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Sample records for electrically-conducting forced convection

  1. Lorentz force sigmometry: a novel technique for measuring the electrical conductivity of solid and liquid metals

    NASA Astrophysics Data System (ADS)

    Alkhalil, Shatha; Kolesnikov, Yurii; Thess, André

    2015-11-01

    In this paper, a novel method to measure the electrical conductivity of solid and molten metals is described. We term the method ‘Lorentz force sigmometry’, where the term ‘sigmometry’ refers to the letter sigma σ, often used to denote the electrical conductivity. The Lorentz force sigmometry method is based on the phenomenon of eddy currents generation in a moving conductor exposed to a magnetic field. Based on Ampere’s law, the eddy currents in turn generate a secondary magnetic field; as a result, the Lorentz force acts to brake the conductor. Owing to Newton’s third law, a measurable force, which is equal to the Lorentz force and is directly proportional to the electrical conductivity of the conductive fluid or solid, acts on the magnet. We present the results of the measurements performed on solids along with the initial measurements on fluids with a eutectic alloy composition of Ga67In20.5Sn12.5; detailed measurements on molten metals are still in progress and will be published in the future. We conducted a series of experiments and measured the properties of known electrical conductive metals, including aluminum and copper, to compute the calibration factor of the device, and then used the same calibration factor to estimate the unknown electrical conductivity of a brass bar. The predicted electrical conductivity of the brass bar was compared with the conductivity measured with a commercial device called ‘SigmaTest’ the observed error was less than 0.5%.

  2. Electro-Convective and Non-Equilibrium Electro-Osmotic Instability of Electric Conduction from an Electrolyte Solution into a Charge Selective Solid

    NASA Astrophysics Data System (ADS)

    Rubinstein, Isaak

    2006-03-01

    Electro-convection is reviewed as a mechanism of mixing in the diffusion layer of a strong electrolyte adjacent to a charge-selective solid, such as an ion exchange (electrodialysis) membrane or an electrode. Two types of electro-convection in strong electrolytes may be distinguished: bulk electro-convection , due to the action of the electric field upon the residual space charge of a quasi-electro-neutral bulk solution, and convection induced by electro-osmotic slip, due to electric forces acting in the thin electric double layer of either quasi-equilibrium or non-equilibrium type near the solid/liquid interface. According to recent studies, the latter appears to be the likely source of mixing in the diffusion layer, leading to `over-limiting' conductance in electrodialysis. Electro-convection near a uniform charge selective solid/liquid interface sets on as a result of hydrodynamic instability of one-dimensional steady state electric conduction through such an interface. We discuss instabilities of this kind appearing in the full electro-convective and limiting non-equilibrium electro-osmotic formulations. The short- and long-wave aspects of these instabilities are discussed along with the wave-number selection principles and possible sources of low frequency excess electric noise experimentally observed in these systems.

  3. Electrical Conductivity.

    ERIC Educational Resources Information Center

    Allen, Philip B.

    1979-01-01

    Examines Drude's classical (1900) theory of electrical conduction, details the objections to and successes of the 1900 theory, and investigates the Quantum (1928) theory of conduction, reviewing its successes and limitations. (BT)

  4. Electrical Conductivity.

    ERIC Educational Resources Information Center

    Hershey, David R.; Sand, Susan

    1993-01-01

    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)

  5. Vegetation forcing and convective motion

    SciTech Connect

    Hong, X.; Leach, M.J.; Raman, S.

    1995-04-01

    A large irrigated vegetation area in a semiarid or relatively dry location is a strong surface forcing of thermal circulations. Several observational studies have found that such thermally induced mesoscale circulation may contribute to the triggering and development of convective clouds. In the western United States, extensive areas of irrigated farmland are surrounded by hot, dry surfaces, such as a steppe. Substantial gradients of sensible heating in the horizontal direction lead to a {open_quotes}farm breeze{close_quotes} circulation from the cooler agricultural area to the warmer steppes found at Boardman, Oregon. These thermally forced circulations may trigger convection by the related convergence and updraft motion under favorable atmospheric conditions. The role of vegetative covering in convective motion is investigated using a mesoscale numerical model. Two- and three-dimensional simulations are described. The effects of atmospheric stability, moisture in the lower atmosphere, moisture in the upper atmosphere, and horizontal heating scale on thermally induced clouds are studied. The horizontal scale of inhomogeneity is also studied using the two-dimensional model. Finally, a realistic vegetation distribution similar to that of the Boardman Regional Flux Experiment is used in the three-dimensional simulations.

  6. Electrical conductivity in Langmuir-Blodgett films of n-alkyl cyanobiphenyls using current sensing atomic force microscope

    SciTech Connect

    Gayathri, H. N.; Suresh, K. A.

    2015-06-28

    We report our studies on the nanoscale electrical conductivity in monolayers of n-alkyl cyanobiphenyl materials deposited on solid surface. Initially, the 8CB, 9CB, and 10CB monolayer films were prepared by the Langmuir technique at air-water interface and characterized by surface manometry and Brewster angle microscopy. The monolayer films were transferred on to solid substrates by the Langmuir-Blodgett (L-B) technique. The 8CB, 9CB, and 10CB monolayer L-B films were deposited on freshly cleaved mica and studied by atomic force microscope (AFM), thereby measuring the film thickness as ∼1.5 nm. The electrical conductivity measurements were carried out on 9CB and 10CB monolayer L-B films deposited onto highly ordered pyrolytic graphite using current sensing AFM. The nanoscale current-voltage (I-V) measurements show a non-linear variation. The nature of the curve indicates electron tunneling to be the mechanism for electrical conduction. Furthermore, analysis of the I-V curve reveals a transition in the electron conduction mechanism from direct tunneling to injection tunneling. From the transition voltage, we have estimated the values of barrier height for 9CB and 10CB to be 0.71 eV and 0.37 eV, respectively. For both 9CB and 10CB, the effective mass of electron was calculated to be 0.021 m{sub e} and 0.065 m{sub e}, respectively. These parameters are important in the design of molecular electronic devices.

  7. The electrical conduction of conjugated molecular CAMs studied by a conductive atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Yamamoto, Shin-ichi; Ogawa, Kazufumi

    2006-09-01

    Monomolecular layers containing pyrrolyl groups between two parallel Pt electrodes on a glass substrate by a chemical adsorption technique using N-[11-(trichlorosilyl)undecyl] pyrrole (PNN) were studied. Polymerization with pure water by applying a DC voltage of 10 V between the two Pt electrodes was carried out, and several electric paths were formed between the two Pt electrodes were identified. Conductive probe of an atomic force microscopy (AFM) was used to examine the electrical polymerized paths through the surface of the polypyrrolyl group in a chemically adsorbed monomolecular layer. With a measurement volume of about 0.2 nm (thickness of the monomolecular layer) × 100 μm (the average width of an electric path) × 100 μm (the distance between the Pt electrode and the Au-covered AFM tip), the resistance at room temperature of one electric path was 5 kΩ under ambient conditions. From the results conducted in an atmosphere, the conductivity of a super-long conjugated polypyrrolyl group without any dopant in a lateral direction was ohmically estimated to be at least 5.0 × 10 5 s/m.

  8. Subcooled forced convection boiling of trichlorotrifluoroethane

    NASA Technical Reports Server (NTRS)

    Dougall, R. S.; Panian, D. J.

    1972-01-01

    Experimental heat-transfer data were obtained for the forced-convection boiling of trichlorotrifluoroethane (R-113 or Freon-113) in a vertical annular test annular test section. The 97 data points obtained covered heat transfer by forced convection, local boiling, and fully-developed boiling. Correlating methods were obtained which accurately predicted the heat flux as a function of wall superheat (boiling curve) over the range of parameters studied.

  9. Supercritical droplet gasification experiments with forced convection

    NASA Technical Reports Server (NTRS)

    Litchford, Ron; Parigger, Chris; Jeng, San-Mou

    1992-01-01

    Preliminary results of a comprehensive experimental program are presented which offer the first direct observations of suspended n-heptane droplet gasifications in pure nitrogen with forced convection without the interference to optical probing associated with a flame. Measurements show attainment of a wet-bulb temperature until reduced pressures exceed about 1.0 under supercritical gas temperatures. Thereafter, temperature measurements indicate fully transient heat-up through the critical temperature. The surface is found to regress in a continuous manner with the measured temperature approaching the critical value at the end of the droplet lifetime under supercritical conditions with very mild level of convection. At increased level of convection for the same ambient conditions, similar sized droplets will undergo significant deformation during the gasification process until partially convected away as a dense vapor cloud as the critical temperature is approached.

  10. Forced Convection Heat Transfer in Circular Pipes

    ERIC Educational Resources Information Center

    Tosun, Ismail

    2007-01-01

    One of the pitfalls of engineering education is to lose the physical insight of the problem while tackling the mathematical part. Forced convection heat transfer (the Graetz-Nusselt problem) certainly falls into this category. The equation of energy together with the equation of motion leads to a partial differential equation subject to various…

  11. Magnetospheric Convection as a Global Force Phenomenon

    NASA Astrophysics Data System (ADS)

    Siscoe, G.

    2007-12-01

    Since 1959 when Thomas Gold showed that motions in the magnetosphere were possible despite plasma being frozen to the magnetic field, magnetospheric convection as a subject of study has gone through several stages (to be reviewed) leading to a recent one that integrates convection into a global system of balance of forces. This area of research has opened by focusing on the region 1 current system as a carrier of force between the solar wind and the ionosphere/thermosphere fluid. An important result to emerge from it is the realization that the force that the solar wind delivers to the magnetosphere in being transferred by the region 1 current system to the ionosphere/thermosphere fluid is amplified by about an order of magnitude. (Vasyliunas refers to this as "leveraging.") The apparent violation of Newton's Third Law results from the main participants in the force balance being not the solar wind force but the JxB force on the ionosphere/thermosphere fluid and the mu-dot-grad-B force on the Earth's dipole. This talk extends the study by considering the global force-balance problem separately for the Pedersen current (a completion of the region 1 problem), the Hall current (thus introducing the region 2 current system), and the Cowling current (bringing in the substorm current wedge). The approach is through representing the ionosphere/thermosphere fluid by the shallow water equations. Novelties that result include force balance by means of tidal bulges and tidal bores.

  12. Electrically conductive cellulose composite

    DOEpatents

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

    2010-05-04

    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.

  13. Electrically conductive diamond electrodes

    DOEpatents

    Swain, Greg; Fischer, Anne ,; Bennett, Jason; Lowe, Michael

    2009-05-19

    An electrically conductive diamond electrode and process for preparation thereof is described. The electrode comprises diamond particles coated with electrically conductive doped diamond preferably by chemical vapor deposition which are held together with a binder. The electrodes are useful for oxidation reduction in gas, such as hydrogen generation by electrolysis.

  14. Forced convection modulates gas exchange in cnidarians

    PubMed Central

    Patterson, Mark R.; Sebens, Kenneth P.

    1989-01-01

    Boundary layer thickness is a potentially important component of the diffusive pathway for gas exchange in aquatic organisms. The soft coral Alcyonium siderium (Octocorallia) and sea anemone Metridium senile (Actiniaria) exhibit significant increases in respiration with water flow over a range of Reynolds numbers encountered subtidally. A nondimensional mass transfer analysis of the effect of forced convection demonstrates the importance of the state of the organism's boundary layer in regulating metabolism in these invertebrates. Flow-modulated gas exchange may limit secondary productivity in subtidal environments. PMID:16594087

  15. Electrically conductive material

    DOEpatents

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

    1993-09-07

    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.

  16. Electrically conductive material

    DOEpatents

    Singh, Jitendra P.; Bosak, Andrea L.; McPheeters, Charles C.; Dees, Dennis W.

    1993-01-01

    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.

  17. Performance of thermal adhesives in forced convection

    NASA Technical Reports Server (NTRS)

    Kundu, Nikhil K.

    1993-01-01

    Cooling is critical for the life and performance of electronic equipment. In most cases cooling may be achieved by natural convection but forced convection may be necessary for high wattage applications. Use of conventional type heat sinks may not be feasible from the viewpoint of specific applications and the costs involved. In a heat sink, fins can be attached to the well by ultrasonic welding, by soldering, or with a number of industrially available thermal adhesives. In this paper, the author investigates the heat transfer characteristics of several adhesives and compares them with ultrasonic welding and theoretically calculated values. This experiment was conducted in an air flow chamber. Heat was generated by using heaters mounted on the well. Thermstrate foil, Uniset A401, and Aremco 571 adhesives were tested along with an ultrasonically welded sample. Ultrasonic welding performed far better than the adhesives and Thermstrate foil. This type of experiment can be adapted for a laboratory exercise in an upper level heat transfer course. It gives students an exposure to industrial applications that help them appreciate the importance of the course material.

  18. Electrically conductive composite material

    DOEpatents

    Clough, Roger L.; Sylwester, Alan P.

    1989-01-01

    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.

  19. Electrically conductive composite material

    DOEpatents

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

    1988-06-20

    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.

  20. Natural and forced convection during solidification

    NASA Astrophysics Data System (ADS)

    Neufeld, Jerome A.

    The following work marries theoretical and experimental approaches to study the interaction of an external shear flow with a solidifying porous medium. The porous medium, a dendritic 'mushy layer', is created when a super-eutectic binary alloy is cooled leading to solid crystals bathed in an interstitial fluid which is compositionally enriched. This compositional enrichment leads to natural buoyant instabilities in the solidifying porous medium coupled with instabilities in the adjoining liquid layer. Theoretically, the effect of an external shear flow on the convective instabilities inherent to this mushy layer is investigated using a linear stability analysis. The external flow is coupled to advective perturbations in the liquid and to flow in the mush through a perturbed mush-liquid interface. A complete numerical solution of the stability of the system is performed and a critical porous medium Rayleigh number is found which is a function of both the external flow speed and the wavenumber of the interfacial perturbations. By neglecting the effects of buoyancy in the liquid and solving only for the pressure perturbations on the corrugated mush-liquid interface induced by the external flow, a reduced model is constructed and solved analytically. These theoretical results are compared with experimental observations obtained in a laboratory flume in which an ammonium-chloride solution is solidified from below at a constant rate. The experimental results reveal that at flow speeds above critical, convection is forced within the mush leading to a series of zero solid fraction tesselations aligned perpendicular to the applied shear flow. The results of the experiments compare favorably to the linear stability analysis.

  1. Electrical Conductivity in Textiles

    NASA Technical Reports Server (NTRS)

    2006-01-01

    Copper is the most widely used electrical conductor. Like most metals, though, it has several drawbacks: it is heavy, expensive, and can break. Fibers that conduct electricity could be the solutions to these problems, and they are of great interest to NASA. Conductive fibers provide lightweight alternatives to heavy copper wiring in a variety of settings, including aerospace, where weight is always a chief concern. This is an area where NASA is always seeking improved materials. The fibers are also more cost-effective than metals. Expenditure is another area where NASA is always looking to make improvements. In the case of electronics that are confined to small spaces and subject to severe stress, copper is prone to breaking and losing connection over time. Flexible conductive fibers eliminate that problem. They are more supple and stronger than brittle copper and, thus, find good use in these and similar situations. While clearly a much-needed material, electrically conductive fibers are not readily available. The cost of new technology development, with all the pitfalls of troubleshooting production and the years of testing, and without the guarantee of an immediate market, is often too much of a financial hazard for companies to risk. NASA, however, saw the need for electrical fibers in its many projects and sought out a high-tech textile company that was already experimenting in this field, Syscom Technology, Inc., of Columbus, Ohio. Syscom was founded in 1993 to provide computer software engineering services and basic materials research in the areas of high-performance polymer fibers and films. In 1999, Syscom decided to focus its business and technical efforts on development of high-strength, high-performance, and electrically conductive polymer fibers. The company developed AmberStrand, an electrically conductive, low-weight, strong-yet-flexible hybrid metal-polymer YARN.

  2. Electrically Conductive Porous Membrane

    NASA Technical Reports Server (NTRS)

    Burke, Kenneth Alan (Inventor)

    2014-01-01

    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.

  3. Forced-convective vitrification with liquid cryogens.

    PubMed

    Lyu, Shaw-Ruey; Huang, Jen-Hung; Shih, Wei-Hung; Chen, Yung-Jiun; Hsieh, Wen-Hsin

    2013-06-01

    Cell cryopreservation by vitrification generally requires using vitrification solutions with high concentrations of cryoprotectants (CPAs), which are toxic and induce osmotic stresses associated with the addition and removal of CPAs. To increase the cooling rate and reduce the CPA concentration required for vitrification, this study proposed an innovative approach, named forced-convective vitrification with liquid cryogens, in which liquid oxygen at a temperature below its boiling point (LOX(bbp)) was used as the cryogen to reduce the generation of insulating bubbles of gaseous oxygen and the sample was subjected to a constant velocity to remove insulation bubbles from the sample. Results show that changing the cryogen from liquid nitrogen at its boiling temperature (LN(abp)) to LOX(bbp), increasing the sample velocity and reducing the test solution volume increased the cooling rate and thereby decreased the CPA concentration required for vitrification. Using the same velocity (1.2 m/s), the cooling rate achieved with LOX(bbp) was 2.3-fold greater than that achieved with LN(abp). With LOX(bbp), the increase in the sample velocity from 0.2 to 1.2 m/s enhanced the cooling rate by 1.9 times. With LOX(bbp), a velocity of 1.2m/s and a test solution volume of 1.73 μl, the CPA concentration required for vitrification decreased to 25%. These results indicate that the new approach described here can reduce the CPA concentration required for vitrification, and thus decreases the toxicity and osmotic stresses associated with adding and removing the CPA. PMID:23545291

  4. Driving forces: Slab subduction and mantle convection

    NASA Technical Reports Server (NTRS)

    Hager, Bradford H.

    1988-01-01

    Mantle convection is the mechanism ultimately responsible for most geological activity at Earth's surface. To zeroth order, the lithosphere is the cold outer thermal boundary layer of the convecting mantle. Subduction of cold dense lithosphere provides tha major source of negative buoyancy driving mantle convection and, hence, surface tectonics. There are, however, importnat differences between plate tectonics and the more familiar convecting systems observed in the laboratory. Most important, the temperature dependence of the effective viscosity of mantle rocks makes the thermal boundary layer mechanically strong, leading to nearly rigid plates. This strength stabilizes the cold boundary layer against small amplitude perturbations and allows it to store substantial gravitational potential energy. Paradoxically, through going faults at subduction zones make the lithosphere there locally weak, allowing rapid convergence, unlike what is observed in laboratory experiments using fluids with temperature dependent viscosities. This bimodal strength distribution of the lithosphere distinguishes plate tectonics from simple convection experiments. In addition, Earth has a buoyant, relatively weak layer (the crust) occupying the upper part of the thermal boundary layer. Phase changes lead to extra sources of heat and bouyancy. These phenomena lead to observed richness of behavior of the plate tectonic style of mantle convection.

  5. Electrically conductive alternating copolymers

    DOEpatents

    Aldissi, M.; Jorgensen, B.S.

    1987-08-31

    Polymers which are soluble in common organic solvents and are electrically conductive, but which also may be synthesized in such a manner that they become nonconductive. Negative ions from the electrolyte used in the electrochemical synthesis of a polymer are incorporated into the polymer during the synthesis and serve as a dopant. A further electrochemical step may be utilized to cause the polymer to be conductive. The monomer repeat unit is comprised of two rings, a pyrrole molecule joined to a thienyl group, or a furyl group, or a phenyl group. The individual groups of the polymers are arranged in an alternating manner. For example, the backbone arrangement of poly(furylpyrrole) is -furan-pyrrole-furan-pyrrole- furan-pyrrole. An alkyl group or phenyl group may be substituted for either or both of the hydrogen atoms of the pyrrole ring.

  6. Parabolic flight experiment "Convection in a Cylinder" - Convection patterns in varying buoyancy forces

    NASA Astrophysics Data System (ADS)

    Dahley, N.; Futterer, B.; Egbers, C.; Crumeyrolle, O.; Mutabazi, I.

    2011-12-01

    Within the project "Convection in a Cylinder" (CiC) heat transfer enhancement is studied for the case of two concentric, vertically aligned cylinders. The cylindrical gap is filled with a dielectric liquid, which viscosity is just few times higher than that of water. The inner cylinder is heated and the outer one is cooled. This setup in a gravitational buoyancy field leads to a fluid movement in a single convective cell with hot fluid rising at the inner boundary and cold fluid sinking at the outer boundary. The top and bottom part of the system shows horizontal movement, again in boundary layers. The strengthening of temperature gradient induces instabilities of that convective motion. If we vary the buoyancy force by means of electro-hydrodynamic effects, the patterns of convection differ from those instabilities rising only from variation of the temperature gradient.

  7. Electrically conductive anodized aluminum coatings

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    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.

  8. A study of forced convection boiling under reduced gravity

    NASA Technical Reports Server (NTRS)

    Merte, Herman, Jr.

    1992-01-01

    This report presents the results of activities conducted over the period 1/2/85-12/31/90, in which the study of forced convection boiling under reduced gravity was initiated. The study seeks to improve the understanding of the basic processes that constitute forced convection boiling by removing the buoyancy effects which may mask other phenomena. Specific objectives may also be expressed in terms of the following questions: (1) what effects, if any, will the removal of body forces to the lowest possible levels have on the forced convection boiling heat transfer processes in well-defined and meaningful circumstances? (this includes those effects and processes associated with the nucleation or onset of boiling during the transient increase in heater surface temperature, as well as the heat transfer and vapor bubble behaviors with established or steady-state conditions); and (2) if such effects are present, what are the boundaries of the relevant parameters such as heat flux, heater surface superheat, fluid velocity, bulk subcooling, and geometric/orientation relationships within which such effects will be produced?

  9. Forced convection heat transfer to air/water vapor mixtures

    NASA Technical Reports Server (NTRS)

    Richards, D. R.; Florschuetz, L. W.

    1984-01-01

    Heat transfer coefficients were measured using both dry and humid air in the same forced convection cooling scheme and were compared using appropriate nondimensional parameters (Nusselt, Prandtl and Reynolds numbers). A forced convection scheme with a complex flow field, two dimensional arrays of circular jets with crossflow, was utilized with humidity ratios (mass ratio of water vapor to air) up to 0.23. The dynamic viscosity, thermal conductivity and specific heat of air, steam and air/steam mixtures are examined. Methods for determining gaseous mixture properties from the properties of their pure components are reviewed as well as methods for determining these properties with good confidence. The need for more experimentally determined property data for humid air is discussed. It is concluded that dimensionless forms of forced convection heat transfer data and empirical correlations based on measurements with dry air may be applied to conditions involving humid air with the same confidence as for the dry air case itself, provided that the thermophysical properties of the humid air mixtures are known with the same confidence as their dry air counterparts.

  10. Electrically Conductive Paints for Satellites

    NASA Technical Reports Server (NTRS)

    Gilligan, J. E.; Wolf, R. E.; Ray, C.

    1977-01-01

    A program was conducted to develop and test electrically conductive paint coatings for spacecraft. A wide variety of organic and inorganic coatings were formulated using conductive binders, conductive pigments, and similar approaches. Z-93, IITRI's standard specification inorganic thermal control coating, exhibits good electrical properties and is a very space-stable coating system. Several coatings based on a conductive pigment (antimony-doped tin oxide) in silicone and silicate binders offer considerable promise. Paint systems using commercially available conductive polymers also appear to be of interest, but will require substantial development. Evaluations were made based on electrical conductivity, paint physical properties, and the stability of spectral reflectance in space environment testing.

  11. Combined forced and free convection in a curved duct

    NASA Technical Reports Server (NTRS)

    Yam, Clement G.; Dwyer, Harry A.

    1992-01-01

    The purpose of this study is to investigate the flow and heat transfer characteristics of a combined forced and free convection flow in a curved duct. Solutions are obtained by solving the low Mach number model of the Navier-Stokes equation using a control volume method. The finite-volume method was developed with the use of a predictor-corrector numerical scheme and some new variations of the classical projection method. Solutions indicated that the existence of a buoyancy force has changed the entire flow structure inside a curved duct. Reversed flow at both inner and outer bend is observed. For moderate Reynolds number, the upstream section of the duct was significantly influenced by the free convection processes. In general, heat transfer is strong at the inner bend of the beginning of the heated section and at the outer bend on the last half of the heated section. The maximum velocity location is strongly influenced by the combined effects of buoyancy and centrifugal forces. A strong buoyancy force can reduce the strength of the secondary flow where it plays an important role in mixing.

  12. Evaluation of T-111 forced-convection loop tested with lithium at 1370 C. [free convection

    NASA Technical Reports Server (NTRS)

    Devan, J. H.; Long, E. L., Jr.

    1975-01-01

    A T-111 alloy (Ta-8% W-2% Hf) forced-convection loop containing molten lithium was operated 3000 hr at a maximum temperature of 1370 C. Flow velocities up to 6.3 m/sec were used, and the results of this forced-convection loop are very similar to those observed in lower velocity thermal-convection loops of T-111 containing lithium. Weight changes were determined at 93 positions around the loop. The maximum dissolution rate occurred at the maximum wall temperature of the loop and was less than 1.3 microns/year. Mass transfer of hafnium, nitrogen, and, to a lesser extent, carbon occurred from the hotter to cooler regions. Exposed surfaces in the highest temperature region were found to be depleted in hafnium to a depth of 60 microns with no detectable change in tungsten content. There was some loss in room-temperature tensile strength for specimens exposed to lithium at 1370 C, attributable to depletion of hafnium and nitrogen and to attendant grain growth.

  13. Electrical Conductivity in Transition Metals

    ERIC Educational Resources Information Center

    Talbot, Christopher; Vickneson, Kishanda

    2013-01-01

    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…

  14. Electrically conductive rigid polyurethane foam

    DOEpatents

    Neet, Thomas E.; Spieker, David A.

    1985-03-19

    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.

  15. Electrically conductive rigid polyurethane foam

    DOEpatents

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

    1983-12-08

    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.

  16. Electrically Conductive Anodized Aluminum Surfaces

    NASA Technical Reports Server (NTRS)

    Nguyen, Trung Hung

    2006-01-01

    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

  17. Lox droplet vaporization in a supercritical forced convective environment

    NASA Technical Reports Server (NTRS)

    Hsiao, Chia-Chun; Yang, Vigor

    1994-01-01

    A systematic investigation has been conducted to study the effects of ambient flow conditions (i.e. pressure and velocity) on supercritical droplet gasification in a forced-convective environment. The model is based on the time-dependent conservation equations in axisymmetric coordinates, and accommodates thermodynamic nonidealities and transport anomalies. In addition, an efficient scheme for evaluating thermophysical properties over the entire range of fluid thermodynamic states is established. The analysis allows a thorough examination of droplet behavior during its entire lifetime, including transient gasification, dynamic deformation, and shattering. A parametric study of droplet vaporization rate in terms of ambient pressure and Reynolds number is also conducted.

  18. Combined effects of a magnetic field and a helical force on the onset of a rotating Rayleigh-Bénard convection with free-free boundaries

    NASA Astrophysics Data System (ADS)

    Chabi Orou, Jean Bio; Pomalégni, Gisèle

    2015-11-01

    We investigate the combined effects of rotation , magnetic field and helical force on the onset of stationary and oscillatory convection in a horizontal electrically conducting fluid layer heated from below with free-free boundary conditions. For this investigation the linear stability analysis studied by Chandrasekhar (1961) is used. We obtain the condition for the formation of a single large scale structure. In (Pomalégni et al., 2014) it was shown the existence of a critical value Scr of the intensity of the helical force for which the apparition of two cells at marginal stability for the oscillatory convection is obtained. Then, we have shown here how the increasing of parameter Ta influences this critical value of the helical force intensity.

  19. Metallization and electrical conductivity of hydrogen in Jupiter.

    PubMed

    Nellis, W J; Weir, S T; Mitchell, A C

    1996-08-16

    Electrical conductivities of molecular hydrogen in Jupiter were calculated by scaling electrical conductivities measured at shock pressures in the range of 10 to 180 gigapascals (0.1 to 1.8 megabars) and temperatures to 4000 kelvin, representative of conditions inside Jupiter. Jupiter's magnetic field is caused by convective dynamo motion of electrically conducting fluid hydrogen. The data imply that Jupiter should become metallic at 140 gigapascals in the fluid, and the electrical conductivity in the jovian molecular envelope at pressures up to metallization is about an order of magnitude larger than expected previously. The large magnetic field is produced in the molecular envelope closer to the surface than previously thought. PMID:8688072

  20. Electrically conductive polymer concrete overlays

    NASA Astrophysics Data System (ADS)

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

    1984-08-01

    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.

  1. Electrically conductive polymer concrete coatings

    DOEpatents

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

    1988-05-26

    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.

  2. Electrically conductive polymer concrete coatings

    DOEpatents

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

    1990-03-13

    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.

  3. Electrically conductive polymer concrete coatings

    DOEpatents

    Fontana, Jack J.; Elling, David; Reams, Walter

    1990-01-01

    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.

  4. Electrical conduction in polymer dielectrics

    NASA Technical Reports Server (NTRS)

    Cotts, D. B.

    1985-01-01

    The use of polymer dielectrics with moderate resistivities could reduce or eliminate problems associated with spacecraft charging. The processes responsible for conduction and the properties of electroactive polymers are reviewed, and correlations drawn between molecular structure and electrical conductivity. These structure-property relationships led to the development of several new electroactive polymer compositions and the identification of several systems that have the requisite thermal, mechanical, environmental and electrical properties for use in spacecraft.

  5. Membrane species mobility under in-lipid-membrane forced convection.

    PubMed

    Hu, Shu-Kai; Huang, Ling-Ting; Chao, Ling

    2016-08-17

    Processing and managing cell membrane proteins for characterization while maintaining their intact structure is challenging. Hydrodynamic flow has been used to transport membrane species in supported lipid bilayers (SLBs) where the hydrophobic cores of the membrane species can be protected during processing. However, the forced convection mechanism of species embedded in lipid bilayers is still unclear. Developing a controlled SLB platform with a practical model to predict the membrane species mobility in the platform under in-lipid-membrane forced convection is imperative to ensure the practical applicability of SLBs in processing and managing membrane species with various geometrical properties. The mobility of membrane species is affected by the driving force from the aqueous environment in addition to the frictions from the lipid bilayer, in which both lipid leaflets may exhibit different speeds relative to that of the moving species. In this study, we developed a model, based on the applied driving force and the possible frictional resistances that the membrane species encounter, to predict how the mobility under in-lipid-membrane forced convection is influenced by the sizes of the species' hydrophilic portion in the aqueous environment and the hydrophobic portion embedded in the membrane. In addition, we used a microfluidic device for controlling the flow to arrange the lipid membrane and the tested membrane species in the desirable locations in order to obtain a SLB platform which can provide clear mobility responses of the species without disturbance from the species dispersion effect. The model predictions were consistent with the experimental observations, with the sliding friction coefficient between the upper leaflet and the hydrophilic portion of the species as the only regressed parameter. The result suggests that not only the lateral drag frictions from the lipid layers but also the sliding frictions between the species and the lipid layer planes

  6. Numerical study of forced convective heat transfer around airships

    NASA Astrophysics Data System (ADS)

    Dai, Qiumin; Fang, Xiande

    2016-02-01

    Forced convective heat transfer is an important factor that affects the thermal characteristics of airships. In this paper, the steady state forced convective heat transfer around an ellipsoid is numerically investigated. The numerical simulation is carried out by commercial computational fluid dynamic (CFD) software over the extended Re range from 20 to 108 and the aspect ratio from 2 to 4. Based on the regression and optimization with software, a new piecewise correlation of the Nusselt number at constant wall temperature for ellipsoid is proposed, which is suitable for applications to airships and other ellipse shaped bodies such as elliptical balloons. The thermal characteristics of a stratospheric airship in midsummer located in the north hemisphere are numerical studied. The helium temperature predicated using the new correlation is compared to those predicted by correlations applicable for spheres and flat plates. The results show that the helium temperature obtained using the new correlation at noon is about 5.4 K lower than that using the correlation of spheres and about 2.1 K higher than that of flat plates.

  7. ARM - Midlatitude Continental Convective Clouds - Single Column Model Forcing (xie-scm_forcing)

    DOE Data Explorer

    Xie, Shaocheng; McCoy, Renata; Zhang, Yunyan

    2012-10-25

    The constrained variational objective analysis approach described in Zhang and Lin [1997] and Zhang et al. [2001]was used to derive the large-scale single-column/cloud resolving model forcing and evaluation data set from the observational data collected during Midlatitude Continental Convective Clouds Experiment (MC3E), which was conducted during April to June 2011 near the ARM Southern Great Plains (SGP) site. The analysis data cover the period from 00Z 22 April - 21Z 6 June 2011. The forcing data represent an average over the 3 different analysis domains centered at central facility with a diameter of 300 km (standard SGP forcing domain size), 150 km and 75 km, as shown in Figure 1. This is to support modeling studies on various-scale convective systems.

  8. Electrical conductivity of ice VII

    PubMed Central

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

    2014-01-01

    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

  9. Boiling inception in trichlorotrifluoroethane during forced convection at high pressures

    NASA Technical Reports Server (NTRS)

    Dougall, R. S.; Lippert, T. E.

    1972-01-01

    The inception of bubbles during forced convection was studied experimentally by using trichlorotrifluoroethane (R-113 or Freon-113). The experiments were performed in a rectangular channel, 12.7 x 9.5 mm in cross section. Heating was from a 3.2 mm wide strip embedded in the longer side of the channel. The pressures studied ranged from 3.6 to 20.7 bar, mass velocities from 700 to 600 kg/sq m/sec, and inlet subcoolings from 26 to 97 C. Photographs of the flow were used to determine when bubbles first appeared on the heated surface. These data were compared with wall temperature measurements and inception theories. A reasonable method for calculating the complete boiling curve was found to agree with these results.

  10. LOX droplet vaporization in a supercritical forced convective environment

    NASA Technical Reports Server (NTRS)

    Hsiao, Chia-Chun; Yang, Vigor

    1993-01-01

    Modern liquid rocket engines often use liquid oxygen (LOX) and liquid hydrogen (LH2) as propellants to achieve high performance, with the engine operational conditions in the supercritical regimes of the propellants. Once the propellant exceeds its critical state, it essentially becomes a puff of dense fluid. The entire field becomes a continuous medium, and no distinct interfacial boundary between the liquid and gas exists. Although several studies have been undertaken to investigate the supercritical droplet behavior at quiescent conditions, very little effort has been made to address the fundamental mechanisms associated with LOX droplet vaporization in a supercritical, forced convective environment. The purpose is to establish a theoretical framework within which supercritical droplet dynamics and vaporization can be studied systematically by means of an efficient and robust numerical algorithm.

  11. Forced convection heat transfer to air/water vapor mixtures

    NASA Technical Reports Server (NTRS)

    Richards, D. R.; Florschuetz, L. W.

    1986-01-01

    Heat transfer coefficients were measured using both dry air and air/water vapor mixtures in the same forced convection cooling test rig (jet array impingement configurations) with mass ratios of water vapor to air up to 0.23. The primary objective was to verify by direct experiment that selected existing methods for evaluation of viscosity and thermal conductivity of air/water vapor mixtures could be used with confidence to predict heat transfer coefficients for such mixtures using as a basis heat transfer data for dry air only. The property evaluation methods deemed most appropriate require as a basis a measured property value at one mixture composition in addition to the property values for the pure components.

  12. Development of a mechanistic model for forced convection subcooled boiling

    NASA Astrophysics Data System (ADS)

    Shaver, Dillon R.

    The focus of this work is on the formulation, implementation, and testing of a mechanistic model of subcooled boiling. Subcooled boiling is the process of vapor generation on a heated wall when the bulk liquid temperature is still below saturation. This is part of a larger effort by the US DoE's CASL project to apply advanced computational tools to the simulation of light water reactors. To support this effort, the formulation of the dispersed field model is described and a complete model of interfacial forces is formulated. The model has been implemented in the NPHASE-CMFD computer code with a K-epsilon model of turbulence. The interfacial force models are built on extensive work by other authors, and include novel formulations of the turbulent dispersion and lift forces. The complete model of interfacial forces is compared to experiments for adiabatic bubbly flows, including both steady-state and unsteady conditions. The same model is then applied to a transient gas/liquid flow in a complex geometry of fuel channels in a sodium fast reactor. Building on the foundation of the interfacial force model, a mechanistic model of forced-convection subcooled boiling is proposed. This model uses the heat flux partitioning concept and accounts for condensation of bubbles attached to the wall. This allows the model to capture the enhanced heat transfer associated with boiling before the point of net generation of vapor, a phenomenon consistent with existing experimental observations. The model is compared to four different experiments encompassing flows of light water, heavy water, and R12 at different pressures, in cylindrical channels, an internally heated annulus, and a rectangular channel. The experimental data includes axial and radial profiles of both liquid temperature and vapor volume fraction, and the agreement can be considered quite good. The complete model is then applied to simulations of subcooled boiling in nuclear reactor subchannels consistent with the

  13. Forced Convection and Sedimentation Past a Flat Plate

    NASA Technical Reports Server (NTRS)

    Pelekasis, Nikolaos A.; Acrivos, Andreas

    1995-01-01

    The steady laminar flow of a well-mixed suspension of monodisperse solid spheres, convected steadily past a horizontal flat plate and sedimenting under the action of gravity, is examined. It is shown that, in the limit as Re approaches infinity and epsilon approaches 0, where Re is the bulk Reynolds number and epsilon is the ratio of the particle radius a to the characteristic length scale L, the analysis for determining the particle concentration profile has several aspects in common with that of obtaining the temperature profile in forced-convection heat transfer from a wall to a fluid stream moving at high Reynolds and Prandtl numbers. Specifically, it is found that the particle concentration remains uniform throughout the O(Re(exp -1/2)) thick Blasius boundary layer except for two O(epsilon(exp 2/3)) thin regions on either side of the plate, where the concentration profile becomes non-uniform owing to the presence of shear-induced particle diffusion which balances the particle flux due to convection and sedimentation. The system of equations within this concentration boundary layer admits a similarity solution near the leading edge of the plate, according to which the particle concentration along the top surface of the plate increases from its value in the free stream by an amount proportional to X(exp 5/6), with X measuring the distance along the plate, and decreases in a similar fashion along the underside. But, unlike the case of gravity settling on an inclined plate in the absence of a bulk flow at infinity considered earlier, here the concentration profile remains continuous everywhere. For values of X beyond the region near the leading edge, the particle concentration profile is obtained through the numerical solution of the relevant equations. It is found that, as predicted from the similarity solution, there exists a value of X at which the particle concentration along the top side of the plate attains its maximum value phi(sub m) and that, beyond this

  14. Computation of forced laminar convection in rotating cavities

    NASA Astrophysics Data System (ADS)

    Chew, J. W.

    1985-05-01

    Finite difference solutions are presented for forced laminar convection in a rotating cylindrical cavity with radial outflow. This forms a simple model of the cooling flow between two compressor disks in a gas turbine engine. If the fluid enters the cavity from a uniform radial source, it is shown that the local Nusselt number changes from that of a 'free disk' near the center of the cavity to that for Ekman layer flow at larger radii. With an axial inlet, the flow, and consequently, the heat transfer, is more complex. If vortex breakdown occurs, then the results are very similar to those for the radial inlet case, but otherwise a wall jet forms on the downstream disk, and the heat transfer from this disk may be several times that for the upstream disk. Variation of mean Nusselt number with rotational speed is qualitatively similar to previously published experimental measurements in turbulent flow. The effect of Prandtl number on heat transfer has also been demonstrated.

  15. Forced convective melting at an evolving ice-water interface

    NASA Astrophysics Data System (ADS)

    Ramudu, Eshwan; Hirsh, Benjamin; Olson, Peter; Gnanadesikan, Anand

    2015-11-01

    The intrusion of warm Circumpolar Deep Water into the ocean cavity between the base of ice shelves and the sea bed in Antarctica causes melting at the ice shelves' basal surface, producing a turbulent melt plume. We conduct a series of laboratory experiments to investigate how the presence of forced convection (turbulent mixing) changes the delivery of heat to the ice-water interface. We also develop a theoretical model for the heat balance of the system that can be used to predict the change in ice thickness with time. In cases of turbulent mixing, the heat balance includes a term for turbulent heat transfer that depends on the friction velocity and an empirical coefficient. We obtain a new value for this coefficient by comparing the modeled ice thickness against measurements from a set of nine experiments covering one order of magnitude of Reynolds numbers. Our results are consistent with the altimetry-inferred melting rate under Antarctic ice shelves and can be used in climate models to predict their disintegration. This work was supported by NSF grant EAR-110371.

  16. Electrically Conductive Metal Nanowire Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Luo, Xiaoxiong

    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

  17. Electrically conducting ternary amorphous fully oxidized materials and their application

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

    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.

  18. Forced-convection boiling tests performed in parallel simulated LMR fuel assemblies

    SciTech Connect

    Rose, S.D.; Carbajo, J.J.; Levin, A.E.; Lloyd, D.B.; Montgomery, B.H.; Wantland, J.L.

    1985-04-21

    Forced-convection tests have been carried out using parallel simulated Liquid Metal Reactor fuel assemblies in an engineering-scale sodium loop, the Thermal-Hydraulic Out-of-Reactor Safety facility. The tests, performed under single- and two-phase conditions, have shown that for low forced-convection flow there is significant flow augmentation by thermal convection, an important phenomenon under degraded shutdown heat removal conditions in an LMR. The power and flows required for boiling and dryout to occur are much higher than decay heat levels. The experimental evidence supports analytical results that heat removal from an LMR is possible with a degraded shutdown heat removal system.

  19. Electrically conductive fibers thermally isolate temperature sensor

    NASA Technical Reports Server (NTRS)

    De Waard, R.; Norton, B.

    1966-01-01

    Mounting assembly provides thermal isolation and an electrical path for an unbacked thermal sensor. The sensor is suspended in the center of a plastic mounting ring from four plastic fibers, two of which are coated with an electrically conductive material and connected to electrically conductive coatings on the ring.

  20. Preparation of Electrically Conductive Polymeric Membranes

    NASA Astrophysics Data System (ADS)

    Encinas, J. C.; Castillo-Ortega, M. M.; Rodríguez, F.; Castaño, V. M.

    2015-10-01

    Cellulose acetate porous membranes, coated with polyaniline, were chemically modified with polyelectrolytes to produce films of varying and controlled porosity and electrical conductivity. The highest electrical conductivity was obtained in membranes prepared with poly(styrene sulfonate) with large pore sizes. The electrical properties as well as scanning electron microscopy (SEM) images are discussed.

  1. System and method for determining velocity of electrically conductive fluid

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

    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.

  2. A Study of Nucleate Boiling with Forced Convection in Microgravity

    NASA Technical Reports Server (NTRS)

    Merte, Herman, Jr.

    1999-01-01

    The ultimate objective of basic studies of flow boiling in microgravity is to improve the understanding of the processes involved, as manifested by the ability to predict its behavior. This is not yet the case for boiling heat transfer even in earth gravity, despite the considerable research activity over the past 30 years. The elements that constitute the nucleate boiling process - nucleation, growth, motion, and collapse of the vapor bubbles (if the bulk liquid is subcooled) - are common to both pool and flow boiling. It is well known that the imposition of bulk liquid motion affects the vapor bubble behavior relative to pool boiling, but does not appear to significantly influence the heat transfer. Indeed, it has been recommended in the past that empirical correlations or experimental data of pool boiling be used for design purposes with forced convection nucleate boiling. It is anticipated that such will most certainly not be possible for boiling in microgravity, based on observations made with pool boiling in microgravity. In earth gravity buoyancy will act to remove the vapor bubbles from the vicinity of the heater surface regardless of how much the imposed bulk velocity is reduced, depending, of course, on the geometry of the system. Vapor bubbles have been observed to dramatically increase in size in pool boiling in microgravity, and the heat flux at which dryout took place was reduced considerably below what is generally termed the critical heat flux (CHF) in earth gravity, depending on the bulk liquid subcooling. However, at heat flux levels below dryout, the nucleate pool boiling process was enhanced considerably over that in earth gravity, in spite of the large vapor bubbles formed in microgravity and perhaps as a consequence. These large vapor bubbles tended to remain in the vicinity of the heater surface, and the enhanced heat transfer appeared to be associated with the presence of what variously has been referred to as a liquid microlayer between the

  3. Electrically Conductive Polyimide Films Containing Gold Surface

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    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.

  4. Electrically conductive connection for an electrode

    SciTech Connect

    Hornack, Thomas R.; Chilko, Robert J.

    1986-01-01

    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.

  5. Electrically conductive polyimides containing silver trifluoroacetylacetonate

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

    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.

  6. Mathematical Modelling of Force Convection in a Two-Phase Thermosyphon in Conjugate Formulation

    NASA Astrophysics Data System (ADS)

    Nurpeiis, Atlant; Nee, Alexander

    2016-02-01

    A nonlinear non-stationary problem of the conductive-convective heat transfer is addressed (under forced convection conditions) in the thermosyphon of rectangular cross-section. The thermal energy supply is carried out through the lower horizontal border. The mathematical model is formulated in dimensionless variables of "velocity vorticity vector - current function - temperature". The current and temperature distribution lines are obtained, illustrating the effect of the Reynolds number on the thermodynamic structures formation in the analyzed object.

  7. Convection

    NASA Astrophysics Data System (ADS)

    Britz, Dieter

    Convection has long been coupled with electrochemistry, and the name hydrodynamic voltammetry has become standard. In electroanalytical chemistry we mainly seek reproducible conditions. These are almost always attained by systems in which a steady convective state is achieved, although not always. Thus, the once popular dropping mercury electrode (see texts such as [74, 257]) has convection around it, but is never in steady state; it might be called a reproducible periodic dynamic state.

  8. Multi-crystalline silicon solidification under controlled forced convection

    NASA Astrophysics Data System (ADS)

    Cablea, M.; Zaidat, K.; Gagnoud, A.; Nouri, A.; Chichignoud, G.; Delannoy, Y.

    2015-05-01

    Multi-crystalline silicon wafers have a lower production cost compared to mono-crystalline wafers. This comes at the price of reduced quality in terms of electrical properties and as a result the solar cells made from such materials have a reduced efficiency. The presence of different impurities in the bulk material plays an important role during the solidification process. The impurities are related to different defects (dislocations, grain boundaries) encountered in multi-crystalline wafers. Applying an alternative magnetic field during the solidification process has various benefits. Impurities concentration in the final ingot could be reduced, especially metallic species, due to a convective term added in the liquid that reduces the concentration of impurities in the solute boundary layer. Another aspect is the solidification interface shape that is influenced by the electromagnetic stirring. A vertical Bridgman type furnace was used in order to study the solidification process of Si under the influence of a travelling magnetic field able to induce a convective flow in the liquid. The furnace was equipped with a Bitter type three-phase electromagnet that provides the required magnetic field. A numerical model of the furnace was developed in ANSYS Fluent commercial software. This paper presents experimental and numerical results of this approach, where interface markings were performed.

  9. Studies of Forced-Convection Heat Transfer Augmentation in Large Containment Enclosures

    SciTech Connect

    Kuhn, S.Z.; Peterson, P.F.

    2001-06-17

    Heat transfer enhancement due to jet mixing inside a cylindrical enclosure is discussed. This work addresses conservative heat transfer assumptions regarding mixing and condensation that have typically been incorporated into passive containment design analyses. This research presents the possibility for increasing decay heat removal of passive containment systems under combined natural and forced convection. Eliminating these conservative assumptions could result in a changed containment design and reduce the construction cost. It is found that the ratio of forced- and free-convection Nusselt numbers can be predicted as a function of the Archimedes number and a correlated factor accounting for jet orientation and enclosure geometry.

  10. Electrical conductivity of Al-bearing bridgmanite

    NASA Astrophysics Data System (ADS)

    Yoshino, T.; Kamada, S.; Ohtani, E.; Hirao, N.

    2015-12-01

    Electrical conductivity measurements of bridgmanite with various Al contents and constant Mg# 90 at room temperature up to 2000 K and 26-28 GPa were performed in Kawai-type multianvil apparatus using impedance spectroscopic analyses. The incorporation of Al into bridgmanite significantly raises the electrical conductivity but it is small conductivity variation with respect to the amount of Al. Synchrotron Mössbauer spectroscopy of recovered samples showed a significant amount of ferric iron in aluminous bridgmanite. The mobility of charge carriers in bridgmanite was calculated from the conductivity and Fe3+/ΣFe. A relation between the logarithm of electrical conductivity and reciprocal temperature is consistent with Fe2+-Fe3+ electron hopping (small polaron) as the dominant conduction mechanism at low temperatures (< 1400 K) and ionic conduction at high temperatures (> 1600 K). Taking various conduction mechanisms into account, we develop an electrical conductivity model for aluminous bridgmanite as a function of Al and Fe content. This conductivity model suggests that the electrical conductivity of aluminous bridgmanite has a maximum at around 0.13 Al per formula unit, and further increase of Al in bridgmanite reduces the conductivity. The conductivity increase observed in the uppermost lower mantle by electromagnetic studies can be explained by increases of Fe and Na content in combination with substitution of Al into bridgmanite with increasing pressure due to the gradual decomposition of majorite garnet.

  11. Electrical Conductivity of Ferritin Proteins by Conductive AFM

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

    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.

  12. A numerical study of Li-SF6 wick combustion - Forced and mixed convective burning

    NASA Technical Reports Server (NTRS)

    Damaso, R. C.; Chen, L.-D.

    1992-01-01

    A numerical study is conducted to study Li-SF6 wick diffusion flames under mixed convective burning conditions at a pressure of 0.01 MPa. Both planar and cylindrical wicks are considered. The model is based on a conserved scalar approach. The objective of this study is to assess the effects of particular parameters on the burning rate and heat transfer. The flat-plate solution yields a fuel mass burning rate per unit surface area following the x exp -1/2 dependence of the classical similarity solution, where x is the streamwise distance. Cylindrical wick geometries yield enhanced burning rates over planar wicks. For the case of mixed convective burning, the burning rate results approach either the forced or natural convective burning limits as ambient streamwise velocity is changed. Critical Richardson numbers specifying these burning limits are determined for a given condition. Reducing gravity results in a lower burning rate because the influence of natural convection is diminished. Under reduced gravity of 1/1000 of the sea-level value, mixed convective burning nearly resembles forced convection.

  13. Electrically conductive proppant and methods for detecting, locating and characterizing the electrically conductive proppant

    DOEpatents

    Cannan, Chad; Bartel, Lewis; Palisch, Terrence; Aldridge, David

    2015-01-13

    Electrically conductive proppants and methods for detecting, locating, and characterizing same are provided. The electrically conductive proppant can include a substantially uniform coating of an electrically conductive material having a thickness of at least 500 nm. The method can include injecting a hydraulic fluid into a wellbore extending into a subterranean formation at a rate and pressure sufficient to open a fracture therein, injecting into the fracture a fluid containing the electrically conductive proppant, electrically energizing the earth at or near the fracture, and measuring three dimensional (x, y, and z) components of electric and magnetic field responses at a surface of the earth or in an adjacent wellbore.

  14. MHD forced convective laminar boundary layer flow from a convectively heated moving vertical plate with radiation and transpiration effect.

    PubMed

    Uddin, Md Jashim; Khan, Waqar A; Ismail, A I Md

    2013-01-01

    A two-dimensional steady forced convective flow of a Newtonian fluid past a convectively heated permeable vertically moving plate in the presence of a variable magnetic field and radiation effect has been investigated numerically. The plate moves either in assisting or opposing direction to the free stream. The plate and free stream velocities are considered to be proportional to x(m) whilst the magnetic field and mass transfer velocity are taken to be proportional to x((m-1)/2) where x is the distance along the plate from the leading edge of the plate. Instead of using existing similarity transformations, we use a linear group of transformations to transform the governing equations into similarity equations with relevant boundary conditions. Numerical solutions of the similarity equations are presented to show the effects of the controlling parameters on the dimensionless velocity, temperature and concentration profiles as well as on the friction factor, rate of heat and mass transfer. It is found that the rate of heat transfer elevates with the mass transfer velocity, convective heat transfer, Prandtl number, velocity ratio and the magnetic field parameters. It is also found that the rate of mass transfer enhances with the mass transfer velocity, velocity ratio, power law index and the Schmidt number, whilst it suppresses with the magnetic field parameter. Our results are compared with the results existing in the open literature. The comparisons are satisfactory. PMID:23741295

  15. MHD Forced Convective Laminar Boundary Layer Flow from a Convectively Heated Moving Vertical Plate with Radiation and Transpiration Effect

    PubMed Central

    Uddin, Md. Jashim; Khan, Waqar A.; Ismail, A. I. Md.

    2013-01-01

    A two-dimensional steady forced convective flow of a Newtonian fluid past a convectively heated permeable vertically moving plate in the presence of a variable magnetic field and radiation effect has been investigated numerically. The plate moves either in assisting or opposing direction to the free stream. The plate and free stream velocities are considered to be proportional to whilst the magnetic field and mass transfer velocity are taken to be proportional to where is the distance along the plate from the leading edge of the plate. Instead of using existing similarity transformations, we use a linear group of transformations to transform the governing equations into similarity equations with relevant boundary conditions. Numerical solutions of the similarity equations are presented to show the effects of the controlling parameters on the dimensionless velocity, temperature and concentration profiles as well as on the friction factor, rate of heat and mass transfer. It is found that the rate of heat transfer elevates with the mass transfer velocity, convective heat transfer, Prandtl number, velocity ratio and the magnetic field parameters. It is also found that the rate of mass transfer enhances with the mass transfer velocity, velocity ratio, power law index and the Schmidt number, whilst it suppresses with the magnetic field parameter. Our results are compared with the results existing in the open literature. The comparisons are satisfactory. PMID:23741295

  16. The electrical conductivity of eclogite in Tibet

    NASA Astrophysics Data System (ADS)

    Guo, Y.; Wang, D.

    2011-12-01

    Qinghai-Tibet Plateau is known as its huge crust and complicated plateau plate tectonics. To understand the geodynamics of this plateau, a variety of geology surveys and geophysical observations were carried out. MT results reveal that the high conductivity zones widely present both in the crust and the mantle. These conductivity anomalies were interpreted as the presence of melt by many researchers. The eclogite is considered as one of candidate rock constituting the lower crust and uppermost mantle. Thus, the electrical conductivity eclogite may provide available information to understand the electrical structure of the crust and the mantle beneath Tibet. The starting material is natural eclogite collected from Pianshishan area, which is located in the middle of Qiangtang. The electrical conductivity of eclogite was measured by using the impedance spectrum method at 1.5, 2.5, 3.5 GPa and 372 ~ 803 K. Oxygen fugacity was controlled by the Mo-MoO2 buffer, The sample temperatures were monitored by a NiCr-NiAl thermocouple. The results show that the pressure weakly affect the electrical conductivity of eclogite. The electrical conductivity of eclogite varies from -5.5 S / m to -1.75 S / m with the temperature increased. The electrical conductivity curves change the slope and alter the conduction mechanism at various pressures. The low-temperature activation enthalpy at 1.5, 2.5, 3.5 GP are 0.380, 0.405, 0.446 eV, whereas high-temperature activation enthalpy are 0.986, 0.986, 1.023 eV, respectively. This results were entrapped to Earth's interior and compared with the magnetotelluric(MT) observations, our model is consistent with one of the electrical conductivity structures derived from geophysical observations.

  17. The Role of Ascent-Forced Convection in Orographic Precipitation: Results from the DOMEX Field Campaign

    NASA Astrophysics Data System (ADS)

    Minder, J. R.; Smith, R. B.; Nugent, A. D.; Kirshbaum, D. J.

    2011-12-01

    Shallow convection is a pervasive feature of orographic precipitation, but its detailed role remains poorly understood. The mountainous Caribbean island of Dominica is a natural laboratory for isolating the role of shallow convection in orographic rainfall. It lies in a region of persistent easterly trade wind flow, and receives much of its rainfall from shallow convection that is forced mechanically by ascent of easterly flow over the Dominican terrain. The Dominica Experiment (DOMEX) has focused on convective orographic precipitation over the island from 2007-2011. The first phase of the project developed a climatology of rainfall and theories to explain the observed enhancement over the terrain. The second phase of the project (Apr-May 2011) has provided a detailed view of 20 individual rainfall events with data from: surface gauges, time-lapse photography, operational radar scans, a mountaintop weather station, and both in situ and remote observations from the University of Wyoming King Air research aircraft. Focusing on ascent--forced convection during DOMEX has revealed a number of the key processes that control the rainfall. Upwind of the island, clouds and water vapor anomalies exist that appear to play a crucial role in seeding the convection over the terrain and determining its vigor. Over the windward slopes the air is readily lifted with little flow deflection. Strong convective cells rapidly develop to produce large rainfall rates. Over the lee slopes of the terrain there is an abrupt transition to a deep and turbulent plunging flow that quickly eliminates convective clouds, but allows for the spillover of rainfall. The air that passes over the island is transformed such that low-levels are dried, warmed and decelerated, and the downwind wake becomes less hospitable to trade wind cumuli.

  18. Electrically conductive connection for an electrode

    DOEpatents

    Hornack, T.R.; Chilko, R.J.

    1986-09-02

    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. 2 figs.

  19. Electrically conductive containment vessel for molten aluminum

    DOEpatents

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

    1984-06-25

    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.

  20. Electrically conductive containment vessel for molten aluminum

    DOEpatents

    Holcombe, Cressie E.; Scott, Donald G.

    1985-01-01

    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.

  1. Effect of a forced Couette flow on coupled convective and morphological instabilities during unidirectional solidification

    NASA Technical Reports Server (NTRS)

    Coriell, S. R.; Mcfadden, G. B.; Boisvert, R. F.; Sekerka, R. F.

    1984-01-01

    The effect of a forced Couette flow, parallel to a horizontal crystal-melt interface during directional solidification of an alloy of lead containing tin, on the onset of convective and morphological instabilities, is calculated numerically via a linear stability analysis. Such a flow does not affect perturbations with wave vectors perpendicular to the flow. For perturbations with wave vectors parallel to the flow, the onset of morphological instability is somewhat suppressed and thermosolutal convection is greatly suppressed. When instabilities occur, they are oscillatory and correspond to travelling waves. For values of the crystal growth velocity for which mixed morphological and convective modes occur, the presence of a forced flow produces sufficient decoupling to allow otherwise degenerate branches to be identified.

  2. Weight and water loss in the neonate in natural and forced convection.

    PubMed Central

    Thompson, M H; Stothers, J K; McLellan, N J

    1984-01-01

    We describe a simple method of determining weight loss and hence water loss of infants in incubators. Unlike previously reported methods, it does not interfere with the microenvironment surrounding the infant. Weight loss of 16 term and 32 preterm infants was measured in both forced and natural convection. No significant increase in water loss was observed in the term infants but in the preterm infants the mean loss in natural convection was 0.85 g/kg/hour compared with 1.26 g/kg/hour in forced convection: in the most extreme situation it was doubled. This water loss represents a substantial energy loss and suggestions to minimise it are discussed. Images Fig. 1 PMID:6497432

  3. Forced-to-natural convection transition tests in parallel simulated liquid metal reactor fuel assemblies

    SciTech Connect

    Levin, A.E. ); Montgomery, B.H. )

    1990-01-01

    The Thermal-Hydraulic Out of Reactor Safety (THORS) Program at Oak Ridge National Laboratory (ORNL) had as its objective the testing of simulated, electrically heated liquid metal reactor (LMR) fuel assemblies in an engineering-scale, sodium loop. Between 1971 and 1985, the THORS Program operated 11 simulated fuel bundles in conditions covering a wide range of normal and off-normal conditions. The last test series in the Program, THORS-SHRS Assembly 1, employed two parallel, 19-pin, full-length, simulated fuel assemblies of a design consistent with the large LMR (Large Scale Prototype Breeder -- LSPB) under development at that time. These bundles were installed in the THORS Facility, allowing single- and parallel-bundle testing in thermal-hydraulic conditions up to and including sodium boiling and dryout. As the name SHRS (Shutdown Heat Removal System) implies, a major objective of the program was testing under conditions expected during low-power reactor operation, including low-flow forced convection, natural convection, and forced-to-natural convection transition at various powers. The THORS-SHRS Assembly 1 experimental program was divided up into four phases. Phase 1 included preliminary and shakedown tests, including the collection of baseline steady-state thermal-hydraulic data. Phase 2 comprised natural convection testing. Forced convection testing was conducted in Phase 3. The final phase of testing included forced-to-natural convection transition tests. Phases 1, 2, and 3 have been discussed in previous papers. The fourth phase is described in this paper. 3 refs., 2 figs.

  4. Experimental investigation of forced-convection heat-transfer characteristics of lead-bismuth eutectic

    NASA Technical Reports Server (NTRS)

    Lubarsky, Bernard

    1951-01-01

    The forced-convection heat-transfer characteristics of lead-bismuth eutectic were experimentally investigated. Experimental values of Nusselt number for lead-bismuth fell considerably below predicted values. The addition of a wetting agent did not change the heat transfer characteristics.

  5. Electrically-Conductive Polyaramid Cable And Fabric

    NASA Technical Reports Server (NTRS)

    Orban, Ralph F.

    1988-01-01

    Tows coated with metal provide strength and conductance. Cable suitable for use underwater made of electrically conductive tows of metal-coated polyaramid filaments surrounded by electrically insulating jacket. Conductive tows used to make conductive fabrics. Tension borne by metal-coated filaments, so upon release, entire cable springs back to nearly original length without damage.

  6. Universal thermal and electrical conductivity from holography

    NASA Astrophysics Data System (ADS)

    Jain, Sachin

    2010-11-01

    It is known from earlier work of Iqbal, Liu [1] that the boundary transport coefficients such as electrical conductivity (at vanishing chemical potential), shear viscosity etc. at low frequency and finite temperature can be expressed in terms of geometrical quantities evaluated at the horizon. In the case of electrical conductivity, at zero chemical potential gauge field fluctuation and metric fluctuation decouples, resulting in a trivial flow from horizon to boundary. In the presence of chemical potential, the story becomes complicated due to the fact that gauge field and metric fluctuation can no longer be decoupled. This results in a nontrivial flow from horizon to boundary. Though horizon conductivity can be expressed in terms of geometrical quantities evaluated at the horizon, there exist no such neat result for electrical conductivity at the boundary. In this paper we propose an expression for boundary conductivity expressed in terms of geometrical quantities evaluated at the horizon and thermodynamic quantities. We also consider the theory at finite cutoff recently constructed in [2], at radius r c outside the horizon and give an expression for cutoff dependent electrical conductivity ( σ( r c )), which interpolates smoothly between horizon conductivity σ H ( r c → r h ) and boundary conductivity σ B ( r c → ∞). Using the results about the conductivity we gain much insight into the universality of thermal conductivity to viscosity ratio proposed in [3].

  7. Electrically conducting polymers for aerospace applications

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    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.

  8. Potential Aerosol Indirect Effects on Atmospheric Circulation and Radiative Forcing through Deep Convection

    SciTech Connect

    Fan, Jiwen; Rosenfeld, Daniel; Ding, Yanni; Leung, Lai-Yung R.; Li, Zhanqing

    2012-05-10

    Aerosol indirect effects, i.e., the interactions of aerosols with clouds by serving as cloud condensation nuclei (CCN) or ice nuclei (IN), constitute the largest uncertainty in climate forcing and projection. Previous IPCC reported aerosol indirect forcing is negative, which does not account for aerosol-convective cloud interactions because the complex processes involved are poorly understood and represented in climate models. Here we report that aerosol indirect effect on deep convective cloud systems can lead to enhanced regional convergence and a strong top-of atmosphere (TOA) warming. Aerosol invigoration effect on convection can result in a strong radiative warming in the atmosphere (+5.6 W m-2) due to strong night-time warming, a lofted latent heating, and a reduced diurnal temperature difference, all of which could remarkably impact regional circulation and modify weather systems. We further elucidated how aerosols change convective intensity, diabatic heating, and regional circulation under different environmental conditions and concluded that wind shear and cloud base temperature play key roles in determining the significance of aerosol invigoration effect for convective systems.

  9. Determination of forced convective heat transfer coefficients for subsonic flows over heated asymmetric NANA 4412 airfoil

    NASA Astrophysics Data System (ADS)

    Dag, Yusuf

    Forced convection over traditional surfaces such as flat plate, cylinder and sphere have been well researched and documented. Data on forced convection over airfoil surfaces, however, remain very scanty in literature. High altitude vehicles that employ airfoils as lifting surfaces often suffer leading edge ice accretions which have tremendous negative consequences on the lifting capabilities and stability of the vehicle. One of the ways of mitigating the effect of ice accretion involves judicious leading edge convective cooling technique which in turn depends on the accuracy of convective heat transfer coefficient used in the analysis. In this study empirical investigation of convective heat transfer measurements on asymmetric airfoil is presented at different angle of attacks ranging from 0° to 20° under subsonic flow regime. The top and bottom surface temperatures are measured at given points using Senflex hot film sensors (Tao System Inc.) and used to determine heat transfer characteristics of the airfoils. The model surfaces are subjected to constant heat fluxes using KP Kapton flexible heating pads. The monitored temperature data are then utilized to determine the heat convection coefficients modelled empirically as the Nusselt Number on the surface of the airfoil. The experimental work is conducted in an open circuit-Eiffel type wind tunnel, powered by a 37 kW electrical motor that is able to generate subsonic air velocities up to around 41 m/s in the 24 square-inch test section. The heat transfer experiments have been carried out under constant heat flux supply to the asymmetric airfoil. The convective heat transfer coefficients are determined from measured surface temperature and free stream temperature and investigated in the form of Nusselt number. The variation of Nusselt number is shown with Reynolds number at various angles of attacks. It is concluded that Nusselt number increases with increasing Reynolds number and increase in angle of attack from 0

  10. Ray-tracing simulations vs. satellite observations of gravity waves forced by deep convection

    NASA Astrophysics Data System (ADS)

    Kalisch, Silvio; Trinh, Thai; Chun, Hye-Yeong; Ern, Manfred; Preusse, Peter; Eckermann, Stephen D.; Riese, Martin

    2015-04-01

    Gravity waves (GW) are a prominent coupling mechanism between their tropospheric sources and the upper stratosphere to mesosphere region. They contribute prominently to the wave driving of the Quasi-biennial-oscillation (QBO) in the tropics and other large scale circulations like the Brewer-Dobson circulation. One important dynamic source of GWs is convection. Convective GWs have considerable short horizontal wavelengths and are therefore not entirely observable by infrared limb-sounding satellite instruments. For this reason, we present the results of GW ray-tracing calculations from convective sources up to the mesosphere. We utilized the Gravity wave Regional Or Global RAy-Tracer (GROGRAT) to perform the GW trajectory calculations. The launch conditions for each GW were calculated using the convective GW source scheme from Yonsei University (South Korea) to quantify the excitation by deep convection. Heating rates, cloud data, and atmospheric background data were provided by the MERRA dataset for the estimation of convective forcing by deep convection and as the atmospheric background for the ray-tracing calculations afterwards. The resulting momentum flux distributions are in remarkable coincidence with typical geographic regions of deep convection in the tropics. Additionally, the momentum flux distributions of higher latitude regions are simulated using a standard launch distribution for GWs. In order to validate our findings we compare our simulation results with satellite measurements of temperature amplitudes and momentum flux from infrared limb-sounding satellite instruments. These validations are complemented with an in-depth analysis of the observational filter for two different satellite instruments (HIRDLS and SABER). Scanning geometry, limitations in the detection of short wavelengths, aliasing effects, and the detector sensitivity are taken into account to quantify the level of uncertainty in our results. This analysis finally shows a good agreement

  11. A Study of Nucleate Boiling with Forced Convection in Microgravity

    NASA Technical Reports Server (NTRS)

    Merte, Herman, Jr.

    1996-01-01

    Boiling is a rather imprecise term applied to the process of evaporation in which the rate of liquid-vapor phase change is large. In seeking to determine the role and significance of body forces on the process, of which buoyancy or gravity is just one agent, it becomes necessary to define the term more precisely. It is generally characterized by the formation and growth of individual vapor bubbles arising from heat transfer to the liquid, either at a solid/liquid or liquid/liquid interface, or volumetrically. The terms 'bubble' boiling and 'nucleate' boiling are frequently used, in recognition of the interactions of surface tension and other forces in producing discrete bubbles at distinctive locations (although not always). Primary considerations are that evaporation can occur only at existing liquid-vapor interfaces, so that attention must be given to the formation of an interface (the nucleation process), and that the latent heat for this evaporation can come only from the superheated liquid, so that attention must also be given to the temperature distributions in the liquid.

  12. Forced Convective Thermal Transport and Flow Stability Characteristics in Near-Critical Supercritical Fluid

    NASA Astrophysics Data System (ADS)

    Hasan, Nusair; Farouk, Bakhtier

    2013-11-01

    Forced convective thermal transport characteristics of supercritical carbon dioxide in vertical flow are numerically investigated. A tube with a circular cross-section and heated side-wall is considered. A real-fluid model for representing the thermo-physical properties of the supercritical fluid along with the fully compressible form of the Navier-Stokes equations and an implicit time-marching scheme is used to solve the problem. Thermo-physical properties of near-critical supercritical fluids show diverging characteristics. Large variations of density of near-critical supercritical fluid in forced convective flow can induce thermo-hydraulic instability similar to density wave oscillations. The developed numerical model is used for studying the effect of geometrical parameters of the tube, wall heat flux and pressure on steady-state convective thermal transport as well as the stability behavior of the supercritical fluid near its critical point. The enhancement or deterioration of heat transfer caused by the temperature-induced variation of physical properties (especially specific heat) is also investigated, as well as the effect of buoyancy on the forced convective flow.

  13. Numerical calculation of the drag force induced by natural convection of spheres at low Grashof numbers

    SciTech Connect

    Dudek, D.; Fletcher, T.H.

    1987-02-01

    When a heated solid sphere is introduced into an ambient fluid, a natural convective flow occurs which results in a drag force on the sphere. This study involves the numerical calculation of both the steady-state and the transient natural convective drag force around spheres at low Grashof numbers. Numerical techniques are taken from Geoola and Cornish. An empirical expression is suggested for the total drag coefficient for Grashof numbers ranging from 4 x 10/sup -4/ to 0.5 and Prandtl number = 0.72: log C/sub DT/ = 1.25 + 0.31 log Gr - 0.097(log Gr)/sup 2/. The dimensionless time required to reach 90% of the steady-state drag force can be approximated by the second-order polynomial: log t/sub 90%/ = 1.32 - log Gr - 0.11(Gr)/sup 2/.

  14. Electrical conductivity in sprite streamer channels

    NASA Astrophysics Data System (ADS)

    Gordillo-Vázquez, F. J.; Luque, A.

    2010-08-01

    We study the electrical conductivity of a sprite streamer channel at three different altitudes (63 km, 70 km and 80 km). We discuss the hypothesis that the electrical conductivity stays constant along the full length of a streamer channel, contrary to expectations based on scaling laws. We then apply this hypothesis and extrapolations from a numerical electrodynamical simulation to study the air plasma kinetics after the passage of a streamer. We test two possible scenarios for the physical origin of trailing sprite emissions: a single pulse and a single pulse with a delayed re-enhancement of the electric field up to the breakdown value. Our simulations show that VLF observations agree with persistent electric fields in the sprite that last several milliseconds and that associative detachment of O- ions may significantly affect the atmospheric conductivity in the presence of sprites.

  15. Electrically conductive palladium containing polyimide films

    NASA Technical Reports Server (NTRS)

    Taylor, L. T.; St.clair, A. K.; Carver, V. C.; Furtsch, T. A. (Inventor)

    1982-01-01

    Lightweight, high temperature resistant, electrically conductive, palladium containing polyimide films and methods for their preparation are described. A palladium (II) ion-containing polyamic acid solution is prepared by reacting an aromatic dianhydride with an equimolar quantity of a palladium II ion-containing salt or complex and the reactant product is cast as a thin film onto a surface and cured at approximately 300 C to produce a flexible electrically conductive cyclic palladium containing polyimide. The source of palladium ions is selected from the group of palladium II compounds consisting of LiPdCl4, PdS(CH3)2Cl2Na2PdCl4, and PdCl2. The films have application to aerodynamic and space structures and in particular to the relieving of space charging effects.

  16. Electrically conducting polyimide film containing tin complexes

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

    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.

  17. Electrical conductivity of acidic sulfate solution

    NASA Astrophysics Data System (ADS)

    Majima, Hiroshi; Peters, Ernest; Awakura, Yasuhiro; Park, Sung Kook

    1987-03-01

    The electrical conductivities of the aqueous solution system of H2SO4-MSO4 (involving ZnSO4, MgSO4, Na2SO4, and (NH4)2SO4), reported by Tozawa et al., were examined in terms of a (H2O) and H+ ion concentration. The equations to compute the concentrations of various species in aqueous sulfuric acid solutions containing metal sulfates were derived for a typical example of the H2SO4-ZnSO4-MgSO4-(Na2SO4)-H2O system. It was found that the H+ ion concentrations in concentrated sulfuric acid solutions corresponding to practical zinc electrowinning solutions are very high and remain almost constant with or without the addition of metal sulfates. The addition of metal sulfates to aqueous sulfuric acid solution causes a decrease in electrical conductivity, and this phenomenon is attributed to a decrease in water activity, which reflects a decrease in the amount of free water. The relationship between conductivity and water activity at a constant H+ ion concentration is independent of the kind of sulfates added. On the other hand, any increase in H+ ion concentration results in an increase in electrical conductivity. A novel method for the prediction of electrical conductivity of acidic sulfate solution is proposed that uses the calculated data of water activity and the calculated H+ ion concentration. Also, the authors examined an extension of the Robinson-Bower equation to calculate water activity in quarternary solutions based on molarity instead of molality, and found that such calculated values are in satisfactory agreement with those determined experimentally by a transpiration method.

  18. Electric conductivity of plasma in solar wind

    NASA Technical Reports Server (NTRS)

    Chertkov, A. D.

    1995-01-01

    One of the most important parameters in MHD description of the solar wind is the electric conductivity of plasma. There exist now two quite different approaches to the evaluation of this parameter. In the first one a value of conductivity taken from the most elaborated current theory of plasma should be used in calculations. The second one deals with the empirical, phenomenological value of conductivity. E.g.: configuration of interplanetary magnetic field, stretched by the expanding corona, depends on the magnitude of electrical conductivity of plasma in the solar wind. Knowing the main empirical features of the field configuration, one may estimate the apparent phenomenological value of resistance. The estimations show that the electrical conductivity should be approximately 10(exp 13) times smaller than that calculated by Spitzer. It must be noted that the empirical value should be treated with caution. Due to the method of its obtaining it may be used only for 'large-scale' description of slow processes like coronal expansion. It cannot be valid for 'quick' processes, changing the state of plasma, like collisions with obstacles, e.g., planets and vehicles. The second approach is well known in large-scale planetary hydrodynamics, stemming from the ideas of phenomenological thermodynamics. It could formulate real problems which should be solved by modern plasma physics, oriented to be adequate for complicated processes in space.

  19. Convectively Forced Gravity Waves and their Sensitivity to Heating Profile and Atmospheric Structure

    NASA Astrophysics Data System (ADS)

    Halliday, Oliver; Parker, Douglas; Griffiths, Stephen; Vosper, Simon; Stirling, Alison

    2016-04-01

    It has been known for some time that convective heating is communicated to its environment by gravity waves. Despite this, the radiation of gravity waves in macro-scale models, which are typically forced at the grid-scale by meso-scale parameterization schemes, is not well understood. We present here theoretical work directed toward improving our fundamental understanding of convectively forced gravity wave effects at the meso-scale, in order to begin to address this problem. Starting with the hydrostatic, non-rotating, 2D, Boussinesq equations in a slab geometry, we find a radiating, analytical solution to prescribed sensible heat forcing for both the vertical velocity and potential temperature response. Both Steady and pulsed heating with adjustable horizontal structure is considered. From these solutions we construct a simple model capable of interrogating the spatial and temporal sensitivity to chosen heating functions of the remote forced response in particular. By varying the assumed buoyancy frequency, the influence of the model stratosphere on the upward radiation of gravity waves, and in turn, on the tropospheric response can be understood. Further, we find that the macro-scale response to convection is highly dependent on the radiation characteristics of gravity waves, which are in turn dependent upon the temporal and spatial structure of the source, and upper boundary condition of the domain.

  20. Effects of vertically ribbed surface roughness on the forced convective heat losses in central receiver systems

    NASA Astrophysics Data System (ADS)

    Uhlig, Ralf; Frantz, Cathy; Fritsch, Andreas

    2016-05-01

    External receiver configurations are directly exposed to ambient wind. Therefore, a precise determination of the convective losses is a key factor in the prediction and evaluation of the efficiency of the solar absorbers. Based on several studies, the forced convective losses of external receivers are modeled using correlations for a roughened cylinder in a cross-flow of air. However at high wind velocities, the thermal efficiency measured during the Solar Two experiment was considerably lower than the efficiency predicted by these correlations. A detailed review of the available literature on the convective losses of external receivers has been made. Three CFD models of different level of detail have been developed to analyze the influence of the actual shape of the receiver and tower configuration, of the receiver shape and of the absorber panels on the forced convective heat transfer coefficients. The heat transfer coefficients deduced from the correlations have been compared to the results of the CFD simulations. In a final step the influence of both modeling approaches on the thermal efficiency of an external tubular receiver has been studied in a thermal FE model of the Solar Two receiver.

  1. Effects of aerosol optical properties on deep convective clouds and radiative forcing

    SciTech Connect

    Fan, Jiwen; Zhang, Renyi; Tao, Wei-Kuo; Mohr, Karen I

    2008-04-23

    The aerosol radiative effects (ARE) on the deep convective clouds are investigated by using a spectral-bin cloud-resolving model coupled with a radiation scheme and an explicit land surface model. The sensitivity of cloud properties and the associated radiative forcing to aerosol single-scattering albedo (SSA) are examined. The ARE on cloud properties is pronounced for mid-visible SSA of 0.85. Relative to the case without ARE, the cloud fraction and optical depth decrease by about 18% and 20%, respectively. Ice particle number concentrations, liquid water path, ice water path, and droplet size decrease by more than 15% when the ARE is introduced. The ARE causes a surface cooling of about 0.35 K and significantly high heating rates in the lower troposphere (about 0.6 K day-1 higher at 2 km), both of which lead to a more stable atmosphere and hence weaker convection. The weaker convection explains the less cloudiness, lower cloud optical depth, less LWP and IWP, smaller droplet size, and less precipitation resulting from the ARE. The daytime-mean direct forcing induced by black carbon is about 2.2 W m-2 at the top of atmosphere (TOA) and -17.4 W m-2 at the surface for SSA of 0.85. The semi-direct forcing is positive, about 10 and 11.2 W m-2 at the TOA and surface, respectively. Both the TOA and surface total radiative forcing values are strongly negative for the deep convective clouds, attributed mostly to aerosol indirect forcing. Aerosol direct and semi-direct effects are very sensitive to SSA when aerosol optical depth is high. Because the positive semi-direct forcing compensates the negative direct forcing at the surface, the surface temperature and heat fluxes decrease less significantly with the increase of aerosol absorption (decreasing SSA). The cloud fraction, optical depth, convective strength, and precipitation decrease with the increase of absorption, resulting from a more stable atmosphere due to enhanced

  2. Aerosol Radiative Effects on Deep Convective Clouds and Associated Radiative Forcing

    NASA Technical Reports Server (NTRS)

    Fan, J.; Zhang, R.; Tao, W.-K.; Mohr, I.

    2007-01-01

    The aerosol radiative effects (ARE) on the deep convective clouds are investigated by using a spectral-bin cloud-resolving model (CRM) coupled with a radiation scheme and an explicit land surface model. The sensitivity of cloud properties and the associated radiative forcing to aerosol single-scattering albedo (SSA) are examined. The ARE on cloud properties is pronounced for mid-visible SSA of 0.85. Relative to the case excluding the ARE, cloud fraction and optical depth decrease by about 18% and 20%, respectively. Cloud droplet and ice particle number concentrations, liquid water path (LWP), ice water path (IWP), and droplet size decrease significantly when the ARE is introduced. The ARE causes a surface cooling of about 0.35 K and significantly high heating rates in the lower troposphere (about 0.6K/day higher at 2 km), both of which lead to a more stable atmosphere and hence weaker convection. The weaker convection and the more desiccation of cloud layers explain the less cloudiness, lower cloud optical depth, LWP and IWP, smaller droplet size, and less precipitation. The daytime-mean direct forcing induced by black carbon is about 2.2 W/sq m at the top of atmosphere (TOA) and -17.4 W/sq m at the surface for SSA of 0.85. The semi-direct forcing is positive, about 10 and 11.2 W/sq m at the TOA and surface, respectively. Both the TOA and surface total radiative forcing values are strongly negative for the deep convective clouds, attributed mostly to aerosol indirect forcing. Aerosol direct and semi-direct effects are very sensitive to SSA. Because the positive semi-direct forcing compensates the negative direct forcing at the surface, the surface temperature and heat fluxes decrease less significantly with the increase of aerosol absorption (decreasing SSA). The cloud fraction, optical depth, convective strength, and precipitation decrease with the increase of absorption, resulting from a more stable and dryer atmosphere due to enhanced surface cooling and

  3. Effects of aerosol optical properties on deep convective clouds and radiative forcing

    NASA Astrophysics Data System (ADS)

    Fan, Jiwen; Zhang, Renyi; Tao, Wei-Kuo; Mohr, Karen I.

    2008-04-01

    The aerosol radiative effects (ARE) on the deep convective clouds are investigated by using a spectral-bin cloud-resolving model coupled with a radiation scheme and an explicit land surface model. The sensitivity of cloud properties and the associated radiative forcing to aerosol single-scattering albedo (SSA) are examined. The ARE on cloud properties is pronounced for mid-visible SSA of 0.85. Relative to the case without ARE, the cloud fraction and optical depth decrease by about 18% and 20%, respectively. Ice particle number concentrations, liquid water path, ice water path, and droplet size decrease by more than 15% when the ARE is introduced. The ARE causes a surface cooling of about 0.35 K and significantly high heating rates in the lower troposphere (about 0.6 K day-1 higher at 2 km), both of which lead to a more stable atmosphere and hence weaker convection. The weaker convection explains the less cloudiness, lower cloud optical depth, less LWP and IWP, smaller droplet size, and less precipitation resulting from the ARE. The daytime-mean direct forcing induced by black carbon is about 2.2 W m-2 at the top of atmosphere (TOA) and -17.4 W m-2 at the surface for SSA of 0.85. The semi-direct forcing is positive, about 10 and 11.2 W m-2 at the TOA and surface, respectively. Both the TOA and surface total radiative forcing values are strongly negative for the deep convective clouds, attributed mostly to aerosol indirect forcing. Aerosol direct and semi-direct effects are very sensitive to SSA when aerosol optical depth is high. Because the positive semi-direct forcing compensates the negative direct forcing at the surface, the surface temperature and heat fluxes decrease less significantly with the increase of aerosol absorption (decreasing SSA). The cloud fraction, optical depth, convective strength, and precipitation decrease with the increase of absorption, resulting from a more stable atmosphere due to enhanced surface cooling and atmospheric heating.

  4. Simulation of forced convection-infrared reflow soldering with nitrogen injection

    SciTech Connect

    Son, Y.S.; Bergman, T.L.; Hyun, M.T.

    1995-12-31

    In this paper, forced convection reflow soldering is simulated using an existing numerical model which accounts for multimode effects and is capable of predicting large and small scale thermal and species concentration phenomena. Soldering is performed in an oven equipped with porous panel heaters through which air or nitrogen is introduced to the reflow environment. The gas is injected selectively through top or bottom infrared heaters in order to (1) dampen gas temperature fluctuations which can be established by thermal buoyancy forces and (2) minimize nitrogen use. The results reveal the utility of general process models of the reflow operation as applied to oven design. The effects of mixed convection on heat and gas species transport in the oven are also revealed, and the potential impact on the solidification process is discussed.

  5. Extinction of a bacterial colony under forced convection in pie geometry.

    PubMed

    Shnerb, N M

    2001-01-01

    The extinction of a bacterial colony, as it is forced to migrate into a hostile environment, is analyzed in pie geometry. Under convection, separation of the radial and the azimuthal degrees of freedom is not possible, so the linearized evolution operator is diagonalized numerically. Some characteristic scales are compared with the results of recent experiments, and the "integrable" limit of the theory in the narrow growth region is studied. PMID:11304286

  6. Forced-convection Heat Transfer to Water at High Pressures and Temperatures in the Nonboiling Region

    NASA Technical Reports Server (NTRS)

    Kaufman, S J; Henderson, R W

    1951-01-01

    Forced-convection heat-transfer data have been obtained for water flowing in an electrically heated tube of circular cross section at water pressures of 200 and 2000 pounds per square inch, and temperatures in the nonboiling region, for water velocities ranging between 5 and 25 feet per second. The results indicate that conventional correlations can be used to predict heat-transfer coefficients for water at pressures up to 2000 pounds per square inch and temperatures in the nonboiling region.

  7. Performance characteristics of a thermal energy storage module - A transient PCM/forced convection conjugate analysis

    NASA Technical Reports Server (NTRS)

    Cao, Y.; Faghri, A.

    1991-01-01

    The performance of a thermal energy storage module is simulated numerically. The change of phase of the phase-change material (PCM) and the transient forced convective heat transfer for the transfer fluid with low Prandtl numbers are solved simultaneously as a conjugate problem. A parametric study and a system optimization are conducted. The numerical results show that module geometry is crucial to the design of a space-based thermal energy storage system.

  8. Estimation of boundary heat flux using experimental temperature data in turbulent forced convection flow

    NASA Astrophysics Data System (ADS)

    Parwani, Ajit K.; Talukdar, Prabal; Subbarao, P. M. V.

    2014-09-01

    Heat flux at the boundary of a duct is estimated using the inverse technique based on conjugate gradient method (CGM) with an adjoint equation. A two-dimensional inverse forced convection hydrodynamically fully developed turbulent flow is considered. The simulations are performed with temperature data measured in the experimental test performed on a wind tunnel. The results show that the present numerical model with CGM is robust and accurate enough to estimate the strength and position of boundary heat flux.

  9. Estimation of boundary heat flux using experimental temperature data in turbulent forced convection flow

    NASA Astrophysics Data System (ADS)

    Parwani, Ajit K.; Talukdar, Prabal; Subbarao, P. M. V.

    2015-03-01

    Heat flux at the boundary of a duct is estimated using the inverse technique based on conjugate gradient method (CGM) with an adjoint equation. A two-dimensional inverse forced convection hydrodynamically fully developed turbulent flow is considered. The simulations are performed with temperature data measured in the experimental test performed on a wind tunnel. The results show that the present numerical model with CGM is robust and accurate enough to estimate the strength and position of boundary heat flux.

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

    PubMed

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

    2012-05-17

    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

  11. Film boiling heat transfer from a sphere in natural and forced convection of freon-113

    SciTech Connect

    Dix, D.; Orozco, J. )

    1990-01-01

    Boiling heat transfer fluxes were measured on a 3.84-cm hollow copper sphere, in both forced convection and pool boiling, as a function of angular position in Freon 113. This paper reports on forced-convection tests run at speeds of 0.5 to 1.9 m/s. These tests were conducted in the stable film boiling region of the boiling curve. Significant heat transfer rates were measured in the vapor wake region of the sphere for flow film boiling. Video observations of the boiling process revealed that the flow film boiling vapor removal mechanism consisted of periodic formation and detachment of a vapor wake in the rear of the sphere. For pool boiling it was found that the heated surface had a uniform rate of energy dissipation in the stable film boiling regime, whereas in forced convection the film boiling rate was dependent on angular position. Pool film boiling tests also showed multiple humps (more than one maximum heat flux) in the boiling curve when the liquid was subcooled.

  12. Response of High Latitude Birkeland Currents and Ionospheric Convection to Transitions in Solar Wind Forcing

    NASA Astrophysics Data System (ADS)

    Anderson, B. J.; Korth, H.; Merkin, V. G.; Barnes, R. J.; Ruohoniemi, J. M.

    2014-12-01

    Recent results from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) indicate that at least some transitions from northward to southward IMF produce a specific sequence in the development of large-scale Birkeland currents. First, a set of Region 1 and Region 2 currents forms on the dayside restricted to within a few hours of noon. After about 40 minutes, currents strongly intensify on the nightside, first near midnight local time associated with substorm onset, and then progressively further toward the dayside via dawn and dusk. Only after an hour or more after the transition to stronger solar wind forcing, is the complete Region 1, Region 2 current system developed. The results imply that the initial response to a transition from weak to strong forcing is convection into the polar cap and lobes without strong return convection to the dayside from the nightside magnetosphere. Return convection from the nightside begins with substorm onset and progresses to the dayside. This analysis is extended by examining a large number of transitions from prolonged auroral quiescence, associated with northward IMF, to southward IMF and the development of large-scale Region 1/Region 2 Birkeland currents, to assess whether the above progression holds in general. In addition, transition events to particularly intense driving, for example, associated with shocks are examined to assess how this ordering of events may be changed for onsets of particularly intense solar wind forcing.

  13. Material transport in a convective surface mixed layer under weak wind forcing

    NASA Astrophysics Data System (ADS)

    Mensa, Jean A.; Özgökmen, Tamay M.; Poje, Andrew C.; Imberger, Jörg

    2015-12-01

    Flows in the upper ocean mixed layer are responsible for the transport and dispersion of biogeochemical tracers, phytoplankton and buoyant pollutants, such as hydrocarbons from an oil spill. Material dispersion in mixed layer flows subject to diurnal buoyancy forcing and weak winds (| u10 | = 5m s-1) are investigated using a non-hydrostatic model. Both purely buoyancy-forced and combined wind- and buoyancy-forced flows are sampled using passive tracers, as well as 2D and 3D particles to explore characteristics of horizontal and vertical dispersion. It is found that the surface tracer patterns are determined by the convergence zones created by convection cells within a time scale of just a few hours. For pure convection, the results displayed the classic signature of Rayleigh-Benard cells. When combined with a wind stress, the convective cells become anisotropic in that the along-wind length scale gets much larger than the cross-wind scale. Horizontal relative dispersion computed by sampling the flow fields using both 2D and 3D passive particles is found to be consistent with the Richardson regime. Relative dispersion is an order of magnitude higher and 2D surface releases transition to Richardson regime faster in the wind-forced case. We also show that the buoyancy-forced case results in significantly lower amplitudes of scale-dependent horizontal relative diffusivity, kD(ℓ), than those reported by Okubo (1970), while the wind- and buoyancy-forced case shows a good agreement with Okubo's diffusivity amplitude, and the scaling is consistent with Richardson's 4/3rd law, kD ∼ ℓ4/3. These modeling results provide a framework for measuring material dispersion by mixed layer flows in future observational programs.

  14. Numerical recovery of certain discontinuous electrical conductivities

    NASA Technical Reports Server (NTRS)

    Bryan, Kurt

    1991-01-01

    The inverse problem of recovering an electrical conductivity of the form Gamma(x) = 1 + (k-1)(sub Chi(D)) (Chi(D) is the characteristic function of D) on a region omega is a subset of 2-dimensional Euclid space from boundary data is considered, where D is a subset of omega and k is some positive constant. A linearization of the forward problem is formed and used in a least squares output method for approximately solving the inverse problem. Convergence results are proved and some numerical results presented.

  15. Electrical Conduction in Transition-Metal Salts

    NASA Astrophysics Data System (ADS)

    Grado-Caffaro, M. A.; Grado-Caffaro, M.

    2016-04-01

    We predict that a given transition-metal salt as, for example, a K2CuCl4·2H2O-type compound, can behave as an electrical conductor in the paramagnetic case. In fact, we determine the electrical conductance in a salt of this type. This conductance is found to be quantised in agreement with previous well-known results. Related mathematical expressions in the context of superexchange interaction are obtained. In addition, we determine the corresponding (macroscopically viewed) current density and the associated electron wave functions.

  16. Electrical conductivity in the early universe

    NASA Astrophysics Data System (ADS)

    Baym, Gordon; Heiselberg, Henning

    1997-10-01

    We calculate the electrical conductivity in the early universe at temperatures below as well as above the electroweak vacuum scale, Tc~=100 GeV. Debye and dynamical screening of electric and magnetic interactions leads to a finite conductivity, σel~T/α ln(1/α), at temperatures well below Tc. At temperatures above, W+/- charge-exchange processes-analogous to color exchange through gluons in QCD-effectively stop left-handed charged leptons. However, right-handed leptons can carry current, resulting in σel/T being only a factor ~cos4 θW smaller than at temperatures below Tc.

  17. Electrical Conductivity Calculations from the Purgatorio Code

    SciTech Connect

    Hansen, S B; Isaacs, W A; Sterne, P A; Wilson, B G; Sonnad, V; Young, D A

    2006-01-09

    The Purgatorio code [Wilson et al., JQSRT 99, 658-679 (2006)] is a new implementation of the Inferno model describing a spherically symmetric average atom embedded in a uniform plasma. Bound and continuum electrons are treated using a fully relativistic quantum mechanical description, giving the electron-thermal contribution to the equation of state (EOS). The free-electron density of states can also be used to calculate scattering cross sections for electron transport. Using the extended Ziman formulation, electrical conductivities are then obtained by convolving these transport cross sections with externally-imposed ion-ion structure factors.

  18. [The electrical conductivity of triggered lightning channel].

    PubMed

    Zhang, Hua-ming; Yuan, Ping; Su, Mao-gen; Lü, Shi-hua

    2007-10-01

    Spectra of return strokes for artificial triggered lightning were obtained by optical multi-channel analyzer (OMA) in Shandong region. Compared with previous spectra of natural lightning, additional lines of ArI 602.5 nm and ArII 666.5 nm were observed. Under the model of local thermodynamic equilibrium, electronic temperatures of the lightning channel plasma were obtained according to the relative line intensities. Meanwhile, with semi-empirical method the electron density was obtained by Halpha line Stark broadening. In combination with plasma theory, electrical conductivity of the lightning channel has been calculated for the first time, and the characteristic of conductivity for lightning channel was also discussed. The relation between the electrical conductivity of channel and the return stroke current was analyzed, providing reference data for further work on computing return stroke current. Results show that the lightning channel is a good conductor, and electrons are the main carrier of channel current. The brightness of artificial triggered lightning channel is usually higher than that of natural lightning, and its current is smaller than that of the natural lightning. PMID:18306764

  19. Effect of forced convection on the collision and interaction between nanoparticles and ultramicroelectrode.

    PubMed

    Jiang, Jing; Huang, Xinjian; Wang, Lishi

    2016-04-01

    Detection of nanoparticle (NP) collision events at ultramicroelectrode (UME) has emerged as a new methodology for the investigation of single NP in recent years. Although the method was widely employed, some fundamental knowledge such as how the NP moves to and interacts with the UME remain less understood. It was generally recognized that the recorded rate of collision was determined by diffusion that should follow Fick's first law. However, significant lower collision frequency compared with that of predicted by theory were frequently reported. Experiments carried out by us suggest that the collision frequency will increase dramatically if forced convection (stir or flow injection) is applied during detection. Furthermore, the collision frequency gradually increases to a maximum and then decreases, along with the increase of the convection intensity. This phenomenon is interpreted as follows: (a) there are two steps for a freely moving NP to generate a detectable collision signal. The first step is the move of NP from bulk solution to the surface of the UME which is mass transfer limited; the second step is the landing of NP on the surface of UME which is affected by many factors and is the critical step; (b) there is a barrier that must be overcame before the contact between freely moving NP and UME. Forced convection with moderate intensity can not only increase the mass transfer rate but also help to overcome this barrier and thus enhance the collision frequency; (c) the landing of NP on the surface of UME can be suppressed by stronger convections, because NP will be swept away by hydrodynamic force. PMID:26802274

  20. Stationary cylindrical vortex in a viscous electrically conducting fluid

    NASA Astrophysics Data System (ADS)

    Baikin, A. N.; Golovin, S. V.

    2013-07-01

    An exact solution of the magnetohydrodynamic equations is constructed which describes steady vortex flow in a stationary cylinder on the axis of which a conductor carrying a known current is located. The solution is obtained under the assumption that the fluid is viscous and has finite electrical conductivity and that the magnetic field has only the axial and azimuthal components in a cylindrical coordinate system. It is found that the action of the Lorentz force is compensated by changing the pressure. Fluid flow occurs from the periphery to the axis of the cylinder under a pressure gradient, with flow rotation and swirling. The fluid flow causes a concentration of the magnetic lines near the axis of the cylinder, providing an exponential decrease in the magnetic field strength with distance from the axis. This flow can be considered as a model of a local increase in the magnetic field strength due to the transfer of its force lines by the flow of the electrically conducting fluid.

  1. Details of Exact Low Prandtl Number Boundary-Layer Solutions for Forced and For Free Convection

    NASA Technical Reports Server (NTRS)

    Sparrow, E. M.; Gregg, J. L.

    1959-01-01

    A detailed report is given of exact (numerical) solutions of the laminar-boundary-layer equations for the Prandtl number range appropriate to liquid metals (0.003 to 0.03). Consideration is given to the following situations: (1) forced convection over a flat plate for the conditions of uniform wall temperature and uniform wall heat flux, and (2) free convection over an isothermal vertical plate. Tabulations of the new solutions are given in detail. Results are presented for the heat-transfer and shear-stress characteristics; temperature and velocity distributions are also shown. The heat-transfer results are correlated in terms of dimensionless parameters that vary only slightly over the entire liquid-metal range. Previous analytical and experimental work on low Prandtl number boundary layers is surveyed and compared with the new exact solutions.

  2. Inductive Measurement of Plasma Jet Electrical Conductivity

    NASA Technical Reports Server (NTRS)

    Turner, Matthew W.; Hawk, Clark W.; Litchford, Ron J.

    2005-01-01

    An inductive probing scheme, originally developed for shock tube studies, has been adapted to measure explosive plasma jet conductivities. In this method, the perturbation of an applied magnetic field by a plasma jet induces a voltage in a search coil, which, in turn, can be used to infer electrical conductivity through the inversion of a Fredholm integral equation of the first kind. A 1-inch diameter probe was designed and constructed, and calibration was accomplished by firing an aluminum slug through the probe using a light-gas gun. Exploratory laboratory experiments were carried out using plasma jets expelled from 15-gram high explosive shaped charges. Measured conductivities were in the range of 3 kS/m for unseeded octol charges and 20 kS/m for seeded octol charges containing 2% potassium carbonate by mass.

  3. Making Complex Electrically Conductive Patterns on Cloth

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

    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.

  4. The electrical conductivity of sodium polysulfide melts

    SciTech Connect

    Meihui Wang

    1992-06-01

    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.

  5. Numerical and experimental study of flows in a rotating annulus with local convective forcing.

    NASA Astrophysics Data System (ADS)

    Scolan, Hélène; Su, Sylvie; Wright, Susie; Young, Roland M. B.; Read, Peter

    2016-04-01

    We present a numerical and experimental study of flows in a rotating annulus convectively forced by local thermal forcing via a heated annular ring at the bottom near the external wall and a cooled circular disk near the centre at the top surface of the annulus. This new configuration is a variant of the classical thermally-driven annulus analogue of the atmosphere circulation, where thermal forcing was previously applied uniformly on the sidewalls. Two vertically and horizontally displaced heat sources/sinks are arranged so that, in the absence of background rotation, statically unstable Rayleigh-Bénard convection would be induced above the source and beneath the sink, thereby relaxing strong constraints placed on background temperature gradients in previous experimental configurations to better mimic in fine local vigorous convection events in tropics and polar regions whilst also facilitating baroclinic motion in midlatitude regions in the Earth's atmosphere. By using the Met Office/ Oxford Rotating Annulus Laboratory (MORALS) code, we have investigated a series of equilibrated, 2D axisymmetric flows for a large range of dimensionless parameters and characterized them in terms of velocity and temperature fields. Several distinct and different flow regimes were identified, depending upon the rotation rate and strength of differential heating. These regimes will be presented with reference to variations of horizontal Ekman layer thickness versus the thermal boundary layer thickness and corresponding scalings for various quantities such as the azimuthal velocity or the heat transport. Experimental investigation of the same setup is carried out with a 1m diameter cylindrical container on a rotating platform: local heating is produced with an electrically heated annular ring at the bottom of the tank and cooling is imposed through a circular disk near the centre of the tank at the upper surface, cooled with circulating water. Different unstable circulation regimes

  6. Heat and momentum transfer model studies applicable to once-through, forced convection potassium boiling

    NASA Technical Reports Server (NTRS)

    Sabin, C. M.; Poppendiek, H. F.

    1971-01-01

    A number of heat transfer and fluid flow mechanisms that control once-through, forced convection potassium boiling are studied analytically. The topics discussed are: (1) flow through tubes containing helical wire inserts, (2) motion of droplets entrained in vapor flow, (3) liquid phase distribution in boilers, (4) temperature distributions in boiler tube walls, (5) mechanisms of heat transfer regime change, and (6) heat transfer in boiler tubes. Whenever possible, comparisons of predicted and actual performances are made. The model work presented aids in the prediction of operating characteristics of actual boilers.

  7. Experimental Validation Data for Computational Fluid Dynamics of Forced Convection on a Vertical Flat Plate

    SciTech Connect

    Harris, Jeff R.; Lance, Blake W.; Smith, Barton L.

    2015-08-10

    We present computational fluid dynamics (CFD) validation dataset for turbulent forced convection on a vertical plate. The design of the apparatus is based on recent validation literature and provides a means to simultaneously measure boundary conditions (BCs) and system response quantities (SRQs). Important inflow quantities for Reynolds-Averaged Navier-Stokes (RANS). CFD are also measured. Data are acquired at two heating conditions and cover the range 40,000 < Rex < 300,000, 357 < Reδ2 < 813, and 0.02 < Gr/Re2 < 0.232.

  8. Experimental Validation Data for Computational Fluid Dynamics of Forced Convection on a Vertical Flat Plate

    DOE PAGESBeta

    Harris, Jeff R.; Lance, Blake W.; Smith, Barton L.

    2015-08-10

    We present computational fluid dynamics (CFD) validation dataset for turbulent forced convection on a vertical plate. The design of the apparatus is based on recent validation literature and provides a means to simultaneously measure boundary conditions (BCs) and system response quantities (SRQs). Important inflow quantities for Reynolds-Averaged Navier-Stokes (RANS). CFD are also measured. Data are acquired at two heating conditions and cover the range 40,000 < Rex < 300,000, 357 < Reδ2 < 813, and 0.02 < Gr/Re2 < 0.232.

  9. A theoretical study of the spheroidal droplet evaporation in forced convection

    NASA Astrophysics Data System (ADS)

    Li, Jie; Zhang, Jian

    2014-11-01

    In many applications, the shape of a droplet may be assumed to be an oblate spheroid. A theoretical study is conducted on the evaporation of an oblate spheroidal droplet under forced convection conditions. Closed-form analytical expressions of the mass evaporation rate for an oblate spheroid are derived, in the regime of controlled mass-transfer and heat-transfer, respectively. The variation of droplet size during the evaporation process is presented in the regime of shrinking dynamic model. Comparing with the droplets having the same surface area, an increase in the aspect ratio enhances the mass evaporation rate and prolongs the burnout time.

  10. A perturbation solution for forced convection in a porous-saturated duct

    NASA Astrophysics Data System (ADS)

    Hooman, K.

    2008-01-01

    Fully developed forced convection through a porous medium bounded by two isoflux parallel plates is investigated analytically on the basis of a Brinkman-Forchheimer model. The matched asymptotic expansion method is applied for small values of the Darcy number. For the case of large Darcy number the solution for the Brinkman-Forchheimer momentum equation is found in terms of an asymptotic expansion. With the velocity distribution determined, the energy equation is solved using the same asymptotic technique. The results for limiting cases are found to be in good agreement with those available in the literature and the numerical results obtained here.

  11. Photovoltaic device having light transmitting electrically conductive stacked films

    DOEpatents

    Weber, Michael F.; Tran, Nang T.; Jeffrey, Frank R.; Gilbert, James R.; Aspen, Frank E.

    1990-07-10

    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.

  12. Single-drop reactive extraction/extractive reaction with forced convective diffusion and interphase mass transfer

    NASA Technical Reports Server (NTRS)

    Kleinman, Leonid S.; Red, X. B., Jr.

    1995-01-01

    An algorithm has been developed for time-dependent forced convective diffusion-reaction having convection by a recirculating flow field within the drop that is hydrodynamically coupled at the interface with a convective external flow field that at infinity becomes a uniform free-streaming flow. The concentration field inside the droplet is likewise coupled with that outside by boundary conditions at the interface. A chemical reaction can take place either inside or outside the droplet, or reactions can take place in both phases. The algorithm has been implemented, and for comparison results are shown here for the case of no reaction in either phase and for the case of an external first order reaction, both for unsteady behavior. For pure interphase mass transfer, concentration isocontours, local and average Sherwood numbers, and average droplet concentrations have been obtained as a function of the physical properties and external flow field. For mass transfer enhanced by an external reaction, in addition to the above forms of results, we present the enhancement factor, with the results now also depending upon the (dimensionless) rate of reaction.

  13. Role of EHD motion in the electrical conduction of liquids in a blade-plane geometry

    SciTech Connect

    Haidara, M.; Atten, P.

    1985-05-01

    A blade-plane electrode assembly is used to study electrical conduction in divergent fields and, more generally, to investigate high field conduction of dielectric liquids. The stationary current-voltage characteristics show two regimes of conduction: a quasi-ohmic regime and a V /SUP a/ one, V being the applied voltage and 3 < ..cap alpha.. < 6. The latter regime corresponds to dominance of charge injection by the blade, as revealed by the field distribution obtained by the Kerr technique. A liquid motion is induced by the Coulomb force which convects charge carriers and results in a decrease of the first transit time following the application of a voltage step. The transient injection currents exhibit a dependence upon the elapsed time during which no voltage is applied, and the possible origin of this phenomenon is discussed. Measurement of the liquid velocity by laser Doppler anemometry also exhibits two different laws of variation with applied voltage consistent with the two current regimes. In the steady-state conditions of the injection-dominant regime, the square of the measured velocity component w/sup 2/ varies as the electrical power input IV (I being the current). This is tentatively interpreted by the viscous dominated character of the induced motion.

  14. Magnetic flowmeter for electrically conductive liquid

    DOEpatents

    Skladzien, Stanley B.; Raue, Donald J.

    1982-01-01

    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.

  15. Magnetic flowmeter for electrically conductive liquid

    DOEpatents

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

    1980-08-18

    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.

  16. Dislocation electrical conductivity of synthetic diamond films

    SciTech Connect

    Samsonenko, S. N. Samsonenko, N. D.

    2009-05-15

    A relationship between the electric resistance of single-crystal homoepitaxial and polycrystalline diamond films and their internal structure has been investigated. It is established that the electrical conductivity of undoped homoepitaxial and polycrystalline diamond films is directly related to the dislocation density in them. A relation linking the resistivity {rho} ({approx}10{sup 13}-10{sup 15} {omega} cm) with the dislocation density {gamma} ({approx}10{sup 14}-4 x 10{sup 16} m{sup -2}) is obtained. The character of this correlation is similar for both groups of homoepitaxial and polycrystalline diamond films. Thin ({approx}1-8 {mu}m) homoepitaxial and polycrystalline diamond films with small-angle dislocation boundaries between mosaic blocks exhibit dislocation conductivity. The activation energy of dislocation acceptor centers was calculated from the temperature dependence of the conductivity and was found to be {approx}0.3 eV. The conduction of thick diamond films (h > 10 {mu}m) with the resistivity {rho} {approx} 10{sup 8} {omega} cm is determined by the conduction of intercrystallite boundaries, which have a nondiamond hydrogenated structure. The electronic properties of the diamond films are compared with those of natural semiconductor diamonds of types IIb and Ic, in which dislocation acceptor centers have activation energies in the range 0.2-0.35 eV and are responsible for hole conduction.

  17. New method for electrical conductivity temperature compensation.

    PubMed

    McCleskey, R Blaine

    2013-09-01

    Electrical conductivity (κ) measurements of natural waters are typically referenced to 25 °C (κ25) using standard temperature compensation factors (α). For acidic waters (pH < 4), this can result in a large κ25 error (δκ25). The more the sample temperature departs from 25 °C, the larger the potential δκ25. For pH < 4, the hydrogen ion transport number becomes substantial and its mode of transport is different from most other ions resulting in a different α. A new method for determining α as a function of pH and temperature is presented. Samples with varying amounts of H2SO4 and NaCl were used to develop the new α, which was then applied to 65 natural water samples including acid mine waters, geothermal waters, seawater, and stream waters. For each sample, the κ and pH were measured at several temperatures from 5 to 90 °C and κ25 was calculated. The δκ25 ranged from -11 to 9% for the new method as compared to -42 to 25% and -53 to 27% for the constant α (0.019) and ISO-7888 methods, respectively. The new method for determining α is a substantial improvement for acidic waters and performs as well as or better than the standard methods for circumneutral waters. PMID:23895179

  18. Electrically conducting superhydrophobic microtextured carbon nanotube nanocomposite

    NASA Astrophysics Data System (ADS)

    Caffrey, Paul O.; Gupta, Mool C.

    2014-09-01

    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 ρ = 761 Ω 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 Ω/K) similar to that of a thermistor was observed.

  19. Anisotropy of electrical conductivity in dry olivine

    SciTech Connect

    Du Frane, W L; Roberts, J J; Toffelmier, D A; Tyburczy, J A

    2005-04-13

    [1] The electrical conductivity ({sigma}) was measured for a single crystal of San Carlos olivine (Fo{sub 89.1}) for all three principal orientations over oxygen fugacities 10{sup -7} < fO{sub 2} < 10{sup 1} Pa at 1100, 1200, and 1300 C. Fe-doped Pt electrodes were used in conjunction with a conservative range of fO{sub 2}, T, and time to reduce Fe loss resulting in data that is {approx}0.15 log units higher in conductivity than previous studies. At 1200 C and fO{sub 2} = 10{sup -1} Pa, {sigma}{sub [100]} = 10{sup -2.27} S/m, {sigma}{sub [010]} = 10{sup -2.49} S/m, {sigma}{sub [001]} = 10{sup -2.40} S/m. The dependences of {sigma} on T and fO{sub 2} have been simultaneously modeled with undifferentiated mixed conduction of small polarons and Mg vacancies to obtain steady-state fO{sub 2}-independent activation energies: Ea{sub [100]} = 0.32 eV, Ea{sub [010]} = 0.56 eV, Ea{sub [001]} = 0.71 eV. A single crystal of dry olivine would provide a maximum of {approx}10{sup 0.4} S/m azimuthal {sigma} contrast for T < 1500 C. The anisotropic results are combined to create an isotropic model with Ea = 0.53 eV.

  20. The effects of buoyancy on the critical heat flux in forced convection

    NASA Technical Reports Server (NTRS)

    Brusstar, Matthew J.; Merte, Herman, Jr.

    1993-01-01

    The critical heat flux (CHF) in forced convection over a flat surface at relatively low flow velocities has been found, not unexpectedly, to depend upon the orientation of the buoyancy. The CHF for R-113 was measured at various heating surface orientations for test section Reynolds numbers ranging between 3000 and 6500. In this flow range, the buoyancy force acting on the vapor generally dominates over the flow inertia, yet the inertia would still be substantial were gravity to be reduced. In the experiments of this study, the CHF is determined for heating surface orientations ranging from 0 deg to 360 deg, for flow velocities between 4 cm/s and 35 cm/s, and for subcoolings between 2.8 C and 22.2 C. The results presented here demonstrate the strong influence of buoyancy at low flow velocities, which diminishes as the flow velocity and subcooling are increased.

  1. Temporal stability of electrical conductivity in a sandy soil

    NASA Astrophysics Data System (ADS)

    Pedrera-Parrilla, Aura; Brevik, Eric C.; Giráldez, Juan V.; Vanderlinden, Karl

    2016-07-01

    Understanding of soil spatial variability is needed to delimit areas for precision agriculture. Electromagnetic induction sensors which measure the soil apparent electrical conductivity reflect soil spatial variability. The objectives of this work were to see if a temporally stable component could be found in electrical conductivity, and to see if temporal stability information acquired from several electrical conductivity surveys could be used to better interpret the results of concurrent surveys of electrical conductivity and soil water content. The experimental work was performed in a commercial rainfed olive grove of 6.7 ha in the `La Manga' catchment in SW Spain. Several soil surveys provided gravimetric soil water content and electrical conductivity data. Soil electrical conductivity values were used to spatially delimit three areas in the grove, based on the first principal component, which represented the time-stable dominant spatial electrical conductivity pattern and explained 86% of the total electrical conductivity variance. Significant differences in clay, stone and soil water contents were detected between the three areas. Relationships between electrical conductivity and soil water content were modelled with an exponential model. Parameters from the model showed a strong effect of the first principal component on the relationship between soil water content and electrical conductivity. Overall temporal stability of electrical conductivity reflects soil properties and manifests itself in spatial patterns of soil water content.

  2. Fundamental Study of Local Heat Transfer in Forced Convective Boiling of Ammonia on Vertical Flat Plate

    NASA Astrophysics Data System (ADS)

    Kim, Jeong-Hun; Arima, Hirofumi; Ikegami, Yasuyuki

    In the present study, the fundamental experiments that investigate characteristics of local heat transfer in forced convective boiling on vertical flat plate with 2-mm channel height are taken to realize plate type compact evaporator for OTEC or STEC. The experiments are performed with ammonia as the working fluid. The experiments are also carried out with the following test conditions; saturated pressure = 0.7, 0.8, 0.9 MPa, mass flux = 7.5, 10, 15 kg/(m2•s), heat flux = 15, 20, 25 kW/m2 and inlet quality = 0.1 ~ 0.4 [-]. The result shows that the wall superheated temperature of forced convective boiling is lower than that of pool boiling. And the heat transfer coefficient increases with an increase in quality and the decrease in the local heat flux and saturated pressure for prescribed experimental conditions. However, local heat transfer coefficients are not affected by mass fluxes in the prescribed experimental conditions. An empirical correlation that can predict the local heat transfer coefficient on vertical flat plate within experimental conditions is also proposed.

  3. Damage Detection in Electrically Conductive Structures

    NASA Astrophysics Data System (ADS)

    Anderson, Todd A.

    2002-12-01

    High-technology systems are in need of structures that perform with increased functionality and a reduction in weight, while simultaneously maintaining a high level of performance and reliability. To accomplish this, structural elements must be designed more efficiently and with increased functionality, thereby creating multifunctional structures (MFS). Through the addition of carbon fibers, nanotubes, or particles, composite structures can be made electrically conductive while simultaneously increasing their strength and stiffness to weight ratios. Using the electrical properties of these structures for the purpose of damage detection and location for health and usage monitoring is of particular interest for aerospace structures. One such method for doing this is Electrical Impedance Tomography (EIT). With EIT, an electric current is applied through a pair of electrodes and the electric potential is recorded at other monitoring electrodes around the area of study. An inverse solution of the governing Maxwell equations is then required to determine the conductivities of discrete areas within the region of interest. However, this method is nearly ill-posed and computationally intensive as it focuses on imaging small changes in conductivity within the region of interest. For locating damage in a medium with an otherwise homogeneous conductivity, an alternative approach is to search for parameters such as the damage location and size. Towards those ends, this study develops an Artificial Neural Network (ANN) to determine the state of an electrically conductive region based on applied reference current and electrical potentials at electrodes around the periphery of the region. A significant benefit of the ANN approach is that once trained, the solution of an inverse problem does not require costly computations of the inverse problem. This method also takes advantage of the pattern recognition abilities of neural networks and is a robust solution method in the presence

  4. Electrically conductive polyurethanes for biomedical applications

    NASA Astrophysics Data System (ADS)

    Williams, Charles M.; Nash, M. A.; Poole-Warren, Laura A.

    2005-02-01

    Electrical interfacing with neural tissue poses significant problems due to host response to the material. This response generally leads to fibrous encapsulation and increased impedance across the electrode. In neural electrodes such as cochlear implants, an elastomeric material like silicone is used as an insulator for the metal electrode. This project ultimately aims to produce a polymer electrode with elastomeric mechanical properties, metal like conductivity and capability. The approach taken was to produce a nanocomposite elastomeric material based on polyurethane (PU) and carbon nanotubes. Carbon nanotubes are ideal due to their high aspect ratio as well as being a ballistic conductor. The choice of PU is based on its elastomeric properties, processability and biocompatibility. Multi-walled nanotubes (MWNTs) were dispersed ultrasonically in various dispersive solutions before being added at up to 20wt% to a 5wt% PU (Pellethane80A) in Dimethylacetamide (DMAc). Films were then solvent cast in a vacuum oven overnight. The resulting films were tested for conductivity using a two-probe technique and mechanically tested using an Instron tensiometer. The percolation threshold (p) of the PU/MWNT films occurred at loadings of between 7 and 10 wt% in this polymer system. Conductivity of the films (above p) was comparable to those for similar systems reported in the literature at up to approximately 7x10-2 Scm-1. Although PU stiffness increased with increased %loading of nanotubes, all composites were highly flexible and maintained elastomeric properties. From these preliminary results we have demonstrated electrical conductivity. So far it is evident that a superior percolation threshold is dependent on the degree of dispersion of the nanotubes. This has prompted work into investigating other preparations of the films, including melt-processing and electrospinning.

  5. Experimental study of forced convection heat transfer during upward and downward flow of helium at high pressure and high temperature

    SciTech Connect

    Francisco Valentin; Narbeh Artoun; Masahiro Kawaji; Donald M. McEligot

    2015-08-01

    Fundamental high pressure/high temperature forced convection experiments have been conducted in support of the development of a Very High Temperature Reactor (VHTR) with a prismatic core. The experiments utilize a high temperature/high pressure gas flow test facility constructed for forced convection and natural circulation experiments. The test section has a single 16.8 mm ID flow channel in a 2.7 m long, 108 mm OD graphite column with four 2.3kW electric heater rods placed symmetrically around the flow channel. This experimental study presents the role of buoyancy forces in enhancing or reducing convection heat transfer for helium at high pressures up to 70 bar and high temperatures up to 873 degrees K. Wall temperatures have been compared among 10 cases covering the inlet Re numbers ranging from 500 to 3,000. Downward flows display higher and lower wall temperatures in the upstream and downstream regions, respectively, than the upward flow cases due to the influence of buoyancy forces. In the entrance region, convection heat transfer is reduced due to buoyancy leading to higher wall temperatures, while in the downstream region, buoyancyinduced mixing causes higher convection heat transfer and lower wall temperatures. However, their influences are reduced as the Reynolds number increases. This experimental study is of specific interest to VHTR design and validation of safety analysis codes.

  6. Single-drop reactive extraction/extractive reaction with forced convective diffusion and interphase mass transfer

    NASA Technical Reports Server (NTRS)

    Kleinman, Leonid S.; Reed, X. B., Jr.

    1995-01-01

    An algorithm has been developed for the forced convective diffusion-reaction problem for convection inside and outside a droplet by a recirculating flow field hydrodynamically coupled at the droplet interface with an external flow field that at infinity becomes a uniform streaming flow. The concentration field inside the droplet is likewise coupled with that outside by boundary conditions at the interface. A chemical reaction can take place either inside or outside the droplet or reactions can take place in both phases. The algorithm has been implemented and results are shown here for the case of no reaction and for the case of an external first order reaction, both for unsteady behavior. For pure interphase mass transfer, concentration isocontours, local and average Sherwood numbers, and average droplet concentrations have been obtained as a function of the physical properties and external flow field. For mass transfer enhanced by an external reaction, in addition to the above forms of results, we present the enhancement factor, with the results now also depending upon the (dimensionless) rate of reaction.

  7. Effect of finite length on forced convection heat transfer from cylinders

    NASA Astrophysics Data System (ADS)

    Quarmby, A.; Al-Fakhri, A. A. M.

    1980-04-01

    Forced convection heat transfer from single cylinders of finite length is investigated experimentally with particular reference to the effect of aspect (length/diameter) ratio of the cylinder. It is found that for aspect ratios greater than 4 there is little further effect as aspect ratio increases to infinity. The disagreement between the correlations proposed by Zukauskas (1972) and Morgan (1975) is considered and resolved in favor of the Zukauskas correlation. A correlation is proposed for heat transfer from cylinders of low aspect ratio which in the limit agrees with the correlation for large aspect ratios and with the generally accepted correlation for turbulent heat transfer from isothermal flat plates for small aspect ratios.

  8. Application of a finite volume based method of lines to turbulent forced convection in circular tubes

    SciTech Connect

    Campo, A.; Tebeest, K.; Lacoa, U.; Morales, J.C.

    1996-10-01

    A semianalytic analysis of in-tube turbulent forced convection is performed whose special computational feature is the combination of the method of lines, the finite volume technique, and a radial coordinate transformation. First, a numerical solution of the momentum equation was obtained by a simple Runge-Kutta integration scheme. Second, the energy equation was reformulated into a system of ordinary differential equations of first order. Each equation in the system controls the temperature along a line in a mesh consisting of concentric lines. Reliable analytic solutions for the temperature distribution of fluids in the region of thermal development can be determined for combinations of Reynolds and Prandtl numbers. Predicted results for the distributions of mean bulk temperature and local Nusselt numbers for air, water, and oils compare satisfactorily with the available experimental data.

  9. Forced convection analysis for generalized Burgers nanofluid flow over a stretching sheet

    NASA Astrophysics Data System (ADS)

    Khan, Masood; Khan, Waqar Azeem

    2015-10-01

    This article reports the two-dimensional forced convective flow of a generalized Burgers fluid over a linearly stretched sheet under the impacts of nano-sized material particles. Utilizing appropriate similarity transformations the coupled nonlinear partial differential equations are converted into a set of coupled nonlinear ordinary differential equations. The analytic results are carried out through the homotopy analysis method (HAM) to investigate the impact of various pertinent parameters for the velocity, temperature and concentration fields. The obtained results are presented in tabular form as well as graphically and discussed in detail. The presented results show that the rate of heat transfer at the wall and rate of nanoparticle volume fraction diminish with each increment of the thermophoresis parameter. While incremented values of the Brownian motion parameter lead to a quite opposite effect on the rates of heat transfer and nanoparticle volume fraction at the wall.

  10. Non-Darcian forced convection analysis in an annulus partially filled with a porous material

    SciTech Connect

    Chikh, S.; Boumedien, A.; Bouhadef, K.; Lauriat, G.

    1995-12-01

    Numerical solutions are presented for fully developed forced convection in concentric annuli partially filled with a porous medium. The porous medium is attached at the inner cylinder, which is maintained at uniform heat flux or at uniform wall temperature while the outer cylinder is adiabatic. The Brinkman-Forchheimer-extended Darcy model was used to model the flow inside the porous medium. The dependence of the fluid flow and heat transfer on several parameters of the problem is thoroughly documented. The inertia coefficient at which the inertial effects reduce the flow rate by 5% is determined as a function of the Darcy number for various thicknesses of the porous substrate. It is also shown that a critical thickness at which the value of the Nusselt number reaches a minimum does not exist if the effective thermal conductivity of the fluid-saturated porous medium is much higher than the fluid conductivity.

  11. Finite difference analysis for developing laminar flow in circular tubes applied to forced and combined convection

    NASA Astrophysics Data System (ADS)

    Collins, M. W.

    1980-03-01

    The complete two-dimensional partial differential equations for developing laminar flow in a circular tube have been treated by a finite difference analysis. Property variation with temperature, especially that of viscosity, is allowed for in a flexible manner. The continuity and momentum equations, and then the energy equations, are solved by direct elimination at each axial step, and a marching procedure used in the axial direction. The stepwise energy balance is rigidly satisfied throughout by using it as a constituent equation in place of the 'explicit' wall thermal boundary condition normally used. The analysis predicts the complete developing hydrodynamic and thermal fields, together with friction factors and heat transfer coefficients. It has been tested for a range of fluid velocity and thermal boundary conditions and for various fluids, including high viscosity oils, water and air. Predictions for constant wall temperature presented here are for forced and combined convection and are compared with experimental data of Test and Zeldin and Schmidt.

  12. Stability improvement of AC superconducting magnet by forced-convection cooling

    SciTech Connect

    Ishigohka, T.; Kasuya, A.; Ninomiya, A.

    1996-07-01

    The authors propose a new improved cooling system of an AC(50/60Hz) superconducting magnet introducing a forced-convection flow of liquid helium. In this system, the flow through the cooling channel between the winding layers is generated by a screw rotating in a cylinder surrounding the magnet. A small experimental device composed of an AC superconducting magnet and a rotating screw was manufactured. The screw was rotated by an extended driving shaft. The experimental result shows that the stability of the magnet is improved by the rotation of the screw. That is, the thermal disturbance (heater input power) which generates the quench of the magnet increases as the rotational speed of the screw does. It is expected that this technique can be successfully applied to superconducting AC power apparatuses as transformers or reactors.

  13. Numerical simulation of combined natural and forced convection during thermal-hydraulic transients. [LMFBR

    SciTech Connect

    Domanus, H.M.; Sha, W.T.

    1981-01-01

    The single-phase COMMIX (COMponent MIXing) computer code performs fully three-dimensional, transient, thermal-hydraulic analyses of liquid-sodium LMFBR components. It solves the conservation equations of mass, momentum, and energy as a boundary-value problem in space and as an initial-value problem in time. The concepts of volume porosity, surface permeability and distributed resistance, and heat source have been employed in quasi-continuum (rod-bundle) applications. Results from three transient simulations involving forced and natural convection are presented: (1) a sodium-filled horizontal pipe initially of uniform temperature undergoing an inlet velocity rundown transient, as well as an inlet temperature transient; (2) a 19-pin LMFBR rod bundle undergoing a velocity transient; and, (3) a simulation of a water test of a 1/10-scale outlet plenum undergoing both velocity and temperature transients.

  14. Effect of Heated Perimeter on Forced Convection Heat Transfer of he i at a Supercritical Pressure

    NASA Astrophysics Data System (ADS)

    Doi, D.; Shiotsu, M.; Shirai, Y.; Hama, K.

    2008-03-01

    The forced convection heat transfer coefficients were measured on two pairs of test plates all 6.0 mm in width and located face to face on inner walls of a rectangular duct. Each pair having length of 20 mm and 80 mm, respectively, was connected in series electrically. The rectangular duct was 420 mm in length and 5 mm×6 mm in inner cross section. The experiments were performed for inlet temperatures from 2.2 to 6.5 K, flow velocities from 0.1 to 5.6 m/s, and at a supercritical pressure of 2.8 atm. Comparison of the obtained Nusselt numbers with the former results with a single test plate showed the clear effect of a heated perimeter. Non-dimensional heat transfer equation including the effect of heated perimeter is presented.

  15. Method of forming an electrically conductive cellulose composite

    DOEpatents

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

    2011-11-22

    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.

  16. Diabatically Forced Frontogenesis Near Surface As Trigger For The Release of Strong Convection

    NASA Astrophysics Data System (ADS)

    Kurz, Manfred

    One prerequisite for the formation of mesoscale convective systems is the existance of moist potentially unstable air masses in the lower troposphere. For the release of the instability, however, often an ascending motion is necessary in order to destroy stable layers on top of the moist air which would prevent convection, and to bring the air to saturation. In this respect the macroscale ascent ahead of an approaching upper trough may function as trigger for the release of convection. Another favourable process is the ascending motion of the warm air within circulations across a frontal zone which undergoes a frontogenesis either in the horizontal wind field or by diabatic effects. During summer time real fronts between different air masses are often ill defined over the continent, and circulatory motions in their neighbourhood remain rather weak. There is, however, a mechanism which may lead to the formation of a very strong temperature contrast near surface within short time. That happens at the edge of larger cloud and precipitation areas during day time due to the different diabatic heat fluxes across the cloud edge: Whereas the temperature below the cloud masses remains more or less constant or is even reduced by evaporation of falling rain, it rapidly increases due to heating from the ground in the area with no or only few clouds. As consequence of this diabatically forced frontogenesis a solenoidally direct circulation across the newly established frontal zone is released with ascent of the heated air, descent of the cooler air and an ageostrophic motion from the cold towards the warm air near surface. At the same time the pressure rises - at least relatively - in the cold air and falls in the warm air so that a pressure gradient is built up between both air masses. If the warm air is potentially unstable, the ascent within the circulation may lead to the release of the instability and the formation of convective clouds ahead of the cloud edge and parallel

  17. Electrical conduction in organic charge transfer complexes under pressure: A theoretical view

    NASA Astrophysics Data System (ADS)

    Singh, Yadunath

    2016-05-01

    We propose a theoretical view of temperature dependent electrical conductivity in organic charge transfer complexes and radical ion salts. Understanding of the basic conduction mechanism under high pressure in these systems is our aim. The mechanism is discussed mainly on the basis of molecular orbital overlap theory, role of charge transfer forces and charge density waves etc.

  18. Free and forced convective cooling of pipe-type electric cables. Volume 1: forced cooling of cables. Final report

    SciTech Connect

    Chato, J.C.; Crowley, J.M.

    1981-05-01

    A multi-faceted research program has been performed to investigate in detail several aspects of free and forced convective cooling of underground electric cable systems. There were two main areas of investigation. The first one reported in this volume dealt with the fluid dynamic and thermal aspects of various components of the cable system. In particular, friction factors for laminar flow in the cable pipes with various configurations were determined using a finite element technique; the temperature distributions and heat transfer in splices were examined using a combined analytical numerical technique; the pressure drop and heat transfer characteristics of cable pipes in the transitional and turbulent flow regime were determined experimentally in a model study; and full-scale model experimental work was carried out to determine the fluid dynamic and thermal characteristics of entrance and exit chambers for the cooling oil. The second major area of activity, reported in volume 2, involved a feasibility study of an electrohydrodynamic pump concept utilizing a traveling electric field generated by a pumping cable. Experimental studies in two different configurations as well as theoretical calculations showed that an electrohydrodynamic pump for the moving of dielectric oil in a cable system is feasible.

  19. Polyelectrolyte multilayers impart healability to highly electrically conductive films.

    PubMed

    Li, Yang; Chen, Shanshan; Wu, Mengchun; Sun, Junqi

    2012-08-28

    Healable, electrically conductive films are fabricated by depositing Ag nanowires on water-enabled healable polyelectrolyte multilayers. The easily achieved healability of the polyelectrolyte multilayers is successfully imparted to the Ag nanowire layer. These films conveniently restore electrical conductivity lost as a result of damage by cuts several tens of micrometers wide when water is dropped on the cuts. PMID:22807199

  20. Determination of forced convection parameters by interferometric imaging of the concentration field during growth of KDP crystals

    NASA Astrophysics Data System (ADS)

    Verma, Sunil; Muralidhar, K.

    2011-07-01

    Growth of a potassium dihydrogen phosphate (KDP) crystal from its aqueous solution has been considered under forced convection conditions. The KDP crystal is grown in a conventional top hanging geometry. Forced convection conditions are created by rotating the crystal about a vertical axis. The rotational RPM is varied in a cycle, creating an accelerated rotation (AR) paradigm. The effect of varying the rotational RPM on the concentration field around the crystal was investigated. Mach-Zehnder interferometry was adopted as an optical technique to image the evolving concentration fields. Six different experiments were performed to obtain the specific set of time periods and rotation rates of the acceleration cycle that result in a uniform concentration field around the growing crystal. The Reynolds number, an index of the strength of forced convection, was optimized through the experiments. The optimized parameters of the accelerated rotation cycle were found to be as follows: maximum rotation rate of 32 RPM, spin up period=40 s, spin down period=40 s, steady period=40 s, and stationary period=40 s. The parametric study further revealed that concentration was highly sensitive to the maximum rotation rate adopted during the AR cycle. It did not depend crucially on the time periods that could be varied by as much as ±25% around the respective average values. Finally, a KDP crystal was grown using the optimized forced convection parameters and the crystal quality was found to be good.

  1. Energetic dynamics of a rotating horizontal convection model with wind forcing

    NASA Astrophysics Data System (ADS)

    Zemskova, Varvara; White, Brian; Scotti, Alberto

    2015-11-01

    We present a new test case for rotating horizontal convection, where the flow is driven by differential buoyancy forcing along a horizontal surface. This simple model is used to understand and quantify the influence of surface heating and cooling and wind stress on the Meridional Overturning Circulation. The domain is a rectangular basin with surface cooling at both ends (the poles) and surface warming in the middle (equatorial) region. To model the effect of the Antarctic Circumpolar Current, reentrant channel is placed near the Southern pole. Free-slip boundary conditions are imposed in the closed box, while zonally periodic boundary conditions are enforced in the channel. The problem is solved numerically using a 3D DNS model based on a finite-volume AMR solver for the Boussinesq Navier-Stokes equations with rotation. The relative contributions of surface buoyancy and wind forcing and the energetic balance are analyzed at a Rayleigh number of 108 and a relatively high aspect ratio of [5, 10, 1] in zonal, meridional and vertical directions, respectively. The overall dynamics, including large-scale overturning, baroclinic eddying, and turbulent mixing are investigated using the local Available Potential Energy framework introduced in [Scotti and White, J. Fluid Mech., 2014]. This research is part of the Blue Waters sustained-petascale computing project, supported by the NSF (awards OCI-0725070, ACI-1238993 and ACI-14-44747) and the state of Illinois.

  2. Improving the electrical conductivity of PEDOT:PSS films by binary secondary doping

    NASA Astrophysics Data System (ADS)

    Zhu, Zhengyou; Liu, Congcong; Xu, Jingkun; Jiang, Qinglin; Shi, Hui; Liu, Endou

    2016-01-01

    In this work, the electrical conductivity of poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) films was effectively enhanced by binary secondary doping. Initially, doping with 5 vol.% dimethyl sulfoxide (DMSO) improved the electrical conductivity from 0.3 S cm-1 to 437 S cm-1 and a further increase to 950 S cm-1 was achieved by adding LiClO4. The conductivity value we report here is one of the highest reported for pretreated PEDOT:PSS films. The obtained maximum electrical conductivity is almost 3000 times higher than that shown by pristine PEDOT:PSS films. The increase in the electrical conductivity is ascribed to the synergistic effect of the two dopants. Fourier transform infrared spectra indicated the absence of any changes to the chemical structure of PEDOT:PSS. Atomic force microscopy images demonstrate an increased surface roughness and suggest the occurrence of conformational changes of PEDOT chains from the coiled to coil-extended one, which is the key reason for the electrical conductivity enhancement. The pretreatments we propose here are rapid, simple and effective for the large-scale preparation of high-conductivity PEDOT:PSS films. [Figure not available: see fulltext.

  3. Hot stage and sample cell design for the solidification of transparent materials with and without forced convection

    NASA Technical Reports Server (NTRS)

    Kaukler, W. F.

    1984-01-01

    A temperature gradient stage design for optical microscopy is described. Exceptional thermal stability is the major feature. The stage is used to study crystal growth phenomena occurring at the solid-liquid interface. The apparatus is designed to use transparent organic solutions as models for the study of metal-like solidification. The stage provides a controlled thermal environment for unidirectional solidification of low melting temperature materials. Freezing rate is regulated by mechanically sliding in the stage a thin glass cell containing the materials being studied. Two cell assemblies are described. One type is used for convection-free and the other for controlled forced convection studies of the solidification interface.

  4. Investigation of combined free and forced convection in a 2 x 6 rod bundle during controlled flow transients

    SciTech Connect

    Bates, J.M.; Khan, E.U.

    1980-10-01

    An experimental study was performed to obtain local fluid velocity and temperature measurements in the mixed (combined free and forced) convection regime for specific flow coastdown transients. A brief investigation of steady-state flows for the purely free-convection regime was also completed. The study was performed using an electrically heated 2 x 6 rod bundle contained in a flow housing. In addition a transient data base was obtained for evaluating the COBRA-WC thermal-hydraulic computer program (a modified version of the COBRA-IV code).

  5. Conceptual Design of Forced Convection Molten Salt Heat Transfer Testing Loop

    SciTech Connect

    Manohar S. Sohal; Piyush Sabharwall; Pattrick Calderoni; Alan K. Wertsching; S. Brandon Grover

    2010-09-01

    This report develops a proposal to design and construct a forced convection test loop. A detailed test plan will then be conducted to obtain data on heat transfer, thermodynamic, and corrosion characteristics of the molten salts and fluid-solid interaction. In particular, this report outlines an experimental research and development test plan. The most important initial requirement for heat transfer test of molten salt systems is the establishment of reference coolant materials to use in the experiments. An earlier report produced within the same project highlighted how thermophysical properties of the materials that directly impact the heat transfer behavior are strongly correlated to the composition and impurities concentration of the melt. It is therefore essential to establish laboratory techniques that can measure the melt composition, and to develop purification methods that would allow the production of large quantities of coolant with the desired purity. A companion report describes the options available to reach such objectives. In particular, that report outlines an experimental research and development test plan that would include following steps: •Molten Salts: The candidate molten salts for investigation will be selected. •Materials of Construction: Materials of construction for the test loop, heat exchangers, and fluid-solid corrosion tests in the test loop will also be selected. •Scaling Analysis: Scaling analysis to design the test loop will be performed. •Test Plan: A comprehensive test plan to include all the tests that are being planned in the short and long term time frame will be developed. •Design the Test Loop: The forced convection test loop will be designed including extensive mechanical design, instrument selection, data acquisition system, safety requirements, and related precautionary measures. •Fabricate the Test Loop. •Perform the Tests. •Uncertainty Analysis: As a part of the data collection, uncertainty analysis will

  6. Electrical conductivity of zirconia stabilized with scandia and yttria

    SciTech Connect

    Kaneko, Hiroyuki; Jin, Fuxue; Taimatsu, Hitoshi . Dept. of Materials Engineering and Applied Chemistry); Kusakabe, Hirotatsu . Tsukuba Research Lab.)

    1993-03-01

    Electrical conductivity of zirconia stabilized with scandia and yttria (Sc[sub 2]O[sub 3] + Y[sub 2]O[sub 3] = 8 mol%) has been measured by the complex impedance method in the temperature range 573 to 1,173 K. With increasing Sc[sub 2]O[sub 3] concentration, electrical conductivity increases at temperatures above 640K, but it decreases below this temperature. Electrical conductivity in the electrolytes examined is a result of two processes: an activation energy of 59 to 79 kJ/mol predominant at high temperatures and an activation energy of 109 to 125 kJ/mol predominant at low temperatures.

  7. Multirelaxation-time lattice Boltzmann model for droplet heating and evaporation under forced convection.

    PubMed

    Albernaz, Daniel; Do-Quang, Minh; Amberg, Gustav

    2015-04-01

    We investigate the evaporation of a droplet surrounded by superheated vapor with relative motion between phases. The evaporating droplet is a challenging process, as one must take into account the transport of mass, momentum, and heat. Here a lattice Boltzmann method is employed where phase change is controlled by a nonideal equation of state. First, numerical simulations are compared to the D(2) law for a vaporizing static droplet and good agreement is observed. Results are then presented for a droplet in a Lagrangian frame under a superheated vapor flow. Evaporation is described in terms of the temperature difference between liquid-vapor and the inertial forces. The internal liquid circulation driven by surface-shear stresses due to convection enhances the evaporation rate. Numerical simulations demonstrate that for higher Reynolds numbers, the dynamics of vaporization flux can be significantly affected, which may cause an oscillatory behavior on the droplet evaporation. The droplet-wake interaction and local mass flux are discussed in detail. PMID:25974585

  8. Multirelaxation-time lattice Boltzmann model for droplet heating and evaporation under forced convection

    NASA Astrophysics Data System (ADS)

    Albernaz, Daniel; Do-Quang, Minh; Amberg, Gustav

    2015-04-01

    We investigate the evaporation of a droplet surrounded by superheated vapor with relative motion between phases. The evaporating droplet is a challenging process, as one must take into account the transport of mass, momentum, and heat. Here a lattice Boltzmann method is employed where phase change is controlled by a nonideal equation of state. First, numerical simulations are compared to the D2 law for a vaporizing static droplet and good agreement is observed. Results are then presented for a droplet in a Lagrangian frame under a superheated vapor flow. Evaporation is described in terms of the temperature difference between liquid-vapor and the inertial forces. The internal liquid circulation driven by surface-shear stresses due to convection enhances the evaporation rate. Numerical simulations demonstrate that for higher Reynolds numbers, the dynamics of vaporization flux can be significantly affected, which may cause an oscillatory behavior on the droplet evaporation. The droplet-wake interaction and local mass flux are discussed in detail.

  9. Forced convective heat transfer in boundary layer flow of Sisko fluid over a nonlinear stretching sheet.

    PubMed

    Munir, Asif; Shahzad, Azeem; Khan, Masood

    2014-01-01

    The major focus of this article is to analyze the forced convective heat transfer in a steady boundary layer flow of Sisko fluid over a nonlinear stretching sheet. Two cases are studied, namely (i) the sheet with variable temperature (PST case) and (ii) the sheet with variable heat flux (PHF case). The heat transfer aspects are investigated for both integer and non-integer values of the power-law index. The governing partial differential equations are reduced to a system of nonlinear ordinary differential equations using appropriate similarity variables and solved numerically. The numerical results are obtained by the shooting method using adaptive Runge Kutta method with Broyden's method in the domain[Formula: see text]. The numerical results for the temperature field are found to be strongly dependent upon the power-law index, stretching parameter, wall temperature parameter, material parameter of the Sisko fluid and Prandtl number. In addition, the local Nusselt number versus wall temperature parameter is also graphed and tabulated for different values of pertaining parameters. Further, numerical results are validated by comparison with exact solutions as well as previously published results in the literature. PMID:24949738

  10. Forced convection heat transfer and hydraulic losses in porous carbon foam

    SciTech Connect

    Straatman, Anthony G; Gallego, Nidia C

    2007-01-01

    Experiments and computations are presented to quantify the convective heat transfer and the hydraulic loss that is obtained by forcing water through blocks of graphitic foam (GF) heated from one side. Experiments have been conducted in a small-scale water tunnel instrumented to measure the pressure drop and the temperature rise of water passing through the foam and the base temperature and heat flux into the foam block. The experimental data were then used to calibrate a thermal non-equilibrium finite-volume model to facilitate comparisons between GF and aluminum foam. Comparisons of the pressure drop indicate that both normal and compressed aluminum foams are significantly more permeable than GF. Results of the heat transfer indicate that the maximum possible heat dissipation from a given surface is reached using very thin layers of aluminum foam due to the inability of the foam to entrain heat into its internal structure. In contrast, graphitic foam is able to entrain heat deep into the foam structure due to its high extended surface efficiency and thus much more heat can be transferred from a given surface area. The higher extended surface efficiency is mainly due to the combination of moderate porosity and higher solid-phase conductivity.

  11. Kinetics modeling of the drying of sunflower stem (Helianthus annuus L.) in a forced convection tunnel

    NASA Astrophysics Data System (ADS)

    López, R.; Vaca, M.; Terres, H.; Lizardi, A.; Morales, J.; Flores, J.; Chávez, S.

    2015-01-01

    The sunflower is an annual plant native to the Americas. It possesses a large inflorescence (flowering head), and its name is derived from the flower's shape and image, which is often used to capture the sun. The plant has a rough, broad, hairy stem, coarsely toothed, with rough leaves, and circular flower heads. The sunflower seeds are appreciated for their oil, which has become a widespread cooking ingredient. Leaves of the sunflower can be used as cattle feed, while the stems contain a fiber that may be used in paper production. Recently this flower has been used in phytoremediation of soils, contaminated with heavy metals. Sunflower has been probed as an efficient phytoextractor of chromium, lead, aluminum, zinc, cadmium from soil. In this work we present the experimental results of the drying of the sunflower stem, cut in 100 mm longitudinal sections, with diameters in the range of 11-18 mm. The aim was to obtain a dry and easy-to-handle final product, since these plants were originally cultivated in order to extract heavy metals from a polluted soil. The dried stems could then be easily confined or sent to recycle premises to concentrate the metals. The drying process was done in forced convection within a hot air tunnel. The used temperature was 60 °C, the velocity of air was 3 m/s and the required times were 8 hours. The initial average wet mass was 28 g and the final value was 5 g, resulting in the aimed product.

  12. Skin-friction drag analysis from the forced convection modeling in simplified underwater swimming.

    PubMed

    Polidori, G; Taïar, R; Fohanno, S; Mai, T H; Lodini, A

    2006-01-01

    This study deals with skin-friction drag analysis in underwater swimming. Although lower than profile drag, skin-friction drag remains significant and is the second and only other contribution to total drag in the case of underwater swimming. The question arises whether varying the thermal gradient between the underwater swimmer and the pool water may modify the surface shear stress distribution and the resulting skin-friction drag acting on a swimmer's body. As far as the authors are aware, such a question has not previously been addressed. Therefore, the purpose of this study was to quantify the effect of this thermal gradient by using the integral formalism applied to the forced convection theory. From a simplified model in a range of pool temperatures (20-30 degrees C) it was demonstrated that, whatever the swimming speeds, a 5.3% reduction in the skin-friction drag would occur with increasing average boundary-layer temperature provided that the flow remained laminar. However, as the majority of the flow is actually turbulent, a turbulent flow analysis leads to the major conclusion that friction drag is a function of underwater speed, leading to a possible 1.5% reduction for fast swimming speeds above 1m/s. Furthermore, simple correlations between the surface shear stress and resulting skin-friction drag are derived in terms of the boundary-layer temperature, which may be readily used in underwater swimming situations. PMID:16153653

  13. Nanofluid flow and forced convection heat transfer over a stretching surface considering heat source

    NASA Astrophysics Data System (ADS)

    Mohammadpour, M.; Valipour, P.; Shambooli, M.; Ayani, M.; Mirparizi, M.

    2015-07-01

    In this paper, magnetic field effects on the forced convection flow of a nanofluid over a stretching surface in the presence of heat generation/absorption are studied. The equations of continuity, momentum and energy are transformed into ordinary differential equations and solved numerically using the fourth-order Runge-Kutta integration scheme featuring the shooting technique. Different types of nanoparticles as copper (Cu), silver (Ag), alumina (Al2O3) and titania (TiO2) with water as their base fluid has been considered. The influence of significant parameters, such as magnetic parameter, volume fraction of the nanoparticles, heat generation/absorption parameter, velocity ratio parameter and temperature index parameter on the flow and heat transfer characteristics are discussed. The results show that the values of temperature profiles increase with increasing heat generation/absorption and volume fraction of the nanoparticles but they decrease with increasing velocity ratio parameter and temperature index parameter. Also, it can be found that selecting silver as nanoparticle leads to the highest heat transfer enhancement.

  14. Experimental study of an upward sub-cooled forced convection in a rectangular channel

    NASA Astrophysics Data System (ADS)

    Kouidri, A.; Madani, B.; Roubi, B.; Hamadouche, A.

    2016-07-01

    The upward sub-cooled forced convection in a rectangular channel is investigated experimentally. The aim of the present work is the studying of the local heat transfer phenomena. Concerning the experimentation: the n-pentane is used as a working fluid, the independent variables are: the velocity in the range from 0.04 to 0.086 m/s and heat flux density with values between 1.8 and 7.36 W/cm2. The results show that the local Nusselt number distribution is not uniform along the channel; however, uniformity is observed in the mean Nusselt number for Reynolds under 1600. On the other hand, a new correlation to predict the local fluid temperature is established as a function of local wall temperature. The wall's heat is dissipated under the common effect of the sub-cooled regime; therefore, the local heat transfer coefficient is increased. The study of the thermal equilibrium showed that for Reynolds less than 1500; almost all of the heat flux generated by the heater cartridges is absorbed by the fluid.

  15. Regressed relations for forced convection heat transfer in a direct injection stratified charge rotary engine

    NASA Technical Reports Server (NTRS)

    Lee, Chi M.; Schock, Harold J.

    1988-01-01

    Currently, the heat transfer equation used in the rotary combustion engine (RCE) simulation model is taken from piston engine studies. These relations have been empirically developed by the experimental input coming from piston engines whose geometry differs considerably from that of the RCE. The objective of this work was to derive equations to estimate heat transfer coefficients in the combustion chamber of an RCE. This was accomplished by making detailed temperature and pressure measurements in a direct injection stratified charge (DISC) RCE under a range of conditions. For each specific measurement point, the local gas velocity was assumed equal to the local rotor tip speed. Local physical properties of the fluids were then calculated. Two types of correlation equations were derived and are described in this paper. The first correlation expresses the Nusselt number as a function of the Prandtl number, Reynolds number, and characteristic temperature ratio; the second correlation expresses the forced convection heat transfer coefficient as a function of fluid temperature, pressure and velocity.

  16. Residual stress measurements in forced convective quenched steel bars by means of neutron diffraction

    SciTech Connect

    Hernandez-Morales, B.; Hawbolt, B.E.; Brimacombe, J.K.

    1996-12-31

    The residual stress distributions in 38.1 mm-dia., forced convective quenched bars of interstitial-free (IF), 1045 carbon, and alloyed steels were determined by neutron diffraction. The IF and 1045 carbon steel quenched bars exhibited compressive axial and circumferential (hoop) residual stresses near the surface and tensile values at the center. The radial residual stresses were tensile at all radial positions, decreasing towards zero near the surface. In contrast, the measured axial and circumferential components of the residual stress tensor in the alloyed eutectoid steel quenched bar were tensile near the surface and decreased to compressive values at the center. The radial component showed a maximum compressive value at the center and approached zero close to the surface. Metallographic analysis and hardness testing of the three steel specimens, revealed that the IF steel had transformed completely to ferrite, while the 1045 carbon steel bar transformed to martensite near the surface and a mixture of pearlite, ferrite and martensite at the center. On the other hand, the alloyed eutectoid steel specimen transformed entirely to martensite with small amounts of bainite near the center of the rod. The observed differences in the residual stress distributions in the three steels were explained based on the sequence of phase transformations that took place during quenching.

  17. Heat Transfer Enhancement in Forced Convective Boiling in Microchannels by Periodic Electrospun Nanofiber Coatings

    NASA Astrophysics Data System (ADS)

    Yarin, Alexander; Freystein, Martin; Kolberg, Felix; Sinha-Ray, Sumit; Sahu, Rakesh; Spiegel, Lucas; Gambaryan-Roisman, Tatiana; Stephan, Peter

    2015-03-01

    To enhance heat transfer in forced convective boiling the microchannel bottom was amended by a nano-texture - periodic rectangular mats of electrospun polymer nanofibers. The fibers were ~ 300-500 nm in diameter and the mat thicknesses were about 6-15 μm. The test fluid was FC-72 and the flow in microchannels contained trains of Taylor bubbles. The role of the nanofibers was to retain the warm microchannel bottom wet, to prevent dry-out and thus to enhance the heat removal rate. In the present experiments the time-average heat flux and heat transfer coefficient at the nanofiber-coated domains were found to be 1.5-2 times higher than those at the uncoated ones. Accordingly, a significant decrease (by 5-8 K) in the superheat was observed at the same Re of 387 and power supply of 36.1 kW/m2. At a higher Re of 432 and lower power supply of 28.1 kW/m2 similar trends in the heat removal rate and surface superheat were found. The significant enhancement of the heat transfer results from the fact that nanofiber mats facilitate wetting of surface under passing Taylor bubbles, thus delaying formation of vapor flow at the channel bottom. The interstices of the nanofiber mat act as the nucleation sites facilitating formation of tiny bubbles, which eventually results in a higher heat removal rate from the surface at a reduced superheat.

  18. Non-Contact Electrical Conductivity Measurement Technique for Molten Metals

    NASA Technical Reports Server (NTRS)

    Rhim, W. K.; Ishikawa, T.

    1998-01-01

    A non-contact technique of measuring the electrical conductivity (or resistivity) of conducting liquids while they are levitated by the high temperature electrostatic levitator in a high vacuum is reported.

  19. Electrical conductivity of rocks at high pressures and temperatures

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

    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.

  20. Measurement of electrical conductivity for a biomass fire.

    PubMed

    Mphale, Kgakgamatso; Heron, Mal

    2008-08-01

    A controlled fire burner was constructed where various natural vegetation species could be used as fuel. The burner was equipped with thermocouples to measure fuel surface temperature and used as a cavity for microwaves with a laboratory quality 2-port vector network analyzer to determine electrical conductivity from S-parameters. Electrical conductivity for vegetation material flames is important for numerical prediction of flashover in high voltage power transmission faults research. Vegetation fires that burn under high voltage transmission lines reduce flashover voltage by increasing air electrical conductivity and temperature. Analyzer determined electrical conductivity ranged from 0.0058 - 0.0079 mho/m for a fire with a maximum temperature of 1240 K. PMID:19325812

  1. Temperature-dependent electrical conductivity of soda-lime glass

    NASA Technical Reports Server (NTRS)

    Bunnell, L. Roy; Vertrees, T. H.

    1993-01-01

    The objective of this educational exercise was to demonstrate the difference between the electrical conductivity of metals and ceramics. A list of the equipment and supplies and the procedure for the experiment are presented.

  2. Electrical conductivity of chlorite at high pressures and high temperatures

    NASA Astrophysics Data System (ADS)

    Eymard, I.; Mibe, K.; Reynard, B.

    2012-12-01

    In the mantle wedge of subduction zones, high electrical-conductivity bodies have been observed. In order to understand the cause of high-conductivity body in subduction zones, we measured the electrical conductivity of polycrystalline chlorite, at pressures from 2 to 4 GPa and at high temperatures up to 850K using complex impedance spectroscopy in a multi-anvil high-pressure apparatus. The electrical conductivity increased slightly with increasing pressure. The obtained electrical conductivity values are higher than serpentine and talc (Reynard et al., 2011; Guo et al., 2011) and are slightly lower than brucite (Fujita et al., 2007). Although the obtained values are higher compared to serpentine, the presence of chlorite alone is not high enough to explain high-conductivity bodies in subduction-zones. Instead, the presence of some amount of saline fluids is inferred.

  3. Measurement of Electrical Conductivity for a Biomass Fire

    PubMed Central

    Mphale, Kgakgamatso; Heron, Mal

    2008-01-01

    A controlled fire burner was constructed where various natural vegetation species could be used as fuel. The burner was equipped with thermocouples to measure fuel surface temperature and used as a cavity for microwaves with a laboratory quality 2-port vector network analyzer to determine electrical conductivity from S-parameters. Electrical conductivity for vegetation material flames is important for numerical prediction of flashover in high voltage power transmission faults research. Vegetation fires that burn under high voltage transmission lines reduce flashover voltage by increasing air electrical conductivity and temperature. Analyzer determined electrical conductivity ranged from 0.0058 - 0.0079 mho/m for a fire with a maximum temperature of 1240 K. PMID:19325812

  4. Control of dynamical self-assembly of strongly Brownian nanoparticles through convective forces induced by ultrafast laser

    NASA Astrophysics Data System (ADS)

    Ilday, Serim; Akguc, Gursoy B.; Tokel, Onur; Makey, Ghaith; Yavuz, Ozgun; Yavuz, Koray; Pavlov, Ihor; Ilday, F. Omer; Gulseren, Oguz

    We report a new dynamical self-assembly mechanism, where judicious use of convective and strong Brownian forces enables effective patterning of colloidal nanoparticles that are almost two orders of magnitude smaller than the laser beam. Optical trapping or tweezing effects are not involved, but the laser is used to create steep thermal gradients through multi-photon absorption, and thereby guide the colloids through convective forces. Convective forces can be thought as a positive feedback mechanism that helps to form and reinforce pattern, while Brownian motion act as a competing negative feedback mechanism to limit the growth of the pattern, as well as to increase the possibilities of bifurcation into different patterns, analogous to the competition observed in reaction-diffusion systems. By steering stochastic processes through these forces, we are able to gain control over the emergent pattern such as to form-deform-reform of a pattern, to change its shape and transport it spatially within seconds. This enables us to dynamically initiate and control large patterns comprised of hundreds of colloids. Further, by not relying on any specific chemical, optical or magnetic interaction, this new method is, in principle, completely independent of the material type being assembled.

  5. Chapter A6. Section 6.3. Specific Electrical Conductance

    USGS Publications Warehouse

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

    2005-01-01

    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.

  6. The electrical conductivity of weakly ionized plasma containing dust particles

    NASA Astrophysics Data System (ADS)

    Li, Hui; Wu, Jian; Yuan, Chengxun; Zhou, Zhongxiang

    2016-07-01

    The effect of charged dust particle on the electrical conductivity of weakly ionized dusty plasma is investigated. It is shown that the additional collision provided by charged dust particles can significantly alter the electrical conductivity of electron-ion plasma. The numerical results indicated that these effects are mainly determined by dust radius, density as well as the charge numbers on dust surface. The obtained results will support an enhanced understanding of the electromagnetic wave propagation processes in dusty plasma.

  7. Electrically conductive, black thermal control coatings for space craft application. II - Silicone matrix formulation

    NASA Technical Reports Server (NTRS)

    Hribar, V. F.; Bauer, J. L.; O'Donnell, T. P.

    1986-01-01

    Five black electrically conductive thermal-control coatings have been formulated and tested for application on the Galileo spacecraft. The coatings consisted of organic and inorganic systems applied on titanium and aluminum surfaces. The coatings were tested under simulated space environment conditions. Coated specimens were subjected to thermal radiation and convective and conductive heating from -196 to 538 C. Mechanical, physical, thermal, electrical, and optical characteristics, formulation, mixing, application, surface preparation of substrates, and a method of determining electrical resistance are presented for the silicone matrix formulation designated as GF-580.

  8. Numerical investigation of 22 seconds of convection under the effect of dielectrophoretic force in an annular gap

    NASA Astrophysics Data System (ADS)

    Crumeyrolle, Olivier; Egbers, Christoph; Mutabazi, Innocent; Dahley, M. Norman; Smieszek, Marlene

    2012-07-01

    We investigate numerically the thermal convection of an annular dielectric liquid sheet under the effect of the dielectrophoretic force, as observed when a dielectric liquid is permeated by an inhomogeneous electric field. This is of particular interest for space applications as natural convection cannot appear and forced convection from moving parts such as pumps is undesirable due to the expected wearing and lower reliability. Hence heat exchanger relying on the dielectrophoretic force to create convection could provide light, compact and reliable heat exchanger for aerospace cooling systems \\cite{crumeyrolleP}. We investigate the case of a radius ratio equal to 0.5 and Prandtl number of 65. This setup is under experimental investigation at LAS, BTU Cottbus, both on ground and during parabolic flight. The 3D linear stability analysis, that takes the finite size of the system into account, shows that the critical mode is non-axisymmetric and under the form of two counteroriented helices, rather than under the form of rolls as predicted in past investigations\\cite{crumeyrolleT}. Due to the short duration of microgravity during parabolic flight (22 seconds), 3D time-dependent DNS are required with realistic initial conditions. The simulations show that the helices are difficult to observe, as the flow pattern is dominated by convection plumes. We report that transient thermal transfer at the inner cylinder is strongly enhanced by those structures, while the thermal transfer close to the outer cylinder is weaker. J.S. Paschkewitz and {D.M.} Pratt, Exp. Therm. Fluid Sci., 21,, 187 (2000). M. Takashima, Q. J. Mech. appl. Math. 33,, 93 (1980).

  9. Magnetothermal Convection of Water with the Presence or Absence of a Magnetic Force Acting on the Susceptibility Gradient.

    PubMed

    Maki, Syou

    2016-01-01

    Heat transfer of magnetothermal convection with the presence or absence of the magnetic force acting on the susceptibility gradient (fsc) was examined by three-dimensional numerical computations. Thermal convection of water enclosed in a shallow cylindrical vessel (diameter over vessel height = 6.0) with the Rayleigh-Benard model was adopted as the model, under the conditions of Prandtl number 6.0 and Ra number 7000, respectively. The momentum equations of convection were nondimensionalized, which involved the term of fsc and the term of magnetic force acting on the magnetic field gradient (fb). All the computations resulted in axisymmetric steady rolls. The values of the averaged Nu, the averaged velocity components U, V, and W, and the isothermal distributions and flow patterns were almost completely the same, regardless of the presence or absence of the term of fsc. As a result, we found that the effect of fsc was extremely small, although much previous research emphasized the effect with paramagnetic solutions under an unsteady state. The magnitude of fsc depends not only on magnetic conditions (magnitudes of magnetic susceptibility and magnetic flux density), but also on the thermal properties of the solution (thermal conductivity, thermal diffusivity, and viscosity). Therefore the effect of fb becomes dominant on the magnetothermal convection. Active control over the density gradient with temperature will be required to advance heat transfer with the effect of fsc. PMID:27606823

  10. The effect of water on the electrical conductivity of olivine.

    PubMed

    Wang, Duojun; Mookherjee, Mainak; Xu, Yousheng; Karato, Shun-ichiro

    2006-10-26

    It is well known that water (as a source of hydrogen) affects the physical and chemical properties of minerals--for example, plastic deformation and melting temperature--and accordingly plays an important role in the dynamics and geochemical evolution of the Earth. Estimating the water content of the Earth's mantle by direct sampling provides only a limited data set from shallow regions (<200 km depth). Geophysical observations such as electrical conductivity are considered to be sensitive to water content, but there has been no experimental study to determine the effect of water on the electrical conductivity of olivine, the most abundant mineral in the Earth's mantle. Here we report a laboratory study of the dependence of the electrical conductivity of olivine aggregates on water content at high temperature and pressure. The electrical conductivity of synthetic polycrystalline olivine was determined from a.c. impedance measurements at a pressure of 4 GPa for a temperature range of 873-1,273 K for water contents of 0.01-0.08 wt%. The results show that the electrical conductivity is strongly dependent on water content but depends only modestly on temperature. The water content dependence of conductivity is best explained by a model in which electrical conduction is due to the motion of free protons. A comparison of the laboratory data with geophysical observations suggests that the typical oceanic asthenosphere contains approximately 10(-2) wt% water, whereas the water content in the continental upper mantle is less than approximately 10(-3) wt%. PMID:17066032

  11. Electrical Conductivity of the Lower-Mantle Ferropericlase

    SciTech Connect

    Lin, J F; Weir, S T; Jackson, D D; Evans, W J; Vohra, Y K; Qiu, W; Yoo, C S

    2007-04-19

    Electrical conductivity of the lower-mantle ferropericlase-(Mg{sub 0.75},Fe{sub 0.25})O has been studied using designer diamond anvils to pressures over one megabar and temperatures up to 500 K. The electrical conductivity of (Mg{sub 0.75},Fe{sub 0.25})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 attributed to the electronic high-spin to low-spin transition of iron in ferropericlase. That is, the electronic spin transition of iron results in a decrease in the mobility and/or density of the charge transfer carriers in the low-spin ferropericlase. The activation energy of the low-spin ferropericlase is 0.27 eV at 101 GPa, similar to that of the high-spin ferropericlase at relatively low temperatures. Our results indicate that low-spin ferropericlase exhibits lower electrical conductivity than high-spin ferropericlase, which needs to be considered in future geomagnetic models for the lower mantle. The extrapolated electrical conductivity of the low-spin ferropericlase, together with that of silicate perovskite, at the lower mantle pressure-temperature conditions is consistent with the model electrical conductivity profile of the lower mantle.

  12. Dimensionless correlations for forced convection in liquid metals: Part I. single-phase flow

    NASA Astrophysics Data System (ADS)

    Argyropoulos, Stavros A.; Mikrovas, Anthony C.; Doutre, Don A.

    2001-04-01

    Two main objectives were addressed in this article. First, a dimensionless heat-transfer correlation for single-phase flow forced convection in liquid aluminum has been derived using a novel experimental method. An aluminum sphere was rotated with a specific tangential velocity in liquid aluminum. Its melting time was measured and correlated with the convective heat-transfer characteristics. The resulting correlation has the following form: % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGceaqabeaadaqdaa% qaaGqaaiaa-5eacaWF1bWaaSbaaSqaaiaadseaaeqaaaaakiabg2da% 9iaaikdacqGHRaWkcaaIXaGaaGimamaaCaaaleqabaGaaGOmaiaac6% cacaaI4aGaaGymaiaaigdaaaGccqGHxdaTciGGsbGaaiyzamaaDaaa% leaacaWGebaabaGaaGimaiaac6cacaaI1aGaaGioaiaaiwdaaaGccq% GHxdaTciGGqbGaaiOCamaaCaaaleqabaGaaGOmaiaac6cacaaIZaGa% aGioaiaaiAdaaaaakeaacaaI1aGaaGymaiaaiAdacaaIYaGaeyizIm% QaciOuaiaacwgadaWgaaWcbaGaamiraaqabaGccqGHKjYOcaaIYaGa% aGymaiaacYcacaaIYaGaaG4naiaaiodacaGGSaqefeKCPfgBaGqbai% aa+bcaciGGqbGaaiOCaiabgIKi7kaaicdacaGGUaGaaGimaiaaigda% caaI0aaaaaa!690C! begin{gathered} overline {Nu_D } = 2 + 10^{2.811} × operatorname{Re} _D^{0.585} × Pr ^{2.386} \\ 5162 ≤slant operatorname{Re} _D ≤slant 21,273, Pr ≈ 0.014 \\ The second objective of the study was to assess the accuracy of various correlations using an annular channel, which was available at an independent setting, at the Alcan Research and Development Laboratory. The correlations investigated were those derived from the current experimental work as well as those derived by other investigators, as presented in their respective published work. Results indicated that when applied to liquid metals, theoretically derived equations as

  13. Micro-gravity: Superconducting coils for crystal growth. Influence of the levitation force on natural convection in the fluid

    NASA Astrophysics Data System (ADS)

    Quettier, L.; Vincent-Viry, O.; Mailfert, A.; Juster, F. P.

    2003-04-01

    This paper presents a novel design of superconducting coils able to generate a micro-gravity environment for protein crystal growth in aqueous solution. The structures have been calculated thanks to a method for “inverse source synthesis problem" developed at the GREEN Choice of the angular offset between the directions of magnetic force field and magnetic field in the working area as well as convection phenomena are also studied.

  14. Investigation of free-forced convection flows in cavity-type receivers. Final yearly report, 1979-1980

    SciTech Connect

    Humphrey, J.A.C.

    1982-01-01

    A summary is provided of the first of three years of experimental and theoretical research on free-forced convection flows in cavity-type solar receivers. New experimental and theoretical results are presented and discussed. The implication of these findings, with respect to the future thrust of the research program, is clarified as well as is possible at the present time. Following various related conclusions a summary and tentative schedule of work projected for year two of research are presented.

  15. Forced convection flow boiling and two-phase flow phenomena in a microchannel

    NASA Astrophysics Data System (ADS)

    Na, Yun Whan

    2008-07-01

    The present study was performed to numerically analyze the evaporation phenomena through the liquid-vapor interface and to investigate bubble dynamics and heat transfer behavior during forced convective flow boiling in a microchannel. Flow instabilities of two-phase flow boiling in a microchannel were studied as well. The main objective of this research is to investigate the fundamental mechanisms of two-phase flow boiling in a microchannel and provide predictive tools to design thermal management systems, for example, microchannel heat sinks. The numerical results obtained from this study were qualitatively and quantitatively compared with experimental results in the open literature. Physical and mathematical models, accounting for evaporating phenomena through the liquid-vapor interface in a microchannel at constant heat flux and constant wall temperature, have been developed, respectively. The heat transfer mechanism is affected by the dominant heat conduction through the thin liquid film and vaporization at the liquid-vapor interface. The thickness of the liquid film and the pressure of the liquid and vapor phases were simultaneously solved by the governing differential equations. The developed semi-analytical evaporation model that takes into account of the interfacial phenomena and surface tension effects was used to obtain solutions numerically using the fourth-order Runge-Kutta method. The effects of heat flux 19 and wall temperature on the liquid film were evaluated. The obtained pressure drops in a microchannel were qualitatively consistent with the experimental results of Qu and Mudawar (2004). Forced convective flow boiling in a single microchannel with different channel heights was studied through a numerical simulation to investigate bubble dynamics, flow patterns, and heat transfer. The momentum and energy equations were solved using the finite volume method while the liquid-vapor interface of a bubble is captured using the VOF (Volume of Fluid

  16. Investigation on magnetoacoustic signal generation with magnetic induction and its application to electrical conductivity reconstruction.

    PubMed

    Ma, Qingyu; He, Bin

    2007-08-21

    A theoretical study on the magnetoacoustic signal generation with magnetic induction and its applications to electrical conductivity reconstruction is conducted. An object with a concentric cylindrical geometry is located in a static magnetic field and a pulsed magnetic field. Driven by Lorentz force generated by the static magnetic field, the magnetically induced eddy current produces acoustic vibration and the propagated sound wave is received by a transducer around the object to reconstruct the corresponding electrical conductivity distribution of the object. A theory on the magnetoacoustic waveform generation for a circular symmetric model is provided as a forward problem. The explicit formulae and quantitative algorithm for the electrical conductivity reconstruction are then presented as an inverse problem. Computer simulations were conducted to test the proposed theory and assess the performance of the inverse algorithms for a multi-layer cylindrical model. The present simulation results confirm the validity of the proposed theory and suggest the feasibility of reconstructing electrical conductivity distribution based on the proposed theory on the magnetoacoustic signal generation with magnetic induction. PMID:17671355

  17. Calibration-free electrical conductivity measurements for highly conductive slags

    SciTech Connect

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

    2000-05-01

    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.

  18. Gravity Wave Forcing of the Mesosphere and Lower Thermosphere: Mountain and Convective Waves Ascending Vertically (MaCWAVE)

    NASA Technical Reports Server (NTRS)

    Fritts, David C.

    2004-01-01

    The specific objectives of this research effort included the following: 1) Quantification of gravity wave propagation throughout the lower and middle atmosphere in order to define the roles of topographic and convective sources and filtering by mean and low-frequency winds in defining the wave field and wave fluxes at greater altitudes; 2) The influences of wave instability processes in constraining wave amplitudes and fluxes and generating turbulence and transport; 3) Gravity wave forcing of the mean circulation and thermal structure in the presence of variable motion fields and wave-wave interactions, since the mean forcing may be a small residual when wave interactions, anisotropy, and momentum and heat fluxes are large; 4) The statistical forcing and variability imposed on the thermosphere at greater altitudes by the strong wave forcing and interactions occurring in the MLTI.

  19. Electrical conduction in macroscopically oriented deoxyribonucleic and hyaluronic acid samples

    NASA Astrophysics Data System (ADS)

    Kutnjak, Zdravko; Lahajnar, Gojmir; Filipič, Cene; Podgornik, Rudolf; Nordenskiöld, Lars; Korolev, Nikolay; Rupprecht, Allan

    2005-04-01

    Measurements of the quasistatic and frequency dependent electrical conductivity below 1 MHz were carried out on wet-spun, macroscopically oriented, calf thymus deoxyribonucleic (DNA) and umbilical cord hyaluronic acid (HA) bulk samples. The frequency dependence of the electrical conductivity in the frequency range of approximately 10-3-106Hz of both materials is surprisingly rather similar. Temperature dependence of the quasistatic electrical conductivity above the low temperature saturation plateau can be well described by the activated Arrhenius law with the activation energy of ≈0.8eV for both DNA and HA. We discuss the meaning of these findings for the possible conduction mechanism in these particular charged polyelectrolytes.

  20. An electrical conductivity model for fractal porous media

    NASA Astrophysics Data System (ADS)

    Wei, Wei; Cai, Jianchao; Hu, Xiangyun; Han, Qi

    2015-06-01

    Archie's equation is an empirical electrical conductivity-porosity model that has been used to predict the formation factor of porous rock for more than 70 years. However, the physical interpretation of its parameters, e.g., the cementation exponent m, remains questionable. In this study, a theoretical electrical conductivity equation is derived based on the fractal characteristics of porous media. The proposed model is expressed in terms of the tortuosity fractal dimension (DT), the pore fractal dimension (Df), the electrical conductivity of the pore liquid, and the porosity. The empirical parameter m is then determined from physically based parameters, such as DT and Df. Furthermore, a distinct interrelationship between DT and Df is obtained. We find a reasonably good match between the predicted formation factor by our model and experimental data.

  1. Electrically conductive resinous bond and method of manufacture

    DOEpatents

    Snowden, Jr., Thomas M.; Wells, Barbara J.

    1987-01-01

    A method of bonding elements together with a bond of high strength and good electrical conductivity which comprises: applying an unfilled polyimide resin between surfaces of the elements to be bonded, heat treating said unfilled polyimide resin in stages between a temperature range of about 40.degree. to 365.degree. C. to form a strong adhesive bond between said elements, applying a metal-filled polyimide resin overcoat between said elements so as to provide electrical connection therebetween, and heat treating said metal-filled polyimide resin with substantially the same temperature profile as the unfilled polyimide resin. The present invention is also concerned with an adhesive, resilient, substantially void free bonding combination for providing a high strength, electrically conductive adhesive attachment between electrically conductive elements which comprises a major amount of an unfilled polyimide resin and a minor amount of a metal-filled polyimide resin.

  2. Electrically conductive resinous bond and method of manufacture

    DOEpatents

    Snowden, T.M. Jr.; Wells, B.J.

    1985-01-01

    A method of bonding elements together with a bond of high strength and good electrical conductivity which comprises: applying an unfilled polyimide resin between surfaces of the elements to be bonded, heat treating said unfilled polyimide resin in stages between a temperature range of about 40 to 365/sup 0/C to form a strong adhesive bond between said elements, applying a metal-filled polyimide resin overcoat between said elements so as to provide electrical connection therebetween, and heat treating said metal-filled polyimide resin with substantially the same temperature profile as the unfilled polyimide resin. The present invention is also concerned with an adhesive, resilient, substantially void free bonding combination for providing a high strength, electrically conductive adhesive attachment between electrically conductive elements which comprises a major amount of an unfilled polyimide resin and a minor amount of a metal-filled polyimide resin.

  3. Sintering, Microstructure, and Electrical Conductivity of Zirconia-Molybdenum Cermet

    NASA Astrophysics Data System (ADS)

    Guo, Yanling; Tang, Lei; Zhang, Jieyu

    2015-08-01

    Monolithic zirconia-molybdenum ( m-ZrO2/Mo) cermets of different compositions (5-40 vol.% Mo) and different initial Mo particles sizes (0.08-13 μm) were prepared by traditional powder metallurgy process. The influences of metal content and initial particle sizes on the densification behavior, microstructure, and electrical conductivity of the cermets were studied. A percolation threshold value was obtained about 17.1 vol.% molybdenum fraction, above which a sharp increase in the electrical conductivity was observed. The temperature dependence of the electrical conductivity of cermets was studied. The cermet containing 5 vol.% Mo showed the ionic nature of the conductivity, while the metallic nature was observed in the samples of Mo fraction up to 16 vol.%. The activation of conductivity for ionic type of conductivity and the temperature coefficient of resistivity as well as the effect of porosity on electronic type conductivity are discussed.

  4. Multi-rate flowing Wellbore electric conductivity logging method

    SciTech Connect

    Tsang, Chin-Fu; Doughty, Christine

    2003-04-22

    The flowing wellbore electric conductivity logging method involves the replacement of wellbore water by de-ionized or constant-salinity water, followed by constant pumping with rate Q, during which a series of fluid electric conductivity logs are taken. The logs can be analyzed to identify depth locations of inflow, and evaluate the transmissivity and electric conductivity (salinity) of the fluid at each inflow point. The present paper proposes the use of the method with two or more pumping rates. In particular it is recommended that the method be applied three times with pumping rates Q, Q /2, and 2Q. Then a combined analysis of the multi-rate data allows an efficient means of determining transmissivity and salinity values of all inflow points along a well with a confidence measure, as well as their inherent or far-field pressure heads. The method is illustrated by a practical example.

  5. Electrical conductivity of Cs2CuCl4 crystals

    NASA Astrophysics Data System (ADS)

    Sorokin, N. I.

    2016-05-01

    The electrical conductivity of Cs2CuCl4 single crystals, synthesized by crystallization from aqueous solutions in the CsCl-CuCl2-H2O system, has been investigated. The temperature dependence of the electrical conductivity of crystals in a temperature range of 338-584 K exhibits no anomalies. The electrical transfer activation enthalpy is Δ H σ = 0.72 ± 0.05 eV and the conductivity is σ = 3 × 10-4 S/cm at 584 K. The most likely carriers in Cs2CuCl4 are Cs+ cations, which transfer electric charge according to the vacancy mechanism.

  6. Electrical conductivity measurements on silicate melts using the loop technique

    NASA Technical Reports Server (NTRS)

    Waff, H. S.

    1976-01-01

    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.

  7. Corrosion-protective coatings from electrically conducting polymers

    SciTech Connect

    Thompson, K.G.; Bryan, C.J.; Benicewicz, B.C.; Wrobleski, D.A.

    1991-12-31

    In a joint research effort involving the Kennedy Space Center and the Los Alamos National Laboratory, electrically conductive polymer coatings have been developed as corrosion-protective coatings for metal surfaces. At the Kennedy Space Center, the launch environment consists of marine, severe solar, and intermittent high acid/elevated temperature conditions. Electrically conductive polymer coatings have been 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.

  8. Corrosion-protective coatings from electrically conducting polymers

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    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.

  9. Electrically conductive doped block copolymer of polyacetylene and polyisoprene

    DOEpatents

    Aldissi, Mahmoud

    1985-01-01

    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.

  10. UV-induced surface electrical conductivity jump of polymer nanocomposites

    SciTech Connect

    Chen Guangxin; Miyauchi, Masahiro; Shimizu, Hiroshi

    2008-05-19

    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.

  11. Contamination from electrically conductive silicone tubing during aerosol chemical analysis

    SciTech Connect

    Yu, Yong; Alexander, M. L.; Perraud, Veronique; Bruns, Emily; Johnson, Stan; Ezell, Michael J.; Finlayson-Pitts, Barbara J.

    2009-06-01

    Electrically conductive silicone tubing is used to minimize losses in sampling lines during the analysis of airborne particle size distributions and number concentrations. We report contamination from this tubing using gas chromatography-mass spectrometry (GC-MS) of filter-collected samples as well as by particle mass spectrometry. Comparison of electrically conductive silicone and stainless steel tubing showed elevated siloxanes only for the silicone tubing. The extent of contamination increased with length of tubing to which the sample was exposed, and decreased with increasing relative humidity.

  12. Measuring the local electrical conductivity of human brain tissue

    NASA Astrophysics Data System (ADS)

    Akhtari, M.; Emin, D.; Ellingson, B. M.; Woodworth, D.; Frew, A.; Mathern, G. W.

    2016-02-01

    The electrical conductivities of freshly excised brain tissues from 24 patients were measured. The diffusion-MRI of the hydrogen nuclei of water molecules from regions that were subsequently excised was also measured. Analysis of these measurements indicates that differences between samples' conductivities are primarily due to differences of their densities of solvated sodium cations. Concomitantly, the sample-to-sample variations of their diffusion constants are relatively small. This finding suggests that non-invasive in-vivo measurements of brain tissues' local sodium-cation density can be utilized to estimate its local electrical conductivity.

  13. Electrostatic Discharge Sensitivity and Electrical Conductivity of Composite Energetic Materials

    SciTech Connect

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

    2013-02-01

    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.

  14. Electrically conducting porphyrin and porphyrin-fullerene electropolymers

    DOEpatents

    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

    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##

  15. Numerical study of forced convection in a turbulent heat sink made of several rows of blocks of square form

    NASA Astrophysics Data System (ADS)

    Bouchenafa, Rachid; Saim, Rachid; Abboudi, Said

    2015-09-01

    Forced convection is a phenomenon associated with the heat transfer fluid flows. The presence of convection affects simultaneously the thermal and hydrodynamic fields, the problem is thus coupled. This form of heat transfer inside ducts occurs in many practical applications such as solar collectors, heat exchangers, cooling of electronic components as well as chemical and nuclear. In this work, we are interested primarily for a numerical study of thermo-hydraulic performances of an incompressible turbulent flow of air through a heat sink composed of several rows of bars of square section. Profiles and the axial velocity fields, as well as profiles and the distribution of the Nusselt number are plotted for all the geometry considered and chosen for different sections. The effects of geometrical parameters of the model and the operating parameters on the dynamic and thermal behavior of the air are analyzed.

  16. On the impact of forced roll convection on vertical turbulent transport in cold air outbreaks

    NASA Astrophysics Data System (ADS)

    Gryschka, Micha; Fricke, Jens; Raasch, Siegfried

    2014-11-01

    We investigated the impact of roll convection on the convective boundary layer and vertical transports in different cold air outbreak (CAO) scenarios using large eddy simulations (LES). The organization of convection into rolls was triggered by upstream heterogeneities in the surface temperature, representing ice and water. By changing the sea ice distribution in our LES, we were able to simulate a roll and a nonroll case for each scenario. Furthermore, the roll wavelength was varied by changing the scale of the heterogeneity. The characteristics of the simulated rolls and cloud streets, such as aspect ratios, orientation of the roll axes, and downstream extensions of single rolls agreed closely with observations in CAO situations. The vertical turbulent fluxes, calculated for each simulation, were decomposed into contributions from rolls and from unorganized turbulence. Even though our results confirmed that rolls triggered by upstream heterogeneities can substantially contribute to vertical turbulent fluxes, the total fluxes were not affected by the rolls.

  17. SOIL ELECTRICAL CONDUCTIVITY AS A MANAGEMENT TOOL IN PRECISION FORESTRY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Apparent soil electrical conductivity (ECa) is a useful measurement and indicator of relative productivity of agronomic crops on some soil types. In non-saline soils, spatial variation in soil ECa is strongly related to texture, topsoil depth and profile variations; factors which spatially correlate...

  18. 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...

  19. Electrically conductive polycrystalline diamond and particulate metal based electrodes

    DOEpatents

    Swain, Greg M.; Wang, Jian

    2005-04-26

    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.

  20. Estimating depth to argillic soil horizons using apparent electrical conductivity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Maps of apparent electrical conductivity (ECa) of the soil profile are widely used in precision agriculture practice and research. A number of ECa sensors are commercially available, each with a unique response function (i.e., the relative contribution of soil at each depth to the integrated ECa rea...

  1. Mechanically stiff, electrically conductive composites of polymers and carbon nanotubes

    DOEpatents

    Worsley, Marcus A.; Kucheyev, Sergei O.; Baumann, Theodore F.; Kuntz, Joshua D.; Satcher, Jr., Joe H.; Hamza, Alex V.

    2015-07-21

    Using SWNT-CA as scaffolds to fabricate stiff, highly conductive polymer (PDMS) composites. The SWNT-CA is immersing in a polymer resin to produce a SWNT-CA infiltrated with a polymer resin. The SWNT-CA infiltrated with a polymer resin is cured to produce the stiff and electrically conductive composite of carbon nanotube aerogel and polymer.

  2. 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...

  3. INCREASING INFORMATION WITH MULTIPLE SOIL ELECTRICAL CONDUCTIVITY DATASETS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Maps of apparent electrical conductivity (ECa) of the soil profile are widely used in precision agriculture practice and research. Because ECa is often strongly related to clay content, soil water holding capacity, and other soil physical properties that also relate to crop productivity, ECa maps ca...

  4. Electrical Conductivity of Thick Films Made from Silver Methylcarbamate Paste

    NASA Astrophysics Data System (ADS)

    Liu, Jianguo; Jiang, Min; Zeng, Xiaoyan

    2013-10-01

    We have explored the electrical conductivity of thick films made from silver methylcarbamate paste using metallic silver as the electrically conductive phase. The paste was composed of 30 wt.% to 90 wt.% organic vehicle and 10 wt.% to 70 wt.% functional phase precursor (silver methylcarbamate). After the paste was sintered, films with thickness of 4.50 μm to 12.70 μm were obtained, in which the elemental percentage of silver varied from about 5 wt.% to above 99 wt.%. Experiments showed that both the electrical conductivity and the elemental percentage were mainly affected by the initial silver content in the paste and the parameters of the sintering process. For given sintering conditions, higher initial silver content led to higher elemental percentage of silver, improving the electrical conductivity of the thick film. The conditions of the sintering process had a significant influence on the evaporation and decomposition rates of the paste components, the elemental percentage of silver, and the microstructure of the thick film. Higher temperatures, longer times, lower heating rates, and more oxygen-rich sintering atmospheres were found to accelerate the evaporation and decomposition and increase the elemental percentage of silver, both of which served to enhance the electrical conductivity. For initial silver contents less than about 10 wt.%, the lowest electrical resistivity of the thick film only reached the order of 10-4 Ω cm, irrespective of the sintering conditions. For contents between 10 wt.% and 25 wt.%, it was possible to attain lowest resistivity values on the order of 10-5 Ω cm. Above 25 wt.%, the lowest resistivity could reach 10-6 Ω cm, comparable to that of bulk silver.

  5. A critical review of predictive models for the onset of significant void in forced-convection subcooled boiling

    SciTech Connect

    Dorra, H.; Lee, S.C.; Bankoff, S.G.

    1993-06-01

    This predictive models for the onset of significant void (OSV) in forced-convection subcooled boiling are reviewed and compared with extensive data. Three analytical models and seven empirical correlations are considered in this review. These models and correlations are put onto a common basis and are compared, again on a common basis, with a variety of data. The evaluation of their range of validity and applicability under various operating conditions are discussed. The results show that the correlations of Saha-Zuber seems to be the best model to predict OSV in vertical subcooled boiling flow.

  6. A Global Model of Mantle Convection that Incorporates Plate Bending Forces, Slab Pull, and Seismic Constraints on the Plate Stress.

    NASA Astrophysics Data System (ADS)

    Lewis, K.; Buffett, B.; Becker, T.

    2008-12-01

    We introduce a global mantle convection model employing mantle density anomalies inferred from seismic tomography to determine present day plate motions. Our approach addresses two aspects that are not usually considered in previous work. First, we include forces associated with the bending of subducting plates. The bending forces oppose the plate motion, and may be comparable in magnitude to other important forces at subduction zones, including slab pull. Second, our model incorporates data from the Global CMT Catalog. We use the focal mechanisms of earthquakes associated with subducting slabs to estimate the relative occurrence of compressional and tensional axes in the down-dip direction of subducting slabs. This information is used to infer the state of stress in the subducting slab, which we use to calculate slab pull forces. We investigate regional variations in slab pull by comparing plate motions derived using seismic constraints with those derived using slab pull forces based solely on the age of subducting plates. Furthermore, we constrain the rheology of subducted plates by comparing plate motions predicted with and without bending forces. Although our current model uses only radial variations in mantle viscosity, we include the capability of permitting lateral variations in viscosity by calculating buoyancy and plate-driven flows using Citcom

  7. Design of Test Loops for Forced Convection Heat Transfer Studies at Supercritical State

    NASA Astrophysics Data System (ADS)

    Balouch, Masih N.

    Worldwide research is being conducted to improve the efficiency of nuclear power plants by using supercritical water (SCW) as the working fluid. One such SCW reactor considered for future development is the CANDU-Supercritical Water Reactor (CANDU-SCWR). For safe and accurate design of the CANDU-SCWR, a detailed knowledge of forced-convection heat transfer in SCW is required. For this purpose, two supercritical fluid loops, i.e. a SCW loop and an R-134a loop are developed at Carleton University. The SCW loop is designed to operate at pressures as high as 28 MPa, temperatures up to 600 °C and mass fluxes of up to 3000 kg/m2s. The R-134a loop is designed to operate at pressures as high as 6 MPa, temperatures up to 140 °C and mass fluxes in the range of 500-6000 kg/m2s. The test loops designs allow for up to 300 kW of heating power to be imparted to the fluid. Both test loops are of the closed-loop design, where flow circulation is achieved by a centrifugal pump in the SCW loop and three parallel-connected gear pumps in the R-134a loop, respectively. The test loops are pressurized using a high-pressure nitrogen cylinder and accumulator assembly, which allows independent control of the pressure, while simultaneously dampening pump induced pressure fluctuations. Heat exchangers located upstream of the pumps control the fluid temperature in the test loops. Strategically located measuring instrumentation provides information on the flow rate, pressure and temperature in the test loops. The test loops have been designed to accommodate a variety of test-section geometries, ranging from a straight circular tube to a seven-rod bundle, achieving heat fluxes up to 2.5 MW/m2 depending on the test-section geometry. The design of both test loops allows for easy reconfiguration of the test-section orientation relative to the gravitational direction. All the test sections are of the directly-heated design, where electric current passing through the pressure retaining walls of the

  8. Numerical investigation of laminar forced convection in Newtonian and non-Newtonian flows in eccentric annuli

    NASA Astrophysics Data System (ADS)

    Fang, Pingping

    1998-12-01

    An extended numerical investigation of fully developed, forced convective laminar flows with heat transfer in eccentric annuli has been carried out. Both Newtonian and non-Newtonian (power-law or Ostwald-de Waele) fluids are studied, representing typical applications in petrochemical, bio-chemical, personal care products, polymer/plastic extrusion and food industries. For the heat transfer problem, with an insulated outer surface, two types of thermal boundary conditions have been considered: Constant wall temperature (T), and uniform axial heat flux with constant peripheral temperature (H1) on the inner surface of the annulus. The governing differential equations for momentum and energy conservation are solved by finite-difference methods. Velocity and temperature distributions in the flow cross section, the wall shear-stress distribution, and isothermal f Re, Nu i,T and Nu i,H1 values for different eccentric annuli (0/leɛ/*/le0.6,/ 0.2/le r/sp/*/le0.8) are presented. In Newtonian flows, the eccentricity is found to have a very strong influence on the flow and temperature fields. In an annulus with relatively large inner cylinder eccentricity, the flow tends to stagnate in the narrow section and has higher peak velocities in the wide section of the annulus. There is considerable flow maldistribution in the azimuthal direction, which in turn produces greater nonuniformity in the temperature field and a consequent degradation in the average heat transfer. Also, the H1 wall condition sustains higher heat transfer coefficients relative to the T boundary condition on the inner surface. For viscous, power-law type non-Newtonian flows, both shear thinning (n<1) and shear thickening (n>1) fluids are considered. Here, the non-linear shear behavior of the fluid is found to further aggravate the flow and temperature maldistribution, and once again the eccentricity is seen to exhibit a very strong influence on the friction and heat transfer behavior. Finally, the

  9. Properties of forced convection experimental with silicon carbide based nano-fluids

    NASA Astrophysics Data System (ADS)

    Soanker, Abhinay

    -fluids. The nano-fluid properties were tested at three different volume concentrations; 0.55%, 1% and 1.6%. Thermal conductivity was measured for the three-volume concentration as function of temperature. Thermal conductivity enhancement increased with the temperature and may be attributed to increased Brownian motion of colloidal particles at higher temperatures. Measured thermal conductivity values are compared with results obtained by theoretical model derived in this work. Effect of temperature and volume concentration on viscosity was also measured and reported. Viscosity increase and related consequences are important issues for the use of nano-fluids. Extensive measurements of heat transfer and pressure drop for forced convection in circular pipes with nano-fluids was also conducted. Parameters such as heat transfer coefficient, Nusselt number, pressure drop and a thermal hydraulic performance factor that takes into account the gains made by increase in thermal conductivity as well as penalties related to increase in pressure drop are evaluated for laminar and transition flow regimes. No significant improvement in heat transfer (Nusselt number) compared to its based fluid was observed. It is also observed that the values evaluated for the thermal-hydraulic performance factor (change in heat transfer/change in pressure drop) was under unity for many flow conditions indicating poor overall applicability of SiC based nano-fluids.

  10. Electrical conductivity of albite melts at high pressures

    NASA Astrophysics Data System (ADS)

    Ni, H.; Keppler, H.

    2009-12-01

    High electrical conductivity observed from magnetotelluric/geomagnetic depth sounding is probably associated with the presence of silicate melts. We investigated electrical conductivity of albite melts, both anhydrous and hydrous with 2.0-5.4 wt% H2O, at 300-1500°C and 0.9-1.8 GPa in a piston-cylinder apparatus. Anhydrous glass was synthesized by fusing oxides and carbonates in 1-bar furnace, and hydrous glasses were prepared by fusing the mixture of glass powder and water in a TZM vessel. A glass cylinder was enclosed between a platinum rod as inner electrode and a Pt-Rh capsule as outer electrode. Platinum wires were used to connect both electrodes to a Solartron 1260 impedance analyzer for conductivity measurements at 3M to 3 HZ. A type-S thermocouple, which was separated from the conductivity circuit, was used to monitor temperature. Furthermore, a Mo foil was employed to reduce the interference from heating circuit. Experimental results demonstrate that the electrical conductivity of albite melt follows an Arrhenius relationship in both glass (<700°C) and liquid (>1100°C) region. In both cases, electrical conductivity increases with water content but decreases with pressure. In the glass region, electrical conductivity can be modelled as logσ = 3.5734 + 0.25534C - (4264+160.43P)/T, where σ is conductivity in S/m, C is water content in wt%, P is pressure in GPa, and T is temperature in K. The above expression implies an activation energy of 82 kJ/mol and an activation volume of 3.1 cc/mol. In the liquid region, electrical conductivity can be modelled as logσ = 2.6906 + 0.065915C - (2339+371.97P)/T, which implies an activation energy of 45 kJ/mol and an activation volume of 7.1 cc/mol. The dominating conduction mechanism in albite melts is suggested to be the motion of sodium cation.

  11. Free and Forced Convection in High Permeability Porous Media: Impact on Gas Flux at the Earth-atmosphere Interface

    NASA Astrophysics Data System (ADS)

    Weisbrod, N.; Levintal, E.; Dragila, M. I.; Kamai, T.

    2015-12-01

    Gas movement within the earth's subsurface and its exchange with the atmosphere is one of the principal elements contributing to soil and atmospheric function. As the soil permeability increases, gas circulation by convective mechanisms becomes significantly greater than the diffusion. Two of the convective mechanisms, which can be of great importance, are being explored in this research. The first one is thermal convection venting (TCV), which develops when there are unstable density gradients. The second mechanism is wind induced convection (WIC), which develops due to surface winds that drive air movement. Here, we report the results of a study on the relationships between the porous media permeability and particle size, and the development and magnitude of TCV and WIC with the development of thermal differences and surface winds. The research included large high-permeability column experiments carried out under highly controlled laboratory conditions, using well-defined single-sized spherical particles while surface winds and thermal differences were forced and monitored. CO2 enriched air, functioned as a tracer, was used to quantify the impact of TCV and WIC on gas migration in the porous media. Results show that in homogenous porous media a permeability range of 10-7 to 10-6 m2 is the threshold value for TCV onset under standard atmospheric conditions. Adding surface wind with an average velocity of 1.5 m s-1 resulted in WIC effect to a depth of -0.3 m in most experimental settings; however, it did not caused additional air circulation at the reference depth of -0.9 m. Furthermore, given the appropriate conditions, a combined effect of TCV and WIC did significantly increase the overall media ventilation. Simulations of temperature profiles in soil under that permeability, showed that as the thermal gradient changes with depth and is a continuous function, TCV cells can be developed in local sections of the profile, not necessarily reaching the atmosphere.

  12. A Structural Electrical Conductivity Model for Oxide Melts

    NASA Astrophysics Data System (ADS)

    Thibodeau, Eric; Jung, In-Ho

    2016-02-01

    A structural electrical conductivity model for oxide melts was developed based on the Nernst-Einstein relationship of ionic conductivity. In the description of ionic conductivity, the effective diffusivities of cations in oxide slags were described as a function of the polymerization of the melt. The polymerization of oxide melts was calculated from the Modified Quasichemical Model, taking into account the short-range ordering in slags. The parameters of this conductivity model were fixed to reproduce the electrical conductivity data in unary and binary melts, and the model can well predict the conductivity data in ternary and higher order system without any additional model parameters. The model is successfully applied to the CaO-MgO-MnO-PbO-Al2O3-SiO2 system.

  13. Electrical Conductivity of HgTe at High Temperatures

    NASA Technical Reports Server (NTRS)

    Li, C.; Lehoczky, S. L.; Su, C.-H.; Scripa, R. N.

    2004-01-01

    The electrical conductivity of HgTe was measured using a rotating magnetic field method from 300 K to the melting point (943 K). A microscopic theory for electrical conduction was used to calculate the expected temperature dependence of the HgTe conductivity. A comparison between the measured and calculated conductivities was used to obtain the estimates of the temperature dependence of Gamma(sub 6)-Gamma(sub 8) energy gap from 300 K to 943 K. The estimated temperature coefficient for the energy gap was comparable to the previous results at lower temperatures (less than or equal to 300 K). A rapid increase in the conductivity just above 300 K and a subsequent decrease at 500 K is attributed to band crossover effects. This paper describes the experimental approach and some of the theoretical calculation details.

  14. Experiment of electrical conductivity at low temperature (preliminary measurement)

    SciTech Connect

    Zhao, Y.; Wang, H.

    1998-07-01

    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.

  15. Electrical conductivity and dielectric property of fly ash geopolymer pastes

    NASA Astrophysics Data System (ADS)

    Hanjitsuwan, Sakonwan; Chindaprasirt, Prinya; Pimraksa, Kedsarin

    2011-02-01

    The electrical conductivity and dielectric property of fly ash geopolymer pastes in a frequency range of 100 Hz-10 MHz were studied. The effects of the liquid alkali solution to ash ratios (L/A) were analyzed. The mineralogical compositions and microstructures of fly ash geopolymer materials were also investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The 10 mol sodium hydroxide solution and sodium silicate solution at a sodium silicate-to-sodium hydroxide ratio of 1.0 were used in making geopolymer pastes. The pastes were cured at 40°C. It is found that the electrical conductivity and dielectric constant are dependent on the frequency range and L/A ratios. The conductivity increases but the dielectric constant decreases with increasing frequency.

  16. Carbonatite melts and electrical conductivity in the asthenosphere.

    PubMed

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

    2008-11-28

    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

  17. Forced organization of flute-type turbulence by convective cell injection

    SciTech Connect

    Iizuka, S.; Huld, T.; Pecseli, H.L.; Rasmussen, J.J.

    1988-03-14

    Nonlinear interactions between flute-type turbulence and an externally excited convective cell in a strongly magnetized plasma are investigated. During the interaction the azimuthal-mode-number spectrum of the turbulence is deformed and a broad spectrum evolves, indicating an inverse cascade. As a result of a modification in phase and amplitude of the fluctuations, an organized structure is created in turbulence. The macroscopic behavior is well explained by a Van der Pol--type equation.

  18. Tuning Electrical Conductivity of Inorganic Minerals with Carbon Nanomaterials.

    PubMed

    Kovalchuk, Anton A; Tour, James M

    2015-12-01

    Conductive powders based on Barite or calcium carbonate with chemically converted graphene (CCG) were successfully synthesized by adsorption of graphene oxide (GO) or graphene oxide nanoribbons (GONRs) onto the mineral surfaces and subsequent chemical reduction with hydrazine. The efficient adsorption of GO or GONRs on the surface of Barite and calcium carbonate-based mineral particles results in graphene-wrapped hybrid materials that demonstrate a concentration dependent electrical conductivity that increases with the GO or GONR loading. PMID:26544547

  19. Vertical microphysical profiles of convective clouds as a tool for obtaining aerosol cloud-mediated climate forcings

    SciTech Connect

    Rosenfeld, Daniel

    2015-12-23

    Quantifying the aerosol/cloud-mediated radiative effect at a global scale requires simultaneous satellite retrievals of cloud condensation nuclei (CCN) concentrations and cloud base updraft velocities (Wb). Hitherto, the inability to do so has been a major cause of high uncertainty regarding anthropogenic aerosol/cloud-mediated radiative forcing. This can be addressed by the emerging capability of estimating CCN and Wb of boundary layer convective clouds from an operational polar orbiting weather satellite. Our methodology uses such clouds as an effective analog for CCN chambers. The cloud base supersaturation (S) is determined by Wb and the satellite-retrieved cloud base drop concentrations (Ndb), which is the same as CCN(S). Developing and validating this methodology was possible thanks to the ASR/ARM measurements of CCN and vertical updraft profiles. Validation against ground-based CCN instruments at the ARM sites in Oklahoma, Manaus, and onboard a ship in the northeast Pacific showed a retrieval accuracy of ±25% to ±30% for individual satellite overpasses. The methodology is presently limited to boundary layer not raining convective clouds of at least 1 km depth that are not obscured by upper layer clouds, including semitransparent cirrus. The limitation for small solar backscattering angles of <25º restricts the satellite coverage to ~25% of the world area in a single day. This methodology will likely allow overcoming the challenge of quantifying the aerosol indirect effect and facilitate a substantial reduction of the uncertainty in anthropogenic climate forcing.

  20. On the electrical conductivity of Ti-implanted alumina

    SciTech Connect

    Salvadori, M. C.; Teixeira, F. S.; Cattani, M.; Nikolaev, A.; Savkin, K. P.; Oks, E. M.; Park, H.-K.; Phillips, L.; Yu, K. M.; Brown, I. G.

    2012-03-15

    Ion implantation of metal species into insulators provides a tool for the formation of thin, electrically conducting, surface layers with experimenter-controlled resistivity. High energy implantation of Pt and Ti into alumina accelerator components has been successfully employed to control high voltage surface breakdown in a number of cases. In the work described here we have carried out some basic investigations related to the origin of this phenomenon. By comparison of the results of alumina implanted with Ti at 75 keV with the results of prior investigations of polymers implanted with Pt at 49 eV and Au at 67 eV, we describe a physical model of the effect based on percolation theory and estimate the percolation parameters for the Ti-alumina composite. We estimate that the percolation dose threshold is about 4 x 10{sup 16} cm{sup -2} and the maximum dose for which the system remains an insulator-conductor composite is about 10 x 10{sup 16} cm{sup -2}. The saturation electrical conductivity is estimated to be about 50 S/m. We conclude that the observed electrical conductivity properties of Ti-implanted alumina can be satisfactorily described by percolation theory.

  1. Electrical conductivity of carbonbearing granulite at raised temperatures and pressures

    NASA Astrophysics Data System (ADS)

    Glover, Paul W. J.; Vine, F. J.

    1992-12-01

    IT has long been recognized that the electrical conductivity of the lower continental crust is anomalously high. Both pore-saturating brines1-5 and conducting films of carbon at grain boundaries6-10 have been proposed to explain this, but the evidence remains inconclusive. Here we report measurements of electrical conductivity at high temperatures and pressures11-13 on samples of carbon-bearing and carbon-free granulites with a range of electrolyte saturations. The application of pressure to nominally dry carbon-free samples reduces the electrical conductivity as a result of a progressive reduction in pore connectivity, whereas the carbon-bearing samples show an increase in conductivity under the same conditions-an effect that we ascribe to reconnection of carbon conduction pathways during compaction. Moreover, we find a greater increase in conductivity with temperature for the carbon-bearing samples. In the light of work indicating that the abundance of carbon in high-grade rocks has been underestimated in the past7,8, our results provide strong evidence for the role of carbon in lower-crustal conductivity.

  2. Electrical conduction by interface states in semiconductor heterojunctions

    NASA Astrophysics Data System (ADS)

    El Yacoubi, M.; Evrard, R.; Nguyen, N. D.; Schmeits, M.

    2000-04-01

    Electrical conduction in semiconductor heterojunctions containing defect states in the interface region is studied. As the classical drift-diffusion mechanism cannot in any case explain electrical conduction in semiconductor heterojunctions, tunnelling involving interface states is often considered as a possible conduction path. A theoretical treatment is made where defect states in the interface region with a continuous energy distribution are included. Electrical conduction through this defect band then allows the transit of electrons from the conduction band of one semiconductor to the valence band of the second component. The analysis is initiated by electrical measurements on n-CdS/p-CdTe heterojunctions obtained by chemical vapour deposition of CdS on (111) oriented CdTe single crystals, for which current-voltage and capacitance-frequency results are shown. The theoretical analysis is based on the numerical resolution of Poisson's equation and the continuity equations of electrons, holes and defect states, where a current component corresponding to the defect band conduction is explicitly included. Comparison with the experimental curves shows that this formalism yields an efficient tool to model the conduction process through the interface region. It also allows us to determine critical values of the physical parameters when a particular step in the conduction mechanism becomes dominant.

  3. Predicting permeability and electrical conductivity of sedimentary rocks from microgeometry

    SciTech Connect

    Schlueter, E.M.; Cook, N.G.W. California Univ., Berkeley, CA . Dept. of Materials Science and Mineral Engineering); Zimmerman, R.W.; Witherspoon, P.A. )

    1991-02-01

    The determination of hydrologic parameters that characterize fluid flow through rock masses on a large scale (e.g., hydraulic conductivity, capillary pressure, and relative permeability) is crucial to activities such as the planning and control of enhanced oil recovery operations, and the design of nuclear waste repositories. Hydraulic permeability and electrical conductivity of sedimentary rocks are predicted from the microscopic geometry of the pore space. The cross-sectional areas and perimeters of the individual pores are estimated from two-dimensional scanning electron micrographs of rock sections. The hydraulic and electrical conductivities of the individual pores are determined from these geometrical parameters, using Darcy's law and Ohm's law. Account is taken of the fact that the cross-sections are randomly oriented with respect to the channel axes, and for possible variation of cross-sectional area along the length of the pores. The effective medium theory from solid-state physics is then used to determine an effective average conductance of each pore. Finally, the pores are assumed to be arranged on a cubic lattice, which allows the calculation of overall macroscopic values for the permeability and the electrical conductivity. Preliminary results using Berea, Boise, Massilon and Saint-Gilles sandstones show reasonably close agreement between the predicted and measured transport properties. 12 refs., 5 figs., 1 tab.

  4. Composite yarns of multiwalled carbon nanotubes with metallic electrical conductivity.

    PubMed

    Randeniya, Lakshman K; Bendavid, Avi; Martin, Philip J; Tran, Canh-Dung

    2010-08-16

    Unique macrostructures known as spun carbon-nanotube fibers (CNT yarns) can be manufactured from vertically aligned forests of multiwalled carbon nanotubes (MWCNTs). These yarns behave as semiconductors with room-temperature conductivities of about 5 x 10(2) S cm(-1). Their potential use as, for example, microelectrodes in medical implants, wires in microelectronics, or lightweight conductors in the aviation industry has hitherto been hampered by their insufficient electrical conductivity. In this Full Paper, the synthesis of metal-CNT composite yarns, which combine the unique properties of CNT yarns and nanocrystalline metals to obtain a new class of materials with enhanced electrical conductivity, is presented. The synthesis is achieved using a new technique, self-fuelled electrodeposition (SFED), which combines a metal reducing agent and an external circuit for transfer of electrons to the CNT surface, where the deposition of metal nanoparticles takes place. In particular, the Cu-CNT and Au-CNT composite yarns prepared by this method have metal-like electrical conductivities (2-3 x 10(5) S cm(-1)) and are mechanically robust against stringent tape tests. However, the tensile strengths of the composite yarns are 30-50% smaller than that of the unmodified CNT yarn. The SFED technique described here can also be used as a convenient means for the deposition of metal nanoparticles on solid electrode supports, such as conducting glass or carbon black, for catalytic applications. PMID:20665629

  5. Simulation of forced convection in a channel with nanofluid by the lattice Boltzmann method

    PubMed Central

    2013-01-01

    This paper presents a numerical study of the thermal performance of fins mounted on the bottom wall of a horizontal channel and cooled with either pure water or an Al2O3-water nanofluid. The bottom wall of the channel is heated at a constant temperature and cooled by mixed convection of laminar flow at a relatively low temperature. The results of the numerical simulation indicate that the heat transfer rate of fins is significantly affected by the Reynolds number (Re) and the thermal conductivity of the fins. The influence of the solid volume fraction on the increase of heat transfer is more noticeable at higher values of the Re. PMID:23594696

  6. Combined Effect of Buoyancy Force and Navier Slip on MHD Flow of a Nanofluid over a Convectively Heated Vertical Porous Plate

    PubMed Central

    2013-01-01

    We examine the effect of magnetic field on boundary layer flow of an incompressible electrically conducting water-based nanofluids past a convectively heated vertical porous plate with Navier slip boundary condition. A suitable similarity transformation is employed to reduce the governing partial differential equations into nonlinear ordinary differential equations, which are solved numerically by employing fourth-order Runge-Kutta with a shooting technique. Three different water-based nanofluids containing copper (Cu), aluminium oxide (Al2O3), and titanium dioxide (TiO2) are taken into consideration. Graphical results are presented and discussed quantitatively with respect to the influence of pertinent parameters, such as solid volume fraction of nanoparticles (φ), magnetic field parameter (Ha), buoyancy effect (Gr), Eckert number (Ec), suction/injection parameter (fw), Biot number (Bi), and slip parameter (β), on the dimensionless velocity, temperature, skin friction coefficient, and heat transfer rate. PMID:24222749

  7. Combined effect of buoyancy force and Navier slip on MHD flow of a nanofluid over a convectively heated vertical porous plate.

    PubMed

    Mutuku-Njane, Winifred Nduku; Makinde, Oluwole Daniel

    2013-01-01

    We examine the effect of magnetic field on boundary layer flow of an incompressible electrically conducting water-based nanofluids past a convectively heated vertical porous plate with Navier slip boundary condition. A suitable similarity transformation is employed to reduce the governing partial differential equations into nonlinear ordinary differential equations, which are solved numerically by employing fourth-order Runge-Kutta with a shooting technique. Three different water-based nanofluids containing copper (Cu), aluminium oxide (Al2O3), and titanium dioxide (TiO2) are taken into consideration. Graphical results are presented and discussed quantitatively with respect to the influence of pertinent parameters, such as solid volume fraction of nanoparticles (φ), magnetic field parameter (Ha), buoyancy effect (Gr), Eckert number (Ec), suction/injection parameter (f w ), Biot number (Bi), and slip parameter ( β ), on the dimensionless velocity, temperature, skin friction coefficient, and heat transfer rate. PMID:24222749

  8. Experimental study of Cu-water nanofluid forced convective flow inside a louvered channel

    NASA Astrophysics Data System (ADS)

    Khoshvaght-Aliabadi, M.; Hormozi, F.; Zamzamian, A.

    2015-03-01

    Heat transfer enhancement plays a very important role for energy saving in plate-fin heat exchangers. In the present study, the influences of simultaneous utilization of a louvered plate-fin channel and copper-base deionized water nanofluid on performance of these exchangers are experimentally explored. The effects of flow rate (2-5 l/min) and nanoparticles weight fraction (0-0.4 %) on heat transfer and pressure drop characteristics are determined. Experimental results indicate that the use of louvered channel instead of the plain one can improve the heat transfer performance. Likewise, addition of small amounts of copper nanoparticles to the base fluid augments the convective heat transfer coefficient remarkably. The maximum rise of 21.7 % in the convective heat transfer coefficient is observed for the 0.4 % wt nanofluid compared to the base fluid. Also, pumping power for the base fluid and nanofluids are calculated based on the measured pressure drop in the louvered channel. The average increase in pumping power is 11.8 % for the nanofluid with 0.4 % wt compared to the base fluid. Applied performance criterion shows a maximum performance index of 1.167 for the nanofluid with 0.1 % wt Finally, two correlations are proposed for Nusselt number and friction factor which fit the experimental data with in ±10 %.

  9. Experimental study of Cu-water nanofluid forced convective flow inside a louvered channel

    NASA Astrophysics Data System (ADS)

    Khoshvaght-Aliabadi, M.; Hormozi, F.; Zamzamian, A.

    2014-09-01

    Heat transfer enhancement plays a very important role for energy saving in plate-fin heat exchangers. In the present study, the influences of simultaneous utilization of a louvered plate-fin channel and copper-base deionized water nanofluid on performance of these exchangers are experimentally explored. The effects of flow rate (2-5 l/min) and nanoparticles weight fraction (0-0.4 %) on heat transfer and pressure drop characteristics are determined. Experimental results indicate that the use of louvered channel instead of the plain one can improve the heat transfer performance. Likewise, addition of small amounts of copper nanoparticles to the base fluid augments the convective heat transfer coefficient remarkably. The maximum rise of 21.7 % in the convective heat transfer coefficient is observed for the 0.4 % wt nanofluid compared to the base fluid. Also, pumping power for the base fluid and nanofluids are calculated based on the measured pressure drop in the louvered channel. The average increase in pumping power is 11.8 % for the nanofluid with 0.4 % wt compared to the base fluid. Applied performance criterion shows a maximum performance index of 1.167 for the nanofluid with 0.1 % wt Finally, two correlations are proposed for Nusselt number and friction factor which fit the experimental data with in ±10 %.

  10. CMB topography and electrical conductivity as additional constraints for the lowermost mantle thermo-chemical structure

    NASA Astrophysics Data System (ADS)

    Deschamps, F.; Yin, Y.; Tackley, P. J.

    2013-12-01

    A variety of seismic observations, including tomographic models, indicate that the lowermost mantle is strongly heterogeneous. Seismic observations further support a thermo-chemical origin for the large scale heterogeneities. In particular, the large low-shear wave velocity provinces (LLSVP) observed by global tomographic images are better explained by a combination of thermal and chemical anomalies. Despite the accuracy of seismic information, uncertainties and trade-off still prevent the determination of a detailed lower mantle thermo-chemical structure. For instance, the nature of chemical heterogeneities and the exact role played by the post-perovskite phase transition are still debated. Additional constraints are needed to discriminate between the possible models of structure and dynamics of the lower mantle. Here, we consider two potential additional constraints, the electrical conductivity and the dynamic topography at the core-mantle boundary (CMB). Unlike density and seismic velocities, electrical conductivity increases with temperature. In addition, it strongly varies with the iron and silicate content. Using appropriate mineral physics data, we calculated a 3D distribution of electrical conductivity in lower mantle from the thermo-chemical structure inferred by probabilistic tomography, which maps iron and silicate excess in the LLSVP. In the lowermost mantle, we observe a belt of high conductivity, with maximum values around 20 S/m located in the LLSVP. Such a belt may trigger electric currents in the lowermost mantle and induce magnetic field variations with period of one year or more. It may thus be seen by global models of electrical conductivity. Unfortunately, such models do not sample yet regions deeper than 2000 km. A second, independent constraint we explored is the dynamic topography at the CMB. We used stagYY to calculate the dynamic topography associated with several models of thermo-chemical convection, and observe strong differences

  11. Pore connectivity, electrical conductivity, and partial water saturation: Network simulations

    NASA Astrophysics Data System (ADS)

    Li, M.; Tang, Y. B.; Bernabé, Y.; Zhao, J. Z.; Li, X. F.; Bai, X. Y.; Zhang, L. H.

    2015-06-01

    The electrical conductivity of brine-saturated rock is predominantly dependent on the geometry and topology of the pore space. When a resistive second phase (e.g., air in the vadose zone and oil/gas in hydrocarbon reservoirs) displaces the brine, the geometry and topology of the pore space occupied by the electrically conductive phase are changed. We investigated the effect of these changes on the electrical conductivity of rock partially saturated with brine. We simulated drainage and imbibition as invasion and bond percolation processes, respectively, in pipe networks assumed to be perfectly water-wet. The simulations included the formation of a water film in the pipes invaded by the nonwetting fluid. During simulated drainage/imbibition, we measured the changes in resistivity index as well as a number of relevant microstructural parameters describing the portion of the pore space saturated with water. Except Euler topological number, all quantities considered here showed a significant level of "universality," i.e., insensitivity to the type of lattice used (simple cubic, body-centered cubic, or face-centered cubic). Hence, the coordination number of the pore network appears to be a more effective measure of connectivity than Euler number. In general, the simulated resistivity index did not obey Archie's simple power law. In log-log scale, the resistivity index curves displayed a substantial downward or upward curvature depending on the presence or absence of a water film. Our network simulations compared relatively well with experimental data sets, which were obtained using experimental conditions and procedures consistent with the simulations. Finally, we verified that the connectivity/heterogeneity model proposed by Bernabé et al. (2011) could be extended to the partial brine saturation case when water films were not present.

  12. Electrical conductivity in two mixed-valence liquids.

    PubMed

    Yao, Wenzhi; Kelley, Steven P; Rogers, Robin D; Vaid, Thomas P

    2015-06-01

    Two different room-temperature liquid systems were investigated, both of which conduct a DC electrical current without decomposition or net chemical transformation. DC electrical conductivity is possible in both cases because of the presence of two different oxidation states of a redox-active species. One system is a 1 : 1 molar mixture of n-butylferrocene (BuFc) and its cation bis(trifluoromethane)sulfonimide salt, [BuFc(+)][NTf2(-)], while the other is a 1 : 1 molar mixture of TEMPO and its cation bis(trifluoromethane)sulfonimide salt, [TEMPO(+)][NTf2(-)]. The TEMPO-[TEMPO(+)][NTf2(-)] system is notable in that it is an electrically conducting liquid in which the conductivity originates from an organic molecule in two different oxidation states, with no metals present. Single-crystal X-ray diffraction of [TEMPO(+)][NTf2(-)] revealed a complex structure with structurally different cation-anion interactions for cis- and trans [NTf2(-)] conformers. The electron transfer self-exchange rate constant for BuFc/BuFc(+) in CD3CN was determined by (1)H NMR spectroscopy to be 5.4 × 10(6) M(-1) s(-1). The rate constant allowed calculation of an estimated electrical conductivity of 7.6 × 10(-5)Ω(-1) cm(-1) for BuFc-[BuFc(+)][NTf2(-)], twice the measured value of 3.8 × 10(-5)Ω(-1) cm(-1). Similarly, a previously reported self-exchange rate constant for TEMPO/TEMPO(+) in CH3CN led to an estimated conductivity of 1.3 × 10(-4)Ω(-1) cm(-1) for TEMPO-[TEMPO(+)][NTf2(-)], a factor of about 3 higher than the measured value of 4.3 × 10(-5)Ω(-1) cm(-1). PMID:25960288

  13. Spatial Variability of Electrical Conductivity in North Mississippi Loamy Soils

    NASA Astrophysics Data System (ADS)

    Twombly, J. E.; Fancher, C. W.; Sleep, M. D.; Aufman, M. S.; Holland, J. V.; Holt, R. M.; Kuszmaul, J. S.

    2004-05-01

    The use of non-contact electrical geophysical methods, such as electromagnetic induction (EM), to characterize and quantify spatial and temporal variations in soil properties is appealing due to low operational costs, rapid measurements, and device mobility. These methods are sensitive to soil electrical conductivity, which can vary with soil moisture, clay content, soil salinity, and the presence of electrically conductive minerals. We conducted a preliminary study to evaluate the controls on EM response in loamy soils present at the University of Mississippi (UM) Soil Moisture Observatory (SMO). The 5 acre SMO is located in a former agricultural field at the UM Biological Field Station, a 740 acre tract of land located 11 miles from the UM campus in Oxford, Mississippi. EM responses were surveyed along two intersecting transects using a Geonics EM38. The apparent electrical conductivity (EC) of the soil was determined in both a vertical and horizontal dipole position, which correspond to deep (~1m) and shallow (~0.5) measurements, respectively. Continuous soil samples were recovered from the transect points and analyzed for soil properties. Except for a weak negative correlation with moisture content, we found little direct correlation between EC and measured soil properties. EC variograms from surveys conducted on different dates consistently show a similar structure. Following a week of rain, three EM 38 surveys were conducted, each a week apart. During this survey period, a nearby meteorological station reported no significant precipitation, and the soils were drying. All EC variograms show similar spatial structures but decreasing amounts of variability consistent with drying and redistribution of soil moisture. These results suggest that soil physical properties, not soil moisture, control the spatial distribution of EC. Temporal variations in the variograms indicate a complex relationship between soil moisture and EC.

  14. Detection of temperature distribution via recovering electrical conductivity in MREIT

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    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.

  15. Rubber-like electrically conductive polymeric materials with shape memory

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

    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.

  16. Electrical conductivity and rheology of carbon black composites under elongation

    NASA Astrophysics Data System (ADS)

    Starý, Zdeněk

    2015-04-01

    Electrical properties of conductive polymer composites are governed by filler particle structures which are formed in the material during the mixing. Therefore, knowledge of the behavior of conductive particle structures under defined conditions of deformation is necessary to produce materials with balanced electrical and rheological properties. Whereas the electrical conductivity evolution under shear can be nowadays studied even with the commercial rheometers, the investigations under elongation were not performed up to now. In this work simultaneous electrical and rheological measurements in elongation on polystyrene/carbon black composites are introduced. Such kind of experiment can help in understanding the relationships between processing conditions and properties of conductive polymer composites.

  17. Software optimization for electrical conductivity imaging in polycrystalline diamond cutters

    SciTech Connect

    Bogdanov, G.; Ludwig, R.; Wiggins, J.; Bertagnolli, K.

    2014-02-18

    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.

  18. Electrical Conductivity Relaxation and Melt Viscosity of Fluorosilicate Glasses.

    NASA Astrophysics Data System (ADS)

    Guo, Yuning

    1995-01-01

    Although silicate glasses have been studied extensively, relatively little attention has been paid to the effects of fluorine on silicate glass networks. Recently, however, the potential for treating fluoride-containing radioactive waste by vitrification using joule-heated melting has made the properties of such glass systems of considerable technological importance. The presence of fluorine produces a melt of much lower viscosity and higher electrical conductivity than the more typical non-fluorine glass melts. From a simple glass structure perspective, fluorine (mono-valent) replaces oxygen (di-valent) in the glass network and thereby reduces the degree of connectivity. This can be used to motivate simple models for the effect of this replacement on properties such as the viscosity and the electrical conductivity. However, studies of the electrical conductivity relaxation of fluorosilicate glasses in the solid state revealed that other basic processes had to be introduced in order to explain the observed results. The experimental data suggest very different mechanisms for the fluorine effects in the solid and molten states. In order to investigate the effects of fluorine on the glass network, electrical conductivity relaxation measurements were made on a group of simple alkali-fluorosilicate glasses (Si, Na, O, F) in both the solid and molten states. In the molten state, the shear viscosities were also measured. The experimental results were found in good agreement with computer simulations performed on the random conductor network and cluster models. In these models, fluorine was assumed to randomly break the silica tetrahedra above the glass liquidus temperature (decreasing the melt viscosity and favoring ionic conduction), and to form alkali fluoride crystals with certain probabilities below the liquidus temperature (increasing the viscosity and reducing the conductivity). The existence of such crystals was later confirmed by X-ray diffraction. The conclusions

  19. Assembly for electrical conductivity measurements in the piston cylinder device

    DOEpatents

    Watson, Heather Christine; Roberts, Jeffrey James

    2012-06-05

    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.

  20. Porosity effect on the electrical conductivity of sintered powder compacts

    NASA Astrophysics Data System (ADS)

    Montes, J. M.; Cuevas, F. G.; Cintas, J.

    2008-08-01

    A new equation for calculating the electrical conductivity of sintered powder compacts is proposed. In this equation, the effective resistivity of porous compacts is a function of the fully dense material conductivity, the porosity of the compact and the tap porosity of the starting powder. The new equation is applicable to powder sintered compacts from zero porosity to tap porosity. A connection between this equation and the percolation conduction theory is stated. The proposed equation has been experimentally validated with sintered compacts of six different metallic powders. Results confirm very good agreement with theoretical predictions.

  1. Compensation Effect in Electrical Conduction Process: Effect of Substituent Group

    NASA Astrophysics Data System (ADS)

    Mitra, Bani; Misra, T. N.

    1987-05-01

    The semiconductive properties of Vitamin A acid (Retinoic Acid), a long chain conjugated polyene, were studied as a function of the adsorption of different vapours. A compensation effect was observed in the electrical conduction process; unlike that in Vitamin A alcohol and Vitamin A acetate the compensation temperature was observed on the lower side of the experimental temperature (T0≈285 K). It is concluded that the terminal \\diagdown\\diagupC=0 group conjugated to the polyene chain plays an important role in the manifestation of the compensation effect. Various conduction parameters have been evaluated.

  2. Phase transformation, thermal expansion and electrical conductivity of lanthanum chromite

    SciTech Connect

    Gupta, Sapna; Mahapatra, Manoj K.; Singh, Prabhakar

    2013-09-01

    Graphical abstract: - Highlights: • Orthorhombic and rhombohedral phases co-exist at ≥260 °C and cubic above 1000 °C. • Polymorphic changes with temperature in air and Ar–3%H{sub 2} are observed. • Lattice volume change in Ar–3%H{sub 2} atmosphere corresponds to Cr{sup 4+} → Cr{sup 3+} transition. • Change in valence state of Cr{sup 4+} to Cr{sup 3+} results in lower electrical conductivity. • Experimental evidence is provided for poor densification of LaCrO{sub 3} in air. - Abstract: This paper addresses discrepancies pertaining to structural, thermal and electrical properties of lanthanum chromite. Experimental evidence is provided to support the hypothesis for poor densification in air as well as reduction in electrical conductivity in reducing atmosphere. Sintering condition for the synthesis of LaCrO{sub 3} was optimized to 1450 °C and 10 h. Thermo-analytical (differential scanning calorimetry – DSC) and high temperature X-ray diffraction (HT-XRD) studies show that orthorhombic lanthanum chromite transforms into rhombohedral structure at ∼260 °C and cubic structure above 1000 °C. Co-existence of the structural phases and the variation in each polymorph with temperature in both air and 3%H{sub 2}–Ar atmosphere is reported. Presence and absence of Cr-rich phase at inter-particle neck are observed in oxidizing and reducing atmospheres respectively. The linear thermal expansion co-efficient was calculated to be 10.8 ± 0.2 × 10{sup −6} °C{sup −1} in the temperature range of RT–1400 °C. Electrical conductivity of lanthanum chromite was found to be 0.11 S/cm in air. A decrease in electrical conductivity (0.02 S/cm at 800 °C) of LaCrO{sub 3}, as observed in reducing atmosphere (3%H{sub 2}–Ar), corresponds to lattice volume change as indicated by peak shift in HT-XRD results.

  3. Forced- and natural-convection studies on solar collectors for heating and cooling applications

    NASA Astrophysics Data System (ADS)

    Pearson, J. T.

    1983-03-01

    Convection in air heating solar collectors for heating and cooling applications was studied. It was determined that improvement in the overall conductance between the absorber and the flowing air was an area that needed much improvement. Studies were performed to obtain several absorber convector configurations which have superior heat transfer performance, modest drop penalties, and a high potential for economical manufacturing. Four surfaces which may be fabricated from aluminum or steel are recommended. Three utilize corrugated sheets bonded to the backplate and/or the back side of the absorber. These three surfaces are recommended for applications where airflow behind the absorber is appropriate. For those applications where airflow above the absorber is appropriate, a louvered surface which can be fabricated from metal or plastic is recommended.

  4. Variability of radiatively forced diurnal cycle of intense convection in the tropical west pacific

    SciTech Connect

    Gray, W.M.; Sheaffer, J.D.; Thorson, W.B.

    1996-04-01

    Strong differences occur in daytime versus nighttime (DVN) net radiative cooling in clear versus cloudy areas of the tropical atmosphere. Daytime average cooling is approximately -0.7{degrees}C/day, whereas nighttime net tropospheric cooling rates are about -1.5{degrees}C/day, an approximately two-to-one difference. The comparatively strong nocturnal cooling in clear areas gives rise to a diurnally varying vertical circulation and horizontal convergence cycle. Various manifestations of this cyclic process include the observed early morning heavy rainfall maxima over the tropical oceans. The radiatively driven DVN circulation appears to strongly modulate the resulting diurnal cycle of intense convection which creates the highest, coldest cloudiness over maritime tropical areas and is likely a fundamental mechanism governing both small and large scale dynamics over much of the tropical environment.

  5. Effect of the magnetic field direction on forced convection heat transfer enhancements in ferrofluids

    NASA Astrophysics Data System (ADS)

    Cherief, Wahid; Avenas, Yvan; Ferrouillat, Sébastien; Kedous-Lebouc, Afef; Jossic, Laurent; Berard, Jean; Petit, Mickael

    2015-07-01

    Applying a magnetic field on a ferrofluid flow induces a large increase of the convective heat transfer coefficient. In this paper, the thermal-hydraulic behaviors of two commercial ferrofluids are compared. The variations of both the pressure drop and the heat transfer coefficient due to the magnetic field are measured in the following conditions: square duct, laminar flow and uniform wall heat flux. The square section with two insulated walls allows for the characterization of the effect of the magnetic field direction. The experimental results show that the heat transfer is better enhanced when the magnetic field is perpendicular to the heat flux. In the best case, the local heat transfer coefficient increase is about 75%. On the contrary, another experimental setup shows no enhancement of thermal conductivity when the magnetic field is perpendicular to the heat flux. Contribution to the topical issue "Electrical Engineering Symposium (SGE 2014) - Elected submissions", edited by Adel Razek

  6. Magnetoacoustic Tomography with Magnetic Induction for Electrical Conductivity based Tissue imaging

    NASA Astrophysics Data System (ADS)

    Mariappan, Leo

    Electrical conductivity imaging of biological tissue has attracted considerable interest in recent years owing to research indicating that electrical properties, especially electrical conductivity and permittivity, are indicators of underlying physiological and pathological conditions in biological tissue. Also, the knowledge of electrical conductivity of biological tissue is of interest to researchers conducting electromagnetic source imaging and in design of devices that apply electromagnetic energy to the body such as MRI. So, the need for a non-invasive, high resolution impedance imaging method is highly desired. To address this need we have studied the magnetoacoustic tomography with magnetic induction (MAT-MI) method. In MAT-MI, the object is placed in a static and a dynamic magnetic field giving rise to ultrasound waves. The dynamic field induces eddy currents in the object, and the static field leads to generation of acoustic vibrations from Lorentz force on the induced currents. The acoustic vibrations are at the same frequency as the dynamic magnetic field, which is chosen to match the ultrasound frequency range. These ultrasound signals can be measured by ultrasound probes and are used to reconstruct MAT-MI acoustic source images using possible ultrasound imaging approaches .The reconstructed high spatial resolution image is indicative of the object's electrical conductivity contrast. We have investigated ultrasound imaging methods to reliably reconstruct the MAT-MI image under the practical conditions of limited bandwidth and transducer geometry. The corresponding imaging algorithm, computer simulation and experiments are developed to test the feasibility of these different methods. Also, in experiments, we have developed a system with the strong static field of an MRI magnet and a strong pulsed magnetic field to evaluate MAT-MI in biological tissue imaging. It can be seen from these simulations and experiments that conductivity boundary images with

  7. A methodology to determine boundary conditions from forced convection experiments using liquid crystal thermography

    NASA Astrophysics Data System (ADS)

    Jakkareddy, Pradeep S.; Balaji, C.

    2016-05-01

    This paper reports the results of an experimental study to estimate the heat flux and convective heat transfer coefficient using liquid crystal thermography and Bayesian inference in a heat generating sphere, enclosed in a cubical Teflon block. The geometry considered for the experiments comprises a heater inserted in a hollow hemispherical aluminium ball, resulting in a volumetric heat generation source that is placed at the center of the Teflon block. Calibrated thermochromic liquid crystal sheets are used to capture the temperature distribution at the front face of the Teflon block. The forward model is the three dimensional conduction equation which is solved within the Teflon block to obtain steady state temperatures, using COMSOL. Match up experiments are carried out for various velocities by minimizing the residual between TLC and simulated temperatures for every assumed loss coefficient, to obtain a correlation of average Nusselt number against Reynolds number. This is used for prescribing the boundary condition for the solution to the forward model. A surrogate model obtained by artificial neural network built upon the data from COMSOL simulations is used to drive a Markov Chain Monte Carlo based Metropolis Hastings algorithm to generate the samples. Bayesian inference is adopted to solve the inverse problem for determination of heat flux and heat transfer coefficient from the measured temperature field. Point estimates of the posterior like the mean, maximum a posteriori and standard deviation of the retrieved heat flux and convective heat transfer coefficient are reported. Additionally the effect of number of samples on the performance of the estimation process has been investigated.

  8. Liquid crystal visualization and computer modeling of enhanced heat transfer on a flat plate in forced convection

    SciTech Connect

    Voegler, G.R.; Anderson, A.M.

    1996-12-31

    This paper presents the results of an experimental and computational study of heat transfer enhancement found in the vicinity of a three dimensional block placed on a constant heat flux plate in turbulent forced convection. The experiments used thermochromic liquid crystals to visualize temperature on the surface. Photographs were taken to establish temperature contour lines at a range of velocities and a variety of block sizes and configurations. The results show heat transfer enhancement exists upstream and downstream of the blocks. The enhancement is caused by a horse shoe vortex which stagnates on the front surface of the block and then wraps around the sides. Thin blocks (narrow in the flow direction) show the best enhancement. The computer simulations used the {kappa}-epsilon turbulence model and had reasonable qualitative agreement with the experiments.

  9. The influence of tip clearance and Prandtl number on turbulent forced convection heat transfer of rectangular fins

    NASA Astrophysics Data System (ADS)

    Park, Hae-Kyun; Chung, Bum-Jin

    2016-02-01

    The turbulent forced convection heat transfer of rectangular fins in a duct was investigated by varying the tip clearance and Pr. Mass transfer experiments using a H2SO4-CuSO4 electroplating system were performed based on the analogy between heat and mass transfers. FLUENT 6.3 was used for calculations. Turbulent models were tested and the Reynolds Stress Model was chosen, which showed a 1.15 % discrepancy with the existing correlation for a simple tube flow when Pr = 2, but 13 % when Pr = 2014. For a more complex fin channel, the discrepancy increased up to 30 %. The optimal tip clearances, corresponding to maximum heat transfer rates, did not vary with Pr, which is explained using the temperature contours. The results were also compared with the laminar case where Pr influenced the optimal tip clearance.

  10. Some aspects of high-order numerical solutions of the linear convection equation with forced boundary conditions

    NASA Technical Reports Server (NTRS)

    Zingg, D. W.; Lomax, H.

    1993-01-01

    A six-stage low-storage Runge-Kutta time-marching method is presented and shown to be an efficient method for use with high-accuracy spatial difference operators for wave propagation problems. The accuracy of the method for inhomogeneous ordinary differential equations is demonstrated through numerical solutions of the linear convection equation with forced boundary conditions. Numerical experiments are presented simulating a sine wave and a Gaussian pulse propagating into and through the domain. For practical levels of mesh refinement corresponding to roughly ten points per wavelength, the six-stage Runge-Kutta method is more accurate than the popular fourth-order Runge-Kutta method. Further numerical experiments are presented which show that the numerical boundary scheme at an inflow boundary can be a significant source of error when high-accuracy spatial discretizations are used.

  11. Spatial-decomposition analysis of electrical conductivity in ionic liquid.

    PubMed

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

    2014-12-28

    The electrical conductivity of room temperature ionic liquid (IL) is investigated with molecular dynamics simulation. A trajectory of 1 μs 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. PMID:25554167

  12. Testing and Optimization of Electrically Conductive Spacecraft Coatings

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    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.

  13. Thermal and Electrical Conductivities of Porous Si Membranes

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    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.

  14. Electrically conductive nano graphite-filled bacterial cellulose composites.

    PubMed

    Erbas Kiziltas, Esra; Kiziltas, Alper; Rhodes, Kevin; Emanetoglu, Nuri W; Blumentritt, Melanie; Gardner, Douglas J

    2016-01-20

    A unique three dimensional (3D) porous structured bacterial cellulose (BC) can act as a supporting material to deposit the nanofillers in order to create advanced BC-based functional nanomaterials for various technological applications. In this study, novel nanocomposites comprised of BC with exfoliated graphite nanoplatelets (xGnP) incorporated into the BC matrix were prepared using a simple particle impregnation strategy to enhance the thermal properties and electrical conductivity of the BC. The flake-shaped xGnP particles were well dispersed and formed a continuous network throughout the BC matrix. The temperature at 10% weight loss, thermal stability and residual ash content of the nanocomposites increased at higher xGnP loadings. The electrical conductivity of the composites increased with increasing xGnP loading (attaining values 0.75 S/cm with the addition of 2 wt.% of xGnP). The enhanced conductive and thermal properties of the BC-xGnP nanocomposites will broaden applications (biosensors, tissue engineering, etc.) of BC and xGnP. PMID:26572457

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

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

    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.

  16. Miniatuization of the flowing fluid electric conductivity loggingtec hnique

    SciTech Connect

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

    2005-10-19

    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.

  17. Magnetoresistance, electrical conductivity, and Hall effect of glassy carbon

    SciTech Connect

    Baker, D.F.

    1983-02-01

    These properties of glassy carbon heat treated for three hours between 1200 and 2700/sup 0/C were measured from 3 to 300/sup 0/K in magnetic fields up to 5 tesla. The magnetoresistance was generally negative and saturated with reciprocal temperature, but still increased as a function of magnetic field. The maximum negative magnetoresistance measured was 2.2% for 2700/sup 0/C material. Several models based on the negative magnetoresistance being proportional to the square of the magnetic moment were attempted; the best fit was obtained for the simplest model combining Curie and Pauli paramagnetism for heat treatments above 1600/sup 0/C. Positive magnetoresistance was found only in less than 1600/sup 0/C treated glassy carbon. The electrical conductivity, of the order of 200 (ohm-cm)/sup -1/ at room temperature, can be empirically written as sigma = A + Bexp(-CT/sup -1/4) - DT/sup -1/2. The Hall coefficient was independent of magnetic field, insensitive to temperature, but was a strong function of heat treatment temperature, crossing over from negative to positive at about 1700/sup 0/C and ranging from -0.048 to 0.126 cm/sup 3//coul. The idea of one-dimensional filaments in glassy carbon suggested by the electrical conductivity is compatible with the present consensus view of the microstructure.

  18. High performance electrically conductive adhesives (ECAs) for leadfree interconnects

    NASA Astrophysics Data System (ADS)

    Li, Yi

    Electrically conductive adhesives (ECAs) are one of the lead-free interconnect materials with the advantages of environmental friendliness, mild processing conditions, fewer processing steps, low stress on the substrates, and fine pitch interconnect capability. However, some challenging issues still exist for the currently available ECAs, including lower electrical conductivity, conductivity fatigue in reliability tests, limited current-carrying capability, poor impact strength, etc. The interfacial properties is one of the major considerations when resolving these challenges and developing high performance conductive adhesives. Surface functionalization and interface modification are the major approaches used in this thesis. Fundamental understanding and analysis of the interaction between various types of interface modifiers and ECA materials and substrates are the key for the development of high performance ECA for lead-free interconnects. The results of this thesis provide the guideline for the enhancement of interfacial properties of metal-metal and metal-polymer interactions. Systematic investigation of various types of ECAs contributes to a better understanding of materials requirements for different applications, such as surface mount technology (SMT), flip chip applications, flat panel display modules with high resolution, etc. Improvement of the electrical, thermal and reliability of different ECAs make them a potentially ideal candidate for high power and fine pitch microelectronics packaging option.

  19. Thermal and Electrical Conductivity Probe (TECP) for Phoenix

    NASA Astrophysics Data System (ADS)

    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

    2009-03-01

    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 augmenting 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.

  20. Thermal and Electrical Conductivity Probe for Phoenix Mars Lander

    NASA Technical Reports Server (NTRS)

    2007-01-01

    NASA's Phoenix Mars Lander will assess how heat and electricity move through Martian soil from one spike or needle to another of a four-spike electronic fork that will be pushed into the soil at different stages of digging by the lander's Robotic Arm.

    The four-spike tool, called the thermal and electrical conductivity probe, is in the middle-right of this photo, mounted near the end of the arm near the lander's scoop (upper left).

    In one type of experiment with this tool, a pulse of heat will be put into one spike, and the rate at which the temperature rises on the nearby spike will be recorded, along with the rate at which the heated spike cools. A little bit of ice can make a big difference in how well soil conducts heat. Similarly, soil's electrical conductivity -- also tested with this tool -- is a sensitive

    indicator of moisture in the soil. This device adapts technology used in soil-moisture gauges for irrigation-control systems. The conductivity probe has an additional role besides soil analysis. It will serve as a hunidity sensor when held in the air.

  1. Lunar electrical conductivity, permeability and temperature from Apollo magnetometer experiments

    NASA Technical Reports Server (NTRS)

    Dyal, P.; Parkin, C. W.; Daily, W. D.

    1977-01-01

    Magnetometers were deployed at four Apollo sites on the moon to measure remanent and induced lunar magnetic fields. Measurements from this network of instruments were used to calculate the electrical conductivity, temperature, magnetic permeability, and iron abundance of the lunar interior. The measured lunar remanent fields range from 3 gammas minimum at the Apollo 15 site to 327 gammas maximum at the Apollo 16 site. Simultaneous magnetic field and solar plasma pressure measurements show that the remanent fields at the Apollo 12 and 16 sites interact with, and are compressed by, the solar wind. Remanent fields at Apollo 12 and Apollo 16 are increased 16 gammas and 32 gammas, respectively, by a solar plasma bulk pressure increase of 1.5 X 10 to the -7th power dynes/sq cm. Global lunar fields due to eddy currents, induced in the lunar interior by magnetic transients, were analyzed to calculate an electrical conductivity profile for the moon. From nightside magnetometer data in the solar wind it was found that deeper than 170 km into the moon the conductivity rises from .0003 mhos/m to .10 mhos/m at 100 km depth. Recent analysis of data obtained in the geomagnetic tail, in regions free of complicating plasma effects, yields results consistent with nightside values.

  2. Strong and electrically conductive nanopaper from cellulose nanofibers and polypyrrole.

    PubMed

    Lay, Makara; Méndez, J Alberto; Delgado-Aguilar, Marc; Bun, Kim Ngun; Vilaseca, Fabiola

    2016-11-01

    In this work, we prepare cellulose nanopapers of high mechanical performance and with the electrical conductivity of a semiconductor. Cellulose nanofibers (CNF) from bleached softwood pulp were coated with polypyrrole (PPy) via in situ chemical polymerization, in presence of iron chloride (III) as oxidant agent. The structure and morphology of nanopapers were studied, as well as their thermal, mechanical and conductive properties. Nanopaper from pure CNF exhibited a very high tensile response (224MPa tensile strength and 14.5GPa elastic modulus). The addition of up to maximum 20% of polypyrrole gave CNF/PPy nanopapers of high flexibility and still good mechanical properties (94MPa strength and 8.8GPa modulus). The electrical conductivity of the resulting CNF/PPy nanopaper was of 5.2 10(-2)Scm(-1), with a specific capacitance of 7.4Fg(-1). The final materials are strong and conductive nanopapers that can find application as biodegradable flexible thin-film transistor (TFT) or as flexible biosensor. PMID:27516283

  3. The Thermal Electrical Conductivity Probe (TECP) for Phoenix

    NASA Technical Reports Server (NTRS)

    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

    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

  4. The influence of molten pool geometry on forced convective heat transfer

    NASA Astrophysics Data System (ADS)

    Wei, Cheng-hua; Fang, Bo-lang; Liu, Wei-ping; Wang, Li-jun; Ma, Zhi-liang

    2015-05-01

    An investigation was conducted to determine the relationship between heat transfer coefficient and molten pool's geometry. It was accomplished by performing an experimental and numerical investigation using a cylinder dimple with two different serials of geometry: (1) cylinder dimples with fixed print diameter D=50mm and different depth, and (2) cylinder dimples with fixed depth d=10mm and different print diameter. The airflow speed varies from 50m/s to 250m/s in the turbulent regime. The results consist of flow characteristics, mainly velocity profile and heat transfer characteristics, including heat transfer coefficient and Nusselt number along flow direction, were obtained. The comparison was held against the smooth surface. Results showed that a centrally-located vortex was formed due to the flow separation. For heat transfer coefficient, such augmentations are present near the downstream edges and diminutions are present near the upstream edges of dimple rims, both slightly within each depression. It was found that the convection heat transfer coefficients with different geometry parameters have similar distribution along flow direction. A uniform piecewise linear function was built to describe the heat transfer characterizes for different molten pool print diameter.

  5. Effect of the coriolis force on the onset of convection in a layer with a fixed heat flux on the boundaries

    SciTech Connect

    Muginov, R.R.; Smorodin, B.L.

    1994-11-01

    The effect of the Coriolis force on the onset of convection in a plane horizontal layer of viscous fluid with a fixed heat flux on the rigid lower and free upper boundaries is investigated. Expressions for the critical Rayleigh numbers and wave number are obtained analytically in the rapid rotation limit.

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

    NASA Astrophysics Data System (ADS)

    Vollrath, Fritz; Edmonds, Donald

    2013-12-01

    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.

  7. Electrical conductivity of condensed molecular hydrogen in the giant planets

    NASA Technical Reports Server (NTRS)

    Smoluchowski, R.

    1972-01-01

    Theoretical interpretation of several phenomena concerning Jupiter and Saturn depends upon the electrical conductivity of molecular hydrogen which, according to present models, forms the outermost layer of both planets. The layer starts at the transition pressure between the metallic and the molecular form of hydrogen, that is around 1 Mbar, and extends to the outside limits of the atmosphere. Whether at the highest pressures (and temperatures) this layer is a solid or a dense fluid is not certain. In any case, the fluid is in supercritical condition so that there is only a gradual transition from dense liquid to a gaseous form. The two theories which require specific values of the conductivity of the condensed molecular hydrogen are those pertaining to the generation of a magnetic field in the liquid hydrogen rather than in the deep metallic interior (HIDE, 1967), and those concerned with the electromagnetic coupling and exchange of angular momentum between the liquid core and the solid molecular hydrogen mantle.

  8. Effect of orientation anisotropy on calculating effective electrical conductivities

    NASA Astrophysics Data System (ADS)

    Myles, Timothy D.; Peracchio, Aldo A.; Chiu, Wilson K. S.

    2014-05-01

    This paper develops an analytical effective medium theory (EMT) equation for calculating the effective conductivity of a mixture based on Maxwell's and Maxwell-Garnett's theories, extended to higher volume fractions using Bruggeman's unsymmetrical treatment (BUT), with a long term goal of extending the treatment to mixtures more representative of real materials in order to calculate their effective electrical conductivity. The development accounts for spheroid shaped inclusions of varying degrees of anisotropic orientation. The orientation is described by the introduction of a distribution function. Two methodologies valid for the inclusion dilute limit were used to evaluate the effective conductivity: one based on Maxwell's far field approach, and the other based on the Maxwell-Garnett in the matrix approach. It was found that while the dilute limit equations for the effective conductivity were different, the final EMT equations derived by applying BUT collapsed to the same formula which was generalized for anisotropic orientation based on the distribution function presented.

  9. Transparent electrical conducting films by activated reactive evaporation

    DOEpatents

    Bunshah, Rointan; Nath, Prem

    1982-01-01

    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.

  10. Ultrahigh electrical conductivity in solution-sheared polymeric transparent films

    PubMed Central

    Worfolk, Brian J.; Andrews, Sean C.; Park, Steve; Reinspach, Julia; Liu, Nan; Toney, Michael F.; Mannsfeld, Stefan C. B.; Bao, Zhenan

    2015-01-01

    With consumer electronics transitioning toward flexible products, there is a growing need for high-performance, mechanically robust, and inexpensive transparent conductors (TCs) for optoelectronic device integration. Herein, we report the scalable fabrication of highly conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) thin films via solution shearing. Specific control over deposition conditions allows for tunable phase separation and preferential PEDOT backbone alignment, resulting in record-high electrical conductivities of 4,600 ± 100 S/cm while maintaining high optical transparency. High-performance solution-sheared TC PEDOT:PSS films were used as patterned electrodes in capacitive touch sensors and organic photovoltaics to demonstrate practical viability in optoelectronic applications. PMID:26515096

  11. Formulation of electrically conductive thermal-control coatings

    NASA Technical Reports Server (NTRS)

    Shai, M. C.

    1978-01-01

    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.

  12. Electrical Conductivity of Parylene F at High Temperature

    NASA Astrophysics Data System (ADS)

    Diaham, S.; Bechara, M.; Locatelli, M.-L.; Tenailleau, C.

    2011-03-01

    The electrical conductivity of both as-deposited and annealed poly(α,α,α',α'-tetrafluoro- p-xylylene) (PA-F) films has been investigated up to 400°C. The static conductivity ( σ DC) values of PA-F measured between 200°C and 340°C appear to be ˜2.5 orders of magnitude lower for annealed films than for as-deposited ones. This change is attributed to a strong increase in the crystallinity of the material occurring above 340°C. After annealing at 400°C in N2, the σ DC value measured at 300°C, for instance, decreased from 3.8 × 10-12 Ω-1 cm-1 to 7.5 × 10-15 Ω-1 cm-1. Physical interpretations of such an improvement are offered.

  13. High temperature electrically conducting ceramic heating element and control system

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

    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.

  14. Development of Tailorable Electrically Conductive Thermal Control Material Systems

    NASA Technical Reports Server (NTRS)

    Deshpande, M. S.; Harada, Y.

    1998-01-01

    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.

  15. Transparent electrical conducting films by activated reactive evaporation

    DOEpatents

    Bunshah, R.; Nath, P.

    1982-06-22

    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.

  16. Facile synthesis of boron nitride nanotubes and improved electrical conductivity.

    PubMed

    Chen, Yongjun; Luo, Lijie; Zhou, Longchang; Mo, Libin; Tong, Zhangfa

    2010-02-01

    A layer of catalyst film on substrate is usually required during the vapor-liquid-solid (VLS) growth of one-dimensional (1D) nanomaterials. In this work, however, a novel approach for synthesizing high-purity bamboo-like boron nitride (BN) nanotubes directly on commercial stainless steel foils was demonstrated. Synthesis was realized by heating boron and zinc oxide (ZnO) powders at 1200 degrees C under a mixture gas flow of nitrogen and hydrogen. The stainless steel foils played an additional role of catalyst besides the substrate during the VLS growth of the nanotubes. In addition, the electrical conductivity of the BN nanotubes was efficiently improved in a simple way by coating with Au and Pd nanoparticles. The decorated BN nanotubes may find potential applications in catalysts, sensors and nanoelectronics. PMID:20352730

  17. Electrically conductive, optically transparent polymer/carbon nanotube composites

    NASA Technical Reports Server (NTRS)

    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

    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.

  18. Lunar magnetic permeability, magnetic fields, and electrical conductivity temperature

    NASA Technical Reports Server (NTRS)

    Parkin, C. W.

    1978-01-01

    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.

  19. Interplanetary double-shock ensembles with anomalous electrical conductivity

    NASA Technical Reports Server (NTRS)

    Dryer, M.

    1972-01-01

    Similarity theory is applied to the case of constant velocity, piston-driven, shock waves. This family of solutions, incorporating the interplanetary magnetic field for the case of infinite electric conductivity, represents one class of experimentally observed, flare-generated shock waves. This paper discusses the theoretical extension to flows with finite conductivity (presumably caused by unspecified modes of wave-particle interactions). Solutions, including reverse shocks, are found for a wide range of magnetic Reynolds numbers from one to infinity. Consideration of a zero and nonzero ambient flowing solar wind (together with removal of magnetic considerations) enables the recovery of earlier similarity solutions as well as numerical simulations. A limited comparison with observations suggests that flare energetics can be reasonably estimated once the shock velocity, ambient solar wind velocity and density, and ambient azimuthal Alfven Mach number are known.

  20. Electrical conductivity of quasi-two-dimensional foams.

    PubMed

    Yazhgur, Pavel; Honorez, Clément; Drenckhan, Wiebke; Langevin, Dominique; Salonen, Anniina

    2015-04-01

    Quasi-two-dimensional (quasi-2D) foams consist of monolayers of bubbles squeezed between two narrowly spaced plates. These simplified foams have served successfully in the past to shed light on numerous issues in foam physics. Here we consider the electrical conductivity of such model foams. We compare experiments to a model which we propose, and which successfully relates the structural and the conductive properties of the foam over the full range of the investigated liquid content. We show in particular that in the case of quasi-2D foams the liquid in the nodes needs to be taken into account even at low liquid content. We think that these results may provide different approaches for the characterization of foam properties and for the in situ characterization of the liquid content of foams in confining geometries, such as microfluidics. PMID:25974485

  1. Electrical conductivity of aqueous solutions of aluminum salts

    NASA Astrophysics Data System (ADS)

    Vila, J.; Rilo, E.; Segade, L.; Cabeza, O.; Varela, L. M.

    2005-03-01

    We present experimental measurements of the specific electrical conductivity (σ) in aqueous solutions of aluminum salts at different temperatures, covering all salt concentrations from saturation to infinite dilution. The salts employed were AlCl3 , AlBr3 , AlI3 , and Al(NO3)3 , which present a 1:3 relationship between the electrical charges of anion and cation. In addition, we have measured the density in all ranges of concentrations of the four aqueous electrolyte solutions at 298.15K . The measured densities show an almost linear behavior with concentration, and we have fitted it to a second order polynomial with very high degree of approximation. The measurement of the specific conductivity at constant temperature reveals the existence of maxima in the conductivity vs concentration curves at molar concentrations around 1.5M for the three halide solutions studied, and at approximately 2M for the nitrate. We present a theoretical foundation for the existence of these maxima, based on the classical Debye-Hückel-Onsager hydrodynamic mean-field framework for electrical transport and its high concentration extensions, and also a brief consideration of ionic frictional coefficients using mode-coupling theory. We also found that the calculated values of the equivalent conductance vary in an approximately linear way with the square root of the concentration at concentrations as high as those where the maximum of σ appears. Finally, and for completeness, we have measured the temperature dependence of the electrical conductivity at selected concentrations from 283to353K , and performed a fit to an exponential equation of the Vogel-Fulcher-Tamman type. The values of the calculated temperatures of null mobility of the four salts are reported.

  2. Gas-Tolerant Device Senses Electrical Conductivity of Liquid

    NASA Technical Reports Server (NTRS)

    O'Connor, Edward W.

    2005-01-01

    The figure depicts a device for measuring the electrical conductivity of a flowing liquid. Unlike prior such devices, this one does not trap gas bubbles entrained in the liquid. Usually, the electrical conductivity of a liquid is measured by use of two electrodes immersed in the liquid. A typical prior device based on this concept contains large cavities that can trap gas. Any gas present between or near the electrodes causes a significant offset in the conductivity reading and, if the gas becomes trapped, then the offset persists. Extensive tests on two-phase (liquid/ gas) flow have shown that in the case of liquid flowing along a section of tubing, gas entrained in the liquid is not trapped in the section as long as the inner wall of the section is smooth and continuous, and the section is the narrowest tubing section along the flow path. The design of the device is based on the foregoing observation: The electrodes and the insulators separating the electrodes constitute adjacent parts of the walls of a tube. The bore of the tube is machined to make the wall smooth and to provide a straight flow path from the inlet to the outlet. The diameter of the electrode/insulator tube assembly is less than the diameter of the inlet or outlet tubing. An outer shell contains the electrodes and insulators and constitutes a leak and pressure barrier. Any gas bubble flowing through this device causes only a momentary conductivity offset that is filtered out by software used to process the conductivity readings.

  3. Durable Microstructured Surfaces: Combining Electrical Conductivity with Superoleophobicity.

    PubMed

    Pan, Zihe; Wang, Tianchang; Sun, Shaofan; Zhao, Boxin

    2016-01-27

    In this study, electrically conductive and superoleophobic polydimethylsiloxane (PDMS) has been fabricated through embedding Ag flakes (SFs) and Ag nanowires (SNWs) into microstructures of the trichloroperfluorooctylsilane (FDTS)-blended PDMS elastomer. Microstructured PDMS surfaces became conductive at the percolation surface coverage of 3.0 × 10(-2) mg/mm(2) for SFs; the highest conductivity was 1.12 × 10(5) S/m at the SFs surface coverage of 6.0 × 10(-2) mg/mm(2). A significant improvement of the conductivity (increased 3 times at the SNWs fraction of 11%) was achieved by using SNWs to replace some SFs because of the conductive pathways from the formed SNWs networks and its connections with SFs. These conductive fillers bonded strongly with microstructured FDTS-blended PDMS and retained surface properties under the sliding preload of 8.0 N. Stretching tests indicated that the resistance increased with the increasing strains and returned to its original state when the strain was released, showing highly stretchable and reversible electrical properties. Compared with SFs embedded surfaces, the resistances of SFs/SNWs embedded surfaces were less dependent on the strain because of bridging effect of SNWs. The superoleophobicity was achieved by the synergetic effect of surface modification through blending FDTS and the microstructures transferred from sand papers. The research findings demonstrate a simple approach to make the insulating elastomer to have the desired surface oleophobicity and electrical conductivity and help meet the needs for the development of conductive devices with microstructures and multifunctional properties. PMID:26714207

  4. Inflow and outflow signatures in flowing wellbore electrical conductivity logs

    SciTech Connect

    Doughty, Christine; Tsang, Chin-Fu

    2002-08-28

    Flowing wellbore electrical-conductivity logging provides a means to determine hydrologic properties of fractures, fracture zones, or other permeable layers intersecting a borehole in saturated rock. The method involves analyzing the time-evolution of fluid electrical-conductivity logs obtained while the well is being pumped and yields information on the location, hydraulic transmissivity, and salinity of permeable layers, as well as their initial (or ambient) pressure head. Earlier analysis methods were restricted to the case in which flows from the permeable layers or fractures were directed into the borehole. More recently, a numerical model for simulating flowing-conductivity logging was adapted to permit treatment of both inflow and outflow, including analysis of natural regional flow in the permeable layer. However, determining the fracture properties with the numerical model by optimizing the match to the conductivity logs is a laborious trial-and-error procedure. In this paper, we identify the signatures of various inflow and outflow features in the conductivity logs to expedite this procedure and to provide physical insight for the analysis of these logs. Generally, inflow points are found to produce a distinctive signature on the conductivity logs themselves, enabling the determination of location, inflow rate, and ion concentration in a straightforward manner. Identifying outflow locations and flow rates, on the other hand, can be done with a more complicated integral method. Running a set of several conductivity logs with different pumping rates (e.g., half and double the original pumping rate) provides further information on the nature of the feed points. In addition to enabling the estimation of flow parameters from conductivity logs, an understanding of the conductivity log signatures can aid in the design of follow-up logging activities.

  5. Vibration damping of elastic waves in electrically conducting media subjected to high magnetic fields

    NASA Technical Reports Server (NTRS)

    Horwath, T. G.

    1992-01-01

    The propagation of vibrational energy in bulk, torsional, and flexural modes, in electrically conducting media can undergo strong attenuation if subjected to high magnetic fields in certain spatial arrangements. The reasons for this are induced Eddy currents which are generated by the volume elements in the media moving transversally to the magnetic field at acoustic velocities. In magnetic fields achievable with superconductors, the non-conservative (dissipative) forces are compared to the elastic and inertial forces for most metals. Strong dissipation of vibrational energy in the form of heat takes place as a result. A simplified theory is presented based on engineering representations of electrodynamics, attenuation values for representative metals are calculated, and problems encountered in formulating a generalized theory based on electrodynamics of moving media are discussed. General applications as well as applications specific to maglev are discussed.

  6. On the concept of leaf boundary layer resistance for forced convection

    PubMed

    Vesala

    1998-09-01

    The definition of leaf boundary layer resistance is reconsidered in respect of the three-dimensional diffusion-controlled mass transport region just above the leaf surface. Due to the existence of this superstomatal air layer, the conventional convective boundary layer is not in direct contact with the surface. Thus, in terms of plant physiology, the diffusive "end correction" to the stomatal resistance should be included in the boundary layer resistance. This is true for laminar as well as turbulent flows. When the surface mole fraction of an exchanged gas is estimated using the boundary layer resistance ignoring the diffusive term may lead to a noticeable error. The self-consistent approach is used to clarify the problems of the boundary layer formation and stomatal interference. If the correction is taken into account, the boundary layer resistance becomes dependent also on stomatal shape and distribution on the leaf. The traditional semiempirical formula corrected by the superstomatal diffusion is applied in numerical calculations. In estimates of the water vapour mole fraction on the surface of a transpiring leaf the relative error ranges from insignificant (quiescent air, large leaf and large stomatal pores) to 20 % (low humidity, strong wind, small leaf and small elliptic pores). The boundary layer resistance can decrease by a factor of 3 when the semiaxis lengths of the stomata increase from 1 and 0.5 &mgr;m to 10 and 5 &mgr;m. The effective thickness of the superstomatal air layer is maximally several millimetres (small stomatal surface concentration and small pores). Copyright 1998 Academic Press Limited PMID:9778427

  7. Convective forcing of mercury and ozone in the Arctic boundary layer induced by leads in sea ice.

    PubMed

    Moore, Christopher W; Obrist, Daniel; Steffen, Alexandra; Staebler, Ralf M; Douglas, Thomas A; Richter, Andreas; Nghiem, Son V

    2014-02-01

    The ongoing regime shift of Arctic sea ice from perennial to seasonal ice is associated with more dynamic patterns of opening and closing sea-ice leads (large transient channels of open water in the ice), which may affect atmospheric and biogeochemical cycles in the Arctic. Mercury and ozone are rapidly removed from the atmospheric boundary layer during depletion events in the Arctic, caused by destruction of ozone along with oxidation of gaseous elemental mercury (Hg(0)) to oxidized mercury (Hg(II)) in the atmosphere and its subsequent deposition to snow and ice. Ozone depletion events can change the oxidative capacity of the air by affecting atmospheric hydroxyl radical chemistry, whereas atmospheric mercury depletion events can increase the deposition of mercury to the Arctic, some of which can enter ecosystems during snowmelt. Here we present near-surface measurements of atmospheric mercury and ozone from two Arctic field campaigns near Barrow, Alaska. We find that coastal depletion events are directly linked to sea-ice dynamics. A consolidated ice cover facilitates the depletion of Hg(0) and ozone, but these immediately recover to near-background concentrations in the upwind presence of open sea-ice leads. We attribute the rapid recoveries of Hg(0) and ozone to lead-initiated shallow convection in the stable Arctic boundary layer, which mixes Hg(0) and ozone from undepleted air masses aloft. This convective forcing provides additional Hg(0) to the surface layer at a time of active depletion chemistry, where it is subject to renewed oxidation. Future work will need to establish the degree to which large-scale changes in sea-ice dynamics across the Arctic alter ozone chemistry and mercury deposition in fragile Arctic ecosystems. PMID:24429521

  8. Convective forcing of mercury and ozone in the Arctic boundary layer induced by leads in sea ice

    NASA Astrophysics Data System (ADS)

    Moore, Christopher W.; Obrist, Daniel; Steffen, Alexandra; Staebler, Ralf M.; Douglas, Thomas A.; Richter, Andreas; Nghiem, Son V.

    2014-02-01

    The ongoing regime shift of Arctic sea ice from perennial to seasonal ice is associated with more dynamic patterns of opening and closing sea-ice leads (large transient channels of open water in the ice), which may affect atmospheric and biogeochemical cycles in the Arctic. Mercury and ozone are rapidly removed from the atmospheric boundary layer during depletion events in the Arctic, caused by destruction of ozone along with oxidation of gaseous elemental mercury (Hg(0)) to oxidized mercury (Hg(II)) in the atmosphere and its subsequent deposition to snow and ice. Ozone depletion events can change the oxidative capacity of the air by affecting atmospheric hydroxyl radical chemistry, whereas atmospheric mercury depletion events can increase the deposition of mercury to the Arctic, some of which can enter ecosystems during snowmelt. Here we present near-surface measurements of atmospheric mercury and ozone from two Arctic field campaigns near Barrow, Alaska. We find that coastal depletion events are directly linked to sea-ice dynamics. A consolidated ice cover facilitates the depletion of Hg(0) and ozone, but these immediately recover to near-background concentrations in the upwind presence of open sea-ice leads. We attribute the rapid recoveries of Hg(0) and ozone to lead-initiated shallow convection in the stable Arctic boundary layer, which mixes Hg(0) and ozone from undepleted air masses aloft. This convective forcing provides additional Hg(0) to the surface layer at a time of active depletion chemistry, where it is subject to renewed oxidation. Future work will need to establish the degree to which large-scale changes in sea-ice dynamics across the Arctic alter ozone chemistry and mercury deposition in fragile Arctic ecosystems.

  9. MHD mixed convection flow of power law non-Newtonian fluids over an isothermal vertical wavy plate

    NASA Astrophysics Data System (ADS)

    Mirzaei Nejad, Mehrzad; Javaherdeh, K.; Moslemi, M.

    2015-09-01

    Mixed convection flow of electrically conducting power law fluids along a vertical wavy surface in the presence of a transverse magnetic field is studied numerically. Prandtl coordinate transformation together with the spline alternating direction implicit method is employed to solve the boundary layer equations. The influences of both flow structure and dominant convection mode on the overall parameters of flow and heat transfer are well discussed. Also, the role of magnetic field in controlling the boundary layers is investigated. The variation of Nusselt number and skin friction coefficient are studied as functions of wavy geometry, magnetic field, buoyancy force and material parameters. Results reveal the interrelation of the contributing factors.

  10. Dynamics, crustal thicknesses, seismic anomalies, and electrical conductivities in dry and hydrous ridge-centered plumes

    NASA Astrophysics Data System (ADS)

    Ruedas, Thomas

    2006-04-01

    3D convection and melting models for ridge-centered plumes in the upper 410 km of the mantle have been computed for dry and hydrous mantles, taking into account the effects of water on melting and viscosity. Dry and hydrous models have fundamentally different flow and melting styles in the melting regime: in the dry model, active upwelling occurs to shallow depth and results in a very thick, narrow plume-generated crust, whereas dehydration stiffening in the hydrous models enforces passive upwelling in much of the melting region and causes the plume crust to be much less thick, but broader in along-ridge direction. The output of the numerical models, i.e. temperature, melting degree, water content, and porosity, is used to compute synthetic models of seismic velocity anomalies and electrical conductivity. For this purpose, combinations of theoretical and empirical relations with recent experimental data are developped. The models predict that the seismic velocity anomaly of the deep, unmolten plume stem is mostly thermal in both water-bearing and water-free plumes, but that the two velocity minima in the anomaly in the melting zone of the plume are much more clearly distinguishable in a water-bearing plume. If one assumes a contribution to the electrical conductivity of hydrous mantle from free protons, and if the water reservoir features large-scale contiguity, one would also expect a strong high-conductivity anomaly in the plume stem which should be visible to magnetotelluric observations. However, comparison with observations suggests that a simple free-proton model may not be applicable.

  11. Forced Convection Heat Transfer of Liquid Hydrogen Through a 200-mm Long Heated Tube

    NASA Astrophysics Data System (ADS)

    Tatsumoto, Hideki; Shirai, Yasuyuki; Shiotsu, Masahiro; Hata, Koichi; Naruo, Yoshihiro; Kobayashi, Hiroaki; Inatani, Yoshifumi; Kinoshita, Katsuhiro

    The heat transfer from the inner side of a vertically- mounted heated tube with a length of 200.0 mm and a diameter of 6.0 mm to a forced flow of liquid hydrogen was measured for wide ranges of flow rate and liquid temperature. The non-boiling heat transfer coefficients agreed well with the Dittus -Boelter equation. The heat fluxes at departure from nucleate boiling (DNB) were higher for higher flow velocities and greater subcooling. The effect of the tube length on the DNB heat flux was clarified through comparison with our previous data. It was confirmed that the experimental data agreed well with the authors' DNB correlation.

  12. Liquid Salts as Media for Process Heat Transfer from VHTR's: Forced Convective Channel Flow Thermal Hydraulics, Materials, and Coating

    SciTech Connect

    Sridharan, Kumar; Anderson, Mark; Allen, Todd; Corradini, Michael

    2012-01-30

    on Cr-carbide on the graphite surface. Ni-electroplating dramatically reduced corrosion of alloys, although some diffusion of Fe and Cr were observed occur through the Ni plating. A pyrolytic carbon and SiC (PyC/SiC) CVD coating was also investigated and found to be effective in mitigating corrosion. The KCl-MgCl2 molten salt was less corrosive than FLiNaK fluoride salts for corrosion tests performed at 850oC. Cr dissolution in the molten chloride salt was still observed and consequently Ni-201 and Hastelloy N exhibited the least depth of attack. Grain-boundary engineering (GBE) of Incoloy 800H improved the corrosion resistance (as measured by weight loss and maximum depth of attack) by nearly 50% as compared to the as-received Incoloy 800H sample. Because Cr dissolution is an important mechanism of corrosion, molten salt electrochemistry experiments were initiated. These experiments were performed using anodic stripping voltammetry (ASV). Using this technique, the reduction potential of Cr was determined against a Pt quasi-reference electrode as well as against a Ni(II)-Ni reference electrode in molten FLiNaK at 650 oC. The integrated current increased linearly with Cr-content in the salt, providing for a direct assessment of the Cr concentration in a given salt of unknown Cr concentration. To study heat transfer mechanisms in these molten salts over the forced and mixed convection regimes, a forced convective loop was constructed to measure heat transfer coefficients, friction factors and corrosion rates in different diameter tubes in a vertical up flow configuration in the laminar flow regime. Equipment and instrumentation for the forced convective loop was designed, constructed, and tested. These include a high temperature centrifugal pump, mass flow meter, and differential pressure sensing capabilities to an uncertainty of < 2 Pa. The heat transfer coefficient for the KCl-MgCl2 salt was measured in two different diameter channels (0.083 and 0.370Ã). In the 0

  13. Electrically-conductive proppant and methods for making and using same

    DOEpatents

    Cannan, Chad; Roper, Todd; Savoy, Steve; Mitchell, Daniel R.

    2016-09-06

    Electrically-conductive sintered, substantially round and spherical particles and methods for producing such electrically-conductive sintered, substantially round and spherical particles from an alumina-containing raw material. Methods for using such electrically-conductive sintered, substantially round and spherical particles in hydraulic fracturing operations.

  14. Detection of Wheat Kernels with Hidden Insect Infestations Using an Electrically Conductive Roller Mill

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A laboratory roller mill system was modified to measure and analyze the electrical conductance of wheat as it was crushed. The electrical conductance of normal wheat kernels is normally low and fairly constant. In contrast, the electrical conductance of wheat kernels infested with live insects is su...

  15. Magnetoacoustic tomography with magnetic induction (MAT-MI) for electrical conductivity imaging.

    PubMed

    Li, Xu; He, Bin

    2009-01-01

    Magnetoacoustic tomography with magnetic induction (MAT-MI) is a recently introduced method for imaging electrical conductivity properties of biological tissue with high spatial resolution close to sonography. In MAT-MI the sample resides in a static magnetic field and a time-varying magnetic stimulation is applied to the sample volume. Through the action of the Lorentz force, the magnetically induced eddy current in the conductive sample causes particle vibrations and generates detectable ultrasound waves. The acoustic signal is then measured around the object to reconstruct images that are related to the object electrical conductivity distribution. The feasibility to reconstruct high spatial resolution conductivity images using MAT-MI method has been demonstrated by both computer simulation and experimental studies. Though MAT-MI technique is still in its developing stage, all the pilot studies suggest that it has potential to become a noninvasive imaging modality for high spatial resolution conductivity imaging of biological tissue and merits further investigations. This paper reviews MAT-MI about its basic theory, reconstruction algorithms and experiment studies. Some technical issues and future research directions are discussed. PMID:19964795

  16. Magnetoacoustic Imaging of Electrical Conductivity of Biological Tissues at a Spatial Resolution Better than 2 mm

    PubMed Central

    Hu, Gang; He, Bin

    2011-01-01

    Magnetoacoustic tomography with magnetic induction (MAT-MI) is an emerging approach for noninvasively imaging electrical impedance properties of biological tissues. The MAT-MI imaging system measures ultrasound waves generated by the Lorentz force, having been induced by magnetic stimulation, which is related to the electrical conductivity distribution in tissue samples. MAT-MI promises to provide fine spatial resolution for biological tissue imaging as compared to ultrasound resolution. In the present study, we first estimated the imaging spatial resolution by calculating the full width at half maximum (FWHM) of the system point spread function (PSF). The actual spatial resolution of our MAT-MI system was experimentally determined to be 1.51 mm by a parallel-line-source phantom with Rayleigh criterion. Reconstructed images made from tissue-mimicking gel phantoms, as well as animal tissue samples, were consistent with the morphological structures of the samples. The electrical conductivity value of the samples was determined directly by a calibrated four-electrode system. It has been demonstrated that MAT-MI is able to image the electrical impedance properties of biological tissues with better than 2 mm spatial resolution. These results suggest the potential of MAT-MI for application to early detection of small-size diseased tissues (e.g. small breast cancer). PMID:21858111

  17. Chemical activity induces dynamical force with global structure in a reaction-diffusion-convection system.

    PubMed

    Mahara, Hitoshi; Okada, Koichi; Nomura, Atsushi; Miike, Hidetoshi; Sakurai, Tatsunari

    2009-07-01

    We found a rotating global structure induced by the dynamical force of local chemical activity in a thin solution layer of excitable Belousov-Zhabotinsky reaction coupled with diffusion. The surface flow and deformation associated with chemical spiral waves (wavelength about 1 mm) represents a global unidirectional structure and a global tilt in the entire Petri dish (100 mm in diameter), respectively. For these observations, we scanned the condition of hierarchal pattern selection. From this result, the bromomalonic acid has an important role to induce the rotating global structure. An interaction between a reaction-diffusion process and a surface-tension-driven effect leads to such hierarchal pattern with different scales. PMID:19658764

  18. Forced convection heat transfer of saturated liquid hydrogen in vertically-mounted heated pipes

    NASA Astrophysics Data System (ADS)

    Tatsumoto, Hideki; Shirai, Yasuyuki; Shiotsu, Masahiro; Hata, Koichi; Naruo, Yoshihiro; Kobayasi, Hiroaki; Inatani, Yoshifumi

    2014-01-01

    Heat transfer from the inner side of vertically-mounted heated pipes to forced flow of saturated liquid hydrogen was measured with a quasi-steady increase of a heat generation rate for wide ranges of flow rate and saturated pressure. The tube heaters have lengths L of 100 mm and 167 mm with the diameter D of 4 mm and lengths of 150 mm and 250 mm with the diameter of 6 mm. The heat fluxes at departure from nucleate boiling (DNB) were higher for higher flow velocity, lower pressures and shorter L/D. The effect of L/D on the DNB heat flux was clarified. It is confirmed that our DNB correlation can describe the experimental data.

  19. Forced convection heat transfer of subcooled liquid hydrogen in horizontal tubes

    NASA Astrophysics Data System (ADS)

    Tatsumoto, Hideki; Shirai, Yasuyuki; Shiotsu, Masahiro; Hata, Koichi; Naruo, Yoshihiro; Kobayashi, Hiroyuki; Inatani, Yoshifumi; Kinoshita, K.

    2012-06-01

    Forced flow heat transfers of liquid hydrogen through horizontally-mounted tubes with the diameter of 3.0 mm and 6.0 mm were measured at the pressure of 0.7 MPa for various inlet temperatures and flow velocities. The measured non-boiling heat transfer coefficients agree with those by the Dittus-Boelter correlation. The heat fluxes at the onset of nucleate boiling and the departure from nucleate boiling (DNB) heat fluxes, where the heat transfer continuously changes to film boiling regime, are higher for higher flow velocity, larger subcooling and larger tube diameter. The DNB heat fluxes for the horizontally-mounted tube are slightly lower than those for the vertically-mounted tube, although the effect of the tube attitude direction disappears for a small tube diameter. The measured DNB heat fluxes agree with the correlation for vertically-mounted tubes.

  20. Forced convection and transport effects during hyperbaric laser chemical vapor deposition

    SciTech Connect

    Maxwell, James L; Chavez, Craig A; Espinoza, Miguel; Black, Marcie; Maskaly, Karlene; Boman, Mats

    2009-01-01

    This work explores mass transport processes during HP-LCYD, including the transverse forced-flow of precursor gases through a nozzle to enhance fiber growth rates. The use of laser trapping and suspension of nano-scale particles in the precursor flow is also described, providing insights into the nature of the gas flow, including jetting from the fiber tip and thermodiffusion processes near the reaction zone. The effects of differing molecular-weight buffer gases is also explored in conjunction with the Soret effect, and it is found that nucleation at the deposit surface (and homogeneous nucleation in the gas phase) can be enhanced/ retarded, depending on the buffer gas molecular weight. To demonstrate that extensive microstructures can be grown simultaneously, three-dimensional fiber arrays are also grown in-parallel using diffractive optics--without delatory effects from neighboring reaction sites.

  1. Electrically conductive and thermally conductive materials for electronic packaging

    NASA Astrophysics Data System (ADS)

    Liu, Zongrong

    The aim of this dissertation is to develop electrically or thermally conductive materials that are needed for electronic packaging and microelectronic cooling. These materials are in the form of coatings and are made from pastes. The research work encompasses paste formulation, studying the process of converting a paste to a conductive material, relating the processing conditions to the structure and performance, and evaluating performance attributes that are relevant to the application of these conductive materials. The research has resulted in new information that is valuable to the microelectronic industry. Work on electrically conductive materials emphasizes the development of electrical interconnection materials in the form of air-firable glass-free silver-based electrically conductive thick films, which use the Ti-Al alloy as the binder and are in contrast to conventional films that use glass as the binder. The air-firability, as enabled by minor additions of tin and zinc to the paste, is in contrast to previous glass-free films that are not firable. The recommended firing condition is 930°C in air. The organic vehicle in the paste comprises ethyl cellulose, which undergoes thermal decomposition during burnout of the paste. The ethyl cellulose is dissolved in ether, which facilitates the burnout. Excessive ethyl cellulose hinders the burnout. A higher heating rate results in more residue after burnout. The presence of silver particles facilitates drying and burnout. Firing in air gives lower resistivity than firing in oxygen. Firing in argon gives poor films. Compared to conventional films that use glass as the binder, these films, when appropriately fired, exhibit lower electrical resistivity (2.5 x 10-6 O.cm) and higher scratch resistance. Work on thermally conductive materials addresses thermal interface materials, which are materials placed at the interface between a heat sink and a heat source for the purpose of improving the thermal contact. Heat

  2. Electrically conducting novel polymer films containing pi-stacks

    NASA Astrophysics Data System (ADS)

    Duan, Robert Gang

    1997-12-01

    The primary focus of this thesis is to expand our knowledge of ion radicals of π-dimers and π- stacks in solutions and apply these insights in the development and understanding of new electrically conducting polymers. Two types of the conducting polymers were investigated. The first is the conducting polymer composites embedded with π-stacks of ion radicals. Flexible and air stable n-typed conducting thin films were prepared from imide/poly(vinyl alcohol) aqueous solutions. Conducting thin films of terthiophene/poly(methyl methacrylate) were cast from hexafluoro-2-propanol. Effects of casting conditions on the morphology and conductivity of the films were investigated. These films were fully characterized by UV- vis, NIR, IR, XRD, SEM and ESR. In the second type of conducting polymer system, PAMAM dendrimers generation 1 through 5 were peripherally modified with cationically substituted naphthalene diimide anion radicals. NMR, UV, IR, CV and Elemental Analysis were used to characterize modified dendrimers. Reduction with sodium dithionite in solution showed anion radicals were aggregated into π-dimers and π- stacks. Formamide was used to cast conducting dendrimer films. ESCA, SEM and optical microscope were used to study the composition and the morphology of the films. XRD showed complete amorphous nature of these films. NIR revealed that the π-stack aggregation depend strongly on the casting temperature and the degree of reduction. Four- probe co-liner conductivity of the films is on the order of 10-2 to 10-1/ S/ cm-1. ESR and conductivity measurements also revealed the isotropic nature of the conductivity. Conductivity/humidity relationship was discovered by accidental breathing over the films. Using a home-made controlled humidity device and PACERTM hygrometer, the conductivity of the films can be varied quickly and reversibly within two orders of a magnitude. This phenomenon was probed with NIR, XRD and quartz crystal microbalance techniques. These

  3. Electrical conductivity of magnetite-bearing serpentinite during shear deformation

    NASA Astrophysics Data System (ADS)

    Kawano, Seiya; Yoshino, Takashi; Katayama, Ikuo

    2012-10-01

    Electrical conductivity of serpentinite with various amounts of magnetite was measured during shear deformation at high pressure and temperatures (P = 1.0 GPa, T = 750 K) corresponding to mantle wedge conditions to evaluate the contribution of aligned magnetite to the bulk conductivity of serpentinite. Under hydrostatic conditions, the sample conductivity considerably increases when the magnetite volume fraction exceeds 25% in volume, suggesting the presence of the percolation threshold for magnetite interconnection. During shear deformation, the conductivity for the samples with less than 25 vol.% magnetite increased by an order of magnitude or higher with increasing shear strain up to 9, which is likely a result of the clustering or realignment of magnetite grains in the serpentinites. However, activation enthalpy was nearly constant before and after deformation experiments, suggesting that shear deformation is unlikely to enhance establishment of interconnection of magnetite. Consequently, more than 25 vol.% magnetite is needed to establish connectivity of magnetite in serpentinite. On the other hand, the conductivity of serpentinite with low volume fraction of magnetite (5%), which is typical concentration of natural serpentinites, is almost similar to that of magnetite-free serpentinites. The present results show that the interconnection of magnetite in serpentinites by shear deformation is not expected as an origin of the high conductivity anomaly occasionally observed at the slab interface in the mantle wedge. The origin of high conductivity, therefore, indicates the presence of aqueous fluid with high salinity rather than the magnetite interconnection.

  4. In situ determination of slurry nutrient content by electrical conductivity.

    PubMed

    Provolo, G; Martínez-Suller, L

    2007-12-01

    Land application of animal slurries has both agronomic and environmental implications. It can be supported by the quantification of available nutrients in the field. A prototype device for indirect measurement of the nutrient content of slurry based on electrical conductivity (EC) was calibrated on manure samples collected from farms with different livestock typologies. The resulting correlations between EC and nutrient contents of slurries from laboratory analyses have shown good agreement (r(2) from 0.73 to 0.95) with total and ammoniacal nitrogen and, with some exception, Potassium, but failed to demonstrate any significant relationship with total phosphorous. The mean errors obtained using the device in field conditions for nitrogen content were always lower or equal to 10%, while the standard deviations were 12-13% for pig and calf slurries, and 20-21% for dairy cow slurry. The results obtained suggest that the equipment, provided the regression line used to convert EC readings to nutrient contents is related to the livestock typology under observation, can provide good support to practical slurry spreading, even though it does not reach an accuracy comparable to laboratory methods and does not give reliable information on phosphorus. PMID:16919932

  5. Electrically Conductive Diamond Membrane for Electrochemical Separation Processes.

    PubMed

    Gao, Fang; Nebel, Christoph E

    2016-07-20

    Electrochemically switchable selective membranes play an important role in selective filtration processes such as water desalination, industrial waste treatment, and hemodialysis. Currently, membranes for these purposes need to be optimized in terms of electrical conductivity and stability against fouling and corrosion. In this paper, we report the fabrication of boron-doped diamond membrane by template diamond growth on quartz fiber filters. The morphology and quality of the diamond coating are characterized via SEM and Raman spectroscopy. The membrane is heavily boron doped (>10(21) cm(-3)) with >3 V potential window in aqueous electrolyte. By applying a membrane potential against the electrolyte, the redox active species can be removed via flow-through electrolysis. Compared to planar diamond electrodes, the ∼250 times surface enlargement provided by such a membrane ensures an effective removal of target chemicals from the input electrolyte. The high stability of diamond enables the membrane to not only work at high membrane bias but also to be self-cleaning via in situ electrochemical oxidation. Therefore, we believe that the diamond membrane presented in this paper will provide a solution to future selective filtration applications especially in extreme conditions. PMID:27396448

  6. Electrical conductivity changes during irreversible electroporation treatment of brain cancer.

    PubMed

    Garcia, Paulo A; Rossmeisl, John H; Davalos, Rafael V

    2011-01-01

    Irreversible electroporation (IRE) is a new minimally invasive technique to kill tumors and other undesirable tissue in a non-thermal manner. During an IRE treatment, a series of short and intense electric pulses are delivered to the region of interest to destabilize the cell membranes in the tissue and achieve spontaneous cell death. The alteration of the cellular membrane results in a dramatic increase in electrical conductivity during IRE as in other electroporation-based-therapies. In this study, we performed the planning and execution of an IRE brain cancer treatment using MRI reconstructions of the tumor and a multichannel array that served as a stereotactic fiducial and electrode guide. Using the tumor reconstructions within our numerical simulations, we developed equations relating the increase in tumor conductivity to calculated currents and volumes of tumor treated with IRE. We also correlated the experimental current measured during the procedure to an increase in tumor conductivity ranging between 3.42-3.67 times the baseline conductivity, confirming the physical phenomenon that has been detected in other tissues undergoing similar electroporation-based treatments. PMID:22254416

  7. Electrically conductive PEDOT coating with self-healing superhydrophobicity.

    PubMed

    Zhu, Dandan; Lu, Xuemin; Lu, Qinghua

    2014-04-29

    A self-healing electrically conductive superhydrophobic poly(3,4-ethylenedioxythiophene) (PEDOT) coating has been prepared by chemical vapor deposition of a fluoroalkylsilane (POTS) onto a PEDOT film, which was obtained by electrochemical deposition. The coating not only maintained high conductivity with a low resistivity of 3.2 × 10(-4) Ω·m, but also displayed a water contact angle larger than 156° and a sliding angle smaller than 10°. After being etched with O2 plasma, the coating showed an excellent self-healing ability, spontaneously regaining its superhydrophobicity when left under ambient conditions for 20 h. This superhydrophobicity recovery process was found to be humidity-dependent, and could be accelerated and completed within 2 h under a high humidity of 84%. The coating also exhibited good superhydrophobicity recovering ability after being corroded by strong acid solution at pH 1 or strong base solution at pH 14 for 3 h. PMID:24702588

  8. VLF waves at satellite altitude to investigate Earth electrical conductivity

    NASA Astrophysics Data System (ADS)

    Leye, P. O.; Tarits, P.

    2015-03-01

    At and near the Earth surface, electromagnetic (EM) fields radiated from VLF transmitters are commonly used in geological exploration to determine the shallow Earth conductivity structure. Onboard satellites such as DEMETER, the electric and magnetic sensors detect the VLF signal in altitude. While we know for surface measurement that the VLF EM field recorded at some distance from the transmitter is a function of the ground conductivity, we do not know how this relationship changes when the field is measured at satellite altitude. Here we study the electromagnetic field radiated by a vertical electric dipole located on the Earth surface in the VLF range and measured at satellite altitude in a free space. We investigate the EM field as function of distance from the source, the height above the Earth surface, and the electrical conductivity of the Earth. The mathematical solution in altitude has more severe numerical complications than the well-known solutions at or near the Earth surface. We test most of the solutions developed for the latter case and found that direct summation was best at several hundred kilometers above the Earth. The numerical modeling of the EM field in altitude shows that the field remains a function of Earth conductivity. The dependence weakens with altitude and distance from the transmitter. It remains more important for the electric radial component.

  9. Guar gum based biodegradable, antibacterial and electrically conductive hydrogels.

    PubMed

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

    2015-04-01

    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] (mol L(-1)) = 0.306 × 10(-1); [AA] (mol L(-1)) = 0.291 × 10(-3) and [hexamine] (mol L(-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

  10. Highly Electrically Conducting Glass-Graphene Nanoplatelets Hybrid Coatings.

    PubMed

    Garcia, E; Nistal, A; Khalifa, A; Essa, Y; Martín de la Escalera, F; Osendi, M I; Miranzo, P

    2015-08-19

    Hybrid coatings consisting of a heat resistant Y2O3-Al2O3-SiO2 (YAS) glass containing 2.3 wt % of graphene nanoplatelets (GNPs) were developed by flame spraying homogeneous ceramic powders-GNP granules. Around 40% of the GNPs survived the high spraying temperatures and were distributed along the splat-interfaces, forming a percolated network. These YAS-GNP coatings are potentially interesting in thermal protection systems and electromagnetic interference shields for aerospace applications; therefore silicon carbide (SiC) materials at the forefront of those applications were employed as substrates. Whereas the YAS coatings are nonconductive, the YAS-GNP coatings showed in-plane electrical conductivity (∼10(2) S·m(-1)) for which a low percolation limit (below 3.6 vol %) is inferred. Indentation tests revealed the formation of a highly damaged indentation zone showing multiple shear displacements between adjacent splats probably favored by the graphene sheets location. The indentation radial cracks typically found in brittle glass coatings are not detected in the hybrid coatings that are also more compliant. PMID:26222837

  11. Mantle electrical conductivity profile of Niger delta region

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

    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.

  12. Copper-Filled Electrically Conductive Adhesives with Enhanced Shear Strength

    NASA Astrophysics Data System (ADS)

    Ho, Li-Ngee; Nishikawa, Hiroshi

    2014-09-01

    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 Ω cm, and significantly high shear strength (above 17 MPa) could be achieved.

  13. Gellan gum-graft-polyaniline--An electrical conducting biopolymer.

    PubMed

    Karthika, J S; Vishalakshi, B; Naik, Jagadish

    2016-01-01

    Grafting of polyaniline (PANI) on to gellan gum (GG) was carried out in the presence of catalytic amount of ammonium peroxydisulfate (APS) as oxidant/initiator under mild acidic conditions by microwave irradiation technique. The grafting condition was optimized by varying the microwave power, exposure time and the composition of the reaction mixture. The graft copolymer GG-g-PANI was characterized by FTIR, TGA, UV/vis, (1)H NMR and SEM techniques. The characteristic peaks at 1506, 1462, 1070 and 830 cm(-1) in the IR spectrum and signals at 7.3, 7.2, 7.1 and 4.0 δ in the (1)H NMR spectrum confirms the grafting process. The TGA data reveals GG-g-PANI to be thermally less stable than GG. The optimum grafting was observed when the reaction mixture containing 0.066 mmol APS, 0.1M aniline, 1M hydrochloric acid and 0.1g/dL GG was exposed to 80 W microwave power for 40s. The DC and AC conductivity of the GG-g-PANI were measured using the 'Two-point probe' method based on which the dielectric properties were evaluated. GG-g-PANI exhibited appreciable electrical conductivity, which increased with the extent of grafting. The results indicate threefold increase in DC conductivity of graft copolymer as compared to GG. PMID:26526174

  14. Optimization and Testing of Electrically Conductive Spacecraft Coatings

    NASA Technical Reports Server (NTRS)

    Mell, Richard J.

    2001-01-01

    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.

  15. Flow and forced-convection heat transfer over forward-facing double steps (effects of step ratio)

    SciTech Connect

    Shakouchi, Toshihiko; Kajino, Itsuki

    1994-07-01

    The flow and heat transfer over a step (a forward- or backward-facing step) result in complicated flow conditions, such as a shear flow field, flow separation, and generation of vortices, and provide some interesting information that improves understanding of the heat transfer on the surface. This is a very frequent flow, and basic to various kinds of chemical equipment, fluid machinery, combustion furnaces, and IC-packages. Recently, there have been many studies on this flow situation by numerical analysis, measurement of mean and fluctuating velocities within the separation bubble using laser Doppler anemometer, and heat transfer analysis. A flow passage having two steps in tiers (forward- or backward-facing double steps) is also frequent, and it is very important to clarify the effects of each step on the flow and the heat-transfer characteristics. This however, has not yet been investigated. This study presents the results of an experimental investigation on the flow and forced convective heat transfer over forward-facing single and double steps. Measurements of velocity and turbulence intensity, flow visualization, pressure distribution, and heat transfer over forward-facing double steps were carried out for various step ratios, L/a (L: step length, a: step height). From these results, the effects of the step ratio on the flow and heat-transfer characteristics were clarified and the following results were confirmed. Heat-transfer enhancement of a double step is considerable compared with that of a single step or a flat plate.

  16. An invariant descriptor for conjugate forced convection-conduction cooling of 3D protruding heaters in channel flow

    NASA Astrophysics Data System (ADS)

    Antonini Alves, Thiago; Santos, Paulo H. D.; Barbur, Murilo A.

    2015-09-01

    In this research, the temperatures of threedimensional (3D) protruding heaters mounted on a conductive substrate in a horizontal rectangular channel with laminar airflow are related to the independent power dissipation in each heater by using a matrix G + with invariant coefficients, which are dimensionless. These coefficients are defined in this study as the conjugate influence coefficients ( g +) caused by the forced convection- conduction nature of the heaters' cooling process. The temperature increase of each heater in the channel is quantified to clearly identify the contributions attributed to the self-heating and power dissipation in the other heaters (both upstream and downstream). The conjugate coefficients are invariant with the heat generation rate in the array of heaters when assuming a defined geometry, invariable fluid and flow rate, and constant substrate and heater conductivities. The results are numerically obtained by considering three 3D protruding heaters on a twodimensional (2D) array by ANSYS/Fluent™ 15.0 software. The conservation equations are solved by a coupled procedure within a single calculation domain comprising of solid and fluid regions and by considering a steady state laminar airflow with constant properties. Some examples are shown, indicating the effects of substrate thermal conductivity and Reynolds number on conjugate influence coefficients.

  17. Free and forced convective cooling of pipe-type electric cables. Volume 2: electrohycrodynamic pumping. Final report

    SciTech Connect

    Chato, J.C.; Crowley, J.M.

    1981-05-01

    A multi-faceted research program has been performed to investigate in detail several aspects of free and forced convective cooling of underground electric cable systems. There were two main areas of investigation. The first one, reported in Volume 1, dealt with the fluid dynamic and thermal aspects of various components of the cable system. In particular, friction factors for laminar flow in the cable pipes with various configurations were determined using a finite element technique; the temperature distributions and heat transfer in splices were examined using a combined analytical numerical technique; the pressure drop and heat transfer characteristics of cable pipes in the transitional and turbulent flow regime were determined experimentally in a model study; and full-scale model experimental work was carried out to determine the fluid dynamic and thermal characteristics of entrance and exit chambers for the cooling oil. The second major area of activity, reported in this volume, involved a feasibility study of an electrohydrodynamic pump concept utilizing a traveling electric field generated by a pumping cable. Experimental studies in two different configurations as well as theoretical calculations showed that an electrohydrodynamic pump for the moving of dielectric oil in a cable system is feasible.

  18. Numerical simulation of fluid flow and forced convection heat transfer from tandem circular cylinders using overset grid method

    NASA Astrophysics Data System (ADS)

    Harimi, Iman; Saghafian, Mohsen

    2012-01-01

    Forced convection heat transfer from two and three isothermal circular cylinders in tandem arrangement is studied numerically. In addition, the flow field and the vortex shedding behavior in the wake of the cylinders are investigated. The governing equations consist of continuity, momentum and energy equations are solved for laminar unsteady flow regime. The numerical simulations are performed with a developed finite volume code using the overset grid method. A general orthogonal boundary fitted coordinate system is used for the grid generation. This simulation is performed for the Prandtl numbers of 0.7 and 7 at the Reynolds numbers of 100 and 200. The spacing ratio L/D is set at 2, 3, 4, 5, 7 and 10. In order to analyze the heat transfer from isothermal cylinders, the mean and local Nusselt numbers and isotherm plots are presented and discussed for different values of the problem parameters. In addition, the mean and instantaneous drag and lift coefficients and Strouhal numbers are computed to elucidate the role of the Reynolds number and spacing ratio. Furthermore, two new correlations for the calculation of the mean Nusselt number, in terms of the spacing ratio and the Reynolds and Prandtl numbers, is proposed. In order to validate the solution, the obtained results are compared with available results in the published literature.

  19. An analysis of laminar free-convection flow and heat transfer about a flat plate paralled to the direction of the generating body force

    NASA Technical Reports Server (NTRS)

    Ostrach, Simon

    1953-01-01

    The free-convection flow and heat transfer (generated by a body force) about a flat plate parallel to the direction of the body force are formally analyzed and the type of flow is found to be dependent on the Grashof number alone. For large Grashof numbers (which are of interest in aeronautics), the flow is of the boundary-layer type and the problem is reduced in a formal manner, which is analogous to Prandtl's forced-flow boundary-layer theory, to the simultaneous solution of two ordinary differential equations subject to the proper boundary conditions. Velocity and temperature distributions for Prandtl numbers of 0.01, 0.72, 0.733, 1, 1, 10, 100, and 1000 are computed, and it is shown that velocities and Nusselt numbers of the order of magnitude of those encountered in forced-convection flows may be obtained in free-convection flows. The theoretical and experimental velocity and temperature distributions are in good agreement. A flow and a heat-transfer parameter, from which the important physical quantities such as shear stress and heat-transfer rate can be computed, are derived as functions of Prandtl number alone.

  20. Theoretical and Computational Study of Forced-Convection Heat Transfer at Supercritical Pressures

    NASA Astrophysics Data System (ADS)

    Zhong, Jianguo

    In the simulation of turbulent fluid flow and heat transfer at supercritical pressures, substantial difficulties have been encountered in the modeling of turbulence and bounda-ry layer. This is due to significant fluid property variations with respect to the local temperature and pressure, especially in the near-wall region of a heated wall, where large temperature differences occur. The classical turbulence models available in literature were typically developed for constant-property fluids, where an empirical wall function in the high-Re k-epsilon model, and a damping function in the low-Re k-epsilon model were derived based on the constant-property data to solve the boundary layer. As it can be found in the existing literature, large differences have been observed between the experimental and numerical simulation results of the heat transfer coefficient predictions in the en-hanced and deteriorated heat transfer situations for supercritical fluids. In this thesis, a novel near-wall treatment method is proposed to treat large property variations in the thermal and velocity sub-layers. In the near-wall region, the supercritical fluids can be considered thermal-conductive and viscous forces dominated. The thick-ness of the viscous sub-layer (VSL) and the conduction sub-layer (CSL) can be related to the wall shear stress and local Prandtl number information by using computational CFD models, such as that implemented in the NPHASE-CMFD code. The fluids' bulk and wall temperature information has been obtained from the literature review of experi-mental measurements. The wall temperature and heat transfer coefficient calculated from the k-epsilon model with the proposed wall treatment method have been found to be in good agreement with experimental data for both heat transfer enhancement and deterioration cases for two most widely used fluids: CO2 and water. The proposed model has been applied in the reactor-scale thermal-hydraulic analysis of different flow path

  1. Instability in Three-Dimensional Magnetohydrodynamic Flows of an Electrically Conducting Fluid

    NASA Astrophysics Data System (ADS)

    Zakir, Hussain; Liu, Chan; Zhang, Nianmei; Ni, Mingjiu

    2013-12-01

    The three-dimensional instability of an electrically conducting fluid between two parallel plates affected by an imposed transversal magnetic field is numerically investigated by a Chebyshev collocation method. The QZ method is utilized to obtain neutral curves of the linear instability. The details of instability are analyzed by solving the generalized Orr-Sommerfeld equation. The critical Reynolds number Rec, the stream-wise and span-wise critical wave numbers αc and βc are obtained for a wide range of Hartmann number Ha. The effects of Lorentz force and span-wise perturbation on three-dimensional instability are investigated. The results show that magnetic field would suppress the instability and critical Reynolds number tends to be larger than that for two-dimensional instability.

  2. Nonlinear optical and electrical conductivity properties of Carbon Nanotubes (CNT) doped in Sol-Gel matrices

    NASA Astrophysics Data System (ADS)

    Pokrass, Mariana; Burshtein, Zeev; Bar, Galit; Gvishi, Raz

    2014-09-01

    Carbon-nanotubes (CNT) are fascinating compounds, exhibiting exceptional electrical, thermal conductivity, mechanical strength, and nonlinear optical (NLO) properties. Their unique structures involve large π-π* electronic clouds. The energy level schemes thus created allow many electronic transitions between the ground and the excited states. The present work involves CNT-doped hybrid organic-inorganic glass composites prepared by a Fast-sol-gel method. Such composite glasses solidify without shrinkage or crack formation, and exhibit promising properties as optical devices. In this work we have studied nonlinear optical and electrical conductivity properties. The CNT composite glasses exhibited enhanced absorption at 532 nm, and saturable absorption at 1064 nm. The enhanced absorption at 532 was attributed to 2-photon absorption; saturable absorption was attributed to depletion of the absorbing ground-state, and was analyzed using the modified Frantz-Nodvik equation. Absorption cross-sections were extracted for the saturable absorption phenomenon. Such CNT composites glasses may be used as "optical limiting" filters in lasers near 532 nm, or as saturable absorbing filters for passive laser Q-switching near 1064 nm. The CNT composites electrical conductivity was studied as a function of the CNT concentration and modeled by a percolation theory. The maximal measured conductivity was σ ≍10-3 (Ωcm)-1 for the CNT composites, representing a conductivity increase of at least 12 orders of magnitude compared to that of pure silica. A quite low percolation threshold was obtained, φc = 0.22 wt.% CNT. Electrostatic Force Microscopy (EFM) and Conductive mode Atomic Force Microscopy (C-AFM) studies revealed that the conductivity occurs at the micro-level among the CNTs dispersed in the matrix.

  3. Electrical Conductivity of Mantle Minerals: A Laboratory View

    NASA Astrophysics Data System (ADS)

    Shankland, T. J.

    2002-12-01

    Since the work of Lahiri and Price (1939) geophysicists have attempted to interpret electrical conductivity profiles of Earth's mantle. As we now know, the basic materials are olivines, pyroxenes, spinels, garnets, and their high-pressure, high-temperature polymorphs. However, beginning in the late 1940s researchers plunged in by measuring conductivities in ultramafic rocks. As inconsistencies appeared over the next couple of decades, it was necessary to define minerals in terms of condensed matter physics\\--an approach needed for extrapolation to extremes of mantle conditions not then available in the laboratory. By these standards mantle minerals are insulators, and for insulators electrical transport properties are difficult to measure reliably. Achieving chemical buffering (principally of oxygen fugacity by Duba and colleagues) in the early 1970s had two big effects: (1) it threw into doubt most of the previous quarter-century of work, and (2) it introduced nearly unprecedented reproducibility. Improved laboratory measurements permitted the role of iron in charge transfer to be defined and interpreted in terms of oxygen-sensitive defect populations. For mantle olivine (~10% fayalite content) there was actually general agreement among several groups for measurements at mantle temperatures. [In both field and laboratory conductivity measurements half an order of magnitude appears to be the level at which disagreements become academic.] Other advances, measurements of mineral conductivity in multi-anvil devices and diamond anvil cells have become possible at mantle pressures and/or temperatures, and the role of crystallographic phase transitions was elucidated. Attention to chemical buffering has led to other advances. For instance, "water" in its various chemical species appears to enhance conductivity, at least in the uppermost mantle. Elemental carbon could also play a role. Finally, an unusual agreement with geophysical observations has been achieved. However

  4. Microstructural Inhomogeneity of Electrical Conductivity in Subcutaneous Fat Tissue

    PubMed Central

    Kruglikov, Ilja L.

    2015-01-01

    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

  5. Electrical Conductivity Mapping of the South Nation River, Eastern Ontario

    NASA Astrophysics Data System (ADS)

    Kingsley, J. E.; Robin, M. J.

    2004-05-01

    The objective of this project is to provide information on small-scale variability of groundwater seepage / leakage at the scale of a small basin. Direct measurement of seepage / leakage is very labour-intensive, and is therefore not feasible at the scale of a basin. An alternative method, which was used in this study, infers groundwater seepage from Electrical Conductivity and Temperature (EC&T) of water at the bottom of the river, based on the assumption that there is a contrast between the incoming groundwater and the river water. These measurements can be made very quickly by dragging an EC&T probe from a boat at a slow speed. This method was used to conduct a pilot survey of EC&T of the main branch of the South Nation River in Eastern Ontario, Canada. The mean EC values were relatively high, indicating relatively poor water quality. Several anomalies were detected along the river as sharp peaks above or below the mean EC value. Some of the peaks were later confirmed zones of seepage, by direct seepage measurements. A very important finding from this data is that areas of groundwater seepage in the SNR are very localized in areas of less than a few tens of meters, indicating that the deep recharge patterns may be the result of fracture flow in the bedrock. Several other anomalies were of anthropogenic origin. Water budget estimates were made from direct seepage measurements in conjunction with the survey results, along with precipitation, runoff, and evapotranspiration. The estimates were compared to the results of traditional hydrograph separation techniques.

  6. Engineering correlations of variable-property effects on laminar forced convection mass transfer for dilute vapor species and small particles in air

    NASA Technical Reports Server (NTRS)

    Gokoglu, S. A.; Rosner, D. E.

    1984-01-01

    A simple engineering correlation scheme is developed to predict the variable property effects on dilute species laminar forced convection mass transfer applicable to all vapor molecules or Brownian diffusing small particle, covering the surface to mainstream temperature ratio of 0.25 T sub W/T sub e 4. The accuracy of the correlation is checked against rigorous numerical forced convection laminar boundary layer calculations of flat plate and stagnation point flows of air containing trace species of Na, NaCl, NaOH, Na2SO4, K, KCl, KOH, or K2SO4 vapor species or their clusters. For the cases reported here the correlation had an average absolute error of only 1 percent (maximum 13 percent) as compared to an average absolute error of 18 percent (maximum 54 percent) one would have made by using the constant-property results.

  7. Magneto-convective instabilities in horizontal cavities

    NASA Astrophysics Data System (ADS)

    Mistrangelo, Chiara; Bühler, Leo

    2016-02-01

    A linear stability analysis is performed to investigate the onset of convective motions in a flat cavity filled with liquid metal. A volumetric heat source is uniformly distributed in the fluid and a horizontal magnetic field is imposed. Walls perpendicular to the magnetic field are thermally insulating, and the top wall is isothermal and the bottom adiabatic. When a magnetic field is applied, electromagnetic forces tend to transform 3D convective flow structures into quasi-2D rolls aligned to the magnetic field. By integrating 3D equations along magnetic field lines, a quasi-2D mathematical model has been derived. A dissipation term in the 2D equations accounts for 3D viscous effects in boundary layers at Hartmann walls perpendicular to the magnetic field. The influence of various parameters on flow stability is investigated. The flow is stabilized by increasing the magnetic field intensity or the electric conductance of Hartmann walls and by reducing the aspect ratio of the cavity. Numerical simulations are performed to verify the analytical results and to describe the main convective flow patterns in the non-linear regime.

  8. Benchmarking of thermal hydraulic loop models for Lead-Alloy Cooled Advanced Nuclear Energy System (LACANES), phase-I: Isothermal steady state forced convection

    NASA Astrophysics Data System (ADS)

    Cho, Jae Hyun; Batta, A.; Casamassima, V.; Cheng, X.; Choi, Yong Joon; Hwang, Il Soon; Lim, Jun; Meloni, P.; Nitti, F. S.; Dedul, V.; Kuznetsov, V.; Komlev, O.; Jaeger, W.; Sedov, A.; Kim, Ji Hak; Puspitarini, D.

    2011-08-01

    As highly promising coolant for new generation nuclear reactors, liquid Lead-Bismuth Eutectic has been extensively worldwide investigated. With high expectation about this advanced coolant, a multi-national systematic study on LBE was proposed in 2007, which covers benchmarking of thermal hydraulic prediction models for Lead-Alloy Cooled Advanced Nuclear Energy System (LACANES). This international collaboration has been organized by OECD/NEA, and nine organizations - ENEA, ERSE, GIDROPRESS, IAEA, IPPE, KIT/IKET, KIT/INR, NUTRECK, and RRC KI - contribute their efforts to LACANES benchmarking. To produce experimental data for LACANES benchmarking, thermal-hydraulic tests were conducted by using a 12-m tall LBE integral test facility, named as Heavy Eutectic liquid metal loop for integral test of Operability and Safety of PEACER (HELIOS) which has been constructed in 2005 at the Seoul National University in the Republic of Korea. LACANES benchmark campaigns consist of a forced convection (phase-I) and a natural circulation (phase-II). In the forced convection case, the predictions of pressure losses based on handbook correlations and that obtained by Computational Fluid Dynamics code simulation were compared with the measured data for various components of the HELIOS test facility. Based on comparative analyses of the predictions and the measured data, recommendations for the prediction methods of a pressure loss in LACANES were obtained. In this paper, results for the forced convection case (phase-I) of LACANES benchmarking are described.

  9. Electrically Conductive Multiphase Polymer Blend Carbon-Based Composites

    NASA Astrophysics Data System (ADS)

    Brigandi, Paul James

    The use of multiphase polymer blends provides unique morphologies and properties to reduce the percolation concentration and increase conductivity of carbon-based polymer composites. These systems offer improved conductivity, temperature stability and selective distribution of the conductive filler through unique morphologies at significantly lower conductive filler concentration. In this work, the kinetic and thermodynamic effects on a series of multiphase conductive polymer composites were investigated. The polymer blend phase morphology, filler distribution, electrical conductivity, and rheological properties of CB-filled PP/PMMA/EAA conductive polymer composites were determined. Thermodynamic and kinetic parameters were found to influence the morphology development and final composite properties. The morphology and CB distribution were found to be kinetically driven when annealed for a short period of time following the shear-intensive mixing process, whereas the three-phase polymer blend morphology is driven by thermodynamics when given sufficient time under high temperature annealing conditions in the melt state. At short annealing times, the CB distribution was influenced by the compounding sequence where the CB was added after being premixed with one of the polymer phases or directly added to the three phase polymer melt, but again was thermodynamically driven at longer annealing times with the CB migrating to the EAA phase. The resistivity was found to decrease by a statistically significant amount to similar levels for all of the composite systems with increasing annealing time, providing evidence of gradual phase coalescence to a tri-continuous morphology and CB migration. The addition of CB via the PP and EAA masterbatch results in significantly faster percolation and lower resistivity compared to when added direct to the system during compounding after 30 minutes annealing by a statistically significant amount. Dynamic oscillatory shear rheology using

  10. Synthesis and applications of electrically conducting polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Ku, Bon-Cheol

    This research focuses on the synthesis and applications of electrically conducting polymer nanocomposites through molecular self-assembly. Two different classes of polymers, polyaniline (PANI) and polyacetylenes have been synthesized by biomimetic catalysis and spontaneous polymerization method. For gas barrier materials, commercially available polymers, poly(allylamine hydrochloride) (PAH) and poly (acrylic acid) (PAA), have also been used and thermally cross-linked. The morphological, optical and electrical properties of amphiphilic polyacetylenes have been studied. Furthermore, barrier properties, permselectivity, pervaporation properties of polyacetylenes/aluminosilicate nanocomposites have been investigated. For processability and electrical properties of carbon nanotube and conducting polymers, substituted ionic polyacetylenes (SIPA) have been covalently incorporated onto single-walled carbon nanotubes (SWNT) using the "grafting-from" technique. In the first study, a nanocomposite film catalyst has been prepared by electrostatic layer-by-layer (ELBL) self-assembly of a polyelectrolyte and a biomimetic catalyst for synthesis of polyaniline. Poly(dimethyl diallylammonium chloride) (PDAC) and hematin have been used as polycation and counter anions, respectively. The absorption spectra by UV-vis-NIR spectroscopy showed that conductive form polyaniline was formed not only as a coating on the surface of the ELBL composites but was also formed in solution. Furthermore, it was found that the reaction rate was affected by pH and concentration of hematin in the multilayers. The feasibility of controlled desorption of hematin molecules from the LBL assembly was explored and demonstrated by changing the pH and hematin concentration. The polymerization rate of aniline in solution was enhanced with decreasing pH of the solutions due to increased desorption of hematin nanoparticles from the multilayers. These ELBL hematin assemblies demonstrated both a way to functionalize

  11. Development of Tailorable Electrically Conductive Thermal Control Material Systems

    NASA Technical Reports Server (NTRS)

    Deshpande, M. S.; Harada, Y.

    1997-01-01

    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

  12. Control of electrical conduction in DNA using hole doping

    NASA Astrophysics Data System (ADS)

    Lee, Hea-Yeon; Taniguchi, Masateru; Yoo, K. H.; Otsuka, Youichi; Tanaka, Hidekazu; Kawai, Tomoji

    2002-03-01

    Control of electrical conduction in DNA using hole doping H.Y.Lee1, M.Taniguchi1, K.H.Yoo2, Y.Otsuka1 H.Tanaka1 and T.Kawai1 1The Institute of Scientific and Industrial Research(ISIR), Osaka University, Osaka, Japan. 2Department of Physics, Younsei University, Seoul, Korea Possible applications of DNA molecules in electronic devices and biosensors were suggested almost ten years ago A DNA structure containing a single type of base pair appears to be a good candidate for conduction along the \\x81E-electron clouds of the stacked bases. There have been lots of investigations on conduction mechanisms of the DNA molecules. However, it is not still clear whether the observed conductions of some DNA molecules come from motions of either ionic charges or other carriers. Although the basic mechanism for DNA-mediated charge transport should be understood for electronic applications, there have been divergent reports on its nature. And I will be present the research for the charge carrier conduction of DNA film under oxygen and iodine gas by using 10¡V100 nm gap. The doping studies using oxygen and iodine gas can provide a definite answer for the carrier conduction mechanism and also a possible method to control the carrier concentration in DNA molecules. Using oxygen and iodine adsorption experiments on the poly (dG)-poly (dC) DNA molecules, we will show that their conductance becomes increased easily by several orders of magnitudes due to the hole doping, which is a characteristic behavior of a p-type semiconductor. On the other hand, we will also show that the poly (dA) - poly (dT) DNA molecules behave as an n-type semiconductor. Our works indicate that the concentration and the type of carriers in the DNA molecules could be controlled using proper doping methods. We expect that this would be a major breakthrough in DNA-based nano-electronics, similar to the fact that the doped conductive has polyacetylene opened up a new field of electronics with exciting implications

  13. The Impact of Model Configuration and Large-Scale, Upper-Level Forcing on CRM- Simulated Convective Systems

    NASA Technical Reports Server (NTRS)

    Tao, W.-K.; Zeng, X.; Shie, C.-L.; Starr, D.; Simpson, J.

    2004-01-01

    Real clouds and cloud systems are inherently three-dimensional (3D). Because of the limitations in computer resources, however, most cloud-resolving models (CRMs) today are still two-dimensional (2D, see a brief review by Tao 2003). Only recently have 3D experiments been performed for multi-day periods for tropical cloud systems with large horizontal domains at the National Center for Atmospheric Research, at NOAA GFDL, at the U. K. Met. Office, at Colorado State University and at NASA Goddard Space Flight Center (Tao 2003). At Goddard, a 3D Goddard Cumulus Ensemble (GCE) model was used to simulate periods during TOGA COARE (December 19-27, 1992), GATE (September 1-7, 1974), SCSMEX (June 2-11, 1998), ARM (June 26-30, 1997) and KWAJEX (August 7-13, August 18-21, and August 29-September 12, 1999) using a 512 by 512 km domain (with 2-km resolution). The results indicate that surface precipitation and latent heating profiles are similar between the 2D and 3D GCE model simulations. However, there are difference in radiation, surface fluxes and precipitation characteristics. The 2D GCE model was used to perform a long-term integration on ARM/GCSS case 4 (22 days at the ARM Southern Great Plains site in March 2000). Preliminary results showed a large temperature bias in the upper troposphere that had not been seen in previous tropical cases. The major objectives of this paper are: (1) to determine the sensitivities to model configuration (i.e., 2D in west-east, south-north or 3D), (2) to identify the differences and similarities in the organization and entrainment rates of convection between 2D- and 3D-simulated ARM cloud systems, and (3) assess the impact of upper tropospheric forcing on tropical and ARM case 4 cases.

  14. The Impact of Model Configuration and Large-Scale, Upper-Level Forcing on CRM-Simulated Convective Systems

    NASA Technical Reports Server (NTRS)

    Tao, W.-K.; Zeng, X.; Shie, C.-L.; Starr, D.; Simpson, J.

    2004-01-01

    Real clouds and cloud systems are inherently three-dimensional (3D). Because of the limitations in computer resources, however, most cloud-resolving models (CRMs) today are still two-dimensional (2D, see a brief review by Tao 2003). Only recently have 3D experiments been performed for multi-day periods for tropical cloud systems with large horizontal domains at the National Center for Atmospheric Research, at NOAA GFDL, at the U. K. Met. Office, at Colorado State University and at NASA Goddard Space Flight Center (Tao 2003). At Goddard, a 3D Goddard Cumulus Ensemble (GCE) model was used to simulate periods during TOGA COARE (December 19-27, 1992), GATE (September 1-7, 1974), SCSMEX (June 2-11, 1998), ARM (June 26-30, 1997) and KWAJEX (August 7-13, August 18-21, and August 29-September 12, 1999) using a 512 km domain (with 2-kilometer resolution). The results indicate that surface precipitation and latent heating profiles are similar between the 2D and 3D GCE model simulations. However, there are difference in radiation, surface fluxes and precipitation characteristics. The 2D GCE model was used to perform a long-term integration on ARM/GCSS case 4 (22 days at the ARM southern Great Plains site in March 2000). Preliminary results showed a large temperature bias in the upper troposphere that had not been seen in previous tropical cases. The major objectives of this paper are: (1) to determine the sensitivities to model configuration (ie., 2D in west-east, south-north or 3D), (2) to identify the differences and similarities in the organization and entrainment rates of convection between 2D- and 3D-simulated ARM cloud systems, and (3) assess the impact of upper tropospheric forcing on tropical and ARM case 4 cases.

  15. Phenomenological and statistical analyses of turbulence in forced convection with temperature-dependent viscosity under non-Boussinesq condition.

    PubMed

    Yahya, S M; Anwer, S F; Sanghi, S

    2013-10-01

    In this work, Thermal Large Eddy Simulation (TLES) is performed to study the behavior of weakly compressible Newtonian fluids with anisotropic temperature-dependent viscosity in forced convection turbulent flow. A systematic analysis of variable-viscosity effects, isolated from gravity, with relevance to industrial cooling/heating applications is being carried out. A LES of a planar channel flow with significant heat transfer at a low Mach number was performed to study effects of fluid property variation on the near-wall turbulence structure. In this flow configuration the top wall is maintained at a higher temperature (T hot ) than the bottom wall (T cold ). The temperature ratio (R θ = T hot /T cold ) is fixed at 1.01, 2 and 3 to study the effects of property variations at low Mach number. Results indicate that average and turbulent fields undergo significant changes. Compared with isothermal flow with constant viscosity, we observe that turbulence is enhanced in the cold side of the channel, characterized by locally lower viscosity whereas a decrease of turbulent kinetic energy is found at the hot wall. The turbulent structures near the cold wall are very short and densely populated vortices but near the hot wall there seems to be a long streaky structure or large elongated vortices. Spectral study reveals that turbulence is completely suppressed at the hot side of the channel at a large temperature ratio because no inertial zone is obtained (i.e. index of Kolmogorov scaling law is zero) from the spectra in these region. PMID:24158263

  16. Numerical investigation of forced convection of nano fluid flow in horizontal U-longitudinal finned tube heat exchanger

    NASA Astrophysics Data System (ADS)

    Qasim, S. M.; Sahar, A. F. A.; Firas, A. A.

    2015-11-01

    A numerical study has been carried out to investigate the heat transfer by laminar forced convection of nanofluid taking Titania (TiO2) and Alumina (Al2O3) as nanoparticles and the water as based fluid in a three dimensional plain and U-longitudinal finned tube heat exchanger. A Solid WORKS PREMIUM 2012 is used to draw the geometries of plain tube heat exchanger or U-longitudinal copper finned tube heat exchanger. Four U-longitudinal copper fins have 100 cm long, 3.8cm height and 1mm thickness are attached to a straight copper tube of 100 cm length, 2.2 cm inner diameter and 2.39 cm outer diameter. The governing equations which used as continuity, momentum and energy equations under assumptions are utilized to predict the flow field, temperature distribution, and heat transfer of the heat exchanger. The finite volume approach is used to obtain all the computational results using commercial ANSYS Fluent copy package 14.0 with assist of solid works and Gambit software program. The effect of various parameters on the performance of heat exchanger are investigated numerically such as Reynolds' number (ranging from 270 to 1900), volume consternation of nanoparticles (0.2%, 0.4%, 0.6%, 0.8%), type of nanoparticles, and mass flow rate of nanofluid in the hot region of heat exchanger. For 0.8% consternation of nanoparticles, heat transfer has significant enhancement in both nanofluids. It can be found about 7.3% for TiO2 and about 7.5% for Al2O3 compared with the water only as a working fluid.

  17. Two-dimensional model simulation of Martian atmospheric convection with condensation of the major component under fixed thermal forcing

    NASA Astrophysics Data System (ADS)

    Yamashita, T.; Odaka, M.; Sugiyama, K.; Nakajima, K.; Ishiwatari, M.; Takahashi, Y. O.; Nishizawa, S.; Hayashi, Y.-Y.

    2011-10-01

    We perform a numerical simulation of cloud convection by using two-dimensional nonhydrostatic model for the purpose of investigating the structure of cloud convection with condensation of the major component when significant high supersaturation is not allowed. In quasi-equilibrium state, horizontally uniform cloud layer is formed above the condensation level, and the dry adiabatic layer is formed below the level. The updraft and downdraft associated with convection extends from near the surface to the top of the model atmosphere. The updraft and downdraft in the cloud layer seem to be maintained by buoyancy in the dry adiabatic layer.

  18. Continental growth on Early Earth: Crustal electrical conductivity models of the Barberton Greenstone Belt, South Africa

    NASA Astrophysics Data System (ADS)

    Weckmann, U.; Kutter, S.; De Wit, M.

    2014-12-01

    The Barberton Greenstone Belt (BGB, South Africa) is one of the few Archean remnants where the tectonic evolution of the Early Earth can be studied. The first formation of the crust is a controversially discussed topic among geoscientists. Tectonics on the Early Earth might have been similar to the plate movement and their driving forces that we observe today. However, regarding that some fundamental conditions like the thermal setting were considerably different at this time other processes like vertical mass transport might have played the governing role in tectonics. Therefore contrasting evolutionary models of the BGB exist, mainly based on a number of geological and petrological studies. However, there is only little information on its deeper architecture. For a better understanding of past processes and the character of the tectonic regime which led to the formation of the BGB, magnetotelluric (MT) surveys were carried out as a part of the German-South African Inkaba yeAfrica research initiative. At approximately 200 MT sites aligned along six profiles (approx. 80 to 110 km length) data was collected during two field experiments in 2009 and 2010. The MT method images the electrical conductivity of rocks and is particularly sensitive to imprints of tectonic processes resulting in persistent mineralization e.g. along shear planes. Against the surrounding of significantly conductive geological units like the Phanerozoic Transvaal cover, the rocks of the BGB are generally characterized by high electrical resistivities. Particularly plutons such as the Dalmein Pluton can be traced deeply into the crust. Contrary, faults of the BGB appear as zones of high conductivity down to a depth of 5 to 10 km. We will present 3D inversion results indicating an extension of the plutons of the western BGB beneath the Transvaal cover and a sharp conductivity contrast of the BGB compared to the eastern batholiths. We will discuss existing models of the evolution of the BGB in view

  19. Numerical Simulation of Natural Convection of a Nanofluid in an Inclined Heated Enclosure Using Two-Phase Lattice Boltzmann Method: Accurate Effects of Thermophoresis and Brownian Forces

    NASA Astrophysics Data System (ADS)

    Ahmed, Mahmoud; Eslamian, Morteza

    2015-07-01

    Laminar natural convection in differentially heated ( β = 0°, where β is the inclination angle), inclined ( β = 30° and 60°), and bottom-heated ( β = 90°) square enclosures filled with a nanofluid is investigated, using a two-phase lattice Boltzmann simulation approach. The effects of the inclination angle on Nu number and convection heat transfer coefficient are studied. The effects of thermophoresis and Brownian forces which create a relative drift or slip velocity between the particles and the base fluid are included in the simulation. The effect of thermophoresis is considered using an accurate and quantitative formula proposed by the authors. Some of the existing results on natural convection are erroneous due to using wrong thermophoresis models or simply ignoring the effect. Here we show that thermophoresis has a considerable effect on heat transfer augmentation in laminar natural convection. Our non-homogenous modeling approach shows that heat transfer in nanofluids is a function of the inclination angle and Ra number. It also reveals some details of flow behavior which cannot be captured by single-phase models. The minimum heat transfer rate is associated with β = 90° (bottom-heated) and the maximum heat transfer rate occurs in an inclination angle which varies with the Ra number.

  20. Experimental validation benchmark data for CFD of transient convection from forced to natural with flow reversal on a vertical flat plate

    DOE PAGESBeta

    Lance, Blake W.; Smith, Barton L.

    2016-06-23

    Transient convection has been investigated experimentally for the purpose of providing Computational Fluid Dynamics (CFD) validation benchmark data. A specialized facility for validation benchmark experiments called the Rotatable Buoyancy Tunnel was used to acquire thermal and velocity measurements of flow over a smooth, vertical heated plate. The initial condition was forced convection downward with subsequent transition to mixed convection, ending with natural convection upward after a flow reversal. Data acquisition through the transient was repeated for ensemble-averaged results. With simple flow geometry, validation data were acquired at the benchmark level. All boundary conditions (BCs) were measured and their uncertainties quantified.more » Temperature profiles on all four walls and the inlet were measured, as well as as-built test section geometry. Inlet velocity profiles and turbulence levels were quantified using Particle Image Velocimetry. System Response Quantities (SRQs) were measured for comparison with CFD outputs and include velocity profiles, wall heat flux, and wall shear stress. Extra effort was invested in documenting and preserving the validation data. Details about the experimental facility, instrumentation, experimental procedure, materials, BCs, and SRQs are made available through this paper. As a result, the latter two are available for download and the other details are included in this work.« less

  1. Numerical Simulation of Natural Convection of a Nanofluid in an Inclined Heated Enclosure Using Two-Phase Lattice Boltzmann Method: Accurate Effects of Thermophoresis and Brownian Forces.

    PubMed

    Ahmed, Mahmoud; Eslamian, Morteza

    2015-12-01

    Laminar natural convection in differentially heated (β = 0°, where β is the inclination angle), inclined (β = 30° and 60°), and bottom-heated (β = 90°) square enclosures filled with a nanofluid is investigated, using a two-phase lattice Boltzmann simulation approach. The effects of the inclination angle on Nu number and convection heat transfer coefficient are studied. The effects of thermophoresis and Brownian forces which create a relative drift or slip velocity between the particles and the base fluid are included in the simulation. The effect of thermophoresis is considered using an accurate and quantitative formula proposed by the authors. Some of the existing results on natural convection are erroneous due to using wrong thermophoresis models or simply ignoring the effect. Here we show that thermophoresis has a considerable effect on heat transfer augmentation in laminar natural convection. Our non-homogenous modeling approach shows that heat transfer in nanofluids is a function of the inclination angle and Ra number. It also reveals some details of flow behavior which cannot be captured by single-phase models. The minimum heat transfer rate is associated with β = 90° (bottom-heated) and the maximum heat transfer rate occurs in an inclination angle which varies with the Ra number. PMID:26183389

  2. The bedrock electrical conductivity structure of Northern Ireland

    NASA Astrophysics Data System (ADS)

    Beamish, David

    2013-08-01

    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

  3. The Wilkes subglacial basin eastern margin electrical conductivity anomaly

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

  4. Effect of Melt Convection at Various Gravity Levels and Orientations on the Forces Acting on a Large Spherical Particle in the Vicinity of a Solidification Interface

    NASA Technical Reports Server (NTRS)

    Bune, Andris V.; Sen, Subhayu; Mukherjee, Sundeep; Catalina, Adrian; Stefanescu, Doru M.

    2000-01-01

    Numerical modeling was Undertaken to analyze the influence of both radial and axial thermal gradients on convection patterns and velocities claiming solidification of pure Al and an Al-4 wt% Cu alloy. The objective of the numerical task was to predict the influence of convective velocity on an insoluble particle near a solid/liquid (s/l) interface. These predictions were then be used to define the minimum gravity level (q) required to investigate the fundamental physics of interactions between a particle and a s/l interface. This is an ongoing NASA founded flight experiment entitled "particle engulfment and pushing by solidifying interfaces (PEP)". Steady-state calculations were performed for different gravity levels and orientations with respect to the gravity vector The furnace configuration used in this analysis is the quench module insert (QMI-1) proposed for the Material Science Research Facility (MSRF) on board the International Space Station (ISS). The general model of binary alloy solidification was based on the finite element code FIDAP. At a low g level of 10(exp -4) g(sub o) (g(sub o) = 9.8 m/square s) maximum melt convection was obtained for an orientation of 90 deg. Calculations showed that even for this worst case orientation the dominant forces acting on the particle are the fundamental drag and interfacial forces.

  5. EFFECTS OF TRITIUM GAS EXPOSURE ON ELECTRICALLY CONDUCTING POLYMERS

    SciTech Connect

    Kane, M.; Clark, E.; Lascola, R.

    2009-12-16

    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 the two radiation sources, an approximate dose equivalence was calculated. The materials were also sensitive to small radiation doses (<10{sup 5} rad), showing that there is a measurable response to relatively small total doses of tritium gas. Spectroscopy was also used to confirm the mechanism by which this sensing device would operate in order to calibrate this sensor for potential use. It was determined that one material (polyaniline) was very sensitive to oxidation while the other material (PEDOT-PSS) was not. However, polyaniline provided the best response as a sensing material, and it is suggested that an oxygen-impermeable, radiation-transparent coating be applied to this material for future device prototype fabrication. A great deal of interest has developed in recent years in the area of conducting polymers due to the high levels of conductivity that can be achieved, some comparable to that of metals [Gerard 2002]. Additionally, the desirable physical and chemical properties of a polymer are retained and can be exploited for various applications, including light emitting diodes (LED), anti-static packaging, electronic coatings, and sensors. The electron transfer mechanism is generally accepted as one of electron 'hopping' through delocalized electrons in the conjugated backbone, although other mechanisms have been proposed based on the type of polymer and dopant [Inzelt 2000, Gerard 2002]. The conducting polymer polyaniline (PANi) is of particular interest because there are extensive studies on the modulation of the conductivity by changing either the oxidation state of the

  6. Validation and development of existing and new RAOB-based warm-season convective wind forecasting tools for Cape Canaveral Air Force Station and Kennedy Space Center

    NASA Astrophysics Data System (ADS)

    McCue, Mitchell Hollis

    Using a 15-year (1995 to 2009) climatology of 1500 UTC warm-season (May through September) rawinsonde observation (RAOB) data from the Cape Canaveral Air Force Station (CCAFS) Skid Strip (KXMR) and 5 minute wind data from 36 wind towers on CCAFS and Kennedy Space Center (KSC), several convective wind forecasting techniques currently employed by the 45th Weather Squadron (45 WS) were evaluated. Present forecasting methods under evaluation include examining the vertical equivalent potential temperature (theta e) profile, vertical profiles of wind spend and direction, and several wet downburst forecasting indices. Although previous research found that currently used wet downburst forecasting methods showed little promise for forecasting convective winds, it was carried out with a very small sample, limiting the reliability of the results. Evaluation versus a larger 15-year dataset was performed to truly assess the forecasting utility of these methods in the central Florida warm-season convective environment. In addition, several new predictive analytic based forecast methods for predicting the occurrence of warm-season convection and its associated wind gusts were developed and validated. This research was performed in order to help the 45 WS better forecast not only which days are more likely to produce convective wind gusts, but also to better predict which days are more likely to yield warning criteria wind events of 35 knots or greater, should convection be forecasted. Convective wind forecasting is a very challenging problem that requires new statistically based modeling techniques since conventional meteorologically based methods do not perform well. New predictive analytic based forecasting methods were constructed using R statistical software and incorporate several techniques including multiple linear regression, logistic regression, multinomial logistic regression, classification and regression trees (CART), and ensemble CART using bootstrapping. All of

  7. Electrical Conductivity Of Diamond Up To 1,200 Degrees C

    NASA Technical Reports Server (NTRS)

    Vandersande, Jan W.; Zoltan, Leslie D.

    1993-01-01

    Report discusses measurements of electrical conductivities of two synthetic diamond films, three synthetic diamondlike films, and two natural type IIa diamonds at temperatures from ambient to 1,200 degrees C. Measurements performed to compare electrical conductivities of state-of-the-art diamond films with those of natural insulating diamond, particularly at temperatures above 700 degrees C.

  8. Sensing the water content of honey from temperature-dependent electrical conductivity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In order to predict water content in honey, electrical conductivity was measured on blossom honey types of milk-vetch, jujube and yellow-locust with water content of 18%-37% between 5-40ºC. Regression models of electrical conductivity were developed as functions of water content and temperature. The...

  9. 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...

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

    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.

  11. Phase transitions in U3O8- z: II. Electrical conductivity measurement

    NASA Astrophysics Data System (ADS)

    Naito, Keiji; Tsuji, Toshihide; Ohya, Fumiaki

    1983-02-01

    Phase transition in U3O8- z was studied by means of electrical conductivity measurement and X-ray diffraction technique in the temperature range from room temperature to 1073 K. It was found that the break in a linear relation between the electrical conductivity and the reciprocal temperature which corresponds to the phase transition varies with the O/U ratio, the heat treatment of the sample and the heating rate during the electrical conductivity measurement. From the electrical conductivity and X-ray diffraction studies, phase transition in ` U3O8- z is concluded to be an order-disorder type based on the configurational change of U(V) and U(VI) ions with structural changes from orthorhombic to hexagonal. A phase diagram in U3O8- z was proposed from the electrical conductivity, X-ray diffraction and heat capacity data.

  12. Impurity effects on electrical conductivity of doped bilayer graphene in the presence of a bias voltage

    NASA Astrophysics Data System (ADS)

    E, Lotfi; H, Rezania; B, Arghavaninia; M, Yarmohammadi

    2016-07-01

    We address the electrical conductivity of bilayer graphene as a function of temperature, impurity concentration, and scattering strength in the presence of a finite bias voltage at finite doping, beginning with a description of the tight-binding model using the linear response theory and Green’s function approach. Our results show a linear behavior at high doping for the case of high bias voltage. The effects of electron doping on the electrical conductivity have been studied via changing the electronic chemical potential. We also discuss and analyze how the bias voltage affects the temperature behavior of the electrical conductivity. Finally, we study the behavior of the electrical conductivity as a function of the impurity concentration and scattering strength for different bias voltages and chemical potentials respectively. The electrical conductivity is found to be monotonically decreasing with impurity scattering strength due to the increased scattering among electrons at higher impurity scattering strength.

  13. High performance heat curing copper-silver powders filled electrically conductive adhesives

    NASA Astrophysics Data System (ADS)

    Cui, Hui-Wang; Jiu, Jin-Ting; Sugahara, Tohru; Nagao, Shijo; Suganuma, Katsuaki; Uchida, Hiroshi

    2015-03-01

    In this study, high performance electrically conductive adhesives were fabricated from a vinyl ester resin, a thermal initiator, silver coated copper powders, and pure silver powders, without using any other coupling agent, dispersing agent, and reducing agent. The heat cured copper-silver powders filled electrically conductive adhesives presented low bulk resistivity (e.g., 4.53 × 10-5 Ω·cm) due to the silver powders that had given high electrical conductivity to the adhesives, and high shear strength (e.g., 16.22 MPa) provided by the crosslinked structures of vinyl ester resin. These high performance copper-silver powders filled electrically conductive adhesives have lower cost than those filled by pure silver powders, which can be well used in the electronic packaging and can enlarge the application prospects of electrically conductive adhesives. [Figure not available: see fulltext.

  14. Investigation of Satellite Measurements in the Presence of Clouds, Forcing Influences on Clouds and Feedback to the Large Scale Following Convection

    NASA Technical Reports Server (NTRS)

    Warner, C.

    1984-01-01

    Satellite measurements during cloudy conditions, forces influencing clouds and large scale feedback following convection were investigated. The following conditions were studied: (1) passing marked thermal features aloft near the northern Bay of Bengal at the time of formation of the July 1979 monsoon depression; (2) recognition of regions of dense high overcast clouds in satellite radiances; (3) evolution of monsoon cloud systems and controlling factors on the clouds, and the effects of the clouds on thermodynamic and wind structures for improvements for numerical models are suggested.

  15. Electrical conductivity measurements of bacterial nanowires from Pseudomonas aeruginosa

    NASA Astrophysics Data System (ADS)

    Maruthupandy, Muthusamy; Anand, Muthusamy; Maduraiveeran, Govindhan; Sait Hameedha Beevi, Akbar; Jeeva Priya, Radhakrishnan

    2015-12-01

    The extracellular appendages of bacteria (flagella) that transfer electrons to electrodes are called bacterial nanowires. This study focuses on the isolation and separation of nanowires that are attached via Pseudomonas aeruginosa bacterial culture. The size and roughness of separated nanowires were measured using transmission electron microscopy (TEM) and atomic force microscopy (AFM), respectively. The obtained bacterial nanowires indicated a clear image of bacterial nanowires measuring 16 nm in diameter. The formation of bacterial nanowires was confirmed by microscopic studies (AFM and TEM) and the conductivity nature of bacterial nanowire was investigated by electrochemical techniques. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), which are nondestructive voltammetry techniques, suggest that bacterial nanowires could be the source of electrons—which may be used in various applications, for example, microbial fuel cells, biosensors, organic solar cells, and bioelectronic devices. Routine analysis of electron transfer between bacterial nanowires and the electrode was performed, providing insight into the extracellular electron transfer (EET) to the electrode. CV revealed the catalytic electron transferability of bacterial nanowires and electrodes and showed excellent redox activities. CV and EIS studies showed that bacterial nanowires can charge the surface by producing and storing sufficient electrons, behave as a capacitor, and have features consistent with EET. Finally, electrochemical studies confirmed the development of bacterial nanowires with EET. This study suggests that bacterial nanowires can be used to fabricate biomolecular sensors and nanoelectronic devices.

  16. Fuel cell assembly unit for promoting fluid service and electrical conductivity

    DOEpatents

    Jones, Daniel O.

    1999-01-01

    Fluid service and/or electrical conductivity for a fuel cell assembly is promoted. Open-faced flow channel(s) are formed in a flow field plate face, and extend in the flow field plate face between entry and exit fluid manifolds. A resilient gas diffusion layer is located between the flow field plate face and a membrane electrode assembly, fluidly serviced with the open-faced flow channel(s). The resilient gas diffusion layer is restrained against entering the open-faced flow channel(s) under a compressive force applied to the fuel cell assembly. In particular, a first side of a support member abuts the flow field plate face, and a second side of the support member abuts the resilient gas diffusion layer. The support member is formed with a plurality of openings extending between the first and second sides of the support member. In addition, a clamping pressure is maintained for an interface between the resilient gas diffusion layer and a portion of the membrane electrode assembly. Preferably, the support member is spikeless and/or substantially flat. Further, the support member is formed with an electrical path for conducting current between the resilient gas diffusion layer and position(s) on the flow field plate face.

  17. Enhancing the electrical conductivity of a hybrid POSS-PCL/graphene nanocomposite polymer.

    PubMed

    Nezakati, Toktam; Tan, Aaron; Seifalian, Alexander M

    2014-12-01

    An electrically conductive polymer using polyhedral oligomeric silsesquioxane (POSS) nanocage incorporated into a modified poly [caprolactone based urea-urethane] (PCL)/graphene hybrid nanocomposite is described. Multilayer graphene flakes (8nm) were homogeneously dispersed into POSS-PCL at 0.1, 2, 5, and 10wt.% concentrations. This dispersion process of the graphene flakes was achieved by the use of stable dimethylacetamide (DMAc), via solution intercalation with POSS-PCL nanocomposites. The impedance spectroscopy of 5.0wt.% and higher concentration of graphene in POSS-PCL represented major improvement in conductivity over pristine POSS-PCL. The percolation threshold occurred at 5.0wt.% graphene concentration, converting the insulator POSS-PCL into a conductive POSS-PCL/graphene hybrid nanocomposite. The structures of the obtained hybrid materials were characterized with atomic force microscopy (AFM), Fourier transform infra-red (FT-IR), and Raman spectroscopy. The conductivity of the resultant nanocomposite polymer was investigated with electrochemical impedance spectroscopy (EIS). Herein, for the first time, we demonstrate a facile method of synthesizing, and describe the electrical properties of a conductive POSS-PCL/graphene nanocomposite polymer. PMID:25240216

  18. Nanostructured Cu-Cr alloy with high strength and electrical conductivity

    SciTech Connect

    Islamgaliev, R. K. Nesterov, K. M.; Bourgon, J.; Champion, Y.; Valiev, R. Z.

    2014-05-21

    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.

  19. Electric conductivity of a hot hadron gas from a kinetic approach

    NASA Astrophysics Data System (ADS)

    Greif, Moritz; Greiner, Carsten; Denicol, Gabriel S.

    2016-05-01

    We calculate the electric conductivity of a gas of relativistic particles with isotropic cross sections using the Boltzmann equation as the starting point. Our analysis is restricted to elastic collisions. We show the perfect agreement with previously published numerical results for a massless quark-gluon plasma, and give results for the electric conductivity of an interacting hadron gas, employing realistic resonance cross sections. These results for the electric conductivity of a hot hadron gas, as created in (ultra)relativistic heavy-ion collisions, are of rich phenomenological as well as theoretical interest and can be compared to, e.g., lattice quantum field theory calculations.

  20. Tunable electrical conductivity in metal-organic framework thin film devices

    DOEpatents

    Talin, Albert Alec; Allendorf, Mark D.; Stavila, Vitalie; Leonard, Francois

    2016-05-24

    A composition including a porous metal organic framework (MOF) including an open metal site and a guest species capable of charge transfer that can coordinate with the open metal site, wherein the composition is electrically conductive. A method including infiltrating a porous metal organic framework (MOF) including an open metal site with a guest species that is capable of charge transfer; and coordinating the guest species to the open metal site to form a composition including an electrical conductivity greater than an electrical conductivity of the MOF.

  1. Effect of gamma irradiation on DC electrical conductivity of ZnO nanoparticles

    SciTech Connect

    Swaroop, K.; Somashekarappa, H. M.; Naveen, C. S.; Jayanna, H. S.

    2015-06-24

    The temperature dependent dc electrical conductivity of gamma irradiated Zinc oxide (ZnO) nanoparticles is presented in this paper. The X-ray diffraction (XRD) pattern shows hexagonal wurtzite structure of ZnO. Fourier Transform Infrared Spectroscopy (FTIR) confirms Zn-O stretching vibrations. UV-Visible spectroscopy studies show that the energy band gap (E{sub g}) of the prepared ZnO nanoparticles increases with respect to gamma irradiation dose, which can be related to room temperature dc electrical conductivity. The result shows significant variation in the high temperature dc electrical conductivity of ZnO nanoparticles due to gamma irradiation.

  2. Fluctuations of Electrical Conductivity: A New Source for Astrophysical Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Pétrélis, F.; Alexakis, A.; Gissinger, C.

    2016-04-01

    We consider the generation of a magnetic field by the flow of a fluid for which the electrical conductivity is nonuniform. A new amplification mechanism is found which leads to dynamo action for flows much simpler than those considered so far. In particular, the fluctuations of the electrical conductivity provide a way to bypass antidynamo theorems. For astrophysical objects, we show through three-dimensional global numerical simulations that the temperature-driven fluctuations of the electrical conductivity can amplify an otherwise decaying large scale equatorial dipolar field. This effect could play a role for the generation of the unusually tilted magnetic field of the iced giants Neptune and Uranus.

  3. Fluctuations of Electrical Conductivity: A New Source for Astrophysical Magnetic Fields.

    PubMed

    Pétrélis, F; Alexakis, A; Gissinger, C

    2016-04-22

    We consider the generation of a magnetic field by the flow of a fluid for which the electrical conductivity is nonuniform. A new amplification mechanism is found which leads to dynamo action for flows much simpler than those considered so far. In particular, the fluctuations of the electrical conductivity provide a way to bypass antidynamo theorems. For astrophysical objects, we show through three-dimensional global numerical simulations that the temperature-driven fluctuations of the electrical conductivity can amplify an otherwise decaying large scale equatorial dipolar field. This effect could play a role for the generation of the unusually tilted magnetic field of the iced giants Neptune and Uranus. PMID:27152784

  4. The mesoscale forcing of a midlatitude upper-tropospheric jet streak by a simulated convective system. 1: Mass circulation and ageostrophic processes

    NASA Technical Reports Server (NTRS)

    Wolf, Bart J.; Johnson, D. R.

    1995-01-01

    The mutual forcing of a midlatitude upper-tropospheric jet streak by organized mesoscale adiabatic and diabatic processes within a simulated convective system (SCS) is investigated. Using isentropic diagnostics, results from a three-dimensional numerical simulation of an SCS are examined to study the isallobaric flow field, modes of dominant ageostrophic motion, and stability changes in relation to the mutual interdependence of adiabatic processes and latent heat release. Isentropic analysis affords an explicit isolation of a component of isallobaric flow associated with diabatic processes within the SCS. Prior to convective development within the simulations, atmospheric destabilization occurs through adiabatic ageostrophic mass adjustment and low-level convergence in association with the preexisting synoptic-scale upper-tropospheric jet streak. The SCS develops in a baroclinic zone and quickly initiates a vigorous mass circulation. By the mature stage, a pronounced vertical couplet of low-level convergence and upper-level mass divergence is established, linked by intense midtropospoheric diabatic heating. Significant divergence persists aloft for several hours subsequent to SCS decay. The dominant role of ageostrophic motion within which the low-level mass convergence develops is the adiabatic isallobaric component, while the mass divergence aloft develops principally through the diabatic isallobaric component. Both compnents are intrinsically linked to the convectively forced vertical mass transport. The inertial diabatic ageostrophic component is largest near the level of maximum heating and is responsible for the development of inertial instability to the north of SCS, resulting in this quadrant being preferred for outflow. The inertial advective component, the dominant term that produces the new downstream wind maximum, rapidly develops north of the SCS and through mutual adjustment creates the baroclinic support for the new jet streak.

  5. Raman Shifting a Tunable ArF Excimer Laser to Wavelengths of 190 to 240 nm With a Forced Convection Raman Cell

    NASA Technical Reports Server (NTRS)

    Balla, R. Jeffrey; Herring, G. C.

    2000-01-01

    Tunable radiation, at ultraviolet wavelengths, is produced by Raman shifting a modified 285-mJ ArF excimer laser. Multiple Stokes outputs are observed in H2, CH4, D2, N2, SF6, and CF4 (20, 22, 53, 21, 2.1, and 0.35 percent, respectively). Numbers in parentheses are the first Stokes energy conversion efficiencies. We can access 70 percent of the frequency range 42000-52000 cm (exp -1) (190-240 nm) with Stokes energies that vary from 0.2 microJoule to 58 mJ inside the Raman cell. By using 110 mJ of pump energy and D 2 , the tunable first Stokes energy varies over the 29-58 mJ range as the wavelength is tuned over the 204-206 nm range. Dependence on input energy, gas pressure, He mixture fraction, and circulation of the gas in the forced convection Raman cell is discussed; Stokes conversion is also discussed for laser repetition rates from 1 to 100 Hz. An empirical equation is given to determine whether forced convection can improve outputs for a given repetition rate.

  6. A critical review of forced convection heat transfer and pressure drop of Al2O3, TiO2 and CuO nanofluids

    NASA Astrophysics Data System (ADS)

    Khurana, Deepak; Choudhary, Rajesh; Subudhi, Sudhakar

    2016-04-01

    Nanofluid is the colloidal suspension of nanosized solid particles like metals or metal oxides in some conventional fluids like water and ethylene glycol. Due to its unique characteristics of enhanced heat transfer compared to conventional fluid, it has attracted the attention of research community. The forced convection heat transfer of nanofluid is investigated by numerous researchers. This paper critically reviews the papers published on experimental studies of forced convection heat transfer and pressure drop of Al2O3, TiO2 and CuO based nanofluids dispersed in water, ethylene glycol and water-ethylene glycol mixture. Most of the researchers have shown a little rise in pressure drop with the use of nanofluids in plain tube. Literature has reported that the pumping power is appreciably high, only at very high particle concentration i.e. more than 5 %. As nanofluids are able to enhance the heat transfer at low particle concentrations so most of the researchers have used less than 3 % volume concentration in their studies. Almost no disagreement is observed on pressure drop results of different researchers. But there is not a common agreement in magnitude and mechanism of heat transfer enhancement. Few studies have shown an anomalous enhancement in heat transfer even at low particle concentration. On the contrary, some researchers have shown little heat transfer enhancement at the same particle concentration. A large variation (2-3 times) in Nusselt number was observed for few studies under similar conditions.

  7. Global Deep Convection Models of Saturn's Atmospheric Features

    NASA Astrophysics Data System (ADS)

    Heimpel, Moritz; Cuff, Keith; Gastine, Thomas; Wicht, Johannes

    2016-04-01

    The Cassini mission, along with previous missions and ground-based observations, has revealed a rich variety of atmospheric phenomena and time variability on Saturn. Some examples of dynamical features are: zonal flows with multiple jet streams, turbulent tilted shear flows that seem to power the jets, the north polar hexagon, the south polar cyclone, large anticyclones in "storm alley", numerous convective storms (white spots) of various sizes, and the 2010/2011 great storm, which destroyed an array of vortices dubbed the "string of pearls". Here we use the anelastic dynamo code MagIC, in non-magnetic mode, to study rotating convection in a spherical shell. The thickness of the shell is set to approximate the depth of the low electrical conductivity deep atmosphere of Saturn, and the convective forcing is set to yield zonal flows of similar velocity (Rossby number) to those of Saturn. Internal heating and the outer entropy boundary conditions allow simple modelling of atmospheric layers with neutral stability or stable stratification. In these simulations we can identify several saturnian and jovian atmospheric features, with some variations. We find that large anticyclonic vortices tend to form in the first anticyclonic shear zones away from the equatorial jet. Cyclones form at the poles, and polar polygonal jet streams, comparable to Saturn's hexagon, may or may not form, depending on the model conditions. Strings of small scale vortical structures arise as convective plumes near boundaries of shear zones. They typically precede larger scale convective storms that spawn propagating shear flow disturbances and anticyclonic vortices, which tend to drift across anticyclonic shear zones, toward the equator (opposite the drift direction of Saturn's 2010/2011 storm). Our model results indicate that many identifiable dynamical atmospheric features seen on Jupiter and Saturn arise from deep convection, shaped by planetary rotation, underlying and interacting with stably

  8. Numerical solution of an inverse electrocardiography problem for a medium with piecewise constant electrical conductivity

    NASA Astrophysics Data System (ADS)

    Denisov, A. M.; Zakharov, E. V.; Kalinin, A. V.; Kalinin, V. V.

    2010-07-01

    A numerical method is proposed for solving an inverse electrocardiography problem for a medium with a piecewise constant electrical conductivity. The method is based on the method of boundary integral equations and Tikhonov regularization.

  9. Simple Method for Estimating the Electrical Conductivity of Oxide Melts with Optical Basicity

    NASA Astrophysics Data System (ADS)

    Zhang, Guo-Hua; Chou, Kuo-Chih

    2010-02-01

    The electrical conductivity of oxide melts is an important physicochemical property for designing the electric smelting furnaces. Although the data of many slag systems have been measured, the quantitative relationships of electrical conductivity to slag composition and temperature are still limited. In this article, a model is proposed based on the optical basicity corrected for the cations required for the charge balance of {{AlO}}_{ 4}^{ 5- } , in which Arrhenius Law is used to describe the relationship between electrical conductivity and temperature. In this model, the activation energy is expressed as a linear function of the corrected optical basicity. Successful applications to CaO-MgO-Al2O3-SiO2 and CaO-Al2O3-SiO2 systems indicate that this model can work well in the electrical conductivity estimation.

  10. 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 ...

  11. Jump in the electrical conductivity of shock-compressed glassy carbon

    NASA Astrophysics Data System (ADS)

    Molodets, A. M.; Golyshev, A. A.; Emel'yanov, A. N.; Shul'ga, Yu. M.; Fortov, V. E.

    2014-04-01

    The effect of high dynamic pressures on the electrical conductivity of the amorphous conducting carbon phase (glassy carbon) has been studied. The electrical conductivity of glassy carbon samples has been measured under the condition of shock compression and subsequent release wave. The history of the shock loading of glassy carbon has been calculated with the developed semiempirical equations of state. It has been shown the electrical conductivity of glassy carbon samples in the compression phase at a pressure of 45(5) GPa decreases abruptly by two orders of magnitude. In the relief phase, partially reversible change in the electrical conductivity of an amorphous carbon sample occurs. The recorded effect has been treated as a result of a partially reversible physicochemical transformation of shock-compressed amorphous carbon.

  12. A promising structure for fabricating high strength and high electrical conductivity copper alloys

    PubMed Central

    Li, Rengeng; Kang, Huijun; Chen, Zongning; Fan, Guohua; Zou, Cunlei; Wang, Wei; Zhang, Shaojian; Lu, Yiping; Jie, Jinchuan; Cao, Zhiqiang; Li, Tingju; Wang, Tongmin

    2016-01-01

    To address the trade-off between strength and electrical conductivity, we propose a strategy: introducing precipitated particles into a structure composed of deformation twins. A Cu-0.3%Zr alloy was designed to verify our strategy. Zirconium was dissolved into a copper matrix by solution treatment prior to cryorolling and precipitated in the form of Cu5Zr from copper matrix via a subsequent aging treatment. The microstructure evolutions of the processed samples were investigated by transmission electron microscopy and X-ray diffraction analysis, and the mechanical and physical behaviours were evaluated through tensile and electrical conductivity tests. The results demonstrated that superior tensile strength (602.04 MPa) and electrical conductivity (81.4% IACS) was achieved. This strategy provides a new route for balancing the strength and electrical conductivity of copper alloys, which can be developed for large-scale industrial application. PMID:26856764

  13. Highly Electrically Conductive Nanocomposites Based on PolymerInfused Graphene Sponges

    PubMed Central

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

    2014-01-01

    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

  14. In situ electrical conductivity measurements of H2O under static pressure up to 28 GPa

    NASA Astrophysics Data System (ADS)

    Liu, Bao; Gao, Yang; Han, Yonghao; Ma, Yanzhang; Gao, Chunxiao

    2016-08-01

    The in situ electrical conductivity measurements on water in both solid state and liquid state were performed under pressure up to 28 GPa and temperature from 77 K to 300 K using a microcircuit fabricated on a diamond anvil cell (DAC). Water chemically ionization mainly contributes to electrical conduction in liquid state, which is in accord with the results obtained under dynamic pressure. Energy band theory of liquid water was used to understand effect of static pressure on electrical conduction of water. The electric conductivity of H2O decreased discontinuously by four orders of magnitude at 0.7-0.96 GPa, indicating water frozen at this P-T condition. Correspondingly, the conduction of H2O in solid state is determined by arrangement and bending of H-bond in ice VI and ice VII. Based on Jaccard theory, we have concluded that the charge carriers of ice are already existing ions and Bjerrum defects.

  15. The electrical conductivity of CuCrZr alloy after SPD processing

    NASA Astrophysics Data System (ADS)

    Lipińska, M.; Bazarnik, P.; Lewandowska, M.

    2014-08-01

    CuCrZr alloys exhibit very good relation between mechanical properties and electrical conductivity. However, for its use in some advanced applications improvement of mechanical strength while preserving high electrical conducting is required. Therefore, in this work a CuCrZr alloy was subjected to a series of thermo-mechanical treatments, including solution annealing and water quenching, SPD processing (using hydrostatic extrusion and ECAP) as well as aging in order to improve mechanical strength. The influence of these processing procedures on microstructure features and mechanical properties was determined by TEM observation and microhardness measurements, respectively. Electrical conductivity of the samples was measured by four-points method. The results have shown that it is possible to improve mechanical strength while preserving good electrical conductivity by a proper combination of SPD processing and heat treatment.

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

    DOEpatents

    Tran, Nang T.; Gilbert, James R.

    1992-08-04

    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.

  17. Electrical Conductivity of Molten CdCl2 at Temperatures as High as 1474 K

    NASA Astrophysics Data System (ADS)

    Salyulev, Alexander B.; Potapov, Alexei M.

    2016-07-01

    The electrical conductivity of molten CdCl2 was measured across a wide temperature range (ΔT=628 K), from 846 K to as high as 1474 K, i.e. 241° above the normal boiling point of the salt. In previous studies, a maximum temperature of 1201 K was reached, this being 273° lower than in the present work. The activation energy of electrical conductivity was calculated.

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

    SciTech Connect

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

    1987-07-01

    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.

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

    USGS Publications Warehouse

    McCleskey, R. Blaine

    2011-01-01

    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.

  20. Sensing the water content of honey from temperature-dependent electrical conductivity

    NASA Astrophysics Data System (ADS)

    Guo, Wenchuan; Liu, Yi; Zhu, Xinhua; Zhuang, Hong

    2011-08-01

    In order to predict the water content in honey, electrical conductivity was measured on blossom honey types milk-vetch, jujube and yellow-locust with the water content of 18-37% between 5 and 40 °C. The regression models of electrical conductivity were developed as functions of water content and temperature. The results showed that increases in either water content or temperature resulted in an increase in the electrical conductivity of honey with greater changes at higher water content and/or higher temperature. The linear terms of water content and temperature, a quadratic term of water content, and the interaction effect of water content and temperature had significant influence on the electrical conductivity of honey (p < 0.0001). Regardless of blossom honey type, the linear coefficient of the determination of measured and calculated electrical conductivities was 0.998 and the range error ratio was larger than 100. These results suggest that the electrical conductivity of honey might be used to develop a detector for rapidly predicting the water content in blossom honey.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    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.

  2. Effects of high magnetic fields on thermal convection of conductive aqueous solution

    NASA Astrophysics Data System (ADS)

    Wang, Yan; Hirota, Noriyuki; Okada, Hidehiko; Sakka, Yoshio

    2015-07-01

    Effects of magnetic fields on the thermal convection in conductive aqueous solutions at ambient temperatures have been studied through heat transport measurements combined with shadowgraph technique-based visualization. The suppression of thermal convection by magnetic field was in fact observed in conductive diamagnetic aqueous solutions of ammonium sulfate. The magnitude of the suppression was found to depend on the applied magnetic field and the electrical conductivity of the sample fluid. These effects are qualitatively understood by assuming that Lorentz force acting on the fluid is a main player. Based on these results, a control method of heat transfer process using high magnetic fields has been demonstrated. It seems feasible to understand the behaviors of liquid metals by using electrolytes aqueous solution combined with a superconducting magnet, since flow conditions thereby are regarded as similar to those for liquid metals in industrial electromagnets.

  3. Experimental investigation of forced convective heat transfer performance in nanofluids of Al2O3/water and CuO/water in a serpentine shaped micro channel heat sink

    NASA Astrophysics Data System (ADS)

    Sivakumar, A.; Alagumurthi, N.; Senthilvelan, T.

    2016-07-01

    The microchannels are device used to remove high heat fluxes from smaller area. In this experimental research work the heat transfer performance of nanofluids of Al2O3/water and CuO/water were compared. The important character of such fluids is the enhanced thermal conductivity, in comparison with base fluid without considerable alteration in physical and chemical properties. The effect of forced convective heat transfer coefficient was calculated using serpentine shaped microchannel heat exchanger. Furthermore we calculated the forced convective heat transfer coefficient of the nanofluids using theoretical correlations in order to compare the results with the experimental data. The heat transfer coefficient for different particle concentration and temperature were analysed using forced convection heat transfer using nanofluids. The findings indicate considerable enhancement in convective heat transfer coefficient of the nanofluids as compared to the basefluid. The results also shows that CuO/water nanofluid has increased heat transfer coefficient compared with Al2O3/water and base fluids. Moreover the experimental results indicate there is increased forced convective heat transfer coefficient with the increase in nano particle concentration.

  4. Intraseasonal Forcing of Lightning and Convective Activity in the Southern Amazon as a Function of Cross Equatorial Flow

    NASA Astrophysics Data System (ADS)

    Petersen, W. A.; Fu, R.; Blakeslee, R.; Chen, M.

    2003-12-01

    Recently, Wang and Fu (2002) developed a monsoon-index (V-index; VI), based on changes in cross-equatorial 925 hPa meridional wind flow in the northwest Amazon. This index appears to be a robust metric of seasonal and intraseasonal changes in precipitation regime (e.g., wet vs. dry) across the Amazon and other parts of South America. While the VI identifies continental-scale variability of the monsoon, it yields no information on structural changes in the convective regime. For example, how does the overall three-dimensional structure of convection change as a function of VI-regime? Similarly, how are transitions in VI-regime manifested in lightning trends? In an effort to answer these questions we have examined four wet seasons (Dec.-Mar., 1998-2001) of TRMM satellite Lightning Imaging Sensor (LIS) and Precipitation Radar (PR) data in addition to two wet seasons (2000-2001) of ground-based Brazilian Lightning Detection Network (BLDN) data over South America. Composited LIS data indicate that the most statistically significant wide-spread response to VI-regime changes occurs over the south-central Amazon (SCAMZ), with other noticeable variations observed over portions of the subtropical Altiplano and Parana River basin. Most notably, over the SCAMZ both LIS and BLDN lightning data suggest for the southerly (northerly) VI-regime: 1) a pronounced widespread increase (decrease) in lightning activity; 2) a marked increase (decrease) in the amplitude of the diurnal cycle of lightning; (3) in association with (1) and (2), a factor of two relative increase (decrease) in the probability of any radar reflectivity pixel exceeding 30 dBZ above the freezing level; (4) an associated 20% increase (decrease) in pixel-mean ice water contents between the 7 and 11 km levels; and (5) an increase (decrease) in the relative frequency of occurrence of large rain rates. Interestingly, while our results suggest the presence of more vertically developed convection, lightning, attendant ice

  5. A New Program To Study Gravity Wave Forcing of The Mesosphere and Lower Thermosphere: Mountain and Convective Waves Ascending Vertically (macwave)

    NASA Astrophysics Data System (ADS)

    Goldberg, R. A.

    Gravity waves provide the dominant forcing of the mesosphere and lower thermo- sphere under solstice conditions via energy and momentum transports from lower al- titudes and their dissipation in the MLT. Despite this, the quantitative aspects of this important forcing are poorly understood at present. Furthermore, dynamical forcing must be considered when evaluating the chemical processes affecting this region. The correlative rocket and ground-based program described here will address the above issues with launch sequences during summer and winter conditions in 2002-2003. In summer, launch sequences coupled with ground-based measurements at the Andøya Rocket Range (ARR) in Norway will address the forcing of the summer mesopause environment by anticipated convective and shear generated gravity waves. Two 12-hr rocket sequences will be employed to provide sensitivity to strong and weak forc- ing conditions, each involving one Terrier-Orion payload accompanied by a mix of MET rockets and balloons, at Andøya Rocket Range (ARR) in Norway. Additional European payloads (MIDAS, Dusty) will enhance the measurements of turbulence and related parameters in the atmosphere. Correlative instrumentation will include the ALOMAR radars and lidars (including the new CSU/CoRA sodium lidar), ESRANGE MST and meteor radars (ESRAD), radiosondes, and TIMED satellite measurements of thermal and constituent structures. The winter program (February 2003) will study the upward propagation and penetration of mountain waves from northern Norway into the MLT at a site favored for such penetration. As the major response will be down- stream (east) of the Norwegian coast and will vary with MLT winds, these motions will be measured with similar 12-hr rocket sequences, but at ESRANGE in Sweden. Ground based measurements will once again include the ALOMAR facilities coupled with radar and lidar observatories as ESRANGE. The data in both cases will be used to define the wave field structure, fluxes

  6. Dehydration of chlorite explains anomalously high electrical conductivity in the mantle wedges.

    PubMed

    Manthilake, Geeth; Bolfan-Casanova, Nathalie; Novella, Davide; Mookherjee, Mainak; Andrault, Denis

    2016-05-01

    Mantle wedge regions in subduction zone settings show anomalously high electrical conductivity (~1 S/m) that has often been attributed to the presence of aqueous fluids released by slab dehydration. Laboratory-based measurements of the electrical conductivity of hydrous phases and aqueous fluids are significantly lower and cannot readily explain the geophysically observed anomalously high electrical conductivity. The released aqueous fluid also rehydrates the mantle wedge and stabilizes a suite of hydrous phases, including serpentine and chlorite. In this present study, we have measured the electrical conductivity of a natural chlorite at pressures and temperatures relevant for the subduction zone setting. In our experiment, we observe two distinct conductivity enhancements when chlorite is heated to temperatures beyond its thermodynamic stability field. The initial increase in electrical conductivity to ~3 × 10(-3) S/m can be attributed to chlorite dehydration and the release of aqueous fluids. This is followed by a unique, subsequent enhancement of electrical conductivity of up to 7 × 10(-1) S/m. This is related to the growth of an interconnected network of a highly conductive and chemically impure magnetite mineral phase. Thus, the dehydration of chlorite and associated processes are likely to be crucial in explaining the anomalously high electrical conductivity observed in mantle wedges. Chlorite dehydration in the mantle wedge provides an additional source of aqueous fluid above the slab and could also be responsible for the fixed depth (120 ± 40 km) of melting at the top of the subducting slab beneath the subduction-related volcanic arc front. PMID:27386526

  7. Dehydration of chlorite explains anomalously high electrical conductivity in the mantle wedges

    PubMed Central

    Manthilake, Geeth; Bolfan-Casanova, Nathalie; Novella, Davide; Mookherjee, Mainak; Andrault, Denis

    2016-01-01

    Mantle wedge regions in subduction zone settings show anomalously high electrical conductivity (~1 S/m) that has often been attributed to the presence of aqueous fluids released by slab dehydration. Laboratory-based measurements of the electrical conductivity of hydrous phases and aqueous fluids are significantly lower and cannot readily explain the geophysically observed anomalously high electrical conductivity. The released aqueous fluid also rehydrates the mantle wedge and stabilizes a suite of hydrous phases, including serpentine and chlorite. In this present study, we have measured the electrical conductivity of a natural chlorite at pressures and temperatures relevant for the subduction zone setting. In our experiment, we observe two distinct conductivity enhancements when chlorite is heated to temperatures beyond its thermodynamic stability field. The initial increase in electrical conductivity to ~3 × 10−3 S/m can be attributed to chlorite dehydration and the release of aqueous fluids. This is followed by a unique, subsequent enhancement of electrical conductivity of up to 7 × 10−1 S/m. This is related to the growth of an interconnected network of a highly conductive and chemically impure magnetite mineral phase. Thus, the dehydration of chlorite and associated processes are likely to be crucial in explaining the anomalously high electrical conductivity observed in mantle wedges. Chlorite dehydration in the mantle wedge provides an additional source of aqueous fluid above the slab and could also be responsible for the fixed depth (120 ± 40 km) of melting at the top of the subducting slab beneath the subduction-related volcanic arc front. PMID:27386526

  8. Electronmagnetic induction probe calibration for electrical conductivity measurements and moisture content determination of Hanford high level waste

    SciTech Connect

    Wittekind, W.D., Westinghouse Hanford

    1996-05-23

    Logic of converting EMI measured electrical conductivity to moisture with expected uncertainty. Estimates from present knowledge, assumptions, and measured data. Archie`s Law has been used since the 1940`s to relate electrical conductivity in porous media to liquid volume fraction. Measured electrical conductivity to moisture content uses: Porosity, Interstitial liquid electrical conductivity, Solid particle density,Interstitial liquid density, and interstitial liquid water content. The uncertainty of assumed values is calculated to determine the final moisture wt.% result uncertainty.

  9. Effect of magnetic field on the forced convection heat transfer and pressure drop of a magnetic nanofluid in a miniature heat sink

    NASA Astrophysics Data System (ADS)

    Ashjaee, Mehdi; Goharkhah, Mohammad; Khadem, Leila Azizi; Ahmadi, Reza

    2014-12-01

    The effect of an external magnetic field on the forced convection heat transfer and pressure drop of water based Fe3O4 nanofluid (ferrofluid) in a miniature heat sink is studied experimentally. The heat sink with the dimensions of 40 mm (L) × 40 mm (W) × 10 mm (H) consists of an array of five circular channels with diameter and length of 4 and 40 mm, respectively. It is heated from the bottom surface with a constant heat flux while the other surfaces are insulated. The heat sink is also influenced by an external magnetic field generated by an electromagnet. The local convective coefficients are measured at various flow rates (200 < Re < 900), magnetic field intensities (B < 1,400 G), and particle volume fractions (φ = 0.5, 1, 2 and 3 %). Results show that using ferrofluid results in a maximum of 14 % improvement in heat transfer compared to the pure water, in the absence of magnetic field. This value grows up to 38 % when a magnetic field with the strength of 1,200 G is applied to the ferrofluid. On the other hand, it is observed that the significant heat transfer enhancement due to the magnetic field is always accompanied by a pressure drop penalty. The optimum operating condition is obtained based on the maximum heat transfer enhancement per pressure loss.

  10. Fast drying of biocompatible polymer films loaded with poorly water-soluble drug nano-particles via low temperature forced convection.

    PubMed

    Susarla, Ramana; Sievens-Figueroa, Lucas; Bhakay, Anagha; Shen, Yueyang; Jerez-Rozo, Jackeline I; Engen, William; Khusid, Boris; Bilgili, Ecevit; Romañach, Rodolfo J; Morris, Kenneth R; Michniak-Kohn, Bozena; Davé, Rajesh N

    2013-10-15

    Fast drying of nano-drug particle laden strip-films formed using water-soluble biocompatible polymers via forced convection is investigated in order to form films having uniform drug distribution and fast dissolution. Films were produced by casting and drying a mixture of poorly water soluble griseofulvin (GF) nanosuspensions produced via media milling with aqueous hydroxypropyl methylcellulose (HPMC E15LV) solutions containing glycerin as a plasticizer. The effects of convective drying parameters, temperature and air velocity, and film-precursor viscosity on film properties were investigated. Two major drying regimes, a constant rate period as a function of the drying conditions, followed by a single slower falling rate period, were observed. Films dried in an hour or less without any irreversible aggregation of GF nanoparticles with low residual water content. Near-infrared chemical imaging (NIR-CI) and the content uniformity analysis indicated a better drug particle distribution when higher viscosity film-precursors were used. Powder X-ray diffraction showed that the GF in the films retained crystallinity and the polymorphic form. USP IV dissolution tests showed immediate release (~20 min) of GF. Overall, the films fabricated from polymer-based suspensions at higher viscosity dried at different conditions exhibited similar mechanical properties, improved drug content uniformity, and achieved fast drug dissolution. PMID:23911341

  11. Numerical analysis of interaction between non-gray radiation and forced convection flow over a recess using the full-spectrum k-distribution method

    NASA Astrophysics Data System (ADS)

    Atashafrooz, M.; Gandjalikhan Nassab, S. A.; Lari, K.

    2016-02-01

    In the present work, the interaction between non-gray radiation and forced convection in a laminar radiating gas flow over a recess including two backward and forward facing steps in a duct is investigated numerically. Distributions of absorption coefficients across the spectrum (50 cm-1 < η < 20,000 cm-1) are obtained from the HITRAN2008 database. The full-spectrum k-distribution method is used to account for non-gray radiation properties, while the gray radiation calculations are carried out using the Planck mean absorption coefficient. To find the divergence of radiative heat flux distribution, the radiative transfer equation is solved by the discrete ordinates method. The effects of radiation-conduction parameter, wall emissivity, scattering coefficient and recess length on heat transfer behaviors of the convection-radiation system are investigated for both gray and non-gray mediums. In addition, the results of gray medium are compared with non-gray results in order to judge if the differences between these two approaches are significant enough to justify the usage of non-gray models. Results show that for air mixture with 10 % CO2 and 20 % H2O, use of gray model for the radiative properties may cause significant errors and should be avoided.

  12. Time-domain reflectometry: Simultaneous measurement of soil water content and electrical conductivity with a single probe

    USGS Publications Warehouse

    Dalton, F.N.; Herkelrath, W.N.; Rawlins, D.S.; Rhoades, J.D.

    1984-01-01

    Two parallel metallic rods were used as a wave guide to measure the dielectric constant and electrical conductivity of soils having different electrical conductivities but the same water content. Measurements showed that the two parameters were sufficiently independent to permit simultaneous determinations of water content and bulk electrical conductivity.

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

    SciTech Connect

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

    1983-09-01

    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.

  14. Electrical conductivity of lawsonite and dehydrating fluids at high pressures and temperatures

    NASA Astrophysics Data System (ADS)

    Manthilake, Geeth; Mookherjee, Mainak; Bolfan-Casanova, Nathalie; Andrault, Denis

    2015-09-01

    Lawsonite is a calcium-aluminum bearing hydrous silicate mineral with CaAl2Si2O7(OH)2.H2O stoichiometry. It is thermodynamically stable in the hydrated oceanic crust. Low-velocity anomalies observed in the cold subducted slabs have been related to the unusual shear wave velocities of lawsonite eclogite. However, electrical conductivity of lawsonite at high pressure and temperature remains unknown. In this study, we measured the electrical conductivity of lawsonite at 7 GPa, and temperatures ranging from 298 K-1320 K. At 1173 K, the electrical conductivity of lawsonite is around 10-1 S/m. A sharp increase of electrical conductivity is observed at temperatures exceeding the dehydration ~1258 K. The high electrical conductivity up to 101 S/m observed in our experiments is due to the presence of highly conductive fluid and could explain the low resistivity observed at 150-250 km depths in subduction zone settings such as NE Japan, northern, and central Chile.

  15. Electrical conductivity of synergistically hybridized nanocomposites based on graphite nanoplatelets and carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Safdari, M.; Al-Haik, M.

    2012-10-01

    In this investigation, a recent model for assessing the electrical conductivity of nanocomposites comprising a single type of conductive nanofiller was expanded to cases with mixtures of nanofillers. The extended model considers electron tunneling as the effective mechanism for insulator-conductor transition. The model was validated with relevant experimental data based on a mono-nanofiller. Using the extended model, the effective electrical conductivity of a nanocomposite comprising both graphite nanoplatelets and carbon nanotubes was investigated. It was observed that the hybridized nanocomposites filled with a mixture of these conductive nanofillers attain, synergistically, enhanced electrical conductivities at lower volume fractions. The lower filler contents assist in preserving the intrinsic properties of the host polymer in support of several applications. It was also observed that the relative aspect ratios of the conductive fillers play significant roles on the electrical conductivity of the hybrid nanocomposite. Simulations revealed that, generally, the addition of minimal amounts of a higher aspect ratio auxiliary phase to a lower aspect ratio main phase enhances the electrical conductivity of the composite by orders of magnitude

  16. Electrical conductivity of synergistically hybridized nanocomposites based on graphite nanoplatelets and carbon nanotubes.

    PubMed

    Safdari, M; Al-Haik, M

    2012-10-12

    In this investigation, a recent model for assessing the electrical conductivity of nanocomposites comprising a single type of conductive nanofiller was expanded to cases with mixtures of nanofillers. The extended model considers electron tunneling as the effective mechanism for insulator-conductor transition. The model was validated with relevant experimental data based on a mono-nanofiller. Using the extended model, the effective electrical conductivity of a nanocomposite comprising both graphite nanoplatelets and carbon nanotubes was investigated. It was observed that the hybridized nanocomposites filled with a mixture of these conductive nanofillers attain, synergistically, enhanced electrical conductivities at lower volume fractions. The lower filler contents assist in preserving the intrinsic properties of the host polymer in support of several applications. It was also observed that the relative aspect ratios of the conductive fillers play significant roles on the electrical conductivity of the hybrid nanocomposite. Simulations revealed that, generally, the addition of minimal amounts of a higher aspect ratio auxiliary phase to a lower aspect ratio main phase enhances the electrical conductivity of the composite by orders of magnitude. PMID:22990008

  17. The mesoscale forcing of a midlatitude upper-tropospheric jet streak by a simulated convective system. 2: Kinetic energy and resolution analysis

    NASA Technical Reports Server (NTRS)

    Wolf, Bart J.; Johnson, D. R.

    1995-01-01

    A kinetic energy (KE) analysis of the forcing of a mesoscale upper-tropospheric jet streak by organized diabatic processes within the simulated convective system (SCS) that was discussed in Part 1 is presented in this study. The relative contributions of the ageostrophic components of motion to the generation of KE of the convectively generated jet streak are compared, along with the KE generation by the rotational (nondivergent) and irrotational (divergent) mass transport. The sensitivity of the numerical simulations of SCS development to resolution is also briefly examined. Analysis within isentropic coordinates provides for an explicit determination of the influence of the diabatic processes on the generation of KE. The upper-level production of specific KE is due predominatly to the inertial advective ageostrophic component (IAD), and as such represents the primary process through which the KE of the convectively generated jet streak is realized. A secondary contribution by the inertial diabatic (IDI) term is observed. Partitioning the KE generation into its rotational and irrotational components reveals that the latter, which is directly linked to the diabatic heating within the SCS through isentropic continuity requirements, is the ultimate source of KE generation as the global area integral of generation by the rotational component vanishes. Comparison with an identical dry simulation reveals that the net generation of KE must be attributed to latent heating. Both the IAD and IDI ageostrophic components play important roles in this regard. Examination of results from simulations conducted at several resolutions supports the previous findings in that the effects of diabatic processes and ageostrophic motion on KE generation remain consistent. Resolution does impact the location and timing of SCS development, a result that has important implications in forecasting the onset of convection that develops from evolution of the large-scale flow and moisture

  18. Force.

    ERIC Educational Resources Information Center

    Gamble, Reed

    1989-01-01

    Discusses pupil misconceptions concerning forces. Summarizes some of Assessment of Performance Unit's findings on meaning of (1) force, (2) force and motion in one dimension and two dimensions, and (3) Newton's second law. (YP)

  19. Turbulent generation and mechanism analysis of forced-convective heat transfer enhancement by applying electric fields in the restricted region near the wall

    SciTech Connect

    Hasegawa, Masato; Yabe, Akira; Nariai, Hideki

    1999-07-01

    The heat transfer enhancement method of applying electric fields only near a heat transfer wall was numerically investigated. Generation of additional turbulence in the near-wall region occurs by the interaction between migrating electric charges and the turbulent flow of weakly electrically conductive fluids such as refrigerants, oils, and chlorofluorocarbon (CFC) alternatives. Based on electrostatic probe experiments, the authors assumed that the current was mainly transferred by the negative charges. They solved the Navier-Stokes equation with a Coulomb force term, the conservation equation of electric current, the Poisson equation of electric potential, and the energy equation. They used the Large Eddy Simulation (LES) method to represent the turbulence. The numerical analysis showed a heat transfer enhancement of 2.8 times for turbulent flow (Re = 1.8 x 10{sup 4}) when applying 5 kV to the near-wall region, 5 mm from the wall. The simulations for different distances between the coupled electrodes showed that an optimum location of the electrodes exists for achieving the lowest electric power input for a given electric field strength. They also evaluated the heat efficiency in a simple heat exchanger system using this heat transfer enhancement method. For the 5 kV/5 mm condition, where 19% of the total input power was consumed by the electric field, they achieved a heat transfer enhancement of 27 times compared to the case when an equivalent, additional amount of input power would be consumed by the pump to increase the flow rate of the heat-transfer fluid.

  20. Noninvasive estimation of transmitral pressure drop across the normal mitral valve in humans: importance of convective and inertial forces during left ventricular filling

    NASA Technical Reports Server (NTRS)

    Firstenberg, M. S.; Vandervoort, P. M.; Greenberg, N. L.; Smedira, N. G.; McCarthy, P. M.; Garcia, M. J.; Thomas, J. D.

    2000-01-01

    OBJECTIVES: We hypothesized that color M-mode (CMM) images could be used to solve the Euler equation, yielding regional pressure gradients along the scanline, which could then be integrated to yield the unsteady Bernoulli equation and estimate noninvasively both the convective and inertial components of the transmitral pressure difference. BACKGROUND: Pulsed and continuous wave Doppler velocity measurements are routinely used clinically to assess severity of stenotic and regurgitant valves. However, only the convective component of the pressure gradient is measured, thereby neglecting the contribution of inertial forces, which may be significant, particularly for nonstenotic valves. Color M-mode provides a spatiotemporal representation of flow across the mitral valve. METHODS: In eight patients undergoing coronary artery bypass grafting, high-fidelity left atrial and ventricular pressure measurements were obtained synchronously with transmitral CMM digital recordings. The instantaneous diastolic transmitral pressure difference was computed from the M-mode spatiotemporal velocity distribution using the unsteady flow form of the Bernoulli equation and was compared to the catheter measurements. RESULTS: From 56 beats in 16 hemodynamic stages, inclusion of the inertial term ([deltapI]max = 1.78+/-1.30 mm Hg) in the noninvasive pressure difference calculation significantly increased the temporal correlation with catheter-based measurement (r = 0.35+/-0.24 vs. 0.81+/-0.15, p< 0.0001). It also allowed an accurate approximation of the peak pressure difference ([deltapc+I]max = 0.95 [delta(p)cathh]max + 0.24, r = 0.96, p<0.001, error = 0.08+/-0.54 mm Hg). CONCLUSIONS: Inertial forces are significant components of the maximal pressure drop across the normal mitral valve. These can be accurately estimated noninvasively using CMM recordings of transmitral flow, which should improve the understanding of diastolic filling and function of the heart.

  1. Composition and Manufacturing Effects on Electrical Conductivity of Li/FeS 2 Thermal Battery Cathodes

    DOE PAGESBeta

    Reinholz, Emilee L.; Roberts, Scott A.; Apblett, Christopher A.; Lechman, Jeremy B.; Schunk, P. Randall

    2016-06-11

    The electrical conductivity is key to the performance of thermal battery cathodes. In this work we present the effects of manufacturing and processing conditions on the electrical conductivity of Li/FeS2 thermal battery cathodes. Finite element simulations were used to compute the conductivity of three-dimensional microcomputed tomography cathode microstructures and compare results to experimental impedance spectroscopy measurements. A regression analysis reveals a predictive relationship between composition, processing conditions, and electrical conductivity; a trend which is largely erased after thermally-induced deformation. Moreover, the trend applies to both experimental and simulation results, although is not as apparent in simulations. This research is amore » step toward a more fundamental understanding of the effects of processing and composition on thermal battery component microstructure, properties, and performance.« less

  2. Facile Synthesis and Electrical Conductivity of Carbon Nanotube Reinforced Nanosilver Composite

    NASA Astrophysics Data System (ADS)

    Pal, Hemant; Sharma, Vimal; Kumar, Rajesh; Thakur, Nagesh

    2012-12-01

    Metal matrix nanocomposites reinforced with carbon nanotubes (CNTs) have become popular in industrial applications. Due to their excellent thermophysical and mechanical properties, CNTs are considered as attractive filler for the improvement in properties of metals. In the present work, we have synthesized noncovalently functionalized CNT reinforced nanosilver composites by using a modified molecular level mixing method. The structure and morphology of nanocomposites are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy dispersive spectroscopy. The electrical conductivity of silver-CNT nanocomposites measured by the four-point probe method is found to be more than that of the pure nanosilver. The significant improvement in electrical conductivity of Ag=CNT nanocomposites stems from homogenous and embedded distribution of CNTs in a silver matrix with intact structure resulting from noncovalent functionalization. The low temperature sintering also enhances the electrical conductivity of Ag=CNT nanocomposites.

  3. Size-dependent electrical conductivity of indium zinc oxide deposited by RF magnetron sputtering.

    PubMed

    Heo, Young-Woo; Pearton, S J; Norton, D P

    2012-04-01

    We investigated the size-dependent electrical conductivities of indium zinc oxide stripes with different widths from 50 nm to 4 microm and with the same thickness of 50 nm deposited by RF magnetron sputtering. The size of the indium zinc oxide stripes was controlled by e-beam lithography. The distance of the two Ti/Au Ohmic electrodes along the indium zinc oxide stripes was kept constant at 25 microm. The electrical conductivity decreased as the size of the indium zinc oxide stripes decreased below a critical width (80 nm). The activation energy, derived from the electric conductivity versus temperature measurement, was dependent on the dimensions of indium zinc oxide stripes. These results can be understood as stemming from surface charge trapping from the absorption of oxygen and/or water vapor, which leads to an increase in the energy difference between the conduction energy band and the Fermi energy. PMID:22849102

  4. “SIGMELTS”: A web portal for electrical conductivity calculations in geosciences

    NASA Astrophysics Data System (ADS)

    Pommier, A.; Le-Trong, E.

    2011-09-01

    Electrical conductivity measurements in the laboratory are critical for interpreting geoelectric and magnetotelluric profiles of the Earth's crust and mantle. In order to facilitate access to the current database on electrical conductivity of geomaterials, we have developed a freely available web application (SIGMELTS) dedicated to the calculation of electrical properties. Based on a compilation of previous studies, SIGMELTS computes the electrical conductivity of silicate melts, carbonatites, minerals, fluids, and mantle materials as a function of different parameters, such as composition, temperature, pressure, water content, and oxygen fugacity. Calculations on two-phase mixtures are also implemented using existing mixing models for different geometries. An illustration of the use of SIGMELTS is provided, in which calculations are applied to the subduction zone-related volcanic zone in the Central Andes. Along with petrological considerations, field and laboratory electrical data allow discrimination between the different hypotheses regarding the formation and rise from depth of melts and fluids and quantification of their storage conditions.

  5. Quantum transport in strongly disordered crystals: Electrical conductivity with large negative vertex corrections

    NASA Astrophysics Data System (ADS)

    Janiš, Václav; Pokorný, Vladislav

    2012-12-01

    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.

  6. Seebeck effect influence on joule heat evolution in electrically conductive silicate materials

    NASA Astrophysics Data System (ADS)

    Fiala, Lukáš; Medved, Igor; Maděra, Jiří; Černý, Robert

    2016-07-01

    In general, silicate building materials are non-conductive matters that are not able to evolve heat when they are subjected to an external voltage. However, the electrical conductivity can be increased by addition of electrically conductive admixtures in appropriate amount which leads to generation of conductive paths in materials matrix. Such enhanced materials can evolve Joule heat and are utilizable as a core of self-heating or snow-melting systems. In this paper, Joule heat evolution together with Seebeck effect in electrically conductive silicate materials was taken into consideration and the model based on heat equation with included influence of DC electric field was proposed. Besides, a modeling example of heating element was carried out on FEM basis and time development of temperature in chosen surface points was expressed in order to declare ability of such system to be applicable.

  7. Electrical conductivity anomaly beneath Mare Serenitatis detected by Lunokhod 2 and Apollo 16 magnetometers

    NASA Technical Reports Server (NTRS)

    Vanian, L. L.; Vnuchkova, T. A.; Egorov, I. V.; Basilevskii, A. T.; Eroshenko, E. G.; Fainberg, E. B.; Dyal, P.; Daily, W. D.

    1979-01-01

    Magnetic fluctuations measured by the Lunokhod 2 magnetometer in the Bay Le Monnier are distinctly anisotropic when compared to simultaneous Apollo 16 magnetometer data measured 1100 km away in the Descartes highlands. This anisotropy can be explained by an anomalous electrical conductivity of the upper mantle beneath Mare Serenitatis. A model is presented of anomalously lower electrical conductivity beneath Serenitatis and the simultaneous magnetic data from the Lunokhod 2 site at the mare edge and the Apollo 16 site are compared to the numerically calculated model solutions. This comparison indicates that the anisotropic fluctuations can be modeled by a nonconducting layer in the lunar lithosphere which is 150 km thick beneath the highlands and 300 km thick beneath Mare Serenitatis. A decreased electrical conductivity in the upper mantle beneath the mare may be due to a lower temperature resulting from heat carried out the magma source regions to the surface during mare flooding.

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

    DOEpatents

    Worsley, Marcus A.; Baumann, Theodore F.; Satcher, Jr, Joe H.

    2016-07-05

    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.

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

    DOEpatents

    Worsley, Marcus A; Baumann, Theodore F; Satcher, Jr., Joe H

    2014-04-01

    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.

  10. Electrical conductivity of MgCO 3 at high pressures and high temperatures

    NASA Astrophysics Data System (ADS)

    Mibe, Kenji; Ono, S.

    2011-05-01

    The electrical conductivity of polycrystalline magnesite (MgCO 3) was measured at 3-6 GPa at high temperatures using complex impedance spectroscopy in a multi-anvil high-pressure apparatus. The electrical conductivity increased with increasing pressure. The activation enthalpy calculated in the temperature range 650-1000 K also increased with increasing pressure. The effect of pressure was interpreted as being the activation volume in the Arrhenius equation, and the fitted data gave an activation energy and volume of 1.76±0.03 eV and -3.95±0.78 cm 3/mole, respectively. The negative activation volume and relatively large activation energy observed in this study suggests that the hopping of large polarons is the dominant mechanism for the electrical conductivity over the pressure and temperature range investigated.

  11. Fluctuations of electrical conductivity: a new source for astrophysical magnetic fields

    NASA Astrophysics Data System (ADS)

    Gissinger, Christophe; Petrelis, Francois; Alexakis, Alexandros

    2016-04-01

    We consider the generation of magnetic field by the flow of a fluid for which the electrical conductivity is nonuniform. We calculate the properties of this effect both analytically and numerically, and find a new amplification mechanism leading to dynamo action for flows much simpler than those considered so far. In particular, the fluctuations of the electrical conductivity provide a way to bypass anti-dynamo theorems. For astrophysical objects, we show through three-dimensional global numerical simulations that the temperature-driven fluctuations of the electrical conductivity can amplify an otherwise decaying large scale equatorial dipolar field. This effect could play a role for the generation of the unusually tilted magnetic field of the iced giants Neptune and Uranus.

  12. Understanding Electrical Conduction States in WO3 Thin Films Applied for Resistive Random-Access Memory

    NASA Astrophysics Data System (ADS)

    Ta, Thi Kieu Hanh; Pham, Kim Ngoc; Dao, Thi Bang Tam; Tran, Dai Lam; Phan, Bach Thang

    2016-05-01

    The electrical conduction and associated resistance switching mechanism of top electrode/WO3/bottom electrode devices [top electrode (TE): Ag, Ti; bottom electrode (BE): Pt, fluorine-doped tin oxide] have been investigated. The direction of switching and switching ability depended on both the top and bottom electrode material. Multiple electrical conduction mechanisms control the leakage current of such switching devices, including trap-controlled space-charge, ballistic, Ohmic, and Fowler-Nordheim tunneling effects. The transition between electrical conduction states is also linked to the switching (SET-RESET) process. This is the first report of ballistic conduction in research into resistive random-access memory. The associated resistive switching mechanisms are also discussed.

  13. Electrical conductivity as a constraint on lower mantle thermo-chemical structure

    NASA Astrophysics Data System (ADS)

    Deschamps, Frédéric; Khan, Amir

    2016-09-01

    Electrical conductivity of the Earth's mantle depends on both temperature and compositional parameters. Radial and lateral variations in conductivity are thus potentially a powerful means to investigate its thermo-chemical structure. Here, we use available electrical conductivity data for the major lower mantle minerals, bridgmanite and ferropericlase, to calculate 3D maps of lower mantle electrical conductivity for two possible models: a purely thermal model, and a thermo-chemical model. Both models derive from probabilistic seismic tomography, and the thermo-chemical model includes, in addition to temperature anomalies, variations in volume fraction of bridgmanite and iron content. The electrical conductivity maps predicted by these two models are clearly different. Compared to the purely thermal model, the thermo-chemical model leads to higher electrical conductivity, by about a factor 2.5, and stronger lateral anomalies. In the lowermost mantle (2000-2891 km) the thermo-chemical model results in a belt of high conductivity around the equator, whose maximum value reaches ∼120% of the laterally-averaged value and is located in the low shear-wave velocity provinces imaged in tomographic models. Based on our electrical conductivity maps, we computed electromagnetic response functions (C-responses) and found, again, strong differences between the C-responses for purely thermal and thermo-chemical models. At periods of 1 year and longer, C-responses based on thermal and thermo-chemical models are easily distinguishable. Furthermore, C-responses for thermo-chemical model vary geographically. Our results therefore show that long-period (1 year and more) variations of the magnetic field may provide key insights on the nature and structure of the deep mantle.

  14. Simultaneous measurement of electrical conductance and thermopower of single benzenedithiol molecular junctions

    NASA Astrophysics Data System (ADS)

    Kaneko, Satoshi; Nakamura, Yuuga; Matsushita, Ryuuji; Marqués-González, Santiago; Kiguchi, Manabu

    2015-06-01

    We have developed a system for the simultaneous measurement of electrical conductance and thermopower of the single benzenedithiol (BDT) molecular junction, which was characterized by inelastic electron tunneling spectroscopy, at low temperature. The simultaneous measurements revealed a negative correlation between the electrical conductance and the thermopower. Strong metal-molecule coupling at the single BDT molecular junction leads to high conductance and low thermopower because of the broadening of the conduction orbital, which explains the negative correlation. The observed fluctuation in conductance and thermopower reflects the change in the metal-molecule contact configuration and molecular orientation.

  15. Ion Pair in Extreme Aqueous Environments, Molecular-Based and Electric Conductance Approaches

    SciTech Connect

    Chialvo, Ariel A; Gruszkiewicz, Miroslaw {Mirek} S; Simonson, J Michael {Mike}; Palmer, Donald; Cole, David R

    2009-01-01

    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.

  16. Remarkable enhancement of the electrical conductivity of carbon nanostructured thin films after compression.

    PubMed

    Georgakilas, Vasilios; Koutsioukis, Apostolos; Petr, Martin; Tucek, Jiri; Zboril, Radek

    2016-06-01

    In this work, we demonstrate a significant improvement in the electrical conductivity of carbon nanostructured thin films, composed of graphene nanosheets and multiwalled carbon nanotubes, by compression/polishing. It is shown that the sheet resistance of compressed thin films of carbon nanostructures and hybrids is remarkably decreased in comparison with that of as-deposited films. The number of the interconnections, the distance between the nanostructures as well as their orientation are highly altered by the compression favoring the electrical conductivity of the compressed samples. PMID:27215186

  17. Electrically conductive doped block copolymer of polyacetylene and polyisoprene. [Soluble in organic solvents

    DOEpatents

    Aldissi, M.

    1984-06-27

    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.

  18. Dynamic electrical conduction in p-type CuIn3Se5

    NASA Astrophysics Data System (ADS)

    Essaleh, L.; Marín, G.; Wasim, S. M.; Alimoussa, A.; Bourial, A.

    2016-04-01

    In this work, ac electrical conductivity measurements were studied for the first time in p type bulk ternary semiconductor compound CuIn3Se5. The dynamic electrical conductivity is analyzed in the frequency range 20 Hz to 1 MHz and temperature from 308 K to 500 K. The relaxation times for the grain and grain boundaries were studied from the second derivative of electric modulus versus frequency at various temperatures. The relaxation time is found to decrease with increasing temperature and to obey the Arrhenius relationship. The values of activation energies for conduction and relaxation times are obtained.

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

    NASA Astrophysics Data System (ADS)

    Binbin, Jie; Chihtang, Sah

    2014-04-01

    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.

  20. The influence of nanoparticle migration on forced convective heat transfer of nanofluid under heating and cooling regimes.

    PubMed

    Kozlova, Sofya V; Ryzhkov, Ilya I

    2014-09-01

    In this paper, laminar convective heat transfer of water-alumina nanofluid in a circular tube with uniform heat flux at the tube wall is investigated. The investigation is performed numerically on the basis of two-component model, which takes into account nanoparticle transport by diffusion and thermophoresis. Two thermal regimes at the tube wall, heating and cooling, are considered and the influence of nanoparticle migration on the heat transfer is analyzed comparatively. The intensity of thermophoresis is characterized by a new empirical model for thermophoretic mobility. It is shown that the nanoparticle volume fraction decreases (increases) in the boundary layer near the wall under heating (cooling) due to thermophoresis. The corresponding variations of nanofluid properties and flow characteristics are presented and discussed. The intensity of heat transfer for the model with thermophoresis in comparison to the model without thermophoresis is studied by plotting the dependence of the heat transfer coefficient on the Peclet number. The effectiveness of water-alumina nanofluid is analyzed by plotting the average heat transfer coefficient against the required pumping power. The analysis of the results reveals that the water-alumina nanofluid shows better performance in the heating regime than in the cooling regime due to thermophoretic effect. PMID:25260328

  1. Effect of microscale protrusions on local fluid flow and mass transport in the presence of forced convection

    SciTech Connect

    Matzen, G.W.

    1997-01-01

    Three-dimensional creeping flow around single, axisymmetric protrusions is studied numerically using the boundary-integral technique. Emphasis is placed upon cylindrical protrusions on plane walls for various height-to-radius (h-to-a) aspect ratios, but cones and sections of spheres protruding from plane walls are also briefly examined. The presented items include shear-stress distributions, shear-stress contours, extents of the fluid-flow disturbance, total forces and torques on the cylinders, streamlines, and skin-friction lines. Also included is a discussion of flow topology around axisymmetric geometries. No flow reversal is observed for cylindrical protrusions with aspect ratios greater than 2.4 to 2.6. At higher aspect ratios, the fluid tends to be swept around cylindrical protrusions with little vertical motion. At lower aspect ratios, the strength of the recirculation increases, and the recirculation region becomes wider in the transverse direction and narrower in the flow direction. Also, the recirculation pattern begins to resemble the closed streamline patterns in two-dimensional flow over square ridges. However, unlike two-dimensional flow, closed streamline patterns are not observed. For arbitrary axisymmetric geometries, the extent of the fluid-flow disturbance can be estimated with the total force that is exerted on the protrusion. When the same force is exerted on protrusions with different aspect ratios, the protrusion with the higher aspect ratio tends to have a greater disturbance in the flow direction and a smaller disturbance in the transverse direction. The total force exerted on cylindrical protrusions with rounded corners is only slightly lower than the total force exerted on cylindrical protrusions with sharp corners.

  2. Inductive Measurement of Plasma Jet Electrical Conductivity (MSFC Center Director's discretionary Fund). Part 2

    NASA Technical Reports Server (NTRS)

    Turner, M. W.; Hawk, C. W.; Litchford, R. J.

    2001-01-01

    Measurement of plasma jet electrical conductivity has utility in the development of explosively driven magnetohydrodynamic (MHD) energy converters as well as magnetic flux compression reaction chambers for nuclear/chemical pulse propulsion and power. Within these types of reactors, the physical parameter of critical importance to underlying MHD processes is the magnetic Reynolds number, the value of which depends upon the product of plasma electrical conductivity and velocity. Therefore, a thorough understanding of MHD phenomena at high magnetic Reynolds number is essential, and methods are needed for the accurate and reliable measurement of electrical conductivity in high-speed plasma jets. It is well known that direct measurements using electrodes suffer from large surface resistance, and an electrodeless technique is desired. To address this need, an inductive probing scheme, originally developed for shock tube studies, has been adapted. In this method, the perturbation of an applied magnetic field by a plasma jet induces a voltage in a search coil, which, in turn, can be used to infer electrical conductivity through the inversion of a Fredholm integral equation of the first kind. A 1-in.-diameter probe using a light-gas gun. Exploratory laboratory experiments were carried out using plasma jets expelled from 15-g shaped charges. Measured conductivities were in the range of 4 kS/m for unseeded octol charges and 26 kS/m for seeded octol charges containing 2-percent potassium carbonate by mass.

  3. Mechanically robust, electrically conductive and stimuli-responsive binary network hydrogels enabled by superelastic graphene aerogels.

    PubMed

    Qiu, Ling; Liu, Diyan; Wang, Yufei; Cheng, Chi; Zhou, Kun; Ding, Jie; Truong, Van-Tan; Li, Dan

    2014-05-28

    The architecture of the nanofiller phase in polymer nanocomposites matters! Polymer hydrogels that can combine stimuli-responsiveness with excellent electrically conductivity and mechanical strength can be fabricated by incorporation of the polymer into an ultralight and superelastic graphene aerogel to form a binary network. PMID:24634392

  4. The effect of temperature on the electric conductivity of poly(dimethyl siloxane) ferromagnetic gel.

    PubMed

    Kubisz, L; Skumiel, A; Hornowski, T; Szlaferek, A; Pankowski, E

    2008-05-21

    In this paper the influence of temperature on the electrical conductivity of a ferromagnetic gel is investigated. The material used was poly(dimethyl siloxane) (PDMS) gel which contained randomly distributed magnetite nanosized particles. The electrical conductivity was measured by means of the two-point dc method. During the heating of the PDMS in the temperature range of 295-460 K the electrical conductivity increased from about 2 × 10(-12) to 2 × 10(-8) S m(-1). A study of the current-temperature dependence obtained during subsequent heating runs revealed two subranges of temperature characterized by different activation energies. The presence of these subranges could be explained either by the liberation of two different types of charge carrier or by the increase in the degree of polymer cross-linking. In the upper temperature subrange (420-460 K) both types of charge carrier probably contribute to the electrical conductivity of PDMS ferromagnetic gel. PMID:21694247

  5. Estimating Depth to Argillic Soil Horizons using Apparent Electrical Conductivity Response Functions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Maps of apparent electrical conductivity (ECa) of the soil profile are widely used in precision agriculture practice and research. A number of ECa sensors are commercially available, each with a unique response function (i.e., the relative contribution of soil at each depth to the integrated ECa rea...

  6. Finite Element Analysis of Hepatic Radiofrequency Ablation Probes using Temperature-Dependent Electrical Conductivity

    PubMed Central

    Chang, Isaac

    2003-01-01

    Background Few finite element models (FEM) have been developed to describe the electric field, specific absorption rate (SAR), and the temperature distribution surrounding hepatic radiofrequency ablation probes. To date, a coupled finite element model that accounts for the temperature-dependent electrical conductivity changes has not been developed for ablation type devices. While it is widely acknowledged that accounting for temperature dependent phenomena may affect the outcome of these models, the effect has not been assessed. Methods The results of four finite element models are compared: constant electrical conductivity without tissue perfusion, temperature-dependent conductivity without tissue perfusion, constant electrical conductivity with tissue perfusion, and temperature-dependent conductivity with tissue perfusion. Results The data demonstrate that significant errors are generated when constant electrical conductivity is assumed in coupled electrical-heat transfer problems that operate at high temperatures. These errors appear to be closely related to the temperature at which the ablation device operates and not to the amount of power applied by the device or the state of tissue perfusion. Conclusion Accounting for temperature-dependent phenomena may be critically important in the safe operation of radiofrequency ablation device that operate near 100°C. PMID:12780939

  7. Analytic formulation for the ac electrical conductivity in two- temperature, strongly coupled, overdense plasma: FORTRAN subroutine

    SciTech Connect

    Cauble, R.; Rozmus, W.

    1993-10-21

    A FORTRAN subroutine for the calculation of the ac electrical conductivity in two-temperature, strongly coupled, overdense plasma is presented. The routine is the result of a model calculation based on classical transport theory with application to plasmas created by the interaction of short pulse lasers and solids. The formulation is analytic and the routine is self-contained.

  8. Application of Skin Electrical Conductance of Acupuncture Meridians for Ureteral Calculus: A Case Report

    PubMed Central

    Lin, Wu-Chou; Chen, Yung-Hsiang; Xu, Jian-Ming; Chen, Der-Cherng; Chen, Wen-Chi; Lee, Chao-Te

    2011-01-01

    Renal colic is a common condition seen in the emergency department (ED). Our recent study showed that measures of electrical conductance may be used as supplementary diagnostic methods for patients with acute renal colic. Here, we describe the case of a 30-year-old male subject with a left ureteral calculus who presented with frequency and normal-looking urine. He had already visited the outpatient department, but in vain. Normal urinalysis and nonobstructive urogram were reported at that time. Two days later, he was admitted to the ED because of abdominal pain in the left lower quadrant. The urinalysis did not detect red blood cells. Ultrasonography did not indicate hydronephrosis. The meridian electrical conductance and index of sympathovagal balance were found to be abnormal. High level of electrical conductance on the left bladder meridian was found. An unenhanced helical computed tomography was scheduled to reveal a left ureterovesical stone. Ureteroscopic intervention was later uneventfully performed, and the patient's pain was relieved. The follow-up measurements showed that the meridian parameters had returned to normal one month after treatment. This case suggests that bladder meridian electrical conductance might be used as a supplemental method for ureteral calculus diagnosis. PMID:24533191

  9. Electric Conduction in Semiconductors: A Pedagogical Model Based on the Monte Carlo Method

    ERIC Educational Resources Information Center

    Capizzo, M. C.; Sperandeo-Mineo, R. M.; Zarcone, M.

    2008-01-01

    We present a pedagogic approach aimed at modelling electric conduction in semiconductors in order to describe and explain some macroscopic properties, such as the characteristic behaviour of resistance as a function of temperature. A simple model of the band structure is adopted for the generation of electron-hole pairs as well as for the carrier…

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Zone soil sampling is a method in which a field sampling is based on identifying homogenous areas using an easy to measure ancillary attribute such as apparent soil electrical conductivity (ECa). This study determined if ECa-directed zone sampling in two fields in northeastern Colorado could correc...

  11. PREDOMINANT PROPERTIES AFFECTING PROFILE SOIL ELECTRICAL CONDUCTIVITY IN THE US MIDWEST

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Commercially available sensors for measuring apparent profile soil electrical conductivity (ECa) can provide an indirect indication of a number of soil physical and chemical properties helpful in characterizing within-field variability for precision agriculture. The objective of this research was to...

  12. Locating groundwater discharge in large lakes using bottom sediment electrical conductivity mapping

    NASA Astrophysics Data System (ADS)

    Harvey, F. Edwin; Lee, David R.; Rudolph, David L.; Frape, Shaun K.

    1997-11-01

    Groundwater-surface water studies that use conventional near-shore piezometers and /or seepage meters are impractical in larger, areal extensive lakes, as they require exorbitant numbers of instruments to quantify groundwater discharge zones. In smaller lakes an electrical conductivity mapping method has proven useful in mapping groundwater discharge zones. The technique identifies groundwater discharge by measuring variations in sediment pore water electrical conductivity and reduces the number of instruments necessary to quantify inflow, thereby lowering instrumentation costs and increasing a study's efficiency. This study sought to determine the technique's applicability in larger lakes. Thus the method was tested within the Hamilton Harbour, at the western end of Lake Ontario. This study found systematic variations between nearshore and offshore sediments and identified three anomalous zones that were thought to represent groundwater inflow. Onshore and offshore piezometers were used to verify the presence of upward gradients and elevated electrical conductivities. The sediment probe survey provided qualitative maps of areas of elevated electrical conductivity indicative of groundwater discharge and allowed a fairly extensive shoreline to be mapped quickly and economically. Survey results guided the installation of nearshore piezometers to discharge zones, eliminating the inefficiency of more conventional "hit or miss" point source installation approaches. This research demonstrated that the sediment probe was a valuable tool for studying groundwater inputs into large lakes.

  13. Electrical conductivity measurement of MgCO3 up to 6 GPa and 1000 K

    NASA Astrophysics Data System (ADS)

    Mibe, K.; Ono, S.

    2012-04-01

    Magnesite, MgCO3, is a naturally occurring carbonate mineral and is stable over a wide range of pressure and temperature. It is known that magnesite is one of the important host phases of carbon in the Earth's deep interior. A knowledge of how magnesite's electrical properties vary as a function of pressure and temperature will be important in interpreting the observed electrical conductivity map of the Earth's interior. We, therefore, measured the electrical conductivity of polycrystalline magnesite at pressures 3-6 GPa at high temperatures using complex impedance spectroscopy in a multi-anvil high-pressure apparatus. Synthetic powdered magnesite (MgCO3)(purity > 99.5%) was used as the starting material. The measured electrical conductivity increased with increasing pressure. The activation enthalpy calculated in the temperature range 650-1000 K also increased with increasing pressure. The effect of pressure was interpreted as being the activation volume in the Arrhenius equation, and the fitted data gave an activation energy and volume of 1.76 ± 0.03 eV and -3.95 ± 0.78 cm3/mole, respectively. The negative activation volume and relatively large activation energy observed in this study suggests that the hopping of large polarons is the dominant mechanism for the electrical conductivity over the pressure and temperature range investigated.

  14. Density, Electrical Conductivity and Viscosity of Hg(0.8)Cd(0.2)Te Melt

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

    The density, viscosity, and electrical conductivity of Hg(0.8)Cd(0.2)Te melt were measured as a function of temperature. A pycnometric method was used to measure the melt density in the temperature range of 1072 to 1122 K. The viscosity and electrical conductivity were determined using a transient torque method from 1068 to 1132 K. The density result from this study is within 0.3% of the published data. However, the current viscosity result is approximately 30% lower than the existing data. The electrical conductivity of Hg(0.8)Cd(0.2)Te melt as a function of temperature, which is not available in the literature, is also determined. The analysis of the temperature dependent electrical conductivity and the relationship between the kinematic viscosity and density indicated that the structure of the melt appeared to be homogeneous when the temperature was above 1090 K. A structural transition occurred in the Hg(0.8)Cd(0.2)Te melt as the temperature was decreased to below 1090 K

  15. 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...

  16. Thermal battery. [solid metal halide electrolytes with enhanced electrical conductance after a phase transition

    DOEpatents

    Carlsten, R.W.; Nissen, D.A.

    1973-03-06

    The patent describes an improved thermal battery whose novel design eliminates various disadvantages of previous such devices. Its major features include a halide cathode, a solid metal halide electrolyte which has a substantially greater electrical conductance after a phase transition at some temperature, and a means for heating its electrochemical cells to activation temperature.

  17. Electrical conductivity of orthopyroxene: Implications for the water content of the asthenosphere

    PubMed Central

    Dai, Lidong; Karato, Shun-ichiro

    2009-01-01

    Electrical conductivity of minerals is sensitive to water content and hence can be used to infer the water content in the mantle. However, previous studies to infer the water content in the upper mantle were based on pure olivine model of the upper mantle. Influence of other minerals particularly that of orthopyroxene needs to be included to obtain a better estimate of water content in view of the high water solubility in this mineral. Here we report new results of electrical conductivity measurements on orthopyroxene, and apply these results to estimate the water content of the upper mantle of Earth. We found that the electrical conductivity of orthopyroxene is enhanced by the addition of water in a similar way as other minerals such as olivine and pyrope garnet. Using these new results, we calculate the electrical conductivity of pyrolite mantle as a function of water content and temperature incorporating the temperature and water fugacity-dependent hydrogen partitioning. Reported values of asthenosphere conductivity of 4 × 10−2−10−1 S/m corresponds to the water content of 0.01–0.04 wt%, a result in good agreement with the petrological model of the upper mantle. PMID:20009379

  18. Relationship between cotton yield and soil electrical conductivity, topography, and landsat imagery

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Understanding spatial and temporal variability in crop yield is a prerequisite to implementing site-specific management of crop inputs. Apparent soil electrical conductivity (ECa), soil brightness, and topography are easily obtained data that can explain yield variability. The objectives of this stu...

  19. ESTIMATING PLANT-AVAILABLE WATER CAPACITY FOR CLAYPAN LANDSCAPES USING APPARENT ELECTRICAL CONDUCTIVITY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Within-field variability of plant available water (PAW) capacity is useful information for site-specific management, but is expensive to assess using traditional measurements. For Missouri claypan soils, relationships between soil apparent electrical conductivity (ECa) and topsoil thickness have bee...

  20. Estimating spatial variations in water content of clay soils from time-lapse electrical conductivity surveys

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil water content (theta) is one of the most important drivers for many biogeochemical fluxes at different temporal and spatial scales. Hydrogeophysical non-invasive sensors that measure the soil apparent electrical conductivity (ECa) have been widely used to infer spatial and temporal patterns of...

  1. Estimating depth to argillic soil horizons using apparent electrical conductivity response functions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Maps of apparent electrical conductivity (ECa) of the soil profile are widely used in precision agriculture practice and research. A number of ECa sensors are commercially available, each with a unique response function (i.e., the relative contribution of soil at each depth to the integrated ECa rea...

  2. Use of fathometers and electrical-conductivity probes to monitor riverbed scour at bridge piers

    USGS Publications Warehouse

    Hayes, D.C.; Drummond, F.E.

    1995-01-01

    Two methods, a fathometer system and an electrical- conductivity probe system, were developed to monitor scour at bridge piers. The scour-monitoring systems consisted of a sensor (fathometer or electrical- conductivity probe), power supply, data logger, relay, and system program. The fathometer system was installed and tested at a bridge over the Leipsic River at Leipsic, Delaware, and at a bridge over Sinepuxent Bay near Ocean City. Maryland. Field data collected indicate that fathometers can be used to identify and monitor the riverbed elevation if post processing of the data and trends in the data are used to determine the riverbed location in relation to the transducer. The accuracy of the system is approximately the same as the resolution of the fathometer. Signal scatter can be a major source of error in the data. The electrical- conductivity probe system was installed and tested at a bridge over the Pamunkey River near Hanover, Virginia. The approximate elevation of the riverbed is determined by comparing conductivities of the surface-water flow with conductivities of submerged bed material from sensors located in each. Field data collected indicate that an electrical- conductivity probe, as tested, has limited usefulness in identifying and monitoring the riverbed elevation during high flows. As the discharge increases, the concentration of sediment in the surface-water flow increases, especially near the riverbed. Conductivities, measured at the sensors in the surface-water flow could not be distinguished from conductivities measured at the shallowest sensor in the submerged bed material.

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

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

    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.

  4. Development of an angular scanning system for sensing vertical profiles of soil electrical conductivity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Apparent soil electrical conductivity (EC**a**) is typically mapped to define soil spatial variability within an agricultural field. Knowledge of the vertical variability of EC**a** is desired to define site-specific behavior of the soil profile. A Pneumatic Angular Scanning System (PASS) was develo...

  5. Combining Proximal and Penetrating Soil Electrical Conductivity Sensors for High Resolution Digital Soil Mapping

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Proximal ground conductivity sensors produce high spatial resolution maps that integrate the bulk electrical conductivity (ECa) of the soil profile. Variability in conductivity maps must either be inverted to profile conductivity, or be directly calibrated to profile properties for meaningful interp...

  6. Estimation of soil physical properties from sensor-based soil strength and apparent electrical conductivity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Quantification of soil physical properties has traditionally been through soil sampling and laboratory analyses, which is time-, cost-, and labor-consuming, making it difficult to obtain the spatially-dense data required for precision agriculture. Soil strength and apparent electrical conductivity (...

  7. Measurements of the vertical atmospheric electric field and of the electrical conductivity with stratospheric balloons

    NASA Technical Reports Server (NTRS)

    Iversen, I. B.; Madsen, M. M.; Dangelo, N.

    1985-01-01

    Measurements of the atmospheric (vertical) electric field with balloons in the stratosphere are reported. The atmospheric electrical conductivity is also measured and the current density inferred. The average vertical current shows the expected variation with universal time and is also seen to be influenced by external (magnetospheric) electric fields.

  8. Effect of temperature-dependent electrical conductivity on transport processes in magnetosolidmechanics

    NASA Technical Reports Server (NTRS)

    Craig, G. T.; Arnas, O. A.

    1975-01-01

    The effect of temperature-dependent electrical conductivity on transport processes for a solid block is analyzed on the basis of a one-dimensional steady-state model under specified thermal boundary conditions. Assumptions are that the solid has an infinitely segmented electrode configuration, the magnetic field (By) may be resolved into a constant applied field and an induced field, the gradient of the electrochemical potential is equal to the electrostatic potential, a constant potential difference is applied externally across each pair of opposite electrodes, and all material properties except electrical conductivity are constant. Conductivity is expressed in normalized form in terms of a baseline conductivity and a constant for the material. The application of the assumptions of the model to the general phenomenological relations yields the governing equations. Solution of these equations gives the distribution of temperature, electric current density, and magnetic field strength along the length of the solid. It is shown that significant differences exist between the case for constant electrical conductivity and the case where electrical conductivity is temperature dependent.

  9. Laboratory studies of the electrical conductivity of silicate perovskites at high pressures and temperatures

    NASA Technical Reports Server (NTRS)

    Li, Xiaoyuan; Jeanloz, Raymond

    1990-01-01

    The electrical conductivities of two silicate perovskites and a perovskite-magnesiowuestite assemblage, all having an atomic ratio of Mg to Fe equal to 0.88/0.12, have been measured with alternating current and direct current (dc) techniques at simultaneously high pressures and temperatures. Measurements up to pressures of 80 GPa and temperatures of 3500 K, using a laser-heated diamond anvil cell, demonstrate that the electrical conductivity of these materials remains below 10-3 S/m at lower mantle conditions. The activation energies for electrical conduction are between 0.1 and 0.4 eV from the data, and the conduction in these perovskites is ascribed to an extrinsic electronic process. The new measurements are in agreement with a bound that was previously obtained from dc measurements for the high-PT conductivity of perovskite-dominated assemblages. The results show that the electrical conductivity of (Mg/0.88/Fe/0.12)SiO3 perovskite differs significantly from that of the earth's deep mantle, as inferred from geophysical observations.

  10. Electrical conductivity of orthopyroxene: implications for the water content of the asthenosphere.

    PubMed

    Dai, Lidong; Karato, Shun-ichiro

    2009-01-01

    Electrical conductivity of minerals is sensitive to water content and hence can be used to infer the water content in the mantle. However, previous studies to infer the water content in the upper mantle were based on pure olivine model of the upper mantle. Influence of other minerals particularly that of orthopyroxene needs to be included to obtain a better estimate of water content in view of the high water solubility in this mineral. Here we report new results of electrical conductivity measurements on orthopyroxene, and apply these results to estimate the water content of the upper mantle of Earth. We found that the electrical conductivity of orthopyroxene is enhanced by the addition of water in a similar way as other minerals such as olivine and pyrope garnet. Using these new results, we calculate the electrical conductivity of pyrolite mantle as a function of water content and temperature incorporating the temperature and water fugacity-dependent hydrogen partitioning. Reported values of asthenosphere conductivity of 4x10(-2)-10(-1) S/m corresponds to the water content of 0.01-0.04 wt%, a result in good agreement with the petrological model of the upper mantle. PMID:20009379

  11. Compartment D115, typical officer's stateroom, starboard side, note electrical conduct ...

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

    Compartment D-115, typical officer's stateroom, starboard side, note electrical conduct on ceiling, corrugated dividing wall, wood furnishings and cabinetry. Ceiling hook may have been used for hanging wet clothing or oilskins. (089) - USS Olympia, Penn's Landing, 211 South Columbus Boulevard, Philadelphia, Philadelphia County, PA

  12. Effect of Soil Water on Apparent Soil Electrical Conductivity and Texture Relationships in a Dryland Field.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Precision farming (PF) research has shown that when high salinity levels are not present, apparent soil electrical conductivity (ECa) is usually strongly correlated with soil texture. Mapping ECa has been promoted as a means for identifying management zones that are needed for variable application ...

  13. New down-hole TDR method for deep profile soil water content and bulk electrical conductivity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Comprehensive irrigation and salinity management both require accurate knowledge of field soil water content and bulk electrical conductivity to depths greater than the root zone depth in agricultural fields. Scientists at the USDA-ARS Conservation & Production Research Laboratory, Bushland, Texas, ...

  14. Electromechanical Actuator Ribbons Driven by Electrically Conducting Spring-Like Fibers.

    PubMed

    Chen, Peining; He, Sisi; Xu, Yifan; Sun, Xuemei; Peng, Huisheng

    2015-09-01

    Electrically conducting fibers are woven into polymer ribbons to prepare electromechanical actuators. The ribbons generate a strain rate of more than 10(3) times that of typical electrochemical actuators, accompanied by a lower operating voltage and faster responsiveness compared to electrostatic and electrothermal actuators. Programmable actuation including bending, contraction, elongation, and rotation are shown with a high reversibility. PMID:26192453

  15. 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...

  16. Column displacement experiments to evaluate electrical conductivity effects on electromagnetic soil water sensing

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Bulk electrical conductivity (EC) in superactive soils has been shown to strongly influence electromagnetic sensing of permittivity. However, these effects are dependent on soil water content and temperature as well as the pore water conductivity. We carried out isothermal column displacement experi...

  17. Remarkable enhancement of the electrical conductivity of carbon nanostructured thin films after compression

    NASA Astrophysics Data System (ADS)

    Georgakilas, Vasilios; Koutsioukis, Apostolos; Petr, Martin; Tucek, Jiri; Zboril, Radek

    2016-06-01

    In this work, we demonstrate a significant improvement in the electrical conductivity of carbon nanostructured thin films, composed of graphene nanosheets and multiwalled carbon nanotubes, by compression/polishing. It is shown that the sheet resistance of compressed thin films of carbon nanostructures and hybrids is remarkably decreased in comparison with that of as-deposited films. The number of the interconnections, the distance between the nanostructures as well as their orientation are highly altered by the compression favoring the electrical conductivity of the compressed samples.In this work, we demonstrate a significant improvement in the electrical conductivity of carbon nanostructured thin films, composed of graphene nanosheets and multiwalled carbon nanotubes, by compression/polishing. It is shown that the sheet resistance of compressed thin films of carbon nanostructures and hybrids is remarkably decreased in comparison with that of as-deposited films. The number of the interconnections, the distance between the nanostructures as well as their orientation are highly altered by the compression favoring the electrical conductivity of the compressed samples. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr09025c

  18. Electrical Conductivity of Molten ZnCl2 at Temperature as High as 1421 K

    NASA Astrophysics Data System (ADS)

    Salyulev, Alexander B.; Potapov, Alexei M.

    2015-02-01

    The electrical conductivity of molten ZnCl2 was measured in a wide temperature range (ΔT=863 K) to a temperature as high as 1421 K that is 417 degrees above the boiling point of the salt. At the temperature maximum of the own vapor pressure of the salt reached several megapascals.

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

    PubMed

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

    2014-11-26

    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 Ω/□, 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

  20. Estimates of olivine-basaltic melt electrical conductivity using a digital rock physics approach

    NASA Astrophysics Data System (ADS)

    Miller, Kevin J.; Montési, Laurent G. J.; Zhu, Wen-lu

    2015-12-01

    Estimates of melt content beneath fast-spreading mid-ocean ridges inferred from magnetotelluric tomography (MT) vary between 0.01 and 0.10. Much of this variation may stem from a lack of understanding of how the grain-scale melt geometry influences the bulk electrical conductivity of a partially molten rock, especially at low melt fraction. We compute bulk electrical conductivity of olivine-basalt aggregates over 0.02 to 0.20 melt fraction by simulating electric current in experimentally obtained partially molten geometries. Olivine-basalt aggregates were synthesized by hot-pressing San Carlos olivine and high-alumina basalt in a solid-medium piston-cylinder apparatus. Run conditions for experimental charges were 1.5 GPa and 1350 °C. Upon completion, charges were quenched and cored. Samples were imaged using synchrotron X-ray micro-computed tomography (μ-CT). The resulting high-resolution, 3-dimensional (3-D) image of the melt distribution constitutes a digital rock sample, on which numerical simulations were conducted to estimate material properties. To compute bulk electrical conductivity, we simulated a direct current measurement by solving the current continuity equation, assuming electrical conductivities for olivine and melt. An application of Ohm's Law yields the bulk electrical conductivity of the partially molten region. The bulk electrical conductivity values for nominally dry materials follow a power-law relationship σbulk = Cσmeltϕm with fit parameters m = 1.3 ± 0.3 and C = 0.66 ± 0.06. Laminar fluid flow simulations were conducted on the same partially molten geometries to obtain permeability, and the respective pathways for electrical current and fluid flow over the same melt geometry were compared. Our results indicate that the pathways for flow fluid are different from those for electric current. Electrical tortuosity is lower than fluid flow tortuosity. The simulation results are compared to existing experimental data, and the potential

  1. Electrical conductivity during incipient melting in the oceanic low-velocity zone.

    PubMed

    Sifré, David; Gardés, Emmanuel; Massuyeau, Malcolm; Hashim, Leila; Hier-Majumder, Saswata; Gaillard, Fabrice

    2014-05-01

    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

  2. Computational analysis of electrical conduction in hybrid nanomaterials with embedded non-penetrating conductive particles

    NASA Astrophysics Data System (ADS)

    Cai, Jizhe; Naraghi, Mohammad

    2016-08-01

    In this work, a comprehensive multi-resolution two-dimensional (2D) resistor network model is proposed to analyze the electrical conductivity of hybrid nanomaterials made of insulating matrix with conductive particles such as CNT reinforced nanocomposites and thick film resistors. Unlike existing approaches, our model takes into account the impenetrability of the particles and their random placement within the matrix. Moreover, our model presents a detailed description of intra-particle conductivity via finite element analysis, which to the authors’ best knowledge has not been addressed before. The inter-particle conductivity is assumed to be primarily due to electron tunneling. The model is then used to predict the electrical conductivity of electrospun carbon nanofibers as a function of microstructural parameters such as turbostratic domain alignment and aspect ratio. To simulate the microstructure of single CNF, randomly positioned nucleation sites were seeded and grown as turbostratic particles with anisotropic growth rates. Particle growth was in steps and growth of each particle in each direction was stopped upon contact with other particles. The study points to the significant contribution of both intra-particle and inter-particle conductivity to the overall conductivity of hybrid composites. Influence of particle alignment and anisotropic growth rate ratio on electrical conductivity is also discussed. The results show that partial alignment in contrast to complete alignment can result in maximum electrical conductivity of whole CNF. High degrees of alignment can adversely affect conductivity by lowering the probability of the formation of a conductive path. The results demonstrate approaches to enhance electrical conductivity of hybrid materials through controlling their microstructure which is applicable not only to carbon nanofibers, but also many other types of hybrid composites such as thick film resistors.

  3. The electrical conductivity during incipient melting in the oceanic low velocity zone

    PubMed Central

    Sifré, David; Gardés, Emmanuel; Massuyeau, Malcolm; Hashim, Leila; Hier-Majumder, Saswata; Gaillard, Fabrice

    2014-01-01

    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

  4. Near-wall measurements of the bubble- and Lorentz-force-driven convection at gas-evolving electrodes

    NASA Astrophysics Data System (ADS)

    Baczyzmalski, Dominik; Weier, Tom; Kähler, Christian J.; Cierpka, Christian

    2015-08-01

    Chemical energy storage systems, e.g., in the form of hydrogen or methanol, have a great potential for the establishment of volatile renewable energy sources due to the large energy density. The efficiency of hydrogen production through water electrolysis is, however, limited by gas bubbles evolving at the electrode's surface and can be enhanced by an accelerated bubble detachment. In order to characterize the complex multi-phase flow near the electrode, simultaneous measurements of the fluid velocities and the size and trajectories of hydrogen bubbles were performed in a water electrolyzer. The liquid phase velocity was measured by PIV/PTV, while shadowgraphy was used to determine the bubble trajectories. Special measurement and evaluation techniques had to be applied as the measurement uncertainty is strongly affected by the high void fraction close to the wall. In particular, the application of an advanced PTV scheme allowed for more precise fluid velocity measurements closer to electrode. Based on these data, stability characteristics of the near-wall flow were evaluated and compared to that of a wall jet. PTV was used as well to investigate the effect of Lorentz forces on the near-wall fluid velocities. The results show a significantly increased wall parallel liquid phase velocity with increasing Lorentz forces. It is presumed that this enhances the detachment of hydrogen bubbles from the electrode surface and, consequently, decreases the fractional bubble coverage and improves the efficiency. In addition, the effect of large rising bubbles with path oscillations on the near-wall flow was investigated. These bubbles can have a strong impact on the mass transfer near the electrode and thus affect the performance of the process.

  5. Influence Of The Redox State On The Electrical Conductivity Of Basaltic Melts

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

    The electrical conductivity is an efficient probe of mass transfer processes within silicate melts and magmas. Previous studies have established that the electrical conductivity is sensitive to parameters such as temperature, melt composition and pressure. In contrast to what is known for Fe-bearing minerals, little attention has been given to the influence of redox state on the electrical conductivity of melts. Experiments were performed on tephritic and basaltic compositions respectively from Mt. Vesuvius and Pu'u 'O'o. Measurements were carried out on cylindrical glass samples (OD: 6 mm, ID: 1 mm, L: 8 mm) drilled from glass obtained by fusing each rock sample at 1400°C in air. A two-electrode configuration was adopted, with the electrical impedance being radially measured. A Pt wire was used as the internal electrode whereas a Pt tube served as the external electrode. Experiments were conducted at 1 atm in a vertical furnace between 1200°C and 1300°C, both in air and in a CO-CO2 atmosphere at a fO2 corresponding to NNO+1. Both reduction and oxidation experiments were performed. In reduction experiments (pure CO2 then CO-CO2 gas mixture), electrical conductivities progressively increase with time. The reverse is observed in oxidation experiments (CO-CO2 gas mixture then pure CO2). These variations of electrical conductivities are correlated with modifications of the Fe2+/Fe3+ ratio in the melt, and are consistent with the respective structural roles of Fe2+ and Fe3+. In both types of experiments, a minimum of about 400 mn is necessary before a plateau is reached, interpreted to reflect the kinetics of attainment of the equilibrium Fe2+/Fe3+ ratio in the melt. Differences between plateau and initial values are typically of a few ohms, much higher than the sensitivity of our measurements (better than 0.1 ohm). When increasing temperature, the time required for reaching plateau values decreases. At NNO+1, the electrical activation energy (Ea) was determined for

  6. Electrical conductivity of Icelandic deep geothermal reservoirs: insight from HT-HP laboratory experiments

    NASA Astrophysics Data System (ADS)

    Nono, Franck; Gibert, Benoit; Loggia, Didier; Parat, Fleurice; Azais, Pierre; Cichy, Sarah

    2016-04-01

    Although the Icelandic geothermal system has been intensively investigated over the years, targeting increasingly deeper reservoirs (i.e. under supercritical conditions) requires a good knowledge of the behaviour of physical properties of the host rock in order to better interpret large scale geophysical observations. In particular, the interpretation of deep electrical soundings remains controversial as only few studies have investigated the influence of altered minerals and pore fluid properties on electrical properties of rocks at high temperature and pressure. In this study, we investigate the electrical conductivity of drilled samples from different Icelandic geothermal fields at elevated temperature, confining pressure and pore pressure conditions (100°C < T < 600°C, confining pressure up to 100 MPa and pore pressure up to 35 MPa). The investigated rocks are composed of hyaloclastites, dolerites and basalts taken from depths of about 800 m for the hyaloclastites, to almost 2500 m for the dolerites. They display different porosity structures, from vuggy and intra-granular to micro-cracked porosities, and have been hydrothermally alterated in the chlorite to amphibolite facies. Electrical conductivity measurements are first determined at ambient conditions as a function of pore fluid conductivity in order to establish their relationships with lithology and pore space topology, prior to the high pressure and temperature measurements. Cementation factor varies from 1.5 for the dolerites to 2.83 for the basalt, reflecting changes in the shape of the conductive channels. The surface conductivities, measured at very low fluid conductivity, increases with the porosity and is correlated with the cation exchange capacity. At high pressure and temperature, we used the two guard-ring electrodes system. Measurements have been performed in dry and saturated conditions as a function of temperature and pore pressure. The supercritical conditions have been investigated and

  7. Measurement and modelling of forced convective heat transfer coefficient and pressure drop of Al2O3- and SiO2-water nanofluids

    NASA Astrophysics Data System (ADS)

    Julia, J. E.; Hernández, L.; Martínez-Cuenca, R.; Hibiki, T.; Mondragón, R.; Segarra, C.; Jarque, J. C.

    2012-11-01

    Forced convective heat transfer coefficient and pressure drop of SiO2- and Al2O3-water nanofluids were characterized. The experimental facility was composed of thermal-hydraulic loop with a tank with an immersed heater, a centrifugal pump, a bypass with a globe valve, an electromagnetic flow-meter, a 18 kW in-line pre-heater, a test section with band heaters, a differential pressure transducer and a heat exchanger. The test section consists of a 1000 mm long aluminium pipe with an inner diameter of 31.2 mm. Eighteen band heaters were placed all along the test section in order to provide a uniform heat flux. Heat transfer coefficient was calculated measuring fluid temperature using immersed thermocouples (Pt100) placed at both ends of the test section and surface thermocouples in 10 axial locations along the test section (Pt1000). The measurements have been performed for different nanoparticles (Al2O3 and SiO2 with primary size of 11 nm and 12 nm, respectively), volume concentrations (1% v., 5% v.), and flow rates (3 103Re<105). Maximum heat transfer coefficient enhancement (300%) and pressure drop penalty (1000%) is obtained with 5% v. SiO2 nanofluid. Existing correlations can predict, at least in a first approximation, the heat transfer coefficient and pressure drop of nanofluids if thermal conductivity, viscosity and specific heat were properly modelled.

  8. Numerical study of forced convection flow and heat transfer of a nanofluid flowing inside a straight circular pipe filled with a saturated porous medium

    NASA Astrophysics Data System (ADS)

    Baqaie Saryazdi, A.; Talebi, F.; Armaghani, T.; Pop, I.

    2016-04-01

    In this paper, the problem of developing forced convection flow of a nanofluid in a constant-wall-temperature circular tube filled with a porous medium is considered. The flow is steady and Brinkman-Forchheimer-extended Darcy equation model is employed. The thermal-equilibrium model is assumed between nanofluid and solid phase. It is also assumed that nanoparticles are distributed non-uniformly inside the pipe, hence the particles volume fraction equation is also coupled with the governing equations. A numerical study has been performed using the Finite-Volume method to analyze heat transfer coefficient of Al2O3 -water nanofluid. The effects of nanoparticles volume fraction and porosity on fluid flow and heat transfer of nanofluids are studied. The results show that the Nusselt number is increased with increasing particles volume fraction. Moreover, the wall shear stresses are increased. Finally, the effect of porosity on particle volume fraction distribution is studied and discussed in detail. We are confident that the reported results are new and original.

  9. Electrically conductive polyimide film containing gold (III) ions, composition, and process of making

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

    An electrically conductive, thermooxidatively stable poltimide, especially a film thereof, is prepared from an intimate admixture of a particular polyimide and gold (III) ions, in an amount sufficient to provide between 17 and 21 percent by weight of gold (III) ions, based on the weight of electrically conductive, thermooxidatively stable polyimide. The particular polyimide is prepared from a polyamic acid which has been synthesized from a dianhydride/diamine combination selected from the group consisting of 3,3',4,4'-benzophenonetetracarboxylic dianhydride and 2,2-bis[4-(4 -aminophenoxy)phenyl]hexafluoropropane; 3,3',4,4'-benzophenonetetracarboxylic dianhydride and 4,4'-oxydianiline; 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride and 4,4'-oxydianiline; and 3,3'4,4'-benzophenonetetracarboxylic dianhydride and 2,2-bis(3-aminophenyl)hexafluoropropane.

  10. Electrical conductivity of solutions of copper(II) nitrate crystalohydrate in dimethyl sulfoxide

    NASA Astrophysics Data System (ADS)

    Mamyrbekova, Aigul K.; Mamitova, A. D.; Mamyrbekova, Aizhan K.

    2016-06-01

    Conductometry is used to investigate the electric conductivity of Cu(NO3)2 ṡ 3H2O solutions in dimethyl sulfoxide in the 0.01-2.82 M range of concentrations and at temperatures of 288-318 K. The limiting molar conductivity of the electrolyte and the mobility of Cu2+ and NO 3 - ions, the effective coefficients of diffusion of copper(II) ions and nitrate ions, and the degree and constant of electrolytic dissociation are calculated for different temperatures from the experimental results. It is established that solutions containing 0.1-0.6 M copper nitrate trihydrate in DMSO having low viscosity and high electrical conductivity can be used in electrochemical deposition.

  11. Femtosecond laser modification aiming at the enhancement of local electric conductivities in SiC

    NASA Astrophysics Data System (ADS)

    Deki, Manato; Yamamoto, Minoru; Ito, Takuto; Tomita, Takuro; Matsuo, Shigeki; Hashimoto, Shuichi; Kitada, Takahiro; Isu, Toshiro; Onoda, Shinobu; Ohshima, Takeshi

    2011-12-01

    Femtosecond laser modification was used to enhance the local electrical conductivities in silicon carbide (SiC). Current-voltage (I-V) characteristics of the laser-modified regions were measured between the ion-implanted metal contacts on SiC. The currents of modified lines increased more than six orders of magnitude when compared with those of the non-irradiated SiC. The current sharply increased in the fluence range from 3.3 to 6.7 J/cm2. From the I-V characteristics and scanning elctroron microscope (SEM) observations, we conclude that the modification related to the formation of the classical laser-induced periodic structures causes the drastic increase of electrical conductivities.

  12. Effects of Contact Resistance on Electrical Conductivity Measurements of SiC-Based Materials

    SciTech Connect

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

    2012-04-17

    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 and its temperature dependence were determined for two types (sputtered gold and porous nickel) electrodes from RT to ~700°C. The specific contact resistance values (Rc) behaved similarly for each type of metallic electrode: Rc >~1000 Ω-cm2 at RT, decreasing continuously to ~1-10 Ω-cm2 at 700°C. 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 ~1/2.

  13. Measurement of the thermal properties of electrically conducting fluids using coated transient hot wires

    SciTech Connect

    Perkins, R.A.

    1994-12-31

    Measurements of fluid thermal properties using the transient hot-wire technique are described. When bare hot wires are used in electrically conducting fluids there are additional measurement uncertainties due to the formation of electric double layers on the surfaces of the wires and the cell wall. If the electrical conductivity of the fluid is large enough there is also significant power generation in the fluid. These measurement uncertainties can be eliminated by electrically insulating the hot wires with a thin film. The use of tantalum hot wires with an anodized layer of tantalum pentoxide is demonstrated with measurements on nonpolar argon and polar 1,1,1,2 tetrafluoroethane (R134a). Although coated tantalum hot wires have been used previously in a transient mode to measure the thermal conductivity of liquids, this work is the first demonstration of the use of coated wires to measure thermal conductivity in the liquid, vapor, and supercritical gas phases.

  14. Electrically conductive, black thermal control coatings for spacecraft application. I - Silicate matrix formulation

    NASA Technical Reports Server (NTRS)

    Bauer, J. L.; Odonnell, T. P.; Hribar, V. F.

    1986-01-01

    The formulation of the graphite silicate paints MH-11 and MH-11Z, which will serve as electrically conductive, heat-resistant thermal control coatings for the Galileo spacecraft's 400 Newton engine plume shield, 10 Newton thruster plume shields, and external shunt radiators, is described, and performance results for these paints are reported. The MH-11 is produced by combining a certain grade of graphite powder with a silicate base to produce a black, inorganic, electrically conductive, room temperature cure thermal control paint having high temperature capability. Zinc oxide is added to the MH-11 formulation to produce the blister resistant painta MH-11Z. The mechanical, chemical, thermal, optical, and radiation characteristics of the coatings are reported. The formulation, mixing, application, and surface preparation of the substrates are described, and a method of determining the electrical resistance of the coatings is demonstrated.

  15. Modeling electric conduction in composite materials based on polypropylene and carbon black

    NASA Astrophysics Data System (ADS)

    Stepashkina, A. S.; Tsobkallo, E. S.; Moskalyuk, O. A.; Aleshin, A. N.

    2015-01-01

    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.

  16. Radiation electrical conductivity of iron tricarbonyl PI-complexes with poly (styrenebutadiene) block copolymers

    SciTech Connect

    Tyutnev, A.P.; Abramov, V.N.; Bronshtein, L.M.; Pozhidaev, E.D.; Saenko, V.V.; Valetskii, P.M.

    1986-04-01

    This paper presents a thorough investigation of the radiation electrical conductivity of an iron-containing block copolymer in which the iron tricarbonyl fragments are built into the main chain of the polymer. The investigations were carried out with a DST-30 poly (styrenebutadiene) block copolymer (30 mass % styrene) and with iron tricarbonyl pi-complexes of this polymer DST-Fe (CO)/sub 3/. The iron tricarbonyl pi-complexes were obtained by reacting the block copolymer with iron dodecacarbonyl in a benzene medium with 10% ethanol in a stream of argon at 80 C. It was found that introduction of iron tricarbonyl into the DST-30 copolymer affects practically all properties of its nonstationary radiation electrical conductivity (NRE). The role of the rapid component of NRE increases with increasing Fe (CO)/sub 3/ content, while the decrease of the delayed component is somewhat slowed down.

  17. Permeability and electrical conductivity changes due to hydrostatic stress cycling of berea and muddy J sandstone

    NASA Astrophysics Data System (ADS)

    Dey, Thomas N.

    1986-01-01

    Cyclic loading affects the electrical conductivity and fluid permeability of kaolinite clay-bearing sandstone. The effective confining pressure on two sandstones was repeatedly raised and lowered between 3.5 and 31.5 MPa. Permeabilities dropped by 30% for Berea sandstone and 90% for Muddy J sandstone after three cycles; however, total pore volume always returned to its initial value after each cycle. Water salinity had little effect on these results. Electrical conductivity showed no change when a very conductive pore fluid, 1 M KCl water, was used, however the conductivity showed the same decreases as permeability when demineralized water was the pore fluid. These results show that clay particle rearrangement in the pores is probably responsible for the permeability changes.

  18. Dielectric properties and electrical conductivity of flat micronic graphite/polyurethane composites

    NASA Astrophysics Data System (ADS)

    Plyushch, Artyom; Macutkevic, Jan; Kuzhir, Polina P.; Banys, Juras; Fierro, Vanessa; Celzard, Alain

    2016-03-01

    Results of broadband dielectric spectroscopy of flat micronic graphite (FMG)/polyurethane (PU) resin composites are presented in a wide temperature range (25-450 K). The electrical percolation threshold was found to lie between 1 and 2 vol. % of FMG. Above the percolation threshold, the composites demonstrated a huge hysteresis of properties on heating and cooling from room temperature up to 450 K, along with extremely high values of dielectric permittivity and electrical conductivity. Annealing proved to be a very simple but powerful tool for significantly improving the electrical properties of FMG-based composites. In order to explain this effect, the distributions of relaxation times were calculated by the complex impedance formalism. Below room temperature, both dielectric permittivity and electrical conductivity exhibited a very low temperature dependence, mainly caused by the different thermal properties of FMG and pure PU matrix.

  19. Electrical conductivity measurements of aqueous fluids under pressure with a hydrothermal diamond anvil cell

    NASA Astrophysics Data System (ADS)

    Ni, Huaiwei; Chen, Qi; Keppler, Hans

    2014-11-01

    Electrical conductivity data of aqueous fluids under pressure can be used to derive the dissociation constants of electrolytes, to assess the effect of ionic dissociation on mineral solubility, and to interpret magnetotelluric data of earth's interior where a free fluid phase is present. Due to limitation on the tensile strength of the alloy material of hydrothermal autoclaves, previous measurements of fluid conductivity were mostly restricted to less than 0.4 GPa and 800 °C. By adapting a Bassett-type hydrothermal diamond anvil cell, we have developed a new method for acquiring electrical conductivity of aqueous fluids under pressure. Our preliminary results for KCl solutions using the new method are consistent with literature data acquired with the conventional method, but the new method has great potential for working in a much broader pressure range.

  20. Technique for Determining the Viscosity and Electrical Conductivity of Semiconducting Liquids

    NASA Technical Reports Server (NTRS)

    Li, C.; Scripa, R. N.; Ban, H.; Lin, B.; Su, C. H.; Lehoczky, S. L.; Feth, S.; Zhu, S.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    A novel apparatus for determining the viscosity and electrical conductivity of semiconducting liquids has been developed at NASA/MSFC. The apparatus is based on the transient torque technique and utilizes a 125 micrometer diameter quartz fiber as a torsion wire and a sensitive angular detector to measure the deflection angle of the crucible containing the liquid. A rotating flow is induced in the semiconducting melt by the application of a rotating magnetic field and measurement of the magnitude and transient behavior of the induced deflection angle allows the simultaneous determination of the viscosity and electrical conductivity of the melt. Measurements at room temperature and up to 900 C were made on high purity melts.