Science.gov

Sample records for ac conductance measurements

  1. Accelerated life ac conductivity measurements of CRT oxide cathodes

    NASA Astrophysics Data System (ADS)

    Hashim, A. A.; Barratt, D. S.; Hassan, A. K.; Nabok, A.

    2006-07-01

    The ac conductivity measurements have been carried out for the activated Ba/SrO cathode with additional 5% Ni powder for every 100 h acceleration life time at the temperature around 1125 K. The ac conductivity was studied as a function of temperature in the range 300-1200 K after conversion and activation of the cathode at 1200 K for 1 h in two cathodes face to face closed configuration. The experimental results prove that the hopping conductivity dominate in the temperature range 625-770 K through the traps of the WO 3 associate with activation energy Ea = 0.87 eV, whereas from 500-625 K it is most likely to be through the traps of the Al 2O 3 with activation energy of Ea = 1.05 eV. The hopping conductivity at the low temperature range 300-500 K is based on Ni powder link with some Ba contaminants in the oxide layer stricture which indicates very low activation energy Ea = 0.06 eV.

  2. AC-Conductivity Measure from Heat Production of Free Fermions in Disordered Media

    NASA Astrophysics Data System (ADS)

    Bru, J.-B.; de Siqueira Pedra, W.; Hertling, C.

    2016-05-01

    We extend (Bru et al. in J Math Phys 56:051901-1-51, 2015) in order to study the linear response of free fermions on the lattice within a (independently and identically distributed) random potential to a macroscopic electric field that is time- and space-dependent. We obtain the notion of a macroscopic AC-conductivity measure which only results from the second principle of thermodynamics. The latter corresponds here to the positivity of the heat production for cyclic processes on equilibrium states. Its Fourier transform is a continuous bounded function which is naturally called (macroscopic) conductivity. We additionally derive Green-Kubo relations involving time-correlations of bosonic fields coming from current fluctuations in the system. This is reminiscent of non-commutative central limit theorems.

  3. AC conductivity and dielectric measurements of metal-free phthalocyanine thin films dispersed in polycarbonate

    NASA Astrophysics Data System (ADS)

    Riad, A. S.; Korayem, M. T.; Abdel-Malik, T. G.

    1999-10-01

    The dielectric constant and the dielectric loss of thin films of metal-free phthalocyanine dispersed in polycarbonate using ohmic gold electrodes are investigated in the frequency range 20-10 5 Hz and within the temperature range 300-388 K. The frequency dependence of the impedance spectra plotted in the complex plane shows semicircles. The Cole-Cole diagrams have been used to determine the molecular relaxation time, τ, The temperature dependence of τ is expressed by thermally activated process. The AC conductivity σ AC (ω) is found to vary as ωs with the index s⩽1, indicating a dominant hopping process at low temperatures. From the temperature dependence of AC conductivity, free carrier conduction with mean activation energy of 0.33 eV is observed at higher temperatures. Capacitance and loss tangent are found to decrease with increasing frequency and increase with increasing temperature. Such characteristics are found to be in good qualitative agreement with existing equivalent circuit model assuming ohmic contacts.

  4. Studies on the activation energy from the ac conductivity measurements of rubber ferrite composites containing manganese zinc ferrite

    NASA Astrophysics Data System (ADS)

    Hashim, Mohd.; Alimuddin; Kumar, Shalendra; Shirsath, Sagar E.; Mohammed, E. M.; Chung, Hanshik; Kumar, Ravi

    2012-11-01

    Manganese zinc ferrites (MZF) have resistivities between 0.01 and 10 Ω m. Making composite materials of ferrites with either natural rubber or plastics will modify the electrical properties of ferrites. The moldability and flexibility of these composites find wide use in industrial and other scientific applications. Mixed ferrites belonging to the series Mn(1-x)ZnxFe2O4 were synthesized for different ‘x’ values in steps of 0.2, and incorporated in natural rubber matrix (RFC). From the dielectric measurements of the ceramic manganese zinc ferrite and rubber ferrite composites, ac conductivity and activation energy were evaluated. A program was developed with the aid of the LabVIEW package to automate the measurements. The ac conductivity of RFC was then correlated with that of the magnetic filler and matrix by a mixture equation which helps to tailor properties of these composites.

  5. AC resistance measuring instrument

    DOEpatents

    Hof, P.J.

    1983-10-04

    An auto-ranging AC resistance measuring instrument for remote measurement of the resistance of an electrical device or circuit connected to the instrument includes a signal generator which generates an AC excitation signal for application to a load, including the device and the transmission line, a monitoring circuit which provides a digitally encoded signal representing the voltage across the load, and a microprocessor which operates under program control to provide an auto-ranging function by which range resistance is connected in circuit with the load to limit the load voltage to an acceptable range for the instrument, and an auto-compensating function by which compensating capacitance is connected in shunt with the range resistance to compensate for the effects of line capacitance. After the auto-ranging and auto-compensation functions are complete, the microprocessor calculates the resistance of the load from the selected range resistance, the excitation signal, and the load voltage signal, and displays of the measured resistance on a digital display of the instrument. 8 figs.

  6. AC Resistance measuring instrument

    DOEpatents

    Hof, Peter J.

    1983-01-01

    An auto-ranging AC resistance measuring instrument for remote measurement of the resistance of an electrical device or circuit connected to the instrument includes a signal generator which generates an AC excitation signal for application to a load, including the device and the transmission line, a monitoring circuit which provides a digitally encoded signal representing the voltage across the load, and a microprocessor which operates under program control to provide an auto-ranging function by which range resistance is connected in circuit with the load to limit the load voltage to an acceptable range for the instrument, and an auto-compensating function by which compensating capacitance is connected in shunt with the range resistance to compensate for the effects of line capacitance. After the auto-ranging and auto-compensation functions are complete, the microprocessor calculates the resistance of the load from the selected range resistance, the excitation signal, and the load voltage signal, and displays of the measured resistance on a digital display of the instrument.

  7. Automated ac galvanomagnetic measurement system

    NASA Technical Reports Server (NTRS)

    Szofran, F. R.; Espy, P. N.

    1985-01-01

    An automated, ac galvanomagnetic measurement system is described. Hall or van der Pauw measurements in the temperature range 10-300 K can be made at a preselected magnetic field without operator attendance. Procedures to validate sample installation and correct operation of other system functions, such as magnetic field and thermometry, are included. Advantages of ac measurements are discussed.

  8. Impedance, AC conductivity and dielectric behavior Adeninium Trichloromercurate (II)

    NASA Astrophysics Data System (ADS)

    Fersi, M. Amine; Chaabane, I.; Gargouri, M.

    2016-09-01

    In this work, we report the measurements impedance spectroscopy technique for the organic-inorganic hybrid compound (C5H6N5) HgCl3, 11/2H2O measured in the 209 Hz-5 MHz frequency range from 378 to 428 K. Besides, the Cole-Cole (Z″ versus Z‧) plots were well fitted to an equivalent circuit built up by a parallel combination of resistance (R), fractal capacitance (CPE) and capacitance (C). Furthermore, the AC conductivity was investigated as a function of temperature and frequency in the same range. The experiment results indicated that AC conductivityac) was proportional to σdc + A ωS . The obtained results are discussed in terms of the correlated barrier hopping (CBH) model. An agreement between the experimental and theoretical results suggests that the AC conductivity behavior of Adeninium Trichloromercurate (II) can be successfully explained by CBH model. The contribution of single polaron hopping to AC conductivity in a present alloy was also studied.

  9. AC Conductivity and Dielectric Properties of Borotellurite Glass

    NASA Astrophysics Data System (ADS)

    Taha, T. A.; Azab, A. A.

    2016-06-01

    Borotellurite glasses with formula 60B2O3-10ZnO-(30 - x)NaF-xTeO2 (x = 0 mol.%, 5 mol.%, 10 mol.%, and 15 mol.%) have been synthesized by thermal melting. X-ray diffraction (XRD) analysis confirmed that the glasses were amorphous. The glass density (ρ) was determined by the Archimedes method at room temperature. The density (ρ) and molar volume (V m) were found to increase with increasing TeO2 content. The direct-current (DC) conductivity was measured in the temperature range from 473 K to 623 K, in which the electrical activation energy of ionic conduction increased from 0.27 eV to 0.48 eV with increasing TeO2 content from 0 mol.% to 15 mol.%. The dielectric parameters and alternating-current (AC) conductivityac) were investigated in the frequency range from 1 kHz to 1 MHz and temperature range from 300 K to 633 K. The AC conductivity and dielectric constant decreased with increasing TeO2 content from 0 mol.% to 15 mol.%.

  10. ac-resistance-measuring instrument

    SciTech Connect

    Hof, P.J.

    1981-04-22

    An auto-ranging ac resistance measuring instrument for remote measurement of the resistance of an electrical device or circuit connected to the instrument includes a signal generator which generates an ac excitation signal for application to a load, including the device and the transmission line, a monitoring circuit which provides a digitally encoded signal representing the voltage across the load, and a microprocessor which operates under program control to provide an auto-ranging function by which range resistance is connected in circuit with the load to limit the load voltage to an acceptable range for the instrument, and an auto-compensating function by which compensating capacitance is connected in shunt with the range resistance to compensate for the effects of line capacitance.

  11. Study of AC electrical conduction mechanisms in an epoxy polymer

    NASA Astrophysics Data System (ADS)

    Jilani, Wissal; Mzabi, Nissaf; Gallot-Lavallée, Olivier; Fourati, Najla; Zerrouki, Chouki; Zerrouki, Rachida; Guermazi, Hajer

    2015-11-01

    The AC conductivity of an epoxy resin was investigated in the frequency range 10^{-1} - 106 Hz at temperatures ranging from -100 to 120 °C. The frequency dependence of σ_{ac} was described by the law: σ_{ac}=ω \\varepsilon0\\varepsilon^''_{HN}+Aωs. The study of temperature variation of the exponent (s) reveals two conduction models: the AC conduction dependence upon temperature is governed by the small polaron tunneling mechanism (SPTM) at low temperature (-100 -60 °C) and the correlated barrier hopping (CHB) model at high temperature (80-120 °C).

  12. Ac conduction in conducting poly pyrrole-poly vinyl methyl ether polymer composite materials

    SciTech Connect

    Saha, S.K.; Mandal, T.K.; Mandal, B.M.; Chakravorty, D.

    1997-03-01

    Composite materials containing conducting polypyrrole and insulating poly (vinyl methyl ether) (PVME) have been synthesized by oxidative polymerization of pyrrole in ethanol using FeCl{sub 3} oxidant in the presence of PVME. The ac conductivity measurements have been carried out in the frequency range of 100 Hz to 10 MHz and in the temperature range of 110 to 350 K. The frequency dependent conductivity has been explained on the basis of a small polaron tunnelling mechanism. {copyright} {ital 1997 American Institute of Physics.}

  13. ac conductance of surface layer in lithium tetraborate single crystals

    NASA Astrophysics Data System (ADS)

    Kim, Chung-Sik; Park, Jong-Ho; Moon, Byung Kee; Seo, Hyo-Jin; Choi, Byung-Chun; Hwang, Yoon-Hwae; Kim, Hyung Kook; Kim, Jung Nam

    2003-12-01

    ac conductance for the electrode effect in Li2B4O7 single crystal was investigated by use of a coplanar electrode applied on the surface of a (001) plate. A coplanar electrode in this material more clearly shows conduction of the electrode effect than a conventional parallel planar electrode. The electrode effect in ac conductance is likely to be controlled by the surface layer, which is a poorly conductive depletion layer possibly filled with vacancies of lithium ions. We found that the surface layer is not locally distributed near the electrodes, but, rather, on the broad area of the surface (001) plane of the material. So we conclude that the electrode effect in ac conduction of Li2B4O7 single crystal is mainly due to the poor conductive surface layer distributed over the whole surface of the (001) plane and is not a secondary phase formed by reaction with the electrode material.

  14. AC Conductivity Studies of Lithium Based Phospho Vanadate Glasses

    NASA Astrophysics Data System (ADS)

    Nagendra, K.; Babu, G. Satish; Reddy, C. Narayana; Gowda, Veeranna

    2011-07-01

    Glasses in the system xLi2SO4-20Li2O-(80-x) [80P2O5-20V2O5] (5⩾x⩾20 mol%) has been prepared by melt quenching method. Dc and ac conductivity has been studied over a wide range of frequency (10 Hz to 10 MHz) and temperature (298 K-523 K). The dc conductivity found to increase with increase of Li2SO4 concentration. The ac conductivities have been fitted to the Almond-West type single power law equation σ(ω) = σ(0)+Aωs where `s' is the power law exponent. The ac conductivity found to increase with increase of Li2SO4 concentration. An attempt is made to elucidate the enhancement of lithium ion conduction in phosphor-vanadate glasses by considering the expansion of network structure.

  15. dc piezoresistance and ac conductance of niobium dioxide

    SciTech Connect

    Guerra Vela, C.

    1984-01-01

    The resistance, R, of monocrystalline n-type NbO/sub 2/ in the semiconducting, distorted rutile-structured phase was measured at temperatures from 196 to 410 K and hydrostatic pressures, P, from one to 6000 atm. R/T increases exponentially with 1/T, and ..delta..R/R increases linearly with P/T at different rates along the a- and c-axes. Conduction is apparently due to adiabatic hopping of small polarons; values were obtained for phonon, electron transfer, and polaron binding energies, the pressure dependences of these energies, and of the small polaron activation energy. An electronic phase diagram is presented also. The complex ac conductivity was also measured using frequencies from 5 to 92 kHz between 1.5 and 300 K along the a- and c-axes of NbO/sub 2/. Above 200 K the real part of the conductivity sigma/sub a/ and sigma/sub c/ were independent of frequency, f, and strongly activated like the dc conductivity. Below 200 K, sigma/sub a/ decreased ever less rapidly until 120 K where a weakly activated regime began in which sigma/sub a/ varied about like f/sup 0.5/ implying transitions of polarons between centers with a characteristic energy difference.

  16. Dynamic conductivity of ac-dc-driven graphene superlattice

    NASA Astrophysics Data System (ADS)

    Kukhar', E. I.; Kryuchkov, S. V.; Ionkina, E. S.

    2016-06-01

    The dynamic conductivity of graphene superlattice in the presence of ac electric field and dc electric field with longitudinal and transversal components with respect to superlattice axis was calculated. In the case of strong transversal component of dc field conductivity of graphene superlattice was shown to be such as if the electrons had got the effective mass. In the case of weak transversal component of dc field conductivity was shown to change its sign if the frequency of ac field was an integer multiple of half of Bloch frequency.

  17. Tevatron optics measurements using an AC dipole

    SciTech Connect

    Miyamoto, R.; Kopp, S.E.; Jansson, A.; Syphers, M.J.; /Fermilab

    2007-06-01

    The AC dipole is a device to study beam optics of hadron synchrotrons. It can produce sustained large amplitude oscillations with virtually no emittance growth. A vertical AC dipole for the Tevatron is recently implemented and a maximum oscillation amplitude of 2{sigma} (4{sigma}) at 980 GeV (150 GeV) is achieved [1]. When such large oscillations are measured with the BPM system of the Tevatron (20 {micro}m resolution), not only linear but even nonlinear optics can be directly measured. This paper shows how to measure {beta} function using an AC dipole and the result is compared to the other measurement. The paper also shows a test to detect optics changes when small changes are made in the Tevatron. Since an AC dipole is nondestructive, it allows frequent measurements of the optics which is necessary for such an test.

  18. Structural and AC conductivity study of CdTe nanomaterials

    NASA Astrophysics Data System (ADS)

    Das, Sayantani; Banerjee, Sourish; Sinha, T. P.

    2016-04-01

    Cadmium telluride (CdTe) nanomaterials have been synthesized by soft chemical route using mercapto ethanol as a capping agent. Crystallization temperature of the sample is investigated using differential scanning calorimeter. X-ray diffraction and transmission electron microscope measurements show that the prepared sample belongs to cubic structure with the average particle size of 20 nm. Impedance spectroscopy is applied to investigate the dielectric relaxation of the sample in a temperature range from 313 to 593 K and in a frequency range from 42 Hz to 1.1 MHz. The complex impedance plane plot has been analyzed by an equivalent circuit consisting of two serially connected R-CPE units, each containing a resistance (R) and a constant phase element (CPE). Dielectric relaxation peaks are observed in the imaginary parts of the spectra. The frequency dependence of real and imaginary parts of dielectric permittivity is analyzed using modified Cole-Cole equation. The temperature dependence relaxation time is found to obey the Arrhenius law having activation energy ~0.704 eV. The frequency dependent conductivity spectra are found to follow the power law. The frequency dependence ac conductivity is analyzed by power law.

  19. AC Conductivity Studies of Lithium Based Phospho Vanadate Glasses

    SciTech Connect

    Nagendra, K.; Babu, G. Satish; Gowda, Veeranna; Reddy, C. Narayana

    2011-07-15

    Glasses in the system xLi{sub 2}SO{sub 4}-20Li{sub 2}O-(80-x) [80P{sub 2}O{sub 5}-20V{sub 2}O{sub 5}](5{>=}x{>=}20 mol%) has been prepared by melt quenching method. Dc and ac conductivity has been studied over a wide range of frequency (10 Hz to 10 MHz) and temperature (298 K-523 K). The dc conductivity found to increase with increase of Li{sub 2}SO{sub 4} concentration. The ac conductivities have been fitted to the Almond-West type single power law equation {sigma}({omega}) = {sigma}(0)+A{omega}{sup s} where 's' is the power law exponent. The ac conductivity found to increase with increase of Li{sub 2}SO{sub 4} concentration. An attempt is made to elucidate the enhancement of lithium ion conduction in phosphor-vanadate glasses by considering the expansion of network structure.

  20. Broadband AC Conductivity of XUV Excited Warm Dense Gold

    NASA Astrophysics Data System (ADS)

    Chen, Z.; Tsui, Y.; Toleikis, S.; Hering, P.; Brown, S.; Curry, C.; Tanikawa, T.; Hoeppner, H.; Levy, M.; Goede, S.; Ziaja-Motyka, B.; Rethfeld, B.; Recoules, Vanina; Ng, A.; Glenzer, S.

    2015-11-01

    The properties of ultrafast laser excited warm dense gold have been extensively studied in the past decade. In those studies, a 400nm ultrashort laser pulse was used to excite the 5 d electrons in gold to 6s/p state. Here we will present our recent study of warm dense gold with 245eV, 70fs pulses to selectively excite 4 f electrons using the XUV-FEL at FLASH. The AC conductivity of the warm dense gold was measured at different wavelengths (485nm, 520nm, 585nm, 640nm and 720nm) to cover the range from 5 d-6 s / p interband transitions to 6 s/ p intraband transitions. Preliminary result suggests that the onset of 5 d-6 s / p band transition shifts from 2.3eV to ~ 2eV, which is in agreement with the study of 400nm laser pulse excited warm dense gold. More detailed analysis of our data will also be presented.

  1. Structural, AC conductivity and dielectric properties of Sr-La hexaferrite

    NASA Astrophysics Data System (ADS)

    Singh, A.; Narang, S. B.; Singh, K.; Sharma, P.; Pandey, O. P.

    2006-03-01

    A series of M-type hexaferrite samples with composition Sr{1-x}La{x}Fe{12}O{19} (x = 0.00, 0.05, 0.15 and 0.25) were prepared by standard ceramic technique. AC electrical conductivity measurements were carried out at different frequencies (20 Hz 1 MHz) and at different temperatures. The dielectric constant and dielectric loss tangent were measured in the same range of frequencies. The experimental results indicate that AC electrical conductivity increases on increasing the frequency as well as the temperature, indicating magnetic semiconductor behavior of the samples. The increase in AC electrical conductivity with frequency and temperature has been explained on the basis of Koops Model whereas dielectric constant and dielectric loss tangent has been explained with the Maxwell Wagner type interfacial polarization in agreement with the Koops phenomenological theory.

  2. Microwave ac Conductivity Spectrum of a Coulomb Glass

    SciTech Connect

    Lee, Mark; Stutzmann, M. L.

    2001-07-30

    We report the first observation of the transition between interacting and noninteracting behavior in the ac conductivity spectrum {sigma}({omega}) of a doped semiconductor in its Coulomb glass state near T=0 K . The transition manifests itself as a crossover from approximately linear frequency dependence below {approx}10 GHz , to quadratic dependence above {approx}15 GHz . The sharpness of the transition and the magnitude of the crossover frequency strongly suggest that the transition is driven by photon-induced excitations across the Coulomb gap, in contrast to existing theoretical descriptions.

  3. ac conductivity and dielectric constant of conductor-insulator composites

    NASA Astrophysics Data System (ADS)

    Murtanto, Tan Benny; Natori, Satoshi; Nakamura, Jun; Natori, Akiko

    2006-09-01

    We study the complex admittance (ac conductivity and dielectric constant) of conductor-insulator composite material, based on a two-dimensional square network consisting of randomly placed conductors and capacitors. We derived some exact analytical relations between the complex admittances of high and low frequencies and of complementary conductor concentrations. We calculate the complex admittance by applying a transfer-matrix method to a square network and study the dependence on both the frequency and the conductor concentration. The numerical results are compared with an effective-medium theory, and the range of applicability and limitation of the effective-medium theory are clarified.

  4. AC Loss Measurements on a 2G YBCO Coil

    SciTech Connect

    Rey, Christopher M; Duckworth, Robert C; Schwenterly, S W

    2011-01-01

    The Oak Ridge National Laboratory (ORNL) is collaborating with Waukesha Electric Systems (WES) to continue development of HTS power transformers. For compatibility with the existing power grid, a commercially viable HTS transformer will have to operate at high voltages in the range of 138 kV and above, and will have to withstand 550-kV impulse voltages as well. Second-generation (2G) YBCO coated conductors will be required for an economically-competitive design. In order to adequately size the refrigeration system for these transformers, the ac loss of these HTS coils must be characterized. Electrical AC loss measurements were conducted on a prototype high voltage (HV) coil with co-wound stainless steel at 60 Hz in a liquid nitrogen bath using a lock-in amplifier technique. The prototype HV coil consisted of 26 continuous (without splice) single pancake coils concentrically centered on a stainless steel former. For ac loss measurement purposes, voltage tap pairs were soldered across each set of two single pancake coils so that a total of 13 separate voltage measurements could be made across the entire length of the coil. AC loss measurements were taken as a function of ac excitation current. Results show that the loss is primarily concentrated at the ends of the coil where the operating fraction of critical current is the highest and show a distinct difference in current scaling of the losses between low current and high current regimes.

  5. 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.

  6. AC Conductivity and Dielectric Relaxation Behavior of Sb2S3 Bulk Material

    NASA Astrophysics Data System (ADS)

    Abd El-Rahman, K. F.; Darwish, A. A. A.; Qashou, Saleem I.; Hanafy, T. A.

    2016-04-01

    The Sb2S3 bulk material was used for next-generation anode for lithium-ion batteries. Alternative current (AC) conductivity, dielectric properties and electric modulus of Sb2S3 have been investigated. The measurements were carried out in the frequency range from 40 Hz to 5 MHz and temperature range from 293 K to 453 K. The direct current (DC) conductivity, σ DC, shows an activated behavior and the calculated activation energy is 0.50 eV. The AC conductivity, σ AC, was found to increase with the increase of temperature and frequency. The conduction mechanism of σ AC was controlled by the correlated barrier hopping model. The behavior of the dielectric constant, ɛ', and dielectric loss index, ɛ'', reveal that the polarization process of Sb2S3 is dipolar in nature. The behavior of both ɛ' and ɛ'' reveals that bulk Sb2S3 has no ferroelectric or piezoelectric phase transition. The dielectric modulus, M, gives a simple method for evaluating the activation energy of the dielectric relaxation. The calculated activation energy from M is 0.045 eV.

  7. AC Conductivity and Dielectric Relaxation Behavior of Sb2S3 Bulk Material

    NASA Astrophysics Data System (ADS)

    Abd El-Rahman, K. F.; Darwish, A. A. A.; Qashou, Saleem I.; Hanafy, T. A.

    2016-07-01

    The Sb2S3 bulk material was used for next-generation anode for lithium-ion batteries. Alternative current (AC) conductivity, dielectric properties and electric modulus of Sb2S3 have been investigated. The measurements were carried out in the frequency range from 40 Hz to 5 MHz and temperature range from 293 K to 453 K. The direct current (DC) conductivity, σ DC, shows an activated behavior and the calculated activation energy is 0.50 eV. The AC conductivity, σ AC, was found to increase with the increase of temperature and frequency. The conduction mechanism of σ AC was controlled by the correlated barrier hopping model. The behavior of the dielectric constant, ɛ', and dielectric loss index, ɛ'', reveal that the polarization process of Sb2S3 is dipolar in nature. The behavior of both ɛ' and ɛ'' reveals that bulk Sb2S3 has no ferroelectric or piezoelectric phase transition. The dielectric modulus, M, gives a simple method for evaluating the activation energy of the dielectric relaxation. The calculated activation energy from M is 0.045 eV.

  8. ac and dc percolative conductivity of magnetite-cellulose acetate composites

    SciTech Connect

    Chiteme, C.; McLachlan, D. S.; Sauti, G.

    2007-03-01

    ac and dc conductivity results for a percolating system, which consists of a conducting powder (magnetite) combined with an 'insulating' powder (cellulose acetate), are presented. Impedance and modulus spectra are obtained in a percolation system. The temperature dependence of the resistivity of the cellulose acetate is such that at 170 deg. C, it is essentially a conductor at frequencies below 0.059{+-}0.002 Hz, and a dielectric above. The percolation parameters, from the dc conductivity measured at 25 and 170 deg. C, are determined and discussed in relation to the ac results. The experimental results scale as a function of composition, temperature, and frequency. An interesting result is the correlation observed between the scaling parameter (f{sub ce}), obtained from a scaling of the ac measurements, and the peak frequency (f{sub cp}) of the arcs, obtained from impedance spectra, above the critical volume fraction. Scaling at 170 deg. C is not as good as at 25 deg. C, probably indicating a breakdown in scaling at the higher temperature. The modulus plots show the presence of two materials: a conducting phase dominated by the cellulose acetate and the isolated conducting clusters below the critical volume fraction {phi}{sub c}, as well as the interconnected conducting clusters above {phi}{sub c}. These results are confirmed by computer simulations using the two exponent phenomenological percolation equation. These results emphasize the need to analyze ac conductivity results in terms of both impedance and modulus spectra in order to get more insight into the behavior of composite materials.

  9. Measuring Salinity by Conductivity.

    ERIC Educational Resources Information Center

    Lapworth, C. J.

    1981-01-01

    Outlines procedures for constructing an instrument which uses an electrode and calibration methods to measure the salinity of waters in environments close to and affected by a saline estuary. (Author/DC)

  10. RG flow of AC conductivity in soft wall model of QCD

    NASA Astrophysics Data System (ADS)

    Bhatnagar, Neha; Siwach, Sanjay

    2016-03-01

    We study the Renormalization Group (RG) flow of AC conductivity in soft wall model of holographic QCD. We consider the charged black hole metric and the explicit form of AC conductivity is obtained at the cutoff surface. We plot the numerical solution of conductivity flow as a function of radial coordinate. The equation of gauge field is also considered and the numerical solution is obtained for AC conductivity as a function of frequency. The results for AC conductivity are also obtained for different values of chemical potential and Gauss-Bonnet couplings.

  11. Random free energy barrier hopping model for ac conduction in chalcogenide glasses

    NASA Astrophysics Data System (ADS)

    Murti, Ram; Tripathi, S. K.; Goyal, Navdeep; Prakash, Satya

    2016-03-01

    The random free energy barrier hopping model is proposed to explain the ac conductivityac) of chalcogenide glasses. The Coulomb correlation is consistently accounted for in the polarizability and defect distribution functions and the relaxation time is augmented to include the overlapping of hopping particle wave functions. It is observed that ac and dc conduction in chalcogenides are due to same mechanism and Meyer-Neldel (MN) rule is the consequence of temperature dependence of hopping barriers. The exponential parameter s is calculated and it is found that s is subjected to sample preparation and measurement conditions and its value can be less than or greater than one. The calculated results for a - Se, As2S3, As2Se3 and As2Te3 are found in close agreement with the experimental data. The bipolaron and single polaron hopping contributions dominates at lower and higher temperatures respectively and in addition to high energy optical phonons, low energy optical and high energy acoustic phonons also contribute to the hopping process. The variations of hopping distance with temperature is also studied. The estimated defect number density and static barrier heights are compared with other existing calculations.

  12. Phonon-Induced Electron-Hole Excitation and ac Conductance in Molecular Junction

    NASA Astrophysics Data System (ADS)

    Ueda, Akiko; Utsumi, Yasuhiro; Imamura, Hiroshi; Tokura, Yasuhiro

    2016-04-01

    We investigate the linear ac conductance of molecular junctions under a fixed dc bias voltage in the presence of an interaction between a transporting electron and a single local phonon in a molecule with energy ω0. The electron-phonon interaction is treated by the perturbation expansion. The ac conductance as a function of the ac frequency ωac decreases or increases compared with the noninteracting case depending on the magnitude of the dc bias voltage. Furthermore, a dip emerges at ωac ˜ 2ω0. The dip originates from the modification of electron-hole excitation by the ac field, which cannot be obtained by treating the phonon in the linear regime of a classical forced oscillation.

  13. Polaron conductivity mechanism in potassium acid phthalate crystal: AC-conductivity investigation

    NASA Astrophysics Data System (ADS)

    Filipič, Cene; Levstik, Iva; Levstik, Adrijan; Hadži, Dušan

    2016-08-01

    The complex dielectric constant, \\varepsilon *(ν ,T), of potassium acid phthalate monocrystal (KAP) was investigated over the broad frequency and temperature range. While the imaginary part of dielectric constant ε‧‧(ν) increases rapidly with increasing temperature in the studied temperature range, the real part of dielectric constant ε‧(ν) increases only at high temperatures; there is almost no change of ε‧(ν) below 200 K. Both values of ε‧ and ε‧‧ are frequency dependent; the values increase with decreasing frequencies. At temperatures below 450 K the ac electrical conductivity and dielectric constant follow simultaneously the universal dielectric response (UDR). The analysis of the temperature dependence of the UDR parameter s in terms of the theoretical model for small polarons revealed that this mechanism governs the charge transport in KAP crystal in the studied temperature range.

  14. AC conductivity and Dielectric Study of Chalcogenide Glasses of Se-Te-Ge System

    NASA Astrophysics Data System (ADS)

    Salman, Fathy

    2004-01-01

    The ac conductivity and dielectric properties of glassy system SexTe79 - xGe21, with x = 11, 14, 17 at.%, has been studied at temperatures 300 to 450 K and over a wide range of frequencies (50 Hz to 500 kHz). Experimental results indicate that the ac conductivity and the dielectric constants depend on temperature, frequency and Se content. The conductivity as a function of frequency exhibited two components: dc conductivity s dc, and ac conductivity s ac, where s ac ˜ w s. The mechanism of ac conductivity can be reasonably interpreted in terms of the correlated barrier hopping model (CBH). The activation energies are estimated and discussed. The dependence of ac conductivity and dielectric constants on the Se content x can be interpreted as the effect of Se fraction on the positional disorder. The impedance plot at each temperature appeared as a semicircle passes through the origin. Each semicircle is represented by an equivalent circuit of parallel resistance Rb and capacitance Cb.

  15. Thermal conductivity Measurements of Kaolite

    SciTech Connect

    Wang, H

    2003-02-21

    Testing was performed to determine the thermal conductivity of Kaolite 1600, which primarily consists of Portland cement and vermiculite. The material was made by Thermal Ceramics for refractory applications. Its combination of light weight, low density, low cost, and noncombustibility made it an attractive alternative to the materials currently used in ES-2 container for radioactive materials. Mechanical properties and energy absorption tests of the Kaolite have been conducted at the Y-12 complex. Heat transfer is also an important factor for the application of the material. The Kaolite samples are porous and trap moisture after extended storage. Thermal conductivity changes as a function of moisture content below 100 C. Thermal conductivity of the Kaolite at high temperatures (up to 700 C) are not available in the literature. There are no standard thermal conductivity values for Kaolite because each sample is somewhat different. Therefore, it is necessary to measure thermal conductivity of each type of Kaolite. Thermal conductivity measurements will help the modeling and calculation of temperatures of the ES-2 containers. This report focuses on the thermal conductivity testing effort at ORNL.

  16. Measurement of coupling resonance driving terms with the AC dipole

    SciTech Connect

    Miyamoto, R.

    2010-10-01

    Resonance driving terms for linear coupled betatron motion in a synchrotron ring can be determined from corresponding spectral lines of an excited coherent beam motion. An AC dipole is one of instruments to excite such a motion. When a coherent motion is excited with an AC dipole, measured Courant-Snyder parameters and betatron phase advance have apparent modulations, as if there is an additional quadrupole field at the location of the AC dipole. Hence, measurements of these parameters using the AC dipole require a proper interpretation of observed quantities. The situation is similar in measurements of resonance driving terms using the AC dipole. In this note, we derive an expression of coupled betatron motion excited with two AC dipoles in presence of skew quadrupole fields, discuss an impact of this quadrupole like effect of the AC dipole on a measurement of coupling resonance driving terms, and present an analytical method to determine the coupling resonance driving terms from quantities observed using the AC dipole.

  17. Temperature correction in conductivity measurements

    USGS Publications Warehouse

    Smith, Stanford H.

    1962-01-01

    Electrical conductivity has been widely used in freshwater research but usual methods employed by limnologists for converting measurements to conductance at a given temperature have not given uniformly accurate results. The temperature coefficient used to adjust conductivity of natural waters to a given temperature varies depending on the kinds and concentrations of electrolytes, the temperature at the time of measurement, and the temperature to which measurements are being adjusted. The temperature coefficient was found to differ for various lake and stream waters, and showed seasonal changes. High precision can be obtained only by determining temperature coefficients for each water studied. Mean temperature coefficients are given for various temperature ranges that may be used where less precision is required.

  18. AC motor controller with 180 degree conductive switches

    NASA Technical Reports Server (NTRS)

    Oximberg, Carol A. (Inventor)

    1995-01-01

    An ac motor controller is operated by a modified time-switching scheme where the switches of the inverter are on for electrical-phase-and-rotation intervals of 180.degree. as opposed to the conventional 120.degree.. The motor is provided with three-phase drive windings, a power inverter for power supplied from a dc power source consisting of six switches, and a motor controller which controls the current controlled switches in voltage-fed mode. During full power, each switch is gated continuously for three successive intervals of 60.degree. and modulated for only one of said intervals. Thus, during each 60.degree. interval, the two switches with like signs are on continuously and the switch with the opposite sign is modulated.

  19. Structural, dielectric and AC conductivity properties of Co2+ doped mixed alkali zinc borate glasses

    NASA Astrophysics Data System (ADS)

    Madhu, B. J.; Banu, Syed Asma; Harshitha, G. A.; Shilpa, T. M.; Shruthi, B.

    2013-02-01

    The Co2+ doped 19.9ZnO+5Li2CO3+25Na2CO3+50B2O3 (ZLNB) mixed alkali zinc borate glasses have been prepared by a conventional melt quenching method. The structural (XRD & FT-IR), dielectric and a.c. conductivityac) properties have been investigated. Amorphous nature of these glasses has been confirmed from their XRD pattern. The dielectric properties and electrical conductivityac) of these glasses have been studied from 100Hz to 5MHz at the room temperature. Based on the observed trends in the a.c. conductivities, the present glass samples are found to exhibit a non-Debye behavior.

  20. Critical field measurements in superconductors using ac inductive techniques

    NASA Astrophysics Data System (ADS)

    Campbell, S. A.; Ketterson, J. B.; Crabtree, G. W.

    1983-09-01

    The ac in-phase and out-of-phase response of type II superconductors is discussed in terms of dc magnetization curves. Hysteresis in the dc magnetization is shown to lead to a dependence of the ac response on the rate at which an external field is swept. This effect allows both Hc1 and Hc2 to be measured by ac techniques. A relatively simple mutual inductance bridge for making such measurements is described in the text, and factors affecting bridge sensitivity are discussed in the Appendix. Data for the magnetic superconductor ErRh4B4 obtained using this bridge are reported.

  1. Calorimetric method of ac loss measurement in a rotating magnetic field.

    PubMed

    Ghoshal, P K; Coombs, T A; Campbell, A M

    2010-07-01

    A method is described for calorimetric ac-loss measurements of high-T(c) superconductors (HTS) at 80 K. It is based on a technique used at 4.2 K for conventional superconducting wires that allows an easy loss measurement in parallel or perpendicular external field orientation. This paper focuses on ac loss measurement setup and calibration in a rotating magnetic field. This experimental setup is to demonstrate measuring loss using a temperature rise method under the influence of a rotating magnetic field. The slight temperature increase of the sample in an ac-field is used as a measure of losses. The aim is to simulate the loss in rotating machines using HTS. This is a unique technique to measure total ac loss in HTS at power frequencies. The sample is mounted on to a cold finger extended from a liquid nitrogen heat exchanger (HEX). The thermal insulation between the HEX and sample is provided by a material of low thermal conductivity, and low eddy current heating sample holder in vacuum vessel. A temperature sensor and noninductive heater have been incorporated in the sample holder allowing a rapid sample change. The main part of the data is obtained in the calorimetric measurement is used for calibration. The focus is on the accuracy and calibrations required to predict the actual ac losses in HTS. This setup has the advantage of being able to measure the total ac loss under the influence of a continuous moving field as experienced by any rotating machines. PMID:20687748

  2. Calorimetric method of ac loss measurement in a rotating magnetic field

    NASA Astrophysics Data System (ADS)

    Ghoshal, P. K.; Coombs, T. A.; Campbell, A. M.

    2010-07-01

    A method is described for calorimetric ac-loss measurements of high-Tc superconductors (HTS) at 80 K. It is based on a technique used at 4.2 K for conventional superconducting wires that allows an easy loss measurement in parallel or perpendicular external field orientation. This paper focuses on ac loss measurement setup and calibration in a rotating magnetic field. This experimental setup is to demonstrate measuring loss using a temperature rise method under the influence of a rotating magnetic field. The slight temperature increase of the sample in an ac-field is used as a measure of losses. The aim is to simulate the loss in rotating machines using HTS. This is a unique technique to measure total ac loss in HTS at power frequencies. The sample is mounted on to a cold finger extended from a liquid nitrogen heat exchanger (HEX). The thermal insulation between the HEX and sample is provided by a material of low thermal conductivity, and low eddy current heating sample holder in vacuum vessel. A temperature sensor and noninductive heater have been incorporated in the sample holder allowing a rapid sample change. The main part of the data is obtained in the calorimetric measurement is used for calibration. The focus is on the accuracy and calibrations required to predict the actual ac losses in HTS. This setup has the advantage of being able to measure the total ac loss under the influence of a continuous moving field as experienced by any rotating machines.

  3. Calorimetric method of ac loss measurement in a rotating magnetic field

    SciTech Connect

    Ghoshal, P. K.; Coombs, T. A.; Campbell, A. M.

    2010-07-15

    A method is described for calorimetric ac-loss measurements of high-T{sub c} superconductors (HTS) at 80 K. It is based on a technique used at 4.2 K for conventional superconducting wires that allows an easy loss measurement in parallel or perpendicular external field orientation. This paper focuses on ac loss measurement setup and calibration in a rotating magnetic field. This experimental setup is to demonstrate measuring loss using a temperature rise method under the influence of a rotating magnetic field. The slight temperature increase of the sample in an ac-field is used as a measure of losses. The aim is to simulate the loss in rotating machines using HTS. This is a unique technique to measure total ac loss in HTS at power frequencies. The sample is mounted on to a cold finger extended from a liquid nitrogen heat exchanger (HEX). The thermal insulation between the HEX and sample is provided by a material of low thermal conductivity, and low eddy current heating sample holder in vacuum vessel. A temperature sensor and noninductive heater have been incorporated in the sample holder allowing a rapid sample change. The main part of the data is obtained in the calorimetric measurement is used for calibration. The focus is on the accuracy and calibrations required to predict the actual ac losses in HTS. This setup has the advantage of being able to measure the total ac loss under the influence of a continuous moving field as experienced by any rotating machines.

  4. Ac-conductivity and dielectric response of new zinc-phosphate glass/metal composites

    NASA Astrophysics Data System (ADS)

    Maaroufi, A.; Oabi, O.; Lucas, B.

    2016-07-01

    The ac-conductivity and dielectric response of new composites based on zinc-phosphate glass with composition 45 mol%ZnO-55 mol%P2O5, filled with metallic powder of nickel (ZP/Ni) were investigated by impedance spectroscopy in the frequency range from 100 Hz to 1 MHz at room temperature. A high percolating jump of seven times has been observed in the conductivity behavior from low volume fraction of filler to the higher fractions, indicating an insulator - semiconductor phase transition. The measured conductivity at higher filler volume fraction is about 10-1 S/cm and is frequency independent, while, the obtained conductivity for low filler volume fraction is around 10-8 S/cm and is frequency dependent. Moreover, the elaborated composites are characterized by high dielectric constants in the range of 105 for conductive composites at low frequencies (100 Hz). In addition, the distribution of the relaxation processes was also evaluated. The Debye, Cole-Cole, Davidson-Cole and Havriliak-Negami models in electric modulus formalism were used to model the observed relaxation phenomena in ZP/Ni composites. The observed relaxation phenomena are fairly simulated by Davidson-Cole model, and an account of the interpretation of results is given.

  5. Low frequency ac conduction and dielectric relaxation in pristine poly(3-octylthiophene) films

    NASA Astrophysics Data System (ADS)

    Singh, Ramadhar; Kumar, Jitendra; Singh, Rajiv K.; Rastogi, Ramesh C.; Kumar, Vikram

    2007-02-01

    The ac conductivity σ(ω)m, dielectric constant ɛ'(ω) and loss ɛ''(ω) of pristine poly(3-octylthiophene) (P3OT) films (thickness ~ 20 μm) have been measured in wide temperature (77 350 K) and frequency (100 Hz 10 MHz) ranges. At low temperatures, σ(ω)m can be described by the relation σ(ω)m = Aωs, where s is ~ 0.61 at 77 K and decreases with increasing temperature. A clear Debye-type loss peak is observed by subtracting the contribution of σdc from σ(ω)m. The frequency dependence of conductivity indicates that there is a distribution of relaxation times. This is confirmed by measurement of the dielectric constant as a function of frequency and temperature. Reasonable estimates of various electrical parameters such as effective dielectric constant (ɛp), phonon frequency (νph), Debye temperature (θD), polaron radius (rp), small-polaron coupling constant (\\Upsilon ), effective polaron mass (mp), the density of states at the Fermi level N(EF), average hopping distance (R) and average hopping energy (W) from dc conductivity measurements suggest the applicability of Mott's variable range hopping model in this system.

  6. AC conductivity and structural properties of Mg-doped ZnO ceramic

    NASA Astrophysics Data System (ADS)

    Othman, Zayani Jaafar; Hafef, Olfa; Matoussi, Adel; Rossi, Francesca; Salviati, Giancarlo

    2015-11-01

    Undoped ZnO and Zn1- x Mg x O ceramic pellets were synthesized by the standard sintering method at the temperature of 1200 °C. The influence of Mg doping on the morphological, structural and electrical properties was studied. The scanning electron microscopy images revealed rough surface textured by grain boundaries and compacted grains having different shapes and sizes. Indeed, the X-ray diffraction reveals the alloying of hexagonal ZnMgO phase and the segregation of cubic MgO phase. The crystallite size, strain and stress were studied using Williamson-Hall (W-H) method. The results of mean particle size of Zn1- x Mg x O composites showed an inter-correlation with W-H analysis and Sherrer method. The electrical conductivity of the films was measured from 173 to 373 K in the frequency range of 0.1 Hz-1 MHz to identify the dominant conductivity mechanism. The DC conductivity is thermally activated by electron traps having activation energy of about 0.09 to 0.8 eV. The mechanisms of AC conductivity are controlled by the correlated barrier hopping model for the ZnO sample and the small polaron tunneling (SPT) model for Zn0.64Mg0.36O and Zn0.60Mg0.40O composites.

  7. Hydraulic Conductivity Measurements Barrow 2014

    DOE Data Explorer

    Katie McKnight; Tim Kneafsey; Craig Ulrich; Jil Geller

    2015-02-22

    Six individual ice cores were collected from Barrow Environmental Observatory in Barrow, Alaska, in May of 2013 as part of the Next Generation Ecosystem Experiment (NGEE). Each core was drilled from a different location at varying depths. A few days after drilling, the cores were stored in coolers packed with dry ice and flown to Lawrence Berkeley National Laboratory (LBNL) in Berkeley, CA. 3-dimensional images of the cores were constructed using a medical X-ray computed tomography (CT) scanner at 120kV. Hydraulic conductivity samples were extracted from these cores at LBNL Richmond Field Station in Richmond, CA, in February 2014 by cutting 5 to 8 inch segments using a chop saw. Samples were packed individually and stored at freezing temperatures to minimize any changes in structure or loss of ice content prior to analysis. Hydraulic conductivity was determined through falling head tests using a permeameter [ELE International, Model #: K-770B]. After approximately 12 hours of thaw, initial falling head tests were performed. Two to four measurements were collected on each sample and collection stopped when the applied head load exceeded 25% change from the original load. Analyses were performed between 2 to 3 times for each sample. The final hydraulic conductivity calculations were computed using methodology of Das et al., 1985.

  8. Microfabricated Thin Film Impedance Sensor & AC Impedance Measurements

    PubMed Central

    Yu, Jinsong; Liu, Chung-Chiun

    2010-01-01

    Thin film microfabrication technique was employed to fabricate a platinum based parallel-electrode structured impedance sensor. Electrochemical impedance spectroscopy (EIS) and equivalent circuit analysis of the small amplitude (±5 mV) AC impedance measurements (frequency range: 1 MHz to 0.1 Hz) at ambient temperature were carried out. Testing media include 0.001 M, 0.01 M, 0.1 M NaCl and KCl solutions, and alumina (∼3 μm) and sand (∼300 μm) particulate layers saturated with NaCl solutions with the thicknesses ranging from 0.6 mm to 8 mm in a testing cell, and the results were used to assess the effect of the thickness of the particulate layer on the conductivity of the testing solution. The calculated resistances were approximately around 20 MΩ, 4 MΩ, and 0.5 MΩ for 0.001 M, 0.01 M, and 0.1 M NaCl solutions, respectively. The presence of the sand particulates increased the impedance dramatically (6 times and 3 times for 0.001 M and 0.1 M NaCl solutions, respectively). A cell constant methodology was also developed to assess the measurement of the bulk conductivity of the electrolyte solution. The cell constant ranged from 1.2 to 0.8 and it decreased with the increase of the solution thickness. PMID:22219690

  9. Ac-electrical conductivity of poly(propylene) before and after X-ray irradiation

    NASA Astrophysics Data System (ADS)

    Gaafar, M.

    2001-05-01

    Study on the ac-electrical conductivity of poly(propylene), before and after X-ray irradiation within the temperature range 300-360 K are reported. The measurements have been performed in a wide range of frequencies (from 0 to 10 5 Hz) and under the effect of different X-ray irradiation doses (from 0 to 15 Gy). Cole-Cole diagrams have been used to show the frequency dependence of the complex impedance at different temperatures. The results exhibit semicircles which are consistent with existing equivalent circuit model. Analysis of the results reveal semiconducting features based mainly on a hopping mechanism. The study shows a pronounced effect of X-ray irradiation on the electrical conductivity at zero frequency σDC. At the early stage of irradiation, σDC increased as a result of free radical formation. As the irradiation progressed, it decreased as a result of crosslinking, then it increased again due to irradiation induced degradation, which motivates the generation of mobile free radicals. The study shows that this polymer is one among other polymers which its electrical conductivity is modified by irradiation.

  10. 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.

  11. Charging in the ac Conductance of a Double Barrier Resonant Tunneling Structure

    NASA Technical Reports Server (NTRS)

    Anantram, M. P.; Saini, Subhash (Technical Monitor)

    1998-01-01

    There have been many studies of the linear response ac conductance of a double barrier resonant tunneling structure (DBRTS), both at zero and finite dc biases. While these studies are important, they fail to self consistently include the effect of the time dependent charge density in the well. In this paper, we calculate the ac conductance at both zero and finite do biases by including the effect of the time dependent charge density in the well in a self consistent manner. The charge density in the well contributes to both the flow of displacement currents in the contacts and the time dependent potential in the well. We find that including these effects can make a significant difference to the ac conductance and the total ac current is not equal to the simple average of the non-selfconsistently calculated conduction currents in the two contacts. This is illustrated by comparing the results obtained with and without the effect of the time dependent charge density included correctly. Some possible experimental scenarios to observe these effects are suggested.

  12. How to Measure Thermal Conductivity

    NASA Astrophysics Data System (ADS)

    Ventura, Guglielmo; Perfetti, Mauro

    The methods to measure the thermal conductivity at low temperature are described: the steady-state techniques, (Sect. 2.2 ); the 3ω technique (Sect. 2.3 ); and the thermal diffusivity measurement (Sect. 2.4 ). Each of these techniques has its own advantages as well as its inherent limitations, with some techniques more appropriate to specific sample geometry, such as the 3ω technique for thin films which is discussed in detail in Sect. 2.4.2 . The radial flux method is reported in Sect. 2.2.4 , the laser flash diffusivity method in Sect. 2.4.1 and the "pulsed power or Maldonado technique" in Sect. 2.3.2 .

  13. AC Conductivity Studies in Lithium-Borate Glass Containing Gold Nanoparticles

    NASA Astrophysics Data System (ADS)

    Shivaprakash, Y.; Anavekar, R. V.

    2011-07-01

    Gold nanoparticles have been synthesized in a base glass with composition 30Li2O-70B2O3 using gold chloride (HAuCl4.3H2O) as a dopant. The samples are characterized using XRD, ESR, SEM and optical absorption in the visible range. AC conductivity studies have been performed at RT over a frequency range 100 to 10 MHz. The dc conductivity is calculated from the complex impedence plot. The dc conductivity is found to be increasing with the increase of dopant concentration. AC conductivity data is fitted with Almond-West law with power exponent `s'. The values of `s' is found to lie in the range of 0.70-0.73.

  14. Gas sensing properties of magnesium doped SnO{sub 2} thin films in relation to AC conduction

    SciTech Connect

    Deepa, S.; Skariah, Benoy Thomas, Boben; Joseph, Anisha

    2014-01-28

    Conducting magnesium doped (0 to 1.5 wt %) tin oxide thin films prepared by Spray Pyrolysis technique achieved detection of 1000 ppm of LPG. The films deposited at 304 °C exhibit an enhanced response at an operating temperature of 350 °C. The microstructural properties are studied by means of X-ray diffraction. AC conductivity measurements are carried out using precision LCR meter to analyze the parameters that affect the variation in sensing. The results are correlated with compositional parameters and the subsequent modification in the charge transport mechanism facilitating an enhanced LPG sensing action.

  15. Measurement of the 225Ac half-life.

    PubMed

    Pommé, S; Marouli, M; Suliman, G; Dikmen, H; Van Ammel, R; Jobbágy, V; Dirican, A; Stroh, H; Paepen, J; Bruchertseifer, F; Apostolidis, C; Morgenstern, A

    2012-11-01

    The (225)Ac half-life was determined by measuring the activity of (225)Ac sources as a function of time, using various detection techniques: α-particle counting with a planar silicon detector at a defined small solid angle and in a nearly-2π geometry, 4πα+β counting with a windowless CsI sandwich spectrometer and with a pressurised proportional counter, gamma-ray spectrometry with a HPGe detector and with a NaI(Tl) well detector. Depending on the technique, the decay was followed for 59-141 d, which is about 6-14 times the (225)Ac half-life. The six measurement results were in good mutual agreement and their mean value is T(1/2)((225)Ac)=9.920 (3)d. This half-life value is more precise and better documented than the currently recommended value of 10.0 d, based on two old measurements lacking uncertainty evaluations. PMID:22940415

  16. ac driving amplitude dependent systematic error in scanning Kelvin probe microscope measurements: Detection and correction

    SciTech Connect

    Wu Yan; Shannon, Mark A.

    2006-04-15

    The dependence of the contact potential difference (CPD) reading on the ac driving amplitude in scanning Kelvin probe microscope (SKPM) hinders researchers from quantifying true material properties. We show theoretically and demonstrate experimentally that an ac driving amplitude dependence in the SKPM measurement can come from a systematic error, and it is common for all tip sample systems as long as there is a nonzero tracking error in the feedback control loop of the instrument. We further propose a methodology to detect and to correct the ac driving amplitude dependent systematic error in SKPM measurements. The true contact potential difference can be found by applying a linear regression to the measured CPD versus one over ac driving amplitude data. Two scenarios are studied: (a) when the surface being scanned by SKPM is not semiconducting and there is an ac driving amplitude dependent systematic error; (b) when a semiconductor surface is probed and asymmetric band bending occurs when the systematic error is present. Experiments are conducted using a commercial SKPM and CPD measurement results of two systems: platinum-iridium/gap/gold and platinum-iridium/gap/thermal oxide/silicon are discussed.

  17. Measurements of AC Losses and Current Distribution in Superconducting Cables

    SciTech Connect

    Nguyen, Doan A; Ashworth, Stephen P; Duckworth, Robert C; Carter, Bill; Fleshler, Steven

    2011-01-01

    This paper presents our new experimental facility and techniques to measure ac loss and current distribution between the layers for High Temperature Superconducting (HTS) cables. The facility is powered with a 45 kVA three-phase power supply which can provide three-phase currents up to 5 kA per phase via high current transformers. The system is suitable for measurements at any frequency between 20 and 500 Hz to better understand the ac loss mechanisms in HTS cables. In this paper, we will report techniques and results for ac loss measurements carried out on several HTS cables with and without an HTS shielding layer. For cables without a shielding layer, care must be taken to control the effect of the magnetic fields from return currents on loss measurements. The waveform of the axial magnetic field was also measured by a small pick-up coil placed inside a two-layer cable. The temporal current distribution between the layers can be calculated from the waveform of the axial field.

  18. Temperature and frequency dependence of AC conductivity of new quaternary Se-Te-Bi-Pb chalcogenide glasses

    NASA Astrophysics Data System (ADS)

    Yadav, Preeti; Sharma, Ambika

    2016-05-01

    The aim of the present work is to study the temperature and frequency dependence of ac conductivity of new quaternary Se84-xTe15Bi1.0Pbx chalcogenide glasses. The Se84-xTe15Bi1.0Pbx (x = 2, 6) glassy alloys are prepared by using melt quenching technique. The temperature and frequency dependent behavior of ac conductivity σac(ω) has been carried out in the frequency range 42 Hz to 5 MHz and in the temperature range of 298-323 K below glass transition temperature. The behavior of ac conductivity is described in terms of the power law ωs. The obtained temperature dependence behavior of ac conductivity and frequency component (s) are explained by means of correlated barrier hopping model recommended by Elliot.

  19. Microwave a.c. conductivity of domain walls in ferroelectric thin films

    NASA Astrophysics Data System (ADS)

    Tselev, Alexander; Yu, Pu; Cao, Ye; Dedon, Liv R.; Martin, Lane W.; Kalinin, Sergei V.; Maksymovych, Petro

    2016-05-01

    Ferroelectric domain walls are of great interest as elementary building blocks for future electronic devices due to their intrinsic few-nanometre width, multifunctional properties and field-controlled topology. To realize the electronic functions, domain walls are required to be electrically conducting and addressable non-destructively. However, these properties have been elusive because conducting walls have to be electrically charged, which makes them unstable and uncommon in ferroelectric materials. Here we reveal that spontaneous and recorded domain walls in thin films of lead zirconate and bismuth ferrite exhibit large conductance at microwave frequencies despite being insulating at d.c. We explain this effect by morphological roughening of the walls and local charges induced by disorder with the overall charge neutrality. a.c. conduction is immune to large contact resistance enabling completely non-destructive walls read-out. This demonstrates a technological potential for harnessing a.c. conduction for oxide electronics and other materials with poor d.c. conduction, particularly at the nanoscale.

  20. Microwave a.c. conductivity of domain walls in ferroelectric thin films.

    PubMed

    Tselev, Alexander; Yu, Pu; Cao, Ye; Dedon, Liv R; Martin, Lane W; Kalinin, Sergei V; Maksymovych, Petro

    2016-01-01

    Ferroelectric domain walls are of great interest as elementary building blocks for future electronic devices due to their intrinsic few-nanometre width, multifunctional properties and field-controlled topology. To realize the electronic functions, domain walls are required to be electrically conducting and addressable non-destructively. However, these properties have been elusive because conducting walls have to be electrically charged, which makes them unstable and uncommon in ferroelectric materials. Here we reveal that spontaneous and recorded domain walls in thin films of lead zirconate and bismuth ferrite exhibit large conductance at microwave frequencies despite being insulating at d.c. We explain this effect by morphological roughening of the walls and local charges induced by disorder with the overall charge neutrality. a.c. conduction is immune to large contact resistance enabling completely non-destructive walls read-out. This demonstrates a technological potential for harnessing a.c. conduction for oxide electronics and other materials with poor d.c. conduction, particularly at the nanoscale. PMID:27240997

  1. Microwave a.c. conductivity of domain walls in ferroelectric thin films

    PubMed Central

    Tselev, Alexander; Yu, Pu; Cao, Ye; Dedon, Liv R.; Martin, Lane W.; Kalinin, Sergei V.; Maksymovych, Petro

    2016-01-01

    Ferroelectric domain walls are of great interest as elementary building blocks for future electronic devices due to their intrinsic few-nanometre width, multifunctional properties and field-controlled topology. To realize the electronic functions, domain walls are required to be electrically conducting and addressable non-destructively. However, these properties have been elusive because conducting walls have to be electrically charged, which makes them unstable and uncommon in ferroelectric materials. Here we reveal that spontaneous and recorded domain walls in thin films of lead zirconate and bismuth ferrite exhibit large conductance at microwave frequencies despite being insulating at d.c. We explain this effect by morphological roughening of the walls and local charges induced by disorder with the overall charge neutrality. a.c. conduction is immune to large contact resistance enabling completely non-destructive walls read-out. This demonstrates a technological potential for harnessing a.c. conduction for oxide electronics and other materials with poor d.c. conduction, particularly at the nanoscale. PMID:27240997

  2. Temperature dependence of conductivity measurement for conducting polymer

    NASA Astrophysics Data System (ADS)

    Gutierrez, Leandro; Duran, Jesus; Isah, Anne; Albers, Patrick; McDougall, Michael; Wang, Weining

    2014-03-01

    Conducting polymer-based solar cells are the newest generation solar cells. While research on this area has been progressing, the efficiency is still low because certain important parameters of the solar cell are still not well understood. It is of interest to study the temperature dependence of the solar cell parameters, such as conductivity of the polymer, open circuit voltage, and reverse saturation current to gain a better understanding on the solar cells. In this work, we report our temperature dependence of conductivity measurement using our in-house temperature-varying apparatus. In this project, we designed and built a temperature varying apparatus using a thermoelectric cooler module which gives enough temperature range as we need and costs much less than a cryostat. The set-up of the apparatus will be discussed. Temperature dependence of conductivity measurements for PEDOT:PSS films with different room-temperature conductivity will be compared and discussed. NJSGC-NASA Fellowship grant

  3. Effect of nanosilica on optical, electric modulus and AC conductivity of polyvinyl alcohol/polyaniline films

    NASA Astrophysics Data System (ADS)

    El-Sayed, Somyia; Abel-Baset, Tarob; Elfadl, Azza Abou; Hassen, Arafa

    2015-05-01

    Nanosilica (NS) was synthesized by a sol-gel method and mixed with 0.98 polyvinyl alcohol (PVA)/0.02 polyaniline (PANI) in different amounts to produce nanocomposite films. High-resolution transmission electron microscopy (HR-TEM) revealed the average particle size of the NS to be ca. 15 nm. Scanning electron microscopy (SEM) showed that the NS was well-dispersed on the surface of the PVA/PNAI films. The Fourier transform infrared (FTIR) spectra of the samples showed a significant change in the intensity of the characteristic peak of the functional groups in the composite films with the amount of NS added. The absorbance and refractive index (n) of the composites were studied in the UV-vis range, and the optical energy band gap, Eg, and different optical parameters were calculated. The dielectric loss modulus, M″ and ac conductivity, σac, of the samples were studied within 300-425 K and 0.1 kHz-5 MHz, respectively. Two relaxation peaks were observed in the frequency dependence of the dielectric loss modulus, M″. The behavior of σac(f) for the composite films indicated that the conduction mechanism was correlated barrier hopping (CBH). The results of this work are discussed and compared with those of previous studies of similar composites.

  4. Instabilities across the isotropic conductivity point in a nematic phenyl benzoate under AC driving.

    PubMed

    Kumar, Pramoda; Patil, Shivaram N; Hiremath, Uma S; Krishnamurthy, K S

    2007-08-01

    We characterize the sequence of bifurcations generated by ac fields in a nematic layer held between unidirectionally rubbed ITO electrodes. The material, which possesses a negative dielectric anisotropy epsilona and an inversion temperature for electrical conductivity anisotropy sigmaa, exhibits a monostable tilted alignment near TIN, the isotropic-nematic point. On cooling, an anchoring transition to the homeotropic configuration occurs close to the underlying smectic phase. The field experiments are performed for (i) negative sigmaa and homeotropic alignment, and (ii) weakly positive sigmaa and nearly homeotropic alignment. Under ac driving, the Freedericksz transition is followed by bifurcation into various patterned states. Among them are the striped states that seem to belong to the dielectric regime and localized hybrid instabilities. Very significantly, the patterned instabilities are not excited by dc fields, indicating their possible gradient flexoelectric origin. The Carr-Helfrich mechanism-based theories that take account of flexoelectric terms can explain the observed electroconvective effects only in part. PMID:17616118

  5. Conductivity (ac and dc) in III-V amorphous semiconductors and chalcogenide glasses

    NASA Astrophysics Data System (ADS)

    Hauser, J. J.

    1985-02-01

    Variable-range hopping, as evidenced by a resistivity proportional to exp(T-1/4), has been induced in many III-V amorphous semiconductors (InSb, AlSb, and GaAs) and even in chalcogenide glasses (As2Te3, As2Te3-xSex, and GeTe) by depositing films at 77 K. It is therefore remarkable that the same procedure failed to generate variable-range hopping in GaSb, which is one of the less ionic III-V semiconductors. Besides differences in the dc conductivity, there are also different behaviors in the ac conductivity of amorphous semiconductors. The low-temperature ac conductivity of all amorphous semiconductors is proportional to ωsTn with s~=1 and n<1, which is consistent with a model of correlated barrier hopping of electron pairs between paired and random defects. However, in the case of a-SiO2 and a-GeSe2 one finds, in addition, that the capacitance obeys the scaling relation C=A ln(Tω-1), which would suggest a conduction mechanism by tunneling relaxation. Furthermore, this scaling relation cannot be fitted to the data for a-As2Te3, a-InSb, and a-GaSb although the functional dependence of C on T and ω are similar.

  6. Iterative Precise Conductivity Measurement with IDEs

    PubMed Central

    Hubálek, Jaromír

    2015-01-01

    The paper presents a new approach in the field of precise electrolytic conductivity measurements with planar thin- and thick-film electrodes. This novel measuring method was developed for measurement with comb-like electrodes called interdigitated electrodes (IDEs). Correction characteristics over a wide range of specific conductivities were determined from an interface impedance characterization of the thick-film IDEs. The local maximum of the capacitive part of the interface impedance is used for corrections to get linear responses. The measuring frequency was determined at a wide range of measured conductivity. An iteration mode of measurements was suggested to precisely measure the conductivity at the right frequency in order to achieve a highly accurate response. The method takes precise conductivity measurements in concentration ranges from 10−6 to 1 M without electrode cell replacement. PMID:26007745

  7. Study on AC-DC Electrical Conductivities in Warm Dense Matter Generated by Pulsed-power Discharge with Isochoric Vessel

    NASA Astrophysics Data System (ADS)

    Sasaki, Toru; Ohuchi, Takumi; Takahashi, Takuya; Kawaguchi, Yoshinari; Saito, Hirotaka; Miki, Yasutoshi; Takahashi, Kazumasa; Kikuchi, Takashi; Aso, Tsukasa; Harada, Nob.

    2016-03-01

    To observe AC and DC electrical conductivity in warm dense matter (WDM), we have demonstrated to apply the spectroscopic ellipsometry for a pulsed-power discharge with isochoric vessel. At 10 μs from the beginning of discharge, the generated parameters by using pulsed-power discharge with isochoric vessel are 0.1 ρ s (ρ s: solid density) of density and 4000 K of temperature, respectively. The DC electrical conductivity for above parameters is estimated to be 104 S/m. In order to measure the AC electrical conductivity, we have developed a four-detector spectroscopic ellipsometer with a multichannel spectrometer. The multichannel spectrometer, in which consists of a 16-channel photodiode array, a two-stages voltage adder, and a flat diffraction grating, has 10 MHz of the frequency response with covered visible spectrum. For applying the four-detector spectroscopic ellipsometer, we observe the each observation signal evolves the polarized behavior compared to the ratio as I 1/I 2.

  8. Skin Conductance Measurement in Communication Research.

    ERIC Educational Resources Information Center

    Goodman, R. Irwin

    1985-01-01

    Describes skin conductance measurement as a physiological procedure to obtain information on onset, duration, intensity, and completion of private physiological responses to parts of films or media products. The mechanics of the technique, how measurements are recorded and analyzed, and types of skin conductance research literature are discussed.…

  9. AC conductivity scaling behavior in grain and grain boundary response regime of fast lithium ionic conductors

    NASA Astrophysics Data System (ADS)

    Mariappan, C. R.

    2014-05-01

    AC conductivity spectra of Li-analogues NASICON-type Li1.5Al0.5Ge1.5P3O12 (LAGP), Li-Al-Ti-P-O (LATP) glass-ceramics and garnet-type Li7La2Ta2O13 (LLTO) ceramic are analyzed by universal power law and Summerfield scaling approaches. The activation energies and pre-exponential factors of total and grain conductivities are following the Meyer-Neldel (M-N) rule for NASICON-type materials. However, the garnet-type LLTO material deviates from the M-N rule line of NASICON-type materials. The frequency- and temperature-dependent conductivity spectra of LAGP and LLTO are superimposed by Summerfield scaling. The scaled conductivity curves of LATP are not superimposed at the grain boundary response region. The superimposed conductivity curves are observed at cross-over frequencies of grain boundary response region for LATP by incorporating the exp ( {{{ - (EAt - EAg )} {{{ - (EAt - EAg )} {kT}}} ) factor along with Summerfield scaling factors on the frequency axis, where EAt and EAg are the activation energies of total and grain conductivities, respectively.

  10. AC and DC conductivity of ionic liquid containing polyvinylidene fluoride thin films

    NASA Astrophysics Data System (ADS)

    Frübing, Peter; Wang, Feipeng; Kühle, Till-Friedrich; Gerhard, Reimund

    2016-01-01

    Polarisation processes and charge transport in polyvinylidene fluoride (PVDF) with a small amount (0.01-10 wt%) of the ionic liquid (IL) 1-ethyl-3-methylimidazolium nitrate ({[EMIM]}^+[{NO}_3]^-) are investigated by means of dielectric spectroscopy. The response of PVDF that contains more than 0.01 wt% IL is dominated by a low-frequency relaxation which shows typical signatures of electrode polarisation. Furthermore, the α a relaxation, related to the glass transition, disappears for IL contents of more than 1 wt%, which indicates that the amorphous phase loses its glass-forming properties and undergoes structural changes. The DC conductivity is determined from the low-frequency limit of the AC conductivity and from the dielectric loss peak related to the electrode polarisation. DC conductivities of 10^{-10} to 10^{-2} {S}/{m} are obtained—increasing with IL content and temperature. The dependence of the DC conductivity on the IL content follows a power law with an exponent greater than one, indicating an increase in the ion mobility. The temperature dependence of the DC conductivity shows Vogel-Fulcher-Tammann behaviour, which implies that charge transport is coupled to polymer chain motion. Mobile ion densities and ion mobilities are calculated from the DC conductivity and the dielectric loss related to electrode polarisation, with the results that less than one per cent of the total ion concentration contributes to the conductivity and that the strong increase in conductivity with temperature is mainly caused by a strong increase in ion mobility. This leads to the conclusion that in particular the ion mobility must be reduced in order to decrease the DC conductivity.

  11. Finding the asymmetric parasitic source and drain resistances from the a.c. conductances of a single MOS transistor

    NASA Astrophysics Data System (ADS)

    Raychaudhuri, A.; Deen, M. J.; King, M. I. H.; Kolk, J.

    1996-06-01

    Layout asymmetry, processing, or hot-carrier stressing can give rise to unequal source and drain parasitic resistances in a MOSFET. In these cases, it is necessary to extract these resistances separately without the aid of other transistors. In this paper, we present a simple method to extract the source and drain parasitic resistances separately. This method, unlike earlier ones that depend on the measurements of the d.c. resistances of several MOSFETs, is based on accurate formulations and measurements of the a.c. conductances with respect to the gate and drain terminals of a single transistor. This allows us to get reasonably accurate estimates of these resistances in a more straightforward manner. We also discuss the main error terms in detail.

  12. AC conductivity and dielectric behavior of CoAl xFe 2- xO 4

    NASA Astrophysics Data System (ADS)

    Abo El Ata, A. M.; Attia, S. M.; Meaz, T. M.

    2004-01-01

    AC conductivity and dielectric properties have been studied for a series of polycrystalline spinel ferrite with composition CoAl xFe 2- xO 4, as a function of frequency and temperature. The results of AC conductivity were discussed in terms of the quantum mechanical tunneling and small polaron tunneling models. The dispersion of the dielectric constant was discussed in the light of Koops model and hopping conduction mechanism. The dielectric loss tangent tan δ curves exhibits a dielectric relaxation peaks which are attributed to the coincidence of the hopping frequency of the charge carriers with that of the external fields. The AC conductivity, dielectric constant, and dielectric loss tangent were found to increase with increasing the temperature due to the increase of the hopping frequency, while they decrease with increasing Al ion content due to the reduction of iron ions available for the conduction process at the octahedral sites.

  13. Electric properties of carbon nano-onion/polyaniline composites: a combined electric modulus and ac conductivity study

    NASA Astrophysics Data System (ADS)

    Papathanassiou, Anthony N.; Mykhailiv, Olena; Echegoyen, Luis; Sakellis, Ilias; Plonska-Brzezinska, Marta E.

    2016-07-01

    The complex electric modulus and the ac conductivity of carbon nano-onion/polyaniline composites were studied from 1 mHz to 1 MHz at isothermal conditions ranging from 15 K to room temperature. The temperature dependence of the electric modulus and the dc conductivity analyses indicate a couple of hopping mechanisms. The distinction between thermally activated processes and the determination of cross-over temperature were achieved by exploring the temperature dependence of the fractional exponent of the dispersive ac conductivity and the bifurcation of the scaled ac conductivity isotherms. The results are analyzed by combining the granular metal model (inter-grain charge tunneling of extended electron states located within mesoscopic highly conducting polyaniline grains) and a 3D Mott variable range hopping model (phonon assisted tunneling within the carbon nano-onions and clusters).

  14. Thunderstorm related variations in stratospheric conductivity measurements

    NASA Technical Reports Server (NTRS)

    Hu, Hua; Holzworth, Robert H.; Li, Ya QI

    1989-01-01

    The vector electric field and polar conductivities were measured by zero-pressure balloon-borne payloads launched from Wallops Island, Virgina during the summers of 1987 and 1988. Data were collected over thunderstorms (or electrified clouds) during 6-hour flights at altitudes near 30 km. The vector electric field measurements were made with the double Langmuir probe high-impedance method, and the direct conductivity measurements were obtained with the relaxation technique. Evidence is presented for conductivity variations over thunderstorms (or electrified clouds). It is found that both positive and negative polar conductivity data do show variations of up to a factor of 2 from ambient values associated with the disturbed periods. Some ideas for possible physical mechanisms which may be responsible for the conductivity variations over thunderstorms are also discussed in this paper.

  15. AC conductivity and dielectric relaxation of tris(N,N-dimethylanilinium) hexabromidostannate(IV) bromide: (C8H12N)3SnBr6.Br

    NASA Astrophysics Data System (ADS)

    Chouaib, H.; Kamoun, S.

    2015-10-01

    The X-ray powder analysis, thermogravimetric analysis, differential scanning calorimetry analysis and complex impedance spectroscopic data have been carried out on (C8H12N)3SnBr6.Br compound. The results show that this compound exhibits a phase transition at (T=365±2 K) which has been characterized by differential scanning calorimetry (DSC), AC conductivity and dielectric measurements. The AC conductivity, the modulus analysis, the dielectric constants and the polarizability have been studied using impedance in the temperature range from 334 K to 383 K and in the frequency range between 20 Hz and 2 MHz. The temperature dependence of DC conductivity follows the Arrhenius law. Moreover, the frequency dependence of conductivity follows Jonscher's dynamical law with the relation: σ(ω , T) =σDC + B(T)ω s(T) . Relaxation peaks can be observed in the complex modulus analysis and after a transformation of the complex permittivity ε* to the complex polarizability α*.

  16. An effective thermal conductivity measurement system

    NASA Astrophysics Data System (ADS)

    Madrid, F.; Jordà, X.; Vellvehi, M.; Guraya, C.; Coleto, J.; Rebollo, J.

    2004-11-01

    In the technical literature, there is a lack of reliable thermal parameters and, often, it is necessary to do in situ measurements for every particular material. An effective thermal conductivity measurement system has been designed and implemented to provide reliable and accurate values for that thermal parameter. The thermal conductivity of a given material is deduced from thermal resistance differential measurements of two samples. All parts of the implemented system as well as practical and theoretical solutions are described, including a power controller circuit exclusively conceived for this application. Experimental considerations to reduce the measurement error are exposed, as well as some results obtained for three different materials.

  17. Transport ac losses of a second-generation HTS tape with a ferromagnetic substrate and conducting stabilizer

    NASA Astrophysics Data System (ADS)

    Li, Shuo; Chen, Du-Xing; Fang, Jin

    2015-12-01

    The current-voltage curve and transport ac loss of a second-generation HTS tape with a ferromagnetic NiW substrate and brass stabilizer are measured. It is found that the ac loss is up to two orders of magnitude larger than what is expected by the power-law E(J) determined by the current-voltage curve and increases with increasing frequency. Modeling results show that the overly large ac loss is contributed by the ac loss in the HTS strip enhanced by the NiW substrate and the magnetic hysteresis loss in the substrate, and the frequency-dependent loss occurs in the brass layer covering the substrate but not in the ferromagnetic substrate itself as assumed previously. The ac loss in the brass layer is associated with transport currents but not eddy currents, and it has some features similar to ordinary eddy-current loss with significant differences.

  18. Thermal conductivity measurements of Summit polycrystalline silicon.

    SciTech Connect

    Clemens, Rebecca; Kuppers, Jaron D.; Phinney, Leslie Mary

    2006-11-01

    A capability for measuring the thermal conductivity of microelectromechanical systems (MEMS) materials using a steady state resistance technique was developed and used to measure the thermal conductivities of SUMMiT{trademark} V layers. Thermal conductivities were measured over two temperature ranges: 100K to 350K and 293K to 575K in order to generate two data sets. The steady state resistance technique uses surface micromachined bridge structures fabricated using the standard SUMMiT fabrication process. Electrical resistance and resistivity data are reported for poly1-poly2 laminate, poly2, poly3, and poly4 polysilicon structural layers in the SUMMiT process from 83K to 575K. Thermal conductivity measurements for these polysilicon layers demonstrate for the first time that the thermal conductivity is a function of the particular SUMMiT layer. Also, the poly2 layer has a different variation in thermal conductivity as the temperature is decreased than the poly1-poly2 laminate, poly3, and poly4 layers. As the temperature increases above room temperature, the difference in thermal conductivity between the layers decreases.

  19. Conductance measurement circuit with wide dynamic range

    NASA Technical Reports Server (NTRS)

    Mount, Bruce E. (Inventor); Von Esch, Myron (Inventor)

    1994-01-01

    A conductance measurement circuit to measure conductance of a solution under test with an output voltage proportional to conductance over a 5-decade range, i.e., 0.01 uS to 1000 uS or from 0.1 uS to 10,000 uS. An increase in conductance indicates growth, or multiplication, of the bacteria in the test solution. Two circuits are used each for an alternate half-cycle time periods of an alternate squarewave in order to cause alternate and opposite currents to be applied to the test solution. The output of one of the two circuits may be scaled for a different range optimum switching frequency dependent upon the solution conductance and to enable uninterrupted measurement over the complete 5-decade range. This circuitry provides two overlapping ranges of conductance which can be read simultaneously without discontinuity thereby eliminating range switching within the basic circuitry. A VCO is used to automatically change the operating frequency according to the particular value of the conductance being measured, and comparators indicate which range is valid and also facilitate computer-controlled data acquisition. A multiplexer may be used to monitor any number of solutions under test continuously.

  20. Absorption and Attenuation Coefficients Using the WET Labs ac-s in the Mid-Atlantic Bight: Field Measurements and Data Analysis

    NASA Technical Reports Server (NTRS)

    Ohi, Nobuaki; Makinen, Carla P.; Mitchell, Richard; Moisan, Tiffany A.

    2008-01-01

    Ocean color algorithms are based on the parameterization of apparent optical properties as a function of inherent optical properties. WET Labs underwater absorption and attenuation meters (ac-9 and ac-s) measure both the spectral beam attenuation [c (lambda)] and absorption coefficient [a (lambda)]. The ac-s reports in a continuous range of 390-750 nm with a band pass of 4 nm, totaling approximately 83 distinct wavelengths, while the ac-9 reports at 9 wavelengths. We performed the ac-s field measurements at nine stations in the Mid-Atlantic Bight from water calibrations to data analysis. Onboard the ship, the ac-s was calibrated daily using Milli Q-water. Corrections for the in situ temperature and salinity effects on optical properties of water were applied. Corrections for incomplete recovery of the scattered light in the ac-s absorption tube were performed. The fine scale of spectral and vertical distributions of c (lambda) and a (lambda) were described from the ac-s. The significant relationships between a (674) and that of spectrophotometric analysis and chlorophyll a concentration of discrete water samples were observed.

  1. Local measurement of thermal conductivity and diffusivity

    SciTech Connect

    Hurley, David H.; Schley, Robert S.; Khafizov, Marat; Wendt, Brycen L.

    2015-12-01

    Simultaneous measurement of local thermal diffusivity and conductivity is demonstrated on a range of ceramic samples. This was accomplished by measuring the temperature field spatial profile of samples excited by an amplitude modulated continuous wave laser beam. A thin gold film is applied to the samples to ensure strong optical absorption and to establish a second boundary condition that introduces an expression containing the substrate thermal conductivity. The diffusivity and conductivity are obtained by comparing the measured phase profile of the temperature field to a continuum based model. A sensitivity analysis is used to identify the optimal film thickness for extracting the both substrate conductivity and diffusivity. Proof of principle studies were conducted on a range of samples having thermal properties that are representative of current and advanced accident tolerant nuclear fuels. It is shown that by including the Kapitza resistance as an additional fitting parameter, the measured conductivity and diffusivity of all the samples considered agree closely with literature values. Lastly, a distinguishing feature of this technique is that it does not require a priori knowledge of the optical spot size which greatly increases measurement reliability and reproducibility.

  2. Local measurement of thermal conductivity and diffusivity.

    PubMed

    Hurley, David H; Schley, Robert S; Khafizov, Marat; Wendt, Brycen L

    2015-12-01

    Simultaneous measurement of local thermal diffusivity and conductivity is demonstrated on a range of ceramic samples. This was accomplished by measuring the temperature field spatial profile of samples excited by an amplitude modulated continuous wave laser beam. A thin gold film is applied to the samples to ensure strong optical absorption and to establish a second boundary condition that introduces an expression containing the substrate thermal conductivity. The diffusivity and conductivity are obtained by comparing the measured phase profile of the temperature field to a continuum based model. A sensitivity analysis is used to identify the optimal film thickness for extracting the both substrate conductivity and diffusivity. Proof of principle studies were conducted on a range of samples having thermal properties that are representatives of current and advanced accident tolerant nuclear fuels. It is shown that by including the Kapitza resistance as an additional fitting parameter, the measured conductivity and diffusivity of all the samples considered agreed closely with the literature values. A distinguishing feature of this technique is that it does not require a priori knowledge of the optical spot size which greatly increases measurement reliability and reproducibility. PMID:26724041

  3. Local measurement of thermal conductivity and diffusivity

    NASA Astrophysics Data System (ADS)

    Hurley, David H.; Schley, Robert S.; Khafizov, Marat; Wendt, Brycen L.

    2015-12-01

    Simultaneous measurement of local thermal diffusivity and conductivity is demonstrated on a range of ceramic samples. This was accomplished by measuring the temperature field spatial profile of samples excited by an amplitude modulated continuous wave laser beam. A thin gold film is applied to the samples to ensure strong optical absorption and to establish a second boundary condition that introduces an expression containing the substrate thermal conductivity. The diffusivity and conductivity are obtained by comparing the measured phase profile of the temperature field to a continuum based model. A sensitivity analysis is used to identify the optimal film thickness for extracting the both substrate conductivity and diffusivity. Proof of principle studies were conducted on a range of samples having thermal properties that are representatives of current and advanced accident tolerant nuclear fuels. It is shown that by including the Kapitza resistance as an additional fitting parameter, the measured conductivity and diffusivity of all the samples considered agreed closely with the literature values. A distinguishing feature of this technique is that it does not require a priori knowledge of the optical spot size which greatly increases measurement reliability and reproducibility.

  4. Local measurement of thermal conductivity and diffusivity

    SciTech Connect

    Hurley, David H.; Schley, Robert S.; Khafizov, Marat; Wendt, Brycen L.

    2015-12-15

    Simultaneous measurement of local thermal diffusivity and conductivity is demonstrated on a range of ceramic samples. This was accomplished by measuring the temperature field spatial profile of samples excited by an amplitude modulated continuous wave laser beam. A thin gold film is applied to the samples to ensure strong optical absorption and to establish a second boundary condition that introduces an expression containing the substrate thermal conductivity. The diffusivity and conductivity are obtained by comparing the measured phase profile of the temperature field to a continuum based model. A sensitivity analysis is used to identify the optimal film thickness for extracting the both substrate conductivity and diffusivity. Proof of principle studies were conducted on a range of samples having thermal properties that are representatives of current and advanced accident tolerant nuclear fuels. It is shown that by including the Kapitza resistance as an additional fitting parameter, the measured conductivity and diffusivity of all the samples considered agreed closely with the literature values. A distinguishing feature of this technique is that it does not require a priori knowledge of the optical spot size which greatly increases measurement reliability and reproducibility.

  5. Local measurement of thermal conductivity and diffusivity

    DOE PAGESBeta

    Hurley, David H.; Schley, Robert S.; Khafizov, Marat; Wendt, Brycen L.

    2015-12-01

    Simultaneous measurement of local thermal diffusivity and conductivity is demonstrated on a range of ceramic samples. This was accomplished by measuring the temperature field spatial profile of samples excited by an amplitude modulated continuous wave laser beam. A thin gold film is applied to the samples to ensure strong optical absorption and to establish a second boundary condition that introduces an expression containing the substrate thermal conductivity. The diffusivity and conductivity are obtained by comparing the measured phase profile of the temperature field to a continuum based model. A sensitivity analysis is used to identify the optimal film thickness formore » extracting the both substrate conductivity and diffusivity. Proof of principle studies were conducted on a range of samples having thermal properties that are representative of current and advanced accident tolerant nuclear fuels. It is shown that by including the Kapitza resistance as an additional fitting parameter, the measured conductivity and diffusivity of all the samples considered agree closely with literature values. Lastly, a distinguishing feature of this technique is that it does not require a priori knowledge of the optical spot size which greatly increases measurement reliability and reproducibility.« less

  6. Ac-loss measurement of a DyBCO-Roebel assembled coated conductor cable (RACC)

    NASA Astrophysics Data System (ADS)

    Schuller, S.; Goldacker, W.; Kling, A.; Krempasky, L.; Schmidt, C.

    2007-10-01

    Low ac-loss HTS cables for transport currents well above 1 kA are required for application in transformers and generators and are taken into consideration for future generations of fusion reactor coils. Coated conductors (CC) are suitable candidates for high field application at an operation temperature around 50-77 K, which is a crucial precondition for economical cooling costs. We prepared a short length of a Roebel bar cable made of industrial DyBCO coated conductor (Theva Company, Germany). Meander shaped tapes of 4 mm width with a twist pitch of 122 mm were cut from 10 mm wide CC tapes using a specially designed tool. Eleven of these strands were assembled to a cable. The electrical and mechanical connection of the tapes was achieved using a silver powder filled conductive epoxy resin. Ac-losses of a short sample in an external ac field were measured as a function of frequency and field amplitude in transverse and parallel field orientations. In addition, the coupling current time constant of the sample was directly measured.

  7. AC Circuit Measurements with a Differential Hall Element Magnetometer

    NASA Astrophysics Data System (ADS)

    Calkins, Matthew W.; Nicks, B. Scott; Quintero, Pedro A.; Meisel, Mark W.

    2013-03-01

    As the biomedical field grows, there is an increasing need to quickly and efficiently characterize more samples at room temperature. An automated magnetometer was commissioned to do these room temperature magnetic characterizations. This magnetometer, which is inspired by a Differential Hall Element Magnetometer,[2] uses two commercially available Hall elements wired in series. One Hall element measures the external magnetic field of a 9 T superconducting magnet and the other measures the same external field plus the field due to the magnetization of the sample that sits on top of the Hall element. The difference between these two Hall elements is taken while a linear stepper motor sweeps through the external magnetic field. The linear motor and data acquisition are controlled by a LabVIEW program. Recently, the system was outfitted for AC circuit measurements and these data will be compared to DC circuit data. In addition, the lowest signal to noise ratio will be found in order to deduce the smallest amount of sample needed to register an accurate coercive field. Supported by the NSF via NHMFL REU (DMR-0654118), a single investigator grant (DMR-1202033 to MWM) and by the UF Undergraduate Scholars Program.

  8. Measurement of AC Induced Flow using Mico PIV

    NASA Astrophysics Data System (ADS)

    Wang, Dazhi; Meinhart, Carl; Sigurdson, Marin

    2002-11-01

    The fluid motion in a wedge-shaped device subject to an AC electric field is measured using Micron-Resolution Particle Image Velocimetry (micro-PIV). The fluorescent polystyrene spherical particles are used as flow tracers. In the non-uniform electric field, the particles in the suspension experience dielectrophoretic forces, which cause difference of velocities between the particles and the fluid. In order to eliminate the velocity difference, two different size particles are used for the micro-PIV measurements to determine the fluid velocity field. A two-color PIV technique is used to determine uniquely the fluid velocity field. The wedge-shaped channel is 100-micron wide at the apex, and fabricated from a 550-micron thick silicon wafer. A voltage of 15Vrms at 100 kHz is applied to the electrodes. The particle volume fraction is set below 0.1% so that the effect of the particles on the fluid can be negligible. Fifty successive images are taken to record particle images and analyzed to estimate the particle velocity fields. The velocity fields of the two different size particles are then used to uniquely determine the underlying fluid velocity. The measured fluid flow is a saddle-point flow, which could be used for precision mixing and transport in microscale devices.

  9. Origin of DC and AC conductivity anisotropy in iron-based superconductors: Scattering rate versus spectral weight effects

    NASA Astrophysics Data System (ADS)

    Schütt, Michael; Schmalian, Jörg; Fernandes, Rafael M.

    2016-08-01

    To shed light on the transport properties of electronic nematic phases, we investigate the anisotropic properties of the AC and DC conductivities. Based on the analytical properties of the former, we show that the anisotropy of the effective scattering rate behaves differently than the actual scattering rate anisotropy and even changes sign as a function of temperature. Similarly, the effective spectral weight acquires an anisotropy even when the plasma frequency is isotropic. These results are illustrated by an explicit calculation of the AC conductivity due to the interaction between electrons and spin fluctuations in the nematic phase of the iron-based superconductors and shown to be in agreement with recent experiments.

  10. 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.

  11. Flow rate measurement in aggressive conductive fluids

    NASA Astrophysics Data System (ADS)

    Dubovikova, Nataliia; Kolesnikov, Yuri; Karcher, Christian

    2014-03-01

    Two non-contact experimental methods of flow rate measurements for aggressive conductive liquids are described. The techniques are based on electromagnetic forces and Faraday's law: Lorentz force is induced inside moving conductive liquid under influence of variable magnetic field of permanent magnets. They are mounted along a liquid metal channel or (in case of the second method) inserted into rotated metal wheels. The force acts in the opposite of fluids' velocity direction and hence it is possible to measure reaction force of it that takes place according to Newton's law on magnetic field source - permanent magnets. And by knowing the force, which linearly depends on velocity, one can calculate mean flow rate of liquid. In addition experimental "dry" calibration and its results are described for one of the measurements' techniques.

  12. Analytic formulation for the ac electrical conductivity in two-temperature, strongly coupled, overdense plasma: FORTRAN subroutine

    NASA Astrophysics Data System (ADS)

    Cauble, R.; Rozmus, W.

    1993-10-01

    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.

  13. Martian Surface after Phoenix's Conductivity Measurements

    NASA Technical Reports Server (NTRS)

    2008-01-01

    NASA's Phoenix Mars Lander's Robotic Arm Camera took this image on Sol 71 (August 6, 2008), the 71st Martian day after landing. The shadow shows the outline of Phoenix's Thermal and Electrical Conductivity Probe, or TECP. The holes seen in the Martian surface were made by this instrument to measure the soil's conductivity. A fork-like probe inserted into the soil checks how well heat and electricity move through the soil from one prong to another.

    The measurements completed Wednesday ran from the afternoon of Phoenix's 70th Martian day, or sol, to the morning of Sol 71.

    The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  14. Measuring Contact Thermal Conductances at Low Temperatures

    NASA Technical Reports Server (NTRS)

    Salerno, Louis J.; Kittel, Peter; Brooks, Walter; Spivak, Alan L.; Marks, William G., Jr.

    1987-01-01

    Instrument measures thermal conductance of pressed contacts in liquid helium. Makes measurements automatically as function of force on pairs of brass samples having various surface finishes. Developed as part of effort to determine heat-transfer characteristics of bolted joints on cryogenically cooled focal planes in infrared equipment. Cylindrical chamber hangs from cover plate in bath of liquid helium. Inside chamber rocker arm applies controlled force to samples. Upper sample made slightly wider than lower one so two samples remain in complete contact even under slight lateral misalignment.

  15. AC hot wire measurement of thermophysical properties of nanofluids with 3ω method

    NASA Astrophysics Data System (ADS)

    Turgut, A.; Sauter, C.; Chirtoc, M.; Henry, J. F.; Tavman, S.; Tavman, I.; Pelzl, J.

    2008-01-01

    We present a new application of a hot wire sensor for simultaneous and independent measurement of thermal conductivity k and diffusivity α of (nano)fluids, based on a hot wire thermal probe with ac excitation and 3 ω lock-in detection. The theoretical modeling of imaginary part of the signal yields the k value while the phase yields the α value. Due to modulated heat flow in cylindrical geometry with a radius comparable to the thermal diffusion length, the necessary sample quantity is kept very low, typically 25 μl. In the case of relative measurements, the resolution is 0.1% in k and 0.3% in α. Measurements of water-based Aerosil 200V nanofluids indicate that ultrasound treatment is more efficient than high pressure dispersion method in enhancing their thermal parameters.

  16. System for absolute measurement of electrolytic conductivity in aqueous solutions based on van der Pauw's theory

    NASA Astrophysics Data System (ADS)

    Zhang, Bing; Lin, Zhen; Zhang, Xiao; Yu, Xiang; Wei, Jiali; Wang, Xiaoping

    2014-05-01

    Based on an innovative application of van der Pauw's theory, a system was developed for the absolute measurement of electrolytic conductivity in aqueous solutions. An electrolytic conductivity meter was designed that uses a four-electrode system with an axial-radial two-dimensional adjustment structure coupled to an ac voltage excitation source and signal collecting circuit. The measurement accuracy, resolution and repeatability of the measurement system were examined through a series of experiments. Moreover, the measurement system and a high-precision electrolytic conductivity meter were compared using some actual water samples.

  17. Measurement of heat conduction through stacked screens

    NASA Technical Reports Server (NTRS)

    Lewis, M. A.; Kuriyama, T.; Kuriyama, F.; Radebaugh, R.

    1998-01-01

    This paper describes the experimental apparatus for the measurement of heat conduction through stacked screens as well as some experimental results taken with the apparatus. Screens are stacked in a fiberglass-epoxy cylinder, which is 24.4 mm in diameter and 55 mm in length. The cold end of the stacked screens is cooled by a Gifford-McMahon (GM) cryocooler at cryogenic temperature, and the hot end is maintained at room temperature. Heat conduction through the screens is determined from the temperature gradient in a calibrated heat flow sensor mounted between the cold end of the stacked screens and the GM cryocooler. The samples used for these experiments consisted of 400-mesh stainless steel screens, 400-mesh phosphor bronze screens, and two different porosities of 325-mesh stainless steel screens. The wire diameter of the 400-mesh stainless steel and phosphor bronze screens was 25.4 micrometers and the 325-mesh stainless steel screen wire diameters were 22.9 micrometers and 27.9 micrometers. Standard porosity values were used for the experimental data with additional porosity values used on selected experiments. The experimental results showed that the helium gas between each screen enhanced the heat conduction through the stacked screens by several orders of magnitude compared to that in vacuum. The conduction degradation factor is the ratio of actual heat conduction to the heat conduction where the regenerator material is assumed to be a solid rod of the same cross sectional area as the metal fraction of the screen. This factor was about 0.1 for the stainless steel and 0.022 for the phosphor bronze, and almost constant for the temperature range of 40 to 80 K at the cold end.

  18. Harmonic analysis of AC magnetostriction measurements under non-sinusoidal excitation

    SciTech Connect

    Mogi, Hisashi; Yabumoto, Masao; Mizokami, Masato; Okazaki Yasuo

    1996-09-01

    A new system for analyzing ac magnetostriction of electrical steel sheets has been developed. This system has the following advantages: (a) AC magnetostriction waveforms can be precisely measured up to 4 kHz, and analyzed to harmonic components; (b) non-sinusoidal flux density can be excited to simulate the distorted waveform in an actual transformer core.

  19. Thermal Conductivity Measurements on consolidated Soil Analogs

    NASA Astrophysics Data System (ADS)

    Seiferlin, K.; Heimberg, M.; Thomas, N.

    2007-08-01

    Heat transport in porous media such as soils and regolith is significantly reduced compared to the properties of compact samples of the same material. The bottle neck for solid state heat transport is the contact area between adjacent grains. For "dry" and unconsolidated materials the contact areas and thus the thermal conductivity are extremely small. Sintering and cementation are two processes that can increase the cross section of interstitial bonds signifcantly. On Mars, cementation can be caused by condensation of water or carbon dioxide ice from the vapor phase, or from salts and minerals that fall out from aqueous solutions. We produced several artificially cemented samples, using small glass beads of uniform size as soil analog. The cementation is achieved by initially molten wax that is mixed with the glass beads while liqiud. The wax freezes preferably at the contact points between grains, thus minimizing surface energy, and consolidates the samples. The thermal conductivity of these samples is then measured in vacuum. We present the results of these measurements and compare them with theoretical models. The observed range of thermal conductivity values can explain some, but not all of the variations in thermal intertia that can be seen in TES remote sensing data.

  20. Transport properties of random and nonrandom substitutionally disordered alloys. I. Exact numerical calculation of the ac conductivity

    NASA Astrophysics Data System (ADS)

    Hwang, M.; Gonis, A.; Freeman, A. J.

    1987-06-01

    Results of exact computer simulations for the zero-temperature ac conductivity of one-dimensional substitutionally disordered alloys are reported. These results are obtained by (i) solving for the eigenvalues and eigenvectors of a Hamiltonian associated with a specific configuration of 500 atoms on a linear chain, (ii) evaluating the ac conductivity of this configuration by using the Kubo-Greenwood formula, and (iii) averaging the resulting conductivities over 20 to 50 different configurations (the number of configurations depends on the type of disorder). In all cases convergence (i.e., a stable result) was obtained and confirmed by another independent approach (the recursive method). For not too weak disorder (defined precisely in the text), these results exhibit a great deal of fine structure that includes high peaks and gaps where the conductivity vanishes. These features are reminiscent of, and are correlated with, the similar kind of behavior of the densities of states of one-dimensional substitutionally disordered alloys. Thus we find that the fine structure in the ac-conductivity spectra of one-dimensional systems provides a rigorous testing ground for judging the validity of analytic theories for calculating the transport properties of substitutionally disordered systems.

  1. Quantitative Thermal Microscopy Measurement with Thermal Probe Driven by dc+ac Current

    NASA Astrophysics Data System (ADS)

    Bodzenta, Jerzy; Juszczyk, Justyna; Kaźmierczak-Bałata, Anna; Firek, Piotr; Fleming, Austin; Chirtoc, Mihai

    2016-07-01

    Quantitative thermal measurements with spatial resolution allowing the examination of objects of submicron dimensions are still a challenging task. The quantity of methods providing spatial resolution better than 100 nm is very limited. One of them is scanning thermal microscopy (SThM). This method is a variant of atomic force microscopy which uses a probe equipped with a temperature sensor near the apex. Depending on the sensor current, either the temperature or the thermal conductivity distribution at the sample surface can be measured. However, like all microscopy methods, the SThM gives only qualitative information. Quantitative measuring methods using SThM equipment are still under development. In this paper, a method based on simultaneous registration of the static and the dynamic electrical resistances of the probe driven by the sum of dc and ac currents, and examples of its applications are described. Special attention is paid to the investigation of thin films deposited on thick substrates. The influence of substrate thermal properties on the measured signal and its dependence on thin film thermal conductivity and film thickness are analyzed. It is shown that in the case where layer thicknesses are comparable or smaller than the probe-sample contact diameter, a correction procedure is required to obtain actual thermal conductivity of the layer. Experimental results obtained for thin SiO2 and BaTiO_{3 }layers with thicknesses in the range from 11 nm to 100 nm are correctly confirmed with this approach.

  2. Signature of Topological Insulators in Conductance Measurements

    NASA Astrophysics Data System (ADS)

    Hong, Seokmin; Diep, Vinh; Datta, Supriyo

    2012-02-01

    Following the discovery of spin-polarized states at the surface of three-dimensional topological insulators (TI) like Bi2Te3 and Bi2Se3, there are intense interests in possible electrical measurements demonstrating unique signatures of these unusual states. A recent interesting proposal suggests that a signature of TI material should be a change in the conductance measured between a normal contact and a magnetic contact when the magnetization of the latter is reversed. However, the generalized Onsager relation suggests that no such change is expected in two-terminal setups and a multi-terminal set up is needed to observe the proposed effect. We present numerical results using a Non-Equilibrium Green Function (NEGF) based model capable of covering both ballistic and diffusive transport regimes seamlessly. Simple expressions based on a semi-classical picture describe some of the results quite well. Finally, we estimate the magnitude of signal expected in realistic samples that have recently been studied experimentally and have shown evidence of surface conduction.

  3. Reflectometer distance measurement between parallel conductive plates

    NASA Technical Reports Server (NTRS)

    Hearn, Chase P.; Neece, Robert T.

    1995-01-01

    This report presents an analytic and experimental investigation of the measurement problem in which a reflectometer is used to determine the distance to a target that is a highly conductive surface parallel to the reflectometer antenna ground plane. These parallel surfaces constitute a waveguide (WG) which can contribute parasitic perturbations that seriously degrade the accuracy of the measurements. Two distinct parallel-plate-waveguide (PPWG) phenomena are described, and their effects on both frequency and time-domain reflectometers are considered. The time-domain processing approach was found to be superior to a representative frequency-domain phase-measurement approach because of less susceptibility to perturbations produced by edge reflections and immunity to phase capture. Experimental results are presented which show that a simple radiating system modification can suppress parallel-plate (PP) propagation. The addition of a thin layer of lossy mu-metal 'magnetic absorber' to the antenna ground plane allowed a measurement accuracy of 0.025 cm (0.01 in.) when a vector network analyzer (VNA) is used as a time-domain reflectometer.

  4. The change in dielectric constant, AC conductivity and optical band gaps of polymer electrolyte film: Gamma irradiation

    SciTech Connect

    Raghu, S. Subramanya, K. Sharanappa, C. Mini, V. Archana, K. Sanjeev, Ganesh Devendrappa, H.

    2014-04-24

    The effects of gamma (γ) irradiation on dielectric and optical properties of polymer electrolyte film were investigated. The dielectric constant and ac conductivity increases with γ dose. Also optical band gap decreased from 4.23 to 3.78ev after irradiation. A large dependence of the polymer properties on the irradiation dose was noticed. This suggests that there is a possibility of improving polymer electrolyte properties on gamma irradiation.

  5. Measuring Thermal Conductivity at LH2 Temperatures

    NASA Technical Reports Server (NTRS)

    Selvidge, Shawn; Watwood, Michael C.

    2004-01-01

    For many years, the National Institute of Standards and Technology (NIST) produced reference materials for materials testing. One such reference material was intended for use with a guarded hot plate apparatus designed to meet the requirements of ASTM C177-97, "Standard Test Method for Steady-State Heat Flux Measurements and Thermal Transmission Properties by Means of the Guarded-Hot-Plate Apparatus." This apparatus can be used to test materials in various gaseous environments from atmospheric pressure to a vacuum. It allows the thermal transmission properties of insulating materials to be measured from just above ambient temperature down to temperatures below liquid hydrogen. However, NIST did not generate data below 77 K temperature for the reference material in question. This paper describes a test method used at NASA's Marshall Space Flight Center (MSFC) to optimize thermal conductivity measurements during the development of thermal protection systems. The test method extends the usability range of this reference material by generating data at temperatures lower than 77 K. Information provided by this test is discussed, as are the capabilities of the MSFC Hydrogen Test Facility, where advanced methods for materials testing are routinely developed and optimized in support of aerospace applications.

  6. Assessing Conduct Disorder: A New Measurement Approach

    PubMed Central

    Reavy, Racheal; Stein, L. A. R.; Quina, Kathryn; Paiva, Andrea L.

    2015-01-01

    The Delinquent Activities Scale (DAS) was used to develop indicators of conduct disorder (CD) in terms of symptom severity and age of onset. Incarcerated adolescents (N = 190) aged 14 to 19 were asked about their delinquent behaviors, including age the behavior was first performed, as well as substance use and parental and peer influences. Assessments were performed for the 12 months prior to incarceration and at 3-month postrelease follow-up. Evidence supports the utility of the DAS as a measure of CD diagnosis, including concurrent incremental validity. Furthermore, CD severity (symptom count) was significantly associated with two peer factors: friend substance use and friend prior arrests, with medium to large effect sizes (ESs). Earlier age of CD onset was associated with earlier marijuana use. This study finds that the DAS is a useful instrument in that it is easy to apply and has adequate psychometrics. PMID:24241820

  7. AC conductivity and electrochemical studies of PVA/PEG based polymer blend electrolyte films

    NASA Astrophysics Data System (ADS)

    Polu, Anji Reddy; Kumar, Ranveer; Dehariya, Harsha

    2012-06-01

    Polymer blend electrolyte films based on Polyvinyl alcohol(PVA)/Poly(ethylene glycol)(PEG) and magnesium nitrate (Mg(NO3)2) were prepared by solution casting technique. Conductivity in the temperature range 303-373 K and transference number measurements have been employed to investigate the charge transport in this polymer blend electrolyte system. The highest conductivity is found to be 9.63 × 10-5 S/cm at 30°C for sample with 30 weight percent of Mg(NO3)2 in PVA/PEG blend matrix. Transport number data shows that the charge transport in this polymer electrolyte system is predominantly due to ions. Using this electrolyte, an electrochemical cell with configuration Mg/(PVA+PEG+Mg(NO3)2)/(I2+C+electrolyte) was fabricated and its discharge characteristics profile has been studied.

  8. AC loss measurements in HTS coil assemblies with hybrid coil structures

    NASA Astrophysics Data System (ADS)

    Jiang, Zhenan; Long, Nicholas J.; Staines, Mike; Badcock, Rodney A.; Bumby, Chris W.; Buckley, Robert G.; Amemiya, Naoyuki

    2016-09-01

    Both AC loss and wire cost in coil windings are critical factors for high temperature superconductor (HTS) AC machinery applications. We present AC loss measurement results in three HTS coil assemblies at 77 K and 65 K which have a hybrid coil structure comprising one central winding (CW) and two end windings (EWs) wound with ReBCO and BSCCO wires with different self-field I c values at 77 K. All AC loss results in the coil assemblies are hysteretic and the normalized AC losses in the coil assemblies at different temperatures can be scaled with the I c value of the coil assemblies. The normalised results show that AC loss in a coil assembly with BSCCO CW can be reduced by using EWs wound with high I c ReBCO wires, whilst further AC loss reduction can be achieved by replacing the BSCCO CW with ReBCO CW. The results imply that a flexible hybrid coil structure is possible which considers both AC loss and wire cost in coil assemblies.

  9. Sensitive bridge circuit measures conductance of low-conductivity electrolyte solutions

    NASA Technical Reports Server (NTRS)

    Schmidt, K.

    1967-01-01

    Compact bridge circuit measures sensitive and accurate conductance of low-conductivity electrolyte solutions. The bridge utilizes a phase sensitive detector to obtain a linear deflection of the null indicator relative to the measured conductance.

  10. Measurements and calculations of transport AC loss in second generation high temperature superconducting pancake coils

    NASA Astrophysics Data System (ADS)

    Yuan, Weijia; Coombs, T. A.; Kim, Jae-Ho; Han Kim, Chul; Kvitkovic, Jozef; Pamidi, Sastry

    2011-12-01

    Theoretical and experimental AC loss data on a superconducting pancake coil wound using second generation (2 G) conductors are presented. An anisotropic critical state model is used to calculate critical current and the AC losses of a superconducting pancake coil. In the coil there are two regions, the critical state region and the subcritical region. The model assumes that in the subcritical region the flux lines are parallel to the tape wide face. AC losses of the superconducting pancake coil are calculated using this model. Both calorimetric and electrical techniques were used to measure AC losses in the coil. The calorimetric method is based on measuring the boil-off rate of liquid nitrogen. The electric method used a compensation circuit to eliminate the inductive component to measure the loss voltage of the coil. The experimental results are consistent with the theoretical calculations thus validating the anisotropic critical state model for loss estimations in the superconducting pancake coil.

  11. Construction of Tunnel Diode Oscillator for AC Impedance Measurement

    NASA Astrophysics Data System (ADS)

    Shin, J. H.; Kim, E.

    2014-03-01

    We construct a tunnel diode oscillator (TDO) to study electromagnetic response of a superconducting thin film. Highly sensitive tunnel diode oscillators allow us to detect extremely small changes in electromagnetic properties such as dielectric constant, ac magnetic susceptibility and magnetoresistance. A tunnel diode oscillator is a self-resonant oscillator of which resonance frequency is primarily determined by capacitance and inductance of a resonator. Amplitude of the signal depends on the quality factor of the resonator. The change in the impedance of the sample electromagnetic coupled to one of inductors in the resonator alters impedance of the inductor, and leads to the shift in the resonance frequency and the change of the amplitude.

  12. Measuring thermal diffusivity of mechanical and optical grades of polycrystalline diamond using an AC laser calorimetry method

    SciTech Connect

    Rule, Toby D.; Cai, Wei; Wang, Hsin

    2013-01-01

    Because of its extremely high thermal conductivity, measuring the thermal conductivity or diffusivity of optical-grade diamond can be challenging. Various methods have been used to measure the thermal conductivity of thick diamond films. For the purposes of commercial quality control, the AC laser calorimetry method is appealing because it enables fairly rapid and convenient sample preparation and measurement. In this paper, the method is used to measure the thermal diffusivity of optical diamond. It is found that sample dimensions and measurement parameters are critical, and data analysis must be performed with great care. The results suggest that the method as it is applied to optical-grade diamond could be enhanced by a more powerful laser, higher frequency beam modulation, and post-processing based on 2D thermal simulation.

  13. Dielectric behavior and ac conductivity study of NiO /Al2O3 nanocomposites in humid atmosphere

    NASA Astrophysics Data System (ADS)

    Ahmad, Mohamad M.; Makhlouf, Salah A.; Khalil, Kamal M. S.

    2006-11-01

    Humidity sensing characteristics of NiO /Al2O3 nanocomposites, prepared by sol-gel method, are studied by impedance spectroscopy. Modeling of the obtained impedance spectra with an appropriate equivalent circuit enables us to separate the electrical responses of the tightly bound chemisorbed water molecules on the grain surfaces and the loosely associated physisorbed water layers. Dependence of the dielectric properties and ac conductivity of the nanocomposites on relative humidity (RH) were studied as a function of the frequency of the applied ac signal in the frequency range of 0.1-105Hz. The electrical relaxation behavior of the investigated materials is presented in the conductivity formalism, where the conductivity spectra at different RHs are analyzed by the Almond-West formalism [D. P. Almond et al., Solid State Ionics 8, 159 (1983)]. The dc conductivity and the hopping rate of charge carriers, determined from this analysis, show similar dependences on RH, indicating that the concentration of mobile ions is independent of RH and is primarily determined by the chemisorption process of water molecules. Finally, the results are discussed in view of a percolation-type conduction mechanism, where mobile ions are provided by the chemisorbed water molecules and the percolation network is formed by the physisorbed water layers.

  14. Calculation of the ac to dc resistance ratio of conductive nonmagnetic straight conductors by applying FEM simulations

    NASA Astrophysics Data System (ADS)

    Riba, Jordi-Roger

    2015-09-01

    This paper analyzes the skin and proximity effects in different conductive nonmagnetic straight conductor configurations subjected to applied alternating currents and voltages. These effects have important consequences, including a rise of the ac resistance, which in turn increases power loss, thus limiting the rating for the conductor. Alternating current (ac) resistance is important in power conductors and bus bars for line frequency applications, as well as in smaller conductors for high frequency applications. Despite the importance of this topic, it is not usually analyzed in detail in undergraduate and even in graduate studies. To address this, this paper compares the results provided by available exact formulas for simple geometries with those obtained by means of two-dimensional finite element method (FEM) simulations and experimental results. The paper also shows that FEM results are very accurate and more general than those provided by the formulas, since FEM models can be applied in a wide range of electrical frequencies and configurations.

  15. 21 CFR 882.1550 - Nerve conduction velocity measurement device.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Nerve conduction velocity measurement device. 882... conduction velocity measurement device. (a) Identification. A nerve conduction velocity measurement device is a device which measures nerve conduction time by applying a stimulus, usually to a...

  16. 21 CFR 882.1550 - Nerve conduction velocity measurement device.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Nerve conduction velocity measurement device. 882... conduction velocity measurement device. (a) Identification. A nerve conduction velocity measurement device is a device which measures nerve conduction time by applying a stimulus, usually to a...

  17. 21 CFR 882.1550 - Nerve conduction velocity measurement device.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Nerve conduction velocity measurement device. 882... conduction velocity measurement device. (a) Identification. A nerve conduction velocity measurement device is a device which measures nerve conduction time by applying a stimulus, usually to a...

  18. 21 CFR 882.1550 - Nerve conduction velocity measurement device.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Nerve conduction velocity measurement device. 882... conduction velocity measurement device. (a) Identification. A nerve conduction velocity measurement device is a device which measures nerve conduction time by applying a stimulus, usually to a...

  19. 21 CFR 882.1550 - Nerve conduction velocity measurement device.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Nerve conduction velocity measurement device. 882... conduction velocity measurement device. (a) Identification. A nerve conduction velocity measurement device is a device which measures nerve conduction time by applying a stimulus, usually to a...

  20. Development of the Exams Data Analysis Spreadsheet as a Tool to Help Instructors Conduct Customizable Analyses of Student ACS Exam Data

    ERIC Educational Resources Information Center

    Brandriet, Alexandra; Holme, Thomas

    2015-01-01

    The American Chemical Society Examinations Institute (ACS-EI) has recently developed the Exams Data Analysis Spread (EDAS) as a tool to help instructors conduct customizable analyses of their student data from ACS exams. The EDAS calculations allow instructors to analyze their students' performances both at the total score and individual item…

  1. AC loss measurement of superconducting dipole magnets by the calorimetric method

    SciTech Connect

    Morita, Y.; Hara, K.; Higashi, N.; Kabe, A.

    1996-12-31

    AC losses of superconducting dipole magnets were measured by the calorimetric method. The magnets were model dipole magnets designed for the SSC. These were fabricated at KEK with 50-mm aperture and 1.3-m overall length. The magnet was set in a helium cryostat and cooled down to 1.8 K with 130 L of pressurized superfluid helium. Heat dissipated by the magnet during ramp cycles was measured by temperature rise of the superfluid helium. Heat leakage into the helium cryostat was 1.6 W and was subtracted from the measured heat to obtain AC loss of the magnet. An electrical measurement was carried out for calibration. Results of the two methods agreed within the experimental accuracy. The authors present the helium cryostat and measurement system in detail, and discuss the results of AC loss measurement.

  2. Second VAMAS a.c. loss measurement intercomparison: a.c. magnetization measurement of hysteresis and coupling losses in NbTi multifilamentary strands

    NASA Astrophysics Data System (ADS)

    Schmidt, C.; Itoh, K.; Wada, H.

    The article summarizes results of part of the second VAMAS a.c. loss measurement intercomparison. This program was carried out at 17 participating laboratories on two sets of multifilamentary NbTi strands (Set No. 1: copper matrix, fil. diam. between 0.5 and 12 μm; Set No. 2: cupronickel matrix, fil. diam. between 0.4 and 1.2 μm). The results reported here were measured by means of a.c. magnetization methods and separated into hysteresis and coupling losses. One laboratory used a calorimetric method. The data scatter in measured hysteresis losses among the participating laboratories was reasonably small for different measuring methods adopted and experimental arrangements used. On the other hand, the data scatter in coupling losses was large, mainly because in most laboratories a.c. losses were measured only at low frequencies (below 1 Hz), where the separation of coupling losses from total losses tends to be inaccurate. The comparison of measured hysteresis losses with the critical state model showed a large disagreement, which is assumed to be due to proximity effect coupling between filaments. 1997 Elsevier Science Limited

  3. The Wechsler ACS Social Perception Subtest: A Preliminary Comparison with Other Measures of Social Cognition

    ERIC Educational Resources Information Center

    Kandalaft, Michelle R.; Didehbani, Nyaz; Cullum, C. Munro; Krawczyk, Daniel C.; Allen, Tandra T.; Tamminga, Carol A.; Chapman, Sandra B.

    2012-01-01

    Relative to other cognitive areas, there are few clinical measures currently available to assess social perception. A new standardized measure, the Wechsler Advanced Clinical Solutions (ACS) Social Perception subtest, addresses some limitations of existing measures; however, little is known about this new test. The first goal of this investigation…

  4. Dielectric properties and study of AC electrical conduction mechanisms by non-overlapping small polaron tunneling model in Bis(4-acetylanilinium) tetrachlorocuprate(II) compound

    NASA Astrophysics Data System (ADS)

    Abkari, A.; Chaabane, I.; Guidara, K.

    2016-09-01

    In the present work, the synthesis and characterization of the Bis(4-acetylanilinium) tetrachlorocuprate(II) compound are presented. The structure of this compound is analyzed by X-ray diffraction which confirms the formation of single phase and is in good agreement the literature. Indeed, the Thermo gravimetric Analysis (TGA) shows that the decomposition of the compound is observed in the range of 420-520 K. However, the differential thermal analysis (DTA) indicates the presence of a phase transition at T=363 k. Furthermore, the dielectric properties and AC conductivity were studied over a temperature range (338-413 K) and frequency range (200 Hz-5 MHz) using complex impedance spectroscopy. Dielectric measurements confirmed such thermal analyses by exhibiting the presence of an anomaly in the temperature range of 358-373 K. The complex impedance plots are analyzed by an electrical equivalent circuit consisting of resistance, constant phase element (CPE) and capacitance. The activation energy values of two distinct regions are obtained from log σT vs 1000/T plot and are found to be E=1.27 eV (T<363 K) and E=1.09 eV (363 Kac conductivity, σac, has been analyzed by Jonscher's universal power law σ(ω)=σdc+Aωs. The value of s is to be temperature-dependent, which has a tendency to increase with temperature and the non-overlapping small polaron tunneling (NSPT) model is the most applicable conduction mechanism in the title compound. Complex impedance spectra of [C8H10NO]2CuCl4 at different temperatures.

  5. Crystal structure, NMR study, dielectric relaxation and AC conductivity of a new compound [Cd3(SCN)2Br6(C2H9N2)2]n

    NASA Astrophysics Data System (ADS)

    Saidi, K.; Kamoun, S.; Ayedi, H. Ferid; Arous, M.

    2013-11-01

    The crystal structure, the 13C NMR spectroscopy and the complex impedance have been carried out on [Cd3(SCN)2Br6(C2H9N2)2]n. Crystal structure shows a 2D polymeric network built up of two crystallographically independent cadmium atoms with two different octahedral coordinations. This compound exhibits a phase transition at (T=355±2 K) which has been characterized by differential scanning calorimetry (DSC), X-rays powder diffraction, AC conductivity and dielectric measurements. Examination of 13C CP/MAS line shapes shows indirect spin-spin coupling (14N and 13C) with a dipolar coupling constant of 1339 Hz. The AC conductivity of this compound has been carried out in the temperature range 325-376 K and the frequency range from 10-2 Hz to 10 MHz. The impedance data were well fitted to two equivalent electrical circuits. The results of the modulus study reveal the presence of two distinct relaxation processes. One, at low frequency side, is thermally activated due to the ionic conduction of the crystal and the other, at higher frequency side, gradually disappears when temperature reaches 355 K which is attributed to the localized dipoles in the crystal. Moreover, the temperature dependence of DC-conductivity in both phases follows the Arrhenius law and the frequency dependence of σ(ω,T) follows Jonscher's universal law. The near values of activation energies obtained from the conductivity data and impedance confirm that the transport is through the ion hopping mechanism.

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

    NASA Astrophysics Data System (ADS)

    Amagai, Yasutaka; Nakamura, Yasuhiro

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

  7. Measurements of the Seebeck coefficient of thermoelectric materials by an ac method

    SciTech Connect

    Goto, T.; Li, J.H.; Hirai, T.; Maeda, Y.; Kato, R.; Maesono, A.

    1997-03-01

    An ac method for measurement of the Seebeck coefficient was developed. Specimens were heated periodically at frequencies in the range 0.2--10 Hz using a semiconductor laser. The small temperature increase and the resultant thermoelectric power were measured with a Pt-Pt 13% Rh thermocouple (25 {micro}m in diameter) through a lock-in amplifier. The Seebeck coefficient of a Pt{sub 90}Rh{sub 10} foil measured by the ac method was in agreement with that obtained from the standard table. The optimum frequency and specimen thickness for the ac method were 0.2 Hz and 0.1--0.2 mm, respectively. The Seebeck coefficients of silicon single crystal and several thermoelectric semiconductors (Si{sub 80}Ge{sub 20}, PbTc, FeSi{sub 2}, SiB{sub 14}) measured by the ac method agreed with those measured by a conventional dc method in the temperature range between room temperature and 1200 K. The time needed for each measurement was less than a few tens of minutes, significantly shorter than that for a conventional dc method.

  8. AC impedance analysis of ionic and electronic conductivities in electrode mixture layers for an all-solid-state lithium-ion battery

    NASA Astrophysics Data System (ADS)

    Siroma, Zyun; Sato, Tomohiro; Takeuchi, Tomonari; Nagai, Ryo; Ota, Akira; Ioroi, Tsutomu

    2016-06-01

    The ionic and electronic effective conductivities of an electrode mixture layers for all-solid-state lithium-ion batteries containing Li2Ssbnd P2S5 as a solid electrolyte were investigated by AC impedance measurements and analysis using a transmission-line model (TLM). Samples containing graphite (graphite electrodes) or LiNi0.5Co0.2Mn0.3O2 (NCM electrodes) as the active material were measured under a "substrate | sample | bulk electrolyte | sample | substrate" configuration (ion-electron connection) and a "substrate | sample | substrate" configuration (electron-electron connection). Theoretically, if the electronic resistance is negligibly small, which is the case with our graphite electrodes, measurement with the ion-electron connection should be effective for evaluating ionic conductivity. However, if the electronic resistance is comparable to the ionic resistance, which is the case with our NCM electrodes, the results with the ion-electron connection may contain some inherent inaccuracy. In this report, we theoretically and practically demonstrate the advantage of analyzing the results with the electron-electron connection, which gives both the ionic and electronic conductivities. The similarity of the behavior of ionic conductivity with the graphite and NCM electrodes confirms the reliability of this analysis.

  9. AC Conduction and Time-Temperature Superposition Scaling in a Reduced Graphene Oxide-Zinc Sulfide Nanocomposite.

    PubMed

    Chakraborty, Koushik; Das, Poulomi; Chakrabarty, Sankalpita; Pal, Tanusri; Ghosh, Surajit

    2016-05-18

    We report, herein, the results of an in depth study and concomitant analysis of the AC conduction [σ'(ω): f=20 Hz to 2 MHz] mechanism in a reduced graphene oxide-zinc sulfide (RGO-ZnS) composite. The magnitude of the real part of the complex impedance decreases with increase in both frequency and temperature, whereas the imaginary part shows an asymptotic maximum that shifts to higher frequencies with increasing temperature. On the other hand, the conductivity isotherm reveals a frequency-independent conductivity at lower frequencies subsequent to a dispersive conductivity at higher frequencies, which follows a power law [σ'(ω)∝ω(s) ] within a temperature range of 297 to 393 K. Temperature-independent frequency exponent 's' indicates the occurrence of phonon-assisted simple quantum tunnelling of electrons between the defects present in RGO. Finally, this sample follows the "time-temperature superposition principle", as confirmed from the universal scaling of conductivity isotherms. These outcomes not only pave the way for increasing our elemental understanding of the transport mechanism in the RGO system, but will also motivate the investigation of the transport mechanism in other order-disorder systems. PMID:26864678

  10. Note: Development of a microfabricated sensor to measure thermal conductivity of picoliter scale liquid samples

    NASA Astrophysics Data System (ADS)

    Park, Byoung Kyoo; Yi, Namwoo; Park, Jaesung; Kim, Dongsik

    2012-10-01

    This paper presents a thermal analysis device, which can measure thermal conductivity of picoliter scale liquid sample. We employ the three omega method with a microfabricated AC thermal sensor with nanometer width heater. The liquid sample is confined by a micro-well structure fabricated on the sensor surface. The performance of the instrument was verified by measuring the thermal conductivity of 27-picoliter samples of de-ionized (DI) water, ethanol, methanol, and DI water-ethanol mixtures with accuracies better than 3%. Furthermore, another analytical scheme allows real-time thermal conductivity measurement with 5% accuracy. To the best of our knowledge, this technique requires the smallest volume of sample to measure thermal property ever.

  11. Fiber - Optic Devices as Temperature Sensors for Temperature Measurements in AC Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Rablau, Corneliu; Lafrance, Joseph; Sala, Anca

    2007-10-01

    We report on the investigation of several fiber-optic devices as potential sensors for temperature measurements in AC magnetic fields. Common temperature sensors, such as thermocouples, thermistors or diodes, will create random and/or systematic errors when placed in a magnetic field. A DC magnetic field is susceptible to create a systematic offset to the measurement, while in an AC magnetic field of variable frequency random errors which cannot be corrected for can also be introduced. Fiber-Bragg-gratings and thin film filters have an inherent temperature dependence. Detrimental for their primary applications, the same dependence allows one to use such devices as temperature sensors. In an AC magnetic field, they present the advantage of being immune to electromagnetic interference. Moreover, for fiber-Bragg-gratings, the shape factor and small mass of the bare-fiber device make it convenient for temperature measurements on small samples. We studied several thin-film filters and fiber-Bragg-gratings and compared their temperature measurement capabilities in AC magnetic fields of 0 to 150 Gauss, 0 to 20 KHz to the results provided by off-the-shelf thermocouples and thermistor-based temperature measurement systems.

  12. Second VAMAS a.c. loss measurement intercomparison: magnetization measurement of low-frequency (hysteretic) a.c. loss in NbTi multifilamentary strands

    NASA Astrophysics Data System (ADS)

    Collings, E. W.; Sumption, M. D.; Itoh, K.; Wada, H.; Tachikawa, K.

    The results of the 2 nd VAMAS measurement intercomparison program on low-frequency (hysteretic) a.c. loss are presented and discussed. Two sets of multifilamentary NbTi strands (Set No. 1: copper matrix, fil. diams 0.5, 1, 3, and 12 μm; Set No. 2: cupronickel matrix, fil. diams 0.4, 0.5, and 1 μm) were subjected to interlaboratory testing. In an initial series of tests, samples in various forms (e.g. wire bundles, coils) were measured mostly by vibrating-sample- and SQUID magnetometry. Considerable scatter was noted especially in the small-filament-diameter a.c.-loss data. In a study of measurement accuracy, a supplementary series of tests compared the results of VSM measurement of a given pair of copper-matrix samples. In the light of all the results, factors contributing to a.c. loss error are discussed and recommendations are made concerning the specification of future a.c.-loss measurement intercomparisons.

  13. Modelling and measurement of ac loss in BSCCO/Ag-tape windings

    NASA Astrophysics Data System (ADS)

    Oomen, M. P.; Nanke, R.; Leghissa, M.

    2003-03-01

    High-temperature superconducting (HTS) transformers promise decreased weight and volume and higher efficiency. A 1 MVA HTS railway transformer was built and tested at Siemens AG. This paper deals with the prediction of ac loss in the BSCCO/Ag-tape windings. In a railway transformer the tape carries ac current in alternating field, the temperature differs from 77 K, tapes are stacked or cabled and overcurrents and higher harmonics occur. In ac-loss literature these issues are treated separately, if at all. We have developed a model that predicts the ac loss in sets of BSCCO/Ag-tape coils, and deals with the above-mentioned issues. The effect of higher harmonics on the loss in HTS tapes is considered for the first time. The paper gives a complete overview of the model equations and required input parameters. The model is validated over a wide range of the input parameters, using the measured critical current and ac loss of single tapes, single coils and sets of coils in the 1 MVA transformer. An accuracy of around 25% is achieved in all relevant cases. Presently the model is developed further, in order to describe other HTS materials and other types of applications.

  14. New ac microammeter for leakage current measurement of biomedical equipment

    NASA Astrophysics Data System (ADS)

    Branca, F. P.; Del Prete, Z.; Marinozzi, F.

    1993-11-01

    A new inexpensive current probe for on-line leakage current measurement of biomedical devices in hospital environment is described. The prototype is designed to detect and measure leakage currents on the ground wire of the device's power cord so that its integrity can be monitored in real time. Realized with a sensing coil specially matched to a low-noise op amp, this probe adds only negligible impedance on the monitored ground lines. From this preliminary study about the device's metrological performances, a sensitivity of 10 nArms for a current range 1-500 μArms has emerged, together with a mean linearity error of 0.03% and a frequency response flat within 1% of gain from 50 to 2000 Hz.

  15. Monitoring colloidal stability of polymer-coated magnetic nanoparticles using AC susceptibility measurements.

    PubMed

    Herrera, Adriana P; Barrera, Carola; Zayas, Yashira; Rinaldi, Carlos

    2010-02-15

    The application of the response of magnetic nanoparticles to oscillating magnetic fields to probe transitions in colloidal state and structure of polymer-coated nanoparticles is demonstrated. Cobalt ferrite nanoparticles with narrow size distribution were prepared and shown to respond to oscillating magnetic fields through a Brownian relaxation mechanism, which is dependent on the mechanical coupling between the particle dipoles and the surrounding matrix. These nanoparticles were coated with covalently-attached poly(N-isopropylacrylamide) (pNIPAM) or poly(N-isopropylmethacrylamide) (pNIPMAM) through free radical polymerization. The temperature induced transitions of colloidal suspensions of these nanoparticles were studied through a combination of differential scanning calorimetry (DSC), dynamic light scattering (DLS), and AC susceptibility measurements. In the pNIPAM coated nanoparticles excellent agreement was found for a transition temperature of approximately 30 degrees C by all three methods, although the AC susceptibility measurements indicated aggregation which was not evident from the DLS results. Small-angle neutron scattering (SANS) results obtained for pNIPAM coated nanoparticles confirmed that aggregation indeed occurs above the lower critical transition temperature of pNIPAM. For the pNIPMAM coated nanoparticles DLS and AC susceptibility measurements indicated aggregation at a temperature of approximately 33-35 degrees C, much lower than the transition temperature peak at 40 degrees C observed by DSC. However, the transition observed by DSC is very broad, hence it is possible that aggregation begins to occur at temperatures lower than the peak, as indicated by the AC susceptibility and DLS results. These experiments and observations demonstrate the possibility of using AC susceptibility measurements to probe transitions in colloidal suspensions induced by external stimuli. Because magnetic measurements do not require optical transparency, these

  16. Calorimetric AC loss measurement of MgB2 superconducting tape in an alternating transport current and direct magnetic field

    NASA Astrophysics Data System (ADS)

    See, K. W.; Xu, X.; Horvat, J.; Cook, C. D.; Dou, S. X.

    2012-11-01

    Applications of MgB2 superconductors in electrical engineering have been widely reported, and various studies have been made to define their alternating current (AC) losses. However, studies on the transport losses with an applied transverse DC magnetic field have not been conducted, even though this is one of the favored conditions in applications of practical MgB2 tapes. Methods and techniques used to characterize and measure these losses have so far been grouped into ‘electrical’ and ‘calorimetric’ approaches with external conditions set to resemble the application conditions. In this paper, we present a new approach to mounting the sample and employ the calorimetric method to accurately determine the losses in the concurrent application of AC transport current and DC magnetic fields that are likely to be experienced in practical devices such as generators and motors. This technique provides great simplification compared to the pickup coil and lock-in amplifier methods and is applied to a long length (˜10 cm) superconducting tape. The AC loss data at 20 and 30 K will be presented in an applied transport current of 50 Hz under external DC magnetic fields. The results are found to be higher than the theoretical predictions because of the metallic fraction of the tape that contributes quite significantly to the total losses. The data, however, will allow minimization of losses in practical MgB2 coils and will be used in the verification of numerical coil models.

  17. 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.

  18. Determination of the Si-conducting polymer interfacial properties using A-C impedance techniques

    NASA Technical Reports Server (NTRS)

    Nagasubramanian, G.; Di Stefano, Salvador; Moacanin, Jovan

    1985-01-01

    A study was made of the interfacial properties of poly(pyrrole) (PP) deposited electrochemically onto single crystal p-Si surfaces. The interfacial properties are dependent upon the counterions. The formation of 'quasi-ohmic' and 'nonohmic' contacts, respectively, of PP(ClO4) and PP films doped with other counterions (BF4 and para-toluene sulfonate) with p-Si, are explained in terms of the conductivity of these films and the flat band potential, V(fb), of PP relative to that of p-Si. The PP film seems to passivate or block intrinsic surface states present on the p-Si surface. The differences in the impedance behavior of para-toluene sulfonate doped and ClO4 doped PP are compared.

  19. Thermal-Conductivity Measurement of Thermoelectric Materials Using 3{{\\upomega }} Method

    NASA Astrophysics Data System (ADS)

    Hahtela, O.; Ruoho, M.; Mykkänen, E.; Ojasalo, K.; Nissilä, J.; Manninen, A.; Heinonen, M.

    2015-12-01

    In this work, a measurement system for high-temperature thermal-conductivity measurements has been designed, constructed, and characterized. The system is based on the 3{\\upomega } method which is an ac technique suitable for both bulk and thin-film samples. The thermal-conductivity measurements were performed in a horizontal three-zone tube furnace whose sample space can be evacuated to vacuum or alternatively a protective argon gas environment can be applied to prevent undesired oxidation and contamination of the sample material. The system was tested with several dielectric, semiconductor, and metal bulk samples from room temperature up to 725 K. The test materials were chosen so that the thermal-conductivity values covered a wide range from 0.37 W\\cdot m^{-1}\\cdot K^{-1} to 150 {} \\cdot m^{-1}\\cdot K^{-1}. An uncertainty analysis for the thermal-conductivity measurements was carried out. The measurement accuracy is mainly limited by the determination of the third harmonic of the voltage over the resistive metal heater strip that is used for heating the sample. A typical relative measurement uncertainty in the thermal-conductivity measurements was between 5 % and 8 % (k=2). An extension of the 3{\\upomega } method was also implemented in which the metal heater strip is first deposited on a transferable Kapton foil. Utilizing such a prefabricated sensor allows for faster measurements of the samples as there is no need to deposit a heater strip on each new sample.

  20. Studies of structural, optical, dielectric relaxation and ac conductivity of different alkylbenzenesulfonic acids doped polypyrrole nanofibers

    NASA Astrophysics Data System (ADS)

    Hazarika, J.; Kumar, A.

    2016-01-01

    Polypyrrole (PPy) nanofibers doped with alkylbenzenesulfonic acids (ABSA) have been synthesized using interfacial polymerization method. HRTEM studies confirm the formation of PPy nanofibers with average diameter ranging from 13 nm to 25 nm. Broad X-ray diffraction peak in 2 θ range 20-23.46° reveals amorphous structure of PPy nanofibers. The ordering or crystallinity of polymer chains increases, while their interplanar spacing (d) and interchain separation (R) decreases for short alkyl chain ABSA doped PPy nanofibers. FTIR studies reveal that short alkyl chain ABSA doped PPy nanofibers show higher value of "effective conjugation length". PPy nanofibers doped with short alkyl chain ABSA dopant exhibit smaller optical band gap. TGA studies show enhanced thermal stability of short alkyl chain ABSA doped PPy nanofibers. Decrease in dielectric permittivity ε ‧ (ω) with increasing frequency suggests presence of electrode polarization effects. Linear decrease in dielectric loss ε ″ (ω) with increasing frequency suggests dominant effect of dc conductivity process. Low value of non-exponential exponent β (<1) reveals non-Debye relaxation of charge carriers. Scaling of imaginary modulus (M ″) reveals that the charge carriers follow the same relaxation mechanism. Moreover, the charge carriers in PPy nanofibers follow the correlated barrier hopping (CBH) transport mechanism.

  1. Measurement of solar cell ac parameters using the time domain technique

    NASA Astrophysics Data System (ADS)

    Deshmukh, M. P.; Kumar, R. Anil; Nagaraju, J.

    2004-08-01

    The instrumentation to measure solar cell ac parameters [cell capacitance (CP) and cell resistance (RP)] using the time domain technique is developed. The cell capacitance (CP) and series resistance (r) are calculated using open circuit voltage decay (OCVD) technique. It is calibrated with the help of an electrical network with passive components similar to ac equivalent circuit of a solar cell consisting of precision resistors and capacitors. The maximum error observed in the measurement of resistor and capacitor value is ±3.5%. The cell resistance (RP) is calculated from I-V characteristics of solar cell. The data obtained in time domain technique is compared with the impedance spectroscopy technique data measured on same solar cell and it is found that the deviation in cell capacitance and resistance are within ±8%.

  2. Effective method to measure back emfs and their harmonics of permanent magnet ac motors

    NASA Astrophysics Data System (ADS)

    Jiang, Q.; Bi, C.; Lin, S.

    2006-04-01

    As the HDD spindle motors become smaller and smaller, the back electromotive forces (emfs) measurement faces the new challenges due to their low inertias and small sizes. This article proposes a novel method to measure the back emfs and their harmonic components of PM ac motors only through a freewheeling procedure. To eliminate the influence of the freewheeling deceleration, the phase flux linkages are employed to obtain the back emf amplitudes and phases of the fundamental and harmonic components by using finite Fourier series analysis. The proposed method makes the freewheeling measurement of the back emfs and their harmonics accurate and fast. It is especially useful for the low inertia PM ac motors, such as spindle motors for small form factor HDDs.

  3. Measurement of the thermal contact conductance and thermal conductivity of anodized aluminum coatings

    SciTech Connect

    Peterson, G.P.; Fletcher, L.S. )

    1990-08-01

    An experimental investigation was conducted to determine the thermal contact conductance and effective thermal conductivity of anodized coatings. One chemically polished Aluminum 6061-T6 test specimen and seven specimens with anodized coatings varying in thickness from 60.9 {mu}m to 163.8 {mu}m were tested while in contact with a single unanodized aluminum surface. Measurements of the overall joint conductance, composed of the thermal contact conductance between the anodized coating and the bare aluminum surface and the bulk conductance of the coating material, indicated that the overall joint conductance decreased with increasing thickness of the anodized coating and increased with increasing interfacial load. Using the experimental data, a dimensionless expression was developed that related the overall joint conductance to the coating thickness, the surface roughness, the interfacial pressure, and the properties of the aluminum substrate. By subtracting the thermal contact conductance from the measured overall joint conductance, estimations of the effective thermal conductivity of the anodized coating as a function of pressure were obtained for each of the seven anodized specimens. At an extrapolated pressure of zero, the effective thermal conductivity was found to be approximately 0.02 W/m-K. In addition to this extrapolated value, a single expression for predicting the effective thermal conductivity as a function of both the interface pressure and the anodized coating thickness was developed and shown to be within {plus minus}5 percent of the experimental data over a pressure range of 0 to 14 MPa.

  4. AC magnetic measurements of the ALS Booster Dipole Engineering Model Magnet

    SciTech Connect

    Green, M.I.; Keller, R.; Nelson, D.H.; Hoyer, E.

    1989-03-01

    10 Hz sine wave and 2 Hz sawtooth AC magnetic measurements of he curved ALS Booster Dipole Engineering Model Magnet have been accomplished. Long curved coils were utilized to measure the integral transfer function and uniformity. Point coils and a Hall Probe were used to measure magnetic induction and its uniformity. The data were logged and processed by a Tektronix 11401 digital oscilloscope. The dependence of the effective length on the field was determined from the ratio of the integral coil signals to the point coil signals. Quadrupole and sextupole harmonics were derived from the point and integral uniformity measurements. 5 refs., 4 figs., 2 tabs.

  5. Direct Measurement of Ab and Ac at the Z0 Pole Using a Lepton Tag

    NASA Astrophysics Data System (ADS)

    Abe, Kenji; Abe, Koya; Abe, T.; Adam, I.; Akagi, T.; Allen, N. J.; Arodzero, A.; Ash, W. W.; Aston, D.; Baird, K. G.; Baltay, C.; Band, H. R.; Barakat, M. B.; Bardon, O.; Barklow, T. L.; Bashindzhagyan, G. L.; Bauer, J. M.; Bellodi, G.; Ben-David, R.; Benvenuti, A. C.; Bilei, G. M.; Bisello, D.; Blaylock, G.; Bogart, J. R.; Bolen, B.; Bower, G. R.; Brau, J. E.; Breidenbach, M.; Bugg, W. M.; Burke, D.; Burnett, T. H.; Burrows, P. N.; Byrne, R. M.; Calcaterra, A.; Calloway, D.; Camanzi, B.; Carpinelli, M.; Cassell, R.; Castaldi, R.; Castro, A.; Cavalli-Sforza, M.; Chou, A.; Church, E.; Cohn, H. O.; Coller, J. A.; Convery, M. R.; Cook, V.; Cotton, R.; Cowan, R. F.; Coyne, D. G.; Crawford, G.; Damerell, C. J.; Danielson, M. N.; Daoudi, M.; de Groot, N.; dell'Orso, R.; Dervan, P. J.; de Sangro, R.; Dima, M.; D'Oliveira, A.; Dong, D. N.; Doser, M.; Dubois, R.; Eisenstein, B. I.; Eschenburg, V.; Etzion, E.; Fahey, S.; Falciai, D.; Fan, C.; Fernandez, J. P.; Fero, M. J.; Flood, K.; Frey, R.; Gillman, T.; Gladding, G.; Gonzalez, S.; Goodman, E. R.; Hart, E. L.; Harton, J. L.; Hasan, A.; Hasuko, K.; Hedges, S. J.; Hertzbach, S. S.; Hildreth, M. D.; Huber, J.; Huffer, M. E.; Hughes, E. W.; Huynh, X.; Hwang, H.; Iwasaki, M.; Jackson, D. J.; Jacques, P.; Jaros, J. A.; Jiang, Z. Y.; Johnson, A. S.; Johnson, J. R.; Johnson, R. A.; Junk, T.; Kajikawa, R.; Kalelkar, M.; Kamyshkov, Y.; Kang, H. J.; Karliner, I.; Kawahara, H.; Kim, Y. D.; King, R.; King, M. E.; Kofler, R. R.; Krishna, N. M.; Kroeger, R. S.; Langston, M.; Lath, A.; Leith, D. W.; Lia, V.; Lin, C.-J. S.; Liu, X.; Liu, M. X.; Loreti, M.; Lu, A.; Lynch, H. L.; Ma, J.; Mahjouri, M.; Mancinelli, G.; Manly, S.; Mantovani, G.; Markiewicz, T. W.; Maruyama, T.; Masuda, H.; Mazzucato, E.; McKemey, A. K.; Meadows, B. T.; Menegatti, G.; Messner, R.; Mockett, P. M.; Moffeit, K. C.; Moore, T. B.; Morii, M.; Muller, D.; Murzin, V.; Nagamine, T.; Narita, S.; Nauenberg, U.; Neal, H.; Nussbaum, M.; Oishi, N.; Onoprienko, D.; Osborne, L. S.; Panvini, R. S.; Park, H.; Park, C. H.; Pavel, T. J.; Peruzzi, I.; Piccolo, M.; Piemontese, L.; Pieroni, E.; Pitts, K. T.; Plano, R. J.; Prepost, R.; Prescott, C. Y.; Punkar, G. D.; Quigley, J.; Ratcliff, B. N.; Reeves, T. W.; Reidy, J.; Reinertsen, P. L.; Rensing, P. E.; Rochester, L. S.; Rowson, P. C.; Russell, J. J.; Saxton, O. H.; Schalk, T.; Schindler, R. H.; Schumm, B. A.; Schwiening, J.; Sen, S.; Serbo, V. V.; Shaevitz, M. H.; Shank, J. T.; Shapiro, G.; Sherden, D. J.; Shmakov, K. D.; Simopoulos, C.; Sinev, N. B.; Smith, S. R.; Smy, M. B.; Snyder, J. A.; Staengle, H.; Stahl, A.; Stamer, P.; Steiner, R.; Steiner, H.; Strauss, M. G.; Su, D.; Suekane, F.; Sugiyama, A.; Suzuki, S.; Swartz, M.; Szumilo, A.; Takahashi, T.; Taylor, F. E.; Thom, J.; Torrence, E.; Toumbas, N. K.; Usher, T.; Vannini, C.; Va'Vra, J.; Vella, E.; Venuti, J. P.; Verdier, R.; Verdini, P. G.; Wagner, S. R.; Wagner, D. L.; Waite, A. P.; Walston, S.; Wang, J.; Ward, C.; Watts, S. J.; Weidemann, A. W.; Weiss, E. R.; Whitaker, J. S.; White, S. L.; Wickens, F. J.; Williams, B.; Williams, D. C.; Williams, S. H.; Willocq, S.; Wilson, R. J.; Wisniewski, W. J.; Wittlin, J. L.; Woods, M.; Word, G. B.; Wright, T. R.; Wyss, J.; Yamamoto, R. K.; Yamartino, J. M.; Yang, X.; Yashima, J.; Yellin, S. J.; Young, C. C.; Yuta, H.; Zapalac, G.; Zdarko, R. W.; Zhou, J.

    1999-10-01

    The parity violation parameters Ab and Ac of the Zbb¯ and Zcc¯ couplings have been measured directly, using the polar angle dependence of the Z0-pole polarized cross sections. Bottom and charmed hadrons were tagged via semileptonic decays. Both the muon and electron identification algorithms take advantage of new multivariate techniques, incorporating for the first time information from the SLD Cˇerenkov Ring Imaging Detector. Based on the 1993-1995 SLD sample of 150 000 Z0 decays produced with highly polarized electron beams, we measure Ab = 0.910+/-0.068\\(stat\\)+/-0.037\\(syst\\), Ac = 0.642+/-0.110\\(stat\\)+/-0.063\\(syst\\).

  6. Ac hysteresis loop measurement of stator-tooth in induction motor

    SciTech Connect

    Son, D.

    1999-09-01

    The properties of ac hysteresis loop of a stator tooth in a 5 hp induction motor was measured and analyzed. The load increase on the motor decreased magnetic induction, however increase the minor hysteresis loops in the high induction region. This effect caused increase in the core loss. Depending on condition of the motor, the core loss of the stator tooth can be 50% greater than the core loss under sinusoidal magnetic induction waveform.

  7. Crystal structure and AC conductivity mechanism of [N(C3H7)4]2CoCl4 compound

    NASA Astrophysics Data System (ADS)

    Moutia, N.; Oueslati, A.; Ben Gzaiel, M.; Khirouni, K.

    2016-09-01

    We found that the new organic-inorganic compound [N(C3H7)4]2 CoCl4, crystallizes at room temperature in the centrosymmetric monoclinic system with P21/c space group. The atomic arrangement can be described by an alternation of organic and organic-inorganic layers parallel to the (001) plan. Indeed, the differential scanning calorimetry (DSC) studies indicate a presence of three order-disorder phase transitions located at 332, 376 and 441 K. Furthermore, the conductivity was measured in the frequency range from 200 MHz to 5 MHz and temperatures between 318 K and 428 K using impedance spectroscopy. Analysis of the AC conductivity experimental data obtained, and the frequency exponent s with theoretical models reveals that the correlated barrier hopping (CBH) model is the appropriate mechanism for conduction in the title compound. The analysis of the dielectric constants ε ‧ and ε ″ versus temperature, at several frequencies, shows a distribution of relaxation times. This relaxation is probably due to the reorientational dynamics of [N(C3H7)4]+ cations.

  8. 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.

  9. Comparison of Measured and Estimated Unsaturated Hydraulic Conductivity

    NASA Astrophysics Data System (ADS)

    Parkes, M. E.; Waters, P. A.

    1980-08-01

    Most studies of empirical estimates of unsaturated hydraulic conductivity functions do not account for water which may be relatively immobile under the conditions in which field measurements of conductivity are made. To investigate this, unsaturated hydraulic conductivity data were obtained for three monolith lysimeters, 80 cm in diameter by 135 cm deep, using the instantaneous profile technique. The lysimeters contained well-structured, freely draining loam soil and moisture measurements were made using a neutron probe. Conductivity estimates were also obtained from laboratory measurements of soil moisture characteristics using the modified Millington and Quirk computational method. Ratios of the calculated to measured conductivities at a matching point near saturation were so large as to suggest that only a minor proportion of the soil pore space was contributing to flow through the whole profile.

  10. Direct measurements of Ab and Ac using vertex and kaon charge tags at the SLAC detector.

    PubMed

    Abe, Koya; Abe, Kenji; Abe, T; Adam, I; Akimoto, H; Aston, D; Baird, K G; Baltay, C; Band, H R; Barklow, T L; Bauer, J M; Bellodi, G; Berger, R; Blaylock, G; Bogart, J R; Bower, G R; Brau, J E; Breidenbach, M; Bugg, W M; Burke, D; Burnett, T H; Burrows, P N; Calcaterra, A; Cassell, R; Chou, A; Cohn, H O; Coller, J A; Convery, M R; Cook, V; Cowan, R F; Crawford, G; Damerell, C J S; Daoudi, M; Dasu, S; de Groot, N; de Sangro, R; Dong, D N; Doser, M; Dubois, R; Erofeeva, I; Eschenburg, V; Etzion, E; Fahey, S; Falciai, D; Fernandez, J P; Flood, K; Frey, R; Hart, E L; Hasuko, K; Hertzbach, S S; Huffer, M E; Huynh, X; Iwasaki, M; Jackson, D J; Jacques, P; Jaros, J A; Jiang, Z Y; Johnson, A S; Johnson, J R; Kajikawa, R; Kalelkar, M; Kang, H J; Kofler, R R; Kroeger, R S; Langston, M; Leith, D W G; Lia, V; Lin, C; Mancinelli, G; Manly, S; Mantovani, G; Markiewicz, T W; Maruyama, T; McKemey, A K; Messner, R; Moffeit, K C; Moore, T B; Morii, M; Muller, D; Murzin, V; Narita, S; Nauenberg, U; Neal, H; Nesom, G; Oishi, N; Onoprienko, D; Osborne, L S; Panvini, R S; Park, C H; Peruzzi, I; Piccolo, M; Piemontese, L; Plano, R J; Prepost, R; Prescott, C Y; Ratcliff, B N; Reidy, J; Reinertsen, P L; Rochester, L S; Rowson, P C; Russell, J J; Saxton, O H; Schalk, T; Schumm, B A; Schwiening, J; Serbo, V V; Shapiro, G; Sinev, N B; Snyder, J A; Staengle, H; Stahl, A; Stamer, P; Steiner, H; Su, D; Suekane, F; Sugiyama, A; Suzuki, A; Swartz, M; Taylor, F E; Thom, J; Torrence, E; Usher, T; Va'vra, J; Verdier, R; Wagner, D L; Waite, A P; Walston, S; Weidemann, A W; Weiss, E R; Whitaker, J S; Williams, S H; Willocq, S; Wilson, R J; Wisniewski, W J; Wittlin, J L; Woods, M; Wright, T R; Yamamoto, R K; Yashima, J; Yellin, S J; Young, C C; Yuta, H

    2005-03-11

    Exploiting the manipulation of the SLAC Linear Collider electron-beam polarization, we present precise direct measurements of the parity-violation parameters A(c) and A(b) in the Z-boson-c-quark and Z-boson-b-quark coupling. Quark-antiquark discrimination is accomplished via a unique algorithm that takes advantage of the precise SLAC Large Detector charge coupled device vertex detector, employing the net charge of displaced vertices as well as the charge of kaons that emanate from those vertices. From the 1996-1998 sample of 400 000 Z decays, produced with an average beam polarization of 73.4%, we find A(c)=0.673+/-0.029(stat)+/-0.023(syst) and A(b)=0.919+/-0.018(stat)+/-0.017(syst). PMID:15783953

  11. Direct Detection of Pure ac Spin Current by X-Ray Pump-Probe Measurements.

    PubMed

    Li, J; Shelford, L R; Shafer, P; Tan, A; Deng, J X; Keatley, P S; Hwang, C; Arenholz, E; van der Laan, G; Hicken, R J; Qiu, Z Q

    2016-08-12

    Despite recent progress in spin-current research, the detection of spin current has mostly remained indirect. By synchronizing a microwave waveform with synchrotron x-ray pulses, we use the ferromagnetic resonance of the Py (Ni_{81}Fe_{19}) layer in a Py/Cu/Cu_{75}Mn_{25}/Cu/Co multilayer to pump a pure ac spin current into the Cu_{75}Mn_{25} and Co layers, and then directly probe the spin current within the Cu_{75}Mn_{25} layer and the spin dynamics of the Co layer by x-ray magnetic circular dichroism. This element-resolved pump-probe measurement unambiguously identifies the ac spin current in the Cu_{75}Mn_{25} layer. PMID:27563981

  12. Direct Detection of Pure ac Spin Current by X-Ray Pump-Probe Measurements

    NASA Astrophysics Data System (ADS)

    Li, J.; Shelford, L. R.; Shafer, P.; Tan, A.; Deng, J. X.; Keatley, P. S.; Hwang, C.; Arenholz, E.; van der Laan, G.; Hicken, R. J.; Qiu, Z. Q.

    2016-08-01

    Despite recent progress in spin-current research, the detection of spin current has mostly remained indirect. By synchronizing a microwave waveform with synchrotron x-ray pulses, we use the ferromagnetic resonance of the Py (Ni81Fe19 ) layer in a Py /Cu /Cu75Mn25/Cu /Co multilayer to pump a pure ac spin current into the Cu75Mn25 and Co layers, and then directly probe the spin current within the Cu75Mn25 layer and the spin dynamics of the Co layer by x-ray magnetic circular dichroism. This element-resolved pump-probe measurement unambiguously identifies the ac spin current in the Cu75Mn25 layer.

  13. Recent Advances in AC-DC Transfer Measurements Using Thin-Film Thermal Converters

    SciTech Connect

    WUNSCH,THOMAS F.; KINARD,JOSEPH R.; MANGINELL,RONALD P.; LIPE,THOMAS E.; SOLOMON JR.,OTIS M.; JUNGLING,KENNETH C.

    2000-12-08

    New standards for ac current and voltage measurements, thin-film multifunction thermal converters (MJTCS), have been fabricated using thin-film and micro-electro-mechanical systems (MEMS) technology. Improved sensitivity and accuracy over single-junction thermoelements and targeted performance will allow new measurement approaches in traditionally troublesome areas such as the low frequency and high current regimes. A review is presented of new microfabrication techniques and packaging methods that have resulted from a collaborative effort at Sandia National Laboratories and the National Institute of Standards and Technology (MHZ).

  14. A wide-frequency range AC magnetometer to measure the specific absorption rate in nanoparticles for magnetic hyperthermia

    NASA Astrophysics Data System (ADS)

    Garaio, E.; Collantes, J. M.; Garcia, J. A.; Plazaola, F.; Mornet, S.; Couillaud, F.; Sandre, O.

    2014-11-01

    Measurement of specific absorption rate (SAR) of magnetic nanoparticles is crucial to assert their potential for magnetic hyperthermia. To perform this task, calorimetric methods are widely used. However, those methods are not very accurate and are difficult to standardize. In this paper, we present AC magnetometry results performed with a lab-made magnetometer that is able to obtain dynamic hysteresis-loops in the AC magnetic field frequency range from 50 kHz to 1 MHz and intensities up to 24 kA m-1. In this work, SAR values of maghemite nanoparticles dispersed in water are measured by AC magnetometry. The so-obtained values are compared with the SAR measured by calorimetric methods. Both measurements, by calorimetry and magnetometry, are in good agreement. Therefore, the presented AC magnetometer is a suitable way to obtain SAR values of magnetic nanoparticles.

  15. Theory of the ac spin valve effect: a new method to measure spin relaxation time

    NASA Astrophysics Data System (ADS)

    Kochan, Denis; Gmitra, Martin; Fabian, Jaroslav

    2012-02-01

    Parallel (P) and antiparallel (AP) configurations of FNF junctions have, in a dc regime, different resistivities (RAP>RP), giving rise to the giant magnetoresistance (GMR) effect, which can be explained within the spin injection drift-diffusion model. We extend the model to include ac phenomena and predict new spin dynamical phenomenon; the resonant amplification and depletion of spin accumulation in the P and AP configurations, respectively. As the major new effect, the spin valve magnetoimpedance of the FNF junction oscillates with the driving ac frequency, which leads to negative GMR effect (|ZAP|<|ZP|). We show that from the spin-valve oscillation periods, measured all electrically in the GHz regime, the spin relaxation times could be extracted without any magnetic field and sample size changes (contrary to other techniques). For thin tunnel junctions the ac signal becomes pure Lorentzian, also enabling one to obtain the spin relaxation time of the N region from the signal width. This work, was published in Physical Review Letters,10, 176604 (2011).

  16. In situ measurement of conductivity during nanocomposite film deposition

    NASA Astrophysics Data System (ADS)

    Blattmann, Christoph O.; Pratsinis, Sotiris E.

    2016-05-01

    Flexible and electrically conductive nanocomposite films are essential for small, portable and even implantable electronic devices. Typically, such film synthesis and conductivity measurement are carried out sequentially. As a result, optimization of filler loading and size/morphology characteristics with respect to film conductivity is rather tedious and costly. Here, freshly-made Ag nanoparticles (nanosilver) are made by scalable flame aerosol technology and directly deposited onto polymeric (polystyrene and poly(methyl methacrylate)) films during which the resistance of the resulting nanocomposite is measured in situ. The formation and gas-phase growth of such flame-made nanosilver, just before incorporation onto the polymer film, is measured by thermophoretic sampling and microscopy. Monitoring the nanocomposite resistance in situ reveals the onset of conductive network formation by the deposited nanosilver growth and sinternecking. The in situ measurement is much faster and more accurate than conventional ex situ four-point resistance measurements since an electrically percolating network is detected upon its formation by the in situ technique. Nevertheless, general resistance trends with respect to filler loading and host polymer composition are consistent for both in situ and ex situ measurements. The time lag for the onset of a conductive network (i.e., percolation) depends linearly on the glass transition temperature (Tg) of the host polymer. This is attributed to the increased nanoparticle-polymer interaction with decreasing Tg. Proper selection of the host polymer in combination with in situ resistance monitoring therefore enable the optimal preparation of conductive nanocomposite films.

  17. Mutation Glu82Lys in lamin A/C gene is associated with cardiomyopathy and conduction defect

    SciTech Connect

    Wang Hu; Wang Jizheng; Zheng Weiyue; Wang Xiaojian; Wang Shuxia; Song Lei; Zou Yubao; Yao Yan; Hui Rutai . E-mail: huirutai@sglab.org

    2006-05-26

    Dilated cardiomyopathy is a form of heart muscle disease characterized by impaired systolic function and ventricular dilation. The mutations in lamin A/C gene have been linked to dilated cardiomyopathy. We screened genetic mutations in a large Chinese family of 50 members including members with dilated cardiomyopathy and found a Glu82Lys substitution mutation in the rod domain of the lamin A/C protein in eight family members, three of them have been diagnosed as dilated cardiomyopathy, one presented with heart dilation. The pathogenic mechanism of lamin A/C gene defect is poorly understood. Glu82Lys mutated lamin A/C and wild type protein was transfected into HEK293 cells. The mutated protein was not properly localized at the inner nuclear membrane and the emerin protein, which interacts with lamin A/C, was also aberrantly distributed. The nuclear membrane structure was disrupted and heterochromatin was aggregated aberrantly in the nucleus of the HEK293 cells stably transfected with mutated lamin A/C gene as determined by transmission electron microscopy.

  18. Measurement of volume resistivity/conductivity of metallic alloy in inhibited seawater by optical interferometry techniques

    SciTech Connect

    Habib, K.

    2011-03-15

    Optical interferometry techniques were used for the first time to measure the volume resistivity/conductivity of carbon steel samples in seawater with different concentrations of a corrosion inhibitor. In this investigation, the real-time holographic interferometry was carried out to measure the thickness of anodic dissolved layer or the total thickness, U{sub total}, of formed oxide layer of carbon steel samples during the alternating current (ac) impedance of the samples in blank seawater and in 5-20 ppm TROS C-70 inhibited seawater, respectively. In addition, a mathematical model was derived in order to correlate between the ac impedance (resistance) and the surface (orthogonal) displacement of the surface of the samples in solutions. In other words, a proportionality constant [resistivity ({rho}) or conductivity ({sigma})= 1/{rho}] between the determined ac impedance [by electrochemical impedance spectroscopy (EIS) technique] and the orthogonal displacement (by the optical interferometry techniques) was obtained. The value of the resistivity of the carbon steel sample in the blank seawater was found similar to the value of the resistivity of the carbon steel sample air, around 1 x 10{sup -5}{Omega} cm. On the contrary, the measured values of the resistivity of the carbon steel samples were 1.85 x 10{sup 7}, 3.35 x 10{sup 7}, and 1.7 x 10{sup 7}{Omega} cm in 5, 10, and 20 ppm TROS C-70 inhibited seawater solutions, respectively. Furthermore, the determined value range of {rho} of the formed oxide layers, from 1.7 x 10{sup 7} to 3.35 x 10{sup 7}{Omega} cm, is found in a reasonable agreement with the one found in literature for the Fe oxide-hydroxides, i.e., goethite ({alpha}-FeOOH) and for the lepidocrocite ({gamma}-FeOOH), 1 x 10{sup 9}{Omega} cm. The {rho} value of the Fe oxide-hydroxides, 1 x 10{sup 9}{Omega} cm, was found slightly higher than the {rho} value range of the formed oxide layer of the present study. This is because the former value was determined

  19. Measurement of thermal conductivity in proton irradiated silicon

    SciTech Connect

    Marat Khafizov; Clarissa Yablinsky; Todd Allen; David Hurley

    2014-04-01

    We investigate the influence of proton irradiation on thermal conductivity in single crystal silicon. We apply laser based modulated thermoreflectance technique to extract the change in conductivity of the thin layer damaged by proton irradiation. Unlike time domain thermoreflectance techniques that require application of a metal film, we perform our measurement on uncoated samples. This provides greater sensitivity to the change in conductivity of the thin damaged layer. Using sample temperature as a parameter provides a means to deduce the primary defect structures that limit thermal transport. We find that under high temperature irradiation the degradation of thermal conductivity is caused primarily by extended defects.

  20. Thermal conductivity of halide solid solutions: measurement and prediction.

    PubMed

    Gheribi, Aïmen E; Poncsák, Sándor; St-Pierre, Rémi; Kiss, László I; Chartrand, Patrice

    2014-09-14

    The composition dependence of the lattice thermal conductivity in NaCl-KCl solid solutions has been measured as a function of composition and temperature. Samples with systematically varied compositions were prepared and the laser flash technique was used to determine the thermal diffusivity from 373 K to 823 K. A theoretical model, based on the Debye approximation of phonon density of state (which contains no adjustable parameters) was used to predict the thermal conductivity of both stoichiometric compounds and fully disordered solid solutions. The predictions obtained with the model agree very well with our measurement. A general method for predicting the thermal conductivity of different halide systems is discussed. PMID:25217938

  1. Measurements of prompt radiation induced conductivity of Kapton.

    SciTech Connect

    Preston, Eric F.; Zarick, Thomas Andrew; Sheridan, Timothy J.; Hartman, E. Frederick; Stringer, Thomas Arthur

    2010-10-01

    We performed measurements of the prompt radiation induced conductivity in thin samples of Kapton (polyimide) at the Little Mountain Medusa LINAC facility in Ogden, UT. Three mil samples were irradiated with a 0.5 {mu}s pulse of 20 MeV electrons, yielding dose rates of 1E9 to 1E10 rad/s. We applied variable potentials up to 2 kV across the samples and measured the prompt conduction current. Analysis rendered prompt conductivity coefficients between 6E-17 and 2E-16 mhos/m per rad/s, depending on the dose rate and the pulse width.

  2. Indirect measurement of thermal conductivity in silicon nanowires

    SciTech Connect

    Pennelli, Giovanni Nannini, Andrea; Macucci, Massimo

    2014-02-28

    We report indirect measurements of thermal conductivity in silicon nanostructures. We have exploited a measurement technique based on the Joule self-heating of silicon nanowires. A standard model for the electron mobility has been used to determine the temperature through the accurate measurement of the nanowire resistance. We have applied this technique to devices fabricated with a top-down process that yields nanowires together with large silicon areas used both as electrical and as thermal contacts. As there is crystalline continuity between the nanowires and the large contact areas, our thermal conductivity measurements are not affected by any temperature drop due to the contact thermal resistance. Our results confirm the observed reduction of thermal conductivity in nanostructures and are comparable with those previously reported in the literature, achieved with more complex measurement techniques.

  3. Non-Contact Conductivity Measurement for Automated Sample Processing Systems

    NASA Technical Reports Server (NTRS)

    Beegle, Luther W.; Kirby, James P.

    2012-01-01

    A new method has been developed for monitoring and control of automated sample processing and preparation especially focusing on desalting of samples before analytical analysis (described in more detail in Automated Desalting Apparatus, (NPO-45428), NASA Tech Briefs, Vol. 34, No. 8 (August 2010), page 44). The use of non-contact conductivity probes, one at the inlet and one at the outlet of the solid phase sample preparation media, allows monitoring of the process, and acts as a trigger for the start of the next step in the sequence (see figure). At each step of the muti-step process, the system is flushed with low-conductivity water, which sets the system back to an overall low-conductivity state. This measurement then triggers the next stage of sample processing protocols, and greatly minimizes use of consumables. In the case of amino acid sample preparation for desalting, the conductivity measurement will define three key conditions for the sample preparation process. First, when the system is neutralized (low conductivity, by washing with excess de-ionized water); second, when the system is acidified, by washing with a strong acid (high conductivity); and third, when the system is at a basic condition of high pH (high conductivity). Taken together, this non-contact conductivity measurement for monitoring sample preparation will not only facilitate automation of the sample preparation and processing, but will also act as a way to optimize the operational time and use of consumables

  4. Estimation of Ionospheric Conductivity Based on the Measurements by Superdarn

    NASA Astrophysics Data System (ADS)

    Lee, Eun-Ah; An, Byung-Ho; Yi, Yu

    2002-06-01

    The ionosphere plays an important role in the electrodynamics of space environment. In particular, the information on the ionospheric conductivity distribution is indispensable in understanding the electrodynamics of the magnetosphere and ionosphere coupling study. To meet such a requirement, several attempts have been made to estimate the conductivity distribution over the polar ionosphere. As one of such attempts we compare the ionospheric plasma convection patterns obtained from the Super Dual Auroral Radar Network (SuperDARN), from which the electric field distribution is estimated, and the simultaneously measured ground magnetic disturbance. Specifically, the electric field measured from the Goose Bay and Stokkseyri radars and magnetic disturbance data obtained from the west coast chain of Greenland are compared. In order to estimate ionospheric conductivity distribution with these information, the overhead infinite sheet current approximation is employed. As expected, the Hall conductance, height-integrated conductivity, shows a wide enhancement along the center of the auroral electrojet. However, Pedersen conductance shows negative values over a wide portion of the auroral oval region, a physically unacceptable situation. To alleviate this problem, the effect of the field-aligned current is taken into account. As a result, the region with negative Pedersen conductance disappears significantly, suggesting that the effect of the field-aligned current should be taken into account, when one wants to estimate ionospheric conductance based on ground magnetic disturbance and electric field measurements by radars.

  5. In vivo electrical conductivity measurements during and after tumor electroporation: conductivity changes reflect the treatment outcome

    NASA Astrophysics Data System (ADS)

    Ivorra, Antoni; Al-Sakere, Bassim; Rubinsky, Boris; Mir, Lluis M.

    2009-10-01

    Electroporation is the phenomenon in which cell membrane permeability is increased by exposing the cell to short high-electric-field pulses. Reversible electroporation treatments are used in vivo for gene therapy and drug therapy while irreversible electroporation is used for tissue ablation. Tissue conductivity changes induced by electroporation could provide real-time feedback of the treatment outcome. Here we describe the results from a study in which fibrosarcomas (n = 39) inoculated in mice were treated according to different electroporation protocols, some of them known to cause irreversible damage. Conductivity was measured before, within the pulses, in between the pulses and for up to 30 min after treatment. Conductivity increased pulse after pulse. Depending on the applied electroporation protocol, the conductivity increase after treatment ranged from 10% to 180%. The most significant conclusion from this study is the fact that post-treatment conductivity seems to be correlated with treatment outcome in terms of reversibility.

  6. A noncontact thermal microprobe for local thermal conductivity measurement.

    PubMed

    Zhang, Yanliang; Castillo, Eduardo E; Mehta, Rutvik J; Ramanath, Ganpati; Borca-Tasciuc, Theodorian

    2011-02-01

    We demonstrate a noncontact thermal microprobe technique for measuring the thermal conductivity κ with ∼3 μm lateral spatial resolution by exploiting quasiballistic air conduction across a 10-100 nm air gap between a joule-heated microprobe and the sample. The thermal conductivity is extracted from the measured effective thermal resistance of the microprobe and the tip-sample thermal contact conductance and radius in the quasiballistic regime determined by calibration on reference samples using a heat transfer model. Our κ values are within 5%-10% of that measured by standard steady-state methods and theoretical predictions for nanostructured bulk and thin film assemblies of pnictogen chalcogenides. Noncontact thermal microprobing demonstrated here mitigates the strong dependence of tip-sample heat transfer on sample surface chemistry and topography inherent in contact methods, and allows the thermal characterization of a wide range of nanomaterials. PMID:21361625

  7. A noncontact thermal microprobe for local thermal conductivity measurement

    NASA Astrophysics Data System (ADS)

    Zhang, Yanliang; Castillo, Eduardo E.; Mehta, Rutvik J.; Ramanath, Ganpati; Borca-Tasciuc, Theodorian

    2011-02-01

    We demonstrate a noncontact thermal microprobe technique for measuring the thermal conductivity κ with ˜3 μm lateral spatial resolution by exploiting quasiballistic air conduction across a 10-100 nm air gap between a joule-heated microprobe and the sample. The thermal conductivity is extracted from the measured effective thermal resistance of the microprobe and the tip-sample thermal contact conductance and radius in the quasiballistic regime determined by calibration on reference samples using a heat transfer model. Our κ values are within 5%-10% of that measured by standard steady-state methods and theoretical predictions for nanostructured bulk and thin film assemblies of pnictogen chalcogenides. Noncontact thermal microprobing demonstrated here mitigates the strong dependence of tip-sample heat transfer on sample surface chemistry and topography inherent in contact methods, and allows the thermal characterization of a wide range of nanomaterials.

  8. Measuring the conductivity dependence of the Casimir force

    NASA Astrophysics Data System (ADS)

    Xu, Jun; Schafer, Robert; Banishev, Alexandr; Mohideen, Umar

    2015-03-01

    The strength and distance dependence of the Casimir force can be controlled through the conductivity of the material bodies, with lower conductivity in general leading to lower Casimir forces. However low conductivity, large bandgap materials which are insulating, have drawbacks as any surface electrostatic charges cannot be easily compensated. This restricts experiments to metallic or highly doped semiconductor materials. We will report on measurements of the Casimir force gradient using the frequency shift technique. Improvements in the measurement technique will be discussed. Measurements of the Casimir force gradient using low and high conductivity silicon surfaces will be reported. The authors thank G.L. Klimchitskaya and V.M. Mostepanenko for help with the theory and the US National Science Foundation for funding the research.

  9. Optical sensor for heat conduction measurement in biological tissue

    NASA Astrophysics Data System (ADS)

    Gutierrez-Arroyo, A.; Sanchez-Perez, C.; Aleman-Garcia, N.

    2013-06-01

    This paper presents the design of a heat flux sensor using an optical fiber system to measure heat conduction in biological tissues. This optoelectronic device is based on the photothermal beam deflection of a laser beam travelling in an acrylic slab this deflection is measured with a fiber optic angle sensor. We measure heat conduction in biological samples with high repeatability and sensitivity enough to detect differences in tissues from three chicken organs. This technique could provide important information of vital organ function as well as the detect modifications due to degenerative diseases or physical damage caused by medications or therapies.

  10. pH measurement of low-conductivity waters

    USGS Publications Warehouse

    Busenberg, Eurybiades; Plummer, L.N.

    1987-01-01

    pH is an important and commonly measured parameter of precipitation and other natural waters. The various sources of errors in pH measurement were analyzed and procedures for improving the accuracy and precision of pH measurements in natural waters with conductivities of < 100 uS/cm at 25 C are suggested. Detailed procedures are given for the preparation of dilute sulfuric acid standards to evaluate the performance of pH electrodes in low conductivity waters. A daily check of the pH of dilute sulfuric acid standards and deionized water saturated with a gas mixture of low carbon dioxide at partial pressure (air) prior to the measurement of the pH of low conductivity waters is suggested. (Author 's abstract)

  11. Estimation of charge-carrier concentration and ac conductivity scaling properties near the V-I phase transition of polycrystalline Na2 S O4

    NASA Astrophysics Data System (ADS)

    Ahmad, Mohamad M.

    2005-11-01

    The conductivity spectra of polycrystalline Na2SO4 have been investigated in the frequency range 42Hz-1MHz at different temperatures below and above the V-I phase transition temperature. The conductivity data have been analyzed using Almond-West formalism. The dc conductivity, the hopping frequency of the charge carriers, and their respective activation energies have been obtained from the analysis of the ac conductivity data, and the concentration of charge carriers was calculated at different temperatures. The power-law exponent n of the conductivity spectra has average values of 0.43 and 0.61 in phases V and I , respectively, which indicates different conduction properties in the two phases. Moreover, scaling of the conductivity spectra at the low- and high-temperature phases was performed in accord with Ghosh’s scaling approach. It is found that the scaling properties depend on the structure of the investigated material.

  12. Noninvasive measurement of conductivity anisotropy at larmor frequency using MRI.

    PubMed

    Lee, Joonsung; Song, Yizhuang; Choi, Narae; Cho, Sungmin; Seo, Jin Keun; Kim, Dong-Hyun

    2013-01-01

    Anisotropic electrical properties can be found in biological tissues such as muscles and nerves. Conductivity tensor is a simplified model to express the effective electrical anisotropic information and depends on the imaging resolution. The determination of the conductivity tensor should be based on Ohm's law. In other words, the measurement of partial information of current density and the electric fields should be made. Since the direct measurements of the electric field and the current density are difficult, we use MRI to measure their partial information such as B1 map; it measures circulating current density and circulating electric field. In this work, the ratio of the two circulating fields, termed circulating admittivity, is proposed as measures of the conductivity anisotropy at Larmor frequency. Given eigenvectors of the conductivity tensor, quantitative measurement of the eigenvalues can be achieved from circulating admittivity for special tissue models. Without eigenvectors, qualitative information of anisotropy still can be acquired from circulating admittivity. The limitation of the circulating admittivity is that at least two components of the magnetic fields should be measured to capture anisotropic information. PMID:23554838

  13. Analytical estimation of skeleton thermal conductivity of a geopolymer foam from thermal conductivity measurements

    NASA Astrophysics Data System (ADS)

    Henon, J.; Alzina, A.; Absi, J.; Smith, D. S.; Rossignol, S.

    2015-07-01

    The geopolymers are alumino-silicate binders. The addition of a high pores volume fraction, gives them a thermal insulation character desired in the building industry. In this work, potassium geopolymer foams were prepared at room temperature (< 70 ∘C) by a process of in situ gas release. The porosity distribution shows a multiscale character. However, the thermal conductivity measurements gave values from 0.35 to 0.12 Wm-1.K-1 for a pore volume fraction values between 65 and 85%. In the aim to predict the thermal properties of these foams and focus on the relationship "thermal-conductivity/microstructure", knowledge of the thermal conductivity of their solid skeleton (λ s ) is paramount. However, there is rare work on the determination of this value depending on the initial composition. By the formulation used, the foaming agent contributes to the final network, and it is not possible to obtain a dense material designate to make a direct measurement of λ s . The objective of this work is to use inverse analytical methods to identify the value of λ s . Measurements of thermal conductivity by the fluxmetre technique were performed. The obtained value of the solid skeleton thermal conductivity by the inverse numerical technique is situated in a framework between 0.95 and 1.35 Wm-1.K-1 and is in agreement with one issue from the literature.

  14. Thermal and Electrical Conductivity Measurements of CDA 510 Phosphor Bronze

    NASA Technical Reports Server (NTRS)

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

    2009-01-01

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

  15. AC photovoltaic module magnetic fields

    SciTech Connect

    Jennings, C.; Chang, G.J.; Reyes, A.B.; Whitaker, C.M.

    1997-12-31

    Implementation of alternating current (AC) photovoltaic (PV) modules, particularly for distributed applications such as PV rooftops and facades, may be slowed by public concern about electric and magnetic fields (EMF). This paper documents magnetic field measurements on an AC PV module, complementing EMF research on direct-current PV modules conducted by PG and E in 1993. Although not comprehensive, the PV EMF data indicate that 60 Hz magnetic fields (the EMF type of greatest public concern) from PV modules are comparable to, or significantly less than, those from household appliances. Given the present EMF research knowledge, AC PV module EMF may not merit considerable concern.

  16. An AC constant-response method for electrophysiological measurements of spectral sensitivity functions.

    PubMed

    de Souza, J M; DeVoe, R D; Schoeps, C; Ventura, D F

    1996-10-01

    A number of methods have been used in the past to measure spectral sensitivity (S(lambda)) functions of electric responses in the visual system. We present here a microcomputer based, AC, constant-response method for automatic on-line measurement of S(lambda) in cells with or without a sustained tonic response. It is based on feedback adjustment of light intensity to obtain constant peak-to-peak amplitudes of response to a flickering stimulus as the spectrum is scanned between 300 and 700 nm in 4 nm steps. It combines the advantages of: (1) on-line presentation of S(lambda) curves; (2) constant light adaptation; (3) sampling of many points; and (4) fast data collection time. The system can be applied to sensitivity or threshold (e.g., S(lambda), dark adaptation, receptive field) measurements of any electrically recorded visual response. PMID:8912193

  17. Method for Measuring Thermal Conductivity of Small Samples Having Very Low Thermal Conductivity

    NASA Technical Reports Server (NTRS)

    Miller, Robert A.; Kuczmarski, Maria a.

    2009-01-01

    This paper describes the development of a hot plate method capable of using air as a standard reference material for the steady-state measurement of the thermal conductivity of very small test samples having thermal conductivity on the order of air. As with other approaches, care is taken to ensure that the heat flow through the test sample is essentially one-dimensional. However, unlike other approaches, no attempt is made to use heated guards to block the flow of heat from the hot plate to the surroundings. It is argued that since large correction factors must be applied to account for guard imperfections when sample dimensions are small, it may be preferable to simply measure and correct for the heat that flows from the heater disc to directions other than into the sample. Experimental measurements taken in a prototype apparatus, combined with extensive computational modeling of the heat transfer in the apparatus, show that sufficiently accurate measurements can be obtained to allow determination of the thermal conductivity of low thermal conductivity materials. Suggestions are made for further improvements in the method based on results from regression analyses of the generated data.

  18. In-Pile Thermal Conductivity Measurement Method for Nuclear Fuels

    SciTech Connect

    Joy L. Rempe; Brandon Fox; Heng Ban; Joshua E. Daw; Darrell L. Knudson; Keith G. Condie

    2009-08-01

    Thermophysical properties of advanced nuclear fuels and materials during irradiation must be known prior to their use in existing, advanced, or next generation reactors. Thermal conductivity is one of the most important properties for predicting fuel and material performance. A joint Utah State University (USU) / Idaho National Laboratory (INL) project, which is being conducted with assistance from the Institute for Energy Technology at the Norway Halden Reactor Project, is investigating in-pile fuel thermal conductivity measurement methods. This paper focuses on one of these methods – a multiple thermocouple method. This two-thermocouple method uses a surrogate fuel rod with Joule heating to simulate volumetric heat generation to gain insights about in-pile detection of thermal conductivity. Preliminary results indicated that this method can measure thermal conductivity over a specific temperature range. This paper reports the thermal conductivity values obtained by this technique and compares these values with thermal property data obtained from standard thermal property measurement techniques available at INL’s High Test Temperature Laboratory. Experimental results and material properties data are also compared to finite element analysis results.

  19. In situ measurement of ceramic vacuum chamber conductive coating quality

    SciTech Connect

    Doose, C.; Harkay, K.; Kim, S.; Milton, S.

    1997-08-01

    A method for measuring the relative surface resistivity and quality of conductive coatings on ceramic vacuum chambers was developed. This method is unique in that it allows one to test the coating even after the ceramic chamber is installed in the accelerator and under vacuum; furthermore, the measurement provides a localized surface reading of the coating conductance. The method uses a magnetic probe is calibrated using the measured DC end-to-end resistance of the tube under test and by comparison to a high quality test surface. The measurement method has also been verified by comparison to high frequency impedance measurements. A detailed description, results, and sensitivity of the technique are given here.

  20. Nerve conduction velocity measurements: improved accuracy using superimposed response waves.

    PubMed

    Halar, E M; Venkatesh, B

    1976-10-01

    A new procedure of serial motor nerve conduction velocity (NCV) measurements with the use of "superimposed response waves" technique (or double stimulus technique) was performed on 29 normal subjects. Six peripheral nerves were tested once a week for four to six weeks. A total of 760 NCV measurements were thus obtained to try to assess the magnitude of error in serial NCV testings. With the double stimulus technique employed, a significant reduction in variations of serial NCV measurements was found. The overall standard deviation of four to six consecutive NCV measurements in the 34 subjects was 1.3 meters per second with a coefficient of variation of 2.4%. These findings obtained with the double stimulus technique have proven to be approximately three times more accurate than results obtained by investigators who studied nerve conduction velocity measurement variation with single stimulus standard NCV testing techniques. PMID:184754

  1. Measurement of thermal contact conductance of SPring-8 beamline components

    NASA Astrophysics Data System (ADS)

    Mochizuki, Tetsuro; Ohashi, Haruhiko; Sano, Mutsumi; Takahashi, Sunao; Goto, Shunji

    2007-09-01

    Direct cooling is adopted for most high heat load components in SPring-8 beamlines. On the other hand, contact cooling is employed for some components such as a graphite filter, aluminum filter, mirror, and cryogenic monochromator silicon crystal. For the thermal design of the contact cooling components, it is important to obtain reliable thermal contact conductance value. The conductance depends on many parameters such as the surface materials, surface roughness, flatness of the surface, interstitial materials, temperature of the contact surface, and contact pressure. An experimental setup is fablicated to measure the conductance at liquid nitrogen temperature and room temperature. The thermal contact conductance of a Si-Cu interface and that of a Si-In-Cu interface are measured at cryogenic temperature at contact pressures ranging from 0.1-1.1 MPa. The conductance of an Al-Cu interface and that of a graphite-Cu interface are measured using gold and silver foils as interstitial materials. The measurements are performed at room temperature and at pressures ranging from 0.5-4 MPa. The experimental setup and the results obtained are presented.

  2. Measurements of prompt radiation induced conductivity in Teflon (PTFE).

    SciTech Connect

    Hartman, E. Frederick; Zarick, Thomas Andrew; Sheridan, Timothy J.; Preston, E.

    2013-05-01

    We performed measurements of the prompt radiation induced conductivity (RIC) in thin samples of Teflon (PTFE) at the Little Mountain Medusa LINAC facility in Ogden, UT. Three mil (76.2 microns) samples were irradiated with a 0.5 %CE%BCs pulse of 20 MeV electrons, yielding dose rates of 1E9 to 1E11 rad/s. We applied variable potentials up to 2 kV across the samples and measured the prompt conduction current. Details of the experimental apparatus and analysis are reported in this report on prompt RIC in Teflon.

  3. VALIDATION OF A THERMAL CONDUCTIVITY MEASUREMENT SYSTEM FOR FUEL COMPACTS

    SciTech Connect

    Jeff Phillips; Colby Jensen; Changhu Xing; Heng Ban

    2011-03-01

    A high temperature guarded-comparative-longitudinal heat flow measurement system has been built to measure the thermal conductivity of a composite nuclear fuel compact. It is a steady-state measurement device designed to operate over a temperature range of 300 K to 1200 K. No existing apparatus is currently available for obtaining the thermal conductivity of the composite fuel in a non-destructive manner due to the compact’s unique geometry and composite nature. The current system design has been adapted from ASTM E 1225. As a way to simplify the design and operation of the system, it uses a unique radiative heat sink to conduct heat away from the sample column. A finite element analysis was performed on the measurement system to analyze the associated error for various operating conditions. Optimal operational conditions have been discovered through this analysis and results are presented. Several materials have been measured by the system and results are presented for stainless steel 304, inconel 625, and 99.95% pure iron covering a range of thermal conductivities of 10 W/m*K to 70 W/m*K. A comparison of the results has been made to data from existing literature.

  4. Thermal Conductivity Measurements in Metals at High Pressures and Temperatures.

    NASA Astrophysics Data System (ADS)

    Konopkova, Z.; McWilliams, R. S.; Goncharov, A.

    2014-12-01

    The transport properties of iron and iron alloys at high pressures and temperatures are crucial parameters in planetary evolution models, yet are difficult to determine both theoretically and experimentally. Estimates of thermal conductivity in the Earth's core range from 30 to 150 W/mK, a substantial range leaving many open questions regarding the age of the inner core, the thermal structure of the outer core, and the conditions for a working geodynamo. Most experiments have measured electrical resistivity rather than directly measuring thermal conductivity, and have used models to extrapolate from low-temperature data to the high temperature conditions of the core. Here we present direct, in-situ high-pressure and high-temperature measurements of the thermal conductivity of metals in the diamond-anvil cell. Double-sided continuous laser heating is combined with one-side flash heating of a metallic foil, while the time-resolved temperature is measured from both sides with spectral radiometry in an optical streak camera. Emission and temperature perturbations measured on opposite sides of the foil were modeled using finite element calculations in order to extract thermal diffusivity and conductivity of foils. Results on platinum and iron at high pressures and temperatures will be presented.

  5. Simultaneous specific heat and thermal conductivity measurement of individual nanostructures

    NASA Astrophysics Data System (ADS)

    Zheng, Jianlin; Wingert, Matthew C.; Moon, Jaeyun; Chen, Renkun

    2016-08-01

    Fundamental phonon transport properties in semiconductor nanostructures are important for their applications in energy conversion and storage, such as thermoelectrics and photovoltaics. Thermal conductivity measurements of semiconductor nanostructures have been extensively pursued and have enhanced our understanding of phonon transport physics. Specific heat of individual nanostructures, despite being an important thermophysical parameter that reflects the thermodynamics of solids, has remained difficult to characterize. Prior measurements were limited to ensembles of nanostructures in which coupling and sample inhomogeneity could play a role. Herein we report the first simultaneous specific heat and thermal conductivity measurements of individual rod-like nanostructures such as nanowires and nanofibers. This technique is demonstrated by measuring the specific heat and thermal conductivity of single ∼600–700 nm diameter Nylon-11 nanofibers (NFs). The results show that the thermal conductivity of the NF is increased by 50% over the bulk value, while the specific heat of the NFs exhibits bulk-like behavior. We find that the thermal diffusivity obtained from the measurement, which is related to the phonon mean free path (MFP), decreases with temperature, indicating that the intrinsic phonon Umklapp scattering plays a role in the NFs. This platform can also be applied to one- and two- dimensional semiconductor nanostructures to probe size effects on the phonon spectra and other transport physics.

  6. Complex AC impedance, transference number and vibrational spectroscopy studies of proton conducting PVAc-NH 4SCN polymer electrolytes

    NASA Astrophysics Data System (ADS)

    Selvasekarapandian, S.; Baskaran, R.; Hema, M.

    2005-03-01

    The polymer electrolytes composed of poly (vinyl acetate) (PVAc) with various stoichiometric ratios of ammonium thiocyanate (NH 4SCN) salt have been prepared by solution casting method. The polymer-salt complex formation and the polymer-proton interactions have been analysed by FT-IR spectroscopy. The conductivity and dielectric measurements are carried out on these films as a function of frequency at various temperatures. The complex impedance spectroscopy results reveal that the high-frequency semicircle is due to the bulk effect of the material. The conductivity is found to increase in the order of 10 -8-10 -4 S cm -1 at 303 K with the increase in salt concentration. The ionic transference number of mobile ions has been estimated by Wagner's polarization method and the results reveal that the conducting species are predominantly due to ions. The transient ionic current (TIC) measurement technique has been used to detect the type of mobile species and to evaluate their mobilities. The dielectric spectra show the low-frequency dispersion, which is due to the space charge effects arising from the electrodes.

  7. Comparison of DC and AC Transport in 1.5-7.5 nm Oligophenylene Imine Molecular Wires across Two Junction Platforms: Eutectic Ga-In versus Conducting Probe Atomic Force Microscope Junctions.

    PubMed

    Sangeeth, C S Suchand; Demissie, Abel T; Yuan, Li; Wang, Tao; Frisbie, C Daniel; Nijhuis, Christian A

    2016-06-15

    We have utilized DC and AC transport measurements to measure the resistance and capacitance of thin films of conjugated oligophenyleneimine (OPI) molecules ranging from 1.5 to 7.5 nm in length. These films were synthesized on Au surfaces utilizing the imine condensation chemistry between terephthalaldehyde and 1,4-benzenediamine. Near edge X-ray absorption fine structure (NEXAFS) spectroscopy yielded molecular tilt angles of 33-43°. To probe DC and AC transport, we employed Au-S-OPI//GaOx/EGaIn junctions having contact areas of 9.6 × 10(2) μm(2) (10(9) nm(2)) and compared to previously reported DC results on the same OPI system obtained using Au-S-OPI//Au conducting probe atomic force microscopy (CP-AFM) junctions with 50 nm(2) areas. We found that intensive observables agreed very well across the two junction platforms. Specifically, the EGaIn-based junctions showed: (i) a crossover from tunneling to hopping transport at molecular lengths near 4 nm; (ii) activated transport for wires >4 nm in length with an activation energy of 0.245 ± 0.008 eV for OPI-7; (iii) exponential dependence of conductance with molecular length with a decay constant β = 2.84 ± 0.18 nm(-1) (DC) and 2.92 ± 0.13 nm(-1) (AC) in the tunneling regime, and an apparent β = 1.01 ± 0.08 nm(-1) (DC) and 0.99 ± 0.11 nm(-1) (AC) in the hopping regime; (iv) previously unreported dielectric constant of 4.3 ± 0.2 along the OPI wires. However, the absolute resistances of Au-S-OPI//GaOx/EGaIn junctions were approximately 100 times higher than the corresponding CP-AFM junctions due to differences in metal-molecule contact resistances between the two platforms. PMID:27172452

  8. Measurement of the anisotropic thermal conductivity of the porcine cornea.

    PubMed

    Barton, Michael D; Trembly, B Stuart

    2013-10-01

    Accurate thermal models for the cornea of the eye support the development of thermal techniques for reshaping the cornea and other scientific purposes. Heat transfer in the cornea must be quantified accurately so that a thermal treatment does not destroy the endothelial layer, which cannot regenerate, and yet is responsible for maintaining corneal transparency. We developed a custom apparatus to measure the thermal conductivity of ex vivo porcine corneas perpendicular to the surface and applied a commercial apparatus to measure thermal conductivity parallel to the surface. We found that corneal thermal conductivity is 14% anisotropic at the normal state of corneal hydration. Small numbers of ex vivo feline and human corneas had a thermal conductivity perpendicular to the surface that was indistinguishable from the porcine corneas. Aqueous humor from ex vivo porcine, feline, and human eyes had a thermal conductivity nearly equal to that of water. Including the anisotropy of corneal thermal conductivity will improve the predictive power of thermal models of the eye. PMID:23933570

  9. Aqueous solubilities of phenol derivatives by conductivity measurements

    SciTech Connect

    Achard, C.; Jaoui, M.; Schwing, M.; Rogalski, M.

    1996-05-01

    The aqueous solubilities of five chlorophenols and three nitrophenols were measured by conductimetry at temperatures between 15 and 48C. The solubilities of 2-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, pentachlorophenol, 2-nitrophenol, 4-nitrophenol, and 2,4-dinitrophenol were studied. Automatic conductivity measurements allow the determination of the solute concentration and, hence, the determination of the solubility. Emulsion formation can also be followed. Results obtained are in good agreement with literature values.

  10. Measurement of soil hydraulic conductivity in relation with vegetation

    NASA Astrophysics Data System (ADS)

    Chen, Xi; Cheng, Qinbo

    2010-05-01

    Hydraulic conductivity is a key parameter which influences hydrological processes of infiltration, surface and subsurface runoff. Vegetation alters surface characteristics (e.g., surface roughness, litter absorption) or subsurface characteristics (e.g. hydraulic conductivity). Field infiltration experiment of a single ring permeameter is widely used for measuring soil hydraulic conductivity. Measurement equipment is a simple single-ring falling head permeameter which consists of a hollow cylinder that is simply inserted into the top soil. An optimization method on the basis of objective of minimum error between the measured and simulated water depths in the single-ring is developed for determination of the soil hydraulic parameters. Using the single ring permeameter, we measured saturated hydraulic conductivities (Ks) of the red loam soil with and without vegetation covers on five hillslopes at Taoyuan Agro-Ecology Experimental Station, Hunan Province of China. For the measurement plots without vegetation roots, Ks value of the soil at 25cm depth is much smaller than that of surface soil (1.52×10-4 vs. 1.10×10-5 m/s). For the measurement plots with vegetation cover, plant roots significantly increase Ks of the lower layer soil but this increase is not significant for the shallow soil. Moreover, influences of vegetation root on Ks depend on vegetation species and ages. Ks value of the Camellia is about three times larger than that of seeding of Camphor (2.62×10-4 vs. 9.82×10-5 m/s). Ks value of the matured Camellia is 2.72×10-4 m/s while Ks value of the young Camellia is only 2.17×10-4 m/s. Key words: single ring permeameter; soil hydraulic conductivity; vegetation

  11. Time-resolved Measurements of Spontaneous Magnetic Deflagration of Mn12 tBuAc

    NASA Astrophysics Data System (ADS)

    Chen, Yizhang; Kent, A. D.; Zhang, Qing; Sarachik, M. P.; Baker, M. L.; Garanin, D. A.; Mhesn, Najah; Lampropoulos, Christos

    Magnetic deflagration in molecular magnets has been triggered by heat pulses and acoustic waves. In this work we report spontaneous magnetic deflagration (i.e. deflagration that occurs without an external trigger) in the axially symmetric single molecule magnet Mn12 tBuAc . Magnetic hysteresis measurements show steps due to resonant quantum tunneling (RQT) below 1K, confirming the spin-Hamiltonian parameters for this material and previous results. Deflagration speeds measured with a newly constructed higher bandwidth (2MHz) setup will be presented as a function of transverse and longitudinal fields Hx ⊗Hz both on and off resonance. A large increase in front velocity near RQT steps is observed in experiments with swept transverse fields and will be discussed in light of models of deflagration. Work supported by NSF-DMR-1309202 (NYU); ARO W911NF-13-1-0125 (CCNY); DMR-1161571(Lehman); Cottrell College Science Award (UNF).

  12. Test Results of the AC Field Measurements of Fermilab Booster Corrector Magnets

    SciTech Connect

    DiMarco, E.Joseph; Harding, D.J.; Kashikhin, V.S.; Kotelnikov, S.K.; Lamm, M.J.; Makulski, A.; Nehring, R.; Orris, D.F.; Schlabach, P.; Sylvester, C.; Tartaglia, Michael Albert; /Fermilab

    2008-06-25

    Multi-element corrector magnets are being produced at Fermilab that enable correction of orbits and tunes through the entire cycle of the Booster, not just at injection. The corrector package includes six different corrector elements--normal and skew orientations of dipole, quadrupole, and sextupole--each independently powered. The magnets have been tested during typical AC ramping cycles at 15Hz using a fixed coil system to measure the dynamic field strength and field quality. The fixed coil is comprised of an array of inductive pick-up coils around the perimeter of a cylinder which are sampled simultaneously at 100 kHz with 24-bit ADC's. The performance of the measurement system and a summary of the field results are presented and discussed.

  13. 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

  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. 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

  16. Measurements of prompt radiation induced conductivity of alumina and sapphire.

    SciTech Connect

    Hartman, E. Frederick; Zarick, Thomas Andrew; Sheridan, Timothy J.; Preston, Eric F.

    2011-04-01

    We performed measurements of the prompt radiation induced conductivity in thin samples of Alumina and Sapphire at the Little Mountain Medusa LINAC facility in Ogden, UT. Five mil thick samples were irradiated with pulses of 20 MeV electrons, yielding dose rates of 1E7 to 1E9 rad/s. We applied variable potentials up to 1 kV across the samples and measured the prompt conduction current. Analysis rendered prompt conductivity coefficients between 1E10 and 1E9 mho/m/(rad/s), depending on the dose rate and the pulse width for Alumina and 1E7 to 6E7 mho/m/(rad/s) for Sapphire.

  17. Determining aerodynamic conductance of spar chambers from energy balance measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The aerodynamic conductance (gA) of SPAR chambers was determined from measurements of energy balance and canopy temperature over a peanut canopy. gA was calculated from the slope of sensible heat flux (H) versus canopy-to-air temperature difference. H and the canopy-to-air temperature were varied by...

  18. Measuring Impulsivity in Adolescents with Serious Substance and Conduct Problems

    ERIC Educational Resources Information Center

    Thompson, Laetitia L.; Whitmore, Elizabeth A.; Raymond, Kristen M.; Crowley, Thomas J.

    2006-01-01

    Adolescents with substance use and conduct disorders have high rates of aggression and attention deficit hyperactivity disorder (ADHD), all of which have been characterized in part by impulsivity. Developing measures that capture impulsivity behaviorally and correlate with self-reported impulsivity has been difficult. One promising behavioral…

  19. Apparatus measures thermal conductivity of honeycomb-core panels

    NASA Technical Reports Server (NTRS)

    1966-01-01

    Overall thermal conductivity of honeycomb-core panels at elevated temperatures is measured by an apparatus with a heater assembly and a calibrated heat-rate transducer. The apparatus has space between the heater and transducer for insertion of a test panel and insulation.

  20. Spectral Measurements from the Optical Emission of the A.C. Plasma Anemometer

    NASA Astrophysics Data System (ADS)

    Matlis, Eric; Marshall, Curtis; Corke, Thomas; Gogineni, Sivaram

    2015-11-01

    The optical emission properties of a new class of AC-driven flow sensors based on a glow discharge (plasma) is presented. These results extend the utility of the plasma sensor that has recently been developed for measurements in high-enthalpy flows. The plasma sensor utilizes a high frequency (1MHz) AC discharge between two electrodes as the main sensing element. The voltage drop across the discharge correlates to changes in the external flow which can be calibrated for mass-flux (ρU) or pressure depending on the design of the electrodes and orientation relative to the free-stream flow direction. Recent experiments examine the potential for spectral analysis of the optical emission of the discharge to provide additional insight to the flow field. These experiments compare the optical emission of the plasma to emission from breakdown due to an ND:YAG laser. The oxygen 777.3 nm band in particular is a focus of interest as a marker for the determination of gas density.

  1. Measuring the hydraulic conductivity of shallow submerged sediments.

    PubMed

    Kelly, Susan E; Murdoch, Lawrence C

    2003-01-01

    The hydraulic conductivity of submerged sediments influences the interaction between ground water and surface water, but few techniques for measuring K have been described with the conditions of the submerged setting in mind. Two simple, physical methods for measuring the hydraulic conductivity of submerged sediments have been developed, and one of them uses a well and piezometers similar to well tests performed in terrestrial aquifers. This test is based on a theoretical analysis that uses a constant-head boundary condition for the upper surface of the aquifer to represent the effects of the overlying water body. Existing analyses of tests used to measure the hydraulic conductivity of submerged sediments may contain errors from using the same upper boundary conditions applied to simulate terrestrial aquifers. Field implementation of the technique requires detecting minute drawdowns in the vicinity of the pumping well. Low-density oil was used in an inverted U-tube manometer to amplify the head differential so that it could be resolved in the field. Another technique was developed to measure the vertical hydraulic conductivity of sediments at the interface with overlying surface water. This technique uses the pan from a seepage meter with a piezometer fixed along its axis (a piezo-seep meter). Water is pumped from the pan and the head gradient is measured using the axial piezometer. Results from a sandy streambed indicate that both methods provide consistent and reasonable estimates of K. The pumping test allows skin effects to be considered, and the field data show that omitting the skin effect (e.g., by using a single well test) can produce results that underestimate the hydraulic conductivity of streambeds. PMID:12873006

  2. Comparison of different methods for measuring thermal conductivities

    SciTech Connect

    Hartung, D.; Gather, F.; Klar, P. J.

    2012-06-26

    Two different methods for the measurement of the thermal conductivity have been applied to a glass (borosilicate) bulk sample. The first method was in the steady-state using an arrangement of gold wires on the sample to create a thermal gradient and to measure the temperatures locally. This allows one to calculate the in-plane thermal conductivity of the sample. The same wire arrangement was also used for a 3{omega}-measurement of the direction-independent bulk thermal conductivity. The 3{omega}-approach is based on periodical heating and a frequency dependent analysis of the temperature response. The results of both methods are in good agreement with each other for this isotropic material, if thermal and radiative losses are accounted for. Our results demonstrate that especially in the case of thin-film measurements, finite element analysis has to be applied to correct for heat losses due to geometry and radiation. In this fashion, the wire positions can be optimized in order to minimize measurement errors.

  3. Thermal conductance measurement of windows: An innovative radiative method

    SciTech Connect

    Arpino, F.; Buonanno, G.; Giovinco, G.

    2008-09-15

    Heat transfer through window surfaces is one of the most important contributions to energy losses in buildings. Therefore, great efforts are made to design new window frames and glass assemblies with low thermal conductance. At the same time, it is also necessary to develop accurate measurement techniques in thermal characterisation of the above-mentioned building components. In this paper the authors show an innovative measurement method mainly based on radiative heat transfer (instead of the traditional convective one) which allows window thermal conductance measurements with corresponding uncertainty budget evaluation. The authors used the 3D finite volume software FLUENT {sup registered} to design the experimental apparatus. The numerical results have been employed for the system optimisation and metrological characterisation. (author)

  4. Thermal Conductivity Measurement of Liquid-Quenched Higher Manganese Silicides

    NASA Astrophysics Data System (ADS)

    Nishino, Shunsuke; Miyata, Masanobu; Ohdaira, Keisuke; Koyano, Mikio; Takeuchi, Tsunehiro

    2016-03-01

    Higher manganese silicides (HMSs, MnSi γ , γ ˜ 1.75) show promise for use as low-cost and environmentally friendly thermoelectric materials. To reduce their thermal conductivity, we partially substituted the Mn site with heavy elements using liquid quenching. Fabricated samples possess a curly ribbon-shape with about a 10- μm thickness and 1-mm width, with high surface roughness. In this study, we determined the thermal conductivity of the curly-ribbon-shaped samples using two independent methods: the 3 ω method with two heat flow models, and the steady-state method using a physical property measurement system (PPMS; Quantum Design). We succeeded in estimating the thermal conductivity at the temperature range of 100-200 K using the PPMS. The estimated thermal conductivity of non-doped HMSs shows a constant value without temperature dependence of 2.2 ± 0.8 W K-1m-1 at 100-200 K. The difference of thermal conductivities of W-doped and non-doped HMSs was not recognized within the measurement error.

  5. Device and method for measuring thermal conductivity of thin films

    NASA Technical Reports Server (NTRS)

    Amer, Tahani R. (Inventor); Subramanian, Chelakara (Inventor); Upchurch, Billy T. (Inventor); Alderfer, David W. (Inventor); Sealey, Bradley S. (Inventor); Burkett, Jr., Cecil G. (Inventor)

    2001-01-01

    A device and method are provided for measuring the thermal conductivity of rigid or flexible, homogeneous or heterogeneous, thin films between 50 .mu.m and 150 .mu.m thick with relative standard deviations of less than five percent. The specimen is sandwiched between like material, highly conductive upper and lower slabs. Each slab is instrumented with six thermocouples embedded within the slab and flush with their corresponding surfaces. A heat source heats the lower slab and a heat sink cools the upper slab. The heat sink also provides sufficient contact pressure onto the specimen. Testing is performed within a vacuum environment (bell-jar) between 10.sup.-3 to 10.sup.-6 Torr. An anti-radiant shield on the interior surface of the bell-jar is used to avoid radiation heat losses. Insulation is placed adjacent to the heat source and adjacent to the heat sink to prevent conduction losses. A temperature controlled water circulator circulates water from a constant temperature bath through the heat sink. Fourier's one-dimensional law of heat conduction is the governing equation. Data, including temperatures, are measured with a multi-channel data acquisition system. On-line computer processing is used for thermal conductivity calculations.

  6. Error and uncertainty in Raman thermal conductivity measurements

    SciTech Connect

    Thomas Edwin Beechem; Yates, Luke; Graham, Samuel

    2015-04-22

    We investigated error and uncertainty in Raman thermal conductivity measurements via finite element based numerical simulation of two geometries often employed -- Joule-heating of a wire and laser-heating of a suspended wafer. Using this methodology, the accuracy and precision of the Raman-derived thermal conductivity are shown to depend on (1) assumptions within the analytical model used in the deduction of thermal conductivity, (2) uncertainty in the quantification of heat flux and temperature, and (3) the evolution of thermomechanical stress during testing. Apart from the influence of stress, errors of 5% coupled with uncertainties of ±15% are achievable for most materials under conditions typical of Raman thermometry experiments. Error can increase to >20%, however, for materials having highly temperature dependent thermal conductivities or, in some materials, when thermomechanical stress develops concurrent with the heating. A dimensionless parameter -- termed the Raman stress factor -- is derived to identify when stress effects will induce large levels of error. Together, the results compare the utility of Raman based conductivity measurements relative to more established techniques while at the same time identifying situations where its use is most efficacious.

  7. Error and uncertainty in Raman thermal conductivity measurements

    DOE PAGESBeta

    Thomas Edwin Beechem; Yates, Luke; Graham, Samuel

    2015-04-22

    We investigated error and uncertainty in Raman thermal conductivity measurements via finite element based numerical simulation of two geometries often employed -- Joule-heating of a wire and laser-heating of a suspended wafer. Using this methodology, the accuracy and precision of the Raman-derived thermal conductivity are shown to depend on (1) assumptions within the analytical model used in the deduction of thermal conductivity, (2) uncertainty in the quantification of heat flux and temperature, and (3) the evolution of thermomechanical stress during testing. Apart from the influence of stress, errors of 5% coupled with uncertainties of ±15% are achievable for most materialsmore » under conditions typical of Raman thermometry experiments. Error can increase to >20%, however, for materials having highly temperature dependent thermal conductivities or, in some materials, when thermomechanical stress develops concurrent with the heating. A dimensionless parameter -- termed the Raman stress factor -- is derived to identify when stress effects will induce large levels of error. Together, the results compare the utility of Raman based conductivity measurements relative to more established techniques while at the same time identifying situations where its use is most efficacious.« less

  8. Frequency and voltage dependent profile of dielectric properties, electric modulus and ac electrical conductivity in the PrBaCoO nanofiber capacitors

    NASA Astrophysics Data System (ADS)

    Demirezen, S.; Kaya, A.; Yerişkin, S. A.; Balbaşı, M.; Uslu, İ.

    In this study, praseodymium barium cobalt oxide nanofiber interfacial layer was sandwiched between Au and n-Si. Frequency and voltage dependence of ε‧, ε‧, tanδ, electric modulus (M‧ and M″) and σac of PrBaCoO nanofiber capacitor have been investigated by using impedance spectroscopy method. The obtained experimental results show that the values of ε‧, ε‧, tanδ, M‧, M″ and σac of the PrBaCoO nanofiber capacitor are strongly dependent on frequency of applied bias voltage. The values of ε‧, ε″ and tanδ show a steep decrease with increasing frequency for each forward bias voltage, whereas the values of σac and the electric modulus increase with increasing frequency. The high dispersion in ε‧ and ε″ values at low frequencies may be attributed to the Maxwell-Wagner and space charge polarization. The high values of ε‧ may be due to the interfacial effects within the material, PrBaCoO nanofibers interfacial layer and electron effect. The values of M‧ and M″ reach a maximum constant value corresponding to M∞ ≈ 1/ε∞ due to the relaxation process at high frequencies, but both the values of M‧ and M″ approach almost to zero at low frequencies. The changes in the dielectric and electrical properties with frequency can be also attributed to the existence of Nss and Rs of the capacitors. As a result, the change in the ε‧, ε″, tanδ, M‧, M″ and ac electric conductivityac) is a result of restructuring and reordering of charges at the PrBaCoO/n-Si interface under an external electric field or voltage and interface polarization.

  9. Simple uniaxial pressure device for ac-susceptibility measurements suitable for closed cycle refrigerator system.

    PubMed

    Arumugam, S; Manivannan, N; Murugeswari, A

    2007-06-01

    A simple design of the uniaxial pressure device for the measurement of ac-susceptibility at low temperatures using closed cycle refrigerator system is presented for the first time. This device consists of disc micrometer, spring holder attachment, uniaxial pressure cell, and the ac-susceptibility coil wound on stycast bobbin. It can work under pressure till 0.5 GPa and at the temperature range of 30-300 K. The performance of the system at ambient pressure is tested and calibrated with standard paramagnetic salts [Gd(2)O(3), Er(2)O(3), and Fe(NH(4)SO(4))(2)6H(2)O], Fe(3)O(4), Gd metal, Dy metal, superconductor (YBa(2)Cu(3)O(7)), manganite (La(1.85)Ba(0.15)MnO(3)), and spin glass material (Pr(0.8)Sr(0.2)MnO(3)). The performance of the uniaxial pressure device is demonstrated by investigating the uniaxial pressure dependence of La(1.85)Ba(0.15)MnO(3) single crystal with P||c axis. The Curie temperature (T(c)) decreases as a function of pressure with P||c axis (dT(c)dP(||c axis)=-11.65 KGPa) up to 46 MPa. The design is simple, is user friendly, and does not require pressure calibration. Measurement can even be made on thin and small size oriented crystals. The failure of the coil is remote under uniaxial pressure. The present setup can be used as a multipurpose uniaxial pressure device for the measurement of Hall effect and thermoelectric power with a small modification in the pressure cell. PMID:17614625

  10. Measurement of Fracture Geometry for Accurate Computation of Hydraulic Conductivity

    NASA Astrophysics Data System (ADS)

    Chae, B.; Ichikawa, Y.; Kim, Y.

    2003-12-01

    Fluid flow in rock mass is controlled by geometry of fractures which is mainly characterized by roughness, aperture and orientation. Fracture roughness and aperture was observed by a new confocal laser scanning microscope (CLSM; Olympus OLS1100). The wavelength of laser is 488nm, and the laser scanning is managed by a light polarization method using two galvano-meter scanner mirrors. The system improves resolution in the light axis (namely z) direction because of the confocal optics. The sampling is managed in a spacing 2.5 μ m along x and y directions. The highest measurement resolution of z direction is 0.05 μ m, which is the more accurate than other methods. For the roughness measurements, core specimens of coarse and fine grained granites were provided. Measurements were performed along three scan lines on each fracture surface. The measured data were represented as 2-D and 3-D digital images showing detailed features of roughness. Spectral analyses by the fast Fourier transform (FFT) were performed to characterize on the roughness data quantitatively and to identify influential frequency of roughness. The FFT results showed that components of low frequencies were dominant in the fracture roughness. This study also verifies that spectral analysis is a good approach to understand complicate characteristics of fracture roughness. For the aperture measurements, digital images of the aperture were acquired under applying five stages of uniaxial normal stresses. This method can characterize the response of aperture directly using the same specimen. Results of measurements show that reduction values of aperture are different at each part due to rough geometry of fracture walls. Laboratory permeability tests were also conducted to evaluate changes of hydraulic conductivities related to aperture variation due to different stress levels. The results showed non-uniform reduction of hydraulic conductivity under increase of the normal stress and different values of

  11. Method of simultaneous measurement of radiative and lattice thermal conductivity.

    NASA Technical Reports Server (NTRS)

    Schatz, J. F.; Simmons, G.

    1972-01-01

    A new technique of high-temperature thermal-conductivity measurement is described. A CO2 gas laser is used to generate a low-frequency temperature wave at one face of a small disk-shaped sample, and an infrared detector views the opposite face to detect the phase of the emerging radiation. A mathematical expression is derived which enables phase data at several frequencies to be used for the simultaneous determination of thermal diffusivity and mean extinction coefficient. Lattice and radiative thermal conductivities are then calculated. Test results for sintered aluminum oxide at temperatures from 530 to 1924 K are within the range of error of previously existing data.

  12. 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.

  13. 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.

  14. System to Measure Thermal Conductivity and Seebeck Coefficient for Thermoelectrics

    NASA Technical Reports Server (NTRS)

    Kim, Hyun-Jung; Skuza, Jonathan R.; Park, Yeonjoon; King, Glen C.; Choi, Sang H.; Nagavalli, Anita

    2012-01-01

    The Seebeck coefficient, when combined with thermal and electrical conductivity, is an essential property measurement for evaluating the potential performance of novel thermoelectric materials. However, there is some question as to which measurement technique(s) provides the most accurate determination of the Seebeck coefficient at elevated temperatures. This has led to the implementation of nonstandardized practices that have further complicated the confirmation of reported high ZT materials. The major objective of the procedure described is for the simultaneous measurement of the Seebeck coefficient and thermal diffusivity within a given temperature range. These thermoelectric measurements must be precise, accurate, and reproducible to ensure meaningful interlaboratory comparison of data. The custom-built thermal characterization system described in this NASA-TM is specifically designed to measure the inplane thermal diffusivity, and the Seebeck coefficient for materials in the ranging from 73 K through 373 K.

  15. Measurement of the ac Stark shift with a guided matter-wave interferometer

    NASA Astrophysics Data System (ADS)

    Deissler, B.; Hughes, K. J.; Burke, J. H. T.; Sackett, C. A.

    2008-03-01

    The dynamic polarizability of Rb87 atoms was measured using a guided-wave Bose-Einstein condensate interferometer. Taking advantage of the large arm separations obtainable in our device, a well-calibrated laser beam is applied to one atomic packet and not the other, inducing a differential phase shift. The technique requires relatively low laser intensity and works for arbitrary optical frequencies. For off-resonant light, the ac polarizability is obtained with a statistical accuracy of 3% and a calibration uncertainty of 6%. On resonance, the dispersion-shaped behavior of the Stark shift is observed, but with a broadened linewidth that is attributed to collective light scattering effects. The resulting nonlinearity may prove useful for the production and control of squeezed quantum states.

  16. Application of inverse heat conduction problem on temperature measurement

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Zhou, G.; Dong, B.; Li, Q.; Liu, L. Q.

    2013-09-01

    For regenerative cooling devices, such as G-M refrigerator, pulse tube cooler or thermoacoustic cooler, the gas oscillating bring about temperature fluctuations inevitably, which is harmful in many applications requiring high stable temperatures. To find out the oscillating mechanism of the cooling temperature and improve the temperature stability of cooler, the inner temperature of the cold head has to be measured. However, it is difficult to measure the inner oscillating temperature of the cold head directly because the invasive temperature detectors may disturb the oscillating flow. Fortunately, the outer surface temperature of the cold head can be measured accurately by invasive temperature measurement techniques. In this paper, a mathematical model of inverse heat conduction problem is presented to identify the inner surface oscillating temperature of cold head according to the measured temperature of the outer surface in a GM cryocooler. Inverse heat conduction problem will be solved using control volume approach. Outer surface oscillating temperature could be used as input conditions of inverse problem and the inner surface oscillating temperature of cold head can be inversely obtained. A simple uncertainty analysis of the oscillating temperature measurement also will be provided.

  17. An AC phase measuring interferometer for measuring dn/dT of fused silica and calcium fluoride at 193 nm

    SciTech Connect

    Shagam, R.N.

    1998-09-01

    A novel method for the measurement of the change in index of refraction vs. temperature (dn/dT) of fused silica and calcium fluoride at the 193 nm wavelength has been developed in support of thermal modeling efforts for the development of 193 nm-based photolithographic exposure tools. The method, based upon grating lateral shear interferometry, uses a transmissive linear grating to divide a 193 nm laser beam into several beam paths by diffraction which propagate through separate identical material samples. One diffracted order passing through one sample overlaps the undiffracted beam from a second sample and forms interference fringes dependent upon the optical path difference between the two samples. Optical phase delay due to an index change from heating one of the samples causes the interference fringes to change sinusoidally with phase. The interferometer also makes use of AC phase measurement techniques through lateral translation of the grating. Results for several samples of fused silica and calcium fluoride are demonstrated.

  18. Thermal conductivity measurements of particulate materials under Martian conditions

    NASA Technical Reports Server (NTRS)

    Presley, M. A.; Christensen, P. R.

    1993-01-01

    The mean particle diameter of surficial units on Mars has been approximated by applying thermal inertia determinations from the Mariner 9 Infrared Radiometer and the Viking Infrared Thermal Mapper data together with thermal conductivity measurement. Several studies have used this approximation to characterize surficial units and infer their nature and possible origin. Such interpretations are possible because previous measurements of the thermal conductivity of particulate materials have shown that particle size significantly affects thermal conductivity under martian atmospheric pressures. The transfer of thermal energy due to collisions of gas molecules is the predominant mechanism of thermal conductivity in porous systems for gas pressures above about 0.01 torr. At martian atmospheric pressures the mean free path of the gas molecules becomes greater than the effective distance over which conduction takes place between the particles. Gas particles are then more likely to collide with the solid particles than they are with each other. The average heat transfer distance between particles, which is related to particle size, shape and packing, thus determines how fast heat will flow through a particulate material.The derived one-to-one correspondence of thermal inertia to mean particle diameter implies a certain homogeneity in the materials analyzed. Yet the samples used were often characterized by fairly wide ranges of particle sizes with little information about the possible distribution of sizes within those ranges. Interpretation of thermal inertia data is further limited by the lack of data on other effects on the interparticle spacing relative to particle size, such as particle shape, bimodal or polymodal mixtures of grain sizes and formation of salt cements between grains. To address these limitations and to provide a more comprehensive set of thermal conductivities vs. particle size a linear heat source apparatus, similar to that of Cremers, was assembled to

  19. Thermal conductivity measurements of proton-heated warm dense matter

    NASA Astrophysics Data System (ADS)

    McKelvey, A.; Fernandez-Panella, A.; Hua, R.; Kim, J.; King, J.; Sio, H.; McGuffey, C.; Kemp, G. E.; Freeman, R. R.; Beg, F. N.; Shepherd, R.; Ping, Y.

    2015-06-01

    Accurate knowledge of conductivity characteristics in the strongly coupled plasma regime is extremely important for ICF processes such as the onset of hydrodynamic instabilities, thermonuclear burn propagation waves, shell mixing, and efficient x-ray conversion of indirect drive schemes. Recently, an experiment was performed on the Titan laser platform at the Jupiter Laser Facility to measure the thermal conductivity of proton-heated warm dense matter. In the experiment, proton beams generated via target normal sheath acceleration were used to heat bi-layer targets with high-Z front layers and lower-Z back layers. The stopping power of a material is approximately proportional to Z2 so a sharp temperature gradient is established between the two materials. The subsequent thermal conduction from the higher-Z material to the lower-Z was measured with time resolved streaked optical pyrometry (SOP) and Fourier domain interferometry (FDI) of the rear surface. Results will be used to compare predictions from the thermal conduction equation and the Wiedemann-Franz Law in the warm dense matter regime. Data from the time resolved diagnostics for Au/Al and Au/C Targets of 20-200 nm thickness will be presented.

  20. Thermal Conductivity Based on Modified Laser Flash Measurement

    NASA Technical Reports Server (NTRS)

    Lin, Bochuan; Ban, Heng; Li, Chao; Scripa, Rosalia N.; Su, Ching-Hua; Lehoczky, Sandor L.

    2005-01-01

    The laser flash method is a standard method for thermal diffusivity measurement. It employs single-pulse heating of one side of a thin specimen and measures the temperature response of the other side. The thermal diffusivity of the specimen can be obtained based on a one-dimensional transient heat transfer analysis. This paper reports the development of a theory that includes a transparent reference layer with known thermal property attached to the back of sample. With the inclusion of heat conduction from the sample to the reference layer in the theoretical analysis, the thermal conductivity and thermal diffusivity of sample can be extracted from the temperature response data. Furthermore, a procedure is established to select two points from the data to calculate these properties. The uncertainty analysis indicates that this method can be used with acceptable levels of uncertainty.

  1. Heating rate controller for thermally stimulated conductivity and thermoluminescence measurements.

    NASA Technical Reports Server (NTRS)

    Manning, E. G.; Littlejohn, M. A.; Oakley, E. M.; Hutchby , J. A.

    1972-01-01

    A temperature controller is described which enables the temperature of a sample mounted on a cold finger to be varied linearly with time. Heating rates between 0.5 and 10 K/min can be achieved for temperatures between 90 and 300 K. Provision for terminating the sample heating at any temperature between these extremes is available. The temperature can be held at the terminating temperature or be reduced to the starting temperature in a matter of minutes. The controller has been used for thermally stimulated conductivity measurements and should be useful for thermoluminescence measurements as well.

  2. The role of probe oxide in local surface conductivity measurements

    SciTech Connect

    Barnett, C. J.; Kryvchenkova, O.; Wilson, L. S. J.; Maffeis, T. G. G.; Cobley, R. J.; Kalna, K.

    2015-05-07

    Local probe methods can be used to measure nanoscale surface conductivity, but some techniques including nanoscale four point probe rely on at least two of the probes forming the same low resistivity non-rectifying contact to the sample. Here, the role of probe shank oxide has been examined by carrying out contact and non-contact I V measurements on GaAs when the probe oxide has been controllably reduced, both experimentally and in simulation. In contact, the barrier height is pinned but the barrier shape changes with probe shank oxide dimensions. In non-contact measurements, the oxide modifies the electrostatic interaction inducing a quantum dot that alters the tunneling behavior. For both, the contact resistance change is dependent on polarity, which violates the assumption required for four point probe to remove probe contact resistance from the measured conductivity. This has implications for all nanoscale surface probe measurements and macroscopic four point probe, both in air and vacuum, where the role of probe oxide contamination is not well understood.

  3. TRISO fuel compact thermal conductivity measurement instrument development

    NASA Astrophysics Data System (ADS)

    Jensen, Colby

    Thermal conductivity is an important thermophysical property needed for effectively predicting fuel performance. As part of the Next Generation Nuclear Plant (NGNP) program, the thermal conductivity of tri-isotropic (TRISO) fuel needs to be measured over a temperature range characteristic of its usage. The composite nature of TRISO fuel requires that measurement be performed over the entire length of the compact in a non-destructive manner. No existing measurement system is capable of performing such a measurement. A measurement system has been designed based on the steady-state, guarded-comparative-longitudinal heat flow technique. The system as currently designed is capable of measuring cylindrical samples with diameters ˜12.3-mm (˜0.5″) with lengths ˜25-mm (˜1″). The system is currently operable in a temperature range of 400 K to 1100 K for materials with thermal conductivities on the order of 10 W/m/K to 70 W/m/K. The system has been designed, built, and tested. An uncertainty analysis for the determinate errors of the system has been performed finding a result of 5.5%. Finite element modeling of the system measurement method has also been accomplished demonstrating optimal design, operating conditions, and associated bias error. Measurements have been performed on three calibration/validation materials: SS304, 99.95% pure iron, and inconel 625. In addition, NGNP graphite with ZrO2 particles and NGNP AGR-2 graphite matrix only, both in compact form, have been measured. Results from the SS304 sample show agreement of better than 3% for a 300--600°C temperature range. For iron between 100--600°C, the difference with published values is <8% for all temperatures. The maximum difference from published data for inconel 625 is 5.8%, near 600°C. Both NGNP samples were measured from 100--800°C. All results are presented and discussed. Finally, a discussion of ongoing work is included as well as a brief discussion of implementation under other operating

  4. Silicate bonding properties: Investigation through thermal conductivity measurements

    NASA Astrophysics Data System (ADS)

    Lorenzini, M.; Cesarini, E.; Cagnoli, G.; Campagna, E.; Haughian, K.; Hough, J.; Losurdo, G.; Martelli, F.; Martin, I.; Piergiovanni, F.; Reid, S.; Rowan, S.; van Veggel, A. A.; Vetrano, F.

    2010-05-01

    A direct approach to reduce the thermal noise contribution to the sensitivity limit of a GW interferometric detector is the cryogenic cooling of the mirrors and mirrors suspensions. Future generations of detectors are foreseen to implement this solution. Silicon has been proposed as a candidate material, thanks to its very low intrinsic loss angle at low temperatures and due to its very high thermal conductivity, allowing the heat deposited in the mirrors by high power lasers to be efficiently extracted. To accomplish such a scheme, both mirror masses and suspension elements must be made of silicon, then bonded together forming a quasi-monolithic stage. Elements can be assembled using hydroxide-catalysis silicate bonding, as for silica monolithic joints. The effect of Si to Si bonding on suspension thermal conductance has therefore to be experimentally studied. A measurement of the effect of silicate bonding on thermal conductance carried out on 1 inch thick silicon bonded samples, from room temperature down to 77 K, is reported. In the explored temperature range, the silicate bonding does not seem to affect in a relevant way the sample conductance.

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

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

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

  6. Analysis of measurements of the thermal conductivity of liquid urania

    SciTech Connect

    Fink, J.K.; Leibowitz, L.

    1984-09-17

    An analysis was performed of the three existing measurements of the thermal conductivity and thermal diffusivity of molten uranium dioxide. A transient heat transfer code (THTB) was used for this analysis. A much smaller range of values for thermal conductivity than originally reported was found: the original values ranged from 2.4 to 11 W . m/sup -1/ . K/sup -1/, with a mean of 7.3 W . m/sup -1/ . K/sup -1/, whereas the recalculated values ranged from 4.5 to 6.75 W . m/sup -1/ . K/sup -1/, with a mean of 5.6 W . m/sup -1/ . K/sup -1/.

  7. Thermal conductivity measurements in a 2D Yukawa system

    NASA Astrophysics Data System (ADS)

    Nosenko, V.; Ivlev, A.; Zhdanov, S.; Morfill, G.; Goree, J.; Piel, A.

    2007-03-01

    Thermal conductivity was measured for a 2D Yukawa system. First, we formed a monolayer suspension of microspheres in a plasma, i.e., a dusty plasma, which is like a colloidal suspension, but with an extremely low volume fraction and a partially-ionized rarefied gas instead of solvent. In the absence of manipulation, the suspension forms a 2D triangular lattice. To melt this lattice and form a liquid, we used a laser-heating method. Two focused laser beams were moved rapidly around in the monolayer. The kinetic temperature of the particles increased with the laser power applied, and above a threshold a melting transition occurred. We used digital video microscopy for direct imaging and particle tracking. The spatial profiles of the particle kinetic temperature were calculated. Using the heat transport equation with an additional term to account for the energy dissipation due to the gas drag, we analyzed the temperature distribution to derive the thermal conductivity.

  8. Thermal conductivity measurements of CH and Be by refraction-enhanced x-ray radiography

    NASA Astrophysics Data System (ADS)

    Ping, Yuan; King, Jim; Landen, Otto; Whitley, Heather; London, Rich; Hamel, Sebastien; Sterne, Phil; Panella, Amalia; Freeman, Rick; Collins, Gilbert

    2015-06-01

    Transport properties of warm dense matter are important for modeling the growth of hydrodynamic instabilities near the fuel-ablator interface in an ICF capsule, which determines the mix level in the fuel and thus is critical for successful ignition. A novel technique, time-resolved refraction-enhanced x-ray radiography, has been developed to study thermal conductivity at an interface. Experiments using OMEGA laser have been carried out for CH/Be targets isochorically heated by x-rays to measure the evolution of the density gradient at the interface due to thermal conduction. The sensitivity of this radiographic technique to discontinuities enabled observation of shock/rarefraction waves propagating away from the interface. The radiographs provide enough constraints on the temperatures, densities and scale lengths in CH and Be, respectively. Preliminary data analysis suggests that the thermal conductivities of CH and Be at near solid density and a few eV temperature are higher than predictions by the commonly used Lee-More model. Detailed analysis and comparison with various models will be presented. The work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Security, LLC, Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  9. Thermal conductivity and emissivity measurements of uranium carbides

    NASA Astrophysics Data System (ADS)

    Corradetti, S.; Manzolaro, M.; Andrighetto, A.; Zanonato, P.; Tusseau-Nenez, S.

    2015-10-01

    Thermal conductivity and emissivity measurements on different types of uranium carbide are presented, in the context of the ActiLab Work Package in ENSAR, a project within the 7th Framework Program of the European Commission. Two specific techniques were used to carry out the measurements, both taking place in a laboratory dedicated to the research and development of materials for the SPES (Selective Production of Exotic Species) target. In the case of thermal conductivity, estimation of the dependence of this property on temperature was obtained using the inverse parameter estimation method, taking as a reference temperature and emissivity measurements. Emissivity at different temperatures was obtained for several types of uranium carbide using a dual frequency infrared pyrometer. Differences between the analyzed materials are discussed according to their compositional and microstructural properties. The obtainment of this type of information can help to carefully design materials to be capable of working under extreme conditions in next-generation ISOL (Isotope Separation On-Line) facilities for the generation of radioactive ion beams.

  10. The unsaturated hydraulic conductivity: measurement and non-equilibrium effects

    NASA Astrophysics Data System (ADS)

    Weller, U.; Vogel, H.

    2010-12-01

    The unsaturated hydraulic conductivity of porous media is a central item in hydraulic modeling. It is hard to measure and therefore in most applications it is represented by some kind of model based on indirect measurements. The validity is hardly ever checked. We have developed a fairly easy and automatic measurement procedure that allows to determine directly the hydraulic conductivity of a sample at different water potentials. The sample is placed on a plate where the potential can be controlled. It is then irrigated from the top with a constant, predefined flow rate. Tensiometers control the water potential within the sample, the topmost one is used to steer the potential at the lower boundary. It can be seen that the sample equilibrates fairly quick to a constant potential throughout the sample, and thus the conductivity of the material at the measured potential is equal to the applied flux while gravity is the only driving force. The change in water content is monitored by a balance. We have measured several materials, soils and sand substrates, with a protocol where we first lower the flux stepwise and then rise it again. The samples reach quick an equilibrium, as can be seen by the control tensiometer. Coming from the wet side, with a high flux, and lowering this flux, we observe a fast drop in potential, and in water content. But then the water potential rises again, while the water content remains constant or drops even slightly. When rising the flux again, we observe the opposite effect, but less pronounced: after the initial rise in water potential while the system adapts to the new flow rate, the potential lowers slightly. This behavior occurs over a certain range of water potential, it is not present in the very wet or very dry range. Also, the range in which it occurs and the magnitude of the effect depends on the studied material: pure sands express the pattern very clearly, it is much less obvious in loamy soils. Also, the relation between water

  11. Experimental measurements of the thermal conductivity of ash deposits: Part 1. Measurement technique

    SciTech Connect

    A. L. Robinson; S. G. Buckley; N. Yang; L. L. Baxter

    2000-04-01

    This paper describes a technique developed to make in situ, time-resolved measurements of the effective thermal conductivity of ash deposits formed under conditions that closely replicate those found in the convective pass of a commercial boiler. Since ash deposit thermal conductivity is thought to be strongly dependent on deposit microstructure, the technique is designed to minimize the disturbance of the natural deposit microstructure. Traditional techniques for measuring deposit thermal conductivity generally do not preserve the sample microstructure. Experiments are described that demonstrate the technique, quantify experimental uncertainty, and determine the thermal conductivity of highly porous, unsintered deposits. The average measured conductivity of loose, unsintered deposits is 0.14 {+-} 0.03 W/(m K), approximately midway between rational theoretical limits for deposit thermal conductivity.

  12. Apparent thermal conductivity measurements by an unguarded technique

    NASA Astrophysics Data System (ADS)

    Graves, R. S.; Yarbrough, D. W.; McElroy, D. L.

    An unguarded longitudinal heat flow apparatus for measuring the apparent thermal conductivity (lambda/sub a) of insulations was tested. Heat flow is provided by a horizontal electrically heated Nichrome screen sandwiched between test samples that are bounded by temperature controlled copper plates and 9 cm of mineral fiber insulation. A determinate error analysis shows lambda/sub a/ measurement uncertainty to be less than + or - 1.7% for insulating materials as thin as 3 cm. Three-dimensional thermal modeling indicates negligible error in lambda/sub a/ due to edge loss for insulations up to 7.62 cm thick when the temperature difference across the sample is measured at the screen center. System repeatability and reproducibility were determined to be + or - 0.2%. Differences of lambda/sub a/ results from the screen tester and results from the National Bureau of Standards were 0.1% for a 10-kg/m(3) Calibration Transfer Standard and 0.9% for 127-kg/m(3) fibrous glass board (SRM 1450b). Measurements on fiberglass and rock wool batt insulations showed the dependence of lambda/sub a/ on density, temperature, temperature difference, plate emittance, and heat flow direction. Results obtained for lambda/sub a/ as a function of density at 240C differed by less than 2% from values obtained with a guarded hot plate. It is demonstrated that this simple technique has the accuracy and sensitivity needed for useful lambda/sub a/ measurements on thermal insulating materials.

  13. Measurement of klystron phase modulation due to ac-powered filaments

    NASA Technical Reports Server (NTRS)

    Finnegan, E. J.

    1977-01-01

    A technique for determining the intermodulation components in the RF spectrum of the S-band radar transmitter generated by having the klystron filaments heated by 400-Hz ac power is described. When the klystron is being operated with 400-Hz (ac) on the filament, the IPM is buried in the 400-Hz equipment interference noise. The modulation sidebands were separated and identified and found to be-67 db below the main carrier. This is well below the transmitter specifications, and operating the filaments on ac would not degrade the spectrum to where it would be detrimental to the radiated RF.

  14. Quantitative measurements of root water uptake and root hydraulic conductivities

    NASA Astrophysics Data System (ADS)

    Zarebanadkouki, Mohsen; Javaux, Mathieu; Meunier, Felicien; Couvreur, Valentin; Carminati, Andrea

    2016-04-01

    How is root water uptake distributed along the root system and what root properties control this distribution? Here we present a method to: 1) measure root water uptake and 2) inversely estimate the root hydraulic conductivities. The experimental method consists in using neutron radiography to trace deuterated water (D2O) in soil and roots. The method was applied to lupines grown aluminium containers filled with a sandy soil. When the lupines were 4 weeks old, D2O was locally injected in a selected soil regions and its transport was monitored in soil and roots using time-series neutron radiography. By image processing, we quantified the concentration of D2O in soil and roots. We simulated the transport of D2O into roots using a diffusion-convection numerical model. The diffusivity of the roots tissue was inversely estimated by simulating the transport of D2O into the roots during night. The convective fluxes (i.e. root water uptake) were inversely estimating by fitting the experiments during day, when plants were transpiring, and assuming that root diffusivity did not change. The results showed that root water uptake was not uniform along the roots. Water uptake was higher at the proximal parts of the lateral roots and it decreased by a factor of 10 towards the distal parts. We used the data of water fluxes to inversely estimate the profile of hydraulic conductivities along the roots of transpiring plants growing in soil. The water fluxes in the lupine roots were simulated using the Hydraulic Tree Model by Doussan et al. (1998). The fitting parameters to be adjusted were the radial and axial hydraulic conductivities of the roots. The results showed that by using the root architectural model of Doussan et al. (1998) and detailed information of water fluxes into different root segments we could estimate the profile of hydraulic conductivities along the roots. We also found that: 1) in a tap-rooted plant like lupine water is mostly taken up by lateral roots; (2) water

  15. Contactless electrical conductivity measurement of metallic submicron-grain material: Application to the study of aluminum with severe plastic deformation.

    PubMed

    Mito, M; Matsui, H; Yoshida, T; Anami, T; Tsuruta, K; Deguchi, H; Iwamoto, T; Terada, D; Miyajima, Y; Tsuji, N

    2016-05-01

    We measured the electrical conductivity σ of aluminum specimen consisting of submicron-grains by observing the AC magnetic susceptibility resulting from the eddy current. By using a commercial platform for magnetic measurement, contactless measurement of the relative electrical conductivity σn of a nonmagnetic metal is possible over a wide temperature (T) range. By referring to σ at room temperature, obtained by the four-terminal method, σn(T) was transformed into σ(T). This approach is useful for cylinder specimens, in which the estimation of the radius and/or volume is difficult. An experiment in which aluminum underwent accumulative roll bonding, which is a severe plastic deformation process, validated this method of evaluating σ as a function of the fraction of high-angle grain boundaries. PMID:27250440

  16. High-Resolution ac Measurements of the Hall Effect in Organic Field-Effect Transistors

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Yi, H. T.; Podzorov, V.

    2016-03-01

    We describe a high resolving power technique for Hall-effect measurements, efficient in determining Hall mobility and carrier density in organic field-effect transistors and other low-mobility systems. We utilize a small low-frequency ac magnetic field (Brms<0.25 T ) and a phase-sensitive (lock-in) detection of Hall voltage, with the necessary corrections for Faraday induction. This method significantly enhances the signal-to-noise ratio and eliminates the necessity of using high magnetic fields in Hall-effect studies. With the help of this method, we are able to obtain the Hall mobility and carrier density in organic transistors with a mobility as low as μ ˜0.3 cm2 V-1 s-1 by using a compact desktop apparatus and low magnetic fields. We find a good agreement between Hall-effect and electric-field-effect measurements, indicating that, contrary to the common belief, certain organic semiconductors with mobilities below 1 cm2 V-1 s-1 can still exhibit a fully developed, band-semiconductor-like Hall effect, with the Hall mobility and carrier density matching those obtained in longitudinal transistor measurements. This suggests that, even when μ <1 cm2 V-1 s-1 , charges in organic semiconductors can still behave as delocalized coherent carriers. This technique paves the way to ubiquitous Hall-effect studies in a wide range of low-mobility materials and devices, where it is typically very difficult to resolve the Hall effect even in very high dc magnetic fields.

  17. Structural characterization, thermal, ac conductivity and dielectric properties of (C7H12N2)2[SnCl6]Cl2.1.5H2O

    NASA Astrophysics Data System (ADS)

    Hajji, Rachid; Oueslati, Abderrazek; Hajlaoui, Fadhel; Bulou, Alain; Hlel, Faouzi

    2016-05-01

    (C7H12N2)2[SnCl6]Cl2.1.5H2O is crystallized at room temperature in the monoclinic system (space group P21/n). The isolated molecules form organic and inorganic layers parallel to the (a, b) plane and alternate along the c-axis. The inorganic layer is built up by isolated SnCl6 octahedrons. Besides, the organic layer is formed by 2,4-diammonium toluene cations, between which the spaces are filled with free Cl- ions and water molecules. The crystal packing is governed by means of the ionic N-H...Cl and Ow-H...Cl hydrogen bonds, forming a three-dimensional network. The thermal study of this compound is reported, revealing two phase transitions around 360(±3) and 412(±3) K. The electrical and dielectric measurements were reported, confirming the transition temperatures detected in the differential scanning calorimetry (DSC). The frequency dependence of ac conductivity at different temperatures indicates that the correlated barrier hopping (CBH) model is the probable mechanism for the ac conduction behavior.

  18. Use of an advanced composite material in construction of a high pressure cell for magnetic ac susceptibility measurements

    NASA Astrophysics Data System (ADS)

    Wang, X.; Misek, M.; Jacobsen, M. K.; Kamenev, K. V.

    2014-10-01

    The applicability of fibre-reinforced polymers for fabrication of high pressure cells was assessed using finite element analysis and experimental testing. Performance and failure modes for the key components of the cell working in tension and in compression were evaluated and the ways for optimising the designs were established. These models were used in construction of a miniature fully non-metallic diamond anvil cell for magnetic ac susceptibility measurements in a magnetic property measurement system. The cell is approximately 14 mm long, 8.5 mm in diameter and was demonstrated to reach a pressure of 5.6 GPa. AC susceptibility data collected on Dy2O3 demonstrate the performance of the cell in magnetic property measurements and confirm that there is no screening of the sample by the environment which typically accompanies the use of conventional metallic high pressure cells in oscillating magnetic fields.

  19. 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.

  20. Scanning Ion Conductance Microscopy for living cell membrane potential measurement

    NASA Astrophysics Data System (ADS)

    Panday, Namuna

    Recently, the existence of multiple micro-domains of extracellular potential around individual cells have been revealed by voltage reporter dye using fluorescence microscopy. One hypothesis is that these long lasting potential patterns play a vital role in regulating important cell activities such as embryonic patterning, regenerative repair and reduction of cancerous disorganization. We used multifunctional Scanning Ion Conductance Microscopy (SICM) to study these extracellular potential patterns of single cell with higher spatial resolution. To validate this novel technique, we compared the extracellular potential distribution on the fixed HeLa cell surface and Polydimethylsiloxane (PDMS) surface and found significant difference. We then measured the extracellular potential distributions of living melanocytes and melanoma cells and found both the mean magnitude and spatial variation of extracellular potential of the melanoma cells are bigger than those of melanocytes. As compared to the voltage reporter dye based fluorescence microscope method, SICM can achieve quantitative potential measurements of non-labeled living cell membranes with higher spatial resolution.

  1. Thermal contact conductance measurements on Doublet III armor tile graphite

    SciTech Connect

    Doll, D.W.; Reis, E.

    1983-12-01

    Several tests were performed on the Doublet III wall armor tiles to determine the cool-down rate and to evaluate improvements made by changing the conditions at the interface between the graphite tile and the stainless steel backing plate. Thermal diffusivity tests were performed in vacuum on both TiC coated and bare graphite tiles with and without 0.13 mm (.005'') thick silver foil at the interface. The results of the armor tile cool-down tests showed improvement when a 0.13 mm (0.005'') silver foil is used at the interface. At 2.1 x 10/sup 5/ Pa (30 psi) contact pressure, the e-folding cool-down times for a TiC coated tile, bare graphite and bare graphite with a 0.06 mm (0.0035'') silver shim were 10 min., 5.0 min., and 4.1 min., respectively. Tests using high contact pressures showed that the cool-down rates converged to approx. 4.0 min. At this limit, the conduction path along the backing plate to the two cooling tubes controls the heat flow, and no further improvement could be expected. Thermal diffusivity measurements confirmed the results of the cool-down test showing that by introducing a silver foil at the interface, the contact conductance between Poco AXF-5Q graphite and 316 stainless steel could be improved by a factor of three to eight. The tests showed an increasing improvement over a range of temperatures from 25/sup 0/C to 400/sup 0/C. The data provides a technical basis for further applications of graphite tiles to cooled backing plates.

  2. Improved direct measurement of A(b) and A(c) at the Z(0) pole using a lepton tag.

    PubMed

    Abe, Kenji; Abe, Koya; Abe, T; Adam, I; Akimoto, H; Aston, D; Baird, K G; Baltay, C; Band, H R; Barklow, T L; Bauer, J M; Bellodi, G; Berger, R; Blaylock, G; Bogart, J R; Bower, G R; Brau, J E; Breidenbach, M; Bugg, W M; Burke, D; Burnett, T H; Burrows, P N; Calcaterra, A; Cassell, R; Chou, A; Cohn, H O; Coller, J A; Convery, M R; Cook, V; Cowan, R F; Crawford, G; Damerell, C J S; Daoudi, M; de Groot, N; de Sangro, R; Dong, D N; Doser, M; Dubois, R; Erofeeva, I; Eschenburg, V; Fahey, S; Falciai, D; Fernandez, J P; Flood, K; Frey, R; Hart, E L; Hasuko, K; Hertzbach, S S; Huffer, M E; Huynh, X; Iwasaki, M; Jackson, D J; Jacques, P; Jaros, J A; Jiang, Z Y; Johnson, A S; Johnson, J R; Kajikawa, R; Kalelkar, M; Kang, H J; Kofler, R R; Kroeger, R S; Langston, M; Leith, D W G; Lia, V; Lin, C; Mancinelli, G; Manly, S; Mantovani, G; Markiewicz, T W; Maruyama, T; McKemey, A K; Messner, R; Moffeit, K C; Moore, T B; Morii, M; Muller, D; Murzin, V; Narita, S; Nauenberg, U; Neal, H; Nesom, G; Oishi, N; Onoprienko, D; Osborne, L S; Panvini, R S; Park, C H; Peruzzi, I; Piccolo, M; Piemontese, L; Plano, R J; Prepost, R; Prescott, C Y; Ratcliff, B N; Reidy, J; Reinertsen, P L; Rochester, L S; Rowson, P C; Russell, J J; Saxton, O H; Schalk, T; Schumm, B A; Schwiening, J; Serbo, V V; Shapiro, G; Sinev, N B; Snyder, J A; Staengle, H; Stahl, A; Stamer, P; Steiner, H; Su, D; Suekane, F; Sugiyama, A; Suzuki, S; Swartz, M; Taylor, F E; Thom, J; Torrence, E; Usher, T; Va'vra, J; Verdier, R; Wagner, D L; Waite, A P; Walston, S; Weidemann, A W; Weiss, E R; Whitaker, J S; Williams, S H; Willocq, S; Wilson, R J; Wisniewski, W J; Wittlin, J L; Woods, M; Wright, T R; Yamamoto, R K; Yashima, J; Yellin, S J; Young, C C; Yuta, H

    2002-04-15

    The parity violation parameters A(b) and A(c) of the Zb(b) and Zc(c) couplings have been measured directly, using the polar angle dependence of the polarized cross sections at the Z(0) pole. Bottom and charmed hadrons were tagged via their semileptonic decays. Both the electron and muon analyses take advantage of new multivariate techniques to increase the analyzing power. Based on the 1993-1998 SLD sample of 550,000 Z(0) decays produced with highly polarized electron beams, we measure A(b) = 0.919+/-0.030(stat)+/-0.024(syst), and A(c) = 0.583+/-0.055(stat)+/-0.055(syst). PMID:11955189

  3. AC conductivity and relaxation mechanism in (Nd1/2Li1/2)(Fe1/2V1/2)O3 ceramics

    NASA Astrophysics Data System (ADS)

    Nath, Susmita; Barik, Subrat Kumar; Choudhary, R. N. P.

    2016-05-01

    In the present study we have synthesized polycrystalline sample of (Nd1/2Li1/2)(Fe1/2V1/2)O3 ceramic by a standard high-temperature solid-state reaction technique. Studies of dielectric and electrical properties of the compound have been carried out in a wide range of temperature (RT - 400 °C) and frequency (1kHz - 1MHz) using complex impedance spectroscopic technique. The imaginary vs. real component of the complex impedance plot (Nyquist plot) of the prepared sample exhibits the existence of grain, grain boundary contributions in the complex electrical parameters and negative temperature coefficient of resistance (NTCR) type behavior like semiconductor. Details study of ac conductivity plot reveals that the material obeys universal Jonscher's power law.

  4. Analyzing the Effects of Capacitances-to-Shield in Sample Probes on AC Quantized Hall Resistance Measurements

    PubMed Central

    Cage, M. E.; Jeffery, A.

    1999-01-01

    We analyze the effects of the large capacitances-to-shields existing in all sample probes on measurements of the ac quantized Hall resistance RH. The object of this analysis is to investigate how these capacitances affect the observed frequency dependence of RH. Our goal is to see if there is some way to eliminate or minimize this significant frequency dependence, and thereby realize an intrinsic ac quantized Hall resistance standard. Equivalent electrical circuits are used in this analysis, with circuit components consisting of: capacitances and leakage resistances to the sample probe shields; inductances and resistances of the sample probe leads; quantized Hall resistances, longitudinal resistances, and voltage generators within the quantum Hall effect device; and multiple connections to the device. We derive exact algebraic equations for the measured RH values expressed in terms of the circuit components. Only two circuits (with single-series “offset” and quadruple-series connections) appear to meet our desired goals of measuring both RH and the longitudinal resistance Rx in the same cool-down for both ac and dc currents with a one-standard-deviation uncertainty of 10−8 RH or less. These two circuits will be further considered in a future paper in which the effects of wire-to-wire capacitances are also included in the analysis.

  5. Incorporating residential AC load control into ancillary service markets: Measurement and settlement

    SciTech Connect

    Bode, Josh L.; Sullivan, Michael J.; Berghman, Dries; Eto, Joseph H.

    2013-05-01

    Many pre-existing air conditioner load control programs can provide valuable operational flexibility but have not been incorporated into electricity ancillary service markets or grid operations. Multiple demonstrations have shown that residential air conditioner (AC) response can deliver resources quickly and can provide contingency reserves. A key policy hurdle to be overcome before AC load control can be fully incorporated into markets is how to balance the accuracy, cost, and complexity of methods available for the settlement of load curtailment. Overcoming this hurdle requires a means for assessing the accuracy of shorter-term AC load control demand reduction estimation approaches in an unbiased manner. This paper applies such a method to compare the accuracy of approaches varying in cost and complexity ? including regression analysis, load matching and control group approaches ? using feeder data, household data and AC end-use data. We recommend a practical approach for settlement, relying on an annually updated set of tables, with pre-calculated reduction estimates. These tables allow users to look up the demand reduction per device based on daily maximum temperature, geographic region and hour of day, simplifying settlement and providing a solution to the policy problem presented in this paper.

  6. Steady heat conduction-based thermal conductivity measurement of single walled carbon nanotubes thin film using a micropipette thermal sensor

    NASA Astrophysics Data System (ADS)

    Shrestha, R.; Lee, K. M.; Chang, W. S.; Kim, D. S.; Rhee, G. H.; Choi, T. Y.

    2013-03-01

    In this paper, we describe the thermal conductivity measurement of single-walled carbon nanotubes thin film using a laser point source-based steady state heat conduction method. A high precision micropipette thermal sensor fabricated with a sensing tip size varying from 2 μm to 5 μm and capable of measuring thermal fluctuation with resolution of ±0.01 K was used to measure the temperature gradient across the suspended carbon nanotubes (CNT) film with a thickness of 100 nm. We used a steady heat conduction model to correlate the temperature gradient to the thermal conductivity of the film. We measured the average thermal conductivity of CNT film as 74.3 ± 7.9 W m-1 K-1 at room temperature.

  7. Steady heat conduction-based thermal conductivity measurement of single walled carbon nanotubes thin film using a micropipette thermal sensor.

    PubMed

    Shrestha, R; Lee, K M; Chang, W S; Kim, D S; Rhee, G H; Choi, T Y

    2013-03-01

    In this paper, we describe the thermal conductivity measurement of single-walled carbon nanotubes thin film using a laser point source-based steady state heat conduction method. A high precision micropipette thermal sensor fabricated with a sensing tip size varying from 2 μm to 5 μm and capable of measuring thermal fluctuation with resolution of ±0.01 K was used to measure the temperature gradient across the suspended carbon nanotubes (CNT) film with a thickness of 100 nm. We used a steady heat conduction model to correlate the temperature gradient to the thermal conductivity of the film. We measured the average thermal conductivity of CNT film as 74.3 ± 7.9 W m(-1) K(-1) at room temperature. PMID:23556837

  8. Synthesis and characterization of cancrinite-type zeolite, and its ionic conductivity study by AC impedance analysis

    NASA Astrophysics Data System (ADS)

    Kriaa, A.; Ben Saad, K.; Hamzaoui, A. H.

    2012-12-01

    The synthesis of cancrinite in the system NaOH-SiO2-Al2O3-NaHCO3-H2O was performed, according to methods described in the literature, in an autoclave under hydrothermal conditions at T = 473 K. The electrical properties of cancrinite-type zeolite pellets were investigated by complex impedance spectroscopy in the temperature range 465-800°C. The effect of temperature on impedance parameters was studied using an impedance analyzer in a wide frequency range (1 Hz to 13 MHz). The real and imaginary parts of complex impedance trace semicircles in the complex plane are plotted. The bulk resistance of the material decreases with rise in temperature. This exhibits a typical negative temperature coefficient of resistance (NTCR) behavior of the material. The results of bulk electrical conductivity and its activation energy are presented. The modulus analysis suggests that the electrical transport processes in the material are very likely to be of electronic nature. Relaxation frequencies follow an Arrhenius behavior with activation energy values not comparable to those found for the electrical conductivity.

  9. SPHINX Measurements of Radiation Induced Conductivity of Foam

    SciTech Connect

    Ballard, W.P.; Beutler, D.E.; Burt, M.; Dudley, K.J.; Stringer, T.A.

    1998-12-14

    Experiments on the SPHINX accelerator studying radiation-induced conductivity (RIC) in foam indicate that a field-exclusion boundary layer model better describes foam than a Maxwell-Garnett model that treats the conducting gas bubbles in the foam as modifying the dielectric constant. In both cases, wall attachment effects could be important but were neglected.

  10. Conductivity tensor of graphene through reflection of microwave measurements

    NASA Astrophysics Data System (ADS)

    Meera, V.; Setlur, Girish S.

    2009-03-01

    The optical response of free standing graphene, with or without a perpendicular magnetic field, doping or gap, is studied theoretically by solving Maxwell's equations. Formulae for the reflection coefficient and the reflected polarization are derived in terms of the polarization of the incident electromagnetic wave in the microwave region, its angle of incidence and the azimuthal angle on the graphene plane. These formulae involve the conductivity tensor of graphene. The behaviour of the reflection coefficient and the reflected polarization with the variation of these parameters may be used to infer the optical conductivity tensor and the anisotropy of the conductivity (by this we mean the presence of non-vanishing off-diagonal components of the conductivity tensor). The conductivity of graphene is important since it provides indirect evidence of the effective relativistic dispersion of the energy of the quasi-particles involved.

  11. Ground level measurements of air conductivities under Florida thunderstorms

    NASA Technical Reports Server (NTRS)

    Blakeslee, Richard J.; Krider, E. P.

    1992-01-01

    Values of the positive and negative polar conductivities under summer thunderstorms in Florida are highly variable and exhibit a significant electrode effect, but the total conductivity usually remains close to values found in fair weather, 0.4 to 1.8 x 10 exp -14 S/m. With these values a method proposed by Krider and Musser (1982) for estimating the total conductivity from changes in the slope of the electric field recovery following a lightning discharge will be extremely sensitive to small time variations in the local Maxwell current density and must be modified to include these effects.

  12. In vivo measurements of electrical conductivity of porcine organs at low frequency: new method of measurement.

    PubMed

    Spottorno, J; Multigner, M; Rivero, G; Alvarez, L; de la Venta, J; Santos, M

    2012-10-01

    Calculations of the induced currents created in the human body by external electromagnetic fields would be more accurate provided that more realistic experimental values of the electrical properties of the body were available. The purpose of this work is to experimentally obtain values for the conductivity of living organs in conditions close to the real situation. Two-electrode in vivo measurements of the bioimpedance of some porcine organs have been performed. From these measurements and taking into account geometrical considerations, the electrical conductivity for the kidney, liver, heart, and spinal cord has been obtained and were found to be higher than the values reported in the literature. Furthermore, a new experimental procedure is proposed where the conductivity is determined from the values of the electrical potential and currents that are induced by an external electromagnetic field created by a coil placed close to the organ under study. PMID:22430866

  13. Experimental and theoretical study of AC electrical conduction mechanisms of Organic-inorganic hybrid compound Bis (4-acetylanilinium) tetrachlorocadmiate (II)

    NASA Astrophysics Data System (ADS)

    Jellibi, A.; Chaabane, I.; Guidara, K.

    2016-06-01

    A new organic-inorganic bis (4-acetylaniline) tetrachlorocadmate [C8H10NO]2[CdCl4] can be obtained by slow evaporation at room temperature and characterized by X-ray powder diffraction. It crystallized in an orthorhombic system (Cmca space group). The material electrical properties were characterized by impedance spectroscopy technique in the frequency range from 209 Hz-5 MHz and temperature 413 to 460 K. Besides, the impedance plots show semicircle arcs at different temperatures and an electrical equivalent circuit has been proposed to interpret the impedance results. The circuits consist of the parallel combination of a resistance (R), capacitance (C) and fractal capacitance (CPE). The variation of the exponent s as a function of temperature suggested that the conduction mechanism in Bis (4-acetylanilinium) tetrachlorocadmiate compound is governed by two processes which can be ascribed to a hopping transport mechanism: correlated barrier hopping (CBH) model below 443 K and the small polaron tunneling (SPT) model above 443 K.

  14. Dual AC Dipole Excitation for the Measurement of Magnetic Multipole Strength from Beam Position Monitor Data

    SciTech Connect

    M. Spata, G.A. Krafft

    2011-09-01

    An experiment was conducted at Jefferson Lab's Continuous Electron Beam Accelerator Facility to develop a technique for characterizing the nonlinear fields of the beam transport system. Two air-core dipole magnets were simultaneously driven at two different frequencies to provide a time-dependent transverse modulation of the electron beam. Fourier decomposition of beam position monitor data was then used to measure the amplitude of these frequencies at different positions along the beamline. For a purely linear transport system one expects to find solely the frequencies that were applied to the dipoles with amplitudes that depend on the phase advance of the lattice. In the presence of nonlinear fields one expects to also find harmonics of the driving frequencies that depend on the order of the nonlinearity. The technique was calibrated using one of the sextupole magnets in a CEBAF beamline and then applied to a dipole to measure the sextupole and octupole strength of the magnet. A comparison is made between the beam-based measurements, results from TOSCA and data from our Magnet Measurement Facility.

  15. Raman, dielectric and AC-conductivity behavior of Dy2O3 contained K0.5Na0.5NbO3 ceramics

    NASA Astrophysics Data System (ADS)

    Mahesh, P.; Pamu, D.

    2016-05-01

    Lead-free piezoelectric (K0.5Na0.5)NbO3+ x wt% Dy2O3 (x = 0 - 1.5) (KNND) ceramics have been prepared by solid state reaction method. The effect of Dy2O3 on the dielectric and electrical conductivity responses of KNN ceramics were investigated in a broad temperature (from 133 K to 673 K) and frequency (106 Hz to 108 Hz) range. Temperature dependent dielectric analysis revealed that the polymorphic phase transition orthorhombic to tetragonal transition temperature (TO-T) shifted from 199°C to room temperature with enhanced dielectric permittivity (ɛ' = 994) with the addition of Dy2O3. The effect of Dy2O3 on structural properties of KNND ceramics are analyzed interms of changes in the internal modes of NbO6 octahedra by using Raman spectroscopy. Temperature dependent (133 K - 306 K) AC-conductivity follows the variable range hopping mechanism in different temperature regimes.

  16. Impedance and AC conductivity study of nano crystalline, fine grained multiferroic bismuth ferrite (BiFeO3), synthesized by microwave sintering

    NASA Astrophysics Data System (ADS)

    Kolte, Jayant; Salame, Paresh H.; Daryapurkar, A. S.; Gopalan, P.

    2015-09-01

    In this paper, major reduction in sintering time,temperautre and significant improvement over final density of sitnered sample is reported for the microwave sintered nanocrystalline BiFeO3 (BFO) ceramic. Also, different sintering time and temperatures have been used to tailor the grain size and the final density of the resulting BFO ceramics synthesized from phase pure BFO nanoparticles ( d ¯ ≈ 10 n m ). Microwave sintering resulted in reducing the sintering time substantially (by 1h), and has resulted in submicron sized grains and high resistivity ˜1.8 GΩ-cm. The AC conductivity is seen to follow the Jonscher's power law behavior, suggesting correlated barrier hopping (CBH) mechanism in the sample. The role of oxygen vacancies at high temperature, due to volatility of bismuth, in dielectric and conductivity behavior is also discussed. Further, the sample displayed dielectric anomaly near magnetic transition temperature (˜180 °C) indicating bearing of magnetic moments on the dielectric properties. Using Impedance Spectroscopy (IS) we have established, the electrical heterogeneity of the ceramic BFO reavealing semiconducting nature of grains and insulating nature of grain boundary. This, formation of network of insulating grain boundaries and semiconducting grains could lead to formation of internal barrier layer capacitance (IBLC) leading to high dielectric constant in microwave sintered BFO.

  17. Direct measurement of ion mobility in a conducting polymer.

    PubMed

    Stavrinidou, Eleni; Leleux, Pierre; Rajaona, Harizo; Khodagholy, Dion; Rivnay, Jonathan; Lindau, Manfred; Sanaur, Sébastien; Malliaras, George G

    2013-08-27

    Using planar junctions between the conducting polymer PEDOT:PSS and various electrolytes, it is possible to inject common ions and directly observe their transit through the film. The 1D geometry of the experiment allows a straightforward estimate of the ion drift mobilities. PMID:23784809

  18. EVALUATION OF HYDRAULIC CONDUCTIVITIES CALCULATED FROM MULTIPORT-PERMEAMETER MEASUREMENTS

    EPA Science Inventory

    A multiport permeameter was developed for use in estimating hydraulic conductivity over intact sections of aquifer core using the core liner as the permeameter body. Six cores obtained from one borehole through the upper 9 m of a stratified glacial-outwash aquifer were used to ev...

  19. Contactless measurement of alternating current conductance in quantum Hall structures

    SciTech Connect

    Drichko, I. L.; Diakonov, A. M.; Malysh, V. A.; Smirnov, I. Yu.; Ilyinskaya, N. D.; Usikova, A. A.; Galperin, Y. M.; Kummer, M.; Känel, H. von

    2014-10-21

    We report a procedure to determine the frequency-dependent conductance of quantum Hall structures in a broad frequency domain. The procedure is based on the combination of two known probeless methods—acoustic spectroscopy and microwave spectroscopy. By using the acoustic spectroscopy, we study the low-frequency attenuation and phase shift of a surface acoustic wave in a piezoelectric crystal in the vicinity of the electron (hole) layer. The electronic contribution is resolved using its dependence on a transverse magnetic field. At high frequencies, we study the attenuation of an electromagnetic wave in a coplanar waveguide. To quantitatively calibrate these data, we use the fact that in the quantum-Hall-effect regime the conductance at the maxima of its magnetic field dependence is determined by extended states. Therefore, it should be frequency independent in a broad frequency domain. The procedure is verified by studies of a well-characterized p-SiGe/Ge/SiGe heterostructure.

  20. Measurement of surface resistivity/conductivity of different organic thin films by a combination of optical shearography and electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Habib, Khaled

    2013-11-01

    Shearography techniques were applied again to measure the surface resistivity/conductivity of different organic thin films on a metallic substrate. The coatings were ACE premium-grey enamel (spray coating), a yellow Acrylic lacquer, and a gold nail polish on a carbon steel substrate. The investigation was focused on determining the in-plane displacement of the coatings by shearography between 20 and 60 °C. Then, the alternating current (AC) impedance (resistance) of the same coated samples was determined by electrochemical impedance spectroscopy (EIS) in 3.0% NaCl solution at room temperature. As a result, the proportionality constant (resistivity or conductivity = 1/surface resistivity) between the determined AC impedance and the in-plane displacement was obtained. The obtained resistivity of all investigated coatings, 40:15 × 106-24:6 × 109Ωcm, was found in the insulator range.

  1. Size-Dependent Relaxation Properties of Monodisperse Magnetite Nanoparticles Measured Over Seven Decades of Frequency by AC Susceptometry.

    PubMed

    Ferguson, R Matthew; Khandhar, Amit P; Jonasson, Christian; Blomgren, Jakob; Johansson, Christer; Krishnan, Kannan M

    2013-07-01

    Magnetic relaxation is exploited in innovative biomedical applications of magnetic particles such as magnetic particle imaging (MPI), magnetic fluid hyperthermia, and bio-sensing. Relaxation behavior should be optimized to achieve high performance imaging, efficient heating, and good SNR in bio-sensing. Using two AC susceptometers with overlapping frequency ranges, we have measured the relaxation behavior of a series of monodisperse magnetic particles and demonstrated that this approach is an effective way to probe particle relaxation characteristics from a few Hz to 10 MHz, the frequencies relevant for MPI, hyperthermia, and sensing. PMID:25473124

  2. Astronaut Mike Fincke Conducts Fluid Merging Viscosity Measurement (FMVM) Experiment

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Astronaut Mike Fincke places droplets of honey onto the strings for the Fluid Merging Viscosity Measurement (FMVM) investigation onboard the International Space Station (ISS). The FMVM experiment measures the time it takes for two individual highly viscous fluid droplets to coalesce or merge into one droplet. Different fluids and droplet size combinations were tested in the series of experiments. By using the microgravity environment, researchers can measure the viscosity or 'thickness' of fluids without the influence of containers and gravity using this new technique. Understanding viscosity could help scientists understand industrially important materials such as paints, emulsions, polymer melts and even foams used to produce pharmaceutical, food, and cosmetic products.

  3. Physical and electrical models for interpreting AC and DC transport measurements in polymer solar cells

    NASA Astrophysics Data System (ADS)

    McIntyre, Max; Tzolov, Marian; Cossel, Raquel; Peeler, Seth

    We have fabricated and studied bulk heterojunction solar cells using a mixture of the low bandgap material PCPDTBT and PCBM-C60. Our transport studies show that the devices in dark have good rectification and they respond to AC voltage as a simple RC circuit. The illumination causes an additional contribution to the impedance, which varies with the level of illumination. One proposed model is that photo-generated charges can become trapped in potential wells. These charges then follow a Debye relaxation process, which contributes to a varying dielectric constant. Another proposed model is based on a RC circuit model with two capacitors which can describe the varying capacitance behavior. The physical mechanism for this model is that photo-generated charges become accumulated at the interface between PCPDTBT and PCBM-C60 and form an additional layer of charge. We will show that our circuit models and their analogous physical models can predict the AC and DC responses of polymer solar cells.

  4. Instrument for Measuring Thermal Conductivity of Materials at Low Temperatures

    NASA Technical Reports Server (NTRS)

    Fesmire, James; Sass, Jared; Johnson, Wesley

    2010-01-01

    With the advance of polymer and other non-metallic material sciences, whole new series of polymeric materials and composites are being created. These materials are being optimized for many different applications including cryogenic and low-temperature industrial processes. Engineers need these data to perform detailed system designs and enable new design possibilities for improved control, reliability, and efficiency in specific applications. One main area of interest is cryogenic structural elements and fluid handling components and other parts, films, and coatings for low-temperature application. An important thermal property of these new materials is the apparent thermal conductivity (k-value).

  5. Reduction of Common-Mode Conducted Noise Emissions in PWM Inverter-fed AC Motor Drive Systems using Optimized Passive EMI Filter

    NASA Astrophysics Data System (ADS)

    Jettanasen, C.; Ngaopitakkul, A.

    2010-10-01

    Conducted electromagnetic interference (EMI) generated by PWM inverter-fed induction motor drive systems, which are currently widely used in many industrial and/or avionic applications, causes severe parasitic current problems, especially at high frequencies (HF). These restrict power electronic drive's evolution. In order to reduce or minimize these EMI problems, several techniques can be applied. In this paper, insertion of an optimized passive EMI filter is proposed. This filter is optimized by taking into account real impedances of each part of a considered AC motor drive system contrarily to commercial EMI filters designed by considering internal impedance of disturbance source and load, equal to 50Ω. Employing the latter EMI filter would make EMI minimization less effective. The proposed EMI filter optimization is mainly dedicated to minimize common mode (CM) currents due to its most dominant effects in this kind of system. The efficiency of the proposed optimization method using two-port network approach is deduced by comparing the minimized CM current spectra to an applied normative level (ex. DO-160D in aeronautics).

  6. Influence of temperature on the electric, dielectric and AC conductivity properties of nano-crystalline zinc substituted cobalt ferrite synthesized by solution combustion technique

    NASA Astrophysics Data System (ADS)

    Rani, Ritu; Kumar, Gagan; Batoo, Khalid M.; Singh, M.

    2014-06-01

    Cobalt-zinc nanoferrites with formulae Co ZnFeO, where x = 0.0, 0.1, 0.2 and 0.3, have been synthesized by solution combustion technique. The variation of DC resistivity with temperature shows the semiconducting behavior of all nanoferrites. The dielectric properties such as dielectric constant (') and dielectric loss tangent (tan are investigated as a function of temperature and frequency. Dielectric constant and loss tangent are found to be increasing with an increase in temperature while with an increase in frequency both, ' and tan , are found to be decreasing. The dielectric properties have been explained on the basis of space charge polarization according to Maxwell-Wagner's two-layer model and the hopping of charge between Fe and Fe. Further, a very high value of dielectric constant and a low value of tan are the prime achievements of the present work. The AC electrical conductivity ( is studied as a function of temperature as well as frequency and is observed to be increasing with the increase in temperature and frequency.

  7. Simultaneous ac and dc magnetic field measurements in residential areas: Implications for resonance theories of biological effects

    SciTech Connect

    Wong, P.S.; Sastre, A.

    1995-10-01

    The goal of this study was to obtain data that could be used to evaluate the applicability of ``resonance`` theories of biological effects in residential settings. The authors first describe a measurement system which allows the study of ac and dc magnetic fields simultaneously in space and in time. Sample measurements were taken near two power lines, two objects and in two residential homes. The results show that the earth`s (dc) magnetic field was unaffected near power lines. The compass orientation of the power line influenced the relative values of the ac components parallel and perpendicular to the dc field. The electric heating system greatly affected the ac field levels in the home, causing the levels to increase from less than 1 mG to a maximum of 7.5 mG during heating. The magnitudes of the dc field in the two homes varied from about 380 to 650 mG, with the larger variations near metallic or magnetic objects such as the refrigerator or a metallic air duct. The earth`s field was elevated above its natural level within a distance of 8 feet from a subcompact passenger car, e.g., the level changed from about 540 to 1,100 mG beside the headlight. A steel chair changed the earth`s field by up to 60 mG within a distance of one foot. These results suggest that some of the narrow ``resonances`` described in laboratory studies may be difficult to observe against the variations in do field amplitude and direction resulting from the presence of everyday metallic objects.

  8. Nanoscale Electromechanics To Measure Thermal Conductivity, Expansion, and Interfacial Losses.

    PubMed

    Mathew, John P; Patel, Raj; Borah, Abhinandan; Maliakkal, Carina B; Abhilash, T S; Deshmukh, Mandar M

    2015-11-11

    We study the effect of localized Joule heating on the mechanical properties of doubly clamped nanowires under tensile stress. Local heating results in systematic variation of the resonant frequency; these frequency changes result from thermal stresses that depend on temperature dependent thermal conductivity and expansion coefficient. The change in sign of the linear expansion coefficient of InAs is reflected in the resonant response of the system near a bath temperature of 20 K. Using finite element simulations to model the experimentally observed frequency shifts, we show that the thermal conductivity of a nanowire can be approximated in the 10-60 K temperature range by the empirical form κ = bT W/mK, where the value of b for a nanowire was found to be b = 0.035 W/mK(2), significantly lower than bulk values. Also, local heating allows us to independently vary the temperature of the nanowire relative to the clamping points pinned to the bath temperature. We suggest a loss mechanism (dissipation ~10(-4)-10(-5)) originating from the interfacial clamping losses between the metal and the semiconductor nanostructure. PMID:26479952

  9. Thermal conductivity of silver loaded conductive epoxy from cryogenic to ambient temperature and its application for precision cryogenic noise measurements

    NASA Astrophysics Data System (ADS)

    Amils, Ricardo I.; Gallego, Juan Daniel; Sebastián, José Luis; Muñoz, Sagrario; Martín, Agustín; Leuther, Arnulf

    2016-06-01

    The pressure to increase the sensitivity of instrumentation has pushed the use of cryogenic Low Noise Amplifier (LNA) technology into a growing number of fields. These areas range from radio astronomy and deep space communications to fundamental physics. In this context manufacturing for cryogenic environments requires a proper thermal knowledge of the materials to be able to achieve adequate design behavior. In this work, we present experimental measurements of the thermal conductivity of a silver filled conductive epoxy (EPO-TEK H20E) which is widely used in cryogenic electronics applications. The characterization has been made using a sample preparation which mimics the practical use of this adhesive in the fabrication of cryogenic devices. We apply the data obtained to a detailed analysis of the effects of the conductive epoxy in a monolithic thermal noise source used for high accuracy cryogenic microwave noise measurements. In this application the epoxy plays a fundamental role since its limited thermal conductivity allows heating the chip with relatively low power. To our knowledge, the cryogenic thermal conductivity data of this epoxy has not been reported before in the literature in the 4-300 K temperature range. A second non-conductive epoxy (Gray Scotch-Weld 2216 B/A), also widely used in cryogenic applications, has been measured in order to validate the method by comparing with previous published data.

  10. MEASUREMENT OF HYDRAULIC CONDUCTIVITY DISTRIBUTIONS: A MANUAL OF PRACTICE

    EPA Science Inventory

    The ability of hydrologists to perform field measurements of aquifer hydraulic properties must be enhanced in order to significantly improve the capacity to solve groundwater contamination problems at Superfund and other sites. The primary purpose of this manual is to provide ne...

  11. MEASUREMENT OF HYDRAULIC CONDUCTIVITY DISTRIBUTIONS: A MANUAL OF PRACTICE

    EPA Science Inventory

    The ability of hydrologists to perform field measurements of aquifer hydraulic properties must be enhanced in order to significantly improve the capacity to solve groundwater contamination problems at Superfund and other sites. he primary purpose of this manual is to provide new ...

  12. Measurements Conducted on an Unknown Object Labeled Pu-239

    SciTech Connect

    Hoteling, Nathan

    2013-11-18

    Measurements were carried out on 12 November 2013 to determine whether Pu-239 was present on an object discovered in a plastic bag with label “Pu-­239 6 uCi.” Following initial survey measurements to verify that the object was not leaking or contaminated, spectra were collected with a High Purity Germanium (HPGe) detector with object positioned in two different configurations. Analysis of the spectra did not yield any direct evidence of Pu-­239. From the measured spectra, minimum detectable activity (MDA) was determined to be approximately 2 uCi for the gamma-­ray measurements. Although there was no direct evidence of Pu-239, a peak at 60 keV characteristic of Am-­241 decay was observed. Since it is very likely that Am-­241 would be present in aged plutonium samples, this was interpreted as indirect evidence for the presence of plutonium on the object. Analysis of this peak led to an estimated Pu-­239 activity of 0.02–0.04 uCi, or <1x10-6 grams.

  13. Conducting Art Therapy Research Using Quantitative EEG Measures

    ERIC Educational Resources Information Center

    Belkofer, Christopher M.; Konopka, Lukasz M.

    2008-01-01

    This study presents a modified, single subject design that measured the patterns of electrical activity of a participant's brain following an hour spent painting and drawing. Paired t tests were used to compare pre and post art-making electroencephalograph (EEG) data. The results indicated that neurobiological activity after drawing and painting…

  14. Measuring Thermal Conductivity of a Small Insulation Sample

    NASA Technical Reports Server (NTRS)

    Miller, Robert A.; Kuczmarski, Maria A.

    2009-01-01

    A multiple-throat venturi system has been invented for measuring laminar flow of air or other gas at low speed (1 to 30 cm/s) in a duct while preserving the laminar nature of the flow and keeping the velocity profile across the duct as nearly flat as possible. While means for measuring flows at higher speeds are well established, heretofore, there have been no reliable means for making consistent, accurate measurements in this speed range. In the original application for which this system was invented, the duct leads into the test section of a low-speed wind tunnel wherein uniform, low-speed, laminar flow is required for scientific experiments. The system could also be used to monitor a slow flow of gas in an industrial process like chemical vapor deposition. In the original application, the multiple- throat venturi system is mounted at the inlet end of the duct having a rectangular cross section of 19 by 14 cm, just upstream of an assembly of inlet screens and flow straighteners that help to suppress undesired flow fluctuations (see Figure 1). The basic venturi measurement principle is well established: One measures the difference in pressure between (1) a point just outside the inlet, where the pressure is highest and the kinetic energy lowest; and (2) the narrowest part (the throat) of the venturi passage, where the kinetic energy is highest and the pressure is lowest. Then by use of Bernoulli s equation for the relationship between pressure and kinetic energy, the volumetric flow speed in the duct can be calculated from the pressure difference and the inlet and throat widths. The design of this system represents a compromise among length, pressure recovery, uniformity of flow, and complexity of assembly. Traditionally, venturis are used to measure faster flows in narrower cross sections, with longer upstream and downstream passages to maintain accuracy. The dimensions of the passages of the present venturi system are sized to provide a readily measurable

  15. Corrosion loss measurement of boiler tubes in a waste incineration environment by A.C. impedance method

    SciTech Connect

    Matsunaga, Yasuo; Nakagawa, Kiyokazu

    1997-08-01

    To monitor the corrosion rate of materials of boiler tubes in simulated waste incineration environment, A.C. impedance measurements were carried out for Alloy 625, SUS347H and STBA24 embedded in NaCl- KCl- NaSO{sub 4}-K{sub 2}SO{sub 4}-Al{sub 2}O{sub 3} mixed synthetic ash deposit at 600 C. Though the ash includes some non-melting component, A.C. impedance measurements can be applied to evaluate corrosion rates in the same manner the corrosion of materials immersed in molten salts. Supposing the difference of impedance between the low frequency and high frequency ({Delta}R) as polarization resistance, a linear relation was obtained between 1/{Delta}R and corrosion losses in air, air-0.1 vol.% HCl and air-10vol.% H{sub 2}O atmospheres. The HCl addition in accelerated the corrosion of all specimens by reducing basicity of the molten salt. On the other hand, the H{sub 2}O addition reduced the corrosion of Alloy 625, but it accelerated the corrosion of SUS347H and STBA24.

  16. Measurements of Electron Temperature and Density, in an AC Pulsed Oxygen Plasma Discharge

    NASA Astrophysics Data System (ADS)

    Yousif, Farook; Martinez, Horacio; Castillo, Fermin

    2007-06-01

    Emission and analytical spectroscopy was applied to investigate O2 plasma, which was generated by an AC discharge between 0.15 and 0.5 Torr pressure. For the diagnostic study, a double Langmuir probe was employed. The derivation of plasma parameters is based on a theoretical description of the double-probe current-voltage characterization in the Thick Sheath Limit (TSL) region [1]. Electron temperature of Te = 1.09 eV and an ion density of ni= 2.08 x 10^10 cm-3 were evaluated at 2 Torr. We present electron temperature and ion density as a function of the pressure at 3 different power discharge levels. Also we present emission spectroscopy in the wavelength range of 200-1100 nm as a function of the pressure. [1] J.D. Swift and J. R. Schwar, Electric Probes for Plasma Diagnostics (New York: Elsevier) 1971.

  17. Electrical Effect in Silver-Point Realization Due to Cell Structure and Bias Voltage Based on Resistance Measurement Using AC and DC Bridges

    NASA Astrophysics Data System (ADS)

    Widiatmo, J. V.; Harada, K.; Yamazawa, K.; Tamba, J.; Arai, M.

    2015-08-01

    Electrical effects related to insulating leakage represent one of the major factors contributing to uncertainties in measurements using high-temperature standard platinum resistance thermometers (HTSPRTs), especially during the realization of the silver freezing point (). This work is focused on the evaluation of the differences in resistance measurements observed when using AC resistance bridges and DC resistance bridges, hereafter, termed the AC-DC differences, as the result of various electrical effects. The magnitude of the AC-DC difference in several silver-point cells is demonstrated with several HTSPRTs. The effect of the cell structure on the AC-DC difference is evaluated by exchanging some components, part by part, within a silver-point cell. Then, the effect of the bias voltage applied to the heat pipe within the silver-point furnace is evaluated. Through the analysis of the experimental results and comparison with the reports in the literature, the importance of evaluating the AC-DC difference as a means to characterize the underlying electrical effects is discussed, considering that applying a negative bias condition to the furnace with respect to the high-temperature SPRT can minimize the AC-DC difference. Concluding recommendations are proposed on the components used in silver-point cells and the application of a bias voltage to the measurement circuit to minimize the effects of the electrical leakage.

  18. Simultaneous measurement of peritoneal glucose and free water osmotic conductances.

    PubMed

    La Milia, V; Limardo, M; Virga, G; Crepaldi, M; Locatelli, F

    2007-09-01

    Ultrafiltration (UF) failure is one of the most important causes of long-term peritoneal dialysis (PD) failure in patients. Osmotic forces acting across small and ultra-small pores generate a UF with solutes through the small pore and free water transport (FWT) through the ultra-small pore. The ability of glucose to exert an osmotic pressure sufficient to cause UF is the so-called 'osmotic conductance to glucose' (OCG) of the peritoneal membrane. Our study proposes a simple method to determine both the OCG and FWT. In 50 patients on PD, a Double Mini-Peritoneal Equilibration Test (Double Mini-PET), consisting of two Mini-PET, was performed consecutively. A solution of 1.36% glucose was used for the first test, whereas a solution of 3.86% glucose was used for the second test. The sodium removal values and the differences in UF between the two tests were used to calculate FWT and the OCG. Patients with UF failure showed significant reductions not only in the OCG and the FWT but also of UF of small pores. The Double Mini-PET is simple, fast, and could become useful to evaluate patients on PD in everyday clinical practice. PMID:17609692

  19. Electric characterization of (Sr, Sr-Ba, Ba) M-type ferrites by AC measurements[Alternating Current

    SciTech Connect

    Huanosta-Tera, A.; Lira-Hueso, R. de; Perez-Orta, O.; Palomares-Sanchez, S.A.; Ponce-Castaneda, S.; Mirabal-Garcia, M.

    2000-02-01

    Considering the electrical conductivity in ceramics, necessary reference should be given to dynamic processes occurring as a function of frequency and temperature. Although the most immediate interest in ferrites lies in their magnetic properties, technological applications require a wider knowledge of general physical properties as well. This is especially applicable when the materials are studied as a function of composition or when adding different modifiers. In this report, the authors present results of the ac and dc electric characteristics of a family of magneto-plumbite-type hexaferrites, where Ba gradually substitutes Sr in the Ba{sub x}Sr{sub 1{minus}x}Fe{sub 12}O{sub 19} compound (0 {le} x {le} 1). The results were determined over a wide range of frequencies and temperatures.

  20. Analyses of temperature-dependent interface states, series resistances, and AC electrical conductivities of Al/p—Si and Al/Bi4Ti3O12/p—Si structures by using the admittance spectroscopy method

    NASA Astrophysics Data System (ADS)

    Mert, Yıldırım; Perihan, Durmuş; Şemsettin, Altındal

    2013-10-01

    In this study, Al/p—Si and Al/Bi4Ti3O12/p—Si structures are fabricated and their interface states (Nss), the values of series resistance (Rs), and AC electrical conductivityac) are obtained each as a function of temperature using admittance spectroscopy method which includes capacitance—voltage (C—V) and conductance—voltage (G—V) measurements. In addition, the effect of interfacial Bi4Ti3O12 (BTO) layer on the performance of the structure is investigated. The voltage-dependent profiles of Nss and Rs are obtained from the high-low frequency capacitance method and the Nicollian method, respectively. Experimental results show that Nss and Rs, as strong functions of temperature and applied bias voltage, each exhibit a peak, whose position shifts towards the reverse bias region, in the depletion region. Such a peak behavior is attributed to the particular distribution of Nss and the reordering and restructuring of Nss under the effect of temperature. The values of activation energy (Ea), obtained from the slope of the Arrhenius plot, of both structures are obtained to be bias voltage-independent, and the Ea of the metal-ferroelectric-semiconductor (MFS) structure is found to be half that of the metal—semiconductor (MS) structure. Furthermore, other main electrical parameters, such as carrier concentration of acceptor atoms (NA), built-in potential (Vbi), Fermi energy (EF), image force barrier lowering (Δ Φb), and barrier height (Φb), are extracted using reverse bias C-2—V characteristics as a function of temperature.

  1. Results from the LADCP measurements conducted in the Eurasian Arctic

    NASA Astrophysics Data System (ADS)

    Goszczko, Ilona; Pnyushkov, Andrey; Polyakov, Igor; Rember, Robert; Thurnherr, Andreas M.

    2015-04-01

    Preliminary results from 114 dual headed LADCP (Lowered Acoustic Doppler Current Profiler) measurements performed during the NABOS (Nansen and Amundsen Basin Observational System) 2013 cruise in the Eurasian Basin of the Arctic Ocean are discussed. Calculated horizontal magnetic field strength for that specific study area and cruise time span equals to 1500-4200 nT which is a critically low value. This affected the heading usability of instruments' compasses, thereby making the obtained ocean currents velocities and directions difficult to assess. Additional data post-processing performed with the LDEO Software (Version IX_9) and dedicated Matlab routines have so far allowed to obtain reasonable velocity profiles only in several cases (with additional information from the SeaBird 911plus CTD, GPS and bottom tracking). Thus, doubts concerning the feasibility of compasses, confirmed by difficulties encountered previously in similar polar locations, rise the necessity of providing an additional heading source which should be mounted together with the Teledyne RDI instruments to gain an unquestionable velocity field.

  2. Spatially localized measurement of thermal conductivity using a hybrid photothermal technique

    SciTech Connect

    David H Hurley; Marat Khafizov; Zilong Hua; Rory Kennedy; Heng Ban

    2012-05-01

    A photothermal technique capable of measuring thermal conductivity with micrometer lateral resolution is presented. This technique involves measuring separately the thermal diffusivity, D, and thermal effusivity, e, to extract the thermal conductivity, k=(e2/D)1/2. To generalize this approach, sensitivity analysis was conducted for materials having a range of thermal conductivities. Experimental validation was sought using two substrate materials, SiO2 and CaF2, both coated with thin titanium films. The measured conductivities compare favorably with literature values.

  3. Evaluation of the electrode performance for PAFC by using acid absorption, acceleration and ac-impedance measurement

    SciTech Connect

    Kim, Chang-Soo; Song, Rak-Hyun; Choi, Byung-Woo

    1996-12-31

    In PAFC, the degradation on cathode electrode caused by carbon corrosion, platinum dissolution and growth is especially severe. An acceleration test is a good technique for evaluating the degradation of electrode performance, because it does not need long time. Coleman et al used thermal cycling and on-off cycling as an acceleration test. Song et al showed that hydrogen shortage decreased the electrode performance more rapidly than that of air shortage in gas shortage test. Honji et al reported that the rate of coarsening of Pt particle is rapid in open circuit potential and this is one of major causes on the performance degradation of electrode. The cathode performance has been studied by using acid absorption, acceleration and ac-impedance measurements as functions of the polytetrafluoroethylene (PTFE) contents and sintering temperatures of the electrode.

  4. Microfabricated AC impedance sensor

    DOEpatents

    Krulevitch, Peter; Ackler, Harold D.; Becker, Frederick; Boser, Bernhard E.; Eldredge, Adam B.; Fuller, Christopher K.; Gascoyne, Peter R. C.; Hamilton, Julie K.; Swierkowski, Stefan P.; Wang, Xiao-Bo

    2002-01-01

    A microfabricated instrument for detecting and identifying cells and other particles based on alternating current (AC) impedance measurements. The microfabricated AC impedance sensor includes two critical elements: 1) a microfluidic chip, preferably of glass substrates, having at least one microchannel therein and with electrodes patterned on both substrates, and 2) electrical circuits that connect to the electrodes on the microfluidic chip and detect signals associated with particles traveling down the microchannels. These circuits enable multiple AC impedance measurements of individual particles at high throughput rates with sufficient resolution to identify different particle and cell types as appropriate for environmental detection and clinical diagnostic applications.

  5. Conductance method for the measurement of cross-sectional areas of the aorta.

    PubMed

    Kornet, L; Jansen, J R; Gussenhoven, E J; Hardeman, M R; Hoeks, A P; Versprille, A

    1999-01-01

    A modified conductance method to determine the cross-sectional areas (CSAs) of arteries in piglets was evaluated in vivo. The method utilized a conductance catheter having four electrodes. Between the outer electrodes an alternating current was applied and between the inner electrodes the induced voltage difference was measured and converted into a conductance. CSA was determined from measured conductance minus parallel conductance, which is the conductance of the tissues surrounding the vessel times the length between the measuring electrodes of the conductance catheter divided by the conductivity of blood. The parallel conductance was determined by injecting hypertonic saline to change blood conductivity. The conductivity of blood was calculated from temperature and hematocrit and corrected for maximal deformation and changes in orientation of the erythrocytes under shear stress conditions. The equations to calculate the conductivity of blood were obtained from in vitro experiments. In vivo average aortic CSAs. determined with the conductance method CSA(G) in five piglets, were compared to those determined with the intravascular ultrasound method CSA(IVUS). The regression equation between both values was CSA(G)=-0.09+1.00 x CSA(IVUS), r=0.97, n=53. The mean difference between the values was -0.29%+/-5.57% (2 standard deviations). We conclude that the modified conductance method is a reliable technique to estimate the average cross-sectional areas of the aorta in piglets. PMID:10199690

  6. A slowly rotating coil system for AC field measurements of Fermilab booster correctors

    SciTech Connect

    Velev, G.; DiMarco, J.; Harding, David J.; Kashikhin, V.; Lamm, Michael J.; Schlabach, P.; Tartaglia, Michael Albert; Tompkins, John C.; /Fermilab

    2007-06-01

    A method for measurement of rapidly changing magnetic fields has been developed and applied to the testing of new room temperature corrector packages designed for the Fermilab Booster Synchrotron. The method is based on fast digitization of a slowly rotating tangential coil probe, with analysis combining the measured coil voltages across a set of successive magnet current cycles. This paper presents results on the field quality measured for the normal and skew dipole, quadrupole, and sextupole elements in several of these corrector packages.

  7. Analysis of variance on thickness and electrical conductivity measurements of carbon nanotube thin films

    NASA Astrophysics Data System (ADS)

    Li, Min-Yang; Yang, Mingchia; Vargas, Emily; Neff, Kyle; Vanli, Arda; Liang, Richard

    2016-09-01

    One of the major challenges towards controlling the transfer of electrical and mechanical properties of nanotubes into nanocomposites is the lack of adequate measurement systems to quantify the variations in bulk properties while the nanotubes were used as the reinforcement material. In this study, we conducted one-way analysis of variance (ANOVA) on thickness and conductivity measurements. By analyzing the data collected from both experienced and inexperienced operators, we found some operation details users might overlook that resulted in variations, since conductivity measurements of CNT thin films are very sensitive to thickness measurements. In addition, we demonstrated how issues in measurements damaged samples and limited the number of replications resulting in large variations in the electrical conductivity measurement results. Based on this study, we proposed a faster, more reliable approach to measure the thickness of CNT thin films that operators can follow to make these measurement processes less dependent on operator skills.

  8. Use of tandem circulation wells to measure hydraulic conductivity without groundwater extraction.

    PubMed

    Goltz, Mark N; Huang, Junqi; Close, Murray E; Flintoft, Mark J; Pang, Liping

    2008-09-10

    Conventional methods to measure the hydraulic conductivity of an aquifer on a relatively large scale (10-100 m) require extraction of significant quantities of groundwater. This can be expensive, and otherwise problematic, when investigating a contaminated aquifer. In this study, innovative approaches that make use of tandem circulation wells to measure hydraulic conductivity are proposed. These approaches measure conductivity on a relatively large scale, but do not require extraction of groundwater. Two basic approaches for using circulation wells to measure hydraulic conductivity are presented; one approach is based upon the dipole-flow test method, while the other approach relies on a tracer test to measure the flow of water between two recirculating wells. The approaches are tested in a relatively homogeneous and isotropic artificial aquifer, where the conductivities measured by both approaches are compared to each other and to the previously measured hydraulic conductivity of the aquifer. It was shown that both approaches have the potential to accurately measure horizontal and vertical hydraulic conductivity for a relatively large subsurface volume without the need to pump groundwater to the surface. Future work is recommended to evaluate the ability of these tandem circulation wells to accurately measure hydraulic conductivity when anisotropy and heterogeneity are greater than in the artificial aquifer used for these studies. PMID:18674844

  9. 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.

  10. 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%.

  11. Apparatus and method for detecting and/or measuring flaws in conductive material

    DOEpatents

    Hockey, Ronald L.; Riechers, Douglas M.

    2000-01-01

    The present invention uses a magnet and sensor coil unilaterial and in relative motion to a conductive material, to measure perturbation or variation in the magnetic field in the presence of a flaw. A liftoff compensator measures a distance between the conductive material and the magnet.

  12. AC field measurements of Fermilab Booster correctors using a rotating coil system

    SciTech Connect

    Velev, G.V.; DiMarco, J.; Harding, D.J.; Kashikhin, V.; Lamm, M.; Makulski, A.; Orris, D.; Schlabach, P.; Sylvester, C.; Tartaglia, M.; Tompkins, J.; /Fermilab

    2006-07-01

    The first prototype of a new corrector package for the Fermilab Booster Synchrotron is presently in production. This water-cooled package includes normal and skew dipole, quadrupole and sextupole elements to control orbit, tune and chromaticity of the beam over the full range of Booster energies (0.4-8 GeV). These correctors operate at the 15 Hz excitation cycle of the main synchrotron magnets, but must also make more rapid excursions, in some cases even switching polarity in approximately 1 ms at transition crossing. To measure the dynamic field changes during operation, a new method based on a relatively slow rotating coil system is proposed. The method pieces together the measured voltages from successive current cycles to reconstruct the field harmonics. This paper describes the method and presents initial field quality measurements from a Tevatron corrector.

  13. Identification of boundaries in the cometary environment from AC electric field measurements

    NASA Astrophysics Data System (ADS)

    Mogilevsky, M.; Mikhailov, Y.; Molchanov, O.; Grard, R.; Pedersen, A.; Trotignon, J. G.; Beghin, C.; Formisano, V.; Shapiro, V.; Shevchenko, V.

    1986-12-01

    Electric fields are measured with the AVP-V experiment in the frequency range 8 Hz - 300 kHz. The field amplitude increases significantly, first at a distance of 2×105km, then at distances of 1.2 - 1.5×105km, and 5 - 7×104km from the nucleus. These phenomena have been observed both on VEGA-1 and VEGA-2. The electric field measurements are compared with data obtained from dust and plasma experiments; possible mechanisms responsible for the existence of these boundaries are discussed.

  14. Second Harmonic Technique for Thermal Conductivity Measurement in a Pulsed Magnetic Field

    NASA Astrophysics Data System (ADS)

    Suzuki, Yoko; Betts, Jonathan B.; Migliori, Albert

    2009-03-01

    We describe a second-harmonic technique to be used eventually to probe the thermal conductivity of LSCO with superconductivity suppressed by high magnetic fields. The technique is suitable for the high-noise environment of pulsed magnets. Unlike the 3φ technique, a heater and a thermometer are mounted separately. Therefore, the 2φ signal is the dominant signal in the thermometer output. The frequencies are chosen so that the thermal penetration depth is smaller than the sample thickness. The thermometer response time and thermal impedance associated with material interfaces are carefully tested and compared to calculation. The calculations are based on exact solutions of the full bulk heat transport equations and produce results different from the lumped-constant approximations often used in ac calorimetry. Work performed under the auspices of the National High Magnetic Field Laboratory.

  15. Atmospheric chemistry suite (ACS): a set of infrared spectrometers for atmospheric measurements on board ExoMars trace gas orbiter

    NASA Astrophysics Data System (ADS)

    Korablev, Oleg; Grigoriev, Alexei V.; Trokhimovsky, Alexander; Ivanov, Yurii S.; Moshkin, Boris; Shakun, Alexei; Dziuban, Ilia; Kalinnikov, Yurii K.; Montmessin, Franck

    2013-09-01

    The ACS package for ExoMars Trace Gas Orbiter is a part of Russian contribution to ExoMars ESA-Roscosmos mission. On the Orbiter it complements NOMAD investigation and is intended to recover in much extent the science lost with the cancellation of NASA MATMOS and EMCS infrared sounders. ACS includes three separate spectrometers, sharing common mechanical, electrical, and thermal interfaces. NIR is a versatile spectrometer for the spectral range of 0.7-1.6 μm with resolving power of ~20000. It is conceived on the principle of RUSALKA/ISS or SOIR/Venus Express experiments combining an echelle spectrometer and an AOTF (Acousto-Optical Tuneable Filter) for order selection. Up to 8 diffraction orders, each 10-20 nm wide can be measured in one sequence record. NIR will be operated principally in nadir, but also in solar occultations, and possibly on the limb. MIR is a high-resolution echelle instrument exclusively dedicated to solar occultation measurements in the range of 2.2-4.4 μm targeting the resolving power of 50000. The order separation is done by means of a steerable grating cross-disperser, allowing instantaneous coverage of up to 300-nm range of the spectrum for one or two records per second. MIR is dedicated to sensitive measurements of trace gases, approaching MATMOS detection thresholds for many species. TIRVIM is a 2- inch double pendulum Fourier-transform spectrometer for the spectral range of 1.7-17 μm with apodized resolution varying from 0.2 to 1.6 cm-1. TIRVIM is primarily dedicated to monitoring of atmospheric temperature and aerosol state in nadir, and would contribute in solar occultation to detection/reducing of upper limits of some components absorbing beyond 4 μm, complementing MIR and NOMAD. Additionally, TIRVIM targets the methane mapping in nadir, using separate detector optimized for 3.3-μm range. The concept of the instrument and in more detail the optical design and the expected parameters of its three parts, channel by channel are

  16. Studies on structural, thermal and AC conductivity scaling of PEO-LiPF6 polymer electrolyte with added ionic liquid [BMIMPF6

    NASA Astrophysics Data System (ADS)

    Chaurasia, S. K.; Saroj, A. L.; Shalu, Singh, V. K.; Tripathi, A. K.; Gupta, A. K.; Verma, Y. L.; Singh, R. K.

    2015-07-01

    Preparation and characterization of polymer electrolyte films of PEO+10wt.% LiPF6 + xwt.% BMIMPF6 (1-butyl-3-methylimidazolium hexafluorophosphate) containing dopant salt lithium hexafluorophosphate (LiPF6) and ionic liquid (BMIMPF6) having common anion PF6 - are reported. The ionic conductivity of the polymer electrolyte films has been found to increase with increasing concentration of BMIMPF6 in PEO+10 wt.% LiPF6 due to the plasticization effect of ionic liquid. DSC and XRD results show that the crystallinity of polymer electrolyte decreases with BMIMPF6 concentration which, in turn, is responsible for the increase in ionic conductivity. FTIR spectroscopic study shows the complexation of salt and/or ionic liquid cations with the polymer backbone. Ion dynamics behavior of PEO+LiPF6 as well as PEO+LiPF6 + BMIMPF6 polymer electrolytes was studied by frequency dependent conductivity, σ(f) measurements. The values σ(f) at various temperatures have been analyzed in terms of Jonscher power law (JPL) and scaled with respect to frequency which shows universal power law characteristics at all temperatures.

  17. 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.

  18. Measurement of the thermal properties of electrically conducting fluids using coated transient hot wires

    SciTech Connect

    Perkins, R.A.

    1994-09-01

    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 tetrafluorethane (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.

  19. A Fast-sampling, Planar Array for Measuring the AC Field of Fermilab Pulsed Extraction Magnets

    SciTech Connect

    DiMarco, E.Joseph; Johnstone, C.; Kiemschies, O.; Kotelnikov, S.K.; Lamm, M.J.; Makulski, A.; Nehring, R.; Orris, D.F.; Russell, A.D.; Tartaglia, Michael Albert; Velev, G.; /Fermilab

    2008-06-25

    A system employing a planar array of inductive pick-up coils has been developed for measurements of the rapidly changing dipole field in pulsed extraction magnets for the Fermilab MuCool project. The magnets are of C-type and deigned to support a peak field of 0.65 T during 8.33 millisecond half-sine pulse at a 15 Hz repetition rate. The coils of the measurement system are fabricated on a single, 97.5 mm wide, 2-layer circuit board. The array of coils is simultaneously sampled at data rates of up to 100 kHz with 10 kHz bandwidth using 24-bit ADC's. A detailed overview of the system and data analysis is presented, along with a characterization of results and system performance.

  20. Development of an in situ thermal conductivity measurement system for exploration of the shallow subsurface

    NASA Astrophysics Data System (ADS)

    Chirila, Marian Andrei; Christoph, Benjamin; Vienken, Thomas; Dietrich, Peter; Bumberger, Jan

    2016-06-01

    In this study, we attempted to develop an in situ thermal conductivity measurement system that can be used for subsurface thermal exploration. A new thermal probe was developed for mapping both the spatial and temporal variability of thermal conductivity, via direct push methods in the unconsolidated shallow subsurface. A robust, hollow cylindrical probe was constructed and its performance was tested by carrying out thermal conductivity measurements on materials with known properties. The thermal conductivity of the investigated materials can be worked out by measuring the active power consumption (in alternating current system) and temperature of the probe over fixed time intervals. A calibration method was used to eliminate any undesired thermal effects regarding the size of the probe, based on mobile thermal analyzer thermal conductivity values. Using the hollow cylindrical probe, the thermal conductivity results obtained had an error of less than 2.5% for solid samples (such as Teflon, Agar Jelly and Nylatron).

  1. Microbial growth and biofilm formation in geologic media is detected with complex conductivity measurements

    NASA Astrophysics Data System (ADS)

    Davis, Caroline A.; Atekwana, Estella; Atekwana, Eliot; Slater, Lee D.; Rossbach, Silvia; Mormile, Melanie R.

    2006-09-01

    Complex conductivity measurements (0.1-1000 Hz) were obtained from biostimulated sand-packed columns to investigate the effect of microbial growth and biofilm formation on the electrical properties of porous media. Microbial growth was verified by direct microbial counts, pH measurements, and environmental scanning electron microscope imaging. Peaks in imaginary (interfacial) conductivity in the biostimulated columns were coincident with peaks in the microbial cell concentrations extracted from sands. However, the real conductivity component showed no discernible relationship to microbial cell concentration. We suggest that the observed dynamic changes in the imaginary conductivity (σ″) arise from the growth and attachment of microbial cells and biofilms to sand surfaces. We conclude that complex conductivity techniques, specifically imaginary conductivity measurements are a proxy indicator for microbial growth and biofilm formation in porous media. Our results have implications for microbial enhanced oil recovery, CO2 sequestration, bioremediation, and astrobiology studies.

  2. Sodium Concentration Measurement during Hemodialysis through Ion-Exchange Resin and Conductivity Measure Approach: In Vitro Experiments

    PubMed Central

    Tura, Andrea; Sbrignadello, Stefano; Mambelli, Emanuele; Ravazzani, Paolo; Santoro, Antonio; Pacini, Giovanni

    2013-01-01

    Sodium measurement during hemodialysis treatment is important to preserve the patient from clinical events related to hypo- or hyper-natremia Usually, sodium measurement is performed through laboratory equipment which is typically expensive, and requires manual intervention. We propose a new method, based on conductivity measurement after treatment of dialysate solution through ion-exchange resin. To test this method, we performed in vitro experiments. We prepared 40 ml sodium chloride (NaCl) samples at 280, 140, 70, 35, 17.5, 8.75, 4.375 mEq/l, and some “mixed samples”, i.e., with added potassium chloride (KCl) at different concentrations (4.375-17.5 mEq/l), to simulate the confounding factors in a conductivity-based sodium measurement. We measured the conductivity of all samples. Afterwards, each sample was treated for 1 min with 1 g of Dowex G-26 resin, and conductivity was measured again. On average, the difference in the conductivity between mixed samples and corresponding pure NaCl samples (at the same NaCl concentration) was 20.9%. After treatment with the exchange resin, it was 14.7%, i.e., 42% lower. Similar experiments were performed with calcium chloride and magnesium chloride as confounding factors, with similar results. We also performed some experiments on actual dialysate solution during hemodialysis sessions in 15 patients, and found that the correlation between conductivity measures and sodium concentration improved after resin treatment (R=0.839 before treatment, R=0.924 after treatment, P<0.0001). We conclude that ion-exchange resin treatment coupled with conductivity measures may improve the measurement of sodium compared to conductivity measures alone, and may become a possible simple approach for continuous and automatic sodium measurement during hemodialysis. PMID:23844253

  3. Conductivity Measurements of Pyrrole Molecules Incorporated into Chemically Adsorbed Monolayer by Conducting Probe Technique in Atomic Force Microscope

    NASA Astrophysics Data System (ADS)

    Yamamoto, Shin‑ichi; Ogawa, Kazufumi

    2006-03-01

    A monomolecular layer containing pyrrolyl groups at the surface was prepared between two parallel Pt electrodes on a glass substrate by a chemical adsorption technique using N-[11-(trichlorosilyl)undecyl] pyrrole (PNN). Then, the pyrrolyl was polymerized with pure water by applying a DC voltage of 10 V between the two Pt electrodes. It was confirmed using an optical microscope that many electric paths were formed between the two Pt electrodes by a decoration technique using electrochemical polymerization in an aqueous medium containing pyrrole after the polymerization. Next, a conductive probe of an atomic force microscope (AFM) was used to examine an electrical polymerized path through the surface of the polypyrrolyl group in a chemically adsorbed monomolecular layer. The resistance of one electric path in the monomolecular layer was measured using an AFM with an attached Au-covered tip at room temperature. With a measurement volume of about 0.2 nm (the thickness of the electric path in the monomolecular layer) × 200 μm (the average width of the 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 4 k Ω under ambient conditions. From the results in the atmosphere, the conductivity of a super long conjugated polypyrrolyl group without any dopant in a lateral direction was ohmically estimated to be at least 6.0 × 105 S/m.

  4. Thermal contact conductance of spotwelded titanium joints - Measurements and a generalized analytical model

    NASA Astrophysics Data System (ADS)

    Flynn, Edward M.; Choi, Paul S.

    1990-06-01

    Measurements and an analytical investigation of the thermal contact conductance of spotwelded joints are presented. Pairs of .081-cm thick sheets of Ti-6Al-4V alloy were resistance welded to form test coupons representing skins and stiffeners. The spotweld number density was varied. Measurements of contact conductance of these coupons were made at temperatures from 120 to 232 C. In addition, a thermal model of the spotweld interface was constructed which yielded good predictions of spotweld conduction, gaseous conduction, and gap radiation.

  5. Thermal conductivity measurements of glass beads and regolith simulant under vacuum conditions

    NASA Astrophysics Data System (ADS)

    Sakatani, N.; Ogawa, K.; Iijima, Y.; Tsuda, S.; Honda, R.; Tanaka, S.

    2013-09-01

    Past studies of in-situ and laboratory measurements of lunar regolith thermal conductivity imply that the conductivity would vary with depth due to change of density and self-weighted stress. In this study, we experimentally investigated the effect of the compressional stress on the thermal conductivity of the glass beads and regolith simulant using a new stress controlling system under vacuum conditions. We experimentally confirmed that the thermal conductivity increases with the compressional stress, which indicates that the regolith layer on the airless terrestrial bodies has various thermal conductivities according to the depth and their gravity.

  6. Length Dependent Thermal Conductivity Measurements Yield Phonon Mean Free Path Spectra in Nanostructures

    PubMed Central

    Zhang, Hang; Hua, Chengyun; Ding, Ding; Minnich, Austin J.

    2015-01-01

    Thermal conductivity measurements over variable lengths on nanostructures such as nanowires provide important information about the mean free paths (MFPs) of the phonons responsible for heat conduction. However, nearly all of these measurements have been interpreted using an average MFP even though phonons in many crystals possess a broad MFP spectrum. Here, we present a reconstruction method to obtain MFP spectra of nanostructures from variable-length thermal conductivity measurements. Using this method, we investigate recently reported length-dependent thermal conductivity measurements on SiGe alloy nanowires and suspended graphene ribbons. We find that the recent measurements on graphene imply that 70% of the heat in graphene is carried by phonons with MFPs longer than 1 micron. PMID:25764977

  7. Length dependent thermal conductivity measurements yield phonon mean free path spectra in nanostructures.

    PubMed

    Zhang, Hang; Hua, Chengyun; Ding, Ding; Minnich, Austin J

    2015-01-01

    Thermal conductivity measurements over variable lengths on nanostructures such as nanowires provide important information about the mean free paths (MFPs) of the phonons responsible for heat conduction. However, nearly all of these measurements have been interpreted using an average MFP even though phonons in many crystals possess a broad MFP spectrum. Here, we present a reconstruction method to obtain MFP spectra of nanostructures from variable-length thermal conductivity measurements. Using this method, we investigate recently reported length-dependent thermal conductivity measurements on SiGe alloy nanowires and suspended graphene ribbons. We find that the recent measurements on graphene imply that 70% of the heat in graphene is carried by phonons with MFPs longer than 1 micron. PMID:25764977

  8. Thermal conductivity measurements of particulate materials: 5. Effect of bulk density and particle shape

    NASA Astrophysics Data System (ADS)

    Presley, Marsha A.; Christensen, Philip R.

    2010-07-01

    Thermal conductivities were measured with a line-heat source for three particulate materials with different particle shapes under low pressures of a carbon dioxide atmosphere and various bulk densities. Less than 2 μm kaolinite exhibited a general decrease in thermal conductivity with increasing bulk density. For the range of atmospheric pressures appropriate for Mars, a reduction in porosity of 24% decreased the thermal conductivity by 24%. Kaolinite manifests considerable anisotropy with respect to thermal conductivity. As the particles align the bulk thermal conductivity measured increasingly reflects the thermal conductivity of the short axis. When kyanite is crushed, it forms blady particles that will also tend to align with increasing bulk density. Without any intrinsic anisotropy, however, kyanite particles, like other particulates exhibit an increase in thermal conductivity with increasing bulk density. Under Martian atmospheric pressures, a reduction in porosity of 30% produces a 30% increase in thermal conductivity. Diatomaceous earth maintains a very low bulk density due to the highly irregular shape of the individual particles. A decrease in porosity of 17% produces an increase in thermal conductivity of 27%. The trends in thermal conductivity with bulk density, whether increasing or decreasing, are often not smooth. Whether oscillations in the trends presented in this paper and elsewhere have any physical significance or whether they are merely artifacts of the precision error is unclear. Clarification of this question may not be possible without higher-precision measurements from future laboratories and further development of theoretical modeling.

  9. Detecting Microbial Growth and Metabolism in Geologic Media with Complex Conductivity Measurements

    NASA Astrophysics Data System (ADS)

    Davis, C. A.; Atekwana, E. A.; Slater, L. D.; Bottrell, P. M.; Chasten, L. E.; Heidenreich, J. D.

    2006-05-01

    Complex conductivity measurements between 0.1-1000 Hz were obtained from biostimulated sand-packed (coarse and mixed fine and medium grain) columns to investigate microbial growth, biofilm formation, and microbial metabolism on the electrical properties of porous media. Microbial growth and metabolism was verified by direct microbial counts, pH changes, and environmental scanning electron microscope imaging. Peaks in imaginary (interfacial) conductivity in the coarse grain columns occurred concurrently with peaks in the microbial cell concentrations. The magnitude of the imaginary conductivity response in the mixed fine and medium grain columns, however, was low compared to the coarse grain sand columns, consistent with lower microbial cell concentrations. It is possible that the pore size in the mixed fine and medium grain sand restricted bacteria cell division, inhibiting microbial growth, and thus the smaller magnitude imaginary conductivity response. The biostimulated columns for both grain sizes displayed similar trends and showed an increase in the real (electrolytic) conductivity and decrease in pH over time. Dynamic changes in the imaginary conductivity arises from the growth and attachment of microbial cells and biofilms to surfaces, whereas, changes in the real conductivity arises from the release of byproducts (ionic species) of microbial metabolism. We conclude that complex conductivity techniques are feasible sensors for detecting microbial growth (imaginary conductivity measurements) and metabolism (real conductivity measurements) with implications for bioremediation and astrobiology studies.

  10. Differential heating: A versatile method for thermal conductivity measurements in high-energy-density matter

    DOE PAGESBeta

    Ping, Y.; Fernandez-Panella, A.; Sio, H.; Correa, A.; Shepherd, R.; Landen, O.; London, R. A.; Sterne, P. A.; Whitley, H. D.; Fratanduono, D.; et al

    2015-09-04

    We propose a method for thermal conductivity measurements of high energy density matter based on differential heating. A temperature gradient is created either by surface heating of one material or at an interface between two materials by different energy deposition. The subsequent heat conduction across the temperature gradient is observed by various time-resolved probing techniques. Conceptual designs of such measurements using laser heating, proton heating, and x-ray heating are presented. As a result, the sensitivity of the measurements to thermal conductivity is confirmed by simulations.

  11. Differential heating: A versatile method for thermal conductivity measurements in high-energy-density matter

    SciTech Connect

    Ping, Y.; Fernandez-Panella, A.; Correa, A.; Shepherd, R.; Landen, O.; London, R. A.; Sterne, P. A.; Whitley, H. D.; Fratanduono, D.; Collins, G. W.; Sio, H.; Boehly, T. R.

    2015-09-15

    We propose a method for thermal conductivity measurements of high energy density matter based on differential heating. A temperature gradient is created either by surface heating of one material or at an interface between two materials by different energy deposition. The subsequent heat conduction across the temperature gradient is observed by various time-resolved probing techniques. Conceptual designs of such measurements using laser heating, proton heating, and x-ray heating are presented. The sensitivity of the measurements to thermal conductivity is confirmed by simulations.

  12. Measurement of soil saturated hydraulic conductivity: The method of constant pressure tubes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Field method to measure the saturated soil hydraulic conductivity is presented that does not require expensive equipment and preserves natural water flow pathways that may be bloked during soil core sampling for laboratory measurements. Vegetation must be removed from the plot prior the measurement...

  13. On the van der Pauw's method applied to the measurement of low thermal conductivity materials

    NASA Astrophysics Data System (ADS)

    Morales, C.; Flores, E.; Bodega, J.; Leardini, F.; Ferrer, I. J.; Ares, J. R.; Sánchez, C.

    2016-08-01

    The electrical van der Pauw's method has recently been extended to measure the thermal conductivity of different elements and compounds. This technique provides an easy way to determine the sample in-plane thermal conductivity by avoiding the influence of the thermal contact resistances. However, the reported calculated error values appear to be underestimated when dealing with the materials with low thermal conductivity (<5 W/Km) at room temperature. The causes of this underestimation are investigated in this communication and it has been found that they are due to the drastic influence of conduction heat losses through the thermo-resistance wires as well as the resulting modification of the sample temperature map. Both phenomena lead to experimental values of the sample thermal conductivity, which are systematically higher than the tabulated ones. The magnitude of this systematic error is ˜100% dealing with the samples of macroscopic dimensions, and low thermal conductivity indicated that the obtained accurate measurements can be quite challenging.

  14. Molecular origins of conduction channels observed in shot-noise measurements.

    PubMed

    Solomon, Gemma C; Gagliardi, Alessio; Pecchia, Alessandro; Frauenheim, Thomas; Di Carlo, Aldo; Reimers, Jeffrey R; Hush, Noel S

    2006-11-01

    Measurements of shot noise from single molecules have indicated the presence of various conduction channels. We present three descriptions of these channels in molecular terms showing that the number of conduction channels is limited by bottlenecks in the molecule and that the channels can be linked to transmission through different junction states. We introduce molecular-conductance orbitals, which allow the transmission to be separated into contributions from individual orbitals and contributions from interference between pairs of orbitals. PMID:17090069

  15. Conductivity measurements of molten metal oxide electrolytes and their evaluation in a direct carbon fuel cell (DCFC)

    NASA Astrophysics Data System (ADS)

    Yarlagadda, Venkata Raviteja

    2011-12-01

    Since Direct Carbon Fuel Cell (DCFC) technology is in a beginning stage, emphasis should be laid on addressing the fundamental aspects. A molten electrolyte is required to facilitate ionic contact between solid carbon fuel and electrolyte in a DCFC Three different metal oxide electrolytes (Bi2O3 , V2O5, and TeO2) have been chosen based on their ability to form stable liquids in air at higher temperatures. Conductivity data beyond their melting points was not readily available for most of the metal oxides. Conductivity studies concerning the above mentioned molten metal oxides have been thoroughly investigated in this study. A four probe measurement method using an AC milliohm-meter at 1 KHz validated by Electrochemical Impedance Spectroscopy (EIS) was used to acquire the conductivity data because of its accuracy when compared to two probe measurement widely used in literature. Also, a DC ohmmeter was used to check whether these metal oxides exhibit electronic conductivity. Experimental results corresponding to the accuracy of DC ohmmeter showed that, it accurately detected the electronic component of the electrolyte. These conductivity studies revealed that the molten oxide electrolytes exhibit high ionic conductivity, in particular, beyond their melting points. Of all the three metal oxides, Bi2O 3 demonstrated high ionic conductivity but with minor stability issues under CO2 environment. Under CO2 environment Bi 2O3 showed a slight decrease in the conductivity. EDX analysis revealed an increase in carbon content by 50 percent per one mole of bismuth which can be attributed to possible carbonate formation. V2O 5 exhibited lower ionic conductivity when compared to Bi2O 3 but had the advantage of lower cost and higher abundance. Also, the higher volumetric expansion of V2O5 upon cooling from its melting point i.e. 690°C caused the alumina crucible containing the metal oxide to break leading to leakage problems. Investigating further, quartz was found to be the best

  16. MEASURING VERTICAL PROFILES OF HYDRAULIC CONDUCTIVITY WITH IN SITU DIRECT-PUSH METHODS

    EPA Science Inventory

    U.S. EPA (Environmental Protection Agency) staff developed a field procedure to measure hydraulic conductivity using a direct-push system to obtain vertical profiles of hydraulic conductivity. Vertical profiles were obtained using an in situ field device-composed of a
    Geopr...

  17. IN SITU APPARENT CONDUCTIVITY MEASUREMENTS AND MICROBIAL POPULATION DISTRIBUTION AT A HYDROCARBON CONTAMINATED SITE

    EPA Science Inventory

    We investigated the bulk electrical conductivity and microbial population distribution in sediments at a site contaminated with light non-aqueous phase liquid (LNAPL). The bulk conductivity was measured using in situ vertical resistivity probes, while the most probable number met...

  18. The Thermal Conductivity Measurements of Solid Samples by Heat Flux Differantial Scanning Calorimetry

    NASA Astrophysics Data System (ADS)

    Kök, M.; Aydoǧdu, Y.

    2007-04-01

    The thermal conductivity of polyvinylchloride (PVC), polysytrene (PS) and polypropylene (PP) were measured by heat flux DSC. Our results are in good agreement with the results observed by different methods.

  19. Measuring the sedimentation rate in a magnetorheological fluid column via thermal conductivity monitoring

    NASA Astrophysics Data System (ADS)

    Cheng, Haibin; Zhang, Xiaopeng; Liu, Guizhen; Ma, Wentao; Wereley, Norman M.

    2016-05-01

    Measuring sedimentation rate of magnetorheological fluids (MRFs) is of great importance when designing and synthesizing MRFs for engineering applications. A method of characterizing sedimentation rate in an MRF column is proposed utilizing thermal conductivity correlated with particle concentration. A series of MRF samples composed of carbonyl iron particles suspended in silicone oil were prepared, and their concentrations (measured as volume fraction, ∅) and thermal conductivities, k, were tested. A calibration curve was developed to relate particle concentration, ∅, to thermal conductivity, k, using this set of MRF samples with known concentration. The particle concentration, ∅, in the MRF column was then monitored by measuring thermal conductivities (k) at a fixed location and using this calibration relationship. Finally, sedimentation rate in the MRF column was determined by examining how particle concentration varied with time. The sedimentation rate measured in the MRF column was validated using visual observation of mudline (boundary between the topmost clarified fluid zone and MRF below).

  20. Compressional stress effect on thermal conductivity of powdered materials: Measurements and their implication to lunar regolith

    NASA Astrophysics Data System (ADS)

    Sakatani, Naoya; Ogawa, Kazunori; Iijima, Yu-ichi; Arakawa, Masahiko; Tanaka, Satoshi

    2016-03-01

    Thermal conductivity of powdered materials under vacuum conditions is a valuable physical parameter in the context of planetary sciences. We report results of thermal conductivity measurements of 90-106 μm and 710-1000 μm glass beads, and lunar regolith simulant using two different experimental setups for varying the compressional stress and the temperature, respectively. We found the thermal conductivity increase with the compressional stress, for example, from 0.003 to 0.008 W m-1 K-1 for the glass beads of 90-106 μm in diameter at the compressional stress less than 20 kPa. This increase of the thermal conductivity is attributed the areal enlargement of the contacts between particles due to their elastic deformation. The thermal conductivity increased also with temperature, which primarily represented enhancement of the radiative heat conduction between particles. Reduction of the estimated radiative conductivity from the effective thermal conductivity obtained in the first experiment yields the relation between the solid conductivity (conductive contribution through inter-particle contacts) and the compressional stress. We found that the solid conductivity is proportional to approximately 1/3 power of the compressional stress for the glass beads samples, while the regolith simulant showed a weaker exponent than that of the glass beads. We developed a semi-empirical expression of the thermal conductivity of the lunar regolith using our data on the lunar regolith simulant. This model enabled us to estimate a vertical distribution of the lunar subsurface thermal conductivity. Our model provides an examination for the density and compressional stress relationships to thermal conductivity observed in the in-situ measurements in Apollo 15 and 17 Heat Flow Experiments.

  1. Thermionic triode generates ac power

    NASA Technical Reports Server (NTRS)

    Kniazzeh, A. G. F.; Scharz, F. C.

    1970-01-01

    Electrostatic grid controls conduction cycle of thermionic diode to convert low dc output voltages to high ac power without undesirable power loss. An ac voltage applied to the grid of this new thermionic triode enables it to convert heat directly into high voltage electrical power.

  2. Electronic energy gap of molecular hydrogen from electrical conductivity measurements at high shock pressures

    NASA Technical Reports Server (NTRS)

    Nellis, W. J.; Mitchell, A. C.; Mccandless, P. C.; Erskine, D. J.; Weir, S. T.

    1992-01-01

    Electrical conductivities were measured for liquid D2 and H2 shock compressed to pressures of 10-20 GPa (100-200 kbar), molar volumes near 8 cu cm/mol, and calculated temperatures of 2900-4600 K. The semiconducting energy gap derived from the conductivities is 12 eV, in good agreement with recent quasi-particle calculations and with oscillator frequencies measured in diamond-anvil cells.

  3. 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.

  4. Hot wire needle probe for in-reactor thermal conductivity measurement

    SciTech Connect

    JE Daw; JL Rempe; DL Knudson

    2012-08-01

    Thermal conductivity is a key property that must be known for proper design, test, and application of new fuels and structural materials in nuclear reactors. Thermal conductivity is highly dependent on the physical structure, chemical composition, and the state of the material. Typically, thermal conductivity changes that occur during irradiation are measured out-of-pile by Post Irradiated Examination (PIE) using a “cook and look” approach in hot-cells. Repeatedly removing samples from a test reactor to make out-of-pile measurements is expensive, has the potential to disturb phenomena of interest, and only provides understanding of the sample's end state at the time each measurement is made. There are also limited thermophysical property data for advanced fuels. Such data are needed for simulation design codes, the development of next generation reactors, and advanced fuels for existing nuclear plants. Being able to quickly characterize fuel thermal conductivity during irradiation can improve the fidelity of data, reduce costs of post-irradiation examinations, increase understanding of how fuels behave under irradiation, and confirm or improve existing thermal conductivity measurement techniques. This paper discusses recent efforts to develop and evaluate an in-pile thermal conductivity sensor based on a hot wire needle probe. Testing has been performed on samples with thermal conductivities ranging from 0.2 W/m-K to 22 W-m-K in temperatures ranging from 20 °C to 600 °C. Thermal conductivity values measured using the needle probe match data found in the literature to within 5% for samples tested at room temperature, 5.67% for low thermal conductivity samples tested at high temperatures, and 10% for high thermal conductivity samples tested at high temperatures. Experimental results also show that this sensor is capable of operating in various test conditions and of surviving long duration irradiations.

  5. Design and Use of a Novel Apparatus for Measuring Capsule Fill Hole Conductance

    SciTech Connect

    Seugling, R M; Nederbragt, W W; Klingmann, J L; Edson, S; Reynolds, J; Cook, R

    2006-11-27

    Description and results of a novel apparatus for determining the flow conductance through a laser drilled hole in a spherical shell for inertial confinement fusion experiments are described. The instrument monitors the pressure of an enclosed volume containing the laser pressure drilled capsule as air bleeds through the hole into the shell. From these measurements one obtains the conductance of the fill hole. This system has proven to be a valuable tool for verifying the conduct conductance into the capsule in a timely and nondestructive manner.

  6. A convenient method of measuring the thermal conductivity of biological tissue.

    PubMed

    Liang, X G; Ge, X S; Zhang, Y P; Wang, G J

    1991-12-01

    The basic principle of the thermal conductivity probe is described. Thin probes were developed based on this principle, with a reproducibility of 5.3% and relative error less than 6.0%. Each measurement can be completed in 90 s and the temperature increase can be controlled within 2 degrees C. Using the probes, the thermal conductivities of pig fat, meat, liver, kidney and live and dead snake head were measured and it was found that water content plays an important role in influencing the magnitude of the thermal conductivity of biological tissues. The probe can be used over a temperature range from -40 to 150 degrees C. PMID:1771182

  7. In-core measurements of U-5 wt % fissium alloy thermal conductivity

    SciTech Connect

    Betten, P.R.

    1985-01-01

    Instrumented subassemblies have inserted into the Experimental Breeder Reactor II (EBR-II) in order to monitor thermal-hydraulic phenomena. For one such subassembly, a time history of the in-core themocouples was evaluated and used to determine the fuel thermal conductivity. Although several researchers have evaluated fuel conductivity for unirradiated conditions, little data is available for long term irradiation. Further, most of the data has been evaluated under laboratory conditions which, while providing exact measurements, may be missing important facets of in-core behavior. The purpose of this paper is to present the in-situ measurements of thermal conductivity over the subassembly lifetime. 7 refs.

  8. Uncertainty Of The Measurement Of DC Conductivity Of Eramics At Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Štubňa, Igor; Trnovcová, Viera; Vozár, Libor; Csáki, Štefan

    2015-01-01

    The electrical DC conductivity is measured at room and elevated temperatures on green ceramic samples prepared from kaolin. The arrangement of the sample, with two platinum wire electrodes inserted in the kaolin prism that was used is suitable for measurements of temperature dependences of the DC conductivity from 20 °C to 1100 °C in the air. The uncertainty analysis taking into account thermal expansion of the sample, homogeneity of the temperature field, measurement regime, corrosion of the electrodes, and overlapping of the electrodes is done for 1000 °C. Uncertainties connected with current and voltage measurements and uncertainties connected with the instruments that were used are also considered. The sum of all the partial uncertainties gives an expanded uncertainty of the conductivity measurement. The uncertainty varies with temperature and reaches the value of ˜ 6.5% at 1000 °C.

  9. 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.

  10. Conductivity Variation Observed by Polarization and Depolarization Current Measurements of High-Voltage Equipment Insulation System

    NASA Astrophysics Data System (ADS)

    Jamail, Nor Akmal Mohd; Piah, Mohamed Afendi Mohamed; Muhamad, Nor Asiah

    2012-09-01

    Nondestructive and time domain dielectric measurement techniques such as polarization and depolarization current (PDC) measurements have recently been widely used as a potential tool for determining high-voltage insulation conditions by analyzing the insulation conductivity. The variation in the conductivity of an insulator was found to depend on several parameters: the difference between the polarization and depolarization currents, geometric capacitance, and the relative permittivity of the insulation material. In this paper the conductivities of different types of oil-paper insulation material are presented. The insulation conductivities of several types of electrical apparatus were simulated using MATLAB. Conductivity insulation was found to be high at high polarizations and at the lowest depolarization current. It was also found to increase with increasing relative permittivity as well as with decreasing geometric capacitance of the insulating material.

  11. Design and Validation of a High-Temperature Comparative Thermal-Conductivity Measurement System

    SciTech Connect

    Jeff Phillips; Colby Jensen; C Xing; H. Ban

    2012-02-01

    A measurement system has been designed and built for the specific application of measuring the effective thermal conductivity of a composite, nuclear-fuel compact (small cylinder) over a temperature range of 100 C to 800 C. Because of the composite nature of the sample as well as the need to measure samples pre- and postirradiation, measurement must be performed on the whole compact non-destructively. No existing measurement system is capable of obtaining its thermal conductivity in a non-destructive manner. The designed apparatus is an adaptation of the guardedcomparative-longitudinal heat flow technique. The system uniquely demonstrates the use of a radiative heat sink to provide cooling which greatly simplifies the design and setup of such high-temperature systems. The design was aimed to measure thermalconductivity values covering the expected range of effective thermal conductivity of the composite nuclear fuel from 10W {center_dot} m{sup -1} {center_dot} K{sup -1} to 70W {center_dot} m{sup -1} {center_dot} K{sup -1}. Several materials having thermal conductivities covering this expected range have been measured for system validation, and results are presented. A comparison of the results has been made to data from existing literature.Additionally, an uncertainty analysis is presented finding an overall uncertainty in sample thermal conductivity to be 6%, matching well with the results of the validation samples.

  12. Ultra-sensitive thermal conductance measurement of one-dimensional nanostructures enhanced by differential bridge.

    PubMed

    Wingert, Matthew C; Chen, Zack C Y; Kwon, Shooshin; Xiang, Jie; Chen, Renkun

    2012-02-01

    Thermal conductivity of one-dimensional nanostructures, such as nanowires, nanotubes, and polymer chains, is of significant interest for understanding nanoscale thermal transport phenomena as well as for practical applications in nanoelectronics, energy conversion, and thermal management. Various techniques have been developed during the past decade for measuring this fundamental quantity at the individual nanostructure level. However, the sensitivity of these techniques is generally limited to 1 × 10(-9) W∕K, which is inadequate for small diameter nanostructures that potentially possess thermal conductance ranging between 10(-11) and 10(-10) W∕K. In this paper, we demonstrate an experimental technique which is capable of measuring thermal conductance of ∼10(-11) W∕K. The improved sensitivity is achieved by using an on-chip Wheatstone bridge circuit that overcomes several instrumentation issues. It provides a more effective method of characterizing the thermal properties of smaller and less conductive one-dimensional nanostructures. The best sensitivity experimentally achieved experienced a noise equivalent temperature below 0.5 mK and a minimum conductance measurement of 1 × 10(-11) W∕K. Measuring the temperature fluctuation of both the four-point and bridge measurements over a 4 h time period shows a reduction in measured temperature fluctuation from 100 mK to 0.6 mK. Measurement of a 15 nm Ge nanowire and background conductance signal with no wire present demonstrates the increased sensitivity of the bridge method over the traditional four-point I-V measurement. This ultra-sensitive measurement platform allows for thermal measurements of materials at new size scales and will improve our understanding of thermal transport in nanoscale structures. PMID:22380117

  13. Thermal Conductivity Measurement of an Electron-Beam Physical-Vapor-Deposition Coating

    PubMed Central

    Slifka, A. J.; Filla, B. J.

    2003-01-01

    An industrial ceramic thermal-barrier coating designated PWA 266, processed by electron-beam physical-vapor deposition, was measured using a steady-state thermal conductivity technique. The thermal conductivity of the mass fraction 7 % yttria-stabilized zirconia coating was measured from 100 °C to 900 °C. Measurements on three thicknesses of coatings, 170 μm, 350 μm, and 510 μm resulted in thermal conductivity in the range from 1.5 W/(m·K) to 1.7 W/(m·K) with a combined relative standard uncertainty of 20 %. The thermal conductivity is not significantly dependent on temperature.

  14. Measurement of the across-plane conductivity of YSZ thin films on silicon

    PubMed Central

    Navickas, E.; Gerstl, M.; Friedbacher, G.; Kubel, F.; Fleig, J.

    2012-01-01

    Across-plane conductivity measurements on ion conducting thin films of a few ten nanometers thickness are challenging due to frequently occurring short-circuits through pinholes in the layer. In this contribution, a method is proposed which allowed across-plane conductivity measurements on yttria stabilized zirconia (YSZ) layers with thicknesses as low as 20 nm. YSZ layers were prepared onto silicon substrates with a thin native silica interlayer and the across-plane conductivity was measured on circular microelectrodes by impedance spectroscopy. The silica interlayer exhibits strongly blocking behavior, which helps to avoid short-circuits through pinholes. Different relaxation frequencies of YSZ and silica make separation of these layers possible. An equivalent circuit is suggested, which allows extraction of YSZ properties, and its validity is proven by varying microelectrodes size and layer thickness. All parameters yield the expected behavior.

  15. Thermal conductivity and diffusivity of biomaterials measured with self-heated thermistors

    NASA Astrophysics Data System (ADS)

    Valvano, J. W.; Cochran, J. R.; Diller, K. R.

    1985-05-01

    This paper presents an experimental method to measure the thermal conductivity and thermal diffusivity of biomaterials. Self-heated thermistor probes, inserted into the tissue of interest, are used to deliver heat as well as to monitor the rate of heat removal. An empirical calibration procedure allows accurate thermal-property measurements over a wide range of tissue temperatures. Operation of the instrument in three media with known thermal properties shows the uncertainty of measurements to be about 2%. The reproducibility is 0.5% for the thermal-conductivity measurements and 2% for the thermal-diffusivity measurements. Thermal properties were measured in dog, pig, rabbit, and human tissues. The tissues included kidney, spleen, liver, brain, heart, lung, pancreas, colon cancer, and breast cancer. Thermal properties were measured for 65 separate tissue samples at 3, 10, 17, 23, 30, 37, and 45°C. The results show that the temperature coefficient of biomaterials approximates that of water.

  16. 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.

  17. Development of a Handmade Conductivity Measurement Apparatus and Application to Vegetables and Fruits

    ERIC Educational Resources Information Center

    Set, Seng; Kita, Masakazu

    2014-01-01

    This paper describes the development of a simple handmade conductivity measurement apparatus based on a Kohlrausch bridge with inexpensive materials. We have examined the reliability of this apparatus with standard solutions and then measured juices of vegetables and fruits as well as a sports drink. Comparisons to total alkali content as…

  18. Estimation of hydraulic conductivities of Yucca Mountain tuffs from sorptivity and water retention measurements

    SciTech Connect

    Zimmerman, R.W.; Bodvarsson, G.S.

    1995-06-01

    The hydraulic conductivity functions of the matrix rocks at Yucca Mountain, Nevada, are among the most important data needed as input for the site-scale hydrological model of the unsaturated zone. The difficult and time-consuming nature of hydraulic conductivity measurements renders it infeasible to directly measure this property on large numbers of cores. Water retention and sorptivity measurements, however, can be made relatively rapidly. The sorptivity is, in principle, a unique functional of the conductivity and water retention functions. It therefore should be possible to invert sorptivity and water retention measurements in order to estimate the conductivity; the porosity is the only other parameter that is required for this inversion. In this report two methods of carrying out this inversion are presented, and are tested against a limited data set that has been collected by Flint et al. at the USGS on a set of Yucca Mountain tuffs. The absolute permeability is usually predicted by both methods to within an average error of about 0.5 - 1.0 orders of magnitude. The discrepancy appears to be due to the fact that the water retention curves have only been measured during drainage, whereas the imbibition water retention curve is the one that is relevant to sorptivity measurements. Although the inversion methods also yield predictions of the relative permeability function, there are yet no unsaturated hydraulic conductivity data against which to test these predictions.

  19. Examination of Humidity Effects on Measured Thickness and Interfacial Phenomena of Exfoliated Graphene on SiO2 via AC-AFM

    NASA Astrophysics Data System (ADS)

    Jinkins, Katherine; Camacho, Jorge; Farina, Lee; Wu, Yan

    2015-03-01

    Tapping (AC) mode Atomic Force Microscopy (AFM) is commonly used to determine the thickness of graphene samples. However, AFM measurements have been shown to be sensitive to environmental conditions such as adsorbed water, in turn dependent on relative humidity (RH). In the present study, AC-AFM is used to measure the thickness and loss tangent of exfoliated graphene on silicon dioxide (SiO2) as RH is increased from 10% to 80%. We show that the measured thickness of graphene is dependent on RH. Loss tangent is an AFM imaging technique that interprets the phase information as a relationship between the stored and dissipated energy in the tip-sample interaction. This study demonstrates the loss tangent of the graphene and oxide regions are both affected by humidity, with generally higher loss tangent for graphene than SiO2. As RH increases, we observe the loss tangent of both materials approaches the same value. We hypothesize that there is a layer of water trapped between the graphene and SiO2 substrate to explain this observation. Using this interpretation, the loss tangent images also indicate movement and change in this trapped water layer as RH increases, which impacts the measured thickness of graphene using AC-AFM.

  20. Thermal-contact-conductance measurement for high-heat-load optics components at SPring-8

    NASA Astrophysics Data System (ADS)

    Takeuchi, T.; Tanaka, M.; Senba, Y.; Ohashi, H.; Goto, S.

    2011-09-01

    Thermal contact in water-cooling or cryogenic cooling-cooling condition is used for forming a high-heat-load component at the synchrotron radiation beamline. In SPring-8, for example, cryogenic cooling is used for silicon monochromator crystal with an indium insertion metal at the interface between a copper block and a silicon crystal. To reduce the strain on the silicon crystal with a low contact pressure and a high thermal conductivity, we require a silicon-indium-copper system and an alternative insertion material such as a graphite foil. To measure the thermal contact conductance in a quick measurement cycle under various thermal-contact conditions, we improve the thermal-contact-conductance measurement system in terms of the setup facilitation, precise temperature measurement, and thermal insulation around a sample.

  1. The thermal conductivity of rock under hydrothermal conditions: measurements and applications

    SciTech Connect

    Williams, Colin F.; Sass, John H.

    1996-01-24

    The thermal conductivities of most major rock-forming minerals vary with both temperature and confining pressure, leading to substantial changes in the thermal properties of some rocks at the high temperatures characteristic of geothermal systems. In areas with large geothermal gradients, the successful use of near-surface heat flow measurements to predict temperatures at depth depends upon accurate corrections for varying thermal conductivity. Previous measurements of the thermal conductivity of dry rock samples as a function of temperature were inadequate for porous rocks and susceptible to thermal cracking effects in nonporous rocks. We have developed an instrument for measuring the thermal conductivity of water-saturated rocks at temperatures from 20 to 350 °C and confining pressures up to 100 MPa. A transient line-source of heat is applied through a needle probe centered within the rock sample, which in turn is enclosed within a heated pressure vessel with independent controls on pore and confining pressure. Application of this technique to samples of Franciscan graywacke from The Geysers reveals a significant change in thermal conductivity with temperature. At reservoir-equivalent temperatures of 250 °C, the conductivity of the graywacke decreases by approximately 25% relative to the room temperature value. Where heat flow is constant with depth within the caprock overlying the reservoir, this reduction in conductivity with temperature leads to a corresponding increase in the geothermal gradient. Consequently, reservoir temperature are encountered at depths significantly shallower than those predicted by assuming a constant temperature gradient with depth. We have derived general equations for estimating the thermal conductivity of most metamorphic and igneous rocks and some sedimentary rocks at elevated temperature from knowledge of the room temperature thermal conductivity. Application of these equations to geothermal exploration should improve estimates

  2. Conductivity Measurements of Synthesized Heteropoly Acid Membranes for Proton Exchange Membrane Fuel Cells

    SciTech Connect

    Record, K.A.; Haley, B.T.; Turner, J.

    2006-01-01

    Fuel cell technology is receiving attention due to its potential to be a pollution free method of electricity production when using renewably produced hydrogen as fuel. In a Proton Exchange Membrane (PEM) fuel cell H2 and O2 react at separate electrodes, producing electricity, thermal energy, and water. A key component of the PEM fuel cell is the membrane that separates the electrodes. DuPont’s Nafion® is the most commonly used membrane in PEM fuel cells; however, fuel cell dehydration at temperatures near 100°C, resulting in poor conductivity, is a major hindrance to fuel cell performance. Recent studies incorporating heteropoly acids (HPAs) into membranes have shown an increase in conductivity and thus improvement in performance. HPAs are inorganic materials with known high proton conductivities. The primary objective of this work is to measure the conductivity of Nafion, X-Ionomer membranes, and National Renewable Energy Laboratory (NREL) Developed Membranes that are doped with different HPAs at different concentrations. Four-point conductivity measurements using a third generation BekkTech conductivity test cell are used to determine membrane conductivity. The effect of multiple temperature and humidification levels is also examined. While the classic commercial membrane, Nafion, has a conductivity of approximately 0.10 S/cm, measurements for membranes in this study range from 0.0030 – 0.58 S/cm, depending on membrane type, structure of the HPA, and the relative humidity. In general, the X-ionomer with H6P2W21O71 HPA gave the highest conductivity and the Nafion with the 12-phosphotungstic (PW12) HPA gave the lowest. The NREL composite membranes had conductivities on the order of 0.0013 – 0.025 S/cm.

  3. Uncertainty analysis on the design of thermal conductivity measurement by a guarded cut-bar technique

    NASA Astrophysics Data System (ADS)

    Xing, Changhu; Jensen, Colby; Ban, Heng; Phillips, Jeffrey

    2011-07-01

    A technique adapted from the guarded-comparative-longitudinal heat flow method was selected for the measurement of the thermal conductivity of a nuclear fuel compact over a temperature range characteristic of its usage. This technique fulfills the requirement for non-destructive measurement of the composite compact. Although numerous measurement systems have been created based on the guarded-comparative method, comprehensive systematic (bias) and measurement (precision) uncertainty associated with this technique have not been fully analyzed. In addition to the geometric effect in the bias error, which has been analyzed previously, this paper studies the working condition which is another potential error source. Using finite element analysis, this study showed the effect of these two types of error sources in the thermal conductivity measurement process and the limitations in the design selection of various parameters by considering their effect on the precision error. The results and conclusions provide valuable reference for designing and operating an experimental measurement system using this technique.

  4. Specific conductance measurements in central and western New York streams - A retrospective characterization

    USGS Publications Warehouse

    Kappel, William M.; Sinclair, Gaylen J.; Reddy, James E.; Eckhardt, David A.; deVries, M. Peter; Phillips, Margaret E.

    2012-01-01

    U.S. Geological Survey (USGS) Data Rescue Program funds were used to recover data from paper records for 139 streamgages across central and western New York State; 6,133 different streamflow measurement forms, collected between 1970-80, contained field water-quality measurements. The water-quality data were entered, reviewed, and uploaded into the USGS National Water Information System. In total, 4,285 unique site visits were added to the database. The new values represent baseline water quality from which to measure change and will lead to a comparison of water-quality change over the last 40 years and into the future. Specific conductance was one of the measured properties and represents a simple way to determine if ambient inorganic water quality has been altered by anthropogenic (road salt runoff, wastewater discharges, or natural gas development) or natural sources. The objective of this report is to describe ambient specific conductance characteristics of surface water across the central and western part of New York. This report presents median specific conductance of stream discharge for the period 1970-80 and a description of the relation between specific conductance and concentrations of total dissolved solids (TDS) retrieved from the USGS National Water Information System (NWIS) database from 1955 to present. The data descriptions provide a baseline of surface-water specific conductance data that can used for comparison to current and future measurements in New York streams.

  5. Temperature dependent electrical conductivity measurement of Qn-(TCNQ)2 grown by different methods

    NASA Astrophysics Data System (ADS)

    Singh, Yadunath

    2013-06-01

    We measured the temperature dependent electrical conductivity on single crystal of charge transfer complex (CTC), Qn-(TCNQ)2 grown by different methods. Where, Qn and TCNQ are representing qunolinium and tetracyanoquinodimethane. The room temperature conductivity is found 100 ohm-1 cm-1 with activation energy 0.021 eV in the sample grown by electrochemical method. Whereas it is found 22 ohm-1 cm-1 with activation energy 0.026 eV for the sample grown by solution growth method. In all conductivity measurements, the observations are carried out along high conducting chain direction, which happens to be needle direction of the single crystal and known as a-direction.

  6. Experimental measurement of the plasma conductivity of Z93 and Z93P thermal control paint

    NASA Technical Reports Server (NTRS)

    Hillard, G. Barry

    1993-01-01

    Two samples each of Z93 and Z93P thermal control paint were exposed to a simulated space environment in a plasma chamber. The samples were biased through a series of voltages ranging from -200 volts to +300 volts and electron and ion currents measured. By comparing the currents to those of pure metal samples of the same size and shape, the conductivity of the samples was calculated. Measured conductivity was dependent on the bias potential in all cases. For Z93P, conductivity was approximately constant over much of the bias range and we find a value of 0.5 micro-mhos per square meter for both electron and ion current. For Z93, the dependence on bias was much more pronounced but conductivity can be said to be approximately one order of magnitude larger. In addition to presenting these results, this report documents all of the experimental data as well as the statistical analyses performed.

  7. Experimental Measurement and Numerical Modeling of the Effective Thermal Conductivity of TRISO Fuel Compacts

    SciTech Connect

    Folsom, Charles; Xing, Changhu; Jensen, Colby; Ban, Heng; Marshall, Douglas W.

    2015-03-01

    Accurate modeling capability of thermal conductivity of tristructural-isotropic (TRISO) fuel compacts is important to fuel performance modeling and safety of Generation IV reactors. To date, the effective thermal conductivity (ETC) of tristructural-isotropic (TRISO) fuel compacts has not been measured directly. The composite fuel is a complicated structure comprised of layered particles in a graphite matrix. In this work, finite element modeling is used to validate an analytic ETC model for application to the composite fuel material for particle-volume fractions up to 40%. The effect of each individual layer of a TRISO particle is analyzed showing that the overall ETC of the compact is most sensitive to the outer layer constituent. In conjunction with the modeling results, the thermal conductivity of matrix-graphite compacts and the ETC of surrogate TRISO fuel compacts have been successfully measured using a previously developed measurement system. The ETC of the surrogate fuel compacts varies between 50 and 30 W m-1 K-1 over a temperature range of 50-600°C. As a result of the numerical modeling and experimental measurements of the fuel compacts, a new model and approach for analyzing the effect of compact constituent materials on ETC is proposed that can estimate the fuel compact ETC with approximately 15-20% more accuracy than the old method. Using the ETC model with measured thermal conductivity of the graphite matrix-only material indicate that, in the composite form, the matrix material has a much greater thermal conductivity, which is attributed to the high anisotropy of graphite thermal conductivity. Therefore, simpler measurements of individual TRISO compact constituents combined with an analytic ETC model, will not provide accurate predictions of overall ETC of the compacts emphasizing the need for measurements of composite, surrogate compacts.

  8. Rolling ball algorithm as a multitask filter for terrain conductivity measurements

    NASA Astrophysics Data System (ADS)

    Rashed, Mohamed

    2016-09-01

    Portable frequency domain electromagnetic devices, commonly known as terrain conductivity meters, have become increasingly popular in recent years, especially in locating underground utilities. Data collected using these devices, however, usually suffer from major problems such as complexity and interference of apparent conductivity anomalies, near edge local spikes, and fading of conductivity contrast between a utility and the surrounding soil. This study presents the experience of adopting the rolling ball algorithm, originally designed to remove background from medical images, to treat these major problems in terrain conductivity measurements. Applying the proposed procedure to data collected using different terrain conductivity meters at different locations and conditions proves the capability of the rolling ball algorithm to treat these data both efficiently and quickly.

  9. D0 Silicon Upgrade: Thermal Conductivity Measurements of Adhesives and Metal Strips

    SciTech Connect

    Jostlein, H.; Schmidgall, N.; /Fermilab

    1995-08-10

    This note is a followup to previous work done relating to thermal conductivity tests for the DO Silicon Upgrade. The testing of adhesives described here was done as outlined in the above mentioned note; therefore, the experimental setup and design for testing adhesives is marginally described here. However, some strips were tested to determine their thermal conductivity which utilized a different testing setup. That setup is described here as well. The measured thermal conductivities of the adhesives show Ablefilm 563K to have the highest thermal conductivity value of 0.89 W/m-K. The strip tests also showed that a consistent thermal conductivity value can be obtained for a strip within 5%.

  10. 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.

  11. Incoherent scatter measurements of E region conductivities and currents in the auroral zone

    NASA Technical Reports Server (NTRS)

    Brekke, A.; Doupnik, J. R.; Banks, P. M.

    1974-01-01

    Data taken by incoherent scatter radar have been used to investigate ionospheric conductivities and electrical currents. During quiet days, the conductivities appear to vary in a way consistent with ionization arising from solar EUV radiation. In the evening hours, enhancements in the northward electric field are found to precede small increases in the conductivities. Strong enhancements of the Hall conductivity relative to the Pedersen conductivity occur during negative bays when the electric field is in a southwestward direction. The ionospheric currents calculated in the geomagnetic east-west direction are in good agreement with the H component measured by a nearby magnetometer; this result indicates that the current causing the ground level magnetic fluctuations is a broad horizontal sheet current. The north-south ionospheric current, however, consistently disagrees with the observed D component in a manner that cannot easily be explained unless currents parallel to the earth's magnetic field are present.

  12. The thermal conductivity of rock under hydrothermal conditions: Measurements and applications

    SciTech Connect

    Williams, C.F.; Sass, J.H.

    1996-12-31

    The thermal conductivities of most major rock-forming minerals vary with both temperature and confining pressure, leading to substantial changes in the thermal properties of some rocks at the high temperatures characteristic of geothermal systems. In areas with large geothermal gradients, the successful use of near-surface heat flow measurements to predict temperatures at depth depends upon accurate corrections for varying thermal conductivity. Previous measurements of the thermal conductivity of dry rock samples as a function of temperature were inadequate for porous rocks and susceptible to thermal cracking effects m nonporous rocks. We have developed an instrument for measuring the thermal conductivity of water-saturated rocks at temperatures from 20 to 350{degrees}C and confining pressures up to 100 MPa. A transient line-source of heat is applied through a needle probe centered within the rock sample, which in turn is enclosed within a heated pressure vessel with independent controls on pore and confining pressure. Application of this technique to samples of Franciscan graywacke from The Geysers reveals a significant change in thermal conductivity with temperature. At reservoir-equivalent temperatures of 250{degrees}C, the conductivity of the graywacke decreases by approximately 25 % relative to the room temperature value. Where heat how is constant with depth within the caprock overlying the reservoir, this reduction in conductivity with temperature leads to a corresponding increase in the geothermal gradient. Consequently, reservoir temperatures are encountered at depths significantly shallower than those predicted by assuming a constant temperature gradient with depth. We have derived general equations for estimating the thermal conductivity of most metamorphic and igneous rocks and some sedimentary rocks at elevated temperature from knowledge of the room temperature thermal conductivity.

  13. Determination of critical current density and transition temperature of YBa sub 2 Cu sub 3 O sub 7 minus x thin films by measurement of ac susceptibility

    SciTech Connect

    Li, Y.; Noh, D.; Gallois, B. ); Tompa, G.S.; Norris, P.E.; Zawadzki, P.A. )

    1990-10-01

    A technique for the determination of the critical current of superconducting thin films by a current-dependent ac susceptibility measurement has been developed. This method has been used to characterize superconducting YBa{sub 2}Cu{sub 3}O{sub 7{minus}{ital x}} films grown {ital in situ} at 1073 K by metalorganic chemical vapor deposition. Two superconducting phases with transition temperatures of 91 and 84 K have been detected by the measurement of ac susceptibility as a function of temperature even though the variation of resistance with temperature indicated a sharp transition. The critical current densities of the two superconducting phases have been determined from the variations of ac susceptibility with current at constant temperature and found to be equal to 1.14{times}10{sup 4} A/cm{sup 2} and 3.6{times}10{sup 3} A/cm{sup 2} at 75 K. The advantages of the technique in comparison to current methods of measurement of critical current are discussed.

  14. Thermal conductivity measurement in clay dominant consolidated material by Transient Hot-Wire method.

    NASA Astrophysics Data System (ADS)

    Garnier, J. P.; Gallier, J.; Mercx, B.; Dudoignon, P.; Milcent, D.

    2010-06-01

    The transient hot-wire (THW) technique is widely used for measurements of the thermal-conductivity of most fluids and some attempts have also been carried out for simultaneous measurements of the thermal-diffusivity with the same hot wire. This technique was also tried to determine thermal properties of soils by the mean of probes which can be considered as wire with some assumptions. The purpose of this paper is to validate the thermal conductivity measurement by the THW technique in geomaterials, composed of compacted sand + clay mineral that can be used for earth construction (Compacted Earth Brick). The thermal transfer behaviors are mainly governed by the texture and moisture of the geomaterials. Thus the investigations were performed (1) in media made of glass beads of different diameters in dry and saturated state in order to observe the role of grain sizes and saturation state on the wire temperature (Δt) measurements and (2) in the compacted clay-geomaterial at different moisture states. The Δt / ln(t) diagrams allow the calculation of two thermal conductivities. The first one, measured in the short time acquisition (< 1s), characterizes the microtexture of the material and its hydrated state. The second one, measured for longer time acquisitions, characterizes the mean thermal conductivity of the material.

  15. Improvements in 3-omega measurement of thermal conductivity for nanostructured materials

    NASA Astrophysics Data System (ADS)

    Zhou, Chuanle; Grayson, M.; Koblmueller, G.

    2011-03-01

    Nanostructured materials have reduced thermal conductivity in order to enhance the thermoelectric figure of merit (ZT). The 3 ω method is widely used for vertical thermal conductivity measurements in the nanostructure materials, especially layered materials. The challenge for this method is to measure the small 3 ω voltage at the third harmonic, above the comparably large ω voltage from the sample at the fundamental frequency, complicated by the nonlinear signal from other components in the measurement circuit. We carefully study the 3 ω method [Cahill, Rev. Sci. lnstrum. 61 (2), 802 (1990)] and develop a strategy to increase the signal to noise ratio of the data, for more accurate results. We also investigate an alternate sample preparation geometry for the 3 ω measurement, so that the heat flow is vertical and linear through the thin film instead of cylindrical as is standard for this method. This results in a direct measurement of the vertical thermal conductivity in such an anisotropic material. New geometries for measuring lateral thermal conductivity will also be proposed and explored.

  16. PCB glass-fibre laminates: Thermal conductivity measurements and their effect on simulation

    NASA Astrophysics Data System (ADS)

    Sarvar, F.; Poole, N. J.; Witting, P. A.

    1990-12-01

    Accurate values of thermal conductivity are required for the simulation of temperature phenomena in electronic circuits. This paper presents the results of measurements carried out to determine the thermal conductivity along and normal to the plane of fibre glass laminates used in the manufacture of printed circuit boards. It has been found that the reinforced fibre-glass substrates used in PCBs are strongly anisotropic with the conductivity normal to the boards being much smaller than tangential to it. The test samples were type FR4 epoxy/glass laminates. An experiment has been designed which determines the thermal conductivity in-the-plane of the laminates by matching the measured temperature distribution along a heated specimen with a finite difference solution. An electrically heated Lees’ disc apparatus is also used to measure the thermal conductivity of these boards in a direction normal to their plane. The samples tested yielded values of 0.343 W/mK and 1.059 W/mK for thermal conductivity through and along the plane of the boards, respectively.

  17. Thermal conductivity measurements in Porous mixtures of methane hydrate and quartz sand

    USGS Publications Warehouse

    Waite, W.F.; deMartin, B.J.; Kirby, S.H.; Pinkston, J.; Ruppel, C.D.

    2002-01-01

    Using von Herzen and Maxwell's needle probe method, we measured thermal conductivity in four porous mixtures of quartz sand and methane gas hydrate, with hydrate composing 0, 33, 67 and 100% of the solid volume. Thermal conductivities were measured at a constant methane pore pressure of 24.8 MPa between -20 and +15??C, and at a constant temperature of -10??C between 3.5 and 27.6 MPa methane pore pressure. Thermal conductivity decreased with increasing temperature and increased with increasing methane pore pressure. Both dependencies weakened with increasing hydrate content. Despite the high thermal conductivity of quartz relative to methane hydrate, the largest thermal conductivity was measured in the mixture containing 33% hydrate rather than in hydrate-free sand. This suggests gas hydrate enhanced grain-to-grain heat transfer, perhaps due to intergranular contact growth during hydrate synthesis. These results for gas-filled porous mixtures can help constrain thermal conductivity estimates in porous, gas hydrate-bearing systems.

  18. Microengineered Conductive Elastomeric Electrodes for Long-Term Electrophysiological Measurements with Consistent Impedance under Stretch

    PubMed Central

    Hu, Dinglong; Cheng, Tin Kei; Xie, Kai; Lam, Raymond H. W.

    2015-01-01

    In this research, we develop a micro-engineered conductive elastomeric electrode for measurements of human bio-potentials with the absence of conductive pastes. Mixing the biocompatible polydimethylsiloxane (PDMS) silicone with other biocompatible conductive nano-particles further provides the material with an electrical conductivity. We apply micro-replica mold casting for the micro-structures, which are arrays of micro-pillars embedded between two bulk conductive-PDMS layers. These micro-structures can reduce the micro-structural deformations along the direction of signal transmission; therefore the corresponding electrical impedance under the physical stretch by the movement of the human body can be maintained. Additionally, we conduct experiments to compare the electrical properties between the bulk conductive-PDMS material and the microengineered electrodes under stretch. We also demonstrate the working performance of these micro-engineered electrodes in the acquisition of the 12-lead electrocardiographs (ECG) of a healthy subject. Together, the presented gel-less microengineered electrodes can provide a more convenient and stable bio-potential measurement platform, making tele-medical care more achievable with reduced technical barriers for instrument installation performed by patients/users themselves. PMID:26512662

  19. Microengineered Conductive Elastomeric Electrodes for Long-Term Electrophysiological Measurements with Consistent Impedance under Stretch.

    PubMed

    Hu, Dinglong; Cheng, Tin Kei; Xie, Kai; Lam, Raymond H W

    2015-01-01

    In this research, we develop a micro-engineered conductive elastomeric electrode for measurements of human bio-potentials with the absence of conductive pastes. Mixing the biocompatible polydimethylsiloxane (PDMS) silicone with other biocompatible conductive nano-particles further provides the material with an electrical conductivity. We apply micro-replica mold casting for the micro-structures, which are arrays of micro-pillars embedded between two bulk conductive-PDMS layers. These micro-structures can reduce the micro-structural deformations along the direction of signal transmission; therefore the corresponding electrical impedance under the physical stretch by the movement of the human body can be maintained. Additionally, we conduct experiments to compare the electrical properties between the bulk conductive-PDMS material and the microengineered electrodes under stretch. We also demonstrate the working performance of these micro-engineered electrodes in the acquisition of the 12-lead electrocardiographs (ECG) of a healthy subject. Together, the presented gel-less microengineered electrodes can provide a more convenient and stable bio-potential measurement platform, making tele-medical care more achievable with reduced technical barriers for instrument installation performed by patients/users themselves. PMID:26512662

  20. A New Guarded Hot Plate Designed for Thermal-Conductivity Measurements at High Temperature

    NASA Astrophysics Data System (ADS)

    Scoarnec, V.; Hameury, J.; Hay, B.

    2015-03-01

    The Laboratoire National de Métrologie et d'Essais has developed a new guarded hot-plate apparatus operating from to in the thermal-conductivity range from to . This facility has been specifically designed for measuring medium thermal-conductivity materials at high temperature on square specimens (100 mm side), which are easier to machine than circular ones. The hot plate and cold plates are similar with a metering section independent from the guard ring. The specimens are laterally isolated by an air gap of 4 mm width and can be instrumented by temperature sensors in order to reduce effects of thermal contact resistances between the specimens and the heating plates. Measurements have been performed on certified reference materials and on "calibrated" materials. Relative deviations between thermal conductivities measured and reference values are less than 5 % in the operating range.

  1. High-precision micropipette thermal sensor for measurement of thermal conductivity of carbon nanotubes thin film

    NASA Astrophysics Data System (ADS)

    Shrestha, Ramesh

    The thesis describes novel glass micropipette thermal sensor fabricated in cost-effective manner and thermal conductivity measurement of carbon nanotubes (CNT) thin film using the developed sensor. Various micrometer-sized sensors, which range from 2 microm to 30 microm, were produced and tested. The capability of the sensor in measuring thermal fluctuation at micro level with an estimated resolution of +/-0.002°C is demonstrated. The sensitivity of sensors was recorded from 3.34 to 8.86 microV/°C, which is independent of tip size and dependent on the coating of Nickel. The detailed experimental setup for thermal conductivity measurement of CNT film is discussed and 73.418 W/m°C was determined as the thermal conductivity of the CNT film at room temperature.

  2. Ac loss modelling and measurement of superconducting transformers with coated-conductor Roebel-cable in low-voltage winding

    NASA Astrophysics Data System (ADS)

    Pardo, Enric; Staines, Mike; Jiang, Zhenan; Glasson, Neil

    2015-11-01

    Power transformers using a high temperature superconductor (HTS) ReBCO coated conductor and liquid nitrogen dielectric have many potential advantages over conventional transformers. The ac loss in the windings complicates the cryogenics and reduces the efficiency, and hence it needs to be predicted in its design, usually by numerical calculations. This article presents detailed modelling of superconducting transformers with Roebel cable in the low-voltage (LV) winding and a high-voltage (HV) winding with more than 1000 turns. First, we model a 1 MVA 11 kV/415 V 3-phase transformer. The Roebel cable solenoid forming the LV winding is also analyzed as a stand-alone coil. Agreement between calculations and experiments of the 1 MVA transformer supports the model validity for a larger tentative 40 MVA 110 kV/11 kV 3-phase transformer design. We found that the ac loss in each winding is much lower when it is inserted in the transformer than as a stand-alone coil. The ac loss in the 1 and 40 MVA transformers is dominated by the LV and HV windings, respectively. Finally, the ratio of total loss over rated power of the 40 MVA transformer is reduced below 40% of that of the 1 MVA transformer. In conclusion, the modelling tool in this work can reliably predict the ac loss in real power applications.

  3. BRINE Distribution in Harite Rocks-Inference from Measured Electrical CONDUCTIVITY-

    NASA Astrophysics Data System (ADS)

    Kitano, M.; Watanabe, T.

    2013-12-01

    Intercrystalline fluid can significantly affect rheological and transport properties of rocks. Its influences are strongly depended on its distribution. The dihedral angle between solid and liquid phases has been widely accepted as a key parameter that controls solid-liquid textures. The liquid phase is not expected to be interconnected if the dihedral angle is larger than 60°. However, observations contradictory to dihedral angle values have been reported. Watanabe (2010) suggested that the grain boundary fluid coexist with a positive dihedral angle. Similar thin fluid films might exist in grain boundaries of crustal rocks, and play important roles in crustal processes. In order to understand the nature of this fluid, we have studied the distribution of brine in halite rocks through measurements of conductivity. A sample was prepared by cold-pressing (the axial stress of 140MPa, 40minutes) and annealing (the temperature of 160°C and 180MPa confining pressure for about 160hours) of wet NaCl powder. During annealing, conductivity of a sample was monitored (2-electrode method) to reach a quasi-stationary value. The volume fraction of water is estimated to be 0.1×0.01% based on the FTIR measurement. Grains are polygonal and their diameters are ~100 μm. The cylindrical (D=9mm, L=3mm) surface of an annealed sample was weakly dried and coated with RTV rubber to suppress the conduction on the surface. Conductivity measurements were made at various pressure and temperature conditions(P<180 MPa, T<180°C). The dihedral angle of NaCl-water system is 66° at P=30MPa and T=30°C, and it becomes smaller than 60° at high pressure and temperature conditions(Holness & Lewis, 1997). Measured conductivity was of the order of 10-7~10-9 (S/m). When the temperature was fixed, a lower conductivity was observed for a higher pressure. The decrease in conductivity was typically 50% for the increase in pressure of 30MPa. For a given pressure, the conductivity increased with increasing

  4. 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.

  5. An affordable and accurate conductivity probe for density measurements in stratified flows

    NASA Astrophysics Data System (ADS)

    Carminati, Marco; Luzzatto-Fegiz, Paolo

    2015-11-01

    In stratified flow experiments, conductivity (combined with temperature) is often used to measure density. The probes typically used can provide very fine spatial scales, but can be fragile, expensive to replace, and sensitive to environmental noise. A complementary instrument, comprising a low-cost conductivity probe, would prove valuable in a wide range of applications where resolving extremely small spatial scales is not needed. We propose using micro-USB cables as the actual conductivity sensors. By removing the metallic shield from a micro-B connector, 5 gold-plated microelectrodes are exposed and available for 4-wire measurements. These have a cell constant ~550m-1, an intrinsic thermal noise of at most 30pA/Hz1/2, as well as sub-millisecond time response, making them highly suitable for many stratified flow measurements. In addition, we present the design of a custom electronic board (Arduino-based and Matlab-controlled) for simultaneous acquisition from 4 sensors, with resolution (in conductivity, and resulting density) exceeding the performance of typical existing probes. We illustrate the use of our conductivity-measuring system through stratified flow experiments, and describe plans to release simple instructions to construct our complete system for around 200.

  6. Direct measurement of thermal conductivity in solid iron at planetary core conditions

    NASA Astrophysics Data System (ADS)

    Konôpková, Zuzana; McWilliams, R. Stewart; Gómez-Pérez, Natalia; Goncharov, Alexander F.

    2016-06-01

    The conduction of heat through minerals and melts at extreme pressures and temperatures is of central importance to the evolution and dynamics of planets. In the cooling Earth’s core, the thermal conductivity of iron alloys defines the adiabatic heat flux and therefore the thermal and compositional energy available to support the production of Earth’s magnetic field via dynamo action. Attempts to describe thermal transport in Earth’s core have been problematic, with predictions of high thermal conductivity at odds with traditional geophysical models and direct evidence for a primordial magnetic field in the rock record. Measurements of core heat transport are needed to resolve this difference. Here we present direct measurements of the thermal conductivity of solid iron at pressure and temperature conditions relevant to the cores of Mercury-sized to Earth-sized planets, using a dynamically laser-heated diamond-anvil cell. Our measurements place the thermal conductivity of Earth’s core near the low end of previous estimates, at 18–44 watts per metre per kelvin. The result is in agreement with palaeomagnetic measurements indicating that Earth’s geodynamo has persisted since the beginning of Earth’s history, and allows for a solid inner core as old as the dynamo.

  7. Direct measurement of thermal conductivity in solid iron at planetary core conditions.

    PubMed

    Konôpková, Zuzana; McWilliams, R Stewart; Gómez-Pérez, Natalia; Goncharov, Alexander F

    2016-06-01

    The conduction of heat through minerals and melts at extreme pressures and temperatures is of central importance to the evolution and dynamics of planets. In the cooling Earth's core, the thermal conductivity of iron alloys defines the adiabatic heat flux and therefore the thermal and compositional energy available to support the production of Earth's magnetic field via dynamo action. Attempts to describe thermal transport in Earth's core have been problematic, with predictions of high thermal conductivity at odds with traditional geophysical models and direct evidence for a primordial magnetic field in the rock record. Measurements of core heat transport are needed to resolve this difference. Here we present direct measurements of the thermal conductivity of solid iron at pressure and temperature conditions relevant to the cores of Mercury-sized to Earth-sized planets, using a dynamically laser-heated diamond-anvil cell. Our measurements place the thermal conductivity of Earth's core near the low end of previous estimates, at 18-44 watts per metre per kelvin. The result is in agreement with palaeomagnetic measurements indicating that Earth's geodynamo has persisted since the beginning of Earth's history, and allows for a solid inner core as old as the dynamo. PMID:27251283

  8. New portable instrument for the measurement of thermal conductivity in gas process conditions

    NASA Astrophysics Data System (ADS)

    Queirós, C. S. G. P.; Lourenço, M. J. V.; Vieira, S. I.; Serra, J. M.; Nieto de Castro, C. A.

    2016-06-01

    The development of high temperature gas sensors for the monitoring and determination of thermophysical properties of complex process mixtures at high temperatures faces several problems, related with the materials compatibility, active sensing parts sensitivity, and lifetime. Ceramic/thin metal films based sensors, previously developed for the determination of thermal conductivity of molten materials up to 1200 °C, were redesigned, constructed, and applied for thermal conductivity measuring sensors. Platinum resistance thermometers were also developed using the same technology, to be used in the temperature measurement, which were also constructed and tested. A new data acquisition system for the thermal conductivity sensors, based on a linearization of the transient hot-strip model, including a portable electronic bridge for the measurement of the thermal conductivity in gas process conditions was also developed. The equipment is capable of measuring the thermal conductivity of gaseous phases with an accuracy of 2%-5% up to 840 °C (95% confidence level). The development of sensors up to 1200 °C, present at the core of the combustion chambers, will be done in a near future.

  9. New portable instrument for the measurement of thermal conductivity in gas process conditions.

    PubMed

    Queirós, C S G P; Lourenço, M J V; Vieira, S I; Serra, J M; Nieto de Castro, C A

    2016-06-01

    The development of high temperature gas sensors for the monitoring and determination of thermophysical properties of complex process mixtures at high temperatures faces several problems, related with the materials compatibility, active sensing parts sensitivity, and lifetime. Ceramic/thin metal films based sensors, previously developed for the determination of thermal conductivity of molten materials up to 1200 °C, were redesigned, constructed, and applied for thermal conductivity measuring sensors. Platinum resistance thermometers were also developed using the same technology, to be used in the temperature measurement, which were also constructed and tested. A new data acquisition system for the thermal conductivity sensors, based on a linearization of the transient hot-strip model, including a portable electronic bridge for the measurement of the thermal conductivity in gas process conditions was also developed. The equipment is capable of measuring the thermal conductivity of gaseous phases with an accuracy of 2%-5% up to 840 °C (95% confidence level). The development of sensors up to 1200 °C, present at the core of the combustion chambers, will be done in a near future. PMID:27370495

  10. Polarizabilities of Adsorbed and Assembled Molecules: Measuring the Conductance through Buried Contacts

    PubMed Central

    2010-01-01

    We have measured the polarizabilities of four families of molecules adsorbed to Au{111} surfaces, with structures ranging from fully saturated to fully conjugated, including single-molecule switches. Measured polarizabilities increase with increasing length and conjugation in the adsorbed molecules and are consistent with theoretical calculations. For single-molecule switches, the polarizability reflects the difference in substrate−molecule electronic coupling in the ON and OFF conductance states. Calculations suggest that the switch between the two conductance states is correlated with an oxidation state change in a nitro functional group in the switch molecules. PMID:21077677

  11. Measurement of the thermal conductivity of dielectric thin solid films with a thermal comparator

    SciTech Connect

    Amsden, C.A.; Gilman, S.E.; Jacobs, S.D.; Torok, J.S.

    1988-04-01

    Low thermal conductivity has important implications for electric and optical applications, where heat deposited in a thin layer must be dissipated to prevent damage. Models which account for thermal transport in thin film structures may have no predictive value if they employ bulk conductivity data. Most techniques utilized to measure the thermal conductivity of thin solid films are difficult and time consuming. The method we have developed is relatively rapid, nondestructive, and is capable of evaluating the samples in a conventional film on substrate geometry. Our thermal conductivity apparatus consists of a control and readout module, signal processing equipment, and an environmentally isolated sample chamber enclosing a sample stage. The commercial unit was converted into a high precision device by temperature controlling both the samples and the sample stage, and by performing averaging of the output signal. The thermal conductivity values obtained are below those of bulk solids. In addition, the conductivities seem to increase with increasing film thickness. Titania seems to have a higher thermal conductivity when deposited by ion-beam sputtering rather than electron-beam evaporation. Some of the electron-beam films were crazed, indicating high levels of stress. The effect of stress and crazing on thermal conductivity is not readily apparent. 11 refs., 1 fig., 1 tab.

  12. The Comparison of Predicted and Measured Hydraulic Conductivities of Soils having Different Physical Properties

    NASA Astrophysics Data System (ADS)

    Zengin, Enes; Abiddin Erguler, Zeynal; Karakuş, Hüseyin

    2015-04-01

    Hydraulic conductivity is one of the most important parameter of earth science related studies such as engineering geology, soil physics, agriculture etc. In order to estimate the ability of soils to transport fluid through particles, field and laboratory tests have been performed since last decades of 19th century. Constant and falling head tests are widely used to directly measure hydraulic conductivity values in laboratory conditions for soils having different particle size distributions. The determination of hydraulic conductivity of soils by performing these methods are time consuming processes and also requires undisturbed samples to reflect in-situ natural condition. Considering these limitations, numerous approaches have been proposed to practically estimate hydraulic conductivity of soils by utilizing empirical equations based on simple physical and index properties such as grain size distribution curves related parameters, porosity, void ratio, etc. Many previous studies show that the hydraulic conductivity values calculated by empirical equations deviate more than two order magnitude than the measured hydraulic conductivity values obtained from convenient permeability tests. In order to investigate the main controlling parameters on hydraulic conductivity of soils, a comprehensive research program was carried out on some disturbed and undisturbed soil samples collected from different locations in Turkey. The hydraulic conductivity values of samples were determined as changing between 10-6 and 10-9 m/s by using falling head tests. In addition to these tests, basic soil properties such as natural water content, Atterberg limits, specific gravity and grain size analyses of these samples were also defined to be used as an input parameters of empirical equations for prediction hydraulic conductivity values. In addition, data from previous studies were also used for the aim of this study. The measured hydraulic conductivity values were correlated with all

  13. Laboratory Thermal Conductivity Measurements in Pure Methane Hydrate Between -5 and -30 ° C

    NASA Astrophysics Data System (ADS)

    Waite, W. F.; Pinkston, J.; Kirby, S. H.

    2001-12-01

    Naturally occurring methane (CH4) hydrate, found extensively in shallow permafrost and continental margin sediment, has generated interest as a potential energy resource, a geohazard, and a contributor to global climate change. The significance of gas hydrate in these roles depends in part on the effects of temperature on their stability, and hence can be sensitive to exchanges of heat with their environment. Thermal properties such as conductivity and diffusivity are therefore important properties governing the response of hydrate-bearing sediment to natural or man-made thermal perturbations. We seek to improve characterizations of hydrate's in situ thermal behavior by making laboratory measurements of thermal conductivity in pure sI CH4 hydrate at near in situ pressures and temperatures. Thermal conductivity measurements are made using the transient hot-wire technique of von Herzen and Maxwell, which requires that a needle probe be positioned along the axis of the cylindrical sample. Hydrate is synthesized around the probe by heating H20 "seed ice" grains in a pressurized methane atmosphere. To insure thermal contact between probe and sample, and to eliminate the porosity required by our synthesis method, samples are radially compacted after synthesis. We tested our methodology on granular ice Ih, compacted under vacuum, and its thermal conductivity is 2.16+/-0.03 W/m”K at -10° C, in agreement with published values. Our preliminary value for conductivity of pure CH4 hydrate, when compacted to less than 5% porosity, is 0.475+/-0.007 W/m”K at -5° C. Conductivity decreases slightly (0.015 W/m”K) with temperature over the range -30 to -5° C. At -30° C, thermal conductivity increases with confining pressure by 0.0125 W/m”K over the range 34.5 to 70.1 MPa. Thermal conductivity measurements above 0° C in pure CH4 hydrate are ongoing.

  14. Development of a direct push based in-situ thermal conductivity measurement system

    NASA Astrophysics Data System (ADS)

    Chirla, Marian Andrei; Vienken, Thomas; Dietrich, Peter; Bumberger, Jan

    2016-04-01

    Heat pump systems are commonly utilized in Europe, for the exploitation of the shallow geothermal potential. To guarantee a sustainable use of the geothermal heat pump systems by saving resources and minimizing potential negative impacts induced by temperature changes within soil and groundwater, new geothermal exploration methods and tools are required. The knowledge of the underground thermal properties is a necessity for a correct and optimum design of borehole heat exchangers. The most important parameter that indicates the performance of the systems is thermal conductivity of the ground. Mapping the spatial variability of thermal conductivity, with high resolution in the shallow subsurface for geothermal purposes, requires a high degree of technical effort to procure adequate samples for thermal analysis. A collection of such samples from the soil can disturb sample structure, so great care must be taken during collection to avoid this. Factors such as transportation and sample storage can also influence measurement results. The use of technologies like Thermal Response Test (TRT) require complex mechanical and electrical systems for convective heat transport in the subsurface and longer monitoring times, often three days. Finally, by using thermal response tests, often only one integral value is obtained for the entire coupled subsurface with the borehole heat exchanger. The common thermal conductivity measurement systems (thermal analyzers) can perform vertical thermal conductivity logs only with the aid of sample procurement, or by integration into a drilling system. However, thermal conductivity measurements using direct push with this type of probes are not possible, due to physical and mechanical limitations. Applying vertical forces using direct push technology, in order to penetrate the shallow subsurface, can damage the probe and the sensors systems. The aim of this study is to develop a new, robust thermal conductivity measurement probe, for direct

  15. Measurement uncertainty for the Uniform Engine Testing Program conducted at NASA Lewis Research Center

    NASA Technical Reports Server (NTRS)

    Abdelwahab, Mahmood; Biesiadny, Thomas J.; Silver, Dean

    1987-01-01

    An uncertainty analysis was conducted to determine the bias and precision errors and total uncertainty of measured turbojet engine performance parameters. The engine tests were conducted as part of the Uniform Engine Test Program which was sponsored by the Advisory Group for Aerospace Research and Development (AGARD). With the same engines, support hardware, and instrumentation, performance parameters were measured twice, once during tests conducted in test cell number 3 and again during tests conducted in test cell number 4 of the NASA Lewis Propulsion Systems Laboratory. The analysis covers 15 engine parameters, including engine inlet airflow, engine net thrust, and engine specific fuel consumption measured at high rotor speed of 8875 rpm. Measurements were taken at three flight conditions defined by the following engine inlet pressure, engine inlet total temperature, and engine ram ratio: (1) 82.7 kPa, 288 K, 1.0, (2) 82.7 kPa, 288 K, 1.3, and (3) 20.7 kPa, 288 K, 1.3. In terms of bias, precision, and uncertainty magnitudes, there were no differences between most measurements made in test cells number 3 and 4. The magnitude of the errors increased for both test cells as engine pressure level decreased. Also, the level of the bias error was two to three times larger than that of the precision error.

  16. Method and apparatus for measuring thermal conductivity of small, highly insulating specimens

    NASA Technical Reports Server (NTRS)

    Miller, Robert A. (Inventor); Kuczmarski, Maria A. (Inventor)

    2012-01-01

    A hot plate method and apparatus for the measurement of thermal conductivity combines the following capabilities: 1) measurements of very small specimens; 2) measurements of specimens with thermal conductivity on the same order of that as air; and, 3) the ability to use air as a reference material. Care is taken to ensure that the heat flow through the test specimen is essentially one-dimensional. No attempt is made to use heated guards to minimize the flow of heat from the hot plate to the surroundings. Results indicate that since large correction factors must be applied to account for guard imperfections when specimen dimensions are small, simply measuring and correcting for heat from the heater disc that does not flow into the specimen is preferable. The invention is a hot plate method capable of using air as a standard reference material for the steady-state measurement of the thermal conductivity of very small test samples having thermal conductivity on the order of air.

  17. Observations of Spacecraft Bearing Lubricant Redistribution Based on Thermal Conductance Measurements

    NASA Technical Reports Server (NTRS)

    Takeuchi, Yoshimi R.; Frantz, Peter P.; Hilton, Michael R.

    2014-01-01

    The performance and life of precision ball bearings are critically dependent on maintaining a quantity of oil at the ball/race interface that is sufficient to support a robust protective film. In space applications, where parched conditions are intentionally the norm, harsh operating conditions can displace the small reserves of oil, resulting in reduced film thickness and premature wear. In the past, these effects have proven difficult to model or to measure experimentally. This paper describes a study addressing this challenge, where bearing thermal conductance measurements are employed to infer changes in lubricant quantity at the critical rolling interfaces. In the first part of the paper, we explain how the lubricant's presence and its quantity impacts bearing thermal conductance measurements. For a stationary bearing, we show that conductance is directly related to the lubricant quantity in the ball/race contacts. Hence, aspects of bearing performance related to oil quantity can be understood and insights improved with thermal conductance data. For a moving bearing, a different mechanism of heat transfer dominates and is dependent on lubricant film thickness on the ball. In the second part of the report, we discuss lubricant quantity observations based on bearing thermal conductance measurements. Lubricant quantity, and thus bearing thermal conductance, depends on various initial and operating conditions and is impacted further by the run-in process. A significant effect of maximum run-in speed was also observed, with less oil remaining after obtaining higher speeds. Finally, we show that some of the lubricant that is displaced between the ball and race during run-in operation can be recovered during rest, and we measure the rate of recovery for one example.

  18. A measurement technique for circumventing hysteresis and conductance drift in carbon nanotube field-effect transistors

    NASA Astrophysics Data System (ADS)

    Tunnell, Andrew; Ballarotto, Vincent; Cumings, John

    2014-01-01

    We present a measurement protocol that effectively eliminates both the hysteresis and the temporal drift typically observed in the channel conductance of single-walled carbon nanotube field-effect transistors (SWNT FETs) during the application of gate voltages. Before each resistance measurement, the gate is first stepped through a series of alternating positive and negative voltages to produce a neutral charge distribution within the device. This process is highly effective at removing the hysteresis in the channel conductance, and time-dependent measurements further demonstrate that the drain current is stable and single-valued, independent of the prior measurement history. The effectiveness of this method can be understood within the Preisach hysteresis model, which we demonstrate as a useful framework to predict the observed results.

  19. A measurement technique for circumventing hysteresis and conductance drift in carbon nanotube field-effect transistors.

    PubMed

    Tunnell, Andrew; Ballarotto, Vincent; Cumings, John

    2014-01-31

    We present a measurement protocol that effectively eliminates both the hysteresis and the temporal drift typically observed in the channel conductance of single-walled carbon nanotube field-effect transistors (SWNT FETs) during the application of gate voltages. Before each resistance measurement, the gate is first stepped through a series of alternating positive and negative voltages to produce a neutral charge distribution within the device. This process is highly effective at removing the hysteresis in the channel conductance, and time-dependent measurements further demonstrate that the drain current is stable and single-valued, independent of the prior measurement history. The effectiveness of this method can be understood within the Preisach hysteresis model, which we demonstrate as a useful framework to predict the observed results. PMID:24394672

  20. Method and Apparatus for Measuring Thermal Conductivity of Small, Highly Insulating Specimens

    NASA Technical Reports Server (NTRS)

    Miller, Robert A (Inventor); Kuczmarski, Maria A (Inventor)

    2013-01-01

    A method and apparatus for the measurement of thermal conductivity combines the following capabilities: 1) measurements of very small specimens; 2) measurements of specimens with thermal conductivity on the same order of that as air; and, 3) the ability to use air as a reference material. Care is taken to ensure that the heat flow through the test specimen is essentially one-dimensional. No attempt is made to use heated guards to minimize the flow of heat from the hot plate to the surroundings. Results indicate that since large correction factors must be applied to account for guard imperfections when specimen dimensions are small, simply measuring and correcting for heat from the heater disc that does not flow into the specimen is preferable.

  1. Effect of metal complexation on the conductance of single-molecular wires measured at room temperature.

    PubMed

    Ponce, Julia; Arroyo, Carlos R; Tatay, Sergio; Frisenda, Riccardo; Gaviña, Pablo; Aravena, Daniel; Ruiz, Eliseo; van der Zant, Herre S J; Coronado, Eugenio

    2014-06-11

    The present work aims to give insight into the effect that metal coordination has on the room-temperature conductance of molecular wires. For that purpose, we have designed a family of rigid, highly conductive ligands functionalized with different terminations (acetylthiols, pyridines, and ethynyl groups), in which the conformational changes induced by metal coordination are negligible. The single-molecule conductance features of this series of molecular wires and their corresponding Cu(I) complexes have been measured in break-junction setups at room temperature. Experimental and theoretical data show that no matter the anchoring group, in all cases metal coordination leads to a shift toward lower energies of the ligand energy levels and a reduction of the HOMO-LUMO gap. However, electron-transport measurements carried out at room temperature revealed a variable metal coordination effect depending on the anchoring group: upon metal coordination, the molecular conductance of thiol and ethynyl derivatives decreased, whereas that of pyridine derivatives increased. These differences reside on the molecular levels implied in the conduction. According to quantum-mechanical calculations based on density functional theory methods, the ligand frontier orbital lying closer to the Fermi energy of the leads differs depending on the anchoring group. Thereby, the effect of metal coordination on molecular conductance observed for each anchoring could be explained in terms of the different energy alignments of the molecular orbitals within the gold Fermi level. PMID:24831452

  2. On the van der Pauw's method applied to the measurement of low thermal conductivity materials.

    PubMed

    Morales, C; Flores, E; Bodega, J; Leardini, F; Ferrer, I J; Ares, J R; Sánchez, C

    2016-08-01

    The electrical van der Pauw's method has recently been extended to measure the thermal conductivity of different elements and compounds. This technique provides an easy way to determine the sample in-plane thermal conductivity by avoiding the influence of the thermal contact resistances. However, the reported calculated error values appear to be underestimated when dealing with the materials with low thermal conductivity (<5 W/Km) at room temperature. The causes of this underestimation are investigated in this communication and it has been found that they are due to the drastic influence of conduction heat losses through the thermo-resistance wires as well as the resulting modification of the sample temperature map. Both phenomena lead to experimental values of the sample thermal conductivity, which are systematically higher than the tabulated ones. The magnitude of this systematic error is ∼100% dealing with the samples of macroscopic dimensions, and low thermal conductivity indicated that the obtained accurate measurements can be quite challenging. PMID:27587145

  3. Using a Divided Bar Apparatus to Measure Thermal Conductivity of Samples of Odd Sizes and Shapes

    NASA Astrophysics Data System (ADS)

    Crowell, J. "; Gosnold, W. D.

    2012-12-01

    Standard procedure for measuring thermal conductivity using a divided bar apparatus requires a sample that has the same surface dimensions as the heat sink/source surface in the divided bar. Heat flow is assumed to be constant throughout the column and thermal conductivity (K) is determined by measuring temperatures (T) across the sample and across standard layers and using the basic relationship Ksample=(Kstandard*(ΔT1+ΔT2)/2)/(ΔTsample). Sometimes samples are not large enough or of correct proportions to match the surface of the heat sink/source, however using the equations presented here the thermal conductivity of these samples can still be measured with a divided bar. Measurements were done on the UND Geothermal Laboratories stationary divided bar apparatus (SDB). This SDB has been designed to mimic many in-situ conditions, with a temperature range of -20C to 150C and a pressure range of 0 to 10,000 psi for samples with parallel surfaces and 0 to 3000 psi for samples with non-parallel surfaces. The heat sink/source surfaces are copper disks and have a surface area of 1,772 mm2 (2.74 in2). Layers of polycarbonate 6 mm thick with the same surface area as the copper disks are located in the heat sink and in the heat source as standards. For this study, all samples were prepared from a single piece of 4 inch limestone core. Thermal conductivities were measured for each sample as it was cut successively smaller. The above equation was adjusted to include the thicknesses (Th) of the samples and the standards and the surface areas (A) of the heat sink/source and of the sample Ksample=(Kstandard*Astandard*Thsample*(ΔT1+ΔT3))/(ΔTsample*Asample*2*Thstandard). Measuring the thermal conductivity of samples of multiple sizes, shapes, and thicknesses gave consistent values for samples with surfaces as small as 50% of the heat sink/source surface, regardless of the shape of the sample. Measuring samples with surfaces smaller than 50% of the heat sink/source surface

  4. Development and application of diagnostic instrumentation for measurement of electron density and conductivity

    SciTech Connect

    Bauman, L.E.

    1990-05-01

    The purpose of this contract was to assemble and demonstrate in the laboratory a Faraday rotation system for measurement of electron density and conductivity, with the intent to produce a system suitable for diagnostic support of the development of pulsed, space-based magnetohydrodynamic (MHD) power systems. Two system configurations were tested: (1) a rotating polarizer and (2) a beam splitting polarizer. Due to the short path length plasma produced in the laboratory flame, the long wavelength 496 {mu}m methyl fluoride laser line was used and only the more sensitive rotating polarizer configuration was used for the demonstration experiments. Electron number densities from 2 {times} 10{sup 19} to 9 {times} 10{sup 19} were measured with good agreement to statistical equilibrium (Saha) calculations using emission absorption-measured flame temperatures and neutral seed atom number seed atom nuclear densities. The electron collision frequencies were measured by transmission measurements. Combining these two measurements gave measured electron conductivities of between 4 and 12 mohs/m. These results compared reasonably well with those found with an electron collision frequency model combined with chemical equilibrium calculations and the emission absorption measurements. Ellipticity measurements of electron collision frequency were not possible due to the short path length of the laboratory plasma. 46 refs., 25 figs., 9 tabs.

  5. Microwave conductance of aligned multiwall carbon nanotube textile sheets

    NASA Astrophysics Data System (ADS)

    Brown, Brian L.; Bykova, Julia S.; Howard, Austin R.; Zakhidov, Anvar A.; Shaner, Eric A.; Lee, Mark

    2014-12-01

    Multiwall carbon nanotube (MWNT) sheets are a class of nanomaterial-based multifunctional textile with potentially useful microwave properties. To understand better the microwave electrodynamics, complex AC conductance measurements from 0.01 to 50 GHz were made on sheets of highly aligned MWNTs with the alignment texture both parallel and perpendicular to the microwave electric field polarization. In both orientations, the AC conductance is modeled to first order by a parallel frequency-independent conductance and capacitance with no inductive contribution. This is consistent with low-frequency diffusive Drude AC conduction up to 50 GHz, in contrast to the "universal disorder" AC conduction reported in many types of single-wall nanotube materials.

  6. Measurement of Apparent Thermal Conductivity of JSC-1A Under Ambient Pressure

    NASA Technical Reports Server (NTRS)

    Yuan, Zeng-Guang; Kleinhenz, Julie E.

    2011-01-01

    The apparent thermal conductivity of JSC-1A lunar regolith simulant was measured experimentally using a cylindrical apparatus. Eleven thermocouples were embedded in the simulant bed to obtain the steady state temperature distribution at various radial, axial, and azimuthal locations. The high aspect ratio of a cylindrical geometry was proven to provide a one-dimensional, axisymmetric temperature field. A test series was performed at atmospheric pressure with varying heat fluxes. The radial temperature distribution in each test fit a logarithmic function, indicating a constant thermal conductivity throughout the soil bed. However, thermal conductivity was not constant between tests at different heat fluxes. This variation is attributed to stresses created by thermal expansion of the simulant particles against the rigid chamber wall. Under stress-free conditions (20 deg C), the data suggest a temperature independent apparent conductivity of 0.1961 +/- 0.0070 W/m/ deg C

  7. A steady-state high-temperature method for measuring thermal conductivity of refractory materials

    NASA Astrophysics Data System (ADS)

    Manzolaro, M.; Corradetti, S.; Andrighetto, A.; Ferrari, L.

    2013-05-01

    A new methodology and an instrumental setup for the thermal conductivity estimation of isotropic bulk graphite and different carbides at high temperatures are presented. The method proposed in this work is based on the direct measurement of temperature and emissivity on the top surface of a sample disc of known dimensions. Temperatures measured under steady-state thermal equilibrium are then used to estimate the thermal conductivity of the sample by making use of the inverse parameter estimation technique. Thermal conductivity values obtained in this way are then compared to the material data sheets and values found in literature. The reported work has been developed within the Research and Development framework of the SPES (Selective Production of Exotic Species) project at INFN-LNL (Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali di Legnaro).

  8. Measurements of middle-atmosphere electric fields and associated electrical conductivities

    NASA Technical Reports Server (NTRS)

    Hale, L. C.; Croskey, C. L.; Mitchell, J. D.

    1981-01-01

    A simple antenna for measuring the vertical electric field in the 'middle atmosphere' has been flown on a number of rocket-launched parachute-borne payloads. The data from the first nine such flights, launched under a variety of geophysical conditions, are presented, along with electrical conductivities measured simultaneously. The data include indications of layered peaks of several volts per meter in the mesospheric field at high and low latitudes in situations of relatively low conductivity. During an auroral 'REP' event the electric field reversed direction in the lower stratosphere, accompanied by a substantial enhancement in conductivity. The data generally do not confirm speculations based only on the extension of the thunderstorm circuit from below or the mapping of ionospheric and magnetospheric fields from above, but seem to require, in addition, internal generation processes in the middle atmosphere.

  9. Thermal conductivity of donor-doped GaN measured with 3ω and stationary methods

    NASA Astrophysics Data System (ADS)

    Churiukova, O.; JeŻowski, A.; Stachowiak, P.; Mucha, J.; Litwicki, Z.; Perlin, P.; Suski, T.

    2015-07-01

    The thermal conductivity of three single crystal samples of n-type gallium nitride with electron densities of 4.0 × 1016, 2.6 × 1018, and 1.1 × 1020 cm-3 has been determined in the temperature range 4-320 K. The measurements were carried out within the ab plane using the stationary method. The thermal conductivity depends strongly on the donor concentration. The analysis within the Callaway approach and the Debye model shows a significant influence of phonon-electron scattering on the thermal conductivity of the samples. In addition, some preliminary results obtained along the c axes of GaN layered samples are presented. The latter measurements have been carried out using the 3ω method.

  10. A steady-state high-temperature method for measuring thermal conductivity of refractory materials.

    PubMed

    Manzolaro, M; Corradetti, S; Andrighetto, A; Ferrari, L

    2013-05-01

    A new methodology and an instrumental setup for the thermal conductivity estimation of isotropic bulk graphite and different carbides at high temperatures are presented. The method proposed in this work is based on the direct measurement of temperature and emissivity on the top surface of a sample disc of known dimensions. Temperatures measured under steady-state thermal equilibrium are then used to estimate the thermal conductivity of the sample by making use of the inverse parameter estimation technique. Thermal conductivity values obtained in this way are then compared to the material data sheets and values found in literature. The reported work has been developed within the Research and Development framework of the SPES (Selective Production of Exotic Species) project at INFN-LNL (Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali di Legnaro). PMID:23742578

  11. Analysis of Thermal-Conductivity Measurement Data from International Comparison of National Laboratories

    NASA Astrophysics Data System (ADS)

    Hay, B.; Zarr, R.; Stacey, C.; Lira-Cortes, L.; Hammerschmidt, U.; Sokolov, N.; Zhang, J.; Filtz, J.-R.; Fleurence, N.

    2013-05-01

    For the first time under the auspices of the Bureau International des Poids et Mesures (BIPM), seven national metrology institutes (NMIs) participated in an international interlaboratory comparison on thermal-conductivity measurements by the guarded hot-plate method. Measurements were conducted successively by all participants on the same set of specimens of insulating materials (mineral wool and expanded polystyrene) at temperatures ranging from 10 °C to 40 °C, according to the International Standard ISO 8302. This protocol aims to minimize issues of material variability by circulating the same pairs of specimens among the laboratories following the strict format of a round-robin test program. This comparison is a pilot study which is intended as a first stage for future key comparisons between NMIs. The descriptive analysis of obtained results shows good agreement between laboratories for the mineral wool (MW) specimens and the thicker specimens of expanded polystyrene (EPS), with relative deviations within the uncertainties of measurement. A positive drift of thermal-conductivity values, which has appeared progressively during the comparison process, seems to be correlated with the size of the metering area of the guarded hot plates used. A statistical analysis was applied to repeated thermal-conductivity measurements at 23 °C, to identify anomalous and outlying data, to assess the within- and between-laboratory variability, and to evaluate the participant laboratories' performance.

  12. Optical approach to thermopower and conductivity measurements in thin-film semiconductors

    SciTech Connect

    Dersch, H.; Amer, N.M.

    1984-08-01

    An optical beam deflection technique is applied to measure the Joule and Peltier heat generated by electric currents through thin-film semiconductors. The method yields a spatially resolved conductivity profile and allows the determination of Peltier coefficients. Results obtained on doped hydrogenated amorphous silicon films are presented.

  13. Using Conductivity Measurements to Determine the Identities and Concentrations of Unknown Acids: An Inquiry Laboratory Experiment

    ERIC Educational Resources Information Center

    Smith, K. Christopher; Garza, Ariana

    2015-01-01

    This paper describes a student designed experiment using titrations involving conductivity measurements to identify unknown acids as being either HCl or H[subscript 2]SO[subscript 4], and to determine the concentrations of the acids, thereby improving the utility of standard acid-base titrations. Using an inquiry context, students gain experience…

  14. A Hot-Wire Method Based Thermal Conductivity Measurement Apparatus for Teaching Purposes

    ERIC Educational Resources Information Center

    Alvarado, S.; Marin, E.; Juarez, A. G.; Calderon, A.; Ivanov, R.

    2012-01-01

    The implementation of an automated system based on the hot-wire technique is described for the measurement of the thermal conductivity of liquids using equipment easily available in modern physics laboratories at high schools and universities (basically a precision current source and a voltage meter, a data acquisition card, a personal computer…

  15. A study of rock matrix diffusion properties by electrical conductivity measurements

    SciTech Connect

    Ohlsson, Y.; Neretnieks, I.

    1999-07-01

    Traditional rock matrix diffusion experiments on crystalline rock are very time consuming due to the low porosity and extensive analysis requirements. Electrical conductivity measurements are, on the other hand, very fast and larger samples can be used than are practical in ordinary diffusion experiments. The effective diffusivity of a non-charged molecule is readily evaluated from the measurements, and influences from surface conductivity on diffusion of cations can be studied. A large number of samples of varying thickness can be measured within a short period, and the changes in transport properties with position in a rock core can be examined. In this study the formation factor of a large number of Aespoe diorite samples is determined by electrical conductivity measurements. The formation factor is a geometric factor defined as the ratio between the effective diffusivity of a non-charged molecule, to that of the same molecule in free liquid. The variation of this factor with position among a borecore and with sample length, and its coupling to the porosity of the sample is studied. Also the surface conductivity is studied. This was determined as the residual conductivity after leaching of the pore solution ions. The formation factor of most of the samples is in the range 1E-5 to 1E-4, with a mean value of about 5E-5. Even large samples (4--13 cm) give such values. The formation factor increases with increasing porosity and the change in both formation factor and porosity with position in the borecore can be large, even for samples close to each other. The surface conductivity increases with increasing formation factor for the various samples but the influence on the pore diffusion seems to be higher for samples of lower formation factor. This suggests that the relation between the pore surface area and the pore volume is larger for samples of low formation factor.

  16. Measurement of submilliwatt, picosecond terahertz emission from a femtosecond-laser-pumped solid-state dc to ac radiation converter based on a ZnSe crystal

    SciTech Connect

    Yugami, Noboru; Ohata, Nobuo; Yaegashi, Kenta; Kawanago, Hiroshi

    2006-11-15

    We measured the terahertz pulse emission from a femtosecond-laser-pumped solid-state dc to ac radiation converter using a 150 fs Ti:sapphire laser pulse for dense plasma diagnostics. The laser-produced ionization front was directly modulated from a periodic electrostatic field to pulsed emission. The central frequency of the emission was measured to be 0.13 THz having a bandwidth of 0.1 THz and a peak power of 0.2 mW. This emission source is suitable for use in various novel diagnostic techniques, such as dense plasma diagnostics.

  17. Performance measurements and operational characteristics of the Storage Tek ACS 4400 tape library with the Cray Y-MP EL

    NASA Technical Reports Server (NTRS)

    Hull, Gary; Ranade, Sanjay

    1993-01-01

    With over 5000 units sold, the Storage Tek Automated Cartridge System (ACS) 4400 tape library is currently the most popular large automated tape library. Based on 3480/90 tape technology, the library is used as the migration device ('nearline' storage) in high-performance mass storage systems. In its maximum configuration, one ACS 4400 tape library houses sixteen 3480/3490 tape drives and is capable of holding approximately 6000 cartridge tapes. The maximum storage capacity of one library using 3480 tapes is 1.2 TB and the advertised aggregate I/O rate is about 24 MB/s. This paper reports on an extensive set of tests designed to accurately assess the performance capabilities and operational characteristics of one STK ACS 4400 tape library holding approximately 5200 cartridge tapes and configured with eight 3480 tape drives. A Cray Y-MP EL2-256 was configured as its host machine. More than 40,000 tape jobs were run in a variety of conditions to gather data in the areas of channel speed characteristics, robotics motion, time taped mounts, and timed tape reads and writes.

  18. Tevatron AC dipole system

    SciTech Connect

    Miyamoto, R.; Kopp, S.E.; Jansson, A.; Syphers, M.J.; /Fermilab

    2007-06-01

    The AC dipole is an oscillating dipole magnet which can induce large amplitude oscillations without the emittance growth and decoherence. These properties make it a good tool to measure optics of a hadron synchrotron. The vertical AC dipole for the Tevatron is powered by an inexpensive high power audio amplifier since its operating frequency is approximately 20 kHz. The magnet is incorporated into a parallel resonant system to maximize the current. The use of a vertical pinger magnet which has been installed in the Tevatron made the cost relatively inexpensive. Recently, the initial system was upgraded with a more powerful amplifier and oscillation amplitudes up to 2-3{sigma} were achieved with the 980 GeV proton beam. This paper discusses details of the Tevatron AC dipole system and also shows its test results.

  19. Thermal-conductivity measurements of tungsten-fiber-reinforced superalloy composites using a thermal-conductivity comparator

    NASA Technical Reports Server (NTRS)

    Westfall, L. J.; Winsa, E. A.

    1979-01-01

    The thermal conductivity (TC) of tungsten-fiber-reinforced superalloys was determined for two composite systems by using a thermal conductivity standard from the National Bureau of Standards and a comparator and technique developed for that purpose. The results were compared with TC data for the nickel-base alloy MAR-M200. The technique lends itself to applications involving thin specimens, such as thin-walled turbine blades. The TC's of the composite systems were considerably higher in both the longitudinal and transverse directions than that of the monolithic superalloys used as the matrices.

  20. Photoacoustic infrared spectroscopy for conducting gas tracer tests and measuring water saturations in landfills.

    PubMed

    Jung, Yoojin; Han, Byunghyun; Mostafid, M Erfan; Chiu, Pei; Yazdani, Ramin; Imhoff, Paul T

    2012-02-01

    Gas tracer tests can be used to determine gas flow patterns within landfills, quantify volatile contaminant residence time, and measure water within refuse. While gas chromatography (GC) has been traditionally used to analyze gas tracers in refuse, photoacoustic spectroscopy (PAS) might allow real-time measurements with reduced personnel costs and greater mobility and ease of use. Laboratory and field experiments were conducted to evaluate the efficacy of PAS for conducting gas tracer tests in landfills. Two tracer gases, difluoromethane (DFM) and sulfur hexafluoride (SF(6)), were measured with a commercial PAS instrument. Relative measurement errors were invariant with tracer concentration but influenced by background gas: errors were 1-3% in landfill gas but 4-5% in air. Two partitioning gas tracer tests were conducted in an aerobic landfill, and limits of detection (LODs) were 3-4 times larger for DFM with PAS versus GC due to temporal changes in background signals. While higher LODs can be compensated by injecting larger tracer mass, changes in background signals increased the uncertainty in measured water saturations by up to 25% over comparable GC methods. PAS has distinct advantages over GC with respect to personnel costs and ease of use, although for field applications GC analyses of select samples are recommended to quantify instrument interferences. PMID:21996285

  1. Thermal conductance measurements of bolted copper to copper joints at sub-Kelvin temperatures

    NASA Astrophysics Data System (ADS)

    Didschuns, I.; Woodcraft, A. L.; Bintley, D.; Hargrave, P. C.

    2004-05-01

    We have measured the thermal contact conductance of several demountable copper joints below 1 K. Joints were made by bolting together either two flat surfaces or a clamp around a rod. Surfaces were gold plated, and no intermediate materials were used. A linear dependence on temperature was seen. Most of the measured conductance values fell into a narrow range: 0.1-0.2 W K -1 at 1 K. Results in the literature for similar joints consist of predictions based on electrical resistance measurements using the Wiedemann-Franz law. There is little evidence of the validity of this law in the case of joints. Nevertheless, our results are in good agreement with the literature predictions, suggesting that such predictions are a reasonable approximation.

  2. Simultaneous reconstruction of permittivity and conductivity using multi-frequency admittance measurement in electrical capacitance tomography

    NASA Astrophysics Data System (ADS)

    Zhang, Maomao; Soleimani, Manuchehr

    2016-02-01

    Electrical capacitance tomography (ECT) is an imaging method mainly capable of reconstructing dielectric permittivity. Generally, the reactance part of complex admittance is measured in a selected frequency. This paper presents for the first time an in depth and systematic analysis of complex admittance data for simultaneous reconstruction of both electrical conductivity and dielectric permittivity. A complex-valued forward model, Jacobian matrix and inverse solution are developed in the time harmonic excitation mode to allow for multi-frequency measurements. Realistic noise models are used to evaluate the performance of complex admittance ECT in a range of excitation frequencies. This paper demonstrates far greater potential for ECT as a versatile imaging tool through novel analysis of complex admittance imaging using a dual conductivity permittivity inversion method. The paper demonstrates that various classes of contactless capacitance based measurement devices can be analysed through complex multi-frequency ECT.

  3. A robust and well shielded thermal conductivity device for low temperature measurements.

    PubMed

    Toews, W H; Hill, R W

    2014-04-01

    We present a compact mechanically robust thermal conductivity measurement apparatus for measurements at low temperatures (<1 K) and high magnetic fields on small high-purity single crystal samples. A high-conductivity copper box is used to enclose the sample and all the components. The box provides protection for the thermometers, heater, and most importantly the sample increasing the portability of the mount. In addition to physical protection, the copper box is also effective at shielding radio frequency electromagnetic interference and thermal radiation, which is essential for low temperature measurements. A printed circuit board in conjunction with a braided ribbon cable is used to organize the delicate wiring and provide mechanical robustness. PMID:24784624

  4. Quantitative Estimation of the Metal-Induced Negative Oxide Charge Density in n-Type Silicon Wafers from Measurements of Frequency-Dependent AC Surface Photovoltage

    NASA Astrophysics Data System (ADS)

    Shimizu, Hirofumi; Shin, Ryuhei; Ikeda, Masanori

    2006-03-01

    A quantitative estimation of metal-induced oxide charge (Qmi) density is performed on the surface of n-type silicon (Si) wafers rinsed with trivalent aluminum (Al)- and iron (Fe)-contaminated RCA alkaline solution by analyzing the frequency-dependent AC surface photovoltage (SPV). Qmi arises from (AlOSi)- or (FeOSi)- networks in native oxide which are responsible for inducing negative oxide charge. On the basis of Munakata and Nishimatsu’s half-sided junction model [C. Munakata and S. Nishimatsu: Jpn. J. Appl. Phys. 25 (1986) 807], the network densities are estimated in depletion and/or weak inversion in which the cutoff frequencies of the frequency-dependent AC SPV curves are defined. It is found that the charge density Qmi increases with the time of exposure to air and it is calculated that about 4% of Al atoms in the native oxide are activated in the form of an (AlOSi)- network for 1 h of exposure. The (FeOSi)- network density is calculated as a function of Fe concentration. As a result, the frequency-dependent AC SPV measurements carried out here enable a successful evaluation of impurity level in a nondestructive and noncontact manner.

  5. Study of AC/RF properties of SRF ingot niobium

    SciTech Connect

    Dhakal, Pashupati; Tsindlekht, Menachem I; Genkin, Valery M; Ciovati, Gianluigi; Myneni, Ganapati Rao

    2013-09-01

    In an attempt to correlate the performance of superconducting radiofrequency cavities made of niobium with the superconducting properties, we present the results of the magnetization and ac susceptibility of the niobium used in the superconducting radiofrequency cavity fabrication. The samples were subjected to buffer chemical polishing (BCP) surface and high temperature heat treatments, typically applied to the cavities fabrications. The analysis of the results show the different surface and bulk ac conductivity for the samples subjected to BCP and heat treatment. Furthermore, the RF surface impedance is measured on the sample using a TE011 microwave cavity for a comparison to the low frequency measurements.

  6. Pump-probe measurements of the thermal conductivity tensor for materials lacking in-plane symmetry

    NASA Astrophysics Data System (ADS)

    Feser, Joseph P.; Liu, Jun; Cahill, David G.

    2014-10-01

    We previously demonstrated an extension of time-domain thermoreflectance (TDTR) which utilizes offset pump and probe laser locations to measure in-plane thermal transport properties of multilayers. However, the technique was limited to systems of transversely isotropic materials studied using axisymmetric laser intensities. Here, we extend the mathematics so that data reduction can be performed on non-transversely isotropic systems. An analytic solution of the diffusion equation for an N-layer system is given, where each layer has a homogenous but otherwise arbitrary thermal conductivity tensor and the illuminating spots have arbitrary intensity profiles. As a demonstration, we use both TDTR and time-resolved magneto-optic Kerr effect measurements to obtain thermal conductivity tensor elements of <110> α-SiO2. We show that the out-of-phase beam offset sweep has full-width half-maxima that contains nearly independent sensitivity to the in-plane thermal conductivity corresponding to the scanning direction. Also, we demonstrate a Nb-V alloy as a low thermal conductivity TDTR transducer layer that helps improve the accuracy of in-plane measurements.

  7. Pump-probe measurements of the thermal conductivity tensor for materials lacking in-plane symmetry

    SciTech Connect

    Feser, Joseph P.; Liu, Jun; Cahill, David G.

    2014-10-15

    We previously demonstrated an extension of time-domain thermoreflectance (TDTR) which utilizes offset pump and probe laser locations to measure in-plane thermal transport properties of multilayers. However, the technique was limited to systems of transversely isotropic materials studied using axisymmetric laser intensities. Here, we extend the mathematics so that data reduction can be performed on non-transversely isotropic systems. An analytic solution of the diffusion equation for an N-layer system is given, where each layer has a homogenous but otherwise arbitrary thermal conductivity tensor and the illuminating spots have arbitrary intensity profiles. As a demonstration, we use both TDTR and time-resolved magneto-optic Kerr effect measurements to obtain thermal conductivity tensor elements of <110> α-SiO{sub 2}. We show that the out-of-phase beam offset sweep has full-width half-maxima that contains nearly independent sensitivity to the in-plane thermal conductivity corresponding to the scanning direction. Also, we demonstrate a Nb-V alloy as a low thermal conductivity TDTR transducer layer that helps improve the accuracy of in-plane measurements.

  8. Time- and Space-Domain Measurements of the Thermal Conductivity in Diamond Anvil Cells

    NASA Astrophysics Data System (ADS)

    Goncharov, A. F.

    2011-12-01

    I will give an overview of recent developments of experimental techniques to measure the thermal conductivity in diamond anvil cell (DAC) under conditions of high pressure and high temperature (P-T) which are relevant for the planetary interiors. To measure the lattice contributions to the thermal conductivity, we developed a transient heating technique (THT) in the diamond anvil cell (DAC) [1]. This technique utilizes a periodic front surface temperature variation (measured by the spectroradiometry) of a metallic absorber surrounded by the material of interest and exposed to a pulsed laser radiation (10 nanoseconds pulses). We extract the thermal diffusivity of minerals by fitting the experimental results to the model finite element (FE) calculations. We have recently modified this technique for microseconds laser pulses as this allows avoiding nonequilibrium heat transfer processes. We have measured the thermal conductivity of Ar up to 50 GPa and 2500 K; the results are in agreement with the theoretical calculations [2] in the limit of high temperatures. In collaboration with a group from the University of Illinois we have utilized a time-domain thermoreflectance (TDTR)- ultrafast (femtosecond) laser pump-probe technique for measurement of the lattice thermal conductivity at high P-T conditions. We have measured the thermal conductivity of MgO up to 60 GPa and 300 K and up to 45 GPa at 600 K. The detailed results of this study will be presented in a separate paper at this Meeting. Finally, we have combined static and pulsed laser techniques to determine the thermal conductivity of Fe and its temperature dependence at high pressures up to 70 GPa and 2000 K [3]. A thin plate of Fe was positioned in an Ar medium, laser heated from one side and the temperature is being measured from both sides of the sample radiometrically. The thermal conductivity has been determined by fitting the results of FE calculations to the experimental results. These examples demonstrate

  9. Spatial relationship between the productivity of cane sugar and soil electrical conductivity measured by electromagnetic induction

    NASA Astrophysics Data System (ADS)

    Siqueira, Glecio; Silva, Jucicléia; Bezerra, Joel; Silva, Enio; Montenegro, Abelardo

    2013-04-01

    The cultivation of sugar cane in Brazil occupies a prominent place in national production chain, because the country is the main world producer of sugar and ethanol. Accordingly, studies are needed that allow an integrated production and technified, and especially that estimates of crops are consistent with the actual production of each region. The objective of this study was to determine the spatial relationship between the productivity of cane sugar and soil electrical conductivity measured by electromagnetic induction. The field experiment was conducted at an agricultural research site located in Goiana municipality, Pernambuco State, north-east of Brazil (Latitude 07 ° 34 '25 "S, Longitude 34 ° 55' 39" W). The surface of the studied field is 6.5 ha, and its mean height 8.5 m a.s.l. This site has been under sugarcane (Saccharum officinarum sp.) monoculture during the last 24 years and it was managed burning the straw each year after harvesting, renewal of plantation was performed every 7 years. Studied the field is located 10 km east from Atlantic Ocean and it is representative of the regional landscape lowlands, whose soils are affected by salinity seawater, sugarcane plantations with the main economical activity. Soil was classified an orthic the Podsol. The productivity of cane sugar and electrical conductivity were measured in 90 sampling points. The productivity of cane sugar was determined in each of the sampling points in plots of 9 m2. The Apparent soil electrical conductivity (ECa, mS m-1) was measured with an electromagnetic induction device EM38-DD (Geonics Limited). The equipment consists of two units of measurement, one in a horizontal dipole (ECa-H) to provide effective measurement distance of 1.5 m approximately and other one in vertical dipole (ECa-V) with an effective measurement depth of approximately 0.75 m. Data were analyzed using descriptive statistics and geostatistical tools. The results showed that productivity in the study area

  10. Flow velocimetry for weakly conducting electrolytes based on high resolution Lorentz force measurement.

    NASA Astrophysics Data System (ADS)

    Resagk, Christian; Ebert, Reschad; Vasilyan, Suren; Wiederhold, Andreas

    2013-11-01

    We demonstrate that a flow velocity measurement can be transformed into a non-invasive force measurement by metering the drag force acting on a system of magnets around a flow channel. This method is called Lorentz force velocimetry and has been developed in the last years in our institute. It is a feasible principle for materials with large conductivity like liquid metals. To evolve this method for weakly conducting fluids like salt water or molten glass the drag force measurement is the challenging bottleneck. Here forces of 10-8 and less of the weight force of the magnet system have to be resolved. In this paper different force measurement techniques get tested and compared. For the current setup the magnet system is attached to a state of the art electromagnetic force compensation balance. Different ways of getting the correct force signal out of the two measurement setups will be presented and discussed. For generalization of the measurement principle the Lorentz force is determined for different fluid profiles. In addition to that we have developed new systematic noise reduction methods to increase the resolution of the force measurement techniques by a factor of ten or larger which we will present here.

  11. Estimation of in-situ thermal conductivities from temperature gradient measurements

    SciTech Connect

    Hoang, V.T.

    1980-12-01

    A mathematical model has been developed to study the effect of variable thermal conductivity of the formations, and the wellbore characteristics, on the fluid temperature behavior inside the wellbore during injection or production and after shut-in. During the injection or production period the wellbore fluid temperature is controlled mainly by the fluid flow rate and the heat lost from the fluid to the formation. During the shut-in period, the fluid temperature is strongly affected by differences in the formation thermal conductivities. Based on the results of the present analysis, two methods for estimating in-situ thermal conductivity were derived. First, the line source concept is extended to estimate values of the formation thermal conductivities utilizing the fluid temperature record during the transient period of injection or production and shut-in. The second method is applied when a well is under thermal equilibrium conditions. Values of the formation thermal conductivities can also be estimated by using a continuous temperature gradient log and by measuring the thermal conductivity of the formation at a few selected wellbore locations.

  12. Measurement of the optical properties of a transparent, conductive carbon nanotube film using spectroscopic ellipsometry

    NASA Astrophysics Data System (ADS)

    Kuwahara, Masashi; Kim, Yeji; Azumi, Reiko

    2015-07-01

    We have measured the complex refractive indices of a transparent, conductive carbon nanotube film by spectroscopic ellipsometry at wavelengths of 300-1700 nm (this includes the visible range). The film was produced on a quartz substrate by the doctor-blade method using single-walled carbon nanotube-polymer ink. The imaginary part of the complex refractive index of the film was found to be lower than 0.09 over the entire wavelength range. This film has a large advantage as a transparent, flexible, and conductive material.

  13. A hot-wire method based thermal conductivity measurement apparatus for teaching purposes

    NASA Astrophysics Data System (ADS)

    Alvarado, S.; Marín, E.; Juárez, A. G.; Calderón, A.; Ivanov, R.

    2012-07-01

    The implementation of an automated system based on the hot-wire technique is described for the measurement of the thermal conductivity of liquids using equipment easily available in modern physics laboratories at high schools and universities (basically a precision current source and a voltage meter, a data acquisition card, a personal computer and a high purity platinum wire). The wire, which is immersed in the investigated sample, is heated by passing a constant electrical current through it, and its temperature evolution, ΔT, is measured as a function of time, t, for several values of the current. A straightforward methodology is then used for data processing in order to obtain the liquid thermal conductivity. The start point is the well known linear relationship between ΔT and ln(t) predicted for long heating times by a model based on a solution of the heat conduction equation for an infinite lineal heat source embedded in an infinite medium into which heat is conducted without convective and radiative heat losses. A criterion is used to verify that the selected linear region is the one that matches the conditions imposed by the theoretical model. As a consequence the method involves least-squares fits in linear, semi-logarithmic (semi-log) and log-log graphs, so that it becomes attractive not only to teach about heat transfer and thermal properties measurement techniques, but also as a good exercise for students of undergraduate courses of physics and engineering learning about these kinds of mathematical functional relationships between variables. The functionality of the experiment was demonstrated by measuring the thermal conductivity in samples of liquids with well known thermal properties.

  14. Predicting thermal conductivity of rocks from the Los Azufres geothermal field, Mexico, from easily measurable properties

    SciTech Connect

    Garcia, Alfonso; Contreras, Enrique; Dominquez, Bernardo A.

    1988-01-01

    A correlation is developed to predict thermal conductivity of drill cores from the Los Azufres geothermal field. Only andesites are included as they are predominant. Thermal conductivity of geothermal rocks is in general scarce and its determination is not simple. Almost all published correlations were developed for sedimentary rocks. Typically, for igneous rocks, chemical or mineral analyses are used for estimating conductivity by using some type of additive rule. This requires specialized analytical techniques and the procedure may not be sufficiently accurate if, for instance, a chemical analysis is to be changed into a mineral analysis. Thus a simple and accurate estimation method would be useful for engineering purposes. The present correlation predicts thermal conductivity from a knowledge of bulk density and total porosity, properties which provide basic rock characterization and are easy to measure. They may be determined from drill cores or cuttings, and the procedures represent a real advantage given the cost and low availability of cores. The multivariate correlation proposed is a quadratic polynomial and represents a useful tool to estimate thermal conductivity of igneous rocks since data on this property is very limited. For porosities between 0% and 25%, thermal conductivity is estimated with a maximum deviation of 22% and a residual mean square deviation of 4.62E-3 n terms of the log{sub 10}(k{rho}{sub b}) variable. The data were determined as part of a project which includes physical, thermal and mechanical properties of drill cores from Los Azufres. For the correlation, sixteen determinations of thermal conductivity, bulk density and total porosity are included. The conductivity data represent the first determinations ever made on these rocks.

  15. Ionic conductivity measurement in magnesium aluminate spinel and solid state galvanic cell with magnesium aluminate electrolyte

    NASA Astrophysics Data System (ADS)

    Lee, Myongjai

    This thesis work is about the experimental measurement of electronic and ionic conductivities in the MgAl2O4 spinel at 500˜600°C range and exploring the fundamental origin of solid-state galvanic cell behavior in the cell of Al|MgAl2O4|Mg, Al|MgAl2O 4|C, and Mg|MgAl2O4|C, in which at least one metal electrode in common with the composition of the electrolyte. For the electronic conductivity measurement, we have used the ion-blocking Gold and Carbon electrodes which are inert with both Mg and Al ions to suppress the ionic conduction from the total conduction. DC polarization method was used to measure the conduction through Au|MgAl2O4|Au and C|MgAl2O4|C specimens. The measured electrical conductivity using Au|MgAl2O4|Au and C|MgAl2O4|C specimens showed 10-9.3 ˜ 10-8.4 (O·cm) -1 at 600˜720°C range following the Arrhenius-type relation. These conductivity data are in agreement with reported data obtained from Pt and Ag ion-blocking electrodes deposited on MgAl2O4 specimens. For the ionic conductivity measurement, we have used the non-blocking Al and Mg electrodes for Al and Mg ionic conductivities, respectively. Ionic conductivity measurement of Al and Mg in separate manner has not been reported yet. In both Al|MgAl2O4|Al and Mg|MgAl2O 4|Mg specimens, gradual increase of conduction was observed once at the initial period before it reaches the steady state conduction. By DC method on the range of 580˜650°C, steady state Al ionic conductivity was measured from Al|MgAl2O4|Al specimen showing 10 -7.7 ˜ 10-6.8 (O·cm)-1 with the activation energy of 1.9eV in sigma = sigma0 exp-QRT formula. There was no difference in the conductivity by the change of the atmosphere from 5%H2 + 95%N2 mixed gas to pure Ar gas. So it was confirmed that the oxygen defect chemistry did not play a role. For Mg ionic conductivity Mg|MgAl2O4|Mg specimen was used and the measured conductivity shows 10-6.7 ˜ 10-4.4 (O·cm)-1 at 400˜550°C with the activation energy of 1.44eV at Ar gas

  16. A simulation of the measurement of electrical conductivity in randomly generated two-phase rocks.

    NASA Astrophysics Data System (ADS)

    Mandolesi, Eric; Moorkamp, Max; Jones, Alan G.

    2014-05-01

    Geological models of the subsurface require detailed data, often unavailable from direct observation or well logs. Hence imaging the subsurface relies on models obtained by interpretation of geophysical data. Several electromagnetic (EM) geophysical methods focus on the EM properties of rocks and sediments to determine a reliable image of the subsurface, while the same electromagnetic properties are directly measured in laboratories. Often these laboratory measurements return equivocal results that are difficult to reconcile with field observations. Recently different numerical approaches have been investigated in order to understand the effects of the geometry and continuity of interconnected pathways of conductors on EM field measurements, often restricting the studies to direct current (DC) sources. Bearing in mind the time-varying nature of the natural electromagnetic sources that play a role in field measurements, we numerically simulate the effects of such EM sources on the conductivity measured on the surface of a randomly generated three-dimensional body embedded in a uniform host by using electromagnetic induction equations, thus simulating a magnetotelluric (MT) survey. A key point in such a simulation is the scalability of the problem: the deeper the target, the longer the period of the EM source is needed. On the other hand, a long period signal ignores small heterogeneous conductors in the target bulk of the material, averaging the different conductivities in a median value. Since most real rocks are poor conductors, we have modeled a two-phase mixture of rock and interconnected conductive elements (representing melts, saline fluids, sulphidic, carbonitic, or metallic sediments, etc.), randomly generated within the background host. We have compared the results from the simulated measurements with the target rock embedded at different depths with electrical conductivity predicted by both Hashin-Shtrikman (HS) bounds and an updated multi-phase Archie

  17. High accuracy thermal conductivity measurements near the lambda transition of helium with very high temperature resolution

    NASA Technical Reports Server (NTRS)

    Fairbank, William M.; Lipa, John A.

    1989-01-01

    Over the past few years extensive thermal conductivity measurements near the lambda point of helium were made. The original goal of measuring the thermal conductivity with a resolution of t = T/T sub lambda -1 of 3 x 10(-8) was reached, but with somewhat less accuracy than was hoped. Subtle effects in the apparatus near the transition were observed which reduced the ability to interpret the results. Nevertheless, for resolution of t is greater than or equal to 10(-7) reliable data was obtained, extending previous measurements by more than an order of magnitude. Deviations from theoretical predictions were observed for t is less than or equal to 3 x 10(-6) leading to the question of the validity of the present renormalization group analysis of transport properties, at least for the case of helium. This anomaly led to closer examination of the boundary effects in the measurements. During the experiments a totally unexpected effect in the very dilute He-3 - He-4 mixtures was observed which led to the explanation of the anomalous results. The concentration dependence of the thermal conductivity near T sub lambda in the superfluid phase was found to deviate strongly from the predictions. The results gave an independent verification of this behavior and caused reanalysis of the Khalatnikov theory of hydrodynamics of the mixtures. An alternative solution was found which is in better agreement with the experiment.

  18. Transient thermal conductivity and colloidal stability measurements of nanofluids by using the 3omega method.

    PubMed

    Oh, Dong-Wook; Kwon, Ohmyoung; Lee, Joon Sik

    2008-10-01

    Nanofluid is a mixture of nanoscale particles of metal, metal oxide or carbon nanotube and heat transfer fluids such as water and ethylene glycol. This work presents the application of the 3-omega (3omega) method for measuring the colloidal stability and the transient thermal conductivity of multi-wall carbon nanotube (MWCNT), Al2O3 and TiO2 nanoparticles suspended in water or ethylene glycol. The microfabricated 3omega device is verified by comparing the measured thermal conductivities of pure fluids with the table values. After the validation, the transient thermal responses of the nanofluids are measured to evaluate the colloidal stability. All of Al2O3 nanofluid samples show a clear sign of sedimentation while the acid-treated MWCNT (tMWCNT) nanofluid and a couple of TiO2 nanofluids with pH control or surfactant addition are found to have excellent colloidal stability. The thermal conductivities of tMWCNT nanofluids in the de-ionized water and ethylene glycol are measured, which are found to be in good agreement with previous data. PMID:19198364

  19. Photoacoustic infrared spectroscopy for conducting gas tracer tests and measuring water saturations in landfills

    SciTech Connect

    Jung, Yoojin; Han, Byunghyun; Mostafid, M. Erfan; Chiu, Pei; Yazdani, Ramin; Imhoff, Paul T.

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Photoacoustic infrared spectroscopy tested for measuring tracer gas in landfills. Black-Right-Pointing-Pointer Measurement errors for tracer gases were 1-3% in landfill gas. Black-Right-Pointing-Pointer Background signals from landfill gas result in elevated limits of detection. Black-Right-Pointing-Pointer Technique is much less expensive and easier to use than GC. - Abstract: Gas tracer tests can be used to determine gas flow patterns within landfills, quantify volatile contaminant residence time, and measure water within refuse. While gas chromatography (GC) has been traditionally used to analyze gas tracers in refuse, photoacoustic spectroscopy (PAS) might allow real-time measurements with reduced personnel costs and greater mobility and ease of use. Laboratory and field experiments were conducted to evaluate the efficacy of PAS for conducting gas tracer tests in landfills. Two tracer gases, difluoromethane (DFM) and sulfur hexafluoride (SF{sub 6}), were measured with a commercial PAS instrument. Relative measurement errors were invariant with tracer concentration but influenced by background gas: errors were 1-3% in landfill gas but 4-5% in air. Two partitioning gas tracer tests were conducted in an aerobic landfill, and limits of detection (LODs) were 3-4 times larger for DFM with PAS versus GC due to temporal changes in background signals. While higher LODs can be compensated by injecting larger tracer mass, changes in background signals increased the uncertainty in measured water saturations by up to 25% over comparable GC methods. PAS has distinct advantages over GC with respect to personnel costs and ease of use, although for field applications GC analyses of select samples are recommended to quantify instrument interferences.

  20. Optical layer development for thin films thermal conductivity measurement by pulsed photothermal radiometry

    NASA Astrophysics Data System (ADS)

    Martan, J.

    2015-01-01

    Measurement of thermal conductivity and volumetric specific heat of optically transparent thin films presents a challenge for optical-based measurement methods like pulsed photothermal radiometry. We present two approaches: (i) addition of an opaque optical layer to the surface and (ii) approximate correction of the mathematical model to incorporate semitransparency of the film. Different single layer and multilayer additive optical layers were tested. The materials of the optical layers were chosen according to analysis and measurement of their optical properties: emissivity and absorption coefficient. Presented are thermal properties' measurement results for 6 different thin films with wide range of thermal conductivity in three configurations of surface: as deposited, added Ti layer, and added Ti/TiAlSiN layer. Measurements were done in dependence on temperature from room temperature to 500 °C. The obtained thermal effusivity evolution in time after the laser pulse shows different effects of the surface layers: apparent effusivity change and time delay. Suitability of different measurement configurations is discussed and results of high temperature testing of different optical layers are presented.

  1. Optical layer development for thin films thermal conductivity measurement by pulsed photothermal radiometry.

    PubMed

    Martan, J

    2015-01-01

    Measurement of thermal conductivity and volumetric specific heat of optically transparent thin films presents a challenge for optical-based measurement methods like pulsed photothermal radiometry. We present two approaches: (i) addition of an opaque optical layer to the surface and (ii) approximate correction of the mathematical model to incorporate semitransparency of the film. Different single layer and multilayer additive optical layers were tested. The materials of the optical layers were chosen according to analysis and measurement of their optical properties: emissivity and absorption coefficient. Presented are thermal properties' measurement results for 6 different thin films with wide range of thermal conductivity in three configurations of surface: as deposited, added Ti layer, and added Ti/TiAlSiN layer. Measurements were done in dependence on temperature from room temperature to 500 °C. The obtained thermal effusivity evolution in time after the laser pulse shows different effects of the surface layers: apparent effusivity change and time delay. Suitability of different measurement configurations is discussed and results of high temperature testing of different optical layers are presented. PMID:25638108

  2. Optical layer development for thin films thermal conductivity measurement by pulsed photothermal radiometry

    SciTech Connect

    Martan, J.

    2015-01-15

    Measurement of thermal conductivity and volumetric specific heat of optically transparent thin films presents a challenge for optical-based measurement methods like pulsed photothermal radiometry. We present two approaches: (i) addition of an opaque optical layer to the surface and (ii) approximate correction of the mathematical model to incorporate semitransparency of the film. Different single layer and multilayer additive optical layers were tested. The materials of the optical layers were chosen according to analysis and measurement of their optical properties: emissivity and absorption coefficient. Presented are thermal properties’ measurement results for 6 different thin films with wide range of thermal conductivity in three configurations of surface: as deposited, added Ti layer, and added Ti/TiAlSiN layer. Measurements were done in dependence on temperature from room temperature to 500 °C. The obtained thermal effusivity evolution in time after the laser pulse shows different effects of the surface layers: apparent effusivity change and time delay. Suitability of different measurement configurations is discussed and results of high temperature testing of different optical layers are presented.

  3. Measurement of thin film thermal conductivity using the laser flash method.

    PubMed

    Ruoho, Mikko; Valset, Kjetil; Finstad, Terje; Tittonen, Ilkka

    2015-05-15

    We present a method to measure the in-plane thermal conductivity of thin films by the laser flash technique. The method uses a well-defined structure for the analysis. We have realized the structure by conformal deposition of ZnO films of different thicknesses using atomic layer deposition onto a 20 μm thick ion track etched polycarbonate membrane as substrate. By using this procedure we could determine the thermal conductivity of the deposited thin film from the total thermal diffusivity of the nanocomposite structures. The method has been used to obtain the in-plane thermal conductivity of the deposited ZnO layers within the thickness range of less than 100 nm. PMID:25900909

  4. Measurement of conductivity and permittivity on samples sealed in nuclear magnetic resonance tubes

    SciTech Connect

    Huang, W.; Angell, C. A.; Yarger, J. L.; Richert, R.

    2013-07-15

    We present a broadband impedance spectroscopy instrument designed to measure conductivity and/or permittivity for samples that are sealed in glass tubes, such as the standard 5 mm tubes used for nuclear magnetic resonance experiments. The calibrations and corrections required to extract the dielectric properties of the sample itself are outlined. It is demonstrated that good estimates of the value of dc-conductivity can be obtained even without correcting for the effects of glass or air on the overall impedance. The approach is validated by comparing data obtained from samples sealed in nuclear magnetic resonance tubes with those from standard dielectric cells, using glycerol and butylmethylimidazolium-hexafluorophosphate as respective examples of a molecular and an ionic liquid. This instrument and approach may prove useful for other studies of permittivity and conductivity where contact to the metal electrodes or to the ambient atmosphere needs to be avoided.

  5. Fabrication, characterization and measurement of thermal conductivity of Fe 3O 4 nanofluids

    NASA Astrophysics Data System (ADS)

    Abareshi, Maryam; Goharshadi, Elaheh K.; Mojtaba Zebarjad, Seyed; Khandan Fadafan, Hassan; Youssefi, Abbas

    2010-12-01

    Magnetite Fe 3O 4 nanoparticles were synthesized by a co-precipitation method at different pH values. The products were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and transmission electronic microscopy. Their magnetic properties were evaluated on a vibrating sample magnetometer. The results show that the shape of the particles is cubic and they are superparamagnetic at room temperature. Magnetic nanofluids were prepared by dispersing the Fe 3O 4 nanoparticles in water as a base fluid in the presence of tetramethyl ammonium hydroxide as a dispersant. The thermal conductivity of the nanofluids was measured as a function of volume fraction and temperature. The results show that the thermal conductivity ratio of the nanofluids increases with increase in temperature and volume fraction. The highest enhancement of thermal conductivity was 11.5% in the nanofluid of 3 vol% of nanoparticles at 40 °C. The experimental results were also compared with the theoretical models.

  6. 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.

  7. Insulator-protected mechanically controlled break junctions for measuring single-molecule conductance in aqueous environments

    NASA Astrophysics Data System (ADS)

    Muthusubramanian, N.; Galan, E.; Maity, C.; Eelkema, R.; Grozema, F. C.; van der Zant, H. S. J.

    2016-07-01

    We present a method to fabricate insulated gold mechanically controlled break junctions (MCBJ) by coating the metal with a thin layer of aluminum oxide using plasma enhanced atomic layer deposition. The Al2O3 thickness deposited on the MCBJ devices was varied from 2 to 15 nm to test the suppression of leakage currents in deionized water and phosphate buffered saline. Junctions coated with a 15 nm thick oxide layer yielded atomically sharp electrodes and negligible conductance counts in the range of 1 to 10-4 G0 (1 G0 = 77 μS), where single-molecule conductances are commonly observed. The insulated devices were used to measure the conductance of an amphiphilic oligophenylene ethynylene derivative in deionized water.

  8. Simultaneous measurement of electrical and thermal conductivities of suspended monolayer graphene

    NASA Astrophysics Data System (ADS)

    Wang, Haidong; Kurata, Kosaku; Fukunaga, Takanobu; Ago, Hiroki; Takamatsu, Hiroshi; Zhang, Xing; Ikuta, Tatsuya; Takahashi, Koji; Nishiyama, Takashi; Takata, Yasuyuki

    2016-06-01

    We measured both in-plane electrical and thermal properties of the same suspended monolayer graphene using a novel T-type sensor method. At room temperature, the values are about 240 000 Ω-1 m-1 and 2100 W m-1 K-1 for the electrical and thermal conductivities, respectively. Based on the Wiedemann-Franz law, the electrons have negligible contribution to the thermal conductivity of graphene, while the in-plane LA and TA modes phonons are the dominant heat carriers. In monolayer graphene, the absence of layer-layer and layer-substrate interactions enhances the contribution of long wave-length phonons to the heat transport and increases the thermal conductivity accordingly. The reported method and experimental data of suspended monolayer graphene are useful for understanding the basic physics and designing the future graphene electronic devices.

  9. Measurement of thin film thermal conductivity using the laser flash method

    NASA Astrophysics Data System (ADS)

    Ruoho, Mikko; Valset, Kjetil; Finstad, Terje; Tittonen, Ilkka

    2015-05-01

    We present a method to measure the in-plane thermal conductivity of thin films by the laser flash technique. The method uses a well-defined structure for the analysis. We have realized the structure by conformal deposition of ZnO films of different thicknesses using atomic layer deposition onto a 20 μm thick ion track etched polycarbonate membrane as substrate. By using this procedure we could determine the thermal conductivity of the deposited thin film from the total thermal diffusivity of the nanocomposite structures. The method has been used to obtain the in-plane thermal conductivity of the deposited ZnO layers within the thickness range of less than 100 nm.

  10. Measurement of conductivity and permittivity on samples sealed in nuclear magnetic resonance tubes

    NASA Astrophysics Data System (ADS)

    Huang, W.; Angell, C. A.; Yarger, J. L.; Richert, R.

    2013-07-01

    We present a broadband impedance spectroscopy instrument designed to measure conductivity and/or permittivity for samples that are sealed in glass tubes, such as the standard 5 mm tubes used for nuclear magnetic resonance experiments. The calibrations and corrections required to extract the dielectric properties of the sample itself are outlined. It is demonstrated that good estimates of the value of dc-conductivity can be obtained even without correcting for the effects of glass or air on the overall impedance. The approach is validated by comparing data obtained from samples sealed in nuclear magnetic resonance tubes with those from standard dielectric cells, using glycerol and butylmethylimidazolium-hexafluorophosphate as respective examples of a molecular and an ionic liquid. This instrument and approach may prove useful for other studies of permittivity and conductivity where contact to the metal electrodes or to the ambient atmosphere needs to be avoided.

  11. 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.

  12. 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.

  13. 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.

  14. A comparison of two transient methods of measuring thermal conductivity of particulate samples.

    NASA Technical Reports Server (NTRS)

    Scott, R. W.; Fountain, J. A.; West, E. A.

    1973-01-01

    A comparison is made of the line source (LS) method and the differential line source (DLS) method of measuring thermal conductivity of particulate materials in vacuum. The DLS method requires more instrumentation in the measuring circuitry (an additional amplifier and a differentiating circuit), but since it does not require a stable temperature to initiate a test, it does not need a sample temperature control system. DLS tests can be taken as the temperature in the samples is rising from liquid nitrogen temperature to room temperature. This eliminates the practice of extrapolating thermal conductivity over this large temperature range. Also, the advantages of reduced test time, data reduction time, and small sample temperature rise enable the experimenter to take about 7-12 DLS tests in the time of 2 LS tests. Test data from the two methods agree very well.

  15. Measurement of temperature-dependent viscosity and thermal conductivity of alumina and titania thermal oil nanofluids

    NASA Astrophysics Data System (ADS)

    Cieśliński, Janusz T.; Ronewicz, Katarzyna; Smoleń, Sławomir

    2015-12-01

    In this study the results of simultaneous measurements of dynamic viscosity, thermal conductivity, electrical conductivity and pH of two nanofluids, i.e., thermal oil/Al2O3 and thermal oil/TiO2 are presented. Thermal oil is selected as a base liquid because of possible application in ORC systems as an intermediate heating agent. Nanoparticles were tested at the concentration of 0.1%, 1%, and 5% by weight within temperature range from 20 °C to 60 °C. Measurement devices were carefully calibrated by comparison obtained results for pure base liquid (thermal oil) with manufacturer's data. The results obtained for tested nanofluids were compared with predictions made by use of existing models for liquid/solid particles mixtures.

  16. Conductive-cooled 2-micron laser development for wind and CO2 measurements

    NASA Astrophysics Data System (ADS)

    Mizutani, Kohei; Ishii, Shoken; Yasui, Motoaki; Itabe, Toshikazu; Sato, Atsushi; Asai, Kazuhiro; Fukuoka, Hirotake; Ishikawa, Takayoshi

    2012-11-01

    We have developing two types of 2micron conductive-cooled lasers for wind and CO2 measurements. One type of lasers is side pumped Tm,Ho:YLF laser operated at 20-40Hz. The laser rod is cooled down to -80C and laser diodes are operated at normal temperature in a vacuum container. With this type of laser, we have built up a coherent lidar system which is used to measure wind and CO2 concentration. Ho:YLF laser end-pumped by Tm:fiber laser is another type oscillator which will be operated at high repetition rate of 200-300 Hz in normal temperature. The laser will have an amplifier. These lasers are conductive-cooled, solid-state, eye-safe and suitable for space applications.

  17. Thermal conductivity and viscosity measurements of ethylene glycol-based Al2O3 nanofluids

    PubMed Central

    2011-01-01

    The dispersion and stability of nanofluids obtained by dispersing Al2O3 nanoparticles in ethylene glycol have been analyzed at several concentrations up to 25% in mass fraction. The thermal conductivity and viscosity were experimentally determined at temperatures ranging from 283.15 K to 323.15 K using an apparatus based on the hot-wire method and a rotational viscometer, respectively. It has been found that both thermal conductivity and viscosity increase with the concentration of nanoparticles, whereas when the temperature increases the viscosity diminishes and the thermal conductivity rises. Measured enhancements on thermal conductivity (up to 19%) compare well with literature values when available. New viscosity experimental data yield values more than twice larger than the base fluid. The influence of particle size on viscosity has been also studied, finding large differences that must be taken into account for any practical application. These experimental results were compared with some theoretical models, as those of Maxwell-Hamilton and Crosser for thermal conductivity and Krieger and Dougherty for viscosity. PMID:21711737

  18. Thermal conductivity of a film of single walled carbon nanotubes measured with infrared thermal imager

    NASA Astrophysics Data System (ADS)

    Feng, Ya; Inoue, Taiki; Xiang, Rong; Chiashi, Shohei; Maruyama, Shigeo

    Heat dissipation has restricted the modern miniaturization trend with the development of electronic devices. Theoretically proven to be with high axial thermal conductivity, single walled carbon nanotubes (SWNT) have long been expected to cool down the nanoscale world. Even though the tube-tube contact resistance limits the capability of heat transfer of the bulk film, the high intrinsic thermal conductivity of SWNT still glorify the application of films of SWNT network as a thermal interface material. In this work, we proposed a new method to straightly measure the thermal conductivity of SWNT film. We bridged two cantilevered Si thin plate with SWNT film, and kept a steady state heat flow in between. With the infrared camera to record the temperature distribution, the Si plates with known thermal conductivity can work as a reference to calculate the heat flux going through the SWNT film. Further, the thermal conductivity of the SWNT film can be obtained through Fourier's law after deducting the effect of thermal radiation. The sizes of the structure, the heating temperature, the vacuum degree and other crucial impact factors are carefully considered and analyzed. The author Y. F. was supported through the Advanced Integration Science Innovation Education and Research Consortium Program by the Ministry of Education, Culture, Sport, Science and Technology.

  19. Conductivities of pig dermis and subcutaneous fat measured with rectangular pulse electrical current

    SciTech Connect

    Cheng, K. |; Tarjan, P.P.; Mertz, P.M.

    1996-12-31

    The authors examined experimentally the relationship between perpendicular and tangential electrical conductivities, {sigma}, and peak current density J, in pig skin dermis and subcutaneous fat specimens by using a four-electrode measuring system with rectangular pulse electrical current (RPEC). They also investigated the relationship of the conductivity, {sigma}, vs. pulse rate, f. The rates were selected at 8, 32, 64, and 128 pulses per second (pps), and the pulse width was fixed at 140 {micro}s. These values are often used in vivo to enhance cutaneous regeneration with RPEC stimulation. It was found that the conductivities may be approximated to be {sigma}{sub d} = [{sigma}{sub dx}{sigma}{sub dy}{sigma}{sub dz}] = [0.38 S/m 0.38 S/m 0.27 S/m] for the skin dermis and {sigma}{sub f} = [{sigma}{sub fx}{sigma}{sub fy}{sigma}{sub fz}] = [0.074 S/m 0.074 S/m 0.045 S/m] for the subcutaneous fat in the conditions of this experiment. These findings implies that the conductivities of the pig skin dermis and subcutaneous fat are anisotropic, i.e., {sigma}{sub x} = {sigma}{sub y} {ne} {sigma}{sub z}. It was also found that the conductivities are independent of current density and pulse rate in the current range from 20 {micro}A/cm{sup 2} to 120 mA/cm{sup 2}.

  20. Estimating Concentrations of Road-Salt Constituents in Highway-Runoff from Measurements of Specific Conductance

    USGS Publications Warehouse

    Granato, Gregory E.; Smith, Kirk P.

    1999-01-01

    Discrete or composite samples of highway runoff may not adequately represent in-storm water-quality fluctuations because continuous records of water stage, specific conductance, pH, and temperature of the runoff indicate that these properties fluctuate substantially during a storm. Continuous records of water-quality properties can be used to maximize the information obtained about the stormwater runoff system being studied and can provide the context needed to interpret analyses of water samples. Concentrations of the road-salt constituents calcium, sodium, and chloride in highway runoff were estimated from theoretical and empirical relations between specific conductance and the concentrations of these ions. These relations were examined using the analysis of 233 highwayrunoff samples collected from August 1988 through March 1995 at four highway-drainage monitoring stations along State Route 25 in southeastern Massachusetts. Theoretically, the specific conductance of a water sample is the sum of the individual conductances attributed to each ionic species in solution-the product of the concentrations of each ion in milliequivalents per liter (meq/L) multiplied by the equivalent ionic conductance at infinite dilution-thereby establishing the principle of superposition. Superposition provides an estimate of actual specific conductance that is within measurement error throughout the conductance range of many natural waters, with errors of less than ?5 percent below 1,000 microsiemens per centimeter (?S/cm) and ?10 percent between 1,000 and 4,000 ?S/cm if all major ionic constituents are accounted for. A semi-empirical method (adjusted superposition) was used to adjust for concentration effects-superposition-method prediction errors at high and low concentrations-and to relate measured specific conductance to that calculated using superposition. The adjusted superposition method, which was developed to interpret the State Route 25 highway-runoff records, accounts for

  1. Summary of round robin measurements of radiation induced conductivity in Wesgo AL995 alumina

    SciTech Connect

    Zinkle, S.J.

    1996-10-01

    This existing data on radiation induced conductivity (RIC) measurements performed on the same heat of the IEA reference ceramic insulator are summarized. Six different sets of RIC measurements have been performed on Wesgo AL995 at dose rates between 10 Gy/s and 1 MGy/s. In general, good agreement was obtained between the different groups of researchers. The data indicate that the RIC at a test temperature of 400-500{degrees}C is approximately linear with ionizing dose rate up to {approximately}1000 Gy/s, and exhibits an approximately square root dependence on dose rate between 1 kGy/s and 1 MGy/s.

  2. A new TDR multiplexing system for reliable electrical conductivity and soil water content measurements

    NASA Astrophysics Data System (ADS)

    Weihermueller, Lutz; Huisman, Sander; Hermes, Normen; Pickel, Stefanie; Vereecken, Harry

    2013-04-01

    Time domain reflectometry (TDR) is a standard method to estimate soil water content and bulk soil electrical conductivity. In many applications, several TDR probes are installed in soil columns or field setups, and they are measured using a multiplexing system. It has been reported that commercially available multiplexers share a common ground, which might lead to inaccurate TDR measurements when probes are installed close together or at sites with high electromagnetic noise. Therefore, a new eight-channel differential multiplexer (50C81-SDM) was developed that allows communication with standard TDR equipment. The 50C81-SDM multiplexer was tested using measurement in electrolyte solutions and a sand tank. In contrast to multiplexers with a common ground, they showed no interference of closely spaced TDR probes. Measurements at a test site also showed the applicability of the 50C81-SDM multiplexer in an environment contaminated with high electromagnetic noise.

  3. Measurement of Apparent Thermal Conductivity and Laser Absorptivity of Individual Carbon Fibers

    NASA Astrophysics Data System (ADS)

    Liu, Jin-hui; Wang, Hai-dong; Hu, Yu-dong; Ma, Wei-gang; Zhang, Xing

    2015-11-01

    The apparent thermal conductivity (ATC) and laser absorptivity (α ) are important properties of miro/nano materials but a challenge to measure due to their small size. In this paper, a simple and effective method employing Raman spectroscopy together with electrical heating is developed to measure thermal properties of micro/nano wires. The sample used in the experiment is very simple and easy to fabricate. The ATC is obtained by measuring the temperature difference induced by changing the electrical heating power; the laser heating power is neither neglected nor needed. Using the laser heating temperature rise and the measured ATC, the absorbed laser power can be calculated. Three individual carbon fibers were studied using the presented method.

  4. A setup for simultaneously measureing the thermopower and electrical conductivity of μm-thickness specimens

    NASA Astrophysics Data System (ADS)

    Chen, Chih-Ting; Lee, P. C.; Chen, Y. Y.; Harutyungyan, Sergey

    2008-03-01

    We report the concept and configuration of our new setup for measurement of thermopower and electrical conductivity for μm-thickness specimens, especially for thermoelectric materials. It is very difficult and tedious to accurately measure the thermopower for specimens with thickness less than ˜100 μm due to the limitations of smallest size ˜25μm of thermocouples. Such are obvious when applied to the measurement of nanowire arrays and multilayer . In order to resolve these difficulties, we developed a new setup with integration of Pt-film thermometers and electrical electrodes on two sapphire chips used to clamp specimens with thickness >40 μm and cross section 2 x 3 mm^2. Use this setup the thermopower and electric conductivity can be measured simultaneously for temperature range 20-400 K. The advantages of the setup are (1) accuracy: the real temperatures of both sides of the sample can be obtained. (2) convenience for loading samples: just assemble the sample between the two microchips and make sure of a good thermal and electrical contacts. A Bi2Te3 nanowire array in AAO template was tested, the thermopower ˜ 50μV/K was measured for diameter ˜ 60 nm of nanowires.

  5. Test Rig for High-Temperature Thermopower and Electrical Conductivity Measurements

    NASA Astrophysics Data System (ADS)

    Boldrini, S.; Famengo, A.; Montagner, F.; Battiston, S.; Fiameni, S.; Fabrizio, M.; Barison, S.

    2013-07-01

    A high-temperature test rig to simultaneously measure electrical conductivity and thermopower is described. The apparatus allows to perform measurements in a controlled atmosphere or vacuum to protect oxygen-sensitive materials. A spring-loaded mounting placed in the cold zone reduces the thermal contact resistance between the sample and two metallic blocks (the hot side and the heat sink) even at high temperatures. The hot-side metal block is periodically heated to obtain the thermopower from the slope of Δ V versus Δ T. Conductivity is measured before each thermopower measurement by a linear four-wire method. The automatic data acquisition and analysis are controlled by a LabView-based interface. Two interchangeable setups are possible. The first one uses silver blocks and K-type thermocouples and is suitable for temperatures from 300 K to about 1000 K. The second one uses W blocks and S-type thermocouples to allow higher-temperature measurements since all the hot-zone parts are made of Al2O3, Pt or W. The device was tested using PdAg alloy and Ni rods and, for the low-temperature range, the NIST standard reference material 3451 (bismuth telluride), strictly confirming the reference data.

  6. Self-consistent magnetic properties of magnetite tracers optimized for magnetic particle imaging measured by ac susceptometry, magnetorelaxometry and magnetic particle spectroscopy

    PubMed Central

    Ludwig, Frank; Remmer, Hilke; Kuhlmann, Christian; Wawrzik, Thilo; Arami, Hamed; Ferguson, R. Mathew; Krishnan, Kannan M.

    2015-01-01

    Sensitivity and spatial resolution in Magnetic Particle Imaging are affected by magnetic properties of the nanoparticle tracers used during imaging. Here, we have carried out a comprehensive magnetic characterization of single-core iron oxide nanoparticles that were designed for MPI. We used ac susceptometry, fluxgate magnetorelaxometry, and magnetic particle spectroscopy to evaluate the tracer’s magnetic core size, hydrodynamic size, and magnetic anisotropy. Our results present a self-consistent set of magnetic and structural parameters for the tracers that is consistent with direct measurements of size using transmission electron microscopy and dynamic light scattering and that can be used to better understand their MPI performance. PMID:25729125

  7. Self-consistent magnetic properties of magnetite tracers optimized for magnetic particle imaging measured by ac susceptometry, magnetorelaxometry and magnetic particle spectroscopy

    NASA Astrophysics Data System (ADS)

    Ludwig, Frank; Remmer, Hilke; Kuhlmann, Christian; Wawrzik, Thilo; Arami, Hamed; Ferguson, R. Mathew; Krishnan, Kannan M.

    2014-06-01

    Sensitivity and spatial resolution in magnetic particle imaging are affected by magnetic properties of the nanoparticle tracers used during imaging. Here, we have carried out a comprehensive magnetic characterization of single-core iron oxide nanoparticles that were designed for MPI. We used ac susceptometry, fluxgate magnetorelaxometry, and magnetic particle spectroscopy to evaluate the tracer's magnetic core size, hydrodynamic size, and magnetic anisotropy. Our results present a self-consistent set of magnetic and structural parameters for the tracers that is consistent with direct measurements of size using transmission electron microscopy and dynamic light scattering and that can be used to better understand their MPI performance.

  8. Apparatus Measures Thermal Conductance Through a Thin Sample from Cryogenic to Room Temperature

    NASA Technical Reports Server (NTRS)

    Tuttle, James G.

    2009-01-01

    An apparatus allows the measurement of the thermal conductance across a thin sample clamped between metal plates, including thermal boundary resistances. It allows in-situ variation of the clamping force from zero to 30 lb (133.4 N), and variation of the sample temperature between 40 and 300 K. It has a special design feature that minimizes the effect of thermal radiation on this measurement. The apparatus includes a heater plate sandwiched between two identical thin samples. On the side of each sample opposite the heater plate is a cold plate. In order to take data, the heater plate is controlled at a slightly higher temperature than the two cold plates, which are controlled at a single lower temperature. The steady-state controlling power supplied to the hot plate, the area and thickness of samples, and the temperature drop across the samples are then used in a simple calculation of the thermal conductance. The conductance measurements can be taken at arbitrary temperatures down to about 40 K, as the entire setup is cooled by a mechanical cryocooler. The specific geometry combined with the pneumatic clamping force control system and the steady-state temperature control approach make this a unique apparatus.

  9. Conductive shield for ultra-low-field magnetic resonance imaging: Theory and measurements of eddy currents

    PubMed Central

    Zevenhoven, Koos C. J.; Busch, Sarah; Hatridge, Michael; Öisjöen, Fredrik; Ilmoniemi, Risto J.; Clarke, John

    2014-01-01

    Eddy currents induced by applied magnetic-field pulses have been a common issue in ultra-low-field magnetic resonance imaging. In particular, a relatively large prepolarizing field—applied before each signal acquisition sequence to increase the signal—induces currents in the walls of the surrounding conductive shielded room. The magnetic-field transient generated by the eddy currents may cause severe image distortions and signal loss, especially with the large prepolarizing coils designed for in vivo imaging. We derive a theory of eddy currents in thin conducting structures and enclosures to provide intuitive understanding and efficient computations. We present detailed measurements of the eddy-current patterns and their time evolution in a previous-generation shielded room. The analysis led to the design and construction of a new shielded room with symmetrically placed 1.6-mm-thick aluminum sheets that were weakly coupled electrically. The currents flowing around the entire room were heavily damped, resulting in a decay time constant of about 6 ms for both the measured and computed field transients. The measured eddy-current vector maps were in excellent agreement with predictions based on the theory, suggesting that both the experimental methods and the theory were successful and could be applied to a wide variety of thin conducting structures. PMID:24753629

  10. Measures of skin conductance and heart rate in alcoholic men and women during memory performance

    PubMed Central

    Poey, Alan; Ruiz, Susan Mosher; Marinkovic, Ksenija; Oscar-Berman, Marlene

    2015-01-01

    We examined abnormalities in physiological responses to emotional stimuli associated with long-term chronic alcoholism. Skin conductance responses (SCR) and heart rate (HR) responses were measured in 32 abstinent alcoholic (ALC) and 30 healthy nonalcoholic (NC) men and women undergoing an emotional memory task in an MRI scanner. The task required participants to remember the identity of two emotionally-valenced faces presented at the onset of each trial during functional magnetic resonance imaging (fMRI) scanning. After viewing the faces, participants saw a distractor image (an alcoholic beverage, nonalcoholic beverage, or scrambled image) followed by a single probe face. The task was to decide whether the probe face matched one of the two encoded faces. Skin conductance measurements (before and after the encoded faces, distractor, and probe) were obtained from electrodes on the index and middle fingers on the left hand. HR measurements (beats per minute before and after the encoded faces, distractor, and probe) were obtained by a pulse oximeter placed on the little finger on the left hand. We expected that, relative to NC participants, the ALC participants would show reduced SCR and HR responses to the face stimuli, and that we would identify greater reactivity to the alcoholic beverage stimuli than to the distractor stimuli unrelated to alcohol. While the beverage type did not differentiate the groups, the ALC group did have reduced skin conductance and HR responses to elements of the task, as compared to the NC group. PMID:26020002

  11. On-chip electrochemical microsystems for measurements of copper and conductivity in artificial seawater.

    PubMed

    Herzog, Grégoire; Moujahid, Waleed; Twomey, Karen; Lyons, Conor; Ogurtsov, Vladimir I

    2013-11-15

    The fabrication and characterisation of microelectrochemical sensors for Cu(2+) and conductivity suitable for operation in the marine environment are presented. The impact of the designs on sensor performance and their adequacy to operate in real conditions are discussed. The sensors, tailored to voltammetric and impedimetric measurements, are fabricated on silicon using photolithographic and thin film deposition techniques. The impedimetric sensor is made of Pt interdigitated electrodes which are used for the measurement of conductivity. The voltammetric sensors are based on a three electrode electrochemical cell with on-chip Ag|AgCl reference and Pt counter and working electrodes, used for detection of copper by underpotential deposition-stripping voltammetry at microelectrode array. The sensors operated in the Cu(2+) concentrations ranging from 0.48 to 3.97 µM with a limit of detection of 0.115 μM. The impact of the temperature, the pH and the salinity of the artificial seawater on the sensitivity for Cu(2+) detection are also considered. Measurements of copper concentration and conductivity are validated using certified reference materials and standard solutions. PMID:24148368

  12. Study of single-nucleotide polymorphisms by means of electrical conductance measurements

    PubMed Central

    Hihath, Joshua; Xu, Bingqian; Zhang, Peiming; Tao, Nongjian

    2005-01-01

    Understanding the complexities of DNA has been a hallmark of science for over a half century, and one of the important topics in DNA research is recognizing the occurrence of mutations in the base-stack. In this article, we present a study of SNPs by direct-contact electrical measurements to a single DNA duplex. We have used short, 11- and 12-bp dsDNA to investigate the change in conductance that occurs if a single base pair, a single base, or two separate bases in the stack are modified. All measurements are carried out in aqueous solution with the DNA chemically bound to the electrodes. These measurements demonstrate that the presence of a single base pair mismatch can be identified by the conductance of the molecule and can cause a change in the conductance of dsDNA by as much as an order of magnitude, depending on the specific details of the double helix and the single nucleotide polymorphism. PMID:16284253

  13. Thermal conductivity measurements via time-domain thermoreflectance for the characterization of radiation induced damage

    DOE PAGESBeta

    Cheaito, Ramez; Gorham, Caroline S.; Carnegie Mellon Univ., Pittsburgh, PA; Misra, Amit; Hattar, Khalid; Hopkins, Patrick E.

    2015-05-01

    The progressive build up of displacement damage and fission products inside different systems and components of a nuclear reactor can lead to significant defect formation, degradation, and damage of the constituent materials. This structural modification can highly influence the thermal transport mechanisms and various mechanical properties of solids. In this paper we demonstrate the use of time-domain thermoreflectance (TDTR), a non-destructive method capable of measuring the thermal transport in material systems from nano to bulk scales, to study the effect of radiation damage and the subsequent changes in the thermal properties of materials. We use TDTR to show that displacementmore » damage from ion irradiation can significantly reduce the thermal conductivity of Optimized ZIRLO, a material used as fuel cladding in several current nuclear reactors. We find that the thermal conductivity of copper-niobium nanostructured multilayers does not change with helium ion irradiation doses of up to 1015 cm-2 and ion energy of 200 keV suggesting that these structures can be used and radiation tolerant materials in nuclear reactors. We compare the effect of ion doses and ion beam energies on the measured thermal conductivity of bulk silicon. Results demonstrate that TDTR thermal measurements can be used to quantify depth dependent damage.« less

  14. Thermal conductivity measurements via time-domain thermoreflectance for the characterization of radiation induced damage

    SciTech Connect

    Cheaito, Ramez; Gorham, Caroline S.; Misra, Amit; Hattar, Khalid; Hopkins, Patrick E.

    2015-05-01

    The progressive build up of displacement damage and fission products inside different systems and components of a nuclear reactor can lead to significant defect formation, degradation, and damage of the constituent materials. This structural modification can highly influence the thermal transport mechanisms and various mechanical properties of solids. In this paper we demonstrate the use of time-domain thermoreflectance (TDTR), a non-destructive method capable of measuring the thermal transport in material systems from nano to bulk scales, to study the effect of radiation damage and the subsequent changes in the thermal properties of materials. We use TDTR to show that displacement damage from ion irradiation can significantly reduce the thermal conductivity of Optimized ZIRLO, a material used as fuel cladding in several current nuclear reactors. We find that the thermal conductivity of copper-niobium nanostructured multilayers does not change with helium ion irradiation doses of up to 1015 cm-2 and ion energy of 200 keV suggesting that these structures can be used and radiation tolerant materials in nuclear reactors. We compare the effect of ion doses and ion beam energies on the measured thermal conductivity of bulk silicon. Results demonstrate that TDTR thermal measurements can be used to quantify depth dependent damage.

  15. Flow Velocimetry for Weakly Conducting Electrolytes Based on High Resolution Lorentzforce Measurement

    NASA Astrophysics Data System (ADS)

    Ebert, R.; Vasilyan, S.; Wiederhold, A.

    We demonstrate that a flow velocity measurement can be transformed into a non-invasive force measurement by metering the dragforce acting on a system of magnets that is arranged around a flow channel. This method is called Lorentzforce velocimetry and has been developed in the last years in our institute. It is a highly feasible principle for materials with large conductivity like liquid metals. To evolve this method for weakly conducting fluids like salt water or molten glass the dragforce measurement is the challenging bottleneck. Here forces of 10-8 and less of the weightforce of the magnet system have to be resolved in the rather noisy environment of the flow channel. In this paper different force measurement techniques get tested and compared. In the first setup the drag-force is acting on the magnets that are hanging as a pendulum with 0.5 m long wires on a mounting. Here the displacement in the range of a few μm can be detected with a laser interferometer and another optical positioning sensor. For the second setup the magnet system is attached to a state of the art electromagnetic force compensation balance. The balance is used in an unusual orientation: It is turned by 90 degrees to measure the horizontally acting Lorentzforce. Different ways of getting the correct force signal out of the two measurement setups will be presented and discussed. For generalization of the measurement principle the Lorentzforce is determined for different fluid profiles. In addition to that we have developed new systematic noise reduction methods to increase the resolution of both force measurement techniques by a factor of ten or larger which we will present here.

  16. Automated multi-point mini-disk infiltrometer measurements of unsaturated hydraulic conductivity

    NASA Astrophysics Data System (ADS)

    Klipa, Vladimir; Sacha, Jan; Snehota, Michal; Dohnal, Michal; Zumr, David; Tacheci, Pavel

    2014-05-01

    Unsaturated hydraulic conductivity function K(h) is one of hydraulic characteristics needed for numerical modeling of water flow and solute transport in the vadose zone. Tension infiltrometer is advantageous tool to conduct the measurement of unsaturated hydraulic conductivity in field under near saturated conditions. Manually operated minidisk infiltrometers are often used for performing infiltration experiments, but their disadvantage is that permanent attendance is needed during experiments. Therefore automatization of the tension infiltrometer is desirable. A new automated multi-disk tension infiltrometer has been designed at the Faculty of Civil Engineering, Czech Technical University in Prague to facilitate the measurements of near-saturated hydraulic conductivity. Infiltration experiment performed by device is simultaneously carried out by six tension mini-disk infiltrometer modules forming a fixed matrix as they are held by a lightweight aluminum frame. This setup is divided into the two groups of three infiltrometers. Each triplet of modules is controlled by Mariotte`s bottle. Therefore it is possible to conduct six simultaneous infiltration experiments at two different pressure heads. Amount of infiltrated water is registered via changes of buoyant force of vertical bar attached to the weighing sensor in each infiltrometer module and recorded automatically using datalogger. Cumulative infiltration and volumetric flux are calculated and displayed in real time. Near saturated hydraulic conductivity is determined from cumulative infiltration data using nonlinear optimization and improved procedure of Zhang. Device developed was to date tested on four experimental locations. Two sites were arable land (Nucice and Kopaninsky stream) and two located in headwater catchments (Sumava and Jizera Mountains). Soils at experimental sites were classified as Cambisols (empirical van Genuchten parameters α and n ranged from 0.007 to 0.043 cm-1 and from 1.13 to 1

  17. 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.

  18. Apparent ac losses in helical BiPbSrCaCuO-2223/Ag multifilamentary tape measured by different potential taps at power frequencies

    NASA Astrophysics Data System (ADS)

    Majoros, M.; Glowacki, B. A.; Campbell, A. M.; Han, Z.; Vase, P.

    1999-03-01

    Transport ac losses in BiPbSrCaCuO-2223/Ag multifilamentary tape in form of a helix with a 3 mm gap between the turns were measured in frequency range 40-125 Hz. Different positions of potential taps on outer and inner surface of the tape were used. Potential wires were led along the tape axis as well as along the axis of the helix. At currents lower than the critical current a strong dependence of measured apparent ac losses on potential taps position and on the form of potential wires was found. Suitably wound contact-less pick-up coils to detect magnetic flux of different magnetic field components were also used. They allowed us to measure the `magnetisation' part of apparent losses even when the sample was in resistive state, as well as the losses at the gap of the tape. Comparison of the losses at the gap of the tape with the existing theoretical model was made.

  19. Getting saturated hydraulic conductivity from surface Ground-Penetrating Radar measurements inside a ring infiltrometer

    NASA Astrophysics Data System (ADS)

    Leger, E.; Saintenoy, A.; Coquet, Y.

    2013-12-01

    fixed time steps, during an infiltration of 5 cm of water, inside a ring infiltrometer. We used the ring to demarcate the infiltration area, and to create reflexions at known depths. GPR reflexions coming from the wetting front as well as the buried edges of the cylinder were recorded. Modeling of the infiltration were made using SWMS-2D, GPR data of the infiltration were computed using GprMax suite programs. We generated 2D water content profiles associated with a saturated hydraulic conductivity value, at each experimental time step with SWMS-2D. Then we convert those profiles to 2D permittivity profiles using the Complex Refractive Index Method relation, to compute the reflexion time of the wetting front. We found the saturated hydraulic conductivity of soil by minimizing the differences between experimental and simulated data. Our retrieved saturated hydraulic conductivity from GPR data was compared to disk infiltrometer measurements.

  20. Dielectric behavior and ac conductivity in Aurivillius Bi4Ti3O12 doped by antiferromagnetic BiFeO3

    NASA Astrophysics Data System (ADS)

    Wu, M. S.; Tian, Z. M.; Yuan, S. L.; Duan, H. N.; Qiu, Y.

    2012-06-01

    Bi5Ti3FeO15 ceramics were synthesized by the solid state reaction. XRD analysis shows a single phase perovskite structure with no impurities identified. Two obvious dielectric anomalies around 1007 and 1090 K were exhibited by this material, indicating that there are two phase transitions. While no peak was found in the tan δ-T curve. In addition, the conduction loss activation energies calculated at 476-639 K, 652-966 K, and 980-1095 K are 0.156, 0.262, and 0.707 eV, respectively. Polarization versus electric field hysteresis loops associated with 2Pr of 6.08 μC/cm2 and 2Ec of 59 kV/cm were obtained.

  1. Thermal conductivity measurements of high and low thermal conductivity films using a scanning hot probe method in the 3ω mode and novel calibration strategies.

    PubMed

    Wilson, Adam A; Muñoz Rojo, Miguel; Abad, Begoña; Perez, Jaime Andrés; Maiz, Jon; Schomacker, Jason; Martín-Gonzalez, Marisol; Borca-Tasciuc, Diana-Andra; Borca-Tasciuc, Theodorian

    2015-10-01

    This work discusses measurement of thermal conductivity (k) of films using a scanning hot probe method in the 3ω mode and investigates the calibration of thermal contact parameters, specifically the thermal contact resistance (R(th)C) and thermal exchange radius (b) using reference samples with different thermal conductivities. R(th)C and b were found to have constant values (with b = 2.8 ± 0.3 μm and R(th)C = 44,927 ± 7820 K W(-1)) for samples with thermal conductivity values ranging from 0.36 W K(-1) m(-1) to 1.1 W K(-1) m(-1). An independent strategy for the calibration of contact parameters was developed and validated for samples in this range of thermal conductivity, using a reference sample with a previously measured Seebeck coefficient and thermal conductivity. The results were found to agree with the calibration performed using multiple samples of known thermal conductivity between 0.36 and 1.1 W K(-1) m(-1). However, for samples in the range between 16.2 W K(-1) m(-1) and 53.7 W K(-1) m(-1), calibration experiments showed the contact parameters to have considerably different values: R(th)C = 40,191 ± 1532 K W(-1) and b = 428 ± 24 nm. Finally, this work demonstrates that using these calibration procedures, measurements of both highly conductive and thermally insulating films on substrates can be performed, as the measured values obtained were within 1-20% (for low k) and 5-31% (for high k) of independent measurements and/or literature reports. Thermal conductivity results are presented for a SiGe film on a glass substrate, Te film on a glass substrate, polymer films (doped with Fe nano-particles and undoped) on a glass substrate, and Au film on a Si substrate. PMID:26335503

  2. Low ac loss geometries in YBCO coated conductors and impact on conductor stability

    SciTech Connect

    Duckworth, Robert C; List III, Frederick Alyious; Paranthaman, Mariappan Parans; Rupich, M. W.; Zhang, W.; Xie, Y. Y.; Selvamanickam, V.

    2007-01-01

    Reduction of ac losses in applied ac fields can be accomplished through either the creation of filaments and bridging in YBCO coated conductors or an assembly of narrow width YBCO tapes. The ac losses for each of these geometries were measured at 77 K in perpendicular ac fields up to 100 mT. While ac loss reduction was achieved with YBCO filaments created through laser scribing and inkjet deposition, the assembly of stacked YBCO conductor provides an alternative method of ac loss reduction. When compared to a 4-mm wide YBCO coated conductor with a critical current of 60 A, the ac loss in a stack of 2-mm wide YBCO coated conductors with a similar total critical current was reduced. While the reduction in ac loss in a 2-mm wide stack coincided with the reduction in the engineering current density of the conductor, further reduction of ac loss was obtained through the splicing of the 2-mm wide tapes with low resistance solders. To better determine the practicality of these methods from a stability point of view, a numerical analysis was carried out to determine the influence of bridging and splicing on stability of a YBCO coated conductor for both liquid nitrogen-cooled and conduction cooled geometries.

  3. Fluid flow volume measurements using a capacitance/conductance probe system

    NASA Technical Reports Server (NTRS)

    Nguyen, T. X.; Arndt, G. D.; Carl, J. R.

    1995-01-01

    A probe system has been developed to measure the flow volume of a single fluid passing through an orifice or flow line. The system employs both capacitance and a conductance probe at the orifice, together with phase detection and data acquisition circuitry to measure flow volume and salinity under low or zero gravity conditions. A wide variety of frequencies can be used for the radio frequency (RF) signal source which is chosen primarily by the capacitance of the orifice probe and the fluid passing through the orifice. Rapid measurements are made using the reflected signal from the orifice probe to determine the 'instantaneous' permittivity of the fluid/gas mixture passing through. The 'instantaneous' measurements are integrated over time to determine flow volume. Analysis reveals that a narrow orifice helps to reduce non-linearities caused by differing flow rates. The geometry of 'deflectors' and 'directors' for the flowing fluid are important in obtaining linearity. Measured data shows that a volume measurement accuracy of approximately four percent can be consistently achieved. The prototype hardware system and associated software have been optimized and are available for further applications. The system has immediate application in low or zero gravity environments for measurements of urine or other liquid volumes.

  4. Lunar magnetic field measurements, electrical conductivity calculations and thermal profile inferences

    NASA Technical Reports Server (NTRS)

    Colburn, D. S.

    1971-01-01

    Steady magnetic field measurements of magnitude 30 to 100 gamma on the lunar surface impose problems of interpretation when coupled with the nondetectability of a lunar field at 0.4 lunar radius altitude and the limb induced perturbations of the solar wind at the Explorer orbit. The lunar time-varying magnetic field clearly indicates the presence of eddy currents in the lunar interior and permits calculation of an electrical conductivity profile. The problem is complicated by the day-night asymmetry of the moon's electromagnetic environment, the possible presence of the transverse magnetic mode, and the variable wave directions of the driving function. The electrical conductivity is calculated to be low near the surface, rising to a peak of .006/ohm meter at 250 km, dropping steeply inwards to a value of about .00005/ohm meter, and then rising toward the interior. A transition at 250 km depth from a high conductivity to a low conductivity material is inferred, suggesting an olivine-like core at approximately 800 C, although other models are possible.

  5. Measurement of local two-phase flow parameters of nanofluids using conductivity double-sensor probe

    PubMed Central

    2011-01-01

    A two-phase flow experiment using air and water-based γ-Al2O3 nanofluid was conducted to observe the basic hydraulic phenomenon of nanofluids. The local two-phase flow parameters were measured with a conductivity double-sensor two-phase void meter. The void fraction, interfacial velocity, interfacial area concentration, and mean bubble diameter were evaluated, and all of those results using the nanofluid were compared with the corresponding results for pure water. The void fraction distribution was flattened in the nanofluid case more than it was in the pure water case. The higher interfacial area concentration resulted in a smaller mean bubble diameter in the case of the nanofluid. This was the first attempt to measure the local two-phase flow parameters of nanofluids using a conductivity double-sensor two-phase void meter. Throughout this experimental study, the differences in the internal two-phase flow structure of the nanofluid were identified. In addition, the heat transfer enhancement of the nanofluid can be resulted from the increase of the interfacial area concentration which means the available area of the heat and mass transfer. PMID:21711823

  6. Electronic conductivity measurement of yttria-stabilized zirconia solid electrolytes by a transient technique

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Zhu, Liangzhu; Virkar, Anil V.

    2016-01-01

    A new oxygen permeation technique is developed to measure the electronic conductivity of yttria-stabilized zirconia (YSZ). The permeation cell is a YSZ disc with an embedded Pt probe and a cavity at the center. Two porous platinum electrodes are applied on the disc surfaces. By applying a small DC bias (0.03 V) across one surface electrode and the embedded probe, oxygen is pumped into the YSZ disc and stored in the cavity. In steady state, a stable Nernst potential is developed between the cavity and the outer surfaces. The Nernst voltage is very close to the applied voltage since YSZ is essentially an ionic conductor. When the DC bias is removed, oxygen permeates out of the cavity leading to a decay of the Nernst potential. Electronic conductivity of YSZ corresponding to the ambient oxygen pressure (∼0.21 atm) is determined by analyzing the time dependence of the decay of Nernst potential. The measured electronic conductivity is in good agreement with values reported in the literature.

  7. Thermal resistance technique for measuring the thermal conductivity of thin microporous membranes

    NASA Astrophysics Data System (ADS)

    García-Payo, M. C.; Izquierdo-Gil, M. A.

    2004-11-01

    The thermal resistance technique for measurement of the thermal conductivity of microporous thin membranes is described. A modified and enhanced Lees' disc apparatus was used. Several samples of membranes were held between a hot copper plate and a cold copper base, and the temperature differences between them were measured using thermocouples under steady-state conditions. The accuracy and reliability of the results were checked by means of a comparative test on a standard bad conductor. A dependence of the thermal resistance on the thickness of the samples was observed. The thermal conductivity of the membrane was deduced from a linear fit of the thermal resistance versus the number of membranes. Better results were obtained when the air layer effect was considered in the linear fit. Several models found in the literature and based on empirical correlations or on theoretical structure models (such as Maxwell's, Fricke's or Misra's models) were tested in order to calculate the effective thermal conductivity of the membrane. These values were compared with the experimental ones and they showed a better agreement than the parallel model commonly used in the literature for the membranes studied in this work.

  8. A flash heating method for measuring thermal conductivity at high pressure and temperature: Application to Pt

    NASA Astrophysics Data System (ADS)

    McWilliams, R. Stewart; Konôpková, Zuzana; Goncharov, Alexander F.

    2015-10-01

    The transport properties of matter at high pressure and temperature are critical components in planetary interior models, yet are challenging to measure or predict at relevant conditions. Using a novel flash-heating method for in-situ high-temperature and high-pressure thermal conductivity measurement, we study the transport properties of platinum to 55 GPa and 2300 K. Experimental data reveal a simple high-pressure and high-temperature behavior of the thermal conductivity that is linearly dependent on both pressure and temperature. The corresponding electrical resistivity evaluated through the Wiedemann-Franz-Lorenz law is nearly constant along the melting curve, experimentally confirming the prediction of Stacey for an ideal metal. This study together with prior first-principles predictions of transport properties in Al and Fe at extreme conditions suggests a broad applicability of Stacey's law to diverse metals, supporting a limit on the thermal conductivity of iron at the conditions of Earth's outer core of 90 W/mK or less.

  9. Measurement of local two-phase flow parameters of nanofluids using conductivity double-sensor probe

    NASA Astrophysics Data System (ADS)

    Park, Yu Sun; Chang, Soon Heung

    2011-12-01

    A two-phase flow experiment using air and water-based γ-Al2O3 nanofluid was conducted to observe the basic hydraulic phenomenon of nanofluids. The local two-phase flow parameters were measured with a conductivity double-sensor two-phase void meter. The void fraction, interfacial velocity, interfacial area concentration, and mean bubble diameter were evaluated, and all of those results using the nanofluid were compared with the corresponding results for pure water. The void fraction distribution was flattened in the nanofluid case more than it was in the pure water case. The higher interfacial area concentration resulted in a smaller mean bubble diameter in the case of the nanofluid. This was the first attempt to measure the local two-phase flow parameters of nanofluids using a conductivity double-sensor two-phase void meter. Throughout this experimental study, the differences in the internal two-phase flow structure of the nanofluid were identified. In addition, the heat transfer enhancement of the nanofluid can be resulted from the increase of the interfacial area concentration which means the available area of the heat and mass transfer.

  10. Graphene Nanopore Support System for Simultaneous High-Resolution AFM Imaging and Conductance Measurements

    PubMed Central

    2015-01-01

    Accurately defining the nanoporous structure and sensing the ionic flow across nanoscale pores in thin films and membranes has a wide range of applications, including characterization of biological ion channels and receptors, DNA sequencing, molecule separation by nanoparticle films, sensing by block co-polymers films, and catalysis through metal–organic frameworks. Ionic conductance through nanopores is often regulated by their 3D structures, a relationship that can be accurately determined only by their simultaneous measurements. However, defining their structure–function relationships directly by any existing techniques is still not possible. Atomic force microscopy (AFM) can image the structures of these pores at high resolution in an aqueous environment, and electrophysiological techniques can measure ion flow through individual nanoscale pores. Combining these techniques is limited by the lack of nanoscale interfaces. We have designed a graphene-based single-nanopore support (∼5 nm thick with ∼20 nm pore diameter) and have integrated AFM imaging and ionic conductance recording using our newly designed double-chamber recording system to study an overlaid thin film. The functionality of this integrated system is demonstrated by electrical recording (<10 pS conductance) of suspended lipid bilayers spanning a nanopore and simultaneous AFM imaging of the bilayer. PMID:24581087

  11. High temperature thermal conductivity measurements on lanthanum sulfides using the flash method

    NASA Technical Reports Server (NTRS)

    Vandersande, J. W.; Wood, C.; Zoltan, A.; Whittenberger, D.

    1988-01-01

    In the past, high temperature specific heat and hence thermal conductivity measurements, using the flash method have not been very accurate. This is due to the difficulty of exactly determining the amount of heat deposited on the front face of a sample during each flash. This problem has now been solved by sputtering a thin layer of graphite on the standard reference and test samples. Data taken shows that the amount of heat deposited can now be determined to within about 2 percent resulting in more accurate thermal conductivity data. The results of measurements on several lanthanum sulfides with stoichiometries between LaS(1.35) and LaS(1.48) are reported and show a minimum in the lattice thermal conductivity at a composition of around LaS(1.41). This is believed to be due to the scattering of low-frequency phonons by large defects, i.e., second phase material (beta-phase) and pores.

  12. A high sensitivity ultralow temperature RF conductance and noise measurement setup.

    PubMed

    Parmentier, F D; Mahé, A; Denis, A; Berroir, J-M; Glattli, D C; Plaçais, B; Fève, G

    2011-01-01

    We report on the realization of a high sensitivity RF noise measurement scheme to study small current fluctuations of mesoscopic systems at milli-Kelvin temperatures. The setup relies on the combination of an interferometric amplification scheme and a quarter-wave impedance transformer, allowing the measurement of noise power spectral densities with gigahertz bandwidth up to five orders of magnitude below the amplifier noise floor. We simultaneously measure the high frequency conductance of the sample by derivating a portion of the signal to a microwave homodyne detection. We describe the principle of the setup, as well as its implementation and calibration. Finally, we show that our setup allows to fully characterize a subnanosecond on-demand single electron source. More generally, its sensitivity and bandwidth make it suitable for applications manipulating single charges at GHz frequencies. PMID:21280842

  13. UNSATURATED FLOW IN A CENTRIFUGAL FIELD: MEASUREMENT OF HYDRAULIC CONDUCTIVITY AND TESTING OF DARCY'S LAW.

    USGS Publications Warehouse

    Nimmo, J.R.; Rubin, J.; Hammermeister, D.P.

    1987-01-01

    A method has been developed to establish steady flow of water in unsaturated soil sample spinning in a centrifuge. Theoretical analysis predicts moisture conditions in the sample that depend strongly on soil type and certain operating parameter. For Oakley sand, measurements of flux, water content, and matric potential during and after centrifugation verify that steady state flow can be achieved. Experiments have confirmed the theoretical prediction of a nearly uniform moisture distribution for this medium and have demonstrated that the flow can be effectively one-dimensional. The method was used for steady state measurements of hydraulic conductivity K for relatively dry soil, giving values at low as 7. 6 multiplied by 10** minus **1**1 m/s with data obtained in a few hours. Darcy's law was tested by measuring K for different centrifugal driving forces but with the same water content.

  14. Measurement of the high-frequency complex permittivity and conductivity of magnetic fluids

    NASA Astrophysics Data System (ADS)

    Fannin, P. C.; Charles, S. W.; Vincent, D.; Giannitsis, A. T.

    2002-11-01

    Measurements of the permittivity, ɛ( ω)= ɛ'( ω)-i ɛ″( ω), and conductivity, σ( ω)= ωɛ0ɛ″( ω), of two ferrofluid samples of ferrite particles in a hydrocarbon carrier, isopar M, over the frequency range 0.1-6 GHz are presented. It is shown that the sample with the highest concentration of particles has the highest permittivity and by means of profile fitting it is demonstrated, for the first time, that σ( ω) has a Debye-type profile. The frequency limitation of the used measurement technique is highlighted and a possible alternative technique capable of measuring in the 20-30 GHz region is presented.

  15. G-300: The first French Getaway Special microgravity measurements of fluid thermal conductivity

    NASA Technical Reports Server (NTRS)

    Perron, J. C.; Chretien, P.; Garnier, C.; Lecaude, N.

    1987-01-01

    Thermal conductivity measurements on liquids are difficult to perform on Earth because of thermal motions due to convection. In microgravity, the convection due to buoyancy is evanescent, and a strong reduction of Rayleigh and Nusselt numbers can be expected. Three low viscosity liquids are selected to carry out the measurements; distilled water (standard) and two silicone oils. A modified hot plate method with a simplified guard ring is used; the reduction of convective motions permitted the use in the experimental cells of larger interplate distances and/or temperature differences than in Earth measurements, improving the accuracy. Comparisons between Earth and orbit results may help to understand the convection occurrence in the cells. Thermal, vibrational, and EMI tests have proved that the design satisfies the NASA requirements.

  16. A high sensitivity ultralow temperature RF conductance and noise measurement setup

    SciTech Connect

    Parmentier, F. D.; Mahe, A.; Denis, A.; Berroir, J.-M.; Glattli, D. C.; Placais, B.; Feve, G.

    2011-01-15

    We report on the realization of a high sensitivity RF noise measurement scheme to study small current fluctuations of mesoscopic systems at milli-Kelvin temperatures. The setup relies on the combination of an interferometric amplification scheme and a quarter-wave impedance transformer, allowing the measurement of noise power spectral densities with gigahertz bandwidth up to five orders of magnitude below the amplifier noise floor. We simultaneously measure the high frequency conductance of the sample by derivating a portion of the signal to a microwave homodyne detection. We describe the principle of the setup, as well as its implementation and calibration. Finally, we show that our setup allows to fully characterize a subnanosecond on-demand single electron source. More generally, its sensitivity and bandwidth make it suitable for applications manipulating single charges at GHz frequencies.

  17. Critical Review of Industrial Techniques for Thermal-Conductivity Measurements of Thermal Insulation Materials

    NASA Astrophysics Data System (ADS)

    Hammerschmidt, Ulf; Hameury, Jacques; Strnad, Radek; Turzó-Andras, Emese; Wu, Jiyu

    2015-07-01

    This paper presents a critical review of current industrial techniques and instruments to measure the thermal conductivity of thermal insulation materials, especially those insulations that can operate at temperatures above and up to . These materials generally are of a porous nature. The measuring instruments dealt with here are selected based on their maximum working temperature that should be higher than at least . These instruments are special types of the guarded hot-plate apparatus, the guarded heat-flow meter, the transient hot-wire and hot-plane instruments as well as the laser/xenon flash devices. All technical characteristics listed are quoted from the generally accessible information of the relevant manufacturers. The paper includes rankings of the instruments according to their standard retail price, the maximum sample size, and maximum working temperature, as well as the minimum in their measurement range.

  18. New contactless eddy current non-destructive methodology for electric conductivity measurement

    NASA Astrophysics Data System (ADS)

    Bouchala, T.; Abdelhadi, B.; Benoudjit, A.

    2015-01-01

    In this paper, a new method of contactless electric conductivity measurement is developed. This method is essentially based on the association of the coupled electric field forward model, which we have recently developed, with a simple and efficient research algorithm. The proposed method is very fast because 1.3 s are sufficient to calculate electric conductivity, in a CPU of 2 GHz and RAM of 3 GB, for a starting research interval of 1.72-17.2 %IACS and tolerance of 1.72 × 10- 5 %IACS. The study of the calculation time according to mesh density and starting interval width has showed that an optimal choice has to be made in order to improve the rapidity while preserving its precision. Considering its rapidity and its simplicity of implementation, this method is more adapted, in comparison to direct current techniques using Van der Pauw geometry, for automated applications.

  19. Separation of conductivity and distance measurements for eddy current nondestructive inspection of graphite composite materials

    NASA Astrophysics Data System (ADS)

    Dufour, Isabelle; Placko, Dominique

    1993-06-01

    This article deals with the study of a process based on the principle of eddy current sensors for the nondestructive evaluation of graphite composite plates. This research has been carried out in the Laboratoire d'Electricitd Signaux et Robotique by the team working on datacollecting sensors for robotics in collaboration with Aerospatiale. Eddy current sensors are characterized by their impedance, which varies when a conducting material is approached in their sensitive area. For a given sensor, the output signal depends directly on the electrical and geometrical properties of the object. In the case discussed here, the interesting data are the distance between the sensor and the object, and its local conductivity. In order to invert the relationships between the sensor signal and the properties of the material, an external parametrical model has been developed. A scanning of the surface with a sensor designed for good spatial resolution measurements gives two accurate maps of the useful data.

  20. Repeatability and Reproducibility of Compression Strength Measurements Conducted According to ASTM E9

    NASA Technical Reports Server (NTRS)

    Luecke, William E.; Ma, Li; Graham, Stephen M.; Adler, Matthew A.

    2010-01-01

    Ten commercial laboratories participated in an interlaboratory study to establish the repeatability and reproducibility of compression strength tests conducted according to ASTM International Standard Test Method E9. The test employed a cylindrical aluminum AA2024-T351 test specimen. Participants measured elastic modulus and 0.2 % offset yield strength, YS(0.2 % offset), using an extensometer attached to the specimen. The repeatability and reproducibility of the yield strength measurement, expressed as coefficient of variations were cv(sub r)= 0.011 and cv(sub R)= 0.020 The reproducibility of the test across the laboratories was among the best that has been reported for uniaxial tests. The reported data indicated that using diametrically opposed extensometers, instead of a single extensometer doubled the precision of the test method. Laboratories that did not lubricate the ends of the specimen measured yield stresses and elastic moduli that were smaller than those measured in laboratories that lubricated the specimen ends. A finite element analysis of the test specimen deformation for frictionless and perfect friction could not explain the discrepancy, however. The modulus measured from stress-strain data were reanalyzed using a technique that finds the optimal fit range, and applies several quality checks to the data. The error in modulus measurements from stress-strain curves generally increased as the fit range decreased to less than 40 % of the stress range.

  1. Design of a dual chamber heat conduction calorimeter for ultrasonic beam measurement

    NASA Astrophysics Data System (ADS)

    Ong, Hang See

    1997-12-01

    The recent emergence of medical ultrasound dosimetry in terms of Thermal and Mechanical Indices gives rise to the need for a device that is capable of measuring ultrasonic output power quickly and accurately. In the research project described in this dissertation, a dual chamber heat conduction calorimeter (HCC) is designed, built, and tested for the purpose of measuring ultrasonic output power of clinical diagnostic ultrasound devices. The HCC is composed of two identical water filled Aluminum wells housed in two separated compartments of an insulated box. The two compartments form the measuring and reference chambers of the calorimeter. The wells are sealed with plastic membranes that constitute the entrance window for the ultrasound. The bottom of each well is stuffed with a 4cm layer of 0.5cm thick rubber pads. These pads serve as a sonic-to-heat energy exchanger. A small resistive heater is embedded in both rubber pads for calibration purposes. Heat is measured with a series of Seebeck effect thermoelectric devices (thermopiles) sandwiched between the well and the heat sink surrounding the wells. The output voltage signal from the thermopiles is amplified, digitized, then analyzed and displayed in term of Thermal Index with a PC-based system. An optimum measurement technique is derived from an electric circuit model that is representative of the HCC. The performance and sensitivity of the HCC is tested and measured, initially with the embedded resistive heaters, then with an experimental transducer, and lastly with transducers from clinical ultrasound scanners.

  2. Application of independent component analysis to ac dipole based optics measurement and correction at the Relativistic Heavy Ion Collider

    NASA Astrophysics Data System (ADS)

    Shen, X.; Lee, S. Y.; Bai, M.; White, S.; Robert-Demolaize, G.; Luo, Y.; Marusic, A.; Tomás, R.

    2013-11-01

    Correction of beta-beat is of great importance for performance improvement of high energy accelerators, like the Relativistic Hadron Ion Collider (RHIC). At RHIC, using the independent component analysis method, linear optical functions are extracted from the turn by turn beam position data of the ac dipole driven betatron oscillation. Despite the constraint of a limited number of available quadrupole correctors at RHIC, a global beta-beat correction scheme using a beta-beat response matrix method was developed and experimentally demonstrated. In both rings, a factor of 2 or better reduction of beta-beat was achieved within available beam time. At the same time, a new scheme of using horizontal closed orbit bump at sextupoles to correct beta-beat in the arcs was demonstrated in the Yellow ring of RHIC at beam energy of 255 GeV, and a peak beta-beat of approximately 7% was achieved.

  3. Conductive Sphere in a Radio Frequency Field: Theory and Applications to Positioners, Heating, and Noncontact Measurements

    NASA Technical Reports Server (NTRS)

    Jackson, H. W.; Watkins, J. L.; Chung, S.; Wagner, P.

    1996-01-01

    An electrically conductive spherical sample located in an electromagnetic field excited by rf (radio frequency) current in a system of coaxial coils is treated theoretically. Maxwell's equations are solved exactly and all integrals in the formulas for the fields are evaluated analytically for the case where the sphere is on the axis and the coil system is modeled by a stack of filamentary circular loops. Formulas are also derived for electromagnetic force exerted on the sphere, excess impedance in the coil system due to the presence of the sphere, and power absorbed by the sphere. All integrals in those formulas have been evaluated analytically. Force measurements are presented and they are in excellent agreement with the new theory. A low-power electromagnetic levitator that is accurately described by the theory has been demonstrated and is discussed. Experimental measurements of excess impedance are presented and compared with theory, and those results are used to demonstrate an accurate noncontact method for determining electrical conductivity. Theoretical formulas for power absorption are evaluated numerically and their usefulness in both rf heating and in making noncontact measurements of a number of thermophysical properties of materials is discussed.

  4. A microprobe technique for simultaneously measuring thermal conductivity and Seebeck coefficient of thin films

    NASA Astrophysics Data System (ADS)

    Zhang, Yanliang; Hapenciuc, Claudiu L.; Castillo, Eduardo E.; Borca-Tasciuc, Theodorian; Mehta, Rutvik J.; Karthik, Chinnathambi; Ramanath, Ganpati

    2010-02-01

    We demonstrate a microprobe technique that can simultaneously measure thermal conductivity κ and Seebeck coefficient α of thin films. In this technique, an alternative current joule-heated V-shaped microwire that serves as heater, thermometer and voltage electrode, locally heats the thin film when contacted with the surface. The κ is extracted from the thermal resistance of the microprobe and α from the Seebeck voltage measured between the probe and unheated regions of the film by modeling heat transfer in the probe, sample and their contact area, and by calibrations with standard reference samples. Application of the technique on sulfur-doped porous Bi2Te3 and Bi2Se3 films reveals α =-105.4 and 1.96 μV/K, respectively, which are within 2% of the values obtained by independent measurements carried out using microfabricated test structures. The respective κ values are 0.36 and 0.52 W/mK, which are significantly lower than the bulk values due to film porosity, and are consistent with effective media theory. The dominance of air conduction at the probe-sample contact area determines the microscale spatial resolution of the technique and allows probing samples with rough surfaces.

  5. Integrating multiple scales of hydraulic conductivity measurements in training image-based stochastic models

    NASA Astrophysics Data System (ADS)

    Mahmud, K.; Mariethoz, G.; Baker, A.; Sharma, A.

    2015-01-01

    Hydraulic conductivity is one of the most critical and at the same time one of the most uncertain parameters in many groundwater models. One problem commonly faced is that the data are usually not collected at the same scale as the discretized elements used in a numerical model. Moreover, it is common that different types of hydraulic conductivity measurements, corresponding to different spatial scales, coexist in a studied domain, which have to be integrated simultaneously. Here we address this issue in the context of Image Quilting, one of the recently developed multiple-point geostatistics methods. Based on a training image that represents fine-scale spatial variability, we use the simplified renormalization upscaling method to obtain a series of upscaled training images that correspond to the different scales at which measurements are available. We then apply Image Quilting with such a multiscale training image to be able to incorporate simultaneously conditioning data at several spatial scales of heterogeneity. The realizations obtained satisfy the conditioning data exactly across all scales, but it can come at the expense of a small approximation in the representation of the physical scale relationships. In order to mitigate this approximation, we iteratively apply a kriging-based correction to the finest scale that ensures local conditioning at the coarsest scales. The method is tested on a series of synthetic examples where it gives good results and shows potential for the integration of different measurement methods in real-case hydrogeological models.

  6. Scanning ion conductance microscopy (SICM): from measuring cell mechanical properties to guiding neuron growth

    NASA Astrophysics Data System (ADS)

    Pellegrino, Mario; Orsini, Paolo; Pellegrini, Monica; Tognoni, Elisabetta; Ascoli, Cesare; Baschieri, Paolo; Dinelli, Franco

    2013-04-01

    Scanning ion conductance microscopy (SICM) is a type of scanning probe microscopy based on the continuous measurement of an ion current flowing through a pipette filled with an electrolyte solution, while the pipette apex approaches a non-conductive sample. This technique can be operated in environmental conditions such as those of cell cultures and does not require a direct contact between probe and sample. It is therefore particularly suitable for the investigation of living specimens. SICM was initially proposed as an instrument that could obtain topographic 3D images with high resolution. Later, simple modifications have been devised to apply a mechanical stimulus to the specimen via a solution flux coming out from the pipette aperture. This modified setup has been employed to measure cell membrane elasticity and to guide the growth cones of neurons for tens of micrometers, by means of repeated non-contact scanning. Both these applications require an accurate measurement of the mechanical forces acting on the cell surface, which can be obtained by combining SICM, Atomic force microscopy (AFM) and inverted optical microscopy in the same apparatus. In this configuration, a SICM pipette is approached to an AFM cantilever while monitoring the cantilever deflection as a function of the pressure applied to the pipette and the relative distance. In addition, the pipette aperture can be imaged in situ by exploiting the AFM operation, so that all the experimental parameters can be effectively controlled in the investigation of pressure effects on living cells.

  7. Mind the bubbles: achieving stable measurements of maximum hydraulic conductivity through woody plant samples

    PubMed Central

    Espino, Susana; Schenk, H. Jochen

    2011-01-01

    The maximum specific hydraulic conductivity (kmax) of a plant sample is a measure of the ability of a plants’ vascular system to transport water and dissolved nutrients under optimum conditions. Precise measurements of kmax are needed in comparative studies of hydraulic conductivity, as well as for measuring the formation and repair of xylem embolisms. Unstable measurements of kmax are a common problem when measuring woody plant samples and it is commonly observed that kmax declines from initially high values, especially when positive water pressure is used to flush out embolisms. This study was designed to test five hypotheses that could potentially explain declines in kmax under positive pressure: (i) non-steady-state flow; (ii) swelling of pectin hydrogels in inter-vessel pit membranes; (iii) nucleation and coalescence of bubbles at constrictions in the xylem; (iv) physiological wounding responses; and (v) passive wounding responses, such as clogging of the xylem by debris. Prehydrated woody stems from Laurus nobilis (Lauraceae) and Encelia farinosa (Asteraceae) collected from plants grown in the Fullerton Arboretum in Southern California, were used to test these hypotheses using a xylem embolism meter (XYL'EM). Treatments included simultaneous measurements of stem inflow and outflow, enzyme inhibitors, stem-debarking, low water temperatures, different water degassing techniques, and varied concentrations of calcium, potassium, magnesium, and copper salts in aqueous measurement solutions. Stable measurements of kmax were observed at concentrations of calcium, potassium, and magnesium salts high enough to suppress bubble coalescence, as well as with deionized water that was degassed using a membrane contactor under strong vacuum. Bubble formation and coalescence under positive pressure in the xylem therefore appear to be the main cause for declining kmax values. Our findings suggest that degassing of water is essential for achieving stable and precise

  8. In vitro and in vivo measures of evoked excitatory and inhibitory conductance dynamics in sensory cortices.

    PubMed

    Monier, C; Fournier, J; Frégnac, Y

    2008-04-30

    In order to better understand the synaptic nature of the integration process operated by cortical neurons during sensory processing, it is necessary to devise quantitative methods which allow one to infer the level of conductance change evoked by the sensory stimulation and, consequently, the dynamics of the balance between excitation and inhibition. Such detailed measurements are required to characterize the static versus dynamic nature of the non-linear interactions triggered at the single cell level by sensory stimulus. This paper primarily reviews experimental data from our laboratory based on direct conductance measurements during whole-cell patch clamp recordings in two experimental preparations: (1) in vitro, during electrical stimulation in the visual cortex of the rat and (2) in vivo, during visual stimulation, in the primary visual cortex of the anaesthetized cat. Both studies demonstrate that shunting inhibition is expressed as well in vivo as in vitro. Our in vivo data reveals that a high level of diversity is observed in the degree of interaction (from linear to non-linear) and in the temporal interplay (from push-pull to synchronous) between stimulus-driven excitation (E) and inhibition (I). A detailed analysis of the E/I balance during evoked spike activity further shows that the firing strength results from a simultaneous decrease of evoked inhibition and increase of excitation. Secondary, the paper overviews the various computational methods used in the literature to assess conductance dynamics, measured in current clamp as well as in voltage clamp in different neocortical areas and species, and discuss the consistency of their estimations. PMID:18215425

  9. ac Stark shift measurements of the clock transition in cold Cs atoms: Scalar and tensor light shifts of the D2 transition

    NASA Astrophysics Data System (ADS)

    Costanzo, G. A.; Micalizio, S.; Godone, A.; Camparo, J. C.; Levi, F.

    2016-06-01

    The ac Stark shift, or light shift, is a physical phenomenon that plays a fundamental role in many applications ranging from basic atomic physics to applied quantum electronics. Here, we discuss experiments testing light-shift theory in a cold-atom cesium fountain clock for the Cs D2 transition (i.e., 6 2S1 /2→6 2P3 /2 at 852 nm). Cold-atom fountains represent a nearly ideal system for the study of light shifts: (1) The atoms can be perturbed by a field of arbitrary character (e.g., coherent field or nonclassical field); (2) there are no trapping fields to complicate data interpretation; (3) the probed atoms are essentially motionless in their center-of-mass reference frame, T ˜ 1 μK; and (4) the atoms are in an essentially collisionless environment. Moreover, in the present work the resolution of the Cs excited-state hyperfine splittings implies that the D2 ac Stark shift contains a nonzero tensor polarizability contribution, which does not appear in vapor phase experiments due to Doppler broadening. Here, we test the linearity of the ac Stark shift with field intensity, and measure the light shift as a function of field frequency, generating a "light-shift curve." We have improved on the previous best test of theory by a factor of 2, and after subtracting the theoretical scalar light shift from the experimental light-shift curves, we have isolated and tested the tensor light shift for an alkali D2 transition.

  10. Inversion layer on the Ge(001) surface from the four-probe conductance measurements

    SciTech Connect

    Wojtaszek, Mateusz; Lis, Jakub Zuzak, Rafal; Such, Bartosz; Szymonski, Marek

    2014-07-28

    We report four-probe conductance measurements with sub-micron resolution on atomically clean Ge(001) surfaces. A qualitative difference between n-type and p-type crystals is observed. The scaling behavior of the resistance on n-type samples indicates two-dimensional current flow, while for the p-type crystal a three-dimensional description is appropriate. We interpret this in terms of the formation of an inversion layer at the surface. This result points to the surface states, i.e., dangling bonds, as the driving force behind band bending in germanium. It also explains the intrinsic character of band bending in germanium.

  11. Estimation of skin conductance at low frequencies using measurements at higher frequencies for EDA applications.

    PubMed

    Nordbotten, Bernt J; Tronstad, Christian; Martinsen, Ørjan G; Grimnes, Sverre

    2014-06-01

    Using low-frequency (LF) alternating current skin conductance (SC) has recently been recommended for electrodermal activity (EDA) measurement, but the method may imply some limitations in sampling rate, which are insufficient for capturing the complete SC waveform. The aim of this study was to assess whether LF SC can be estimated based on skin admittance (SA) measurements at higher frequencies allowing higher sampling rates. SA measurements from 1 Hz to 70 kHz were gathered from 20 healthy human participants, and an interval from 500 Hz to 10 kHz was used to fit a Cole model to the measured SA by means of the nonlinear least squares method. The LF extrapolation of this fit was used to estimate the LF SC at 1, 10, 22 and 30 Hz. The method produced an overestimation of SC by approximately 20%, and the variation in LF SC was preserved by approximately 95%. The overestimation is most likely due to different frequency dependence behavior (dispersion) of SC at the lowest frequencies, which is not accounted for by a single dispersion model. In conclusion, the SA method using high frequency is unsuitable for estimation of the LF SC level, but can probably be used in EDA measurements, which are scored based on the variations in SC. PMID:24844405

  12. Percolation threshold determination of sputtered silver films using Stokes parameters and in situ conductance measurements.

    PubMed

    Hafezian, Soroush; Baloukas, Bill; Martinu, Ludvik

    2014-08-20

    This work presents a straightforward approach to determine the percolation threshold of silver thin films deposited by magnetron sputtering on various oxide layers at room temperature. The proposed method is based on the observation of the coupling of p-polarized light with local surface plasmons. By measuring the first Stokes parameter in real time, one can determine the moment at which the nano-islands of silver begin to coalesce into a continuous film. We confirm the results by in situ and ex situ conductance measurements. The method is then used to assess the percolation threshold on different oxide seed layers such as ZnSnO, ZnO, TiO2, and SiO2. PMID:25321107

  13. Noncontact conductivity and dielectric measurement for high throughput roll-to-roll nanomanufacturing

    PubMed Central

    Orloff, Nathan D.; Long, Christian J.; Obrzut, Jan; Maillaud, Laurent; Mirri, Francesca; Kole, Thomas P.; McMichael, Robert D.; Pasquali, Matteo; Stranick, Stephan J.; Alexander Liddle, J.

    2015-01-01

    Advances in roll-to-roll processing of graphene and carbon nanotubes have at last led to the continuous production of high-quality coatings and filaments, ushering in a wave of applications for flexible and wearable electronics, woven fabrics, and wires. These applications often require specific electrical properties, and hence precise control over material micro- and nanostructure. While such control can be achieved, in principle, by closed-loop processing methods, there are relatively few noncontact and nondestructive options for quantifying the electrical properties of materials on a moving web at the speed required in modern nanomanufacturing. Here, we demonstrate a noncontact microwave method for measuring the dielectric constant and conductivity (or geometry for samples of known dielectric properties) of materials in a millisecond. Such measurement times are compatible with current and future industrial needs, enabling real-time materials characterization and in-line control of processing variables without disrupting production. PMID:26592441

  14. Noncontact conductivity and dielectric measurement for high throughput roll-to-roll nanomanufacturing.

    PubMed

    Orloff, Nathan D; Long, Christian J; Obrzut, Jan; Maillaud, Laurent; Mirri, Francesca; Kole, Thomas P; McMichael, Robert D; Pasquali, Matteo; Stranick, Stephan J; Liddle, J Alexander

    2015-01-01

    Advances in roll-to-roll processing of graphene and carbon nanotubes have at last led to the continuous production of high-quality coatings and filaments, ushering in a wave of applications for flexible and wearable electronics, woven fabrics, and wires. These applications often require specific electrical properties, and hence precise control over material micro- and nanostructure. While such control can be achieved, in principle, by closed-loop processing methods, there are relatively few noncontact and nondestructive options for quantifying the electrical properties of materials on a moving web at the speed required in modern nanomanufacturing. Here, we demonstrate a noncontact microwave method for measuring the dielectric constant and conductivity (or geometry for samples of known dielectric properties) of materials in a millisecond. Such measurement times are compatible with current and future industrial needs, enabling real-time materials characterization and in-line control of processing variables without disrupting production. PMID:26592441

  15. Noncontact conductivity and dielectric measurement for high throughput roll-to-roll nanomanufacturing

    NASA Astrophysics Data System (ADS)

    Orloff, Nathan D.; Long, Christian J.; Obrzut, Jan; Maillaud, Laurent; Mirri, Francesca; Kole, Thomas P.; McMichael, Robert D.; Pasquali, Matteo; Stranick, Stephan J.; Alexander Liddle, J.

    2015-11-01

    Advances in roll-to-roll processing of graphene and carbon nanotubes have at last led to the continuous production of high-quality coatings and filaments, ushering in a wave of applications for flexible and wearable electronics, woven fabrics, and wires. These applications often require specific electrical properties, and hence precise control over material micro- and nanostructure. While such control can be achieved, in principle, by closed-loop processing methods, there are relatively few noncontact and nondestructive options for quantifying the electrical properties of materials on a moving web at the speed required in modern nanomanufacturing. Here, we demonstrate a noncontact microwave method for measuring the dielectric constant and conductivity (or geometry for samples of known dielectric properties) of materials in a millisecond. Such measurement times are compatible with current and future industrial needs, enabling real-time materials characterization and in-line control of processing variables without disrupting production.

  16. Scale effect of hydraulic conductivity measurements in Pre-Illinoian and Wisconsinan tills in Iowa

    SciTech Connect

    Bruner, D.R. . Geological Survey Bureau)

    1993-03-01

    Two long-term study sites have been established as the basis for a multi-year study of the hydrogeologic properties of glacial tills in Iowa. One is located in Eastern Iowa in Pre-Illinoian till and has had laboratory permeameter tests conducted on Shelby tube samples, collected during construction of piezometers, from the zone to be screen. These piezometers were used to run bailer tests and perform a pumping test. The other site is located in North-Central Iowa in Wisconsinan till and has piezometers constructed to run bailer and pumping tests. Results from both sites has shown that the bulk hydraulic conductivity increases as larger volumes of till are tested. There is consistently at least one order of magnitude increase between bailer and pumping test results. There is also at least three orders of magnitude increase between laboratory permeameter and pumping test results. A system is proposed to conduct pumping tests using vibrating wire transducers hydraulically pushed into the ground to monitor water levels before, during and after the test, and record the measurements to a datalogger.

  17. Measurement and Simulation of Thermal Conductivity of Hafnium-Aluminum Thermal Neutron Absorber Material

    NASA Astrophysics Data System (ADS)

    Guillen, Donna Post; Harris, William H.

    2016-05-01

    A metal matrix composite (MMC) material composed of hafnium aluminide (Al3Hf) intermetallic particles in an aluminum matrix has been identified as a promising material for fast flux irradiation testing applications. This material can filter thermal neutrons while simultaneously providing high rates of conductive cooling for experiment capsules. The purpose of this work is to investigate effects of Hf-Al material composition and neutron irradiation on thermophysical properties, which were measured before and after irradiation. When performing differential scanning calorimetry (DSC) on the irradiated specimens, a large exotherm corresponding to material annealment was observed. Therefore, a test procedure was developed to perform DSC and laser flash analysis (LFA) to obtain the specific heat and thermal diffusivity of pre- and post-annealment specimens. This paper presents the thermal properties for three states of the MMC material: (1) unirradiated, (2) as-irradiated, and (3) irradiated and annealed. Microstructure-property relationships were obtained for the thermal conductivity. These relationships are useful for designing components from this material to operate in irradiation environments. The ability of this material to effectively conduct heat as a function of temperature, volume fraction Al3Hf, radiation damage, and annealing is assessed using the MOOSE suite of computational tools.

  18. Annual layers in the Roosevelt Island (coastal Antarctica) ice core determined from conductivity and calcium measurements

    NASA Astrophysics Data System (ADS)

    Simonsen, Marius; Vallelonga, Paul; Kjær, Helle; Neff, Peter; Bertler, Nancy; Svensson, Anders; Dahl-Jensen, Dorthe; Riis, Marie

    2015-04-01

    The Roosevelt Island Climate Evolution (RICE) Project aims to determine the stability of the Ross Ice Shelf and thus the West Antarctic Ice Sheet in a warming world. A 764 m ice core (79.36° S, 161.71° W) was drilled in 2011-13 at the summit of the Roosevelt Island ice dome, a location surrounded by the Ross Ice Shelf. The site has high accumulation (0.26 m ice equivalent) and a mean annual temperature of -23 °C. From 2012 to 2014, continuous flow analysis (CFA) of the ice core enabled continuous measurements of conductivity, acidity, calcium and insoluble dust particle concentrations along the core. The RICE ice core features high background levels of sulphate and marine salts, due to the low altitude of the site (550 m asl) and its proximity to open ocean. At Roosevelt Island, calcium is influenced by both dust and marine salt inputs. By investigating the residual offset between conductivity and calcium, it has been possible to calculate non-sea salt conductivity and hence determine impurity layers deriving from volcanic eruptions. We present a preliminary chronology for the last 2000 years of deposition in the RICE ice core, composed of counted impurity layers and constrained by a limited number of large, well-dated volcanic eruptions.

  19. Indirect determination of cyanide compounds by ion chromatography with conductivity measurement

    SciTech Connect

    Nonomura, M.

    1987-09-01

    Ion chromatography (IC) is a suitable analytical technique for the determination of anions. The cyanide is not detected by the conductivity detector of the ion chromatograph due to its low dissolution constant (pK = 9.2). This paper describes an IC procedure for the determination of free cyanide and metal cyanide complexes that uses a conductivity detector. It is based on the oxidation of cyanide ion by sodium hypochlorite to cyanate ion (pK = 3.66). Therefore, cyanide ion can now be measured indirectly by the conductivity detector. In this procedure, optimum operating conditions were examined. In addition, the interferences from anions and reducing agents were investigated. The method was applied to the determination of metal cyanide complexes. The coefficients of variation (%) for CN/sup -/ (1.05 mg/L), Zn(CN)/sub 4//sup 2 -/ (CN/sup -/, 0.80 mg/L), and Ni(CN)/sub 4//sup 2 -/ (CN/sup -/, 0.96 mg/L) were 1.1%, 1.5%, and 0.5%, respectively. The proposed method proved to be useful for the determination of cyanide compounds in natural water and waste water.

  20. Measurement of effective thermal conductivity of wheat as a function of moisture content

    SciTech Connect

    Tavman, S.; Tavman, I.H.

    1998-07-01

    Grain drying and storage are one of the main activities of agricultural industry. Increasing energy costs have stressed the importance of calculation of heat and mass transfer in a grain bulk in order to be able to optimize drying facilities. Another limitation during drying is the preservation of grain structure and its nutritional values, Muehlbauer and Christ have shown that damage to the grain structure and grain nutritional value is dependent upon grain temperature and drying time. Therefore, proper conditions during drying and storage of cereal grains require the knowledge of the thermophysical properties of the grains. The effective thermal conductivity of two varieties of Triticum durum wheat and a wheat product, bulgur, is determined at different moisture contents and at ambient temperature by the transient lime heat source method. The moisture contents of the samples ranged from 9.17 to 38.65% wet basis and the bulk densities ranged from 675 to 827 kg/m{sup 3}. Under those conditions, the measured effective thermal conductivities ranged from 0.159 to 0.201 W/m.K. The effective thermal conductivity is found to be linearly increasing with moisture content. The results are also in good agreement with literature values.