bong Keun; Aratani, Naoki; Lim, Jong Kuk; Kim, Dongho; Osuka, Atsuhiro; Yoo, Kyung-Hwa

2005-09-01

434

Proton-irradiation-induced anomaly in the electrical conductivity of a hydrogen-bonded ferroelastic system  

SciTech Connect

An anomalous abrupt drop in the electrical conductivity has been observed at the ferroelastic phase transition of a proton-irradiated system of hydrogen-bonded TlH{sub 2}PO{sub 4}. As a result of the high-resolution {sup 31}P NMR chemical-shift measurements, distinct changes in the atomic displacements due to the irradiation were identified in the ferroelastic and paraelastic phases. Besides, {sup 1}H NMR spin-spin relaxation measurements revealed a change due to the irradiation in the proton dynamics at the ferroelastic phase transition, apparently accounting for the much-reduced electrical conductivity in the paraelastic phase of the irradiated system.

Kim, Se-Hun [Department of Physics and Institute for Nano Science, Korea University, Seoul 136-713 (Korea, Republic of); Faculty of Science Education, Jeju National University, Jeju 690-756 (Korea, Republic of); Lee, Kyu Won; Lee, Cheol Eui [Department of Physics and Institute for Nano Science, Korea University, Seoul 136-713 (Korea, Republic of); Lee, Kwang-Sei [Department of Nano Systems Engineering, Center for Nano Manufacturing, Inje University, Gimhae 621-749, Gyeongnam (Korea, Republic of)

2009-11-01

435

Ion Pair in Extreme Aqueous Environments, Molecular-Based and Electric Conductance Approaches  

SciTech Connect

We determine by molecular-based simulation the density profiles of the Na+!Cl! ion-pair association constant in steam environments along three supercritical isotherms to interrogate the behavior of ion speciation in dilute aqueous solutions at extreme conditions. Moreover, we describe a new ultra-sensitive flow-through electric conductance apparatus designed to bridge the gap between the currently lowest steam-density conditions at which we are experimentally able to attain electric conductance measurements and the theoretically-reachable zero-density limit. Finally, we highlight important modeling challenges encountered near the zero-density limit and discuss ways to overcome them.

Chialvo, Ariel A [ORNL; Gruszkiewicz, Miroslaw {Mirek} S [ORNL; Simonson, J Michael {Mike} [ORNL; Palmer, Donald [ORNL; Cole, David R [ORNL

2009-01-01

436

Electrically conductive doped block copolymer of polyacetylene and polyisoprene. [Soluble in organic solvents  

DOEpatents

An electrically conductive block copolymer of polyisoprene and polyacetylene and a method of making the same are disclosed. The polymer is prepared by first polymerizing isoprene with n-butyllithium in a toluene solution to form an active isoprenyllithium polymer. The active polymer is reacted with an equimolar amount of titanium butoxide and subsequently exposed to gaseous acetylene. A block copolymer of polyisoprene and polyacetylene is formed. The copolymer is soluble in common solvents and may be doped with I/sub 2/ to give it an electrical conductivity in the metallic regime.

Aldissi, M.

1984-06-27

437

Electrical conductive nanopolymers based on bisphenol F epoxy resin reinforced with nano polypyrrole  

NASA Astrophysics Data System (ADS)

In this study, spherical polypyrrole (PPy) nanostructure has successfully served as nanofiller for obtaining epoxy resin polymer nanocomposites (PNCs). The effects of nanofiller loading level on mechanical properties, thermal stability, electrical conductivity, and dielectric properties were systematically studied. The dynamic storage and loss modulii were studied, together with the glass-transition temperature (Tg) being obtained from the peak of tan delta. The PPy nanofillers could increase the electrical conductivity. Finally, the real permittivity was observed to increase with increasing the PPy loading, and the enhanced permittivity was analyzed by the interfacial polarization.

Bitarafhaghighi, Vahidreza

438

On the origin of electrical conductivity in the bio-electronic material melanin  

NASA Astrophysics Data System (ADS)

The skin pigment melanin is one of a few bio-macromolecules that display electrical and photo-conductivity in the solid-state. A model for melanin charge transport based on amorphous semiconductivity has been widely accepted for 40 years. In this letter, we show that a central pillar in support of this hypothesis, namely experimental agreement with a hydrated dielectric model, is an artefact related to measurement geometry and non-equilibrium behaviour. Our results cast significant doubt on the validity of the amorphous semiconductor model and are a reminder of the difficulties of electrical measurements on low conductivity, disordered organic materials.

Bernardus Mostert, A.; Powell, Ben J.; Gentle, Ian R.; Meredith, Paul

2012-02-01

439

Pressure dependence of electrical conductivity of (Mg,Fe)SiO 3 ilmenite  

Microsoft Academic Search

The electrical conductivity of (Mg0.93Fe0.07)SiO3 ilmenite was measured at temperatures of 500–1,200 K and pressures of 25–35 GPa in a Kawai-type multi-anvil apparatus equipped\\u000a with sintered diamond anvils. In order to verify the reliability of this study, the electrical conductivity of (Mg0.93Fe0.07)SiO3 perovskite was also measured at temperatures of 500–1,400 K and pressures of 30–35 GPa. The pressure calibration was carried\\u000a out using in

Tomoo Katsura; Sho Yokoshi; Kazuyuki Kawabe; Anton Shatskiy; Maki Okube; Hiroshi Fukui; Eiji Ito; Akifumi Nozawa; Ken-Ichi Funakoshi

2007-01-01

440

Model simulations of strong atmospheric conductivity disturbances and induced responses of the Global Electric Circuit  

NASA Astrophysics Data System (ADS)

Electrical conductivity in the troposphere and stratosphere is an important quantity that determines the distribution of currents in the GEC (Global Electric Circuit), as well as the potential difference between the Earth and the ionosphere. Recently, progress in modeling atmospheric conductivity has been achieved by integrating the conductivity calculation into an AC-GCM (atmospheric chemistry general circulation model), which provides all relevant data. In this study, WACCM (Whole Atmosphere Community Climate Model) is used for conductivity calculations and an analysis of the effects of strong disturbances on the GEC. This includes volcanic eruptions of Pinatubo in 1991 and the super volcano Toba, polar stratospheric clouds, radioactive releases, and the recent strong galactic cosmic ray maximum. In general, there is a decrease in conductivity from enhanced aerosol number densities, resulting from volcanic eruptions or polar stratospheric clouds. Conductivity is increased by additional ionization sources such as radioactive releases, or galactic cosmic ray increases such as during the last solar minimum. The effects of such events on conductivity, column and total resistance, and estimate effects on current distribution and the earth-ionosphere potential difference will be quantified. Percentage change in conductivity at 20 km altitude two months after the Toba volcanic eruption (WACCM model simulation). The enhanced aerosol concentrations lead to a "conductivity hole" between 30°S and 45° N.

Baumgaertner, A. J.; Lehto, E.; Neely, R. R.; English, J. M.; Zhu, Y.; Lucas, G.; Thayer, J. P.

2013-12-01