Science.gov

Sample records for electrical resistivity

  1. Electrical Resistivity Imaging

    EPA Science Inventory

    Electrical resistivity imaging (ERI) is a geophysical method originally developed within the mining industry where it has been used for decades to explore for and characterize subsurface mineral deposits. It is one of the oldest geophysical methods with the first documented usag...

  2. Electrical resistivity probes

    DOEpatents

    Lee, Ki Ha; Becker, Alex; Faybishenko, Boris A.; Solbau, Ray D.

    2003-10-21

    A miniaturized electrical resistivity (ER) probe based on a known current-voltage (I-V) electrode structure, the Wenner array, is designed for local (point) measurement. A pair of voltage measuring electrodes are positioned between a pair of current carrying electrodes. The electrodes are typically about 1 cm long, separated by 1 cm, so the probe is only about 1 inch long. The electrodes are mounted to a rigid tube with electrical wires in the tube and a sand bag may be placed around the electrodes to protect the electrodes. The probes can be positioned in a borehole or on the surface. The electrodes make contact with the surrounding medium. In a dual mode system, individual probes of a plurality of spaced probes can be used to measure local resistance, i.e. point measurements, but the system can select different probes to make interval measurements between probes and between boreholes.

  3. Electrically Variable Resistive Memory Devices

    NASA Technical Reports Server (NTRS)

    Liu, Shangqing; Wu, Nai-Juan; Ignatiev, Alex; Charlson, E. J.

    2010-01-01

    Nonvolatile electronic memory devices that store data in the form of electrical- resistance values, and memory circuits based on such devices, have been invented. These devices and circuits exploit an electrically-variable-resistance phenomenon that occurs in thin films of certain oxides that exhibit the colossal magnetoresistive (CMR) effect. It is worth emphasizing that, as stated in the immediately preceding article, these devices function at room temperature and do not depend on externally applied magnetic fields. A device of this type is basically a thin film resistor: it consists of a thin film of a CMR material located between, and in contact with, two electrical conductors. The application of a short-duration, low-voltage current pulse via the terminals changes the electrical resistance of the film. The amount of the change in resistance depends on the size of the pulse. The direction of change (increase or decrease of resistance) depends on the polarity of the pulse. Hence, a datum can be written (or a prior datum overwritten) in the memory device by applying a pulse of size and polarity tailored to set the resistance at a value that represents a specific numerical value. To read the datum, one applies a smaller pulse - one that is large enough to enable accurate measurement of resistance, but small enough so as not to change the resistance. In writing, the resistance can be set to any value within the dynamic range of the CMR film. Typically, the value would be one of several discrete resistance values that represent logic levels or digits. Because the number of levels can exceed 2, a memory device of this type is not limited to binary data. Like other memory devices, devices of this type can be incorporated into a memory integrated circuit by laying them out on a substrate in rows and columns, along with row and column conductors for electrically addressing them individually or collectively.

  4. Electrical resistivity of composite superconductors

    NASA Technical Reports Server (NTRS)

    Davis, J. H.; Lee, J. A.

    1983-01-01

    In addition to its superconducting properties, a superconductor is usually characterized by poor thermal conductivity and relatively high electrical resistivity in the normal state. To remedy this situation a study of superconducting properties of Cu-rich CU-Nb wires prepared by directionally solidified and cold-rolled technique was conducted. Some of the specimens were prepared by melting, directional solidification and diffusing in Tin. A total of 12 wire specimens was tested. Each specimen was analyzed by plotting experimental data into the following curves: the graph of the residual resistivity as a function of the specimen current at 4.3 K; and the graph of the electrical resistivity as a function of the temperature at a constant current.

  5. Measuring Electrical Resistivity Of Compacted Powder

    NASA Technical Reports Server (NTRS)

    Shlichta, Paul J.

    1991-01-01

    Slightly modified micrometer used in conjunction with special cup to measure electrical resistance of specimen of powder as function of packing fraction. Powder pressed between anvils of micrometer, which make electrical contact with specimen. Device used in manufacturing batteries to determine effective electrical conductivities of powders loaded into plastic sheets to make battery substrates. Coupled with good mathematical description of expected conductivity of particulate composite as function of packing density. Also serves as tool for evaluating conductivity of dispersed phase, as well as evaluating electrical resistances of interparticle contacts.

  6. Resistance after firing protected electric match

    DOEpatents

    Montoya, Arsenio P.

    1981-11-10

    An electric match having electrical leads embedded in flame-producing compound is protected against an accidental resistance across the leads after firing by a length of heat-shrinkable tubing encircling the match body and having a skirt portion extending beyond the leads. The heat of the burning match and an adjacent thermal battery causes the tubing to fold over the end of the match body, covering the ends of the leads and protecting them from molten pieces of the battery.

  7. Pedotransfer functions in soil electrical resistivity estimation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Surface electrical resistivity tomography (ERT) is recognized as a powerful non-invasive soil survey and monitoring method. Relationships between ER and soil water contents that are needed to infer the spatial distribution of soil moisture from the ERT results, are known to reflect soil properties. ...

  8. Release Resistant Electrical Interconnections For Mems Devices

    DOEpatents

    Peterson, Kenneth A.; Garrett, Stephen E.; Reber, Cathleen A.

    2005-02-22

    A release resistant electrical interconnection comprising a gold-based electrical conductor compression bonded directly to a highly-doped polysilicon bonding pad in a MEMS, IMEMS, or MOEMS device, without using any intermediate layers of aluminum, titanium, solder, or conductive adhesive disposed in-between the conductor and polysilicon pad. After the initial compression bond has been formed, subsequent heat treatment of the joint above 363 C creates a liquid eutectic phase at the bondline comprising gold plus approximately 3 wt % silicon, which, upon re-solidification, significantly improves the bond strength by reforming and enhancing the initial bond. This type of electrical interconnection is resistant to chemical attack from acids used for releasing MEMS elements (HF, HCL), thereby enabling the use of a "package-first, release-second" sequence for fabricating MEMS devices. Likewise, the bond strength of an Au--Ge compression bond may be increased by forming a transient liquid eutectic phase comprising Au-12 wt % Ge.

  9. Temperature dependent electrical resistivity of liquid Sn

    NASA Astrophysics Data System (ADS)

    Prajapati, A. V.; Sonvane, Y. A.; Patel, H. P.; Thakor, P. B.

    2016-05-01

    The present paper deals with the effect of temperature variation on the electrical resistivity (ρ) of liquid Sn(Tin). We have used a new parameter free pseudopotential along with screening Taylor et al and Farid et al local field correction functions. The Percus-Yevick Hard Sphere (PYHS) reference system is used to describe structural information. Zeeman formula has been used for finding resistivity with the variation of temperature. The balanced harmonies between present data and experimental data have been achieved with a minimal deviation. So, we concluded that our newly constructed model potential is an effective one to produce the data of electrical resistivity of liquid Sn(Tin) as a function of temperature.

  10. Electrical resistance tomography for imaging concrete structures

    SciTech Connect

    Buettner, M.; Ramirez, A.; Daily, W.

    1995-11-08

    Electrical Resistance Tomography (ERT) has been used to non-destructively examine the interior of reinforced concrete pillars in the laboratory during a water infiltration experiment. ERT is a technique for determining the electrical resistivity distribution within a volume from measurement of injected currents and the resulting electrical potential distribution on the surface. The transfer resistance (ratio of potential to injected current) data are inverted using an algorithm based on a finite element forward solution which is iteratively adjusted in a least squares sense until the measured and calculated transfer resistances agree to within some predetermined value. Laboratory specimens of concrete pillars, 61.0 cm (24 in) in length and 20.3 cm (8 in) on a side, were prepared with various combinations of steel reinforcing bars and voids (1.27 cm diameter) which ran along the length of the pillars. An array of electrodes was placed around the pillar to allow for injecting current and measuring the resulting potentials. After the baseline resistivity distribution was determined, water was added to a void near one comer of the pillar. ERT was used to determine the resistivity distribution of the pillar at regular time intervals as water was added. The ERT images show very clearly that the water was gradually imbibed into the concrete pillar during the course of the experiment. The resistivity decreased by nearly an order of magnitude near the point of water addition in the first hour, and by nearly two orders of magnitude by the end of the experiment. Other applications for this technology include monitoring of curing in concrete structures, detecting cracks in concrete structures, detecting rebar location and corrosion state, monitoring slope stability and the stability of footings, detecting and monitoring leaks from storage tanks, monitoring thermal processes during environmental remediation, and for detecting and monitoring contaminants in soil and groundwater.

  11. Electrical resistance tomography of concrete structures

    SciTech Connect

    Daily, W.; Ramirez, A.; Binley, A.; Henry-Poulter, S.

    1993-10-01

    The purpose of this work is to determine the feasibility of using Electrical resistance tomography (ERT) to nondestructively examine the interior of concrete structures such as bridge pillars and roadways. We report the results of experiments wherein ERT is used to image the two concrete specimens in the laboratory. Each specimen is 5 inches square and 12 inches long and contained steel reinforcing rods along its length. Twenty electrodes were placed on each sample and an-image of electrical resistivity distribution was generated from current and voltage measurements. We found that the images show the general location of the reinforcing steel and, what`s more important, delineate the absence of the steel. The method may therefore be useful for determining if such steel has been destroyed by corrosion, however to make it useful, the technique must have better resolution so that individual reinforcing steel units are resolved.

  12. Soil Identification using Field Electrical Resistivity Method

    NASA Astrophysics Data System (ADS)

    Hazreek, Z. A. M.; Rosli, S.; Chitral, W. D.; Fauziah, A.; Azhar, A. T. S.; Aziman, M.; Ismail, B.

    2015-06-01

    Geotechnical site investigation with particular reference to soil identification was important in civil engineering works since it reports the soil condition in order to relate the design and construction of the proposed works. In the past, electrical resistivity method (ERM) has widely being used in soil characterization but experienced several black boxes which related to its results and interpretations. Hence, this study performed a field electrical resistivity method (ERM) using ABEM SAS (4000) at two different types of soils (Gravelly SAND and Silty SAND) in order to discover the behavior of electrical resistivity values (ERV) with type of soils studied. Soil basic physical properties was determine thru density (p), moisture content (w) and particle size distribution (d) in order to verify the ERV obtained from each type of soil investigated. It was found that the ERV of Gravelly SAND (278 Ωm & 285 Ωm) was slightly higher than SiltySAND (223 Ωm & 199 Ωm) due to the uncertainties nature of soils. This finding has showed that the results obtained from ERM need to be interpreted based on strong supported findings such as using direct test from soil laboratory data. Furthermore, this study was able to prove that the ERM can be established as an alternative tool in soil identification provided it was being verified thru other relevance information such as using geotechnical properties.

  13. An introduction to electrical resistivity in geophysics

    NASA Astrophysics Data System (ADS)

    Herman, Rhett

    2001-09-01

    Physicists are finding that the skills they have learned in their training may be applied to areas beyond traditional physics topics. One such field is that of geophysics. This paper presents the electrical resistivity component of an undergraduate geophysics course at Radford University. It is taught from a physics perspective, yet the application of the theory to the real world is the overriding goal. The concepts involved in electrical resistivity studies are first discussed in a general sense, and then they are studied through the application of the relevant electromagnetic theory. Since geology majors comprise the bulk of the students in this class, the math used is only that which is typically required of geology majors. The final results are given in a form that practicing geophysicists may use in the field. A method is presented for constructing an inexpensive apparatus for measuring electrical resistivity in both a tabletop laboratory setting and in the field. This apparatus is truly "plug and play" since its assembly and use requires only the most basic knowledge of electronics. This apparatus is tested in a tabletop laboratory setting as well as in two field surveys.

  14. Delineation of graves using electrical resistivity tomography

    NASA Astrophysics Data System (ADS)

    Nero, Callistus; Aning, Akwasi Acheampong; Danuor, Sylvester K.; Noye, Reginald M.

    2016-03-01

    A suspected old royal cemetery has been surveyed at the Kwame Nkrumah University of Science and Technology (KNUST) campus, Kumasi, Ghana using Electrical Resistivity Tomography (ERT) with the objective of detecting graves in order to make informed decisions with regard to the future use of the area. The survey was conducted on a 10,000 m2 area. Continuous Vertical Electrical Sounding (CVES) was combined with the roll along technique for 51 profiles with 1 m probe separation separated by 2 m. Inverted data results indicated wide resistivity variations ranging between 9.34 Ωm and 600 Ωm in the near surface. Such heterogeneity suggests a disturbance of the soil at this level. Both high (≥ 600 Ωm) and low resistivity (≤ 74.7 Ωm) anomalies, relative to background levels, were identified within the first 4 m of the subsurface. These were suspected to be burial tombs because of their rectangular geometries and resistivity contrasts. The results were validated with forward numerical modeling results. The study area is therefore an old cemetery and should be preserved as a cultural heritage site.

  15. Electrical resistance tomography from measurements inside a steel cased borehole

    DOEpatents

    Daily, William D.; Schenkel, Clifford; Ramirez, Abelardo L.

    2000-01-01

    Electrical resistance tomography (ERT) produced from measurements taken inside a steel cased borehole. A tomographic inversion of electrical resistance measurements made within a steel casing was then made for the purpose of imaging the electrical resistivity distribution in the formation remotely from the borehole. The ERT method involves combining electrical resistance measurements made inside a steel casing of a borehole to determine the electrical resistivity in the formation adjacent to the borehole; and the inversion of electrical resistance measurements made from a borehole not cased with an electrically conducting casing to determine the electrical resistivity distribution remotely from a borehole. It has been demonstrated that by using these combined techniques, highly accurate current injection and voltage measurements, made at appropriate points within the casing, can be tomographically inverted to yield useful information outside the borehole casing.

  16. Rational Experimental Design for Electrical Resistivity Imaging

    NASA Astrophysics Data System (ADS)

    Mitchell, V.; Pidlisecky, A.; Knight, R.

    2008-12-01

    Over the past several decades advances in the acquisition and processing of electrical resistivity data, through multi-channel acquisition systems and new inversion algorithms, have greatly increased the value of these data to near-surface environmental and hydrological problems. There has, however, been relatively little advancement in the design of actual surveys. Data acquisition still typically involves using a small number of traditional arrays (e.g. Wenner, Schlumberger) despite a demonstrated improvement in data quality from the use of non-standard arrays. While optimized experimental design has been widely studied in applied mathematics and the physical and biological sciences, it is rarely implemented for non-linear problems, such as electrical resistivity imaging (ERI). We focus specifically on using ERI in the field for monitoring changes in the subsurface electrical resistivity structure. For this application we seek an experimental design method that can be used in the field to modify the data acquisition scheme (spatial and temporal sampling) based on prior knowledge of the site and/or knowledge gained during the imaging experiment. Some recent studies have investigated optimized design of electrical resistivity surveys by linearizing the problem or with computationally-intensive search algorithms. We propose a method for rational experimental design based on the concept of informed imaging, the use of prior information regarding subsurface properties and processes to develop problem-specific data acquisition and inversion schemes. Specifically, we use realistic subsurface resistivity models to aid in choosing source configurations that maximize the information content of our data. Our approach is based on first assessing the current density within a region of interest, in order to provide sufficient energy to the region of interest to overcome a noise threshold, and then evaluating the direction of current vectors, in order to maximize the

  17. Complex Electrical Resistivity for Monitoring DNAPL Contamination

    SciTech Connect

    Stephen R. Brown; David Lesmes; John Fourkas

    2003-09-12

    Nearly all Department of Energy (DOE) facilities have landfills and buried waste areas. Of the various contaminants present at these sites, dense non-aqueous phase liquids (DNAPL) are particularly hard to locate and remove. There is an increasing need for external or non-invasive sensing techniques to locate DNAPLs in the subsurface and to track their spread and monitor their breakdown or removal by natural or engineered means. G. Olhoeft and colleagues have published several reports based on laboratory studies using the complex resistivity method which indicate that organic solvents, notably toluene, PCE, and TCE, residing in clay-bearing soils have distinctive electrical signatures. These results have suggested to many researchers the basis of an ideal new measurement technique for geophysical characterization of DNAPL pollution. Encouraged by these results we proposed to bring the field measurement of complex resistivity as a means of pollution characterization from the conceptual stage to practice. We planned to document the detectability of clay-organic solvent interactions with geophysical measurements in the laboratory, develop further understanding of the underlying physical and chemical mechanisms, and then apply these observations to develop field techniques. As with any new research endeavor we note the extreme importance of trying to reproduce the work of previous researchers to ensure that any effects observed are due to the physical phenomena occurring in the specimen and not due to the particular experimental apparatus or method used. To this end, we independently designed and built a laboratory system, including a sample holder, electrodes, electronics, and data analysis software, for the measurement of the complex electrical resistivity properties of soil contaminated with organic solvents. The capabilities and reliability of this technique were documented. Using various standards we performed measurement accuracy, repeatability, and noise immunity

  18. Cone-based electrical resistivity tomography

    NASA Astrophysics Data System (ADS)

    Pidlisecky, Adam

    Determining the 3-D spatial distribution of subsurface properties is a critical part of managing the clean-up of contaminated sites. Most standard hydrologic methods sample small regions immediately adjacent to wells or testing devices. This provides data which are not representative of the entire region of interest. Furthermore, at many contaminated sites invasive methods are not acceptable, due to the risks associated with contacting and spreading the contaminants. To address these issues, I have developed a minimally invasive technology that provides information about the 3-D distribution of electrical conductivity. This new technique, cone-based electrical resistivity tomography (C-bert), integrates the existing technologies of resistivity cone penetration testing (RCPT) with electrical resistivity tomography. Development of this tool included the creation of new software and modeling algorithms, the design of field equipment, field testing, and processing and interpretation of the resulting data. I present a 2.5-D forward modeling algorithm that incorporates an effective correction for the errors caused by boundary effects and source singularities. The algorithm includes an optimization technique for acquiring the Fourier coefficients required for the solution. A 3-D inversion algorithm is presented that has two major improvements over existing algorithms. First, it includes a 3-D version of the boundary correction/source singularity correction developed for the 2.5-D problem. Second, the algorithm can handle any type of acquisition geometry; this was a requirement for the development of C-bert. C-bert involves placing several permanent current electrodes in the subsurface and using electrodes mounted on a cone penetrometer and at the surface to measure the resultant potential field. In addition to these measurements, we obtain the standard suite of RCPT data, including high resolution resistivity logs. The RCPT data can be used to generate a realistic

  19. Discontinuities detection using transmission electrical resistivity imaging

    NASA Astrophysics Data System (ADS)

    Lesparre, Nolwenn; Cabrera, Justo; Boyle, Alistair; Grychtol, Bartłomiej; Adler, Andy

    2015-04-01

    In the context of nuclear waste storage, low permeability clays are investigated as potential geological barrier. Discontinuities in such formations might facilitate the radionuclide transport to the environment. The underground platform of Tournemire (Aveyron, France) presents the opportunity to perform in-situ experiments to evaluate the potential of geophysical methods to detect and characterize the presence of discontinuities in the sub-surface. In this work, we apply transmission electrical resistivity tomography to image the medium surrounding a regional fault. A specific array of electrodes were set up, adapted for the characterization of the fault. Electrodes were placed along the tunnel as well as at the surface above the tunnel on both sides of the fault. The objective of a such geometry is to acquire data in transmission across the massif in addition to classical protocol such as Schlumberger or dipole-dipole in order to better cover the sounded medium. 3D models considering the gallery geometry, the topography and the injection of current in transmission through the massif were developed for the analysis of such particular data sets. For the reconstruction of the medium electrical resistivity, the parametrization of the inverse problem was adapted to the geometry of the experience in a scope to reduce the inversion under-determination. The resulting image obtained with classical protocols and transmission current injection is compared to an image obtained using only classical protocols to better highlight the interest of a transmission experiment in terms of resolution and penetration depth. The addition of protocols in transmission allows a better coverage of the sounded medium so the resulting image presents a better resolution at higher depths than the image resulting from a single profile of electrodes. The proposed configuration of electrical resistivity measurements in transmission is then promising for hydrogeophysical studies, in particular for

  20. Determination of electrical resistivity of dry coke beds

    SciTech Connect

    Eidem, P.A.; Tangstad, M.; Bakken, J.A.

    2008-02-15

    The electrical resistivity of the coke bed is of great importance when producing FeMn, SiMn, and FeCr in a submerged arc furnace. In these processes, a coke bed is situated below and around the electrode tip and consists of metallurgical coke, slag, gas, and metal droplets. Since the basic mechanisms determining the electrical resistivity of a coke bed is not yet fully understood, this investigation is focused on the resistivity of dry coke beds consisting of different carbonaceous materials, i.e., coke beds containing no slag or metal. A method that reliably compares the electrical bulk resistivity of different metallurgical cokes at 1500{sup o} C to 1600{sup o}C is developed. The apparatus is dimensioned for industrial sized materials, and the electrical resistivity of anthracite, charcoal, petroleum coke, and metallurgical coke has been measured. The resistivity at high temperatures of the Magnitogorsk coke, which has the highest resistivity of the metallurgical cokes investigated, is twice the resistivity of the Corus coke, which has the lowest electrical resistivity. Zdzieszowice and SSAB coke sort in between with decreasing resistivities in the respective order. The electrical resistivity of anthracite, charcoal, and petroleum coke is generally higher than the resistivity of the metallurgical cokes, ranging from about two to about eight times the resistivity of the Corus coke at 1450{sup o}C. The general trend is that the bulk resistivity of carbon materials decreases with increasing temperature and increasing particle size.

  1. The electrical resistivity method in cased boreholes

    SciTech Connect

    Schenkel, C.J.

    1991-05-01

    The use of downhole current sources in resistivity mapping can greatly enhance the detection and delineation of subsurface features. The purpose of this work is to examine the resistivity method for current sources in wells cased with steel. The resistivity method in cased boreholes with downhole current sources is investigated using the integral equation (IE) technique. The casing and other bodies are characterized as conductivity inhomogeneities in a half-space. For sources located along the casing axis, an axially symmetric Green's function is used to formulate the surface potential and electric field (E-field) volume integral equations. The situations involving off-axis current sources and three-dimensional (3-D) bodies is formulated using the surface potential IE method. The solution of the 3-D Green's function is presented in cylindrical and Cartesian coordinate systems. The methods of moments is used to solve the Fredholm integral equation of the second kind for the response due to the casing and other bodies. The numerical analysis revealed that the current in the casing can be approximated by its vertical component except near the source and the axial symmetric approximation of the casing is valid even for the 3-D problem. The E-field volume IE method is an effective and efficient technique to simulate the response of the casing in a half-space, whereas the surface potential approach is computationally better when multiple bodies are involved. Analyzing several configurations of the current source indicated that the casing response is influenced by four characteristic factors: conduction length, current source depth,casing depth, and casing length. 85 refs., 133 figs., 11 tabs.

  2. Iron aluminide useful as electrical resistance heating elements

    DOEpatents

    Sikka, V.K.; Deevi, S.C.; Fleischhauer, G.S.; Hajaligol, M.R.; Lilly, A.C. Jr.

    1997-04-15

    The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, {<=}1% Cr and either {>=}0.05% Zr or ZrO{sub 2} stringers extending perpendicular to an exposed surface of the heating element or {>=}0.1% oxide dispersoid particles. The alloy can contain 14-32% Al, {<=}2% Ti, {<=}2% Mo, {<=}1% Zr, {<=}1% C, {<=}0.1% B, {<=}30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, {<=}1% rare earth metal, {<=}1% oxygen, {<=}3% Cu, balance Fe. 64 figs.

  3. Iron aluminide useful as electrical resistance heating elements

    DOEpatents

    Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier S.; Hajaligol, Mohammad R.; Lilly, Jr., A. Clifton

    2001-01-01

    The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, .ltoreq.1% Cr and either .gtoreq.0.05% Zr or ZrO.sub.2 stringers extending perpendicular to an exposed surface of the heating element or .gtoreq.0.1% oxide dispersoid particles. The alloy can contain 14-32% Al, .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Zr, .ltoreq.1% C, .ltoreq.0.1% B, .ltoreq.30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, .ltoreq.1% oxygen, .ltoreq.3% Cu, balance Fe.

  4. Iron aluminide useful as electrical resistance heating elements

    DOEpatents

    Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier S.; Hajaligol, Mohammad R.; Lilly, Jr., A. Clifton

    1997-01-01

    The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, .ltoreq.1% Cr and either .gtoreq.0.05% Zr or ZrO.sub.2 stringers extending perpendicular to an exposed surface of the heating element or .gtoreq.0.1% oxide dispersoid particles. The alloy can contain 14-32% Al, .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Zr, .ltoreq.1% C, .ltoreq.0.1% B, .ltoreq.30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, .ltoreq.1% oxygen, .ltoreq.3% Cu, balance Fe.

  5. Iron aluminide useful as electrical resistance heating elements

    DOEpatents

    Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier S.; Hajaligol, Mohammad R.; Lilly, Jr., A. Clifton

    1999-01-01

    The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, .ltoreq.1% Cr and either .gtoreq.0.05% Zr or ZrO.sub.2 stringers extending perpendicular to an exposed surface of the heating element or .gtoreq.0.1% oxide dispersoid particles. The alloy can contain 14-32% Al, .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Zr, .ltoreq.1% C, .ltoreq.0.1% B, .ltoreq.30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, .ltoreq.1% oxygen, .ltoreq.3% Cu, balance Fe.

  6. Theoretical relationship between elastic wave velocity and electrical resistivity

    NASA Astrophysics Data System (ADS)

    Lee, Jong-Sub; Yoon, Hyung-Koo

    2015-05-01

    Elastic wave velocity and electrical resistivity have been commonly applied to estimate stratum structures and obtain subsurface soil design parameters. Both elastic wave velocity and electrical resistivity are related to the void ratio; the objective of this study is therefore to suggest a theoretical relationship between the two physical parameters. Gassmann theory and Archie's equation are applied to propose a new theoretical equation, which relates the compressional wave velocity to shear wave velocity and electrical resistivity. The piezo disk element (PDE) and bender element (BE) are used to measure the compressional and shear wave velocities, respectively. In addition, the electrical resistivity is obtained by using the electrical resistivity probe (ERP). The elastic wave velocity and electrical resistivity are recorded in several types of soils including sand, silty sand, silty clay, silt, and clay-sand mixture. The appropriate input parameters are determined based on the error norm in order to increase the reliability of the proposed relationship. The predicted compressional wave velocities from the shear wave velocity and electrical resistivity are similar to the measured compressional velocities. This study demonstrates that the new theoretical relationship may be effectively used to predict the unknown geophysical property from the measured values.

  7. Mapping Contaminant Remediation with Electrical Resistivity Tomography

    NASA Astrophysics Data System (ADS)

    Gerhard, J.; Power, C.; Tsourlos, P.; Karaoulis, M.; Giannopoulos, A.; Soupios, P. M.; Simyrdanis, K.

    2014-12-01

    The remediation of sites contaminated with industrial chemicals - specifically dense non-aqueous phase liquids (DNAPLs) like coal tar and chlorinated solvents - represents a major geoenvironmental challenge. Remediation activities would benefit from a non-destructive technique to map the evolution of DNAPL mass in space and time. Electrical resistivity tomography (ERT) has long-standing potential in this context but has not yet become a common tool at DNAPL sites. This work evaluated the potential of time-lapse ERT for mapping DNAPL mass reduction in real time during remediation. Initially, a coupled DNAPL-ERT numerical model was developed for exploring this potential at the field scale, generating realistic DNAPL scenarios and predicting the response of an ERT survey. Also, new four-dimensional (4D) inversion algorithms were integrated for tracking DNAPL removal over time. 4D ERT applied at the surface for mapping an evolving DNAPL distribution was first demonstrated in a laboratory experiment. Independent simulation of the experiment demonstrated the reliability of the DNAPL-ERT model for simulating real systems. The model was then used to explore the 4D ERT approach at the field scale for a range of realistic DNAPL remediation scenarios. The approach showed excellent potential for mapping shallow DNAPL changes. However, remediation at depth was not as well resolved. To overcome this limitation, a new surface-to-horizontal borehole (S2HB) ERT configuration is proposed. A second laboratory experiment was conducted that demonstrated that S2HB ERT does better resolve changes in DNAPL distribution relative to surface ERT, particularly at depth. The DNAPL-ERT model was also used to demonstrate the improved mapping of S2HB ERT for field scale DNAPL scenarios. Overall, this work demonstrates that, with these innovations, ERT exhibits significant potential as a real time, non-destructive geoenvironmental remediation site monitoring tool.

  8. Electrical Stimulation for Drug-Resistant Epilepsy

    PubMed Central

    Chambers, A; Bowen, JM

    2013-01-01

    Objective The objective of this analysis was to evaluate the effectiveness of deep brain stimulation (DBS) and vagus nerve stimulation (VNS) for the treatment of drug-resistant epilepsy in adults and children. Data Sources A literature search was performed using MEDLINE, EMBASE, the Cochrane Library, and the Centre for Reviews and Dissemination database, for studies published from January 2007 until December 2012. Review Methods Systematic reviews, meta-analyses, randomized controlled trials (RCTs), and observational studies (in the absence of RCTs) of adults or children were included. DBS studies were included if they specified that the anterior nucleus of thalamus was the area of the brain stimulated. Outcomes of interest were seizure frequency, health resource utilization, and safety. A cost analysis was also performed. Results The search identified 6 studies that assessed changes in seizure frequency after electrical stimulation: 1 RCT on DBS in adults, 4 RCTs on VNS in adults, and 1 RCT on VNS in children. The studies of DBS and VNS in adults found significantly improved rates of seizure frequency, but the study of VNS in children did not find a significant difference in seizure frequency between the high and low stimulation groups. Significant reductions in hospitalizations and emergency department visits were found for adults and children who received VNS. No studies addressed the use of health resources for patients undergoing DBS. Five studies reported on adverse events, which ranged from serious to transient for both procedures in adults and were mostly transient in the 1 study of VNS in children. Limitations We found no evidence on DBS in children or on health care use related to DBS. The measurement of seizure frequency is self-reported and is therefore subject to bias and issues of compliance. Conclusions Based on evidence of low to moderate quality, both DBS and VNS seemed to reduce seizure frequency in adults. In children, VNS did not appear to be as

  9. Correlating electrical resistance to growth conditions for multiwalled carbon nanotubes

    SciTech Connect

    Lan, Chun; Amama, Placidus B.; Fisher, Timothy S.; Reifenberger, Ronald G.

    2007-08-27

    A correlation between growth temperature and electrical resistance of multiwalled carbon nanotubes (MWNTs) has been established by measuring the resistance of individual MWNTs grown by microwave plasma-enhanced chemical vapor deposition (PECVD) at 800, 900, and 950 deg. C. The lowest resistances were obtained mainly from MWNTs grown at 900 deg. C. The MWNT resistance is larger on average at lower (800 deg. C) and higher (950 deg. C) growth temperatures. The resistance of MWNTs correlated well with other MWNT quality indices obtained from Raman spectra. This study identifies a temperature window for growing higher-quality MWNTs with fewer defects and lower resistance by PECVD.

  10. Correlating electrical resistance to growth conditions for multiwalled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Lan, Chun; Amama, Placidus B.; Fisher, Timothy S.; Reifenberger, Ronald G.

    2007-08-01

    A correlation between growth temperature and electrical resistance of multiwalled carbon nanotubes (MWNTs) has been established by measuring the resistance of individual MWNTs grown by microwave plasma-enhanced chemical vapor deposition (PECVD) at 800, 900, and 950°C. The lowest resistances were obtained mainly from MWNTs grown at 900°C. The MWNT resistance is larger on average at lower (800°C) and higher (950°C) growth temperatures. The resistance of MWNTs correlated well with other MWNT quality indices obtained from Raman spectra. This study identifies a temperature window for growing higher-quality MWNTs with fewer defects and lower resistance by PECVD.

  11. State Waste Discharge Permit Application: Electric resistance tomography testing

    SciTech Connect

    Not Available

    1994-04-01

    This permit application documentation is for a State Waste Discharge Permit issued in accordance with requirements of Washington Administrative Code 173-216. The activity being permitted is a technology test using electrical resistance tomography. The electrical resistance tomography technology was developed at Lawrence Livermore National Laboratory and has been used at other waste sites to track underground contamination plumes. The electrical resistance tomography technology measures soil electrical resistance between two electrodes. If a fluid contaminated with electrolytes is introduced into the soil, the soil resistance is expected to drop. By using an array of measurement electrodes in several boreholes, the areal extent of contamination can be estimated. At the Hanford Site, the purpose of the testing is to determine if the electrical resistance tomography technology can be used in the vicinity of large underground metal tanks without the metal tank interfering with the test. It is anticipated that the electrical resistance tomography technology will provide a method for accurately detecting leaks from the bottom of underground tanks, such as the Hanford Site single-shell tanks.

  12. Thermal conductivity and electrical resistivity of porous materials

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

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

  13. Experimental study on the electrical resistivity of soil cement admixtures

    NASA Astrophysics Data System (ADS)

    Liu, Song Yu; Du, Yan Jun; Han, L. H.; Gu, M. F.

    2008-05-01

    Recently in China, soil cement is widely used to improve the soft ground in the highway construction engineering. Literature studies are mainly investigating the mechanical properties of the soil cement, while its properties of the electrical resistivity are not well addressed. In this paper, the properties of the electrical resistivity of the reconstituted soil-cement and the in situ soil cement columns are investigated. The test results show that the electrical resistivity of the soil cement increases with the increase in the cement-mixing ratio and curing time, whereas it decreases with the increase in the water content, degree of saturation and water cement ratio. A simple equation is proposed to predict the electrical resistivity of soil cement under the condition of the specified curing time and water cement ratio. It is found that the electrical resistivity has a good relationship with the unconfined compression strength and blow count of SPT. It is expected that the electrical resistivity method can be widely used for checking/controlling the quality of soil cement in practice.

  14. Electrical resistance tomography using steel cased boreholes as electrodes

    DOEpatents

    Daily, William D.; Ramirez, Abelardo L.

    1999-01-01

    An electrical resistance tomography method using steel cased boreholes as electrodes. The method enables mapping the electrical resistivity distribution in the subsurface from measurements of electrical potential caused by electrical currents injected into an array of electrodes in the subsurface. By use of current injection and potential measurement electrodes to generate data about the subsurface resistivity distribution, which data is then used in an inverse calculation, a model of the electrical resistivity distribution can be obtained. The inverse model may be constrained by independent data to better define an inverse solution. The method utilizes pairs of electrically conductive (steel) borehole casings as current injection electrodes and as potential measurement electrodes. The greater the number of steel cased boreholes in an array, the greater the amount of data is obtained. The steel cased boreholes may be utilized for either current injection or potential measurement electrodes. The subsurface model produced by this method can be 2 or 3 dimensional in resistivity depending on the detail desired in the calculated resistivity distribution and the amount of data to constain the models.

  15. Electrical resistance tomography using steel cased boreholes as electrodes

    DOEpatents

    Daily, W.D.; Ramirez, A.L.

    1999-06-22

    An electrical resistance tomography method is described which uses steel cased boreholes as electrodes. The method enables mapping the electrical resistivity distribution in the subsurface from measurements of electrical potential caused by electrical currents injected into an array of electrodes in the subsurface. By use of current injection and potential measurement electrodes to generate data about the subsurface resistivity distribution, which data is then used in an inverse calculation, a model of the electrical resistivity distribution can be obtained. The inverse model may be constrained by independent data to better define an inverse solution. The method utilizes pairs of electrically conductive (steel) borehole casings as current injection electrodes and as potential measurement electrodes. The greater the number of steel cased boreholes in an array, the greater the amount of data is obtained. The steel cased boreholes may be utilized for either current injection or potential measurement electrodes. The subsurface model produced by this method can be 2 or 3 dimensional in resistivity depending on the detail desired in the calculated resistivity distribution and the amount of data to constrain the models. 2 figs.

  16. Four-terminal electrical testing device. [initiator bridgewire resistance

    NASA Technical Reports Server (NTRS)

    Robinson, Robert L. (Inventor); Graves, Thomas J. (Inventor); Hoffman, William C., III (Inventor)

    1987-01-01

    The invention relates to a four-terminal electrical connector device for testing and measuring unknown resistances of initiators used for starting pyrotechnic events aboard the space shuttle. The testing device minimizes contact resistance degradation effects and so improves the reliability of resistance measurements taken with the device. Separate and independent voltage sensing and current supply circuits each include a pair of socket contacts for mating engagement with the pins of the initiator. The unknown resistance that is measured by the device is the resistance of the bridgewire of the initiator which is required to be between 0.95 and 1.15 ohms.

  17. Slime thickness evaluation of bored piles by electrical resistivity probe

    NASA Astrophysics Data System (ADS)

    Chun, Ok-Hyun; Yoon, Hyung-Koo; Park, Min-Chul; Lee, Jong-Sub

    2014-09-01

    The bottoms of bored piles are generally stacked with soil particles, both while boreholes are being drilled, and afterward. The stacked soils are called slime, and when loads are applied on the pile, increase the pile settlement. Thus to guarantee the end bearing capacity of bored piles, the slime thickness should be precisely detected. The objective of this study is to suggest a new method for evaluating the slime thickness, using temperature compensated electrical resistivity. Laboratory studies are performed in advance, to estimate and compare the resolution of the electrical resistivity probe (ERP) and time domain reflectometry (TDR). The electrical properties of the ERP and TDR are measured using coaxial type electrodes and parallel type two-wire electrodes, respectively. Penetration tests, conducted in the fully saturated sand-clay mixtures, demonstrate that the ERP produces a better resolution of layer detection than TDR. Thus, field application tests using the ERP with a diameter of 35.7 mm are conducted for the investigation of slime thickness in large diameter bored piles. Field tests show that the slime layers are clearly identified by the ERP: the electrical resistivity dramatically increases at the interface between the slurry and slime layer. The electrical resistivity in the slurry layer inversely correlates with the amount of circulated water. This study suggests that the new electrical resistivity method may be a useful method for the investigation of the slime thickness in bored piles.

  18. Electrical resistivity of coal-bearing rocks under high temperature and the detection of coal fires using electrical resistance tomography

    NASA Astrophysics Data System (ADS)

    Shao, Zhenlu; Wang, Deming; Wang, Yanming; Zhong, Xiaoxing; Tang, Xiaofei; Xi, Dongdong

    2016-02-01

    Coal fires are severe hazards to environment, health and safety throughout the world. Efficient and economical extinguishing of these fires requires that the extent of the subsurface coal fires should be delineated. Electrical and electromagnetic methods have been used to detect coal fires in recent years. However, the resistivity change of coal-bearing rocks at high temperature is rarely investigated. The resistivity characteristics of coal fires at different temperatures and depths are seldomly researched as well. In this paper, we present the results of measurements of several coal-bearing rocks' resistivity and permeability under high temperature. Two major causes for the change in resistivity with increasing temperature are recognized, there are the increase of charge carriers and thermal fracturing, of which the first one is probably the dominant cause. A set of 2-D simulations is carried out to compare the relation of resolution and efficiency of coal fires detection to temperature and depth when adopting the electrical resistance tomography. The simulation results show that the resolution and efficiency decrease with the decrease of temperature and the increase of depth. Finally, the electrical resistance tomography is used to delineate coal fires in the Anjialing Open Pit Mine. Most low-resistivity regions are verified as coal-fire areas according to the long-term monitoring of borehole temperature. The results indicate that the electrical resistance tomography can be used as a tool for the detection of coal fires.

  19. Electrical Resistivity Measurements of Hot Dense Aluminum

    NASA Astrophysics Data System (ADS)

    Benage, J. F.; Shanahan, W. R.; Murillo, M. S.

    1999-10-01

    Electrical transport properties of dense aluminum are measured in the disordered liquidlike phase using a well-tamped, thermally equilibrated, exploding wire z pinch. Direct measurements of the electrical conductivity have been made using voltage and current measurements. Our measurements span the minimum conductivity regime, at higher densities than have been produced previously. We find that some Ziman-like theoretical predictions are in fair agreement with the data and one Ziman-like theoretical approach is in good agreement, in contrast to other experiments performed in similar regimes which indicate poor agreement with such theories.

  20. Influence of Electrical Resistivity and Machining Parameters on Electrical Discharge Machining Performance of Engineering Ceramics

    PubMed Central

    Ji, Renjie; Liu, Yonghong; Diao, Ruiqiang; Xu, Chenchen; Li, Xiaopeng; Cai, Baoping; Zhang, Yanzhen

    2014-01-01

    Engineering ceramics have been widely used in modern industry for their excellent physical and mechanical properties, and they are difficult to machine owing to their high hardness and brittleness. Electrical discharge machining (EDM) is the appropriate process for machining engineering ceramics provided they are electrically conducting. However, the electrical resistivity of the popular engineering ceramics is higher, and there has been no research on the relationship between the EDM parameters and the electrical resistivity of the engineering ceramics. This paper investigates the effects of the electrical resistivity and EDM parameters such as tool polarity, pulse interval, and electrode material, on the ZnO/Al2O3 ceramic's EDM performance, in terms of the material removal rate (MRR), electrode wear ratio (EWR), and surface roughness (SR). The results show that the electrical resistivity and the EDM parameters have the great influence on the EDM performance. The ZnO/Al2O3 ceramic with the electrical resistivity up to 3410 Ω·cm can be effectively machined by EDM with the copper electrode, the negative tool polarity, and the shorter pulse interval. Under most machining conditions, the MRR increases, and the SR decreases with the decrease of electrical resistivity. Moreover, the tool polarity, and pulse interval affect the EWR, respectively, and the electrical resistivity and electrode material have a combined effect on the EWR. Furthermore, the EDM performance of ZnO/Al2O3 ceramic with the electrical resistivity higher than 687 Ω·cm is obviously different from that with the electrical resistivity lower than 687 Ω·cm, when the electrode material changes. The microstructure character analysis of the machined ZnO/Al2O3 ceramic surface shows that the ZnO/Al2O3 ceramic is removed by melting, evaporation and thermal spalling, and the material from the working fluid and the graphite electrode can transfer to the workpiece surface during electrical discharge

  1. Influence of electrical resistivity and machining parameters on electrical discharge machining performance of engineering ceramics.

    PubMed

    Ji, Renjie; Liu, Yonghong; Diao, Ruiqiang; Xu, Chenchen; Li, Xiaopeng; Cai, Baoping; Zhang, Yanzhen

    2014-01-01

    Engineering ceramics have been widely used in modern industry for their excellent physical and mechanical properties, and they are difficult to machine owing to their high hardness and brittleness. Electrical discharge machining (EDM) is the appropriate process for machining engineering ceramics provided they are electrically conducting. However, the electrical resistivity of the popular engineering ceramics is higher, and there has been no research on the relationship between the EDM parameters and the electrical resistivity of the engineering ceramics. This paper investigates the effects of the electrical resistivity and EDM parameters such as tool polarity, pulse interval, and electrode material, on the ZnO/Al2O3 ceramic's EDM performance, in terms of the material removal rate (MRR), electrode wear ratio (EWR), and surface roughness (SR). The results show that the electrical resistivity and the EDM parameters have the great influence on the EDM performance. The ZnO/Al2O3 ceramic with the electrical resistivity up to 3410 Ω·cm can be effectively machined by EDM with the copper electrode, the negative tool polarity, and the shorter pulse interval. Under most machining conditions, the MRR increases, and the SR decreases with the decrease of electrical resistivity. Moreover, the tool polarity, and pulse interval affect the EWR, respectively, and the electrical resistivity and electrode material have a combined effect on the EWR. Furthermore, the EDM performance of ZnO/Al2O3 ceramic with the electrical resistivity higher than 687 Ω·cm is obviously different from that with the electrical resistivity lower than 687 Ω·cm, when the electrode material changes. The microstructure character analysis of the machined ZnO/Al2O3 ceramic surface shows that the ZnO/Al2O3 ceramic is removed by melting, evaporation and thermal spalling, and the material from the working fluid and the graphite electrode can transfer to the workpiece surface during electrical discharge

  2. Skin electrical resistance does not change following infraclavicular block.

    PubMed

    Lehavi, Amit; Kiorescu, Alexander; Abecasis, Philippe; Baskevitch, Arkady; Katz, Yeshayahu

    2012-06-01

    Peripheral nerve blocks are common and effective means for anesthesia for limb surgery. The evaluation of the success of a peripheral blockade is based on the loss of sensation, with no objective means of detecting a successful block. The autonomic innervation to the upper extremity, which controls both the vascular tone and the activity of sweat glands, is supplied by nerve fibers accompanying the somatic nerve fibers. Previous studies have shown changes in both skin temperature and electrical resistance of the skin following brachial plexus block. We studied 20 patients undergoing hand surgery under infraclavicular brachial plexus block. The electrical resistance of the skin on the palmar aspect of the forearm was continuously recorded on the block arm and on the contralateral arm using a commercial skin resistance monitor. No statistically significant change in the electrical resistance of the skin was observed during 20 minutes after placement of the block. These results strongly suggest that the electrical resistance of the skin cannot be used to predict a successful infraclavicular block. PMID:22848979

  3. Electrical resistivity of Au-ZnO nanocomposite films

    SciTech Connect

    Argibay, N.; Goeke, R. S.; Dugger, M. T.; Rodriguez, M. A.; Michael, J. R.; Prasad, S. V.

    2013-04-14

    The electrical resistivity of electron beam codeposited gold and zinc oxide (Au-ZnO) films was investigated over the full composition range. The electrical resistivity was shown to increase monotonically with increasing ZnO content, with three characteristic regimes of behavior associated primarily with (1) grain boundary electron scattering due to grain refinement at ZnO volume fractions below 0.3, (2) percolation theory for ZnO volume fractions at and above the percolation threshold (f{sub c} = 0.85), and (3) a transition region between these where it was proposed that resistivity was influenced by the formation of Au-Zn complexes due to an oxygen deficiency in the deposited ZnO. The electrical resistivity of the composite films remained below 100 {mu}{Omega} cm for ZnO volume fractions below 0.5. A model combining the general effective media equation and Mayadas-Shatzkes grain boundary electron scattering model was shown to generally describe the composition dependence of electrical resistivity for the investigated oxide dispersion hardened metal-matrix composite thin films.

  4. Using electrical resistance tomography to map subsurface temperatures

    DOEpatents

    Ramirez, Abelardo L.; Chesnut, Dwayne A.; Daily, William D.

    1994-01-01

    A method is provided for measuring subsurface soil or rock temperatures remotely using electrical resistivity tomography (ERT). Electrical resistivity measurements are made using electrodes implanted in boreholes driven into the soil and/or at the ground surface. The measurements are repeated as some process changes the temperatures of the soil mass/rock mass. Tomographs of electrical resistivity are calculated based on the measurements using Poisson's equation. Changes in the soil/rock resistivity can be related to changes in soil/rock temperatures when: (1) the electrical conductivity of the fluid trapped in the soil's pore space is low, (2) the soil/rock has a high cation exchange capacity and (3) the temperature changes are sufficiently high. When these three conditions exist the resistivity changes observed in the ERT tomographs can be directly attributed to changes in soil/rock temperatures. This method provides a way of mapping temperature changes in subsurface soils remotely. Distances over which the ERT method can be used to monitor changes in soil temperature range from tens to hundreds of meters from the electrode locations.

  5. Using electrical resistance tomography to map subsurface temperatures

    DOEpatents

    Ramirez, A.L.; Chesnut, D.A.; Daily, W.D.

    1994-09-13

    A method is provided for measuring subsurface soil or rock temperatures remotely using electrical resistivity tomography (ERT). Electrical resistivity measurements are made using electrodes implanted in boreholes driven into the soil and/or at the ground surface. The measurements are repeated as some process changes the temperatures of the soil mass/rock mass. Tomographs of electrical resistivity are calculated based on the measurements using Poisson's equation. Changes in the soil/rock resistivity can be related to changes in soil/rock temperatures when: (1) the electrical conductivity of the fluid trapped in the soil's pore space is low, (2) the soil/rock has a high cation exchange capacity and (3) the temperature changes are sufficiently high. When these three conditions exist the resistivity changes observed in the ERT tomographs can be directly attributed to changes in soil/rock temperatures. This method provides a way of mapping temperature changes in subsurface soils remotely. Distances over which the ERT method can be used to monitor changes in soil temperature range from tens to hundreds of meters from the electrode locations. 1 fig.

  6. Modeling the Electrical Contact Resistance at Steel-Carbon Interfaces

    NASA Astrophysics Data System (ADS)

    Brimmo, Ayoola T.; Hassan, Mohamed I.

    2016-01-01

    In the aluminum smelting industry, electrical contact resistance at the stub-carbon (steel-carbon) interface has been recurrently reported to be of magnitudes that legitimately necessitate concern. Mitigating this via finite element modeling has been the focus of a number of investigations, with the pressure- and temperature-dependent contact resistance relation frequently cited as a factor that limits the accuracy of such models. In this study, pressure- and temperature-dependent relations are derived from the most extensively cited works that have experimentally characterized the electrical contact resistance at these contacts. These relations are applied in a validated thermo-electro-mechanical finite element model used to estimate the voltage drop across a steel-carbon laboratory setup. By comparing the models' estimate of the contact electrical resistance with experimental measurements, we deduce the applicability of the different relations over a range of temperatures. The ultimate goal of this study is to apply mathematical modeling in providing pressure- and temperature-dependent relations that best describe the steel-carbon electrical contact resistance and identify the best fit relation at specific thermodynamic conditions.

  7. High electrical resistivity carbon/graphite fibers

    NASA Technical Reports Server (NTRS)

    Vogel, F. L.; Forsman, W. C.

    1980-01-01

    Carbon/graphite fibers were chemically oxidized in the liquid phase to fibers of graphite oxide. Resistivity increases as high as 10,000 times were obtained, the oxidized fiber decomposed on exposure to atmosphere. A factor of 1,000 remained as a stable increment. The largest change observed was 1,000,000 times. Best results were obtained on the most highly graphitized fibers. Electrochemical oxidation yielded a lower increase--about 10 times, but provided a controllable method of synthesis and insight to the mechanism of reaction. Tensile tests indicated that the strength of the fiber on oxidation was decreased by no more than 25 percent.

  8. Electrical resistance tomography experiments at the Oregon Graduate Institute

    NASA Astrophysics Data System (ADS)

    Daily, W.; Ramirez, A.; LaBrecque, D.; Barber, W.

    1995-04-01

    Three controlled experiments were conducted at the Oregon Graduate Institute (OGI) with the purpose of evaluating electrical resistance tomography for imaging underground processes associated with in-situ site assessment and remediation. The OGI facilities are unique: a double-wall tank 10 m square and 5 m deep, filled with river bottom sediments and instrumented for geophysical and hydrological studies. At this facility, liquid contaminants could be released into the confined soil at a scale sufficiently large to represent real-world physical phenomena. In the first test, images of electrical resistivity were made before and during a controlled spill of gasoline into a sandy soil. The primary purpose was to determine if electrical resistivity images could detect the hydrocarbon in either the vadose or saturated zone. Definite changes in electrical resistivity were observed in both the vadose and saturated soils. The effects were an increase in resistivity of as much as 10% above pre-release values. A single resistive anomaly was imaged, directly below the release point, principally within the vadose zone but extending below the phreatic surface. The anomaly remained identifiable in tomograms taken two days after the release ended with clear indications of lateral spreading along the water table. The second test involved electrical resistance measurements before, during, and after air sparging in a saturated soil. The primary purpose was to determine if the electrical images could be used to detect and delineate the extent of the zone influenced by sparging. The images showed an increase of about 20% in resistivity over background values within the sparged zone and the extent of the imaged zone agreed with that inferred from other information. Electrical resistivity tomography measurements were made under a simulated oil storage tank in the third test. Comparison of images taken before and during separate releases of brine and water showed effects of changes

  9. Resistance after firing protected electric match. [Patent application

    DOEpatents

    Montoya, A.P.

    1980-03-20

    An electric match having electrical leads embedded in flame-producing compound is protected against an accidental resistance across the leads after firing by a length of heat-shrinkable tubing encircling the match body and having a skirt portion extending beyond the leads. The heat of the burning match and an adjacent thermal battery causes the tubing to fold over the end of the match body, covering the ends of the leads and protecting them from molten pieces of the battery.

  10. Equivalent Electrical Circuit Representations of AC Quantized Hall Resistance Standards

    PubMed Central

    Cage, M. E.; Jeffery, A.; Matthews, J.

    1999-01-01

    We use equivalent electrical circuits to analyze the effects of large parasitic impedances existing in all sample probes on four-terminal-pair measurements of the ac quantized Hall resistance RH. The circuit components include the externally measurable parasitic capacitances, inductances, lead resistances, and leakage resistances of ac quantized Hall resistance standards, as well as components that represent the electrical characteristics of the quantum Hall effect device (QHE). Two kinds of electrical circuit connections to the QHE are described and considered: single-series “offset” and quadruple-series. (We eliminated other connections in earlier analyses because they did not provide the desired accuracy with all sample probe leads attached at the device.) Exact, but complicated, algebraic equations are derived for the currents and measured quantized Hall voltages for these two circuits. Only the quadruple-series connection circuit meets our desired goal of measuring RH for both ac and dc currents with a one-standard-deviation uncertainty of 10−8 RH or less during the same cool-down with all leads attached at the device. The single-series “offset” connection circuit meets our other desired goal of also measuring the longitudinal resistance Rx for both ac and dc currents during that same cool-down. We will use these predictions to apply small measurable corrections, and uncertainties of the corrections, to ac measurements of RH in order to realize an intrinsic ac quantized Hall resistance standard of 10−8 RH uncertainty or less.

  11. Electrical Resistivity Changes in Saturated Rock under Stress.

    PubMed

    Brace, W F; Orange, A S

    1966-09-23

    Electrical resistivity of water-saturated crystalline rock such as granite, diabase, dunite, or quartzite changes by an order of magnitude prior to fracture of the rock in compression. The effect observed even under high confining pressure is due to formation of open cracks which first appear at one-third to two-thirds the fracture stress.

  12. Using electrical resistance probes for moisture determination in switchgrass windrows

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Determining moisture levels in windrowed biomass is important for both forage producers and researchers. Energy crops such as switchgrass have been troublesome when using the standard methods set for electrical resistance meters. The objectives of this study were to i) develop the methodologies need...

  13. Electrical Resistivity Changes in Saturated Rock under Stress.

    PubMed

    Brace, W F; Orange, A S

    1966-09-23

    Electrical resistivity of water-saturated crystalline rock such as granite, diabase, dunite, or quartzite changes by an order of magnitude prior to fracture of the rock in compression. The effect observed even under high confining pressure is due to formation of open cracks which first appear at one-third to two-thirds the fracture stress. PMID:17749731

  14. Seasonal Variations in Subsurface Electrical Resistivity in a Floodplain Aquifer

    NASA Astrophysics Data System (ADS)

    Esker, A.; Marshall, S. T.

    2015-12-01

    In an attempt to create a three-dimensional model of a floodplain aquifer along the New River in western North Carolina, we have collected numerous DC electrical resistivity profiles over the course of six years. Unfortunately, the electrical resistivity of geologic materials can be partially controlled by temperature and water content which both vary temporally. To determine the extent to which resistivity data is affected by temporal variations at our site, we conducted multiple DC electrical resistivity surveys collected at the same location at various times of the year to quantify changes in the resistivity patterns. We use a Wenner array that offers a large signal to noise ratio, but relatively few data points, and a Dipole-Dipole array that produces more data, but is more sensitive to noise. For each data acquisition date, we measure the depth to water at seven boreholes parallel to the survey to determine if any of the collected resistivity surveys can be independently used to detect the water table and if any changes affect subsurface resistivities. We created a stacked model of all surveys of the same array type, and compare to each survey to qualitatively and quantitatively identify changes in the subsurface patterns. Results indicate there are few major changes in the qualitative subsurface patterns with time. RMS errors between the stacked model and different surveys range from 56 to 201 Ohm-m and percent differences range from 5.84% to 21.50%. The surveys with largest RMS errors correspond to days that had a significant change of water table level from the static level. Our preliminary results suggest that so long as surveys are collected during similar water table conditions, data from multiple years should yield similar results. Furthermore, the subsurface resistivity values and GPR surveys do not clearly delineate the water table levels, suggesting that near surface geophysical methods many not be able to detect the water table at our site.

  15. Electrical resistance of complex two-dimensional structures of loops

    NASA Astrophysics Data System (ADS)

    Gomes, M. A. F.; Hora, R. R.; Brito, V. P.

    2011-06-01

    This work presents a study of the dc electrical resistance of a recently discovered hierarchical two-dimensional system which has a complex topology consisting of a distribution of disordered macroscopic loops with no characteristic size and a distribution of several types of contacts between loops. In addition to its intrinsic interest in the important context of low-dimensional systems and crumpled systems, the structures under study are of relevance in a number of areas including soft condensed matter and packing of DNA in viral capsids. In the particular case discussed here, the loops are made of layers of graphite with a height of tens of nanometers deposited on a substrate of cellulose. Experiments with these systems indicate an anomalous electrical resistance of sub-diffusive type. The results reported here are explained with scaling arguments and computer simulation. A comparison with the dc electrical properties of percolation clusters is made, and some other experimental issues as future prospects are commented.

  16. Measuring the electrical resistivity and contact resistance of vertical carbon nanotube bundles for application as interconnects

    NASA Astrophysics Data System (ADS)

    Chiodarelli, Nicolo'; Masahito, Sugiura; Kashiwagi, Yusaku; Li, Yunlong; Arstila, Kai; Richard, Olivier; Cott, Daire J.; Heyns, Marc; De Gendt, Stefan; Groeseneken, Guido; Vereecken, Philippe M.

    2011-02-01

    Carbon nanotubes (CNT) are known to be materials with potential for manufacturing sub-20 nm high aspect ratio vertical interconnects in future microchips. In order to be successful with respect to contending against established tungsten or copper based interconnects, though, CNT must fulfil their promise of also providing low electrical resistance in integrated structures using scalable integration processes fully compatible with silicon technology. Hence, carefully engineered growth and integration solutions are required before we can fully exploit their potentialities. This work tackles the problem of optimizing a CNT integration process from the electrical perspective. The technique of measuring the CNT resistance as a function of the CNT length is here extended to CNT integrated in vertical contacts. This allows extracting the linear resistivity and the contact resistance of the CNT, two parameters to our knowledge never reported separately for vertical CNT contacts and which are of utmost importance, as they respectively measure the quality of the CNT and that of their metal contacts. The technique proposed allows electrically distinguishing the impact of each processing step individually on the CNT resistivity and the CNT contact resistance. Hence it constitutes a powerful technique for optimizing the process and developing CNT contacts of superior quality. This can be of relevant technological importance not only for interconnects but also for all those applications that rely on the electrical properties of CNT grown with a catalytic chemical vapor deposition method at low temperature.

  17. Electrical Resistance Technique to Monitor SiC Composite Detection

    NASA Technical Reports Server (NTRS)

    Smith, Craig; Morscher, Gregory; Xia, Zhenhai

    2008-01-01

    Ceramic matrix composites are suitable for high temperature structural applications such as turbine airfoils and hypersonic thermal protection systems. The employment of these materials in such applications is limited by the ability to process components reliable and to accurately monitor and predict damage evolution that leads to failure under stressed-oxidation conditions. Current nondestructive methods such as ultrasound, x-ray, and thermal imaging are limited in their ability to quantify small scale, transverse, in-plane, matrix cracks developed over long-time creep and fatigue conditions. Electrical resistance of SiC/SiC composites is one technique that shows special promise towards this end. Since both the matrix and the fibers are conductive, changes in matrix or fiber properties should relate to changes in electrical conductivity along the length of a specimen or part. The effect of matrix cracking on electrical resistivity for several composite systems will be presented and some initial measurements performed at elevated temperatures under stress-rupture conditions. The implications towards electrical resistance as a technique applied to composite processing, damage detection (health monitoring), and life-modeling will be discussed.

  18. Recent Advances in Electrical Resistance Preheating of Aluminum Reduction Cells

    NASA Astrophysics Data System (ADS)

    Ali, Mohamed Mahmoud; Kvande, Halvor

    2016-06-01

    ABSTRACT There are two mainpreheating methods that are used nowadays for aluminum reduction cells. One is based on electrical resistance preheating with a thin bed of small coke and/or graphite particles between the anodes and the cathode carbon blocks. The other is flame preheating, where two or more gas or oil burners are used. Electrical resistance preheating is the oldest method, but is still frequently used by different aluminum producers. Many improvements have been made to this method by different companies over the last decade. In this paper, important points pertaining to the preparation and preheating of these cells, as well as measurements made during the preheating process and evaluation of the performance of the preheating, are illustrated. The preheating times of these cells were found to be between 36 h and 96 h for cell currents between 176 kA and 406 kA, while the resistance bed thickness was between 13 mm and 60 mm. The average cathode surface temperature at the end of the preheating was usually between 800°C and 950°C. The effect of the preheating methods on cell life is unclear and no quantifiable conclusions can be drawn. Some works carried out in the mathematical modeling area are also discussed. It is concluded that there is a need for more studies with real situations for preheated cells on the basis of actual measurements. The expected development in electrical resistance preheating of aluminum reduction cells is also summarized.

  19. Soil characterization using electrical resistivity tomography and geotechnical investigations

    NASA Astrophysics Data System (ADS)

    Sudha, Kumari; Israil, M.; Mittal, S.; Rai, J.

    2009-01-01

    Electrical Resistivity Tomography (ERT) has been used in association with Standard Penetration Test (SPT) and Dynamic Cone Penetration Test (DCPT) for Geotechnical investigations at two sites, proposed for thermal power plants, in Uttar Pradesh (UP), India. SPT and DCPT tests were conducted at 28 points and two ERT profiles, each measuring 355 m long, were recorded using 72 electrodes deployed at 5 m spacing. Electrical characterization of subsurface soil was done using borehole data and grain size analysis of the soil samples collected from boreholes. The concept of electrical resistivity variation with soil strength related to the grain size distribution, cementation, porosity and saturation has been used to correlate the transverse resistance of soil with the number of blow counts ( N-values) obtained from SPT and DCPT data. It was thus observed that the transverse resistance of soil column is linearly related with the number of blow counts ( N-values) at these sites. The linear relationships are site-specific and the coefficients of linear relation are sensitive to the lithology of subsurface formation, which was verified by borehole data. The study demonstrates the usefulness of the ERT method in geotechnical investigations, which is economic, efficient and less time consuming in comparison to the other geotechnical methods, such as SPT and DCPT, used for the purpose.

  20. Electrical Resistivity Monitoring of Voids: Results of Dynamic Modeling Experiments

    NASA Astrophysics Data System (ADS)

    Lane, J. W.; Day-Lewis, F. D.; Singha, K.

    2006-05-01

    Remote, non-invasive detection of voids is a challenging problem for environmental and engineering investigations in karst terrain. Many geophysical methods including gravity, electrical, electromagnetic, magnetic, and seismic have potential to detect voids in the subsurface; lithologic heterogeneity and method- specific sources of noise, however, can mask the geophysical signatures of voids. New developments in automated, autonomous geophysical monitoring technology now allow for void detection using differential geophysics. We propose automated collection of electrical resistivity measurements over time. This dynamic approach exploits changes in subsurface electrical properties related to void growth or water-table fluctuation in order to detect voids that would be difficult or impossible to detect using static imaging approaches. We use a series of synthetic modeling experiments to demonstrate the potential of difference electrical resistivity tomography for finding (1) voids that develop vertically upward under a survey line (e.g., an incipient sinkhole); (2) voids that develop horizontally toward a survey line (e.g., a tunnel); and (3) voids that are influenced by changing hydrologic conditions (e.g., void saturation and draining). Synthetic datasets are simulated with a 3D finite-element model, but the inversion assumes a 2D forward model to mimic conventional practice. The results of the synthetic modeling experiments provide insights useful for planning and implementing field-scale monitoring experiments using electrical methods.

  1. Characterization of fracture aperture field heterogeneity by electrical resistance measurement.

    PubMed

    Boschan, A; Ippolito, I; Chertcoff, R; Hulin, J P; Auradou, H

    2011-04-01

    We use electrical resistance measurements to characterize the aperture field in a rough fracture. This is done by performing displacement experiments using two miscible fluids of different electrical resistivity and monitoring the time variation of the overall fracture resistance. Two fractures have been used: their complementary rough walls are identical but have different relative shear displacements which create "channel" or "barrier" structures in the aperture field, respectively parallel or perpendicular to the mean flow velocity U(→). In the "channel" geometry, the resistance displays an initial linear variation followed by a tail part which reflects the velocity contrast between slow and fast flow channels. In the "barrier" geometry, a change in the slope between two linear zones suggests the existence of domains of different characteristic aperture along the fracture. These variations are well reproduced analytically and numerically using simple flow models. For each geometry, we present then a data inversion procedure that allows one to extract the key features of the heterogeneity from the resistance measurement.

  2. High precision measurement of electrical resistance across endothelial cell monolayers.

    PubMed

    Tschugguel, W; Zhegu, Z; Gajdzik, L; Maier, M; Binder, B R; Graf, J

    1995-05-01

    Effects of vasoactive agonists on endothelial permeability was assessed by measurement of transendothelial electrical resistance (TEER) of human umbilical vein endothelial cells (HUVECs) grown on porous polycarbonate supports. Because of the low values of TEER obtained in this preparation (< 5 omega cm2) a design of an Ussing type recording chamber was chosen that provided for a homogeneous electric field across the monolayer and for proper correction of series resistances. Precision current pulses and appropriate rates of sampling and averaging of the voltage signal allowed for measurement of < 0.1 omega resistance changes of the endothelium on top of a 21 omega series resistance of the support and bathing fluid layers. Histamine (10 microM) and thrombin (10 U/ml) induced an abrupt and substantial decrease of TEER, bradykinin (1 microM) was less effective, PAF (380 nM) and LTC4 (1 microM) had no effect. TEER was also reduced by the calcium ionophore A-23187 (10 microM). The technique allows for measurements of TEER in low resistance monolayer cultures with high precision and time resolution. The results obtained extend previous observations in providing quantitative data on the increase of permeability of HUVECs in response to vasoactive agonists.

  3. A unique data acquisition system for electrical resistance tomography

    SciTech Connect

    Daily, W.; Ramirez, A.; Zonge, K.

    1996-01-04

    Unique capabilities are needed in instrumentation used for acquiring data to do electrical resistance tomography (ERT). A data acquisition system is described which has a good combination of the required capabilities and yet is field rugged and user friendly. The system is a multichannel detector for high data rates, can operate over a wide range of load conditions, will measure both in phase and quadrature resistance at frequencies between 0.0007 Hz and 8 kHz. The system has been used in both the field and laboratory to collect data with a typical accuracy between 1 and 10%.

  4. Aeromagnetic and electrical resistivity surveys of Ascension Island

    SciTech Connect

    Ross, H.P.; Nielson, D.L.

    1995-12-31

    As part of an evaluation of the geothermal energy potential, the University of Utah Research Institute conducted a detailed aeromagnetic survey of Ascension Island, South Atlantic Ocean, in 1983. Interpretation of the data, supported by three-dimensional numerical modeling, indicated structural features and a low-magnetization area near the center of the island. Reconnaissance and detailed electrical resistivity surveys were completed in 1984 and these identified a zone of low apparent resistivity which corresponds to anomalous temperatures and alteration well above a high-temperature geothermal system.

  5. Development of a Landslide Monitoring System using Electrical Resistivity Tomography

    NASA Astrophysics Data System (ADS)

    Hen-Jones, R. M.; Hughes, P. N.; Glendinning, S.; Gunn, D.; Chambers, J.; Stirling, R.

    2015-12-01

    Current assessments of slope stability rely on the use of point sensors, the results of which are often difficult to interpret, have relatively high associated installation and maintenance costs, and do not provide large-area coverage. A new system is currently under development, based on the use of integrated geophysical - geotechnical sensors to monitor ground water conditions via electrical resistivity tomography. This study presents the results of an in-situ electrical resistivity tomography survey, gathered over a two year investigation period at a full-scale clay test embankment in Northumberland, UK. The 3D resistivity array comprised 288 electrodes, at 0.7m grid spacing, covering an area of approximately 90 m2. The first year of investigation involved baseline data collection, followed by a second year which saw a series of deliberate interventions targeted at weakening the slope, to determine whether corresponding geotechnical property changes would be reflected in resistivity images derived from ERT. These interventions included the manual extension of four tension cracks already present in the slope, and the installation of a sprinkler system, eight months later. Laboratory methods were employed to derive a system of equations for relating resistivity to geotechnical parameters more directly relevant to slope stability, including moisture content, suction and shear strength. These equations were then applied to resistivity data gathered over the baseline and intervention periods, yielding geotechnical images of the subsurface which compared well with in-situ geotechnical point sensors. During the intervention period, no slope movement was recorded, however, tensiometers at 0.5 m and 1.0 m depths showed elevated pore pressures, with positive pressures being recorded at depths less than 0.5 m. Resistivity images were successful in capturing the extension of the tension cracks, and in identifying the development of a potential shear failure plane as water

  6. Thermal conductivity and electrical resistivity of porous material

    NASA Technical Reports Server (NTRS)

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

    1971-01-01

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

  7. Negative differential electrical resistance of a rotational organic nanomotor

    PubMed Central

    Sadeghi, Hatef; Sangtarash, Sara; Al-Galiby, Qusiy; Sparks, Rachel

    2015-01-01

    Summary A robust, nanoelectromechanical switch is proposed based upon an asymmetric pendant moiety anchored to an organic backbone between two C60 fullerenes, which in turn are connected to gold electrodes. Ab initio density functional calculations are used to demonstrate that an electric field induces rotation of the pendant group, leading to a nonlinear current–voltage relation. The nonlinearity is strong enough to lead to negative differential resistance at modest source–drain voltages. PMID:26734524

  8. Electrical resistivity of V-Cr-Ti alloys

    SciTech Connect

    Zinkle, S.J.; Gubbi, A.N.; Eatherly, W.S.

    1997-04-01

    Room temperature electrical resistivity measurements have been performed on vanadium alloys containing 3-6%Cr and 3-6%Ti in order to evaluate the microstructural stability of these alloys. A nonlinear dependence on Cr and Ti concentration was observed, which suggests that either short range ordering or solute precipitation (perhaps in concert with interstitial solute clustering) has occurred in V-6Cr-6Ti.

  9. Complex electrical resistance tomography of a subsurface PCE plume

    SciTech Connect

    Ramirez, A.; Daily, W,; LeBrecque, D.

    1996-01-01

    A controlled experiment was conducted to evaluate the performance of complex electrical resistivity tomography (CERT) for detecting and delineating free product dense non-aqueous phase liquid (DNAPL) in the subsurface. One hundred ninety liters of PCE were released at a rate of 2 liters per hour from a point 0.5 m below ground surface. The spill was conducted within a double walled tank where saturated layers of sand, bentonite and a sand/bentonite mixture were installed. Complex electrical resistance measurements were performed. Data were taken before the release, several times during, and then after the PCE was released. Magnitude and phase were measured at 1 and 64 Hz. Data from before the release were compared with those during the release for the purpose of imaging the changes in conductivity resulting from the plume. Conductivity difference tomographs showed a decrease in electrical conductivity as the DNAPL penetrated the soil. A pancake-shaped anomaly developed on the top of a bentonite layer at 2 m depth. The anomaly grew in magnitude and extent during the release and borehole television surveys data confirmed the anomaly to be free-product PCE whose downward migration was stopped by the low permeability clay. The tomographs clearly delineated the plume as a resistive anomaly.

  10. Rolling resistance of electric vehicle tires from track tests

    NASA Technical Reports Server (NTRS)

    Dustin, M. O.; Slavik, R. J.

    1982-01-01

    Special low-rolling-resistance tires were made for DOE's ETV-1 electric vehicle. Tests were conducted on these tires and on a set of standard commercial automotive tires to determine the rolling resistance as a function of time during both constant-speed tires and SAE J227a driving cycle tests. The tests were conducted on a test track at ambient temperatures that ranged from 15 to 32 C (59 to 89 F) and with tire pressures of 207 to 276 kPa (30 to 40 psi). At a contained-air temperature of 38 C (100 F) and a pressure of 207 kPa (30 psi) the rolling resistances of the electric vehicle tires and the standard commercial tires, respectively, were 0.0102 and 0.0088 kilogram per kilogram of vehicle weight. At a contained-air temperature of 38 C (100 F) and a pressure of 276 kPa (40 psi) the rolling resistances were 0.009 and 0.0074 kilogram per kilogram of vehicle weight, respectively.

  11. Metallic nanowire networks: effects of thermal annealing on electrical resistance.

    PubMed

    Langley, D P; Lagrange, M; Giusti, G; Jiménez, C; Bréchet, Y; Nguyen, N D; Bellet, D

    2014-11-21

    Metallic nanowire networks have huge potential in devices requiring transparent electrodes. This article describes how the electrical resistance of metal nanowire networks evolve under thermal annealing. Understanding the behavior of such films is crucial for the optimization of transparent electrodes which find many applications. An in-depth investigation of silver nanowire networks under different annealing conditions provides a case study demonstrating that several mechanisms, namely local sintering and desorption of organic residues, are responsible for the reduction of the systems electrical resistance. Optimization of the annealing led to specimens with transmittance of 90% (at 550 nm) and sheet resistance of 9.5 Ω sq(-1). Quantized steps in resistance were observed and a model is proposed which provides good agreement with the experimental results. In terms of thermal behavior, we demonstrate that there is a maximum thermal budget that these electrodes can tolerate due to spheroidization of the nanowires. This budget is determined by two main factors: the thermal loading and the wire diameter. This result enables the fabrication and optimization of transparent metal nanowire electrodes for solar cells, organic electronics and flexible displays.

  12. Metallic nanowire networks: effects of thermal annealing on electrical resistance.

    PubMed

    Langley, D P; Lagrange, M; Giusti, G; Jiménez, C; Bréchet, Y; Nguyen, N D; Bellet, D

    2014-11-21

    Metallic nanowire networks have huge potential in devices requiring transparent electrodes. This article describes how the electrical resistance of metal nanowire networks evolve under thermal annealing. Understanding the behavior of such films is crucial for the optimization of transparent electrodes which find many applications. An in-depth investigation of silver nanowire networks under different annealing conditions provides a case study demonstrating that several mechanisms, namely local sintering and desorption of organic residues, are responsible for the reduction of the systems electrical resistance. Optimization of the annealing led to specimens with transmittance of 90% (at 550 nm) and sheet resistance of 9.5 Ω sq(-1). Quantized steps in resistance were observed and a model is proposed which provides good agreement with the experimental results. In terms of thermal behavior, we demonstrate that there is a maximum thermal budget that these electrodes can tolerate due to spheroidization of the nanowires. This budget is determined by two main factors: the thermal loading and the wire diameter. This result enables the fabrication and optimization of transparent metal nanowire electrodes for solar cells, organic electronics and flexible displays. PMID:25267592

  13. Detecting Cracks in Ceramic Matrix Composites by Electrical Resistance

    NASA Technical Reports Server (NTRS)

    Smith, Craig; Gyekenyesi, Andrew

    2011-01-01

    The majority of damage in SiC/SiC ceramic matrix composites subjected to monotonic tensile loads is in the form of distributed matrix cracks. These cracks initiate near stress concentrations, such as 90o fiber tows or large matrix pores and continue to accumulate with additional stress until matrix crack saturation is achieved. Such damage is difficult to detect with conventional nondestructive evaluation techniques (immersion ultrasonics, x-ray, etc.). Monitoring a specimen.s electrical resistance change provides an indirect approach for monitoring matrix crack density. Sylramic-iBN fiber- reinforced SiC composites with a melt infiltrated (MI) matrix were tensile tested at room temperature. Results showed an increase in resistance of more than 500% prior to fracture, which can be detected either in situ or post-damage. A relationship between resistance change and matrix crack density was also determined.

  14. Electrical resistivity tomography investigations on a paleoseismological trenching study

    NASA Astrophysics Data System (ADS)

    Berge, Meriç Aziz

    2014-10-01

    Two-dimensional electrical resistivity tomography (ERT) investigation was performed in a paleoseismological trenching study. Data acquisition strategies such as the selection of electrode configuration and electrode intervals of ERT application were investigated in this paper. The ERT results showed that the Wenner and Wenner-Schlumberger arrays yielded similar results for subsurface characteristics whereas the DD array provided slightly different results. The combined usage of these arrays produced satisfactory images of the subsurface resistivity distribution. In addition, the electrode spacing tests revealed that a suitable interpretation of subsurface geology can be obtained from a 5 m electrode interval. However, a suitable trenching location defined by successful 2D resistivity models was obtained for 1 m electrode spacing. Therefore, the comparison of the trench and ERT results was also possible. The results of trenching and ERT studies substantially support each other.

  15. Detecting Damage in Ceramic Matrix Composites Using Electrical Resistance

    NASA Technical Reports Server (NTRS)

    Smith, Craig E.; Gyekenyesi, Andrew

    2011-01-01

    The majority of damage in SiC/SiC ceramic matrix composites subjected to monotonic tensile loads is in the form of distributed matrix cracks. These cracks initiate near stress concentrations, such as 90 deg fiber tows or large matrix pores and continue to accumulate with additional stress until matrix crack saturation is achieved. Such damage is difficult to detect with conventional nondestructive evaluation techniques (immersion ultrasonics, x-ray, etc.). Monitoring a specimen.s electrical resistance change provides an indirect approach for monitoring matrix crack density. Sylramic-iBN fiber- reinforced SiC composites with a melt infiltrated (MI) matrix were tensile tested at room temperature. Results showed an increase in resistance of more than 500% prior to fracture, which can be detected either in situ or post-damage. A relationship between resistance change and matrix crack density was also determined.

  16. Electrical Resistivity of an Elasmobranch's Ampullary Jelly in Varying Electric and Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Brown, Brandon; Hughes, Mary E.

    2001-03-01

    The ampullae of Lorenzini are believed to function as the electroreceptive organs in elasmobranch fishes. Though the entire excised organs have been the subject of electrical transport measurements, the jelly that fills the ampullae -- composed primarily of glycoproteins with proteins and dissolved salts -- has received less scrutiny. The specific electromagnetic properties of the jelly contribute to electroreception, and we hope to supply useful parameters to modeling efforts via precise electrical characterization. We report preliminary resistivity measurements from ampullary jelly removed, post mortem, from an adult triaenodon obesus (white-tip reef shark). We present data over a broad range of applied electrical currents. We also present data of the resistivity as a function of applied magnetic field strength.

  17. Cyclic electric field stress on bipolar resistive switching devices

    NASA Astrophysics Data System (ADS)

    Schulman, A.; Acha, C.

    2013-12-01

    We have studied the effects of accumulating cyclic electrical pulses of increasing amplitude on the non-volatile resistance state of interfaces made by sputtering a metal (Au, Pt) on top of the surface of a cuprate superconductor YBa2Cu3O7-δ. We have analyzed the influence of the number of applied pulses N on the relative amplitude of the remnant resistance change between the high (RH) and the low (RL) state [(α=(RH-RL)/RL] at different temperatures (T). We show that the critical voltage (Vc) needed to produce a resistive switching (RS, i.e., α >0) decreases with increasing N or T. We also find a power law relation between the voltage of the pulses and the number of pulses Nα0 required to produce a RS of α =α0. This relation remains very similar to the Basquin equation used to describe the stress-fatigue lifetime curves in mechanical tests. This points out to the similarity between the physics of the RS, associated with the diffusion of oxygen vacancies induced by electrical pulses, and the propagation of defects in materials subjected to repeated mechanical stress.

  18. Connection equation and shaly-sand correction for electrical resistivity

    USGS Publications Warehouse

    Lee, Myung W.

    2011-01-01

    Estimating the amount of conductive and nonconductive constituents in the pore space of sediments by using electrical resistivity logs generally loses accuracy where clays are present in the reservoir. Many different methods and clay models have been proposed to account for the conductivity of clay (termed the shaly-sand correction). In this study, the connectivity equation (CE), which is a new approach to model non-Archie rocks, is used to correct for the clay effect and is compared with results using the Waxman and Smits method. The CE presented here requires no parameters other than an adjustable constant, which can be derived from the resistivity of water-saturated sediments. The new approach was applied to estimate water saturation of laboratory data and to estimate gas hydrate saturations at the Mount Elbert well on the Alaska North Slope. Although not as accurate as the Waxman and Smits method to estimate water saturations for the laboratory measurements, gas hydrate saturations estimated at the Mount Elbert well using the proposed CE are comparable to estimates from the Waxman and Smits method. Considering its simplicity, it has high potential to be used to account for the clay effect on electrical resistivity measurement in other systems.

  19. Using electrical resistance probes for moisture determination in switchgrass windrows

    SciTech Connect

    Chesser Jr., G. D.; Davis, J. D.; Purswell, J. L.; Lemus, R.

    2011-08-01

    Determining moisture levels in windrowed biomass is important for both forage producers and researchers. Energy crops such as switchgrass have been troublesome when using the standard methods set for electrical resistance meters. The objectives of this study were to i) develop the methodologies needed to measure MC in switchgrass using electrical resistance meters, ii) to determine the effects of pressure and probe orientation on MC measurement and iii) to generate MC calibration equations for electrical resistance meters using switchgrass in the senescence growth stage. Two meters (Meter 1, Farmex HT-PRO; Meter 2, Delmhorst F-2000) were selected based on commercial availability. A forage compression apparatus was designed and constructed with on-farm materials and methods to provide a simple system of applying pressure achievable by any forage producer or researcher in the field. Two trials were performed to test four levels of moisture contents (10, 20, 30, and 40%), five pressures (0, 1.68, 3.11, 4.55, 6.22 kN/m 2; 0, 35, 65, 95, 130 lb/ft 2), and two probe orientations (axial and transverse) in a 4x5x2 factorial design. Results indicated that meter accuracy increased as pressure increased. Regression models accounted for 91% and 81% of the variation for Meter 1 and Meter 2 at a pressure of 4.55 kN/m 2 (95 lb/ft 2) and a transverse probe orientation. Calibration equations were developed for both meters to improve moisture measurement accuracy for farmers and researchers in the field.

  20. Optical device with low electrical and thermal resistance Bragg reflectors

    DOEpatents

    Lear, K.L.

    1996-10-22

    A compound-semiconductor optical device and method are disclosed. The optical device is provided with one or more asymmetrically-graded heterojunctions between compound semiconductor layers for forming a distributed Bragg reflector mirror having an improved electrical and thermal resistance. Efficient light-emitting devices such as light-emitting diodes, resonant-cavity light-emitting diodes, and vertical-cavity surface-emitting lasers may be formed according to the present invention, which may be applied to the formation of resonant-cavity photodetectors. 16 figs.

  1. Optical device with low electrical and thermal resistance bragg reflectors

    DOEpatents

    Lear, Kevin L.

    1996-01-01

    A compound-semiconductor optical device and method. The optical device is provided with one or more asymmetrically-graded heterojunctions between compound semiconductor layers for forming a distributed Bragg reflector mirror having an improved electrical and thermal resistance. Efficient light-emitting devices such as light-emitting diodes, resonant-cavity light-emitting diodes, and vertical-cavity surface-emitting lasers may be formed according to the present invention, which may be applied to the formation of resonant-cavity photodetectors.

  2. Evaluation of the radiation resistance of electrical insulation materials

    NASA Astrophysics Data System (ADS)

    Perrin, Sh.; Schönbacher, H.; Tavlet, M.; Widler, R.

    2002-12-01

    The qualification of insulating materials for electrical cables is often accomplished according to the IEC 60544 standard of the International Electrotechnical Commission. The mechanical properties of the polymeric insulators are tested prior and after irradiation at relatively high dose rates. To assess the ageing of selected materials under realistic service conditions, usually at lower dose rate, an IEC Working Group has proposed extrapolation methods (IEC 61244-2), one of which is applied here for a cable sheathing material from Huber+Suhner. The method is found to be suitable to compare radiation resistance data of different materials irradiated under different conditions.

  3. Electric-field-driven resistive switching in dissipative Hubbard model

    NASA Astrophysics Data System (ADS)

    Li, Jiajun; Aron, Camille; Kotliar, Gabriel; Han, Jong

    Understanding of solids driven out of equilibrium by external fields has been one of the central goals in condensed matter physics for the past century and is relevant to nanotechnology applications such as resistive transitions. We study how strongly correlated electrons on a dissipative lattice evolve from equilibrium when driven by a constant electric field, focusing on the extent of the linear regime and hysteretic non-linear effects at higher fields. We access the non-equilibrium steady states, non-perturbatively in both the field and the electronic interactions, by means of a non-equilibrium dynamical mean-field theory in the Coulomb gauge. The linear response regime is limited by Joule heating effects and breaks down at fields orders of magnitude smaller than the quasi-particle energy scale. For large electronic interactions, strong but experimentally accessible electric fields can induce a resistive switching by driving the strongly correlated metal into a Mott insulator. Hysteretic I- V curves suggest that the non-equilibrium current is carried through a spatially inhomogeneous metal-insulator mixed state.

  4. Electrical Resistivity of natural Marcasite at High-pressures

    NASA Astrophysics Data System (ADS)

    Parthasarathy, Gopalakrishnarao

    2013-06-01

    Marcasite is considered to be a common iron sulfide in reducing Martian sediments and may enclose microbial remains during growth and hence study of marcasite may have significance in the search for fossil life on Mars. The high-pressure phase stability investigations of marcasite are useful in understanding the sulfide mineralogy of Martian surface, affected by meteorite impacts. The sulfides were characterized by electron microprobe micro analyses (EPMA), powder X-ray diffraction, DTA, and FTIR spectroscopic measurements. The samples were powdered using a porcelain mortar and pestle. The chemical composition of the sample was determined by an electron probe micro-analyzer (EPMA). High-pressure electrical resistivity measurements were carried out on natural marcasite, and marcasite rich samples (Marcasite 95 mol % pyrite 5 mol %) up to 7 GPa. Marcasite sample shows a discontinuous decrease in the electrical resistivity at 5. 2 (+/- 0.5) GPa indicating a first order phase transition. The Differential thermal analyses and the Fourier transform infrared spectroscopic measurements on the pressure quenched sample shows the characteristics of pyrite, indicating the pressure induced marcasite-to -pyrite transition of the natural marcasite at 5. 2 (+/- 0.5) GPa. The observation of marcasite to pyrite phase transition may be useful in estimating the pressure experienced by shock events on the Martian surface as well as the meteorites where marcasite- pyrite phases coexist. Financial support from CSIR-SHORE-PSC0205.

  5. Review of Electrical Resistivity Measurements of Dense Aluminum

    NASA Astrophysics Data System (ADS)

    Benage, John F.

    1999-11-01

    We have completed an analysis of recent experiments that were done at Los Alamos and other laboratories that measured the electrical resistivity of aluminum at conditions where the aluminum is in a dense, strongly coupled, plasma state. Strongly coupled plasmas occur in laboratory systems of high energy density whenever material is rapidly heated to plasma conditions, such as laser heated plasmas and ohmically heated metals. The properties of these plasmas cannot be treated using standard plasma theory, which treats the correlations among particles as a small effect. Many theories have been developed which predict the properties of such plasmas, but little experimental data exists with which to compare. These recent experiments provide data for a more comprehensive comparison of electrical resistivity with dense plasma theories. The experiments were carried out under a wide range of conditions, from temperatures << 1 eV up to 25 eV and densities from nearly solid density to << 1comparison of the data with various theoretical predictions. From this comparison we draw some conclusions concerning under what conditions these theories are accurate. A discussion of yet unresolved issues will also be presented.

  6. 30 CFR 7.407 - Test for flame resistance of electric cables and cable splices.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) at an ambient temperature of 104 °F (40 °C). (8) Monitor the electric current through the power... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Test for flame resistance of electric cables... Electric Cables, Signaling Cables, and Cable Splice Kits § 7.407 Test for flame resistance of...

  7. 30 CFR 7.407 - Test for flame resistance of electric cables and cable splices.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) at an ambient temperature of 104 °F (40 °C). (8) Monitor the electric current through the power... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Test for flame resistance of electric cables... Electric Cables, Signaling Cables, and Cable Splice Kits § 7.407 Test for flame resistance of...

  8. 30 CFR 7.407 - Test for flame resistance of electric cables and cable splices.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) at an ambient temperature of 104 °F (40 °C). (8) Monitor the electric current through the power... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Test for flame resistance of electric cables... Electric Cables, Signaling Cables, and Cable Splice Kits § 7.407 Test for flame resistance of...

  9. 30 CFR 7.407 - Test for flame resistance of electric cables and cable splices.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) at an ambient temperature of 104 °F (40 °C). (8) Monitor the electric current through the power... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Test for flame resistance of electric cables... Electric Cables, Signaling Cables, and Cable Splice Kits § 7.407 Test for flame resistance of...

  10. 30 CFR 7.407 - Test for flame resistance of electric cables and cable splices.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) at an ambient temperature of 104 °F (40 °C). (8) Monitor the electric current through the power... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Test for flame resistance of electric cables... Electric Cables, Signaling Cables, and Cable Splice Kits § 7.407 Test for flame resistance of...

  11. Fabrication of an Electrically-Resistive, Varistor-Polymer Composite

    PubMed Central

    Ahmad, Mansor Bin; Fatehi, Asma; Zakaria, Azmi; Mahmud, Shahrom; Mohammadi, Sanaz A.

    2012-01-01

    This study focuses on the fabrication and electrical characterization of a polymer composite based on nano-sized varistor powder. The polymer composite was fabricated by the melt-blending method. The developed nano-composite was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FeSEM), and energy-dispersive X-ray spectroscopy (EDAX). The XRD pattern revealed the crystallinity of the composite. The XRD study also showed the presence of secondary phases due to the substitution of zinc by other cations, such as bismuth and manganese. The TEM picture of the sample revealed the distribution of the spherical, nano-sized, filler particles throughout the matrix, which were in the 10–50 nm range with an average of approximately 11 nm. The presence of a bismuth-rich phase and a ZnO matrix phase in the ZnO-based varistor powder was confirmed by FeSEM images and EDX spectra. From the current-voltage curves, the non-linear coefficient of the varistor polymer composite with 70 wt% of nano filler was 3.57, and its electrical resistivity after the onset point was 861 KΩ. The non-linear coefficient was 1.11 in the sample with 100 wt% polymer content. Thus, it was concluded that the composites established a better electrical non-linearity at higher filler amounts due to the nano-metric structure and closer particle linkages. PMID:23443085

  12. Monitoring Damage Accumulation in Ceramic Matrix Composites Using Electrical Resistivity

    NASA Technical Reports Server (NTRS)

    Smith, Craig E.; Morscher, Gregory N.; Xia, Zhenhai H.

    2008-01-01

    The electric resistance of woven SiC fiber reinforced SiC matrix composites were measured under tensile loading conditions. The results show that the electrical resistance is closely related to damage and that real-time information about the damage state can be obtained through monitoring of the resistance. Such self-sensing capability provides the possibility of on-board/in-situ damage detection and accurate life prediction for high-temperature ceramic matrix composites. Woven silicon carbide fiber-reinforced silicon carbide (SiC/SiC) ceramic matrix composites (CMC) possess unique properties such as high thermal conductivity, excellent creep resistance, improved toughness, and good environmental stability (oxidation resistance), making them particularly suitable for hot structure applications. In specific, CMCs could be applied to hot section components of gas turbines [1], aerojet engines [2], thermal protection systems [3], and hot control surfaces [4]. The benefits of implementing these materials include reduced cooling air requirements, lower weight, simpler component design, longer service life, and higher thrust [5]. It has been identified in NASA High Speed Research (HSR) program that the SiC/SiC CMC has the most promise for high temperature, high oxidation applications [6]. One of the critical issues in the successful application of CMCs is on-board or insitu assessment of the damage state and an accurate prediction of the remaining service life of a particular component. This is of great concern, since most CMC components envisioned for aerospace applications will be exposed to harsh environments and play a key role in the vehicle s safety. On-line health monitoring can enable prediction of remaining life; thus resulting in improved safety and reliability of structural components. Monitoring can also allow for appropriate corrections to be made in real time, therefore leading to the prevention of catastrophic failures. Most conventional nondestructive

  13. Electrical resistivity imaging study of near-surface infiltration

    NASA Astrophysics Data System (ADS)

    Lampousis, Angelos

    High resolution electrical resistivity images (ERI method) were obtained during vadose zone infiltration experiments on agricultural soils in cooperation with Cornell University's Agricultural Stewardship Program, Cooperative Extension of Suffolk County, Extension Education Center, Riverhead, New York [ as well as Cornell University's Long Island Horticultural Research & Extension Center (LIHREC) in Riverhead, New York]. One natural soil was also studied. Infiltration was monitored by means of image analysis of two-dimensional array resistivity generated by a Syscal Kid Switch resistivity system (Griffiths et al., 1990). The data was inverted with the computer program RES2DINV (Loke, 2004). The agricultural soils considered were Riverhead sandy loam (RdA), Haven loam (HaA), and Bridgehampton silt loam (BgA). The natural site was located in the Catskill Mountains of New York State. The soils there are classified as Schoharie silty clay loam. The electrical images of the three sites were compared against established soil properties, including particle size distribution, available water capacity, and soluble salts (from the literature), as well as against site-specific soil samples and penetrometer data, which were collected along with the geophysical measurements. This research evaluates the potential of acquiring high resolution, non-destructive measurements of infiltration in the uppermost 1.5 meter of the vadose zone. The results demonstrate that resistivity differences can detect infiltration in soils typical of the north-eastern United States. Temporal and spatial variations of soil water content in the upper 1.5 meters (relevant to agriculture) of the subsurface can be monitored successfully and non-destructively with ERI. The sensitivity of the method is higher in subsurface environments that demonstrate high overall apparent resistivity values (e.g. high sand content). Under conditions of increased soil heterogeneity, instead of the formation of a continuous

  14. Resistive graphene humidity sensors with rapid and direct electrical readout

    NASA Astrophysics Data System (ADS)

    Smith, Anderson D.; Elgammal, Karim; Niklaus, Frank; Delin, Anna; Fischer, Andreas C.; Vaziri, Sam; Forsberg, Fredrik; Råsander, Mikael; Hugosson, Håkan; Bergqvist, Lars; Schröder, Stephan; Kataria, Satender; Östling, Mikael; Lemme, Max C.

    2015-11-01

    We demonstrate humidity sensing using a change of the electrical resistance of single-layer chemical vapor deposited (CVD) graphene that is placed on top of a SiO2 layer on a Si wafer. To investigate the selectivity of the sensor towards the most common constituents in air, its signal response was characterized individually for water vapor (H2O), nitrogen (N2), oxygen (O2), and argon (Ar). In order to assess the humidity sensing effect for a range from 1% relative humidity (RH) to 96% RH, the devices were characterized both in a vacuum chamber and in a humidity chamber at atmospheric pressure. The measured response and recovery times of the graphene humidity sensors are on the order of several hundred milliseconds. Density functional theory simulations are employed to further investigate the sensitivity of the graphene devices towards water vapor. The interaction between the electrostatic dipole moment of the water and the impurity bands in the SiO2 substrate leads to electrostatic doping of the graphene layer. The proposed graphene sensor provides rapid response direct electrical readout and is compatible with back end of the line (BEOL) integration on top of CMOS-based integrated circuits.We demonstrate humidity sensing using a change of the electrical resistance of single-layer chemical vapor deposited (CVD) graphene that is placed on top of a SiO2 layer on a Si wafer. To investigate the selectivity of the sensor towards the most common constituents in air, its signal response was characterized individually for water vapor (H2O), nitrogen (N2), oxygen (O2), and argon (Ar). In order to assess the humidity sensing effect for a range from 1% relative humidity (RH) to 96% RH, the devices were characterized both in a vacuum chamber and in a humidity chamber at atmospheric pressure. The measured response and recovery times of the graphene humidity sensors are on the order of several hundred milliseconds. Density functional theory simulations are employed to further

  15. Electrical resistivity tomography at the DOE Hanford site

    SciTech Connect

    Narbutovskih, S.M.; Halter, T.D.; Sweeney, M.D.; Daily, W.; Ramirez, A.L.

    1996-01-01

    Recent work at the DOE Hanford site has established the potential of applying Electrical Resistivity Tomography (ERT) for early leak detection under hazardous waste storage facilities. Several studies have been concluded to test the capabilities and limitations of ERT for two different applications. First, field experiments have been conducted to determine the utility of ERT to detect and map leaks from underground storage tanks during waste removal processes. Second, the use of ERT for long term vadose zone monitoring has been tested under different field conditions of depth, installation design, acquisition mode/equipment and infiltration chemistry. This work involves transferring the technology from Lawrence Livermore National Laboratory (LLNL) to the Resource Conservation and Recovery Act (RCRA) program at the DOE Hanford Site. This paper covers field training studies relevant to the second application for long term vadose zone monitoring.

  16. Electrically resistive coating for remediation (regeneration) of a diesel particulate filter and method

    DOEpatents

    Phelps, Amanda C.; Kirby, Kevin K.; Gregoire, Daniel J.

    2012-02-14

    A resistively heated diesel particulate filter (DPF). The resistively heated DPF includes a DPF having an inlet surface and at least one resistive coating on the inlet surface. The at least one resistive coating is configured to substantially maintain its resistance in an operating range of the DPF. The at least one resistive coating has a first terminal and a second terminal for applying electrical power to resistively heat up the at least one resistive coating in order to increase the temperature of the DPF to a regeneration temperature. The at least one resistive coating includes metal and semiconductor constituents.

  17. Infiltration front monitoring using 3D Electrical Resistivity Tomography

    NASA Astrophysics Data System (ADS)

    Oxarango, Laurent; Audebert, Marine; Guyard, Helene; Clement, Remi

    2016-04-01

    The electrical resistivity tomography (ERT) geophysical method is commonly used to identify the spatial distribution of electrical resisitivity in the soil at the field scale. Recent progress in commercial acquisition systems allows repeating fast acquisitions (10 min) in order to monitor a 3D dynamic phenomenon. Since the ERT method is sensitive to moisture content variations, it can thus be used to delineate the infiltration shape during water infiltration. In heterogeneous conditions, the 3D infiltration shape is a crucial information because it could differ significantly from the homogeneous behavior. In a first step, the ERT method is validated at small scale (<1m) studying a suction infiltrometer test. The experiment is carried out in a pit filled with a homogenous silty-sandy soil. It is instrumented by 17 resistivity probes and 3 commercial capacitive moisture content probes to provide local measurements of the moisture content variation. The Multiple Inversion and Clustering Strategy (MICS) (Audebert et al 2014) is used to delineate the infiltration patern. A satisfying agreement between infiltration delineation and sensor measurements is obtained with a few centimeter accuracy on the moisture front location. In a second step, the same methodology is applied at a larger scale (> 10m). Two examples of leachate injection monitoring in municipal solid waste landfills are used to put forward benefits and limitations of the ERT-MICS method. Effective infiltration porosities in a range between 3% and 8% support the assumption of a flow in heterogeneous media. Audebert, M., R. Clément, N. Touze-Foltz, T. Günther, S. Moreau, and C. Duquennoi (2014), Time-lapse ERT interpretation methodology for leachate injection monitoring based on multiple inversions and a clustering strategy (MICS), Journal of Applied Geophysics, 111, 320-333. Keywords: ERT, infiltration front, field survey

  18. Low-thermal-resistance, high-electrical-isolation heat intercept connection

    SciTech Connect

    Niemann, R.C.; Gonczy, J.D.; Nicol, T.H.

    1993-07-01

    A method for providing a low-thermal-resistance, high-electrical-isolation heat intercept connection is presented. Electrical conductors often require the removal of heat produced from their normal operation. The heat can be removed by mechanical connection to a refrigeration source. Such connections require both effective heat removal (low thermal resistance) and effective electrical isolation (high electrical resistance and high dielectric strength). Such connections should be straightforward to fabricate and provide reliable performance that is independent of operating temperature. The connection method described here involves clamping, by thermal interference fit, an electrically insulating cylinder between an outer metallic ring and an inner metallic disk.

  19. Low-thermal-resistance, high-electrical-isolation heat intercept connection

    SciTech Connect

    Niemann, R.C.; Gonczy, J.D. ); Nicol, T.H. )

    1993-01-01

    A method for providing a low-thermal-resistance, high-electrical-isolation heat intercept connection is presented. Electrical conductors often require the removal of heat produced from their normal operation. The heat can be removed by mechanical connection to a refrigeration source. Such connections require both effective heat removal (low thermal resistance) and effective electrical isolation (high electrical resistance and high dielectric strength). Such connections should be straightforward to fabricate and provide reliable performance that is independent of operating temperature. The connection method described here involves clamping, by thermal interference fit, an electrically insulating cylinder between an outer metallic ring and an inner metallic disk.

  20. Applications of electrical resistance tomography to subsurface environmental restoration

    SciTech Connect

    Ramirez, A.L.; Daily, W.D.

    1994-11-15

    We are developing a new imaging technique, Electrical Resistance Tomography (ERT), to map subsurface liquids as flow occurs during natural or clean-up processes and to map geologic structure. Natural processes (such as surface water infiltrating the vadose zone) and man-induced processes (such as tank leaks and clean-up processes such as steam injection), can create changes in a soil`s electrical properties that are readily measured. We have conducted laboratory and a variety of field experiments to investigate the capabilities and limitations of ERT for imaging underground structures and processes. In the last four years we have used ERT to successfully monitor several field processes including: a subsurface steam injection process (for VOC removal), an air injection process (below the water table) for VOC removal, water infiltration through the vadose zone, radio-frequency heating, ohmic heating, and tank and pond leaks. The information derived from ERT can be used by remediation projects to: detect and locate leaks, determine the effectiveness of clean-up processes, select appropriate clean-up alternatives, and to verify the installation and performance of subsurface barriers.

  1. Investigations of discontinuous permafrost using electrical resistivity tomography

    NASA Astrophysics Data System (ADS)

    Lewkowicz, Antoni

    2016-04-01

    We have used electrical resistivity tomography (ERT) extensively over the past five years to examine frozen ground characteristics at natural and disturbed sites within the discontinuous permafrost zones of northern Canada. Examples of pure research include investigations to delimit permafrost patch size, to examine changes in permafrost conditions at altitudinal treeline, and to assess permafrost thickness in palsa bogs. Applied research has included hazard mapping where ERT, in association with boreholes, has been used to characterize permafrost conditions in different terrain units at Yukon communities as part of planning for climate change adaptation. ERT has also been used to examine temporal change through repeated surveys at sites equipped with permanent arrays. Rapid change is occurring at sites which were subject to recent forest fire in the Northwest Territories. Gradual reductions in average resistivity at sites along the Alaska Highway in Yukon and northern British Columbia indicate progressive increases in unfrozen moisture while ground temperatures at the same sites have increased only very slightly. We conclude that ERT should become a standard technique for the investigation of discontinuous permafrost sites and should be incorporated as a monitoring technique within international programs such as the Global Terrestrial Network for Permafrost.

  2. Electrical resistivity tomography study of Taal volcano hydrothermal system, Philippines

    NASA Astrophysics Data System (ADS)

    Fikos, I.; Vargemezis, G.; Zlotnicki, J.; Puertollano, J. R.; Alanis, P. B.; Pigtain, R. C.; Villacorte, E. U.; Malipot, G. A.; Sasai, Y.

    2012-10-01

    Taal volcano (311 m in altitude) is located in The Philippines (14°N, 121°E) and since 1572 has erupted 33 times, causing more than 2,000 casualties during the most violent eruptions. In March 2010, the shallow structures in areas where present-day surface activity takes place were investigated by DC resistivity surveys. Electrical resistivity tomography (ERT) lines were performed above the two identified hydrothermal areas located on the northern flank of the volcano and in the Main Crater, respectively. Due to rough topography, deep valleys, and dense vegetation, most measurements were collected using a remote method based on a laboratory-made equipment. This allowed retrieval of information down to a depth of 250 m. ERTs results detail the outlines of the two geothermal fields defined by previous self-potential, CO2 soil degassing, ground temperature, and magnetic mapping (Harada et al. Japan Acad Sci 81:261-266, 2005; Zlotnicki et al. Bull Volcanol 71:29-49, 2009a, Phys Chem Earth 34:294-408, 2009b). Hydrothermal fluids originate mainly from inside the northern part of the Main Crater at a depth greater than the bottom of the Crater Lake, and flow upward to the ground surface. Furthermore, water from the Main Crater Lake infiltrates inside the surrounding geological formations. The hydrothermal fluids, outlined by gas releases and high temperatures, cross the crater rim and interact with the northern geothermal field located outside the Main Crater.

  3. Contribution of 3-D electrical resistivity tomography for landmines detection

    NASA Astrophysics Data System (ADS)

    Metwaly, M.; El-Qady, G.; Matsushima, J.; Szalai, S.; Al-Arifi, N. S. N.; Taha, A.

    2008-12-01

    Landmines are a type of inexpensive weapons widely used in the pre-conflicted areas in many countries worldwide. The two main types are the metallic and non-metallic (mostly plastic) landmines. They are most commonly investigated by magnetic, ground penetrating radar (GPR), and metal detector (MD) techniques. These geophysical techniques however have significant limitations in resolving the non-metallic landmines and wherever the host materials are conductive. In this work, the 3-D electric resistivity tomography (ERT) technique is evaluated as an alternative and/or confirmation detection system for both landmine types, which are buried in different soil conditions and at different depths. This can be achieved using the capacitive resistivity imaging system, which does not need direct contact with the ground surface. Synthetic models for each case have been introduced using metallic and non-metallic bodies buried in wet and dry environments. The inversion results using the L1 norm least-squares optimization method tend to produce robust blocky models of the landmine body. The dipole axial and the dipole equatorial arrays tend to have the most favorable geometry by applying dynamic capacitive electrode and they show significant signal strength for data sets with up to 5% noise. Increasing the burial depth relative to the electrode spacing as well as the noise percentage in the resistivity data is crucial in resolving the landmines at different environments. The landmine with dimension and burial depth of one electrode separation unit is over estimated while the spatial resolutions decrease as the burial depth and noise percentage increase.

  4. Advances in the application of in situ electrical resistance heating

    SciTech Connect

    Smith, Gregory J.; Beyke, Gregory

    2007-07-01

    Electrical Resistance Heating (ERH) is an aggressive in situ thermal remediation technology that was developed by the U.S. Department of Energy from the original oil production technology to enhance vapor extraction remediation technologies in low permeability soils. Soil and groundwater are heated by the passage of electrical current through saturated and unsaturated soil between electrodes, not by the electrodes themselves. It is the resistance to the flow of electrical current that results in increased subsurface temperatures, and this is typically applied to the boiling point of water. It is estimated that more than 75 ERH applications have been performed. Capacity to perform these projects has increased over the years, and as many as 15 to 20 of these applications now being performed at any given time, mainly in North America, with some European applications. While the main focus has been to vaporize volatile organic compounds, as one would expect other semi-volatile and non-volatile organic compounds have also been encountered, resulting in observations of chemical and physical reactions that have not been normally incorporated into environmental restoration projects. One such reaction is hydrolysis, which is slow under normal groundwater temperatures, becomes very rapid under temperatures that can easily be achieved using ERH. As a result, these chemical and physical reactions are increasing the applicability of ERH in environmental restoration projects, treating a wider variety of compounds and utilizing biotic and abiotic mechanisms to reduce energy costs. For the treatment of oil and coal tar residues from manufactured gas plants, a process TRS has called steam bubble floatation is used to physically remove the coal and oil tar from the soils for collection using conventional multi-phase collection methods. Heat-enhanced hydrolysis has been used to remediate dichloromethane from soils and groundwater at a site in Illinois, while heat-enhanced biotic and

  5. Estimation of tree root distribution using electrical resistivity tomography

    NASA Astrophysics Data System (ADS)

    Schmaltz, Elmar; Uhlemann, Sebastian

    2016-04-01

    Trees influence soil-mantled slopes mechanically by anchoring in the soil with coarse roots. Forest-stands play an important role in mechanical reinforcement to reduce the susceptibility to slope failures. However, the effect of stabilisation of roots is connected with the distribution of roots in the ground. The architecture and distribution of tree roots is diverse and strongly dependent on species, plant age, stand density, relief, nutrient supply as well as climatic and pedologic conditions. Particularly trees growing on inclined slopes show shape-shifting root systems. Geophysical techniques are commonly used to non-invasively study hydrological and geomorphological subsurface properties, by imaging contrasting physical properties of the ground. This also poses the challenge for geophysical imaging of root systems, as properties, such as electrical resistivity, of dry and wet roots fall within the range of soils. The objective of this study is whether electrical resistivity tomography (ERT) allows a reliable reproduction of root systems of alone-standing trees on diverse inclined slopes. In this regard, we set the focus on the branching of secondary roots of two common walnut trees (Juglans regia L.) that were not disturbed in the adjacencies and thus expected to develop their root systems unhindered. Walnuts show a taproot-cordate root system with a strong tap-root in juvenile age and a rising cordate rooting with increasing age. Hence, mature walnuts can exhibit a root system that appears to be deformed or shifted respectively when growing at hillslope locations. We employed 3D ERT centred on the tree stem, comprising dipole-dipole measurements on a 12-by-41 electrode grid with 0.5 m and 1.0m electrode spacing in x- and y-direction respectively. Data were inverted using a 3D smoothness constrained non-linear least-squares algorithm. First results show that the general root distribution can be estimated from the resistivity models and that shape

  6. Electrical resistivity characteristics of diesel oil-contaminated kaolin clay and a resistivity-based detection method.

    PubMed

    Liu, Zhibin; Liu, Songyu; Cai, Yi; Fang, Wei

    2015-06-01

    As the dielectric constant and conductivity of petroleum products are different from those of the pore water in soil, the electrical resistivity characteristics of oil-contaminated soil will be changed by the corresponding oil type and content. The contaminated soil specimens were manually prepared by static compaction method in the laboratory with commercial kaolin clay and diesel oil. The water content and dry density of the first group of soil specimens were controlled at 10 % and 1.58 g/cm(3). Corresponding electrical resistivities of the contaminated specimens were measured at the curing periods of 7, 14, and 28 and 90, 120, and 210 days on a modified oedometer cell with an LCR meter. Then, the electrical resistivity characteristics of diesel oil-contaminated kaolin clay were discussed. In order to realize a resistivity-based oil detection method, the other group of oil-contaminated kaolin clay specimens was also made and tested, but the initial water content, oil content, and dry density were controlled at 0~18 %, 0~18 %, 1.30~1.95 g/cm(3), respectively. Based on the test data, a resistivity-based artificial neural network (ANN) was developed. It was found that the electrical resistivity of kaolin clay decreased with the increase of oil content. Moreover, there was a good nonlinear relationship between electrical resistivity and corresponding oil content when the water content and dry density were kept constant. The decreasing velocity of the electrical resistivity of oil-contaminated kaolin clay was higher before the oil content of 12 % than after 12 %, which indicated a transition of the soil from pore water-controlled into oil-controlled electrical resistivity characteristics. Through microstructural analysis, the decrease of electrical resistivity could be explained by the increase of saturation degree together with the collapse of the electrical double layer. Environmental scanning electron microscopy (ESEM) photos indicated that the diesel oil

  7. Investigating electrical contact resistance losses in lithium-ion battery assemblies for hybrid and electric vehicles

    NASA Astrophysics Data System (ADS)

    Taheri, Peyman; Hsieh, Scott; Bahrami, Majid

    2011-08-01

    Lithium-ion (Li-ion) batteries are favored in hybrid-electric vehicles and electric vehicles for their outstanding power characteristics. In this paper the energy loss due to electrical contact resistance (ECR) at the interface of electrodes and current-collector bars in Li-ion battery assemblies is investigated for the first time. ECR is a direct result of contact surface imperfections, i.e., roughness and out-of-flatness, and acts as an ohmic resistance at the electrode-collector joints. A custom-designed testbed is developed to conduct a systematic experimental study. ECR is measured at separable bolted electrode connections of a sample Li-ion battery, and a straightforward analysis to evaluate the relevant energy loss is presented. Through the experiments, it is observed that ECR is an important issue in energy management of Li-ion batteries. Effects of surface imperfection, contact pressure, joint type, collector bar material, and interfacial materials on ECR are highlighted. The obtained data show that in the considered Li-ion battery, the energy loss due to ECR can be as high as 20% of the total energy flow in and out of the battery under normal operating conditions. However, ECR loss can be reduced to 6% when proper joint pressure and/or surface treatment are used. A poor connection at the electrode-collector interface can lead to a significant battery energy loss as heat generated at the interface. Consequently, a heat flow can be initiated from the electrodes towards the internal battery structure, which results in a considerable temperature increase and onset of thermal runaway. At sever conditions, heat generation due to ECR might cause serious safety issues, sparks, and even melting of the electrodes.

  8. Electrical Resistivity Imaging to Quantify Spatial Soil Heterogeneity

    NASA Astrophysics Data System (ADS)

    Guber, A. K.; Hadzick, Z. L.; Garzio, A.; Pachepsky, Y. A.; Hill, R. L.; Rowland, R. A.; Golovko, L. A.

    2008-12-01

    Electrical resistivity (ER) sounding is increasingly being used as non-invasive technique to reveal and map soil heterogeneity. The objective of this work was to evaluate effects of soil properties on the electric resistivity and to observe these effects in spatial context in coarse-textured soil. The studied soil had the sandy loam texture. The 20x20-m study plot was located at the ARS Beltsville OPE3 site. Relationship between ER, bulk density, and soil water contents was first studied in disturbed 80-cm3 soil samples taken at 10 depths with 20 cm increment. Soil water contents were brought to 6 predefined levels in each sample and were in the range from air dry to 0.27g g-1. Soil bulk density varied in the range from 1.28 to 1.45 g cm-3. The ER in soil samples decreased as the gravimetric water content increased. The ER decrease became more pronounced as bulk density decreased. Next, soil samples were taken at field water contents from 10 depths at 12 locations. Particle size distributions, pH, water content and ER were measured in each sample. Bulk density values in part of the soil profiles below 80 cm ranged from 1.5 to 1.8 g cm- 3 and no dependence between ER and water content could be established in this soil layer where the lowest values of ER were recorded. The increased conductivity of the soil solid phase could be a possible reason for that since soil in this part of the profile had pH values two or more units less than in the upper part. The lowest sand contents corresponded to highest ER values in this soil layer. Finally, the vertical electrical sounding (LandMapper ERM-02) was used to infer spatial distribution of soil resistivity along a 9-m transect for different dates when soil was dry and when it was relatively uniformly wetted with long low- intensity rain. The Wenner-Shlumberger array with 31-electrodes spaced 30-cm apart was used. Soil temperature and water content with multisensor capacitance probes (SENTEC) were monitored at 10 depths down

  9. CORRIGENDUM: Multiscale electrical contact resistance in clustered contact distribution Multiscale electrical contact resistance in clustered contact distribution

    NASA Astrophysics Data System (ADS)

    Lee, Sangyoung; Cho, Hyun; Jang, Yong Hoon

    2010-06-01

    The authors wish to explain the similarity between some figures in the above paper (hereafter called the JPD paper) and in their other publication, Lee S, Jang Y H and Kim W 2008 Effects of nanosized contact spots on thermal contact resistance J. Appl. Phys.103 074308 (hereafter called the JAP paper), and to explain the differences between the two papers, which are not explicitly stated in the JPD paper. The main objective of the JAP paper is to calculate the thermal contact resistance of the nanosized contact spots in multiscale contact. During the process of multiscale analysis, the thermal conductivity varies, especially below the phonon mean free path. The JPD paper deals with the electrical contact resistance in the multiscale contact distribution with an assumption of constant electrical resistivity, which is known as a different kind of physics in a larger characteristic length scale. There are similar figures in the JPD paper and the JAP paper: figures 6, 7 and 8 in the JPD paper and figures 3, 4 and 5 in the JAP paper. Two research works were performed on the basis of a specific microcontact distribution. In the JAP paper, the scale of the contact distribution is in the range of the phonon mean free path of Si, which is a very small size of contact distribution. In the JPD paper, the scale of contact distribution is in the continuum scale, which is larger than the phonon mean free path. In addition, due to the characteristics of a fractal surface which repeatedly generates a similar shape of contact distribution in the different length scales, the shape of contact distribution looks similar, but the total sizes of domain in the JPD and JAP figures are different. The projected areas L × L of fractal surface of the JAP paper and JPD paper are 10 μm × 10 μm and 10 mm × 10 mm, respectively. The length scale is already stated in the JAP paper, but not in the JPD paper. Thus, we have to state that the figures were adapted from the JAP paper without clear

  10. Electric-field-modulated nonvolatile resistance switching in VO₂/PMN-PT(111) heterostructures.

    PubMed

    Zhi, Bowen; Gao, Guanyin; Xu, Haoran; Chen, Feng; Tan, Xuelian; Chen, Pingfan; Wang, Lingfei; Wu, Wenbin

    2014-04-01

    The electric-field-modulated resistance switching in VO2 thin films grown on piezoelectric (111)-0.68Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 (PMN-PT) substrates has been investigated. Large relative change in resistance (10.7%) was observed in VO2/PMN-PT(111) hererostructures at room temperature. For a substrate with a given polarization direction, stable resistive states of VO2 films can be realized even when the applied electric fields are removed from the heterostructures. By sweeping electric fields across the heterostructure appropriately, multiple resistive states can be achieved. These stable resistive states result from the different stable remnant strain states of substrate, which is related to the rearrangements of ferroelectric domain structures in PMN-PT(111) substrate. The resistance switching tuned by electric field in our work may have potential applications for novel electronic devices. PMID:24634978

  11. Predicting and tracking spatiotemporal moments in electrical resistivity tomography

    NASA Astrophysics Data System (ADS)

    Ward, W. O. C.; Wilkinson, P. B.; Chambers, J.; Bai, L.

    2015-12-01

    Visualisation is an invaluable tool in the study of near sub-surface processes, whether by mathematical modelling or by geophysical imaging. Quantitative analysis can further assist interpretation of the ongoing physical processes, and it is clear that any reliable model should take direct observations into account. Using electrical resistivity tomography (ERT), localised areas can be surveyed to produce 2-D and 3-D time-lapse images. This study investigates combining quantitative results obtained via ERT with spatio-temporal motion models in tracer experiments to interpret and predict fluid flow. As with any indirect imaging technique, ERT suffers specific issues with resolution and smoothness as a result of its inversion process. In addition, artefacts are typical in the resulting volumes. Mathematical models are also a source of uncertainty - and in combining these with ERT images, a trade-off must be made between the theoretical and the observed. Using computational imaging, distinct regions of stable resistivity can be directly extracted from a time-slice of an ERT volume. The automated nature, as well the potential for more than one region-of-interest, means that multiple regions can be detected. Using Kalman filters, it is possible to convert the detections into a process state, taking into account pre-defined models and predicting progression. In consecutive time-steps, newly detected features are assigned, where possible, to existing predictions to create tracks that match the tracer model. Preliminary studies looked at a simple motion model, tracking the centre of mass of a tracer plume with assumed constant velocity and mean resistivity. Extending the model to factor in spatial distribution of the plume, an oriented semi-axis is used to represent the centralised second-order moment, with an increasing factor of magnitude to represent the plume dispersion. Initial results demonstrate the efficacy of the approach, significantly improving reliability as the

  12. Measuring turbulence in a flotation cell using electrical resistance tomography

    NASA Astrophysics Data System (ADS)

    Meng, Jun; Xie, Weiguo; Runge, Kym; Bradshaw, Dee

    2015-11-01

    Measuring turbulence in an industrial flotation environment has long been problematic due to the opaque, aggressive, and abrasive three-phase environment in a flotation cell. One of the promising measurement techniques is electrical resistance tomography (ERT). By measuring the conductivity distribution across a measurement area, ERT has been adopted by many researchers to monitor and investigate many processes involving multiphase flows. In the research outlined in this paper, a compact ERT probe was built and then used to measure the conductivity distribution within a 60 l flotation cell operated with water and air. Two approaches were then developed to process the ERT data and estimate turbulence-related parameters. One is a conductivity variance method and the other is based on the Green-Kubo relations. Both rely on and use the fluctuation in the ERT measurement caused by bubbles moving through the measurement area changing the density of the fluid. The results from both approaches were validated by comparing the results produced by the ERT probe in a 60l flotation cell operated at different air rates and impeller speeds to that measured using an alternative turbulence measurement device. The second approach is considered superior to the first as the first requires the development of auxiliary information which would not usually be known for a new system.

  13. Electrical resistance sensors record spring flow timing, Grand Canyon, Arizona

    USGS Publications Warehouse

    Adams, E.A.; Monroe, S.A.; Springer, A.E.; Blasch, K.W.; Bills, D.J.

    2006-01-01

    Springs along the south rim of the Grand Canyon, Arizona, are important ecological and cultural resources in Grand Canyon National Park and are discharge points for regional and local aquifers of the Coconino Plateau. This study evaluated the applicability of electrical resistance (ER) sensors for measuring diffuse, low-stage (<1.0 cm) intermittent and ephemeral flow in the steep, rocky spring-fed tributaries of the south rim. ER sensors were used to conduct a baseline survey of spring flow timing at eight sites in three spring-fed tributaries in Grand Canyon. Sensors were attached to a nearly vertical rock wall at a spring outlet and were installed in alluvial and bedrock channels. Spring flow timing data inferred by the ER sensors were consistent with observations during site visits, with flow events recorded with collocated streamflow gauging stations and with local precipitation gauges. ER sensors were able to distinguish the presence of flow along nearly vertical rock surfaces with flow depths between 0.3 and 1.0 cm. Laboratory experiments confirmed the ability of the sensors to monitor the timing of diffuse flow on impervious surfaces. A comparison of flow patterns along the stream reaches and at springs identified the timing and location of perennial and intermittent flow, and periods of increased evapotranspiration.

  14. Electrical resistance sensors record spring flow timing, Grand Canyon, Arizona.

    PubMed

    Adams, Eric A; Monroe, Stephen A; Springer, Abraham E; Blasch, Kyle W; Bills, Donald J

    2006-01-01

    Springs along the south rim of the Grand Canyon, Arizona, are important ecological and cultural resources in Grand Canyon National Park and are discharge points for regional and local aquifers of the Coconino Plateau. This study evaluated the applicability of electrical resistance (ER) sensors for measuring diffuse, low-stage (<1.0 cm) intermittent and ephemeral flow in the steep, rocky spring-fed tributaries of the south rim. ER sensors were used to conduct a baseline survey of spring flow timing at eight sites in three spring-fed tributaries in Grand Canyon. Sensors were attached to a nearly vertical rock wall at a spring outlet and were installed in alluvial and bedrock channels. Spring flow timing data inferred by the ER sensors were consistent with observations during site visits, with flow events recorded with collocated streamflow gauging stations and with local precipitation gauges. ER sensors were able to distinguish the presence of flow along nearly vertical rock surfaces with flow depths between 0.3 and 1.0 cm. Laboratory experiments confirmed the ability of the sensors to monitor the timing of diffuse flow on impervious surfaces. A comparison of flow patterns along the stream reaches and at springs identified the timing and location of perennial and intermittent flow, and periods of increased evapotranspiration.

  15. Electrical resistance sensors record spring flow timing, Grand Canyon, Arizona.

    PubMed

    Adams, Eric A; Monroe, Stephen A; Springer, Abraham E; Blasch, Kyle W; Bills, Donald J

    2006-01-01

    Springs along the south rim of the Grand Canyon, Arizona, are important ecological and cultural resources in Grand Canyon National Park and are discharge points for regional and local aquifers of the Coconino Plateau. This study evaluated the applicability of electrical resistance (ER) sensors for measuring diffuse, low-stage (<1.0 cm) intermittent and ephemeral flow in the steep, rocky spring-fed tributaries of the south rim. ER sensors were used to conduct a baseline survey of spring flow timing at eight sites in three spring-fed tributaries in Grand Canyon. Sensors were attached to a nearly vertical rock wall at a spring outlet and were installed in alluvial and bedrock channels. Spring flow timing data inferred by the ER sensors were consistent with observations during site visits, with flow events recorded with collocated streamflow gauging stations and with local precipitation gauges. ER sensors were able to distinguish the presence of flow along nearly vertical rock surfaces with flow depths between 0.3 and 1.0 cm. Laboratory experiments confirmed the ability of the sensors to monitor the timing of diffuse flow on impervious surfaces. A comparison of flow patterns along the stream reaches and at springs identified the timing and location of perennial and intermittent flow, and periods of increased evapotranspiration. PMID:16961484

  16. Use of electrical resistivity to detect underground mine voids in Ohio

    USGS Publications Warehouse

    Sheets, Rodney A.

    2002-01-01

    Electrical resistivity surveys were completed at two sites along State Route 32 in Jackson and Vinton Counties, Ohio. The surveys were done to determine whether the electrical resistivity method could identify areas where coal was mined, leaving air- or water-filled voids. These voids can be local sources of potable water or acid mine drainage. They could also result in potentially dangerous collapse of roads or buildings that overlie the voids. The resistivity response of air- or water-filled voids compared to the surrounding bedrock may allow electrical resistivity surveys to delineate areas underlain by such voids. Surface deformation along State Route 32 in Jackson County led to a site investigation, which included electrical resistivity surveys. Several highly resistive areas were identified using axial dipole-dipole and Wenner resistivity surveys. Subsequent drilling and excavation led to the discovery of several air-filled abandoned underground mine tunnels. A site along State Route 32 in Vinton County, Ohio, was drilled as part of a mining permit application process. A mine void under the highway was instrumented with a pressure transducer to monitor water levels. During a period of high water level, electrical resistivity surveys were completed. The electrical response was dominated by a thin, low-resistivity layer of iron ore above where the coal was mined out. Nearby overhead powerlines also affected the results.

  17. Electrical resistivity imaging for unknown bridge foundation depth determination

    NASA Astrophysics Data System (ADS)

    Arjwech, Rungroj

    Unknown bridge foundations pose a significant safety risk due to stream scour and erosion. Records from older structures may be non-existent, incomplete, or incorrect. Nondestructive and inexpensive geophysical methods have been identified as suitable to investigate unknown bridge foundations. The objective of the present study is to apply advanced 2D electrical resistivity imaging (ERI) in order to identify depth of unknown bridge foundations. A survey procedure is carried out in mixed terrain water and land environments with rough topography. A conventional resistivity survey procedure is used with the electrodes installed on the stream banks. However, some electrodes must be adapted for underwater use. Tests were conducted in one laboratory experimentation and at five field experimentations located at three roadway bridges, a geotechnical test site, and a railway bridge. The first experimentation was at the bridges with the smallest foundations, later working up in size to larger drilled shafts and spread footings. Both known to unknown foundations were investigated. The geotechnical test site is used as an experimental site for 2D and 3D ERI. The data acquisition is carried out along 2D profile with a linear array in the dipole-dipole configuration. The data collections have been carried out using electrodes deployed directly across smaller foundations. Electrodes are deployed in proximity to larger foundations to image them from the side. The 2D ERI can detect the presence of a bridge foundation but is unable to resolve its precise shape and depth. Increasing the spatial extent of the foundation permits better image of its shape and depth. Using electrode < 1 m to detect a slender foundation < 1 m in diameter is not feasible. The 2D ERI method that has been widely used for land surface surveys presently can be adapted effectively in water-covered environments. The method is the most appropriate geophysical method for determination of unknown bridge foundations

  18. A one-dimensional model of solid-earth electrical resistivity beneath Florida

    USGS Publications Warehouse

    Blum, Cletus; Love, Jeffrey J.; Pedrie, Kolby; Bedrosian, Paul A.; Rigler, E. Joshua

    2015-11-19

    An estimated one-dimensional layered model of electrical resistivity beneath Florida was developed from published geological and geophysical information. The resistivity of each layer is represented by plausible upper and lower bounds as well as a geometric mean resistivity. Corresponding impedance transfer functions, Schmucker-Weidelt transfer functions, apparent resistivity, and phase responses are calculated for inducing geomagnetic frequencies ranging from 10−5 to 100 hertz. The resulting one-dimensional model and response functions can be used to make general estimates of time-varying electric fields associated with geomagnetic storms such as might represent induction hazards for electric-power grid operation. The plausible upper- and lower-bound resistivity structures show the uncertainty, giving a wide range of plausible time-varying electric fields.

  19. A one-dimensional model of solid-earth electrical resistivity beneath Florida

    USGS Publications Warehouse

    Blum, Cletus; Love, Jeffrey J.; Pedrie, Kolby; Bedrosian, Paul A.; Rigler, E. Joshua

    2015-01-01

    An estimated one-dimensional layered model of electrical resistivity beneath Florida was developed from published geological and geophysical information. The resistivity of each layer is represented by plausible upper and lower bounds as well as a geometric mean resistivity. Corresponding impedance transfer functions, Schmucker-Weidelt transfer functions, apparent resistivity, and phase responses are calculated for inducing geomagnetic frequencies ranging from 10−5 to 100 hertz. The resulting one-dimensional model and response functions can be used to make general estimates of time-varying electric fields associated with geomagnetic storms such as might represent induction hazards for electric-power grid operation. The plausible upper- and lower-bound resistivity structures show the uncertainty, giving a wide range of plausible time-varying electric fields.

  20. Electrical resistivity and piezoresistivity of Ni-CNT filled epoxy-based composites

    NASA Astrophysics Data System (ADS)

    Jiang, Jinbao; Xiao, Huigang; Li, Hui

    2013-04-01

    This paper investigates properties about electrical resistivity and piezoresistivity of multi-wall carbon nanotubes (MWCNTs)-filled epoxy-based composite and its further use for strain sensing. The MWCNTs dispersed epoxy resin, using MWCNTs in the amount of 1.5~3.0 vol.%, was first prepared by combined high-speed stirring and sonication methods. Then, the MWCNTs dispersed epoxy resin was cast into an aluminum mold to form specimens measuring 10×10×36 mm. After curing, DC electrical resistance measurements were performed along the longitudinal axis using the four-probe method, in which copper nets served as electrical contacts. The percolation threshold zone of resistivity was got as MWCNTs in the amount of 2.00-2.50 vol.%. Further compressive testing of these specimens was conducted with four-probe method for resistance measurements at the same time. Testing results show that the electrical resistivity of the composites changes with the strain's development, namely piezoresistivity. While for practical strain sensing use, signals of electric resistance and current in the acquisition circuits were both studied. Results show that the signal of current, compared with that of resistance, had better linear relationship with the compressive strain, better stability and longer effective section to reflect the whole deformation process of the specimens under pressure. Further works about the effects of low magnetic field on the electrical resistivity and piezoresistivity of Ni-CNTs filled epoxy-based composites were presented briefly at the end of the paper.

  1. Thermal Expansion and Electrical Resistivity Studies of Nickel and ARMCO Iron at High Temperatures

    NASA Astrophysics Data System (ADS)

    Palchaev, D. K.; Murlieva, Zh. Kh.; Gadzhimagomedov, S. H.; Iskhakov, M. E.; Rabadanov, M. Kh.; Abdulagatov, I. M.

    2015-11-01

    The electrical resistance, ρ (T), and thermal expansion coefficient, β (T), of nickel and ARMCO iron have been simultaneously measured over a wide temperature range from (300 to 1100) K. The well-known standard four-probe potentiometric method was used for measurements of the electrical resistance. The thermal expansion coefficient was measured using the quartz dilatometer technique. Both techniques were combined in the same apparatus for simultaneous measurements of the electrical resistance and TEC for the same specimen. The combined expanded uncertainty of the electrical resistance and thermal expansion coefficient measurements at the 95 % confidence level with a coverage factor of k = 2 is estimated to be 0.5 % and (1.5 to 4.0) %, respectively. The distinct ρ (T) scattering contribution (phonon ρ _{ph}, magnetic ρ m, and residual ρ S) terms were separated and extracted from the measured total resistivity. The physical nature and details of the temperature dependence of the electrical resistance of solid materials and correct estimations of the contributions of various scattering mechanisms to the measured total resistivity were discussed in terms of the anharmonic effect. We experimentally found simple, universal, physically based, semiempirical linear correlations between the kinetic coefficient (electrical resistance) and a thermodynamic (equilibrium) property, the thermal expansion coefficient, of solid materials. The developed, physically based, correlation model has been successfully applied for nanoscale materials (ferromagnetic nickel nanowire). A new s-d-exchange interaction energy determination technique has been proposed.

  2. Electrical Properties of Materials for Elevated Temperature Resistance Strain Gage Application. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Lei, Jih-Fen

    1987-01-01

    The objective was to study the electrical resistances of materials that are potentially useful as resistance strain gages at 1000 C. Transition metal carbides and nitrides, boron carbide and silicon carbide were selected for the experimental phase of this research. Due to their low temperature coefficient of resistance and good stability, TiC, ZrC, B sub 4 C and beta-SiC are suggested as good candidates for high temperature resistance strain gage applications.

  3. Corrosion-resistant, electrically-conductive plate for use in a fuel cell stack

    DOEpatents

    Carter, J. David; Mawdsley, Jennifer R.; Niyogi, Suhas; Wang, Xiaoping; Cruse, Terry; Santos, Lilia

    2010-04-20

    A corrosion resistant, electrically-conductive, durable plate at least partially coated with an anchor coating and a corrosion resistant coating. The corrosion resistant coating made of at least a polymer and a plurality of corrosion resistant particles each having a surface area between about 1-20 m.sup.2/g and a diameter less than about 10 microns. Preferably, the plate is used as a bipolar plate in a proton exchange membrane (PEMFC) fuel cell stack.

  4. Measurement and modelling of moisture-electrical resistivity relationship of fine-grained unsaturated soils and electrical anisotropy

    NASA Astrophysics Data System (ADS)

    Merritt, A. J.; Chambers, J. E.; Wilkinson, P. B.; West, L. J.; Murphy, W.; Gunn, D.; Uhlemann, S.

    2016-01-01

    A methodology for developing resistivity-moisture content relationships of materials associated with a clayey landslide is presented. Key elements of the methodology include sample selection and preparation, laboratory measurement of resistivity with changing moisture content, and the derivation of models describing the relationship between resistivity and moisture content. Laboratory resistivity measurements show that the techniques utilised (samples and square array) have considerable potential as a means of electropetrophysical calibration of engineering soils and weak rock. Experimental electrical resistivity results show a hierarchy of values dependent on sample lithology, with silty clay exhibiting the lowest resistivities, followed by siltstones and sands, which return the highest resistivities. In addition, finer grained samples show a greater degree of anisotropy between measurement orientations than coarser grained samples. However, suitability of results in light of issues such as sample cracking and electrical conduction must be identified and accounted for if the results are to be accurately up-scaled to inverted model resistivity results. The existence of directional anisotropy makes model calibration curve selection more difficult due to variability in the range of measured laboratory resistances. The use of larger measurement array size means that experimental data will be more representative of bulk lithological properties. In addition, use of electrodes with a relatively high surface area (wide diameter) help maintain low contact resistances and repeat measurement error, relative to narrow electrodes. Variation exists between the fit of experimental data and petrophysical models. Model fit is best for clay-dominated samples but fits less well for sand-dominated samples. Waxman-Smits equation is appropriately applied in this investigation as all samples have considerable clay mineral content, as is shown in non-negligible CEC results. The

  5. Resistive memory effects in BiFeO3 single crystals controlled by transverse electric fields

    NASA Astrophysics Data System (ADS)

    Kawachi, S.; Kuroe, H.; Ito, T.; Miyake, A.; Tokunaga, M.

    2016-04-01

    The effects of electric fields perpendicular to the c-axis of the trigonal cell in single crystals of BiFeO3 are investigated through magnetization and resistance measurements. Magnetization and resistance exhibit hysteretic changes under applied electric fields, which can be ascribed to the reorientation of the magnetoelectric domains. Samples are repetitively switched between high- and low-resistance states by changing the polarity of the applied electric fields over 20 000 cycles at room temperature. These results demonstrate the potential of BiFeO3 for use in non-volatile memory devices.

  6. Fabrication of intermetallic coatings for electrical insulation and corrosion resistance on high-temperature alloys

    SciTech Connect

    Park, J.-H.; Cho, W.D.

    1996-11-01

    Several intermetallic films were applied to high-temperature alloys (V alloys and 304, 316 stainless steels) to provide electrical insulation and corrosion resistance. Alloy grain growth at 1000 C for the V-5Cr-5Ti alloy was investigated to determine stability of the alloy substrate during coating formation by CVD or metallic vapor processes at 800-850 C. Film layers were examined by optical and scanning electron microscopy and by electron-energy-dispersive and XRD analysis; they were also tested for electrical resistivity and corrosion resistance. Results elucidated the nature of the coatings, which provided both electrical insulation and high-temperature corrosion protection.

  7. An Ultra-Precise System for Electrical Resistivity Tomography Measurements

    SciTech Connect

    LaBrecque, Douglas J; Adkins, Paula L

    2008-12-09

    The objective of this research was to determine the feasibility of building and operating an ERT system that will allow measurement precision that is an order of magnitude better than existing systems on the market today and in particular if this can be done without significantly greater manufacturing or operating costs than existing commercial systems. Under this proposal, we performed an estimation of measurement errors in galvanic resistivity data that arise as a consequence of the type of electrode material used to make the measurements. In our laboratory, measurement errors for both magnitude and induced polarization (IP) were estimated using the reciprocity of data from an array of electrodes as might be used for electrical resistance tomography using 14 different metals as well as one non-metal - carbon. In a second phase of this study, using archival data from two long-term ERT surveys, we examined long-term survivability of electrodes over periods of several years. The survey sites were: the Drift Scale Test at Yucca Mountain, Nevada (which was sponsored by the U. S. Department of Energy as part of the civilian radioactive waste management program), and a water infiltration test at a site adjacent to the New Mexico Institute of Mines and Technology in Socorro, New Mexico (sponsored by the Sandia/Tech vadose program). This enabled us to compare recent values with historical values and determine electrode performance over the long-term as well as the percentage of electrodes that have failed entirely. We have constructed a prototype receiver system, made modifications and revised the receiver design. The revised prototype uses a new 24 bit analog to digital converter from Linear Technologies with amplifier chips from Texas Instruments. The input impedance of the system will be increased from 107 Ohms to approximately 1010 Ohms. The input noise level of the system has been decreased to approximately 10 Nanovolts and system resolution to about 1 Nanovolt at

  8. Using electrical resistivity imaging to understand surface coal mine hydrogeology

    NASA Astrophysics Data System (ADS)

    Hester, E. T.; Greer, B. M.; Burbey, T. J.; Zipper, C. E.

    2015-12-01

    Understanding the hydrology of disturbed lands is important given the increasing human footprint on earth. Surface coal mining has caused significant land-use change in central Appalachia in the past few decades. The mining process breaks up overburden rock above coal seams, and then replaces that material at the mine location and in adjacent unmined valleys (valley fills). The freshly exposed rock surfaces undergo weathering which often alters water quality and ultimately aquatic communities in effluent streams. One of the most common water quality effects is increased total dissolved solids (TDS), which is usually measured via its surrogate, specific conductance (SC). The SC of valley fill effluent is a function of fill construction methods, materials, and age. Yet hydrologic studies that relate these variables to water quality are sparse due to the difficulty of implementing traditional hydrologic measurements in fill material. We tested the effectiveness of electrical resistivity imaging (ERI) to monitor subsurface geologic patterns and hydrologic flow paths in a test-case valley fill. We paired ERI with artificial rainfall experiments to track infiltrated water as it moved through the valley fill material. Results indicate that ERI can be used to identify the subsurface geologic structure and track advancing wetting fronts or preferential flow paths. We observed that the upper portion of the fill profile contains significant fines, while the deeper profile is primarily composed of large rocks and void spaces. The artificial rainfall experiments revealed that water ponded on the surface of compacted areas until it reached preferential flow paths, where it infiltrated quickly and deeply. We observed water moving from the surface down to >10 m depth within 75 minutes. In sum, vertical and lateral preferential flow paths were evident at both shallow (through compacted layers) and deep (among boulders) locations. Such extensive preferential flow suggests that a

  9. Fracture network characterisation of a landslide by electrical resistivity tomography

    NASA Astrophysics Data System (ADS)

    Szalai, S.; Szokoli, K.; Novák, A.; Tóth, Á.; Metwaly, M.; Prácser, E.

    2014-06-01

    In contrary to most of the landslide studies which concentrate to the sliding surface in this paper the fracture system of a loess landslide is investigated. The continuity and geometry, orientation and dip of the major fractures are crucial parameters for assessing rock stability and landslide evolution. Rain infiltrating moreover easily into the rock mass through fractures providing lubrication for the material to slide, and increases the self-mass of the material increasing the slumping rate. Fracture maps enable beside of the characterisation of the fractured area the delineation of the endangered area of slow-moving landslides in due time and getting information about its inner structure. For constructing such maps Electrical Resistivity Tomography (ERT) measurements have been carried out using different geoelectric configurations. In spite of the high density of the fractures and their changing physical parameters in function of their water content - which make the interpretation rather difficult - a number of fractures have been detected and more or less well localised. On the basis of the present research the application of the Schlumberger and the Pole-Dipole arrays is recommended to fulfil the aim of the study. The optimised Stummer array is at the same time the only array which presents conductive anomalies (supposedly water filled fractures), as well, and indicates that fractures elongate deep downwards. Because these features seem to be realistic based on field observations or theoretical considerations the Stummer array may be a very good tool for completing e.g. P-Dp measurements. The study area could have been divided by all arrays into differently fractured zones, which assists a lot in understanding the landslide structure and evolution. It was shown, moreover, that in the still passive area there are thick fractures, too, verifying its dangerousness, as well. The ERT results enabled localising the rupture surfaces of future slumps which proved to

  10. 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.

  11. Modeling the electrical resistivity of deformation processed metal-metal composites

    SciTech Connect

    Tian, Liang; Anderson, Iver; Riedemann, Trevor; Russell, Alan

    2014-09-01

    Deformation processed metal–metal (matrix–reinforcement) composites (DMMCs) are high-strength, high-conductivity in situ composites produced by severe plastic deformation. The electrical resistivity of DMMCs is rarely investigated mechanistically and tends to be slightly higher than the rule-of-mixtures prediction. In this paper, we analyze several possible physical mechanisms (i.e. phonons, interfaces, mutual solution, grain boundaries, dislocations) responsible for the electrical resistivity of DMMC systems and how these mechanisms could be affected by processing conditions (i.e. temperature, deformation processing). As an innovation, we identified and assembled the major scattering mechanisms for specific DMMC systems and modeled their electrical resistivity in combination. From this analysis, it appears that filament coarsening rather than dislocation annihilation is primarily responsible for the resistivity drop observed in these materials after annealing and that grain boundary scattering contributes to the resistivity at least at the same magnitude as does interface scattering.

  12. Electrical earth resistivity surveys near brine holding ponds in Illinois. Environmental geology notes

    SciTech Connect

    Reed, P.C.; Cartwright, K.; Osby, D.

    1981-04-01

    Electrical earth resistivity surveys were conducted in the vicinity of five oil field brine holding ponds to develop a methodology for identifying elevated levels of soluble salts near oil fields. The five sites, all in similar hydrogeologic environments, were distributed across the main oil producing region of Illinois. Four of these sites were selected for detailed study of a possible relationship between changes in apparent electrical earth resistivities and changes in water quality.

  13. Electrical contact resistance degradation of a hot-switched simulated metal MEMS contact.

    SciTech Connect

    Dugger, Michael Thomas; Dickrell, Daniel John, III

    2005-03-01

    Electrical contact resistance testing was performed by hot-switching a simulated gold-platinum metal microelectromechanical systems contact. The experimental objective was to determine the sensitivity of the contact resistance degradation to current level and environment. The contact resistance increased sharply after 100 hot-switched cycles in air. Hot-switching at a reduced current and in nitrogen atmosphere curtailed contact resistance degradation by several orders of magnitude. The mechanism responsible for the resistance degradation was found to be arc-induced decomposition of adsorbed surface contaminants.

  14. Silicone oil contamination and electrical contact resistance degradation of low-force gold contacts.

    SciTech Connect

    Dugger, Michael Thomas; Dickrell, Daniel John, III

    2006-02-01

    Hot-switched low-force gold electrical contact testing was performed using a nanomechanical test apparatus to ascertain the sensitivity of simulated microelectromechanical systems (MEMS) contact to silicone oil contamination. The observed cyclic contact resistance degradation was dependent on both closure rate and noncontact applied voltage. The decomposition of silicone oil from electrical arcing was hypothesized as the degradation mechanism.

  15. Method and device with adjustable focusing for measuring the electric resistivity of geological formations

    SciTech Connect

    Desbrandes, R.

    1983-10-25

    The method of the invention comprises determining the variation of the electric potential on both sides of a central electrode in a borehole, detecting the two levels of the borehole where the potential gradient is zero, and measuring the electric resistivity of the geological formation between these two levels.

  16. Electrical Resistivity of Natural Diamond and Diamond Films Between Room Temperature and 1200 C: Status Update

    NASA Technical Reports Server (NTRS)

    Vandersande, Jan W.; Zoltan, L. D.

    1993-01-01

    The electrical resistivity of diamond films has been measured between room temperature and 1200 C. The films were grown by either microwave Plasma CVD or combustion flame at three different places. The resistivities of the current films are compared to those measured for both natural IIa diamond and films grown only one to two years ago.

  17. Electrical properties of deuteron irradiated high resistivity silicon

    NASA Astrophysics Data System (ADS)

    Krupka, Jerzy; Karcz, Waldemar; Avdeyev, Sergej P.; Kamiński, Paweł; Kozłowski, Roman

    2014-04-01

    We have investigated resistivity changes introduced on the high-resistivity p-type silicon wafer by the irradiation with deuteron beam with an energy of 4.4 GeV performed in the NUCLOTRON superconducting accelerator. Two contactless techniques were used for the measurements of resistivity changes: namely the microwave split post dielectric resonator (SPDR) technique and capacitance measurements in the frequency domain. The first technique allows resistivity measurements in the plane of the wafer, while the second one in the direction perpendicular to the wafer. The resistivity map obtained with the SPDR technique enabled us to obtain a permanent fingerprint of the accelerator beam intensity profile. It has been shown that after the irradiation, the material resistivity increased to ˜3.9 × 105 Ω cm in the wafer region exposed to the maximum beam intensity. Complementary studies of the properties and concentrations of radiation deep-level defects were performed by the high-resolution photo-induced current transient spectroscopy (HRPITS). These studies have shown that the irradiation of the high resistivity silicon with 4.4-GeV deuterons results in the formation of several types of deep-level defects responsible for the charge compensation.

  18. Methods for detecting and locating leaks in containment facilities using electrical potential data and electrical resistance tomographic imaging techniques

    DOEpatents

    Daily, William D.; Laine, Daren L.; Laine, Edwin F.

    2001-01-01

    Methods are provided for detecting and locating leaks in liners used as barriers in the construction of landfills, surface impoundments, water reservoirs, tanks, and the like. Electrodes are placed in the ground around the periphery of the facility, in the leak detection zone located between two liners if present, and/or within the containment facility. Electrical resistivity data is collected using these electrodes. This data is used to map the electrical resistivity distribution beneath the containment liner or between two liners in a double-lined facility. In an alternative embodiment, an electrode placed within the lined facility is driven to an electrical potential with respect to another electrode placed at a distance from the lined facility (mise-a-la-masse). Voltage differences are then measured between various combinations of additional electrodes placed in the soil on the periphery of the facility, the leak detection zone, or within the facility. A leak of liquid through the liner material will result in an electrical potential distribution that can be measured at the electrodes. The leak position is located by determining the coordinates of an electrical current source pole that best fits the measured potentials with the constraints of the known or assumed resistivity distribution.

  19. Methods for detecting and locating leaks in containment facilities using electrical potential data and electrical resistance tomographic imaging techniques

    DOEpatents

    Daily, W.D.; Laine, D.L.; Laine, E.F.

    1997-08-26

    Methods are provided for detecting and locating leaks in liners used as barriers in the construction of landfills, surface impoundments, water reservoirs, tanks, and the like. Electrodes are placed in the ground around the periphery of the facility, in the leak detection zone located between two liners if present, and/or within the containment facility. Electrical resistivity data is collected using these electrodes. This data is used to map the electrical resistivity distribution beneath the containment liner between two liners in a double-lined facility. In an alternative embodiment, an electrode placed within the lined facility is driven to an electrical potential with respect to another electrode placed at a distance from the lined facility (mise-a-la-masse). Voltage differences are then measured between various combinations of additional electrodes placed in the soil on the periphery of the facility, the leak detection zone, or within the facility. A leak of liquid though the liner material will result in an electrical potential distribution that can be measured at the electrodes. The leak position is located by determining the coordinates of an electrical current source pole that best fits the measured potentials with the constraints of the known or assumed resistivity distribution. 6 figs.

  20. Methods for detecting and locating leaks in containment facilities using electrical potential data and electrical resistance tomographic imaging techniques

    DOEpatents

    Daily, William D.; Laine, Daren L.; Laine, Edwin F.

    1997-01-01

    Methods are provided for detecting and locating leaks in liners used as barriers in the construction of landfills, surface impoundments, water reservoirs, tanks, and the like. Electrodes are placed in the ground around the periphery of the facility, in the leak detection zone located between two liners if present, and/or within the containment facility. Electrical resistivity data is collected using these electrodes. This data is used to map the electrical resistivity distribution beneath the containment liner between two liners in a double-lined facility. In an alternative embodiment, an electrode placed within the lined facility is driven to an electrical potential with respect to another electrode placed at a distance from the lined facility (mise-a-la-masse). Voltage differences are then measured between various combinations of additional electrodes placed in the soil on the periphery of the facility, the leak detection zone, or within the facility. A leak of liquid though the liner material will result in an electrical potential distribution that can be measured at the electrodes. The leak position is located by determining the coordinates of an electrical current source pole that best fits the measured potentials with the constraints of the known or assumed resistivity distribution.

  1. Influence of Ultraviolet/Ozonolysis Treatment of Nanocarbon Filler on the Electrical Resistivity of Epoxy Composites.

    PubMed

    Perets, Yulia; Matzui, Lyudmila; Vovchenko, Lyudmila; Ovsiienko, Irina; Yakovenko, Olena; Lazarenko, Oleksandra; Zhuravkov, Alexander; Brusylovets, Oleksii

    2016-12-01

    In the present work, we have investigated concentration and temperature dependences of electrical conductivity of graphite nanoplatelets/epoxy resin composites. The content of nanocarbon filler is varied from 0.01 to 0.05 volume fraction. Before incorporation into the epoxy resin, the graphite nanoplatelets were subjected to ultraviolet ozone treatment at 20-min ultraviolet exposure. The electric resistance of the samples was measured by two- or four-probe method and teraohmmeter E6-13. Several characterization techniques were employed to identify the mechanisms behind the improvements in the electrical properties, including SEM and FTIR spectrum analysis.It is established that the changes of the relative intensities of the bands in FTIR spectra indicate the destruction of the carboxyl group -COOH and group -OH. Electrical conductivity of composites has percolation character and graphite nanoplatelets (ultraviolet ozone treatment for 20 min) addition which leads to a decrease of percolation threshold 0.005 volume fraction and increase values of electrical conductivity (by 2-3 orders of magnitude) above the percolation threshold in comparison with composite materials-graphite nanoplatelets/epoxy resin. The changes of the value and behavior of temperature dependences of the electrical resistivity of epoxy composites with ultraviolet/ozone-treated graphite nanoparticles have been analyzed within the model of effective electrical conductivity. The model takes into account the own electrical conductivity of the filler and the value of contact electric resistance between the filler particles of the formation of continuous conductive pathways. PMID:27550050

  2. Influence of Ultraviolet/Ozonolysis Treatment of Nanocarbon Filler on the Electrical Resistivity of Epoxy Composites.

    PubMed

    Perets, Yulia; Matzui, Lyudmila; Vovchenko, Lyudmila; Ovsiienko, Irina; Yakovenko, Olena; Lazarenko, Oleksandra; Zhuravkov, Alexander; Brusylovets, Oleksii

    2016-12-01

    In the present work, we have investigated concentration and temperature dependences of electrical conductivity of graphite nanoplatelets/epoxy resin composites. The content of nanocarbon filler is varied from 0.01 to 0.05 volume fraction. Before incorporation into the epoxy resin, the graphite nanoplatelets were subjected to ultraviolet ozone treatment at 20-min ultraviolet exposure. The electric resistance of the samples was measured by two- or four-probe method and teraohmmeter E6-13. Several characterization techniques were employed to identify the mechanisms behind the improvements in the electrical properties, including SEM and FTIR spectrum analysis.It is established that the changes of the relative intensities of the bands in FTIR spectra indicate the destruction of the carboxyl group -COOH and group -OH. Electrical conductivity of composites has percolation character and graphite nanoplatelets (ultraviolet ozone treatment for 20 min) addition which leads to a decrease of percolation threshold 0.005 volume fraction and increase values of electrical conductivity (by 2-3 orders of magnitude) above the percolation threshold in comparison with composite materials-graphite nanoplatelets/epoxy resin. The changes of the value and behavior of temperature dependences of the electrical resistivity of epoxy composites with ultraviolet/ozone-treated graphite nanoparticles have been analyzed within the model of effective electrical conductivity. The model takes into account the own electrical conductivity of the filler and the value of contact electric resistance between the filler particles of the formation of continuous conductive pathways.

  3. Electrical resistance of CNT-PEEK composites under compression at different temperatures

    PubMed Central

    2011-01-01

    Electrically conductive polymers reinforced with carbon nanotubes (CNTs) have generated a great deal of scientific and industrial interest in the last few years. Advanced thermoplastic composites made of three different weight percentages (8%, 9%, and 10%) of multiwalled CNTs and polyether ether ketone (PEEK) were prepared by shear mixing process. The temperature- and pressure-dependent electrical resistance of these CNT-PEEK composites have been studied and presented in this paper. It has been found that electrical resistance decreases significantly with the application of heat and pressure. PMID:21711952

  4. Electrical resistance of CNT-PEEK composites under compression at different temperatures

    NASA Astrophysics Data System (ADS)

    Mohiuddin, Mohammad; van Hoa, Suong

    2011-06-01

    Electrically conductive polymers reinforced with carbon nanotubes (CNTs) have generated a great deal of scientific and industrial interest in the last few years. Advanced thermoplastic composites made of three different weight percentages (8%, 9%, and 10%) of multiwalled CNTs and polyether ether ketone (PEEK) were prepared by shear mixing process. The temperature- and pressure-dependent electrical resistance of these CNT-PEEK composites have been studied and presented in this paper. It has been found that electrical resistance decreases significantly with the application of heat and pressure.

  5. Resistance and internal electric field in cloud-to-ground lightning channel

    SciTech Connect

    Cen, Jianyong; Yuan, Ping Xue, Simin; Wang, Xuejuan

    2015-02-02

    Cloud-to-ground lightning with six return strokes has been recorded by slitless spectrograph and the system of fast antenna and slow antenna. The physical parameters of the discharge channel have been obtained based on the combination of spectra and synchronous radiated electric field. The resistance and internal electric field of the channel are studied as the focus in this paper. The results show that the resistances per unit length of the lightning channel are in the order of 10{sup −2}–10{sup −1 }Ω/m and the internal electric field strengths are in the order of 10{sup 3 }V/m.

  6. Percolation of gallium dominates the electrical resistance of focused ion beam deposited metals

    SciTech Connect

    Faraby, H.; DiBattista, M.; Bandaru, P. R.

    2014-04-28

    Metal deposition through focused ion beam (FIB) based systems is thought to result in material composed of the primary metal from the metallo-organic precursor in addition to carbon, oxygen, and gallium. We determined, through electrical resistance and chemical composition measurements on a wide range of FIB deposited platinum and tungsten lines, that the gallium ion (Ga{sup +}) concentration in the metal lines plays the dominant role in controlling the electrical resistivity. Effective medium theory, based on McLachlan's formalisms, was used to describe the relationship between the Ga{sup +} concentration and the corresponding resistivity.

  7. Electrical Resistance of Ceramic Matrix Composites for Damage Detection and Life-Prediction

    NASA Technical Reports Server (NTRS)

    Smith, Craig; Morscher, Gregory N.; Xia, Zhenhai

    2008-01-01

    The electric resistance of woven SiC fiber reinforced SiC matrix composites were measured under tensile loading conditions. The results show that the electrical resistance is closely related to damage and that real-time information about the damage state can be obtained through monitoring of the resistance. Such self-sensing capability provides the possibility of on-board/in-situ damage detection or inspection of a component during "down time". The correlation of damage with appropriate failure mechanism can then be applied to accurate life prediction for high-temperature ceramic matrix composites.

  8. Electrical resistivity tomography at the search of groundwater near Anapa town in the south of Russia.

    NASA Astrophysics Data System (ADS)

    Kvon, Dina; Vladimir, Shevnin; Boris, Nikulin; Albert, Ryjov; Alexey, Skobelev

    2013-04-01

    Electrical resistivity tomography at the search of groundwater near Anapa town in the south of Russia. Kvon D. A.(1)*, Shevnin V.A.(1), Nikulin B. A.(1), Ryjov A. A.(2), Skobelev A. O.(1) (1)Geophysical dept., Faculty of Geology, Moscow state university; (2)VSEGINGEO Due to acute shortage of fresh drinking water near Anapa town (not far from the Black Sea), geophysical investigations were performed for searching and mapping aquifers in the area, where, according to rare wells exist probability to find fresh underground water. Geophysical explorations were carried out by Electrical resistivity tomography (ERT) method and water resistivity measurements. The resistivity of fresh groundwater is 15 Ohm.m, its salinity is 0.4 g/l. The structure of the area has been obtained by previous geological and hydrogeological studies and boreholes drilling. Geological structure of the area consists of two parts: the upper part of cross-section presented by loose lacustrine-alluvial sediments of Upper Pleistocene - Holocene, the lower part presented by hard rocs of carbonate-flysch formation of Upper Cretaceous age consisted of marl and limestone. Prospective areas to find underground water are: water-bearing horizon of upper Pleistocene-Holocene sediments, which is presented by gravel layer (base layer of modern lacustrine-alluvial sediments), and fractured zones in hard rocks of the carbonate-flysch formation of Maastricht age (Supseh formation). Analysis of rocks' resistivity obtained from Electrical resistivity tomography followed by calculation of rock resistivity on known petrophysical parameters (in Petrowin program created by A. A. Ryjov) [Shevnin et al., 2007]. The calculation showed that there is low clay content in carbonate rocks of the studied area, and the rock is limestone, not marl. Measurement of rock samples with X-ray radiometric method showed high calcium content (30-35%) or 75-87.5% limestone. This fact shows that flysch formation of the area is mainly

  9. Dependence of the Anomalous Resistivity on the Induced Electric Field in Solar Flares

    NASA Astrophysics Data System (ADS)

    Wu, Guiping; Huang, Guangli; Ji, Haisheng

    2010-09-01

    Anomalous resistivity is a critical parameter for triggering the fast magnetic reconnection and interpreting the eruption of solar flares in the nearly collisionless coronal plasma. However, the mechanism for the production of anomalous resistivity and its evolution are weakly understood. In this paper, the one-dimensional Vlasov equation was numerically solved with the typical solar coronal parameters and realistic mass ratio in the presence of strong inductive electric field, and the relationship between the anomalous resistivity and the reconnecting electric field was inferred for the area near the center of reconnecting current sheets. Our principal findings are summarized as follows. (1) The relationship between the anomalous resistivity and the reconnecting electric field E 0 may be represented by ηeff = [10.82-10.99 exp (-0.36 E 0)]Ω m. (2) If E 0 is small enough, it may be described by ηeff = [4.02 E 0 - 0.18]Ω m, which is basically consistent with the early experimental results on the plasma response to the applied electric field. (3) In comparison with theoretical formulas for the current-driven ion-acoustic and Buneman anomalous resistivities, if E 0 is small, the anomalous resistivity may be due to the ion-acoustic instability; if E 0 is large, the anomalous resistivity may be due to the Buneman instability. These results are also basically consistent with early experiments.

  10. Electric stimulations mediated beta lactam resistance reversal and correlation with growth dynamics of community acquired methicillin resistant Staphylococcus aureus.

    PubMed

    Kainthola, Anup; Uniyal, Akshat; Srivastava, Nidhi; Bhatt, Ajay B

    2015-08-01

    The community associated methicillin resistant Staphylococcus aureus (CA-MRSA) is a serious issue of public health. Here, we conducted an experimental approach to determine: (i) the optimal significant stimulation range of electrical current for effective checking of CA-MRSA growth; (ii) the effect of electrical stimulations on methicillin susceptibility and possible beta lactam resistance reversal; and (iii) the variation in the level of ATP as function of exposure to electric current. An 8 chambered electrical system was developed for DC flow in control and test sets, with and without drug (oxacillin 4 mg/ml). Measurement of growth by CFU/ml and spectrometry, susceptibility and ATP levels were calculated and interpreted. Linear pattern in reduction of ATP was observed with respect to the intensity of electric current (EC) and an enhanced inhibitory effect was explicit with 1000 microampere (μA) with 30 min exposure. At 4000 μA exposure to DC at 180 min and in combination of drug (μA+D), the growth of CA-MRSA was substantially checked to 0.23 absorbance in comparison to current without drug and the effect of DC electrical current to the culture showed that 10 μA, 100 μA and 4000 μA current exposure in combination of oxacillin (μA+D), markedly reduced the CFU to an average of 256.4. ATP level was linearly reduced with exposure to EC.

  11. Results of Electrical Resistivity Data Collected near the Town of Guernsey, Platte County, Wyoming

    USGS Publications Warehouse

    McDougal, Robert R.; Abraham, Jared D.; Bisdorf, Robert J.

    2004-01-01

    As part of a study to investigate subsurface geologic conditions as they relate to ground-water flow in an abandoned landfill near the town of Guernsey, Wyoming, geophysical direct current (DC) resistivity data were collected. Eight vertical resistivity soundings and eight horizontal resistivity profiles were made using single channel and multi-channel DC instruments. Data collected in the field were converted from apparent resistivity to inverted resistivity with depth using a numerical inversion of the data. Results of the inverted resistivity data are presented as horizontal profiles and as profiles derived from the combined horizontal profile and vertical sounding data. The data sets collected using the single-channel and multi-channel DC systems provided for the resistivity investigation to extend to greater depth. Similarity of the electrical properties of the bedrock formations made interpretation of the resistivity profiles more difficult. High resistivity anomalies seen in the profiles are interpreted as quartzite lenses and as limestone or metadolomite structures in the eastern part of the study area. Terrace gravels were mapped as resistive where dry and less resistive in the saturated zone. The DC resistivity methods used in this study illustrate that multi-electrode DC resistivity surveying and more traditional methodologies can be merged and used to efficiently map anomalies of hydrologic interest in geologically complex terrain.

  12. Thermal treatment of low permeability soils using electrical resistance heating

    SciTech Connect

    Udell, K.S.

    1996-08-01

    The acceleration of recovery rates of second phase liquid contaminants from the subsurface during gas or water pumping operations is realized by increasing the soil and ground water temperature. Electrical heating with AC current is one method of increasing the soil and groundwater temperature and has particular applicability to low permeability soils. Several mechanisms have been identified that account for the enhanced removal of the contaminants during electrical heating. These are vaporization of liquid contaminants with low boiling points, temperature-enhanced evaporation rates of semi-volatile components, and removal of residual contaminants by the boiling of residual water. Field scale studies of electrical heating and fluid extraction show the effectiveness of this technique and its applicability to contaminants found both above and below the water table and within low permeability soils. 10 refs., 8 figs.

  13. Unconventional drop in the electrical resistance of chromium metal thin films at low temperature

    NASA Astrophysics Data System (ADS)

    Ohashi, M.; Ohashi, K.; Sawabu, M.; Miyagawa, M.; Kubota, T.; Takanashi, K.

    2016-09-01

    We studied the electrical resistance of single-crystal and polycrystalline chromium films. The ρ (T) curve of single-crystal films decrease with decreasing temperature and show humps at around 300 K consistent with the bulk chromium being an itinerant antiferromagnet. In the polycrystalline films, on the other hand, the ρ (T) curves deviate from those of the bulk chromium. Moreover, we observed sudden decrease in the resistance around 1.5 K. Although previous studies suggested that chromium films become superconductive (Schmidt et al. (1972) [12]), it is difficult to conclude whether a superconducting transition occurs because the electrical resistivity is not zero in all films. No anomaly was detected by resistance measurements around room temperature, and the sudden decrease in the resistance at low temperature may be attributed to the suppression of antiferromagnetic interaction by thinning down the chromium element.

  14. Electrical Resistivity as an Indicator of Saturation in Fractured Geothermal Reservoir Rocks: Experimental Data and Modeling

    SciTech Connect

    Detwiler, R L; Roberts, J J

    2003-06-23

    The electrical resistivity of rock cores under conditions representative of geothermal reservoirs is strongly influenced by the state and phase (liquid/vapor) of the pore fluid. In fractured samples, phase change (vaporization/condensation) can result in resistivity changes that are more than an order of magnitude greater than those measured in intact samples. These results suggest that electrical resistivity monitoring of geothermal reservoirs may provide a useful tool for remotely detecting the movement of water and steam within fractures, the development and evolution of fracture systems and the formation of steam caps. We measured the electrical resistivity of cores of welded tuff containing fractures of various geometries to investigate the resistivity contrast caused by active boiling and to determine the effects of variable fracture dimensions and surface area on water extraction from the matrix. We then used the Nonisothermal Unsaturated Flow and Transport model (NUFT) (Nitao, 1998) to simulate the propagation of boiling fronts through the samples. The simulated saturation profiles combined with previously reported measurements of resistivity-saturation curves allow us to estimate the evolution of the sample resistivity as the boiling front propagates into the rock matrix. These simulations provide qualitative agreement with experimental measurements suggesting that our modeling approach may be used to estimate resistivity changes induced by boiling in more complex systems.

  15. Simultaneous electrical resistivity and mass uptake measurements in bromine intercalated fibers

    NASA Technical Reports Server (NTRS)

    Jaworske, D. A.

    1986-01-01

    Changes in mass and electrical resistivity of several types of pitch-based and vapor-grown graphite fibers were monitored during reaction with bromine. The observed threshold pressure dependent reaction suggested that the fibers were intercalated. In the fully brominated compound, the mass was increased by 44 percent and the resistivity was improved by a factor of 17. In the residue compound, the mass was increased by 22 percent and the resistivity was improved by a factor of 5. Fibers possessing different degrees of graphitization had surprisingly similar changes in both mass and resistivity.

  16. Studying ground water under Delmarva coastal bays using electrical resistivity

    USGS Publications Warehouse

    Manheim, Frank T.; Krantz, David E.; Bratton, John F.

    2004-01-01

    Fresh ground water is widely distributed in subsurface sediments below the coastal bays of the Delmarva Peninsula (Delaware, Maryland, and Virginia). These conditions were revealed by nearly 300 km of streamer resistivity surveys, utilizing a towed multichannel cable system. Zones of high resistivity displayed by inversion modeling were confirmed by vibradrilling investigations to correspond to fresh ground water occurrences. Fresh water lenses extended from a few hundred meters up to 2 km from shore. Along the western margins of coastal bays in areas associated with fine-grained surficial sediments, high-resistivity layers were widespread and were especially pronounced near tidal creeks. Fresh ground water layers were less common along the eastern barrier-bar margins of the bays, where sediments were typically sandy. Mid-bay areas in Chincoteague Bay, Maryland, did not show evidence of fresh water. Indian River Bay, Delaware, showed complex subsurface salinity relationships, including an area with possible hypersaline brines. The new streamer resistivity system paired with vibradrilling in these investigations provides a powerful approach to recovering information required for extension of hydrologic modeling of shallow coastal aquifer systems into offshore areas.

  17. Electrical resistivity surveys in Prospect Gulch, San Juan County, Colorado

    USGS Publications Warehouse

    McDougal, Robert R.

    2006-01-01

    Prospect Gulch is a major source of naturally occurring and mining related metals to Cement Creek, a tributary of the upper Animas River in southwestern Colorado. Efforts to improve water quality in the watershed have focused on Prospect Gulch because many of its abandoned mines and are located on federal lands. Information on sources and pathways of metals, and related ground-water flow, will be useful to help prioritize and develop remediation strategies. It has been shown that the occurrence of sulfate, aluminum, iron, zinc and other metals associated with historical mining and the natural weathering of pyritic rock is substantial. In this study, direct current resistivity surveys were conducted to determine the subsurface resistivity distribution and to identify faults and fractures that may act as ground-water conduits or barriers to flow. Five lines of resistivity data were collected in the vicinity of Prospect Gulch, and cross-section profiles were constructed from the field data using a two-dimensional inversion algorithm. The conductive anomalies in the profiles are most likely caused by wet or saturated rocks and sediments, clay rich deposits, or high TDS ground water. Resistive anomalies are likely bedrock, dry surficial and sub-surface deposits, or deposits of ferricrete.

  18. Module Three: Resistance; Basic Electricity and Electronics Individualized Learning System.

    ERIC Educational Resources Information Center

    Bureau of Naval Personnel, Washington, DC.

    In this module the student will learn of the opposition offered to electron flow, what this opposition does, why it is needed, and how it is used. The module is divided into four lessons: characteristics of resistance, resistors, resistor values, and ohmmeters. Each lesson consists of an overview, a list of study resources, lesson narratives,…

  19. Experimental determination of the electrical resistivity of iron at Earth's core conditions.

    PubMed

    Ohta, Kenji; Kuwayama, Yasuhiro; Hirose, Kei; Shimizu, Katsuya; Ohishi, Yasuo

    2016-06-01

    Earth continuously generates a dipole magnetic field in its convecting liquid outer core by a self-sustained dynamo action. Metallic iron is a dominant component of the outer core, so its electrical and thermal conductivity controls the dynamics and thermal evolution of Earth's core. However, in spite of extensive research, the transport properties of iron under core conditions are still controversial. Since free electrons are a primary carrier of both electric current and heat, the electron scattering mechanism in iron under high pressure and temperature holds the key to understanding the transport properties of planetary cores. Here we measure the electrical resistivity (the reciprocal of electrical conductivity) of iron at the high temperatures (up to 4,500 kelvin) and pressures (megabars) of Earth's core in a laser-heated diamond-anvil cell. The value measured for the resistivity of iron is even lower than the value extrapolated from high-pressure, low-temperature data using the Bloch-Grüneisen law, which considers only the electron-phonon scattering. This shows that the iron resistivity is strongly suppressed by the resistivity saturation effect at high temperatures. The low electrical resistivity of iron indicates the high thermal conductivity of Earth's core, suggesting rapid core cooling and a young inner core less than 0.7 billion years old. Therefore, an abrupt increase in palaeomagnetic field intensity around 1.3 billion years ago may not be related to the birth of the inner core. PMID:27251282

  20. Assessment of groundwater vulnerability to leachate infiltration using electrical resistivity method

    NASA Astrophysics Data System (ADS)

    Mosuro, G. O.; Omosanya, K. O.; Bayewu, O. O.; Oloruntola, M. O.; Laniyan, T. A.; Atobi, O.; Okubena, M.; Popoola, E.; Adekoya, F.

    2016-02-01

    This aim of this work is to assess the degree of leachate infiltration at a dumpsite in Agbara industrial estate, Southwestern Nigeria using electrical resistivity techniques. Around the dumpsite were 45 vertical electrical sounding (VES) stations and 3 electrical resistivity tomography profiles. Current electrode spread varied from 300 to 600 m for the electrical sounding. Electrode configuration includes Schlumberger and Wenner array for sounding and profiling. The state of leachate contamination was tested using parameters such as aquifer vulnerability index, overburden protective capacity and longitudinal unit conductance (Si) derived from the apparent resistivity values. Four principal geoelectric layers inferred from the VES data include the topsoil, sand, clayey sand, and clay/shale. Resistivity values for these layers vary from 3 to 1688, 203 to 3642 123 to 388, and 67 to 2201 Ω m with corresponding thickness of 0.8-2.4, 2.5-140, 3-26 m and infinity, respectively. The leachate plume occurs at a maximum depth of 10 m on the 2-D inverse models of real electrical resistivity with an average depth of infiltration being 6 m in the study area. The correlation between longitudinal conductance and overburden protective capacity show that aquifers around the dumpsite have poor protective capacity and are vulnerable to leachate contamination. Leachate infiltration is favored by the absence of lithological barriers such as clay which in the study area are either mixed with sand or positioned away from the aquifer.

  1. Experimental determination of the electrical resistivity of iron at Earth’s core conditions

    NASA Astrophysics Data System (ADS)

    Ohta, Kenji; Kuwayama, Yasuhiro; Hirose, Kei; Shimizu, Katsuya; Ohishi, Yasuo

    2016-06-01

    Earth continuously generates a dipole magnetic field in its convecting liquid outer core by a self-sustained dynamo action. Metallic iron is a dominant component of the outer core, so its electrical and thermal conductivity controls the dynamics and thermal evolution of Earth’s core. However, in spite of extensive research, the transport properties of iron under core conditions are still controversial. Since free electrons are a primary carrier of both electric current and heat, the electron scattering mechanism in iron under high pressure and temperature holds the key to understanding the transport properties of planetary cores. Here we measure the electrical resistivity (the reciprocal of electrical conductivity) of iron at the high temperatures (up to 4,500 kelvin) and pressures (megabars) of Earth’s core in a laser-heated diamond-anvil cell. The value measured for the resistivity of iron is even lower than the value extrapolated from high-pressure, low-temperature data using the Bloch-Grüneisen law, which considers only the electron-phonon scattering. This shows that the iron resistivity is strongly suppressed by the resistivity saturation effect at high temperatures. The low electrical resistivity of iron indicates the high thermal conductivity of Earth’s core, suggesting rapid core cooling and a young inner core less than 0.7 billion years old. Therefore, an abrupt increase in palaeomagnetic field intensity around 1.3 billion years ago may not be related to the birth of the inner core.

  2. Physical Modelling on Detecting Buried Object Using Electrical Resistivity Imaging (ERI)

    NASA Astrophysics Data System (ADS)

    Hazreek, Z. A. M.; Nizam, Z. M.; Azhar, A. T. S.; Aziman, M.; Shaylinda, M. Z. N.

    2016-07-01

    This study focused on the evaluation of electrical resistivity method (ERM) for buried object detection and its relationship due to the different stiffness of material. In the past, the conventional method to detect the buried structure was face some limitation due to the time and cost. For example, previous approach related to the trial and error excavation has always expose to some risky outcome due to the uncertainties of the buried object location. Hence, this study introduced an alternative technique with particular reference to resistivity method to detect and evaluate the buried object with different strength of stiffness. The experiment was performed based on field miniature model (small scale study) using soil trial embankment made by lateritic soil and various concrete cube strengths (grade 20, 25 and 30) representing buried object with different conditions. 2D electrical resistivity test (electrical resistivity imaging) was perform using ABEM Terrameter SAS4000 during the data acquisition while the raw data was process using RES2DINV software. It was found that the electrical resistivity method was able to detect the buried concrete structures targeted based on the contrast of the electrical resistivity image produced. Moreover, three different strength of concrete cube were able to be differentiated based on the electrical resistivity values (ERV) obtained. This study found that the ERV of concrete cube for grade 20, 25 and 30 were 170 Ωm, 227 Ωm and 503 Ωm, respectively. Hence, this study shows that the ERV has a strong relationship with different stiffness of material thus applicable to be a useful alternative tool in underground structure detection.

  3. INORGANIC PLUME DELINEATION USING SURFACE HIGH RESOLUTION ELECTRICAL RESISTIVITY AT THE BC CRIBS & TRENCHES SITE HANFORD

    SciTech Connect

    BENECKE, M.W.

    2007-05-29

    A surface resistivity survey was conducted on the Hanford Site over a waste disposal trench that received a large volume of liquid inorganic waste. The objective of the survey was to map the extent of the plume that resulted from the disposal activities approximately 50 years earlier. The survey included six resistivity transects of at least 200m, where each transect provided two-dimensional profile information of subsurface electrical properties. The results of the survey indicated that a low resistivity plume resides at a depth of approximately 25-44 m below ground surface. The target depth was calibrated with borehole data of pore-water electrical conductivity. Due to the high correlation of the pore-water electrical conductivity to nitrate concentration and the high correlation of measured apparent resistivity to pore-water electrical conductivity, inferences were made that proposed the spatial distribution of the apparent resistivity was due to the distribution of nitrate. Therefore, apparent resistivities were related to nitrate, which was subsequently rendered in three dimensions to show that the nitrate likely did not reach the water table and the bounds of the highest concentrations are directly beneath the collection of waste sites.

  4. Detection of Cracks Using 2d Electrical Resistivity Imaging In A Cultivated Soil

    NASA Astrophysics Data System (ADS)

    Samouëlian, A.; Cousin, I.; Richard, G.; Bruand, A.

    Variations of soil structure is significant for the understanding of water and gas trans- fer in soil profiles. In the context of arable land, soil structure can be compacted due to either agriculture operation (wheel tracks), or hardsetting and crusting processes. As a consequence, soil porosity is reduced which may lead to decrease water infiltra- tion and to anoxic conditions. Porosity can be increased by cracks formation due to swelling and shrinking phenomenon. We present here a laboratory experiment based on soil electrical characteristics. Electrical resistivity allows a non destructive three di- mensional and dynamical analysis of the soil structure. Our main objective is to detect cracks in the soil. Cracks form an electrical resistant object and the contrast of resis- tivity between air and soil is large enough to be detected. Our sample is an undisturbed soil block 240mm*170mm*160mm with an initial structure compacted by wheel traf- fic. Successive artificial cracks are generated. Electrodes built with 2 mm ceramic cups permit a good electrical contact at the soil surface whatever its water content. They are installed 15 mm apart and the electrical resistivity is monitored using a dipole-dipole and wenner multi-electrodes 2D imaging method which gives a picture of the subsur- face resistivity. The interpreted resistivity sections show the major soil structure. The electrical response changes with the cracks formation. The structure information ex- tracted from the electrical map are in good agreement with the artificially man-made cracks. These first results demonstrate the relevance of high resolution electrical imag- ing of the soil profile. Further experiments need to be carried out in order to monitor natural soil structure evolution during wetting-drying cycles.

  5. Permanent electrical resistivity measurements for monitoring water circulation in clayey landslides

    NASA Astrophysics Data System (ADS)

    Gance, J.; Malet, J.-P.; Supper, R.; Sailhac, P.; Ottowitz, D.; Jochum, B.

    2016-03-01

    Landslides developed on clay-rich slopes are controlled by the soil water regime and the groundwater circulation. Spatially-distributed and high frequency observations of these hydrological processes are important for improving our understanding and prediction of landslide triggering. This work presents observed changes in electrical resistivity monitored at the Super-Sauze clayey landslide with the GEOMON 4D resistivity instrument installed permanently on-site for a period of one year. A methodological framework for processing the raw measurement is proposed. It includes the filtering of the resistivity dataset, the correction of the effects of non-hydrological factors (sensitivity of the device, sensitivity to soil temperature and fluid conductivity, presence of fissures in the topsoil) on the filtered resistivity values. The interpretation is based on a statistical analysis to define possible relationships between the rainfall characteristics, the soil hydrological observations and the soil electrical resistivity response. During the monitoring period, no significant relationships between the electrical response and the measured hydrological parameters are evidenced. We discuss the limitations of the method due to the effect of heat exchange between the groundwater, the vadose zone water and the rainwater that hides the variations of resistivity due to variations of the soil water content. We demonstrate that despite the absence of hydrogeophysical information for the vadose zone, the sensitivity of electrical resistivity monitoring to temperature variations allows imaging water fluxes in the saturated zone and highlighting the existence of matrix and preferential flows that does not occur at the same time and for the same duration. We conclude on the necessity to combine electrical resistivity measurements with distributed soil temperature measurements.

  6. [Numerical simulation and application of electrical resistivity survey in heavy metal contaminated sites].

    PubMed

    Wang, Yu-ling; Nai, Chang-xin; Wang, Yan-wen; Dong, Lu

    2013-05-01

    In order to analyze the effects of electrical resistivity in heavy metal contaminated sites, we established the resistivity model of typical contaminated sites and simulate the DC resistivity method with Wenner arrays using the finite element method. The simulation results showed that the electrical method was influenced by the contamination concentration and the location of pollution. The more serious the degree of pollution was, the more obvious the low resistivity anomaly, thus the easier the identification of the contaminated area; otherwise, if there was light pollution, Wenner array could not get obvious low resistivity anomalies, so it would be hard to judge the contaminated area. Our simulation results also showed that the closer the contaminated areas were to the surface, the more easily the pollution was detected and the low resistivity anomalies shown in the apparent resistivity diagram were influenced by the Layered medium. The actual field survey results using resistivity method also show that the resistivity method can correctly detect the area with serious pollution. PMID:23914547

  7. Relationship between electrical skin resistance and rectal temperature in man during physical exercise.

    PubMed

    Grucza, R

    1984-01-01

    Electrical skin resistance (ESR) and rectal temperature (Tre) were examined in 13 unacclimated human subjects performing bicycle exercise at an intensity of 50% VO2max. After the beginning of exercise the electrical skin resistance decreased according to an exponential curve with a delay of 4 min and time constant of 9 min. The dynamic parameters of ESR were shorter than those reported for sweating. Statistical analysis showed a correlation between individual time constants of ESR and increases in rectal temperature of the subjects (r = 0.705, p less than 0.01). It is concluded that measurement of dynamics of the electrical skin resistance may be useful for estimation of thermal effects in exercising subjects.

  8. Understanding Electrical Conduction States in WO3 Thin Films Applied for Resistive Random-Access Memory

    NASA Astrophysics Data System (ADS)

    Ta, Thi Kieu Hanh; Pham, Kim Ngoc; Dao, Thi Bang Tam; Tran, Dai Lam; Phan, Bach Thang

    2016-05-01

    The electrical conduction and associated resistance switching mechanism of top electrode/WO3/bottom electrode devices [top electrode (TE): Ag, Ti; bottom electrode (BE): Pt, fluorine-doped tin oxide] have been investigated. The direction of switching and switching ability depended on both the top and bottom electrode material. Multiple electrical conduction mechanisms control the leakage current of such switching devices, including trap-controlled space-charge, ballistic, Ohmic, and Fowler-Nordheim tunneling effects. The transition between electrical conduction states is also linked to the switching (SET-RESET) process. This is the first report of ballistic conduction in research into resistive random-access memory. The associated resistive switching mechanisms are also discussed.

  9. Fabrication of intermetallic coatings for electrical and corrosion resistance on high-temperature alloys

    SciTech Connect

    Park, J.H.; Cho, W.D.

    1994-10-01

    Several intermetallic films were fabricated to high-temperature alloys (V-alloys and 304 and 316 stainless steels) to provide electrical insulation and corrosion resistance. Alloy grain-growth behavior at 1000{degrees}C for the V-5Cr-5Ti was investigated to determine the stability of alloy substrate during coating formation by chemical vapor deposition (CVD) or metallic vapor processes at 800-850{degrees}C. Film layers were examined by optical and scanning electron microscopy and by electron-energy-dispersive and X-ray diffraction analysis and tested for electrical resistivity and corrosion resistance. The results elucidated the nature of the coatings, which provided both electrical insulation and high-temperature corrosion protection.

  10. Electrical resistivity of nanoporous gold modified with thiol self-assembled monolayers

    NASA Astrophysics Data System (ADS)

    Hakamada, Masataka; Kato, Naoki; Mabuchi, Mamoru

    2016-11-01

    The electrical resistivity of nanoporous gold (NPG) modified with thiol self-assembled monolayers (SAMs) has been measured at 298 K using a four-probe method. We found that the adsorption of thiol SAMs increases the electrical resistivity of NPG by up to 22.2%. Dependence of the electrical resistivity on the atmosphere (air or water) was also observed in SAMs-modified NPG, suggesting that the electronic states of the tail groups affect the electrons of the binding sulfur and adjacent surface gold atoms. The present results suggest that adsorption of thiol molecules can influence the behavior of the conducting electrons in NPG and that modification of NPG with SAMs may be useful for environmental sensing.

  11. Developing a theoretical relationship between electrical resistivity, temperature, and film thickness for conductors.

    PubMed

    Lacy, Fred

    2011-12-22

    Experimental evidence has made it clear that the size of an object can have an effect on its properties. The electrical resistivity of a thin film will become larger as the thickness of that film decreases in size. Furthermore, the electrical resistivity will also increase as the temperature increases. To help understand these relationships, a model is presented, and equations are obtained to help understand the mechanisms responsible for these properties and to give insight into the underlying physics between these parameters. Comparisons are made between experimental data and values generated from the theoretical equations derived from the model. All of this analysis provides validation for the theoretical model. Therefore, since the model is accurate, it provides insight into the underlying physics that relates electrical resistivity to temperature and film thickness. PACS: 73.61.At; 73.50.Bk; 72.15.Eb; 72.10.d; 63.20.kd.

  12. Delineating the Groundwater Recharge Zone in the Pingtung Plan , Taiwan with Electrical Resistivity Surveys

    NASA Astrophysics Data System (ADS)

    Wu, C.; Chang, P.; Chang, L.; Chen, J.; Huang, C.

    2012-12-01

    In this study we used the two-dimensional electrical resistivity imaging (ERI) method, as well as the core records of monitoring wells to help determine the groundwater recharge zone in Pingtung plain in southwestern Taiwan. Pingtung fluvial plain is one of the major groundwater resources in Taiwan which is composed of several alluvial fans deriving from the uplifted mountain area to the east and north of the plain. The thick gravel layer constitutes the main recharge area of the upper alluvial fans and the conductive clay sediments dominate most of the lower fans. With the core records, we found that, the gravel layers have higher resistivity (mostly over 200 Ohm-m) and the resistivities of the clayey layers are low (about 1~10 Ohm-m). Therefore with the resistivity surveys we can have more confidences for determining the boundary of the groundwater recharge area in the area in-between the monitoring wells. In the past two years, we have finished 24 two-dimensional electrical resistivity imaging profile lines from Meinong to Fangliao, the lines are oriented in the east-west direction, and each line was about 400 meters long. With the inverted results, we are able to characterize two major alluvial systems and their recharge zones in the Pingtung fluvial plain. The resistivities we measured almost are consistent to the core records of monitoring wells except for the Wanluan site, which shows thick gravel layer in the drilling records but has low resistivity in the nearby resistivity survey. A reasonable explanation is that the electrical resistivity is sensitive to clayey materials with lower resistivities. The intercalated clay within the gravel layers is not shown in the churn drilling records.

  13. Fully Electrical Modeling of Thermoelectric Generators with Contact Thermal Resistance Under Different Operating Conditions

    NASA Astrophysics Data System (ADS)

    Siouane, Saima; Jovanović, Slaviša; Poure, Philippe

    2016-09-01

    The Seebeck effect is used in thermoelectric generators (TEGs) to supply electronic circuits by converting the waste thermal into electrical energy. This generated electrical power is directly proportional to the temperature difference between the TEG module's hot and cold sides. Depending on the applications, TEGs can be used either under constant temperature gradient between heat reservoirs or constant heat flow conditions. Moreover, the generated electrical power of a TEG depends not only on these operating conditions, but also on the contact thermal resistance. The influence of the contact thermal resistance on the generated electrical power have already been extensively reported in the literature. However, as reported in Park et al. (Energy Convers Manag 86:233, 2014) and Montecucco and Knox (IEEE Trans Power Electron 30:828, 2015), while designing TEG-powered circuit and systems, a TEG module is mostly modeled with a Thévenin equivalent circuit whose resistance is constant and voltage proportional to the temperature gradient applied to the TEG's terminals. This widely used simplified electrical TEG model is inaccurate and not suitable under constant heat flow conditions or when the contact thermal resistance is considered. Moreover, it does not provide realistic behaviour corresponding to the physical phenomena taking place in a TEG. Therefore, from the circuit designer's point of view, faithful and fully electrical TEG models under different operating conditions are needed. Such models are mainly necessary to design and evaluate the power conditioning electronic stages and the maximum power point tracking algorithms of a TEG power supply. In this study, these fully electrical models with the contact thermal resistance taken into account are presented and the analytical expressions of the Thévenin equivalent circuit parameters are provided.

  14. Fracture Surface Area Effects on Fluid Extraction and the Electrical Resistivity of Geothermal Reservoir Rocks

    SciTech Connect

    Roberts, J J; Detwiler, R L; Ralph, W; Bonner, B

    2002-05-09

    Laboratory measurements of the electrical resistivity of fractured analogue geothermal reservoir rocks were performed to investigate the resistivity contrast caused by active boiling and to determine the effects of variable fracture dimensions and surface area on water extraction. Experiments were performed at confining pressures up to 10 h4Pa (100 bars) and temperatures to 170 C. Fractured samples show a larger resistivity change at the onset of boiling than intact samples. Monitoring the resistivity of fractured samples as they equilibrate to imposed pressure and temperature conditions provides an estimate of fluid migration into and out of the matrix. Measurements presented are an important step toward using field electrical methods to quantitatively search for fractures, infer saturation, and track fluid migration in geothermal reservoirs.

  15. A digitally controlled system for effecting and presenting a selected electrical resistance

    NASA Technical Reports Server (NTRS)

    Fletcher, James C. (Inventor); Ross, Walter L. (Inventor)

    1989-01-01

    A digitally controlled resistance generator is described, in which resistors having values selected according to an expression 2(sup N-1)(R), where N is equal to the number of terms in the expression, and R is equal to the lowest value of resistance, are electrically inserted into a resistive circuit in accordance with a parallel binary signal provided by an analog-to-digital converter or a programmable computer. This binary signal is coupled via optical isolators which, when activated by a logical 1, provides a negative potential to some or all of the gate inputs of the normally on field effect transistors which, when on, shorts out the associated resistor. This applied negative potential turns the field effect transistors off and electrically inserts the resistor coupled between the source terminal and the drain terminal of that field effect transistor into the resistive circuit between the terminals.

  16. On the Modeling of Electrical Effects Experienced by Space Explorers During Extra Vehicular Activities: Intracorporal Currents, Resistances, and Electric Fields

    NASA Technical Reports Server (NTRS)

    Cela, Carlos J.; Loizos, Kyle; Lazzi, Gianluca; Hamilton, Douglas; Lee, Raphael C.

    2011-01-01

    Recent research has shown that space explorers engaged in Extra Vehicular Activities (EVAs) may be exposed, under certain conditions, to undesired electrical currents. This work focuses on determining whether these undesired induced electrical currents could be responsible for involuntary neuromuscular activity in the subjects, possibly caused by either large diameter peripheral nerve activation or reflex activity from cutaneous afferent stimulation. An efficient multiresolution variant of the admittance method along with a millimeter-resolution model of a male human body were used to calculate induced electric fields, resistance between contact electrodes used to simulate the potential exposure condition, and currents induced in the human body model. Results show that, under realistic exposure conditions using a 15V source, current density magnitudes and total current injected are well above previously reported startle reaction thresholds. This indicates that, under the considered conditions, the subjects could experience involuntary motor response.

  17. Electrical resistivity well-logging system with solid-state electronic circuitry

    USGS Publications Warehouse

    Scott, James Henry; Farstad, Arnold J.

    1977-01-01

    An improved 4-channel electrical resistivity well-logging system for use with a passive probe with electrodes arranged in the 'normal' configuration has been designed and fabricated by Westinghouse Electric Corporation to meet technical specifications developed by the U.S. Geological Survey. Salient features of the system include solid-state switching and current regulation in the transmitter circuit to produce a constant-current source square wave, and synchronous solid-state switching and sampling of the potential waveform in the receiver circuit to provide an analog dc voltage proportions to the measured resistivity. Technical specifications and design details are included in this report.

  18. Investigations of temperature dependences of electrical resistivity and specific heat capacity of metals

    NASA Astrophysics Data System (ADS)

    Eser, Erhan; Koç, Hüseyin

    2016-07-01

    In this study, we calculated the electrical resistivity and heat capacities of some ideal metals (Cu, Pt, and Pd) using a method that it employs the statistical model and Debye functions. The method is used to provide a simple and reliable analytical procedure for wide temperature range. The results obtained for the electrical resistivity and heat capacity have been compared with the results in literature. The results obtained at low temperature are in excellent agreement with experimental and theoretical results. Finally the used approximation and analytical method are a useful approach to calculate thermophysical properties of metals.

  19. Temperature dependent electrical resistivity of gallium and antimony in a liquid form

    NASA Astrophysics Data System (ADS)

    Prajapati, A. V.; Sonvane, Y. A.; Thakor, P. B.

    2016-05-01

    Present paper deals with the effects of temperature variation on the electrical resistivity (Ω) of liquid Gallium (Ga), and Antimony (Sb). We have used a new parameter free pseudopotential with a Zeeman formula for finding it. To see the effects of screening Farid et al local field correction function is used with the Charged Hard Sphere (CHS) reference system. Analysis and comparison between the plotted graphs, based on present computed data and other experimental data defines and conclude that our newly constructed model potential is an effective one to produce the data for the temperature dependent electrical resistivity of some liquid semiconductors.

  20. Electron Acceleration by Cascading Reconnection in the Solar Corona. II. Resistive Electric Field Effects

    NASA Astrophysics Data System (ADS)

    Zhou, X.; Büchner, J.; Bárta, M.; Gan, W.; Liu, S.

    2016-08-01

    We investigate electron acceleration by electric fields induced by cascading reconnections in current sheets trailing coronal mass ejections via a test particle approach in the framework of the guiding-center approximation. Although the resistive electric field is much weaker than the inductive electric field, the electron acceleration is still dominated by the former. Anomalous resistivity η is switched on only in regions where the current carrier’s drift velocity is large enough. As a consequence, electron acceleration is very sensitive to the spatial distribution of the resistive electric fields, and electrons accelerated in different segments of the current sheet have different characteristics. Due to the geometry of the 2.5-dimensional electromagnetic fields and strong resistive electric field accelerations, accelerated high-energy electrons can be trapped in the corona, precipitating into the chromosphere or escaping into interplanetary space. The trapped and precipitating electrons can reach a few MeV within 1 s and have a very hard energy distribution. Spatial structure of the acceleration sites may also introduce breaks in the electron energy distribution. Most of the interplanetary electrons reach hundreds of keV with a softer distribution. To compare with observations of solar flares and electrons in solar energetic particle events, we derive hard X-ray spectra produced by the trapped and precipitating electrons, fluxes of the precipitating and interplanetary electrons, and electron spatial distributions.

  1. Acidic Barren Slope Profiling using Electrical Resistivity Imaging (ERI) at Ayer Hitam area Johor, Malaysia

    NASA Astrophysics Data System (ADS)

    Azhar, A. T. S.; Hazreek, Z. A. M.; Aziman, M.; Haimi, D. S.; Hafiz, Z. M.

    2016-04-01

    Recently, non-destructive method such as the electrical resistivity technique has become increasingly popular in engineering, environmental, mining and archeological studies nowadays. This method was popular in subsurface profiling due to its ability to replicate the images of the subsurface indirectly. The soil slope found in Batu Pahat, specifically in Ayer Hitam, is known to be problematic due to its barren condition. This location is believed to contain futile soil due to its difficulty in supporting the growth of vegetations. In the past, acidic barren slope assessment using non-destructive method was rarely being used due to several reasons related to the equipment and knowledge constraints. Hence, this study performed an electrical resistivity imaging using ABEM Terrameter LS in order to investigate the acidic barren slope conditions. Field data acquisition was based on Schlumberger and Wenner arrays while RES2DINV software was used to analyze and generate a 2-D model of the problematic subsurface profile. Based on electrical resistivity results, it was found that the acidic barren slope studied consists of two main zones representing residual soil (electrical resistivity value = 10 - 600 Ωm) and shale (electrical resistivity value = 20 - 2000 Ωm). The results of resistivity value were correlated with the physical mapping and the in situ mackintosh probe test for verification purposes. It was found that the maximum depth of the mackintosh probe test was 1.8 m due to its ground penetration limitation. However, the results of the resistivity section managed to achieve greater depth up to 40 m. Hence, the correlation between electrical resistivity and mackintosh probe results can only be performed at certain depth of the acidic barren slope profile in contrast with the physical mapping which able to define the whole section of the barren soil slope structure. Finally, a good match of electrical resistivity results calibrated with mackintosh and physical

  2. Characterization of Contact and Bulk Thermal Resistance of Laminations for Electric Machines

    SciTech Connect

    Cousineau, J. Emily; Bennion, Kevin; DeVoto, Doug; Mihalic, Mark; Narumanchi, Sreekant

    2015-06-30

    The ability to remove heat from an electric machine depends on the passive stack thermal resistances within the machine and the convective cooling performance of the selected cooling technology. This report focuses on the passive thermal design, specifically properties of the stator and rotor lamination stacks. Orthotropic thermal conductivity, specific heat, and density are reported. Four materials commonly used in electric machines were tested, including M19 (29 and 26 gauge), HF10, and Arnon 7 materials.

  3. Electrical resistivity and equation of state measurements of a dense aluminum plasma

    SciTech Connect

    Benage, J.F. Jr.; Shanahan, W.R.

    1992-01-01

    In this paper we report results of experiments to measure the electrical resistivity and equation of state for a dense strongly coupled aluminum plasma. These plasmas are near solid density and have temperatures in the 15--20 eV range with {Gamma} = 2--3. Our initial results indicate a significant reduction in pressure below the ideal gas law value and initial resistivity measurements agree with a model by Rinker within error bars.

  4. Electrical resistivity and equation of state measurements of a dense aluminum plasma

    SciTech Connect

    Benage, J.F. Jr.; Shanahan, W.R.

    1992-09-01

    In this paper we report results of experiments to measure the electrical resistivity and equation of state for a dense strongly coupled aluminum plasma. These plasmas are near solid density and have temperatures in the 15--20 eV range with {Gamma} = 2--3. Our initial results indicate a significant reduction in pressure below the ideal gas law value and initial resistivity measurements agree with a model by Rinker within error bars.

  5. Electrical Resistivity Study of a Pleistocene Riverbed in Saltville, VA

    NASA Astrophysics Data System (ADS)

    Herman, R. B.; Whisonant, R. C.

    2008-05-01

    A shallow capacitively coupled resistivity survey was performed in Saltville, VA, in an area of suspected buried Pleistocene river deposits. Previous excavations in the sediments beneath the Saltville valley floor had been performed to recover late Pleistocene megafaunal remains and possible Clovis-age human artifacts. These digs encountered a zone, one to two meters deep, of gravel-sized rock fragments, including some boulders up to 75 cm. in diameter. These large clasts are rounded, show some imbrication (shingle-like overlapping indicative of current flow), and have been interpreted as river channel deposits. Carbon 14 dates from the megafaunal bones within and just above the gravel bed yielded dates of 14,500 years BP. Resistivity signals in a number of locations were consistent with cobbles and boulders deposited in a river channel. These signals are generally bowl- shaped areas with large circular (2-d scans) anomalies near the center, and smaller circular anomalies tapering out towards both sides. The bowl-shaped anomalies are within 3 meters of the surface. With several lines imaged in this survey a rough path of the riverbed, along with a number of branchings is traceable in the survey area. An exploratory hole confirmed the presence of a layer of rounded cobbles and boulders 1.3 meters deep beneath one of the survey lines.

  6. Elastic and Electrical Properties Evaluation of Low Resistivity Pays in Malay Basin Clastics Reservoirs

    NASA Astrophysics Data System (ADS)

    Almanna Lubis, Luluan; Ghosh, Deva P.; Hermana, Maman

    2016-07-01

    The elastic and electrical properties of low resistivity pays clastics reservoirs in Malay Basin are strongly dependent on the complex nature of the clay content, either dispersed or laminated/layered. Estimating the hydrocarbon pore volume from conventional electrical log, i.e. resistivity log, is quite a challenge. The low elastic impedance contrast also found as one of the challenge thus create a problem to map the distribution of the low resistivity reservoirs. In this paper, we evaluate the electrical properties and elastic rock properties to discriminate the pay from the adjacent cap rock or shale. Forward modeling of well log responses including electrical properties are applied to analyze the nature of the possible pays on laminated reservoir rocks. In the implementation of rock properties analysis, several conventional elastic properties are comparatively analyzed for the sensitivity and feasibility analysis on each elastic parameters. Finally, we discussed the advantages of each elastic parameters in detail. In addition, cross-plots of elastic and electrical properties attributes help us in the clear separation of anomalous zone and lithologic properties of sand and shale facies over conventional elastic parameter crossplots attributes. The possible relationship on electrical and elastic properties are discussed for further studies.

  7. Influence of Ultraviolet/Ozonolysis Treatment of Nanocarbon Filler on the Electrical Resistivity of Epoxy Composites

    NASA Astrophysics Data System (ADS)

    Perets, Yulia; Matzui, Lyudmila; Vovchenko, Lyudmila; Ovsiienko, Irina; Yakovenko, Olena; Lazarenko, Oleksandra; Zhuravkov, Alexander; Brusylovets, Oleksii

    2016-08-01

    In the present work, we have investigated concentration and temperature dependences of electrical conductivity of graphite nanoplatelets/epoxy resin composites. The content of nanocarbon filler is varied from 0.01 to 0.05 volume fraction. Before incorporation into the epoxy resin, the graphite nanoplatelets were subjected to ultraviolet ozone treatment at 20-min ultraviolet exposure. The electric resistance of the samples was measured by two- or four-probe method and teraohmmeter E6-13. Several characterization techniques were employed to identify the mechanisms behind the improvements in the electrical properties, including SEM and FTIR spectrum analysis.

  8. The electrical resistivity of some graphite types as used in electrothermal atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Rademeyer, C. J.; Human, H. G. C.; Faure, P. K.

    This paper describes the measurement of the electrical resistivity of four types of graphite as used in electrothermal atomic absorption spectrometry (ETAAS). Results are presented for temperatures in a range between 140 and 1800°C. From 1200°C on the resistivity was found to depend linearly on temperature. The regression coefficients for the corresponding straight portions of the experimental curves are given to provide data for extrapolating the resistivity values to 2500°C and to calculate the dynamic temperature characteristics of the graphite tubes in ETAAS.

  9. Parallel electric fields in extragalactic jets - double layers and anomalous resistivity in symbiotic relationships

    SciTech Connect

    Borovsky, J.E.

    1986-07-01

    After examining the properties of Coulomb-collision resistivity, anomalous (collective) resistivity, and double layers, a hybrid anomalous-resistivity/double-layer model is introduced. In this model, beam-driven waves on both sides of a double layer provide electrostatic plasma-wave turbulence that greatly reduces the mobility of charged particles. These regions then act to hold open a density cavity within which the double layer resides. In the double layer, electrical energy is dissipated with 100 percent efficiency into high-energy particles, creating conditions optimal for the collective emission of polarized radio waves. 102 references.

  10. Parallel electric fields in extragalactic jets - Double layers and anomalous resistivity in symbiotic relationships

    NASA Technical Reports Server (NTRS)

    Borovsky, J. E.

    1986-01-01

    After examining the properties of Coulomb-collision resistivity, anomalous (collective) resistivity, and double layers, a hybrid anomalous-resistivity/double-layer model is introduced. In this model, beam-driven waves on both sides of a double layer provide electrostatic plasma-wave turbulence that greatly reduces the mobility of charged particles. These regions then act to hold open a density cavity within which the double layer resides. In the double layer, electrical energy is dissipated with 100 percent efficiency into high-energy particles, creating conditions optimal for the collective emission of polarized radio waves.

  11. Electrical Resistivity Tomography in the characterisation of wetting patterns of historical masonry

    NASA Astrophysics Data System (ADS)

    López-González, Laura; Gomez-Heras, Miguel; Ortiz de Cosca, Raquel Otero; García-Morales, Soledad

    2016-04-01

    Electrical Resistivity Tomography (ERT) is a geophysical technique widely used to identify subsurface structures based on electrical resistivity measurements made at the surface. In recent years this technique has been used for surveying historic buildings and characterise the subsurface of walls by using non-invasive EKG electrodes. This methods is used to locate wet areas based on the lower electrical resistivity wet materials have in relation to dry ones. A good knowledge of the wetting patterns of historic buildings during, for example, rainfalls is crucial to understand the decay processes that take place in the building and plan interventions. This paper presents results of transects of Electric Resistivity Tomography of walls of the Monastery of Santa Maria de Mave (Palencia, Spain), a 9th century Romanesque building, during rainfall. ERT transects were performed with a GeoTom device (Geolog2000) in areas with and without buttresses to understand how this architectural detail affected the wetting dynamics of the building. The ERT results were integrated with other resistivity-based techniques and Thermohygrometric survey in a GIS and showed how lower resistivity surface measurements ERT correspond with areas of higher humidity. Resistivity-based techniques measured and evaporation focal points take in the interior of the building mark the outer ground level. The highest moisture content measurements do not always correspond to the visibly most damaged areas of the wall. The consecutive ERT transects show the wall getting wetter as rainfall progresses. The comparison of the measurements obtained of a wall affected by water obtained with GIS mapping, allowed to quickly studying the development of moisture in the wall over time, which is essential for a correct diagnosis of the building. Research funded by Madrid's Regional Government project Geomateriales 2 S2013/MIT-2914

  12. A theoretical study of electrical and thermal response in resistance spot welding

    SciTech Connect

    Na, S.J.; Park, S.W.

    1996-08-01

    The effect of contact resistance including constriction and contamination resistance has been a major hurdle for the thermoelectrical analysis of the resistance spot welding process. In this paper, a simple model was suggested and used for calculating the electrical and thermal response of the resistance spot welding process to investigate the influence of contacting forces on the formation of weld nuggets. The electrode surface of the contact interface was assumed to be axisymmetric and its microasperities to have a trapezoidal cross-section. These microasperities were considered as the one-dimensional contact resistance elements in the finite element formulation. The contamination film was assumed to be a nonconducting oxide layer, which is very brittle, so that it is broken to some number of pieces when a contacting pressure is being applied. The crushed films were assumed to be distributed at regular intervals and to conserve their size and number during the welding process. The simulation results revealed that the proposed model can be successfully used to predict the effect of the contact resistance on the electrical and thermal response of the resistance spot welding process.

  13. Abnormal drop in electrical resistivity with impurity doping of single-crystal Ag

    PubMed Central

    Kim, Ji Young; Oh, Min-Wook; Lee, Seunghun; Cho, Yong Chan; Yoon, Jang-Hee; Lee, Geun Woo; Cho, Chae-Ryong; Park, Chul Hong; Jeong, Se-Young

    2014-01-01

    Resistivity is an intrinsic feature that specifies the electrical properties of a material and depends on electron-phonon scattering near room temperature. Reducing the resistivity of a metal to its potentially lowest value requires eliminating grain boundaries and impurities, but to date few studies have focused on reducing the intrinsic resistivity of a pure metal itself. We could reduce the intrinsic resistivity of single-crystal Ag, which has an almost perfect structure, by impurity doping it with Cu. This paper presents our results: resistivity was reduced to 1.35 μΩ·cm at room temperature after 3 mol% Cu-doping of single-crystal Ag. Various mechanisms were examined in an attempt to explain the abnormal behavior. PMID:24965478

  14. Abnormal drop in electrical resistivity with impurity doping of single-crystal Ag.

    PubMed

    Kim, Ji Young; Oh, Min-Wook; Lee, Seunghun; Cho, Yong Chan; Yoon, Jang-Hee; Lee, Geun Woo; Cho, Chae-Ryong; Park, Chul Hong; Jeong, Se-Young

    2014-06-26

    Resistivity is an intrinsic feature that specifies the electrical properties of a material and depends on electron-phonon scattering near room temperature. Reducing the resistivity of a metal to its potentially lowest value requires eliminating grain boundaries and impurities, but to date few studies have focused on reducing the intrinsic resistivity of a pure metal itself. We could reduce the intrinsic resistivity of single-crystal Ag, which has an almost perfect structure, by impurity doping it with Cu. This paper presents our results: resistivity was reduced to 1.35 μΩ · cm at room temperature after 3 mol% Cu-doping of single-crystal Ag. Various mechanisms were examined in an attempt to explain the abnormal behavior.

  15. A study of the deposition of carbide coatings on graphite fibers. [to increase electrical resistance

    NASA Technical Reports Server (NTRS)

    Suplinskas, R. J.; Henze, T. W.

    1979-01-01

    The chemical vapor deposition of boron carbide and silicon carbide on graphite fibers to increase their electrical resistance was studied. Silicon carbide coatings were applied without degradation of the mechanical properties of the filaments. These coatings typically added 1000 ohms to the resistance of a filament as measured between two mercury pools. When SiC-coated filaments were oxidized by refluxing in boiling phosphoric acid, average resistance increased by an additional 1000 ohms; in addition resistance increases as high as 150 K ohms and breakdown voltages as high as 17 volts were noted. Data on boron carbide coatings indicated that such coatings would not be effective in increasing resistance, and would degrade the mechanical properties.

  16. Electrical resistance determination of actual contact area of cold welded metal joints

    NASA Technical Reports Server (NTRS)

    Hordon, M. J.

    1970-01-01

    Method measures the area of the bonded zone of a compression weld by observing the electrical resistance of the weld zone while the load changes from full compression until the joint ruptures under tension. The ratio of bonding force to maximum tensile load varies considerably.

  17. Ion Permeability of Artificial Membranes Evaluated by Diffusion Potential and Electrical Resistance Measurements

    ERIC Educational Resources Information Center

    Shlyonsky, Vadim

    2013-01-01

    In the present article, a novel model of artificial membranes that provides efficient assistance in teaching the origins of diffusion potentials is proposed. These membranes are made of polycarbonate filters fixed to 12-mm plastic rings and then saturated with a mixture of creosol and "n"-decane. The electrical resistance and potential…

  18. High School Students' Understanding of Resistance in Simple Series Electric Circuits.

    ERIC Educational Resources Information Center

    Liegeois, Laurent; Mullet, Etienne

    2002-01-01

    Studies the understanding that 8-12 grade high school students were able to develop with regard to the interrelationships between resistance, potential difference, and current concepts (Ohm's law). Explores the immediate effects of exposure to electricity courses on the intuitive mastery of these relationships. (Contains 32 references.)…

  19. Imaging hydrological processes in headwater riparian seeps with time-lapse electrical resistivity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The activation of subsurface seepage in response to precipitation events represents a potentially important pathway of nitrogen (N) delivery to streams in agricultural catchments. We used electrical resistivity imaging (ERI) and shallow piezometers to elucidate how seep and non-seep areas within the...

  20. Aerodynamic resistance reduction of electric and hybrid vehicles

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The generation of an EHV aerodynamic data base was initiated by conducting full-scale wind tunnel tests on 16 vehicles. Zero-yaw drag coefficients ranged from a high of 0.58 for a boxey delivery van and an open roadster to a low of about 0.34 for a current 4-passenger prototype automobile which was designed with aerodynamics as an integrated parameter. Characteristic effects of aspect ratio or fineness ratio which might appear if electric vehicle shape proportions were to vary significantly from current automobiles were identified. Some preliminary results indicate a 5 to 10% variation in drag over the range of interest. Effective drag coefficient wind-weighting factors over J227a driving cycles in the presence of annual mean wind fields were identified. Such coefficients, when properly weighted, were found to be from 5 to 65% greater than the zero-yaw drag coefficient in the cases presented. A vehicle aerodynamics bibliography of over 160 entries, in six general categories is included.

  1. Electrical resistivity characterization and defect detection on a geosynthetic clay liner (GCL) on an experimental site

    NASA Astrophysics Data System (ADS)

    Sirieix, C.; Fernández Martínez, J. L.; Riss, J.; Genelle, F.

    2013-03-01

    In this paper we analyze the onsite characterization of a geosynthetic clay liner (GCL) that serves to ensure the impermeability of a landfill cap by DC electrical methods. The imaging of the GCL geoelectrical properties is a challenging problem because it is a very thin (between 4 and 7 mm thick) and resistive layer (from 100,000 to 2,000,000 Ω·m) depending on meteorological conditions and aging. We compare results obtained using electrical resistivity tomography (ERT) using two different kinds of arrays (dipole-dipole DD and Wenner-Schlumberger) on an experimental site with engineered defects. To confirm these results and to find the real onsite GCL resistivity we have performed sampling of the posterior distribution of this parameter using vertical electrical sounding (VES) inversions. Different VES methods were extracted from ERT with DD array and converted into a Schlumberger array. As a main conclusion the dipole-dipole array provides a better resistivity resolution of the defects than the Wenner-Schlumberger array. On ERT images, the defect detection seems to be impossible if the GCL has very high resistivity, as it happened when it was put in place. Taking into account the equivalence rules, the inversions are in both cases (ERT and VES) compatible. The GCL resistivity estimated from PSO (particle swarm optimization) varies from 3.0 105 to 1.106 Ω·m depending on saturation conditions during the twenty first months of its placing. Then, the resistivity dropped to 4.104-9.104 Ω·m, indicating a probable chemical damage of the GCL due to aging. Finally the fact that the VES inversions are solved via PSO sampling allows for the detection of a very thin and resistive layer and opens the possibility of performing micro VES surveys along the landfill to detect possible GCL defects.

  2. Characterization and monitoring of subsurface processes using parallel computing and electrical resistivity imaging

    SciTech Connect

    Johnson, Timothy C.; Truex, Michael J.; Wellman, Dawn M.; Marble, Justin

    2011-12-01

    This newsletter discusses recent advancement in subsurface resistivity characterization and monitoring capabilities. The BC Cribs field desiccation treatability test resistivity monitoring data is use an example to demonstrate near-real time 3D subsurface imaging capabilities. Electrical resistivity tomography (ERT) is a method of imaging the electrical resistivity distribution of the subsurface. An ERT data collection system consists of an array of electrodes, deployed on the ground surface or within boreholes, that are connected to a control unit which can access each electrode independently (Figure 1). A single measurement is collected by injecting current across a pair of current injection electrodes (source and sink), and measuring the resulting potential generated across a pair of potential measurement electrodes (positive and negative). An ERT data set is generated by collecting many such measurements using strategically selected current and potential electrode pairs. This data set is then processed using an inversion algorithm, which reconstructs an estimate (or image) of the electrical conductivity (i.e. the inverse of resistivity) distribution that gave rise to the measured data.

  3. Structure-property relationships in Waspaloy via small angle scattering and electrical resistivity measurements

    SciTech Connect

    Whelchel, R.; Gerhardt, Dr. Rosario; Littrell, Ken

    2010-01-01

    The mechanical properties in superalloys are controlled by the distribution of the {gamma}{prime} precipitate phase. Electrical measurements have been shown to be sensitive to certain aspects of the precipitation process and show promise for predicting the evolving microstructural state in superalloys. Aging experiments were conducted on Waspaloy samples for temperatures between 600 and 950 C for times ranging from 2min to 500h. Particle size distributions were obtained by modeling of small angle scattering (SAS) data, whereas, small precipitate size information, strain, and lattice mismatch data were obtained from X-ray diffraction. The microstructural information was then used to create a figure of merit of electron scattering intended to correlate electrical properties to the precipitate microstructure. The proposed figure of merit shows an empirical correlation with the electrical resistivity data, demonstrating the sensitivity of the resistivity measurements to the precipitation process and coarsening behavior.

  4. The use of rivets for electrical resistance measurement on carbon fibre-reinforced thermoplastics

    NASA Astrophysics Data System (ADS)

    DeBaere, I.; Van Paepegem, W.; Degrieck, J.

    2007-10-01

    The use of fibre-reinforced thermoplastics, for example in the aeronautical industry, is increasing rapidly. Therefore, there is an increasing need for in situ monitoring tools, which preferably have limited influence on the behaviour of the material and which are easy to use. Furthermore, in the aeronautical industry composites are very often attached with rivets. In this study, the possibility of the use of rivets as contact electrodes for electrical resistance measurement is explored. The material used is a carbon fibre-reinforced polyphenylene sulphide. First, the set-up used is discussed. Then, static tensile tests on the laminate are performed. The possible influence of an extensometer on the measurements is examined. Furthermore, failure predictability is assessed. It may be concluded that the proposed set-up with the rivets can be used for electrical resistance measurement, with the ability to predict failure, and that the extensometer has a negative influence on the resistance measurement.

  5. Monitoring six-phase ohmic heating of contaminated soils using electrical resistance tomography

    SciTech Connect

    Ramirez, A.L.; Daily, W.D.

    1994-09-01

    Electrical resistance tomography (ERT) was used to monitor six-phase ohmic heating used for the insitu remediation of volatile organic compounds from subsurface water and soil at the Savannah River Site, near Aiken, South Carolina. The changes in electrical conductivity caused by six-phase ohmic-heating in a clay layer located in the vadose zone were monitored during a period of approximately 2 months, before, during and after heating. From an array of electrodes located in 4 boreholes, we collected electrical resistivity data between five pairs of adjacent holes pairs. This data was used to calculate tomographs which showed the electrical conductivity changes along five vertical planes. The difference tomographs show the combined effects of moisture redistribution and heating caused by six-phase heating and vapor extraction. The tomographs show that most of the clay layer increased in electrical conductivity during the first 3 weeks of the 4 week long heating phase. At this time, the electrical conductivities near the center of the heating array were twice as large as the pre-heat conductivities. Then the electrical conductivity started to decrease for portions of the clay layer closest to the vapor extraction well. We propose that the conductivity decreases are due to the removal of moisture by the heating and vacuum extraction. Parts of the clay layer near the extraction well reached electrical conductivities as low as 40% of the pre-heating values. We propose that these regions of lower than ambient electrical conductivities are indicators of regions where the vapor removal by vacuum extraction was most effective. At the end of the heating phase, our estimates suggest that the clay saturation may have dropped to as low as 10% based on the observed conductivity changes.

  6. Subsurface electrical resistivity structure around the Noubi fault system, central Japan, by MT survey

    NASA Astrophysics Data System (ADS)

    Omura, K.; Matsuda, T.; Yamada, R.

    2009-12-01

    Subsurface electrical resistivity around active faults is an important property to investigate the position and the geometry of the faults, the scale of the fracture zones related to the fault activity, and the amount of water and/or clay minerals in fault zones. We performed MT (magnetotelluric) surveys with remote reference method across the Noubi active fault system, central Japan, in order to image the electrical resistivity structure in and around the faults, and to obtain fundamental information on the earthquake generation mechanism. The Noubi fault system, about 80 km long, activated at 1891 Noubi Earthquake, consisting of the Nukumi, the Neodani, and the Umehara faults, which slipped left laterally by 1 - 7 m at the 1891 earthquake. Seismological and geomorphologic studies revealed different features between these three faults; the amount of lateral slip of the Neodani fault was larger than those of the Nukumi and the Umehara fault at 1891 Noubi earthquake (Matsuda, 1974; Mikumo and Ando, 1976); the average recurrence intervals of activation of the Nukumi and the Neodani fault were shorter than that of the Umehara fault (The Headquarters for Earthquake Research Promotion, 2005). Survey areas are mainly covered by the Mino sedimentary complex formed in the Jurassic - Cretaceous period that consists of mudstone, sandstone, limestone, basalt, chart, and siliceous mudstone. But the Hida belt that consists of metamorphic and granitic rocks covers northeast area of the Nukumi fault. Three survey lines of about 20 km length were set crossing normal to the surface fault traces of the Nukumi, Neodani and Umehara faults. And 10 - 12 MT measurement sites were arranged with the same interval on the survey lines. We measured two components of electric field and three components of magnetic field by a 'MTU-5' system made by Phoenix Geophysics Ltd. at three different sampling frequencies to cover frequency bands of 0.0003 - 317 Hz of electric and magnetic field. Applying

  7. Electrical resistance response of polyaniline films to water, ethanol, and nitric acid solution

    NASA Astrophysics Data System (ADS)

    Yin, Hong-Xing; Li, Meng-Meng; Yang, H.; Long, Yun-Ze; Sun, Xin

    2010-08-01

    This paper reports on electrical resistance vs. aging time for the response of polyaniline films under exposure to water, ethanol and nitric acid (HNO3) solution. Camphor sulfonic acid-doped polyaniline films were prepared by a “doping-dedoping-redoping" method, the morphology and microstructures of the films were characterized by a scanning electron microscope and an x-ray diffractometer, the electrical resistance was measured by a four-probe method. It was found that a lower amount of water molecules infiltrating the film can decrease the film's resistance possibly due to an enhancement of charge carrier transfer between polyaniline chains, whereas excessive water molecules can swell inter-chain distances and result in a quick increase of resistance. The resistance of the film under exposure to ethanol increases and becomes much larger than the original value. However, HNO3 solution can decrease the film's resistance sharply possibly owing to doping effect of protonic acid. These results can help to understand the conduction mechanism in polyaniline films, and also indicate that the films have potential application in chemical sensors.

  8. Electrical resistivity and porosity structure of the upper Biscayne Aquifer in Miami-Dade County, Florida

    NASA Astrophysics Data System (ADS)

    Whitman, Dean; Yeboah-Forson, Albert

    2015-12-01

    Square array electrical soundings were made at 13 sites in the Biscayne Aquifer distributed between 1 and 20 km from the shoreline. These soundings were modeled to investigate how resistivity varies spatially and with depth in the upper 15 m of the aquifer. Porosity was estimated from the modeled formation resistivity and observed pore fluid resistivity with Archie's Law. The models were used to interpolate resistivity and porosity surfaces at -2, -5, -8, and -15 m elevations. Modeled resistivity in the unsaturated zone is generally higher than 300 Ω m with the resistivity at sites with thick unsaturated zones greater than 1000 Ω m. Resistivity in the saturated zone ranges from 30 to 320 Ω m. At many sites in the western portions of the study area, resistivity is constant or increases with depth whereas sites in the center of the Atlantic Coastal Ridge exhibit a distinct low resistivity zone (ρ < 45 Ω m) at elevations ranging between -5 and -10 m. At one site near the shore of Biscayne Bay, the resistivity is less than 10 Ω m at -5 m elevation reflecting the presence of salt water in the aquifer. The estimated porosity ranges between 14% and 71% with modal values near 25%. The porosity structure varies both with depth and spatially. Western sites exhibit a high porosity zone at shallow depths best expressed in a NE-SW trending zone of 40-50% porosity situated near the western margin of the Atlantic Coastal Ridge. This zone roughly corresponds in depth with the Q5 chronostratigraphic unit of the Miami Fm. which constitutes the upper flow unit of the Biscayne Aquifer. The highest porosity (>50%) is seen at elevations below -5 m at sites in the center of the Atlantic Coastal Ridge and likely corresponds to solution features. The general NE-SW trend of the resistivity and porosity structure suggests a causal connection with the Pleistocene paleogeography and sedimentary environments.

  9. Rough surface electrical contact resistance considering scale dependent properties and quantum effects

    SciTech Connect

    Jackson, Robert L.; Crandall, Erika R.; Bozack, Michael J.

    2015-05-21

    The objective of this work is to evaluate the effect of scale dependent mechanical and electrical properties on electrical contact resistance (ECR) between rough surfaces. This work attempts to build on existing ECR models that neglect potentially important quantum- and size-dependent contact and electrical conduction mechanisms present due to the asperity sizes on typical surfaces. The electrical conductance at small scales can quantize or show a stepping trend as the contact area is varied in the range of the free electron Fermi wavelength squared. This work then evaluates if these effects remain important for the interface between rough surfaces, which may include many small scale contacts of varying sizes. The results suggest that these effects may be significant in some cases, while insignificant for others. It depends on the load and the multiscale structure of the surface roughness.

  10. Earthquake resistant construction of electric transmission and telecommunication facilities serving the Federal government report

    SciTech Connect

    Yokel, F.Y.

    1990-02-01

    The vulnerability of electrical transmission and telecommunication facilities to damage in past earthquakes, as well as available standards and technologies to protect these facilities against earthquake damage are reviewed. An overview is presented of measures taken by various Federal agencies to protect electrical transmission and telecommunication facilities against earthquake hazards. It is concluded that while most new facilities which are owned and operated by Federal agencies are presently designed to provide some, though not necessarily adequate, earthquake resistance, there generally is no effort to retrofit existing facilities. No evidence was found of requirements to protect electrical transmission and communication facilities which have major contractual obligations to serve the Federal Government and only limited seismic design requirements are stipulated for electrical transmission systems constructed with Federal funding.

  11. Laboratory measurements of electrical resistivity versus water content on small soil cores

    NASA Astrophysics Data System (ADS)

    Robain, H.; Camerlynck, C.; Bellier, G.; Tabbagh, A.

    2003-04-01

    The assessment of soil water content variations more and more leans on geophysical methods that are non invasive and that allow a high spatial sampling. Among the different methods, DC electrical imaging is moving forward. DC Electrical resistivity shows indeed strong seasonal variations that principally depend on soil water content variations. Nevertheless, the widely used Archie's empirical law [1], that links resistivity with voids saturation and water conductivity is not well suited to soil materials with high clay content. Furthermore, the shrinking and swelling properties of soil materials have to be considered. Hence, it is relevant to develop new laboratory experiments in order to establish a relation between electrical resistivity and water content taking into account the rheological and granulometrical specificities of soil materials. The experimental device developed in IRD laboratory allows to monitor simultaneously (i) the water content, (ii) the electrical resistivity and (iii) the volume of a small cylindrical soil core (100cm3) put in a temperature controlled incubator (30°C). It provides both the shrinkage curve of the soil core (voids volume versus water content) and the electrical resistivity versus water content curve The modelisation of the shrinkage curve gives for each moisture state the water respectively contained in macro and micro voids [2], and then allows to propose a generalized Archie's like law as following : 1/Rs = 1/Fma.Rma + 1/Fmi.Rmi and Fi = Ai/(Vi^Mi.Si^Ni) with Rs : the soil resistivity. Fma and Fmi : the so called "formation factor" for macro and micro voids, respectively. Rma and Rmi : the resistivity of the water contained in macro and micro voids, respectively. Vi : the volume of macro and micro voids, respectively. Si : the saturation of macro and micro voids, respectively. Ai, Mi and Ni : adjustment coefficients. The variations of Rmi are calculated, assuming that Rma is a constant. Indeed, the rise of ionic

  12. Some considerations on electrical resistivity imaging for characterization of waterbed sediments

    NASA Astrophysics Data System (ADS)

    Orlando, Luciana

    2013-08-01

    The paper focuses on defining the performance and limits of ERI in the detection and sedimentary characterization of near-bottom thin layers. The analysis of the resolution of floating and submerged cables, and the effect of the accuracy of a priori information (resistivity and thickness) in the data inversion, is based on theory, models and actual data. Theoretical models show that the actual reconstruction of the near water-bottom sediments, in terms of geometry and resistivity, can be obtained only with the submerged cable, however, the data, unlike that acquired with the floating cable, require a priori information on water resistivity and thickness for the data inversion. Theoretical forward models based on wrong a priori water thickness and resistivity information influence the inverted model in different ways, depending on the under- and over-estimation of water resistivity and thickness, and the resistivity contrast of the water-solid layer; however a water-solid resistivity contrast of less than 2 and within 10% of error in water resistivity has no effect. Overestimating water resistivity depicts a ground similar to the actual ground in terms of resistivity, more so than the underestimation of water resistivity. Moreover, the data inversion is less influenced by water parameter error in the case of low resistivity contrast in the water-solid layer, than it is for high resistivity contrast. Wenner and Schlumberger arrays give comparable results, while a dipole-dipole array seems to be more sensitive to the accuracy of apparent resistivity measurements and a priori information on water. The theoretical considerations were validated by actual data acquired with a submerged cable on the Tiber River. The study has shown that if highly accurate measurements are made of water thickness and resistivity, then electrical resistivity imaging from the submerged cable can be used in addition to, or even to substitute, seismic data for the reconstruction of the features

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

    SciTech Connect

    Youngblood, G. E.; Thomsen, E. C.; Henager, C. H.

    2013-11-01

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

  14. A thermomechanical study of the electrical resistance of Cu lead interconnections

    NASA Astrophysics Data System (ADS)

    Liu, D. S.; Chen, C. Y.; Chao, Y. C.

    2006-05-01

    The choice of liquid crystal display (LCD) driver packaging technology significantly influences the display performance of flat panel displays. Tape automated bonding (TAB) is generally the method of choice for connecting the LCD and the LCD driver circuit in flat panel displays. To achieve a finer pitch, an easier assembly, and a greater connection reliability, the design of the inner Cu lead must not only consider thermomechanical failure aspects, but must also maintain an acceptable joint resistance. This paper proposes an analytical model to predict the unit change in resistance of the copper foils used for TAB inner lead interconnections under various thermal environments and stressstrain states. The analytical model is based on a constitutive equation of the copper foil and the working principle of strain gages. Copper foil specimens are tensile tested at temperatures of 25°C, 50°C, 75°C, and 100°C at strain rates of 0.2/min. and 0.5/min., respectively, to confirm the validity of the developed analytical model. The numerical results and the experimental data are found to be in good agreement. Hence, the analytical method provides the means of predicting the thermal effect on the electrical and mechanical properties of the copper foils. Finally, by implementing finite-element method (FEM) solutions in the developed analytical model, this study constructs electrical resistance design charts to predict the variation in the electrical resistance of the copper foils under different thermal-mechanical conditions.

  15. Electrical resistivity of single crystals of LaFeAsO under applied pressure

    NASA Astrophysics Data System (ADS)

    McElroy, C. A.; Hamlin, J. J.; White, B. D.; Weir, S. T.; Vohra, Y. K.; Maple, M. B.

    2014-09-01

    Measurements of electrical resistivity under applied pressure were performed on single-crystalline samples of LaFeAsO grown in a molten NaAs flux. We observe a smooth suppression of spin-density wave order under nearly hydrostatic applied pressures up to 2.6 GPa and in quasihydrostatic pressures up to 14.7 GPa. Similar to some of the other reports on single and polycrystalline samples of LaFeAsO, these crystals exhibit a resistivity that increases as temperature is lowered. By fitting an Arrhenius law to the the semiconducting-like temperature dependence of the electrical resistivity, we extract an energy gap that is suppressed with pressure and vanishes near 10 GPa. This is accompanied by the emergence of a metallic temperature dependence of the electrical resistivity. A similar behavior is also observed in diamond anvil cell experiments carried out to ˜37GPa. Complete transitions to a bulk superconducting phase are not observed in any of the experiments.

  16. Electrical resistance tomography for imaging the spatial distribution of moisture in pavement sections

    SciTech Connect

    Buettner, M.; Ramirez, A.; Daily, W.

    1995-11-08

    Electrical Resistance Tomography (ERT) was used to image spatial moisture distribution and movement in pavement sections during an infiltration test. ERT is a technique for determining the electrical resistivity distribution within a volume from measurement of injected currents and the resulting electrical potential distribution on the surface. The transfer resistance (ratio of potential to injected current) data are inverted using an algorithm based on a finite element forward solution which is iteratively adjusted in a least squares sense until the measured and calculated transfer resistances agree to within some predetermined value. Four arrays of ERT electrodes were installed in vertical drill holes 1.22 m (4 ft) placed at the comers of a square 61 cm (2 ft) on a side into a pavement section which is used for a truck scale ramp on U.S. Highway 99 just north of Sacramento, CA. Water was introduced slowly into the pavement through a shallow hole in the center of this pattern and ERT data were collected in various planes as the water infiltrated into the pavement and subgrade materials over a period of several hours. The ERT data were inverted, and the resulting images show (1) the basic structure of the pavement section and (2) the movement of water through the image planes as a function of time during infiltration. An interesting result is that the water does not appear to drain from the section toward the shoulder as had been expected based on the design.

  17. Inspection of earthen embankment dams using time lapse electrical resistivity tomography

    NASA Astrophysics Data System (ADS)

    Case, Jared S.

    According to the National Inventory of Dams (NID), the number of dams across the United States is approximately 85,000. Many of these dams are more than 50 years old and need vast attention to ensure their safety. It is difficult to obtain a full assessment of the dam just by visual inspections alone. This is because many problems associated with dam failure occur internally, which makes it difficult to be observed by the dam inspectors. Examples of these flaws are piping and seepage (flow of water through or around dam walls). It is in this area where geophysical methods can aid in obtaining a more confident evaluation of a dam's integrity. Electrical resistivity is one geophysical technique that would be useful in detecting internal flaws associated with seepage and piping because it is sensitive to moisture changes. A study is being conducted to examine the feasibility of electrical resistivity tomography (ERT) to map and monitor internal compromised zones within earthen embankment dams. Two quarter-scaled earthen embankment dams were built at the United States Department of Agriculture (USDA) Agriculture Research Service (ARS) Hydraulics and Engineering Research Unit (HERU) in Stillwater, Oklahoma. These two dams were constructed with known internal compromised zones that are susceptible to seepage and piping. Electrical resistivity surveys were conducted on the completed dams using a 56 electrode dipole-dipole array. The collected data was then processed using electrical resistivity tomography (ERT) imaging software and evidence of these two compromised zones was easily visible. Also, additional surveys were conducted in order to monitor the changes in electrical signatures associated with changes in these zones due to filling of the reservoir and environmental/climate changes.

  18. Monitoring radio-frequency heating of contaminated soils using electrical resistance tomography

    SciTech Connect

    Ramirez, A.L.; Daily, W.D.

    1993-09-01

    Electrical resistance tomography (ERT) was used to monitor a radio-frequency heating process for the insitu remediation of volatile organic compounds from subsurface water and soil at the Savannah River Site, near Aiken, South Carolina. A dipole antenna located in a horizontal well in the unsaturated zone was used to heat a contaminated clay layer. The heat-induced changes were tomographically imaged by their effects on the formation electrical resistivity. The resistivity changes observed appear to be related to heating and vaporization of the pore water, formation of steam condensate, and infiltration of rainwater through the heated zones and adjacent areas. There is a clear asymmetry downward in the resistivity decreases associated with the heating process. The resistivity decreases observed in the vicinity of the heating well are believed to be caused by the heating and downward migration of warm water originally located within a radius of a few feet around the heating well; the magnitude of the change is between 10--20%. The decreasing resistivity implies an increasing rate of radio wave attenuation as heating progressed; therefore, the rate of energy deposition around the heating well increased while the penetration distance of the radio waves decreased. Saturation changes in the clay near the antenna during heating were estimated to be 50--55% based on the observed resistivity decreases. Resistivity changes observed at distances greater than 3 meters to one side of the antenna appear to be related to rainwater infiltration. We propose that gaps in near surface clay layers allow rainwater to migrate downward and reach the top of clay rich zone penetrated by the antenna borehole. The water may then accumulate along the top of the clay.

  19. Influence of plant roots on electrical resistivity measurements of cultivated soil columns

    NASA Astrophysics Data System (ADS)

    Maloteau, Sophie; Blanchy, Guillaume; Javaux, Mathieu; Garré, Sarah

    2016-04-01

    Electrical resistivity methods have been widely used for the last 40 years in many fields: groundwater investigation, soil and water pollution, engineering application for subsurface surveys, etc. Many factors can influence the electrical resistivity of a media, and thus influence the ERT measurements. Among those factors, it is known that plant roots affect bulk electrical resistivity. However, this impact is not yet well understood. The goals of this experiment are to quantify the effect of plant roots on electrical resistivity of the soil subsurface and to map a plant roots system in space and time with ERT technique in a soil column. For this research, it is assumed that roots system affect the electrical properties of the rhizosphere. Indeed the root activity (by transporting ions, releasing exudates, changing the soil structure,…) will modify the rhizosphere electrical conductivity (Lobet G. et al, 2013). This experiment is included in a bigger research project about the influence of roots system on geophysics measurements. Measurements are made on cylinders of 45 cm high and a diameter of 20 cm, filled with saturated loam on which seeds of Brachypodium distachyon (L.) Beauv. are sowed. Columns are equipped with electrodes, TDR probes and temperature sensors. Experiments are conducted at Gembloux Agro-Bio Tech, in a growing chamber with controlled conditions: temperature of the air is fixed to 20° C, photoperiod is equal to 14 hours, photosynthetically active radiation is equal to 200 μmol m-2s-1, and air relative humidity is fixed to 80 %. Columns are fully saturated the first day of the measurements duration then no more irrigation is done till the end of the experiment. The poster will report the first results analysis of the electrical resistivity distribution in the soil columns through space and time. These results will be discussed according to the plant development and other controlled factors. Water content of the soil will also be detailed

  20. Influence of plant roots on electrical resistivity measurements of cultivated soil columns

    NASA Astrophysics Data System (ADS)

    Maloteau, Sophie; Blanchy, Guillaume; Javaux, Mathieu; Garré, Sarah

    2016-04-01

    Electrical resistivity methods have been widely used for the last 40 years in many fields: groundwater investigation, soil and water pollution, engineering application for subsurface surveys, etc. Many factors can influence the electrical resistivity of a media, and thus influence the ERT measurements. Among those factors, it is known that plant roots affect bulk electrical resistivity. However, this impact is not yet well understood. The goals of this experiment are to quantify the effect of plant roots on electrical resistivity of the soil subsurface and to map a plant roots system in space and time with ERT technique in a soil column. For this research, it is assumed that roots system affect the electrical properties of the rhizosphere. Indeed the root activity (by transporting ions, releasing exudates, changing the soil structure,…) will modify the rhizosphere electrical conductivity (Lobet G. et al, 2013). This experiment is included in a bigger research project about the influence of roots system on geophysics measurements. Measurements are made on cylinders of 45 cm high and a diameter of 20 cm, filled with saturated loam on which seeds of Brachypodium distachyon (L.) Beauv. are sowed. Columns are equipped with electrodes, TDR probes and temperature sensors. Experiments are conducted at Gembloux Agro-Bio Tech, in a growing chamber with controlled conditions: temperature of the air is fixed to 20° C, photoperiod is equal to 14 hours, photosynthetically active radiation is equal to 200 μmol m‑2s‑1, and air relative humidity is fixed to 80 %. Columns are fully saturated the first day of the measurements duration then no more irrigation is done till the end of the experiment. The poster will report the first results analysis of the electrical resistivity distribution in the soil columns through space and time. These results will be discussed according to the plant development and other controlled factors. Water content of the soil will also be detailed

  1. ENVIRONMENTAL MONITORING OF LEAKS USING TIME LAPSED LONG ELECTRODE ELECTRICAL RESISTIVITY

    SciTech Connect

    MYERS DA; RUCKER DF; FINK JB; LOKE MH

    2009-12-16

    Highly industrialized areas pose challenges for surface electrical resistivity characterization due to metallic infrastructure. The infrastructure is typically more conductive than the desired targets and will mask the deeper subsurface information. These challenges may be minimized if steel-cased wells are used as long electrodes in the area near the target. We demonstrate a method of using long electrodes to electrically monitor a simulated leak from an underground storage tank with both synthetic examples and a field demonstration. The synthetic examples place a simple target of varying electrical properties beneath a very low resistivity layer. The layer is meant to replicate the effects of infrastructure. Both surface and long electrodes are tested on the synthetic domain. The leak demonstration for the field experiment is simulated by injecting a high conductivity fluid in a perforated well within the S tank farm at Hanford, and the resistivity measurements are made before and after the leak test. All data are processed in four dimensions, where a regularization procedure is applied in both the time and space domains. The synthetic test case shows that the long electrode ERM could detect relative changes in resistivity that are commensurate with the differing target properties. The surface electrodes, on the other hand, had a more difficult time matching the original target's footprint. The field results shows a lowered resistivity feature develop south of the injection site after cessation of the injections. The time lapsed regularization parameter has a strong influence on the differences in inverted resistivity between the pre and post injection datasets, but the interpretation of the target is consistent across all values of the parameter. The long electrode ERM method may provide a tool for near real-time monitoring of leaking underground storage tanks.

  2. Monitoring of olive oil mills' wastes using electrical resistivity tomography techniques

    NASA Astrophysics Data System (ADS)

    Simyrdanis, Kleanthis; Papadopoulos, Nikos; Kirkou, Stella; Sarris, Apostolos; Tsourlos, Panagiotis

    2014-08-01

    Olive oil mills' wastes (OOMW) are one of the byproducts of the oil production that can lead to serious environmental pollution when they are deposited in ponds dug on the ground surface. Electrical Resistivity Tomography (ERT) method can provide a valuable tool in order to monitor through time the physical flow of the wastes into the subsurface. ERT could potentially locate the electrical signature due to lower resistivity values resulting from the leakage of OOMW to the subsurface. For this purpose, two vertical boreholes were installed (12m depth, 9 m apart) in the vicinity of an existing pond which is filled with OOMW during the oil production period. The test site is situated in Saint Andreas village about 15km south of the city of Rethymno (Crete, Greece). Surface ERT measurements were collected along multiple lines in order to reconstruct the subsurface resistivity models. Data acquisition was performed with standard and optimized electrode configuration protocols. The monitoring survey includes the ERT data collection for a period of time. The study was initiated before the OOMW were deposited in the pond, so resistivity fluctuations are expected due to the flow of OOMW in the porous subsurface media through time. Preliminary results show the good correlation of the ERT images with the drilled geological formations and the identification of low resistivity subsurface zone that could be attributed to the flow of the wastes within the porous layers.

  3. Electrical Resistivity Monitoring of an Active Hydrothermal Degassing Area at Solfatara, Phlegrean Fields.

    NASA Astrophysics Data System (ADS)

    Vandemeulebrouck, J.; Byrdina, S.; Grangeon, J.; Lebourg, T.; Bascou, P.; Mangiacapra, A.

    2015-12-01

    Campi Flegrei caldera (CFc) is an active volcanic complex covering a ~100 km² densely populated area in the western part of Naples (Italy) that is presently showing clear signs of unrest. Solfatara volcano, a tuff cone crater formed ~4000 yrs B.P. ago by phreato-magmatic eruptions represents the main degassing outflow of CFc. Magmatic gases which are exsolved from a ~8 km deep magmatic reservoir mix at 4 km depth with meteoric hydrothermal fluids then reach the surface in the Solfatara area. These hydrothermal and magmatic gases, mainly H2O and CO2, are released through both diffuse degassing structures and fumaroles. In the frame of the MedSuv (Mediterranean Supervolcanoes) FP7 european project , we are performing a time-lapse electrical resistivity monitoring of an active degassing area of Solfatara. Using a 500-m-long cable and 48 electrodes, an electrical resistivity tomography (ERT) is performed on a two-day basis since May 2013. The time-lapse inversion of the ERT gives an image of the temporal variations of resistivity up to 100 m depth that can be compared with the variations of ground deformation, CO2 flux, soil temperature and seismic ambient noise. Resistivity variations can originate from fluid composition, gas ratio and temperature. For example, the abrupt change of resistivity that was observed mid-2014 during a period of uplift and gas flux increase, could be associated with the rise of hydrothermal fluids.

  4. Electrical earth-resistivity surveys near brine holding ponds in Illinois

    SciTech Connect

    Reed, P.C.; Cartwright, K.; Osby, D.

    1981-04-01

    Electrical earth resistivity surveys were conducted in the vicinity of five oil field brine holding ponds to develop a methodology for identifying elevated levels of soluble salts near oil fields. The five sites, all in similar hydrogeologic environments, were distributed across the main oil-producing region of Illinois. Four of these sites were selected for detailed study of a possible relationship between changes in apparent electrical earth resistivities and changes in water quality. The resistivity surveys clearly indicate the direction and extent of salt water migration around the holding ponds. Apparent resistivity measurements can be used to approximate quality of the ground water because there is a direct relationship between the resistivity and water quality. This relationship can be used to indicate relative salinities; however, the relationship should be used with caution in making estimates of water salinity. Brine migration has not affected the regional water quality, and appears to be of limited regional significance. Studies of water chemistry from observation wells at the selected holding pond sites indicated that some attenuation of the brine is occurring.

  5. Modeling and analysis of direct-current electrical resistivity in the Durham Triassic basin, North Carolina

    USGS Publications Warehouse

    Brown, C. Erwin

    1987-01-01

    Sixty-two Schlumberger electrical soundings were made in the Durham Triassic basin in an effort to determine basin structural geometry, depth of the sedimentary layers, and spatial distribution of individual rock facies. A digital computer program was used to invert the sounding curves of apparent resistivity versus distance to apparent resistivity versus depth. The apparent-resistivity-versus-depth data from the computer-modeling program were used to construct a geoelectric model of the basin that is believed to accurately represent the subsurface geology of the basin. The largest depth to basement in the basin along a resistivity profile (geoelectric section) was determined to be 1,800 m. A resistivity decrease was observed on certain soundings from depths of 100 to 1,000 m; below a 1,000-m depth, apparent resistivity increased to the bottom of the basin. Resistivity values for basement rocks were greater than 1,000 ohm-m and less than 350 ohm-m for the sedimentary layers in the basin. The data suggest that the basin contains a system of step faults near its eastern boundary. ?? 1987.

  6. Characterization of Contact and Bulk Thermal Resistance of Laminations for Electric Machines

    SciTech Connect

    Cousineau, Emily; Bennion, Kevin; Devoto, Douglas; Naramanchi, Sreekant

    2015-07-06

    Thermal management for electric motors is important as the automotive industry continues to transition to more electrically dominant vehicle propulsion systems. The transition to more electrically dominant propulsion systems leads to higher-power duty cycles for electric-drive systems. Thermal constraints place significant limitations on how electric motors ultimately perform. As thermal management improves, there will be a direct trade-off among motor performance, efficiency, cost, and the sizing of electric motors to operate within the thermal constraints. During the development of thermal finite element analysis models and computational fluid dynamics models for electric motors, it was found that there was a lack of open literature detailing the thermal properties of key materials common in electric motors that are significant in terms of heat removal. The lack of available literature, coupled with the strong interest from industry in the passive-stack thermal measurement results, led to experiments to characterize the thermal contact resistance between motor laminations. We examined four lamination materials, including the commonly used 26 gauge and 29 gauge M19 materials, the HF10 and Arnon 7 materials. These latter two materials are thinner and reduce eddy currents responsible for core losses. We measured the thermal conductivity of the lamination materials and the thermal contact resistance between laminations in a stack, as well as investigated factors affecting contact resistance between laminations such as the contact pressure and surface finish. Lamination property data will be provided and we also develop a model to estimate the through-stack thermal conductivity for materials beyond those that were directly tested in this work. For example, at a clamping pressure of 138 kPa, the 29 gauge M19 material has a through-stack thermal conductivity of 1.68 W/m-K, and the contact resistance between laminations was measured to be 193 mm^2-K/W. The measured bulk

  7. Research on geo-electrical resistivity observation system specially used for earthquake monitoring in China

    NASA Astrophysics Data System (ADS)

    Zhao, Jialiu; Wang, Lanwei; Qian, Jiadong

    2011-12-01

    This paper deals with the design and development of the observational system of geo-electrical resistivity on the basis of the demands for exploring the temporal variations of electrical properties of Earth media in the fixed points of the networks, which would be associated with the earthquake preparation. The observation system is characterized by the high accuracy in measurement, long term stability in operation and high level of rejection to the environmental interference. It consists of three main parts, configuration system measurement system, the calibration and inspection system.

  8. Exploring electrical resistance: a novel kinesthetic model helps to resolve some misconceptions

    NASA Astrophysics Data System (ADS)

    Cottle, Dan; Marshall, Rick

    2016-09-01

    A simple ‘hands on’ physical model is described which displays analogous behaviour to some aspects of the free electron theory of metals. Using it students can get a real feel for what is going on inside a metallic conductor. Ohms Law, the temperature dependence of resistivity, the dependence of resistance on geometry, how the conduction electrons respond to a potential difference and the concepts of mean free path and drift speed of the conduction electrons can all be explored. Some quantitative results obtained by using the model are compared with the predictions of Drude’s free electron theory of electrical conduction.

  9. Thermospheric topside neutral density, ionospheric anomalous electric field and resistivity measurements by active experiment at EISCAT

    NASA Astrophysics Data System (ADS)

    Kosch, Michael; Ogawa, Yasunobu; Rietveld, Michael; Blagoveshchenskaya, Nataly; Yamazaki, Yosuke

    2016-07-01

    We have developed an active ground-based technique to estimate the topside thermospheric neutral density as well as topside ionospheric anomalous electric field and resistivity at EISCAT, combining the EISCAT UHF radar, HF heater and optics. When pumping the ionosphere the F-region electron temperature is significantly raised, increasing the upward plasma pressure gradient in the topside ionosphere, resulting in observed ion up-flow along the magnetic field line. Simultaneously, pump-induced suprathermal electrons produce artificial optical emissions. Using the modified ion-momentum equation, the thermospheric neutral density is estimated. Alternatively, using the MSIS model the field-aligned anomalous electric field is estimated. From the optical data the suprathermal electron flux is estimated, giving an estimate of the anomalous resistivity. Results from recent observations at EISCAT are presented.

  10. Review of electrical resistivity measurements of dense aluminum and comparison to theory

    NASA Astrophysics Data System (ADS)

    Benage, John F.

    2000-05-01

    Four recent experiments that measured the electrical resistivity of aluminum at conditions where the aluminum is in a dense, strongly coupled, plasma state have been analyzed. The properties of dense, strongly coupled plasmas cannot be treated using standard plasma theory, which treats the correlations among particles as a small effect. Many theories have been developed which predict the properties of such plasmas, but there is little experimental data with which to compare. These recent experiments provide data for a comprehensive comparison of electrical resistivity with dense plasma theories. The experiments were carried out under a wide range of conditions, from temperatures <1 eV up to 25 eV and densities from nearly solid to <1% solid. The data from these experiments are compared with various theoretical models, the best of which give predictions consistent with the data for most of the experimental conditions, but not all. A discussion of yet unresolved issues is also presented.

  11. Electrical Resistivity Investigations of the Kurşunlu (Manisa/Turkey) Geothermal Area

    NASA Astrophysics Data System (ADS)

    Sarı, Coşkun; Timur, Emre

    2016-04-01

    It is of considerable importance to explore the geological structure around active faults, especially near-surface unconsolidated layers, to estimate the faults' activity. There are numerous case studies to investigate geothermal reservoirs and surrounding active faults using geophysical exploration methods; however, only a few cases have been verified in detail by comparison with other geological information. Electrical resistivity data provide a substantial contribution to the geophysical mapping and monitoring of geothermal reservoirs. We applied electrical methods, which can be effective for exploring to several hundred meters depth, to reveal geological structures covered by thick Quaternary alluvium formations. Geothermal activity around city of Manisa in Gediz Graben (Western Turkey) has been investigated by many researchers and many geothermal boreholes were drilled in order to produce electricity and for heating purposes. The Kurşunlu geothermal area is with the southern side of the Gediz Graben in 2 km west of Salihli, Manisa, Turkey. According to rising demand on thermal water around Salihli, geophysical studies were performed using the Vertical Electrical Sounding (VES) measurements at 16 stations around the area of Kurşunlu hot springs, and they were interpreted using both one and two-dimensional modelling. Vertical and horizontal resistivity sections were mapped, and it was determined that two low-resistivity layers exist both in the North (stations 1,2 and 4) and the South (stations 6 and 10) part of the survey area. As a result of the studies, the boundaries of the low-resistivity layer were mapped and test drilling locations were recommended.

  12. Correlation between index properties and electrical resistivity of hydrocarbon contaminated periodic marine clays

    NASA Astrophysics Data System (ADS)

    Tiwari, P.; Shah, M. V.

    2015-09-01

    Hydrocarbon contamination is a measure issue of concern as it adversely affects the soil inherent properties viz. index properties and strength properties.The main objective of this research work is to determine Electrical resistivity to study and correlate with soil index properties and engineering propertiescontaminated with hydrocarbon at the rate of 3%, 6% and 9% for the period of 15, 30 45 and 60 days and compare it with the results obtained for non-contaminated marine clay. Electrical resistivity of virgin marine clay (bentonite which is expansive in nature) and hydrocarbon contaminated clay for each percent of contamination is obtained in the laboratory for each period and its co-relation with index properties and engineering properties is proposed. CEC, EDAX tests were performed to evaluate the effect of ions of montmorillonite clays and their penetrability into hydrocarbon- clay matrix. The correlations at the end of each period for each percentage of contamination thus enabled to integrate index properties of non-contaminated and hydrocarbon contaminated marine clays with Electrical resistivity.

  13. Influence of salinity and moisture content in electrical resistivity tomography readings in geomaterials used in construction

    NASA Astrophysics Data System (ADS)

    Gomez-Heras, Miguel; Fort, Rafael; Garcia Morales, Soledad

    2014-05-01

    Wetness and salts are among the main agents hindering the performance of any porous building material. There are a number of techniques based on electrical properties for the detection of these agents in buildings, such as portable moisture meters and electric resistivity tomography (ERT). These methods are used to locate wet areas based on the lower electrical resistivity wet materials have in relation to dry ones. However, as both moisture and salts contribute to low resistivity readings, the ERT readings may have a degree of uncertainty. This research aims to study the contribution of salinity and moisture content on the readings of ERT by testing laminated gypsum boards in the laboratory with solutions with different compositions (i.e. sodium chloride, magnesium sulphate and a mixture of both) and concentrations of salts. An industrial product, such as the laminated gypsum board, was chosen to minimize the effects that heterogeneities in composition and physical properties could have in the ERT readings and facilitate the interpretation of the wetness/salt content difference. Gypsum board was soaked with a fixed amount of the chosen solutions and several ERT transects were performed with a GeoTom device (Geolog2000) while drying. Results show the influence salinity of solutions have in drying process, and how the salt content remaining within the pores of geomaterials impact on ERT results. Research funded by Geomateriales (S2009/MAT-16) and CEI Moncloa (UPM, UCM, CSIC) through a PICATA contract and the equipment from RedLAbPAt Network

  14. Electrical resistivity tomography, VES and magnetic surveys for dam site characterization, Wukro, Northern Ethiopia

    NASA Astrophysics Data System (ADS)

    Haile, Tigistu; Atsbaha, Solomun

    2014-09-01

    Geophysical surveys involving the techniques of electrical resistivity imaging, electrical sounding and magnetics were employed to characterize the ground conditions at a proposed dam site at Hizaeti-Afras, Wukro, North Ethiopia. The techniques were utilized to map the depth to the competent formations, their relative suitability for foundation work and the presence and extent of weak zones in the subsurface. The work has mapped the different lithologic units of the subsurface and determined the depth to the basement rocks in the area. Through correlation of the inverse model resistivity sections of the imaging surveys, the geoelectric section of the sounding survey and the magnetic profile plots with available borehole lithologic logs, it is shown that the results very well supplement the geotechnical point data in addition to providing a wider coverage in mapping areas of weak ground that could otherwise be missed with widely spaced borehole information. The combined results of the survey show the proposed dam axis to be unsuitable. The power of the electrical resistivity imaging technique and its potential to map the shallow subsurface with adequate resolution are illustrated. The result is a strong suggestion that geophysical techniques can be used to assist and extrapolate borehole geotechnical data especially when large area is to be used for development of large infrastructure.

  15. Electrical Resistivity Investigation of Gas Hydrate Distribution in Mississippi Canyon Block 118, Gulf of Mexico

    SciTech Connect

    Dunbar, John

    2012-12-31

    Electrical methods offer a geophysical approach for determining the sub-bottom distribution of hydrate in deep marine environments. Methane hydrate is essentially non-conductive. Hence, sediments containing hydrate are more resistive than sediments without hydrates. To date, the controlled source electromagnetic (CSEM) method has been used in marine hydrates studies. This project evaluated an alternative electrical method, direct current resistivity (DCR), for detecting marine hydrates. DCR involves the injection of direct current between two source electrodes and the simultaneous measurement of the electric potential (voltage) between multiple receiver electrodes. The DCR method provides subsurface information comparable to that produced by the CSEM method, but with less sophisticated instrumentation. Because the receivers are simple electrodes, large numbers can be deployed to achieve higher spatial resolution. In this project a prototype seafloor DCR system was developed and used to conduct a reconnaissance survey at a site of known hydrate occurrence in Mississippi Canyon Block 118. The resulting images of sub-bottom resistivities indicate that high-concentration hydrates at the site occur only in the upper 50 m, where deep-seated faults intersect the seafloor. Overall, there was evidence for much less hydrate at the site than previously thought based on available seismic and CSEM data alone.

  16. Microgravity conditions and electrical resistivity of liquid alloys with critical mixing

    SciTech Connect

    Itami, T.; Masaki, T.; Kuribayashi, K.; Sato, E.; Hinada, M.; Yamashita, M.; Kawasaki, K.

    1997-03-01

    The phenomena of two-liquid phase separations are significantly influenced by the gravity on the ground because of the difference in the densities of the constituent components, particularly, in the case of liquid alloys with critical mixing. In this paper, experimental techniques and results ar reported for the measurements of the electrical resistivity for typical liquid alloys with critical mixing, such as Bi-Ga, under microgravity by the use of a rocket S520-19 belonging to ISAS (Institute of Space and Astronautical Science, Japan). It was found that the temperature coefficient of the electrical resistivity, on cooling of the homogeneous liquid phase, increases with the approach to the critical temperature. This trend under microgravity by the rocket experiment is more pronounced compared to the trend of the reference experiment on the ground. In addition, the supercooling of homogeneous liquids under microgravity is larger than that on the ground. These differences are explained by the difference in the degree of the growth of concentration fluctuations, the concentration fluctuations are far greater under microgravity than on the ground. Therefore, it is found to be very important to study the process and the critical phenomena of two-liquid phase separations under microgravity. Measurement of electrical resistivity is an effective method to obtain information about the process, the critical phenomena, and the supercooling of two-liquid phase separations in liquid alloys with critical mixing.

  17. A method to investigate the electron scattering characteristics of ultrathin metallic films by in situ electrical resistance measurements

    SciTech Connect

    Trindade, I. G.; Sousa, J. B.; Fermento, R.; Leitao, D.

    2009-07-15

    In this article, a method to measure the electrical resistivity/conductivity of metallic thin films during layer growth on specific underlayers is described. The in situ monitoring of an underlayer electrical resistance, its change upon the incoming of new material atoms/molecules, and the growth of a new layer are presented. The method is easy to implement and allows obtaining in situ experimental curves of electrical resistivity dependence upon film thickness with a subatomic resolution, providing insight in film growth microstructure characteristics, specular/diffuse electron scattering surfaces, and optimum film thicknesses.

  18. Characterization of subsurface stratigraphy along the lower American River floodplain using electrical resistivity, Sacramento, California, 2011

    USGS Publications Warehouse

    Burton, Bethany L.; Powers, Michael H.; Ball, Lyndsay B.

    2014-01-01

    In July 2011, the U.S. Geological Survey, in cooperation with the U.S. Army Corps of Engineers, completed a geophysical survey using electrical resistivity along an approximately 6-mile reach of the lower American River in Sacramento, California, to map near-surface lithological variations. This survey is a part of a manifold and comprehensive study of river-flow dynamics and geologic boundary-property knowledge necessary to estimate scour potential and levee erosion risk. Data were acquired on the left (south or west) bank between river mile 5 and 10.7 as well as a short section on the right bank from river mile 5.4 to 6. Thirteen direct-current resistivity profiles and approximately 8.3 miles of capacitively coupled resisistivity data were acquired along accessible areas of the floodplain between the levee and river bank. Capacitively coupled resistivity was used as a reconnaissance tool, because it allowed for greater spatial coverage of data but with lower resolution and depth of investigation than the DC resistivity method. The study area contains Pleistocene-age alluvial deposits, dominated by gravels, sands, silts, and clays, that vary in both lateral extent and depth. Several generations of lithologic logs were used to help interpret resistivity variations observed in the resistivity models.

  19. Imaging Rainfall Infiltration Processes with the Time-Lapse Electrical Resistivity Imaging Method

    NASA Astrophysics Data System (ADS)

    Zhang, Gang; Zhang, Gui-Bin; Chen, Chien-chih; Chang, Ping-Yu; Wang, Tzu-Pin; Yen, Horng-Yuan; Dong, Jia-Jyun; Ni, Chuen-Fa; Chen, Su-Chin; Chen, Chao-Wei; Jia, Zheng-yuan

    2016-06-01

    Electrical Resistivity Imaging (ERI) was carried out continuously for 10 days to map the subsurface resistivity distribution along a potentially hazardous hillslope at the Jieshou Junior High School in Taoyuan, Taiwan. The reliability of the inverted resistivity structures down to about 25 m depth was examined with synthetic modeling using the same electrode arrangements installed on land surface as in field surveys, together with a DOI (depth-of-investigation) index calculated from the ERI data. The subsurface resistivity distribution is consistent with results from well logging. These ERI recordings were taken daily and provided highly resolved imagery of the resistivity distribution underground and illustrated the dynamical fluid-flow behavior due to heavy rainfall infiltration. Using Archie's law, the resistivity distribution was transformed into a map of relative water saturation (RWS), which is strongly correlated with the rainfall infiltration process. We then found that the averaged RWS is significantly correlated with daily precipitation. Our observations indicate that time-lapse ERI is effective in monitoring subterraneous rainfall infiltration; moreover, the preferential flow paths can be delineated according to the changes in averaged RWS derived from the ERI data.

  20. Electric-pulse-induced resistive memory effect of PZT buffered perovskite thin film

    NASA Astrophysics Data System (ADS)

    Xing, Zhongwen; Wu, Naijuan; Ignatiev, Alex

    2006-10-01

    A large electric-pulse-induced resistance (EPIR) switching effect has been observed in the lead zirconate titanate (PZT) buffered perovskite thin films, such as Pr0.7Ca0.3MnO3 (PCMO). Such a resistive memory device is comprised of a PCMO epitaxial layer on a c-oriented YBCO bottom electrode layer and a thin PZT buffer layer grown on top of the PCMO layer. A silver top electrode was deposited on the PZT/PCMO/YBCO heterostructure to complete the resistive device fabrication. There are two advantages for the memory properties comparing the PZT buffered device with a non-buffered thin film device. First, the EPIR resistance ratio [defined as (Rmax-RMin)/ RMin] is significantly increased. The other is that the pulse voltage needed to switch the resistive device is reduced from ±10 V to ±3 V in magnitude. These results suggest that PZT-buffered perovskite thin film resistive devices are very promising for memory applications. In addition, an effective tunneling model is developed to explain the EPIR effect. It is found that the tunneling at interfaces plays an important role in the charge transport, which is in good agreement with existing experiments.

  1. Electrical carotid sinus stimulation: chances and challenges in the management of treatment resistant arterial hypertension.

    PubMed

    Chobanyan-Jürgens, Kristine; Jordan, Jens

    2015-09-01

    Treatment resistant arterial hypertension is associated with excess cardiovascular morbidity and mortality. Electrical carotid sinus stimulators engaging baroreflex afferent activity have been developed for such patients. Indeed, baroreflex mechanisms contribute to long-term blood pressure control by governing efferent sympathetic and parasympathetic activity. The first-generation carotid sinus stimulator applying bilateral bipolar stimulation reduced blood pressure in a controlled clinical trial but nevertheless failed to meet the primary efficacy endpoint. The second-generation device utilizes smaller unilateral unipolar electrodes, thus decreasing invasiveness of the implantation while saving battery. An uncontrolled clinical study suggested improvement in blood pressure with the second-generation device. We hope that these findings as well as preliminary observations suggesting cardiovascular and renal organ protection with electrical carotid sinus stimulation will be confirmed in properly controlled clinical trials. Meanwhile, we should find ways to better identify patients who are most likely to benefit from electrical carotid sinus stimulation.

  2. Effects of boiling on electrical resistivity of microporous rocks from the Geysers

    SciTech Connect

    Roberts, J.; Duba, A.; Bonner, B.; Kasameyer, P.

    1997-12-31

    In a laboratory study of cores from borehole SB-15-D in The Geysers geothermal area, we measured the electrical resistivity of metashale with and without pore-pressure control, with confining pressures up to 100 bars and temperatures between 20 and 150{degrees}C, to determine how the pore-size distribution and capillarity affected boiling. We observed a gradual increase in resistivity when the downstream pore pressure or confining pressure decreased below the phase boundary of free water. For the conditions of this experiment, boiling, as indicated by an increase in resistivity, is initiated at pore pressures of approximately 0.5 to 1 bar (0.05 to 0.1 MPa) below the free-water boiling curve, and it continues to increase gradually as pressure is lowered to atmospheric. A simple model of the effects of capillarity suggests that at 145{degrees}C, less than 15% of the pore water can boil in these rocks. If subsequent experiments bear out these preliminary observations, then boiling within a geothermal reservoir is controlled not just by pressure and temperature but also by pore-size distribution. Thus, it may be possible to determine reservoir characteristics by monitoring changes in electrical resistivity as reservoir conditions change.

  3. Electrical Resistivity Tomography Monitoring of Soil Remediation for a Garbage Dump

    NASA Astrophysics Data System (ADS)

    shi, X.; Luo, Z.; Zhang, Y.; Fu, Q.; Xu, Z.

    2011-12-01

    Electrical resistivity tomography (ERT) survey was firstly used to investigate the distribution of contaminated soil in a garbage dump area, Wuhan city, China. The result shows that sulfated soil resistivity is about 4 to 7 ohm-m, which is relatively lower than normal soil resistivity of about 15 to 25 ohm-m. The distribution of contaminated soil was delineated using ERT images. Then, ERT survey was carried out in this area for monitoring of remediation of contaminated soil and groundwater. Werner measurements with 60 electrodes of 1 m spacing were taken during the 9-well oxygen injection and nutrition liquid injection period. The difference of apparent resistivity between before gas injection and after gas injection was used to delineate the channel of gas and the trace of gas migration in the porous garbage dump. The electrical resitivity changes between before and after nutrition liquid injection were used to analyze the liquid migration and distribution. The dynamic procedures of gas and water migration are outlined. The results suggest that ERT is a powerful technique for monitoring of soil remediation.

  4. Noncontact technique for measuring the electrical resistivity and magnetic susceptibility of electrostatically levitated materials.

    PubMed

    Rustan, G E; Spyrison, N S; Kreyssig, A; Prozorov, R; Goldman, A I

    2012-10-01

    We describe the development of a new method for measuring the electrical resistivity and magnetic susceptibility of high temperature liquids and solids. The technique combines a tunnel diode oscillator with an electrostatic levitation furnace to perform noncontact measurements on spherical samples 2-3 mm in diameter. The tank circuit of the oscillator is inductively coupled to the sample, and measurements of the oscillator frequency as a function of sample temperature can be translated into changes in the sample's electrical resistivity and magnetic susceptibility. Particular emphasis is given on the need to improve the positional stability of the levitated samples, as well as the need to stabilize the temperature of the measurement coil. To demonstrate the validity of the technique, measurements have been performed on solid spheres of pure zirconium and low-carbon steel. In the case of zirconium, while absolute values of the resistivity were not determined, the temperature dependence of the resistivity was measured over the range of 640-1770 K and found to be in good agreement with literature data. In the case of low-carbon steel, the ferromagnetic-paramagnetic transition was clearly observable and, when combined with thermal data, appears to occur simultaneously with the solid-solid structural transition. PMID:23126782

  5. Corrosion resistance and electrical properties of carbon/chromium-titanium-nitride multilayer coatings on stainless steel

    NASA Astrophysics Data System (ADS)

    Feng, Kai; Li, Zhuguo; Lu, Fenggui; Huang, Jian; Cai, Xun; Wu, Yixiong

    2014-03-01

    High electrical conductivity and corrosion resistance are central to advances in wider application of metallic bipolar plates in polymer electrolyte membrane fuel cell (PEMFC). In this study, C/Cr-Ti-N multilayer coatings are deposited by physical vapor deposition and the effect of Cr:Ti ratio on the corrosion resistance and interfacial contact resistance (ICR) are systematically investigated. Scanning electron microscopy (SEM) result shows that the carbon layer is compact and uniform. Excellent corrosion resistance of 0.127 μA cm-2 current density at operating voltage in PEMFC cathode environment and low ICR of 2.03 mΩ-cm2 at compaction force of 150 N cm-2 are achieved when Cr:Ti ratio is 2:4 and 3:3, respectively. The significant enhancement in surface conductivity is probably because that the current comes from carbon paper is homogenized by two electrically conductive layers and flows to the passive film with much more contact area. After polarization, ICR increase to 3.07 mΩ-cm2 and 3.02 mΩ-cm2 in the simulated PEMFC cathode and anode environment, respectively. However, the Raman spectroscopy results disclose that the bonding type of top carbon film before and after polarization shows little difference. The results indicate that C/Cr-Ti-N multilayer coating with Cr:Ti ratio of 2:4 achieves the optimal composition.

  6. Disentangling the physical contributions to the electrical resistance in magnetic domain walls: a multiscale study.

    PubMed

    Seemann, K M; Garcia-Sanchez, F; Kronast, F; Miguel, J; Kákay, A; Schneider, C M; Hertel, R; Freimuth, F; Mokrousov, Y; Blügel, S

    2012-02-17

    We analyze the origin of the electrical resistance arising in domain walls of perpendicularly magnetized materials by considering a superposition of anisotropic magnetoresistance and the resistance implied by the magnetization chirality. The domain wall profiles of L1(0)-FePd and L1(0)-FePt are determined by micromagnetic simulations based on which we perform first-principles calculations to quantify electron transport through the core and closure region of the walls. The wall resistance, being twice as high in L1(0)-FePd than in L1(0)-FePt, is found to be clearly dominated in both cases by a high gradient of magnetization rotation, which agrees well with experimental observations.

  7. Delineation of an electrical resistivity anomaly, Malpais area, Beowawe KGRA, Eureka and Lander Counties, Nevada

    SciTech Connect

    Smith, C.

    1980-07-01

    A simple numerical model of previously released bipole-dipole resistivity data shows the margin of the graben to be anomalously conductive below the Malpais. The conductive area has been delineated with data from a dipole-dipole resistivity survey run in April 1980 for this study. Detailed numerical models of these data define a 1250 m wide body with resistivities less than 20 ohm-m that appear to connect The Geysers and the graben boundary. The minimum depth to the conductor is interpreted to be 375 m; its depth extent is undetermined. The electrical data do not resolve whether the anomaly below the Malpais may be the product of a defunct hydrothermal system or the signature of an active system. If thermal gradient data detect an enhanced heat flow anomaly in the same area, the Malpais may be a viable geothermal exploration target within the Beowawe KGRA.

  8. Electrical resistivity measurements of brine saturated porous media near reservoir conditions: Awibengkok preliminary results

    SciTech Connect

    Bonner, B; Duba, A; Roberts, J

    1999-06-28

    Laboratory measurements of the electrical resistivity of rocks and synthetic rocks with confining pressures up to 100 bars and temperatures between 20 and 211 C were performed to further investigate how the pore-size distribution and capillarity affects boiling in porous media. Similar to previous measurements on samples from The Geysers, CA, we observed a gradual increase in resistivity when pore pressure was decreased below the phase-boundary pressure of free water, an indication that boiling is controlled not only by temperature and pressure, but also by pore size distribution. Other important phenomena observed were strong resistance fluctuations during boiling that may be chaotic, and salt deposition that caused sample cracking. If confirmed in further experiments, these results may lead to a new geophysical diagnostic for locating boiling in high permeability areas of geothermal reservoirs and for methods of permeability alteration.

  9. Self-potential and electrical resistivity studies of the Cove Fort-Sulphurdale Geothermal System, Utah

    SciTech Connect

    Ross, H.P.; Blackett, R.E.; Sperry, T.L.

    1997-12-31

    A detailed self-potential (SP) survey was completed at the Cove Fort-Sulphurdale geothermal area during 1995 and 1996. The survey documents a low-amplitude dipolar anomaly within the producing steam field and sharp, negative anomalies which align with mapped structures in the sulfur pit to the south. Three broader SP anomalies, also of relatively low amplitude, were mapped 1 to 2 km west and northwest of the known steam field. One anomaly coincides with the northwestern limit of a very low resistivity (4 ohm-m) area which extends southeast to the steam field, and is open to the west where the other two SP anomalies occur. Electrical resistivity data were modeled to obtain the intrinsic resistivity distribution at various depths, and these are correlated with SP data and structures interpreted from aeromagnetic and gravity data, and geologic mapping. Three potential drilling targets have been identified which could provide new information about the main hot water reservoir.

  10. Determination of anisotropic karst features in the Biscayne Aquifer using multi electrical resistivity imaging techniques

    NASA Astrophysics Data System (ADS)

    Yeboah-Forson, A.; Whitman, D.

    2012-12-01

    The Biscayne Aquifer of Southeast Florida is characterized by limestone cavities and solution hole features that are often beneath the surface and are difficult to detect and quantify accurately. Electrical resistivity imaging (ERI) is often used to image the subsurface for detection of cavities and other karst features. A recent regional study of electrical anisotropy derived from rotated square array measurements measured coefficients of anisotropy of 1.12 or less. At one particular site however, the coefficient of anisotropy was found to be as high as 1.36 with the average minimum resistivity direction trending 105°. The highest values of anisotropy are found at squares array sizes equivalent to effective depths of 4-9m. The cause of this higher anisotropy and its associated orientation was investigated using a combination of azimuthal 2-D profiles and a 3-D tomography survey using a mixed dipole gradient array. Results indicate a low resistivity zone at a depth of 5-10 m in the saturated zone (10-40Ωm) trending 109° in the 2-D profiles and the presence of low resistivity zone (14-43Ωm) trending 90-105° in the 3-D model. This observed lower resistivity zone is at least 50% lower than the surrounding resistivity. Although further geophysical studies are planned at the site, the primary analysis from these three contrasting ERI techniques indicates that the cause of higher anisotropy might be due to the presence of a solution cavity oriented in the E-SE direction.

  11. Electrical Resistivity Monitoring for Leachate Distribution at Two Foot-and-Mouth- Disease (FMD) Burial Sites

    NASA Astrophysics Data System (ADS)

    Lee, S.; Kaown, D.; Lee, K.; Leem, K.; Ko, K.

    2011-12-01

    The main objective of this study was to provide the basic information on leachate distribution with time changes through the electrical resistivity monitoring for a certain period of time in the Foot-and-Mouth-Disease (FMD) burial facilities which is needed to prevent further soil and groundwater contamination and to build an effective plan for stabilization of the burial site. In this study, dipole-dipoles surveys were carried out around two FMD burial sites in Iceon-si, Gyeonggi-do. The FMD burial facility installed at Daewall-myeon is consists of one block but, at Yul-myeon, it is divided into 2 blocks named A and B blocks. Dipole-Dipole surveys with 8 lines at Yul-myeon and 3 lines at Daewall-myeon were carried out. The observed leachate distribution along survey lines was not clearly evident as time passes at Daewall-myeon site, but, at Yul-myeon site, the leachate distribution around the survey lines showed a decrease of resistivity around the burial facility. At and around A and B blocks of Yul-myeon site, interpretations of the survey data show low resistivity zones below 10 Ωm from a depth 3 m to 10 m and such low resistivity zones of the A block are thicker than the B block by about 5~10 m. From the geochemical data and resistivity survey at two FMD burial sites, it is inferred that the groundwater within a 50-meter radius around burial facilities of the Yul-myeon site are contaminated by leachate. The general resistivity distribution around the burial site is seemed affected by the leachate with high electrical conductivity. The detail distribution patterns can be explained by local distributions of soil and weathered rocks and associated leachate flow. This subject is supported by Brain Korea 21 and Korea Ministry of Environment as 'The GAIA Project (173-092-009)'.

  12. The data preprocessing in apparent resistivity pesudo-section construction of two-dimensional electrical resistivity tomography survey

    NASA Astrophysics Data System (ADS)

    Zhou, Q.

    2015-12-01

    Although three-dimensional (3-D) electrical resistivity tomography (ERT) survey has become a popular practice in the site characterization and process monitoring, the two-dimensional (2-D) ERT survey is still often used in the field. This is because that the 2-D ERT survey is relatively easy to do and the focus of site characterization is on the information of 2-D cross section, not necessarily of the 3-D subsurface structure. Examples of such practice include tunnel line and crossing fault survey. In these cases, depending on the property of surface soil to be surveyed, the 2-D ERT survey with pole-pole array may occasionally make us obtain quality good data, however it often gives us a suit of data set both with real and erroneous ones that incorporated the effects of electrode contact and not far enough far electrodes. Without preprocessing, the apparent resistivity pseudo-section constructed from this kind of data set may quite deviate from the real one and the information obtained from it may be misleading and even completely incorrect. In this study, we developed a method of far electrode dynamic correction that is appropriate for raw data preprocessing from 2-D pole-pole array ERT survey. Based on this method, we not only can find and delete the abnormal data points easily, but also can position the coordinates of far electrodes actually working in the field, thus delete the far electrode effects and make best use of the looked strange data points. The method also makes us to be able to judge the effects of electrode contact and avoid using such data points in the following apparent resistivity pseudo-section construction. With this preprocessing to the data set, the constructed apparent resistivity pseudo-section is demonstrated to be more approximate to the real one. This makes the following reversion calculation more robust. We'll introduce this far electrode dynamic correction method and show application examples in the meeting.

  13. Rainfall infiltration process in mountain headwater region using electrical resistivity tomography

    NASA Astrophysics Data System (ADS)

    Ono, M.; Yamamiya, K.; Shimada, J.

    2008-12-01

    Many researchers have studied about the hydrological process, especially rainfall-runoff process, in the headwater region using multi hydrometric methods. Since the possibility has been recognized that bedrock groundwater has important role to play in the rainfall-runoff process, it is important to comprehend the rainfall infiltration process within fluctuations of bedrock groundwater. However, we would need many hydrological instruments to understand this process precisely. So we have applied electrical resistivity tomography (ERT) method to understand rainfall infiltration process in the area that is estimated the contribution of bedrock groundwater for rainfall-runoff processes. Resistivity changes with the saturation rate of the pore fluid in the subsurface material. So it is possible to estimate spatial and temporal distribution of subsurface water by using ERT. In this study, we will estimate rainfall infiltration process in mountain headwater region using resistivity method. The study area is the Mamushi-dani watershed in Shiranui, Kumamoto, Japan. We described the bedrock groundwater storage systems using resistivity method in this watershed previously. Resistivity has been observed at 2 measurement lines in slope areas of this watershed. Both measurement lines have 47m in length, 1m electrode spacing and 48 electrodes. We used the multi-electrode system, NEXT-400(Kowa Co. Ltd., Japan) for measuring apparent resistivity and the application software, E-tomo (Diaconsultant Co. Ltd., Japan) for inversion of apparent resistivity data. The observed resistivity data were compared with water head observed at borehole and specific discharge observed at foot of the watershed. Inverted resistivity profiles and observed hydrological data showed the interface between saturated and unsaturated zone. During rainfall occurs, resistivity in surface area gets lower than that before the rainfall and resistivity in some part of unsaturated area shows increasing tendency. Both

  14. The `L' Array, a method to model 3D Electrical Resistivity Tomography (ERT) data

    NASA Astrophysics Data System (ADS)

    Chavez Segura, R. E.; Chavez-Hernandez, G.; Delgado, C.; Tejero-Andrade, A.

    2010-12-01

    The electrical resistivity tomography (ERT) is a method designed to calculate the distribution of apparent electrical resistivities in the subsoil by means of a great number of observations with the aim of determining an electrical image displaying the distribution of true resistivities in the subsoil. Such process can be carried out to define 2D or 3D models of the subsurface. For a 3D ERT, usually, the electrodes are placed in a squared grid keeping the distance between adjacent electrodes constant in the x and y directions. Another design employed, consists of a series of parallel lines whose space inter-lines must be smaller or equal to four times the electrode separation. The most common electrode arrays frequently employed for this type of studies are the pole-pole, pole-dipole and dipole-dipole. Unfortunately, ERT surface sampling schemes are limited by physical conditions or obstacles, like buildings, highly populated urban zones, and geologic/topographic features, where the lines of electrodes cannot be set. However, it is always necessary to characterize the subsoil beneath such anthropogenic or natural features. The ‘L’ shaped array has the main purpose to overcome such difficulties by surrounding the study area with a square of electrode lines. The measurements are obtained by switching automatically current and potential electrodes from one line to the other. Each observation adds a level of information, from one profile to the other. Once the total levels of data are completed, the opposite ‘L’ array can be measured following the same process. The complete square is computed after the parallel profiles are observed as well. At the end, the computed resistivities are combined to form a 3D matrix of observations. Such set of data can be inverted to obtain the true resistivity distribution at depth in the form of a working cube, which can be interpreted. The method was tested with theoretical models, which included a set of two resistive cubes

  15. Investigation of degree of saturation in landfill liners using electrical resistivity imaging.

    PubMed

    Kibria, Golam; Hossain, Md Sahadat

    2015-05-01

    During construction of compacted clay liners and evapotranspiration (ET) covers, quality control involves laboratory and field tests in individual lifts. However, the available methods may be inadequate to determine non-uniform compaction conditions, poor bonding of lifts, and/or variable soil composition. Moreover, the applicability of the available methods is restricted, in many instances, when spatial variability of the subsurface is expected. Resistivity Imaging (RI) is a geophysical method employed to investigate a large area in a rapid and non-destructive way. High resistivity of clay liner soil is an indication of a low degree of saturation, high air-filled voids, and poor lift bonding. To utilize RI as a quality control tool in a landfill liner, it is important to determine the saturation condition of the compacted soils because compaction and permeability of liner soil are functions of degrees of saturation. The objective of the present study is to evaluate the degree of saturation of a municipal solid waste (MSW) landfill liner, using RI. Electrical resistivity tests were performed in the laboratory, at varied moisture contents and dry unit weights, on four types of soil samples, i.e., highly plastic clay (CH), low plastic clay (CL), Ca-bentonite, and kaolinite. According to the experimental results, electrical resistivity of the specimens decreased as much as 15.3 times of initial value with increase in the degrees of saturation from 23% to 100%. In addition, cation exchange capacity (CEC) substantially affected resistivity. A multiple linear regression (MLR) model was developed to correlate electrical resistivity with degree of saturation and CEC using experimental results. Additionally, RI tests were conducted on compacted clay liners to determine the degrees of saturation, and predicted degrees of saturation were compared with the in-situ density tests. The study results indicated that the developed model can be utilized for liner soils having CEC

  16. Three dimensional modeling and inversion of Borehole-surface Electrical Resistivity Data

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Liu, D.; Liu, Y.; Qin, M.

    2013-12-01

    After a long time of exploration, many oil fields have stepped into the high water-cut period. It is sorely needed to determining the oil-water distribution and water flooding front. Borehole-surface electrical resistivity tomography (BSERT) system is a low-cost measurement with wide measuring scope and small influence on the reservoir. So it is gaining more and more application in detecting water flooding areas and evaluating residual oil distribution in oil fields. In BSERT system, current is connected with the steel casing of the observation well. The current flows along the long casing and transmits to the surface through inhomogeneous layers. Then received electric potential difference data on the surface can be used to inverse the deep subsurface resistivity distribution. This study presents the 3D modeling and inversion method of electrical resistivity data. In an extensive literature, the steel casing is treated as a transmission line current source with infinite small radius and constant current density. However, in practical multi-layered formations with different resistivity, the current density along the casing is not constant. In this study, the steel casing is modeled by a 2.5e-7 ohm-m physical volume that the casing occupies in the finite element mesh. Radius of the casing can be set to a little bigger than the true radius, and this helps reduce the element number and computation time. The current supply point is set on the center of the top surface of the physical volume. The homogeneous formation modeling result shows the same precision as the transmission line current source model. The multi-layered formation modeling result shows that the current density along the casing is high in the low-resistivity layer, and low in the high-resistivity layer. These results are more reasonable. Moreover, the deviated and horizontal well can be simulated as simple as the vertical well using this modeling method. Based on this forward modeling method, the

  17. The Behaviour of Laboratory Soil Electrical Resistivity Value under Basic Soil Properties Influences

    NASA Astrophysics Data System (ADS)

    Hazreek, Z. A. M.; Aziman, M.; Azhar, A. T. S.; Chitral, W. D.; Fauziah, A.; Rosli, S.

    2015-01-01

    Electrical resistivity method (ERM) was a popular indirect geophysical tools adopted in engineering, environmental and archaeological studies. In the past, results of the electrical resistivity value (ERV) were always subjected to a long discussion and debate among the related parties such as an engineers, geophysicists and geologists due to its lack of clarification and evidences in quantitative point of view. Most of the results produced in the past was always been justified using qualitative ways which difficult to be accept by certain parties. In order to reduce the knowledge gap between those parties, this study has performed a laboratory experiment of soil box resistivity test which supported by an additional basic geotechnical test as referred to particle size distribution test (d), moisture content test (w), density test (ρbulk) and Atterberg limit test (LL, PL and PI). The test was performed to establish a series of electrical resistivity value with different quantity of water content for Clayey SILT and Silty SAND soil. It was found that the ERV of Silty SAND (600 - 7300 Ωm) was higher than Clayey SILT (13 - 7700 Ωm) due to the different quantity of basic soil properties value obtained from the basic geotechnical test. This study was successfully demonstrated that the fluctuation of ERV has greatly influenced by the variations of the soil physical properties (d, w, ρbulk, LL, PL and PI). Hence, the confidence level of ERV interpretation will be increasingly meaningful since it able to be proved by others parameter generated by laboratory direct test.

  18. Electrical voltages and resistances measured to inspect metallic cased wells and pipelines

    DOEpatents

    Vail III, William Banning; Momii, Steven Thomas

    2003-06-10

    A cased well in the earth is electrically energized with A.C. current. Voltages are measured from three voltage measurement electrodes in electrical contact with the interior of the casing while the casing is electrically energized. In a measurement mode, A.C. current is conducted from a first current carrying electrode within the cased well to a remote second current carrying electrode located on the surface of the earth. In a calibration mode, current is passed from the first current carrying electrode to a third current carrying electrode located vertically at a different position within the cased well, where the three voltage measurement electrodes are located vertically in between the first and third current carrying electrodes. Voltages along the casing and resistances along the casing are measured to determine wall thickness and the location of any casing collars present so as to electrically inspect the casing. Similar methods are employed to energize a pipeline to measure the wall thickness of the pipeline and the location of pipe joints to electrically inspect the pipeline.

  19. Electrical voltages and resistances measured to inspect metallic cased wells and pipelines

    DOEpatents

    Vail, III, William Banning; Momii, Steven Thomas

    2000-01-01

    A cased well in the earth is electrically energized with A.C. current. Voltages are measured from three voltage measurement electrodes in electrical contact with the interior of the casing while the casing is electrically energized. In a measurement mode, A.C. current is conducted from a first current carrying electrode within the cased well to a remote second current carrying electrode located on the surface of the earth. In a calibration mode, current is passed from the first current carrying electrode to a third current carrying electrode located vertically at a different position within the cased well, where the three voltage measurement electrodes are located vertically in between the first and third current carrying electrodes. Voltages along the casing and resistances along the casing are measured to determine wall thickness and the location of any casing collars present so as to electrically inspect the casing. Similar methods are employed to energize a pipeline to measure the wall thickness of the pipeline and the location of pipe joints to electrically inspect the pipeline.

  20. Electrical voltages and resistances measured to inspect metallic cased wells and pipelines

    DOEpatents

    Vail, III, William Banning; Momii, Steven Thomas

    2001-01-01

    A cased well in the earth is electrically energized with A.C. current. Voltages are measured from three voltage measurement electrodes in electrical contact with the interior of the casing while the casing is electrically energized. In a measurement mode, A.C. current is conducted from a first current carrying electrode within the cased well to a remote second current carrying electrode located on the surface of the earth. In a calibration mode, current is passed from the first current carrying electrode to a third current carrying electrode located vertically at a different position within the cased well, where the three voltage measurement electrodes are located vertically in between the first and third current carrying electrodes. Voltages along the casing and resistances along the casing are measured to determine wall thickness and the location of any casing collars present so as to electrically inspect the casing. Similar methods are employed to energize a pipeline to measure the wall thickness of the pipeline and the location of pipe joints to electrically inspect the pipeline.

  1. Electrical limit of silver nanowire electrodes: Direct measurement of the nanowire junction resistance

    NASA Astrophysics Data System (ADS)

    Selzer, Franz; Floresca, Carlo; Kneppe, David; Bormann, Ludwig; Sachse, Christoph; Weiß, Nelli; Eychmüller, Alexander; Amassian, Aram; Müller-Meskamp, Lars; Leo, Karl

    2016-04-01

    We measure basic network parameters of silver nanowire (AgNW) networks commonly used as transparent conducting electrodes in organic optoelectronic devices. By means of four point probing with nanoprobes, the wire-to-wire junction resistance and the resistance of single nanowires are measured. The resistance RNW of a single nanowire shows a value of RNW=(4.96 ±0.18 ) Ω/μm . The junction resistance RJ differs for annealed and non-annealed NW networks, exhibiting values of RJ=(25.2 ±1.9 ) Ω (annealed) and RJ=(529 ±239 ) Ω (non-annealed), respectively. Our simulation achieves a good agreement between the measured network parameters and the sheet resistance RS of the entire network. Extrapolating RJ to zero, our study show that we are close to the electrical limit of the conductivity of our AgNW system: We obtain a possible RS reduction by only ≈20 % (common RS≈10 Ω/sq ). Therefore, we expect further performance improvements in AgNW systems mainly by increasing NW length or by utilizing novel network geometries.

  2. Influence of processing history on the mechanical properties and electrical resistivity of polycarbonate - multi-walled carbon nanotubes nanocomposites

    NASA Astrophysics Data System (ADS)

    Choong, Gabriel Y. H.; De Focatiis, Davide S. A.

    2015-05-01

    In this work we investigate the effects of compounding temperature and secondary melt processing on the mechanical response and electrical behaviour of polycarbonate filled with 3 wt% carbon nanotubes. The nanocomposites were melt compounded in an industrial setting at a range of temperatures, and subsequently injection moulded or compression moulded. The surface hardness, uniaxial tensile properties and electrical resistivity were measured. Secondary melt processing is found to be the dominant process in determining the final mechanical properties and resistivity of these materials.

  3. Electro-location, tomography and porosity measurements in geotechnical centrifuge models based on electrical resistivity concepts

    NASA Astrophysics Data System (ADS)

    Li, Zhihua

    This research was focused on the development of electrical techniques for soil characterization and soil dynamic behavior assessment. The research carried out mainly includes (1) development of a needle probe tool for assessment of soil spatial variability in terms of porosity with high-resolution in the centrifuge testing; (2) development of an electro-location technique to accurately detect buried objects' movements inside the soil during dynamic events; (3) collaborative development of a new electrode switching system to implement electrical resistivity tomography, and electro-location with high speed and high resolution. To assess soil spatial variability with high-resolution, electrical needle probes with different tip shapes were developed to measure soil electrical resistivity. After normalizing soil resistivity by pore fluid resistivity, this information can be correlated to soil porosity. Calibrations in laboratory prepared soils were conducted. Loosening due to insertion of needle probes was evaluated. A special needle probe tool, along with data acquisition and data processing tools were developed to be operated by the new NEES robot on the centrifuge. The needle probes have great potential to resolve interfaces between soil layers and small local porosity variations with a spatial resolution approximately equal to the spacing between electrodes (about half of the probe diameter). A new electrode switching system was developed to accurately detect buried objects' movements using a new electro-location scheme. The idea was to establish an electromagnetic field in a centrifuge model by injecting low-frequency alternating currents through pairs of boundary electrodes. The locations of buried objects are related to the potentials measured on them. A closed form expression for the electric field in a rectangular specimen with insulated boundaries was obtained based on the method of images. Effects of sampling parameters on spatial resolution and tradeoffs

  4. 3-D Time-lapse Electrical Resistivity Monitoring of Injected CO2 in a Shallow Aquifer

    NASA Astrophysics Data System (ADS)

    Doetsch, J.; Vest Christiansen, A.; Auken, E.; Fiandaca, G.; Graham Cahill, A.

    2013-12-01

    Contamination of potable groundwater by leaking CO2 is a potential risk of carbon sequestration. With the help of a field experiment, we investigate if surface electrical resistivity tomography (ERT) can detect dissolved CO2 in a shallow aquifer. For this purpose, we injected CO2 at a depth of 5 and 10 m and monitored its migration using 320 electrodes on a 126 m × 20 m surface grid. A fully automated acquisition system continuously collected data and uploaded it into an online database. The large amount of data allows for time-series analysis using geostatistical techniques for noise estimation and data interpolation to compensate for intermittent instrument failure. We estimate a time-dependent noise level for each ERT configuration, taking data variation and measurement frequency into account. A baseline inversion reveals the geology at the site consisting of aeolian sands near the surface and glacial sands below 5 m depth. Directly following the injection, we image the CO2 gas phase in the aquifer as an increase in resistivity and the higher water saturation in the unsaturated zone as a decrease in resistivity. At later times, the 2-D and 3-D time-lapse inversions clearly image the dissolved CO2 plume with decreased electrical resistivity values. We can image the geochemical changes induced by the dissolved CO2 until the end of the acquisition, 120 days after the injection start. During these 120 days, the CO2 migrates about 40 m in the expected groundwater flow direction (towards south-west). Water electrical conductivity (EC) sampling using 68 sensors in 31 wells allows for very good verification of the ERT results. Water EC and ERT results generally agree very well, with the water sampling showing some fine scale variations that cannot be resolved by the ERT. The ERT images have their strength in outlining the plume's shape in three dimensions and in being able to image the plume outside the well field. These results highlight the potential for imaging

  5. Electrical Resistivity Measurements in Sandstone During CH4 Hydrate Formation and CH4-CO2 Exchange

    NASA Astrophysics Data System (ADS)

    Birkedal, K.; Hauge, L.; Ersland, G.; Graue, A.

    2012-12-01

    The electrical properties of hydrate bearing sediments change with mineralogy, porosity, hydrate saturation, brine salinity, and mobility of the formation brine. Reliable calibration data is therefore essential for correct interpretation. Electrical resistivity measurements have been conducted on homogeneous Bentheim sand during CH4 hydrate formation. Various initial conditions (salinity and Sw) were used to determine the robustness of resistivity as a measure of hydrate saturation. Two setups with different electrode-arrangements were used; the first setup was a four electrode core holder without imaging capabilities, the second a two-electrode core holder used in combination with MRI to calibrate saturation data. The agreement between the two setups was good and there was little variation in phase angle. An initial resistivity decrease was observed at the initiation of hydrate growth for all experiments. This effect was more pronounced with lower initial salinities. Further increase in hydrate saturation resulted in reduced pore connectivity and increased tortuosity which resulted in increased resistivity (45-2487 kΩ). Only CH4 and water were used to form hydrate. The brine NaCl concentration of the remaining brine solution therefore increased during hydrate growth. Dynamic Rw and R0 values were incorporated into Archie's equations to account for changes in brine composition during hydrate formation. Resistivity was also measured during exchange between CH4-hydrate and CO2. There was an immediate resistivity and pressure response as CO2 was introduced to the system. This may be explained by higher water activity and CO2-hydrate growth at the trans-axial core face as CO2 is the preferred guest molecule at the experimental conditions. A spontaneous exchange therefore occurs, where the change in enthalpy accelerates the exchange. The resistivity showed a continuous decreasing trend after CO2 was introduced. This is explained by local in-equilibrium where

  6. The Influence of Basic Physical Properties of Soil on its Electrical Resistivity Value under Loose and Dense Condition

    NASA Astrophysics Data System (ADS)

    Abidin, M. H. Z.; Ahmad, F.; Wijeyesekera, D. C.; Saad, R.

    2014-04-01

    Electrical resistivity technique has become a famous alternative tool in subsurface characterization. In the past, several interpretations of electrical resistivity results were unable to be delivered in a strong justification due to lack of appreciation of soil mechanics. Traditionally, interpreters will come out with different conclusion which commonly from qualitative point of view thus creating some uncertainty regarding the result reliability. Most engineers desire to apply any techniques in their project which are able to provide some clear justification with strong, reliable and meaningful results. In order to reduce the problem, this study presents the influence of basic physical properties of soil due to the electrical resistivity value under loose and dense condition. Two different conditions of soil embankment model were tested under electrical resistivity test and basic geotechnical test. It was found that the electrical resistivity value (ERV, ρ) was highly influenced by the variations of soil basic physical properties (BPP) with particular reference to moisture content (w), densities (ρbulk/dry), void ratio (e), porosity (η) and particle grain fraction (d) of soil. Strong relationship between ERV and BPP can be clearly presents such as ρ ∞ 1/w, ρ ∞ 1/ρbulk/dry, ρ ∞ e and ρ ∞ η. This study therefore contributes a means of ERV data interpretation using BPP in order to reduce ambiguity of ERV result and interpretation discussed among related persons such as geophysicist, engineers and geologist who applied these electrical resistivity techniques in subsurface profile assessment.

  7. Time-lapse electrical resistivity tomography of a water infiltration test on Johannishus Esker, Sweden

    NASA Astrophysics Data System (ADS)

    Ulusoy, İnan; Dahlin, Torleif; Bergman, Bo

    2015-05-01

    Managed aquifer recharge (MAR) is an efficient way to remove organic matter from raw water and, at the same time, reduce temperature variation. Two MAR sites were constructed by Karlskrona municipality on Johannishus Esker in Sweden. One of these sites, Vång, was monitored for electrical conductivity and electrical resistivity (using electrical resistivity tomography - ERT) during a 9-week tracer infiltration test. The aim of the monitoring was to map the pathways of the infiltrated water, with the overall goal to increase the efficiency of the MAR. ERT proved useful in determining both the nature of the esker formation and the water migration pathways. In Vång, the esker ridge follows a tectonically controlled paleo-valley. The fault/fracture zone in the bedrock along this paleo-valley was mapped. During the tracer test, the infiltrated water was detected in the area close to the infiltration ponds, whereas far-situated observation wells were less affected. For sequential infiltration and recharge periods in MAR, the timing of the well pumping is another important factor. Natural groundwater flow direction was a determinant in the infiltration process, as expected. ERT measurements provide supplementary data for site selection, for monitoring the functionality of the MAR sites, and for revealing the geological, hydrogeological and structural characteristics of the site.

  8. Four-point probe electrical resistivity scanning system for large area conductivity and activation energy mapping.

    PubMed

    Shimanovich, Klimentiy; Bouhadana, Yaniv; Keller, David A; Rühle, Sven; Anderson, Assaf Y; Zaban, Arie

    2014-05-01

    The electrical properties of metal oxides play a crucial role in the development of new photovoltaic (PV) systems. Here we demonstrate a general approach for the determination and analysis of these properties in thin films of new metal oxide based PV materials. A high throughput electrical scanning system, which facilitates temperature dependent measurements at different atmospheres for highly resistive samples, was designed and constructed. The instrument is capable of determining conductivity and activation energy values for relatively large sample areas, of about 72 × 72 mm(2), with the implementation of geometrical correction factors. The efficiency of our scanning system was tested using two different samples of CuO and commercially available Fluorine doped tin oxide coated glass substrates. Our high throughput tool was able to identify the electrical properties of both resistive metal oxide thin film samples with high precision and accuracy. The scanning system enabled us to gain insight into transport mechanisms with novel compositions and to use those insights to make smart choices when choosing materials for our multilayer thin film all oxide photovoltaic cells. PMID:24880411

  9. A load-lock compatible system for in situ electrical resistivity measurements during thin film growth

    NASA Astrophysics Data System (ADS)

    Colin, J. J.; Diot, Y.; Guerin, Ph.; Lamongie, B.; Berneau, F.; Michel, A.; Jaouen, C.; Abadias, G.

    2016-02-01

    An experimental setup designed for in situ electrical resistance measurement during thin film growth is described. The custom-built sample holder with a four-point probe arrangement can be loaded into a high-vacuum magnetron sputter-deposition chamber through a load-lock transfer system, allowing measurements on series of samples without venting the main chamber. Electrical contact is ensured with circular copper tracks inserted in a Teflon plate on a mounting holder station inside the deposition chamber. This configuration creates the possibility to measure thickness-dependent electrical resistance changes with sub-monolayer resolution and is compatible with use of sample rotation during growth. Examples are presented for metallic films with high adatom mobility growing in a Volmer-Weber mode (Ag and Pd) as well as for refractory metal (Mo) with low adatom mobility. Evidence for an amorphous-to-crystalline phase transition at a film thickness of 2.6 nm is reported during growth of Mo on an amorphous Si underlayer, supporting previous findings based on in situ wafer curvature measurements.

  10. A load-lock compatible system for in situ electrical resistivity measurements during thin film growth.

    PubMed

    Colin, J J; Diot, Y; Guerin, Ph; Lamongie, B; Berneau, F; Michel, A; Jaouen, C; Abadias, G

    2016-02-01

    An experimental setup designed for in situ electrical resistance measurement during thin film growth is described. The custom-built sample holder with a four-point probe arrangement can be loaded into a high-vacuum magnetron sputter-deposition chamber through a load-lock transfer system, allowing measurements on series of samples without venting the main chamber. Electrical contact is ensured with circular copper tracks inserted in a Teflon plate on a mounting holder station inside the deposition chamber. This configuration creates the possibility to measure thickness-dependent electrical resistance changes with sub-monolayer resolution and is compatible with use of sample rotation during growth. Examples are presented for metallic films with high adatom mobility growing in a Volmer-Weber mode (Ag and Pd) as well as for refractory metal (Mo) with low adatom mobility. Evidence for an amorphous-to-crystalline phase transition at a film thickness of 2.6 nm is reported during growth of Mo on an amorphous Si underlayer, supporting previous findings based on in situ wafer curvature measurements. PMID:26931861

  11. Electrical Resistivity Imaging of Seawater Intrusion into the Monterey Bay Aquifer System.

    PubMed

    Pidlisecky, A; Moran, T; Hansen, B; Knight, R

    2016-03-01

    We use electrical resistivity tomography to obtain a 6.8-km electrical resistivity image to a depth of approximately 150 m.b.s.l. along the coast of Monterey Bay. The resulting image is used to determine the subsurface distribution of saltwater- and freshwater-saturated sediments and the geologic controls on fluid distributions in the region. Data acquisition took place over two field seasons in 2011 and 2012. To maximize our ability to image both vertical and horizontal variations in the subsurface, a combination of dipole-dipole, Wenner, Wenner-gamma, and gradient measurements were made, resulting in a large final dataset of approximately 139,000 data points. The resulting resistivity section extends to a depth of 150 m.b.s.l., and is used, in conjunction with the gamma logs from four coastal monitoring wells to identify four dominant lithologic units. From these data, we are able to infer the existence of a contiguous clay layer in the southern portion of our transect, which prevents downward migration of the saltwater observed in the upper 25 m of the subsurface to the underlying freshwater aquifer. The saltwater and brackish water in the northern portion of the transect introduce the potential for seawater intrusion into the hydraulically connected freshwater aquifer to the south, not just from the ocean, but also laterally from north to south. PMID:26085452

  12. Investigating Root Zone Soil Moisture Using Electrical Resistivity and Crop Modeling

    NASA Astrophysics Data System (ADS)

    Diker, K.; Van Dam, R. L.; Hyndman, D. W.; Kendall, A. D.; Bhardwaj, A. K.; Hamilton, S. K.; Basso, B.

    2011-12-01

    An accurate understanding of soil moisture variability is critical for agroecological modeling and for understanding the implications of climate change for agriculture. In recent years, electrical resistivity (ER) methods have successfully been used to characterize soil moisture in a range of environments, but there remains a need to better link these data to climate variability, soil textural properties, and vegetation and root dynamics. We present results for a novel ER measurement system at the Great Lakes Bioenergy Research Center (GLBRC) in southwest Michigan. Permanent multi-electrode arrays were installed beneath a range of annual and perennial biofuel crop types including corn, soybean, various grasses, and poplars. The ER arrays provide both high spatial resolution 2D and high temporal resolution 1D apparent resistivity data (4 week and 2 hour intervals, respectively). These data, along with a forward simulation of electrical resistivity in the soil column, are used to calibrate and refine root growth dynamics modules within the crop growth and soil hydrologic model SALUS (System Approach to Land Use Sustainability). Simulations are compared to 1D TDR-inferred soil moisture data. Variability in root zone dynamics among different biofuel cropping systems is explored. Total water use and efficiency, along with profile root water extraction, vary considerably among the crops.

  13. Analytical model for the dynamic resistivity of electrically-exploded conductors

    SciTech Connect

    Lee, R.S.

    1986-10-10

    A detailed model for the dynamic resistivity of an exploding conductor presents many difficulties. An electrically-exploded conductor undergoes significant hydrodynamic expansion as it is heated. Resistivity is a function of both the temperature and density of a conductor and realistic models for resistivity over the range of parameter space experienced by an exploding conductor are quite complex. See for example, the model of Lee and More (1984). Calculation of the hydrodynamic expansion of the conductor during and subsequent to the explosion is likewise dependent on detailed knowledge of the equation of state for the conductor in a range where few experimental data exist. A further complication is the strong magnetic field which couples the hydrodynamic expansion to the currents flowing in the expanding material. In spite of the difficulties, progress is being made on detailed modeling of fuses and exploding conductors (Lidemuth and co-workers, 1985). A simpler approach has proved to be quite useful for modeling the electrical behavior of exploding bridgewire and slapper detonators and for modeling the explosionss of large conductors exploded with large capacitor banks. In the work described here, a simple, empirical model was developed which can be expressed as a closed-form algebraic expression involving four parameters. This model has been used in a computer code which will calculate the burst times and burst currents for up to 15 conductors exploded in series in a capacitor-discharge circuit.

  14. Time-Lapse Electrical Resistivity Investigations for Imaging the Grouting Injection in Shallow Subsurface Cavities

    PubMed Central

    Farooq, Muhammad; Kim, Jung Ho; Song, Young Soo; Amjad Sabir, Mohammad; Umar, Muhammad; Tariq, Mohammad; Muhammad, Said

    2014-01-01

    The highway of Yongweol-ri, Muan-gun, south-western part of the South Korean Peninsula, is underlain by the abandoned of subsurface cavities, which were discovered in 2005. These cavities lie at shallow depths with the range of 5∼15 meters below the ground surface. Numerous subsidence events have repeatedly occurred in the past few years, damaging infrastructure and highway. As a result of continuing subsidence issues, the Korean Institute of Geosciences and Mineral Resources (KIGAM) was requested by local administration to resolve the issue. The KIGAM used geophysical methods to delineate subsurface cavities and improve more refined understanding of the cavities network in the study area. Cement based grouting has been widely employed in the construction industry to reinforce subsurface ground. In this research work, time-lapse electrical resistivity surveys were accomplished to monitor the grouting injection in the subsurface cavities beneath the highway, which have provided a quasi-real-time monitoring for modifying the subsurface cavities related to ground reinforcement, which would be difficult with direct methods. The results obtained from time-lapse electrical resistivity technique have satisfactory imaged the grouting injection experiment in the subsurface cavities beneath the highway. Furthermore, the borehole camera confirmed the presence of grouting material in the subsurface cavities, and hence this procedure increases the mechanical resistance of subsurface cavities below the highway. PMID:24578621

  15. Imaging pathways in fractured rock using three-dimensional electrical resistivity tomography

    USGS Publications Warehouse

    Robinson, Judith; Slater, Lee; Johnson, Timothy B.; Shapiro, Allen M.; Tiedeman, Claire; Ntlargiannis, Dimitrios; Johnson, Carole D.; Day-Lewis, Frederick D.; Lacombe, Pierre; Imbrigiotta, Thomas; Lane, Jr., John W.

    2016-01-01

    Major challenges exist in delineating bedrock fracture zones because these cause abrupt changes in geological and hydrogeological properties over small distances. Borehole observations cannot sufficiently capture heterogeneity in these systems. Geophysical techniques offer the potential to image properties and processes in between boreholes. We used three-dimensional cross borehole electrical resistivity tomography (ERT) in a 9 m (diameter) × 15 m well field to capture high-resolution flow and transport processes in a fractured mudstone contaminated by chlorinated solvents, primarily trichloroethylene. Conductive (sodium bromide) and resistive (deionized water) injections were monitored in seven boreholes. Electrode arrays with isolation packers and fluid sampling ports were designed to enable acquisition of ERT measurements during pulsed tracer injections. Fracture zone locations and hydraulic pathways inferred from hydraulic head drawdown data were compared with electrical conductivity distributions from ERT measurements. Static ERT imaging has limited resolution to decipher individual fractures; however, these images showed alternating conductive and resistive zones, consistent with alternating laminated and massive mudstone units at the site. Tracer evolution and migration was clearly revealed in time-lapse ERT images and supported by in situ borehole vertical apparent conductivity profiles collected during the pulsed tracer test. While water samples provided important local information at the extraction borehole, ERT delineated tracer migration over spatial scales capturing the primary hydrogeological heterogeneity controlling flow and transport. The fate of these tracer injections at this scale could not have been quantified using borehole logging and/or borehole sampling methods alone.

  16. Cycling exercise to resist electrically stimulated antagonist increases oxygen uptake in males: pilot study.

    PubMed

    Matsuse, Hiroo; Shiba, Naoto; Takano, Yoshio; Yamada, Shin; Ohshima, Hiroshi; Tagawa, Yoshihiko

    2013-01-01

    A hybrid training system (HTS) has been developed as the combined application of electrical stimulation (ES) and volitional contractions (VC), using electrically stimulated eccentric antagonist muscle contractions as a resistance to voluntary agonist muscle contractions. The purpose of the present study is to compare the metabolic cost between cycling exercise using HTS as added resistance (HTC) and unloaded cycling exercise (ULC). Twelve male subjects exercised on a leg cycle ergometer. After 5 min rest and 5 min warm up, they performed ULC for 5 min or HTC for 5 min. During rest and each exercise, the steady state of oxygen uptake (VO2), carbon dioxide output (VCO2), expired ventilation (VE), respiratory exchange ratio (RER), and heart rate (HR) were measured. The values of VO2, VCO2, VE, and HR during HTC were significantly greater than during ULC (p < 0.05). Relative VO2 was 16.7% +/- 2.1% of peak VO2 during ULC, and it was 21.1% +/- 3.4% during HTC. However, there was no significant difference in RER between ULC and HTC. These findings indicate that the combined application of VC and ES could lead to a greater increase in metabolic cost. HTS seems to be applicable as a resistance of motion. PMID:23934874

  17. Imaging Pathways in Fractured Rock Using Three-Dimensional Electrical Resistivity Tomography.

    PubMed

    Robinson, Judith; Slater, Lee; Johnson, Timothy; Shapiro, Allen; Tiedeman, Claire; Ntarlagiannis, Dimitrios; Johnson, Carole; Day-Lewis, Frederick; Lacombe, Pierre; Imbrigiotta, Thomas; Lane, John

    2016-03-01

    Major challenges exist in delineating bedrock fracture zones because these cause abrupt changes in geological and hydrogeological properties over small distances. Borehole observations cannot sufficiently capture heterogeneity in these systems. Geophysical techniques offer the potential to image properties and processes in between boreholes. We used three-dimensional cross borehole electrical resistivity tomography (ERT) in a 9 m (diameter) × 15 m well field to capture high-resolution flow and transport processes in a fractured mudstone contaminated by chlorinated solvents, primarily trichloroethylene. Conductive (sodium bromide) and resistive (deionized water) injections were monitored in seven boreholes. Electrode arrays with isolation packers and fluid sampling ports were designed to enable acquisition of ERT measurements during pulsed tracer injections. Fracture zone locations and hydraulic pathways inferred from hydraulic head drawdown data were compared with electrical conductivity distributions from ERT measurements. Static ERT imaging has limited resolution to decipher individual fractures; however, these images showed alternating conductive and resistive zones, consistent with alternating laminated and massive mudstone units at the site. Tracer evolution and migration was clearly revealed in time-lapse ERT images and supported by in situ borehole vertical apparent conductivity profiles collected during the pulsed tracer test. While water samples provided important local information at the extraction borehole, ERT delineated tracer migration over spatial scales capturing the primary hydrogeological heterogeneity controlling flow and transport. The fate of these tracer injections at this scale could not have been quantified using borehole logging and/or borehole sampling methods alone.

  18. Electrical Resistivity Tomography (ERT) Applied to Karst Carbonate Aquifers: Case Study from Amdoun, Northwestern Tunisia

    NASA Astrophysics Data System (ADS)

    Redhaounia, Belgacem; Ilondo, Batobo Ountsche; Gabtni, Hakim; Sami, Khomsi; Bédir, Mourad

    2016-04-01

    The Amdoun region is characterized by a high degree of karstification due to the climate impact (±1500 mm year-1) and the development of fracture network. Survey using electrical resistivity tomography (ERT) is deployed to provide a cost-effective characterization of the subsurface karst environments. A total of seven ERT profiles with lengths of 315 m were evaluated at the Béja governorate (NW Tunisia). The area represents a small syncline of Boudabbous limestone rocks (Lower Eocene), which is covered by a thin layer of clay. In this study, an ERT survey was conducted to examine the spatial distribution and shape of underground cavities in the karst area in Jebel Sabah anticline and Aïn Sallem-Zahret Medien syncline. In this study, geological, hydro-geological and electrical resistivity tomography (ERT) methods were applied to determine the geometry of the perched aquifer in the Amdoun region (NW Tunisia). The area is characterized by fractured and karstic limestone aquifer of Late Cretaceous (Abiod Fm.) and Lower Eocene (Boudabbous Fm.). The aquifers have a karstic functioning and drain aquifers of economical interest, despite some wells exploiting them. Seven resistivity profiles were conducted along the survey area at three sites. The orientation, extension and the degree of inclination of those profiles are shown in the location map. The correct resistivity data were interpreted using Earth Imager 2D software. The results of the interpreted geo-electrical sections showed that the resistivity of the carbonate aquifer varied between 2.5 to over 5794 Ωm. The thickness of the perched aquifer ranged from 15 to 50 m, while its depth from the surface lies between 10 and 60 m. The ERT not only provided precise near surface information, but was also very useful for establishing the 3D geometry and the position of several potential cavities and karts. The results show the presence of small to large isolated cavities at various depths. The low resistivity of cavities

  19. Environmental monitoring of leaks using time-lapsed long electrode electrical resistivity

    NASA Astrophysics Data System (ADS)

    Rucker, Dale F.; Fink, James B.; Loke, Meng H.

    2011-08-01

    Highly industrialized areas pose challenges for surface electrical resistivity characterization due to metallic infrastructure. The infrastructure is typically more conductive than the desired targets and will mask the deeper subsurface information. The risk of this occurring may be minimized if steel-cased wells are used as long electrodes in the area near the target. We demonstrate a method of using long electrodes to electrically monitor a simulated leak from an underground storage tank with both synthetic examples and a field demonstration. Although the method of using long electrodes has been proposed by others, no time-lapse resistivity data have been collected, modeled, and analyzed within a nuclear waste tank farm environment. Therefore, the main objective of this work was to test whether the long electrode method using steel-cased wells can be employed to spatially and temporally track simulated leaks in a highly industrialized setting. A secondary objective was to apply a time-lapse regularization procedure in the inverse modeling code, similar to the 4D tomography approach by Kim et al. (2009), and to test the procedure's effect on the quality of the outcome regarding plume intensity and position. For the synthetic examples, a simple target of varying electrical properties was placed beneath different types of layers of low resistivity to simulate the effects of the infrastructure. Both surface and long electrodes were tested on the synthetic domain, and the test cases covered a variety of survey parameters including low and high electrode density, noise, array type, and the explicit location of the wells relative to the target. All data were processed in four dimensions, where the regularization procedure was applied in both the time and space domains. The synthetic test case showed that the long electrode resistivity method could detect relative changes in resistivity that was commensurate with the differing target properties. The surface electrodes

  20. Temperature and volumetric water content petrophysical relationships in municipal solid waste for the interpretation of bulk electrical resistivity data

    NASA Astrophysics Data System (ADS)

    Pilawski, Tamara; Dumont, Gaël; Nguyen, Frédéric

    2015-04-01

    Landfills pose major environmental issues including long-term methane emissions, and local pollution of soil and aquifers but can also be seen as potential energy resources and mining opportunities. Water content in landfills determine whether solid fractions can be separated and recycled, and controls the existence and efficiency of natural or enhanced biodegradation. Geophysical techniques, such as electrical and electromagnetic methods have proven successful in the detection and qualitative investigation of sanitary landfills. However, their interpretation in terms of quantitative water content estimates makes it more challenging due to the influence of parameters such as temperature, compaction, waste composition or pore fluid. To improve the confidence given to bulk electrical resistivity data and to their interpretation, we established temperature and volumetric water content petrophysical relationships that we tested on field and laboratory electrical resistivity measurements. We carried out two laboratory experiments on leachates and waste samples from a landfill located in Mont-Saint-Guibert, Belgium. We determined a first relationship between temperature and electrical resistivity with pure and diluted leachates by progressively increasing the temperature from 5°C to 65°C, and then cooling down to 5°C. The second relationship was obtained by measuring electrical resistivity on waste samples of different volumetric water contents. First, we used the correlations obtained from the experiments to compare electrical resistivity measurements performed in a landfill borehole and on reworked waste samples excavated at different depths. Electrical resistivities were measured every 20cm with an electromagnetic logging device (EM39) while a temperature profile was acquired with optic fibres. Waste samples were excavated every 2m in the same borehole. We filled experimental columns with these samples and measured electrical resistivities at laboratory temperature

  1. The projects of Disaster-Resistant Information Communication Network at the Research Organization of Electrical Communication, Tohoku University

    NASA Astrophysics Data System (ADS)

    Iwatsuki, Katsumi

    2012-12-01

    After the East Japan Great Earthquake, Tohoku University has established Research Organization of Electrical Communication to achieve the most advanced disaster-resistant information communication network in the world. In this paper, we will introduce our projects of "Disaster-Resistant Information Communication Network" based on industry-academia-government collaboration.

  2. Electrical Resistivity Imaging and Quantification of Water Content Distribution during Infiltration and Redistribution in Soils

    NASA Astrophysics Data System (ADS)

    Singha, K.; Mirus, B. B.; Nimmo, J. R.; Perkins, K.

    2006-12-01

    Controlled by precipitation, evapotranspiration, recharge, and soil-hydraulic properties, water content is difficult to measure extensively in heterogeneous, natural environments without disturbing the subsurface. Time-lapse electrical resistivity imaging (ERI) is a cost-effective, minimally invasive method for imaging changes in water content in the vadose zone. Quantifying the relation between resistivity and water content, however, is challenging due to 1) spatially variable resolution, 2) spatial variability in the properties that relate resistivity to water content, 3) possible variability of soil-water salinity, and 4) the need for introduction of auxiliary information to achieve a unique solution of the inverse problem. Although quantitative integration of ERI data into hydrogeologic studies is complicated by these problems, the ERI technique provides copious and spatially exhaustive soft data that would otherwise be unavailable in this heterogeneous environment, especially over the multi-meter scale. We developed a methodology for analyzing ERI measurements in terms of water content, and applied it to ERI data collected during infiltration/redistribution experiments conducted in two soil types in the Mojave National Preserve. One experiment was conducted in an active wash, the other in a highly developed Pleistocene soil. In both, changes in water content through time were estimated from ERI to a depth of approximately 1.5 m during and after ponded infiltration in a 1-m diameter ring. Approximately 40 snapshots over approximately one week along intersecting two-dimensional lines were collected through time for both experiments. To reduce ambiguities in our interpretation, we use numerical simulations of water and electrical flow to convert estimated resistivity to water content, calibrating for variations in resolution, spatially variable petrophysical properties, and fluid salinity on the relation between water content and estimated resistivity

  3. Epikarstic storage and doline structural characterization with time-lapse geophysics (seismic refraction & electrical resistivity)

    NASA Astrophysics Data System (ADS)

    Valois, R.; Galibert, P.; Guérin, R.; Mendes, M.; Plagnes, V.

    2011-12-01

    Karst formations are one of the most challenging environments in terms of groundwater, engineering and environmental issues. Geophysical methods can provide useful subsurface information in karst regions concerning groundwater vulnerability assessment, exploitation or hazard estimation. First, dolines are studied as preferential pathways for the protection of karstic aquifer in south France. Geophysics helps to characterize lateral and underground morphologies of such objects and is able to detect doline hidden by the soil cover too. Electrical resistivity and seismic refraction tomographies provide information about dolines filling and could help to propose a genesis scenario. Time-lapse resistivity measurements show that the studied doline is more vulnerable to infiltration on its sides than at its centre. The epikarst could be defined as a perched aquifer above the massive carbonate rocks; it constitutes a highly fractured zone, which water stock capacities. So, the epikarst was investigated with 3D seismic refraction and results show an important velocity anisotropy linked to the fracturing and weathering of the dolostone. The 3D model presents also some large heterogeneities: a corridor with highly weathered dolostone and an unweathered pinnacle. The corridor is probably situated on vertical joints, which have conducted aggressive water. The associated weathering with residual weathered-rock keeping its initial volume could create a "ghost-rock" corridor. So, the epikarst in the dolostones of the Causse du Larzac (France) seems to be composed by "ghost-rock" developed around a specific direction of fractures. Time-lapse electrical resistivity and seismic refraction velocity were carried out on this epikarst to observe the influence of water saturation on the measurements. The results show important variations for both seismic and electrical methods and are localized in the first 6 m: in the weathered zone. So, time-lapse measurements could more easily identify

  4. Electrical resistance tomography to monitor unsaturated moisture flow in cementitious materials

    SciTech Connect

    Hallaji, Milad; Seppänen, Aku; Pour-Ghaz, Mohammad

    2015-03-15

    Traditionally the electrically-based assessment of the moisture flow in cement-based materials relies on two- or four-point measurements. In this paper, imaging of moisture distribution with electrical resistance tomography (ERT) is considered. Especially, the aim is to study whether ERT could give information on unsaturated moisture flows in cases where the flow is non-uniform. In the experiment, the specimens are monitored with ERT during the water ingress. The ERT reconstructions are compared with neutron radiographs, which provide high resolution information on the 2D distribution of the moisture. The results indicate that ERT is able to detect the moisture movement and to show approximately the shape and position of the water front even if the flow is nonuniform.

  5. Skid resistance performance of asphalt wearing courses with electric arc furnace slag aggregates.

    PubMed

    Kehagia, Fotini

    2009-05-01

    Metallurgical slags are by-products of the iron and steel industry and are subdivided into blast furnace slag and steel slag according to the different steel-producing processes. In Greece, slags are mostly produced from steelmaking using the electric arc furnace process, and subsequently are either disposed in a random way or utilized by the cement industry. Steel slag has been recently used, worldwide, as hard aggregates in wearing courses in order to improve the skidding resistance of asphalt pavements. At the Highway Laboratory, Department of Civil Engineering of Aristotle University of Thessaloniki research has been carried out in the field of steel slags, and especially in electric arc furnace (EAF) slag, to evaluate their possible use in highway engineering. In this paper, the recent results of anti-skidding performance of steel slag aggregates in highway pavements are presented.

  6. Surface and subsurface damage detection in cement-based materials using electrical resistance tomography

    NASA Astrophysics Data System (ADS)

    Ruan, T.; Poursaee, A.

    2016-04-01

    Cement-based materials are widely used in infrastructure facilities. However, often the degradation of structures leads to the failures earlier than designed service life. Thus, non-destructive testing techniques are urgently needed to evaluate the health information of the structures. In this paper, the implementation of Electrical Resistance Tomography (ERT) was investigated. This low cost, radiation free and easy to perform modality is based on measuring the electrical properties of the material under test and using that to evaluate the existence of defects in that material. It uses a set of boundary potentials and injected current to reconstruct the conductivity distribution. An automatic measurement system was developed and surface damages as well as subsurface damages on mortar specimens were investigated. The reconstructed images were capable to show the presence and the location of the damages.

  7. Using electrokinetic phenomena and electrical resistance tomography to characterize the movement of subsurface fluids

    DOEpatents

    Ramirez, A.L.; Cooper, J.F.; Daily, W.D.

    1996-02-27

    This invention relates generally to the remote detections of subsurface liquid contaminants using in combination a geophysical technique known as ERT and an EKS. Electrokinetic transport is used to enhance the ability of electrical resistance tomography (ERT) to detect position and movement of subsurface contaminant liquids, particles or ions. ERT images alone are difficult to interpret because of natural inhomogeneities in soil composition and electrical properties. By subtracting two or more ERT images obtained before and after field induced movement, a high contrast image of a plume of distinct electrokinetic properties can be seen. The invention is applicable to important subsurface characterization problems including, as examples, (1) detection of liquid-saturated plumes of contaminants such as those associated with leaks from underground storage tanks containing hazardous concentrated electrolytes, (2) detection and characterization of soils contaminated with organic pollutants such as droplets of gasoline; and (3) monitoring the progress of electrokinetic containment or clean up of underground contamination. 1 fig.

  8. Microstructure and electrical resistance evolution during sintering of a Ag nanoparticle paste

    NASA Astrophysics Data System (ADS)

    Scola, J.; Tassart, X.; Vilar, C.; Jomard, F.; Dumas, E.; Veniaminova, Y.; Boullay, P.; Gascoin, S.

    2015-04-01

    Silver nanoparticle pastes are promising materials for high temperature interconnection particularly above 400 °C. Reliability is a major concern in interconnection and it mainly depends on the behavior under the stress induced by thermal cycling. The joint microstructure is then a crucial parameter for reliability and determines the electrical, mechanical and thermal properties. Here, an investigation procedure is proposed to describe the microstructure of a joint and to monitor its evolution in real-time during the sintering. Combining electron and x-ray diffraction with electrical resistance measurement and secondary ion mass spectroscopy, our method is used on a sample made out of a home-made silver nanoparticle paste. The influence of the chemical composition of the paste on the microstructure is discussed as well as the compatibility of the paste for oxide interconnection.

  9. Skid resistance performance of asphalt wearing courses with electric arc furnace slag aggregates.

    PubMed

    Kehagia, Fotini

    2009-05-01

    Metallurgical slags are by-products of the iron and steel industry and are subdivided into blast furnace slag and steel slag according to the different steel-producing processes. In Greece, slags are mostly produced from steelmaking using the electric arc furnace process, and subsequently are either disposed in a random way or utilized by the cement industry. Steel slag has been recently used, worldwide, as hard aggregates in wearing courses in order to improve the skidding resistance of asphalt pavements. At the Highway Laboratory, Department of Civil Engineering of Aristotle University of Thessaloniki research has been carried out in the field of steel slags, and especially in electric arc furnace (EAF) slag, to evaluate their possible use in highway engineering. In this paper, the recent results of anti-skidding performance of steel slag aggregates in highway pavements are presented. PMID:19423603

  10. Stray Electric Field Due to the Carbon Foil Resistance in Hydrogen Beam-Foil-Spectroscopy Measurements

    NASA Astrophysics Data System (ADS)

    Singer, W.; Dehaes, J. C.; Carmeliet, J.

    1980-01-01

    We have measured the linear polarization of the Hβ transition at 486.1 nm excited by passage of a 110 keV proton beam through perpendicular carbon foils. We have observed that the polarization depends upon the beam intensity and on the relative position of the foil and its holder. We have shown that these dependences are linked to the presence of a stray electric field at the immediate vicinity of the foil. The field is due to the potential distribution at the foil surface resulting from the electron radial flow in the high foil electric resistance (about 50 kΩ). It introduces a perturbation which in our case is more important than the temperature effect observed by Gay and Berry (Phys. Rev. A19, 952 (1979)). The field is proportional to the beam current density and is reduced for large foil and beam diameters.

  11. Using electrokinetic phenomena and electrical resistance tomography to characterize the movement of subsurface fluids

    DOEpatents

    Ramirez, Abelardo L.; Cooper, John F.; Daily, William D.

    1996-01-01

    This invention relates generally to the remote detections of subsurface liquid contaminants using in combination a geophysical technique known as ERT and an EKS. Electrokinetic transport is used to enhance the ability of electrical resistance tomography (ERT) to detect position and movement of subsurface contaminant liquids, particles or ions. ERT images alone are difficult to interpret because of natural inhomogeneities in soil composition and electrical properties. By subtracting two or more ERT images obtained before and after field induced movement, a high contrast image of a plume of distinct electrokinetic properties can be seen. The invention is applicable to important subsurface characterization problems including, as examples, (1) detection of liquid-saturated plumes of contaminants such as those associated with leaks from underground storage tanks containing hazardous concentrated electrolytes, (2) detection and characterization of soils contaminated with organic pollutants such as droplets of gasoline; and (3) monitoring the progress of electrokinetic containment or clean up of underground contamination.

  12. Electrical resistivity imaging in transmission between surface and underground tunnel for fault characterization

    NASA Astrophysics Data System (ADS)

    Lesparre, N.; Boyle, A.; Grychtol, B.; Cabrera, J.; Marteau, J.; Adler, A.

    2016-05-01

    Electrical resistivity images supply information on sub-surface structures and are classically performed to characterize faults geometry. Here we use the presence of a tunnel intersecting a regional fault to inject electrical currents between surface and the tunnel to improve the image resolution at depth. We apply an original methodology for defining the inversion parametrization based on pilot points to better deal with the heterogeneous sounding of the medium. An increased region of high spatial resolution is shown by analysis of point spread functions as well as inversion of synthetics. Such evaluations highlight the advantages of using transmission measurements by transferring a few electrodes from the main profile to increase the sounding depth. Based on the resulting image we propose a revised structure for the medium surrounding the Cernon fault supported by geological observations and muon flux measurements.

  13. Effect of high pressure on the electrical resistivity of Ge−Te−In glasses

    SciTech Connect

    Prasad, K. N. N.; Varma, G. Sreevidya; Asokan, S.; Rukmani, K.

    2015-06-24

    The variation in the electrical resistivity of the chalcogenide glasses Ge{sub 15}Te{sub 85-x}In{sub x} has been studied as a function of high pressure for pressures up to 8.5GPa. All the samples studied undergo a semi-conductor to metallic transition in a continuous manner at pressures between 1.5-2.5GPa. The transition pressure at which the samples turn metallic increases with increase in percentage of Indium. This increase is a direct consequence of the increase in network rigidity with the addition of Indium. At a constant pressure of 0.5GPa, the normalized resistivity shows some signature of the existence of the intermediate phase. Samples recovered after a pressure cycle remain amorphous suggesting that the semi-conductor to metallic transition arises from a reduction of the band gap due to pressure or the movement of the Fermi level into the conduction or valence band.

  14. Electric Field Control of the Resistance of Multiferroic Tunnel Junctions with Magnetoelectric Antiferromagnetic Barriers

    NASA Astrophysics Data System (ADS)

    Merodio, P.; Kalitsov, A.; Chshiev, M.; Velev, J.

    2016-06-01

    Based on model calculations, we predict a magnetoelectric tunneling electroresistance effect in multiferroic tunnel junctions consisting of ferromagnetic electrodes and magnetoelectric antiferromagnetic barriers. Switching of the antiferromagnetic order parameter in the barrier in applied electric field by means of the magnetoelectric coupling leads to a substantial change of the resistance of the junction. The effect is explained in terms of the switching of the orientations of local magnetizations at the barrier interfaces affecting the spin-dependent interface transmission probabilities. Magnetoelectric multiferroic materials with finite ferroelectric polarization exhibit an enhanced resistive change due to polarization-induced spin-dependent screening. These results suggest that devices with active barriers based on single-phase magnetoelectric antiferromagnets represent an alternative nonvolatile memory concept.

  15. Damage Characterization in SiC/SiC Composites using Electrical Resistance

    NASA Technical Reports Server (NTRS)

    Smith, Craig E.; Xia, Zhenhai

    2011-01-01

    SiC/SiC ceramic matrix composites (CMCs) under creep-rupture loading accumulate damage by means of local matrix cracks that typically form near a stress concentration, such as a 90o fiber tow or large matrix pore, and grow over time. Such damage is difficult to detect through conventional techniques. Electrical resistance changes can be correlated with matrix cracking to provide a means of damage detection. Sylramic-iBN fiber-reinforced SiC composites with both melt infiltrated (MI) and chemical vapor infiltrated (CVI) matrix types are compared here. Results for both systems exhibit an increase in resistance prior to fracture, which can be detected either in situ or post-damage.

  16. Electrical resistivity of polypyrrole nanotube measured by conductive scanning probe microscope: The role of contact force

    NASA Astrophysics Data System (ADS)

    Park, J. G.; Lee, S. H.; Kim, B.; Park, Y. W.

    2002-12-01

    Polypyrrole (PPy) nanotubes were synthesized using the pores of track-etched polycarbonate membrane as a template. Its size depends on the pore diameter of template, range from 50 to 200 nm. Direct I-V measurements of PPy nanotube (diameter of 120 nm) deposited on Au were done using a metal-coated tapping-mode atomic-force-microscope tip. Linear I-V characteristics are observed, and the resistance is decreased as the contact force is increased. Using the Hertz model, the elastic modulus E and electrical resistivity ρ are estimated to be E˜1 GPa and ρ˜1 Ωcm. These values are consistent with those obtained in bulk PPy film.

  17. Electrical transport properties of TiCoSb half-Heusler phases that exhibit high resistivity

    NASA Astrophysics Data System (ADS)

    Xia, Y.; Ponnambalam, V.; Bhattacharya, S.; Pope, A. L.; Poon, S. J.; Tritt, T. M.

    2001-01-01

    Electrical transport measurements have been performed on doped and undoped TiCoSb half-Heusler phases. The semiconducting properties are found to be more robust than those reported for MNiSn (M = Ti, Zr, Hf ). Undoped TiCoSb phases exhibit large n-type Seebeck coefficients and high resistivities that reach -500 µV K-1 at 300 K and ~1500 Ω cm at 4.2 K, respectively. A tendency towards carrier localization is seen in several disordered phases. The effects due to n-type and p-type dopants are readily manifested in the thermopower, from which moderately heavy electron and hole band masses are inferred. The unusual properties measured are consistent with the prediction of a wide bandgap for the TiCoSb phase. A resistivity minimum is observed at 500-600 K for undoped and V-doped TiCoSb. Consequently, the semiconducting gap has not been determined.

  18. An innovative application of electrical resistivity methods for detecting faults in the mining industry

    SciTech Connect

    Fromm, A.J.; Taylor, R.W. ); Shapiro, A.R.; Curley, P.G.; Barden, D.E. )

    1992-01-01

    A drilling program, intended to define Silurian dolomite reserves and hydrogeologic conditions at a potential quarry near the Sandwich fault system of northeastern Illinois, revealed the presence of a 30 meter brecciated zone. For concerns over the community, quarry operations, and economic projections a geophysical investigation was conducted to access the possible existence of a fault within the site. The interpretation of the geophysical survey would then be used to guide an expanded drilling program, which would further define subsurface conditions. A discontinuity in the apparent resistivities of subsurface materials was delineated by nineteen electrical depth soundings. The discontinuity suggested the possibility of a fault along the southern end of the property. Four azimuthal resistivity surveys indicated isotropic conditions, which supported the absence of fault enhanced permeability throughout most of the property. Significant anisotropy calculated from a fifth azimuthal survey, near the southern end of the property, indicated a fault trending 300 degrees with a secondary porosity of approximately 3 percent.

  19. Electrical resistivity of some palladium-silver alloys containing hydrogen at 4.2 K

    NASA Technical Reports Server (NTRS)

    Smith, R. J.; Otterson, D. A.

    1974-01-01

    The electrical resistivities of the alloys 90at.%Pd - 10at.%Ag, 80at.%Pd - 20at.%Ag, 70at.%Pd - 30at.%Ag, 60at.%Pd - 40at.%Ag, and 50at.%Pd - 50at.%Ag were measured as functions of absorbed hydrogen x at 4.2 K. These results show a minimum in the resistivity for all the alloys except 90Pd-10Ag; they show a maximum for all the alloys except for 50Pd-Ag. We associate the shapes of the plots with a modification of the Pd D-band because of the substitutional alloying of Ag and the interstitial absorption of hydrogen.

  20. Eradication of multidrug-resistant A. baumannii in burn wounds by antiseptic pulsed electric field

    PubMed Central

    Golberg, Alexander; Broelsch, G. Felix; Vecchio, Daniela; Khan, Saiqa; Hamblin, Michael R.; Austen, William G.; Sheridan, Robert L.; Yarmush, Martin L.

    2014-01-01

    Emerging bacterial resistance to multiple drugs is an increasing problem in burn wound management. New non-pharmacologic interventions are needed for burn wound disinfection. Here we report on a novel physical method for disinfection: antiseptic pulsed electric field (PEF) applied externally to the infected burns. In a mice model, we show that PEF can reduce the load of multidrug resistant Acinetobacter baumannii present in a full thickness burn wound by more than four orders of magnitude, as detected by bioluminescence imaging. Furthermore, using a finite element numerical model, we demonstrate that PEF provides non-thermal, homogeneous, full thickness treatment for the burn wound, thus, overcoming the limitation of treatment depth for many topical antimicrobials. These modeling tools and our in vivo results will be extremely useful for further translation of the PEF technology to the clinical setting, as they provide the essential elements for planning of electrode design and treatment protocol. PMID:25089285

  1. Improved measurements of the apparent resistivity for small depths in Vertical Electrical Soundings

    NASA Astrophysics Data System (ADS)

    Faleiro, E.; Asensio, G.; Moreno, J.

    2016-08-01

    In this work, a full simulation of a Vertical Electrical Sounding of a multilayer soil using a Wenner array is performed when both the active and the measurement electrodes consist of bare rod length L buried vertically at ground level. The apparent resistivity is calculated for a wide range of values of the separation between the electrodes using the values of the potential between the measuring electrode and a proposed function that characterizes the behavior of the electrodes used which substantially improves the measurements for small depths. The results allow comparing the values of apparent resistivity obtained by known calculation expressions with the results found by using a characteristic function of the electrodes, which is proposed in this paper. In order to obtain a complete vertical sounding of the soil, the convenience of using adapted methods to the type of electrode used in the sounding is discussed.

  2. Research on temperature control with numerical regulators in electric resistance furnaces with indirect heating

    NASA Astrophysics Data System (ADS)

    Diniş, C. M.; Popa, G. N.; Iagăr, A.

    2016-02-01

    The paper is an analysis of two-positions (hysteresis) regulators, self-tuned PID controller and PID controller for temperature control used for indirect heat resistance furnaces. For PID controller was used three methods of tuning: Ziegler-Nichols step response model, Cohen-Coon tuning rules and Ziegler-Nichols tuning rules. In experiments it used an electric furnace with indirect heating with active power of resistance of 1 kW/230V AC and a numerical temperature regulator AT-503 type (ANLY). It got a much better temperature control when using the Cohen-Coon tuning rules method than those of Ziegler-Nichols step response method and Ziegler-Nichols tuning rules method.

  3. A One-Dimensional Model of the Electrical Resistance Sintering Process

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

    In this work, a theoretical model for the processing technique usually known as electrical resistance sintering (ERS) under pressure is proposed and validated. This technique consists of the consolidation of a metallic powder mass under compression by means of a high-intensity electrical current that passes through the aggregate. The electrical current heats the powder mass by the Joule effect. The model is numerically solved by the finite differential method, in which the added difficulty of the thermal-mechanical coupling of the process has been taken into account. To simplify the numerical resolution, a one-dimensional scheme has been considered for both the powder densification mechanical problem and the heat generation and transmission problem. Furthermore, the theoretical predictions obtained after solving the model are compared with the data recorded by the ERS equipment sensors during electrical consolidation experiments with iron and titanium powders. The reasonable agreement between the theoretical and experimental curves suggests that the model, despite its simplifications, reproduces the main characteristics of the process.

  4. Discrete drops in the electrical contact resistance during nanoindentation of a bulk metallic glass

    NASA Astrophysics Data System (ADS)

    Singh, Gaurav; Narayan, R. L.; Asiri, A. M.; Ramamurty, U.

    2016-05-01

    Simultaneous measurement of the electrical contact resistance (ECR) during nanoindentation of a Pd-based bulk metallic glass (BMG) shows discontinuities in the current during the loading segment. Through an analysis of the effective change in the contact area that occurs due to the plastic flow via shear banding, we show that the current surges, which are synchronous with the displacement bursts, are associated with shear band nucleation and/or propagation. The potential of nano-ECR measurements for monitoring plastic events in BMGs is discussed.

  5. Heat dissipation due to ferromagnetic resonance in a ferromagnetic metal monitored by electrical resistance measurement

    SciTech Connect

    Yamanoi, Kazuto; Yokotani, Yuki; Kimura, Takashi

    2015-11-02

    The heat dissipation due to the resonant precessional motion of the magnetization in a ferromagnetic metal has been investigated. We demonstrated that the temperature during the ferromagnetic resonance can be simply detected by the electrical resistance measurement of the Cu strip line in contact with the ferromagnetic metal. The temperature change of the Cu strip due to the ferromagnetic resonance was found to exceed 10 K, which significantly affects the spin-current transport. The influence of the thermal conductivity of the substrate on the heating was also investigated.

  6. Measurement of the electrical resistivity of a dense strongly coupled plasma

    NASA Astrophysics Data System (ADS)

    Benage, J. F., Jr.; Shanahan, W. R.; Sherwood, E. G.; Jones, L. A.; Trainor, R. J.

    1994-05-01

    We present measurements of the electrical resistivity of a dense strongly coupled plasma. This plasma is created in a comprehensively diagnosed capillary discharge that produces uniform well-characterized dense plasmas. Data for polyurethane at densities ρ=0.01ρ0, where ρ0=1.265 g/cm3, and temperatures in the 25-30 eV range are compared with several dense plasma theories, and show a significant disagreement. These results are of importance for the modeling of pulsed power experiments and the understanding of transport processes in many astrophysical plasmas.

  7. Saturation of electrical resistivity of solid iron at Earth's core conditions.

    PubMed

    Pozzo, Monica; Alfè, Dario

    2016-01-01

    We report on the temperature dependence of the electrical resistivity of solid iron at high pressure, up to and including conditions likely to be found at the centre of the Earth. We have extended some of the calculations of the resistivities of pure solid iron we recently performed at Earth's core conditions (Pozzo et al. in Earth Planet Sci Lett 393:159-164, 2014) to lower temperature. We show that at low temperature the resistivity increases linearly with temperature, and saturates at high temperature. This saturation effect is well known as the Mott-Ioffe-Regel limit in metals, but has been largely ignored to estimate the resistivity of iron at Earth's core conditions. Recent experiments (Gomi et al. in Phys Earth Planet Int 224:88-103, 2013) coupled new high pressure data and saturation to predict the resitivity of iron and iron alloys at Earth's core conditions, and reported values up to three times lower than previous estimates, confirming recent first principles calculations (de Koker et al. in Proc Natl Acad Sci 109:4070-4073, 2012; Pozzo et al. in Nature 485:355-358, 2012, Phys Rev B 87:014110-10, 2013, Earth Planet Sci Lett 393:159-164, 2014; Davies et al. in Nat Geosci 8:678-685, 2015). The present results support the saturation effect idea. PMID:27026948

  8. Xenopus laevis oocytes infected with multi-drug–resistant bacteria: implications for electrical recordings

    PubMed Central

    O'Connell, Denice; Mruk, Karen; Rocheleau, Jessica M.

    2011-01-01

    The Xenopus laevis oocyte has been the workhorse for the investigation of ion transport proteins. These large cells have spawned a multitude of novel techniques that are unfathomable in mammalian cells, yet the fickleness of the oocyte has driven many researchers to use other membrane protein expression systems. Here, we show that some colonies of Xenopus laevis are infected with three multi-drug–resistant bacteria: Pseudomonas fluorescens, Pseudomonas putida, and Stenotrophomonas maltophilia. Oocytes extracted from infected frogs quickly (3–4 d) develop multiple black foci on the animal pole, similar to microinjection scars, which render the extracted eggs useless for electrical recordings. Although multi-drug resistant, the bacteria were susceptible to amikacin and ciprofloxacin in growth assays. Supplementing the oocyte storage media with these two antibiotics prevented the appearance of the black foci and afforded oocytes suitable for whole-cell recordings. Given that P. fluorescens associated with X. laevis has become rapidly drug resistant, it is imperative that researchers store the extracted oocytes in the antibiotic cocktail and not treat the animals harboring the multi-drug–resistant bacteria. PMID:21788613

  9. Saturation of electrical resistivity of solid iron at Earth's core conditions.

    PubMed

    Pozzo, Monica; Alfè, Dario

    2016-01-01

    We report on the temperature dependence of the electrical resistivity of solid iron at high pressure, up to and including conditions likely to be found at the centre of the Earth. We have extended some of the calculations of the resistivities of pure solid iron we recently performed at Earth's core conditions (Pozzo et al. in Earth Planet Sci Lett 393:159-164, 2014) to lower temperature. We show that at low temperature the resistivity increases linearly with temperature, and saturates at high temperature. This saturation effect is well known as the Mott-Ioffe-Regel limit in metals, but has been largely ignored to estimate the resistivity of iron at Earth's core conditions. Recent experiments (Gomi et al. in Phys Earth Planet Int 224:88-103, 2013) coupled new high pressure data and saturation to predict the resitivity of iron and iron alloys at Earth's core conditions, and reported values up to three times lower than previous estimates, confirming recent first principles calculations (de Koker et al. in Proc Natl Acad Sci 109:4070-4073, 2012; Pozzo et al. in Nature 485:355-358, 2012, Phys Rev B 87:014110-10, 2013, Earth Planet Sci Lett 393:159-164, 2014; Davies et al. in Nat Geosci 8:678-685, 2015). The present results support the saturation effect idea.

  10. Modelling the electrical resistivity response to CO2 plumes generated in a laboratory, cylindrical sandbox

    NASA Astrophysics Data System (ADS)

    Kremer, T.; Maineult, A. J.; Binley, A.; Vieira, C.; Zamora, M.

    2012-12-01

    CO2 capture and storage into deep geological formations is one of the main solutions proposed to reduce the concentration of anthropic CO2 in the atmosphere. The monitoring of injection sites is a crucial issue to assess for the long term viability of CO2 storage. With the intention of detecting potential leakages, we are investigating the possibility of using electrical resistivity tomography (ERT) techniques to detect CO2 transfers in the shallow sub-surface. ERT measurements were performed during a CO2 injection in a cylindrical tank filled with Fontainebleau sand and saturated with water. Several measurements protocols were tested. The inversion of the resistances measured with the software R3T (Binley and Kemna (2005)) clearly showed that the CO2 injection induces significant changes in the resistivity distribution of the medium, and that ERT has a promising potential for the detection and survey of CO2 transfers through unconsolidated saturated media. We modeled this experiment using Matlab by building a 3D cellular automaton that describes the CO2 spreading, following the geometric and stochastic approach described by Selker et al. (2007). The CO2 circulation is described as independents, circular and continuous gas channels whose horizontal spread depends on a Gaussian probability law. From the channel distribution we define the corresponding gas concentration distribution and calculate the resistivity of the medium by applying Archie's law for unsaturated conditions. The forward modelling was performed with the software R3T to convert the resistivity distribution into resistances values, each corresponding to one of the electrode arrays used in the experimental measurements. Modelled and measured resistances show a good correlation, except for the electrode arrays located at the top or the bottom of the tank. We improved the precision of the model by considering the effects due to CO2 dissolution in the water which increases the conductivity of the

  11. Microstructures, mechanical properties, and electrical resistivity of rapidly quenched Fe-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Naohara, T.; Inoue, A.; Minemura, T.; Masumoto, T.; Kumada, K.

    1982-03-01

    By the rapid quenching technique, ductile supersaturated ferrite solid solution with high hardness and strength as well as unusual electrical properties has been found in Fe-Cr-Al ternary system. This formation range is limited to less than about 35 at. pct Cr and 23 at. pct Al. The ferrite phase has fine grains of about 10 μm in diameter. Their hardness, yield strength, and tensile fracture strength increase with increase in the amounts of chromium and aluminum, and the highest values reach about 290 DPN, 720 MPa, and 740 MPa. These alloys are so ductile that no cracks are observed even after closely contacted bending test. The good strength and ductility remain almost unchanged on tempering for one hour until heated to about 923 K where a large amount of Cr2Al compound begins to precipitate preferentially along the grain boundaries of the ferrite phase. The room-temperature resistivity increases with increasing chromium and aluminum contents and reaches as high as 1.86 μ Ώ m for Fe50Cr30Al20 alloy. Also, the temperature coefficient of resistivity in the temperature range between room temperature and 773 K decreases with increasing chromium and aluminum contents and becomes zero in the vicinity of 20 to 30 at. pct Cr and 15 at. pct Al. Thus, the present alloys may be attractive as fine gauge high-resistance and/or standard-resistance wires and plates because of the unusual electrical properties combined with high strength and good ductility.

  12. Electrical resistivity and geotechnical assessment of subgrade soils in southwestern part of Nigeria

    NASA Astrophysics Data System (ADS)

    Adebisi, N. O.; Ariyo, S. O.; Sotikare, P. B.

    2016-07-01

    The subgrade soils in areas underlain by the slightly Migmatized to Non-migmatized Metasedimentary and Metaigneous rocks of Southwestern Nigeria have been considerably investigated. However, a serious research which employs electrical resistivity method for insight into the profile development, as well as estimation of resistance to deformation for predicting the stability of flexible highway pavements is yet to be carried out. In this study, Vertical Electrical Sounding (VES) were carried out after a reconnaissance survey based on stable and unstable locations on the road. Index and strength tests related to road construction were also carried out on bulk samples obtained from stable and failed (unstable) locations of the Ago-Iwoye/Ishara highway. Results show mostly three (3) layers in the profiles with H, HK, and HKH curve types. The subgrade soils below the stable locations have better vertical and interval variations in the resistivities (89-1095 Ωm) to a depth of 3.4 m as against those from the failed portions. Those from the stable locations also have higher specific gravity (2.72), low-medium plasticity and A-2-6 kaolinitic clayey soils with higher compacted density (2090 kg/m3) compared to subgrade soils from the failed locations. On the basis of Califonia Bearing Ratio (CBR), subgrade soils at stable locations have greater strength than those obtained from failed locations. Estimated resistance to deformation (R-value) and resilient modulus (MR) proved to be the overriding parameters for predicting the stability of the flexible highway pavements.

  13. Flexural fatigue performance and electrical resistance response of carbon nanotube-based polymer composites at cryogenic temperatures

    NASA Astrophysics Data System (ADS)

    Wei, Zhijuan; Takeda, Tomo; Narita, Fumio; Shindo, Yasuhide

    2014-01-01

    We study the flexural failure and electrical resistance change of carbon nanotube (CNT)-based polymer composites under cyclic loading at cryogenic temperatures. Fatigue tests were performed on CNT/polycarbonate composites at room temperature and liquid nitrogen temperature (77 K) using the three-point bending method, and the measurements of the specimen electrical resistance were made during the tests. Also, the specimen fracture surfaces were examined by scanning electron microscopy (SEM) to verify the failure mechanisms of the nanocomposites. The dependence of the mechanical and electrical responses of the nanocomposites on the temperature and the nanotube content was then discussed.

  14. Internal Structure of Periglacial Landforms: Assessment using 3D Electrical Resistivity Imaging (ERI)

    NASA Astrophysics Data System (ADS)

    Emmert, Adrian; Kneisel, Christof

    2015-04-01

    The occurrence of internal heterogeneities within periglacial landforms (e.g. frost table topography or varying ice content) is in most cases not inferable from the surface. Hence, to develop an enhanced understanding of the interaction between surface and subsurface processes, it is necessary to analyse the internal structure of different periglacial landforms and landform elements. The assessment of the internal structure is provided by the application of three-dimensional Electrical Resistivity Imaging (ERI). ERI is the technique of merging datum points from several parallel and perpendicular performed two-dimensional ERT (Electrical Resistivity Tomography) measurements and inverting the data set with a 3D inversion algorithm (sometimes also referred to as quasi-3D ERT). The application of this method has proven to be a valuable tool for mapping the spatial extent of isolated permafrost bodies and associated subsurface conditions. In this contribution, we present results from four ERI measurements, carried out in summer 2014 at different investigation sites in the Swiss Alps: Three measurements were performed on pebbly rockglaciers of different size and topographical position and one measurement was performed on a solifluction slope. Each of the 3D survey grids consists of 17 to 32 single 2D ERT surveys (Dipol-Dipol or Wenner-Schlumberger array) and covers an area of between 6000 m² and 7000 m², depending on the specific survey grid set-up. The inversions of the data sets were performed using the two different inversion algorithms of the software products "RES3DINV" and "BERT" (Boundless Electrical Resistivity Tomography) for a comparative analysis and to further support the geomorphological interpretation of the geophysical models. Each of the resulting resistivity models shows strong small-scale spatial heterogeneities between the investigated landforms but also within landform elements. For the investigated rockglacier sites, these structures include

  15. High resolution electrical resistivity tomography of golf course greens irrigated with reclaimed wastewater: Hydrological approach

    NASA Astrophysics Data System (ADS)

    Tapias, Josefina C.; Lovera, Raúl; Himi, Mahjoub; Gallardo, Helena; Sendrós, Alexandre; Marguí, Eva; Queralt, Ignasi; Casas, Albert

    2014-05-01

    Actually, there are over 300 golf courses and more than three thousand licensed players in Spain. For this reason golf cannot be considered simply a hobby or a sport, but a very significant economic activity. Considered as one of the most rapidly expanding land-use and water demanding business in the Mediterranean, golf course development generates controversy. In the recent years there has been a considerable demand for golf courses to adopt environmentally sustainable strategies and particularly water authorities are forcing by law golf managers to irrigate with alternative water resources, mainly reclaimed wastewater. Watering practices must be based on soil properties that are characterized by samples removed from the different zones of the golf course and submitted to an accredited physical soil testing laboratory. Watering schedules are critical on greens with poor drainage or on greens with excessively high infiltration rates. The geophysical survey was conducted over the greens of the Girona Golf Club. Eighteen electrical resistivity tomographies were acquired using a mixed Wenner-Schlumberger configuration with electrodes placed 0.5 meter apart. Small stainless-steel nails were used as electrodes to avoid any damage in the fine turfgrass of greens The resistivity meter was set for systematically and automatically selects current electrodes and measurement electrodes to sample apparent resistivity values. Particle size analysis (PSA) has been performed on soil materials of any putting green. The PSA analysis has been composed of two distinct phases. The first has been the textural analysis of the soils for determining the content of sand, silt, and clay fraction via the use of a stack of sieves with decreasing sized openings from the top sieve to the bottom. Subsequently, the hydraulic conductivity of the substrates has been evaluated by means of Bredding and Hazen empirical relationships. The results of this research show that the electrical resistivity

  16. Carbon fiber polymer-matrix structural composites for electrical-resistance-based sensing

    NASA Astrophysics Data System (ADS)

    Wang, Daojun

    This dissertation has advanced the science and technology of electrical-resistance-based sensing of strain/stress and damage using continuous carbon fiber epoxy-matrix composites, which are widely used for aircraft structures. In particular, it has extended the technology of self-sensing of carbon fiber polymer-matrix composites from uniaxial longitudinal loading and flexural loading to uniaxial through-thickness loading and has extended the technology from structural composite self-sensing to the use of the composite (specifically a one-lamina composite) as an attached sensor. Through-thickness compression is encountered in the joining of composite components by fastening. Uniaxial through-thickness compression results in strain-induced reversible decreases in the through-thickness and longitudinal volume resistivities, due to increase in the fiber-fiber contact in the through-thickness direction, and minor-damage-induced irreversible changes in these resistivities. The Poisson effect plays a minor role. The effects in the longitudinal resistivity are small compared to those in the through-thickness direction, but longitudinal resistance measurement is more amenable to practical implementation in structures than through-thickness resistance measurement. The irreversible effects are associated with an increase in the through-thickness resistivity and a decrease in the longitudinal resistivity. The through-thickness gage factor is up to 5.1 and decreases with increasing compressive strain above 0.2%. The reversible fractional change in through-thickness resistivity per through-thickness strain is up to 4.0 and decreases with increasing compressive strain. The irreversible fractional change in through-thickness resistivity per unit through-thickness strain is around -1.1 and is independent of the strain. The sensing is feasible by measuring the resistance away from the stressed region, though the effectiveness is less than that at the stressed region. A one

  17. Comparing spatial series of soil bulk electrical conductivity as obtained by Time Domain Reflectometry and Electrical Resistivity Tomography

    NASA Astrophysics Data System (ADS)

    Saeed, Ali; Dragonetti, Giovanna; Comegna, Allessandro; Garre, Sarah; Lamaddalena, Nicola; Coppola, Antonio

    2016-04-01

    Conventional ground survey of soil root zone salinity by direct soil sampling are time consuming, costly and destructive. Alternatively, soil salinity can be evaluated by measuring the bulk electrical conductivity, σb, in the field. This approach is faster and cheaper, and allows a more intensive surveying. Measurements of σb can be made either in situ or with remote devices. Time domain reflectometry (TDR) sensors allow simultaneous measurements of water content, θ, and σb. They may be calibrated for estimating the electrical conductivity of the soil solution (σw). However, they have a relatively small observation window and thus they are thought to only provide local-scale measurements. The spatial range of the sensors is limited to tens of centimeters and extension of the information to a large area can be problematic. Also, information on the vertical distribution of the σb soil profile may only be obtained by installing sensors at different depths. In this sense, the TDR may be considered as an invasive technique. Compared to the TDR, other geophysical methods based for example on the Electrical Resistivity Tomography (ERT) techniques represent an alternative in respect to those traditional for soil salinity characterization. In order to deduce the actual distribution of the bulk electrical conductivity, σb, in the soil profile, one needs to invert the signal coming from ERT sensors. The latter, in turn, depends on the specific depth distribution of the σb, as well as on the electrical configuration of the sensor used. With these premises, the main aim of this study is to estimate the vertical σb distribution starting from resistivity data series measured using the ERT method under different salinity conditions and using TDR data as ground-truth data for calibration and validation of the ERT sensor. This way, limited measured TDR data may be used for translating extensive ERT apparent electrical conductivity, σa, measurements to estimate depth

  18. Electrical resistivity of substitutionally disordered hcp Fe-Si and Fe-Ni alloys: Chemically-induced resistivity saturation in the Earth's core

    NASA Astrophysics Data System (ADS)

    Gomi, Hitoshi; Hirose, Kei; Akai, Hisazumi; Fei, Yingwei

    2016-10-01

    The thermal conductivity of the Earth's core can be estimated from its electrical resistivity via the Wiedemann-Franz law. However, previously reported resistivity values are rather scattered, mainly due to the lack of knowledge with regard to resistivity saturation (violations of the Bloch-Grüneisen law and the Matthiessen's rule). Here we conducted high-pressure experiments and first-principles calculations in order to clarify the relationship between the resistivity saturation and the impurity resistivity of substitutional silicon in hexagonal-close-packed (hcp) iron. We measured the electrical resistivity of Fe-Si alloys (iron with 1, 2, 4, 6.5, and 9 wt.% silicon) using four-terminal method in a diamond-anvil cell up to 90 GPa at 300 K. We also computed the electronic band structure of substitutionally disordered hcp Fe-Si and Fe-Ni alloy systems by means of Korringa-Kohn-Rostoker method with coherent potential approximation (KKR-CPA). The electrical resistivity was then calculated from the Kubo-Greenwood formula. These experimental and theoretical results show excellent agreement with each other, and the first principles results show the saturation behavior at high silicon concentration. We further calculated the resistivity of Fe-Ni-Si ternary alloys and found the violation of the Matthiessen's rule as a consequence of the resistivity saturation. Such resistivity saturation has important implications for core dynamics. The saturation effect places the upper limit of the resistivity, resulting in that the total resistivity value has almost no temperature dependence. As a consequence, the core thermal conductivity has a lower bound and exhibits a linear temperature dependence. We predict the electrical resistivity at the top of the Earth's core to be 1.12 ×10-6 Ωm, which corresponds to the thermal conductivity of 87.1 W/m/K. Such high thermal conductivity suggests high isentropic heat flow, leading to young inner core age (<0.85 Gyr old) and high initial

  19. Identifying Hydrologic Flowpaths on Arctic Hillslopes Using Electrical Resistivity and Self Potential

    NASA Astrophysics Data System (ADS)

    Voytek, E.; Rushlow, C. R.; Godsey, S.; Singha, K.

    2015-12-01

    Shallow subsurface flow is a dominant process controlling hillslope runoff generation, soil development, and solute reaction and transport. Despite their importance, the location and geometry of flowpaths are difficult to determine. In arctic environments, shallow subsurface flowpaths are limited to a thin zone of seasonal thaw above continuous permafrost, which is traditionally assumed to mimic to surface topography. Here we use a combined approach of electrical resistivity imaging (ERI) and self-potential measurements (SP) to map shallow subsurface flowpaths in and around water tracks, drainage features common to arctic hillslopes. ERI measurements delineate thawed zones in the subsurface that control flowpaths, while SP is sensitive to groundwater flow. We find that areas of low electrical resistivity in the water tracks are deeper than manual thaw depth estimates and variations from surface topography. This finding suggests that traditional techniques significantly underestimate active layer thaw and the extent of the flowpath network on arctic hillslopes. SP measurements identify complex 3-D flowpaths in the thawed zone. Our results lay the groundwork for investigations into the seasonal dynamics, hydrologic connectivity, and climate sensitivity of spatially distributed flowpath networks on arctic hillslopes.

  20. Surface roughness and electrical resistivity of high-purity zinc irradiated with nanosecond visible laser pulses

    NASA Astrophysics Data System (ADS)

    Butt, M. Z.; Ali, Dilawar; Tanveer, M. Usman; Naseem, S.

    2014-06-01

    Six specimens of 99.995% pure zinc in the form of strips (15 mm × 8 mm × 0.5 mm) were irradiated with Q-switched pulsed Nd:YAG laser (λ = 532 nm, E = 50 mJ, τ = 6 ns, repetition rate = 10 Hz) in vacuum ∼10-3 Torr. The specimens were irradiated with 50, 60, 70, 80, 90 and 100 laser shots; the laser fluence and laser intensity at the irradiation spot were 4.24 J/cm2 and 7.07 × 108 W/cm2, respectively. Surface morphology of laser irradiated specimens was examined by both optical and scanning electron microscopes. Crater area as well as heat affected area were measured by optical microscope using Motic software. Scanning electron microscope (SEM) examination revealed different features, e.g., wavelike structures, ridges, dips, micro cones, cavities, nano and micro size droplets, as well as solid flakes, etc., on the surface. These features are a result of splashing, hydrodynamic and exfoliational sputtering. Average surface roughness was measured from SEM micrographs using Nanotec software WSxM 5.0 develop 1.1. The electrical resistivity was determined by four-point probe technique. It is observed that average surface roughness and electrical resistivity vary with the number of laser shots in an identical manner, and are therefore found to be directly related to each other.

  1. Electrical Resistivity and Ground Penetrating Radar Investigation of Presence and Extent of Hardpan Soil Layers

    NASA Astrophysics Data System (ADS)

    Thao, S. J.; Plattner, A.

    2015-12-01

    Farming in the San Joaquin Valley in central California is often impeded by a shallow rock-hard layer of consolidated soil commonly referred to as hardpan. To be able to successfully farm, this layer, if too shallow, needs to be removed either with explosives or heavy equipment. It is therefore of great value to obtain information about depth and presence of such a layer prior to agricultural operations. We tested the applicability of electrical resistivity tomography and ground penetrating radar in hardpan detection. On our test site of known hardpan depth (from trenching) and local absence (prior dynamiting to plant trees), we successfully recovered the known edge of a hardpan layer with both methods, ERT and GPR. The clay-rich soil significantly reduced the GPR penetration depth but we still managed to map the edges at a known gap where prior dynamiting had removed the hardpan. Electrical resistivity tomography with a dipole-dipole electrode configuration showed a clear conductive layer at expected depths with a clearly visible gap at the correct location. In our data analysis and representation we only used either freely available or in-house written software.

  2. The (RH+t) aging correlation. Electrical resistivity of PVB at various temperatures and relative humidities

    NASA Technical Reports Server (NTRS)

    Cuddihy, E. F.

    1985-01-01

    Electrical products having organic materials functioning as pottants, encapsulants, and insulation coatings are commonly exposed to elevated conditions of temperature and humidity. In order to assess service life potential from this method of accelerated aging, it was empirically observed that service life seems proportional to an aging correlation which is the sum of temperature in degrees Celsius (t), and the relative humidity (RH) expressed in percent. Specifically, the correlation involves a plot of time-to-failure on a log scale versus the variable RH + T plotted on a linear scale. A theoretical foundation is provided for this empirically observed correlation by pointing out that the correlation actually involves a relationship between the electrical resistivity (or conductivity) of the organic material, and the variable RH + t. If time-to-failure is a result of total number of coulombs conducted through the organic material, then the correlation of resistivity versus RH + t is synonymous with the empirical correlation of time-to-failure versus RH + t.

  3. Resistance modulation in VO2 nanowires induced by an electric field via air-gap gates

    NASA Astrophysics Data System (ADS)

    Kanki, Teruo; Chikanari, Masashi; Wei, Tingting; Tanaka, Hidekazu; The Institute of Scientific; Industrial Research Team

    Vanadium dioxide (VO2) shows huge resistance change with metal-insulator transition (MIT) at around room temperature. Controlling of the MIT by applying an electric field is a topical ongoing research toward the realization of Mott transistor. In this study, we have successfully switched channel resistance of VO2 nano-wire channels by a pure electrostatic field effect using a side-gate-type field-effect transistor (SG-FET) viaair gap and found that single crystalline VO2 nanowires and the channels with narrower width enhance transport modulation rate. The rate of change in resistance ((R0-R)/R, where R0 and R is the resistance of VO2 channel with off state and on state gate voltage (VG) , respectively) was 0.42 % at VG = 30 V in in-plane poly-crystalline VO2 channels on Al2O3(0001) substrates, while the rate in single crystalline channels on TiO2 (001) substrates was 3.84 %, which was 9 times higher than that using the poly-crystalline channels. With reducing wire width from 3000 nm to 400 nm of VO2 on TiO2 (001) substrate, furthermore, resistance modulation ratio enhanced from 0.67 % to 3.84 %. This change can not be explained by a simple free-electron model. In this presentation, we will compare the electronic properties between in-plane polycrystalline VO2 on Al2O3 (0001) and single crystalline VO2 on TiO2 (001) substrates, and show experimental data in detail..

  4. Modeling and analysis of electrical-resistivity soundings made in Jurassic-Triassic basins of the eastern United States

    SciTech Connect

    Brown, C.E.

    1985-01-01

    Electrical-resistivity soundings obtained with a Schlumberger field array were used to define the structure, stratigraphy, and depth to basement in the Durham-Wadesboro, Dan River, Richmond, Culpeper, and Newark-Gettysburg Jurassic-Triassic basins in the eastern United States. Geoelectric cross sections constructed from field data processed by computer show that depth to basement rocks and stratigraphic layers differ significantly within and among basins. The cross sections show that resistivities of the intrabasin sedimentary rocks tend to increase with depth, indicating a general decrease in porosity or clay content with depth. Shale layers were found to have 2 to 5 times lower resistivity than sandstone, conglomerate, and limestone. Very massive sedimentary layers have characteristically higher resistivity than thin interbedded layers. Some limestones have resistivities as high as 2200 ohm-meters. Lateral discontinuities, such as faults and facies changes, are inferred where electrical-resistivity soundings were made at close spacing to permit detailed mapping. The sounding data were interpreted by a computer-based model that automatically inverts the sounding curve into layer thicknesses and average layer resistivities. Electrical-resistivity modeling is very useful in understanding subsurface conditions in a variety of geologic environments.

  5. Electrical resistivity tomography applied to a complex lava dome: 2D and 3D models comparison

    NASA Astrophysics Data System (ADS)

    Portal, Angélie; Fargier, Yannick; Lénat, Jean-François; Labazuy, Philippe

    2015-04-01

    The study of volcanic domes growth (e.g. St. Helens, Unzen, Montserrat) shows that it is often characterized by a succession of extrusion phases, dome explosions and collapse events. Lava dome eruptive activity may last from days to decades. Therefore, their internal structure, at the end of the eruption, is complex and includes massive extrusions and lava lobes, talus and pyroclastic deposits as well as hydrothermal alteration. The electrical resistivity tomography (ERT) method, initially developed for environmental and engineering exploration, is now commonly used for volcano structure imaging. Because a large range of resistivity values is often observed in volcanic environments, the method is well suited to study the internal structure of volcanic edifices. We performed an ERT survey on an 11ka years old trachytic lava dome, the Puy de Dôme volcano (French Massif Central). The analysis of a recent high resolution DEM (LiDAR 0.5 m), as well as other geophysical data, strongly suggest that the Puy de Dôme is a composite dome. 11 ERT profiles have been carried out, both at the scale of the entire dome (base diameter of ~2 km and height of 400 m) on the one hand, and at a smaller scale on the summit part on the other hand. Each profile is composed of 64 electrodes. Three different electrode spacing have been used depending on the study area (35 m for the entire dome, 10 m and 5 m for its summit part). Some profiles were performed with half-length roll-along acquisitions, in order to keep a good trade-off between depth of investigation and resolution. Both Wenner-alpha and Wenner-Schlumberger protocols were used. 2-D models of the electrical resistivity distribution were computed using RES2DINV software. In order to constrain inversion models interpretation, the depth of investigation (DOI) method was applied to those results. It aims to compute a sensitivity index on inversion results, illustrating how the data influence the model and constraining models

  6. An experimental and computational investigation of electrical resistivity imaging for prediction ahead of tunnel boring machines

    NASA Astrophysics Data System (ADS)

    Schaeffer, Kevin P.

    Tunnel boring machines (TBMs) are routinely used for the excavation of tunnels across a range of ground conditions, from hard rock to soft ground. In complex ground conditions and in urban environments, the TBM susceptible to damage due to uncertainty of what lies ahead of the tunnel face. The research presented here explores the application of electrical resistivity theory for use in the TBM tunneling environment to detect changing conditions ahead of the machine. Electrical resistivity offers a real-time and continuous imaging solution to increase the resolution of information along the tunnel alignment and may even unveil previously unknown geologic or man-made features ahead of the TBM. The studies presented herein, break down the tunneling environment and the electrical system to understand how its fundamental parameters can be isolated and tested, identifying how they influence the ability to predict changes ahead of the tunnel face. A proof-of-concept, scaled experimental model was constructed in order assess the ability of the model to predict a metal pipe (or rod) ahead of face as the TBM excavates through a saturated sand. The model shows that a prediction of up to three tunnel diameters could be achieved, but the unique presence of the pipe (or rod) could not be concluded with certainty. Full scale finite element models were developed in order evaluate the various influences on the ability to detect changing conditions ahead of the face. Results show that TBM/tunnel geometry, TBM type, and electrode geometry can drastically influence prediction ahead of the face by tens of meters. In certain conditions (i.e., small TBM diameter, low cover depth, large material contrasts), changes can be detected over 100 meters in front of the TBM. Various electrode arrays were considered and show that in order to better detect more finite differences (e.g., boulder, lens, pipe), the use of individual cutting tools as electrodes is highly advantageous to increase spatial

  7. Monitoring solute fluxes: Integrating electrical resistivity with multi-compartment sampler techniques

    NASA Astrophysics Data System (ADS)

    Bloem, Esther; Fernandez, Perrine; French, Helen K.

    2016-04-01

    The impact of agriculture, industry, airport activities on soil and water quality is strongly influenced by soil heterogeneity. To improve risk assessment, monitoring, and treatment strategies, we require a better understanding of the effect of soil heterogeneity on contaminant movement and better methods for monitoring heterogeneous contaminated transport. Sufficient characterization of spatial and temporal distribution of contaminant transport requires measurements of water and solute fluxes at multiple locations with a high temporal resolution. During this presentation, we will show a newly developed instrument, which combines multi-compartment sampling with electrical resistivity measurements, to observe spatial and temporal fluxes of contaminants. Solute monitoring is often limited to observations of resident concentrations, while flux concentrations govern the movement of solutes in soils. Bloem et al. (2010) developed a multi-compartment sampler (MCS) which is capable of measuring fluxes at a high spatial resolution under natural conditions. The sampler is divided into 100 separate compartments of 31 by 31 mm. Flux data can be recorded at a high time resolution (every 5 minutes). Tracer leaching can be monitored by frequently sampling the collected leachate while leaving the sampler buried in situ. To optimize the monitoring of tracer leaching and measure real solute fluxes the multi-compartment sampler has been extended with 121 electrodes. The electrodes are mounted at each corner of each compartment to measure the electrical conductivity above each compartment while water percolates through the compartments. By using different electrode couples, the setup can also be used to image above the multi-compartment sampler. The instrument can be used for detailed studies both in the laboratory and in the field. For laboratory experiments a transparent column is used which fits perfect on top of the MCS. We present a selection of the integrated electrical

  8. Good electrical contacts for high resistivity (Cd,Mn)Te crystals

    SciTech Connect

    Witkowska-Baran,M.; Mycielski, A.; Kochanowska, D.; Szadkowski, A. J.; Jakiela, r.; Witkowska, B.; Kaliszek, W.; Domagala, J.; Lusakowska, E.; Domukhovski, V.; Dybko, K.; Cui, Y.; James, R. B.

    2008-10-19

    We consider that semi-insulating (Cd,Mn)Te crystals may well successfully replace the commonly used (Cd,Zn)Te crystals as a material for manufacturing large-area X- and gamma-ray detectors. The Bridgman growth method yields good quality and high-resistivity (10{sup 9}-10{sup 10} {Omega}-cm) crystals of (Cd,Mn)Te:V. Doping with vanadium ({approx} 10{sup 16} cm{sup -3}), which acts as a compensating agent, and annealing in cadmium vapors, which reduces the number of cadmium vacancies in the as-grown crystal, ensure this high resistivity. Detector applications of the crystals require satisfactory electrical contacts. Hence, we explored techniques of ensuring good electrical contacts to semi-insulating (Cd,Mn)Te crystals. Our findings are reported here. Before depositing the contact layers, we prepared an 'epi-ready' surface of the crystal platelet by a procedure described earlier for various tellurium-based II-VI compound crystals. A molecular beam epitaxy (MBE) apparatus was used to deposit various types of contact layers: Monocrystalline semiconductor layers, amorphous- and nanocrystalline semiconductor layers, and metal layers were studied. We employed ZnTe heavily doped ({approx} 10{sup 18} cm{sup -3}) with Sb, and CdTe heavily doped ({approx} 10{sup 17} cm{sup -3}) with In as the semiconductors to create contact layers that subsequently enable good contact (with a narrow, tunneling barrier) to the Au layer that usually is applied as the top contact layer. We describe and discuss the technology and some properties of the electrical contacts to semi-insulating (Cd,Mn)Te.

  9. Acute Response to Unilateral Unipolar Electrical Carotid Sinus Stimulation in Patients With Resistant Arterial Hypertension.

    PubMed

    Heusser, Karsten; Tank, Jens; Brinkmann, Julia; Menne, Jan; Kaufeld, Jessica; Linnenweber-Held, Silvia; Beige, Joachim; Wilhelmi, Mathias; Diedrich, André; Haller, Hermann; Jordan, Jens

    2016-03-01

    Bilateral bipolar electric carotid sinus stimulation acutely reduced muscle sympathetic nerve activity (MSNA) and blood pressure (BP) in patients with resistant arterial hypertension but is no longer available. The second-generation device uses a smaller unilateral unipolar disk electrode to reduce invasiveness while saving battery life. We hypothesized that the second-generation device acutely lowers BP and MSNA in treatment-resistant hypertensive patients. Eighteen treatment-resistant hypertensive patients (9 women/9 men; 53±11 years; 33±5 kg/m(2)) on stable medications have been included in the study. We monitored finger and brachial BP, heart rate, and MSNA. Without stimulation, BP was 165±31/91±18 mm Hg, heart rate was 75±17 bpm, and MSNA was 48±14 bursts per minute. Acute stimulation with intensities producing side effects that were tolerable in the short term elicited interindividually variable changes in systolic BP (-16.9±15.0 mm Hg; range, 0.0 to -40.8 mm Hg; P=0.002), heart rate (-3.6±3.6 bpm; P=0.004), and MSNA (-2.0±5.8 bursts per minute; P=0.375). Stimulation intensities had to be lowered in 12 patients to avoid side effects at the expense of efficacy (systolic BP, -6.3±7.0 mm Hg; range, 2.8 to -14.5 mm Hg; P=0.028 and heart rate, -1.5±2.3 bpm; P=0.078; comparison against responses with side effects). Reductions in diastolic BP and MSNA (total activity) were correlated (r(2)=0.329; P=0.025). In our patient cohort, unilateral unipolar electric baroreflex stimulation acutely lowered BP. However, side effects may limit efficacy. The approach should be tested in a controlled comparative study.

  10. Monitoring High Velocity Salt Tracer via 4D Electrical Resistivity Tomography - Possibility for Salt Tracer Tomography

    NASA Astrophysics Data System (ADS)

    Doro, K. O.; Cirpka, O. A.; Patzelt, A.; Leven, C.

    2014-12-01

    Hydrogeological testing in a tomographic sequence as shown by the use of hydraulic tomography, allows an improvement of the spatial resolution of subsurface parameters. In this regard, recent studies show increasing interest in tracer tomography which involves sequential and spatially separated tracer injections and the measurement of their corresponding tracer breakthrough at different locations and depths. Such concentration measurements however require large experimental efforts and can be simplified by geophysical tracer monitoring techniques such as electrical resistivity. In this study, we present the use of 4-D, cross-hole electrical resistivity tomography (ERT) for monitoring salt tracer experiments in high velocity flow fields. For our study, we utilized a set up that enables the conduction of salt tracer experiments with complete recovery within 84 hours over a transport distance of 16 m. This allows the repetition of the experiments with different injection depths for a tomographic salt tracer testing. For ERT monitoring, we designed modular borehole electrodes for repeated usage in a flexible manner. We also assess the use of a high speed resistivity data acquisition mode for field scale tracer monitoring ensuring high spatial and temporal resolution without sacrificing data accuracy. We applied our approach at the Lauswiesen test site, Tübingen, Germany. In our 10 m × 10 m tracer monitoring domain with 16 borehole electrodes, we acquired 4650 data points in less than 18 minutes for each monitoring cycle. Inversion results show that the tracer could be successfully imaged using this approach. The results show that repeated salt tracer tests can be efficiently monitored at a high resolution with ERT which gives the possibility for salt tracer tomography at field scale. Our results also provide a data base for extending current hydrogeophysical inversion approaches to field scale data.

  11. Acute Response to Unilateral Unipolar Electrical Carotid Sinus Stimulation in Patients With Resistant Arterial Hypertension.

    PubMed

    Heusser, Karsten; Tank, Jens; Brinkmann, Julia; Menne, Jan; Kaufeld, Jessica; Linnenweber-Held, Silvia; Beige, Joachim; Wilhelmi, Mathias; Diedrich, André; Haller, Hermann; Jordan, Jens

    2016-03-01

    Bilateral bipolar electric carotid sinus stimulation acutely reduced muscle sympathetic nerve activity (MSNA) and blood pressure (BP) in patients with resistant arterial hypertension but is no longer available. The second-generation device uses a smaller unilateral unipolar disk electrode to reduce invasiveness while saving battery life. We hypothesized that the second-generation device acutely lowers BP and MSNA in treatment-resistant hypertensive patients. Eighteen treatment-resistant hypertensive patients (9 women/9 men; 53±11 years; 33±5 kg/m(2)) on stable medications have been included in the study. We monitored finger and brachial BP, heart rate, and MSNA. Without stimulation, BP was 165±31/91±18 mm Hg, heart rate was 75±17 bpm, and MSNA was 48±14 bursts per minute. Acute stimulation with intensities producing side effects that were tolerable in the short term elicited interindividually variable changes in systolic BP (-16.9±15.0 mm Hg; range, 0.0 to -40.8 mm Hg; P=0.002), heart rate (-3.6±3.6 bpm; P=0.004), and MSNA (-2.0±5.8 bursts per minute; P=0.375). Stimulation intensities had to be lowered in 12 patients to avoid side effects at the expense of efficacy (systolic BP, -6.3±7.0 mm Hg; range, 2.8 to -14.5 mm Hg; P=0.028 and heart rate, -1.5±2.3 bpm; P=0.078; comparison against responses with side effects). Reductions in diastolic BP and MSNA (total activity) were correlated (r(2)=0.329; P=0.025). In our patient cohort, unilateral unipolar electric baroreflex stimulation acutely lowered BP. However, side effects may limit efficacy. The approach should be tested in a controlled comparative study. PMID:26831195

  12. Characterization of a dismissed landfill via electrical resistivity tomography and mise-à-la-masse method

    NASA Astrophysics Data System (ADS)

    De Carlo, Lorenzo; Perri, Maria Teresa; Caputo, Maria Clementina; Deiana, Rita; Vurro, Michele; Cassiani, Giorgio

    2013-11-01

    Electrical resistivity methods are widely used for environmental applications, and they are particularly useful for the characterization and monitoring of sites where the presence of contamination requires a thorough understanding of the location and movement of water, that can act as a carrier of solutes. One such application is landfill studies, where the strong electrical contrasts between waste, leachate and surrounding formations make electrical methods a nearly ideal tool for investigation. In spite of the advantages, however, electrical investigation of landfills poses also challenges, both logistical and interpretational. This paper presents the results of a study conducted on a dismissed landfill, close to the city of Corigliano d'Otranto, in the Apulia region (Southern Italy). The landfill is located in an abandoned quarry, that was subsequently re-utilized about thirty years ago as a site for urban waste disposal. The waste was thought to be more than 20 m thick, and the landfill bottom was expected to be confined with an HDPE (high-density poli-ethylene) liner. During the digging operations performed to build a nearby new landfill, leachate was found, triggering an in-depth investigation including also non-invasive methods. The principal goal was to verify whether the leachate is indeed confined, and to what extent, by the HDPE liner. We performed both surface electrical resistivity tomography (ERT) and mise-à-la-masse (MALM) surveys, facing the severe challenges posed by the rugged terrain of the abandoned quarry complex. A conductive body, probably associated with leachate, was found as deep as 40 m below the current landfill surface i.e. at a depth much larger than the expected 20 m thickness of waste. Given the logistical difficulties that limit the geometry of acquisition, we utilized synthetic forward modeling in order to confirm/dismiss interpretational hypotheses emerging from the ERT and MALM results. This integration between measurements and

  13. Spatial focusing of electrical resistivity surveys considering geologic and hydrologic layering

    SciTech Connect

    Gail L. Heath; Alex Fuman; Ty P.A. Ferre'

    2007-03-01

    Electrical resistivity tomography (ERT) has shown great promise for monitoring transient hydrologic processes. One advantage of ERT under those conditions is the ability of a user to tailor the spatial sensitivity of an ERT survey through selection of electrode locations and electrode combinations. Recent research has shown that quadripoles can be selected in a manner that improves the independent inversion of ERT data. Our ultimate interest lies in using ERT data along with measurements from other sensors, which typically can provide high-quality data from shallow regions of the subsurface, in a joint inversion. As a result, we do not consider the selection of quadripoles specifically for inde-pendent ERT inversion. Rather, we present an approach to focusthe spatial sensitivity of ERT surveys in specificsubsurface regions with the assumption that those data, when interpreted along with other measurements that are sensitive to those regions, will lead to more complete hydrologic characterization. Because we are interested in monitoring rapid processes, our approach is designed to efficiently identify optimal quadripoles. This is achieved by separating the optimization from the inversion grid, significantly reducing computational effort. We extend our previous work to consider the use of both surface and borehole ERT electrodes and to consider the impacts of horizontally layered electrical conductivity conditions. Results confirm the ability of the method to focus survey sensitivity while showing the importance of incorporation of prior knowledge of the subsurface electric conductivity structure in designing optimal ERT surveys.

  14. Dynamic Inversion for Hydrological Process Monitoring with Electrical Resistance Tomography Under Model Uncertainty

    SciTech Connect

    Lehikoinen, A.; Huttunen, J.M.J.; Finsterle, S.; Kowalsky, M.B.; Kaipio, J.P.

    2009-08-01

    We propose an approach for imaging the dynamics of complex hydrological processes. The evolution of electrically conductive fluids in porous media is imaged using time-lapse electrical resistance tomography. The related dynamic inversion problem is solved using Bayesian filtering techniques, that is, it is formulated as a sequential state estimation problem in which the target is an evolving posterior probability density of the system state. The dynamical inversion framework is based on the state space representation of the system, which involves the construction of a stochastic evolution model and an observation model. The observation model used in this paper consists of the complete electrode model for ERT, with Archie's law relating saturations to electrical conductivity. The evolution model is an approximate model for simulating flow through partially saturated porous media. Unavoidable modeling and approximation errors in both the observation and evolution models are considered by computing approximate statistics for these errors. These models are then included in the construction of the posterior probability density of the estimated system state. This approximation error method allows the use of approximate - and therefore computationally efficient - observation and evolution models in the Bayesian filtering. We consider a synthetic example and show that the incorporation of an explicit model for the model uncertainties in the state space representation can yield better estimates than a frame-by-frame imaging approach.

  15. Assessment of contamination by intensive cattle activity through electrical resistivity tomography

    NASA Astrophysics Data System (ADS)

    Sainato, Claudia M.; Losinno, Beatriz N.; Malleville, Horacio J.

    2012-01-01

    The intensive animal production is considered highly risky for groundwater and soil because of high mobility of some contaminants from animal wastes. The aim of this work was to obtain an electrical conductivity image of unsaturated and saturated zones at a feedlot (cattle feeding field) at the surroundings of Buenos Aires city (Argentina) in order to detect the most critical sectors of the field, with regard to contamination by animal wastes. Dipole-dipole electrical soundings (electrical resistivity tomography) were performed at the corral zone and the surroundings. 2D and 3D models of conductivity were obtained. Even if there is a calcareous plate below some parts of the corrals and soil compaction is high, vertical infiltration or subsurface runoff may have occurred since these sites, with high animal charge, show soil conductivities higher than the surroundings. The models showed higher conductivities of saturated zone increasing in the direction of groundwater flow. These results were taken into account for further designs of soil and groundwater sampling. Groundwater conductivity was three times greater downgradient from the corrals with high concentrations of nitrates and phosphorous. A zone of high conductivity was found below a small channel of effluents from the corrals.

  16. Electrical Stimulation Improves Microbial Salinity Resistance and Organofluorine Removal in Bioelectrochemical Systems

    PubMed Central

    Feng, Huajun; Zhang, Xueqin; Guo, Kun; Vaiopoulou, Eleni; Shen, Dongsheng; Long, Yuyang; Yin, Jun

    2015-01-01

    Fed batch bioelectrochemical systems (BESs) based on electrical stimulation were used to treat p-fluoronitrobenzene (p-FNB) wastewater at high salinities. At a NaCl concentration of 40 g/liter, p-FNB was removed 100% in 96 h in the BES, whereas in the biotic control (BC) (absence of current), p-FNB removal was only 10%. By increasing NaCl concentrations from 0 g/liter to 40 g/liter, defluorination efficiency decreased around 40% in the BES, and in the BC it was completely ceased. p-FNB was mineralized by 30% in the BES and hardly in the BC. Microorganisms were able to store 3.8 and 0.7 times more K+ and Na+ intracellularly in the BES than in the BC. Following the same trend, the ratio of protein to soluble polysaccharide increased from 3.1 to 7.8 as the NaCl increased from 0 to 40 g/liter. Both trends raise speculation that an electrical stimulation drives microbial preference toward K+ and protein accumulation to tolerate salinity. These findings are in accordance with an enrichment of halophilic organisms in the BES. Halobacterium dominated in the BES by 56.8% at a NaCl concentration of 40 g/liter, while its abundance was found as low as 17.5% in the BC. These findings propose a new method of electrical stimulation to improve microbial salinity resistance. PMID:25819966

  17. Characterization of electrical resistivity as a function of temperature in the Mo-Si-B system

    SciTech Connect

    Beckman, Sarah E.

    1999-12-10

    Measurements of electrical resistivity as a function of temperature from 25 to 1,500 C were conducted on polycrystalline samples in the Mo-Si-B system. Single phase, or nearly single phase, samples were prepared for the following phases: Mo{sub 3}Si, Mo{sub 5}SiB{sub 2}, Mo{sub 5}Si{sub 3}B{sub x}, MoB, MoSi{sub 2}, and Mo{sub 5}Si{sub 3}. Thesis materials all exhibit resistivity values within a narrow range(4--22 x 10{sup {minus}7}{Omega}-m), and the low magnitude suggests these materials are semi-metals or low density of states metals. With the exception of MoSi{sub 2}, all single phase materials in this study were also found to have low temperature coefficient of resistivity(TCR) values. These values ranged from 2.10 x 10{sup {minus}10} to 4.74 x 10{sup {minus}10}{Omega}-m/{degree} C, and MoSi{sub 2} had a TCR of 13.77 x 10{sup {minus}10}{Omega}-m/{degree} C. The results from the single phase sample measurements were employed in a natural log rule-of-mixtures model to relate the individual phase resistivity values to those of multiphase composites. Three Mo-Si-B phase regions were analyzed: the binary Mo{sub 5}Si{sub 3}-MoSi{sub 2} system, the ternary phase field Mo{sub 5}Si{sub 3}B{sub x}MoB-MoSi{sub 2}, and the Mo{sub 3}Si-Mo{sub 5}SiB{sub 2}-Mo{sub 5} Si{sub 3}B{sub x} ternary region. The experimental data for samples in each of these regions agreed with the natural log model and illustrated that this model can predict the electrical resistivity as a function of temperature of multi-phase, sintered samples within an error of one standard deviation.

  18. Analytical model for the dynamic resistivity of electrically-exploded conductors

    NASA Astrophysics Data System (ADS)

    Lee, R. S.

    1986-10-01

    A detailed model for the dynamic resistivity of an exploding conductor presents many difficulties, since it undergoes significant hydrodynamic expansion as it is heated. Resistivity is a function of both the temperature and density of a conductor and realistic models for resistivity over the range of parameter space experienced by an exploding conductor are quite complex. Calculation of the hydrodynamic expansion of the conductor during and subsequent to the explosion is likewise dependent on detailed knowledge of the equation of state for the conductor in a range where few experimental data exist. A further complication is the strong magnetic field which couples the hydrodynamic expansion to the currents flowing in the expanding material. In spite of the difficulties, progress is being made on detailed modeling of fuses and exploding conductors. A simpler approach has proved to be quite useful for modeling the electrical behavior of exploding bridgewire and slapper detonators and for modeling the explosions of large conductors exploded with large capacitor banks. In the work described here, a simple, empirical model was developed which can be expressed as a closed-form algebraic expression involving four parameters. This model has been used in a computer code which will calculate the burst times and burst currents for up to 15 conductors exploded in series in a capacitor-discharge circuit.

  19. Small scale monitoring of a bioremediation barrier using miniature electrical resistivity tomography

    NASA Astrophysics Data System (ADS)

    Sentenac, Philippe; Hogson, Tom; Keenan, Helen; Kulessa, Bernd

    2015-04-01

    The aim of this study was to assess, in the laboratory, the efficiency of a barrier of oxygen release compound (ORC) to block and divert a diesel plume migration in a scaled aquifer model using miniature electrical resistivity tomography (ERT) as the monitoring system. Two plumes of contaminant (diesel) were injected in a soil model made of local sand and clay. The diesel plumes migration was imaged and monitored using a miniature resistivity array system that has proved to be accurate in soil resistivity variations in small-scaled models of soil. ERT results reflected the lateral spreading and diversion of the diesel plumes in the unsaturated zone. One of the contaminant plumes was partially blocked by the ORC barrier and a diversion and reorganisation of the diesel in the soil matrix was observed. The technique of time-lapse ERT imaging showed that a dense non-aqueous phase liquid (DNAPL) contaminant like diesel can be monitored through a bioremediation barrier and the technique is well suited to monitor the efficiency of the barrier. Therefore, miniature ERT as a small-scale modelling tool could complement conventional techniques, which require more expensive and intrusive site investigation prior to remediation.

  20. Oxidation Resistant, Cr Retaining, Electrically Conductive Coatings on Metallic Alloys for SOFC Interconnects

    SciTech Connect

    Vladimir Gorokhovsky

    2008-03-31

    This report describes significant results from an on-going, collaborative effort to enable the use of inexpensive metallic alloys as interconnects in planar solid oxide fuel cells (SOFCs) through the use of advanced coating technologies. Arcomac Surface Engineering, LLC, under the leadership of Dr. Vladimir Gorokhovsky, is investigating filtered-arc and filtered-arc plasma-assisted hybrid coating deposition technologies to promote oxidation resistance, eliminate Cr volatility, and stabilize the electrical conductivity of both standard and specialty steel alloys of interest for SOFC metallic interconnect (IC) applications. Arcomac has successfully developed technologies and processes to deposit coatings with excellent adhesion, which have demonstrated a substantial increase in high temperature oxidation resistance, stabilization of low Area Specific Resistance values and significantly decrease Cr volatility. An extensive matrix of deposition processes, coating compositions and architectures was evaluated. Technical performance of coated and uncoated sample coupons during exposures to SOFC interconnect-relevant conditions is discussed, and promising future directions are considered. Cost analyses have been prepared based on assessment of plasma processing parameters, which demonstrate the feasibility of the proposed surface engineering process for SOFC metallic IC applications.

  1. DC-Electrical Resistivity Imaging for embankment dike investigation: A 3D extended normalisation approach

    NASA Astrophysics Data System (ADS)

    Fargier, Yannick; Lopes, Sérgio Palma; Fauchard, Cyrille; François, Daniel; Côte, Philippe

    2014-04-01

    Levee, dike and earth embankment dam structures are difficult to assess because of their length and complexity. Managers often include geophysical investigations in the overall dike condition assessment and the DC-Electrical Resistivity Imaging (ERI) method is particularly applicable owing to its cost-effectiveness and its potential sensitivity to internal erosion. However, due to the truly 3D nature of embankment dikes, implementing inline longitudinal tomographies along with conventional 2D inversion is likely to yield image artefacts. 3D effects from external causes (geometry, water reservoir) can be predicted and therefore we present a new approach based on redefining the normalisation principle to derive apparent resistivities from the measured data. The aim is to provide a set of pre-processed apparent resistivities that are not contaminated by external 3D effects and that yield more reliable results when processed within a 2D conventional inversion scheme. The presented approach is successfully applied to synthetic and real data sets, proving superior to the conventional 2D approach, although data acquisition approach is the same thus keeping the same cost-effectiveness.

  2. Use of vertical electrical resistivity profiles to characterize the riverbed of losing-disconnected rivers

    NASA Astrophysics Data System (ADS)

    Lamontagne, Sebastien; Davis, Aaron; Crosbie, Russell; Taylor, Andrew; Munday, Tim

    2014-05-01

    There are few field techniques available to estimate infiltration rates from losing-disconnected rivers, where infiltration rates are often constrained by the presence of clay layers with a low hydraulic conductivity. It is hypothesized that, in this environment, the bulk of the infiltration would occur in 'hotspots' where the clay layer is thin or absent. Infiltration was estimated over a 2 km section of Billabong Creek (Murray-Darling Basin, Australia) using vertical electrical sounding (VES) resistivity to characterize the continuity and thickness of the riverbed clay layer. Both a towed in-river survey over the whole study reach and three fixed array measurements at the shoreline at selected areas were used. Using locations with measured high and low resistivity, the resistivity profiles were constrained by coring the riverbed to measure vertical variations in riverbed texture, porewater content and porewater salinity. The VES showed that the clay layer was continuous along the study reach and varied in thickness between 1 m and >4 m. Using a simple steady-state model, infiltration rates along the study reach were estimated to vary between 1700 and 7800 m3 km-1 year-1, with an average of 3400 m3 km-1 year-1. This methodology can provide independent estimates of infiltration rates at a scale suitable for the calibration of regional groundwater models.

  3. High Pressure Study of Electrical Resistivity of CeB6 to 136 GPa

    NASA Astrophysics Data System (ADS)

    Forouzani, Neda; Lim, Jinhyuk; Schilling, James; Fabbris, Gilberto; Fisk, Zachary

    2014-03-01

    Since the 1960's the dense Kondo compound cerium hexaboride (CeB6) has attracted a great deal of interest. To investigate whether this material might evolve into a topological insulator under sufficient pressure, we have carried out four-point electrical resistivity measurements on CeB6 over the temperature range 1.3 K to 295 K in a diamond anvil cell to 136 GPa. Although a transition into an insulating phase is not observed, the evolution of the initial dense Kondo state under such extreme pressures is of considerable interest. As reported in earlier studies to 13 GPa, the temperature of the resistivity maximum near 3 K initially increases with pressure. We observe that between 33 and 53 GPa the resistivity maximum disappears and by 83 GPa CeB6 appears to have settled into a Fermi liquid state. The marked changes observed under pressure suggest that a change in valence and/or a structural transition may have occurred. Synchrotron x-ray diffraction measurements are being carried out to investigate possible changes in crystal structure under extreme pressures. Work at Washington Univ. supported by NSF DMR-1104742 and Carnegie/DOE/NNSA DE-FC52-08NA28554.

  4. Electrical resistance tomography for monitoring the infiltration of water into a pavement section

    SciTech Connect

    Buettner, M.; Daily, B.; Ramirez, A.

    1997-07-03

    Electrical resistance tomography (ERT) was used to follow the infiltration of water into pavement section at the UC Berkeley Richmond Field Station. A volume of pavement 1m square and 1.29 m deep was sampled by an ERT array consisting of electrodes in 9 drilled holes plus 8 surface electrodes. The data were collected using a computer controlled data acquisition system capable of collecting a full data set in under 1 hour, allowing for nearly real time sampling of the infiltration. The infiltration was conducted in two phases. During the first phase, water was introduced into the asphalt-concrete (AC) layers at a slow rate of about 8 ml per hour for a period of about 6 days. In the second phase, water was introduced into the asphalt-treated-permeable base (ATPB) layer at a more rapid rate of about 100 ml/h for about 2 days. The ERT images show that water introduced into the upper AC layers shows up as a decrease in resistivity which grows with time. The images also appear to show that when water moves into the layers below the ATPB, the resistivity increases; an unexpected result. There are some indications that the water moved laterally as well as down into the deeper ATPB and the aggregate base. The images also show that when water is introduced directly into the ATPB and aggregate layer, the water moves into the the underlying materials much more quickly.

  5. Thermal Conductivity and Electrical Resistivity of FeTe1-xSx Sintered Samples

    NASA Astrophysics Data System (ADS)

    Kikegawa, Takako; Sato, Kazuki; Ishikawa, Keisuke

    The temperature dependence of thermal conductivity and the temperature and magnetic field dependence of electrical resistivity have been measured for FeTe1-xSx polycrystalline samples. The samples were prepared by solid state reaction with a three-step procedure. For FeTe0.8S0.2 and FeTe0.7S0.3, zero resistivity due to the superconducting transition was observed not only in oxygen post-annealed samples but also in as-grown ones. These samples include the certain amount of impurities FeTe2 and Fe3O4. The formation of these ion compounds reduces the excess Fe atoms leading to the appearance of the zero resistivity in as-grown samples. Positive magnetoresistivity and/or negative magnetoresistivity, which were extremely small, were observed for FeTe and S-doped samples. The magnetoresistivity curves show B2 dependence. It was observed that the thermal conductivity κ of FeTe exhibits a hump structure below 72 K which corresponds to the crystal structural and magnetic transitions. The enhancement of κ due to the superconducting transition could not be detected for as-grown FeTe0.8S0.2 and FeTe0.7S0.3 because of the absence of the bulk superconductivity in the as-grown samples and the extremely small ratio of the electronic contribution to κ.

  6. An analytical model and parametric study of electrical contact resistance in proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Wu, Zhiliang; Wang, Shuxin; Zhang, Lianhong; Hu, S. Jack

    This paper presents an analytical model of the electrical contact resistance between the carbon paper gas diffusion layers (GDLs) and the graphite bipolar plates (BPPs) in a proton exchange membrane (PEM) fuel cell. The model is developed based on the classical statistical contact theory for a PEM fuel cell, using the same probability distributions of the GDL structure and BPP surface profile as previously described in Wu et al. [Z. Wu, Y. Zhou, G. Lin, S. Wang, S.J. Hu, J. Power Sources 182 (2008) 265-269] and Zhou et al. [Y. Zhou, G. Lin, A.J. Shih, S.J. Hu, J. Power Sources 163 (2007) 777-783]. Results show that estimates of the contact resistance compare favorably with experimental data by Zhou et al. [Y. Zhou, G. Lin, A.J. Shih, S.J. Hu, J. Power Sources 163 (2007) 777-783]. Factors affecting the contact behavior are systematically studied using the analytical model, including the material properties of the two contact bodies and factors arising from the manufacturing processes. The transverse Young's modulus of chopped carbon fibers in the GDL and the surface profile of the BPP are found to be significant to the contact resistance. The factor study also sheds light on the manufacturing requirements of carbon fiber GDLs for a better contact performance in PEM fuel cells.

  7. Fabrication of pixilated architecture large panel organic flexible solar cell by reducing bulk electrical resistance

    NASA Astrophysics Data System (ADS)

    Panag, Jasmeet Singh

    This study investigates experimentally the photovoltaic behavior and performance of a new pixilated architecture of large organic photovoltaic panels made of a large array of high-aspect ratio three-dimensional pillars surrounded by a matrix of polymer photoactive material. A least addressed problem in organic and thin-film solar cells is the high bulk resistance of cathodic and anodic layers that result in drastic reduction of currents and power conversion efficiency (PCE). For such panels to be practical and commercially competitive, this huge bulk-resistance has to be minimized as much as possible. In this study, therefore, we introduce a new novel architecture that essentially compartmentalizes large panels into smaller modules that are connected to each other in a parallel fashion. In this architecture, the metal cathode layer is applied on the top as a series of lines whereas the anodic layer is independently connected to the pixilated cells at the bottom. As a result, these modules act like independent pixel cells wherein the damage from process and operation is limited individual pixel cells. The factors considered in validating the pixilated architecture presented here consisted of effect of number of pixels on efficiency and bulk electrical resistance. In addition, the study shows that pixilated architecture offers more uniform photoactive layers, and hence better photovoltaic performance because of the compartmentalization.

  8. Electric-pulse-induced resistance switching effect and related properties in manganite oxide structures

    NASA Astrophysics Data System (ADS)

    Xing, Zhongwen

    Rapid advances in information technology rely on high-speed and large-capacity nonvolatile memories. The novel electric-pulse-induced resistance (EPIR) switching effect has been obtained in the Pr0.7Ca 0.3MnO3 (PCMO) film sandwiched between two metal electrodes. The EPIR effect encompasses the reversible change of resistance of the PCMO device under the application of short, low voltage pulses. This reversible resistance switching at room temperature is very attractive for today's computing technology with its wide applications as a resistance random access memory (RRAM) due to its nonvolatility, fast write/read/erase speed, low power-consumption, and high radiation-hardness. In the first half of the dissertation I give a brief overview of the PCMO oxide and the EPIR switching effect, and an introduction to sample preparation and characterization. In the second half of the dissertation I present several research results. First, the resistance switching in Fe-doped PCMO (PCMFO) thin films is studied. Unlike in the PCMO-based EPIR devices, where the Ag/PCMO interface plays a crucial role, both the Ag/PCMFO interface and the bulk PCMFO are found to have significant contributions to the EPIR switching of the PCMFO-based device. A possible explanation is to extend the pulse-driven oxygen ion/vacancy motion model near the metal/PCMO interface region to the bulk PCMFO. Second, a thin ferroelectric PbZrTiO3 (PZT) layer is inserted between the top electrode and PCMO film as a buffer layer in the EPIR device. Compared with the Ag/PCMO/YBCO devices, the insertion of the PZT buffer into the Ag/PCMO interface is found to greatly increase the EPIR ratio and significantly decrease the threshold pulse voltage necessary to switching the resistive device. They are attributed to the resistive change of the depletion region at the Ag/PCMO interface including the PZT buffer, in which ferroelectric polarizations play a crucial role in the enhanced EPIR switching effect. Finally, we

  9. Multiple pulse-heating experiments with different current to determine total emissivity, heat capacity, and electrical resistivity of electrically conductive materials at high temperatures.

    PubMed

    Watanabe, Hiromichi; Yamashita, Yuichiro

    2012-01-01

    A modified pulse-heating method is proposed to improve the accuracy of measurement of the hemispherical total emissivity, specific heat capacity, and electrical resistivity of electrically conductive materials at high temperatures. The proposed method is based on the analysis of a series of rapid resistive self-heating experiments on a sample heated at different temperature rates. The method is used to measure the three properties of the IG-110 grade of isotropic graphite at temperatures from 850 to 1800 K. The problem of the extrinsic heating-rate effect, which reduces the accuracy of the measurements, is successfully mitigated by compensating for the generally neglected experimental error associated with the electrical measurands (current and voltage). The results obtained by the proposed method can be validated by the linearity of measured quantities used in the property determinations. The results are in reasonably good agreement with previously published data, which demonstrate the suitability of the proposed method, in particular, to the resistivity and total emissivity measurements. An interesting result is the existence of a minimum in the emissivity of the isotropic graphite at around 1120 K, consistent with the electrical resistivity results.

  10. Electrical Resistance of SiC/SiC Ceramic Matrix Composites for Damage Detection and Life-Prediction

    NASA Technical Reports Server (NTRS)

    Smith, Craig; Morscher, Gregory; Xia, Zhenhai

    2009-01-01

    Ceramic matrix composites (CMC) are suitable for high temperature structural applications such as turbine airfoils and hypersonic thermal protection systems due to their low density high thermal conductivity. The employment of these materials in such applications is limited by the ability to accurately monitor and predict damage evolution. Current nondestructive methods such as ultrasound, x-ray, and thermal imaging are limited in their ability to quantify small scale, transverse, in-plane, matrix cracks developed over long-time creep and fatigue conditions. CMC is a multifunctional material in which the damage is coupled with the material s electrical resistance, providing the possibility of real-time information about the damage state through monitoring of resistance. Here, resistance measurement of SiC/SiC composites under mechanical load at both room temperature monotonic and high temperature creep conditions, coupled with a modal acoustic emission technique, can relate the effects of temperature, strain, matrix cracks, fiber breaks, and oxidation to the change in electrical resistance. A multiscale model can in turn be developed for life prediction of in-service composites, based on electrical resistance methods. Results of tensile mechanical testing of SiC/SiC composites at room and high temperatures will be discussed. Data relating electrical resistivity to composite constituent content, fiber architecture, temperature, matrix crack formation, and oxidation will be explained, along with progress in modeling such properties.

  11. On the computation of a retina resistivity profile for applications in multi-scale modeling of electrical stimulation and absorption

    NASA Astrophysics Data System (ADS)

    Loizos, Kyle; RamRakhyani, Anil Kumar; Anderson, James; Marc, Robert; Lazzi, Gianluca

    2016-06-01

    This study proposes a methodology for computationally estimating resistive properties of tissue in multi-scale computational models, used for studying the interaction of electromagnetic fields with neural tissue, with applications to both dosimetry and neuroprosthetics. Traditionally, models at bulk tissue- and cellular-level scales are solved independently, linking resulting voltage from existing resistive tissue-scale models as extracellular sources to cellular models. This allows for solving the effects that external electric fields have on cellular activity. There are two major limitations to this approach: first, the resistive properties of the tissue need to be chosen, of which there are contradicting measurements in literature; second, the measurements of resistivity themselves may be inaccurate, leading to the mentioned contradicting results found across different studies. Our proposed methodology allows for constructing computed resistivity profiles using knowledge of only the neural morphology within the multi-scale model, resulting in a practical implementation of the effective medium theory; this bypasses concerns regarding the choice of resistive properties and accuracy of measurement setups. A multi-scale model of retina is constructed with an external electrode to serve as a test bench for analyzing existing and resulting resistivity profiles, and validation is presented through the reconstruction of a published resistivity profile of retina tissue. Results include a computed resistivity profile of retina tissue for use with a retina multi-scale model used to analyze effects of external electric fields on neural activity.

  12. On the computation of a retina resistivity profile for applications in multi-scale modeling of electrical stimulation and absorption

    PubMed Central

    Loizos, Kyle; RamRakhyani, Anil Kumar; Anderson, James; Marc, Robert; Lazzi, Gianluca

    2016-01-01

    This study proposes a methodology for computationally estimating resistive properties of tissue in multi-scale computational models, used for studying the interaction of electromagnetic fields with neural tissue, with applications to both dosimetry and neuroprosthetics. Traditionally, models at bulk tissue- and cellular-level scales are solved independently, linking resulting voltage from existing resistive tissue-scale models as extracellular sources to cellular models. This allows for solving the effects that external electric fields have on cellular activity. There are two major limitations to this approach: first, the resistive properties of the tissue need to be chosen, of which there are contradicting measurements in literature; second, the measurements of resistivity themselves may be inaccurate, leading to the mentioned contradicting results found across different studies. Our proposed methodology allows for constructing computed resistivity profiles using knowledge of only the neural morphology within the multi-scale model, resulting in a practical implementation of the effective medium theory; this bypasses concerns regarding the choice of resistive properties and accuracy of measurement setups. A multi-scale model of retina is constructed with an external electrode to serve as a test bench for analyzing existing and resulting resistivity profiles, and validation is presented through the reconstruction of a published resistivity profile of retina tissue. Results include a computed resistivity profile of retina tissue for use with a retina multi-scale model used to analyze effects of external electric fields on neural activity. PMID:27223656

  13. Microgravity and Electrical Resistivity Techniques for Detection of Caves and Clandestine Tunnels

    NASA Astrophysics Data System (ADS)

    Crawford, N. C.; Croft, L. A.; Cesin, G. L.; Wilson, S.

    2006-05-01

    The Center for Cave and Karst Studies, CCKS, has been using microgravity to locate caves from the ground's surface since 1985. The geophysical subsurface investigations began during a period when explosive and toxic vapors were rising from the karst aquifer under Bowling Green into homes, businesses, and schools. The USEPA provided the funding for this Superfund Emergency, and the CCKS was able to drill numerous wells into low-gravity anomalies to confirm and even map the route of caves in the underlying limestone bedrock. In every case, a low-gravity anomaly indicated a bedrock cave, a cave with a collapsed roof or locations where a bedrock cave had collapsed and filled with alluvium. At numerous locations, several wells were cored into microgravity anomalies and in every case, additional wells were drilled on both sides of the anomalies to confirm that the technique was in fact reliable. The wells cored on both sides of the anomalies did not intersect caves but instead intersected virtually solid limestone. Microgravity also easily detected storm sewers and even sanitary sewers, sometimes six meters (twenty feet) beneath the surface. Microgravity has also been used on many occasions to investigate sinkhole collapses. It identified potential collapse areas by detecting voids in the unconsolidated material above bedrock. The system will soon be tested over known tunnels and then during a blind test along a section of the U.S. border at Nogales, Arizona. The CCKS has experimented with other geophysical techniques, particularly ground penetrating radar, seismic and electrical resistivity. In the late 1990s the CCKS started using the Swift/Sting resistivity meter to perform karst geophysical subsurface investigations. The system provides good depth to bedrock data, but it is often difficult to interpret bedrock caves from the modeled data. The system typically used now by the CCKS to perform karst subsurface investigations is to use electrical resistivity traverses

  14. Constraining 3-D electrical resistance tomography with GPR reflection data for improved aquifer characterization

    NASA Astrophysics Data System (ADS)

    Doetsch, Joseph; Linde, Niklas; Pessognelli, Mirco; Green, Alan G.; Günther, Thomas

    2012-03-01

    Surface-based ground penetrating radar (GPR) and electrical resistance tomography (ERT) are common tools for aquifer characterization, because both methods provide data that are sensitive to hydrogeologically relevant quantities. To retrieve bulk subsurface properties at high resolution, we suggest incorporating structural information derived from GPR reflection data when inverting surface ERT data. This reduces resolution limitations, which might hinder quantitative interpretations. Surface-based GPR reflection and ERT data have been recorded on an exposed gravel bar within a restored section of a previously channelized river in northeastern Switzerland to characterize an underlying gravel aquifer. The GPR reflection data acquired over an area of 240 × 40 m map the aquifer's thickness and two internal sub-horizontal regions with different depositional patterns. The interface between these two regions and the boundary of the aquifer with the underlying clay are incorporated in an unstructured ERT mesh. Subsequent inversions are performed without applying smoothness constraints across these boundaries. Inversion models obtained by using these structural constraints contain subtle resistivity variations within the aquifer that are hardly visible in standard inversion models as a result of strong vertical smearing in the latter. In the upper aquifer region, with high GPR coherency and horizontal layering, the resistivity is moderately high (> 300 Ωm). We suggest that this region consists of sediments that were rearranged during more than a century of channelized flow. In the lower low coherency region, the GPR image reveals fluvial features (e.g., foresets) and generally more heterogeneous deposits. In this region, the resistivity is lower (~ 200 Ωm), which we attribute to increased amounts of fines in some of the well-sorted fluvial deposits. We also find elongated conductive anomalies that correspond to the location of river embankments that were removed in 2002.

  15. Electrical and Magneto-Resistivity Measurements on Amorphous Copper-Titanium Alloys at Low Temperatures

    NASA Astrophysics Data System (ADS)

    Fan, Renyong

    1992-01-01

    The anomalous transport properties of highly disordered metallic glasses, which require corrections to the classical Boltzmann theory, are due to quantum interference effects of the scattered electron waves. These corrections provide new contributions to the resistivity: "weak localization" and "electron-electron interaction". To study these quantum interference effects, we have made the highest-precision measurements, so far, of the resistances of the amorphous rm Cu_{50}Ti_{50 } and rm Cu_{60}Ti _{40} ribbons at much lower temperatures than before (15mK < T < 6K) and in small magnetic fields (0T < B < 0.2T). To measure the resistance and temperature accurately, we developed a novel method: measuring the resistance perpendicular to the ribbons with potassium as the non-superconducting glue between the CuTi ribbons and two Cu electrodes in order to make excellent electrical and thermal contact. With this method, we were able to measure the resistances with a relative precision of Deltarho/rho = 10^{-7}-10 ^{-8} and temperatures reliably down to 15mK with an error of less than 1mK. The zero field resistances and magnetoresistances were analyzed using weak localization theories that include the Zeeman splitting and electron-electron interaction theories. Possible background contributions from the K layers, the Cu electrodes, and their boundaries are quantified in the analysis. In zero field, these background contributions were negligible for T<3K. At zero magnetic field and T<0.15K, we found that electron -electron interaction dominates the resistance, while weak localization makes a nontrivial contribution to the resistance for T>0.15K. In contrast, at the lowest temperatures, the magnetoresistances were dominated by weak localization with Zeeman splitting and Maki-Thompson superconducting fluctuations. For higher magnetic fields and lowest temperatures (B/T > 1 T/K), we find discrepancies between our data and the theoretical calculations. We found that most of the

  16. Electrical Resistivity and Seismic Surveys at the Nevada Test Site, Nevada, April 2007

    USGS Publications Warehouse

    Haines, Seth S.; Burton, Bethany L.; Sweetkind, Donald S.; Asch, Theodore H.

    2008-01-01

    In April 2007, the USGS collected direct-current (DC) electrical resistivity data and shear- (S) and compressional- (P) wave seismic data to provide new detail of previously mapped, overlapping fault splays at two administrative areas in the Nevada Test Site (NTS). In NTS Area 7, we collected two-dimensional DC resistivity data along a transect crossing the Yucca Fault parallel to, and between, two transects along which resistivity data were collected in a previous study in 2006. In addition, we collected three-dimensional DC resistivity data in a grid that overlies part of the 2007 transect. The DC resistivity data show that the fault has a footwall that is more conductive than the hanging wall and an along-strike progression of the fault in a location where overlapping splays are present. Co-located with the northernmost of the two 2006 DC resistivity transects, we acquired S- and P-wave seismic data for both reflection and refraction processing. The S-wave data are corrupted by large amounts of converted (P-wave) energy likely due to the abundance of fractured caliche in the shallow subsurface. The P-wave data show minimal reflected energy, but they show clear refracted first arrivals. We have inverted these first arrival times to determine P-wave seismic velocity models. The seismic model for the transect in Area 7 shows low velocities extending to the base of the model at the location of the Yucca Fault, as well as low velocities at the eastern end of the transect, in the vicinity of the adjacent crater. These new surveys provide further detail about the geometry of the Yucca Fault in this location where it shows two overlapping splays. We collected P- and S-wave seismic data along a transect in the southern part of NTS Area 2, corresponding with the location of a 2006 DC resistivity transect that targeted a set of small faults identified with field mapping. Again, the S-wave data are difficult to interpret. The P-wave data show clear first arrivals that we

  17. Electrical Resistivity and Seismic Surveys at the Nevada Test Site, Nevada, April 2007

    SciTech Connect

    Seth S. Haines; Bethany L. Burton; Donald S. Sweetkind; Theodore H. Asch

    2009-03-30

    In April 2007, the USGS collected direct-current (DC) electrical resistivity data and shear- (S) and compressional- (P) wave seismic data to provide new detail of previously mapped, overlapping fault splays at two administrative areas in the Nevada Test Site (NTS). In NTS Area 7, we collected two-dimensional DC resistivity data along a transect crossing the Yucca Fault parallel to, and between, two transects along which resistivity data were collected in a previous study in 2006. In addition, we collected three-dimensional DC resistivity data in a grid that overlies part of the 2007 transect. The DC resistivity data show that the fault has a footwall that is more conductive than the hanging wall and an along-strike progression of the fault in a location where overlapping splays are present. Co-located with the northernmost of the two 2006 DC resistivity transects, we acquired S- and P-wave seismic data for both reflection and refraction processing. The S-wave data are corrupted by large amounts of converted (P-wave) energy likely due to the abundance of fractured caliche in the shallow subsurface. The P-wave data show minimal reflected energy, but they show clear refracted first arrivals. We have inverted these first arrival times to determine P-wave seismic velocity models. The seismic model for the transect in Area 7 shows low velocities extending to the base of the model at the location of the Yucca Fault, as well as low velocities at the eastern end of the transect, in the vicinity of the adjacent crater. These new surveys provide further detail about the geometry of the Yucca Fault in this location where it shows two overlapping splays. We collected P- and S-wave seismic data along a transect in the southern part of NTS Area 2, corresponding with the location of a 2006 DC resistivity transect that targeted a set of small faults identified with field mapping. Again, the S-wave data are difficult to interpret. The P-wave data show clear first arrivals that we

  18. Electrical Resistivity Tomography of the Karstic Aquifer of Bittit spring (Middle Atlas, Morocco)

    NASA Astrophysics Data System (ADS)

    Qarqori, Kh.; Rouai, M.; Moreau, F.; Saracco, G.; Hermitte, D.; Boualoul, M.; Dauteuil, O.; Biessy, G.; Sahbi, H.

    2009-04-01

    The Tabular Middle Atlas reservoir is one of the most important aquifers in northern Morocco. It is mainly a water table fractured reservoir consisting of Lias limestone and dolomite. The matrix permeability is very low and water flows essentially along open fractures and karsts. The Bittit Spring belongs to this karstic system and constitutes an important aquifer lying at the junction between the tabular reservoir and the Sais basin. Bittit spring, with an average annual discharge of about 1600 l/s, contributes largely to water supply of the big city of Meknes. Groundwater circulation is complex due to tectonics and to presence of karstic Quaternary travertine overlying Lias carbonate. In Bittit area, travertine is mostly covered by Quaternary basalt. Up to now water flow paths and the underground karst organization remain misknown, and turbidity affects the water quality after rain events. To highlight these issues, an integrated geophysical survey was performed in this area in the framework of a French-Moroccan scientific project. The geophysical imaging was carried out mainly by Electrical Resistivity Tomography (ERT). Resistivity data were acquired by an ABEM Terrameter SAS1000 and a multi-electrode Lund system imaging using a Wenner array configuration of 64 electrodes and 5m spacing, reaching a depth of about 50m. Topographic corrections and 2D inversion models were performed using Res2Dinv software package. Seven 2D resistivity high resolution images have been obtained allowing to detect, delineate important fractures and also to hydrogeological characterization of the underground karst. A borehole of 100m depth was drilled in order to correlate and calibrate geophysical data and proposed models. Two sub-vertical fracture families have been identified with NE-SW and NW-SE directions respectively. These results correlate well with fracture data analysis gathered from remote sensing Spot images at large scale, and from local field fracture scanline surveys. A

  19. Hydrogeological application of electrical resistivity tomography: Implementing a fixed-electrode strategy

    NASA Astrophysics Data System (ADS)

    Pezeshkpour, Parsa

    The requirements of environmental assessments and of understanding and monitoring in-situ mass and heat processes in porous media have led to the development of geophysical methods for remote mapping and monitoring of contaminant plumes and fluid migration. With the possible exception of seismic approaches, electrical methods known as Electrical Resistivity Tomography (ERT) have become the most widely studied and used for these purposes. Wherever a sufficient contrast in ground resistivity is generated by human or natural processes, monitoring the resistivity structure over time may give insight into these processes. ERT has monitoring applications in processes such as Enhanced Oil Recovery (EOR), Slurry Fracture Injection (SFI), and monitoring transport processes in hydrogeology. A permanent electrode arrangement for long term monitoring removes the effects of Earth's heterogeneity and anisotropy when a process is analyzed as a function of time. As a starting point on the work described in this thesis, ERT data were collected from a Cambridge, Ontario, sand pit before, immediately after and one week following a 11000 liters slurry injection. These measurements verified that ERT could detect changes caused by the injection and later movement of this conductive mixture in the ground. The commercial equipment used for these measurements was not well suited to the tasks, mainly because it was extremely slow. Further, there was a lack of robust and user-friendly three-dimensional modeling software to use as a means of predicting response and---eventually---as the engine of an inversion routine. Finally, it was difficult to analyze the injection situation in terms of how best to place a limited number of surface and borehole electrodes to most effectively monitor the injection fluids. The remainder of the thesis addresses these problems. The first objective was to design and construct a more suitable ERT measurement system. The second objective was to adapt SALTFLOW as

  20. Moisture distribution during conventional or electrical resistance oven baking of bread dough and subsequent storage.

    PubMed

    Derde, Liesbeth J; Gomand, Sara V; Courtin, Christophe M; Delcour, Jan A

    2014-07-01

    Electrical resistance oven (ERO) baking processes bread dough with little temperature gradient in the baking dough. Heating of the dough by means of an ERO is based on the principles of Joule's first law and Ohm's law. This study compared the changes in moisture distribution and physical changes in starch of breads conventionally baked or using an ERO. The moisture contents in fresh ERO breads are generally lower than those in conventional breads. During storage of conventionally baked breads, water migrates from the crumb to the crust and moisture contents decrease throughout the bread crumb. Evidently, less moisture redistribution occurs in ERO breads. Also, the protons of ERO bread constituents were less mobile than their counterparts in conventional bread. Starch retrogradation occurs to similar extents in conventional and ERO bread. As a result, the changes in proton mobility cannot be attributed to differences in levels of retrograded starch and seem to be primarily determined by the overall lower moisture content.

  1. Stable transformation of Populus and incorporation of pest resistance by electric discharge particle acceleration.

    PubMed

    McCown, B H; McCabe, D E; Russell, D R; Robison, D J; Barton, K A; Raffa, K F

    1991-02-01

    Three different target tissues (protoplast-derived cells, nodules, and stems) and two unrelated hybrid genotypes of Populus (P. alba x P. grandidentata 'Crandon' and P. nigra 'Betulifolia' x P. trichocarpa) have been stably transformed by electric discharge particle acceleration using a 18.7 kb plasmid containing NOS-NPT, CaMV 35S-GUS, and CaMV 35S-BT. Four transformed plants of one hybrid genotype, NC5339, containing all 3 genes were recovered and analyzed. Two expressed GUS and one was highly resistant to feeding by 2 lepidopteran pests (the forest tent caterpillar, Malacosoma disstria, and the gypsy moth, Lymantria dispar.) Pretreatment of the target tissues, fine-tuning of the bombardment parameters, and the use of a selection technique employing flooding of the target tissues were important for reliable recovery of transformed plants.

  2. Diffusion in liquid metal systems. [information on electrical resistivity and thermal conductivity

    NASA Technical Reports Server (NTRS)

    Ukanwa, A. O.

    1975-01-01

    Physical properties of twenty liquid metals are reported; some of the data on such liquid metal properties as density, electrical resistivity, thermal conductivity, and heat capacity are summarized in graphical form. Data on laboratory handling and safety procedure are summarized for each metal; heat-transfer-correlations for liquid metals under various conditions of laminar and turbulent flow are included. Where sufficient data were available, temperature equations of properties were obtained by the method of least-squares fit. All values of properties given are valid in the given liquid phase ranges only. Additional tabular data on some 40 metals are reported in the appendix. Included is a brief description of experiments that were performed to investigate diffusion in liquid indium-gallium systems.

  3. Development of superconducting YBa2Cu3O(x) wires with low resistance electrical contacts

    NASA Technical Reports Server (NTRS)

    Buoncristiani, A. M.; Byvik, C. E.; Caton, R.; Selim, R.; Lee, B. I.; Modi, V.; Sherrill, M.; Leigh, H. D.; Fain, C. C.; Lewis, G.

    1993-01-01

    Materials exhibiting superconductivity above liquid nitrogen temperatures (77 K) will enable new applications of this phenomena. One of the first commercial applications of this technology will be superconducting magnets for medical imaging. However, a large number of aerospace applications of the high temperature superconducting materials have also been identified. These include magnetic suspension and balance of models in wind tunnels and resistanceless leads to anemometers. The development of superconducting wires fabricated from the ceramic materials is critical for these applications. The progress in application of a patented fiber process developed by Clemson University for the fabrication of superconducting wires is reviewed. The effect of particle size and heat treatment on the quality of materials is discussed. Recent advances made at Christopher Newport College in the development of micro-ohm resistance electrical contacts which are capable of carrying the highest reported direct current to this material is presented.

  4. Method for reducing formation of electrically resistive layer on ferritic stainless steels

    SciTech Connect

    Rakowski, James M.

    2013-09-10

    A method of reducing the formation of electrically resistive scale on a an article comprising a silicon-containing ferritic stainless subjected to oxidizing conditions in service includes, prior to placing the article in service, subjecting the article to conditions under which silica, which includes silicon derived from the steel, forms on a surface of the steel. Optionally, at least a portion of the silica is removed from the surface to placing the article in service. A ferritic stainless steel alloy having a reduced tendency to form silica on at least a surface thereof also is provided. The steel includes a near-surface region that has been depleted of silicon relative to a remainder of the steel.

  5. Microstructural characterization and hardness properties of electric resistance welding titanium joints for dental applications.

    PubMed

    Ceschini, Lorella; Boromei, Iuri; Morri, Alessandro; Nardi, Diego; Sighinolfi, Gianluca; Degidi, Marco

    2015-06-01

    The electric resistance welding procedure is used to join a titanium bar with specific implant abutments in order to produce a framework directly in the oral cavity of the patient. This investigation studied the effects of the welding process on microstructure and hardness properties of commercially pure (CP2 and CP4) Ti components. Different welding powers and cooling procedures were applied to bars and abutments, normally used to produce the framework, in order to simulate the clinical intraoral welding procedure. The analyses highlighted that the joining process did not induce appreciable changes in the geometry of the abutments. However, because of unavoidable microstructural modifications in the welded zones, the hardness decreased to values lower than those of the unwelded CP2 and CP4 Ti grades, irrespective of the welding environments and parameters. PMID:26045042

  6. Tracking tracer motion in a 4-D electrical resistivity tomography experiment

    NASA Astrophysics Data System (ADS)

    Ward, W. O. C.; Wilkinson, P. B.; Chambers, J. E.; Nilsson, H.; Kuras, O.; Bai, L.

    2016-05-01

    A new framework for automatically tracking subsurface tracers in electrical resistivity tomography (ERT) monitoring images is presented. Using computer vision and Bayesian inference techniques, in the form of a Kalman filter, the trajectory of a subsurface tracer is monitored by predicting and updating a state model representing its movements. Observations for the Kalman filter are gathered using the maximally stable volumes algorithm, which is used to dynamically threshold local regions of an ERT image sequence to detect the tracer at each time step. The application of the framework to the results of 2-D and 3-D tracer monitoring experiments show that the proposed method is effective for detecting and tracking tracer plumes in ERT images in the presence of noise, without intermediate manual intervention.

  7. Microstructural characterization and hardness properties of electric resistance welding titanium joints for dental applications.

    PubMed

    Ceschini, Lorella; Boromei, Iuri; Morri, Alessandro; Nardi, Diego; Sighinolfi, Gianluca; Degidi, Marco

    2015-06-01

    The electric resistance welding procedure is used to join a titanium bar with specific implant abutments in order to produce a framework directly in the oral cavity of the patient. This investigation studied the effects of the welding process on microstructure and hardness properties of commercially pure (CP2 and CP4) Ti components. Different welding powers and cooling procedures were applied to bars and abutments, normally used to produce the framework, in order to simulate the clinical intraoral welding procedure. The analyses highlighted that the joining process did not induce appreciable changes in the geometry of the abutments. However, because of unavoidable microstructural modifications in the welded zones, the hardness decreased to values lower than those of the unwelded CP2 and CP4 Ti grades, irrespective of the welding environments and parameters.

  8. Electrical resistivity under extreme conditions in the Ce3Ir4Sn13 heavy fermion compound

    NASA Astrophysics Data System (ADS)

    Collave, J. R.; Borges, H. A.; Ramos, S. M.; Hering, E. N.; Fontes, M. B.; Baggio-Saitovitch, E.; Eichler, A.; Bittar, E. M.; Pagliuso, P. G.

    2014-01-01

    We have performed measurements of temperature dependent electrical resistivity ρ(T) under pressures up to 27 kbar and down to 0.1 K on single crystals of the Ce3Ir4Sn13 heavy fermion compound. At ambient pressure (P=0) we have identified in the ρ(T) data interesting features associated with the presence of crystalline field effects, magnetic correlations, Kondo single impurity scattering and, possibly, a low temperature structural phase transition. All these features were mapped as a function of pressure which allowed us to construct a pressure-temperature phase diagram with these temperature scales. We have also carried out measurements of ρ(T) as a function of magnetic fields up to H=8 T and the important temperature scales in ρ(T) were followed with field. Enlightened also by temperature dependent specific heat experiments we discuss the possible microscopic origins of the features found in our ρ(T) data.

  9. Demonstration of combined zero-valent iron and electrical resistance heating for in situ trichloroethene remediation.

    PubMed

    Truex, M J; Macbeth, T W; Vermeul, V R; Fritz, B G; Mendoza, D P; Mackley, R D; Wietsma, T W; Sandberg, G; Powell, T; Powers, J; Pitre, E; Michalsen, M; Ballock-Dixon, S J; Zhong, L; Oostrom, M

    2011-06-15

    The effectiveness of in situ treatment using zero-valent iron (ZVI) for nonaqueous phase or significant sediment-associated contaminant mass can be limited by relatively low rates of mass transfer to bring contaminants in contact with the reactive media. For a field test in a trichloroethene (TCE) source area, combining moderate-temperature subsurface electrical resistance heating with in situ ZVI treatment was shown to accelerate TCE treatment by a factor of about 4 based on organic daughter products and a factor about 8 based on chloride concentrations. A mass-discharge-based analysis was used to evaluate reaction, dissolution, and volatilization processes at ambient groundwater temperature (~10 °C) and as temperature was increased up to about 50 °C. Increased reaction and contaminant dissolution were observed with increased temperature, but vapor- or aqueous-phase migration of TCE out of the treatment zone was minimal during the test because reactions maintained low aqueous-phase TCE concentrations.

  10. Technique for anisotropic extension of organic crystals: Application to temperature dependence of electrical resistance

    NASA Astrophysics Data System (ADS)

    Yamamoto, Takashi; Kato, Reizo; Yamamoto, Hiroshi M.; Fukaya, Atsuko; Yamasawa, Kenji; Takahashi, Ichiro; Akutsu, Hiroki; Akutsu-Sato, Akane; Day, Peter

    2007-08-01

    We have developed a technique for the anisotropic extension of fragile molecular crystals. The pressure medium and the instrument, which extends the pressure medium, are both made from epoxy resin. Since the thermal contraction of our instrument is identical to that of the pressure medium, the strain applied to the pressure medium has no temperature dependence down to 2K. Therefore, the degree of extension applied to the single crystal at low temperatures is uniquely determined from the degree of extension in the pressure medium and thermal contractions of the epoxy resin and the single crystal at ambient pressure. Using this novel instrument, we have measured the temperature dependence of the electrical resistance of metallic, superconducting, and insulating materials. The experimental results are discussed from the viewpoint of the extension (compression) of the lattice constants along the parallel (perpendicular) direction.

  11. Removal of oxides from alkali metal melts by reductive titration to electrical resistance-change end points

    DOEpatents

    Tsang, Floris Y.

    1980-01-01

    Alkali metal oxides dissolved in alkali metal melts are reduced with soluble metals which are converted to insoluble oxides. The end points of the reduction is detected as an increase in electrical resistance across an alkali metal ion-conductive membrane interposed between the oxide-containing melt and a material capable of accepting the alkali metal ions from the membrane when a difference in electrical potential, of the appropriate polarity, is established across it. The resistance increase results from blocking of the membrane face by ions of the excess reductant metal, to which the membrane is essentially non-conductive.

  12. Coexistence of electric field controlled ferromagnetism and resistive switching for TiO{sub 2} film at room temperature

    SciTech Connect

    Ren, Shaoqing; Qin, Hongwei; Bu, Jianpei; Zhu, Gengchang; Xie, Jihao; Hu, Jifan E-mail: hu-jf@vip.163.com

    2015-08-10

    The Ag/TiO{sub 2}/Nb:SrTiO{sub 3}/Ag device exhibits the coexistence of electric field controlled ferromagnetism and resistive switching at room temperature. The bipolar resistive switching in Ag/TiO{sub 2}/Nb:SrTiO{sub 3}/Ag device may be dominated by the modulation of Schottky-like barrier with the electron injection-trapped/detrapped process at the interface of TiO{sub 2}/Nb:SrTiO{sub 3}. We suggest that the electric field-induced magnetization modulation originates mainly from the creation/annihilation of lots of oxygen vacancies in TiO{sub 2}.

  13. Electrical Resistance as a NDE Technique to Monitor Processing and Damage Accumulation in SiC/SiC Composites

    NASA Technical Reports Server (NTRS)

    Smith, Craig; Morscher, Gregory N.; Xia, Zhenhai

    2008-01-01

    Ceramic matrix composites are suitable for high temperature structural applications such as turbine airfoils and hypersonic thermal protection systems. The employment of these materials in such applications is limited by the ability to process components reliable and to accurately monitor and predict damage evolution that leads to failure under stressed-oxidation conditions. Current nondestructive methods such as ultrasound, x-ray, and thermal imaging are limited in their ability to quantify small scale, transverse, in-plane, matrix cracks developed over long-time creep and fatigue conditions. Electrical resistance of SiC/SiC composites is one technique that shows special promise towards this end. Since both the matrix and the fibers are conductive, changes in matrix or fiber properties should relate to changes in electrical conductivity along the length of a specimen or part. Initial efforts to quantify the electrical resistance of different fiber and different matrix SiC/SiC composites will be presented. Also, the effect of matrix cracking on electrical resistivity for several composite systems will be presented. The implications towards electrical resistance as a technique applied to composite processing, damage detection, and life-modeling will be discussed.

  14. Novel experimental design for high pressure-high temperature electrical resistance measurements in a "Paris-Edinburgh" large volume press.

    PubMed

    Matityahu, Shlomi; Emuna, Moran; Yahel, Eyal; Makov, Guy; Greenberg, Yaron

    2015-04-01

    We present a novel experimental design for high sensitivity measurements of the electrical resistance of samples at high pressures (0-6 GPa) and high temperatures (300-1000 K) in a "Paris-Edinburgh" type large volume press. Uniquely, the electrical measurements are carried out directly on a small sample, thus greatly increasing the sensitivity of the measurement. The sensitivity to even minor changes in electrical resistance can be used to clearly identify phase transitions in material samples. Electrical resistance measurements are relatively simple and rapid to execute and the efficacy of the present experimental design is demonstrated by measuring the electrical resistance of Pb, Sn, and Bi across a wide domain of temperature-pressure phase space and employing it to identify the loci of phase transitions. Based on these results, the phase diagrams of these elements are reconstructed to high accuracy and found to be in excellent agreement with previous studies. In particular, by mapping the locations of several well-studied reference points in the phase diagram of Sn and Bi, it is demonstrated that a standard calibration exists for the temperature and pressure, thus eliminating the need for direct or indirect temperature and pressure measurements. The present technique will allow simple and accurate mapping of phase diagrams under extreme conditions and may be of particular importance in advancing studies of liquid state anomalies.

  15. Novel experimental design for high pressure-high temperature electrical resistance measurements in a "Paris-Edinburgh" large volume press

    NASA Astrophysics Data System (ADS)

    Matityahu, Shlomi; Emuna, Moran; Yahel, Eyal; Makov, Guy; Greenberg, Yaron

    2015-04-01

    We present a novel experimental design for high sensitivity measurements of the electrical resistance of samples at high pressures (0-6 GPa) and high temperatures (300-1000 K) in a "Paris-Edinburgh" type large volume press. Uniquely, the electrical measurements are carried out directly on a small sample, thus greatly increasing the sensitivity of the measurement. The sensitivity to even minor changes in electrical resistance can be used to clearly identify phase transitions in material samples. Electrical resistance measurements are relatively simple and rapid to execute and the efficacy of the present experimental design is demonstrated by measuring the electrical resistance of Pb, Sn, and Bi across a wide domain of temperature-pressure phase space and employing it to identify the loci of phase transitions. Based on these results, the phase diagrams of these elements are reconstructed to high accuracy and found to be in excellent agreement with previous studies. In particular, by mapping the locations of several well-studied reference points in the phase diagram of Sn and Bi, it is demonstrated that a standard calibration exists for the temperature and pressure, thus eliminating the need for direct or indirect temperature and pressure measurements. The present technique will allow simple and accurate mapping of phase diagrams under extreme conditions and may be of particular importance in advancing studies of liquid state anomalies.

  16. Combined DC Resistivity Survey and Electric Conductivity- Dielectric Permittivity Measurement at Sag Pond near Lembang Fault, West Java, Indonesia

    NASA Astrophysics Data System (ADS)

    Iryanti, Mimin; Srigutomo, Wahyu; Bijaksana, Satria; Setiawan, Tedy

    2016-08-01

    Lembang Fault is a normal fault situated at the southern flank of Tangkuban Parahu Volcano in West Java Indonesia. The fault's movement may have caused the formation of sag pond in the vicinity of its which is characterized by the soil layers of the sag pond. The characteristics of the soil can be examined based on its electrical properties such as conductivity (the inverse of resistivity) and dielectric permittivity. Direct field measurement was conducted using DC-resistivity Wenner-Schlumberger method on the sag pond as well as laboratory resistivity measurement of cores taken from the sag pond. Two resistivity crosssections were obtained after performing 2D inversion of the data which reveal that the resistivity distribution consist of a resistive layer (40-60 ohm.m) overlying a medium resistive layer (30-35 ohm.m). The third layer has relatively low resistivity of 16-25 ohm.m. At the intersection of these two lines we took coring samples down to depth of 5 m below surface and measured the electrical conductivity and dielectric permittivity for each 1 cm of sample using EM-50 data logger. Results from both field and laboratory measurement were analysed to get a better understanding of the sag pond.

  17. Neuromuscular Electrical Stimulation–Induced Resistance Training After SCI: A Review of the Dudley Protocol

    PubMed Central

    Yarar-Fisher, Ceren; Mahoney, Edward T.; McCully, Kevin K.

    2015-01-01

    Background: Neuromuscular electrical stimulation (NMES), often referred to as functional electrical stimulation (FES), has been used to activate paralyzed skeletal muscle in people with spinal cord injury (SCI). The goal of NMES has been to reverse some of the dramatic losses in skeletal muscle mass, to stimulate functional improvements in people with incomplete paralysis, and to produce some of the health benefits associated with exercise. Objective: The purpose of this brief review is to describe a quantifiable resistance training form of NMES developed by Gary A. Dudley. Methods: People with motor complete SCI were first tested to confirm that an NMES-induced muscle contraction of the quadriceps muscle could be achieved. The contraction stimulus consisted of biphasic pulses at 35 Hz performed with increasing current up to what was needed to produce full knee extension. Four sets of 10 knee extensions were elicited, if possible. Training occurred biweekly for 3 to 6 months, with ankle weights being increased up to an added weight of 9.1 kg if the 40 repetitions could be performed successfully for 2 sessions. Results: Many participants have performed this protocol without adverse events, and all participants showed progression in the number of repetitions and/or the amount of weight lifted. Large increases in muscle mass occur, averaging 30% to 40%. Additional physiological adaptations to stimulated muscle have also been reported. Conclusions: These results demonstrate that the affected skeletal muscle after SCI responds robustly to progressive resistance training many years after injury. Future work with NMES should determine whether gains in lean mass translate to improved health, function, and quality of life. PMID:26689694

  18. Exploration of resistive targets within shallow marine environments using the circular electrical dipole and the differential electrical dipole methods: a time-domain modelling study

    NASA Astrophysics Data System (ADS)

    Haroon, Amir; Mogilatov, Vladimir; Goldman, Mark; Bergers, Rainer; Tezkan, Bülent

    2016-05-01

    Two novel transient controlled source electromagnetic methods called circular electrical dipole (CED) and differential electrical dipole (DED) are theoretically analysed for applications in shallow marine environments. 1-D and 3-D time-domain modelling studies are used to investigate the detectability and applicability of the methods when investigating resistive layers/targets representing hydrocarbon-saturated formations. The results are compared to the conventional time-domain horizontal electrical dipole (HED) and vertical electrical dipole (VED) sources. The applied theoretical modelling studies demonstrate that CED and DED have higher signal detectability towards resistive targets compared to TD-CSEM, but demonstrate significantly poorer signal amplitudes. Future CED/DED applications will have to solve this issue prior to measuring. Furthermore, the two novel methods have very similar detectability characteristics towards 3-D resistive targets embedded in marine sediments as VED while being less susceptible towards non-verticality. Due to the complex transmitter design of CED/DED the systems are prone to geometrical errors. Modelling studies show that even small transmitter inaccuracies have strong effects on the signal characteristics of CED making an actual marine application difficult at the present time. In contrast, the DED signal is less affected by geometrical errors in comparison to CED and may therefore be more adequate for marine applications.

  19. Eradication of multidrug-resistant pseudomonas biofilm with pulsed electric fields.

    PubMed

    Khan, Saiqa I; Blumrosen, Gaddi; Vecchio, Daniela; Golberg, Alexander; McCormack, Michael C; Yarmush, Martin L; Hamblin, Michael R; Austen, William G

    2016-03-01

    Biofilm formation is a significant problem, accounting for over eighty percent of microbial infections in the body. Biofilm eradication is problematic due to increased resistance to antibiotics and antimicrobials as compared to planktonic cells. The purpose of this study was to investigate the effect of Pulsed Electric Fields (PEF) on biofilm-infected mesh. Prolene mesh was infected with bioluminescent Pseudomonas aeruginosa and treated with PEF using a concentric electrode system to derive, in a single experiment, the critical electric field strength needed to kill bacteria. The effect of the electric field strength and the number of pulses (with a fixed pulse length duration and frequency) on bacterial eradication was investigated. For all experiments, biofilm formation and disruption were confirmed with bioluminescent imaging and Scanning Electron Microscopy (SEM). Computation and statistical methods were used to analyze treatment efficiency and to compare it to existing theoretical models. In all experiments 1500 V are applied through a central electrode, with pulse duration of 50 μs, and pulse delivery frequency of 2 Hz. We found that the critical electric field strength (Ecr) needed to eradicate 100-80% of bacteria in the treated area was 121 ± 14 V/mm when 300 pulses were applied, and 235 ± 6.1 V/mm when 150 pulses were applied. The area at which 100-80% of bacteria were eradicated was 50.5 ± 9.9 mm(2) for 300 pulses, and 13.4 ± 0.65 mm(2) for 150 pulses. 80% threshold eradication was not achieved with 100 pulses. The results indicate that increased efficacy of treatment is due to increased number of pulses delivered. In addition, we that showed the bacterial death rate as a function of the electrical field follows the statistical Weibull model for 150 and 300 pulses. We hypothesize that in the clinical setting, combining systemic antibacterial therapy with PEF will yield a synergistic effect leading to improved

  20. Eradication of multidrug-resistant pseudomonas biofilm with pulsed electric fields.

    PubMed

    Khan, Saiqa I; Blumrosen, Gaddi; Vecchio, Daniela; Golberg, Alexander; McCormack, Michael C; Yarmush, Martin L; Hamblin, Michael R; Austen, William G

    2016-03-01

    Biofilm formation is a significant problem, accounting for over eighty percent of microbial infections in the body. Biofilm eradication is problematic due to increased resistance to antibiotics and antimicrobials as compared to planktonic cells. The purpose of this study was to investigate the effect of Pulsed Electric Fields (PEF) on biofilm-infected mesh. Prolene mesh was infected with bioluminescent Pseudomonas aeruginosa and treated with PEF using a concentric electrode system to derive, in a single experiment, the critical electric field strength needed to kill bacteria. The effect of the electric field strength and the number of pulses (with a fixed pulse length duration and frequency) on bacterial eradication was investigated. For all experiments, biofilm formation and disruption were confirmed with bioluminescent imaging and Scanning Electron Microscopy (SEM). Computation and statistical methods were used to analyze treatment efficiency and to compare it to existing theoretical models. In all experiments 1500 V are applied through a central electrode, with pulse duration of 50 μs, and pulse delivery frequency of 2 Hz. We found that the critical electric field strength (Ecr) needed to eradicate 100-80% of bacteria in the treated area was 121 ± 14 V/mm when 300 pulses were applied, and 235 ± 6.1 V/mm when 150 pulses were applied. The area at which 100-80% of bacteria were eradicated was 50.5 ± 9.9 mm(2) for 300 pulses, and 13.4 ± 0.65 mm(2) for 150 pulses. 80% threshold eradication was not achieved with 100 pulses. The results indicate that increased efficacy of treatment is due to increased number of pulses delivered. In addition, we that showed the bacterial death rate as a function of the electrical field follows the statistical Weibull model for 150 and 300 pulses. We hypothesize that in the clinical setting, combining systemic antibacterial therapy with PEF will yield a synergistic effect leading to improved

  1. Examining diel patterns of soil and xylem moisture using electrical resistivity imaging

    NASA Astrophysics Data System (ADS)

    Mares, Rachel; Barnard, Holly R.; Mao, Deqiang; Revil, André; Singha, Kamini

    2016-05-01

    The feedbacks among forest transpiration, soil moisture, and subsurface flowpaths are poorly understood. We investigate how soil moisture is affected by daily transpiration using time-lapse electrical resistivity imaging (ERI) on a highly instrumented ponderosa pine and the surrounding soil throughout the growing season. By comparing sap flow measurements to the ERI data, we find that periods of high sap flow within the diel cycle are aligned with decreases in ground electrical conductivity and soil moisture due to drying of the soil during moisture uptake. As sap flow decreases during the night, the ground conductivity increases as the soil moisture is replenished. The mean and variance of the ground conductivity decreases into the summer dry season, indicating drier soil and smaller diel fluctuations in soil moisture as the summer progresses. Sap flow did not significantly decrease through the summer suggesting use of a water source deeper than 60 cm to maintain transpiration during times of shallow soil moisture depletion. ERI captured spatiotemporal variability of soil moisture on daily and seasonal timescales. ERI data on the tree showed a diel cycle of conductivity, interpreted as changes in water content due to transpiration, but changes in sap flow throughout the season could not be interpreted from ERI inversions alone due to daily temperature changes.

  2. Cost-reduction method for delamination monitoring using electrical resistance changes of CFRP beam

    NASA Astrophysics Data System (ADS)

    Todoroki, A.; Ueda, M.

    2004-02-01

    Delamination is a significant defect of laminated composites. The present study employs an electrical resistance change method in an attempt to identify internal delaminations experimentally. The method adopts reinforcing carbon fibers as sensors. In our previous paper, an actual delamination crack in a Carbon Fiber Reinforced Plastics (CFRP) laminate was experimentally identified with artificial neural networks (ANN) or response surfaces created from a large number of experiments. The experimental results were used for learning of the ANN or regression of the response surfaces. For the actual application of the method, it is indispensable to reduce the number of experiments to suppress the total experimental cost. In the present study, therefore, FEM analyses are employed to make sets of data for learning of the ANN. First, electrical conductivity of the CFRP laminate is identified by means of the least estimation error method. After that, the results of FEM analyses are used for learning of the ANN. The method is applied to actual delamination monitoring of CFRP beams. As a result, the method successfully monitored the delamination location and size only with ten experiments.

  3. Identification of Karstic Caves by Utilizing Two-Dimensional Electrical Resistivity Imaging (ERI) Method

    NASA Astrophysics Data System (ADS)

    Uçar, Fatih; Aktürk, Özgür

    2015-04-01

    The region consisting of easily soluble rocks is generally defined as karstic terrain and it is characterized by surface collapse and small or large scale dissolution voids on rock surface. Formation and expansion of these voids may cause dangerous situation during surface/subsurface construction works. Therefore, it is important to determine the location, size and dimension of karstic caves. Geophysical investigations are very helpful in determining the boundaries of geological subsurface structures. In order to determine subsurface profile and characteristic of soil, surface geophysical methods can be successfully applied. Electrical Resistivity Imaging (ERI) is the most important methods among the convenient and commonly used methods to determine subsurface profile. By using this method, cavernous and weathered zones can be determined easily. Within the scope of this study, near surface profiles were determined by utilizing ERI at Akdeniz University Campus and Masa Dağı region located in the city of Antalya, Turkey. The results obtained from four different locations in the Akdeniz University campus compared only with Vertical Electrical Sounding (VES) analyses. Since topographic cross-section is clearly seen in two different locations around Masa Dağı location, ERI results were superimposed with topography and also compared with VES. As a result, presences of subsurface cavities were determined and illustrated using 2D colorful images. Keywords: ERI, VES, Karstic terrain, Cave, Antalya

  4. Instrument for evaluating the electrical resistance and wavelength-resolved transparency of stretchable electronics during strain

    SciTech Connect

    Azar, A. D.; Finley, E.; Harris, K. D.

    2015-01-15

    A complete analysis of strain tolerance in a stretchable transparent conductor (TC) should include tracking of both electrical conductivity and transparency during strain; however, transparency is generally neglected in contemporary analyses. In this paper, we describe an apparatus that tracks both parameters while TCs of arbitrary composition are deformed under stretching-mode strain. We demonstrate the tool by recording the electrical resistance and light transmission spectra for indium tin oxide-coated plastic substrates under both linearly increasing strain and complex cyclic strain processes. The optics are sensitive across the visible spectrum and into the near-infrared region (∼400-900 nm), and without specifically optimizing for sampling speed, we achieve a time resolution of ∼200 ms. In our automated analysis routine, we include a calculation of a common TC figure of merit (FOM), and because solar cell electrodes represent a key TC application, we also weigh both our transparency and FOM results against the solar power spectrum to determine “solar transparency” and “solar FOM.” Finally, we demonstrate how the apparatus may be adapted to measure the basic performance metrics for complete solar cells under uniaxial strain.

  5. Ion permeability of artificial membranes evaluated by diffusion potential and electrical resistance measurements.

    PubMed

    Shlyonsky, Vadim

    2013-12-01

    In the present article, a novel model of artificial membranes that provides efficient assistance in teaching the origins of diffusion potentials is proposed. These membranes are made of polycarbonate filters fixed to 12-mm plastic rings and then saturated with a mixture of creosol and n-decane. The electrical resistance and potential difference across these membranes can be easily measured using a low-cost volt-ohm meter and home-made Ag/AgCl electrodes. The advantage of the model is the lack of ionic selectivity of the membrane, which can be modified by the introduction of different ionophores to the organic liquid mixture. A membrane treated with the mixture containing valinomycin generates voltages from -53 to -25 mV in the presence of a 10-fold KCl gradient (in to out) and from -79 to -53 mV in the presence of a bi-ionic KCl/NaCl gradient (in to out). This latter bi-ionic gradient potential reverses to a value from +9 to +20 mV when monensin is present in the organic liquid mixture. Thus, the model can be build stepwise, i.e., all factors leading to the development of diffusion potentials can be introduced sequentially, helping students to understand the quantitative relationships of ionic gradients and differential membrane permeability in the generation of cell electrical signals.

  6. Monitoring snowmelt induced unsaturated flow and transport using electrical resistivity tomography

    NASA Astrophysics Data System (ADS)

    French, Helen K.; Hardbattle, Carol; Binley, Andrew; Winship, Peter; Jakobsen, Leif

    2002-10-01

    The flow and transport of a non-reactive tracer and melt water was monitored in a heterogeneous coarse sandy unsaturated zone in southeastern Norway, during the snowmelt of 2001. Electrical resistivity tomography (ERT) as well as conventional suction cup techniques was employed. A frozen solution of NaBr in water was supplied as a line source on the ground surface above two parallel vertical profiles monitored by the two measurement systems prior to the onset of snowmelt. The two monitored vertical profiles were separated by approximately 1 m. The results were analysed by visual comparison of images and by the use of spatial moments analysis. The two measurement approaches showed that the system was affected by the presence of preferential flow paths during the early stages of the snowmelt, perhaps due to ice near the surface, but the major part of the plume moves uniformly later in the snow-melting period. After most of the tracer plume has reached the depth monitored by both systems (i.e. below 0.4 m depth) there is a good consistency between the two datasets. Spatial moment calculations on the basis of ERT cannot be used to describe the movement of tracer alone, as the resistivity is affected by changes in both saturation levels and tracer concentration. Nevertheless, ERT appears to be an appropriate method to characterise regions of localised high infiltration in this type of soil. The method therefore constitutes a possible alternative and supplement to suction cups in a monitoring system.

  7. Behavior of the electrical resistivity of MnSi at the ferromagnetic phase transition

    NASA Astrophysics Data System (ADS)

    Petrova, Alla E.; Bauer, E. D.; Krasnorussky, Vladimir; Stishov, Sergei M.

    2006-09-01

    The itinerant helical ferromagnet MnSi reveals a number of remarkable features, which include tricritical phenomena at the phase transition line, Fermi-liquid breakdown, and so-called partial spin order in the paramagnetic state at high pressures. These features, probably interconnected, so far have no satisfactory explanations though several ideas have been suggested. Some current ideas focus on specifics of the spin fluctuations in the paramagnetic phase of MnSi close to the phase transition line. We report here the results of electrical resistivity measurements of a single crystal of MnSi across its ferromagnetic phase transition line at ambient and high pressures. Contrary to previous work in the field we made use of compressed helium as a pressure medium. Sharp peaks of the temperature coefficient of resistivity characterize the transition line. Analysis of these data shows that at pressures to ˜0.35GPa these peaks have fine structure, revealing a shoulder at ˜0.5K above the peak. That confirms the “abnormal” spin behavior in the narrow region above the Curie point and indicates the existence of a nontrivial fluctuation mode in the paramagnetic phase of MnSi . It is symptomatic that this structure disappears at pressures higher than ˜0.35GPa , which was identified earlier as a tricritical point.

  8. Advanced electric-field scanning probe lithography on molecular resist using active cantilever

    NASA Astrophysics Data System (ADS)

    Kaestner, Marcus; Aydogan, Cemal; Lipowicz, Hubert-Seweryn; Ivanov, Tzvetan; Lenk, Steve; Ahmad, Ahmad; Angelov, Tihomir; Reum, Alexander; Ishchuk, Valentyn; Atanasov, Ivaylo; Krivoshapkina, Yana; Hofer, Manuel; Holz, Mathias; Rangelow, Ivo W.

    2015-03-01

    The routine "on demand" fabrication of features smaller than 10 nm opens up new possibilities for the realization of many novel nanoelectronic, NEMS, optical and bio-nanotechnology-based devices. Based on the thermally actuated, piezoresistive cantilever technology we have developed a first prototype of a scanning probe lithography (SPL) platform able to image, inspect, align and pattern features down to single digit nano regime. The direct, mask-less patterning of molecular resists using active scanning probes represents a promising path circumventing the problems in today's radiation-based lithography. Here, we present examples of practical applications of the previously published electric field based, current-controlled scanning probe lithography on molecular glass resist calixarene by using the developed tabletop SPL system. We demonstrate the application of a step-and-repeat scanning probe lithography scheme including optical as well as AFM based alignment and navigation. In addition, sequential read-write cycle patterning combining positive and negative tone lithography is shown. We are presenting patterning over larger areas (80 x 80 μm) and feature the practical applicability of the lithographic processes.

  9. Final Report, FY 2001 200 East Vadose Test Site Hanford Washington Electrical Resistance Tomography

    SciTech Connect

    Ramirez, A.; Daily, W.; Binley, A.

    2001-06-30

    This report covers the electrical resistance tomography (ERT) work performed at the Hanford Reservation, 200 East Area Vadose test (Sisson and Lu) site during the period March 23 through May 5,2001. The purposes of the ERT work were to: (1) Compare and contrast the development of the highly concentrated sodium thiosulfate plume (FY 01 work) with the fresh river water plume observed during FY 00. (2) Use the resistance images to infer the dynamics of the plume during two or three of the sodium thio-sulfate releases and during the water ''chaser'' release. (3) Determine the influence of the site's steel casings on the ability to construct reliable ERT images. (4) Determine if the steel casings at the site can be used as long electrodes to provide useful images of at least one release. (5) Develop quantitative estimates of the noise in the data and its effect on reconstructed images. Eleven electrode arrays (nine electrodes arrays available for the FY00 work), each with 15 electrodes, were installed at the site. These were used to perform 3D surveys before, during, and after 3 different spills.

  10. Sensing uniaxial tensile damage in fiber-reinforced polymer composites using electrical resistance tomography

    NASA Astrophysics Data System (ADS)

    Lestari, Wahyu; Pinto, Brian; La Saponara, Valeria; Yasui, Jennifer; Loh, Kenneth J.

    2016-08-01

    This work describes the application of electrical resistance tomography (ERT) in sensing damage in fiber-reinforced polymer composites under uniaxial quasi-static tension. Damage is manifested as numerous matrix cracks which are distributed across the composite volume and which eventually coalesce into intralayer cracks. Hence, tensile damage is distributed throughout the volume, and could be more significant outside the sensor area. In this work, tensile damage of unidirectional glass fiber-reinforced polymer composites (GFRP) and plain weave carbon fiber-reinforced polymer composites (CFRP) is sensed by utilizing a spray-on nanocomposite sensor, which is then instrumented by boundary electrodes. The resistance change distribution within the sensor area is reconstructed from a series of boundary voltage measurements, and ERT is implemented using a maximum a posteriori approach and assumptions on the type of noise in the reconstruction. Results show that this technique has promise in tracking uniaxial damage in composites. The different fiber architectures (unidirectional GFRP, plain weave CFRP) give distinct features in the ERT, which are consistent with the physical behavior of the tested samples.

  11. Distribution-based fuzzy clustering of electrical resistivity tomography images for interface detection

    NASA Astrophysics Data System (ADS)

    Ward, W. O. C.; Wilkinson, P. B.; Chambers, J. E.; Oxby, L. S.; Bai, L.

    2014-04-01

    A novel method for the effective identification of bedrock subsurface elevation from electrical resistivity tomography images is described. Identifying subsurface boundaries in the topographic data can be difficult due to smoothness constraints used in inversion, so a statistical population-based approach is used that extends previous work in calculating isoresistivity surfaces. The analysis framework involves a procedure for guiding a clustering approach based on the fuzzy c-means algorithm. An approximation of resistivity distributions, found using kernel density estimation, was utilized as a means of guiding the cluster centroids used to classify data. A fuzzy method was chosen over hard clustering due to uncertainty in hard edges in the topography data, and a measure of clustering uncertainty was identified based on the reciprocal of cluster membership. The algorithm was validated using a direct comparison of known observed bedrock depths at two 3-D survey sites, using real-time GPS information of exposed bedrock by quarrying on one site, and borehole logs at the other. Results show similarly accurate detection as a leading isosurface estimation method, and the proposed algorithm requires significantly less user input and prior site knowledge. Furthermore, the method is effectively dimension-independent and will scale to data of increased spatial dimensions without a significant effect on the runtime. A discussion on the results by automated versus supervised analysis is also presented.

  12. Changes in the electric resistivity of CrN subsequent to oxygen dissolution

    NASA Astrophysics Data System (ADS)

    Nagasawa, Shinobu; Suzuki, Kazuma; Sato, Aoi; Suzuki, Tsuneo; Nakayama, Tadachika; Suematsu, Hisayuki; Niihara, Koichi

    2016-02-01

    Single-phase epitaxial chromium oxynitride thin films containing 11 to 45 mol % oxygen were successfully synthesized on MgO(100) substrates by pulsed laser deposition at 773 K while controlling the ambient oxygen partial pressure. The film compositions were subsequently analyzed by Rutherford backscattering spectroscopy and electron energy-loss spectroscopy, while crystal phases were identified by X-ray diffractometry using the Bragg-Brentano and glancing incidence configurations and by in-plane φ scanning. The microstructures were observed by transmission electron microscopy. The electrical resistance of the films was determined by either the two- or four-probe method. The Cr(N,O) thin film having 11 mol % oxygen exhibited a metallic temperature dependence. In contrast, the films containing oxygen of 13 mol % or higher showed a semiconducting (or insulating) temperature dependence. This resistivity change is believed to result from enhanced electron correlation brought about by increases in oxygen content, sufficient to transform the Cr(N,O) thin film into a Mott insulator.

  13. An integration of aeromagnetic and electrical resistivity methods in dam site investigation

    SciTech Connect

    Aina, A.; Olorunfemi, M.O.; Ojo, J.S.

    1996-03-01

    Aeromagnetic map and electrical resistivity sounding data obtained along eight traverses were examined at two sites across the Katsina-Ala River. The principal goals of this exercise were to define depths to the bedrock, bedrock relief, geologic structures, define the nature of the superficial deposit, and select probable minor and major axes for hydroelectric power dams. The aeromagnetic map shows that the basement rocks trend roughly northeast-southwest, which correlates with the strike of foliation measurements made on rock outcrops along the river channel. A network of cross cutting lineaments, suspected to be faults/fractures that trend approximately northeast/southwest and northwest/southeast, was also delineated from the magnetic map. The depths to the bedrock estimated from resistivity depth sounding data at site 1 generally vary from 1--53.1 m. Depths to the bedrock estimated at site 2 range from 1.9--19.5 m. The superficial deposit varies from clay to sandy clay, to clayey sand (with boulders in places), and to sand and laterite. The bedrock relief is relatively flat and gently undulates along most of the traverses, with an overall dip towards the river channel. Traverses E-F or I-J at site 1 and K-L at site 2 are probable dame axes. These traverses are characterized by relatively thin overburden thicknesses and rock heads dipping toward the river channel, thereby reducing the likelihood of water seepages from the flanks of the proposed dam axes.

  14. Upper mantle electrical resistivity structure beneath back-arc spreading centers

    NASA Astrophysics Data System (ADS)

    Seama, N.; Shibata, Y.; Kimura, M.; Shindo, H.; Matsuno, T.; Nogi, Y.; Okino, K.

    2011-12-01

    We compare four electrical resistivity structure images of the upper mantle across back-arc spreading centers (Mariana Trough at 18 N and 13 N, and the Eastern Lau at 19.7 S and 21.3 S) to provide geophysical constraints on issues of mantle dynamics beneath the back-arc spreading system related to the subducting slab. The central Mariana Trough at 18 N has the full spreading rate of 25 km/Myr, and shows characteristic slow-spreading features; existence of median valley neovolcanic zone and "Bull's eyes" mantle Bouguer anomaly (MBA) along the axes. On the other hand, the southern Mariana Trough at 13 N shows an EPR type axial relief in morphology and lower MBA than that in the central Mariana Trough (Kitada et al., 2006), suggesting abundance of magma supply, even though the full spreading rate is 35 km/Myr that is categorized as a slow spreading ridge. At the Eastern Lau spreading center, crustal thickness and morphology vary systematically with arc proximity and shows the opposed trends against spreading rate: The full spreading rate increases from 65 km/Myr at 21.3 S to 85 km/Myr at 19.7 S, while the crustal thicknesses decrease together with morphology transitions from shallow peaked volcanic highs to a deeper flat axis (Martinez et al., 2006). Matsuno et al. (2010) provides a resistivity structure image of the upper mantle across the central Mariana subduction system, which contains several key features: There is an uppermost resistive layer with a thickness of 80-100 km beneath the central Mariana Trough, suggesting dry residual from the plate accretion process. But there is no evidence for a conductive feature beneath the back-arc spreading center at 18 N, and this feature is clearly independent from the conductive region beneath the volcanic arc below 60 km depth that reflects melting and hydration driven by water release from the subducting slab. The resultant upper mantle resistivity structure well support that the melt supply is not abundant, resulting in

  15. Gas production and transport during bench-scale electrical resistance heating of water and trichloroethene

    NASA Astrophysics Data System (ADS)

    Hegele, P. R.; Mumford, K. G.

    2014-09-01

    The effective remediation of chlorinated solvent source zones using in situ thermal treatment requires successful capture of gas that is produced. Replicate electrical resistance heating experiments were performed in a thin bench-scale apparatus, where water was boiled and pooled dense non-aqueous phase liquid (DNAPL) trichloroethene (TCE) and water were co-boiled in unconsolidated silica sand. Quantitative light transmission visualization was used to assess gas production and transport mechanisms. In the water boiling experiments, nucleation, growth and coalescence of the gas phase into connected channels were observed at critical gas saturations of Sgc = 0.233 ± 0.017, which allowed for continuous gas transport out of the sand. In experiments containing a colder region above a target heated zone, condensation prevented the formation of steam channels and discrete gas clusters that mobilized into colder regions were trapped soon after discontinuous transport began. In the TCE-water experiments, co-boiling at immiscible fluid interfaces resulted in discontinuous gas transport above the DNAPL pool. Redistribution of DNAPL was also observed above the pool and at the edge of the vapor front that propagated upwards through colder regions. These results suggest that the subsurface should be heated to water boiling temperatures to facilitate gas transport from specific locations of DNAPL to extraction points and reduce the potential for DNAPL redistribution. Decreases in electric current were observed at the onset of gas phase production, which suggests that coupled electrical current and temperature measurements may provide a reliable metric to assess gas phase development.

  16. Gas production and transport during bench-scale electrical resistance heating of water and trichloroethene.

    PubMed

    Hegele, P R; Mumford, K G

    2014-09-01

    The effective remediation of chlorinated solvent source zones using in situ thermal treatment requires successful capture of gas that is produced. Replicate electrical resistance heating experiments were performed in a thin bench-scale apparatus, where water was boiled and pooled dense non-aqueous phase liquid (DNAPL) trichloroethene (TCE) and water were co-boiled in unconsolidated silica sand. Quantitative light transmission visualization was used to assess gas production and transport mechanisms. In the water boiling experiments, nucleation, growth and coalescence of the gas phase into connected channels were observed at critical gas saturations of Sgc=0.233±0.017, which allowed for continuous gas transport out of the sand. In experiments containing a colder region above a target heated zone, condensation prevented the formation of steam channels and discrete gas clusters that mobilized into colder regions were trapped soon after discontinuous transport began. In the TCE-water experiments, co-boiling at immiscible fluid interfaces resulted in discontinuous gas transport above the DNAPL pool. Redistribution of DNAPL was also observed above the pool and at the edge of the vapor front that propagated upwards through colder regions. These results suggest that the subsurface should be heated to water boiling temperatures to facilitate gas transport from specific locations of DNAPL to extraction points and reduce the potential for DNAPL redistribution. Decreases in electric current were observed at the onset of gas phase production, which suggests that coupled electrical current and temperature measurements may provide a reliable metric to assess gas phase development. PMID:25084057

  17. Feature enhancement from electrical resistivity data in an archaeological survey: the Sapelos hillfort experiment (Boticas, Portugal)

    NASA Astrophysics Data System (ADS)

    Alves, Mafalda; Bernardes, Paulo; Fontes, Luís.; Martins, Manuela; Madeira, Joaquim

    2015-06-01

    The PoPaTERVA project is developing applied research regarding the comprehension of the multi-layered cultural background of the Terva Valley Archaeological Park, in Boticas, Portugal. One of the main aspects focused on the project is the appliance of remote sensing techniques to enhance non visible archaeological features. An earth resistance tomography (ERT) survey was carried out at the Sapelos hillfort, by the specialized SINERGEO geophysicist's team, using a Wenner-Schlumberger array. The resulting data was analyzed by the authors in order to extract and verify valid archaeological features regarding the settlement's structures. There are several adequate systems that can be used to visualize the surveyed data (x, y, z, Ω). However, the authors preferred the open source Visualization Toolkit (VTK) from Kitware Inc., since it supports several visualization and modelling techniques that are useful for interpretation purposes in archaeological contexts: for instance, it is possible to represent the archaeological site as a virtual scale model, which can be freely manipulated. For the Sapelos hillfort, two distinct visualizations were developed to represent the acquired electrical resistivity data. The first one is used to create a comprehensive volume from the surveyed data, which is imported as structured 3D points and mapped into a 3D volume. However, this representation does not provide the necessary insight for analysis purposes, so a second visualization is needed to cluster the relevant data for archaeological research. This visualization is based on contouring algorithms that generate isosurfaces from scalar resistivity values (Ω), therefore enhancing the features with potential archaeological interest.

  18. Fluoride-added Pr-Fe-B die-upset magnets with increased electrical resistivity

    SciTech Connect

    Marinescu, M.; Liu, J. F.; Gabay, A. M.; Hadjipanayis, G. C.

    2009-04-01

    This work reports the effect of NdF{sub 3}, DyF{sub 3}, and CaF{sub 2} additions on the electrical resistivity and magnetic properties of Pr-Fe-B hot-pressed and die-upset permanent magnets. Composite magnets were synthesized from ground Pr{sub 14.5}Fe{sub 79.5}B{sub 6} melt-spun ribbons blended with 5 wt % of fluoride fine powders and consolidated by hot pressing at 650 deg. C, followed by die upsetting at 800 deg. C. While CaF{sub 2} is stable at the processing temperatures, the rare earth atoms separate from their fluorides to a certain degree with the assistance of the Pr-rich phase from the magnet matrix. Addition of fluorides increased the resistivity of the hot-pressed specimens by more than 200%. The resistivity of the die-upset specimens measured perpendicularly to the direction of the applied pressure, which is also the direction of magnetization, is, however, only slightly increased compared to the magnet counterparts without the fluoride addition. The intrinsic coercivity of Pr{sub 14.5}Fe{sub 79.5}B{sub 6} die-upset specimens is increased from 14.5 kOe to 15.3, 17.1, and 17.7 kOe for the addition of CaF{sub 2}, DyF{sub 3}, and NdF{sub 3}, respectively, at a slight expense of the residual flux.

  19. Application of electrical resistivity tomography to map lithological differences and subsurface structures (Eastern Sudetes, Czech Republic)

    NASA Astrophysics Data System (ADS)

    Stan, Dominika; Stan-Kłeczek, Iwona

    2014-09-01

    The aim of this study is to determine the subsurface lithological variability and thickness of each metamorphic rocks unit by means of geophysical methods, which were presented within the framework of SEDIBUD. Research was performed on the ridge and the steep eastern slope of the Orlik massif (1204 m) in the Hrubý Jesenik range of the Eastern Sudetes, the Czech Republic. To obtain a spatial image of a geological rock mass, the non-invasive and relatively rapid method of electrical resistivity tomography (ERT) was used, which resulted in the creation of six profiles using the Dipole-Dipole and Wenner-Schlumberger arrays. As complementary methods, vertical electrical sounding (VES) and seismic refraction tomography were chosen. Fifteen measuring points along two profiles obtained by vertical electrical sounding allowed the determination of the following in the vertical section layers of different resistivity and thickness at direct points in contact primarily with Devonian quartzite rocks and weathered covers. In a series of field studies, a four-layered rock mass was examined in which the first layer is of fine-grained materials with medium- and large-size clasts, the second layer is quartzite, the third is gneiss and the fourth is phyllite. The five profiles measured by seismic refraction tomography made it possible to draw the boundary between the studied phyllites, gneisses and quartzites. In addition, geophysical surveys and the results of mineralogical composition analysis allowed us to determine the nature and thickness of the weathered layers present on the massif area, which, in the upper sections, are predominantly a clayey loam partially covered with blocks. The inclination of the slope is associated with an increase in the fraction of coarse material. The majority of the thickness of these layers is related to the local flattened surfaces and the presence of numerous streams, which contributed to the accumulation of the sediments that were also

  20. Development of a Laboratory Experiment to Derivate the Thermal Conductivity based on Electrical Resistivity Measurments

    NASA Astrophysics Data System (ADS)

    Vienken, T.; Firmbach, L.; Dietrich, P.

    2014-12-01

    In the course of the energy transition, the number of shallow geothermal systems is constantly growing. These systems allow the exploitation of renewable energy from the subsurface, reduced CO2 emission and additionally, energy storage. An efficient performance of geothermal systems strongly depends upon the availability of exploration data (e.g. thermal conductivity distribution). However, due to high exploration costs, the dimensioning of smaller plants (< 30 kW) is generally based on literature values. While standard in-situ-tests are persistent for larger scale projects, they yield only integral values, e.g. entire length of a borehole heat exchanger. Hence, exploring the distribution of the thermal conductivity as important soil parameter requires the development of new cost-efficient technologies. The general relationship between the electrical (RE) and the thermal resistivity (RT) can be described as log(RE) = CR log(RT) with CRas a multiplier depending on additional soil parameter (e.g. water content, density, porosity, grain size and distribution). Knowing the influencing factor of these additional determining parameters, geoelectrical measurements could provide a cost-efficient exploration strategy of the thermal conductivity for shallow geothermal sites. The aim of this study now is to define the multiplier CRexperimentally to conclude the exact correlation of the thermal and electrical behavior. The set-up consists of an acrylic glass tube with two current electrodes installed at the upper and lower end of the tube. Four electrode chains (each with eight electrodes) measure the potential differences in respect to an induced heat flux initiated by a heat plate. Additional, eight temperature sensors measure the changes of the temperature differences. First, we use this set-up to analyze the influence of soil properties based on differing homogenous sediments with known chemical and petro-physical properties. Further, we analyze the influence of the water

  1. Measurement of effective bulk and contact resistance of gas diffusion layer under inhomogeneous compression - Part I: Electrical conductivity

    NASA Astrophysics Data System (ADS)

    Vikram, Ajit; Chowdhury, Prabudhya Roy; Phillips, Ryan K.; Hoorfar, Mina

    2016-07-01

    This paper describes a measurement technique developed for the determination of the effective electrical bulk resistance of the gas diffusion layer (GDL) and the contact resistance distribution at the interface of the GDL and the bipolar plate (BPP). The novelty of this study is the measurement and separation of the bulk and contact resistance under inhomogeneous compression, occurring in an actual fuel cell assembly due to the presence of the channels and ribs on the bipolar plates. The measurement of the electrical contact resistance, contributing to nearly two-third of the ohmic losses in the fuel cell assembly, shows a non-linear distribution along the GDL/BPP interface. The effective bulk resistance of the GDL under inhomogeneous compression showed a decrease of nearly 40% compared to that estimated for homogeneous compression at different compression pressures. Such a decrease in the effective bulk resistance under inhomogeneous compression could be due to the non-uniform distribution of pressure under the ribs and the channels. This measurement technique can be used to identify optimum GDL, BPP and channel-rib structures based on minimum bulk and contact resistances measured under inhomogeneous compression.

  2. Characterizing a shallow groundwater system beneath irrigated sugarcane with electrical resistivity and radon (Rn-222), Puunene, Hawaii

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this study, we use a combination of electrical resistivity profiling and radon (222Rn) measurements to characterize a shallow groundwater system beneath the last remaining, large-scale sugarcane plantation on Maui, Hawaii. Hawaiian Commercial & Sugar Company has continuously operated a sugarcane...

  3. Determination of the diffusion coefficient of hydrogen in metals from the rate of change in the electrical resistance in desorption

    SciTech Connect

    Mikitishin, S.I.; Fedorov, V.V.; Sergienko, O.M.; Sokolovskii, O.R.; Spas, Y.M.

    1985-07-01

    A proposed method of measuring the diffusion coefficient of hydrogen D from the rate of change in electrical resistance in degassing of hydrogenimpregnated specimens is presented. Distinguished by simplicity, the method makes it possible to determine the coefficients with any method of hydrogen impregnation in a broad temperature range.

  4. Tank Leak Experiment at the Monk Tank Site, 200 East Area: Electrical Resistance Tomography-Preliminary Results

    SciTech Connect

    Ramirez, A.; Daily, W.D.; Binley, A.

    2001-09-20

    This report covers the electrical resistance tomography (ERT) work performed at the Mock Tank site, 200 East Area, Hanford Reservation, during the months of July and August, 2001. The work reported herein is to be considered preliminary because it is work in progress. Some of the analyses and interpretation of results are incomplete at this time.

  5. Joint 3D seismic travel time and full channel electrical resistivity inversion with cross gradient structure constraint

    NASA Astrophysics Data System (ADS)

    Gao, J.; Zhang, H.

    2015-12-01

    Near surface geophysical exploration for the purpose of engineering design or construction For this reason, geophysical imaging demands a higher resolution and a better quantitative interpretation. Seismic travel time tomography and direct current resistivity tomography are two main methods for the near surface survey. Because of the limited coverage of observation system and the complex physical relationship between physical parameters and observations, individual geophysical method suffers issues of non-uniqueness and resolution limitation to some degree. We have developed a joint inversion method to combine seismic travel time tomography and full channel resistivity tomography. For the full channel resistivity survey, it uses two electrodes for power supply and all the other electrodes for recording. Compared with the traditional resistivity method, it collects more data and has a better model converge. Our joint inversion strategy relies on the structure constraint enforced through minimizing cross gradients between seismic velocity and resistivity models (Gallardo, 2003). For resistivity tomography, sensitivity kernels are obtained through the adjoint method by solving the electrostatic field equation with the finite-difference method. For seismic travel time tomography, ray paths and travel times are calculated using the fast marching method. We have tested our joint inversion method for a 2D cross-hole problem where two small zones with high and low velocity/resistivity anomalies. Seismic/electrical sources/receivers are installed in two boreholes. For separate seismic inversion, the smearing effect is evident and two anomaly zones are distorted and misplaced. For separate electric resistivity inversion, although two anomaly zones are positioned correctly their values are not accurate. By joint inversion, two velocity anomaly zones are clearly imaged and the smearing effect is greatly reduced. In comparison, for the resistivity model, the two anomaly zones

  6. Damage mechanisms characterization of carbon fiber/epoxy composite laminates by both electrical resistance measurements and acoustic emission analysis

    SciTech Connect

    Ceysson, O.; Salvia, M.; Vincent, L.

    1996-04-15

    Carbon fiber reinforced plastics (CFRP) offer high specific mechanical properties (performance vs weight ratio). Since carbon fibers are electrical conductors ({rho} = 2.10{sup {minus}5} {Omega}.m), the measurement of the variations of electrical resistance appears to be a valuable technique for damage detection. In the case of CFRP samples, conductivity is not isotropic but depends on the orientation of the carbon fibers. The electrical conduction of (0{degree}) unidirectional (UD) CFRP parallel to the fibers is due to the current flow along the fibers. This can be modeled using the parallel resistance approach. In this present work, the variation of the electrical conductivity can be taken as an indicator of the evolution of various types of damage in classical longitudinal UD but also in ({+-} 45{degree}) CFRP laminates. By comparison with a more classical non-destructive technique such as Acoustic Emission, it has been shown that it is possible that the electrical resistance measurement allows one to monitor in-situ the evolution of various internal damage nucleation and growth in CFRP such as fiber fractures, intraply matrix cracks and interply delaminations.

  7. Adjoint-state inversion of electric resistivity tomography data of seawater intrusion at the Argentona coastal aquifer (Spain)

    NASA Astrophysics Data System (ADS)

    Fernández-López, Sheila; Carrera, Jesús; Ledo, Juanjo; Queralt, Pilar; Luquot, Linda; Martínez, Laura; Bellmunt, Fabián

    2016-04-01

    Seawater intrusion in aquifers is a complex phenomenon that can be characterized with the help of electric resistivity tomography (ERT) because of the low resistivity of seawater, which underlies the freshwater floating on top. The problem is complex because of the need for joint inversion of electrical and hydraulic (density dependent flow) data. Here we present an adjoint-state algorithm to treat electrical data. This method is a common technique to obtain derivatives of an objective function, depending on potentials with respect to model parameters. The main advantages of it are its simplicity in stationary problems and the reduction of computational cost respect others methodologies. The relationship between the concentration of chlorides and the resistivity values of the field is well known. Also, these resistivities are related to the values of potentials measured using ERT. Taking this into account, it will be possible to define the different resistivities zones from the field data of potential distribution using the basis of inverse problem. In this case, the studied zone is situated in Argentona (Baix Maresme, Catalonia), where the values of chlorides obtained in some wells of the zone are too high. The adjoint-state method will be used to invert the measured data using a new finite element code in C ++ language developed in an open-source framework called Kratos. Finally, the information obtained numerically with our code will be checked with the information obtained with other codes.

  8. The influence of temperature on the electrical resistivity of the cellular polypropylene and the effect of activation energy.

    PubMed

    Vila, Floran; Dhima, Pranvera; Mandija, Florian

    2013-01-01

    In this paper, we determine the surface and volume electrical resistivity of the 50 μm thick cellular polypropylen (VHD50), for the temperature range 393-453 K. For this we use a contemporary methodology, which consist of a voltage measurement across the sample, with a known current flowing through it. This methodology includes a three-electrode system, which allows us to estimate the resistivity of the samples, based on their corresponding total resistances. The electric fields applied for a time interval of 1 min are of the order of 200 kVm (-1). The order of magnitude of surface and volume electrical resistivity is 10(13) Ω and 10(11) Ωm, respectively. For both types of the resistivity, the temperature dependence is an increasing or decreasing exponential function, depending on the type of the activation energy, (its average value for the temperature range mentioned above is 41,20 kJmol (-1)), totally confirmed by the corresponding theoretical interpretation, conditioned by the ionic conduction. The methodology and equipment used, as well as the satisfying accordance with the results, found out directly or indirectly with the consulted literature, confirm the high accuracy of experimental measurements. PMID:25674393

  9. Monitoring water flows with time-lapse Electrical Resistivity Tomography on the Super-Sauze landslide

    NASA Astrophysics Data System (ADS)

    Gance, J.; Sailhac, P.; Malet, J.-P.; Grandjean, G.; Supper, R.; Jochum, B.; Ottowitz, D.

    2012-04-01

    in sub-surface soil temperature. Two high-resolution optical cameras are installed on stable crests on the side of the cross-sections and time-lapse stereoscopy is used to reconstruct the displacement field to locate the electrodes in space and time (in order to take into account changes in the dipole geometry). The apparent electrical resistivity values were inverted with a time-lapse approach using an initial model constructed from statistical analysis of resistivity data and a priori knowledge on the landslide structure from a previous geotechnical model. The near surface apparent resistivity can vary of ten percent without any input of water. This shows the importance of temperature effect on the measurement. The temperature correction is handled from a complete study of the soil temperature propagation solving the heat equation with several temperature probes placed at different depths in soil and in the water table. The results are interpreted in combination to hydrological data (rain, water table level). The acquisition of 8 ERT all over the studied area, in different directions permits to create by interpolation a 3D electrical resistivity model of the area. This model shows the importance of the bedrock topography because high water content areas are visible at the theoretical hydrological network computed from the 3D geotechnical model of Travelletti and Malet (2011). Transversal waterflow circulation not predicted are also visible and permit to interpret the results taking into account the 3D structure of the landslide. A 250 m long P-wave tomography acquired on the studied profile and inversed with a quasi-Newton algorithm that uses Fresnel wavepaths and the finite bandwidth of the source signal, specially developed for the study of very heterogeneous soils, shows a very good correlation with electrical resistivity and permits to propose a geotechnical model of the profile. Spatially heterogeneous water flow patterns are identified and the presence of a

  10. Unipolar conductivity of SrTiO3 crystals with light-induced drop in electrical resistance

    NASA Astrophysics Data System (ADS)

    Shablaev, S. I.; Grachev, A. I.

    2016-05-01

    This paper reports on the results of the experimental investigation of unipolar (diode) current-voltage characteristics of local regions in high-resistance SrTiO3 crystals that experienced a light-induced drop in electrical resistance. This behavior has been explained by the influence exerted on the electrical conductivity by the irradiated region in the Schottky barrier of one of the contacts. The ideality factor of the Schottky barrier has been determined and the barrier height for a number of regions has been estimated from measurements of the forward branch of the current-voltage characteristics. An analysis of the specific features in the behavior of the reverse branch of the current-voltage characteristics has revealed that, in the SrTiO3 crystals with p-type conductivity, the resistance switching occurs through a pure electronic mechanism, in contrast to models based on electrochemical processes, in particular, the migration of oxygen vacancies.

  11. Electrical Characterization of Temperature Dependent Resistive Switching in Pr0.7C0.3MnO3

    NASA Astrophysics Data System (ADS)

    Lopez, Melinda; Salvo, Christopher; Tsui, Stephen

    2012-02-01

    Resistive switching offers a non-volatile and reversible means to possibly create a more physically compact yet larger access capacity in memory technology. While there has been a great deal of research conducted on this electrical property in oxide materials, there is still more to be learned about this at both high voltage pulsing and cryogenic temperatures. In this work, the electrical properties of a PCMO-metal interface switch were examined after application of voltage pulsing varying from 100 V to 1000 V and at temperatures starting at 293 K and lowered to 80 K. What was discovered was that below temperatures of 150 K, the resistive switching began to decrease across all voltage pulsing and that at all temperatures before this cessation, the change in resistive switching increased with higher voltage pulsing. We suggest that a variable density of charge traps at the interface is a likely mechanism, and work continues to extract more details.

  12. [The electrical resistance and impedance of mammalian muscles during the first days after slaughter. I: bovine diaphragm].

    PubMed

    Brini, R; Brusco, A; Massari, M; Pallotti, C

    1980-08-15

    In the view of characterizing the animal tissues with respect to their physical properties, the AA. have investigated on the behaviour of the electrical responses of bovine diaphragmatic muscle. In particolar the resistance and the impedance (at a fixed frequency of 20 Hz, sinusoidal wave) have been checked in samples from the 4th up to the 148th hour after slaughter. The results of these experiments show that, during the maturation of the meat, there is a decrease of the values of the resistance and of the capacitive reactance. On the basis of the data acquired, the only hypothesis explaining the course of the research could be that the electrical properties of the meat are greatly influenced in a very relevant way by capacitive structures and in lower degree by a pure resistive medium.

  13. Application of Electrical Resistivity Method for Detecting Shallow Old Gold Mine Workings: An Example from Boksburg, South Africa

    NASA Astrophysics Data System (ADS)

    Diop, S.; Chirenje, E.

    2011-12-01

    Subsidence has been observed at several locations along the northern perimeter of the Central Witwatersrand Mining Basin south of Johannesburg, South Africa. Previous studies have defined the extent and distribution of hundreds of open ventilation shafts and surface collapses linked to areas of known and suspected shallow undermining. Many collapses appear to be in a meta-stable state prone to further collapse, which could and have led to casualties. Identification of zones of incipient instability is therefore an urgent state responsibility to protect life and property, as much of these abandoned mine lands have been invaded by shack dwellers. This paper outlines the results of an investigation using 2D electrical resistivity tomography (ERT) in combination with a standard geotechnical engineering drilling exploration, with the aim of identifying areas of incipient instability and possible future collapse. The electrical resistivity data were acquired via a network of intersecting survey lines using a SYSCAL Pro multimode resistivity imaging system equipped with 72 electrodes. The dipole-dipole and the Schlumberger arrays with an electrode spacing of 5 and 10 m were used. Inversion of the data was carried out using the commercially available software package RES2DINV. Analysis of the electrical resistivity data and conventional site investigation data proved to be a highly effective means of characterizing dangerous, abandoned mine openings of various sizes, depths and origins. Survey results also successfully confirmed the position of known shafts and shallow underground workings. These appeared as electrically well-defined features corresponding extremely closely to both underground plans and invasive site investigation data. The findings obtained from this study offer practical considerations for modeling shallow subsurface conditions, along the Boksburg area; to enable the reliable identification of hazardous areas constituting a potential threat to human

  14. Monitoring a shallow geothermal experiment in a sandy aquifer using electrical resistivity tomography: a feasibility study

    NASA Astrophysics Data System (ADS)

    Hermans, Thomas; Vandenbohede, Alexander; Nguyen, Frederic; Lebbe, Luc

    2010-05-01

    The use of low-enthalpy geothermal ressources is increasingly growing in Europe and around the world. This domain constitutes an essential field of research and development in the diversification of energy ressources to hinder global warming. The advantages of very low temperature systems are, first, that they are much more available than the geothermal high temperature, since the underground often contains important shallow aquifers (e.g. alluvial plains), and second, that their exploitation involve relatively low costs of implementation. Very low energy systems exhibit underground fluid with a temperature ranging from 5 to 30 ° C, which may be used for cooling or heating. The two main modes of exploitation of geothermal energy rely on the extraction of the hydrothermal fluid in the aquifer from wells and on the circulation of a heat transfer fluid in a closed and buried geothermal circuit. Underground heat exchange and overall exploitation system design may be undertaken in an optimized and sustainable fashion if the parameters governing the coupled heat transport and flow equations are know to a certain degree. As for many underground reservoir problems, sufficient knowledge on the distribution of the parameters of interests (e.g. thermal conductivity, thermal diffusivity, thermomechanic dispersitivity, effective porosity) must be obtained to perform reliable predictions. Designing novel experiments to estimate those parameters in-situ is therefore essential. In this framework, we examine the feasibility of a thermal tracer experiment similar to the ones performed in hydrogeology or hydrogeophysics. The test consists in following the evolution of a heat plume through the underground as it is injected in one well and pumped to another one. The thermal tracer evolution is followed by gathering electrical resistivity (ERT) images in a time-lapse framework over 10 days. In this contribution, we examine the potential of ERT to image such thermal plume and its

  15. Capacitively-Coupled Resistivity measurements to determine frequency dependent electrical parameters in periglacial environment - theoretical considerations and first field tests.

    NASA Astrophysics Data System (ADS)

    Przyklenk, A.; Hördt, A.; Radić, T.

    2016-05-01

    Capacitively-Coupled Resistivity (CCR) is conventionally used to emulate DC resistivity measurements and may provide important information about the ice content of material in periglacial areas. The application of CCR theoretically enables the determination of both electrical parameters, i.e. the resistivity and the electrical permittivity, by analyzing magnitude and phase shift spectra. The electrical permittivity may dominate the impedance, especially in periglacial areas or regions of hydrogeological interest. However, previous theoretical work suggested that the phase shift may strongly depend on electrode height above ground, implying that electrode height must be known with great accuracy to determine electrical permittivity. Here, we demonstrate with laboratory test measurements, theoretical modelling and by analysing the Jacobian matrix of the inversion, that the sensitivity towards electrode height is drastically reduced if the electrical permittivity is frequency dependent in a way that is typical for ice. For the fist time, we used a novel broadband CCR device "Chameleon" for a field test located in one of the ridge galleries beneath the crest of Mount Zugspitze. A permanently ice covered bottom of a tunnel was examined. For the inversion of the measured spectra, the frequency dependance of the electrical parameters was parameterized in 3 different ways. A Debye Model for pure ices, a Cole-Cole Model for pure ices and a dual Cole-Cole Model including interfacial water additionally. The frequency-dependent resistivity and permittivity spectra obtained from the inversion, including low and high frequency limits, agree reasonably well with laboratory and field measurements reported in the literature.

  16. Optical and electrical characterization of high resistivity semiconductors for constant-bias microbolometer devices

    NASA Astrophysics Data System (ADS)

    Saint John, David B.

    The commercial market for uncooled infrared imaging devices has expanded in the last several decades, following the declassification of pulse-biased microbolometer-based focal plane arrays (FPAs) using vanadium oxide as the sensing material. In addition to uncooled imaging platforms based on vanadium oxide, several constant-bias microbolometer FPAs have been developed using doped hydrogenated amorphous silicon (a-Si:H) as the active sensing material. While a-Si:H and the broader Si1-xGex:H system have been studied within the context of photovoltaic (PV) devices, only recently have these materials been studied with the purpose of qualifying and optimizing them for potential use in microbolometer applications, which demand thinner films deposited onto substrates different than those used in PV. The behavior of Ge:H is of particular interest for microbolometers due to its intrinsically low resistivity without the introduction of dopants, which alter the growth behavior and frustrate any attempt to address the merits of protocrystalline a-Ge:H. This work reports the optical, microstructural, and electrical characterization and qualification of a variety of Si:H, Si1-xGex:H, and Ge:H films deposited using a plasma enhanced chemical vapor deposition (PECVD) process, including a-Ge:H films which exhibit high TCR (4-6 -%/K) and low 1/f noise at resistivities of interest for microbolometers (4000 -- 6000 O cm). Thin film deposition has been performed simultaneously with real-time optical characterization of the growth evolution dynamics, providing measurement of optical properties and surface roughness evolutions relevant to controlling the growth process for deliberate variations in film microstructure. Infrared spectroscopic ellipsometry has been used to characterize the Si-H and Ge-H absorption modes allowing assessment of the hydrogen content and local bonding behavior in thinner films than measured traditionally. This method allows IR absorption analysis of hydrogen

  17. Long-Term Monitoring of Infiltration at a Managed Aquifer Recharge Site Using Electrical Resistivity Probes

    NASA Astrophysics Data System (ADS)

    Cockett, R.; Pidlisecky, A.; Knight, R. J.

    2010-12-01

    As part of an effort to understand the hydrogeologic parameters that influence the performance of a managed aquifer recharge project, four Electrical Resistivity Imaging (ERI) probes were installed beneath an artificial recharge pond to monitor changes in bulk electrical resistivity as a function of time. The probes were three meters long and installed to a depth of two meters below the pond bottom, with a one-meter section of the probe extending into the water. Resistance measurements were obtained through a group of 21 electrodes below the pond bottom, and a group of 4 electrodes in the water column. Spacing between electrodes in each group was 10 cm, while spacing between the subsurface and water column electrodes was 75 cm. While one probe failed immediately, the remaining three have been in operation for two years beneath the pond. A total of 96 measurements were made on each probe, every 18 minutes for two operational seasons (January - August). These seemingly simple measurements have provided tremendous insight into the subsurface flow at the base of the pond, and the challenges associated with using these data in a quantitative manner. Inversion of these data using an axially symmetric cylindrical inversion approach with both a L-1 and L-2 norm demonstrates that, despite the use of direct-push methods for probe emplacement, there is a significant disturbed zone adjacent to the probes. This disturbed zone adjacent to the probe leads to a violation of a one-dimensional assumption, and therefore complicates interpretation of the data. We note that, had we only used a traditional sampling array along the probe (e.g. a fixed a-spacing Wenner array), we would not see this disturbed zone and our calculated resistivity estimates would be influenced by the disturbed zone. In addition to being able to detect, and subsequently account for, the disturbed zone, the high temporal sampling rate of these measurements gives us the ability to generate robust error estimates

  18. A Study of Metallurgical Factors for Defect Formation in Electric Resistance Welded API Steel Pipes

    NASA Astrophysics Data System (ADS)

    Joo, Min Sung; Noh, Kyung-Min; Kim, Wan-Keun; Bae, Jin-Ho; Lee, Chang-Sun

    2015-06-01

    A critical assessment has been made for the electric resistance welded API-J55 and P110 steel pipes to clarify the metallurgical factors crucial to the occurrence of welding defects. Electric resistance welding (ERW) is widely accepted due to its low cost and high efficiency of production as a conventional manufacturing technology for the steel pipes. However, ERW pipes are vulnerable to the defect formation because its welding zone has different characteristics compared to the base material. It has been found that there were two major crack types in the investigated steels: surface crack and hook crack (J-shaped crack). Macroscopic examinations suggested that the causes and occurrences of the cracks were distinct among the investigated steels. The small surface cracks were largely occurred in the API-J55 steel pipes. The microstructure in the vicinity of crack was identical to the matrix, but it was found that the formation of the surface cracks was attributed to the sulfur and oxide inclusions. The energy dispersive X-ray spectroscopy (EDS) analysis showed that the cracks were associated with hydrogen and clusters of complex oxide inclusions with calcium such as Al-Ca-O and Fe-Ca-O. Moreover, sulfur was found to be the major culprit for the surface crack formation in the statistical evaluation. On the other hand, most of the hook cracks were large in size and occurred in the API-P110 steel pipes even though the sulfur level was very low, where the phosphorous was critical to the occurrence of hook crack. Although the EDS analysis showed the similar oxides compared to the case of surface cracks, B and P segregation were found in secondary ion mass spectrometry and electron probe micro analyzer analyses. In the vicinity of the hook cracks, martensite (locally hardened microstructure) was formed because the segregation enhances the hardenability. Eventually, the crack propagates along the martensite which was the band of ferrite and pearlite. It is postulated that

  19. Digital photogrammetric analysis and electrical resistivity tomography for investigating the Picerno landslide (Basilicata region, southern Italy)

    NASA Astrophysics Data System (ADS)

    de Bari, Claudia; Lapenna, Vincenzo; Perrone, Angela; Puglisi, Claudio; Sdao, Francesco

    2011-10-01

    Digital photogrammetric analysis and Electrical Resistivity Tomography (ERT) techniques were applied to evaluate the volume of material involved in a complex roto-translational slide occurred in the territory of Picerno (Basilicata region, southern Italy). Analytical and digital photogrammetric techniques facilitated a multi-temporal analysis of aerial photos for the years 1997, 2004 and 2006. In order to identify different geomorphologic features (scarps, terraces and trenches) of the landslide and their development, the analytical and digital photo interpretation was performed at the maximum scale of 1:5000. Geological and geomorphological surveys were carried out to verify photo-interpretation results. Digital Elevation Models (DEMs) for 1997, 2004 and 2006 were produced by applying the Grid Adaptive method. The differential DEMs (2006-1997; 2006-2004; 2004-1997) for the most dangerous part of the landslide allowed us to recognize the areas affected either by deposition or erosion and also estimate any altitudinal changes in each geomorphologic unit. To detect the sliding surface and estimate the thickness of the sliding material, several transversal and longitudinal ERT profiles were obtained. The electrical images of subsurface supported by stratigraphical data from boreholes were integrated with the information from the DEMs. The altitudinal changes and the sizes of the source and accumulation areas allowed us to estimate the volume of material involved in the mass movement. The fusion of data from different sensors allows us to gather indications on the surface and subsurface characteristics of the landslide providing useful information for landslide mitigation activities. Such an approach can help both to improve our knowledge and overcome the drawbacks of each methodology.

  20. Visualizing Hyporheic Flow Paths in Three Dimensions Using Time-Lapse Electrical Resistivity Tomography

    NASA Astrophysics Data System (ADS)

    Kohler, B.; Hall, R. O., Jr.; Carr, B.

    2015-12-01

    The hyporheic zone, the region underneath/surrounding a stream where surface and subsurface waters - and subsequently solutes - are exchanged and interact, is important for many biogeochemical, hydrological, and ecological processes. However, it has remained difficult for researchers to sufficiently describe solute transport within the hyporheic zone, due, in part, to the great degree of heterogeneity of the subsurface. Thus, more direct and invasive sampling techniques are limited in their usefulness. We used an indirect approach for measuring the hyporheic zone, employing 3D time-lapse electrical resistivity tomography (ERT), with a pole-dipole configuration, downstream of a constant-rate addition of an electrically conductive salt tracer (Cl-) as a solution via a high-precision peristaltic pump. This method allowed us to measure the extent of subsurface dynamics of streams in Wyoming's Laramie and Snowy Range mountains, as it yields a three-dimensional view of solute transport and exchange within the hyporheic zone. We found that the physical size of the hyporheic zone and the rate of exchange between the hyporheic and surface waters, as estimated from 3D ERT, are largely related to sediment properties (i.e. grain size distribution) and the extent of tailing of the solute's breakthrough curve (length of time for the solute to flush from the subsurface post cessation of the pump upstream). Coarser sediments with a relatively large porosity, such as gravels and sands, allowed for more subsurface exchange, and larger flow paths, than finer sediments with tighter packing structures, such as clays. Stream reaches that showed a higher degree of tailing in the breakthrough curve, traditionally implying a large transient storage zone, had larger and more active hyporheic zones as measured by 3D ERT. We therefore believe further investigations with 3D ERT will better our understanding of hyporheic exchange and stream solute transport.

  1. Nanosecond electric pulses induce DNA breaks in cisplatin-sensitive and -resistant human ovarian cancer cells.

    PubMed

    Linghu, Lingjuan; Tan, Yafang; Lou, Yi; Hu, Lina; Yang, Hongchun; Yu, Tinghe

    2013-01-11

    Human ovarian cancer cells COC1 and COC1/DDP (cisplatin-resistant subline) were exposed to 6 kV/cm nanosecond electric pulses (nsEP) with a pulse length of 8, 16 or 24 ns. The potential in a subcellular unit was calculated using a multilayer dielectric spherical model, and area under the voltage-time curves (AUC) integrated with a lower limit of 0.2V. Cell viability was determined, and double-stand and total DNA breaks detected with the neutral and alkaline comet assays. nsEP evoked a higher voltage and AUC in nucleoplasm, and the levels in COC1 cells was just above those in COC1/DDP cells. Comets only appeared in the alkaline assay demonstrating single-stand DNA break. Fewer DNA break (16.51% vs. 35.13% at 24 ns, p=0.0150) and more survival (22.42% vs. 13.19% at 24 ns, p=0.0015) occurred in COC1/DDP cells despite an equal electric energy and almost equal cell sizes. 24-ns EP led to higher rates of cell-death and comet. The comet rate correlated with cell-death fraction in either cell line (r=0.5701, p=0.0135; r=0.5110, p=0.0302). There was no a correlation between the tail length, tail moment or Olive tail moment and cell-death rate. The data showed that response of chemosensitive cells differed from that of chemoresistant cells and DNA damage contributed to percent of cell death. PMID:23211598

  2. Applying petrophysical models to radar travel time and electrical resistivity tomograms: Resolution-dependent limitations

    USGS Publications Warehouse

    Day-Lewis, F. D.; Singha, K.; Binley, A.M.

    2005-01-01

    Geophysical imaging has traditionally provided qualitative information about geologic structure; however, there is increasing interest in using petrophysical models to convert tomograms to quantitative estimates of hydrogeologic, mechanical, or geochemical parameters of interest (e.g., permeability, porosity, water content, and salinity). Unfortunately, petrophysical estimation based on tomograms is complicated by limited and variable image resolution, which depends on (1) measurement physics (e.g., electrical conduction or electromagnetic wave propagation), (2) parameterization and regularization, (3) measurement error, and (4) spatial variability. We present a framework to predict how core-scale relations between geophysical properties and hydrologic parameters are altered by the inversion, which produces smoothly varying pixel-scale estimates. We refer to this loss of information as "correlation loss." Our approach upscales the core-scale relation to the pixel scale using the model resolution matrix from the inversion, random field averaging, and spatial statistics of the geophysical property. Synthetic examples evaluate the utility of radar travel time tomography (RTT) and electrical-resistivity tomography (ERT) for estimating water content. This work provides (1) a framework to assess tomograms for geologic parameter estimation and (2) insights into the different patterns of correlation loss for ERT and RTT. Whereas ERT generally performs better near boreholes, RTT performs better in the interwell region. Application of petrophysical models to the tomograms in our examples would yield misleading estimates of water content. Although the examples presented illustrate the problem of correlation loss in the context of near-surface geophysical imaging, our results have clear implications for quantitative analysis of tomograms for diverse geoscience applications. Copyright 2005 by the American Geophysical Union.

  3. Calibration of seawater intrusion models: Inverse parameter estimation using surface electrical resistivity tomography and borehole data

    NASA Astrophysics Data System (ADS)

    Beaujean, J.; Nguyen, F.; Kemna, A.; Antonsson, A.; Engesgaard, P.

    2014-08-01

    Electrical resistivity tomography (ERT) can be used to constrain seawater intrusion models because of its high sensitivity to total dissolved solid contents (TDS) in groundwater and its relatively high lateral coverage. However, the spatial variability of resolution in electrical imaging may prevent the correct recovery of the desired hydrochemical properties such as salt mass fraction. This paper presents a sequential approach to evaluate the feasibility of identifying hydraulic conductivity and dispersivity in density-dependent flow and transport models from surface ERT-derived mass fraction. In the course of this study, geophysical inversion was performed by using a smoothness constraint Tikhonov approach, whereas the hydrological inversion was performed using a gradient-based Levenberg-Marquardt algorithm. Two synthetic benchmarks were tested. They represent a pumping experiment in a homogeneous and heterogeneous coastal aquifer, respectively. These simulations demonstrated that only the lower salt mass fraction of the seawater-freshwater transition zone can be recovered for different times. This ability has here been quantified in terms of cumulative sensitivity and our study has further demonstrated that the mismatch between the targeted and the recovered salt mass fraction occurs from a certain threshold. We were additionally able to explore the capability of sensitivity-filtered ERT images using ground surface data only to recover (in both synthetic cases) the hydraulic conductivity while the dispersivity is more difficult to estimate. We attribute the latter mainly to the lack of ERT-derived data at depth (where resolution is poorer) as well as to the smoothing effect of the ERT inversion.

  4. Challenges and opportunities for fractured rock imaging using 3D cross-borehole electrical resistivity

    SciTech Connect

    Robinson, Judith; Johnson, Timothy C.; Slater, Lee D.

    2015-02-02

    There is an increasing need to characterize discrete fractures away from boreholes to better define fracture distributions and monitor solute transport. We performed a 3D evaluation of static and time-lapse cross-borehole electrical resistivity tomography (ERT) data sets from a limestone quarry in which flow and transport are controlled by a bedding-plane feature. Ten boreholes were discretized using an unstructured tetrahedral mesh, and 2D panel measurements were inverted for a 3D distribution of conductivity. We evaluated the benefits of 3D versus 2.5D inversion of ERT data in fractured rock while including the use of borehole regularization disconnects (BRDs) and borehole conductivity constraints. High-conductivity halos (inversion artifacts) surrounding boreholes were removed in static images when BRDs and borehole conductivity constraints were implemented. Furthermore, applying these constraints focused transient changes in conductivity resulting from solute transport on the bedding plane, providing a more physically reasonable model for conductivity changes associated with solute transport at this fractured rock site. Assuming bedding-plane continuity between fractures identified in borehole televiewer data, we discretized a planar region between six boreholes and applied a fracture regularization disconnect (FRD). Although the FRD appropriately focused conductivity changes on the bedding plane, the conductivity distribution within the discretized fracture was nonunique and dependent on the starting homogeneous model conductivity. Synthetic studies performed to better explain field observations showed that inaccurate electrode locations in boreholes resulted in low-conductivity halos surrounding borehole locations. These synthetic studies also showed that the recovery of the true conductivity within an FRD depended on the conductivity contrast between the host rock and fractures. Our findings revealed that the potential exists to improve imaging of fractured

  5. Effects of Neuromuscular Electrical Stimulation and Resistance Training on Knee Extensor/Flexor Muscles.

    PubMed

    Pantović, Milan; Popović, Boris; Madić, Dejan; Obradović, Jelena

    2015-07-01

    Neuromuscular electrical stimulation (NMES) has recently drawn a lot of attention as means for strengthening of voluntary muscle contraction both in sport and rehabilitation. NMES training increases maximal voluntary contraction (MVC) force output through neural adaptations. On the other hand, positive effects of resistance training (RT) on muscle strength are well known. The aim of this study was to investigate effects of a 5-week program of NMES compared to RT program of same duration. Sample of 15 students' of faculty of sport and physical education (age 22 ± 2) were randomized in two groups: NMES (N = 7) and RT (N = 8). NMES group performed NMES superimposed over voluntary muscle contraction, RT group performed resistance training with submaximal loads. Subjects were evaluated for knee isokinetic dynamometry on both sides (60° and 180° s). After intervention no significant difference between groups were observed in isokinetic dynamometry (p = 0.177). However, applying pair sample t test within each group revealed that peak torque increased in NMES-group (p = 0.002 for right knee extensors muscles, p = 0.003 for left, respectively, at 60° and p = 0.004 for left knee extensors muscles, at angular velocity 180°). In RT group (p = 0.033 for right knee extensors muscles, p = 0.029 for right knee flexor muscles, at angular velocity 60°). Our results indicate that NMES has equal potential if not in some way better than classical RT having in mind that overload on locomotor apparatus during NMES is minimal and force of muscle contraction is equal on both sides, for enhancement of knee muscles concentric peak torque.

  6. Hydrogeological bedrock inferred from electrical resistivity model in Taichung Basin, Taiwan

    NASA Astrophysics Data System (ADS)

    Chiang, C. W.; Chang, P. Y.; Chang, L. C.

    2015-12-01

    The four-year project of the study of groundwater hydrogeology and recharge model was indicated by Central Geological Survey, MOEA, Taiwan (R.O.C.) to evaluate recharge groundwater areas in Taiwan where included Taipei, Taichung Basins, Lanyang and Chianan Plains. The groundwater recharge models of Lanyang Plain and Taipei Basin have successfully been estimated in two years ago (2013-2014). The third year of the project integrates with geophysical, geochemistry, and hydrogeology models to estimate the groundwater recharge model in Taichung Basin region. Taichung Basin is mainly covered by Pre-Pleistocene of thick gravel, sandy and muddy sediment rocks within a joint alluvial fan, whereas the depth of the hydrological bedrock remains uncertain. Two electrical resistivity geophysical tools were carried out utilizing direct current resistivity and audio-magnetotelluric (AMT) explorations, which could ideally provide the depth resolutions from shallow to depth for evaluating the groundwater resources. The study has carried out 21 AMT stations in the southern Taichung Basin in order to delineate hydrological bedrock in the region. All the AMT stations were deployed about 24 hours and processed with remote reference technique to reduce culture noises. The quality of most stations shows acceptable in the area which two stations were excluded due to near-field source effect in the southwestern basin. The best depth resolution is identified in 500 meters for the model. The preliminary result shows that the depths of the bedrock gradually changes from southern ~20 m toward to ~400 m in central, and eastern ~20 m to 180 m in the western basin inferred from the AMT model. The investigation shows that AMT method could be a useful geophysical tool to enhance the groundwater recharge model estimation without dense loggings in the region.

  7. Direct quantification of transendothelial electrical resistance in organs-on-chips.

    PubMed

    van der Helm, Marinke W; Odijk, Mathieu; Frimat, Jean-Philippe; van der Meer, Andries D; Eijkel, Jan C T; van den Berg, Albert; Segerink, Loes I

    2016-11-15

    Measuring transendothelial or transepithelial electrical resistance (TEER) is a widely used method to monitor cellular barrier tightness in organs-on-chips. Unfortunately, integrated electrodes close to the cellular barrier hamper visual inspection of the cells or require specialized cleanroom processes to fabricate see-through electrodes. Out-of-view electrodes inserted into the chip's outlets are influenced by the fluid-filled microchannels with relatively high resistance. In this case, small changes in temperature or medium composition strongly affect the apparent TEER. To solve this, we propose a simple and universally applicable method to directly determine the TEER in microfluidic organs-on-chips without the need for integrated electrodes close to the cellular barrier. Using four electrodes inserted into two channels - two on each side of the porous membrane - and six different measurement configurations we can directly derive the isolated TEER independent of channel properties. We show that this method removes large variation of non-biological origin in chips filled with culture medium. Furthermore, we demonstrate the use of our method by quantifying the TEER of a monolayer of human hCMEC/D3 cerebral endothelial cells, mimicking the blood-brain barrier inside our microfluidic organ-on-chip device. We found stable TEER values of 22 Ω cm(2)±1.3 Ω cm(2) (average ± standard error of the mean of 4 chips), comparable to other TEER values reported for hCMEC/D3 cells in well-established Transwell systems. In conclusion, we demonstrate a simple and robust way to directly determine TEER that is applicable to any organ-on-chip device with two channels separated by a membrane. This enables stable and easily applicable TEER measurements without the need for specialized cleanroom processes and with visibility on the measured cell layer.

  8. Uncertainty quantification of CO₂ saturation estimated from electrical resistance tomography data at the Cranfield site

    DOE PAGESBeta

    Yang, Xianjin; Chen, Xiao; Carrigan, Charles R.; Ramirez, Abelardo L.

    2014-06-03

    A parametric bootstrap approach is presented for uncertainty quantification (UQ) of CO₂ saturation derived from electrical resistance tomography (ERT) data collected at the Cranfield, Mississippi (USA) carbon sequestration site. There are many sources of uncertainty in ERT-derived CO₂ saturation, but we focus on how the ERT observation errors propagate to the estimated CO₂ saturation in a nonlinear inversion process. Our UQ approach consists of three steps. We first estimated the observational errors from a large number of reciprocal ERT measurements. The second step was to invert the pre-injection baseline data and the resulting resistivity tomograph was used as the priormore » information for nonlinear inversion of time-lapse data. We assigned a 3% random noise to the baseline model. Finally, we used a parametric bootstrap method to obtain bootstrap CO₂ saturation samples by deterministically solving a nonlinear inverse problem many times with resampled data and resampled baseline models. Then the mean and standard deviation of CO₂ saturation were calculated from the bootstrap samples. We found that the maximum standard deviation of CO₂ saturation was around 6% with a corresponding maximum saturation of 30% for a data set collected 100 days after injection began. There was no apparent spatial correlation between the mean and standard deviation of CO₂ saturation but the standard deviation values increased with time as the saturation increased. The uncertainty in CO₂ saturation also depends on the ERT reciprocal error threshold used to identify and remove noisy data and inversion constraints such as temporal roughness. Five hundred realizations requiring 3.5 h on a single 12-core node were needed for the nonlinear Monte Carlo inversion to arrive at stationary variances while the Markov Chain Monte Carlo (MCMC) stochastic inverse approach may expend days for a global search. This indicates that UQ of 2D or 3D ERT inverse problems can be performed

  9. Uncertainty quantification of CO₂ saturation estimated from electrical resistance tomography data at the Cranfield site

    SciTech Connect

    Yang, Xianjin; Chen, Xiao; Carrigan, Charles R.; Ramirez, Abelardo L.

    2014-06-03

    A parametric bootstrap approach is presented for uncertainty quantification (UQ) of CO₂ saturation derived from electrical resistance tomography (ERT) data collected at the Cranfield, Mississippi (USA) carbon sequestration site. There are many sources of uncertainty in ERT-derived CO₂ saturation, but we focus on how the ERT observation errors propagate to the estimated CO₂ saturation in a nonlinear inversion process. Our UQ approach consists of three steps. We first estimated the observational errors from a large number of reciprocal ERT measurements. The second step was to invert the pre-injection baseline data and the resulting resistivity tomograph was used as the prior information for nonlinear inversion of time-lapse data. We assigned a 3% random noise to the baseline model. Finally, we used a parametric bootstrap method to obtain bootstrap CO₂ saturation samples by deterministically solving a nonlinear inverse problem many times with resampled data and resampled baseline models. Then the mean and standard deviation of CO₂ saturation were calculated from the bootstrap samples. We found that the maximum standard deviation of CO₂ saturation was around 6% with a corresponding maximum saturation of 30% for a data set collected 100 days after injection began. There was no apparent spatial correlation between the mean and standard deviation of CO₂ saturation but the standard deviation values increased with time as the saturation increased. The uncertainty in CO₂ saturation also depends on the ERT reciprocal error threshold used to identify and remove noisy data and inversion constraints such as temporal roughness. Five hundred realizations requiring 3.5 h on a single 12-core node were needed for the nonlinear Monte Carlo inversion to arrive at stationary variances while the Markov Chain Monte Carlo (MCMC) stochastic inverse approach may expend days for a global search. This indicates that UQ of 2D or 3D ERT inverse problems can be performed on a

  10. Tracking snowmelt in the subsurface: time-lapse electrical resistivity imaging on an alpine hill slope.

    NASA Astrophysics Data System (ADS)

    Thayer, D.; Parsekian, A.; Hyde, K.; Beverly, D.; Speckman, H. N.; Ewers, B. E.

    2015-12-01

    In the mountain West region the winter snowpack provides more than 70% of our annual water supply. Modeling and predicting the timing and magnitude of snowmelt-driven water yield is difficult due to the complexities of hydrologic systems that move meltwater from snow to rivers. Particular challenges are understanding the temporal and spatial domain of subsurface hydraulic processes at relevant scales, which range from points to catchments. Subsurface characterization often requires borehole instrumentation, which is expensive and extremely difficult to install in remote, rugged terrain. Advancements in non-invasive geophysical methods allow us to monitor changes in geophysical parameters over time and infer changes in hydraulic processes. In the No-Name experimental catchment in the Medicine Bow National Forest in Wyoming, we are conducting a multi-season, time-lapse electrical resistivity imaging survey on a sub-alpine hill slope. This south-facing, partially forested slope ranges from 5 degrees to 35 degrees in steepness and consists of a soil mantle covering buried glacial talus deposits of unknown depth. A permanent grid of down-slope and cross-slope electrode arrays is monitored up to four times a day. The arrays span the entire vertical distance of the slope, from an exposed bedrock ridge to a seasonal drainage below, and cover treed and non-treed areas. Geophysical measurements are augmented by temperature and moisture time-series instrumented below the surface in a contiguous 3 meter borehole. A time-series of multiple resistivity models each day from May to July shows the changing distribution of subsurface moisture during a seasonal drying sequence punctuated by isolated rain events. Spatial patterns of changing moisture indicate that soil and gravel in the top two meters drain into a saturated layer parallel to the slope which overlies less saturated material. These results suggest that water from snowmelt and rain events tends to move down-slope beneath

  11. The effect of the resistive properties of bone on neural excitation and electric fields in cochlear implant models.

    PubMed

    Malherbe, T K; Hanekom, T; Hanekom, J J

    2015-09-01

    The resistivity of bone is the most variable of all the tissues in the human body, ranging from 312 Ω cm to 84,745 Ω cm. Volume conduction models of cochlear implants have generally used a resistivity value of 641 Ω cm for the bone surrounding the cochlea. This study investigated the effect that bone resistivity has on modelled neural thresholds and intracochlear potentials using user-specific volume conduction models of implanted cochleae applying monopolar stimulation. The complexity of the description of the head volume enveloping the cochlea was varied between a simple infinite bone volume and a detailed skull containing a brain volume, scalp and accurate return electrode position. It was found that, depending on the structure of the head model and implementation of the return electrode, different bone resistivity values are necessary to match model predictions to data from literature. Modelled forward-masked spatial tuning curve (fmSTC) widths and slopes and intracochlear electric field profile length constants were obtained for a range of bone resistivity values for the various head models. The predictions were compared to measurements found in literature. It was concluded that, depending on the head model, a bone resistivity value between 3500 Ω cm and 10,500 Ω cm allows prediction of neural and electrical responses that match measured data. A general recommendation is made to use a resistivity value of approximately 10,000 Ω cm for bone volumes in conduction models of the implanted cochlea when neural excitation is predicted and a value of approximately 6500 Ω cm when predicting electric fields inside the cochlear duct.

  12. Chemical bonding, optical constants, and electrical resistivity of sputter-deposited gallium oxide thin films

    SciTech Connect

    Ramana, C. V. Rubio, E. J.; Barraza, C. D.; Miranda Gallardo, A.; McPeak, Samantha; Kotru, Sushma; Grant, J. T.

    2014-01-28

    Gallium oxide (Ga{sub 2}O{sub 3}) thin films were made by sputter deposition employing a Ga{sub 2}O{sub 3} ceramic target for sputtering. The depositions were made over a wide range of substrate temperatures (T{sub s}), from 25 to 600 °C. The effect of T{sub s} on the chemical bonding, surface morphological characteristics, optical constants, and electrical properties of the grown films was evaluated using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), spectroscopic ellipsometry (SE), and four-point probe measurements. XPS analyses indicate the binding energies (BE) of the Ga 2p doublet, i.e., the Ga 2p{sub 3/2} and Ga 2p{sub 1/2} peaks, are located at 1118.0 and 1145.0 eV, respectively, characterizing gallium in its highest chemical oxidation state (Ga{sup 3+}) in the grown films. The core level XPS spectra of O 1s indicate that the peak is centered at a BE ∼ 531 eV, which is also characteristic of Ga-O bonds in the Ga{sub 2}O{sub 3} phase. The granular morphology of the nanocrystalline Ga{sub 2}O{sub 3} films was evident from AFM measurements, which also indicate that the surface roughness of the films increases from 0.5 nm to 3.0 nm with increasing T{sub s}. The SE analyses indicate that the index of refraction (n) of Ga{sub 2}O{sub 3} films increases with increasing T{sub s} due to improved structural quality and packing density of the films. The n(λ) of all the Ga{sub 2}O{sub 3} films follows the Cauchy's dispersion relation. The room temperature electrical resistivity was high (∼200 Ω-cm) for amorphous Ga{sub 2}O{sub 3} films grown at T{sub s} = RT-300 °C and decreased to ∼1 Ω-cm for nanocrystalline Ga{sub 2}O{sub 3} films grown at T{sub s} ≥ 500–600 °C. A correlation between growth conditions, microstructure, optical constants, and electrical properties of Ga{sub 2}O{sub 3} films is derived.

  13. Electrical Resistivity Imaging and Hydrodynamic Modeling of Convective Fingering in a Sabkha Aquifer

    NASA Astrophysics Data System (ADS)

    Van Dam, Remke; Eustice, Brian; Hyndman, David; Wood, Warren; Simmons, Craig

    2014-05-01

    Free convection, or fluid motion driven by density differences, is an important groundwater flow mechanism that can enhance transport and mixing of heat and solutes in the subsurface. Various issues of environmental and societal relevance are exacerbated convective mixing; it has been studied in the context of dense contaminant plumes, nuclear waste disposal, greenhouse gas sequestration, the impacts of sea level rise and saline intrusion on drinking water resources. The basic theory behind convective flow in porous media is well understood, but important questions regarding this process in natural systems remain unanswered. Most previous research on this topic has focused on theory and modeling, with only limited attention to experimental studies and field measurements. The few published studies present single snapshots, making it difficult to quantify transient changes in these systems. Non-invasive electrical methods have the potential to exploit the relation between solute concentrations and electrical conductance of a fluid, and thereby estimate fluid salinity differences in time and space. We present the results of a two-year experimental study at a shallow sabkha aquifer in the United Arab Emirates, about 50 km southwest of the city of Abu Dhabi along the coast of the Arabian Gulf, that was designed to explore the transient nature of free convection. Electrical resistivity tomography (ERT) data documented the presence of convective fingers following a significant rainfall event. One year later, the complex fingering pattern had completely disappeared. This observation is supported by analysis of the aquifer solute budget as well as hydrodynamic modeling of the system. The transient dynamics of the gravitational instabilities in the modeling results are in agreement with the timing observed in the time-lapse ERT data. Our experimental observations and modeling are consistent with the hypothesis that the instabilities arose from a dense brine that infiltrated

  14. Electrical Resistivity Imaging of Tidal Fluctuations in the Water Table at Inwood Hill Park, Manhattan

    NASA Astrophysics Data System (ADS)

    Kenyon, P. M.; Kassem, D.; Olin, A.; Nunez, J.; Smalling, A.

    2005-05-01

    Inwood Hill Park is located on the northern tip of Manhattan and has been extensively modified over the years by human activities. In its current form, it has a backbone of exposed or lightly covered bedrock along the Hudson River, adjacent to a flat area with two tidal inlets along the northern shore of Manhattan. The tidal motions in the inlets are expected to drive corresponding fluctuations in the water table along the borders of the inlets. In the Fall of 2002, a group of students from the Department of Earth and Atmospheric Sciences at the City College of New York studied these fluctuations. Electrical resistivity cross sections were obtained with a Syscal Kid Switch 24 resistivity meter during the course of a tidal cycle at three locations surrounding the westernmost inlet in the park. No change was seen over a tidal cycle at Site 1, possibly due to the effect of concrete erosion barriers which were located between the land and the water surrounding this site. Measurements at Site 2 revealed a small, regular change in the water table elevation of approximately 5 cm over the course of a tidal cycle. This site is inferred to rest on alluvial sediments deposited by a small creek. The cross sections taken at different times during a tidal cycle at Site 3 were the most interesting. They show a very heterogeneous subsurface, with water spurting between blocks of high resistivity materials during the rising portion of the cycle. A small sinkhole was observed on the surface of the ground directly above an obvious plume of water in the cross section. Park personnel confirmed that this sinkhole, like others scattered around this site, is natural and not due to recent construction activity. They also indicated that debris from the construction of the New York City subways may have been dumped in the area in the past. Our conclusion is that the tidal fluctuations at Site 3 are being channeled by solid blocks in the construction debris, and that the sinkholes currently

  15. Dynamic thermal characteristics of heat pipe via segmented thermal resistance model for electric vehicle battery cooling

    NASA Astrophysics Data System (ADS)

    Liu, Feifei; Lan, Fengchong; Chen, Jiqing

    2016-07-01

    Heat pipe cooling for battery thermal management systems (BTMSs) in electric vehicles (EVs) is growing due to its advantages of high cooling efficiency, compact structure and flexible geometry. Considering the transient conduction, phase change and uncertain thermal conditions in a heat pipe, it is challenging to obtain the dynamic thermal characteristics accurately in such complex heat and mass transfer process. In this paper, a "segmented" thermal resistance model of a heat pipe is proposed based on thermal circuit method. The equivalent conductivities of different segments, viz. the evaporator and condenser of pipe, are used to determine their own thermal parameters and conditions integrated into the thermal model of battery for a complete three-dimensional (3D) computational fluid dynamics (CFD) simulation. The proposed "segmented" model shows more precise than the "non-segmented" model by the comparison of simulated and experimental temperature distribution and variation of an ultra-thin micro heat pipe (UMHP) battery pack, and has less calculation error to obtain dynamic thermal behavior for exact thermal design, management and control of heat pipe BTMSs. Using the "segmented" model, the cooling effect of the UMHP pack with different natural/forced convection and arrangements is predicted, and the results correspond well to the tests.

  16. Core-scale electrical resistivity tomography (ERT) monitoring of CO2-brine mixture in Fontainebleau sandstone

    NASA Astrophysics Data System (ADS)

    Bosch, David; Ledo, Juanjo; Queralt, Pilar; Bellmunt, Fabian; Luquot, Linda; Gouze, Philippe

    2016-07-01

    The main goal of the monitoring stage of Carbon Capture and Storage (CCS) is to obtain an accurate estimation of the subsurface CO2 accumulation and to detect any possible leakage. Laboratory experiments are necessary to investigate the small scale processes governing the CO2-brine-rock interaction. They also provide a means to calibrate the results coming from field scale geophysical methods. In this work we set up an experimental system which is able to perform Electrical Resistivity Tomography (ERT) measurements on centimeter-scale rock samples at various P-T conditions. We present the results of two new experiments related to CO2 monitoring, performed on a cylindrical (4 × 8 cm) Fontainebleau rock sample. In the first one, we have quantified the CO2 saturation at different volume fractions, representing zones from a deep saline aquifer with varying degrees of saturation. In the second one, we have monitored and quantified the effect of CO2 dissolution in the brine at a pressure of 40 bar during eight days, emulating the invasion of CO2 into a shallow aquifer. Results highlight the importance of accounting for the contribution of surface conductivity in highly CO2-saturated regions, even in clay-free rocks, and also for brine conductivity variation due to CO2 dissolution. Ignoring any of these effects will end up in a CO2 saturation underestimation. We present a modified CO2 saturation equation to account for these two influences.

  17. Demonstration of Combined Zero-Valent Iron and Electrical Resistance Heating for In Situ Trichloroethene Remediation

    SciTech Connect

    Truex, Michael J.; Macbeth, Tamzen; Vermeul, Vincent R.; Fritz, Brad G.; Mendoza, Donaldo P.; Mackley, Rob D.; Wietsma, Thomas W.; Sandberg, Greg; Powell, Thomas; Powers, Jeff; Pitre, Emile; Michalsen, Mandy M.; Ballock-Dixon, Sage; Zhong, Lirong; Oostrom, Martinus

    2011-06-27

    The effectiveness of in situ treatment using zero-valent iron to remediate sites with non-aqueous phase or significant sediment-associated contaminant mass can be limited by relatively low rates of mass transfer to bring contaminants in contact with the reactive media. For a field test in a trichloroethene source area, combining moderate-temperature (maximum 50oC) subsurface electrical resistance heating with in situ ZVI treatment was shown to accelerate dechlorination and dissolution rates by a factor of 4 to 6 based on organic daughter products and a factor 8-16 using a chloride concentrations. A mass-discharge-based analysis was used to evaluate reaction, dissolution, and volatilization at ambient groundwater temperature (~10oC) and as temperature was increased up to about 50oC. Increased reaction and contaminant dissolution were observed with increased temperature, but volatilization was minimal during the test because in situ reactions maintained low aqueous-phase TCE concentrations.

  18. Comparison of measuring strategies for the 3-D electrical resistivity imaging of tumuli

    NASA Astrophysics Data System (ADS)

    Tsourlos, Panagiotis; Papadopoulos, Nikos; Yi, Myeong-Jong; Kim, Jung-Ho; Tsokas, Gregory

    2014-02-01

    Artificial erected hills like tumuli, mounds, barrows and kurgans comprise monuments of the past human activity and offer opportunities to reconstruct habitation models regarding the life and customs during their building period. These structures also host features of archeological significance like architectural relics, graves or chamber tombs. Tumulus exploration is a challenging geophysical problem due to the complex distribution of the subsurface physical properties, the size and burial depth of potential relics and the uneven topographical terrain. Geoelectrical methods by means of three-dimensional (3-D) inversion are increasingly popular for tumulus investigation. Typically data are obtained by establishing a regular rectangular grid and assembling the data collected by parallel two-dimensional (2-D) tomographies. In this work the application of radial 3-D mode is studied, which is considered as the assembly of data collected by radially positioned Electrical Resistivity Tomography (ERT) lines. The relative advantages and disadvantages of this measuring mode over the regular grid measurements were investigated and optimum ways to perform 3-D ERT surveys for tumuli investigations were proposed. Comparative test was performed by means of synthetic examples as well as by tests with field data. Overall all tested models verified the superiority of the radial mode in delineating bodies positioned at the central part of the tumulus while regular measuring mode proved superior in recovering bodies positioned away from the center of the tumulus. The combined use of radial and regular modes seems to produce superior results in the expense of time required for data acquisition and processing.

  19. Effect of argon gas pressure on residual stress, microstructure evolution and electrical resistivity of beryllium films

    NASA Astrophysics Data System (ADS)

    Luo, Bing-Chi; Li, Kai; Zhang, Ji-Qiang; Luo, Jiang-Shan; Wu, Wei-Dong; Tang, Yong-Jian

    2016-02-01

    The residual stress in beryllium films fabricated on K9 substrates by using magnetron sputtering deposition is measured by using a curvature method and is theoretically estimated by using the Nix and Clemens (NC) model. The experimental results indicate that the 1.3-μm-thick film is always in a tensile state for pressure variations in the range from 0.4 to 1.2 Pa. When the sputtering gas pressure is increased, the average stress increases at first, after which it decreases by a remarkable amount. The observed descending trend of the tensile stress when the sputtering gas pressure is beyond 0.6 Pa is mainly attributed to the grain size in the film being larger than that in the film when the pressure is below 0.6 Pa. The maximal residual stress of 552 MPa at a sputtering gas pressure of 0.6 Pa is close to the tensile strength (550 MPa) of the corresponding beryllium bulk material and is about 8 times smaller than that calculated by using the N-C model. In addition, the surface morphologies of the as-fabricated films reveal fibrous grains while the cross-sectional morphologies are characterized by a coarsening of columnar grains. The measured electric resistivity of each film strongly depends on its porosity and the sizes of its grains.

  20. Improving Indonesian peatland C stock estimates using ground penetrating radar (GPR) and electrical resistivity imaging (ERI)

    NASA Astrophysics Data System (ADS)

    Terry, N.; Comas, X.; Slater, L. D.; Warren, M.; Kolka, R. K.; Kristijono, A.; Sudiana, N.; Nurjaman, D.; Darusman, T.

    2014-12-01

    Tropical peatlands sequester an estimated 15% of the carbon pool from peatlands worldwide. Indonesian peatlands account for approximately 65% of all tropical peat, and are believed to be the largest global source of carbon dioxide emissions to the atmosphere from degrading peat. However, there is great uncertainty in these estimates due to insufficient data regarding the thickness of organic peat soils and their carbon content. Meanwhile, Indonesian peatlands are threatened by heightening pressure to drain and develop. Indirect geophysical methods have garnered interest for their potential to non-invasively estimate peat depth and gas content in boreal peatlands. Drawing from these techniques, we employed ground penetrating radar (GPR) and electrical resistivity imaging (ERI) in tandem with direct methods (core sampling) to evaluate the potential of these methods for tropical peatland mapping at 2 distinct study sites on West Kalimantan (Indonesia). We find that: [1] West Kalimantan peatland thicknesses estimated from GPR and ERI in intermediate/shallow peat can vary substantially over short distances (for example, > 2% over less than 0.02° surface topography gradient), [2] despite having less vertical resolution, ERI is able to better resolve peatland thickness in deep peat, and [3] GPR provides useful data regarding peat matrix attributes (such as the presence of wood layers). These results indicate GPR and ERI could help reduce uncertainty in carbon stocks and aid in responsible land management decisions in Indonesia.

  1. The implanted electrical resistance strain gauge: in vitro studies on data integrity.

    PubMed

    Crawshaw, A H; Hastings, G W; Dove, J

    1991-01-01

    The aim of this research is to investigate, and thus counter, the adverse effects of tissue fluid ingress on the performance of the electrical resistance strain gauge when used in ascertaining in vivo loading on a spinal implant. Moisture absorption has been minimized by adopting maximum metallic coverage in a package comprising stainless steel foil on vacuum-injected pacemaker grade epoxide. In a simulation of the implanted environment, cyclic strain wet endurance testing in saline suggests that, in the body, the fall in indicated quasi-dynamic strain would be less than 1.5% at 24 weeks post-operation (the longevity needed to span adequately the bony fusion phase). This implies that stiffening of the fusion mass will be deducible to a similar accuracy (from stepped-load exercises), in which creep is a secondary effect. However, crucial information (from quasi-static (passive) studies) regarding remodelling and load-sharing processes would be subject to a total signal error (primarily due to grid corrosion) in excess of 16% by 24 weeks, since long-term drifts are not inherently cancelled. Signal compensation is therefore additionally required, and an approximate empirical characterization of total error versus time has been derived. PMID:1875386

  2. The use of soil electrical resistivity to monitor plant and soil water relationships in vineyards

    NASA Astrophysics Data System (ADS)

    Brillante, L.; Mathieu, O.; Bois, B.; van Leeuwen, C.; Lévêque, J.

    2015-03-01

    Soil water availability deeply affects plant physiology. In viticulture it is considered a major contributor to the "terroir" effect. The assessment of soil water in field conditions is a difficult task, especially over large surfaces. New techniques are therefore required in order to better explore variations of soil water content in space and time with low disturbance and with great precision. Electrical resistivity tomography (ERT) meets these requirements for applications in plant sciences, agriculture and ecology. In this paper, possible techniques to develop models that allow the use of ERT to spatialise soil water available to plants are reviewed. An application of soil water monitoring using ERT in a grapevine plot in Burgundy (north-east France) during the vintage 2013 is presented. We observed the lateral heterogeneity of ERT-derived fraction of transpirable soil water (FTSW) variations, and differences in water uptake depend on grapevine water status (leaf water potentials measured both at predawn and at solar noon and contemporary to ERT monitoring). Active zones in soils for water movements were identified. The use of ERT in ecophysiological studies, with parallel monitoring of plant water status, is still rare. These methods are promising because they have the potential to reveal a hidden part of a major function of plant development: the capacity to extract water from the soil.

  3. Nonlinear inversion of electrical resistivity imaging using pruning Bayesian neural networks

    NASA Astrophysics Data System (ADS)

    Jiang, Fei-Bo; Dai, Qian-Wei; Dong, Li

    2016-06-01

    Conventional artificial neural networks used to solve electrical resistivity imaging (ERI) inversion problem suffer from overfitting and local minima. To solve these problems, we propose to use a pruning Bayesian neural network (PBNN) nonlinear inversion method and a sample design method based on the K-medoids clustering algorithm. In the sample design method, the training samples of the neural network are designed according to the prior information provided by the K-medoids clustering results; thus, the training process of the neural network is well guided. The proposed PBNN, based on Bayesian regularization, is used to select the hidden layer structure by assessing the effect of each hidden neuron to the inversion results. Then, the hyperparameter α k , which is based on the generalized mean, is chosen to guide the pruning process according to the prior distribution of the training samples under the small-sample condition. The proposed algorithm is more efficient than other common adaptive regularization methods in geophysics. The inversion of synthetic data and field data suggests that the proposed method suppresses the noise in the neural network training stage and enhances the generalization. The inversion results with the proposed method are better than those of the BPNN, RBFNN, and RRBFNN inversion methods as well as the conventional least squares inversion.

  4. Low resistance silver contacts to indium phosphide - Electrical and metallurgical considerations

    NASA Technical Reports Server (NTRS)

    Weizer, Victor G.; Fatemi, Navid S.

    1993-01-01

    The electrical and metallurgical behavior of the Ag-InP contact system has been investigated. Specific contact resistivity (Rc) values in the low 10 exp -6 Ohm sq cm range are readily achieved on n-InP (Si: 1.7 x 10 exp 18/cu cm) after sintering at 400 C for several minutes. The low Rc values, however, are shown to be accompanied by dissolution of InP into the metallization, resulting in device degradation. An analysis of the sinter-induced metallurgical interactions shows this system to be similar to the well-characterized Au-InP system, albeit with fundamental differences. The similarities include the dissociative diffusion of In, the reaction-suppressing effect of SiO2 capping, and especially, the formation of a phosphide layer at the metal-InP interface. The low post-sinter Rc values in the Ag-InP system may be due to the presence of a AgP2 layer at the metal-InP interface; low values of Rc can be achieved without incurring device degrading metallurgical interactions by introducing a thin AgP2 layer between the InP and the current carrying metallization.

  5. Detection of Old Mine Tunnels in Mexico City Highlands by Electric Resistivity Image Methods

    NASA Astrophysics Data System (ADS)

    Chavez, R. E.; Tejero, A.; Cifuentes-Nava, G.; HernaNdez-Quintero, J.

    2013-12-01

    Electrical Resistivity Tomography (ERT) methods have been applied to study cavities or subsurface subsidence threatening urbanized areas. Unfortunately, ERT-3D techniques carried out on heavily urbanized areas become a difficult task, since parallel ERT arrays cannot be deployed. Then, a conventional regular grid cannot be carried out. We present a subsidence problem located in a densely populated portion of Mexico City highlands. Since the damaged houses are in the middle of a highly populated low-class neighborhood, an unconventional ERT array had to be applied. At first, a ';T'-array formed by two perpendicular transects was applied, deployed within a small alley, that stretched from the house entrance. This study determined a tubular structure beneath the houses following an irregular path at depth. Finally, houses were demolished due to the extensive damaged in their foundations. This made possible to carry out a second ERT-3D study, which included a dipolar array called ';L' and ';Corner' arrays. Such a new work defined a similar tubular structure. The cavity entrance was discovered, when excavations were made, although its precise shape could not be defined. The ERT-3D interpretation contributed to locate and accurately determine the geometrical characteristics of the geological feature that caused the collapse of dwellings.

  6. Geometric correction factor for transepithelial electrical resistance measurements in transwell and microfluidic cell cultures

    NASA Astrophysics Data System (ADS)

    Yeste, J.; Illa, X.; Gutiérrez, C.; Solé, M.; Guimerà, A.; Villa, R.

    2016-09-01

    Transepithelial electrical resistance (TEER) measurements are regularly used in in vitro models to quantitatively evaluate the cell barrier function. Although it would be expected that TEER values obtained with the same cell type and experimental setup were comparable, values reported in the literature show a large dispersion for unclear reasons. This work highlights a possible error in a widely used formula to calculate the TEER, in which it may be erroneously assumed that the entire cell culture area contributes equally to the measurement. In this study, we have numerically calculated this error in some cell cultures previously reported. In particular, we evidence that some TEER measurements resulted in errors when measuring low TEERs, especially when using Transwell inserts 12 mm in diameter or microfluidic systems that have small chamber heights. To correct this error, we propose the use of a geometric correction factor (GCF) for calculating the TEER. In addition, we describe a simple method to determine the GCF of a particular measurement system, so that it can be applied retrospectively. We have also experimentally validated an interdigitated electrodes (IDE) configuration where the entire cell culture area contributes equally to the measurement, and it also implements minimal electrode coverage so that the cells can be visualized alongside TEER analysis.

  7. Structural transition in the humic matrix of soil gels and the electrical resistivity of soils

    NASA Astrophysics Data System (ADS)

    Fedotov, G. N.; Shoba, S. A.

    2015-11-01

    The structural organization of the organic matrix of humic substances in soils has been analyzed, and the conclusion has been drawn that the existence of humic matrix is determined by contacts between the hydrophilic sites of humic particles in dry soils and between their hydrophobic sites in wet soils. It follows from the advanced supposition that the wetting-drying process should cause a structural transition (reorganization of the humic matrix), which should affect the properties of soils. To verify this supposition, the effect of soil moisture on the electrical resistivity of soil-water extracts, suspensions, and pastes has been studied. It follows from the studies performed that soil electrolytes are fixed in dry soils during drying and are gradually released into solution. However, beginning from a specific soil water content, the release of electrolytes occurs almost immediately after their contact with water. The obtained data suggest that an energy barrier should be overcome for the release of electrolytes from the soils with water content below the specific limit. There is no energy barrier for the soils with water content higher than this limit. The existence of structural transition in the humic matrix of soil gels well explains these results. The effect of energetic impacts on the structural transition has been studied. It has been shown that the study of structural transition should avoid operations that increase the number and amplitude of energy fluctuations in the systems.

  8. In-situ Study of Nanostructure and Electrical Resistance of Nanocluster Films Irradiated with Ion Beams

    SciTech Connect

    Jiang, Weilin; Sundararajan, Jennifer A.; Varga, Tamas; Bowden, Mark E.; Qiang, You; McCloy, John S.; Henager, Charles H.; Montgomery, Robert O.

    2014-08-11

    An in-situ study is reported on the structural evolution in nanocluster films under He+ ion irradiation using an advanced helium ion microscope. The films consist of loosely interconnected nanoclusters of magnetite or iron-magnetite (Fe-Fe3O4) core-shells. The nanostructure is observed to undergo dramatic changes under ion-beam irradiation, featuring grain growth, phase transition, particle aggregation, and formation of nanowire-like network and nano-pores. Studies based on ion irradiation, thermal annealing and election irradiation have indicated that the major structural evolution is activated by elastic nuclear collisions, while both electronic and thermal processes can play a significant role once the evolution starts. The electrical resistance of the Fe-Fe3O4 films measured in situ exhibits a super-exponential decay with dose. The behavior suggests that the nanocluster films possess an intrinsic merit for development of an advanced online monitor for neutron radiation with both high detection sensitivity and long-term applicability, which can enhance safety measures in many nuclear operations.

  9. Observation of trapped gas during electrical resistance heating of trichloroethylene under passive venting conditions.

    PubMed

    Martin, E J; Kueper, B H

    2011-11-01

    A two-dimensional experiment employing a heterogeneous sand pack incorporating two pools of trichloroethylene (TCE) was performed to assess the efficacy of electrical resistance heating (ERH) under passive venting conditions. Temperature monitoring displayed the existence of a TCE-water co-boiling plateau at 73.4°C, followed by continued heating to 100°C. A 5cm thick gas accumulation formed beneath a fine-grained capillary barrier during and after co-boiling. The capillary barrier did not desaturate during the course of the experiment; the only pathway for gas escape being through perforated wells traversing the barrier. The thickness of the accumulation was dictated by the entry pressure of the perforated well. The theoretical maximum TCE soil concentration within the region of gas accumulation, following gas collapse, was estimated to be 888mg/kg. Post-heating soil sampling revealed TCE concentrations in this region ranging from 27mg/kg to 96.7mg/kg, indicating removal of aqueous and gas phase TCE following co-boiling as a result of subsequent boiling of water. The equilibrium concentrations of TCE in water corresponding to the range of post-treatment concentrations in soil (6.11mg/kg to 136mg/kg) are calculated to range from 19.8mg/l to 440mg/l. The results of this experiment illustrate the importance of providing gas phase venting during the application of ERH in heterogeneous porous media.

  10. Integration of electrical resistivity imaging and ground penetrating radar to investigate solution features in the Biscayne Aquifer

    NASA Astrophysics Data System (ADS)

    Yeboah-Forson, Albert; Comas, Xavier; Whitman, Dean

    2014-07-01

    The limestone composing the Biscayne Aquifer in southeast Florida is characterized by cavities and solution features that are difficult to detect and quantify accurately because of their heterogeneous spatial distribution. Such heterogeneities have been shown by previous studies to exert a strong influence in the direction of groundwater flow. In this study we use an integrated array of geophysical methods to detect the lateral extent and distribution of solution features as indicative of anisotropy in the Biscayne Aquifer. Geophysical methods included azimuthal resistivity measurements, electrical resistivity imaging (ERI) and ground penetrating radar (GPR) and were constrained with direct borehole information from nearby wells. The geophysical measurements suggest the presence of a zone of low electrical resistivity (from ERI) and low electromagnetic wave velocity (from GPR) below the water table at depths of 4-9 m that corresponds to the depth of solution conduits seen in digital borehole images. Azimuthal electrical measurements at the site reported coefficients of electrical anisotropy as high as 1.36 suggesting the presence of an area of high porosity (most likely comprising different types of porosity) oriented in the E-W direction. This study shows how integrated geophysical methods can help detect the presence of areas of enhanced porosity which may influence the direction of groundwater flow in a complex anisotropic and heterogeneous karst system like the Biscayne Aquifer.

  11. Module Five: Relationships of Current, Voltage, and Resistance; Basic Electricity and Electronics Individualized Learning System.

    ERIC Educational Resources Information Center

    Bureau of Naval Personnel, Washington, DC.

    This module covers the relationships between current and voltage; resistance in a series circuit; how to determine the values of current, voltage, resistance, and power in resistive series circuits; the effects of source internal resistance; and an introduction to the troubleshooting of series circuits. This module is divided into five lessons:…

  12. Effect of fast neutrons on the electric resistivity of porcelain for application in fast-neutron dosimetry

    SciTech Connect

    Fadel, M.A.; Abdel-Fattah, W.I.; Abdulla, A.A.; Kadum, A.A.

    1982-11-01

    The electric resistivity (rho) of quartz and alumina porcelain was measured before and after irradiation with different fluences (phi) of fission neutrons in the range of 10/sup 7/-10/sup 12/ n/cm/sup 2/ and at different temperatures in the range of 20-90/sup 0/C. The results showed that the activation energy (..delta..E) for quartz porcelain decreased progressively with the increase of phi, while it remained approximately constant for alumina porcelain. Moreover, the electric resistivity of alumina porcelain decreased with the increase of phi. However, there were no measureable effects of /sup 60/Co ..gamma.. doses up to 0.6 Mrad on the electric resistivities of the samples. An empirical formula for calculating phi from the measured value of ..delta..E for quartz porcelain was achieved. A semiempirical formula for calculating phi for the resistivity data for the alumina porcelain is given. The effect of neutron energies on the induced changes in (rho) for the alumina porcelain was investigated. Additionally, the effect of storage at 50/sup 0/C for periods up to 3 weeks on these changes were also measured.

  13. A Nondestructive Evaluation Method: Measuring the Fixed Strength of Spot-Welded Joint Points by Surface Electrical Resistivity.

    PubMed

    Shimamoto, Akira; Yamashita, Keitaro; Inoue, Hirofumi; Yang, Sung-Mo; Iwata, Masahiro; Ike, Natsuko

    2013-04-01

    Destructive tests are generally applied to evaluate the fixed strength of spot-welding nuggets of zinc-plated steel (which is a widely used primary structural material for automobiles). These destructive tests, however, are expensive and time-consuming. This paper proposes a nondestructive method for evaluating the fixed strength of the welded joints using surface electrical resistance. A direct current nugget-tester and probes have been developed by the authors for this purpose. The proposed nondestructive method uses the relative decrease in surface electrical resistance, α. The proposed method also considers the effect of the corona bond. The nugget diameter is estimated by two factors: R Quota, which is calculated from variation of resistance, and a constant that represents the area of the corona bond. Since the maximum tensile strength is correlated with the nugget diameter, it can be inferred from the estimated nugget diameter. When appropriate measuring conditions for the surface electrical resistance are chosen, the proposed method can effectively evaluate the fixed strength of the spot-welded joints even if the steel sheet is zinc-plated.

  14. Case histories of electrical resistivity and controlled-source magnetotelluric surveys for the site investigation of tunnel construction

    SciTech Connect

    Kwon, H.S.; Song, Y.; Yi, M.J.; Chung, H.J.; Kim, K.S.

    2006-12-15

    In tunnel construction, the information regarding rock mass quality and the distribution of weak zones is crucial for economical tunnel design and to ensure safety. Usually, the rock mass grade is estimated by observing recovered cores obtained by drilling or by physical parameters calculated in a laboratory using core samples. However, the high drilling cost limits the number of boreholes; furthermore, rough terrains can reduce the access of drilling machines to the survey sites. In such situations, surface geophysical methods such as electrical resistivity or controlled-source magnetotelluric (CSMT) can provide a rough estimate of the rock mass condition over the planned tunnel route. These methods can also map weak zones (faults, fractures, coal bearing zones, and cavities), which are characterized by a lower resistivity than the surrounding fresh rock mass. We present two successful applications of the electrical resistivity and CSMT methods to the site investigation of tunnel construction over a rough terrain. The first example demonstrates that the boundary of the bedrock and weak zones related to the distribution of coaly shale and coal seams were estimated to extend beyond a few hundred meters below the rough surface. The second example shows that the developing direction and depth of cavities, which are mainly related to the weak zones in limestone, were successfully interpreted by a three-dimensional (3-D) electrical resistivity survey with the aid of borehole test results.

  15. Temperature Dependence of Electrical Resistance of Woven Melt-Infiltrated SiCf/SiC Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Appleby, Matthew P.; Morscher, Gregory N.; Zhu, Dongming

    2016-01-01

    Recent studies have successfully shown the use of electrical resistance (ER)measurements to monitor room temperature damage accumulation in SiC fiber reinforced SiC matrix composites (SiCf/SiC) Ceramic Matrix Composites (CMCs). In order to determine the feasibility of resistance monitoring at elevated temperatures, the present work investigates the temperature dependent electrical response of various MI (Melt Infiltrated)-CVI (Chemical Vapor Infiltrated) SiC/SiC composites containing Hi-Nicalon Type S, Tyranno ZMI and SA reinforcing fibers. Test were conducted using a commercially available isothermal testing apparatus as well as a novel, laser-based heating approach developed to more accurately simulate thermomechanical testing of CMCs. Secondly, a post-test inspection technique is demonstrated to show the effect of high-temperature exposure on electrical properties. Analysis was performed to determine the respective contribution of the fiber and matrix to the overall composite conductivity at elevated temperatures. It was concluded that because the silicon-rich matrix material dominates the electrical response at high temperature, ER monitoring would continue to be a feasible method for monitoring stress dependent matrix cracking of melt-infiltrated SiC/SiC composites under high temperature mechanical testing conditions. Finally, the effect of thermal gradients generated during localized heating of tensile coupons on overall electrical response of the composite is determined.

  16. Challenges of using electrical resistivity method to locate karst conduits-A field case in the Inner Bluegrass Region, Kentucky

    USGS Publications Warehouse

    Zhu, J.; Currens, J.C.; Dinger, J.S.

    2011-01-01

    Conduits serve as major pathways for groundwater flow in karst aquifers. Locating them from the surface, however, is one of the most challenging tasks in karst research. Geophysical methods are often deployed to help locate voids by mapping variations of physical properties of the subsurface. Conduits can cause significant contrasts of some physical properties that can be detected; other subsurface features such as water-bearing fractures often yield similar contrasts, which are difficult to distinguish from the effects of the conduits. This study used electrical resistivity method to search for an unmapped karst conduit that recharges Royal Spring in the Inner Bluegrass karst region, Kentucky, USA. Three types of resistivity techniques (surface 2D survey, quasi-3D survey, and time-lapse survey) were used to map and characterize resistivity anomalies. Some of the major anomalies were selected as drilling targets to verify the existence of the conduits. Drilling near an anomaly identified by an electrical resistivity profile resulted in successful penetration of a major water-filled conduit. The drilling results also suggest that, in this study area, low resistivity anomalies in general are associated with water-bearing features. However, differences in the anomaly signals between the water-filled conduit and other water-bearing features such as water-filled fracture zones were undistinguishable. The electrical resistivity method is useful in conduit detection by providing potential drilling targets. Knowledge of geology and hydrogeology about the site and professional judgment also played important roles in locating the major conduit. ?? 2011 Elsevier B.V.

  17. Temperature and concentration dependences of the electrical resistivity for alloys of plutonium with americium under normal conditions

    SciTech Connect

    Tsiovkin, Yu. Yu. Povzner, A. A.; Tsiovkina, L. Yu.; Dremov, V. V.; Kabirova, L. R.; Dyachenko, A. A.; Bystrushkin, V. B.; Ryabukhina, M. V.; Lukoyanov, A. V.; Shorikov, A. O.

    2010-01-15

    The temperature and concentration dependences of the electrical resistivity for alloys of americium with plutonium are analyzed in terms of the multiband conductivity model for binary disordered substitution-type alloys. For the case of high temperatures (T > {Theta}{sub D}, {Theta}{sub D} is the Debye temperature), a system of self-consistent equations of the coherent potential approximation has been derived for the scattering of conduction electrons by impurities and phonons without any constraints on the interaction intensity. The definitions of the shift and broadening operator for a single-electron level are used to show qualitatively and quantitatively that the pattern of the temperature dependence of the electrical resistivity for alloys is determined by the balance between the coherent and incoherent contributions to the electron-phonon scattering and that the interference conduction electron scattering mechanism can be the main cause of the negative temperature coefficient of resistivity observed in some alloys involving actinides. It is shown that the great values of the observed resistivity may be attributable to interband transitions of charge carriers and renormalization of their effective mass through strong s-d band hybridization. The concentration and temperature dependences of the resistivity for alloys of plutonium and americium calculated in terms of the derived conductivity model are compared with the available experimental data.

  18. Role of electrical resistance of electrodes in modeling of discharging and charging of flooded lead-acid batteries

    NASA Astrophysics Data System (ADS)

    Gandhi, K. S.

    2015-03-01

    Electrical resistance of both the electrodes of a lead-acid battery increases during discharge due to formation of lead sulfate, an insulator. Work of Metzendorf [1] shows that resistance increases sharply at about 65% conversion of active materials, and battery stops discharging once this critical conversion is reached. However, these aspects are not incorporated into existing mathematical models. Present work uses the results of Metzendorf [1], and develops a model that includes the effect of variable resistance. Further, it uses a reasonable expression to account for the decrease in active area during discharge instead of the empirical equations of previous work. The model's predictions are compared with observations of Cugnet et al. [2]. The model is as successful as the non-mechanistic models existing in literature. Inclusion of variation in resistance of electrodes in the model is important if one of the electrodes is a limiting reactant. If active materials are stoichiometrically balanced, resistance of electrodes can be very large at the end of discharge but has only a minor effect on charging of batteries. The model points to the significance of electrical conductivity of electrodes in the charging of deep discharged batteries.

  19. The use of electrical resistivity techniques to detect an underground conduit in the karst regions of the Inner Bluegrass

    SciTech Connect

    Bonita, J.; Sendlein, L.V.A. . Dept. of Geological Sciences)

    1993-03-01

    Electrical resistivity studies conducted within the Inner Bluegrass Karst Region have been employed to map the presence of a fracture controlled solution that drains the royal Spring Basin. Exist theories by authors such as Thrailkill (1982) suggest that the Inner Bluegrass Karst Region is divided into basin and interbasin areas, with the zone of active meteoric water circulation at deep depths below the surface in basin areas and flow within a few meters of the surface in interbasin areas. Initial resistivity soundings were performed along various traverses to access information on the underlying lexington Limestone. Sounding curves calculated form the modeling program RESIX indicate that low resistivity zones occur at two distinctly different depth intervals, denoting the boundary between the basin and interbasin areas. Information from electric resistivity profiles within this now defined basin area indicate resistivity anomalies trending in linear segments of N45W and N40E. Fracture and joint orientation measurements at roadcuts and on topographic maps and air photographs also indicate a preferential orientation parallel to the orientation of the linear segments of the conduit.

  20. Inter-electrode tissue resistance is not affected by tissue oedema when electrically stimulating the lower limb of sepsis patients.

    PubMed

    Durfee, William K; Young, Joseph R; Ginz, Hans F

    2014-05-01

    ICU patients typically are given large amounts of fluid and often develop oedema. The purpose of this study was to evaluate whether the oedema would change inter-electrode resistance and, thus, require a different approach to using non-invasive electrical stimulation of nerves to assess muscle force. Inter-electrode tissue resistance in the lower leg was measured by applying a 300 µs constant current pulse and measuring the current through and voltage across the stimulating electrodes. The protocol was administered to nine ICU patients with oedema, eight surgical patients without oedema and eight healthy controls. No significant difference in inter-electrode resistance was found between the three groups. For all groups, resistance decreased as stimulation current increased. In conclusion, inter-electrode resistance in ICU patients with severe oedema is the same as the resistance in regular surgical patients and healthy controls. This means that non-invasive nerve stimulation devices do not need to be designed to accommodate different resistances when used with oedema patients; however, surface stimulation does require higher current levels with oedema patients because of the increased distance between the skin surface and the targeted nerve or muscle.

  1. Inter-electrode tissue resistance is not affected by tissue oedema when electrically stimulating the lower limb of sepsis patients.

    PubMed

    Durfee, William K; Young, Joseph R; Ginz, Hans F

    2014-05-01

    ICU patients typically are given large amounts of fluid and often develop oedema. The purpose of this study was to evaluate whether the oedema would change inter-electrode resistance and, thus, require a different approach to using non-invasive electrical stimulation of nerves to assess muscle force. Inter-electrode tissue resistance in the lower leg was measured by applying a 300 µs constant current pulse and measuring the current through and voltage across the stimulating electrodes. The protocol was administered to nine ICU patients with oedema, eight surgical patients without oedema and eight healthy controls. No significant difference in inter-electrode resistance was found between the three groups. For all groups, resistance decreased as stimulation current increased. In conclusion, inter-electrode resistance in ICU patients with severe oedema is the same as the resistance in regular surgical patients and healthy controls. This means that non-invasive nerve stimulation devices do not need to be designed to accommodate different resistances when used with oedema patients; however, surface stimulation does require higher current levels with oedema patients because of the increased distance between the skin surface and the targeted nerve or muscle. PMID:24758395

  2. Effect of electrical stimulation-induced resistance exercise on mitochondrial fission and fusion proteins in rat skeletal muscle.

    PubMed

    Kitaoka, Yu; Ogasawara, Riki; Tamura, Yuki; Fujita, Satoshi; Hatta, Hideo

    2015-11-01

    It is well known that resistance exercise increases muscle protein synthesis and muscle strength. However, little is known about the effect of resistance exercise on mitochondrial dynamics, which is coupled with mitochondrial function. In skeletal muscle, mitochondria exist as dynamic networks that are continuously remodeling through fusion and fission. The purpose of this study was to investigate the effect of acute and chronic resistance exercise, which induces muscle hypertrophy, on the expression of proteins related to mitochondrial dynamics in rat skeletal muscle. Resistance exercise consisted of maximum isometric contraction, which was induced by percutaneous electrical stimulation of the gastrocnemius muscle. Our results revealed no change in levels of proteins that regulate mitochondrial fission (Fis1 and Drp1) or fusion (Opa1, Mfn1, and Mfn2) over the 24-h period following acute resistance exercise. Phosphorylation of Drp1 at Ser616 was increased immediately after exercise (P < 0.01). Four weeks of resistance training (3 times/week) increased Mfn1 (P < 0.01), Mfn2 (P < 0.05), and Opa1 (P < 0.01) protein levels without altering mitochondrial oxidative phosphorylation proteins. These observations suggest that resistance exercise has little effect on mitochondrial biogenesis but alters the expression of proteins involved in mitochondrial fusion and fission, which may contribute to mitochondrial quality control and improved mitochondrial function.

  3. Re-Inversion of Surface Electrical Resistivity Tomography Data from the Hanford Site B-Complex

    SciTech Connect

    Johnson, Timothy C.; Wellman, Dawn M.

    2013-05-01

    This report documents the three-dimensional (3D) inversion results of surface electrical resistivity tomography (ERT) data collected over the Hanford Site B-Complex. The data were collected in order to image the subsurface distribution of electrically conductive vadose zone contamination resulting from both planned releases of contamination into subsurface infiltration galleries (cribs, trenches, and tile fields), as well as unplanned releases from the B, BX, and BY tank farms and/or associated facilities. Electrically conductive contaminants are those which increase the ionic strength of pore fluids compared to native conditions, which comprise most types of solutes released into the subsurface B-Complex. The ERT data were collected and originally inverted as described in detail in report RPP-34690 Rev 0., 2007, which readers should refer to for a detailed description of data collection and waste disposal history. Although the ERT imaging results presented in that report successfully delineated the footprint of vadose zone contamination in areas outside of the tank farms, imaging resolution was not optimized due to the inability of available inversion codes to optimally process the massive ERT data set collected at the site. Recognizing these limitations and the potential for enhanced ERT characterization and time-lapse imaging at contaminated sites, a joint effort was initiated in 2007 by the U.S. Department of Energy – Office of Science (DOE-SC), with later support by the Office of Environmental Management (DOE-EM), and the U.S. Department of Defense (DOD), to develop a high-performance distributed memory parallel 3D ERT inversion code capable of optimally processing large ERT data sets. The culmination of this effort was the development of E4D (Johnson et al., 2010,2012) In 2012, under the Deep Vadose Zone Applied Field Research Initiative (DVZ-AFRI), the U.S. Department of Energy – Richland Operations Office (DOE-RL) and CH2M Hill Plateau Remediation

  4. Characterization and calibration of seawater intrusion models using electrical resistivity tomography (Invited)

    NASA Astrophysics Data System (ADS)

    Nguyen, F. H.; Kemna, A.; Antonsson, A.; Engesgaard, P. K.; Beaujean, J.

    2009-12-01

    The urban development of coastal regions create seawater intrusion (SWI) problems which threatens groundwater quality and coastal ecosystems. To study SWI, one needs both robust measuring technologies, and reliable predictions. A key aspect in the calibration of SWI models involves reproducing measured groundwater chloride concentrations. Drilling such multi-screen wells to obtain a whole concentration profile is a risky task if reliable information about the position of the salt wedge is not available. Electrical resistivity tomography (ERT) is increasingly being used to characterize seawater intrusion and constrain corresponding models, given its high sensitivity to ion concentration in groundwater and its relatively high spatial resolution. We have investigated the potential of ERT using field data from a site in Almeria, SE Spain and synthetic data. Simulations have been run for several scenarios, with a simple hydrogeological model reflecting the local site conditions. The simulations showed that only the lower salt concentrations of the seawater-freshwater transition zone could be recovered, due to the loss of resolution with depth. We quantified this capability in terms of image appraisal indicators (cumulative sensitivity) associated with the measurement setup and showed that the mismatch between the targeted and imaged parameter values occurs from a certain threshold. Similarly, heterogeneity may only be determined accurately if located in an adequately sensitive area. Inversion of the synthetic data was performed by coupling an inversion code (PEST) with a finite-difference density-dependent flow and transport modeling code (HTS). The numerical results demonstrate the capacity of sensitivity-filtered ERT images to constrain transverse hydraulic dispersivity and longitudinal hydraulic conductivity of homogeneous seawater intrusion models. At the field site, we identified SWI at the scale of a few kilometers down to a hundred meters. Borehole logs show a

  5. Contribution of 3D inversion of Electrical Resistivity Tomography data applied to volcanic structures

    NASA Astrophysics Data System (ADS)

    Portal, Angélie; Fargier, Yannick; Lénat, Jean-François; Labazuy, Philippe

    2016-04-01

    The electrical resistivity tomography (ERT) method, initially developed for environmental and engineering exploration, is now commonly used for geological structures imaging. Such structures can present complex characteristics that conventional 2D inversion processes cannot perfectly integrate. Here we present a new 3D inversion algorithm named EResI, firstly developed for levee investigation, and presently applied to the study of a complex lava dome (the Puy de Dôme volcano, France). EResI algorithm is based on a conventional regularized Gauss-Newton inversion scheme and a 3D non-structured discretization of the model (double grid method based on tetrahedrons). This discretization allows to accurately model the topography of investigated structure (without a mesh deformation procedure) and also permits a precise location of the electrodes. Moreover, we demonstrate that a complete 3D unstructured discretization limits the number of inversion cells and is better adapted to the resolution capacity of tomography than a structured discretization. This study shows that a 3D inversion with a non-structured parametrization has some advantages compared to classical 2D inversions. The first advantage comes from the fact that a 2D inversion leads to artefacts due to 3D effects (3D topography, 3D internal resistivity). The second advantage comes from the fact that the capacity to experimentally align electrodes along an axis (for 2D surveys) depends on the constrains on the field (topography...). In this case, a 2D assumption induced by 2.5D inversion software prevents its capacity to model electrodes outside this axis leading to artefacts in the inversion result. The last limitation comes from the use of mesh deformation techniques used to accurately model the topography in 2D softwares. This technique used for structured discretization (Res2dinv) is prohibed for strong topography (>60 %) and leads to a small computational errors. A wide geophysical survey was carried out

  6. Time Differential Electrical Resistivity for Water Resource Assessment: A Case Study in Cura‡ao, Netherlands Antilles

    NASA Astrophysics Data System (ADS)

    Coles, D.; Vichabian, Y.; Sogade, J.; Spiertz, P.; Morgan, F. D.

    2003-12-01

    A method of groundwater prospecting is presented that capitalizes on changes in electrical resistivity arising from annual variability in subsurface fluid flow. According to Archie's Law, effective resistivity is a function of pore fluid resistivity, saturation, and porosity. For competent Earth materials, short-term temporal changes in near-surface porosity are negligible because changes in effective pressure are small with respect to the bulk moduli of the materials. Therefore, annual variability in effective resistivity is dependent only on fluid flow via changes in saturation and, to a lesser extent, pore fluid resistivity. Aquifer detection is but the first step; thereafter, it is necessary to estimate permeability, capacity, and, importantly, sustainability. Time differential resistivity is well matched to the task because it detects prospective aquifers and also illuminates their natural hydrodynamics. Explicitly, this method captures an undeveloped aquifer's seasonal volumetric variability, which is important as engineers reconcile monthly demand with monthly supply. The best scenario would be to detect a capacious, intermediate-resistivity (high pore fluid resistivity and high porosity) zone that is invariant from season to season (clays and ore bodies excepted). Less desirable, but still manageable, is the case where a large, porous formation undergoes significant seasonal resistivity variation; it behaves as a subterranean river with little lag-time between meteoric water input and groundwater throughput; carefully timed extraction and storage would be required in this case. A suite of thirty-eight electrical resistivity soundings were collected from the wet and dry seasons at Plantages PortoMari, an ecotourist plantation on the semiarid island of Cura‡ao, N.A. The data were analyzed with special attention paid to wet-to-dry season resistivity ratios. The results suggest two possible courses of action. (1) A hypothetical limestone terrace was detected

  7. Effects of coupling between sample and electrode on the electrical resistivity measurements of conductive samples

    NASA Astrophysics Data System (ADS)

    Lee, T. J.; Lee, S. K.

    2015-12-01

    A resistivity measurement system for conductive core samples has been setup using a high resolution nano-voltmeter. Using the system, in this study, various coupling effects between electrodes and the samples are discussed including contact resistance, lead resistance, temperature dependence, and heat produced within the samples by applied current. The lead resistance was over 10 times higher than the resistance of the conductive samples such as graphite or nichrome, even though the electrodes and lead lines were made of silver. Furthermore, lead resistance itself showed very strong temperature dependence, so that it is essential to subtract the lead resistance from the measured values at corresponding temperature. Minimization of contact resistance is very important, so that the axial loads are needed as big as possible unless the deformation of sample occurs.

  8. Extraction of temperature dependent electrical resistivity and thermal conductivity from silicon microwires self-heated to melting temperature

    NASA Astrophysics Data System (ADS)

    Bakan, Gokhan; Adnane, Lhacene; Gokirmak, Ali; Silva, Helena

    2012-09-01

    Temperature-dependent electrical resistivity, ρ(T), and thermal conductivity, k(T), of nanocrystalline silicon microwires self-heated to melt are extracted by matching simulated current-voltage (I-V) characteristics to experimental I-V characteristics. Electrical resistivity is extracted from highly doped p-type wires on silicon dioxide in which the heat losses are predominantly to the substrate and the self-heating depends mainly on ρ(T) of the wires. The extracted ρ(T) decreases from 11.8 mΩ cm at room-temperature to 5.2 mΩ cm at 1690 K, in reasonable agreement with the values measured up to ˜650 K. Electrical resistivity and thermal conductivity are extracted from suspended highly doped n-type silicon wires in which the heat losses are predominantly through the wires. In this case, measured ρ(T) (decreasing from 20.5 mΩ cm at room temperature to 12 mΩ cm at 620 K) is used to extract ρ(T) at higher temperatures (decreasing to 1 mΩ cm at 1690 K) and k(T) (decreasing from 30 W m-1 K-1 at room temperature to 20 W m-1 K-1 at 1690 K). The method is tested by using the extracted parameters to model wires with different dimensions. The experimental and simulated I-V curves for these wires show good agreement up to high voltage and temperature levels. This technique allows extraction of the electrical resistivity and thermal conductivity up to very high temperatures from self-heated microstructures.

  9. ELECTRICAL RESISTANCE HEATING OF SOILS AT C-REACTOR AT THE SAVANNAH RIVER SITE

    SciTech Connect

    Blundy, R; Michael Morgenstern, M; Joseph Amari, J; Annamarie MacMurray, A; Mark Farrar, M; Terry Killeen, T

    2007-09-10

    Chlorinated solvent contamination of soils and groundwater is an endemic problem at the Savannah River Site (SRS), and originated as by-products from the nuclear materials manufacturing process. Five nuclear reactors at the SRS produced special nuclear materials for the nation's defense program throughout the cold war era. An important step in the process was thorough degreasing of the fuel and target assemblies prior to irradiation. Discharges from this degreasing process resulted in significant groundwater contamination that would continue well into the future unless a soil remediation action was performed. The largest reactor contamination plume originated from C-Reactor and an interim action was selected in 2004 to remove the residual trichloroethylene (TCE) source material by electrical resistance heating (ERH) technology. This would be followed by monitoring to determine the rate of decrease in concentration in the contaminant plume. Because of the existence of numerous chlorinated solvent sources around SRS, it was elected to generate in-house expertise in the design and operation of ERH, together with the construction of a portable ERH/SVE system that could be deployed at multiple locations around the site. This paper describes the waste unit characteristics, the ERH system design and operation, together with extensive data accumulated from the first deployment adjacent to the C-Reactor building. The installation heated the vadose zone down to 62 feet bgs over a 60 day period during the summer of 2006 and raised soil temperatures to over 200 F. A total of 730 lbs of trichloroethylene (TCE) were removed over this period, and subsequent sampling indicated a removal efficiency of 99.4%.

  10. Thermal conductivity and electrical resistivity of gadolinium as functions of pressure and temperature

    NASA Astrophysics Data System (ADS)

    Jacobsson, P.; Sundqvist, B.

    1989-11-01

    The electrical resistivity ρ and the thermal diffusivity a of gadolinium have been measured as functions of T in the range 45-400 K. The thermal conductivity λ has been calculated from a and experimental data for the specific-heat capacity, cp. λ can be analyzed in terms of simple models for the lattice and electronic components above the Curie temperature TC~=291.4 K. Below TC an additional term, identified as a magnon (spin-wave) thermal conductivity λm, is found. ρ and λ have also been studied as functions of T and P in the range 150-400 K and 0-2.5 GPa. The Lorenz function L=ρλ/T increases by about 20%/GPa under pressure due to a very strong pressure dependence of the lattice thermal conductivity. The pressure coefficients of ρ and λ are -5.1×10-2 and 0.22 GPa-1, respectively, at 300 K (above TC), and 0 and 0.16 GPa-1 at 200 K (below TC). TC and the spin-reorganization temperature Tr~=219 K both decrease under pressure, at the rates -14.0 and -22.0 K/GPa, respectively. Although the magnitude of λm cannot be accurately calculated from the zero-pressure data for λ, the temperature dependence of dλ/dP allows us to distinguish between several models and assign a value of λm~=1.5 W m-1 K-1, or 16.0% of λ, at 200 K.

  11. Factors affecting gas migration and contaminant redistribution in heterogeneous porous media subject to electrical resistance heating.

    PubMed

    Munholland, Jonah L; Mumford, Kevin G; Kueper, Bernard H

    2016-01-01

    A series of intermediate-scale laboratory experiments were completed in a two-dimensional flow cell to investigate gas production and migration during the application of electrical resistance heating (ERH) for the removal of dense non-aqueous phase liquids (DNAPLs). Experiments consisted of heating water in homogeneous silica sand and heating 270 mL of trichloroethene (TCE) and chloroform (CF) DNAPL pools in heterogeneous silica sands, both under flowing groundwater conditions. Spatial and temporal distributions of temperature were measured using thermocouples and observations of gas production and migration were collected using front-face image capture throughout the experiments. Post-treatment soil samples were collected and analyzed to assess DNAPL removal. Results of experiments performed in homogeneous sand subject to different groundwater flow rates showed that high groundwater velocities can limit subsurface heating rates. In the DNAPL pool experiments, temperatures increased to achieve DNAPL-water co-boiling, creating estimated gas volumes of 131 and 114 L that originated from the TCE and CF pools, respectively. Produced gas migrated vertically, entered a coarse sand lens and subsequently migrated laterally beneath an overlying capillary barrier to outside the heated treatment zone where 31-56% of the original DNAPL condensed back into a DNAPL phase. These findings demonstrate that layered heterogeneity can potentially facilitate the transport of contaminants outside the treatment zone by mobilization and condensation of gas phases during ERH applications. This underscores the need for vapor phase recovery and/or control mechanisms below the water table during application of ERH in heterogeneous porous media during the co-boiling stage, which occurs prior to reaching the boiling point of water.

  12. An extended L-curve method for choosing a regularization parameter in electrical resistance tomography

    NASA Astrophysics Data System (ADS)

    Xu, Yanbin; Pei, Yang; Dong, Feng

    2016-11-01

    The L-curve method is a popular regularization parameter choice method for the ill-posed inverse problem of electrical resistance tomography (ERT). However the method cannot always determine a proper parameter for all situations. An investigation into those situations where the L-curve method failed show that a new corner point appears on the L-curve and the parameter corresponding to the new corner point can obtain a satisfactory reconstructed solution. Thus an extended L-curve method, which determines the regularization parameter associated with either global corner or the new corner, is proposed. Furthermore, two strategies are provided to determine the new corner-one is based on the second-order differential of L-curve, and the other is based on the curvature of L-curve. The proposed method is examined by both numerical simulations and experimental tests. And the results indicate that the extended method can handle the parameter choice problem even in the case where the typical L-curve method fails. Finally, in order to reduce the running time of the method, the extended method is combined with a projection method based on the Krylov subspace, which was able to boost the extended L-curve method. The results verify that the speed of the extended L-curve method is distinctly improved. The proposed method extends the application of the L-curve in the field of choosing regularization parameter with an acceptable running time and can also be used in other kinds of tomography.

  13. Factors affecting gas migration and contaminant redistribution in heterogeneous porous media subject to electrical resistance heating

    NASA Astrophysics Data System (ADS)

    Munholland, Jonah L.; Mumford, Kevin G.; Kueper, Bernard H.

    2016-01-01

    A series of intermediate-scale laboratory experiments were completed in a two-dimensional flow cell to investigate gas production and migration during the application of electrical resistance heating (ERH) for the removal of dense non-aqueous phase liquids (DNAPLs). Experiments consisted of heating water in homogeneous silica sand and heating 270 mL of trichloroethene (TCE) and chloroform (CF) DNAPL pools in heterogeneous silica sands, both under flowing groundwater conditions. Spatial and temporal distributions of temperature were measured using thermocouples and observations of gas production and migration were collected using front-face image capture throughout the experiments. Post-treatment soil samples were collected and analyzed to assess DNAPL removal. Results of experiments performed in homogeneous sand subject to different groundwater flow rates showed that high groundwater velocities can limit subsurface heating rates. In the DNAPL pool experiments, temperatures increased to achieve DNAPL-water co-boiling, creating estimated gas volumes of 131 and 114 L that originated from the TCE and CF pools, respectively. Produced gas migrated vertically, entered a coarse sand lens and subsequently migrated laterally beneath an overlying capillary barrier to outside the heated treatment zone where 31-56% of the original DNAPL condensed back into a DNAPL phase. These findings demonstrate that layered heterogeneity can potentially facilitate the transport of contaminants outside the treatment zone by mobilization and condensation of gas phases during ERH applications. This underscores the need for vapor phase recovery and/or control mechanisms below the water table during application of ERH in heterogeneous porous media during the co-boiling stage, which occurs prior to reaching the boiling point of water.

  14. Factors affecting gas migration and contaminant redistribution in heterogeneous porous media subject to electrical resistance heating.

    PubMed

    Munholland, Jonah L; Mumford, Kevin G; Kueper, Bernard H

    2016-01-01

    A series of intermediate-scale laboratory experiments were completed in a two-dimensional flow cell to investigate gas production and migration during the application of electrical resistance heating (ERH) for the removal of dense non-aqueous phase liquids (DNAPLs). Experiments consisted of heating water in homogeneous silica sand and heating 270 mL of trichloroethene (TCE) and chloroform (CF) DNAPL pools in heterogeneous silica sands, both under flowing groundwater conditions. Spatial and temporal distributions of temperature were measured using thermocouples and observations of gas production and migration were collected using front-face image capture throughout the experiments. Post-treatment soil samples were collected and analyzed to assess DNAPL removal. Results of experiments performed in homogeneous sand subject to different groundwater flow rates showed that high groundwater velocities can limit subsurface heating rates. In the DNAPL pool experiments, temperatures increased to achieve DNAPL-water co-boiling, creating estimated gas volumes of 131 and 114 L that originated from the TCE and CF pools, respectively. Produced gas migrated vertically, entered a coarse sand lens and subsequently migrated laterally beneath an overlying capillary barrier to outside the heated treatment zone where 31-56% of the original DNAPL condensed back into a DNAPL phase. These findings demonstrate that layered heterogeneity can potentially facilitate the transport of contaminants outside the treatment zone by mobilization and condensation of gas phases during ERH applications. This underscores the need for vapor phase recovery and/or control mechanisms below the water table during application of ERH in heterogeneous porous media during the co-boiling stage, which occurs prior to reaching the boiling point of water. PMID:26638038

  15. Evaluating four-dimensional time-lapse electrical resistivity tomography for monitoring DNAPL source zone remediation.

    PubMed

    Power, Christopher; Gerhard, Jason I; Karaoulis, Marios; Tsourlos, Panagiotis; Giannopoulos, Antonios

    2014-07-01

    Practical, non-invasive tools do not currently exist for mapping the remediation of dense non-aqueous phase liquids (DNAPLs). Electrical resistivity tomography (ERT) exhibits significant potential but has not yet become a practitioner's tool due to challenges in interpreting the survey results at real sites. This study explores the effectiveness of recently developed four-dimensional (4D, i.e., 3D space plus time) time-lapse surface ERT to monitor DNAPL source zone remediation. A laboratory experiment demonstrated the approach for mapping a changing NAPL distribution over time. A recently developed DNAPL-ERT numerical model was then employed to independently simulate the experiment, providing confidence that the DNAPL-ERT model is a reliable tool for simulating real systems. The numerical model was then used to evaluate the potential for this approach at the field scale. Four DNAPL source zones, exhibiting a range of complexity, were initially simulated, followed by modeled time-lapse ERT monitoring of complete DNAPL remediation by enhanced dissolution. 4D ERT inversion provided estimates of the regions of the source zone experiencing mass reduction with time. Results show that 4D time-lapse ERT has significant potential to map both the outline and the center of mass of the evolving treated portion of the source zone to within a few meters in each direction. In addition, the technique can provide a reasonable, albeit conservative, estimate of the DNAPL volume remediated with time: 25% underestimation in the upper 2m and up to 50% underestimation at late time between 2 and 4m depth. The technique is less reliable for identifying cleanup of DNAPL stringers outside the main DNAPL body. Overall, this study demonstrates that 4D time-lapse ERT has potential for mapping where and how quickly DNAPL mass changes in real time during site remediation.

  16. Comparison of wet/dry mapping and electrical resistivity sensors to characterize patterns of intermittency

    NASA Astrophysics Data System (ADS)

    Costigan, K. H.; Goss, C. W.; Jaeger, K. L.; Goebel, P. C.

    2015-12-01

    Intermittent rivers are those that cease to flow at some point(s) in space and time along their course and are present in all climates and terrestrial biomes. The prevalence of drying is increasing, even in temperate biomes that we typically do not associate with river drying or dry climates. There have been several techniques employed to characterize patterns of intermittency but field mapping and use of electrical resistivity (ER) sensors are the most common. Field mapping has long been used to study intermittency, but this method is limited by its inability to capture the rapidly changing configuration of intermittent streams that often occur during wetting and drying events. ER sensors enable researchers to remotely record channel-water presence at fine spatiotemporal scales which will better capture seasonal dynamics in transient lotic systems. Here, we compare field mapping and ER sensor recordings of stream intermittency for 10 forested headwater streams in northeastern Ohio. Field mapping occurred approximately biweekly while the ER sensors recorded at 30-minute intervals from April through November 2014. Although ER sensors offer many advantages to stream mapping, our study revealed several limitations of ER sensors including requiring re-securing after flows moved sensors, burial in sediment that results them in recording subsurface water, and the small spatial scale the sensors are representative of. Nevertheless, ER sensors provide a low cost, high performance, and method that requires minimal data interpretation to monitor the presence and absence of water in channels at a specific location. The latest generation of ER sensors also record temperature, which can help in differentiate standing and flowing water. Aspects other than timing, duration, and frequency of flow such as the resumption (advancing) and recession (retreating) rates or magnitudes can be characterized with ER sensor arrays.

  17. Observation of trapped gas during electrical resistance heating of trichloroethylene under passive venting conditions.

    PubMed

    Martin, E J; Kueper, B H

    2011-11-01

    A two-dimensional experiment employing a heterogeneous sand pack incorporating two pools of trichloroethylene (TCE) was performed to assess the efficacy of electrical resistance heating (ERH) under passive venting conditions. Temperature monitoring displayed the existence of a TCE-water co-boiling plateau at 73.4°C, followed by continued heating to 100°C. A 5cm thick gas accumulation formed beneath a fine-grained capillary barrier during and after co-boiling. The capillary barrier did not desaturate during the course of the experiment; the only pathway for gas escape being through perforated wells traversing the barrier. The thickness of the accumulation was dictated by the entry pressure of the perforated well. The theoretical maximum TCE soil concentration within the region of gas accumulation, following gas collapse, was estimated to be 888mg/kg. Post-heating soil sampling revealed TCE concentrations in this region ranging from 27mg/kg to 96.7mg/kg, indicating removal of aqueous and gas phase TCE following co-boiling as a result of subsequent boiling of water. The equilibrium concentrations of TCE in water corresponding to the range of post-treatment concentrations in soil (6.11mg/kg to 136mg/kg) are calculated to range from 19.8mg/l to 440mg/l. The results of this experiment illustrate the importance of providing gas phase venting during the application of ERH in heterogeneous porous media. PMID:22115093

  18. 3D Electrical resistivity tomography monitoring of an artificial tracer injected within the hyporheic zone

    NASA Astrophysics Data System (ADS)

    Houzé, Clémence; Pessel, Marc; Durand, Veronique

    2016-04-01

    Due to the high complexity level of hyporheic flow paths, hydrological and biogeochemical processes which occur in this mixing place are not fully understood yet. Some previous studies made in flumes show that hyporheic flow is strongly connected to the streambed morphology and sediment heterogeneity . There is still a lack of practical field experiment considering a natural environment and representation of natural streambed heterogeneities will be always limited in laboratories. The purpose of this project is to propose an innovative method using 3D Electrical Resistivity Tomography (ERT) monitoring of an artificial tracer injection directly within the streambed sediments in order to visualize the water pathways within the hyporheic zone. Field experiment on a small stream was conducted using a plastic tube as an injection piezometer and home-made electrodes strips arranged in a rectangular form made of 180 electrodes (15 strips of 12 electrodes each). The injection of tracer (NaCl) lasted approximatively 90 minutes, and 24h monitoring with increasing step times was performed. The physical properties of the water are controlled by CTD probes installed upstream and downstream within the river. Inverse time-lapse tomographs show development and persistence of a conductive water plume around the injection point. Due to the low hydraulic conductivity of streambed sediments (clay and overlying loess), the tracer movement is barely visible, as it dilutes gradually in the pore water. Impact of boundary conditions on inversion results can lead to significant differences on images, especially in the shallow part of the profiles. Preferential paths of transport are not highlighted here, but this experiment allows to follow spatially and temporarily the evolution of the tracer in a complex natural environment .

  19. PILOT-SCALE FIELD VALIDATION OF THE LONG ELECTRODE ELECTRICAL RESISTIVITY TOMOGRAPHY METHOD

    SciTech Connect

    GLASER DR; RUCKER DF; CROOK N; LOKE MH

    2011-07-14

    Field validation for the long electrode electrical resistivity tomography (LE-ERT) method was attempted in order to demonstrate the performance of the technique in imaging a simple buried target. The experiment was an approximately 1/17 scale mock-up of a region encompassing a buried nuclear waste tank on the Hanford site. The target of focus was constructed by manually forming a simulated plume within the vadose zone using a tank waste simulant. The LE-ERT results were compared to ERT using conventional point electrodes on the surface and buried within the survey domain. Using a pole-pole array, both point and long electrode imaging techniques identified the lateral extents of the pre-formed plume with reasonable fidelity, but the LE-ERT was handicapped in reconstructing the vertical boundaries. The pole-dipole and dipole-dipole arrays were also tested with the LE-ERT method and were shown to have the least favorable target properties, including the position of the reconstructed plume relative to the known plume and the intensity of false positive targets. The poor performance of the pole-dipole and dipole-dipole arrays was attributed to an inexhaustive and non-optimal coverage of data at key electrodes, as well as an increased noise for electrode combinations with high geometric factors. However, when comparing the model resolution matrix among the different acquisition strategies, the pole-dipole and dipole-dipole arrays using long electrodes were shown to have significantly higher average and maximum values than any pole-pole array. The model resolution describes how well the inversion model resolves the subsurface. Given the model resolution performance of the pole-dipole and dipole-dipole arrays, it may be worth investing in tools to understand the optimum subset of randomly distributed electrode pairs to produce maximum performance from the inversion model.

  20. A study of the effect of seasonal climatic factors on the electrical resistivity response of three experimental graves

    NASA Astrophysics Data System (ADS)

    Jervis, John R.; Pringle, Jamie K.

    2014-09-01

    Electrical resistivity surveys have proven useful for locating clandestine graves in a number of forensic searches. However, some aspects of grave detection with resistivity surveys remain imperfectly understood. One such aspect is the effect of seasonal changes in climate on the resistivity response of graves. In this study, resistivity survey data collected over three years over three simulated graves were analysed in order to assess how the graves' resistivity anomalies varied seasonally and when they could most easily be detected. Thresholds were used to identify anomalies, and the ‘residual volume' of grave-related anomalies was calculated as the area bounded by the relevant thresholds multiplied by the anomaly's average value above the threshold. The residual volume of a resistivity anomaly associated with a buried pig cadaver showed evidence of repeating annual patterns and was moderately correlated with the soil moisture budget. This anomaly was easiest to detect between January and April each year, after prolonged periods of high net gain in soil moisture. The resistivity response of a wrapped cadaver was more complex, although it also showed evidence of seasonal variation during the third year after burial. We suggest that the observed variation in the graves' resistivity anomalies was caused by seasonal change in survey data noise levels, which was in turn influenced by the soil moisture budget. It is possible that similar variations occur elsewhere for sites with seasonal climate variations and this could affect successful detection of other subsurface features. Further research to investigate how different climates and soil types affect seasonal variation in grave-related resistivity anomalies would be useful.

  1. Geomorphology of the Alluvial Sediments and Bedrock in an Intermontane Basin: Application of Variogram Modeling to Electrical Resistivity Soundings

    NASA Astrophysics Data System (ADS)

    Khan, Adnan Ahmad; Farid, Asam; Akhter, Gulraiz; Munir, Khyzer; Small, James; Ahmad, Zulfiqar

    2016-05-01

    The study describes a methodology used to integrate legacy resistivity data with limited geological data in order to build three-dimensional models of the near subsurface. Variogram analysis and inversion techniques more typically found in the petroleum industry are applied to a set of 1D resistivity data taken from electrical surveys conducted in the 1980s. Through careful integration with limited geological data collected from boreholes and outcrops, the resultant model can be visualized in three dimensions to depict alluvium layers as lithological and structural units within the bedrock. By tuning the variogram parameters to account for directionality, it is possible to visualize the individual lithofacies and geomorphological features in the subsurface. In this study, an electrical resistivity data set collected as part of a groundwater study in an area of the Peshawar basin in Pakistan has been re-examined. Additional lithological logs from boreholes throughout the area have been combined with local outcrop information to calibrate the data. Tectonic activity during the Himalayan orogeny has caused uplift in the area and generated significant faulting in the bedrock resulting in the formation of depressions which are identified by low resistivity values representing clays. Paleo-streams have reworked these clays which have been eroded and replaced by gravel-sand facies along paleo-channels. It is concluded that the sediments have been deposited as prograding fan-shaped bodies and lacustrine deposits with interlayered gravel-sand and clay-silt facies. The Naranji area